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Toua las autras exemplairas originaux sont fiimte en common^ ant par la premiere page qui comporte une empreinte dimpreeaion ou dINuatration at an tarminant par la darniire page qui comporte une telle empreinte. Un dee symbolee suivants sppareltre sur le derniire imege do cheque microfiche, selon le ces: le symbole — ^ signifie "A SUIVRE". le symbole ▼ eignifie "FIN". Les cortee. plenchee. tebleeux. etc.. peuvent Atre filmie A doe teux do reduction diff*rents. Lorsque le document est trop grend pour *tre reproduit en un soul clich*. it est film* * psrtir do i'engie supArieur geuche. do gauche i droite. et do heut en bas. en prenent le nombre d'imegee n^ceesoire. Les diagrammes suivants illustrent la mtthode. 12 3 1 2 3 4 5 6 I J m mtm mmmmmmm Human Anatomy /^n^' ^mmiHmKmmmmmmm HUMAN ANATOMY INCLUDING STRUCTURE AND DEVELOPMENT AND PRACTICAL CONSIDERATIONS BY THOMAS DWIGHT. M.D.. LL.D. PAttHAit nopmoii or anatomy in iia«vabd UNIVEWTV CARL A. HAMANN, M.D. novnaoi ot amatomv m wnrBUM unuvs imivsasiTV J. PLAYFAIR McMURRICH. PH.D. PKOPmnK or anatohv in the UNIVnSITT o MICHIGAN GEORGE A. PIERSOL, M.D.. SC.D. norKuoii or anatomy in the umvEEarrr < PENNSYLVANIA J. WILLIAM WHITE, M.D.. PH.D.. LL.D. • EAETOH PEOPEMOE Or SUEGBKY IN THE UNIVBEIITT Or PEMMSVLVAMIA TH SEVENTEEN HUNDRED AND THIRTY-FOUR ILLUSTRATIONS. OF WHICH FIFTEEN HUNDRED AND TWENTY-TWO ARE ORIGINAL AND LARGELY FROM DISSECTIONS BY JOHN C. HEISLER. M.D. P^OrEMOE or ANATOMY IN THE MBOICO-CHIEUKOICAL < Ol LEGE EDITED BY GEORGE A. PIERSOL VOL. II. PHILADELPHIA & LONDON / / J. B. LFPPINCOTT COMPANY .Id OS] €,'! wmmmm pnppMP«fi»«iiip Copyright, 1906, by J. B. Lippincott Company. Copyright, 1907, by ]. B. Lippincott Company. Copyright, 1908, by ]. B. Lippincott Company. Entered at Stationers' Hall, London, England. All fiiffhts RfSfrved^ IHeTMTTnD AND niNTID IT i. ■. IIWIMOTT COWMV , rHILAHirHI*, U.IA tjm-':^ • CONTENTS. VOL. II. THE NERVOIS SYSTEM. General Considerations The Nervous Tissues The Ner\e-Cells The Nerve-Fibres Neur(M;lia The Nerve-Trunks The Ganglia Development of th.- Nervous Tis.sues . . . Nerve-Terminations Motor Endings Sensory Endings The Ckntral Nervous System. The Spi.nai. Cord Membranes Cord-Segments Form of the Spinal Cord Columns of the Cord Gray Matter Central Canal Microscopical Structure White Matter Fibre Tracts Blood- Vessels of Spinal Cord Development of Spmal Cord Practical Considerations : Spina' "oril. . Malformations Injuries Localization of Lesions The Brain General Description General Development Derivatives from the Khombencephiilon The Medulla Oblongata Internal Structure The Pons Varolii Internal .Structure The Cerebellum Lobes and Fissures Architecture Internal Nuclei Cerebellar Cortex Ceret)ellar Peduncles The Fourth Ventricle Development of the Hind-Brain Derivatives The Medulla The Pons The Cerebellum The Mesencephalon The Cor|K>ra Ouadrigemina The Cerebral Peduncles The Sylvian Aqueduct Internal Structure of the Mid-Brain The Tegmentum The Cnista . . . The Median Fillet The Posterior longitudinal Fas- ciculus 996 997 997 1000 1003 1006 1007 IU09 1014 1014 lojc IU2I IU22 1024 IU26 1027 1028 1030 1030 1036 J039 1047 1049 I051 105 1 1052 1053 i'>55 1056 1058 1063 1063 1068 1077 1078 1082 1084 1088 uxS8 109U ■09.? 1096 tloo I lot 1 >>o3 : 1 103 ' "05 I 1106 ■ 1 107 I I 108 ; III2 ! III3 III5 III5 III6 The Mesencephalon — Omtinued Development of Mi !>ral Corte- . 1192 the Khinencephak.m 1 193 The Corpus Striatum 1 193 The Diencephalon 1193 The Cerebral Commissures 1 194 Measurements of the Brain 1 195 V ^1« CONTENTS. // rAns The Membranes of the Brain 1 197 The Dura Mater 119** ! The I'ia Mater "oa The Arachnoid 1*03 ] The Pacchionian Bodies 1 Jos The Blood-Vessels of the Brain 1206 Prainical Considerations : The Brain and Its Membranes 1*07 | Congenital Errors of Development . iao7 ; The Meninges >«>8 Cerebral Hemorrhage 1*09 , Cerebral l^ocalization 1210 Cranio-Cerebral Topography 1214 The Peripherai. Nervous Svstbsi. The Cranial Nerves lajo The Olfactory Nerve i J»o The Optic Nerve 1223 The Oculomotor Nerve 1225 , The Trochlear Nerve 1228 The Trigeminal Nerve 1230 The Gasserian Ganglion 1232 The Ophthalmic Nerve and Branches 1233 The Ciliar>- Ganglion 1236 The Maxillary 'Ner\-e and Branches 1237 The Spheno-Palatine Gang- lion 124" The Mandibular Nerve and Branches 1242 The Otic Ganglion >246 The Submaxillary Ganglion 1247 Practical Considerations: The Tri- geminal Nerve 1248 The Abducent Nerve 1249 The Facial Ner\e 1250 Practical Considerations 1254 The Auditory Nerve '256 The Glosso-Pharyngeal Nerve 1260 The Vagus or Pneumogastri'' Nerve 1265 Practical Considerations 1272 The Spinal Accessory Nerve 1274 Practical Considerations 1275 The Hypoglossal Nerve 1275 Practical Considerations 1277 The Spinal Nerves 127S The Posterior Primary Divisions 1279 The Cervical Nerves 1281 The Thoracic Nerves 1282 The Lumbar Nerves 1282 The Coccvgeal Nerve 1284 The Anterior Primary Divisions 1284 The Cervical Nerves 1285 The Cervical Plexus and Branches 1286 The Phrenic Nerve >290 Practical Considerations 1292 The Brachial Plexus and Branches 1292 The External Anterior Thoracic Ntrve "97 The Mus< ulo-Cutaneous Ner\'e 1298 The Me3o3 The Internal Cutaneous Nerve 1303 The Ulnar Ner\e 1303 Practical Considerations 1306 The Subscapular Nerves 1306 The Circumflex Nerves 1307 Practical Considerations 1308 The Musculo-Spiral Nerve 1308 Practical Considerationf 1314 The Thoracic Nerves I3»4 Practical Considerations 1318 The Lumbar Plexus and Branches 1319 The llio-Hypopastric Ner\'e 1320 The Ilio-Inguinal Nerve 1321 The (;enito-Crural Nerve 1322 The pxtemal Cutaneous Nerve 1324 The Obturator Nerve 1324 The Accessory Obturator Ner>e 1324 Thf Anterior Crural Nerve 1327 Practical Considerations : Lumbar Plexus 1330 The Sacral Plexus and Branches 1331 The Great Sciatic Nerve i335 The External Popliteal Nerve 1336 The Anterior Tibial Nerve 1336 The Musculo-Cutaneous 1338 The Internal Popliteal Nerve 1339 The Posterior Tibial Nerve 1342 The Pudendal Pleyusand Branches 1345 The Smai Sc' ic Nerve 1348 The Pudi< Ntn.; 1349 The Coc ygeal plexus 1352 Practical Considerations: Sacral Plexus 1352 The Svmpathetic Nerves 1353 General Constitution and Arrange- ment »355 The Gangliated Cord 1356 Rami Communicantes 135* Cer\iro-Cephalic Portion of Gangliated Cord 1358 The Superior Cervical Ganglion 1359 The Middle Cervical Ganglion 1362 The Inferior Cervical Ganglion 1362 Thoracic Portion of Gangliated Cord 1364 The Splanchnic Nerves 13*4 Lumbar Portion of Gangliated Cord 1366 Sacral Portion of Gangliated Cord 1367 The Plexuses of the Sympathetic Nerves 1367 The Cardiac Plexus 1367 The Solar Plexus 1368 Subsidiary Plexuses 13*9 The Hypogastric Plexus 1374 Subsidiary Plexuses 1374 Practical Considerations: The Sympa- thetic Nerves 1375 Development of the Peripheral Nerves. . 1375 THE ORGA OF SENSE. The Skin. General Description I38« Structure >3»» The Hairs '389 •-itnictHrf '39' The Nails 1394 The Cutaneous Glands I397 The Sebaceous Glands i397 The Sweat Glands 1398 Development of the Skin and its Append- ages 1400 CONTENTS. ve PAGII The Nose. The Outer Ncsf 140 Cartilazes o( the Nose I4r Practical Considerations : The ExN mal Nose ,07 The Nasal Fossie 1409 The Vestibule 1409 The Septiin 14 10 The Lateral Wall. 1410 The Nasal Mucous Membrane 1413 The Olfactory Region 1413 The Respiratory Region 1415 Jacobson's Organ 1417 Practical Considerations : The Nasal Cavities 1417 The Accessory Air- Spaces 1421 The Maxillary Sinus 142: The Frontal Sinus 1423 The Ethmoidal Air-Cells 1424 The Sphenoidal Sinus 1425 Practical Considerations : The Accessory Air-Spaces 1426 Development of the Nose 1429 The Okoan op Taste The Taste-Buds 1433 Structure 1434 Development 1436 The Eve. The Orbit and its Fasc _ 1436 Practical Considerations 1438 The Eyelids and Conjunctiva 144 1 Practical Considerations 1446 The Eyeball 1447 Practical Considerations 1448 The Fibrous Tunic 1449 The Sclera 1449 The Cornea 1450 Practical Considerations 1453 The Vascular Tunic 1454 The Choroid 1455 The Ciliary Body 1457 Practical Considerations 1459 The Iris 1459 Practical Consideratioas 146 1 The Nervous Tunic 1462 The Nervous Tunic— £0«A««/-(/ Tlie Retina 1462 Practical Consideratlbiis 1468 The Optic Ner\e 1469 Practical Considerations 1470 The Cr)-stalline Lens 1471 Practical Considerntion'^ 1473 The Vitreous Body 1473 Practical Consideration^ 1474 The Suspensory Apparatus of the Leii«. . '475 The Aqueous Humor and its Chamlwr. . 1476 Practical Considerations 1476 The I^chr>'mal Apparatus 1477 The Ijichr\mal Ctland 1477 The lachrymal Pass-iges 1478 Practical Considerations 1479 Development of the Eye 1480 The Ear. The F 'mal Eiir 1484 Tht 'ricle 1484 The External Audito, mal 148; Practical Co^isideratic 1490 The Middle Ear 149a The T'. nin iiiic C.;vity 1492 The M;>.iibr:'.na Tympani 1494 The A.: 't^ry Ossicles 1496 The Mu' ).i~ Moiiibrane 1500 ' ie Eustachir. Tube 1501 ; ne Ma.stoid Cells 1504 Pract. Consid. : The Middle Ear 1504 The TympiHiic Cavity 1504 The Tympanic Membrane 1505 The Eustachian Tube 1507 The Ma.stoid Process and Cells 1508 The Internal Ear 1510 The Os-seous Labyrinth 1311 The Vestibule 1511 The Semicircular Canals 15 12 The Cochlea 1513 The Membranous Ijibyxinth 1514 The Utricle 1514 The Saccule 1515 The Semicircular Canals 1515 The Cochlear Duct 1517 The Nerve of the Cochlea 1521 Developni.;nt of the Ear 1523 THE GASTRO-PULMONARY SYSTEM. General Considerations 1527 Mucous Membranes 1528 Structure 1528 Glands 1531 T\-pes of Glands 1531 Simple Tubular Glands 1532 Compound Tubular Glands .... 1532 Tubo-Alveolar Glands 153a Serous Glands 1534 Mucous Glands 1534 Simple Alveolar 1535 Compound Alveolar Glands. . . . 1535 Development of Glands 1537 The Alimentary Canal. The Mouth 1538 The Lips, Cheeks and Vestibule 1538 The Teeth 1542 Description of Individual Forms. . . . 1543 Structure of the Teeth 1548 The Enamel 1548 The Dentine 1550 The Teeth— CofUinueJ The Cementum 1552 The Alveolar Periosteum 1553 Implantation and Relations of the Teeth 1554 Development of the Teeth 1556 First and Second Dentition 1564 The Gums 1567 The Palate .' . 1567 The Hard Palate 1567 The Soft Pali 1568 The Tongue 1573 General Description 1573 The Glands of the Tongue 1575 The Muscles of the Tongue 1.^77 The Sublingual Space 1581 The Salivary Glands '. 1582 The Parotid Gland 1582 The Submaxillary Gland 1583 The Sublingual Gland 1585 Structure of the Salivary Glands. ... 1585 Development of the Oral Glands. ... 1589 "PMNM *«Milii VIH CONTENTS. // Practical Considerations : The Month . . . 1589 Malformations: Harelip and Cleft Palate' 1589 The Lips 159° The Gums 159° The Teeth 1591 The Roof of the Mouth 1593 The Floor of the Mouth 1593 TheCHeeks i594 The Tongue i594 The Pharynx 1596 The Naso-Pharynx 1598 The Oro-Pharynx 1598 The Laryngo-Pharynx 1598 The Lymphoid Structures 1599 The Faucial Tonsils 1600 The Pharyngeal Tonsil 1601 Relations of the Pharynx 1601 Development and Growth of Pharynx 1603 Muscles of the Pharynx 1604 Practical Considerations : The Pharynx . . 1606 The CEsophagus 1609 General Description 1609 Course and Relations 1609 ^ Structure 1611 1 Practical Considerations : C£sophagus . . 1613 j Congenital Malformations 1613 ' Foreign Bodies 1613 < Strictures 1614 ; Carcinoma 1614 Extrinsic Disease 1614 Diverticula 1614 The Abdominal Cavity 1615 The Stomach 1617 General Description 1617 Peritoneal Relations 1619 Position and Relations 1619 ; Structure 1621 Growth 1629 Variations 1629 Practical Considerations : The Stomach 1619 Congenital Malformations 1629 Injuries of the Stomach 1630 Ulcers and Cancer 1631 Dilatation and Displacement 1631 Operations on the Stomach 1632 The Small Intestine 1633 General Description 1633 Structure 1634 The Duodenum 1644 Ouodeno-Jejunal Fossa; 1647 Interior of the Duodenum 1648 The lejuno-Ileum 1649 The Slesentery and Topography .... 1650 Meckel's Diverticulum 165a Practical Considerations: The Small In- testine 1652 The Peritoneal Coat 1652 The Muscular Coat 1653 The Mucous and Submucous CohIs 1653 Ulcers of the Duodenum 1653 Infection 1654 Typhoid Ulcers 1654 Contusion and Rupture 1654 Obstruction ifjj Operations 1656 The Large Intestine 1657 General Description 1657 Structure 1657 The Ca.H-um i66o The Vermiform Appendix 1664 Peritoneal Relations !66.s Pericaecal Fosss 1666 PAGB The Large Intestine— r Thedl-ndsofCowper f^f? General Description: If^ Strllrture^r^'""'"" '984 Development ::::::::::' J^ i The Female REPRODtcrivE Organs. ' The Ovaries „ General Description:::': \^l Position and Fixation ... J^ Structure '9* Follicles and Ova: ,'^2 The Human Ovum . : ,^ Corpus Luteum l^ Development. 99° Variations '993 i The Fallopian Tubes "vanes. . 1995 General Description ; : J'S Course and Relations. ,3 Structure '997 Development 'and Changes. JS^ Variations.. '999 Practical Conaderations :' the Faliopjan '^ Rudimentary" ojaas': ;: ^999 The Epoophoron !~° Gartner's Duct ^°" The Paroophoron: : ???' Thete'"^'''""'''^^'-'-----'--''-'^^^ Generai biesinption . : : : !^f Attachments and Peritoneal" Rela- ' tions «.^ The Round Ligament .... jnol Position and Relations. . . ^ Structure. . ""z Development 'andChan^." : : ; ^ PracticT r «l'i»n-'l!llP''^^cy • ' ' ' Considerations : 't"'"'"e™ions : Utenis and Attachments . . . 30I2 Congenital Abnormalities 1 97 J Compartments of Pelvii: : ^J? frfrdTi^aenr'-'''--- •■ i Thel^ali^^''^'-----^-^-..-^ Gej^«.De;.ription';::::::::::::::-;| Structure *°'^ Development: *"7 Variations. *'"' Practicil .Considerations: the Vagina Mm Rela^mnstoUterineCervix™;^,'! The Labia a/id' ihe'Vwtibul'e : : : ^^ The Labia Ma ora .. . ??" The Mons Pubis "" The Labia Minora': !??! The VMttbHle *°" Joaj CONTENTS. The Clitoris joa4 The Bulbus Vestibuli aoas The Glands of Bartholin 2026 Pract Consid.: The External Genitals . . J027 The Mammary Glands J027 General Description 2027 Structure 2029 Milk and Colostrum 2030 Development 2032 Variadons 2033 Practical Considerations : The Mammary Glands 2033 The Nipple J033 Paths of Infection. 2034 Carcinoma 2035 | Practical Considerations : The Mammary Glands — ContiHued Removal of the Breast 2036 Development of Reproductive Organs. . 2037 General Consiclerations 2037 The Indifferent Stage 2o3« Differentiation of the Male Type. 2038 Descent of the Testis 2040 Differentiation of the Female Type 2042 Descent of the Ovary 2041 The External Organs 2043 In the Female 2044 In the Male WW, joJJ Summary of Development 2045 The Female Perineum ] 2046 /,/ 4' VOLUME II. THE CENTRAL NERVOUS SYSTEM THE NERVOUS TISSUES THE SPINAL CORD THE BRAI!* THE PERIPHERAL NERVOUS SYSTEM ' THE CRANIAL. SPINAL AND SYMPATHETIC NERVES THE ORGANS OF SENSE THE GASTRO-PULMONARY SYSTEM THE ALWENTARy CANAL AND ITS GLANDS THE ACCESSORY ORGANS OF NUTRITION OR THE DUCTLESS GLANDS THE RESPIRATORY ORGANS THE URO-GENITAL SYSTEM // ■; -m; Fro. 834. THE NERVOUS SYSTEM. The nervous system — the complex apparatus by which the organism is brought into relation with its surroundings and by which its various p4rts are united into one coordinated whole — consists essentially of structural units, the neurones, held together by a special sustentacular tissue, the neuroglia, assisted by ingrowths of connective tissue from the investing membrane, the pon the integument or other sensory surface and, by means of its procec (nerve-fibre), conveys such impulse from the periphe./ towards the central aggregations of nerve-cells that commonly lie in the vicinity of the body-axis. Functionally, such a path constitutes a centripetal Qfc ajferent fibre (a). The impressions thus carried are transferred to the second element, the motor neurone {B), which in response sends out the impulse originating within the cell-body (nerve-cell) along the process known as the centri- fugal or efferent fibre {e), to the muscle-cell and causes contraction. The simple relations of the foregoing apparatus are, in fact, superceded by much greater complexity in consequence of the introduction of additional neurones by which the afferent impressions are distributed to nerve-cells situated not only in the immediate vicinity of the first neurone, but at different and often distant levels. Although very exceptionally the relation between the neurones may perhaps be that of actual continuity in consequence of a secondary union of their processes (Held), the view concerning the constitution of the nervous system most worthy of confidence, notwithstanding the bitter attacks by certain histologists, regards the neurones as separate and distinct units. While chained together to form the various paths of conduction, they are probably seldom, if ever, actually united to one another but only intimately related, sir their processes, although in close contact, are not directly continuous, — contigui ut not continuity being the ordinary relation. During the evolution of ihe nerx'ous system from the simpler type, the cell- bodies of the neurones forsake their primary superficial position and recede from the periphery. In vertebrates this recession is expressed in the axial accumulation of cell-bodies either within the wall or in the immediate vicinity of the neural tube (brain and spinal cord), from or to which the processes pass. The nervous system is often divided, therefore, into a central AnA a peripheral portion. The former, also known as the ccrrbro- spinal axis, includes the brain and spinal cord and contains the chief axial collections of nerve-cells ; the peripheral portion, on the contrary, 996 Diaffnm showing fundamental units -stem. A, sensory neurone, conducting afferent impulses hv its pro- cess (a) from periphery [S); B,, motor neurone sending efferent impulses by its process {e) to muscle. THE NERVOUS TISSUES. 997 contains the nerve-cells of the sensory ganglir and is principally composed of the nerve-fibres that pass to and from the end-organs. Intimately associated with and in fact a part of the peripheral nervous system, but at the same time possessing a certain degree of independence, stands the sympathetic system, which provides for the innervation of the involuntary muscle and glandular tissue throughout the body and the muscle of the heart. When sectioned, the fresh brain and spinal cord do not present a uniform appear- ance, but are seen to be made up of a darker and a lighter substance. The former, the^rav matUr, owes its reddish brown color not only to the numerous nerve-cells that it contains, but also to its greater vascularity ; the hue of the lighter substance, X\x white matter, is due to its chief constituents, the medullated nerve-fibres, in conjunction with its relatively meagre vascular supply. THE NERVOUS TISSUES. The Neurones — The neurones, the essential morphological units of the nervous system, consist of the cell -body and the processes. The latter, as seen in the case of a typical motor neurone f Fig. 835 j, are of two kinds : (a) the branched protoplasmic extensions, the dendrites, which may be multiple and form elaborate arborescent ramifications that establish relations with other neurones, and (b) the single unbranched axone (neuraxis, neurite) that ordinarily is prolonged to form the axis-wlinder of a nerve-fibre, and, hence, is often termed the axis-cylinder process. The dendrites are usually uneven in contour and relatively robust as they leave the cell-body, but rapidly become thinner, due to their repeated branching, until they are reduced to delicate threads that con- stitute the terminal arborizations, the telodendria, formed by the end-branches. The latter are beset with minute varicosities and finally end in terminal bead-like thickenings. The axones, slender and smooth and of uniform thickness, are much less conspicuous than the dendrites. They may be short and only extend to nearby cells ; or they may be of great length and con- nect distant parts that lie either wholly within the Fig. 835. Dendritn Collaleral Fig. 836. Dendritn Telodcndrioii IMagram of tv-plcal neurone. Arburintion of axone Diarrem of nerve-cell of type if, in which axone fa not prolonged .IS ner\-e-nbre. cerebro-spinal axis (as from the brkin-cortex to the lower part of the spinal cord) or extend beyond (as from the lower part of the cord to the plantar musclw of the foot ). 998 HUMAN ANATOMY. /; ^^ ' ! ill 1 I Fig, ScniidiagtHmnntic represenution of structure f)f neurone : u, axone. On reaching their destination the axones terminate in end-arborizadons (telodendria) of various forms, in a manner similar to the dendrites. According to the distribution of their axones, the neurones are divided into two classes. In those of the first, known as fe//s of type / the axone is continued as a nerve-fibre and is, therefore, relatively long. Soon after leaving the cell-body such axones give off delicate lateral processes, the collaterals, which, after a longer or shorter course, break up into arborizations ending in relation with other and often remote neurones. Neurones of the second and much less fa-equent class, cells of type II, possess short axones that are not continued is ner\e-fibres, but almost immediately break up into complex end-arborizations or neuropodia (Kolliker), limited to the gray matter. The processes of the sensory neurones, as in the case of those constituting the spinal and other ganglia connected with afferent nerves, are so modified during development (Fig. 839) that later both dendrites and axones arise in common from the single robust stalk of an apparendy unipolar cell. Branching T-like, one process (the dendrite) passes towards the periphery and the other (the axone) extends to and into the cerebro-spinal axis. The nerve-cells, as the bodies of the neurones are called, possess certain structural details in common, although in some instances they present characteristics that suffice to identify them as belonging to particular localities. Nerve-cells are relatively large elements, those in the anterior horns of the spinal cord measuring from .070-. 150 mm. in diameter, and contain a large spherical nucleus, poor in chromatin but usually pro- vided with a conspicuous pic. 838. nucleolus. Their ry/i^Aww varies in appearance with the method of fixation and staining to such an extent that considerable uncertain- ty exists as to the relation of many described details to the actual structure of the jUs. It may be accepted as established, however, that the cell-body of the neurone consists ol Aground substance, homogeneous or finely jfranular, in which delicate y?*/-///"'» ^"""^ P»^ from opposite sides of the spherical cell-body, are found in the retina and the ganglia Dtacram ahowini; transfornwtiun of young bipolar Hnwry neurone into one of unipniar tvpr lOOO HUMAN ANATOMY. connected with the acoustic nerve. An interesting modification of bipolar neurones is presented by the olfactory cells, whose dendrites are represented by the extremely short processes embedded within the nasal mucous Fig. 840. membrane, whilst the axones are prolonged as the 1 fibres of the olfactory nerves into the cranial cavity to end in lelodendria within the glomeruli of the olfactory bulb. The cell-bodies of the multipolar neurone*, \? which possess one axone and several dendrites, vary T in form (Fig. 841). Some, as those within the sym- S pathetic ganglia, are approximately spherical and of moderate size, with short delicate dendrites ; many are of large size and irregularly stellate form, the dendrites passing out in all directions, as seen in the conspicuous motor neurones within the gray matter of the spinal cord ; others possess a regular and characteristic form, as the flask-shaped cells of Purkinje within the cerebellum, or the pyramidal cells of the cerebral cortex. Certain multipolar neurones within i!u- cerebral cortex, and especially those constituting the chief components of the granule layer, of the cerebellum, are distinguished by the small size of their cell-bodies and the peculiar ramifications and claw-like telodendria of their dendrites (Fig. 945J. Within the cerebellar cortex are likewise found examples of A Bipolar neurones; a.fromolfactory mucous membrane — dendrite is above; *, from retina. (Atodi/ird/rom Cajal.^ KlO. 841. Si 1} Multipolar nerve-celli of various forms ^ ^, from spinal cord; A, from cerebral cortex; C from cerebellar cortex (Purkmjecell) ; a, axone; c, implantation cune. the multipolar neurones of Goljji's type II, whose a-vones almost iniinediately undergo elaborate branching within the gray matter to which they are confined. The Nerve-Fibres. — From the foregoing considerations it is evident that the nerve-fibres are not independent elements, but that all ai e the processes of neurones — either the axones of those that are prolonged into fibres ( type I;, or the dendrites of those situated within the spinal and other sensory peripheral ganglia. Although neurones exist which are not continuetl as nerve-fibres, the latter are always connected THE NERVOI.S TISSUES. loui Fio. 84J. Axi!t.c> limlcrs Axolctnmu Medullary shivtli NfMieof ki«ii\it-r N'enrileniinff Medullatcd iicrve-Hhrt^, ms mi-ii in IuhkI- tudinal sections of spinal nerve. •: *pn. with neurones. Recognizing, therefore, that the nerve-Abres are only procc-s.-M» < if neurones, their separate description is iustified only as a matter of convtiiience. The fundamental part of every nerve-fibre is the central cord, commonly know n as the axis-cylinder, which is composed of threads of great . Medullated ner\-e-fibres becoming nonmedullated oti approaciiing tiieir termination. ''. 335. Dependinjr upon the presence or absence of the medullar}' .she.ith throughout the greater part of their course, nerve-fibres are distinguished as medullated or non- ' .\rchiv f. mikros. Anat u. Entwick., Bd. 66, 1905. • Journal of Comparative Neurology, vol. xiii., 1903. . THE NERVOUS TISSUES. 1003 ■^ :)ninedullatcd fibre!* Ill kmgitudiiialiection of iplenic iwn-e. < 310. meduUated. The meduUated fibres constitute the jjpeat majority of th<»se making; up the peripheral nerves and the tracts of the cerebro-spinal axis ; the component fibres of the latter, however, while medullated are without the neurilemma. The nonmedfillated fibres, on the other hand, are chiefly prolongations ( uxones ) fr<»m the ganglion cells of the sympathetic system, although in the case of the olfactory nerves the fibres are also without a myelin-coat. The dis- tinction between these two classes of fibres is relative rather than Fiu. 846. absolute, sine? every medullated ner\e-fibre becomes nonmed- ullated before reaching its termination, central or peripheral. Medullary nerve-fibres vary greatly in thickness, the smallest hav- ing a diameter of only .001 mm., whilst the largest may measure as much as .030 mm. According to their diameter, sa determined by Kolliker, the medullated fibres may be grouped as fine (.002-.004 mm.), medium (.aoj-.oo9 mm.), and coarse (.010-.020 mm.). In general, the thicker fibres are the longer and are the processes of large nerve-cells ; conversely, the finer have shorter courses and belong to small cells. Although !;ubject to many exceptions, die motor fibres are usually the thicker and the sensory the smaller. Since there are many more nerv-e-fibres ihan nerve-cells, it is evi- dent that die fomier must undei^go division along their course. Such doubling always ocnirs at a point corresponding to a node of Ranvier, never within the intcrnodal segment, the sheaths being continued over the two resulting fibres. On approadiing their peripheral termination the l>ranching becomes more frequent and the medullary sheath thinner until it ends, after which the axis-cylinder continues invested with only the attenuated neurilemma. The latter, now reduced to an extremely delicate covering beset with occasional nuclei, soo.t^ or later disappears, the naked axis-cylinder alone being prolonged to end finally in the varicose threads of the telodendrion. The nonmcduUditd nerve-fibres proper, also termed pale fibres ox fibres ofReinak, include those that are without the myelin sheath throughou' -ir course. They are chiefly the axones of sympathetic neurones. Devoid of medullary sheath, these fibres, often .oca mm. or less in diameter, consist of only the ax:sral tube, certain elements, the spongioblaits, being devoted to the production of the neuroglia, whili others, the neuroblasts, give rise to the neurones. At first the supporting tissue is represented by greatly elongated, radially disposed fibre-cells that often extend the entire thickness of the wall of the neural canal. Later, the neurogliar elements become differentiated into (a) those bordering the lumen of the canal, which are partly retained as the ependymal cells, and ( b^ those w hich have early migrated to more peripheral locations and gi\en rise to stellate cells that are converted into spider-like elements, the astrocytes. Seen in chrome-silver preparations (Fig.' 847) these appear as irregular triangular or quadrilateral cells from whose angles numerous delicate fibrillae extend lietween the surrounding nerxous elements. According to Rubaschkin, ' the astro- cytes .. transformations from larger branched gliogenetic cells, by the conversion of wh. ■ r bust protoplasmic processes the delicate _/fM7/tf- that later form the chief ' Archiv f. inikros. Anat. u. Entwick., Bd. 64, 1904. Youiijf neuroKlia cells; uirocytes. from brain of child. X 300. I004 HUMAN ANATOMY. i Fig. 848. constituents of the neuroglia arise. So long as neuroglia is being produced, as in the nervous axis of young animals, the large gliogenetic cells are present and directly concerned in the production of additional fibrillae, their cytoplasm becoming pro- gressively less granular and reduced through the various transition phases until in «ie hnal condition, as the small g^/ta cells, little more than the nucleus remains During these changes very many fibrillie lose their connection with the cells and in conjuncuon with the glia threads still attached to the astrocytes, form an elaborate interlacement in which the neuroglia cells, now reduced and for the most part devoid of processes, he scattered at uncertain intervals. In all parts of the central nervous system the mature neuroglia consists of essentially the same tissue, the differences presented in certain localities depending largely upon vanations in its compactness. Everywhere the chief part of the sup- porting tissue consists of the intricate felt-work of fibriUa?, glia-fibres, as they are called, which are usually free but to some extent connected with the spider-cells or astrocytes. Where, however, the neuroglia borders the neural tube (the ventricles ot the brain and the central canal of the spinal cord ) as the ependymal layer its arrangement exhibits peculiarities that call for later special mention. In the immediate vicinity of the neurones the felt-work of the fibrillK is unusually close so that the cell-lKxIies and the r.xrts of the processes are surrounded by a protecting sheath, the g/ta-cafisu/e. This diminishes along the dendrites, and after these begin to branch the neuroglia no longer forms a complete special investment. The medullated nerve-fibres within the brain and spinal cord ;, ■ also provided with delicate neurogliar sheaths which replace the neurilemma which on these fibres is « anting. These sheaths are prolonged for some distance on the fibres of the roots of the spinal nerves. The fibres of the optic nerve and of the olfactor>- tract are accompanied through- out their length by neurogliar sheaths, those of the remaining cranial nerves losing these envelopes shortly after leaving the brain (Rubiischkin). Beneath the pia mater the neuroglia is especially dense and forms the external subpial layer that every- where in\ests thener\ous mass, following all the inequali- ties of its surface. In this manner the pia mater is excluded and, except where its connective-tis.sue strands accompany the bhxKl-vessels that enter the nervous mass, takes no part in the make-up of the supporting stroma. Thi subpial layer consists of a dense felt-work of glia-fibres. disposed in various planes, which are partly free and partly the processes of spider cells. Internally the layer fades into the adjoining difTuse neuroglia without demarcation. At the periphery the fibres often exhibit a radial disposi- tion, their outer ends usually l)eing somewhat expanded. Within the white matter the neuroglia, both in its distri- bution and density, is fairly uniform, although special tracts often separate the larger bundles of nerve-fibres. Its arrangement within the gray matter presents less uniformity, since more or less marked condensations cKcur where the nerve-cells are collected into nuclei, as conspicuously seen in the interior olive. Where the neuroglia lH>rders the neural tube > especially the central canal of the spinal cord) it F.p«iid>mjii leiis uiid •.ijaceut iieurn- constitutes the ependvmal layer, the neculiari- Klia smrouiHlhiK central canal of spinal .• , ,. , ,,', ' . , "~7 7* ' !"<- 1'i.v-uiiaii coniofcat. 75. (A'i<*iijiA*/ii.j ties of Which call tor special mention. 1 he imme- diate lining of the tube consists of a sin>;le layer of pyramidal epithelial elements, the ,iidyinaf cil/s. whose free surfaces or bases look towards the lumen, and the ajiices towards the surrounding nervous tissue. At least during the earlier years in man, and throughout life in inany lower mammals, tlu' free surface of each cell is beset with a niimlx'r of hair-like jirocesses that in their relations with the ''yto|)lasin correspond to ordinary cilia. The pointed distal end of the ependymal cell is prolonged into a conical jirocess that is directly continued into usually a single neurogliar fibre which, after a course of uncertain length becomes THE NERVOUS TISSUES. 1005 lost in the surrounding complex of glia-fibres. In young tissue the apical processes often exhibit evidences of breaking up into a number of fine fibrillie. Where the processes enter robust tracts of neuroglia, as in the posterior longitudinal septum of the spinal cord, they are of unusual length. In addition to the radially directed fibres connected with the ependymal cells, the tibre-complex of the ependymal zone includes many fibrillx that are circularly and longitudinally disposed. Scattered glia cells, some stellate but mosdy small, are also present and represent the elements from which the neuroglia-fibrillje have been derived. In the preceding account of the elements composing the nervous tissues the neurones have been regarded as the morphological units, each retaining its individual ana'omical inde|)en- dence, although functionally closely related with other similar units. This conception, com- moply referred to as the Neurone Doctrine and strikingly formulated by VValdeyer in 1891, stands in contrast to the prior views by which actual continuity was attributed to the nerve-cells by means of the union assumed to exist within tlie terminal net-works of tlieir processes. The independence and true relation of the neurone was established largely through the convincing embryological investigations of His and the renewed study of the ner\e-cells as denionstmted by the improved applications of the Golgi silver-impregnations, supplemented by the inethrK] of vital staining by methylene blue introduced by Ehrlich. The Neurone Doctrine has gained wide acceptance and the sup|X)rt of the most distinguished anatomists, among those who have materially strengthened its position being K<)lliker, Ram6n y Cajal, Retzius, LenhossC-k, Waldeyer, van Gehuchten, and Edinger. The neurone conception, securely founded as it is upon a vast mass of evidence collected from a wide field by the most painstaking and accurate observation, has not escaped challenge, and at present is assailed by a group of histologists headed by Apdthy and Bethe, who not only bitterly oppose the integrity of the neurone as an independent unit, but also strive to depose the nerve-cell from its dignity as the fundamental physiological factor. In 1897 Ap.^thy' published his observations on the structure of the ganglia of certain invertebrates, iis revealed by a new mercuric gold-chloride method, and thereby established the important fact that the cell-body and processes of the neurone are pervaded by fine neurofibrilUe, thus confirming the fibrill.ir structure of the nerve-cell advanced by Max .Schultze more than a ciuarter of a century bf fore. Following ApSthy, Bethe» investigated the tissues of the higher animals and succeeded in dem- onstrating the existence of the neurofibrillce within the neurones of man. According to these observers, the neiirofibrilte, although interlaced without junction within the cell-l)odies, are independent threads, that are not confined to the neurones but pass Ijeyond and unite with fibres from other sources. The neurofibrill.-e, therefore, and not the nerve-cells, are the essen- tial elements of the nervous system, the cells being only intenxised along the path of conduc- tion. Indeed, according to these views, the neurofibrillx are independent of and, in a sense, foreign to the nerve-cells, leaving or entering the latter at pleasure and oonstltutinf. by their union a continuous path of conduction from the receptive element to the muscle-fibre. Ap.'lthy, moreover, assumes the existence throughout the central nervous system of a fibrillar net-work formed outside and between the nerve-cells by the nenrofibrilla? from which the axones may arise independently of the nerve-cells. It is evident that it such lie the case the conception of the neurone as an individual unit falls. The criticism made by the newer school, that the supporters of the neurone theory relied upon methods which inadequately demonstrated the ultimate terminal relations (the assumed union in net-works) has bten met by the introduction of the still newer methods of Beil.schow- sky and especially of C.ijal, which have yielded preparations that demonstrate that the neuro- fibrilk-e everywhere form net-works jvithhi the cell-bodies of the neurones, are confined to their processes, .ind even in their ultiiuate endings form ununited terminal arborizations. It seems, indeed, that, at present at least, the defenders of the neurone t'neory mav with justice charge their opiHinents in turn with depending upon methods thai only partial Iv show the relations of the iieurofibrillie within the neurones. Retzius. than whom no niore experienced an ^'T "*"-'^'"=" ""'' ''''"'"''^ ^"hin the spinal ..ord Tb^L ! ( T) the f H^r^ fh «'"" ?' ^'^'^, "^"'■"""^ *'»*"'" '^^ 'P^ «"d other sensory ganil J and (3) the efferent axones o neurones within the sympathetic ganglia that accomlanv musc'StSn^ ""^ periphery and serve for the innervadon^f the involun^ muscle of the blood-vessels and of the skin and the glands " The nerve-fibres, the various kinds usually more or less intermingled are Ttri'f A"'*''';'''"^ ^Tf'' l^''^ '^•"^^ '" ""'"'^^ *"d diameter a?co;drng defin^teXl f A '^ "^"^ ^^' '^^^ '"""• ^'^ '""'*^"1»« « surrounded by a definite sheath of dense connective tissue, the perineurium, which is directly con- unuous with the delicate fibro-el^tic tissue prolonged between the individual ner^e- fibres as the endoruurmm When well represented, the sheath of the hinicdus consists of concentric lamellae of fibrous tissue which enclose perineuria! lymph^^s. Fig. 849. ^^^'^^':> ■ . ;a Epineurium ' Blood-vcnels — •' . "'wr , ■ ■■■ — ■ Peniieurium Transverse teclion of small nerxe-trunk composed o( looMly uniteJ funiculi, y ». The latter, lined by flattened connectivc-tissuf plates, are in relation with the clefts between the nerve-fiores. on the one hand, and with the lymphatics with n the inter t-vl^r'"" ""/''" ."'^'■- .^'^^^'■"' -'^ "''"■■»'• "^^ neA-eiscomposS of several funiculi, these are loosely Ixiund togetiier and the entire trunk .so formed is investS and^S" • "^ Tr"' '"""f"^'"^' ^h*^//''"""''"'". in which course the blood-vSels and lymphatics. These enve opes of the nerve-trunk are c.ntinued over its branch^ even onto its sma lest suMivisions. The last representative of thLe coverines is seen on the mdividual fibres as the sheath of Henle, that surrounds the fib?e neurZmt '"'""^ ""^ ''"' ''''''''' ''^'''''"^^ "' '""""-"- ti'ue ....Li^le die „,pH,Il'^r'r"'"'''''yr "' "'^ "^■'■^'-funk (Fig. 850), the transverselv cut individual medullated nerve-hbres apjvar as small ciicles, sharply defined bv a fine outZeTthe neunlemma , each enclosing a deeply stained doi (the axis-cyiinder i. mi on , The interval between the latter and the neurilemma, corresponding t the 'mce occupied by the mye^n, usually appears dear and unstained with the exception 0^ delicate and uncertain suggestions of „„.n,branous septa. In contrast wh 1. unstained appearance m sect ons tinge.1 with carmine, aft'er the action of osmicncid or special hem.itoxyl,n staining (VVeigert) the med.illarv substance exhibits a chk color and the axis-cyl.nder appears surrounded bv a d..p!v tint«l rin^ The neu i- THE NERVOUS TISSUES. ,007 lemma nuclei are o^ionally seen as deeply stained crescentic figures that partially embrace the nerve-fibre, lymg beneath the neurilemma within depressions in the medullary substance. Fig. 850. Pcriiicuriuia Nervt-fibre Epinmrium Blood-vcsKi Tr.nsver« .otion of '•"•«»l»»«"e««d of «rv,sfibr« held tog«h,r by endoneurium .nd sunounded by perineurium, x 175. J'^*^ '" o-oss-section. the nonmedullated fibres appear as small irregularly round figure arranged m groups that correspond to bundles (Fig. 851). When numerous, the latter are aggregated v k- 3«^ into seconr'iry bundles between which extend delicate connective- tissue septa, continuous with the general envelope investing the nerve- trunk. The medullary substance being wanting, the pale fibres are of small size and often possess a diameter of less than .001 mm. The Ganglia The cell- bodies of the neurones that consti- tute the sensory pathways within the peripheral nerves and of tho neu- rones of the sympathetic system are collected at various points into aggregations known as ganglia. Fam". examples of t'le latter are thr .,pinal ganglia on the posterior roots of the spinal nerves, certain cranial ganglia (as the frtsserian connected with the fifth nerve, the Voustic with the eighth, and those on the tnmks of the seventh, ninth and tenth cranial nerves), and the .sympathetic ganglia along the gangliated cords and within various plexuses of the sympathetic-. A longitudinal section of a spinal ganglion (Fig, 852), which niav be taken as a type of such collections, shows the entire ovoid mass to be enclosed bv a fibrom capsule continuous with that ensheathing the nerves. Immediately bi^neath the capsule the ganglion-cells are arranged in a fairh continim,!* lavor ofvarvincr thick ness, while tlie cells, more deeply placed, are broken up into groups by the tracts of Inter-fascicular septum Transverae section of small splenic nrrve consisting chiefly of nonmedullated fibres. :■ aoo. UHW WW1 1008 HUMAN ANATOMY. intervening nerve-fibres, a small amount of connective tissue prolonged from the endoneurium of the nerve-bundles and accompanying the blood-vessels being also 5 KiG. 852. Posterior root (Kraory) Spinal cord Spinal ganglion Fig. 853. Nerve-6bre8, cut transversely Nerve-cell Anterior (motor) root Common trunk of spinal nerve Anterior division Section of spinal nerve, showinn its roots, jtanxliun. common trunk and primar> divisiuns. X 10. present. The cliief ganglion-cells are from .060-.080 mm. in diameter, but some measure as much as .170 mm. and others as little as .025 mm. In sections (Fig. 853) they usually appear round or oval, since only exceptionally are their processes to l5e seen. Each cell is enclosed by a richly nucleated capsule which is continuous with the sheath of the ner\'e-fibres. Mci of the many other oval nuclei that are conspicuous in sections of the ganglia belong to the neurilemiiu of the ner\'e-fibres and, hence, are seen as chains e.x- tending in different planes. Although by far the greater number of the ner\'e-cells within the spinal ganglia are (a) the cell-bodies c)f the sensory neurones, whose processes course within the spinal ncr\ ts, additional ner\()us ele- ments are also present. According to Dogiel ' among these are ib) cells of type J/, which, while closely resembling tht chief neurones in the form and appearance of their cell-bodies, differ from them in possessing processes that are confined to the ganglion and end in fine ramifications over or beneath the capsules of other ganglion -cells. The cell-bodies of the neurones of type II are in turn surrounded by end-ple.xuses of probabl>- ' Anatomischer Anzeiger, Ud. xii., 1896. Cainule Ner\e(ibres Section of spinal KtinKlion, showing tierve-ceth surrounded by nucleated capsules. >. ^^ i Dwgram ol conMilueiiU of spinal nnglion ; bloc lines reorr- SSJ?H!.r"rS^V'''JTB'A''"'^"*''™"j '*f'PH, anterior and postcnor roots; AD. PI>. anterior and posterior primary divi- sions ol spinal nerve; «C, ramus commuiiicans. "•»'>•"" DEVELOPMENT OF THE NERVOUS TISSUES. 1009 in^t^L ^^ (^«"-, f'"a"y (^) a few multipolar nenvasis of our knowledge conct. ig these proces.ses. Although in its principal features the histogenesis is similar in all parts of the neural tube, in that portion which becomes the spinal cord the changes are most typical and will, therefore, be here described. During the approximation and closure of the neural tube the cells composing its wall undergo active prolife- ration, whereby the wall, at first composed of only one or two rows of definitely outlined cells, is converted into a multinucleated tract in w hich the cell boundaries dis- appear and the nuclei lie embedded within a general protoplasmic sheet or symrfwrn (Hardesty»). The large dividing elemenU within the latter, the germinal <;«.~- J •. . . . '"'"'''■' °'H'*' *re conspicuous on account of their mitotir figures and are situated close to the lumen of the neural tube. His regarded thVrn m ^TZ\ cell, directly concerned in the prtxluction of the neurones, a conclusioM^wevir t^aThX^^I ' Jouriidt of Morpliologj-, 1099. 'Amer. Journal of Ana'tomy, vol. iii.. 1904 64 ilm Segment from lateral wall ot neural tube of p^ embryo of 5 mm ■ syncytium replacinK dlsllhctlv outlineil lells. a. inner .one; / ^rminal cells; ilm. Internal limllinir mein- jrane; w, peripheral zone ; r. radial strands of cytoplasm. < &»,. (ffardrslr.) f?, lOtO HUMAN ANATOMY. teen sustained (koUiker, Schaper and others) since the primary germinal cells probably only represent proliferating elements engaged in forming what for a time is an undifferentiated tissue. The cells composing the neural wall are at first in close contact, their blended cytoplasm (synotiumj forming an almost unbroken sheet. Soon, however, this continuity is internipted in consequence of the longitudinal expansion of the tissue and the appearance of spaces, a. id the r^nrn^"''f .!f '*'" ■"* ',"*° " '■'^''"'^ reticulum, the myelospongium of His, which b,:comes condensed at the inner and outer margins of the wall of the neural tube into the intental and external Itmiling tnemorane. The meshes of the reticulum enlarge, the intervening nucleated tracts of cytoplasm elongate . and the increasing nuclei become radially disposed. By reason of these changes the elemfnts ^ T^D , ','J^ ^"""^ ' ™''"""»'- 'o™ and radial arrangement and become the primary ependymal cells. The remaining elements, appropriately named the indifferent cells ^^^?^^ >l1""^^* '" """!!*' >n consequence of the continued division of the germinal cells and gradually become collected as the nuclear layer at some distance beyond the ependymal zone. theomr^rH r"f r'^^"'^'*"?, P^^'Ph^al portion of the supporting framework adjoining the outer border of the neural wall becomes denser and free from nuclei and is converted into p o , the»Mr^j»a/s«»«<-{Randschleierof elm • 5 • His), that is continuous with the delicate reticulum per\-ading the other parts of the wall. The in- different cells later differentiate into (a) the spongioblasts from which the characteristic constitu- . ,„ ^, .^^ ^^^ ^^^^ . ^."^^ of the definite supporting fSHFr-4's;^SJij^^^^^^JS£^^^^^^^S^St tissue, the neuroglia, are derived, iw,,ri.t-^ >\TV^as»*SiSi'^iS— -«5&'^ ^ . "■?" 4 ''■* ^•"''I'^y""'? ""1 "'■""entiation of ependymal (a) , ,.„t,cr ... i/»», Wm, internal and external limiting (*) and marginal (»i) layers; membrane ; g, dividing cell ; p, pia mater. , radial nuclear 690- {//at drily.) IJ IH I f ^S^^j?s^^zS^;i?^S3Sss?is (Hardestyl, the gradual transformation of the spongioblasts and their descendants into fibrill* establishes a more definite framework that replaces the primar%- net-work f myelosponfrium ^ ind eventually, ii> conjuntlion with the fibriila; derived from the processes of the ependymal Mils i DEVELOPMENT OF THE NERVOUS TISSUES. loii gives rise to the definite supporting tissue, the neuroglia. According to Hardesty the irlia-fibres ar.se w.th.n the syncytial tissue independently of the neuroglia cells a view i^K op^kb^ totheobservaionsof Rubaschkin, who attributes.to the descendants of the" pii^LbE h" gUagenetic ceUs. a positive role in the production of the fibres. Accepting th^ Sticks ^ he last-named investigator, the successive stages of the cells concerned in the prXuon C the general neurog liar tissue are represented by the spongioblasts, the glwge,utk^^stvL "Jtrocytes. and, finally, the gtia cells. The primary e^Jy,Hal ele\nents fre ^c^^ by he epi hehum which lines the ventricles and the central canal of the spinal cord. Theh^peri X n,^^ f i"'"'^*^ "■;? '" ^"^.V^ transformed into glia-fibres and thus, along «^le processes of the spider cells, contribute to the formation of the neurogliar elt-work The accompanying illustration (Fig. 857), taken from Hardestys paper, affords an histrucive re«'^^r'?r h"",^ ='PP^r"« ^ ^^^ >??"« supporting tissue'after Jn,; staining ^th a p^ov^^ reagents (Benda) and after silver precipitation methods (Golgi) upon which so much reliant e„"^r^h" P""*"- The silver picture shows the classic long „eu'^lia?fibr« Txtendinnhe entire thickness bu fails to reveal the wealth of supporting tis.sJe and nuclei. To what extent the mesoblastic ingrowths that follow the penetrating young blood-vesseU in to the nlr^ wall Uke ^rt in the production of the distinctive neurogliar f'^amewor^s aZi tt^ y difficuTtTo erem™rii"'rSr^ ' '''' '"'^' '""'' '°"^^^'' '^""'"''"^ '" '"^ support'^^fr'S^l'oi: Histogenesis of the Neurones.— The neuroblasts are distinguishable with certeintv from th^ gSftrthr^i^teranT "-^''"^ *''" — P— • THe -7 TpSTot peripherally directed ends of the f « s developing nerve-cells, invade the "'' ' marginal zone, and later emerge from the wall of the immature cord as the ventral or anterior root-fibres of the spinal nerves (Fig. 858). The deeper tint of their distal ends after staining, their tendency to collect in con- verging groups, and the uniform width of the '>utgrowing nerve- processes are distinctive charac- teristics of the neuroblasts ( His ' ). The first, and for a considerable time the only proces.ses with which the neurones are provided cor- respond to the axones that be- come the axis-cylinders of the efferent (motor) nerves. Subse- quently other processes, the den- drites, grow out in various direc- tions from the cell-bodies of the young neurones. Sthecmn^ite A^i^.TtK fi^^^u''''^''^"*^*^^ investigations, and the findings upon ReUius) "'""P""*' "'•=°^ "^ 'he fibre is based are open to different interpretation (K.illiker, The morr'SoblSs'^a'nd 'ti^/ development of the peripheral spinal ner^.es is briefly as follows: th^k^^s aM of S ZL h! ^T^- *"'"''' >f«»K"°"-«"'' ^^^ out pre\ elcpiiiK iiileii'uslal nerve u( pig *".>.?"' ""n"'-.; lipof nerve is composed -;"--j : lipof nerveisco otSbrils surrounded by sheath-cells, x 360 (Bard fen.) ^?,^J^ K "'*''* "* "•'""f •*«*'»* P'«P««^ve!y tmaller and more compact unUI. fib^ enHn^ h'^.k""""" f""' ""ey correspond to the axis-cylindrrs of the individ\i.l nerve! hbrps, enclosed by the »w*n/m»«a and its cells. The endonfuriMtn appears comparatively late and, like the neurilemma, is a product of the mesoblast. Later, condensations of the mesoblast around the definite bundles of nerve-fibres and about the entire nerve-trunk provide the periiteurium and the epineurium respectively. During its course to the periphery the young nerve gives rise to numerous branches, the points of outgrowth being indicated by a preparatory increase of the peripheral cells which often form a tubular projection into which the nerve- librillx grow. The proximal plexuses (such as the brachial or lumbar) are formed during the outgrowth of the nerves from the region of the central nervous system ; the coarser distal plexuses arise during the extension of . . -, . „ ""^ branches to the various parts for which they are destmed ; whilst the finer tertninal plexuses are established during the development of functional unity between the nerve-fibres and the structures to which they are distributed. The tnedullary sheath is a comparatively late acquisition, since it does not appear until about the fourth month of ftetal life. Within the central nervous system the tracts of nerve- fibres obtain their medullary coat at different times (some not until after birth), a variation that IS of niuch service in enabling the anatomist to trace the course of the individual paths of con- duction. The origin and method of formation of the medullary substance has been, and in fact still IS, a subject of discussion. It is, however, certain that its production is not dependent upon the neurilemma, since the medullated fibres within the cerebro-spinal a.xis are devoid of this sheath, and. further, that the myelin sometimes appears before the neurilemma ( Kolster, Bardeen ). While it is doubtful whether the myeHn is directly formed from the outer part of the axis-cylinder, as suggested by Kiilliker, it is probable that this structure exerts some influence resulting in the deposit of the myetin- droplets either from the blood (Wlassak), or from the apparently fluid substance that after a time surrounds the axis-cylinder (Bardeen). Regarding the formation of \heframeuiori supporting the droplets of myelin, Hardesty' inclines to the view that certain sheath cells, which appear during mediillation, are probably concerned. From the foregoing account it is evident that the axis-cylinder is derived from the ectoblast and the neurilemma from the mesoblast; the origin of the medullary sheath is still undetermined, but most probably is mesoblastic. Development of the Oanglia.— The origin of the afferent (sensorj) neurones, whose cell-bodies are situated within the spinal and other ganglia, is entirely different from that of the efferent (motor) ones above described. In the case of the spinal ner\es, the development of the ganglia pro- ceeds from a group of ectoblastic cells that form a ridge, the ganglion-crest, on the margin of either lip of the still open neural tube (Fig. 860), just where the general ectoblast passes into that lining the groove. On approximation of the lips of the latter, the cells of the ganglion-crests fuse into a wedge-shaped mass that completes the closure of the neural tube and constitutes a centre of proliferation from which the cells migrate outward over the dorsolateral wall of the tube. The proliferation is not uniform but most marked at points that correspond to the mesoblastic somites, in consequence of which a series of segmentally arranged cell-aggregations appears on each side of the neiinil tulie. These collections are the anlages of the spinal ganglia. Within them certain cells soon become fusiform and, a.ssuming the r61e of «eiirohlasts, seiul out a process from either end. One process— the axone-grows centrally, while the other— the dendrite— extends peripherally and becomes the chief part of a sensory nerve-fibre. The subsequent growth of the neurone is not svmmetrical, but to one side, and so TraiiftverM sections o! dorsal reKton of human embryos, showing early differ- eiitjation of spinal RanBlion; ^, ^.neural tube still open; C, D, tube closeo i a, KanKlion-riclf^s; A, fused ridaes; r. out- growth (o form KEittglioit : a. ectoblast. '^ a.v>. (LemkossH.) • ' Amer. Journal of Anatomy, vol. iv., 1905. Fig. DEVELOPMENT OF THE NERVOUS TISSUES. ,013 ordered that the two processes are approximated and finallv joined to th» r.11 k^i„ k., common stalk (Fig 839). the neurone being thus conve.JI^'^in'^":^ unij^ar "n^oV/ell The centrally direaed processes, the later posterior "nipoi.Tr ganglion-cell, root-fibres of a spinal nerve, grow into the develop- ing cord and enter the peripheral zone (later the white matter) to end, when their development is completed, at various levels in relation with neu- rones formed within the neural axis. The peri- pherally directed processes of the spinal sensory neurones, on the other hami, mingle with the axones from the motor neurones to form the mixed nerves distributed to the various parts of the body. The essential parts of the sensory neurones, the cell-body and the processes, are derived from ectoblastic elements, whilst the sheaths, whether of the nerve-cells, of the fibres or of the entire ganglion, are contributed by the mesoblast. The development of the sympathetic ganglia, which include essentially three sets— those of the ganghated cords, those of the prevertebral plexuses (cardiac, solar and hypogastric), and the terminal —has given rise to much discussion. According to one view, the sympathetic neurones have an independent origin and cily s. condarily form con- nections with the cerebro-spinal nerves. The other view, on the contrary, regards the sympathetic neurones as the direct descendents of neurogenetic elements derived from the developing spinal nerves The evidence in support of the last view is so convincing that there is little question as to the correctness of its principle, although many details of the process, as relating to man, are still to be studied. It is, however, equally true that the sympatnetic ganglia are neither produced by constriction and isolation of parts of the spinal Fig. 862. KaiRlia, as sometimes assumetl. .-.t*-™*^,.'**^'''" ".' P"'* "' 'lofsal reRioii t,( human embryo, showing developinK s|'">al fpmgUoii; rf.-, °oM sl '">•«■ 'P'"*' 8«nitlion on dor«l nor by the migration of fully difTerentiateil ganglion - cells, but, as eniph.-isized by N'eu- mayer. from iinditTerentiated neuroblasts which unilergo in loco their development. The earliest suggestions of definite synip.ithetic ganglia in the human embrjo apiie.ir aliout the beginning of the soond filial mtMith as aggregatii ms of cells .It the distal ends of the visceral r.inii of the developing spinal nerves. Frrnn these itlls art- derived the derinite sympa- thetic neiironesofthegaiigliated cord, as well as those which loJNnv the mesial Ingrowth of the spinal fibres for the pro- fhution of the prevertebral and termin.il ganglia. The lateral g-inglia thus fomud c-onstitiiti- for a time a series of isol.ited nixies : snl)seqM nllv fhisc are connected bvtlie differentiation of sympathetic axones uliicb efferent splanchnic nerves, whilst 'Ctt^^f^l:^^ 'T^^^:^::::: ^'•^K^^i.-Krtr^r^'iii.— S^y-'p^^-^ IOI4 HUMAN ANATOMY. NERVE-TERMINATIONS. The terminations of the fibres composing the peripheral nerves — the axones of certain motor neurones situated within the cerebro-spinal axis and the sympathetic system and the dendrites of the neurones of the sensory ganglia — supply the means by which the various structures of the body are brought into intimate relation with the nervous system. Some of these terminations transfer impulses resulting in muscular contractions ; others conve]' impressions that produce various sensations „ -^ (pain, pressure, muscle-sense, **'°' "^ temperature). The nerve- terminations, therefore, may be grouped according to func- tion into motor and sensory endings. Motor NERVE-ENDmcs. The motor endings in- clude (a) terminations of the axones of neurones situated within the motor nuclei of the spinal cord and brain- stem that pass to voluntary muscle ; (3) terminations of sympathetic neurones that end in involuntary muscle and (f) in cardiac muscle. Endings in Voluntary Muscle. — On approaching their peripheral destination the medullated nerve-fibres branch repeatedly, each fibre in this manner coming into relation with a number of mus- cle-fibres. When the med- ullated nerve-fibre reaches the .End- plate Fig. 864. Motor mrve-cndings in voluntary muscle ; bundle of nerve-fibres is seen separating to supply the individual muscle-fibres. X l6o. .... ... , "»»<»icu iici vc-iiure reacnes me muscle-fibre which it supplies, its medullary sheath abruptly ends and the neurilemma becomes inseparably fused with the sarcolemma, whilst the axis-cylinder passes beneath this sheath to terminate in an end-plate. The latter appears as an oval area, from . 040-. 060 mm. in its greatest diameter, which is applied to the muscle-substance ; in profile it shows a slight projection beyond the contour of the muscle-fibre, known as the eminence of Doye^e. Embedded within a general nucleated sheet of granular protoplasm, the sole-plate, lie the brush-like terminal arborizations of the axis-cylinder formed of irregular varicosites and club- shaped ends. From the details of the development of the motor end plates, as described by Bardeen, it is probable that the granular sole-plate and its nuclei are differentiated from the sarcoplasm and the nuclei of the muscle-fibre respectively. The much discussed relation of the end-plate to the sarcolemma — whether outside or beneath— seems to be decided in favor of a subsarco- lemmal position, since the muscle-sheath appears sub- sequently to the formation of the motor-ending, a fact that explains the apparent piercing of the sarcolemma by the axis-cylinder. I'sually each muscle-fibre is pro- vided with a single motor end-plate, which may lie at an equal or unequal distance from the ends of the fibre. Exceptionally two end-plates may be found on one muscle-fibre, in which case the endings lie near each other. Motor ner\'e.endinr in voluntarv muRcle; a, axone terminating: in enc{- plate ; fi, neurilemma ; *, sole-plaie. x 400. NERVE-TERM I NATIONS. 1015 Fit;. ,S65. Ncnrr-cndinx in involununr niucl«. {//mirr.) Endings m Involuntary liuicle.— The terminations of the a.xoncs of the sympatheUc neurones supplying the nonstriatsd muscle are comparatively simple The neuroncii contributrng the immediate fibres of distribution usually occupy the nodal points of plexuses from which bundles of nonmedullated nerve-fibres extend to and enclose the muscle fasciculi. Entering the latter the nerve-fibres divide into delicate varicose threads that pass between the muscle-cells, parallel with their long axes. As they course within the mtercdlular substance, the varicose fibrils give off short lateral branches that end, as does also the parent fibre, in minute terminal knots on the surface of the muscle-cells, often in the vicinity of the nucleus. Probably by no means every muscle- cell individually receives a nerve-ending, a longitudinal group including three or four rows of muscle-cells lying between two adjoining terminal ner\e-fibriU luber). Endings in Cardiac Muscle.— These, also the termi- nauonsof sympathetic neurones, have been stud.ed by, among others, Cajal, Retzius, Berkley and Huber. According to the last-named investigator, the varicose ner\'e-fibrils may be followed between the muscle-cells, during which course side branches arise that, as well as the mam fibnl, termmate on the muscle elements in endings of varying com- plexity. In some cases these are merelv minute simple end-knots, resembling those found m mvoluntary muscle ; in other cases they are more elaborate and consist of a group of secondary fibnllae bearing nodular endings, the whole recalling somewhat the motor end-plates m striped muscle. It is probable that most of the cardiac muscle-cells are m direct relation with nerve-endings (Huber). Sensory Nerve-Endings. Since the sensory endings are the peripheral terminal arborizations of the neurones whose cell-bodies he in the spinal and other sensory ganglia, such teloden- dna are functionally the beginnmgs of the paths conducting the sensory stimuli to the central nervous system. According to their relations to the surrounding tissue the sensory endings are broadly grouped into free and encapsulated. Free Sensory Endings.— These endings include vast numbers of nerve- terminations found in the skin and the mucous membranes, chiefly within the epithelium but to some extent also within the connective tissue strata. As a rule the sensory '^ afferent) ner\'e-fibrcs do not branch to any extent until near their peripheral o tination, where they undergo repeated divisions, always at a node of Kanvier and in various directions. The medullary sheath of the main fibre is retained unti close to its termination, although some of its branches may course as nonmedullated fibres for a considerable distance before ending or entering the epithelium,, in the .:'. --and the same general plan applies to the mucous mem- branes—the fibres de:. irted for the epidermis lose their myelin coat beneath the basement membrane and enter the epithelium as vertically coursing nonmedullated fibrils. Within the epidermis they break up into numerous delicate fibrils which undergo further divi- sion into still finer varicose threads that ramify between the cells of the stratum germinativum and terminate in minute free end-knobs (Fig. 866). Although an intracellular position of these nerve- endings has been described by various writers, it is probable that the endings are extracellular and lie upon the surface of and not within the epithelial elements. Similar, but far less numerous, free end- ings, varicose and dub-like in form, occur within , . . , t'»*^ connective tissue layers of the skin and the tunica propria of mucous membranes. Within the integument, conspicuous end- ramihcations of sensory neurones surround the hair follicles, lying upon the outer surface of the glassy membrane. / » r Fio. 866. Free sensory endines within epidermis 01 rabbit ; in several places ner\e-fibrilli terminate in end-knobs. (Doxirl.^ ioi6 HUMAN ANATOMY. Fig. .S67. in!^"L.^.''i'', "' ^'^'V '>'"« "l">in inter- Junction of cpithclmm and connective tiuue (»'erMiM«'^* P«Ming into epithelium. X 160. Fig. «68. «r. ^*"; **'^*"' 'if"' "' *««'kel, found in the deeper layers of the epidermb. represent a scmewhat more differentiated form of inn^ithelial termina^ST^ suggest transitions to the more specialized end- organs. In these endings the nerve-fibrils, terminate in cup-shaped expansions or menisci, against which rest the modified epithelial cells. The latter may be regarded as an imperfectly differentiated neuroepilhelium, examples of which are seen in the gustatory cells in the taste buds and in the highly specialized visual and auditory cells in the retina and in the oi^n of Corti respectively. Encapsulated Sensory Endings.— In their most highly developed forms these end- mgs (corpuscula nervomin tcnninalia) arc represented by relatively lai^e special end- organs in which the terminations of the axis- cylinder are enclosed within an elaborate laminated capsule. The latter, however, is more often present as a much simpler and thinner envelope consisting of strands of fibrous mor7l^^!'\°"J''""* ^*r^'i the intraepiihelial tactile cells above noted and the ^rinThetrS.!?.?^/^'''''/"^"'^."^' ^^'^^^ *"''"' '^^ ^"""^^'ve tissue, Tr. seen in the corpuscles of Grandry (no found in man but conspicuous in the skin covering th • * iil and in the tongue of many water-fowl), in whi.U the nerve ends in a disc-like expansion enclosed btlN^een largt- modified epithelial cells and the neuromuscular ami neurotendinous end-organs, presently to be descrilml (page 1020). • , T''^ J^''°"P °' simpler encapsulated endings mc udes three well-known examples : the end-lnilbs and the genital corpuscles of A'rausc and the cor- puscles of Meissuer, all of which possess a common strijctural plan— interwoven telodendria emliedded withm a semifluid interfibrillar substance ar.d surrounded by a thin fibrous envelope The End-Bulbs of Krause.— These endings include a variety of irregularly spherical or ellipsoidal bodies found in the edge of the eyelid, the conjunctiva and corneal margin, the lips and the oral mucous membrane, the glans penis and clitoridis and probably other parts of the integument hijihiy endowed with sensibility. Within the conjunctiva, as described bv Dogiel , they he superficially placed within the con- nective tissue near the summit of the papilla and folds, when such elevations e.xist, but always close beneath the epithelium. They vary considerably in size, often being small (.002-.004 mm.), but some- times measuring from .05-10 mm. in diameter, l sually a single ner\ e-fibre, exceptionally two or even more, enters each bull), losing its medullary she:ith as it pierces the thin fibrous capsule Within the latter the nerve, now represented bv the naked axis-cylinder, divides into from two to four branches, which, after c, ., , . desrribine: several ann^!l.^r or spiral turns ^ive off iTs^Ttricatfj';'' ">K-''^t further division, the terminal threads forn^ing a more or less intricate maze within the semifluid substance enclosed by the fibrous capsule. 'Archivf. mik. Anat., B cnd-bulhs of Krause from human conjuTiitiv.T. iDogiW.t I Fig. 871 G«niul corpudTlr from interunwnt 01 peni* ; nerve divides before piercinc capsule and lerminates in inlricale eiid- windings. ( Dofirl. ) Gcniul rotpuscle from Inieg- umeiil ul human i litoris. . iQ, NERVE-TERMINATIONS. ,0,7 to »hJ5,!.?*"*-n-' Corpu.clet^These endings, most numerous (from on. to lour InH Tf^"" millimeter) m the deeper strata of tl,e corium covering t»,e glans penis rr"r4utl!i t'STeS^*^ '" ^"^ ""«•''-""« ^ ^' »'''«--•«• ^ ^ oudine an J from .02 to .35 F'c- 8to. mm. in diameter. They present the same general architecture as the end- bulbs, but are of larger size, possess a somewhat thicker capsule, and contain a more intricate interlacement of the termi.nal nerve-fibrillie. The latter are derived from the subdivision of two or three medullated fibres that enter near the base nf the corpuscle and are beset with varicosities and club-shaped terminal enlargements. t™lf ^TJJ" '^P'"'*.' 5°"»«''"S °[ *^v«"' connective tissue lamell* possessing flat- whS. h "T "J!^'-*' ^"'^'"^ the semifluid or granular interfibrilbr substance in which the cnd-arbonzations are embedded. roH„I*!ff !;°T"*''"°^**u ".*"*'— '" '"^" ""^«= ^'^ niost numerous in the conum of the skin covering the flexor surface of the fingers and toes. Thev are also found m other regions possessing sensibility in a high degree, such as the £ margin of the eyelid, nipple, penis and clitoris, as well Is onThe dorsum of the ha^d and foot and the radial surface of the forearm On the volar surface of the distal phalan.x of the fingers, where they occur in greatest numbers, *^^ twenty are found to the square millimeter (Meissner). The corpuscles occupy the summit of the papillae and ridges of the connective tissue stratum of the skin, and lie close beneath the cuUcle. with their long axes perpendicular to the ir^'^-j'" ^^^'^ ^^^^ ■'"■^ elongated irregular ellipsoids, often somewhat sinuous in outline and in the larger papilla- mav be joined at the deeper end with others to form a compound corpuscle. They are relatively large, l)eing from .12- 18 mm. long and about one-third as wide Depending upon the size, each corpuscle is sup- plied by one or more nerve-fibres which enter in the vicinity of the base, as the deeper end is called, and, on piercing the cajjsiile and losing the medullary sheath, divide into a nuinlKr of naked axis-cylinders. These pass across the corpuscle in parallel or spiral windings and are beset with fusiform and pvriform v.iricnsities similar enlargements marking the ends of the temiin.il threads. The entire fibrillar interlace- ment IS cmbeddetl within a semifluid substance and enclosed by a thin nucleated fibrous capsule. I r 1 . . . . '^^^ Corpuscles of Ruffini — These emi- ings are also found with n the skin but if Hrr-t^r U,-^!= „ ,m i '"^^e emi the subro'ium Thp„ ,r„ ^ 1 "*""• . ^ ^^ ncepor levels, near and sometimes wiilim n len^h^^^.i f ^ x '"Y^*' T""' sometimes measuring as much as 1. ,, mm. in length and o an elongated fusifqrm contour. The iien'e-fibres often tAvon; t^m;:!^.'!! r"T"rJf " "^^ ^'^j?^"'^ °" '^^ '^^'' '-« '^^^^^^^hr near ^ne end e a in the medullary sheath for some distance after penetrating 'the capsule and throughou" Fig. 872. Corpuscle of Meissner lying within papilla pi conum of skrii from fiiiRer; only deeper layers of overlying epidermis are shown ; », enleriiii; iierve-hbre. < 370. IOI8 HUMAN ANATOMY. Fig. Cylindrical end-bulh Irom con- nective tiuue layer of skin. X 180. iSiymoMowicx.) a number of bold curves and twistings. After the disappearance of their sheaths, the naked axis-cylinders undergo repeated divisions, the resulting tibrilia; becoming varicose and intertwined and ending in free terminal knob-like enlargements. In contrast to the foregoing end-organs, in which the axis-cylinder subdivides into numerous terminal threads disposed as more or less elaborate inter rvtinings, a second group is distinguished by the possession of a thick lamitMted capsule that encloses a cylindrical core or inner bulb containing the slightly branched axis-cylinder. These endings, of which the Pacinian corpuscle is repre- sentative, are relatively large and ellipsoidal. A transitional form, connecting them with the spherical end-bulbs, is presented by the cylindrical end-bulbs of Krause. These are found in various parts of the corium, the oral mucous membrane and between the bundles of striped muscle and of tendon. , , ... ^^^y ^^^ irregularly cylindrical in form, often more or ICM bent, and consist of a thin laminated capsule that encloses a core of semifluid substance in which lies the centrally placed axis-cylinder. The latter, after losing the medullary sheath on entering at the proximal end of the capsule, traver^ss the core without branching until near the distal pole, where it ends in a single or sliehtly subdivided terminal enlargement. The Vater-Pacinian Corpuscles.— These structures, the most highly special- ized sensory end-organs, are relatively large ellipsoidal bodies, from .05-. 15 mm in length and about one-third as much in breadth, situated within the connective tissue m many parts of the body. In man they are found in Fig. 874. the deeper layers of the '* connective tissue layer of the skin, especially on the palmar and plantar aspects of the fingers and toes, in the connective tissue in the vicinity of the joints, in tendons, in the sheath of muscles, in the periosteum and in the tunica propria of the serous membranes, the peritoneum, pleura and pericardium. They are particularly large in the mesentery of the cat, where they may be readily de- tected with the unaided eye as oval pearly bodies some- times two millimeters or more in length. The most conspicuous part of the Pacinian body IS the robust capsule that constitutes almost the en- tire bulk of the corpuscle and consists of from one to three dozen thin con- centric hmella' i>f fijiroiis tissue. The surfac es of the lamellae .lie covered with endothelial plates whose nuclei appear as fusiform thicken- ings, along the concentric stria- of the corpuscle. The axis of the Pacinian body Vater-Pacinian corpuKles Irom titin of child'a finiter Iranavertc wction ' - ' ' . ._... ., _ . ..,.,,, , A. lonrttndlnal nerve entering capsule to reach inner bulb. 1 8s- NER V E- i £r_ VTIONS. 1019 tl,« n*^!? ^T"*^K^ "'■"^I'V^' Po'e of the corpuscle, the fibrous (Henle's) sheath of the nerve-hbre blends w.th the outer lamella, of the capsule, while the medu larv coat ,s retained during the somewhat tortuous path of the tibre through the capS Fig. 875. t^^SSS'^S^''^^'^^'^^^^^^ through the core, being as the naked axis-cylinder. At a variable distance but often just before gaining the distal poi' of the core, the axis- cylinder divides into from two to four branches, each of which terminates in a slightly expanded end-knot. Some- times shortly after penetrat- ing the capsule, the nerve- fibre splits into two or more axis-cylinder which then share the common envelope of semifluid axial suh»tance. Similar end-organs, the corpuscles of Herbst, occur in the velvety skin covering the bill and in the tongue of wa^er-fowl. They closely resemble the Pacinian bodies of mammals, but differ in being generally smaller, relatively broader, and in exhibiting a row of cubic-,1 cell, withm the core and around the axis-cylinder. These cells are regard Lh, J '""'T^Gc^ii M*^^ ^^"-^ ^"^'"^'"^ '^^ tactile JjsT^inlKrSt CO p^^^^^ .f ^ J fi Golg'-Mazroni corpuscles, found in the subcutaneous tiLsue o^the nuTn fro^ ^h f .?• ^-^ '""'»"'«''«"« of 'he ordinary Pacinian end-organs ThevC LTanchedSs!yindT'"^'"^ ''^'' '^'"^"*' ^ ^'^^'-'^ '^^^ -- aS^i ZT. NeuromuBcuJsir Endiiigs.-First described by Kblliker and bv K,lhn„ although previously seen by Weissmann. these end-o^rgalis Sen termid ^t^.' ^dUs, are now regarded as sensory endings that are prSly c^"cJrnTd1n^fford" ing impressions as to tens on or " mnsrlp «»t,c-» •• xu T ^ ^Y. " "' ^nord- Undtnoits) end-organs have been demonstrated ^ ^ """^^ » may a. tw™,y. ..riped m^&uS,. mSSttSTnt blS-i™;^ "nTSr spersed connective t ssue. These intrafusal ifA^^r L» .iT if^ .^P '"'^'^" tUe of the surrounding muscTe irSr^rT ,'„,=li '' ![-^ ""'=''• ^"^" f^'"" equah)nal region than near the poles of the spindle ^ diameter m the The intrafusal fibres collectively are surrounded hv a thin .,,-^i,i t.„„, ^,.„„p,. ,He a.rial sHcaih, b/twe.n wh^a^d Se L'X Shr;"riS t030 HUMAN ANATOMY. Nerve-Abn Capsule lymph-space. Each spindle receives usually severa! medullated nerve-fibres, which, after incorporation of their sheaths of Henle with the capsule, pierce the latter at various points and proceed to the individual muscle-fibres. The terminal relations of the nerves to the intrafusal fibres have been studied by means of the newer methods especially by Ruffini, Huberand DeWittand Dogiel. After repeated division during their course through the cap- sule and periaxial space, the ner^'e-fihres pierce the axial sheath, lose their medullary coat and terminate either as one or more ribbon-like branches that encircle the mus- cle-fibres in annular or spiral windings, or, after further subdivision, as branched telo- dendria in which the ultimate fibrils end in irregular spherical or pyriform enlargements. Neurotendinous End- ings. — These end-organs, described by Golgi and sub- sequently more fully investi- gated by Kolliker, Ciaccio, and Huber and DeWitt, in their general architecture resemble closely the sensory endings in muscle. They lie embedded within the intrafascicular con- nective tissue and are usually found in the vicinity of the junction of muscle and tendon. Like the neuromuscular end- ings, the tendon-spindles are long fusiform structures, from I. -1. 5 mm. in length, sur- roimded by a fibrous capsule. The latter encU)ses a group of from eight to twenty intrafusal tendon fasciculi, which are smaller and apparently less niaturi- than those of the sur- rounding tendon-tissue. The intrafus;ii fasciculi are invested by a fibrous axial sheath be- tween which and the capsule \\w< a periaxial lymph-space. On reaching the spindle, after repeated branching, the medullated nerve-fibres pene- trate the capsule, with which their fibrous ( Henle's ) sheaths blend, and undergo further division. The medullary coat is lost after they pierce the axial sheath, the naked axis- cylinders breaking up into smaller fibrils that extend along the intrafusal fasciculi. The terminal ramifications, applied to the surface of the fasciculi, vary in details (Huber). Some arise as short lateral branches that partly encircle the fasciculi and end in irregular plate-like expansions, while other's terniinatc between the smaller fasciculi. Nerve-fibre A, neiironili!ii:ular endirii;; B, iicnoteMdltiMUs emlliiK in tnnKitudi- nal wi'tlnn, mrlhyliMichluestainiiii; .■'lo. ( Drawn (rum (ircpiinUoii niadt' iiy Professor Ihiliei i THE CENTRAL NERVOUS SYSTEM. . theJn.^T^y'l "^'°"' T'J"" '"^'"'^'^ "'^ ''P'"^' '^"'■'l «"d 'h*- brain. In principle these parts are to be regarded as the walls of the primary neura/ tube niodirted bv rir\hT;:in"'orr'?°".' """' -- nfter'acqui^g their dt^nr'r'etu l.ns enclose the remains o the canal, as represented l)v the system of ventricular si. ires In contrast to the spinal segment of the neural tube, which always en^^s TX tiv^'y simple cylinder the spinal cord, the cephalic segment earlydilTere ttes i o three /r/«,ar,- cerebral vesicles, the anterior and posterior of which subdivide ^.^ hve secondary brain-vesicles are present. Coincidendy marked flex ire o lu cephalic segment occurs at certain points and in consequence this ilrt^^f the neurd tube becomes bent upon itself to such a degree that the a.xis of the anterior es cle lies almost parallel with that of the spinal segment (Fig. 9,2 F om heT^' r WdetS t '^ ^ •'* sinuously int ceUalic Lgment of "h™^^ uescnoea ( page 1060) whiU . relatively straight sp nal segment proceeds the ?he oriS llln' '"^r^::- '" ^'^''^^ P™'^^ grcfwth':.nd diffemuE ctv 'r Ilir^ • ^' "''"-^»"«' t"l^ '"t» •'«n almost solid cylinder, the minute central cina alone remaining as the representative of the once conspicuous lumen THE SPINAL CORD. cerebm-sDtd*'axl'''^aS"r'* "PI"-"''^ '^ ^^at part of the central ner^•ous system, or cereoro-spina^ axis, which lies within the vertebra canal. Its UDoer limit wher.. if becomes continuous with the medulla oblongata, is in a meite'^'^nvSnal sCicl AcrnrLfT '*^'"^''^^*'°" «" '^^ «^«rd itself to indicate exacdy its junc^n wShe'brLin posterior arch of the atlas. For practical purposes, however the lower marain ot cord rr •"«?""■". ^f"^,*"h sufficient ac^y the upp^ hmn t^rSna cord. Below, he spinal cord terminates somewhat abruptly in a no nted en7 Thj fuXr'^^S:" The levl'r -?^«Pr''^'•'^ ^^ betE Ve K'fnd'loJd uimDar\ertebr». The level to which the cord extends inferiorlv however ii s..hi...f astTot^c^meT^ rSi ^T T'y •"'T «'' '^'«'' ^ '''^^^^^ of th^^y JK tht luX Jerteb^^V W°a!;S "j" ^'T - ^ "RP^r border of the b■ P**^**^^ '""« '•>'"''*• The w.iKhl (. o«.). or about .-^^^KCvwH^hritrn^ somethInK less than 30 grammes When tresh th. spina, «.rd ^^^^ c;;^^*^i^i;;:tu';;^i,c!fi;!"S; !^ '^^. lOJI I022 HUMAN ANATOMY. Fig. 877. JH^-^^Jx' Medulla Pedicles, cut . '.^M •Lamina;, cut to Transverse processes Pedicle** -Dural iheath C^ If'^ XII T- -//■ Pedlcles< . End of dural sheath Posterior divisions of sacral nerves 4 Sheath of filuni - End of filuni -Coccyx Si.injil cord encloM.1 in unopened duml sheath lyine within ™h Liu'^'n""!" .' ;■•""' ""'r ™,n'l'l«'l> re>novedonriShls,le, partialiy on left, to c«|)os<- dorsal aspect of dura: first and last netAvsofcervical.lhoracic.lun,h,rnnd.acr!!U.-,>,,= =rrindir,i«t b> Italic fiKuresi corresponding vrrtebnr by Roman numerals Th^ Membranes of the Cord. — The spinal cord, together with the roots of the thirty-one pairs of spinal nerves, lies within the vertebral canal enclosed by three protecting membranes, ormeninges, which, from without inward, are (i ) the dura mater, (2) the aracAnoidea, and (3 ) the pia mater, all of which are directly continuous through the foramen magnum with the corres- ponding coverings of the brain. The external sheath, or theea, formed by the dura, is a robust fibro-elastic tubular envelope, much longer and considerably wider than the cord, that does not lie against the wall of the vertebral canal, but is separated by an interval containing thin-walled plexiform veins and loose fatty con- nective tissues (Fig. 879). The dural sheath, about .5 mm. in thickness, extends to the level of the second sacral vertebra and is, therefore, considerably longer than the spinal cord. The part of the sac not occupied by the cord encloses the longitudinal bundles of root-fibres, that pass obliquely to the levels at which the correspond- ing ner\es leave the vertebral canal, and a fibrous strand, the //urn ter- minate, prolonged from the cord to the lower end of the spine. The pia constitutes the imme- diate investment of the cord and supports the blood-vessels destined for the nutrition of the enclosed ner\ous cylinder. The pial sheath is composed of an outer fibrous and an inner vascular layer, the connective tissue of the latter ac- companying the blood-vessels into the substance of the cord. The arachnoid, a delicate veil- like structure made up of interfacing bundles of fibro-elastic tissue, lies between the other two membranes anil invests loosely the inner surface of the dura and closely the outer surface of the pia. It effectually subdivides the considerable space between the external and internal sheaths into two compartments, the one beneath the dura, the subdural spate, being little more than a capil- lary cleft filled with modified lymph, and the other, the sutnirar/inoid space, between the arachnoid and THE CENTRAL NERVOUS SYSTEM. loaa The spinal cnrcl. therefore, haiurs Fig. Arachnoid \'ertehral artery Molulla the pia, containinjr the cerebrospinal fluid. suspended within the tube of dura, surrounded by a cushion of fluid— an arrangement well adapted to insure the nervous cylinder against the inju- rious effects of shocks and of undue pressure during changes in the position of the spine. Both spaces, but par- ticularly the subarachnoid, are crossed by fibrous trabecule and thus imper- fectly subdivided into secondary com- partments, all of which are lined with endothelium. The spinal cord is fixed within the loose dural sheath not only by the root- fibres of the spinal nerves that pass between the cord and the outer envelope but also by two lateral fibrous bands, the ligatnenta denticulcUa, that are continu- ous with the pia along the cord, one on each side. Mesially they are attached between the anterior and posterior root- fibres and externally to the inner surface of the dura by the tips of pointed pro- cesses, about twenty-one in all, that stretch across the subarachnoid space which they imperfectly divide into a general anterior and a posterior com- partment. The ligaments, covered by prolongations of the arachnoid, extend the entire length of the cord, the first pro- cess being attached to the margin of the foramen magnum, immediately above the vertebral artery as it pierces the dura. The succeeding ones meet the dura between the pairs of spinal nerves, the lowest process lying between the last thoraac and the first lumbar nerve. In the cervical and thoracic region, a — ^ r-». >.u,».,u lu aiirm. median fibrous band, the septum posticum, connects the posterior surface of the cord Fig. 879. jjgi,_ Spliwl cord * ' Potterior root Spinal coni, covered with arachnoid and pia 1,. l!?'*'' I*"^ P' 'P'™' «"•|«al netv«. of the thoracic region occurs to such an extent that this part of the cord once more equals, if indeed not exceeds, the corresponding portion of the spine. While the cervical cord keeps fairly abreast the cervical portion of the vertebral LX>lumn, the lumbar and sacral segments are left far behind. The results of these changes are seen in the course of the root-fibres, which in the neck, below the third nerve, run somewhat downward to their points of emergence, and in the thoracic region pass more horizontally, while those of the lumbar and sacral nerves descend almost vertically for a considerable distance— in the case 01 the last sacral nerve 28 cm. (Testut)— before reaching their appropriate levels. The large and conspicuous leash of descending root-fibres, seen upon open- ing the dural sheath, constitutes the Cauda equina, in the midst of which the glistening silvery filum terminale is distinguishable. It is evident, there- fore, that in most cases the level of the cord-segment and that of the vertebra bearing the same designation do not correspond. likewise, it must be re- membered that, although in general the spinal nerves are named in accordance with th' vertebrjE immediately below which they escape, in the neck there are eight cervical spinal nerves and only seven vertebrae, the first or sub- occipital nerve emerging between the atlas and the skull, and the eighth between the last cervical and first thoracic vertebra ; hence, except the last one, they correspond with the vertebra below. I026 HUMAN ANATOMY. Form of the Cord — After removal of its membranes and the root-fibres, the Fig. 883. Medulla Cervical Thoracic Lumbar f-acral CcKCVKWll Filum spinal cord is seen to differ from a simple cylinder in the following respects. It is somewhat flattened in the antero-posterior direction, so that the sagittal diameter is always less than the transverse diameter, and its oudine in cross-sections, therefore, is not circular but mpre or less oval ; its width is not uniform on account of two conspicuous swellings that are associated with the origin and reception of the large nerves supplying the limbs. The upper or cervical enlargement ( intumescentia cervicalis) begins just below the upper end of the cord and ends opposite the second thoracic vertebra, having Its greatest expansion at the level of the fifth and sixth cervical vertebrae, where the sagittal diameter is about 9 mm. and the transverse from 13-14 mm. The lower or lumbar enlargement (intumescentia lumbalis) begins opposite the tenth thoracic vertebra, slightly above the origin of the first lumbar nerve, and fades away in the conus medullaris below. It appears very gradually and reaches its maximum opposite the twelfth thoracic vertebra, where the cord has a sagittal diameter of 8. 5 mm. and a transverse diameter of from 1 1-13 mm. (Ravenel). The lumbar enlargement is associated with the great nerve-trunks supplying the lower limbs. The inter- vening part of the thoracic region is the smallest and most uniform portion of the cord and is almost circular in out- line. Where least expanded, opposite the middle of the thoracic spine, the cord measures 8 mm. in its sagittal and 10 mm. in its transverse diameter. These enlarge- ments appear coincidentiy with the formation of the limbs, are relatively small during foetal life, and acquire their full dimensions only after the limbs have attained their definite growth. In a general way, a similar relation between the size of the enlargements and the degree of development of the limbs is obser\'ed in the lower animals. At the tip of the conus medullaris the spinal cord is prolonged into a delicate tapering strand, the filum terminate, that consists chiefly of fibrous tissue con- tinued from the pia mater and invested by arachnoid. It extends to the bottom of the pointed and closed end of the dural sac, which it pierces at the level of the second sacral vertebra and, ensheathed by a prolongation of dura (vaj^ina terminalis), as the Jilum terminate externum, proceeds downward through the lower end of the sacral canal for a distance of about 8 cm. (3^ in.), finally to be attached to the periosteum covering the posterior surface of the coccyx. The part within the dural sac, they?/«w terminate internum, is about 16 cm. (6«^ in.) in length and surrounded by the ner\e-bundles of the Cauda equina (Fig. 882), from which it is readily dis- tinguished by its glistening silvery appearance. The upper half or less of the internal filum contains the ferminal part of the central canal of the spinal cord walled by a thin and variable layer of nervous sulwtance in which small nerve-cells are usually present. The minute bundles of nerve- fibres often found adhering to the filum, which sometimes may be fnllnwed to and even thmuiih the dural sheath, are lenardeU by Rauber as representing one or two additional (second and third) coccygeal nerves, homologous with the caudal nerv es of the lower animals. V spinal rtird denuded of mem- branes and nerves, showinK pro- portions of its leiiKth rnntributed ny flifTer?nt reKJim*- and position and relaHvesizeof cnlarftcments.as viewed from before ; semidiaKram- niaiir. ha«ed on measurements : one-third actual size. THE CENTRAL NERVOUS SYSTEM. ,027 The Columns of the Cord. -Inspection of the surface and particularly of cross-sections of the spinal cord (Fig. 885) shows the latter to be pallially divided m H H„?l!lh^';?'^T^''\T'* u^ ^^ ^y " •""*^" *^'*f» •" '^«"' ""d a partition in the midline behind. The cleft, the anterior median fissure (essura m^iana anterior) e.xtends the enure length of the cord, and is continued on the upper part of the filum tenninale. It is mirrow, from 2-3.5 mm. in depth, penetrating for less than one-third of the ventrodorsal diameter of the cord, and occupied by a process of pia mater. Along its floor, which lies immediately in front of the white commissure. It is frequently deflected to one side of the mid-line and presents a slight expansion The separation into halves is completed by the posterior median septum (septum mediaaum posterlus), the so-called posterior inedian fissure With the ex cepdon of a shallow groove in the upper cervical cord, the lumbar enlargement and the conus medullans, no fissure exists, but in its place a dense partition extends from the posterior surface to the middle of the interior of the cord, ending inclose relation to the gray commissure. .!=»■ ^* '*ar»'^«'' °f the septum is a subject of dispute, according to some anatomists con- sisting excliBiyely of condensed neur^lU, while others regard it a.s composed of pial ti™ue blended with the neuroglia and. therefore, of both mesoblastic and ectoblas^c origin The latter view is substaiiuated by the mode of development of the posterior septum, the immature pial covering of the deve oping blood-vessels being imprisoned within and fused with ThVneC! n^har partition denved from the expanding dorsal halves of the developing cord (page loso) The application of differential stains also demonstrates the composite nature of the septum. E^ch half of the spinal cord is further subdivided by the lines along which the root-fibres of the spinal nerves are attached. The root-line of the dorsal (sensory) fibres is relatively straight and narrow, and marked by a slight hirrow. the postero- lateral sulcus (mIcim lateralis posterior) that lies from 2.5-3.5 mm. lateral to thr- posterior septum and is evident even on the intereegmentol intervals where the root- fibres are practi«lly absent. The ventral root-line, marking the emergence of the antenor (motor) fibres, is much less certain, since the bundles of fibres of the indi- vidual nerves do not emei^e in the same vertical plane, but overlie one another to some extent, so that each group occupies a crescentic area, whose greatest width cor- responds in a general way with that of the subjacent ventral horn of gray matter The anterior root-line, which lies from 2-4 mm. lateral to the median fissure is neither indicated by a distinct furrow nor con- - Fio. 884. tinuous. In this manner two longitudinal xxi s, the posterior columns (fuaiculi posteriores) are marked off between the posterior median septum and the sulci of the posterior root- lines. These columns include something less than one-third of the circumference of the cord, and are about 6 mm. in width in the thoracic cordand 8 mm. and 7 mm. in the cervi- cal and lumbar enlarge- ments respectively. The tracts included ■Medulla on 4 nerve l>i)tsiil rcxrts of 5 cerv. ner\'e .l,-.ViPP*-5J'' "' 'P'.""' "f"! viewed (rom behind .fler partial removal of dnral S^«KV.?."ltT?"f*"" *Jf '"dicmted bv group, of convergViK bun.lle, of port,r"r IS^.^.^.IiJEL"''' *■".«"* •" '•'J. ">''"« *'"'''' '••« int"venebfal foramina; •pinal accenory nerve ia seen aacending on each aide. between the dorsal and ventral root-linos constitute the lateral columns (funiculi laterales) and those between the ventral root-lines and anterior median fissure are the antenor columns (funiculi anteriores). Such subdivision into anterior and lateral I I038 HUMAN ANATOMY. riefi'nite^Hi'r^T" V^ """l"^' ^"^^ "'''»^" superficiaUy nor internally is there reeLd^ f^ToS " ^'*^" ''"^ "■''^'"- 'T'^^y "«y ^' therefore, conven=-nUy regarcled as forming a common antero-lateral column that on each ^iH^ P^mK.^-3 something more than two-thirds of the semicircumf"7ence of the cord In th^ 1^^ Z:'^\Tfy^r '''°"'"' '^"^'^l ^'"^ I^'^rior colunm is suW.Vided by I shSw ZrTrJ^A- ?'" '5-^ """• '»'«-■'•»' to the posterior medium septum Thifth^ Fig. 885. ■Pwterior median Mptum Anterior median fiaanre Anterior column Anterior white commiuure matter forms a comma-shaped area, the broader end of which lies in front and the narrower behind, with the concavity directed laterally. The convex surfaces of the tracts of the two sides, which look towards each other and the mid-l.ne ^re crnnected extend^ ■^"^^"^•^^?^*y "^T' '^^ K^ay Commissure (commisLra griS that d^«m.tr '■°!f '^^'"«l-»'f • "«.»«"y somewhat in advance of the middTof fKg tt^ diameter, and encloses the minute central canal of the cord Bv th.r™^?;^ connecting band, or central gray matter, is divided into a doiSi an/a ven^TLrt tK^l'^TivTly. ' "'^"'■^'■''■y ^-'-■--. which lie behind and in fronToHS' . While the posterior median septum reaches the dorsal surface of th^ ot^« nr.^ *^ Fk;. 8X6. THE CENTRAL NERVOUS SYSTEM. ,029 Each crescent of gray matter is divisible into three parts— the ventral and the dorsal extremity, that project beyond the transverse gray commissure and constitute the anienor Md posterior horns or comua of the gray matter (columnae eriseae) and the iHtermediateportion (pars iotermedia) that connects the cornua and receiv^ the commissure The two horns differ markedly from each other and. although varyine in details in different levels, retain their distinctive features throughout the cord The anterior cornu (columna urisea anterior) is short, thick and rounded" and separated by a considerable layer of white matter from the surface of the cord throuirh which the ventral root-fibres proceed to their points of emergence in the root-arei Ihe blunt tip of the antenor horn is known as the caput cornu, r,nd the dorsal por- Uon by which it joins the commissure and the pars intermedia c^s the basis cornu The posterior cornu (columna grisca posterior) presents a marked contrast in Ijeing usually relatively long, narrow and pointed, and in extending peripherally almost to the postero-lateral sulcus. The tip or apex of the dorsal horn is formed of a A-shaped stratum of peculiar character, the sub- sUntia gelatinosa Rolandi, that appears lighter in tint (Fig. 885) and somewhat less opaque than the subjacent and broader portion of the horn, caput cornu, which it covers as a cap. More ventrally the posterior horn is usually somewhat contracted, to which portion the term, cen>ix cornu (cervix columnae posterioris) is applied. In the lower thoracic cord, however, this constriction is replaced by a slight bulging located on the mesial side of the junction of the posterior cornu with the gray commissure. This enlargement corres- ponds to the location of a longitudinal group of nerve- cells constituting the column of Qarke. The fairly sharp demarcation between the gray and white matter is interrupted along the lateral border of the crescent by delicate prolongations of gray matter into the surrounding lateral column (Fig. 888). The subdivisions of these processes unite to form a reticulum of gray matter, the meshes of which are occupied by longitudinally coursing nerve-fibres, the whole giving rise to an interlacement known as \\\^ processus -r for- matio reticularis. Although to some extent present in the greater part of the cord, this structure is most marked in the upper cervical region, where it exists as a conspicuous net-work filling the recess that indenu the lateral border of the pars intermedb and the neck of the posterior horn of the grav crescent. In the thoracic and upper parts of the cervical cord, therefore in regions in which the enlargements are wanting, the formatio reticularis is condensed into a compact process of gray matter that is directed outward (Fig. 885) and known as the lateral cornu (columna latc-ralis). Diagram showing amount of and while Rialtcr in rrla.iun In i Taken as a whole, the gray matter, which in cross-sections appears as the H-shaped area fomied bv the two crescents and tfie commissure, constitutes a continuous column whose irregular contour depends not only upon the peculiar disposi- tion of the p;ay matter, but also upon the variations in its amount at Different levels of the cord. Thus, at the level of the third cervical nerve the gray matter constitutes somewhat more than one-fourth of the entire area of the rord : at that of the seventh nerve about one-third, while in the thoracic region between the seojnd and eleventh nerves, it is reduced to abiut one-sixth At the hst thoracic ^■;"ctL^^Xs^r«S^S:'rer ^^'^ ^'l «"^ '-bar^wolfiffhltJ-Thrt^S respectively, in the sacral cord the relative amount of gray matter increases until, at the level Kray ■■--.' 7 — .— ■^.— ■".. ... entire area ol cotil, an>l relative lenifths oi aird-segmcnn; the latter are iriilicated by divisions on left margin of figure— ' C, IT, I L. 1 S, first seKmenl ofcer\ i- ral, thorac'c, lumbar and sacral rej(ions respectively; itark lone nex» left bor- der represents the gray matter, light lOne the white matter, outer dark loni- the entire area of cord. IDoKa.'Js.m.i I030 HUMAN ANATOMY. « ith^^ .hi ^ nerve It reaches three-fourths. The absolute amount of gray matter is neatest ^^« sun^^r K™*.'";::^'^''''^"'™"' °* '^ '°"^' ^^"^ *» '* ^irec^y delated to thelai^e fo^r^!^ ,?^ '^T^ *^' u'".'^- ^ co-nparing the tracts ol white matter and the gray column it ^ tw .h "^ "^''V" ^ '"*" '^'"^ °^ ^^ '""''«^ ~'<1 'hese are of approximately eW^ area h!^ .h LT' ""^ ^^"^ """"'' ^''°*^"' "^ *»"««• '" 'h« '«maining\egions on rt^ othe; f,^m "f ™rf 'f Tn ' P;.'^""!'"*"^' '" ""^ K^^'"^' "•■•« "' 'he thoracic L^exceerng tL Jray Jrom four to five fold and m the cervical cord bemg from two to Uiree times greater. tr«luT*'fK^'"*"* Canal—Where well represented, the central canal (canalis cen- trails), the remains of the once conspicuous neural tube, appears L a minme opening ,n the gray commissure, about .2 mm. in diameter and hard vvisiblTSh the unaided eye In the child it extends the entire length of the cord and tlow ends bhndly m the upper half of the filum terminale. aSvc. it o^ns Tnto the lo^er hdf o thet'^nir"^;'''' ''°'" ^^'l^ " ?^ P'-°'°"^«' downward^hrough the K^ slwL K • °^'°"»^^ '"^".the spinal cord. In not over one-fifth of adult subjects, however, is the canal retained as a pervious tube throughout the cord its umen usually being partially or completely obliterated for 'onger or shorter stretches the lumen l^t disappearing in the lower part of the cord. Within the conus tw"i^*' *'^* ''^"H;*' ^'Pa' regularly e-xhibits an expansion, the sinus terminalis i.,o^'"^ ^u"^ the ongin of the coccygeal nerve and extends caudally for from «-io mm., with a maximum frontal diameter of i mm. or over. middIHrfe°™l'ri,°! 't ''^"'SL"'"'' ~'"P'f'^'" "«»"' 50 per cent, of subjects beyond U effi^,-H K^^ f *• ° ^ '^^"^^ "" a physiological accompaniment of advancing age. It don ^ MnX^^f 7Tif "' '""^ P™ ""«"°" of the ependyma-cells limng the canal, in c^njunc- ^n in cr^^^tlnl U^ ^"""•"^^"K neurogliar fibres ( Weigert). The form of the canal, as ^h Jh "P»^-f Stj"""' 's veO' variable and uncertain owing to the changes incident to the use smaneJr.Lt"hoLiir •'^'■"""' *''^ "^" well preserved the lumen is round or ovafand e^an^m^n ?.^T ^'T \ '" ^""^ ^^'""^' "^ '" ""e upper cervical cord and in the lumbar miv^^M f laiKer and often appears pentagonal in outline, whilst in others the calibre X,i^ ^.1, V f^'-'j^l'""- . The position of the cemral canal varies at different levX n rela ion to the ventral and dorsal surfaces of the cord. In the middle of the lumbar reefon i" occupies approximately the centre of the cord, but above, in the thoracic and cervicalsegments Hn^l w "^T: '^ ^^"'"' '^^" ""= '^°'^' ='"^»"- ^hile below it gradually app oaXsle dorsal surface, but always remains closed. FP'"-"^"e* me »™, JJe"«'"n may be made of a remarkable structure named Reusne^'s fibre, after ite discov- erer that as a longitudinal thread of great delicacy lies free within the cental can Jo iheTord r lowJsT^rt of Tht."' f^ '"f lir '^"'?i-"J^ '^^ "«= "^"y "' '"e mesencephalon ab^ve o L^Jh!^ T" he cord-canal below. The interpretation of this structure as an artefact which considering its extraordinary position is most natural, seems untenable in view of the positive testimony confirming its existence as a preformed and true structure in n.anv vertebrates, given by several subsequent observers and especially by Sargent - Its na ure and significance are probtematic. Although the existence of thiTfibre has l*en eubl shed i, many vertebrates, even in birds, it has not yet been discovered in man. * MICROSCOPICAL STRLCTIRE OF THE SPINAL CORD. The three chief components of the spinal cord— the nerxe-cclls, the iktv e-fibres and the neuroglia— vary in proportion and disposition in the white an.i gray matter It IS therefore desirable to consider the general structure of the cord Wore describ- ing Its detailed characteristics at different levels. //T**/* °'"*^ Matter.--Tlie most distinctive elements of the ywiv n.atter are the multipolar ner-.e-cells which he embedded within a coi..,,lex sponge-like rnatri.^ formed by the various p.ocesses— dendrites, axones and collaterals— from other i-.eurones the supporting neuroglia and the blood-vessels. In two loc^Iities-immdi .teK around the central canal and capping the dorsal cornu— the grav matter vari.-s in its anpeanince and constitution and exhibits the modifications peculiar to the central and Rolandic substantia gelatmosa the details of which call for later description page 10^4) The nerve-cells of the anterior horn are multipolar, in .-rnss-sections the cell-ixxlies appe iring irregularly polygonal and in longitudinal section.-; fusiform in out- ' Bulletin of Harvard Museum of Comp. Zoology, vol xl\ 1904. MICROSCOPICAL STRirTlRK OF SPINAL CORU. ,03. line. They may vary from .065-. 1^=, i„ .iuineter, unless unusually small when thev measure from .030-.080 mm. ( K..ll.ker 1. Ju a typical e.xample, as rer.resented bv one of the ventral radicular celU jriving; orifiin to anterior root-fibres, from three to ten dendritic processes radiate in various planes, divide dichotomouslv with decreasing width and hnally end in terminal arljorizations. In contrast to therobust dendrites beset with spines, th^ i.xone is smooth, slender and directly continuous with the axB-cyhnder of a r»i.,. i bre of a spinal nerve and unbranched, with the exceptions of delicate lateral pr.Kesses that are given off almost at rij;ht anules These processes, the collaterals, arise at a variable distance from the cell-b.jdy, but' usual! v close to the latter and always before leaving the gray matter. They rcix-atedly divide and follow a recurrent course within the anterior horn. After apt)r<>i)riate staining the cytopUsm of the nerxe-cells exhibits conspicuous accumulations of the deeply staining tigroid substance that lie within the meshes of the reticulum formed bv delicate neurofibnlla-, ' the cell-body but also extend into the various processes. The fibrillie, however, do not pass beyond the limits of the neurone to which they belong (Retzius). Each nerve-cell possesses a spherical or ellipsoidal nucleus, from .010 to .020 mm. in its greatest diameter, which is en- closed by a distinct nuclear membrane and usually contains a single nucleolus, exceptionally two or three. Within the cytoplasm an accu- mulation of brownish- yellow pigment granules is usually present near one pole, often in the vicinity of the implanta- tion cone from which the axone springs. In addUion to the con- spicuous ventral radicular cells above described, the anterior horn contains other ner\'ous elements, some of which, the com- missural cells, send their XrlheTLrf!.,/r''"°'™'""''r'*l''*''^°P''°''''^ ■''"•■ "' 'he cord, while the axones of opS side "''' '"'" *'"' ''°'""'"' °' ^^'"^^ ""•"" "f ^^"^ *""'^' '"" frequentU ,„. •^''t """"'""f*' .««"». which with few exceptions occupy the median portion of tho anlenor honj, resemble m size and contour the radicular cells, but differ from thnXr i V s- ^C^lx^^^rZt)- ^■'^ '"'•''^"•^ "' '•"^ '''■"''"«" -^^ ^i^^""^'' '"^"^'''^ the inner .a . " , whif. mllr Th """^ ^^^ '"' "-^^ ^'■'' ^"-"missure and a few end within the adjacent white matter. The axones traverse the anterior white commissure to gain the vt ..r.,I column 'he opposite s,rle. in which they e-.-,.r divi.-fe T-Hk- ^-Ho a.cr:.uinK .ind descent Ue ™ undivided turn brainward. " "«-.steii. on-. „r snarin^v r!!^r^ ?!i'' ""."i"'''* '"■'""' ^""-^ "'an the root-celi , are only spanngly represented in the anterio iist.n^-u.shed bv the course of their axones, which usually pass to the ant .,n,e si.le. In some cases, however Nerve-fihrcs of whitt* matter Anierior root-fibres Portion of anierior u.rnu of ijray matter, showing multiiM)lar nerve-cells, ■ 120. 1033 HUMAN ANATOMY, i^ ] I I the axone divides into two, rarely three, fibres, one of which crosses by way of the anterior white commissure to the opposite ventral column, while the othe: passes to the ventral column of the same side. As well seen in cross-sections, although the nervelaleral group Mesial group " - - -^ "^ Transverse section ol lower cervical cord, showing grouping of iwrv»<-ells ; Nisal staining, x so. made up of more than a single aggregation of cells. This feature is particularly evi- dent in the lateral collection, in which an anterior and a posterior subdivision are recognized as the veniro-laleral and the dorso-lateral group that occupy the corre- sponding angles of the anterior horn. The mesial collection, situated within the ventral angle, is likewise, but much less clearly, divisible into a ventro-nusial and a dor so-mesial group, of which the latter is variable and at many levels wanting. In a general way the pronounced presence of these cell-groups influences the outline of the anterior horn, so that corresponding projections of the gray matter mark their position. This relation is conspicuously exemplified in the cer\ical and lumbo-sacral enlargements, in which the presence of lar^e lateral cell-groups is directly associated with a marked increase in the transverse diameter of the anterior horn. Conversely, when these cell-columns become smaller or disappear, the corresponding elevations on the surface of the anterior horn diminish or are absent. Owing to such variations the contours of the gray core are subject to constant and sometimes abrupt change, MICROSCOPICAL STRUCTURE OF SPINAL CORD. 1033 The TWittD-fnediao cell-column is the most constant, since, as emphasized by the pains- taking studies of Bruce,' it is interrupted only between the levels of the fifth lumbar and first sacral nerve in its otherwise unbroken course through the length of tlie cord, as far as the level of the fifth sacral nerve. An augmentation of this tract in the fourth and fifth cervical segments is probably associated with the spinal origin of the phrenic nerve (Bruce). The dono-mesial cell-column is much less constant, being represented only in the thoracic region, in a few cervical segments and at the level of the first lumbar nerve. In agreement with van Gehuchten and others, Bruce regards the continuity of the mesial group as presump- tive evidence of its close relation to the dorsal extensor muscles of the trunk. The ventro-Iateral cell-column appears first at the level of the fourth cervical nerve, increases rapidly in the succeeding segments and fades away at the lower part of the eighth cervical seg^ment It reappears in the lumbar enlargement, reaching its maximum at the level of the first sacral nerve and, diminishing rapidly through the upper part of the second, disappears before the third sacral segment is reached. The dorao-lateral cell-column, in places the most conspicuous collection of the anterior horn, begins above at the lower part of the fourth cervical segment and, increasing rapidly, attains its greatest development in the neck in the fifth and sixth segments. It suffers a marked reduction at the level of the seventh cervical nerve, which is followed by a sudden increase in the next segment in which the column presents an additional collection of ner\'e-cells known as the accessory dorso-lateral or post-postero- lateral group. Below the level of the second thoracic nerve the dorso-lateral cell-column is unrepresented as far as the second sacral segment where it reappears, somewhat abruptly, and attains its maximum size in the fourth and fifth lumbar segments. The column then diminishes and ceases at the lower part of the third sacral seg- ment Within the sacral cord, between the levels of the first and third nerve inclusive, the dorso-lateral cell-group is augmented by an accessory group. From the third lumbar to the sacral nerve-levels, an additional compact collection of nerve-cells occupies a more median position in the anterior horn and constitutes the central group. From the position of the greatest expansions of the lateral cell-columns — within the cervical and lumbo-sacral enlargements — it is evident that they are associated with the large nerves sup- plying the muscles of the limbs. Further, according to Bruce, in a general way the size of the radicular cells bears a relation to that of the muscles supplied, the smaller dimensions of the cervical cells, as compared with those of the lumbo-sacral reg.on, corresponding with the smaller size of the upper limb in comparison with that of the lower one. In addition to the nerve-cells assembled within the foregoing more or less well defined groups, some scattered cells are irregularly distributed through the anterior horn and do not strictly belong to any of the groups. Below the level of the first coccygeal nerve, the cells of the anterior horn become so diminished in number, that they are no longer groiiped with regularity, but, reduced in size, lie uncertainly distributed within the gray matter as far as the lower limits of the conus medullaris. The nerve-cells of the posterior horn are neither as large nor as regularly disposed as the anterior horn cells. Only in one locality, along the median border of the base of the posterior horn, are they collected into a distinct tract, the column of Clarke ; otherwise they are scattered without order throughout the gray matter of the posterior comu. Since, however, the latter comprises certain areas, the cells of the posterior horn may be divideid into (i) the cells of Clarke' s column, (2) the cells of the substantia gelatinosa Rolandi, and (3) the mner cells of the caput comu. The cells of CUrke'e column form a very conspicuous collection which extends from the level of the seventh cervical nerve to that of the second lumbar m.-rve and is best developed in the lower thoracic region of the cord. Although confined chiefly to the dorsal portion of the cord, and hence sometimes designated as the "dorsal nucleus," Clarke's column is represented to a slight degree in the sacral and upper cervical regions (sacral and cervical nuclei of Stilling) . In cross-sections the cell-column appears an a group of multipolar cells that occupy the mesial border of the base of the posterior horn and, where the column is best developed (opposite the oiigin of the twelfth thoracic nerve), correspond to an elevation on the surface of the gray matter. The cells usually are about .030 mm. In diameter, pfilygonal in outline and possess a relatively large number of richly branched dendrites that radiate chiefly within the limits of the group (Cajal). The axones commonly spring from the anterior or taternl margin of the cells and course ventrally for a considerable distance before bending outward toward the lateral column of white matter within which, as constituent fibres of the direct cerebellar tract (page 1044), they turn brainward. ' TopOKfrtphlcai Atlas of ihe .Spinal Cord, 1901, »034 HUMAN ANATOMY. f (^ I 5-; The nerve-eelU of the aubaUntia relatinosa Rolandi, also known as Gierke's cells, include innumerable small stellate, less frequently fusiform or pear-shaped elements that measure only from .006-.020 mm., although exceptionally of larger size. Their numerous short dendrites are irregularly disposed and branched. The axones, which always arise from the dorsal pole of the cell, are continued partly to the white matter of the posterior column, within which they divide into ascending and descending limbs, and partly to the gray matter itself, within which they run as longitudinal fibres. Under the name of the marginal cella are described the much larger (035-055 """• ) ner\e-cells which occupy the border of the substantia gelatinosa. They are spindle-shaped or pyramidal in form, their long axes lying parallel or the apices directed towards the Rolandic substance respectively, and constitute a one-celled layer enclosing the substantia gelatinosa, into which many of their tangentially coursing dendrites penetrate. Their axones pass through the substantia gelatinosa and probably continue for the most part within the lateral column, although some enter the posterior column (Cajal, Kolliker). The inner cella of the posterior horn are intermingled with niunerous nervous elements of small size irregulariy distributed within the head of the dorsal comu. The inner cells proper are triangular or spindle-shaped in form and, on an average, measure about .050 mm.; they are, therefore, larger than the ordinary cells of the Rolandic :,ubstance. The dendrites arise Fig. 889. White nwUet of poMcrior column C»llt of Clarke's column Subilanlia geUtinoaa cenlrali* Central canal Part of craaa-iection of cord, ahowinK cella of Clarke's column in base of poalerior hom. X 1 10. from the angles or ends of the cells and diverge in all directions. The axones pas.art of the gray inalter ol the cord MICROSCOPICAL STRUCTURE OF SPINAL CORD. «o35 Those of the first class, or intcnncdio-Uteral cells, are associated with the forniatio reticu- laris and its condensation, the lateral horn, and hence are often spoken of as the group or column of the lateral horn. These cells form a slender tract of small closely packed elements that is represented through almost the entire length of the cord, although best marked in the upper third of the thoracic region and partially interrupted in the cervical and lumbo-sacral segments. Where the forniatio reticuliiris is condensed with a distinct lateral horn, as in the thoracic region, the cells occupy the projection, but elsewhere lie within the base of the gray net- work. As a continuous cell-column the tract extends from the lower part of the eighth cervical segment to the upper part of the third lumbar.being most conspicuous at the level of the third and fourth thoracic nerves (Bruce). Practically suppressed in the cer\ical region between the eighth and third s^ments, above the latter the column reappears along with the formatio reticularis. Below, it is again seen within the third and fourth sacral segments. Tlie nerv <:el!s are multi- polar or fusiform in outline, from .015-.045 mm. in their longest diameter, conUi.i little pigment, and are provided with a variable number of dendrites, of which two are usually larger than the others. These arise from opposite poles of the cell and send branches, for the most part, into the adjacent white matter. The axones pass directly into the lateral columns and become ascending or descending fibres ; a few axones, however, enter the anterior column of the same side (Ziehen) . The cells of the second class, or intermediate cells, are irregularly disposed and only in the upper part of the cord present a fairly distinct middle group (VValdeyer). They are polygonal or fusiform in outline, small in size (seldom exceeding .035 mm.) and provided with irregular dendrites. The axones are continued chiefly within the lateral cr *'imn of the same side, although some pass to the anterior column and a few probably cross to the opposite side. A small number of isolated nerve-cells are usually to be found within the white matter, out- side but in the neighborhood of the gray core. These, the outlying celU of Sherrington," by whom they have been studied, occur most frequently in the vicinity of the more superficially placed cell-columns. Within the anterior columns they lie in 'he paths of the fibres proceeding to the anterior white commissure ; in the lateral columns they are in proximity to the intermedio- lateral group of the lateral horn and formatio reticularis and to the cells of the .substantia Rolandi ; an:* in the posterior columns, where they are relatively numerous, they are associated wi.h the "■ J«cts leading to the column of Clarke. The outlying cells are regarded as eleme' . d from their usual position during the course of the differentiation and growth of thi M . gray matter. Similar displacement sometimes affects the cells of the spinal gangli ' then may be encountered within the cord. T , . tiuroglia of the Gray Matter. — As in other parts of the cord, so in the gray matter the neuroglia is everywhere present as the supporting framework of the nervous elements, the cells and fibres. The gen- '^'^ eral structureof neuroglia having been described (page 1004), it only re- mains to note here the special features of its arrangement within the gray matter. In general, the felt-work of the neu- rogliar fibrils is more compact than that per- meating the white matter, being somewhat denser at the periphery than in the deeper parts of the pray matter. There is, however, no hard boun- dary between the sup- porting tissue of the two, since numerousgiiii fibrils extend outward from the frame-work of the gray matter to be lost between the nerve fibres of the adjoinins columns. This feature is marked in the anterior horn, where the glia fibrils form septa of considerable thickness that diverge into the surrounding columns ; further ' Proceedings Royal Society, vol. 30, 1890. Poitcrior nMdian nepluin Paramedian nptum ■uhdividing poucrior column Anterior median fiuure Anterior column Transverte section of cord allKhtly ma)(nifi«t, lihowing Kvneral nrnmnenient of neuroKlia. ^ 10. I036 HUMAN ANATOMY. i' ^% If i Fig. 891. the conspicuous processes of the formatio reticularis and the projecting lateral horn consist largely of neuroglia. The larger nerve-cells and their robust processes are ensheathed by interlacements of neuroglia fibrilke. In the several parts of the posterior horn the amount of neuroglia varies. Thus, the apex consists almost exclusively of glia tissue, while within the Rolandic substance the number of glia fibres and cells is unusually small. Within the caput and remaining parts of the posterior horn the neurogliar elements are similar m quantity and disposition to th^ Suhpial tayet .l!Vr' "»" ' o( neuroglia Peripheral part of trannrene lectlon of spliul cord, thowliit nerve-Rbtc* rabdividcd Into ini>ups by inKTowth of •ttbplal layer of neuroclia. X i]o. having an extended course being larger than shorter ones ; it follows that the fibres occupying the peripheral parts of the white matter, particularly in the lateral columns, are more frequently of large diameter than those near the gray matter. The immediate surface of the white substance beneath the pia mater is formed by a con- densed tract of neuroglia, the tubpial lajrtr, from .0J0-.040 mm. in thickness, that is devoid of nervous elements and forms the definite outer boundary of the cord. This lone consists of a dense interlacement of circular, longitudinal and radial neuroglia fibrils among which numer- ous glia cells are embedded. From the deeper surface of this ensheathing layer numerous bundles of fibrillae penetrate between the subjacent nerve-fibres to become lost in the general supporting ground-work. At certain places the bundles are replaced by robust septa by which the nerve-fibres are imperfectly divided into groups or tracts, as conspicuously seen in the pos- terior column where the paramedian septum, effects an imperfect subdivision into the tract of Goll and of Rurdach. The blood-vessels that enter the nervous substance from the pia, accom- panied by connective tiMue, i»re surrounded by tubular iiheat* > -• Fibre-Tracts of the White Matter.— Although microscopical examination of ordinary sections of the cord aflords slight indication of a subdivision of the columns of white matter into areas corresponding with definite fibre-tracts, yet the combined evidence of anatomical, pathological, embryological and experimental investigauon establishes the existence of a number of such paths of conduction. With few exceptions, they are, however, without sharp boundaries and illy defined adjoining tracts often overlapping, and depend for their presence upon the fact that nerve-fibres having the same function and destination proceed in company from the same group of nerve-cells ( nucleus ) along a similar course. In addition to being pro- vided with paths of conduction necessary for the performance of its function as a centre for independent (reflex) impulses in response to external stimuli, the cord contains tracts that connect it with the brain, as well as those that bring the various levels of the cord itself into as sociation. The white matter, therefore, contains three classes of fibres : ( i ) those entering the cord from the periphery and other parts of the body ; ( 2 ) those entering it from the brain ; and ( 3 ) those arising from the nerve-cells situated withm the cord itself. The first two constitute the exogenous, the last the endogenous tracts. It IS evident that some of these fibres constitute pathways for the transmission of impulses from lower to higher levels and hence form ascending tracts, while others, which conduct impulses in the opposite direction, form descending tracts. Since it is impossible to distinguish between these fibres by mere inspection of sections of the adult normal cord, and, moreover, extremely difficult and practically impossible to follow in such preparations the longer fibres throughout their course, advantage is taken of other means by which differentiation of individual tracts is feasible. Such means include chiefly the experimental and embryological methods. The experimental method depends upon the law discovered by Waller, more than h.ilf a century ago, that when the continuity of a nerve-fibre is destroyed, either by a pathological lesion or by the experimenter's knife, the portion of the nerve-fibre (the axone of a neurone) beyond the break, and therefore isolated from the presiding nerve-cell, undergoes secondary degeneration, while the portion remaining connected with the cell usually undergoes little or no change. It should be pointed out, however, that occasionally the connected portion of the fibre, and even the nerve-cell itself, undoubtedly exhibits changes known as retrograde degen- eration, which, although uncertain as to occurrence and cause, may at times prove a source of error in deducing conclusions. If a lateral section of one-half of the cord of a living animal be made, and, after the expiration of from three to four weeks, transverse sections be cut and appropriately prepared (by the methods of Marschi or of Weigert), certain groups of nerve- fibres will present degenerative changes. It will be seen, however, that the degenerated tracu in sections taken from above the lesion are not the same as those in sections from below the division, showing that certain fibres have been involved in opposite directions, those arising from ner e-cells lying below the lesion being affected with a.scending deKeneration, and those from cells situated above with descending degeneration. In this manner, by careful study of consecutive sections, much valuable information has been gained as to the origin, course, ter- mination and function of many fibre-tracts within the central nervous system. The embryological method, also productive of important advances in our knowledge of the nervous pathways, is based on the fact, first demonstrated by Meckel, that the nerve-fibres of the central nervous system do not all acquire their medullary sheath at the same time. Taking advantage of such variation, as suggested by Meynert and later extensively carried out by I'lechsig and others, upon staining sections of embryonal tis.sue with reagents that color especially the medullary substance, it is possible to differentiate and follow certain fibre-tracts ' In the ffttal cord with great clearness, since only those tracts are stained in which the myelin is already formed. It is of interest to note that, in a general way, the order in which the different strands of the cord acquire their medullary coat accords with the sequence in which nervous function is assumed by the fcctus and child. Thus, the paths required for spinal reflexes (the posterior and anterior root-fibres) are first to become medullated (fourth and fifth feetel months); those bringing into association the different segments of the cord next (from the fifth to the seventh month ) acquire myelin ; those ronnertinK thr mrd with the cerebellum follow somewhat later, while those establishing relations with the cerebral cortex are last and do not begin to medullate until shortly before birth. .^~?"^ WHITE MATTER OF THE SPINAL CORD. 1039 Baaed on the collective evidence contributed by these methods — ^anatomical, physiological, and developmental — it is possible to locate and trace with fair accuracy a number of fibre-tracts in the cerebro-spinal axis. Since they are undergoing continual augmentation or decrease, their actual area and position are subject to variation, so that the detailed relations in one region of the cord differ from those at other levels. Tne accompanying schematic figure, therefore, must be regarded as showing only the general relations of the most important paths of the cord, and not as accurately representing the actual form and size of the fibre-tracts. It must also be appreciated that the definite limits of these tracts in such diagrammatic Fig. 893. Awociation tracts Rubrotpinal tract VcitibulO'Spinal tract SpiiHHiulainic tract Spinoolivan' tract (Hclwrg) Ccrcbitxpinal tract Veitibulo-ipinal tract Tecto-spinal tract Diagram of •piiul cord, ahowins poahion of chief tracts and relation 1 of their component flbres to ner\-e~cellt ; 1-5. poMerior rool-fibrea enterina root-nme (R.Z.) and Liaaauer'i tract (L.). open drclea (0) indicate that fihi« pau upand down; c.c.collateraU from lonaaacendlna tracu (1, >) to anterior root^cella; 3. fibrea emlinf; around rella • .ilS^'i ">'"">" : *. nbrea forming direct cerebellar tract ; 7. 8, abrei formina t^owera' tract ; 9, 10, fibres from tataral and direct pyramidal tracta ; ii, 11, anterior root-libm ; V.F., ventral Oeld : O.F., oval Seld : C.B., comma Dunale. representations seldom exist in reality, since the fibres of the adjacent paths in most cases overlap, or, indeed, extensively intermingle, so that the fields seen in cross-sections may be shared by strands belonging to different fibre-systems. The Fibre-Tracts of the Posterior Column. — The subdivision of the posterior column of white matter by the paramedian septum into two general parts has been noted (page loaS). Of these the inner one is the postero-median fasciculus, or tract of GoU (fosciculus gracilis), and the outer one is the postero- lateral fasciculus or tract of Burdach (fasciculus cnneatus). These tracts are so intimately associated with the fibres entering by the posterior roots of the spinal nerves, that the general relations and behavior of these fibres must be considered in order to understand the composition of the posterior columns, as well as that of certain secondary paths. All sensory impulses that enter the spinal cord do so by way of the posterior root-fibres. The latter are the centrally directed processes (axones) of the neuror . whose cell-bodies lie within the spinal ganglia situated on the dorsiti nrnts of tV spinal nerves. They convey to the cord the various impulses collected ^^ tho peripherally directed processes (the sensory ner\es) from the integument, mucous membranes, muscles, tendons and joints from .ill parts of the body, with the exception of those served by the cranial nerves. The impulses thus conducted are transformed into the impressions of touch, muscle-sense, heat, cold and pain. The .ast ht'u\)i |..' portion of these neurones, as constituents of paths within the cord, that we are here concerned. On entering the spinal cord along the postero-lateral groove, the dorsal root- hbres for the most part penetrate the tract of Burdach, close to the inner side of the posterior Ijorn. Some of the more external root-fibres, however, do not enter Bur- dach s tract, but form a small adjoining field, the tract of Lissauer. that lies im- medately dorwl to the apex of the posterior horn. Soon after gaining the posterior column, with few exceptions, each dorsal root-fibre undergoes a >- or I- like divi- sion into an ascending and a descending limb, which assume a longitudinal course and pass upward and downward in the cord for a variable distance, the descending limb being usually the shorter. During their course from both, but particularly from the descending limb and from the proximal part of the ascending fibre, collateral branches are given of! which bend sharply inward and pass horizontally into the gray matter to end chiefly in relation with the neurones of the posterior horn, from which cells secondary paths arise. Not only the collaterals, but also the main stem-fibres of the descending and shorter ascending limbs end in the manner just described. In addi- tion to the short collaterals destined for the cells of the dorsal horn, others, the ventral reflex collaterals, pursue a sigmoid course, traversing the substantia gelatinosa Rolandi and the remaining parts of the posterior horn and the intermediate gray matter, to end in arborizations around the radicular cells of the anterior horn, and thus complete important reflex arcs, by which impulses transmitted through the dorsal roots directly impress the motor neurones. The latter are usually of the same side, but some collaterals cross by way of the anterior commissure to terminate in relation with the anterior horn cells of the opposite side. It is probable that a considerable number of such anterior fiK, ju » J u I , . ^^^^ ^^^^^ collaterals are given off from the hbres (hat ascend in the long tracts of the posterior column to the medulla oblongata ** ith possibly the exception of certain fibres which pass direcdy to the cerebellum ( Hoche), all the sensory root-fibres (axones of neurones of the I order) end afound the neurones situated either within the gray matter of the spinal cord or within the nuclei of the medulla ; thence the impressions are conveyed by the axones of these neurones of the II order to higher centers, to be taken up, in turn, bv neurones of the III or even higher order, in the sequence of the chain required to complete the path lor the conduction and distribution of the impulse. The most important groups of the collaterals and stem-fibres of the posterior roots are: ' '■ lu^ Lf ^ ascending tracts passing chiefly to the nuclei of the medulla. 2. The fibres passing to the cells of the column of Clarke. 3. The collaterals passing to the anterior horn cells. 4- The fibres entering the posterior horn from the tract of Burdach and of Lissauer to end about the neurones of the II order situated within the gray matter of tfie posterior horn and the intermediate gray matter. The direct ascending posterior tract includes the dor^ root-fibres that paiw uninterruptedlyr upward within the posterior column as far as the nuclei of the medulla. On entering the cord they lie at first within the tract of Burdach, but in their ascent are gradually displaced medianly and dorsally by the continued addition of other root-fibres from the succeeding higher nerves. In consequence, in cross niajtram showinK division of poMerior root-fibm inio asccndiDK and descnidinK hranches: lonit fibre sends collaterals ti. anlt-rior rool cells: other fibres end at diflerent levels aro.ind cells in grav matter of posterior Irorn ; S. G., spinal ganglion* WHITE MATTER OF THE SPINAL CORD. 1041 sections of the cord in the cervical region the long fibres entering by the lower nerve-roots occupy the inner part of GoU's column, but are excluded from the median septum, except behmd, by a narrow hemiellipucal area, which with its mate of the opposite side forms the oval field of Flechsig. The fibres entering by the lower thoracic nerves he more laterally, while those entering by the upper thoracic and cervical nerv« appropriate the adjoining part of Burdach's tract, the lateral area of which, next the posterior horn, is occupied chiefly by the posterior root-hbres. It must be understood that while in a general way the fibres of the long ascendine tracts have the disp«BUon just indicated, they are so intertwined and mingled with ^ strands t«»sing to and from the gray matter that the definite outlines of their conventional area, as reprinted in diagrams, are wanting. Collectively the "<="icu fibres composing this tract are of medium or pm g,^, small size, but acquire their medullary coat ' very early, myelination beginning about the fourth fcetal month, although not completed until the ninth (Bechterew). The termination of the long ascend- ing fibres is chiefly in relation with the neurones within the lower part of the medulla — the fibres of GoU's tract end- ing about the cells of the nucleus gracilis and those of Burdach's tract about the cells of the nucleus cuneatus. From these stations paths of the II order convey the impulses to the cerebel- lum, by way of the inferior cerebelkr peduncle, and to the higher sensory centres by way of the mesial fillet, as later described (page 1115). Whether certain of the component fibres of these ascending tracts are directly continued to the cerebellum, and perhaps to the mesial fillet, without undergoing inter- ruption in the nudei of the meduUa is stUI uncertain, although supported by the Statements of Hoche, Kolliker, Solder and others f> ff J ^rt ^I'n ~°»:?>>f«*P*"»inK to Clarke's column occupy the middle and median part of Burdach s tract, mingled with those of the long ascending paths. After cours- ing longitudinally, usually for some distance, within the posterior column, they bend outward, and, sweeping m graceful curves, enter the gray matter to end about Clarke s cells. It is noteworthy that the level at which they end is often considerably higher than hat at which the root-fibres enter the cord, an arrangement which explains the fact that lesions of the lowermost of these strands may be followed as ^cending degenerations into the thoracic region (Mayer). On entering the gray matter the terminal arborization of a single root-fibre usually ends in relation with several neurones of Clarke's column (Lenhoss^k). The imj^ortant sensory path of 2 thL'^'ifeuron^.*" ^ cerebellar iract (page 1044). arises as the kxones ^tinnlol rh"**r*°'/if^**,*'^?" *'' "'^ ^^"""^' •'*"■" «^« «" collaterals, not continu- ations of the stem-hbres, far the greater part of which come from the fibres of the SiI^^?k'"^ '^''^Ty^'^*-. V"^ collaterals penetrate the gray matter princi- pally at the median border of the head of the posterior horn, behind Clarke's column but partly also through the substantia Rolandi, and thence pass ventrally or ventro-laterally _ with a shghdy curved or sigmoid course, towards thVanterior horn. As they enter the latter the collaterals diverge more and more and are distributed to the vanous groups of the anterior horn cells, chiefly in relation with the lateral groups of radicular cells from which the ventral root-fibres ari.se ; they thus establish rl ^if" ^} ^y *'*"''' ^^^"y '•"?">«« conveyed by the posterior root-fibres impress the motor neurones, while, at the same time, these impulses are transmitted £6 Section of spinal cord u Umi o( aecond cervical •••• nwnt; fomiatio rrticttlaris filli bay between posterior and antenor comna; subauntia aelatinoaa caps apex o« pos- terior comu. Drawn from Weij — '^" -—-—-. "^^ by Professor Spiller. X 6. Kia.iifUB« VMps BfJCX Ol pOS' Weisert-nal preparation made I II 1043 HUMAN ANATOMY. cornua..^ ,v. pottero-UtenI ^U «!^# !u ^ *•"" ascendinfr stem-fibres. Although the anterior reflex collat- oau are, for the most psut m relation with the cells of the same side, it is probaWe hridcr^ t^.^'t^ ^ ^'y.^' ^^ posterior commissure, and possibly also by the an. ^r wh&r l£ 7^^^ ventral horn cells. It is doubtful, on the other hand. S^or ^t T^^Tu°' "^^^"^"^ of the posterior roots pass directly to th^ antenor column other of the same or opposite sides ( Ziehen). t«t. ^i! ?,?!■♦? J^'DPr"!"' .*? *•** posterior horn include those which pene- trate the substantia Rolandi, either as collateraU or stem-fibres of Bunlach^ or of Lissauer's tracts, to end Ho. 896. about the neurones within the Rolandic substance or within the head of the pos- terior horn. Their longitudi- nal course within Burdach's tract is ordinarily short ; they then bend horizontally and enter the gray matter of the fMMterior horn, within which they soon terminate in end-arborizations around the neurones of the II order. Some fibres, however, do not undergo T-division until after entering the posterior SMi«. nf «^..i --«• .. 1 . . . ^ , . horn, where, within the Ro- ?S^I~-=1^'''«'L^4^"'^^^^ '^"*^'*^ ^"•^^"'^e or caput ..ro.uuer.i«.icu.. Pr.p.r.tU by ProTe-or ^Hiter. X 6. comu, they then bihircate, .• . ... in some cases the ascendin? limbs pursuing a verticd course within the gray matter, particulariy of the caput cornu, for some distance before ending about the head-cells of the posterior horn 1 he tract of Lissauer, or marginal zone, situated immediately behind the apex of the dorsal horn, receives the lateral group of the posterior root-fibres. These are all of unusuaUy small size and, after a short longitudinal course in which the descending limbs predominate, they turn h Izontally and, both as collaterals and stem-fibres, penetrate the substantia Rolant about whose cells and those of the caput comu they end. From the foregoing description, it is evident that the dorsal root-fibres destined for the postenor horn terminate in relation with neurones of the II order represented chiefly bjr the cells of the substantia gelatinosa Rolandi, including the marginal cells and the inner cells of the caput comu. The ^ndary or endogenout tracts of the posterior column arise as axones from the neurones of the 11 order (the marginal cells, the cells of the substantia Rolandi and the head- cells) situated withm the posterior horn and include ascending and descending paths. n 7"^ ••'=«°<**n« seconjUry tract is composed of the axones derived from the posterior horn cells of the same and, by way of the posterior commissure, opposite side, which pass into the postenor column. In a general way, they occupy the ventral field, although sharing it with ftcattered strands of root-fibres and of descending endogenous fibres. The destination of the fibres of this pending tract is uncertain, some fibres pursuing a short and others a longer course within the postenor column before entering the gray matter at higher levels to end in relation w.th the postenor horn cells, or, perhaps, in some cases, with the neurones within the nuclei of the medulla (Rothmann). The descending secondary tracts, as shown by degenerations following lesions involvine the postenor coluinn, occupy varying but fairiy well differentiated areas. In the cervical and upper thoracic cord they are collected into the comma bundle of SchulUe, which extends from near the neck of the posterior horn dorsally along the median margin of Burdach's tract In the lower thoracic and lumbar cord they fonn an elongated half-ellipse along the posterior median septum which with the con^sponding bundle of the opposite side, produces the oval Beld of FlrchsiK. Still lower, in the sacral cord, they lie at the junction of the median septum and the posterior surface of the cord as the medio-donal triangular bundle of Gombault and fhilippe. Additional descending endogenous fibres are .scattered in the ventral field It is co™5?i!!?Lff *?!.™' "^ ■' •«»»' »' •««nU> «rvic«l •Cdnenl : anterior WHITE MATTER OF THE SPINAL CORD. ,043 likely that these areas represent the principal aggregations of the downward coursing limbs of the axones, after their T-like branching, oerived from the posterior horn cells of the same and opposite sides. In the cervical ^^ region these axones are col- p|Q_ gg. lected into bundles which ap- ' pear as the comma tract ; in the lower thoracic curd these are replaced by, without being directly continuous with, those forming the oval field, and these in turn by the axones of the triangular bundle. No one of these fields is exclusively devoted to the descending limbs of endogenous fibres, since in all the presence of exogenous posterior root- fibres has been demonstrated. "^Kc Fibre -Tracts of the Lateral Column. — These include: (i) the lateral pyramidal, (2) the direct cerebellar, (3) the ascending antero-lateral, and (4) the lateral ground- bundle. for^Jll* ^*K*f'* ?u Z'°*^i pyramidal tract (fasciculus cerebrospinalis lateralis) forms the chief path by which motor impulses originating in the cerebral cortex are conveyed to the spinal cord. It stands in close relation with the direct pJ^ZZ ™tt if th^Tj^^n ""k.""- ^'^."^ continuations of the conspicuous pyramidal paths of the medulla oblongata and may be followed upward through the ventral Slebll hlmS'"' '''"r"' and the cerebral peduncles into the white matter o?the ^HJ?nJ^T ,? !r S"1 «".t° '•'^ '^«'?«=*' «'^y '»»"^'- ^^^'^' in the motor areas S^rl^rii TK^*^^«^'''*"u"= 'l'""'^' "^ '^^ nerve-cells from which th.- pyramiSj !nrlT • '"'^[™P"°? '■•on' the superficial gray matter of the cerebral hemi- motrTtr^oJ^T '^''^i^ '" the cord, constituting long descending (corticifugTl) rnotor tracts. On reaching the lower part of the medulla, from 80^0 per cent of the component fibres of each pyramid cross to the opposite sideX way of the f«^Tl^''•H'l^P''^'^' 'P^^*^ '"^5) and, entering die cord, d^cTnd as the latend pyramidal tract; the remaining fibres (on an average, ab<^ut irSer cent ) pass downward into the ventral column of the cord as the difect pyi^m daftract! ..I..J^„^ ^^"^T^u '^l^""^^ pyramidal tract passes outward to enter the kteral bradel^»n^ • ^''r^ «^«^hanging its former median and superficia ToS ZLrf^ !i K °'^ Uteral one. Since its fibres are continually entering the gray matter to end about the radicular cells from which the anterior root-fibres of the hTltdrthe"fourth'r*=7''"^""'^^'y '""'^ '" ^'^^ - '' ^-^-ds" intS It aUu tne level of the fourth sacral nerve, it ceases to ex st as a distinct strand although ^elT^'^K^^'™'^' '^"^"^ ''""^'^'^ "f fib'-*^ »« '»^ =»« the orison of the'cocS Sss ilni'ore mark^";^ ""*, ''^'''' ^'"'^^ '" '^' ^''''^ ^"^^ ^"^^^ e.largemS fo tll:T4eToto7lSne^"es''""'"^^ °" *'='^°""' "' '''' ''^'^''"^ «' '"^^ '^^'-^"^'^ seen Kr^tfon^nT.h '" "'^^ fu "'^>*""' P''^^"''''^' '""=' ^'^^^ ■■" different levels. As ^sider^b^ sis ?hL m«L?T' *°-''^'^ u'*^°" °' *e cord, the tract occupies an area of f^I^f^ ill', "nesially lies again.st the posterior horn and laterally is in contact with the direc cerebellar tract, by which it is excludedfr-.m the peripher%' I„ fron uh, rr iK lim" ^« of "heT^ ce^befc™J if^^^^ "^'''^ '^^ diminution and disap,War- a^^ro^ches andTfinaHv reLr^^K i'" ""= 1°"'." H"""""^ °^ '^e cord, the pyramidal field approacnes ana hnally reaches the surface, which relation it retains as it grows smaller, the 'i^m 1044 - T*g %^ -'^ HUMAN ANAluNfY. reduction affecting the more deeply placed fibres. o{ the pyramidal tract in cross-section changes fr lyi., Fig. 898. Section ci spinal enrd at level of sixth thoracic segment ; slender itostcrior cnrnua covered with sub- stantia gelalinosa ; pfistero-lateral angle marks greatest width of anterior comit. X 6. Preparation hv Pro- fessor Spiller. oasequun :e c! these variatioas, the form I wedge-sh.i; le to 'liangular, with the base a' the ;)••' i.htr; and o apex dirvtted uiw.irl. Durit", I ' Mr descent the fibres t)f the pyriimi !?1 tract j, . ■ off at different levels col- tatemls which i'ciif the indi\ i lal fibres ^wt^ping in short curves through th^ iiterveniiiK ground- bundle of the lateral column to gain the radicular cells around which thi > end. By means of its collaterals, each pyramidal fibre establishes rela- tion with several cord-segments. The fibres of this tract are relatively tardy in acquiring Iheir medullary coat, which proce^s dots not bejjin until the last month of fcetal lii< and is not com- pleted until after the seconu year. The direct cerebellar tract (fas* ciculus cerebellttsptnalis). is an important ascending path of the second order that establishes communication between the reception sensory cord-nucleus formed by Clarke's cells and the cerebellum. In cross-sections of the thoraci< legion, the tract forms a superfiLial flattened comet-shaj)ed field that occupies the dorsiil halt of the lateral column, extending froni the ajje.x of the posterior horn forward along the periphery of the cord, to the outer side of the lateral pyramidal tract, to about the .interior plane of the gray commissure. Its ventral end, particularly in the lower cer\ical region, is broadest and projects somewhat into the lateral column in advance of the lateral pyramidal field. Although as a compact strand the direct cerebellar tract begins at the tenth thoracic segment, it is represented by isolated nores in the lumbo- sacral region. The fibres collectively are large and become niedullated about the sixth fcetal month (Bechterew). In a general way the fibres having the longest course occupy the dorsal part of the tract and those having the shortest the ventral (Flatau). Arising as the axones of the cells of Clarke's column, the components of the tract pass in curves almost horizontally outward through the gray matter ami lateral column to the peripheral field, on gaming which they bend sharply brainu ird and ascend without interruption to the medulla. Their further course includes sage through the dorso-lateral field of the medulla as far as the inferior < peduncle, by which the fibres reach the cerebellum to end in relation with the worm, on, probably, both the same and the opf)osite sides. The tract of Gowers (fasciculus anterolatcralis ^nperficialis) constitutes another pathway of the II order, which connects the cord r h the cerebellum an 1 probably also establishes relations with the cerebrum. In cross-sections the tract ippcars somewhat uncertainly defined owing to the intermingling of its fibre- ith adjoining strands, but in the main it includes a superticial crescentic fi<„ h.. the direct cerebellar and lateral pyramidal tracts bel md. extends alon>; ;ii> of the cord for a variable distance, and usually ends in front in the viciit ventral nerve-roots. The inner btjundary. separating the tract in questii lateral ground-bundle, lacks in sharpness and is overlaid by the adjoinin Below, the tract appears about tlu; middle of the lumbar region and throughout the remainder of the cord. As Gowers' tract ascends, it fai! the considerable increase in size that might be expected in view of thi additions that it receives. In explanation of this, the pnbahlo mingling oi -.mie its fibres with those of the direct cerebellar tract, rather ihan their ending in t! curd, seems the iiuwt plausible (Ziehen). The exact origin of the constituents of Ciowers' tract is st i uncertain, but it i- verj- likely that its fibres are chiefly the axones of the neurones marginal and inner cells) situated within the posterior horn, partly frosn the same and partlv from the if pas- bellar iiuerior lose of ;• inches margin of th- om th -trantis. itinues ) show litii 'sal WHlTt MATTER OF THK SPINA CORD. «o45 opposite sKk^, with contributions, |X)s?iib!y, in mattt-r. A ter traver>inK tht- cord, the lateral ft portion of he pons, the tnct ascends the brain stem to the vicinity ol he inferior cor- pora quadrigeinina. Here ti ,f major part ui the fibres turn backward anti ' superior cerebellar peduncle a medullaiy velum, reach the end mostly in th supert< >r » the same side a Possibly .1 part ' t! cells of the intermediate gray .li vi the m<-i99 by way of the 1 the supi ior •rebellii' to , - im, par'U n partly cro»*ed (Hirhi j. ■t the cerelieli- T conttrigent m.iy share the j. .th of tlv dir t nuii^ar tract md in this way rea< li the certoeilum by its inie ri'ir peduncle Ziehen 1: is probable that .ill fibres from Gowers tract ■ co and onprisfs a numVx r of 1' nfr exogenous paths that descend from the br as f lonp iirendin md mar shorter endogenous strands, both asc de^ ..-diiig. These ... ' /mrff .xury chiefly the central parts of the lat anci. Ill a gener;» way, ■ dose to the gray matter, within an are;. twi id postern r horn kwwn ^ the boundary zone. They 1 .» is tield, as - a tt .» of th. ir fibres lie scattered ai icts occupvi he i, ..re lateral portions of the ground limite<: to exogenous t Section of spinal cord at "I of I'-wt^r per Mth Jumtiar segment; gray n, n-r rtlaf Iv I in amount ; anterior comua bulky. Pr' .itio.^ Profeuor Spiller. x 6. wel' an( viiumn f ante- c\ lot he I ..^'er the rilires of just medial ers (tractus whie postenor horn of the .,,.:. -site side, the a.xones crossing in the ant. ior commissure to pursue a course bramward within the antero-lateral ground-bundle Alth. this tTr. < e scattered and not collected into a compact strand, their chief !3..i-f the groimd-himdle .nre orcupieH by the lone exogenous paths, int'.'rmingled, however, with the longer intrinsic fibres. Section of spinal cord at level of lower part of cuccyf;eal segment^ dilleretiliation of ror- nua is uncertain. Preparation by Professoi Spiller. v g. WHITE MATTER OF THE SPINAL CORD. 1047 The endoftitous fibie* arise as the axones, chiefly of the inner cells of the posterior horn, as well as froin %v /"^"^ '*"' ^^^ ^"'•''^ ^"^y matter with the T vX A \' / K\LMIBi/7 fTVA exception of the most peripheral zone. i , 'VV"' >* JB-^ ^i3^\ ^^^ \a'»ac, toj|;ether with the white I't ^ S|' tl^^^W ■v>^;r!;ir\ matter, receives its supply from * 10. WHITE MATTER OF THE SPINAL CORD. 1049 intervertebral efferents carry the Wood into the vertebral, intercostal, lumbar and lateral sacral veins. A part of the blood from the intrapial ple.xus is conducted upward by the anterior and posterior median veins into the venous net-work covering the pons and thence into the lower dural sinuses. Definite lymphatic vessels within the spinal cord are unknown. Development of the Spinal Cord.— A sketch of the general histogenetic processes leading to the differentiation of the neurones and the neuroglia has been tg: r>n (page 1009) ; it remains, therefore, to consider here the changes in the neural tube by which the definite spinal cord is evolved. From the time of its closure, probably aboiii the end of the second week of fittal life, the neural tube presents three regions :— the relatively thick laUral ivalls and the thin ven- tral and dorsal intervening bridges, the >?oor- and roof-plates, that in front and behind complete the boundaries of the canal in the mid-line. By the fifth week the lateral walls exhibit a distinct differentiation into three zones— the inner ependymat layer, the middle nutlear layer and the outer marginal layer, surroimded by the external limUing membrane. In contrast to the other two, the marginal zone is almost devoid of nuclei and, beyond affording support and perhaps assisting m providing a medullary coat, plays a passive r6le in the production of the nervous elements. By this time the bmr-T general oval contour of the developing cord, as seen in cross-sec- tions, has become modified by the conspicuous thickening of the antero-lateral area of the nuclear layer into a prominent mass on each side, whereby the reticular marginal layer is pushed out- FiG. 904. Roof-plaw Fig. 905. Roof'i>Utc Ooraaliom Epntdynwl laj'cr Vmtnil root-fibres Ncurobluu <■ Floor-plate Developing iplruil cord o( (bout lour week*. X 100. (M».) Ploor-plaie Ventral root-fibm Oevelopinc "plnal cord of about five weeki. X 60. (Mj.) ward With corresponding Increase in the width of the entire ventral part of the cord which is now broadest in front. Within this thickened ventro-lateral part of the nuclear layer' later the antenor horn of gray matter, as early as the fourth week young neurones are seen :rom which axones grow outward through the marginal zone and pierce the external limiting membrane as the representatives of the antenor root-fibres of the spinal neives. Postero-laterally the thin nuclear layer to covered by a somewhat projecting thickened area within the marginal layer known as the oval bundle, whose presence ii. due to the ingrowth of the developing tlorsal root- e^f the"'fdurth*S(H,"r*' °' '*" '"'""' '^"''"""' ^^'''^ ^^^ begins as early as the ^ .'!lf^'"'"' *','*' '^"f* "Changes, the lumen of the cord becomes he^rt-shaped inconsequence UtTaTIL'iJl^T.i?^''' '""*"«,"''«» transver^, diameter, with corresponding bulging of the Irl^ff ^".1 II^*?'! ""'""*■■ " '«'K«'"dlnal furrow appears by which the side iails of the tul« HT,r ^. t^"-°i "^ '"f"' *''■? f*^^"/""'' «he zrntral tones (the alar and basal lamina- of rlrtlln,J?.^ .u K • " '' °' T*'^ importance, since in the cord-segment, and also with less ^fiKll the brain-segment of the neural tube, these tracts are definitely connected with the ^~ ,^ ^' "5'"" "•''^''!!' «" '^^' '""* ^"'' "'« '*"'«'^- ""'1 »he ventral zone with the m^w roots In advance 01 the fto.,r-plale the venlrafly protruding halves o( Ok- corti include a tm>ad and sMIow furrow which marks the position of the anterior median fissure. During the sixth week the form of the tube-lumen becomes further modified by the elongation and narrow- I050 HUMAN ANATOMY. mg of the dorsal part o£ the canal in consequence of the approximation of its walls, which in the course of the seventh week is closer and, by the end of the second month is completed by the meeung and fusion of the adjacent inner layers, with obliteration of the intervening cleft and the proouction of the posterior median septum in its place. Since the partition is formed by the union of the inner (epeiidymal) layers, it is probable that the septum is to be regarded as e^ntially neurogliar in origin and character. It must be remembered, however, that a certain amount of mesoblastic tissue may be later introduced in company with the blood-vessels which subsequently invade the septum. The remaining and un-.losed part of the lumen for a time resembles m ouUine the conventional spade of the playing card, with the s.em directed ventrally ; but later gradually diminUhes in size and acquires the • ontour of the definite central canal. During these alterations in the extent and form of its lumen, the gray maUer of the develop- ing cord markedly increases, especially behind where the posterior horn appears as a projection beneath the broadening mass of the ingrowing dorsal root-fibres. As the posterior horn becomes better defined, the rootrbundle becomes meso-laterally displaced, lying behind the horn and then constitutes the tract of Burdach. Goll's tract is formed somewhat later and at about the third month appears as a narrow wedge-shaped area that is introduced between the mid-line and Burdach s tract. Towards the erfd of the second month, the anterior white commissure is indicated by the oblique transverse ingrowth of axones into the most ventral part of the floor- plate as they make their way to the opposite side. Meanwhile the anterior median fiaiure has Fig. 907. GoU'i tnct BunUch's tnct Pia nialer Anterinr columii Developing spinal con] of about acven and one-half weeks. K^^. {His.) wHh |4a] procca column Developing aijinal cord of about three months. Xjo. (Mi.) become deeper and narrower in consequence of the increased bulk of medio-ventral parts of the cord. As the fissure is thus differentiated the process of mesoblastic tis.sue, which from the earheit suggestion of the groove occupies the depres.sion, is correspondingly elongated and affords a passage for the blood-vessels destined for the nutrition of the interior of the cord Until the third month the gray matter, derived from the nuclear layer, is much more voluminoui than the surrounding marginal layer, whkrh, so far as the contribution of nervous elements is concerned, is (lassive, since ite conversion into the white matter depends upon the ingrowth of axones from the neurones situated either within or outside the cord. The development of the individual fibrf tracts includes two stages, between the comole- tion of which a considerable, and sometimes a lone, period intervenes. The first marks the invasion of the supporting tissue of the marginal mne by the ingrowing axones as naked axis- cylinders ; the second witnesses the clothing of these fibres with myelin. The period between the appearance of the tract and the development of the medullary coat is variable In some cases, as in the great cerebro-spinal motor paths, although the fibres gro-.v into the cord durint the fifth month of fietal life, myelination does not begin until shortly before birth and is not completed until after the second year. In other cases, as in the direct cerebellar a period of three months, from the third to the sixth, elapses. It is probable that the acquisition of the medullary coat commences before the functional activity of the fibres hegln-i although su<;h stimulation undoubtedly assists ; further myelination proceeds gradually along the course of the fibres and in the direction of conduction. PRACTICAL CONSIDERATIONS: SPINAL CORD. 105 1 Based on the observations of Flechsig, His, Bechterew, and otliers, the time of the appearance and of the development of the medullary coat of some of the fibres within the spinal cord may be given. Pibm of Anterior root Burdach's tract GoU's tract Pyramidal tracts Direct cerebellar tract Cowers' tract Appear about 4th week during 4th week about 9th week end of 5th month beginning of 3rd month ■"•".*• ^^^^ *'" W in the different poS of the spine, being greatest m the dorsal region. ^ lesion^f'Vi"!^''*!?!"^ 1"'' molecular disturbance and without obvious gross T^^ "*• although more frequent than has been supposed, is rare because of (a) the arrangement of the different constituents of the vertebral column wSb^ means of its curves, the elastic intervertebral discs, its numerous joh^l and the large amount of cancellous tissue in the vertebral bodies, is able to bSe up and fnT^ln^'^''";'^''' '?■■'" °' r*"^ ^^u*^^ "' ^•'«'*^"'=^ •• ('^ the situatioS^f'thrcorS in the centre of the column, where, as the most frequent serious injuries to the spine are caused by extreme forward flexion, it is somewhat removed fr^m dange? "n accordance with a aw of mechanics that "when a beam, as of timber. TexS to breakage and the force does not exceed the limits of the strength o the KiaT one division resists compression, another laceration of the particles, while thlthS' between the two, is in a negative condition" (Jacobson) ; Or) the suspension of th^ cord m the surrounding cferebro-spinal fluid (-like a cate^ liar hung by a thread m a phial of water' •-Treves) by its thecal attachments and nerN-e-roots (rf) S connection above with the cerebellum, itself resting on ,,n elastic ^^^ieW' which minimizes the transmission downward of violence applied to the craniS SeTgr'oi^Ie -r ;rffctl^ ^''"^"'''°" ^^ undoubtedly^'Sue to hemorrhTgHr Th. 2li"/""' "' '^'^ f"^*^ may occur from sprains, as in forced flexion of the spine S. ^ ''"^H^;!!''"'* """" *^7''"' "'^ ""'^ '^"^ d"« to fracture-dislocations o? the spine, the cord being more or less crushed between the upper and lower fragments It IS so delicate a structure that it may be thoroughly disorganized without evrdeni mjury to the membranes or alteration of its internal foAn. tL paral^ss of the parti bdow will be complete or partial according to whether the whole or^nly .. ^rt^l he ransverse section of the cord at the seat of injury is destroyed. Since when he lesion IS complete everything supplied by the conf below the seat of the Sn » paralyzed the higher the injurv to the cord the greater the gravity of the^ When the atlas or axis is fractured and displaced the^ital centres^n the meSilla^ Z^tr ■] ±'*''' "•'*y, '■'=''"" '"""«J'«ely. The phrenic nerves which ar^e chieiw from the fourth cervical segment, but partly from the third and fifth ™J^Jf are also paralyzed and respiration ceases. scgmenis. PRACTICAL CONSIDERATIONS: SPINAL CORD. 1053 la/raciure-dislocations of the spine it is the body of the vertebra which is most frequenUy fractured, the hgaments yielding posteriorly and permitting the dislocation, rhe fractured edges of bone are. therefore, in front of the cord ; and, as the upper fragment passes forward, the anterior or motor portion of the cord is pressed and crushed agamst the sharp upper edge of the lower fragment In partial transverse lesions of die cord the paralysis below the lesions affects, therefore the motor columns of the cord more than the sensory columns which are in ' part posterior. ^ The most frequent seat of fracture-dislocation of the spine is in the thoraco- lumbar region (page 145). Fortunately, it U this variety which offers the best prognosis, since the cord ends usually just below the lower border of the first lumbar vertebra, and the cauda equina being more movable and tougher than the cord Itself, it can better evade the encroachment on the canal, although in spite of these facts, it is not infrequendy injured in such lesions. The bodies of the lumbar vertebra are the largest and most cancellous, the intervertebral discs the thickest and most elastic, so that crushing of them occurs with less tendency to invade the canal and injure the cord than in any other portion of the spine. In caries inal nerves escape troni vertcbnil cututl. THE BRAIN. 1055 r paralysis (poiio-myelitis), will lead to atrophy of the corresponding muscles. The vasomotor centres are also in the anterior horns, probably in the intermedio-lateral tnict. til J Sensory impulses pass to the posterior horns through the posterior roots, and some of them soon cross to the opposite side of the cord, others ascending in the posterior column. The lemniscus is probably the chief sensory tract in the medulla oblongata, pons, and cerebral peduncles. Every segment of the spinal cord contains centres for certain group of muscles, and for reflex movements associated with them. A reflex begins in the stimulation of a sensory nerve. The impulse thus created passes to a centre in the cord and thence is transmitted to a motor nerve, thus producing a contraction of the muscle supplied by that nerve. The complete path of this impulse is called a reflex arc. The sensory impulse may be transmitted to different segments of the cord and thence out through the corresponding motor roots. Thus a complicated reflex arc is produced. It is to be assumed, however, that the impulse will take the shortest route, so that simple reflexes will have their reflex arc chiefly in those segments of the cord in which the posterior root enters. Each segment of the cord is connected with fibres from the brain to which must be ascribed the hmctinn of reflex inhibition. If the inhibitory fibres are irritated, the reflexes are impaired from stimulation of inhibition. If the conductivity of these fibres is destroyed, the reflexes are increased; but if the reflex arc is broken at any point, the reflexes are lost Among the most important of these are the skin and tendon reflexes. . The centres for the bladder, rectum, and ^xual apparatus, are located in the sacral segment of the spinal cord at and below the third sacral segment. They regulate the functions of these or^ns and are associated in some unknown way with the brain. (See mechanics of urination, ps^e 1914). Htemalo-rhachis, or hemorrhage into the membranes of the cord (e.\tramedullary hemorrh^e), may result from an injury to the spinal column, as a fracture or a severe sprain. The bleeding inay be from the plexus of veins between the dura and bony wall of the canal (most frequent), or from the vessels between the dura and the cord. In either case the symptoms will be much the same. There will be a sudden and severe pain in the region of the spine, diffused some distance from the seat of the in- jury, due to irritation of the meninges, and pain transferred along the distribution of the sensory ner\'es coming from the affected segments of the cord, accompanied by abnormal sensations, as tingling and hyperiesthesia. In the motor distribution there will be muscular spasm, or sometimes a persistent contraction of the muscles. Gen- eral convulsive movements, retention of urine, and, later, symptoms of paralysis may appear, but .is a rule the latter is not complete. Hamalo-myelia, or hemorrhage into the substance of the cord (intramedullary hemorrhage) from traumatism, usually occurs between the fourth cervical segment of the cord and the first dorsal (Thorburn), and is commonly due to forced flexion of the spine, which is most marked in this region, as in falls on the head and neck. The cord has been crushed in such accidents without fracture of the spine and with only temporary dislocation. The hemorrhage is usually chiefly in the gray matter and may be only punctate in size, or may Ut large enough to extend far into the white matter, or even outside the cord into 'a.c sulKirachnoid Space. The symptoms usually .ippear immediately after the injury and are bilateral, suggesting a total transverst; U^sion. There will be much pain in the back, occasionally extending along the a.-ms i\tforamina of Monro, by which they communicate with the unpaired and mesially placed third ventricle, is seen in sagittal sections. Both the roof and the floor of the irregular third ventricle are thin, whilst its lateral wails are formed by two robust masses, the optic thalami, the mesial surface Corpus cilkMum liKldufn Fig. 910. Frontal lobt, mnUl «uf&ce. Anterior comnlMUM Foranira of Monro I.Aiiiim cincrcs' Optic commlwui FI«or .if tMr.1 vcwridc MammflUry body Ailuc«1uct at SylvluC' Poaft< Simplified drawing of brain u i 0|)tic ttujamuft. donal surface l.atcnl wall of third VMttlclc {o|Mk thalamua) Cnvtinl ptdundt Hoof of Syh Un •<|ueiltKt Icdplul : ijikutioiw Wimmmi - the primary brain -vesicles. The positeriur uf liiHe. the JHed-brain.' jji 1 the longer, exceeding the combined lei%;th at the- ii^ter cso > Mtc.- 911 alter a sbtM^ time when viewed from behind it presents ^i eiongaOitd luzui^e> out troin tb«- lciw<-r lattrcal wall. For a time the optic vesicle communicatee wrtli lim' main ^aviiy of lie forv- brain by a wide opening. This gradually becomes rv<\^raiR Himl-brvin Reconitnictioii ol bf^iii of human embr^ ; uf about Iwc wevlH(j.a mm.); w4, outer surface; S, inner surface; HP. neural pore, wbere fore-brain ia still open ; ci, aniagc oi corpus striatum ; or, uptic reccas leailinc into optic vesicle ;*/, hypothalamic region. (Mu.) evagination is attached by a hollow stem, the optic stalk, which later takes part in the formation of the optic nerve that connect-, the eye with the brain, the vesicle itself giving rise (page 1482) to the iier\'ous coat «f the eye, the retina. By the time the optic ev^nation is formed, the front part i>f the fore-brain shows a slight bulging, narrow below and broader and rounded above, and separated from the optic outgrowth by a slight furrow. This is the first suggestion of the anlage of the hemisphere or /and into the conspicuous primary cerebral hemispheres. The lower ]iart of the fore-brain includes the region that later, after differentiation and outgrowth from the hemisph»Tc, receives the nerves of smell and is known as the rhinencephalon. A slight ridge (Fig. 911, ^), projecting inward from the roof of the fore-brain, suggests a subdivision of the general space into a posterior and an anterior region. 'This Use trf the trrm hindhrain is at variance with its oldci siKnifiCiiiCr, .still reUiiicii j.y some German writers, as indtcatinK the upper division fmetencephalon) of the posterior primary vesicle. In view, however, of the now t^neral application of fore-brain and mid-tirain to the other primarj,- vesicles, it seems more consistent fo include hind-brain in the series, as h.i5 been done by Cunningham, with a distinct gain not only in convenience, but in avoiding terms which in their Anfflinsed form are at best awkward and tmncces.sarv. i ) ! t 1060 HUMAN ANATOMY. The latter, the outwardly bulging pallium or hemisphere-anlage, is limited below by the optic recess, the entrance into the optic vesicle, and, farther front, by a flattened triangular elevation that marks the earliest rudiment of the cor^s slrialuw. The posterior or thalamic region extends backward to the mid-bram, from which it is separated by the slight external constriction and corresponding internal ridge. During the fourth week the demarcations just noted become more definite, so that the primar)' anterior vesicle is imperfectly subdivided into two secondary compart- mc-nts, the telencephalon, conveniently calletl the end-brain, and the dienceph- alon. Considered with regard to the details presented by the interior of the fore- brain, the four areas recognized by His are evident. These are (Fig. 912) the region of the pallium and of the corpus striatum, respectively above and below in the telencephalon, and the region of the thalamus and of the hypothalamus ri-spec- tively above and below in the diencephaion. Between the protruding hemispheres, the telencephalon is closed in front and below by a thin and narrow wall, the lamina termiiialis, which defines the anterior limit of the brain-tube. While the more detailed account of the further c'exelopment of these regions will be given in connection with the description of the several divisions of the brain. MUl-brain F>';. 9Ii. Diencephaion Thalxmeiicephalan Telencenhmlun Pcllium Mitl-hrain Sptnal rct Kei-niiMructiiin o( brain of human rmbr\o iil about four weeka (ft.'i mm.); A. r.uler Mtrfare; B, inner i.urfac(; /, iMhmm ; <«. a|>crturi- of opilc atalk ; • ^. ccrrbral |ie Iral flraurr : M, cefilialic flexure. Krnw n trom Hi» miKlct. it iii.iy Ik- piiintid out here, in a miieral way, that the pallium gives ri.se to the cim- spiiiious ci rebral lieinisphires, which, joinc*! IhIow bv a onmmon lamina, ex|)und out- ward, upward and iKickward and rapidly dwarf ihe other jwrts of the brain -tube which arc thus gratlually roverejl «i\tr. Thestri.ite area thickens into the i<«rj>us striatum, wli'ch appears as a sfiking prc>ininen;ii)al cavity of the li)rc-hrain enclosed by the dodopinjr cerebral lu inisphcrc, atiil at first is large and thin-walled and comiiiunicates by a wide o|)ening with the remainder of the braiti- vesiclc. The uiie(iual growth and thickening, which sulwequently nKxIily the burrounding walls, reduce this large aperture until it persists as the small foramen of Monro, bv which the lateral ventricle communicati-s with the third vetitricle. The latter represents what is lt keep pace with the adjoining vesicles, and in the fully formed brain is representeti by the parts surrounding the aqueduct of Sylvius. Neither does it subdivide, but, w hile its entire wall is converted into nervous tissue, retains its primary simplicity to a greater dqrree than any of the other brain-segments. The lateral and ventral walls of the mkl-brain contribute the cerebral peduncles ; its roof gives rise to the corpora quadrigemina ; and its cavity persists as the narrow canal, the aqueduct of .Sylvius, that connects the third and fourth ventricles. The posterior vesicle, the hind-brain, or rhombencephalon, the largest of the primary brain-segments, is the seat of striking changes. These include thicken- ing and sharp forward flexion of the ventro-lateral walb, in consequence of which the floor of the space becomes broadened out opposite the bend and as-sumes a lozenge- shaped outline. The hind-brain Ls conventionally subdivided (Fig. 013) into a superior part, the metencephalon, and an inferior part, the myelencephalon> Its cavity, common to both subdivisions, persists as the fourth ventricle. The extreme upper part ot the metencephalon, where it joins the mid-brain, early exhibits a constriction, which by His has been termed the inthmun rhom- bcncephali and regarded as a distinct division of the brain tube. In the fully formed brain, the isthmus corresponds to the uppermost part of the fourth ventricle, just below the Sylvian aqueduct, roofed in L^ the Sijperior medullary velum that stretches between the superior cerebellar peduncles. The thickened and markedly bent \entro- lateral wall of the metencephalon gives rise to the pons Varolii, whilst in the roof of the ventricle appears a new mass of nervous tissue, the cerebellum. The myelencephalon, soon limited lx;low by the cervical flexure, shares in the ventral thickening seen in the preceding division. Its floor and particularly its sides, the latter at the same time spreading apart, form the medulla oblongata, which below gradually tapers into the spinal cord. Its roof, in which thinness is always a prominent feature, becomes more attenuated as development proceeds and is converted into the inferior medullary \ elum and the tela chorioidea that close in this l>art of the fourth ventricle. The subsequent invagination of this membranous portion of the ventricular roof by the pia mater brings about the production of a choroid plexus similar to that seen in the roof of the third ventricle. From the foregoing sketch of the changes affecting the embryonic brain-tulx', it is evident that the anterior and tKisterior primary vesicles undergo subdivision, «hile the mid-brain remains undivided, five secondary brain-vesicles — the telencepha- lon, the diencephalon, the mesencephalon, the metencephalon and the myelencepha- lon — replacing the three primary ones. In consetjuence of the unequal growth of various parts of the cejihalic segment of the neural tube, the latter becomes bent in the sagittal plane at certain jHiints, so ihat, when viewed from the side, the axis of the developing human l.niin ilescribes an S-like curve (Fig. 912). These flexures, to which mcidental reference has been made, bring about a disturbance, for the mcwt part temporary, in the relations of the brain-segments, which in the lower vertebrates follow in regular < irder along an axis practicallv straight. In the developing human bniin, in which they .ire most conspicuous, tliere are three flexures — the cephalic, cervical, and |M)nlin( . The first of these, the cephalic flexure which appears towards the end <>f the second week and before the neural tube has completely closetl, is firimary and involves the entire head. It takes place in the region of the mid-brain anci lies I 1062 HUMAN ANATOMY. Mnracephalon Tdcnccphftlon Cotpat ftriMum Optic Mctcnccphalon Myeknccphaloii above the anterior end of the primary gut-tube and of the notochord. At first the axis of the fore-brain lies about at right angles with that of the rhombencephalon, (P'ig. 911) but, with the in- FiG. 913, creasing size of the middle Dienceptaion ^„^ anterior vesicles, the angle of the flexure becomes more acute until the long axis of the fore-brain and of the rhombencephalon are almost parallel (Fig. 912). During the fourth week a second ventral bend, the cervical flexure, appears at the lower end of the hind- brain and marks the separa- tion of the encephalic from the spinal portion of the neural tube. The cer\ical flexure, which also involves the head, is most evident at the close of the fourth week, when it is almost a right angle ( Fig. 912): after this it becomes less pronounced in consequence of the elevation of the head which succeeds the period when I'.ie embryonic axis is most bent. The third flexure appears about the fifth week in the part of the metencephalon in which the pons is later developed and, hence, is termed the pontine flexure. It concerns chiefly the ventral wall, which is in consequence for a time ventrally doubled on itself ; subsequently this flexure almost entirely disappears. In contrast to the preceding bends, this flexure is only partial and involves chiefly the ventral and only slightly the dorsal wall of the neural tube ; on the exterior of the embryo its presence is not detectable. The developmental relations of the chief party of the fully formed brain to the embryoiiic brain-vesicles are shown in the accompanying table. '1'ABUi Showing Relations op Rrain-Vbsiclbs and Thuk DBRiXATrvxa. Ventral Don$i\ xonc ai brain-wall tHacnm ihowiuc five cerebral vnicle* ■nd doraal and veiilral loncs ••( their wall ; faaieil on brain of cmbr>'o o( (our and one-half weeka. ( Hti. ) PaiMAav Skcmrnt Suci.NriAKV Skumknt DKaivATivna Allleri-tr vnicle Proaencaphaleo Tvlencrptmltiii [)icncr|thalt>n Cerebral hemispheres Ollactory lobes Corpura striuta OlHic llialanii Optic nerves and Ira.-Ii* Suhthalamiv tCKnicntn lnter|iediniculHr Ktniclurrft Pineal and pituitary btMlifs lateral ventricles \ __,,,■-_. K<>r»mina<.( Monro / "*"""'> Anterior |»art of Ihira I'entricic Posterior part of third venirici* Mid.ll-\lriKeniinA A'|i»'»t(ii t i»l S)lvtu«t PilSliTli.I \. -!■ If Rhombsnkephalttn or lllnd-ltiiihi M.lill. .-plLil., M\< U it> < |e!luni hiii-riiir iiii'tttillarv velum Kiturth ventricle Notwitlistiiin'iii]^ the great • lian'^fH in jHwition aiul n'liition which inaiiy |>art» of the human hniin siiflir iliirinif ortion of the occipital lM)ne, willi its dorsiil surface within the vallecula In'twecn the hemispheres of the cerelH'JUini. .Superficially, in many respects the medulla appears to Ik- the direct continuation of the spinal conl. Thus, it is dividetl into lateral halves l>y the prolongation of the anterior and jxisterior metiian fissures : each half is sulKlivided bv a ventro-lateral and a dorst)-iati'ral line of nerve-n)ots into tracts that seemingly are continuations of . I 1 i j ! 1064 HUMAN ANATOMY. the anterior, lateral and posterior columns of the cord. This correspondence, how- ever, is incomplete and only superficial, since, as will be evident after studying the internal structure of the medulla, the components of the cord, both gray and white matter, are rearranged or modified to such an extent that few occupy the same posi- tion in the medulla as they do in the cord. The anterior median fiaiure is interrupted at the lower limit of the medulla, for a disUnce of from '1-7 mm. , by from five to seven robust strands of nerve-fibres that pass obliquely . dss the hirrow, interlacing as they jiroceed from the t»o sides. These strands constitute the decussation of the pyramids (decnssatio pyramidum), whereby the greater number of the fibres of the important motor paths pass to the opposite sides to gain the lateral columns of the coixl, in which they descend as the lateral pyramidal tracts. The fibres that remain uncrossed occupy the lateral por- tions of the pyramids and, converging towards the median fissure, descend on either side of the latter within the anterior columns as the direct pyramidal tracts. The Optic tract MammilUry body Poni (faasilar groove) Middle cereliellar pedmcli Anterior mcdimii iiMure' Orrbellum' Roil bundle* n< ninth and tenth nert'e!* InlmdibaluB-. Cerebral peduncle Interpeduncular apace Tiigcninal nerve Middle cerebellar peduncle Inl«rk>r cerebellar peduncle (Realilomboay) Olivary eminenc* Arcuate fibre* PytBmidal decvaaation RoiH bundle* ol twelfth nerve /' Anterior root* o( firat •|>inal nervt Hrainstem viewed iron in iront, showinc ventral aapcct of medulla, pom and mid-brain. decussation varies in distinctness, sometimes the component strands being so buried within the fissure that they are scarcely evident, or even not at all apparent, on the surface and can be satisfactorily seen only when the lips of the groove are separated. .Above the decussation the anterior median fissure increases in depth in conse- (|uence of the greater projection of the bounding pyramidal tracts. Its upper end, just below the inferior border of the pons, is marked by a slightly expanded triangular depre^ion, the foramen ftecum. The posterior median fissure, the direct continuation of the corresponding groove on the cord, extends along only the lower half of the mediilla, since above that limit it disiipiiears in consequence'of {a) the separation and divergence of the dorsal tracts ol the bulb, which below enclose the fissure, to form the lower lateral iMundarics of the loxenge-shapetl fourth ventricle (fossa rhomboidalis). and (*) the gradual luickward tlisplactment of the central canal within the closed part of the medulla until, at the lower angle ol the ventricle, it opens out into that space. Kiich half of the meme distance to the side of the ventral and dorsal median fissures rcs|)ectively. One of these, the antero-lateral furrow, marks the line of emergence of the root-fibres of the hypoglossal nerve, which, being entirely THE MEDULLA OBLONGATA. 1065 motor, correspond to the ventral roots of the spinal nerves with which they are in series. The other groove, the postero-lateral furrow, continues upward in a general way the line of the dorsal spinal root-fibres and marks the attachment of the hbres of the ninth, tenth and bulbar part of the eleventh cranial ner\'es. Unlike the posterior root-fibres of the cord, which are exclusively sensory, those attached along this groove of the medulla are pardy efferent and partly afferent, the fibres belong- ing to the spinal accessory being entirely motor, while those of the glosso-pharyngeal and the pneumogastric include both and, therefore, are mixed. The Antenor Area. — This subdivision of the medulla, also known as the pyra- mid, includes the r^on lying between the anterior median fis.sure and the antero- lateral furrow. Superficially it appears as a slighUy convex longitudinal tract, from 6-7 mm. in width, that continues upward Fic. 916. Cerebral cortex the anterior column of the cord. Each pyramid constitutes a robust strand, which below beginsat thedecussationand, increas- ing slighdy as it ascends, above disappears within the substance of the pons. Just before its disappearance, or, strictly speak- ing, after its emergence, the pyramid is slighdy contracted on account of the increased width d,. tlie bounding furrows. Its chief components being the descending motor paths formed by the cortico-spinal fibres, of which approximately four-fifths [Kiss to the opposite side by way of fhe decussation to gain the lateral pyramidal tract, it is evident thnt only to the extent uf the direct pyramid -Olivary eminence -Arcuate librra Lateml area of medulla Brniiistem viewed from the side. ahowlnR lateral aspect of medulla, pona, and mid-brain the restiform body. The components of the lateral column of the cord traceable into the inetliilla — thi- direct cerebellar and Gowurs' tract and the long paths of the lateral groiind-buiKllf— for the most jjart, with the exceptiim of the direct cerebellar tract, pass iHMicath or to the outer side of the olive. The superficially placed direct cere- bellar tract gradually !i-a\es the lateral area anil pas-ses outward and Ixjckward to join tht! inferior cerelx-Uar pediinile by which it reaches the cerebellum. The Posterior Area. — The iM>steri()r region oi the medulla is bounded laterally by the fibres of the ninth and tenth nerves ; and niesially, in the lower half of the bull), by the posterior median fissure and, in the upi^r half, by the diverging sidi-s of the fmirili ventricle. Below, the posterior area receives the prolongations of the tracts of Col! and of Hurdath, which within the metliilla are known as the funic- ulus gracilis and funiculus cuneatus respectively, ant! are separated from each other by the ]>ariiinedian sulcus. Beginning with a witlth of al)»iit 2 nun., the gra- cile funiculus increases in breadth .~s it ascends until, just Infore reaching the lower end of the fourth ventricle, it e.xpaiuls into a well-marked swelling, the clava. alxiut 4 mm. wide, which is caused by a subj.icent a'cumiilation of grav matter. Then, diverging from its fellow ol the opposite side to Ixnind the ventricle, after a short course it loses its identity us a distinct strand and Ix-coines continuous with the i THE MEDULLA OBLONGATA. 1067 inferior cerebellar peduncle or restiform body. The expansion within the upper part of the funiculus gracilis, the clava, contains the nucleus gracilis ( nucleus funiculi gracilis), the reception sution in which the long sensory fibres of GoU's tract are interrupted. The triangular interval included between the gracilc funiculi, where these begin to diverge, corresponds to fhe level at which the central canal of the cord ends by opening out into the fourth ventricle. A thin lamina, the obex, closes this interval and is continuous with the ventricular roof. Along the outer side of the gracile fasciculus and separated from it by the para- median furrow, extends a second longitudinal tract, the funiculus cuneatus, which at the lower end of the medulla receives the column of Burdach. Slightly above the lower level of the clava, the cuneate strand also exhibits an expansion, the cuneate tubercle (tuberculum dnereum), that is less circumscribed, but extends farther upward than the median elevation. Beneath this prominence lies an elongated mass of gray matter, the nucleus cuneatU8( nucleus funiculi cuneati), around whose cells the long sensory fibres of Burdach' s tract end. Still more laterally, between the roots of the ninth and tenth ner\'es and the cuneate strand, the posterior area of the medulla presents a third longitudinal eleva- tion, the funiculus of Rolando. The latter is caused by the increased bulk of the Fig. 918. Inferior coHlculiu Cerebral peduncle Median fo Median tulriu Middle cerebellar peduncle Acoustic atrbe Acoustic trivone Restiform body AtUchmeiit o( ventricular rool Obex Funiculus cuneatus rmralnin Superior trochlear nerve Orebellar peduncle . Floor ol fourth ventricle Fovea superior Eminmtia teres Trigonum hypogloai*! Trlssnum vaci (fovea inferioi ) FttniculUB sepatans — ~- Area pnslrema Funiculus gracilis - — Laleial area Mey thi | umii. c of the fourth ventricle, the lower lateral boundary of which it largely forms, into a robust rope-like strand that diverges as it ascends, Above, it abuts against ami fuses with the literal continu.ition of the pons and then, l)ending hackw-nrd, enters the overhanging cerebellum as the inferior cerebellar peduncle. This straml, also known as the restiform body ( conius restiforme), is seemingly the direct prolongation of the gracile .md cuneate funiculi. Such, however, is not the rase, since the fibres passing from these tracts to the cerebellum bv "ay of the restiform ImmIv are the axonen of the gracile and cuneate nuclei and, therefi)rc, new links in the chain of condmtiun. k/ . ! 1068 HUMAN ANATOMY. The inferior cerebellar peduncle is the most direct path by which the cerebellutn is connected with the medulla and the spinal cord. In addition to the tracts originating in the cord and desdned 'or the cerebellum (the direct cerebellar and possibly part of Cowers' tract), it coniprises probably fibres passing in both direc- tions; that Ls, from the cells within the medulla to the cerebellum, and from the cerebellar cells to the medulla. A more detailed account of theK components will be given in connection with the structure of the medulla (page 1072). l'p>m c\n>x inspection of the surface of the medulla, the direct cerebellar tract is seen as an obliquely cuursing band that at the lower level of the olive leaves the lateral area and gradually passes backward, over the upper and outer end of the Rolandic tubercle, to join the restiform body, within which it continues its journey to the cerebellum. The anterior superficial arcuate j^bres also enter the restiform body, after sweeping around the inferior pole of the oUve, or crossing its surface, and the upper part of the funiculus of Rolando. Additional contributions, the posterior superficial arcuate fibres, proceed to the restiform body from the gracile and cuneate nuclei of the same side. Just before bending backward to enter the cerebellum, the restiform body '» crossed by a variable number of superficial strands, the stric acuaticc, that may be traced from the floor of the fourth ventricle and around the inferior (leduncle to the cochlear nucleus. INTERNAL STRICTURE OF THE MEUt'M.A OBLONGATA. As already pointed out, the correspondence between the spinal cord and the metlulla is only superficial, sections across the medulla rev^raling the presence of con- siderable mass<-s of gray matter and important tracts of nerve-fibret not representetl Fiii. 919. Flf. tjji FIk. wr Wnlral i A ) (till ilorMi < H\ ■■poin of hrain Mem, thowinc livch -f Mctionii whiih follow. in the curd, as well as the rearrangement, modification or (lisap|>earance of spinal tracts which are prolongeil into the bulb. In consequence, the medulla, even at its lower end, ori-sents new features, and towards its upper limit \aries so greatly from the cmd titat but slight resemblance to the latter is retained. The character- istic features displaved by transverse sections of the metlulla at different levels de|)env and interspersetl among the fibres of llie formatio reticularis. The Poatenor Nuclei and the Arcuate Fibres.— The robust tracts <>f white matter { nerve-fibres/ prolonged into the gracile and cuncatc funiculi from the tracts of Goll and of Burdach become invaded by new masses of gray matter, the nucleus gracilis anonents enp«'ars within the funiculus ciuicatus as a dorsiilly Prnfcwor Spillar liecomes a prominent mottletl area, sharply ilefined Hurrlach tibrcs. The cuneate nucleus extends to a I070 hUMAN ANATOMY. ! I t^racilis and, even after the disappearance of the latter, continues as a striking coll'c- tion of gray matter beneath the dorsal surface of the medulla, from which it is separateid by the posterior superficial arcuate fibres. Within the upper part of the fasciculus cuneatus the gray matter becomes subdivided into two mas.M-s (Fig. 924), the more superficial and continuous of which is called the nucleus cuneatus extemus, and the deeper and more broken one, the nucleus cuneatus inlemus. Owing to the increased bulk of the fasciculi of the posterior area occasioned by the appearance and expansion of the contained nuclei, the dorsal horns uf the gray matter are displac(>d laterally and forward, su that they come to tie on a level with the central canal. Meanwhile the posterior cornua themselves, especially the capping substantia gelatinosa, materially gain in bulk and now appear as two club-shaped masses uf gray matter that cause the dorso-lateral projections of the Rolandic tubercles seen on the Fig. 933. Nudcin Kracili* Fanicalai (cncilli FMiicnliift cuneatus Spinal root o< V nerve Substantia (elatintiaa Accessoo' oHvan' nucleui Anti*rf>latcnil jcrouiid-huiidle .'\nitrrior supeificial arcuate fibres' Nuclcua cuncatua Centi»t gray matter Uccp arcuate fibres Fibres o( XII nerve Sensory dccuMatkiii Pyramidal tracts Traosveme Ktion of medulla nl level C. Fll. 9iq, <,li..«in sensory decuMution, postrlior nuclei and pyramidal traits • 5H- Preparation by Pro(e»sor Spillcr surface, fkniath the latter and v losely overlying the outer bi)rd( r of the extensive area of thi siiljstantiu gelatinosa, a crescentic tract of the longitudinally coursing nerve- fibre.-i marks the position of the descending root of the trigeminal ner\-e (Fig. 922). The cliief purpose of the gracile and cuneatc nuclei being the reception of the long sensorv tnicts continued from the cord and the distribution of impulses so rcoeivetl t'> :hc ccnbellum :ind to the higher centres, it is evident that new paths of the seconil order must arise within these nuclei. About on a level with the upper limit of the pynimidal or mot<.i decussation, fibres emerge from the gracile and cuneate nuclei, sweep forward ami inward in bold i-ur\'es and cross the median raphe to the op|K>site side of the medulla, immediately behind the pyramids (Fig. 922). They then turn sharply upward and form the beginning t)f the imjjortant sensory pathway known as the median fillet (lemniscus medialis) thn? connects the medullary nuclei with the higher centres, as the superior corpora qiiatli i^emina and the optic thalannis. The first fibres that emerge ii, this manner from the gracile and cuneate nuclei constitute a fairly well defined strand to which the name sensory decussation or decussation of the fillet is given. It must not Ix- supjiosed, however, that with this decus,satioii 'he cros.sing ceases, for, quite the contrary, it is only the iK-ginning in extenileil series of sensory fibres that pass across the raphe at various levels tliKiughout the hrain-stem. .As many longitudinally coursing fibres are encountered by those sweeping from side to side, an interweaving of vertical and horizontal fibres occurs, which results in the |>riKluction of the characteristic formatio reticularis that constittit*-* a large jxirt of t!v inediilla, as well as of the dnrs;il or tegmental portion^ -1 THE MEDULLA OBLONGATA. 107 1 J of the pons and cerebral crura. A feeble expression of a somewhat similar structure is seen in the reticular formation within the lateral column of the spinal cord. The Arcuate Fibres. — These originate as the axones uf the ci lis of the gracile and cuneate nuclei and include three sets. The first, the deep arcuate fibres, f 'puKlosr. Florence R. Sabin. X 5- matter, the inferior olivary nucleus (nnckms olivaris inferior), which in bvorable transverse sections appears as a conspicuous sinuous C-like figure. The nucleus resembles a greatly crumpled bag, of which the closed end lies beneath the corresponding superficial protuberance and the mouth, or hHum, looks mesidly and somewhat dorsally. When reconstructed and viewed from the side (Fig. 925), the plications of the lateral and dorso-lateral surfaces display a general antero-lateral disposition. On the ventral surface the grooves radiate from the ventral border of the hilum (Sabin). The greatest length of the inferior olivary nucleus is from 12-15 mm., its transverse diameter is about 6 mm., and its vertical one about one millimeter less. The somewhat compressed hilum measures sagittally from 8-9 mm. The plicated lamina of gray matter composing the wall of the sac is from .2-. 3 mm. in thickness and contains numerous small irregularly spherical nerve-cells, each provided with a variable number of dendrites and an axone, embedded within a compact feltwork of neuroglia fibres. The interior of the gray sac is filled with white matter consisting of nerve-fibres that, for the most part, stream through the hilum and thus constitute the olivary peduncle. These strands, known as the cerebello-olivary fibres, connect the cerebellar cortex with the inferior olivary nucleus and probably pass in both directions. Many fibres, the axones of the olivary neurones, issue from the hilum on the one side, cross the mid-line and, sweeping through the opposite olivary nucleus either by way of the hilum or directly traversing the gray lamina, continue their course to the restiform body and thence to the cerebellum. Other fibres originate in the cells of the cerebellar cortex and proceed in the opposite direction along the same pathway to end in relation with the cells of the inferior olivary nucleus. The further links in the chain of conduction are uncertain ; according to KoUiker it is prob- Fig. 916. able that from some erf _^arr!^::=j!r7r;S^:5Z3?!tes. Cerehelloollvary •traiids the olivary cells, fibres pass downward into the antero-lateral ground- bundle of the cord. The accessory olivary nuclei are two irregular plate-like masses of gray matter that lie respectively mesially and dorsally to the chief olive. The first of these, the mesial accessory olivary nu- cleus (nucleus nlivarU accesHorius mesialis) is a sagittally placed lamina, from lo-i i mm. in length, which lies between the tract of the fillet and the root-fibres of the hypoglossal ner\'e. It extends be- low the inferior olive and, therefore, is encountered in transverse sections at a lower level— immediately above the pyramidal decussation— than the main nucleus. According to the recon- structions of Sabin, the nucleus comprises three dorso-ventral columns of cells, of Section of inferior olivary nucleus, shnwinn pllratrri sheet of gray substance traversed by strands of i-erehello-olivary fibres. X i« THE MEDULLA OBLONGATA. 1073 which the lower and middle are <»ntinucn« -d.'J-PPjJ^^^Tr^.luT' tZ snudl isolated -^ «' g^n^^S .Sen^tiTU^^^^^ ^ that its plane Wenor or spinal end of the ""/^^^J*^*™^ the chid olive. Higher, when the bobh^ueandpara^elwiththevenuaisu^e represented by a narrow latter a well ctccadliiKraolaf vMttbuUi Mm Medlaji Nucloa nulbulu . Vlbno) IX MTYC , Spinal root of V B«iv« SubMsMU gcUliwMO Facnatio i«ilculayra.i.iai tract, which ^^PP^^J-^^h^^trer'nS of the field with the exception of a very narrow peripheral zone that intervenes Fig. 931. cell Nerve- Lon«itndliml TrjnsvetM nbret fibres Median raphe Portion ol ln.n,v.r« «ctlon of medull.. .howing median raphe and adjacent (orm.tio rellculari. alba. X .y. between the pyramidal fibres a..d the suriace along the median 1 -e and the ventral Sp^ct of the'^^edulh. This .ne i. tr..yersed by (2) the .nten. ^"P-jJ^-^^^^^^^ fibres, among which is lodged an irregular column of nerve-cells that constitute (?,) 1076 HUMAN ANATOMY. the arcuate nucleus. The latter lies at first chiefly on the ventral and, higher, on the mesial aspect of the pyramidal tract. The cells of this nucleus, small and fusiform, are the origin of not a few of the superficial arcuate fibres, although those from the dorsal nuclei continue their course over the nucleus without interruption. At the upper end of the medulla, the cells of the arcuate nucleus increase in number and mingle with those of the nucleus of the raphe and the pontine nucleus. Dorsal to the pyramid and immediately next the mid-line lies (4) the compact tract of the median fillet, composed of longitudinal fibres that are the upward continu- ation of the deep arcuate fibres, which, from the sensory decussation to the upper limit of the cuneate nucleus, bend sharply brainward after crossing the mid-line. The fillet-tracts are also known as the interolivary stratum, as they constitute a compact and laterally compressed field l)etween the inferior olivary nuclei. Lateral to the fillet, between the latter and tl. • hypoglossal fibres, lies (5) the mesial accessory- olivary nucleus. (6) The posterior longitudinal fasciculus appears in cross-section as a compact oval or laterally flattened strand, which lies next the raphe and immediately beneath the gray matter covering the floor of the fourth ventricle. This important path will be later described (page 11 16). The remaining space of the anterior compartment, between the pyramid and the ventricular gray matter, is occupied by the formatio reticularis alba, so designated in distinction to the formatio grisea on account of its meagre number of nerve-cells, since, with the excep- tion of those scattered in the immediate vicinity of the mid-line (nucleus raphe), few cells are present. The Formatio Reticularis. — Repeated mention has been made of the reticu- lar formation produced by the interweaving of the horizontal and vertical fibres. Whilst particularly conspicuous within the medulla at the levels occupied by the gracile, cuneate and inferior olivary nuclei, on account of the prominence oi the arcuate and cerebello-olivary fibres, the formatio reticularis does not end with the disappearance of these nuclei and fibres, but is prolonged upwaro, although less marked, by transversely coursing fibres derived from the reception-nuclei of various cranial nerves— the vagus, glosso-pharyngeal, auditorv, feicial, and trigeminal— from whose neurones axones of the second order arise that sweep across the mid-line to join chiefly the fillet tract or to end, perhaps, about nerve-cells of other nuclei. In this manner the formatio reticularis finds representation within the dorsal or tegmental areas of the pons and the cerebral crura. The longitudinal fibres within the formatio reticularis grisea are derived from many sources. Some are the continuation of Gowers' tract ; some belong to the long strands concerned in establishing reflex paths connecting the corpora quadrigemina, nucleus rubrum, vestibular and olivary nuclei with the spinal cord ; some are the axones of tegmental neurones and pursue shorter courses, both descending and ascending, as association fibres linking together different levels of the brain-stem ; while still others are the pro' ongations of the spino-thalamic and other long tracts of the antero-lateral ground- bundle of the cord. The longitudinal fibres of the formatio alba are chiefly the components of the mesial fillet and of the posterior longitudinal fasciculus with, possibly, the addition of short association fibres proceeding from the nerve-cells that arc found within the anterior area. \ \\\ The details of a transverse section passing just beneath the lower border of the i>ons (Fig. 931) vary considerably from those of the level shown in Fig. 930. The ventral half of the medulla has lost in width in consequence of the disappearance of the superficial olivary emi- nence, the inferior olive being at this level represented by only a few irregular plications. The pyramids, likewise, are narrower, and separated by the broadened anterior median fissure. The mesial fillet and the posterior longitudinal fasciculus are now widely separated by the inter- vening nucleus centralis inferior that appears between them along the raphe. The nuclei of the hypoglossal and glosso-pharyngeal nerves are no longer seen, but instead, along the floor of the ventricle underlying the area acustica, appears a large triangular mass of gray matter, the mesial vestibular nucleus. F.xtemal to the latter the lateral or Deiters' tmcleus and the descending or spinal acoustic root lie close to the restiform body, which in transverse section presents a bean-shaped outline. Between the restiform body and the descending trigpminal mot, the fibres of the mesial or vestibular part of the auditory nerve pass backward to gain the vestib- ular nuclei. The outer surface of the restiform body is closely related to a considerable THE PONS VAROLII. 1077 Se the fibres o| the coch.«^ f^^'^^t^rrLl^^f th^^^rizontally inward, many nucleus is the starting pomt of a ^^"[^"^^ intem^ingle wWi those from the opposite traversing the fillet and "^'"^ ♦'^ 'S^^";^ TJ^pMes, that within the pons .xcupies tS^-low^ffof^r tegrinSon^hirtt separates from the ventral, .n F.g. ,3« Fici. 93i. SubttBBda (ClaUi MnUl >eHI>iutei nucl«u> Vcnml cochlear nuclcu* Corhlcu nCTTC and wnttJ cocMmrnocWiM Tnpuoidal «brt«' / Pyninktel tnct ' T™™v.«e «ct.on o, .«.«,. .. .eve, H, Fi, ,. = .^-^-SXl' -^i"'^^.^^.''^^'^^^""''' root! of auditory nerve »re enterinj in retotlod 10 re«lltorm Doaiei. a 4 h- only the beginning of this .r^t is visible, ^ut => W ^^he cllcW^^^^^^^ trapeaiidal fibres are shown in force. Strands °' fi''^™"' 'Cmld w^vu ■ these mark the restiform body and proceed beneath 'he ventrjcular fl~r to *^^^^^ ^^^ course of the stria acusHca ««*"^"T I- o!wr„« the «»^/W Mr /a«a/»^. '- -^^- «- strands of root-fibres pass dorso-medmlly. THE PONS VAROLII. "•^"Vhe ventral surface of the pons, strongly convex transversely ^fd less so ^n 1078 HUMAN ANATOMY. ridges are produced by the underlying pyramidal tracts in their journey through the pons from the cerebral peduncles to the medulla. The transverse striation indicates the general course of the superficial fibres towards thf cerebellum. The lateral surface, continued from the ventral without interruption, above is rounded and sloping and separated from the cerebral peduncles by a distinct furrow. Below, it passes insensibly into the middle cerebellar peduncle, into which the lower and lateral part of the pons is prolonged. Whilst the superficial striation in a general way follows the contour of the |x>ns, a broad band ( fasciculus obliquuH pontis) from the upper part of the ventral surface sweeps-obliquely backward and downward and overlies the more horizontally directed middle and lower fibres. The free portion of the dorsal surface of the pons contributes the upper half of the floor of the fourth ventricle and is, therefore, not visible until the roof of that cavity is removed. Above the middle peduncle, the sides of th^? pons are blended with the overlying superior cerebellar peduncles, which, in conjunction with the intervening superior medullary velum, complete "dorsally the ring of tissue sur- rounding the narrowed superior end of the fourth ventricle. INTERNAL STRUCTURE OF THE PONS VAROLII. Viewed in transverse sections the pons is seen to include two clearly defined areas, the ventral and the dorsal (Fig. 933). The ventral part (pars basilaris) presents a characteristic picture in which the lai^e pyramidal tracts are covered in Fig. 933. AhliKcat ftarm f^mersliic ficUl (ifam VaHbolu Bbia SplDtl root of V .01ivar>' peduocle 'onnatio reticularis irte,£nicat'.iin P>Tami(tal ransverse Abrcs Transverse section of jhjiis at level I. Fijf. 919: showing Keneral subdivision into veniral and dorsal (tegmental) :iu-n» and nuclei ol sixth and seventh nerves, x 3. i \ \ 1 and excluded from the surface by a conspicuous layer of superficial transverse fibres (stratum supcrficlalc pitntis), that laterally sweep backward into the cerebellar peduncle and are traversed by the root-fibres of the seventh and eighth nerves. The pyra- mids no longer appear as compact fields, but are broken up into smaller bundles by the transverse strands of ponto-cerebellar fibres. This subdivision becomes more marked at higher levels of the |X)ns (Fig. 936), in which the int<: weaving of the longitudinal and transverse bundles produces a coarse feltwork (stratum complexum ). At the upper border of the |X)ns, the scattered pyramidal bundles become once more collected into two compact strands, which are continued into the central part of the cmsta of the cerebral pedimclc. The dnrs.1l limit of the ventral field is occtipied by a well marked deeper layer of transverse fibres (stratum profundum pontis). A considerable amount of gray matter, collectively known as the pontine nucleus ^■mPPPBIWP!" THE PONS VAROLII. 1079 Portion ol cioM-MCtion oT pon., .bowing cells ot pontine nucleus. .' 300- t^£^':^'^n^^'^' » -1- Sid. o, ,h. .,^u. »ph.. Th. ,pp«r- ance of certain new masses p,G. 534, oJ eray matter and of nerve- fibres, together with change in the position of the hiiei, produce details that vary with the level of the section. When this passes above the lower margin of the pons (Fig. 933). two diverging and obliquely cut strands of fibres, coursing from the ventricular floor towards the ventral a.spect, mark the root- fibres of the sixth and seventh cranial nerves and divide the dorsal region, on each side, into three areas. The middle area, between the abducent fibres mesially and the facial fibres laterally, contains three important coUectionsof nerve- cells. One of th«f- tj;^ ""- .. .^ ^^ the floor of the ventricle and beneath the deus of the sixth nerve, lies close to inc produce, and ives rounded prominen.^ of the ^^^^1^^^^^^^^''' jh^lbrJ V.^.. an oblUiuely origin to the root-fibres of the ^^"^^"V^X and cut through not only the dorsal ventral path, slightly ^^^f, ^'oons to g^n hs lower bord^er, along which they but also the ventral part of ''^^/"^^ ."/'"in favorable sections the nucleus of the 3: i:::^::^''^r^:^^"^^^^^ ^-^ ventriCe by the arching fibres of ^'^^ SthTc^onspicuous nucleus 0/ , the middle ar^.^e-^^^^^^^^^ oHvarlsVior). «- --£ TuS oT^h foVs^u^ tra^' o'f tlsve'rse fibres, an indentation on the dorsal ^"r'\« "^ ^^.^ from the ventral cochlear nucleus known as the corpus trapezoidcs. that ^^f "4;;™,"'bo"„dary of the dors;il area, n^edially and ^t^-^dly aids in defining^^^^^^^ ^^^^.^^ j „^,.^,„ The superior olive (Hg. 933) 's *" '^;, .H"' ^- ^.V; ..ith the cerebral cortex, and interposed in the path connecting the auditory nuclei x^n .^^ ^^ ^^^^^^.^ closed related with the ^^;-';^,^\^^^^^^^ others to the abducent uting numerous fibres to the '■'ttf;' j^^ f^l^. ^. ^^rf„„^/^ of the superior obve. that nucleus which are seen *^,'lt'=^ ^.^"^^^t' and bring tbis centre into relation with pass towards the nucleus «V 11 til of ne^e-ceUs between the fibres of the trape- ^S; r''i*X-S'.tSrir»^«in;rji These «b,os «e prob^Uy derived from the olivar>- nucleus (Obersteiner). j ^^^^^^ The facial nucleus, a conspicuous but boken ma . ^.^ ^^^. >^^^^, (Fig. 933). includes several groups of J^^f ^^ emergTng facial fibres. From the t\e superior olive and to the inner sule o^he emerging^ ^^^^^ ^^^^^ ^^^ io8o HUMAN ANATOMY. a compact strand that, as the ascending portion of the nerve, courses beneath the eminentia teres seen on the ventricular floor, close to the mid-line, until it bends outward and, arching around the abducent nucleus, (..ntinues ventrally as the emeiving root-fibres. The ventral part of the inner area and the adjoining part of the middle one are occupied by the field of the mesial fillet which, at the level under consideration, no longer has its longest axis directed dorso-ventrally, but approximately horizontij. The tract now appears as a modified oval, somewhat compressed from before hack- ward, the thicker inner end of which reaches the raphe while the tapering outer end lies near the superior olive. The posterior IcgitueHnal fasciculus is seen as a com- I>act strand, immediately beneath the gray matter of the ventricular floor and at the side of the raphe. To the outer side of the emerging facial fibres, and therefore in Fig. 935. McrniccpbaHc root el V- Posterior longitudinal iatclculin Saperlcr cerebellar pedanclc Inferior cerebellar peduncle Scmory lri(eminal nucleni Middle cerebellar pedum Motor trigeminal 'nucleus ^^j^;^^ Motor fibres of V J 'Trigeminal nerve Superior olive Median fillet Deep transverse pontine fibres Pyramidal tracts Middle transverse pontine fibres Transverse section ol pons at level J, Fig. 919, showing root of trigeminal nerve with its nuclei. Preparation by Profctior Spiller. X3- the lateral pontine area, appear the substantia gelatinosa and the associated spinal root of the trigeminal ner\'e. Just behind the latter the descending vestibtdar root lies close to the inner side of the lestiform body. The collection of nerve-cells marking Deitirs' nucleus is seen beneath the ventricular floor in close relation with the descending vestibular root. Sections passing at the level of Fig. 935, and, therefore, about three millimeters above that of Fig. 933, show interesting details connected with the nuclei and roots of the trigeminal nerve. At this level the nuclei and roots of the sixth and seventh nerves are no longer seen. The median filet appears on each side as a compressed oval, the long axis of which is hori- zontal and whose inner end almost touches the raphe. Just above the outer end of the fillet, the cerebral extremity of the superior olive is still visible, to whirh a few strands of trans\erse fibres— the last of the trapezoid body— pass. The lateral boundary of the ventral part of tlie pons is defined by a hugh tract of obliquely cut fibres that marks the entering sensory root of the trigeminal nerve. On following this tract dorsally it is seen to enter a large mass of gray matter, the sensory nucleus of tht; (rigeniiiial nerve. This ganglion, composed of closely packed small multipolar cells, corresponds to an accumulation of the substantia gelatinosa, which, it will be remembered, is to be seen in all the preceding lower levels intimately related THE PONS VAROLII. 1081 .^•_-/ ««./ o« the fifth nerve. A second and more compact ganglion, the to Ae tUueuAngo, ^P"^ ."^ Z^^^Ja^ldit and slightly farther back. It contains large ,„ctar MUcU^ol the ^'^"'^J^^^J^i ^ the sensory nucleus, and is separated m„ltipotarcete.ext«djtoa«««wta^^^^^ jj^ ^ ^^ passjrHrsially from the tatter by a strando^ fibr« whKh ^ °^ ,„ ^^e motor nucleus of the oppo- ^"^ 'IS.^'^SI^.^^of dTeSSs^ Stueitsof the motor trigeminal root. A«W.tK>nal site side. These fibres are part of »« "°™~ m^sfncet>luilu root, are seen in the interval between components ol the tatterthe drsce»dtv ^j,"^f3^ thTvwtricle. The .notor root itself is U^^SSr-^ ^n-Sr^rous^rnd^b^ie^sLds of fibres that emerge from the motor '^^^Z close to the inner ^^'^.'^.^S'^Tii^r^or. beyond the conventional Uiteral to the sem»ry nucleus andnx^nof the fifUija^ > ^^^^ cefbeltar limit, of the pons, the 'f^ ''^y^^^^'^^^^.^einio which the corresponding ^Sf^ J.L'^lsrdn^'^.e ^tr'mii^.e tract, joinir* the tegmentum to the Fifiyix wpote ■•*ill"ni ' Fkioc of f>uitk inmkic Hcicaccplulk root uf trifcmlaut rynmidal tiftctk Tr.„.v«« ^.on o.„po^^« -- r&%.-.-X^^^^^^^ ''"""'' border onto the free poste ior surface of the projertrng part of '•'f. P°"*- "T'T' „^ ^.,,1, „, SL'nded with the rob^ arms, the -{'I- ^HT*' Th^ttrt^ S^^ S in bf the .-^l^."' io83 HLMAN ANATOMY. ^lurarfD^nu to this part <)< the ventricle (poKv 1097). Mesial to these celb the /oji^norAm^- Itulinal fascituhu shows, in transvenie section, as a triangular field close to and on each side of the ra(>he. The most conspicuous feature 01 the dorsal part of the section is the comma-shaped fibre- tract of the superior cerebellar peduncle (brKhlnai CMjuacUviM ). The thicker part of the tract lies dorsally and its thinner edge cuts into the lateral part of the posterior area of the pons about half way between >ts dorsal and ventral boundaries. Between the cerebellar tract and the lateral angle of the ventricle, a slender crescentic strand of transversely cut fibres marks the tUicmding motor or mesencepkalic root of the trigeminal nerve. The tract of the median foUet no longer touches the raphe, but lies as a compressed and horizontally elongated oval along he ventral border of the dorsal field. The three-cornered area included between the outer end of the mesial fillet, the cerebellar arm and the surface, contains a curved triangular tract that sweeps backward and insinuates its pointed dorsal extremity along the outer side of the cere- bellar strand. This tract is the lateral fillet (Icmniacus lauralls), an important part of the pathway by which auditory impulses are carried from the reception-nuclei of the eighth nerve to the inferior corpora qiadrigemina, the internal geniculate body and the cerebral cortex. A collection of small nerve-cells, embedded within the outer angle of this tract, gives rise to a number of its component fibres and is, therefore, known as the nucleus of the lateral fillet (dikUu* IcnniKus lauralis). An additional group, between the lateral fillet and the cerebellar tract, constitutes the nucleus tegmenti lateralis (Kolliker). The remainder of the tegmenul area is occupied by the formatio reticularis. THE CEREBELLUM. The cerebellum — the "little brain," in contrast to the cerebnjm or "^jreat brain" — is placed in the posterior fossa of the skull and beneath the tent-like shelf of dura, the tentorium, which separates it from the overlying posterior part of the Fig. 937. Pons Anteriot ckcfscentk lobule Grmt horiiontal, fissure' Postenxaperior lobr Poslero-inferior lobule Middle cerebellar peduncle Medulla Accessory flocculu Flocculus Biventral lobule P>-raRiid Posterior cerebellar notch Tuber Cerebellum viewed from in front and below; pons and medulla occupy greater j>art of vallecula and mask worm. cerebral hemispheres. It lies behind the pions and medulla and the fourth ventricle, with the roof of which space it is intimately related. By means of its three peduncles — inferior, middle and superior — the cerebellum is connected with the medulla, the pons and the mid-brain respectively. The general form of the cerebellum is that of an ellipsoid, compressed from above downward and constricted, save on the dorsal aspect, by a median groove of varying proportions. Its greatest dimension is the transverse diameter, about 10 cm. (4 in. ) ; Its least is the vertical {j, cm. ), while in the sagittal direction the cerebellum measures about A cm. in the mid-line and about 6 cm. at the side. The cerebellum weighs about n\\. (5 oz. ) and constitutes approximately one-tenth of the entire brain-weight The conventional division into a narrow median part, the worm, and the two lateral expansions, the hemispheres, while convenient for the description of the cerebellum of man, is not warranted by recent coiapaiative aiul developmental THE CEV .BELLUM. 1083 Ul inese uic •••»«• .w ------ r rindsura cerebelH anterior), which is lUy by the cerebellar hemispheres i occupied by :he inferior corpora Fig. 938. f SylvUn •quedwt y SufjcnormeduUvy v«hia J cii- ,. Cmith Rradle' A)lk and other9\ since some d«^ ='• s-^^ii '"SeSr'huSrinftry '^^^^ -^ -"^^ -^- ^M^<^ significance - ^M;,^^^^^ fi.sure, in • . • or less 'The surface of th • cerebellum » 7*^ ^^''J, ^^J^d^^^ed by shallow ..efts into well defined ar«9, th ^"'''•J^^?^ ^"^^^^ tSTusually pursue a curved course narrow trac.-. He> 1. from f ^ ^«^'™l%i,el to one a-other and to the within a giver lobu' and. «" » J^^^ *^^; ™ute4ike folia, or on makinR a section sulci bounding t .. .fact. O" *^P^ "^ '^n^hat the i«ttem of the folia is gr«uly across the plications (Fig. 943)- " ^'» »f^^ ^.J^^^i., „„ ,he deeper and hidden extended by the presence of numerous^dmon^^^^^ ^ ^.^^ ^^^K^ ^^^ ^^^^^^ aspects of the >«'^tt„*^''J "* ri^^nhe cerete^^ is everywhere formed by a \Vhether free or sunken the "tenor ot "« cere j^ ^ „udullary layer coriicallayrroi f'^'^f j,-^"" ' ' ' (^^"^g \o this a^^^ sagittal sections "J Th^fceSC* e\^^'^*l'=e jy:;e^^^ branching tracts of white and gray matter, designated as the ^r^w/^ (^«• 9^^^^ comprising the narrow central j^a^T'irp"."^ «?^ " ■ - - much larger than the postenor » 'd »x>unded and behind by the antenor part of the worm, quadrigemina and the superior cerebellar peduncles and intervening superior medul- lary velum. The pos'c or border is interrupted .■ a Jler median indentui..->.i. the posterior i»otch (inclsura ccrebelll posterior), which is bounded on each side by the hemispheres and at the bottom by the hind part of the worm, and contains the crescenttc fold of dura known as the falx cerebelli. The upper surface ot the cerebellum is modelled by the overlying tentorium and presents a slight median trans- versely furrowed ridge that cor- responds to tho upper surface of the middle divi>«on. o™";^ j^, ^^^^ ^j^^.^^^j ^ of this surface lies r h^rt'srncrii^rirh-a^^^^^^^ not^.. ^^rs;^^^'^:^ 1^-;::^;^^^^^^^^ orm":rfra^.y towards the posterior "^he lower surface of the ce^bdl^m is m^^^^^^^^ ^s^middiir^hTwrht^^^ ^^^- ^^^ -"^ of the valley receives the dorsal surfa, ."l^^ie m^uUa. ^ The cerebellum i^i"-X^fiL'sure S«Ss Tor&is «rebelli).'^ThJ sulcus cleft, the great honzontal fissure (suUm^ junction of two begins in ^JP^J- ^^VSVi'^^i Jhe^^^^^^^^^^ ^^^^^^- '^' ^"^ "•'"""'' '?::; SSjio^md'the a>c'uXen« ofihe cerebellu^ but sometimes is intern^pted Telm chorloldea- 'Pyrminift «- . «i,llt.l MCllon ol br.iiiH.teni .nd cerebjllum. showiiiK fourth M' -' '••i'^'Sltt^J. Sylvian aqu«luct,.n.l cerebellar worn.. io84 HUMAN ANi»TOMY. on the worm, and cuts deeply into the lateral and posterior portions of the hemispheres and the worm behind. It is, however, visible on the upper aspect < the cerebellum only for a short distance as it approaches the posterior notch, the remainder of its course being masked by the overhanging border of the hemisphere. Although of cardinal importance in the usual description of the human cerebellum, the great horizontal sulcus is of secondary morphological significance, being a secondary fissure that is developed relatively late in man and feebly or not at all m many other animals. ....... , w . u Both the vermis and the hemispheres are subdivided mto tracts, or lobules, by the deeper fissures ; these are grouped into lobes, in the conventional division d the human cerebellum, by regarding each median division of the worm as associated with a pair of lateral lobules, one for each hemisphere. Lobes and Fissures of the Upper Surface.— The subdivisions of the superior worm are, from before backward :— (i) the lingula, (2) the lobulus cent raits, (3) the culmen, (4) the clivus, and (5) the folium cacuminis. With the exception of the lingula, which usually is unprovided with lateral expansions, these median tracts are connected respectively with (i) the alte lobuli centralis, (2) the anterior crescentic lobule, (3) the posterior crescentic lobule, (4) the posterosuperior lobule. Lobus Lingnta.— The Ungula, the extreme anterior end of the superior worm, is not free, but lies attached to the upper surface of the superior medullary velum, covered by the over- hanging adjacent part, lobulus centralis, of the worm, which must be displaced to expose the Fig. 939. Cllvui Great horiionltl Ahuk Ptntero-inlerior lobule Tuber Cerebellum viewed from above. structure in question. The lingula consists of a tongue of gray matter composed of five or six rudimentary transverse folia, that overlies the median and lower part of the superior medullary velum and, therefore, is behind the upper part of the fourth ventncle (Fig. 938 • Occasionally the lingula is prolonged laterally by rudimentary folia onto the superior cerebellar petluncles in which case these extensions, known as the .!> llngul. (vlncula llngulae) are reckoned as the lateral divisions of the lobus lingulse. ... j . * .u Lobu. Centr.liB.-The median part of the subdivision includes the second segment of the upper worm, the central lobule (lobalu. centr.ll.), that lies chiefly at the bottom of the anterior no ch and is visible to only a very limited extent on the upper surface "f the cerebellum The cemral lobule consists of from 15-18 folia, but not infrequent y is divided into two sets of leaflets which then are collectively somewhat more numerous. It is se|«rated from the ingul.i by the precentral fl.aure and from the culmen by the poatcentral fl.aure. On each side the central ^.lia are prolonged into a triangular tract that curves along the side of the anterior notch, form- ing a lateral wing-like lobule, the ala (ala lobaH centralla). The two al*. in conjunction with the median wom^, seRment, constitute the lobus centralis. . , , , . . ,„ „^,- Lobut Culminia.-The third division of the upper worm includes the most proimiieiu part of the upper surface of the hemisphere and. being the crest or summit of the general elevaUon. mam THE CEREBELLUM. 1085 . . 11^ .1- ^imM (nlBca ■oBlkuH). It is formed by a half dozen or more the monticnius. is ««»*»«, "^"i"^'"*!:"'^^^ a lunate area of the hemisphere known longer «ulshorterfol«t^t.ateraUya«^n^^^^^ ^ ,^„ ;, ^he most as the .nteriof cre.centic »»»»^«J»'" .'"C.Tem^ and te a broad crescentic tract hmited culmen and «ceives *« "7^?,f^^ifSrt o?X pr^liv^^ sulcus, which on account of its mor- of the worm by a d**? ^^'^'/il'^ !*,'^^l,^^^^a L„a (Elliot Smith). Laterally the cl.vus .s pholoRical importance has been ^J^ ^cent^Tlobule (par. pcWrior loball quadraagulari.) connected "" e»<=h "^f ^ f ^^S^t ^ is^^tedXmThe ^ behind by the pctcUval ;.*::t "^.r-P^Ht/^^tn:").'"^^^ two posterior crescentic lobules constitute the lobus clivi. , ^ . . .„ j _~,t..rinr are retarded by German anatomists as J^Z.-^^, "t'^ ^^T^^^^'^^ 'o- then become (mum v.r-UV varies ^J '" ;^. ^»!^^ iidudS^ly only one^r two. e.xceptionally ihe clivus abo... and the ^^'^Z,^^ir^^L level of the adjoining parts of as many as five or V*\^^\l°^'t.*S^^ It oAer times it is so sunken and buried that the worm, of which it fo"™ *f P°^^"°!^„ ^S the div-us and tuber, with either of ta p,esen« can be demo|»trated °^'y^« ^ "^S^ifieant in comparison with the large which it is occasionally jomed. At best 11 o • » ^he postero-supenor lobule crescentic tracts, the P~t«";»»PrTL fh^ «,;ilin^^^^^ S^ "he upper cerebellar hemisphere of (lobulu. ««U»n.rl. P~"ri»'Li!S"nd li^^rd^ In front it Separated from the p<»terior Uichitformsthemostexpandedand lateral ^r«:t in ^ limited by the great horizontal S" whlctl^v^^iCrirThe^^^^^^ cacuminis and the two postero-supenor lobules constitute the lobus cacummis. I .= »vn Fissures of the Lower Surface. -The inferior surface of received. The bottom 01 »"«= *~'^y hrain-stem is in place, s covered and not the inf*"^';^"™' *J;:L JhTrd (F^^^^^^ Aft- «"'<'-l °' '"^^ ^^ ^"' seen, except at its po«*«"° V„ '!r,Xl&r oeduncles and the medullary vela, not medulla by cutting tht-^-J^ the *:*J,"^ UtaSTthe lobulus centralis and its only the entire mfenor worm is "E?^- °";^ j separated on each side related parts o the hemisphere are i«sevi ^^.^^ ^^^^ ^^^^^ tZ^T^^) th?>wX (") tHe W'(3) the ..W.-/ Mu^e and (4) the postero-in/erior lobule. , K... NoduU-The nodul. (aodalii.). the most anterior segment of the inferior worm^ varies^rhi^raJ!:.^^^^^ '•'"^^fSlva^f Ihe hemisphere a.,ocia^«i w'^the nod^^^he «occu^^^^ distance from the worm and "PPeat* on either ''"l^. "• ''^^ .^'^^'^"^.^'p^^^^nd the group of short 'T"!^'- J,"» ^^)^ w^^r^^ o^ \tta t^u^ tU^^^ manrin ;rr^n'^ri':;?r^nUc"Kirof'Jh'e upper suHace':"ln addition to the chief Boccules. I086 HUMAN ANATOMY. composed of from ten to twelve leaflets, a second and smaller set, known as tiiepara/hccuius or acceaory fiocctUus, lies behind and lateral to the main group, often completely buned beneath the overhanging margin of the biventral lobule. In the embryo and in many mammals, the paraflocculus Ls of considerable size and then shares the relatively much greater development U the flocculus than seen in the adult human brain. The connection between the flocculiB and the nodule is established by the lateral part of the mferior medullary velum, which constitutes the peduncle of white matter for the floccular folia. In this manner the nodule and the two flocculi, with the intermediate part cA the medullary velum, coastitute the lobus noduli. . • » j Lobus Uvul«.— The uvula, the next part of the inferior worm, is laterally compressed between the deeper parts of the two tonsils. It varies in form and often appears as a narrow ridge-like structure, triangular on section, of which the median crest alone is seen when the tonsils are in place. The uvula is limited in front by the poatnodular flaaure, and behind by the prepyramidal. which late.. Uy, as the post-ton.illar fiaaure. curves .mtward along the postero- lateral border of the tonsil. The free median surface of the uvula i usually cleft into two or three major subdivisions, which in turn are scored by shallower incisions, so that from six to ten leaflets are present. Some two dozen additional folia mark the hidden lateral surfaces, the entire number being thus usually raised to thirty or more. :,.... . The^OT.a or iny^dala (u>B.ill.), the segnient of the hemisphere associated with the uvula is a pyramidal mass lying between the worm and the biventral lobule and forming the central lone of the general quadrant embracing the lower surface of the entire hemisphere The free convex inferior surface of the tonsil is irregulariy triangular in outline and bounded by a rela- tively straight median margin (along the sulcus valleculae), an outwardly arched postero-lateral Fio. 940. Lobulus ccnttmlis Soprrior cerebellar peduncle Middle cerebeltar peduncle Inferior me the J-f^vula^'^oT, the"?:::^ marked with short transverse folia, stretches from the posterior part "' '•'^^ "^"i-* .«"%'^^™ of the space occupied by the tonsil to the upper and lateral part of the ""^^^^X J ^'d thus known as the funowd band (.!«. uvula.) connects the worm w«h »'r'^n"^P^7^e, of the joins the uvula and the two tonsils into the lobus uvul;. The p<»terior ho™" °V|!l urowed band is free, whilst its anterior one is continuous wi.h the 'f ri°^. J"^''^';'^^^ "^'^^ After removal of the tonsil by cutting through ts ""If^-'^'f/"', ^'^'^,V » '^^uf,,eTnd 4ofed which is bounded medially by the tn-ula and laterally by ♦he hwentral lobu^ and r^^^^ in bv the furrowed band and the inferior velum. To this space the older anatomists gave the "'"\2i'i^.m\di.* -The'^mld (pyraml.) the segment of the inferior worm lying behind the uvula and^:tont IVZ.r, is '.Lrtly covered by the tonsils. Posterior .0 the latter THE CEREBELLUM. 1087 H is seen .t the botto. o. the .va..-|a ^^w^-^e n^'^ f ^^^^^^^ where it forms the most P'"™"™* ^'!^J? ^m uTadiaLnt parts of the worm by the mass, attached by a narrow stalk and «=P":"f*^"Jfl,^S,er«rby the sulci vallecula:, pc-j^unidal and po.tpyr.mid.1 ft..ur.. ami horn the »^P"^™ jj^ ^^ose towards the ?te^vex inferior surface usually P«T „rf^The' toter S .emoval of the tonsil, a uvula being longer *an. 'ho«e d'r^»^„^ov^^„*;,/:L^h sid^^^^^ ^rm^drAr^nt-riafflo? rbi^::!'.obe. which, in this manner, is b«,ught into divisions which to«^herappea^ the -^^f^f ^^J-;:^ ^readU, of .5 mm. and more. The more contracted than *« .'"J'="2~X variable the lobule being not only sometimes much arched po.tpyn^.d^fl«.ur.^ j„^ ^ „^t terior division of the • . -^ „J^d lies tenSSTthe greP.t horizontal fissure when that sulcus is continuous ^r t:e^id^;le'3n tj^^^^^^^^ Tnt^^S Sllprin^n* S^m'T^Lmlltll;: ol' white matter. The tuber is of a genera. Fig. 941. Root irf fourth ventricle Superior cerebellar peduncle Middle cerebeltar peduncle. Floccului Great taoriiontal fissuie' Superior worm (lobulus centralli) PoBtero-inferlor lobule' Biventral lobule' Position of removed tonsil Inferior metlulUiry velum I'vula Furrowed band Pyramid Tuber Cerebellum, aeen from below after removal of tontlli. conical form, with the base di,*cted towards the PV™-'^' ';?'" ^J^^^^J^iil/^J^^t'^lfpr^^^^^^^^ postpyramidal fissure, and its apex projec.inif into the Pp^t^""' "X'^^, viewed from" kfew. from 1-4, superficial folia, which model the posterior pole of the worm, as viewea '"""^TlutrTs directly connected on each side with r. .considerable c-^^^-^^^-f •J,''^ po.t.ro.inf.rior lobule (lobalu. «m«anari. Inferior), that is «'"'t^ '"'"'"* ^^ *J^,hori- nJension of the postpyramidal fissure ' "'«V'"'*''»^"";*»'> »"^^^;"^5,;*'*ex^nd zontel fissure. After emerging from the sulcus vallecula, the '""» .."P'°r,,!r' hnrder a "unate tract, from ,5-.5 n^- in it'' widest part, that forms the '•:rf'"'^P^'^Tnt^tv^o of the hemisphere. The postero-inferior lobule is usually described /« f'^'*^'! "J" '^..'J parts, an anterior and a posterior, by the po.tgraci 1. ft..ur. '•"'«« '"'''"'PXr'^;^,^ quite frequently further subdivision of the superficial folm. [O"/^-^.'" ™'"^*^'„'^^ " I defining three sublobules. The anterior of the two conventional ""W^^^* '^e E tract of fairiy uniform width to which the name /oht/u' zrart/is is applied. The 'unaw *;:^teri;r aS much less regular in contour and foliation. ,"<""- »*"„/tXisbnin'^ Mule (lobulu. «mllun.ri. Inferior) and sometimes pres,...s evidence "« ^^'^te the two secondary crescentic areas. The postero-mft-nor lobules and the tuber constitute lobus tuberis. io88 HUMAN ANATOMY. In recapitulation, the foregoing cerebellar lobes, with their component worm-segments and associated hemisphere-tracts, and the intervening fissures may be followed in order, fro>" the anterior and superior end of the worm to its front and lower pole. Although not agreeing with a morphological division, such grouping' is convenient as applied to the adult human cerebellum. The Lobes of the Cerebellum. WORM hemisphere Lingula (Vinculum lingulx) SiJcMs precentralis Lobulus centralis Ala lobuli centralis - Sulcus postcentraKs Culmen monticuli Lobulus lunatus anterior — Sulcus preclivalis Clivus monticuli Lobulus lunatus posterior Sulcus poslcKvalis Folium cacuminLs Lobulus postero-superior Sulcus horizoutalis Tuber vermis Lobulus postero-inferior Sulcus postpyramideUis Pyramidis Lobulus biventer Sulcus prepyratnidiUis- Uvula Tonsilla Sulcus postnodularis Nodulus Flocculus LOME Lobua lingulje Lobua centrali* Lobua culminia Lobua cUvi Lobua eacuminla Lobua tubcris Lobua pjpramidis Lobua uvuls Lobua noduli Architecture of the Cerebellum.— With the exception of where the robust peduncular collections of nerve-fibres enter the hemispheres and immediately above the dorsal recess of the fourth ventricle, the cerebellum is everywhere covered by a continuous superficial sheet of cortical gray matter which foUows and encloses the sub- divisions of the white core. The latter, as exposed in sagittal sections of the hemi- sphere is seen to be a compact central mass of white matter, from which stout stems radiate into the various lobules. From these, the primary stems, secondary branches penetrate the subdivisions of the lobules, and from the sides of these, in turn, smaller tracts of white matter, the tertiary branches, enter the individual folia. Over these ramifications of the white core, the cortical gray matter stretches as a fairlv uniform layer about 1.5 mm. thick, that follows the complexity of the folia and fissures. The resulting arborization and the contrast between the white and gray matter are particularly well shown in sections passing at right angles to the general direction of thfe folia This disposition is especially evident in median s^ttal sections (Hg. 938). where the less bulky medullary substance of the worm, also known as the fjwjftwj trapezoideum, and ite radiating branches produce a striking picture, to which the name, arbor vita cerebelli, is applied. . j vu tk« ^„,*;.,oi The Internal Nuclei.-In addition to and unconnected with the cortical layer four paired masses of gray matter, the intemal nuclei-one of considerable size and three small— lie embedded within the white matter. The d^tate nucleus (nucleus dentatns). or corpus denialum, the largest and most important of the internal nuclei, consists of a plicated sac of gn.y m^XXtr 7^1 9S0 and resembles in many respects the inferior ohvarv ""^l""'-. Jj*5j'^ lattfr, it is a crumpled thin lamina of gray matter which is folded on '^« «nto a ^uch, enclosing w&te matter, through whose media ly d'"^^. """^uncr The Tilum emerge many fibre-constituents of the superior cerebellar ?«!""<:'«• The deSenuckus never encroaches upon the core of the worm, but lies embedded Shin the anterior part ol the median half of the hemisphere, with its long axis ' Modified from SchSfer and Thane in Quain's Anatomy, Tenth Edition. THE CEREBELLUM. 1089 ^ed forward and somewhat inw^ ajjd .herdore 'Jj^f^V^Sie^"^";^^^^^^^^^ plane. Anteriorly the nucleus r«ch« the evel^« a 'J^-^yke of\he hemuphere measures from 15-2? "J"!" ', "^l/^^w^ oTSaymatter-the nucleus fastigii. the Of the other paired internal coUecUo > °* 8"^ """^.y. fa,ti«i, or the roof nucleus emboUformis and the "-^^thb^l^o': ^h^woS:.'^n^^^^^ part nucleui. IS the best defined. " 'r^^'^'u^^^id.iine and to its fellow of the oppo- Fio. 943- Superior worm Nncteos futisii Nnclciii floboiu* Nnclcui anbolUormi* Rotiform body (cxtemat diviiion) Noclcui denUti Keitllormbody^ attered along the fissures, in which situation they are also often of less typical pyi iorm shape. They possess a large flask -like body, about .060 mm. in diameter, from the pointed and outwardly directed end of which usually one, sometimes more, robust dendritic process arises. The chief process, relatively thick and very short, soon divides into two branches, which at first diverge and run more or less horizontally and then turn sharply outward to assume a course vertical to the suriac^ and undergo repeated subdivision. The arrangement of the larger dendrite' is very striking and recalls the branching of the antlers of a deer. The smaller prot .ses arise at varying Central limb of white matter Transverse section of cerebellar folium, showing relations of cortex to underlying white matter. X lo. THE CEREBELLUM. 1091 "" Ota, -» »^». .!» rrsi;£~T„,'s£i^h„'s':Jdnx';Lls mpregnations (Fig. 944). "» ^ Ivlfu^" f .k^ molecular layer. The dendritic olt^nTeaches almost '« the ouj^r^ boundan^ t a nr^zSieTxYending acrc«s the ramification of each cell is ^ '^"f°'.^^^^„' „,. _._,..i ^th the plane of the folium, folium and, hence, when ^''f -"^f '" ^°"' ^ ^^^^^ of the molecular these expansions are found to »^. "'"^"^J- ° ''^f^h^PSdnje^ells. The axones of layer that are unmvaded by 'j^**^"^ "f -1^^^^^^ boe cdls. J;ei^^°",^^,S'c^„esponding the surface, enter the molecular layer, *'»»?'" ^^ich, at ™^ ^^^^ni branch^ "" T^ iS!L°M.ll.t. cell, are pr=... in v;»vinn number, b«t are "ever numer- *.'-f.5ffWRK^x'="«:^>SS»'^"''°-* I093 HUMAN ANATOMY. several richly branched dendrites pass in various directions, but Uu^dy uito the molecular layer. The axone is most distinctive, as very soon after leavmg the ceU it splits up into an arborization of unusual extent and complexity, which, however, is wnfined to the granular layer. These cells, therefore, belong to those of type II (page 998). Since by their processes they are brought into mOmate relation with ai^mber of other neurones, the elements under consideration are probably of the nature of association cells. ..... , „ ,t- ^ The nerve-fibres encountered within the cerebellar cortex (Fig. 945) comprise three chief varieties. ( i ) The first of these includes the axones of the cells of Purkinje which contribute no inconsiderable portion of the fibres passing from the cerebellar cortex to other parts, either of the cerebellum itself or of the cerebrum and brain-stem. (2) The moss-fibres destined especially for the granular layer, which upon enter- Fio. 945- Molecular layer Giaanlc layer White matter Moaa-Abrc* Asonea of Purkinje celb .Oimbing fibrea Diaatammatlc r«on.tniclion of p„.t J fol.um. illustnwinit relatiom of nerve^ells and «btCT of cer^lmr cor^ ttx ; fS?^ iTKhowTcut transversely and longitudinally j a, Purkinie cella ; ». gnnule .ell. ; «^ ^d^taeand into the opposite hemisphere Mialler behind this nucleus, are conunued ac««the ™^^^S«issation» cro;"r^i-"'«^crehyX?e^^c= *^ T^ 1:/JZ'7::^^^^^mTJ^^P^ beWnd the roof-nucleus and consists of a from that of the cerebellar ~™™''*"^"„'"?^,f^'^„„dfetaHy Girting its dorsal margin „ucle;^s;i:?::3^re^tr^^c^^wo::;;rat!;e^^t^^ fres are continued upward through the velar frenum and into the infenor ^-f ge",^ col^-^ ^^^^ ^ ^ medullary tree^ In addition to the foregomg tracts tne "J"™J" ,. ^v longitudinally coursing fibres not only of the hemispheres but dso o^«^ *^™;^"',SS imo thf «rebelL peduncles as r a&1'SK^nna^l:i wThicirfhl^'S^^^^^^ is brought into relation with o-her parts of the brain and spinal cord. Fibre-Tracts of the Cerebellar Peduncles. Repeat^i mention has been made of the^rtjre. robust a-^J^^Jtite^---. wl te'clSurto coSer more in detail the constituents of these important •^^^he Inferior Cerebellar Pedunde.-This robust stalk (corpus restiforme), , 7 n« the restiform body, includes not only the tracts connecting the cere- Suum'wTh th?i n^ Srbm ^^^ that link (he cerebellum and the medulla. Two diSns the spinal and the M6ar, are therefore often recognized. The chirf constituents of the inferior Muncte^« : ^^ ^^^^ ^^ ^,^^^^,^ ^^,^„„ 1094 HUMAN ANATOMY. 3. The olhro-c«rab«llar Abraa, chiefly from the opposite inferior olivary nucleus but to a limited extent also from the nucleus of the same side. They contribute in large measure to the iormation of the lateral part of the restiform body and, on reaching the cerebellum, end within the cortex of the hemisphere and worm, as well as within the fibre-complex enveloping the nucleus dentatus. Whilst for the most part afferent, it is probable that some of the fibres within the tract are efferent and hence conduct impulses m the contrary direction. 4. Fibm Itom the nucleus latcnlis of the medulla, which pass to the cortex of the cere- bellar hemisphere. 5. Pibraa ftom the atenata nudaus, which pass to the cerebellar cortex. 6. The noclso-cerabaUar tract, comprising fibres from the cells within the reception-nuclei of the trigeminal, facial, vestibular, gtosso-pharyngeal and vagus nerves. The tract occupies the median part of the peduncle and ends chiefly in the roof-nucletis of the same and of the opposite side. 7. Other fibres pass in reversed direction from the roof-nucleus to the dorso-laterai (Deiters' ) vestibular nucleus of the auditory nerve and thence, as the veslibalo-apiaal tract, descend through the medulla into the antero-lateral column of the cord. 8. Additional vestibular (and, possibly, other sensory) fibres pass without interruption by way of the restiform body to the roof-nuclei and constitute the direct scasotjr caieballar tract of Edinger. The Middle Cerebellar Peduncle.— The middle peduncle (brachinm pontia), which continues the pons laterally into the medulla of the cerebellum, transmits the fibres whereby the impulses arising within the cerebral cortex are conveyed to the cerebellum. It does not esUblish direct connections between the cerebellar hemi- spheres, as it might be supposed to do from its transverse position and intimate relation with the cerebellar hemisphere, such bonds from side to side passing exclusively by way of the commissures within the worm. The chief constituents of the middle peduncle are : I. The continuations of the fronto-cerebeUar and tcmpoto-occipito-eerebeUar tracu, the fibres of which arise from the cortical cells within the frontal, temporal and occipital lobes respectively, descend through the internal capsule and the cerebral crus, and end around the cells of the pontine nucleus. From the latter cells arise the ponto-ccrcbeUar fibres, the imme- diate constituents of the middle peduncle, that for the most part cross the mid line and traverse the peduncle to be distributed to all parte of the cortex of the hemispheres and of the worm and, possibly, also to the nucleus dentetus. A small number of these fibres do not decussate, but pass from the pontine cells to the cerebellar cortex of the same side. It should be remembered that the pontine nuclei are also influenced by cortical impulses that descend by way of the pyra- midal tracts, since numerous collaterals from the component fibres of these motor paths end around the pontine cells. _ . „ ,. l ,. • , 2 Efferent cetebcllo-pontine fibrea, distinguished frdfh the afferent fibres by their larger diameter, originate as axones of the Purkinje cells and pass from the cerebellar cortex through the middle peduncle into the dorsal part of the pons, where, after crossmg the mid-lme, they are believed (Bechterew) to end within the tegmentum in relation with the cells of the nucleus tegmenti situated close to the raphe. The assumption, often made, that many of the efferent cerebello-pontine fibres end around the cells of the nucleus pontis, lacks the support of the more recent observations. • The Superior Cerebellar Peduncle.— The superior peduncle (brachinm con- jonctlvum) forms, with its fellow of the opposite side, the important pathway by which the cerebellar impulses are transmitted to the higher centres and, eventually, to the cerebral cortex, as well as indirectly to the spinal cord. Its chief constituents are (i) the cerebello-rubral and (2) the cetebello-thalamfc fibres collectively known as the cerebello-tegmental tract. The principal components of the latter are the fibres arising from the cells of the dentate nucleus, which, emendnK *">"» the hilum of the corpus dentatum and receiving augmentations from the roof-nucleus and, probably, to a limited extent from the cortex of the worm, become consolidated into the rounded arm that skirts the supero-lateral boundary of the fourth ventricle. Converging with the tract of the opposite side towards the mid-line, the peduncle sinks ventr.illy and disappears beneath the corpora quadn- gemina many of ite fibres continuing their course through the t««mentum of the cerebral peduncle into the subthalamic region and the thalamus. On reaching a level corresponding to that of the upper third of the inferior colliculi of the quadrigemina bodies, the tracte of the two side! meet and begin to intermingle, the decussation of die superior peduncle (Fig. 1 112) thus estab- THE CEREBELLUM. t095 IS^Ution to the ««>» o'.r.'''* *^'n^teTthe m.Jority tnmsfcr their impulses to fibjr» that temipted fibre*. From the thatamus the impukes are H°- 94° carried by the thalamo-cer«bell»r Posterior nuclei "^ ro-»pin«l tract , VestibuUir From n. lateralis Ant. superf. arcuate Post, auperf. arcuate Direct cerebellar Diagram lllut^tlna ^h.d «mp«,^-. °' «'S!rXr^^'u"c«e?sn paMmgl>y inferior Peduncle ( IP^ f«, ■ ;,. i,*?! bUcV ; C, cerebrum : T. SlTblSe: thoae by f^dle pedunci ■ _^^are »ia« . _^ ^ ^^^^^^^ thalamaa; IC. internal capaue: «• "^ "Xtar! laliral. and inferior olivanr nucleua: P. pontine nucleus; v, I. o. vesuou"" ■» ,_j,u,i nne on; i, a. Sllclerf'.,'^«eStlon nuclei of «;\fj^, "«ir^onthfued'^d?wnwar.l a. rubro- cerebe lo-rubral (ibr», one erf "^ich (4) » "Jl^i^j ^ thalamocortical; ;!l^r,2.i.i'ner8"^-^i!SlSl^puip^^^^^^^^^ pin..M:.«be.l.r fibre.. rubro-thalamo-comcai waci ..» j-„^ „„,h a« arre«orv to this an indirect path, Zd the cortico-spinal tract form the """^ *rect p^h A^««^ry to^ ^^^ ^^^ ^ impulses by way of the^cortico-ponto^erebellar ^^« «^^;'^,,„^. assumed as probably taking part in securmg the neces8ar> muiui 1096 ■ 'i i ' '■ \ i 1 1 LV t HUMAN ANATOMY. THE FOURTH VENTRICLE. The fourth ventricle (vcntricvlM q«arta«), the persistent and modified hind-brain segment of the primary neural canal, is an irregular triangular space between the pons and the medulla in front, and the inferior cerebellar worm and the superior and Werior medullary vela behind. The lateral boundaries are contributed by the supe- rior and inferior cerebellar peduncles. Its long a-xln is approximately vertical and about 3 cm. in length, measured from the lower extremity, where the ventricle »» direcdy continuous with the central canal enclosed within the medulla and spinal cord, to the upper end, where it passes into the aqueduct of Sylvius. lis wi 1th is greatest (about 2.75 cm.) somewhat below the middle, where this dimension is increased by two lateral recesses, one on each side, that continue the cavity of the ventricle over the restiform body. The Floor of the Fourth Ventricle.— The floor of the ventricle, really its anterior wall, when viewed from behind after removal of the cerebdlum and the medullary vela, appears as a lozenge-shaped area (fossa rhomboidea). The upper half of the floor is formed by the dorsal or ventricular surface of the pons and is bounded Fio. 947. iyhrtan wiMilact Saperior poMertor raccn iVventrick Latcrml recess Posterior cominiBsiiri Sylvian aqacdnct Isthmus 'Superior median sulcus Superior lateral sukus Foramen uf Luscbluk Superior posterior Lower end of ventricle containin( foramen of Macendie Castof cavity of fourth ventricle i ^, from the side; *, from above. XI. (Kettius.) laterally by the upwardly converging superior cerebellar peduncles. The lower half is formed by the ventricular surface of the open part of the medulla and is bounded by the downwardly converging inferior cerebellar peduncles and the clava. The narrow lower angle of the rhombic area, long known as the calamus scriptorius, corresponds to the interval between the davae, where the central canal of the cord communicates wii.. the fourth ventricle. The upper angle, situated beneath the superior medullary velum and, therefore, described by some anatomists as belonging to the isthmus of the hind-brain (rhombencephalon), marks the lower end of the Sylvian aqueduct. The length of the rhombic fossa is about 3 cm. , and its breadth, greatest at the level of the auditory nerve, is about 2 cm. In consequence of the elevation of its lateral boundaries, the floor appears sunken and corresponds approximately with the frontal plane, being almost vertical. It i& divided into symmetrical lateral portions by a median groove (sulcus medianus longi- tudinalis sinus rtaomboidalis), and into an upper and a lower half by transverse mark- ings, the acoustic striae (striae acusticae), which on each side arise from the nuclei of the cochlear nerve, wind over the restiform body and cross the floor of the ventricle to disappear within the median furrow. At its lower end, where it sinks into the central canal of the cord, the median groove becomes somewhat wider, the resulting depression being sometimes designated the ventriculus Aurantii. Roofing in the ventricle at this point and bridging the cleft separating the posterior columns, lies a thin triangular sheet of loose vascular tissue, the obex, which laterally is continuous THE FOURTH VENTRICLE. 1097 i •«=r*^ iSr*:::^ S^ t "S^^u^ A^S" ««« divergence, or they .nay weU-iiMtfked bands that crosa «« ^"yj*=T" j^ ^y be irregularly disposed or constitute a fan-shaped group m ^^'^^the jnu^ may c^^ ^.^y ^^ ^ ^^^^^ *"«wT'''L;.h ^^'JrbT^rSSnS^ yStiTe^uenUy one band diverges from marked on both as »« *^ ""r~8"Ee y upward and outward. This strand, spe- 'X^^^^:^oXJiZ^^. is seido. equally distinct on the two "'^^vS^^fSr 'dSr^? ^"e'iUtricuUr Boor, that lying below the acoustic • ^^iJ^^thr^e^lneral fields of triangular oudine. The one next the medun Est; j-^j ts^ui^oTsn^ -=■ c^ .- *. ^ Fig. 948. Fovn •op*'**' " Corpora qwiui intercalatus, that occupies a superficial position in the ventricular floor and partly ovei the hypoglossal nucleus. ihe fovea vagi (ala cinerea), which lies lateral to the nucleus intercalatus, corresponds to the middle and superficial third of the vago-glosso-pharyngeal nucleus, the entire extent of the latter including a tract measuring about 13 mm. in length by 2 mm. in breadth, that stretches irom beneath the vestibular nucleus above to over 2 mm. beyond the inferior angle of the ventricle. The lower third of the area of the vagus nucleus is partly within the ventricle; immediatelv above the obex this intraventricular portion is covered by « layer of loose vascular tissue and appears as an upwardly diverging pointed fieltl, area postrema of ReUius. This is separated from the ala cinerea by a translucent ridge, the funiculus leparant, composed of thickened ependymal neuroglia (Streeter). ' nas Menchenhim, i8q6. •Amer. Journal of Anal. Vol II, 1903. THE FOURTH VENTRICLE. 1099 Trtachorioidet iihI choroid plain The prominence of the eminentia teres is due to the underlying nucleus of the sixth nerve, enclosed by the knee of the facial ; for it, therefore, Streeter proposes the naine emmenti. abdu- ^I^ The longitudinal ridge that continues upward and boon^sthe median fovea, the las ^kuthor interprets as due to a field of gray matter, th.n in the vicinity °< ']•« »f<^"«"' eminence and thicker above, to which the name nudeui uicertu. is applied Lateral to the nSTn^rtus and the facicvabducent eminence, lies the fovea antenor which elongated and deor^d area (nearly 6 mm. k>ng by i mm. wide) is due to the exit of the root of the fifth ne^rtt ml^ Aerefore, be called the fove. trigemini. The medi«, portion of the elevated ™tic area includes the elongated and irregularly lozenge-shaped ve.ubuUr area, that Ti^u^^u .6 mm. in length by 4 nun. in breadth and extends from the fovea antenor rS^i) to the nucleus gracilis. The lateral part of the area acu«t.ca ^ occup^edby the cortle« area, which stretches into the recessus lateralis and overlies the nudeua cochlewii. The Roof of the Fourth Ventricle.— Viewrd in median sagittol section (Fig. 018-) the roof of the fourth ventricle appears as a tent-like structure, whose wings, where they come together, bound a space, the recessus tecti, that penetrates the cerebellar medulla between thesupenor '^'"- "S" and inferior worm. The upper wing of the tent is formed by the superior med- ullary velum, the triangular sheet of white matterstretch- ing from beneath the quadrigeminal bodies above to the medullary substance of the cerebellum below, and is over- laid by the rudimen- tary cerebellar folia of the lingula. It must be understood that the ventricular surface of the velum eoendima-S are'all other parts not only of the fourth ventricle but of all the venSS c?vid«. LaterallVthe superior medullary velum is attached to the superior cerebellar peduncles, which to a limited extei.t share in closing in this P'" Th?Lw?£f'o7the ^comprises two parts, an upper and thicker crescentic nlate of white matter, the inferior medtdlary velum, and a lower and extremely thin membrane he tela chorioidea. Medially the inferior medullary velum is attached SrTomed stance to the front and lower surface of the nodules, which it excludes, iSyregaSfrom the ventricle, whilst laterally the velum is prolonged to the floccuhis its fib;es becoming continuous with the white core of th.s subdivision of the cerebellum. The nervous constituents of thevclum extend only as far as its crLcentic lower border, beyond which the roof of the ventricle, in a morphological ^"e is formed by the ependymal layer alone. This, however, is supported by a Tacking of Dial ti^ue. which, in conjunction with the ependyma forms the tela Chorioidea^ On nearing the lower angle of the ventricle, the roof presents a trian- gular thickening, the obex, that closes the cleft between the clav« and lies behind f above) the nib of the calamus scriptorius. , 1 -.u »i. On each side the obex, which consists of a layer of white matter fused with the undeZng ependyma, is continuous with the slightly thickened margin of the roof The tSa ventri^:ul . whose line of attachment passes from the rhva ..pward and outwa*d over the cunelle tubercle of the ineduHa and the rctiform hnat of the ventral laminae, in conjuncUon with which the^^^^J.^^I'^J^^^^^^^^ ^ ^^'^ '^iucuiu. cidently with the outward mi- supmtoi j^","J^^j.,^, gration of the dorsal laminae, the ventral zones also thicken and assume a much more hori- zontal position, with their inner ends sei>arated superficially by a median furrow and, deeper, by the compressed remains of the floor-plate. Very early and before the flattening out of the myelencephalon has advanced to any marked extent, the de- marcation between the dorsal and ventral zones is evident as a lateral longitudinal groove on the ventricular surface of the iiiyelcniephalon. Indica- tions of this division persist and in the adult medulla are represented by the fovea pos- terior and the sulcus lateralis seen of the flt>or of the fourth venti'-'C. As in the cord-seg- ment, 30 in the myelencepha- lon the lateral walls are the only regions of the neural tube in which neuroblasts are devel- oped, the roof-plate and the floor-plate containing spongioblasts alone. Very iiirly and l"o«. showiiiK three stajres in dwetoitment of medulla; A, about four and a half weeks; fl, about six weeks; C about etjrht weeka ; rp. roof-plate : r, raphe : rf, v, dorsal (alar) and ventral (ha»1> laminir ; r/, rhombic lip; Ir, lateral recess; /j, fasciculus solitarius; ci . restiform \kv\v ; xii, hvpo|rlostial ner\*e ; Jf', spinal root of trifteminus ; lo, iiiferior olivary nucleus. ( His. ) DFAELOPMENT OF HIND-BRAIN DERIVATIVES. 1103 duplicature, directed towards the brain cavity, the mesoblast grows and later 'l.^ve'ops blood- veLls, and is converted into a vascular complex that eventually forms the choroid plexus of he S ventricle. From the manner of iU development, it s evident that the plexus is excluded S^yie ependymal layer from the ventricular space, outeide of wh.ch the P'"' b'"Vf ;7^^'!; therefore really lie. The conversion of the upper part of the pnmary velum mto the thicker definite nferior medullary velum follows the addition of nervous substance during the develop- ment of tb^"^eWlum. ^Similar thickening of the roof-sheet at the lower angle o. the ventricle results in the production of the obex and the tuiniie. , ■ u t The Pon. -The pons arises as a thickening of that part of the metencephalon which forms the anterior wall of the pontine flexure. In its essential phases the development of the (wns probably closely resembles that of the medulla, since the early metencephalon presents the same ^^1 feature as does the myelencephalon. Thus, the ventral «.nes of its lateral walls pla, ^ active rAle in the production of the tegmental portion of the pons and the ""f'^'"* ""«•""* the motor root-fibres of the fifth, sixth and seventh nerves, whilst the fioor-plate becomes the .•aphe. In addition to providing the rec-eption-nuclei of the sensory cranial nerves, ana. per- haps, the pontine nuclei, the dorsal zones contribute the neuroblants which Fic. 955. ^ become the nervous elements of the ^ cerebellum. As in the medulla, so in the pons the great ventral tracts are secondar>' and relatively late additions to the tegmentum, which must be re- garded as the primary and oldest part of this segment of the brain-stem, the bulky ventral nervous ma.sses taking form only after the appearance of the cerebro-spinal and cerebro-cerebellar paths. In a manner analagous to that by which the sensory part of the vagus is at first loosely applied and later in- corporated with the medulla, the sen- sory fibres of the trigeminus are for a time attached to the surface of the dorsal zone of the pons, subsequently becoming covered in and more deeply placed by the addition of peripheral tracts. Likewise the fibres of the audi- tory nerve come into relation with the superficially situated reception-nuclei of the cochlear and vestibular nerves. The Cerebellum.— The develop- ment of the human cerebellum pro- ceeds from the roof-plate and adjacent parts of the dorsal zone . of the lateral walls of the metencephalon. In an embr>o 22.8 mm. long, the cerebellar ■niage consists of two lateral plates , , . ,c.- „x 4,,„, inected by anarro-v thin intervening lamina representing the roof-plate (Fig. 95a). Alter apposition of the lateral plates, which soon occurs, this bridge disappears, the developing rebellum for a ■■ appearing as an arched lamina enclosing the upper part of the cavity of „,e hind-brain (Kuiiii.m')- . , j „ . j- 1 The subsequent development of the human cerebellum has been recently carefully studit <1 by Bolk » in a series of about forty foetuses, hardened in formalin and ranging from 5 to 30 cm. in their entire (crown-sole) length. The following account is based largely on these investigations. In a f.Etus of 5 cm., about nine weeks old, the cerebellar anlage is represented by a horseshoe- shaped thickening of the metencephalic roof, the cerebellar lamina, whose upper margin is con- nected by the encephalic fold with the mid-brain and whose lower border has attached to it the primary velum— the thin rhomboida! roof-plate of the myelencephalon. Median sagittal section of the cerebellar lamina at this stage ( Fig. 955. ^) sh"*' its form to be asymmetrically biconvex, the more convex surface encroaching upon the brain-cavity. In a slightly t)lder f»etus (Hg. 955, B) the cerebellar lamina has become triangular, in section presenting a supenor, an anterior and an inferior suriace. From its attachment along the superior margin of the lamina the inferior velum dips forward toward the pontine flexure and, forming a transversely cresentic ' Miinchner med. Abhand., 1895. •Petrus Camper, 30 Deel. 1905- Median Uf{iUa1 sectionn showiHR four early stages of develop- ment of human cerebellum, from fictuses from 5 to q cm. long; ml>. mid-brain ; c. cerebellum ; in, iv, superior and mferior medul- lary velum : vc, ventricular cavity ; rf, cavity of diencephalon ; A. pons ; m. medulla ; J. spinal cord ; r/. incisura fastiml ; /, sulcul primariut ; j, sulcus postnodularis. {Drawn/rom figures of Bolt.) „o4 HUMAN ANATOMY. fold the PlUa chorioidea, bounds a narrow recess that extends along the inferior surface of the cerebellaflamina. This recess is only temporary and is soon obliterated by the subsequent at- tachment of the roof-membrane to the inferior surface of the cerebellarlamma The succeedmg staee ( Fie QSS C\ emphasizes the alteration in the planes of the cerebellar surfaces, the former suiirior now becoming the anterior, the anterior the inferior and the inferior the posterior. From the posterior margin of the dorsal surface the choroid fold dips into the bnun-Kravity. Between themid-brain and the cerebellum now stretches the first definite indication of the later superior medullary velum, in agreement with His, Bolk recogniz^ Oiat the former intraven- tricular (inferior) surface has now become an extraventricular one and that the permanent attach- ment of the plica chorioidea corresponds to a secondary and not to the primary line of union. The stage represented in Fig. 955. D is important, since it marks the beginning of the first fissures One of these, the sulcus pritnarius (the ^ssura prima of Elliot Smith ) appears as a transverse groove on the upper part of the anterior surface and thus early establ.>hes the hinda- mental division of the cerebellum into an anterior and a posterior lobe. The other fissure appears in the median area near the posterior margin of the cerebellum '«'»'''*« ^"''""f^J*^ nodularis. On each side (Fig. 956. -« ) an additional fissure cuts off a narrow tract that embraces the postero-lateral area of the cerebellum. This fissure, Hf^^ sulcus floccuUns, for a time reinair« unused with the postnodular sulcus; but later, with its fellow, 't becomes continuous wuh the postnodular sulcus and thus defines a narrow band-like tract, the median part of which Fig. 956. Six ,.a,^. in devrfopm™. of human «„b.num 'rom^'«'Mr °' "s'lilsPn^^ulA*:'"/, " fn%py™m'daTu ;'"".: (^ ength; /. sulcus P"m«riu» (preclival)-,^, s. Hwcuians . j, s. ix.»^^^ roof-mimbnme ; >, ateral recew; :rKfusTS.Tu^i??,'i:;r:!i;s^.SS'n'>?7cTur' ^ eventually l^ecomes the nodule, the lateral portions the flocculi, whilst the i"'«™K strips become the fioccular peduncles and part of the inferior ."^«;- J"^ J^^^;"';^^^," third furrow appears on the posterior cerebellar lobe. This is 'heyi-v«.. ..,»«rf« (E^^^^ or the infrapvramidal sulcus. Very shortly a fourth groove appears ^»""^ the su'cus prim^^ and marks the beginning of the prepyramidal fissure. In this -"/Xh from ^hind toward posterior lobe is eariy subdivided by three fissures into four areas, which '™'" °^^^^^^^^^ «{e sulcus primarius, give rise to the nodule, the uvula, the pyramid and a still ""differentiated one Hv .'he subsequ^ent appearance of additional furrows, this "»"°-/,X^o7the ce ebLuur^ tulK.r, the folium cacuminis and the ...vus. Meanwhile on the »"*7°J°*^ °' '^",j*^ts'^"ke^ three short transverse fissures appear, by which the antenor end of '^^/.^T^. \"^* '^^?:;'^„^^^^ up into areas that, while establishing subdivisions of mon^hological value (BolVc • are later lost in the uncertain foliation of the tlnKuta and lobulus ccntnihs of 'he njatuirrerehellum^ .\fter the fundamental subdivision of the median area (worm) has ^".^f^°"lP''^rf,^,;,^^,^ lateral masses (hemispheres) of the cerebellum become subdivided into •!! fi"' ^^^j^^^'j";^^^^^^^^ by fissures that appear during the fourth and fifth months of foetal We. The lateral extensions THE MESENCEPHALON. 1105 on^he upper suHace of ^e P<«te"<^ >"^- Bv'he^f^^^^^^ 7\Wu^posMivai fissur,) and the about the end of the fifth month, and is at first represented "V » ™,^, ^.^ ;„ ^^ ..^Hance lateral tracts (postero-supenor lobules) . Th.s Part of the «orm, ^ • ^^ .„ ^ these with the cortical expansion of ^^e surrounding j^m and he„ce^or^^^^^ .^ ^^y^ and «nks into the relative •n-'*'g"'fi«^»"'=%''^»' ^^d^owth aXxpans^^ of the peripheral matured cerebellum. In ^rr'"^"^ °'fi«uri,'^f Sdar> lr^&^^ im,x,mnce, as portions of the human cerebellum some figures of ^^"^''^^ "^^„„,'^ „.,„ ,{,„„ ,h„«, of the horizonul. become excessive y ^e^f«"^ J»nd^^^ This are derived the earliest constituente of the granule layer. "e»"*l?"'^*'™"„ ? ,„,_^^^^ con. natal life. THE MESENCEPHALON. Notwithstanding its considerable size and prominent position in the embryo, in its mature nondiSn d.e mesencephalon, or mid-brain, forms the smallest -"^ least con- picuous division not only of the brain-stem but also of the -'"'^e bra.n^ Neverthe- less the manv fundamental tracts which it contains, as well as the new paths ana comblnationTUSari^^ it. substance, confer on the mid-brain an importance 7" iio6 HUMAN ANATOMY. not suggested by its size. Its upper limit corresponds with an oblique plane passing through the base of the pineal body and the posterior border of the corpora mam- millaria ; its lower one is indicated on the ventral surface by the upper border of the pons and on the dorsal aspect by the upper margin of the superior medullar}- velum. As seen in sagittal sections (Fig. 938,) the mid-brain is about 11 mm. in length, although when measured on the ventral surface it is slighriy shorter (9 mm. ) and on the dorsal aspect a little longer ( 1 3 mm. ). Its greatest breadth is approximately 23 mm. The mid-brain is traversed longitudinally by a canal, the Sylvian aqueduct, which, however, lies much nearer the dorsal than the ventral surface of the brain-stem. When the several parts of the brain are undisturbed, only a portion of the ventral aspect of the mid-brain can be seen. Its dorsal and lateral surfaces are hidden by the overhanging cerebral hemispheres, the splenium of the corpus callosum and the puKinar of the thalamus being in close relation with these surfaces respectively. Notwithstanding its ventral position and apparent removal from the exterior of the brain behind, the dorsal surface of the mid-brain is, in fact, directly continuous with Kio. 957. TriKonum habenulae Pulvinar CoUiculus superior Cerebral peduncle Fouith nerve Pons Superior terebellar |>eduncie Tsrnia thalami Commissura habenulae Pineal btxiy Median geniculate body Brachiuin inferior CoUiculus inferior Frenulum \v\\ Lingula Cerebellum, cut surface Ml J-hrain viewed from behind ; upper part of cerebellum has been removed to expose superior medullary velum with lingula. and a part of the free posterior surface of the brain. It is, therefore, covered with the pia mater, as may l)e demonstrated by drawing aside the overhanging cerebral hemispheres. In silit the mid-ljrain occupies the opening bounded by the tento- rium and thus connects the divisions of the brain which lie within the posterior cra- nial fossa (ccrebiUum, pons and medulla) with those (cerebral hemispheres) that lie above. Its cavity, the Sylvian aqueduct, establishes direct communication between the third and fourth ventricles. The mid-brain includes two main subdivisions, a smaller dorsal part, the qitadrif;eminal plalc, which roofs in the .Sylvian aqueduct and bears the corpora quadrigemina, and a much larger ventral part, made up by the cerebral peduncles. Tlie quadrigeminal plate lies Ix^hind the plane of the roof of the Sylvian aqueduct and extends from the base of the pineal body alx)ve to the upper margin of the anterior niedullary xeliim below. Its dorsal surface is subdivided into four white rounded elevations, the corpora quadrigemina, by two grooves, one of which is a median longitudinal furrow and the other a transverse furrow that crosses the first one at right angles and slightlv below its middle point. The upper part of the longi- tuilinal groove, l>etween the iij)per pair of elevations, broadens into a shallow trian- gular depression, the pineal fossa ( triKonum stihpinealc) in which ri*sts the pineal body. Below, the mid-furrow ends at the base of the frenum of the superior medul- lary velum. THE MESENCEPHALON. 1 107 Pnlrinar Superior collicul Inferior collicul Superior medullary h-elum' Superior cerehellar peduncle' Lin{{u! Middle cerebellar peduncle, cut Fig. 958. Superior hrachinm Median geniculate body Lateral geniculate hcxly Tractus tranRvcrsus Cerebral pwluncle Uptic tract The elevations forming the upper pair of quadrigeminal bodies, the coUicuh auoeripres. are the la^er and more conspicuous, and measure from 7-8 mm. in ?en??h about 10 mm. in breadth, and 6 mm. in height. Laterally e.ch superior col- IkuC is continued into an arm. the superior brachium (braehium quadriReminum Srius) which is defined by a groove above and below, and pa^ upward and ^utwlrd between the optic thalamus and the median geniculate body, to be lost Shin aritdStly cir'!:umscribed oval eminence, the later, geniculate body 7«™is «nicttlatum Uttsrale). which lies beneath the pulv.nar. In like manner «,ch ortrsmaUw lower pair of quadrigeminal bodies, the coll.culi infenore. (about 6 mm rength by 8 mm. in breadth and 5 mm. in height) « prolonged laterally into the inferior brachium (brachium qaadrigemioum Inferius). which in turn ends in the sharply defined median geniculate body (corpus Reoiculatummedialc). an oval elevatbn about 10 mm. in length. Ventrally the quadrigeminal plate becomes direcdy continuous with the adjacent part of the cerebral pedunclw. The cerebral peduncles (peduncuH cerebri), also called the cerebral crura, constitute the bulky ventral part of the mid-brain. Dorsally the two peduncles are fused into a continuous tract, the tegmentum, which contributes the side-walls and floor of the Sylvian aqueduct and blends on each side with the overiying quadn- aeminal plate. Ventrally the peduncles are unfused and appear on the inferior sur- face of the brain as two robust stalks (Fig. 993)- These emerge from the upper border of the pons and pass, diverging at an angle of from 70-85°. upward and out- ward to enter, one on each siJ.e. the cerebral hemi- sphen - just where the peduncles are crossed by the outwardly winding optic tracts. At the pons each peduncle possesses a breadth of from 12-15 mm., which increases to from 18-20 mm. at the upper end of the stalk ; the borders of each peduncle are. therefore, not quite parallel, but slightly di- verging. Neither are the mesial margins of the pe- duncles in contact as they issue from the pons, but separated by an interval disUnceSn^cr«i™; unTJ at their upper ends the peduncles are about n «"«"• apart. SSrciaUy each peduncle is formed by strands of fibres which do not pursue a stricriy^on^tudinal course, but wind spirally from withm outward ; in consequence of this arrangement the surface of the peduncle presents a characteris ic twisted or roi-Hke strfation. The regularity of this marking is sometimes disturb by a Smlv defined strand of ribr« (tractus peduncularis transversus) that winds over the m« an border and ventral surface of the peduncle, passes upward and outward ac oss hf hteral swfacc of the mid-brain, to te lost in the vicinity of the medial geniculate todv The depressed triangular area included between the diverging V^duncles is the Soeduncular fossa, the floor of which is pierced by numerous minute openings h-tftSm" small bloo' .'''^Y .'.S corresponds with a depression, the recessus posterior; another, but less market Ss " the recessus anterior, is Ix.unded by the postero-med.an surfaces o 'r ma nn illary bodies. A shallow lateral groove (sulcus mcscncepha. lateralis extends along the outer surface of the peduncle, whilst al.Mig its inner aspect, .md Sore looking into the interpeduncular fossa, runs the median or oculomotor groove (sulcus ner>i oculomotorius ^ that is more distinct than the lateral furrow and Dono-lateral aspect of mid-brain. i i 1108 HUMAN ANATOMY. marks ihe line along which the root-fibres of the third cranial nerve emerRe. On transverse section ( Fig. 963) these furrows are seen to correspond with the edges of a crescentic field of deeply pigmented gray matter, the Bubatantia nigra, by which each peduncle is subdivided into a dorsal portion, the tegmentum, and a ventral part, the crusta (basis pedunctili). The latter lies ventral to the superficial lateral and median furrows, and contributes largely to the bulk of the free part of the peduncle. When traced upward it is found to enter the cerebral hemisphere and become continuous with the internal capsule. It contains the great motor tracts and is the chief pathway by which efferent conical impulses are transmitted to the lower lying centres. The tegmentum, on the contrary, in a general way is associated with the sensory tracts, and, above, enters the subthalamic region (page 1 127). The dorao-lateral surface of the mid-brain, just where it passes into that of the superior cerebellar peduncle, shares with the latter a triangular area, the trigo- FiG. 959. Emerging 6bra of fourth nerve Fourth nerve, cut Lateral fiUet Posterior longitudinal laiwiculus Tegmental field Mesial fillet . ition of fourth nerve .Sylvian aqueduct Central Kray mbstancc Mesencephalic root of trigen. jus Subatantia ferruglnea Superior cerebellar peduncle Decussation of cerebellar peduncle P\'ramidal Transverse fibres Transverse section of hrain-stem at level L (Fig. 919). lunctlon of pons and mid-brain : superior cerebellar pedun- cles are heKinning to ntinuations of the lateral fillet, as axones of the cells of the inferior coUiculus, or /.. nbres forming the lateral root of the optic tract, also known as the inferior commissure of Gudden. Within this fibre-capsule lies an oval mass of gray matter, the nucleus corporis geniculati medialis, from whose cells axones proceed chiefly towards the cerebral cortex in continuation of the auditory paths of which the inferior coUiculus and the median geniculate body are important stations. 1 Connections of the Inferior CoUiculus and Median Geniculate Body.— Mention has been made, when describing the reception-nuclei of the cochlear portion of the auditorj- nerve ( (xige 1076) , that the tract of the lateral fillet takes oripn to an important extent from the cells of these nuclei, and, further, (page 1082), that the fillet-fibres end around either the cells of the inferior coUiculus, or thosi of the median geniculate body. It is evident, therefore, that these parts of the mid-brain stand in intimate relation with the parts concerned in conveying auditoo' impulses. The more detailed account of the chaining together of the neurones forming sucli paths is deferred until the auditory nerve is considered (page 1257) The connection of the fibres com- posing the median root of the optic tract with the median geniculate body and the inferior coUic- ulus has been established beyond doubt ; further, that this pan of the optic tract is not concerned in conducting visual impulses, is shown by the fact that these fibres remain unaffected under condi-ions 1 after removal of the eyes) that lead to degeneration of the fibres of retinal origin. The destination and significance of the fibre-systems included within the median root of the optic tract are only imperfectly understood, but it may be accepted as certain that they can no longer be regarded as merely establishing a bond between the median geniculate and indirectly the inferior quadrigeminal bodies of the two sides, as implied by the name commissure, since many of these fibres are probably directed after decussation to the lenticul.ir nucleus (globus pallidus), while others possibly may end on the same side in the subthalamic nucleus ( p.iKe 1128). The gray matter of the inferior coUiculus, like that of the superior, gives rise to fibres of the tecto-buibar and tecto-spinal tracts, presently to be described (page iiii). The superior coUiculus is composed of a number of alternating layers of white and ^rav matter. The latter, however, is not aggregated into a definite nucleus, as in the case of the inferior coUiculus, but is broken up into uncertain zones by the tracts of nerve-fibres. Although as many as seven layers have been described, some of these are so blended that only four weU-defined strata can be readily distinguished. From the surface inward these are : THE MESENCEPHALON. lilt """• r'^r.C'^c^^u2::^l^hT,l;>ruffi:: but .^^^ a„U n-t .nar..c. over U« celU contained '" '*> * j^P "r/[,7^„ whilst their dendrite* are directed ,*npherally. I he :^j:l r- -- cX^'el^irS of «ray matter, but is invaded by nu.ny meduUated nerve-fibres. ,„^^- «.hich consists of a complex of gray matter and ner^e-fibres, u . ^ ^^^iS^tr^nrTe'rived frL the optic tract which gain the side of the colliculu. the latter mdudmKsn^n^ration by Professor Spiller. ontir oaths as well as by the prominence of parts of the stratum in animals Pofessing only ri^rmenS 4ua \^ths^Edinger). The stratum opticum. however, consists by "o " eans exclusSof fibres, but contains, especially in its dee,,er p..rt. numerous nerve-cells of large size, around which the end-arborizations of the optic fibres terminate intersnerse^it^- -ide desrpml within the tearmenta! field to end partly in r. lation witl l^em cTei withinX b;ain-st;^ (tractu. t«tn-bulbaris Utetj.!..^ and partly with-n t . ;^mal cord tra««s ..cto.,pina..s later.!..), ^he mediaUy situated fibres sw;eep arotmd the S^ matter and, for the most part, cross the raphe imrned.ately ^^"♦"'"^^.'^XTnrther course fasciculus, thus establishing the fountain decussation of Meynert ( Fig. 96"' T he further course 1 1 12 HUMAN ANATOMY. of these fibres is downward tlirougli the brain-stem and into tlie anterior column of the cord (tractus lecto-spinalis medialis). \Vhether these fibres are interrupted in small secondary nuclei within the tegmentum, or pass unbrokenly from the collicular cells to the cord is undetermined. It is probable that, as constituents of a spino-tectal path, fibres also ascend from the spinal cord to the quadrigeminal bodies. According to Kolliker, some of the radial fibres are traceable through the tegmentum, passing to the outer side of the red nucleus and piercing the tract of the median fillet, and into the substantia nigra, whose cells they probably Join as axones. The commiuure of the superior colliculi is formed by fibres that cross the mid-line to the opposite quadrigeminal body and probably includes, in addition to the axones of cells within the colliculi themselves, fibres from the fillet and optic tracts. The most important connections of the superior colliculus, as may be anticipated from the foregoing description of its structure, are : I. With the optic tract, directly or indirectly from the lateral geniculate body, by way of the superior brachium. 2. With the cerebral cortex of the occipital lobe by way of the superior brachium and the optic radiation (page 1175). 3. With the posterior sensory colunms of the spinal cord, indirectly by way of the median fillet. 4. With the cochlear nuclei by way of the lateral fillet, thus establishing a path for audito-visual reflexes. 5. With nuclei of the third, fourth and sixth cranial ner\'es, controlling the eye-muscles, especially the oculomotor, by way of the posterior longitudinal fasciculus. 6. With the lower levels of the brain-stem and the spinal cord by way of the tecto-bulbar and tecto-spinal tracts. The lateral geniculate body belongs to the diencephalon and may be regarded as a special- ized part of the tfptic thalamus ; the consideration of its structure therefore, properly falls with that of the metathalamus (page 11 26). The Tegmentum. — The tegmental regrion of the mid-brain includes, as seen in transverse sections (Fig, 961), the U-shaped area extending from the quadri- geminal bodies behind to the crescents of the substantia nigra in front. In the vicin- ity of the central gray matter that surrounds the Sylvian aqueduct, the tegmentum consists chiefly of a foundation resembling the formatio reticularis seen at lower levels. This substance is produced by the intermingling of transverse or arcuate and longitudinal fibres and a meagre amount of gray matter with irregularly distributed ner\'e-cells, that fills the interstices between the strands of nerve-fibres. The more lateral and ventral parts of the tegmentum are to a large extent occupied by the prominent fibre-tracts belonging to the fillets and to the superior cerebellar peduncles, or by collections of gray matter, as the red nuclei. Special groups of nerve-cells and of nerve-fibres mark the origin and course of the oculomotor and trochlear nerves. ■11 111 "1 « The details of the tegmentum vary with the level of the plane of section. Thus, at the lower end of the mid-brain the tracts of the cerebellar peduncles approach the mid-line as they ascend and those of the fillets assume a more lateral position ; whilst at higher levels these tracts, which lower in the mid-brain are so conspicuous, either terminate to a large extent, or become so broken up as to no longer form impressive bundles. In sections passing through the lower pole of the inferior quadrigeminal bodies (Fig. 960), the zone overlying the substantia nigra is occupied to a great extent by the median fillet, which here appears as a broad but thin crescentic or comma-shaped field, whose outer and thicker end lies at the peripher>' and abuts against the base of the dorsally arching tract of the lateral fillet. At the inner end of the median fillet, near the mid-line, an isolated group of obliquely cut fibres sometimes indicates the position of the lemnisco-crustal bundle that appears ventrally among the robust strands of the crusta. Taken together, the two fillets form a compact tract, the outer contour of which, at the level now considered, resembles a horizontally pl.iced Oothic arch, the summit of the curve lying at the surface and the lower and upper limits of tht arch tieing the median and lateral fillets respectively. The lateral fillet continues the sweep of the fillet-stratum along the peripher)- of the tegmentum until it embraces the lower pole of the inferior colliculus in the manner previously described (page 1110). Dorsal to the tract of the median fillet, and separated from the latter by a thin layer of com- pact foundation-suttstance, the ventral tegmental field, lies the broad curved band formed by the blending of the two superior cerebellar peduncles. At lower levels ( Fig. 936) these stalks are separate and appear as laterally placed and conspicuous crescentic areas of transversely cut fibres ; hut opposite the lower limit of the inferior quadrigeminal bo' nucleus Sagittal section of brain-stem ; plane of section i, '-mewhat lateral to mid-line. ■ by PrnlesMtr Spilier. j. Pretmrnlion As seen in cross-sections passing through the superior ^l^^^^t^T'"'""' ^''^1^;;;;';^%''^,^^^ the tegmentum differ considerably from those at the levels P'.^^''°";'>- *'*'tf •..^''^^.^1 *e con 1 1 14 HUMAN ANATOMY. i i.ua 9 The most conspicuous object within the tegmentum in the superior half of the mid-brain is a large round reticulated field on each side of the median raphe, which marks the position of the red nucleus (nucleus ruber). This body, also called the nucleus tcgmenti, is of an irregular ovoid form (Fig. 963) and of a reddish tint when seen in sections of the fresh brain. Its lower limit corresponds with the level of the lower margin of the superior colliculus, whilst its upper pole extends into the subthalamic region. Its diameter increases towards the upper end and its long axis converges as it ascends, so that the upper enlarged portions of the two nuclei lie close to the mid-line and nearer each t>ther than do the lower poles. Each nucleus consists of a complex of gray matter and nerve-fibres. The latter preponderate below, where the red nucleus receives the fibres of the superior cerebellar peduncle, and are much less numerous above, since many fibres come to an end around the rubral cells. These elements are very variable in shape and size (.020.-060 mm.), but are most often irregularly triangular or stellate. The red nuclei constitute not Fig. 963. turtle fibivs joining su[)CTior coUii ulus thaluutf Part of iiiettiAn IfrnicuUte nucleus MnlUn t:riii(ulate Iwdy VMitro-lat«T«l tiiicl«i« of' thiril n< Knot (iht«s of third Lateral ifcnkulatr hodjt ^ratuni intcrinediiiin ■Crmtoofcetebml |*,iiincle Suhslailtla nllira Fnierirdlir flhwt of otultmuitf-r nerve Transversa section of midbrain at level O (FIr. 9l9).|nMinK through superior colliculus »nd Reiiiciilatc bodies; red nucleus, itnl nuclei and root-fibres of oculomotor nerve. Welgert-P»l staininf. X 3- Preparation by Professor Spiller. only important stations in the path connecting the cerebellum and spinal cord, but also probably contribute links in chains uniting the cerebral cortex and the internal nuclei with the cord. Whilst some fif the constituents of the superior cerebellar peduncle |>a.ss around the red nucleus and continue as ccrcbello-thalamie fibres uninter- ruptedly to the optic thalamus, the majority of the fibres of this arm end around the ceils of the nucleus. Of these many give off axones that i)roceed brainward as rubro- thalamic fibres ; others emerge from the ventro-medial surface of the nucleus, cross the mid-line (decussation of Korel ) and bend downward as the rubro-spinal tract. The latter descends within the tegmentum of the mid-brain and pons, traverses the niithilla and finally enters the lateral column of the cord as one of the important but un< < riainly defined descending tracts. Other fibres enter the red nucleus on its lateral aspect and establish v^onnections between the cerebral cortex (Dejerine), and proiwbly also the corpus striatum (Edinger), and the nucleus. P'rom the cells of the latter the path is continued hv fibres which join the rubro-spinal tract, and in this manner establish an indirect motor path that supplements the cortico-spinal tracts identified with the pyramidal. THE MESENCEPHALON. 1115 The Crusta.— The crusta, or pes pfdunculi. appears in transverse sections , v\.r ohx \ as a bold sickle-shaped field that occupies the most ventral portion of the Sbr^n'Ttco^fstscSieflyononKitudinallyco^^^ fhe internal capsule, are pacing from various parts of the cerebral cortex to louer evels in The brain stem andthe spinal cord. The lonRitudmal hbres are separated • y LinHl^ bv the invasion of numerous strands frum the tibre-comple.x. known as Tstratm^'Uer^^^^^ which lies along the ventral border oj the substantia nigra Thrfibres of the crusta comprise three general sets: the rortuo-fion/n.e, the ^''''thetorticoVonUn^^^^^^^^^ those passing from the cells of the cerel.al rt.v to the cells of the m.ntine nucleus as links in the cortico-cereliellar paths, Thev are repr2nt«l by the fronto-pontine and the temp,ro.o cranial nerves connected with the brain-stem. From the cells within the more iii6 HUMAN ANATOMY. extensive of such nuclei, as those within the column of substantia gelatinosa accom- panying the spinal root of the trigeminus, numerous arcuate fibres sweep towards the raphe and, with few exceptions, cross to join the median fillet of the opposite side. In this manner provision is made for the transmission to the higher receptive centres of sensory impulses collected not only by the strands of the posterior column of the cord, but also by the sensory fibres of the cranial nerves attached to the brain-stem. Although the principal components of the fillet-tract are the bulbo-tecto- thalamic strands, some fibres running in the opposite direction are also present. Some of these probably arise from cells within the optic thalamus and the corpora quadrigemina. Others are efferent strands which establish connections between the cortical gray matter and the nuclei of the motor cranial nerves, especially the facial and hypoglossal. These cortico- bulbar tracts descend within the crusta to the lower end of the cerebral peduncle ; then, leaving the latter, they traverse the stratum intermedium and in the upper part of the pons join the median fillet and descend within its ventro - median part as far as the superior end of the hypoglossal nucleus. During their course, the fibres of this cnistal fillet, as it is called, for the most part undergo decussation on reaching the levels of the motor nucleus for which they are destined ; some fibres, however, possibly end around the cells of the nucleus of the same side. The Posterior Longi- tudinal Fasciculus. — This bundle (fasciculus longitudinulis dorsalis) is an association path of fundamental importance, be- ing present in all vertebrates. As a distinct strand it begins in the superior part of the mid-brain and thence is traceable as a con- tinuous tract through the teg- mental region of the pons, the dorsal and lateral "ventral field of the medulla into the anterior ground-bundle of the spinal cord. Throughout the greater part of its course through the brain-stem, its position is constant, the fasciculi of the two sides lying close to the median raphe and immediately beneath the gray matter flooring the Sylvian aqueduct and the fourth ventricle (Figs. 959, 961). In the lower part of the medulla, the bundle gra .aally leaves the ventricular floor and rests upon the dorsal border of the median fillet, and, at the level of the pyramidal decussation, where the fillet no longer intervenes, lies behind the pyramid and at some distance from the mid-line. Lower, it assumes a more ventral position, to the medial side of the isolated anterior cornu, and, finally, enters the anterior column of the cord to be lost within the upper part of the ground bundle. The f.xsciculus includes association fibres of varying lengths, some of which are ascending and others descending paths. The constitution of the bundle is, there- fure, continually chanxiaj;, tlic loss of certain fibres being replaced by the addition of others. Its fibri'S are among the very first in the brain to become medullated, and liegin to acquire this coat during the fourth fcEtal month ( Hiisel). Superior coltlculus SenNory decussatioii Posterior nuclei Posterior tracts Spino-thalamic Spinal ganglion Diagram showing chief afferent constituents of median fillet. (senHory part) I.\. X nerves (sensory part) THE MESENCEPHALON. III? Fig. 965. Notwithstamlin. the admitted i-porta„« oMhe -f^^^-f^^V^^.l^'^'ir^^^^ iS rir:sir.e%^T;:ix^^^^^^^^^^^^ ^"TKe'u7;"^nd^ortHTrrc.ts . -Id«.«e^-^r^o^^^^^^^^^^ the ceHs of the nudeu. of .h. I^*""" "Ti'^^C t^r ^t-^^dfng he ^^^"r'rend of the Sylvian t:^T:'''TZ^^k^:^ '^^SrSngent tales origin fron, a nuc.eus (n. fa. d™inon«it«din.lU dorMll.) whhin the gray matter of the fl^r of the third ventricle in the vicinity of the corpus mam- mUlare. The contributions from both these sources ,om Se f^iculus as crossed fibres from the nude, of the °PP°fVte fibres arising from the vestibular (Deiters) nucleus constitute an important element of the ^sterior longitudinal bundle, since they estebhsh reflex paths for ^uilibration impulses. T''^ fi''"=^> .'t^ "^,^,io„, uncrossed, join the fasciculus and pass m both directions^ S pling brainward have as their chief objective point L ocilomoTor nucleus, although the nuclei of the sixth and fourth nerves receive fibres or collatera s. In this manner the filaments supplying the various ocular musdes Tre brought under the influence of the vestibular impulses. I, is pmbable that the facial nucleus likewise receives collaterals, if not main stems, of the vesjibulo-nuclear fibr^ V Upon dinical and experimental evidence, it may be as.sumed that fibres pass by way of the longitudinal bundle ^Tthe abducent nucleus to that part of the oculomotor nucleus sending fibres to the internal rectus tn-f ^ ° *e opposite side (perhaps also from the nucleus of the third ^er^to that of the abducens of the same side), by which arrangement the harmonious action of the internal and eSal recti musdes is insured. Basing their '^J^f^^^-^ upon similar evidence, many anatomists accept the e^tencLof fibres which pass by way of the p*»tenor longitudinal bundle from the oculomotor nucleus tothe cells of the facial nucleus (page 125 «) f™"'^**"^'' P'^ cwnieator superdlii. In this manner fibres supplying the orbiculans P»'Pf''"™",.""VJLto~SSrL su^^^^^^ -xp'^ined. A the coordinated action of th«je «"J^^'^^'' ' , J "^^^^^^^^ bundle between the . similar connection is P'°t'^'''y f ^"'*^~ ^e faciaT^iierve whereby the closely a.ssociated nucleus of the hypoglossal and that of the '*S1?^' "f^^: *J^,„ Jf the posterior fasciculus areas lietween the afferent and efferent paths. ««ociation fibres the various levels of cerebellum. DEVELOPMENT OF THE MESENCEPHALON. of the cerebral hemispheres in man, the mid-brain becomes co^e j, ,^.,g s^:r!S^r iisrjti^ntn. ii°"-r.ES5n i ,»,«.„ ,«o,„« eventually reduced to the narrow Sylvian aqueduct. OiaKTam sh.)»i>i|! ihief consliluents of pcteriorlongiludinal fasciculus. 111. IV^I VII, XI!. iiuclri of respective nerves •' DN, vestibular (Deilersl im cleus- CN, common nucleus of posterior commissure and posterior longitudinal bsciculus. III8 HUMAN ANATOMY. The dorsal zones of the lateral wall of the mid-brain give rise to the quadrigeminal plate, whose external surface is at first smooth but later marked by a temporary median longitudinal ridge. AUtut the third ftetal month, with the exception of its lower end, which persists as the frenulum veli, this ridge is succeeded by a longitudinal groove bounded on either side by an elevation. The elevations of the two sides mark the appearance of the corpora bigemina, cor- responding to the optic lobes of the lower vertebrates. During the fifth month, an obliquely transverse furrow forms on each side, by which the paired elevations are subdivided into four eminences, the corpora quadrigemina. About this time the corpora geniculata, which however belong developmentally to the diencephalon, are also differentiated and for awhile are rela- tively very large and prominent. The ventral zones greatly thicken and give origin to the tegmentum, including the nuclei of the oculomotor and of the trochlear nerves and, perhaps, the red nuclei, and the mantle layer of the cerebral peduncles with the interpeduncular substance. The floor-plate becomes com- pressed between the expanding ventral zones of the l.-iteral walls and probably is represented by the raphe. Since the fibre-systems of the crustae are, for the most part, derived from sources nutside the brain-stem, their appearance within the peduncles follows a secondary ing^rowth, and only after such invasion do the cerebral crura present their characteristic ventral prom- inence. The cortico-pontine tracts share with the pyramidial fibres the characteristic of tardy niyelination, since they do not acquire their medullary coat until some time after birth. Among the eariiest of the cortico-bulbar fibres to become medullated ( a few weeks after birth ) are those destined for the motor cranial nerves by way of the crustal or pyramidal fillet of Flechsig. .According to Kolliker, the stratum intermedium, which is closely related to the substantia nigra, not only in position but also by the destination of many of its fibres, contains a consider- able number of medullated fibres by the ninth foetal month. THE FORE-BRAIN. It will be recalled that the fore-brain, the anterior primary cerebral vesicle, gives rise to two subdivisions, the telencephalon and the diencephalon (page 1060). Since the latter lies immediately in front of the mid-brain, in following the order in which the brain-segments have been described, the diencephalon next claims attention. THE DIENCEPHALON. Strictly considered upon the basis of the classic subdivision suggested by His, the diencephalon, or inler-drain, includes (i) a large dorsal portion, the thalamen- cephalon and (2) a small ventral portion, the pars mammillaris hypothatni, together with ( 3 ) the enclosed remains of the posterior part of the cavity of the fore-brain, as represented by the greater part of the third ventricle. The thalamen- cephalon, in turn, includes : (a) the thalamus, (^) the epithalamus, comprising the . pineal Ixxiy, the habenular region and the posterior commissure, and (r ) the meta- thalamus, including the corpora geniculata. Since, however, the description of the third ventricle and its surrounding structures — the essential features of this segment of the adult brain — requires the inclusion of parts belonging to the telencephalon ( pars optica hypothalami), it will be more convenient to disregard their strict ilevclopmcntal relations and include the representatives of the pars optica in the consideration of the diencephalon. The Thalamus. — After removal of the overlying structures — the corpus callo- suin, the fornix and the velum interpositum — the thalami (thalami), also called the optic thalami, are seen as two conspicuous masses of gray matter separated by a narrow cleft, the third \entricte. Each th.tlamus is an ovoid ganglionic mass, blunt wedge-shaped, .is seen in crr>ss-sections (Fig. 967), whose long axis extends from the narrow anterior pole backward and outward. Of its four surfaces, the lateral and ventral are blended with the surrounding nervous tissue, and the mesial and dorsal are to a large extent free. The large superior surface is irregularly triangular in (iiidine, slightly convex in the frontal plane and markwily so in the s.-igittal, and covered with a thin layer of nerve-fibres, the Stratum zonale, which imparts a whitish color. This stratum is composesii!<-. T.;itrra!ly, thr- suporinr surface ih separated from the caudate luicleus by a gro<)\e which f)bliquely crosses the floor of the lateral \entriclc and lodges a narrow band of fibres, the taenia semicircularis (stria terminalis) and, in its anterior part, the vein of the corpus striatum. In its front half, where it bounds the THE DIENCEPHALON. 1 1 19 ventricle the inner border is sharply defined from the m^sia surface by a delicate hut weU defined r^dge, t«nia th-iami. produced by ine thickening of the ependyina nf heS ventricle, alo-.g its line of reflection onto the membranous roof and 1 Underlying strand of nerve-fibres, the stria medullaris. Traced backward, the tenia Sami becomes continuous with the stalk of the P'"«»l b'^y. B'^^^'-'^" ^i^ ridge and the diverging mesial border of the upper surface of the thiJamus. is nduded a narrow depr^Jd triangular area, known as the tngonum habenul« It li« on a distinctly lower level than the adjoining convex upper surface of the ha lamus Since it contains a special nucleus and belongs to the epithalamus, its dc'Sion will be deferred until that region is considered page . .23). The upper surface s not quite even, but subdivided by a shallow oblK,ue furrow, which runs from before backward and outward and marks the position of the over ving latera border of the fornix. External to this hirrow lies a free marginal zone that forms a mrt of the floor of the lateral ventricle ; internal to it is an attached inner zone ov^t ffich the velum interpositum is united to the thalamus. By the attachment of this lie. 966. .Corpus canoKtim Septum ludduia Taenia semicircularis and vena terminaliii Ttenia chorloidea Furrow for fornix Tsnia Ihalami Trigonum habenulK Pulvinar Corpora quadrigeniina Caudate in leus Anterior pillars of fornix Foramen of Monro Anterior commissure Middle commiHHurc in HI ventricle Thalamus Posterior commissure Pineal Iwily l.iMfi^ila sheet to the fornix above and to th- thalamus below, direct communication between the tWrd and kteral ventricles is shut off save through the foramen of Monro. In fron he su^rior surS ends on the rounded elevation (tuberculum antenus thalam. ) wSh maXr anterior pole of the ganglion. -^^^^^^Z^ fmmediate lining of the ventricle, the ependyma. The upper boundary of the r.Rs al 3 Sts sharply define.l hv the ta-nia thalami, which behind is continuous w. h tlu- mlk of the ^i^eal body (Fig 966). Us lower limit is i"^-;^;;',,^'^^:;^ "lie furrow, the sulcus hypothalamicus. which separates the Jf^si-i surf-ices hvnothalamic re^nons. Somewhat in advance of their middle, the mesial surlaits dihe two thalami are r .nnected bv a bridge of gray matter, known as the middle comSure (massa intermedia), usually about 7-S mm. ,n diameter juu Tvai in section, but very variable in thickness and form. F--"»he -eagre numlx of medullatcH nrrve fibres that it contains, its importance, at cas m "i- "• ,^ ' "^ to brsm'in The lateral surface of the thalamus is inseparab y blended w.tl. lu- adiacenT hick and conspicuous stratum of white matter, the internal capsule which nten.eni between the thalamus and the more laterally placed lenticular m. k:1 HUMAN ANATOMY. nucleus, and establishes the important pathway transmitting the fibre-tracts con- necting the cerebral cortex with the thalamus and with the lo^^L•r levels by way of the crusta of the cerebral peduncle. Since the innumerable fibres which pass to and from the thalamus along its ventro-lateral surface interlace, this surface is covered by a distinct reticulated stratum, to which the name external medullary lamina is applied. The ventral surface is also attached, but instead of being imited with the internal capsule, as is the lateral, it rests uf>on and is intimately blended with the upward prolongation of the tegmental portion of the cerebral peduncle, here known as the subthalamic tegmental region, presently to be described (page 1127). Fig. 967. Mifhlle c 2;r "*c£ a large par. o. the hht» Fig. 968- Corpus caUodum Choroid plexus Latenl ventricle Stratum zonsle Caudate nucleus Genu of internal capsule Thalamus, mesial nucleus Thalamus, latiil nucleuA Internal capsule PttUmi Gyrus callosus Cingulum Corinu calloaum iriate vein Caudate nucleus Taenia semidrcularls Internal medullary lamina Globua pallidus Anterior pillars of fornix l.amina dnerea External medul- lary lamina Mammillo- tbalamic tract Futamen Globus pallidus Thalamo-tegmental ' tract Olfactory 6br«s Anterior cnrnmiasarc Oblique frontal section through thalamus and snterior commissure ; Weigert-Pal MainiuR. X |. ^ Preparation by Professor Spiller. coursing within the anterior pillar of the fornix are carried to the thalarnus( page „sq The entire ventral part of the thalamus is occupied by an illy-defined ma^ o gray matter, known as the ventral nucleus which lacks «harp definition from the overlying nuclei and in fact is continuous with the lateral nucleus. The ventraJ nucleus Snts a differentiation into the nucleus centralis of Luys, which occupies a mSal'^^sition and appears round in section (Fj^/o). a"d re^^^^^^^ the red nucleus and the posterior commissure and the nucleus «r'=*^°';!?»"; .^"'"^ ies ventro-lateral to the preceding nucleus and is crescentic in ouriine. The ^f nt-^ nucleus is of importance, not only because it receives the great sensory paths, but a so "^account of ite phylogenetic rank, since, according to Edinger. it, .together with the gangUonhabenute, represents the oldest of the thalamic nuclei and is found through- *'"'*ConnTcSs1)'f^he Thalamus.-Broadly considered, the thalamus may be regarded as a great ganglionic internode interposed ui the corticipctal paths around vwTelU mSt of'^the^ constituents of the important secondary P^ths conveying aSt impulses from the spinal cord, the brain-stem and the cerebellum end, 7' II33 HLMAxN ANATOMY. : and from whose cells corticipetal fibres pass to all parts of the cerebral cortex and to the corpus striatum. P'urther, it must be understood that the thalamus receives fibres from all parts of the cerebral cortex, and, lastly, that from it proceed efferent fibres to the lower centres within tht brain-stem and the cord. It is evident, therefore, that the connections of the thalamus are very intricate and far reaching. I. The lower thalainocipetal trmcts include : (a) those passsing directly from the spinal cord, as the spino-thalatnic and probably a part of Gowers' tract ; (b) those passing from the various nuclei by way of the median fillet; (f) those pa.ssing from the cerebellum, either directly, as the cerebello-thalamic Fig. 969. tract, or, after interruption in the red nucleus, as the rubro-thala- mic; (d) probably other tracts which arise within the tegmen tal area of the brain-stem. The fibres from the various sources enter the under surface of the thalamus to end within the ven- tral nucleus, or by means of the internal medullary lamina to be distributed to the other nuclei. 2. The thalamic radiation comprises the fibres which stream from the latero-ventral surface of the thalamus to all parts of the hemisphere { thalamo-cortical) , some cros.sing by way of the corpus callosum to the oppo- site side, as well as those which pa.ss in the opposite direction ( corlico-thalamic ) towards the ganglion. Although as they traverse the external medullary lamina the fibres are not particu- larly grouped, their various rela- tions to the cortex or other parts are established by different and more or less definite paths. These are designated as the stalks of the thalamus, of which a frontal, a parietal, an occipital and a ventral are conventionally distinguished. The anterior or frontal stalk emerges from the fore-part of the lateral surface of the thalamus, traverses the an- terior part of the internal capsule between the caudate and lentic- ular nuclei, to which it distributes fibres, and finally gains the cortex of the frontal lobe. From the cells of this region, cortUo- Ihalamic fibres follow in reversed order the paths just mentioned, thus establishing a double relation between the cortex and the basal ganglion. In addition to the preceding cortico-thalamic fibres, the antero-ventral part of the thalamus receives a strand from the cortex of the olfactory bulb. The parietal stalk leaves the lateral surface of the thalamus and enters the internal capsule and often the lenticular nucleus, in 'ts course to the parietal cortex. Other corticipetal fibres, destined for the parietal and adjacent parts of the frontal lobe, are the continuations of the path of the mesial fillet. To a large extent these fibres pass from the ventral thalamic nucleus outward to the under surface of the lenticular nucleus, then bend upw.ird and traverse the lenticular nucleus by way of the medullary- strire or the globus pallidus to gain the cortex. Other fibres continue the fillet- path by entering the internal capsule and thus, perhaps, directly proceed to the cortex. Tlie occipital stalk includes the fibres that connect the thalamus with the visual cortical areas of the occipital and parietal lobes. They is.sue from the lateral surfat-e of the pulvinar, and as the Median fillet Spino-thalamic DiaKram showtnfc chief connections of thalamus ; lilack fibres rep- resent afferent tracts endinK in thalamus and thalanio-i-ortical paths; red fibres are the cortico-thalamic and strio-thalamic paths; /.thal- amus; C. /,, caudate and lenticular nuclei; C ^'.corpus callosum; /■. /', 7; O, frontal, patietal, temporal and occi[>ital lolws ; Fx^ fornix; J/. mammillar>' body; Pd, cerebral peduncle; SC, IC, superior and in- ferior collicuti ; A*, red nucleus ; Ps, pons ; /. frontal stalk ; 2, parietal stalk ; J, /, lenticular and temporal parts of ventral stalk ; 5, occipital •talk. THE OlENCKFHALON. «>-,^ ventricle to end in the cortex. Ihe '«"""•"" . K , ^u^..^.^ „f ,he thalamus, include two systems^ ^;"-'«:« j'","^; t. rp^«s d. u^w^S and ou.v.ard Umath the from the lateral »'«',.~'^ ""^^'^'k*.,;, ^^tir-.^w pedunculari., c.mtinues laterally into lenticular nucleus. U. '"*"i',^'^;,X'';^;,„l IoIk- ; itV u,n*r ,«.rt. the ansa UntkHtarn. r ?"I^:\he adi3.lr1i'r o 0^ iSal nucleus wh^i. Inters to Rain the ,.utan...,. closely skirts the ''"'■'^*^"* "V™, ;' ,,' _„.,„„, ,,.. way of the medullary laminif. to reach the direct route of the '"'«=™»',f' ."T'''^; ., ,^^„ „, ^hite matter which covers the superior aspect 3. The .tratum »«>".•»«• »h« thin '-^V" « 7^^^^, fibresderiveil from the optic tract or the "' '"'^ '"iTon"' Th.^'f'rom tlTc Cra rtf"" .Kct su,.rficially cro.s the external genic- optic radiation Th<«* ''"■"/.";;. "TL „hile those from the .x:cipital cortex by way of the t^.'^:^^^^z'X^:''^^^^rr'''- - ^^ — --"= '-'-"^ '''-- f^m the temporal cortex by way of the ventral stalk. TheEoithalamus.-rnder this suMivision of the thalamencc-phctlon are • I J 1 (^^i^^triironum habenulw, (2) the pineal body, and (3) ^S^^ posterior riSn-i Srum^^^ as^K^iated with^he su,x.rior and posterior Ix^un- daries of the third ventricle. Fic. 97" Veins of r.alen in velum inlerpositum nannlion hahenula: External medtillary lamina Internal capsule Optic tract Subthalamic nucleus Oblique fronUl «Cion thmuKh^thaJlamu- and ,uWb^aU,m Weigert-Pal staining. X |. Th- trigonum habenulae is the narrow trianRular area Iv-nR Jf «^;;n ;J^ sharpy dSed edge (t*.iia thalami) of the ventnctilar -^-^^'^^f^.^i^^ dive^ginK mesial border of the upper surface of the \ha -ni"^,,';;™ '>,„'a^'£hS i; Its surface is depressed and at a lower leve than that of ho thalamus ^^^^^^\ continuous with a mesially curvinR strand the pmeaj^dt^nclc-e^^^^^^^^ ridge of thickened ependyma marking the taenia thalan"; ^..1 .nd c" ire"by of ner^.e-tibres, the stria mcduUaris. while at a still '^'i^^^l^^'''^,.^'''^^^ the superficial fibres is situated an aggregation of ^'^'''! "*l\^;'^.^1^,,3l"rU 1 1 24 HUMAN ANATOMY. m > til -:h :, ;5: lucidum and the olfactory area, and ( 2 ) cartiro-habeHiilar fibres, which spring from the cortical cells within the hippocampus or the adjacent region, and by way of the fornix and its anterior pillar are carried to the fore-end of the thalamus, whence they pass backward within the medullary striii. (3) ^M^tx tkalamo-habenular fibres als«> probably join the stria medullaris from the interior of the thalamus. Whilst many of the fibres compf>sing the stria end around the cells of the ganglion habenular, some continue backward, without interruption, within the strand known as the jxtluncle of the pineal Ixxly, cross to the other side in the bundle bearing the name, commissura habenulce, and end in relation with the cells of the opposite habenular nucleus. The g-anglion habenulo- (Fig. 970), in turn, gives origin to an im|}ortant bundle, the fasciculus retroflexus of Meynert, which arches down- ward and backward, pa.ssing at first between the central gray matter of the third ventricle and the thalamus proper, and later to the medial side of the red nucleus, to reach the base of the brain, and for the most pwrt to end around the cells of the interpeduncular ganglion. This nucleus, which in many animals is a well-defined collection of cells, in man is represented by a more scattered median cell-group within the posterior perforated substance close to the anterior border of the pons. The fasciculus, also termed the habenulo- peduncular tract, receives contribu- tions from the ganglion habenula; of both sides, some fibres having cro.~-sed in the habenular commissure ; although the majority of its fibres end, mostly crossed, in the interpeduncular ganglion, not a few may be traced farther caudally within the tegmentum of the brain-stem (Obersteiner), as may also the fibres from the cells of the ganglion interpedunculare. The Pineal Body. — The pineal body (corpus pineale), also often called the epiphysis, is a cone-shaped organ, from 8-10 mm. in length, attached to the posterior extremity of the roof of the third ventricle. It is slightly compresseil from above downward and Kio. 971. rests, with its apex pointing backward, on the dorsal as|}ect of the mid-brain in the trian- gular pineal depression between the superior corpora quadrigemina (Fig. 966). Its base, as its anterior end is called, is attached abcve to the comml - sura habenulze, from which on each sidf a narrow but distinct ridge, the pineal stalk, curves forward to be- come continuous with the stria medullaris. Below, its base is united with the posterior com- missure of the brain overlyine the entrance into the ylvian aqi;e- duct. Between the habenular and posterior commissures a small pointed diverticulum, xhc pineal recess, e.xtends from the third ventricle for a \ ery short distance into the pineal body, and thus recalls the early condition in -vhich .he organ is de\eloped as a tubular outgrowth in the roof-plate of the diencephalon. This relation to the thin ventricular roof the body retains, its apex later becoming closely surrounded by and embedded within the loose vascular tissue of the pia '.sater. The structure of the pineal body, as seen in cross-section (Fig. 971 ), includes a reticular framework of connective tissue trabecuke, whose meshes are tilled with Calcare m-, ci)iicrt;i<»ii Connect tisHut .^1 St'ction of pineal body showinfr calcareous conrreliohti ur braiii sand. X l,v>. i t' THE DIENCKPHAI.ON >>25 l.riitKular urta \ Retinal area Blood Uiverticulom dividinK into tubnla lal ••ctlon of pinnil orgmn nnbr\o. Lacerla agilii) 1 . A .,;t»,«i;il r.-lU which ofu-n contain bmwnish pin- n.unaecl or so^etu^e, e..n«.U^q.t^^^^^ ,H.- anu-rior ,«rt. ,,roba.,1v :;::::;ath!i^'in':;r:K;,:!;:;d\.itLa .. the h...u.^k .-.. a ae„.c nct-woru o. neuroKlia fibres in the L.iider piirt, ,,-,^j ,., the pineal b >«»^""^'"'^ "^j^^^ of purpose in the hipher types, to the invertebrate visual organ su^ed a pc^^^^^^^ ,^ „„, „„,y an assumption tha was '*'"="f ''*"^. ^^ J^Hetel ^^^^^^ POsi'i«n °" '»^ ''««' ^^' ^'""^, is borne by a sUlk but reaches an '"t«^™^' '"P^,, "^^ orean was. therefore, designated through or lying within a n-oaloramen^m^^^^^^^ Whilesucha thepin.rieye.athouRh protably mnoexist^^^^^^^ embryonic relations in many reptile^ superficial position in the adult is very "«^fP"°r' ," „„ ., l^e pineal body, at least in such (Fig. 97») are very suggestive of the P;:°b«ble «gn^ca^ °» an eyTThes^ conclusions are for^^a rudimentary sense °'K^"; »^^8^„"f ,o^'^„7t^^^^ in man, which is likewise suggestive m formmg ou^ co^^'^"s 'r^^Zls representing a very imperfectly develop and ^eatly modified sensory structure AUhough strictly belonging to the telencephalon, men- tion may here be made of a second evagination, know as the ^.p^y.i.!which arises from the roof-plate of the fore-brain ThXuch appears in advance of the pineal outgrowth and s atenvporary s^cture. seemingly being in nature comparable to a^^mwardly directed choroid plexus. The paraphysis has be^n described in the lower vertebrates, including reptiles and Wrds, in some mammals «"<> 'ndeed according to the observations of Francotte and of Ewing Taylor, it is not improbable that a corresponding evagination is recognizable in the early human embryo. Fig. 973- Small portion of pine»l bod>(leartcrcro»»e» cut tail of caudate nacleua) Median geulcuiale body Hippocampus Superior cerebellar peduncle rront.1 .ection oi brain pu.l>« through poaterior pole. oC Ihalaml. pii»*l body and brainilem. rablv blended with the ventral surface of the thalamus, which thus obliquely overlies Se teStiorof the tegmental or senst,ry portion of the cerebral stalk. Through tWs ar^the im^rtant tSamocipetal paths^the fillet and of the superior cerebellar D^uncles reach the thalamus, and witliin it are seen the upper extremities of the St^^gHao? the mid-brain the su6siaHfia nigra and the red nucleus, and a new S dXv matter, the corpus subihalamicum. The substantia nigra presents the ^me chfrTcteristra here as in the peduncle, being conspicuously dark and overlying ?h^crusSbr^ As it ascends, ^decreases in bulk from within outward until at the'evS of the mammillary body, the substantia nigra is m. longer recognizable. The conn^tions of the cells within the substantia nigra are imperfectly understood Jut iHs^obable that they receive many fibres from the caudate nucleus and the puumen and. perhaps, als^ from the frontal cortical areas. From the cells on the other hand, fibres pass into the tegmentum and into the crusta and thence to lower levels. According to Bechlerew, some fibres join the fillet-tract and thus relch the superior quadrigeminal bodies. At first the red nucleus is a v.r> prominent feaCe in frontal sections of the subthalamic region (Fig. 970). api,eanng II38 HUMAN ANATOMY. I jl as a circular area of gray matter enclosed by a zone of cerebello-thalamic fibres ; farther forward it, too, gradually diminishes and disappears at a level somewhat behind that of the corpora mammillaria. The connections of the red nucleus have been considered in connection with the superior cerebellar peduncle (page 1095) ; suffice it here to recall its twofold significance as an interruption station for many of the cerebello-rubro-spinal and for the cerebro-rubro-spinal tracts. The corpus subthalamic um (nucleus hypothalamicus), or nucleus 0/ Luys, is a mass of deeply tinted gray matter peculiar to the subthalamic region and unrepresented in the mid-brain. It appears in cross-section (Fig. 970) as a small biconvex area, immediately dorsal to the tract of crustal fibres and lateral to the red nucleus and the substantia nigra. As the latter diminishes, the subthalamic nucleus expands to take its place and, where fully represented, measures from 3-4 mm. in thickness and from 10-12 mm. in its longest diameter, and extends superiorly considerably beyond the level of the red nucleus. Histologically the subthalamic body is distinguished by a dense net-work of fine meduU,' id nerve-fibres, enclosing pigmented multipolar nerve- cells of medium size, and by an unusually close mesh-work of capillary blood-vessels. The dorsal surface of the nucleus is defined by the overlying lateral part of the field Fig. 976. Septum luddum Choroid plexuii Fonmen o( Monro n«nu of corpus calloaum Roatnim of corpua calloaum Anterior commiaaun l.amia« dnem Optic recna Optic commiaaute Anterior lobe of pituitary tiody Poaterior lobe of pftt '• Body of fornix Velum interpoaitum coveriti<^ Thalamua. [thalamus mesial autfacc Tenia thalami plenium lommiaaura habenulie Pineal recess ituilary body lafundibulum' Pineal body Posterior commissure ^^Quadriiceminal plate Sylvian aqueduct Cerebral peduncle Middle commlaaure Sulcua hypothalamictu Mammillary body , Amerior pillar of tbmix Tuber cinereum Right lateral wall of third ventricle : velum interpoaitum coven auperlor aurface of thalamus. of Porel, as the stream of fibres passing between the red nucleus and the thalamus and the internal capsule is called. From the ventral surface of the nucleus, fibres pierce the adjacent crusta and join the ansa lenticularis to gain, probably, the globus pallidus; other perforating fibres perhaps connect the subthalamic body with Meynert's and Gudden's commissures (Obersteiner). The ventro-medial ends of the bodies of the two sides are connected by a bridge, the cominissura hypothalamica, which traverses the floor of the third ventricle above the mammillary bodies. In addition to connecting the two subthalamic nuclei, the commissure contains decussating fibres from the anterior pillars of the fornix and, according to Edinger, probably fibres from the fore-end of the posterior longitudinal fasciculus. The corpora mammillaria (corpora mamlllaria), also railed the corpora albi- caniia, are two hemispherical elevations, about 5 mm. in diameter, which lie close to the mid-line within the interpeduncular space on the basal suriace of the brain (Fig. 993). They are almost but not (juite in contact, being separated by a narrow interval which immediately behind the little bodies deepens into the anterior recess mn'" ing the front end of the shallow median furrow that grooves the posterior perforated sub- stance. The posterior surfaces of the mammillary bodies indicate the anterior limit of the ventral surface of the mid-brain. When examined in section (Fig. 970"), THE DIENCEPHALON. 1 139 each body is seen to be composed of an outer layer white matter encl(«ing a core ^eraVsubstance, known collectively as the nucleus mammiUans The latter.. suMiv^ded into a medial and lateral part by fibres from the downward archmg ante, rior pillar of the fornix, which penetrate the gray matter as well as mvest to a larj,e extent ^ exterior. Only a part of ( i ) the fornix fibres however, end directly in the Sa^mUkry nuclei, since^ome pass above and behind the ganglion to gain the hv J^c ^mmissure (page .128) and. after decussation to end in the mam- SuSTtody of the opposite side. From the dorsal part of the medal nucleus SSSisH^from thedl one by its larger nerve-cells, emerges a disUnct and com^ bundle of fibers (Fig. 967 ). which on clearing the nucleus, separat^ into two Sr One of these, known as (2) the fnammiUcthalamic tract, or the bundle oTvkqiAzyr, course, upward and forward, a '. ends within the anterior nucleus of the tlmlamus : n this manner it completes the paths by which the cortical olfactory centr« withiA the hippocampus major are connected (by way of the fimbria, body and ^terior pUlar of tKmix and the mammiUo-thalamic strand) with the thalamus TFie 1S9) That fibres pass between the latter and the mammiUary nucleus in bothdir^iions, is shown by the fact that destaiction of either of these centra is fol- lowed in turn by ascending or descending degeneration of the fibres. (3) The Sh^part of the bundle issuing from the mammUlary nucleus arches backward and do^,^ and, as the mammiUo ^gmental tract, is trac^ble into the tegmentum of SHTd brain to the vicinity of the inferior colliculus. (4 Under the name^ pedm^ c^^ corporis mammUlarU, another mammillo-tegmental tract « described. This sb-and ^ngs from the lateral mammiUary nucleus, and coursing backward and downw^ along the medial mar^n of the cruste. enters the tegmentum Its d^- S^tion is uncertain, but according to KoUiker the tract probably ends '" the ce""^ gray matter surrounding the Sylvian aqueduct m proximity wrth the trochlear Sur Other, but much less well established, strands have been descnbedby LenWk as proceeding forward from the peripheral layer of the mammillar>- body ovTr^ tuber cinereum. Concerning their further course httie is known with *'^'^The" tuber cinereum is the first of a series of median outpouchings which model the thin sheet of gray matter constituting the floor and the anterior wall of ^ifthii ventricle and bdong to the pars optica of the hyjK,thalamus. As seen from he exterior (Fig. 993). the tuber cin«eum is a median elevation placed between the mammilUr^ boSes behind and the optic chiasm in front, and the cerebral peduncles Td t^ Sic tracts at the sides. T^ether with the infundibulum it forms the most dependent part of the third ventricle and consists of a thin layer of gray matter, less than 1.5 min. thick, that is continued forward as the attenuated extension o the im- portant sheet found within the mid-brain and fourth ventricle. In addition to the fibre- Sds coming from the mammiUary bodies noted by Lenhoss^k^ this investigator and KoUiker credit the tuber cinereum with possessing small paired composite gang- lia, the nuclei tuberis and the nuclei supraoptici of KoUiker Concerning their con- nections nothing is definitely known. The anterior part of the tuber immed.atel. Sd the optic chiasm, descends abruptly and somewhat forward to form * funnel- shaped stalki the infundibulum, to whose lower end or apex is attached the pos- teri^obe of the pituitary body (Fig. 976), Although in tlie very young child the infundibulum retains to some extent its orig nal character as »,hollow outgrow^ from the ventricle, in the mature subject this cavity, the rece.tu. nfundibuli. has mostlv disappeared and the stalk is solid, save for a slight diverticulum within its "'''"The pitlrior'^'pi of the tuber cinereum. between the root of the infundibulum and the mamillary bodies, exhibits occasionally in the adult brain and almost con- stantly in that of the foetus, a smaU rounded median projection flanked on each side by a slight elevation. To this modelling Retzius has applied the name, ''«";'•«"« saccularis in recognition of its similarity to the evagination (saccus vasculosus) f.uind in fishes. The eminence encloses a shallow iwuch, recessus saccularis, which opens into '"J^ *J\'jJ,i\^"/"bon the posterior or cerebral lobe retains few histological features suggesting its nervous origin. Of the demonstrable interfacing fibres, with fusiform enlargements and elong-atetl nuclei, none can be identified as ner\e-fibres, while of the numerous celts which the lobule contains, only a few of large size and pigmented cytoplasm uncertainly resemble ner\«us elements. With the exception of possibly neurogliar cells, the existence of definite nervous tissue within the cerebral lobe of the mature human hy|)ophysis is doubtful. .... The optic tracts and commissure are elsewhere described (page 1223), suffice it at this place to mention their relation to the interpeduncular structures. The t)ptic tracts diverge biickward and wind around the ventral surface of the cere- bral peduncles (Fig. 993). Their medial ends are fused into a transversely flattened white band, the optic commissure or chiasm. The latter is connected with the front nur{.ice of the tiibtr rinoretim, whilst above the chiasm the anterior wall of the ventricle consists of a ilelicate sheet of gray matter, the lamina cinerea ( lamiaa termlnalis). This structure lies in the mid-line, passes almost vertically upward, with a slight forwardly directed curve, and becomes continuous with the rostrum of the corpus THE DlENCEl'HALON. ii3> caUosum. Just before meeting the latter, the lamina passes in front of the anterior '^"^ The Thtd'vi'nTricieiThe ^ ventricle (veotriculus tertius cerebri) is the narrow cleft-like si«ce that separates the medial surfaces of the thalami (big. 966)- r^Imewhat broader behiJId and much deeper in front, where it comes mto close relation with the exterior of the brain, the interpeduncular lamina alone .ntervenmR. S Tom the side, as in mesial sagittal sections (Fig 996). the ou'l'nf ««, ^e ventricle b irregular y comet-shaped, with the broader end above and behmdand the UunS (^inV^ccti downward and forward ( Fig. 978). Behmd. it commun.ca es wi"Ke Cvian aqueduct, and through this canal indirectly w.th the fourth ventricle; Ser brly U connects with the two lateral ventricles by means of the Gramma of Monro Its sagittal diameter, measured between the anterior commissure and the We of the pirell body, is approximately 2. 5 cm. The lateral wall of the ventricle J^fg 9r6) ^formed chiefly by that part of the thalamus which lies below the level of h; ?L a thalami. On this surface, slightly in advance of the middle, '« «een he small oVal field of the middle commissure, and in front of this the downward curv ng ekvatbn produced by the anterior pillar of the fornix. Between the latter and the Snent'^amerior tubercle of the thalamus lies the foramen of Monro (foramen Kent" c« are), which establishes communication between the third and the cor- Fig. 978. Pineal ncf* Suprapineal recfsa' Posterior commissure Sylvian aqueduct Middle commiHure Foramen of Monro Anterior commissure Mammillary body Infundibulum ' Optic recesa optic chiasm Cast of third ventricle, viewed from the side. >, J. {Krlxms.) responding lateral ventricle, and transmits the trunk formed by '^e union of the vein of the corpus striatum and the choroid vein. A shallow furrow on the ventric- ular wall the sulcus hypothalamicus leads from the foramen backward and some- what downward (Fig. 976). It is of importance as indicating, even in the adult brSi, the demarcation towec. the thalamencephalon and the hypothalamus_pa ts derived respectively from the dorsal and ventral zones of the embryonic brain-% esice^ The roof of the ventricle extends from the foramina «^M«nrc^ bo imded alx ve and in front by the arching piliars of tlic fornix, to the pin^l body liehind, o%er which it pouches out into the %ra/,ineal recess, as the little dwertK"'"^ ^^^^^^^^^ The body is termed. The immediate and morphological roof consists "' the delicate epenTmal layer, which is attached to the t^nfa thalami on each side and stretch ng aS^he interthalamic cleft, closes in the ventricle. The ependymalayehtw ever is backed by a vascular folu of pia mater, which, in conjunction «'th t^^ epUhelTal layer, constitutes the ve/um iHterposilum. This structure is more Jul y Scril^ in'connection with the lateral vemricles (page ..62): ^-tits relation .0 the third ventricle finds appropriate mention at this place. As '" ^J^ " "* f. JJ^. fourth ventricle and in the lateral ventricles, so in the third does the % ascula. Mssut of the pia mater invaginate the ependymal layer to form vascular fnnges which pro ect ^l™he ventriL (Fig. 97/). A doubfe line of -ch invaginations han^i {rom the roof of the third ventricle and constitutes the chorotd plexus of that ^jace^ Since the ependyina everywhere covers th.::>c pial procPS-^-s, it is evident th-it tne fringes are. Trktiy regarded, outside the ventricle and excluded by the continuous layer of the epithelium. 1133 HUMAN ANATOMY. The posterior wall of the third ventricle is very short and includes the base of the pineal body, with the opening into the minute pineal recess, the posterior com- missure and the orifice leading into the Sylvian aqueduct. The floor slopes rapidly downward and forward (Fig. 976) and comprises a small part of the tegmentum of the cerebral peduncles, the posterior perforated substance, the mammillary bodies, and the tuber cinereum with the infundibulum — structures already described and included within the interpeduncular area on the base of the brain. Corresponding with the position of the superficial elevation, the ventricle exhibits the diverticulum of the inhindibulum. The optic chiasm marks the anterior limit of the floor and the beginning of the anterior wall. Immediately above the chiasm the anterior wall exhibits a diverticulum, the optic recess, from which the lamina cinerea ascends to join the rostrum of the corpus callosum, in its course passing close to and in front of the anterior commissure. The latter structure shows on the front wall of the Fig. 979. Cavity tn wptum lucidiim Corpun cmlkwum. cut Caudate nucleus Internal capsule Putamen of lenticular nucleus cm anterior end of fornix Anterior pillars of fornix Anterior commissure Lamina cinerea, above, optic recess Lateral ventricle Epeudyma covering ^ tKnia xemicirculans and vena terminaliH Thalamus, anterior tubercle Foramen of Monro lamina cinerea Optic chiasm Portion of frontal section of brain (mssinjc through foramina of Monro, showing anterior wall of third ventricle modelled by anterior commissure and pillars of fornix. ventricle as a transverse ridge between the descending and slightly diverging anterior pillars of the fornix (Fig. 979). Although distinctly modelling the ventricular walls, all of these bands are excluded from the ventricle by its ependymal lining. THE TELENCEPHALON. The telencephalon, or end-brain, consists of two fundamental parts, the hemi- ■phaerium and the pars optica hypothalami. The latter includes : ( i ) the lamina cinerea {lerminalis), (2) the optic commissure, (3) the tuber cinereum and (4) the pituitary body, all of which have been already considered, as a matter of con- venience, in connection with the diencephalon and the third ventricle. The hemi- sphere comprises: d) the pallium, (2) the rhinencephalon, and (3) ^e corpus striatum. The first of these subdix^sions undergoes such enormous development in the anthropoid apes and in man, that the pallium becomes the dominating factor and, expanding upward, laterally and backward as the great cerebral mantle, not only forms the chief bulk of the cerebrum, but overlies the derivatives of the other brain- segments to such an extent that these parts are to a large measure covered and deposed from their primary position on the free dorsal suriace of the brain. In conse- quence in man, in whom the pallium reaches its highest development, the thalami, corpora qiiadrigemina and the cerebellum are maskeid by the hemispheres and occupy topographiaillv a dependent position. The rhinencephalon, on the coiitrary, is in man only feebfy developed and rudimentary in comparison with the conspicuous and bulky ciirresponding structures possessed by animals in which the sense of smell is highly developed. The corpus striatum, consisting of two large masses of gray THE TELENCEPHALON. U33 matter the caudate and the lenticular nucleus, represents the internal nucleus of the Sbmin Certain commissural structures, as the corpus callosum, the -ntcnorcon,. S™ and ih^/onnx are to be regarded as secondar>- and ^ ser^'mg to connect d^L hX« of the great brain. The immediate free or outer surface of the Pall.um .s Sen^hTre formed by a thin peripheral layer of cortical gray matter which as an unb?Ien sh«;t clothL the various ridges and intervening iy^rxo^-^Xh^ convolutions and?.«r«-which model the exterior of the cerebrum and prov.de the nec^ry extent ^surface. Beneath the cortical gray substance hes the M matter which coSutes the bulk of the hemisphere and consists of the tracts of nerve-hbres pa*. W to and from the cortex, as weU as of those connecting the various regions_o the cortS^thTe another. Embedded within the core of white matter and lying much nearer the basal than the superior surface of the hem^phere (F'g- >«^).;»;^ rrous Sum is closely related tVthe ventricular cavity by means o the caudate nucC oT he one hand, and to the cortical gray matter by the lenticubr nucleus on the other In -iew oi the rudimenury condition of the rhinencephalon and the over^shadowin, development of the pallium inman, it is usual and convenient o Sd most of the pam derived from the telencephalon as belonging to he hemSes%e latter term being used in a less restricted sense than warranted by a precise interpretation of its developmental significance. The Cerebral Hemispheres. Viewed from above, the human brain presents an ovoid form the narrower end being dSed forward ;nd the broader backward, the greatest width corrjpond.ng Sh^he parietal eminences (Fig. 984)- T^e convex sujfacefo^^^^ hemisDhereTis divided by a deep median sagittal cleft, the lonptudinal nwure iSSud^alls cerebri), that, for a distance less than one-third of ,te length iSSly Sd more than one-third posteriorly. '?o«"P»«t«ly, 'T*^*^ ^'^^ S.'/t sDhwr In its middle third or more, the fissure is interrupted at a depth of about T, m' by thi arched upper surface of the corpus callosum the chief connect,.on between the hemispheres, ^he upper and back part of the longitudinal fissure, throughout its length, is occupied by the sickle-shaped mesial fold of dura rnater the /X «rr*n, which incompletely subdivides the space occupied by the Srebmm into two compartments. Under the name, transverse fissure (lissura Sv7«a cerebri), is kometim^ described the deep deft which separates the Ser^ferior surface of the hemisphere from the cerebellum the corpora quad- Smina and the pineal body. This cleft, so .f'^ent after the bramh^b^^^ removed from the skull, when the parts are m situ is filled behind by the tentortum cerehelli and in front by a fold of pia. . . , , , The hemispheres are advantligeously studied after being separated from each other by Sta^ section, and from%he brain-stem by cutting across the mid-brair. When exai^ned after such isolation, especially when hardened before removal from the skulleach hemisphere presents a dorso-lateral. a mesial and an '"fenor surface The dorio-lateral surface (1 ig. 980) is convex both from before backward and from above downward and closely conforms to the opposed inner surface of the Sal vault. The mesial surfa'ce (Fig. 987) « flat and vertical and bounds the loniritudinal fissure. It is in contact with the sagittal fold of dura, the falx cerebri. exc?p" in front and below where the partition is narrow; here the mesial surfaces of the hemispheres, covered of course by the pia and «™<=hnoid, lie in apposition The inferior surface (Fig. 989) « irregular, its »PP^^'''"'«t^.,f *3^ *X resting in the anterior cerebral fossa of the cran«l floor the middle third in he lateral part of the middle fossa, whilst the posterior th- is supported by the upp'r aTr^t of the tentorium, which separates it from f bjacent cerebe lum^ At^he jVmcture of its anterior and middle thirds the uitenor su-face o he fm sphere is crossed transversely, from within outward, by the stem of jjie Sylvian fissure and thus subdividctl into an antenor an.l a If't^^^/'^f:*; /.'T X„ and smaller, known as the orbital area, rests upon the orbital plate of he fmntal bone and is modelled by this convex bony shelf '"»«», <=.°"^,P?";J'"ffitf'„""r^ cavity from side to side. The tract behind the deep Sylvian cleft is at first convex H34 HUMAN ANATOMY. I and rounded, as it lies within the middle fossa, but traced backward it passes insensibly into the tentorial area, supported by the tentoriu.:i cerebelli. This area is concave from before backward and directed inward as well as downward, in correspondence with the characteristic curvature of the tent-like dural septum. The borders separating the surfaces of the hemisphere are the dorsu-mesial, the infero-lateral and the infero-mesial. The dorso-mesial border inter\'ene8 between the mesial and lateral surfaces and, therefore, follows the arched contour of the hemisphere beneath the vaulted calvaria. The infero-lateral border, between the lateral and inferior surfaces, is better defined in front, where it separates the orbi- tal area from the external surface as the archefl superciliary border (Cunningham), than behind, where it is so rounded off as to scarcely be recognizable as a distinct margin. The infero-mesial border intervenes between the mesial and the inferior surface of the hemisphere. It is well marked in front, where it limits the orbital area mesially, and again liehind. where it corresponds to the line of juncture between Fig. 980. Ijiteral aspect of left cerebral hemisphere; dono.median iurface Is somewhat foreshortened ; red lines indicate bound.irie!« separatinK parietal, temporal and occipital lobes ; r. Rolandic fissure ; i. g., i. g., its superior and inferior (fenu; .V, .V. S-^, .V* ajc. vertical, horizontal, posterior and ascendine limbs 01 Sylvian fissure: i.p. c, s. p. c, inferior and superior preienlral ; sf., if., superior and inferior frontal ; p.m.. paramedian ; m./., mid-frontal ; d., dla)(unal, here continuous with inferior nrecentral ; ^>. ^, ^./i. inferior, superior, horizonlal and occipital limbs of niter-parietal; p. t;.. parieto-occipital; /', /* asc, superior temporal and its upturned limb; /», /• ajc, middle temporal and its upturned limb; /. o., l.-ansverse wcipllal ; /. o , lateral occipitaf; A., arm centre; i>. T. O.. pars basalts. trianKularis and urbilalis ; Arc. p-a., arcus parieto-occipitalis. the fal.x cerebri and the tentorium and marks the division between the mesial surface and the tentorial area. This margin has been designated the internal occipital border by Cunningham. The extreme anterior end of the cerebral hemisphere is known as the frontal pole (polus frontalis), and the most projecting part of the posterior end as the occipital pole (polus occipitalis), while the tip of the subdivision of the hemisphere which projects below the Sylvian fissure constitutes the temporal pole (polus tem- poralis). A short distance l)ehind the latter, the inferior surface exhibits a well defined petrosal depression (imprcssio petrosa): this is caused by the elevation cross- ing the petrous portion of the temporal bone which corresponds to the position of the superior semicircular canal. Under favorable conditions of hardening, the infero- mesial asj)ect of the occipital pole sometimes displays a broad shallow groove which marks the commencement of the lateral sinus. The groove is usually better marked on the right side than on trie left, in accordance with the larger size of the right sinus .IS commonly found ; occasionally these relations are reversed, and frequently no groove is recognizable on the side of the smaller sinus. In brains hardened in situ, tile gently arching cune of the hind-half ot the infero-lateral Ixirtlcr of the hemi- sphere is interrupted by a more or less evident indentation, the preoccipital notch (inclsura prai-occipitalis ), at a (joint about 3.75 cm. (1 [■-. in.) in front of the o< cipitai pole ( Fig. 9«o). This notch, prominent in the child but later variabl' in THE TELE^CEPHALON. "35 its distinctness, is produced by a fold of dura over the paneto-mastoid l-utu-^^ •'nj Jtove the highest Vrt of the lateral sinus (Cunmngham) It .s of .mpo^nce fn the toDoeraphy of the brain, since it is often taken as the lower 1 mit of the IrUto^ZpllTL, establishing the conventional div^. on on the lateral surface of {he hemisphere between the parietal and occipital lobes (page ii43)- The complex modelling^ the surface of the cerebral hemispheres, the charac- teristic feature o1 the human brain, is produced by the presence of 'rregular eleva^ ttons the convolutions or gyri, separated by the intervening furrows, the fissures or sulci! Although presenting many variations in the details of their arrangement nLtonly in different individuals but even in the hemispheres of the same bnun. the convdutions and fissures of every normal human brain are grouped according to a aenS and definite plan to which the brain-patterns, whether elaborate or s'njple.m fhe mi Snfor^ The fissures differ gready not only as to their depth as observed nthTfuS fomed brain, but also as to their relation with the developing hemi- sphere a ve^Tew. known as the complete fissures, involving the entire thickness of the wall of the cerebral vesicle and in consequence Producing corresponding eleva- tions on the internal suHace of the ventricular cavities. Of such total sulci the most m^i^nt^rmanent ones are : (i) the hippocampal fissure which Fod"C« the p^- Xn known as the hippocampus major within the lateral ventricle ; (2) the ante- rior part of the calcarine fissure, which gives "se to the calcar avis ; and ( 3 ) the fore-Srt of the collateral fissure, which is responsible for ^^e variable conaterale^^^ nencr The choroidal and the parieto-occipital fissure are also complete fissures of tefal ife but give rise to invaginations which do not permanently model the ventric- uto wSs The remaining fSrrows merely impress the surface of the hemispheres and are termed incomplete fissures. Their depth varies, «" ^''"^ ^''^ ^"« """y "^ few millimetres and in others as much as 2.5 cm., with an average o about cm. fhe height of the convolutions usuaUy exceeds their width, the latter, in turn bcMUg commonly somewhat greater at the surface than at the bases of the gy;ri. It is evi- dent before, that th"^ convoluted condition of the hemispheres proudes a ^^ead^^ increased area of cortical gray matter without unduely adding to the bulk of the brain Se extent of the sunken surface being estimated as twice that of the exp^ed The larger and longer adjacent convolutions are frequently connected b> short ridees the annectant gyri, which have no place in the typical arrangement. They may^ris the bottom of^ the intervening fissure and ordinarily be entirely liidden H^om vkw (»ri profundi): or they may be superficially placed (gjri transit.vi) and materially add to the complexity of the surface configuration. The cause and origin of the cerebral convolutions are still subjects for discussion The fact that at the time the fissures begin to appear, towards the end of the fifth fecial month, tne suria* of Ae young brain is not in close conuct with the cranial wall, disproves the assumption that the latter is directly responsible for the production of the fissures and convolutions, it is probable that the immediate cause of the surface modelling must be sought m the ""fl"/"' CTowth and consequent localized tension which affect the hemispheres, excessive growth m the longitudinal axis resulting in transverse furrows, and that In the opposite axis producing fissures extending lengthwise. Whether the excessive expansion is cjiused by increase in the gray or ■ white matter is uncertain, although local augmentation of the cortical gray substance is prol> ably the more important factor. After the beginning of the eighth month when the p-owmg brain comes Into contact with the cranial wall, the convolutions, which before were to a large extent unrestrained f id therefore relatively brojid and roundwi. sulTer compression, the results of which are seen in the flattening ami closer packing of the gyri and the narrowing and deepen- ing of the intervening fissures. By the end of f.ctal life the salient features of the plan ot arrangement have been establish^, although the final deUils of the brain-pattern are not acquired until sometime after birth. The Cerebral Lobes and Interlobar Fissures.— For the purposes of description and topography, the cerebral hemispheres are subdivided into more or less definite tracts, the lobes, by certain sulci, uppropn.itely know-n as the inter- lobar fissures. With few exceptions, however, the lobes so defined have little fundamental importance, since their recognition is warranted by convenience and not by morphological significance, in most cases the conspicuous limiting sulci being 01 1136 HUMAN ANATOMY. secondary importance, while those of primary value are comparatively obscure in the hilly formed human brain. The interlobar fissures, six in number, are : ( i ) the fissure of Sylvius, (2) the central fissure, (3) the parielihotcipital fissure, (4) the collateral fissure, (5) the calloso-marginal fissure and (b) the limiting sulcus of Reil. The lobes marked ofi by these fissures with varying degrees of certainty are : ( i ) y^'i fronted, (2) the parietal, (3) the temporal, {4) the occipital, (5) the limiic, and (6) the insula. An additional division, (7) the olfactory lobe, although of impor- tance as representing the peripheral part of the rhinencephalon of osmatic animals (as those possessing the sense of smell in a high degree are called), is not related to the foregomg sulci and comprises the rudimentary olfactory bulb and tract and associated parts (page 1151). It will be of advantage to describe the interlobar fissures as pre- paratory to a detailed consideration of the lobes. The fissure of Sylvius (fissura cerebri lateralis) is the most conspicuous fissure of the hemisphere. It begins on the inferior surface of the brain in a depression, the vallecula Sylvii, which opens out on the anterior perforated space. The first part of the fissure, its stem, passes horizontally outward to the lateral surface of the hemi- sphere, forming a deep cleft which separates the orbital area from the underlying tem- FiG. 981. Rolandic tmarc Inferior ptcccntnl mlciM Inferior fr AfW'Ttiflinir limti Pc«terior limh- taleiM OrbiUI surface HoriionUI limb Portion of laterxl surface of riclit hemisphere, showing ascending, horiiontal and posterior limbs of Syh-ian ■int. - ~ " • •• - • • — ' J — Li.-..- » . . , ... 688ure radiating from Sylvian poi ST, superior temporal gyrus. B, T, O, pars baaalis, triangularis and orbitalis of inferior frontal gyrus ; poral pole. On reaching the surface at the Sylvian point, the fissure divides (Fig. 981 ) into («) a short anterior horizontal branch, {b) a somewhat longer anterior ascending branch, and (c) a long posterior branch. The anterior horizontal branch, (ramus anterior horizoatalis), about 2 cm. in length, extends forward into the inferior frontal gyrus parallel to and just above the infero-lateral border, and forms the lower limit of the pars triangularis (page 1141). The anterior ascending branch (ramus anterior ascendens) passes upward and slightly forward into the hind-part of the inferior frontal convolution for a distance of about 3 cm. The frequendy observed variations in the relation and arrangement of the anterior branches of the Sylvian fissure — the ascending and horizontal limbs in many cases arising from a common arm, sometimes being fused into a single sulcus, or again being absent — are due to atypical growth of the opercula, particularly of the frontal. The posterior branch (ramus posterior), the main continuation of the fissure and about 8 cm. in length, is directed horizontally backward, with a slight inclination upward. It forms a very evident boundary between the anterior parts of the parietal and temporal lobes which it separates by a deep cleft that usually ends behind in an ascending limb surrounded by the angular gyrus (Fig. 980). Not infrequently the fissure ends by dividing into two short arms, one of which penetrates the pwrietal lobe while the other arches downward into the temporal lobe. THE TELENCEPHALON. "37 Fig. 98a. The forai and retetions ot the fissure of Sylvius are ao dependent upon the growth ol the «,rroJndinTSm ttatV^tch of the a|tal bnun the ^..rR-to-...ui cu^p^oduce^ . iistinct invagination of the wall of the cerebn.m ami om therrfX ^ .. c mplete fissure. In the adult bra.n. howx-ver. dl trac o^ th> L L disappeared in consequence of the growth and th,cken>nu ..( ,h. waU which ^ ibsequently takes place (Cunnmghan, '. The .;o»ateral fiasure (fiiwara collatcralls ) - a v. inferior surfa. e of the hemisphere^ It begn s behi.ul a 1, ocripifc. IK>1*- and extends forward, crossin, the teuton and Wial t. ., the calcarine fissure, until opposite th. .>8t. sum vhere it mc ts the hippocampal gyrus. It form .« the laterai K)undary of the last-named coi well toward tue t wral pole, near which it eith> riirveci iuirow, tl nrisura temporalis, which m tts-«re. separates tli jwer or hippocampal part iotK;^ According to Cunningham, the collater three ■ sstin ' parts— a posterior or occipital, an later becon c one continuous furrow^ Of these (liate, and usually also the tempf>ral, ar mi t At coV. teral protuberance and the coll. i! age 1 164). The occipital portion of ti , es no ive rise to any elevation. Thr calloso-marginal fissure (sulcu thei in, o\ f tl A sul- inds, afold- ,tri< "'ar .iikiii sulcus the the outer sidt the .irallel with, How * the corpus callo- lightiy outward. e temporal area 'ts with a short the collateral i the temporal ^ , cpresented by edia; sm; ,, inporal — which primal \ divisions, the interme- tissiires," producing respectively ...i, seen in the lateral ventricle re is ! ver complete and, therefore, calloso-marginai nssurc tsu.u. .. «iili) « the most conspicuous sul- c> , the medial surface of the hemusphetc. where it appears .is a curN«l urrow miunue atov^^nd concentric with the arch, d upper surface of the corpus call.^um k teufns Sont below the fore-en.l of this ndge, iust aU.ve the anterior ..eriorated soacesw^P^ around the genu of the cor call «um and .rches backward al.n.- the latter Tt^cture almost L far as th. .pi ■ . where it turns upward (ramus «ar- Xu" LI reaches the supero-mesial the hemisphere ;-h.-t d^ta^^^^^ hind the overturned end of the Roland ^^ure. By its course the cidliKjO-marginal S marks of! on the anterior two-t..rds of the mesial surface of the hemisphere helar^S Convolution of the fronUl lobe from the callosal gyrus of the l.|nbic lo be^ the ^mewhat uncertain posterior boundary of th<- latter beyond the sulcus being SiS b7the inconspi^ous postlimtic /issuer . ^''''"NrlutTthc c"C- tricallv with the splenium. The frequent ^■arlatu.ns n xW ^'^'^'^^J^^^^'J^^ marginal fissure depend upon irregularities in the ar^.^.-ment and hism. of the three separate furrows by the union of which a roniinuoa- ^«icus is lormed. three scpantteUi y^^ ^ ^^.^ ^^^ ^.^^^.^ ^.^ ^ , that incompletely surrounds tiu- msub an,, u„«^e.tlv ^-^-^ZS^^'^'^'Z^ of the central cortex from H. d.-^- '^« ot th^ enclosmg 'TT"^*^ ''^, ^^ J*! I'" ^;„: consists of Uiree parts-n -^«^ -^m; th^ island ^,^°'" f'^^J ^-^^^.f , i'Tn" 1 tal lobes an anterior inr ny m »«« .etween tiw insula and the fron al lobe, ana tal loDes, an anierwr. , *•._ .^ j^^ ..^ ^ »i.„ jjand from the limbic lobe, a posterior, imperfr- ^-s—- ■'=■ ' — «^^ '■" — i-^ju^j The Frontal ;^obe--The fronw? M*e (totas Ir^Malis) is the largest of the subdivisions of the liem,s,«..re ami inriad^ approxin. ly one-th.rd of th.- hem.- 1140 HUMAN ANATOMY. cerebrum. It appears on each of the three aspects of the hemisphere and has, therefore, a dorso-lateral, a mesial and an inferior surface. On the external surface of the hemisphere it is bounded behind by the central fissure, which separates it from the parietal lobe, and below by the fore-part of the Sylvian fissure, which intervenes between it and the temporal lobe. On the mesial surface the frontal lobe includes an irregular -1 , marked off by the calloso-marginal sulcus, the longer upper limb ending behind the central fissure. On the inferior surface of the hemisphere, the frontal lobe includes the concave orbital area, bounded behind by the transversely directed stem of the Sylvian fissure, which sulcus thus separates it from the temporal lobe. The principal fissures on the dorso-lateral surface of the frontal lobe are: ( i ) the inferior precentral, (2) the superior precentral, (3) the superior frontal and (4) the inferior frontal. The inferior precental sulcus which consists of a longer vertical and a short transverse limb and has a general T or T fc>rm. The vertical limb begins above the fissure of Sylvius and in front of the central fissure and extends upward parallel to the latter and separated from the lower part of the precentral convolution. The horizontal limb passes obliquely forward and upward and cuts for a variable distance into the middle frontal convolution. Fre- quently the inferior precentral sulcus is directly continuous with the inferior frontal hirrow; sometimes it opens below into the Sylvian fissure and above may join the superior. The superior precental sulcus prolongs upward the anterior boun- dary oithe precentral convolution. It lies parallel with the up{)er half of the Rolandic fissure, but does not usually, although sometimes reach the upper margin of the hemisphere. Almost constantly it receives the posterior end of the superior frontal sulcus with which it forms a H shaped furrow. The superior frontal sulcus extends forward from the preceding fis-surc with a course which corresponds in general with the supero-mesial border of the hemisphere and thus marks off a longitudinal marginal tract, the superior frontal convolution. Anteriorly the superior frontal may join the median frontal sulcus, while its posterior end may incise the precentral convolution. Often the course of the fissure is interrupted by superficial annectant gyri which connect the adjacent borders of the upfier and middle frontal convolutions. The inferior frontal sulcus begins behind in the interval between the hori- zontal and vertical limbs of the inferior precentral furrow, or in confluence with one of these. In its general course it arches forward and downward towards the anterior or superciliary margin of the hemisphere and terminates a short distance behind this border by bifurcating into a transverse limb. The line of the fissure is often obscureti by superficial annectant gyri and complicated by small secondary furrows which pass from it into the bordering middle and inferior frontal convolutions. The convolutions .-m the dorso-lattral surface of the frontal lobe are the pre- central, the superior frontal, the middle frontal and the inferior frontal. The precentral gyrus (gynis ceotralis anterior), also known as the ascending frontal, is bounded behind by the central fissure and in front by the superior and inferior precentral sulci. Below it is limited by the Sylvian fissure, whilst its upper end is continuous with the paracentral lobule of the mesial surface. Anteriorly it is connected with all three frontal convolutions. A short distance above its middle, it sends backward a conspicuous projection, triangular or rounded in outline, which encroaches upon the postcentral gyrus and correspondingly modifies the line of the Anterior Mpcct of ccrabral hcmlapherai, hardened in t'iM; tf,if, »uperior and inferior fronul fiuurn ncuian; ' ''' ' * ' ' ^ ' parame ; M./, mid-fronul; f-m., fronUMnarcinal. THE TELENCEPHALON. 1141 the external surface and reaches the trontaJ P^j^ " ' . . ^ precentral convolu- Inferior frontal nilcu* Fig. 986. Inferior precentr»t aulciu .Rotandle fissure AicendinK limb Orbiul anrfacc. HoriionUl limb' Ponltrior limb i_ .11. i«l iriinluUris ( D md orblUlis fO) of above and below by the superior and the «-/;|j;» -',7„;irJ;;'r^mf al^^^^ Anthropoid apei. is almost constantly subdi.ded into an^PP^"^^ j , ^^^^en dWisTon byV- -^?/-''^"f- !"S^^^^^^ to forrn the {;£: a sh^ort disunce above th;; Hupe-ihary TO^^ ,^^,^^ ^^^. .^^^, ^ The inferior fronta gyrus, the J""^^", J J,7„„"i t,,. anterior limbs of the frontal sulcus a.ul arches f'™ ""^ f ^^^^'l^h the lower end ..f the pre- Sylvian fissure. Below and behind it is conm^^^^^ ^^^ ^ ^ ^ ^^^^ .^,^.^j^^ central convolution by a narrow bridge ^"™^;,^ „f the Svlvian fissure the central sulcus. By the .''''«^^'«»\"K,^" • •^rj' • io h S^ portions--tlu. /,an f^salh. inferior frontal gyrus is \"^; "'M^^telyJ udcd ..m. mr p^^^^ ^^^^j.^ , the />/0// .' ! '„^ although constant the fronto-parietal operculum and "« ^^"^^^ J^ ; i*^, !^^\,„„';,,..rd and forward across furrow, the shIchs dmgonaln, «h.ch «™ "''Xliv distinct, the diagonal sulcus 1143 HUMAN ANATOMY. apex towards the Sylvian point. The pars orbitalis lies below the horizontal limb and is continued around the margin of the hemisphere onto the orbital surface of the frontal lobe. It b evident, from the description of the boundaries of the Syl ian fissure already given (page 1137), that the preceding subdivisions of the inferior frontal gyrus correspond with certain of the opercula — the pars basalis with the anterior part of the fronto -parietal, the pars triangrularis with the frontal and the pars orbitalis with the orbiul operculum. The posterior extremity of the inferior frontal gyrus on the left side is known as Broca's convolution and has long been regarded as the centre for the movements for articulate speech, although the accuracy of this view has been questioned. According to Marie, Broca's convolution has no relation with speech, a conclusion, however, so far not convincingly supported. The convolution is sometimes better developed on the left than the right side of the brain, the pars triangularis particularly being increased. As previously noted, the development of this wedge — the frontal operculum — bears a direct relation to the degree of independence of the two anterior limbs of the Sylvian fissure. The mesial surface of the frontal lobe {Y\%. 987), includes only one convolution, the marginal gyrus, which lies between the dorso-mesial margin of the hemisphere and the calloso-marginal sulcus (page 11 39), and by the latter is separated from the limbic lobe. It is -^-shaped and directly continuous with the superior frontal gyrus above and with the gyrus rectus on the orbital surface below. Its posterior end is almost completely cut off from the rest of the gyrus by an ascending limb (sulcus para- ceatralis) from the calloso-marginal sulcus, the portion so isolated forming the front part of the paracentral lobule, which is bounded behind by the upturned end (ramus marKinaiis) of the calloso-marginal sulcus and contains, near its hind border, the termination of the fissure of Rolando. By means of an annectant convolution passing below the last-named furrow, the frontal part of the paracentral lobule is con- tinuous with the part contributed by the parietal lobe. The middle of the mar- ginal gyrus is often incompletely subdivided by a shallow longitudinal groove, the mesial frontal sulcus, into an upper and a lower tract, whilst its anterior and lower end is uncertainly cleft by two or three short downward curving furrows, the sulci rostrales. The orbital surface of the frontal lo6e is marked by two fissures, the olfactory and the orbital and by three chief convolutions, the inner, the middle and the outer orbital. Although such division is convenient for the purposes of description, it must be remembered that these orbital gyri are not separate convolutions, but largely the inferior p)ortions of tb, »"^"'*"'^,r'. <;«„,« but behind and postero-mfe- A= Ritandic fissure. It, P""^"' 'r'""^J,"SKuS?d™riron, >he potal Kcipiul lobe. » b»g. Iv ";'"»"f^ 1 144 HUMAN ANATOMY. (66 per cent.), <"■*'* both (55 per cent.), the inferior limb may remain ununited ( 17 per cent ). When jomed, the two limbs together form a continuous postcentral sulcus which parallels the fissure of Rolando and bounds the postcentral convolution behind. In rare instances the inferior postcentral sulcus opens below into the Sylvian fissure. The ■uperior postcentral sulcus lies behind and parallel with the upper part of tfie fissure of Rolando, gaining the superior margin of the hemisphere between the incisions of the Rolandic Sssure and the upturned end of the calloso-marginal sulcus. Although in 59 per cent, of the brains studieil by Retzius the fissure was confluent with the horizontal limb, in 24 r^er cent, it remained isolated. The horizontal limb passe backward and slighriy upward and separates the superior and inferior parietal convolutions from each other. It is usually continuous in front with one or the other or with both postcentral sulci and behind with the Lateral upcct ol left ildc of bnin. /-A, lon(itudimlliM«n: r.,*-.. r. Rolandic fiHiii»' i <.- . », i..<..i.. . j i..diu r^ESf^'"!^'"" °""""' • "■ '""' ••"«'"" '«"•»"' "« »» «pJ^^m».f^.?f«?rSdaii'?LUf IJosteri(»r or occipital limb. As a rule it joins a continuous postcentral sulcus in which case the three furrows form a h- shaped fissure, which subdivides the parietal l""'' '•«-' ""« of this furrow, the sulcus lies in the occipital lobe and behind the arcus paneto-occipitalis ends by bifurcating into two widely diverifent arms, which constitute the transverse occipital sulcus. The chief corn'o/utions on the exUrnai surface of the parietul lobe are three— the postcentral, the superior parietal and the inferior parietal. II ''",*i<| PO'tcent"! gyrus, also calletl the ascending parietal, forms the posterior wall of the fissure of Rolando, and itself is bounded behind by the |Kwtcentral sulcus either by the continuous fi.ssure or by its iwo divisions. The lower end of the gyrus IS connected with the precentral convolution in front and with the inferior parietal one behind by the annectant gyri closing the lower ends of the central and postcen- THE TELENCEPHALON. "45 ^1 ..,!« r«n«tivelv Above, the convolution is continuous with the precentral ^S»™1». S,.TS modelling o1.L«,™J .urface ol ,he hem.ph.re and *ti »iCr;.rilS''S^' ^"KlSr «« ,« hetweej .upeH„ .Z5f„TC™ £ iKirijoiBl limb of the inlerfmietiil .ulcus and the »u|kto- ■^S h^« rfJh^ hembphere. Behind, it U limit«i by the oven-raed o., er end ""'1,fiS.'£'SiS»';°^™i^rSiXS?- between the corded i„te,pan«al b condnuou. «.th the «Jp«M <^^^^^ ^^^e^inuio^ ol the fi« and fissure. It lies behind and below ^^e front pirtoJthe^mer^^^ ^.^^ ^^^ whose lower end it b'jlV.*'^^ P^^l JS^r^n^r S ang^ surmounts superior temporal and ^ehmd w.th th. angubj^^^ .^^^ the upwardly ^'^"^J f "'^ °' '^^^f^TvolS^ It is commonly imperfectly sepa- the superior and middle temporal /^"J'"'""" , jhe postparietal gyrua rated Irom the postparietal gyrus by a P'j""?*: *""^?,*^L temooVal sulcus and below Rolandic fissure in front; below '' « •^l^!^"y^„d itTcontinuation, the post-limbic c.lloso.marg.,« Uucus to^^ by the q-dra^lobule upturned terminal limb of th^<=''"'»*;-7;.«'"^'^"f„r m^f^^^^^^ is usually 'he, b?:nlt mor'e%urwsX'/.™^^^^^ whSlncise the up,.r margin the Sita?"=^r;ni the adjacent parts^o, .He hemisph^^^^^^ , f.^rS fand t of the alpectH of the hemisphere and pos*«^^ee or a h^al.^a m._^ ^^^ ^^ .^^ inferior or tentorial suriT.e. A «'^"-™f^.'^SS ^Ts a backward prolongation of „f man and of the anthropml apes and is dcve lop^^^^^^ 'K rS\reV:hui '^"extZ rsSnl^rhmited by the internal parieto. S^t^ ^tf^. boundary^ ^^T ^l^lSif 1 ^it ,>arieto-occipitat Ime ^l--^^ " ^^'V t„"'^''":L jS^ as.KC its demar- S*^ tr-^r^SeSl; r^cci^llLfu^r. Ind temporal .L being here 1 146 HUMAN ANATOMY. directly continuous, and depends upon the recognition of an arbitrary line which may be drawn, as suggested by Cunningham, from the preoccipital notch on the infero-lateral border to the isthmus of the limbic lobe, just below the splenium of the corpus callosum. The external sm/ace of the occipital lobe is modelled by two well-defined fissures, the transverse occipital and the lateral occipital, and by two somewhat uncertain convolutions, the superior and the inferior occipital (Fig. 988). The transverse occipital sulcus is, as above pointed out, the widely diver- gent terminal bifurcation of the interparietal fissure, whose last segment beyond the outer end of the parieto-occipital sulcus enters the occipital lobe to end in the manner just indicated. Fig. 989. Inferior .ipKi of «rehr.l hemi»ph»rM. io /.».. ,.„., internal, transvcrx and external orbital fSiaurea' I./., incisura temporalii; «/.. calcarine. «/.. .ullaieral :«-/.. occi|.iio.tenuK.ralfi™ur« """««• The lateral occipital sulcus arches horizontally forward below the lower end ot the precedmg furrow, not mfreiiuently dividing into an ascending and a descending The superior and inferior occipital gyri are the upper and lower areas into which the outer aspect of the (Mrcipital lobe is somewhat uncertainly subdivided by the lateral occipital sulcus. Secondary furrows and ridges often obscure the charac- tenstic modelling of this surface, whilst annectant convolutions connect itsuyri with the parietal and temporal lobes. The mesial surface of the occipital lobe presents one sulcus, the calcarine fissure a triangular tract, the cuncus, and jwrt of the gyms lingualis. The calcarine fissure Ijesfins by a forked cxtrrmitj, the longer lower limb of which incises the occipital jjole in the impression made on the hemisphere by the lateral sinus. It then continues forward, slightly arched, a short distance above the border of the lobe formed by the junction of the falx cerebri and the tentorium, and THE TELENCEPHALON. "47 ends, after a short bend outward. Iw citing '■^j'-£f ^"^., ^£ spl.nium of the corpus ^^^^^^^f J«J ^^ J^" ^^ ct. the isiAm^^hich extremity of the hippocampal gyrus '"to f "^^°* . ^'^roader lower arm. which links the gyrus with the «11<^1 ^^S^d f^fonn gyri A short distance establishes contmuUy ^l*^" J* •VPP"?^S„^'' the lower end of the parieto- infrontof its middle, the calcanne fissure IS pineaov ^^^ T'^^.'iX U« rtS^ar'rnei^hh^u^usuaUy 'appearing as one diverging limbs li« ^"^ . "^"^;„;,m and calcarine sulci are ncompletely iseparated continuous fissure, the P*"«'«-^"P'^„^t fh? cuneus with the limbic lobe. The by a deep annectant ?yn>f. ^^'^j^ k„ a^nd sunken gyrus into an anterior and a Jloirine ^ure .^H ^^^^;^t%s'^^,rar^l^tH::jss!^^, is shorter and shallower gilt r^rthTeaSr iX L'thTS U ^n on the inner boundary of the posterior horn of the >fte«^ J'^ntride. ^^^ ^^^ ,t The cuneu. forms »h; ch.d^'l°^t%^eto-Stal sulcus in front and the is triangular m outlme f^ Uf ,^^f ^£^ S^above and behind it reaches the ^^^'^6^':'^fSi'^'iFT^7^ I- -rf- is frequently impressed by one or more shallow vertical Junows. . j j^ irregular elongated Uition. The By™ »» '.»'» ""f *^ -..TS;, J the h-nUphere .nd appsais on a,rf therefor, bear, the i""™^"^^^ ^^IL^ymoSS bj ineg-l.r sh.no. ..te„T!iv^s%"rsi4"S^43£Ss:3jh^^^^^ tl™ to the «»•»*', P"»''te''"S~S'i5?»^he la^»lnclades .S irreg' ™'"Tte iSporrf Lote-The temporal lobe include, *ti"r.l"'ly Py"™"" £Ul^,e<'.T;^?tStSlrd tht=.:;.™rS2!»';Ut!:S« .he ,«ip„al •"' '•fjnl^'S- lobe pr.«nt. three ™H„ce,. tt» eoovex '^^^^SSIZ Si'aS-^^-^yrb^ert'&Sf^l^M^S^^^^^^ 1 148 HUMAN ANATOMY. inferior temporal (Fig. 988), all of which correspond in the general direction of their course with the posterior limb of the Sylvian fissure and extend backward and slighdy upward. The superior temporal sulcus, also called the parallel sulcus in recognition of the similarity of its course with that of the posterior limb of the Sylvian fissure, is the first in the series of longitudinal furrows, the third of which appears not on the outer, but on the inferior aspect of the lobe. It begins near the temporal pole, run? parallel with the posterior limb of the Sylvian fissure and ends by cutting upwar mto the inferior parietal convolution, whose angular gyrus surrounds the upturned extremity of the sulcus. The middle temporal sulcus, the second in the series, lies below the pre- ceding fissure, whose direction in a general way it follows. It is, however, much less certainly marked and in most cases is not a continuous furrow, as is the superior sulcus, but broken by superficial annectant convolutions into a number of separate pieces, the exact sequence of which is often difficult to follow. The upturned end of the middle temporal sulcus cute into the lower parietal convolution towards the pos- terior limb of the interparietal sulcus (Fig. 988) from which, however, it is separated by the arching postparietal gyrus. Fig. 990. RoUndic fiMura Rijcht cerebim. iieinlipliere. with opercula displaced to expoK island of Reil. The superior temporal gyrus intervenes between the posterior limb ot the Sylvian fissure and the superior temporal sulcus. Ite lower end lies at the tempural pole, whilst above the tract is continuous with the supramarginal and angular gyri of the parietal lobe. The middle temporal gyrus, between the upper and middle temporal sulci, is connected with the subjacent convolution by the bridges which interrupt the sec- ond temporal furrow. Above and behind it is continuous with the angular and jjostparietal convolutions. The inferior temporal gyrus occupies the rounded infero-lateral margin of the hemisphere, and appears on both the lateral and the inferior surface of the lol)e, Iwing continuous with the fKrcipital lobe behind (Fig. 988). Its upper boundary, formed by the middle temporal sulcus, is indistinct ; its lower and mesial limit Ls (k'fiic'd l)y the inferior temporal sulcus, which separates it from the occijjito- temporal gyms. The inferior surface of the temporal lobe is rounded in front, where it rests in the anterior cerebml fossa, but behind is modelled by the upper surface of the ten- torium cerebelli and is, therefore, concave from Ijefore backward and slightly convex from side to side. It j)resents one fissure, the inferior temporal, ami one convolu- tion, the anterior jKirt of the nccipito-temporal. The inferior temporal sulcus, also called the occipitotemporal, courses longi- tudinally a short distance internal to the infero-lateral border of the hemisphere and THE TELENCEPHALON. 1149 partes the infenor .^r.Uro^ £^-^1X:^'L'lZ.JT£^ '^l^nT^uS^dZXc^^P^ lobi^hich. therefore, claims it as one of .ts Cws The suJcas Is «rely co'l.tinuous, usually being broken by annectant gyn '""-TroiVtol'mprrr^^^^^^^^^ is. as its names imply, a , Honn trartSnSng partly to the Scdpital and partly to the temporal lobe Ff.^^8oT Ite twoTnd? i/ front and behind, are pointed and connect«l by a L Vr^nierveninetrart which is commonly broken up by secondary furrows. TheiLSSoi^f the gyrus, including approximately its anterior two-th.rds • !mKd ^t^^n the converging collateral fissure mesially and the mfenor ,s embraced l«tweentne co « « ^ posterior limit is the line drawn from r'^rl^lS no^cft'o'thJ i^thTuTof the^mbic lobe, immediately beneath the *""'*^e iiSLT«"/«.f.7X ^e^poral late is direct«l towards the insula and The ^''P*^^^"'J":''„J^ On separating the wa Is of the Sylvian fissure to e^x^lrXSturia^of ?h"eTe';^poraflobe often exhibits^eral shaUow tra^er!^ fui^ows and indistinct gyri ; the deep aspect of the temporal pole being similarly indented. Fiu. 991. Sulcus aubdividins prccrntral lobule Cut surface of frontal lobe Rolaudic fiasuic Sy the calloso-marginal sulcus in front and aboxc, by the postlimbic sulcus behind, and by the anterior part of the collateral fissure below. Its demarcation from the anterior part of the temporal lobe is effected by the inconspicuous rhinal sulcus ( fissura rhinica), or incisura temporalis, which feeble furrow in man represents the important and fundamental ectorhinal fissure of the lower animals. The callosal gyrus ((orus ciiiKuli), also called the gyrus /oniicatus (not to be mistaken, however, with the same iiaiiie as applied li> the entire limbic lobe), begins at the anterior perforated space, l>clow the recurved rostrum of the corpus callosum. Thence it winds around the genu of the latter and follows the convex dorsal surface of the corpus callosum, separateii however from it by the narrow callosal sulcus (sulcus corporis callosi). On reaching a point just below the splenium, around which THE TELENCEPHALON. US' it hM(h the caUosal zyna is markedly reduced in width by the encroachment o the L^e figure X rwrrowed tapering tract thus formed being the upper ,«rt of the SAmu. ( Whim «ri fomlortDrwhich below joins the similarly reduced upper end S?hrWpt!jSm^"<^nv"ution'and so establishes the continuity between the two •"^The hiJjSc.mp.1 gyru. (on.s hlppocmpi) curves forward from the isthmus akMK the S border of the tentorial surface of the hemisphere towards the apex Tdfe ten^S lobe which, however, it fails to reach (Fig. 9"). ts anterior i^mityTdisSSly thickened and forms a rounded hook-like projection, the S. wWch is recirvcd and directed backward and mward. The uncus is .Li fc^rim fh^ loex of the temporal lobe by the mcisura temporalis (fissnra ffif wS the hi'pp-mpl" co3""- » -W'' f '"'^-"yK-'y *'^ ""^""a S'^f^'the CO lateral fiS. Although blended with the ?y"-,hjppocamp. and pan ui lilt limbic lobe the uncus, strictly considered, belongs to the SntjhaVKd no tote Jrm'Cic lobe (Turner. Elliot Smith). The posterior end of the hipp.Kampal convolution is incised by the antenor extremity of the Scarinl Lur^ and ^divided into two parts ; of these the upper aids in formmg ^eTthmus and is continuous with the callosal gyrus. whOst the lower one blends with the front part of the gyrus lingualis of the occipital lobe. , . _^ „ . The iSinencephalon.-Aldiough a division of hmdamental importance and diflerentfatS^at a very early period in the development of the human telencephalon. fnTh^bSn of manltl re^r^nted by structures, which to a great 5«f"* '^V-^' menurvand feeble expre^ions of the bulky corresponding parts m the brains of manv d the lower anin^ls. Its small size in man. as compared with the voluminous Sure^ ^T!n some mammals in which the rhinencephalon constitutes a large «[Ji of the^tire hemisphere, is no doubt associated with the relatively feeble olfac- ^ Je^ t^Lsed by man. It is probable, however, that other and unknown f^c^o^^ r^'^e forThe development of this part of the hemisphere to a degree SrSonate to the olfactory capacity of the animal, as striking y observed among fhe'^lX vertebrates. Th. conclusions deduced from commuative studies empha- size the fundamental character of the rhinencephalon as P»'y'°8«"«t?«=f y.^'"^ J^ oldest Lrt of the hemisphere. Indeed of such primary "no-Ph^l^g'?^ JJK^'*^''"^^ Tt^e Ainencephalon that it is termed the archipaUum, ^s distinguished from he LS^S wh?ch comprises almost the entire remainder of the hemisphere with the excpotion of its nudeus. the corpus striatum. ... .. ^ ^ir-- excepUon^Mts ^^^ ^^, ^^^ rhinencephalon includes the rudimentary olfac- tory llbT-represented by the olfactory bulb, the olfactory tract «"th •« ^?«'!' ^^^ olfactory trigone, and the parolfactory area-and the uncus and a number of acces- wry ^rtifincluding the anterior perforated space, the g>rus subcalbsus. the sep- tum luddum. the fornix, the hippocampus and the gyrus dentatus. Some of these acceMory st^ctures can be understood only after their relations to outer parts of ?he^^ W been considered. Deferring the details of certain of these struc- tures, as the septum lucidum. the fornix, and the hippocampus '"'»)«•■. until the lateral ventricles are described (page .160,. it will suffice for the present to point out their general features as related to the rhinencephalon ^ . . „ ,„j The Olfactory Lobe.— This division of the adult human brain is small and rudimentary and comprises the olfactory bulb, the olfactory tract the olfactory CiXe anJ the parolfactory area (Fig. 993). Of these all but the last he on the inferior surface of the brain, whilst the parolfactory area occupies a small space on the mesial aspect of the hemisphere. The olfactory bulb (bulbus olfactorius) is an elongated irrcgulariy oval swell- ing, about 10 mm. long, from 3-4 mm. wide and about 2.5 mm. thick which bchinrt is continuous with the olfactory tract and below receives the olfactory filaments. Ite upper surface underiies the olfactory sulcus of the orbital aspect of the frontal lobe, and its under one rests upon thr .-rihriform plate of the ethmoid hone, through the apertures of which the bundles of the olfactory nerve-fibres ascend from the nasai mucous membrane to the bulb. , The ttrueture of the olfactory bulb shares the Reneral mdimentary condition which cnarac- terizes the lobe in man, the bulb having lost the central cavity ( w)./r.f«/i{ small nerve-cells \.'i-'ose dendrites also enter the glomeruli. (3) The stratum of central fibres includes the centrally directed axones of the mitral and other nen-e-cells which constitute the second link in the complicated paths by which the olfactory stimuli are carried to the cortical areas. The outer zone of this stratum is known ^■»^• 993- olfactory bulb' OUactoiy ti Meatal otfmctory Mria Lateral olfactory atna Island of Rcil Anterior perforated space Cut surface of temporal lobe Cerebral peduncle oroased by optic tract lateral geniculate tMxly Olfactory snlcua Parolfactory area Tnberculum olfactorium Trigonum olfactorium Optk chiasm, partly cut away Mammillary tiody in interpeduucular space -~ Oculomotor nerve Cerebral peduncle Pulvinar Median geniculate body Sylvian aqueduct Anterior part of inferior surface of brain, showing parts of olfactory lobe and stracturea within interpednn- cular space ; tip of right temporal lobe has been ren^oved. as the granular layer and consists of many small nerve-cells intermingled with the fibres. The deeper part of the stratum of nerve-fibres encloses some larger nerve-cells of stellate or enlongated form. The central part of the bulb, which represents the obliterated ventricular space, is filled by a gelatinous substance resembling modifieid neuroglia. The olfactory tract (tractus olfactorius) is a narrow band of light color, which extends from the olfactory bulb in front to the olfactory trigone behind (Fig. 993). It measures about 2 cm. in length and 2.5 mm. in width, but is broader at its pos- terior extremity, from which the olfactory stria, as its roots are called, diverge. Its ventral surface is flat and its narrow dorsal one ridged, the tract appearing in transverse section more or less triangular in outline. The structure of the olfactory tract further emphasizes the rudimentary condition of the part in man. The ventral aspect and the rounded adjoining borders consist of : ( 1 ) a stratum of nen'e-fihrrs, longitudinally coursing and therefore tran^Jversely «it in cross-sections, which covers the sides and dorsal surface of the tract and is reduced to an extremely thin and rudimen- tary sheet. Next follows (a) a gelatinous stratum, which represents the obliterated ventricular cavity seen in many lower animals. Succeeding this and forming the thickest layer of the tract lies (3) the dorsal stratum of gray matter, which still retains its importance as a tract of cortical gray substance from which fibres pass to other parts of the hemisphere (page 1313). TME EEi-tKCEPHALaN ««53 usually two. the ."'f^'^'f '^^ir ^Th, •<.«,/ ^/na l-m«K sharply inward, passes along the inner manfin o'."* "^^J .-ST th*- caHosal^t". partly the .«ilK^lli«al It can be traced to^^T* -^\<--,nd« an .mter .-rf an inner the last onr fading lateral root is "lepre^^twl by "^Zr^^^^^t^^. An a.Witional intrrmedimtr away in the sub*ta«ce ot the ^T^ y^^^^,^ i, ,^, smks into the unteri«r itria is sometimes recogiBJMhfe mt a short iiwh? \MmmK perforated space^^ ^„„_ . ,„ ollacl.ri.*) is 'he thr^-sinvcx arealml^ct^hrtli:"'.^^ olSTry ' «« ;i:^ tS^I.^^'rr p\om the --n<^'^- K.^^.;:,^^^ htZlS^cTig^^ is The triangular areajern «" J"^ '"^ ""^ jj^ devauon. the tubercmium really the under aspect of a «"'«^'«^^ J^^T^ithin the afoctor>- «.lcus a.^ is jccept at its bw;, the trigone. Reuius regards !• ihi- Fig. 994- ForanMti of Monm Anterior ptlltr 'of fombc .Anterior 'commiMofe Rottnim of . cunxM callumB Septuio luct"!"" y -Uiniii" Snkas piirolf««orlM poiaenor (nnerc* Portion oi me.al .»rf«» d ri^t l.en.iH*««, lowing nm» .ubcallo.u» and p«roll»ctory area. olfactorium, which, ho'> therefore superhciaUy - -^i this part of the hemispht as a constant deep convc lution, gvm^ tuberis olfme- tortus, from which proceed two riches, ifrrus c'fatio ritts medialis and ItUeraii . These bend respectively inward and outward and support the white strands of ner\ e-fibres. the stria olfac- torii, which are usually de- scribed as the roots ck the olfactory tract. The tuber- tulum olfactorium contains ;, considerable amount ot grav matter, which is a part ot the peripheral olfactory cortex ami, with other por- tions of this sheet, shares in the n ption of axones from the mitral cells and in the ongin rhineno^halon. ^^^^ ^.^ ^^ ^ „ ^^^, he mesiMTuS:: of%heTmisphere-;*iust-'in front of -d bdow t^e ,yrus .«^^W -list 1™:- =rW^:«qS^|f^ "^^Sl^^^^ ^y i^e large -^^ ^ ^^^^td ^^ irLfgrrp^rx i^^rrii^Tht-dsri^ ^^~;::^ ^^ Iron? mS of the space, are disposed with some regularity in parallel ro^s an.l 7.1 of fibres passing to other parts of the HUMAN ANATOMY. decrease in «ze as the^ approach the inner border (Foville). The substance of the space proper consists of a thin sheet of ^;ray matter containing groups of nerve-ceUs, some of which constitute the nuclei of primary centres interposed in the paths connecting the olfactory lobe with the secondary (cortical) olfactory centres (page 1233). In addition to the white strands of nerve-fibres composing the olfactory striae which after a longer or shorter superficial course sink into the substance of the perforated space, an obliquely directed narrow ribbon-like tract, the diagonal band 0/ Broca, may be sometimes made out along the Inner margin of tiie area perforata. In front it is continuous with the subodlosal gyrus and behind passes along the optic tract towards the anterior end of the hippocami»l convdution. The band is of interest as being probably the beginning, on the basal sur&ice of the brain, of at least Fig. 995. a part of the fibre-trarts contained within the rudimentary supracallosal gyrus (page 1157) that, in turn, is prolonged into the gyrus dentatus. The uncut is the thickened anterior extremity of the gyrus hippocampi, recurved around the front end of the hippocampal fissure (I^'R- 993)- Antero-infenorly it is sefiarated from the adjacent part of the temporal lobe by the inconspicu- ous incisura temporalis or rhinal sulcus, which in animals possessing a well developed rhinencephalon constitutes a definite boundary be- tween this part of the hemisphere and the pallium. With its deeper surface the uncur is in close relation with the anterior perforated space, whilst uostero-mesially it is connected with the fimbria (|)age 1165) and the gyrus dentatus (page 11 66). Although seemingly a part of the limbic lobe, the comparative studies art of the olfactory brain. The accettory parts of the rhinencephalon include structures which, for the most |>art, constitute collective'y an elaborate path by which the olfactory a)rtical centres are connectwl with each other, on the one hand, and with the optic thalamus and lower levels on the other. Since these structures are by |M>sition closely asso- ciated with parts of the brain still to l)e described, with the exception of the anterior perforateb ; drawinx iiKlwin |iut o( balb lying vaiitral to atrophic ventricular area. X 90b THE TELENCEPHALON. "55 • u- A^A =.nH thM as the denute gyrus, extends forward along the inner sur- as Its hind-end and then, as ine ucnutic kj • lucidum ( pane 1 159). a sickle- face of the hjppocampus to the uncus, ^he '"P^^^^.S. ™e ^^us ^losum and RHINENCEPHALON. I. Ptriph*r*l Portion Amittior ftrl.- I. Bulbin oltactoritn 1. Trmclm olfactonu* J. Tubcrculum oltaciorium oirACTOKV UME \ 4! Are« poioltortori* PMleriar part : «. Subounlla periormU »nl«nof 6. Gyino rabollaoitt II. Control Portion I. Gym calkan* J. Gyittt hippocampi 1. Gyroi uoctnotiu 4. Hippocmmpw 5. GyrM dcnUltn i. Cymi npn'^lh MUltn npnrallaaiM Architecture of the Cerebral Hemispheres. are connected in the intervening ^rt of t^«'^'^"f " .^^. ^^ ^ ■^^^ course. On corpus callosum. which floor, the figure Jo « ^f « ThS bridge eUher in the frontal making sections of the h«'"«P»'^^^^'^y= ''l^ J^Tt^JCi^^^^ thin red UoUtliM ctalralis I ulmrtt Fall tcMUl, i:al Siraicht siain FoUuni cacuntiall Tul«t rti , ■ ■MfffWduacHtor MammUhrr ^Hf »f llMH 4d«l llM, ■aallar aitiry Carimrj MaadHgaailav At|ti». luct of Sylvf L . SupaHor mrivXm^ talaai HouHk vaabMla Ckovoltlal ptaaut' Meiial Hcrtlon of hrnln \m .ti/m. Hhowinie relaUonn tn akull and dura; rerrhmt faU hati been partly removed, l*ul ai«« hnoid and pin niv <«lill in iil.trt- how(.'\'i-r, is separated from it by the intervening callosal sulcus (huIcun corporis callttNl ). Altliiiugh ci>n»istiiig pnu-tically exclusively of transversely coursing nervt-fihri-s, whiili prexlucf a corri'S|M)nding cross striatum, thi' ii[)|ier surface of the corpus I'dlliisuiii •: Fig. 997 I is covcn-d by a thin atrophic layer of gray matter ( induHvum uriNCum I which laterally is coiitiiuioiis with the cortical sulistance .of the callosiil gyrus :,nne, the atria medialia, is placed . ..ise to the strand of the opposite side and with it constitutes the so-i'ailcd iicnrs of Lancisi. The other strand, the atria iateralia, ur htnia Inla, lies farther oiituanl an -'ace o. the gy,rus SHbca/Zosus .i *«"*" ""^'l"!Jz;r^( pie gg.,; while the lateral stria is Kmisphere '■"^^''^^^'y^S^ '''^'^e . 53^^'^^ the anterior ,M.rforHt«l continued into the ar^^««^J^^^^^^^ ,p,e„iun,. the stri* and ^ray Sr o?^tt%oSll!=^"- -"""-- -'"^ '"^ ^™^ '^""'"'^ "^'*' '^ way of the latter with the uncus ^^^ exhibits a very The under surface ™ ^ne c )n ^^^ ^^^^, ^„j body of evident transverse smationj^^^^^^^^ ^, ^^^^^ ^ij , ,, ,he SJrpl^nel'Se atuSto t^^ sejtum lucidum in front and to the tnan«ular Kio. 997- FronUl piile MnUI longiluilinal rpprr «iirf«c« of conjun calkrtwnt l^alrrHl longJtudiiial •trill Forcf |>s aiiti'rior Trnnnvcriir fibres Tnprliini Hun-clw )»>«lrrlur .Ocdpital pule Slilrnilllli Ctrebral heniinulwrcn from which un •Ide loiiKitwHnal »»rl« »n.l Ihiii !•>•« ol «rmy m«u»r '-o^'r !'PP«.'_5''™'.^,S'., i^',,.n.. txHly of the fornix behind, the .onn.s rallnsum i. fn-e an.l .^.^'f "I *'**; J,','^ Z^dvma which lines the ventricular spac-s. In -"-« qnence of th^ J" ^^ j^; "« shorter than the lenifth of the hemisphero., from ni<.st parts of «hicn it rece SS the latter are S.ns<.lidaU.d at. he ends .,1 the ^^:f:^J^,r^^^, the K.MU1 and the spleniuin. On frainm^r the lateral margins "^^ J^'J ' , ,^ ,,,,. its fibres are no longer restrained ''"' ra.lu.te in a d.recUrnw ^ra4U^^ U«l) towards the cortex an.l interscrt the ^^''-^/''j' "= V'^'^J •. m the oo.n- Those traversing the thinner lx.dy a"*' upper iwrt "*t''^,''P''^""''i,p '.,,., ..^u^^, ,„L.re pass laterally and in each hemisphere from a thin '«' ' .fi"'*^'^^^!?.,^;^!;; szd:;rrstiS:^\^ear^"'" i^'^^^^^z^i t ti58 HUMAN ANATOMY. ■At pole of the hemisphere, whibt those constituting the greater part of the splenium are consolidated into a robust strand, the forceps posterior, which sweeps abruptly backward into the occipital lobe and in its course produces a curved ridge on the fore-part of the inner wall of the posterior horn of the lateral ventricle. The Fornix. — The forn-x is an arched structure, white in color, and composed, for the most part, of two crescentic tracts of longitudinally coursing ner\'e-fibi«s. The two ends of these narrow crescents are free for some distance, but along their '.nedial borders the intervening parts are connected with the under surface of the cor- pus callosum and with each other (Fig. 998), thus producing a triangular field, the body (corpus fomlcis), whose apex is directed forward and is prolonged into two slender diverging stalks, the anterior pillars, and whose lateral angles are con- tinued into the (lovnwardiy arching posterior pillars. The upper surbce of the body is subdivided into an attached and an unattached area. The former is a small Fio. 998. Bcdy of fornix Mntiitnillary hndii Splenium of oorpu* calloiHtin Lyri FmmirKinof fornix I'ndrr surface of corpuiicalloHum Cut KurfacTH of hrmiftplicrv :)Cptuiu lucidum Anurior pillar of foniix rndvT aurface of fccnii of curpimcalkmum f>iKKe(itnti 111 hrniii, tthowini^ under surlact* of foniiit and corpus cattoauni narrow trian^ile. the posterior and broader p;irt of which corrcKponds with the attach- ini'nt of the fornix to the under surface of the corpus callosum ; whilst the anterior part is a mere mesial strip denoting the line along which the arching fornix is bli-iuU>d with the Sf|>tiim lucidum, the sickle-shaped {Kirtition that tills the interval l»etween the corpus callosum and the fornix and se|)aratis the anterior horns of the lateral ven- tricles. On either side of the attachtxl field, the fornix presents a smooth and some- what thicker marginal zone, which forms part tif the floor i>f the lateral ventricle and, ace, either extends later- ally as a horizontally directeJi(|iiely towanls the thalamus up« -jnmjjan. ^^ ^^^e'S ?h%'l: t^SrcFrXa^dtn^'on'e^^de. the upper and anterior they show as ndges I rig. 97^^^ ^^^ ^^^ ^ ^^^^ opening. a large extent in the mammdlary nuclei (Fig. 96?). The connm^ons^oi staUo^s are d^ri^d dsewhere (P^^^^.J-^ j -ffir^'U^^de'^Ur^^^^^ Tntn ^"ly^'tnS/^Tl^^^ZrtrSi^^^^^^^^ the connection between connection with the olfactory nerve (page 1222). . . .^ divereing TJi.. noaterior oilUn of the fornix (crura fomkU). the wiaeiy «»«n{»'B backward ?roon^tions from the lateral anglesof its body, are at ^r.t ^XUch^^ Se under s'iriace'^f th- corpus callosum. They then turn ,«>»»*„» .^•;"/*'»^Xhl around the posterior ends 0I the optic thalami enter the descendmg horn, ol the lateral v.-ntrWes and arch downward along the dorso-mesial border .il the conspicu ot 4m-S. the elevations which mark the inferior h"r- "Hhe k^end -^^^^^^^^ On reaching this situation, however, th.^ P«t^^^^^^ sidi-sof the triangle are all curv«l and its anterior angle, receivetl within t>ie nenci ii6o HUMAN ANATOMY. Corpus calliMum. wirfftcc Anterior nillnr of fornix y of the fornix. The septum consists of two thin layers (laminae septi pelluddi), between which lies a narrow cleft (cavnm septi pellucidi) to which the misleading name, fifth ventricle, has long been applied. This space, very variable in extent and width, is usually so narrow and contains such a small quantity of modified lymph, that the lamime forming its walb are in apposition. It is entirely closed and, therefore, cut of! from the true ventricular system ; neither is it lined with ependyma! The septum lucidum in man is the rudimentary representation of what in many of the lower (macrosmatic) animals is a much more important tract of cortical substance. In some animals, as for e.\ample, the rabbit, cat and dog, the septum is solid, a cleft never appearing within it Notwithstanding the reduction which it has suffered in man, the septum exhibits in its structure its relation to the cortex, comprising, from its clefi outward : ( i ) a thin layer of nerve-fibres, (2) an uncertain layer of gray matter containing numerous nerve-cells of pyramickl form, and, next to the lateral ventricle, (3) a layer of nerve-fibres, the ventricular surface of which is clothed with y°- 99» the usual ependyma. It Boity of fornix . i_ li ^t. ^ ' - IS probable that axones proceeding from the cells within the septum lucidum are constituents of the olfactory strands within the fornix, which pass to the hippocampus and the uncus, and of the tirnia semicircularis (page 1 162), terminating in the amygdaloid nucleus (page 1172). The Lateral Ven- tricles.— The lateral ventricles (ventricula late- rales) are a pair of irreg- ular cavities contained within the cerebral hemi- spheres. They are devel- oped as outpouchings from the original cavity of the end-brain and for ;i time coininunicate with this space by wide openings. The latter, however, fail to keep iwce in their growth with the expansion of the hemispheres, and in the fully (leyelopetl brain are represented by the small apertures, the foramina of Afonro, which maintain communication between the lateral and third ventricles^ the last- named s|)ace representing the primary cavity of the fore-brain. When \ iewed from above, after removal of its roof, the corpus callosum and its lateral extensions, each lateral \entricle appears as an elongated, irregularly curved cavity (Fig. icxio), which extends for aljout two-thirds of the entire length of the hemisphere and, in addition, penetrates the temporal lobe almost to its pole. It is lined, as are all the other true ventricles, with i «lelicate epithelial layer, the tpfndyma. which likewise clothes the structures which encroach ujMin its lumen, as the caudate nucleus and the thalamus, as well as those which seemingly hang free uithin it, as the choroid |)lexus an Inn, Im«<1< |-uraiii«n iif Monro LcnlkuU niirlcu«. T»bU teniUirL-ubiri* llf|n>wain|H>o Collateral rmiiiM" Fim'.H.t Posterior i-illar .if timhria CoIUlrtiil i»'i*riitfr UKC in thiioniiiM niitrittili Bull) of fxifp* [lorteri"* Cakv •«)> p.nwrtorttoni'il Utor.*l .rnlffLle 'Sri4u'iii M-(4iim >.inii».»ntrri'*i>il [ IhffMi*! I>lr«< k -|*i.|> off.«.. (-hlrM -.lr<»rn(ltnt(ii infrrier h< from «l..vr .ftrr v>nM r..,«ov,1 of Corp,., mil.,-.,,.. , n.l 1 -unv U> ...m. wal 'is for„u-d in front l.y the hind part of th. .q.t.n , U-cu,.-n an.l 'Hh.n.i he h Iter .V the fornix wlu-r. it i. .U.ached f. th.; .uu or ,u. .. .- of ,iu . -!'----"; -\ .listinrt lateral wall is wanting, tho veniri.K' lx-ing here .l.-s.-il bv On mk ti .. of the o« an r.K.f. Its floor is constitute.! by several ,ln..t.ns of ,m,«.r tame hich Ll tm without inward, are: fn the ra.o^af<- ,„uln,s : 2. .an o .!..,ue Irr "ulws intcrmedlus). which .xtemis from bc-iorc t.ackwan a.fl outward. riwXn tTc^ite nucleus and the thahunus, an.l lodg.-«. in a.ld.t.on t., th.^ v.-.n ^th < rpus St iatUP,, a white iK.n.l of n.rv fibres known as the /,/•«'" L aW, «r Z :■- narrow portion ..f the upp.r surface of the thalamus, whi.h .. Il62 HUMAN ANATOMY. • ilerior horn almost completely masked by the overlying choroid plexus; (4) the choroid plexus of the lateral ventricle ; and (5) the lateral edge of the/bnwjr. The caudate nucleus will be subset .'^ntly described (page 1169), suffice it to note its rapid diminution in size, as it cur\cs backward and downward on the roof of the inferior horn. The taenia semicircularis is more or less hidden by the superficially placed vein of the corpus striatum (vena termlnalis), which lies immediately beneath the epen- dyma and shaws as a distinct sinuous ridge. Receiving tributaries from the adjacent parts of the thalamus, the caudate nucleus and the walls of the anterior horn, includ- ing the septum lucidum, the vein passes to the foramen of Monro, where, meeting with the choroid vein at the apex of the velum interpositum, it fprms with the last- named vessel the vein of Galen. The tenia semicircularis, the band-like tract of nerve-fibres which occupies the sulcus intermedius, is probably a part of the complex pathway by which the pri- mary and secondary olfactory centres are united. Its component fibres arise partly "n the anterior perioral ttl space and partly in the septum lucidum from which centres, reinforced by hbres from the anterior commissure, they converge towards the sulcus intermedius which they Fig. iooi. then follow. After leaving the iKKly of the lateral ventricle they descend with- in the roof of the inferior horn, in close relation to the recurved tail of the caudate nucleus, to end within the amygdaloid nucleus (page 11 72). ■ The choroid plexus ( plexus choriuidetis ventdt ili lateralis) is a cuiiv uluted vascular comi)lex which occupies the lateral margin of the pi;.' .sheet, the velum interpt»itum. within the body of the laterp' ventricle, and, in addition, (k-scends along the inferior horn of the lateral ventricle to its tip. I n order to understand the relations of the choroid pkxus, those ot the larger i-heet, of which it is part, must be dcscrilxxl. The velum interpositum ^tela chorloitlca ventnculi tcrtii) is a delicate sheet of pia mater whc^se upper suiiace i.s exposed alter removal of the corpus callosum and the body of the fornix. VVhen viewetl from above (Fig. rioa) it is trian.^^^ular in outline, its apex iyinj,; at the fiirainina of Monro aiul iis lateral basal angles extending into the descending horns of the lateral ventricles. Its inferior surface forms tht- roof of the third ventricle, beyond which on each side it coven; the greater part of the upper surface of the thalamus .ind, in turn, is overlaid by the fornix. Behind, the velum interpositum is continuour. l)oneath the splenium of the cor|)us callosum with the pia mater investinr the <>xternal surface of the hemv^pheie. This relation rejulily gives rise to the impression that the pial tissue has gjiiiied entrance to the ventricles by growing forward through the cleft beneath the splenium and the fornix. That such, however, is not the case will Ik' [K>inted out later, when the development of this sheet is considered (page 1194). TKe relation of the velum interpositum to the ventricular cavities should he carehiliy noted by tracing the ependyma from the caudate nucleus inward. Leaving the convex surface of this structure, the ventricular lining covers the sulcus terminalis with its vein, and passes for a short distance over the adjoining outer part of the upwr surface of the th.ilamus. This zone ( lamine afGxa ) narrows in front and behind, and where broa3 ) of piu mater contai.iins the convolu- '^*^?t™ive^STonS"hV choroid JlexJ is com,M«ed. Each projec.u.n tions of WofKl-vesM-soiwrncn u.e ^oiUarv romplex fonned by the teruun.il (^o««s choriold«.« --;;^,,^i;/i^„i^'J'!;S.. which Kain tJinterior of the twigs of the ^"*^"°^,*"" .•^'i^-i rts^„re in the inferior horn of the lateral ventricle : hemisphere throuRh the '^J";"^^ J'"""'^ '" , jh,. ..,,endvmal laver (lamina chorioidea '^t 'l^.'it^lKr-o.r'rhlEr:,..; i„v„U„. U,. va^-uU, pro. Fk;. I002. Anterior end of fornix, cut Hippocampus Velum iuterpositum. Ciioroid ul.xun in inferior horn of luurKl ventricle epicnium, under MrfBce — PuMerior liorn of lateral ventricle Lateral pnn^of fornix under •urfa'^ .Corpti* caliosum .('Riidnte nucleus rhoroid plexii« nverlyiug I'aranien of Monro Vein of corpu« slnaium Choroid vi' 1 inplt^u* .Veins of (".alcu Crud of fornix and (Kxlcriot _fi>rcep!i of corpus calUi-um, cut I'ndcr surface of fornix, "l.vrn Cot -lUrrioT end otiiix it» under nutlace. ictions constitnting the choroidal plexus, .th^ epcmlyma ^^^S^j^ ^jlll^ the taenia fornicis to the thin lateral margin uf the f.irni.x, '"^V\'^" J? ",'',. ,., ,u,. Smer*sit!im protrudes to expand into the choroid plexus u.thm the IhkIv of ,hc ''"'It plexus ,s not confin^ to this part of the space. »";'«"""-«»«' "^j;'';^:::!';::; to the lower end of the inferior horn. The relation of the vascular pial ju*^^^ to hi:«te;:Jon of the ventricle is. however., th.- ..me as w.thm^^^^^^^^ !^ji*;^j«a I- m iilf 1 164 HUMAN ANATOMY. the entire choroid plexus of the lateral ventricle, the (-|><'iidyma is torn away and an artificial opening is produced, which may be followed, as a curved narrow cleft, from the lower end of the inferior horn upward above the hip|x>canipus and omt the dorsal surface of the thalamus, beneiith the fornix and the splenium, to the exterior of the hemisphere. When tiared forward from its attachment along the upper surface of the thalamus, the line of the reflection of the ependyma, tenia chorioidea, leads to just above the foramen of Monro CFig. 103 1), where it is joined by the similar line of the opposite ventricle. From thi.s point the choroidal line of ependymal reflection is continuous with the taenia thalami, the sharp ridge which marks the junction of the superior and mesial suriace of the thalamus ( pstge 11 19). Leaving the surface of the latter along this ridge, the ependymal layer covers the under side of the velum interpoaitum, as well as the double row of vascular villous projections, which, one on each side of the mid-line of the roof, constitute the choroid plexus of the third ventricle (Fig. 974). Although similar in its general structure, thi-- vascular fringe is much smaller and less conspicuous than that within the lateral ventricle. It is evident from the foregoing description, that communicntion between tlie third and lateral ventricles is completely interrupted by the attachment of the ependymal layer and that at only one place, the foramen of Monro (page 1161 ), does such communication exist. It Ls of interest to note that these several lines of ependymal reflection — the ta-nia chorioidea, the ta-nia thalami and the t£eni.i fomicis and its prulunKation, the txnia fimbria: — form a contin- iiuiis line which mor|)holn)(ically marks the transition of the thicker nerxuus pan of the wall of the hemisphere into the thin and atrophic area, vvhirh early undergoes an invaionation leading to tlie prtKluction of voluminous va.scular structures iaier seen in the delinite choroid plexuses i>f the lateral and third ventricles. Along the m.-uTfin of the choroidal fissure, at Hhich such iiivaKination primarily occurs, the white matter of the hemisphere iM-ronies condensed intn the tract of the fornix and its downward prolongation, the fimbria. These structures, together with the reflected ( |>endyma and the septum lucidum, are regarded, therefore, as modified imrts of the mesial surface of the hemisphere. The inferior horn (cornu inferius), iUso called \.\\e deicfm/hig horn, begins alx»\e at the hind-end of the body of the \'entricle, thence curves biickward and outward around the thalamus, and sweejis downward and forward and a little inward ( Fig. 1000) into the temporal lobe well t(i«ard> its tip, which, however, it fails to reach by about 2 cm. Its descent is not only very abrupt, but limited for the most part to almost a vertical plane ; hence this part of the \ (Utricle does not diverge to any consideraH1» extent be- yond the planpri fbeK>rus hip- |x>catnpi, ju.-t to liie outer side of which the I'j>»er end of the inferior horn lies. The roof oi this cornu is formed chiefly hy the tapetum of the I'tMfiitlyni.t III liiUTai and third venuicic ; v|ifnd\ma in represetitrtl hv red line; c, i\ riirpun talloMiim; /■', fornix, ft'. soH.-allefl ventricle t(( Verica: (\ 7'. caudnte nurleus and thalamui*. THE TELENCEPHALON. 1165 collatenlta) that extends for a variable disUnce along the outer |wrt of «he flo. r ^ .hTSlerior horn This elevation is uncertain as to prominence and len^t! . Imt of the '"'"'"' ?T;.ncd does not reach the lower extremity of the ^ . .uric e. r:Li:i!^r;om tht Int<of the .an ol .he early hemisphere by the .n,er.or »"" A l^'o^d SuSfelevation. constant and much more co.«picuous than the «.UaterremSence and separated from the latter by a groove, forms the mner ,Mrt ..f iXrlnd the adjoining mesial wall ot the inferior horn of the latera ventricle^ Vhisdevat"on known as the hippocampus, is the most promment feature o he hi and curv« downward and inward to the extreme lower hm.t of this part of the horn ana c*";v« ""*" , i„,.^gi^tion of the hemisphere by the hippocampal CTe ThVlower enS^Tthe hiJ?K.n,pus is dLstinctiy broader and s.>mewhat Sened and nSric^ by a number of oblique shallow furrows and mterxenmg low SaSS ridgTStaOones hippocampi ). These confer on the upper surface and ^rSfy on^e outer rounded border of the elevation, a corrugated ^^'d "Otch^ Tp^rance ( Fig. .004). which suggests a fancied rescmbUnce to a paw, the lower end of the projection being known as the pes hippo- campi. The upper surface and the anterior and lateral border of the pes are free and well defined, but its deeper suriace and inner border, to a large extent, are blended with the surround- ing piirts of the hemisphere. The intimate structure of the hippocampus is described with that of the cerebral cortex (page 1181). The dorso-mesial aspect of the hippocampus is over- laid by a white flattened Iwnd, the fimbria (fimbria hippocampi), which, although bearing a special name, is the direct prolongation of the j>isterior cms of the fimbria, continued from the lateral angle of the corpus fornicis into the inferior horn. Us concave mesial margin is smooth, rounded and free Hn hit>(wc4lit|4 Inferior honi o( lift l«ler«l venlrklc, viewed from abovi-. rhS^uTuoustaTerif'^.rder is thin and shan^ and give, attachment throt^^h- out its SitiJe length to the delicate ependymal layer which completes the mes.a wa 1 md hus clmes in the descending horn ( Fig. 1005 )• Above narrow and then brLer on rSg the pes .!u fimbria becomes abruptly reduced to a i,arrow MrTnd which may be foUowe.! ,i..ng the inner margin of the pes to the uncus whtre it eS graced upward the fimbria passes without mterruptum into the posterior hmb of the fornix, of which, as already noted, it is the d.rc. . downwa d Songation Beginning in the uncus, the fimbria continually r.^e.xes acc«>ss'.r^ Ses n"n th.- .mderlving hipp' hod; Pontine flesnre Spinal cord Pons Floor of IV venlrlde Medulla Cervical (lexnr« Reconstruction of brain of human foetus of 3 months (50 mm. ) ; mesial nurface. X 4M. Drawn from Rla model. the intervening velum interpositum, it follows that the plexuses converge towards and meet over the foramina — a relation which they retain in the adult brain. The backward expansion of the hemispheres is accompanied by a corresponding backward prolongation of the young pia mater covering the roof of the diencephalon, later the third ventricle. After the corpus callosum and the fornix have been superimposed, the impression is given from the relation of the stnicturcK, as seen in t)ie completed brain, that the pia has gained its position over the rP"^'«.^^« ^^ IS by the corpus callosum. S pyriform area. The '»\'Vr't:^ZS^^Zk^m ^^T^^'^^^^ P°^ <^ "^ «=?'- ™„4iS; thin and •» converted '"^/^^ '^P^'^'^,K^f the anterior pill^ of the fornix by losum forward and downward, f"^ *;^ .^^7„'^ ^h^^^^^ to the basal surface of he fibres which pass from the gyrus d^nt-^ "^ana tne nip^ v ^^.^ although thm ; brain, the septum »«cid«™^";!^ '^^ l^eL by a na^ow cleft, the socalled fifth ven- ::ir wSu S.SS St ni^^Te^y-' Uning. and. therefore, is no part of Fig. 1032. Choroidal fiamirc Priman- gyrus dentatu* Roof-plate of 111 ventricle (tunia thalaml) Thatamiw Posterior commiasure Uuadrigeminal plate Mid-brain cavity Cerebral peduncU Cereliellum IV ventricle Corpus calloaum Roatruni iieptum lucidum Anterior commi»»ur« III ventricle Olfactory lohe Lamina lerminalia Optic chia»m Pit\iitary body . Medulla Me.ial.uriac.o.le.thalfolhumanf«tu.offo»rih«onth. X.. (^.«W.) the system of true ventricular '^^r;..'i^'^^^^n.TZ:i:^ ^^^^^ S^eSd" opinions differ. The older view. »h»t the space represen«^ fa^stained neither by its nkl fissure cut off during the d^^e oF«nent of tl^e c^^ _^,^ .^ ^^j^^ ^^ rtiUon history nor by the adult ""^.tion o th« sepUim 1^^^^^^^ Y ^^^^ Marchand.' His and is solid and no space exits. ^"J^*'"' ''"V^^oiiKque^^^ of the growth, increasing bulk and others, regard the spl tting «« «;^^^^,„ ind ?Sion of the fo^ix along its under suriace^ backward extension of the con>uscallosum »"<^ \^^^"*^ ^^,, forward along the mesial suriace the primary upper part of the h.ppocamps«extenfl^^ fissure, being later repre^ of the hemisphere, entirely d^^PV^^' '™ °*d ng po^dTof the gyrus dentatus is reduced ::r XttS'c^^S rilfrr thT^gitud^nS'stria. found upon the uPper surfa. of the corpus call'-- m. „„ . ,xt MEASUREMENTS OF THE BRAIN. The brain f^ts within the cranial c- so accurately tha^^^^^^^^ ^0^"^' the general shape of the skull. b«='"K .^'^ '^ '^^L °"v «^^^^^^^ The usual length subjects and shorter and ""^^ ^Ph"'-*^ the SEl ^le? is from ,60-170 mm. of tie brain, measured from the ronta to the ocapitai po ^^^ tSrL'rmt^trut^t (S'")^o^'^th seL and its greatest verti- ' •\rchivf Anatom. «. Entwicktlung. 1903. > Archiv f. mikros. Anatom . Bd. xxxvu., 1891. II96 HUMAN ANATOMY. cal dimension through the hemisphere is about 125 mm. (5 in.). The female brain is commonly somewhat shorter than that of the male, and, therefore, relatively broader and deeper. The weight of the brain has been the subject of repyeated investigation with results that fairly agree. The conclusions of Handmann", based on recent examina- tions of 1014 brains (546 male and 468 female) from persons ranging in age from fifteen to eighty-nine years, are of interest since they confirm in the main the results obtained from previous observations; The average weight of the adult brain (from 15-49 years), without the dura but surrounded by the arachnoid and pia, is 1370 grams (48.6 oz. ) for men and 1250 grams (44.4 oz. ) for women. The weight of these membranes, including the enclosed arachnoid fluid, has been estimate*! at 56 gm. and 49 gm. in male and female brains respectively (Broca). The brain iially attains its maximum weight about the eighteenth year, perhaps somewha arlier in women, no increase taking place after the twentieth year. Subsequent to the sixtieth year in both sexes a progressive diminution occurs, by the age of eighty the brain having lost approximately one-fifteenth of its entire weight ( Boyd ). Including the brains of individuals between fifty and eighty-nine years in his series, Handmann found the average weight to be 1 355 gm. (47. 8 oz. ) for men and 1 223 gm. (40. 3 cz. ) for women. Approximately 81.5 per cent, of adult male brains have a weight be- tween 1200 and 1500 gm. ; 8.8 per cent, one cf from 950-1200 gm. ; whilst 20.3 per cent, possess a weight over 1450 gm. Correspondingly, about 84 per cent, of female brains weigh between 1 100-1400 gm. ; 44 per cent between 1 200-1 350 gm. ; and 46 per cent, below 1 200 gm. The average weight of the brain of the new-born male child is 400 gm. (140Z. ) and that of the female one is 380 gm. (13.40Z. ). During the early years of childhood the brain rapidly becomes heavier, its weight being doubled by the end of the first year and trebled by the completion of the sixth year. At first the increase affects the brain equally in both sexes ; later the young female brain fails to keep pace in its growth with the male one, the differences becoming progressively more marked. Whilst the brain-weight and stature stand in direct ratio in the new-born and in children up to 75 cm. in length, irrespective of age and sex, after attaining such .stat- ure the relation is irregular and uncertain. Likewise in the adult, Handmann found no constant ratio between the stature and the brain-weight, although in general a lower average weight of the brain is found in short individuals than in those of mod- erate and of large height. The relative brain-weight, as expressed in the ratio between each centimeter of height and the brain-mass, Handmann found to be 8. 3 gm. for each centimeter of height in men and 7.9 gm. in women, a slightly higher proportion in favor of the male subject being thus observed. The average ratio of the weight of the adult brain to that of the entire body is approximately 1 150 (Ober- steiner). In the new-born child this ratio is much greater, being, as determined by Mies, I :5.9. Of the entire weight of the brain, the hemispheres contribute 78.5 per cent., the brain-stem 11 per cent., and the cerebellum 10.5 percent, ;iO material difference being observed in the two sexes (Meynerl). The extent of the superficial surface of the cortex has been determined, at least approximately, by Wagner, who by completely covering the convolutions with gold leaf concluded that the large brain of the mathematician Gauss ( 1492 gni. ) presented an aggregate area of 221,000 sq. mm., or not quite one-iialf square meter. Of this entire area alxnit twice as much lay along the sides and bottoms of the fissures, tlierefore sunken, as upon the exjxised surface. The estimate of the same observer concerning the brain of a workman placed the area at 187,672 sq. mm. The significance of brain-weight as an index of intellectual capacity has long excited inter- est. Accumulating data prove beyond question that, as applied to individuals, the weight of the brain is an untnistworthy index of relative intelligence. For whilst in a number of conspic- uous examples the weight of the brains of men of acknowledged intellectual superiority has been markedly above the average, it is equally tnie that some of the heaviest brains recorded have been those of persons of ordinary, and indeed in some cases of even decidedly inferior, intelli- gence. I'"urllicr, the brains of not a few men of remarkable achievement in the fields of Science, ' Archiv f. Anat. u. Entwickelung., 1906. 11 THE MEMBRANES OF THE BRAIN. "97 „. Letters =u,d of Art have po^se^ -^t'lJ tarSoT ^';^:r;Z ^^Z^^^ "^^ " In this connection it must be ^'r"'*,""'^^^ **' ^^^ ^wer o! retaining impressipns; ^diflerent brains vary in the.r c=^.t^«or ^^^'r tt^notwit^tanding the possible lu. ^n- that. in short, differences of 'f^'^^'^J^^^-jL^^i'' matter, especially of certain regions con- eral weight of a brain, the amount of '•'f .<=""^.^?' «"^ ™ist •„ u^ual abundance. Moreover, ^med i^ some particular P^^- »' "f ^?^^^^r\> JS „crease of the functioning as.socia- it is probable, from the investigations of l^?** • "*" °"^ ^v excessive exercL-* of certain parts tion fibres takes place in response to the ^^^^^^^J^^^^X "dividual, brain-weight alone li the cortex. It is evident. ^^JP'^'^' **\J^„S I»wer, and that brains which, judged afford- tittle dependable •"°™^rw^„*^i^"S!Tay h^ve b;^n exceptional in the amount of from .L. f weight. «PP»r«nt'y'^^^heunS canity of their neurones. _ cortical gray matter and. perhaps, n the """f ^*^"\" ^^^ or to races, brain-weight has "* Co^idered. however, in ^-'»f°"J^, ^[^/^'^S^i^^rind culture. In this connection been found to correspond to the genial P^« °«„~f^^g, brain-weight of the male negro the observations of Bean' are s''pestive^ " d ,c6o em ■ that of the male Caucasian i34« P" • to be ,292 gm., with extremes of .010 gn^and^^5feK^^.t^« ^^,.,^i^^, j^^ rfa-ss o the with extremes of 1040 gm. and i555 K"" .{:°Vj'\heir brains was greater than that of the white subjects examined. *e average w«ght«^the^braiM high-class negroes. Bean concludes hat ♦^«^^"^'''"^t^j; relatively and absolutely smaller, frontal lobe. and. therefore, that the .mteriorassoc^a^^^^^^ ^^5^^^ ^ ,^ ^i The observations of E. A. Spitzka concerning i j ■ ,he brains of men of con- sagittal section, call attention to the """''"»\f,'f °*£,~pou7o^^^ thus examined var^a- ^cuous intellectual power. Moreover in he part^cu^^^^^ .^ ^^^ ^^„^, ^^^.^^ tions in the details of the callosa strikingly ^««K^t*^*^» cMosxxm as a trustworthy index as to of the persons during life The Y'^hdity ofAe area oHhe^^^^^^ ^^^^^ ^^ ^^ Bean, intelle^ual capacity has been ^"°^^y^^^^^^^^i,^l^ight, aiid that not infrequently that callosa of uncommon size «f««"y h«l°"K *° e^JTof low intelligence, as exemplified by the *^''jrtarirngti;;?:fnl°^^^^^^^^^^^ - — «-■" 'o— ^'^'- and even from negroes. THE MEMBRANES OF THE BRAIN. Like the spina, cord, the brain i-;a^^>i:^. T^rS^^--^ 5") which, from without tnward, are^ .^JJ^^^P^^^o ihe inner surface of the cra- the pia mater. The first o[ »''^.'^"'^'y l']_ addition, by means of its processes nium. of which it constitutes he P^'^^«,^""^;i"„^,;\"hf e^^^^^^ of nervous tissue, serves to support and guard from .""^^^ P^^^^iJ/^^^s for the nutrition of the The pia mater is the vascular tunic «^^^5y'"g 'J\\;\X el^emal surface of the organ ; irain'^and. therefore li^ in contact with f P^J^^jP*^ ^^f f ™ tie coats, is free from whilst the arachnoid, the l^/""^\!^"tir^he intracranial lymph-paths. Although blood-vessels but is •"'''"^'^•y/^if,*!^^:*^ '^VskuU an^^^^^ "^^J the dura and the pia are closely f"f '='^^1,*°. '^v dSto two compartments by the are separated by an '"f^^^lf if '; '"^t^ ^tw^n the dura and the arachnoid and is arachnoid. The outer of t' ^clefte »u^ ^l^^n\ht arachnoid and the pia s the called the subdural sp >e othe^'f ^^^ j^ y,^^,, ^ mere capillary cleft, the subarachnoid space. /'aX^taT mall amount of a clear light straw- arachnoid lying against tl, a. and conwi although much more cana- colored fluid of the nature of IJ'^P'^: J*'^ '^^"rab^^ulx of arachnoid tissue tiiat cious than the subdural, is ^i^^^^-^^J^y ^^^^^^^ rather than of an in many places it acciuires the character «» » «P^"KS j ^ suburachnoitl spaces unbroken channel. \Vhilst -"'''t°'"'";«"y J'^;„",Si\";^are{ul artificial injections are distinct and nowhere S"'"™""!^,*'^;!^ £°" Se cerebro-spinal fluid finds its into the subdural cle t. it '^P.■•«^^le that^rin^ hfe th^ <:ere ^ ^^^^^^ way through the thm P»"'^'«" °' 'f ''£irth^^ fluid, a modified The interstices of the arachnoid ^«^^^H^ „r*^^J^\'^hin the ventricles. After dis- lymph, which is produced by he ^^Jf^'f £XoS space by way of the foramen SferanTtSn^rtiSao^f &t^ s£Sn"the aVnu Jtc^ rU o, the fourth ! Hie r,m«shimrinde <|ps Menschen, iqo? ' Amcr. Journal of Anat., vol. v., 1906. » Amer. Journal of Anat., vol. iv., 1905- 1 198 HUMAN ANATOMY. ventricle (page iioo). The paths by which the fluids collected within the brain- membrane are carried oil, thereby insuring under normal conditions the prevention of excessive intracranial tension, will be considered with the description of the dura and arachnoid, suffice it here to mention the sheaths contributed by these envelopes along the nerve-trunks as they leave the cranium and the Pacchionian bodies as the most im[>ortant. The Dura Mater. — This structure (dura mater encephali) is a dense and inelas- tic fibrous membrane, which lines the inner surface of the cranial cavity and sends partitions between the divisions of the brain. In contrast to its relation within the vertebral canal, where it is separated from the bony wall by a considerable space (page 1022), within the brain-case the dura everywhere lies closely applied to the bone — a relation essential in hilfilling its function as a blood-carrying organ for the nutrition of the cranium. Around the margins of the larger foramina, over the pro- jecting inequalities of the fossae and along the lines of the more imjxjrtant sutures, the attachment of the dura to the skull is particularly close, and at some of these points Fig. 1033. : i] 'Falx cerebri Junction of falx and tentorium Tentorium cerehel!i Opening Tor hrain-nteni' ntphngma Mllee : margins of tentorium Portion of skull removed, showing partitions of dura in place. — the foramina and the ununited sutures — the dura is continuous with the periosteum covering the exterior of the skull. On separating the dura from the bone, as may be readily done beneath the calvaria, except along the line of the sagittal suture, its outer surface is marked with the conspicuous ridges produced by ihe meningeal blood-vessels, which lie much nearer the outer than the inner surface of the mem- brane and hence give rise to the corresponding furrows seen on the inner aspect of the skull. In addition, the roughened surface of separation is beset with fine fibrous processes, the larger of which contain minute blood-vessels, that have been drawn out of the canals affording passage for the nutrient twigs. The inner aspect of the dura, on the contrary, is smooth and shinny and clothed with a layer of endothelium which lines the outer wall of the subdural spwce. As the nerves enter the foramina in their exit from the cranium, they receive a tubular prolongation of the dura which accompanies the nerve-tnmk for a short distance as the dural sheath^ separated from the nerve by the underlying subdural cleft, and finally becomes con- tinuous with the epineurium, whilst the subdural space communicates with the lymph-clefts \yithin the connective tissue envelopes of the nerves. The dural sheath THE MEMBRANES OF THE BRAIN. 1199 «.rround,ng the optic nerve through its entire length is noteworthy on account of its unusual thickness and completeness (l««V\"3^ , , partSn., which protet ln.«rd a»d '"Ifi™ !^f^h. brata SS "ll " enclcie the 5mpanm»ts occpM by the 1«^^;~>™ ?< ™c» Evf b^r desnibrf with fcr^— eivii^^^TrtJAss^^-s localiti^in which the Pacchionian bodies may a,me into rj;^^^^^ ^^^ stream. The septa thus formed by dupUcatur« of the mn«^^^^^ V^^^^ falx cerebri, (2) the tentorium cerebelh, (3) the/a/* fw-^^w*. anu ^4; ^'^"f hTflSic'^cerebn is a sickle-shaped V^^S'^:S^:^:'^TXv^^S. ffg^r the longitudinal fissure separating the cerebri hem.spher«^It^^^^^^ ^^^^^S.^ border is attached in the mid-hne and extends fr«"\ ^^e cnsti gam bone in front to the internal occipital P^^^^^^^^^^^'^i^Hn „^^^^^^ longitudinal sinus. The latter channel appear J'^^g^ ^ay "r of the dura and the .OM). the "P-rd placed base ^mg the out^^^^^^^ ,f ,he falx is sides the separated lamella of the talx. ine •°''^y^J'" . , (^e hind part of free and more sharply arched than is the"PP«r, and extends Jro^^ .^ the cristi galli to the highest poino the tent^um W'f^/" J^. ^^.j. encloses the inferwr lanpludinal sinus. The b^^ tne m ^^ ^^^ mately at 45° with the horizontal plane, and attached « the uppe ^^^ tento^um in the sagitta plane. A»«"?this junction li« he .^^^^^^ ^^^^ narrow forepart of the alx is the thmnest portion «' the F^rtmon an ^ ^ especially cWing the latter half of life, the ^^*t of perforations^ w -^^j^^^ numerous as to reduce this part of the ^Pt«"» t^^ '^"^^^^^^^^ pathological slSSncI Tnd '7^^:J'^^Z'^.r:^^o:.. ..l partition seen in some ''niieunt^rlutn cerebelU is the large tent^Je Pa-Uion^^^^^^^^^^^^^^ tenor fossa of the skull and separates the <=^;^^^^"'^^ *'7 J^^^enUc. the longer parts of the cerebral hemispheres. In its gfn^";j°n^ '^ '^ S margins of the ?^nvex border lying behind and attached to t J^^P"^*^; "^X e^^^^^ posterior cranial fossa, and the shorter con^ve ^"tenor Iwrder c"rv j^^^ ^ ^ upward from the anterior chno.d P/f «!^:. ^f„^"X^^eISl plane, and in this is attached by its entire width to the fax ^^.^li" ^PK ^'^^'^^'^^J^ „f he tent-like manner the partition is mamumed m « J^^f ^t X* J^^d y ^^^^^ convexity fold are. however, not simply fla . but P'-^T'^^^^ f^'^',„,e of the under surface of ihe'^StiSs tTciS^^^^^^^^ "PP^^ -•'- "' ^'^ --'-"""' I200 HUMAN ANATOMY, ' 1 1 of the petrous portion of the temporal bone, and thence to the posterior dinoid pro- cess. From the internal occipital protuberance as far as the parietal bone, this line of attachment corresponds with the course of the enclosed lateral sinus (page 867; ; but beyond, the venous channel leaves the tentorium in its descent to the jugular fora- men, the farther attachment of the tentorium enclosing the superior petrosal sinus. Since the anterior border of the tentorium springs, on each side, from the anterior dinoid process, it follows that the two margins of the crescentic septum intersect in advance of the apex of the petrous bone, the posterior border turning inward to the posterior dinoid process, whilst the anterior margin is connected with the anterior process. The free tentorial border, in conjunction with the dorsum sellae, defines an arched opening, the incisura tentorii, through which the mesencephalic portion of the brain-stem is continued into the cerebral hemispheres, the highest point of this aperture lying just behind the splenium of the corpus callosum. Fig. 1034. ^Skin Superior longitudinal sinus- F«Ix cerehri Fibro.ipan«nrMic layers o( icmlp ParieUI layer of dun Posterior horn of lateral ventricle Tentorium Left lateral sinus. Superior wonS' Inferior kMicitndi- nal sinus, cut obliquely 'osteriorhom of lateral veuirici* 'entoriom Richt lateral slnii* 'erebellum Inferior worm (Vcipltal sinus Frontil section of liead, viewed from behind, showing relations of dura mater to cerebral hemispheres and cerebellum and position of sinuses. The falx cerebelli is a small sickel-shaped dural fold which descends in the mid-line from the under surface of the tentorium, with which its broader upper end is attached, towards the foramen magnum. In the vicinity of this opening its apex bifurcates into smaller folds that fade away on either side of the foramen. Its poste- rior border, attached to the vertical internal occipital crest, contains the small occipital sinuses, or sinus when these channels are fused. The narrow crescent projects into the posterior cerebellar notch and thus intervenes between the hemispheres of the cerebellum. The diaphragma sellze is an oval septum of dura, which roofs in the pituitary fossa and is continuous on either side with the visceral or Inner layer of the wall of the cavernous sinus. The diaphragm contains a small aperture, the foramen dia- phragmatis, through which the infundibulum connects the enclosed pituitary body with the brain. The structure of the dura presents the histological features of dense fibro- elastic tissue, in which the elastic constituents, however, are greatly overshadowed by the white fibrous bundles. The inner surface of the dura is covered with endo- THE MEMBRANES OF THE BRAIN. I301 thdial plates which constitute the -™edbte ^^ w^^];^^-^^^ ^Sch^cA endothelium ^"«*'"« ^.^.i/ 1«*1^« Tte o^ter or periosteal Sped as ■^-^<-^-'^?^,^^^^t£:^''Z£rly:^ contain^a wide- laS^Ua is less comi»ct ^^5^ ncherin c^ tnan^ « j;^^ ^ ^^^^^^ tissue are meshed net-work of capillary ^ «od-v«aeJ- ^"^^^j j^e two ends of the falx STLTo^^^X^^^^^^ s:5o^vStacta^nSs:i;^^ ^-^^^-^ JLint.the fibres within the tentonum P^l^f "^^y- ^ irain-saml or acrrvulus, are P° Minute c^-^^"' Sr/he iw^ no^^^^^ especially in subjects of not infrequenuy «°""J '"^^.V^ '^Uons of particles o&ium carbonate and advanced years. They consist oi ^K^***" , .,, J^ounded by a capsule of fibrous phosphate arranged in concentnc ^^V^"^ ^'^J^^'^^ "Lt may be so numer- Fig. 1035. Medullary bimncli Larger plal arlery- Ite matter "'ptrnlr:';!. cer..»l con.., -.o,.„. capnur, .uppiv «. ^r •"<• «- — >< '«• internal maxillary, vertehnd --^inf ghaiy^geal a^^^^ JheJ^-^ destined, for the most part, for the ""t^of^J^ Some Lper/oratinfr arUrUs ;t^^^Th?UraT;trmSfe w-itfthrSHcr^ vessefs. ihilst others are i;SrpalK::;:^un^in^^^^^^^^^ -^ ^'-^^^^^ "" tL venous «i""««,^rlL indudtSp^ly^yn^Pathetic filaments, distributed The nerves of the dura include P""*^'P="2,Jf Xes The immediate sources to the blood-vessels and to t^bone and sen^ry^fibres.^ T^^^^ ^^^ ^^^ are the meningeal twigs contnbued by he t"gemmu.. f^^^^j, ^^^ ,,^iy £:o™Xryt^^^^^^^^^ ^"S s^u^;ltL comVnionship by ^means of I303 HUMAN ANATOMY. Gray- mmttcr White matter the commui sitions which these cranial nerves have with the plexuses surroundings the arteriesi or with the superior cervical ganglion. The sensory nerves of tho dura form a rich net-work of delicate twigs from which filaments lu..ve been traced to the inner surface in relation to which some end in bulbous expansions. The Pia Mater. — ^This membrane (pia mater encephali) lies next the nervous substance and, being the vascular tunic supporting the blood-vessels for the nutrition of the brain, follows accurately all the inequalities of its exterior. It not only closely invests the exposed surface d the cerebrum and cerebellum, but penetrates along the sides and to the bottom of all the fissures as well, although within the small shallow fissures of the cerebellum a distinct process of pia mater can not be demonstrated. Additionally, in certain places where the wall of the brain-tube is very thin, the pia pushes before it the attenuated layer and seemingly gains entrance into the ventricles. Examples of such invs^nation are afforded in the relations of the velum interpositum and the choroid plexuses to the lateral and third ventricles (pa^e 1162) and of the similar plexuses m the roof of the Fig. 1036. fourth ventricle (ps^e 1 100). The pia also contributes a sheath to each nerve, or to its larger component bundles, as the nerve leaves the brain at its super- ficial origin, which sheath surrounds the nerve during its intracranial course and for a variable distance beyond its emergence from the dural sac The pia is so thin that the larger vessels, especially at the base of the brain, lie within the subarachnoid space, although in most cases they are enclosed within a delicate investment of piai tissue. The smaller vessels, however, ramify within the pia and in this situation divide into the twigs which directly enter the subjacent nervous tissue. As they penetrate the latter they are accompanied by a sheath of pia, which thus gains the ner\'ous substance within which it fol- lows the subdivisions of the arteriole, even their smallest ramifications. Whilst within the pia the larger arteries form frequent anastomoses, the smaller twigs remain isolated and, being "end-arteries," on entering the subjacent gray matter break up into terminal ramifications which furnish tiie only supply for a pardcular district. The capillary net-work within the cortical gray matter is much closer than that within the subjacent white matter (Fig. 1035), in which the vessels are comparatively meagre. Here and there larger medullary branches are seen traversing the cortex, to which they contribute but few twigs, to gain the white matter within which they find their distribution. The contrast in richness between the supply of the gray substance and that of the adjoining white matter is not limited to the cerebral cortex, but is also well shown when the internal nuclei are examined (Fig. 1036). The veins emerge from the surface of the brain, but do not retain a definite relation to the arteries, since, instead of following the latter to their points of entrance, they for the most part seek the dural sinuses into which they empty. The special invaginating layers of pia mater, the velum interpositum (page 1 162) and the choroid plexuses of the lateral and third ventricles, and the choroid plexus of the fourth ventricle (page iioo) have been described in connection with the appro- priate parts of the brain. Attention may be again called to the manner in which the velum interpositum and the associated plexuses are formed (page 11 94), and to the Portion of injected dentate nucleus of cerebellum, show- ing capillary supply of internal nucleus, x ao. THE MEMBRANES OF THE BRAIN. IJ03 Fig. 1037. Vucular tuft backward (page U94)- oresents little for special mention The The mtructure of .he pa J» !!_ P'^^J^ti^e tissue enveU.pe in which inter- membrane consists essentally of a d«"l'^t^ "'""g'^^i^^^^i^^ji^ fibrw and conuining Sdng bundles of white fibrous t.s«ue-te™^^^^^^ ^^^ numerous nucei. are the '^^'^' 'f^'^'^-^u^^jthin which are prolonged the lymph- the brain, they receive *'?^»'*'''^,P'fJT^^ Along the basal surface spaces enclosed between th- »-bec^f ^f th^ P^'^^'^^,^ ^^e pia frequently conuins of the brain, especially on the v ^""^f^ .^P^^j ™ "^^Hs These may be so numerous, deeply pigmented branch^ Tt £ memb^ne appeari of a disJnct brownish hue. roSirt^iSeJS ^cattid' iTd^t^-^e^li^^leHes. AdditioJ nerve- fibres, probably sensory in Jun^'on- XJr in s^ai numbers, the mode of their ending is uncertain, although terminal bul- bus expansions and tactile corpuscles have '^"TK^Arachnoid.-This covering (arachnoidea encephaU)..the intermediate membrane of the brain, is a delicate con- Se tissue envelope that intervenes between the dura «t"'«"y ^'^'^ /^^ Pj^ internally. In contrast to the If t-nf^fj membrane, which follows closely aU Je irregularities of the sunken as well as of the fre^surface of the cerebrum, the arachno^ is intimately related to the convolutions only along their convexities, and on ^vmg at the m^ns of the inter%ening fissures stretches across these furrows to the con- volutions beyond. From this arrangement it follows that intervals, more or less m- angular on section, are left over the lin« of the fissures between the arachnoid and the fold of pia whirH dips into the sulcus. These clefts form . system of mtercom- municating channels which are ^J^Ae summits of the convolutions, the arachnoid general subarachnoid «P^<=^-. °^!' *?u,t"^nstitute practically a single membrane. and piaaresointimatelyunited that they con^^^^^^ connected only by the whilst, where parteu by th^ ^^Z^lcShol^^r. where the intervening cleft trabecule of arachnoid ti^ue In ^^^ous That the space is occupied by a delicate is not wide, these trabecule »^f J°. 7'"/ °"' ^^^^^^ Where, reticulum and becomes converted •"^° ^^^y^^^J^'^considerable size, as it does on on the other hand, the ^f^'^l'^^'^/^f^P^f^i^P^re reduced in number to relatively few the basal suriace of the brain, the *^*^"r .f ^ '^^Xoid to the pia mater. Over long, cobweb-like threads that expend fr^^^^^^ ^,^ J^^^, id foUows. the upper and outer aspects of »"« ^f ^'/V"' ^ Qn the ventral surface, however, it in a general way, Uie contour dt^br^". On the v. ^^ ^^ ^^^ ^^.^^^_^^ ^^^^._ SS^K'^^:^:lsSm^K 1^. t'^rc^rnT^^^^^^^^^TTl^^^i ^er^l suUvisions are recognized according to locality. ..„K.ii„™Mi„ilaris^ the largest of these spaces. Velum inter- poftittim Small portion oJ in)«trf choroid pkxut ot lateral small pu. ventricte-.iurfaceview. I204 HUMAN ANATOMY. magnum with the posterior part of the subarachnoid space d the cord. The arach- noid passes from the back |»rt of the under aspect of the cerebellum to the posterior surface of the medulla and thus encloses a considerable space which at the sides of the medulla is continuous with the upward prolongation oi the anterior subdural space of the cord. The lower part of the brain-stem is thus completely surrounded by the subarachnoid cavity. The ventral surface of the pons is enveloped by the upward extension of the anterior part of the spinal arachnoid, the cleft so enclosed constituting the cisterna pontis, of which a median and two lateral subdivisions may be recognized. From the upper ventral border of the pons the arachnoid passes forward to the orbital surface of the hronUl lobes, covering the corpora mam- millaria, the infundibulum and the optic chiasm, and laterally to the adjacent project- ing temporal lobes and thence, covering in the transverse stem of the Sylvian fissures. Fig. 1038. Olfactory tract. Optic chiaun Intemftl cmrotid artery Kasilar artery Vertebral arteriei Eztctuioa along laigittKlilial fiiaure Extenaion akMiK Sylvian fiaanrc Cisterna liaialis ClMaiia pootia Cistenia maittta Inleriur aspect o( braiti covered with i^-i and arachnoid, showing large aubarachuoid spacca. to the frontal lobes. This large space, which includes the deep depression on the basal surface of the brain, is the cisterna basalis. It is imperfectly subdivided by incomplete septa of arachnoid tissue into secondary compartments, one of which lies between the peduncles (cisterna interp«laris), another behind the optic commis- sure (cisterna chiasmatis) and a third above and in front of the chiasm (cisterna laminae terminalis). Anteriorly the cisterna basalis is continued over the convex dorsal surface of the corpus callosum (cisterna corporis callosi), and on either side along the stem of the Sylvian fissure (cisterna fissurae lateralis). Within the median region of the cisterna tesalis lie the large arterial trunks forming the circle of Willis. These vessels are invested with delicate sheaths of arachnoid, which accompany the smaller branches until they enter the vascular membrane to become pial vessels. The arachnoid also contributes sheaths to the cranial ner\'es as they pass from their superficial origins to the points where they pierce the dura, these sheaths over- lie those derived from the pia and, as do the latter, accompany the nerve-trunks for a THE MEMBRANES OF THE BRAIN. iios ; ^ccWonton body mn. n(l«t«i mwltallv \^ CrrtlTal vtin N^^^MBii Fig. 1039. Ccrcbnl vrin Aitery in '■', f '■^•'^aiaHi^^. .|iK'^ ?%*^^n kmsUndlaal >inu*. Sheaths into a subdural and a subarachnoid perineural con^partment. directly contin- uous with the corresponding intracranial spaces, ventricles As previously noted, the "f^'^^^?'",^ £^h tS[Scl^ escapes tLough the openings m ^^'^'^''^^^^^^ space. After and the foramina of ^uschka (page i 00) m^^^^^ fiUing the cistema magna and the o»%'^8^X ite way into the smaller spaces on and surrounding the spmal «=«'?• ^Jf^'^^J^.'^'th? e*^^^^ mass of nervous tissue is the exterior of ^^e c-^^j^ ..i-^jJ^^S^^^^ particularly at the base ^rt£ somtSi^trmiT^^^^^ - '-- -^- — ^ conditions, the maintenance of mtra- cranial and intracerebral pressure Fig. .04 within due limits. The paths by wl» ch this is accomplished include : (i ) tne extension of »''e subarachnoid space along the nerve-trunks, and (2) the villous projections of arachnoid tissue. the Pacchionian bodies, along the course of the dural blood-sinuses. The Pacchionian bodies (gran- ulaUones arachnoidales) are numerous cauliflower-like excrescences of the arachnoid, for the most part small but occasionally reaching a diameter ot S mm. or over, which lie on the outer surface of the membrane along the course of the dural venous sinuses Their favorite site is on either side ot the superior longitudinal sinus where ^^^^^^ ^^^ ^.^^ -^ ^ . they occur in groups, ^'h. ugh th> occur ns ^^^ ^ iX* Sets 'riStS\Crr /W,. ..r'*W-««. in « „«»» Diagram »ho«.n. r..a|i.r« o. ^cchjojj.^.L^JJ^Ju;" 12o6 HUMAN ANATOMY. they encroach upon the lumen of the main channel itself, within which they appear as irregularly rounded projections on its lateral walls. Whatever their relation, whether with the sinus or the lateral diverticula, the Pacchionian bodies never lie free within the blood-space, but are always separated from the latter by the dural wall. 0\er the summit of the elevation the dura becomes jjreatly attenuated, but never entirely disappears, so that only a thin membrane and the subdural cleft, theoretically present but practically more or less obliterated, intervene between the subarachnoid spaces and the blood-stream. This partition offers little obstruction to the passage of the cerebro-spinal fluid, which, unless the pressure within the venous channel is higher than that within the subarachnoid space, passes from the latter into the sinus and thus relieves the intracranial tension. When well developed, as they often are after adolescence but never during childhood when they are small and rudimentary, the Pacchionian bodies are frequently lodged in depressions within the calvaria, whose inner surface is sometimes so deeply pitted that the bone in places is translucent. THE BLOOD-VESSELS OF THE BRAIN. The course and distribution of the individual blood-vessels supplying and drain- ing the nervous tissue of the brain have been described in the sections on the Arteries (page 746) and the Veins (page 861). It remains, therefore, only to consider at this place the more general relations concerning these vessels. The arteries supplying the brain are derived from two chief sources — the inter- nal carotid and the vertebrEd arteries. After entering the cranium these vessels and their branches form the remarkable anastomotic circuit known as the circle of Willis (page 760). The latter gives off, in a general way, two sets of branches, the gang- lionic — for the most part short vessels which soon plunge into the nervous mass to supply eventually the overlying intetial nuclei, the corpora striata and the optic thalami — and the cortical, which pursue a superficial course and are carried by the pia mater to all parts of the extensive sheet of cortical gray substance, as well as to the .vjbjaccnt tracts of medullary white matter. The medulla oblongata and the pons are supplied by branches from the anterior spinal, the vertebral, the basilar and the posterior cerebral arteries. These branches gain the nervous substance as two sets, the radicular and the median. The radicular branches follow the nerve- roots and, just before reaching the superficial origins of the nerves, divide into peripheral and central twigs, the former being distributed superficially and the latter following the root-fibres to their nuclei. The median branches are numerous minute vessels which ascend within the median raphe towards the floor of the fourth ventricle and assist the centrally directed twigs of the radicular branches in supplying the nuclei of the nerves situated within that region. Those supplying the nuclei of the hypoglossal and the bulbar portion of the spinal accessory nerves are derivations from the anterior spinal arteries ; those to the nuclei of the vagus, the glosso- pharyngeal and the auditory are from the vertebral as they join to form the basilar ; whilst those to the nuclei of the facial, the abducent and the trigeminal are from the basilar. The choroid plexus of the fourth ventricle is provided with branches from the posterior cerebellar arteries. The cerebellum receives its supply from three arteries, the anterior and posterior in- ferior and the superior, cerebellar. The general course of these vessels is approximately at right angles to the direction of the fissures and folia of the hemispheres. In the mid-brain the interpeduncular space is provided with branches from the basilar and the posterior cerebral arter- ies ; the cerebral peduncles with those from the posterior communicating and the terminal part of the basilar ; and the corpora quadrigcmina with those from the posterior cerebral, additional twigs passing from the superior cerebellar to the inferior colliculi. The thalamus is supplied by branches, all end-arteries, from different sources, those for its antero-median portion being from the posterior communicating, those for its antero-lateral por- tion from the middle cerebral, whilst those for its remaining parts, as well as for the pineal and the geniculate bodies, iire from the posterior cerebral. The last vessel also supplies the velum interpositum and the choroid plexus of the third ventricle. The structures ou tlie base of the brain, such as the corpora mammillaria, the tuber cine- reum, the infut.r'ibulum and the pituitary body, receive twigs from the posterior communicating arteries. The optic i-hiasm and tract are supplied with branches from the anterior cerebral, the anterior eomn.utii'.tliiig. the internal carotid, the pwjterior communicating .ind the anterior choroidal arteries. PRACTICAL CONSIDERAnC>NS: THK HRAIN. 1207 The corpu..tri.tum. both the caudate and Wnucuiarnuc..^^ ftomS^m^lecerebral artery' which Pi-'--}^^':^'^^:^:'^:^Z'tuXn6c^l.r nucleus ^ticulo^triate and lenticulo-thalam.c ^f^^'^'i'^^^^Ss and the thalamus. One of the and the internal capsule and •-— ^ L^uter ^ " of the putamen. w.« named by Charcot S:anterior and lower part of *e ctoroda^^^^^^ the hj^ampus. The posterior chorouia ent portion of the vascular ~'nP>^; "'''^y,'^^^^^^^^^ i^Trived from the posterior cerebral artery, usually represented by_ a numb r "^ ^^^^^^^^'^j^' ,^^ ,,,„„, mterpositum. it completes and enters the upper part of the n^^"'^^- ^"'^'. ^ie b,5y of tl'c- lateral ventricle, the choroid plexus in the ^e^^^ndrng hom and m the ^^^^^^ ^^ ^^^ ^„,^rior. middle and The cerebral hemLpheres are supplied by ff ^"™>^ . , j ^^^ jg distributed to the posterior cerebral arteries Of ^l^^- *«J"^,t "^^'^^ Jot K the external surface of the ^st extensive area, which f^^races the greater i^rt but no ^^^.^^^ ^^^^^^ ^^^ hemisphere. This vessel also ^PP'i;*^^ "^^™bra, iT^ntially the artery of the mesia anterior part of the temporal lobe. The ?n™^^^™ j^^ an adjoining zone on the external surface, the anterior two-th.rds of wh.ch. '" ^^ ^^^^'^j ^^e posterior cerebral is chiefly on • and on the orbital surface, it suppl es. J}^.^'^°"^^^ region, and in addition an adjommg the mesial and tentorial surface of the °^^^P"^°; ^^P^™ /'^ follows, therefore, that, with the strip along the postero-in erwr "'.^^K'" °* *^^^;™S by the posterior cerebral artery, all of rrv^nt'^r.rifis'^f'Thet^isp^^^^^^^^^ -"'-The .^n..l lob. is supplied by the anterior -ebral anery^^^^^^^^ over the superior and the anterior »*"-'»'';^^^ "'^'^^^^.'S^!^, ^^^^^ internal to the orbital sulcus st-Lii^'^r^^^^iT^^^^^^^ ^'^ '--'- "' ^" """''' '''''''' ''"' V p-rieul lob. is supplied by the ^^^ rrtTg^h^r^XKeK!!^^: exception^ a narrow strip along the "PP^^,^"'^!! ' *^hr^^;ip°S lobe is supplied exclusively districT*!:.";i;rirert=;*'rhf^r7^^^ vicim^ of the isthmus. Whilst that ollhe p^terior cerebral includes the remamder of the lobe. The veins returning the blood .^--^V'^trwltuSd 1'^^^^^^^^^^ sinuses, and they therefore on y to ^''/"'*^J*X""^£;^^^ of vXes. The superior arteries. They are further d«t«ngu.shed by the ateenc^^^^^ ^.^^^ ^^^ cerebral veins, after emerging from ^'^^^/^^^^'j'o;"^ "for the most part, towards over the convex aspect f jhe hem^ph^re and PJ^-„«^^;£^ directly or'lhrough the the superior longttudmal ^^"^ ^„^f V'tfvei^ draining the structures situated lacunae laterales, by from 12-15 f"'"""; , ^ ..^^v to the paired lesser veins of C.alen, falx cerebri and the tentorium cerebelli. PRACTICAL CONSIDERATIONS. THE BRAIN AND ITS MEMBRANES. Con,.niial Errors of /^-/''/^--'•-^'^"t^^^^^^^^ t^l brain an^d its membranes f- -^^ ^^^Tr"^^^^ cet>halus), it may escape from the skull K^-^^f^P"r'\ '' .here may be arrest of I208 HUMAN ANATOMY. The most common enlargement of the head, hydrocephalus, is due to a retention of cerebro-spinal fluid within the cranium, ordinarily within the ventricles, but some- times in the subarachnoid space. It is usually a congenital condition ; its cause is not clearly known. It is believed by many that it is due to a prenatal inflam- mation of the ventricular ependyma, and by others to a disarrangement of the orifices of communication between the ventricles (Luschka, Monro, and Neurath). The aqueduct of Sylvius has been found obliterated, and inflammatory processes have been seen about the foramen of Monro. Congenital defective ossification of the skull may result in a gap through which may protrude a portion of the meninges with or without brain substance. If such a protrusion consists of a meningeal sac containing only fluid, it is called a meningocele. If it contains a portion of the brain also, it is an encephalocele, and if the protruded portion of the brain encloses a portion of a ventricle, a hydrencephalocele. Such tumors may be concealed from view at the base of the skull, or in the pharynx, or may protrude into the nose or orbit. They are usually in the median line and most frequently in the occipital region. Next in frequency they occur at the fronto-nasal suture, and more rarely in other parts of the skull. Pressure on the tumor will often reduce it partly or completely within the cranium, but in the latter case symptoms of pressure on the brain will arise. Violent expiratory efforts, as in crying or coughing, which increase the cerebral congestion, render the tumor more tense. The Meninges. — Diseases of the meninges are relatively more common than those of the brain proper, and many conditions often spoken of as brain diseases are affections of the meninges, the pia being closely adherent to the brain and extending into the fissures. Inflammation of the dura is called pachymeningitis, of the pia and arachnoid together lepto-meningUis. External pachymeningitis is usually secondary to disease of the cranial bones, traumatism, infection, or tumors. It is most frequently the result of ear disease, and is therefore generally of surgical interest. Internal pachymeningitis is apt to be associated with effusions of blood in o the subdural spiace ; they may cover a considerable area without producing marked symp- toms, or they may be encapsulated (haematomata of the dura mater), and may reach the size of a man's fist, causing compression of the brain. Occasionally they become purulent. The blood or pus may gravitate to the base of the brain in the region of the cerebellum, pons, and medulla, when the pressure symptoms will be more serious ; or it may find its way into the spinal canal. The dura is ecpecially adherent at the base of the skull and, to some degree, at the sutures of the vault. In the rest of the vault it is loosely attached, and accord- ing to Tillaux, particularly so in the temporal region. Collections of blood may accumulate between the dura and the bone {extradural hemorrhage). This variety of intracranial hemorrhage is commonly the result of rupture of one of the branches of the middle meningeal artery in the temporal region, the effused blood separating the loosely attached dura. If the blood is poured out rapidly, compression symptoms will soon appear, but if the hemorrhage is slow, the escape of cerebro-spinal fluid into the spinal canal permits of more delay in the appearance of these symptoms. The patient has often time to recover, at least partially, from the unconsciousness of concussion before that of compression appears ; and it is this recovery of mtelligence which is most characteristic of the condition. There will often be localizing symptoms indicating the part of the brain cortex which is irritated or compressed. Subdural hemorrhage may follow the rupture of a number of small vessels, either of the pia or dura under a depressed fracture ; or it may come from a large vessel, particularly the middle cerebral. The symptoms and treatment are very much the same as in the extradural variety. In children extradural hemorrhage is very rare, because of the relatively firmer attachment of the dura during the period of growth. The blood may escape under the scalp through a line of fracture in the skull ; or, what is more likely, it may pass through a tear in the ^ 3 '"-^J^,". J._ ,_, f. ._ (a-2Vi n.) from the surface, normal circumstances the ventricle is from 5-5.0 cm. (,* ^y9 -j subarachnoid s|,ace. 3^^^i„„^„j .^e brain. h.n,arr„aj,e is the «""«» frequent the production of miliary aneurisms^ A sudden s r^ ^^^'^^^^..^ ,^p^,^,, tension and ruptures one of these diseased vessels, piMng rise i | depending on the seat and extent of the hcmoirhaRC. I2IO HUMAN ANATOMY. The cortex is supplied by pial vessels distinct from those supplying the basal ganglia and adjoining regions. The latter come direcdy from the branches of the circle of Willis at the base. The cortical vessels anastomose ; those in the region of the basal ganglia do not. The latter are "end arteries," so that when one is plugged by an embolus the part supplied is deprived of blood and undergoes necrosis (softening of the brain). In such a case the cordcal supply would not be permanendy interfered with. VVhen a cortical arteriole is blocked, the anastomosis may furnish a sufficient collateral circulation to prevent necrosis in the affected part, but cortical softening is e.\ceedingly common. When one of the arteries forming the circle of Willis is occluded, as an internal carotid by ligation of the common carotid, the anastomosis in the circle is so free that, in most cases, no marked effect is apparent. Cerebral disturbances, as delirium or convulsions, do occur in some cases, and in some are fatal. Even when both carotids are ligated, with an in- ter\'al of some days or weeks, the operation is not more frequendy followed by cere- bral disturbances than when only one is tied (Pilz). A case in which the patient lived after one carotid and one vertebral had been obliterated by disease, and the other carotid ligatured, has been reported (Rossi). In another case, although both carotids and both vertebrals had been occluded, the patient lived a considerable time afterward, the cerebral circulation being maintained through the medium of anas- tomosis of the inferior with the superior thyroids, and the deep cervical with the occipital artery (Davy). Occasionally ligation of the carotid has been followed by hemiplegia. The most common seat of intracerebral hemorrh^e is near the basal ganglia in the region of the internal capsule. The artery most frequendy at fault is a branch of the middle cerebri, the lenticulo- striate, or artery of Charcot (page 1207). Hemor- rhages occur with less frequency in other portions of the cerebrum, and much more rarely in the pons, medulla oblongata, and cerebellum. The symptoms produced by the hemorrhage are the result of destruction of tissue and of pressure upon adjacent parts, and will vary according to the seat of the lesion. Tumors or inflammatory products will produce essentially the same symptoms. Cerebral Localization. — In order to understand the nature of the symptoms pr-jduced by brain lesions it will be necessary to study at least some of the functional areas of the cortex and their paths of conduction through the brain substance. Taylor has summarized as follows the researches of His and of Flechsig, which are of comparatively recent date and have thrown new and valuable light upon the functions possessed by the cortical regions of the brain, by the study of their mode of development. Flechsig succeeded in following the various tracts through their myelination. The tracts which are functional earliest receive their myelin before the others. He has shown that the fibres in the spinal cord, medulla, pons and corpora quadrigemina are almost entirely meduUated when the higher parts show littie or no myelin. In the new-born child the cerebrum is almost entirely immature, and proportionately few of its fibres are meduUated. According to Flechsig, the sensory paths in the brain first become meduUated, and may be observed devdoping one after another, beginning with that of smell and ending with that for auditory impulses from the periphery to the cortex. In this way it has been ascertained that the individual sensory paths terminate in tolerably sharply circumscribed cortical regions, for the most part widely removed from one another, being separated by masses of c^jrtical substance which remain for a consid- erable period immature or undeveloped. The cortical sense areas thus mapped out correspond entirely to those regions of the surface of the brain which pathological observation has shown to stand in relation to the different qualities of sensation. Olfactory fibres are found to end mainly in the uncinate gyrus. Visual fibres have been traced to the occipital lobe in the neighborhood of the calcarine fissure, and auditory fibres to the temporal lobe. Flechsig has further observed that new paths begin to develop from the points where certain of the sense fibres terminate and pur- sue a downward course. They can be followed from the cortex to the medulla and to the motor nuclei of the cord. These descending paths are mainly those known as the pyramidal or rnotor tracts, and the area from which they proceed, commonly called the Rolandic region, is, according to Flechsig, concerned also in the sensation PRACTICAL CONSIDERATIONS : THE BRAIN. I3II Of touch ; he calls it the --£(,-- JUl"ffiLt^^^^^^^^^^ eonvolution,.^he P--^^f t'exS' "0^^^ ^^^ temperature. ^"^ ll?.^d Tendon^nse Suilibrium, etc. This cortical region probably repre- muscle- and 5^"°°" f "f ' ^""^entres rather than a single sensory area, and in TdSoVrtrngTsenUTfie^rre som^thetic areal tHe ,r.ai n,otor r.,.on "-^^^t^JheiTthis sensory-motor area and the various sensory areas are fully taken into , thirpstm Sin atout two-thirds of the cortex which appear to have noth- •'T"l irkh the SLr7 nJThsig calls these regions of the cortex - assoaa- ;^ LtX' ■ al heSvLV furnish arrangements for uniting the various central "^""Vhe b^t known cortical areas are the motor, speech, visual, and auditory, al- The best ''"?r^".'-""'~' „_ Unnwled^e are beine made from Ume to time. Re- though new contnbut^ons to o^^^^^^ .^ ^^^ ^^^^^ ^j ^^^^^^ cently. Gr"n^"™/"f ^hern^^^^^ ^^ the chimpanzee and gorilla, that the 2r"^eat£ founTinMe w^ole len^h of the precentral convolution and the en- Fig. 1041. Lcit crebr.1 hemi.phere illu^nnlng dtap.mm.tic.ny molor zone .nd lu .ubdivl.ion.. (MUU.) tire length of the central fissure. It did not at any point extend ^^f ^ f X"^^ f^«ure They demonstrated other important facts in ^°^^^''ZZnth\Z\^x.,rth behind nie centrm fissure. i3ia HUMAN ANATOMY. In the lower one-third or fourth of the motor zone are found the motor centres for the /ace and tongue, that is, for the fadal and hypoglossal nerves. In the middle third or half are the arm centres. In the upper part of the region and paracentral lobe, are the centres for the lower extremity. Localized lesions of the motor zone may therefore produce a paralysis limited to one part controlled by the affected por- tion of the cortex, as of the face, arm or leg (monoplegia). The lesion is much more likely to involve two adjacent areas, as of the face and arm, or of the arm and leg, giving rise to a combined paralysis ; but no single lesion, unless it were crescentic in form, could involve at the same time the leg and face areas without including the intervening arm area. Within each of the larger areas a more s[>ecialized differentiation is possible, although none of them can be sharply defined, not even the larger. That the facial centre lies in the lower part of the anterior central convolution is certain, and it is believed that the upper and lower muscles of the face are each represented by a sepa- rate centre. In the upper and forward part of the bce-ar^a are represented the movements of the cheek and eye-lids ; in the posterior part the movements of the pharynx, platysma and jaws. Fig. I0I43. Diasntm illiutrating protwblc reUtioni oi physiological areu and centres of latenl aspect of left cerebral hemisptacre. (MUU.) In the arm-area it is considered as certain that the centre for the movements of the thumb and index finger is below; above is that for the finger and hands; and in the highest part is that for the shoulder. In the posterior parts of the second frontal convolution and in a portion of the third frontal convolution are the centres for the associated lateral movements of the eyes and lateral movement of the head (Beevor and Horsley). Our knowledge of the more special localization within the leg centre is not at all exact, and the many views held are very contradictory. It is believed that the centres for the movements of the thigh, knee, foot, and toes, are arranged in the order named, from before backward on the lateral border of the hemisphere and in the paracentral lobe. A narrow zone for the movements of the trunk, as shown by Griinbaum and Sherrington, is located between the upper border of the arm-area and the lower border of the leg-area. It is now considered probable, however, that the cutaneous sensory centres are posterior to and in close contact with the motor centres in the postcentral convolution, while other centres for stereognostic perception and the muscular sense are located in the s'lperior and inferior parietal convolutions. The speech centres are in the posterior part of the third left frontal convolution (Broca's convolution), in right-handed people in the first left temporal convolution, and perhaps in the left angular g^rus. PRACTICAL CONSIDER. iTlONS : THE BRAIN. I3I3 In Broca-s convolution is . probably ^he centre for^^^^^^^ a„d a le«on *"« P"'t%'?TXl?l IdtotS The exiMence ol . motor although it is probably near the centre for smell. Fig. 1043. The auditory centre, as indicated, is in the upper tempo|Blc.nvolutbn^ It « aUh»gh the tactions of •»7i"^ U!SeSve S'ut notable .ymptoms ol any "p^yX^'taSS," tSSl i.l'the'^JSronLihe,, the H. .ide bein„ perhaps and of the temporal to nearmff .'"^ !,„__„ .„_tre while the lateral a.spect of the '4K -"£^eiI=iSr^»5s==r!ifn i'S,;SEpr.o|^!^p'™^^^^^^^ I3I4 HUMAN ANATOMY. i also by a lesion in the lateral portion of the occipital lobe, if it extends inwards sufficiently to interrupt the optic radiations. In spite of extensive researches the functions of the central ganglia are very little known. Lesions of the cerebellar hemispheres may not produce distinct phenomena until the median lobe or vermiform process is involved, when two especially charac- teristic symptoms will almost certainly develop. These are a peculiar disturbance of equilibrium with a staggering gait (cerebellar ataxia), and a troublesome vertigo. Although the patient can scarcely stand alone he may possibly be able to perform the most delicate movements with his upper extremities. The vertigo occurs only in standing or walking, and is then almost always present. Nystagmus is also a frequent symptom. Vomiting is very often present, but is not characteristic, since it is equally frequent in other brain diseases. Extending along the floor of the aqueduct of Sylvius and of the fourth ventricle, that is, along the cerebral peduncles, pons and medulla, we find the nuclei of origin of the motor fibres of the cranial nen-es. It should be borne in mind that the con- trolling centres of these nerves are in the cerebral cortex. Many automatic centres, as of circulation, respiration, sweating, and regulation of heat, as well as the motor and sensory tracts are found in the medulla. Cranio-Cerebral Topography. — In order that the surgeon may expose and recognize certain areas of the cortex, it becomes very important that the relations between these areas and the corresponding external surface be well understood. For this purpose advantage is taken of the landmarks of the skull (page 241). From these bony points, ridges and depressions, by means of lines and measurements, the known cortical areas may be accurately mappied out. The upper limit of each cerebral hemisphere is indicated, approximately, by the median line at the top of the skull from the glabella to the external occipital protu- berance, due allowance being made for the superior longitudinal sinus, which lies under the skull, in the longitudinal fissure, between the two hemispheres. The lower limit is represented by a transverse line, in front, just above the upper margin of the orbit. At the side of the skull the line passes from about a half inch abo\e the external angular process of the frontal bone to just above the external auditory meatus. From here it passes to the external occipital protuberance ; this part of the line corresponding, approximately, to the lateral sinus. The cerebellum lies immediately below this line. Of the brain fissures, those of greatest importance in cerebral localization are the Rolandic and Sylvian, since by means of these all the best known cortical centres can be located. Of the two, the fissure of Rolando is much the more important, because the motor, the most definitely known cortical area, is associated with it. Its upper limit is at a point about 12 mm. (one-half inch) behind the mid-point between the glabella and the inion, and about one-half inch from the median line. It passes outward, downward, and forward, approximately, at an angle of 71° with the median sagittal line of the skull. It is 8.5 cm. (3.)^ in. ) long (Thane), and ends below just alx)ve the fissure of Sylvius. Near its lower end it turns rather suddenly downward, so that, in this part, it is not in the line of the angle of 71°. Many methods have been devised for the purpose of making the line of the fissure on the scalp. Chiene' s method con^\^\s o\ folding an ordinary square sheet of paper on the diagonal line, thus dividing an angle of 90° in half, making two of 45°. One of these angles of 45° is again halved in a similar manner, making two new angles each of 221^°. The paper is then so unfolded that one of the angles of 22 J^ " is added to that of 45°, making a new angle of 67)^° ; this will be sufficiently near that of the fissure of Rolando for all practical purposes. Horslcy's cyrtotneler consists of two strips, either of thin, flexible metal or of parchment paper, each graduated in inches. The lateral arm is placed at an angle >f 67° with the long arm, the apex of the angle being at a point 12 mm. or one-half inch behind the mid-point of the long arm. Le Fort simply drew a line from the beginning of the fissure, above, to the mid- dle of the zygoma, below, and marked off on this line the proper length of the fissure. PRACTICAL CONSIDERATIONS: THE BRAIN. I3I5 A^lerson and MacUins sugg«t :^ -^- j^j^^^^^^^^ the inion ; (2) a frontal me fro^J^^* "^^-"^'S^ ^^^ , ^^) a squamosal Une from of the ear at the level, of '^\^P^.^''l,t£;^L:^iL kvel of the superior the most external pomt of t^^ external ang^arp ^ ^^^^^ ^^^^^ Lder of the orbit to ti« J"««J-" ° ^'^f^r^bfhind ^^^^^ line. The upper ex- and prolonged for about 3-7 ^m- t'>^ w^thVm to lie between the mid-sagittal pomt tremi'ty of. the central figure w.s found ^X f -^^^i^J^^^^^^Uy of thiXure thev and a pomt i8 mm. (H «n.) '^'"IJ^,"' g _,_. (ii in ) in front of iw unction with located near the squamosal hne. about '» ?""/ ^J^/^'rtion of the Sylvian fissure « Fiamrc of Rolando Une for Rolandic fissure Interparietal fiiaurt. External parieto- occipital fisanrt ParieUl eminence Inlou Lateral lini Posterior limb of Sylvian fi^i»ure Une for Sylvian fissure Vertical Iiml> of Sylvian fissure Horizontal limli of Sylvian fissure Glabella Nasion Sen..dl.r."."-.i« view of head, showing reUtion o, Rolandic and Sylvian fissure, and Wnea. Th. /issureo/S,i.,us begins an^-ioriy «PP^x^^^^^^^^^^ in.) behind the ^al -«^i%h'J"J^eU emin^? ATtr'aight line <^tween the^ a point 1 8 mm. ( H "»• ) oeiow ine P*""f , / . ;„ ) long. The an- two points will represent the fi^"'^;,*]"^^'* *^"^^^ he main portion of the fissure terior^S mm...fi in ) «« "onT^ «X^The ^^ertLl limb ascends for about ^,t ct ^T"^^^^^^^^^ r^ariefrniit^n^^TiX convolution, and behind with the ?n^>f'-£J»^ ^„ .^^ ^^sial surface of the brain. The paHeto-ocdpUal fissurtj^ "i^LTftri^htaJeleTt^ the longitudinal fissure The external limb passes otUwards ^^"'^^^^/J "^^^ in front of the l.tmbda. on the external suHaceforaW2^5<^.andh«fr^^^^^^^^^^ ^^ ^^^ ^ . ^erior^f'j^^ll/l^TL' lt«^^^^^ sulcus passes directly backward I3l6 HUMAN ANATOMY. from the supraorbital notch, and parallel to the longitudinal fissure to within i8 nun. ( ^ in. ; of the lisaure of Rolando. The inferior frontal sulcus is represented, approximately, by the anterior end of the temporal ridge. In the parietal lobe the most important sulcus is the intraparietal. It begins near the horizontal limb of the Assure of Sylvius, and passes upward and backward about midway between the fissure of Rolando and the parietal eminence. It then turns backward, running about midway to the longitudinal fissure and the centre of the parietal eminence. Above the sulcus, in front, lies the ascending parietal convolution, just posterior to the fissure of Rolando and behind the sufterior pari- etal lobule. Below the sulcus, anteriorly, is the supramarginal convolution, and posteriorly, the angular g>Tiis. Lateral ventricle Pmterior horn of lateral vrutride (Ii Inion Lateral sinuS' Middle meninffeat artery, poaterior branch ; inferior horn of lateral ventricle wen beneath Middle meningeal artery, anterior branch SemiiliaKramnutic \-iew of head, showing position of ventricles, lateral sinus and middle meningeal arteries as projected on skull. The temporal lobe lies below the fissure of Sylvius and extends forward as far as the edge of the malar bone. The first temporal sulcus lies about one inch below and parallel with the fissure of Sylvius, and the second about i8 mm. ( Yi, in. ) lower. The occipital lobe lies posterior to the parieto-occipital fissure and the tem- poral lobe. The motor tracts are made up of the fibres passing from the motor portion of the cortex in the Rolandic region to the motor nuclei from which arise the nerves supplying the muscles which the cortical areas control. After leaving the cortex the fibres pass downward in the corona radiata, and converge to the posterior limb of the internal capsule. The motor fibres of the cortico-bulbar and cortico-spinal tracts, occupy the genu and adjacent third of the internal capsule (page 1x88), although Dejerine holds that the whole posterior limb is motor. They continue their course downward through the crura cerebri, pons, and medulla ; in the lower part of the latter the greater number cross to the opposite side and pass down in the cord as the lateral or crossed pyramidal tract. A small number, sometimes absent, pass down PRACTICAL CONSIDERATIONS : THE BRAIN. I3I7 on the same side We have already seen that lesions of the cortex produce mono- Tje^ TnkL laree enough to involve the whole motor zone, but cort.ca hemipleKia &ch mS common than cortical monoplegia. In the internal capsule the motor fiC^are SST^ether so compactly that a small lesion, as an apoplectic hcmor- S. wiKequenSyrnterrupt the whofe tract and give a hem.plegm of the opposite ''*^'' ^I't'lfe'^ilulla and cord tne tracts of both sides are so close together that a lesio^may e^Uv par^"yze toth sides (paraplegia) ; indeed, diseases of the cord fre- SentirfnvXe'he whole transverse section para yzing sensation f'^.^l'l X2«he queniiy mv j^ fo^^ the common fonn of cerebral jiaralysis ; />e^ i,,veMrf by™ hSfh of pia mater. Iraver«a (or a longer or sbotter dounn (he .nb- rtSd .race ofcral the arac^hnoid and Irom the Utler acquires an additional. bS il, Tot eJSS^e. heath. It then enter, a canal in the dura mate, that -\-tissnSi"rcb'tq'A«^^ I320 HUMAN ANATOMY, Number. Name. I. II. IIL Olfactory : Optic: Oculomotor IV. V. Trochlear : Trigeminal : VL Vlt Abducent : Facial : Certain of the cranial nerves are entirely motor ; some convey the impulses of special sense ; while others transmit impulses of both common sensation and motion. A general comparison of these relations, as now usually accepted, is afforded by the allowing summary : THE CRANIAL NERVES. Function. Special sense of smell. Special sense of sight. Motor to eye-muscles and levator pal- pebrae superioris. Motor to superior oblique muscle. Common sensation to structures of head. Motor to muscles of mastication. Motor to external rectus muscle. Motor to muscles of head (scalp and face) and neck (platysma). Probably si cretory to submaxillary and sublingual glands. Sensory (taste) to anterior two-thirds of tongue. Hearing. Equilibration. Special sense of taste. Common sensation to part of tongue and to pharynx and middle ear. Motor to some muscles of phaiynx. Common sensation to part of tongue, pharynx, oesophagus, stomach and respiratory organs. Motor (in conjunction with bulbar part of spinal accessory) to muscles of pharynx, oesophagus, stomach and intestine, and respiratory organs ; inhibitory impulses to heart. XI, Spinal Accrssorv : Spinal Part : Motor to stemo-mastoid and trapezius muscles. XIL Hypoglossal : Motor to muscles of tongue. VIII. IX. Auditory, (a) Cochlear division : (it) Vestibular division : Glosso-Pharvngeal : Pneumouastric OR Vagus: Practical Considerations. — Lesions may affect a cranial nerve within the brain or in its peripheral portion. A central lesion dinicalljr is one above the nucleus of the nerve, and may be cortical or may encroach upon its intracerebral connections. It may merely irritate the nerve or may paralyze it. By a peripheral lesion is meant one involving the nucleus or the fibres of the nerve below the nucleus. THE OLFACTORY NERVE. The olfactory nerve (n, olfactorias), the first in the series of cranial nerves, presents some confusion in consequence of the name, as formerly employed, being applied to the olfactory bulb and tract as well as to the olfactory filaments — struc- tures of widely diverse morphological values. As already pointed out (page 1151), the olfactory bulb and tract (Fig. 993), with its roots, represent, as rudimentary structures, the olfactory lobe possessed by animals in which the sense of smell is highly developed. It is evident that these structures, formerly regarded as parts of the first cranial nerve, are not morphological equivalents of simple paths of cpnduc- tion. On the other hand such paths are represented by a scries of minute filaments, the true olfactory nerv'es, that connect the perceptive elements within the nasal mucous membrane with the rudimentary olfactory lobe. The olfactory nerves proper, some twenty in number, are the axones of the peripherally situated neurones, the oZ/ador)' ce//s (page 1414), which lie within the limited olfactory area. The latter embraces in extent on the outer nasal wall less THE OLFACTORY NERVE. I23I t. • 1 ...^^» «f tJiP winerior turbinate bone and a somewhat larger field Sfth^^dra'^t up^rpa^rt ofthrn^ ^7.-. The olfactory nerves (Fig. .048). Fig. 1047. M*Hl nerve, cxt. br. Exit ext. br. mint ncrre Olfactory bulb tlfaetory iierve-6brc» n upper Knt. nawl br. leckeV> ganglion Jl'pper post, najil br». J Meckel's ganglion Naao-palatine nerve rSup. ant.naialbr. ol I Meckel's gangl. and Iinf. ant. nanal br. of ■nt. descending palatine nerve A posterior nasal br. Meckel's ganglion Ant descending palaUne nerve, the middle patoUne appearing poateriorlr Kigbtn....fo....bo,in,d.MHbut.o^o,o,^.o^«-^n«;^^^^^^ whose fibres are nonmeduUated, exhibit a plexifomi arrangement w|thin the deeper ^Hf the n^S muTous membrane, pass upward througli the cnbniorm plate of Fig. 1048. CriaU gaitt Masai ncnrt Tnt. (seput) br. of nasal nerve olfactory bulb Bat. l>r. aaial nerve, eat Maao-palatlne ncrvt Olfactory nerve-Bbrea .Sphenoidal sinu< An upper ant. nasal br. of Meckel's ganglion ■Naso-palatine nerve An upper ant. nasal br. 'of Meckel's ganglion usiachian oriSce Vomer, posterior botdet >h paUte, cut nmially Right na-l fo-a .bowing a.-r.but,on^of^UJjc.ory^^».-.^- ™^«P"' ««; »«co en.bra„e Has the ethmoid bone and enter the under suHace of the olfactory bulb. Within the alter the ner^efibrM end in tenninal arborizations in relation with the dendnt.c ^^X^^ ofTe m!t^ cells (Fig. 995). sharing in the production of the peculiar olfactory gloniemli. 1333 HUMAN ANATOMY. Central and Conical Connections. — The impulses conveyed by the olfactory nerves and received by the mitral cells of the olfactory bulb, which cells may be regarded as constituting the end-station or receptioH-nucleus of the peripheral path, are carried to neurones situated either within the gray matter of the olfactory tract, the anterior perforated space or the adjacent part of the septum lucidum (Fig. 1049). Fibres connecting the olfactory centres of the two sides pro- ceed from the cortex of the tract by way of the anterior commissure, forming tticpars olfactoria of the latter, to end in relation with the cells within the opposite tract or bulb. From the.se primary centres the impulses are transmitted by different paths to the secondary or cortical cntres situated in the anterior part of the hippocampal convolution in the vicinity of its uncus, including the hippocampus major and the nucleus amygdalx. I. The most direct path Ls by way of the lateral root of the olfactory tract (page 11 53), by which fibres from cells within the trigonum olfactorium pass, skirting the Sylvian fissure, to the anterior part of the gyrus hippocampi to terminate in relation with the cortical cells of that -onvolution. Fin. 1049. Diagram showing most imporunt connections of olfactory tracts ; LC lamina cribrosa ; H, olfactory bulbs : TV, olfactory tract : Tg. olfactory trigone ; Ls, Ms, lateral and mesial striK ; ^.anterior commissure : CC, corpus calk>- sum; SL, septum lucidum: F.r, anterior pillar of fornix; M, mammillary body; m-l. maniminn.thalamic tract; ^A anterior perforated space; ri^w.'taeniasemicircularis; r, thalamus; A'w, fimbria descending on hippocampus; V, uncus ; AN, amygdaloid nucleus ; TL, temporal lobe. 2. Fibres from the ct\U within the olfactory trigone (page 1153) and the anterior perfo- rated space (page 1 153) pass into the septum lucidum and, reinforced by others from cells of the septum, enter the fornix ; thenc* continuing backward and downward by way of the fimbria they reach the hippocampus major. 3. Fibres from "-ells within the olfactory trigone turn inward and by way of the medial root of the olfactory tract gain the gyrus subcallosus ; thence they pass plong the upper suriace of the corpus callosum within Its longitudinal strix and descend by way of the de'itate gyrus to reach the anterior end of the hippocampus major. 4. Fibres from colls within the anterior perforated space and septum lucidum, joined by accessions from the opposite olfactory tract by way of the anterior commissure, converge to the txnia semicircularis (page 1 162) and, passing along the floor of the lateral ventricle, descend within the roof of the descending horn to end in the amygdaloid nucleus (Dejerine). During their ascent from the anterior perforated space, some fibres diverge almost at right angles and pass backward directly to the optic thalamus. The coimectioiis between the cortical centres of olfaction and the optic thalamus, as well as those lietween the olfactory centres of the two sides, by \— 'y of the fornix, are described on page 1 167. Practical Considerations. — Lesions of the uncinate ^rus may cause loss of the sense of smtH on one t"»r both sides. Paralysis of the olfactory nert't with loss of smell may also occur in fractures of the base of the skull in the anterior fossa, involving the cribriform plate. THE OPTIC NERVE. 1323 THE OPTIC NERVE. ,„ addition to the fibres of -«-' -^l^i^^.^'^es^KTe 'oTl^Sir^y^cC- nerve contains a ~nsiderable num^r i-Pi;^-^''',:,^'? J'^lt^^^ ^s toward the cemed in sight. Some of these P»'^vf ?,""£^ f ^..^ primary visual centres or from sympa- retina, originating w«hm the bmm from t^^^^^^ ^,^ retinal blood- thetic neurones, and Pf°»f ^> ^^*'^,JoX way of a centre situated within the medulla. ^^^tm^rS'irrrfg^deT^^c^^^^^^^^ to the oculomotor nucleus the impulses resulting in reflex pupillary movements. The oDtic nerve (Fie. 1198) extends from the eyeball, which it leaves about muscles, it traverses the opt.c foramen m he ^s^^^^^^^^ .^^^^^^ ophthalmic.artet ■[^:^^^Z^:^r^':^:r:i.y.. opposite^i^e 'with which it or part of the optic commissure m the vic.nity of the olivary .he internal carotid artery. The entire length of the optic nerve d whkh the intraorbital part includes from 2(^30 mm. thus -^ (-« -stt" Tr °s:\r^^; rne:tu?::i^st£ central artery of the retina, which, ^""^ '^^ .^?^P''"^"" ^^^a h from the pia mater lEXnSs ^d tz:;f&^^^^^^^^ - — - - - ^- '^^^'h *o'o"?c'clCSut^^^^^^ by the meeting of the converging beneath the floor of the third ventricle m ^^ f "^^.jJ^'l'oSSrTy into the two optic tion with the inferior surface of the brain . « ^^^ 'f f ; H^'^Ses called, the optic tracts. On reaching the ^'^'^l^JJ^f '^[nf^^'s'^iLV) un^«go partial d;:ussation, fibres, estimated at upwards of ha fa ^^/^j^f ^^;i,"ng to the mesial part of the those from the nasal o": '""f.^ ^^^^^^^^ te™Ur o^ter half continue into the opposite optic tract, while those from tli« ^^""P"™ . commissural loop con- lat^l part of the tract of the same side^ I.'^TJS TlthoughToLerly accented. nectingThe two optic nerves ^as m>t been ^tabl^hed, aUhmigh . ^^.^7^, ^^^ Occasional instance have ^^f^^f^^;^ J J„^^^^^^ that normally obtains optic fibres was ^^PP'^'^' *^^^^^^^^ few rodents (mouse, guinea-pig). Lfi;r o^^tmnSSrE ^:l^n., the optic fibres passing directly into the tract of the same side. of the cranii"- joins to fon eminence, n. is from 30-4 allowing for 1324 HUMAN ANATOMY. The entire commissure, however, is not composed of optic fibres, since its posterior part is formed bya bundle, known as Qudden's commiasurc (commltMira inferior) (page mo), which passes forward along the mesial side of the optic tract, loops around the posterior angle of the commissure and enters the opposite tract These fibres have no connection with the path of sight-impulses, but are probably chiefly related with the median or internal geniculate bodies and the inferior corpora quadrigemina ([>age iiio). The optic commissure also contains fibre-strands that arch around its posterior angle, par- allel with, but separated by a thin layer of gray matter from Gudden's tract. Concerning the origin and destination of these fibres, termed Meynert's commiasurc (comiiiiaaura anperior), little b known. By some they are regarded as continuations of the mesial fillet that, after decussa- FiG. lo.so. Diacram thowinv coune of nllnal fibre* fn optic palliwav and their connection with basal Kanglia and primary cortical centres ; •maUer llRure illuMralca path of llcht-ray and multina impulte through retina : K. retina : ON. OC. OT^ OR, optic ner\'e. chiaitm, tract and radiation, f.pulvlnar; Eg, SQ, lateral geniculate and superior quadrlgem- inal bodies ; Oc Cx, occlpiul conea ; ///, ly, yi, nuclei of cye-muaci* nerves. tion, pass to the globus pallidus of the lenticular nucleus of the opposite side. Others deny such relations, while Kolliker describes them as bending upward, traversing the ventral part of the cerebral peduncle, to end within the corpus subthalamicum (page 1128). Additional commissural fibres (commlaaura aaaata) descend from the floor of the third ventricle and from the [K-duncle of the septum lucidum, by way of the lamina terminalis, to the front and upper part of the optic chiasm ; other fibres pass from the ventricular floor to the back of the chiasm. For the most part these fibres cross to the opposite side to be lost in the sub- stance of the optic commissure. Although regarded as in a way constituting a ventral optic root, their connections and significance are not understood. The optic tract (Fig. 993) is the continuation of the optic nerve, its chief constit. Its being the crossed and uncrossed retinal and the supplementar}' fibres. On leaving the commissure, the tract diverges in front of the interpeduncular space, mesial to the anterior perforated space and the termination of the internal carotid artery, and sweeps outward and backward from the base of the brain around and close to the corebral peduncle, becoming flatter and broader as it proceeds. Near THE OCULOMOTOR NERVE. 1225 ™.»-^«r ^nA thf tract exhibits a furrow that indicates a subdivision into a mesia/ .tspostenor end the trart exniDiBaiu ^^ ^^^ ^^^ ,^ . A'n^i^.i Connt-ion* — Arising as axones of the retinal neurones, the optic *^*^ :^'^^^^^^^xLuTrh^comn^i.sur^ and tract and end in relation with nerve-fibres are contmuedbackwaratnrougnine , ; ,^ ,^,^^81 geniculate and the the neurones of the pnmanr ^^^^^^'^ ^mthX^r^ s^mcu\Me b^y ih^^ superior quadngemnal body ^ I >s.h^^ ™ ^.i^„,, fi^r^ terminate, relatively few pass- number 80 per cent, accordrng to "™^^?*' 7 ', t^^ , cpiUer) The cortical conntctioni are ing to the pulvinar «"<>jh? ^"P!"°r^"^tS Jt^K^c^^^^^ »'* the optic radia- rreTp;yd^>^r«e|r^9'£^ geniculate and quadngem.^^^^ , .p,^io„, of sight are vety St^r/ndT; Jchlnr^uc^'mpr^^^^ being capable of affecting numerous motor and -■^^hfe^^pathbywhichpupina^impulsesreadU perhaps »--'«{^ " ^o^l^U^ fi^r^e't^uSy ^^^^^^^^ o'f^? '^^!.\-^^'' quadngeminal body, ^^P)^,,^^;^,"^^^^'"^^ Neurones the immediate connecting hnks pro- but end withm the supenorcoUiculus, from wntw«neuro existence of a more ceed to the oculomotor «»^^^^^''^S^^^Zt^P'^Z,^M;.,\usuchc<^ih^ rir l^^tTeri/rS^^^nflp^f ^^^^^^ pass .- the medullary centre ^ward by way of the posterior longitudinal fasaculus (Bach). Practical Con.ideration..-The cranial nerves of the o" w"l ^ discussed in connection with that organ. THE OCULOMOTOR NERVE. doS surface of the posterior longitudinal fasciculus (F.g. 963). The nucleus is from ^ mm. in lengOj^nd extends 'r°"^P»-^-rcorTaririm^ caudal pole of the supenor ;i"»^nKem.na^tod.es. ^"^^.^jP^^^ ^ , „,„„^ ,,.er^•al. In contact with the nucleus of the '"""''."^.'^'J'"' 'f,^^"„f „„„ or less distinct cell-groups, its entirety the oculomotor "%'•="^ '"5.'"^f„i^J^S^,^' omirnce « « hich vary in importance as well as in the.r '"f 'y.''"^' P~'"'"!"7hat exten one on each side, tant and instant are two long ^JT "^f ."L^^'i^i^nS^^^ Each nucleus tapers slightly along the dorsal surface of the P<^'f"°' '??f '"°;^"'t which, from their relative towards either end and consists of two '''j'y ^'')y"^^^„*"'^^;e°„„ent nerve-cells include positions, are termed the ''ors^r.Mt :MreU-^roup^^^^^^ .^ ^.,^^^_ UK.se of large, medium and small size, »»'''. ^/K^.-T^^X^";' the third nerve arise. Dislo- :L^:^''™Xt'S«i:lrctus'r rr^^^^^^ "--ceUs .hat lie scattered rong -Te^ beneath the fibres °' ^^^^^ P^lj'^l^-S "t^l^^^^^^^^ surface is .he ta.^r- Dorsal to the chief nucleus and P'^t'^'y^^^^wS^ nucleus. This tract, much i„g column of sm..nnefvertion of the outer wall of the cavernous sinus and leaves the cranium by entering the orbit through the sphenoidal fissure. On gaining the median end of the fissure the ner\'e divides into a superior and an inferior branch, which enter the orbit by passing between the two heads of the external rectus muscle, in company with, but separated by, the nasal branch of tbo trigeminal nerve, the sixth nerve lying below. Branches and Distribution. — ^The superior branch (ramus saperlor) (Fig. 1051), the smaller of the two, passes upward, over the optic nerve, to the superior rectus muscle, which, together with the levator palpebrx superioris, it supplies. In both cases the nerve enters the ocular surface of the muscle. The inferior branch (ramns inferior) (Fig. 1051) is directed forward and, after giving of! twigs to the ocular surface dt the internal and inferior recti, is continued below the eyeball, between the inferior and external straight muscles, to supply the inferior oblique, whose posterior border it enters. This, the longest branch of the oculomotor nerve, in addition to sending one or two fine twigs to the inferior rectus, contributes a short thick ganglionic branch (Fig. 1051), which joins the postero-inferior part of the ciliary ganglion (page 1336) as its short or motor root and conveys fibres destined for the sphincter pupilke and ciliary muscles. Sensory fibres from the ophthalmic division of the fifth nerve are distributed to the muscles along with the fibres of the third, having joined the latter before it entered the orbit. Similarly in the wall of the cavernous sinus, the nerve is joined by sympathetic fibres from the cavernous plexus on the internal carotid artery. Vmriationa.— These consiist, for the most part, of unusual branches which at times seeminely replace one of the other motor orbital nerves. Thus, the third nerve may give a branch to the external rectusj either in addition to, or to the exclusion of the sixth, which may be absent ; or it may give a filament to the superior oblique. Minor deviations in the course of its branches, such as piercing the inferior rectus or the ciliary ganglion, have also been recorded. THE TROCHLEAR NERVE. The fourth or trochlear nerve (n. trochlearis), also called the pathetic, is the smallest of the cranial series and supplies the supierior oblique muscle of the eyeball. The deep origin of the nerve is from the trochlear nucleus, a small oval collection of cells situated in the ventral part of the gray matter surrounding the Sylvian aque- duct, that extends from oppiosite the upper part of the inferior quadrigeminal body to the lower pole of the superior collicuius. This nucleus, about 2 mm. in length, lies near the mid-line and immediately below (caudal to) that of the third nerve, from which, however, it is distinct, being separated by a narrow interval from the ventral part of the oculomotor nucleus. It lies in intimate relation with the pos- terior longitudinal fasciculus in a distinct depression on the dorsal surface of that bundle (Fig. 960). In structure the trochlear nucleus resembles that of the oculo- motor, its nerve-cells including those of large, medium and small size. Arising from the nucleus, the root-fibres of the fourth nerve pursue a course uf considerable length within the mid-brain before gaining their superficial origin. THE TROCHLEAR NERVE. 1329 Leaving the upper and lateral part of the nucleus as axones of the t;;«^hlear "euron^ ,>^,trands of ftbres pass outward and backward within the gray matter of the floor cerebellar peduncle. ^_- 1 -M e«.«.l Connections—The trochlear nucleus is directly connected with the Fio. iQSJ. OrWWmlc ill«. V. MX* MailUuy dtr. V. acrr* Hwdlbutor div. V. Mrr* C»iilcutat««M«llo«"'VII. •€•»•(•[«« of !«•• TM,cirt C«ll<«> Side. By means of the posterior longitudinal bundle it is ^">l^''^'°^l'!^°^^^^^': ?„"£" superior olive and its peduncle. Course and Distribution— Emerging at its superficial origin, the nerve is directed "mard over the superior cerebellar peduncle, then winds forward around Jhe^^er sSce Tthe cerebral peduncle, parallel to and between the posteno, Sebral and superior cerebellar arteries, and appears at the base of the brain (F.g^ cereDrai »"« P ^ ^ ^^ ^^e floor of the cranium, the nerve entere the dura 123° HUMAN ANATOMY. the external rectus muscle and, directed medially, crosses above the levator palpebrse superioris and superior rectus and reaches the superior oblique, which it enters on the upper surface close to the external border (Fig. 1056). The communications of the trochlear nerve, as it courses in the wall of the cavernous sinus are : (i) filaments from the carotid sympathetic plexus; (2) fibres of common sensation from the ophthalmic division of the fifth. Variations The course of the trochlear nerve Ls sometimes throug;h instead of over the levator palpebrae superioris. Unusual branches to sensory nerves, as the frontal, supratroch- lear, the iirfratrochlear and the nasal, are probably due to the aberrant course of sensory fibres from the trifacial. Tlie fourth nerve occasionally sends a branch to the orbicularis palpebrarum. THE TRIGEMINAL NERVE. The fifth, trigeminal or trifacial nerve (n. trigeminus), the largest of the cranial series, is a mixed nerve and consists of a large sensory part (portio major) and a much smaller motor portion (portio minor). The former supplies fibres of common sensation to the front part of the head, the face, a portion of the external ear, the eye, the nose, the palate, the naso-pharynx in part, the tonsil, the mouth and the tongue. The motor portion is distributed to the muscles of mastication, the mylo- hyoid and the anterior belly of the digastric. The relation of the fibres composing these two parts to the cells within the brain-stem is, therefore, very different, in the case of the motor fibres the ceUs being a nucleus of origin and in that of the sensory fibres one of reception. The Sensory Part. — ^The fibres comprising the sensory part of the trigeminal nerve, which convey sensory impulses from the various head-structures, are the pro- cesses of cells lying outside the central axis in the Gasserian ganglion on the sensory root The portions of the fibres between the periphery and the ganglion correspond to elongatecf dendrites, while the much shorter centrally directed constituents of the sensory root, connecting the ganglion with the brain-stem, are the axones of the Gasserian neurones. The general resemblance between the fifth cranial nerve and a typical spinal nerve is strikmg, in each case the sensorv root bearing a ganglion and the motor root proceeding from cells within the central nervous axis. Proceeding brainward as axones of the Gasserii cells, the sensory fibres of the trigeminal nerve become consolidated into the la-^c sensory root, which passes through an opening in the dura mater (Fig. 1033) situated beneath the attachment of the tentorium cerebelli to the posterior clinoid process. Coursing backward through the posterior fossa of the cranium it enters the brain-stem on the lateral sur- face of the pons, slightly behind the superior border, as the conspicuous group of robust bundles that mark the superficial origin of the nerve (Fig. 1046). Just above it is the superficial origin of the motor root, from which it is separated by a small bundle of pontine fibres which belong; to the middle cerebellar peduncle. Below and in line with it are the superficial origins of the facial and auditory nerves. Entering the tegmental portion of the pons, close to the overlying superior cerebellar peduncle, the sensory fibres soon come into relation with the extensive triceminal reception- nueleua, a columnar mass of gray matter within the lateral part of the tegmentum (Fig. 935). This nucleus extends from the middle of the pons through the entire length of the medulla and into the spinal cord as far down as the level of the second cervical segment, where it becomes continuous with the substantia gelatinosa of the cord. The rounded and enlarged upper end of this tapering column is described as the seneory nucleus of the fifth nerve, althougli it com- prises only a small part of the reception-nucleus. The latter, in turn, is the upward prolongation of the subttantia geUtinosa Rolandi, conspicuous in all cross-sections of the lower pons and medulla as an oval field of gray matter (Fig. 930I. On nearing this column the sensory fibres divide into ascending and descending branches, much in the same way as the posterior root-fibres bifurcate within the posterior columns of the cord. The ascending fibres, distinctly finer than the descending, soon penetrate the sensory nucleus and the substantia gelatinosa and end in arborizations around the neurones of the reception nucleus. The coarser descending fibres become collected into a compact bundle, the descending or spinal root (tractas spiaalii a. triiemlnl), whose medially directed concavity closely embraces the lateral surface of the column of gray substance. Beginning with its descent, the THE TRIGEMINAL NERVE. laji _ „ , ^ .^ fih,-, oi«t bend mediaJly. enter the adjacent substentU gel- .pinal root jdves oB collmtermb «»^.°^'* ™1^^^^ that nucleus. Since the number of Sa and etHl in '"^^f'^J^J^ J^«^?o< AeVpinal root, the tract is Upering. fibre, is thus Pr<>S«»»'^«='y ,'«i'«^,^^,SS»> ^ »"«» *>*'" '^ "P**' ^'{."^ '"! becoming smaller and smaller as it »fP™™ JJ*''^; fii,,,v disappears. In its descent through latter, at about the level f »^';^°^^X ^"'^ e ,^X^^'^«-«. '" *e lower part o. the brainstem the spinal •'^^ ^,?T,*l^'So(H;ieparated from it by the vestibular divusion the pons lying to the '"ner srfe of ^f;^",^*^ ^7he medalla. occupying a position close rf the auditory nerve, and lower « *^«latK substance oJ the tuberculum Rolandi. to the surface as it resU upon *« «^~~ ^"^he trigeminus ( Fig. 1054). by way either o Thec«tralcofm«ettoM«»fth«a«i«>nrP~tottneing^.n^ ^^^^ ^, thecollateraU of the fibres of ttesinnjarootor^^^^^^ ^^,„^^ ^^ ,,i, the reception neutows, »« ^"^^"l^lL^'^'^^Snt p^^^ for sSch distributions are : ""•"rB^rnTth:? ?L*^ate S^":ir'tKls^ the recepUon-nudeus ..ross the raphe to jom the opposite mesial fillet p^^. ,^j^ and ascend to the optic thalamus and thence, after interruption in the cells oi the latter, by axones of thalamic neu- rones to the c-i.bral cortex. It « prob- able that so: f of the arcuate fibres do not cross the mid-line, but ascend within the mesial fillet of the same side. It is also probable that collaterals of the arcuate fibres pass to the trigeminal, facial and glosso-pharyngeo-vagal motor i. By axones from the cells of the reception nucleus that enter the infe- rior cerebellar peduncle of the same side and pass to the cerebellar cortex as con- stituents of the Muc/eo-tereMiar tract. 3. By collaterals that are distrib- uted to the nuclei of origin of the hypo- Klossal and of the motor part of die trv- geminus and facial nerves, whereby these 'mportant motor nen,es are brought directly under the influence of the sensory part of the fifth. The Motor Part.— In con- trast to the median position of the nuclei of origin of the oculomotor, trochlear, abducent and hypc^lM- sal nerves, the deep origin of the ""*-r" """-.■••Rc-r-u.ertan Rangiioii wun aiv..™.. >-. some dMtance from the raphe and fall into series with the laterally arlrmlxli'c^aTi^i^^^rfh^ facial, the g.osso-pharyngeal and the vagus. within 6ram-«ein; '''^'\'^;^''^%/i, smsory and mcHor //, ///) of seniory p«rt of •"^« i,r,,n,t; gelatinoU ; Sp.K. spi- 5S.mi.11'nSSSJ. : ca. citico-bulbT fibre.. ,. The largest contingent of the motor fi;'--l;|!:.Sf (T^^t ThTn^clercon! «,urones within the chief motor nucleus (m«.« ~«;»„"^ll^fi„rwhich lies in the upper si-a. of a short columnar collect|on of ^fV '"""f^^^^ °"„^eus. It is composed of large stel- part of the pons, close to the medmn »''»;^^^"^^"^'l^ outward through the teginentum Erii'-sur^stSn^thT^s.^'^^^^ rt^irs-^trfrurv::^^ i^=f become incorporated in the "I^^^l'^^/;;^; 'ZZ r^t, the descending me.enc.ph.Uc root 2. A second and smaller ^o^*"'"'"* "'''I? !? "'^^ from cells lying within the lateral part (,«IU d.K.nd.n. -. trig.n.ini '"^'"'•'iK.^f aauldu^ In cr^sections (Fig. 936) this root i ^LTs^'-d^^rcr^nll^bu^^^^^^ the mid-brain to join the larger tract 1 33a HUMAN ANATO^'Y of fibres from the chid motor nucteus. In its downwfl I ourse th- nK-«encephalic root b joined by numerous fibres which h«ve their origin in the • j'liented <.-el s of th'j subst- ntia ierru- ginea (page 1081) of the same and, possibly, of the oppo- itu :iidc The fibres from these various sources — the mese "ephalir .1 cleus, the substan- tia ferruginea and the motor nucleus — become consoi.dated into tht motor root of the trigeminal nerve, whose superficial origin (Fi^ 1046; is jint iKne that of the sensory root, from which it is separated by some oi the superficial uansversc- fibres of the pons. Leaving the side of the pons, the motor root follows the sairsf course to and through the dura mater as does the sensory, 10 the inner side of which it lies. It eventually passes beneath the Gasserian ganglion to become ex tisivdy an integral portion of the mandibular division of the trigeminal. The cortical connection! of the motor root are established by fibres that arise from cells within the cortical i^ay matter of the lower third of the precentral convolution. Thence, as constituents ortion of the mandib- ular nerve, while its narrow- concave posterior margin is con- tinued into the sensory root of the fifth nerve. The ganglion lies in Meckel' s space (cavern Meckelii), a cleft produced by a delamination nf the dura mater anil >mes in relation internally witli iie cavernous sinu- and the internal carotid artery. Be- neath, but unconnected with ii. are the motor root of the trifacial and the great superficial fietrosal nerve. I -triK- ture it resembles a spinal ganglion, being composed of the ■ laracteristically mo»tifi«.rd neurones, from whose single processes proceed the peripherally directed denontes and the centrally coursing axones. In addition to the three large trunks given off from the anterior margin, tc branches of the Gasserian ganglion include some fine meningeal filamer.'.x which arise from the posterior end of the ganglion and are distributed to the a>i.^ cent dura mater. GuKrian ganglion of left side viewed from above; seniory motor roots and ttirec divisions of trigeminal ncr\-e are seen. Communications. — At its inner side the t'lasserian ganglion receivo iiiaments from the adjacent carotid plexus of the sympathetic, which end in relation with the cells of the ganglion. Divisions of the Trigeminal Nerve. — These arc three in muiljer, the oph- ihaimic, the maxillary and the mandibular nerves. They arise from the anterior THE TRIGEMINAI NFRVK "33 ^. «l the (ia«erian ffanfriion, tl o tormatior of the mandibular ,erx-e being com- eyelid, the conjunctiva, t»»e eyenau i y » ^ anten.-r por- Branches ana u» nouasni laehntii^l (x) i\\k fronla and r.^ the recurrent, (2) &'- communualmg, (3) thi /of/ir)'"' '• ^'^> J (J) IS I^*?^ whi4 t e last thr, e a- tenn.n •! branches Fig. lojf SttpiBtochlcur neni N«M>1 lltrrvt- lUctorj- Imlti* nhliiai** ^nwMCle r, twrr^e CM' V <" I""* ptJcc' iaam ■nal rarotid ry — -, Oyyv- ; raci ' VI uerve- III. nenra >»pr«orWul n»T\e .Lachrymal gtaml Lmtor palpebru iperiori* luprrior rectus Frontal nerve External recto* Lachrymal nerve Ophthalmic division of V. ner Maxillary division of \' nerv Mandibular divtaioii i-«- Gaiaerian ganglion Mcatu* auditorius interii- VH. nerve, motor part Para intermedia •VIII. nerve - ■--^.„'?rj^hii3.=,S!i:vlsl:M^^^^^^ ' Gataerian th. its \ ,e recurrent branch (n. tentorii) arises shortly after ^^e nerve leav^the U p^ across and is adherent to the trochlear nerve and is distributed H:'c\Cmt;i?cVS;tr«ch:i^ire three slender fi.a.en-hic^^^^^ e the nerve breaks up into its terminal branches ; ^-^yj"*" '^l^^'^'^r^rinK .riS and sixth ner^-es': to whose muscles thcys"I|P>y ^^.^' ^ ^^^^, Its 1 «e through the cavernous sinus, the ophthalmic n^rrve r«: Warn. .Its from the cavernous sympathetic plexus. «ji«t of tiie i. The lachrymal nerve (n. lacrimalis) (Fig 10 J" J»^ ^ ^^^ terminal branches. It lies to the outer side ^^^l.^,; :„^"^Xa ^ It passes outer angle of the sphenoidal fissure in its own »h'^ °*^ ^SZl^ tlw ..rhit. above the origin of the orbital muscles and courses »7;^^1^ T ^ ^ "ces the above the external rectus, to the upper outer angle <» tbe ^, ^^^llT^'^if ,,„„. S^bSl fascia near the external canthus to tenmn^ ''^^^gTex^ canthl Eum the lachrymal gland, the upper eyelid and the ston .if«t»Kl tne extendi 1*34 HUMAN ANATOMY. Within the orbit the lachrymal nerve communicate* with the temporal branch of the temporo-malar nerve and on the face with the temporal branch of the facial. The latter is one of the numerous sensory-motor communicaUons between the terminal fibres of the fifth and seventh nerves. V«ri«tkm».— Occasionolly the lachrymal nerve seems to be partly derived from the troch- lear : the true source of such fibres, however, is probably the ophthalmic nerve, by waX °* "* communicating branch to the fourth Considerable variation is found in <»™||«ct«on with the temporal branch of the temporo-malar nerve. The techrymal nerve or the tempora^ branch of the temporo-malar may be absent, the place of either being taken by the other, or the 'achryma may be small at its origin and later increased to normal sue by accessions from the temporal branch of tlie temporo-malar. 4. The frontal nerve (n. fronUlis) (Fig. 1053) is the largest branch of the ophthalmic. It enters the orbit, invested by its own dural sheath, through the sphenoidal fissure and above the orbital muscles and passes directly forward between the periosteum and the levator palpebra superioris. At a variable point, usually about the middle of the orbit, it divides into its terminal branches, the (a) stipra- trochUar and (*) the supraorbita/. a. The ■upratTochlear nerv* (o. MpratfKhlcarii) is the smaller of the two terminal branches. It passes inward and forward over the pulley of the superior oblique and thence between the orbicularis palpebrarum and the frontal bone, leaving the orbit at its upper inner angle Near the pulley it gives off a branch which joins the infratrochlear (Fig. 1057) and at the edge of the orbit supplies filamente (nn. palpcbralts Miperiore*) to the skin and conjunctiva of the upper eyelid. It then turns upward and subdivides into a number of small branches which pierce the substance of the fronUlis and orbicularis palpebrarum muscles to supply the inner and lower part of the forehead. . j. , .. , b. The auprwirbital n«ve (n. Mprawbiulii) (Fig. 1056) continues directly the course of the fronUl nerve. It lies close to the periosteum throughout i» entire orbital course and leaves the orbit through the supraorbital notch or foramen. In this situation it sends a small filament to the frontal sinus to supply its diploe and mucous membrane. As it leaves the orbit it sup- plies some fine twigs to the upper eyelid and then divides into a larger outer and smaller inner branch. These pass upward on the forehead beneath the frontalis muscle, occasionally occupy- ing quite deep grooves in the frontal bone, and terminate by being distributed to the scalp and pericranium. The outer branch extends back neariy to the occipital bone, while the inner passes only a short distance posterior to the coronal suture. Both branches of the fronUl, the supratrochlear and the supraorbital, communicate with branches of the facial nerve and thereby supply sensory filaments to muscles supplied by the seventh. Variations.— The nerve may divide before leaving the orbit and in that event only the outer branch passes through the normal osseous channel. The inner sometimes has a special groove, named by Henle ihefroHtal nolek. 5. The naaal nerve (n. nasocillaris) (Fig. 1057) is intermediate in size between the lachrymal and the frontal. It enters the orbit, clothed in dura mater, through the sf)henoidal fissure, between the heads of the external rectus and between the superior and inferior divisions of the oculomotor nerve. Turning obliquely in- ward, it crosses the optic nerve and passes beneath the superior oblique and superior rectus muscles and above the internal rectus. Thence it traverses the anterior eth- moidal foramen to enter the cranial cavity, where it passes forward in a groove in the lateral part of the cribriform plate of the ethmoid bone. Leaving the cranium through the nasal fissure, the nerve enters the nasal fossa, where it breaks up into its three terminal branches. Branchee.— These are : (a) the ganj^Honic, (o) the /ongr cilia/y, (r) the tn/ra- trochlear, (d) the internal nasal. (<•) the external nasal and (/) the anterior nasal, of which the last three are terminal branches. a. The ganglionic brunch (radix loaga) (Fig. 1057) usually leaves the nerve between the heads of the external rectus and passes forward aUing the outer side of the optic nerve to enter the upper posterior portion of the ciliary ganglion, of which it forms the sensory or long root. *. The /(W»e- HOary hranrhes (bb. dllares loa«l) { Fir, 1058) are two in number. They pass forward along the inner Side of the optic nerve and, after joining one or more of the short ciliary nerves, pierce the sclerotic coat of the eye to be distributed to the iris, ciliary muscle and cornea. THE TRIGEMINAL NERVE "35 orbital wall and beneath tf.e ?"P^™' °^''^^;L"i^£ U re^ivw a 'filament (the supratrochlear , rrt.aZ'^ J::e%" 'TZ^^ t^e1i;in offilJeT?yeUd and root o. the nose, as we., .s »"^T"T^?;wt;«fori-"^^^^^^^^^ ^^'^- .048) supplies themucousmenw brane »!«;« -^ S^fi" W.M^^^^^^^ (Fig. ,047) supplies the front part of the middle and inferior turbinate bones and outer waU of the n^^*^^ downward in « groove in U.e ^d^tiTKe ri ^•'^^hrt^ltwr the l^er end of the na.. bone and the Fig. 1057. gopnior oblique miiKl latemal rectus muncl itUfBtrochlear l>r. of n«»al Nasal nei Olfactory bul Levator palpebrse «uper|-, oria, inverted III. nerve, auperior divinon FronUl nerv Optic nerve Internal carotid artery- — III. nerv' Pdoi. dUplaced backward- Cerebial peduncle _^Le»ator palpetwie Mipefloito iperior rectu* ichr>mal gland erve to inferior obllqat ;xtemal rectus muacte -Ciliary ganglion 'Nasal nerve Lacbrymal nerve Maxillary division of v. ihthalmic division of V 'Mandibular division of V :rian ganglion .VI. nerve 'IV. nerve VII. nerve VIII. nerva >,^' Deep., dissection ofHght orbit. vi.«d.romabove;b™.cb.so.na..l nan-. -K«n. nenre sent^bres tothe third and sixth n^"^^^*,. .'",*„ ,u!^,uoratrochlear. Branches to the "nfmtr^h ear branch, the ^^ficiency ^mg su|jp ed I y thejupr^^^^^^^ rental and ethmoidal sinuses ?';f,d^r\'^„^*,^.^';^rS^^^^^ posterior ethmodal foramen to men. and a branch has ^t*" '"'"d «h^h jms^^^^^^ K I_^k^ ^^^ ^„ ^^^^ by Luschka The 0.ngli. ...eclated wlththeTri^^^^^^^^^^ t»3fi HUMAN ANATOMY. with the ophthalmic nerve, the spheno-palatine with the maxillary and the otic and submaxillary with the mandibular. Each is the recipient of three rools — a motor, a sensory and a sympathetic — and from each ganglion branches are given of! to more or less contiguous structures. . The significance of these bodies — whether of the nature of spinal or sympathetic ganglia— has long been a subject of discussion. The close resemblance of their nerve-cells to the stellate neurones of undoubted sympathetic ganglia, as shown by the investigations of ReUius, KoUiker and others, as well as the results of experimental studies (Apolant), justifies the conclusion that these ganglia are properly regarded as belonging to the sympathetic group. They are, therefore, probably stations in which certain motor and secretory fibres conbibuted by various nerves end in arborizations around sympathetic neurones, from which axones pass for the immedi- ate supplv of involuntory muscle and glandular tissue. The fact that these small ganglia are derivations of the early Gasserian ganglion is in accord with the mode of origin of the sympathetic ganglia elsewhere (page 1013). lamoal carotid iV. Her** Cvabcal peduncl^ Levfttoff (MlpchrsB sujicTiorls Supetlnr obllqiie niincle LachrynMl ^UmK SupcTtot rectus -nuicle .Long cHUry bnmdic* irf nasit aerv« Eit. rectus. Intertluii iBfrrior obllqtM muacle MM<«« inshellar p«iluiKle Caaaerun tfannnaa Eat. rectuf muicla VI. I t^angltunic Itianih of naul Short ciliary ■ - . .htolnf. obtlqua Infcrfor mrtut niuKlc DIucctlon of rt|[ht orbit alter removal of Its lateral wall; external aixl anperior cye-mutclea have been cut and diaplaced to txpoK ciliary ganglionand nervca. The Ciliary Ganglion. — The ciliary, ophthalmic or lenticulat ganglion (k. citiare) (Fig. 1058), as it is varyingly called, is a small reddish mass, about 3 mm. long in the antero-posterior direction, and approximately quadrilateral in out- line. It is compressed laterally and to each angle is attached one or more bundles of nerve-fibres. It lies near the apex of the orbit on the outer side of the optic nerve, between the latter and the external rectus muscle and anterior to the ophthalmic artery. The nerve-cells within the ganglion are chiefly multipolar elements, which closely resemble sympathetic neurones (Retzius) and send their axones towards the eye by way of the short ciliary nerves. Roots. — All of these enter the posterior margin of the ganglion. The motor or short root (radix brevls), the thickest of the roots and sometimes double, is an off- shoot from the branch of the oculomotor nerve which supplies the inferior oblique muscle. It is short and comf>arativcly robust and joins the postero-inferior portion of the ganglion. The sensory or lonff root (radix loni{a) arises from the nasal branch of the ophthalmic, leaving the latter between the heads of the external rectus. It is long and slender and passes forward to enter the upper posterior angle of the gang- lion, occasionally being fused with the sympathetic root. The sympathetic root (radix THE TRIGEMINAL NERVE t237 — ^..^ 5, a tinv filament which arises from the cavernous plexus and rims forward to rochms Ite ^^ ''^,'^,,!°'fLl J^SkTS. lo™™l abo«. and Wo. Ih. optic nerve. The lower set is uie '"""= ... { tg const luent branches cervical gangliated cord and (*) ^^^ "^'^f ?* "f-7?"Si^er muscle of the iris, which, while Fibres suppl>-ing the chary 7"^'^!^ J;'^"^ "L™'*^^ the axones oJ the stellate in a sense the cominuat.on.s »/ *»«=.^'°"'"X^ (1; jS^al fitaes which transmit sensory f^XtrhTiSenro/^Ll^K if ^ni^^^^^^^ the Ion, ciliary nerves. V.ri.tion..-The motor root °«-'«5-"y {"^^ fo^a 'c^mm^^^ f^nfofeTtran^ noted above, the sensory and sympathetic roots frequently !?.TJL"hlv to the scattering of its lachrymal, from the abducent and from the sP^^^J^lfblfihe lone ciliary nerves convey- 'i^tTi^l^n noted, the defiden^P^^Wyl^^^^ ^^^^ i„^ Sfl iS^f of th™ fibres a palattnam), also known as Meckel's, the spheno-maxillary or the nasal ganglion, is a small triangular reddish-gray body, with the apex directed posteriorly, situated in the upper portion of the spheno-maxillary fossa. It b flat on its mesial surface, and convex on its lateral, and measures about 5 mm. in length. It lies in close proximity to the spheno-palatine foramen and just beneath the maxillary branch of the trigeminal nerve (Fig. 1061). The ganglion is regarded as belonging to the series of sympathetic nodes, and consbts of an interiacement of nerve-fibres in which are embedded numerous stellate sympathetic neurones. Roots.— The sensory root consists of two, sometimes three, short stout filaments, the spheno-palatine nerves (on. sphenopalatinn, which pass direcdy downward from the lower mai^n of the maxillary nerve to the upper border of the ganglion. While some few of the fibres of this root are axones of the sympathetic ganglion-cells, the great majority are dendrites of the cells of the Gasserian ganglion which pass to a limited extent through, but mostly around, the spheno-palatine ganglion independenUy of its cellular elements. They are continued entirely into the various trunks that are usually described as branches of distribution of the ganglion (see below). The ptotor root is the great superficial petrosal nerve (a. petnwus soperficialis major) which, in all probability, carries sensory as well as motor fibres. It arises from the facial nerve in the facial canal, passes through the hiatus Fallopii and a groove in the petrous portion of the temporal bone and then under the Gasserian ganglion to reach the cartilage occupying the middle lacerated foramen. Here the great super- ficial petrosal nerve is join^ by the sympathetic root, the great deep petrosal, (n. petrostts profundus), which is a branch from the carotid plexus. The two great petrosal nerves fuse over the cartilage at the middle lacerated foramen to form the Vidian nerve (n. canalis pteo'goidei [Vidll]) (Fig. io6i), which traverses the canal of the same name and enters the spheno-maxillary fossa to join the spheno-palatine ganglion. In its course through the canal the Vidian nerve gives off a few tiny nasal branches, which, composed of trigeminal and sympathetic fibres, supply the pharyngeal ostium of the Eustachian tube and the posterior part of the roof of the nose and the nasal septum. While in the canal, the Vidian nerve receives a filament from the otic ganglion. In addition to supplying (accordinR to many anatomists) motor fibres to the levator palati and azygos uvula muscles, some of the facial fibres are especially destined for Klandular struc- tures. Such fibres are probably interrupted around the stellate cells of the spheno-palatine ({anglion, the axones of which then complete the paths for the secretory impulses. The sensory constituents of the great superficial petrosal ner\e are, perhaps, of two kinds : {a) fibres from the cells of the geniculate ^ganglion of the facial to the palatine taste-buds, and (A) recurrent trigeminal fibres, that, by way of the maxillary, spheno-palatine and great superficial petrosal nerves, are distributed with the peripheral branches of the Vidian or of the facial nerve. The great deep petrosal nerve represents the association cord belttxcn the superior cer\'!cal s>Tnpathetic and the spheno-palatine ganglion. Many of Its fibres end in arborizations around the stellate spheno-palatine cells, from which, in turn, axones pass to blood-vessels and glands by way of the ganglionic branches of distribution. THE TRIGEMINAL NERVE. 1 341 terior palatine nerves. Fig. 1061. liiHlliiikl int. oradd artery Po«t.lnr. poilerlovpBtettM GfMt MpcrtcUl ^petWMa "err* GfcMrfcfppctrcMl serve fnmi canXld plexus Oik gaagUoB. ct4 CMtlliC^af EusUdliM tube, cut .tBi.br.effitcendinK MViM sup. ccrv. B^anl. Hit tar. of sscenflinif ^k u« . »< — — ■• » rsnusof »up. cciv. gsatflkm Sup.rerv. pumrlkto of sywpatbctk iBt- I aroOd utcrj Uvuls Superior constttctoc I^vslor paUt* Tensor pelel* . c ut above Dt««tlon .howlng .ph«o-p.l.lln. and oUc (..«». viCT«d from wi.hin. („. ..-.« p~ur..r» .-f.H.«.) . which, -^n^^t'^^x rLruTriit Kits: plate of the palate bone enter th« nasaHo»a and su W V *« ~ y^,^ ^„j i^^. anterior portion of the inferior turbinate bone and '♦^^"°^°^';!^' for^^rf )„ , groove on the nor nasal meatuses. Emerging from its «^»"f \»^« ^"\" "^^^^P^ame^rof the naso-palatine inferior aspect of the hard palate ""^ 'noscula^w w.th the termi^^^^ ^ ^h^ nerve. U suppUes the hard palate and its mucous rnembr^^^^^^^ ^^^ ^^^„ mam^nJI^Vcr^^hShThe^at^^r^^^^^^^ — ^ -'^ ^""^ ^ ™^ membrane of the soft palate and tonsil. They are : (a) the AJJ/^nor w/^r/or «'" one or two «an«nts to Uietemp^^^ ,. The external P*«W^* ^'^iVtRKc^^^ It fnten. the usually Ukes its origin as a common trunic wun uic deep surface of the exten^d pterygojd ^ ft,„di „terlor et posterior) 3. The deep temporal "erve* t" tempw-^ v accompanies (F«. -063). are "''*^>^'^'F^H5n tLLeS^terygoid.afte^ ^ ihe t C3l nerve between the heacb of the externa^^^^^ ^.^^^^ k^ upward to supply the anterior F"^ "" °* J'^^^^Srg^W ^^ then upward'dose outward across the "PPer.">«'^" «* ^''l the t^£ra7muscle. It often fuses with St£^ra.;^oroV5LS^^tTte"^^^^^^^ pklaHne tarn Mkguw.Mchank lympMl IM. Int. pwrgoU muKlc iDferUir ilcaul •*"' UmmiU.V.mtnt Di»«llon .howint Ut.nil view ot .pheno-patatln. and Cic pngli.. TU» ^./^«r freauently accompanies the nerve to the masseter for STariaSe'^tanL'rfiThichTturn^s u J along the bone to enter the deep surface of the posterior portion of the musde. sensory. It • ^^ '^^'^ '"TitrS:: ix^erXteC ^ anda^Sr de^p te'mporal 'Jlerve. arises in common with ^^e external pi n^g ^^ ^^^ ^^^^^^^ pterygoid, and is accompan.ed by the la"er between ^"^ j j j ^es the outer Passing downward on the inner f'^^^^^J^^^J^.X^vr^l branches which form a surface of me buccinator, where it b^eaJ" "P ^"^° j, ^f ^^e facial nerve. Some of plexus around the \^'^J«"?' ^^'^^'^^'Je "o s"^p"y ^'^^ •""'^''"' membrane of the hr^'SrZZlrtL'^TX^orZ'^.lK K the others supply the sUm of the cheek. V.rUtlon..-1-tead of lying .0 t^e inne-icfe jhe^rv-iay^^^^^^^^^ [JlS ^Irj^e L^i^tan'^'^SfeS '^""^l^^r^rS^i'^r^^r^^^^^ foramen in the alveolar border !^ssr "44 HUMAN ANATOMY. of the mandible, just anterior to the ramus. It has been seen in one case to arise directly fiun the Gasaerian gai^ion and emerge from the cranium through a special foramen situated between the foramina rotundum and ovale. The Posterior Division of the mandibular nerve is sensory, with the exception of the mylo-hyoid nerve. It passes downward beneath the external pterygoid and, after givii^ on the two roots of the auriculo-temporal nerve, terminates by dividing into tne lingual and the in/eriot dented nerve. Brandies. — These are : (i) the auriculo-temporal, (2) the lingual and (3) the inferior dental. 1. The auriculo-temporal nerve (o. aarkuloteaporalis) (Fig. 1063) arises just below the foramen ovale by two roots which enclose between them the middle meningeal artery. It passes backward beneath the external pterygoid muscle and between the spheno-mandibular ligament and the neck of the mandible, and then turns upward through the parotid gland between the tem|x>ro-mandibular articulation and the external ear. Emerging from the upper margin of the gland, the nerve passes over the root of the zygoma and ascends to the temporal region behind and in company with the superficial temporal artery. Branches.— These are : («) the articular, (i) the parotid, (<■) the mea/al, (d) the anterior auricular and (e) the superficial temporal. The last three are terminal branches. a. The articular branches (rr. irticnlarcs) are one or two delicate filaments which enter the posterior portion of the tempor-mandibular articulation. *. The parotid branches (rr. parotldci) pass to the gland; they arise either from the auriculo-temporal or from its communicating filaments with the facial nerve. c. The meaul branches (nn. nieaiui auditorll exural) are two in number, an upper and a lower. They enter the external auditory canal between the bone and the cartilage and supply the skin covering the corresponding parts of the meatus, the upper branch in addition sending a twig (r. Bcobranae tynpaoi) to the tympanic membrane. d. The anterior auricular nerves ( nn. anricnlares aateriores) . usually two in number, supply skin of the tragus and of the upper anterior portion of the auricle. e. The superficial temporal nerve (rr. umporales rapcrlkiain) (Fig. to68) breaks up into a number of fine twigs which supply the skin of the temporal region and of the scalp almost to the sagittal suture. The auriculo-temporal communicates by its roots, close to their origin, with branches from the otic ganglion, and by its parotid and superficial temporal branches with the facial nerve. By the first of these communications secretory fibres of the glosso-pharyngeal and sympathetic fibres are carried to the parotid gland ; by means of the second junction sensory trigeminal fibres accompany the peripheral motor filaments of the facial. Variations.— In a specimen found in the anatomical laboratory of the University of Pennsyl- vania, the middle meningeal arter>', instead of passing between the two roots of the nerve, pierced the anterior one. 2. The lingual nerve (n. lioKualis) (Fig. 1079) is the smaller of the terminal branches of the mandibular nerve. Lying internal and anterior to the inferior dental nerve, it passes downward beneath the external pterygoid as far as the lower border of that musc'e. It is usually connected with the inferior dental nerve by an oblique strand of fibris which occasionally crosses the internal maxillary artery and, close to its origin, it is additionally joined at an acute angle by the chorda tympani nerve. After emerging from under cover of the external pterygoid, it passes between the internal pterygoid and the ramus of the mandible. It then turns inward, forward and downward under the mucous membrane of the floor of the mouth, cross- ing over the superior border of the superior constrictor of the pharynx and the deep portion of the submaxillary gland, and passes under the submaxillary duct between the mylo-hyoid and hyo-glossus muscles. Reaching the side of the tongue the nerve continues forward to the apex. lying just beneath the mucous membrane. Branches.— The lingual nerve supplies small filaments to the subliagu.il gland, the floor and side of the mouth, the side of the tongue and the lower gum. . It gives off the sensory root of the submaxillary ganglion and its terminal filaments (rr. lingualcs) pass upward through the muscles of the tongue to supply the mucous THE TRIGEMINAL NERVE. "45 membrane of the anterior two-thirds of the donwm. Its fibres have their main termination in the filiform and hii^form papiUa. ■ a ,u :„«-^, The Ungual nerve commumcate* with the chorda tympani and the inferior dental and in its anterior portion forms loops with the hypoglossal. \. The inferior dentil nerve (n. aWeotaris Inferior) (Fig. 1063) is the larger of the terminal branches of the mandibular. Lying posterior and external to thi- Ungual, to which it is connected by a small nerve strand, it passes downward and foXrd under cover of the external pterygoid. Living the lower margin of hat musde it runs between the ramus of the mandible and the spheno-mand.bular Ugament and enters the inferior dental canal, along which it courses in company Zy«(MMlfcr p m t m Uatm dhrMon oT mMdOMtar Deep waipMal briBcIni StMory (llriflonornMiitHbiilavnnva, Intcnul picrygtiiJ ucnr«. CVtrda tympaid Middle iiienliiKcal aitcry Aiirlado> icmporal Bcrrc. SupwAcUl tcmpoTAl «t«ry, tnavQIftry utcry Conncctioa between auric ulo^cmponl and facial nrrvn. Facial laferior dental Part of mawUblc Parotid ffbod Submaxill-iry gangHon IHgaitric muw-lc. anierloc belly KiUary Klatul 0_.„.. ..„..„. n,.....«Ur „«v. .™. .U J.™„CH« . ™na,«._J.. - P--". «-«-■ — « '~ With the inferior dental artery, and supplies filaments to the t^^^; "^ 'f ^^ ^J^^^j^jl'^/h^j n.«p.n Hprp the nerve breaks up nto ts terminal branches, one ol whicti. tne SSrconUnTes wtthTnX li^ndibl^ to the mid-line, while the other and larger, the mental, emerges at the mental foramen. . . . Branches.— These are : (a) the mjfiohyotd, (*) ihe denial, (.f ; me ii«:«<' and (rf) the menial, of which the last t«o are terminal branches. a. The m,/<^A>»,V/ nerve (n. «yl.hy..d«..) (Fig. '«f 3) Js the onl^ m«or strand^^ the posterior division of the mandibular nerve. It ar««; <™^ and "ward K my7«^hyoid Wore the latter enters its bony canal and passes <»°*"*f^'J"^ T*e^e^e descends into groove, sometimes a -nal for part ot^ way. m the^^^^^ the digaslr c Ir angle and reaches Ihc inferior stmace . ' breaks up into bdnu overlain by the submaxillary gland and the facial artenr »"d vein. It he« breai^^ "P laments which supply the mylo-hyoid muscle and ^^e -tenor belly^f the d^-t"- ^^^ ,,, *. The denial branchti rr. dentale. iafcriorw) are given ?Vj *"^"^\/,.^ (,i„„ inferior denul canal. They combine a.ui unite to form the ^njenor dental plexus ^n« \ 134^ HUMAN ANATOMY. 4*aulia l«brt»r) which supplies filaments to the molar and pfcmolar teeth, one filament to each fanK, and the adjacent portion of the gum. ...... c. The incisor hrcmck (a. olTMiarto laftriM' ■■ttricr) is the smaller of the terminal divisKMis and continues forward within the mandible the course of the inferior dental nerve from the menul foramen to the mid-line. It supplies the canine and incisor teeth. d The mental nerve (n. mentalis) (Fig. 1063) is much the larger terminal branch of the inferwjr dental. Emerging from the mental foramen, it breaks up under cover of the depressor anguli oris muscle into a number of filaments which supply the skin of the chin and the integument and mucous membrane of the lower lip. It forms a fa-ee co-imunication with the supramandibular branch of the facial nerve. The Otic Ganglion.— The otic or Arnold' i ganglion (%. oticum (Fig. 1064) is one of the two ganglia associated with the mandibular nerve. It is a small flattened Fio. 1064- OpHkdak «lati muscle and the cartilaginous portion of the Eustachian tube and pasteriorly wi.h the middle meningeal artery. It is a sympathetic ganglion and con- tains numerous stellate neurones which are characteristic of such structures. Roots.— Of the communications that the otic ganglion receives from several sources, some are regarded as its roots, of which the sensory root is contiTbiited by small superficial petrosal nerves (n. petrosus saperficlalis minor). The latter establish connection between the otic ganglion and the petrous ganglion of the K'"sso- pharyngeal nerve by way of its tympanic branch (page 1075) on the one hand and, by means of communicating filaments, between the otic and the geniculate ganglion of the facial nerve on the other. As the continuation of the tympanic ner\e, after union with the filaments from the geniculate ganglion, the small superficial petrosal leaves the upper and fore part of the tympanic cavity, traverses a small canal in the temporal bone, and emerges on the upper surface of the latter, to the outer side of the hiatus Fallopii. It then turns downward, passes through the petro-sphenoidal fissure or through a special canal in the sphenoid bone, and joins the otic ganglion. THE TRIGEMINAL NERVE i»m •"^- m mc^r root is a branch from the '^^^^V^^^^^^ tT^- root is r«>r«ented by one or ^°.^^^^^^J^Z^^:^ir^ the Vkto, meningeal artery. The ganghon also receives the Ji^*««#«« "•■^ - w A »..m>w.r ol delicate strands pa«) trom the aoc jjanglion to aci;:' Fir., ii^.s. Ophthatmk Masiliuy OccipiulU ••Jor Occipiulio minor Mandibular. Maxittarjp MaadiboUr ^Optithalmic Cirvical picmus / -.^ DiaKran,. .how.n, di«ribuUon u. c«an«.». branch- o. .ri^.na. and ««i«. apina. nerv-. (Fig. io6.,) is a r«>d«h.tnangular or f.jform tK^y,^^^^ connected with its Ireatest length, and « the sm^lest ^l^^^^^Jl^, Lbmaxillary gland and the fifth nerve. It is situated above the de^ Submaxillary duct and th. lingual upon the hyo-glossus -""^^ »"f J^^^^^^^" by tTThort sknder filaments. The nerve, apparently suspended from th^Jatter oy tw ^^^ ^^^ ganglion proceeds from the facial by ^ray of the '^"""^ '7 . I , ^^ the facial artery. and the sympatMicrcon^ ^T"^,TmSSS^^^ a number of fibres which Br.nche..-The branches of chstnbutm^^^^^^ ^^^^^ submaxillary rtSil^rrcoSmtratif'Shr^rX^ 1348 HLMAN ANATOMY. the Ungual nerve and, after accompanying it for a short distance, are distributed to the sublingual gland. The sensory fibres, processes of the Gasserian neurones, tra- verse the submaxilbry ganglion without interruption ; the secretory fibres from the facial end, at least in part, around the stellate sympathetic neurones of the ganglion, from which cells axones pass to the alveoli of the submaxillary and sublingual glands ; while other sympathetic filamenU proceed, as the axones of stellate celb either within the submaxillary or a more remote sympathetic ganglion, to supply the ^andular tissue and ducts, as we'l as to accompany the peripheral branches of the lingual nerve. Practical Co-'aidentiona.— The fifth cranial nerve is the sensory nerve of the face and the motor nerve to the muscles of mastication. It is more frequently the seat of excessively painful neuralgia than any other nerve in the body. Extra- cranial lesions are much more commonly the cause of such neuralgia than intracra- nial. The neuralgia is rarely bilateral, and usually does not involve all three divisions of the nerve. It rather atucks one or two divisions, or only a branch of one, the first and second divisions being most frequentiy involved. Certain tender regions can almost always be found, as over the points of emergence of the nerve on the face, at the supraorbital, infraorbital and mental foramina, where in an interval from pain pressure may produce a paroxysm. The supraorbital notch or foramen can usually be lelt at the junction of the inner and middle thirds of the supraorbital margin. The mental foramen is in the lower jaw, below and between the two bicuspid teeth, while the infraorbital foramen lies just below the lower margin of the orbit in a straight line between the supraorbital and mental foramina. When the first division is the seat of neuralgia, the disease is almost always con- fined to the supraorbital branch. Excision of this branch will usually give relief for alx>ut two years, sometimes permanently. The same may be said of the infraorbital nerve when the disease is confined to the second division. The infraorbital may be excised at the foramen, through the mucous membrane of the mouth or by an in- cision in the skin along the lower margin of the orbit. Through the latter the orbital tissues may be raised and the nerve reached farther back in its canal, which in its anterior part has a thin bony covering. By going through the antrum of Highmore from the cheek, just below the infraorbital foramen, the second division, with Meckel's ganglion attached to it may be excised at its emergence from the skull. The anterior wall of the antrum is opened by a trephine or chisel and the floor of the infraorbital canal in the roof of the antrum is gouged away so that the nerve is ex- posed and followed to the posterior wall of the antrum. This wall is then opened, the spheno-maxillary fossa exposed and the ner^•e is divided at the foramen rotundum and removed with the ganglion. The bleeding will be severe, since large and numerous branches of the internal maxillary artery surround the ganglion and are divided. When the neuralgia is confined to the inferior dental nerve the mental branch may be excised at its foramen through the mucous membrane of the mouth. The inferior dental itself is more frequenriy attacked through a trephine opening in the ascending ramus of the lower jaw. It may with greater diflficult;^ be reached through the mouth, the incision being made along the anterior niargm of the descending ramus, and the .soft tissues separated from the inner surface of the ramus until the dental spine marking the dental foramen is exposed; the inferior dental nerve and artery will be found entering the canal. The nerve may then be exposed and ex- cised with due regard for the accompanying vessels and the internal maxillary artery, from which the inferior dental branch has just been given off. The buccal ner\e is sometimes the seat of neuralgia, and may be reached by an incision through the cheek in front of the coronoid process and the insertion of the tendon of the temporal muscle The nerve can l>e reached irom the mouth in the same situation. When the peripheral operations for trigeminal neural|{ia (tic douloureux) have failed to effect a cure, or when the neuralgia pi imarily shifts from one branch to an- other, indicating .-xn extensive central involvement, the Gasserian ganglion must be THE ABDUCENT NERVE. 1249 ^oved or the «~ory root resected The ^dl is o^-j^ jj^^il^yrr^Xr and the unopened dura (unless unavoidably t^^^^^ ^^^ ^^ ^j,^ of the skull until the ganglion lying °" »J^'f^*i3 „J^ and r^oved. The temporal bone between the twolayers °« '*^^"j^v'y„^,PTit comes through the midSe meningeal artery is ."P«« [y «r^„ more"^ dangerous hemorrhage, how- foramen spinosum. A P?^''''^^^"^^. ^^u'^^t^" gSion is intimately «^ated SlJc ^jLnTesT r eyT ar^t^ i^oJ'c^r fr^m^ damage to the first di.^sion o. *•= "fflinpal nerve is sometime divid^ K^ilJ^a^strpifig \^^^ To Se^r^e.!ltSe^rrrc;us^%x^^^^^^^ ™^»-- -^-y between the tongue and the alveolus o the lower jaw. ; ; ^^gin. is rare. :3ri»Yn<»e.Jl»ryi.x»«lexte™l auditory me.t». • THE ABDUCENT NERVt The sixth or abducent nervej •"-«".) is «c^^^^^^^ external rectus muscle of the eyeball. J^^ ^fJPiSfrof^ultipolar neurones which (nuctos n. abdacenUs) (Fig. 933). *™"rSJ^"Jand under Se gray matter of the lies in the dorsal part of the te?™'"!"'",^ Vl%Cr to thrsSiL a^^^ beneath the floor of the fourth ventricle. It « «t";^^f »"»r™^ Sm^^ by tS^fibres of the facial eminentia teres and ventral to »"d wUhm tl« loop form^^ ^ .^ ^.^^. nerve. Leaving the nucleus on its '""f^f P^ J' ^'l^ X "..ner side oi the superior which pass backward and ven^ro-U eralj^. Jxjng ^ he nine ^^ ^,^1^^^^^ '^^""" , . « ..«— A, in the case c' the third and fourth nerves, tne Centfl «id Cortieri <^««'*»"'-;^,uJ"J^reri^low'tudinal fasciculus, some of the nucleus of the sixth receives, by way of ^e I^J^"°[ '"^ establishment of a reflex-path fibres of the pedicle of the ''"P«"o^ohve, thus con^pletin^^^ between the auditory appa^tus and the ^"'^ J^J^^,"f^Ludi„al fasciculus with the oculo- «M:ond connection is effected ^V n^'""?"' *",h^XLrnudeus is brought into relation with rmXra1.\t=x by'way oS^pV^mSt^t of the opposite side. Cour.. .nd Di.tnbution,-After leaving the s^^^^^^ SaSnt nerve, which at its superfaal onpn is fla^.uul oft^"JP;^y„'^ J ,,^„, ,5 „,„,., becomes consolidated and ro"n«|«l' ''"^ .'^'^^1""^*™ l,^.„ over the sphenoid bone the lower surface o, the |K>n. It the^"^ ^^Ig forThe'iifth nerve^Fig ,05a) at a po nt medial and slightly P«*terior to ine o,k:ii k • ,; j j process and Thence it runs forward through a ""t^^';^^"^,?^'^^;^^^*^;"' L a^ passes to the outer side of the '"««"7^f *;?^:;^ ",^^^ Here it lies somewhat Kirtion o. the temporal bone to enter t"^*; ";• y. \"""* ^'"„,, eventually reaching the lielow and to the ..uter side o the l";;^-^"!"-^"';' ""^f^^S throuRh L sphenoidal outer wall of the anterior portion of the simis. cntcni the >rn.t tr g ^^^ 1^^^^^,,,,;^ muscle which, "^^^^-"'r,"^;^ i^ traverses the cavernous orbit a small sensory filament from the ophthalmic nerve. 79 125° HUMAN ANATOMY. Variatioiu. — The nerve may be absent on one side, the external rectus being supplied by a branch from the oculomotor. It may have its superficial origin by several widely separated strands, the accessory fasciculi emerging from between the fibres of the pyramid or through the lower border of the pons. THE FACIAL NERVE. The seventh or feicial nerve (n. facialis) is a mixed nerve and consists of two parts, a larger motor and a smaller sensory. The former supplies with motor fibres the muscles of expression, the extrinsic and intrinsic muscles of the external ear, the stylo-hyoki, the posterior belly of the digastric, the platysma myoides and per- haps also the levator palati and the azygus uvulse. Certain of the motor fibres are peculiar and as secretory fibres are destined for the supply of the submaxillary and sublingual glands. The sensory part of the facial conveys gustatory fibres to the anterior two-thirds of the tongue. The sensory part is commonly known as the^rf intermedia of Wrisberg (n. intermedias) which, instead of being a distinct nerve, may with propriety be regarded as the sensory portion of the seventh — a view strongly supported upon morphologi- cal grounds. The sensory fibres are processes of the cells situated within the Fir.. 1066. Brain-fftem with nuclei of cranial nervM »hown (liacrammatically ; motor nuckl and fibre* are bine; acnaory nuclei and fihrefl arc red. a, oculomotor nerve; A.troi-hTear nerve; c, motor part of trijceminal nerve; The motor p«ti, by far the larger o^ 'he ^ a^d con t,^^^^ ieaUv and functionallphe more .mpo^m^^^ 9, )! an oval cI£tion^>f soV of the motor root is from the /'^«', ™'"^^_li^-^l^^^^ measures about 5 mm. in half dozen groups of large """'^'fj^^' Z^^on d the teZTntum of the pons. It length, and is situated m the posterior P""^'"" soS r^ of the trigeminal nerve UesVl' '^^ ^°"^'^ :r^"t^rSi of \he c^ius Spezoldes ; higher up it is and, in its lower part, dose to *« ^^^ ™ ";'bv the superior olive, to the upper tilted dorsally ancf separated '^^.^J^^ JJ^ada/^uS". situate;d dose to the ™£l ^iVrtt^fr^fhl^^n^lSTforc^^^^^^^ descripUon into a radicular, an ascending and an emergent portion. Then.^upward jd a^^^^^ ^^^ ^^^^ ^ ^^ ^^^ i„ ascending porHon of the seventh nerve l^'^'^^^j'^^fourth ventricle, beneath which it runs this situation the nerve is separated from the ""^^ ° *f T" i„,„^iately dorsal to the p«s- within the funiculus teres, only bv^h^ '•r^JTc^rnucleus TlHe^ now bends abruptly tenor longitudinal bundle and mesial to the f""^Vrr/^Wfo« of its course, during which it outward at a right angle and enters "P°" 'j^^.^^'J^^'^^kward and vemrivlaterally, be- whereby the nucleus is brought under the """Xiu'd nuXr of root-fibres are connected («) While not beyond dispute, it ».?''*?"'= ^^"heTvidence adduced from clinical observa- wiih the facial nucleus of the "PP°«"^»^f-,J*^J^^"of a%^al group of cells from which tions and pathological findings P«)mte to t»«f*'»^™^°' dT!r,j,,i* muscles. These fibres, arise the fib«s ''"PP'vinK.the "rbicuUns ^pe^an^m^nd fro^^^^^^ sometimes called the "^^^Z-""' "^^'^'Xsuw^ by he seventh n^ve' (r) The latter, the occurrence of paralysis of the other n*™ J^^Wneo X ^ j^s. probably morever, is brought into association w th \»»^^;*"»\""'^^^";|^„^^^^ to the impulses o( within the posterior longitudinal '»«:'7'"''- » ^ *^^^*;'^ the e^ Ids (rf ) Connection with the sight and hearing, as shown by «''«J'!'°"''\'^„"'r^^, "he ' J^^^^ °' '^ "'"*='•* "* h^los«l nerve ha.s been '"^"n'f^ m exp^ana ion o the^™'^'^"^^^^ „„a,, ,he influence of the lips with those of the t°np«-««nt.*',''f ^ J*^ dissipation is f.iund the jrmicuM^ StL^rhefe^«:irsKtXn :t;rL^. A^er emerging from 1253 HUMAN ANATOMY. the stylo-mastoid foramen the nerve passes downward, outward and forward through the parotid gland, and divides, just posterior to the ramus of the mandible, into its terminal branches, the temporo-facial and the cervico-facial. The filaments of these branches freely join with one another and form the fan-like parotid plexus (plezns parotldan), also called pes anserinus. The geniculate gangUon (g. genicall) is a small oval or fusiform thickening on the facial nerve, at the > ,it where it turns backward (genlculum A. facialis), and contains unipolar neurones, whose axones form the sensory root of the facial n&rvc and whose dendrites form the sensory fibres oA distribution of the seventh. The so-called branches of the geniculate ganglion— the great and external superficial petrosal nerves and the branches to the tympanic plexus — are only in part comfKMed of fibres connected with the ganglion cells ; they are, therefore, more appropriately regarded as branches of the faci^ nerve. Branches and Distribution. — Within the facial canal, the facial nerve gives off: (i) the greai suptrfidal petrosal, (3) the branch to the tympanic plexus, (3) the external superficial petrosal, (4) the stapedial, (5) the chorda tympani and Fio. 1067. k^^: Dtafnin ihowliir brudm taA eooiMctioiu of (ai:i«l nervt withia taeU canal. (6) the communicating branch to the vagus. The first three are closely connected with the geniculate ganglion. Outside the facial canal arise: (7) \he posterior auric- ular, (8) the digastric, (9) the stylo-hyoid, (10) the temporo-/acial Awi (11) the cervico-facial nerve. The last two nerves arise in an uncertain manner from that irregular plexiform expansion, known as the pes anserinus, into which the facial broadens within the substance of the parotid gland after emerging from the stylo- mastoid foramen. I . The great superficial petrosal nerve (a. petrosus siipcrficialis major) (Fig. 1063), while issuing directly from the gangliim, contains motor fibres in addition to the scnsoty. It leaves the facial canal through the hiatus Fallopii, enters the middle cranial foss;» and pa.sscs forward under the Gas-serian ganglion and over the cartilage of the middle lacerated foramen. The nerve then crosses the outer side of the internal carotid artery to reach the jxisterior opening of the Vidian canril, where it is joined by the gre.1t deep petrosal nerve (page 1360) from the carotid sympathetic plexus, with which it unites to form the I'idian nertr. The latter traverses the Vidian canal to the spheno-maxillary fossa and there enters the posterior asjiect of the :ipheno-palatine ganglion, whose motor and symi)athetic roots it contributes. The probable relations and destination of these fibres have been considered in connection with the spheno-palatine ganglion (page 1340). 3. The communicating branch to the tympanic plexus (r. anactomoticiii enm pirzn tympfenico) traverses a tiny canal in the tem[X)ral bone to reach the tympanic cavity, where it joins the main continuation of the tympanic plexus of the THE FACIAL NERVE. "53 the parotid gland. .„^_«-j^ oetrosal nerve is very small and is not always 4. The •t«P«*»?l»SS LTwTOhbd the pyramid in the posterior wall d ifZ^^rTc S:i^!l.r^ '^^ntacc^s to the muscle by pass.ng through a mbute ^ce in the base of the pyramid. 1068. TvMponl bniKh erf :4wtaid branch o( grtat ftuflculai Mftlar terioris'ant! is called the infraorbital plexus (Fig. 1068). The nasal and infratrochlear nerves communicate with the infraorbital at the side of the nose. II. The cervico-facial division (r. cervicofaclalls) (Fig. 1087) is the smaller of the terminal branchts of the facial and resembles in its general arrangement the temporo-facial. It passes downward, outward and forward through the parotid gland and finally breaks up into three branches. Branches. — These are : {a) the buccal, {b) the supramandibular and (f) the inframandibular. a. The bnccal branch (rr. baccaln) may be single or multiple. It crosses the masseter and supplies the buccinator and orbicularis oris muscles. It communicates on the outer surface of the burcinator muscle with the sensory buccal branch of the mandibular division of the trigeminal nerxe. THE FACIAL NERVE. Tr»n»ver«e r«cial artery Hranchcs of Iht facial ncm Superficial temporal artery "55 * The sui,ramindilmlar branch (r. o,.,il~l». »..dib«I.rl.) passes for* ard between the U,we*iip^^ch,„ and ^^^^^^^^^^^'^^^^^^.^ of the inferior dentai. .^ Its filaments commwuct. *''\"^°*M'°(" "^^ew from the lower margin of the paroUd c. The inframandxbular *~"^*J'i "^'^ >/^'K'ST jaw. Piercing the deep cervical £St ifp^^^^forrSr^n'l.^a'^drJs^^ .^beneath the platysma myoides ^-S^:oSr^. l\t-t^%^:^^S'^^ch of the cerv^alp.... convtJsif) or of P?r.^y^-. J^J^^^rcoT/nSto 4^^ benches it usually involves more <=«'7'«°"/ t^he evt Ton ly the orbicularis is involved it is ^led bepharc the muscles about t^f^y^, " .™ \^ involved, stasmm nictilans. The facial nerve spinal accessory. i„^„-,mnn If the r«t/ra/ lesion— as a tumor, abscess nerve will result, and the , p^j ,069. paralysis will usually be confined to the lower branches of the nerve m the face and neck, the upper branches escaping probably because of bi- lateral innervation of the upper muscles of the face. A cortical isolated paralysis of this type is exceedingly uncommon. If the lesion, as an apo- plectic hemorrhage, is in the internal capsule, a hemiplegia on the same side as the facial paral- ysis will be associated with it, and this also usually occurs when the lesion is cortical. A lesion in the upper part of the pons will give rise to a similar condition, . . .u„ r.r.ns tho facial nerve will be paralyzed Lif it i-^'h« middle orlowerp^^^^^^^ ^ crossed pard- on the side of the lesion the l'"" P'fK*^ .'^,V'^{° :.. fibres cross to the opptJSite side ysis). This is explained by the fact f ^' ^J^ ™ and trunk cross in thrinodulla. andShere wilMje a hemiplegia of the jp^^^^^^^^^ .^^ ^^.^ ^^ „,^. ,, Us The peripheral P'f 7" °\ ^'^'^ ^s^n of the facial nucleus in the pons givei r .c terminal filaments on the face, but a IcMon o tne i ^^^ ^^^^^. to much the .tme ^V-l'^^-Xrhv ut-rXs 5^^^^^^^^^ tumors, Jtc. In its long cranial portion may be myo.vtd ^ tutKrcu^ \ m^ ^f ,he s.^fl tissues, course through the ^ »"°P'?,"/,;!"!;';;j"*f ,t ^^^^^^^ «kuU in the middle fossa. Parotid gland Parotid duct Maweter muacle DiMection ahowing «"»"»"; "'Ij'i'l "12 ' they cTos» maweter mur.ci«- .lanches a» ^^^^■f- 1356 HUMAN ANATOMY. When all branches of the iacial are paralyzed the symptoms are characteristic. Only one side of the forehead wrinkles ; the tears fail to enter the canaliculi, and flow over the cheek ; the eye cannot be doaec • foreign bodies on its surface are not removed by the lid, and conjunctivitis from irritation results. The affected half of the face is expressionless, and the comer of the mouth on that side remains partly open and hangs down, so that the saliva tends to run out The mouth is drawn to the opposite side ; the upper lid cannot be elevated, and whistling b impossible because the orbicularis cannot now pucker the lips ; food lodges in the affected side of the mouth, because the buccinator muscle is paralyzed, and, for the same reason, the mucous membrane often gets caught between the teeth. In those cases of facial paralysis in *hich the lesion of the nerve is posterior to ihe styio-mastoid foramen, attempts have been made recently to restore hmction to the peripheral portion by dividing the trunk posterior to the parotid gland, and anastomosing the peripheral end to a neighboii ig cranial nerve, as the spinal accessory or the hypoglossal. The results have not been entirely satisfactory The line of the main tru.ik of the nerve is from the slight depression between the banc of the ear and the mastoid process, forward and slighdy downward. It passes through the deeper portion of the parotid gfand. • THE AUDITORY NERVE. The eighth or' auditory nerve (n. acnstictis) is not only, as its name implies, the nerve by which sound impulses are transmitted to the brain, but also the nerve of equilibration. It consists of two portions, the cocUear, the true nerve of hearing, and the vestibular, which is concerned with equilibration. Traced from the brain toward the ear, the auditor)- nerve arises at its super- ficial origin by two roots, a mesial (radix vestibnlaris) and a lateral (radix coch- learis), which embrace the inferior cerebellar peduncle, the mesial passing to the inner and the lateral to the outer side of the peduncle. The nerve thus formed by the union of the.se two i.iots, leaves the surface of the brain-stem at the postenor border of the pons, where it is adherent to the middle cerebellar peduncle. To its inner side and closely associated with it are the motor and sensory roots of the facial nerve (Fig. 1046), which lie within a groove on the mesial surface of the auditory and with it enter and traverse the internal auditory canal. Witl.in the latter, the auditory nerve separates into two divisions, of which the superior and larger is the vestibular nerve (n. vestlbull) and the inferior and smaller is the cochlear nerve (n. cochleae). Although in a general way these divisions continue the corresponding roots, this agreement, as to the source of their fibres, is not complete, since, as will be more fully noted, strands of vestibulai fibres are incorporated with the cochlear nerve. On reaching the bottom of the internal auditory canal, the facial nerve leaves the meatus and enters the facial canal, while the fibres of the auditory nerve dis- appear through apertures in the lamina crihros.i (Fig. 201) to gain the several parts of the membranous labyrinth of the internal ear. During their joimey through the meatus, the vestibular and facial trunks arc connected (fila anastouiica) by a branch which passes from the pars intermedia to the vestibular ner\'e, and by one from the latter to the geniculate ganglion. These apparent communications between the seventh and eighth nerves are, in fact, only aberrant strands of facial fibres that return to the seventh after temporary association with the auditory. The vestibular nerve divides into three terminal branches which pass through aper lures in the cribriform plate above the falciform crest and supply: ( 1 ) the utricle, (2) the superior AnA (3) \)\k external semicircular canal. Not all the fibres of the vestibular root, however, are included in these branches ; of the three branches given off by the cochle:ir ner%e two, 14) those to the saccule and ^5) to the posterior semi- circular canal arc vestibular fibres incorporated with the cochlear, although reem- ingly derived from the cochlear nerve. The remaining branch of the cochlear nerve contains the cochlear fibres proper, which traverse the numerous foramina of the tractus spiralis foraminosus and the central canal of the modiolus to supply the organ of Corti within the memhrenous cochlea. THE AUDITORY NERVE. 1257 ^ r'sLfo^V a„iThSr'X4^'t.^t they ie the processes ,axo„es) ol SSfe-^s situa^ somewhere along the course driie wrve. It is necessary, consequently, to ik thTJS oripin of these fibres in the gangha ^inKg on the divisions of the nerve In ^^iO^on of the hmctional differences d the ^*L» of the eighth nerve, .t .s desirable to trace separately the pathway followed by the S^l^^veyed by Sch of these components. Phciml Central and Corticml Connection* of U„ 7*)- Thb structure consKts of a ^n"« ^of^i^lar^neirones which .occupie^. the sp.r^ i::^r^elion^itMhe^roepithe.ial cells o.mpr^ ^iSgtte inner and outer hairviduf cell."^ Leaving the ganglfon the axones of K ceUs enter the bony canals withm the ir>Kliolus. foruhkh they emerge at the tractus spiralis toram.- no^s and are^M into a single bundle, the aKh- tea "^.^e proper. The latter, however, soon rece ves uo^sionTone of which consists of fibres from he Se ^nd the other from the ,K«tenor sem,- ^rcul^Tcanal From what has been said, it is -videm S theS accessions are ,«rt, o' the ve^ubular -^^^^ ^ ^.^^ ^^ cochlear root. and. lieyond their temporary ""^P^"'""!^;^;^,^^^^*" into relation with their nucleus ... recep- Onreachli.K the medulla, the c.Khlear fibres come mi collectively consl.tute the tion. which includes t.o superfica «K^^K~^S omL parts (Fig. 93») of whi.h one. .couetic nucleus (n.Kle«. «""' "•^- nLle jrr™ "coustu n„c/eus {n«cit^ .cc.Mor..»). hes the vertrul cochlear "«>««' "'''IS^^^nflpLd the ^r. the Uteral cochlear nudeu.. -r tuber- ventral to the interior cerebellar Pf ""^^'^j ""f ,'„4^^^ neduncle and .«upies the .Mrem. culum acatticum. r.sts upon the dorso-lateral f"™" J ;^, j^ „, the fl.x.r of the fourt:, .. >v ovuer part of the triangular acoustic area ^T" '" L^Vfibres T^ in arb.>r;«a.i<.ns around th. ste - tricle ^ge 1097 )■ The greater numl>er ;^J,«^»;'7'i^[f j^, ^ution with the more elongatt-d. late c lls.f thev.mr.il ga.igWon. wh.le ''^^'-'r^ ^"^"^J^^ subdivisions of the reception u^fo-n. ceil, of the lateral nucleus. From the "~XrSthe axones of the cells of the nucleus, the auditory pathway ,s '^""t.^^^^^'^^/trthe^s^^^^^ »»>•= ''P'"'' '""' 'i T ventral nucleus passing for the most iK.rt ^^n" al to tne re ^^^^^ ^^,^^p ^^,,^,„^ ,he trigeminus t. form the cor^s (^'''rt"- .^^'^^^^'X ZZ he e,,endyma of the flo..r of the *'^'^tfc„rpu.trap..oid...theconspic„oi«tmnsve.^ua.th^^^ ,heventrarV?gion of the ,«ns m ;t--3"";,P„7Jj' ^jTum^ number of fibres that spring within the ventral cochlear ""^•'':".''- ''"PP f„7^^^^^^^ ,,.,„ the large cells found within the from the lateral nucleus, n »f f 'f " '' 5 l"*f^"^'o;stitute the nudeu. trapeaoideu.. In cU«e trapezoid Ixxly. on each side of themid-lme. that con n ^^^ ^^^^^._,^ ^,,^.^. , „ relation with the dors;,! surface of th'Jo'pusJ^a^^K^^ ^ ^^,^^^ „,,^..^ either side of the median raphe, ''r'* ''^^ ""^f^e Sear fibres, chiefly from the opi^.site collection of nerve-cells around *»"'^^"«"yXh thc^art of the lateral fillet principally take. hut also from the same side, end and from which tm. tracx RMondruction o« left memhrinouii laby- !^i >ra Hen dmukk to ampullat ol semi- ""LlJr cl^. STd to macula o( utncl. and ncculc. X M. ^SIrrrtrr.) 1258 HUMAN ANATOMY. origin (Fig. 1079). Not all of the fibres arising from the superior olivary nucleus, however, enter the lateral fillet. A considerable number leave the dorsal surface uf the nucleas and, as its pedmule, pass to the abducent nucleus and, by way of the posterior longitudinal fasciculu.s, to the nuclei of the other eye-muscle nerves. In this manner reflex paths are establisheil by which the motor nerves, including probably the facial, are brought under the influence of audi- tor)' impulses. Within the tract of the fillet and a short distance beyond the superior olive, Lh encountered a group of nerve-cells, the nnclcai of the lateral flUet (nucleus lenaiacl lauralis). While numerous additions to the fillet are received from these cells, their relation to the cochlear fibres is uncertain. The characteristics, course and destination of the lateral fillet have been dsewhere described (page io8a). Sufllice it here to recall that, so far as the auditory fibres are concerned, the tract terminates chiefly in the inferior colliculus of the quadrigemina and the median geniculate body. In addition to its constituents through the corpus trapezoides, the lateral fillet receives con- siderable accessions of cochlear fibres by way of the atria acuaticje. These strands consist of the axones, for the roost part, of the cells lying within the tuberculum acusticum, but to a limited Fig. 1071. ni«ijiv.m 5iho'vinj{ rontiet.tion8 of auditory nerve ; cochlear fibre* and coniwctidw are in black, vcatibular in red ; C, C'H hit', - G^, Kantflion spirale ; lAC, tnternai auditory canal , I C, DC, vential and doraal cochlear nuclei ; Rfi^ rctttit>rni iKidy; jTO, sujKrior olive; 7*^. trapeioid hody; .^r.S/, aiiiustic striae ; yt/, nucleus of lateral fillet itF); MF, nu'^ian 'fillet; fO, inferior quadrifeminal body; ^(7. mcdi.in senicitlate body; ^^, auditory radiation ; rC tempc'ai cortei; 7; thalamus; SC, aemicirrular canal; f ', vestibule ; Kf#, veatibular fanfflion; My, median veiiiljular nucleua ; DN. lateral (Ueilera') \rstibular nuckui; I'j/, vealibulo-apmal fibre; O, cerebellum. extent also ui the axoi.es of the ventral cochlear nucleus, which wind over the latero-dorsal surface of the inferior cerebellar ()eduncle, pass medially beneath the ependyma of the floor of the fourth ventricle as far as the median groove, and, crossing to the opposite side, then sweep ventrally thriitigh the dorsal n-xiun of the medulla or pons to join the tract uf the lateral fillet, and so proceed in company with the other cochlear fibres to the higher levels. By no means all of the c(>m|x>nent fibrtn of the acoustic strix follow the lateral fillet, since some after decussa- tion turn brainward, pos.sibIy joining the mesial fillet, whilst 'ithers may enter the posterior longitudinal fiisciculus to assist in establishing reflex paths influx ing the motor nerves. The auditory path, by which the impulses gathered from the organ of Corti by the cochlear fibres are conducted to the cerebral cortex, includes the following components ( Fig. 1071 ) : I. Peripheral neurones of the ganglion spirale, whose axones (the cochlear fibres) pass to the reception-nucleus -.entral and lateral cochlear nuclei). ?. Neurones of liio cochlear nuclei, which .send their axones : {,1) by way of the corpus trap les to the superior olivary nucleus, chiefly to that of the opposite side but also to that of the s.iine side, or to the lateral fillet or its nucleus without interruption in the olive ; (5) by way of the strix aciisticx through the tegmentum to join the trapezoidal fibres. 3. Neurones of the superior olivary nucleus or of the fillet-nucleus, whose axones pa.ss by way of the lateral fillet i«iil>h«ral, C««tna and Cortical C<»"»«^/*^* °^,, .^e bioolar nerve-cells situated within v«rtiKr«n 6t the »';*«7^';^^;:^^or^r;i- J^S^^^ which lie, at th.- l«n«n ,he small vatlbul-r ,«.fUon (■lV'^^Jj^^ ^' theJcells constitute the five branches of d»- S.:S:;i:ri'::^ria;;::l.eT!S ?Sro«Kh the vanous openm^s m the mner wall of the bony 1 .byrinth. in the manner above S^bed (page «56 ). to reach t^ spedaliKKl areas, the mac«a- atMshca S the saccule, the utncle and the :;;;jLll*of the semicircular canals.«*e« the nerve-filaments end. really begin. „ intimate relation with the neun. epithelium. While the centrally directed akones of the nettrones ""PPly-ng *e utricle and the supenor and extena^ Lmicircular canals become cons"''^^ to form the vestibular nerve of d««"Pt"^« anatomy, those from the sacctile and the pK««rior semicircular canal Jointhe^h- tear fibres and with these course within t^ «K:hlear nerve umil the latter and the vestibular nerve unite to form the common aud.u.ry tnmk. Where the common trunk separates into the two roots the vestibular hbres leave the cochlear and Pennanently a.s>.umetheir natural companionship with the remain- ing fibres of the veslibularroot. The vestibular fibres enter the brainstem at a slightly higher level than does the cochlear root l>'nK "]«"»'»?^''; latter and the ventral c«K:hle«r nucleus and pass dcrsally within the pons between the inferior cerebellar peduncle and the ^^ vestibular fibres divide spinal trigeminal root. On reiichmg » '!^«' "T"^ ™ 1^ ^.hjch. after condensing into an Soshort upward and l"-?!^^ ,^"7'*»"^;r«„aTn ^^^ the cells of the ascending and a d«K*ndinK root restive y^ end .^^^^^ vestibular nucleus of reception. T^'^^.^^'f'',, 'h\ " tHde (iMge 1097). are uncertain, since the u" the are., --custica '" /he floor of he fourth^e^^^^^^ neurones directly related to *e v«t^u^ar^bres contn >^^,|,^,.„,, ^^..^^bly have only an a large diffuse complex of cells ?"^\'''^' "'■*"*. hln reconstructe. I a- has been successfully f„iirfct connection wi.h .'^e ve^ 'bu^ jne^ \\hen^^^^^^^^^ ^.,„ . .., ,,.„ „, p^rts^ done by Sabin. this complex has the form '•n°« " " '•'«• ' ^ , „ mesial to the tract Sran extended irregulariytrian«u^^arnjassf^ j.,,^^ ^^ „> „,„.,.„, lotted by the ascending ""'\;,'r^/'^' "."J,;^^^^^ ,0 the inner ..,.1 partly to the outer side mass of cells which lies alxjveihe larger. m^^^ triangula- mass approaches the ^''•' '^Sz:^ micro^opicaiiy ^^^^^:^^:^^rt:::^^ a taperixg caudally directed ""'^'-^;^ « ^i^h con m^^^^^ ^^ , ^he large vestibular root. (A) .in f ''»'^"'^'' .^T^'^Sus ,• fproU^ upward the superior angle. The first mass and ( r) an .'r«K«'»M>yrannd.. nudeu^^^^^^ ^J^^,^^^ , „„^ ,,„ „ „. vesUbular^.). of these suWi visions (a1 is '>™'« ";'*;"/ •P'."" , .,„£ m,dlall.. n. v.atibulnri»>. als.> as the ch,fj the second (*) -^.^^l^^^Zi^l^"^^^^^^^ > '""-'- "P«''°' ^"'*"'" ""''~" " ' HUiliUiar the r-t"-.^ Nucleua cunealus .Cloacd part of medulla Veallbular nuclei a. .hown^in^reconaimctlon by Dr. Florence I260 HUMAN ANATOMY. nadaut i>t Bechtenw. The small mass corresponds with the Utcial veMibnlar nucleus (nac. latcnilU a. vestibolarto) or nucleus of Deiters. The fibres of the descending root end around the neurones within the spinal nucleus in a manner similar to that in which the constituents of the spinal root of the trigeminus terminate in relation with the neurones within the substantia gelatinosa, whilst those of the ascending vestibular root end around the cells within the remain- ing vestibular nuclei. Although much uncertainty and conflict of opinion exist as to the details of the secondary paths by which the impulses carried by the vestibular fibres are distributed, it may be accepted as established that fibres pass from the nuclei of reception : (a) to the cerebellum (chiefly to the roof nucleus of the opposite side and, possibly, also to the nuclei globosus and emboliformis) as coh5tituents of the nucleo-cerebellar tract, by which the impulses of equilibration are carried to the great coordinating centres, {d ) as arcuate fibres ventro-medially into the tegmentum of the pons, cross the mid-line and bend upward or downward to pass to other levels, some fibres, however, remaining on the same side. From the character of the impulses it is probable that only relatively few vestibular fibres join the median fillet to ascend to the optic thalamus. Other connections of the nuclei include : (r) commissural fibres between Bechterew's nucleus of the two sides, (rf) fibres to the abducent nucleus, (*) crossed and uncrossed fibres '-om Deiters' nucleus to the posterior longitudinal fasciculus and (/) fibres from the same nucleus to the spinal cord. It must be understood that by no means all of the neurones of Deiters' nucleus are con- cerned in transmitting afferent impulses to the cerebellum, for, as a matter of fact, many are links in the path by which the cerebellar cells exercise coordinating influences over the root- cc-iia of the spinal nerves. Starting in the cerebellum, such efferent impulses are carried by efferent fibres which descend through the median part of the inferior cerebellar peduncle and probably end around certain of the cells within Deiters' nucleus. From these cells, in turn, originate the fibres of the vestibulo-spinal tract, which, after traversing the medulla, enter the antero-lateral column of the cord and end in relation with the motor root-cells. A shorter and more direct path for vestibular reflexes is probably formed by the collaterals of the vestibular fibres that end around the spinal neurones of Deiters' nucleus. It must not be forgotten that Deiters' nucleus is the origin for important contributions to the posterior longitudinal fasciculus (page 1 117), by which the vestibular impulses impress the nuclei of the motor and, perhaps to a limited degree, also those of the sensory nerves. Practical Considerations. — The auditory nerve is rarely the seat of primary disease. It is most frequently affected consecutively to disease of the middle and in- ternal ears. It is sometimes, though seldom, paralyzed in fractures of the base of the skull. Operations on this nerve have been performed for relief from pei'sistent and annoying- tinnitus. THE GLOSSO-PHARYNGEAL NERVE. The ninth or glosso-pharyngeal nerxe (n. glossopharyngcus) is a mixed nerve, containing motor and sensory fibres, the latter including those transmitting the impulses of the special sense of taste. The motor element is quite small and sup- plies only the stylo-pharyngeus muscle and secretory fibres to the parotid gland, while the sensory fibres are distributed to the mucous membrane of the middle ear, fauces, tongue and pharynx. The Nuclei of the Glosso-Pharyngeal, Vagus and Accessory Nerves. — In the description of the medulla (page 1073) attention was called to the presence of nuclei common to a greater or less extent to the series of lower lateral nerves including the seventh, nmth, tenth and vagal part of the eleventh, which, with the exception of the last named, are mixed nerves. The motor fibres of these nerves differ from those of the series of median motor nerves — the third, fourth, sixth and twelfth — (a) in the more lateral situation and less compact grouping of their cells of origin and (d) in the less direct course they follow to reach the surface of the brain. To avoid repeti- tion, the general arrangement and characteristics of the nuclei related to the glosso- pharyngeal, vagus, and accessory part of the eleventh nerve will be here described. The Motor Nuclei. — These include the root-cells within the dorsal nucleus and those constituting the nucleus ambiguus. The dorsal nucleus (nucleus dorsalis), a nucleus both of origin and of reception for the fibres of the ninth and tenth nerves, is a narrow elongated tract of nerve-cells, whose upper three-fourths underlies the floor of the fourth ventricle, stretching from the stria acusticae above to the tip of the ventricle below, and whose lower fourth extends into the closed part of the THE GLOSSOPHARYNGEAL NERVE. 1261 Fig. 1073. «»H„lla u. the level of the nucleus gracilis. It lies immediately lateral to the lower ^rt o the S£ vSt bul^ nudeuTand the upper part of the hvpogossd nuc eus K. inner tWrd being covered by the spinal vestibular nucleus and its lower third Serffi Se hy^gt^ nuc Js. Its'^^.iddle third corresponds to the >'.« r«^^ mg ^9) and comes into intimate relation with the ventricular fl««^ Jhen viminpd in cross^ctions (Fig. 928) the nucleus appears pnsmatic in outiine and r^n to ^nsSTTs^S^oupsd cells, of which the median contains the larger and more co^S^uous elem^s and corresponds to the dorsal motor n«<=^"f ' The remainSroups, the dorsal sensory nucleus, are composed for 'he most j«r^ of of the pyramidal decussation, and is best developed in its upper part. In transverse sections of the medulla (Fig. 927). the tract is distinguishable within the formaUo reticularis grisea, midway between the dorsal accessory olivary nucleus and the substantia gelaU- nosa, as a small and inconspicuous group of cells. Arising as axones of the latter, the loosely grouped motor fibres at first pass dorsally to the vicinity of the ventricular floor, then bend sharply outward, and, as in the case of the vagus, join with the similar fibres preced- ing from the dorsal motor nucleus to form the emergent root strands. The Sensory Nuclei. — The nuclei receiving the afferent fibres of the lateral mixed nerves in question include the sensory part of the dorsal nucleus (nu- cleus alae clnereae), above de- scribed, and a tapering column of gray matter, the spinal nucleus (nucleus tractus solitarii), which resembles the corresponding niamm showin. connection. ol root fibra of gloMO-ph«rynge«l nucleus of the trigeminus. The .nd^'pl^^lgr. ?.rv«^nd^. .en^^^^^^^ spinal nucleus is closely associated ^^'^:^J'TuinT^nA°lZ^^rP^^^^^ tsS."?.' J^a' with a conspicuous longitudinal .tKn;S!"r^rr.rc^rrvigl".'^S«'iW^^^ tract of caudally directed nbres, j^p^ moiian Riiei. hrll largest constituent of the fasciculus ; whilst the tTi.rd, tKe vagus, adds fibres that course within the lowest segment of the tract. 1262 HUMAN ANATOMY. within the dorsal nucleus and the nucleus ambicuus. The ninth nerve shares these motor nuclei to only a limited extent, such of its fibres as are efferent arising from the uppermost part of the cell-columns. Those taking origin from the nucleus ambiguus pass at first toward the floor of the fourth ventricle ; they then abruptly change their direction by bending outward and, joining the fibres arising from the dorsal motor nucleus, proceed ventro-laterally through the gray reticular formation, just ventral to or across the spinal root of the trigeminus, to emerge at their superiK-ial origin along the bottom of the postotivary sulcus, incorporated with the afferent fibres in the five or six root-fasciculi forming the entire ninth nerve. The cortical con- nections of the motor fibres are established by cortico-bulbar fibres that arise from cells situated within the gray matter of probably the lower part of the precentral gyrus. After traversing the motor path through the corona radiata, internal capsule, cerebral peduncle and pons, the cortical fibres end, on reaching the upper level of the medulla, in arborizations aroimd the motor root-cells chiefly of the opposite side. Fig. 1074. Olbctorybulbf, OpMc iBtcnul carotid vtery Optic cMum v. BCrrc. ftcnsocy fact- Ccfcfanl p«duiicl<.J. Middle peduncle of ccrctjclluni' IX.JCudXI. Dcrve« Lachrynul glaad Supratrochleu Bene Superior rectiM muscle l.evalce palpcbne Mjperioria Lachrymal Bctvc IV. I Mandibular nerve VII. nerve, motor pan ParalntcnncdU VIII. Si^ieriar peduncle of cerebellum, cut IX..X.aBdXI.nerve< Floor of IV. ventricle 'Spianl portiona of XI. nervet Interior aspect of base of skull, viewed from above and hehind. showing particularly posterior group of cranial nerves passing from brain-stem to points of emergence through dura ; posterior part of skull has been removed. Central Connections of the Sensory Part of the Olosso-Pharyngeal Nerve. — ^The afferent or sensory fibres of the glosso-pharyngeal nerve are the axones of cells within the jugular and petrous ganglia situated along the upper part of the nerve-trunk. Entering the skull through the jugular foramen, the sensory fibres approach the brain-stem in the five or six delicate root- bundles that reach the medulla along the groove between the olivary eminence and the inierior cerebellar peduncle. Passing to the ventral side of the spinal root of the triger->inus, or traversing this field, in company with the motor fibres, the afferent fibres continue dorso- mesially through the formatio reticularis grisea towards the dorsal nucleus. Just before reach- ing the latter, however, the sensorj' fibres separate into two groups, a medial and a lateral. The fiist and smaller of these continues its course to the dorsal sensory nucleus, around the cells of which its fibres end. It is probable that the cells constituting the upper groups of the dorsal sensory nucleus are particularly concerned in receiving the impuls«» giving rise to gustatory impressions, since the glosso-pharyngeal is recognized as the ner\'e of taste. Considering the fact that the afferent fibres of the facial nerve, which constitute the pars intermedia of VVrisberg, are distributed peripherally chiefly by the chorda tympani, are also concerned in conveying taste-impulses and end, in part at least, in the same nucleus as does the ninth, the sensory portion of the seventh nerve may be regarded, at least functionally, if not from a morphological standpoint, as an aberrant strand of the glusso-pharyngeal. THE GLOSSOPHARYNGEAL NERVE. 1 26 J The second and much Urger group turns outward and abruptly downward to form the chief constituent of the spinal tract, the latctculm •oUt«iu». In transverse sections ( Fig. 927) the latter appears as a conspicuous, compact, rounded bimdle, that lies lateral to the dorsal nucleus and behind the strands of root-fibres. The solitary fasciculus is accompiinied through- out its course by a slender column of gray matter, which lies partly on the surface 01 the bundle and partly amongst its fibres and contains numerous ner%e-cells of small size which constitute the reception-staUon for the greater number of the afferent fibres of the ninth ner\ e. Since these fibres ire continually ending at different leveU in their descent, it follows that both the fascic- ulus and its nucleus gradually diminish in size. unUl, at about the level of the sensory decussa- tion, they are no longer distinguishable. Course and Distribution.— Leaving the superficial origin along the groove separating the olivary eminence from the inferior cerebellar peduncle, the isolated root-fasciculi, about half a dozen in number and in series with those of the vagus, assemble to form a single trunk, which passes outward in front of the flocculus of the cerebellum to the jugular foramen. As it traverses thu, foramen, the glosso-pharyn- FiG. 1075. Diagram ihowing tympanic plexua and connections o( gloMo-pharyngeal nerve. geal lies external and anterior to the tenth and eleventh nerves and in its own separate dural sheath. It occupies a groove, or sometimes a bony canal, in the fora- men and in this situation presents two thickenings, t)\c jugular axiA petrous ganglta. Emerging from the foramen, the nerve passes between the internal carotid artery and the internal jugular vein and, dipping beneath the styloid process, follows a downward course along the posterior border of the stylo-pharyngeus muscle, with which it passes between the internal and external carotid artenes. Turning gradually forward, it reach^ the outer side of the stylo-pharyngeus muscle and stylo-hyoid ligament and disappears beneath the hyo-glossus muscle to break up into its terminal branchesto the tongue (Fig. 1079). Ganglia of the Glosso-Pharyngeal Nerve.— In the course of the nerve two ganr'ia are found, the jugular and the petrous. They contain aggregations of neurones whose dendrites constitute the peripheral sensory fibres and whose centrally directed axones form the sensory root-fibres of the nerve. ... Thejugulai- ganglion (g. superins) which may be regarded as a detached portion of the petrous ganglion, lies m the upper part of the groove occupied by the glossc -^ryngeal nerve in its transit through the jugular foramen. It is variable in siz. and not always present and measures only from 1-2 mm. m length. The gapglion does not include the entire thickness of the nerve but only the inferior ijortion, the fibre* of the superior jwrtion passing umntemiptedly over it. 1364 HUMAN ANATOMY. The petrous ganglion (g. pctrosam) is larger than the jugular and involves the entire nerve. It is oval or fusiform in shape, n»easures from 4-5 mm. in length, and is lodged within a slight depression in the lower part of the groove for the nerve in the jugular foramen. . , . ^, . , •. c The communications of the petrous ganglion include filaments (a) from the superior cervical ganglion of the sympathetic, (6) to the auricular branch of the vagus and sometimes (c) to the ganglion of the root of the vagus. Branches.— The branches of the glosso-pharyngeal nerve are: (i) the (ym- panic, (2) the pharyngeal, (3) the muscular, (4) the tonsillar and (5) the lingual. I. The tympanic nerve (n. tympanlcus) or Jacobsoris nerve, arises from the petrous ganglion as its most important branch and traverses a tiny canal in the osseous bridge between the jugular fossa and the carotid canal. Entering the tym- panic cavity and receiving fibres from the carotid plexus of the sympathetic by way of the small deep petrosal (n. caroticotympanicus), the tympanic nerve pawes upward and forward in a groove on the promontory and breaks up in this situation to form the tympanic plexus (plexus tympanlcus Oacobsonl] ). After distributing filaments to the mucous membrane lining the tympanic cavtty and the associated air-spaces (mastoid cells and Eustachian tube), its fibres reassemble and join with a filament from the geniculate ganglion to continue as the small superficial petrosal nerve to the otic ganglion (Fig. 1075). ,,. , , . Branches.— These are : (a) the small superficial petrosal nerve, (6) the trancA to the fenestra oralis, (c) the branch to the fenestra rotunda, (rf) the branch to the Eustachian tube, {e) the branch to the mastoid cells and (/) the branch to the great superficial petrosal nerve. a The stnall superficial petrosal nerve (n. pctroms raperficUlis minor) (Fig. 1075) is the continuation of the tympanic ner\e, formed by a reassembling of the fibres of the plexus, sup- plemented by a filament from the geniculate ganglion of the facial. It traverses a canal which begins at the anterior superior portion of the tympanic cavity, passes beneath the upper end of the canal for tlie tensor tympani and appears on the superior surface of the petrous portion of the temporal bone, to the outer side of the cranial opening of the hiatus Fallopii. While in the canal it sometimes receives a communicating branch from the great superficial petrosal nerve. It leaves the cranium through a canal in the greater wing of the sphenoid, or through the fissure between the greater wing and the petrous portion of the temporal bone, and on reaching the bast of the skull, joins the otic ganglion as its sensory root ( Fig. 1075). ..... b. The branch to the fenestra ovalis supplies the mucous membrane in the neighborhood of the oval window. c. The branch to the fenestra rotuuda is distributed to the mucous membrane over and around the fenestra. ,. ,. d. The branch to the Eustachian tube supplies the mucous membrane lining the osseous portion of that canal. e. The branch to the mastoid cells supplies the mucous lining of these cells. / The branch to the great superficiat petrosal nerve joins the latter in the hiatus Fallopii. 2. The pharyngeal branches (rr. pharyngel) number two or more, of which the largest descends along the course of the internal carotid artery and joins the pharyngeal branch (S of the vagus and sympathetic to form the pharyngeal plexus, which supplies the mucous membrane and muscles of the pharynx. The smaller pharyngeal branches pierce the superior constrictor and are distributed to the mucous membrane lining the upper portion of the pharynx. 3. The muscular branch (r. stylopharyngeus) enters the stylo-pharynegus, and, after giving off fibres for the supply of that muscle, passes through it to be distributed to the mucous membrane of the pharynx. 4. The tonsillar branches (rr. tonsillares) are given off near the base of the tongue. They are slender filaments which form a plexiform ramification, the circulus tonsillaris, around the tonsil. From this plexus filaments are distributed to the tonsil, the soft palate and the faucial pillars. 5. The lingual branches (rr. linguales) are the two terminal filaments of the nerve. The larger posterior branch passes upward and separates into a nwnher of filaments which supply the circumvallate papillae and the mucous membrane covering THE VAGUS NERVE. 1265 ihe Dosterior part of the doreum of the tongue, the glosso-epiglottic and phaiyngo- SgCc fo ds^and Ihe lingual surface of the epiglottis. The --"»"-; -ff-"'' ^^'"""^ !uppUes the mucous membrane of the side of the tongue half way to the Up. Fig. 1076. \ DteaMric.i bdly in part [. cer^kal 1 Sptoat acc«Mory ncrrc - Ocr^rfttUs miBOc nerv* . II. ccrvkal n HypoKlawal(XlI'> ■ Sup, cerv. nagl. of «ymr"thrtc- *^ Br. Uon II. cerv. atn»^ to ip. wcQtr^ III. cervical iier»«- CommtinicuM IqrpoBloNl - GcMtaufk.»iwliuperf.c«rv.n«r»«»- IV. cervical ntr V. cervical nerve Br.lBrfaomboldcl-. ' cxienal "plerjK'wi [.br.V.Bvrvc f) Chorda I f lympanincrve k-Int. pteryiioid r t-dKrof or^l mu- (out mcmtvane CloHO-phao ngcal serve -Mental nrrxr inf. tirntal nerrc. It«ta) {Mirtioo iubtinKual vlasd ibmasUlarr uaaiX'- -Styto-|))uryiveu» • TlijfO-hjotil bt. XII. o«r<« h^/^A Cominunicatlag br. tn s|i. acLcawry - A cutaneous br._ ^^//.£ 111 ndcM hypogloMl ■-til.tanr"*"'""*' rhnoic ncrr« .ScalnusuUco jubda'iu utny D«p diMection of neck .howln, ninth, tenth, eleventh .nd twelfth cfnial nerve, and their branch... THE VAGI ^ "NERVE. The tenth vaeus or pneumogastric nerve (n. vagus) is the longest and most widely distributed of the cranial series. Starting in the cranium, .t passes th^gh The neck thorax and upper part of the abdomen before breaking up mto Us terminal Irancht: In adSn^to ceVmin filaments concerned with special functions distnb- Sio^he heart and abdominal viscera, it contains both motor and «e"««7y Jfr^^;. Some of the motor constituents of the nerve arise from its own origin, but the ma^or hv^rhaps are contributions of th^ arcessorius va^i, the so-called accessory part of h'L'^pinaraccLory nerve. The vagu, suppli«, motor fibres to the mu^^f j^J^^"^^^ soft oalate (with the exception of the tensor palati and, probably, part y the levator ^irind Sygos uvute). pharynx. CBsoohagtis. stomach and ^-^^^^^.f"^;"^^^^ exception of the rectum), and to those of the larynx, trachea, and bronchi ^"d their "ffiTons. It distributes sensory fibres to the dura mater, externa ear, phar^ nx, ^phagus, stomach, larynx, trachea, bronchi and subdivisions and pericardium. So ia66 HUMAN ANATOMY. Special fibres are furnished to the heart, liver, spleen, pancreas, kidneys, suprarenal bodies and intestinal blood-vessels. It is generally admitted that the bulbar or accessory portion of the eleventh nePi'e forms an integral part of the motor division of the vagus, and, hepce, should be included with the efferent fibres of the tenth. As to the ultir ite distribution of these accessor)- fibres, and conversely of the vagus motor fibres proi>er, much discussion and many conflicting views have existed and, even at present, a consensus of opinion can scarcely be said to have been reached. After reviewing the evidence, both anatomical and experimental, Van Gehuchten ' concludes that the accessory fibres are distributed chiefly, if not indeed exclusively, to the larynx through the Infe- rior laryngeal branch of the vagus, and are continued neither to the heart nor to the stomach. The efferent vagus fibres proceeding to the heart are inhibitory in function ; whetfier they directly reach the cardiac muscle is doubtful, since, reasoning from analogy, it is probable that the vagus fibres end around sympathetic neurones whose axones are the filaments coming into immediate relations with the muscle-fibres. Of the efferent fibres of the vagus distributed to the stomach and other parts of the digestive tract, some are secretory, while others, possibly, influence the caliber of die blood-vessels, in both cases being interrupted in sympathetic ganglia before gain- ing their destination. Deep Origin of the Motor Portion. — As stated above, the efferent fibres of the v^;us consist of two sets, vagus fibres nroper and those derived from the acces- sory portion of the spinal accessory. T' -^ r have their deep origin in the nu- cleus ambiguus and the dorsal motor , .'ries with the motor fibres of the ninth nerve; the accessory fibres a~ •-. nucleus ambiguus only. The detailed description of these nuclei ha > )age 1260). The fibres arising from the nucleus ambiguus at first p. ^~ toward the floor of the fourth ventricle, then bend sharply outward ...i,., idensed into compact strands that receive the fibres originating from the motor cells of the dorsal nucleus, proceed, ventro-laterally in company with the sensory fibres, to their superficial origin along the postero-lateral groove behind the olivary eminence. Central Connections of the Sensory Portion. — The afferent root-fibres of the vagus are the axones of the neurones lying within the ganglia of the root and of the trunk situated on the upper part of the nerve. The centrally directed processes jMss into the medulla, in company with the motor strands, and divide into two sets. Those forming the larger of these end in arborizations around the cells within the lower portion of the dorsal sensory nucleus ; those of the smaller set bend downward and enter the fasciculus solitarius to terminate in arborizations around the cells of the spinal nucleus of reception. (For details of these nuclei see page 1260). As in the case of the other mi.xed nerves — the fifth, seventh and ninth — the secondary- paths distributing the sensory impulses include (a) fibres that pass from the recep- tion-nuclei to the tract of the mesial fillet, and so on to the great brain, and (b) those that pass to the cerebellum. Course and Distribution. — The vagus, disregarding its accessory fibres which at first are incorporated in a common trunk with the eleventh nerve, arises from its superficial origin by a row of twelve or fifteen filaments which emerge from the surface of the medulla along the postero-lateral sulcus between the olivary eminence and the inferior cerebellar peduncle. These fasciculi lie in series with those of the ninth nerve above and of the eleventh below (Fig. 1046). After leaving the surface of the brain-stem, the converging rootlets of the vagus fuse to form a single flattened trunk, which passes outward beneath the flocculus of the cerebellum to the jugular foramen (Fig. 1074). The trunk leaves the cranium through the rear division of the middle compartment of this foramen, invested by a dural sheath shared by the spinal accessory nerve. In this situation it presents a ganglionic enlargement called the ganglion of the root. Emerging from the jugular foramen, the vagus bears a second thickening, the ganglion of the trunk, and enters the carotid sheath, through which it passes downward the entire length of the neck. Within the carotid sheath the nerve lies at first between the internal carotid arterj- and the internal jugular vein, and then between the common carotid artery and the vein, occupying the posterior groove between these vessels. At the root of the ' Anatomic du Systfeme Nerveux, 1906. THE VAGUS NERVE. 1267 KiG. 1077. nerv., .h.^.,^/«». g: «' rrfh^i-^'T^^tJ^^ oMhe\.i;» "h. greater part of the jugular foramen. ia68 HUMAN ANATOMY. The cammttiiieatioiM o( this ganglion include filaments which pass between the ganglion ami («) the facial and (4) spinal accessory nerves, (< ) the superior cervical ganglion o< the sympathetic nerve and {d) thp petrous ganglion of the glosso-phar>-ngeal. The ganglion of the trunk (g. nodoram) or lower ganglion (Fig. 1077) is a reddish, flattened, fusiform group of ner\'e-«.ells. It lies beneath the jugular foramen, about i cm. below the ganglion of the root, and measures from 1.5-2 cm. in length and about 4 mm. in diameter. The accessory part of the spinal accessory nerve passes over the ganglion on its way to fuse with the vagtis, which it does usually immediately beyond the ganglion. The communications of this ganglion include filaments which pass between the ganglion and (a) the hypoglossal .ind (A) spinal accessory nerx'es, (c ) the loop between the first and second cervical nerves and ( "de and of the posterior inferior portion of the external auditory meatus. While traversing the temporal bone the auricular nerve communkatM with the facial and, after reaching its area of distribution, with the posterior auricular nerve. Variatioos.— The auricular nerve may be absent or may fuse with the main trunk of the iadaL its fibres under these drcumsunces probably reachinn their destmation through the pos- terior auricular nerve. Its branch of communication with the facial may l>e alwcnt. 1 The pharyngeal branchea (rr. pharyoKei), usually an upper and a lower but sometimes more or only one, are given of! from the upper portion of the gang- FlG. LvMt iMHl •( oMnri MttM 1079. PMutnocuIrk ■•'« lafctioc deMil ««"« Spinal accccaory BCn* Fart o( hdal on HypoiloaMi Stylo-phaiyBCCua nii«cl«' Olaaao-phaiyagaal nerve I. cervical nerve PncumoKaatric nerve -vupenor cervkajganjllon of ayui|flUMnc Superior laffynffcal nerve DannBitom hypogloirt U.ccTTlcal III. centcal ntr.f Middl* cenical ff»OKli«ML Bnuichea from Inf. cervical gasiflton Infartor cervldl cardfftc of aympailhrtic Recurrent laryngeal' nerve Internal mammaij artery , , _. Cartilage athetic. In thf lower part of the larynx the external laryngeal nene inosculates with the terminal fibres of the internal laryngeal. At the inferior portion of the larynx, the internal laryngeal nerve communicates with the terminal filaments erf the external laryngeal, and in this way supplies sensory 'ibres to the mucous membrane lining the lower part of the larynx and to the muscles. Variation. — Instead of passing to the inner side of the intern ' carotid artery tin- ncr\'e .;.- lie external to it. a. The external laryngeal branch (r. externns), much smaller than the in- ternal, pa.sses downward ufion the inferior constrictor of the pharynx and beneath the infrahyoid muscles to the crico-thyroid muscle, which it supplies. It sends filaments also to the inferior pharyngeal constrictor and gives off a cardiac twig which joins the superior cer\'ical cardiac branch of the sympauetic. Variations — The external laryn^al has been seen to send filaments to the thyroid gland, the pharyngeal plexus, the stemo-hyoid, stemo-thyroid, thyro-hyoid and crico-arytenoideus lat- eralis muscles and to the mucous membrane ot the vocal cord and lower portion of the lar)-nx. b. The internal laryngeal branch (r. intcrnus), larger than the external, passes downward and inward between the middle and inferior constrictors of the pharynx and enters "the larynx by piercing the thyro-hyoid membrane By means of its epiglottic, pharyngeal, descending and communicating branches, it supplies the mucous membrane covering the internal and pharyngeal sur^ces of the larynx and the mucous membrane of the base of the tongue. Variation. — Instead of pit-rcing the thyro-hyoid membrane the nerve may obtain entrance to the lar>'nx through a small foramen in the thyroid cartilage. 5. The superior cervical cardiac branch (rr. cardiaci superiores — both cervi- cal cardiacs) arises from the vagus in the upper part of the neck. It either joins a cardiac branch of the vagus or passes independently down the neck and along the side of the trachea to end in the deep cardiac plexus (Fig. 1 132). 6. The inferior cervical cardiac branch leaves the vagus at the root of the neck. On the right side it courses along the side of the innominate artery and either independently, or after joining one of the other cardiac nerves, enters the deep car- diac plexus. The left passes in front of the arch of the aorta and joins the superior cervical cardiac branch of the left sympathetic to form the superficial cardiac plexus (Fig. 1132). 7. The inferior or recurrent laryngeal nerve (n. recnrrens) (Fig. 1080) differs on the two sides in the early part of its course. The right nerve is given oft at '^mm mm "!¥» THE VAGUS NERVE. 1271 .h^ root of the nee • aRUS crosses the anterior surface of the subdavianartcr>-. I^whidiD^inr , under and behind the artery and ascends. The /r// ««^* STu o iJTn » ' ..^"crosses the anterior a.s,>ec\ of the aortic arch, andafter Sne Wow andUhmdlhe arch, lateral to the obliterateasses upward iH>stenor o he '3 shSu.. either anterior or posterior to the inferior thyro.d arterv-. occup.es the Fiu. 1080. ,,.,,rt» Mtvlal «■*''"•■*•'" ■*' Ififkffioff cfTvh:*! gmatfUs*. t,.,iKtM« of tym|»ttmlc !• Jmooarr bcUKb o(M«na'P"'^°";.,7l«!?irfarlwna^tfc first thoracic. In one instance the nerve left ?hrsubduril°Z* bjfow t?fe fi^t cei^iiSl H^rve'^and re-entered at a higher level. Quite fre- Ihe su'~"™,flf "^j^rJi^ ,he ,terno-mastoid muscle. In one reported case the nerNe ended in ouentlyitfails topierw the^emo^mastow^^ ^ fourth cervical nerves. te'STfa^s have SX^id Wd^tiL ^oom of.the University of Pennsylvania. R^ly it ^ves off a filamem which joins the n. descendens cerv.calis. Practical Considerations.— The spinal accessory nerve supplies the sterno- deido-mastoid and trapezius muscles. A few fibres of the second and third cer^'.cal ne?v« enter into the ^pply of the stemo-mastoid. but the muscle is almost com- SeTefy under the control of t^he spinal accessorj-^ The cervical nerves take a greater part in the supply of the trapezius, so that paralysis of the spinal accessory does not ''"'^p^mWe'^r"pe"t will^ the head backward and toward the affected side anTwiU pull the scapula toward the spine. In spasm of the f erno^m^toid as in -'vry neck," the chin will be turned to the opposite side and elevated, whUe the Lar will look forward. If both stemo-mastoids are m contraction the chin will be n the med^ line and will be drawn toward the sternum. Paralysis of one muscle will JirXe a condition somewhat similar to that produced by a spasm of the opposite °"^' The spinal accessory nerve enters the under surface of the sterno-mastoid muscle near the iuncUon of its upper and middle thirds, where it may be reached by an TncTsiin along Ae anterior border of the muscle. The nerve emerges from the muscle near the middle of its posterior border. THE HYPOGLOSSAL NERVE. The twelfth or hypoglossal nerve (n. hypoglossus) is a purely motor nerve and supplied th^musculaturVof the tongue, intrinsic as well as extnnsic, with the excep- tion of the palato-glossus. Cntna .nd Coiticri Conneetteni.-The hypoglossal nerve takes its deep origin from severda^ia^wl groups of neurones called the hypoflo.«lnucleu. (nuCu. .. hyPOfKo-n Tpig 949rwhkh underiies the floor of the fourth ventricle. This n!«^'«« '« » """."^ elonKated collection of large multipolar cells, measuring about 18 mm. m length by a mm. fn wWtiT tharpartly corresponds in position to the tng^m hypoglosst in the floor of the ourthvCT rice The entire nudeusrhowever, is more exteasive than the tngonum and Ixt^nds C the level of the stri^ acusticx above into the closed part of the m^^duHa ».s fa down as the decussation of the pyramids (Fig^ 9«7). U «- ,yi"^^;"f ^^e^^o^'^^h v^^^^^^^^^^ to the central canal of the medulla and the median groove in the floor of »•'« fourth ventncle^ r?ose to the mid-line and its fellow of the opposite side. The large sire and branched form o^he neVle-^Hs com^^ the nudeus. as wdl as their venttjil position m relation to the'tnUaT^a. emp^siJ the close co-espondence of thesej^m™^ ^.^ S^y'mattel the motor roots of the spinal nerves. Indeed, as noted later (page 1380), '"^P^V "J;!^" ;nci™?nethrhvpoKlossal nucleus is the morphological equivalent of the bases of the antenor c'rir' tmSr^er arising and beTore leaving the ""^«- /''f, /-'^^f'":^ into a number of fasciculi which, emerpng from the ventral aspect of the nucleus, take a ventr"^ cour^Tnd trTverse' the infernal between the gray and white ^etio^ar formations^ From'his situation the hypoglossal fibres continue the r ~"«f;° ^^ ''"^""V^j^^'^'^itt medulla bv oas-sine for the most part, l)etween the nucleus of the inferior olive and the mesial TcJlry oC nudJus. althoug'J, quite a number of the strands penetrate tiie ventral portion °' %tTn^r:onn^tnV of- the hypoglossal nucleus include :(«) crossed fibres from the nuclei of throprshrlde; (*) fibr^rom. and probably also to. the PO?»«""r '""P*"''": feSus by mearorwhich the nudeus of the twdfth is brought into relation with the nude Toth.r cranial nerves • and (c\ fibres which join the dorsal bundle of bchUtz. a system of •iSudinTfibr^Tnderbing the floor of '-e fourth ventride and traceable upward beneath U.e%Man aqueduct, but'conceming wha lestina.ion and «""-"°- 'f ' :;:,^"„7:_,,,„ur The cortical centre of the hypoglossal nenje P"'*^Wy ''*•*'''''" '^''".^^'^"^eKtl^h^ extremity of the precentral convolution. The fibres arising as the axones oJ the «'" wiinin *hTa™a i^s, over ti^ upper border of the lenticular nudeus and through the mtemal capsule and X^d Tn the ^afn^tem within the medten part of the pyramidal tract as far as tiie 1276 HUMAN ANATOMY. medulla. The cortko-nudear fibres then bend dorso-medially and, for the most part but not entirely, cross llie raphe to enter the ventro-tateral surface of the hypoglossal nucleus of the opposite side and end in arborizations around the root-cells. Course and Distribution. — The hypoglossal takes its superficial origin from the surface of the brain-stem in the form of from ten to fifteen slender tasciculi, which emerge from the ventral surface of the medulla in the groove between the olivary eminence and the pyramid (Fig. 1046}. Fig. 1083. //^ 1. thoracic ncrra l>iUAnuKh of V. nerte ^ Chorda tympani nerve Internal pterygoid niuKlc Edge of oral mucous nieml>rane rlosso-pharyngeal nerve Mental nerve Inferior dental nerve, cut uMlngual gland laalllary ganglion yto-h)iT>id muscle 'Thyfo-hyoldbranchof XII. nerve -Superior laryngeal nerte .Descendens hypoglossi ; sympathetic cord is to its outer »ide Vagus Dcrve Cxteraal laryngeal nerve Omo-hyold muv 1r. > ut Ffirenic nerve Middle cm ical ganglion of sy ntpalheilc -Scalenus anttcus muscle 5Uiclav(an artery De«p dissection of neck showing branches of vo^us, spinal accessory and h>-poglossal nerves. These root-bundles pass outward, dorsal to the vertebral artery, and assemble into two groups, which pierce the dura mater separately at a point opposite the anterior condyloid foramen. Either within this canal or as they leave the cranium through its external opening they unite into a single trunk. Arriving at the inferior aspect of the base of the skull, the deeply placed hypoglossal ner\'e descends and hooks around the ganglion of the trunk o* the vagus, to which it is closely attached by connective tissue. It then take: downward and forward course between the internal carotid artery and th" internal jugular vein. Arriving at the inferior margin of the posterior belly of the digastric, the nerve winds around the occipital artery .md cnitrses downward and forward to the otitcr side of the external and internal carotid arteries. It then continues forward above the hyoid bone to the under surface of the tongue, passing beneath the tendon of the digastric, THE HYPOGLOSSAL NERVE. 1277 under the stvlo-hyoid and mylo-hyoid muscles and over the hyo-glossiis (Fig. 1082) It temS by piercing tL genio-hyo-glossus and breaking up into a number of fibres for the supply of the lingual muscles. C«nmimiction..-Immediately after emerging from the anterior ™"''y>°''* ♦°™"*"',i,''] •inv^^n^n^ts with the superior cervical ganglion of the sympathetic (4) one or two a tiny '^'*J°""!! jj^"" i^j^een the first and second cervical nerves and {c) several fibres •^'"Jll-I^te thTnervI wi MhetSon 0I the trunk of the vagus. At the point wljere the hypo- associate the 3^ ^'"L'i'^A^^ cross, id) the lingual branch of the vagus joins the twelfth ; K the nerv"e fes^-Th SyWid and u4« the hyo-glossus muscle, it communi- rates with (e) the lingual branch of the mandibular nerve. Branches.— The branches of the hypoglossal nerve are : (i) the meningeal, ( ,\ thi. descendinir, ( \) the thyro-hyoid and (4) the Itngual. . (2) the rf«««rf»«^ W J^^^ J „eninge«s) consists o one or two minute filaments^whic" supply the dura mater of the posterior cranud fossa and the d.ptoe S the .ScioilS bone As the hypoglossal is motor in hinction, it is likely that these it a^SribCted to the ner^^^y the loop between the first and second cer^-lcal "*'^?' The descending branch (r. descendens), or r. descendens hyfioghssi,^ in realitv only to rLited extent a branch of the twelfth, since the greater number "( ^^fihr^ arc accessions to the hypogkjssal from the first and second cervical rl« T^ere is r^n however, tobdieve that these cervical nerves are not the SliveLurce d Sbf« of th^ descendens hypoglc«si. but that some anse fro. the^e Is oT^the hypoglossal nucleus. The descend ng branch arises near the point where the hyi^lS nerve hooks around the occipital ^^ery »nd runs downwam rnd?nward Wont of or within the carotid sheath. It gives of! a branch to the an- terior My o Sie omo-hyoid and, about the middle of the neck joins the descend- n^ce^ica nerve, or «. cimmumcans hypoglossi, from the second and third ce^icalTer^es. A W or plexus, termed the ansa kypcglosn, is thus formed and ^om?t filamfnts are supplied to the sterno-hyoid and stemo-thyroid muscles and to the posterior b.Uy of -.omo^h^o^ .. \ f »K» Wn «sal as its fibres can be traced back to the cervical Sus 1t L give^oh t4t;eThe ner^e'dips beneath the stylo-hyoid muscle and P^ down biwnd the greater comu of the hyoid bone to reach its distribution to the thyro-hydd muscle. ^^^^^^ ^^^^^^^^ ^^^ --P'n/'^'rh !l?d 1 1i;ctrih„tion of the hypogl(»sal. As the nerve lies beneath the mylo-hyoid mtscle £rts LeVen o^^ to the hyo-glo^us the stylo-glossus a^d the muscle "l^^""" ". K gen b-hyoid are in aU probability de- ^vl^'fSm the cervix Ple^^^^ hyWo-^ origin. After giving off the above-named branches, the hypoglossal nerve breaks up into the terminal fifamenu wWch pierce the genio-hyo-glossus to supply it and the l.ngualis muscle. w.,i..i„n. — Occasion.illy the hypoglossal has been found to possess a posterior root bear- ^"^V^^'lli^S-^ Si is to^regarded as a persistence of the temporary embryonal ing a ganiflion. .^n's condition is " ^ -^ . ^ posterior root and a ganglion of Konep stage during which «''f. n^'^%;i'Xui oridn wasMwated at the p«-:ut:.ior aspect of theme- (page 1380). In one case the ^"P*™"^' ®"S'" *^ beUveen the rcotlets of orSn and in rare d\;ila. Quite freq-jej^'y ^^JL^m^'L c?S fSament siTutted eitV^^^^^ Se genio-hyo- instances behind them. Sometimes a crc«sniam« i^ connects the two hypoglossal glossus a"d Kjmio-h^o^u^^es or .^^^^^^ ^^ ^^^ mylo-hyoid. tg digas- nerves. Rarely the "yPOK'"'***' ''~,^'' „„ ,i,p r Hem endens hvpog'ossi seems to be derived, trie or the "tylo-hyo.d musde^ ,?« ™tu\?n iheSa^s trLres can be traced back to §?aTc?i\rprrbtderi:X^H^iri^^^ °^ f^'- va^"- The r. descen- dens hy^glo^i may send a b^ch to the stemo-masto.d muscle. Practical" Considerations.— Involvement of the hypoglo^al nerve usually . ^^If^ith other cranial nerves is frequent in bulbar disease. The most character- LT* mjt^mt aVe'i^^^ fongu'e, when protruded to the affected side, caused 137* HUMAN ANATOMY. by the unopposed action of the muscles of the opposite side. The nerve may be injured by operative or other wounds in the submaxillary region or in the mouf' , as in gun-shot wounds. It can be easily reached in the submaxillary region by the same incision as that used for ligating the lingual artery (page 736). It passes for- ward to the tongue, just above the hyoid bone, and forms the upper boundary of the small "lingual triangle," which is exposed when the submaxillary gland b elevated. THE SPINAL NERVES. The cranial division of the somatic nerves having Ijeen considered, the spinal group next claims attention, the visceral or splanchnic (sympathetic) nerves being reserved for a final and separate description. The spinal nerves (nn. spinales) mclude a series of usually thirty-one pairs of symmetrically disposed trunks which pass laterally from the spinal cord and emerge from the vertebral canal through the intervertebral foramina (Fig. 880). Elach nerve arises from the cord by a dorsal sensory and a ventral motor root, which sepa- rately traverse the subarachnoid and subdural spaces and evag^nate or pierce the pia mater, arachnoid and dura mater. Within the intervertebral foramina the roots unite to form a common trunk, which carries with it a sheath composed of the three membranes, the contribution of the arachnoid and pia, however, soon ending, whilst the dural covering is prolonged to become continuous with the epineural sheath of the nerve. Nomenclature. — ^The spinal nerves are designated not relative to the position at which they arise from the cord, but according to their point of emergence from the vertebral canal. They are divided, therefore, into the cervical, thoracic, lumbar, sacral and coccj-geal groups. With the exception of those in the cervical region, the individual nerves are named according to the vertebra below which they emerge from the vertebral canal. On account of the disprojxtrtion between the eight cer\'i- cal ner\-es and the seven cervical vertebrae, this arrangement necessarily can not prevail in the neck. The first cervical nerve, often called the suboccipital nerve, emerges between the occipital bone and the atlas ; the second emerges below the first vertebra, the third below the secopd and so on down to the eighth, which traverses the foramen between the seventh cervical and first thoracic vertebral segments. Constitution. — Every spinal nerve arises by two roots, a posterior sensory and an anterior motor, the latter being composed of the axones proceeding from the motor neurones situated within the gray matter of the anterior cornu of the spinal cord, whilst the fibres composing the posterior or sensory root are the axones of the neurones within the ganglia which are invariably present on these roots. The formation of the common trunk, by the union of the two roots, affords opportunity for the two varie- ties of fibres to intermingle, so that the anterior and posterior primary divisions into which the common trunk divides contain both sensory and motor fibres. In addition to these fibres, which are destined for the somatic muscles and the integument, others are added from the sympathetic neurones for the supply of the outlying involuntary muscle and glandular tissue occurring in the regions to which the spinal nerves are distributed. It is evident, therefore, that the terms "motor" and "sensory," as applied to the somatic blanches of the spinal nerves, are relative and not absolute, since in all cases the nerves passing to the muscles contain sensory and sympathetic fibres in addition to those ending as motor filaments in relation with the striated muscle fibres. Likewise, in the case of the sensory branches distributed to the integ- ument, sympathetic filaments (motor to the involuntary muscle of the blood-vessels and secretory to the glands) accompany those concerned in collecting sensory impulses. On the other hand, where they retain their typical plan, as in the case of the thoracic nerves, the spinal ner\'es contribute motor fibres which end around the sympathetic neurones to supply motor impulses either to the involuntary muscle of the organs, by way of the splanchnic efferents, or to the outlying involuntary muscle along the somatic nerves m the manner above described. The sensory, posterior or dorsal roots (radices posteriores) of the spinal ner\'«- are usually larger than the motor, a condition due to the increased number of tht.i filaments and the greater size of those filaments (fila radicularia). The fas- ciculi which form the sensory root are attached to the cord along the postero-lateral POSTERIOR PRIMARY DIVISIONS OF SPINAL NERVES. 1279 o. o «^ntinuous series called the posterior root zone (Fig. 884). These E?^^Skruas;sss.t'Sp:^^5i«'v£ spinal ganglio|V aggregations of ner^'e-cells found on the The "P'J**^ 8""f ' .%,\^_,*^e°vM a 852V They are usually ovoid in shape, Tn'^!^ 'r^ in length Tdare^asto^ly bifid at ^heir proxiLl ends They ?^^ist"tf a cluster of unipolar neurones, whose centrally directed axones form he n!^.lro^t of the spinal nerve a.id whose dendrites e.xtend peripherally as the L2 A^thoueh s'ia^ed ^^ond the dural sheath of the cord, with the e.xcept.on ofthe gang&of the ^SygLl nerve, they are invested by a prolongation of it. terior or both roots of one of the nervw ■""y^'O^f'^f^e Srior root having its own. "'^"0iSiS*^J^ran.^n'*°deSch3'^5^^^^^^^^ Wna. ganglia hyp<:^;astric nerve XII. thoracic, lateral cu- taneous br. Superficial dissection, showinit cutaneous branrhe« of posterior divi&inns and lateral cutaneous branches of anterior divisions of spinal nerves. dorsal muscles and integument. At the two extremities of the spinal series the division into internal 'uid external branches does not prevail^ the first cervical, THE CERVICAL NERVES. 1281 »K- fo..rth and fifth sacral and the coccygeal nerve lailing in this respect. Down to the muscles before reaching their cutaneous distnbuUon. THE CERVICAL NERVES. The first cervical nerve (n. wbocclplUlls). the first of the spinal series, « .v«S in sLver^lrra^ Its posterior rocit is either insignifi«.nt or entirely absent. fn^^D^t^rioriivtS^hich does not divide into internal and external branches. » Urte?tC the anterior and usually does not send of! any direct cutaneous branch. S nerTJa^ do^Uy between the occipital bone and the Po^.^"-' «<=^' »^* It^ and t.^^ the suboccipital triangle, occupying a posUion below and posterior to die vertebral artery. SupeHicial to it is the complexus muscle BrSSesi-rtese are : (i) the muscular, (a) the communuatxng and (3) the "''"T^he muscular branches supply the superior and inferior oblique, the com- P'^^'ir ^4.t^tTn^i^^tTxo^l ?X3Te"^nd cervi«d, nerve. It ^Ue to tie compSus! amercing which muscle it communicates w.th the great ***^'tte^.^k and close to the vertebra is a series of loops between the p<«terior '^ The second cervical nerve is distinguished by the size of its posterior division. ^^^ Ths Se (Fig 1087) passes upward over the inferior oblique, pierces The complex^ and ^^zius. ^alid accompanies the occipital artery to the s^p. 5 the ^sS half of ^hich it is the main -"-H-erve. It become supe^^^^^^^ SpS 5s£rartrsprld\^r i^nrmlr^^ b^^ci^^wth^^y the scalp as far forward as the vertex. The reat occipital nerve communicte. with the small and least occipiul and the posterior and great auricular nerves. rxlrrK^h*i5:iyt-ora"cSrSi2'fiia^ The third cervical nerve has a smaller posterior division than has the second Passine backward, the former helps to form the postenor cen-.cal Pl«"^ ""^^^J'^J^ in^ eltS and internal branches. The external branch (r. Uitenilis) supplira ac^^cS i« and th" .W/.W branch (r. mcdiaUs), known a, the '^^ ^^ / W S3 Zrve (a. occipitalis tertias), pierces the complexus. ^PlS^'"^,*"";.^?*""' '° supply the skin of the occipital and posterior cervical regions (Fig. 1083). 1382 HUMAN ANATOMY. In addition to assisting in the (ormation o< the poatcrior cervical plextis it commanicatea with tlie gnat occipital nerve. The fourth, fifth, sixth, seventh and eighth cervical nervea have quite small posterior primary divisions (rr. poatcrlorcs). The fourth, fihh and sixth divide mto the usual external and internal branches (rr. Uteralcs ct aMdiales), which supply respectively the adjacent muscles and the dorsal integument. The seventh and eighth usually have no cutaneous branches and are distributed solely to the deeper muscles of the back. A communicatinc filament from the foutth may aid in the formation of the posterior cervical plexus. Variations. — The cutaneous branches of the fifth and sixth may be ver>- small or absent entirely. THE THORACIC NERVES. The posterior primary divisions (rr. posteriorcs) of the thoracic or dorsal ner\'es (nn. tboracales) follow the general arrangement of dividing into external and internal branches. Of these the internal branches of the upper six are mainly cutaneous and the external entirely muscular. In the lower six, on the contrary, the external branches are principmlly cutaneous and the internal entirely muscular. The external branches (rr. lateralcs) gradually increase in size from above downward. They pierce or pass under the longissimus dorsi to reach the interval between that muscle and the ilio-costalis, eventually reaching and supplying the erector spinx. Those from the lower half of the thoracic nerves distribute sensory fibres for the supply of the skm overlying the angles of the ribs (Fig. 1083). The internal branches (rr. mediales) of the upper six or seven pass dorsally between the multifidus spinae and semispinalis muscles. After innervating the trans- verso-spinales they become superficial close to the median dorsal line and supply the skin of the back, sometimes extending laterally beyond the vertebral border of the scapula. The internal branches of the lower nerves traverse the interval between the longissimus dorsi and the multifidus spinx and supply the latter muscle. Variationa. — The sixth, seventh and eighth thoracic nerves may give off cutaneous twigs from both external and internal branches. The first thoracic nerve may have no cutaneous branch. THE LUMBAR NERVES. The posterior primary divisions (rr. posteriores) of the lumliar nerves (nn. lum- bales) divide into the usual external and internal branches. The external branches (rr. laterales) of all five lumbar nerves enter and sup- ply the erector spinse, those of the lower two terminating there. From the external branches of the first, second and third arise cutaneous offshoots (nn. clunium supe- riores) of considerable size (Fig. 1083). These pierce the ilio-costalis and the aponeurosis of the latissimus dorsi above the crest of the ilium and supply the skin of the gluteal region as far forward as the great trochanter. From the fifth a branch passes downward to inosculate with a similar branch of the first sacral nerve to aid in the formation of the posterior sacral plexus. The internal branches (rr. mediales) turn directly backward and supply the multifidus spinae muscle. THE SACRAL NERVES. The posterior primary divisions (rr. postciiores) of the sacral ner\-es (nn. sacrales), with the exception of that of the fifth, emerge from the vertebral canal through the posterior sacral foramina. The first, second and third pass outward under cover of the multifidus spinx and divide into external and internal branches. The external branches (rr. laterales) of the first, second and third sacral nerves unite over the upjjer part of the sacrum with a similar branch of the fifth lumbar and with the fourth sacra! nerve to form a series of loops, the posterior sacral plexus THE SACRAL NERVES. 1383 I'rr- FiG. 1084. Part of maUilWii» •p*n« mi»cle Loom of rommonicfttlon between V. luinbar. and I . II. *«m1 III. pottCTior Mcral nerves' ■ braiKlMtftMi From XII." tlwrscic iierw ■V. lumbar nerve, poftterior divtekn X. HcrmI nerve, po»terior diviai. II. Mtcral nerve, posterior di 111. iacni! nerve, po*it IV. Mctmlnervr Itviikm V.MCfmlixf" Coo yi{««l "> IV M .^^ » s««rferuT _ _- '•f "^ ■•*' fan of Ml •MKlHnMt — CuUMOuShr of IV.ulcit^ ' hm tMo »"■• ' levator Mii !*■' *"■ Dinection thowing Wt posterior sacral pleM«. breaking up as do the others into »>*" 7^"4'^^^i^^",7^ t^e posterior sacro- other and ujh^he -cjea - ^^^^>^ ^^I^ ^^S pl^e the ^^eat sacro-sciatic fi^S ale^giTe" offrbJ dSuted to the integument in the coccygeal region (Fig. 1081). 1384 HUMAN ANATOMY. THE COCCYGEAL NERVE. The posterior primary division (r. po«tcrior) of the coccygeal nerve (■. coccy- gCM) does not divide into internal and external branches. It unites with the fourth and fifth sacral to form the posterior sacro-coccygeal nerve, whose course and distri- bution are described above. THE ANTERIOR PRIMARY DIVISIONS OF THE SPINAL NERVES. The anteiior primary divbions (rr. anteriorcs) of the spinal nerves, like the posterior (rr. posuriorcs), contain fibres from both the anterior and posterior roots and, with the exception of those of the first and second cervical nerves, are larger than the posterior. After liberation from the main trunk at the intervertebral foramina, they pass ventrally and supply the lateral and anterior portions of the neck and trunk, as well as the limbs. Shortiy after leavii^ its foramen, each anterior division is joined by a slender bsciculus from the gangliated cord of the sympathetic, called the gray ramus communicant (page 1357). Branches to the sympathetic system are given off from some of the thoracic, lum- Fio. 1085. ijiy, g„d sacral nerves, in the shape of small fasciculi of medullated fibres, called the wUte rami communicanles. These are destined for the various structures of the splanchnic area and consti- tute the visceral or splanch- nic distribution of tt<'> spinal nerves. The remainder of the fibres are supplied to the body wall and ex- tremities and constitute the somatic distribution of the rferves. In the case of the cervical, first and some- times second thoracic, lum- bar, sacral and coccygeal nerves, plexuses of a greater or less degree of intricacy are interposed between the origin and distribution of DiacTun illustratinc constitution and division ol typical spinal nerve ; '~ ■'X, amcriot and poMerior roots; SG, spinal isnc- k;AD, PD, anterior and posterior primary divls- PC, LC, AC. posterior, lateral and anterior ctttancons biancbcs; 5C, spinal cord; .<*, /"i-. . lion ; CT, common trunk ; AD, PD, anterior and RC, ramus communicans ; Sy, sympathetic gaa(iioa and cord. the nerves. This renders the tracing of anyrset of fibres a matter of extreme difficulty, but in the greater portion of the thoracic region the original segmental and less complex arrangement persists. A typical spinal nen'e (Fig. 1085), such as one of those in the mid-thoracic region, is arranged as follows. The constitution of the main trunk (page 1278) and the distribution of its posterior branch (page 1279) have already been described. The anterior primary division (r. anterior) leaves the intervertebral foramen and almost immediately is connected with the gangliated cortl by gray and white rami communicantes. It then enters an intercostal space through which it courses between the external and internal intercostal muscles, both of which it supplies. At the side of the chest it gives off a lateral cutaneous branch (r. cutancus lateralis), which distributes a few tiny motor twigs and then pierces the external intercostal muscle to supply the skin over the kiteral portion of the trunk. On reaching the superficial Ktscia it usually breaks up into two branches, a larger anterior (r. anterior) and a smaller posterior (r. posterior). Havinp; given of! the lateral cutaneous branch, the main anterior primary division continues its forward course nearly to the mid-line, where it pier.t - the muscle and becomes superficial as the anterior terminal ctuaneous branch ( ineus anterior). THE CERVICAL PLEXUS. 1285 •^±;.C^ andThe aSfer^^^n "« Snd? of the anterior ..rima^ ^ST^ -STmu^^ ierivrtheir nerve- • " " fro... both .he antenor and the poaterior primary divisions. THE CEk NERVES. ^;S^: TSc J-CKument and diaph^^^ T^^^ ,='0.^ .^d fourth c^nmumcatejrcdy and fo^^ ^^fP jli,,, ,he fifth. *"l"':i.„^h and eSh°h aid^^y STfirst and sometimes by the second th«jracic form U^ Sl;;*"/?^!^!^; which Wl- the upper extrem.ty and the Uteral thoracic wall. THE CERVICAL PLEXUS. Th, «rvical Dlexus (plexo* cervicalta ) is formed by the union of the anterior priml^ dSiTn «iJ^) of the upper four cerv.cal nerve, (F.g. to86). After traversing the p,„ n^. intervertebral foramina, they pass behind the vertebral artery and emerge, the first be- tween the recttM capiUs lateralis and the rectus capitis anticus minor muscles, and the others first between the inter- transversales muscles and then between the rectiu capitis anticus major and scalenus me- dius muscles. Each is joined bjr a gray ramus communicans, derived either from the superior cervical ganglion of the sympathetic or from the association cord be- tween the superior and middle cervical ganglia. Under cover of the stemo-mastoid the four nerves are connected to form the cervical plexus. The second, third and fourth each divide into an ascending and a descending branch ; the first does not divide. Dimgnm lllostralint plan of cervical plexus. first does not divide. :rr«nilar series of loops that constitute the 1286 HUMAN ANATOMY. and the diaphragm, whilst others communicate with the ninth, eleventh and twelfth cranial and the sympathetic nerves. The Cervical Pi.Exrs. Superficial Branches. A. Ascending branches : 1. Small occipital 2. Great auricular B. Transverse branch : 3. Superficial cervical C. Descending branches : 4. Suprasternal 5. Supraclavicular 6. Supraacromial II. Deep Branches. D. External branches : 7. Muscular 8. Communicating E. Internal branches : 9. Muscular 10. Phrenic 11. Communicating I. The superficial branches are purely sensory-. They become superficial at the postti ior border of the stemo-mastoid, slightly above its middle, and from that point radiate in all directions to reach their cutaneous destinations (Fig. 1087). I. The small occipital nerve (n. occipitalis minor) (Fig. 10S7) may be either single or double. It originates from the second and third cervical nerves, or from the second only, and passes backward and upward beneath the deep fascia along or overlapping the posterior border of the stemo-mastoid muscle, where it gives of! (a) the cervical branches. It pierces the deep fascia at the upper angle of the occipital triangle and breaks up into its terminal branches : {b) the auricular, (<•) the mastoid and () a /ower set of branches. a. The upper branch.. ( rr. ,up.r.or«.) fonn an «'X' o,it"ZfalK^^^^^^^^^^ ubr branch -fTe facial nerve, »«'«;. ^'"tlnd^'s'hruJasteTerioma^^^^^ the mandible. of the iQwer part of the neck to the mid-hne as tar down a» llie sternum. 1388 HUMAN ANATOMY. Variation. — The superficial cervical, instead of a single nerve, may arise as two or more filaments from the cervical plexus. The descending branches (nn. snpraclavictilares) (Fig. 1A89) arise from the third and fourth cervical nerves and pass downward in the anterior margin of the occipital triangle along the posterior edge of the stemo-mastoid. On nearing the clavicle they break up into three distinct ;ets : (4) the suprasUmal, (5) the supra- clavicular and (6) the supraacromial. Fig. 1088. Third occipital nerve ^ Great ocdpitat nerve Bmndi from III. cervical, donat diviaion Branches trom IV. cer- vical, donal division Inosculation between facial nerveand ■mall occipital and great auricular Stemo-cleido-mastoid muscle Great auricular nerve Small occipital nerve , Superficial cervical nerve flnperilclal descending branch of cervical plezuH; the leader crosses the suprasternal brsncn ^~^n«l accessory nerve Moacnlar branch to trapezius branches Supraacromial branches Dinection showing superficial (^.anchcs o( cervical plexus and posterior cutaneous branches. 4. The suprasternal branches (rr. supraclaviculares anteriores) are the smallest. They pass over the lower end of the stemo-mastoid and the inner end of the clavicle and supply the skin of the chest as far down as the angulus Ludovici. One or two filaments terminate in the sterno-clavicular articulation. 5. The supraclavicular branches (rr. supraclaviculares mcdii) pass across the middle of the clavicle and supply the integument of the chest as far down as the third or fourth rib, inosculating with twigs from the anterior cutaneous branches of the upper thoracic nerves Variation. — A twig may perforate the clavicle. THE CERVICAL PLEXUS. 1289 fi The •uor.acromial branchei (rr. wpnidaviailares poateriorw) cross the da- ,„d P^te^or assets of the sh^^^^^^^^^ ^^ ^^P^ -^^^Ki Both arisUig beneath the stemo-mastoid. the former pass away from and the latter toward t^ -^^,"J- °'.?„^^^^^^^^ are distributed as foUows:- ,„.^xr=:::?in=:^tir^t^:^s^^ ««no-mMtoid plexus p.e. ,089. \ MitfCuUrbvt. 10 compleaui aiid Wvtatcr from occlp. »^|or Third ocdpitri »ef »• Fascial ««ptui« from Hg»m«rtB« nvt^m Gnat occipital oerrt Ractui capMt pnrticu Branch to obliquua Sfriacof lI.carTkatT«rtia Transverse profew II. thoratic vertcbrft I.evatar anguH Kapul^i; Trapezius Di«e.lio„ ol right »ld. of ■.«k, Aowin, d^r retatlon. »l cmical n«v». *. The «.p.«iu. receives fibres from t'ie^;;|^'^i ^^.^ ".^^^^^^^^ and acr.,mpany the descendmp b™"f « « ^^e supeM ^t tn^^^^^^^ ^^^ '^^^^ ^ ,^^,^ wHich^fiUmentsa^d^.^^^^^^^^ ""''°j:?he":c'L«u.m.diu.and(.).c.l.nu.po«ticu.alsoreceivefibresfromthethir^ 8. The communicating branches form P«i"ts of contact -^ "">- J^ - ^rld-™he^air1; ta-7;S i^^^ stemo-mastoid and subtrapezial plexuses. I390 HUMAN ANATOMY. 9. The muscular branches are dbtributed to (a) certain prevertebral muscles and to {6) the genio-hyoid and the infrahyoid muscles. a. The rectus capitis amicus major and minor and the rectus capitis lateralis are supplied by a iilament arising from the loop between the first and second cervical nerves. The intertrans- versales, the longus colli and a portion of the rectus capitis anticus major receive their supply from the second, third and fourth, and the upper part of the scalenus anticus receives a twi^ from the fourth cervical nerve. 6. The genio-hyoi<^ ^d the four muscles of the infrahyoid group are innervated by the cervical plexus in a rather roundabout manner. From the first and second cervical nerves are given off one or more branches which join the hypoglossal nerve shortly after its appearance in the neck. These fibres for a time form an integral portion of the hypoglossal and eventually escape from it as the nerve to the genio-byoid, the nerve to the thjrro-hsroid and the n. descen- dens hypoglossi (Fig. 1082). The last-mentioned nerve leaves the hypoglossal at the point where the latter crosses the internal carotid artery and then descends in the anterior cervical triangle. In front of, or sometimes within, the carotid sheath it forms a loop of communication, called the hypoglossal loop or ansa eervicalis (anca hypoglossi) by inosculation with the descending cervical nerve (n. deaceadens eervicalis) (Fig. 1082). This descending cervical nerve is derived from the second and third cervical nerves and at first consists of two twigs which later unite in front of the internal jugular vein. From this point it passes downward and inward as a single trunk to reach its point of entrance into the ansa hypoglossi. The ansa may be either a simple loop or a plexus and is situated anterior to the carotid sheath at a variable point in the neck. From it branches are given off to the stemo>hyoid, the stemo-thyroid and the posterior belly of the omo-hyoid (Fig. 1076). 10. The phrenic nerve (n. phrenicus), although an internal muscular branch of the cervical plexus, is of such importance as to merit a separate description. Whilst mainly the motor nerve to the diaphragm, it contains some sensory fibres ; in this connection it may be pointed out that the phrenic is not the only motor nerve to the diaphragm, the lower thoracic nerves aiding in its innervation. The phrenic arises mainly from the fourth cervical nerve but receives additional fibres from the third and fifth (Fig. 1090). It passes down the neck on the scalenus anticus, which it crosses from without inward, and at the base of the neck accompanies that muscle between the subclavian artery and vein. At the entrance to the thorax it passes over the root of the internal mammary artery from without inward and backward, occupying a position behind the stemo-davicular articulation and the point of junc- tion of the subclavian and internal jugular veins. It then follows a course almost vertically downward, over the apex of the pleura and through the superior and middle mediastina, to the upper surface of the diaphragm. The right phrenic (Fig. 1090) is shorter than the left on account of its more direct downward course and the greater elevation of the diaphragm on that side. It crosses the second part of the ~ -bclavian artery and accompanies the right innominate vein and the superioi cava on tlieir lateral aspert. It then passes in front of the root of th« and finishes it* course by de- scending between the lateral aspect of the pt lum and the . - 'astinal pleura. Nearing the diaphragm it breaks up at the antero-lat»ral asjject of the quadrate foramen into its terminal branches, a few of which enter the abdomen through this opening. The left phrenic (Fig. 1090), having to wind around the left side of the heart and reach the more inferior half of the diaphragm, is longer than its fellow, about one-seventh longer (Luschka). Entering the thorax between the subclavian artery and the left innominate vein it crosses the anterior face of the left vagus ner\e and continues its downward course by passing over the left side of the aortic arch. Reaching the middle mediastinum it courses in front of the root of the lung, behind the lower left angle of the pericardium, and descends to the diaphragm between the pericardium and the mediastinal pleura. It breaks up into its terminal branches before arriving at the thoracic surface of the diaphragm, which it enters at a point further frt)m the median line and more anterior than d-'ws tho right. Branches of the phrenic nerve are : («) the p/eura/,{6) the pericardiac and (f) the terminal. S5S THE CERVICAL PLEXl'S. 1391 Th- „i«ir.lbnnche« two in number, are almost microscopic in size, and are given tinal pleura. Mricardlacii.^ is a tiny filament which is usually given off the t«^'^^-^^ ^^^,„,v divides antero-lateral to the opening for the inferior vena cava mto (<.<,) an anterior and (A*), a R<«t«i°'^,'^^- ^^^„ the pleura into five or six fine twigs, which spread out j:^:.::^^n'^^r::^T^r:LZ^TJn.,or ^n ^ ... right costal portion of the Fig. 1090. ScBieniw mediiM mutel Vagus ne V. cervical nerve' Scalenus amicus muscle- rnper trunk of brachial plema VII. cervical nerve Superior i ntercostal artery' VIII. c«ivic«ii»itT« — — =■" I. thoncic nerre- - Clavicle;: — — jv. phrenic nerve Internal mam* — _ mary artery I nnomlnate vdM "^ Yen* c«v» supetioi — Uimg, mcalal lurlics ^StenKxleidtvinastoid Vagus nerve Internal jugular vein SubclaWan artery Omo-hyoid muscle Subclavian vein Clavicle 'SubcUvtusmoKte Lrib Pericardium - lluutwliint Mrml Vagus nerve Phrenic nerve Lunic, mesial uiriace. thowiniE hilum _ IV. rib Diaphragm, up- t>er surface VII. rib Oissecion-iowlngphrenic nerve.. P.pj---";--Jiil|S;X '«»—«' ' lung, are pun«i aside; KhraVI. and to the fnlcifonn lipment of the liver in the J-^J^ °*;'^^;,^^' ^^^^ quadrate abdominalis dexter ). The former supplies «"^ '""""r J""'"" ^^....ent branch which accompanies The latter traverses the quadrate foramen and firstpvesoffarecurre^^^ the inferior vena cava back to the right auricle. Aler giving oflth^s branch un^^ peritoneum some of its fibres «"»«' ^t'''-^*''"'' ZroMhe diaehrar^^ dUphr.gm.tic 139* HUMAN ANATOMY. laUral bratuh supplies the corresponding part of the left costal portion. The posterior branch (r. phreniCMbdcminalii liiiiiUr) is distributed to the left lumbar portion of the mus'-le of the diaphragm and usually either a filament passes to the left semilunar ganglion or seve.-al small threads to the coeliac plexus, one of which can be traced to the left suprarenal body. The phrenic nerve communicate* in the lower part of the neck with the middle or inferior cervical ganglion of the sympathetic. At the inferior aspect of the diaphragm it communicates, on the right side, with the diaphragmatic plexus of the sympathetic and, on the left side, with the semilunar ganglion or the cceliac plexus. Variations.— The phrenic may receive additional roots from the nerve to the subclavius, the nerve to the stemo-hyoid, the second or the sixth cervical nerve, the n. descendens cervi- calis or the ansa h)rpoglossi. It may arise exclusively from the nerve to the subclavius or, aris- ing normally, may give a branch to that muscle. It sometimes passes along the lateral border of or pierces the scalenus anticus muscle. Instead of descending behind the subclavian vein it may pass anterior to it or even through a foramen in it. . The accetsory phrenic nerve anses either from the fifth alone or from the fifth and sixth cervical nerves and, entering the thorax either anterior or posterior to the subclavian vein, joins the phrenic at the base of the neck or in the thorax. II. The eommunieating branches of the internal set effect unions with (a) the sympathetic, ifi) the vagus and (<-) the hypoglossal a. The tuperior cervical ganglion of the aympathetic or the association cord connecting the superior and middle ganglia sends gray rami communicates to the first, second, third and fourth cervical nerves. b. The ganglion of the trunk of the vagus is sometimes connected by means of a tiny nerve with the loop between the first and second cervical nerves- c. The hypoglossal nerve receives, just below the anterior condyloid foramen, a good .si? A branch from the loop between the first and second cervical nerves. This communication f; mishes sensory fibres to the hypoglossal nerve which subsequently leaves the latter as its men- ingeal branch ; other spinal fibres leave the twelftii as the n.de£cendens hypoglossi and as the nerves to the genio-hyoid and thyro-hyoid muscles. Practical Considerations. — Of the motor nerves of the cervical plexus the phrenic is most commonly the seat of trouble and this may result in or be associated with spasm or paralysis of the diaphragm. The involvement of the diaphragm may be part of a progressive muscular paralysis, as from lead poisoning, or from injuries or diseases of the spine. The nerve may be compressed by tumors or abscesses of the neck, or be injured in wounds of the neck. It passes downward under the stemo- mastoid muscle and on the scalenus anticus, from about the level of the hyoid bone. It is covered and somewhat fixed by the layer of deep fascia covering the scalenus anticus muscle. The clonic variety of spasm, singultus or hiccough, is very common, and is occasionally though rarely dangerous by preventing rest and sleep ; it may complicate apoplexy, peritonitis or chronic gastric catarrh. If only one phrenic is paralyzed the disturbance of function is slight and not easily recognized. In a bilateral paralysis, as from alcoholic -.leuritis, respiration depends almost entirely on the intercostal muscles, since the diaphragm is completely paralyzed. Dyspncea, therefore, occurs on slight exertion. The epigastrium is depressed rather than prominent and the lower border of the liver is drawn upward. The superficial branches of the cervical plexus emerge together through the deep fascia near the middle of the posterior border of the sterno-mastoid muscle, and from this point pass in various directions. The auricularis magnus passes upw;ard and forward over the sterno-mastoid to the ear and parotid gland, the occipitelis minor along the posterior margin of the same muscle to the scalp, and the superficial cervical branch obliquely forward and upward to the submaxillary region. The descending branches are three in number and {)ass respectively in the direction of the sternum, clavicle and acromion. They gi\e rise to little or no disturbance when wounded. THE BRACHIAL PLEXUS. The brachi.^1 plexus (plexus brachialis") is a somewh.at intricate interlacement of the anterior primary divisions of usually the lower four cervical and first thoracic iier\'es. To these are sometimes added a branch from the fourth cervical, a branch from the second thoracic, or branches from both of these nerves. The fasciculi form- THE BRACHIAL PLEXUS. "93 ina this Dlexus emerRe in the interval between the scalenus amicus and medius and rSe.^ Afer entering the axilla'its component parts, whUe ly'ng nia.nly to the ™i» mEfSyrnd before dl,idmB>.o iu te™in.l b™ch« .< l,e.enclo« Posterior cord of plexus Circumflex ner\'e Deltoid muacle / Median ner\-e , I'liiar nen'u ^ MuscuIo-«*piral nerve / , Internal cutaneous ner\'e / Lesser internal cutaneous ner\*e Internal anterior thoracic nerve Insertion of scalenus anticus .Posterior thoracic nerve I. rib n. rib Inner cord of plexus Middle suhticapulnr nerve Lower subscapular nerve Deep dissection of neck, showing constitution of right brachial plexus. Practical Considerations.— Sensory disturbances are rather rare in the distribution of the brachial plexus of nerves, but motor troubles are comparatively common and are sometimes associated with disturbances of sensaUon. The whole plexus, or only an individual branch, may be involved. The most common cause IS iniurv such as dislocation of the head of the humerus, a fracture of the clavicle, or a forced apposition of the clavicle to the first rib. Other causes are the pressure of tumors or the constitutional effects of poisons and infections. I he plexus is so superficial above the clavicle that it can be felt or even seen in thin people. Branches.— These fall naturallv into two groups, those given off from the fupraclavicular and those from the infraclavicular portion of the plexus. THE BRACHIAL PLEXUS. 1295 I. Supraclavicular Branches ,. Suprascapular 4- Muscular Posterior scapular Posterior thoracic Communicating to the phrenic nerve II. Infraclavicular Branches From Outer Cord: 6. External anterior thoracic 7. Musculo-cutaneous 8. Median (outer head) H. From Inner Cord : 9. Internal anterior thoracic ID. Lesser internal cutaneous 11. Internal cutaneous 12. Ulnar 13. Median (inner head) C. From Posterior Cord : 14. Subscapular 1 5. Circumflex 16. Musculo-spiral I. The Supraclavicular Branchea.-These are given ofi at various levels while the plexus is still in the neck. „„„,«,iari«^ fFie 10Q2) arises from ,. The suprascapular nerve (n. ^-P^f^ff ^.l/^ 'f ^n^in^ from the fifth the posterior surface of the outer trunk most «\ f^^^^^/^'^i^h'^'^rerior cervical cerv ioTl nerve and the remainder from Je «.xth It trav«s« U^ l^^^^.j, y ^^^ triangle above the upper border of the P!^"^"^^*"^ ""{ .^e^ap^^ it passes through trapezius muscles. Reaching the superior 3" fj^^f^f P^fj ^mers the supra- the%rascapular notch,.under the supras^puW^^ spinous fossa. After giving off a branch forthe ^"PP'^ *"^ , J u^ment of the Ia a tiny filament to *e jH,.tmor j^rUon d ^^^^ f^^^ ^^^ shoulder, It passes through the g'^^!^*?""'!!^!^^^ "{ the infripinous fossa, the scapular artery and van. Having become »" *^P*"| ?^ „" ^ "branch to the ner^e supplira the infraspinatus muscle and often gives ott a orancn shoulder joint. V«i.tion..-It may receive additional fibres f™-" ^Vou^h cem- ' ""es■m^no^or^^h^ entirelyTrom ?he fifth. X rare anomaly is 'he^PvineofloU branch to ^. es m^^^ ^^^^^.^ posterior thoracic nerve, rom the dorsal ^ -toSes downward and backward Traversing the substance of the «:alenus medius it P»^^ *?™'p ^^^.^^e of the toward the vertebral border of the scapula. >•"« "P^^'^'fi^i^S "the levator levator anguli scapulae and the '>^«"^bo.de.. It supphes a h amemj^ ^.^^^ 5Son;?t:r2- ^^^^^^^^^^ -- -' minor muscles. Variation.— It may pierce the levator anguli scapula;. , The posterior thoracic (n. thoracaUs Iohrus) also called the lo;;^ =t"a1S«Kirirr?i5T'tnSSnT.r„i«a ,he „e,v. descend, on 1396 HUMAN ANATOMY. the inner wall, lying posterior lo the brachial plexus and the axillary veasela, and upon the lateral aspect of the serratus magnus. It gives ofi successive tw.gs to the digita- tions of the last-named muscle, which alone it supplies The fibres derived «rom the fifth cervical nerve supply the upper par, those from the sixth the middle and those from the seventh the lower part of the muscle. V«fimtk>M.-The contribution from the fifth nerve sometimes fails to join the main nerve »■*»■•""■• *"."■ .... -L 1:_;.-.: — . T-k. ..^^t ns.-The contribution from the mth nerve somenmes laus lo join and goes directly to its distribution to the upper digitations. .The root from Ui inay^nbsent An additional root may be contributed by the eighth cervical i Practical Conaiderations.— The posterior thoracic nerve may be paralyzed by an injury in the suprascapular region or in the axilla, by carrying heavy weiehts upon the shoulder, or as a result of infectious disease, cold or rheu- ma&m. The most noticeable sign is a prominence of the scapula (winged scapula), from the failure of the paralyzed serratus magnus muscle to hold the vertebral border of the scapula close to the thorax. That border and the inferior angle project and Fig. 1093. AoonW Mundc atUir CapWk* Lcwcr fnlrnul ciitiomiM nerve' Loot tbotacic artwy iBtCTcMto-humcral nvt.' Subecapulw aitcrv ' LatfeMiniM dor^ °V .Im^^^E °^erces The loop between the anterior thoracic nerves gives off a filament ^hich p^ercra the pectoralis minor and ends in the sternal part of the pectoralis major, to both of which muscles it is distributed. V.rUtlon..-This nerve may supply fibres to the clavicular portion of the deltoid and to the acromio-clavicular articulation. 82 1398 HUMAN ANATOMY. 7. The Muscuix)-Cutaneous Nerve. The musculo-cutaneous nerve (a. niiKiilociiUiicm) (Fig. 1098) derives its fibres from the fifth and sixth, and sometimes the seventh, cervical ner\-es and is a branch of the outer cord. The nerve to the coraco-brackialis muscle, derived from the seventh or sixth and seventh nerves, is usuall) each portion of the tiuiscle. The nerves to the biceps and brachialis anticKs are given off while the musculo-cuuneous is in transit between thuse muscles. b. The humeral branch accompanies the nutrient branch of the brachial artery into the humerus. c. The articular branch aids in the supply of the elbow joint d. The terminal part (n. cataoeua anubracUi lauralU) (Fig. 1103) of the musculo-cutaneous divides into two branches, (aa) an anterior and (M) a posterior. aa. The anterior branch descends in the antero-lateral portion of the superficial fascia of the forearm (Fig. 1104). It inosculates above the wrist with the radial nerve and supplies the in- tegument of the antero-lateral part of the forearm. It also distributes fibres to the skin over the thenar eminence, to the wrist joint and to the radial artery. bb. The posterior bran h passies downward and backward and supplies the skin of the postero-lateral portion of the forearm down to or slightly beyond the wrist joint (Fig. 1103 ). It inosculates with the radial nerve and with the inferior extenukl cutaneous branch of &e musculo- spiral. Variations.— Instead of piercing the coraco-brachialis the nerve may adhere to the median or its outer head for some distance down the arm, and then either as a single trunk or as several branches pass between the biceps and brachialis anticus muscles. Sometimes onl v a part of the nerve follows this course, joining the main trunk aher the tatter's transit through the muscle. The muscular part only or the cutaneous part only may pierce the muscle. The nerve may be accompanied tnrough the muscle by fibres of the median which rejoin the latter below the coraco-brachialis. The nerve may remain independent and fail to pierce the coraco-brachialis, either passing behind it or between it and the associated head of the biceps. It may perforate not only the cnraco-brachialis but also the brachialis antictis or the short head of uie biceps. Rarely the entire outer cord, after giving off the external anterior thoracic, may traverse the coraco-brachialis. Anomalies in dist...yution include a branch to the pronator radii terej, the supply of the skin of the dorsum of the hand over and adjacent to the first metacarpal bone, a branch to the dorsum of the thumb in the absence of the mdial nerve and the givmg off cf dorsal digital nerves to both sides of the ring finger and the adjacent side of the little finger. 8. The Median Nerve. The median nerve (n. medianus) (Fig. 1098) consists of fibres which can be traced to the sixth, seventh and eighth cervical and first thoracic ner\'es. It arises by two heads, an outer and an inner, which are derived respectively from the outer Ad inner cords of the plexus, the former containing fibres from the sixth and seventh cer\'ical and the latter fibres from the eighth cervical and first thoracic ner\'es. The two heads, the inner of which usually crosses the main artery of the upper extremity at about the point where the axillary becomes brachial, unite either in front of or to the outer side of the artery. From the point of fusion of the two heads the nerve passes down the arm in close relation with the brachial artery, usually lyinj;; Lateral or antero-lateral to the artery in the upjjer part of the arm, and as the elbow is neared, gradually attaining the inner side by crossing obliquely the anterior surface of the arter)- (Fig. 1098). It passes through the cubital fossa beneath the median-basilic vein and the bicipital fascia, and enters the forearm between the heads of the pronator radii teres muscle, the deep head of THE BRACHIAL PLEXUS. 1299 which ieparatw the nerve from the ulnar artery. It follows a straiKht amneikmu The fo^S^ accom,«nied by the median artery, lying upon the flexor prdundu, Fio. 1095. r«MaM. . Median nerve ' Brachial artery . Edge of Iricepa Sop. ext. cil«UlraI- :nf. emt. coUnc«iu« »ir. miiacuUwpJtal- .UbMr nerve -laferlor profunda artery >|n«cu!'""'""e""'> IK rve, ant. a _ poat. lira. MuwuloHipiral 1 riiBierlor Interomeooa neT»«- Radiali Supinator bre»ta- Pronator imdii tr Kxtenaor carpi nd. longiat- Kxtennor carpi rad. t>re»if median nerve* -BracUalla aniicu* *Bicepa tendon nator radii teren. humeral head -Articniar branchea of median nenre ■ Flexor carpi radiali* - Flexor sublimia digitomm - Ulnar nenre -Ulnar artery - Flexor profundus digitonim - Flexor carpi ulnaria - Palmar cutaneous br. of ulnar -DotMl cntaneouj br. of ulnar nerve - Flexor sublimiR dlgitorum .ridfoTm hone -Oeep br. of ulnar nerve -Palmaris bre\i», reflected -Abductor minimi digiti -Flexor brevi» minimi digiti ^Digital bra. of ulnar nerve 0,»ecao„ or right upp.rextrem.,^o„mg^.;;^^^-,'S^c.^^^ .n«..,. n...nt h. been diritorum and covered by the flexor sublimis digitorum. Near the wrist the rSr^comes more superficial, with the tendons of the flexor sublime digitorum I300 HUMAN ANATOMY. and palmaris longus lying mesial and that of the flexor carpi radiaiis lateral to it (Fig. 1095). It passes into the hand beneath the anterior annular ligament, at the lower margin of which it spreads out into a reddish gangliform swelling, which lies upon the flexor tendons. Below this point it breaks up into its terminal branches. Branches. — The median, as is the case with the ulnar, gives ofi no branches in the arm. In the forearm the branches are : (a) the arlicular, (i) the muscular. (f) the anterior interosseous and (d) the pa/mar cutaneous, and in the hand : (e) the muscular and {/) the digital. a. The articular branch consists of one or two tiny twigs which supply the anterior portion of the elbow joint. Musciilo-spiral nerve Cephalic vein Posterior interosseous nerve Brachio-radialis muscle Radial nerW' Radial recurrent artery- Communications 1>etweeQ deep and superficial veins Cutaneous branch of musculo- cutaneous nerve' Radial vein. Radial artery. Fig. 1096. Brachial artery Median nerve Brachial vein Tendon of biceps Internal cutancou* nerve Bicipital fascia -Median nerve Pronator radii tere* Superficial dii^cctlon ol right arm, showin: •elalioni of nerves to blood-vestelt on front of elbow. b. The muscular branchet (rr. muKulareti) (Fig. 1095) consist of a fasces of nerv-e-bundles which arise from the median a short distance below the elbow. They are distributed to the pronator radii teres, the flexor carpi radialb, the palmaris longus and that portion of the flexor sublimis digitorum which arises from the inner condyle and from the ulna. Two additional fllaments from the median supply the flexor sublimis, one entering the radial head and the other that (>ortion which flexes the index flnger. c. The anterior interosseoui nerve (n. intcromeuR antebrachii volaria) (Fig. I098) arises from the posterior aspect of the median a short distance below the elbow. It passes down the forearm, accompanied by the anterior interosseous artery, on the anterior surface of the interosseous membrane between the flexor longus polllcis and the flexor profundus digitorum. At the upper margin of the pronator qimdratus muscle it dips under that muscle and continue* down for some distance, Anally entering the deep surface of the pronator quadrattis. THE BRACHIAL PLEXUS. 1 301 It supplies the flexor longus pollicis, the radial half of the flexor profundus digitonim ant! 'he pronator quadratus. It distributes filaments to the interosseous membrane, the anterior intci isseous vessels, the shafts of the radius and ulna (the twigs to these bones entering them with the nutrient arteries) , the periosteum of the radius and ulna and the radio-can>al articulation. d. The palmar cutaneous branch (r. cuUneus palmarU) (Fig. 1097) leaves the mechan at a var>'ing distance above the wrist. It becomes superficial near the upper margin of the anterior annular ligament by piercing the deep fascia between the flexor carpi radialis and the palmaris longus. It supplies the skin of the palm and inosculates with the palmar cutaneous branch of the ulnar and with filaments of the radial and musculo-cutaneous nerves. e. The muscular branch in the hand (r. muscularis) (Fig. 1097) is a short ner\'e which arises below the anterior annular ligament and curves outward toward the base of the thumb. It breaks up into filaments which supply the abductor pollicis, the opixinens pollicis and the superficial head of the flexor brevis pollicis. /. The digital branches (Fig. 1097) are five in number and, with the exception of the twigs supplying the two outer lumbricales, are purely sensor)-. They arise from the median a short distance below the anterior annular ligament of the wrist (nn. dinitalw volares communes) and pass c'istally beneath the superficial palmar arch and over the flexor tendons. As they approach the interdigital clefts they pass between the primar\- divisions of the median portion of the palmar fascia and become more superficial as they continue along the borders of the fingers (nn. digitales volares propril). The ftrst lies along the radial side of the thumb and inosculates around its radial asspect with the radial nerve. The second occupies the ulnar side of the thumb. The third gives off a branch to the first lumbricalis and supplies the radial side of the index The fourth supplies the second lumbricalis and then divides into two branches w hich are distributed to the adjacent sides of the index and middle fingers. The fifth, after being connected with the ulnar nerve by a stout filament (r. anastomot- icus cum n. aloare), divides for the supply of the adjoining aspects of the middle and ring fingers. . j •. • In the fingers these nerves lie anterior to the vessels and in their course toward the tip of the finger they give off anterior and posterior branches, the latter supplying the skin over the middle and distal phalanges of the index, middle and ring fingers and over the distal phalanx of the thumb. Twigs are supplied to the interphalangeal articulations and near the end of the finger each of the five breaks up into two terminal branches, one of which is destined for the sensitive skin over the anterior portion of the distal phalanx and the other for the matrix of the nail. Variations.— Some of these are described on page im8. The fibres usuallj,' contributed to the median nerve by the first thoracic may be wanting. Efither the outer or the inner head may consist of two nerve-bundles. The point at which the heads unite is a very vanable one and has been found as far down as the elbow. The heads may enclose the axillary vein instead of the arter>'. In those instances, many of which have been found in the anatomical rooms of the University of Pennsylvania, in which a .single large branch of the axillary artery gives off the two circumflex artenes, the suliscapular and the two profunda artenes, this trunk, instead of the axillary artery, is embraced by the heads of the median nerve. The inner hwd, the outer head or the median itself may pass behind the axillary artery instead of in front The outer head lias been seen to arise in the middle of the arm anci pass behind the artery to join the inner head. One instance has been reported in which the median entered the forearm over the pronator radii teres instead of between the heads of that muscle. It has been seen lying on the superficial surface of the flexor sublimis digitonim. The median may be cleft for a short distance in the forearm, giving passage to the ulnar artery or one of its branches, to the su|jerficial long head of the flexor longus pollicis or to an extra palmaris longus muscle. A communication m the arm between the median and ulnar nerves has been noted in one instance. A similar connectum in the forearm, occurring in numerous ways, is found in from ao-as per cent, of cases examined. A connection with the ulnar in the hand may pass either from the ulnar to the median or from the median to the ulnar. The anterior interosseous has been seen to receive a filament Irom the musculo-spiral through the interos.seous membrane, and inosculation lietween the two interos.seous ner\es has been noted at the lower part of the forearm ; according to Kaiiber, this is the normal arrangement One case has been described m which the abductor indicis was supplied by the median. Fhiring the exchange of position between the digital bran^ of the median nerve and the digital arteries the former are often pierced by the latter. I he fifth digital branch may arise in the forearm and enter the hand independently. Practical Considerations. — A pure paralysis of the median nerve is rare, and is almost always traumatic in origin. The paralysis is more commonly a part of a more extended invlvcment of the brachial plexus. When this nerve is paralyzed above there is inabi.ity to pronate the forearm or flex the wrist properly, smce the 1302 HUMAN ANATOMY. pronators and all the flexors except the flexor carpi ulnans and the ulnar half of the flexor prohindus digitorum are supplied by it. The second phalanges of the middle and index fingers cannot be flexed, although the first phalanges can be flexed and the second and third extended in all the fingers through the interossei muscles ; flexion of the third phalanges of the little and ring fingers can be accomplished by the ulnar half of the flexor profundus, which is supplied by the ulnar ner\e. The Fig. 1097. BrachioradtaliH tendon Branch of radial nerve Palmar cutaneous br. of median nerve Median nerve Flexor carpi radialis tendon Abductor pollidi Opponen* potlida Abductor polticia Digital bra. of median nerve Adductor^ tiansversus polUcia' Flexor sublimit diifitomm Flexor carpi ulnaris Palmai cutaneous )>r. of ulnal ner%e, lying upon ulnar arter>' Ulnar ner\'e Pisiform bone - Deep branch of ulnar nervr Abductor minimidigiti Palmaria bre\-is. reflected Digital brs. of ulnar nerve pponen.4 minimi d>Kiti .Flex, brevis minimi digiti SuMHtdal dlM«etlon of right palm, shewing branches of median and ulnar nerves ; pan of anterior annular ligament hat been removed to expose median nerve. thumb cannot be flexed or abducted, although it may be adducted. One of the most characteristic features of the hand is lost— that is, the ability to appose the thumb to any one of the fingers, as in picking up small objects. In wounds of the axilla the median is the nerve most frequently injured, the musculo-spiral least frequently, as the median lies more superficially and the musculo- spiral behind the vessels. In the arm the median can be easily found to the inner side of the biceps and coraco-brachialis muscles, where it lies on the brachial vessels. At the elbow it is found to the inner side of tne brachial artery, the guide to which is the biceps tendon which in turn lies just to the outer side of the artery. At about the middle of the wrist the ner\'e lies under the palmaris longus tendon. THE BRACHIAL PLEXUS. 1303 9. The Internal Anterior Thoracic Nerve. The internal anterior thoracic nerve (n. thoracaUs anterior m' Ualis) (Fig. loqO arises h-om the inner cord and consists of fibres derived frc.a the eighth cenfical and first thoracic nerves. It passes forward between the ax.Uary artery and vein and. after giving ofl a branch which forms a loop with a similar branch from the external anterior thoracic, pierces the pectoralis minor in which some of 'ts Jibrea terminate. The remainder enter the deep surface of the pectoralis major to supply the lower part of the sternal portion of that muscle. v..^.fion.— The fibres which supply the pectoralis major may wind around the lower bordeT^hrpJ^ctorallsiSr Filaments from S of the anterior tLracic nerves may supply the integument of the axillary and mammary regions. ID. The Lesser Internal Cutaneous Nerve. The lesser internal cutaneous nerve (n. cutoneiis brachil medialis) (Fig. 1093). also called the »frxe of Wrisberg, can be traced to the first thoracic nerve It Seslrom the inner cord usually in common with the internal cutaneous. After SgTtTpoint of origin, it descends in the arm along the inner side of the axillary and bSilic veins, pierces the deep fascia about the middle of the arm and supplier the integument of the inner aspect of the upper extremity as ar down as the elbow. At a vanable point it forms a loop with the intercosto-humeral nerve. v.ri«ion. —The lesser internal cutaneous nerve may be absent. It may receive fibres either nerve may be deficient, the other usually recompensing for the deficiency. II. The Internal Cutaneous Nerve. The internal cutaneous nerve (o. cutaneus antebrachU medialis) (Fig. 1094) comDrfees fibr« from the eighth cervical and first thoracic nerves. It has its origin She inner cord of the plexus usually as a common trunk with the lesser internal cu^eous nerve. After distributing some small filaments to^^^e integument of the .inner arm below the axilla, it runs down the arm between the brachial artery and SKrvSnTnd at about the middle of the upper arm breaks up into its terminal branches, (a) the anterior and (*) the/wfewr. a. The .nterior br«»ch (r. v.lari.) passes over, sometimes ""'»«;•»''«. ™^?"-^";'^ vein and supplies the skin of the ulnar half of the forearm as far down as the wnst (Fig. H04). It inosculates with the superficial branch of the ulnar ner\-e. ... , .. . ... „„__, 4 The pcterior branch (r. ulnarl.) turns obliquely around the inner side of the upper nart of the foCm and^pplies the integument as far around as the ulna down to the lower ^hW or fourth oHhrioS It unites above the elbow with the lesser internal cutaneoi« ne^elKe fo«arwith the anterior branch of the internal cutaneous and sometimes with the dorsal ramus of the ulnar. 12. The Ulnar Nerve. The ulnar nerve (n. ulnaris) (Fig. 1092) is the largest branch of the inner cord Its fibres can be traced to the eighth cer^•ical and first thoracic nerves and sometimS by a root from the outer cord, to the seventh cervical. Arising from rinrcorVb^tween the axillary artery and vein and posterior to the jn^^^' cutaneous ner^'e it pursues a downward course in front of the tnceps and to the inner side of the axillary and brachial arteries. Reachms; the middle of the arm it "Sows an inward and l^ckward direction, in which it is accompanied bX the .deru, orofunda artery and passing either over the inner margin of or through the interna fnSScuTar i^'ptum and in^ont of the inner head of the f c^^- f ,=^1 ^^'-^^^^^^^ between the internal condyle of the humerus and ^^e olecranon (Fig. 10^). U becomes an occupant of the forearm by passing between the ^^ads of the flexor carpi uhiaris muscle, a situation the nerve shares with the lufenor prohmda atid posterior I3«H HUMAN ANATOMY. ulnar recurrent arteries. From this point the nerve follows a straight course to the wrist, lying in the forearm upon the flexor profundus digitorum and covered by the Fig. 1098. Musculocutaneous ner\-e Outer hfatl of median nenc Inner head of median nt:r\-« Long head of bicepS' Short head of biceps, everted Coraco-brach iat is Musculocutaneous ner\ Branchialis anticu: Musculo-spiral nerve' CtttaDcous branches of niuscubxutancoi Brachio>fadiaUs Posterior interosseous nerve Biceps tendon Radial artery Supinator brevis Ext. carpi radialis longior Ext. carpi radialis brevior Radial Prcmator radii teres, cut Flexor longus polHcis- Palmar cutaneous branch of mtdian Opponens pollici« Pectoralis minor Internal cutaneous Ulnar nerve Interna] cutaneous branch of musculo-spiral nerve Inferior profunda artery Muscular branch f^ musculo-cutaneous >uperficial flexots, origin Articular branches of median nerve rticular branches of ulnar nerve Flexor carpi ulnaris Ulnar artery interior interosseous nerve nterior interosseous artery Inar nerve Flexor profundus (]ij{itorum, cut Palmar cutaneous branch ronalor quadratus, cut 'Dorsal branch of ulnar nerve Deep brar ch of ulnar nervt Abductor minimi dlRiti Opponens minimi diiciti Flexor brevis minimi digiti 3rd and 4th flexor tendons with ^rd and 4th lumbricales, turned forward Dissection of right upper extremity, showing deeper brmnchea of nerves of anterior surface. flexor carpi ulnaris. At about the middle of its course through the lower arm it approximates the ulnar vessels, dose to the inner side of which it lies. At the THE BRACHIAL PLEXUS. 1305 wrist, accompanied by the ulnar artery it pierces the deep fasca J^^f ^bov^J^ TnnuUr ligament, to the outer side of the pisiform bone, and enters the hand b> Sing su^rfici^ to the anterior annular ligament (Fig 1097). After crossing ihe ligament it divides into its ..rminal branches, the sufier/lna/ and the deep. Branches.-None are given off in the arm. In the forearm they are (a) the articu/ar, (d) the muscu/ar, (c) the cuianecus and (rf) the '''';^''/ f ^«^* '^ '^ hand. The terminal branches in the hand are : {e) the superjiaai and (/) the deep. a The wticulw brwich consists of one or two filaments which leave the ulnar as it lies in the interval brtw^n the olecranon and the internal condyle. They pierce the internal part of the capsular ligament and supply the elbow joint. ... .. , . . ■ u-w^ «» ♦!,» A The mu.cul« branches arise from the ulnar in the immediate neighborhood of the elbow and supply the flexor carpi ulnaris in toto and the ulnar half of the flexor profundus dSor2 They consist of severkl fine twigs which leave the ulnar nerve as it lies between the heads of^he fl;';^"^^'^-^^;. are two small filaments which arise by a common trunk at about ihe r^iddle of the forearm. One. which is inconstant, after piercing the deep asc.a. runs downward to inosculate with a twig from the internal cutaneous. The other, the p.lm.r cut™u. br^cMr. c«ta«.us palmari.) (Fig. 1097 ). lies superficial to the ulnar artery, which n^anirto th; hand ataost as far as%he superficial palmar .'rh It sends filaments to rt™r artery and breaks up into a number of tiny threads which v , - -ly the '"^^Ktiment of the h^ttenar re^on and inosailate with other cutaneous twigs of the ulnar, with the internal cutaneous and with the palmar cutaneous branch oi the median. ... ,„,„t ^hirh rf The dor.ia branch to the h«»d (r. dorMli. manu.) is a good sized trunk which leavef "the ulnanTthe^pper part of the lower half of the forearm. To n=ach the dorsum of the htnTit ^<^d^wnwa°d andbackward between the tendinous portion of the flexor carp. uh"arii\K^e ^aft of the ulna, giving off a branch over the dorsum of the wnst to supply S^at ^gton and inosculate with a twig from the radial nerve. Opposite the head of the ulna^ ^lits into three branches (nn. dlglwles dorMlw for the supply o tl e fingers. The ulnar or tenet te«.ch courses along the inner side of the little finger to ramify m its integument as far as ^ w" thfnaT The middle br«.ch follows the fourth met^arsal interval and divides into wo fil^ents. one extending along the radial side of the little finger « far as the base of d^e naU and the other along the ulnar side of the ring finger as far as the proximal side of the rnguarph^anT The radial or outer branch passes toward the base of the space between^e rinS middle fingers and inosculates with the branch from the radial ner^_e for he same ckft U div^es into two Lb-branches and in connection with the radial supplies the advent sides o^ the ringlnd middle fingers (Fig. l.oa). At the lateral aspect of the fingers all of these bra..cnes innwiilate with the palmar digital cutaneous nerves. . ,„ » t • .. inosculate witntnep terminal branch (r. «.p.rficlali. n. nW^H») {Fig. ,097) furnishes small w,'« to the palmaris brevis muscle, to the integument of the ball of the little finger and ^metim^to Ae fourth lumbricalis. It then divides, one of its subdivisions supplying the Xr swTrf the little finger while the other breaks up into two portions which course along the adjoining rides of the litde and ring fingers. The ultimate distribution of these filaments is similar to that of the digital branches ofthe median nerve (page 1301. „j .u„, A ^^ of communication passes between the branch for the little and nng fingers and that from thrrtLlian for the ring and middle fingers. From the latter Uny threads are supplied to the inteeumcnt and vessels of the palm. »i._ j.„„ /•The deep terminal branch (r. profondu. a. «ln.rU) (Fig. 1099) accompanies the deep branch of thf^narTrtery and sinks deeply into the palm between the abductor and flexor mWmi dieiti muscles. It passes internal to and below the uncus of the unciform bone, in which ™ve for Swerve is ^metimes found, crosses the palm with the deep Pflmar arch under thf ^p flexor tendons and breaks up into terminal twigs on its arrival ?t the adductor tmns- versus oollicis (Fig. 1199). Muicular branche. rr. masculare.) are furnished to the abductor op^ne^s^d flexor minimi digiti. the third and fourth lumbricales, the pa mar and dorsa^ interossei the adductores obliquus and transversus pollicis and the deep head of the flexor bre- "s ^b. ArticuUr branche. are supplied to the intercarpal and metacarpo-phalangea^ artic- uatC and^ny perforating branche. accompany the posterior perforating arteries be ween the heads of the s^ond. thW and fourth dorsal interosseous muscles and inosculate with the terminaltwiesof the posterior interosseous nerv-e (Rauber). termi^p. o. . po ^^^^^ communicates freely and in maijy different situahons w^h the m^"n and this dose imeriacing is paralleled by their simi^ritj- m d«trib~„ Both |^^^ off no branches above the elbow, both supply the elbow jomt, between them they supply all the mu^°^"thrflexor surface of the forearm, both send filaments to the wnst ^.int and the integ- IZrnt^ the palm and between them all U.e mu.scles of the hand, the palmar aspect of all the digits and the interphalangeal articulations are Innervated. iyif> HUMAN ANATOMY. Further description of the communications ol the ulnar nerve, in addition to those just mentioned, will be found in connection with the median nerve (page 1301). Variations.— The ulnar may have a root from the seventh cervical nerve by way of the outer cord, or may be derived from the eijchth cervical only or from the seventh and eigjhth. It may pass in front of the internal condyle or lie behind the condyle and slip forward dunnt; flexion of the elbow. Connecting twigs have been seen passing from the ulnar to the internal cutaneous, to the median in the upper arm and to the musculo-spiral. Frequently there is an associating branch in the forearm between the median and the ulnar. Muscular twigs have been noted as passing to the inner head of the triceps, the flexor sublimis digitorum, the first and second fumbncales and the superficial head of the flexor brevis pollicis. Deficiencies in the branch to the dorsum of the hand have been observed to be compensated for by the radial, the inferior external cutaneous branch of the musculo-spiral or the internal cutaneous. In a specimen with absence of the radial nerve all four fingers were supplied by the ulnar. The dorsal terminal filaments of the ulnar tend to encroach on the radial side of the hand and in one ca.se reached the dorsum of the first phalanx of the thumb. Practical Considerations. — In paralysis of the ulnar nerve, flexion of the wrist ii impaired, and also (on account of the flexor carpi ulnaris paralysis) lateral motion toward the ulnar side (adduction). There is difficulty in spreading the fingers, as all the interossei are supplied by this nerve. The hand will be " clawed" from the paralysis of the interossei, which now fail to resist the action of the extensors on the proximal phalanges, and of the flexors on the distal and tnedial, except in the middle and ring fingers where the flexor profundus — its ulnar half being paralyzed— has only a slight influence on the di-stal phalanges. Besides the flexor carpi ulna 'is, the ulnar half of the flexor profundus and the interossei, the ulnar ner\'e supplies all the hypothenar muscles, the adductor pollicis, the inner half of the flexor brevis pollicis and the two ulnar lumbricales ; consequently the hypothenar eminence dis- appears and the thenar eminence shows atrophy in ulnar paralysis. This nerve is involved particularly in those whose occupations require them to press their elbows against hard objects or to strike blows frequently with the ulnar border of the hand. It may be injured in fractures of the elbow, particularly of the internal condyle. In the forearm and wrist it is the nerve most frequentiy injured. It is found on the inner side of the brachial artery in the upper half of the arm, but in the lower half it passes posteriorly to the bony interval between the internal condyle and the olecranon, where it is readily located by pressure, which causes a tingling sensation down the forearm. The same sensation is often produced by blows on the elbow, the nerve being compressed between the internal condyle and the olecranon. It is the structure most frequently damaged in excisions of the elbow. In the lower two-thirds of the forearm it lies to the radial side of the flexor carpi ulnaris muscle and to the ulnar side of the ulnar artery. At the wrist it passes over the anterior annular ligament in the same relation to the ..rtery and to the radial side of the pisiform bone. 14. The Subscapular Nerves. The subscapular nerves (nn. subscapulares) (Fig. 1092) arise from the posterior cord and are usually three in number. Together they supply the three muscles which form the posterior boundary of the axillary space. The upper or short subscapular nerve is composed of fibres which are prolonged from the fifth and sixth cer\'ical nerves. It often is either double in origin or divides into two branches shortly after leaving the posterior cord. It arises behind the circumflex nerve and after a short course enters the inner surface of the f ubscapularis near the upper margin of that muscle. The middle or long subscapular nerve (n. thoracodorsalis), the largest of the three, arises from the rear aspect of the posterior cord, behind the origin of the musculo-spiral ner\'e. Its fibres are derived from the sixth, seventh and eighth cervical nerves, the majority of them coming from the seventh. It takes a course downward and outward on the posterior axillary wall behind the axillary artery, and accompanies the subscapular artery to the deep surface of the latissimus dorsi, before entering which it breaks up into a number of strands. The lower subscapular nerve obtains its fibres from the fifth and sixth cer- vical nerves. It arises from the posterior cord behind the origin of the circumflex THE BRACHIAL PLEXUS. •307 and passes downward and outward beneath the axillary artery and the circumflex and musculo-spiral nerves. It sends fibres to th.- inferior p)rtion of the subscap- ularis muscle and terminates in the substance of the teres major. Variation..- As retjards oriifin the upper may arise from either the fifth or the sixth cervi- cal nenV^the middle from the seventh alone or from the seventh and eiRluh »r rarely by an SduISna filament from the fifth, and the lower from the fifth, sixth and seventh or tri.m the fifth or sUth alone. As regards distribmion. the nerves to the lower part of the sut«|capulans and to the teres major mayproceed separately from the brachial plexus or the latter nerve may be a branch of the circumflex 15. The Circumflex Nerve. The circumflex or axillary nerve (n. asillaris) (Fig. 109O is .me of the terminal branches of the posterior cord and contains fibres which are derivatives of the fifth Fig. 1099. Median nerve Flcxtir Inngus poUiciit Pulttuir ctiUneoust br. of median nerve OppontfUit iHilltcis- Adductor obliquu» pollicii, Flex. l>rev. poll., inner head Flex. hrev. poll., outer head Adductor pollidii Adductor tranftversuff poll. An articular branch Flex. prof, digitomni, in part Ulnar ner^-c Flex, carpi ulnaris Pisiform bone Deep br. of ulnar nerve Articular br. of ulnar l-nciform hone I '«"' Articular bra. of ulnar nerve [evcrtt-d Abductcr minimi Uigiti, Opponent minimi difEiti Second palmar inter- osseous Third dorsal interosseous Third palmar inter- Fourth dorsal [os-seous interosseous Flex, brevis minimi digit! Oi-«tionCr.,h. P.-,-<^KJ^-:a°^:lSSiJX^^il^^^^ ""- "^ "^^ and sixth cervical nerves. It arises near the lower margin of the subscapularis and posterior to the axiUarj- artm-. Accompanied by the poster^r circumflex artery it takes a backward course through the quadrilateral space, bounded above by the subscapularis and the teres minor, below by the teres major, internally by the i3o8 HUMAN ANATOMY. humeral head of the triceps and externally by the humerus. Having tre versed thi> s|)ace it winds around the surgical neck of the humerus and reaches the outer aspect of the shoulder. Branches. — These are : (a) the articular, (i) the cutaneous and (<•) the muscu/ar. a. The articular branchea are usually two in number. The upper arises near the origin of the circumflex and the lower during the passage of the nerve through the quadrilateral space. They supply the anterior inferior portion of the capsular ligament of the shoulder. A third articular branch is described as passing up the bicipital groove, supplying a twig to the upper end of the humerus and one to the neighboring portion of the capsular ligament of the shoulder. *. The cutaneou* branch (n. cuUncus bractail laUralU) arises as a common trunk with the nen,-e to the teres minor. It becomes superficial between the long head of the triceps and the posterior border of the lower third of the deltoid and is distributed to the integument over the posterior half of the deltoid and the posterior suriace of the upper half of the arm. One or two cutaneous filaments are derived from the muscular branches to the deltoid. They pierce the deltoid and are distributed to the skin over the lower portion of that muscle. c. The muacular branchea (rr. muacalares) innervate (aa) the teres minor and (bb) the deltoid. aa. The nerve to the terea minor arises from the circumflex at the posterior margin of the quadrilateral space and enters the middle of the posterior inferior border of the muscle which it supplies. t>b. The deltoid branchea comprise the largest portion of the ner\e and consist of its termi- nal fibres. The terminal portion of the circumflex forms a bow, with its convexity in contact with the deep surface of the deltoid, extending around the upper part of the humerus almost as far forward as the anterior margin of the deltoid muscle. It grac' illy diminishes in size as the resuh of the departure of a series of twigs which enter and supply tlie fasciculi of the deltoid. Variationa.— The circumflex may receive very few or no fibres from the sixth cervical nerve. It may pierce the subscapularis and may supply that muscle. It may give origin to the nerve to the teres major and has been observed to furnish filaments to the long head of the triceps and to the infraspinatus. Practical Considerations. — The circumflex nerve is frequendy paralyzed from injuries to the shoulder, as in birth palsies when pressure is made in the axilla. It undergoes special strain in dislocations of the shoulder, the nerve being stretched over the head of the humerus and often lacerated. Other branches of the brachial plexus may be injured in this dislocation. Since the circumflex passes around the humerus at about the level of the surgical neck it is sometimes damaged in fractures in that situation. The most prominent symptom in paralysis of this nerve is loss of the rotundity of the shoulder h^m atrophy of the deltoid muscle. As the circumflex winds around the posteri> r surface of the humerus and reaches the anterior part of the deltoid mus^': from behind, incisions for reaching the shoulder joint, as in excisions, should o^ made anteriorly, since only the terminal branches of the circumflex will then be divided ; paralysis of the deltoid is thus prevented. i6. The Musculo-Spiral Nerve. The musculo-spiral nerve (n. radialis) (Fig. iioo), the larger terminal branch of the posterior cord, is in fact the continuation of the latter. Its component fibres are derivatives of the sixth, seventh and eighth, and sometimes of the fifth, cervical nerves and it is distributed to the muscles and integument of the extensor surface of the arm, forearm and hand. After separating from the circumflex, it passes down- ward behind the axillary artery and over the surface of the latissimus dorsi and teres major muscles. Accompanied by the superior profunda artery, it turns backward on the inner aspect of the arm and, entering the musculo-spiral groove and traversing the interval between the internal and long and the external head of the triceps, reaches the lateral a.spect of the arm. It then takes a forward course through the external intermuscular septum and becomes an occupant of the cleft between the brachioradiaiis and the brachialis anticus. Continuing in this space as far as the level of the external condyle of the humerus the nerve divides into its terminal branches, Xht posterior interosseous And the radial {¥\^. 1095). THE BRACHIAL PLEXUS. 1309 Branches. — These are : (a) the cutanfous, (6) the muscular, (r) the humeral, ((/} the articular and {e) the terminal. Fig. 1 100. Scipulmr head of triceps Superior profunda artery Portion ol ejrtenul licad of iricepa, everted Mnacular branch Olecranon Anconeua Extensor carpi ulnaris Eztenior loocui pollicit Eztenaor indicii Mucvloipiral nerve Upper external cutancoui nerve External head ol iricepi Brachialii anticus Lower external cutaneoua nerve External condyle Extensor carpi tadialis kmgiar Extensor carpi radialis brevior Supinator brevis Posterior inteioaseona ner>'e Extensor communis digitonim Extensor minimi digiti Extensor ossis metacarpi poUicIa Extensor bre\'is polHcia Kxtensor longiis poUicis nanKlifomi enlargement on posterior interosseous nerve Deep dissection of extensor surface of ri^^ht upfier extremity, showing conrse and branches of musculo^piral ner>-e. «. The cutaneous branches are three in number, an internal and two external. The intemal cuuneous branch frequently arises from the musculo^piral in common with IJIO HUMAN ANATOMY. the branches to the long and inner heads of the triceps. It phsses tnckward, posterior to the intercosto-humeral nerve, and after piercing the deep fa.scia, spreads out to be distributed to the integument over the inner head of tlie triceps to within a short distance of the elbow ( Fig. i lot ). It is accompanied by a small artery-. The ■uparior cstcmal cutaneous branch (n. couacu* bracbil posterior) (Fig. iioi) arises from the musculo-spiral posterior to the external intermuscular septum and pierces the deep fascia below the middle of the arm, between the external head of the triceps and the brachialis anticus. It pasiies down with the cephalic vein and is distributed to the integument of the external anterior portion of the arm down to or slightly below the elbow. The inferior external cutaneous branch (a. cutaocua aatihrachii dornatis) (Fig. iio3) arises and becomes superficial similarly to and in common with the superior. After passing down the Fig. iioi. 'Cut:itiei>iu* lirancheM of circumHrx nerve Branch of InterttMto- humenil nerve Int. cutaneoufl branch of mn*. culospiral nerve L.eiwcr internal cutaneoitA, joine*! below the leader by branch of intervoato-hu- nicral nerve Sup. ext. ciitaneoua bnitch of inii!*. culo^piral nt;rv»; inf. ext. cutaneoua branch of niiiH. culo-apiral nerve Post. cutaneoiiH branch of musciilo- cutaiiei>U!t nen>'e irom pof«t. branch of internal cutaneous nerve Superficial dissection of right arm, showing cutaneous nerves of posterior surface. arm it enters the forearm by crossing the dense fascia stretched between the olecranon and the internal condyle of the humerus. From this point it continues its downward course along the posterior aspect of the forearm as far down as the wrist or even onto the dorsum of the hand. It is distributed to the skin of the posterior portion of the arm between the areas supplied by the other cutaneous branches of the musculo-spiral and to that part of the posterior cspect ot the forearm between the portions supplied by the posterior branch ol the internal cutaneous and the posterior branch of the musculo-cutaneous. In the neighborhood of the wrist it inos- culates with the musculo-cutaneous and sometimes with the branch to the dorsum of the hand from the ulnar. b. The muscular branches (rr. muttcnUrtM) are given off (aa) before the miLscnlo-spiral enters the musculo-spiral groove and (bb) after leaving the groove. aa. Before entering the groove branches arise for the supply of the three heads of the triceps and the anconeus. THE BRACHIAL PLEXLS. 13»« Int. cuuneou* ,(_^ branch of mu»- ^^ Milu-Hpiral nerv« Lcwrr int. c» tancouii nerve thr ulnar nerve. Inf. cxt. cmanc'tiiiH branch of niuncuto- •piral nerve Int.cutan^MM nerve, poat. branch Post, cutaneous far. of niuticiilu- cutaneuun nerve The branch for the lonf hc«l of the trieep*, before its entrance into the miwcle, breaks up into four or five filaments. ., „ . . . . The nerve supply of the inner head of the triecpa is usually effected by two branches, an upper and a lower. The upper is short and enters the muscle soon after kavinjt the musculo- spiral. The lower, called the coUaUral ulnar branch, is longer and extends for a considerable distance along the inner suriace of the triceps in close as.sorialion with Posterior to the internal intermuscular septum it enters its muscle. Tiny r'"- "oj. filaments accompany the collateral ulnar artery to the capsular ligament of the elbow. The nerves to the outer head of the tricepa and to the anconeus take their origin as a single trunk. The former passes directly to the inner surface of the outer head, while the latter leaves the musculo-spirnl groove and tra- verses the outer portion of the internal head of the triceps until the aiKoneus is reached. bb. After leaving the groove and while lying in the cleft between tlie brachialis anticus and the brachio- radialis, twigs are given off for the supply of the brachio-radialis, the extensor carpi radialis longior and the brachialis anticus. The nerve to the brachio-radialis enters the mesial surface of that muscle and usually supplies a filament to the capsule of the elbow. The nerve to the extensor carpi radialis longior may arise either from the posterior interos-seous or directly from the musculo-spiral. The nerve to the brachialis anti- cus, while usually present, is not con- stant. It enters and supplies the lateral portion of that muscle. c. The humeral branches com- prise one which is supplied to the periosteum of the extensor surface of the iiumerus and one which enters the shaft of the humerus with the nutrient artery, when tlie latter arises as a branch of the superior profunda. d. The articnlar branches are des- tined for the elbow. They arise from the musculo-spiral as it lies between the brachialis anticus and the brachio- radialis, from the ulnar collateral nerve and from the nerve to the anconeus. e. The terminal branches of the musculo-spiral arises at about the level of the external condyle and in the fis- sure between the brachialis anticus and the brachio-radialis. They com- prise (aa) the posterior interosseous and (W) the radial. Inf. ext. cutanemifl liranch muwulo^piral I>om1 branch of ulnar ocrvc From ulnar nervi From niedinn nerve Superfirial difuection of riifht forearm, showing cutaneous nerves of posterior surface. aa. The posterior interosseous nerve (r. profundus n. radialis) ( Fig. iiDo) is the larger of the tcrtniiial brunchea and is mainly motor in function. Its fibres can be traced back to the sixth, seventh and sometimes the eighth cervical nerve. Shortly after its origin it approaches the supinator brevis, through a fissure in whose substance it makes its way to the lateral side of the radius, in this way reach- 13" HUMAN ANATOMY. ing the posterior aspect of the forearm. Here it Ukes a po«ti«.>n between the two layers of the extensor muscles and rapidly decrcast's in size by giving of! in quick succession branches to the neighboring muscles. As a much attenuated nerve it reaches the posterior surface of the interosseous membrane at the junction of the middle and lower thirds of the forearm. From the inter\'al between the e.xtensores longus and brevis pol- FiG. 1 103. licis it courses along sapnuicTomtai bn. ccrrkmi pinna the membrane, Cov- ered in turn by the ex- tensor longus pollicis, the extensor indicis and the tendons of the extensor longus digitorum, finally reaching the dorsum of the wrist, where it presents a small gancliform swelling. In the lower fourth of Its course it is son* times called the t ■ tern al interosseoi. : nerve. Branches of the posterior interos- cuuncous ner\e seous nerve comprise two sets: those given off before and after traversing the supina- tor brevis. CuUneottfl hr«. circumflex nerrtt Sup. cxt. cuUneota br ; f miwculo- spiral ticrre Inf. cxt. cutaneon* br. of miMculo- spiral nerve MusctiIo.^tttaneott. ner^'p. post. cuUn< brancb Muscuio-cutaneoiu nerve, ant cutaneous brancb Mu.sculo-cutaneo'U. post. cutaneouB br. :>"/<< Internal cutaneoua nerve Those arising be- fore the ner%'e enters the muscle comprise the nerves for the extensor carpi radialis breinor and the supinator brevis. The latter receives two filaments, which supply the two strata of muscle consequent upon the de- lamination of I he supin- ator brevis by the pos- terior interosseous nerve. Quite frequently the nerve to the exten- sor carpi radialis long- ior arises from this por- tion of the posterior interosseous. The branches giv- en off mfter leaving the muscle include the sup- ply ot the extensor car- pi ulnaris, the extensor I >mtnunis digitorum, the extensor minimi digiii, the three extensors of tlie thumb .\A the extensor indicts. 1 he first three ot these muscles are supplied by a branch which leaves the posterior inter- osseous soon after its emergence from the supinator brevis. This ner\'e divides intcj two branches, one of which is distributed to the extensor carpi ulnaris and the otb f> the r. main- ing two muscles. The extensor communis digitorum receives adrti' n fro> twig which arises from the posterior interosseous further down the fs Superficial dissection of ri|{;ht arm, sbowlni; cutaneous nerves of anterior surface ; cephalic vein is seen passing up to delto-pectoral interval ; basilic vein pierces deep fascia at lower inner aspect of arm. THE BRACHIAL PLEXLS. »3t3 Inf. exl. cutanrowt br. of muncwlo- Bpinit nerves Munculo-cuU ncf>u<* tirrve. anl ciitaneotui hr Muftcnlo-cuta- Dcouft nerve, pout. cutaneous br. lA"!»!»cr internal cutaneouH nr. vo Internal cutaneouii nerve Ant. br. internal frutaneoua nerve The extensor ossis nutacarpi polHHt and the extensor bre,-is pollUii are innervate. I hy a branch arising below the precedinK. which breaks up into two dtTurrrnt twigs, one of which '^"^The*r«-/«u<^ W«-t Pollicu is the recipient of a small filan«nl. wh.^h arises fron^ the posterior interosseous a short distance below the preceding ner\e. The extensor indiris is sup- plie Fcctormlis minor mtiade vical plexus PcctonlU major mnscle \ \^ Lesser internal V cutaneous nerve Fig. 1105. Descending branch of supcrticialis colli Suprasternal and supra* clavicular branches of cervical plexus Rectus abdom- inis, cut Anterior branch of X. thoracic nerve Anterior branch of XI. thoracic Anterior branch of XII. thoracic nerve Hypofpiitric portion of ilit^ nypoKSStric uer\'e Aponeurosis of external oblique mus- cle, cut edge Zlio-inguiual nerve Dissection Hhowmg thoracic, ilio-hypottmstric and illo-inguinat nerves equivalent of a lateral cutaneous branch. In addition to the lateral cutaneous, the anterior cutaneous branch may albo be wanting, the area typically supplied by the absent branch being served by the descending branches of the cervical plexus. THE THORACIC NERVES. 1317 The second thoracic nerve sometimes contributes fibres to the brachial plexus. The posterior ramus of its lateral cutaneous branch is called the intercoslo-humeral nerve. The intercosto-humeral nerve (n. intercostobrachialis) (Fig. 1105) is quite large and pierces the inner axillary wall betv^^en the second and third nbs. Enter- inir the axilla, it crosses that space toward the arm and communicates with the lesser internal cutaneous nerve from the brachial plexus. After piercing the deep fascia, the intercosto-humeral nerve supplies the internal and posterior poUion of the integ- ument of the upper half of the arm. a few of its fibres extending slightly beyt :id the margin of the scapula. • . \_ t • » 1 The third thoracic nerve may form an inosculation with the lesser internal cutaneous nerve. ,. , , ,. , .. 'u a The twelfth thoracic or the sub-ostal nerve lies below the last rib and therefore does not occupy an intercostal space, but passes outward below the external arcuate ligament and anterior to the quadratus lumborum muscle. It contributes a twig to the lumbar plexus which passes down to )oin the first lumter nerve Its lateral cutaneous branch is not confined in its distribution to the abdominal wall, since, after piercing the internal oblique and sending a hlanient to the lower digitation of the external oblique, it penetrates the substance of the latter muscle at a point from 2-10 cm. above the crest of the ilium and supplies the integument of the gluteal region as far down as the upper mai^n of the great trochanter ^^^g. J ^^3 -^^^^.^ ^^^.^ are : (i) the muscular and (2) the cutaneous. I. The muscular branches (rr. muiculare*) may be divided into two groups: (a) the thoracic "^ ^a^ The'thi^cta muscular branches arise from the first to the seventh inchisive and supply the external and internal intercostals, the subcostals, the levatores coitarum. the serratus Dosticus superior, the triangularis stemi and the rectus abdominis. . , ,. The branches to the intercostal and siUicostal muscles are distributed throughout the course .f each nerve. The first to be given off is the largest and courses forward for some distance along the lower part of the intercostel space. The others vary greatly in number and size. The branches to the tevafores costarum consist of fine threads, one arising from each nerve beyond the anterior costo-transverse ligament. They pierce the external intercostal muscles and enter the deep surface of the muscles which they supply. The branches to the serratits posticus superior arxe from the upper four nerves. After piercing the external intercostal muscles they pass along the outer margin of the ilionrostalis and suddIv the four digitations of their muscle. .u The branches to the triangularis sterni are terminal continuations of the third to the seventh intercostal nerves. After piercing the internal intercostal muscles they pass /o^^a/d betvveen the triangularis stemi and the internal intercostals or. in the case of the «^^''"«';: »"t^.'l°V° "^o transven«ilis muscle. In addition to supplying the tri.ingulans stemi the seventh sends fibres to the first dieitation of the transversalis. 3 . .t. j The branches to the rectus arise from the fifth, sixth and seventh and enter the deep surfa^ °!^l^^^^ muscular branches arise from the eighth to the twelfth inclusive and are distributed to the intercostals, the subcostals, the levatores costarum, the serratus posticus inferior, the external obique. the internal oblique, the transversalis. the rectus, the pytamidalis and the '"'"''"'■ni^branches to the intercostal, subcostal and levatores costarum muscles, with the excep- tion of arising from the lower thoracic nerves, resemble in origin, course and distribution those '"^''Vh^hrllt'^^^ToxlTs^atusposticus inferior are largerthan those to the serratus posticus s«,,erior. They arise from the ninth, tenth and eleventh nerves and pass around the lateral maririn of the ilio-costalis to reach their destination. . , , The branches ro\:t^ft external oblique, X\^ internal o.lique and the /ni«^r Wm compnse numero.^ fine twigs which supply those muscles and arise from the lower five thoracic nerves as thev course forward lietween the transversidis and the internal Ob ique. they ^^;;^J^^™ ^^ ^^ ,^^ ^^^f^ 3ri^ from .he eighth to the twelfth nerves inclusive after they have entered the sheath and as they pierce the rectus on their way to the surface. The brancht- to the pyramidalis are derived from the twelfth thoracic and first lumbar "'"'"^The branche^ to the diaphragm are supplied to its costal portion and consist the skin and substance of the mammary gland. Those from the seventh to the eleventh supply the integument of the abdomen as far anterior as the lateral margin of the rectus The anterior branch from the twelfth has a filament which passes over the iliac crest to the integument of the gluteal region, usually sending a branch as far as the great trochanter. It maintains a more or less even balance with the corresponding branch of the first lumbar nerve, each supplying any deficiency in the other. 6. The anterior cutaneous Inanches (rr. cntaaei anteriores) are the terminal fibres of the thoracic nerves. Those from the upper six (rr. cottnci pcctoralea anteriores) pierce the pectoralis major near the lateral margin of the sternum and supply the adjacent integument of the thorax. Filaments (rr. mammarii mcdiales) are distributed to the skin of the mesial portion of the mam- mary gland. The anterior cutaneous branches from the lower six (rr. cutanei aMomioales ante- riores) vary in position. They consist of the terminal filaments which perforate the anterior portion of the rectus sheath at a situation anywhere between the linese alba and semilunaris. Those from the seventh become superficial near the ensiform cartilage, those from the tenth supply the region of the umbilicus and those from the twelfth are distributed to the area located midway between the umbilicus and the pubic crest (Fig. 1105). Practical Considerations. — Of the branches of the thoracic spinal nerves, the anterior or intercostals suffer most frequently from sensory disturbances, and the posterior from motor disturbances. Intercostal neuralgia may result from pressure, as from aneurism or spinal disease, or it may be due to injury. The lower mtercostals enter into the supply of both the thoracic and the anterior .abdominal walls, the pleura also being supplied by them. Pain referred to the abdominal wall and rigidity of the abdominal muscles may therefore be due to diseases within the chest, as pleurisy. Such diseases in the upper part of the chest may cause pain to extend down the arm along the intercosto-humeral nerve, which is the lateral cuta- neous branch of the second i.itercostal nerve, or sometimes of the second and third intercostals. The pain of intercostal neuralgias often becomes intense, especially after violent expiratory efforts, as in couehing and sneezing ; not infrequently after the pain ceases, herpes zoster appears in tne line of the nerve affected. This m../ be a trophic disturbance or an extension of the inflammation along the nerve endings to the skin. Maslodynia, or the so-called "irritable breast of Cooper," is due to intercostal neuralgia, and occurs in the female during the child-bearing period. The lower intercostal nerves, with the ilio-hypogastric and ilio-ingumal, supply the muscles of the abdominal wall, and are frequently injured by the incisions made in abdominal operations, thus leading to more or less impairment of the muscles sup- plied and favoring the later development of hernia. The incision should therefore, so far as possible, be made in the line of the fibres of the muscles (page 535). The intercostal nerves continue their oblique line through the abdominal mus- cles. The pain from Pott's disease is often transferred along the nerves coming from the affected segment of the cord. In this way pain in the abdominal region may THE LUMBAR PLEXUS. 1319 result from this disease, and an abdominal lesion may be suspected; thus has occurred more particularly in children. A feeling of tightness is sometimes observed about the abdomen, corresponding to the course of one or more pairs of these nerves and may be due to impaired sensation in them. Since the abdommal musdra are supplied chiefly by the seven lower intercostal nerves, they are concerned in respiration. When they are contracted as m general peritonitis, the lower ribs become immobile, and breathing Ukes place chiefly in the upper portion of the chest. THE LUMBAR PLEXUS. The lumbar plexus (plexus lumbalis) lies in the substance of the psoas magnus muscle anterior to the ti^nsverse processes of the lumbar vertebra, and consists of a series of loops formed by the anterior primary divisions of the first, second and third lumbar nerves, the smaller subdivision of the fourth lumbar and sometimes a branch from the twelfth thoracic nerve. The remainder and major portion of the fourth lumbar nerve unites with the entire anterior primary division of the fifth to form a conjoint trunk, the lumbo-sacral cord (tmncus lumbosacralis), which passes into the pelvis to become a constituent of the sacral plexus (Fig. 1106). The lumbar nerves increase in thickness from above downward, the first being only 2 5 mm., while the fifth attains a diameter of 7 mm. The length of the nerves from their exit at the intervertebral foramina to their point of division vanes considerably, in the case of the first being i mm. or less, of the second 10 mm. and of the third from 20-25 nim. , ,„. ,^ l <= .. 1 u Constitution and Plan.— In forming the plexus (Fig. 1106), the first lumbar nerve divides almost immediately after its exit from the vertebral column into an upper and a lower branch. The upper, which may receive a contribution from the twelfth thoracic nerve, becomes the Hio-kypogastricdtnA ilio-inguinal nerves. The lower branch, near the body of the second lumbar vertebra joins the upper part of the second lumbar nerve, which, like the first, divides into an upper and a lower branch. The union of the lower branch of the first and the upper branch of the second results in the formation of the genUo-crural nerve. Sometimes fibres from the first aid in the formation of the anterior crural and obturator nerves. The lower branch of the second, all of the third and that part of the fourth which enters the lumbar plexus divide into smaller anterior and larger posterior trunks. From the union of the anterior branches of these three the obturator nerve is formed, and from the union of the posterior results the an- terior crural nerve. The posterior por- tions of the second and third nerves give off from their dorsal aspect small branches which anite into the external cutaneous nerve. The accessory obturator Fig. 1106. Uiatmm IlliutnUnc plan of lumbar plexui. cutaneous nerve. inca«cjji»»^ •^i'.-'—" .,,,,,. ^. . „t nerve, when it exists, arises from the third and fourth lumbar between the roots ot the anterior crural and obturator nerves. Communications.— All of the lumbar nerves receive gray rami communicantes from the gangliated cord of the sympathetic ; and from the first and ^nd, and possibly the third and fourth, white rami communicantes pass to the lumbar portion of the gangliated cord. I320 HUMAN ANATOMY. Variations. — That portion of the fourth lumbar nerve, mn.fitrcalis, which joins the lumbo- sacral cord, is usually less than half of the parent truiik, but varies from one-twentieth tu nine-tenths. When large, it may be joined by a branch from the third lumbar, and when small the fifth lumbar may contribute to the lumbv plexus, the fibres going to the ante- rior crural alone or to the anterior crural and obturator nerves. The branch to the lumbo- sacral cord from the fourth lumbar mav be absent and in such an event the fifth is the only furcal nerve sending fibres to both the lumbar and the sacral plexus. It is thus possible to have as furcal nerves the third and fourth, the fourth alone, the fourth and fifth or the fifth alone, and according to the high or low position of these there is found a corresponding origin of the branches of the lumbar plexus. In this manner are accounted for the ktgh vaatow, or prefixed viA postfixed types of plexus. Branches of the lumbar plexus are : 1. The Muscular 5. The External Cutaneous 2. The Ilio-Hyf)ogastric 6. The Obturator 3. The Ilio-Inguinal 7. The Accessory Obturator 4. The Genito-Crural 8. The Ante w >r Crural I. The Muscular Branches. The muscular branches (rr. musculares) supply the quadratus lumborum, the psoas magnus and the psoas parvus. The branches to the quadratus lumborum arise from the upper three or four lumbar nerves, and sometimes from the last thoracic, and pass directly into the quadratus. The branches to the psoas magnus arise mainly from the second and third lumbar nerves, there sometimes being additional ones from the first and fourth. They pass directly into the muscle. The branches to the psoas parvus consist of filaments from the first or second lumbar nerve which reach the muscle by piercing the underlying psoas magnus. 2. The Ilio-Hvpogastric Nerve. The ilio-hypogastric nerve (n. illohypoKastricus) (Fig. H07) is the uppermost branch of the plexus and is somewhat larger than its associate, the ilio-inguinal. Whilst it derives the major portion and sometimes all of its fibres from the first lumbar nerve, it usually receives others from the twelfth and occasionally the eleventh thorycic. It emerges from the lateral margin of the upper portion of the psoas magnus and runs, below and parallel with the twelfth thoracic nerve, outward and downward, posterior to the kidney and anterior to the quadratus lumborum. Reaching the crest of the ilium, it pierces the transversalis muscle and occupies the intermuscular space between the internal oblique and the transversalis. After coursing along this interval as far as the middle of the iliac crest, it divides into its terminal branches, (a) the iliac and (b) the hypogastric, which correspond morphologically with the lateral and anterior cutaneous branches of the thoracic nerves. There are also some (<■) muscular branches. a. The iliac branch (r. cutaneus lattmlis') pierces the internal and external obliques about the middle of the iliac crest and is distributed to the integument of the anterior gluteal region which covers the gluteus medius and the tensor fascis femoris (Fig. 1083). It forms an inosculation with the lateral cutaneous branch of the twelfth thoracic nerve and maintains an even balance with it, deficiency in the development of either being recompensed for by a com- pensating increase in size of the other. 6. The hypogastric branch (r. cutanea* anterior) continues the direction and course of the main trunk between the transver.s.ilis and the internal oblique almost to the linea alba. Near the anterior superior spine of the ilium it forms an inosculation with the ilio-inguinal ner\'e. As it approaches the region of the internal abdominal riiig it begins to pu.sh its way gradually through the internal oblique and gain the interval between the internal and the exter- nal oblique (Fig. 1 105). A short distance superior and internal to the external abdominal ring it traverses a tiny foramen in the aponeurosis of the external oblique and breaks up into fibres of termination which supply the integument of the suprapubic region. c. Muscular branchci (it. muacularca) arise from the hypogastric branch in its course through the abdominal wall and supply the \ ansversalis, the internal oblique and the external oblique. THE LUMBAR PLEXUS. 1331 Variationa.— The iliac branch luay be absent, its place being taken by the lateral cutaneous branch of the twelfth thoracic nerve. The hypogastric branch may inosculate with the twelfth thoracic and may supply the pyramidalis muscle. 3. The Ilio-Inguinai. Nerve. The iljo-inguinal ner\'e (n. iUoinRuinalls) (Fig. 1107) is the second branch of the lumbar ple-xus and is somewhat smaller than the ilio-hypogastnc. Its fibres usually arise from the first lumbar nerve, with accessions from the twelfth thoracic. Fig. I 107. |: XII. rib XII. tbonck nerve Qoadratus lumboram Pioai magnn* External obliqtw LpStervl culAneous branch ol XII. doraal nerve Internal oblique Trantvenalis Ilio-hypogaatric nerve Ilio-inguinal nerve Iliac branch of ilio-hypogastric Lateral cutancona branch of XII. doraal nerve External culaneoua nerve Anterior crural nerve Genital branch of genitoV. lumbar ganglion V. lumbar nerve Pail of V. lumbar ganglion Genito.crural ni' ' I. sacral ganglion . aacral nerve n. sacral nerve IV. sacral ganglion Obturator nerve ,Accessor>- obturator n^'vt Hypogaatric branches of ifioniypogaatric nerve Ilio-inguinal nerve Branch of internal cutaneous nerve Deep dissection, showing nerves arising from lumbar plexus and lower p.-irt uf sympathetic gangliated cord. Sometimes it arises entirely from the twelfth thoracic or from the second lumbar <>r from the loop between the first and second lumbar nerves. It occasionally forms a common trunk of considerable length with the ilio-hypogastric. In the early part 1322 HUMAN ANATOMY. of its course it ftarallels the ilio-hypogastric, appearing at the edge of the psoas magnus, crossing the quadratus lumboruin behind the kidney and piercing the trans- versalis to reach the intermuscular cleft between the transversalis and the internal oblique (Fig. 1105). While in the last situation it inosculates with the ilio-hypo- gastric and continues forward to enter the inguinal canal, from which it emerges either through the external abdominal ring or through the external pillar of the ring, infero-lateral to the spermatic cord. Some of the branches of the ilio-inguinal supply the integument of the u|^r inner portion of the thigh. Other! 'no. acrotain antcriiircs) are distributed tu the pubic region and the base of the penis and scrotum or, in the female (na. labUIn anuriort*), the mons Veneris and lahi.i majora. Tiny motor filaments ( rr. mniculam) are given off in the course of the nerve to the- transversalis, the internal oblique and the external oblique. Variation*. — The ilio-inguinal may be small and terminate near the iliac crest bv joining the ilio-hypogastric, which then sends off an inguinal branch with the course and distribution of the absent portion of the ilio-inguinal. The nerve may be absent entirely and replaced by either branch, usually the genital, of the genito-crural. It may give off a lateral cutaneous or iliac branch for the supply of the integument in the region of the anterior superior spine of the ilium. The ilio-inguinal may partially replace the genital branch of the genito-crural or, in rare in- stances, the extem.- and bends forward toward the posterior wall of the inguinal canal. It then enters the canal either by piercing the infundibuliform or the transversalis fascia and, lying internal to and below the spermatic cord, traverses the canal and enters the scrotum (Fig. 1108). It sends a filament to the external iliac artery and supplies the cremaster muscle, the skin of the scrotum and the integument of the thigh immediately adjacent to the scrotum. In the female it is smaller and accompanies the round ligament of the uterus to the labium majus, to whose in- tegument it is distributed. It communicates with tlie ilio-inguinal nerve and with the spermatic plexus of the sympathetic. *. The crural branch (n. tamtmlnguinalis) consists of fibres from the second lumbar nerve. It courses down on the anterior surface of the psoas magnus, lateral to the genital branch and to the external iliac vessels, and enters the thigh by passing beneath Poupart's ligament. One of its filaments traverses the saphenous opening, while the remainder of the nerve pierces the fascia lata to the outer side of the opening (Fig. 1107). Its branches vary considerably in size and length and are distributed to the cuUneous area of the upper an*;rior part of the thigh between the regions supplied by the external cutaneous and ilio-inguinal nerves, sometimes extending downward as far as the middle of the thigh. It furnishes a minute branch to the femoral artery and inosculates with the middle cutaneous nerve. c. Muscular liranches to the internal oblique and transversalis are frequently given off by the genital branch. Variations.— The genital and crural branches may arise as separate offshoots of the lumbar plexus and either of them may be derived entirely from the first or the second lumbar nerve. The genital branch sometimes contains fibres from the twelfth thoracic. Absence of the genito- cnir.il or of cither hmnrh m.iv occur, the fibres of the genital branch being contamed m the ilio- ■ inguinal and those of the crural in the external cutaneous or the anterior crural. The genittl branch may replace or reinforce the ilio-inguinal nerve; the crural branch may act similarly toward tlie external or the middle cutaneous nerve. A specimen found in the anatomical labo- ratory of the University of Pennsylvania showed unusually extensive distribution of the cnual THE LUMBAR PLEXUS. 1323 branch. It was lareer than nonnal, its size being that of the normal external cutaneous, and it emerged from the deep fascia below Poupart's ligament directly anterior to the femoral vem. It Kic. 108. Phu parvm CWnilo-crunil iwne Anterior crural External cuuncou* nervi Gtniul bianch of g«nitor. int. cutaneous Internal saphenous Dissection of right thign, showing branches of anterior crural and obturator nerves, escaping from which it dips down in the interval between the obturator membrane and the obtur- ator extemus muscle. From this situation its fibres pass through the deep surface into the substance of tlie muscle. m tjtS HUMAN ANATOMY. astular. the the ik»r ongus and e tein the deep h The •mtrior branch y r. alcrlar), the more Muierficiat. dCM ettds in fr<>m of the obturatoi extern ,-> atn' adductor l>revis mu-v les and '-etwijcn the pectineungt»> Having reamed the interval belwf n the atkiin.tortr> itrc\a and Urngmt ii .-{mi. :es into ii> terminxil branches. Ranches ut the anterk>r divwwm are: iaa) tht irHeular, hi) the . c-tUaneout, (Mi the wmmtimf a/tug ainJ iff) the rascu/ . aa. The articular branch leaves the obturatiMr .i the inferior xnaa%\ forntiien and passes throuKh the cotyloid notch tt; supply the hip joint bi. The muacular branchaa supply the adduclores e>'>:vis and l< kus and the gracit- -i. The branch to the a^awtor ArrMJ enters the mtiaclt learthe" -r margt'i ■( the anterior surf are. The branch to the adductor longus aers the CKislrior surf a e i. the mu- le and -iome- times gives off the cutanfous braiu-k of t! ■ i>bturator , se« >elow) The branch to thr groiilis (Kuses it> -ard behitf! th«- ikhirl surface of its musrle. re. The cui~plies the integument of the lower inner portion of the thigh and >>• leath the sartcxius tonri' an Inosculation with branches of the internal rutaneous and inter it sapheiHHi^ nerves, called the aubaartorial or obturator pleaut. dd. 'The commumicating branchesci mtXd iw'lgi, viiac\t .iiiiit in the pelvis with theaccessory obturator nerve and in 'he thigh anterior to the cat>=Miar U|;ament f the hip joint with the anterior crural. ft. The vascular bt fh enters Hunter's canal akmK t^ niesial edt; and spreads m ' over tht awer portion of th"- superficial femoral artery c. The p. erior branch frntmUnj, th- deeper, pierces the obturator exter - mnscle ' discends m the kit be ween the adductor and in the lattt ituation > into its tfrmin 'tin.. Branches' t the pa ; diviN : re:^. .\c mms< ^Utr ivi (bb) \.l\e articuiar. aa. The inutcutar bianche* sup)!- the obi ator externus. the adductor magnus and the adductor br.- . i- The 111 ah to the oA//.- itor . -&•n«i<^ i.sadd>: obturator wntch supplies that mu e. It arises division and enters the superfici.i ! ~ . rface of tJie mus- The bran< h to the adducU magttus is astioct' the latter as th- '-onjoinl nerve p;; -ses through the si The brani 'o the adductor brcvis enters the the adductor longus -rior fibres of the < brevis and magnus. present only wher .he usual bb. The arti- ilar bran The branch to the hip pectineus to be distributPfl t The brani h tf > the ».• division. Vs- « i edwith f.tcetotht iii masmu l.ir fibres! nnii "1( The ner\-. cont finaliv terminat' .il tt> tf twig tram the main trunk of the m the poster >r surface of the posterior =6. ^ wit!-, ;ranch from the anterior liivi- >n is absent. ^ are destined for the suppl> of the hip and knee joints. / consists of otie or two fine twigs which pass beneath th< ■ .tntero-median portion of the capsular ligament. <>rthe geniculate branch continues the course of the posterim i-%'e to the adductor magnus, it courses down the anterior sur .. mch it pierces at the lower portion of the thigh. Here its muscu- nor to the adductor brevis. On the left side the normal arranifemen' specimen In the same laboratory the branch from the m.'»' tn?-* .luscle lay to the outer instead of the inner side of the oh* ' -r 7. The Accessory Obturator Nerve. imiimr {jiejnifi.. accessory obturator nerve is an inconstant branch of th' v.nd in 29 per cent, of the cadavers examined (Eislcr). it: rd and fourth lumbar nerves, with an occasional root from the fifth : i may be i'- d from the third alone. The roots of origin are situated rietw^een th»«se of the ant( nor crural and the obturator, and the nerve may be intimately associ^'ed with either of these two, usually the former. THE LUMBAR PLEXl S. «3a7 The accessory obturator courses downward mesial to the pscKis maj^us ami beneath the iliac fascia, and leaves the pelvis by passing over the horizontal ramus .»! the pub< i and under the pectineus. In the latter situiition it breaks up in' its branches, one of which (a) supplies the pectineus, anotler (*) the hip )oint, nile ti -! tl'ird (f) inosculates with the anterior di^ -ion of the obtur ->r mne. Somi- times it ia very small and its fibres pass only to i.ie hip joint " ins of its in- o- !ation with the obturator some of its tibrt-s may reach the add i. -s lon^us and bit m and gracilis muscles, as well as the integumfnt of the inner r snon ol the thigli 8. The Ant jr Ciurai. N rve. The anteri b'attch oi the 1 crural or femoral nei ve ( n. bar plexus, arises from tht- t nerves, it as.- s obliquely downward md fenraralbi t Fig. i io8 . the largest -t, secon . third and fourth lumbar anfi emerge> it .nt ^lIe5 it. '.acus, covered I ■ become an oc ■<■ side of the twar'l (M^iterii to the psoas magnus, m bineath the middle < i-iterai iii.«rgin nt that muscle. Thence se between the out jre ,t the p^ and the mesial edge of the le iliac fascia, as far .a.-, jupart's ^.i lent, under which it passes ijant of the anterior portion of th' thigh. The ner\e lies to the ternal iliac and femoral v<- Is, m the abdomen being separatetl the ■i.li- H. m by the psoas magnus, but, as the ,h is reached, gradually nearing them Scarpa's triangle the nerve lies in apposition to the fenwral sheath. In ediate neighborhood of Poupart's ligament, the anterior crural nerve rapidly 'nto a number of >chea, which may be grouped into {6) a superfici. The nerve to the femoral aiteiy usually takes • "^ aiises higher, sometimts as a distinct branch from the t- interior crural as far as Poupart's ligament, leaving tli the femoral sheath. At the ligament it gives off fine twigs ot the femoral vessels and from them tmy filaments jxiss twigs are distributed to the deep femoral artery anil traverses the nutrient foramen of the femur, after supp b. The anterior or auperficial division is mainly sensory twigs to the anterior and mesial surfaces of the '■ Branches of this division are : (aa) the middle cut. aa. The middle cutaneous ner.fe i rr. cataoci anterieres ) m external and an internal, both iX u hich contain motor as The external branch passe^ i'i>wtiward under the sartorii Si-fn ofl a row of fine twigs which enn-r the upper portion of the nerve pierces the sartoriu U '.he junction of the upper and mid<' way throuph the fascia lata aiwi splits into fine filaments which sup| rectus lemoris as far as the knee. The internal branch is sometimes united in the upper part of it It supplies twigp to the saOorius but seldom pierces that muscle, u .interior. This f)ranch, like the external, is distributed to the anter as far down as the knee and frequently inosculates with the crural br.n Variations. — S«>niPtinies the middle cutaneous arises from th rural or from the lumbar plexas and replaces in toto or in pa i?enito-cnual. x'wV 'he ner\e to tin ral .igs ' ^bb) th- io)coii as sens< .J who<" emusi Ir ■stcrior ■%!: e he rontin. -n K I hen pii..ut- ..ument over .urse »itl e e.i- em. Uy pa.s.sin. ntenwl inul integunuiit of the thigh ■! oi the gciuloect of the foot, on which it extends only as far as the metacarpo-phalangeal articulation of the great toe (Fig. 1 1 18) . Btanchea of the internal saphenous are : the commmmcaimg, the infrapaUUar, the articu- lar and the terw mal. The commimicaHng bnauk arises beneath the sartorius at about the middle of the thigh and inosculates with filiunents from the obturator and internal cutaneous nerves to form the subsarloricl or obturator plexus. The infrapatellar branch (r. iafrapatelUrit) (Fig. 1117) arises at the lower part of the thigh. It perforates the sartorius and the fascia lata and spreads out beieath the integument of the knee, where it inosculates with terminal filaments of the internal, the middle and some- times the external cutaneous nerve to form Hm patellar plexus (Fig. 1117) . The articular brmneh (r. articalarla) is an inconstant twig whidi supplies the inner portion of the capsule of the knee joint. The termiual branches ate distributed to the integument of the anterior internal portion of the leg and the posterior half of the dorsum and mesial side of the foot Practical Considerations. — All the branches of the lumbar plexus have motor and sensory fibres, both of which are af!e<:ted in paralysis. The lesion is usually central, involving the spinal cord, a3 in tabes dorsalis, fracture of the spine or Pott's disease, and involves several nerves, or all of them below the seat of the lesion ; the individual branches are not often affected. The ilio-kypo^astric may be divided by the incision in kidney operations or nuky be included m the sutures. This nerve and the ilw-inguinal are sometimes involved in operations in the inguinal region. . The genito-crural sends one branch through the inguinal canal to the cremaster muscle, and another under Poupart's ligament to the skin of the inner side of the thigh, just bdow the ligament Gende irritation of the skin here will cause retraction of die testicle (cremaster reflex), especially in children. The anterior crural has been paralyzed by the pressure of tumors in the pelvis, has been involved in a psoas abscess, and has been injured in fracture of the pubic ramus and — rarely — in fractures of the femur. If the lesion involving the nerve is within the pelvis the paralysis would afiect the ilio-psoas, quadriceps extensor femoris, sartorius and pectineus. If the lesion is outside the abdomen the ilio-psoas will escape. A complete jiaralysis would prevent flexion of the hip, or extension of the knee. The patient is then compelled to avoid flexion of the knee in walking. There will be anesthesia in the parts supplied by the middle and internal cutaneous, and lonp; saphenous nerves, that is, in the thigh along the anterior and iner surface (middle and internal cutaneous), except in the upper third (crural branch of the genito-crural), and along the inner surface of the leg and inner border of the foot to the ball of the big toe (long saphenous). The long saphenous vein and nerve lie close together, about a finger's breadth behind the inner border of the tibia. In the thigh, while they have the same general direction, the vein lies in the superficial fascia, the nerve under the deep fascia. The nerve in the thigh is, therefore, not so liable to injury as is the vein. Since the anterior crural breaks up into numerous branches just below Poupart's ligament, its trunk in the thigh is very short. It lies slighdy external to the femoral artery and can be exposed by an incision extending downward from the middle of Poupart's ligament. Paralysis of the obturator nerve would interfere with adduction of the thigh as well as with internal and external rotation. It may be caused by pressure within the pelvis, as by the child's head in difficult labor, by a tumor or by an obturatoi hernia. Paralysis of the obturator is usually found in conjunction with paralysis of the anterior crural. The nerve may be irritated in coxalgia, in sacro-iliac disease, and on the left side in carcinoma or faecal impaction in the sigmoid flexure. On account of its ter- minal distribution pain in the knee is usually complained of whenever this nerve or one of its branches is involved. THE SACRAL PLEXUS. 1331 THE SACRAL PLEXUS. The Moial or sciatic plexus (plexm sacralU) (Fig. 1 1 12) is formed by a portion o( the fourth lumbar nerve, all of the hfth lumbar, the entire first sacral and parts of the second and third sacral nerves. As previously sUted (page 1320) the fourth lumbar nerve or n. furcalis splits into two portions, a larger upper and a smaller lower the former contributing to the lumbar plexus and the latter uniting with the fifth lumbar nerve. The lower portion of the fourth lumbar having passed downward behind the internal iliac vessels, divides into anterior and posterior branches, which hue respectively with similar branches of the fifth lumbar, the Fic. ma. two trunks thus formed compris- ing the lumbo-sacral cord (tmncitt lambosacralis). This double structure emerges from the mesial margin of the psoas magnus, passes down over the brim of the pelvis and constitutes the lumbar contribution to the sacral plexus. The first and second sacral nerves leave their foramina, pass laterally, anterior to the pyriformis, and split into anterior and posterior branches. The third sacral nerve or «. bi- geminus divides, not into ante- rior and posterior branches, but into upper and lower, the upper becoming a constituent of the sacral and the lower a portion of the pudendal plexus. Con- verging toward the lower por- tion of the great sacro-sciatic f«^ramen, the posterior portion of the lumbo-sacral cord and the posterior branches of the first and second sacral nerves hue and form the external fcpliteal or pertmeal and some voxaxttpos- tfriornerva. The anterior por- tion of the lumbo-sacral cord, the anterior branches of the first and second sacral nerves con* k«M«r MMTi* D« around the great sciatic nerve and its distribution. This nerve compnses t-vo «332 HUMAN ANATOMY. essential and frequently independent elements, the internal popliteal or tibial and thf external popliteal or perone^. Typically the sciatic divides into these two ner\es in the lower part of the thigh ; very often, however, they are distinct from the outset, arising independendy from the plexus, bein^ separated in the great sacro-sciatic fora- men by the inferior fibres of the pyriformis muscle and passing through the thigh as contiguous but ununited structures. Moreover, even when the sciatic appears tf> be a single cord, dissection will reveal its duality in origin and course. The branches of the sacral plexus may be grouped as follows : — Collateral Branches. A. Anterior branches : I. Muscular 3. Articular B. Posterior branches : 3. Muscular 4. Articular II. Terminal Branches. A. Anterior branch : 5. External p>oplit^-al B. Posterior branch : 6. Internal popliteal COLLATERAL BRANCHES. The collateral branches comprise two sets, designated according to the portion of the plexus from which they arise as the anterior and the fiostenor. The anterior collateral branches include : ( i ) the muscular branches and (2) the articular branches. Fig. 1 1 13. Superior ctoteal ncm, giving a br. to pyrifonni* Paou magntu, cut- Ext. ilUc artery. Obturator nerve Pubic bone. meaial aurface Obturator internua •• White line " of pelvic faacia Nerve to obtcntor internua andgemellua auperior Anterior , " CTunI nerve . lumbar nerve **-!. aacral nerve Bra. to pyriformis U- II. aacral ganglion II. aacral nerve Visceral br. of II. aacni) nerve III. aacral ganglion I V. aacral ganglion iV. gaagltoalSMnlMlow) Levator aui Coccygcus Br. to levator ani Diaaeclkm ot right half of pelvia. Viaccral bn. of III. and IV. aacral nerves V. aacral nerve (ventral division) 'Coccygeal nerve (ventral division) Iridic nerve ; the small adatic nerve ia juat in front Br. to sphincter ani, piercing levator am ahowing aacral and pudcudal pleanaea: section ia not meaial, but to left of mid-lme. I. The muscular branches supply {a) the quadratus femoris, {b) the obtura< tor intemus, the gemelli and (r) the hamstring muscles and the adductor magnus. a. The nerve to the quadratui femoria arises from the anterior surface of the upper portion of the plexus, ite fibres coming from the fourth and fifth lumbar and first sacral nerves. It is frequently united in the first part of its course with the nerve to the obturator Intemus. Having traversed the great sacro-sciatic foramen it courses downward anterior to the great sciatic nerve. COLLATERAL BRANCHES. 1333 the obturator intemus and the gemelli and posterior to the capsular ligament of the hip. Reachine the upper margin of the quadratus femoris it passes anterior to that muscle and terminates in fibres which enter the anterior sur ice of the muscle for which it is desuned. In addition to supplying the quadratus femoris it sends twigs to the gemellus tn/enor and to the hip Joint Variatiana.— The nerve to the quadratus femoris may supply the upper portion of the adductoTmagnus and may send filaments to the superior gemellus, either as an additional or as a sole supply. b The nerve to the obturator faitetnos has an origin one step lower than that of the preceding nerve, with which it is frequently associated for a short d^tance. It arises from the anterior Lpect of the fifth lumbar and first and second sacral nerves and leaves the pelvis through the ereat Mcro-sciatic foramen, below the pyriformis and the great sciatic nerve and lateral to the ^dic ner%e and vessels (Fig. 1.14). Crossing the spine of *« !«^hium it course antenorly through the lesser sacro-sdatic foramen and enters the ischio-rectal fossa, where it termiMtes by splitting into filaments which enter the posterior surface of the obturator intemus. A small branch of this nerve supplies the gemellus superior. , ^ ^ . av. u- 1. t„™,. »i,» c The nerve to the hamstring muscles consists of a bundle of fibres which forms the mesial' edge of the gluteal portion of the sciatic nerve. Arising from the anterior aspect of the plexus and deriving its fibres from the fourth and fifth lumbar an- Urst, second and third sacra^ nerves it descends in close connection with the sciatic, lying first anterior to the latter aid then to the'inner side (Fig. 1115)- In the thigh the nerve breaks up into two «» erf fibres^ »" ul>ter and a lower. The upper set leaves the sciatic below the tuber ischu and sendsfibres to the upper portion of the semitendiuosus and the long head of the biceps /emons. ">« lower set arisw further down in the thigh and funishes twigs to the semunembraHosus, the addue/or magmu and the lower part of the semilendinosus. 2 The articular branches are derived from the nerve to the quadratus femoris and sometimes from the anterior aspect of the sciatic. After descending between the capsule of the hip and the gemeUi they supply the postenor porUon of the capsular ligament of the hip joint. , n .u The posterior collateral branches comprise, like the anterior, (3) the muscular ind {\) Xhc articular branches. . • .an .u 3 The muscular branches include («) the nerve to the pyriformis, (*) the superior and (r) the inferior gluteal nerves and (rf) the nerve to the short head of the biceps. a The nerve to the pyriformia may be either single or double. It arises from the dorsal a.spect of the second or first and second sacral nerves and enters the anterior surface of its mi«cle. There may be an additional filament from the root to the superior gluteal nerve con- tributed by the first sacral nerve. , . .^ , . , b. The auperior gluteal nerve (n. gloutns wperior) (Fig. 1114) arises by three roots from the dorsal surface of the posterior portion of the lumbo-sacral cord and the first sacral nerve. Its fibres being derivatives of the fourth and fifth lumbar and first sacral nerves. After passing alx>ve the pyriformis muscle in company with the superior gluteal artery and vein, it 'eaves the pelvis through the great sacro-sclatic foramen and divides into (aa) a superior and (bb) an inferior branch. , , . t. .1 aa. The superior branch (Fig. 1114) is the smaller of the two, and after passing beneath the gluteus medius and along the upper margin of the gluteus minimus reaches and enters the middle of the inner surface of the former muscle, of which it is only the partial nerve supply. bb The inferior branch, larger than the superior, is the conUnuation of the mam trunk. After a forward course between the glutei medius and minimus in company with the lower branch of the deep portion of the superior gluteal artery, it reaches the under surface of the tensor fascia: femoris (Fig. 1114). It supplies the glutei medius and minimus and its terminal fibres constitute the supply of the tensor fascia femoris. . . . • c The inferior gluteal ntrv* («. glntaeu. Inferior) (Fig. 1114) w fonned by twigs which arise from the dorsal surface of the posterior |>art of the lumbo-sacral cord and the hrst, and s<»me- times the second, sacral nerve. It is frequently fused in the eariy part of its course with the small sciatic nerve and not infrequently with the nerve tt) the short head of the biceps. It usually sends a small branch down to join the small sciatic nerve. Passing beneath the nynformis it emerges from the pelvis Into the gluteal region through the great sacro-sciatic foramen, super- Icial to IIh: great sciatic nerve. Immediately up-Mi altering the Hittnck it breaks up fan-wise Into a number of twigs which enter the deep surface of the gluteus maximus about midway Ijetween the origin and insertion. 1334 HUMAN ANATOMY. d. The MTV* to Um ahott hnd of th* biceps (Fig. 1115) apparently arises from the lateral margin of the upper part of the great sciatic nerve. The fibres comprising it can be traced back to the fifth lumbar and first and second sacral nerves, sometimes in combination with the roots of the inferior gluteal nerve. Leaving the great sciatic in the middle of the thigh, often as a common trunk with the articular branch, it enters the substance of the short head of the biceps. Fig. 1 1 14. niuteiM niaximua Br. from V. Inmbarnerve I. ucral nev^r. r dtviikHi Cufaacoythr. from loop of pMtcfior ttCfah II. Kscral liuslcTlor dlvi»loa' major Narvt to quMkma femorls TcBdoB of otituntof IntrrniM th MfndluiftiipctlutdlKivc !>dUiul>( ' Dcen dincetlon o( rlfht buttock, showini CTnergmce ol (rat uAaXle mrv* below pyrifomiLi mnicte; alio miucular bnncfaM and poaterior dlviaiona oi aacial nenra. 4. The articular branches supply the knee and are usually two in number. The upper arises either in common with the nerve to the short head of the biceps or independently from the lateral portion of the great sciatic. Descending on the pos- terior surface of the femoral head of the biceps it passes between the external condyle of the femur and the tendon of the biceps and supplies the lateral portion of the capsular ligament of the knee. The lower arises from the external popliteal nerve in the upper portion of the popliteal space and divides into two portions which supply the lateral and posterior portions of the capsular ligament of the knee. From the branch to the posterior part of the capsule is given off a tiny thread to the sup)erior tibio-fibular articulation. TERMINAL BRANCHES. The terminal branches of the sacral plexus are the external and the iiUemaf popliteal, and these are usually fused in tlie upper part of their course into the great sciatic nerve. TERMINAL BRANCHES. 1335 The Great Sciatic Nerve. The great sciatic nerve (n. Ischladlcns). the largest nerve of the entire human body, is a thick bundle of nerve-fibres derived from both the anterior and postenor portions of Fig. 1115. Gluten* niHximiM' Gmt aciattc nerve Great MCTD-sciatic ligament Small Kiatic nerve Tuber iKhli Great itciatic nctrc ' Br>. to nemitendlnoaua Adductor magnu* BicejM, long head SemitendinoauH Scmimembranonia ■ Br. to adductor magnua, Br. to nemimembranoauii bcmimembranoMii Popliteal artery Articular liranch .^ Poplitcnl vein «^ Communicauii libialla— - Glttteua medina PyrUorais Gcmellua superior Obturator internum Gemellus inferior Obturator eztcraus Trocbanter major Quadratus femoris Glutens ntaaimus Br. to bleep* Bicepa, short head Int. popliteal nerve hJctemal popliteal ner»« Atttcnlar branch Aiygoa articular branch Pcmnr, popliteal surface \ Muscular branches Gastrocnemiua __ Commuoicans tlbularis Deepdi«e«ion of posterior siirtaceoj right thigh '^"'F^^^^^Sm^'^I^^"^^^'" into eitemal popliteal (peioneal) and rntemal popliteal (tibial) nerves. the sacral olexus (Fie. 1 1 12). Properly it consists of two elements onlv, the ex- iern^l^SdSrtai popliteal nerves, the former from the posterior and the latter niK: 1336 HUMAN ANATOMY. from the anterior portion of the plexus, its constituent fibres being derivatives of all of the spinal nerves contributing to the sacral plexus. Bound up with it and apparently integral portions of it, are the nerve to the hamstring muscles and the nerve to the short head of the biceps. From within outward, the four components are arranged in the following order: the r,er\'e to the hamstrings, the internal popli- teal nerve, the external popliteal nerve and the nerve to the short head of the biceps. Arising from th ' apex of the sacral plexus and proceeding as its direct continua- tion, the great sc. .c leaves the pelvis through the greater sacro-sciatic foramen below the pyriformis muscle and above the geiv.t;llus superior. In the form of a thick flat trunk, about 1.5 cm. wide, it turns downward and lies aiiterior to the gluteus maximus and posterior to successively the gemellus superior, the tendon of the obturator intemus, the gemellus inferior, the quadratus femoris and the upper portion of the adductor magnus, being accompanied in the upper part of its course by the sciatic artery and the arteria comes nervi ischiadici. Lying external to the nerve is the great trochanter and internal to it is the tuberosity of the ischium (Fig. 1 1 15 ). Entering the thigh by emerging from beneath the gluteus maximus, the nerve lies under cover of the hamstrings and at a varying posiuon in the thigh it splits into its terminal divisions: (5) the external popliUid and (6) the intemcU popliteal. As previously stated (page 1333), these nerves may be separate from their origin. 5. The External Popliteal Nerve. The external popliteal or peroneal nerve (n. peronaens comannis) (Fig. 1115) is homologous with the musculo-spiral of »he upper extremity. It comprises fibres derived from the posterior portionS;of the fourth and fifth sacral and first and second lumbar nerves. As a part of the great sciatic, it follows the course in the thigh just described and after the bifurcation of the sciatic enters the popliteal space as an inde- pendent nerve. In the upper part of the popliteal space it lies beneath the biceps and later inclines gradually outward between the tendon of the biceps and the outer head of the gastrocnemius. Passing over the lattor, it reaches the under surface of the deep fascia posterior to the head of the fibula, 2-3 cm. below which it divides into its terminal branches. Branches of the external popliteal nerve are :' the cutaneous and the terminal. The cv >neous branches axe: (a) the sural and {b) the peroneal communi- cating.- a. The im .1 branch (n. cnuncas rara* lateralis) (Fig. 11 19) consists of one or more, usually two, filaii.ents which arise in the popliteal space, frequently in common with the peroneal communicatintf nerve. Becoming; superficial by piercing the deep fascia overlying the outer head of the gastrocnemius, it is distrihuted to the integument of the upper two thirds of the lateral aspect oi the leg. Its degree of development is in inverse ratio to that of the small sciatic and short saphenous nerves. b. The peroneal communicating nerve (r. aMttomoticas peronaeat) (Fig. it 19), also called the n. commumcans fibularis, is larger than the preceding. Leaving the peroneal in the popliteal space, often in combination with the sural nerve or nerves, it descends beneath the deep fascia and over the lateral head of the gastrocnemius to the middle of the leg. Here it is usually joined by the tibial communicating branch, from the internal popliteal and the joint trunk so formed (Fig. 1135) is called the external or short saphenous nerve (page ^42). The terminal branches comprise: (a) anterior tibial and (c) the muscu 'o- cutaneous. the recurrent articular, (6) the a. The recurrent articular •^r recurrem tibial branch ( Fig. ii 16) is the smallest of the three. Given off a short distance below ilv? head of the fibula it pa.sses forward under the peroneus longus and the extensor longus digitonim, courses upward in the musculature of the tibialis amicus and divides into filaments which supply the upper fibres of the tibialis anticus, the anterior portion of the knee joint, the superior tibio-fibular articulation and the periosteum of the external tuberosity of the tibia. 6. The Anterior Tibial Nerve. The anterior tibial nerve (n. peronaens profundas) originates below the head of the fibula in the inter\'al between the peroneus longus and the fibula. After winding TERMINAL BRANCHES. J 337 externally around the head of the fibula beneath the peroneus longus, the extensor proprius hallucis and the extensor longus digitorum it reaches the anterior aspect of Fig. 1 1 16. Eitemor kHigiM dlKitorum Antrrior libtal artery- Anterior tibial nervc- MuncalcxttiaiMOiis ncrve- Pcrooens lootu*. laid opat Tibialit anticus- Ezteiuor kHigiu difitorum. Hnd ol fibula Peroneal nerve Recurrent tibial branch Branch to eatcnaor longiu digitonim Muscular branch to pcronci ftroneua brevia External braiKh of musculo-cutaneou* Peroneus toiiKU* tendon Peroneus brevis temlon riicin of extensor brevis digitorum .External saphenous ncr\-e Dissection of antero-hlrrsl sarfare of tf^t leg "w! of .inmnni nf font, shnarai; antrrior tibial and musculo-cutaneous nerves. the leg. Lying on the anterior surface of the interosseous membrane it joins the anterior tibial vessels 8-12 cm. below its origin and accompanies these vessels 1338 HUMAN ANATOMY. down the front of the leg as far aa the ankle, lying first to their outer side, then anterior to them and at the ankle to the outer side again (Fig, i Ii6). Branches of the anterior tibial nerve are : (aa) the muscu/ar, {66) the articular. (<•<•) the external and {dd) internal terminal. aa. The mttMuUr brancbM are distributed to the tibialis anticus, the extensor lon^us digitonim, the extensor proprius hallucis and the peroneus tertius. The nerves to the tibialis anticus consist of two twigs, an upper and a lower. The upptr arises at the orisin of the anterior tibial, passes beneath the peroneus longus and the extensor longus digitoram and enters the upper portion of the muscle. The lower arises in the interval between the tibialis anticus and the extensor longus digitorum and passes obliquely downward into the substance of the tibialis anticus. The nerve to the extensor longus digUorum arises inunediately below the preceding and enters the inner surface of the muscle which it supplies. The nerves to the extensor proprius hallucis, usually two in number, arise in the middle ot the leg and enter the substance of their muscle. The nerve to the peroneus tertius is usually derived from the nerve to the extensor longus digitonim. A*. The articular branch leaves the anterior tibial above the antenor annular ligament and is distributed to the forepart of the ankle-joint cc. The internal terminal branch (Fig. 1117) courses forward in the foot under the inner tendon of the extensor brevis digitorum and lateral to the dorsalis pedis artery, and reacht > the base of the first digital cleft. Here it splits into two branches (nn. digitaira dorulea balliKiH Uuralis «t digit! tccundi nedUlis), which supply the contiguous sides of the «reat and second toes and inosculate with branches of the musculocutaneous nerve. In the region of the tarsus it sends off the first dorsal interosseous nerve, which supplies the first dorsal interosseoiis musclt- , the mesial meUcarpal articulations and the first and second metacarpo-phalangeal joints. Liki- the other interosseous nerves, it sends a filament between the heads of its dorsal interosseous muscle for the supply of the adjacent articulations (Ruge). dd. The external terminal branch (Fig. 1118) passes laterally over the tarsus under cover of the extensor brevis digitorum, to which muscle it sends branches. From it are given off two to four, usually three, dorsal interosseous branches, which decrease in size from within outward, the fourth often being lacking and the third quite rudimenUry. These interosseous nerves art distributed to the adjacent articulations and sometimes to the second and third dorsal inter- osseous muscles. The fibres from the anterior tibial to the dorsal interosseous muscles are usually not their sole supply, the external plantar supplying constant branches for their innerva- tion. From the latter are probably derived the motor innervation and frcim the occasional ante- rior tibial branches some extra sensory filaments. This branch usually ends in a ganglifonji enlargement, from which its branches are distributed. Variations.— The anterior tibial sometimes supplies the mesial side of the great toe or the adjacent sides of the second and third toes. In one case the anterior tibial supplied the outer three and one-half toes, the inner toe and one-half Ijein^ innervated by the musculo-cutoneons nerve. Rarely the anterior tibial has no digital distribution whatsoever. c. The Musculo-Cutaneous Nerve. The musculo-cutaneous nerve (n. peronaens snperficialis) (Fig. 11 16) continues the course and direction of the external popliteal. Descending through the leg in a fascial tube in the septum between the peroneal muscles and the extensor longus digitorum it becomes superficial by piercing the deep fascia anterior to the fibula in the lower third of the leg. It may make its superficial appearance as a single ner\e or as two branches. Branches of the musculo-cutaneous are: (a * cutaneoua ner»« From IntcriMl -ruiancoua uer^*e From Imcmal - cutaneous nerve I CutaneouH F patellar br. Int. ^MaphenottH nerve .Int. nphenona nerve M. The iataniiatafiBiaatbranch(a.caUMdsdM«alliM4lalit) (Fig. 1117). larger than the external, passes obliquely inward in front o< the ankle and then forward over the dorsum of the foot Cutaneous twigs are distributed to the anterior aspect of the lower third '"c 1 "7- of the leg and the dorsum of the foot. Just below the anterior annular ligament the nerve breaks up into an inner, a middle and an outer branch. The inner branch inosculates with the internal saphenous nerve, from which it receives an accession of fibres, and passes forward to supply the integument of the mesial aspect of the foot and great toe. The middle branch follows the first metatarsal space and inosculates with the inner branch »f the anterior tibial nerve. The outer branch courses down the second metatarsal space and divides into ihe two dorsal digital nerves (no. dlgitatea doruln pedis) which supply the contig- uous sides of the second and third toes. This branch is sometimes derived from the external terminal part of the musculo- cutaneous. cc. The external terminal branch la. calaacoa dersalli intcrmedius) (Fig. 1 1 1 7 ) courses down the leg anterior to the ankle and lateral to the inner branch, fciving off twigs to the antero-lateral por- tion of the integument of the lower part of the leg and dorsum of the foot. Having reached the foot it breaks up into inner and outer branches. The inner branch divides into dorsal digital branches for the supply of the adjacent sides of the third and fourth toes, mA^'^ outer branch, after receiving an accession of fibres through inoscula- tion with the external saphenous, divides similarly into twigs for the contiguous sides of the fourth and fifth toes. The dorso-lateral aspects of the terminal phalanges and the nails receive ?.ddi- tional filaments from the plantar nerves- Variations.— Deficiencies in the in- ternal branch are usually supplied by the anterior tibial nerve and m the ex- ternal by the short Siiphenous. In c.ise the external branch ends at the dorsum of the foot, the external saphenous, which would fill the varnncy at the digits, has its root from the external popliteal more strongly deve1o|)ed than usual, and thus the toes are supplied in an unusual manner but still by tibrLS from the ex- ternal popliteal ner\'e. -Crest or tiliia Int. Maphrnoua " nerve Int. saphenolu 'vein Int. terminal br. muAculo- ' cutaneous nerve Int. terminal - br. ant. tibial nerve 6. The Internal Popliteal Nerve. The internal popliteal or tib- ial nerve fn. tibialis) (Fig. 11 15) is of greater size than the external and corresponds in its distribution to the combined median and ulnar nerves of the arm. Arising from the anterior portion of the sacral plexus, it includes fibres derived from the fourth and fifth lumbar Superficial diatection a( right le* and tuul.diuwlug cuuneons nerves of anterior surface. IMO HUMAN ANATOMY. and first, second and third sacral nerves. Leavinjf the pelvis through -^ grtMr sacro-sciatic foramen below the pyriformis, ;ind fiassing through tb«- gimesi rejjinr and upper part of the thigh as the inner portion of the great sdatk: nwve. h kBcomc an independent trunk at the point of bifurcation of the sciatir Ei inij|iw i ium beneath the hamstring musdea and descending vertically throtqeii the miimt of ttit Fig. iiiS. MiMculo-caUncou* ncnre Fibula ExirititorlofifftiH dixttorum tendon Prronrm tcrtina tmdon Anterior tlMal nerve Articular l)ninchc« to ankle joint Peroneua loogua tendon External aaphenooa nerr* Muaculo cutaneoua nerve— external diviaiaa External division of anterior tibial nerve Extenaor brevia digitorum Metalanal liranchea of external division of anterior titiial nerve External saphenous nerve l>igital limnches of external division of ntuaculo- cutaneoua nerve .Eatensor proprius " " ' tendon teacmalab'* "»mi)* .;v'^^^ Extensor bievis digitoram Internal division of musrolo* cutaneous nerve Anterior tiliial nerve— internal branch Dissection of dorsum o{ right foot, showing distribution o< anterior tibial, muaculo-cuuiieous, and inietiial and external saphenous nerve*. popliteal space, it gradually attains the inner side of the jKipiiteal vesstis, crossing them superficially from without inward. In the lower part of the space the nerve lies posterior to the popliteus muscle and anterior to the plantaris and the gastroc- nemius. At the lower border of the popliteus muscle the internal popliteal becomes the posterior tibial nerve (Fig. 1 1 19). TERMINAL BRANCHES. 134« r) the o at the intemai popliteal *f< . («) the articulmr, (b) the musftUar, ■MS and (rf) itite pmUriinr tiimi Fig. 1119. TIIMI(IURm*0|.<'' >'>• liilwriMr ciwnMl kTrs.ulw :wm^t% flualHta auKto Ctt. kni «
  • s^iA\\^ SS5^thi3t^or liSSSTof'the Joint, while Ae lower accompanies the irfenor mtern.,! SSr art^ When a third b present it accompanies the superior mtemal ar^Kiular arter> Sihe Seal plexus a number of fine filaments are furnished to the posenor portion ... fll^kne^ S and an occasional twig enters the popllteu, muscle by piercing its posterior '"*'«■ The muwular branche. (rr. m.Kalart.) comprise two sets, those given off from Ih. part above thTSon of the sciatic nerve and tho.e given off below. The former hav-e bee., d^ted on w> 1333. The latter consist of a Kries of five twigs which mnervate the irastrocnemius the soleus, the plantaris and the popliteus. ■^ ^r^«to the gastrJnemiu,, salens and plantaris consist of two stout nerve trunks, an upp^ ^d a W-. The upper arises m the middle of the popliteal space and enters the iTteKl^o" thTinner head rfthe gastrocnemius. The lower anses a short distance below he up^r^d frequency combined with the nerve to the plantaris. divides into two branches, a shorter for Ae outer head of the gastrocnemius, and a longer, which enters the superior bor- SeJ^of The soleus. the upper part of^which muscle it supplies. From the nerve to the plantaris '''"™^1."rS"rtU°J:;^/"::^«'"a complex structure, with a distribuUon much wider than ^Tm^i^in it. naiT Aiter n^aching the lower "J^f" °' ♦^HKeTwa and nerve turns forward, ascends between the antenor aspect of the muscle and «he tmw, and «^ Se M eri^?Vuria« of the popliteus. A branch supplies the periosteum of the tibia and AeHnters^he nutrient foramen ofThat bone Another, the interosseous hanch (.. int.r«i^.. «^ri.TM^reSfiret posterior to and then between the layers of the nterosseous membrane S^t to ^owe mar^n. Termi.-I fibres a.* dUtributed to the P*n«rteum of the tibia and toTe ?nferiorSZ£ articulation. Other filaments reach the Ubialis posticus muscle an.l the superior tibio-fibular prticulation. <:. The cutaneous branch is the /»ia/rw»w<««««ir«Av«#ri'« J'^""^'',™ TxS luieolus, thVlateral portion of the heel (rr. calcd l.wr.l..) t^e dorso-Uteral Sn of the foot (». ««».«. do".U. lateralU) and the outer half of «h« dorsum o the fifth ^ Twigs are furnished to the ankle, and to the astragalo''^. lon^ kaiiucis and /«..« di^lorun. leave the posterior tibial •iKJut the middle of the leg and paf ^ i' .ectly to their muscles. 1344 HUMAN ANATOMY. '• -n bb The intamal caleanMii nerve (rr. cakaael B«dUlM) arises from the posterior tibial at the lower part of the leg and becomes superficial by traversing an opening in the intern ! annular ligament Dividing into two sets of twigs, internal ealcanean and caleanM-pUntar, it is distributed to the integument of the internal aspect of the heel and postenor portion of the solv. ec. The articular branches are two tiny twigs, given ofl beneath the wtemal annular ligament, which supply the ankle joint .u .v _». > rfrf/The Internal plantar nerve (o. flaataris Mdlalto) ( Fig. I m ), larger than the external, resembles in its distribution the median nerve m the hand. From the pomt of division of the posterior tibial nerve it courses forward in the foot in company with the internal plantar artery. lyirat first above the internal annular ligament and the ealcanean head of the abductor hallucis Midthen between the abductor hallucis and the flexor brevis digitorum. Passing thence for- ward between the flexor brevis hallucis and the flexor brevis digitorum it divides into two ter- FlG. lUI. C«lc«neo-pUnUt cutaneoiu br. of tibial nerve Articular br. (unualljr ■ tw. of tibial nerve) Br. to aliductor baltncia Int. pUntar nerve Bm. to Hex. brevl« digitorum I. andll.lumbricales Digital bm. of int. plantar nerve Flexor btevia digitorum Ext. plantar nerve Br. to abductor minimi digitl Abductor minimi digiti Flexor acceiaoriui Br. to flex, accewwrius Supcrftdal br. est. ptanur Mfvc Bra. to flex. brev. minimi digiti Deep br. ext. plantar nerve Digital branch Bra. to inlerosMi of fourth upacr Digital branch II. and IV. lumbricalea Diweclion o( riglit foot, .h..wliig liilernil aud external planter nervei and their branchea. minal branches, an inner and an onter. In addition to the terminal branches It gives oft certain collateral^ TJlUteral branches are muscular, cutaneous and articular in distribution. The muscular supply the abtluctor hallucis and the flexor brevis diRitorum. TX^f^ cutaneous pass T^Z^r, the muscles jtist mentioned to 1* distributed to the inteRument of the inner portion of the sole The articular furnish innervation to the inner tarsal and tarso-metatersal Joints. The terminal branches are an inner or mesial and an outer or lateral. . , , , The inner ..r mesial terminal branch (Kig. i lai ) courses forward upon the under surface o the abductor hallucis, pierces the plantar fa.soia ,x«terior to the tarso-metttarsal articulation of he gr^-tt tol' and terminates by exlentlinR along the mesial side of that toe asUs inner planta digital nerve. In its course it furnishes filaments to the mner surface of the foot and a twig to the mesial head of the flexor brevis hallucis. THE PUDENDAL PLEXUS. »345 The outer or l«t«niltennlii«lbtmiich (Fig. iiai) U larger than the inner and U simted below the distal portion of the flexor brevis digitorum and above the deep plantar fasaa. After a short forward course it splits into two branches, the lateral of which soon divides into h«ro. There are thus formed three plantar digital nerves (an. dlKiutea plantare. commnii*.), e?jJi of which at the distal end of its n ;tatarsal space divides into two digital nerves { an. diglule. ,U>Ufts pnprii), the inner supplying the contiguous sides of the great and second toes, and the middle and outer being distributed similarly to respectively the second and third and third and fomSTtoes The inner of the three sends a filament to the first lumbricalis, the middle some- times to the second lumbricalis. while the outer forms an inosoilation with the external plantar nerve In addition to innervating the muscles enumerated and the integument erf the plantar sur- bceof the mesial three and one-half toes, each of the digital nerves sends tiny filaments toward the dorsum for the supply of the naib and the tips of the to«. tt The external plmntat nerve (a. plaatarto UtcralU) ( Fig. 1121 ) is a smaller nerve dian the internal and corresponds in its arrangement and distribution with the pataiar branch of the ulnar nerve. After string from the internal plantar beneath the internal annular ''ipment. it Stows a coursein company with the external plantar artery obliquely forward "jd o"tw»fd ab^the flexor brevis digitorum and below the flexor accessorius.Rwch.ng the mtenra^ between the abductor minimi digiti and the flexor brevis digitorum it divides near the head of the fifth metatarsal bone into superficial and deep terminal brancfaM. „ , , .. ■„, Bwach.. of the external planter, like those of the internal, toclude : colMerat and Urmxnal ''"^tSJ colUteral bruichcs comprise muscular and cutaneous twigs. The muicular branches «e given of! soon after the origin of the parent nerve and supply the flexor acc«ssonus and the Victor minimi digiti. The cutaneous branches ate a series of small twigs which follow the sentum between the flexor brevU digitorum and the abductor minimi dipu and become super- fcial by piercing the deep plantar fasda. They supply the integument of the lateral poruon of The tcnninal branches are : the superficial and the deep. .... u . .u The anpetflcial or cutwieous branch (r. wperidaUi) inoscuUites with a branch of the internal planter and continues forward in tiie interval between the flexor brevis digitorum and the abductor minimi digiti, eventually splitting into an external and an internal branch. The external branch (Fig. iiai) sends filaments to the flexor minimi digiU and the inter- ossei muscles of tiie fourtit metatarsal space, after which it becomes cutwieous near the fifth metetarao-phalangeal articuUtion and continues forward as the plantar digital nerve for the '"''"•Th^'^einal 'branch (Fig. iiai) courses forward in tiie fourtii metetersal space, at whose distal end it separates Into two filaments which supply tiie opposed surfaces erf tiie /°"f* "«<> fiftii toes. Thedigital branches send filaments dorsally for tiie nails and tiie \xi» o tiie toes. The d.« or muscular branch (r. profaataa) accompanies the external planter artery in an obliauelv forward and outward course above the adductor obliquus halluas and the flexor a^riSd betow tiie interossei muscles. It forms an arch (Fig. i»i) whose conve«ty is directed forward and outward, and terminates in tiie region of tiie base of the great toe. h rom the convex aspect of the arch are given off tiie filaments which innervate the interossei muscles of tiTfim. ^Sond. third and sometimes tiie fourti, interosseous space. Otiier muscular twigs supply tiie adductiires obliquus and transversus hallucis and tiie outer three lumbncales, the branch to tiie second lumbricalis first passing beneath the adductor transversus hal ucis The branches to all of tiiese muscles enter their deep surface. In addition to the muscular distribu- tion, articular twigs are furnished to tiie tarsal and tetso-metetarsal articulations. THE PUDENDAL PLEXUS. The pudendal plexus (plexus padendus) is the downward continuation of the sacral plexus, and, whilst each retains more or less its individuality as a dwtinct structure, there is no sharp line of demarcation between the two. Considerable interlacinff and overlapping is the rule, so that often some of the mii>ortant branches of the pudendal plexus are derivatives to a large extent from the elements giMng rise to the sacral plexus. n t .u .^1.;.. The pudendal plexus (Fig. 1 122) is situated on the posterior wall of the peUiij and is formed by contributions from the anterior primary divisions of the first, second and third sacral nerves, from the entire anterior primary divisions of the fourth and fifth sacral and from the coccygeal nerve. , . , „, „.„; Communication«.— The nerves helping to form the plexus receive gray rami communicantes from the gangliated cord of the sympathetic, which join them shortly after the nerves emerge from their inter\ertebral foramina. 8S 1346 Branches. — Tb" FlO. 1 133. Diactmm lllmlratiiiK ptan of pudendal and roccy(cml plexiuei. HUMAN ANATOMY. branches of the pudendal plexus are : (i) the visceral, (2) the muscular, (3) the perforating cu- taneous, (4) the small sciatic, (5) the pudic and (6) the satro-coaygeal. 1. The visceral branches arc really white rami communicantes. They are derived from the second and third or third and fourth sacral nerves and arc distributed to the pelvic viscera by way of the pelvic plexus of the sympathetic. The details of these nerves are des- cribed with the pelvic plexus of the sympathetic (page 1374)- 2. The muscular branches furnish innervation to the levator ani, the coccygeus and the external sphinc- ter ani. They arise from a loop-like interlacement of nerve-fibres, formed by the third and fourth sacral nerves, with sometimes the addition of fibres from the second. The nerve to the external spAincter pierces the great sacro-sciaiic ligament and the coccygeus muscle, sending filaments to the latter, and enters the ischio-rectal fossa, lying between the edge of the gluteus maximus and the sphincter ani externus. It supplies the Fig. 1123. From II. lumbar ner%*e ./ ^..'From 1. lumbar From III. lumbar ncn-e Cutaneoua br». po»t. diviiiiona of ■acral ncma CoccyiiMt nenrM, poCcrW diriaioni Coccymal nerve anterior dlTision From ani. V. lacral FromnntlV. «cTal Inferior hemnr rhoidal nerve» I Iliac hm. of ilio- ' hypogaitric Gluteal brB. <>( •mall wiatic ner^-e Inferior pudendal nerve Superficial diwecion ol right buttock and adiucnt regloni, ihowlnr cuunBJU. nerv... THE PUDENDAL PLEXUS. '347 An est. femoral br. of •mall ndatic pcrterior portion oJ the external sphincter and distributes sensory fibres to the mtnniment over the ba^ of the ischio- ^'O- ««*»• rectal fossa and the tip of the coccyx. Vartotkm.— This nerve, inrtead of pierc- ing the coccygeus, may pass between that mils cle and the levator anL The nerve to the levator ani is derived usually from the third and fourth, sometimes the second and third, sacral nerves and en- ters the muscle by piercing its mesial surface. 3, The perfo- rating cutaneous nerve (Fig. 11 26) is an inconstant branch, being found in about two thirds of the bodies examined. It springs from the dor- sal aspect of the second and third sac- ral nerves and at its point of origin may be associated with the pudic or the snail sciatic. Passing downward and back- ward it pierces the great sacro-s c i a t i c ligament in company with the coccygeal branch of the sciatic artery and- winds around the lower bor- der of, or in rare in- stances pierces, the gluteus maxim us. Perforating the deep fascia slightly lateral to the coccyx, it be- comes superficial and is distributed to the integument over the inner and lower por- tion of the gluteus maximus. SomHIcUiI dl.»ectlon of rluht bullock ai..l ihiRh. thowlng cuuneoui Vwiatkm.. -In- '«"" "^ ««*•'*' ""*•"• &nf/S"n«^mpany the pudic nene or pass between the ligament »~'^he K,"Uju. maximus. It may be replaced by a branch of the small saatic or by a nerve, called by tisler From CXI. mta* ncoui nerve 1348 HUMAN ANATOMY, Ae ». perforan, coccygrus majcr, which arise, from the third and fourth or fourth and fifth Mcral and pierces the coccygeus muscle. Fig. 11J5. Friim obturalpr n«rv« From inlemal cuuiwooi Internal uphcnoiu n«r« liuier malleolus External 1 .iliaiiMU bramhes From snull Kiilic mr^e Small Kimtic nerve Sural from peroneal nerve Peroneal communicating Pan st lural branch Tibial communicating Exii'tnal saphenous ner\e i:xt. braiirh <>l muscukxutaneous Anlciior branch oJrxl Mphelinn" Cut.ini'ii" iier\es ot (Kwterior lurface of right leg. 4. Tm: Smai.i. S( iatic Nkrve. The small sciatic nerve (n. cutancus fcmorls posterior) (Fig. tJI4) js a purely sensory structure. It originates from the back of the lirst, setoiul ami thiril. or Hi THE PUDENDAL PLEXUS. 1349 from only the second and third, sacral nerves, the upper root usually being aMOCi- S^th one of the roots of the inferior gluteal nerve and the lower root with the SoSng cuuneous or the pudic nerve. Leaving the pel vjs through the gr«t S^^tk foramen below the pyriformis. it descends m the gluteal region between thr^^ ischu and the great trochanter, posterior to the great sciatic nerve and anterior to the gluteus miximus. accompanied by the inferior glutei nerve and the Stk W Emerging into the tliigh at the lower border of the gluteus ma.x.rnus h S,^thu.^downwaS beneath the deep fascia and 9uperfic«l to the hamstnng muS to a short distance above the knee, where it pierces the deep, and become r«^pant of the superficial, fascia. Thence it pas-scs downward through the roof d th^Ste^ space and through the upper part of the calf. ,n the latter situation accomSSing the external saphenous vein and inc^culating with the external ^^DhTnCs ne?ve. It rarely extends beyond the middle of the calf tapering off into tiny thr«d^ which are dis^buted to the skin of the posterior surface of the upper half or two thirds of the leg (Fig. 1125.) . . . . . /i> ,i,_ Branches of the small scnatic nerve are: (a) the tn/ertor pudendal, (6) the gluteal, (<■) ihe femoral and (d) the sural. a The Inferior pudendal or perine.1 br.nch (rr. peri—ta) (Fig. 11*8) leaves the parent SBto^rlnS^^^^^^^^ „e^e1!S withthr;irineal and inferior hemorrhoid.1 bruKhes of the pudic nerve. It may •'"'n^-^nJ-urS'-STncbe. (rr. d-l^i •-f.ri.r..) (He. ..^,4) consist of two. three or^or? Stout fiuTetS? which arise W the small sciatic n .Sort d»tanj= above the nfcrior margin of the gluteus maximus. around which they wind. Piercing ihe fasr^ lata Sually Uiey turn upward over the lower portion of the gluteus maximum and are d.s- ribu S tc^^hTskin of the inferior gluteal region, as far exten«My a, the great trochanter and ntSy almost to tiae coccyx. The outer branches oyeriap the t.-rmmal twigs of the p^enor hTAm-h of the external cutaneous nerve and the posterior primary divisions of the first. se« ond !::;d thii^ Ju^terTrv^^e inner branches ^times pierce the great sacro-sciatic liga- ment • they reinforce or may replace the perforating cutaneous nerve. . , , . ; TTie femoral branch.. (Fig. , 1*4) consist of two series of twigs, an internal and an external, which pierce the fa.scia laU of the posterior aspect ol the thigh and supply the inttgu- "^"'rf'TheTS^rbranch.. (Fig. 1125) are usually two terminal twigs which innervate t.. a vaiying extent the integument of the back of the leg. ''ometjmes not emending beyoiK^ the confines of the popliteal space and sometimes continuing all the way to the ankle They in^Xn-ith the «temal sliphenous nerve, and when they are lacking their place is Uken l.y the external saphenous. Variation* —In those cases in which the internal and external popliteal nerves are separate from Th"i^dpitn?y the small sciatic also is double. The ventral portion accompanies r^ntemal Seal and gives <.ff the inferior pudendal and internal femoral branches while ^ Xr^l iSrtion accomr««nies the external popliteal «nd gives off the gluteal and externa -: oraltraK sSmeun.es the small sciaticas joined in the thigh by a branch from the great ? , uirfc. 5. The Pudic Nerve. (n. pudcndus) arises from thi- front of the second, third and as main root coming from the third and there being a doubtful oot irom tne nrs.. Leaving the pelvis by way of the great sacro-sciatic foramen iietween the pyriformis and the coccygeus and below the great sciatic nerve, it jias-ses forward with the internal pudic artery and the ner^e to the obturator liiternus, over the base of the lesser sacro-sciatic ligament to the spine of the ischium ( Pig. U26). Rcachine the small s^icro-sciatic foramen internal to the internal pudic artery the ner\e traverses thi? opening and enters the ischio-rectal fos.sa. where it gives of! the inferior hemorrhoidal nerve. The main trunk coursi-s forward in a canal (Alcock's) in the obturator fascia on the outer wall of the ischio-rectal fossa The pudic iRT\v' •' .'iih sacral nerves, ijot from the first. I350 HUMAN ANATOMY. (Fig. 1126), at whose anterior portion the ner\e appi caches the base of the tri- angular ligament and divides into its terminal branches, the perineal and the dorsal nerve of the penis or ^litoris. Branchei of the pudic nerve are : (a) the inferior hemorrhoidal tierve, (A) the perineal nerve and (c) the dorsal nerve of the penis or clitoris. a. The inicrior hcmarThoiiUl nerve (na. hcoMrrhoidalea iaferiorts) (Fig. 11 27) is usually given off by the pudic upon entering the ischio-rertal fossa, but it may be derived directly fr.mi the plexus, its fibres being offshoots of the third and fourth satral nerves. In company with tht iiiferior hemorrhoidal vessels it passes mesially across the base of the Lschio-recul fossa toward Fig. 1136. CaccyfMl Mm. I CunaCMM hffUKlMS froMI lonfM .4 \' luniliw 4ad 1. II. Bad HI. mlysI Bcfv**. tMnl>;r.M dItWiaa Branch of IV. flacral ncnrc X ^^(perforaiingcuuniou*) Levator ■ni and anal fMcia ^^^.Pttdic npiA'c Ciit edge of 'obturator faacU Inferior n...nor- — rhoiflnl neive Intrmal pwlic •rtrry Prrinnl dlvlnioa •( pudk Be Itanil serve ol cittart* VnlTi' lucimhikbtta partly n-n>ov"d to expuae pudic wrvc and accompanying blood-v^iael. in ca.rtl on outer wall of lichiu-racul lossa. the anus, oa approximating which it splits into a numlier of filaments, which supply he external sphincter and ihe iiit< icimient <•« the anal rcRion, and inosculate with the small sciatic, pudic and fourth s.icni! iKives. 6. The perineal nerve (■. peilMl) (Fig. 1126) is one of the tenninal branches of the pudic and arises at the bifurcation of that nerve near the p- cavemoms Nerve to hulb Nerve to trmn>- versiu perinei MuKulu be. ol l>nta«l di«l«t"fl ot \twUc Btrvr Oomat nerve of peniH r.itxawtahr. ofMrliwal (lhi>ionof |)««rlM4 •ulxricUlK frrlncal dlvbloll of liudiciicrre iBfrfinr hmurTlMld*] n«rvr SfWiKlcr aai llcrt'fawU <-f iHittock Clau clltatdk ntep Uycr of tHuvul^ lil,'4iiirnl Oorml nrrvr '-f > lit-*t« Supcrltclal |M-nnrdl Frora IV. iKnl mtm left linn) DitMciion of female perineum, r.h.«ring nervei; «iul fawia in position on right tide of body, removrf on {C^Mn- (».scl« removed on ri«hl ».rae, of the sacrum or of the innominate bone, from pressure of tumors in the pelvis or of the child's head in labor or from the use of forccjis. It is the structure in greatest danger in dislocation of the hip, since the head of the fcinur in the most frequent varieties sweeps backward against this nerve. In the reduction of these (xistenor liisloc.itions the nerve has been hooked up by the head and made to pass across the front of the neck of the bone. From its close relation to the head and neck, it may l)e injured in violent movements of the hip joint without dislocation. It passes out of the pelvis through the greater sacro-sriatic foramen, below the pyriformis muscle, and after cur\inK outward and downwarrl under the gluteus maxi- mus muscle it continues its course, approximately, in a line from a point midway THE SYMPATHETIC SYSTEM OF NERVES 1353 beween the Rreater trochanter and the tuberosity of the ischium above to the iniddle of !^,«nUteal soace below. At about the unction of the middle and lower thirds of t tCh kdiSintoX internal and external popiiteal nerves. Below the gluteus m^xS"iU9cle it is comparatively superficial, so thut tenderne« of the ner%e. as S^ns^t^^iT easily eliJted by pn-siure. At the point where it emerges rom uX^ S^te :s maiimus it b Ldily r«»ched for operation. After averucal in^ S trough the skin and fascia at this level the bice,^ muscle u exposed The tower m3 of the gluteus maximus is raised and Uie biceps drawn inward when Se ne^n be easily hooked up with the finger. Because of the great importance erf tKei^e to the lower extrei/iity it is not advisable to excise or div.de it as this would Sralyze ts whole area below. Stretching is the only justifiable operaUon. rithouiTSe r«ulte obtained are often disappointing;, and the operation may caus« a^ten«iritL According to Trombetto. it wSl reauS-e a tension equal to the weigh onsX to break it. and it is more likely to yield at its attachment o the spinal «H^ thS el^X^e. It should, therefore, tolerate a stretching torce of from too to ^\T(T^»T A safe working rule is to use a force sufficient to r.«se the affected limb from the table, the patient lying in the prone position. UhTbeen observed that when the paralysis is Jue to »«"'«= F^»;^"jr. '*"* „»r..« of the sacral olexus within the pe vis it is often confined to the peroiual or ex- ?^7 iJw «^V or iTmost marked in it. This has been explained by the fact Shf2br« forThe ^oneal nerve lie close together direcdy on the pelvic bones Lnd a^ tSore. pa&arly exposed to pressure. They arise for the most par felX luiX-Si^cral cord, formed by the fourth and fifth lumbar and first sacral S"es wS He^lr^^on the innomWe crest, the rest of the plexus lying on the •"^riSlS d the external popliteal or per^al nene the extensors of the foot and toUTe tibialis anticus and the peronei muscles are involved. The foot han^s dowi^m its own weight (foot drop), and turns in from paralysis of the perone.. S^me ^ the anterior tibial muscle escapes. In walking t^^ .^nee must Ik= un- dXflexS^ prevent the toes from dragging on the ground and the arch of the foot 1 tottenS from the loss of the support given to the arch by the peroneus U.ngus^ H ?SS^ is disturbed it will be only^to a slight extent oyer the anterior part of the WatoutThe shin, and outward from this on the dorsum o the foot and toes, but not ?the ^d« of the foot. The peroneal nerve may be divideti accidentally in a sub- ™4neoS tenotomy^! the bice^tendon for contraction at the knee, the nerve lying dSe^TheTnner Lder of the tendon. It may be injured by external violence. ^ U^ around the head and neck of the fibula, where if necessary an incision will S^S^ it ; or it may be injured by pressure, as in prolonged knee hng. '^^n^>^iH di the intemJ popliteal nene all the other muscles of the leg. in- cluding ^S^cid and deep fleTors. the tibialis jx)sticus the plantar muscles and inteSi Ir^Ked. Thellatient cannot extend the ankle and therefore canriot iSnd^Thb t<^. The toes <^not be flexed or moved sideways Sensation is dis- tS^ on the^ner and posterior surface of the leg. the outer border of the f.«t, the "'"^ CWS^;"e':^^'S^-^ the flexors o, the knee also are involve^ Lrul\1fo.;a?d\f tU'iadnCp?^^^ which is supplied by the anterior . n.ral nerve. __. ,„^ THE SYMPATHETIC SYSTEM OF NERVES. The sympathetic portion (systema nervorum sympathetiaim) of the peripheral ncrvmis s;ffl£s f^m that afready de.crib«l-the ^P;-'-^^']--^' ^^^^ -in beine particularly concerned in carrying efferent and afferent 'm|>"f^ »« and fnmX^th^racic a J abdominal organs (collectively termed the .punchmc area\ Contrast to the great somatic fskeletal) masses of voluntary muscle. Whilst tue Lhsf^the afferent or sensory impulses conducted from the splanchnic area differ CZ in" ,ortanrr«J;ct from those formed by the cerebro-spinal nerves, the efferen IZr^Z are JLuliar (. ) in supplying the involuntary an>n^"Hi9?IQPPi!PPP THE SYMPATHETIC SYSTEM OF NERVES. «355 Constitution and General Arrangement. — ^The sympathetic system st r\ es to receive, rearrange and distribute the visceral filaments of the cerebro-spinal nervei;, Fig. 1130. latvuknitltoolc cwd of tympaOmilk Thyroid cutilacc [tynpatfMtic Superior cervical cudUc bnoch of MkkDc cervk«l gaot^loa Infcilor cerrkal gaagUoa I. tfMrack gugUoa Right recurrat Urymgeal man* CeoifaiDcd cwlcal cardtoc brmwjwt RJtht Ytgm (of aympMhetk Inlnior cer%-icaJ cardiac branch of va(i» Left middle aad inferior cervical cvtttacs of typatfceWc Diucction thowins right gangiiatad cord of Byaipathctic and itt bnochat. and to complete, by the interposition of one or more of its especial neurones, the path for the impulses brought by such tibres to the objective organs. It compriaei 1356 HUMAN ANATOMY. two principal parts, the gangliated cords and the plexuses, with their associated ^""^The gangliated cord (tnincus sympatheticus). one of a symmetrically placed pair of gangliated trunks situated anterior or lateral to the bodies of the vertebr* (Fie. 1133), begins in the head and extends through the neck, thorax and abdo- men to the lowlr portion of the pelvis. In the head it consists of a P exus of fibres continued up from the neck in an intricate interlacement which foUous the internal carotid artery ; and in the pelvis it terminates by the two cords forming a loop or fine inosculation, situated anterior to the coccyx and containing the coccygeal ganglion or ganglion impar. . 1 j- »• . 1 The plexuses (plexus sympathetlci) are a series of more or less disUnct col- lections of groups of nerve-cells (gangli ) and fibres, situated mainly in the axial line and giving off and receiving fibres co- lected with the vanous viscera of the trunk. The component elements of the p! .uses and, indeed, of the entire sympathetic system, are the ^awWia and the «<• e-fibres. The ganglia, whilst foUowing a general plan of arrangement a. .0 number, size and position, are subject to wide individual variations and, moreover, where they approach a segmental type, as in the gangliated cord, there is considerable deviation from the arrangement presented by the cerebro-spinal system. A ^nglion may or may not be connected with a spinal nerve, but it is always ...iked by association cords with other ganglia. According to their position, three varieUes of ganglia are recognized. One group includes the prevertebral ganglia (g. tmnci sym- patheUd), those found as nodes in the gangliated cord ; a second vanety comprise the collateral or intermediate ganglia (g. plexuuin sympathetlcorum), which Ue either on the peripheral branches of the gangliated cord or in a prevertebral plexus ; whilst to the third set belong the innumerable minute terminal ganglia, composed of nerve-cells which lie at or Bear the visceral distnbuUons of the sympa- thetic fibres. , , . , .• L Each ganglion consists of an indefinite number of mulupolar neurones, which possess one axone and a number of dendrites, the whole cluster of cells being enclosed in an envelope of fibrous tissue. The axone is often meduUated in the immediate vicinity of its cell, but usually loses this sheath as it gets farther and farther away from its origin. The course taken by the axone of a prevertebral gang- lion-cell may be one of three : (i) it may pass by means of an association cord into an adjoining prevertebral ganglion, (2) it may proceed as a constituent of a gray ramus communicans to join a spinal nerve or (3) it may follow a splanchnic efferent toward a viscus. . The nerve-fibres encountered within the sympathetic system include two sets : (a) those derived from the cerebro-spinal system, which are usually meduUated, and (*) the sympathetic fibres proper, for the most part nonmedullated, although as stated above, many of the axones possess a medullary sheath for a short distance beyond their origin from the nerve-cell. This distinction between meduUated and nonmedullated fibres is, however, somewhat indefinite, since the meduUated spinal fibres often become nonmedullated before terminating, whilst the sympathetic fibres occasionally are meduUated throughout their course. Rami Communicantes.— Where the typical segmental arrangement prevails, as in the thoracic region, each spinal nerve is connected with the adjacent gangliated cord by a pair of short nerve-trunks, known as the rami communicantes (Fig. 1 129). These are divided into two groups, the white rami and the^ray rami, a distinction de|)ending primarily upon the difference in the appearance of the strands when seen in the fresh condition ; this distinction, moreover, corresponds with the histological difference above noted — white rami appearing so in consequence of the prepon- derance of opaque meduUated fibres, and the gray rami possessing the darker tint on account of the absence of the refracting myelin coat. The rami communicantes pass directly between the spinal ner\ ( s and the gangliated cord, in relation to the latter joining either a ganglion or an association cord between nodes. The white rami communicantes are composed almost exclusively of the 1 ■ :eral branches of certain of ihc spinal nerves which use the sympathetic system as the pathway by which they arrive at their destination. They consist of fasciculi of THE SYMPATHETIC SYSTEM OF NERVES. »357 meduUated nerve-fibres derived from both the anterior and the posterior roots ol the spinal nerves. The fibres arising from the anterior root are called the splanch- nic efferent fibres and those from the posterior root the splanchnic afferent. Not all of the spinal nerves, however, give off white rami, these strands of communication forming a thoraco-lumbar group, from the first or second thoracic to the second or tnird lumbar nerve inclusive, and a sacral group, derived from the second and third, or third and fourth sacral nerves. The cervical nerves do not give off white rami. The splanchnic efferent fibres are the axones of cells located within the lateral horn of the gray matter of the spinal cord. They furnish motor impulses to the unstriped muscle of the vessels and viscera, and secretory ones to the glands of the splanchnic area ; they also convey motor impulses to the heart. Leaving the spinal cord by way of the anterior root, they pass peripherally, enter a white ramus communicans and reach the gangliated cord. One of three courses is then pursued by these fibres : ( i ) they may end at once by forming arborizations around cells in the ganglion which they first enter, (2) they may pass through this ganglion, thence up or down through an association cord to end around the cells of a node of the gangliated cord above or below the level of entrance, or (3) they may course through the gangliated cord and one of its visceral branches, and terminate in arborizations around the cells of a prevertebral or of a collateral ^glion. It is possible that in some cases the spinal eflerents may continue without mterruption through the several divisions of its path as far as the terminal ganglia. In any event, whether ending in the gangliated cord, the prevertebral, the collateral or the terminal ganglia, the cerebro-spinal fibre as such probably never actually jains the tissue of the oi^n, the last link in the path of conduction being supplied by a sympathetic neurone. The splanchnic afferent fibres are the sensory fibres of the splanchnic area and consbt of the dendrites of cells situated within the intervertebral ganglia on the pos- terior roots of the spinal nerves. Whilst the greater number of these fibres are fotind in the white rami, a few are thought to be constituents of the gray rami. Beginning in the viscera, they run centrally, without interruption, through the terminal and collateral ganglia, through the gangliated cord and the white (or gray) rami to the spinad nerve, and thence after commg into relation with the cells of the ganglion of the posterior root, they pass by way of the posterior roots into the spinal cord. The gray rami comtnunicantes are bundles of axones of sympathetic neu- rones which pass from the gangliated cord to each one of the entire series of spinal nerves. The reason of this generous provision will be evident when the purpose of the communications effected by the gray rami is recalled, namely, to provide sympa- thetic filaments to the outlying muscles and glands by way of the convenient path afforded by the distribution of the somatic nerves. Mingled with the gray fibres, a few of the medullated variety are often encountered ; these are probably pardy splanchnic afferent fibres and partly medullated sympathetic fibres. Variation in the origin of the gray rami from the gangliated cord is not uncommon ; they may arise either from a ganglion or from the association cord between two ganglia ; after leaving the gangliated cord, a single ramus may divide and supply two spinal nerves ; or the reverse may happen, two or more rami arising independendy and either separately or after fusing, joining a single spinal nerve. The hirther course of the sympathetic fibres, after having joined the spinal nerves by way of the gray rami, is as follows : ( i ) they may course peripherally along with the anterior or posterior primary divisions "f the spinal nerve and convey vasomotor, pilomotor or secretory impulses to the involuntary muscle and glands of the somatic area ; or (2) they may enter the spinal canal by way of the anterior or posterior nerve-roots and be distributed to the spinal meninges, but tint to the nervous coluinn. According to Dogiel, it is probable that a small number of axones of sympathetic neurones enter the root-ganglia of the spinal nerves to end in arborizations around cells of type II (page 1008). The association cords (Fig. 1130) are the longitudinally disposed bundles of fibres comprising the interganglionic portion of the ganjfliated cord ; they contain both white .ind gray fibres. The gray ones are the axones of sympathetic neurones whi.h are either passing between adjacent or more remote ganglia, or taking an upward or 1358 HUMAN ANATOMY. downward course before passing distally to their "!^^^ JP^^^^^^ distributioa The white fibres are either spinal splanchnic efferent or afferent hbres. The ^J« "^^^^ ^^ distribution from the gangliated cord include the scma^tc and the visceral The somatic branches are the rami comniuniamtes ; the vis- ceral benches comprise the splanchnic efferents, which consist of both white and gray efferent fibres, as wdl as the white splanchnic afierents. THE CERVICO.CEPHALIC PORTION OF THE GANGLIATED CORD. The cervico-cephalic portion of the gangliated cord (Pf^** "P***"*^/^,^;^^^^^^^ sjstematis sympatheUci) consists of a series of ganglia, "s^^^X /^^.*^' ^^^^^^^^^ two, connected by composite association cords (Fig. 1131)- It lies postenor to the Fig. II 31. Lower head of cvtcnul ptctygoM irukIc Intenul pierygow muirlr I Buccal ■ Aurfculo4tnipoi«l oenw Intenul carotid artcnr \ Fneuinofaftric » Inferior dental ncnrv Spinal acceaiory nerve^^ Put of facial nen- Stylo-pharyngeui. n»»de <^o«o-|)haryiigeal na've' I. ccrvkal nerve PneumoKastric nerve. Supenrtr cervkal ganglfaa of sympathetic Superior larynieeal bcKcndens hypogloaai lI.cenrtcaliierTe' 111. cervical nerve IntervaniElloBlc as' tord of i»yini>atbeiic Mfddit ccrrical gangUoo laferW cervical ■angUoa Branch to 1 . thoracic Inferior cervical cardUc ^ of sympathetic Ungual nerva External laryD|[eal branch Superior cervical cardiac ef • sympathetic Middle cervical cardiac of sympathetic Rcrurtcn* laryntfeal nerva Middle cerrRal cardiac ot Common Ipneumotfaalric carotid artery Infcrior cervical canUacof p— uaiunaitric Recurrent laryngeal nerve lotemal mammary artery CartiUiceof I. rill - Clavicular fiuet uf sternum -^ Deep dissec'Jon of neck, showing: cervical portion of lympAthetlc gangliAted cord »nd its conncctiom. caroti ' sheath and anterior to the prevertebral fascia and the rectus capitis anticus major and scalenus anticus muscles. Inferiorly it is continued into the thoracic portion of the gangliated cord, and superiorly, at the base of the skull, it forms an intricate plexus around the internal carotid artery, in whose company it enters the mmgmfiimmwn!^i9mmimim''mmmm THE SYMPATHETIC SYSTEM OF NERVES. »359 cranium. The small ganglia connected with the trigeniinal nerve — the ciliary, the spheno-palatine, the otic and the submaxillary — are regarded as outlying nodes be- longing to the cephalic continuation of the gangliated cord. The dominant characteristic of this portion is the absence of white rami, the spinal fibres present reaching the cervical region from the upper thoracic nerves by way of the association cord between the highest thoracic and lowest cervical gang- lion, around whose cells, as well as those of the higher cervical ganglia, the processes of the spinal neurones end. The distribution of the cervical portion of the cord includes pupillo-dilator fibres, cardio-accelerator fibres, vasomotor fibres to the arteries of the head, neck and upper extremities, pilomotor fibres to the integument of the head and neck, motor fibres to tlie involuntary muscles of the orbit and eyelids and secretory fibres to the glands. The branches consist, as elsewhere, of two groufs, somatic and visceral, the former reaching their area of distribution by way of certain cranial and spinal nerves, and the latter, either alone or in conjunction with other nerves, forming plexuses which accompany blood-vessels and supply various viscera and vessels of the head, neck and thorax. The ganglia of the cervical portion include a superior, a middle and an inferior. The Superior Cervical Ganglion. — The superior cervical ganglion (g. cervi- cale snperius) (Fig. 1077) is the largest of the entire sympathetic series, measuring 2-3 cm. in length and 4-6 mm. in width. It rests posteriorly on the rectus capitis anticus major muscle opposite the second and third cervical vertebrae, with the internal carotid artery anterior to it and the vagus nerve to its lateral aspect. \Vith the typical reddish-gray hue of the sympathetic ganglia, it is fusiform in outiine, although it may present constrictions, usually three, which indicate its composition of four fused ganglia. The somatic branches consist of (i) rami communicantes and (2) some of the communicating: branches to the cranial nerves. 1. The rami communicantes consist of four gray rami which join the anterior primary divisions of the first four cervical nerves. 2. The communicating branches to the cranial nerves are pfiven off from the upper portion of the ganglion, ( I ) one joining the petrous ganglion of the glosso- pharyngeal, (2) others entering the ganglia of the root and trunk of the vagus and (3) another joining the hypoglossal nerve. In addition to these there is frequently given of! from the lower portion of the ganglion (4) a branch which joins the exter- nal laryngeal ner\-e. The visceral branches comprise : (i) \.he pharyngeal , (2) the superior cervi- cal cardiac , {,2)) ^^ '^''^^'^**^^^ ^^^^^^ ^^ ''■'^^^^^'^^• 1. The pharyngeal branch or branches (rr. lao'nsopharjnKei) arises from the antero-mesial aspect of the ganglion and courses obliquely inward and downward posterior to the carotid sheath to reach the surface of the middle constrictor of the pharynx. Here it unites with the pharv'ngeal branches of the glosso-pharyngeal and vagus nerves to form the pharyngeal plexus (page 1269), from which fibres are distributed to the muscles and mucous membrane of the pharynx, a few filaments joining the superior and external laryngeal nerves. 2. The superior cervical cardiac nerve (n. cardiacus superior) (Fig. 1131) arises as two or three twigs from the ganglion, with sometimes an additional filament from the association cord between the superior and middle ganglia. It courses down- ward anterior to the longu , colli muscle in the posterior part of the carotid sheath, crosses the anterior or the posterior surface of the inferior thyroid artery, and then descends in front of the inferior laryngeal nerve. At the base of the neck the course of ihe nerve begins to differ on the two sides. The right nerve enters the thorax either anterior or posterior to the subclavian artery and accompanies the innominate artery to the aorta, where it enters the deep cardiac plexus, a few fibres passing to the anterior surface of the aorta. On the way down a few twigs join the inferior thyroid artery and with it enter and supply the substance of the thyroid body. The left nerve upon entering the thorax joins the common carotid artery, alonpj whose lateral and anterior surfaces it courses to the aorta, upon reaching which it 1360 HUMAN ANATOMY. joins the superficial cardiac plexus. In some instances the nerve remains behind the carotid artery and joins the deep cardiac plexus. A pretracheal branch, derived from the loop between the superior cer\ical cardiac nerve and the inferior laryngeal, descends anterior to the trachea and is dis- tributetl to the pericardium and the anterior pulmonary plexus (Drobnilc. ; The superior cervical cardiac nerve communicates freely m the neck with the middle cardiac and other branches of the sympathetic, and with the external laryngeal and superior cervical cardiac branches of the vagus. In the thorax it mosculates with the inferior laryngeal nerve. Variations.— The superior, as well .^s the other cardiac nerves, presents a considerable deirree of variation, sometimes to so grea: an extent as to show no resemblance to the accepted typical plan of arraneement. It is sometimes absent, especially on the nght side, and m such event appears to be replaced bv a branch from the vagus or from the external ljir>nKeal ner\e. It may have no independent course, but join one of the other sympathetic cardiac nerves and reach its destination as a part of the latter. 3. The vascular branches comprise plexiform nerve-structures which accom- pany the terminal divisions of the common carotid artery. They consist of : (a) the external carotid branch and (*) the internal carotid branch. a. The external carotid branch (n. caroticus extemns) (Fig. 1061) joins the external carotid artery and furnishes subsidiary plexuses which accompany the branches of that vessel. Iii addition to supplying vasomotor fibres to the external carotid tree, sympathetic filaments are fumbhed to two of the ganglia of the trigem- inal ner\ e. A branch (radix g. submaxillaris) from the plexus on the facial artery (plexus maxiUaris externns) joins the submaxillary ganglion as its sympathetic root, and one or more, the smallest deep petrosal nerve, from the plexus on the middle meningeal artery (plexus meoingeus), forms the sympathetic root of the otic ganglion. Ganglia of microscopic size have been described on these vascular plexuses. The most important of these, the temporal ganglion, is situated on the external carotid at the point of origin of the posterior auricular artery and is said to receive a filament of communication from the stylo-hyoid branch of the facial nerve. b. The internal carotid branch (n. caroticus internus) is apparently an upward, cranial extension of the superior ganglion (Fig. io6i). Ascending beneath the internal carotid artery, it accompanies that vessel into the carotid cand, where it divides into two plexuses, the carotid and the cavernous, the former ramifying on the lateral and the latter on the mesial aspect of the artery. While the individuality of these two is distinct, there are numerous fine fibres connecting them as they pass upward into the cranium. The carotid plexus (plexus caroticus internus) is located on the lateral or outer surface of the internal carotid artery at its second bend. In addition to supplying fine plexuses which accompany the branches of the artery to their ultimate ramifica- tions, the following arise from the carotid plexus : (aa) the carotid branches, (bb) the communicating branch to the abducent nerve, (cc) the communicating branches to the Gasserian ganglion, {dd ) the great deep petrosal nerve and (<■<-) the small deep petrosal nerve. aa. The carotid branches consist of numerous fine twigs which are supplied to the internal carotid arterj-. tib. The communicating branch to the abducent nerve consists of one or two twigs which join the nerve as it lies in the wall of the cavernous sinus in close proximity to the internal carotid artery. cc. The communicating branches to the Oasserian ganglion comprise several small fila- ments which pass to the ganglion ; they usually arise from the carotid but sometimes are deriv'< from the cavernous plexus. dd. The great deep petrosal nerve courses forward to the posterior end of the Vidian canal, where it joins the great superficial petrosal to form the I'idian nerz'e (page 1059), finally en- tering Meckel's ganglion as its sympatbetic root. ee. The small deep petrosal nerve or «. tarotUo-tympanicUS joins the tympanic plexus (page 1075), a structure formed by the tympanic branch of the glosso-pharyngeal, a filament from the geniculate ganglion of the facial nerv'e and the small deep petrosal nerve. In addition mm. pmn^Himp mmm w^rnm THE SYMPATHETIC SYSTEM OF NERVES. 1361 to funiishinK twigs to the mucous membrane of the middle ear and vicinity, this plexus con- tributes a large part of the sma/l superficial pel ic sat nene, which joins the otic ganglion as iu sensory root (page 1246)- The cavernous plexus (plexus caTernosus) lies inferior and internal to the internal carotid artery and in intimate relation with the ravernoiis sinus. Its branches are: {aa) the carotid branches, (66) the communicatiiifr branch to the oculo- motor turve, ice) the communicating branch to the trochlear nerve, {dd) ihc com- municating hranch to the ophthalmic division of the trigeminus nene, (<•<•) a branch to the ciliary ganglion and (,//) hranchcs to the pituitary body. Fig. 1 132. SupcrtOT cffrvkal ctnliac bnndi of •ympathctk SupOTlor ccrvkAl canHac bnach of vacw MIdillc ccnrical KanKliua MkUle vCT\kal canUac bnach of sylniMdMtic (of iy>p«lkMH Inf. «.er>i<:al cardUc braach oL cenriul gBimHoa Middle ccnrkal unttK faniKh of vawus Inf. gcrvkal unfiai. bniKh of vftgua illrmlc oenre Lea vacua Mrv« Rccuimt laryncral Mwe I -Ht iMlmooary aftcty -Pulmooary vcina ilma«iar>- orHka Masial tut6..c of IM PcrkardiuM DiMection showing c««li«c br«nch« of pneumogMtric nerv« and or sympathrtic cord»; aortic arcli and brenchc* and pulmonary artery partially removed ; pericardium laid open. aa The carotid branches are distributed to the internal carotid artery. bb. The communicating branch to the oculomotor nerve joins the latter about at the point where it breaks up into its superior and inferior divisions. . , , u cc. The communicating branch to the trochlear nerve, sometimes deriscd from the carotid plexus, joins the trochlear in the wall of the cavernous sinus. dd. The commun ting branch to the ophthalmic division of the trigeminus nerve joins the mesial surface of that nerve. ... , > • .1 ee. The branch to the ciliary ganglion (radices sympathetlcae g. dllarls) ^nses in the cranium and enters the orbit through the sphenoidal fissure, either as an independent structure or jointly with the nasal or with the oculomotor nerve. As the sympathetic root (radix media), it enters the upper posterior angle of the ciliary ganglion (Fig. 1058), eiUier alone or as a common trunk with the sensory root. 86 »362 HUMAN ANATOMY. ff. The branebM to th* pituitary body consist of several tiny filaments which enter the substance of that body. 4. The vertebral branches consist of two or three filaments which pass baclcward, pierce the prevertebral muscles ..nd are distributed to the bony and lijja- mentous structures of the upper portion of the vertebral column. The Middle Cervical Ganglion.— The middle cervical ganglion (g. cervicale medium), a structure not infrequently absent, consists of one or two collections of nerve-cells situated posterior to the carotid sheath in the neighborhood of the inferior thyroid artery (Fig. 1131). It lies about tJie I el of the sixth cer\'ical vertebra and represents the fusion of two primitive cervical ganglia. The BOtnatic branches are : ( i ) the gray rami ctmimunicantes and ( i ) the subclavian loop. I. The gray rami communicantes arise either from the ganglion or from its upper or lower association cord. Tliey consist of two trunks which pass backward and join the anterior primary divisions of the fifth and sixth cervical nervej. 3. The subclavian loop (ansa snbclavia [Viettssenii] ) is a nerve, frequently double, which passes over the subclavian artery and joins the inferior cervical gang- lion sending twigs (plexus subclavius) to the subclavian artery and its branches and to the phrenic nerve. The visceral branches are: (i) the thyroid plexus and (2) the middle cervical cardiac nerve. In case of absence of the middle cervical ganglion, these branches arise from the intergaiiglionic association cord between the superior and inferior ganglia. I. The thyroid plexus (plexus thyreoldeus inferior) consists of several fine inosculating twigs which accompany the inferior thyroid artery into the substance of the thyroid body. 3. The middle cervical cardiac nerve (a. cardiacus medius) (Fig. 1131) differs in its course on the two sides of the body. Descending in the neck, where it inosculates with the superior cervical cardiac and inferior laryngeal nerves, it ftasses, on the right side, either anterior or posterior to the subclavian artery, to the front of the trachea where it receives filaments of inosculation from the interior laryngeal nerve. On the left side it enters the thorax between the common carotid and subclavian arteries. On both riirht and left sides it terminates posterior to the arch of the aorta by entering corresr iding sides of the deep cardiac plexus. Variations. — ^The Kangliated cord, in the region of the middle g;anglion, may lie posterior to the inferior thyroid artery or may be bifurcatra, the artery lying between the two portions. The Inferior Cervical Ganglion. — The inferior cervical ganglion (g. cervicale infenus) (Fig. 1079) is situated at the root of the neck, over the first costo-central articulation, between the neck of the first rib and the transverse process of the seventh cervical vertebra. In shape it is irregular, being flat, round or cres- centic, and it is often fused with or only partially separated from the first thoracic ganglion. Situated in the external angle between the subclavian and vertebral arteries it is usually connected above with the middle ganglion by an association cord and by the subclavian lorai-|c if*' " 1 pwtMly bl«IMle«i wKh ii (rr4af cervical fantflloa II. thoracic gangUon Dissection showing thoracic, lumbar and sacral portions of riKht gangliated corj anil their branches. 2. The inferior cervical cardiac mrvr- (n. cardiacus Inferior) (Fig. 1132), sometimes arising from the first thoracic ganglion, descends in the thorax posterior to «364 HUMAN ANATOMY. the subclavain artery, inosculates with the middle cen ical cardiac and inferior lar>nRtal lerves and terminatesi in the dctp cardiac plexus. THE THORACIC PORTION OF THi: GANGLIATED CORD. The thoracic portion of the gangliated curd (pars, thoracalis syitematlM sympa- thrtlcl) consists of a series of eleven, twelve, ten or even fewer irrejjularly triangular, fusiform or oval ganglia (rk. thomealla), situated lateral to the bodicfc of the thoraci.- vertebne, covered by parietal pleura and interconnected by association cords which lie anterior to the intercostal blood-vessels (Fig. 1133). The largest of the ganglia is the first, which is situated at the mesial end of the first intercostal space and is not infrequently hised with the inferior cer\'ical ganglion. The location of tho thoracic ganglia corresponds usually to the heads of the ribs, the lowest being placed anterior to the head of the twelfth rib and at the upper margin of the twelfth thoracic vertebra. A characteristic of the thoracic ganglia is the almost wnvaiym^ presence 0/ uhit,- rami communicantes, all of the series, with the poM'We exception of the first, receiving these rami from the thoracic spinal nerves. They consist of an upper and a Iffiter series, the former coming from the upper five nerves and coursing head-ward to enter and be distributed mainly by way of the cervico-cephalic portion of the gangliated cord ; and the lower arising from the lower seven and being distributed to certain thoracic and abdominal structures. As elsewhere, so here from each of the ganglia b given of! a gray ramus communicans to a thoracic spinal nerve. The somatic branches of the thoracic portion of the gangliated cord are chiefly the gray rami communicantes. These arise from each of the thoracic pnglia and, m close proximity to the white rami, pass backward and join the anterior pri- mary divisions of all the thoracic spinal nerves. The visceral branches "rise from the ganglia and their association cords and consist of gray splanchnic efferent and white splanchnic efferent and afferent fibres. The splanchnic afTerent fibres have no sympathetic connections, and consist merely of tracts which ciny impulses from the splanchnic area through the thoracic and spinal ganglia to the postenor roots of the -nnal thoracic nerves. The splanchnic efferent fibres, afit-r priS:>ing through the gangliated cord or its peripheral branches, form links with the ceUs of the collateral or terminal ganglia, from which nonmeduUated axones are derived for the supply of various visceral or vascular structures. Those of the upper series are distributed mainly as branches of the cervical ganglia ; while those of the lower series, from the sixth to the twelfth thoracic nerves inclusive, in the thorax supply the aorta and lungs with vasomotor fibres. Beloxv the thorax their distribution is quite extensive, including, in conjunction with the vagus, viscero-inhibitory fibres for the stomach and intestine, motor fibres for a portion of the circular muscle of the rectum, vasomotor fibres for the abdominal aorta and its branches and secretory and sensory fibres for the abdominal viscera. The thoracic gangliated cord is peculiar in containing, along with the visceral fibres dis- tributed by its splanchnic eflerents, many efferents proceeding from the spinal cord destined for regions supplied by way of the limb nerves arising from the cervical and lumbo-sacral segments of the spinal cord. In order to provide gray rami at appro- priate levels to join the spinal nerves the spinal efferents course both up and down m the gangliated cord beyond the thoracic region. In this manner the thoracic nerves, in addition to giving off the splanchnic efferents, provide vasomotor, pilo- motor and secretory filaments for the greater part of the lower half of the body. The visceral branches comprise : (i) Has pulnumary branches, (2) the aortic branches and {y) the splanchnic nerves. 1. The pulmonary branches (rr. pulmonates) are derived from the second, third and fourth ganglia and proceed forward to join the posterior pulmonary plexus. 2. The aortic branches arise from the upper four or five ganglia and, after furnishing a few fine twigs to ' ■ vertebrae and their ligaments, inosculate around the thoracic aorta in the for a fine plexus (plexus aorticus thoracalis). 3. The splanchnic nerves ( nn. sptaachnici) (Fig. u^.'i") are three tnink.s which anse from the lower part of the thoracic cord and are distributed to structures situated in the abdominal cavitv. ^mmmmmmmmm iVnVMB**PIK*MP

    e pierces the cms of the diaphragm and enters the upper end of the semilunar ganglion, some of its fibres being traceable to the suprarenal body and the renal plexus. In the thoracic portion of its course is developed the greai splanchnic ganglion (g. splanchnicum ) from 1366 HUMAN ANATOMY. which, as well as from the nerve itself, are given off filamei.ti for the supply of the oesophagus, the thoracic aorU and the vertebra. Sometimes m the thorax it s divided and forms a plexus with the small splanchnic and m this event several sni.ul ganglia are present. This nerve consists mainly (four-fifths, accordmg to Rudmger ) of meduUated fibres, which are direct continuations of white rami from as far up as the third thoracic nerve or even higher. l • l ■ The small splanchnic nerve (n. splanchnicus minor) arises from the ninth and tenth, or tenth and eleventh gangua or from adjacent portions of interganglionic cords. Entering the abdomen by piercing the cms of the diaphragm either in association with or in close proximity to the great splanchnic, it terminates in that portion of the semi- lunar ganglion called the aoriico-renal ganglion. The least splanchnic nerve (n. splanchnicus imus) arises from the lowest of the thoracic ganglia and may receive a filament from the small splanchnic, from which it occasionally takes origin. Piercing the diaphragm in company with the gangli- ated cord it terminates in the renal plexus. ..,,,.. A fourth splanchnic nerve is rarely Resent It is described by Wnsberg as having been found in eight cadavers out of a large number examined. It is formed by filaments from the cardiac nerves, aided by twigs from the lower cervical and upper thoracic ganglia. THE LUMBAR PORTION OF THE GANGLIATED CORD. The lumbar portion of the gangliated cord (pars abdominalis systematis sympa- thetici) (Fig. 1 134) consists usually of four small oval ganglia connected by association cords. There may be a decided increase in the number of the ganglia, as many as eight having been found, and, on the other hand, occasionally there are fewer than four, there being under these circumstances a compensatory increase in the size of the ganglia present. The lumbar portion of the sympathetic lies nearer the median line than does the thoracic, the cords being placed anterior to the bodies of the lumbar vertebra and the lumbar vessels, along the mesial border of the psoas magnus, on the left side being partially concealed by the aorta and on the right by the inferior vena cava. It is connected with the thoracic portion by a small association cord, which passes either through or posterior to the diaphragm, and with the sacral portion by a cord which descends behind the common iliac artery. White rami communi- cantes are received from the first, the second and sometimes the third lumbar nerve, additional white fibres being derived from the lower thoracic nerves by way of the gangliated cord. The somatic branches comprise: (i) the white and (2) the gray rami comtnunicantes. These are the longest to be found in the body, on account of the distance between the ganglia and the intervertebral foramina. They accompany the lumbar vessels and pass teneath the fibrous afches from which the psoas magnus takes origin. 1. The whitt rami communicantes are derived from the upper two or three lumbar nerves and join the upper ganglia or the adjacent portion of the inter- ganglionic cord. They contain splanchnic efferent and afferent fibres, which continue downward the distribution of the thoracic portion of the gangliated cord, including vasomotor and secretory fibres for the lower extremities, pilomotor fibres, vaso- motor fibres for the abdominal vessels, motor fibres for the circular musculature of the rectum and inhibitory fibres for the longitudinal muscle of the rectum. Fibres peculiar to the lumbar region include vasomotor ner\'es of the penis and motor fibres tor the bladder and uterus, those to the bladder supplying the sphincter as well as the circular and longitudinal muscle-fibres, those to the last-mentioned group being inhibitory. 2. The gray rami communicantes are irregular in number and arrange- ment, sometimes a single one dividing rnd joining two lumbar nerves and sometimes two to five passing to a single spinal nerve. The visceral branches vary c« 'Left v»iiut nert e Right va);u« nf-r\ e Aorti •Branches of Jefl vagus Dissection showing gastric mnd hepatic plexuses. vagus. Inferiorly it is continued into the superior mesenteric and aortic plexuses and from it arise the coronary, hepatic and splenic plexuses. The gastric plexus (plexus gastricus superior) accompanies the gastric artery along the lesser curvature of the stomach, inosculates with both vagus nerves and distributes branches which run for a short distance beneath the peritoneum and then enter and supply the deeper coats of the stomach. The hepatic plexus (plexus hepaticus) traverses the lesser omentum in company with the bile duct, the hepatic artery and the portal vein and, after inosculating with fibres of the left vagus, enters the liver, in which it ramifies. In addition to its terminal distribution it contributes filaments to the right suprarenal plexus and furnishes offshoots which follow the collateral branches of the hepatic artery, sup- plying the areas to which these arteries are distributed. The splenic plexus (plexus lienalis), which surrounds the splenic artery, receives accessions from the left semilunar ganglion and the right vagus and enters the spleen. Branches of the plexus accompany the branches of the splenic artery and are distributed similarly. THE SYMPATHETIC SYSTEM OF NERVES. 1371 The diaphragmatic or phrenic plexus (plexus phrenicus) is derived from the upper portion of the semilunar gan^^lion and accompanies the phrenic branch of the abdommal aorta to the diaphragm, the right being larger than the left. After supplying some filaments to the suprarenal body, it enters the musculature of the diaphragm and there unites with the phrenic ner\e from the cervical spinal plexus. At the point of inosculation, on the right side only, near tli suprarenal Ixxly and on the under surface of the diaphragm, is a small ganglion call the phrenic ganglion (g. phrenicum). From it are given of! branches to the supi, 'renal body, the inferior vena cava and the hepatic plexus. The suprarenal plexus ( plexus suprarenalis) arises from the lateral aspect of the semilunar ganglion and is joined by tilaments trom the diaphragmatic and renal Fig. 1138. t ~>sstin>«p4plalc» itextra ^th |ilcxub' Pyloric artery with plexus' (.iastro-d u odeiul artery wtth plexus. Hepatic artery with plexus, Ittf. rancreatico duodenal artery Sup. pancreatlco- . duodenal artery Hancreai, cut' Sup. tnrsRiteric ulary with plexus' Duodenum Stninach, lurnrd up r.astro-*^ploif.T ' lira with pir^us Ri|{htva)Oi" nerve < iMtric artery with plcxtis .Sfilenic artery with plexus Sple< Diwection showing j^astric, hepatic ftnd splenic plexuKi; Btomai-h has been tunied up ami part of pancrcoB removed- plexuses. It ronsists mainly of mcdullated fibres and, while very short, is made up of a number of filaments and is of considerable size. Numerous tiny ganglia are scattered throughout ihe meshes of this plexus. The renal plexus (plexus renalis) is derived mainly from the aortico-renal ganglion, additional fibres being contributed by the smallest splanchnic nerve, some- times by the small splanchnic, and by the aortic and suprarenal plexuses ; there is occasionally present a twig from the first lumbar ganglion. Entering the hilum of the kidney with the •• lal artery, the plexus splits up and ramifies in the renal sub- stance. In its couri>c along the artery a number of ganglia of varying size, called the renal ganglia are found. In addition to supplyincc the kidney, filaments .ire furnished to the spermatic plexus and to the ureter, and on the right side to the inferior vena cava. 13.72 HUMAN ANATOMY. The spermatic plexus (plexus spennaticus) follows the course of the spermatic artery through the abdomen, inguinal canal and scrotum, inosculating with filaments which arise in the pelvis and accompany the vas deferens and its artery to the scrotum. It is derived from the renal and aortic plexuses, a small spermatic gang- lion being situated at the point of origin of the fibres contributed by the aortic plexus. The ovarian plexus (plexus ovaricus), arising similarly to the spermatic, accompanies the ovarian artery and is distributed to the ovary, the oviduct, the broad ligament and the uterus. In the broad ligament it inosculates with ♦»•" - pelvic fibre«; which constitute the uterine plexus. those Fig. 1 139. Hepatic artery and plcxu9 Superior mesenteric arterj- Termination of ileum -Transverse coloD Splenic artery .Jejunum Duodenum Superior mesen- teric artery and plexus Dissection showing hepatic and superior mesenteric plexuses ; transverse colon has been turned up. The superior mesenteric plexus (plexus mesentericus superior) (Pig. 1139), firm in texture aiu' "ontaining a large admixture of meduUated fibres, is continuous with the ccEliac 1 s above and with th^ aortic below. Its fibres are derived from the semilunar g. .j;lia, the coeliac plexus and the right vagus. Situated in the root of the plexus and lying below and to the right of the origin of the superior mesen- teric artery is the superior mesenteric ganglion. (g. mesentericum superius), from which a number of the fibres of the ple.xus arise. Accompanying the superior mesenteric artery, the plexus gives off subdivisions which correspond to and follow the course of the branches of that artery, supplying filaments to the small intestine, the ccecum, the vermiform appendix and the ascending and transverse coloi As THE SYMPATHETIC SYSTEM OF NERVES. «373 the fibres approach the distal ed^^e of the mesentery some of them leave the vessels and form minute independent plexuses from which filaments pass to the gut. The aortic plexus (plexus aortlcus al 'ominalis) (Fig. 1136) is the direct downward extension of the solar. Embracing the aorta, it extends from the origin of the superior mesenteric artery above to that of the inferior mesenteric below, and is connected with the semilunar ganglia and with the renal and superior mesenteric plexuses superiorly and with the hypogastric inferiorly. It consists of a pair of Fig. 114a Aorta Renal mnKlion Onrian artery Mrrveirom aortic plesiM. . MH^ / / ,y^ ^flvarian vein Ovarian veiii^\. Ovarian artery.. Uretet - Right ovaty- Falkfilaa ttifa*- Usament of_ ovary Diiaectlon thowlnf hypogaitrie and pelvic plezuaes. symmetrically placed nerve trunks situated at the sides of the aorta and connected with each other by several branches which lie anterior to that vessel ; filaments from the lumbar ganglia join the main cords of the plexus. It gives of! the inferior mes- enteric plexus, sends contributions to the suprarenal, renal and spermatic or ovarian, supplies filaments to the aorta and inferior vena cava and terminates in the hypo- gastric plexus. The inferior mesenteric plexus (plexus mesenterlcus inferior) is derived from the left portion of the aortic plexus and follows the course and distribution of the artery for which it is named. Situated a short distance beyond its origin is the small inferior mesenteric ganglion. From this plexus branches arc »374 HUMAN ANATOMY, distributed to the descending and sigmoid colons and to the upper portion of the rectum. . . The hypogastric plexus (plexus hypoRastrictis) (Fig. 1 140), the contmuation of the aortic, lies on the posterior wall of the pelvis in the angle between the common iliac arteries, and enclosed in a firm investment of fibrous tissue. In addition to the fibres derived from the aortic plexus, others are contributed by the lumbal ganglia, and the resulting intricate interlacement, in which there are no ganglia, constitutes the hypogastric plexus. It supplies the pelvic contents and at its lower end divides into the two pelvic plexuses. The pelvic plexuses (plcsns hypoRastrlci inferiores), (Fig. 1140) the terminal divisions of the hypog;istric, are situated lateral to the rectum and to the vagina in the female. They comprise fibres derived from the hypogasstric plexus and from the upper part of the sacral portion of the gangliated cord, aided by the visceral branches 0/ the pudendal plexus, all of these forming an elaborate net-work, in which are dotted numerous small ganglia. The completed structure follows the course of the internal i! .ic artery, around whose branches it sends derivatives for the supply of the peUic contents. The hemorrhoidal plexus (plexus hemorrhoidalis medius) arises from the upper portion of the pelvic plexus and after inosculating with the superior hemorrhoidal branches (nn. hemorrholdales superiores) of the inferior mesenteric plexus, are distributed to the rectum. The vesical plexus (plexus vesicalis) consists of branches of the pelvic which accompany the vesical arteries to the lateral and inferior portions of the bladder, after reaching which they leave the vessels and split into small twigs for the supply of the bladder, some filaments going to the ureter, the vas deferens and the seminal vesicle. The prostatic plexus (plexus prostaticus) comprises a number of nerves of con- siderable size and is situated between the lateral aspect of the prostate gland and the mesial surface of the levator ani muscle. After furnishing twigs to the prostatic urethra, the neck of the bladder and the seminal vesicle, it continues forward as the ca vemous plexus. The cavernous plexus (plexus cavernosus penis) extends forward through the triangular ligament and the compressor urethra muscle to the dorsum of the base of the penis, where it receives some communicating filaments from the pudic nerve. After supplying branches to the apex of the prostate gland and the membranous urethra, the plexus terminates by breaking up into (1) the small and (2) large cavernous nerves of the penis. 1. The small cavernous nerves (nn. cavernosi penis minores) pierce the fibrous envelope of the crus penis and end in filaments which supply the erectile tissue of the corpus cavernosum. 2. The large cavernous nerve (n. cavernosus penis major), consisting mainly of medullated fibres, passes directly along the dorsum of the penis, giving off fila- ments which enter the substance of the corpus cavernosum. At about the middle of the body of the penis it inosculates with the dorsal nerve of the penis, both of these nerves sending twigs to the corpus spongiosum. The utero-vaginal plexus (plexus uterovaginalis) corresponds to the prostatic plexus of the male and consists of two portions : (i) the uterine plexus and (2) the vaginal plexus. 1. The uterine plexus (plexus uterinus) is derived from the pelvic plexus and is supplemented in its distribution by the visceral branches from the pudendal plexus. These fibres accompany the uterine vessels along the side of the uterus, most of them entering the cervix and the lower portion of the body of the uterus. They inoscu- late with fibres from the ovarian plexus and in their meshes are found many small ganglia, a collection of which is located near the cer^•ix uteri and is called the gang- lion cervicale. 2. The vaginal plexus (plexus vaKinalls) arises from the lower part of the pelvic and comprises mainly fibres derived from the visceral branches of the puden- dal plexus. It supplies the vagina and the urethra and continues forward as the cavernous plexus of the clitoris (plexus cavernosus clitoridis). DEVELOPMENT OF PERIPHERAL NERVES. «375 Practical Considerations. — The cervical sympathetic may be injured by deep wounds of the neck, or may be compressed by tumors, abscesses or aneurisms. It supplies motor fibres to the involuntary muscles of the orbit and eyelids, vasomotor filM'es to the face, neck and head, dilator fibres to the pupil, accelerator fibres to the heart and secretory fibres to the salivary glands. If it is irritated, some or all of the following symptoms will be present : the palpebral fissure will open wider, the eyes will be protruded, the skin of the face and neck will be pale and cold, the pupils dilated, and the sweat, nasal secretion and saliva diminished. Section or destruction of the cervical sympathetic will give the opposite symptoms. The cervical sympathetic has been removed for epilepsy, glaucoma and exoph- thalmic goitre. The greatest success has been obtained in the last condition, espe- cially by Jonnesco, who advises this procedure in hysteria, chorea, and tumors of the brain, as well as in the above-mentioned conditions. It may be excised through an incision anterior to the stemo-ma.stoid, as it lies f)osterior to the carotid sheath on the prevertebral fascia. The smK-rior cervical ganglion is the largest and lies oppojte the transverse processes of ;he second and third vertebra-. Branches of it go upward along the external and internal carotid arteries, the ascending branch passing along the internal carotid artery through its bony canal in the basie of the skull to form the carotid and cavernous plexuses, both of which arc n illy parts of one plexus arranged around this artery. Other branches communicate with the cranial nerves, the pharyngeal nerves and the superficial cervical cardiac nerve. The middle cervical ganglion is the smallest, lies on the inferior thyroid artery oppo- site the sixth cervical vertebra and is in danger in the ligation of that artery. The inferior ganglion, intermediate in size between the other two, lies in a depression between the neck of the first rib and the transverse process of the seventh cer\'ical vertebra. The branches of the upper four or five thoracic ganglia of the sympathetic enter into the supply of the thoracic viscera, but the branches of the lower seven or eight form the splanchnic nerves and go to the supply of the abdominal viscera through the solar plexus and its extensions into other sympathetic plexuses of the abdomen. It is of interest and importance to observe that those intercostal nerves corresponding in their origin from the spinal cord with the ganglia giving off the splanchnics, together with the first two lumbar nerves, the ilio-hypogastric and ilio-mguinal, supply the abdominal wall with motor and sensory branches. In this way the same segments of the spinal cord supply the abdominal viscera as well as the skin and muscles over them. A similar arrangement of the nerves is seen in the joints, where the same nerves supply the skin covering the joint, the muscles which move it, and the joint structures. As a result of this, when necessary, all parts of the joint act in sympa- thy. In an inflammation of the joint the skin becomes sensitive, tending to ward of! interference, and the muscles become rigid, preventing motion and favoring rest. In a similar manner the abdominal muscles become rigid to protect inflamed viscera underneath, the muscles of one side only if the inflammation is localized to one side, but the muscles of both sides if a general peritonitis is present. DEVELOPMENT OF THE PERIPHERAL NERVES. The manner in which the nerve-fibres composing the peripheral nervous system develop from the primary cells, the neuroblasts, has been indicated in the previous sketch of their histogenesis given on page loii. It remains, therefore, to describe briefly at this place the more important features of their morphogenesis. The fundamental fact has been repeatedly empha- sized, that efferent or motor fibres are outgrowths from neurones situated within the cerebro- spinal axis, whilst all afferent or sensory fibres arise from cells placed outside this axis and within the ganglia located along the course of the ner\'es. It is evident, furthermore, that the efferent constituents of the peripheral nerves have their nuclei of origin within the spinal cord or brain and grow outward, as axones, to their destinations. The afferent fibres, on the other hand, proceed in Ixjth directions, the axones early growing centrally to join the nerx-ous axis, hence, having usually a short course, being represented by the entering sensory roots. The dendrites grow in the opposite direction and contribute the sensory fibres that extend often to remote parts of the body. Whilst in the lowest vertebrates, the amphioxus and the cyclos- tomes, the ventral and dorsal roots of the spinal nerves remain distinct, in the higher types they join to form the mixed nerve, which typically divides into the anterior, posterior and 1376 HUMAN ANATOMY. visceral divisions. .Such t>-pical divisioii. however, is displayed only by «»»«f ."P?"' "^* ^r"- tSd to that part of the trunk in which the primary seRmentation is retained. nan«1y. the thS «X.^^re the skeletal muscular, and vascular segments, a. well as thenerves, SLKnUty. In the other parts of the spinal «:ri^ the cervical and Uie '««"bo-sacral, wtere^ovision ik made for the supply of the highly differentiated musculature of the ex- SiSm a number of cord-segnients. the nerves early unite to form plexuses from v^hich &e~ t^nks pow out. an arr^gement well adapted for the dutribut.on «^ Jb^H Jro.,. different sources without undue multiplication of nervous paths. Concerning the factors which pUrthe^oung nerve to its destination with such remarkable constancy, nothing » known. STt it n«y be alsumcd that these are probably influences of a physical character, the developing nerve Sklng the path offering least resistance. The visceral division of the spmal nerve, to which refeAnce tas been mlde, corresponds to the white ramus ^T'T"'^. P^™ °f ,^^ certain of the thoracic and lumbo^cral nerves. These splanchnic fibres differ from the »matic efferent ones in Uking their origin fmm cells which occupy a "'"^ '»t«^, P«?'""" within the gray matter of the spinal cord than do the root-cells giving rise to the motor fibres d»ttaed fofthe skeletal muscl^. WhiUt the great majority of the f'«'<^h"«Lfi^res reach the i«mus of communication by way of the anterior root, some few perhaps traverse the posterior or sensory toot and its ganglion before continuing their course to the s>-mp.-»thetic The senjor) fiL^T^bed within the anterior root. of the spinal nerv«i are not »«»»» ^""^"^ "'^r! roots, which are exclusively motor, but recurrent meningeal twigs destined for the membranes *^ ^'•^Jcranial Nenre^-From the preceding account of these nerves, it is evident that the optic nerve differs morphologically widely from an ordinary nerve, since 1» "V'V ^^K^^''^^';;'; aWlified outlyin;; j^rtion of the brain. Its development may be omitted, therefore, from this series and appropriately considered in connection with the development of the eye (page 148a). There is sufficient reason, as will appear later, for regardmg the hypoglossal nerve as a cranially displaced member of the spinal series. Of the remaming nerves, only the olfactory and auditory are purely sensory ; the third, fourth, sixth and eleventh are exclusively motor ; and the ftfth, seventh, ninth and tenth are mixed, the motor strands taking ongin from the neu- rones within the brain-stem, while the sensory ones are derivations from the neurones lying within the ganglia connected with the afferent fibres. Although at first sight the tngeminus closely corresponds to a spinal nerve in the pos.session of ai g^ghated sensory Md a motor -root, critical examination of the origin of its motor fibres discloses an important differ- ence, liamely that they arise from the lateral nuclei and not from the mesial, which correspond to collections of ventral root-cells. A similar difference also appears between the efferent trigeminal fibres and those of the eye-muscle nerves, the latter arising from groups of root-nx. Following the pnraple already emphasized the motor fibres of the cnmial nerves grow from the brain outward, while the sensory ones extend centrally from the ganglia of the nerves associated with the brain. The cranial and spinal nerves appear on the surface of the neural tube at a very eariy period, their presence being conspicuous by the end of the fourth week (Fig. 901). The olfactory nerve is developed in connection with the epithelial lining of the primary olfactory pit (page 1429). As early as the end of the first fcetal month, in the human embrjo, cells corresponding to neuroblasts appear in 'he anlage of the olfactory organ. 1-rom these elements processes soon grow brainward, nucleated tracts indicating the formation of the later olfactory fibres. The cell-bodies of the younj neurone migrate so that for a time their position DEVELOPMENT OF PERIPHERAL NERVES. «377 b no kMiger within the prinutfy epithelium, but deeper and within a cell aggregation known ai the olfattory gangHoH. The neurones, however, retain connection with the olfactory epithe- lium by means of their peripherally directed procesfies, which correspond to dendrites, and with the brain by means of their axooes. With the thickening of the olfactory epithelium which sub- sequently occurs, the peripheral fibres and their nuclei comes to lie entirely within the epithelial stratum and persist as the olfactory cells, whose centrally directed processes form the olfactory filaments that end as arboriiations within the characteristic olfactory glomeruli. The first cranial nerve Is peculiar in the superficial position of its cell-bodies and in the extreme shortness of iu dendrites, whkh are represented b>' the rod-like fibres of microscopic length extending from the cell-bodies toward the free suriace of the olfactory mucous membrane. This superficial position of the olfactory neurones is regarded as an unusual persistence of the primary condition of all sensory elements and as evidence of the archaic nature of the olfactory nerves. Fig. II4I. Sapcrior oolliculi Mid-fanin. Ibody inferior coUlculiu Oculomotor ncnrc Trachlcmr ncrrc Cerebellum TriKeminal nerve Auditory nerve GtoMo-pharynf^Rl nerve Vaffus nerve Spinal acccMory nenre lencephalon Median geniculate body Pallium Rhinencephalon Optic Malk nferior part of III. ventricle Facial .lerve Hypaglaaaal nerrt Reconstruction of brain of human embryo of four and one half wceki (io.j mm.); outer iuriace, thowiag devalopinc nervef. X »• Drawn from Hi* model. The optic nerve is so inherently a derivative of the cerebral and optic vesicle, that its develoj)- ment is appropriately considered with that of the eye (pa- " • moreover, its morpholoiacul significance being so at variance with that of the other may be omitted from further discussion in the series now being described. The oculomotor nerve being strictly a motor nerve much in common in its mode of formation with the ventral root of a spinal nerve, with which it is homologous. The nerve originates as an outgrowth from a group of neuroblasts, which occupies the ventral zone about the middle of the mesencephalon. From these neurones, visible in the fourth wep' In the human embryo, the axones proceed as a converging group of fibres which, piercing i c .all of the brain-tube close to the mid-line, appear on the ventral suriace of the brain-stem as the fibres of the thiid nerve. Although by some regarded as possessing a transient rudimentary dorsal root that early entirely disappears, thus bringing the nerve of a cranial myomere into close correspondence with those of the spinal series, it is doubtful whether such structure is usually present, the suppression of the dorsal portion of the nerve being complete. Soon after its for- mation, the main trunk undergoes division into a smaller upper and a larger posterior limb, which foreshadow the superior and inferior divisions of the mature nerve. The trochlear nerve, although springing from a central group of neuroblasts in clo?« proximity with those giving rise to the third, is peculiar in the course of its axones. Instead of maintaining a ventral course, these proceed dorsally and become superficial on the upper f dorsal) aspect of the hind-brain, piercing the plate which later becomes the superior medul- 87 1378 HUMAN ANATOMY. Urv velum As in the case of the third, so lor the trochlear an abortive transient dorsal gantdion aiid root have been described (Martin). If present these must be regarded as ex- ceptional and not constant features. . . j.« ■ , • The uicemlnal nerve is a mixed nerve and therefore takes its ongin differently for its two roots. The motor one is developed from a series of neuroblasts, which he at some distance from the mid-line within the wall of the neural tube, at a position corresponding to the junction of the dorsal ind ventral zones of the mid-l)rain and metencephalon. The axones of these neuroblasu grow forward and converge to the surface of the later pons at a position close to where the ingrowing sensory fibres join the neural tube. The sensor>- fibres are the axones of neurones located within the Gasserian ganglion The latter is derived as a ventrally dir«^«l outgrowth from the ectoblast of the roof of the hind-br;un, with which it remains attached for a short time, but later becomes entirely separated. The neuroblasts acquire a bipolar form, one set of processes, the axones, growing centr.illy to establish secondary connections with the hind-brain as the large sensory root, while the others, the dendrites, extend peripherally into the substance of the fronto-nasal and maxillary processes to form the ophthalmic and maxillary nerves anil into the mandibular process to form, in conjunction with the smaller motor root. Fig. 1142. Reconstruction of brain and cranial nervet of pig tmbn-oj cranial nerves indicated byfigures; ci<3. cerv|ca1 spinal nerves ; in connection with seventh nerve.,/ J.^.larp superficial petroaal ; chp., chorda tympani : /a., facial , /. a., vagus KiiiKlia of root and trunk; tow., commisi.ttral extension 01 ganglion 01 root; t, I- roriep s hypoglossal ganglion. (F. T. Lrwii.) the mandibular division of the trigeminus from the ganglion ridge. Provision for the ciliary ganglion is made early by the migration of cells from the major ganglion along the de- veloping ophthalmic division. Similar migrations along the other divisions give rise to the spheno-palatine, the otic and the submaxillary ganglia. The later histological characteristics of these cells, as well as their mode of origin, warrant the view that the ciliary ganglion, as well as the otiiers connected with the trigeminus, belong to the -ympathetic system. On entering the wall of the brain-tube, the bulk o* the sensory trigeminal fibres assume a longitudinal course and early establish the tract of the spinal cord. The atHlucent nerve developes, in a manner identical with the third and fourth, from a median group of cells occupying the ventral zone of the upper part of the hind-brain. In the human embryo of about four and a half weeks (Fig. 1141), the nerve appears at its super- ficial origin mesial to the Gasserian ganglion. The root-fibres early consolidate into a compact strand. The facial nerve being a mixed one also arises from a double source, its motor fibres taking origin from efferent neuroblasts situated in the ventro-lateral wall of the metencephalon. In contrast to the direct ventral course of the axones of the mesial motor nerves, those of the facial pursue a path to the surface of the brain-stem even more indirect than that taken by the lateral motor fibres of the other mixed nerves. Proceeding as the axones of neuroblasts lying within the lateral part of the ventral zone of the wall of the hind-brain, they are directed dor- sally, then grow forward, turn outward and, finally, ventrally to gain emergence from the brain. The sensory portion of the facial is topographiciUly closely connected during its development with the auditory, the nuclei of the two nerves often being designated the facial-acoustic com- plex. The three components of this aggregation— the geniculate, the cochlear and the vestibu- lar ganglia — are primarily derived from an ectoblastic cell-mass in the vicinity of the otic vesicle. DEVELOPMENT OF PERIPHERAL NERVES. "379 Th« neuroblast of the facial cunstituetit, the Kenkulate KaiiKlion, hmmJ their centrally tlirccte.l processes tu the brain-stem as the pars intermedia, whilst their (leripherally KrowinK tlemlritt^ contribute the sensory fibres, pay-^inK by way of the chortia tympani ami the greater ami lesser superficial petrosal nerves. The geniculate KaoKlion and the (lars intermedia curres|Miiid, therefore, to a dorsal root The auditory nerve, althouich for a time closely related in {losition (Fiij. 1103) with the facial (geniculate) ^anKlion, developes entirely independently and at notinte has more than an incidental relation. The primary auditory nucleus is defined in human eml>r>-o« by the beKin- ning of the fourth week as an elongated ellipsoidal ma.ss in -contact with the anterior wall of the otic vesicle. According to Streeter', the nucleus very shortly exhibits a diflerentiation into a superior and an inferior part, from the latter of which soon appears a third portion. This third portion, the later ganglion spirale, early manifests • tendency to coil in conse(|uence of its close relations with the Fio. 114.^. V*f«a root gans. AcccMorjr root K*ng. /4 IX. nM (ang. KroHcp Gang, nodos. N. laryg. tup. XII. with r.dcwcnil.' ductus cochlearis. The major part of the primary acoustic complex, including the superior and most of the inferior part, becomes the vestibular ganglion, from the neuroblasts of which centrally directed axones pass to the young brain- stem as the vestibular nerve, while the dendrites become connected at certain places with the semicircular canals, the utricle and the saccule. The grouping of the vestibular rami seen in the adult is early foreshadowed in the develop- ing nerve, since from the upper pan of the vestibular ganglion grows out the su- perior division of the vestib- ular nerve which, supplies the utricle and the ampulizs of the superior and external semicircular canals (Fig. 1070) . The lower part of the ganglion, in addition to fur- nishing the anlage for the cochlear nerve, gives off the inferior division of the vestib- ular nerve, by which the saccule and the posterior canal are supplied. During the subsequent growth of the structures, the neurones of the spiral ganglion send ax- ones towards the brain which become the cochlear nerve, whilst their dendrites-grow peripherally into the ductus cochlearis and are represented by the minute filaments extending from the cells of the spiral ganglion to the auditory cells of Corti's organ. The glosso-pharyngcal nerve is a mixed nerve and has, therefore, a double origin. Its motor fibres arise from neuroblasts situaied in the dorsal part of the ventral zone of the wall of the hind-brain just posterior to the otic vesicle. The sensory part of the nerve, along with that erf the vagus, ofTers greater complexity, since it is developed, as shown by Streeter*, from two sources. The ganglion of the root (g. superius or jugular ganglion) arises very eariy as a small mass of cells derived from the ganglion-crest of the land-brain. It varies in size and soon ceases to grow, which behavior, in connection with the preponderating ingrowth of the motor fibres, accounts for the well-known inconstancy of the structure. The ganglion of the trunk (g. petrosum) arises, according to Streeter, not from the neural crest but in relation with the ectoblast of the second visceral furrow. M first ununited with the smaller ganglion superius, the ganglion of the root subsequently becomes joined to it, the two nodes • Amer. Jour, of Anatomy, vol. vi., 1907. 'Amer. Jour, of Anatomy, vol. iv., 1904. Sympathetic Vasna Reconatruction of peripheral nervea of human embryo of five weeks (14 mm.) >; 13. (Slrtrler.) 1380 HUMAN ANATOMY. being later closely related, both as to position and fibres. An outgrowth of distally directed fibres establishes the main trunk of the ner%e, while a forwardly growing strand represents the later tympanic branch. . , . j • .1. • j 1 The v«fu» and ipinal accesiory nerve* are so mseparably related m their development that their origin must be regarded as proceeding from a common vagus complex. The latter comprises three elements : (a) a series of motor roots, which arise from the ventral zone of the hind-brain and extend from near the glosso-pharyngeal anlage m front as far as the third or fourth spinal segment below ; (*) a partially subdivided, but at first contmuous, ganglionic mass, which arises from the ganglion-crest of the hind-brain and represents the root-ganglia ; (c) a secondary ventral cell-mass, the primitive ganglion of the trunk, which, as in the case of the glosso-pharvngeal nerve, is developed in close relation with the ectoblast of the posterior branchial furrows. Whilst the motor rootlets persist and become the efferent root-fibres of the later vagus and aci-essory nerves, the dorsal or crest-ganglia soon exhibit differences in their growth, the one situated farthest forward outstripping the others and becoming the vagal gang- lion of the root, and the remaining ones becoming the accessory root-ganglia. These latter constitute a chain which below meets with the spinal dorsal ganglia. Primarily, therefore, the entire length of the vagus complex is occupied by a series of mixed nerve strands possessing both motor and sensory elements. The head-end of the series later becomes predominatingly sensory, while in the tail-end of the same the motor character prevails. The ventral vagus nucleus is attached secondarily to the dorsal nucleus by centrally growing fibres, while from its distal end extend the dendritic processes which constitute the trunk of the vagus and 11 . branches. In consequence of the intergrowth of these afferent and efferent fibres, the definite tenth ner\'e in the usual sense, with its two ganglia, becomes established. Although for a short period the accessor)- part of the complex is provided with both motor and sensory parts, the latter are subsequently overpowered by the efferent fibres, so that the presence of the rudimen- tary ganglionic elements within the accessorius can be demonstrated only by microscopic exam- ination ( Streeter) . From the preceding facts it is evident that the estimate of the eleventh nerve as an integral part of the vagus is well founded. The hypoglossal nerve appears in the human embryo, towards the close of the third week, as several strands which grow from the ventral zone of the wall of the hind-brain and are in series with the ventral root-fibres of the upper cervical spinal nerves. Soon the separate root- lets converge and consolidate into a common trunk, from which, by the end of the fifth week, the chief branches of distribution arise. The production of the wide-meshed net-work which distinguishes the communications between the upper cervical and hypoglossal nerves results from the separation of fibres which are at first closely adjacent, the subsequent migration of tho growing tongue-muscles drawing the hypoglossal fibres away from the spinal nerves, except at such points where they have become enclosed in a common sheath. There is good reason for regarding the hypoglossal nerve as representing the ventral roots of trunk-nerves, which have been cephalicly displaced and drawn within the cranium. Moreover, the observations of Froriep and others upon adult mammals and of His upon the human embryo have shown the presence of a rudimentary dorsal ganglion and abortive dorsal root-fibres. The occasional presence of a rudimentary ganglionic mass, known as Froriep's ganglion, attached to the fibres of the adult hypoglossal nerve in man is to be interpreted as the persistent dorsal element which ordinarily disappears. ... . j , From the preceding sketch it is evident that in no instance, as observed in the usual adult condition in man, is there complete correspondence between the members of the cephalic series and those of the trunk. The group of purely sensory nerves— the olfactory, optic and auditory— includes one, the optic, which is so exceptional in its fundamental relations as to lie without the pale of peripheral nerves in their strict sense. The remaining two sensory nerves are held to be primarily the equivalents of constihients of a peculiar system of sensoo' organs, best developed in fibres, known as the organs of the lateral line. The third, fourth, sixth and twelfth, the ventral motor nerves, are undoubtedly associated with head-somites, although the exact number and nerve relations of such mesoblastic segments are uncertain ; in fundament?' nificance, therefore, these nerves agree with (hose of the trunk-series, although moilii. . by the suppression of their dorsal or sensory constituents. The mixed nerves— the fifth, seventh, ninth and tenth (the eleventh being reckoned as part of the vagus)— are unrepresented in the spinal series and belong to the branchiomeres represented by the visceral arches. Of these ner\es, the trigeminus most nearly accords in constitution with a typical spinal ner\e, since, with the exception of ventral motor constituents which are wanting, it pos- sesses as does the typical spinal nerve, both somatic (general cutaneous) sensory and visceral sensory fibres. A further resemblance is found in the ch.iracter of the gray matter constituting the reception-nucleus for the sensory fibres of the trigeminus, since this column is comixjsed of substantia gelatinosa continuous with the Rolandic substance capping the posterior co;nu of the cord. A similar, although less imim.itc, arrangement is seen in the column of ijray matter accom- panying the descending root (funiculus solitarius)of the facial, glosso-pharyngeal and vagus nerves. THE ORGANS OF SENSE. The cells directly receiving the stimuli producing the sensory impressions of touch, smell, taste, sight and hearing are all derivations of the ectoblast — the great primary sensory layer from which the essential parts of the organs of special sense are differentiations. The olfactory cells — nervous elements that correspond to ganglion cells — retain their primary relation, since they remain embedded within the invaginated peripheral epithelium lining the nasal fossse, sending their dendrites towards the free surface and their axones into the brain. Usually, however, the nerve cells connected with the special sense organs abandon their superficial position and lie at some disUnce from the periphery, receiving the stimuli not directly, but from the epithelial receptors by way of their dendrites. In the case of the most highly specialized sense organs, the eye and the ear, the percipient cells lie enclosed within capsules of mesoblastic origin, the stimuli reaching them by way of an elaborate path of conduction. THE SKIN. Since the extensive integumentary sheet that clothes the exterior of the entire body not only ser\es as a protective investment, an efficient regulator of body temperature and an important excretory structure, but also contains the special end- organs and the peripheral terminations of the sensory nerves that receive and convey the stimuli producing tactile impressions, the skin may be appropriately considered along with the other sense-organs of which it may be regarded as the primary and least specialized. On the other hand, the correspondence of its structure with that of the mucous membranes, with which it is directly continuous at the orifices oil the exterior of the body, emphasizes the close relation of the skin to the alimentary and other mucous tracts. This general investment, the tegmentum commune, includes ihe skin proper, with the ppecialized tactile corpuscles, and its appendages — the hairs, the nails and the cutaneous glands. Its average superficial area is approximately one and a half square meters. The skin (cutis), using the term in a more restricted sense as applied to the covering proper without its appendages, everywhere consists of two distinct portions — a superficial epithelial and a deeper connective tissue stratum. The formci , the epi- dermis, is devoid of blood-vessels, the capillary loops of which never reach f .rther than the subjacent corium, as the outermost layer of the connective tissue stratum is called. The thickness of the skin, from .5-4 mm., varies greatly in different parts of the body, being least on the eyelids, penis and nympha, and greatest on the palms of the hands and soles of the feet and on the shoulders and back of the neck. In general, with the exception of the hands and feet, the skin is thicker on the extensor and dorsal surfaces than on the opposite aspects of the body. Of the entire thick- ness, the proportion contributed by the epidermis is variable, but in most localities it is about . i mm. Where exposed to unusual pressure, as on the palms of laborers or on habitually unshod soles, the epidermis may attain a thicknes.s of 4 mm. As seen during life, the color of the skin results from the blending of the in- herent tint of the tissues with that of the blood within the superficial vessels. When the latter are empty, as after death, the skin assumes the characteristic pallor and ashen hue. Where the capillaries are numerous and the overlying strata thin, the skin exhibits the pronounced rosy color of the lips, cheeks, ears and hands. Where, on the contran,', the contents of fewer vessels shimmer through the epidermis, the paler tint of the limbs and trunk is produced. In certain localities — especially over the mammary areoUe after pregnancy, the axillw, the external jiiniul organs and around the anus — the .skin presents a more or less pronounced brownish color owing to the unusual quantity of pigment within the 1,181 1382 HUMAN ANATOMY. Fig. I 144. Imprint of dorsal surface of left hand near ulnar border; radiatiiiK lines are produced by creases connecting points at which hairs emerge. epidermis. The amount of skin-pigment not only differs permanently among races ^ (white, yellow and black) and indi- viduals (blond and brunette), but also varies in the same person witli age and exposure, as contrasted by the rosy tint of the infant and the bronzed tan of the weather beaten mariner. Unless bound down to the underlying tissues, as it is over the scalp, external ear, palms and soles, the skin is ireely movable. Its physical properties include con- siderable extensibility and marked elasticity. By virtue of the latter the temporary displacement and stretch- ing produced by movements of the joints and muscles is overcome and the smoothness of the skin, so con- spicuous in early life, is maintained. With advancing age the elasticity becomes impaired and folds are no longer effaced, resulting in the perma- nent wrinkles seen in the skin of old people. Certain folds and furrows, however, are not only permanent and ineffaceable. appearing in the foetus, but are fairly constant in position and form. One group, produced by fle.xion of the joints, includes the conspicu- ^^^ ous creases on the flexor surface of the wrist, palm and fingers, and the similar markings on the soles of the feet. The other group, more extensive but less striking, includes the fine grooves that connect the points of emergence of the hairs and cover the trunk and extensor surface of the limbs with a delicate tracery (Fig. 1 144). The surface modelling of the skin covering the palms, soles and flexor aspects of the digits is due to the disp<3sition of numerous minute ridges ( cristae cutis) ami furrows (sulci cutis). The cutaneous ridges,, A\v3\ii . 2 mm. in width, correspond to double rows of papilla which they cover, the sweat glands opening along the summit of the crests. The patterns formed by the cutaneous ridges (Fig. 1145) remain throughout life unchanged and are so ilistinctive for each indiviilual that they afford a reliable and practical means of identi- fication.' In addition to the various longitudinal, trans- verse and oblique ranges of ridges that cover the greater part of the hand, groups of concentrically arranged ridges occupy the volar surface over the distal phalanges, the pads between the metacarpo-])halangeal joints ami the middle of the hypothenar eminence. These highly chari. teristic areas^ the so-called tactile pads (tonili tactilcs) are most strikingly developed over the bulbs of the fingers, where the ridges are often tlisposed in whorls rather than in regular o\als. The markings of corrcspontling areas of the two hands are symmetrical antl sometimes identical. Structure.— The two parts of which the skin is everywhere composed— the epidermis and the connec- tive tissue stratum — are derivatives of the ectoblast and of the mesoblast respectively. The connective tissue portion includes two layers. '■ijS0** Imprint of palmar surface of Ml middle finger, showing iirr iiigcment of cutaneoua ridges; transverse in tcrruptians arc produce! by firxi'-t* creases over joints. THE SKIN. 1383 the corinm and the tela subcutanea, which, however are so blended with each other as to be without sharp demarcation. The corium or derma, the more superficial and compact of the connective tis:;ue strata, lies immediately beneath the epidermis from which it is always well defined. With the exception of within a few localities, as over the forehead, external ear and perineal raphe, the outer surface of the corium is not even but beset with elevatiois, ridges, or papillae, which produce corresponding modelling of the opposed undev .surface of the overlying epidermis. The pattern resulting from these eleva- tions varies in different regions, being a net-work with elongated meshes over the ktck and front of the trunk, with more regularly polygonal fields over the extremi- FiG. 1 146. Fig. I 147. Portion of corium from palmar surface of hand after removal of epi- dermis ; each ran^e includes a double row of papillae, which underlie the superficiat cutaneous ridxes and en- close openings of sweat glands ; latter appear as dark points along ranges 01 iKipillse. X 5. Small portion of preceding; specimen, showing papillae under higher mai^Tiifica- tton ; orifices of torn sweat glands are seen between papillae. X 24. ties and with small irregular meshes on the face (Blaschko). The best developed papilUe are on the flexor surfaces of the hands and feet, where they attain a height of .2 mm. or more and are disposed in the closely set double rows that underlie the cutaneous ridges on the palms and soles above noted. The papilla afforil favorable positions for the lodgement of the terminal capillary loops and the special organs of touch and are accordingly grouped as vascular and taiiilc. In recognition of the elevations, which in vertical sections of the skin appear as isolated projections, the corium is subdivided into nn outer papillary stialiim (corpus paplllare), containing the papillae, and a deeper reticular stratum (tunica r-opria), composed of the closely interlacing bundles of fibrous and elastic tissue aiat are continued into the more robust and loosely arranged trabecuhe of the tela subcutanea. These two strata of the corium, however, are so blended that they pass insensibly and without definite boundary into each other. Although coir;, jsed of the same histological factors — bundles of fibrous tissue, elastic fibres and con- necti\e tissue cells — the disposition of these constituents is much more compact in the dense reticular stratum than in the papillary layer, in which the connecti\-e tissue bundles are less closely interwoven. ' While the general course of the fibrous bundles within the corium is parallel or oblique to the surface, some strands, continued upw.ird from the underlying subcutaneous sheet, are vertical and traverse the stratum reticulare either to bend over and join the horizontal bundles or to break up and disappear within the papillary stratum. The elastic tissue. 1384 HUMAN ANATOMY. which constitutes a considerable part of the corium, occurs as fibres and net-works, which within the reticular stratum form robust tracts corresponding in their disposition with the general arrangement of the fibrous bundles. Towards the surface of the corium, the elastic fibres become finer and more branched and beneath the epidermis anastomose to form the delicate but close subepithelial elastic net-work that IS present over the entire surface of the body with the exception, possibly, of the eyelids (Behrens). The tela subcutanea, the deeper layer of the connective tissue portion of the skin, varies in its thickness, and in the density and arrangement of its component bundles of fibro-elastic tissue, with the amount of fat and the number of hair-follicles and glands lodged within its meshes. The latter are irregularly round and enclosed by tracts of fibrous tissue, some of which, known as the retinacula cutis, are prolonged fron e corium to the deepest parts of the subcutaneous stratum. Here they often bk a into a thin but definite sheet, t\x fascia subcutanea, which forms the innermost boundary of the skin and is Fig. 1 148. Epidermis Papillary stratum Reticular stratum Hair follicle Retiiuculum Fat Section of skin, showing its chief layers— epidermis, corium and tela subcutanea. X 17. connected with the subjacent structures by strands of areolar tissue. Where such loose connection is wanting, as on the scalp, face, abiiomen (linea alba), palms and soles, the skin is intimately bound to the underlying muscles or fascia ancl lacks the independent mobility that it elsewhere enjoys. The integument covering the eye- lids and penis is peculiar in retaining to a conspicuous degree its mobility although devoid of fat. VVhere the latter is present in large quantity, the term panniculus adiposns is often applied to the tela subcutanea. In places in which the skin glides over unyielding structures, the interfascicular lymph-spaces of the tela subcutanea may undergo enlargement and fusion, resulting in the production of the subcutaneous mucous bursae. These are found in many localities, among the most constant bursa being those over the olecranon, the patella and the metatarso-phalangeal joints of the little and the great toe. The bursje in the latter situation, when abnormally enlarged, an- familiar as bunions. In addition to the strands of involuntary muscle associated with the hairs as the arrectores pilorum, unstriped muscular tissue is incorporated with the skin in the mammary areola? and over the scrotum and penis (tunica dartos). The facial muscles having largely cutaneous insertions, the skin covering the face is invaded by tracts of striated muscular tissue that penetrate as far as the corium. THE SKIN. i3«5 The epidermis or cuticle, the outer portion of the skin, consists entirely of epithelium and, being partly horny, affords protection to the underlying corium with its vessels and nerves. The thickness of this layer varies in different parts of the body. Usually from .08-. 10 mm. , it is greatest on the fle-xor surfaces of the hands and feet, where it reaches from .^-.g mm. and from 1.1-1.3 mm. respectively (Drosdofi). . . The cuticle consists of two chief layers, the deeper stratum frcrmtnaltvum, con- taining the more active elements, and the stratum corneum, the cells of which undergo cornification. Between these layers lies a third, the stratum internudium, that is Fig. II49- Stratum conicum Spiral duct of sweat gland Stratum lucidum stratum gcrmmativum Corium (Ion of section of skin ,'mm sole of foot, showing layere of epidermis. X 70. ordinarily lepresented by only a single row of cells to which the name, stratum granulosum, is usually applied. This layer marks the level at which the conversion of the epithelial elements into horny plates begins and also that at which the separation effected by blistering usually occurs. On the palms and soles, where the epidermis attains not only great thickness but also higher differentiation, four distinct layers may be recognized in vertical sec- tions of the cuticle. From the corium outward, these are: (i) the stratum germina- tivum, (2) the stratum granuhsum, {3) the stratum lucidum and (4) the stratum corneum. The first two represent the portion of the epidermis endowed with the greatest vitality and powers of repair and the last two the horny and harder part. The stratum germinativum, or stratum Malpighi, rests upon the outer sur- face of the corium, by the papiilic of which it is iinpri:s3t;d and, hence, when viewed from beneath after being separated, commonly presents a more or less evident net-work of ridges and enclosed pits, the elevations corresponding to the Ill 1386 HUMAN ANATOMY. Stratum corneum Stratum lucidum Stratum granulosum Stratum germinativum Deepest cells of epidermis Corium Pi.rtion of preceding preparation, sliowinn in more detail layers of epidermis; only deeper part of stratum corneum is represented. > 2ho. interpapillary furrows and the depressions to the papilla?. In recognition of this reticulation the name, rete Malpighi, is sometimes applied to the deepest layer of the epidermis. As in other epithelia of the stratified squamous type, the deepest cells are columnar and lie with Fig. 1 150. their long axes perpen- dicular to the supportinjf connective tissue. The basal ends of the colum- nar cells are often slijiht- ly serrated and fit into corresponding indenta- tions on the corium. Their outer ends are rounded and received between the super- imposed cells. Succeed- ing the single row of columnar elements, the cells of the stratum germinativum assume a pronounced polygonal form, but become some- what flatter as they approach the stratum granulosum. The num- ber of layers included in the germir al stratum is not only uncertain, but varies with the rela- tion to the papillae, being greater between than over these projections. The finely granular cytoplasm of the cells of the stratum germinativum contains delicate but distinct fihrilla, which, longitudinally disposed in the deep columnar cells, in the polvgonal elements (Fig. 1151), radiate from the nucleus towards the periphery (Kromaycr). The fibrillse are not confined to the cells, but extend beyond and pass across the intercellular lymph-clefts as delicate protoplasmic bridges that connect the units of the \arious layers of the stratum and confer upon them the character- istics of the so-called ' ' prickle cells. The stratum granulosum is e.xceptionally well marked on the palms and soles and in these localities includes from two to four rows of polygonal cells, SDint'what horizontally compressed, that stand out conspicuously in stained sections by reason of the intensely colored particlcswithin theircytoplasm. The nature of the peculiar substance, deposited within the body of the cells as |)articles of irregular form and size, is still uncertain. To it R.invier gave till" name of cicidin and Waldeyer that of keraiohyalin. .Since the nuclei of the cells in which the deposits occur always exhibit e\idences of degenera- tion, it is probable that keratohyalin is in some way derived from disintegra- tion of the nucleus (Mertsching) ancl represents ■\ tr.insitinn st.^s^p in the process ending in cornification of the succeeding layers of the cuticle (Brunn). The stratum lucidum, usually wanting in other localities, in the palm and sole appears as a thin, almost homogeneous layer, separating the corneous from the Fihrillje Portion of horizontal section of skin, shciwinjf intracellular fihrilla* within cells of stratum Rerminativum. -" Soo. m^ THE SKIN. 1387 PiKmenlal epidertniH granular layer. With the latter it constitutes the stratum intermetlium. As indicated by its name, the stratum lucidum appears clear and without distinct cell lK)undaries. although suggestions of these, as well as of the nuclei of the component elements, arc usually distinguishable. The cells of tha stratum lucidum are uniformly cornified and differ, therefore, from those of the overlying layers in which the process is often confined to a mantle zone. ... The stratum corneum includes the remainder of the epidermis and consists of many layers of horny epithelial cells that form the exterior oi the skin. Where no stratum lucidum exists, as is usually the case, the corneous layer rests uixin the stratum granulosum, from which its horny elements arc being continually recruited. During their migration towards the free surface, the cells lose their vitality and become more flattened until the most superficial ones are converted into the dead homy sc.iles that are being constantly displaced by abrasion. The pigmentation of the skin, which even in white races is conspicuous in certain regions (page 1381), depends upon the presence of colored j)articles chiefly within the epidermis, although, when the dark hue is pronounced, a few small branched pigmental connective tissue cells may appear within '"'*'■ ' the subjacent corium. The dis- tribution of the pigment particles varies with the intensity of color, in skins of lighter tints being principally, and sometimes en- tirely, limited to the columnar cells next the corium. With increasing color the pigment particles invade the neighlxaring layers of epithelium until, in the dark skin of the negro, they are found within the cells of the straivnn corneum but always in diminishing numbers towards the iree surface. Even when the cells are dark and densely packed, the colored particles never encroach upon the nuclei, which, therefore, appear as con- spicuous pigment free areas. _ i. ■ t a The source of the pigment within the epidermis is uncertain, bv some being found in an assumed transference of the colored particles from the corium, by means of wandering cells or of the processes of pigmented connective tissue cells that penetrate the cuticle, and by others ascribed to an independent origin »w siOt within the epithelial elements. While it may be accepted as established^ that at times the connective tissue cells are capable of modifying pigmentation (Karg), it is equally certain that the earliest, and probably also later, intracellular pigmenta- tion of the epidermis appears without the assistance of the connective tissue or migratory cells. The blood-vessels of the skin arc confined to the connective tissue portion and never enter the cuticle. The ar/trics are derived either from the trunks of the subjacent layer as special cutaneous branches destined for the integument, or indi- rectly from muscular vessels. When the blood supply is generous, as in the palms and soles and other regions subjected to unusual pressure or exposure, the arteries ascend through the subdermal layer to the deeper surface of the corium where, having subdivided, thev anastomose to form the subcutaneous plexus (rcte artcriosum cutaneum). P>om the latter some twigs sink into the subdermal layer and contribute the capillary net-works that supply the adii>ose tissue antl the sebaceous glands. Other twigs, more or less numerous, pass outward through the deeper part of the corium and vvithin the more superficial stratum unite into a second, subpapillary plexus (rete arteiiosum subpapillare), that extends parallel to the free surface and Section of skin, surroundinK anus. showinR pigmentation of deeper layer of epidermis. > 50. w^m 1388 HUMAN ANATOMY. Fig. 1 153. 1 ui Papilla r> loops beneath the bases of the papilke. The latter are supplied by the terminal twigs whicli ascend vertically from the subpapillary net-work and break up into capillary loops that occupy the papillae and lie close beneath the epidermis (Fig. 11 53). With the exception of the loops entering the hair-papilla, the capillaries enclosing the hair- follicles arise from the subpapillary plexus. The arrangement of the cutaneous veins, more complex than that of the arteries, includes four plexuses (retes veoosum) lying at different levels within the corium and extending parallel to the surfaces. The first and most superficial one is formed by the union of the radicles returning the blood from the papilla-. The component veins lie below and parallel to the rows of papillx and im- mediately beneath the bases of the latter. At a slighdy lower level, in the deeper part of the stratum [>apillare, the ve- nous channels proceeding from the subpapillary net- work join to form a second plexus with polygonal meshes. A third occurs about the middle of the corium, while the fourth shares the position of the subcutaneous arterial plexus at the junction of the corium and subdermal strata. The deepest plexus receives many of the radicles returning the blood from the fat and the sweat glands, the re- mainder being tributary* to the veins accompany- ing the larger arteries as they traverse the tela subcutanea. The lymphatics of the skin are well repre- sented by a close super- ficial plexus within the papillary stratum of the corium into which the terminal lymph-radicles of the papilla; empty. The relation of these channels to the interfascicular connective tissue spaces is one only of indirect comiminication, since the lymphatics are provided v/ith fairly complete endothelial walls. It is probable tliat the lymph-paths within the papillae are closely related to the intercellular clefts of the epidermis, according to Unna, indeed, direct communications existintr. Mieratory leucocytes often find their way into the cuticle where they then appear as the irregulariv stellate cells of Lans^crhans seen between the epithelial elements. A wiile-ineshed deep plexus of lymphatics is formed within the subdermal layer, from which the larger lymph-trunks pass along with the subcutaneous blood-vessels. 5>ection of injected skin, showinj^ general arrangement ot bIoon diflercmes in the curvature of the follicle ' and the form of the hair. In the ciise of straight hairs the follicle is unbent and the shaft is cylindrical, and therefore circular in cross- section ; hairs that are wavy or curly spring from follicles more or less IkiU and are flattened or grooved, with corresponding oval, reniform, irn-gularly triangular or indented outlines when transversely cut. Arrangement of the Hairs. — Since the buried part of the hair, the root, is never vertical but always oblique to the surface of the skin, it follows that the free part, the sJia/t, is also inclined. The direction in which the hairs jwint, however, is by no means the same all over the body, but varies in different regions although constant for any given area. This disposition depends upon the peculiar placing of the hair-roots which in certain localities incline towards one another along definite lines, an arrangement that results in setting the shafts in opposite directions. As these root-lines are not straight but spiral, on emerging from the skin the hairs diverge in whorls (vortict. -ilorum), the position and number of which are fairly definite. Such centres include : (i ) the coaspicuous vertex whorl on the head, usually single but sometimes double; (a) Hu: facial whorls surrounding the openings of the eyelids; (3) the auricular whorls at the external auditory meatus ; (4) the axillary whorls in the armpits ; and (5) the inguinal whorls, just below the groin ; additional (6) but less constant lateral whorls .nay be located, one on each side, about midway between the axilla and the iliac crest and (Kjmewhat beyond the outer border of the rectus muscle. These whorls, all paired except the first, apportion the entire surface of the body into certain districts, each covered by the hairs proceeding from the corresponding vortex. The whorl-dlstricts, moreover, are irregularly subdivided into secondary areas by lines, the hmir- rangea (flumlna pilontm), along which the hairs diverge in opposite directions. Additional lines, the converging hair-rangca, mark the meeting of tracts pointing in different directions and in places also assume a spiral course. In consequence of these peculiarities the body is aivered with an elaborate and intricate hair-pancm, that is most evident on the fcetus towards the close of gestation ; later in life the details of the pattern are uncertain owing to its partial eflfacement by the constant rubbing of clothing. Structure.— Each hair consists of two parts, the shaft, which projects beyond the surface, and the root, which lies embedded obliquely within the skin, the deepest part of the root expanding into a club-shaped thickening known as the bulb. The root is covered with a double investment of epithelial cells, the inner and outer root- sheaths, which, in turn, are surrounded by a connective tissue envelope, the theca. Th 'ntire sac-like structure, consisting of the hair-root and its coverings, constitutes the hair-follicle (folliculus pili). At the bottom of the latter, immediately beneath the bulb, the wall of the follicle is pushed upward to give place to a projection of connective tissue, the hair-papilla', which cames the capillary loops into close relation with the cells ■ "wt active in the production of the hair. Save in the case of the finest hairs (' ugo), which are limited to the corium, the hair-follicles traverse the latter and end at varying levels within the fat-laden subdermal layer (panniculus adiposus). In a general way the follicle may be regarded as a narrow tubular invagi- nation of the epidermis, at the bottom of which the hair is implanted and from the entrance of which the shaft projects. The most contracted part of the follicle, the neck, lies at the deeper end of the relatively wide funnel-shaped entrance to the sac. Closely associated with the hair-follicle, which they often surround, are the sebaceous glands that pour their oily secretion at the upper third of the follicle into the space between the shaft and the wall of the sac. The Hair-Shaft. — In many thick hairs, but by no means in all, three parts can be distinguished — the cuticle, the cortex and the mfdvlla. The latter, however, is usually wanting in hairs of ordinary diameter, being often also absent in those of large size. ' Frederic : Zeitschr. (. Morph. u. Anthropol., Bd. ix., 1906. 1393 HUMAN ANATOMY. Fic. ii5j. The Ctttid* of the hair appears as a transparent outermost layer marked by a net-work of fine sinuoai lines, the irregular meshes ot which have their kNigest diameter placed obli(|ut-!y transverse. These lines corresp»jnd to the free borders of extremely thin glassy cuticle-platfs that overlie the hair as tiles on a roof, the imbrication involv- inK from four to six layers. Seen in profile (Kig. 1155). th«^ contour of the hair-«haft, therefore, is not smooth Init serratrd, the minute teeth formed by the free margins of the scales lieinK directed towards the tip of the hair. After isolation by suitable reagents, the cuticular elements appear as transparent structureless cslls, quadrilateral in outline and curved to con- form to the hair-shait which they cover. The cortical substance, often indeed constituting practi- cally the entire shaft, consists ot elongated fusiform cells so compactly arranged that the individual elements are only dis- tinguishable after the action of disassociating reagents. In addition to the remains of the shrunken nuclei the Aair- spindlfs, as these modified epithelial cells are called, possess fibrillx that pass between adjacent cells similar to the inter- cellular bridges in the epidermis. A variable amount of pigment, present either as a diffuse tint of the spindles, or as granules within or between the same, is -x mn ,t.nnt ccn-titucnt of the cortical substance. In blond hair the color is chiefly diffuse, the pigment granules being often entirely wanting ; in hair of darker shades, the granules predominate and increase in intensity of color as well a.s in qiuintity. As the hair grows ou*ward from the bulb, it loses much of its moisture, and in consequence later contains minute air-vesicles that replace the fluid previously occupying the clefts between the hair-spindles. Even when conspicuous, the medulla does not extend the entire length of the hair, often being interrupted and always disappearing before reaching the tip. The medulla, when well represented, is seen as an axial stripe, somewhat uneven in outline, that varies with illumin' 'ion, with transmitted light appearing as a dark band and with reflected light as a light one. Thi.-. pf-culiarity depends upon the presence of air imprisoned between the shrunken and irregular »w dntlary <•<•/&— -dried and comified epithelial elements which are con- nected by branching proc'sses into a net-work incompletely filling the medulla. The air within the shaft is a factor modifying the color of the hair, since the resuking reflex tends to lessen the intensity of the tint direcdy Portion o( ibaft of hair: h, ihatt covered witli cuticle; j, cuticle re- moved to expose cortical aubatance; M, medulla .-135. a, d, iiolatcd cella of cuticle and of cortical respectively. X 340. referable to the pigment ; this diminution affects par- ticular)' the lighter shades, as in dark hairs the large amount of pigment masks the reflex. Fig. 1 1 56. Uuter rtnt'Sheaih Hair surrounded by inner root-sheatli Adipose tissue The Hair-Folli- cle. — This structure consists essentially of ( I ) a connective tissue sheath, the theca, con- tributed by the cerium ; ( 2)an epithelial lining, the outer rovl-sheath, continued from the deepest layer of the epidermis; and (X) the inner root-sheath, an epithelial investment probably differentiated within the follicle, and not a direct prolonjra- tion from the cuticle. The theca folliculi includes three strata : an outer, composed of loosely db- posed longitudinal bundles of fibrous tissue with few cells and elastic fibres ; a middle one, made up of closely placed circular bundles ; and a very thin, homogeneous inner coat, the ii^lassy membrane, which represents an unusually w'.'U developed Fibrous tissue Horizontal section of scalp, showing iroup of transveraely cut hair-lollicles, X 65. THE HAIRS. «39.^ basement membrane separating corium from cuticle, (jreatly attenuated, it is prolonged over the hair-papilla, which, as a special vaiicularized thickfninjj of the connective tissue of the follicle, carries nutrition to the bulb of the growing; hair. The outer root-theath is the continuation of the stratum gcrminativunt alone, the other layers of the epidermis thinning out and disapptarinR iK-forc reaching the neck of the follicle. Its cells present the characteristics of those of the germinating layer, with exceptionally well marked fibrilKe. On approaching the lc\el of the papl'^a, the outer root-sheath, which farther above consists of numerous layers, rapidly diminishes in thickness until, on the sides of the papilla, it is reduced to a single row of low columnar cells. The inner root-theath, which b best developed over the middle third of the hair-root and fades away on reaching the upper third, includes three layers. The outer, known as Henle's layer, consists of a single row of flat polygonal cells, often partially separated by ovaf spaces. Their nuclei are very indistinct or invisible Fio. 1157. Thcca funiculi Middle layer Hcnie't layer oi inner root-sheath Outer root-sheath Tranaverse lection of hairfollicle, showing hair ■urronnded by internal and external root-sheaths. :■ 285. within the comilied cytoplasm. The middle or Huxley's layer, also hoi^ny in nature, often comprises only one stratum of nucleated cuboid;il cells, but in the thicker hairs two or even three rows of irregularly interlocked cells may be preseiit. The third layer, known as the sheath aiHcle, resembles the external coat of the hair, against which it lies, in being extremely thin and composed of flat horny plate-.,. The latter, however, are always nucleated and so disposed that they are opposed to the serrations of the thicker hair-cuticle. Traced towards the bottom of the follicle, the root-sheaths and the hair, which above are sharply defined from one another, become more and more alike until, in the immediate vicinity of the hair-papilla, they blend into a still imperfectly differentiated mass of cells. The deepest elements of this complex, however, are cutioidal or low columnar and form an uninterrupted tract over the papilla, continuous with the outtmnost crlts of tlie outer root-sheath. It is fmtn the proliferation of these deepest cells that the formative material, or matrix, is provided to meet the requirements of growth and replacement of the hairs. Without anticipating the account of the detailed changes described in connection with the development of the hair (page 1401 ), it may be here noted that of the three parts of the hair, the medulla is produced by 88 ^ 1394 HUMAN ANATOMY. the cells overlying the summit of the papilla, while those converted into the cortical substance, cuticle and inner root-sheath occupy the sides of the papilla and deepest part of the follicle. With few exceptions, the hair follicles are associated with two or more sebaceous glands, rarely with only one, the ducts of which open into the sac in the vicinity of the neck. The glands usually lie on the side towards which the hair inclines, but sometimes, especially in the case of the smaller hairs, they may completely surround the follicle. Since these glands are outgrowths from the srme tissue that lines the follicles, their ducts pierce the outer root-sheath, bringing their oily secretion into direct relation with the hairs. The structure of the sebaceous glands is described with the cutaneous glands (page 1397). Most of the larger hair-follicles, particularly those of the scalp, are provided with ribbon-like bundles of involuntary muscle, called the arrectores pilonim in recog- nition of their effect on the hairs. They arise from the superficial part of the corium, passobliquelydownwardto be inserted Fig. 1 158. W^^ mto the sheath of the hair-follicle near the junction of corium and subdermal tissue and on the side corresf>onding with the inclination of the hair and the situation of the sebaceous glands. Since the latter are closely embraced by the muscular bands, contraction of the muscles exerts pressure u[)on the glands and facilitates the discharge of their secretion (^sebum) — hence these muscles are sometimes also designated expressores sebi. The effect of con- traction of the arrectores pilorum is often conspicuously seen on the surface in the condition known as "goose- flesh" {cutis anseriHd),'>K\i&[e.the hairs and surrounding tissue appear to be unusually elevated owing to the upward pull on the hair-follicles and the consequent erection of the hairs in the opposite direction. The blood-vessels supplying the hair-follicle, which in a sense con- stitute a special system for each sac, include the capillary loops ascending within the hair-papilla and the net-work of capillaries surrounding the follicle immediately outside the glassy membrane. The first are derived from a small special twig that ascends to the follicle, and the second from the subpapillary net-work of the corium. With the exception of those draining the papilla, which are tributary to the deeper stems, the veins join the subpapillary plexus. The nerves distributed to the follicles follow a fairly definite arrangement. As shown by Retzius, usually each hair-sac is supplied by a single fibre, sometimes by two or more, which approaches the follicle immediately below the level of the mouth of the sebaceous glands. After (jenetrating the fibrous sheath as far as the glassy membrane, the nerve-fibre separates into two divisions that encircle more or less completely the follicle and on the opposite side break up into numerous fibrillae constituting a terminal arborization. The nerve-endings usually lie on the outer surface of the glassy membrane within the middle third of the follicle and only exceptionally are found within the outer root-sheath or the hair-papilla. THE NAILS. The nails (untpies), the homy plates overlying the ends of the dorsal surfaces of the fingers and toes, correspond to the claws and hoofs of other animals and, like them, are composed exclusively of epithelial tissue. They are specializations of the Plpillary Portion of section of injected tcalp, show'i j- rapil!ary net-works surrounding liair-fotticles and twigA enteriflf papilUc. < 20. THE NAILS. 1395 epidermis and, therefore, may be removed without mutilation when the cuticle is taken off after maceration. The entire nail-plate is divided into the body (corpus unguis). whii.n includes the exposed portion, and the root (radix unguis), which is embedded beneath the skin in a pocket-like recess, the nail-groove (sulcus unguis). The modified skin supporting the nail-plate, both the body and the root, constitutes the nail-bed (solum unguis), the cutaneous fold overlying the root being the nail-wall (vallum unguis). The side° of the quadrilateral nail-plate are straight and parallel and at their distal ends connected by the convex free margin (margo liber) that projects for a variable distance beyond the skin. The proximal buried border (margo occultus) is straight or slighriy concave, more rarely somewhat convex, and often beset with minute serrations (Brunn). Both surfaces of the transversely arched nail are smooth and even, with the exception of the longitudinal parallel ridges that often mark the upper aspect. Inspection of the latter during life shows color-zones, the translu- cent whitish crescent formed by the projecting portion of the nail being immediately followed by a very narrow yellow band that corresponds to the line along which the stratum comeum of the underlying skin meets the under surface of the plate. The Diatal pontons o( fingen, ahowinK rctations o( nail ; A wu drawn from livins rabject ; B mnd C are lateral and under vei«n respectively of Inner surface of cuticle with nail ; nothing; but the epidermal structures are present, the cuticle and nail having been removed together, a. A. distal and proximal borders of nail ; r, under surnce of nail ; rf, nail in section ; e, Ibie of dellectioii of cuticle to under surface of nail ; /, lunula ; g, nail-wall ; h, cuticle in section. succeeding and larger part of the nail is occupied by the broad pink zone which owes its rosy tint to the blending of the color of the blood in the underlying capillaries with that of the horny substance. On the thumb constantly, but on the fingers often only after retraction of the cuticle, is seen a transversely oval white area, the so-called lunula, which marks the position of the underlying matrix. Additional white spots, irregular in position, form and size, are sometimes seen as temporary markings. The thickness of the nail-plate — greatest on the thumb and large toe and least on the last digits — diminishes towards the sides, but in the longitudinal direction, between the lunula and the free margin of the nail, is fairly uniform ; beneath the white area, however, the under surface of the nail shelves of! towards the buried border, where it ends in a sharp edge. Structure. — The substance of the nail-plate (stratum comeum unguis) consists entirely of flattened homy epithelial cells, very firmly united -tntl containing the remains of their shrunken nuclei. These cornified scales are 1. isposed in lamellx, which, in transverse section, pursue a course in general parallel with the dorsal sur- fact;. In nails which pos.sess the longitudinal rid>;i:s, however, the latter coincide with an upward arching of the lamellae dependent upon the conformation of the nail matrix (Brunn). In longitudinal section the lamellation is oblique, extending 1396 HUMAN ANATOMY. from above downward and forward, parallel to the shelving under surface beneath the white area that rests upon the matrix. Minute air- vesicles, imprisoned between the horny scales, are constant constituents of the nail-substance. When these occur in unusual quantities, they give rise to the white spots in the nail above mentioned. Corresponding respectively to the colored zones— the white, rosy and yellow— the dorsal surface of the nail, the nail-bed is divided into a pro.ximal. seen on Fig. ii6o. Subculineoiu tinuc Stratum germinativum Stratum comeum Transformation zone Matrix Longitudinal Mction of proximal part of nail lying within the nail groove. X 3». a middle and a distal region, each of which exhibits structural differences. The most important of these regions is the proximal, known as the matnx, which lies beneath the white area and alone is concerned in the production of the nail. The corium of the nail-bed varies in the different regions in the arrangement and size of its elevations Within the proximal third of the matrix, these elevations occur in the form of low papilla; which decrease in height and number until they disappear, a smooth field occupying the middle ot the matrix. This even field is succeeded by one possessing closely set, low, narrow longitudinal ridges, that at the distal margin of the lunula suddenly give place to more pronounced, but less numerous broader, linear elevations. These continue ^ far as the distal end of the nail-lxd and are then replaced by papillae. Owing to the strong fibrous bands and the absence of the usual layer of fatty subdermal tissue, the corium of the nail-bed is closely attached to the bone. The fibrous reticulum formed by the interfacing of the longitudinal with the vertical bundles contains few elastic fibres, since these are entirely wanting beneath the body of the nail and only present in meagre numbers within the matrix. In view of its genetic activity, the relations of the epidermis underlying the nail are of especial interest. While the stratum germinativum of the skin covering the finger tip passes directly and insensibly onto the nail-bed, the entire extent of which it invests (atratum wrmina- tivum unRuU), the stratum corneum ends on reaching the under suriace of the nail-plate, the line of apposition corresijonding to the narrow yellow zone which defines the distal boundary of the rosv area Beneath the latter, therefore, the epidermis of the nail-bed consists of the stratum eemiinativum alone, which, without comification of any of its cells, rests against the under sur- face of ihtr nail. Beneath the white zone, that is, within the matrix, the epidermis includes a half dozen or mor. layers of the usual elements of the stratum germinativum, surmounted by a like number of strata of cells distinguished by a peculiar brownish color. On reaching the "«" these moflified epithelial elements, which appear white by reflected light, are not circumscribed, but pass over into the substance of the nail, into the ron,stitucnt cells of which they are dinrtly con- verted Their cytoplasm presents a marked fibrillation to which, according to Brunn. the light appearance of the cells is referable as an interference phenomenon and not as a true pigmente- tion. ThU peculiarity of the celU, coupled with the relatively small size of subjacent capillaries. THE CUTANEOUS GLANDS. 1397 Nail-bed Nail-plale Stratum corneiim and Stratum germinativum of nail-wall Eponychium Margin of nail probably accounts for the tint distinguishing the white area. Since the transformation of tlie cells of the stratum germinativum into those of the nail-plate is confined to the matrix, it is evi- dent that the continuous growth of the nail Ukes Fig. 1161. place along the floor and bottom of the nail-groove, the last formed increment of nail-substance pushing forward the previously dif- ferentiated material and thus forcing the nail to- wards the end of the digit. The relation of the epi- dermis of the nail-wall to the substance of the plate is one of apposition only, production of the nail oc- curring in no part of the fold. Over the greater extent of the latter all th- typical constituent cntide are represen' within the most p portion the stratum ,' nativum alone is present, the stratum comeum fad- ing away, ^^^^ere the homy layer exists, it rests directly upon the nail, but is differentiated from the latter by being less dense and by its respoase to stain-s. As the nail leaves the groove, a part of the stratum germinativum of the nail-wall is prolonged distally for a variable distance over the dorsal surface of the nail-plate as a delicate membranous sheet, the eponychium, which usually ends in a ragged abraded border. Corium Trantvenc section of nail- wall and adjacent part of nail-plate and nail-bed. v qo. THE CUTANEOUS GLANDS. These structures include two chief varieties, the sebaceous and the sweat glands, together with certain modifications, as the ceruminous glands within the external auditory canal, the circumanal glands, the tarsal and ciliary glands within the eyelid and the mammary glands. In all the epithelial tissues — the secreting elements and the lining of the ducts — are derivatives of the ectoblast and, therefore, genetically related to the epidermis. The Sebaceous Glands. Although these structures (glandulae scbacae) are chiefly associated with the hair-follicles, in which relation they have been considered (page 1394), sebaceous glands also occur, if less f- ^quently, independently and in those parts of the skin in which the hairs are wanting, as on the lips, angles of the mouth, prepuce and labia minora. The size of these glands bears no relation to that of the hairs, since among the smallest (.2-.4 mm.) are those on the scalp. The largest, from .5-2.0 mm., are found on the mons pubis, scrotum, external ear and nose. Conspicuous aggre- gations, modified in form, occur in the eyelid as the Meibomian glands. Depending upon the size of the glands their form varies. The smallest ones are each little more than a tubular diverticulum, dilated at its closed end. In those of larger size the relatively short duct subdivides into several expanded compartments, which, in the largest glands, may be replaced by groups of irregular alveoli, with uncertain ducts that converge into a short but wide common excretory pas-sage. Structure'. — The structural components of these glands include a fibroits envelope, a membrana propria and the epithelium, the first two being continuous with the corresponding crverings of the hair-follicle. Tho epithelium continued 1398 HUMAN ANATOMY. Alveoli Sebaceous glands from skin covering nose. into the ducts and alveoli of the sebaceous glands is directly prolonged from the outer root-sheath of the epidermis, where associated with the hair-follicles, or from the epidermis where the hairs Pig. 1162. are wanting. The periphery of the alveolus is occupied by a single, or incompletely double, layer of flattened and imper- fectly defined basal cells, that rest immediately upon the mem- brana propria and are distin- guished by their dark cytoplasm and outwardly displaced oval nuclei. Passing towards the centre of the alveolus, the next cells contain a number of small oil drops which, with each suc- cessive row of celb, become larger and appropriate more and more space at the expense of the protoplasmic reticulum in which they are lodged. In consequence, the cells occupy- ing the axis of the alveoli, which are completely filled and with- out a lumen, contain little more than fat As the cells are escaping from the glands they lose their nuclei and individual outlines and, finally, are merged as debris into the secretion, or sebum, with which the hairs and skin are anointed. The necessity for new cells, created by the continual destruction of the glandular elements that attends the activity of the sebaceous glands, is met by the elements recruited from the Fig. 1163. proliferating basal cells, which in turn pass towards the centre of the alveolus and so displace the accumulating secretion. The Sweat Glands. These structures (Klandulae sudoriferae), also called the sudoriparous glands, are the most important representatives of the coiled glands (glandulae glomi- formes) often regarded as constituting one of the two groups (the setaceous glands being the other) into which the cutaneous glands are divided. They occur within the integument of all parts of the body, with the exception of that covering the red margins of the lips, the inner surface of the prepuce and the glans penis. They are es- ecially numerous in the palms and soles, in the former locality numbering more than iioo to the square centimetre (Horschelmann), and fewest on the back and buttocks, where their number is reduced to about 60 to the square centimetre ; their usual quota for the same area is between two and three hundred. Modified simple tubular in type, each gland consists of two chief divisions, the bodv (corpus) or gland-coil, the tortuously wound tube in which secretion takes place, and the exrretor}' duct (ductus sudoriferns) which opens on the surface of the skin, exceptionally into a hair-follicle, by a minute orifice, the sweat pore (poms tiuduriferus), often distinguishable with the unaided eye. The body of the gland, irregularly spherical or flattened in form and yellowish red in color, consists of the windings of a single, or rarely branched, tube and com- monly occupies the deeper part of the corium, but sometimes, as in the palm and Cells from alveoli of sebaceous gland . showing reticulated protoplasm due to presence of oil droplets. X Too. THE CUTANEOUS GLANDS. 1399 S.genninativum scrotum, lies within the subdermal connective tissue. The coiled jM)rtion of the gland is not entirely formed by the secretory segment, since, as shown by the recon- structions of Huber, about one fourth is contributed by the convolutions of the first part of the duct. On leaving the gland-coil, in close pro.\imity to the blind end of the gland, the duct ascends through the corium with a fairly straight or slightly wavy course as far as the epidermis. On entering the latter its further path is marked by conspicu- ous cork-screw-like windings, which, where the cuticle is thick as on the palm, are close and number a dozen or more and terminate on the surface by a trumpet-shaped orifice, the sweat-pore. In its course through ^*°- "^ the corium the duct never traverses a papilla or ridge, but always enters the cuti- cle between these ele- vations. On the palms and soles, where the pores occupy the sum- mit of the cutaneous ridges, the ducts enter the cuticle between the double rows of papillae. Structure. — The secreting portion of the gland-coil, called theampu/ia on account of its greater diameter, possesses a wall of remarkable structure. The thin external sheath, composed of a layer of dense fibrous tissue and elastic fibres, supports a well defined membrana propria. Immediately within the latter lies a thin but compact layer of invol- untary muscle whose longitudinallydisposed spindle - shaped ele- ments in cross-section appear as a zone of irregularly nucleated cells that encircle the secreting epithelium and displace it from its customary position against the basemt li membrane. This muscular tissue enjoys the distinction, sharing it with the muscle of the iris, of being developed from the ectoblast. The secreting cells constitute a single row of low columnar epithelial elements, that lie internal to the muscle and surround the relatively large lumen. Their finely granular cytoplasm contains a spherical nucleus, situated near the base of the cell, and in certain of the larger glands, as the axillary, includes fat droplets and pigment granules. These are liberated with the secretion of the gland and when present in unusual quantity account for the discoloration produced by the perspiration of certain individuals. In the case of the ceruminous glands, the amount of oil and pigment is constantly great and confers the distinguishing characteristics on the ear-wax. The sudden and conspicuous reduction in the size of the tube which marks the termination of the secreting segment and the beginning ./ tl:" duct, is accompanied by changes in the structure of its wall. In addition to a leduction of its diameter to Fat-cells Coiled p«rt at •weat-gUiid Section of »kin (rom palm, showing diHerent pans of sweat-glands extending from surface into tela subcutanea. X 6;. I400 HUMAN ANATOMY. one-half or less of that of the ampulla, the duct loses the layer of muscle and becomes flattened, with corresponding changes in the form of its lumen. The single row of secreting elements is replaced by an irregular double or triple layer of cuboidal cells, which exhibit an homogeneous zone, sometimes described as a cuticle, next the lumen. On entering the epidermis, the duct not only loses its fibrous sheath and membrana propria, but the epithelial coastituents of its wall are soon lost among the cells of the stratum germinativum, so that its lumen is continued to the surface as a spiral cleft bounded only by the comilied cells of the cuticle. Apart from mere variations in size, certain glands — the circumana/, the ciliarv and the ceruminous — depart sufficiently from the typical form of the coiled glands to entitle them to brief notice. The circumanal glands, lodged chiefly within a zone from 12-15 ^^- ^^^^ *"S- DEVELOPMENT OF SKIN AND APPENDAGES. 1401 Fiu. 1 166. Sections of developing Rkhi.showinfc earliest stafcrs in formation of hair-follicles; in D epithelial cylinder is invading mesoblast. > 90. of a deeper row of cuboid or low columnar cells, covered by a superficial sheet, known as the epitrichium, composed oi' flattened elements often lacking in definition, and nuclei. During the succeeding weeks the cpitrichial cells become swollen and vesicular and differentiated from the underlying elements, which meanwhile are engaged in producing the epidermis. The epitrichium persists until the sixth month, when it becomes loosened and IS cast off. During the third and fourth months the ectoblastic cells have so multiplied, that from four to five layers are present, those next the mesoblast being columnar and rich in protoplasm, while the more superficial are irregular and clearer. By the middle of the fifth month, by which time the layers have increased to almost a dozen, the outer cells become horny and assume the characteristics of a stratum comeum, while the deepest ones represent the stratum germi- nativum, with an intervening transitional zone. About the sixth month desquamation of the surface cells begins, the discarded epitrichial and other scales mingling with the secre- tion from the sebaceous glands, which meanwhile have been developed, as constituents of the white unctuous coating, the vernix caseosa (smegma embryonnm), that covers the surface of the foetus, especially in the folds and creases. Ehiring the last weeks of gestation the epidermis acquires considerable thickness and a sharper differentiation of its c .mponent strata. The connective tissue part of the skin is developed as a superficial condensation of the mesoblast, that during the first month consists of closely placed spindle cells. Coinci- dently with the appearance of the fibrous fibrillae, in the third month, differentiation takes place within the condeiised mesoblastic tissue, which so far exists as a uniform zone, into a superficial and more compact layer and a deeper and looser one ; the former becomes the corium and the latter the tela subcutanea. Within the last layer soon appear larger or smaller groups of round cells in which oil drops, at first minute and then of increasing: diameter, indicate the beginning of their conversion into adip>ose tissue. By the sixth month the panniculus adiposus is established. About the fifth month the line marking the junction of cuticle and corium becomes uneven in consequence of the development of the papill^p and ridges of the corium and the attendant invasion of the epidermis. Certain of the mesoblastic cells are transformed into the component elements of the involuntary muscle that occurs either associated with the hair follicles as the arrectores pilorum, or as i'le more extended tracts of the dartos. The Hairs. — ^The primary development of the hair begins about the end of the third month of foetal life as localized proliferations of the epidermis. In section these appear as lenticular thickenings and on the surface as slight projections. Very soon solid epithelial cylinders sprout from the deeper surface of these areas and invade the subjacent corium to form the anlages of the hair-follicles. The original uniform outline of these processes is early replaced by a flask-shaped contour in consequence of the enlargement of their ends which in their growth surround connective tissue processes to form the hair-papillee. The embryonal connective tissue immediately surrounding the epidermal ingrowth diflerenliates into iht; fibrou.s xhealh and the glassy membrane. Meanwhile and'even before the formation of the papilla the epithelial contents of the young follicles differentiate into an axial strand of spindle cells that later undergo keratinization and become the hair-shaft that grows by subsequent additions Fio. 1 167. Halr-follide Papilla Developing skin, showing later stages of (orma- tion of halr-K>nicles ; surrounding mesoblast is forming hal^-papina and fibrous sheath of follicle. ■ 90- I402 HUMAN ANATOMY. from the matrix surmounting the piipiUa. In addition to forming the outer root- sheath the peripheral elements contribute the matnx-cells that occupy the furidus of the follicle and surround the papiUa. The cells covering the summit and adjacent sides of the papilla are converted into elongated spindles that later gradua|ly l)ecomf horny and assume the characteristics of the cortical substance of the hair. VV hen present, the medulla is developed by the transformation of the cells occupying the summit of the papilla, which enlarge, become les.s granular and grow upward as an axial strand that invades the chief subsUnce of the hair and accumulates kerato- hyalin within its cells. At first present as minute drops, this substance increases in quantity until it occupies the cells in the form of large vesicles. The subsequent disappearance of these, followed by shrinkage of the cells and the introduction <.f air, completes the differentiation of the medulla. The pigment particles, w-hich appear later, are first evident in the hair-bulb and probably arise within the epithelia tissue. The elements of the hair-cuticle and of the inner root-sheath are differentiated from the matrix-cells at the sides of the papilla. The tall columnar elements become eloneatpd and converted into the cornihod plates of the cuticle both of the hair and of the inner root-sheath. The layers 1168. of Huxley and of Henle are derived from cells that soon exhibit granules of keratohyalin, so that on reaching the level of the summit of the papilla the process of cornification has been estab- lished. This is especially marked in the elements of Henle' s layer, in which the deposit takes the form of a longi- tudinal fibrillation. The growth of the hair takes place exclusively at the lower end of its bulb, where, so long as the hair grows, the conversion of the matrix- cells into the substance of the hair is continuously progressing. By this pro- cess the sutetance already differentiated is pushed upward by the cells under- going transformation and these in turn are displaced by the succeeding elements. In this way, by the addition of new increments in its bulb, the hair is forced onward and, in the c^ of those first formed, through the epidermis that still blocks the mouth of the follicle. This eruption begins on the scalp and regions of the eyebrows about the fifth fcetal month and on the extremities about a month later. The hairs covering the Jirtus are soon shed, durinR the last weeks of gestation and immedi- ately following birth, and are replaced by the stronger hairs of childhood. These latter, too, .irt- continually falling out and being renewed until puberty, when in many localities, as on the scalp, fiice axillx and external genital organs, they are gradually replaced by the much longer and thicker hairs that mark the advent of sexual maturity. Even .ifter attaining their mature growth, the individual life of the hairs is limited, those on the scalp probably retaining their vitahty for from two to four years and the eyelashes for only a few months ( Pincus). During the years of greatest vitality not only are the discarded hairs replaced by new ones, but the actual number of hairs may increase in consequence of the development of additional follicles from the epidermis after the manner of the primary formation. When from age or other cause the hair-follicles loose their productive activity and, therefore, are no longer capable of replacing the atrophic hairs, more or less conspicuous loss of hair results, whether only tem- porary or permanent evidently depending upon the recuperative powers of the follicles. The change of hair that is continually and insensibly occurring in man, in contra-st to the conspicuous periodic shedding of the coal seen in other animals, includes the atrophy of the old hair on the one hand, and the development of the new on the other. , . . . The eariiest manifestations of this atrophy, as seen in longitudinal sections of the hair- follicle are reduction in the size anearance of its middle and distal [)arts, are subsequently seen as a thin mem- brane covering the proximal part of the nail-plate. As yet the young nail-plate has not come into relation with the epidermis of the nail-groove, since it is still confined to the primitive area. But during the fifth month the proximally growing root invades more and more the sulcus until it attains its definite relations with the nail-wall. Meanwhile the nail-bed beneath the developing root undergoes thickening and becomes the matrix, while the cells containing keratohyalin gradually disappear from the distal region of the nail-area in consequence of their com- pleted conversion into the nail-substance. Subse- quently these cells are limited to the proximal nail-producing zone of the matrix from which, after the initial formation of the primary nail-substance, the nail alone receives the additions necessary for its continued growth. In consequence of the resulting forward growth the nail pushes its way through the elevated distal boundary of the nail-field, the epithelium lying above the nail-plate being lost, while that below remains as the representative of the sole-plates that are well marked in many other animaU. 1 IG. 11701. t; ?^' , .,'J .1 , i, Section of ftetal skin, showing develop* ing sweat-Klands ; a. is less advanced than b and c. X itx). 1404 HUMAN ANATOMY. The Sweat Glands. — The development of these, the most important members of the group of coiled glands, begins during the fifth foetal month as solid epithelial sprouts from the under surface of the epidermis. At first cylindrical in form, these processes soon acquire a club-shaped lower end and .'jr a time resembii.- developing hair-follicles. The terminal segment of the gland-anlage enlarges in diameter and thus early differentiates the later ampulla. With subsequent increase in length, the characteristic coils soon appear, after which a lumen makes its appearance in the ampullary segment and gradually extends to the surface. Practical considerations of the skin find mention in connection with the various regions, to which the reader is referred. THE NOSE. Although only a si part of the nasal chambers is occupied by the periphp'al olfactory or^ap man, the greater part forming the beginning of the respiratory tract, comparative anatomy and embryology establish the primary significance of the nasal groove and its derivations as the organ of smell, the relation of the nose to respiration being entirely secondary. The nose, therefore, is appropriately grooped with the organs of special sense, notwithstanding its relation to the proper production of voice and to taste and the rdle that it plays in varying facial expression. The nose consists of two portior.:, the outer nose (nasiis ezternus) and the inner chamber (cavnm nasi), which is divided by the median partition into the right and left nasal fossae The outer nose forms the prominent triangular pyramid that projects from the glabella forward and downward, supported by a bony and cartilaginous framework and covered by muscles and integument. Its upper end or root (radix nasi) springs from below the glabella from the frontal bone, with which it usually forms an angle and from which, in consequence, it b separated by a groove. When the latter is wanting and the rounded median ridge, or dorsum, of the nose continues the plane of the forehead, the nose is said to be of the Grecian type. The dorsum ends below in a free angle or point (apex nasi), the upper or bony part of the dorsum, often termed the bridge, in the aquiline type of nose forming a more or less conspicuous angle with the cartilaginous part. The sides of the nose (partes laterales nasi) descend from the root with increas- ing obliquity until they reach the broadest part of the nasal pyramid, or base, which is pierced by the openings of the nostrils or anterior nares (nares). Just before meeting the base, each lateral surface expands into the mobile and rounded xving (ala nasi) that forms the outer wall of the nostril and is limited above by a shallow groove, the alar sulcus. Under the influence of the attached muscles, the alae are subject to dilitation, compression, elevation and depression and thereby participate in modifying facial expression. In addition to the endless minor variations of form that the outer nose presents, which, apart from individual distinction, have little significance, the relation of its greatest breadth across the alae to its total length, from root to tip, is of sufficient anthropological inlportance to receive attention in the classification of the races of ,.,_,,.,. , , , . ... /greatest breadth X ioo\ mankmd. This relation, the cephalometnc nasal index I — , — — r ) ^ \ greatest length / varies with different races, according to Topinard the index of the white races being below 70 {leptorhines), that of the yellow and red races between 70 and 85 {mesorhines) , and that of the black races above 85 {plafyrhines'). THE CARTILAGES OF THE NOSE. The cordiform nasal opening ('apertiir.'j pyriformis) of the f.-jcLi! skeleton, hounded by the free margins of the nasal and superior maxillary bones, is enclosed and continued to the anterior nares by the nasal cartilages and contiguous fibrous tissue. These cartilages are usually considered as including five chief plates, the unf>aired septal and the paired upper and lower lateral, and a variable number of smaller THE CARTILAGES OF THE NOSE. >405 supplemental pieces (cartilaKines minoreii). The conventional di«-ision of the iin»t three, however, is unwarranted, since embryologically and niorpholoKically they constitute one piece (cartllaso mediana nasi), which even in the adult iii represented by the connected septal anil upper lateral plates. The cartilage of the leptum (cartilagu scpti nasi) (Fi^. 1171) completes the median partition that divides the right and left nasal fossa? from each other and represents the anterior extremity of the primordiid cartilaginous cranuni. It is irregularly rhomboidal in form and so placed that its superior angle lies al}' instances in conjunction with the follicles of the delir.ite hairs that cover all parts of tl <; surface. On the alie the closely ]>lucctl ((lands are of exceptional size and oir'H tiy dints readily seen as minute depressions. Vessels. — In order to compensate for the e.xposed [)osition, the external nose is generously supplied with aritfies, derived chiefly from the facial and ophthalmic, which are united by numerous anastomoses with each other as well as with branches from the infraorbitit. The veins are all tributary to the angular vein, which U-jjins at the inner canth< >nd descends along the side of the nose to the facial trunk, receiving in its course the dorsal, lateral, and alar branches. The angular vein communicates with the ophthalmic and the veins of the nasal fossa. The lymphatki are arranged in three sets (Kiittner). The first, beginning at the root of the nose, passes above the upper eye-lid and along the supraorbital ridge to the jiarotid nodes. The second group, formed by the superficial and deep lym- phatics at the nasal root, skirts the lower margin of the orbit and ends in the lower parotid nodes. The third and most important set includes from 6 to 10 trunks that follow the blood-vessels and end in the submaxillary nodes. The nerves supplying the outer nose include the motor branches of the facial to the muscles and the sensory twigs from the trifacial to the skin, distributee! by the infratrochlear and nasal branches of the ophthalmic and by the infraorbital of the superior maxillary. PRACTICAL CONSIDERATIONS T'.,. EXTERNAL NOSE. The Nose may be congenitally absent, or bifid, or imperfect, as from absence of the septum or of one nostril, or — very rarely — of both nostrils. As to its external aspect it may be of various types, e.g. : Grecian, when the dorsum is on a practi- cally continuous straight line with the forehead, with no marked naso-frontal groove ; aquiline, with the dorsum slightly arched ; rounded, with the arch much more pronounced; foetal — "pug" — with the bridge depressed and the nostrils directed somewhat forward. The foetal type is simulated in the new bom by the subjects of inherited syphilis in whom the bridge of the nose is often much depressed as a result either of (a) imperfect development following the severe specific coryza that affects the nasal mucosa and, through the close apposition of the latter to the periosteum of the fragile nasal bones, interferes with their nutrition ; or {b) by actual caries or necrosis of those bones or of the septum favored by the same conditions. In acquired syphilis the similar nasal deformity is practically always the result of the destruction of the septum, or, less frequently, of the nasal bones, by late (tertiary) lesions. As a consequence of faulty development in the anterior mid-portion of the frontal bone the membranes of the brain may protrude, forming a meningocele, which is more common at the naso-fiontal junction than elsewhere. Occasionally the defect permitting the protrusion exists in the cribriform plate of the ethmoid, and the meningocele occupies the nasal fossa, having under these circumstances been mistaken for a nasal polyp and removed, death resulting from subsequent septic meningitis The cosmetic importance of the nose is so great, the diseases producing deformity so frequent, and the susceptibility of the organ to injury so marked, that much ingenuity has been expended upon devices to restore it when lost, or to improve its appearance. In the Tagliacotian operation a cutaneous flap is taken from the arm »-hich is held close to the nose by a complicated dressing until the flap is firmly united in its new position, when its pedicle is detached from the arm. The Indian method is more particularly anatomical, since the flap taken from the fr)re- head is 50 fashioned that ii rviuivcs intact the blood froiti thr fr;;::lul branch of t'lc ophthalmic artery *rom the internal carotid, the ophthalmic receiving at the origin of the frontal an important anastomosis from the angular b- inch 1 if the facial arterv, which is given off from the external carotid artery. Fo -rtia! deformities flai)s may be taken from the sides ac<' ling t- the size and si >m .•( the deficiency. ■:^kk 1408 HUMAN ANATOMY. As upon other parts of the face, plastic operations are very successful owing to the free blood supplyT Acne rosacea is common on account of the ready response " vSarity of the nose to external irriuting influences, and to internal disturbances of the circulation, as from heart and lung disease chronic gastritis, and alcoholism. Furuncles and superficial infections are frequent because of the number of sebaceous and sweat g' -nds present. Lupus and-in the alar sulcus-rodent ulcers are com- mon because of the constant exposure of the nose to external irritation and to Lering of temperature, depressing its vital res stance. Frost-bite of the nose is also common, eslJecially about the tip. because of its exposed position and the lack of protection to the delicate vessels from overlying tissues. . The nerve supply to the nose is likewise very free, as is shown m a practical manner by the min which accompanies inflammatory conditions, espeaaUy those involving the lower cartilaginous portion where the skin and subcutoneous tissues are ver^ adherent Thrresulting exudate is therefore much confined, pressing upon the nerves ; thb accounts also for the frequency with which gangrene occurs under these circumstances. , . u j »t. Watering of the eyes from irritation of the skin or mucous membrane of the nose is due to the free nerve supply, and to the fact that the same nerve, the tri- eeminal. supplies the nose and the lachrymal apparatus ; as a porUon of the nasal chamber is supplied by a branch of the ophthalmic nerve, raising the eyes to the sun will often give the added irritation necessary to precipitate a sneeze when the nasa stimulus suggests one, but is not quite strong enough unaided. Cough and bronchial asthma have resulted from nasal affections due to the indirect relations between the fifth cranial nerve and the pneumogastric. As the olfactoiy portion of the nasal fossa is in the upper portion of the cavity, an earnest effort to recognize an odor or to enjoy one to the utmost, is accompanied by a deep inspiration through the nose with dilatation of the nostril. In paralysis of the facial nerve the involvement of the dilatores naris has been thought to explain the lessening of the olfactory sense sometimes seen in this condition. Paralysis of the levatores al£e nasi muscles has permitted the nostrils to close during inspiration, causing stridor and mouth-breathing. The loss of the sense of smell is a not uncommon result of severe blows, especially on the forehead, and may be due to (a) concussion of the olfactory bulbs ; (6) fracture of the cribriform plate of the ethmoid ; (f) injury to the olfactory roots where they cross the lesser wing of the sphenoid ; or (rf) lesion of the olfactory nerves where they traverse the cribnform foramina. Sneezing from irritation of the nose is probably due to the indirect relationship between the fifth pair and the vagus and may be so violent that serious injury may result, as in cases in which a subcoracoid luxation of the shoulder, a fracture of the ninth nb, and the rupture of all the coverings of a large femoral hernia were produced by this act (Treves). , . , , . i . » » The abundant sweat and sebaceous glands in the skin of the nose account for the frequency with which acne vulgaris attacks it. The alae, the only movable por- tions, take part in the movements of expression, as in contempt and scorn. Fractures of the nose are common because of its exposed position, and of the frequency of blows and other forms of violence applied to the face. Their chief importance depends upon the prominence of the nose as a feature of the face, any change in its shape attracting general attention. The h^cture occurs most com- monlv in the lower part, because of the greater weakness of the bones and their greater prominence at that level. In its upper part, the relative depression of the dorsum, the greater thickness of the bones, and their more firm support, make fracture less common. On the other hand, the higher fractures are more dangerous because of their possible relation with the cribriform plate and sinuses of the ethmoid bone. tJie frontal sinuses and the nasal duct. Involvement of the cribriform plate is m effect a compound fracture of the base ©f the skull, exposing the meninges to the danger of infection. Fractures of the nose are almost always compound, because of the intimate adhesion of the mucous membrane to the bone, with little intervening tissue, so that when the bone breaks the overiying adherent tissue la torn through This accounts for the practically uniform occurrence of epistaxis, on account of which it is often difficult to detect the presence of escaping cerebro-spinal fluid when the THE NASAL FOSS/E. 1409 cribriform plate is also fractured. On the other hand, the rich glandular supply of the mucous membrane, which makes the usual mucous secretion exceptionally free, may, in a post-traumatic coryza, result in a watery discharge of such quantity as to suggest the f'scape of the cerebro-spinal fluid. Emphysema within the orbit and under the skin may result from the communication of the nose with the ethmoidal or frontal siniises. In the effort to keep the nose clear of blood by blowing, the air is forced into the sulxrutaneous tissues. In fractures at the lower part, the deformity is frequently lateral, because of the greater exposure to side blows, and the tendency of the cartilaginous ahe and septum to avoid crushing. In the upper part depression is more likely, because of the tendency to escape any but forces from in front, »he greater force necessary to produce the fracture, and the presence of a bony septum underneath, which crushes rather than bends. When the deformity has been replaced there are no strong muscles to repro- duce it, so that litde or no effort is necessary to maintain the fragments in position. The deformity must be reduced early and the reduction maintained, because owing to the free blood supply, union is usually rapid, sometimes occurring in a week. One must bear in mind in reducing the deformity that the roof of each nasal fossa is not more than 2-3 mm. wide, and that, therefore, a narrow rigid instrument is necessary to press die fragments upward into their normal positions. THE NASAL FOSSi€. The cavity of the nose is divided by the median septum into two nasal fossae which extend from the anterior to the posterior nares, or choono!, through which they open into the naso-pharynx. They comn unicate more or less freely with the accessory air-spaces within the frontal, ethmoid, sphenoid and maxillary bones, into which, as a lining, the mucous membrane of the nasal fosss is directly continued. Seen in frontal section ( Fig. 1176), each fossa is triangular in its general outline, the apex being above at the narrow roof and the base below on the floor. The smooth median wall is approximately vertical and meets the floor at almost a right angle, while the sloping lateral wall is modelled by the projecting scrolls of the three turbinates, which overhang the corresponding meatuses. In sagittal sections (Fig. 1 174) the contour of the fossa resembles an irregular parallelogram from which the upper front corner has been cut off, so that in front the upper border slopes downward to correspond with the profile of the outer nose. 1 he greatest length of the fossa, measure^ along the floor, is from 7-7.5 cm. (23^-3 in. ) and its greatest height from 4-4.5 cm. The width is least at the roof, where it is less than 3 mm., and greatest in the inferior meatus a short distance above the floor, where it expands to from 15-18 mm. The Vestibule. — The anterior part of the fossa, immediately above the open- ing of the nostril and embraced by the outer and inner plates of the lower lateral cartilage and adjoining portion of the septum, is somewhat expanded and constitutes the vestibule (vestibulum nasi), a pocket-like recess prolonged towards the tip being the ventricle (recessus apicis). These spaces are lined by delicate skin, directly con- tinuous with the external integument and tighdy adherent to the underlying cartilage, and, in the lower half of the vestibule, containing numerous sebaceous glands and hairs. In the vicinity of the nostril the hairs, known as vibrissa, are coarse and long and curved downward to afford protection to the nasal entrance. Over the upper part of the vestibule, the skin is smooth and closely attached to the lower lateral cartilage, the upper margin of the outer plate projecting as a slightly arching ridge, the limen vestibuli, which forms the superior and lateral boundary of the vesti- bule and marks the line of transition of the skm into the mucous membrane that lines the remaining parts of the nasal fossa. Above and beyond the vestibule, the nasal fossa rapidly expands into a triangular space, the atrium nasi, that lies in advance of the entrance into the middle na«al meatus. Above and in front the atrium is bounded by a low and variable ridge, the (if^gcr nasi, that represents a rudimentary naso-turbinate, which in many mammals attains a large size. The space lying in front of the agger, extending 89 I4IO HUMAN ANATOMY. from the limen to the cribriform plate of the ethmoid and roofed in by the forepart of the arched upper boundary of the fossa, is long and narrow in consequence of the approximation of the median and lateral walls. It leads from the nasal aperture to the summit of the nasal fossa and to it Merkel applied the name carina nasi. The Nasal Septum. — The median wall consists of the partition formed chiefly by the perpendicular plate of the ethmoid, the vomer and the septal cartilage, cov- ered on both sides by mucous membrane. The extreme lower and anterior part of the septum, consisting of the alar cartilage and the integument, is flexible, and there- fore called the membranous portion, or septum mobile ; the terms bony and cartilagi- nous portions are applied to the remaining parts of the septum supported by bone and cartilage respectively. While during early childhood its position is median, in the great majority of adults the septum presents more or less asymmetry and lateral deflection, most often Fig. 1 174. Frontal sinus ^Superior tutWnate Sphenoethmoidal rvccM Opening of sphenoidal sinus Superior meatus Fossa nf Rosenmiiller OpeninK o! Eustachian tube to the right. Thiji deviation may affect the septal cartilage alone, may be limited to the bones (in 53 per cent, according to Zuckerkandl), or may be shared by both. The most common seat of the deflection is the junction of the ethmoid and vomer, in the vicinity of the spheno-ethmoidal process, or along the union of the vomer and the septal cartilage. The asymmetry may involve the entire septum, which then is oblique ; or it may take the form of a simple bulging towards one side, a double or sigmoid projection ; or be an angular deflection resembling a fc'd, crest or spur that projects into one, sometimes both, of the fossae (Heymann). Although the mucous membrane covering the nasal septum is generally smooth and of fairly constant thickness, its surface is marked by inequalities caused chiefly by variations in the amount and development of the glandular and vascular tissue, (ine such accumulation, the tuberndum septi, is relatively constant and on the septum about opposite the anterior end of the middle turbinate. During early life a series of from four to six or more oblique ridges, plicte septi, often model the lower and posterior part of the septum, extending from below upward and forward. Slightly above the anterior nasal spine, the septal mucosa presents the minute openings lead- ing into the rudimentary oi^an of Jacobson. Behind, the margin of the bony septum is covered by mucous membrane of unusual thickness which, therefore, forms the immediate free edge of the partition separating the posterior nares. The Lateral Wall.— The lateral wall of the na.snl fossa: is characteris>..;a!!y modelled by the projecting scrolls (conchae nasi) of the three turbinates. The latter partly subdivide each fossa into three lateral recesses, the superior, middle, and THE NASAL FOSSAE. 1411 inferior meatuses. These are overhung by the correspo Jing bony concha, the superior meatus being roofed in by the upper turbinate and the inferior lying between the lower turbinate and the floor of the fossa. That part of the nasal fossa between the conchae and the septum, into which the recesses open medially, is sometimes called the meatus nasi communis. The details of the nasal fossa as seen within the macerated skull have been described in connection with the skeleton (.page 223). In the recent condition, when the soft parts are in place, while their general contour is preserved, the compartments of the fossae are materially reduced in size by the thickness of the mucous membrane and the erectile tissue that cover the bony framework. The Superior Meatus. — Corresponding to the small size of the upper turbinate, the superior meatus (meatus nasi snperior), or ethmoidal fissure, is narrow and groove-like and littie more than half the length of th.. middle one. It is directed downward and backward and is floored by the convex upper surface of the middle concha. When the upper turbinate is r^laced by two scrolls (conchae superior et suprema) — a condition that Zuckerkandl regards as very frequent, if indeed, not the more usual — the meatus is accordingly doubled. Into the upper and front part of the superior meatus the posterior ethmoidal air-cells open by one or more orifices Fig. 1 1 75, Frontal liniu Probe in infundibulum Middle turbiraie, partly. removed Hiatua aemilanarb' Ethmoidal bulla^ -''''-' Jl>eiiiii(pi A({»erna»i. of maxiHarv %\nn% into infundibu.um- Ventrici LI men nasi' VeuibulC' Probe in nMo-lachrymol duct Opcnin( of middle ethmoidal cells Superior turbinate, partly removed Opening into sphenoethmoidal rcceia ^ -i^^,^..^SphenoidaI sinus Openins of posterior rthmolrl cells into superior meatus Naso.phar>-nx Opening of Eustach- ian lube Inferior meatua Inferior turbinate, partly renovcd Middle meatua Lateral wall of naaal ; portlon a of tnrMnale bones have been removed to eapose openings into air spaces. of variable size. Above and behind the upper turbinate and in front of the body of the sphenoid bone lies a diverticulum, the ^heno-ethmoidal recess, into the posterior part of which opens the sphenoidal sinus. The Middle Meatus. — The recess beneath the middle turbinate (meatus nasi medius) is spacious and arched to conform with the contour of the middle and inferior conchae which constitute its roof and floor respectively. On elevating, or still better removing close to its attachment, the middle turbinate bone, a deep crescentic groove, the infundibulum, is seen on the outer wall of the fossa overhung by the anterior half of the concha. The crescentic cleft leading from the middle meatus into the infundibulum is the hiatus semilunaris,* which t-xtends from above downward and backward, with its convexity directed forward. Its anterior boundary is a sharp crescentic ridge due to the uncinate process of the ethmoid covered with thin mucous membrane, while behind it is limited by a conspicuous elevation produced by the corresponding underlying bony projection of the ethmoidal bulla. ' Some confusion exist?; in tlie use of this term, siiicc It Is ofttm applied to the tnitire grno^x and not merely to the cleft which leads from the meatus into the btoovp. The name is here employed a-H indicating the lunate cleft and not the Rroove (which is the infimdihiilnm ), as oriKinally used by Zuckerkandl, who introduced it. See Antomie der Nasenhohle, Wien, i88», page 39. ^;,!-*X:k 141 2 HUMAN ANATOMY. When the infundibnlum does not end blindly above, which it often does (page 194), its upper extremity, usually somewhat expanded, receives the openmg of the frontal sinus, ostium frontaU. The sinus is, however, not dependent upon the infundibulum for its communication with the middle meatus, smce, as pomted out by Zuckerkandl, between the front of the atUchment of the middle turbinate bone and the uncinate process of the ethmoid there exists a passage which leads to the ostium frontale. Into the upper part of the infundibulum usually open some of the anterior ethmoidal air-cells ; lower in the groove lies the oval or slit-like ostium maxillare the chief communication of the antrum of Highmore. When the latter is provided with an additional orifice, as it is in 10 per cent. (Kallius), the smaller accessory communication opens into the inhindibulum a few millimeters behmd the principal aperture. Above the hiatus semilunaris, either on or above the bulla •* usually seen tlie slit-like opening through which the middle ethmoidal cells com>nuiicate with the meatus. The Inferior Meatus.— T\(\% passage (meatus nasi inferior), the largest of the three, measures from 4.5-5.5 cm. in length, its anterior end lying from 2.5-3-5 "«. behind the tip of the nose. At first relatively contracted, it abrupdy expands, not Fir. ii7< Scalp Cerebral hemiipherc. Superior longitudinal ainot Bone 'alx cerebri Ethmoidal cella Lower end of probe lying in liiatus semilunaris Middle turbinate. Probe passim from antrnni into. intuiidibulum Inferior turbinate Nasal septum Right eyeball Hiatus semilunaris Middle meatus Maxillary sinna Inferior meatut Floor of na!alatina. Although the two tubes of mucous membrane may join to form a single incisive canal, they usually retain their independence (Leboucq, Merkel). They are often closed and impervious ; sometimes, however, even in the adult communication is retained betweer the nasal and oral cavities. The posterior nares or choante, the apertures through which the nasal fossie communicate with the naso-pharynx, one on either side of the septum, resemble in form somewhat a Gothic arch (Fig. 1354). They are relatively much lower in the new- bom child than in the adult, in which they measure about 3 cm. in height and '1.5 cm. in breadth (Zuckerkandl), although individual variation is considerable. Each ofiening is bounded below by the horizontal plate of the palate bone ; laterally by the inner surface of the internal pterygoid plate of the sphenoid ; above by the vaginal process of the sphenoid and the ala of the vomer ; and mesially by the vertical posterior borders of the vomer. Over this bony arch the nasal mucous membrane is continuous with that lining the pharynx. Laterally the posterior limit of the nasal fossa in the recent condition is indicated by a furrow (sulcus nasalis posterior) that extends from the under surface of the sphenoid downward to about the junction of the hard and soft palates. Behind this furrow, about on a level with the lower border of the inferior turbinate, lies the opening of the Eustachian tube (Fig. 1 174). Since the turbinates end approximately i2 mm. in advance of the choanae, the outlines of these optenings are unbroken by the scrolls that model the lateral wall of the nasal fossae, all three conchse, however, being visible through the posterior nares. THE NASAL MUCOUS MEMBRANE. Beyond the limen that marks the limit of the integument clothing the vestibule (page 1409), the nasal fossa is lined by mucous membrane continuous with that of the naso-pharynx through the choanje. Since in addition to lining the tract over which the respired air passes the nasal mucous membrane contains the cells receiving the impressions giving rise to the sense of smell, it is appropriately divided into a respir- atory and an olfactory part. The Olfactory Region. — The highly specialized regio olfactoria is quite limited in extent and embraces an area situated over the middle of the upper tur- binate and the corresponding Jjart of the septum. According to Brunn, ' whosr conclusions are here presented, the olfactory area of each fossa includes only about 350 sq. mm. , the septum contributing something more than one-half of the entire surface. Accordingly the specialized field is by no means coextensive with the upper turbinate bone, as it reaches neither its lower nor posterior border (Fig. 1 177). The anterior margin of the area, which lies about I cm. behind the front wall of the nasal fossa, is irregular in outline owing to the invasion of the specialized region by the adjacent ' Archiv f. mikros. Anat., Bd. 39, 1893. HH HUMAN ANATOMY. Fig. 1177. respiratory mucous membrane, tongues or even islands of the latter projecting into or being surrounded by the former. Upon the evidence derived from careful dissection of the olfactory mucous membrane, however, it is difficult to avoid the conclusion that Brunn's areas are too limited, as nerve-fila- ments clearly attached to the olfactory bulb are usually traceable onto the upper part of the middle turbinate bone. In fresh preparations the olfactory area usually, but not always, can be approximately mapped out by the yellowish hue, lighter or darker, that distinguishes it from the respiratory region in which the mucous membrane exhibits a rosy tint. The epithelium contains two chief con- stituents — the supporting and the olfactory cells. The supporting cells are tall cylindrical elements, about .06 mm. in height, that extend the entire thickness of the epithelium. Their outer and broader ends are of uniform width and contain the oval nuclei which, lying approximately at the same line and staining readily, form a deeply colored and conspicuous nuclear stra- tum at some distance beneath the free margin. Between the latter and the row of nuclei, the epithelium presents a clear zone devoid of nuclei. The inner part of the supporting cells is thinner and irregular in contour and often' terminates by splitting into two or more basal processes that rest upon the tunica propria. Between these ends lie smaller pyramidal elements, the basal cells, that ... Hptum (s) ha« been partiany separated and turned upward ; dark field shows olfactory area on lateral and meswl walls of fossa, as mapped out by Hrumn.. Right nasal fossa, any Fig. I 178. Outer zone Nuclear layer of supporting cells Olfactory cell* Blood-vessel - Glands, Bundle of olfactory nerves « .;ii?STii'5^S;;jsi^^M<'^ ^^mmm A^M.L ^% Section of olfactory mucous membrane ; epithelium displays outer nuclei-free and nuclear layers formed by supporting cells and broad stratum containing nuclei of olfactory cells. ■ 300. probably represent younger and supplementary forms of the sustentacular cells. The granular protoplasm of the basal processes often contains pigment particles. The olfactory cells, the perceptive elements receiving the smell-stimuli, con- sist of a fusiform body, lodging a spherical nucleus enclosed by a thin envelope of cytoplasm, and two attenuattnl processes, a peripheral and a central. The olfactory cells are in fact sensory neurones that have retained their primitive position within the surface epithelium, as in many invertebrates, instead of receding, as is usual ir- THE NASAL MUCOUS MEMBRANE. 1415 the higher animals, to situations more remote from the exterior. The slender peripheral process of the olfactory cell, which corresponds to the dendrite of the neurone, is of uniform thickness and ends at the surface in a small hemispherical knob that projects slightly beyond the general level of the epithelium and bears from 6-8 minute stiff cilia, the olfactory hairs. The length of the peripheral pr.icesses. being dependent upon the position of the nuclei, vanes, since the latter occupy dif!e-ent levels within the epithelium in order to accommodate their greater numlxT— about 60 per cent, in excess of those of the supporting cells (Brunn ). The central Fig. ii8a Fig. 1179. Ulfactoo' cell Suppoitlnc cell Nerve-fibre Section of human olfactory mucoui membrane, silver pre|iaration ; two olfactory cells are seen, one of which sends nerve-libre towards brain. X jjs- (Btunn.) Isolated elements of epithelium of olfactory mucous membrane ; 0, olIactor>- cells ; *, sup- porting cells. X looo. (Ariuu).) processes of the olfactory cells, much more delicate than the peripheral, are directly continueti, as the axis-cylinders, into the subjacent nonmedullated nerve-fibres within the tunica propria, from which they pass through the cribriform plate to enter the brain and end in the arborizations within the olfactory glomeruli of the bulbus olfactorius (page 1152). The tunica propria is differentiated into a superficial and a deep layer by the adenoid character of the stratum immediately beneath the epithelium. The superficial layer, from .015-. 020 mm. thick, consists of closely packed irregularly round cells, resembling lymphocytes, and meagre bundles of delicate connective tissue. The deep layer, on the other hand, contains robust bundles of fibro-elastic tissue and relatively few cells. A distinct membrana propria is wanting within the olfactory region. The glands of Bowman ( glandulae olfactoriae) are characteristic of the olfactory region and probably elaborate a specific secretion (Brunn). They open onto the free surface by very narrow ducts that lead into saccular fusiform dilatations, into which the tubular alveoli open. The ducts possess an independent lining of flattened cells that extend as far as the surface and lie between the surrounding epithelial ele- ments. The dilatations are clothed with flattened or low cuboidal cells, which are replaced by those of irregular columnar or pyramidal form . "n the tubular alveolar. From th-j character of their secretion the glands of Bov are probably to be reckoned as serous and not mucous (Brunn, Dogiel). The Respiratory Region. — The mucous membrane lining of the respiratory region differs greatly in thicknc-ss in various parts of the nasal fossa. In situ.-itinns where the contained cavernous tissue is well represented, as over the inferior turbinate, : may reach a thickness of several millimeters, while when such tissue is wanting, as on the lateral wall, it is reduced to less than a millimeter. I4I6 HUMAN ANANOMY, The epithelium is stratified ciliated columnar in type, from .050-. 070 mm. thick, and includes the tall surface cells, bearing the cilia, betweer* the inner ends of which lie the irre^larly columnar basal cells. Numerous elements exhibit various stages of conversion into mucous-containing goblet cells. The current produced by the cilia is toward the posterior nares. Beneath the epithelium stretches the membrana propria or basement membrane, that varies greatly in thickness ; although in certain localities feebly developed, it is usually well marked and measures from .010-. 020 mm. in thickness (Brunn). Fig. 1181. Eptthelium GUuidi Section of respiratory mucous membrane covering nasal septum, x 75. Under pathological conditions its thickness may increase fourfold or more. In many places the membrana propria is pierced by minute vertical channels, the basal canals, in which connective-tissue cells and leucocyctes are found, but never blood-capillaries (Schiefierdecker). The tunica propria consist:^ of interlacing bundles of fibro-elastic tissue which are most compactly disposed towards the subjacent periosteum. The looser super- ficial stratum is rich in cells and here and there contains aggregations of lymphocytes that may be regarded as masses of adenoid tissue (Zuckerkandl). In certain parts of the nasal fossa the stroma of the mucous membrane contains vascular areas com- posed of numerous intercommunicating blood-spaces that confer the character of a true cavernous tissue. These specialized areas, the corpora cavernosa, as they are called, are especially well developed over the inferior and the lower margin and posterior extremity of the middle conchae, and less so over the posterior end of the upper turbinate and the tuberculum septi. When typical, they occupy practically the entire thickness of the mucous membrane from periosteum to epithelium, the interlacunar trabecuhf containing the glands and blood-vessels destined for the sub- epithelial stroma. The blood-sinuses, the general disposition of which is vertical to the bone (Zuckerkandl), include a superficial reticular zone of smaller spaces and a deejjer one of larger lacimoe. The engorgement and emptying of the cavernous tis.sue is controlled by nervous reflexes and probably has warming of the inspired air as its chief purpose (Kallius). The glands of the respiratory region are very numerous, although varying in size, tubo-alveolar in form and, for the most part, mixed mucous in type. The chief ducts open on the free surface by minute orifices barely distinguishable with the unaided eye. Their deeper ends branch irregularly into tubes that bear the ovoid terminal alveoli. The latter are lined with mucous-secreting cells, between which lie Fig. 1 183. PRACTICAL CONSIDERATIONS: THE NASAL CAVITIES. 1417 the crescentic groups of serous cells that sump the Rlaiuls is mixed (Stohr). Exceptionally exclusively serous glands are also encountered (Ka'.ius). JacolMon'8 Organ.— Mention has been made of the r. .mentary »t«;««^<"''e (orwmod vomeronasale) found in man. almost constantly in the new-b<)rn child and frequentiy in the adult, as a represenutive of the organ of Jacobson that is present, in varying degrees of perfection, in all amniotic vertebrates ( Peter). 1 n many animals possessing in high degree the sense of smell (macros- matic), the oi^n is well developed and hinctions, serving possibly as an accessory and outlying surface by which the first olfactory impressions are received (Seydel). In man the organ is represented by a laterally compressed tubular diverticulum, from 1.5-6 mm. in length, that passes backward and slighdy upward to end blindly be- neath the mucous membrane on each side of the septum. The entrance to the tube is a minute aperture situated near the lower border of the septum, above the anterior nasal spine and the rudimentary vomerine cartilage. The median wall of the diverticulum is clothed with epithe- lium composed of tall columnar cells resembling those of the olfactory region, but the characteristic olfac- tory cells are wanting. The epithe- lium covering of the lateral wall corresponds to that of the respiratory region. In macrosmatic animals branches oi the olfactory nerve are traceable to Jacobson' s organ in which are found olfactory cells. PRACTICAL CONSIDERATIONS : THE NASAL CAVITIES. The nasal cavities have certain important clinical relationships which may be classified as (i) physiological— (a) respiratory, phonatory and olfactory ; (*) sexual ; (2) topographical— (a) the nasal chamber and the vestibule ; (*) the premaxillary, maxillary, and palatal portions ; (r) the septum, and the turbinate bones. I. (a) The air passing out from the pharynx, being confined to the plane of the posterior nares, is not carried up to the olfactory region, so that the odors on the expired breath are not appreciated. When the communication between the respira- tory and olfactory portions is cut off, as by swelling of the mucous membrane at the region of union of these portions, loss of smell supervenes. Discharge which may accumulate about the middle turbinate bone or in the upper portion of the vestibule cannot be removed by the act of blowing the nose, for the reason above assigned that the air of expiration cannot pass within the olfactory portion. The act of blowing the nose, or the process of washing out the nose by a current thrown in from the naso-pharynx, will wash out the inferior meatus with ease, provided the discharge is not inspissated, and the parts of the floor of the nose are normal (Allen). An abnormal width or patency of the respiratory portion of the fossa — especially of the inferior meatus — due to imperfect development of the inferior turbinates, has been thought (Lack), by diminishing the vis a tersro in blowing the nose and thus favoring the retention and decomposition of the nasal mucus, to contribute to the occurrence of atrophic rhinitis (oz«na). The value of the nose as an accessory organ of phonarion consists in its action as a resonating cavity which adds quality, color and individuality to the voice. This hincrion of the nose becomes strikingly Portion of Ironul section through nual fontr of liittcn, (howint orgmn of Jacobson. X ao. I4i8 HUMAN ANATOMY. apparent when, as durinjj an acute coryza, the fossae are more or less completely obstructed and the voice becomes flat and entirely without resonance- (6) The relations between the nasal chambers and the sexual apparatus are of practical importance and have as an anatomical basis the analO|{y between the mucosa covering much of the turbinates and part of the septum, and the erectile tissue of the penis, and the sympathy between the erectile portions of the generative tract and erectile structures — e. g. , the nipple — in other parts of the body. 2. (a) The distinction between the nasal chamber and the vestibule is, in the main, based upon the difference in their lining membrane, that of the vestibule being simply a continuation inward of the external integument to the line (limeti nasi) at which the nasal fossa proper begins. The vestibular cavity is provided with rigid hairs (to aid in arresting foreign particles carried in with the air current), and sebaceous glands, and is especially susceptible to eczematous or furuncular affections. Diseases of the vestibule may, therefore, be dealt with as though they were affections of the skin ; while diseases of the mucosa of the nasal chambers are to be treated on the same principles as those of the mucous membranes generally, with special refer- ence to its erectile character and to its close relation to the underlying periosteum and bone. (*) Thesutural lines of the premaxilla, of the maxilla, and of the palatal bones aid in determining the boundaries of the subdivisions of the nasal chamber, which are indicated to some degree by the production of the planes of the su*- res of the roof of the mouth, vertically upward through the nasal chambers. (f) The morphological significance of the septum, placed as it is ! .e median line of the face of the embryo, with the turbinate bones lodged to its ■ ijht and left sides, remains the same in the skull of the adult, notwithstanding the .. Jt that, with cultivated races at least, the septum is usually deflected through the greater part of its course from the median line. This deflection has been said to be due to the persistent growth of the septal bones in a vertical plane after their edges have united — the apex of the deflection being often found at the junction of the ethmoid and vomer ; any preponderance in strength of one of these bones w ill cause bending of the weaker — usually the perpendicular plate of the ethmoid. The usual direction of the deflection is to the left, and this has been thought to be due to the habit of using the right hand in blowing the nose. Asymmetry of the nasal chambers is a result of the deflection. One of these chambers, commonly the left, is much smaller than its fellow of the opp te side, and may be occluded, when the right chamber will be larger than normal and possess both osseous and erectile structures which have undergone physiological hypertrophy. Care should be taken to distinguish between such hypertrophy and the effects of diseased action (Allen). The anterior nares are directed downward and are on a lower plane than the floor of the nose. To examine the interior of the nose the movable nostril must therefore be elevated and the head thrown backward. The speculum shaped for the purpose should not be passed beyond the dilatable cartilaginous portion. With good light one mav see the anterior part of the middle turbinate bone, a larger portion of the inferior turbinate, the beginning of the middle meatus, and get a freer view of the inferior meatus, the septum and the floor of the nose. The lower orifice of the nasal duct cannot be seen, although it is only about an inch from the orifice of the nostril, and three-fourths of an inch above the floor of the nose. This is due to the fact that it is concealed behind the attached and depressed anterior end of the inferior turbinate. To expose better the structures in the external wall of the narrow and rigid nasal fossa, various procedures have been adopted. Rouge made an opening into the anterior nares from the mouth, by incising in the angle between the upper lip and the gum. By separating the alar cartilages from the bones and dividing the cartilag- inous septum the movable anterior portion of the nose can be turned upward, giving a full exposure of the nasal fossa;, without leaving an unsightly scar. To permit a freer exploration with the finger, Kocher divided the septum as far back as possible with scissors. He also divided the roof of the nose near the septum, turning the divided parts aside. An osteoplastic flap may be made by extending this incision upward, dividing the bone in this line and making a second incision around PRACTICAL CONSIDERATIONS: THE NASAL CAVITIES. 1419 the ake and along the side of the nose, again dividing the bone. The Hup thus formed can be turned upward, after breaking the bridge of bone between the up|)er ends of the two incisions, exposing the na^ fossa. The finger can be passed backward through the nostril far enough to meet the finger of the other hand passed tu the posterior nares through the mouth. The posterior nares can be examined by the rhinoscopic mirror or by the finger introduced through the mouth. Posterior rhinoscopy, like laryngoscopy, is carried out with difficulty, because the region of the naso-pharynx ia sensitive and is intol- erant of intrusion. In the act of swallowing, the epiglottis protects the larynx by closing the laryngeal ' .pening, and the soft palate rises against the posterior wall of the pharynx, preventing regurgitation into the nose. When the rhinoscopic mirror is used the same thing occurs, so that the view of the larynx and naso-pharynx is shut of!. Considerable difficulty is sometimes ex|>erienced in training the patient to overcome this tendency. The employment of the nasal douche is based upon the same mechanism. When the stream of fluid passed through one nostril reaches the posterior part of the nose, its progress toward the mouth is obstructed by the elevated soft palate, and it therefore passes around the posterior edge of the septum and back through the opposite nasal fossa. With the rhinoscopic mirror in good position, and the soft palate quiet, one may see the posterior nares divided by the septum, the turbinated bones, and the meati (especially the middle turbinate and the middle meatus), the roof of the naso- pharynx and the orifices of the Eustachian tubes. The finger introduced through the mouth can feel the same structures, and can recognize naso-pharyngeal adenoids, tumors, or abscesses. The mucous membrane over the turbinates, owing to the presence of a rich venous plexus, is one of the most vascular in the body, and resembles erectile tissue (page 1968). This and the general vascularity of the nose partly explain the great frequency of epistaxis. The excessive supply of blood to the mucosa may be {a) for the purpose of enabling it to raise the temperature and add to the moisture of the inspired air : (i) to favor the activity of the numerous mi'^ius glands, the free secre- tion of which together with the acdon of the cilia of the epithelial cells is required to remove the dust and the micro-organisms that are filtered from the air during inspi- ration by the \abrissae and the cilia themselves ; (f ) to endow it with sufficient vitality to resist the pathogenic action of such micro-organisms. In spite of this defensive quality, the constant exposure to atmospheric irritants often leads to congestions and coryzas, which if long continued and frequently repeated result in hypertrophy of the mucous membrane. This may require removal by cauterization or excision to relieve the consecinent obstrucdon. The mucous membrane is somewhat less closely attached to the septum than to the neighboring parts, and hence hfematomata of the septal submuco? I are not infrequent after an injury to the nose. Such hsmatomata are almost invariably infected and proceed to suppuration forming septal abscesses, the constitutional symptoms (toxaemia) of which may give rise to anxiety if their local cause is overlooked. Epistaxis is common not only because of (a) this vascularity of the mucosa, but also by reason of (6) the frequency of trauma to the nose ; the relation of its veins (f ) to the general venous current so that they may be congested in cardiac or in pul- monary disease, or in straining, or in paroxysms of coughing, as in whooping cough ; and (d) to the intracranial sinuses, so that nose-bleed may be a symptom of cerebral congestion or tumor ; (e) the bleeding may be vicarious, as in cases of suppressed menstruation (an illustration of the sexual relations of the nasal apparatus); (/) it not uncommonly follows ulceration — simple, tuberculous or syphilitic — and in obstinate cases such ulcers should always be sought for. The source of hemorrhage from the nose is most frequendy in the anterior part, particularly on the septum, and is then onlinarily controlled with ease. Usu.-illy the ptient should be kept upright, with the head back, (not in the usual iwsitiun icu:i ing over a basin, increasing the tension of the vessels of the neck and head) and should be made to take deep breaths with the arms raised, thus fr'ly expanding the thorax and depleting the cervical veins and, indirectly, the faci:i'. ind ophthalmic into which the veins of the nose empty. If ordinary means fail, and this is more likely I420 H MAX ANATOMY. if the bleeding point is ,',nor, iht- posterior iiares may be [dug^ed. For this purpose a loiig silk lig n is ju.vwi through the nose to the phar>nx and out through the mouth, b> i.raiis of . lltllo.q's r mnula i»r a soft cathet T > the middle of the ligature i it'achwi a :.!uk o< gau. slightly larger than the posterior nares, which is Uien drawi; h. tiie \i.ii rior end oi the ligature into the nasal lossii, which it should tightly fill. Postnasal adrnoids orij;. latein tii',- loimidly excessive lymphoid tissue — pharj n- geal tonsil — of the postnasal sj/aci-, nl whi' !i tissui they are a simple hypertropliy. The growth forms a mass m the vault oi tlie naso-jilwrynx and often extends down- ward and forward, filling tip RosenmuUer's toss;r and involving the orifices of the Eustachian tubes. The tonsils are a)mmonly ilx. enlarijed. The symptoms proiluced are : (a) obstn ted nasai respiration, more marked during sleep, when the mouth is closed by tlic approximation ui the tongue to the palate ; (^) asa result of this, broken rest and " night terrors" . and i r) as a further consequence (and also from deficient oxygenation), deterioration of the genera 1 health, delayed or arrested growth, and anemia ; (d) intermittent partial deafni ^ and recurrent attacks of catarrhal or suppurati\ e otitis media ; * >' ) pigeon-breast from inecjuality of intra- and extra-thoracic atmosphtric pressure. The early removal of adenoids that product iiny or all ^ f these symptoms is usually indicated, and is facilitated l/V their friabilit\ and by the toughness and to such an e.xtent as to make it bend and ob^" ict a greater or lesser degree. T' e remo\al of tl. in practiced in these ca.ses (Taylor . or the bulla itself m;i the cutting forceps or curette. Over-development ■ times be so great as to occasion ol)struction of the upp nasal fossa. The floor of the nose is the widi-st part, and si is gradu ,il and downward in the upright position, so that collecting •jcu'* tend-, u Kward and drop ii'lii the throat. Rliinuiillis. wlneii are incrn»i..rtjOii- •"•: i loreign bodv. are most frequently found in i o inferior meatus, whic st. The jKisterior nares are below the level of the respiratory portion discharge above the middle turbinate cannot be blo« from the nose. r portion of the inferior turbinate slopes downward an' forward, and its am .loi .d is attached itative inflammation which diffit ulties arising from ' will differentia it :ro"i tme The middle turbin-^te o> (j.-ess agai St the ue oppoHte nasal ii He turbiiHi is somei be oHite i.ti- hy mear. he bul'- thH. -idaJis may portif the. Ti-rspondini. THE ACCESSORY MR-SPACKS. 1421 so neai thi" nosi- that H^' roomiest |h»rtion of i ,. inferior nw-atiw is the • nirance ih air into the lower [»art oi the nasal U>-iSii is the fkior >f postern 1! Thercfi '< . (,hstriutntal heaiLirhe, 1 v involving the l)y implicating antrum ; ( /) gr.ve iitraorhiul ither the ethmoi- cells or the sphei >idal r-inur-es ng the perineur.i, or perivascular s leaths, or '-v through I If cribriform foramina to the fl(H>r i.i the anter^ -r tension to the retnipharyngeal lymph node [wge <»5= 1, 11= • isal lymphatics empty, may result in a retrophar^ igt I ao- sces- . I'T (A I infe-tion (pyogenic or tuberculous) of 'he submaxillary preaur iar. r de«t) cervical nxles may follow nose diseases. Tht /raver of tht ■ mf)licaUoi! bv tun her e tension t frontai sinu^ ■» : (f) or intracranial disea^ basal ni«Mim>f.tis by way of he ' !iph.i» cranial uwsa , (, ,t whi«-h rrrtain erf lae 'he resf>iratory e ache , !■ way 1 xti nding a. M- oi course, .^MKiatui with the severer infective l.tms .1 p ivths — comnsonly sarcomatous — may begin in 'e nasal cha in .my of the iirccttons above mentioned. THE ACCESSORY AlR-SPAf :S. The I isal toss.1 co muiicate with a number of rei ■ Hrt within the -iurroun^ bones, which are filled with membrane dir>i naM>-|>har>'nv TefnfK>ral muscle MasftettT nnisi le Internal pteryguiil mUM Ic KuMarhian tulw ConHvle iif man.lible Internal carotid arter> Portion of tninsver« sect, .n of head passinc ^;s7;«»tb nastst - of the section has been drawn -.u<^ iw aasal \am LKterna, ^cT>jioid muscle jgaiK ,A jtoHMnmuUer -jar jaat brio* umldle turtnnates : tht- inferior surface ' mud either sfiAces if^ view«l from below. ethmoidal air-cells, all paitt' ai»<- «ithifl rhe orrespoortmc ^>ones. -Sinct- llu- mucous membrane is thin and sntirr ?wlv adh»-««* ■ the bof=«- tlw form of the cavi- ties as obser\'ed in tht- rcc-nt rimditton cor»*5«rtrfids rlosely to that seen in tlu- macerated skull. The r.tzea«d <-xt«)t of tbespuw-'es var\' not on; t different j>eriods ■ 423 HUMAN ANATOMY. of life, but also often on the two sides of the same individual ; their communications with the nasal fossx, however, are fairly constant. The Maxillary Sinus.— This space, (sinus maxillaris), or the atUrum of Highmore, the largest of the pneumatic cavities, lies to the outer side of the nasal fossa and resembles in its general form a three-sided pyramid (FIr. 1184). It occupies the greater part of the superior maxillary bone, so that its walls, with the exception of the postero-inferior one, are very thin and often in jjlaces of paper)- delicacy (Fig. 256). The median wall, or base, is directed toward the iiasal fossa, from which it is separated by a thin osseous partition in the formation of which the vertical plate of the palate bone, the uncinate process of the ethmoid, the maxillary process of the inferior turbinate and a small part of the lachrymal bone assist. The apex lies at the zygomatic process of the maxilla. The upper or orbital wall is thin and often Fig. 1184. Vestibule Anterior ethmoidal cclli Left imxillan' ■iniu Inferior meatus Place wliere f ronul sinus was attaclied Anterior ethmoidal cells Maitillary sinus Posterior ethmoidal cells Left sphenoidal cell Right sphenoidal cell Naso-pharynx . Cast of nasal fossae and accessory airspaces, viewed from above ; casU of froaul sinuses have been removed ; natural aiie. (KalKiu.) modelled by the ridge containing the infraorbital canal. The anterior wall presents towards the face and is varyingly impressed by the canine fossa. The postero- inferior wall is normally the thickest, but is sometimes reduced by extension of the sinus into the adjacent alveolar border. The sinuses are often so modified by local enlargements that the typical pyramidal form is lost and their dimensions materially influenced. As an indication of the size of the average sinus, a sagittal diameter of 35 mm. (ij< in.), and a vertical and frontal one of 27 mm. (about i in.) each '( kallius), may be uken as approximate measurements. Not infrequently, however, considerable asymmetry exists even to the extent of one antrum being almost twice as large as the other. The usual cajiacity of the antrum is between 12-18 cc. (i}i-4H fl. dr. ) with an averse of approximately 15 cc, or 4 fl. dr. (Braune and Clasen). The antrum communicates indirectly with the middle meatus by means of an aperture (ostium maxillare) that pierces the upper and anterior part of the base to open into the infundibulum. and thence by way ol the hiatus semilunaris, into the THE ACCESSORY AIR-SPACES. >t23 meatus. The ostium, which is usually in the lateral wall of the infundibulum, about one centimeter from the upper end of the hiatus, is an oval or elliptical cleft of variable size, with extremes (A length from 3-19 mm. (Zuckerlcandl), and from 2-5 mm. in width. An additional communication (ostinm accessorium), present in about 10 per cent., likewise opens into the infundibulum, lying behind the chief aperture. It is ordinarily small, its diameter being only a few millimeters. The mucous membrane lining the maxillary sinus is directly continuous with that covering the lateral wall of the nasal fossa. With the exception of being thinner, it corresponds in structure with the mucous membrane of the respiratory region, being invested with ciliated columnar epithelium and possessing numerous, although small and scattered, tubo-alveolar glands. VarUtiona.— The investigations of Zackerkandl (Kallius) have shown that enlarj^ment of the maxillary ;'iiis may be produced by: (i) hollowing out of the alveolar process (alveolar recess) ; (2) excavation of the floor of the nasal fossa by extension of the alveolar recess between the plates of the hard palate (palatal recess); (3) encroachment of the sinus into the frontal process of the maxilla ; 4) hollowing out of the zygomatic process of the malar bone (malar recess) ; (5) extension to and appropriation of an air-cell within the orbital process of the palate bone (palatal recess). Contraction of the maxillar>- sinus, on the other hand, may follow : ( I ) imperfect absorption of the cancellated bone on the floor of the sinus, or secondary thickening of its walls ; (i) encroachment due to approximation of the facial and nasal wiills, unusual depression of the canine fossa, excessive bulging of the lateral nasal wall, or imperfectly erupted teeth. The crescemic projections which quite commonly are seen protruding from :he walls into the interior, occasionally are replaced by septa that completely divide the sinus into two cavities, each having its independent opening into the nasal fossa, but not being in communication with each other. These partitions vary in position and direction, sometimes subdividing the antrum into an anterior and a posterior compartment, and at others, into an upper and a lower chamber. In the last case the lower space may communicate with the inferkir meatus (Zuckerkandl, Briihl). Fig. I 185. Right frontal sinus (.eft frontml sinus Pastasc leftdinK into ^ infundibulum and f middle meatus Nasal _eptum Portion jf frontal section exposinn frumal sinuses which ai^ asymmetncal. The Frontal Sinus. — The air-spaces between the outer and inner tables of the frontal bones (sinns fnintales) are very variable in extent and form. The relative development and general position of these cavities are usually indicated by the degree of prominence of the superciliary ridges, but by no means invariably, since numerous exceptions to this correspondence occur. The sinuses are frequently t|uite asymmetrical (Fig. 1 185), one cavity being enlarged, somelliitcs at the expense of the other, with accompanying displacement of the intervening septum. The latter, usually approximately median in position, is often very thin, but only rarely 1424 HUMAN ANATOMY. incomplete, so that the spaces very seldom communicate. Numerous instances have been observed in which one sinus was entirely wanting. The average dimensions of the frontal sinus, as given by A. L. Turner, mclude a height of 31 mm. (i>^ in.), a width of 30 mm., and a depth of 17 mm. The capacity varies from 3-8 cc. (Bruhl). These spaces are not recognizable in the new-bom child, first appearing about the seventh year, after the absorption of the cancellated bone. It is not until after puberty, however, that they atuin their full size. They are usually larger in the male than in the female. The typical pyramidal form of the space is often modified by the enlargement of the sinus beyond its usual limits, since when exceptionally developed it may extend into the orbital plate of the frc ntal bone, at times reaching as far as the lesser wing of the sphe.ioid, or into the median orbital wall, or laterally into the external angular process, or, exceptionally, into the nasal spine beneath the root of the nose. On the other hand, the frontal sinus may be encroached upon by projecting ethmoidal cells. The frontal sinus communicates with the middle nasal meatus through either the infundibulum, or a passage between the anterior attachment of the middle turbinate and the uncinate process, or both. Its aperture (ostium frontalis) lies from 2-10 mm. from the upper end of the hiatus semilunaris. The frontal sinus is lined by a prolongation of the respiratory nasal mucous membrane, diminished in thickness but otherwise of its usual structure. Fig. n86. Sphenoidal tinui Frontal sinus Superior meatus Middle meatus Naso-pharynx Choana (poMerior naria) Maxillary sinua Cast at naaat foMae and accestor)' airtpacci, viewed from riKhl tide : lutuial size. (AViMrMJ.) The Ethmoidal Air-Cells. — These spaces Ccellulae ethmoidales) include a series of pneumatic cavities, very variable in number and size, that from birth lie between the upper part of the nasal fossae and the orbits, from which they are se{)arated by osseous plates of papery thinness. They are all lined with mucous membrane which rovers the thin bony partitions that separate the spaces from one another. When these partitions are deficient, as they often are in old subjects, the intervening septa are entirely membranous. The ethmoidal air-spaces, completed by the articu- lation of the ctfimoid with the frontal, maxillar>', Iachr>'mal, sphenoid and palate bones, usually form three groups, the anterior, the middle and the posterior cells. Every space communicates with the nasal fossa, either directly by means of an inde|>enaent aperture, or indirectly through one or more cells of the same group. Sometimes the cells are «o fused that two general cavities, an anterior and a poste- rior, repliice the corresponding groups. When typically arranged, the anterior cells communicate with the middle meatus by means of apertures that open into the upper part of the infundibulum. The middle cells also open into the middle meatus, THE ACCESSORY AIR-SPACES. 1425 usually by a crescentric cleft upon or above the ethmoidal bulla, but sometimes into the infundibulum. The posterior cells communicate with the superior meatus by one or more openings overhung by the upper concha. Very exceptionally the ethmoidal cells may communicate with the sphenoidal or the maxillary sinuses, or may extend into the substance of the middle turbinate bone. The mucous membrane clothing the ethmoidal cells is exceedingly thin, but corresponds in its general structure, even in possessing glands, with that lining the respiratory region of the adjacent nasal fossae. The Sphenoidal Sinus. — The paired air-spaces (sinus sphenoidales) produced by the absorption of the cancellated tissue within the body of the sphenoid bone are separated by an osseous p.irtition and seldom communicate. They are very variable in size and often asymmetrical, with corresponding displacement of the septum. A length of 22 mm., a width of 15 mm., and a height ci 12 mm., are the approximate dimensions of the averse sinus. The capacity of the latter, as determined by Briihl, is from 1-4 cc. When large, the spaces may appropriate not only a lai^e part of the sphenoid, extending into both wings, the pterygoid processes and the rostrum, but also include the boalar process of the occipital bone. Not infrequently one or Fig. 1187. Anterior cUimoidal celU Probe puecs to middl* mekto* Sphenoidal sinuaes Piluiury body Op«iln(« ol •phenoldal •iniu and poaterior ctlimoidal cell* Intenial carotid artery I'union of Mction of fronn formalin-hardened head, expoainx ethmoidal and ipbenoidal air-apacea; viewed from above. more of the jxisterior ethmoidal air-cells projects or opens into the sphenoidal sinuses. Very exceptionally these spaces may come into close relations with or even open into the maxillary antrum (Zuckerkandl) — a condition normally found in some apes. The sphenoidal sinus of each side communicates with the nasal fossa by means of the spheno-ethmoidal recess, above the superior turbinate and close to the roof of the fossa, by an aperture that pierces the upper part of the anterior wall of the sinus. Through .this opening, redu'«d in the recent condition, the respiratory mucous membrane is prolonged into the sinus which it lines. The palatal sinus, the small air-space within the orbital process of, the palate bone, communicates indirectly with the nasal fossa by either the posterior ethmoidal cells or the sphenoidal sinus into which it opens. Vessels.— Of the arteries supplying the nasal fossa the spheno-palatine branch of the internal maxillaf)' is the largest and most important. Entering the nose through the spheno-palatine foramen, it divides into external (posterior nasal) and internal (naso-palatine) branches, which supply an extended tract reaching from the posterior to the anterior nares. The external branches are distributed to the turbinate 90 I42( HUMAN ANATOMY. bones and the mucous membrane of the meatuses, indudine the lower part of the olfactory region, and in addition send twigs to the ethmoidal cells and the frontal and maxillary sinuses. The naso-palatine artery supplies the septum and upper part of the olfactory region. Numerous smaller, and for the most part collateral, twigs derived from the anterior and posterior ethmoidal branches of the ophthalmic pass to the upper part of the fossa; from the descending palatine, branches are distributed to the posterior part; and from the lateral nasal and septal, branches from the facial twigs supply the nostril. In addition to those from the posterior nasal, the antrum receives branches h-om the infraorbital. The sphenoidal sinus is supplied chiefly by the pterygo-palatine artery. The ultimate distribution is effected by capillary net-works which supply the periosteum, the glands and the tunica propria. The veins returning the blood from the rich venous plexuses and the cavernous tissue within the nasal mucous membrane follow three chief paths passing (a) forward to the facial vein, (*) backward to the spheno-palatine, and (f) upward into the ethmoidal veins. The latter communicate with the ophthalmic vein and the veins and superior sagittal sinus within the dura mater. A communication of greater importance, however, is established by a vein that accompanies the anterior ethmoidal artery through the cribriform plate into the anterior central fossa and empties either into the venous plexus of the olfactory tract or into one of the larger veins on the orbital surface of the frontal lobe (Zuckerkandl). The lymphatics within the mucous membrane are represented by an irregular plexus of lymph-vessels in addition to perineural lymph-sheaths surrounding the olfactory nerve-bundles. Both sets may be filled by mjection from the subarachnoid space. The larger lymphatics pass backward toward the posterior nares and join two trunks, one of which is continued to the prevertebral node and the other to the hyoid nodes. According to Schiefferdecker, the basal canals (page 951) communi- cate with the lymphatics and probably hcilitate the escape of fluid which aids the glands in keeping moist the epithelium lining the nasal fossae. The nerves include the special olfactory fibres concerned in the sense of smell, and those of common sensation derived from the ophthalmic and superior maxillary divisions of the trigeminal nerve. The lateral wall of the nasal fossa is supplied from several sources, including the upper posterior nasal branches from Meckel's ganglion and the lower posterior nasal branches from the larger palatine ner\'c- behind, and, in front, the external division of the nasal nerve and the nasal branch of the anterior superior dental, which also distributes twigs to the floor of the fossa. The septum receives its chief supply from the naso-paladne nerve, supplemented by branches from Meckel's ganglion behind and by the internal division of the nasal nerve in front. The mucous membrane lining the antrum receives filaments from the infraorbital nerve by means of its supenor dental branches. The frontal sinus is supplied by twigs from the supraorbital and the nasal nerves ; the ethmoidal air-cells by minute branches from the nasal, and the sphenoidal sinus by filaments from the spheno-palatine ganglion. PRACTICAL CONSIDERATIONS : THE ACCESSORY AIR-SPACES. Trauma of the accessory sinuses — with the exception of the maxillary antrum, which may be involved in extensive (crushing) fractures of the face— usually takes the form of perforating wounds, commonly from falb on sharp objects. The thinness of their walls, and the ease with which they may het traversed by such a vulnerating body, are well illustrated by a case in which a fall forward on to the tip of an umbrella resulted in a wound which began on the face above the bicuspid teeth, passed through the maxillary sinus, the sphenoidal sinus, and entered the cranium, the ferrule of the umbrella being found embedded in the pons (Treves). Inflammation of the accessory sinuses is not infrequent, on account of the con- stant exposure of the nasal mucosa to atmospheric sources of infection. It has a tendency to become chronic because (a) the openings of the sinuses are small and — with the exception of the frontal— are badly placed for drainage ; {b) the ciliated epithelium, on the activity of which the removal of the sinus contents depends, is apt to be so damaged by the primary inflammation that retention of secretion occurs ; (f) the mucosa around the different ostia is so loosely atUched that it readily PRACTICAL CONSIDERATIONS: ACCESSORY AIR-SPACES. 1427 becomes oedematous and is thrown into folds which later are obstructive ; (rf) foreign bodies (as a carious tooth, in the case of the antrum) have little chance for (»cape, and mucous cysts, polyps, and lesions of the sinus walls (pyogenic, syphilitic or tuberculous caries or necrosis) are not uncommon ; (<•) one cavity may be infected from another, pus from the frontal sinus entering the ethmoidal cells, or pus from either of these entering the antrum through its normal opening, or through a perforation of its wall in the vicinity of the infundibulum (Lack). In the greater number of cases, the chief— often the only— symptom of chronic suppuration of the accessory sinuses, is a purulent nasal discharge. Spontaneous recovery is practically impossible, and in the great majonty of cases, operaUon— for disinfection and drainage— becomes necessary. The cavities (as one may act as a reservoir of pus coming from another) may have to be attacked in a definite order. Ordinarily it is possible to determine whether the pus comes from the sinuses that open into the same passage within the middle meatus— the anterior group— or from those which open more posteriorly, above the middle turbinate bone— the posterior group If no definite evidence can be obtained as to which of the anterior group is involved, it would be well to attack first the antrum, then the ethmoidal cells, and then the frontal sinus. If the posterior group is affected it is usually proper to remove the posterior portion of the middle turbinate and open the posterior ethmoidal cells, later, if necessary, opening the sphenoidal sinus. Occasionally, as in ozxna (on account of the width of the inferior meatus and the atrophy of the inferior and middle turbinates), the opening of the sphenoidal sinus can be seen from the front, and then this sinus may be explored first (Lack). The frontal sinuses do not appear as distinct spaces until about the seventh year, and are developed by a separation of the two tebles of the skull, with more or less resulting prominence above the superciliary ridges. There may be a greater relative bulging toward the interior of the cranium, so that the prominence of the superciliary ridges is no indication of the size of the cavities of the sinuses. They are often very irregular in size, one being larger at the expense of the other, the septum deviating to one or the other sido accordingly. It 'u therefore, difficult, at times, to decide which side is involved by disease. Fracture of the skull over a frontal sinus does not imply that the cranial cavity is opened, even when depression exists. The frequent presence in these fractures of em- physema within the orbit and in the subcutaneous tissue, results from the entrance of air through the communication with the nose, when the latter is blown. The dependent position of its opening into the middle meatus or the infundibulum, provides better drainage for discharges than is the case in the other sinuses, and probably accounts for the relative infrequency of empyema of this sinus, although this advantage is partly off- set by the length, narrowness, and tortuosity of the canal, which render it easily liable to obstruction. Swelling of the mucous lining of the oudet of the frontal sinus may thus occlude the canal, and result in abscess (empyema). If this remains undrained the pus would tend to burrow through the weakest point of the wall, which usually leads it through the floor of the cavity into the orbit, giving rise to an orbital cellulitis, and to displacement of the eyeball. It later tends to escape through the inner portion of the upper eyelid. In some cases it extends through the posterior wall of the sinus into the cranial cavity, causing a septic meningitis, or an extradural or brain abscess. Extensive necrosis of the frontal bone may follow sinus disease, as the frontal diploic vein, which empties into the frontal vein at the supraorbital notch, receives blood from the sinus. If free drainage ij maintained these complications are very rare, but if drainage is defective it is imperative to open the sinus early. This may be done externally, the anterior wall being removed by a chisel or trephine. The incision may be verti- cal or along the superciliary ridge from the inner end to the supraorbital notch, sometimes dividing the supraorbital vessels. The thinness of the nasal portion of the floor of the sinus is marked — as well as that of the orbital portion — and therefore frontal sinus suppuration is, as a rule, associated with infection of some of the anterior ethmoidal cells, which- surgically — may perhaps be considered as forming a part of that sinus (Lack), although Kiimmel notes that he has seen the ethmoidal cells perfectly intact in a series of cases of frontal sinusitis. 1428 HUMAN ANATOMY. i Attempts have been made to pass a probe into the ostium frontale from the nose, but this is exceedingly difficult because of the concealed position of its orifice behind the anterior end of the middle turbinate bone, and sometimes because of its tortuous course. Efforts to reach the sinus through the nose are usually made by removing the anterior end of the middle turbinate bone, at the same time opening the anterior ethmoidal cells which are frequently involved by the same inflammatory process. By this method an aperture is left for the permanent discharge of the sinus into the nose, whereas by the e.xtemal method the opening into the nose may remain closed. The maxillary sinus, or antrum of Highmore, is the largest and most important of the accessory sinuses of the noso. It is most frequently the seat of pathological processes, as infections and tumors. Infection may reach it from the nose through the opening in the middle meatus, when it may be secondary to disease of the frontal and anterior ethmoidal sinuses, the opening^ into all three being closely associated ; or it may be caused by caries of the teeth, especially of the first and second molars, the roots of which frequently produce prominences in the floor of the antrum, or may very exceptionally extend mto its cavity. Occlusion of the small orifice with retention of the pus frequenth causes great pain from pressure on the infraorbital nerve in the roof of the antrum. The pus may burrow into the nose, the ethmoidal cells, or the orbit. The normal orifice is too high on the internal wall for drainage, and is too small for effective irrigation, which may be provided for (a), if the cause is a carious tooth, by removing a tooth and making an opening through the roof of the socket into the antrum ; this affords dependent drainage, but permits the entrance of food from the mouth ; (*) by perforating the bony wall between the antrum and the inferior meatus with or without removing the anterior end of the inferior turbinate ; or (r) by making an opening through the thin anterior wall, above the roof of the second bicuspid tooth, at the level of the canine fossa. A tumor of the maxillary sinus may be either benign or malignant. Its growth will lead to enlargement of the cavity, and to the following symptoms, one or more of which will predominate, according to the direction it takes : (a) inward, through the thin inner wall of the sinus, causing epistaxis, obstructed respiration, epiphora from pressure on the na.sal duct ; (6) inward and backward, involving the naso- pharynx and interfering v.ith both respiration and deglutition ; ic) forward, pushing the anterior wall — also thin — before it and obliterating the inframalar depression in the cheek; (rf) upward, causing infraorbital neuralgia (as the infraorbital nerve runs in the roof of the sinus), toothache from compression of its middle and anterior superior dental branches, face ache from involvement of the other branches of the superior maxillary, and later exophthalmos and diplopia ; (e) downward, pushing down the arch of the hard palate so that the roof of the mouth on the affected side becomes convex, and, by pressure on the superior dental nerves, causing se\ere odontalgia in the upper teeth, which later become loosened. Benign growths may be removed through an opening made by cutting away the anterior wall. Malignant growths necessitate excision of the superior maxilla. In diseases of the sphenoidal sinuses their intimate relation with the brain above, the optic ner\e and ophthalmic artery abo\e and to the outer side, and, along the outer wall, with the internal carotid artery, the cavernous sinus and the nerves passing through the sphenoidal fissure, should be borne in mind. Such diseases may lead to (a) optic neuritis and blindness, if the optic ner\e is involved; (b) to general ophthalmoplegia if the third, fourtii, tiie ophthalmic division of the fifth, the sixth, and the symiwthetic filaments fri>ni the cavernous plexus (all transmitted through the sphenoidal fissure) arc implicateti ; (r) to cavernous sinus thrombosis if the ophthalmic \ein — passing through the same fissure — is infected. Tumors of the pituitary b' fossa in the sella turcica and just almvf the roof nf the sintis — m.-iy penetrnte its c.ivity. The ojiening of each sinus is in the upper part of the anterior wall, a very unsuitable position for drainage, in the presence of infection. Encroachment on any of the surrounding structures might lead to serious results. The anterior wall may be exjxised and attacked by the surgeon, but only with consitlerable difficulty, l)ecause of its deep situation and its DEVELOPMENT OF THE NOSE. 1429 restricted avenue of approach through the nasal fossa. The chief obscar is the middle turbinate bone, which must be removed before the orifice can be seen or the anterior wall removed. Any efforts at cleaning pathological tissue from the sinus must be made with due regard for the important structures just outside and the thin intervening bone. Inflammation of the ethmoidal cells is most frequently associated with the presence of myxomatous polypi within the nose. Infection may extend (a) upward to the cranial cavity, either directly or by way of the ethmoidal veins, or into the cavernous sinus via the ophthalmic vein, or to the longitudinal sinus — especially in children — by the small vein traversing the foramen ciecum ; (*) outward to the orbit, causing an orbital cellulitis; (c) to the lachrymal sac (on account of the contiguity of the lachrymal bone) causing dacryo-cystitis. A valuable, but not always reliable, sign of involvement of the ethmoidal cells, is localized pain at the inner canthus of the eye (Kiimmel), and swelling of the mucous membrane around the middle turbinate may in this — as in infection of the other sinuses — be considered an imptortant symptom. In order to evacuate the diseased cells, the middle turbinate (as in the case of the sphenoidal sinus) must be removed before the ethmoidal cells can be exposed. As, in the large majority of cases at least, the condition is coincident with similar infection of the frontal sinus, the anterior cells may be easily reached from the floor of the latter after it has been opened. The optic nerve, the trochlear nerve, the superior oblique ocular muscle and the anterior and posterior ethmoidal arteries, are the most important structures endangered during this operation. DEVELOPMENT OF THE NOSE. The earliest trace of the nasal aniage appears about the beginning of the third week of foetal life as a thickening of the ectoblast to form the nasa/ area at each side of the anterior portion ol the head. About one week later the convexly cres- centic outline of this area gives place to a slight depression that deepens into the ol/actorv pit or fossa in consequence of the increased thickness of the surrounding mesoblast. The encircling ridge thus produced is best marked on the mesial and lateral boundaries of the fossa (Kallius), where the resulting elevations foreshadow the developme.it of the inner and outer nasal processes. With the forward growth and union of the maxillary process of the first visceral arch with the median nasal process, or processus globularis, to complete the upper boundary of the primitive oral cleft (page 62), the margin of the entrance of the nasal pit becomes closed in below. Subsequently, howe\-er, the lateral n -sal process extends medially above the maxillary process until it meets the median aasiil process and thus becomes the immediate lower and lateral boundary of the opening of the fossa. The latter grows and deepens chiefly upward, towards the brain, and backward and in consequence the olfactory organ for a time consists of two blind pouches, separated by the frontal prtKess, lying above the primitive oral cavity. These pouches invade the mesoblast until their blind posterior ends reach the primitive oral cavity between which rnd the olfactory diverticula a thin ijartition, composed of the two abutting layers of epithe- lium, alone intervenes. This septum, bucco-nasal membrane of Hochstetter, iMjcomes attenuated and finally ruptures, the resulting openings, the primitive choaiite, estab- lishing communication between the nasal fossa; and the primitive oral cavity. That part of the roof of the latter which extends from the choans to the nasal apertures constitutes the primitive palate, and contributes not only the anterior portion of the definite palate, but also the tissue forming the lips (Hochstetter). The primitive palate includes contributions from different sources, its middle portion being from the median nasal process and its lateral portions being derived from the lateral nasal process in front and from the maxillary process behind (Peter). Subsequent to the formation of the primitive palate, about the fifth week, the primitive nasal fossa? increa.se in size, sink deeper into the head between the metlian 1)lane and the eye, and come into closer relation with the brain. The nasal fossa-, lowcver, in acquiring their definite expansion additionally appropriate a considerable portion of the primitive oral cavity which becomes separated from the remainder of that space by the formation of the definite palate. Mb 143° HUMAN ANATOMY. Nasal area Fore-brain Nasal area Forc-brain The first step in the production of the latter is the appearance, about the ninth week, of the palatal ridges, wedge-shaped elevations that grow downward and in- ward from the maxillary processes. In front these ridges begin at the primitive choanx, where they are continuous with the primitive palate, and extend backward as far as the tympanic pouches. At first almost sagittal in their plane, the palatal ridges become gradually converted into horizontal plates that come into contact and finally unite along their Fig. ii8H. opposed median edges to com- Fore4>rain plete the roof of the mouth am. the floor of the nasal fossae and the definite or secondary ckoante, this fusion being accomplished by the end of the third month. Coincidently with these changes the pnmitive choana- elongate and come to lie on either side of the posterior por- tion of the nasal septum to which the frontal process has now become reduced. The union of a pair of outgrowths from the palatal plates, beyond their point of fusion beneath the choanae, produces the uvula, while the remaining ununited portions of the ridges give rise to the palato-pharyngeal arches. For a time the nasal sep- tum is still incomplete, since it has not yet reached the palate, and the nasal fossx communi- cate by means of a cleft between the septum and the palate. With the downward gi- vth of the partition this con. • lica- tion is obliterated, the itum joining the f>alate along thi line of the median suture. The formation of the ante- rior part of the floor of the nasal fossa: is more complex since, according to Peter,' in this region the palatal processes do not come in contact with each other owing to the interposi- tion of a portion of the partition that separates the primitive choanae. The palatal plates, however, fuse with this wedge of tissue along the line of appo- sition except at one point on each side, where the epithelium persists as a solid strand leading downward and inward from the fore part of the floor of the nasal fossa to the roof of the oral cavity. These strands acquire a lumen and become the incisive canals (page 1413 ) that may persist thrnsighntit life and establish communication between the nasal and oral chambers. The further differentiation of the nasal fossae of man follows the same funda- mental plan that applies to other mammals, but is modified by the reduction that Lateral nasal proceu Nasal fossa Fore-brain Nasal fossa Naso-fronlal proceis Procnsus globularis Frontal sections -os. illustrating early staKes in ilevelopment of^nose ; in A. nasal area shows as Ihirkeiiinir of ectoblast ; in 11, nasal area is slightly depreaaed ; in C and D, nasal fosfat are forming, x 30, ' Anatom. Anxeiger, Bd. xx., 1902. DEVELOPMENT OF THE NOSE. 1431 Cartilajtinout captuli* EthnKMurMnal Fig. 1189. Maxill»turbiiial NmwHoi >>alaul ;>rocan' Onl c«vtt; TOBKtK Frontal Mctlon through dcvelopinf naial f« communicate; palaulproccaaet are forminK, and onl cavity which X15- occurs in the production of the relatively feebly developed human olfactory apparatus. With this differentiation is associated the formation of the turbinates and the intervening clefts (the meatuses) and of the acces- sory air-spaces. Thestud- iesof Zuckerkandl, Killian, Schoenemann, Peter' and others have shown that the tvpical development of the conchae proceeds from jacobaon'iorgaa three primary outgrowths from the lateral nasal wall in regions later correspond- ing to the maxilla, ethmoid and nasal bones. These elevations, appropriately known as the maxillo-tur- binal, the elhmo-turbinal and the naso-turbinal, un- dergo differentiation that lea& to the simple or com- plex definite arrangement of the conchae found in various animals. In man the maxillo-turbinal, later the inferior turbinate, first appears and pre- cedes the ethmo-turbinal plate that later is supplemented by a second scroll, thus producing the middle and superior turbinates respectively. The naso-turbinal, alwavs nidimentary in man, is represented by a small ridge that appears in front of the ethinti-turbinal and above the maxillo-turbinal plates and persists as the agger nasi. The ethmo-turbinal is most intimately related to the true olfactory area and undergoes, even in man, conspicuous subdivision. Although finally reduced to two (the upper and middle turbinates), in the human foetus, just before birth, five ethmo- turbinal plates defined by six grooves are present (Killian). Persistence in excess of the usual complement accounts for the presence of the supernumerary ethmoidal turbinates so often observed. As interpreted by Killian, the subsequent modifications of the ethmo-turbinab and the intervening furrows, either by further expansion or by fusion, are not only intimately concerned in producing details modelling the lateral wall of the nasal fossa, as the uncinate process, ethmoidal bulla, hiatus semilunaris and infundibulum, but also associated with the first appearance of the accessory air-spaces. The earliest establishment of these spaces pre- Kici. 1 190. cedes the appearance of the carti- lage that later encloses them, their relations to the skeleton being, therefore, secondary (Kallius). The ethmoidal air-cells and the sphenoidal sinus are primarily con- strictions from the nasal fossae, while the maxillary and frontal sinuses are more or less direct extensions from the same cavities. The maxillary sinus ap- pears about the middle of the third foetal month as a minute epithe- lium-lined sac within the mcsoblast at the side of the nasal fossa, from which if has been evaginated ; by the ixth month it measures some 5 mm., and at birth has acquired the size of a pea. Until the eruption of the milk teeth provides the ' in Hertwig's Handbuch d. Entwikelungslehre, Lief. 4 and 5, 1902. Fore-lnain Nanal aperture Lateral naaal proceas Maxillary process Primitive choana Palatal process Part o( head of fortus 15 mm. in length, showing primitive choanw and palate, v 8. 1 Pfter.) iMi 1432 HUMAN ANATOMY U Fig. 1 191. Fon-brain Infnrua] «•• MUalfoua •Lstciml nasal proceu •Median naial process 'ProccMiLH globularis Maxillaiy proctia Mandibubr proccis Anterior end of head ol (oetui 10.3 nun. in len(tli, slmwinK early devciopment of external iioee. X H. iPrlrr.) necessary room for expansion, its growth is retarded. Aher the sixth year, when the eruption of the permanent teeth begins, the antrum loaes its general spherical outline and gradually acquires the definite pyramidal fomi. The frontal sinua formed as an extension of tlie nasal foaaa during the third fuetal month, is for a time so small that it is usually regarded as absent at birth. Although indistincdy seen during the third year, not until about the seventh is the sinus a definite sfnce ; it remains small, how- ever, untn puberty, after which its adult proportiotu are. gained. The sphenoidal sinus, primarily arises by the constriction and partial isolation of a part of the primitive nasal fossa. Although its development begins during the thirti foetal month, the space remains so rudimt.i- tary that not until the seventh year has absorption of the cancellous bone progressetl sufficiently to make the sinus apfiarent. Notwithstanding its rudimentary condi- tion in man, the organ of Jacobson devel- ops at a very early period, beginning as a groove-like depression on the median wall of the nasal pit. This groove is con\'erted into a tubular pouch that soon becomes laterally compressed and, by the middle of the third month, measures about .5 r .n. in length and receives twigs from the olfac- tory nerve ( Kallius). After the fifth foetal month the organ suffers regression and becomes rudimentarv and variable in comparison with the perfection it attains in animals possessing olfactory sense in a high degree. The development of the outer nose is closely associated with the changes affecting the median and lateral nasal processes — prommences considered in connection with the formation of the upper boundary of the primitive oral cleft (page 62), Reference to Fig. 1 192 shows the median nasal processus, separated by a distinct furrow that soon Ixcomes filled and partially obliterated by ingrowth of young connective tissue, as does likewise the groove between the globular and maxillary processes. At first sepa- rated by a relatively wide interval, the infranasal nasal area of His, the nasal apertures are brought nearer togetlier by the rapid narrowing of the iiiterpost'd portion of the frontal process. E\pntually the tissue be- tween theglobular processes bocomes the philtrum ol the upper lip and that b- tween the nasal opt-.ings ■ )ersisth as the partition between the nostrils. By the end of the second month the external nose is defined, but is verj' broad and flat and lim- ited above by an arched furrow that separates the convex nasal margin (His) from the forehead. The nos- trils, originally placed high and for a long time directed forward, grad- ually descend and assume a hori- zontal plane as the middle of the arched nasal margin grows downward and forward to become the p«oint of the nose. These changes, however, are not accomplished until near the end of gestation and at birth the bridge of the nose is still small and flat which, in connection with tlif general breadth of the organ, imparts to the infantile nose its peculiar stumpy api)earance. Not until long after birth, and, indeed, not until after puberty, does the outer nose acquire its definite individual form in Fig. I 193. Forc^wain Head of fcrtni of about Infranasal area Nasal aperture Lateral nasal process Medial nasal uroceKs Processua globularis Mandibular process 3n da\-it. showing de\-eloping nose. 13. IK.ibl.) THE ORGAN OF TASTK. U33 which family and racial characteri»tics are often so strikingly ri-produced. From the second until the sixth month the nostrils are occluded by epithelial plugs which subsequently undergo >;radual resolution, so that before birth the niisal a|>ertures are unobstructed. The catiiiages of the outer nose are derived from the common carti- laginous capsule that constitutes the primary nasal skeleton. Subdivision into the individual plates is probably effected by ingrowth of the surrounding connective tissue ( Mihalkovics, Kallius). THE ORGAN OF TASTE In the description of the tongue and its papillx (page 1575), reference is made to the presence of specialized epithelial structures, the tatte-budt, that ser\e for the reception of gustatory stimuli. These bodies collectively constitute the peripheral sense-organ of taste and as such will be here considered. As implied by their name, the taste-buds (calyculi gustatorii) are irregular ellip- soidal or conical bodies, sometimes broadly oval but more often slender in outline, and in the adult mea.sure from .070-. 080 mm. in length and about half as much or Fiu up J. Lyiaphoid nodulct Foramen cKCiun Anterior palatine arch Folia lingnc rungiform papilU Pan 01 doraum ot tonpie, showinx papilUe. less in breadth. Since they lie entirely within the epithelium clothing the mucous membrane, the necessary access to the interior of the buds is afforded by minute pore-canals, each of which, beginning on the free surface at the outer taste-pore, \eads through the intervening layer of epithelium to the inner pore that caps the subjacent pole of the bud. By means of these canals the sapid substances dissolved in the fluids of the mouth reach and impress the gustatory cells within the taste-buds. Pore-canals are not, however, invariably present, since, as pointed out by Graberg, certain taste-buds remain immature and retain their embryonal form and relations, being broad and conical and in contact with the free surface. In such buds the gusUtory cells are few, onlv two or three, and so superficially placed that a dis- tinct canal is absent Occa.>tionally double buds are encountered in which two (fustatory bodies are implanted by a common base, but partly retain their inde- pendence in having separate distal poles, each provided with its separate taste-pore and canal. . •. « The chief position of the taste-buds is within the epithelium lining the sides of the annular groove on the circumvallate papilla, the buds being more numerous and closely placed on the median than on the lateral wall of the furrow. Their number 1434 HUMAN ANATOMY. has been variously estinuted, but it it probable that from loo to 150 represents the maximum for a single pafHlla, in many cases the quoU being less than one half Fio. 1 194. Annu'ar wall tvr- round inir IMpilla MuKleof loncuc Section of citviunvmllalc papilla (rum Uwigne o( child. K 70. Fig. "95- of these fibres (Grabei^). The locality of next importance numerically is the papillx foliatse on the sides of the tongue in the furrows of vhich, even in man, the taste-buds are plentiful. Additional situations, in which, however, the taste-buds are very sparingly and uncertainly distributed, include the fungiform papillae, the soft palate, the posterior surface of the epiglottis and the mesial surface of the arytenoid cartilages. Within the fungiform papillx a few buds may be found on the free surface, where the epithelium is thinnest. Over the soft palate their distribution is irregular and uncertain, while in the larynx the buds are lim- ited to the areas covered by squamous epithelium. According to Davb, between fifty and sixty taste- buds of varying size may be counted on the epiglottis within an area 3 mm. in diameter. Structure. — Wherever found, the taste-buds consist exclusively of epithelial tissue and, in cor- resjjondence with other sense organs, include two chief varieties of elements — the supporting cells and the more highly specialized neuro-epithelium, the gustatory cells, among which lie the terminal fibrills of the nerve of taste. The supporting cells are represented prin- cipally by elongated epithelial elements that occupy both the superficial and deeper parts of the taste- buds of which they contribute the chief bulk. They vary in their individual contour, being lanceolate, wedge-shaped or columnar, according to the model- ling to which they are subjected by the neighboring cells. They possess large, clear, vesicular nuclei that contain litde chromatin and, therefore, stain faintly. The position of the nucleus is inconstant, in some cells being near the base and in others in the middle or nearer the apex. The peripheral ends of the Taste-bud Taste-pore < — ~ Epithelium Taste^bttd Taste-buda in section ; upper one siiowa gustatory hairs ptofecting into pore-canal. rms: wmojm of t^^ste. 1435 i.a'j I i.i 1.' Fig. 1196. ( )Ut«T tllKtV-pi si^>purting cells, somewhat bhRit««<' ami Hm H mk H a«d hesrt with a namw cutiouUir cone, are closely grou|>nl in b<«i«« ttw nmmuimr ipenii^ <■• the inner ta«te-pi>rt', through which project the stiff tsur mtttxmm^ (if rJK- tfustai*"- cells. Thmr det'|xT or central ends are prolonged wma mw or ammv f»rf»topl»sinir i^iicesses which unite with simitar extensions u« the IjnmI ceils, as iAm? pet-^iar supporting cells .tr tlte base of the bud are called. The 6asa/ ceils are madiAed «aM«macuiar •■It-mertts. pr(>babi> epithelial in iMiure, which occupy the lower iourth ' the buds, resting i«pon thf sufijacent epithelium and, in turn, affording support Vi,yr the eiongatvd celi«* Although differing 111 siz«- and details of lorm, th«- basal <•»-!»* ^re provided wit!' >val nuclei and are gen«Tally more or less branched, by iiwbw»< of their protopl"«'«nir processes they are uniteccsms i'l«e peripheral ones, as noted, extend not only as far as the inner tiiste-jxtre, but through the latter and into the ainal by meais of the gustatory hairs into which the taste cells are prolonged. The centrally directed ends are usually much the shorter and join the processes of the basal cells. The number of gustatory cells within a single tast' bud varies, in exceptional cases only two )r three being present, but more often they are almost as numerous as the suppf>rting cells (Grabcrg). The capi'.lary clefts observed within and around 'he taste-buds — the intra- sub- and peri-bulbar juice-spjices described by Grabcrg — are regarded by some as existing during life and, therefore, not as artefacts. To these intercellular clefts the last-named authority attributes the func- tion of insuring and facilitating an active lymph-circulation within and around the taste-buds, .liiereby is effected the prompt removal of foreign substances that might prove delett .ioiis if too long retained in close relation with the delicate sensory elements. Hermann has shown that the taste-buds are the seat of continual degeneration and repair, sometimes, indeed, entire buds undergoing regression. Whether such destructive processes are to be ascribed directly to the invasion of leucocytes, al- though the latter are nornwlly found in insignificant numbers within the buds, is still a subject of discussion. The nerves distributed to the gustatory l>odies are the fibres of the glosso- pharyngeal, the nerve of taste. From the rich subepithelial plexus numerous twigs ascend into the epithelium, one set going directly into the taste-buds and the other ending within the surrounding tracts of epithelium. Since the last set —the intrr- bulbar fibres — probably have no concern with the impressions of taste and serve to convey sensory stimuli of other value, it suffices to note that after repeated division ( eiitnil vniph-space Hani cell DiaKTamnulU: MHrtiofi illnstratinK architecture of taate-hud \l»tahetgA ' Anatomische Hefte, Bd. xii., Hf. 2, 1890. • Bardeleben's Handbuch d. Anatomic des Menschen, Lief. 13, 1905. 1430 HUMAN ANATOMY. \''V^., F-'ic;. 1 197. Partial))' sepaimled cells of UUr- bud with tenninal filaments uf gusu- tory nerve. X Jio. lAnutetm.) the ultimate fibriUae terminate in minute bead-like endings that lie free between the epithelial cells, either near the free surface or at a deeper level. The ner\es distributed to the taste-buds— the intrabulbar fibres — enter at the basal pole. Usually numbering from two to five for each bud, on gaining the interior of the latter they undergo rapid division and become numerous. A majority of the resulting fibrillx ascend in tortuous windings towards the apex of the bud in the vicinity of which some end, while others recurve and end at lower levels. The fibrilliE terminate in free, usually minute knob-like endings, that lie between and often in close contact with the supporting and gustatory cells. It is probable that in no instance do the nerve-fibrillse actually unite with the gustatory cells, the relation being one of appKMition and not of continuity. Development. — ^The earliest evidences of the taste-buds ' appear, about the third foetal month, within the deepest stratum of the immature epithelium as groups of cctoblastic cells that are distinguished by their large size and elongated form from the surrounding v.pithelial elements. The anlage tends to become conical, the ape.x gradually reaching the free surface and the base resting or slightly encroaching u|K>n the subjacent connective tissue, from which it is only indistinctly defined. The primary slender form of the developing bud is later replaced by one of broad conical proportions in which the wide base is supported directly by the connective tissue without the interposition of epithelium. For a time the height of the young taste-bud equals the entire thickness of the epithelium, the position of its apex being marked by a slight depression on the free surface. In consequence of the rapid increase of the surrounding epithelium, thb depression gradually deepens until the bud, which meanwhile has grown but slightly, lies at the bottom of a narrow funnel-shaped passage, the pore-canal (Gral^rg). Previous to the fifth month, the constituents of the taste-bud are apparently of the same character and not until towards the end of gestation is the differentiation between the supporting and gustatory cells clearly established. The definition of the tastc-t>uds from the surrounding tissue is sharpened by the apfiearance of the so-called fxlrabulbar cflls, flattened protecting epithelial ejements in which partial cornilicatiun probably takes place ( Kallius). Coincidently many of the conical embryonal buds gradually assume their more slender and ovoid mature form. Before birth the taste-buds are j)resent not only on the sides but also over the summit of the circumvallate papilUe. While exceptionally some of ihose in the latter situation may rt-main, as a rule they disappear and, hence, in the adult the gustatory bodies an- usually confined to the sides of the papilhe. Likewise the complement of taste- buds on the fungiform papilla; is much larger at birth than later (StahrM, giving to these papilhe an importance during early childhood that subsequently is lost THE EYE. .Although the organ of sight (orKanitn visus), strictly regardcKl, consists only of thi- f\i-l)all or inlolx- of the eyi it is closely asst>ciatetl with other structures, as the eyelids, the lachrymal apiKiratus, the t)rbital fascia and fat and the ocular muscles, which scr\e for its {)rotection, support and change of axis. The description of some, at U'ast, of these accessory structures therefore appropriately here finds place. THE ORBIT AND ITS FA.SCI/F-. The walls of the orbit h.i\e l>een described in connection with the skull (page 232 ) ; suffici- it here to iMiint out that in its general form the orbital r.ivity resembles a pyramid, ^M) modified by the rounding of its angles that it approximates an irregu- lar cone. The base corresponds with the orbital opening on the face and the apex 'Gmbert; : Shol(>K. Arbeiten, Bd. vlii., 1898. '/eits<-hr. f. Moriihul. u. Anthropol., Bd. 4, igui. THE ORBIT AND ITS FASCIA. 1437 with the optic foramen. The median walls of the two orbits are slightly divergent behind, but almost parallel with the sagittal plane au.l with each other ; the lateral wails are obliquely placed and with the sagittal plane form an angle of about 48° and, therefore, with each other one of something more than a right angle.^ The axis of the orbit is directed inward and upward, forming an angle of from : s'-so" with the horizontal plane, and one of about 45° with the orbitel axis of the op|)osite side, which it intersects in the vicinity of the sella turcica. The width of the orbital en- trance is about 4 cm. and the height about 5 mm. less, while the depth of the orbit is approximately 4 cm. The space, therefore, is much more capacious than necessary to accomodate the eyeball and the associated muscles, blood-vessels and nerves. The interspaces thus left are occupied by the orbital fat (corpus adiposum orbitae ), sup- ported by a framework of connective tissue lamellae prolonged from the orbital fascia which, in turn, is continuous with the periosteum lining the orbit. The latter, also known as the periorbita, is thin but resistent and at the various openings in the walls of the orbit continuous with the periosteum covering the adjacent surfaces of the skull. Fig. 1198. Niial loiM-. Anterior ethmoidal cell*. Meiitt orbiul wmIL '.ntenuil rectus mu«cl« Potterior ethmoidal cell Conlnnrtival lac Anterior chamber Corncn Lent Vitreoiu chamber Check liKsment Orbiul wall Eatemal racHu muclc Sclera Orbital (at Optic na\t HoriionUl •cctloa ol ri(ht orbit ahowing eye in poaition. The eyeball does not rest directly in contact with the fatty cushion fonning the walls of the cup-shaped recess in which it lies, but is separated from the surrounding adipose tissue t)V a fascial investment, the captule of Tenon 'jwge 504). This sheet covers tlic posterior three-fourths of the eyeball and encloses, between it and the eye, the space of Tenon. The latter in front begins beneath the conjuctival sac. close to the corneal margin, and behind ends in the vicinity of the optic nerve. It inal 1 Median palpebral linainem l.achrymal punrtum and catialiculua Nasal duct ^ Opening of nani durt in inferior naial mcatua Maxillary sinui Diiacction of orbit and ad|acem atructuret. >howinK palpebral faacia, liichr>'mal Mc and naial duct. palpelral fascia or septum orbHale (Hcnle), which stretches across the orbital entrance and materially strengthens and aids the eyelid in closing this aperture. Above, the septum is attached to the border of the orbit, just behind the margin, from which it extends downward to become firmly united with the common fascial investment of the levator pal|>ebne superioris and superior rectus and, still loner, with the up|)er convex border of the superior tarsal plate. On each side the septum blends with the corresponding |)alpebral ligament, while Ix^low it passes from the orl)itril margin to the mlorior tarsal plate, after becoming united with the 8h< ith of the iiifiTior rectus. The septum orbital is not of uniform thickness, but is strongest above, especially towards the sides, and wejikest l)eneath the lower eyelid ; further, in a general way, the sheet is more robust ne:ir its [x-ripheral bony attach- ment than where it joins the tarsal plates. In conjunction with the [lalpebral liga- ments, it is so strong behind the angles of the eye that in these localities, particularly medially, it is very unyielding and capable of resisting forward displacement. The int'-rnai union of the lev.aor palpebr^ superioris with the septum orbitale enables this inuscif when it contracts to tens^ the fascial diaphragm. Practical Considerationa. — The orbital cavity is somewhat pyramidal in shape and its anterior or ba-sal portion is cKxupied chiefly by the eyel>all, which lies slightly nearer the r(M)f and the outer wall than the lower and inner walls. Its diameter PRACTICAL CONSIDERATIONS: ORBIT AND FASCIit. i439 is greatest just back of its anterior margin, which is thickened and offers the best protection to the eye from injury. The upper margin is most market! and with the eyebrow offers a good protection to the eye in that direction. The inner margin is not prominent, but is well reinforced by the bridge of the nose. The outer edge is least prominent, and on that side palpation is possible as far back as the equator of the globe. For this reason, and because the outer walls converge backward while the inner •valla are parallel, incisions for reaching the interior of the orbit are Ijest made on the outer side. The walls are thin and easily fractured by direct violence, as from canes and similar objects, which sometimes enter the adjacent cavities, as the ethmoidal. Tumors may encroach upon the orbital space either by causnig the absorption of the thin intervening bone, or by growing through one or more of the openings in its wall, as through the optic foramen and sphenoidal fissure from the cranial cavity, the nasal duct from the nose, or the spheno-maxiUary fissure from the temporal or zygomatic ioaax. The eyeball occupies about one-fifth of the orbital cavity, the remainmg space being filled by nerves, vessels, muscles, the lachrymal gland, fat, and a system of fasciae. In the ordinary case a straight edge placed against the upper and lower margins of the orbit will just touch the closed lids' covering the apex of the cornea, but will not compress the eye. A straight line between the two lateral margins would pass back of the cornea, on the outer side posterior to the ora serrata and on the inner side at the junction of the ciliary body and iris. An exophthalmos is a protrusion forward of the ball, and is usually due to pressure from behind, more rarely to paralysis of the recti muscles. Some of the more common causes of retrobulbar pressure are orbital cellulitis or abscess, tumors, distension of the orbital vessels, and excess of fat. Rnophthalmos, due to exhausting disease, is more apparent than real, but a true sinking of the globe may be due to paralysis of Miiller's muscle due to lesion of the sympathetic, to atrophy of the retro-bulbar cellular tissue caused bv trophic dis- turbance, to fracture and depression of the orbital bones with cicatricial adhesion and contraction, and to injury of Tenon's capsule and the check ligaments. InJIammation of the capsule, or Tenonitis, may be due to constitutional poison or to infection following operations involving it, as in tenotomy of the ocular muscles. It may be an extension from an inflammation of the eyeball. The inflam- matory exudate in the capsule and adjacent tissues will sometimes cause a slight exophthalmos, and the eye will be immobile. All the extrinsic muscles of the eye pierce the capsule about the equator of the globe to reach their insertions in it. Each muscle receives a tubular investment from the capsule, which fuses with the proper sheath of the muscle and leaves a small bursa on the anterior surface of each. To open the capsule for a tenotomy, the incision is made just back of the cornea, and goes through only the conjunctiva and outer layer of the capsule. The desired tendon is easily found and brought out with a hook, when it is divided. The capsular prolongation about the tendon prevents retraction of the stump after the division, and so preserves the function of the muscle. This is aided by expansions of the capsule passing to the margins of the orWt and continuous with the perios- teum. Those passing from the internal and external recti are stronger than the others and are called the internal and external cheek ligaments. They are uniti-d by a layer of fascia (suspensory ligament of the cyelwU) passing under the eyeball so that the eye is supported after the bony floor of the ked at is lowered, and ujjward only when the object is turned far toward the healthy side. One eye must be closetl to prevent double vision or diplopia. Of the single paralyses, that of the sixth nervf is most frequent on account of its extended course from its origin in the brain to its peripheral termination in the external rectus, rendering it liable to involvement by adjacent |>athological processes, as meningitis, tumors, or hemorrhages. .Such lesions may invoKe it alone, or together with a series of cerebral ner\'es, paralyzed one after another from a progrcss- inv; pathological condition, which would then probably l)e at their central origin, or in the wall of the cavernous sinus, where they are close together. The sixth ner\e may Ik- {laralyzed by a fracture of the base of the cranium in the middle f<>s.sa. When the ophthaimir divi'sion of the /i/th »ert'f is paralyze*!, there follows anesthesia of the conjiinctix'a of the globe and upper lid, and of the other piirts 8upplieed recess, about 5 mm. long, known as the lachrymal lake (lacus lacrimalis). The palpebral fissure, which possesses an average length of 30 mm. and a height of from 12-14 mm. , is subject to considerable individ- ual variation in size, thereby exposing a vari- able amount of the eyeball. In consequence, the appearance of a larger or smaller eye is produced, an impres.sion, however, that depends upon the size of the opening between the lids and not upon differences in the eyeball itself, the diameters of which, under normal conditions, are practically constant. The height of the palpebral fissure in young children is relatively greater than in the adult, a jjeculiarity that confers the characteristic wide-eyed appearance in early life. The upper lid is not only much the broader, its height being about double that of the lower one, but also the more movable and the chief agent in closing the palpebral opening. When the latter is closed the free edges of the two lids are in contact through- out their length, the anterior margin of the upper one overlapping slightly the corre- s|X)iiding edge of the lower. The line of apposition is somewhat arched, with the convexity directed downward, and falls below a horizontal line passing through the inner canthus. ' When the eyeli-i5o in the upper lid and alniut half as many in the lower. With the exception of about 5 mm. next the inner angle, where the lids lx)rdor the lachrymal lake and the eyelashes are alwent, the cilia are arranged in a double or triple row, with the longest (8-12 nmi. ) in the centre of the upper Ht'iies, Although their follicles occupy a zone of from 1-2 mm. in width, the free enils of the cilia lie practically in a single row the longer and more closely set upper lashes either crossing or overlying the shorter ones of the lower lid. 'Con>uncHva Tliree views i»t hvtiiK eye. showi'iif relntlotiit of eyeltall to |)a)pebr:il fissure aii;ir in the nictitating membrane. Likewise the small group of alveoli sometimes (ouml within the base ot the foil! is regarded as the homologue of the Harderian gland of the lower types. The [>oints at which the slightly curvetl iMJundarieii of the lachrymal lake pass into the more architl «?dges of the eyelids arc er.i|)himi/ .-.ii.i ins, the lach- rymal papillae, each of which is piert(.'tl hy a inin-it.' apc'ratiin- the punctum lacrimalis, th.nt marks the Ixginning of the canals l>y which the tears are normals- carried off from thi.' conjunctival s;ir. Structure of the Eyelids. — The eyelid comprises five layers which, from without inward, .ire: (i) the sh'n, (2^ the siihiHlaneoHS lissiw, ( ,V) the rUH.uii/ur layer, (4) \\wi tarso-fmdal layer VimX (5) ihf ronjiinrliva. The skin covering the outer surface of the eyelids is distinguished hy its unusual delicacy, being thin and l)esel with very fine downy and widely scattered hairs, pro- vided with sehirivHis f. .Hicles ; small sweat glands also (K-cur. It presents numerous Mriliomiati iliK-t Clandu of Moll Cilia 'r:l].ebral ligaments which branch into upper and lo\ver limbs for the attachment of the tarsal plates The upper tarsus is the more arched and br(«der, measuring about 10 mm. or about double the lower t)late in both cases the median ends of the crescents being blunted and less pointed than the lateral. The plates are approximately i mm. in thickness and consist 01 d..astlv felted fibrous tissue, and are blended in front and below with the subcu- tan<.(.us tissue, above with the septum orbitale and the insertion of the lid-niuscles, and behind with the conjunctiva. , 1 ,1, In addition »o preserving the cur^•ature of the lids, the tarsal pl.ttcs lod^e tb. linear series of the Meibomian or tarsal glands ( glandulae tarsalcs). The»e stru. tures, between thity and forty in number in the upper lid and about one-third less in the lov er one, consist of a chief tubular duct, placed vertically ami lined by stratified squamous epithelium, which is Inset with numerous simple or branched, irregr ar, flask-shaped alveoli. The latter contain cuboidal epithelial elements that resemble in appearance and condition those found in sebaceous follicles, to which class, in fact the tarsal glands belong. They secrete an oily substance, sebum palpebrarum, which is .lischarged through the minute punctiform orifices of the ducts that, on everting the edires of the lids, are seen as a row of dark iK>ints just external to the sharp con - juncti^l Uirder of the eyelid. In this manner the latter is kept lubricated, and thus, 'indci- usual conditions, maintains an effective barrier against the overflow of the tears from the conjunctival sac. Within the free edge of the evehds. just in advance of the ur..,al plates lie the glands Of Mcll. and the glands of Zeiss. The former THE EYELIDS AND CONJLNCTIVA. 1445 are coileci tubules, resembling moditied swoat glands, the latter sebaceous jtland:;, the ducts of >vhich usually open close to or into the mouths of the follicles of the eye-lashes. The palpebral conjunctiva lines the ocular surface of the eyelids. Slme the latter are developed as integumentary folds, at first the conjunctiva resembles the skin, but after the temporary closure of the lids, from the middle of the third month until shortly before birth, it loses its original character, and later, Ixithed continu- ously with the secretion of the tear-gland, assumes the translucently rosy tint and general appearance of a mucous membnjnc, as which the conjuncti\a is often regarded. Over the tersi the )>alpebral conjunctiva is so tightly adherent to the underlying fibrous plate, that the tunica propria i^! reierce the tarsi. The li0^iM'^i 1446 HUMAN ANATOMY. m former receives lymph from the skin and muscles, the latter from the Meibomian glands and the conjunctiva. The larger vessels on tin rwiter side pass to the pre- auricular and parotid lymph-nodes, and those on the inner or mesial side follow the tributaries of the facial vein and enter the subtnaxillary lymph-nodes. Nerves of the Eyelids. — The sensory nenes are branches of the ophthalmic and superior maxillary divisions of the trigeminal. The upper lid is supplied mainly by the frontal and supraorbital nerves, the lower lid by the infraorbital nerve. On the nasal side these nerves are supplemented by twigs from the supra- and infratrochlear branches of the ophthalmic, and on th« outer side by terminal filaments from the lachrymal nerve. The main branches lie between the tarsi and the orbicularis muscle, sending branches forward to the skin and l>ackward through the tarsi to tht- conjunctiva and Meifxjmian glands. In .nddition a marginal plexus is formed near the edge of each lid, which supplies the adjacent [larts and the follicles of the cilia. The motor nerve to the levator palpebrae is a branch of the superior division nt the oculomotor ner\'e ; the orbicularis palpebrarum is supplied by the facial, and tlu- involuntary muscle of the lids by fibres from the sympathetic. Practical Considerations. — The Eyebrows. — ^The hair of the eyebrows may be absent, dark brows may show white patches (piebald eyes), or they may hi- entirely white, as in albinos. Incisions in this area, as for neurectomy in supra- orbital neuralgia, should be made in the line of the brow and within the limits of thi- hair, so that the scar which results may be hidden. Dermoid cysts occur in the line of the orbito-nasal fissure of the fa-tus, and are most frequent near the outer end of the brow, under the orbicularis palpebrarum, next to the periosteum. Usually they art no larger than a cherry, and in some instances lie deep in the orbit, when they would be difficult of diagnosis. More rarely they occur at the inner angle of the orbit, when they may be connected with the tlura. In such cases they would be difficult of removal and might be confused with meningocel s. F.piranlhus is a crescentic fold of skin lying over the inner canthus and the inner end of the palpebral fissure. It m:iy be associated with a congenital defect in the briilge of the nose. In many children a slight tendency to it is seen before the briflgc of the nose has reached its full development, while in those races which have little or no bridges to their noses, a slight epicanthus is normal. Until this condition is suspected, these children are often thought to have convergent squint, l)ecausi- the cornea is ne.iri-r f) the skin than in a normal eye. Very rarely the lids may fail to develop (ablcpharia ) ; less rarely a cleft in the margin of the lid is seen, usually to the median side of the centre of the lid (colo- bonia), and most frequently in llie upper lid. 5>ometiniMire fx-ing present. This is probably due to a persistence of the early foetal condition, in w'ln ;i the two lids are adherent. It is called ankylo-blcpharon. Lagophthahnus is an incomplete closure of the lids, and is -ometmes congenital, sometimes the result of paralysis of the facial nerve which supplies the orbicularis muscle. Voluntary contraction of this muscle will usually close the lids in the les>,er degrees of the congenital variety, but in uleep they arc not closed. Since the eye turns up as the lids are brought together, the cornea is concealetl. Ptosis is a drooping of the upper lid, and when congenital is usually associate >sterior portion of the globe. Congenital opacities of the conua may occur and may be completp or partial. In some of the ca-ses reported of the complete variety the anterior elastic lamina was absent, and the anterior layers of the stroma were not laminated as usual, but crossed each other, and among them were found blood-vessels. The partial varieties may consist of a dense white opaque ring at the margin of the cornea, as though the sclera had extended into the cornea, or they may resemble an arcus senilis in which a perfectly clear strip of cornea divides the opaque line from the margin of the sclera. The cornea in health is transparent, and almost all pathological lesions render it opaque. It is the most exposed and therefore the most frequently injured part of the eye. Wounds of the cornea heal readily under favorable circumstances, showing that its nutrition is good, although there are no vessels in it, except within 1-2 mm. of its margin. When the cornea is inflamed, however, new vessels may form from those at the margin and extend a variable distance inward. Under the influence of 1454 Hill HUMAN ANATOMY. initating conditions a superficial inflammation may develop, covering the comea with a new vascular tissue ( pannus). the deeper layers still being bloodless. Owing to a very free nerve-supply the cornea is very sensitive. . As in the sclera, weakness of the cornea leads to bulging, from internal pressure. The c;i ses of weakness may be congenital and acquired. Congenital conical cornea or kerataconus may occur, and it is believed that some congenital defect predisposes to the same condition that occurs in the adult. It is not due to weakening from pre- vious ulceration or injury of the cornea, and the exact cause is not known. A staphyloma of the cornea is a similar condition in which the protuberance is due to the distention of a cicatrix, to the posterior surface of which the iris may be attached (anterior synechiae of the iris). The cicatrix involves all the layers of the cornea, and is the result of a perforating ulcer. If the ulcer had been a non-per- forating one, and the iris did not adhere to its posterior surface, the protrusion of the comea would then be called a keratectasia. If all the layers of the comea to the posterior elastic lamina had been destroyed by the ulcer, and this layer had bulged through the weakened spot like a hemial pouch it would be rolled a keralocele. . ArcHS senilis is usually a sign of old age. Modern investigation indicates that it is due to a fatty Hz^eneration of the substantia propria, the exact nature of the fatty material being . - It first appears as a crescent above, then below, and finally a complete cii • 1. It never interferes with sight. It is occasionally seen in children. The Vascular Tunic. The midoi ocular coat of the eye (tunica vasctilosa ocuH), or uveal tract, consists of a vascular connective tissue sheath, which lies internal to the outer fibrous Fig. i2u8. Anterior cliamber Pupil Circulua arteriosus minor Artery joining ring Vena vorticosa Short ^lost. ctliary .irtery Ciliary nerve I^ong posterior ciliary artery Circulua arteriosus major Anterior ciliary artery Ciliary nerres ■Venous whorl Optic nerve Injected eyeball, showing arrangement of ciliary arteries and of choroidal %'eins. X 3. Drawn from preparation made by Professor Keitter. tunic. It extends from the entrance of the optic nerve to the pupil and includes three portions, which from behind forward are the choroid, the ciliary body and the iris. The choroid and ciliary body are in contact with the sclera, but the iris bends IHE VASCULAR TUNIC. >455 sharply inward and floats in the aqueous humor, incompletely dividinK the spiice anterior to the crystalline lens into a posterior and an anterior i hamlier. The Choroid. — The choroid (tuoica choriuidca) forms the [KKiterior two-third* of the vascular coat. It lies between the sclera and the retina and e.\tends from the optic nerve entrance to the anterior limit of the ^'°- '*°9- visual part of the retina at the ora serrata, its main function being to supply nutrition to the nervous tunic. It is a delicate coat, which has a thickness of .1 mm. near the nerve and gradually diminishes in thickness towards the ora serra*-., where it measures only .06 mm. The tntter surface is roughened by the tra- becule of connective tissue which cross the suprachoroidal lymph- space and connect the choroid with the overlying sclera. The connection is main- tained partly also by the larger vessels and nerves, which lie within this space during their course forward and send branches to supply the choroid. The inner Fig. 1210. SecticMi vA choroid, y. 275. Large vein Artery Surface view o( injected liuman choroid, thowinfi venous radicles converging to (orm larger veins, x iS. surJacenX the choroid is smooth and covered by the pigiv ed cells of the retina, which are so closely attached that they frequently adher. ^ the choroid when the membranes are separated. Posteriorly, the choroid helps to form the lamina crib- rosa, the fenestrated membrane through which the optic nerve-fibres pass ; anteriorly it is continuous with the ciliary body. ■vqMWiiinHi mifi^mmmimm 1456 HUMAN ANATOMY. Fig. 121 1. Portion o( iii)«cted chorioc»pillari» layer ol human choroid. X 130. Structure of the Choroid The choroid consists of four layers, which from without inward, are : (i ) the /amtHa suprathorioidea, (2) the choroid pr^r, which contains the larger vess short anterior side, at right angles lie ligament toward the lens. 'Ir. i^ns ; the ciliary ring, the cil ry pro- 1214. Cuifica Canal ol Schlen it« liipiinHmt niiarf mnsi k- (radial Kbrcai Silcri Meridional fibrvs Ci1iar>- proccaaes Circular fibres Choroi*' Meridional section of ciliary rCKion, showing ciliary biv i «<-s» The ciliary ring, or orbiculus ciliaris, < sts 1 ^aiiooth mm. in width, in advance of the ora serrata. '^-•■' stnicturL , in the absence of the choriocapillaris, its vessti m a lortfjis and returning the blood from the iris and cili.ir bou ■ the vena- its inner surface, delicate meridionally placetl i<>i' Is mak' union of which the ciliary processes are forme* : The ciliary processes constittitc the ^^-tnainder rf. th?- \r.rtfr p ciliary body. They form an annular series of folds, about seventy in m surround the lens and act as points of attachment to its suspend 92 1 of tissue, 4 ' he choroid U.1I directton ticosse. Ofi their ajjpf.ii ince, by th«^ ^ of the ^)er, which . ligament. ^■■li! mmmmmt^KK^ 145* HUMAN ANATOMY. Commencing by the union of several plicationa of the orbiculus ciliaris, they rapidly increase in height and breadth, until they reach an elevation of from .8-1 mm., and then fall suddenly to the iris level. They consist c ' a rich net-work of vessels em- bedded in a pigmented connective tis-sue stroma, lik' >hat of the choroid. The inner surface is covered with a homogeneous - 1< ubrar , which is continuous with the membrana vitrea of the choroid, on the inn< : sur' .e of which is placed the double layer of cells representing the ciliary portion ui the retina (pars ciliaris retina). Each ciliary process Ls composed of a number of irregularly projecting folds « 'icli increase in height as the u'.i is approached. Fig. Coinca 1315. r.mtcr aitniil tint lri( Lmmt aitarU rinc Ciliary proccu' Canal of Schlcmni ^Corneal loop Pnfotal.'nc branch Conjunctival v««a*li Anterior ciliary w 1 Communication between Retinal ve»ael»' choroidal and optic vessels Central retinal vessels Vena vortlcoaa Sapplylng choroid Short posterior ciliary artery .Loiif post' or ciliary artery CommunicatinK twig Inner sheath vessels Outer sheath vessels Communication between optic 'and sheath vessels Diagram illustrating circulation of eyeball. (Lettr.) The ciliary muscle occupies the outer portion of the ciliary body, lying between the sclera and the ciliary processes. It forms an annular prismatic band of involuntary muscle, which in meridional sections has the form of a right-angled triangle, the hypothenuse being the outer side, next to the sclera, and the right angle facing the lens. Its main fibres arise from the sclera and pecti> te ligament, at the corneo-scleral junction internal to the canal of Schlemm, and run in a meridional direction backward along the sclera to be inserted into the choroidal stroma (hence their name, tensor chorioidete). The inner angle of the triangle, at the base of the iris, is occupied by a band of circularly disposed fibres, which consti- tute the circular ciliary muscle of Afiiller. Belween the circular and meridional portions, the fibres assume a radial direction and arc separated by considerable connective tissue, which in the deeply pigmented races may contain many branched f^mmmmmmifmi^mimiKm mmmffmm PRACTICAL CONSIDERATIONS: THE VASCILAR Tl NIC. 1459 ^ ;ginented celb, but in the white races n free from pigment. In hyperopic eyes the .ircular bundlea are usually better developed than in myopic or ■«. The blood-vessels d the ciliary body arise from the anterior and the long ciliary arteries. They form a ring around the root of the iris, the circulus arlrriosus iridis major, from which vessels arc sent inward to supply the iris, ciliary 'iusc!e and ciliary processes. The veins from the ciliary muscle empty chiefly into the anterior ciliary veins; those from the ciliary processes, ..nd a few from the ciliary muscle pass backward and become tributary to the venie voriirostr. The nerves of the ciliary Ixxly are derived from the anterior branches of the long and short ciliary nerves, which form an annular plexus within the ciliary muscle. Four iets of fibres probably exist : ( i ) sensory fibres, largely subscleral in distribu- tion ; (2) vasomotor fibres runni j to the blood-vessel walls ; (3) motor fibres sup- plying; the muscle bund' s ; (4) fibres terminating within the interfascicular tissue of the ciliary muscle. Practical Considerationa. — Congenital coioboma of the choroid, as of the iris, usually occurs in the lower part, along the line of the foetal ocular cleft. In tht defect the sclera r .ows pearly white through the ophthalmoscope, with here and there a little pigm .it and a few ciliary vessels. The retina is frequently absent, but its occasional presence explains why this area is not always blind. In acute exudative inflammation of the choroid, foci of inflammation are seen scattered over th** fundus, and are characteristic. They form yellowish spots between the choroid and retina, and are later convened into connective tissue, binding the choroid and retina together. The two iayent become atrophic finally, the layers of rods and cones disappearing. The exudate may extend into the retina ard even into the vitreous, producing opacities. Sarcoma is the common tumor of the choroid and is usually pigmented. Carcinoma of the choroid is always a metastatic gro"-th, usually a metastasis from a carcinoma of the breast. Adenoma, angioma, and enchondroma of the choroid have been described. FupllUry iMryiii AnMriw entlotlwlluiii Stroma or Irta The Iris. — The iris forms the anterior segment of the vascular tunic and is visible through the cornea. Slighdy to the inner side of its centre is placed an approximately circular opening, the pupil. The Fig. iai6. periphery of the iris, or ciliary border, is attached to the ciliary body behind and receives tibres from the pectinate ligament an- teriorly. The free border, which forms the margin of the pupil, rests upon the anterior surface of the lens. The iris measures II mm. in diameter and about .4 mm. ir. thick- ness. The pupil varies from 1-8 mm. in diameter. The color of the iris, viewed from in front, varies in different individuals and g^ves the color to the eyeball. It is dependent partly upon the amount of pigment within the iris stroma, and pardy upon the density of the pigmentation of the cells on its posterior surface. In light blue eyes, the stroma contains very little pigment and the posterior pigment layer, seen through it, gives it a bluish tint ; whereas in brown eyes the stroma contains so much pigment that the posterior pigment layer is totally obscured and the iris appears brown. The anterior surface is marked by a number of fine, radiating lines, or ridges, which indicate the position of the blood-vessels. Concentric to the pupillary margin, at a distance of from 1-2 mm., is an irregular ridge, the circulus arteriosus iridis minor, which divides the iris into a pupillary and a c'Hary zone which are often differ- ently colored. The pupil is surrounded by a narrow black border. The posterior Sphincter nuKle nvmcntcd [«n lrl. PRACTICAL CONSIDERATIONS: THE IRIS. 1 46 1 The nen'cs of the iris are branches of the ciliary nerves. They follow the course of the blood-vessels and, branching, form a plexus of com'T>iinicating nonmedullated fibres, which supply sensory, motor and vasomotor imr .0. The human iris i)n)b- ably contains no ganglion cells. Practical Considerations. — ^The iris may be partially or completely absent, when by bringing down the eyebrows and partially closinjr the lids, the p;itient will make an effort to shut off the excess of light, as in albinism, and the eye will frequently be nystagmic. A congenital coloboma or deficiency in the iris is usually in the lower pi»rt, and may be associated with a corresponding defect in the ciliary bcxly and choroid. The pupil may be eccentric in position (corectopia), unusually small (microcoria), irregular in shape (discoria), or it may be represented by several pupils (iMilycoria). The pupillary membrane of the icetus, covering the pupil, not infrequently persists for a short time after birth. A portion of it persisting permanently is one of the commonest congenital anomalies of the eye. The color of the iris varies according to the amount and location of the pigment in it. When the coloring matter is absent from the stroma, and present only in the posterior layer of epithelium, the eye is blue. If such an iris is thicker than usual the opacity will be greater and the eye will tend to be grayish. When there is pig- ment only in slight amount in the stroma, the eye is greenish, and when in marked quantity in the stroma, the eye is brown or even black, as in negroes. The deepest tints of brown are usually called black. In albinism there is an absence of pigment in the iris, and in the other parts of the body where pigment is usually found. The eyes are pinkish in color, because the light enters through the tunics and is not absorbed by the choroid and retina, owing to the absence of pigment in it. The retina is therefore intolerant of light, so that the patient tries to shut it out by screwing up the eyebrows and lids, and by contraction of the iris. He will frequently show nystagmus or oscillation of the eyeball, and amblyopia, or subacuteness of vision. The two eyes are not always of the same color, and even in the same eye, one part of the iris may be blue and another brown (piebald iris). One eye may have Its color permanently changed as the result of inflammation, so that the difference in color may be an important diagnostic sign of previous disease The iris acts as a colored curtain to shut off excess of light, as more or less light is necessary for the definition of images. Too much light impairs the defini- tion and injures the retina. The pupils are usually of equal size in health, and any marked inequality has a pathological significance. The iris does not hang in a verti- cal plane, but is pushed slightly forward and supported at its pupillary margin by the lens. If the lens is absent or dislocated, the pupillary margin of the iris may tie seen to quiver with the movement of the eyes. The ins in spite of its great vascu- larity may not bleed much when wounded, probably because of the contraction of its abundant muscular fibres. The iris is continuous with the ciliary body, and through the latter with the choroid, the three taken together making up the uveal tract, or middle tunic of the eye. Any inflammation of the one may easily spread to the others. This usually occurs, but as the inlammation is predominant in one, we speak of an iritis, a cyclitis, or a choroiditis, and not of the whole pro- cess as a uveitis. In an iritis the exudation which affects the stroma as well as the anterior and posterior aqueous chambers can be studied by inspection. It thickens and discolors the iris, renders the aqueous fluid turbid, and leaves a deposit on the contiguous surfaces of the cornea and lens. Since the pupillary margfin of the iris is in confcict with the lens on the posterior surface the exudate causes adhesions of this margin to the lens (f)osterior synechia;). Since the pupil is contracted in inflammation, when these adhesions form, dilatation of the pupil normally or under the influence of atropine, gives rise to a very irregular pupil, the unattached portion dilating, the attached portions not. Sight need not be affected if the pupil is large enough. If the whole margin of the pupil is attached to the lens, or the pupil is occluded by exudate, the normal flow of fluid from the posterior to the anterior chamber cannot take place, and glaucoma (vide supra), 1462 HUMAN ANATOMY. a disease due to increased intraocular tension from retention results. It is neces- sary, therefore, in iritis to keep the pupil dilated, so as to prevent such adhesions as far as possible. The Nervous Tunic. The Retina. — The retina, the light perceiving portion of the eye, with its con- tinuation, the optic ner\'e, in contrast to the other sense organs represents a portion of the brain itself, and develops in close. connection with it. It is a delicate mem- brain, which extends from the optic nerve entrance to the pupillary border. The functionating portion, or pars optica retina, reaches as far forward as lY\eoraserrata, where it termmates as an irregular, wavy line ; anterior to this the retina is repre- sented by an atrophic portion, consisting of the double layer of cells co\ering the Fibre layer Ganglion cells Inner plexifortn layer Cerebral layer Sustentacular cell Neuroepithelial laj'er Pigmented layer Inner nuclear layer (bipolar nerve-cells) Outer plexiform layer 1 Outer nuclear layer (bodies of visual cells\ Rods and cones Pigmented layer Choroid Diagram illustrating structure ot retina and relations of three fundamental layers. (Gteeff.) ciliary body and the iris, already referretl to in the description of these structures, and known respectively as the pars ciliaris retina, and pars iridica retina. The pars optica retinae is closely ap]>lied to the inner surface of the choroid and is in contact with the hyaloid membrane investing the vitreous body. It grad- ually diminishes in thickness from .4 mm. at the posterior pole to .1 mm. near the ora serrata. During life the membrane is transparent and possesses a purplish red color, owing to the presence in its outer layers of the so-called visual purple ; after death the retina rapidly becomes opaque and has the appearance of a grayish \cil. The inner surface is smooth and presents at the posterior pole of the eye, a small circular or transversely oval yellow spot, the maatla lutea, from 1-2 mm. in diam- eter. At the centre of the macula is a small depression, the fovea centralis, fron .2-. 4 mm. in diameter, in which position the retina is reduced in thickness to . i mm. The entrance of the optic nerve forms a conspicuous spot of light color, situatetl 3 mm. to the na.sal side of the macula lutea. This area, called the optic papilla or porus opticus, is in form of a vertical oval, about 1.5 mm. in its horizontal and THE NERVOUS TUNIC. 1463 1.7 mm. in its vertical diameter. At its centre is often seen a well-marked excavation, the optic cup, from the bottom of which emerge the blood-vessels which supply the retina. Bein)^ insensible to visual impulses, the optic entrance corresponds to the ' ' blind-spot. Structure of the Retina. — The retina is composed of nervous elements which are supported by a specialized sustentacular tissue or neuroglia. Morphologically it must be considered as composed of two lamellx, which correspond to the outer and inner walls of the optic vesicle (page 1482) from which it is developed. These fun- damental divisions of the retina are : ( i ) the external lamella, the pigmented layer on the outer surface ; and (2) the internal lamella, which includes the remaining layers of the retina. The inner lamella may be subdivided further into the neuroepithelial and the cerebral layers. Sections of the retina, made perpendicularly to its surface (Fig. 1 220), show under the microscope from without inward the following layers : — I. OirrRK I.AVKR OV OPTIC VESICLK IR INNBR LAYER OF OrTIC VBSICLB {•■ Layers of the Retina. Pig^mented layer I Pigmented layer J. Layer of rods and cones 3. Layer of bodies of visual cells or outer nuclear layer 4. Outer plexiform layer 5. Layer of bipolar cells, or inner nuclear layer 6. Inner plexiform layer 7. Layer of ganglion cells 8. Layer of nerve-fibres Ncuro- ' epithelial layer Cerebral layer To these nervous layers must be added two delicate membranes, ( i ) the membrana limitans interna, which bounds the inner surface of the retina, and (2) the membrana limitans externa, which lies between the outer nuclear layer and the layer of rods and cones. These membranes represent the terminal portions of the supporting neu- rogliar fibres, ox fibres of Miiller. The pigmented layer, formed of deeply pigmented cells, constitutes the most external layer of the retina and represents the xjuter wall of the foetal optic vesicle. It is composed of hexagonal cells, from .012-.018 mm. in diameter, the protoplasm of which is loaded with fine, needle-shaped crystals of pigment (fuscin). The outer portion of the cells is almost free from pigment and con- tains the nucleus. From the inner border fine proto- plasmic processes extend inward between the rods and cones of the neuroepithelial layer. Under the influence of light, the pigment particles wander into these processes and, under such conditions, the pigmented cells may remain attached to the retina when the latter is separated from the choroid. Ordinarily, the pigmented layer ad- heres to the choroid and, hence, was formerly considered to be a part of that membrane. The pigmented cells are separated by a distinct intercellular cement substance and in some of the lower animals contain colored oil droplets and particles of a highly refracting myelin-like substance {myeloid granules of Kiihne). The layer of rods and cones, although usually described as a distinct stratum, is only the highly specialized outer zone of the layer of visual cells and, therefore, constitutes the outer portion of the neuroepithelial division of the retina. It is com- posed, as its name indicates, of two elements, the rods and the cones, which arc the outer ends of the rod and cone visual cells. They are closely set, with their long axes perpendicular to the surface of the retina. The rods far outnumber the cones, except in the f< i centralis, in which location cones alone arc found. In the macula each cone is sui : unded by a layer of rods ; elsewhere the cones are separated by intervals occupied by three or four cones. The rods of the human retina (Fig. 1221) have an elongated, cylindrical form, and measure approximately .060 mm. in length and .020 mm. in diameter. Each rod Pigmented cells from outer layer of retina ; lurface view. X 250. 1464 HUMAN ANATOMY. Fig. ijjo. Fibre o( Miiller is composed of an outer and an inner segment, of about equal length. The outer segment possesses a uniform diameter, is doubly refracting, and readily breaks up into minute disks. It is invested with a delicate covering of neurokeratin, contains myeloid (Kuhne) and is the situation of the visual purple or rhodopsin. The inner rod segment is somewhat thicker and has an ellipsoi. lal form. It is siri' refracting, homogeneous in structure (rapidly becoming granular after death) and im its inner extremity sends the delicate rod-fibre through the external limiting mciMbrane into the outer nuclear layer where the nucleus of the rod visual cell is found. The cone visual cell is composed of the same general divisions as the rod-cell, including the specialized outer part, the cone, and the body within the external nu- clear layer. The cones are shorter than the rods, and, except in the fovea, have a length of .035 mm. Elach one (Fig. 1221) is comjxjsed of an outer narrow cone- shaped segment, and an inner broader segment, which is distinctly ellipsoidal in form, with a diameter of .060 mm. The inner segment is double the length of the outer, and is continued inward as the conefibre with its nucleus in the outer nuclear layer. In the fovea, where the cones alone are found, they are of approximately the same length as the rods, and possess about one half the usual diameter. The outer nuclear layer, the inner portion of the neuroepi- theleal layer, is composed of the bodies of the rod and cone visual cells, which show chiefly as the nuclei, the so-called rod- and cone- granules. The rod-granules oc- cupy an elliptical enlargement of the attenuated rod-fibres. They exhibit a transverse striation and are placed at varying levels within the layer. The rod-fibres are con- tinued as a thin protoplasmic pro- cess into the outer reticular layer, where they form small end-knobs which are associated with the outer terminals of ihe small nerve-cells, the rod-bipolars. The cone-gran- ules are less numerous than those of the rods, display no transverse markings, and are found only in the outer portion of the nuclear layer, near the external limiting mem- litternal limitinR membrane Ganglion cell Fibres of Miiller Bipolar nerve cells Blood-vesMi Layer of visual cells Nucleus of cone- cell Cone- Rod Pigment layer Section of human retina from near posterior pole. brane. The cone-fibres, the attenuated bodies of the cone visual cells, are broader than the corres|K)nding parts of the rods and are continued through the outer nuclear layer as far as the outer portion of the external plexiform layer, where they end with a broad base, from which delicate processes extend inward to interlace with the terminal arborizations of the cone-bipolars. The outer nuclear layer is about .05 mm. in thickness. The outer plexiform layer is a narrow granular looking stratum, between the outer and the inner nuclear layer, and constitutes the first of the cerebral layers of the retina. It is composed of ie dendritic arborizations of the bipolar nerve-cells of the succeeding layer, which lie 1 « close relation with the centrally directed proces- ses from the foot-plates o- the cone-cells and with the end-knobs of the ro«i-fibres. In addition to these constituents of the plexiform layer, numerous fibres arising from the protoplasmic processes of the horizontal cells of the inner nuclear layer also take part in its formation. THE NERVOUS TUNIC. •465 Fig. 1 221. The inner nuclear layer, the most complicated of the retinal strata, measures .035 mm. in thickness near the optic disc. It contains nervous elements of three main types — the horizontal cells, the bipolar cells, and the amacrinc cells — and, associated with these, the nuclei of the sustcntacular cells. The horizontal cells form the external layer, and were formerly included in die outer plexiform layer. They have flattened cell-bodies and send out from five to seven dendrites, which divide into innumerable branches and, passing into the outer plexiform layer, terminate in close association with the Ixises ot the rotl and rone visual cells. Each horizontal cell possesses also an axone, which is directed outward through the outer plexiform layer, and ends in a richly branched arborization alxiut the visual cells. A second type of large horizontal cells is also described, some of which send axis-cylinder pro- cesses through the inner nuclear layer to form terminal arborizations in the inner plexiform layer. The function of the horizontal cells is not well understood, but they prob- ably serve as a.ssociation fibres between the visual cells. The bipolar cells, the ganglion cells of this layer, are of two chief varieties, the rod-bipolars and the cone- bipolars. They are oval cells, each sending an axone inward toward the inner plexiform layer, which ends in communication with the large nerve-cells of the ganglion cell layer, and a dendrite outward which is associated with the end terminals of the visual cells and with the arboriza- tions of the horizontal cells. The dendrites of the rod- bipolars form an arborescence of vertical fibrils, which enclose from three to twenty end knobs of the rod -fibres, whilst their axis-cylinders pass entirely through the inner plexiform layer and usually embrace the cell-body of one of the lai^e ganglion cells. The dendrites of the cone- bipolars, on the other hand, bear horizontal arborizations "•hich interlace with the fibrils from the foot-plates of the .le-cells. Their axones penetrate less deeply into the .ner plexiform layer than do those of the rod-bipolars, coming in contact at various levels with the peripherally directed dendrites of the ganglion cells. The amacrine cells are placed in the inner portion of the nuclear layer. Formerly considered as sustentacu- lar elements, they are now recognized as nerve-cells, although, as their name indicates, no distinct axone can be demonstrated. They pr-ssess, however, richly branched dendritic processes, which ramify in the inner plexiform layer and end either as the brush-like arborizations of the disuse amacrines, or as the horizontally branching arborizations of the stratiform amacrines. A third type, known as association amacrines, is also described. They connect widely separated amacrine cells of the same layer (Cajal). The nuclei of the sustentacular cells, the fibres of Muller, will be described later (page 1466). The inner plexiform layer, .04 mm. in thickness, appears granul.ir, similar to the corresponding outer zone, and is composed of the interlacing axones of the bipolar, amacrine and horizontal cells 'rom the inner nuclear layer and the dendrites of the large ganglion cells in the sub'acent retinal layer. Intermingled with them arc also the fibres of Miiller, which form conspicuous vertical strise, with lateral offshoots within the stratum. The layer of ganglion cells, consists, throughout the greater part of the retina, of a single row of large multipolar neurones, each with a cell-body containing a vesicular nucleus and nucleolus and showing, like many other ganglion cells of the central nervous system, typical NissI bodies and a fibrillar structure. Near the macular region, the ganglion cells are smaller but more numerous and arranged as several superimposed layers; toward the ora serrata, on the contrary, the individual Visual cells Irom human ret- ina, A, cone.€c11; B, rodH-t;U, tj, b, outer and inner segments ; c, attenuated bodies (Ahres). with nucleus [d) and central ends («*); em, position of external limiting membrane. X 750. (Grteff.) 1466 HUMAN ANATOMY. Fig. 1232. cells are .separated by considerable intervals. Their axones, or a.xis-cylinder pro- cesses, pass inward and become the nerve-fibres of the fibr layer. Converging toward the optic entrance, they become consolidated into the optic nerve and pass to the brain. The dendrites of the ganglion cells, one to three in number, run outward into the inner plexiform layer and end as richly branched arborizations. These, like those of the amacrine cells, terminate either difiusely, or in horizontal ramifica- tions limited to definite strata, in connection with the centrally directed processes from the bipolar cells. The nerve-nbre layer is composed silmost entirely, but not exclusively, of the axones of the ganglion cells of the preceding layer. The individual fibres, from .005-. 05 mm. in diameter, are collected into bundles of varying size, which take a horizi 'ntal course and converge toward the optic disc. The are normally devoid of medullary sheaths, but acquire them after passing through the lamina cribrosa of the sclera. A few of the fibres are centrifugal, arising from ganglion cells within the brain, and terminate apparently in connection with the association amacrines of the inner nuclear layer. In the macular region, the nerve-fibres are prac- tically absent, those from the retinal area lying direcriy to the temporal side of the macula arching above and below the yellow spot. From the macula itself, a special strand, known as the maculo-papillary bundle and composed of about twenty-five fasciculi, passes directly to the nerve-disc. The suBtentacular tissue, the neuroglia of the retina, exists in two forms — as \}as. fibres 0/ Miiller and as the spider cells. The fibres of Miiller are modified neuroglia fibres which pass vertically from the inner surface of the retina through the succeeding layers as far as the bases of the rods and cones (Fig. 1222). The inner extremities of the fibres possess conical expansions, which are in apposition and form an incomplete sheet, known as the membrana limitans interna. As the fibres traverse the retmal layers, they give off delicate lateral oflEshoots, which break up into a fine supjxjrting reticu- lum. Within the inner nuclear layer each fibre presents a broad expansion, in which is situated the oval nucleus of the sustentacular cell, the fibre of Miiller. After traversing the outer nuclear layer their broadened peripheral ends come into contact and form a continuous sheet, the membrana limitans externa. From the latter deli- cate offshoots continue outward and embrace the bases of the individual rods and cr ,es. In addition to the robust fibres of Muller, neuroglia cells, in the form of spider cells, are found in the nerve-fibre and ganglion cell layers. These cells send out long delicate processes which extend between the processes and cells and thus help to support them. The Macula Lutea. — The structure of the retina undergoes important modifi- cations in two areas, at the macula lutea and at the ora serrata. In the former the ganglion cells increase rapidly in number as the macula is reached, so that instead of forming a single layer they are distributed in from eight to ten strata. The inner nuclear layer is also increased in thickness. Within the fovea centralis, however, in order to reduce to a minimum the layers traversed by the light-rays, the cerebral layers are almost entirely displaced, only the absolutely essential retinal strata — the pigment cells and the visual cells with their necessary connections — being retained within the area of sharpest vision (Fig. 1223). On approaching the fovea, the ganglion cells rapidly decrease in number, until at the centre of the depression, they are entirely absent and the ner\'e-fibre layer, therefore, disappears. The bipolar Supporting fibres of Muller from retina of ox; Golei preparation. THE NERVOUS TUNIC. 1467 cells are present as an irregular layer within the fused remains of the two plexiiurni layers. The most conspicuous elements are the visual cells, which in this position are represented solely by the cones, which have about twice their usual length and thickness, the increase in length being contributed by the outer segments. The cone-cell nuclei become removed from the external limiting membrane ; the cone- fibres are therefore lengthened, pursue a radial direction, and constitute the so-callctl Iiilcrnal limiting membrane Inner plexiform layer Ganglion cells Bipolar cells Outer Pigmented Cone Cones plesiform layer layer visual cells Section of human retina through fovea centralis. ^ Ho. fibre-layer of Henle. Opposite the centre of the fovea, the choroid is thickcneil by an increase in the choriocapillaris. The yellow color of the macula is diie to a diffuse coloration of the inner retinal layers. The Ora Serrata. — The visual part of the retina ends anteriorly in an irregu- lar line, the ora serrata. Within a zone of about i mm. in width, the retina dimin- ishes in thickness from .50 to .15 mm., in consequence of the abrupt disappearance of its nervous elements. The rods disappear first ; then the cones become rudimen- tary, and finally cease ; the ganglion cells, nerve-fibre layer and inner plexiform layor fuse, and the two nuclear layers unite and lose their characteristics, most of the nuclei present being those of the supporting fibres of Miiller, which are here highly developed. These elements p^^ ^ continue beyond the ora serrata (Fig. 1224) as the transparent cylindrical cells composing the inner layer of the pars ciliaris retinte, the densely pigmented cells of the outer layer being a direct continuation of the retinal pigmented cells. These two strata of cells are prolonged over the ciliary body and the iris as far as the pupillary margin, over the iris constituting the pars iridica reiinie. As the columnar cells pass forward, they gradually decrease in height, and at the junction of the ciliary body and the iris the cells of both layers become deeply pig- mented, with consequent masking of the boundaries of the individual elements. The cells of the anterior layer are of additional interest as gi\ ing rise to the dilatator muscle of the iris. The aggregation incident to the convergence of the nerve-fibres from all parts of the retina produces a marked thickening of the fibre-layer around the optic disc, and as the fibres turn outward to form the optic nerve the other layers of the retina, together with those of the choroid, suddenly cease. On the temporal side a narrow meshwork of intermediate tissue separates the nerve-fibres from the other retinal strat but at the nasal side this tissue is absent. The ganglion cells dis- appear first whilst the pigmented cells, with the lamina vitrea of the choroid, extend furthest inward. The blood-vessels of the retina are deri"'a from .- single artery, the arleria centralis retina, which enters the optic nerve at a point from 15-20 mm. behind the eveball, and, with its accompanying vein, runs in the axis of the nerve and IHpoluceUt' VlsiuU cellsi Pitfilienlfd ,jm Layer Section of human retina through ora serrata. showing transition of pars optica into pars ciliaris. x 165 1468 HUMAN ANATOMY. emerges slightly to the nasal side of the centre of the optic disc. Here the artery divides into two main stems (Fig. 1225), the superiorand inferior papillary branches, each of which subdivides at or near the disc-margin into superior and inferior nasal and temporal branches which run respectively mesially and laterally, dividing dichotomously as end arteries, no anastomosis existing. The macular region is supplied by special macular branches, the center of the fovea, however, being free from blood-vessels. The larger branches from the central artery course within the nerve-fibre layer, and send fine twigs peripherally inward to form an inner and an outer plexus, the former on the outer surface of the inner plexiform layer, and the latter within the inner nuclear layer. Beyond the outer plexiform layer the vessels do not penetrate, the visual cells being dependent for their nourishment upon the choriocapillaris of the choroid. At the nerve entrance an indirect communication exists between the arteria centralis and the posterior ciliary arteries, through the medium of the small branches which constitute the circulus arteriosus Zinni. Fig. laas. I'eniporHl -Vusal Normal fundus of right eye as seen with ophthalmoscope ; central retinal vessels seen emerxing from optic aerve; arteries are lighter, veins darker vessels; fovea centralis shows as light point in macular region, which lies in temporal field and is devoid of large vessels. The l)nnphatics of the retina are represented chiefly by the perivascular lym- phatic spaces which surround all the veins and capillary blood-vessels. These spaces may be injected from the subpial lymph-space of the optic ner\'e, and by the same method communications may be demonstrated between (i) this space and the interstices between the nerve bundles which converge toward the optic papilla, ( 2 ) a space between the membrana limitans interna and the hyaloid membrane of the vitreous, and (3) a narrow cleft between the pigmented cells and the layer of rods and cones. Practical Considerations. — All pathological conditions of the retina ap- pear as opacities, and thus interfere with sight. The medullary sheaths of the optic nerve-fibres end at the lamina cribrosa. Rarely the sheaths around these may extend some distance into the retina, showing as a white striated margin around the optic disc and continuous with it. Sometimes the blood-vejascls of the retina may enter at the margins of the optic disc, instead of at its centre, as usual, which IS then free of vessels and very pale. At the entrance of the optic nerve, the fiinsparency of the retina is lessened by the thickening of its fibre-layer PRACTICAL CONSIDERATIONS: THK RETINA. 1469 The integrity of the central artery of the retina is necessary to the preservation of sight. The branches of this vessel are distributed to the retina only, and have no communication with those of the other coats, nor do they anastomose with one another. If the main artery or one of its branches is plugged with an embolus, the area supplied by the blocked vessel is then deprived of sight. The retina may undergo inHammatory change in nephritis, syphilis, diabetes, and other constitutional diseases. Of all these inriammations of the retina, that tlue to kidney disease (albuminuric retinitis) is the most characteristic. Besides the signs of general intiammation, as haziness of the retina, choked disc, distended retinal arteries, or hemorrhages into the retina, pure white or even silvery patches often occur ; they are due to fatty degeneration. Retinitis without these charac- teristic changes may occur from albuminuria, so that the urine should be examined in all cases of retinitis. The retina between the optic nerve and the ora serrata is held in apposition to the choroid only by the support afforded by the vitreous body. It may be readily detached from the choroid by such causes as injury, e.xtravasaiion of blood or serum between the two layers, or by tumors of the choroid. In contusions of the eye the retina is sometimes torn alone, although this is rare. The retina does not tear as easily as the choroid, as is shown by the fact that in ruptures of the choroid the retina is generally not lacerated. Glioma is the only tumor found in the retina, and occurs exclusively in children, usually under three years of age. A rare tumor arising from the pars ciliaris retinse has been described, to which the name teralo-tieuroma has l)een applied by Verhoeff. The Optic Nerve. — The extraocular portion of the optic nerve has been de- scribed elsewhere (page 1 223). Likewise, the three sheaths — the dural, the arachnoid Fig. 1226. Phyaiologicml cxca%-ation Lamina cribroMa Fibre-layer ^^-j^J r . j ; Subarachnoid AfMce Subdural space Pial aheath Central retinal veaaela within optic nerve Section d eyeball through entrance of optic nerve. X ». and the pial — which, with the subdural and the subarachnoid lymph-spaces, are con- tinued over the nerve as prolongations of the corresponding brain-membranes (page 949). On reaching the eyeball, the dural sheath bends directly outward, its fibres commingling with those of the outer third of the sclera (Fig. 1226) ; the arachnoid ends abruptly on the inner wall of the intervaginal space ; whilst the pia arches outward to form part of the inner third of the sclera, but sends longitudinal fibres as far as the choroid. As the nerve-fibres enter the eyeball, for convenience assuming that they are passing from the brain toward the retina, they traverse a fenestrated I470 HUMAN ANATOMY. Bkmd-vraicl Bundini '*f nrr\x-librr> IntFTfaadaiter connective liMue TtamverK Mction o{ part of oMic nerve. ahowin( Mvcnl taKkuli of nerve-nbrei. X 125. membrane, the lamina cribroaa. which is formed by interkcinu bundles from the inner third of the sclera and from the pial sheath. As they penetrate the lamina cribrosii they lose their medullary sheaths ; in consequence the optic nerve is reduced one third in diameter. The intervaginal lymph-space ends abruptly, bemg separated from the choroid Fio. 1 217. by the fibres of the pia which arch outward to join the sclera. The nerve projects slightly into the eyeball on account of the thickness of the layer of arching nerve- fibres and forms, therefore, a circular elevation, known as the optic papilla or optic diac, about 1.5 mm. in diameter, the center of which is occupied by a fun- nel-shaped depression, the so-called physiological exca- vation. The axis of the nerve is occupied by the central artery of the retina, which gives off minute branches for the nutrition of the nerve, that anastomose with the pial vessels, and, through the circulus arteriosus Zinni, with branches of the posterior ciliary arteries. When seen in transverse sections (Fig. 1227). 'he optic ner\e appears as a mosaic of irregula/ polygonal areas composed of bundles of medullated nerve-fibres surrounded by connective tissue envelopes. Although provided with medullary sheaths, the optic fibres are devoid of a neurilemma, in this respect agreeing with the nerve-fibres composing the central nervous system. The entire nerve corresponds to a huge funiculus, the perineurium being represented by the pial sheath, and the endoneurium by the interfascicular septa of connective tissue prolonged from the pia between the bundles of fibres. Numerous connective tissue cells occur along the strands of fibrous tissue. Practical Considerations. Any disturbance of the optic nerve-fibres passing from the retina to the cortex of the brain (page 1225) will cause disturbance of vision, and within certain limits the lesion may be localized by the character of the symptoms produced. The most characteristic symptom from a lesion on one side ' ^ the chiasm is a homonymous lateral hemianopsia, — that is, the right or the le. ich eye will be blind. This is explained by the fact that the optic tracts a. . up of fibres coming from the corresponding lateral halves of both retinae, — ...., the fibres from the right half of each retina pass to and make up the right optic tract, and pass therefore to the right half of the brain. It will thus be seen that anything com- pressing the optic fibres of the right side behind the chiasm, for instance a hemorrhage, would produce a blindness — more or less complete according to the extent of the fibres involved — of the right half of each eye. Since most of the optic fibres enter the lateral geniculate bodies, a lesion there always causf-5 hemianopsia, or half-eye blindness. Lesions of the optic thalamus, or of the superior quadrigeminal body, may also by compression of the adjacent optic tract produce hemianopsia. In the optic radiation are other than optic fibres, so that hemianopsia may or may not follow lesions in that tract, according to whether optic fibres are involved or not. The exact course of the visual fibres in the optic radiation is uncertain. If the visual area of the brain cortex is involved by the lesions, no other symptoms will be present, but the hemianopsia will be complete and homonymous — that is, the corresponding halves of the two eyes will be blind. THE CRYSTALLINE LENS I47« -n()u> 'he • •he ht'inui ' nostitis '•ssure half Ma). this nee «t, u- distun lit' blH"ltM.'ss >'l le -that I ol « he opiit A.- ^cope arkfd ' .s\»ollci, Aol "di. ii. i .Hidition ro .1 j»r«tnides li.i*. iwc urt'- '>ptiv rHiintis. Ilv No per Vpend »,*» ol the .«{ th*- brain. .-.urh irciim- on \\y. whole, v-eption, -f has no thr various \\ t! c form of If the lesion affect the chiasm, as from tumor;! of ti try fNxly. d the body of the sphenoid bone, tuberculous or sypli. iiv, •- uMJn on the mesial portion of the chiasm involving the decu of each eye supplied by these fibres will be blind (h Since the nasal half of each eye perceives the temporal variety ot half-blindness is called bitemporal kemianopiir If the optic fibres of one side in front of the chiasn of vision will affect one eye only, so that the occurreno eye, without other ktiown cause, with good sight in the in front of the chiasm. Inflammation of the intraocular end of the optic m or papilla— ^\\ei rise to the condition to which the nar- is applied, which is then recognizable with the ophth or independently of the signs of inflammation there are and the evidence of mechanical compression, so that t! into the vitreous- beyond ^ to ^ mm., the phenomc sent. This variety of papillitis, as well as more mo< constitutes one of the important symptoms of brain a cent, of the cases. The development of the papilbuK dot upon the size of the growth, nor upon its situ - -•n, ex' medulla are less apt to originate optic neuritis th. iiose ii Usually a bilateral condition, it is sometimes un. ateral, dei stances it suggests that the cerebrum is the seat o! the grow is. in favor of the tumor being on the same side as the neuriti- however, optic neuritis, although an important symptom localizing significance. Other intracranial causes of optic ii' u types of meningitis (when the ophthalmoscopic picture oft' •' ^y^, the so-called "descending nearitis " ), abscess and soft- ening of the brain, cerebritis, hydrocephalus and aneu- •^■c-. ijjii. rism. In addition to the intracranial causes of papillitis, this phenomenon may arise from a general infection — for example, influenza, syphilis, rheumatism, smaU-pox, etc. — and is then known as infectious optic neuritis. It is also caused by various toxic agents, by anaemia, by menstrual disturbances, nephritis, and other constitu- tional disorders (de Schweinitz). Injuries of the optic nerve are most frequently the result of fractures of the base of the skull at the optic foramen, the nerve being injured by the fragments. It may be wounded by foreign bodies entering the orbit, with or without injury of the eyeball. The Crystalline Lens. The lens, the most important part of the refractive apparatus of the eye, is a biconvex body situated on a level with the anterior plane of the ciliary body, from which it is suspended by the suspensory lif^ament, or zonule of Zinn. Its anterior surface supports the pu- pillar>- margin of the iris, and its posterior surface rests m a depression, the patellar fossa, on the anterior sur- face of the vitreous body. It is completely transparent and enclosed in a transparent elastic membrane, the lens capsule. Together with the capsule, the lens measures from 9-IO mm. in its transverse diameter, and about 4 mm. in thickness from pole to pole. The convexity of its two surfaces is not the same, that of the posterior being greater than that of the anterior. Neither are these convexities constant, since they &re continually changing with the variations in lens-[X)wer incident to viewing distant or near objects. The radius of curvature of the anterior surface is approxi- mately 9 mm. and that of the posterior surface 6 mm. when the eye is accommodated Meridional lection of human lens and its cafMule; anterior epithelium and transitional sonc are seen, v 7- (Babuchin.) '472 HUMAN ANATOMY. Fio. FracnicnU of iaoUicd l«»-flbrM; A. from superficial laycri; B. fiom dL'cpcr laycni C, young fibres with nuclei. X 275. for disUnt objects ; these radii are reduced to about 6 and 5 mm. respectively in accninmodation for near objects. The anterior surface is therefore more afft-ctwl in the act of accommodation, the lens becomes more convex and its aniero-posterior diameter increases from 4 to 4.4 mm. The superficial portion of the lens beneath the capsule is compf)sed of soft c«>mpres8ible material, the substantia (ortUalis ; the consistency gradually increases toward the centre, especially in later life, so that the central portion, the hmcUhs lentis, is much firmer and dryer. The atructure of the lens includes the capsule and its epithelium and the lens subsunce. The capsule, which entirely surrounds the lens, is a transparent, struc- tureless, highly elastic membrane, which, while resistent to chemical reajjents, cuts easily and then rolls outward. It is thickest on the anterior surface, where it measures from .010-.015 mm., and thinnest at the posterior pole (.005-. 007 mm. ). In the adult the lens b devoid of Uood- vessels, but during a part of fcetal life it is surrounded by a vascular net-work, the tunica vascuiosa lentis, which is supplied chiefly by the hyaloid artery. This temporary vessel is the terminal branch of the central artery of the r ina and passes from the optic disc forward thr ...j^h the hyaloid canal or canal of Cloquet in the vit- reous to the posterior surface of the lens. The vascular lens tunic and the hyaloid artery are temporary structures and usually disappea be- fore birth. Exceptionally they may persist, the tunic being rfnresented by the pupillary membrane and the artery by a fibrous strand within a.d vitreous, stretchmg from the optic disc towards the lens. The capsule probably represents an exudation product t\ the cuticular elemedts from which the lens- substance is developed. The anterior portion of the capsule is lined by a sin- gle layer of flat polygonal cells, the epithelium of the lens capsule, which represents morphologically the anterior wall of the original lens-vesicle (page 1480). On ap- proaching the equator of the lens, these cells become elongated, and gradually converted into the young lens- fibres, the nuclei of which form a curved line, with its convexity forward, in the superficial part of the lens. The lens-substance is composed of long flattened fibres, the cross-sections of which have a compressed hexagonal outline, from .005-. 01 1 mm. broad and from .002-.004 mm. thick, held Fig. 1231. together by an interfibrillar cement substance. These fibres are modified epithelial elements, which develop by the elongation of the original ectoblastic cells of the poste- rior layer of the lens-vesicle. The subsequent growth of the lens depends upon a similar modification of the anterior capsule-cells, the re- gion where this transforma- tion occurs being known as the transitional zone. The individual lens-fibres vary greatly in length, those form- ing the outer la- ■ -^ being longer and thicker than those which constitute the nucleus of the lens. T^i edges of the fibres are finely serrated, and, as the points of the serrations of a '- nt fibres are in contact, fine intercellular channels are left for the Fig. IJ30. Lens-fibres seen in transverse section. X s8o. Adult crystalline lens, showinic Iciia-stars; A, anterior; *. posterior surface ; radiating lines of juncture meet at central area. X 4- (Arnold.) THE VITREOUS BODY. U73 paatage of nutritive fluid. The fibres are su arranged that their ends terminate alun^ definite radiating stria?, or /ens-stars, which in the yuun>; lens are three in number on each surface. In the adul' lens additional rays incre;u>e the number ti) from six to stinct but distinguishable with the ophthalmoscope. The I the [X)le of one surface of the lens terminate at the end of I the other, and conversely ; the intervening fibres take up In adult life the lens-fibres become more condensed, the lens loses its clear ;. v>arance, and assumes a yellowish tint. This change affects the nucleus first and the periphery later, coincidently the lens becoming less elastic as the result of its loss of water. nine, the stri^ bein) lens-fibres which cf->'- one of the ra.'' intermediate [» Practical Contiderationa. — The lens may be congenitally absent (aphakia), or it may be abnormal in size, shape, position, or transparency. Its anterior or posterior surface may be abnormally convex (lenticonus). Congenital anomalies of position (ectopia Icntis) occur rarely. The lens may remain in its fa-tal position in the vitreous chamber, or it may be displaced in an equatorial direction from faulty development and weakness of some part of the suspensory ligament. This weakness usually occurs below so that the lens moves upward. The ligament may be absent in its whole circumference, when the lens may be protruded into the anterior chamber. Cohboma or parti^ deficiency of the lens is very rare. It is with comparative frequency associated with a similar defect in the iris, ciliary body and choroid, and, like it, is usually in the lower portion. A defect of the corresponding part of the suspensor)' ligament is occasionally present. Traumatic luxation of the lens may take place into the vitreous or aqueous chamber. It may occur laterally through the coats of the eyeball into the capsule of Tenon or under the conjunctiva. That into the vitreous is most frequent. The capsule of the lens is strong and elastic. It is at the same time brittle, breaking like thin glass when torn as by a sharp instrument For this reason it is sometimes called the vitreous membrane. The anterior layer of the capsule is con- siderably thicker than the posterior, and is more liable to pathologic' changes, pro- ducing opacities. Wounds of the capsule f)ermit the aqueous fluid lu reach the lens fibres, which then become swollen, opaque, and finally disappear from the dissolving action of the aqueous. Advantage of this is taken in the needling operation (dis- cission ) for the removal of a cataract. In chil'* Hi ''e 'ens substance is of nearly equal consistency throughout, but as age advan ei thf. the nude ■■■ ^^ old age tit are inte'fe reflection older peo,.i' A cai I) much more c ■•la! portion becomes gradually more condensed, and is called wtr.-!i»?r't-d nucleus, however, does not exist until adult life. In L.T! '')sti: its i'Jits'icity so that the changes neces-sary for accommodation . d '.V ith, and "^iijjht : i disturljed. The hardened nucleus permits a greater li -it 'iv;n •• (.• (>i ler portion, so that the lens is more readily seen in a.;-.i tV pu; !l ii! es more or less its blackness. V is an op,vii V of the lens, or its capsule, but that of the lens is so ii !ion tli.i.' • !k. of the capsule, that by the word cataract the lenticular is usually meant ■,;!'-;■:> i^- iv .d is otherwise qualified. All cataracts are at .sometime partial, and the ^ ^ita according to their location, anterior polar or capsular, posterior polar or capsular, centnil or nuclear, lamellar, perinuclear and cortical. Cataract occurs sometimes in the young, and is then soft ; that is, the lens has no nucleus. The ViTREors Body. The vitreous body (corpus Titreum) fills the space between the lens and the retina, being in close contact with the retina and acting as a support to it a» far forward as the ora serrata. Here it becomes ser""ited from the retina and passes to the posterior surface of the lens, presenting a ; : How depression, the fossa hya- loidea or patellar fossa, on its anterior sur&ce for the reception of the lens. The fresh vitreous is a semifluid, perfectly transparent mass which const ^s of about 98. 5 per cent, of water. The structure of the vitreous has been a subject of protracted dispute, but recent investigations have established beyond question that it possesses a framework, 93 >474 HUMAN ANATOMY. Portion of adult vitreous body, showinf? felt-work of fibres and atrophic traces of cells. X 450. (Retzims.) composed of delicate, apparently unbranched fibrils, which pass in all directions through the vitreous space and form the meshes in which the fluid constituents of the mass are held. The surface of the vitreous is enclosed by a delicate boundary layer, called the hyaloid membrane, formed by condensations of the fibrils, which are here arranged parallel to the surface, and closely felted. It is, however, not a true membrane, but only a con- FiG. 1J32. densation of the vitreous fibres. The vitreous is attached firmly to the retina at the nerve entrance and at the ora serrata, iK'tween these points the hya- loid being indistinct. As the vitreous leaves the retina, the Ixjundary layer becomes thicker, in some cases to lie- come thin again or absent in the region of the patellar fossa. The central part of the vitreous is occupied by a channel, the hyaloid canal, also known as the canal of Stil- ling or the canal of Cloqiiet, which is about one millimeter wide and extends from the optic entrance toward the pos- terior pole of the lens. During fcetal life this canal lodges the arieria hya- loidea, the continuation of the central artery of the retina, which passes to the lens and assists in forming the embryonal vascular envelope surrounding the lens. Usually the embryonal connective tissue, together with the blood-vessel, disappears ; occasionally, however, delicate remnants of this tissue can be detected. The normal adult vitreous ordinarily contains no cells, but some are occasionally seen near the surface, beneath or on the hyaloid membrane. They are amicboid, often contain vacuoles and are to be considered as modified leucocytes. In addition a few branched connective-tissue cells may be present. Practical Considerations. — Congential abnormalities of the vitreous are due either to a persistence of some part of its foetal vascular apparatus or to an atypical development of the tissue from w hich it is formed. The remains of these structures may occasionally be seen as a filamentous band, free at one end, which floats in the vitreous, the other end being attached to the optic disc behind, or the posterior sur- face of the lens in front. The strand may be attached at both ends, with or without a patent arterj-. Small rounded gray bodies, apparendy cystic and attached to the disc, are occasionally seen. They are in some way the remains of the foetal vascular ap])aratus. The congenital opacities sometimes seen at the posterior pole of the lens are probably derived from the posterior fibro-vascular sheath of the lens. Materials from the blood are readily absorbetl by the vitreous, as the bile in jaundice. Miiscee volitantes are the flocculi, seen liy the patient as black spots be- fore the eyes, and are sometimes made up of inflammatory e.xudate from inflam- mation of the internal or middle coat of the eye. They may be due to blood from traumatic or s|X)ntaneous hemorrhage into the \itreous. Musca* \-olitantcs arc often seen independently of any vitreous disease and are due to the shadows thrown upon the retina by naturally formed elements in the vitreous body, perhaps the remains of embryonic tissue. Some of the vitreous may be lost and rapidly replaced with- out seriously disturbing sight. In the removal of cataract, the suspensory ligament may lie diviikxl and an embarra.ssing loss of vitreous may result. .•\ foreign body in the vitreous chamber generally gi\es rise to a serious inflam- mation, which may destroy the eye. If loose, it tencls by gravity to settle in the lower portion, and usually rests on the posterior part of the ciliary Ixidy ( T. Collins). Rarely, in the absence of infection, it has remained for years without setting up inflammation. The rule is, hi.wever, to remf)ve them, when recent, as early as possible, as inflammation may set in at any time. In most cases the foreign body SUSPENSORY APPARATUS OF THE LENS. '475 Cornea Canal of Srhlemm, can be exactly localized by the X-ray, and if of iron or steel, may often be removed by a magnet. The accident is always serious and may Ik- followed by a virulent inflammation, demanding an excision of the globe to prevent a sympathetic involve- ment of the other eye. Because of the risk of infection and loss of fluid, operative interference in the vitreous chamber is usually to be avoidetl. Sympathetic ophthalmitis y or more accurately, infective irido-cycUtis, or uveitis, is an inflammation of one eye, usually called the " sympathizer," owing to injuiy or disease of the fellow eye, usually called the "exciter." Traumatisms of the ciliary region (danger zone) which have set up an irido-cyclitis or uveitis are responsible for fully 80 per cent, of the cases of so-called sympathetic inflammation. This disease was formerly supposed to be due to reflex action through the ciliary nerves, and this theory in a modified form is sti' .laintained by a few clinicians. The ' ' mi- gration theory" propounded by Leber and Deutschmann that the inflammation is a progressive process in the continuity of the tissue of one eye to the other by way of the optic nerve apparatus and is of bacterial origin, has not been proved. It is believed by some investigators that the bacteria which enter the primarily affected eye produce a toxin which causes the disease, and by others that it represents an endogenous infection produced by invisible bacteria, that is, that it is a metastasis (de Schweinitz). The Suspensory Apparatus of the Lens. The lens is held in position by a series of delicate bands, wiiich pwss from the vicinity of the ora serrata over the ciliary processes to be attached to the [leriphery of the lens. These fibres collectively con- Fig. 1*33. stitute the suspen- sory ligament, or zonula of Zinn, a structure of impor- tance not only for the support of the lens but also in assisting the ciliary muscle in effecting the changes in the curvature of the lens incident to accommodation. The zonula is not, as for- merly believed, a con- tinuous membrane, but is composed of a complicated system of fibres. The latter, varying in thickness from .005-. 022 mm., arise chiefly from the cuticular membrane covering the pars ciliaris retina in the vicinity of the ora serrata. The investigations of Retzius, Salzmann and others indicate that some fibres arise also from the mem- brana limitans interna of the pars optica retina, whilst others pass into and end within the vitreous body. The greater number of the fibres pass forward chiefly in the depressions between the ciliary processes, and along the sides of the latter, closely applie- reKlon, showing ciliary processes anil suspensory ligament of lens, v 20. 1476 HUMAN ANATOMY. the lens equator. The fibres are so closely interlaced that it is possible to inject air between them and so produce a beaded ring surrounding the lens. This appearance was long interpreted as demonstrating the presence of a delicate channel, the canal of Petit encircling the lens. The existence of a definite channel, however, is no longer accepted, the sj-ace capable of inflation being part of the larger circumlental space, which is filled /ith fluid and communicates, by means of fine clefts, with the posterior chamber. t u- u In addition to the chief zonular fibres, accessory bands occur, some of which pass from the ciliary processes to the long zonular fibres, whilst others extehd from point to point on the ciliary processes. The origin of the vitreous body and of the suspensor>- ligament has long been and still is a matter of dispute. The fact that these structures are very closely connected, that fibres from the suspensory ligament pass through the vitreous, and, in some cases at least, end in that body, renders it probable that the two structures have a common genesis. Anatomiste are divided, however in their views, some believing the structures in question to be denved from the mesoblast which enters the choroidal cleft with the blood-vessels, whilst others assign to them an ectoblastic origin, either from the lens-vesicle, or from the retina (inner wall of the second- ary optic vesicle). In many of the lower animals the vitreous contains no blood-vessels, and, further, since the vitreous is formed without the presence of embryonal connective tissue, the prwumption is strong that the vitreous arises from the retina. That the ectoblast in mam- mals, however, is the sole source" of the vitreous has not been proven ; moreover, the close histological resemblance of the vitreous to embryonal connective tissue suggests with mu'-h force the probability that the mesoblast has at least some share in the formation of thevitrtoi body. The Aqueous Humor and its Chamber. The aqueous humor is the transparent fluid which fills the space between the anterior surface of the vitreous body and the posterior surface of the cornea. In chemical composition it closely resembles water, containing only traces of albumin and extractives, and differing from lymph in its low percentage of albumin. It is produced chiefly by the blood-vessels of the ciliary processes, the ins taking probably little or no part in the process. The albumin of the blood is separated by the action of the double layer of cells covering the pars ciliaris retina, which act either as a filter- ing medium (Leber), or as a secreting epithelium (Treacher Collins). The aque- ous humor is constantly being produced and is carried off through the spaces of Fontana into the canal of Schlemm, and also through the lymph-spaces in the ins, its quantity being an important factor in determining intraocular tension. With the exception of a few migratory leucocytes, the aqueous humor is devoid of morpho- logical elements. __ .■••... u The space occupied by the aqueous humor is incompletely subdivided by the iris into two compartments, the anterior and posterior chambers. The anterior chamber (camera ocull anterior) is bounded in front by the cornea, and behind by the iris and lens, and has a depth at its centre of from 75-8-5 mm. The posterior chamber (camera oculi posterior) is the small annular space, triangular m cross-sec- tion, which has for its anterior boundary the iris, and is limited laterally by the ciliary processes, and medially and posteriorly by the lens and the vitreous body. The spaces betweT the fibres of the suspensory ligament communicate with the poste- rior chamb , are filled with aqueous humor, and are, therefore, only a part of the posterior chamber. Practical Considerations. — When the cornea is perforated as by a wound or by ulceration, the aqueous is forced through the opening so rapidly that the iris is swept along by it, and unless great care is observed it will become adherent to the margin of the corneal opening (anterior synechia). The aqueous humor is of importance in the removal of foreign matter. Blood will often lie removed in a few days. Suppuration of the adjacent tissue may lead to the collection of pus in the anterior chamber (hypopion). Hyphaemia is a collec- tion . blood in this chamber, and of itself is not a grave condition, although it may be a sign of a more serious disease. LACHRYMAL APPARATUS. 1477 Glaucoma is a disease due to excessive intraocular tension which, u iless re- lieved, progressively increases until the eye is destroyed, and which almost always involves the other eye. The abnormal tension is the result of disturbance in the outflow of the intraocular fluid. This fluid is an exudation from the blood-vessels of the ciliary body. From the posterior chamber the fluid passes through the pupil to the anterior chamber. It then escapes in the angle formed by the iris and cornea by passing through the lym_.h-spaces in the ligamentum pectinatum and by diffusion reaches the canal of Schlemm. Thence it passes out by the anterior ciliary veins. Obstruction in the path of this current oc-.rs usually either in the lymph- channels of this region, or at the pupil from adhesion of the whole pupillary margin to the lens, or from occlusion of the pupil by inflammatory exudate, in iritis. Iridectomy frequently gives relief in both varieties ; in the former by opening up the lymph-spaces near the corneal angle of the anterior chamber, the incisions being carried well into this angle ; in the latter by making a new opening for the current between the posterior and anterior chambers. The symptoms, like the cause, may be explained largely u[>on an anatomical basis. The venae vorticosae pass obliquely through the sclerotic and are therefore compressed and obstructed by the distension. Their blood is then compelled to escape through the anterior ciliary veins, which penetrate the sclerotic more at a right angle, and are consequently distended. CEdema of the cornea results causing a superficial haziness. The cornea is insensitive from paralysis of the anterior ciliary nerves. Usually the anterior chamber is shallow because the lens and iris are pushed forward by the obstructed fluid behind, and the ciliary nerves being paralyzed the pupil is dilated and immobile, giving a staring expression. The optic disc is at first hypersemic, and is consequently markedly depressed from the intraocular tension, giving rise to one of the most important symptoms, pathological cupping of the disc, or the glaucomatous cup. The great pain in glaucoma is due to compression of the sensory nerves of the ciliary body and iris against the unyielding sclera. The distended retinal veins can be seen through the ophthalmoscope. A condition analogous to glaucoma, hydrophthalmos, occurs in children, and is either congenital or acquired very early in life. Unless relieved it almost always produces blindness. THE LACHRYMAL APPARATUS. The lachrymal apparatus consists of the gland secreting the tears, situated in the anterior and outer portion of the orbital cavity, and the systenv of canals by which the tears are conveyed from the mesial portion of the conjunctival sfic to the inferior nasal meatus. The lachrymal gland (glandula lacrimalis), resembling in shape and size a small almond, con.ists of two fairly distinct parts — the superior orbital portion and the inimor palpebral or accessory portion. The former occupies the fossa lacrimalis in the frontal bone and is the larger portion. It mea.sures 20 mm. in length, 12 mm. in breadth and reaches from the edge of the superior palpebral muscle, along the upper margin of the orbit to the suture between the frontal and malar bones. The upper convex border is attached to the periosteum of the fossa by means of a number of bundles of connective tissue, which are inserted into its capsule. Below, it rests upon a fascial arch, which runs from the trochlea to the fronto-malar s\iture. The lower or palpebral portion of the gland, glandula lacrimalis inferior, is somewhat smaller than the upj)er and separated from the latter by the fascial expansion already mentioned. Its lower concave surface rests upon the fornix of the conjunctiva, extending laterally almost to the outer canthus. The ducts from both pun ions of the gland are exceedingly fine, those from the upper portion, from three to six in number, passing downward through the inferior portion. Some of the ducts from the lower gland join those coming from above ; others run independently, in all about a dozen ducts opening into the conjunctival sac along a line just in front of the fornix. In structure the glands correspond to the tulx)-alveolar type, and resiMnblc the serous glands in their general rhamrtcr. The acini of the lower portion are separated by robust septa of connective tissue, which contain considerable lymphoid tissue. 1478 HUMAN ANATOMY. The arteries of the gland are derived from the lachrymal, and the veins enij)! • into the ophthalmic vein. The nerves include sensory fibres from the lajhrymai branch of the ophthalmic, as well as secretory fibres from the sympathetic. Accessory lachrymal glands Arc found in both the upper and Icwer fornices, from eight to thirty being present in the upper lid and from two to four in the lower. They are very small and situated chiefly near the outer angle of the palpebral fissure. Fig. IJ34. Alveoli Ducts Beginning o{ duct Section of lachrymal gland, under low magnification, showing general arrangement of alveoli. X ao. Fig. IJ35. The lachrymal passages ( Fig. 1 236) begin by minute openings, the lachrymal puncta, which are usually placed at the summit of the conical lachrymal papilla:. The latter occupy the margins of the eyelids, near the mesial e.xtremity, at a point where the arched palpebral borders passes over into the approximately horizontal boundaries of the lachrymal lake. The upper punctum is situated 6 mm. from the inner canthus ; the lower one is slightly larger and a trifle farther removed from the canthus. The puncta open into the lachrymal canaliculi, which at first are vertically directed, then bend abruptly icsi^illy and, taking a nearly horizontal course parallel th the borders of the lachrymal lake, run as far as the ntr canthus, •• 1 •■re they empty usually b\ a common anal into the lai al and slightly posterior wall of the lachrymal sac. Occasionally the two canaliculi do not unite but open separately into a diverticulum of the sac, known as the sinus of Maier. Elach canaliculus is from 8-10 mm. in length. The lumen of the canal measures only . I mm. in diameter at the punctum, presents a diverticulum I mm. in diameter at the bend, anil continues with an appro.ximately uniform calibre of .5 mm. in its horizontal portion. The Structure of the canaliculi includes a lining of stratified .squamous epithelium, which rests upon a delicate tunica propria rich in elastic fibres, muscular fibres from the orbicularis palpebrarum affording additional support. The muscle bundles run parallel to the horizontal portion of the canaliculi, but are arranged as a circular sphincter about the vertical portion. The lachrymal sac (saccus lacrimalis ) may be regarded as the uppt-r diiaieti portion of the naso-lachrymal duct, the lower part of which passes through a bony canal and opens into the inferior nasal meatus leneath the lower turbinate Imne, AK-eoli of larlir^'mal gland more liishly magnified. X 235. PRACTICAL CONSIDERATIONS : LACHRYMAL APPARATUS. 1479 Cast of tear-psiaa«ces ; C, canaliculi ; .V, lachrymal sac; /}, iiaso-lachrymal duct ; nat- ural size. {Dii'ight.) The sac is about 15 mm. lonjj, and 5-6 mm. in diameter when distended. It is situated near the inner canthus and lies within tlie deep lachrymal jjr' and the lachrymal bone. Its dosed upper end, or /loiifi/s. e.\tends beneath the internal tarsal ligament and some of the fibres of the orbicularis palpebrarum, whilst its orbital surface is covered by the fibres of the liUer muscle, which spring from the lachrymal bone and are known as the Ifiisor tarsi or Hormr' s muscle. The lower end of the sac narrows where it passes into the nasal iluct. The wall is lined with a tiouble layer of columnar epithelial cells, which in part are provided with cilia. It is composed of libro-elastic tissue and is loosely connectetl with the periosteum. The nasal or naso-lachrymal duct, the lower portion of the tear-jiassage, is situated within the bony canal formed by the superior ma.xiliary, lachrymal and infe- rior turbinate bones. It varies in length from 12-24 nmi. . according to the position of the lower opening, and is from 3-4 mm. in diameter. Its direction is also subject to individual variation, but is slightly backward, as well as downward, and is usually indicated by a line drawn from the inner canthus to the anterior edge of the first upper molar tooth. The duct opens into the lower nasal meatus, at a point from 30-.^5 mm. behind the poste- rior margin of the anterior nares. The aperture may be imperfectly closed by a fold of mucous membrane, the so- callt?d valve of Hastier {^Xka lacrimalis). The structure of the duct includes a lining of mucous membrane which is clothed with columnar epithelium and may contain glandular tissue in the lower portion. The mucous membrane is sep- arated from the periosteum by areolar tissue and a venous ple.xus ; it may present additional folds, resembling valves, the best marked of which is situated at the junction of the sac and the duct. The arteries supplying the lachrymal duct are from the nasal and the inferior palpebral. The large and numerous veins mostly join the nasal plexus and empty into the ophthalmic and facial. The nerves are derived from the infratrochlear division of the nasal branch of the ophthalmic. Practical Considerations. — The most fretjuent congenital error of develoj)- ment in the lachrymal apparatus is found in connectitm with the canaliculus. It may be entirely absent, or, what is more common, may appear only as a groo\e, the edges having failed to unite. This union of the edges may occur only in part, so that the canaliculus may have two or more openings. The lachrymal gland is rarely the seat of inflammation. Hypertrophy or enlargement may be con^i nital or syphilitic. Prolapse or dislocation forward may occur so that the gland can l)e seen or felt below the upp-r outer margin of the orbit ; it has been excised in extreme cases. Cysts are due to occlusion . t one or more ducts. The ducts of the gland open into the outer third of the upper conjunctival fornix, and the tears sweep over the front of the eye towards the puncta untler the influence of gravity and the contractions of the orbicularis muscle. The lower punctutn is frequently everted so that it no longer dips into the lacus lacri nails, and the tears, instead of finding their w.iy into the normal pass.ige, flow over the lower lid on to the cheek (epiphora). Tliis is usually the first step in the development of ectropion or turning out of the lid ( vide supra). When thi eversion cannot be cor- rected, the canaliculus is usually slit up on its posterior siile so as to form a groove dipping into the lacus, from which the tears may again l)e taken up by the natural passages. The most (winmon cause of epipiiora is obstruction of the lachrymal passages. This occurs most frequently at the junction of the lachrymal sac and nasal duct, which is the narrowest part of the duct. The method of correcting su.h an obstruction is by the use of sountls, which are passed from the punctum with or without first slitting the canaliculus. The rule is to A\x. the c.ina'iculus when the sound- ing is to be kept up for any length of time, hut if it is performed for diagnosis only, the slitting is not done. The upper canaliculus is shorter but narrower than the lower, ■■Ml :, i% Mil 1480 HUMAN ANATOMY. which is usually selected, as there is less danger of laceration of the lining mucous membrane leading to narrowing or occlusion of the canaliculus by scar tissue. Congenital fistulte sometimes result from non-closure of the groove from which the sac and nasal duct are formed. The lachrymal sac is situated at the inner side of the inner canthus, behind the inner palpebral ligament, which is the best guide to it, and crosses about the junction of the upper and middle thirds of the sac. A collection of mucus or pus in the lachrymal passage is usually in the sac, and when not otherwise relieved, it tends to discharge itself through the skin below the tendo-oculi, and frequendy lower than the level of the sac. The abscess is therefore opened below the tendon and external to the inner edge of the lachrymal groove. The line of the sac and duct, taken together, is approximately from the inner canthus to the space between the second premolar and first molar teeth. It opens below into the inferior meatus of the nose, just below and behind the anterior end of the inferior turbinate bone, which conceals it from view at the anterior naris. The sac and duct form a slightly curved line with its convexity backward, and its course downward, backward and slightly outward. To pass a probe along the lachrymal passage, the lower lid is everted by the thumb so that the punctum may be seen. The probe should be entered into the punctum vertically. It should then be turned horizontally and passed through the canaliculus to the inner wall of the lachrymal sac. It is then made vertical and passed along the duct — i.e., downward, slightly backward, and outward to the nose. DEVELOPMENT OF THE EYE. The development of the eye begins as a lateral diverticulum which very early appears on either side of the fore-brain (Fig. 911). These outgrowths, the primary optic vesicles, are hollow and directly communicate with the general cavity of the primitive brain by means of the optic stalks, which are at first broad, but later become narrowed. As the development proceeds, the transver-ely placed optic stalks gradually assume a more oblique axis, and, after the differentiation of the fore-brain into its two subdivisions, open into the diencephalon or inter-brain. The primary optic vesicle expands until it comes into contact with the surface ectoblast. The next important step is a thickening of the wall of the vesicle where it is in con- tact with the ectoblast (Fig. 1338). In consequence of the rapid multiplication of its cells, this portion of the wall becomes invaginated and, as a result, the cavity of the primary optic vesicle is gradually obliterated, the application ot FlG. 1237. the invaginated portion of the wall to the inner sur- face of the uninvaginated part of the vesicle biinging about the formation of a cup-shaped structure pro- vided with a double wall. This cup is called the secondary optic vesicle and from it the retina is developed, which must be considered, therefore, as a modified portion of the brain itself. Coincidentally with the invagination of the optic vesicle, the overlying ectoblast undergoes active proliferation and pushes into the space vacated by the receding invaginated wall, thus producing a depression known as the lens-pit. The lens-pit ( Fig. 1238) deeix-ns and becomes cup-shaped ; the edges of its anterior walls approacli each other and then fuse, and In this manner form a closed sac, the lens- vesicle. This remains for a time connected with the surface ectoblast, but later becomes separated from it and forms an Isolated sac of epidermal tissue, which, hy the proliferation of its cells, becomes converted into a solid structure and constitutes the rrystalline lens. At first the lens-vesicle fills the cavity of the optic cup completely, but with till.- deepening ot the latter, a space appears l)etween Its anterior wall and the lens-vesicle, which gniclually widens and forms the vitreous cavity. The space between the lens-vesicle and the ectoblast is imaded by a prwess from the surrounding mesoblast, which pushes in from l!ie side. Kruti» liiis liij;rowth is ceed to the centre of the pupil and liieak up into their terminal loops. The portion of the net-work covering the pupillary area is ( Mlletl the membrana pupil- laris, whilst the remainder is known as the membrana capsularis. Tiiis v;iscui.ir sheet is usually entirely at)Sorl)«l Ixjfore birth, but occasionally portions of it may be seen |>ersisling in tlie form of fine threads in the pupillary space, or on the posterior pole of the hns. The retenlioii of such strands is sometimes associated with the |)ersistence of portions of the hyaloid .irtery. Fio. 1239. ■— Ectoblast 1 Outer layer .ip of optic cup Inner layer Anterior wall Optic stalk Posterior wall uf Icnh-Kac Lens-sac closed ; outer and inner layers of sec- ondary oplic vesicle now almost in contact. .• 30. I4i>3 HUMAN ANATOMY. Fio. 1240. ■~~ MeNoblast — Lipof opticcup FccUl cleft Sagittal s«rtion of dpvelopitiK eye at same staae as precvdinK specimen, showing invagi- tiatTon of optic vesicle along ftctal cleft. X 30. Development of the Retina. — As already pointed out, the retina develops fn>in the walls n of the lens- vesicle from the overlying ectc iliUxst, the meso- blast insinuates itself fwtueen these structures, in addition to surrounding tliC entire ecto- blastic optic vesicle. The portion surrounding the optic vesicle posteriorly thickens rapidly and becomes differentiated into the vascular tunic, or choroid, whilst the outer layer Ije- comes the fibrous tunic, or sclera. The choroid ap|)ears first, the pigmentation of its cells being evident by the seventh month. The meso- blastic process tietween the lens and the ecto- blast is very thin at first, but subse<|Uently splits into two layers. The anterior of these becomes the substantia propria of the cornea and its lining endothelium. The latter produces tiK- membrane of Descemet. The ixjsterior mesoblastic la>er carries blood-vessels which help to form the capillary net-work surrounding the lens. The s|)ace between the two mesoblastic layers represents the future anterior chamber of the eye. .About the fourth f(Ltal month the aii- tt'rior lip of the optic vesicle pushes forward in advance of the lens and carries with it additioii.il mesoblastic tissue. From this the iris is developed, the stroma being formed by the mesoblast, whilst the posterior pigmented portion represents the anterior part of the optic vesicle, from which the dilatator muscle (and, according to some authorities, also the sphincter pupilla!) is derived. The ciliary processes are produced by the rapid lateral expansion of the walls of the t'pper eyelid Outer pigmented retinal layer Inner retinal layer Meaoblant Lens, now solid Optic nerve Vascular vitreous tissue Ectoblast Lipof retinal co:i t Much later stage, showing; lens now solid ; lavers of optic vesicle converted into retinal coat : vascular vitreous tissue; condensation and invasion of mesoblast. ' 20. THE EAR. I4«.^ optic vesicle, about the fourth or fifth month, in consequence of which folds in the nieinlir.iiu- ariiie, into which blood-vessels and other mesodermic elements extend. The corneal stroma becomes blended with the sclera, thenceforth the two forminK a continuous tunii-. Development of the Vitreous Body. — As already stated, the vitreous liody is at present re- garded as developing chiefly by proliferation of the cells of the inner w.ill of the optic vesicle, especially from its anterior or ciliary portion. The suspensory ligament ot the lens is ilerived from the same source. The cells develop into the fibres which iorm the line net-work of the vitreous boinna, it possesses no framework of cartilage and, hence, is soft and inelastic. The helis forms the scroll-like margin of the ear, sweeping from the upper part of the tragus in front to the lobule behind. It is more or less rolled upon itself so that its margin looks forward. On the anterior edge of the heli.x. near the junction of its upper and middle thirds, is sometimes found a small triangular ele- vation, the car-point or tubercle of Darwin, which is of interest as representing, ac- cording to the last-named authority, the erect pointed extremity in the expanded ears of certain (juatirupeds. It is said to l)e constant in the foetus of about the sixth month and to be more common in the male than in the female. In front of and p.irallel to the helix, is a curved ridge, the antihelix which tx-gins at the antitragus below, forms the concave posterior boundary of the concha, and divides above it into a siipi-rinr and an inferior rnis tx-twoen which lies the fossa of the antihelix or the fossa triangularis. .\ narrow groove between the helix and the antihelix marks the fossa of the helix or the scaphoid fossa. The elevations on the external surface of the auricle are represented by depressions on the cranial surface, and conversely the depressions on the external Cavum coiichi Antitragus Foua triangularin Cnini antihcHcifi 'Cymba conchw Crus heliciA Incisura anterior Tragus ^incisura intertragica Lobillus Ri'hl auricle, outer aspect. THE EXTERNAL EAR. «4»5 surface are represented by eminences. Thus, th? concavity oi the conchu is represented on the cranial surface b^ the eminentia conchae; the antihi-lix by the fosaa antihelicis ; the fossa triangularis by the eminentia fosase triangu- laria ; the scaphoid fossa, by the eminentia tcaphK. The other elevations and depressions corresjKjndinjf to those of the outer surface are not sten on the cranial surface, except in the dissected cartilage denudetl of the inte>;unient. Structure of the Auricle. — The auricle consists of integument and an enclosed plate of yellow elastic cartilage continuous with that of the meatus. It is also provided with several unimportant ligaments and muscles. The lobule, however, contains no cartilage, but only fibrous tissue and fat enclosed within the intek>umentary fold. The skin of the auricle is thin and closely adherent to the cartilage, es|>ecially on the outer jurface. In certain parts it contains fine hairs and sebaceous and sweat glands. The hair follicles are especially abundant over the tragus, antitragus and the notch lying between them, the hairs guarding the entrance into the external auditory canal, known as tragi, being exceptionally long. The sebaceous glands are espiecially well developed in the cavity of the concha. Cartilage of the Auricle. — The cartilage of the auricle may be divided into two parts : (a) the scroll-like plate forming the tragus and external auditory canal, and {6) the large irregular plate forming the main cartilage. These two clivisions Fig. 1344. s Itucitioii of •urlcularis nipcrior Obllquiu Helkii major Tragicui IMale of tragus ami estrmal auditory canal auda hclicia Cartilaginous framework oi right auricle, with intrinsic auricular muscles; A, outer, B, inner surface. are connected by a cartilaginous isthmus lying between the incisura intertragica on its outer side and the deep fissure, (Incisura terminalis auris), which in the isolated cartilage is seen between the posterior wall of the outer meatus and the anterior border of the lower part of the concha, on its inner side. Two smaller clefts, the fissures of Santorini, are found between the three plates which form the carti- laginous scroll supporting the tragus and outer end of the external auditory canal. The cartilage of the tragus is an irregular plate and subject to considerable variation. The depressions and elevations of the cartilage proper corrtspond in general to the surface modelling of the auricle, but are sharply marked, especially on the cranial aspect. A deep notch, the fissura antitragohelicina, separates the lower part of the helix from the antitragus, thus defining the caudal process (cauda belicis), as the lower extremity of the cartilage forming the helix is called. The spina helicis is a small conical projection, directed forward and down- ward, opposite the first bend of the helix. This serves for the attachment o* the anterior ligament. The upper end of the tragus-plate fits into an angle formed by the junction of the beginning of the helix and the upper end of the anterior border of the concha. In addition to the elevations and depressions already referred to, on the mesial surface is found a ridge, the ponticulus, which extends downward and forward over the eminence of the concha and serves for the attachment of the posterior auricular muscle (Fig. 1244, B). I486 HUMAN ANATOMY. Ligaments of the Auricle. — The extrinsic ligaments of the auricle, thnae which attach the auricle to the temporal bone, (orm a more or less continuous mass of fibres. These are separated somewhat arbitrarily and de»cribetl as the anterior and posterior ligaments. The anterior ligament extends from the helix and the tragus to the root of the zygoma. The posterior ligament extends from the emi- nence of the concha and ponticulus to the anterior jwrt of the mastoid process. A number of bands of fibrous ti-s-sue, the instrinsic ligaments, bind the parts of the cartilage tr^cthcr. The Muscles of the Auricle. — These include the extrinsic and the intrinsic muscles. The extrinsic muscles of the auricle, those which extend from the head to the auricle and move it as a whole, have been described under the muscular system (page 483). They are the anterior, superior and posterior auricular muscles. The intrinsic muscles, six in numl)er, consist of small strands of muscle-fibres attacheil to the skin, which extend from one part of the auricle to another and are confine«. oblis- terior auricular artery suimlies a variable number «>f branches to the auricle. I'sually two of theiie are jjiven oft Ik-Iow and one above the |)osterior auricular muscle. These branches are lar^;er and longer than those from the superficial tem|H>ral. After rami- fyinn over the cranial surface of the auricle, they reach its outer surface bv piercing; the aur'cle or by [Kt-ssinK over its free margin. They supply the posterior part of the outer surface and anastomose with the bnmches of the su|>erticial teniiHiral. The veins of the auricle accompany the arteries and include: («) tlit' anterior auricular, which empties into the su|H'rficial tcminiral ; (^) the |H>sterior auricular, three or four in numl>er, which join a ple.xus Ix-hind the ear which empties nrincipally into the e.xternal jugular vein, but .ilso unites with the jx>sterior facial veni. Com- munications with the mastoid emissiiry vein of the lateral sinus also fr<.'?nd backward over the helix to end ir. the jxwterior auricu- Fic. 1246. A. perforan^ 'foftaaf triaiiKularis A. helicts A. atiricul^riK imst. ftij|i. A. temporalis . , ro»l"ior *^ aiiru-ular muscle A. perforans_ cymb» A. candle heliciv A. trati TaroiUl branch Arteriea of right auricle, .4. Literal surface; B, postero-meaial surlace. KSckicathr.) lar nodes that overlie the insertion of the sterno-mastoid muscle. Those from the upper pjirt of the cranial surface piiss mainly to the posterior auricular nodes, some being tributary to the e.xternal jugular nodes. A number of stems frt)ni the lower part of the auricle and from the lobule terminate in the parotid nodes. Nerves of the Auricle. — The motor nen'es supplying the intrinsic muscle's of the auricle are from the temporal and posterior auricular branches of the facial nerve, the former l)eing distributed to the muscles of the helix, tragus and antitragus, whilst the ptwterior auricular supplies the tranverse and oblique muscles. The sen- sory nenrs includi; branches from : (a) the great auricular nerve, which supplies the integument of the lower three-quarters of the inner surface of the auricle, with the exception of a small portion near the meatus, and sends filaments to the outer surface of the lobule and adjacent area ; (6) the small occipital nerve, which supplies the upper one-quarter of the inner surface ; ( r) the auricular branch of the vagus, w hich supplies the small muscles on the back of the concha and a limited cutaneous area near the meatus ; and ((/) the auriculotemporal nerve, which tlivides at the level of 'he tragus, and sends filaments from its auricular branches to the outer surface of the .luricle. The External AuniroRV Canal. The external auditory canal (meatus acusticus) leads from the cavity of the concha to the tympanic membrane, which closes its inner extremity. Although the adult meatus \aries considerably in size and direction, it is usually tortuous. In a general way, in its external jwrtion the canal extentis somewhat forward and inward, perhaps slightly upward ; then, in its middle portion, almost directly ^ 1488 HUMAN •N-TOMY. Internal auditory canal inward, possibly slightly backward ; and finally, in its internal portion, forward, downward and inward. Its supcro-posterior wall measures about 25 mm. (i m.) m length, and the anterior wall about 35 mm. ( i -)« in.), the greater length of the anterior wall be- ing due to the obliquity of the drum-head and the outward protrusion of the tragus. The canal is almost as long in the infant as in the adult. Structure.— The external auditory canal is composed of an outer cartilagino-membranous (cartilaginous) and of an inner bony portion, both of which, as well as the external surface of the tympanic membrane, are lined by skin. The car- tilagino- membranous part contributes something more than one-third of the entire length of the canal, and is a continuation of the cartilage of the auricle. The cartilage of the canal, histologically of the elastic type, does not form a complete tube, but is deficient at its upper back part, where ii is filled in by fibrous tissue. On approaching the bony portion, this deficiency in the cartilage is more marked and the fibrous tissue correspondingly increased. Two or more slit-like apertures, the fissures of Santorini (incisurae cartiiaK- inis meatus acustici esterni) are usually found traversing the cartilagino-membranous Fig. 1248. Lateral (inu* Frontal section paaiini through right ear, showing external, middle, and internal divisions; section is seen from in front. Condyle of Jaw Cartilaginous canal Tymjianic membrane External audiuiry canal Maatoid cells ^ Bony canal 'Eustacliian tube Internal carotid artery ympanic cavity Lateral sinus Horitontal section puslng through right ear, viewed from tielow. canal nearly at right angles (Fig. Ii45); ^ ll»«=y are filled with fibrous tissue, they permit the anastomosb between the vessels of the anterior and posterior surfaces THE EXTERNAL EAR. 1489 Seban ous ^I-'tni! CartilaKc of the ear. At its inner end the cartilajjino-membranous meatus is attached to the inferior and lateral edges of the osseous meatus, the fibrous part Ix'iiij; continuous superiorly and posteriorly with the periosteum lining of tlie osseous 1 anal. The osseous portion of the tulw, about 14 mm. in length, is longer and narrower than the cartilagino-membranous part. At its inner end it ])resents a narrow groove, the sulcus tympanicus, for the insertion of the tympanic membrane. The sulcus e.xtends around the sides and floor of the canal, but is deficient above. The skin lining the external auditory canal is closely attachetl to the untlerlying cartilaginous portion of the tube, the skin me.isures alxtut 1.5 mm. in thick- ness, but is much thinner within the bony canal, e.xcept along the roof, where it remains relatively thick. Over the outer surface of the tympanic membrane the skin is reduced to a very delicate and *'*^- '*49- smooth investment, covered by a corre- spondingly attenu- ated epidermis, and a suggestion of sub- cutaneous tissue. Numerous fine hairs and large sebace- ous glands occur in the cartilagfinous portion, but dimin- ish in size and fre- quency towards the bony canal, in which they are entirely wanting. Within the cartilaginous meatus and along the roof of the bony tube, the skin is closely be- set with the large coiled ceruminous glands, which re- semble in structure modified sweat glands. Like the latter, the cerumin- ous glands consist of a deeper and wider coiled portion, the secretory segment, and a long narrow excretory duct, which ends in most c;ises inde- pendently on the free surface of the skin, but sometimes, particularly in the very young child, it opens into the duct of a sebaceous gland. The cuboidal secreting cells contain yellowish brown pigment particles and granules resembling fat. The ear-wax or cerumen is, as usually found, the more or less dried mixture of the secretions derived from both varieties of glands, together with discarded squamous epidermal cells. Vessels. — The arteries distributed to the external auditory canal are irom three sources: (a) anterior branches of the superficial temjMjral supply the external por- tion of the meatus ; (b) the deep auricular artery, a branch of the internal maxillary, passes to the deeper portions ; whilst (f) the posterior auricular provides branches for the jxjsterior and sujjerior surfaces. The arteries destined for the interior of the ?anal pierce the membranous roof of the cartilaginous meatus, the fissures of Santo- r'sij .Tid the fibrous tissue connecting the cartilaginous with the bony portion of the i ibe. They form capillary net-works within the j)erichondrium and periosteum and. Cartilage Hair fonicle Corium Transverse section of skin lininK cartiUiRinous portion of external auditory canal, v 30. :490 HUMAN ANATOMY. Concha External auditory canal Memhrana flaccida Depression for malleus \ within the skin, around the glands and the hair follicles, some extending on to the upper part of the membrana tympani. The deeper veins of the meatus, which drain the bony and a small part of the cartilaginous meatus, empty into the venous plexus behind the articulation of the lower jaw, those from the upjjer wall of the meatus extending upward to join the venous plexus which spreads out over the skull. The lymphatics of the external auditory canal arise from a cutaneous net-work from which trunks pass in three general groups, as do those of the auricle. ( i ) The trunks of the posterior group arise in the posterior wall of the external meatus and empty, for the most part, into Fig. lajo- the posterior auricular (ma.st<-.id) nodes. Some, however, avoid this first station and join the efferent vessels of the upper nodes of the superior deep cervical chain. (2) The inferior group includes a vari- able number of trunks coming from the lower wall of the external audi- tory meatus, some of which pass to the nodes placed along the course of the external jugular vein at its exit from the parotid, whilst others end in the mastoid nodes. (3) The anterior group is from the concha and the anterior wall of the meatus. These vessels are tribu- tary to the parotid nodes, more particularly to the anterior auricular nodes situated immediately in front of the tragus. Nerves. — The sensory nerves supplied to the external auditory canal are derived from the auriculo-temporal branch of the trigeminus and from the auricular branch of the pneumogastric. The latter, also known as Arnold's nerve, perforates the wall of the meatus and supplies its lining membrane. Practical Considerations : The Auricle. — The auditory mechanism may be said to consist of two portions — that which conducts the sound and that which receives it. The former is represented by the external and the middle ear : the latter, by the internal ear. The function of the auricle is to collect and intensify the sound-waves and to direct them into the external auditory canal. That it does not play a very important part in hearing is shown by the fact that its removal has been followed by comparatively little loss in the acuteness of hearing (Treves). Complete absence of the auricle is exceedingly rare ; partial defect ( microtia) is more frequent ; while congenital fistulse are comparatively- common. These fistula are considered to be due to defective closure of the first branchial cleft. According to His, however, they are due to deficient union of the crus helicis and the crus r.iipratragicus. If a fistula closes at its orifices, a retention cyst, sometimes dermoid, may result. The ear may be abnormally large (macrotia), or, as a result of defective union of the rudimentary tubercles from which the auricle is developed, auricular appendages ( polvotia) may l)e met with. A supernumerary auricle may very rarely be found on the side of the neck at the orifice of one of the lower branchial clefts. Owing to the rich blood-supply of the auricle, wounds heal rapidly. When, however, they occur near the external auditory meatus and are large, cicatricial closure of the canal must be guarded against. Frost-bite is frec|uent l5ecai..ie of the exposure to cold and the lack of protec- tion to the blood-vessels from overlying tis.sues, since little more than skin covci-s them. An intense reactive congestion follows, and frequently leads to gangrene. I'mljo Tympanic membrane Cast of right external auditory canal, seen from be- hind ; natural siie. Drawn from cast made liy Profeasor Randall. PRACTICAL CONSIDERATIONS: THE EXTERNAL EAR. 1491 The skin is closely adherent to the underlying tissues, especially on the anterior surface, so that the exudate is under much ten? m, interferinti with the bl Facial nervc^ Vestibul Internal aurtitorj' canal' Cochlea Articular surface for incus Epitympanic space Lateral ligament Handle of malleus External auditory canal Tympanic membrane, cut Prohc In Eust^achian tube Promontory tympanic cavity Frontal section Ihrouub right ear. viewed from behind. ■' ^%. auditory canal. It is lined with mucous membrane and contains, in addition to the air which enters by way of the Eustachian tube, the chain of ear ossicles. Its short- est diameter, that between the middle of the tympanic membrane and the wall of the labyiinlh, is iilxjul 2 nun. The antero-postcrior diameter is about 12 n • :., whilst the distance from the roof (tegmen tympani) to the floor, the supero-inferior diam- eter, is about 1 5 mm. THE MIDOLK KAR. 1493 The cavity of the tympanum is subdivided into_ three parts : ( i ) the a/riiim or tympanic cavity proper; (2) the cavum epilympcnicum, the upper part of tlie space which ovp'lies the atrium ; and (3) the antrum, which leads into the mastoid cells. The atrium (Fijj. 1251) resembles in shape a short cylinder with concave ends, the outer end beinjj formed by the tymp;mic mentbranc and its Ixmy marj^in, whilst the inner end is formed by the outer wall of the labyrinth. The cavum epitympanicum or attic occupies the space between the atrium and the roof and constitutes approximately one-third ( about 5 mm. ) of the supero- inferior diameter. It contains the head of the malleus and the Ixxly of the incus (Fig. 1252). It extends considerably over the external auditory canal anil is bounded laterally by a wedge-shaped jxjrtion of the temporal bone, called the scutum. The antrum tympanicum is an irregularly pyramidal space commimicating with the upper back part of the tympanicum by a triangular orifice. Its dimensions vary, but its average length is about 1 2 mm. , its height 8. 5 mm. , and its width 6. 7 mm. It is larger in the infant than in the adult, and its lumen is frequently lessened by bands of mucous membrane which stretch across it and thus encroach upon the space. Its roof is formed by the tegmen tympmni sometimes called the tegmcn antri in this location. Its external w? ' '0 formed by the squamous portion of the Fig. lasi. Superior liKament of incus ' of mall mallftui Superior liKament of malltus Head of—"-- ^ Chorda tjmipani nerve. Tensor tympani' Pro c e s sus cochlea riformiS' Eustachian tulje «"Epitynipantc space ^—IncuK rbi» iilar prot'ess, for staphs 'Handle of malleus —Tympanic membrane Inner aspect of outer wall of rii;ht tympanic cavity, Aiowlnn; incus and malleas and tympanic menibrane in position. X 2K. temporal bone, and on its internal one is seen the outer wall of the horizontal semicir- cular canal. The thin mucous membrane of the antrum is closely united with the periosteum and possesses a layer of low nonciliated squamous epithelium. The walls of the tympanic cavity present many irregularities and depres- sions and the boundaries are not sharply defined. As the direction of the supero- inferior axis of the cavity is not perpendicular but oblique, it follows that the outer wall, composed of the tympanic membrane and its Iwny margin, is, accurately speaking, the infero-lateral wall, whilst that formed by the labyrinth is the dorso- mesial wall. For convenience of •description, however, there may be recognized with advantage an external and an internal, a superior and an inferior, and an anterior and a posterior 7. '495 the malleus handle and at the periphery of the membrane. The ileitis are most numerous at the handle of the malleus and periphery of the membrane and communicate with those of the exter- nal meatus and tympanic cavity. The lymphatics are arranjjed similarly to the blood-vessels in two sets, one under the skin and the other under the mucous membrane. They communicate freely with each other and probably empty partly into the lymph-nodes situated over the mastoid process and in the region of the tragus, and partly into the lymph-tracts of the Eustachian tulie and thence event- ually into the retropharyngeal and deep cervical nodes. Fig. IJ53. Epithelium of tympanic surface Tympanic cavity MucouH memlirane '*' ' , .'.?"'^' !£-.f^'^>-fH' 'Jj-. ' )j]' '' Epidermis of canal Blood-vessels' Epidermis of drum-head V '- O-^^J-i^^ Subepidermal layer External auditory canal Corium of skin lining canal Epidermis passing outo 'drum-head Bone Radial fibres of annulus fihrosus - ' - ■ ''-V^X -'.■.. ^^v» ' Section through attached margin of tympanic membrane, showing continuation of skin and mucous membrane over its outer and inner surtaces respectively. < 75. Drawn from preparation made by Dr. Ralph Butler. The nerves supplying the tympanic membrane are derived chiefly from the auriculo-tem- poral branch of the trigeminus, supplemented by twigs from the tymp.inic plexus and by the auricular branch of the vagus. They accompany, for the must part, the blood-vessels and, in addition to supplying the latter, form both a sulx:utaneous and a submucous plexus. The inner wall (paries labyrintlu^a) of the tympanic cavity separates it from the internal ear. It presents for examination a number of conspicuous features. The promontory appears as a well-marked buljjinn of the inner wall near its middle (Fig. 1254) and corresponds to the first turn of the cochlea. The branches of the tympanic plexus arc found in the mucous membrane co\ering it. At the biittom of a niche, whose anterior Ixirder is formed by the lower posterior margin of the promontory, lies the round window (fenestra cochlea). It is closed by the secondary tympanic membrane (membrana tympani secundaria), which separates the tympanic cavity from the scala tympani of the cochlea (Pig. 1259). The membrane is attached in an obliquely placed groove, is slightly concaA-e toward the tympanum, and measures from 1.5-3 mm. in diameter. The oval window (fenestra vestibull) lies at the Ijottom of a depression, the fossula vestibuli, in the upper back part of the inner wall, above the round window, and leads into the vestibule. It is somewhat kidney-shaped, its upper border being concave, its lower slightly convex. In the recent state the oval window is closed by the foot-plate of the stapes and ll.e ligament which connects the os-siclc with the sides of the window (Fig. 1260). The longest diameter of the latter is about 3 mm. and its shortest 1.5 mm. Abov" the oval window a well-marked _. 1496 HUMAN ANATOMY. ridjje indicates the position of the facial canal or aquednctits Fallopii. This ridge is bordered posteriorly and su{)eriorly by tlie ele\ation which corres])onrms nearly a right angle with the short process. At its lower end it is I)ent sharply inward and con.stricted into a neck, which terminates in a rounded tnt)ercle, the processus orbicularis^ that articulates with the head of the stap -. In the futus this process is separated from the rest of the long process. 1498 HUMAN ANATOMY. The lUpn (stirrup), as its name im|>licrs, is stirrup-shaptxl and consists of a head, neck, two crura and a base ur foot-plate. The external surface of the small rounded head is hollowed out for articulation with the orbicular process of the incus. Just below this is the constricted ntck, from which the two crura diverge to become attached to the foot-plate near its lower Fig. 1257. Heact. Aniirior cni" I'pper edge Posterior "Lower edge Koot-pltitc Right itapct, A, cceii front .-ibove; B, mesUI surface of foot-plate. X iVi. margin. The anterior crus is shorter and straighler than the posterior, both being .slightly curved. The fool-plate consists of a lamina of bone .-ind corresponds to the bean-shape of the oval window, into which it nearly fits. The upper edge of the foot-plate is convex ; its lower edge is almost straight, being slightly hollowed out near its middle. Articulationi of the Osiidei.— In the malleo-incudal joint, both articular surfaces are covered with a thin layer of hyaline cartilage. The fairly well-develoi>ed capsular ligament, reinforced mesially, is fastened to the depres.sed margins of the articular surfaces. A wedge- shaped meniscus of fibro-cartilage projects from the upper wall of the capsule between the sur- FiC. tjjS. Sup. ligament Hend of malleus External ligament Mem. Aacciila or Shrapiiell's membrane Pnissak's space Neck 'Short process Chorda tympani Tendon of tensor tympani artilage 'Epidermis Menibrana propria ^fucous membrane Menibrana tensa .\nnulus tendinosns Frontal section passing through malleus and tympanic membrane. X 60. Drawn from preparation made by Dr. Ralph Butler. manubrium handle moves inward, its lower cog catches the rorres|X)nding rog of the incus and the long process of the latter must follow. If the handle moves outward, the lower cog moves away from the incus and the latter moves but little" (Politzer). The articulation of the incus and •tape* is a very delicate but true joint. Both the slightly convex surface of the lenticular process of the incus and the slightly concave surface of ihe head of the sta|x» are covered with hyaline car- tilage and united by a capsular ligament made up largely of elastic fibres and thickened on the posterior surface. So etimes a meniscus of fibro-cartilage separates the two articular surfact.i. The articulation of th£ stapes and oval window is effected by the margins of the window and the foot-plate of tht^ stapes. These surfaces, as well as the vestibular aspect of the stapes, are cov- ered with a layer of hyaline cartilage. The cartilage of the foot-plate and that of the window^ are connected by a liga- ment of elastic fibres, forming a syn- chondro.-iis. In addition to the ligaments con- cerned in the foregoing articulations, four bands attach the ossicles to the tym- panic walls and prevent their excessive movement ; of these, three connict the malleus and one the incus. 1. The superior ligament of the malleus extends from the tegmen tympani to the head of the malleus. (Figs. 1253 and 1258.) 2. The interior ligament of the malleus is a strong, bro;id, fibrous band arising from th» anterior part of the head and neck of the malleus. Some of its fibres are attached to the ante- rior end of the annulus tympanicus (spina tympanica major) and other fibres pass through the Glaserian fissure to become attached to the spine of the sphenoid. These fibres correspond to the remains of the embryonic process of Meckel of the malleus and envelop the processus gracilis. THE MIDDLE EAR. 14yV 3. The latml ligament of th« mallaua is somewhat fan-shii|>eam Mv\ (a) the s/afifiiius. The tenaor tympani Ls a diminutive spindle-shaped muscle, al)out 1.25 cm. Iouk. lyin*; in the bony canal directly above the osseous part of the Eustachian tulie, from which it is ixirtly Fig. 1259. FaciHl iirr\-e kainu!* titrictihlft ampulla rift riricle Foot of atapa Secoiulnry tym- pantc memtiratie F.xtrrnal auditury canal Promontory Drnm-heacI or tympanic membrane Tympanic cavity Vertical Hction through human middle and internal ear. X i%i. Drawn from preparation made by Dr. Ralph Butler. separated by the bony scroll, the processus coch/eariformis. The posterior fibres ari.se from the top of the cartilage of the Eustachian tube and the adjoininj; part of the g^reat wing of the sphenoid. Some of the fibres are connected with the tensor palati muscle and others arise from the wall of the canal which the muscle tKCupies. The fibres converge in a feather-like manner to the tendon, which begins within the muscle about the middle ni lie canal, and, pass- ing through the tympanic opening of the canal, turns at nearly a right aii^le over the end or rostrum of the processus ctKhleariformis to be inserted into the anterior part of the inner margin of the malleus-handle just below the short process. The tendon is almost per- pendicular to the plane of the tympanic membrane, is oblique to the long axis of the manu- brium and is enveloped, along with the muscle-belly, in a fibrous sheath. The tensor tympani and tensor palati muscles receive their nerve supply from the same source, namely, the trigem- inus, through the otic ganglion The stapedius muscle lies within the triangular canal of the eminentia pyramidalis, arising from its floor and sides. Its fibres converge to the tendon, which, passing through the opening at the apex of the canal, extends forward, slightly upward, and outward, to he inserted into the lower posterior part of the head of the stapes. Some of the fibres of the tendon also pass to the 1500 HUMAN ANATOMY. lenticular priM-css and the capmilnr liKament. Theteiui.iii :s ire<|uently fnvelo|>ed in a fold oi iiiiicoUH nienibranr. A branch of the fm i.'l nerve ji.issi ihroufth a small oritice Iwtwtfn tlic Fallopian canal and the canal for the sta|iedius to sii|)|>lv tiii> mus«-|e. Movement* of the Oitides.— When the tyni|Kinic menihrane and malleus-handle are nu>\ eil inward, the lonjt priness of the incus is also moved ir.w.ird and pushes the head of the sta|>es inuard, anil sliKhtly upward. This cans^-s pressure u|H>n the li(|uid within the labyrinth, and, since the bony walls ot the labyrinth are ineliistic, the membrane of the round window is bulged outward. As the tym|>iinic membrane rt .■ ,; its normal |iusition, these movements are re- versed. When on the other hand the tympai.:,- membrane is moved outward, the movement of the lonK pr>K:ess of the incus is very sdifht liecause of the untiH-kint; of the malleo-incudal articu- lation. Contraction of the tensor tympimi rnusclc draws the centre of the tympanic membrane inward and in this way increa,se>» the tensi Ml of the membrane and of the posterior part of the axial ligament of the malleus, especially of »s external |)ortion. Ci mtraction of the stapedius muscle pulls the hea»l of the -.ta|ies Ixickward, thus liltinR the anterinr end of the foot-plat-- out- uaril. the posterior end acting as a fulcrum. The Mucous Membrane of the Tympanum. — The tympanic cavity is lined by a thin transparent mucous membrane, closely adherent to the periosteum and continuous with that of the Eustachian tube and naso-pharyn.x anteriorly, and Fig. 126" 1 posterior cniH of !»tapcA Lower end of iucuH Malleus handle Interiml ftiidito- ry canal Cocliltar nerve 'Hsal turn of C€x:hlea Tympanic cav-it j (lorizontal wction through human mi MIe atid intenial ear : stapes occludes oval window, v 5U. Drawn from preparation made by l3r. Ralph Butler. with that of the mastoid cells posteriorly. It covers the ossicles and their liKiiments, the muscle's, the tendons ,ind the chtirda tympani ner\e, and ff)rms a number of folds e.\tending across the cavity. These folds vary in location, direction and number, and form pouches within the tympanum. The attic is divided into an external and an internal compartment by the incus, the head of the malleus, the sup'^rior lijjament of tlic malleus and the superior malleo- incudal fold of mucous membrane. The external compartment is bounded on the ;. liter .side by the external tympanic v. ,;;, and i;; itself sui.dividcd inio a super; r ant; an inferior space by the externil lii;.unent of the malleus. The inferior divi- "ii i;s called Prussak's space and is xmnded externally ' Shrapnell's membram i- nally by the neck of the inalleiis, inferior'- ' •'■ ■ pnv ■; of the hammt superiorly by the external ligament id 'ig. 1 258). A numbci of THK MIDDI.K KAR. ISO I inconstant folds of mucous incinbranc, extern! from the will of tfie tviniMiium u> tl>e malleus and the incus. The most consta of these is the unti r nialK >-inciiii.il plica, which stretches iMckward to the |>osterioi ligament ot llie inii;s. Ailuitioiial folds frecjuentlv extend l)etween the cura of the stapes and from tli in lo tile wall of the tyin|)itnuni. The epithelium of the tympanic mucosal vari<- in ditTereiu pans .f the civity. Over the proinontt)ry, the ossicles and the tympanic membrane, it conMstsvi .1 -.iiinle layer of low cuboidal nonciliatenv wall. The secondary tympanic membrane closing the fenestri cmhliie, bulges somewhat toward the cochlea and is attached to the bony crest or ridge of the win- dow by its widened rim. It onsists of three layers, of which tin- middle one is a I'.i-linct fibrous lamina propria, which is covered on the tvmpinic surface bv nuicou-. membrane, and on the other side by an extension of the lining of the perilymphatic S|>ace. The lamina propria is composetl of radially disposed buntlles c>f fibrous tissue. The outer mucous stratum is formed of a thin fibr.ous tunica propria, invested by a single layer of flattened nonciliated epithelial cells, similar to those covering the neighboring promontory. The innermost stratum of the membrane includes a thin layer of subendothelial fibrous tissue, over which stretches a layer of endothelial plates. Vessels and Nerves of the Tympanun..- The arteries supplying the tympanic cavity are from five sources. 1. The stylo-mastoid branch of the posterior auricula- artery passes through the stylo-mastoid foramen and the Fallopian aqueduct, and sends a iKanch to the sta- {ledius muscle and three branches to the posterior part of the tympanic cavity. One of these passes to the floor, one through the canal for the chorda tympani nerve, and one to the posterior part of the oval window. 2. The tympanic branch of the ir^ternal maxillary artery enters the tympanic cavity through the Glaserian fissure and supplies the anterior part of the cavity, including the anterior ligament of the malleus, the pranying the carotid artery. The tensor tympani nwscle receives its supply from the trigeminus: the stapedius muscle from the facial. Although the chorda tympani nerve has an intimate topographical relation to the sjiace, which it traverses close to the outer wall, it gives no filaments to the structures within the tympanum. The EisTACHiAN Tube. The Eustachian tube Ctnba auditiva) is a canal, partly bony and partly cartilagi- nous, extending from the Literal wall of the naso-pharynx backward, upward and out- ward to the anterior part of the tympanum, fn the adi-'.t it measures about 37 mm. {xYi m.) in length, of which approximately the upper third (tympanic portion^ ^*v»| I502 HUMAN ANATOMY. belongs to the bony division, whilst the remainder is contributed by the cartilaginous division of the tube. With the sagittal plane it forms an angle of 45«', and with the horizontal plane one of about 3.°. With the long axis of the external auditory canal it forms an angle of from las'-US". opening outward. The cartilaginous and bony divisions of the tube do not lie exactly in the same plane, but join at a very obtuse angle opening outward. The tube has somewhat the shape of an hour glass, being wider at the ends and narrowed at the junction of the cartilaginous and bony portions into the isthmus, where its height is about 3 mm. and its breadth about half as much. The osseous or tympanic portion (pars ossca) about 12 mm. long, is bounded above by the tegmen tympani and the canal for the tensor tympani muscle, from which it is incompletely separated b)r the processus cochleariformis. Below and internal to it lies the canal for the carotid artery. Its lumen is irregularly triangular in cross-section. Fig. 1261. Tvmpanic membrane Tympanic cavity Antrum Condyle of jaw Baailar proccM Internal auditory canal Right internal carotid artery External audi-, tory canal Parol id eland- FiKMof KOMn-- CartlliKC ol_ Euftlai-hUn tube husuchUn tub«- l-evator palati- Tenaor palati- Huiiulu pnce — Tympuik memhianr _Extenial auditory meatus -Parotid gland ^External pterygoid muscle -Ramus of jaw Internal pter>'goid 'muscle -Soft palate -Masacter muscle Palatal raphe ^Vestibule Palatal nigte- (fi*" Incisor canal - ^Buccinator muscle Incisive pad' Anterior part of section through head at plane shown in small outline liitnre, viewed from below; left Eustachian tube exposed throughunt iu length. Drawn Irom preparation made by Professor Dwight. The cartilaginous or pharyngeal portion (pars cartila){iaea) is about 25 mm. (I in.) in lenjfth and attached to the rough oblique margin of the anterior end of the osseous portion of the tube. Its posterior wall is formed by a plate of cartilage rcartllago tubae aaditivae), the upper margin of which is curled outward upon itself to form a gutter, which appears on transverse section as a hook, whose inner and outer plates are known as the mesial and lateral lamina respectively. The interval between the margins of this cartilaginous groove presents outward and forward and is filled up with a strong fibrous membrane, thus completing the canal. Therefore part of the anterior wall and the posterior superior wall of the tube are formed by this cartilage and the rest of the anterior wall and all of the inferior by fibrous tissue. The cartilage is attached to the base of the skull and frequently is deficient in places, sometimes being divi'led into se\<'ral pieces. At birth the cartilage is entirely of the hyaline variety, but later this is more or less extensively replaced, jiarticulary in the pharyngeal division, by fibrocartilage, except iu the upper part where the hyaline cartilage THE MIDDLE EAR. »503 persists. It is this cartilage, covered by the cushion of mucous membrane, thai confers the characteristic Gothic arch contour to the lower opening, the osteum pharyngeum, of the tube. The Mucous Membrane of the Eustachian Tube. — The Eustachian tube is lined throughout its length with mucous membrane, which differs some- what in the cartilaginous and osseous portions. That in the former resembles the mucous membrane of the naso-pharynx, with which it is directly continuous, whilst that of the osseous division resembles, to some extent, the mucous membrane of the tympanic cavity. The epithelium of both divisions consists of the ciliated stratified columnar type, with some goblet cells, but the cells in the pharyngeal division, especially in the lower part, are taller than those of the tympanic portion, which are low cuboidal. In the tympanic portion ihe mucous membrane is closely united with the perios- teum and contains very few mucous glands and little or no adenoid tissue. In the cartilaginous division, on the contrary, the epithelium overlies a layer of adenoid Fig. 1363. Lateral lamina oblique ntuKle-fibres' Lumen of tube Tetisor palati (dilator tuba.)— .Mesial lamina of cartilage of tube ™l^¥'' Levator palati^ Tmniverve section of cartilaginous Eustachian tube, .v 7. tissue, often called the tubal tonsil. This tissue is especially abundant in children, and beneath it are found numerous mucous glands which open on the free surface of the tube. These glands extend nearly to the perichondrium and sometimes can l)e traced even through the Assures in the cartilage into the surrounding connective tissue. A considerable amount of adi{X)se tissue often occupies the submucosa of the lower and lateral walls. The submucous layer is well developed in the cartilaginous division of the tube, particularly in the outer membranous wall. It consists of loosely arranged tibro-clastic tissue, ^hich supports the mucous glands and the larger vessels and nerves. The muscles of the Eustachian tube are the levator and the tensor palati , the contractions of which not only affect the palate, but also produce changes in the position of the floor and in the lumen of the tube. These muscles are described in connection with the palate Tpage 159.^), suffice it here to note their close relations to the Eustachian tube, beneath and to the inner side of which the levator lies, and to the outer side of which the tensor extends. By reason of the intimate attachment which both muscles have to the cartilage of the tube, since both take partial origin from this structure, contraction of their fibres tend to draw apart the walls of the canal and they thus serve as dilators. Such action is particularly true of the tensor palati, many of '504 HUMAN ANATOMY. whose fibres are inserted into tibrous tissue completing the lateral wall of the tube (Fig. 1262), this part of the muscle being designated the dilator tubte. In addition to opening the tube, the levator palati elevates its floor. The blood-vessels of the Eustachian tube include the arteries, which arise from the ascending pharyngeal and from the middle meningeal and the Vidian branches of the internal maxillary; and the veins, which communicate with those of the tym- panum and of the pharynx and also form a plexus connecting with the cavernous sinus. The nerves are supplied from the tympanic plexus and from the pharyngeal branches from the spheno-(>alatine ganglion. The Mastoid Cells. The antrum tympanicum communicates posteriorly with a variable number of irregular pneumatic cavities, the mastoid cells (cellulae mastoideae), so called because the majority of these sjiaces occupy the mastoid process. Unlike the antrum, these cells are not developed at birth. As the mastoid process develops, the original diploetic structure is usually more or less replaced by larger cavities forming the pneumatic type. In a study of one thousand bones, Randall found that scarcely two per cent, of mastoids could be classed as diploetic, and only some ten per cent, as combining a notable amount of diplne with pneumatic spaces ; further, that no mastoid is absolutely pneumatic, although some senile bones show a single thin-walled cell occupying the greater part of the process. The pneumatic cells of this region may extend to the sigmoid portion of the lateral sinus ; into thr occipital bone ; into the squamous portion of the temporal bone and above the external auditory canal ; into the root of the zygomatic process ; into the floor of the Eustachian tube close to the carotid canal, . ii' occasionally as far as the apex of the petrous portion of temporal bone. Th' "^ are lined by a very thin mucous membrane, which is continu- ous with ■ J antrum and of the tympanic cavity. It is closely united with the perios u possesses a layer of low nonciliated squamous epithelium. The I- '. essels supplying the mastoid cells are the arteries derived from the stylo-n i. ■.. and the middle meningeal, and the veins, which communicate with those of the tympanum and the external wall of the mastoid process. Some of the veins are tributary to the mastoid emissary and the lateral sinus, whilst others puss beneath the superior simicircular canal through the cranial wall to join the dural veins. The nerves are the mastoid ramifications of the tympanic plexus. Practical Considerations : The Tympanum. — This cavity is continuous anteriorly with the nasopharynx by way of the Eustachian tube, and posteriorly with the mastoid antrum and air cells by way of the attic, so that infection, which is very common in the pharynx, may extend throughout this whole tract. The tympanic cavity extends above the limits of the membrane about 5-6 mm. as the attic, and about 2-3 mm. below as the "cellar" or hypotympanic recess. Secre- tions on the floor, therefore, may not be seen through the membrane. The defective drainage which results from the lower level of the floor of the tympanum, as com- pared with that of the external meatus, is one of the causes of the frequency of chrcnic otitis media with purulent discharge, even after the early evacuation of the products of inflammation in the acute stage. On the internal wall the facial nerve passes in a curve over the vestibule in the angle between the roof and inner wall of the tym|ianum, then downward in the slightly projecting Fallopian canal with a concave turn above and behind the oval window, continuing its course downward at the junction of the posterior and inner wall to emerge below from the skull at the stylo-mastoid foranien. This canal offers considerable resistance to caries in its immediate neighborhood, although the disease not infrequently communicates itself to the nerve. Such involvement of the nerve is often the prodromal symptom of a fatal cerebral affection (Politzer). At birth this portion of the Fallopian canal is very thin and translucent, and is deficient as it arches over the oval window, so that involvement of the nerve is much more common in children than in adults. PRACTICAL CONSIDERATIONS: THE MIDDLE EAR. 1505 Roofing in the antrum and the passage leading into it from the attic is a thin layer of bone (tegmen antri), which is particularly thin over the antrum and separates these spaces 'rom the middle fossa of the skull. Not infrequently there are membranous defects in the tegmen, upon which the dura rests (Macewen). Pus frequently passes through this bony plate, or its deficiencies, to the temporo- sphenoidal region of the brain, which is the most frequent seat of brain abscess. Fractures of the base of the skull in the middle fo«sa may pass through the tegmen, rupturing the adherent dura, and permitting cerebro-spinal fluid to pass into the tympanum. If there is coincident rupture of the tympanic membrane, the fluid will likely appear at the external auditory meatus, or if the membrane remains intact, the fluid may pass to the pharynx through the Eustachian tube. Often the hearing in chronic plastic otitis media is better during a great noise than when the surroundings are more quiet, because the stiffened ossicles transmit additional ordinary sounds more readily after they have been loosened by the more violent vibrations; or it may be because the auditory nerve, owing to the greater irritation, becomes more sensitive (Urbantschitsch). The various relationships of the tympanum as involved in infectious disease should be understood from the standpoint of etiology and from that of sequelae or complications. Infection may reach the tympanum from (a) the naso-pharjrnx through the Eustachian tube (scarlatina, diphtheria, pharyngitis, tonsillitis, rhinitis); or (6) the mastoid antrum and cells posteriorly, 't may extend from the tympanum (a) upward, by perforation of the tegmen, often deficient at places, leading tD external pachymeningitis, or to subdural abscess ; the dura, arachnoid, and pia mater at this level are fused, so that when the dura is ulcerated through, a diffuse meningeal infection does not ensue, but the process tends rather to spread into the brain along the perivascular lymphatic sheaths of the pial vessels, resulting in an abscess in the temporal lobe (Taylor); (*) to the internal jugular vein through venules that penetrate the fundus tympani to empty into the jugular bulb, and thence to the lateral sinus ; (<•) to the superior petrosal sinus and the dura mater of the middle fossa of the skull by the structures (veins and areolar tissue) passing through the petro-squamous suture ; (ed)us muscle, the posterior pouch lA the drum-head, the chorda tympani, and the fwsterior fold (pathologic). The/Vf/rro- inferior quadrant contains the round window, the tympanic cells in the floor of the tympanic cavity and the bulb of the jugular vein. The flaccid portion or Shrapnell's membrane corresponds to the neck of the malleus and Pnissak's space (Briihl-Politzer). The bulb of the jugular vein may be larger than usual in which case it may encroach upon the posterior half of the membrane. Moreover, it may have an imperfect bony covering when it will be in danger during paracentesis tympani, the place of election of which is in this portion of the membrane. For the same reason, pus in the middle ear may more readily encroach upon the vein. The posterior inferior quadrant is selected for openings to evac- uate effusions in the tympanum, because it is less sensitive and vascular than the rest of the membrane and corresponds to less important structures. The opening also gives better drain- age than through any other portion. It should be borne in mind that the floor of the tympanum is 2-3 mm. below the mferior margin of the drum head, so that in the upright position perfect drainage can- not be obtained. The tym- panic membrane has an internal mucous lining, an external cutaneous and an inter\'cning fibrous layer. It, therefore, has lii'i- elasticity, so that, while smj... openings often heal rap- A permanent opening, however. I^ottcricrMd 1'rull,ih'»fold PiMterkw lilfamCBt MFnilirslu lUalda Anl*rior lent malleus ^ntertof (old KouBd window rroinontorv Light reflea Normal dnitn.heac] of right tide ai m«ii with mirror. X 6. idly, large openings close slowly, or not at all. does not of necessity produce deafness. With an aural speculum and good light, one may locate the various structures as follows : Above and in front is seen the short process of the malleus as an ap[>ar- ently prominont point. From this point two streaks pass to the periphery, showing the division between the tense portion of the membrane and its flaccid portion (Shrapnell's membrane), seen only in a roomy meatus. E.xtending backward and downward from this point is seen a whitish streak ending at thv; umbo. This is the long process or handle of the malleus. Directed downward and forward from the umbo is an area of li^ht with its apex at the umbo and its base near the periphery of the membrane. It is triangular in shape and is due to the funnel shape of the membrane and the resulting light-reflex. Above and in front of the short process of the malleus is the membrane of Shrapnell. Through the grayish translucent tym- panic membrane the contents of the tympanum may sometimes be seen, changing apparently the coloi of the membrane. Its conical shape has been proven by trial and mathematically to be the most favorable for the reception of sound waves. The vibrations are traiisinilted thi'uugh the oasiclt»i lression called Rosenmiiller's fossa, the depth of which is increased in cases of enlargement of the pharyngeal tonsil and which may then lead to difficulty in the passage of a catheter into the Eustachian tube. It may also, when recognized, serve as a useful guide to the orifice of the tube. Injury to the orifice of the tulje during operations in the naso-pharynx, or at the posterior ends of the turbinates, may lead to cicatricial contraction and occlusion, thus causing defective hearing. Ulcerations in the naso-pharynx may produce a like effect. The length of the tube is about 37 mm. ( i ys in. ) and its pharyngeal opening is about 2;, mm. ( i in. ) lower than the tympanic. Its i:pper third (12 mm.) is bony, and its lower two- thirds (25 mm.) cartilaginous. The narrowest part, the isthmus, is at the junction of these two jxartions. The kimtn of the cartilaginous portion forms a somewhat S-shaped slit, the walls being in actual contact, except during the act of swallowing, when the slit opens so that air may reach the tympanum and equalize the atmospheric pressure on the two sides of the tympanic membrane. In the bony portion, though the lumen is smaller, it is open. In cases of obstruction of the tube at its pharyngeal end — as by pressure from a growth, or from a thickened mucosa — the outside pres- sure predominates, the tympanic membrane is pushed inward, and buzzing or "singing in the ears" results. Whenever the palate is raisetl or deglutition takes place, the tensor palati and palato-pharyngeus contract, and in so doing open the Eustachian tube by traction on the fibrous tissue which unites the outer borders of the fibro-cartilaginous scroll of which the tube is composed. Concussion of the tympanic membrane from loud reports, as from the firing of great guns, is minimized by breathing with the mouth open, thus elevating the soft palate, opening the Eustachian tube, and equalizing the pressure on the two sides of the membrane. Inflation of the tympanum is accomplished through the Eustachian tube, and is employed for diagnostic, prognostic, and therapeutic purposes. Several methotls are in use. Valsalva's consists of a vigorous expiratory effort while the nose and mouth are kept closed. Politzer inflates the tympanum through one nostril by a vigorous compression of a rubber air-bag, while the patient is in the act of swallow- ing. The opposite nostril and mouth are closed. The most satisfactorj' methoti in difficult cises is by means of the Eustachian catheter. The instrument is jiassed tip downward ilong the floor of the nose until it drops into the post nasal space and the ()osterior wall of the pharynx is reached. The tip is then turned gently outward and withdrawn about i cm. when the slight resistance of the cartilaginous rim is felt. After gliding forward over this prominence, it will engage in the orifice of the tube. The ring at the proximal end of the catheter — which is in the plane of the the curve of the beak and thus shows the position of the latter — is then directed toward the external meatus of the same side (Bonnafont). The catheter may lie withdrawn, and the tip at the same time l)e turned to the opposite side from the one to be catheterized, so that the lieak of the instrument catches on the edge of the vomer. It is then turned upward through 180', and thus enters the tubal opening (Frank, l.owenbergj. l5o8 HUMAN ANATOMY. Foreign bodies may lodge in the tube during vomiting, or a broken piece of the bougie may be left in. They will usually esca|je during vomiting or hawking, or they may be removed by an instrument if visible. If the tube is normal, a bougie I >2 mm. in diameter will easily pass the isthmus, the narrowest part. Strictures may be dilated or applications made by bougies. Narrowing of the lumen may occur near the isthmus from chronic inflammation or, at the pharyngeal orifice, from the pressure of pharyngeal adenoids, tumors, or polypi. Mastoid Process and Cells. — The mastoid process which is formed by the posterior extremity of the petrous bone, is relatively small at birth and contains no air cells except the antrum. The antrum is almost constant, although its size varies. In the infant it will hold a small pea, while in the adult its average len^h is from 12- 15 mm. (one-half inch or slightly more), its height 8-10 mm., and its width about 7 mm. (Briihl). It is the means of communication between the tympanum and the mastoid cells, so that infection finds an easy passage from the former to the latter. Its distance from the external surface of tht r,astoid process will depend upon the size of its cavity. This is usually from 12-14 mm. Anteriorly the antrum opens into the attic portion of the tympanum, and is in almost a direct line through that cavity with the Eustachian tube. A probe passed up the tube from the pharynx would pass through the attic into the antrum and would strike the joint between the incus and the stapes. The axis of the external canal would strike the line at an angle of about thirty degrees. The floor of the antrum ii below the level of the entrance into the attic, so that pus in the antrum tends rather to enter the mastoid cells. Sometimes nearly all the ma.stoid cells are pneumatic ; more frequently they are diploetic at the tip of the mastoid process, and pneumatic above (page 148). Pus in the air sf>aces may reach the diploetic region by breaking down the thin intervening septa. Those cases in which there are no mastoid spaces are probably sclerotic from pathological causes. Thus a chronic inflammation of the mastoid may give rise to new bone formation, filling the diploe and causing eburnation. This would tend to prevent the outward progress of pus and would favor its extension toward the interior of the cranium. The suprameatal spine is about 10-12 mm. above the floor of the antrum, which corresponds to a point about half way up the posterior wall of the bony meatus, and lies about 5 mm. posterior to the inner end. Thus bulging of the pc»terior wall of the meatus may result from disease in the antrum. The squamo-mastoid suture is frequendy seen on the surface of the mastoid process in children, and may give pas- sage to pus from the antrum to the surface. Through deficiencies in the mastoid process near its tip pus may find its way into the sheath of the sterno-cleido-mastoid muscle, or along the large blood-vessels into the neck. The bony wall between the antrum and posterior fossa of the skull is thin and cancellous, and may show deficiencies through which pus may reach the posterior fossa. In the fossa on the posterior surface of the mastoid process is the groove for the sigmoid sinus, which is frequently infected from disease of the antrum. Such infection may extend from the antrum to the posterior or cerebellar fossa of the skull, causing meningitis, septic thrombus of the lateral sinus, or a subdural or cerebellar abscess. The [X)ssible lines of extension of nia.stoid inP.animation may be summarized as follows (after Taylor) : (i ) Upward, from absorption of the thin tegmen antri, or through the veins passing up through foramina in the tegmen (causing external pachymeningitis in the floor of the middle cranial fossa), or through the remains of the petro-squamous suture (causing thrombosis of the superior petrosal sinus). (2 ) Downward, by emissary veins, or through a sinus at the lower part of the mastoid in the digastric fossa (causing cellulitis lieneath the sterno-niastoid, or travelling aloni^ the stvlo-glossus, stylo-pharyngeus and stylo-hyoid to the retro-pharyngeal region). (3) Forward, through the thin bony layer separating the external auditory meatus from the antrum .ind the mastoid cells f causing discharge from the meatus if the perforation is complet', or if it remains subperiosteal, directing the pus outward to a point just back of th.- pinna). (4) Outward — especially in children — through the thin post-auditory process of the squamous bone, or through the open masto- PRACTICAL CONSIDERATIONS: THE MinOLE EAR. i5<>9 squamous suture (causing a fluctuating adenomatous postauricular swelling, pushing the pinna forward and ntaking it unduly prominent). (5) Inward, either through venules passing to the sigmoid sinus, or through caries of the wall of the sigmoid groove (causing external pachymeningitis, or subdural absces.s, <>r suppurative basal meningitis, or cerebellar abscess — by way of the cerebellar veins emptying into the lateral sinus— or, most frequently, sigmoid sinus thrombosis). The sigmoid sinus is usually about i cm. behind the suprameatal spine, but is occasionally so far forward as to lie just beneath the external surface of the mastoid process, and immediately behind the bony wall of the meatus. Owing to its close relation to the mastoid antrum and cells, no other cranial sinus is so frequently the seat of infective inflammation. In infants, however, it is seldom seen, owing »o the foUow^ig facts ; First, the mastoid cells are not developed in them, though the antrum exists ; secondly, the squamous covering of the antrum is not yet soldered to the mastoid, and therefore, purulent matter finds a reatiy exit, not being enclosed in a ccmj;!t:te oony casing ; thirdly, more numerous exits for the venous blood exist in infants than in adults ; and fourthly, the sigmoid sinus rests on a flatter osseous surface than in adults, the bony gutter which imbeds the adult sinus being not yet fully formed. In infants the internal ear is more exposed than in adults to pathological encroachments from the middle ear, hence in them leptomeningitis is apt to ensue, which frequently ends fr ally, and that so rapidly as to prevent the formation of sigmoid sinus thrombosis (Macewen). When the sigmoid sinus is infected, extension may occur to the venous channels associated with it, esp>ecially to th'. internal jugular, anterior condylar, and deep veins of the neck into which the anterior condylar empty themselves. Evidence of involve- ment of these may be found in two areas, — along the internal jugular, and in the upper third of the posterior cervical triangle. Pain on pressure over the inflamed veins may be elicited even when the patient is deeply somnolent or semi-conscious. Thrombosis of the internal jugular when marked, is very easy of detection, as it lies so super- ficially. The finger perceives a cord-like formation to the inner side of the sterno- mastoid on the outer side of the artery, though the latter is sometimes overlapped by it. This may extend the whole length of the internal jusrular, but it is f. .'^uendy confined to the upper third. The entire thrombus may oe disintegrated and its par- ticles carried by the current to the lung, where they may set up >..ective infarction. They may be carried to the lungs by the veins passing into the posterior cervical triangle which flow through the vertebral and other channels to the subclavian (Macewen). The complication most to be feared in middle ear disease is the spread of the infection to the interior of the cranium. This may occur by direct extension of the carious process through the bone : more rarely through me labyrinth and internal auditory canal or the aqueducts ; or, still more rarely along the small blood-vessels or connective tissue fibres which pass through the bone between the middle ear and the dura. Very exceptionally the pus may find its way through the thin anterior wall into the carotid canal and along this to the cranial cavity. Although otitis media appears to occur on both si'les with equal frequency, the right side of the head has been said to be more frequently affected by intrarraiiial sequelae. If so, this is probably due to the greater size of the lateral sinus and the sigmoid sinus on the right side. Consequently the right sigmoid sinus encroaches more upon the petrous and the ma.stoid portions of the temporal bone, es|)ecially at the sigmoid knee, and the distance between the lower border of the tympanum and the antrum on the one hand and the sigmoid sinus on the other, is less than between the corresponding points on the left side (Macewen). Involvement of the internal ear from otitis media is comparatively rare. This portion of the ear is developetl independently of the rest, and, after necrosis, may be extruded in sequestne, in which may be recognized the structure t)f the labyrinth. If the pus associated fails to escape externally, there is danger of its passing through the internal auditory meatus and aquitductus vestibuli to the brain. Affections of the semi-circular canals produce disturbances of equilibrium. The sinus is in danger in operations on the antrum, the external opening for which should be immediately behind the meatus, and the centre of the opening 2-3 ^aam 15IO HUMAN ANATOMY. mm. below the level of its upper wall. If the sinus is in an abnormally anterior posi- tion, the posterior wall of the meatus must be removed to gain more nwm. The facial nerve is also in great danger in these o|>erations, and has frequently been injured. It lies in the inner wall of the mouth of the antrum, and is therefore, in front of it. The antrum is appro.ximately about 12 mm. (one-half inch) in a direc- tion very slightly inward, forward, and upward from a point on the external surface, 5 mm. (josterior to the suprameatal spine. The anterior edge of the opening made to reach the antrum, should be at this point, and its upper edge 3 mm. below the spine. It should never be carried deeper than i '2 cm. ( ^g in. ) from the anterior edge of the external opening, for fear of injuring the facial nerve or external semi- circular canal. As the situation of the mastoid antrum is the key to the position in all o[)erations upon either the antrum itself or the mastoid cells, Macewen has noted three points in the anatomy of the mastoid that may govern the surgeon in reaching the antrum without (a) ojjening the sigmoid groove and injuring its enclosed sinus; (b) encroaching upon the Fallopian canal and destroying the facial nerve ; (f ) invading the middle cerebral fossa ; (er cent.), the bone was diseased, but not the dura, in one (2.5 per cent. ), and the bone was healthy in two ( 5 per cent. ) ( Korner). It follows from this list of cases, that after a thorough exposure of the antrum antl the ear cavities, the carious process should be followed inward to the dura or brain. In case an abscess in the temporo-sphenoidal lobe cannot be reached in this way the skull may be opened by a trephine, or by an osteo-plastic resection immediately above the ear. A cerebellar abscess might be reached by an opening one and one-half inches behind the centre of the bony meatus and one inch below Reid's base line. THE INTERNAL EAR. The internal ear consists essentially of a '.lighly complex membranous sac, con- nected with the |)eripheral ramifications of the auditory nerve, and a bony capsule, which encloses all parts of the membranous structure and is embedded within the substance of the petrous portion of the temporal bone. These two parts, known respectively as the membranous and the bony labyrinth^ are not everj-where in close apposition, but in most places are separated by an interx-ening space filled with a fluid, the perilymph, the inner sac lying within the osseous capsule like a shrunken cast within a mould. The membranous labyrinth is hollow and everywhere filled with a fluid, called the endotymph, which nowhere gains access to the cavity occupied by the perilymph. The internal ear is closely related, on the one side, with the Ixjttom of the internal auditory canal, which its inner wall contributes, and with the inner wall of the tympanic cavity on the other. Its entire length is about 20 nmi. , and its long axis corresponds closely with that of the pyramidal or petrous THE INTERNAL K R. »5>« poitiun of the temporal bone. The position of approximately its posterior third » indicated by the transverse ridge that crosses the upper surface of the temp>ral bone a short disUnce Iwhind the internal auditory meatus. The irregular cavity of the bony labyrinth, hi Slowed out in the temporal bone, comprises three subdivis- FiG. 1264. Tytnimitic cavity Facial canal Cuchlea- ScniicirciiUir canaW Vcatibule Internal auditory cmnal Right temporal bon«, upper part ol petroni panion hat bam removed to show bony labyrinth lying In position. ions :- a middle one, the vestibule, an anterior one, \\\e cochlea, and a posterior one, the semicircular canals. Both the front and hind divisions communicate freely with the vestibule, but neither communicates with the membranous labyrinth nor, in the recent condition, with the tympanic cavity. Although corresponding in its general form with the bony compartments of the cochlea and semicircular canals, the membranous labyrinth less accurately agrees in its contour with the bony vestibule, since, instead of presenting a single cavity, it is subdivided into two unequal compartments, known as the saccule and the utricle, which are lodged within the bony vestibule. The divisions of the membranous labyrinth are, therefore, four, which from before backward are : the membranous cochlea, the saccule, the utricle and the membranous semicircular canals. The Osseous Labyrinth. The Vestibule. — The vestibule (vestlbulum), the middle division of the lx)ny labyrinth lies between the cochlea in front and the semicircular canals behind and communicates freely with both. It is an irregulariy elliptical cavity, measu'ing about 5 mm. from before back- •^ • Fk;. 1265. Superior ampulla Common cru»>^ Superior canal Horizontal Lodges utricle Lodges saccul Cochlea Posterior canal ward, the same from above downward , and from 3-4 mm. from without inward. The lateral (outer) wall separates it from the tympanic cavity, and contains the oval window with the foot-plate of the stapes. The medial (inner) wall, directed toward the bottom of the internal audi- tory canal, presents two depressions separated by a ridge, the crista vestibuli, .^ ,. ^l j the upper pointed end of which forms the pyramidahs vestibuli. The anterior and smaller of these depressions is the spherical recess ( recessus sphaericus) and lodges the saccule. In the lower part of this fossa, about a dozen minute peiforations mark the position of the macula cribrosa media for the passage of branches of the vestibu- lar iier\e from the bottom of the internal auditory canal to the saccule. The posterior and larger depression is the elliptical recess (recessus ellipticus). Behind the lower Pnftterior ampulla Cast of right lioiiy labyrinth, mesial aspect. ■. l. 1513 HUMAN ANATOMY. Cnw cummnnc- — ., AqiurductiiM WHtilmli Kecnwuw ;les to the long axis of the (letrous portion of the temporal bone, whilst the plane of the longest canal, the pos Fig. 1267. Small mil i:r posterior canul Cms commune Facial canal Oval (vestibular) window' Lamina !«|firalis - Round (ctjchlear) window Small end df horizontal canal Ampulla nr posterior canal Section of riffht bony lahyrinth passinfp through plani canal ; posterior wall of vestibule is seen from bctore. of sniierior semicircular 4- terior (canalis posterior) is approximately parallel to it. The external portion of the horizontal semicircular canal forms a prominence on the inner wall of the middle ear aljove the facial canal, while the upper part of the superior semicircular canal produces the conspicuous elevation, the eminentia arcuata, seen on the superior THE INTERNAL EAR. »5«3 surface of the petrous bone. The semicircular canals open into the fxisterior part of the vestibule by five apertures (Fig. 1267), the undilatcd ends of the superior and posterior canals joining to form a common limb (Qru» communej. The horisontal can^ (canalis lattralis) alone communicates with the vestibule by two distinct oyxn- ings. Its ampulla is at its outer end and lies at the upper part of the vestibule above the oval window, from which it is separated by a groove corres|x)nding to the facial canal. Lying above and close to this opening is placed the anipuUary end of the superior canal. The ampullary end of the postenor canal lies on the ffotir of the vestibule, near the opening of the no.>-diIated end of the horizonkil canal and of the canalis communis. In the wall of the ampulla of the posterior canal, a number of small openings (macula cribroaa inferior) provide for the entrance of the sjiecial branch of the vestibular nerve destined for this tube. The Cochlea. — The bony cochlea a>nstitute3 the anterior |)art of the labyrinth and appears as a short blunt cone, about 5 mm. in height, whose ba.se forms the an- terior wall of the inner end of the internal auditory meatus. Its apex is directed hori- Fio. 116.S. Sca1« v«»tib«li Scala tympan' Modiolus Am cochlnrb Area veHtibuIarid inferior. Internal auditory canal Foramen ningularc HamuluH, overlyinK hclii-iHrrnia 1-aminu KpiraliH Canalis spirMliM niiMHuli Facial cniuil C'-'hla falciformi;* Area veHtibularit huliertiir Cochlea and bottom of internal auditorj- canal exposed by vertical section p«MinK parallel with «ycoma ; prejara- lioii hal been turned so that cochlea rests with its base downwanl and apex pouiiiiiu upwaul. X 5. zontally outward, somewhat forward and downward, ami reaches almost to the Eusta- chian tube. Its large lower turn bulges into the tympanic cavity and produces the conspicuous ele\ation of the promontory seen on the inner wall of the middle ear (Fig. 1269). The bony cochlea consists essentially of a tapering central column, the modiolus, around which the bony canal, about 30 mm. long, makes something more than two and a half spiral turns, the dasa/, middle and apical. The conical modiolus has a broad concave base which forms part of the base of the cochlea (basis cochlea), and a small apex which extends nearly to the apex of the cochlea, or cupola (cupula). It is much thicker within the lowest turn of the canal than above, and is piercetl by many small canals for the nerves and vessels to the spiral lamina (Fig. 1268). The axis of the motliolus, from base to apex, is traversed by the central canal, whilst a more peripherally situatetl channel, the canalis spiralis, encircles the modiolus and contains th- spiral ganglion and a spiral vt-in. Prtiject- ing at a right angle from the modiolus into the canal of the bony cochlea is a thin shelf of bone, the lamina spiralis ossea, which is made up of two delicate bony plates between which are fine canals containing the branches of the cochlear nervx'. The spiral lamina begins between the round window and the lower wall of the I u HI MAN ANATOMY. vi»iibulc (F'lK. uf^), and after wiin injf spintUy »rounchlca, ciuls in a h(H>k-lik< prt)ces^ th< hamulus which forms jKirt of the th«- \i> indary ..( thf lulicotrema Fig. i ->y,>. The- canal 'if the ! .ny cochlea effe( —tl by the usscouh H-ral lanr membranous spiral lamina which str»-tches u ,m the i l.iininu, to whii li it is attachci to the outer vml the upper diviL^iun <.f the caivd is illt-d the scala v ubu! the vestibule, whilst the !• iwer ivision, tl scala tympai fxiitial division of the is completed by the edge ot the ossi-niiH 1 (Vn: .71). The ! conr nicates with would '.-n into the tympanic cavity, were it t,< ajHix »i tht cochlea i lose to i e beginning of tl scala tyni- |wni at the round • mdow is the jiner ontice of the aquaeductus cochlec (dacttis |)erilyaphati«is), 1 i.uter ..(.rni Vxin- m a depri .ion on the lower surface of the i>v inii-stablishes a coinniiuiicati "1 lietween the -viiKirachP'tii > lace and the scala tympani. Ihc internal auditory canal c< nmuiiicates with the cranial cavity by an o\ at ofxiiing on the jiost. nor surface of rh< .vramidal portion of the tem|>oral bin from whirh it exteiuls 0111* ;er inferior fossa by a transv i' ridv;*-. th' crista falciform^s. l^i the inter .r f>,in nf the superior fossa ( area Li.ialls ojK-ning of tht fa<.ial canal iMpMArductus FalUipii) lor the transmission of th« ner\ In its posterior part ti <■ openi j:3 (area vestibularis soperior) 1 brai !ies of the vestibular ner\ -winch -.upi the utricle and the ampulhe sup ior and horizontal semicir. iilar can.us. >,ese oixnin^s apix.ar in the n. >ril)ii>s.i ,iH«ri«>r on ;i.> inner surl.u if the 1j labyrinth (page 15:2). The rior part .1 she inferior 1"-^ is -alletl the area cochlearis and is (K-rforated y the oiM-ninf th. ce'tral can;d of the modiolus. Surroundiii Tous 1, II aj es of 1 le tractus spiralis foraminosus for s bran' es of i •• cochlear licrve to the two lower turns •' th- he are.i K-hlea ml siparaled from it by a ridge, lies tli ner\es i< . th these ojaMii lare, which th. aciu ■ th, ire .iis- iilea. >ul< area vvsCibu= .cculc. Th ,:- Behind • .. ieads into a t. iafi .iru 'S8ul of the maciii.i cribrosii inferioi tined fur the ampulla of the p.i «r) wit!; its small openings for . cribr<.^,i nietlia, described alxive, ferior is a large opening, the fort ■ H other end of which are the .sn; il transmit-, the branch of the vt-stibiilar nerve des- >r semicii. iilar canal. •sag ine(i ifv singu- lenings Tm. MKMBRANors Labyrinth. n mbranous i.ibyrinth ( labyrinthus membranaceus) lies . me bony kbvrii: iiich it resembles in general form. This agreement least inarkeit v»Tthin n st-stibule, since here the single division of the bony capsule is occupied '\ v. comi>artments of the membranous sac, the utricle and the s.i• M^i\ cii» ductus etk^ lymphaticus and a narrow channel, the canalis uiricui&-«accu<«m The Utricle. — The utricle (utriculus) occup.t-s thr rctesMus 4ii^*icus in the u|)|)er back part of the vestibule. It is larger tlu-ai the ^ccule and communicates with the three membranous semicircular caruls. Att.4cb.-|H-nn<)st of whieh is rcspresentetl by a blinil sac, (ruin -3.5 mm. in U-UKtli i«>sf i>en f i ) tin- ampulla of th. in>erior semicircular anal and (.2) ' of the horiz'-ntid canal, /nto the utricn.iis /»o/>nii.f »\Kn t ^) the sinus superi> hicli ies withi. he crus Cf)mmune and receives in turn the nonampullatetl ei >l thi ,ii!>erior -id posterior semicircular canals: i4» thi non- ampullated end of the hn /..utal s< licircular canal; and (5) the ani)mlla of the posterior semicircul.ir ca 'li through tlie 'lus posterior. On the anterolateral wall •f the recessus ut' li ,, p|,i,.t(.i the m.ti ula acustica of the utricle, whilst from its Fic;. ijli/. Ilaniiiln« Hrllnrtrema I'actat cBtinl Vr*tilnilar(iivHl iwimlow 1 yiiilMiilii' cavily Promi.mon.- ProlKT l»a«.M*s thruUKH cochlear t round RiKht hony i-tKhlea (tartially expo^*' Scala tynijinni antero-mesial w.ill sprinjjs I. utricle that joins even a suutu iiulolymphaticus. The Saccule. — Thes,i. 3 bv 2 mm. in size, which o pait (jf the vestibule, 10 whii i>> flattened laterally and at its li iii.illv reuniena, vhich connects the with bulges Kirk. v.ird forminj,' the sir. triculans, that of he utricle. The small iial, the ductus (.nilolyinphaticiis, ari> froir ductus endolymphaticus ])asses thn blind ■iilateil extremity, the saccus en of the dura i inter below the openinj.: ■ the recessus sphericus branches of tli. macuii acustica .siiccnli on the anterior v is the -ery small tulx- passing from tlii wall of the cochlear duct near the csecuri: is called. The Membranous Semicircul lares oci upy alxjut "iie thinl of the di \ytr- -..su if; t.s u . lul ,U c. '■! coi t with lied linj; > fonii '' >.iccii T'lf rill! to tnc! in a 'wfii the Liyrs ' ih "he ooeninj}!^ tn eiui r ami |.-.:" to tlw- The canaas reunicns iccule inl- uiy lilt iMfSterio; ' '!'• .iq»a-- sa ule. ivver part of the vestibulare, as its blind vi-stibui.. inals. — These tul)es (ductus sem uT of the osseous canals and coi' i* t I5i6 HUMAN ANATOMY. FiO. Trahectllic Memhranoutt canal to them in number, name and form. They are closely united along their convex margins with the bony tube (Fig. 1270), whibt their opposite wall lies free in the perilymphatic space, "'*'• being attached only by irregular vascular con- nective tissue bundles, ligamenta labyrin- thi canaliculorum, which stretch across this space. Like the bony canals, each of the membranous tubes possesses an aftipulla, which in the latter is relatively much larger than in the former, being about three times the size of the rest of the tube. The part of the ampulla corre- sponding to the con- vexity of the semicir- cular canal is grooved on the outer surface at the entrance of the ampullary nerves. On the corresponding in- ternal surface is a pro- jection, the septum Pelitymphatic, spflce TrmhcculK Bony wall Truuvene wctlon of ■nperior ntnidreular canml. thowiiiK Riationi o( mcmbnuia to bony tube. >: 3$. transversum, which partially divides this space into two parts and is surmounted by the crista acustica, which contains the endings of the vestibular nerves. The crescent-shaped thickening beyond each end of the crista is called the planum semilunatum. Structure of the Utricle, Saccule and Semicircular Caaalt -The veatibule and the bony ■emicircular canals are lined by a very thin periosteum composed of a felt-work of resistant fibrous tissue, containing pigmented connective tissue cells. Endothelium everywhere lines the perilymphatic space between the membranous and osseous canals, covering the free inner sur- face of the periosteum, the fibrous trabeculse, and the outer or perilymphatic surface of this part of the membranous labyrinth. The walls of the utricle, saccule and membranous semicircular canals are made up of (a) an outer fibrous conn f dive /issue lamella and («) an inner epithelial lining, the latter consisting throughout the greater part of its extent of a single layer of thin flattened polyhedral cells. Be- neath the epithelium, especially in the region of the maculse, is (r) a thin, almost homogeneous hyaline tnembrane, with few cells. This middle layer presents in places on its inner surface small papillary elevations covered by epithelium. On the concave side of each of the .semicircular canals is a strip, the raphe, of thickened epithelium in which the cells become low cylindrical in type. In the plana semilunata they are cylindrical in type. Over the regions receiving the nerve-fibres, the maculx actisticae and the crista; acusticx, the epithelium undergoes a marked alteration, changing from the Indifferent covering cell* into the highly specialized neuroepithelium. The macula acusticK are about 3 mm. k)ng by 3 mm. broiul, the macula of the saccule bemg a little narrower { i. 5-1.6 mm.-) than that of the utricle (2 mm. ). At the margin of these areas the cells are at first cuboldal, next low columnar, and then abruptly increase in length, until they measure from .030-.035 mm., in contrast with their usual height of from .cx)3-.ocj4 mm. The acoustic area includes two kinds of elements, the sustentacular or fibre-cells and the hair-cells. The sustentacHlar cells are long, rather narrow, irregulariy cylindrical elements and extend the entire thickness of the epithelial layer, resting upon a well-developed basement-membrane by their expanded or divided basal proces.ses. At a variable distance from the ba.se, they present a swelling etielosmg an oval nucleus and terminate at the surface in a culicular zone. The cylin- drical hair'cells are broader but shorter than the SKstentacular cells, and reach from the free surface only as far as the middle of the epithelial layer, where each cell terminates usually in a THE INTERNAL EAR. 1S17 rounded or somewhat swollen end containing a spherical nucleus. The central end, next to the ' free surface, exhibits a differentiation into a cuticular zone, similar to that covering the Inner ends of the sustentacular elements. From the free border of each hair-cell, a stiff robust hair (.oao-.o25 mm. long) projects into the endolymph. This conical process, however, is resolv- able into a number of agglutinated finer hairs or rods. The free surface of the neuroepithelium within the saccule and the utricle is covered by a remarkable structure, the so-called otolith mcmtiranc. This consists of a gelatinous membrane in which are embedded numberless small crystalline bodies, the otoliths or ear-stones. Between it and the cuticular zone is a space, about .030 mm. in width and filled with endolymph, through which the hairs project to the otolith membrane. The otoliths (otoconia) are minute crystals, usually hexagonal in form, with slightly rounded angles, and from .009-.011 mm. in length. They are composed of calcium carbonate with an organic basis. On reaching the macula the nerve-fibres form a subepithelial plexus, from which fine bundles of fibres pass toward the free surface. The fibres usually lose their medullary substance in passing through the basement membrane and enter the epithelium as naked axis-cylinders. Passing between the sustentacular cells to about the middle of the epithelium, they break up Into fine fibrillae, which embrace the deeper ends of the hair-cells and give oS fine threads that pass as free axis-cylinders between the cells to higher levels. The criau acuatica and the planum aemilunatum are covered with neuroepithelium similar to that of the maculse. The hairs of the hairerilymph and are brought into relation with the subarachnoid space through the aquaeductus cochlex. They are lined by a delicate (ibrous periosteum, usually covered on the surface which is in contact with the enclosed perilymph, by a single layer of endothelial plates. In some localities, however, as on the tympanic surface of the basilar membrane, the lining cells retain their primitive mesoblastic character and never become fully differentiated into endothelium. The third compartment, the ductus cochiearis, is triangular on cross-sectiun (Fig. 1 271), except at its ends, and bounded i>y Reissner's membrane above, by the basilar membrane and a part of the osseous spiral lamina below, and by the outer wall of the bony cochlea externally. Save for the narrow channel, the canalis reuniens, by which it communicates with the saccule, the cochlear duct is a closed tube and contains endolymph. It begins below as a blind extremity, the cscum vestibulare, lodged within the recessus cochiearis of the vestibule and, after making two and three-quarter turns through the cochlea, ends above at the cupola of the cochlea in a second blind extremity, the caecum cupulare, or lagena, which is attached to the cupwia and forms a part of the boundary of the helicotrema. Architecture and Structtire of the Cochlear Duct. — Reittner'a membrane (membrana vctitih- ularls), the delicate partition separating the cochlear duct from the scala vestibuli. befrins on the upper surface of the lamina spiralis, about .2 mm. medial to the free edge of the iHjny shelf, and extends at an angle of from 40-45" with the lamina spiralis os.sea to the outer wall of the cochlea, where it is attached to the periosteum. Notwithstanding its excessive thinness ( .003 mm. ), it consists of three layers : (a) a ver)- delicate middle slratum of connecHi'e tissue, (b) the endothelium covering the vestibular side, and (c) the epithelium derived from the coch- lear duct, and contains sparingly distributed capillary blood-vessels. The outer wall of the cochlear duct (Fig. 1372) is bounded by a part of a thickened cres- centic cushion of connective tissue, whose convex surface is closely united with the bony wall and whose generally concave surface looks toward the cochlear duct. This structure, the liga- mentum tpirale, extends slightly above the attachment of Reissner's membrane and to a greater dist.ince below the attachment of the b<-isilar membrane, thus forming part of the outer walls of the scala; vestibuli and tympani. At its junction with the ba.silar membrane it presents a marked projection, the crista basilaris, whilst a very slight elevation marks the (wint of attach- ment of the membrane of Reissner. The part of this ligament lying between these projections corresponds to the outer wall of the cochlear duct. Its concave free inner surface is broken by a third elevation, the prominentia spitalia, or accessory spir ' ligament, distinguished usually by the presence of one large (vas prominems) or several smaii blood-vessels. The lower and smaller of these two divisions of the outer wall is called the lulcus spiralis extcmus and is lined by cul)oidal epithelium, whilst the larger upper division is occupied by a peculiar va.scular structure, the stria vascularis, which contains cipillary blood-vessels within an epithelial struc- ture. Its surface is covered with pigmented irregular polygonal epithelial cells, and its deeper strata consist of cells which, especially in the superficial layers, resemble the surface epithelium, but in the deeper layers assume more and more the character of connective tissue. t)ver the prominentia spiralis the cells become flat and polyhedral. The ligamentum spirals is composed of a peculiar connective tissue, rich in ceils and blood- vessels. Its thin outer layer forms the jHjriosteum and is denser than the adjacent loose con- nective tissue. The latter is broiidest opposite the scala tympani, where its fibres converge towards the crista biisilaris. Opposite the outer wall of the cochlear duct it again becomes more conipjict and is rich in cells and blood-vessels. An internal layer extending from near the prominentia spiralis to the basilar membrane consists of ,. hyaline, noncellular tissue. Some authors claim to have found smooth muscle-fibres in the ligamentum spirale. The tympanic wall or floor of the cochlear duct (Fig. 127a) comprises the basilar mem- brane, extending from the basilar crest to the outer end of the bony spiral lamina, and the limbus laminie spiralis, which includes this wall from the attachment of Reissner's membrane to the end of the bony lamina. The limbus (crlma *plrali*) is a thick mass of connective tissue upon the upi>er surface of the outer end of the os.seous lamina spiralis. Its outer extremity is deeply gr(K)ved to form a gutter, the sulcus spiralis intemus, the projections of the limbus above ami below the .sulcus forming rcspccti > cly its superior (vestibul.ir) .ind inferior (tjmpanir) labia. The up(>er surface of the limbus is marked by clefts and furrows which are most conspicuous near the outer margin of the upper lip ( labium vestibulare ) , where the irregular projections l>etween THE INTERNAL EAR. •5«9 the furrows form the so-called auditory teeth, because of their fancied resemblance to incisor teeth. The lower Up (lablun lympaakum ) is continuous externally *ii' the liasilar membrane and is perforated near its outer end by some 4000 apertures (foramina ntrvou) trinsmittinK minute branches of the cochlear nerve. The epithelium covering the elevated portions of the limbus, includiuK the auditory teeth, is of the flat polyhedral variety, the intervt- niiiu furrows anng to be an extension of those of the lower lip of the limbus, whilst straight and more distinct fibres stretch from the outer rods of Corti to the spiral ligament and coastitute the so-called auditory atringa. According to the estimate of Ketzius, there are 24,. 100 Fig. \rj». ■stria viiKoilariH 'KelMiirr's memhrant? Pmmincntin *p4rali« Membrana tectoria S|>iral lixament Criiita iHiHitariH Nerve-fibm« Vas spiralii Uuiic Cioai-icctian of d"..-liu cochleai U from human cochlea. \ ^u. Uiawn frDm prapara'ioii made by Dr. Ralph Butler. of these special fibres. Their length iVicrea.ses from the Iwse toward the apex of the cochlea, in agreement with the corresponding increase in breadth of the basilar membrane. The tympanic lamella contains numbers of fusifonn cells of immature character interspersed with fibres. In this location the differentiation of the m -soblastic cells lining the tympanic c.inal has never a vanced to- the production of typical end>>thelial plates, the free surface of the lamella being inver>teasilar membrane forms the organ of Corti, the highest example of specialization of ncuro-epithelium. The Organ irf CortL — The organ of Cork (organon B|iiralr) consists in a general way of a series of epithelial arches formed by the interlocking of the upper ends • jf uonvir^jing and greatly modified epithelial cells, the pillaraor rodaof Corti, uiv>n the inner ,in.' .mli-i -iji..^ 01 wLith rrst groups of neuroepithelial elements — the auditory and the auatentscular ceils, t'lio triangui:'.r space included between the converging pillars of Corti ^ilwve and ihe b.i.s;'^ miivbr^ne tx.-low constitutes the tunnel of Corti, which is, therefore, only an intercellular spar. ..: unusu il size. It contains probably a st>ft semifluid intercellular substance serving i'>si)i>port ihe nerve-fib ils traversing the space (Fig. 127,,). The pillara or roda of Corti, cxiin;;;.'LHl in -.let,- 1!. j)mv< to K- composed of two jwns, the ilensei substance of the |)illur proper, aiiJ a llni \\> <)'<.' pioi.. plasmic envelope, which presents atridug-ularthickeningat the base dircc.ed tow. ird the -aviiy oi the tunnel. Each pillar possesses a slender slightly sigmoid, longitudinr.'A strir\;cd hody. vhuse tS20 HUMAN ANATOMY. upper end terminates in a triangular kead, and whose lower extremity expands into the /oo/ resting upon the basilar membrane. The inner pillar is shorter, more nearly vertical and less curved than the outer ; its head exhibits a single or double concave articular facet for the recep- tion of the corresponding convex surface of the head of the outer rod. The cuticular substance of lx>th pillars adjoining the articular surfaces is distinguished by a circumscribed, seemingly homogeneous oval area of different nature. The upper straight border of the head of each pil- lar is prolonged outwardly into a thin process or head-plate, that of the inner lying uppermost and covering over the head and inner part of the plate of the outer pillar. The head-plate of the latter is longer and projects beyond the termination of the plate of the inner rod as the phalan- geal process, which unites with the adjacent phalanges of the cells of Deiters to form the mem- brana reticularis. The inner pillars of Corti are more numerous, bui narrower than the outer elements, from which arrangement it follows that the broader outer rods articulate with two and sometimes three of the inner pillars, the number of the latter in man being estimated by Retzius at 5600, as against 3850 of the outer rods. Immediately medial to the arch of Corti, resting upon the inner rods, a single row of spe- cialized epithelial elements extends as the inner auditory or hair-celU. These elements, little more than half the thickness of the epithelial I'/er in length, possess a columnar body contain- ing an oval nucleus. The outer somewhat constricted end of each hair-cell is limited by a Ouier hair- cells Hensen's cells Celb of Deiters Fig. 1273. Niiel* apace Inner liair-cellii MembniiM tectoriit Section showing details of Cortl's ornan from human cochlea ; owinx to slight obliquity of section, width is some- what exaggerated, x 375. Drawn from prefiaration made by Dr. Ralph Butler. sharply defined cuticular zone, from the free surface of which project, in man, some twenty-five rods or hairs. The inner hair-cells are less numerous (according to Retzius about 3500), as well as shorter and broader, than the corresponding outer elements. Their relation to the inner rods of Corti is such, that to every three rods two hair-celli are applied. The inner auctcntacular cells extend throughout the thickness of the epithelial layer and exhibit a slightly imbricated arrangement as they pass over the sides of Corti's organ to become continuous with the lower cells of the sulcus spiralis. The cells covering the basilar membrane from the outer pillar to the ba.silar crest comprise three groups: (a) those composing the outer part of Corti's organ, including the outer hair- cells and cells of Deiters ; (*) the outer supporting cells, or cells ofHensen; (f ) and the low cuboidnl elements, the cells of Oaudius, investing the outermost part of the basilar membrane. The outer auditory or hair-celli are about five times more numerous ( approximately 1 8,000 according to Waldeyer) than the corresponding inner elements, and in man and apes are dis- posed in three or four rows. They alternate with the peculiar end-plates or " phalanges " of Deiters' cells, which separate the ends of the hair-cells and join to form a cuticular mesh-work, the membrana reticularis, through the openings of which the hair-cells reach the free surface. The inner row of these cells lies directly upon the outer rods of Corti, so placed that each cell, as a rule, rests upon two rods. The cells of the second row, however, are so disposed that each cell lies opposite a single rod, whilst the third layer repeats the arrangement of the first In conse- quence o( ihls grouping, these elements, in conjunction with the " phalanges," appear iti surf;!Ce views like a checker-board mosaic, in which the oval free ends of the auditory cells are included between the peculiar compres.sed and indented octagonal areas of the end-plates of Deiters' cells THE INTERNAL EAR. 1521 Cells oi Hnncn Deitert' cella Outer hair-cells Plate-like processes ol hair-cell Outer pillar cella Inner hair-cells (Fig. 1374). The outer hair-cells are cylindrical in their general fomi, tenniiiatinK about the mid- dle of the epithelial layer in slightly expanded rounded ends, near which the spherical nuclei are situated. The outer sharp' defined ends of the cells are distinguished by a cuticular border su|>- porting about twenty-five rigid auditory rods or hairs which project beyond the level of the nieni- brana reticularis. The deeper end of each outer hair-cell contains a dense yellowish enclosure, known as the body o/Kelzius, which is triangular when seen in profile. The bodies are absent in the inner hair-cells. The cella of Deiter* have much in common with the ruds of Corti, like these being special- ized sustentacular epithelial cells which extend the entire thickness of the epithelial stratum to terminate in the peculiar end-plates or phalanges. It follows, that whilst the free surface of Corti's organ is composed of both auditory and sustentacular cells, the elements rtsting upon the basi- lar membrane are of one kind alone — the cells of Deiters. The bodies of the latter consist of two parts, the elongated cylindri- cal <"A;V//or/io« of the cell, con- Fig. 1174. taining the spherical nucleus and resting upon the basilar mem- brane, and the greatly attenuated pyramidal phalangeal process. A system of communicating in- tercellular clefts, the spaces of Nuel, lie between the auditory and supporting cells ; like the tunnel of Corti, these spaces are occupied by a semifluid intercel- lular substance. The cells of Deiters are arranged, as a rule, in three rows, although in places within the upper turns four or even five alternating rows are sometimes found. Each cell contains a fine filament, theyC&r; ofRetztHS, which begins near the middle of the base with a conical expansion, and extends through the cell-body to the apex of the phalangeal process, where, according to Spee, it splits into .seven or more fine end-fibrils, that extend into the cuticular superficial layer under and about the phalanges. The membrana tectoria or Corti's membrane stretches laterally from the upper lip of the llmbus, above the sulcus spiralis and Corti's organ, as far as the last row of outer hair-cells. The membrane is a cuticular production, formed originally by the cells covering the rt^ion of the auditory teeth and the spiral sulcus. Medially it rests upon the epithelial cells, but farther outward it becomes separated from the free edge of the auditory teeth and a.s.sumes its conspic- uous position over the organ of Corti. The membrane seems to be composed of fine resistant fibres, held together by an interfibrillar substaiKe. During life the membrane is probably soft and gelatinous, and much less rigid than its appearance indicates after the effect of reagents. The lower surface of the free portion of the membrane, opposite the inner hair-cells, is mod- elled by a shallow furrow, which indicates the position of a spirally arranged band known as the stripe of Hensen. Like the basilar membrane, the membrana tectoria increases in width from the base towards the apex of the cochlea. The outer sustentacular cells or cells of Hensen form an outer zone immediately external to the last Deiters' cells. These elements resemble the inner sustentacular cells, but differ somewhat in form and arrangement. In coivsequence of their oblique position, the bodies are not only greatly elongated, but also imbricated. They do not contain the fibres of Retzius. The cells ol Claudius are the direct continuations of Hensen's cells, and laterally pass uninterruptedly into the low columnar elements covering the remaining part of the basilar membrane. They consist of a simple row of cuboidal cells possessing clear, faintly granular protoplasm and spherical nuclei. The Nerves of the Cochlea. — The branches of the cochlear division of the auditory nerve enter the base of the cochlea through the tradus spiralis foramhiosus (page 1514), those destined for the apical turn traversing^ the central canal of the modiolus. From the modiolus a series of stout lateral branches diverge at quite regular intervals through canals which coiuinuiiicate uith the peripheral spiral canal within the base of the bony spiral lamina. Within the peripheral canal the nerve- fibres jo'n numerous aggregations of bipolar nerve-cells, which continue along the Corti's organ viewed from above, showing mosaic formed by rillats and Deiters' cells ; outer ends oi auditory cells occupy mesihes of cuticula r net-work. {Xelximsi. m^ kW m 1533 HUMAN ANATOMY. 'i^ spiral canal and collectively constitute the ganglion tpirale. From these cells numerous dendrites are given of!, which pass ^ong the canals within the spiral lamina towards its margin, the twigs meanwhile subdividing to form an extensive plexus contained within corresponding channels in the bone. At the edge of the spiral lamina bundles of fine fibres are given of!, which escape at the foramina ner\'ina of the labium tympanicum and enter the epithelial layer close to the inner rod of Corti. During or before their passage through the foramina, the nerve-fibres lose their med- ullary substance and proceed to their destination as fine naked axis-cylinders. The radiating bundles pass within the epithelium to the mesial side of the base of the inner pillar ; here they divide into two sets of fibrillse, one, the mesial spiral fasciculus, going to the inner hair-cells and the other, the lateral spiral fasciculus, passing between the inner pillars to reach the tunnel of Corti. Within this space fibnllae are given off which, after crossing the tunnel, escape between the outer rods into the epithelium lying on the lateral side of the arch. The further course of the fibrilla; seems to be such that some extend between the outer pillar of Corti and the first rows of hair-cells, whilst succeeding groups of fibrillae course between the rows of Deitcrs' Fici. 1275. 'Stiperuir canal RnHiIar membrane Branches of cochlear nerve to Corti'8 organ Membranous cochlea Canalis rcunienn opening into cochlear duct mterior canal Blinil Mac of ductus cuchlearis Branch of veatibular nerve to p* Membranous labyrinth of five months ftctus. fjostero-mesial aspect : u, utricle ; jj, */, sujierioi .md )K»stcrinr utric- ularsinus; j, saccule; hj, utriculo-saccular canal ; cr, canalis reuntens; pa, posterior ampulla. X 6. ^/tetzins). cells to reach the remaining hair-cells. The relation between the nerve-fibrils and the auditory cells is in all cases probably close contact and not actual junction with the percipient elements. The p.-iths by which the impulses collected from the audi- tory cells are conveyed to the cochlear nucleus, and thence to the higher centres, are descrilxid in connection with the Auditory Nerve (page 1258). Blood- Vessels of the Membranous Labyrinth. — The arteries supplying the internal ear arise from the internal auditory artery, supplemented to a limited extent by branches from the stylo-mastoid. The auditory artery, a branch of the kisilar, after entering the internal auditory meatus divides, according to Sicbenmann, into three branches : — ( i ) the anterior vestibular, ( 2 ) the cochlear proper, and ( ^ ) the vestibulo-cochlear artery. 1. The vestibular artery accompanies the utriculo-ampullary nerve and sup- plies the upper part of the vestibule, including the posterior part of the utricle with its macula, the saccule and the crista of the upper and outer ampullae of the corre- sjxjnding semicircular canals. 2. The cochlear artery pursues a spiral course. It gives of! three branches, two of which are distributed tchlea is mucR more generous than that of the others. The veins by which the blwxl escai)es from the cochlea include : ( I ) the vein of the vestibular aqueduct, which empties into the superior petrosal sinus ; (2) the vein of the cochlear aqueduct, which empties into the internal jugular and (3) the venous ple.xus of the inner au- structure, and the accessory parts, com- prising the middle ear, with its ossicles iiiiU a.ssociated cavities, and the external auditor)' canal and the auricle. The developmental history- Fig 1276. Hind-ttrahl Auditory pit Dorvi! aorta Orophar>-nx I visceral fiirniw of the organ of hearing pro|)er in its early stages is largely an account of the growth .nnd differentiation of the ectoblastic otic vesicle, since from this is produced the imix)rtant membranous tube, the enveloping fibrous and osseous structures being com|Kiratively late contributions from the mesoblast. Development of the I-abyrinth.— The internal ear appears as a thickening .ind soon afte' depression of the ectoblast within a small area on either side of the cephalic end of die neural tube, at a level correspond- ing to alxjut the middle of the hind-brain (Fig. 1276,. This depression, the auditory pit, is widely o|)en for a considerable time -.wA distinguished by the greater thickness of its depressed wall, which contrasts strongly with the adjacent ectoblast. After a time the lips of the pit approximate until, by their final union, the cup-like depression is converted into a closed sac, the otic vesicle. This sac, after severing all conne<-tion with the ectoblast, gradually recedes from the sur- face in consequence of the growth o* the inter\-ening mesobUustic layer ; it next loses its sphe- roidal form and becomes somewhat pe,nr-sha|ied. with the smaller end directed tlorsally. The smaller end rapidly elongates into a clul>shaped diverticulum, the receiius endolymphaticus, which later becomes the ductus and the saccus endolymphaticus. The remainder of the otic S.1C soon exhibits a subdivision into a larger dilatation, the vestibutar pouch, and a smaller ventral om, \Yiv cochlear poHch {Vxfi. 1297). Frontal section of early rabbit embryo, <>l!f pits. V, 40. I5H HUMAN ANATOMY. 1 1 Fig. 1277. Hinil-brain Otic sac The Minieircular canals differentiate from three folds which grow from the vestibular pouch opposite the attachment of the ductus endolymphaticas. The central parts of the two walls of each fold unite and undergo absorption, while the peripheral part of each fold remains open, thus forming a semicircular tube, one end of which becomes enlarged to form the ampulla. The superior vertical canal appears first, and the horizontal or external last. The growth of the epithelial diverticula is later accompanied by a condensation of the surrounding mesoblast, which differentiates into an external layer, the future cartilaginous and later bony .psule ; a layer internal to this becomes the perichondrium and later periosteum. A second mesoblastic layer Is formed from the cells immediately surrounding the otic vesicle, whilst the space between these fibrous layers is filled by a semi-gelatinous substance which later gives place to the perilymph occupying the perilympnatic space. Within the ampullx, which early develop, the epithelial lining undergoes specialization, accompanied by thickening of the meso- blastic wall wittiin circumscribed area.s, to form the cristae acusticx. Coincidently with the development of the semicircular canals, a diverticulum, the cochlear canal, appears at the lower anterior end of the membranous sac. This tube, oval in section, grows forward, downward, and inward, and represents the future cochlear duct. After attaining considerable length, further elongation is accompanied by coiling and the assumption of the permanent disposition of the tube. The epithelium of the cochlear tube early exhibits a distinction, the cells of the upper suri.ice of the somewhat flattened canal becoming attenuated, whilst those on the lower wall undergo thickening and further differentiation. The flattened cells form the epithelial covering of Reissner's membrane and of the outer wall, and the taller elements are converted into the complicated structures of the tympanic wall of the ductus cochlearis, including the crista, the sulcus, and the organ of Corti. The development of these structures includes the differentiation of two epithelial ridges ; from the inner and larger of these is derived the lining of the sulcus spiralis and the overhanging membrana tectoria. The outer ridge is made up of six rows of cells, the inner row becoming the inner hair-cells, the outer three rows becoming the outer hair-cells, whilst the two rows between these two groups form the rods of Corti. The cristii appears between the sulcal cells and the cochlear axis a<; a thickening of the spiral lamina. The cochlear outgrowth of the primary otic vesicle- forms the membranous cochlea, or scala media, alone, the walls of the adjacent divisions, the scala vestibuli and seals tympani, resulting from the changes within the surrounding mesobla-st. The latter differentiates into two zones, an outer, which becomes the cartilaginous, and finally os.seou.s, capsule, and an inner, lying immediately around the membranous can.-il, which for a time constitutes a stratum of deli- cate connective tissue between the denser capsule and the ectoblastic canal. Within this layer clefts appear, which gradually extend until two large spaces bound the membranous cochlea above and below. These spaces, the scala vestibuli and tht- scala tympani, are separated for a time from the scala media by a robu.st septum consisting of a mesoblastic layer of considerable thickness and the wall of the ectoblastic tube. With the further increa.se in the dimensions of the lymph- spaces, the partitions separating them from the co- .lear duct are correspondingly reduced, until, finally, the once broad layers are represented by frail and attenuated structures, the membrane of Rcisuner and the basilar membrane, which consequently include an ectoblastic stratum, the .r, thelial layer, strengthened by a mesoblastic lamina, represented by the sub- stantia propria .md its endothelioid covering. Thv- main sac of the otic vesicle from which the foregoing diverticula arise constitutes the primitive ni?mbrancus vestibule, and later subdivides into the saccule and utricle. This separa- tion begins as an annular constriction of the primitive vestibule, incompletely dividing the vesicle into two compartments. The still relatively large ductus endolymphaticus, the direct successor of the recessus endolymphaticus, unites with the narrow canal connecting these vesicles in such a manner that each space receives one of a pair of convergi:!-; limbs, an arrangement foreshad- owing the permanent relations of the parts. Even before the subdivision of the primitive vestibule Is established, the vestibular end of the cochlear canal becomes constricted, so that communication Ixrtween this tube and the future sacCTile is maintained by only a narrow passage, later the canalis reunicns. The dex-el- opment of the maculae acustica: of the saccule and utricle depends upon the specialization of Part of frontal KCtioR ci bead o{ rahbit cffibrvo ; otic sac is svparatcti from ectoblast and beginning ku elunsatc. X 40. DEVELOPMENT OF THE EAR. «525 Well of brmin-vciiicle' Endolymphatic Trwtm Vcitihiiter ]xiiich Otic vesicle ibowi dillemitialion into three subdiviiioa*, endo- lymphatic, vestibular and cochlear. X 4o- the epithelium within certain areas associated with the distribution of the auditory ner\'es. The ner\e-fibres form their ultimate relations with the sensor)' areas by secondary growth into the epithelial structures. Development of the Auditory Nerve*. — The vestibular and cochlear ner\-es, according to Streeter', develop from a KanKlion-ma.ss first seen at the anterior edge of the otic vesicle. This consists of an upper and lower part from the dorsal and ventral portion Pic. , j-g. of which peripheral ner\'e branches , are developed, whilst a single stem connects it with the brain. The nerves destined for the utricle and the superior and external ampulla develop from the upper part of the ganglionic mass, while the nerves which supply the saccule and posterior ampulla develop from the lower part of this ma.ss. The stem extending centrally from the ganglion toward the brain beconns the vestibular nerve. The spiral ganglion begins its development at the ventral border of the lower part of this mass, the cochlear nerve growing toward the brain while the peripheral division containing the ganglion extends into the membranous cochlea. From the foregoing sketch, it is evident that the membranous labyrinth is genetically the oldest part of the internal ear, and that it U, in fact, only the greatly modified and specialized closed otic vesicle surrounded by secondary mesoblastic tissues and spaces. Development of the Fig. IJ79. Middle Ear.— The tympanic cavity and the Eustachian tube are formed essentially by the backward prolonga- tion and secondary expansion of the inner entoblastic por- tion of the first branchial fur- row, the pharyngeal pouch. The dorsal part of the latter, in conjunction with the adja- cent part of the primitive pharynx, gives rise to the sec- ondary Mo-fymfianic space (fuchs); the posterior end of this becomes dilated to form the tympanic cavity, while the segment interven- ing between the tympanic diverticulum and the pharynx is converted into the Eusta- chian tube. The first and second branchial arches con- tribute the roof of the tym- panic cavity. The ear oaiides are de- veloped in connection with the primitive skeleton of the visceral arches. The ntallrus Endolymphatic duct Wall of brain- Canalicular recCM ■Utricnlo- Haccular pouch Surface Cochlear duct Further diBerentiation of otic vesicle into endolymphatic duct, utriculo- •accular pouch and cochlear duct. and incui represent specialized parts of the cartilaginous rod of the first arch, the tensor tynv pani being developed from the muscular tissue of the same arcli. nie ilafit^i is develoix^ trom the second arch. The mesoblast which surrounds the structures of the tympanic cavity during their development becomes spongy nnd finally degenerates toward the end of furtal life. 'Amer. Jour, of Anatomy, Vol. VI., 1907. 1536 HUMAN ANATOMY. Th« air-ctUs of the temporal bone, includiBg those of the mastoid process, are formed later by a process of absorption. The qrmpanie membrane results principally truni chants which take place in die first branchial arch ; it is originally thick and consists of a niesoblastic middle stratum, covered on its outer sur&KX by the ectobiast and on its inner surface l>y the entoblast. Development of the Estamal Bar. — The median p«>rtion of the ectoblastic groove of the fimt branchial furrow becomes deepened to form the outer part vk the estemal aaditoiy canal. lOlAHMS •». Di«Knim inmntint devdopnwnt of human membranous cochic* ; primiry otic vesicle subdivides into vcMibular and cochlear pouches and endolymphatic appendage ; cochlear pouch becomes ductus cochlearis ; from vestibular pouch are derived utricle, saccule and aemicirciilar canals ; whilst endolymphatic appendage gives rise to endo- lymphatic sac and duct, (^retler. ) white the surrounding parts of the first and second arches <1evelop into the auricle. About the fourth week of foetal life, the thickened posterior mar^n of the first arch is broken up into three tubercles by two transverse furrows. Similarly on the adjoining margin of the second arch, a second vertical row of three tubercles is fonned and, in addition, behind these a longitudinal groove appears marking off a posterior ridge. From these six tubercles and the ridge are differ- entiated the various parts of the auricle, the lowest nodule of the first arch becoming the tragus, the remaining f)nes with the ridge giving rise to the helix, whilst from the three tul)ercles oi the second arch are developed, from above downuard, the antihelix, the aiiHtragus and thr lobule 1 THE GASTRO-PULMONARY SYSTEM. GENERAL CONSIDERATIONS. The fnod-stuffs required to compensate the continual loss occasioned by the tissue-changes within the body are temporarily stored within the digestive tube. During this sojourn the food is subjected to the digestive processes whereby tht- sub- stances suiuble for the nutritive needs of the animal are separated by absorption frtjm the superfluous materials which, sooner or later, are cast out as excreta. Closely associated with digestion, and in a sense complementary to it, is the respiratory func- tion by which the supply of oxygen is assured. In the lowest vertebrates these two life-needs, food and oxygen, are obtained from the water in which the animal lives, this medium containing both nutritive materials and the air required for the perform- ance of the respiratory interchange of gases (oxygen and carbon dioxide). Fig. 1 381. Wainsn body ' NMucberd Oral cavity Pharyngeal / poiichi. Heart L""*! ' *-'"' \ \ Stomach l^nct«a> Cloacal orifice *•"*«"' HindKW Saxiital Kction of ichcnatlc vertebral* ( Motlijifi' from FIrisckmamm 1 Since, therefore, in these animals both food and oxygen are secured from the same source, the water, the digestive and respiratory organs form parts of a single gastro-pulmonary apparatus. This close relation is seen in the lower vertebrates (fishes), in which the anterior segment of the digestive tube is connected on either side with a series of pouches and apertures, the branchial clefts, bordered by the vascular gill-fringes by means of which the blood-stream is brought into intimate relation with the air-containing water. When the latter element is forsaken as a permanent habitat and the animal becomes terrestrial, a more highly specialized apparatus, suited for aerial respiration, becomes necessary. This need results in the development of the lungs. The latter, however, retain the intimate primary relation to the digi-stive tract, and are formed as direct ventral outgrowths from the gut-tube. The vertebrate digestive tract early becomes differentiated into three divisions : fore-gut, mid-gut, and hind-gut. The first includes the mouth, pharynx, oesopha- gus, and stomach, and serves for the mechanical and chemical preparation of the food materials. The second comprises the longer or shorter, more or le?s convoluted small intesiine, and forms the segment in which absorption of the nutritive materials chiefly takes place. The third embraces the large intestine, and contains the super- fluous remains of the ingested materials which are discarded from the body at the i$>7 I52« HUMAN ANATOMY anal opening. Aaaociated with the mid -gut are t»<< iti^«M\ securing it necessitates incrt-ased specialization in tkr ttmn w^nein' <>f th*- diKL-stivc tube ; hence the addition o( acressory organs, as ctw liiiw, orai glands, ii>ngue, and teeth, the latter often serving as (prehensile as w»ill as taaiiBicatury uruuns. Reference to the early relations of the emteryn to t*e vtteliiiu- site |rt^ ja) recalls the important fact that the greater pan ot the )pt( tract at tormed W tht: con- striction and separation of a p«irtion of the yoik-sac by the appmximatK^n ami ducmrc of two ventral folds, the splanchnopleura. Swcr the li«»«T coniiist.s of two linj-rs, the entoblast and the visceral lamitu of the nies«»blast, the rwu.- resultiiii,' fr»>m tit" union of the splanchnopleuric folds possessc-s a lining directly tien«ed from the inner j^eriii- layer, supplemented externally by mesobtast. The iattrr nrfitribuies iln- oonn-ctixe tissue, muscular and vascular constituents of the digestiv- mtw, whilt the c^pitbetiuni and the associated glandular elements are the products ol iie «ntoblaM. MUCOLS MEMBRANES. The apiertures <. the digestive, respiratory, ar. tions at which the ini ument becomes continHo ' passages communicatinj^ with the exterior. The t'lo. laSi. i: r>i« Mrinary tracts mark loca- witt\ u. V, tUs of cavities and >ti,>s of I'll! spaces cnflstitute Kpilh,*';um Papilla ot lunica propria «ki !i- pM^ b>- bkMHt- vnMls Coniw' t.so. mucous membranes. The latter, however, not cnly form the free surface of the chief tracts, but also that of the ducts and lubes continued into the glands which are developed as outgrowths from the mucous membranes. Temporarily in the higher types and permanently in such of the lower animals as possess a common cloacal space, all the ir.iicous membranes of the body are con- tinuous. After acquiring the definitive arrangemint whereby the uro-genitiil tract becomes separated from the digesti\e tube, these membranes in man and mammals (except monotremata) form two great tracts, the gastra-pulmonary and the genito- urinary. The free surfaces of the mucous membranes are kept continuallv moist by a viscid, somewhat tenacious secretion, the mtu7is, derivetl from the glands ; they are thus protected from the drying and irritating influences of the air, foreign substances, and secreted or excreted matters with which they .-jre hn-.-.jtjh! into contact. Structure. — Every mucous membrane comprises two distinct parts : the epi- thelium, which forms the immediate free surface and furnishes protection for the more delicate tissues beneath ; and the tunica propria, a connective-tissue layer which constitutes the stroma and gives place and support to the terminal branches of the MICOUS MEMBRANKS. 15J9 Fto. 11S3. EiJithclium Btrrves and the hlno(f-v»!s<«<4s and the btyinninn^i of tlic lymph-nuliclL-s. Thus i< -aIII be s«!en thar the )iy tlie epkbeliunn of the former, wkdf fjoth the coriuin nd tb»- tiinira pn i^a i^ tiiKk- che coin»»^'tive-twi»u«f basis over wiMrh thi- e?pithelial ..lyer stretches. .A strai-.mi o< atdmucims tissue, corre^ipondin); ««h the subcutaneous layer in the sk .onmrts the mucoiiH membnuM' with the sumionding ^ttructures. The epithelium iiiay be stquatnous or columnar, sMinple or jaratitied. Its char- acter is usiuilly determined Iw the crNidittuns ti> which it is subjected ; thus, where ciwerinK surfaces exp«i«elumnar in trpe. in kKsdities in which the existence of < current favors the iunclton of un orKUW either as a means of freeing the surface from secretion or particles of foreign maOer. #s in the respiratory tract, «)i" of propul- sion through a tube, as in the epididymis or the oviduct, the epithelium i.-* of the ciliated columnar variety. Mcxlitications of ti»e epithelial cells, diw to (he pro-t-nce of pigment or of secretion, distinguish certain qiucimis membranes, as those clolhirikj the oiacr»»ry region and the lai^e intestine rc»ptrcti\ '-ly. The limutt propria or stroma consists fjf interlai mg bundles of fibro-eUistic tis.sue which support spindle or stek^te connective-tissue celb. The latter usually lie within thj uncertain clefts betueen the stroma bundles, which may be re- gi'rded as lymph-spaces. In many localities the surface of the tunica profjria is beset with numerous cle- vatntis or papitltr. nver which th- epitbeliuan extend.s. Such irregu- larities. wiM3i slight, may not modify the free surface of the mucous mem- brane, sinc»- the epithelial layer com- pletely tills the depressions between the ele\ations : when more pro- nounced, the papilla- or folds of the connective tis.sue produce the con- spicuous modelling of the surface seen in the papilla- of the tongue or the ruga? of the vagina. The papillse contain the terminal loo|)s of the blood-vi-.-sels and the ner\'es supplying the mucour i!r:'in'5JO HUMAN ANATOMY. ■ circular and a lo,ip?udinal. The inner surface of the stratum is often broken by processes of muscular tissue which penetrate the tunica propria well towards the epithelium. The muscularis mucosae belongs to the mucous membrane, and there- fore must be distinguished from the muscular coat proper, which is frequently a conspicuous additional layer in the digestive tract. Mucous membranes are atuched to the surrounding structures by a submucous layer of areolar tissue. The latter varies in thickness and density, consequently the firmness of the union between the mucous and submucous straU differs greatly in various localities. Usually the atuchment is loose, and readily permits changes in position and tension of the mucosa, which, in the relaxed conditior. is often thrown mto temporary folds or ruga, as in the oesophagus and stomach. In other places the folds are permanent and not effaced by distention of the organ ; a conspicuous example of such arrangement is seen in the valvule conniventes of the small intestine, in which the submucous tissue forms the basis of the elevation. The blood-vessels supplying mucous membranes reach the latter by way of the submucous tissue, in which the larger branches divide into the twigs which pass into Fig. 1184 Voa-vast'ular rpithelium Tcrmina! capillary loopa Tunk-a propria Larnr branclm withia •unmut'OM Section u( iiiJevtcU or;il muc-.ut ni«nitifane the mucosa. Within the deefier parts of the tunica propria the smaller arterial branches bi'tak up into the capillaries forming the subepithelial and papillary net- works, the vascular loops being limited to the connective tis.sue stroma and never entering the epithelium. The venous stems usually follow the arteries in their gen- eral course. When glands arc present, the capillaries surround the tubules or alveoli with ritii net-works in close relaticm to the basement membrane. The lymphatics within mucous membrares are seldom pn-sent as definite chan- nels, since they begin as the uncertain interfascicular clefts l)etwcen the bundles of stroma-tissue. Towards the deeper parts of the mucosa the lymph-paths becf)me more definite, and exist as delicately walled varicose paiHa^es which converge towards the submucous tissue. Within the latter the lyiiiph-ves-sels form net-works richly providefl with valv«-s and the accompanying dilatations. The Htrtrs distributed to mucous membranes include cerebral or spina; and sympathetic branches, the latter supplying especially the involuntary muscle of the GLANDS. «53t stroma and of the blood-vessels. Surfaces highly endowed with general and tactile sensibility are proxnded with a generous supply of twigs containing medulbted tibres. As the latter pass towards their ultimate destination ( for convenience aiuuming that all are peripherally directed) they lose their medullated character and, as naked axis- cylinders, form the subepithelial plexuses, from which delicate tilaments ()ass into the papillae, where they terminate either as free club-shaped or special sensory endings. It IS probable that in places the nerves penetrate between the epithelial cells forming the layers next the basement epithelium and terminate in varicose free endings. GLANDS. Certain of the epithelial cells lining the mucous membranes of the body become modified to assume the rAle of secretion-forming organs or glands, the products of which are poured out upon the free surface and keep the latter moist. The latter purpose is secondary in the case of many important glands, as the parotid, pancreas, Fio. taSs. Diagram >huwtnKtyp« of (land*. a.«, tubular; /■•, alveolar ur lactrular a. limplc; b, colled; c-d, iiicreaiiiigh complex compound tubular; t, iubo«iv«olar ; /, simple ; ^ *-i. profreMively complex compound alveolar. or liver, since these organs supply special secretions for particular ends. Aggrega- tions of the secreting elements vary greatly in size, form, and arrangement, as well .« in the character of their prcxiucts. The simplest type is the unicellular gland UwnA in the lower forms; in principle this is represented in man and the higher animals by the goblet-cills soi-n in pro- fusion in mucous membranes covered with columnar epithelium. The secrc-tion poured out by these goblet-cells serves to protect and lubricate the surface of tin- mucous membranes in which they occur. The term "gland," houiver, usu:illy implies a more highly developed organ composed of a collection of serrt'ting epithe- lial elements. Glands are classified according to their form into two chief groups, the tubular and the alveolar, each of which occurs as simple or compound. It sh)uKl !«.■ empha- sized that °n many instances no sharp distinction tietween these conventional groups ':i'< ; Wk 1532 HUMAN ANATOMY. opening on tnucoua mcinbranc Eiurctory duct exists, some important {glands, as the salivary, being in fact a blending of the two types ; such glands are, therefore, appropriately termed tubo-alveolar. In the least complex type, the simple tubular, the gland consists of a cylindrical depression lined by epithelium directly continuous with that covering the adjacent sur- face of the mucous membrane, as an outgrowth of which the gland originally devel- oped. In such simple gland the two fimdamental parts, tYic fundus and the duct, are seen in their primary type. The fundus includes the deeper portion of the gland in which the epithelium has assumed the secretory function, the cells becoming lai^er and more spherical in form, while in structure the distinction between the spongioplasm and hyaloplasm is usually marlcxl in consequence of the particles of secretion stored up within the meshes of the s()on^ioplastic net-work, which is often sharply displayed. The duct connects the fundus with the free surface and carries off the products elabo- rated within the gland. It is lined with cells which take no part in secretion and hence retain for some distance the character of the adjacent surface epithelium. Dilatation of the fundus of the primitive type produces the simpK; alveolar or saccular gland ; division of the fundus and part of the duct gives rise to the compound tubu- lar variety ; repeated cleavage and subdivi- sion of the duct, with moderate expansion of the associated terminal tracts, lead to the production of the tubo-alveolar type. Simple tubular glands may be minute cylindrical depressions of practi- cally uniform diameter, as the crypts of Lieberkuhn in the intestine, or they may be somewhat wavy and slighdy expanded at the fundus, as often seen in the gastric glands towards the cardiac end of the stomach. When the torsion becomes very pronounced, as in the sweat-glands, the coiled variety results. Compound tubular glands pre- sent all degrees of complexity, from a simple bifurcation of the fundus and artion of the excretory ducts. In the larger glands the latter form an claUirate system of pas- sages arranged after the general plan shown in the accom|Kuiying diagram ( Fig. 1285). Traced from the terminal compartments, or alveoli, of the gland, the duct- system begins as a narrow canal, the intermediate duct, lined by low culx>idal or flat- tened cells directly continuous with the glandular epithelium of the alveoli. After a short course the tube increases in diameter and becomes the intralobular duct, which is often conspicuous on account of its tall and sometimes striated or rod-epithelium. The further path of the excretory tubules lies within the connective tis.sue sepai[ating the divisions of the glandular suljstance, and embraces the interlobular and the inter- lobar ducts, the latter joining to form a single main excretory duct which o|)ens ujK>n the free surface of the mucous membrane. The last-named {Passage is linetl for some distance by cells resembling th<>8e covering the adjacent mucous membrane ; w here these are stratified squamous in type, this character is maintained for only a limited Fio. laS;. Mucous alveoli Serous alvtoll Sevtion of |K»ietiot part o( (oiikuc. showinR »lv«ili «>! Mfoui uiul mu«MU lypn of glandi. extent, Ixfore the interlobar ducts are reached gradually giving place to a simple, sometimes at first ilouhle, layer of columnar oj)ithluntar\- nniscle. In the case of the large ducts the latter is usually dis|)oseil as a tr:insvers«- and longi- tudinal layer, to which, as in the hc|>atic duct '( Hendrickson). a thinl oblicjue one may Ik- atldt-tl. Hiflerential stains show the presence of a large amount of elastic.!. " The glandular epithelium lining the aivtoii rests u|)on the limiting l«s.inent membrane .is a single laver of irregularly spherical or |X)lygonal secreting cells ; these do not completelv Jill the alveolus, but leave an intercellular deft into which the proihict ot the cells is (Kuiretl .nml in which the system of excretory ducts Ingins r)e|H'nciiiig ii|M>n the iKciiliaritit-s of the ceiis and the character of their secretion, glands are divided into serous and mucous. »534 HUMAN ANATOMY. Fig. 1266. The serous glands are distinguished by cells which are distincdy granular, generally pyramidal in form, with nuclei situated in the vicinity of the centre. The secretion elaborated by such glands is thin and watery. The general appearance of the cells dejiends upon the number and size of the granules stored within their cyto- pla.sm, and changes markedly with the variations of functional activity of the gland. When a serous gland is in a condition of rest, the cells are loaded with secretion, and appear, therefore, larger and coarsely granular. After active secretion, on the contrary, the cells are exhausted and smaller and contain little of their product, often e.xhibiting differentiation into a clear outer zone, free from granules, and a darker innet.zone, next the lumen, in which the granules still remain. The mucous glands elaborate a clear, viscid, homogeneous secretion, which, when present in considerable quantity, as during rest, distends the cells, crowding the nuclei to the periphery against the basement membrane, and gives to the glandu- lar epithelium a clear and transparent appearance in marked contrast to the granular character of the elements of a serous gland. During rest, when loaded and distended with mucoid secretion, the transparent cells possess well-defined outlines, and present a nar- row peripheral zone con- tiining the displaced nuclei and granular protoplasm. After prolonged activity the exhausted cells contain rela- tively Utile mucoid secre- tion, and hence the threads of spongioplasm are im longer widely sejwratetl, but lie closely ; in consequence of these changes the cells lose their former transjwr- ency and resemble the elements of serous glands, becoming smaller, d^irker, and more granular than th.' cells of the quiescent mucous gland The alveoli of mucous glands often contain small crescentic groups of sin.iU granular cells lying iK-twecn the usual larger clear ele- ments and the l)a.scincnt membrane ; these are the interpretation of which has as groups of cells serou!) cells Duct Mucous cdls neniilune H-rttnii ul hutiiai) »iuhliiiKua1 Klancl. Khowinje Mrrous cells ftrrangeil as demi- luneH. • 300. rrtsfents of Gianuzsi, or demilunes of Heidrnhain, the caused nuuh discussion. The older view rj-ganUtl the cn-scent (iilTcring from the surrounding ones only in their st.nge of activity and not in their I'ssential characters, all the cells within the alveolus Ix-ing of the same nature. The iippusite view, advanced by Ebner over a quarter of a century' ago, has received sup- port from more recent critical studies by Kiichenmeister. Sojger, Op[H-l, R. Krause, .mil others, who have shown that the cells composing the crescents ditTer from the mucus-containing elements, elaborate a sfx-cial secretion, and are similar to, if not identical with, those tilling the alveoli f>f serous glands. According to thj'se obsen-ers, the crescents are groups nf serous cells compressed and tlisplaced by the preti of Hubmmx- illary Kl»i>d of dofE. sliouiiiK u-rmitia) ifuctH aiid sci'rrtion-t'.i|iillaiit> iiiissiiiK to iTwcrntic (Ktimilt-ttk K^'^^ufis of !*rou» cclln. ^ joo. {KrUims.) formerly thought to be the case, since extensions of the lumen pass between the mucous cells to reach the demilunes. In addition to the main alveolar lumina, always narrow in st-rous and wider in mucous acini, the existence of intercellular passa^^es, or secretion-capillaries, has been established for marw glands, especially by the employment uf the Golgi and other special methods. These clefts penetrate laterally be- tween the glandular epithelium frt>ni the a.xial lumen towards the basement membrane, partially enclosing the secreting cells with a branching system of minute canals. Alveoli containing exclusively mucous cells do not possess these intercellular canaliculi, the axial lumen alone being present. In acini of ihe serous type the accessory channels are representeical fl:isk-like form, as seen in the skin of amphibians, art- not found in man. The dilated sphericiil fundus is iiiutl with clear and distended secreting cells, in which the nuclei are displaced towards the periphery by the mucus elalxiratetl within the ejiithelial elements. In the higher animals this type of gland is represented, somewhat nunlifietl, by the simple sebaceous follicles. Compound alveolar or saccular glands constitute a group much less exten- sive than formerly supposed, sinc-e careful study of the form and arrangement of many organs, as the salivary glands, pancreas, etc., has sh.iwn that these are more appro- priately regardetl as tubo-alveolar than as brancheil siiccular glands. The latter, nowever, still have representitives in the larger sebaceous and Meilximian glands. The most conspicuous example of the compound s;iccular or racemose typi' is the lung, which in its devclojiment and the arrangement of the air-tubes and the s;u-like terminal cjimpartments corrt-sponds tJ) this variety. The blood-vessels distributed to glands are always numerous, since secretory activity implies a generous blood-supply. In the case of the smaller and simpler glands, the capillaries within the mucosa form a mesh-work outside the basi'menl membrane enclosing the glandular epithelium. The large cotupmmd glands ;ire pro- vided with a vascular system which usually corres[M)ncls in its (general arrangem»-nt to that of the excretory ducts, following the tM ts of the intcrlolKir .uxl iiiKriolnilar areolar tissue and its extensions In-tween the p.. iips of the alveoli. ()>i reaching the individual acini, the capillaries form net-works which surround the hisj-ment mem- brane enclosing the alveoli, thus bringing the bioiHl-current into close, but ni>t direct, relation with the secreting cells, an arrangement favoring the stiection by tile proto- plasm of the particular substances icfiuired for the function of the gland. V\'hen tiie relation between the glandular epithelium and the capillaries is unusually intimate. i4? >» 1536 HUMAN ANATOMY. as in the case of the liver, a distinct basement membrane is sometimes wanting, a delicate sup]x(rtinjj reticulum alone inter\^ening between the blcxni-stream and the protoplasm of the cells. Although subject to local deviations, conspicuously excep- tional in the liver, the veins follow in general the coun>c of the arterial branches, the larger bkxKi-vessels, together with the main excretory ducts, the lymphatics, and the nerves, occupying the principal extension of the connective tissue into the glandular mass. The lymphatics are represented by the larger trunks which follow the excretory ducts and freely anastomose within the interlobular areolar tissue. After the intra- lobular portion of the vessel is reached, its definite character is gradually lost until the lymphatic channels are to be recognized only as the clefts between the bundles of connective tissue separating the alveoli. Fig. 1 290. Fig. 1391. lnjc»tcr;iiie, shtmiiiK cnpilLiry nel-wurk ^utioutKlingtubiilarjitatKis. ' ^s. Section of siibma Rfft««-^ tfland of rabbit : umier half >'i tiKUre shown rftstrinuiioii trf iieive-fibres to .ilv roti ; luwrr half sho^K's terminal f1il< ts aiul Mrcrtrtii>i)-ia|Hllalics. X 390- \,Hft.ti4s.i The nerves supplying the larger glands include fil)res from two sources, the cranial or s])inal nerves and the syin{)athetii-. They follow the interlobular excretory ducts, around which plexuses are formed, ganglion-cells being frequent at the jwunts of junction. The stronger twigs contain a prefKuulerating projjortion >[ ihi-lc medullated fibres, which l>ecoMie progressively less in size and num'nr in iheir course towards the alveoli. I'pon reaching the latter the nerves consist uimos; <-',!inlv of nonmedullate;nx. The upper part, the naso- pharynx, is behind the nasal chambers which open into it, the oropharynx is Le added the mylo-hyoid muscle forming the floor. When the lips are opened and the lower jaw dropped, the mouth is a true cavity extending to the pharynx ; when these parts are closed, the tongue fills practically the whole space. It is convenient, however, to speak of the cavity of the mouth. This space is subdivided into the vestibule or preoral cavity and that of the oral cavity or mouth proper. The former is the region between the closed lips and cheeks in front and the closed jaws and teeth behind. When the lips are closed, it communicates with the mouth proper only by a small passage behind the wisdom-teeth, in front of the ramus of the jaw. THE LIPS, CHEEKS, AND VESTIBULE. The orifice of the mouth (rima oris) is a transverse slit of variable length bounded by projecting folds,— the lips. These, like the cheeks, with which they arc- continuous, are composed of complicated layers of muscle, covered externally Dy skin and internally by mucous membrane. 153S BOH K.ifliil THE LIPS, CHEEKS, AND VESTIBILE. 1539 Fat is found irregularly dispowd anions the muscles of the cheeks in varying quantity, but in the depression in front of the maibeter and superiiciiil to the tniccinator there is a distinct ball of fat enclosed by a ca|)sule, which is the remnant of the so- Fic. PfOlUI ll 'idal tiniu OrbJvularitDns Gcni .Orifice ot Euilachiui labc Gcnio-hj-oid Mylo hyoii Hyoid bone' XKfW)phai^us Sagitul iwtiian of hratt nf ytiuiiKxluU, ihrrc-luunhii tmlunil itiae. called "button" of infanc)- —a collection which ^ivcs resistance to the cheek and pre- vents it from beinjj flatteneil by atmospheric pressure during nursing. The mucous membrane is reflected from the cheeks onto the jaws, where it covers the gums. This line of reflection at the middle of the lower jaw is 7 or S mm. from the alveolar m. m I540 HUMAN ANATOMY. border and about twice as far from it in the upper. In botfj jaws, but especially in tlie lower, the line approaches the teeth as it |>asses tiackward. There is a distinct fold or frenum of mucous membrane passing; from the anterior nasu] spine to the middle of the upper lip. The free ed^e is often irregular, and may have a nodular enlargement. A much smaller fold is often found on each side in the region of the bicuspids. A median fold to the lower li|> is small and inconstant. Extr:rnally the lips present a red region of modified mucous membrane, intermediate between the skin of the face and the mucous membrane of the mouth. A sagittal section through either lip shows these three parts. In the new-bt)rn the intermediate ' part is subdivided into two, of which the inner — rather the broader — more closely resem- bles true mucous membrane than the latter. After death in the young child it assumes a brownish color, which has been mistaken for the effect of acid. In the adult these two subdivisions lose their distinctness. The lower lip is the larger and Fto. iaQ4. -^ — Nasal M'ptum MaxillaT\ ainus " — Mucous mfm- brati«*iiMT iliK Jkilatt* Mylo-hyoid Plat ysilKi Antriior belly of ili^itriC' GcniO'hyoiU'^ (^•■nio-KloflBUS Frortal section. showinK oral cavity and lower part of nasal Iosmf ; plane of section xypMia. Three-fourths natural sise. — ■ — Submental artery throuKh anterior end of fuller, showing more red except towards the angles of tli( mouth, where it disap- pears. Its lower border is slightly indented in the middh The upper lip shows a more marked indentation below a little gutter, the philtrmn. running down from the nasal septum. A slight median prominence of the lower «lge of the upper lip is the tubercle, which interrupts the straightness of the cleft when the lips are closed, making the line resemble a Cupid's bow. The muscles of the lips an- a complicated interlacement from many sources. The orbicularis oris, formerly supposed to form a sphincter, has no separate exist- ence. The general plan is as follows. The upper fibres of the buccinator enter the lower lip and pass out at the opjx)sitc ringle to ascend into the upper part of the other buccinator. Those of the lower part traverse the upper lip in a similar manner. The layer formed by the buccinator lies under the mucous membrane near the border of the lips, and bends forward so that its cdjjc is nearest the skin at about its junction ' Gttu Nc--tattcr : Ucbcr den Lippcnsaum, etc., I::a;:g. :>is:>crt., Munich, 1894. THE LIPS. CHEEKS. AND VESTIBULE. 154' with the free red surface. In the lower lip the qmadraiHs (depressor labii inferioris) runs upward under the skin to breiik up into fibres ending in the lips. The tri- angularit (de]>rf«M)r an^uli oris) passes Pio. tigs. rhiiti Tabcfcic Labial ration, from life, reduced one-fiftli. nt the angle vk the mouth into the up|ier lip and ends as a series of sciKtrate fibres inserted into the mucous membrane, many of them crossing; the middle line. This muscle, before it breaks up, is in the same plane as the buccinator, but farther from the edge of the lips. Some (^rman au- thors, by grouping together the various muscles of the upper lip, have made a utperior quadratus and triangularis which are dis|>osed in a similar manner to the lower ones. Besides these there .ire two muscles, the zygomaticus, de- scending, and the risorius, ascending, which meet at the oral angles and end there in the skin or mucous membrane, or in both. There are also numerous fibres, seen only with the microscope in sagittal sections, passing from the skin to the mucous membrane ; these consti- tute the rectus.* Labial (landi Fibres of orbicularis, oris Ttansitiuii into true, mucous membrane Modified mucouii membrane InteKumcnt .Sebaceous gland Tratisition into modified skin Sagittal section of lip of young child. X 30. The mucous membrane, which is siiii«jth, is so closely attachfd to the muscles that it follows the movements of the latter. Mucotis glands are lodged in its ' Aeby : Archiv f. mikro. Anat., Bd. xvi., 1879. 'iHr "11 k^ 1542 mmmm HUMAN ANATOMY. deeper parts and in the scanty submucous tissue. They are named iadia/, bticcal, and molar, according to their situation. The labial glands are gathered into a series of groups near the inner border of the lips, the buccal glands are smaller and scattered, and the molar glands are well-defined groups opposite the molar teeth. The duct of the parotid gland {q.v.) opens into the vestibule, the space between the lips and cheeks externally, and the teeth and alveolar processes internally. Separating the vestibular space from that of the mouth proper behind the alveolar processes is a prominent fold of mucous membrane over the pterygo-maxillary ligament. This fold appears at the inner side of the last upper molar and runs downward and outward to that of the lower. The space behind the teeth when the mouth is closed is small, but a tube some 5 mm. in diameter can be passed through it. Vessels.^The arteries supplying the lips, which are very vascular, are chiefly the coronary branches of the facial arteries, each of which forms an arch meeting ite fellow in each lip. The vessel lies between the muscles and the glands of the mucous membrane, n».arly opposite the line of junction of the latter and the intermediate por- tion. The pulsation is easily felt through the mucous membrane. The veins, less regular, lie on the outer side of the muscles. The lymphatics empty into the glands at the angle of the jaw, excepting those near the median line of the lower lip, which run into the suprahyoid glands. Nerves. — The mucous membrane of the cheek is supplied by the buccal branch of the inferior maxillary division of the fifth cranial nerve, the lips by the terminal branches of its second and third divisions. THE TEETH. In form the teeth present three parts, — the body or crown, coated with enamel ; a somewhat constricted part, the neck, covered by the gums ; and the root or fang, which, covered by the cementum, is fixed in the socket. The greater part of the tooth is composed of the dentine and surrounds the pulp-cavity, to which minute openings in the root or roots transmit vessels and nerves. The shape of the crowns is the basis of classification. Thus, in the front teeth the crown is flattened so as to have a chisel-like shape, adapted to cutting, hence these are termed incisors ; the canine teeth have the crown forming a single point or cusp ; the bicuspids have two, and the multicuspids, or molars, several cusps. The crowns of all the teeth may be considered as modifications of a simple cone, or as combinations of several cones.' In man the teeth come in two sets, the temporary or milk and the permanent teeth ; the total number of the former is twenty, that of the latter thirty-two. The number and arrangement of the teeth of any animal is expressed in its dental formula ; this for man, for the left half of the mouth, may be written as follows : Temporary Teeth : i* f ' »fi ' ^^ ? X a = aoV Permanent Teeth : i? f ' W' m^ ( 21 » 3 V 8 It will thus be seen that in the milk-teeth there are no bicuspids and one molar les« Since the typical mammalian dental formula \% i\ c ^ bi- m ■', it may be assumed 3143 that in man three pairs have been suppressed. These suppressed teeth are occasion- ally represented by supernumerary ones ; from the position of the latter it is probable that the missing teeth are the second incisors and the first and fourth bicuspids. To avoid confusion in the nomenclature of the teeth from the cur\'e of the jaws, it is customary to speak of the labial and lingual surfaces of the incisors and canines, and of the facial, or buccal, and //'«^«s are separated by a furrow from which small ramifications often run onto the buccal one. The lin- gual cusp has an unbroken surface. The buccal cu.sp of the first bicuspid is more prominent than the lingual, but in the second they reach the same plane. The bor- der of the enamel is convex towards the root on both the buccal and lingual aspects, the ends of these curves meeting on the other sides. The fang is compressed with a groove on the sides next its neighbors. That of the second is often bifid just at the tip, but that of the first is very often, per- haps usually, divided into two throughout, having a buccal and a lingual root. Sometimes the former is subdivided, so that it has three like a molar. The root has in general a backward slant. The lower bicuspids have smaller grinding surfaces on the crowns than the upper, but the roots are longer, and the crowns, .seen from the side, are at least as large. The first has a well-developed buccal cusp, curving in from the buccal surface, and a very small lingual one connected to the former by a ridge interrupting the fissure between them, which gives the tooth something of the effect of a small canine. The second, like that of the upper jaw, has the two cusps in one plane ; the lingual one is sometimes double, and the plane is often obscure. The flattened fang is but faintly grooved, if at all, and is rirely bifid. Th^ Pulp-cavity vX the bicuspids ends in an expansion below each cusp, that under the buccal being the larger. In the upper teeth the cavity is much compressed from side to side in the root. In the first upper bicuspid there are usually two pro- longations to the point of the fang, even when the r jot is not split. In the second the cavity generally agrees with the conformation of the r(M>t. In the lower teeth the cavity is less compressed and is tolerably roomy as it enters the root. It is usually single, but may split. First premolar teeth left side, labial l.-)) and lateral \H\ asiieits. (AWrfv.) of 1546 HUMAN ANATOMY. The Molars. — ^These teeth — three on each side— are distineuished by the large crown, into which the neck expands, the number of cusps on tne surface, and the greater subdivision of the root. Those of the lower jaw are the larger ; and in both jaw 3 the first is the largest and the last (called from its late appearance the wisdom- tooth) the smallest. The crowns are convex on both the buccal and lingual sides, but nearly plane on the others. The enamel ends in a nearly straight line all the way round. The grinding surfaces are four-sided ; those of the upper are somewhat dia- mond-shaped, the buccal anterior angle being rather in front ; those of the lower are learly parallelograms, the long diameter being antero-posterior. Typical upper molars have four cusp>s at the angles ; typical lower ones have an additional cusp at the posterior border ; but in the upper jaw the first is the only one that can be called typical. In the upper molars the largest cusp is the anterior lingual, which is connected by a ridge (the cingulum) to the posterior buccal. The posterior lingual cusp is the smallest. A minute rudimentary cusp is found on the lingual surface of the anterior lingual cusp, usually too small to reach the grinding surface, and often hard to recog- nize. Not counting this, the first upper molar has four cusps ii more than 90 per cent. Owing to the cingulum, the grooves on the grinding surface are best described as two oblique ones, the first from the anterior border to the middle of the Fio. J 303. Firat Fig. 1304. Upper molmrs Til Another first Lower molars Sccood ^^iMrrr^i First .*>*^j Another first Second Second molar teeth of left side, labial M) ftod laterml (A) aspects. (Uidy.) Triturating surfaces of molar teeth of right side. The upper margin of the figures corresponds to the labial surface. ( Lridy. ) buccal, the second from the lingual border to the middle of the buccal. They are deepest at the middle. They appear on the buccal and lingual sides, deeper on the former but rarely reach the gum. They may end in a pit, a favorite seat of caries (Tomes). The crown of the second upper molar presents three chief forms (Miihl- reiter). It may have four cusps and differ but slightly from the first molar. The lingual surface is relatively narrower and the posterior lingual cusp smaller. In the second form the last-mentioned cusp is wanting. The cingulum persists and the g^rinding surface is approximately triangular. The third form is compressed from side to side into a very narrow diamond, with the anterior buccal cusp in front and the posterior lingual behind. Three and four cusps are about equally common in this tooth in Caucasians, but the lower races have more often four. The crown of the upper wisdom-tooth presents many remarkable variations. The fKJSterior lingual cusp is wanting in about two-thirds of the cases. The crown may be strongly com- presse . as has been described for the second molar, but with greater variation. In size th wisdom-tooth may be very large or very small. The crowns of the lower molars are divided by a crucial fissure, the main line running antero-posterioriy. The hind part of this splits so as to enclose the fifth cusp, which is ntrar or actually at the buccal side. The cfTcct of this is to form a cavity at the crossing of the lines in the middle of the crown. The lines on the sides mmmm THE TEETH. 1547 of the crowns are leas deep than in the upper jaw. Sometimes the fifth cusp is wanting, in which case the posterior part of the furrow does not divide and the arrangement is remarkably symmetrical. Very rarely the first molar has a sixth cusp on the lingual side. The first molar has five cusps m more than 90 per cent. ; the second four only in more than 80 per cent. ; the third four rather more often than five. The buccal cusfis of the lower molars are worn down earlier than the lingual ones. The following; tables from the independent researches of Rose ' and of Zuckerkandl show the percentage of frequency of different groupings of cusps. Although there is some discrepancy in the percentages, both agree as to the most and least common arranKement in both jaws. These statistics, like those of the separate teeth, anpty to Europeans. (It is to l)e remembered that a certain percentage of teeth cannot be includiea.) Urraii Jaw. Molara. • « i Percent. Rom. Zttck. LoWBH Jaw. Molan. ' ' i Per Cent. R6m. Zoek Cusps. . Cusps . . Cusps . . ■ -4 4 4 • -4 4 3 • -4 3 3 19.9 9.6 28.9 28.7 37-9 601 Cusps . . Cusps . . Cusps . . • 5 5 5 •545 • 5 4 4 19.8 11. 5 304 305 404 500 Fig. '30S- Ths/angs of the first and second upper molars are two buccal and one lingual, which latter is much the largest. It is often, especially in the first molar, grooved on the lingual side. It is conical and strongly divergent. It often shows a tendency to subdivision, which may actually occur, although rarely. The two buccal ones are compressed antero-posteriorly and nearly vertical. The front one is the broader, and is grooved before and behind. This is often tl.e case with the other. The roots of the upper wisdom-tooth are smaller ; the lingual is less divergent, and may be connected by a plate with one of the buccal ones. AH may be fused more or less completely into one. The roots of the inferior molars are two : an anterior and a (x>sterior, of which the former is rather the larger, both compressed from before backward and, especially the first, deeply grooved, suggesting the fusion of two. Sometimes, again especially in the first, each root is bifid. Those of the wisdom-tooth are usually nearer together, and are frequently fused into a common coni- cal root. A(>art from their position in the jaws, the roots of the molars, excepting the upper wisdom-tooth, have a back- ward slant of varying degree. Their twbts and curves are ren^arkably uncertain. Sometimes they converge and some- times diverge unduly, hooking in either case under bone, so as to make extraction difficult or impossible. The pu/p- cavify of the molars is large, especially at the level of the neck. In the upper teeth it is distincdy wider transversely than from before backward. It has as many prolongations towards the surface as there are cusps. There is a canal in each root of the upper teeth. Those in the buccal fangs are compressed, that in the lingual cylindrical. The anterior fong of the lower molars has two canals which develop from a single one. The posterior fang has but one. The milk molars are hi'o m number. Like the perma- nent ones, the lower are the larger ; but, unlike them, the second tooth is larger than the first in both jaws. The crown of both first molars presents a prominence on the buccal sur- face near the root. The crown of the first upper molar is rather su^estive of a bicuspid, although there are two buccal cusps and one lingual. The first mferior molar is relatively narrow and long from before backward. The length of the buccal side is greater than that of the second permanent one. The second molars resemble very closly the first permanent ones. The upper has four cusps and a cingulum, the lower five cusps. The hollow in the crown of the tem- porary molars is relatively deeper than that of the permanent ones, but smaller and more divergent. They straddle the crowns of the developing bicuspids. * Anatom. Anzeiger, Bd. vii., 1892. WW Tempormry molar lerth {A, first; B, second) of left side. TrtturalitiK surfaces of crowns also shown. {IMdv.) iH*^ 1 1 le' '548 HUMAN ANATOMY. TOOTH-STRUCTURE. In principle, and among the lower vertebrates, in fact, as well, teeth may be regarded as hardened papillae of the oral mucous membrane ; they consist, therefore, of two chief parts, — the connective-tissue core and the epithelial capping. Of the three constituents present in typical mammalian teeth, the enamel is the derivative of the ectoblastic epithelium, the dentine, with the pulp, and the cementum being con- tributions of the embryonal connective tissue. The Enamel. — This, the hardest tissue of the body, covers the crown, being thickest on the cutting edge or grinding surface of the tooth. It gradually thins away Fig. 1306. iripcsof Ret2iui (longitudinal) Contour lii SchrcKcr's lines Prism-stripes oJ Schreger (light and ^.___^_, ,^^„_^_ dark) .Gum Pulp-tiuue Dentine Cementum Alveolar periosteum Osseous tissue of jaw Root-canal ' Sagittal section of canine tootti m sttm. Semi-diagrammatic. towards the neck, around which its terminal border appears as a more or less distinct and often serrated edge. The external surface of the enamel, especially in young teeth, often e.xhibits a line striation composed of horizontally disposed lines. Under a hand-glass these lines are seen to be minute elevations, the enamel-ridges, which encircle the crown. The remarkable hardness of this tissue is due to the large amount (97 per cent. ) of earthy material and the small proportion of organic matter, which latter in adult enamel averages only about 3 per cent. ; in infantile enamel the amount of animal material is from five to six times greater (Hoppe-Seyler). STRUCTURE 01 THE TEETH. >549 Fio. 1307. The enamel — the product of epithelial cells, the amelobiasis — consists of an a(;gre- eation of five- or six-sided columnar elements, the enamel-prisms, which measure from .0035-.0045 mm. in diameter and from 3-5 mm. in len^h. Their genera! disposition is at right angles to the surface of the dentine u|X)n which they rest, on the one hand, and to the exterior of the crown on the other. They usually extend the entire thickness of the enamel, and are of slightly larger diameter at the surface of the tooth than next the dentine, in this manner com- pensating for the increase in the external circumference of the crown. The assumption that additional prisms are intercalated at the periphery is not supported by the manner of the production of the enamel-columns. The latter run for a short distance almost at right angles to the surface of the dentine, then bend laterally for a considerable {lart of their course, but assume a vertical disposition on approaching the external surface. In addition -.o these general curves, the ranges of enamel- columns possess a spiral arrangement, in consequence of wh'"' he t irallelism of the prisms, as seen in ground- irbed and their bundles are apparendy sect' intPi Grouiid-sectiofi o< enamel, showing ranset of ciunwl-prl«iia. x yio. ;■' itely transverse sections enamel pre- sen' which the hexagonal areas represent the ti ne ii.dividual prisms. Critically examined, the areas consist of a darker central portion surrounded by a narrow lighter peripheral zone. The interpreta- tion of the latter has been various, many observers regarding such lines as cement- substance holding together the prisms. According to Walkhof!,' however, what is usually regarded as cement-substance is a cortical, apparently homogeneous layer of less thoroughly calcified material which encloses the denser central portion of the prism and acts as a cushion, thereby reducing the effect of pressure. After the decalcifying action of acids, the prisms may be ouUined by stains which color the very meagre amount of true cement-substance which exists between the enamel- columns and appears as delicate lines defining the prisms. Under favorable conditions, especially, but not only, after the action of acids, the enamel-prisms exhibit alternate light and dark transverse markings. The true rela- tions of these bands are to be appreciated only by accurate focusing in thin sections passing exactly parallel to the axes of the prisms ; otherwise the obliquity of section produces the optical distortions often represented in the assumed wavy contour of the enamel-rods. The varicose appearances commonly seen def)end upon the beaded form and consequently scalloped border of the denser central portion of thf prisms, which give a corresponding arrangement to the lighter cortical substance which fills the minute inequalities of that portion ; the true oudine of the enamel-prism, how- ever, is smooth and straight, and not varicose, as the optical impressions lead one to believe and as usually pictured. According to Williams, the apparent varicosities depend upon the spherical form of the enamel-globules of which the prisms are built up. When an axial longitudinal section of a tooth is examined by reflected light, the enamel displays a series of alternate dark and light bands,— the /mw-j/r/]^« ^ Schreger. These markings extend generally vertical to the surface of t^^e enamel, and depend upon the relation of the ranges of the enamel-prisms to the xes of the light-rays. Rotation of the illuminating pencil through 180° effects the change of the dark stripes to ligf"* ones and 7nce versa. Each stripe includes from ten to twenty enamel-prisms, and ii. .nvisible by transmitted light. In addition to the foregoing markings, the enamel often presents, in radial longi- tudinal sections, brownish pandlel lines, the stripes of Retsius, which run in the general direction of the contour of the tooth, but at an angle of from 1 5° to 30° with the free surface. Seen in sections cut at right angles to the tooth-axis, these stripes appear as a series of concentric lines encircling the crown |}arallel to and near the surface ; in the middle and deeper parts of the enamel they are less evident or entirely I Normale Htstologie mensch. Zahne, 1901. iliPWniipMippippipi! '550 HUMAN ANATOMY. Fig. 1308. Umgiludinal ground Kct ion d enamel, treated with acid, showing disposition of range* of enamel-prismt (*./') in .stripes of Schreger. Left thin) of figure shows alternate light (s) and dark (I'l bands as seen by re- flected light. X aoo. (£tnrr.) absent. The interpretation of the stripes of Retzius !s still a Subject of di.^pute. The brown appearance of the stripes by transmitted light only, by reflected light appear- ing bluish white, disproves the assumption that they depend upon the presence uf pigment within the enamel. The widely accepted view of Ebner, that the stripes are due to air contained in the interfascicular clefts, has been modified by Walkhofi, who regards the markings as due to local diminution in the calcification of the enamel-prisms during certain periods in the growth of the tissue when the central as well as the cortical substance of a great number of columns fails to take up sufficient lime salts. The enamel-cuticle, or membrane of Nasmylh, forms a continuous investment of the crown of the newly erupted tooth. In the course of time it dis- appears from the areas exposed to wear, but over the protected surfaces it may persist during life. The membrane (.009-.0!8 mm. in thickness) is transparent and remarkably resistant to the action of acids, less so to alkalies, affording admirable protection to the underlying enamti. After separation from the latter by acids it appears structureless, or at most granular. The inner surface of the membrane presents markings and slight irregularities which correspond to the free ends of the subjacent enamel-prisms. The origin of the enamel-cuticle has been much discussed, and even now is not without some uncer- tainty. It may be regarded as established that it rep- resents the remains of part of the tissue once concerned in the production of the enamel. The latter is formed, as more fully described on page 1561, through the agency of the epithelial cells constituting the inner layer of the enamel-organ. With the completion of their task as enamel builders, these cells produce a continuous cut'jular envelope which persists as Nasmyth's membrane, the epithelial elements o' fte enamel-organ, so far as they are concerned in forming enamel, subsequently u>-generating. The enamel-cuticle is continuous with the cortical substance of the prisms, with which it agrees in opti(^ and chemical properties, — a. relation which confirms the identity of origin of Nasmyth's membrane and the enamel-columns. The Dentine. — The dentine or ivory resembles bone both in its genesis and chemical composition, being a connective tissue modified by the impregnation of lime- salts. Dentine exceeds bone in hardness, containing a larger proportion (72 per cent.) of earthy matter and a smaller amount (28 per cent.) of organic substance. When decalcified by acids, the reniaining animal material retains the previous form of the dentine and yields gelatin on prolonged boilitig. Dentine, like bone, is formed through the agency of specialized connective-tissue cells, the odontoblasts, but differs from osseous tissue in the small number of these cells which become imprisoned in the intercellular matrix. When this occurs, as it exceptionally does in normal human dentine and more frequently in pathological conditions or in the lower animals, the dentine-cells correspond to the bone-corpuscles, both being connective-tissue elements lying within lymph-spaces in the calcified intercellular substance. Examined in dried sections under low magnification, the dentine presents a radial striation composed of fine dark lines which extend from the pulp-cavity internally to th» enamel or the cementum externally. These dark lines are the dentinal tubules, filled with air, which are homologous with the lacunae and canaliculi of bone, and contain the processes of the odontobli...ts. In the crown, as seen in longitudinal sections, the course of the dentinal tubules is radial to the pulp-cavity ; in the root their disposition is horizontal and almost parallel. The canals, however, are not straight, but sigmoid, the first convexity being directed towards the root, the second towards the crown. In addition to these primary curves, which are especially marked in the crown, the dentinal tubules present numerous shorter secondary curves which STRUCTURE OF THE TEKTH. '55» impart to the individual canaliculi a spiral course. The cause of the latter Kollinann refers to the more rapid growth of the dentinal fibres than of the slowly forming dentinal matrix. In consequence of the correspondence of the cur\aturc of the di-n- tinal tubules, the tooth-ivory exhibits a series of linear markings, Sthreget' i /ines, which nm parallel to tht> inner surface of the dentine. These markings nnist not l)e confounded with the contour lines of Owen (pwge 1552), also within the dentine, or with Schreger's prism-stripes within the enamel (Fig. 1306). The dentinal tubules are minute canals, from .OD13-.002 mm. in diameter, which begin at the pulp-cavity with the largest lumen and extend to the outer surface of the dentine, to end beneath the enamel or cementum. Each spirally coursing canal undergoes branching of two kinds, a dichotomous division at an acute angle in the vicinity of the pulp-cavity, resulting in two canaliculi of equal diameter, and a lateral branching during the outer third of their course whereby numerous twigs are given of! with a corresponding dimi- nution in the size of the cana- Fig. 1309. liculi ; the terminal tubes, often reduced in diameter to mere lines, frequently anas- tomose with one another or form loops. The dentinal tubules are occupied by the delicate dentinal fibra, the processes of the odonto- blasts, which in the young tooth constitute a net-work of protoplastic threads through- out the dentine of importance for the nutrition of the tis- sue. The relation of the den- tinal tubules on the external surface of the dentine varies on the crown and root. In the former situation the free surface of the dentine pre- sents crescentic depressions, filled by the enamel, in which the tubules appear as ab- ruptly terminating or cut of! ; on the root, on the contrary, where the dentinal surface is smooth, the tubules stop in curved ends or loops beneath the cementum, only in very exceptional cases communi- cating with the canaliculi of the latter. The immediate wall of the dentinal tubules is formed by a delicate membrane, the sheath of Neumann, which in appropriate transverse sections appears as a con- centric ring. On softening the decalcified dentine by acids or alkalies, the sheaths may be isolated, since they resist the action of the reagents which attack the sur- rounding intertubular substance. The sheaths of Neumann are formed through the agency and at the expense of the dentinal fibres, the latter being smaller in old than in young dentine. The sheaths, therefore, may be regarded as specialized parts of the intertubular matrix, distinguished by less complete calcification and greater density. The intertubular ground-substance of ien'.ine resembles that of bone in being composed of bundles of extremely delicate fibrilLx of fibrous connective ti.ssuc. The latter, best seen in decalcified tissue, swell on treatment with water containing acids or alkalies, and yield gelatin after prolonged boiling. The disposition of the bundles Ground-section of dried tooth including adjacent enamel and denline. - 300. m i? I 1 55" HUMAN ANATOMY. uf fibrillse — more regular in dentine than in bone -is longitudinal and parallel to the primary surfaces of the dentine. In addition to the fibres which extend lengthwise, others run obliquely crosswise in the layers of dentine. The bundles of fibrillse measure from .003-. 003 mm. in diameter, and appear in transverse sections as small punctated fields. The librillie are knit together by the calcified organic matrix, in which the lime salts are deposited in the form of spherules, the interstices between which are later filled and calcification thus completed. When, as often happens, the latter process is imperfect, irregular clefts, the interglobular spaces, remain, the con- tours of which arc formed by the spheres or dentinal globules of calcareous materia!. The interglobular spaces are of irregular form and uncertain extent, being usually largest in the crown. At the border between the dentine and the cementum there exists normally a distinct zone, \^i^ granular layer of Tomes (Fig. 1311), composed of Fig. 1310. Plllp^iisuv Oranular layer of denliiu- Ccmctitum Alveolar periosteum Transverse section of root of lower canine tooth. X 30. closely placed interglobular sjiaces of small size ; under low magnification in ground- sections the spaces appear as dark granules, hence the designation of the zone. Since the existence of these spaces depends upon imperfect calcification of the intertubular Rround-substance, the dentinal tubules are unaffected and pass through the spaces on their course to the surface of the dentine, several of the canals traversing the larger spaces. The contour lines of Owen, or the incremental lines of Salter, appear as linear markings, which usually run obliquely to the surface of the dentine (Fig. 1 306). They probably depend upion v ' 'ions in calcification incident to the growth of the dentine, and resemble the i ,iobular spaces in their origfin. The contour lines are best marked in the crown and are only exceptionally seen in the fang. As pointed out by Walkhoff, the lines of Owen and those of Retzius in the enamel are usually present at the same time, since both are expressions of iin|jerfect calcification. The Cementutn. — The cement, or crusta petrosa of the older writets, forms an investment of slightly modified osseous tissue from the neck of the tooth to its STRICTURE OF THE TEETH. «553 l)«uin Ginnular layer of TomcR « u A 1^' apex. Beginnini; where the enamel ceases, or overlapping; the latter to a small extent, as a layer only .02-.03 mm. thick the cement gradually increa-ses in thick- ness until over t'le root, t^peciall) hetweei ihe fanKs of the molars, its deptli reaches sevaral millimetres. When well i'- .lope the cement u.sually presents two layers, — an inner, almost homogeneous straium '- .t the dentine, in which the cement-cells are absent, and an outer supplemental layer which exhibits the appearance of true bone- tisaue. The ground-substance of cemen- tum differs from that of ordinary bone in containing, according tt> Bibra, slightly less organic matter and a great number of fibre-bundles that extend vertically to the lamellae, corresponding to Sharpey's fibres. The lacunx are larger than those of bone and vary greatly in their number and form ; their processes, the canaliculi, are unusually long and elaborate. As in bone, so these lymph-spaces contain con- nective-tissue cells, the cetnent-corpMsiles. The lamella* are so disposed that the lac \xat lie generally parallel with the long axis of the tooth, their processses extend- ing vertically to the free surface. While connecting with one another by means of the canaliculi, the lacuna? very rarely communicate with the 'lentinal tubules, the latter terminating ■ blind endings. The union between the outer surface of the cement and the pericementum is in- timate, since the latter is in »act the alve- olar periosteum from which the cement was derived ; this close relation is indi- cated by the roughness which the outer surface of the cement presents when macerated. Although at times feebly developed under normal conditions, typical Haversian canals are found only in con- ditions of hypertrophy. The Alveolar Periosteum. — The periosteum investing the jaws likewise lines the sockets receiving the roots of the teeth, which are by his means securely held in place. The name pericementum is often applied to this special part of the peri- osteum, which clothes the alveoli on the one hand and covers the cement on the other, thereby fulfilling the double r6le of periosteum and root-membrane. The latter consists of tough bundles of fibrous tissue, elastic tissue being almost want- ing, which are prolonged into the penetrating fibres characterizing the cementum on one side and into the fibres of Sharpey of the alveolar wall on the other. The fibrous bundles run almost horizontally in the upper part of the root, but become more oblique towards the apex of the fang. In the latter situation the pericemen- tum loses its dense character and becomes a loose connective tissue through which the blood-vessels and nerves pass to reach the tooth. The less dense portions of the root-membrane between the penetrating bundles of fibrous tis.sue contain, in addition to the vessels and nerves, irregular groups of epithelial cells which appear as cords or net- works within the connictive-tissue . oma. These groups are the remains of the epithelial sheath which surrounded the young tooth during its early development. They have sometimes been described as glands, lymphatics, and other structures, their true nature being unrecognized. At the alveolar mar- gin the pericementum is directly continuous with the tissue composing the gum, the fibrous bundles being so disposed immediately beneath the enamel-border that they form an encircling band of dense fibrous tissue, the ligamentum circulare dentis of Kolliker, which aids in maintaining tirmer union between the tooth and the alveolar wall. Lacuna Ground-Kctfon of root of dri«i1 tnolh including adjacent drntine and ccmentum. X 300. :r 1 1 *. 1554 HUMAN ANATOMY. Fio. 131a. The Pulp. — ^The contents of the pulp-cavity is the modified tissue of tl mesoblastic dental papilla remaining after the completed formation of the dentine. The major part of the adult pulp consists of a soft, very vascular connective tissue containing tew or no elastic elements, but numerous irregularly distributed cells of uncertain form. The general type of the tissue resembles the embryonal, both in the character of the fibrous tissue and of the cells, which are round, oval, or stellate with long processes. The fibrous bundles and the more elongated cells are most regu- larly disposed around the blood-vessels and nerves, which they invest in delicate fibrous sheaths. The peripheral zone of the pulp, next the dentine, presents the greatest special- ization, since in this situation lie the direct descendants of the dentine-producing cells, the odontoblasts. In this locality the pulp, especially in older teeth, presents three layers. The outer ( . 04-. 08 mm. thick ) consists of several rows of large cylindrical elements, of which the most sufterificial are arranged vertically to the free surface of the pulp, after the manner of an epithelium. These are the odontoblasts, now no longer active, about .025 mm. in length and .005 mm. broad, which send out long, delicate processes (the dentinal fibres) into the den- tal tubules externally, and shorter ones towards the pulp-tissue. When very young they probably possess also lateral processes. The deeper cells of the odontoblastic layer are less regularly disposed and less cylindri- cal in form. The second, or U'eil's layer, best seen in older teeth, is characterized by absence of cells, the fibrous tissue and the cell-processes forming a clear, cell-free zone which separates the striking layer of odontoblasts from the subjacent third or in- termediate layer. The latter consists of nu- merous small round or spindle-cells, closely placed, but irregularly disposed, which grad- ually blend with the ordinary pulp-tissue. The blood-vessels supplying the pulp are from three to ten small arteries which soon after entering the pulp-cavity break up into very numerous branches from which a rich capillary net-work is derived. In human teeth the capillaries usually do not invade the layer of odontoblasts, although at times the vascular loops may extend between these cells. The venous radicles form larger veins which follow the course of the arteries. Distinct lymphatics have not been demonstrated within the pulp. The nerves are numerous, each fang receiving a main stem and several additional smaller twigs, which in a general way accompany the blood-vessels in their coarser distribution. On reaching the crown-pulp the larger twigs are replaced by finer branches, which divide into innumerable interwoven fibres. The latter, on reaching the margin of the pulp, form a peripheral plexus beneath the layer of odontoblasts, from which terminal non-medullated fibrillae are given off. Some of these end beneath the odontoblasts in minute knot-like swellings ; others penetrate the odonto- blastic layer to terminate in pointed free endings. There is no trustworthy evidence supporting the view that the nerves directly communicate with the odontoblasts or enter the dentine. Section o{ periphery of pulp-tinue of young tooth. X 175. IMPLANTATION AND RELATIONS OF THE TEETH. The Permanent Teeth. — Elach fang is implanted in a socket corresponding to it in shape, so that the pressure is transmitted from the surface of the conical fang throughout, except at the very tip, which has a hole for the vessels and nerves. A corresponding hole in the socket communicates with the dental canals. The human IMPLANTATION AND RELATIONS OF THE TEETH. 1555 teeth are all in contact with their neighbors, there being no break or diastema in the upper jaw between the incisors and canines for the points of the canines of the lower jaw. The canines project very little beyond the line of the free edges. The crowns increase in size from the incisors to the first molars and then decrease. The ver- tical distance from the gum to the free edge regularly diminishes from the median incisors backward, with the exception of the canines. The lines of the teeth above and below are practically of the same length. When the mouth is closed the superior canines lie to the outer side of the Fio. 1313. inferior ones, opposite the ends of " * ' ' the lips ; thus the median upper incisors impinge on both the lower ones of the same side, and the upper lateral incisors strike both the lower lateral and the canine. In the same way the point of the cusp of the upper first bicuspid rests between the points of both the inferior ones, and that of the second on both the second lower and the first molar. The first upper molar has, perhaps, a quar- ter of its grinding surface on that of the inferior second molar, but a smaller part of the second upper molar rests on the lower wisdom- tooth. The smaller size of the upper wisdom-tix>th brings its posterior border into line with that of the lower. This arrangement causes the opposed crowns to interlock to a certain extent, but not so closely that grinding movements cannot occur between them. The advantage of each tooth coming in contact with two is evident after the loss of a tooth, as the one cor- responding to it is not rendered useless. In the upper jaw the incisors have a marked Dental arches seen from before. Letters in thi>ach row more nearly vertical. This implies less difference in curve between the jaws. The line of meeting of the teeth is more horizontal. The crowns increase in size from the incisors backward. In the young child the antrum is but a small pouch, and the roots of the first teeth and the sacs of the second lie in diploetic tissue. The first permanent molar, as its fangs grow, is nearest the antrum, having extended above it by the end of the second year. In its early stages the first bicuspid is too far forward to have any relation to the antrum, and the second reaches only its extreme anterior border. The second permanent molar is at first behind rather than below it, and the third is still higher. As these descend they swing around the antrum. Thus the roots of only the first permanent molar are in approximately the same relation to the antrum throughout. DEVELOPMENT OF THE TEETH. About the beginning of the seventh week of foetal life the ectoblastir epithelium presents a thickening along the margins of the oral cavity. The ridge-like epithelial proliferation, or labio-dental strand, so formed grows into the surrounding mesoblast and divides into two plates which, while still continuous at the surface, diverge almost at right angles at the deeper plane. The lateral or outer plate is vertical, and cor- responds to the plane of separation which soon occurs in the differentiation of the borders of the lips and jaw. The median or inner plate grows more horizontally into the mesoblast, and is the one intimately concerned in the tooth development ; for this DEVELOPMENT OF THE TEETH. 1557 reason it is termed the dental ledge. It will be seen that the formerly described pri- mary stage of the dental groove is unfounded, since the furrow that does exist is secondary and not directly related to the formation of the teeth, but to the differ- entiation of the lips. During the third fcetal month the anlages for the entire set of milk-teeth become evident along the dental bar, coincidcntly, by the eleventh week, the completion of the labial furrow separating the lip from the original epithelial strand with which the dental ledge alone for a time remains attached. The anlages of the milk-teeth are indicated by club-shaped epithelial outgrowths which grow down from the deeper surface of the dental ledge to form the enamel- Flo. 1316. Keconstructioni of oral ectoblast of human embryos ; only epithelium of lips, mouth, and cnamelorffans shown. A, embryo ol 2.5 cm. length; m, oral opeuinx; ^, labial epithelium; /, to the ordinary type of stratified epithelium are seen. The intermediate layer is best marked over the upper part of the crown, at the sides thinning out and entirely dis- DEVELOPMENT OF THE TEETH. 1561 appearing at the margin of the enamel-organ, v ere the outer and inner layers of the latter are continuous. The modified epithelial tissue of the middle layer, sometimes called the enamel-pulp, is greatest in amount just prior to, or during the t)eginning of, active tooth-formation, about the fifth or sixth fcctal month. The inner layer of the enamel-organ comprises a single row of closely set, tall, cylindrical elements, the enamel-cells, adamanloblasts, or ameloblasts, through the active agency of which the enamel is produced. The ameloblasts are liest developctl where they cover the apex of the dental papilla, the location of the earliest formed den- tine ; in this situation the cells measure from .025-.040 mm. in length and froni .004-.007 mm. in breadth. They possess an oval nucleus about .010 mm. long, which usually lies close to the outer end of the cell, embeddtd in cyto|)lasm exhibit- ing a reticulum and often minute granules. The ameloblasts are united with one another by a small amount of cement-substance, and are define*! fnu ; the interme- diate layer by a fairly distinct border. Opf)osite the sides of the den li papilla, cor- responding to the limits of the future crown, the ameloblasts gradually diminish in height until they are replaced by low cubical cells which, at the margin of the enamel- organ, are continuous with the epithelium of the outer layer. Preparatory to the for- mation of the dentine of the tooth-root, this margin grows downward towards the base of the elongating dental papilla, which is thus embraced by the extension r>f the Fig. 1320. Oral epithelium Atrophic epithelial net-work Dental groove Enamel_ ,j,4 Dentine ., Epithelial iheath Position of mesoblaslic dental papilla Reconstruction of developing lower incisor tooth from embryo of 30 cm. length, about twenty-four weeks. {Drawn from Host's modtl.) enamel-organ. The investment thus formed constitutes the epithelial sheath (Fig. 1320), a structure of importance in determining the form of the tooth, since it serves as a mould in which the young dentine is subsequently deposited ; there is, however, insufficient evidence to regard the epithelial sheath as an active or necessary factor in the production of the dentine. The formation of the enamel, in contrast to that of the dentine, results fiom the activity of ectoblastic epithelium, and may be regarded as a cuticular development carried on by the ameloblasts. The earliest stage in the production of enamel is the appearance of a delicate cuticular zone at the inner end of the ameloblast ; this fuses with similar structures tipping the adjoining cells to form a continuous homo- geneous mass. The latter soon exhibits differentiation into rod-like segments, the enamel-processes, or processes of Tomes, which are extensions from the ameloblasts and are the anlages of the enamel-prisms, and the interprismatic substance. The latter becomes greatly reduced in amount as the development of the enamel-columns progresses ; the major part, becoming incorporated with the processes of Tomes, forms the cortical jxjrtion of the enamel -prisms, while the remainder persists as the cement-substance which exists in meagre quantity between the mature prisms. The enamel-processes are for a time uncalcified, but with the more advanced formation of the enamel-prisms the calcareous material, which is deposited as granules and spherules, appears first in the axis of the prism, later invading the periphery (Ebner). The 1 ■ 1 ■R i ■ 1 ^^1 1 1562 HUMAN ANATOMY. enamel increases in thicknejis by the addition of the last-formed increments at the inner ends of the ameloblasts, the same cells sufficing for the deposit of the entire mass. Owing to the expansion of the external surface of the crown, the diameter of Fio. 13J1. Intermediate layer ai enamel-urgaii meloblaats .YouiiK enamel with Tumcs's proceiM* Dentine Laat-formed dentin* Odontoblasts . Embr>-unal pulp-tissue Section of developing tooth through junction of enamel and dentine. ^ 400. Fig. 1323. the enamel-prisms augments towards their outer ends to compensate for the increased area which they must fill, since no additional prisms are formed. The complex curvature of the enamel-prisms and the oppositely directed ranges of the latter, producing the appearance of Schreger's stripes, result from changes in the position of the enamel-cells incident to the growth of the crown, since the axes of the newly formed prisms correspond with those of the ameloblasts, variations in the direction of which affect the disposition of the enamel-columns. The earliest formed enamel lies in close apposition with the oldest dentine con- stituting the membrana praeformativa ; the last devel- oped immediately beneath the ameloblasts. The enamel, therefore, is deposited from within outward, or in the reversed direction followed by the growth of the dentine. The oldest strata of both substances lie in contact ; the youngest on the extreme outer and inner surfaces of the tooth. After the requisite amount of enamel has been pro- duced, differentiation into prisms ceases, in consequence of which the last-formed enamel remains as a continu- ous homogeneous layer investing the free surface of the crown, known as the membrane of Nasmyth. The Tooth-Sac. — Coincidently with the develop- ment of the enamel-organ and the growth of the dental {>apilla, the surrounding mesobiast undergoes differen- tiation into a connective-tiiBue envelope known as the dental or tooth-sac. The latter not only closely invests the enamel-organ, but is intimately related to the base of the dental papilla, with which it is continuous. In contrast to the epithelial enamel-organ, which is entirely without blood-vessels, the Isolated ametohlasts from in- cisor of new'bom child, a, basal plate ; d, ciiticiilar border ; f, pro. cesses of Tomes; d, homogeneous mass still covering process. X 400. DEVELOPMENT OF THE TEETH. »5*3 inner port of the tooth-sac is richly provided with capillaries, and therefore is an important source of nutrition to the developing dental germ. The i>art of the sac opposite the root of the young tooth is at first prevented from cummg into direct contact with the dentine by the double layer interpu!>ed by the epithelial sheath. This relation is maintained until the development of the cement begins, when the vascular tissue of the dental sac breaks through the epithelial sheath to reach the surface of the dentine, upon which the cementum is deposited by the mesoblast. In consequence of this invasion, the epithelial sheath is disrupted mto small groups or nests of celb which f>ersist for a long time as epithelial islands within the fibrous tissue of the alveolar periosteum into which the dental sac is later converted. The formation of the cementum takes place through the agency of the mesoblastic tissue in a manner almost identical with the development of subperiosteal Fig. 1323. Jtwi o( child of six years, showing all tcmporao' teeth in place with permanent teeth in various stages of development. bone, the active cement-producing cells, or cementoblasts, corresponding to the osteo- blasts which deposit the osseous matrix upon the osteogenetic fibres of the periosteum. A conspicuous feature of cementum is the unusual number of transversely disposed bundles of fibrillae, or Sharpey's fibres, among which many are imperfectly calcified. The cementum appears first in the vicinity of the neck of the tooth, and progresses towards the apex of the root as the dentine of the fang is deposited. After the tooth is fully formed, the layer of cement continues to grow until thickest at the apex, which it completely invests, with the exception of the canal leading to the entrance of the pulp-cavity. The cement being deposited directly upon the homogeneous layer con- stituting the external surface of the dentine, the firm connection between the two portions of the teeth is one of adhesion rather than of union. Later secondary changes may exceptionally bring the canaliculi of the cement into communication with the terminations of the dentinal tubules. During the changes incident to the '564 HUMAN ANATOMY. completed tooth-development the tissue of the dental sac becomes denser, the part opposite the root persisting as the pericementum which intimately connects the cementum with the alveolar wall, while the more superficial part blends with the tissue forming the gum. The development of the permanent teeth is early provided for by the dif- ferentiation of the anlagcs of the secondary denul germs during the growth of the first. This provision includes the thickening and outgrowth of the dental bar to form the enamel-organ of second dentition, and later the appearance of a new dental p;i- pilla beneath the epithelial cap. The enamel-organ for the first permanent molar appears about the seventeenth week of ftetal life, followed soon by the corresponding dental papilla. The germs of the permanent incisors and canines, including the papillie, are formed about the twenty-fourth week ; those for the first bicuspids are seen at about the twenty-nintli week, and those for the second bicuspids about one month later. The interval between the formation of the enamel-organ and the asso- ciated dental papilla increases in the case of the last two permanent molars. While the enamel-germ of the second molar appears about four months after birth and the corresponding papilla two months later, the enamel-organ for the third molar, or wisdom-tooth, which is visible about the third year, precedes its papilla by almost two years. The First and Second Dentition and Subsequent Changes.— At birth the jaws contain the twenty crowns of the milk-teeth, the still separate cusps of the first permanent molars, one of which has begun to calcify, and the uncalcified rudi- ments of the permanent incisors and canines behind and above the corresponding milk-teeth of the upper jaw, behind and below those of the lower. At birth the bony plate above the alveoli of the upper jaw is separated by a littie diploe from the floor of the orbit. The milk-teeth come through the gum in five groups at what are called dental periods, separated by intervals of rest. The grouping is more regular than the time of eruption. The teeth of the lower jaw have a tendency to precede their fellows of the upper. TABLE OF ERUPTION OF MILK-TEETH.' I. II. III. IV. V. Denial Pcriodi. Six to eight months. Eight to ten months. Twelve to fourteen months. Eighteen to twenty months. Twenty-eight to thirty-two months. Groups of Teeth. Two middle lower incisors. Four upper incisors. Two lateral lower incisors and four first molars. Four canines. Four second molars. The inter\'al between the first and second periods is practically nothing. It is very common to have the first two groups appear together. After this every inter\ al IS longer than the preceding one. In the matter of time no part of development is more irregular than that of the teeth. The first incisors occasionally appear earlv in the fifth month and sometimes not till the tenth, or even later. The first dentition is sometimes complete at or shortly after the close of the second year. The roots are not fully formed when the crowns pierce the gums. The first set of teeth is in its most perfect condition between four and six years. Calcification of the second set begins in the first molar before birth, in the incisors and canines at about six months, the bicuspids and the second upper molar in the third year, the second lower molar at about six, and the wisdom-tooth at about twelve. The first permanent molars come into line with the milk-teeth, piercing the gums before any of the latter are lost. Before eruption the upper first molars lie nearer the median line and farther forward than the lower. The roots of the incisors are absorbed and the crowns fall out to make way for their successors. The molars do the same for the bicuspids which grow between their roots. The permanent superior canines are developed above the interval between the lateral permanent incisors and the first bicuspid, which are almost in contact. An expansion of the jaw is necessary for them to come into place. The inferior ones have more room. Both are somewhat external to their predecessors. The second upper molar comes down from abovo and behind, " From Rotch's Pediatrics. DEVELOPMENT OF THE TEETH. 1565 and so does the wiadom-tooth much later. The inferior second molar is formed almost in the angle between the body and ramus. The inferior wisdom-tooth, Ix-fore it cuts the gum, faces forward, inward, and slightly upward. To the table from Pio. 13*4. PcnwiiMnt midani, Prrmancnt mola I'emunetit canine Iticuspidii .rrrmanent in*-f^>r» Ti'tn|>orary caninr rt'miMiran inohirs IVimaiieiit incisurs TfniiMirary canine Permanent canine Hicuspids Jaws of child of ten years. thowinK partially erupted permanent teeth with temporary canines and molars Mill in place. Rotch we add one from Livy,' who made observations -ral thousand children of English and Irish operatives. TABLE OF ERUPTION OF PERMANENT TEETH." Years. Groups. Years. Croups. 6 Four first molars. 10 Four second bicuspids. J Four middle incisors. II Four canines. Four lateral incisors. la Four second molars. 9 Four first bicuspids. 17 to 25 Four wisdom-teeth. TABLES SHOWING TIME OF ERUPTION OF PERMANENT TEETH.' Bo vs. Ag«s. 9 10 II '! 13 '4 15 I* ToUI. Lateral incisors .... i 42 9 4 i i . . . . 59 First bicuspids i 76 12 i 9° Second bicuspids ..... 59 i^ 5 ' "" Canines 18 28 25 8 . . . . . . 79 Second molars 5 4a 6? VS 184 78 12 663 • British Medical Journal, 1885. « From Rotch. • From Livy. 1566 HUMAN ANATOMY. GlKU. *«••• » lo II 11 ij 14 I) 16 ToUI. lateral incixors 34 8 4 j6 First bictiHpidx 56 i^^i j 1 1 . . . '. 73 SccoikI bicuspids ji 16 2 a . . 71 Second molars 5 44 8u j88 149 66 14 ^46 ( It seems possible from the method employed that, especially in the case o< the second molars, the tables may err on the side of overstatinK the age. ) Livy's researches show that in the first dentition the first molars, incisors, and canines come through first in the lower jaw. In miwt cases the bicuspids come first in the upper. The second molars come first in the lower jaw, unless their appearance is delayed, in which case the order is uncertain. The date of the appear- ance of the second molar can be only an approximate guide to the age. VVhen it is present the child is unlikely to be under twelve. The change in the shape of the jaw— namely, the lengthening necessary for a longer row of larger teeth, as well as the widening required to make room for the canines— t>egin> in the course of the second dentition and continues after its close, as the second molar doe.> not at once assume its permanent position in regular line with the rest. It w.xs pointed out in the section on the growth of the face that the greatest activity of growth Likes place at the paiis.s of dentition. The roots of the permanent teeth are by no means fully developed at their eruption. With their perfection the sockets are formed around them by the harmonioun moulding of the parts involved. Homolofies — Tnerf are two chief evolutioniiry theories of the origin of the mammalian teeth : one, the concres< -nee theory, is that they are formed by the growing together „.' originally separate rones, the primuive reptilian teeth. This view is supported by Kiise ' and Kukenthal." at lea.st for the- bicuspids and molars. Cope,* whom Osborn* has followed, advanced the differentiation theory, according to which the many cusps of the molars have arisen as outgrowths from a primitive cone. This is based on comparative anatomy and paieontolog)-. According to this, there was first the ctmf, in the upper jaw called yJne prolocone and in the lower the/»ro/o- (.■OHid. Two secondary cusps next appeared respectively before and behind it \.\\e paraione and tnetacone of the upper teeth and \.\\k faraeonid ana metaconid ol the lower. The next change is for these to move to the labial side in the upper jaw and to the lingual in the lower. Thus the primitive cone and these two secondary ones Jorm the points of a triangle with the base outward in the upiier jaw and inward in the tower. A prolongation, the talon or heel, is next developed on the posterior end of the tooth, and rises into a single cusp, the hypocone in the upper jaw and the hffoconid in the lower. The last, however, has Iwo secondary cusps spring from it, Ihe enlocontd and the hypoconid. According to this theory, the fiararonid ol the lower teeth has disappeared in the human molars owing to want of room consequent on the develop- ment of the talon of the upper teeth. The following table shows the homologies of the cusps of the hiunan luolars acxordiog to Osborn. Upper MotARs. Anterior lingual . Protocone. ) Anterior buccal Paracone. V Forming the triangle. Posterior buccal Metacone. ) Posterior lingual Hypocone. The talon. Lower Molars. Anterior buccal Protoconid. 1 „ . r ^ Anterior lingual Metaconid. 1 '*^'""''"* °' tnangle. Posterior buccal H)poconici. ) Posterior lingual Entoconid. } The talon. Posterior Hypoconulid. J R.ise has advanced, in support of his theory of concrescence, thai calcification begins sepa- rately for each cusp. Osborn jxiints out that R.ise has shown that they ossify ver\- nearlv in the order of their alleged evolution. Schwalbe' professes himself un.ible to deci'de on the relative merits of the two theories. Variations. -Variations of the cusps and of the fangs have been descril)ed with the teeth. Those of niinil)er affect chiefly the incisors and molars. An additional incisor may occur on one or both sides in either dentition, not verv rarely in the upper jaw, but extrem<"ly so in the lower, the condition in the latter being more stable. Extra upper incisors are often more or less displaced to the rear and implanted obliquely-. Thev are particularly common in cases of cleft pal:ite ; not impossibly the presence of additional teeth predisposes to the non-union of the ' Anatoni. Anzeiger. Hd. vii., iHq2. ' Jenaische Zeitschrift, Ikl. xxviii.. 1893. ' Journal of .\torpholog>'. i8,SS. i.S.St). ♦ .Vmerican Naturalist, i8S,S, and International Dental Journal, 1895. ' Anatoni. -Xn/eiger, Bd. ix., 1894. THE GUMS. IS67 pictiMxilUry and the maxillonr bones, or to the non-union oi two parts al the fiHmer, su|)piMinK that two Mich parts really exM. The extra inciitor nviy a|>piireiitlv a|>t)enr on the meUun •■itfe of the first, between the nret and second, or between the lattrr and the ranintr. Tu aicnuiit for this Rosenberg' asserts that the typical number h five, a» in the oiHMKum, of which the iiecond and fourth are the two persistent ones, and that either the first, tnircl, or fifth nviy occasionully present itself. Th. Ktilliker * records a case of rieht cleft (talate in which, besidcH the fiHir regular iiK'isurs, three were found between the cleft ami the rixht canine. Ah cases of exces.s of incisors are much more common titan of deficiency, the diHii|)|)earance of the U(>|>er lateral one does not seem imminent ; still, there are signs of deitetterativn. The crown is less s<|iiare than that of the central, it is occasionally pointed, often unusually smill, sometimes not reachiiiK the line th is late in coming through the gum, and occasioiully it never does. It seems sometimes to be wanting and often is ruuimentary. It has t>een seen represented by three detached cusps, an apimrent confirmation of K(>se's views of the homology of the teeth. The entire dental series may be unusually large or small. In the former case the fare is prognathous, probably as a result oi the increase cI space required for the teeth. The up|>er central incisors are occasionally very large without increase in size of the other teeth. Thes;ime is true of the molars ; in which case the number oi cusps is generally greater, but the converse does not occur when the molars are unusually small.* The points of the canines may project beyond the line of the other teeth am 1 e molars may increase in size from the first to the third. Teeth are sometimes remai kably displaced. The superior canines, owing to their hii;h origin in the setond dentition, are particularly subject to it. They may appear on the front of the jaw, in the antrum, the nose, or the back oi the mouth. The molars, and especially the wisdom-teeth, are also erratic. THE GUMS. This term b used rather vaguely to indicate the mucous membrane aitd sub- mucous tissue covering the alveolar processes and closely attached to the necks of the teeth. Whether the neck is entirely surro- ded by it varies in different indi- viduals as the teeth are not in all equally close ; as a rule, owing to the ordinary expansion of the crown from the neck, at lea.st a little of the gum is found l:)etween the teeth. It is some 3 mm. thick, dense, firmly fastened to the bone, and is neither very vascular nor very sensitive. In structure the gums resemble other parts of the oral mucous membrane, con- sisting of the epithelium and the connective-tissue layer. The latter, directly con- tinuous with the periosteum of the alveolar border and the pericementum, is comjiosed of closely fitted bundles of fibrous tissue and beset with numerous papilbe. On young teeth the epithelium is prolonged for from .5-1 mm. over the enamel and often for a short additional distance over the cement, ending in an abrupt margin. In the immediate vicinity of the tooth the papillae sometimes exhibit infiltrations of lym- phoid cells. The gums are without glands. The structures sometimes described as such, as the " glands of Serres," consist of nests of epithelial cells derived from the remains of the atrophic embryonal epithelial sheath (page 1563). THE PALATE. The Hard Palate. — ^The shape and proportions of the hard palate have been discussed with the bones (p^e 228), so we ha\e here to do only with its mucous covering. This is very firmly fastened to the rough surface of the bones by dense connective tissue which is particularly thick at the sides, doing much to fill up the angle between the roof and the alveolar process. On either side near the front, extending onto the inner surface of the alveolar processes, is a series of raised ridges ( Fig. 1 325 ) , in the main transverse, although slightly convex anteriorly, the analogues of the palatal ruga of most mammals. They never extend behind the first molar tooth, are numerous and prominent in childhood, but much reduced in middle age, and occasionally wht>lly lost. ' Morphol. Jahrbuch. Bd. xxii., 1895. Nova Arte des Leopold. Carol. Akad. der Naturforscher, Bd. xliii., i88a. • Magitot : Traits des Anomalies du Syst^me Dentaire, 1887. ■■it 1568 HUMAN ANATOMY. Just behind the incisors, at or before the incisor canal, there is a small raised pad or fold of mucous membrane, on either side of which the orifice of the incisor canal is often found. When pervious, it is very minute, admitting merely a bristle. Behind this the palate presents a median rc^he of paler color than the resc, which may Fio. 1325. OrtficM of palatine glands Inclwr pad with orifice of inciaor canal Raphe Mucous membrane removed to show layer of glands Soft palate Superior dental arch and lalate ; palatal rugsc occupy aiilerii)r (art. Soft palate partially cut away. run to the root of the uvu'a or may stop short of it, bt-injf often deflected to the left. A little behind the pad this line may be interruptetl by a pale oval elevation or more often a depression. The membrane of the roof of the mouth is nowhere bright red ; that of the hard palate, however, is paler than the rest. There are no glands in the o\al white space, but there is a continuous layer on either side of it. The orifices of the glands are easily seen with a lens, sometimes with the naked eye. A little in Fig. 1.136. "i^Krtfe^: Muscular fibres of tongue Dorsal sitr " tongue f/ ^^' Anterioi pillar of fauces iMica triangularis'^ Tonsil -Soft palate .Supratonsillar tons Uvula Posterior pillar of fauces Epiglottis Sagittal section through palate, uvula, and tongue, showing right lateral wall of fauces; tongue has been pulled downwani by hook. front of the origin of the soft palate the mucous membrane becomes deeper colored. These differences in color are more striking in children. The Soft Palate.— This structure consists of a fold of mucous membrane, con- tinuous with the hard palate, enveloping seveml l.iyprs of interlacing muscular fibres. at least i cm. in thickness at iu origin. Its lower border is the edge of the fold. THE PALATE. I5«9 This is concave on each side, and presents a median elongation, the uvula, which varies from a short prominence to a cord 2 cm. in length. Thus the palate has a lower surface lookmg downward and forward and an upper one looking upward and backward. When the mouth is closed the palate and uvula rest against the tongue ; when open they hang free, but the muscles inside can modify their shape and position. Median sections show the tip of the uvula often reaching within half Fio. 1337- Pharynfml miicoat mcfflbran* endon o( tenaor pkUtI Levator palati PalXopharj-ngciu Masses of glands Oral mucous membrane Transverse section of soft palate near its anterior attachment. X 4. an inch of the tip of the epiglottis. Possibly muscular relaxation allows it to descend somewhat farther than in life, but it is certain that no very great elongation is neces- sary for it to touch that organ and give rise to great discomfort. The soft palate can be raised so as to touch the back of the pharynx and close all communication between the nose and the mouth. Two folds, the pillars of the fauces, each the reflection of the mucous membrane over a muscular bundle, start from the palate on either side. The anterior pillar, enclosing the palato-glossus muscle, arises from the front of the palate near the uvula, some distance anterior to the edge, and, curving downward, runs to the tongue at the junction of the middle and posterior thirds, separating the mouth from the pharynx and forming the posterior border of the sublingual space. The posterior pillar starts from the lower border of the palate on either side of the uvula, covering the palato-pharyngeus, and runs down the throat to the superior cornu of the thyroid cartilage, the lower part being indistinct. Some of the muscular fibres within it go to the upper border of the thyroid cartilage in front of the horn, but the fold is not often found so low, except in frozen sections, in which it appears at the sides of the back of the pharynx. A deep triangular recess on either side, between the anterior and posterior pillars, contains the tonsil. This region is often vaguely described as the isthmus of the fauces, one being left in doubt whether it belongs to the pharynx or to the mouth. In the preceding pages the pharynx is described as beginnmg at the anterior pillar. The reasons for this divi- Fio. 1328. Fibres of azygos uvulie Phar>'ngeal mucous membrane Fibres of palato-pharynj^us lands sion are developmental, morphological, and phys- iological. The part of the tongue anterior to this fold is of- mandibular (buccal) origin, while the part behind it comes from the pharynx. The sur- face of the former is sup- plied by the mandibular ner\e, the third division of the fifth, and the latter by the glossopharyngeal. The mucous membrane of the posterior third does not bear papillse (except the circumvallate papillae near the junc- tion of the two regions), but is rich in adenoid tissue and glands, differing in both respects from the part in front of it. The arrangement of the transverse fibres of the glosso-palati muscles in the substance of the tongue suggests a sphincter at the entrance of the ph-irynx. Ftn.illy, in degltttition it is in passing this line that the bolus ceases to be under the control of the will. 99 Masses of glands Oral mucous membrane Transverse section of soft palate near base of uvula. X 4. i?i> m .'*§-* I •a -i i t57o HUMAN ANATOMY. The following layers compose the soft palate from above downward : ( i ) The pharyngeal mucous membrane. (2) A fibro-muscular iayer. The fibrous portion IS the expansion of the tendons of the tensor palati muscles. It is strong and tense near the hard palate, gradually dwindles lower down, and joins the pharyngeal aponeurosis at the sides. Below this is the complex of the muscles. (3) A glan- dular layer opening into the mouth. This is soiiit; 5 mm. thick at its origin and {}ractically continuous throughout most of the palate. It is interrupted at the median line near the hard palate by a septum of muscular and fibrous tissue, is wanting near the free edge of the palate a littie on either side of the root of the uvula, and is con- tinued down the uvula as a cylindrical string of glands nearly to the tip, through and about which run the fibres of the azygos uvulae muscle. Irregular glandular collections are found near the latter, especially at the base of the uvula. (4) A lower layer of mucous membrane. The mucous membrane of the soft palate is red on the pharyngeal and pale on the buccal surface ; on both sides it presents papillae, those on the upper surface Fig. 1339. Glandi AponcurMic tissue Oral mucous membrane Sagitto-lateral Mction of soft palate. X 15. especially being near the base. The most common form, slender and elongated, is scattered over the entire buccal surface and the front of the uvula (Riidinger). Thicker short papillae are also found near the beginning of the pharyngeal surface. Small adenoid collections occur on the upper surface, as well as small glands situated in the depth of the mucous membrane. The orifices of the chief glandular layer pierce the inferior palatal surface. The Muscles of the Soft Palate.— Some of the muscles arise in the soft palate ; others run into it. Isolation of the individual sets of fibres is not always possible. The tensor palati ( dilatator tuba) { Fig. 1 330) arises from the scaphoid fossa at the root of the internal pterygoid plate, from the spine of the sphenoid, and from the outer membranous part of the Eustachian tube. It descends vertically along the internal pterygoid plate as a round, red, and distinct muscle, which becomes tendinous as it turns inward under the hamular process at right angles to its previous course, after which it broadens into the fibrous expansion in the soft palate already described, above the other muscles. A bursa lies between the tendon and the hamular process. THE PALATE. »57« The levator palati (Fig. 1330) arises from the base of the skull at the apex of the petrous portion of the temporal bone and from the cartilaginous part of the Eustachian tube beside it. At first thick, it passes downward, forward, and inward with the tube, and, leaving it, expands into a layer which spreads out through the soft palate. Some of the anterior fibres from the tube go to the back of the hard palate, con cituting the salpingo-palatinus, while others descend in the lateral wall of the pharynx, covered by mucous membrane, beneath the salpingo-pharyngeal fold. The great body of the fibres crosses the middle line in the front part of the soft palate. Most of them descend in the opposite side. Some seem to form loops with an upward concavity with fibres from the fellow-muscle. Near the hard palate this decussation completely divides the glandular layer (Fig. 1327). The azygOB uvulae (Fig. 1331), although probably a double muscle originally, soon (even at birth) becomes practiodly a smgle one. Arising from the tendinous fibres of the tensor palati just behind the postenor nasal spine, it soon becomes mus- cular and increases in size. Its course b downward into the uvula, but on reaching the base it is already broken up into separate bundles which pass about and through Pio. 1330. Hmid |»bt* HamuUr Tensor palati Levator palati palate (rut) External pterygoid plate Posterior nares .Opening ot Kustachian tufa* Cut edge of pharynx Mass of t» Jcnoid tissue Fossa of Rosenmiiller (opened) Styloid process Occipital condyle Inferior surface o( skull with upper part of opened pharynx and palaul muscles attached ; viewed from behind. the glandular core of the uvula. The belly of the- muscle lies near the dorsal surface, between the fibrous expansion of the tensor palati and the levator palati, which decus- sates on its oral surface. The palato-pharyngeus (Fig. 1331) has a complicated origin in mure than or. .yer from the Iwrder of the hard palate, from the lower surface of the apo- .urosis, and perhaps from fibres of the levator palati. Certain fibres, either arising in the middle line or coming from the other side, pass downward and outward over the azygos uvulae ; others lie beneath the glandular layer. Some of the fibi.-* seem to continue the course of the salpingo-pharyngeus of the opposite side, witii- out being directly continuous. The muscle passes down near the edge of the soft palate and then in the posterior pillar into the side of the pharynx, where it min- gles with the stylo-pharyngeus. A part is inserted into the upper border of the thyroid cartilage, and sometimes into the superior horn. It also expands, together with the stylo-pharyngeus, into a thin layer just beneath the mucous membrane of the back of the pharynx, which meets its fellow in the median line where it is inserted into the pharyngeal aponeurosis. Its lower limit is a curved line with the concavity looking upward and outward, behind the larynx (Fig. 1361). (This fnirt 1572 HUMAN ANATOMY. of the muscle must be dissected from behind, after removing the constrictors of the pharynx. ) The palato-glosBUS (Fig. 1339) is a small bundle arising from near the middle line of the oral side of the lower part of the soft palate, forming by its projection the anterior pillar of the fauces, in which it runs to the tongue, where it joins the trans- verse fibres. The pair of muscles act as a sphincter tending to close the passage from the mouth to the pharynx. A thin expansion from this muscle passes over the tonsil. Vessels. — The arteries of the palate (both hard and soft) come chiefly from the descending palatine, which, emerging from the posterior palatine canal, runs for- ward along the inner side of the base of the alveolar process. It sends a few branches Fio. 1331. Nasal Mptum Eustachian tube SalpifiRO- pharyiiKcu: l.i.-\:it(ir iialatl Falato-pharyni I'jtuto-pharyngel Stylo-phao'ngi i Poslerior surface of tongue Posterior cri«>«ryteiK>id .(Esophagus Muscles o( palate and phannx, seen from behind ; pharynx laid open. inward and backward to the front of the soft palate, which is supplied on the side by a branch either from the facial or from the ascending pharyngeal. It is to be noted that no vessel is likely to interfere with the division of the tensor palati at the inner side of the hamutar process. The veins of the hard palate follow in the main the arteries. Those of the upper side of the soft palate join the plexus of the zygomatic fossa. The larger ones of the under side connect with the veins of the tonsil and the root of the tongue. The lymphatics n\ the h.ird palate ani of the tindor side of the soft palate form a rich plexus. Those on the upper side of the latter are small. The chief current is to the deep glands of the neck. THE TONr.lE. «57.T Nerves. — The tensor palati is supplied by the mandibulai iivision of the fifth pair, the other muscles by the pharyngeal plexus. The mucous membrane of the hard palate is supplied by the anterior palatine nerve and terminal branches of the naso-palatine. That of the soft palate is supplied by the other palatine nerves and by branches from the glosso-pharyngeal. THE TONGUE. The tongue is a median muscular organ attached, to the floor of the mouth, the symphysis of the jaw, and the body and both horns of the hyoid, covered with mucous membrane, which when the mouth is closed it practically fills (Fig. 1339). The root is the attached f)ortion, extending from the hyoid to the symphysis, com- posed of the genio-glossi and the hyo-glossi muscles. The tip is the free anterior end, flat both above and below when extended, and surrounded by mucous mem- brane. Behind this the tongue is a solid mass. The dorsum in its anterior two- thirds is convex from side to side, and rests against the hard and sofl palates ; the [wsterior third, nearly vertical, looks backward, forming the front wall of the pharynx when the mouth is closed. There is a median groove in the upper part of this pos- terior third, continued for a little distance onto the top, in which the uvula rests. This hind portion is so broad that the edges of the tongue reach quite to the sides Fig. 1332. Anterior tongue anlage II arch III arch Larynx Reconstruction of floor of primitivt oro-phar>'njt of embryo 12.J mm. in length. X l& \Hit.) Under surface of tongue of new-bom chilfl of the pharynx. In the anterior two-thirds the edges of the tongue are prominent, overhanging the sides. Developme- ' -hows that the tongue has a double origin, the posterior third arising' from I . of the pharynx and overlapp'ng on each side the anterior two- thirds, which rom a median ir> hss, the tuberculum impar. of buccal origin ( Fig. 1332). The /(_ lossal duct co. • to the surface at the junction of these parts, which in the infant are separated by th» sulcus terminalis. As will later be evident, the manner of development is of much significance. The mucous membrane of the lateral and inferior surface is thin and smooth with small papillae at the tip. In the middle it forms a fold, the frtnum, running from near the tip to the floor of the mouth. In infancy this is occasionally so short as to restrain the tip of the tongue from the motions necessary for nursing. Often it is hardly visible. The plica fimbriata and the plica sublingualis are two folds on either side of the front part of the under surface, of which the former with ragged edges is the outer, the longer, and the larger. Both are distinct in the infant and (especially the latter) lost or poorly marked later. The plicx fimbriate bound a triangular space which Gegenbaur considers a rudiment of the undcr-tongue of some mammals. The mucous membrane of the dorsum is divisible into two wholly differ- ent regions : the one comprising the anterior two-thirds, the other the posterior ver- tical third. The line of .separation, or sulats terminalis, is, however, not transverse, but, starting at the side from the anterior pillar of the fauces, runs backward and inward to meet its fellow. This is not usually visible in the adult ; but its place is 1574 HUMAN ANATOMY. easily recognized, as just before it is a V-shaped arrangement of circumvallate papillx, the median apex being at or near a small depression, the foramen cacum, which marks the termination of the foetal duct through the tongue from the thyroid. In the adult this may be a short tunnel or a depression, into which the ducts of several glands open. According to Miinch,' it is always behind the hindmost circumvallate Fig. 1334. Cut o'goma Pterygoid plates Euatachian tnbe Cut and reflected s4)tt palatt Anterior poitioii of head has been removed by frontal section passing through plane of posterior nares : the soft palate cut in mtd-line and turned aside, exposing posterior wall of phar"' x ; tongue drawn forward and downward. papilla. The mucous membrane covering the dorsum of the tongue is closely beset with elevations, ox papillee, of which there are three varieties, the filiform, fungiform, and circumvallate. In general they consist of a core of connective-tissue stroma cov- ered with stratified squamous epithelium ; the projection formed by the connective tissue bears minute secondary papillae, which, however, do not model the free sur- ' Morpholog Arbeiten, Bd. vi., 1896. THE TONGUE. «575 lace of the mucous membrane. The anterior two -thirds of this surface are rough with fungiform and filiform pafnlla ; the lormer, less numerous, appear as red points chiefly near the edges, while the filiform are everywhere, but arranged in par- allel rows continuing forward the lines of the circumvallate papillx. At the edges of the tongue, just in front of the end of the anterior pillar of the fauces, close inspec- tion, especially with a lens, will generally show a small series of minute transverse parallel ridges, corresponding to the papilla foliatte of rodents in a rudimentary con- dition. The papUlct circumvallcUa are fungoid papillae surrounded by a depression bounded externally by a low annular wall. The usual number of these papilla- is from nine to ten, rangmg from six to sixteen (Miinch). The sides of the V in which they are disposed are not very symmetrical. Usually there is at lea.st one median papilla behind the apex, and very rarely one or two before it. The circumvallate papillae are of especial interest as being the most important seat of the gustatory end- F«o- 1335- Filiform papilla. Surface epithelium coveririK fungiform papilla Projections of tunica pro- pria coiutituting basis o( papilla •2^„Conneciive-tissue stroma of mutous membrane .Muscular tissue of t(. -.gue Section of lingual mucous membrane, showing filiform and fungiform papills. X Tj. organs, or taste-buds, which lie embedded within the epithelium lining the groove encircling the central elevation. A detailed description of the tasie-buds is given with the organs of special sense (page 1433). The surface of the vertical posterior third of the tongue is smooth, in the sense that there are no papillae nor roughnesses, but it is studded with masses of lymphoid tissue, sometimes called the lingual tonsil (Fig. 1334), which make numerous eleva- tions on its surface. The mucous membrane of the back of the tongue is continued in a thinner layer onto the front of the epiglottis. It presents the median glosso- epiglottic fold, containing fibro-elastic tissue and muscular fibres of the genio-glc^i, which separate two little depressions, the glosso-epiglottic fossa. These may be with- out any definite lateral boundary, or may be embraced by the small lateral glosso- epiglottic folds, the internal borders of which are concave. The mucous membrane is firmly attached to the subjacent muscles in the anterior two-thirds of the tongue, but less firmly behind. Glands of the Tongue. — The lingual glands include both serous and mucous varieties, which are distributed as three group : (i) serous glands, (2) posterior mucous glands and (3) anterior mucous glands. IS7* HUMAN ANATOMY. The tubo-alveolar glands surrounding the circumvallate and the foliate papillx are the only ones of a purely serous type ; their thin, watery secretion is no doubt an important medium in conveying sapid substances to the taste-buds situated in this Epithelium coverinir Bliform papilla CBplllary loops within connective-tissue basis of papilla HK- Mucous membrane Muscular tissue Injected mucous membrane and subjacent areolar and muscular tissue from upper surface of tongue. X 60. Fio. 1337. Annular wall 1^ Serotu gland Muscular tissue »•• >■!> » •- Section across circumvallate papilla from child's tongue, showing central portion and encircling fold. X w. vicinity. The glands encircling the circumvallate papillse constitute an annular group some 4 mm. wide and about twice as deep. Those about the papillae foliata form an elongated group, about 3.5 mm. in width, which extends from 8-15 mm. in front of THE TONGUE. «577 the base of the palato-glossal fold. Anteriorly towards the dorsum the serous glands remain isolated ; posteriorly they come into contact with the mucous glands, so that alveoli of both varieties may be included within a single microscopical hold ( Fig. 1 287 ). The posterior third of the dorsum, from the circumvaltate papilla- backward, possesses a rich, almost continuous layer of mucous glands, 5 mm. or more in thick- ness, which lie beneath the mucous membrane and mingle with the lymphoid tissue. Since the alveoli lie among the muscles at some depth, the excretory ducts often attain a length of from 10-15 mm., and open on the free surface in close asstKiation with the lymph-follicles. The anterior mucous glands (Fig. 1287) are disposed principally as two elon- gated groups, glandula linguaUs anteriores, or glands of Nuhn, or of Blandin (from 15-20 mm. in length, 7-9 mm. in width, and somewhat less in thickness), which lie on either side of the mid-line, near the tip of the tongue, among the mus- cular bundles. They meet in front, but diverge behind, where they may be con- Fic. 1338. LympliHiodct Clandi itterlacin|( fibrous and muscular bundles Section from posterior third of child's tongue, showin); lymph-nodea constituting a part of lingual tonsil, y jo. tinned backward by additional collections of mucous glands along the edges of the tongue. The ducts — five or six in number— open on the folds occupying the under surface of the tongue near the frenulum. Muscles of the Tongue.— These include two groups, the extrinsic and the intrinsic muscles. The former pass from the skull or hyoid bone to the tongue ; the latter comprise the particular muscles both arising and ending within the organ. Their general arrangement is as follows. Under the mucous membrane is a dense sheath of longitudinal fibres, surrounding the others completely near the apex, and farther back wanting at the middle of the under surface where the fibres of the genio-glossi and hyo-glossi enter the organ. This outer layer is the cortex. The inner part is divided into two by a vertical median septum of areolar tissue, which is quite dense in its upper part. It is sickle-shaped, with the point in front and not reaching the apiex. The inner jwrtion, or medulla, is composed of transverse muscle-fibres inter- posed between layers of those called vertical, which in fact present many degrees of obliquity. The extrinsic muscles are the genio-glossus, the kyo-glossus, the stylo-glossus, and the palato-glossus, to which may be added, from its jx)sition, the genio-hyoid. All of these are in pairs and symmetrical. 1378 HUMAN ANATOMY. The (enio-hyoid (Fig. 1339) is a coller-tion of fleshy fibres extending cluae to the median line, from the iniFerior genial tubercle to the anterior surface of the body of the hyoid bone. It is a thick band, four-sided on transverse section, with rounded angles, and expands laterally on approaching its insertion. A layer of areolar tissue separates it from its fellow. Nerve. — ^The nerve-supply is from the hypoglossal, but probably consists of fibres derived from the cervical nerves. ActioH. — ^To draw the hyoid forward and upward ; or, when fixed below, to depress the mandible. The genio-glouus (Fig. 1339) arises just above the preceding by short ten- dinous fibres from the superior genial tubercle. Its inferior fibres run horizontally backward to the base of the tongue, passing over the hyoid bone to the base of the epiglottis ; the fibres above these, inserted successively into the mucous membrane of Fio. 1339. Stinnp of nuMder Hatnul; •"«■"» SlyToid. Superior constrictor Plerygo-mandibuUr ligament Stylo-KlOMtu. Hvoid bone, Thyro-hyotd Inferior conitrictor. Phar)!!!^! and extrinsic lingual muacle* the dorsum of the tongue near the middle line, are at first oblique, then vertical, and finally concave anteriorly as they approach the apex, so tliat the muscle is fan-shaped when seen from the side. Each muscle is separated from its fellow by the median septum. Nerve. — The hypoglossal. Action. — ^The complex action of this muscle includes retraction of the tongue by the anterior fibres, drawing forward and protrusion by the posterior fibres, and depres- sion, with increased concavity, of the dorsum by its middle part. The hyo-glo8Sus (Fig. 1339), external to the preceding, from which it is sepa- rated by areolar tissue, arises from the side of the body of the hyoid, the whole of the greater horn, and the lesser horn. The last portion, rather distinct from the rest, is described sometimes separately as the chondro-glosbus. The whole muscle, applied to the side of the tongue, forms a layer of fibres directed upward and for- THK TONC.UE. »579 ward ; towards the front its fibres are almost longitudinal. The fibres from the lesser horn run on the dorsum beneath the mucous membrane, forming a part of the super- ficial longitu.'inal system. Nerve. — The hy|x»t{l(>ssal. Actum. — To depress the sides of the tongue, thereby increa.sing the transverse convexity of the dorsum ; the muscle also retracts the protruded tongue. The ttylo-glOMut (Fig. 1339) arises from the tip of the styloid process and from the beginning of the styio-maxillary ligament It is a small ribbon-like muscle with an anterior and a posterior surface, but as it descends it twists so as to lie along the outer side of the tongue, which it reaches in the region of the circumvallate papills. On joining the tongue the fibres divide into an upper and a lower bundle, both of which are chiefly longitudinal, although some fibres blend with the transverse scries. It is soon lost in the sheath of longitudinal fibres. Nerve. — The hypoglossal. Action. — To retract the ton"".- and to elevate the sides, thus aiding in pro- ducing transverse concavity of the uorsum. The palato-glosaus (Fig. 1339) arises from the anterior or buccal aspect of the palate, and descends within the fold forming the anterior pillar of the fauces to the tongue, where it joins the transverse fibres, passing between the two parts of the stylo-glossus. Nerve. — From the pharyngeal plexus, the motor fibres coming probably from the spinal accessory nerve. Action. — To elevate the tongue, to depress the soft palate, and, with its fellow by approximating the anterior pillars, to close the fauces. Lonyitodinml fibres Fio. 1340. TranivrrM fibn* Plio fimbriata Glandi Trantverse Mctioo of ton(iie of child, near tip. Vertical fibrea The intrinsic muscles are the lingualis, the transversus, and \.\\e perpendicu- laris (Fig. 1340). The lingualis, sometimes divided into a superior and an inferior, comprises the greater ni .Tiber of »Vf longitudinal fibres, — all, in fact, that do not come from the extrinsic muscles. ' ;»e thickness of this layer is some 5 mm. The transversus furnishes nearly all the transverse fibres, the most important extrinsic contribution being from the palato-glossus. It arises from the septum and runs outward to the mucous membrane ; as it approaches the cortex the fibres break up into bundles, among which pass groups of the fibres of the lingualis. The trans- versus is arranged in a series of vertical layers, between which pass layers of the vertical set. Thus a horizontal section has the effect of a series of transverse fibres like the bars of a gridiron with the cut ends of the vertical fibres between them and the longitudinal fibres cf the lingualis at either side. Near the apex fibres of this system run directly from the mucous membrane of one side to that of the other. The perpendicularis is the name given to the few vertical fibres that do not come from the extrinsic muscles. They occur chiefly at the tip and sides, passing from the lower to the upper mucous membrane. Nerve. — All the intrinsic muscles are supplied by the hypoglossal. Action. — The tongue is protruded chiefly by the action of the posterior fibres of the genio-glossus, drawing the posterior part of the tongue forward, assisted, perhaps, by the contraction of the transversus. It is withdrawn by its own weight. The r5«o HUMAN ANATOMY. lon^tudiiul system, the various paits of which can act separately, turns the tip in any direction. The styio-f^loMus and palato-glos.sug raise the posterior portion, paitiirularly at the edges, but the latter probably acts more on the palate than on the tongue. VcMeU. — The principal arteries supplying the tongue are branches of the lingual, elsewhere described (page 735). Although there may be a trifling ana.sto- mosis at the tip between the vessels of the opposite sides, there is no communication sufficient to re-establish the circulation at once, so that ligation of either artery will render that half of the tongue bloodless for an operation. The veins consist of four sets on each side, communicating freely with one another. They are ( i ) the dorsal veins forming a submucous plexus on the back of the tongue above the larynx and joining those of the tonsil and pharynx, (2) two veins accompanying the artery and iiometimes forming a plexus about it, (3) two with the lingual nerve, (4) two with the hypoglossal nerve. Of these latter, the one below the ner\e is the larger and is the ranine vein, running on the under surface of the tongue on either side of the frenum. The lymphatics present a rich net-work on the anterior two-'hirds of the dorsum. The multitude of spaces throughout the organ communicate with ly.n- Fio. 1341, Lonjcitudinal fibre* Glandi Ponion ol sublingual glatid Vcrlira! libreii Traii!.\crsf (ilires Septum Gcnio-glossua Hyo-Klossua Tnnfvcne Mction of tongue of child, throuKh middle third. ■ j. phatics. Some from the median part empty into the suprahyoid glands, but most go to the submaxillary and to the deep cervical glands. Nerves. — The motor fibres are supplied by the hypoglossal, aided probably by the facial through the chorda tympani. Those of common sensation are from the lingual branch of the fifth for the anterior two-thirds and from the glosso-pharyngeal for the remainder, excepting the region just in front of the epiglottis, which is supplied by the superior laryngeal from the vagus. The glosso-pharyngeal area somewhat overlaps the posterior third, as it supplies the circumvallate and foliate papillae. The chief fibres of special sense are derived from the glosso-pharyngeal, their principal distribution being to the taste-buds on the circumvallate papillae. Re- garding the source of the taste-fibres to the anterior parts of the tongue opinions still differ. According to many anatomists, these fibres reach their destination through the chorda tympani, since the latter nerve is supposed to receive taste- fibres from the ninth by way of the pars intermedia of Wrisberg, which accompanies the facial. According to Zander,' Dixon,' Spiller,' and others, however, the view attributing fibres of special sense for the anterior part of the tongue partly to the fifth nerve is correct. Growth and Changes. — At birth the tongue is remarkable chiefly for its want of depth, as shown in a median section, which depends on the undeveloped condition of the jaws. This is gradually corrected coincidently with the growth of the face. ' Anatomischer Anzeiger, Bd. xiv., 1897. • Edinburuh Medical Journal, 1897. ' University of Pennsylvania Medical Bulletin, March, 1903. THE SUBLINGUAL SPACE. 15*1 The drcumvallate papilla ' are imperiectly developed lor some time aher birth, so much so that it w not easy to recognize them. The foliate papilla- arc al^M) rtlativily undeveloped. On the other hand, the funKif«>rm papilla- are proiK>rtionatcly both larger and more numerous than in the adult. The development of the adenoid tiswuc at the bat'- of the tongue occurs during the last two months of Icctal life. In places the connective tissue surrounding the ducts of the mucous glands l)ecomes infiltrated with leucocytes and is transformed into lymphoid tissue (Stohr). THE SUBLINGUAL SPACE. This space is between the lower jaw and the tongue, above the mylohyoid, and bounded behind by the fold of the anterior pillar of the fauces pas.sing to thi- tongue. It is lined with thin, smooth mucous membrane reflected from the mandible to the tongue and attached lightly to the parts beneath. With the mouth closed, this space is filled by the tongue. It is best examined in the living subject when the tip of the tongue is against the upper incisors. A fold of mucous membrane, the/rr«««», Fio. 134a. Plica fitnbriata ■SublitifTual riMjfr .OriAcra (if submaxillary and sublingual duct-t Sublingual space, tongue pulled up. if well developed, passes in the middle line from the tongue to end over the floor of the mouth. Close to its termination on either side is a smooth elevation caused by the sublingual gland, which in the present position is drawn upward under the tongue. A varying number of gland-ducts perforate the mucous membrane with orifices hardly visible to the naked eye. Internal to these swellings at the lower end of the frenum is a small enlargement on each side of the median line, so closely blended, however, as to seem but one ; these elevations, the caruncula sahvares, mark the point at which the duct of the subma.xillary gland opens on each side This duct runs along the floor of the sublingual space between the mylo-hyoid muscle and the mucous membrane, a smalt part of the gland usually accompanying the duct a short distance over the muscle, forming a prominence, the sublingual ridge (plica snbHnKtialis^. \ constant group of inlands is found in the mucous membrane below the incisors.' • Stahr: Zeitschrift fur Morph. und Anthrop., Bd. iv.. Heft 2, 1902. • The sublingual bursa alleRcd to exist on either side of the frenum has not been described, since it is at most extremely uncommon. 1582 HUMAN ANATOMY. THE SALIVARY GLANDS. These, besides the mucous follicles of the mouth, are the parotid, the submax- illary, and the sublingual glands of the two sides. They are all reddish gray in color and of about the same firmness, excepting the parotid, which is denser. The Parotid Gland. — The parotid is the largest of the salivary glands, weigh- ing from 20-30 gm. , with a considerable range beyond these limits. It is situated behind the upper part of the ramus of the lower jaw, which it overlaps both within and without. Its limits in both directions are very variable. The prolongation for- ward over the masseter muscle may become nearly distinct from the rest of the gland, F'o- 1343- .Facial artery Rxtemal jugular, vein Mylo-hyoid ^'DigaHtric, anterior belly ^Submaxillary gland Superficial dissection, showing parotid and submaxillary glands undisturbed. and is then known as the socia parotidis. The sheath of the parotid is a strong fibrous envelope continuous with the cervical fascia in front of the sterno-mastoid, closely applied to the glandular substance and continuous with the partitions that pass through the organ, so that it can be dissected off from the gland only with difficulty. The parotid is divided into many small compartments or lobules by these resisting septa of ♦'ibrous tissue, the quantity of which gives it toughness. The shape of the p-arotifl, as well as its size, is variable, since it grows where it can among more or less rosii-ting structures. Its f^hape and relations, therefore, may be considered together. Relations. — The parotid nmipies a ravity bounded in front by the ramus of the jaw, covered by the masseter and internal pterygoid muscles ; behind by the THE SALiVrt.^V .LANDS. 1583 external auditory meatus, the tympanic plate, the base of the styloid process, and t' f front of the adas These two walls meet above at the Glaserian tissure. The pos- terior wall is prolonged laterally by the posterior belly of the digastric, the stylo- hyoid, and more externally by the stemo-mastoid muscles. The styloid process as it descends becomes internal, and the stylo-glossus and stylo-pharyngeus, together with the fascia known as the stylo-maxillary ligament, bound the posterior part of the gland internally. In front of the styloid process there is no wall to the space occupied by the parotid the gland resting against the areolar tissue mixed with fat that lies on the outer wall of the pharynx. The widest part of this cavity is at the surfekce, where the foscia is connected with the capsule of the gland. The largest expanse of the parotid is, therefore, external. It overlaps the jaw and may reach down to the angle and be separated merely by fibrous tissue from the submaxillary gland. A constant, but very variable, prolongation on the face below the zygoma accompanies the duct The parotid gland reaches upward between the joint of the jaw and the external auditory meatus and tympanic plate. Internally it lies against the structure: above described, always resting on the inner side of the internal pterygoid muscle and extending to the great vessels and nerves which separate it from the side of the pharynx. There may or may not be a higher prolongation inward through the space in front of the styloid process. The internal carotid artery, inter- nal jugular vein, and pneumogastric nerve are close against the lower part of the inner surface of the gland. The external carotid artery enters the gland from the Inner side and divides into its temporal and internal maxillary branches, besides giving of! the posterior auricular, and sometimes the occipital arteries, within its substance. The external jugular vein is formed within the gland and emerges from its lower side. Near the skull the great vessels and nerves are separated from the gland by the styloid process. The faciS nerve enter? the gland on its posterior side and passes through It obliquely so as to become more superficial as it travels forward, lying external to the external carotid artery and jugular vein. Before emerging from the gland the facial nerve breaks up into its two great divisions, the branches of which begin to subdivide within the glandular mass. The auriculo-temporal nerve also pa.sses through the upper part of the gland, emerging on its outer aspect. A varying number of lym- phatic glands lie in the substanr'i of the parotid, mosdy in the more superficial part. They are small and not easy to find. A larger one, said by Sappey to be constant, b in the gland just in front of the ear. The parotid or Stenson's duct is formed by two chief tributaries, and emerges from the front of the gland, above its middle, running forward and a little down- ward across the masseter muscle to turn in sharply at its anterior border. It then crosses a collection of fat and runs obliquely through the buccinator muscle and the oral mucous membrane to empty into the vestibule of the mouth opposite the second, often the first, superior molar tooth. The length is some 40 mm. and the diameter 3 mm. The termination is a mere slit. Its walls are firm and resistant. The general direction of the duct is that of a line from the lower side of the concha of the ear to midway between the border of the nostril and the red edge of the lip. The transverse facial artery lies above it, on leaving the gland, and a plexus of veins surrounds it. Vessels. — The arteries of the parotid gland are derived from several sources ; although numerous, none of them is large. Besides several small branches from the external carotid itself while in the gland-substance, there are twigs from the temporal, especially from its transverse facial branch, from the posterior auricular, the mtemal maxillary, and probably from an occasional branch that may pass through the gland. The veins form quite a plexus through the gland and open into the sys- tem of the temporo-maxillary and of the external jugular. Of the lymphatics much remains to be learned, but they probably empty into both the deep and the -iper- ficial cervical nodes. Nerves are from the facial, auriculo-temporal, and great auricular, besides sym- pathetic fibres from the carotid plexus. The Submaxillary Oland.— This gland, weighing from 7-10 gm., lies largely under cover of the lower jaw. just before the angle, in a fosM on the inner side of the bone. As, however, the skin is carried inward under the jaw at this 1584 HUMAN ANATOMY. point, the gland appears on the surface. It projects but little, if at all, on the outer side of the jaw, but curls around the posterior border of the mylo-hyoid muscle and extends for some distance in the floor of the mouth, under the mucous mem- brane, in the angle between the mylo-hyoid and the hyo-glossus, sometimes reach- ing the sublingual gland (Fig. 1344). It lies in a capsule derived from the cervical fascia, which is so loosely attached that the gland can easily be isolated. The anterior end of the posterior belly of the digastric and of the stylo-hyoid pass behind and beneath it. The hypoglossal nerve and the lingual vein lie beneath it, as does the first part of the lingual artery, until the latter f>asses under the hyo-glossus. Its sublingual branch runs along the inner side of the prolongation of the gland. Fig. 1344. Buccinator Parutid gland Internal pterygoid' (cut) Superior constrictor. Digastric. Stylo-hvoid- Stylo-glo'ssUB- Stylo-pharyngeus. Occipital artery Internal carotid Middle constrictor Facial artery External carotid Lingual artery Superior thyroid, artery Inferior constrictor Oral mucous lembrane Dc«ppr pofUua of 9iit>- ntaxllI«ry^Un(l ut mandible ubmaxlllary duct Sublingual gland G«n{o«iossus Mylo-hyoVd (cut) inio-hyoid Stump of digastric, anterior belly ibmental artery •ubmaxillary gland, superficial part Great comu of hyoid bone Hyo-glossus rhyro-hyoid Deeper dissection, showing rehilions of salivary glanda. to which it sends vessels. The facial artery lies beneath the gland before reaching the border of the jaw. The facial vein is superficial to it. The lingual nerve lies above the prolongation. The submaxillary or Wharton's duct runs from the front of the main body of the gland aloiijr the floor of the mouth under the mucous membrane, often accom- panied f.xtcrnally by the prolonjration of the gland. It is from 4-5 cm. long, with a diameter of 3 mm. Its walls are decidedly thinner than those of the parotid duct. Anteriorly it rises to open into the mouth by a little papilla on the side of the frenum linguae, the last few millimetres running in a fold of mucous membrane. The lingual norvc passes under the duct from without inward soon after it leaves the gland. The sublingual artery is beside it and a plexus of veins around it. STRUCTURE OF THE SALIVARY GLANDS. 1585 Vettels. — The arteries of the sublingual gland are derived from the facial and the sublingual branch of the lingual. The veins are from the corresponding ones. The lymphatics go to the submaxillary glands. Nerves. — ^The gland receives filaments from the sympathetic plerus accompa- nying the facial artery, from the lingual nerve, and from the submaxillary ganglion. The Sublingual Gland. — This differs from the two preceding glands in having no capsule. It lies in loose areolar tissues on the mylo-hyoid muscle, at the front part of the sublingual space. Its weight is 3 or 4 gm. Each gland rests internally against the genio-glossus, and anteriorly they touch one another. They are more readily separated into lobes than the others. Testut regards them as aggregations of separate glands. The sublingual glands are covered by the mucous ii.^ iibrane of the floor of the mouth, which they press upward into rounded swellings on either side Fig. 1345. ••^„l .!,llllllll'llU)ll)l)i)i,ir ..> Openinfr of anterior. linKual glands Frenum. .Caruncle and openinK of submaxillary duct Gcnio-hyoid ylo-hyoid Cut fibres of difastric Section acrou anterior part of floor o( month, itaowing relationi ol sablingual gland* to mucons membrane and muKlcs. of the beginning of the h-enum. The lingual nerve and the submaxillary duct are on the inner side. The sublingual or Rivini's ducts vary in number from four to twenty or more. They open for the most part in the floor of the mouth, but some may join Wharton's duct. Bartholin's dud is an inconstant one, larger than the others, that usually opens close to the outer side of Wharton's duct, which it follows. Vessels. — The arteries are from the sublingual branch of the lingual and the submental branch of the facial, which latter sends minute twigs through the mylohyoid muscle. The blood escapes into ' e ranine vein. The lymphatics run to the sub- maxillary nodes. Nerves are from the sympathetic, the lingual, the submaxillary ganglion, and, according to some, from the chorda tympani. STRUCTURE OF THE SALIVARY GLANDS. The three chief salivary glands possess in common the tubo-alveolar type of structure; depending upon the character of their secreting cells and products, the func- tionating organs represent both the serous and mucous varieties. The parotid is a pure serous gland ; the submaxillary is a mixed one, the alveoli containing serous cells predominating ; the sublingual, also a mixed gland, consists chiefly of mucous alveoli, the serous cells being limited to the marginal groups con»tit«iting the demilunes of Heidenhain. 100 1586 HUMAN ANATOMY. The parotid gland consbts entirely of serous alveoli, although mucus-pro- ducing acini may occur in the accessory lobules situated along the duct of Stenson. The primary lobules are made up of alveoli, from .015 to .020 mm. in diameter, lined with epithelial cells, which are somewhat pyramidal in form, since they are broader next the basement membrane and narrower towards the cleft-like lumen. The rest- ing cells, fresh and examined without the addition of reagents, appear filled with numerous minute, glistening granules which lie embedd^ within a less strongly refracting substance. The granules, however, are readily affected by reagents, often undergoing partial or comphte solution; hence the reticulated appearance of the pro- toplasm frequendy obser\'eii in glandular epithelium after fixation. The nuclei of the serous cells are usually of spherical form and contain distinct nucleoli and delicate Fig. 1346, iMerlobular duct Aiteo'. Interlobular septum Section of small lobule of parotid gland, y 80. chromatm net-works. The sptem of excretory canals begins at the alveoli as the intermediate tubules, which in the parotid are relatively long, about .010 mm. in diameter, and lined with low, flattened cells, directly continuous with the taller alveolar epithelium, on the one hand, and with that of the intralobular ducts on the other. The latter, or salivary tubules of Pfluger, of langfer diameter (about .035 mm.) than that of the immediately preceding or succeeding segments of the canal^ are clothed with a single layer of columnar cells, some .014 mm. in height, which present a peculiar differentiation into an inner and an outer zone. The former, next the lumen of the tube and containing the nucleus, appears finely granular or almost homogeneous, while the outer or basal zone exhibits a longitudinal striation composed of rows of minute granules. After treatment with certain reagents, the striated zone STRUCTURE OF THE SALIVARY (.LANDS. 15*7 breaks up into delicate rod-like processes, in recognition of which the cells lining the intralobular tubules are often designated rotl-epitheliuin. An active secretory r61e has been ascribed to these cells, R. Krause' having succeeded in demonstrating an excretory function by means of sodium sulphindigotate. The interlobular and inter- lobar ducts gradually increase in size and possess a lining of columnar cells which are usually arranged as a single layer. In the larger canals, however, the epithelium consists of two imperfect rows, since smaller cells lie ne.\t the basement membrane, w«idged in between the larger typical elements. The columnar cells continue until near the termination of the main excretory duct, where they give place to the stratified squamous epithelium prolonged from the oral mucous membrane. Fio. 1347. Intermediate duct ^ Tubular alveolus Alveolar lumen Interlobular duct Connective ttatw Section of parotid xtand, showing serous alveoli. X 270- The submaxillary gland differs in structure from the parotid in possessing both serous and mucous alveoli, the latter forming approximately one-fifth of the entire organ. The alveoli containing serous cells correspond closely with those^ "J the parotid, being from .020 to .030 mm. in diameter and filled with elements loaded with minute granules. Not infrequently the cells exhibit differentiation into an inner granular and an outer almost granule-free zone. The mucous alveoli are often some- what lai^er than the serous, reaching a diameter of .040 mm. or more. The mucus- protlucing cells present the usual appearance and share the acinus with typical demi- lunes consisting of cells identical with those lining the serous alveoh. The mucous acini are direcUy connected with those of the serous type. Intermediate tubules connect alveoli of both kinds with the intralobular cana^; those beginning in mucous acini are shorter (.035-. 060 mm. ) and less nchly branched than the tubules originatifH; in serous alveoli. The latter measure from .060-^ 140 mm. in length, and repeatedly divide ; they are lined with low cubical cells which are gradually transformed from the alveolar epithelium in contrast to the abrupt transition seen in the tubules connected with mucous acini. The cells lining the intralobular tubules of the submaxillary gland exhibit the characteristic rod-like striation seen in the parotid, the rod-epithelium sometimes containing yellowish pigment RT^""'^- The interlobular and interlobar ducts resemble those of the parotid gland. The chief excretory duct possesses, in addition to a subepithelial elastic layer, a weakly developed stratum of longitudinally disposed involuntary muscle. Goblet-cells appear between the columnar elements lining the duct. The sublingual gland, being of the mixed mucous type, resembles in striicture the labial and buccal glands, and consists of a series of individual lohules, opening by half a dozen or more separate ducts, rather than a compact single orj^an. In com- ' Archiv f. mikro. Anat., Bd. xlix., 1897. 1588 HUMAN ANATOMY. mon with other mucous glands, the sublingual lobules do not possess intralobular tubules lined with the characteristic rod-epithelium. The interlobular ducts subdi- vide into smaller canals which extend within the primary lobules and give of! wider passages lined with cubical epithelium. Towards the end of these terminal canals Duct .MucouB alvcoH Sefous klveoll Section of lubnuxillary gland, ihowing Mroiu and mucoua alveoli. X rjo. the mucous cells appear, at first isolated or in groups, increasing in numbers until they form the entire lining of the passage and become the secreting elements occupy- ing the tubular alveoli of the gland. The latter vary from .030-.060 mm. in diam- eter, and are clothed with cells averaging .015 mm. high. The condition of the Fio. 1349. -Mucous cells Duct. Crescents ol serous cells Section of sublingual gland, showing serous cells grouped as crescents. X 370. alveoli as regards the mucus-bearing cells varies greatly even in the same lobule. At times .m entire primary lobule is composed of acini filled with mucous cells ; at others empty and gorged alveoli alternate, or the depleted acini may predominate. Uncer- tainty as to the presence of the demilunes also exists, since these may be absent in PRACTICAL CONSIDERATIONS: THE MOUTH. 1589 certain well-developed alveoli filled with larj^e mucous cells, or they may be present in considerable numbers. Mucous celb are much less numerous m the sublin}{ual glands of young infants tlian in the adult organ. The relatively wide lumen of the alveoli and the more reticulated appearance of their epithelium serve to distinguish the exhausted sublingual gland from the parotid of similar condition. The normal secretions of the oral glands, mucous as well as serous, contain no formed elements ; occasionally accidental granules or cell remains arc present. The characteristic spherical so-called salivary corpuscles which occur in varying numbers in the mixed oral secretion have no relation to the salivary glands, since they are only modified leucocytes escaped from the lymphoid tissue of the faucial and Imgual tonsils. On gaining the oral cavity, these cells are affected bv the saliva and liecome greatly swollen, the granular remains of their cytoplasm exhibiting molecular motion m a marked degree. , , ,. Development of the Oral Glands.— The earliest traces of the saltvary glands are seen during the second foetal month. The anlage for the submaxillary gland first appears about the sixth week; next that for the parotid about the eighth week ; a little later that for the sublingual. The parotid anlage develojis from the oral ectoblast along the lateral groove separating the upper and lower jaws The submaxillary and sublingual glands arise from a ridge-like anlage of the bucca epithelium occupying the hirrow marking the angle between the tongue and the flooi of the mouth, the anlage for the sublingual lying nearer the tip of the tongue. At first the parotid and submaxillary lie about equally removed from the oral opening, but later migration occurs, the former passing backward and the latter forward. The development of the gland in each case begins as a solid cylindnral out- growth from the deeper layer of the oral epithelium, which presents a local thicken- ing The cylinder rapidly lengthens and branches, so that by the eighth or tenth w^k the submaxillary and parotid glands respectively consist of a mam stalk and terminal buds. The anlage of the sublingual gland gives off epithelial buds on acquiring a length of about i mm. The primary sprouts of the anlage subdivide and eventually become the smaller ducts and the glandular tissue. Meanwhile the imme- diately surrounding mesoblast undergoes condensation, and contributes the connective- tissue envelope with its prolongations between the lobules and acini supporting the blood-vessels and ner\es. Towards the close of the third month, whUe the gland- tubules are still solid, the lumen of the hiture main .xcretory duct appears «" the epithelkl cylinder, extending from the free suriace towards the alveoli. The latter acquire their lumen during the fifth month. The smaller oral glands, including those of the lips, cheeks, tongue, and palate, develop much later than the larger salivary, since their anlages appear during the fourth month. The details of their development correspond m general with those attending the formation of the larger oral glands. PRACTICAL CONSIDERATIONS : THE MOUTH. The chief congenital deformities of the mouth are harelip and cleft palate. Harelip results from a failure of the developmental procedures concerned in forming and differentiating the nasal and buccal cavities. These processes have already been described in connection with the formation of the face (page 59). Upon the down- growth of the fronto-nasal process depends the formation of the vomer, the perpen- dicular plate of the ethmoid and the external nose, and of the intermaxillary bone and that portion of the upper lip corresponding to the four incisors. The partiUon separating the nasal from the oral cavity, later the hard and soft palates, is formed by the union of the horizontal palatal plates from the buccal aspect of the two maxillary processes (Fig. 76). When the frontal and maxillary processes fail to unite on one side, single harelip results, the cleft in one side of the lip lying opposite the space between the upper canine and lateral incisor, or between the latter and the central inci-sor When union between the maxillary and the frontal processes fails on both sides double harelip follows, the lateral incisors often being absent and the inter- maxiilary bone with the central incisors and the median portion of the lip occupying a position beneath the nasal septum. I590 HUMAN ANATOMY. Fig. 1350. New-l>orn i-liiUI with duuble haKlip. Cleft palate is caused by faulty union between the palatal processes of the maxillary arches. The cleft is always in the middle line, and may involve only the uvula and soft palate, may extend to the |X)sterior margin of the intermaxillary bone, or may diverge from that point on one or both sides and run forward through the alveolus, being then associated with single or double hare- lip, the cleft or clefts in the alveolus corresponding in position to the deficiencies in the lip (page 63). The Lips. — The mucous membrane of the lips and the adjacent skin are often affected by herpes labialis, which may be associated with gastro-intestinal disturbance, or may be purely neurotic in its origin, following mentd depression or anxiety. It is found in the distribution of the second and third divisions of the fifth pair which supply sensation to the upper and lower lips re- s|)ectively. The vascularity of the lips, while it leads to excessive exudate and large swelling after contused or lacerated wounds, favors rapid heal- ing and the avoidance of infection after surgical wounds. In few places equally exposed to con- tact with infectious organisms was healing by "first intention' ' so common before the intrcxluction of antisepsis. The coronary arteries run between the mucous membrane and the orbicu- laris oris. They are therefore more often severed by wounds extending from within outward — usually made by the teeth— than by those beginning externally. The coro- naries anastomose very freely. In arresting hemorrhage from them by direct ligature b<)th ends should be tied. If a wound of the lips is united by pins and figure-of- eight sutures, the pins should be passed close to the inner edges of the wound so that the coronaries may be compressed between the pins and the sutures. The vascu- larity of the lips renders chancres of that region, like those of the face, exceptionally large both in depth and in superficial area. It also adds greatiy to the extent of furuncular or carbuncular infection in this region, the occurrence of which is favored by the large number of hair and sebaceous follicles present. The danger of infective sinus thrombosis (intracranial) as a result of such infection here or elswhere on the face is much increased by the free anastomosis between the valveless facial vein and its tributaries and the ophthalmic vein, which is also without valves. As might be expected, nsvi are frequent in the lips. In the male the lower lip is the favorite seat of epithelioma. Either infection or diminished tissue resistance from minor trauma- tisms, or from tobacco-irritation in smokers, is supposed to explain this clinical fact. The mucous glands of the lip are not rarely the seat of retention-cysts from obstruc- tion of their ducts. The Gums.— The mucous membrane of the lips is continuous with that cover- ing the fibrous tissue of the gums, but the latter is slightly less vascular and much less sensitive. The gums are sometimes congenitally hypertrophied ; the condition is usually associated with defective or aberrant developmental processes often affecting the mentality. They are also often found hypertrophied in edentulous old persons or m persons with badly fitting artificial dentures. They are the frequent seat of inflam- mation from various causes, the most common of which are the decomposition of food and the deposition of calcium salts— tartar— about the necks of the teeth. Infec- tion frequendy follows the liyperaemia produced by these forms of irritation. When it is confined to the space between the mucous membrane and the fibrous tissue, it causes a limited superficial abscess, — "gum-boil;" if it gains access to the sub- periosteal space, it may cause a form of alveolar abscess, the usual variety of which IS, however, due to infection secondary to dental caries, and is situated about the root of a tooth {x>ide infra). Tartar is found most abundantly near the openings of the submaxillary and sub- lingual ducts,— «>., near the inner surfaces of the lower incisor teeth. Mercury and lead cause gingivitis probably by the actual presence of their salts in quantity suffi- cient to act as irritants, their deposition from terminal capillaries being favored by the PRACTICAL CONSIDERATION'S : THK MOUTH. 1591 frequent hyperaemia due to the vascularity and the warmth and moisture of the region, together with slight but repeated trauma during m;»stic:itii.n. The gingivitis of scur\y or of purpura is merely a local evidence of a constitutional condition, iuul is hemorrhagic rather than inflammatory. During dentition the resistance of the gums may cause backward pressure Ujxin the nervous and vascular supply of the pulp of the tooth, giving rise to some |)ain and sometimes to grave reflex disturbances, especially in infants. The insensitive gum then becomes exceedingly tender and is swollen and cedematous. The wiik-sprcad relations of the fifth nerve render long-continued irritation of its dental branches dan- gerous. "Lancing" the gums is the obvious remedy. It is especuiUy apt to be needed over the molars and cuspids, and the lines of incision should be planned so as to release fully the presenting surfaces of those teeth. The Teeth. — Alveolar Abscess. — The line of penetration in dental caries is often in the direction of the pulp, through which infection extends to the "apical space" between the root of the tooth and its socket, containing the ves.sels and nerves and some loose connective tissue. This space soon becomes filled with pus, the cavity enlarges, and reaches the compact bone on the surface of the alveolus (the density of which impedes the process somewhat) ; but finally the bone is perforated, usually through the thinner external or buccal wall of the alveolus. The periosteum usually yields opposite the gum immediately over the apex of the tooth,where it is reinforced by mucous membrane only. If the root of the tooth is a long one or the abscess has gone deeply into the bone, the pus may reach the periosteum at a point where it is supported by the muscular uid fibrous tissues of the cheek. The pus may then strip the periosteum from the jione so as to cause extensive necrosis. This is less likely to (Kcur in the alveolus of the upper jaw or in the hard palate, on account of their free blo«xl-supply derived from several sources. In cases of this type in either jaw, a sinus followed by a depressed, adherent, and disfiguring cicatrix is liable to result (Roughton). Alveolar abscess is also influenced in its course by the situation of the particular tooth involved. In the maxilla, abscesses connected with the canines or incisors may point into the nasal cavity or on the under surface of the hard palate. The pus is more likely, however, to descend by gravity alongside of the root to the edge of the gum, or to follow the canal of the root into the pulp-cavity. Abscesses connected with the upper molars, es- pecially the first, or, more rarely, those in relation to the cuspids, maj point in the antrum. They occasionally o-^n on the face in front of the an- terior bor-'er of the masseter. The relation of the apex . the root to the mucous membrane of the gum often determines the point of opening. If the apex in the case of the lower teeth is above, or in that of the upper teeth is below the line of reflection of the mucous membrane from the cheek to the gum, the abscess tends to point in the mouth. If the contrary is the case, pointing on the face or neck may result. In syphilis the first teeth exhibit mdforma- tions characteristic of perversions of nutrition or of inflammation of the gums sufficiendy severe to affect the blood-supply to the tooth-sacs. The enamel may be deficient, opaque or chalky, the dentine soft or friable, the teeth irregular in size and uneven in position. ... u j The permanent teeth may show the same general aberrations as to growth and nutrition that are produced bv stomatitis from digestive derangements or from lo- tected dentine ; lour lower incisors present peg* like excrescences due to loss of enamel and cxpoanre of dtrtine. {HutckmtoH.) Hi 1592 HUMAN ANATOMY. The typical (and pathognomonic) syphilitic teeth—" Hutchinson's teeth"-^«c the upper permanent central incisors. The type is observed in its pe-fection soon after the extrusion . , at the expense of the anterior suriace and border of the tooth. Typical Hutchinson's teeth are. fur- thermore, reduced m length and narrowed,— " stunted ;" their angles are rounded oft, the lateral and inferior borders merging in a curved line ; they deviate from nor- mahty in direction, their axes being obliquely convergent, or more rarely divergent instead of parallel. / 8 . The other surgical relations of the teeth and of the dental tissues which are of chief importance are concerned wit '-e new growths originating in dental elements The odontomaia are divided by S i as follows, and the classification should be remembered in studying the anatomical development of the teeth : (i) Persistent portions of the epithelial sheath (page 1561), taking on over- E)wth, may give rise to an epithelial odontome (multilocular cystic tumor). (2) pansion of the tooth-follicle with retention of the crown or root of an imperfectly developed tooth results in 9l follicular odontome (dentigerous cyst). (3) Hyper, trophy of the fibrous tooth-sac causes a fibrous odontome ^ especially frequent ii nckets, ^-hich usually affects the osteogenctic fibrous membranes. (4) If the fore- going hypertrophy occurs and the thickened capsule ossifies, a cementome results. ( 5 ) If this takes place irregulariy, small malformed teeth— " denticles"— may form in large num'..'.-s and occupy the centre of the tumor (compound follicular odontome ) . (6) Tumors of the root, after the full formation of the crown, are of necessity com- posed of dentine and cementum only, enamel not entering into them (radicular odontomaia). (7) Tumors composecl of irregular conglomerations of enamel, den- tine, and cementum, and often made up of two or more tooth-germs fused together, constitute composite odontomaia. All these growths can be understood only by ^reful study of the normal development of the teeth. They are rarely diagnosed before operation, which is therefore in some cases needlessly severe. Sutton says very truly, " In the case of a tumor of the jaw the nature of which is doubthil, par- ticulariy in a young adult, it is incumbent on the surgeon to satisfy himself, before proceeding to excise a jjortion of the mandible or maxilla, that the tumor is not an odontome, for this kind of tumor only requires enucleation. In the case of a follicular odontome it is usually sufficient to excise a portion of its wall, scrape out the cavity, remove the tooth if one be present, stuff the sac, and allow it to close by the process of granulation. ' ' The Roof of the Mouth and the Palate.— The mucous membrane cov- ering the hard palate is so fused with the periosteum as practically to be inseparable from it It is dense, resistant, and comparatively insensitive. A vertical trans- verse section of the roof of the mouth (Fig. 1294) shows the mucous membrane to be thickest laterally and thinner in the median line. Cleft palate (page 1590) results from imperfect fusion between the horizontal palatal plates of the maxillary processes of the first visceral arch. It is always in the middle line. It may involve the soft palate and uvula. If it extends forward as far as the alveolus, it follows the line between the maxilla and the premaxillary bone, usually terminating in a harelip (page 1589) opposite the interval between the lateral mcisor and canine teeth. If it separates the maxillae on both sides from the pre- maxillary bone, it is almost always associated with double harelip. The toughness of the muco-periosteum of the hard palate facilitates ths forma- tion of flaps in operations for the closure of such a cleft. In dissecting uo the flaps it b well to keep close to the bone and to avoid the descending or posterior pala- tine branches of the internal maxillar>' artery. These vessels, on which the nutri- tion of the flaps as well as of the bone depends, emerge from the posterior palatine canal at a point on the line of junction of the hard and soft palates 8 mm. (>^ in.) anterior to the hamular process and a little to the inner side of the last molar tooth. They run forward in a shallow groove just internal to the outer border of the hard palate. They are nearer to the bone than to the mucous surface, but their pulsa- tions can often be felt by the finger. For these reasons incisions in uranoplasty PRACTICAL CONSIDERATIONS: THE MOUTH. 1593 should be made close to the alveolus and the bone should be hugged as the flaps are raised. In troublesome bleeding from these arteries the posterior palatine canal may be plugged by a sharpened stick, which should previously be sterilizeti. When the clelt involves only the soft palate, staphylorrhaphy is required. The muscles that tend to pull the edges apart are the tinsor palati and levator palati. The former turns atound the hamular process and passes almost horizon- tally towards the median line, the latter lies close to the posterior surface of the soft palate and runs obliquely from above downward and inward. These muscles may be divided by various incisions, the simplest being a section of the velum near its lateral border and parallel with the cleft. The hamular process may be felt behind and a little intf rnal to the last molar tooth. The pterygo-mandibular ligament may be felt passing from the hamular process to the posterior end of the mylo-hyoid ridge of the lower jaw just behind the last molar tooth. The fold ol mucous membrane covering it may be seen when the }aws are separated widely. The lingual branch of the fifth nerve Fig. 135a. may be felt between the mucous membrane and the bone anterior to the base of the pttrygo- mandibular ligament and below the last molar. With a finger passed behind the last molar, the swell of the alveolar ridge can be recognized as it nar- rows to pass into the ramus. The nerve is below and parallel with that ridge. It is sometimes divided for the relief of the unbearable pain of carcinoma of the tongue. Thit; may be done by entering the point of a curved bistoury a little less than three-quarters of an inch be- hind and below the last molar and cutting on the bone towards the tooth. The Floor of the Mouth. — ^The mylo-hyoid muscle, extend- ing from the symphysis to the last molar tooth, separates the buccal cavity from the neck. Infections or neoplasms beginning above this muscle are first recognized through the mouth ; those below it in the neck. The sublingual gland, for example, lies altogether above it and directly beneath the mucous membrane of the floor of the mouth ; the duct of the submaxillary gland occupies a similar position. Affections of these structures, therefore, manifest themselves in the mouth. The submaxillary gland, however, lies partly beneath the poste- rior border of the mylo-hyoid. Accordingly, disease of this gland is apt to show most markedly beneath the jaw (Fig. 267, page 247). " Ludwig's angina " (page 553) may spread to the loose connective tissue between the my'.o-hyoid muscle and the mucous membrane of the floor of the mouth. That membrane is reflected from the under surface of the tongue to the alveoli and is divided anterioriy by the frenum lingua. On either side of this may be seen the ridges indicating the situation of the sublingual glands, and close to the frenum at the inner end of the ridge the papillae at the opening of Wharton's ducts, into which a fine probe may be pawed (Fig. 1352). The inelastic character of the walls of the latter should be remembered as explaining in part the intense pain caused by an impacted submax- illary calculus. This is also in part due to the close relation of the duct to the —Anterior lingua; Klund —Cut Hurlacc ol mucuua niembrwie ■LfTiKual vein i^l.injeual aner>- Siibmaiillar)' duct — Sublinxual gland Disaectionof under surface ol tongue and aublinxtjal >P*c*i mucout membrane removed and tongue drawn upvrard and for- ward Irom mouth. 1594 HUMAN ANATOMY. lintfual nerve. The relation of that nerve to the floor of the mouth posteriorly has already been described ( page 1 249). The fold of mucous mtmbrane constituting the frenum may be abnormally short and prevent the free movements of the tongue, interfering with sucking during; infancy and with articulation later. When its division is necessary, it should be ciit through close to the jaw, and with blunt-pointed scissors directed away from the tongue so as to avoid the ranine veins which may be seen close to it on the under surface of the tongue. The ranine arteries lie farther out and are more deeply situated, being placed beneath two converging raised fringed lines of mucous membrane, the plica fimbnattt. ' A sublingual bursa is described by Tillaux as a triangular space situated lietween the genio-hyo-glossus and the mucous membrane, its tip being at the frenum its ba.se at the sublingual gland. Its existence, by no means constant, is said by Tillaux to explain the occurrence of the acute cystic tumor (grenouillelte), "acute ranula " which IS occasionally met with in this region. Ilanulae— ordinary retention cysts— are common in the floor of the mouth, and branchiogemc cysts, due to the incomplete closure of the first branchial cleft, are sometimes found there. The Cheeks — The buccal limits of the cheeks are accurately indicated by the reflections of mucous membrane lining them. By making outward tr.iction on the angle of the mouth that membrane can be seen and palpated, and ulceration, as from a jagged tooth or beginning epithelioma, or mucous patches, or abscess, or new growths, can easily be detected. The papilla indicating the opening of the parotid duct may be seen or felt opijosite the upper second molar tooth. A fine probe may be made to enter the duct for a short distance, the normal curves then interfering with its passaee (F«- »343)- ^^ Lipoma originating in the "boule de Bichat" (page 493) can be recognized. As the jaws are separated and closed the anterior border of the masseter may be seen and felt. The important structures of the cheek- -the facial vein and artery and the parotid duct— are all anterior to this line (Fig. 691). The Tongue. — Congenital deformity of the tongue is rare. Forked tongue —normal in some birds and reptiles and in seals— is rare ; it is usually in asso- ciation with other developmental defects, as cleft palate. Congenital absence has been noted (de Jussieu). Macroglossia {lymphangioma cavemosum, Virchow) is a congenital affection in which the lymph-channels and lymph-spaces are dilated and the lymphoid tissue throughout the tongue, but especially at the base, greatly increased. The tongue may attain an enormous size, and has even, by pressure, caused deformities of the teeth and alveolar arches and luxation of the mandible. The foramen c.srum, indi- cating the junction of the pharyngeal and buccal parts of the tongue, is the superior termination of the foetal thyro-glossal duct. ' ' Ducts lined with epithelium have been found leading from the foramen cscum to accessory glands about the hyoid bone It IS probably from these glandular and epithelial collections about the hyoid bone that certain deep-seated forms of cancer of the neck are developed. Some of these take the form of malignant cysts" (Treves). The upper surface of the tongue has for centu.ies '., en the objea of especial observation in disease. The practical value of these olwer rations is not univer- sally conceded, and too much weight has been placed upon tiiem ; but there can be no doubt that some help in prognosis and even in diagnosis in digestive de- rangements, in fevers, and in various toxaemias may be obfcilned by inspection of the tongue. The "fur," so carefully studied, consists of a mixture of desquamated nithelial cells food ^articles, and micro-organisms of various kind uvcrlying living epithelium which may be abnormally proliferating. The surface between the circumvallate papilla is apt to be the most heavily coated, either in health or disease, because it is the least mobile part of the tongue and IS not kept clean by friction, as are the sides and tip. The appearance of PRACTICAI- CONSIDERATIONS: THK MOITH. ISMS the coating and of th« tongue its*" va'ii-* (jreatlV' but it may be said that dry- HISS not due to niouth-brcathin^;, hut In.ui deficient setretion. as in ievtrs ; Jari-- Hfss, from decomposition and desiccation ol the coalill^^ or from iinj>erfect oxy- genation of the blood ; roughnfss, from papillary overgrowth with marked epithelial proliferation and desquamaticm ; redness, from epithelud denutlation ; and stiff- ness, slowness, ox tremulousfsf in protrusi»)n, from either thick, inrtexilde coating, muscular weakness, or nieu;-' hebetude, are uniformly regarded us unfavorable conditions. , . i • i Unilateral furring of the tongue has been observed m cases of dental canes, ol fractured skull, and of intracranial disease, in all three instances the furring Iwnig on the side on which there was irritation of the branches of the tilth pair of nerves. In some of them it was confined to the anterior two-thirds ol the upper surface,— /.<■. , to the distribution of the lingual branch of the fifth ( Hilton ). In tonsillitis the tongue will often be furred over its posterior part only — i.e., the portion which, like the tonsil, receives its nerve-supply from the glosso- pharyngeal (Jacobson). Unilateral furring in the presence of to-pharyng«*l fold Fosu or Kuuamiaiat LiMUcliian tuljc ynicnltonbU Iplnco-imiallne fold —SilpinRo- pharyagcal ioU Gcnio.h>'oid Hyoid 'osterior wall ol pharynx lato-pharyngcal fold iar\ ngo^eplglottic ■ Id Cuneiform tuberciv .Tubercle of Santoriai ricoid cartilage Tracheal cattilai Sagittal Mclion of head, slightly In right of median phine ; toiigiw has hren pulled down. posterior pharj'njjeiil wall. The jjreatest depth in this direction (,V4 cm. ) is st the side, from the anterior pillar to the posterior waU. Behind the cricoid cartilage the 1598 HUMAN ANATOMY. front and back walls are probably in contact In the female several of these distances are smaller. Thus the pharynx is in horizontal sections at most levels a transverse The naso-pharynx, broad from side to side and short from before backward pMses msensibly mto the oro-pharynx when the soft palate is not raised so as to cut oB communication. Anteriorly are the nasal openings, described with the nose Ihe separation of the two regions on the lateral wall is determined by the naso- pharyngeal fold ^\iiz\i runs from the base of the skull to the beginning of the soft palate. 1 his fold is very irregular in course and development. It occasionally is grooved so as to present a hirrow. Sometimes the hirrow takes the place of the fold and at other times the fold joins that in front of the opening of the Eustachian tube This onfice is on a level with the end of the inferior turbinate bone and less than I cm. behind it It is usually a triangular opening without a distinct border below although It may be oval or even round. •^; ; longest diameter is about i cm. The end of the cartilage of the tube curves < ver the top of the opening from the front and descends along its posterior border, producing a strong fold of the mucous mem- brane, the salpingopharyngeal, which descends to be lost in the lateral wall of the oro-pharynx, or even sooner. The salpingopalatine fold in front of the opening of the Eustachian tube is, as a rule, less prominent and very variable. It is formed above by the bent end of the cartilage, and below by a small band of fibrous tissue the saiptngo-palatine ligament, running from the cartilage into the soft palate. The fossa of Rosenmitller is a deep pocket at the angle of the pharynx between the posterior wall and the back of the projection of the cartilage of the tube. Its anterior and posterior walk are almost in contact and are often connected by accidental adhesions. This is the broadest part of the naso-pharynx. Adenoid collections-the tubal tonsils— ^^\oyxrA in varying degree about" the' orifice'of' the 'tub^r«peci^'l'y The bdly of the levator palati muscle makes a prominence over the fold behind it ^ „. „ in the lateral wall below the tubal orifice. The oro-phaiynx opens into the mouth at the anterior pUlar of the fauces I he posterior pillar, covenng the palato-pharyngeus muscle, runs down the side of the pharynx as the palato-pharyngeal fold. It may be traced to the base of the superior horn of the thyroid cartilage, or, as is most common, it is lost on the lateral wall a little higher. The pharyngo-epigloUic fold above mentioned arises from the front of the epiglottis ntar the lateral edge and runs upward and backward across the pharynx. It may end soon, or A may reach the palato-pharyngeal fold or crossing this, may extend eN-en as far as the salpingo-pharyageal one. It contains muscular or tendinous fibr-s from the stylo-pharyngeus. If well marked, it may bound below the niche containing the tonsil. The anterior wall of the oro-pharynx IS formed, the mouth being closed, by the posterior vertical part of the tongue The respiratory tract, passing through the nose, and the digestive, passing through the mouth, cross each other m the oro-pharynx. so that the former is the anterior below this point th» ^!!f il!i'''"i°'?*"P'?*i *'!* '*?!"?* P^^* *^ ">* pharynx, is. roughly speaking, the oart below the level of the hyoid bone. It is separated fr«m the oro-pharynx by the pharyngo-epiglottic fold. In the middle of it is the opening of the larynx behind the epiglottis and enclosed by the aryteno-epiglottic and interarytenoid folds Ihe sinus pyrtformts is a depression on either side of the entrance of the larynx between the aryteno-epiglottic fold and the arytenoid cartilage internally and a part of the great wing of the thyroid cartilage and the thyro-hyoid membrane externally It IS open behind. The thin mucous membrane lining the sinus has a transverse fold, formed by the supenor laryngeal nerve, in front between the hyoid bone and the thyroid cartilage. The lower part of the palato-pharyngeal fold is seen in frozen sections near the superior horn of the thyroid cartilage at the lateral aspect of the cleft, which IS all that appears of the pharynx. The anterior wall behind the aryte- noid rartilages and the structures between them slants backward as it descends Behind^ the cricoid cartilage it is vertical Here the pharynx narrows to join the The mucous membrane of the pharynx is smooth, except for the elevations caused by collections of lymphoid follicles. It is more loosely attached and more THE PHARYNX. 1599 disposed to be thrown into folds in the lower (lart. Mucous glands, on the other hand, are numerous in the upper part, scarce below ; they lie partly within the mucosa and partly in the submucous tissue and between the muscular bundles. The character of the pharyngeal epithelium varies in different localities. In the nasal pharynx the stratified ciliated columnar cells of the nasal fossa are continued as the covering of the pharyngeal mucous membrane, while the oro-pharynx is clothed with stratified squamous epithelium continued from the mouth. The last-named ty[)e of epithelium likewise covers the greater part of the laryngeal portion. The exact distribution of the two varieties of cells*is subject to considerable individual variation. The ciliated columnar type extends laterally to include the openings of the Eustachian tubes, but lower down gives place to the L.|Uamous. By no Fio. Bate of skull I3S4- Naial Mptnm Naso-pharynxtal fold Lymphoid tiuue Posterior pillar of fauces. Faucial tonsil PharyfiKo.«ptglottic fold Cut edge of pharyns. Unia Dorsum of tonf u* Gloaao-epijelottic fossa Median KloKso.epiKlo(tic fold EpiKloltis. tnnied back linus pyrifnrmia Posterior surface of larynx Pharynx opened from behind ; epiKloltis turned back. means the entire posterior surface of the soft palate is clothed with ciliated colum- nar cells, since the entire uvula and the edges of the palato-pharyngeal folds are invested with stratified squamous epithelium. The latter also covers the jM>sterior wall of the pharynx and extends above as far as the vault. When covered with ciliated epithelium, the mucous membrane is redder, thicker, and contains more glands, but fewer papitlse, than in those parts in which the squamous cells prevail. While containing much lymphoid tissue, fat is limited to a few deeply seated lobules of adipose tis.sue. Lymphoid Structures. — The upper part of the pharynx contains many lymphoid collections which make the surface uneven. They are much less frequent below. The larger and more o)nstant masses are called ' ' tonsils. ' ' These include the faucial tontiU in the oro-pharynx, between the pillars of the fauces, the pkaryn- i6oo HUMAN ANATOMY. Pio. 1355. ules geal tonsil in the upper part of the pharynx, the tubal tonsils at the openings of the Eustachian tubes, especially on the posterior fold, and the lingual tonsil, con- sisting of the scattered adenoid collections over the posterior third of the tongue. Many additional lymph-nodules are scattered over the sides and roof, so connected as to form a lymphoid ring at the upper part of the pharynx. Thefaucial tonsils (Figs. 1326, 1353) are theoretically two almond-shaped masses of adenoid tissuo. placed one on each side of the oro-pharjr t, between the pillars of the fauces. The linjf diameter is vertical, and they have un outer and an inner surface and an anterior and a posterior border. The length is conventionally put at from 20-25 mm., the breadth at 15 mm., and the thick- ness at 10 mm. Practically, however, there is no definite shape nor size. In childhood the tonsil generally projects as a globular mass. If it extends more than Mightiy be- yond the level of the faucial pillars, it is said to be enlarged. After middle life it rises usu- ally but little froni the floor of the niche. The shape of the free surface gives no clue to the size of the deep surface. In structure the tonsil is a mass of adenoid tissue en- closed in a fibrous capsule which is crossed on both the deep and free surfeices by a thin layer of muscular fibres. The superficial layer belongs to the [talato-glossus ; the deep or external layer arises from the superior con- strictor and passes to the tongfue. Beyond this externally are fat and areolar tissue. The closely adherent mucous membrane covers the free surface, which is full of pits from i or 2 mm. to i cm. in depth. The larger ones often expand be- low the orifice, so that they may collect and retain secretions. A small free space, the supratonsillar fossa, lies above the tonsil at the apex of the niche containing it ; at the front of this there is very often a series of crypts with detached adenoid tissue about them, bur- rowing under the anterior pillar from behind and making a pouch beneath a fold, the plica trian- gularis. The adenoid tissue is continuous below with that of the tongue. The mucous membrane of the oro-pharynx shows many scattered lymphoid follicles in its walls, especially on the sides at and above the level of the tonsils. Vessels. — The arteries sup- plying the faucial tonsil are de- rived from .several sources, and the arrangement of the vessels is extremely irreguHr ; the branch from the ascending pharyngeal and that from the facial artery — one or both — enter its base, while twigs from the lingual and descending palatine arteries. Section through fiucial tonsil, showing general dis- position of lymphoid tissue. X 30. Fig. 1356. L^pliocytes, in\'ading Epitheliiun Blood-vessel Ponion of ttncUl tonsil, showing epithelial lining of crypt invaded by escaping lymphocytes. X 325. THE PHARYNX. 1601 and perhaps others, reach it beneath the mucous membrane. Under ordinary cir- cumstances the tonsil a not very vascular, but receives a large quantity of blood when inflamed. There is a venous plexus communicating with the veins of the pharynx. The lymphatics probably communicate both with those of the dorsum of the tongue and with the glands near the angle of the jaw. Nerves.— Tm nervous supply is from the fifth and the glosso-pharyngeal. (The rela'ions of the tonsils are given with those of the pharynx, page 1602.) The pharyngeal tonsil (Fig. 1353), sometimes called the third tonsil, is a median mass of adenoid tissue m the postero-superior wall of the pharynx, which reaches its greatest development in early childhood, generally dwindlmp; after the twelfth year. When well developed, it lies below the occipital and the basi-sphenoid, nearly fUling the space from the nasal septum to the back of the pharynx and almost touching on either side the folds made by the tubal cartilages. Its thickness in the median line is nearly i cm. Thus without being hypertrophied it nearly fills the naso- pharynx. The pharyng«J tonsil is a lobuUted organ, the swellings bemg often regu- Fio. 1357. Foi«m«c«:am cri«a«.lU Gcnio-hyoid Mylo^hyoid Hyoidbonc Thyroid cartilage [ Fttultuy body Cnnlo-pharyngcal canal Pharynccal toasil Cccipiul bone PhaO'OBOi toiuU Anterior arch o( attea Xdontold proceia -Uvula Epiglottis Third cervical vettcbra Vantricle o( larynx -Cricoid cartilage Anterior portion of meaial sagitui lection of child'i head, pitifaably of about three yeare. Reduced one-fourth. larly arranged around a central depression ; consequently it presents many pockets. The central one, which varies widely, is often improperly called the bursa pharyngea. It has absolutely nothing to do with the canal from the mouth to the sella turcica, through which a process of the oral tissue passes in early foetal life to the pituitary body (Fig. 1357), being decidedly behind that past. ^. Neither is it the true bursa pharyngea, since this term is more properly applied to a structure of uncommon occurrence, — namely, a still more posterior pocket in the mucous membrane leading from the roof of the pharynx, just behind its tonsil, into a small recess not over 1.5 cm. in length, on the under side of the basilar pt^cess. Relations of the Pharynx. — The structures behind the posterior wall have been mentioned (page 1596). The tip of the normal uvula hangs on a level near the lower part of the axis or the top of the third cer% ical vertebra. The tip of the epi- glottis is usually opposite the lower part of the third. The second and third cervical vertebrae are those behind that part of the phar>-nx seen through the open mouth. The pharynx ends at about the top of the seventh cer\'!cal vertebra. The lateral wall of the pharynx is very narrow, except in the region of the tonsils, where it reaches for- ward to the anterior pillar of the fauces. From the top of the thyroid downward it 1 603 HUMAN ANATOMY. Fio. 1358. Pharyngeal toasil of child one year old. (Sckwaiac*.) Lymph-nodulc is nothing more than the fold around the end of a transverse linear cleft. The whole lateral aspect is covered by a thick layer of areolar tissue, continuous with that of the carotid sheath. It is most convenient to give the relations of the lateral wall from below upward, excepting the nerves. The upper part of the lobes of the thyroid gland comes very close to the lower part of the pharynx, and may even touch it without undue enlargement. They separate the common carotid from the pharynx. A little higher this vessel is on the outer side of the great wing of the thyroid cartilage, but if the h«id be turned to one side the vessel of the other side will rest on the pharynx. The common carotid artery is very dose to the pharynx just before its division. The inter- nal carotid lies against it until it reaches the skull. The beginning of the external carotid with its lingual and facial branches is also against it. The ascending pharyngeal artery runs along it, the middle meningeal lying agiinst its upper part. The internal jugular vein is, probably, nowhere in direct contact with the pharynx unless just below the skull. The submaxillary gland touches it at the angle of the jaw. The sympathetic nerve comes in contact with the back or side of the pharynx. The vagus lies against the pharynx behind the internal carotid ; on reaching the common carotid, however, Fic. 1359. jj jg in [ggg direct contact. Its superior laryngeal branch crosses the pharynx to reach the thyro-hyoid membrane. The spinal accessory and the glosso-pharyngeal nerves lie against the upper part of the pharynx. The faucial tonsil lies about 2.5 cm. above the angle and opposite a vertical line di- viding the ramus of the jaw^ into a front and a back half. It lies between the pillars of the buces, and is separated from the mucous membrane by a thin layer of muscular fibres. The lower end reaches the tongue, the adenoid tissue being at times continuous between them. The tonsil is covered by the sujserior con- strictor. External to this is a yielding mass of areolar tis- sue, continuous with that of the carotid sheath, into which the tonsil may force its way if enlarged. This areolar tis- sue is bounded in front by the internal pterygoid muscle, and is pierced by the stylo- glossus and the stylo-pha- ryngeus, which subdivide it, leaving a small part of it be- tween them and the tonsil. At this level both carotids are at a considerable dis- tance from the tonsil. The internal is posterior and external, about 2 cm. distant. According to Zuckerkandl, a transverse line through the posterior pillar will pass Bundles of muscular tis- aue of constric' torv Surface epithelium Sagittal section of poaterior wall of pharvnx of child, showing part of pharyngeal tonsil. THE PHARYNX. 1603 2 cm. in front of the vessel. The external carotid is placed more d.rectly outward and is rather the nearer of the two. The parotid gland, according to Tillaux. sends a process in front of the styloid process, which reaches the lateral wall. This extension, however, does not seem to be by any means constant. , . t ,■ Development and Growth of the Pharynx.-An account of the formaUon of the primitive pharynx is included in the Development of the Alimentory Tract f oaee iW). the later changes being here noted. In the section on the bones it was shown tlat the chief peculiarities of the infant skeleton in this region are due to the small size of the face and the more horizontal base of the skull The nasopharynx has very little height, while, owing to the peculiar disposition of the parts, it has nearly the same anteroposterior diameter as in the adult. It is relatively broad and long, but very shallow. The tongue, in proportion, is much less thick at the base than later. The larynx is small, and, moreover, is placed higher m relation to the vertebral column, so that the termination of t!>e pharynx is also higher. The position of the larynx at different ages is considered with that organ (page i8a8). The soft palate is in the main horizontal at birth and about on a level with the top ol the atlas. The uvula is rudimentary. In a child of probably not over three years we have found the tip of the uvula rather below the middle of the body ol the axis. In Synwngton s section of a girl of thirteen it is pretty nearly in the adult i»siUon In mfancy the soft palate probaWy closes the passage into the naso-pharynx from below less perfecUy than later. -, • %. u The oiieninz of the Eustachian tube, although neceanarily m the nasopharynx, is in the foTtus below the level of the hard palate. At birth it is at about that level, but rather below than above it According to Disse, there is but litde change for nine months, after which the opening is on the levd of the inferior meatus. Proba- bly the adult position is generally reached after puberty. The ojwiing is smau in the infant and young chQd, and, owing to want of development of the cartifage, . ... •• , . \^"-^: .1 •. :• ._J «^«_.ui,ur,»lu halt a amall ffVlsa of KOSen- there is but a ! miiller. The before birth ina young tiiuu, aiiu, v*w 11115 •" "—•••■>" — -• — 1 y to slight elevation about it and consequendy but a small fossa ot Kosen s entire adenoid system Escat : fevoltition de la Cavit6 Naso-Pharynglenne, 1894. • Archiv f. mikro. Anat, Bd. xli., 1902. II i6o4 HUMAN ANATOMY. THE MUSCLES OF THE PHARYNX. The arnuigement of the muscular tissue differs from the ordinary one of the digestive tract, inasmuch as the outer layer is approximately circular and the longi- tudinal fibres are largely internal. The chief elements are the three constndon, which overlap one another from below upward, the sMo-pkaryngeus, the palato- pkuryngeus, and certain accessory and rather irregular bundles of muscular fibres. tatmial caiMM » IntcniAl jognlai V Fic. 1360. Coodykis ,C«atral Mtachmeiuol pharynx Tip oi cnal corna c4 hyoid bone< Thyro-hyoid liniiicnt Superior coma ol tk|naid carUlacc Middle COUUtelOT Inferior comtrtetor onitlludinal muscle of mo^aetn Mwclea of pharynx from behind ; portion of interior constrictor has been removed. The superior constrictor (Figs. 1339, 1360) arises from the lower part of the internal pterygoid plate, from the hamular process, the pterygo-mandibu!ar Hjjament whi(;h is stretched from it to the lingula of the lower jaw, from the neighboring end of the mylo-hyoid ridge, and from the side of the tongue. From this origin the fibres pass backward to meet: their fellows in a median raphe, which extends almost the THE PHARYNX. 1605 entire lenrth of the posterior wall oJ the oharynx. being atuched abov to the ^hS^ngeil tubercle o^he under side of the basUar P/«=««: J**^ JP^' , ^^j^^^ The muscle is concave on either side, not reachmg the bwe of the skull and passing under £ Eustachian tube, the vacant space being Wledby the P'^O'ngeal aponeu- rosis The lower fibres pass somewhat downward as well as backward. Thepterjgo- Sibular Hgament s^rates the superior constrictor from the bV^"-'"-"' *"f which it woulJ otherwise be continuous, forming a circle around the almientar>- canal. Fic i3 '36o) arises from the lower end of the stvlo-hvoid ligament, from the lesser horn of the hyoid bone, and from the upper border of the greater horn. The iibrcs diverge from this narrow ongm. the upj^r reaching the pharyngeal tubercle, the lower going to neariy the lower end oJ the pharynx, and all meeting their fellows in the median raphe. It conceals a consider- able part of the preceding muscle. it*' i6o6 HUMAN ANATOMY. The inferior constrictor (Figs. 1339, 1360), the thickest of the three, arises from the posterior part of the outer aspect of the cricoid cartilage, from ihe oblique line and the triangiilar surface below and behind it on the thyroid cartilage, including the inferior horn. It overlaps the preceding muscle, its upper fibres reaching to some 3 cm. below the base of the skull and the lower ones bemg nearly horizontal. The median raphe, which receives almost all the fibres, is wanting bielow. The lowest fibres are circular and continuous with the circular fibres of the gullet. The atylo-pharyngeus (Fig. 1361; arises from the inner side of the styloid process near its root and descends to the interval between the superior and middle constrictors near the hyoid bone, where it passes under the latter and ends by expand- ing in the side of the pharynx, some of its fibres going to the posterior border of the thyroid cartilage and others joining the expansion of the palato-pharyngeus. A bundle from the thyroid division passes to the side of the epiglottis, forming on the wall of the pharynx the fold known as the plica pharyngo-epighttita. The fibres of the superior constrictor may be inseparable from the upper part of this layer. The salpingo-pharjmgeus has been described in connection with the levator palati (page 157 1). VariuioM.— Additioaal muscles are very common, beinc chiefly kxigitudinal bundles due to splittiiiy /Aao'«lf m^ "••u<'^', araing from tlie occipital bone . . eitlier side of the median Ifaie and descending to be lost in the posterior pharyngeal wall ; there may be an azygos muscle instead. Bands may arise at the side from the peuous portii .1 of the temporal bone or tlie spine of the sphenoid. Actions. — ^The general action of the pharyngeal muscles is sufficiently evident ; the constrictors decrease the siie of the pharynx, probably drawing the larynx upward and backward at the same time. The longitudinal muscles raise the larynx and pharynx, acting chiefly on the latter. Vessels. — The arteries of the pharynx are from many sources and are irregu- lar. The chief is the ascending pharyng^, which runs up near the posterior lateral angle. Occasionally, when enlarged, it b seen pulsating on the posterior wall. Branches from the facial play an un rtain part The veins form the pharyngeal plexus situated outside of the constrit :i and communicating in all directions. The chief outlets are by a pair of veins on each side, one going up to the internal jugular near the base of the skull and the other down to the external jugular or some of its tributaries (Luschka). A submucous plexus is particularly developed in the lower posterior wall, which opens into the pharyngeal plexus by several branches piercing the inferior constrictor. The following are nearly constant : a superior and posterior one near the middle line, one running outward on each side near the back of the thyroid cartilage, forming a part of the origin of the pharyngeal vein, and one passing forward to the superior thyroid vein.' The lymphatics, which are numerous, run in the upper part to the prevertebral nodes and to the deep cerviral system, as do the lower ones at another level. The presence of lymphatic nodes behind the naso-pharynx is of practical importance, as they are sometimes inflamed and may suppurate. They lie near the foss£E of Rosenmiiller. Nerves. — The constrictors are supplied by the pharyngeal plexus, the lower receiving fibres also from the recurrent laryngeal. The stylo-pharyngeus b supplied by the glos.so-pharyngeal. The nerves of the mucous membrane are from the glosso- pharyngeal, the pneumogastric, and the sympathetic, to a great extent in a plexiform arrangement. PRACTICAL CONSIDERATIONS : THE PHARYNX. The pharynx may be said to present only three sides for consideration, but its continuity above with the nares, anteriorly wilh the mouth, and below with the ori- fices of the larynx and oesophagus associates it intimately with the diseases of those regions. The naso-pharynx and the lar\'ngeal relations will be considered with the Respiratory Passages (fiage 1829). • Bimar et 1-apeyre : Comptes rendus de I'Acad. des Scienres. Paris, tome cv., 1887. PRACTICAL CONSIDERATIONS: THE PHARYNX. |6(>7 The posUrior wall of the pharynx » separated from the anterior surfaces of the bodies of the first five cervical vertebr* only by some loose connective tissue and by the prevertebral fascia and muscles. Through it. by pushint; the finger up above the soft palate, the basilar process of the occipital bone may be felt, and below the bodies ofthe upper four cervical vertebr*— in children the upper six— may be pjil- pated. The hard palate, or the lower margin of the posterior nares. and the anterior arch of the atlas are on the same level. , . ^ . u i h In disease of the body of the sphenoid, m fracture of the base of the skull involving the basilar process, or in fracture or dislocation of the cervical vertebne the information gained by this examination will often be of great value. The retropharyngeal alveolar tissue— which is necess;irily loose to permit ot the movements of the pharynx during d^lutition and of ite disteiaibility— is some- times the seat of infection which may have gained access through the pharynx itsell, or through the lymphatics which spring from the posterior nares, the summit ol the pharynx and the prevertebral muscles, and which empty into a lymph-gland situ- srted between the prevertebral fascia and the pharyngeal wall. Abscess in this situation may by gravity descend by the side of the cesoph^us into the mediasti- num and has been known to reach the base of the thorax (page 553, Fig. 54o)- During its descent it may cause much dyspnoea by setting up adema in the region of the glottis. Usually it first pushes forward the posterior wall of the pharynx, and can be recognized as a fluctuating swelling and opened by direct inciMon. Collections of fluid resulting from tuberculous disease of the cervical vertebra may occupy the same space after perforating the thin prevertebral fascia and may take the same course, or they may be guided by the lateral expansions of that fascia to the posterior and lateral portions of the root of the neck or to the axilla (page ssa Fie 545)- As in these cases the avoidance of mixed infection » very important,' such tuberculous collections, when they require opening, should be approached through the neck by an incision along the postenor border of the stemo-mastoid. ... ^ « j » Retropharyngeal abscess of any type should never be allowed to open spon- toneously on account of the danger of immediate suffocation from flooding of the larynx with pus. ... . , , „ ... In cases of fracture of the posterior fossa of the base of the skull, with hemor- rhage into the pharynx (fracture of the basilar process), or of the middle fossa, with hemorrhage reaching the pharynx through the Eustachian tube (fracture of the petrous portion of the temporal), the need for frequent and persistent attempts to make and keep the pharynx as neariy aseptic as possible should never be forgotten. , ., j The adenoid tissue .A the posterior wall— the pharyngeal tonsil— may undergo hypertrophy, cause deafness or respiratory obstruction, and rec^uire removal. The iaieral walls of the pharynx are in such close relation with the internal carotid artery that in aneurism of that vessel the pulsations may most easily be '«t and seen through the pharynx. In many instances the vessel has twen opened in penetrating wounds of the pharyngeal wall by foreign bodies. The internal jugular vein is not so exposed to injury and is more rarely wounded. In one instance of pulsating tumor of the pharynx, pressure on the external carotid arrested the pulsa- tions (Barnes). ,,.,,. u « u The styloid process and a rigid or ossified stylo-hyoid ligament can be teit through the lateral wall. Attempts have been made (in cases of hysterical persist- ence of pharyngeal symptoms after the supposed swallowing of a foreign body) to remove these stnictures or a cornu of the hyoid bone, under the impression that they were the offending substances. The pharynx is very distensible, and foreign bodies, if not ol great size, are apt to pass through it as far as the level of the cricoid cartilage, where its diameter is only 18 mm. ( Ji in.). In an adult this point is beyond the reach of an average finger, as it is about the entrance of the oesophagus, which is about six iiv.nes from the incisor teeth. ^„A• For the removal of impacted foreign bodies, or for operation on malignant dis- ease, the pharynx may be reached, after a preliminary tracheotomy, by an incision \ l6o8 HUMAN A\ATOM\. through the neck from a point midwa^ u.-tween t! e symphysis and the angle of the jaw to the cricoid cartilage, dividing die platvs-i ai J th< -mio-hyoid and iwpa- rating the posterior belly of the diga^iri* ii.d lii .; vlo-hvoiu from the hyoid bone • or a subhyoid pharyngotomy will give < < «w tt. : , ■ lower walls of the pharynx by division of the superficial fascia, the ster la-hyoid md fhyroid mu»cU-s, the thyro- hyoid ligament and membrane, and the mucous in. mbraae of the pharynx at' the level of the lower margin of the hyoid Iwne. These oj-erations are more interest- ing anatomically than surgically. The tonsils, as seen from the mnuth, are situated Mween the arches of th«- palate and the base of the tongue. Ihey may be aim., t concealed in these re- cesses or may project into the pharynx, and when hypcrtrophied may actually meet m the middle line. They rest on the superior constri< tor muscles and move with those muscles during the act of deglutition. Thev are somewhat elevated and with- drawn from the pharynx by the coincident contraction of the stylo-pharyngei -Swallowing is therefore apt to be painful in all forms of tonsillitis. If not t nlarged, they are often almost hidden in persons who have large palato-glossi musrles, and therefore prominent anterior palatal arches.. Externally they .re separated by the pharyngeal aponeurosis and the superior constrictor muscle (r .m the pharyngo- maxillary space. This space is bounded bv these fibro-muscular structures internally, the internal pterygoid muscle extemaily, and the antero lateral aspects of the bodies of the second and third cervical vertebra. It is occupied by some con- nective tissue and fat. According to Zuckerkandl, the stylo-pharyngeus and stylo- glossus muscles divide the space into an anterior portion in relation to the tonsil and a posterior in relation to the internal carotid artery and internal jugular vein. Tonsillitis in the lacunar or follicular form does not usually mvoKe the stroma of the gland, the infection and the exudate being limited to the tonsillar crypts and to the surface. In the suppurative form the infection is deeper, the stroma is afiected, and the resulting abscess may in rare cases become peritonsillar, extend to the cellular tissue of the pharyngo-maxillary space, and open the internal carotid artery. Usually, as the infection progresses, even if this space is invaded, the out- ward extension is limited by the internal pterygoid muscle, and the swelling and the ulceration or necrosis take the line of least resistance, — i.e., towards the pharynx, where tonsillar abscesses often open spontaneously. During an acute tonsillitis the palato-glossus and its covering of mucous mem- brane, with the soft palate on the afiected side, are tense, thinned, and spread out over the surface of the tonsil. Abscesses may be evacuated by im ision directly through these structures and from above downward in a direction p.. illel with the anterior pillar. — that is, with the fibres of the palato-glossus. Tlie vascular relations of the tonsil should be remembered in th s operation or in tonsillotomy for hypertrophy. The internal carotid is nearly i.- rm. (i in.) behind and to the outer side of the tonsil. The external carotid is snii farther re- moved, as it lies outside of the stylo-glos n^ and stylo-pharynjreut mu^des. Its ascending pharyngeal branch is nearer the t,,fi,.l than either of the mam trunks, and in a case of accidental wounding by a foreign body has been the hemorrhage. Wounding of the tonsillar branch of the facia! rtei proved fatal after tonsillotomy, and either this \essel or the fac t- It is tortuous where it passes between the stylo clossus and d^astru n ably involved in cases of grave hemorrhage after this operation lymphatics surrounding the follicles of the tonsils communicates deep cervical lymph-glands behind and beneath the angle of the jaw are therefore commonly enlarged in affections of the tonsils, and w palpable are sometimes mistaken for the tonsils themselves. Th- however, be palpated externally, except in ca.ses nf new growth, as .> offered by the constrictor, the internal pterygoid, ■■• nd other structur*^ ini between the tonsils and the skin causes thcni to pro;- ct tcvrards the pharyn projection may be a cause of various forms of ill healt' associated with oxygenation, of chronic phar>ngitis from mouth-breatt. ng, of thickened tion, and even of alterations in the fades or in the skeleton breast" (page 167). >ui.e of fatal has likewBf especial !v if scles, is y-^i-^ f'he pU s t HTtly " the These g. nds 1 tender nr attpr caiino! he : "^istrnr g., "pi J eon- THE (KSOPHAGl^ 1609 Thephi«l 'o*"^'* «/»)!."*•»» °!,»J"°i! jxrowth in and about the Eustachian tubt vents Jirect pressure .y the enlarged t cough mav follow irrita on with which the .-, i.al nds jom ient»n^ are tl adenitis of the ne k-. those .tococ. ajute arth js ( inciodinu many as. ol so- endocardt'is may follow : trWinp 'sore thro; In intervention o( the soft palate pre- ^ up<>n ■' «t canal. ReHcx spasmodic laments by inspis-'^ited secre- 11 the 'li iii|)0»iiion of - "'h larvnjje.i r' ->ult» ' ren :ulou.-> uch t may be a permant.tt ca\ 1 v. have been des. nbed erv variouiay. 1 robably the most marked be«ir.r,insr, wi"^ diam< er of fjerhaps only 14 mm. There is ^^c hrouK^ .he diapunif: n. often one at the pomt where the crossed le guli t, and another where the latter goes beh -1 tl bronchu. \feh er ' has ..-scribwl thirteen places, at any >t ao strution. I con -ipond to the points of entrance ot inc ^o him, hav meu. 'mic significance. Occasionally d,:,iied, the diam. r ex ding 3 cm. It is probably coi, oaWine throueh th. Aragm it presents a hinnel-like expan^.-jn. pa,.Mng tnrougn t^. ^^^^as^ _ P^^^^ ^^^^ its course the gullet is surrounded by much 3^ tissue and frequently sends fibres from ite mus< ilar coat to ne.ghlw- Tp^ WhUe following the general direction of the vert ^ «^'''7"- "l^^" '"^^"^^ n.ft ffiy. below the bihircationof the t,^hea the gullet • or 2 c^ m • mnt f the spine. Direcdy after its beginning it inclines to i > that Mwn it pr. ts by one-half beyond the left border of the trachea. ..•^' seen, in a hild .he two tub^ lie side by side. Just above the bifurcation ,. e j^^^^^ea the c^phagus m«te the arch of the aorta, which, so to speak, pushes ,t to the right ; it I.e.. how- Tv^ alwai beWnd the beg^miing of the left bronchus, while to a less degree, or even nor;t K ?in relationIS the Tight one. Owing to the influence . f the aorta the SC let ^ LSier to the right; l^t. leaving the spine, it lies behind th. "^^^;^-^ S^a plS^mewhat anterior to that of the aorta, and "ear the duijjhm^^i ^^^^u front of the aorta to the left of the median line, passes into the abitomer -ar the tower border of the tenth thoracic vertebra, ami ™"'^^'"^'V?>' "W''J"'^'>; i T£ end^ in the stomach. Hardly more than i cm. «hich l«^ hehmd the left U^* .f the HvS and in Kt of the left pillar of the dia,>hr^m. c l-- ^ to he subd«ph«g- matic when examined from {(ithout. The li^; ^ s^ ^JTw^e 'o Tsi^en and the stomach, however. i> very clear on ^ mm-r -'*«^- •;*";^ ,he left o the chance in the nature of the epithelial lining llmv*- 1* .*en a fold on the left o the e^T the gullet, usually at Ihe upper ^ b^ ^piir t, 01^2- 5 mm ■c<^d. w^uch perhaps, .acts as a valve against reynirv a,,, .on The «**whragmatic t>«n ..about 3 cm. long. Sometimes the longitudinal lold t the gwe -een. i- p...,^i .nto the stomach, but usually it ends in a gradui*! e> and Physiolog>. vol. xxxiv.. I9i»- i6io HUMAN ANATOMY. At &st the oesophagus lies behind the trachea on the prevertebral fascia, the lobes of the thyroid gland touching it on either side. As it descends to the left' the trachea is pardy on the right. The left recurrent laryngeal nerve runs on the from. The right one is in relation with only the very beginning of the gullet. The rikjht inferior thyroid artery is against it. On the right also a chain of lymphatics in the areolar tissue lies very close to it. The left carotid and subclavian arteries are very near it, if not in actual contact. As may be inferred, the gullet and the aorta are Fio. 1363. Superior cornu of thyroid cartilage Thyroid body Left common carotid- Left subclavian artery Arch of aorta- Left pulmonary arter y Left bronchuft^ Left pulmonary vein- Thyroid body RiKht carotid Right aabcbirian artery — Innominate artery —Trachea — Superior vena cava Right bronchua Cardiac end of stomach. Abdominal aorta- Spleen. -Right pulmonary veins — -Aiygos major vein — .Diaphragm Inferior vena cava l*oftterior surface of liver Rifrht luiirarcnal body Si«ht kidney CEaophagus and related structures, teen from behind. Lungs have btvn pulled aside and posterior part of dhiphraam removed. * spirally entwined. The thoracic duct and the vena azygos major are in contact with it from the diaphragm to above the roots of the lungs, the former lying between it and the aorta as far as the level of the aortic arch, the latter, at first more posterior than the duct, passing as it rises behind the oesophagus and finally arching forward close to its right side. The left vena azygos, such left intercostal veins as open into the azygos major, and the right intercostal arteries pass behind the gullet. The pncti- mogastrics reach it in the thorax : the right after crossing the subclavian artery and THE CESOPHAGUS. 1611 the left liter crossinif the aorta. The nerves then break up into plexuses, from which thev ernerire near the diaphragm, the left in front, the riKlit behind the food-tube. On en-erinic the thorax, the cESoph^?us is in contact with the left pleura, and con- tinues to be untU separated from it by the aorta. Behind the pericardium it is in contact with the right pleura, and just before passing through the diaphragm it is in contact with both. • .i. ■ » . a .„i... Muscular fibres bind the oesophagus to various neighboring structures. A toler- ably constant band attaches it to the left bronchus, and others may go obliquely to the right bronchus. Several irregular bands, mosUy muscular, pass from it to various parts of the pleurae and pericardium. •. t t ,., Structure.— The wall of the oesophagus (3.5-4 mm. thick) consists of four Fio. 1363. Epithelium Tunica propria of mucous membrane Muacularis mucosa; ,GUind.ducU, obliquely cut Lonfcltudlnal bundles of non- striated muscle Bundles of striated fibres Tiansvene section of cnophacus, Junction of middle with upper third. X as- layers, which, from within outward, are the mucous, the submucous, the muscular, and the fibrous coats. ...,,,.' _j « - ,..„;— The mueous ct>ai, usually thrown into longitudinal folds, is composed of » j""l«^ propria formed of fibrous connective tissue and delicate elastica and covered with stratified squamous epithelium. Beneath the latter the surface of the stronria-layer presents longitudinal ridges and papillae, between which pass the ducts of the glands m their course to the free surface. The deeper part of this layer is occupied by a mus- culans mueosie, the involuntary muscle of which begins at the cricoid cartilage, hrst l6l2 HUMAN ANATOMY. appearing in the continuation of the elastic lamina of the pharynx. At the upper end only slightly developed, the muscularis mucosa becomes more robust until in the lower portion of the oesophagus it is conspicuous. The submucous coat, between the mucous and muscular layers, although consid erable, is not dense, and therefore allows free motion of the former upon the latter as well as the formation and efiacement of folds. It is continuous with the pharyn- geal fascia above. The asophttgeal glands are of two kinds,— the ordinary mucous, situated within the submucous coat and scattered throughout the length of the tube, and special glands withm the tunica propria limited to the two ends of the oesophagus The last mentioned correspond in structure to those found at the cardiac orifice of the stomach ; they are therefore known as the upper and lower cardiac vesophageal glands (J. Schaffer). r a & The usual secretory structures are small tubo-alveolar mucous glands in which mucus-producing cells are alone present, crescents of serous elements being absent The ducts are commonly somewhat tortuous, and often present dilatations or ampullae; p,_ 5 the smaller tubes are clothed with simple ^ * columnar epithelium. In the larger the epithelium may be stratified, and near the free surface assume a squamous character. The cardiac glands at the lower end of the cesophagus are continuations of those situated about the entrance of the gullet into the stomach, in connection with which organ they are more fully described (page 1624). They form oval or pyrami- dal groups of branched tubular glands, the bases of which lie against the muscularis mucosae, the narrow parts being directed towards the free surface onto which their wavy or tortuous ducts open. The upper cardiac glands form, according to Schaf- fer,' a constant, though variable, group around the superior end of the oesophagus. Lymphatic tissue occurs within the mucosa 01 the oesophagus as more or less distinct aggregations. Sometimes these . . are in the fo.m of small diffuse areas of mfiltration around the ducts of the mucous glands ; in other places, especially towards the lower end, distinct lymph-nodules are present (Fig. 1364). The muscular coat consists of an inner circular and an outer longitudinal layer, although the disposition of the individual bundles is often irregular and oblique, and above somewhat intermingled. In the upper third of the tube the muscular tissue consists entirely of striped fibres, the circular ones being continuous with the simi- lariy disposed fibres of the inferior constrictor of the pharynx. The longitudinal fibres arise from a tendon attached to the median ridge of the cricoid cartilage and to the fajjcia covering the posterior crico-arytenoid muscles, whence they descend to embrace the gullet. They are few at the top behind, but lower down the circular and longitudinal layers are distinct and symmetrically disposed. Towards the middle of the oesopl.agus the muscular coat includes both the striated and non-striated form of tissue, the involuntary variety gradually predominating until in the lower third it alone is present. The fibrous coat is pooriy developed above the diaphragm, consisting of the areolar tissue which connects the gullet to the surrounding structures. After piercing the diaphragm, the peritoneal investment contributes a limited serous tunic which from this point on is well represented. Vessels. — The arteries are links in the chain running the whole length of the alimentary canal. The highest are from the inferior thyroids, succeeded by those ' Beitrage «ir Histologie mensch. Orjtane, Bd. vi. Muscular , tissue Section uf niucoUN membiaiic uf u»o|>h«pu, showhir l>niph-liodc. ,■ 55. PRACTICAL CONSIDERATIONS: THE (ESOPHAGI'S. 1613 from the thoracic aorta and the gastric. The r««J are interesting only iM»«n«ch s^the^pper ones open into the azygos system and that of the mfenor thyroid above and theatric system below ; they thus form a communication between the general and the portal venous systems. The lymphatics— noX. numerous-go to the nodes of the deeper part of the neck and of the postenor mediastmum. Nerves are from the oesophageal plexus. . The mechanism of the closure of the cardiac end of the stomach is most properly considered with the cEsophagus, depending as it does partly on the «hrection of that tX^Sy on the relation^ the d&phragm to it. and partfy on the folds of mucous meSlHw at its orifice. Frozen sections (Fig. 1509). both horizontal and frontal (GuS') show that the termination is almost horizontal. Dissections of the dia^ Dhrwn from above demonstrate that the anangement of the muscular hbres is that of rSter although a weak one. The projection of the folds into the stomach b a hiSer pro S.* It has been shown tkat the cardia wiU r««t moderate pressure SSnbJ^w upward, butwiU yield to considerable force The action of the long^- SliSl fiTresTom both the cricoid cartilage and the diaphragm is to ddate the tube. PRACTICAL CONSIDERATIONS: THE (ESOPHAGUS. Cmgenital mal/ormatums are rare, as yet unexplained «™bryologically. and usu- ally faud The esophagus may be double, deficient, or absent. Most commonly There Se an upper culTsac and a lower segment opening into the stomach, some- tim« communi^ting with the respiratory passage. Cases in which there has been rSi^Ko-pleurc^cuUneou, fistula are possibly associated with this malformation mSdhkn. Osier). Congeniul diverticula are found, and Francis sugg«ts Aree tC^fo their occurrence : first, that they might be analogous to he diverticula wl^h were found in some of the Sauropsida and in ruminant animals, orming the fi«t two ^mpartments of the stomach ; secondly, that they were foetal vanelies StSs To tKophageal diverticulum from which the larynx, trachea and lungs are f^mXandSly.%hat they resulted from a failure in the mtenial closure of a ''™^^^'*^^^^^^di*y *,'ib:{ity, and constrictions of the normal oesophagus and ito relations to surrounding structures are of importance with reference tp Jp^eg" todies to stricture, to disease of the gullet with possible extension to ne ghboring oSS 0° to extrinsic disease involving the oesophagus either by mechamcal pressure or traction or bv extension to its walk. u »-w4 Foreign bodies, if moderately smooth or regular in shape, are apt to be an-ested at one of the three relatively constricted i rtions.-i.r (i), and ^0*^ ^o™™^';/: at the commencement. 15 cm. (6 in.) .'rotn the inc«or teeth, wh^h (*th the head midway between flexion and extension) is opposite the lower edge of the cncoid cartilage and the sixth cervical vertebra. At this point its »>'«^"««l, *^'.f'«f '* ' "J mm. (approximately Ji in.) ; foreign bodies arrested here are ^«»y,'"/he lower pharynx (2) At the point, about 10 cm. (4 in. lower, where the left bronchus crosses the Esophagus ^d where the lumen is again lessened by pre^ure (the dis- tance occupied by the left bronchus in crossing the (Esophagus is about 25 cm. ). (») At the diaphragmatic opening, where the diameter is once more reduced to U mm. by the constriction of the muscular and tendinous fibres surrounding the ojening- Vis point is about 12.5 cm (5. '"•) below «he level of the left brond^^^^^ aS therefore, approximately. 38 cm. (15 -...) from the >""«"■ t'«^'h. The majority of foreign bod i« that pass completely from the pharynx and are arrested in the «sopha|us are stopped at or about the level of the left bronchus. Many of them can be extracted through the mouth by suitable instruments ; others require an oesophagotomy, which may be done through an incision along the antenor lx,rder of the left sterno-mastoid muscle from the cricoid cartilage to the sternum. Ihe longitudinal fibres of the esophagus will be recognized a little to the left of the trachea, at the bottom of the space between the sterno-thyroid muscle anc the common carotid artery. An oesophageal bougie passed through the mouth will aid in the recognition roove between deltoid and (lectoralls major temum Acromion Deltoid Leit limR X-rib cartilaj^ Mnea semilunaris cuUili Anterior superior iliac spine Line of PouiKirt's liifament \'t imilorm apiwndix — Spermatic cord cmeri^ine at external abdtmiitial Anterior surface of body, drawn from photoicraph. General relations of thoracic and abdominal organs to txidy-wall are shown by colored outline. sist as free folds, while others fuse with the abdominal walls. The term mesctUery is vaguely applied to that [lortion going to the jejunu-ileuni, while other parts arc distin- guished by the name of thi; part of the intestine to which they are attacheii, as nieso- colon. The term omentum is applied to folds attached to the stom.Hch, as the gastro- hepatic omentum. The peritoneal sac is entirely closed, except in the temale at the upper end of the oviduct, where the mucous membrane of the K\\\\c ani7 in contact and lubricated with a thin layer of serous fluid, secreted by the membrane, by which friction between the organs and movable surfaces "reduced to a minimum. The serous membrane, consisting of the cndothehum and the hbro-elastic tunica orooria. is attached to the subjacent fasciae of the abdominal wall and the organs by a layer of subperitoneal tissue, an areolar stratum forming a more or less intimate connection between the serous coat and the structures which it covers The relations and attachments of the peritoneum observed in the adult are in some places entirely different from those existing in eariy life ; hence the history of th^hanges occurring during development is essential for understanding the complex relations found at later periods. PLAN OF THE DIGESTIVE TRACT BELOW THE DIAPHRAGM. The subdUphragmatic digestive tube is divided into the stomach the small intes- tine and the large intestine. The small intestine is subdivided into the duodenum and the '/«•««*-./?««. The former of these is an imperfect ring or horseshoe-shaped portion from 25-30 cm. C.<^i2 in. ) long, all of which, except the first inch or two. C on the posterior abdominal wall behind the peritoneum in the adult ; hen comes seething over 6 m. (usually about 21.5 ft.) of intestine thrown in o folds by ite aSment to the free Uge of'the mesentery. The upper two-«ths o this « cabled the /««««« and the rest the ileum; but. as the division is absurd.it is better to speak of this portion of the small intestine as the jejuno-tleum, sometimes a"ud ng toThe upper part as jejunum and to the lower as ileum It ends at the right iliac ossa by joining the large intestine, a little over ..5 «• (usually about 55 .«t) «onK. which fa subdivided imo the cacum, a blind pouch, and th^ colon, which is ascend- inir in the right flank, transverse across the middle of the abdomen and descending on the left. This is followed at the crest of the ileum by the sigmoid flexure, a free fold attached to the left of the pelvis, usually reckoned as a part of the colon, which, after crossing the left sacro-iliac joint, descends in the hollow of the sacrum, to become the rectum at the third sacral vertebra. The termination of the gut. passing through the thickness of the floor of the pelvis, is the anal canal. Two large glands —the liver and the pancreas— pour their secretions into the second part of the duo- denum, from which they originally sprouted. , „ . • .u ^„,^- The liver, the stomach, and the spleen occupy neariy all the space in the dome- like upper zone of the abdomen ; the right kidney, caecum, and ascending colon on the Tight, the left kidney and the descending colon on t' • left, occupy the lower lateral r^esses, leaving the middle space— shallow in the umbilical region and deep below it— for all the rest of the intestines, except such parts as can be squeezed mto the preceding regions, and for the greater part of the pancreas. THE STOMACH. The stomach, the most dilated part of the digestive tube, follows the oesopha- irus Ivine in the upper part of the abdomen below the diaphragm on the left, and passing downward and inward across the median line. In the eariy embryo it la a tubular dilatation, but it becomes flattened from side to side and the posterior border develops excessively, so that it rises above the upper opening and descends below the lower one. The stomach also swings on its long axis, so that its posterior border is carried to the left and the original left side to the front. The lesser curva- ture is that part of the right border of the stomach between the two orifices. It is straight or neariy so, and runs downward and forward to near its end, when it rises and passes to the right. The lessier omentum, originally the .interior mesenterv-.is attached to it. The grecUer curvature is more difficult to define. It is usually erroneously described as identical with the line of attachment of the greater omentum. It is more accurate to define it as the line from one orifice to the other which passe? along the left side of the stomach and separates the anterior from the postenor asp^t. The greater omentum-the original posterior mesentery— is attached to the greater curvature all along except at the upper part, where it passes onto the pos- terior surface. 13* I6i8 HIMAN ANATOMY. Gastro-phrcnic. ligament CKsophagus GKatrD>hcpaiic omentum Pandua Pylonu- Anterior aspect of stomach, moderately distended. The shape of the stomach may be compared to that of a pear, somewhat flat- tened, with the large end up and the point bent to the right. The fundus is the highest part of the stomach which projects upward above the level of the end of the Obsophagus. The greatest breadth of the stomach is at about the level of the oeso- phageal or cardiac orifice, and exceeds the antero- posterior diameter. The fundus generally contains air, if nothing else, and is somewhat distended, '■3*^' although thrown into uncertain contours by the partial contraction of its walls. Towards the lower ox pyloric end the stomach gradu- ally becomes more tubular, but the termination is often dilated into a cavity known as the antrum Pylori. The constriction on its left may be very slight, so that the antrum is hardly to be seen, or it may be so deep as to be mistaken for the pylorus. The antrum may be double or even triple. Sometimes, on the other hand, the terminal part of the stomach is tubular and to be dis- tinguished from the intestine only by its thick walls. Fig. 1368 shows such a .:ase which seems to extend beyond the usual limits of the stomach. The superior or cardiac orifice faces upward and to the right, being much nearer the front than the back of the stomach. Its diameter is at least 2 cm. and may be much more. When the stomach is distended a well-defined groove appears between the fundus and the left of the o-sophagus. Further details have been given with the gullet (page 1609). The position ot the lower orifice or pylorus may not be recognizable on the outer surface, or it may be marked by a groove. Internally, it presents a distinct ring caused by the thickening of the layer of circular muscular fibres, improperly called the valve of the pylorus, which raises the mucous membrane. This can always be felt through the walls. It is only by touch that the position of the pylorus can be certainly recognized when the Fig. 1367. parts are unojjened. The gastric cavity gradually narrows towards the pylorus on the stomach side, but from the duo- denum there seerts to be a (terforated partition across the tube like an optical diaphragm. The opening, although nearly always elliptical, is sometimes almost circular. Some of the larger openings in a series of thirty casts' showa long diameter of from 17-18 mm. and a short one of from 13-15 mm. Some of the smaller openings measure 6x7 mm. and 8x8 mm. We have observed more extreme figures at both ends of the series than those quoted. It is difficult to say whether some of the smaller ones would admit of greater dilatation. Probably 13x15 mm. is not far from the average size. The position of the longer axis of the orifice is uncertain, although it usually runs down- ward and bai-kward." Owing to the difference in size of the two ends of the organ, the axis 0/ the ' DwiRht ; loumal of Anatomy and Physioloftj-, vol. xxxi., 1897. ' Berry and Crawford : Ibid., vol. .xxxvi., 1902. Gastro-spletiic omentum. Gastro-plirenic liKameiit. I'ncovered area CEsophajcus Posterior, surface (sastro-hepatic nmentum jreater omentum fcut) Fundus Right aspect of stomach, moderately distended. THE STOMACH. l6ly Fio. 1368. Pyloru Outline of sliimach with conttricicd and greatly eton- gatcd pyloru*. iUmuuk » necessarUy oWique. although the kss^r cunature is vertical until near its end The axis slants downward and to the right as well as forwani, the pyloric portion being disregarded. The stomach is sometimes c.>m,«ratively tubular, the Wdus being but little developed, although the cardiac opening is always on the riirht side This is a continuation of the loetal form, and is more often seen in ^ women. There is often (possibly normally ) a hint of a con- striction about the middle. The above description, which is essentially the conven- tional one, is that of a distendetl stomach. The constrictions marking off a single, double, or even triple antrum pyU.ri are due to the contraction— which generally i)ersists for some hours after death— c.f bundles of the circular tibrcs. buch constrictions sometimes become fixed. The trui- shape of the stomach in life when non-distended is very different, but not yet thoroughly known. It is rather tubular, owing to the contraction of the muscles in its walls. The fundus is puckered and more or less constricted off from the rest, as is shown by the study of hardened bodies (Fig. 1369). ... 1 j t .„„,«« »k« Weight and Dimensions.— Not only is the normal development o! the stomach very variable, but it is impossible to define the limits between the normal and the pathological ; naturally, therefore, statements differ widely and are of little value According to Glendinning, the weight is 127 gm. (4J4 of). 'or man and a little less for woman. The greatest length, directed nearly vertically, is some 25 cm. ( ID in ) the greatest breadth from lo-i 2 cm. (4-5 «"• ). and >ts diameter from betore backward from 7-5-'C «"■ ( .W '"• )• The average adult capacity is said to range from 6OCV-2000 cc. (1.25-4-25 pints), with an averse of 1200 cc (2.50 pints). Peritoneal Relations.— The greater omentum, the origin.d posterior mesen- tery passes to the back of the stomach just to the left of the oesophagus, where its layers diverge so as lo leave a small triangular part behind it attached to the dia- ohragm without peritoneal covering. The lower of the diverging lines runs to the lesser omentum. The line of attachment then passes across the posterior surface ol the fundus near the top, but posterior to ihe greater curvature. At the left of the stomach the line of insertion is at u *„ the greater curvature, and continues F'O- >309- so till it reaches the pylorus. The Caru«c end fold passing to the diaphragm at the beginning is the g astro-phrenic ligament. This is joined by the gastro-pancreatic fold on the pos- terior abdominal wall which con- veys the coronary artery to the right of the cardiac opening. This last fold is important in relation to the topography of the peritoneum, but not to the stomach. The lesser omentum is attached along the whole of the lesser curvature, ex- C(.j't that its posterior layer may leave it below the cardia to join on the back of the stomach the layer of the greater omentum which forms the itiferior border of the non-serous j , , .„. ., i k . »„ trianele With the exception of this tnangle, and of the trifling interval between the lines of attachment of the omenta, the whole organ is invested by peritoneum. Position and Relations.— The cardie opening is opposite the tenth thoracic vertebra and not far from the- level of. hut from .^ -10 rm^ f 3-4 in. ^ behind the sixth left costal cartilage, about 12 mm. (>. in.) to the left of the median hne The lesser curvature descends vertically in an antero-posterior plane, parallel to the left border of the ensiform, but slanting strongly forward, until it suddenly turns to the Pylorua Stomach with purltrred fundus, seen from behind and soinewhal from left ; hardened by iormalin. l630 HUMAN ANATOMY. Non-peritonral area ardiac orifice right, rises, and ends opposite the space between the ensiform and the end of the eighth or ninth right cosul cartil^e, on a level with the first lumbar vertebra or the disk below it, about 1.3 cm. (>^ in.) from the median line. The pyloric orifice is affected to such an extent by changes incident to variations in distention that it is manifesdy impossible definitely to fix the position of the lower end of the stomach. The pylorus is usually separated from the anterior abdominal wall by the over- lapping liver, when the stomach is empty lying near the mid-line. According to Addison, a point 1 2 mm. ( Y, inch ) to the right of the median plane midway between the top of the sternum and the pubic crest will ordinarily correspond to the position of the pylorus. The fundus is at the top of the left side of the abdomen under the diaphragm, reaching the level of the sternal end of the fifth costal cartilage. The anterior surface, looking upward as well as forward, b covered by the left and quad- rate lobes of the liver. A varying part of it touches the diaphragm in front of the former. The extent of this must depend on the size of both organs. The liver may separate it entirely from that part of the diaphragm below the pericardium, or the stomach may be gainst the diaphragm in the anterior part of this region. A small triangular part of the stomach, normally in contact with the front wall of the abdo- men, bounded below by the greater curvature, is seen, on opening the abdomen, between the liver and the line of the left costal cartilages. This appearance ga\e rise to the old error that the stomach is placed transversely. According to Tillaux, the stomach in its most con- FiG. 1370. tracted state always descends tu a line between the ends of the ninth costal cartilages. The pos- terior surface, forming a part of the anterior wall of the lesser peritoneal cavity, rests against the transverse mesocolon, which lies on the organs at the back of that space, so as to make a part of the concavity for it which Bir- mingham' has well called the stomach-bed (Fig 1371). This hollow is made by the diaphragm on the left of the aorta, by the left suprarenal cafMule, the gas- tric surface of the spleen, the antero-sujjerior surface of .the pancreas, and U5u.illy by the upper part of the left kidney, although exceptionally this may be shut fiff from the stomach by the spleen and pancreas. The left crus of the diaphragm nakes a deep indentaii )ii in the stomach to the left of the car- dia. The riliac axis and the semilunar ganglia are rather to the right of the lesser cur\'ature. Ihe transverse mesocolon continues the lower part of the stomach-bed forward to the transverse colon, which lies below the stomach, following its curve when the stomach is distended. The splenic flexure of the colon is close against it. Whin free from solid contents, the stomach is usually found in dissecting-room subjects hanging more or less vertically in longitudinal folds containini; more or less air and fluid ; but during life, as already stated, it is in a contracted and puckered condition, the long axis running strongly forward as well as downward. With dis- tention the stomach enlarges at first upward, backward, and to the left, then forward against the abdominal walls. The upper part enlarges chiefly backward, the lower forward. This does not impl}' a forward swing of the greater curvature such as has been described. The pyloric end is moved to the right, it may be as far as the gall-bladdiT. The antrum may thus, according to Birmingh.im, be carried to the right of the pylorus. The lattrr rarely m- -ves more th.iii 5 em. to the ri^l-.t of the median line. Except in its last part, the Ksser curvature continues essentially vertical, as seen from before. The transverse colon is driven downward unless it be so much distended as to offer effectual resistance. ' Journal of Anatomy and Physiology, vols, xxxi., x\\\.. 1897, 1901. Pylorul Pos'.erior aspect of st<> i<-h at I'H tit, sliuwing perttoiieal telatiotis. THK STOMACH. 1621 Structure.— The walls of the stomach, thickest and most resistant near the pylorus, consist of four coate,— the mucous, the submucous or areolar, the muscu- *The* mucous coat or mueosa is soft and velvety, easily movable on the lax subjacent areolar tissue, thickest near the pylorus, and pre^nts "l^*")' /'jY* "' K^ which during distention are more or less completely effaced. The folds are m the Fig. I37>- FalcifomtliKan^cnt Ascending colon llsum. Lcfl V)br 01 livet Trantv«rM mesocoloo DescendiMR cc'oo SiKHioid main longitudinal, especially at the pyloric end. but many smaller ones run in all '^'^%Z%/>itMium covering the free surface of the mucous membrane consists of a I633 MIMA.N ANATOMY, transparent columnar cells clothing the stomach. The line o: liansition is zigiajj and well defined, the oesophageal suriace being paler than the highly vascular red gastric mucosa. At the pylorus the mucous membrane is raised into a ring, chicriy VIII rilKanUajcc Truiivcrse mestx-olun Kio. 1373 VII rilvcanilacc Emiform cani'krr VII riWaniUi* / VI rilM^rtilajir Kalcifurm lixamcnt VI rib-caniUtc Pylorir antrum ut »tfMitat-li r.iia[ihraKnt Jejunum Right Hupra- renal b'tdi XI rib Xfl rib XII vertebra XII rib Frozen section ac^o^s body at level of twelfth th«»rai-ic vertebra. in consequence of the local thickening of the circular fibres of the muscular coat, but also in part on account of the increased thickness of the mucosa itself, which in this part of the stomach may measure over 2 mm. At the cardia it is thinnest, — .5 mm. or less, — while in the intermediate rejjion it is about i mm. The increased thick- ness at the pyloric end is due to the considerable depth of the depressions, or Fig. 1374. Fig. 1373- Surface view fil mni-oim membrane frrtm p\Ioricen»I of stomarh. N:itural size. Surface view of Kastri< iiiucous membrane, show, ins reticular apiiearnnce due to orifices of groups of uasliicKlanils. ■ jo. gastric crypts, into which open the gastric ijlands. Beyond the summit of the pyloric ring the mucous membrane assumes the characteristics of the intestine. In addition to the larger ruga, the gastric surface exhibits a mammillattd condition THK STUM At M i6i,^ coittistinR of small Hygonal irca* pitwd by tiw - r-pt« *ft«rh reanv* the .-n»c« of the K'*^"^'**-^^^^^ gland* constitute iw.. pnnc^wd b»«i|», «»/»«*... ami tlw #r/^V Wa*^*; the former occupy the maj.^ i«.rt .- th.- .«wiad,, iwUuliinf the '"«*** '^e interior and posterior walls, an.i the - urv'atu«* ibr latter » . ur ,. the ,,vU.r.' hfth of the organ An additional fundus va«ety-«k« ^W/u, .-'"A- - > pr.se,,!^! l.y a narrow zonular uroup in the immwliate vicmm- <« the u-s..,^^.i^(e..l ^n>r.i;. Th^ fundus eupeptic glami*-tfae ^-rtric «l»ls pr..,«-r--:o.>»«« ... u^m.^.a« closely srt tubules, uiimlly somewha. « -y ««J fcm«^ ,4-' mm l.m.: wh.d. ext*n.l the entire thickness of th. mucosa and abut ;H£«..«t the „u.«:u*..ns u.«c.««e L.- h MStric cVypt. corresponding t., tte ^^rrr/rn-V *«r/ usualv ,ec.-.v.-s a »:roup of s^ - S of th^smaller ?ub„les*^ which mdude the -W and /-«rf*. of i .e kU«I, tl^ ^nstricted commencement of the tubule co«titu. .,.g: the nea At the l^ter p««.t«.n Fic. 1375 _(.a«rii Klan't- »J i^^i^J^r^ M iistriilanii Must iilari'' Seros.'! 4 jhli'iuflv iut i-irculai Tnmsversf stc lion of stoma.!, ilelt en.l i. 5ho»i.iK KM,.rjl arranmiiKiU o( cmts. the columnar epithelium prolonged into the crypts from the free suriace becomes lower and modified into the secreting elements. The cells lining the gastric tul.ules are of two Icmds. the chief and the parietal. The chief, central or adelomorphous cells correspond I., ordinary glandular epi thelium. being low columnar or pyramidal, ..nd surroumlin- a cir.nU.r lumen from !S t™ .oo7^mm. in diameter. ' During certain >.ages of digest,.,,, they -ontam numerous granules, which are probably concerne.l in producing P^I"*'". The parietal cells, known also as acid, o.xynti.-, ..r delomorphous although rela- tivclv few u- conspicil"U'= eler-.e,,!-. which oc-u-.N- the periphery of the gland tul>es Their position is indicated by protrusions of .he profile of the g.xstnc tutn.les caused by the cells lying immediately l^neath the b;isement membrane. The parietal ce Is although arranged with little regularity, are most numerous in !he™tyof he neck where they may equal or eyen outnumber the central cells : in the bod> of the 1 634 HUMAN ANATOMY. gland they decrease in number towards the fundus, in which locality they may be almost absent. Their protoplasm is finely granular and lighter than that of the chief cells. The parietal cells, although apparently excluded by the central ones, are con- nected with the gland-lumen by means of lateral intercellular secretion-capillaries ; the iatter extend from the axial space to the peripherally situated elements, over which they form characteristic basket-like net-works. The pyloric glands, branched tubular in type, differ from the fundus glands in the excessive width and depth of their excretory ducts, into which a group of relatively short but very tortuous gland-tubules opens, and in the simple character of their lining. The latter consists of Fic. 1176. IVfper portion of KitMrJc glands from ftirhlus. sno^inK two varii'iit's (if ;initiK iTlU and ftrcnrtion-capitlarirvt » unnt-.tHiK [liirt- eta! cclK witli lumen. ■ 41,1. a single layer of low columnar or pyramidal elements, which corre- spond to and resemble the chief cells of the fundus glands. Their secretion often reacts as mucus ( Bensley). Owing to the tortuous course of the pyloric tubules, the deeper parts of the glands are cut in all planes, portions of the same tubule often appearing as isolated transverse, oblique, or longitudinal sections. The transitional or in- termediate zone connecting the py- loric and adjoining portions of the stomach contains both forms of glands, those of the fundus variety with parietal cells being intermin- gled with the pyloric type. Towards the intestine the change of the ,jy- loric glands into those of the duo- denum is gradual, the gastric tubules sinking deeper until, as the glands of Brunner, they occupy the sub- mucous coat of the intestine. The cardiac glands form a narrow annular group, some 5 mm broad, surrounding the orifice oi the gullet, into which ihey are con- tinued for a short distance (page 161 2). These glands, which in some animals constitute a much wider zone ( in the hog almost a third of the entire stoniiich), are to be re- garded as modified fundus glands (Oppel), since they possess similar epithelium, including usually a few parietal cells. Their excretory ilucts or crypts, lined with the gastric epithelium, often exhibit ampulln- like dilatation.s. Among the tvpi- ral tubules are a few shorter ones which recall the gl.->nds of I.Ii-Iht- since they contain 1,'oblet- cells and exhibit a cuticular border Ihicf cell Parietal cell kiihn of the intestine (J. SihiiffiT ). The s/roma or tunica propria of the gastric mucous membrane consists of a loose fibro-elastic connective tissue containing numerous cells anil resembling lym- phoid tissue, which fills the interstices between the glands and, in conjunction with the extensions of the nmscularis mucosa-, forms envelopi-s and partitions for the groups of tubules constituting the deeper parts of the gastric glands. In THE STOMACH. 1625 the vicinity "I the pylorus, and sometimes also at the cardia, a number of small lymphatic nodes— the so-called lenticular glands— normMy occupy the deeper parts of the mucosa ; occasionally they are of sufficient size to almost reach the tree siirfcicc The muscuiaHs mucosa, as in other parts of the intestinal tube consists of a wcU-marked collection of involuntary muscle, deeply situatecj next the submucous coat Two layers are usually distinguishable, an inner circular and an outer longi- FiG. 1377- Mucous coal Siibimicous coal .Circular miisi le LonKitndinal ni«*clc iStrnimcoat Transverse section o( stomach, pyloric end rusa is rut across, showing mucosa sup|K>ried by core ol submucous tissue ■ io. tudinal. Towarils the mucosa numerous bundles of muscle-cells extend between the Elands and in places penetrate almost as far as the epithelium. The submucous coat consists of la.x connective tissue, allowing the mucous membrane to move freely on the muscular layer. It contains blood-vesse! of con- 8impti-iiudr. kjo. with the lonjjitiidin.nl fibres of the (tsophagus. Along the lesser cijr\ ature, and to a !<^-> extent along the frreatcr, these fibres are collected into bantis ; over the front and the hack of thostoin.uh they are oblique. At the antrum pylori, although the layer is rontinuiMis all around, it presents an anterior and a posterior hand, — the pyloric ligaments. —\\\M (lass o\er folds of all the layers internal to them, thus forming; the duplicature .it the beginninu; of the :i.H.um. At the pylorus itself the loniijitudin.il layer, which has t)ecome thicker, sends a series of fibres through the circular ti.ire-i. sulKliviilin^; them into n.any groups, CFig. isgi"). The innermost muscular layer ■> insists i)\ fbliqiie fibres spreading out from the cardia o\er the front ami Ixick of the stomach. They are continuations of the circular fibres of THE STOMACH. 1627 ut glands the Bullet and diverge to either side, showing a well-marked border near the lesser curvature. Their p^terior expansion is the stronger. The diverging hbres are lost near the pylorus, while in the vicinity of the fundus they mingle with the circular ones that form the whorl. The latter, according to Birmingham, is formed by this '*y^''xhe"8erou8 coat corresponds in structure with other portions of the perito- neum, consisting of the endothelium of the free surface, iKrnealh which lies the fibro-elastic stroma attached ^^^ ^^^^ to the muscular tunic. Blood-Ve8»elB.— The arteries of the stomach, de- rived from the cceliac axis, are arranged in two arches aloog the lines of atuchment of the omenta ; hence that which is attached to the greatei cur- vature below passes behind it on the fundus. The arch along the lesser curvature is formed by the coronary ar- tery, which sends an oesopha- geal branch upward tf) meet the lowest of the oesophageal arteries, and joins the py- loric branch of the hepatic artery below. The arteries of the greater omentiini are the right and left ga.stro-epi- ploic, reinforced behind the fundus by the vasa brevia of the splenic artery. The gastro-epiploicadextra passes dow n on the right of the first part of the duodenum close to the pylorus ; branches arising on the front at that region may nearly or quite makt an arterial ring around the organ. The coronary arterv supplies the longer branches to the walls, there being a richer arterial distri- bution on the back than on the front and at the cardiac than at the pyloric end. The general i)l;in is as follows : on the anterior surface seveml arteries, of which some four ^^^ ^_^, ___ ^^ ^^_^^;^, „..n,hranr fmn, pvlork «nd of M..n>a. h. ^ho« are large ones, run from the i,iK Kinnils i m m varimis levtis. ■ i<». S^ch"S:S. ^r^iclSsive lateral branches to inosculate with those from their en" s finallv.'^he main vessel breaks up into branches th.-it meet ^^-^ greater curvature. On the posterior surface the chief trunks d.vule witl less reg«- hritv. At first the artenes\,re just beneath the perit<,ne«m, between the folds .1 which they gain the stomach ; presently they enter and pierce the muscular coat, the omer p.,rtsof which are supplied during their passage. On reaching the ^^'-l^^'- coat the arteries, now reduced, but still of con .ider.nble s,/e, .livule into smaller branches some of which pa.ss to the muscular tunic, while the ma).. rity enter the mucou coat. The latter soon break up into capillaries which surround the gland- 1638 HUMAN ANATOMY. tubules with a dose mesh-work. Somewhat larger capillaries constitute a superficial plexus beneath the epithelium encircling the orifices of the gastric crypts. The veins, relatively wide, begin in the subepithelial capillary net-work and traverse the gland-layer, between which and Fig. 1380. Pyloric rinj Stomach tanwd inside out, •howinc dincction of obliuur ami circular mnacular coati. the muscularis mucosae they form a plexus ; .' om the latter radicles pass into ; t; submucous coat, in which the venous trunks run paral- lel with the arteries, but lie nearer the mucosa (Mall). The emerging tributaries are often provided with valves at their junction with the larger gastric veins. The l)nnphatics originate within the mucous membrane, be- neath the epithelium, as wide, ir- regular capillary channels which freely communicate with one an- other and pass between the glands as far as the muscularis mucosa- ; at this level they form a plexus from which vessels descend mto the areolar coat to join the wide-meshed submucous plexus. Larger lymphatics pierce the muscular tunic and unite to form the chief channels which escape from the walls of the stomach along both curvatures to empty into the lymph- notles which occur in these situations. The nerves supplying the stomach are from the pneumogastric and the sympathetic, and contain both medullated and nonmedullated fibres, the latter predominating. On Fic. 1381. reaching the organ, the stems pierce the exter- nal longitudinal muscu- lar layer, between which and the circular layer they form \.\\cp/cxus of Auerbach. The points of juncture in this net- work are marked by mi- croscopic sympjithetic ganglia, from which non-meduUated fibres supply the involuntary muscle. Leaving the intramuscular plexus, twigs pass obliquely through the circular muscular tunic, ami on gaining the submucous coat form a second net- work, the picxtis of Mf issuer. Numerous non-medullated fibres leave the latter to enter the mucous coat, in which some end in deli- CJite ple.xuses supplv- ing the gastric glands < Kytmannw ), as well as 111 special endings in the muscularis mucos«> (Berkley ). Large medullate»- » Retch's Pediatrics. 1630 HUMAN ANATOMY. denuni (the fixation being du to the relation of the superior mesenteric arterv and to the root of the mesocolon in front), while above the cardiac end is suspcndicl from the^phagus and held in place by the gastro-phrenic and gastro-splenic iiira- nients The transverse colon may then lie in front of the stomach and may, if djs- tended be uken for it. The empty stomach lies upon the posterior alxlominal wall If the emptmess is habitual, the pylorus will resemble the first portion of the tluodenum and regurgitation of duodenal contents is exceptionally easy The • gnawing pains of hunger or starvation (distinct from the sensation of' hunt'or itsel ) are at leswt partly due to the traction on the nerve plexuses and filaments resulting from this altered petition, and can, therefore, in many cases be relieved teniporanly and partially by tightening th^ clothing about the waist and abdomen giving support to the viscera. When the stomach is distended the enlargement, which occurs at first upward and backward and towards the left side, raises the arch of the diaphragm in that region and with it the heart and jiericardium. The gastric plexuses derived from the two pneumogastrics and the associated sympathetic fibres, together with the coronary plexus from the sympathetic, are all in close relation with the lesser curvature, especially its cardiac end. It is not, therefore, difficult to understand how this change m the position of the stomach aids in producing the flushed face, embarrassed respiration, and irregular heart action often seen in various forms ot dyspepsia or after overeating. If distention continues, the right lobe of the liver IS also pushed upward, the pylorus moves to the right, and the transverse colon downward ; the stomach comes in close contact with the anterior wall of the abdomen, the " scrobiculus cordis" (page 171) is obliterated, and a tympanitic note replaces the norm ' resonance. ' Conversely, cardiac disease may cause vascular congestion of the stomach catarrh, dyspepsia, or even hiematemesis. The " black vomit" of moribund per- sons IS due to a similariy produced distention and rupture of the stomach capillaries 1 he |)osition of the stomach varies with the respiratory movements In forced inspiration the cardiac opening descends about one inch with the crura of the dia- phragm ; the pylorus reaches about the level of the umbilicus. Eructation of stomach contents in its typical form is accomplished by con- traction of the muscular walls of the stomach ; vomiting by compression of the stomach against the under surfaces of the liver and diaphragm through contrac- tion of the abdominal muscles. This is associated with contraction of the circular pyloric fibres and relaxation of the oblique fibres at the cardia, and is probably aided l)y contraction of the stomach walls themselves. It is ob\ ious that a full stomach is more easily and directly compressed in this way, and therefore the ingestion of large quantities of fluids favors emesis. Vomiting IS a clinical symptom often of the greati-st significance, and should he studied in relation to the pneumogastric and sympathetic distribution to the stomach, lungs, and abdominal viscera ; and its various causes— central, reflex and direct— should be worked out systematic.-illy. Injuries of the StomarA.— The changes in pfwition and the degree of distention are of the utmost importance in trauma expended upon the stomach, which if quite empty, almost certainly escapes contusion and rupture. It is, at any rate, much less trequintly ruptured than the intestines on account of its thicker walls and nf the protection afforded it by the overhanging ribs and the interposed liver The ■ stomach-t)ed ( page 1 620 ) supplies an elastic and movable Iwse of support which also favors its escape from injury. In penetrating or gunshot wounds its condition as to emptiness or the reverse IS even more important. When either wall is opened by rupture or wound, eversion of the mucous membrane, which is favored l.v its thickness and by the laxity of the sulmiucous connective tissue, may temi>orarily plug the opening; and through the lormat.on of .i.lhesions permit of spontaneous cure. The diflerent directions of he museul.T fibres m the three layers of th.u cat ordinarily prevent wide separa- M.n of the margins of the wound, and thus also favor its closure by natural processes In i-scape of stomach contents through ulceration, wound, or rupture if the poste- rior wall IS involved, the le.sser omental cavity is infected, and a localized— sub- PRACTICAL CONSIDERATIONS: THE STOMACH. 16.^1 ohrenic— abscess may follow ; if the anterior wall is opened, infection of the general oeritoneal cavity and septic peritonitis are more likely to result. On account of the Murse of the blood-vessels (page 1627), wounds parallel with the a.xw of the curva- tures are attended by free bleeding, especially if near those liorders of the stomach. Wounds running more or less at right angles to the curvatures and removed from them are much Ic^s likelv to open large vessels. The vessc- U just Ijeneath the sur- face of the mucous membrane are numerous but smaller. Bleeding from tlicm may be controlled by separate suture of the mucosa, which is facilitated by it.s thickness and by the looseness of the submucous cellular tissue. „ . , • Ulcers of the stomach are found most often on the posterior wall at the pyloric end and along the lesser curvature. It has lH.-en suggested that they originate in a bacterial necrosis of the epithelium, which is favored by the al)sence of the fun. us or peptic glands (page 1623) at this region, and is followetl by - digestu.n of the subkcent tissues. Allen thinks that the immense preponderance of pyloric ulcers is an illustration of the Maw of localization of diseased action, -viz., that parts enioving the most rest are least liable to involvement by structural disease. W lu-n they cause hemorrhage, it is apt to be from the branches of the coronary artery. 1 or- foration occurs with much greater frequency in ulcers situated on the anterior wall, which is the one with the greatest range of motion in van-ing stages of digestion and degrees of distention, and also during the moveiner.ts of respiration. I ertora- tion from such ulcers with spontaneous cure may result in adhesions between the stomach and pancreas, colon, duodenum, or gall-bladder, and may be followed bv fistula; communicating with those viscera. They may perforate the diaphragm and cause empyema. They have opened into the pericardium and mto a ventricle ot the" heart An ulcer may be so surrounded by adhesions that, even when on the anterior wall, perforation does not cause a general joeritonitis, but a locali/.etl atwcess. If this is, for example, in the splenic region, it will be obsenecl that there is i.nmo- bilitv of the upper left quadrant of the abtlomen with restriction of the respiratory movements of the left thora.x, both occasioned by the connection between the splanchnic and the intercostal nerves through the sympathetic ganglia. The local- isation of such collections of pus after perforation of the anterior wall near he cardia is favoretl by the " costo-colic' ' fold of peritoneum extending from the . la- phragm opposite the tenth and eleventh ribs to the splenic flexure of the colon and forminri'art of the left portion of the -stomach-bed.- This fold, especially with the patient supine, forms a - natural well." contaming the spleen and a part of the stomach, into which any fluid exudate or stomach contents may gravitate ^ ^Cancer of the stomach occupies by preference the pyloric region. When the erowth becomes palpable, but before it is ti'd d'^n by adhesions to neighlx)ring organs, it often illustrates the mobility of the pyionc end of the stomach (v,df supra), as it can be pushed even ,across the mid- line of the botly into the splenic '^*^^'*Carcinoma, according to its situation, may extend in the cours-- of the lym- phatic vessels running along the lesser curvature in the gastro-hepatic omontuni ami emptying into the lymph-nodes near the cieliac axis and hepatic l)lood-vv->stIs. or along the greater curvature an.l the cardia to the retro-.tsophageil ir!an..s f tie retro-pvloric lymph-nodes mav l)e inv.ided in cancer of the pylorus. It» .arly r. n;- nition as a tumor obviously depends upon its anatomical site. If it oc( im>u-s 'he fundus the cardia, the lesser curvature, or the upper and ouu-.|ng pon-ins ■■( .li.; anterior wall, the ribs and the liver intervene and prevent palpatioi" of tne i;r<'\via ; an.l if on the posterior wall, the depth at which the tumor lies renders its palp xvax difficult and unsatisfactory. . 1 . _ i j Dilatation of the stomach { srastreclasis ) may l>c due to simiile hypertropin <.t the pyloric muscle, may follow stricture of the pylorus or duotlenum .rom cic.itriza- lion of an ulcer, or may result from pyloric occlusion, as from carcinomatous growth invading the pylorus itself, or from pressure of an extrinsic tumor, or a displ.ic.-.l liver or right kidney. The distention is often extreme, and in some instances the outline of the distended stomach can plainly be seen, the lesser curvature a couple o( inches below the ensiform cartilaj;e and the greater curvature passing obliquely ■SPHWHFiWB'^W^ 16^2 HUMAN ANATOMY. from the tip of the tenth rib on the left side, toward:! the pubea, and then curving upward to tlie right costal ; margin (Osier). The dilaution may l»e of any degree, the lower border of the stomach sometimes reaching to the level of the pubes. Displacement of the stomach (gastroptosis) is attended by (^re.it stretching of the gastro-hepatic, gastro-splenic, and gastro-phrenic folds. It is sometimes a dila- t.ition with the stomach vertical instead of oblique rather than a true descent of the whole organ. Three forms are described : (i ) a slight descent of the pylorus, and with it of the lesser curvature, so that the latter comes from l)eneath the liver ; (2) " vertical stomach," already alluded to; (3) a descent of the lesser curvature, the pylorus remaining fixed, making a U-shaped stomach (Riegel). The last is very rare. All forrt s are favored by the use of corsets or dotl^ing constricting the lower thora.x. especially in women with flaccid aNlominal walls. The displ.icement may be con- genital, or may be due to primarv elongation or rela.xation of the pentoneal folds which act as ligaments, or to malposition or displacement of other abdominal visccr.i. Hernia of the stomach is usually diaphragmatic and often congenital. The viscus may enter the thorax through a stab wound or rupture, or through weakened or enlarged spaces at («) the central tentlon, ( *) the posterior inferior muscular area. (r) the interval botwoen the sternal and costal fibres, (d) the (esophageal foramen, ( e ) the fissure between the lumbar and costal portions, or ( / ) the point of passage of the sympathetic trunk ( Sultan ). These possible locations have been mentioned in the order of frequency. The hernia may carry the peritoneum with it {true hernia), as in cases c' partial rupture or non-penetrating wound of the diaphragm, or may avoid or pass tiirough the peritoneum {false hernia). The latter are more common. All forms are found most frequently on the left side in consequence of the presence of the liver on the right side. Opf'itio'ts on the Stomach. — The stomach is most accessible for operation through a triangular space, apex upward, bounded on the left by the eighth and ninth costal cartilages, on the right by the free edge of the liver, and below bv a horizontal line joining the ti|)s of the tenth costal cartilages and corresponding approximatf'I\ to the line o' the transverse colon. The tenth cartilage has a dis- tinct tip and plays over the ninth cartilage, producing a peculiar cre]>itus ( LabW ). If the incision is median, it passes between the recti muscles; if lateral and vertical, it is made through the rectus or along its outer edge ; if oblique, through the rectus and the external and internal oblique and transversalis. The terminal branches of either the superior or deep epigastric artery may be divided, or the latter vessel itself it the vertical incision is prolonged downward. As the blood-supply of the stomal h comj-s from three distinct sources — the gastric, hepatic, and splenic arteries — and the anastomoses are ver>' numerous, the nutrition of the flaps, even after extensive resection, is usually maintained, in the al«ence of infection or of cardio-\asciilar disease. On tiie contrarj-, in operations on the intestines the greatest care must !)e exercised in tlealing with the mcsenterv to preserve the vitality of the gut. I'pon exposing the stomach, it is well to bear in mind its obliciue position and the facts that the pylorus is the only part that is really transverse that thrce- fourtlis of the stomach ate to the left of the middle line, tli.it the upper part of the cardia is an inch atxive the level of the lowe: end of the tesophagus, and that the l.irger part of the greater cur^■ature is directed to the kft and of the lesser curvature to the right. According to .Meinert, the pylorus lies Iwhind the intersection of a transverse horizontal line draw n through the tip of the xiphoid cartilage with the riy;ht costal liorder ; while the lower curvature, fx-ginning at the latter point, crosses the mid-line and ascends, describing a half-circle around an antero-posterior hori- zontal line drawn rhrough the xiphoid tip. The relations of the stomach in general have been described Cpage 1619). The transverse colon — especfilly in cases of (esophageal s'tricture in which the stomach is contracted and rests far Kick and well up under the diaphragm — mav pr(>sent itself, and has lieen mistaken for the stoma-li. The gut. however, is thinner, not so THE SMALL INTESTINK. '^^3 Dinkiah and the longitudinal baml, the sacculations, an.l the epiploic appentlaRiii on its lower aspect may ue seen. H any doubt exists, the undir siiilace of the U It lobe of the liver should be followed up by the fiiiRer to the triiiHvcrs- hssurc ami then down on the gastro-hepatic omentum to the lessi-r curvature of tlie stomach. The dependent greater omentum and the gastro-epiploic arury «.n the nr-attr cur- vature aid in the recognition of the stomach. , , , • In gaslroiomy—a^ for foreign body, for exploration, or for retrograde dilatation of the asophagus— the incision may l.c vertical and midway l).tweeii the two curva- tures to minimize the hemorrhage (i/V^- f«/»- m.) from them, or vertical down to the left rectus, the fibrc-s of which may be separ.itcd without division. In either case a part of the anterior wall of the stomach, made conical by traction, is brought out, carried upward beneath a bridge of skiii. and fixed to the margins of a second opening over the costal cartilages. V ari.v.is nioo- ifications are employed, all with the idea of securing a valvular or sphincteric con- dition in or about the orifice so as to prevent leakage of the stomach contents. In Av/f^ro/^/aj/v— applicable to simple hypertrophic stenosis or cicatricial stric- ture-an incision is^ made from the stomach to •'e duodenum through the pylorus and parallel to the long axis of the tract at «t point Its borders arc then separated as widely as possible so that their mid-points becom.; the eiuls of the opening, the edges of which are then sutured together m this position, materially widening the lumeii of the canal. .t, u 1 ,„,„ In bylorectomy or ^astrectornvhr^v portions of the stomach, or the whole organ, are e-xcised for malignant disease ; in the former the omental connections of the Dvlorus must be severed and the right gastro-epiploic, the pyloric, and the gastra- diiodenal arteries Jividetl ; in the latter, in addition, the pneumogastric nerves below the diaphragm and many more vascular trunits. Partial gastrectomies, as for the excision of a nodular carcinoma or of a gastric ulcer, are much less serious. Division of the gastro-hepatic omentum, which holds the stomach up under the costal margins, will facilitate thefreei.ng of the pylorus and lesser cur%ature and permit of ready access to the lesser peritoneal cavity. The gastro-colic omentum attached to the region of disease can then he made tcnso by The tiiigers passed behind and beneath the pylorus and can be li>;..trd and divided (Mayo). . , . • ( .J. \n zastro enterostomy— xi a palliative in cancerous pyloric stenosis or tor the treatment of gastric ulcer-the intestinal canal (usually that of the jcjui-.um, as the highest movable portion of the small intestine) is made directly continuous with the stomach cavity by the esUblishment of a permanent fistula botween the two. 1 he posterior wall of the stomach a now usually selected because of I's nearness to the eiunuin It may be reached through the transverse mesocolon, me gre.it. r o",, rx-MV with the transverse colon having been turned upward ; or the gastro-colic omentum may be torn through or divided. . , . 1 Gastroplasty (analogous to pyloroplasty) has been done in cases of hour-glass stomach following cicatricial contraction after gastric ulcer. Occ.isionally in these cases the constricting band has been mistaken for a thickened, contracted pylorus. Adhesions sometimes connect the constrictions with neighboring parts, as with the right rectus muscle (Elder) or the liver (Childe). THE SMALL INTESTINE. The stomach is followed by the long and complicated tube of the small intestine, divided into the duodenum and the jr/uno-i/eum. According to Treves, the average length in the male is 6.8 m. (22 ft. 6 in.) and in the female neariy 15 cm. (6 in. ) more This excess, however, would prol»bly not be confirmed by a larger series. In the male the extremes were 9.7 m. (,ii ft. 10 in.) and 47 m- ('S ft. ^'n)- '" the female 8.9 m. (29 ft. 4 in. ) and 5-7 m. ( 18 ft. 10 in. ). The outer waU of the tube is regular, without sharp folds or sacculation, , beyond the duodenum. Ihe »u3 .*..'_ ■& I^M HIMAN ANATOMY. circumference is greatest in the durxlenum (not always at the siune point), beyond whicli it gradually decnases, the diameter of the gut at its lowt- r f nd being nearly one-third smaller than at the beginning. Since certain iitnictural ftatures are com- mon to the entire small intestine, it will be convenient to consider these in this place, further details being given with the descriptions of the special parts. Fio. 1383. Traiisveiiic tolut Pall iiorm liKamenl -Stumach Grratpr omentum (cut Hurfare > Coils of jejunum Dc-scending colon Sigmoid ffexurr AlKloniiiial nrKans of (nrmalin suhjicl. Stomach was unusually large, ffivinff an exaKKerate«l impression of its transverse iHtsition. Structure. — The small intestine, as <>t!u r parts of the alimentary tube below the diaphragm, consists of fonr coats, the mucous, the suSmucous, the muscuiar, and the serous. The mucous coat, in addition to the j^landular structures, possesses folds and vilh that not only greatly increase its surface, hut also contribute peculiarities which aid in ditTcrcntiatinj^ between typical portions taken from various regions. The THE SMALL INTESTLNK. ift-.'i fMMimm covering the free suriace consists of a sinnle ay. r of cylindrical cells uhu h exhibit a striated cuticular border next the intestinal !.uncn. 1 us U.rder lacks stabUitv. and is resolvable into minute prisniatic hkIs. placctl vcrt.ailly and j.roUil.ly continuous with the spongioplastic thre-.ids within the U-dy " t'le evil In nui.y XcL especially over the viUi. m.uns-pr.KlucinK Koblet-c. lis share the frc-e suriace with the onlinary epithelial elements. Hetween the latter ni.nratory hucKrytes are always to be seen. The siratua or tunica (jropria of the mucous cmt re-scnihles lymphoid tissue, being composed of a connective-tissue reticulum cntanunu numerous small round cells similar to lymphocytes. This stroma hUs the siM.es iKtwt^n tin- glands and forms the core of the villi over which the .pithelunn stretchc-s. Ihe deip- Fiii. I384. Villu!! Puct of Brunner'j ii'>"'la Muscularis mucosic Brnnner 5 Klamls ilice nl kI*ih) of l.ichrrktihn _ Bnioner's glandt Circulur mincic - LonKi.uflinal tniiBcl« Tra.„verM Mction nl small .iHMline (lower p«rt ol diK«l«ii"m . ,h..wi.iK (eneral arnnKemcui of c«i». < qo. est part of the mucous coat is occupied by > ■ ell-marke'tructures within the alimentary tube to which the term glands has been applied include two entirely different groups, the true and tht false glands. Fig. 1386. Strom* of «nnic» propria luriace epithelium .Goblct-celt :iand of Lieberkiihn Muscularis mucosc Circular muscle- Tramverw section of small intestine (jejunum), showing villi cut lengthwise. X 150. The former are really secreting ..rans,— the glands of Lieberkiihn and of Brvinner ; the latter are more or less extensive accumulations of adenoid tissue, and are appro- priately spoken of as lymphatic nodules or follicles. The glands of Lieberkuhn are simple tubular depressions which are found not only throughout the entire small intestine, but in the large as well. They are very closely set narrow, and extend the thickness of the mucous coat as far as its mus- cular layer. In length they vary from . 3-. 4 mm. and in diameter from 060- o«o nim. The fundus of the glands is slightly expanded and in exceptional cases divided. The lining of the crypts rests upon a delicate basement membrane, and consists of a single ' Imemat. Monatsschrift f. Awit. u. Ph\'sio!.. Bd. xi.. 1894. 1638 HUMAN ANATOMY. layer of columnar cells directly continuous with those covering the villi. They differ from the latter in being only about half so high (.018 mm. ) and in not presenting the characteristic cuticular border. This last gradually disappears as the cells dip into Fig. 1387 .('.ohleicell .Capillao' Cuticular hiirder cpithtrliuii) Fig. 1388. Transverse section of sinKic intestinal villus, showing relation ol epithelium, stroma, and vessels, x 350. Surface view of mutous membrane from end of jejunum showinK valvulie cotini- ventes. Stippled appearance is due to villi coverinK folds. Natural size. the follicles to become the lining of the glands. Under low magnification the sur- face of the small intestine presents numerous pits, the orifices of the glands, which almost entirely fil! the spaces between the bases of the villi ; with the exception of Fio. 1389. Submucous coat Villi Lonffiludiiial muscle Serous coat Longitudinal section of duodenum ; valvulie coniiiventes cut across, showinK relation t.f these folds to villi. the areas immediately over the lymph-nodules, where they are partially pushed aside, these glands are present in all parts of the intestine. They, howe\er, take no part iii absorption, never containing fatty particles during periods in which such substances THE SMALL INTESTINE. 1639 «re seen within the epithelium of the villi. It is worthy of note that even in the adult mito^ figur^are frequently observed within the cells linnjR L'^berkuhn s ^h»nds Sough such evidences of cell-division are rare an.unK the elements covering the Fig. 1390. Uuct oi Bruiiner's Klandt Villul Gland of Liebcrkubn LongUudinal «c.io„ of duodenum, showing Brunner', and Uebcrkuhn', Kl.nd,. vHII, and U-mph-node. y .00. villi Bizzozero therefore regards the lining of these glands as an active source for he regeneration of the intestinal epithelium by the product.on of ".^/l-"«;^ ^s ^ m the viUi, so also in these glands goblet-cells he among the usua epithelial elements . likewise migratory leucocytes are present between the gland-cells. Fio. 1 39 1. Pyloric glands • Mucous coat Stomach Duodenum Looiritudinal section through junction of stomach and duo.lenun,, showing transition of pyloric into duodenal glands ; Loogltuainai section >nro g ^ ,'hiekenii.g of circular muscle 10 (orm sphincter pylori, v l). The glands of 3runner. also o'ten appropriately termed the duodena/ fr^ands, are limited to the first division of the small intestine. Beginning at the PY^orua, where they are most numerous and extensive, they gradually decrease in number and 1640 HUMAN ANATOMY. size, being sparingly present beyond the opening of the bile-duct and entirely want- ing at the lower end of the duodenum. These glands are direct continuations of the pyloric glands of the stomach, with which they agree in all essential details. While, however, their gastric representatives are confined to the mucous coat, FiG. 1393. Surface views of mucous membrane from upper (.4) ar:d lower (ff) pan of ileum. showiiiK folds and soliur^ IvmDh- nodules. The velvety appearance is due to the villi. Natural siie. * " ~ "■'> '>"'P" Brunner's glands chiefly occupy the submucosa, the migration taking place at the pyloric ring ( Fig. 1 39 1 ) . The duodenum, therefore, possesses a double layer of true glands,— those of Lieberkithn within the mucous coat, beneath which, in the .submu- cosa, he those of Brunner. The individual glands, tubo-alveolar in type, form some- what flattened spherical or polygonal masses, measuring from .5-1 mm., which con- sist of richly branched tubules, ending in dilatations. Their excretory ducts pierce the mucous coat and open either directly on the free surface or into the crj'pts of Lieberkiihn. While narrower than the flask-shaped alveoli, the epithelium of the ducts is the same as that found in the deeper parts of the tubules. Ptc. 1393. The clear, low columnar cells lining the duodenal glands are proba- bly identical in nature with those of the pyloric glands, the varia- tions in size and granularity some- times observed depending upon differences in hinctional condition. Brunner's glands correspond to the pure mucous type (Bensk \ ). Lymph - Nodules. — the lymphatic tissue within the intesti- nal tube occurs in the form of cir- cumscribed nodules, which may remain isolated, as the solitary nod- ules, or be collected into consider- able masses, as Peyer s patches. The solitary nodules vary greatly in number and size, some Surface view of mucous membrane o( ileum. X jo. times being present in profusion in all parts of the small intestine, at other times almost wanting ; they are usually scanty in the upper and more numerous in the middle and lower parts. They appear as small whitish elevations, spherical or pvri- forni la shape, and from . 2-2 or even 3 mm. in diameter, at the bottom of small pits. THE SMALL INTESTINE. 1641 The walls of the btter, however, are so closely applied to the nculules that the exist- ence of the pit is not at first evident. Villi are wanting over the prominence of the nodules ; likewise the glands of Lieberkuhn, the orifices of which are arrannetl as a wreath aroiiiul the nmlules. Ihe Fio. T394. latter are ftmnd as much on one side of the intestinal tube as on the other. In structure the solitary noa.ph,Uci .««re.ati) are collections of solitary lymph-nodules, the individual follicles being blended by mterv'ening ^'l;^"""' 'f "•;• They are seen in the lower half of the small intestine, especia ly near the h.wer end (ileum) ; exceptionally they are found in the upper part of the jejunum in the vicinity of the duodenum. The patches appear as slighdy raised, elongated ovals. Fig. 1395. Suhmncous fold supportinR mucosa with villi Surface view of portion of mucoun mnnbnne at ileum, ahowing Piyers palcTand solitary lymph-nodutes. Natural ilze. Transverse section of ileum, showiiiK Pcyer's intch cut across. X 10. always on the side of the intestine opposite to the attachment of the mesentery. Their „sua! number is about thirtv, although as few as eighteen and as many as eighty-one have been counted (Sappey). In length they ordinarily measure from 1643 HUMAN ANATOMY. Mucous root Submucous coat 1-4 cm. and in breadth from 6-16 mm. ; exceptionally their length may reach 10 cm. or mure. In general the size of the patches increases as the termination of the ileum is approached. Each patch contains usually from twenty to thirty Ivmph-nodulcs, although as many as sixty or less than ten may be present. The individual nodules are commonly somewhat pear-shaped, .iid when well developed occupy both the mucous and submucous coats, their smaller end almost reaching the epithelium and their base the muscular tunic. The free surface of the patches is modelled by minute pits, from .4-2 mm. in diameter, and low intervening ridges ; the former mark the positions of the component nodules, the latter that of the blending internodular tissue. The villi and the crypts of Lieherkiihn are present over the areas between the pits, although less developed than beyond the patch. In their minute structure the lymph-nodes composing the patch closely correspond to the solitary nodules, the aggregated nodules Ik*- FiG. 1396. ing blended into a con- tinuous mass by the les.s dense adenoid tissue which fills the sfiaces between the individual follicles. The entire patch is defined from the surrounding struc- *'ires by an imperfect apsule. The submucous coat is lax, but not enough so to allow the gg displacement of the val- vulae conniventes, ex- cept at the lower part. As in other segments of the intestinal tube, the submucosa contains blood- and lymph-ves- sels of considerable size and the nerve-plexus of Meissner. The muscular coat, about .4 mm. thick, consists of an outer longitudinal and an inner circular layer. The latter is some two or three times as thick as the former and is pretty regularly arranged. The Transvcnescctionotinjectedsinallintestine.showingKcncraldistribulion. XS5. thin longitudinal layer, thickest at the free bor- der, is often imperfect, especially at the attachment of the mesentery. The entire muscular coat diminishes in thickness from above downward. The serous coat, with the exception of that of the duodenum, completely sur- rounds the gut except at the line of attachment of the mesentery, where the two layers of peritoneum diverge, leaving an uncovered space between their jjst large enough for the pas.sage of the vessels and nerves. Its structure resembles that of the serous coat of the stomach (page 1627), and includes the fibro-elastic stroma covered with the endothelium. The blood-vessels supplying the small intestine are distributed to the walls of the tube in a manner closely agreeing with the arrangement found in the stomach (page 1627) ; the same general plan applies also to the large intestine. The arteries, which pass to the intestine between the peritoneal folds constituting the mesentery, THE SMALL INTKSTINE. if•^^ aJter supplying the serous coat, penetrate the muscular tun.c to reach the submucos^ Within the latter branches arise which, in conjunction with those directly ^o^^•>> «'» durine the passage through the muscular coat, supply the muscular tissue. 1 he more Snportant knd larger arterial twigs from the vessels of the submucosa enter the murous coat, in which some break up into capillanes forming net-works surrounding the gland-tubules and supplying the muscular and stroma tissue ; others p;iss directly towards the villi, which they enter and supply by capillary net-works occupying he ^rioherv of the projections. The veins of the intestinal walls commence within the muc^ beneath the epithelium and, gradually enlarging :is they descend, U-come Uibutary to the larger veins within the submucosa. The l.-itter follow the arteries in their pMsagc through the muscular tunic, uniting to form the larger emergent venous channels which accompany the arterial ti unks between the peritoneal folds. The lymphatics of the small intestine. Umg known as the /acU-a/s \um their conspicuous milky appearance when filled with emulsifiecl fat dunng certain stage, nf digestion, begin as tlie absorbent or chyle-vessels within the villi, l" add.tu.n to these radicles commence within the stroma-tissue of the mucosa, in which the lym- Bimnch oJ imsenteric «nery. Mcsenterii- vein LymphiKKlc Lymphatics Nerves Cut edjfe of removed peritoneum f Portion of sm 11 intestine .nd me«ntery.,howinK .rterle., nerve, .nd lymphatic,: latter ta^^ quicksilver. Anleriiir layer of mesentery has been remo\eiorn» the hepatic artery, and the bile-duct 'T^ <^~N *'*'* ^^^ connective tissue about them. ^~^T" / ^^ /wVV i> '^ This structure is strong enough to de- .f ,,J^ i^*'^ k^W * '^ **'^* '" ^ *^'"^ ^ ligament. The ^' jl^ft^ I \. ^ j| Cr>^^ d- "^ duodenum is therefore nearly a ring sus- f^tj^'" I ^ fcy^lk ' "m P*"*^^ ^^ **" points, one near the ^^P^/fWtnA m jitf^itL "dr ''^^'""'nK and tne other (to be de- ^6fy«i(lv^r ^5^^l^ J scribed later) at the end. In the adult *^^H^m|P^ T^J B^ Jr ^^ shape is more or le!»s a modification ijpiBBM'^ ^>ts "" 'Ve'iicond ff XK^ends vertically. forminK an acute angle with the firs. It is bent so sharply that a fold of the entire thickness often projects mto the gut 1 fie^ .m ?he riKhtTicie of the vertebral bodies beside the vena cava, and IkIuiuI res son h^ right suprarenal capsule and kidney, being in contact also *•'♦^'he Ih^^'v;^ '•' J - btter the renal vein, ^d the beginning of the ureter The precise relations NMth The right kidney are Uncertain, owing to the variations both of that organ and of the duodm m It lies on the right against the ascending colon and on the left against fhe hl^Z the pancreas, which may overlap it in front. The b.le-duct runs along the left SldTe and pt-^ obliqiiely through the intestinal wall, to empty, m conjunction with the pancreatic duct, some lo cm. from the pylorus. S log ical. The mean of the female duodenun., m whK:h «x the \ -s U^attfe lower than that of the male, but not stnkinRly «>. Th*- uirU and the third^rts"" the U-form is rather Uss sharp than that betwe<.n .be , s it is opposite ,v«Ti- jirohably . mosl rei^uent, leen the second and the second. Mill Its front 'hi' Villa tv-nds to lird part . . jiiarter i >f ^se than thf es]xi-ially li a-, nds is tin list' -h. i Sitrfttr* The bird part curls around the spinal column, passing U>rv. then to the left with a slight ascent till it reaches the aorta. cava and has the pancreas above it. which, with the first and sect, enclose. The head of the pancreas may. howeve;, more or less o\ as it dfMis the second, and also insinuate itself behind it. In U >s Ui. the cases the third part crosses the aorta, its course being more trai one iust described. It may be connected to the aorta by areolar t.ss if it run only just beyond the aorta, a fold of peritoneum may interv. The fourth part usually begins at an obtuse angle with the thi. on the front of the spine to the top of the second lumbar vertebra. . it overlaps the aorta and usually ends either directly over it or just at fifty-four observations the duodenum was on the right of the aorfci unt; its final fle.xure twenty-six times. It was wholly on the right of the aort.i The fourth part lay in front of the aorta eleven times and the thrrt p u crossed it eleven times. It Is clear from the above that it is exceptional tor denum to reach the left kidney and ureter, but it may do so when it real the aorta The tail of the pancreas is behind it, as is usually a part of the U renal capsule. The head of the pancreas may be so develoi>ed ;ls to overlaj. this is rare The mesentery of the small intestine usually rises above on its troni face and gradually crosses it to the right. It may be very neariy siirround.. peritoneum, or the posterior surface may be without it. Sometimes, although r^ ihe last part stops short of the second lumbar. In the V -shaped duodenum th. . and fourth parts are in one. This form evidently is wholly to the right of th- . except, perhaps, the very end. It sometimes ascends along the right side of tl h. iliac artery, and then on the right or front of the aorta. The duodenum en. sharp turn, the duodeno-jejunal flexure. The very top of the gut at the h suspended from the left cms of the diaphragm and from the areolar tis.sue a^. he coelmc axis by the duodenal suspensory musele of Treitz, a small triangular v,„,l ot .nuscular and fibrous tissue, which reaches the gut where it « ""covered h> (K-nto^ neum and is sjiid to join the layer of longitudinal muscular fibres. This Land and the duodeno-hepatic ligament hold all the duodenum after the very beginning sus- pended and fixed so that only the beginning is movable. It is further secured by t«4A HITMAN ANATOMY. thf retro-peritoneal connective tissue and by the peritoneal reflections. The shape allows the food from the stomach as well as the fluid j>oured inii> it from the li\ir and [Kincreas to accumulate and thus to act as an S-lrap to prevt iit the pa**sii^e of ji;ises from the intestine into the stomach. At the same time the ^jreat dcv.* - neiii of the valves tends to retaril the |>assage (»f the fixxi. Peritoneal Relations. — The peritoneum of the front and l>ack of the ston..tcii is continued alon^ the ri^ht and left sides of the tirst p;u-t of the duodenum respec- FlG. Ijpq. RIkM lung Cut dia|>hniKni Hv;iatic veins K t^H iu|>rarcnal body. Caatro-hrpMtk onicniufli Pr'i)« In fiir&ntcn at Wln<.l<.w RiRht kidney B«KinninKU[. (luiMlciium Bc'KitininK of traiisvene c<>i*>ii^ Head of pai)rreaa_ Lefi luDfC Pericardium CavaloprnJii^' iti diaphraKni CE!K>phaKU!i Spleen Left ftupraretial body Left kidney Sjilenic flexure , ail ui panirrt-as •eft end of cut ■ttaiisverM colon .Jejunum SU|»erior mesen- teric artery X.eft mesocolon .Cut rt of mesentery SiKinuid flexure Abdomen of formalin subject : peritoneum partially dissected off, exposing or^pans $» si/m on posterior wall ; transverse loloii. mesocolon, mesentery, and jejuno-ileum removed. ti\ely. These layers meet above alonjr the jjreater portion of the first part lo form the lesser omentum, which ends posteriorly, as already stated, by forming the hepatico- duodenal lijfament, consisting? of the vessels enterinjr the portal fissure of the liver with their enveloping connective tissue. The free ed^e where the peritoneum passes behind the lijjament is on the inner side rather than above the ^t. Just back of this or <.f tht • .en ol Winslow. The aitachnu-nt ..I the urtaur fold the upper surface of omemum. which is continuev. irom the greater curvature of the stomach on o the under side of the duodenum, passes alonK its mkM-ior surface to the second wrt where in the adult it has .used with the mesentery cf the transverse, colon. The jari- roneunloi the ri^ht side of the first part of the duodenum l.K.ks nuo the general neriton.al cavity and that of th<- left side into the lesser cavity. •^ T relations of the rem;iinder of the duodenum necc-ss;inly vary with the dis- tcntion of the intestine ; but it is correct to say that it las iHh.nd the pntoneum oS to the change into connective tissue subsequent to the (usum oi the s.r us membrane of the riRht side of the duodenum .nd that of the p<«tenor aUlonunal wST Verv o ten when the fourth part lies in front of the aorta a ' .Id of jKrUon.um Ses some distance in between them from the lef. : hut ns l>'-^'^'/.»'*''»;»;;;';.;*'"^" SeRUt is distended. The pancreas, when it overlaps the second, th.r.l. or , n en the ourd^ part, more or less displaces the peritoneum. Ihe dumlenum .s c ossed by he attachment of the mesentery of the jejuno-ileum and by that o ^-^l^-^ rnesocolon. The series of changes by which this has occurred is dealt with unth-r Fm. 1400. Transvcrae oiooiuloii }tjanuin Uuodctmm tltUXK-Ilill ll'.--.1 BmiKli..! If ft lolu artiry inferior Hutwlenal f(H,lUl Dencc thug culuh Mesemery of small inustiiiv Duodeno-Wan.1 junction, showimt duixlCTal fo.s« ; i«)ununi turm^d to the right. Peritoneum (page 1742). the adult condition alone being hereconsidere.i The line oflttachment'of the transverse mesocolon crosses the second part of he duodenum a litde below the deep flexure which on the front separates it from the hrst. 1 he Dosition of the line of attachment of the mesentery of the jeju.io-ileum vanes with S^ sha^ and position of the duodenum. Should the latter have its third part crossing the aorta, the attachment ol the mesentery will cross the third part only, pacing somewhat obliquely downward to the right. In the more usual arrangement In which the fourth part of the du.xlenum either ends on the front of the Mot crosses it only just before its termination, the lint of attachment starts on the Iront of the fourth part or somewhat on the right of it and descends on more or less sometimes on the whole length of this portion, or else lies just to the right of it anti ?h«i crosses the third part. In the ca.se of the V-shaped duodenum the m.-sentery runs down on or along the right of the oblique portion. •. „ ,„ Duodeno-Jeiunal Fossae.— Several pockets farmed by folds of peritoneum are found near the end of the duodenum in the greater cavity of the peritoneum Some arc vascular.-that is. containing a vessel at or near the edge of the foul, while others are not. We have adopted the classification of Jonnesco, who descrit>e>s hve forms. 1648 HUMAN ANATOMY. 'l\\e inferior d dettal fossa (Fig. 1400) is the most common form, occurring, according to Jonnesco, in 75 per cent. , and to Treves in 40 p>er cent. It is non- vascular, formed by a fold of peritoneum passing from the left of the fourth part of the duodenum to the |K)sterior wall, with a free concave edge looking upward. The pocket extends down behind this fold for a variable distance. It may reach the fourth lumbar vertebra. The superior duodenal fossa occurs in 50 per cent. This corresponds to the preceding, only it runs upward behind a fold, with a concave free edge lookini; downward, passing from the duodeno-jejunal flexure to the posterior wall on the left. The pocket is less deep than the preceding. It is usually vascular, the in- ferior mesenteric vein running in the fold, sometimes near its edge. These two fossse frequently coexist, and the left ends of the folds may be continuous, so as to form a large C-shaped fold, oj.en to the right, with a pocket under both the upper and the lower limbs. In this case the vein may be in the vertical part of the fold. An arterial arch, formed either by the ascending branch of the left colic artery or by the left branch of the middle colic, is often very close to the vein. Such a pouch may extend deeply under the fourth part of the duodenum. The mesocolic fossa,^ found in 20 per cent., and always alone, is a little pocket on the top of the duodeno-jejunal flexure under a fold from the posterior layer of the transverse mesocolon. When th s membrane is reflected so as to show it, the fossa appears to run upward. The in- Fio. 1401. ferior mesenteric vein may be in the fold. The paraduodenal fossa is in the peritoneum of the posterior abdominal wall, less intimately connected with the gut than the others. It is a pocket formed by the superior branch of the left colic artery raising a fold of the perito- neum. The mouth of the pouch is to the right. It is not uncom- mon in the infant, rare in the adult. The retroduodenal fossa is an uncommon pouch under the third and fourth parts of the duodenum, extending upward with the mouth below. Interiorof the Duodenum. — The mucous coat is smooth in the first part and overlies the glands of Brunner (page «639), which lie chiefly within the submucosa and form a continuous layer for some 4 or 5 cm. ; beyond they are scattered for some distance farther. The villi are small at the beginning, but soon attain their complete size. The valvulae conniventes are at first absent for about 4. 5 cm. , appearing at the end of the first part, and are almost at once large, near together, and non-effaceable. A very large one is formed by the folding in of the wall at the junction of the first and second parts ; beyond this the valves at once reach their greatest development. In the second piart the bile-papilla is seen in the back part of the left or inner wall, from 8.5-10 cm. (about 3>4-4 m-) beyond the pylorus, or rather below the middle, through which the common bile-duct and the duct of the pancreas pass to open by a common orifice. The papilla is almost always overhung by a valvular fold (Fig. 1401 ), and when non-distended is only some 5 mm. long. The accessory duct of the pancreas often opens 2 or 3 cm. above the main one through a much smaller and inconstant papilla. The submucous coat holds the mucous membrane pretty firmly in place, so that the folds are permanent. ' Jonnesco calls this also the fossette duodeno-jejunale ; but, althouKh following him other- wise, we have retained duodeno-jejuiiat as the generic name. Surface view ol mucous membrane of duodenum ; entrance of bile and pancreatic ducts shown by probe, which lies in bile-duct. P.ipilia is surrounded by hood-like fold. .Natural ai«. THE JEJUNO-ILEUM. 1649 Fig. 1403. Abnormal fitrm and fourse of liuo- denum. (Sckiejfff) - deckrr. I Blood-Vessels — /^r/^r/W.-The duodenum, like the stomach, is attached to m^S %he heX artiy gWes oLhe pyloric, which sends some ins.gn.hcant S to he bepnning of the duodenum, and the gastro-duodenal. wW?h runs oTthe left of the first part ''"^ sends off the supenor nancreatico-duodenal. which passes downward and to the left m he concS of the duodenum between it and the pancreas, lymg rathro^ the front of the duodenum, of which t is the ch.ef artery. The superior is met by the inferior pancreat.co-duodenal artery whfch a^ from the right side of the superior mesenteric and d^cends along the right of the fourth part of the duoden"™ The superior mesenteric distributes one or two small twigs to the very ^"' t£ ^^rSoric vein.-larger than the artery of the same =u:gr:i?rp£^ft'e\i^e=^^^^^^ "'"?!;: S^^^-^hKo^uZr^^^^^^^^^ other parts of the small intestine, are from the solar plexus. higher, described a^loop to *« '«t tehma tnepemone associated with other errors there was a mesenterium commune. THE JEJUNO-ILEUM. The ieiuno-ileum includes the remainder of the small intestine which, disposed in folds atfa'ched on one side to the mesentery, "^ends from the ducxlen^^^^^^^ tn thp ra-cum its leneth be ng. therefore, approximately 6.75 m. ^nearly 22 u. ), 01 wh ch the fi«i wo fiffhs are conventionally credit^ to the jejunum and the remmn- W three fifths to the ileum. It is a cylindrical tube contmually decreasing in size. The 5 ameti« Ire variously stated. T«tut giving the mean diameter f the upper part as fTom 25-30 mm. and that of the lower as from 20-25 mm. These >=»ter figures Cur own measurements confirm, since on thirty-seven •"fl'"''^,-?-""^'" °' ''^^i";^ end the average diameter was 24 mm., the extremes being 17 and 37 mm Chaput and LenoHe' assert that the inferior circumference is reduced internally to 32 mm f on inflated specimens to 50 mm.) bv a valve near the cacum This valve, which te have found Tabout one-third of the cases, is remarkable in being always s.u- Tted on the posterior aspect of the gut. generally at a sharp bend ; it often contains a smal" arterrand is probably fon^ed by the folding in of the muscular coat. Its J^sTtbn S JrVntly neartheVint at which the ileum »-^™J«J-j;K„»Sime: wall of the cscum. but it may be 2.5 cm. or more higher. The valve is sometimes douWe. and Ws'in height f'rom 2 ^m. to t cm We have not o"nd. however that this fold is necessarily the narrowest point of this part of the gut. A p^ccc o^ the intestine from the upper part of the ejunum weighs more than one of eq"*' "ea rom thTlowir part of the ilium, owing to the greater thickness of the wal s o^he former and to the greater development of the valves •" that part. The structure of this part of the small intestine has already been descnbed (page 1634). ' Arch, fur Anat. iinfl F.ntwicklng., 1887. • Bull. See. Anat. de Paris, 1894. 104 t650 HUMAN ANATOMY. The Mesentery and Topography of the Jejuno-Ileum. — Since consid- eration of the mesentery is indispensable for the study of the disposition of the folds and relations of the small intestine, this structure next claims attention. The serous covering of the gut itself requires no further description than to note that it com- pletely surrounds the bowel, except at the double line of its attachment, where there IS left space just large enough for the passage of the vessels and nerves. The attached b«>rtler of the mesentery (Fig. 1399) extends from the left of the tront of the first Fio. 1403. Right lungf. DiaphraK'n (cut)- Hepatic vein Behind Spigeli lobe RiKht suprarenal body. Probe in forann of Winilow Right kidney. Beginning. of duodenum Left end nf, transverse colon Duodeni Jejunum Ascending colon. Ileum. Left lung ^sophagtts ipleen Left suprarenal body Lt^t kidney Formalin subject; liver, Momach, transverrc mefiorolnn. and colon ha\'e been removed, leaving other abdominal organs ih situ ; attachment of ^ iit (teritoneum tmlicated by white linu. or second lumbar vertebra, immediately below the end of the duodenum, where the superior mesenteric artery enters it, to the right sacro- iliac joint, a distance of about 15 cm. (6 in. ). The relations of the upper part of the fold are determined by the shape and position of the duodenum. Probably the usual course of the mesenteric attachment is from the front of the aorta downward on the fourth part of the duo- denum, across the vena cava to the right sacro-iliac joint. With a V-shaped duo- THE JEJUNO-ILEUM. l65» denum the line of the mesentery is usually on the right of the gut ; with a duodenum that crosses the aorU the line is across the third part. The lower end of the mesen- terv is determined by the degree of adhesion of the right mesocolon to the alxlomi- nal wall. It rarely stops short of the sacroiliac joint, but it may be continued farther into the right iliac fossa. The free or intestinal border of the mesentery is some 6 m. or about 20 ft. long. In the middle the distance between the borders is from 20-22.5 cm. (»-9 in.). Near its origin, in the first si.x inches of the intestine, the mesentery h;>s reached a breadth of from 12-15 cm. (5-6 in. ). At the lower end its breadth is more uncer- tain, being usually slight, only from 2.5-5 cm. for the last six inches. It increases with age, presumably concurrently with the increase of girth. The mesentery con- tains vessels and nerves as well as lymphatic nodes between its folds- these stnic- tun-s may lie in a considerable mass of fat, adding to the thickness, which is much greater, on account of the size and number of the vessels, m the upj)er part than m the lower. The larger lymph-nodes and .he fat accumulate chiefly near the Fio. 1404. spinal border, where the mesentery may be very thick and heavy, while the part near the intestine, except in the case of excessive fatty accumula- tion, is always thin and yielding. It is evident that the mesentery with an attached border of only 15 cm. (6 in.) and a free one of 6 m. (20 ft.) must be very much folded ; and further, that while the intestinal border must pre- sent a vast number of totally irregular and transitory folds, changing with the movements of the gut, the heavier and more fixed part of the mesentery near the root must present certain chief folds the position of which is tolerably stable. Henke ' has shown that if the hand be introduced among the coils of intes- tines in the line of the left psoas muscle and carried upward, it enters the con- cavity of a horseshoe- shaped fold of the mesentery, and that the intestines easily fall apart to either side. The coils on the left are in the main transverse and those to the right chiefly vertical. This ., „ , • 11 ;„ ;„»,„». clan although sometimes obscure, is often beautifully clear especially m infants. Weinberg ' from studies on the new-born infant, has carried the plan into further details. He finds that the upper two-fifths of the intestine are arranged in trans- verse folds in the upper left part of the abdomen : the middle fifth lies in the left iliac region without definite arrangement ; the last two-fifths are in the median part and in the right iliac region, disposed in the main vertically Still, cases occur at all ages in which the plan is obscure. Mall* has traced the plan of the intestines throughout development, and incidentally confirms Weinberg s state- ments The following account of the normal arrangement in the adult is essentially according to his researches. The gut is to be conceived as arranged in spiral coi s travelling from the left hypochondriac region to the right iliac fossa, successive coils being in 'le main parallel. Starting from th. iuodenum, there are two transverse folds in me left hypochondrium, followed by long fold that goes across the body and back. Some less distinctly transverse fol.ls occupy the left iliac fossa. Ihe ' Arch, fiir Anat. und EntwicklnR., 1801 ' Internal. Moiialssi-hrih fiir Anat. und Ph)-8., Bd. xiii., i^. • Arch, fur Anat. und Entwicklng., 1897. Supplement Bd. Typical ilisposilion of folds of m»entery shown after removal of jeiuiio-ileum. i. end of rtant. if not the chief, factor ,n the l>rt''».ted with teXness of the surface of the'abdomen, or with ng.dity of the abdominal muscles and is usually relieved by firm pressure. -supporting and contr. Uing the Xtel' s^nent of gut. The abdominal wall may be moved freely oyer the under- lying viscera. It mav thus be 'Vstinguished from the early pain of peritonitis. ^ SL greater thickness of t ner^ircular-coat causes longitudinal wounds to gape more than transverse 01 The latter are more apt to gape if they are at he frerborderof the gut. where ... longitudinal hbres are most numerous. As the muscSr coat in itf entirety lessens in thickness from above downward, wounds of L jejunum gape more than those of the ileum Intestinal P»l«=tures usually, and very small wounds not infrequenriy. are closed by muscular action, so that healing SXe without extravaktion of intestinal contents. Sljghdy larger wounds ma^b^ stopped bv a plug of mucous membrane. This is favored in the u,^er 3on of the tube'bv the presen-e <.f the vah'uhe conniventes and in the lower part W the bxity of the submucosa. This eversion of the mu. ous membrane, caused by muscular contraction, must always be overcome in the suture of intestinal wounds, since the mucous surfaces will not unite with each other. . 1 The mucous and submucous coals and their contained glandular and vascu- lar structures are subject to many varieties of disease. I catarrhal mflammaiwn affecTthe mucosa of the small intestine, it is apt, if locali^ed in the duodenum, to be associated with gastritis and to extend into the bile-ducts causing jaundice If fn thele uno-ileum,''it may be mistaken for colitis ; usually, if in the s'-nall intestiiie the diarrh.^a is less marked, the colicky P='i"^='^« R'-^=«»^'-;.»^,;.'^^y«"\' I* ,^ 'T,^!' less mucus is found in the stools, and tenesmus is absent Neither d''odemt.s e,u- nitis, nor ileitis can, however, positively be diagnosticated from one another or from general intestinal catarrh f Osier). ., „i ,a, r^l Ulcers of the duodenum are in the vast majority of cases ( 242 oJt of 262. Lol- lin quoted by Weir) situated within 5 cm. (2 in.) of the pylorus (the mcr. movable portbn of the duodenum) and are most often on the =»nterior wall, especially its n" side. The peritoneum of the right side of the f^rst part of the duodenum looks ,Uo the general peritoneal cavity, and of the left side into the lesser cav.tv( page ■ 647). When petlforation follows, the general peritoneal cav.ty is therefore .key to be in ected. and the death of one-half of the subjects of perforating dut.dcnal ulcer K,m general peritonitis is thus accounted for. The second part of the duodenum is i654 HUMAN .'NATOMY. in close relation on the lower part of the right aspect with the liver and gall-bladder, on the upper part of the left aspect with the head of the pancreas and foramen of VVinslow, and posteriorly is pardy uncovered by peritoneum and rests on areolar tissue and the common bile-duct. The general relations of the duodenum (page 1645) explain the remaining lesions following duodenal ulcer, — e.g., perforations into the gall-bladder, liver, or colon ; opening of the hepatic artery or the aorta, or of the superior mesenteric 01 f)ortal vein ; or the development of subphrenic abscess. As compared with the symptoms of gastric ulcer, pain is apt to be lew on account of the relative immobility of the duodenum ; vomiting after feeding is later ; hemorrhage is often greater on account of the larger vessels that may be involved ; bloody stools are more common, as is jaundice from the involvement of the bile-duct. In exposure of this part of the duodenum it is well to remember the suggestions of Pagenstecher (quoted by Weir),— viz., that the fundus of the gall-bladder when distended lies in front of the duodenum ; that by raising and drawing forward the transverse colon, which lies in front of and below the horizontal portion of the duo- denum, the tirst portion is revealed ; and that by pushing the stomach and pylorus to the left and elevating the liver, access to the region of perforation may be gained. In emaciated patients with contracted stomachs the duodenum may be found lying above the level of the transverse colon. Infection through the mucous coat has already been spoken of. If of the tuber- culous variety, it affects chiefly the lower part of the ileum, and tends, as is charac- teristic of that disease, to follow the course of the vessels which run from their entrance at the mesenteric attachment transversely around the gut. If such ulcers cicatrize, they are therefore especially prone to lead to si ricture of the intestine, a very rare sequel of typhoid ulceration, which, affecting the same portion of the small intestine, extends in the line of the agminated lymph-nodules, — i.e., longitudinally. The tuberculous ulcer sometimes produces a slow general peritonitis, rarely a local- ized abscess, much more rarely an acute perforation with general septic peritonitis, as the process is so slow that protecti\e adhesions to neighboring coils of gut or to the parietal peritoneum have time to form. Typhoid ulcers cause perforation in 6. 58 per cent. ( Fitz ) of all cases. The large majority of perforations occur in the ileum, most of them within 60 cm. (2 ft. ) of the ileo-cacal junction. In operation this should therefore be sought for and the ileum followed upward from that point. The ulceration may so thin the intestinal wall as to permit of leakage and the production of general peritonitis without actual perforation ; or it may be accompanied by such an extensive exudate as to make the ileum palpable, a condition which, in conjunction with localized tenderness and abdominal rigidity {vide supra), has led to many mistaken diagnoses of appendicitis in cases of typhoid fever. Syphilitic ulceration of the small intestine is rare, but is said to be most frequent in the upper portions ( Rieder). The lymphatics of the mucous and submucous coats empty into the mesenteric lymph-nodules (page 1643) and convey to them various forms of infection or disease, — typhoid, carcmomatous. tuberculous, etc. The veins emptying into the vena porta through the superior mesenteric are likewise channels of infection, ulceration of the biwel sometimes resulting in abscess of the liver. Contusion and rupture of the small intestine are favored by its exposure to trauma through its close apposition to the abdominal wall, which, if relaxed, offers but little protection. The interposition of the greater omentum with its con- tained fat is a slight safeguard, but the movement of the coils of gut upon one another and their elasticity are of much more value. Contusion here, as elsewhere, may be followed later by infection and ulceration. Traumatic rupture is much more frequent in the jejunum and ileum than in any other portions the alimentary canal (of 219 cases, 79 per cent, were in the small intestine, 11. 5 lei cent, in the colon, and 9.5 per cent, in the stomach, Petrv). The duodenum suffers very infrequently on account of its sheltered position ; other- iitering layer Intussusceptum PRACTICAL CONSIDERATIONS: THE SMALL INTESTINE. 1655 wise its lower portion-the most fixed part of the intestine-would P^obabl>' be more ^n in ur«l The upper portion of the e unum, which partakes somewhat of this Sffv T^re commoK ruptured than any other part. So, too. the m,.st fixed Srt^^f the «eum-Ta° nLrest the ileo-c*cal junction-is most often the site of rup- rS An inTcerlted or irreducible hernia may constitute a fix«l point ..f the gut i„a favor iB^Sure elsewhere from trauma to the surface of the abdomen. RuDtu^ero the imestin. , like wounds or obstruction, are more serious he W kS tCv^re si uat^ The nervous disturbance and shcK:k are Krcater, possibly •"If Jcounr of the moTe' immediate relation of the lesion and of the rt;sult.n« p^«tho- on account ot the "T^ L^p^'"; , ^^ ^r to the pericardial jjortion o. the dia- 'SLtcrU:) vomitfnfbS ns eTrlier^nd il morJ^severe for\he s^me reason ; tract Investigation has shown (Cush- ine and Livingood. and later Lorrain Fto. i4o<. Smith and Tennant) that the bacteria flora in the upper portion of the intestinal tract is moic scanty than in the lo\yer portion ; and it is true that peritonitis following intestinal wounds, operative or accidental, is dependent for its charac- teristics upon the bacteria at the site ot lesion, and that the prognosis should be favorable in proportion to the scarcity and innocuousness of the micro-organ- isms present. But the anatomical con- ditions, by adding to shock, favoring intestinal extravasation, and minimizing the chance of a reparative peritonitis, are more than sufficient to counterbalance the relative dearth of bacteria. It should be remembered that the position of the wound or contusion on the surface of the abdomen is of but slight value in determining the area of gut in- volved Thus, a jejunal fistula following ''''^^::S'oi the small int^tinemav be due to^r^/J;.^ Si^l^^ intestinal concretions and gall-stones ^h^t ha^-e vOccrated in o the ^»^^^ J;^ „, is then most apt to occur at the '1«"-'=*'^='V ^nnLirtioT of a -oil or knu.kle the canal at that point : (*) ianJs pr"duang -"^^^l^'^^^ ,^ .,,i„„, p,Hto- of gut. such bands arising from the elongation "« ^^l^f J?"^. ^ ^verticulum (page nitis. from inflammatory attachment of the '7^^^^"^,'^* f^"„^^^^^^ through ,652). of adventitious diverticula (from P''^.^'''>'^.y^l"^^^Z appendices the muscular coat), or of the appendix Euher the p^^^^^^ pp^^^^^ epiploic^, the omentum, or the mesentery m^^^ uberculous ulcer in the ileum or Intussuscipiens L»tiKil"<»i'>al section of intussuscepted K«t. ** layers. AhowitiK I6s« HUMAN ANATOMY. ileum when its mesentery has been elongated by prolonged stretching, as in the presence of an old hernia (Maylard); (<•) internal hernia, as into the ducKleno- jejunal, perioecal, or intersigmoid fossa, or through the foramen of Winslow .,r through an aperture in the omentum (page 1758), which may be traumatic or may be one of the rounded openings due to congenital atrophy of a comparatively viis- cular area of the mesentery of the terminal portion of the ileum and embraced w-ithm the ileocolic artery and the lowest vasa intestini tenuis ; (/) hemite throiijfh the usual hernial apertures or regions of the parietes (page 1762); {g) intussuscep- tion, one form of which is due to irregular contraction of the circular fibres of the muscular coat, so that as the peristaltic wave passes downward a segment of gut, made smaller by this contraction, is forced into the portion immediately beneath it! which IS of larger calibre as a result of having failed to contract at the proper time ; {h} pressure from without, as from tumors, which, as they must meet with counter- resistance and relative fixity of the gut to produce constriction, most often affect tl.- duodenal (as in cancer of the pancreas), upper jejunal, or ileo-cacal segments- (t) Pentonitis, the relation of which to intestinal obstruction will be subsequently explained (jwge 1756); 'J) tumors of the intestines themselves, not very frequent iii the small intestine, but most often found at its two extremities. The position of the different portions of the small intestine varies greatly. The lower end of the duodenum, the upper end of the jejunum, and the lower end of the Ileum are the most fixed points. A description of the normal arrangement of the coils of the jejuno-ileum h;is been given (page 1651). Of the duodenum only the first portion has lieen found involved in internal herniae. The more or less vertical coils of the jejunum, and especially those of the terminal portion of the ileum which occupy the pelvis when the bladder, rectum and sigmoid are not distended, are those most \ikc\y, for a priori reasons, to be found m inguinal or femoral enteroceles, but clinical evidence in support of this is not conclusive, fn umbilical hernia the jejunum is apt to be involved, and the gravity of this form of hernia, when strangulated, is supposed to be partly due to this fact as well as to the effect upon the circulation of the constricted coil produced by the sharp edge of the cicatricial tissue which surrounds the openine and aggravated by the downward pull, through gravity, of the remainder of the intestines. When the stomach is full the intestines are depressed ; when it is empty thev rise, so that in the left hypochondriac region they may be in contact with the dia- phragm. If the colon is distended, the small intestine can occupy but little of the lumbar, epigastric, or hypochondriac regions. Conversely, if the small intestine is distended it may so fill the pelvis and compress the rectum as to prevent the pas.sage of a tube or bougie into the sigmoid, and thus give rise to a mistaken diag- nosis of obstruction at that point. If the spleen is enlarged, they are carried down- ward and to the nght ; if the liver, downward and to the left ; if the bladder or uterus, upward. In ascites they are above the fluid, -/.p of intestine out of the abdomen so that u.th the loop oLailel wUh the long axis of the body, its mesentery is stretched an.l s ra.ghtened Hs^y to determine which is the up,,er end of the loop, and so to follow the gu eitheMoVards he dumlenum or the c^um. as may Ik- dc-s.red The fng-r should L p^ down to the spine, keeping in close contact with the mesentery ; f remat^n one side until the posterior attachment is reached, .t is evident hat hTret no twistof the loop and that its up,K.r portion .s normally the portion nearest the Stomach. As Jp after Ux.p is examined, .f the mtestn,e ka.ls m an unwS direction the color becomes pal.r. and the walls become thicker own g to the vE.- con^iventes and to the increase in the submucous and ■^•«^"J»^ ^^^'^^ ,.^„^ Oti,> r methods of locating with accur.icy a given coil of lx>wel are ( i) bv m. ans of the length of U^e vasa rect^ (3-5 cm. in the upper and i cm. or less .n the lower «>iSonr (2) by the vascular loo^ from which the vasa recta originate, which are Sa^ in the first four feet of th^mesentery. Secondary U^ops appear as we g.> farther down until in the lower third there is a net-work of .>ops ; (3 by the loops or ■ kinetre^" rt the intestinal attachment of the mesentery. »--t v.s^le by trans- mitted liffht Below the first eight feet these lunettes disappear (Monks) ?SofoJr-ior temporary relief of obstruction or distention or for the removal of a fordgn b^y-i« done at'as Iowa point as circumstances permit, through a transverse incision at the part opposite the mesenteric attachment. F^rZoZ-L establishment of a permanent fistu a f..r the purpose if it is a /«•««; /?mo7 feeding the patient in cases of obstruction of the alimentary tract ^tovTi openingTor if it is an i/roslom; of relieving fecal accumulation m cases of otetructZ It a ower point-is done by suturing the selected knuckle o gut to i^S peritoneum by a double" line of sutures and openmg the l«wel between ^^^"^En/er^rtomv and .ntrro-anastcmosis (either lateral or end-to-end) require for their performance, so far as anatomy goes, application of the facts and principles to which reference has already been made. THE LARGE INTESTINE. The ireneral plan ut the large intestine has already been given (page 1617). It is easTlv cuSirhed from thefmall intestine, not so much by its greater sue as b> '^'^heTSof'-'the^tS i^ntirefr'o^XrroTrhrappendix to the beginning of thlrlctuS is? according to Treves, about ..4 -. (4 ft « - ) - ^^ '-" ^.^ " (^\n \ less in woman. The extremes were 2 m. (6 ft. 6 m. ) and i m (t, it. 3 m. )• ^xldinTthe duld part of the rectum, the capacity decr^ses from .d>ov. Ow.rig both to variation and to occasional cases of «'''^-"'-,'^°"';«^;„'%=V" in to .1 cm tention the diameter is very uncertain. It may vary from 7 cm. ( 2^ in ) to 3- 5 cm. (i*Tn) without the more extreme figures implying a pathological condi o„^ * Structure.-The mucous coat of the large intestine agrees in its essential structure with that of the small gut, consisting of a stroma resemb mg adenoid t.ssi.e covered by as ngle laver of columnar epithelium exhibiting a cuticular border. The chef difference on the other hand, is (he absence of villi, in consequence of which Sr velvety appearance imparted by the latter is not seen in the large intestine^ VrivuirconniVentes are also wanting, although there are P';"J-.'^t>""5,.>";" f^ '^^^f;^ ffu involving all or a part of the coats internal to the serous tunic. Tne muscularis ScosL IrKegular'^in its development, being feebly represented in the colon and "^'^?KLS'^';iS;^"in general resemble those of the small intestine, but are lal^ger (about .45 "im. in length), and form a more regular and less inter- 1658 HUMAN ANATOMY. nipted layer of parallel tubules. The largest ones are in the rectum, where they measure 7 mm. (Verson). The lining of the glands is conspicuous on account of the great number of goblet-cells, which in the middle and upper parts of the tubules Fio. 1406. iig or Liebtrrkiibirs xtaridi. often exist in such profusion that the ordinary cells are almost entirely replaced ; towards the deepest part, or fundus, of the glands they are comparatively infrequent. The presence of goblet-cells in such numbers accounts for the considerable amount of mucus normally poured into the large intestine. Fio. 2407. Litfberkufan's j{!andS' Solitary lymph-nodulc. Murr>uo. Muro« ol lar« intmiline sectioned parallel to free .urfice^-vJini Lieberkuhns ulands cut croMWise; Xtd'^jTmtJyb, intervening .tromaof mucous mem- brane. X W5- Fio. 1411. Peritoneal coat i_Adipose limue Artery Portion of descendine colon, somewhat 'l]»«"f|^;?J"»' ing sacculations. lOTM, and epi^Io'i appcntw Longitudinal section of epiploic appendage. fii';r=J:.ss^r.xr»^^^;£^^^^^^^^^^ i6te HUMAN ANATOMY. Maroutcual The mutCttUr coat consists of a thicker layer of interna] circular fibres and of an pxternni lonK:itu(linal one, the fibres of which are in nu>st places collectetl inl.. three bunds. Although lon^itudinul fibres exist between these, they are few iiixl apparently not quite universal. Beginning in the c*cum, :it the Ul^M.■ i.f the vcrnii form appendix, the three bands, or titHiu coli, continue alonjj the large intestine as far p,g as the sigmoid Hexure, over whiili and the rectum the hands an- only two, and no longer sharjiy defined. In the rectum ont- is on the front and the other — the stronger— behind. The circul.ir fibres increase very much tow ards the end of the rectum, the muscu- lar apparatus of which will reci.i\ e special description (page 1675). The aeroua coat which once surrounded the gut, in certain places disappears during de\el<>p- ment. and in others its arrange- ment becomes modified by now relations with other peritoneal layers. These features will be described with the parts con- cerned. In structure it corre- sponds with the serous coat of other parts of the intestinal tube. The appendicea epiploicae are little fringes or bags of perito- neum containing fit hanging from the large intestine. They may be as much as 2. 5 cm. ( i in. ) in length, and are very prominent in fat subjects, but in thin ones may be overlooked. They are found particularly on the inner aspects of the ascending and descending colon and on the lower one of the transverse colon. It is often stated that they occir along one of the bands, but this relation is at least not constant, although they are generally arranged in a single line. They are found al.so on the sigmoid flexure. It is usu- ally stated that they are not pres- ent during childhood. Oddono.' , ,, , , , , however, has shown that they ap- pear m the fifth month of fcetal life, first on the descending colon and sigmoid flexure. We have seen them before birth. The blood-vessels, lymphatics, and nerves of the large gut in general oilow the arrangement already described in connection with the small intestine (page 1642). THE C^XfM. The caecum, or blind g.it, the first p.irt of the large intestine, is a pouch haniMnu downward at the junction of the ileum and colon, fro-.T> which the vermiform appendix arises. The ileum opens into the large intestine ' a transverse orifice placed in- ' Dal Bollettino della Societe Medico-Ch ,. a di Pavia, 1889. Serous cctal Transverse section of injected larite intestine, showing .listribution of arteties to coats. > 30, THE C/ECIM. 16'Si Anterior band AKrixlitiK loi.jti temally and somewhat pmtcriorl> . Fn.m the t..|. <.l th.- ileum ;. deep furr.«» p.-;^ Seiorlv |«rtly ar..u.ul the RUt. ami a U-hs ...ark.,! onv h louml .n l...„t. ffioZh starting a. just .tated.\he furnm. at once .' a lutle, ... a. t.. rq.rc-- «nM uly the mUUIle l.f the orirtce. Th.-,^- .erve a, . .nal Unnulary Utween t^e c*cum ami the colon. « hk h are much alik, r . naracter> The averaKC K Tthe aecum in the a Berry : The Anatomy of the Caecum, Anat. Anzeiger, Bd. x., 1895. IWum R«Kinnir ; ■> terior wall rerii form appendix. ,, aomewhat inflatrd ; (mrt nl an- ..^aecml valve ami orifice o( vt-rmi- ififia HUMAN ANATOMY. specimens, is as follows: average of upper segment 25 mm., of lower 33 mm. The largest pair was an upper of 37 mm. and a lower of 44 mm. : the smallest ol 12 mm. and 3 mm. respectively. The last, perhaps, was pathological ; the next smallest was 14 mm. and 19 mm. We have seen a caecum with the upper seg- ment entirely wanting. The absence of both has been observed. The average length of the ileo-c£ecaI opening on 30 similar specimens was 31 mm., the e.\trenies being 46 mm. and 21 mm. It is probable that, o» ing to the shrinking of the tissues, these dimensions of the opening are excessive. Although the lower fold is the larger, the upper overlaps it almost invariably, so that when the valve is closed the two edges do not come in contact, the orifice being closed by the application of the lower fold to the under surface of the upper one. Inflated specimens show that the upper fold is tense, while the lower remains flaccid. .Much difference of opinion exists as to the completeness of the closure of the ileo-crecal valve, and experiments do not agree. If the experiment of injecting water or air from the colon be performed in situ, the closure is more likely to be perfect than if the parts have been removed. These experiments, however, do not represent the true con- FiG. 1414. AscemliiiK colon Anteritir hand lleoHTarcal artery — ■ Superior ileo-ca-cal fossa Mesenlery Meso-appendix Vermiform apjieiidix/ Ceecum and related structures seen from the left. Ileum Appendicular artery ditions during life, since the tonicity of the muscular fibres of the gut is lost, and, ill tlie opened abdomen, the pressure of the viscera on the end of the ileum is less than normal. In life the valve probably is efficient. The orifice of the vermiform appendix is very variable. In some cases the cipciiiii narrows to it so gradually that it is hard to say where it begins ; in others it fjegins suddenly with an oval or round opening measuring from 5 mm. or less to I cm. or more. The valvr w hich often is found at the orifice is not usiially a true valve, but the projection made by the wall at the union of caciini and ajipen- dix in the entering angle when it arises obliciuely. According to Struthers, there is nf) valve when it arises at right angles. Owing to its usual upward course, the fold is most often on that side when present. We ha\e seen a true valve as a small independent fold ; usually, however, there is no effective guard to the entrance of the appendix. Position. — The ca- .m is situated in the right iliac fossa, resting on the iliac fascia covering the ilio-p.,o; muscle, above the outer part of Poupart's ligament. m THE C^XUM. 1663 about half below and half above the level of the anterior superior iliac spine. Sorne- S^infe to the shortness ..f the ascending coon, the cu-cu.n rc-mains in the S'isition under the liver, or it may be arrested at any p;irt of its descent. It Sra?d "hangs down into the pelvis, and when the lower part u the >"esemcry is "onV particulaVly if the lower part of the ascending colon be not attached to the n^fmor wall it may be very freely movable. In cases of „usenUr,nm .ommune K 1ms to be no anatomical reason why it should not be anywhere I he c^um^ sometimes turned up over the lower part of the ascending colon but ue c^not aeree with Curschmanns ' statement that this is not rare In these cases the aCndffriseT^^om near the highest point of the c*cum. VVe have seen the cecum fn The pmbtlTcal region with two vertical coils of small intestine occupying Mk- right "^"''structure.-The description of the structure of the large intestine already given (page 1657J applies in general to the aecum. Its mucous membrane, like Fig. I4I5- Lymph-nodules. Lieberkiilins ttlands Groups ol tal<«ll8 Mucous coat Submucoua tiuue LonKitudinal section throuRh lunction of appendix with circuni. V n. that of the rest of the large intestine, has no villi. This change occurs near the ma gS of each segment of the ileo-ca-cal valve, the villi gradually d.mm.sh.ng and finally disappearing before the free edge of the folds is reached ( La nger). The KndLf lo^n^ntudinal muscular fibres always en.l at ^h^" ^ase of the aprn-^^^^^ the precise manner of their termination is uncertain. According to .Struthcrs eac^i band bifurcates as it approaches the appendix, and the divisions, meeting hose o the others, form a ring around a weak spot close about it. .\ccord.ng to Told the ring is formed by the circular layer. The arrangement is not always ^''''^ «" "^S incline to think the latter the more common. The coats of the ca-cum ■''r- «" """^ in the appendi.x. The lumen of the latter is small, except near the entranc. ..nrt the walir may be in contact. The lymph-no.lules of the appendix are exce«l.ngly numerous and large, in places fusing into masses of considerable size, which en- > Deutsches Archiv fur Klin. Med.. lUl. liii., 1894. ' EdinbufKli Mediiat Journal, 1S9.V • SitzuHRsber. Acad. Wissen., Wien, Bd. ciii., 1894. 1664 HUMAN ANATOMY. croach upon the mucosa and its glands to reach almost the free surface. The la)-er of circular muscular fibres is i mm. thick, or abom twice the thickness' of the lon- gitudinal one. Both layers have interruptions, so that the submucous and subperi- toneal layers are in places continuous. This occurs particularly along the insertion of the fold of peritoneum called the mesentery of the appendi.x. The vermiform appendix (processus vermifornis) is a long, slender, worm- like diverticulum from the ca^um, formed of all the coats of the intestine. Its length varies from i cm. (^3 in.) to 24 cm. (9^3 in. ;, the average being probably about 8.4 cm.' (3^ in.). Monks and Blake,' Irom the records of 641 autopsies at the Boston City Hospital, give the average length as 7.9 cm. (3 in. », with the extremes as above. Berry finds that the appendix is on the average about i cm. longer in Flo. 1416. Longitudinal muscle .Circular muscle OI>liquely cut glands Submucous coat Transverse section of vermiform appendix, x 12. the male ; others find no particular difTerence. The diameter at the base is 6 mm. and at the apex 5 mm. Its usual origin is .i .n the postero-median aspect of the cecum. According to Berry, this occurs .11 more than 90 per cent., the point of origin being i . 7 cm. distant from the end of the ileum. This is very important as showing a relatively fixed point of origin, as the general direction of the appendix is very uncertain. That of the distal half especially is largely a matter of chance. Moreover, the position after death is, except in certain cases, no guide to that during life. The appendix is attached to the caecum and to neighboring structures by a |>eritoneal fold to be descrilied later. If this fold be long and narrow, the movements of the appendix are much restricted ; if the base of the fold be short and its attachment to the a|)pendix a long one, the appendix is thrown into coils. ' Fawcftt and Blatchford (for the avt, „v! length) : Proceetlings of the Anatomical Society of Great Britain and Ireland, Journal of Anatomy and PhysioloR)-, vol. xxxlv., 1900. ' Boston Medical and Surgical Journal, Noveinber 17, 1902. THE CiCCUM. 1665 Thi, to a ereater or less extent, is the normal condition. There is no doubt that in 7he .^iSt Srity of cases the appendix is wholly behind the c«:um meswl to it or^iTt Monks and Blake fiund a reference to this point in the records o «2 autoi It was 'down and in" 179 times, "behind ' with no statement o the dSrio4 times, "down" 79 times, and "in' 62 Umes. Jhus in almost hree-qSers of the cases it was in one of these positions It ran ".»P 5^ tirn". •uD and in" M times, and "up and out" 29 times. n (, cases it was out. Sly in 18. on the right of the caecum m 19. and behind it in 75- ^oUl absence ofihe appendix is extr,^ely rare, but has been observed by ourselves and others. ni.ii..,.ti«n of the C«Tlty of the Appendix.— The adenoid tissue of tiie yermiform ap- Coinadent with this at^Wj^y '!.A,''D2'^i}" Ribbert* found in 400 specimens more or f»iS„-i5.^'S2r^& ^^:rIiBr^i^ cW^e After fifty it occurred in more than »>r«r cent He found^^ver^^^^^^ ^^i'^^^^ SrfT 2w'°™endix is in no way connected with it. only a small fold of peritoneum passing from the ileum o die cJcum at the side most removed from the mesentery. Berry found this fossa in 74 P"^^"yj^j^Q.^.Qiig Fossa.-In the great majority of cases the fiosterior sur- face of the c»:um lies free in the abdominal cavity, covered by its original peri- toneum At a variable distance from it the back of the colon becomes adherent to he ^terior abdominal wall and to the front of the right kidney = h«n;« /h^^.'*; or may be especially if the colon be drawn away from the wall, a fold on either side stretching fr^^he gut to the wall. These are the ligaments of the colon, the exler- SSheintemJ The former runs outward and downward from the side of the ^ion along the abdominal wall, or perhaps across the lower end of J- J"d"^y ; "•^'^ presents a free concave border overhanging a pouch running upward and outward The internal or mesian fold is the more often distinct, and is formed chiefly by he inser ion of the mesentery. According to its degree of development, the free ale - form edge overhangs a pouch, looking downward and ";'ore or Jess o the right^ The fold may be continued downward either to the right or to the left. In the former case it may form a pocket, of which the lower end opens upward. It is cH th^dore.^tet with boththese folds well developed a retro-colu fossa exists wS is shown when the caecum is turned up. Its greatest depth « in the middle be£d the colo* and it is continued downward on either side under the folds caused by these ligaments. Should either ligament be wanting there can be no Lid on that side. Some authors have thought it best to describe an external and an internal fossa under each of the ligaments, of which the internal b the more fre- quent ; it is more simple, however, to dercribe only one. The f<«sa may be sub- divided by a median fold. Very often there is 1 ,0 definite fossa at all. The internal part is more commonly well developed than the external. „^ .„„„,;„,« The subceecai fossa is an uncommon pouch, sometimes small and sometimes large, situated above the middle of the iliac fossa. It seems to be due to an irregu- lar development of the iliac fascia, which forms a pocket in itself, with the mouth above, guarded in front by a semilunar fold. The fossa is ined by the parietal peri- toneum It may unite with the inner fold of the retro-colic fossa, or the two may exist at the same time. It may contain the appendix, even a part of the c«:um. or. according to Jonnesco, coils of the small intestine. . ^ ., ,. l t. Blood- Vessels.— The artery supplying the cscum is the ileocolic a branch of the superior mesenteric artery, which sends to it both an anterior and a larger posterior branch, which ramify downward over the front and t«ck of the caecum A large branch from the posterior division nins between the folds of the posterior retinaculum ; less constantly a smaller vessel cours^ in the anterior one. The segments of the ileo-cacal valve are very vascular The artery of '*' J""«?fr^ appendix arises from the posterior division of the ileo-colic, crosses the back of the ileum, and runs in the fold of peritoneum to the end of the appendix. The mw of the caecum are arranged on much the same plan as tne arteries. That oJ the appendix is relatively more important, receiving tributaries from the front and the back of the caecum. It passes behind the end of the iK uin to the ileocolic vein. The lymphatics are divided into a posterior and an anterior set. 1 he lormer empty into small nodes on the back of the caecum beneath its peritoiveal covenn^^ The anterior ones are in or near the fold between the cjecum and colon. The appendix contains a 1-rge lymph-sinus at the base of tho fnllicW. Lymphatics pass through the interruptions of the muscular layer. They may enter a node in the peritoneal fold iq the angle between the c«cum and ileum. There are several possible communi- i668 HUMAN ANATOMY. cations : one with nodes in the mesentery ; one with nodes on the left of the as- cending colon behind the peritoneum ; one with nodes of the iliac fossa ; and, in the female, one with the system of the ovary. There is a constant lymph-node at the angle between the ileum and colon.' The nerves supplying the cxcum and appendi.x are derived from the superior mesenteric plexus. Their mode of distribution within the gut has already been given (page 1643). Development and Growth. — At birth and for some years after the caecum is very small and the foetal or cornucopia shape is more frequent than later. The appendix is relatively rather long. In eleven cases below ten years Berry ' found the average length of the caecum 28 mm. and the breadth 37 mm. In eighteen cases he found the average length of the appendix 74 mm. (2 7/g in. ). Ribbert gives the following lengths of the appendix : at birth, 34 mm. ; up to five years, 76 mm. (3 in. ) ; from five to ten years, 90 mm. (3}4 in. ). At birth the caecum is usually higher than in the adult, since it has not de- scended to its permanent position and the adhesion of the mesentery of the ascend- ing colon has not occurred in the lower part of the flank. It is often rather above the anterior superior spine of the ilium. In five of about thirty-five observations on young children, mostly newly-born, it was so free from fixed attachment that it could hardly be said to have any definite position. THE COLON. The asce ding colon extends from the csecum to the under side of the liver, where it ma.:es a sudden bend — the hepatic flexure (flexura coll deztra) — and be- comes the transverse colon, which crosses the abdomen to the splenic flexure (flexura coli sinistra) at the spleen, whence, as the descending colon, it passes to the crest of the ilium. From that point to the middle of the third sacral vertebra it is known as the sigmoid flexure. The three bands of the colon or tanitt coli, formed by accu- mulations of longitudinal fibres, are each about i cm. broad. Their disposition in the walls of the gut is difficult to follow and is not constant. The following arrange- ment is probably the most usual. In the ascending colon one is in front and two behind, one of the latter being near the outer and the other near the inner aspect. On reaching the transverse colon, the anterior becomes the inferior, while the external becomes the superior, receiving the attachment of the transverse meso- colon. The internal also lies on the upper surface, but behind the preceding. On the descending colon they resume their original positions, but tend to grow indis- tinct. They are still more so in the sigmoid flexure, and before the rectum is reached there are but two bands, an anterior and a posterior, of which the latter is the stronger. The interior of the colon shows the sacculated condition, but there are no folds or valvulae conniventes like those of the small intestine. The solitary lymph-nodules continue, much like those of the jejuno-ileum. Relations. — The ascending colon is in the right flank against the psoas and quadratus lumborum, but does not overlap the latter unless greatly distended. It lies in front of the lower end of the right kidney, projecting but little beyond its outer border, with the second part of the duodenum on its inner side. It ends with the hepatic flexure, which makes a large impression on the under side of the right lobe o{ the liver directly anterior to the kidney. It is often completely covered in front by the small intestine. The transverse colon is suspended between its beginning, the hepatic flexure, and its end, the splenic flexure, like a festoon, forward and downward ; for the ends are near the back of the abdominal cavity. The splenic flexure, in front of the lower part of the spleen, is both higher and more posterior than the hepatic one. The transverse colon is covered abo\'e and in front by the greater omentum. It runs along the liver, touching the gall-bladder and the greater curvature of the stomach, amimd which it ascends to the spleen. The splenic flexure m;iy or may ' Lockwood : ProceedinKS of the Anatomical Society of Great Britain and Ireland, Journal of Anatomy and Physiolog)-, vol. xxxiv., 1900. ' Anat. Anzeiger, Bd. x., 1895. THE COLON. t6«9 not rest against the under side of the diaphragm, according to its distention and that of the stomach. It rests behind and Jielow on the small intestine. It may or may not be in immediate relation to the tail of the pancreas. The descending colon descends partly in front, but still more external to the kidney, and after passing the kidney rests wholly on the quadratus lumlxinim. Although more externally placed than the ascending colon, it does not usually j)roje. :t lieyond that muscle. It' may be very much contracted and sacculated. The sigmoid flexure (colon siemoideuiii ), the continuation of the large intestuu-, begins at the crest of the ilium as a loop of very varying length, which js attached by I eft side ol abdomen: >m«ll Intefitine turned to risiht. exposinR mesentery, mesocolon of desrending colon, ,.ii"*;™,, ; ^k : toth small and large intestine is extremely irregular, as shown by the follov. .. Obterver. Dwight DwighL Treves. Dwight. Treves. Treves. Age. 10 months. 10 months. I year. 3 years. 6 years. 13 years. Small Intntine. 670 cm. 435 cm. 490 cm. l.mrgc lnt»tiiK. 78 cm. 90 cm. 76 cm. 84 cm. 91.5 cm. 107 cm. As the sigmoid flexure is relatively lar^e in the infant and the pelvis very small, (he convexity of the loop lies in the right side of the abdomen. V«i..ion.._The mesentery of the -?" 'f-l'lJ-l^UlSen^rk I^n'e?^^^^^^^ «,lon may remain ^"-h/d -^^^ *;°"^^^^^^ ihe^i^Vr hind be so dition known as «"<'»''""'",;^??'^^'- umann^ has Seen its mwentery long enough to be long as to make secondary folds. Curechmann nas seen flexures. In the latter case twisted. The nansverse colon may V*„*^ort *antme one or dot^^ ^^ ^, Probabtv the ascending and the descendmg colon are .^ost »^« *^^J"^^^d in the middle like an V( much more often the transverse If «•"" "^V, *^ *'^J°"|o"^morat the left than the right. A with the middle point at the pelvis .^°„ J!n This^rt o" the gut, when over large, may double fold of the transverse . ^lon has Wn seen_ ' '?^« P2^^°^^5i„|"co,„n may also present X S-Eiir irSSe. £%&" £.:fre'X.S o. tio .ncce^lve loia.. > Deutsches Archiv fiir Klin. Med., Bd. lin.. 1894. 1673 HUMAN ANATOMY. Blood-Vessela.— The arteries of the colon are derived from the superior ami the inferior mesenteric. The former supplies the citcum, the ascending and tlu' transverse colon, and a varying amount of the descending colon. The supply of tin latter is completed by the inferior mesenteric, which is iUao distributed to the sigmoid flexure. The general plan includes a series of anastomoses between neighbor in(> branches, by which long arterial arches run near the border of the gut, to which they give off irregular twigs. There is no system of straight vessels as in the greater |iart of the small intestine. In the sigmoid flexure there is a recurrence of the superimposed arches, which may be three in number. The superior hemorrhoidal branch of the inferior mesenteric artery runs in the last part of the mesentery of the sigmoid, and often divides in it into two branches, which run side by side on the hack of the gut towards the rectum. The veins are disposed much the same as the arteries, but with a system of straight vessels from the intestine. The lymphatica, which are many, empty into lymph-nodes on the posterior wall of the abdomen, which are a part of the same system as those of the small intestine. The nerves are from the i,>,peri )r and inferior mesenteric plexuses, which are derived chiefly from the solar and the aortic plexus respectively. THE RECTUM, ANAL CANAL, AND ANUS. The Rectum.— The rectum begins at the middle of the third sacral vertebra, the point at which usually the mesentery that restrains the sigmoid flexure termi- nates. It was formeriy described as beginning at the left sacro-iliac joint, but this division, which is unwarranted, is falling into disuse. The rectum descends Fio. 1420. RecUl folds „ Bladder Seminal veslite ■Symphysis pubis Hemorrhoidal veitii Utelhra Bulb of penis Internal sf>hincter LeTator ani Internal sphint-ter Veins of mucosa of anal canal i * Fold of mucous membrane Kxternal sphincter Sagitul section of pelvis passing Ihrouxh rectum, anal canal, bladder, and urethra. alimj; ihe hollow of the sacrum and coccyx, passes the point of the latter, and con- tinues until it reaches the lower and back part of the prostate gland in the male or the vagina in the female. ' Its length is about 12.5 cm. (approximately 5 in. ). The gut is then continued by the anal canal, sometimes called the sphincteric portion of THE RECTUM, ANAl. CANAL, AND ANUS. 1673 the rectum, situated in the thickneM ol the pelvic floor, and directed downwanl and backward, makinif a sharp angle with the rectum pro|K;r. ¥he r«i« pro^r, having p^d t!,e lip of the coccyx, rests on ihe leva or am mu«: le ahhouKh'^se^rited from iTas well as from the s;»crum and cncyx. by tl e deiS rectal fLia.^The rectum, although not exh.b.tu.g the iH.ucung seen u fhe^olon s sacculated, presenting, when distended, usually three f -}-«;;'"• " which the lowest and largci.t. called the ampulla, may measure 25 cm. (y-a m. .. or Tven more in circumference. The saccule, are separated by deep cre.>scs. pass ng ItoutTo thirds around the gut. caused by a folding m of all the c.«ts uUernal t- the tw^ bands of longitudinal muscular fibres. The folds form the valves oj /*'.""'"'■ to be described with its interior. In the male the ampulla extends agamst th. k,ck o^ the prostate and the lower part of the seminal vc-s.cles and the termmal parts the va-sa deferentia. to all of which it b connected by areolar tissue. A picket of iri^^um intervenes higher up. the walls of which, however, come m cont..ct wh.n ^e hollow organs are distended. In the female the end of the ampulla - -ga" st he posterior wall of the vagina from about opposite the level of the ..s uter tu the junc?U,n of the middle and lower thirds. There is above this a fold of ,H.ntoneu.u corresponding to that of the male. Glands uf mucoM Levator ani Intrnial uphincttr Luiigitudiiial muscle External sphinctei Elternal sphincter Skin Anal glands Anal K'aixiii Frontal section through anal canal The Anal Canal.— This part of the large intestine (pars analis recti) is situ- ated in the thickness of the pelvic floor and extends downward and backward. It differs from the rest of the intestinal canal in having no lumen under ordinary cir- cumstances, when the sphincters surrounding it are contracted. The anus is the very vaguely used name of the termination of the anal canal. It is deeply situate.l between the nates, especially in the female : its distance from the tip of the coccyx, variously stated by different observers, may be said to be about 5 cm (2 m. ) Much confusion h^ arisen from the difficulty of defining the Itiwer end o t he anal canal, since the skin, which is puckered up by the external sphincter and the cor- rugator cutis ani, somewhat resembles mucous membrane, so that the canal appears longer than it really is. The anatomical boundary, the ano-rcclal groove, the so- called while lineoi Hilton, is a slight zigzag furrow, usually to l)e seen on the living and not on the dead. It lies a little above the lower limit of the internal sphincter, which covered by dilated veins, projects towards the potential lumen alwve the external si.lilnctct, and is I cm. or more within what, on a superficial examination, would be called the anus. When the dUsected rectum is laid open, much is evidently a part of the skin which during life is drawn into the canal by the contraction of the muscles • hence the length of the canal is very variously stated. .Seldom does it 1 674 HUMAN ANATOMY. Fio. 141a. measure as much as 15 mm. from its upper end tn the ano-rectal groove ; prubul>ly this distance is usually about i cm., while what may practically be called the canal is twice as mu^h, or even more. It is longer in men than in women. In the male tho beginning ol the anal canal is near the lower part of the prostate and the mem- branous urethra, at a point from 3. 5-4 cm. in front of and somewhat lower than tlit- tip of the coccyx. Lower stil!, the bulb oi the ur>.'hra is separated from the anal canal by the pyramidal mass' of connective tissue constituting the perineal My. The latter is du^ placed bl"at the lower end of the a^al canal the latter w hrmly attached to the '"'^The mu.CuUr coat ol the rectum is thicker than that of ih,: . olon riachinR to , mni The thickeninK is greatest in the layer of th.,- circular hbrc.. 1 he l..ng.tu. A^a7 ones although forming a continuous layer, are for the n.ost part coll. . ed t I ,„,! Kark into the two tends already mentioned, of which the posterior i!« the Kr'nd'Th^rreconcemell^^^^ "^'l'^ 'rTlr^'nusde Kn hypertrophy of the circular muscles, while the external sphiiuler is .y">'««j^^ o? the oenneum It has been thought advisable to here descr.U' togetlu r the Iscles'^and some of the fasci* of the'rectum and anus, including some that are largely extrinsic. THE MUSCLES AND FASCIA OF THE RECTUM AND ANUS. The levator ani( Figs. 1423. 1424) arises from thebackof theNHly.f th.iuil..s, .l^mtmidlav between the upVr and lower border, very close to the middle line, id hTncrfromtre'' white Une" formed by the splitting of the ,m..1vic fascia as ?.r « the sdnTof the ischium. The anterior fibres from the pubic bone p:us9 Inflow lhe"r!^ur^me goin^ to i« capsule, as a strong muscular bundle to the central Fm. 14*3. BalhocavenMMUi- I»chio-cavenio»u» — Trans, perinei - super! Obturator internus White line - Levator ani _ Coccygeus . TrianKUlar lig- ^meiit. itif i.tyer Pcrint-al i-cnlrc ruhen«ity of isctiium \nus > }bturator fascia Kxternal sphincter - levator ani t '.luteus maximus (cut) . Greater sacro- Kiatic ligament Coccyx. Muscli-s of pelvic floor and perineum from below. point of the perineum and he front and sides of the rectum, in which some of them end The remainder of this set passes with the fibres from the white line to the side of the coccyx and to a fibrous band ( liuaineotuni anococcjgcuin ) runi.ms from it to the anus. This latter part of the muscle is thinner and more transversely placed than the former. In the female the pubic portion sends some fibres to the vagina and some around it to the central point of the perineum. The fibres, for the most 1676 HUMAN ANATOMY. part in both sexes, pass by the rectum so as to compress it, although some enter Its walls and mingle with those of the sphincters. Nen5' ( tbturalor inteniiiH Ampulla Cowper'9 Kland 5cmln.il vrsici* . Ant*Tior »»ll of rci tiiiti l.pvilur ani Prostate xlaiid Obturator extcriius Puhir ntniua Corpus cavcniOBuni / Ischio-cavemosua Triangular ligament, inferior layer BulboK-aveniottUS I Colles's fawia Triangular ligament, superior layer Trans, perniei su|Krrf. Bulb of penis Krontal section or pelvis passing just behind the bladder, posterior surface. from the pelvis, mingle with those of the rectum. The recto-coccyi^eus of Treitz arises from the anterior surface of the coccyx above the pelvic floor and mingles with both the longitudinal and circular fibres at the back of the rectum. It is said to con- sist of striated fibres at its origin. Bundles of fibres are described as arising from the fascia on the deep surface of the transversus perinei profundus muscle and pass- ing to the front of the gut. The corr'igalor cutis ani is a small system of muscular fibres radiating from the submucous tissue at the anus to the deep side of the skin, which it tends to pucker. Actions. — The function of the sphincters is to keep the anal canal closed. They differ, inasmuch as the external, although mostly acting automatically, is under the control of the will and he internal is not. The levator ani has a more complicate*] and in part an appa;cntl--- inconsistent .irtinn, since it may pull the anus upward and probably dilate it, a" it pulls its borders apart under the resistance of 1678 hijman anatomy. the descending faeces, while at other times, by its antero-posterior fibres, it may compress the sides of the gut. To the action of the levator is probably due the control of the fieces which sometimes persists after division of the sphincter, unless, indeed, the upper part of the latter has escaped. The Ischio-Rectal Fossa. — This space is a deep, roughly pyramidal hollow, filled chiefly with fat, on either side of the rectum. The base is at the skin between the tuberosity of the ischium and the anus, bounded in front by the line of reflection of the deep perineal fascia and behind by the great sacro-sciatic ligament and the edge of the gluteus maximus. The base measures some 5 cm. ( 2 in. ) from before backward and half as much crosswise. The fossa is bounded externally by the tuber- osity of the ischium and above the latter by the obturator fascia, internally by the external sphincter and the under surface of the levator ani. The space narrows above to a line at the splitting of the pelvic fascia ; hence it can only vaguely be called pyramidal. The depth of the fossa is about 5 cm. (2 in. ). Fig. 1436. Venous plexus Pelvic fascia , Anterior wall uf bladder Superior p Obturalor inlernus Diaphnifnnatic fascia Obturalor fascia Levator ani CluteuK maximus Ischiu-rectal fossa Obturator extenius External sphincter { Anns Internal sphincter Oblique transverse section IhrouKh pelvis in plane shown in small outline fixure. The diaphragmatic fascia, the inward continuation of the pelvic fascia which covers the upper surface of the levator ani, reaches the side of the rectum as a bed of areolar tissue beneath the peritoneum, and is more or less closely attached to the gut, sometimes by muscular bands, as already stated. The systematic description of this fascia is given elsewhere (ftage 559). The rectal fascia is a dense layer of areolar tissue surrounding the rectum below the reflection of the peritoneum, being continuous below with the preceding fascia. It is particulariy dense behind the rectum, which it separates from the sacrum and coccyx. The anal fascia is a web-like areolar sheet covering the -inder side of the levator ani. A superficial fascia between the skin and the base of the ischio-rectal fossa can be artificially dissected, but is of litde importance. THE MUSCLES AND FASCIA OF THE RKCTIM AND ANIS. 1679 Pio. 1437. Internal hemorrhoidal vein I Le\-ator ani Peritoneal Relation^ of the Rectum.-The posterior surface of the highest of the posterior wall "'Jl^e perns, mc Douglas,— known from its anterior deep pouch in front °';'^7^^""^;;[;'^„^''^^rr^r/.-Ui«^/ in the female. In man wall as the recto-vtsiral in the male anu " ^ /^ and the UDOer part of the seminal this pouch separates the rectum ^■•"''"/^^"^fthe vagina ^T^he distance of the line vesicles and in woinan from the upper part «« ^J^^^^"^^j ^^^ .^juch-from the ano- of reflection oi peritoneuin-that is to say '^^^^v given -H however, by the word rectal groove may be as little asscm (2 nO.asusuallyMven, ^, . , . . anus^ be understood what is P-jf "^,f ^ f/^"^^^ ^tended, the pouch LconiidelJbV^iJS^^HTthelL^u^.1;?^^^^^^^^^ testine or the sigmoid flexure. The redo-veskal folds in the male, although described with the bladder (page 1905) , should be mentioned here. They are reckoned among the false ligaments of the bladder, and bound laterally the pouch just described ; extending backward from the bladder around the rectum to the sides of the sacrum, they tend to divide the cavity of the pelvis into an upper and a lower com- partment. Their free edges are semi- lunar and sharp, and cur\e around the rectum above the ampulla, which they partially roof in. Thesfe liga- ments contain more or less fibrous tissue. In the female they are less developed, although important, and, arising from the uterus instead of the bladder, are known as the sacro-utertne JoWs. _, ^ . Blood-Vessels.— The artenes supplying the rectum are derived chiefly from the three hemorrhoidals. The superior hemorrhoidal, the ter- mination of the inferior mesenteric WMm^mm. Zr^^^:L .ucous and cutaneous -^ = "j^^^^^^^^^ the ways between the superior and external hemorrhoidal veins. i ne lau Middle hemorrhoidal, vein Internal sphincter External, sphincter Iroove ■External hemorrhoidal vein Frontal leclion of wall of anal canal, showing relations of hemorrhoidal veins. (O/u.) i68o HUMAN ANATOMY. a circle of smaller dilatations just l>elow the line of demarcation, in the region that is reckoned as skin, but is practically puckered into the anus. There are communi- cations between the two systems, some of which pierce the muscular coat. Lymphatics — The principal lymphatics of the rectum, after joining the lymph-nodes situated along the superior hemorrhoidal veins, pass to the sacral glands on the front of the sacrum. In the lower part of the bowel a ver>- rich plexus is found under the skin around the anus, which drains into the superior internal inguinal glands, and a still richer one 'inside, which at the lower part is concentrated on the columns of the rectum, but few vessels lying in the pouches. A considerable system of lymphatics exists also in the muscular layer. Most of those of the inside of the anus run to a few small lymph-nodules discovered bv Gerota ' on the back of the muscular coat of the rectum, distributed with the branches of the superior hemorrhoidal artery. Nerves.— The nerve-supply of the rectum includes both sympathetic and cerebro-spmal fibres. The former are derived chiefly from the inferior mesenteric and the pelvic plexuses, accompanying the superior and middle hemorrhoidal arteries respectively. The cerebro-spinal fibres are contributed by the second, third, and fourth sacral nerves. The skin around the anal orifice is supplied by the inferior hemorrhoidal branch from the pudic nerve. Growth. — At birth the rectum is tubular and generally relatively small. We do not remember to have seen a well-marked ampulla at that period. At least frequently the anal canal is very long,— about I cm. The transverse folds of the rectum are apparent in the latter months of pregnancy. We have found an ampulla with a circumference of 13 cm. (5 in. ) at three years. In the same specimen the valves were well developed, and, except in size, it resembled the rectum of the adult. The peculiarities of the infantile sacrum have their effect on the course of the rec- tum, which is necessarily straighter than in the adult and does not run so far forward in front of the coccyx. PRACTICAL CONSIDERATIONS: THE LARGE INTESTINE. The Caecum. — This part of the large intestine may remain undescended in its fujtal position in the left hypochondrium, at a point above and to the left of the umbilicus, the ileum opening directly into it in this locality ; or it may be found in the right hypochondrium just below the liver, or at any level between that and its normal situation. The csecum is rudimentary in man and other meat-eating animals, being much more capacious and of greater functional importance in the herbivora. The caecum is larger, more distensible, and more superficial than any other portion of the large intestine, and more mobile than any other portion except the sig- moid. On account of its mobility it is selected for the operation of iliac colostomy when that operation is done on the right side. As a result of the inspissation of the intestinal contents, which first occurs here, it is a common seat of fecal impaction, or of distention by gases arising from fermen- tation. The increase in numbers of the intra-intestinal pathogenic bacteria due to imiiaired inhibiting power, which, as we descend the gut, first beconsis marked in the lower ileum, continues in the caecum. As in the former situation v.here it prob- ably aids in determining the localization of typhoid and tuberculous le..ions, so in the caecum, in conjunction with fecal accumulation, or with disturbance of circulation from distention, such augmentation adds to the frequency and severity of catarrhal inflammations and of stercoral ulcers, which are found oftener here than elsewhere. Fecal concretions (the formation of which is favored by intestinal catarrh just as is that of renal calculi by catarrhal pyelitis) are often found in the c»cum, and undoubtedly by mechanical irritation favor here, as they do in the appendix, epi- thelial necrosis and subsequent infection. In the erect position gravity aids in bringing about these pathological condi- tions, since the caecum, having no mesentery of its own, and yet completely covered by peritoneum (so that it is never anchored to the posterior parietes or to the iliac fossa by areolar tissue), depends upon its attachments to the colon and ileum to hold ' Arch, fur Anat. und Entwicklng., 1895. PRACTICAL CONSIDERATIONS : THE LARr.E INTESTINE. 1681 it in position. It has often been part of the contents of rJKht inguinal or femoral t,„,nia anfl has even been found in such hernise on the left siUe. •^ The hiflu^nce of gravity in retaining ' .cal masses and fav..rmg concretu.n « illnstmt^bv the Lt that foreign bodies small enough to p^iss through the ileo-c^eca. " Ive aS prone to remain in the c^cum. where they have u, many casc-s guen nse Kieh on the^omen will empty a moderately distended caecum. """^°;*""K3»/» » usually competeu, to preveut fc r«urr. of !«»'"■«« to^ Wieffin), and occurs most commonly (70 per cent, of all cases) in ""luri • The ileo-c^al valve forms the summit or apex of the intussusceptum. and may pass Sougl^thTentlrTcolon (the intussuscipiens). aching the rectum oi^an^^ colic intussusception-in which the ileum passes hrough the vaUc, the caecum -''l^:^^^^:^:^::^^^^ CltSlnrtrU P-ureon the mesen. entering and returning layers of gut (Hg. 1405)- ' "^^", .^e nassa^e through it of narrows the lumen of the intussusceptum so as to prevent the passage tnroug spine of the .hum Appendix—On account of the frequency with which it i. I to 5^'.\^"^'^^„f,^P,YdX here considered, even at the risk of repetition. '^''''^:;^^;'^n^'£^- The appendix is an apparently f-fjonl^s orga found oaty^n manf in certain of the anthropoid apes, and m the wombat. An analo- 106 t683 HUMAN ANATOMY. gous organ exists in some of the rodents and marsupials, but it is a long, taperiii; cecum rather than an appendix strictly compiarable to that of man. The appr a least impairing L SS ve Swer of the intestinal epithelium ; («) the relatively greater length o^ the ISirryoung ,>ersons (in infants one-tenth and in adults one-nvenuth 1 lenXof the large intLtine, according to RiblK-rt) increasing the ^^*culty of draiiag? and r^ssiWy (r) the tendency to shrinkage or obliteration after middle lifp _a process to be expected in a rudimentary organ. • 1 < ., . w t.. • 6 h^i^t not be forgotten, in interpreting the foregoing anatomical f^cts as to («) the mZentary character of the appendix, (*) the --"'^-^^^.^^^^^^^^^ the intestinal tract (p^ige .'^^^^ „*"° *;'7;' ^^^^of either mechanical or chemical ready to take on pathogenic action m t^^ 1' "f"^'; / ' ^^^^^^ ^^ainago of the eariy ■'"t"S,^r5te "tXtr, ,h. pain i, leU in ,he ri„1„ ili»e lc»«.. over ihf St iliac fossf^ is often, but perhaps not necessarily, diK- to peritonitis, and in anv event arises from the fact that those muscles receive their nene-supply mnianvfrom'he six lower intercostals, while the superior mesenteric plexus gets fts contribution from the spinal system through the splanchnics, derived from some «' '': XS^'^mmonlv follows, has litde ...ation *" gastric. conditi^sis^or^ narilyreflex and due to reversed peristalsis, and is apt tu be assoc.atcu with moderate fever and slightlv increased pulse-rate due to autotoxamia. Other and later symptoms are mentioned in the next section. 1684 HUMAN ANATOMY. Results and ComplicalioHs 0/ Appendicitis. — A cursory review of the anatomicil relations of the appendix, considered in conjunction with the [lathological varietit - of appendicitis, will explain the varying results of this disease. The appendix i> entirely intraperitoneal in its situation and becomes primarily the focus of intrai>eritn neal lesions, although in certain cases {iHde infra), from pathological changes, it iiiid the ;wsociated exudate or abscess may be either practically or really extraperitonejil That focus may be isolated by adhesions between the peritoneal coverings of thi neighboring structures— the coils of small intestine, the ca-cum or colon, the jiarieto — or may become the starting-point of a general septic peritonitis. In the former cast the usual local symptoms of inflammation or of abscess will follow according to the be- havior of the exudate, which may remain plastic or may liquefy and become purulent. In the latter case, to the above-mentioned symptoms — which are much intensified, as a rule--are added general rigidity from involvement of larger areas of the abdominal wall, distention and tympany from paresis of the small intestine (page 1756), and from the same cause obstinate vomiting and more or less complete intestinal obstruction. The acuteness of the attack, the presence or absence of gross perforation or gangrene, and the anatomical position of the individual appendix will often determine the localization or diffusion of the septic infection. The usual anatomical situations of appendix abscess may be summarized as fol- lows, (i) Anterior, the ciecum forming the posterior wall, agglutinated coils of intestines the inner wall, and — after the abscess has attained some size — the parietal peritoneum the anterior wall. (2) Posterior, the hinder surface of the ca-cum forming the anterior wall, especially if the appendix is post-c»cal in posi'on, or if a septic lymphangitis has extended backward between the layers of the meso-appendix. Such an abscess is extraperitoneal, and may originate in an appendix which, it is believed by some, was ab initio either wholly or partly extraperitoneal (4 per cent. , Bryant), or, as seems more probable, had become so through pathological causes (38 per cent., Ferguson, page 1666). The abscess b limited by the fascia transver- salis anteriorly and the fascia iliaca posteriorly, and by their fusion at Poupart's liga- ment inferiorly, although rarely it may follow the femoral vessels downward and appear on the thigh, or may perforate the parietes above the outer third of Poupart's ligament, or may make its way into the peritoneal cavity, or into the pelvis, escaping through the obturator or the sacro-sciatic foramen. It may ascend (following some- times the retro-colic fossa, page 1667) to the perinephric or even to the subphrenic region. (3) Inner, the inner surface of the colon and csecum and the mesocolon bounding it postero-extemally and adherent coils of small intestine antero-intemally. If the parietal peritoneum does not form part of the anteriv.' wall of such an ab- scess, the general peritoneal cavity must be traversed 'n reaching and evacuating it. (4) Inferior, the abscess occupying part of th' pelvic cavity with agglutinated intestinal coils bounding it superiorly. All these abscesses may perforate into the cavity of the peritoneum, but sponta- neous opening into the cacum, colon, rectum, small intestine, bladder, or on the sur- face of the body has frequently (Kcurred { Finkelstein, quoted by Mynter). The various symptoms which may result from the propinquity of the abscess to other structures should be worked out anatomically,— t-.;?^., ( i ) oedema of the abdominal wall over the abscess; (2) flexion of the thigh, extension of which is painful from involvement of the ilio-psoas ; or marked lumbar tenderness (perinephric) ; or immobility of the right lower thorax (subphrenic) ; (3) tympany over an ill-detined swelling, from in- terposition of coils of small intestine between the abscess and the parietes ( although this may be simulated by the escape of intestinal g;»ses through a gross perforation into the cavity of an aliscess of any type) : or (4) vesical nr rtrte/ irritation. Anatomical Points relating to the Treatment of Appendicitis.— T)\e medical treatment of this disease is of anatomical interest only in its relation to the possibility of removing the mechanical causes and favoring either resolution or localizing adhe- sions. Opium for the purpose of lessening peristalsis and thus permitting omental ;tnd intestinal adhesions to wall of! the apjiendix has still some advocates, especially when combined with gastric lavage and exclusive rectal alimentation (Ochsner). But the received views as to etiology {vide supra) and clinical experience are both overwhelmingly in favor of purgation and starvation as preventing or removing the PRACTICAL CONSIDERATIONS: THE LARGE INTESTINE. 1685 constipation which, when involvinR the c-wrum. may. by causing irritetion and swell- [ne of mucous membrane, by ena.uratjement o. bacteml growth, by favonnR the- for- matinn of fecal concretions, by producing traction on the meso-apijen.h.x. <.r by direct Sure upon the appendicular vessels, start the cham of ,«tholoK.cal phenonuna E begbning with hyperemia, hypersecretion, and imperfect drainage pnK:ee< To disiemVon, ulceration. ^rforation, or gangrene, with their assc^mted degrees ..f •^"^Sns^iStioTifprtSiTin the majority of cases of appendicitis ( 3H out of 69. McCosh). ar^d not only acts as a causative factor, but has a prejudicial effect on he resVU In 22 cases ofVritonitis from appendix disease occurring at the London Sital there were 9 c^es of constipation, with 4 deaths and 13 cases in which thrbowe s were loose or e;isily moved, with 2 deaths. In another series of cases r Richardson) there was 8 per cent, of constipation among those that recovere.1 and is Srce^ among those that died (White). No other important ,K>int of nK-dical treatment is in dispute and none has any anatomical bearing !,„..,,„, „f operation for appendicitis will, of course, vary with the scat and character of the d'se^e^ preferable method of access in removal of an appendix very early in an attack, or during an interval, or when neither abscess nor extensive adhesions .are present, is as follows. The incision begins one inch above a line drawn rom the anS superior spine to the umbilicus, and crosses that line one and a half inches interna to^he iliac spine. It should pass downward and inward and be »»-" thr^ nches long. The skin and aponeurosis of the external oblique are divided in that direction ; the internal oblique and transversalis fibres are separated in a direction aimSt at right angles to the first incision ; the transversalis fascia and peritoneum are divided on the same line with the internal obhc^ue. ..vt.^„ The advantages of this incision are thus described by its originator. Muscu- lar and tendinous fibres are separated, but not divided, so that muscular action can- not tend to draw the edges of the wound apart, but rather to actnely approximate them Excepting during the incision of the skin, almost no bleeding occurs The ascia transveVsalis not &ing drawn away by the retraction of the deepest layer o muscular fibres, this fascia is easily completely sutured, and thus greater strength of repair is assured" (McBurney). .„„„i.., „, More room may be obtained and the transverse severance of niuscular or fascial fibres still minimized by stripping the external oblique aponeurosis up to the mSbn line, dividing the anterior sheath of the rectus in the line of the separation of the internal oblique and transversalis fibres, lifting up and retracting the rectus towards the median line, ligating the epigastric vessels (which will be seen lying on the thin transversalis fascia over the peritoneum), and then extending the original peritoneal incision as far inward as may be necessary (Weir). ... 2 In later operations it is best to be guided by the situation of the tumor or the area of tenderness or dulness. inclining to approach it from without inward. An oblique incision well out towards the upper third of Poupart s ligament will l)e less likelv to open the general peritoneal cavity unneces.sarily in cases of abscess, and less lik.iy to be followed byventral hernia. In retroperitoneal abscess an incision so placed will not infrequently open the abscess without going through the peritoneum at all. ... •!•••„ »!,« X In the presence of general purulent peritonitis a vertical incision on the outer border of the rectus or a long median incision will best enable the appendix to be dealt with and at the same time permit of the efficient cleansing and irrigation of the peritoneal cavity and the introduction of drainage. •, u . 1 4. After the peritoneal opening is made the appendix can often easily be found and brought out of the wound. If this is not done readily, the colon should be identified— the first portion of intestine found att.iched to the posterior wall as the finger is passed along that wall inward from the incision— and the anterior muscular band traced downward to the base of the appendix. , ,• • • t The Colon and Sigmoid Flexure.— Like the other main sulxlivisions ot the intestinal tract, the colon is larger at its commencement than at its termin ation. measuring on the average 8 cm. (3>^ in.) in diameter at the c^scwm m^L^ c""- t«86 HUMAN ANATOMY. ! (i^ in.) at thf lower end of the sigmoid flexure. Its average capacity in iiif.iiu> of »i.\ months is >^ litre (i pint); in children two years old, 1.25 litres (2.5 pints i; and in adults, 4.5 litres (9 pints). It is normally ualpable through most of its extent, the more deeply phu.d hejjatic and splenic flexures excepted, the former Iwing lieneath the liver, the latti r l>ehind the cardiac end of the stomach. The ascending and descentling portions .ir«.- usually overlapped in front by the jiiore mobile small intestine, which, if not dis tended, can Ik; displaced towards the median line. The thickened and sometinio tender edge of a chronically congested or inflamed citcum can often be rolled under the finger against the floor of the iliac fossa, and has been mistaken for the appendix. The colon is susceptible of great distention, and in cases of obstruction in tin sigmoid flexure or rectum it may occupy most of the abdomen, push up the dia phragni, displace the heart, and occasion dyspncia and palpitation. Distention either from gas or fecal accumulation renders the colon visible, as well as palpable, except at the flexures. In chronic obstruction in the rectum or sigmoid its peristaltic movements may be seen through the thinned abdominal w .ills. In the common iIeo-ca?cal variety of mtussusception the tumor can often \yc seen as well as felt, and sometimes the progress of the intussusceptum along the colon can be traced with the eye. Tumors of the colon or upper end of the sigmoid are often visible in thin pa- tients, especially when they have contracted anterior parietal attachments. Distention of the colon gives rise to prominence and outward curving of the flanks, as the patient lies supine, and to fulness below the costal arches and the margin of the liver. The anterior surface of the belly— taking the umbilicus as a centre — is relatively flat. In distention of the small intestine the swelling is most marked in the latter region. Normally the colonic percussion-note is of somewhat lower pitch than that of the small intestine, but of higher pitch than that of the stomach, the variation being due to the difference in the size of these viscera and in the thickness of their walls. In general gastro-intestinal distention the same variations are often observable. A large quantity of fluid faeces in the colon will give rise to f)ercussion dulness in the flanks, which may disappear when the patient is turned on his side. That sign is therefore not conclusive evidence of the presence of free fluid in the peri- toneal cavity, unless the condition of the colon is known. Rupture from distention— a rare occurrence — will usually be incomplete, the mucous membrane remaining unbroken. Idiopathic dilatation of the colon has been seen in young children, chiefly amon;- those affected with rickets. Displacements. — The caecum and ascending colon or the sigmoid and descend- ing colon may be found in inguinal or femoral herniae, may be at the median line of the body, or may even lie in the iliac fossa of the opposite side. A misplaced, movable, or enlarged kidney may cause variation in the position of the colon. " When the left kidney occupies the iliac fossa or is situated over the left sacroiliac synchondrosis there is generally no sigmoid flexure in the left iliac fossa ; but the descending colon passes across the middle line, and the rectum commences on the right side of the sacrum" (Morris). Paranephric tumors, by pressure on the colon, have produced such marked symptoms of intestinal obstruction as to be mistaken for intussusception ( Ibid. ). The transverse colon, as the most movable of the three divisions of the colon proper, is peculiarly liable to assume abnormal positions, usually as a result of habitual constipation or secondary to obstruction lower in the gut. It can readily be understood how the weight of fecal masses may in time exaggerate the normal downward curve of the transverse colon, resting only on the easily displaced sni.ill intestine, and carry it towards the pubes. which it sometimes reaches. The normal level of the middle or lower portion of the transverse colon is at the upper umbilical or the lower epigastric region, or on the line separating those two regions. The [josition of the transverse colon in relation to the stomach varies greatly within normal limits. If the stomach is empty, it is behind the colon; if full or distended, it will iflikkthe latter downward and overlap it from in front PRACTICAL CONSIDBRATIOXS : THE l.AROK IXTh-iTIHE .6., iJ^^T C iuU tl» in«.is«.tn.n of i..u-stin«l c.nunls. an,l il.. .«.™ily f" presence ol tnc saccuii, im. iimi , . ,^ ,n^.. ^m- iiUni, unJ tuberculous ulcerat.on '« '^;^/f„^^^,; ."^/.J Z iL .ectum. sigmoia. clcscondinn account for its -'-"- sus^epUb^^^^^^^ (pa«e .680) IpPnT/ht^'atlrnlrX^^^^^^ it .nor. frequenUy the ^t of car- '^n\£TanVJi:e^!tS£n\^ producing stricture and obstruction, .ay ex- tend 'into and involve any of the "«>?J^"".f.^,f;'i;;rtio„ of the Ix^wel upon an axis usual cause is habitual «^«"«t,paUon The gut. l^commR ,^^^^^^^^^ ^esc^iRmoid. tention hangs over '"f »J^^ P^'jf^,:,"^^^" o Thegut in thT effort to rid itself of the Irreeular contraction of the muscular layer 01 mc ^ -?. sr tvriKKi tr^.n^o-1;. -^^^^^^^ ,„d only indi,«lly .ith the solar ptos Tte r^SJon o^^hj ^"^ M ,^.|^. order to understand .-.'W (a) a renal, P*"" J ••jj^either the ascending or de- ., , ^^TsJp^uS gS- £^c - r:ii:^l^^ liver may ^acuate scendingcolon; (/>)asuppurat.n^^^^^^ gastro-colic fistula may become es- t688 HUMAN ANATOMY. of the abdominal aorta may burst into the g»t, the blood paiMini; between the l.i\ 1 1 - of the transverse mesocolon ; (*■) an iliac aljsccss may dischar{{e into the ca-iiuii . i sigmoid flexure ; (/) the latter may by ulceration communicate with the bladiKr m vagina ; (jf) or may, in chronic fecal distention, produce left-sided varicocele (ili< more frequent ) by pressure on the left spermatic vein. The angulation at the junction of the lower enti of the sigmoid flexure with tht first part of the rectum, caused by the greater mobility of the former an'! !'« descent by gravitation to a lower level, often constitutes an olMUcle to the pas.s.igc . i bougie or tube, or sometimes even of liquids, into the sigmoid. In various examinations anil in washing out the colon it is therefore frequently desirable to put the patient in the kiRc chest posture, which ofti ii, by gravity, lessens or removes this cause of obstruction Usually a tube cannot be passed completely through the sigmoid flexure, l)ui often carries the latter with it by engaging in a sacculu> or a fold of mucous nitm brane. The tip of the instrument may Ijc felt through the abdominal wall at a iK)int at or beyond the mid-line, which ma>' lead to the mistaken belief that it has entered the colon. Exceptionally it is possible to make it do so, the passage of the tiil)c being facilitated by the injection through it, as it advances, of an oily liquid in siif ficient quantity to distend as well as lubricate the sigmoid curve. Wounds of the latge intestine are less dangerous than those of any other jMirtion of the intestinal tract becaus*? (a) the lessened fluidity of the intestinal contents dimin- ishes the risk of fecal extravasation, and {b) if the wound passes through the lumbar parietes and involves only the fxjsterior wall of the gut, the opening may be entirely extraiJeritoneal. According to Treves, a mesocolon is found in connection with the ascending colon approximately once in four times, and with the descending colon once in three and one-half times. In 75 cases out of 100, therefore, such a wound of the colon would be attended by a minimum of danger. In operations on the large intestine it may be identified by (a) the longitudinal bands, especially the anterior and inner, the posterior being uncovered by peritoneum and therefore less conspicuous, and being placed alon^ the attached border of the ascending and the dc-scending colon ; {b) the epiploic appendages found more abun- dantly along the inner ban ' and on the transverse colon ; (c) its sacculi which may be seen, and its fecal concretions which may often be felt ; and in addition, as compared with the small intestine, (d) its lesser mobility, greater diameter, and the absence of the palpal Je transverse ridges of the vaU uI.t conniventes. It should be remem- bered that when it is greatly distended the longitudinal bands and sacculi are almost or ciuite obliterated, and that the epiploic appendages — peritoneal pouches filled with fat — ^are absent on the posterior ai-pect of the gut and in the rectum. Colostomy. — (a, Lumbar. — If the descending colon is opened through the loin, it should be through an incision following the oblique supra-iliac crease. The course of tht gut corresponds to a verucal line 1 2 mm. ( J^ in. ) external to the centre of the crest of the ilium. The incision crosses this at its middle, therefore a little below the kid- ey or on a level with its lower edge, and divides the posterior fibres of the external oblique, the anterior ones of the latissimtis dorsi and those of the internal oblique, the lumbar fascia, the posterior fibres of the transversalis muscle, and the transversalis fa.scia. At this lc\-el the descending colon lies in the angle Ijetween the psoas and quadratus lumborum muscles. In the absence of a mesocolon (64 per cent. ) the operation should be extraperitoneal. (^) Inguinal. — An incision similar to that often employed in appendix cases and lartjely interim ular may be made, its centre being 4 cm. (about iJ4 in. ) from the left anterior su|h lior spine on a line from that point to the umbilicus. The sig- nioid flexure, the portion of gut to be opened, may be recognized by the ta-nia-. the sacculi, the appendages, etc. The various operations to effect anastomosis between portions of intestine ahoxe and below ficcluded, diseased, or gangrenous areas depend for their success in many instances upon the mobility of the intestine and therefore upon the exi~ cnce and the length 111 a ni -Mjcolon. In colectomy, or complete resection of a portion of the large intestine, the usual cr.re as to the vascular supply of the retained gut, the inversion of its edges w\(\ thr approximation of serous surfaces must be exercised. PRACTICAL CONSIDERATIONS- THE l.ARC.K INTESTINK. I'-s., The Rectum and Anu».— In rcUiion to it» discasts and injuries th.- rictuni «avI^t?onv"„?nriyt^Jivided into two .x.rtion. : ( . » th.^vu, fro.n th. ,.r- '''^ TnTaS childtr thiSwc'S^tL of the rectum is strajghter. more vertical more of anVwomS orga'^. and more movable than later m life. The su,,,>ort Svln hv the f™l reflections from the rectum to the other pelvic organs .s less, on f^oantVf theTndeviSd condition of the pr.«tate and uterus. The sacral curve r: ':;;^'^e ItrrZidcilrand th^e superior hemorrhoidal t^UnesCPj 7 7 .; and of the terminal branches of the inferior mesenteric vems to the feci con- tents of the sigmoid and rectum, exposing them to frequent pressure. 1690 HUMAN ANATOMY. It may now- readily be understood how, in the presence of the above pre- disposing conditions, hemorrhoids may result from (a) direct pressure upon the veins, as in constipation, pregnancy, ovarian or prostatic enlargements ; (6) indirect pressure through the column of blood, as in hepatic or splenic disease, or from the contraction of the diaphragm and abdominal muscles, as in coughing or lifting heavy weights, or as in straining due to the presence of stricture or vesical cal- culus or cystitis ; and (c) irriutiun of the rectum or anus, causing congestion of the hemorrhoidal veins. It will be seen that chronic constipation is a possible cause of hemorrhoids under each of the above headings : the fecal masses press upon the veins, irritate the rectal mucosa, and necessitate straining for their expulsion. Ulceration of the rectum and anal canal, whether from inflammation or infec- tion following trauma (from indurated faeces or from foreign bodies), or caused by dysentery, tuberculosis, syphilis, or cancer, is of anatomical interest in its relation, first, to the vascular and nervous supply of the parts, and, next, to the surrounding regions. The rectum proper is characterized, as Hilton long ago showed, by great distensibility and little sensibility ; the anal canal strongly resists distention and is extremely sensitive. The rectum is supplied largely from the sympathetic system through the infe- rior mesenteric and hypogastric plexuses. The anal ner\e-supply is chiefly from the sacral plexus, especially the fourth sacral and the pudic nerves, the filaments of which enter the gut at about the level of the "white line" which marks the junc- tion of skin and mucous membrane and also the demarcation between the internal and external sphincters. The motor and sensory supply to the anal canal is far in excess of that to the rectum. Corresponding differences are observed in the vascu- lar supply. Although the inferior mesenteric artery brings through the superior hemorrhoidal a relatively large amount of Uood to the rectum, it contributes but little to the anal canal, which is richly vascularized by the pudic arteries. These facts explain the extraordinary absence of subjective symptoms often observed in cases of large fecal accumulation, malignant growths, or extensive ulceration, when the rectum alone is involved. They likewise explain (through the association of the pudic, the fourth sacral, and other branches of the sacral plexus) the great pain of anal ulceration (fissure) or of inflamed and protruding hemor- rhoids and the associated muscular cramps in the limbs, the vesical irritation or spasm (often causing post-operative retention of urine), the lumbar !nd iliac pains, and other reflex phenomena so common in anal disease. The great power conferred upon the sphincters by their unusually rich nerve- supply, and developed by the resistance they must frequently and necessarily offer to the peristaltic action of the intestines and to the descent by gravity of feculent matter, enables these muscles, especially the external sphincter, through their obstinate and almost continuous reflex spasm, to become not only a cause of the excessive pain of fissure, but also an obstacle to healing. It is therefore usually requisite in the treat- ment of such ulcers to paralyze the sphincters by overstretching, often supplemented by either partial or complete section of the external sphincter. The higher an ulcer in the rectum the more amenable it is to treatment by physiological rest (Hilton). Ulceration in the rectum, as elsewhere in the intestinal tract, may result in stricture, or in fistulous connection with neighboring organs or tracts, as the bladder or vagina. Lymph infection proceeding from the rectum involves the pelvic and lumbar glands, especially those lying on the front of the sacrum ; if from the anal canal, the upper and inner inguinal glands are involved. The lymphatic distribution, like that of the ner\'e8 and blood-vessels, is thus seen to be quite different for the rectum and for the anal canal. If infection spreads by vascular rather than lymphatic channels, it usually travels by way of the portal vessels and affects organs connected with the digestive system, especially the liver. Thus a not uncommon secjuel of dysentery is hepatic abscess. On the other Iiand, emboli from external hemorrhoids have been known to enter the general venous circulation and have caused death. I PRACTICAL CONSIDERATIONS: THE LARGE INTESTINE, .r.,. Subcuuneous or submucous infection invoK^^^^^ tuberculous), and may extend f ° ^fj'^t;;;" S^J^ther of the^b.,ve varieties of space, and. beginning as an "'•'*'^-^«^«l^f*^„^"^ ?"" the proximity of the rec- fiWula. Such abscesses are very frequent because om a j v character of the Turn, the frequency of rectal ulceraUon and ^^e 'nva^ly scpt.c rectal contents : (*) the poorly ^»^"'^„"f ! J ?"^ ^estL ; ^ the aWnce of ing the fossa ; (r) the effect of pvity m 'nducing ^^T^/t^e slight but often iles competent to faciliute «he -etum of venou "ood (^)/;^^^^ .^e fossa repeated trauma caused by '^P^K'^'^K . ^r J«^™"^' \ ^ ^y^ ^he expc«ure of a sufficient barrier to the progress of *^ ^t^;^„X^^'^^^and the tuberosity of the limited by the obt"mtorfa^«. the obturator^ m^^^^ ^^. ^^^^^^ ischium (Fig '426). Internally Mow the ^^^^ resistance, and accordingly, mm. (H «n. ) above the anus. '» ""f J^ P°' ;„ ^^^^y be found about on the hne when it results in fe'"la^ t»^f.'"^""*]°Cm^Zfo^ bring prevented by the blend- between the sphincters, .ts higher ex« from the (^ ^^"f P^ ,^ ^.j.^^he bowel- i„goftheanalandrecto-v«.calfa^a^ and the le^a^^^^^^^ .^ ^^^ wall. If it reaches the surface ? '^J .^ch Jm and the edge of the gluteus maxi- between the anus and the tuberosity «* '^^ '"^^'T fro„t (Fig. H^J)- This mus behind and the --efle^;"" "'/t! '^^P ^utt m^^^^ the external sphincter, external opening .s apt t^^Too^^ Irfy on acc3 of the suffering caused by Such abscesses should be «f "^.fX ^" ^th sacral (on its way to supply the pressure on the twigs of ^he «™^' ^^*'^v'^^i°"^^^ Tu^rficia! perineal nerves, and external sphincter), the '"««="««■ •^'='"°y^*'°''*,i^", , an^^^ extension upward also to avoid the formation o fistula, and t°J°^f jJ. *"y„P^^^ tissue between the and a resulting ;^r/.,V cellultUs ^^l^.'''y^'^^l^l^''^§^Xn^^ They should be recto-vesical and pelvic fasci* ^"^ '.^^ .P!"f "^7he wal s ^nnot definitely be ap- opened widely to permit of Pfi^f^^^^'^X^^' dialinVfro^ the anus, so as to avoid proximated; the incision *h«">^ »^ ,«"/J•"^'?S^& such an abscess, the 5,e hemorrhoidal vessels. In ^^^f P'.^f "^/„°J, *^^^^^^^^ usually divide the incision should ""ite the externa and internal «P^^;"8f- ^^ j^,^ j^ not per- ^-t:^:l^ aS. f f ^itri;r^ jSs^k r^K^s LrJ'sr;evTnrg^tt'=^^^^^^ ^^^^ - - '^ ---^ through the medium of t^etriangdar ligament ^^^ ^^^ .^^^^ Fistula requires ?P-"7" ^f^^"^,^ ^^rX mSar coat of the gut itself, and ir^l^^n^VS^^rLX^^^^:;:'^^^ -penally irritate and sometimes ''^'SS^ the rectum may ^^^^^:,Xi^l^JS'^ two or three inches of the anus. , '" »^'''°V^^^' and'^SrWoo^ which may streak the from contact of fsces with an ">f^™*f„^""'^^^^^^^^ ^hi-^h should be care- stools, there are symptoms due '" ''* ^"/'Xw ^f ^e Lrum, it will press upon the fully studied. If it extends ^.^'^^^^ 'J'^,,;™ sdatica^umbago. sacro-iliac disease, sacral plexus, causing pain ^^^^^^^l^^ ^S^J'S J symptoms in the male may Sr^Ksi,^;SngY^ iirerSip.e'and iniracuble fistul.. m 1693 HUMAN ANATOMY. The relations oi the rectum a^e of much practical importance Those urith ft,- pentoneum have been described (page 17s?) Th* fart tfia^h?; J™?^ 1 * in suprapubic lithotoS^TpLVtectomyf^ In tli'e feUl^r^T^- "'"• °' pushes the hindus uteri Va?d and to3s the pubei "*' '"^ *''""'"'" Enlargement of the prostate may so dep' gready to diminish its lumen. Occasio produced thereby. Acute prostatic inf recognized by rectal touch, as may similai are, for obvious reasons, apt to be associ. painful defecation. (n\ fio^T^^'^u" ^^t ''!■*"'"• ?* '°'' ^''"^'«" «' carcinoma, it may be approached (a komMou,, when the d.se^ is near the anus, by isolating the lower Kf the Si f .^K""•' '? ■'"'''''^'^' ^^^ '"^'^'°" "«y ''^ "nade outside the extemTsnhinc tTe'ir,siLirr"re^t^""t°h: ta;:;^! t-^ch'' ? fn "«2:™tftde eased segmen of ^t invaginated into it and excised, and U^e reSder of th,l rectum and sigmoid united (Maunsell). U) It may be reach^ C,; ^n ^ , or b/sriKrhcTi^r^ '^ '^^ «"«"• ^^ ^-^'""^ ^i*. the anterior wall of the rertum as !■ ptoms of rectal obstruction are • and prostatic abscess may be "ins of the seminal vesicles. They 'th rectal irritation, tenesmus, and PRACTICAL CONSIDERATIONS: THE LARGE INTESTINE. Km «ve a sensation of a broad muscular band around the bowel" (CripP*)- T»^« « S^^ dSt Dosteriorly and represents the posterior edge of the levator am. It is 1^1 fSL CTtf^ anus. A patulous condition of tl.. anus or a cavernous or CuoSi*^'' condTtion of the rectum should suggest stricture, the muscles below whtlT^ng no function to perform, become enlarged t"'* >'"'^'"«\ ,tnre '^' rSv tiX eriD of the finger, with marked tenderness, should suggest tissure. tionaly tight gnpotneng , increased area of bowel wi.l be made vesicles and in som^c^aporuon^^^^^^ ,he rectum explain tate and at the «*1"' ^^'^^'^^^jch during defecation, their contents are *:reS into^e'urlt^KrrScr^^^^ mises. exciting the apprehension "* *?„PSer th^l^Sr'm™^^^^^^^^^ to its bas-fond. and evenif not dis- -4sSH^cifei^:sa^i^t^£^a..so '^ Tn femST/l^o-vaginal walls and the os uteri '-X .^j^J -^^Sll^^^ ss3-fs3ss:ss|»=gs under normal conditions, and tense, tender, and bulging if an abscess occupies admission ol air. and inspection is thus 'acihtateri. ^ (c) By iaugies stricture may be recognized but '^[^ JJ*,"** '^^T'"" Lids-is action dL to^ contact with one of the -fjf^b^S^^^ST si'^^^^^^^ Ss not mistaken for a contracUon. It should be remembered too t^^^^ tne ^ to the .traeture. menSonc. ,. «)( . ) *«»f'"° " ^^f 3l'e«, S^o-iKhiatic t694 HUMAN ANATOMY. arch ; (5) the internal iliac artery through most of its course ; (C) in the female the uterus and the ovaries. If the hand will enter the sigmoid flexure, most of the abdo- men may be explored. Examination through the rectum by this method is distinctly dangerous from the risk of laceration of the gut. It is therefore not in much favor. DEVELOPMENT OF THE ALIMENTARY TRACT. Reference to the cross-section of a young mammalian embryo (Fig. 1428) shows the early relation between the primitive gut and the yolk-sac, of which latter the former is evidently a part. The longitudinal section of a very young human embryo (Fig. 46, page 39) emphasizes the wide communication between the two. The differentiation of the gut from the yolk-sac is accomplished by the approximation and union of the two splanchnopleuric folds which consist of the entoblast internallv continuous with that of the yolk-sac, and the visceral layer of the mesoblast exte'r- nally. As the union of the splanchnopleurae proceeds, the gut-tube becomes closed Fio i4a8. Neural tube Amniotic lac. Amnion, Body-<»vity_/, Vitelline vein. Open K"t-tulw Transverse section of esrly rabbit embryo. %h< Myotome •Xotochord Primitive aorta Bodyni»»V»ir anal groove, indicates the position at which the membrane breaks through to establish the cloacal orifice in those forms, as birds and mono- FiG. I4JO. Mid-brain Optic vesicle. Fore-brain ind-brain I pharyng. pouch Ventral aorta n pharyiig. pouch ■III phary-ng. pouch .Gut-tube Duct of Cuvier Aorta Liver Vitelline duct Vitelline Neural tube artery Gut-lube, lower part Belly-stalk Reconstruction of sagittally sectioned human embr>o ?^,v '^■"■■''' sJiowinK relations of dixestive tube, x 26. {ji/ler His modrl.) I pharyng. pouch 3 aortic bow II pharjng. pouch 3 aortic bow III pharyng. pouch 4 aortic bow IV pharyng. pouch Lung-anlage Allantoic duci. L'n-.bilical artery- Reconstruction of digestive tube of preceding em- bryo ; aortic bows and trunk also shown. X 36. (Aftrr His model.) ^ o,?lv7J^rM cloaca persists. In the higher mammals the cloacal stage is only temporary, the cloaca becoming subdivided into two compartments by the for- mation of a septum, which grows downward to meet the cloacal membrane The anterior compartment becomes the uro-genital sinus, the posterior the rectum. wffh th.';,'''"""'""-^ f , ooP -h.cK LxTe. • from the ston.ach ventrally. its closed end or arcf. being attached o he vUeline ducT and then returns to the posterior body-wall to be continuous with the Sinai Snent. which maintains itrsagittal relations in close attachment wUh th^o™^Snmd.;r^' of the bodv-c.ivity. The inferior limb of the loop early shows WinnSdifferentStion into large int^tine. the junction of the latter with the smdl Stbe beingTndicated by the flight c<-ecal expansion. Even at this period a defi- SrSular relation has been established by the three main segments of the gastro- 107 1698 HUMAN ANATOMY. intestinal tube and its mesentery. Within the meaogastrium course the three branches oi the coeliac axis ; the superior mesenteric artery passes within the mesen- tery between the limbs of the intestinal loop, while the inferior mesenteric artery is distributed to the last part of the intestinal tube. The subsequent changes which the intestinal tube exhibits during its growth have been carefully studied in reconstructions by Mall,' whose conclusions differ materially from the prevailing views. According to this investigator, the rapidly augmenting liver-mass occupies so large a portion of the still small abdominal cavity that there Ls no space left for the expansion of the intestinal tube. In consequence of this con- dition the greater part of the gut is early displaced from the abdominal cavity into the coelom within the umbilical cord, the upper limb of the U-loop then lying to the right and the lower to the left. The growth of the small intestine — more rapid than that of the large — soon results in the production of six primary coils, the identity of which is retained not only throughout development, but can be established even in the adult (Mall). The first part of the gut-tube, continuous with the stomach and receiving the ducts of the liver and the pancreas, increases relatively little in its Fio. 1 43 J. Future diaphngm Anterior mesentery (falcifurm ligament) Anterior menentery (gastr^hepatic omentum) Umbilical vein Body-cavity, Connection of. vitelline btallc jSujierior menen- leric artery Mesenterium commune Inferior mesenteric artery Allantoic duct Cloaca deginninjc of large Intestine Diagram showing early relations of anterior and posterior mesentery. { Based tm JIgurta of Mall and Toldt.) length, and therefore does not become secondarily convoluted, as do the remaining coils of the small intestine. This part is later represented by the duodenum. The outer primary coils undergo great elongation, and consequently present secondary convolutions of increasing complexity, all of which for a considerable time (uniil the embryo has attained a length of about 30 mm. ) are retained within the umbilical ccelom. About this period the lower part of the body grows rapidly, resulting in increa.sed space within the peritoneal cavity, which now affords room for the tempo- rarily displaced gut-coils. In consequence of these changes the intestine returns to the abdominal cavity, and in embryos of 40 mm. length the coils no longer lie within the umbilical cord. Mall has shown that their return to the abdominal cavity occurs ill a definite order, the upper part of the small intestine being first withdrawn, the large intestine with its ciecal dilatation last. On re-entering the abdomen the upper part of the smalt gut passes to the left hypochondriac region, while the lower segment of the small iiitestine with the caecum takes up a position towards the right hypo- chondriac region. Coincident with this migration the large intestine is differentiated ' Arch, fur An.it. u. Physiol., Supplement Bd., 1897. DEVELOPMENT OF THE ALIMENTARY TRACT. 1699 to the segment in front of the bend. Once back .m »^^„l.^^;^^,y ,^y ;„ the saR.ttal plane of the cord, are arranpl gen- erally at right angles to the long ax» of the bcKly. and the antero-}x«tenor colon becomes transverse ( Mall ). m consequence of these changes the p«jr- tion of the large g..t that lay w.thm the cord now lies obliquely acr.«s tht ab- domen in front of the ducKlenu.n the remaining coib of the small mtestme Cg placed below. The oecum therefore, occupies a position beneath tSe liver on the right side, as a slight dilatation at the beginning of the Tiinsverse colon. . The ca-^«Po""K 1^^^ to ^^ «or s^^e time after birth, tions of the large intestine, however con^«eto^ relations and it is not until the third y-^'^^'^^^^^'^i he transverse and ascending colon The anomalous anangement ^^P^* °" ™ ^^^j^ ^^e usually dependent upon ""'^ *':^r"eroomenraSe' imSffig to t^ke up a transverse and superior Sot a^d hrcrlitJringTrelations with the small intestine. hain«ii embryo ot 17 mni.vert«-br.«Bl«pn ^^^^ ^,^, umbilical vein ; ft . I"™" y"!" ' ;„ '(f,, and in th» Iw" Fio. US*" Fio. 1435- Stion of (oramen of Wioslow. X 8. (.Vail.) » ^Wrrht literal diverticulum from the larger The c«cum, which ^^J «PP^^"f4^Su^ (fS. 1432T. increases in size until inferior Umb of the primary Ujoop^f the gut^^^^^ ^ ^1 ; i^tinr m"'^vJS"ofT^rl^ the cLum. however, is not uniform, since its 'Anatom. Anzeiger. Bd. xvi., 1899. 1700 HUMAN ANATOMY. if dependent terminal portion does not keep pace with that nearest the intestine. I li, ajjical sefrment of the aecum remains proportionately small, and persisis as the \« i mifornr appendix. The latter, therefore, corresponds to the unexpandetl morplio logical termination of the caKum. This relation is evident at birth, when the apin ndi v forms the direct ce)ntinuation of the funnel-shaped c*cum ; it is exceptionally r. tainetl in the adult as the fcetal type of caecum occasi«)nally observed. Usually tli. cacum continues to expand with the colon, the demarcation of the apiiendix 1.. coming progressively more emphiusized. until the relative size of the two tulx-s cmn monly seen is established. The usual displacement of the appendix, so that it aris.s from the left and posterior wall of the ciecum, results from the later unequal exp;insi..n of the right side of the latter, whereby the origin of the appendix is pushed to th. left. Differentiation of the walls of the intestinal tube begins eariy in the third month by the formation of longitudinal folds, at first in the upper part, later the entin length of the small intestine. These folds increase in number and size, and siil»it- quently break up transversely into areas from which the villi are formed. The lattoi first apjjear in the upper part of the .mall intestine in embryos of about 30 mm in length (Berry'), and gradually .v^end to the lower segments, the villi Ikmiil- present throughout the small intestine in embryos of about 10 cm. in length \'illi also exist tempora-ly in the large intestine, but later undergo absorption, so th.it shortiy after birth . y have completely disappeared, while those within the small intestine have pr- -j increased in numbers and .size. Early in the fourth month tin intestinal glands , pear in the upper part of the tube as minute diverticula clothed with e.xtensions the entoblastic lining of the gut. The glands of Brunner de\ elon somewhat later during the same month as outgrowths of the entoblast. During the fourth month the mesoblastic stratum, from which arise all parts of the intestinal wall except the epithelial elements of the mucosa and the glands, undergoes differentia- tion into the muscular and areolar layers ; by the close of the fifth month all coat.s of the intestine are well defined. Differentiation of the Body-Cavity.— Owing to the precocious develop ment of the mammalian heart, the latter organ is formed by the approximation and hision of two lateral aniages, at first widely separated, in consequence of which union the upper part of the ventral body-wall is closed, while the more caudally situated is still incomplete, the gut-tube being but imperfectly separated from the yolk-sac. With the more advanced closure of the ventral body-wall the abdominal canity is de fined. The primary ccelom, according to His, may be divided, therefore, into an upper and a lower portion, the parietal and the trunk-cavity respective!) . These spaces communicate on either side by an extension of the parietal cavity, xh^i parietal reass of His. The ventral portion of the parietal cavity, which from its e:!rliest api>ear- ance contains the heart, becomes the pericardial cavity, and is, therefore, appropri- ately named Xhe pericardial cvlom (MalD. The upper part of the parietal recess, since It later contains the lung and forms the greater portion of the surrounding lung-sac, may similariy be designated the pleural cielom. For a time the separation between the pericardial and pleural coeloms is imperfect, owing to the incompleteness of the postero-lateral walls of the heart-.sac. This deficiency is corrected by the growth and difTerentiation of \he pulmonarv ridge (Mall), a structure that extends from the liver along the dorsal wall of the duct of Cuvier to the dorsal attachment of the early fold suspending the heart, or mesocardium. Mall has shown that the pul- monary ridge grows headward as the pleuro-pencardial membrane, which completes the separation between the heart and lung-sacs, and later tailward to form the pleuro- Peritmeal membrane, which sui sequentiy aids in closing the communication between the pleural and peritoneal cavities. At first, immediately below the young heart lies the wall of the wide yolk-stalk embedded within the mesoblastic tissue of which the two large vitelline veins passs in their course towards the lower end of the heart. With the formation of the body- wall and the narrowing of the yolk-stalk, the enlarged vitelline veins, in their journey towards the heart, produce a broad fold which projects horizontally into the body- ' Anatom. Anzeiger, Bd. xvii., 1900. ' Johns Hopkins Hospital Bulletin, vol. xii., 1901 Journal of Morphology, vol. xii., 1897. DEVELOPMENT OF THE ALIMENTARY TRACT. I7f>l cavity and extends from the ventral wall to the sinu» venosus, its medan part be- neath the heart beinj; attached dorsally to the gut-tulx;, while its lateral expansions form the floor of the pleural ccelom. This imperfect piirtition, the s,ftum IraHS- ■ersum of His, also affords passage for the two ducts of Cuvier, formed on each side bv the union of the primitive jugular and cardinal veins, to gain the sinus venosus ; the septum transversuin receives the hejiatic outgrowth from the prinutive ducxlenum, which soon develop a conspicuous liver-mass within the sul»stance of the st-ptuin. The rapid increase in the mass of the developing liver is attendevl by grent thicken- ing of the septum transversum. |>articularly towards its dorsal etlge. Ciicidently with this augmentation, the septum differentiiites into a thinner up|>er antl a thicker lower stratum, the former constituting the floor of the pericardial cavity and sur- rounding the ducts of Cuvier, the latter enclosing the liver. Fio. 143*- Tniihea, Pericardial uc Septum traiuvcrkum Lotip of small intoliiie extend ifiK into cord Vitelline vesseh' Caecui Reconitructlon of human embr>o of 17 mm. vertex hreech lenKth. X 14. ^Mall.) The subsequent development of the liver is attended by progressive, although only partial, separation of the inferior layer from the superior stratum of the septum transversum, the latter layer remaining as the primitive, but still imperfect, dia- phragm between the pleuro-pericr iial and peritoneal divisions of the body-cavity. The dorsal attachment of the septum transversum, at first high in the cer\'ical region, gradually recedes tailward. On reaching the level of the fourth cervical segment the fourth myotome is prolonged into the upper layer of the septum to supply muscular tissue to what now becomes the diaphragm. The latter, however, is still incomplete dorsally, owing to the existence on each side of the communication between the pul- monary B id peritoneal sacs. This opening is gradually closed by the backward growth '> Iha diaphragm and the forward and downward extension of the pleuro- peritoneal membrane until the aperture between the thoracic and abdominal cavities is effaced and the diaphragm is complete. 1702 Ht MAN ANATOVIV li i Development of the Peritoneum. -Th. attachmtnt of the -rimitiv. . , menury tube. fr™.> tht -csophaKUs downward, lu the ,H,Ht. rior wall ,„ the 1„ cavuy by means.,, .. sauttaf fold, the />hm^.o' mrsenUrv. lu.s already !.ee„ , 'pasre 1697) I-ikewtse tht- conventional divi m of this dupli, iture into a iou,r attac hers.. me", K»>tr,um U h.nd the stomach. The ventral mes. ntcry is a. t,r. attachluLve , , theseplm,. transversum and in front to the body all' as fa. a> ,. en'. : ,ce of th.' umbilical vem. which .^upies its Umrer free horde, as far a.s the liver /.s already PlO. 1437. Vertebral column. Spinal con I Lun«. Pleural Mc- Communication between pleu- ral and perito- neal t :.vitica , ^.-5»«- . Spleen M^fi Se\uaiK>and4 Kidney Alri-.i ' r Wolffian body Stom.li h Omenta' u- Greater unn ntum Pi-^, i>( MKitlal 'section ingi incidentalb the lai he diaphras:!!! by tin note rotr. ilea- the sept tainit^ the i v. > of 4aminat i tht -des ami ij of folc; ^tached a > • liver .Teyond s- e> ;. '. {'■ ,t x\y siispt sorj c!osiiij4 tin surface of 1 dij^estive tuL. i, bilt-duct, pori.il vei, II . , ahowinx thoracic and abdominal oritana. x 15. ng its development is almost entirely free th. nstitutes the gastro-hepatic or lesser omentum and contair»- the and hepatic artery. ■in^versi! ' later.1l e.\ '■e Mjiarati, >(■ !!\er do ] ■-' tliaphni ends all F.VEI.OI'NfENT OF THE AI.IMENTARN IKAl I >7r>.l in general, the ser>.js niembranes lining the pleural and peritoneal cidoms rep- resent the specialized nie8obl.i>uc laver forming the immediate l).)nn(lary of thest cavitie;. The peritonei n, therdore, covering the lower surfaci- oi the uaphrav'm md certaii surfaces of ! he liver is derived from those |)ortions ..( tht st| ;mn trai\!*- ^umthit con-itiif- the up|)er and lower walls of the hep 'ic reccssts which rt- ,trumeiual in ft. n the liver from its primary position wiili.u he st-ptum. iwration of the i trom the diiiphragm is incomplete not only abovt . .is alru.. ^ •ted, but also bi ad ; consetpiently the greater part .f the |)<»ittri(tr surface of lo .in remains atta hed to the (M)Sterior body-wall by iiclar tLs- an. h non-p. ,i- "eal, the remains f thi periphi-r .1 portion of the I. r layer ol the -ipiuin traiis- suin, which beco nes tlie f^ri «um of the liv >ein^ reflecteti i' the sules backward as the .w tarv //.'an /'.i. ...,., Coincidrntly with the dev pment of the liver ami its hi— ration fr. n the sep- ■um transver^um, hestoin.i h u> rgoes change in its axi^. which ijecomes less > ortical and more obliquely traiisv. -• and in consequence its ; uch- 't to th hver. the primitive ga;*' ht-padt net urn, is drawn tow the tight and assumes a Fio. i4j8. -ural cube Myotont. t'mbilical v«inai Umbilical artery Body-wall conlinuous with amnion^ Transverse !>t >i«n rff rabbit embryo of eleven and a half day» ahowint primitive r: transverse position almost at right angles to its former sagittal , lions in the position of the stomach and its anterior mesentery triuni, whifh liecomes elongated and twisted towards the right td lit order tn iiairatain its attachments to the greater curvature. ii changei is nt- .roduction of a p. K-'ket liehind ih ■ stomach, the floor which are the lesogastrium, the roof be'my: -.he iinder surface of th |H>'-k»-t, the /f,r ■ sac of the peritoneum . cor.iiiuiiiicatcs with the rem. tlK pt-ritoneal cavtty on the right by me;.'i^ o) a i>.issage liehind the di-placc ..r ;ra.s^.>-hepatic .nnentum, the free bordi r oi the latter bounding the open ;ht f.iiiach ■U of th«^ left wah Ol \cr. T 'tis ling pai f e>-cr lead iii!^ int- the passage or vcsiibuU (page 1749) The opening, at first la- laf diminishes in size and becomes the foramen of Winslow, which leads i . the ijreater prritoneal sac into the vestibule of the lesser. H^»iwCT«-h tpe stotnach vet v -oon appear- an extension of the pock. which ushes ou' tetween the stomach above and the transverse colon below. This , ntru- m, the omefft ■! sac, continues t ' sjrow downward and forms an apron whi-h i-r, .11- the greate mentum, covers th'- loops nf the small intestine. On re to Ftg. 1439, it vident that the greater -imenium at tirst comprises a dupli. the 1704 HUMAN ANATOMY. ^\,. >:....., anterior and the posterior fold of which each consists of two serous surfaces enclosing; a thin stratum of intervening; tissue ; there are, therefore, four serous layers inchiil.d within the original omental curtain. Tracing the posterior fold of the latter upward. it is seen to pass over the transverse colon and the mesocolon, without attachmi'iii, to reach the posterior body-wall. On gaining the latter, the anterior or inner ser separation is no longer possible, since the posterior layer of the greater omentum ami the transverse mesocolon and colon become fused, the intervening serous suriaces and space bfing obliterated in consequence. Thereafter the periton.-i layers of the greater omentum are attached to and apparendy enclose the large gut, one pa.ssini; as the upper, the other as the lower serous layer of the transverse mesocolon. I consequence of these fusions the serous surfaces originally behind the pancreas als. . disappear, and the gland thenceforth assumes its permanent, although secondary, retroperitoneal relation. Subsequendy the originally distinct folds constituting the greater omentum fuse, and after birth usually appear as a single sheet attached abovi- to the greater curvature of the stomach and behind and below to the transverse colon. The excessive volume of the right half of the liver not only induces the o!) liquity and rotation of the stomach, but likewise influences the disposition of the in- testinal coils on their return from the umbilical coelom into the peritoneal ca\ ity. The duodenal s^ment necessarily follows the migration of the pylorus ; its begin ning, therefore, lies to the right, while the lower end passes to the left with the jejunum. Since the most available space within the abdomen, to the left and below, is appropriated by the coils of the small intestine which first return to the peritoneal cavity, the most movable portion of the elongating large intestine, the trans\ ersc colon, is displaced upward and assumes an obliquely transverse position beneath tin- stomach and liver, above the rapidly increasing volume of the coils of the small gut. The latter tend to displace the descending, later also the ascending, colon later- ally and backward. In consequence of these influences and changes the transverse colon crosses and lies in front of the duodenum, which is thus pushed against ihv abdominal wall. The serous investment of the duodenum undergoes obliteration where such contact is maintained, and later occurs chiefly on the anterior surface of this part of the gut (Fig. 1403). Reference to the original relation of the primitive mesentery (Fig. 1432) in- cluded between the limits of the U-loop shows the principal dorsal attachment of the mesentery to be the comparatively limited area along the body-wall opposite the urn bilical loop. The intestinal margin of the mesentery, on the contrary, rapidly expands to keep pace with the increasing length of the gut-coils, the result being that thu mesentery attached to the upper — soon right — limb of the umbilical loop assumes more and more the form of a rufHe, towards the edge of which ramify the branches of the superior mesenteric artery supplying the small intestine, — the later vasa intes- tini tenuis. The branches distributed to the left or colic limb of the U-loop pass to the large gut through a mesentery only slighriy wavy. When the arrangement of the intestinal coils takes place, the small gut occupying the left and lower parts of the peritoneal cavity and the large intestine being reflected upward and a ;ross the duodenuin, twisting or "rotation" takes place around a fixed point marking the duodeno-jejunal junction. This location also corresponds in general to the early position of the superior mesenteric arter>', the relations of the branches of which are also affected by the rotation of the mesentery, since thereafter the vessels passing to the coils of the small intestine lie on the left and those to the large gut on the right side, — the opposite of their original situation. On assuming its position in front of the duodenum, the attachment of the trans- verse colon is at dr-'.t a limited sagittal one. With the backward displacement of the duodenum, the mesentery of the transverse colon also comes into relation with the posterior parietal peritoneum and acquires a secondary attachment extending cross- THE LIVER. 170S wise, thus forming the dorsal connections of the transverse mesocolon which exist until hision takes place between this duplicature and the posterior fold of the omental sac. Since originally all parts of the large gut possess a mesentery, the descending colon and sigmoid are for a time provided with a free mesocolon. In consequence of the increasing bulk of the small intestine the descending colon is pushed not only to the left, but also against the body-wall. The intervening serous surfaces usually disappear behind the gut, which later, therefore, ordinarily possesses a peri- toneal coat only in front and at the sides. In a considerable number of cases, how- ever, this fusion and obliteration do not teke place, the mesocolon, although displaced towards the left, then persisting as a free mesentery for this segment of the gut. The fold attached to the sigmoid for a time allows of great mobility ; subsequently this is reduced, although partly retained as the definite mesosigmoid. The rectal segment of the large gut retains its primary sagittal situation, but loses the greater part of its peritoneal coat, becoming attached to the posterior pelvic wall by areolar tissue. . . .■■ The ascending colon and caecum, in their downward growth towards the right iliac fossa h-om the hepatic flexure, carry with them a peritoneal covering. This remains Fio. 1439. A /I c ago. pgo. DiaKtsRii illiutratinfr fomulion of grater omentum and omental nac. A showa duixlenum and inncrras in mesoxastrium unattached; in ^ these organs are pertlv against posterior abdominal wall, postertnr wall nf IcAwer prriumeal cavity is still free; in Cduodenum and pancreas lie against posterior abdominal wall, posterior wall of omental sac has fused with transverse mesocolon, a, aorta ; rf. diaphragm ; /, li\*er; //, falciform ligament ; ni'. um- bilical vein ; s, stomach ; Ic, transverse colon attached by transverse mesocolon {Imc) ; Ji, small Inlcslinc attached by tne5enter>- («); p, pancreas; du, duodenum; Ifis, lesser peritoneal sac: os, omental sac; /«, lesser omentum; /^o, greate. omentum ; ajro and pgo^ its anterior and posterior layers ; /, fusion between posterior wall of lesser peri* toneal sac and transverse mesocolon. {After Kollmann and ftertwtf,) unattached over the caecum and appendix, but forms secondary connections where the ascending colon comes into contact with the abdominal wall ; hence this part of the colon usually posses.ses a serous coat only anteriorly and laterally. Sometimes, however, obliteration of the serous covering does not take place, the ascendinc -olon being attached by a mesocolon. The vermiform appendix being primarily an outgrowth from the large g ince it represents the morphological apex of the caecum, is completely investta with jieritoneum and is without a mesentery. Later the appendicular artery, in its course from the ileo-colic to the appendix, produces a serous fold which stretches from the left layer of the mesentery of the ileum to the caecum and appendix. This fold, the meso-appendix, is, therefore, functionally, but not morphologically, a true mesenterj'. THE LIVER. The liver (hepar), the l.irgest gland in the body, is formed of very delicate tissue disposed around the ramifications of the portal vein. It is developed in the anterior mesentery, its mesoblastic elements having a common origin with the diaphragm. 1706 HUMAN ANATOMY. [ : I : i while its duct and glandular elements are derived from a sprout from the duodenum ; hence the liver, as are other j?;lands connected with the digestive tract, is an nut- growth and appendage uf the Jimentary tube. Its peculiar shape is chiefly duu ti> the pressure of surrounding organs, as its tissue is so plastic that it is moulded l)\ them. In the adult it becomes firmer from the increase of connective tissue, Ixit under normal circumstances >t is always verv soft, and, unless hardening agents arc used before its removal, collapses into a flattened cake-like mass affording littk- information as to its true form. Indeed, it is only in the present generation, since the introduction of adcqi'.ate methods of hardening in situ, that this has bt-tn learned. The 'iver in general may be described as an ovoid mass which in the yniiti^ fcetus nearly fills the abdomen, but in the adult has the appearance of having ha^ in.), dne peculiar form of liver occasionally met with shows great increase of the right lol>e, partictilarly in the vertical direction, with a want of development of the left lobe, which is thin and short (Fig. 1456). The weight is, with considerable variations generally from 1450-1750 gm. , or approximately from 3-35^ lbs., and in the aihilt is about one-fortieth of the body weight. The specific gravity is given at from 1005-1006. The color is a reddish brown. The naked eye can recognize that tin surface is covered with the outlines of polygons from 1-2 mm. in diameter. These are the lobnlfs, each of which is surrounded by vessels and ducts in connective tissue, and contains in the middle a vessel, the beginning of the system of the hepatic \ein. Sometimes the centre of the lobule is lighter than the periphery, sometimes tin reverse, depending upon whether the blood has stagnated in the portal or hepatic system resjiectively. THE LIVER. 1707 Surfaces. — In its natural form, as shown in specimens hardened before removal from the body, the liver presents five surfaces. The superior surface is in the main convex, looking upward beneath the diaphragm. The anterior surface, directed forward, is continuous with the former, on the hardened liver a fairly distinct line marking the change of direction that separates them. The right surface faces towards the right and is separated in a similar way from the superior. It passes insensiWy into the anterior surface. In a flaccid liver, in which the normal form has been lost, these three surfaces are indistinguishable, constituting the old superior surface. In the hardened organ the three represent a dome, of which the flattened upper surface is slighdy separated from the others. The posterior surface is on the back of the right lobe. The inferior surface is moulded over the organs beneath it. The borders are best described from the 'posterior surface as a starting-point. The upper border of the latter separates it from the superior and right surfaces ; the lower border from the inferior. On the right these i ict at a mor- or less acute angle. On the left the posterior surface narrows to a border, first thick and then sharp, which runs around the liver, separating first the upper and lower surfaces of the left lobe and later the lower from the anterior and right ones, until finally it reaches the right end of the lower border of the posterior surface. Along the front of the liver the border is sharp and directed downward, overhanging the concave lower surface. A conspicuous incision, the umbilical notch (incisura umbilicalLs), in the anterior border marks the place at which a sickle-like fold of peritoneum, the/a/«- form ligament, conveying the obliterated umbilical vein, now the round ligament (liKamentnm teres hepatis), to the lower surface, reaches the liver. The falciform ligament is continued back between the top of the liver and the diaphragm, and marks of! on the anterior and superior surfaces a large right lobe and a small left one. The superior surface (Fig. 1440) includes the upper part of both lobes and is moulded to the opposed surface of the diaphrs^. The top of the right lobe fills in the whole of the space below the correspondii^ half of the diaphr^m, but the left lobe does not usually reach the walls of the abdomen, unless in front. It may, however, touch the left wall. Well-hardened livers show a sl«ht cardiac depression on the left lobe beneath the heart. The posterior border of the superior surface is marked on the right lobe by the reflection of the peritoneum onto the diaphragm above the triangular posterior surface, and on the left by the rounded postenor border of the liver The right and anterior surfaces lie against the diaphr^m, except where the anterior rests against the abdominal wall between the costal arches, and offer little for description. . . , . The posterior surface (Figs. 1441, 1456), on the back of the nght lob., con- sists of a triangular non-peritoneal area and of the lobe of i^igelius. The former, adherent to the diaphragm, extends from the inferior vena cava to the right, where it ends in the point formed by the meeting of the upper and lower borders. The greatest vertical dimension of the non-peritoneal area is not over 7.5 cm. (3 in.), and the transverse not over 1 2. 5 cm. (5 in. ). A triangular hollow at the lower border of this space, just to the right of the vena cava, receives the right suprarenal capsule, which rests also on the lower surface. To the left of this depression is a deep furrow for the inferior vena cava, which som< times at the top is converted into a canal. Still farther to the left is the lobe of Spigelius (,l">w«» caudatas), — a four-sided prism placed vertically on the back of the liver, bouiiding a part of the lesser cavity of the perito- neum. The lower end, which hangs iree, is continuous on the right with the caudate lobe (processus caadatua). It often presents on the left of the lower end a distinct tubercle, the tuber papillare (His), which is by no means constant. The Spigelian lobe lies between the fossa of the vena cava on the right and t\iK fissure of the ductus -.enosus on the left The latter joins the former in front of this lobt . just below the dinphragm, so that the lobe ends in a point above. It more or less encircles the vena cava, sometimes meeting the right lobe behind it. The vena cava is frequently over- lapped by a projection from the right lobe, and sometimes the overiappinrj is done both by this and by the lobe of Spigelius. The prismatic slia^e of the latter is well shown by transverse sections. The amount of attachment to the rest of the liver varies, and the shape of the lobe with it. Sometimes the figure of the ductus 1708 HUMAN ANATOMY. venosus makes but a small angle with the portal fissure, so that it is a three- instcui : of a four-sided prism. It is also influenced by the depth of the fossa for the vcii.i cava, at times being attached merely by a line of tissue. To the left of the tissin. of the ductus venosus the posterior surface of the liver is continued as the postiric .r border. This at first is thick, and presents a rounded wsopkagetU impression for the end of the gullet to the left of which it becomes sharp. The inferior surface (Fig. 1442) of the liver is subdivided by a system i.f fissures formerly described as resembling an H. This description must be moditicd by recognizing that the posterior limbs of the H are not horizontal, but run vertically on the hind surface of the liver, and that the cross-piece — the portal fissure — is not in the middle, but very near the posterior border of the inferior surface. The oltl error came from studying distorted livers in which the posterior surface had flattened out so as to be reckoned a part of the inferior. The portal or transverse fissure (porta hepatls) is of an entirely dif!erent nature from the others. It is the hi/um of the organ for the passage of the vessels and ducts ; while the other fissures more properly deserve the name, being due to the pressure of the g^U-bladcier and of vessels. The portal fissure is from 4-5 cm. ( i yi-2 in. ) long. It transmits the por- tal vein, the hepatic artery, the subdivisijns oi the gall-duct, the lymphatics, and SpigctiAn lobe Fio. 1441- Falciform ligament Fitsure for. ductus venosus Tuber omental*- ■Vena cava .Non-peritotieal surface Suprarenal .vein OWKeretcd nmbtltral win Quadrate lobe Caudate lobe Gall-bladder Posterior surface of same liver ; peritoneal reflection indicated by white line. Rijfht lateral ligament I the nerves, all enveloped in a mass of areolar tissue known as G/isson's capsule. The large portal vein is posterior. The hepatic artery lies before it on the left ami the hepatic duct, formed by two chief tributaries, lies before it on the right. The lesser omentum is attached to the lips of the fissure outside of these structures. At its left end the portal fissure receives the umbilical fissure, which runs backward from the notch in the anterior border and contains the obliterated umbilical vein, in the adult known as the round ligament. This fissure is very often bridged over. Continuous with the umbilical fissure, the fissure of the ductus venosus ascends the posterior surface, only a small part of it being on the inferior aspect. In foetal life it contained the blood -channel (ductus venosus) which established a short cut between the umbilical vein and the inferior vena cava ; after birth it is reduced to a cord of fibrous tissue (liKamentum venosum). At the left end of the portal fissure the falciform liga- ment joins the lesser omentum, the latter being continued backward in the fissure of the ductus venosus. The fossa for the gall-bladder (fossa vesicae felles) is a depres- sion on the under surface of the right lobe, in which that organ rests. It may or vn-As nnt indent the anterior border. Broad in front, the foH,sa narrows t" a fissure behind that joins the right end of the portal fissure. The quadrilateral region on the under surface of the right lobe, bounded by the portal fissure behind, the border of the liver in front, the gall-bladder on the right, and the umbilical fissure on the left, THE LIVER; 1709 is the quadrate lobe (lobes qaadratus). Behind the portal fissure the lower end ol the lobe of Spigelius appears on the inferior surface, with the groove for the vena cava on its rwht and the fissure of the ductus venosus on its le» The caudate lobe (proctasos candatns) is a rounded ridge, particulariy developed in eariy life, running from the under side of the right lobe, just behind the right part of the portal fissure and in front of the vena cava, obliquely backward and to the left into the lower end of the lobe of Spigelius. A groove caused by the hepatic artery separates it from the tuber papillare. The caudate lobe overhangs the foramen of Winslow. In the adult it is sometimes rounded, sometimes sharp, and not always to be distinguished. The under side of the liver, being moulded over the neighboring organs, presents many irregularities dependent on their pressure. The posterior part of the under side of the right lobe is hollowed into the renal impression, a concavity fitting closely over the right kidney. The suprarenal capsule rests against the liver to the left of this, at the beginning of the caudate lobe on the under surface and also on the posterior surface. The first part of the duodenum rests against and moulds the under side of the right lobe between the renal impression and the gall-bladder. This area of con- Fio. 144a. Spicdiui lob* CRiophatcal iMprawioa Vena cava Richt capniUur vein Fiuure fac| ductus vcnoftua! Hepatic atttry Portal vein Common bile-duct' Oblitciatcd umlrfllcal vein Quadrate kibe . Cyntic dud Gail-Uadder Inferior and porterior .urfacet ol lame liv«. _ It rnu*. he clearly underrtood that »|» Sfi*'";"^*"? «" "^ areon tlie poMerior lurface, Uie limit d Uie interior surface behind being the traraverse fiwure. tact can hardly be called an impression, for the surface here is slightly convex. In front of the renal impression is a hollow for the colon of very varying size. It may be almost wanting, or it may be very deep. It may be confined to the right part of the under surface, or it may compress the front of the gall-bladder and indent the quadrate lobe, and even the left one. The under side of the right lobe presents also one or more occasional fissures which seem in the main to diverge from the right end of the portal fissure and from the fossa for the gall-bladder. They are more common in the foetus, and some of them occur more or less frequently in anthropoid apes.' The under side of the left lobe is in general concave, resting against the fundus and anterior wall of the stomach. Near the posterior part of the umbilical fissure on the left lobe is a rounded prominence,— /K*^r omentale,—d\iii to the growth of the liver against the non-resisting lesser omentum. The Blood- Veasele.— The portal vein, some 15 mm. or more in diameter, dividw into a right and a left branch, 10 mm. or over in diameter, of which the nRht is a little the larger and shorter. From the right end of the transverse fissure it runs • Thombtm : Journal of Anatomy and Physiology, vol. xxxiii., 1899. m. I7IO HUMAN ANATOMY. backward in a curve to the right of the vena cava, keeping in the lower part of the liver and giving of! successively a series of large branches to the front and ri^ht of the organ. Smaller branches arise from the sides of these. The r^ht prmiary division soon gives ofi a large superior branch almost equal to itself, which describes a similar but smaller curve at a higher level. The general course of the left subdi- vision is towards the posterior angle of the organ, giving branches chiefly from its anterior side, and also one that supplies the greater part of the quadrate lobe. The lobe of Spigelius generally receives a chief branch near its lower end, which run:- upward within it. This branch is most often from the left subdivision, but it may be from the right, or from the vessel directly behind the end of the portal vein. There are several systems of so-called accessory portal veins around the liver in the lesser omentum near the gall-bladder, about the diaphr^m. and, most important, in the falciform ligament, where the parumbilical veins communicate with veins of the integument of the abdominal walls. These accessory vessels, small and incon- spicuous under normal conditions, may become enlarged and important channels Fio. 1443. Portions of inferior and poMrrior rartaces [ia lava is siimewnat diitplaccd forward, its course beinz more vertical when supporteil on |H>steriiir sur- face. Large tipjier branch of riRht division of [lortal vein i« hidden by liver-iubstance. Portal vein ai>d hruiiL-litr^ are purple \ hepatic artery, red ; ncpatic veira and vcn* cava, blue ; bile^ucta, jrellow. «t>, oblitetated umbilical vein , vc, inferior vena cava. for the return of the blood conveyed by the portal vein when the hepatic circula- tion is obstructed. Inder such conditions the blood finds its way from the portal vein into the accessory veins and by the anastomoses of the latter into the general circulation. The hepatic veins carrying off the blood from the liver arise as the intra- lobular veins,, which empty into the sublobular, which join larger vessels con\ ergiiig towards the vena cava. At first the general direction of the small branches is paral- lel fo that of those of the portal system of the same size ; but the hepatic branches always travel alone. The direction of the large branches as they near the vena cava is at right angles to that of the portal. The arrangement of the hepatic branchis is in the main like that of the portal, but near the edge of the liver we find more instances of the union of two rather small trunks meeting symmetrically like the arms of t Y. The main trunks of the right lobe run between the upper and lower br.incheh of the portal. The upper end of the vena cava is considerably en!arj,rr*>. ,7ia HUMAN ANATOMY. •ympathedc fibre* accompwy the hepatic artery, forming the hepatic plexus, to the transverse fissure, where, together with the fibres from the vagus, they pass into the liver along with the interlobular vesseU, to the walls of which they are chiefly dutributed According to Berkley, the interlobular plexuses give oH fine intralob- ular twigs which terminate between the liver-cells. STRUCTUP OF THE LIVER. In its hindamental arrangement the liver corresponds lo a modified tubular gland, the system of excretory ducts of which is an outgrowth from the pri-nary gut-tube. Early in fastal life, however, the terminal divisions of the tubules unite to form net-works, after which the tubular character of the liver becomes progressively Blood-cmpillarici Blood -capillaries Snbi'cbalar bnuicb of hepatic vdn DtaKram of hepatic lobule ; portions of (inure reprwent median lonriludinal •"J'"" "i '*<''^yP»"* "f '""iJJ^i!! section!, also nhown Branches of porul vein are purple ; of hepatic artery, led ; at bUe^ducU, yefiow. Intralobular bile-capillaries are black. more masked by the intergrowth of the cell-cords and the la^e veins. Among some of the lower vertebrates, as in certain vermiform fishes or cydostomes {Myxitu), the primary tubular arrangement is retained. " The glandular tissue composing the liver is subdivided into small cylindrical masses, the lobules, by the connective tissue which, in continuation of the fibrous STRUCTURE OF THE LIVER. «7»S ...uelooe or (t^uU, investing the exterior, at the transverse fiwure enters the or^-anind accoiipanies the interlobular vessels in their ramifications as the capsuie Z^GlissoH (cpMla fibroM). The distinctness with which the lobules are defined deJendi upon tiTe amount of this interlobular tissue In ceru.n animals, notably M ^e hoTthis is great, the lobules being completely surrounded and pUinly dis- ShaWe as sharply marked polygonal areas. In the human liver on the con- r ,rv the interlobular connective t»sue is present m small amount, the lobules, in conswuence, being poorly defined and unceruin in outline. , . . , . , ^he Lobular ilood- Vessels.— Since the arrangement of the blood-vessels is the salient feature in the architecture of the fully formed lobule, it is desirable to Itudv the vascular distribution before considering the disposition of the hepatic cells. As already described, the branches of the portal vein, the functional blood-vessel of the organ, ramify within the capsule of Glisson and encircle the periphery of the obule ; inasmuch L these vessels supply the divisions of glandular tissue with bUiod for the performance of their secretory rdle, they correspond with the inter- lobular arterioles of ordinary glands. , . . . , .: .• i Numorous minute branches are given ofi from the interlobular ramifications of the portal vein which enter the periphery of the adjacent lobules antl break up mto Central vein Section o» liver Injected from taepatk vein, «liowin« intralobatar capiltary net-work Portal vein X 100. the intralobular capillary net-work. The disposition of the latter is in general radial, the capillaries converging towards the middle of the lobule, where they join to form the central or intralobular vein, the beginning of the system of the hepatic veins by which the blood passing into the lobules is eventually carried into the inferior vena cava. The general course of the central vein corresponds to the long axis of the lobule (Fig. 1444). and hence in cross-sections of the latter the vein appears as a transversely cut canal towards which the capillary vessels converge (Fig. 1445). The capillary' network within the lobule is composed of channels with a diameter usually of about .010 mm. ; the widest capillaries — some .020 mm. in diameter — are found in the iminediate vicinity of the afferent and efferent veins, the narrowest occupying the intermediate area. The meshes of the vascular net- work vary from ,oi5-.040 mm. in their greatest dimension, those at the periph- ery being broader and more rounded, while those near the centre are narrower and more elongated. The central vein occupies the long axis of the lobule and increases in size as it proceeds towards the base of the lobule, as the side of the latter through which the vein escapes is termed. It begins usually about midway 108 I7»4 HUMAN ANATOMY. <■-■• between the base and the opposite tide of the lobule, by the confluence of the capil- larica, which, after the central vein i« formed, open directly into the lattti i, lower planes. in those lobuleti which form part of the exterior of the liver tii< central vein ascends almost to the free surface ; otherwise its commcncemi-nt is separated from the periphery by about one-half the thickness of the lobule. Im mediately on emerging from the lobule the central vessel opens into the sub/obulai vein, which runs generally at right angles to its intralobular tubularies and along and beneath the bases of the lobules, the outlines of which are often seen through tlu' waHs of the vein. The channels for the sublobular veins are thus surrounded by the boMs of the lobules, a single central vein returning the blood from each. The Fto. 1446. fitv HcfMtlc ancry^ Purul vein. Bile^dnct. {^,:r >.v -■:.'-:-» . Central (intra lobular) vein .Interlobular connective tiBsue •v^^^-: i'/V ■.:■'<■ /.•'.. -v-vm-- >v.- Section of unbijt^ \7>5 outline and measure usually from .015-.025 mm. in their lonRest dimension. Each cell comes into contact with from six to nine other elements, the surfaces of con»»ct beinrf plane from mutual pressure. Always one side, often more than one, cxhibitt a sliallow depression which indicates the surface of former contact with a capillary ami emphasizes the intimate relation existing between the blootl-vesstis and the cells. The latter Ue against at least one capillary and sometimes several, this relation being dcDcndent upon the size of the blood-channeU. The larger the latter, as at the Dcriphery and near the centre of the lobule, the greater the nmnUr of cells with wilv one or two capillary facets ; conversely, where the capillaries are of smaU diameter, the cells come into contact with three or four. The livcr-cell consists ot finely granular protoplasm which sometimes exhibits a differentiation into an outer and an inner zone. It a without a cell-membrane, although the peripheral zone of its cytoplasm is condensed, especially when it forms part of the wall of the bile- canaliculi. The nucleus, of vesicular form and from .006-.008 mm. in diameter, contains a small amount of chromatin and usually a nucleolus. Occasional cells are conspicuous on account of their large size, as weU as the unusual diameter of Fio. 1447- Section ol onin)ected liver, ihowdiK cords of hepatic cell* between cmpHUry blood veueh. X 450. their nucleus. Such cells, according to Reinke,' undergo direct division and pro- liuce the double nucleated elements constantly encountered in sections of normal liver. Centrosomes have also been observed in resting hepatic cells. Particles of gtvcogen, minute oil droplets, and granules of bile-pigment are more or less constant constituents of these elements. The fat-containing cells are most numerous at the periphery of the lobule, those enclosing pigment particles near the centre The Bile-Capillaries.— These minute canals, representing the lumma of ordinary tubular glands, form a net work cf intercommunicating chanmls throughout the lobule closely related to the liver-cells. Whereas in the usual atrangement a single surface of several gland-cells borders the lumen, in the exceptional case of the liver the excretory channels are bounded by the opposed surfaces of only two cells, the bile-capillary occupying but a small part of the surfaces, on each of which it mr-4eh a narrow, c^ntrallv situated groove. Moreover, not only a single surface of the hepatic cell takes part in bounding the canaliculi, but the latter are found between all surfaces where two liver-cells are direcriy in contact, so that each hepatic element comes into direct relation with a number of bile-capillaries. The latter, ' Vcrhandlung d. Anatom. Gesellschaft, 1898. I7'6 HUMAN ANATOMY. however, never lie on the narrow sides of the Hver-celb ofiposed to the blot vcsspU, the bile-canal never separating the blood-capillary from the cell. While tl picuoRiinating direction of the bile-capillaries is radial and corresponds to il.- Fio. 144S. ' tin ^T •. -Blood-«|>iair>' .BII«-vmi>*Uanr .Uvcr-ccll FlO. >449- j}' ^'z:': '-1^ ^ ^^ ':^. '^^ Section of liver in wliick both blood- mA bilc-capilkric* tatv* been mJccMd : the latter MimMnd the Individual livrr ctlli. X 3110. similar general disposition of the cylinders or leaflets of hepatic tissue, the ncii.il arrangement is converted into a net-work by the numerous cross-branches. Tlie rt-sulting meshes correspond in size with the individual liver-ct 'Is, \}hich, in appio- priate sections, often appear almost com- pletely surrounded by the bile-capillaries. The latter possess no walls other than the substance of the liver-cells between which they lie. The diameter of the bile-capil- laries, from .001-.002 mm., remains prac- tically the same throughout the lobule until the canaliculi reach the extreme periphery. At this point the liver-cells abruptly dimin- ish in height and are transformed into the low cuboidal cells lining the excretory tubes that pass from the lobule into the surround- ing connective tissue to become tributaries to the larger interlobular bile-ducts. The ultimate relations between the bile-capillaries and the liver-cells is still a subject of discussion. Based upon the evi- dence supplied by injections and silver impregnations, it is believed by some (Kupffer, R. Krause, and others) that ex- tensionsof the bile- capillaries normally exist within the substance of the cells, thus form- ing intracellular secretion canaliculi. The latter are sometimes pictured as ending in connection with minute dilatations or secretion varuoles. It is by no means certain that such appearances are not artifacts, or at least due to changes after death of Section o^ liver treated by Golci ailver methoH. frhowlug pan of intralubuWi (Mft-wurk uf bit«-i.-itiiii- lanes. X aoo. STRUCTURE OF T» L1VP:R. I7«7 ^ c** Tfce •icretion vsKucrte.. protwWy im- to the oorfesceoce ol mimite Llcrf bfle e«« only as trwMCTt d*taita. and cannot be rrtrarded as constant ^ of the h«iwbc celta. Holmgren ' iiwert> thr existence «t • ' ,aK:e-cana k uli '"**• °' *"* ^^ " wMwn the liw- m .030-.050 mm. in diameter, constitute a net-wors over the exterior ' Anatomischer Anzeiger, Bd. xxii., No. 1, 1902. ' Ibid., Bd. xxi., No. i. 1901. I7I8 HUMAN ANATOMY. surface of the lobule. They consist of a dense fibro-elastic coat lined with cylindri cal epithelium, some .oao mm. thick, which latter is continued into the low cuboid. il or flattened cells that form the lining of the excretory channels connecting the intra lobular net-work of bile-capillaries with the bile-ducts. Beginning as the small vessels that surround the lobules, they become tributary to the larger bile-ducts, which increase in diameter as they approach the transverse fissure. In the vicinity of the latter these trunks join into the two main lobular ducts forming the hepatic duct. The largest bile-vessels possess bundles of unstriped muscle which in tho hepatic duct are arranged principally as a longitudinal layer, supplemented by cir cular and oblique bundles (Hendrickson). m Gall-bUdder Vena cava Probe tn ror*iB«a THE BILIARY APPARATUS. In addition to the small interlobular bile-vessels already described, the systrni of canab receiving and conveying the secretion of the liver to the intestinal tract consists of the hepatic duct, the excretory tube of the organ ; the galt-bUulder, a ren ervoir in which the bile ac Fio. i4S»' cumulates during intervals of digestion; the cystic duct, the continuation of the bile- sac opening into the side ot the hepatic duct ; and the common bile-duct, which, al- though formed by the union of the other two, is in struc- ture and direction really the continuation of the hepatic duct. The hepatic duct (duc- tus hepaticus) is formed be- low the hilum by the unior of its two — a right and a left — chief tributaries. The latter issue from the porta! fissure, one on each side, and generally unite with the hepatic duct nearly in the shape of a T, the last-nainetl canal forming almost a rij,'ht angle with each of its tribu- taries. Tracing the chief ducts into the liver, the left branch runs at first in front of the left division of the portal vein, while ihe right one usually crosses it. \Ve have seen the hepatic duct issue from the right lobe and, forming a loop in the fissure, leave it with the left division of the portal vein, receiving branches alonjj its convexity from the various parts of the liver. .Sometimes the chief ducts are longer than usual, and meet to form the hepatic duct at an acute angle farther from the liver. The length of the hepatic duct, therefore, varies with these details, prol)a- bly l)eing usually from 20-40 mm. ( %-\ 4 in.), with a tliameter of from 4-6 mm. It lies in the gastro-hepatic omentum, in front of the portal vein and to the right of the hepatic artery, and inclines downward to the inner side of the second part of the duodenum, resting previously on the top of the first part. The hepatic duct Paiicmtic duct Superior mrwntcric vein Superior meaenleric artery Portions trf liver, iiuodenuit. nnd pancreas, <.howiiiK biliary and pancreatic duLlk ; head uf pancffus fumed Daclt. THE BILIARY APPARATUS. 1719 ends at the point at which the cystic duct opens into it The duct a lined *tidi mucous membrane, covered with simple columnar epitheliuni, and presentt many minute pi's, into which open the onfices of numerous sm^ tubular glands. Its walls consist of fibro-elastic connective tissue and unstnped muscular nbres. Ihe 1 itter neither numerous nor separated into a dislmct layer, are grouped for the most 'part into longitudinal bundles, but there are also circular and oWioue ones. The gtll-bUdder (vesica fellea) is a pear-shaped recepUde for the bUe, rest- ing in its fossa on the under side of the liver, with the large end forward. The lone axis runs also somewhat inward. The length is from 8-io cm. (3^-4 in.) and the capacity some 50 c.c (about ij^ fl. oz.). It narrows to a point where ir usually bends to the left and ends in the cystic duct without definite external demarcation. The bent terminal portion, or neck, about i cm- long. » •nof* «' less closely bound beneath the peritoneum to the side of the gall-bladder, so that before this is separated it sometimes looks as il the duct arose from the side of ' * The'fundua of the gall-bladder lies near the end of the ninth right costjd carti- laee. The neck is at the right end of the porul fissure. Anteriorly the bladder rests on the transverse colon, behind which it lies first to the nght of and then above the first part of the duodenum. Fio. 1453. Fio. 1454- ill-bUuUcr .Cymcdnct SuTtecc view o( poniuo ot mucoui membrane at gall- bladder, xu. Hepatic duct Portion of (all-bladder and biliary pamagei laid open, ahowing surface of mucous membrane. Natural liie. The wall of the gail-bladder is very resistant, being composed of a mixture of fibrous tissue and of unstriped muscular fibres. Most of the latter are disposed circu- larly, but oblique and longitudinal ones are interwoven. The fibro-muscular tunic is lined by a layer of mucous membrane which is very adherent to it. The mucous membrane, covered with simple columnar epithelium, presents slightly raised ndges marking of! a net-WDrk of small irregular spaces some 5 mm. in diameter. The small bifurcated tubular glands are few and may be wanting. The bent portion, or neck, is separated from the bladder by a strongly raised fold. There are, or may be, one or two smaller folds within the neck, the separation of which from the duct is usually arbitrary. ..... , , Vessels of the GalUBUdder.— Wr/^n«.— The chief distribution of the cystic artery, a branch of the hepatic, is on the free under surface, which it ap- proaches from the left, running on the cystic duct. There is a smaller branch which lies deeply on the right between the gall-bladder and the liver-substanr^'. l/eins.— The superficial veins join the cystic artery and empty into the nght division of the portal vein. According to Sappey, a number of small veins run directly into the li-er-tissue joining the portal system. The lymphatics, for the most ' For the musculature of the biliary apparatus, see Hendrickson : Johns Hopkins Hospital Bulletin, Nos. 90, 91, 1898. I730 HUMAN ANATOMY. part, empty into the nodes in the portal fissure. Some open into a node said u ■ lie in the angle at the bend of the nock. The nerves are from the solar plexus through the hepatic plexus. The peritoneal relations of the bladder and ducts are considered with those <>: the liver (p^e 1731). The cystic duct (dsctm cystkns), 3 or 4 cm. in length, with a diameter of from 2-5 mm., passes in a fold of peritoneum from the neck of the gall-Uadder to the gastro-hepatic omentum, where it joins the hepatic duct at an acute angle or. rather, opens into its side. It is said sometimes to present an enlargement at its end. In its natural condition it looks externally like the other ducts, but if distended and dried it presents a series of irregular folds ffiving the impression of a spiral fold which, in the adult at least, a closer inspection does not confirm. Structure. — In structure the cystic duct presents much more of a muscul.ir layer than the others. This is thickest at the upper part, and consists chiefly of circular fibres. These enter, especially near the beginning, the valvular folds of the mucous membrane, which is clothed with simple columnar epithelium. In the fu:tiis there is a fairly distinct spiral valve, most developed In the upper part, and, in fact, starting in the neck of the gall-bladder. later the continuous spiral ridge {vtUvula spiralis HetsUri) usually atro- Pio. I4SS. phies and is broken up at many places, leaving detached fol; A, papilla laid open, thowioc floor of ampulla. One-half natural aiie. ■i-i THE BILIARY APPARATUS. i7ai lutanc* of I cm. The structure of the common duct is much the same as rtiat r^^ewtic ~nto ning but little muscular tissue and that not well defined^ The n?a S'ns a fusifom dilatation, the ampulla (of Vater), which may be i cm. rt«C^Se^dS ™toThis the bile-durt and the duct of the pancre=« usually ''I^^Timmon orific^ Be these orifices common or distinct, each « sur- roCdS irlT "Cumulation of the circular muscular fibres wh.ch amounts p a X,Sr Th^ gl^ds. which are found throughout the common duct, are particu- ,o thefSS of serous membrane, is entirely inappropriate. It .s «" ?»" reUmed ^,t the wmrneration of five ligaments as separate enuues is antiquated. The round but the f*""^""" hcMtte) is a cord of fibrous tissue, the remains of the ''S?,'^edutMSve?n mSfrom the umbUicus to the left end of the portal fiSLTlt-^SaS JHe duLs venosus. is represented by fibrous t^ue(lljj.. ^Z^ veaoMB) in the fissure of that name. The round ligament lies against the ^SSfor an inchor more above the navel and then Pa*«?,*«^''*^';;'l ."!»''« t^ZZo\x\l falciform ligament, a fold of peritoneum presumably detached froni t^ interior wkll a/d from the diaphragm by the development of this vein. The Fio. 1456- (XtophagoU Impi •Mioa Left coronary ligaincnt RifM coroiiar> liKamciit Ridhl trmiiKuuir -linmnmil Saprarmal imiireMton PoMerior turfacc ^^entral wall of the gut-tube n.nXtelv above the widely open vitelline duct. This evagination. the first ind^ cronSlhc hepatic anlage. extend, into the primitive ventral or anterior mesentery ' Carmichael : Journal of Anatomy and Physiology, vol. xxxvii.. 190J. 17*4 HUMAN ANATOMY. which connects the stomach and the duodenum with the anterior body-wall. Th< hepatic diverticulum grows forward and upward into the anterior mesentery until it comes into relation with the imperfect partition which partially separates the thoracic and abdominal divisions of the body-cavity. This partition, the septum transversuni. primarily consists of lateral folds, projectmg at right angles from the anterior mesen- tery, caused by the large vitelline veins traversing the anterior mesentery on their way to the sinus venosus of the early heart. The relation of these structures is more fully considered in connection with the development of the diaphragm (pagt-' 1 701); for the present purpose it is sufficient to note that the liver-anlage early comes into relation with the septum transversum. The ventral portion of the pri- mary liver-evagination, ctothed with the entoblastic lining of the g^t-tube, very soon dilferentiates into two diverticula : the one nearer the head, or hepatic division, pro- duces the liver proper ; the other, or cystic division, later becomes the gall-bladder and its duct. These divisions are gradually removed from the primitive duodenum by the growth of the primary diverticulum, which at one end becomes converted into a tube connected with the digestive canal and at the other bifurcates into the hepatic and cystic channels. This tube, evidendy later the common bile-duct, is at first short and wide, but later rapidly lengthens. Uver-anta] CyMic diverticulum. Cul-tubc. — -Hepatic dlvrrticulum Dorsal iiaiicrealic divertii-utuni portion of ugittal kcction oi early rabbii rmbryo, showing Hver-anlase and duds, v 95. The cells lining the longer hepatic diverticulum undergo marked proliferation and produce the liver-mass which invades the septum transversum almost as far as the sinus venosus and surrounds the vitelline veins. The formation of the liver-mass follows at first the type of development seen in tubular glands, outgrowths of the hepatic tube branching and subdividing to form solid sprouts and buds cf.mposed of epithelial cells. In some of the lower animals, as the amphibians, the tubular type is retained in the adult organ; but in the higher forms, including man, the tubular character of the young liver is soon lost and replaced by the reticular arrangernent produced in consequence of the growing together and union of the terminal divis- ions of the gland. Coincidently with the formation of the net-work of glandular tissue by the junction of the cylinders of hepatic cells, the meshes of the reticulum become occu- pied by blood-vessels derived from vitelline veins. These arc now represented at the hepatic anlage by vrnaus stumps from which numerous afferent branches (vrtier hepatic^ adrrhrnles') penetrate the liver-mass to become the portal system. The division, subdivisitin, and union of these blood-vessels keep pace with the increasing complexity of the net-work of hepatic cords, the intergrowth of these constituents eventually leading; to the intimate relations between the hepatic secreting tissue and the intralobular capillaries seen in the fully developed organ. The cell-trabecula' composing the primary hepatic net-work are partly solid and partly hollow ; the THE BILIARY APPARATUS. 17*5 Cummuii bile-duct , »«. «kh a DOrtion of those without a lumen, are converted into the system of ^ « DTfferSbn of the developing liver into lobules does nut oca.r until the u"^^' n^nrfhrfoCrth fatal month, by which time the larger blood-vessels and SK elcome' su^roJ^S by condeLtions of the mesoderm which form the "•""rndSS^of the formation of the hepatic blood-v|ssels are con.id^^^^^^ rS :^ tSKrSar ^ rLSn We iPve^r^incL'ngth'r .S ^Teiiv ^r Vie re a OM of the placental circulation to the liver are secondary The amount of the placental blood, the development *'°- '*''°- of the ductus venosus brings relief by establish- ing a short cut by which the excess of placental blood passes directly into - the ascending vena cava. The development of the gall-bUdder and its duct proceeds, as already indicated, from the more caudallv pi ced cystic di- vision of tht primary he- patic diverticulum. The subsequent changes in- clude the j^rowth and ex- pansion of ^he terminal portion of the primitive cystic canal to form the bile-sac, its elongated stalk becoming the cystic Juct, while differentiation Id'^L'^S^^n^^'^^hl^^ produces the distinguishing details of the fully formed "''^"with the conversion of the primary liver-mass into the more definite or^n, the relations of the ventral mesentery, into which the early liver-anlage grows, become hanr d For a ti,:;e the developing liver lies within the septum transversum. but ater wiih the fon.ution of the diaphragm, it separates from the latter and projects to the h ...iv-cavav, .his projection results in a differentiation of the ventral m^entery into threi vv...ts : (a) the middle portion, the ^V-'i^ «« *»^!^»^ '^";;^,'= Zv^r'Jbv the urouinj. 'iver to form its serous investment ; d the anterior portion, Xh cxten Is P.m n.e ont surface of the liver to the umbilicus and becomes he falciform lit vn-nl enciosimr the umbilical vein, later the ligamentum ter.^s ; (f) the posterior iH>rtion, which stretches between the digestive tub. and the nver and ns the gastro-heiwtic, ..r lesser omentum, maintains similar relations and encloses the " '*Tn the fn is aided by its downward mcvement from gravity. It has been suggested (Jacobson) that such movement must slightly open the inferior vena cava, which is then immetliately compresse ,iCi-rs.sory portal veins (particularly those in the falciform ligament) and tt.- unra -niatic, nara-umbilical. and epigastric veins ; (6) the veins of Retznis and t.c retjopc. noneal veins • (c) the hemorrhoidal and the inferior mesenteric veins ; (d ) the gastric and the oesophageal veins. An operation has been employed to establish a better and more satisfactory comj>ensatory circulation in cases of cirrhosis by effecting adhesions between the suriaces of the liver and the spleen and the diaphragmatic pentoneum, on the one hand, and the parietal peritoneum and omentum, on the other. When compression of the liver is carried lieyond physiological limits, as from contusion or from forced flexion, rupture results. This is more frequent in the liver than in the i>ther abdominal viscera on account of its size, its fnability, ito fixity its close diaphragmatic a id jiarietal relations, and its great vMCulanty. A similar dbjunction of liver-substance may occur from a fall on the feet from a height. It is grave in proportion to the extent of the rupture and to its involvement or non- involVement of the peritoneal covering. Ruptures confined to the liver-substance, ~ i f not reaching the surface,— and moderate in extent, are not infrequently recovered from The commonest seat of rupture of the liver is near the falciform and coro- nary ligaments, with which the rupture is apt to be parallel. If they are extensive enough to reach the surface of the organ, death often results from hemorrhage, the intimate association of the hepatic substance with the thin-walled vosseb preventing their retract! .-»n or collapse. Hemorrhage is also favored by the dirtct connection of the valveltrs hepatic veins with the vena ca\ ; and by the absence of valves in the portal veias. According to the situation of the rupture, the blood may be poured into the general peritoneal cavity ; into that portion of it known as the subheput.r space and bounded below by the transverse mesocolon ; or into the retropentnn. «i space' behind the liver and ascending colon. The local symptoms will vary with rVt situation of the collected blood. Wmivd. of the liver should be considered with reference to its relations to the parictes, especially on t'.iL- riylit side, where, on account of its grer.tPi bulk, it is more often injured. Except at the subcostal angle, where a small part of the interior surface lies against the abdominal wall (the lower edge being on a line ft^twcen the eighth left and the ninth right costal cartilages), the lower ribs and costal cartilages surround the liver. Thus stab wounds must pass between them, while fracture of the ribs with depression may penetrate the interposed diaphragm and then the liver- substance. Anterioriy, a little internal to the mammary line, the liver may reach to the fourth intercostal space or even quite to the level of the nipple, and niiiy be directly wounded throughout that area. Laterally it is not usually found a»x>ve the bixth interspace. Posterioriy a stab wound through tiie sixth, seventh, or eighth intercostal space, or even down to the level of the tenth tlorsal spine, would pene- trate four layers of pleura, the thin concave base of the right lung, and the preMing them between the finger and thumb, the former being placed ju»t withn, the foramen of Winslow and the latter externally on the gastro- hepatic omentum. Eniargement of the liver, if uniform (congestion, muldple afaKew, penhepatitis. fatty ilegeneration, hypertrophic cirrhosis), causes a bulging of the right lower nl)s and their cartiWes and an increa.se of the area of absolute ptrmssum dulntss. Tli. upper limits of the latter should normally be found at the sterno- xiphoid junction ii> the median line, the sixth intercostal space in the right mammary line, the seventli rib in the- axillary line, and the lower border of the ninth nb in the scapular Imt A mo ^'t* |r extravaffibile first flows into the targe peritoneal pouch t>«"nded aboveby ** \^^^ nf the liver below by the ascending fayer of the transverse mesocolon c^viiS^ dS Jrum^t^ly. externally by th'e peritoneum lining the panet« ^r to Se crest of the Uium. posteriorly by the ascendmg mesocolon covenng the kidnev and internally by the peritoneum covenng the spine (2) that this tlTuch «7'l^ «^ay and thoWir thmugh a lumbar mosion ; and (3) fft fa caMble of holding n4riy a pint of fluid before it overflows into the gteii^S cavity through the fonunen of Winslow or over the pelvic bnm ^^""^iLion of the gall-bfadder is ordinarily due to ( .) inflammatory obstruction of thecShirt (chobmgitis) ; (2) mechanical obstruction of the cystic duct usu- aiXTrte iSpaSion^ gall-stones; (3) acute cholecystitis, (a) catarrhal (*) suDtSive; or (4) obstru^on of the common duct from »«"?«-; "^- ™"'=^™»« 3y from impaction of a calailus in that duct before the gall-bladder has become Sed «>nt.^ted. and formed adhesions. The gall-bladder 'tseU may be the pS^'s.^ of a malignant growth. It is impossible to feel the normal gall-bladder ^''Tnwt-nrdthet4-bladd« from any cause usually takes place in a down- ward and forward directio'n on a line which, beginning a little b^io* ^he "inth c^ta^ «ible later.ally. and --«^'Xrdeie^ds pable groove between it and the lower edge of the liver. The swellmg descends 109 I730 HUMAN ANATOMY. t f ■' I !. during inspiration. If the cause of the enlargement is inflammatory and adhesiv e peritonitis has resulted, the tumor may be fixed so that it does not move with i as- piration ; but there is then, especially in acute cases, apt to be pain and tender- ness over the swelling or at a point between the ninth costal cartilage and the umbilicus. It may be mentioned here that the diagnosis between the chronic form of gall- l:^dder disease and movable kidney is not always easy ; that the two conditions not infrequendy coexist in the same person ; and that the possibility of error is increa.st"d by the fact that they are each met with much oftener in women than in men, and that the right kidney is far more frequendy movable than the left. The anatomical explanation is that in women with flabby abdominal walls either tight lacing or a relatively slight jar or strain tends to produce displacement of both the kidney and the liver, the latter resulting in tension or angulation and con- sequent obstruction of the bile-ducts. The two conditions also act reciprocally, descent of the liver causing displacement of the kidney, which, through its traction upon the duodenum, tends to obstruct the bile-ducts. A movable kidney, as compared with an enlarged gall-bladder, is less influenced by respiration ; has a wider range of motion, especially in the long axis of the body ; is more influenced by position ; slips backward towards the loin instead of upward beneath the liver ; is less often visible and less frequendy tender on pressure, which b apt to cause a sickening sensation analogous to testicular nausea (page 195 1). Acuie cAaUcysiiiis (phl^monous) is due to infection. The colon or typhoid bacillus, or the pneumococcus, streptococcus, or staphylococcus, may reach the gall- bladder either through the blood, as during a pneumonia, by lymphatic and vascular channels, as after an appendicitis, or through the intestine and bile-ducts, as in some of the post-typhoidal cases. The symptoms are (a) generalized abdominal pain, due to the association of the cystic plexus, through the cceliac, with the superior mesenteric ; (6) pain below the right costal margin passing towards the epigastrium,— 1>. , referred to the cceliac and solar plexuses, — and towards the right scapular region, hrom the association of the phrenic and the supra-acromial nerves through the fourth cervical (page 1758) ; (f) rigidity over the right hypochondrium, due to the connection between the splanch- nics and the intercostals ; {d ) nausea, vomiting, and prostration, due at first to the close relation of the cystic plexus with the coeliac and solar plexuses, later to toxxmia and to peritonitis ; («f ) localized tenderness at the junction of the upper and middle thirds of a line drawn from the ninth rib to the umbilicus, — i.e., over the fundus of the inflamed gall-bladder; (/) distention and paresis of the intestines, due sometimes to a localized peritonitis affecting the hepatic flexure of the colon and simulating an acute intestinal obstruction. Gangrene has occurred, emphasizing the clinical and pathological resemblance of this condition to appendicitis, but is very rare, illustrating the importance of one anatomical factor— the scanty blood-supply— in causing the gangrene which is so exceedingly common in that disease (page 1682). Bacterial infection and absence of drainage (and therefore tension) are two conditions predisposing to gangrene, present in both cases ; but the third— thrombosis of the nutrient vessels— determines the frequency of gangrene in the appendix, which is supplied by only one nutrient artery, and is relatively ineffective in the case of the gall-bladder, uhich has a rich blood-supply through the large cystic artery and also through the anastomoses of iis branches with the hepatic vessels where the gall-bladder is fixed to the liver (Mayo Robson). . -^"'/.Vwa of the gall-bladder (suppurative cholecystitis), due usually to chole- lithiasis, obstructive catarrh, and infection through the ducts, may discharge itself in various directions determined by the occurrence of inflammatory adhesions. The most common communication is with the cutaneous surface, the pus having been evacuated through the parietes beneath the costal margin in 50 per cent, of Cour- voisier's 184 cases, and in the umbilical region, where it was conducted by the sus- pensory ligament, in 29 per cent. The colon or duodenum beneath, the subphrenic space or pleural cavity above, and the right prcncphric periloneal pouch— watieil off by adhesions — have been favorite seats for the spontaneous evacuation of pus PRACTICAL CONSIDERATIONS: THE BILE PCCT. 17.^1 and gall-stones in old cases of empyema of the gall-bladder. Its anatomical relations to surrounding structures and spaces should therefore be carefully studied. Cholelithiasis.— hs the norma! e.xpulsive efforts of the muscular walls of the gall-bladder are usually aided by the contraction of the abdominal muscles dunng exercise gall-stones are more commonly found in persons of sedentary habits, in invalids,' and in females, especially in multipara. Tight lacing, by depressing both liver and gall-bladder, as well as kidney {vide supra), is also a distinct predisposing cause Bacterial infection with the colon or typhoid bacillus, and more rarely with other organisms, is, however, a frequent exciting cause of the hypersecretion and epithelial proliferation which lead to the formation of gall-stones. The presence of stones in the gall-bladder may be unaccompanied by symptoms, or may cause the development of such phenomena as either have no distinct ana- tomical bearing (biliary fever and secondary visceral lesions) or as have already been considered (abscess of the liver, empyema of the gall-bladder, fistula, etc.). There are mechanical accidents, however, connected with the emigration of the stones which will be considered from the anatomical stand-point in relation to the biliary ducts. ^, . j • . The Cystic and Common Bile-Ducts.— The cystic duct is the narrowest portion of the biliary passages. Its calibre would permit the passage of a probe through it into the hepatic duct, but the irregular folds of its mucous membrane (sometimes regarded as constituting a "spiral valve,"— the valve of Heister) usu- ally effectually prevent satisfactory probing. Its muscular fibres are better devel- oped than are those of the other biliary ducts. The passage of a stone through it is attended by (i) colicky pains of the sort usually associated with violent mus- cular contraction ; (2) continuous paim resembling thai due to an acute cholecystitis (the two conditions being often mistaken one for the other), and due (a) to the slow prcMjressof the stone in the cystic duct, in which it takes a rotary course owing to the arrangement of the mucous folds ; (*) to the acute inflammation which usually accompanies an attack ; and {c) to the stretching and distention of the gall-bladder by retained secretions (Osier). The pain may be even more intense, and is apt to be accompanied by (3) vomiting, ^) pro/use sweating, and (5) great depression of the circulation, all due to reflex irritation of the sympathetic plexuses and the pneumo- gastric. There may be (6) a rigor, either purely nervous or due to retained secre- tions and a concurrent lithaemic inflammation. In he latter case there will he (7) fever from the accompanying toxamia. If the stone passes into the intestine, all the symptoms usually disappear. It may cause (8) intestinal obstruction, and is a far more common factor in the pro. duction of this condition than are enteroliths. Of 149 cases of this type of obstruc- tion, 133 were due to gall-stones and only 16 to enteroliths, and 10 of these had gall-stone nuclei. Although a stone of considerable size may pass through the duct, those large enough to bring about intestinal obstruction usually enter the duodenum by ulceration. If the stone becomes impacted in the cystic duct, (9) dilatation o{ the gall-bladder with mucus (hydrops) occurs ; or (10) cholecystitis, acute or chronic, may follow {vide supra). Calcification and atrophy of the gall-bladder are not uncommon sequelse. ^. ■ • . u The stone may pass into and obstruct the common duct. This is about three times the diameter of the cystic duct, and. therefore, many stones which have given rise to the above symptoms pass through it easily. If a stone permanently occludes it, there will usually be deep and persistent jaundice, clay-colored stools, vague and dull hepatic and shoulder pain, rarely colicky in character, and absence of sejitic phenomena and of enlarged gall-bladder, the latter symptom occumng m not more than 10 or 12 per cent, of cases of calculous common-duct obstruction. A stone may pass as far as the ampulla of Vater and act as a " ball-valve." in which case there will be variable jaundice and ague-like paroxvsms of chills, fever, and sweating, accompanied by hepatic pains and gastric disturbance (Osier). The mechanical effect of a stone in such a position, plus the resulting nerve irritation and infective cholangitis, sufficiently explains these phenomena. Occlusion of the cuinmon ducts may occur from other r.iu.ses, a.s stricture follow- ing ulceration due to stone, the presence of lumbricoid worms, echinococci, etc., or 173* HUMAN ANATOMY. ii i '■ . ii even of foreign bodies which have been swallowed. Pressure from extrinsic causes i- far more frequent, however, as a cause of occlusion. It may be due to carcinoma of the lymph-nodes in the transverse fissure, secondary to rectal or to gastric cancer or to enlargement of the head of the pancreas from new growth or from inflammation or to aneurism of branches of the coeliac axis. In these cases, contrary to what is found in occlusion from gall-stones, the gal! bladder is usually enlarged. Congenital obliteration of the ducts may occur. Operations on the Gail-Bladder and Biliary Ducts. — A vertical incision, at leasi 7.5-10 cm. (3-4 in. ) in length from the costal mar^n downward, made over tht middle of the right rectus muscle, the fibres of which are separated, will usualK satisfactorily expose the gall-bladder. If it is necessary to open either of the ducts, the incision may be prolonged upward in the interval between the xiphoid cartilage and the costal cartilages. If the liver b then dra\' 1 downward from beneath the ribs and rotated upward and outward and the trans' rse colon fe drawn downward, the subhepatic space will be well exposed, bounded y the under surfeice of the liver above and externally, the colon and transverse m- ocolon below, and the duoderum and pyloric end of the stomach internally. In this position, especially if a sand ; ig has been placed beneath the back opposite the liver, so as to push the spine forward, the cystic and common ducts are brought close to the surface, the angle between them is effaced, the region of entrance into the duodenum is in full view, and ■ncisivyn for drain- age of the gall-bladder (cholecystostomy), or for the extraction of a calculus either from the gall-bladder (cholelithotomy) or a duct (choledocjiotomy), or for the re- moval of the gall-bladder (cholecystectomy) becomes possible. If there are many and troubl^me adhesions, the fundus and body of the gall-bladder being buried and not recognizable, it is well first to locate the hepatico-duodenal fold of peritoneum, — the right border of the lesser omentum, — in which the common duct may be traced from its duodenal termination upward, the portal vein lying behind it and the hepatic artery to the left. The cystic and hepatic ducts may then be identified. The ducts may often best be examined by passing the forefinger of the left hand through the foramen of Winslow, the back of the surgeon l^ing turned towards the patient. The duct, the portal vein, and the hepatic artery may thus easily be grasped between the thumb and finger. The close relation of the lower end of the common duct to the vena cava should be remembered in operations upon it. This portion may be reached, if necessary, as in some cases of stone impacted at the duodenal papilla, by opening the second portion of the duodenum and slitting up the duct as it lies iii the inner and posterior wall of the intestine, where it may be felt as a cord. The duct may be reached at a higher point by an incision through the perito- neum to the right of the duodenum, the latter being freed posteriorly and drawn towards the median line. In cases in which the common duct is permanently obstructed a portion of the duodenum or jejunum may be anastomosed with the gall-bladder (cholecystenteros- tomy) by direct suture. THE PANCREAS. The pancreas, the " abdominal salivary gland," lies moulded across the spinal column with its head on the right, enclosed in the loop of the duodenum, and its tail on the left, in contact with the spleen. It is of a light straw color running into red, according to the amount of blood within the organ. The weight ranges from 30-150 gm. ( 1-5 oz.) or even more. The specific gravity is about 1045. The length in situ is approximately 15 cm. (about 6 in.). It consists of an enlarged descending part on the right, the head, and of a long body placed transversely, which is needlessly divided into nerk, body, and tail. When the organ is removed from the body and straightened it somewhat resembles a revolver in shape, the head being the handle. The gland, however, is so modelled by the surrounding parts that its true form is seen only in its undisturbed position, or after hardening in situ be* .e removal from the body. The head (caput pancrestin) is a rotmded hwx irregular disk packed into the space between the first and third parts of the duodenum, and lying close against the V'' THE PANCREAS. 17.W 1 (t of the second part. It overlaps both the second and third parts antenorly, and tnds to insinuate itsel; behind them. We have seen it overlapping the fourth part ll«> So much has been said of the variations of the duodenum ( page 1644 ) that it must be evident that the head of the pancreas can hardly have any certain size or !;haoe Its diameter from above downward is probably rarely less than 7 cm. and m »rbe ereater. It U separated from the neck by a groove on the front of the gland r the MStro-duodenal branch of the hepatic artery. It rests behind on the infenor vena cava, sometimes on the right renal vein, and may approach the right suprarenal body. It is opposite the first and second lumbar vertebrae and often a i>art of the third lumbar vertebra. .... .• u • The body (corpus pancreatis). including the neck and tail, is pnsmatic. having a />aslfrior, an antfro- superior, and a narrow in/frior surface It is so tortuous in Us natural Uition as to seem shorter than it is. Starting on the right of the spine at the levefof the first lumbar vertebra, it passes around it to the left and backward and again forward to the spleen, which it may or may not cross. Towards its end it also turns downward. Fig. 1461. Ponal vein Hepatic artery Left >uprarenal body --Left Itldney RUht Mprarenal. Vena cava" First part of ___. duodenum f_ Right kidney Spleen Tail of paiKreas Splenic flexure of colon Resinning of je]unum Superior mes- enteric artery Superior mes- enteric vein Descending colon Vena cava Anterior aspect of pancreas m situ ; the organ is exceptionally broad, and covers more of left kidney than usual ; peritoneum has been removed. The neck is the part (2-3 cm. in length) which crosses the portal vein with a forward convexity, being deeply grooved by the vein on its posterior surface. The left extremity of the body is the tail (cauda pancrcitis), the end of which is very variable in form. If it lies in front of the spleen it is more or less pointed, but if it ends against the gastric surface of that organ it may have a true terminal concave surface, fitting it accurately (Fig. 146 1). The posterior surface has first (from the neck towards the left) the deep groove for the portal vein, which may be entirely surrounded by glandular tissue. Beyond this it lies on the vena cava, then on the aorta between the coeliac axis and the superior mesenteric artery, which groove it above and below. It next lies on the left pillar of the diaphragm, the left suprarenal capsule, and thi left kidney. The left end may have a concave surface resting on the gastric surface of the spleen, or mmmmn IPPHW 17.^4 HUMAN ANATOMY. it may extend across this surface, or rest on the bas.il one. There are two horizun tal grooves on the posterior surface. The lower, which is the longer and deeper, i^ caused by the splenic vein. It extends from the left end to the groove for the [hkuu vein, inclining to the lower border as it approaches it A smaller groove for tlir splenic artery lies above the former from the left to near the aorta. The antero-supierior surface, the largest of the three, slants downward and for wd, presenting a concavity which forms a part of the stomach-bed. It is (ui the average some 4 cm. broad, but may exceed 5 cm. There is often a swelling— tlu omenta/ tuberosity (tuber omentale)— to the left of the neck opposite the aorta. This is behind the lower end of the vertical part of the lesser curvature of the stomach, and is in contact with that organ rather than with the omentum. The .nferior surface, the smallest, rarely as much as 2 cm. in breadth, rests on the lower layer of the transverse mesocolon. It is rounded and irregular! except where it lies above the duodeno-jejunal fold, where • is smooth and concav e. To the right of this it b grooved by the superior mesenteric artery. The borders at which the surfaces meet call for no special description beyond that both the inferior ones are grooved by the superior mesenteric artery and the upper by the cceliac axis. Structure.— While agreeing in its general structure with other serous salivary glands, as the parotid, the pancreas differs in certain particulars. The most im- Fig. 1463. S«lion ol pancm> under 1' w magn ideation, showing (encrml trrangnnent of lobul«. x 30. portantof these are the tubular, rather than saccular, form of the alveoli, the marked differentiation of a granular zone in the protoplasm of the secreting cells, the absence of specialized intr .lobular ducts, and the presence of the islands of Langerhans. The chief pancreatic duct gives off numerous lateral interlobular branches which are lined with a single layer of columnar epithelium, about .006 mm. in height, the direct continuation of that clothing the lai^e ducts, in which the cells are from two to three times as tall. The canals springing from the interlobular ducts after enter- ing the lobules possess a layer of flattened epithelial plates some .012 mm. long by .003 mm. high, and correspond to the intercalated or intermediate ducts. The in- tralobular canals being wanting, the relatively long intermediate ducts pass directly into the tubular alveoli, within which their attenuated epithelium protrudes as the centro-arinal cells. The relation of the latter to the usual glandular elements lining the alveolus is pt^-uliar, the thinned-out and spindle duct-cells being surrounded ex- ternally by the si rcting cells. The tubular veoli of the gland, often tortuous and sometimes divided, possess a well-defined membrana propria against which lie the secreting ceils. The latter THE PANCREAS. 17.VS Alvcolu* are usually of a blunted pyramidal shape. althouRh many aberrant forms are seen. with an average length of about .010 mm. During functional inactivity their cyto- plasm exhibits two well-differentiated zones : an inner one, ne.xt the lumen, which is hiirhly granular, and an outer one. next the basement membrane, which is free from eranulM and at times almost homogeneous. The round or oval nucleus occupies the external area. The relative breadth of these two zones varies with the func- tional activity of the cells. During fasting, when the latter are stored with zymogen particles the granular zone is very broad and the outer homogeneous one corre- spondingly narrow. With beginning discharge of the pancreatic secretion during digestion the granular zone diminishes and reaches its minimum, almost dis- appearing when the gland is exhausted. The return of the latter to a condition o rest is accompanied by the formation and gradual accumulation of a new store ol zymogen particles until the granular zone is again restored to ;ts maximum. Occa- sionally in fixed tissue the parietal cells exhibit within their cytoplasm a body termed t\i Johns Hopkins Hospital Bulletin, September, 1900. Section of pancreas. thowinK Interlobular connective tissue with vessels and duct surrounded by tubular alveoli. X 3oo. 1736 HUMAN ANATOMY. tion from the surrounding glandular tissue and their close relation with the bloo,i vessels, the opinion is held by many that they produce some substance which pasM directly into the blood and may be regarded, at least provisionally, as concerned , internal secretion. ' •■■=" i.. The Pancreatic Ducts—The gland is surrounded by a fibrous sheath whicii sends in many processes dividing it into small lobules. The chief excretory canal .■ the adult IS therf«rf of IVirsung (ductus pancreaticus), which, beginning near the ui,i of the tail, runs through the middle of the pancreas towards the right, and ben.l downward as it passes through the head. Branches sprout from the main d" , at nght angles, which receive bunches of smaller ramifications. The diameter ..i H„rt t« tK*"" ' n ^f.u *^"i 5 mm. It descends just in front of the common bil. duct to the wall of the duodenum and empties in common with it at the pai)ill i a\S' ^f\^'' u ^1™'"*"?" ^^""y o'ten '» in the floor of the ampulla (diverUculum duodenale) so that the papilla presents but one opening. The tribuUry ducts of th, head are larger than the others. A particularly lai^e one-the duct of Santorim p (ductus pancreaUcus acces- * *■ uorius)— is in the early sUge of development the chief duct of the head, and consequently of the gland. In the adult it usually descends from the right to empty into the duct of Wirsung as the latter turns downward. In about half the cases, according to Schirmer,' it opens independently into the duodenum, some ,i cm. above the papilla and more anteriorly. The or- ifice is usually surrounded by a small raised ring. Even when so terminating it retains its connection with the duct of Wir- sung. Thus fluid in the body of the pancreas may in such cases pass into the duodenum by either duct of Santorini may pass either directly into the gut or th^uSf thTl^cfof ' Vfc StheT,':rTly'£^rc"hK Sle",''ex"J%ro?yTct •"^*"^'^^" ^^' '''"'''''' anH th.''lnV°"' *° **"* Peritoneum—Although developed in both the posterior on them„"H°^K'"!?^"*^'!f • '^^ P*"f 't'"' °*'"^ *° '^^ '^'"'S^^ ^y which the spleen on the left and the descending part of the duodenum on the right have come to lie against the posterior abdominal wall, is entirely retroperitoneal. The posterior sur- face with the possible exception of the end of the tail, which may be surrounded bv peritoneum, is attached to the parts behind it by connective tissue. The layers of peritoneum co%'ering the antero-superior and the inferior surfaces meet to form the ™Zfjr"°»K "•' Z^'""^ " «t^<:hed along the border between these surfaces, and L*Tlh r ^ "^•'" '"'T^ *''' ^^'"^' ^"'^ """y sometimes rise towards the left artlrv rrn?ilT"P7'''..' ""'^''''^.i r ^^^ gastro-pancreatic fold, made by the gastric artery, crosses the gland upward from a point a varying distance below the cceliac Vessels— The ar/eries are many small branches derived from th- splenic hepatic, and superior mesenteric. As the splenic runs along the top of the posterior ' Beitrage zur Geschichte und Anatomie des Pancreas, Basel, 1893. .Conncctlve- liMuc envelope .Capillary blood-ve* Modified epilhelial cells .Alveotiu wilh ordinary cells Section of pancreas, showinc island of L4inferliana. X soo. THE PANCREAS. 17,^7 surface it sends a series of branches into the upper part of the body and tail The hepatic runs along the top of the front of the head and n nection and becomes tributary to the duct of Wirsun^. Variations from this ar- rangement are often encountered, the different combinations being due to deviatiuns Fio. 1466. Diagrunniatic reconstructions, showing development of paiKreas and relations to liver-ducts, a, commnn UW- duct; A, hepatic and c c>-stic ducts; (/, right and e left ventral pancreatic nti1aee«; /, dorsal pancreas aiui irs duct ( jr) ; A, junction of common bite (a) and ventral pancrvatic (1/ ) ducts. Alter fusion of ventral and dorsal pan- creas, d biecomes duct of Wirsung, g duct of Santorini, and 1 head of pancreas. from the ordinary prc^ess of development as to the fusion of the two parts and per- sistence of their canals. The areas of Langerhans are developed from the same entoblastic outgrowths as give rise to the ordinary glandular tissue (Laguesse, Pearce"). The connective- tissue septa are derived from the ingrowing mesoblast. Variations — The pancreas has been seen to surround the descending part of the duodenum. Small accessory pancreases have been found in the walls of the intestine. Although usually in the duodenum, they may be in the stomach or at the bepnning of the jejunum, and occasion.illy some distance from it. Presumably they are parts of the gUind which became separated at .in early stage and were drawn by the growth of the intestine away from their original position.' PRACTICAL CONSIDERATION , : THE PANCREAS. Certain abnormalilies that may affect surgical procedures or may of themselves produce symptoms of disease should be mentioned. Accessory pancreases are found in various localities and may be mistaken for new growths. The anterior wall and the two curvatures of the stomach and the walls of the small intestine, especially the duodenum, are the situations in which such glands are most frequently found. They have ducts opening into the intestine. An accessory gland has been found to the right of the duodenum entirely dis- tinct from the main gland. Perhaps the most important anomaly is one in which the gland completely .surrounds the .second part of the duodenum, constricting it and causing dilatation of the first jx)rtion and of the stomach. Several cases have been reported. The common bile-duct may also be contained within the head of the pan- creas, as may the superior mesenteric vessels within its body. The accessory pan- creatic duct may be absent, or there may be three ducts, all opening into the duodenum. Movable Pancreas. — The gland may fall forward or downward (when it may sometimes be felt below the stomach), or it may be a part of the contents of a dia- phragmatic hernia, or may even — but with great rarity— be contained within the sac of an umbilical hernia. Injuries. — The situation of the pancreas behind the lesser jieritoneal cavity and the stomach and between the spleen and the duodenum, the partial protection it receives from the costal arch, and the depth at which it lies render its uncompli- • American Toiimal of Anatomy, vol. ii., 1903. » Sinker : Virchow's Archiv, Bd. xxi., 1861. PRACTICAL CONSIDERATIONS: THK I'ANCRKAS. 1739 cited injury of very rare occurrence. In only three fatal cases in which all other ilHlominal viscera escaped has it been found to be ruptured. In less severe cases it has been bruised or torn, hemorrhage has occurred, a 1 ipidly enlargiiHJ, fluctuating epigastric tumor has formed, and the patient has recov- ered ifter a Uparotomy, evacuaUon of the blood-cyst, and drainage. In such cases it is probable that the traumatism has caused a laceration of the jKwterior layer of the l.-sser sac of the peritoneum ( with which the pancreas is intimately adherent ) and of the pancreas itself. Blood, or blood with pancreatic secretion, is |M>ured into the lesser sac, causing adhesive peritonitis and sealing the foramen of Wmslow. The lesser cavity, now converted into a closed sac, is distended with serous exudate, l)l.x)d and pancreatic fluid. After evacuation and drainage, the pancreas may con- tinue to pour its secretion into the cyst-cavity through the origmal peritoneal tear iRobsonand Moynihan). . ., . _ u- u •. Panerta/i/is.—The close relation of its duct to the co:.imon bile-duct, which it often joins at the ampulla and before reaching the duodenum, explains the frequent issociation c: (pUl-stones with chronic inflammation of the pancreas. A small ball- valve calculus in the ampulla has been thought, by occluding the duodenal onhce, to convert the two ducts into a continuous channel, permitting, if the gall-bladder is functionally active, the entrance of bile into the pancreatic duct (duct of Wirsung) and causing pancreatitb. A larger stone might occlude alvo the orifices of both the pancr itic duct and the bile-duct and produce in both glands the troubles associated will tained secretions. In the pancreas these troubles are lessened by the fact that occlus ,1 of the main pancre?.tic duct does not of necessity completely obstruct the egress of the pancreatic fluid COpie). In about 50 per cent, of bodies the acces- sory duct (duct of Santorini) communicates within the gland with the mam duct and opens into the duodenum by a separate orifice about 2.5-3-5 cm- (\-^f^ •"• ) nearer the stomach than the papilla at which the ampulla of Vater opens (Schirmer). Nevertheless, just as jaundice follows occlusion of the common bile-duct by forcing the secretion of the li-er back upon that gland, whence it finds its way into the inter- stitial tissue, the lymphatics, the thoracic duct, the blood, and the tissues at large, so the fat-splitting ferment of the pancreatic juice, in cases of occlusion of the pan- creatic duct, finds its way beyond the parenchyma of the gland and causes fat- necrosis, first in the vicinity of the pancreas, later over widespread areas (Opie). There can, at any rate, be no question of the etiological association of gall- stones with many cases of pancreatitis ; but it is probable that in a large proportion, in addition to mechanical pressure or inde »ndently of it, bacterial invasion follow- ing inflammation of the ducts or of the duov. wm is an important factor. The anatomical symptoms of acute pancreatitU depend upon the close associa- tion of the gland (a) with the solai plexus through the coeliac, superior mesenteric, and splenic plexuses ; (*) with the duodenum ; (t) with the bile-ducts ; (llen gland through the 1740 HUMAN ANATOMY. abdominal wall. In gastroptoais the normal pancreas may easily be felt above i: stomach and might readily be mistaken for a new growth. Usually the swell ini; ,, behind the stomach and above or behind the colon. In suppurative pancreatitis ih collection ol pus may push the stomach forward, or may I come superficial, titli. i above or below it ; it may, starting at the pillar of the diaphragm, and guided by ih, pnoas-sheath or the iliac fascia, reach the iliac region ; it may occupy the ar'jf.l.,; tissue of the loin, becoming a perirenal abscess ; it may open into either the stoma. 1 1 or duodenum. When confined to the pancreas, it will usually be recognized diirii, an exploratory operation. It may be drained posteriorly by an incision at the cost." vertebral angle, or anteriorly through a large tube surrounded by gauxe packing. Cancer of the pancreas usually affects the head of the gland, which account.-) f..r the fretjuency with which obstructiGn of the common bile-duct and of the duodenum occurs m such cases. The hirther growth of the tumor may cause compression of the pylorus, of tlu cardiac end of the stomach, of the whole stomach by forcing it against the anterii n abdominal wall, of the colon, the ureter, the portal vein, the vena cava, the aort.i the splenic vessels, and the superior mesenteric vein (Robson and Moynihan). If the tumor extends to the right, there are apt to be jaundice and intestinil obstruction ; if upward, in addition to these symptoms, pyloric obstruction ami pastric dilatation ; if backward, ascites and cedema of the lower limbs. The pancreas may be approached for operation through a median incision, and reached, above the stomach, through the gastro-hepatic omentum ; below the stom ach, through the gastro-epiploic omentum or the transverse mesocolon, the omentum having been turned upward. It has been exposed (in a case of hydatid cyst b^ an incision beginning at the tip of the twelfth rib and passing forward in' tlu direction of the umbilicus. Indirect drainage in chronic pancreatitis by means oi cholecystostomy has given excellent results (Robson). In cases of nephrectomy the relations, of its tail to the left kidney and renal vein should be remembered. The relations of the vena porta, the vena cava, tht aorta, the superior mesenteric artery, and the cceliac axis are so close that wlun complicated by adhesions or infiltration, as in chronii inflammations or new growths, operations for total excision of the pancreas bc_ iie formidable and ha\f rarely been undertaken. The close relation of ?he pylorus — especially when th.- Stomach is depressed by a new growth — to the neck of the pancreas should W remembered in pyloroplasty or pylorectomy, as should the proximity of the spleen to the other extremity of the pancreas in cases of splenectomy. THE PERITONEUM. The peritoneum is the serous membrane lining the abdominal cavity and reflected over the viscera. Like all serous membranes, it consists of a free mesothelial sur- face and a deeper layer of fibro-elastic tissue, the tunica propria. Beneath the latter a variable amount of subperitoneal tisstte connects the peritoneum with the structures which it covers. The quantity of this areolar layer differs in various localities, and it is at times difficult to decide just what is really a part of the serous membrane proper. It is convenient to look upon the peritoneum as having a right side and a wrong side ; the former is the free mesothelial surface, the latter the areolar which is attached to other structures. Thus it may be compared to a wall-paper of a room without door or window, of which the right side is always free and the wrong side adherent to walls or to projections from them. Should a flue traverse the room, it is easy to imagine it invested by a continuation of the paper on the walls. It passes through the room, but is not within the closed sac formed by the right side of the paper. While it is true that during development the mesothelial covering grows pari passu with the tissue beneath it, the conception that projections of organs into the peritoneal cavity carry the serous membrane before them is very convenient and justified. The peritoneum of the f- . s is the onlv serous membrane that is not a closed sac, on account of the op gs of the Fallopian tubes. The blood- vessels for the viscera, around which the peritoneum If thrown, must pass on its wrong side. To return to the simile of the flue in the chamber ; if this should need THE PERITONEUM. «74i support, we can imagine it susi)ended in the middle by a series of cords wl might be all enclosed in one fold of paper from the ceiling. This would be a m«. leryanA the cords would be blood-vessels going to the gut. The cords, of course, would be on the wrong side of the paper and the vessels on the areolar side of the mem- brane. A fold of peritoneum may contain lar^e vessels ; nd strong bundles of fibres, arid at other places be no more than a duplicature of r ?mbrane. The former are the mesenUrus and certain bands caUed " lir . ■ '.ents, the latter piictt or folds. Tlie complications of the F-.. 1467. Diaphrafm [>« ritoneum are reduced us much as possible by biudymg it in the light of development, the account of which has been already j;iven(page 170J). Here only some of the chief IKjints and general prin- ciples are recapitulated. In the early foetus the peritoneum is merely the lining of the abdomen, the parietal peritoneum, which covers the Wolffian bo'iies and the beginning of the abdominal walls, and certain median folds called mesenteries, con- veying blood-vessels to the gut, within which cer- tain accessory organs are developed. There b a posterior mesentery ex- tending from the spine to the whole length of the alimentary canal below the diaphragm, to which it carries vessels from the aorta, and an anterior mesenterj- running to the upper part of this canal from the anterior abdom- inal wall (Pig. 1433). The original posterior mesentery is divided into three regions, each of which conveys a particu- lar arten,?. I. The mesen- tery of the stomach and of the duodenum, con- taining the coeliac axis. It is to be noted that this region mav be subdivided into two parts, the upper formed by the stomach and the first part of the duodenum, the lower formed by the remainder of the duodenum. The latter originally arches forward, both ends being fixed at the spine. 2. The mesentery of the st of the small intestine and of the ascending and the transverse colon, containing the superior mesenteric artery. 3. The mesentery of the remainder of the large intestine, con- taining the inferior mesenteric artery. The anterior mesentery, in which the liver is developed, reaches the stomach and the upper part of the duodenum, extending on the antetior wall as low as the Diajrram showing general arrangement of |>t^ritoneuin. which is represented by the blaclc line ; arrow passes from greater into lesser sac through foramen 01 Winslow. A, liver; .V, stomach; /*, pancreas; /J. duodenum; TC, trans- verse colon ; /, small intestine ; R, rectum ; B, bladder ; V, utenia. 1742 HUMAN ANATOMY. umbilicus (Fig. 1432). The umbilical vein runs in its iiee lower border io the per ta' fissure of the liver, whence its continuation, the ductus venosus, , .sses to the in erior vena cava. The anterior mesentery, containing the liver, is opposite to ilif nusogoitrium, or mesentery of the stomach, which contains the spleen. The |>;i]i- creas, although developed in both the anterior and the posterior mesenteries, liis chiefly in the latter. As the jejuno-ileum enlarges it hangs in loops from the s|)iiu'. carrying folds of mesentery with it surrounding the vesseb. The multiplication <arietal peritoneum is thus replaced by fusion with what once belonged to a mesentery. The stomach undergoes rotation, so that the original left side becomes the anterior and the posterior border the greater curvature. The mesogastrium grows out of all proportion, so as not only to describe a curve to the left, but to han^; downward in a free fold. The loop of the duodenum turns to the right, so that all of it, except the first part, lies against the posterior abdominal wall. The head of the pancreas is carried with it. The serous covering of the back of the duodenum ( in its new position), that of its mesentery, and that of the back of the head of the pancreas disappear, fusing with the f)arietal peritoneum of the fjosterior abdominal wall. The mesentery attached to the jejuno-ileum and to most of the large intestine becomes twisted as the gut returns into the abdomen from the umbilical cord, so that the caecum is thrown upward and to the right to lie under the liver, whence it descends to its permanent place ; hence the original right and left sides of the mesentery change places. The mesentery of the ascending colon fuses with the posterior covering of the right side of the abdomen ; that of the descending colon to the sigmoid flexure does the same on the left. The sub- or retroperitoneal tissue is very important. As above stated, there is a thin fibro-elastic layer supporting the mesothelial cells, which is a part of the serous membrane, although it is not present in the earlier stages. Beneath this tunica propria there may be a continuous mass of connective tissue, to be compared to dense, sfKjnge-like cobwebs, which serves as a packing between different organs and around vessels, nerves, and ducts. It may contain a large amount of fat. This is particularly developed about retroperitoneal viscera and along the aorta. The Carietal peritoneum is usually thin where no fusion with another layer nor with isciae has occurred. We shall describe ( i ) the peritoneum of the anterior and lateral abdominal walls, with its prolongations onto the diaphragm and into the pelvis ; (2) the folds denved from the anterior mesentery ; (3) those from the posterior mesentery from above downward. Most matters of detail are discussed with the various organs having peritoneal relations. The Anterior Parietal Peritoneum. — Four folds diverge from the umbili- cus, three running downward, symmetrically disposed, — namely, a median fold (plica ufflbilicalis media), expanding to the top of the bladder covering the urachus, a fibrous cord representing the atrophied intra-embryonic segment of the allantoic duct, and two lateral folds (plies umbilicales taterales) containing fibrous cords, the obliterated hypogastric arteries, continuous with the permanent superior vesical arte- ries. If the bladder be distended, they can be traced to its upper lateral aspects : otherwise to the sides of the pelvis. The fibrous tissue of the obliterated arteries becomes very scanty near the umbilicus. The supravesical fossa (fovea supravcsi- calls) or depression lies on each side above the piibes, between the median and lateral folds. On the outer side of the latter, above the middle of Poupart's ligament, is the internal or median inguinal fossa (fovea inguinalis medialis), which is very THE PERITONEUM. >743 jctinrt uid often extends inward under the obliterated hypogastric artery. Farther '^ t a ve^ sSTfold (plica epigastrica). caused by the deep epigastric artery, runs ulard tnd iWdirom the external iliac artery just as '^e latter pa«es under Pou- ^H^. lirament The txtemal or lateral inguinal fossa (fovea inpiinalis lateralis) rTh^eSv just external to thb fold, but the fold is barely raised and a fossa not P^SrS out The inUmal abdominal ring (annulus Inguinal.s abdommal.s ) « ^ hi, f^ about I cm. above the middle of Poupart's ligament. A slight fold cauS S^'e v^ de erens or the round ligament, is described as running downward causea oyine V however, that the structure can be only lmrS.r^i^r to >h.n, b derived In.™ the mooiMne. of the <»lo». which Fig. 1468. Umbiliciu — Uiu...ic>lveiii Rectus muKle External inguinal fossa Anterior crural nerve Ext. iliac artery External iliac vein Internal inguinal fossa Supravesical fossa •• Anterior superior Iliac spine (cut) Median umbilical fold (urachus) lateral umbilical fold Epigastric fold Internal abdominal ring Vas deferens _ _ __ Peritoneum Summit of bladder ^ Bladder (cut I Pubic bone (cut) Frontal section o. formalin sub)ect. showing posterior «^ o. abdominal wall, covered with ,*rl.oneum. have fallen over onto the posterior abdominal walls. It will he considered later. Se irieul peritoneum is^lso to be traced onto the under suriace of the da- phraS untilfar back it meets the folds derived from the mesenteries. On either siW the bundle of fibres arising from the ensiform cartilage there is an mter- rliption in the muscle of the diaphragm, where only areolar tissue separates the ^''''■^r^:iT;^Z^t^^^-^^^o the pelvis, where it meets the mesen- tery of th^Toon'^and is continued over the bladder,. and in the female over the uterus and Fallopian tubes. Nowhere is the comparison to a wall-paper so apt M here where the %ritoneum can be traced from the walls "ver the .nequalit.es formed bv the upper surfaces of the pelvic organs. The depression between the wldder and the r^e'ctum in the male, the rccto-vesical pouch (excavat o recto- ves calls) n the female is subdivided into the utero-vesical pouch (excavatio utero-vesicalls) and V^redTuicrinhonch (excavatio recto-uterina). The latter and deeper, also known l^Zl pouch of Douglas (cavum DouKlasi). is bounded latera ly by the ^^ero-s^^^ folds SL. recto-uterin*). which pass from the lower part of the uterus backward 1744 HUMAN ANATOMY. and outward to the side of the rectum and the pelvic wall. The peritoneal f .ll investing the uterus extends laterally on either side as the broad ligament (liiianiiu- tum latnm) to blend with the parietal peritoneum covering the sides of the peh i^. Below, the broad ligament is attached to the pelvic floor, its superior margin bciii<,r the free edge of the fold. On either side of the rectum, between the gut and tiiv wall of the pelvis, lies the pararectal fossa, the size of which varies with the disti ii tion of the intestine. The special features of the peritoneum are described with the rectum (page 1679) and with the uro-genital system (page 1905). The arrangement over the anterior half of the lateral wall of the true pelvis is different according to sex, since in the female there is the line of attachment of tiie broad ligament of the uterus and the fossa for the ovary. Otherwise the featurt^ are about the same, the vas deferens of the male and the round ligament of tlit female causing similar folds. These structures run backward from the internal riiii; along the wall of the pelvis, turn down to the side of the bladder, and bound externally and posteriorly X\ie paravesical fossa bei veen the pelvic wall and the Fig i46q. Bladdci I I Internal-^-, abdominal ring Trans verse -^ vrsical fold External iliac- vessels Left ureter — Sigmoid flexure' Urachus —Vas deferens -_J5per Hiati c \rsbcls — Sup. vesical utny ~£xt. iliac arter> -Ureter -Vas deferens Recto-vesical fold Ireter _ Peritoneum (cut) Internal iliac arter>- Left common iliac arter>- If' * Pelvic peritoneum from above and behind, showing folds and fosss. bladder when the latter is not distended. A transverse fold of peritoneum, plica vesiccUis transversa,'^ passes laterally from the upper suriace of the empty bladder and subdivides the paravesical fossa into an anterior and a posterior compartment. The vas deferens, or round ligament, forms (the body being upright) the lower side of the obturator triangle, which is completed in front by the external iliac vein and behind by the ureter, wtiich crosses the external iliac vein at the apex. The obtu- rator vessels and nerve lie in the floor of this triangle. In the female it is crossed by the lateral attachment of the broad ligament of the uterus, behind which is the fossa for the ovary (fossa ovarica). The Anterior Mesentery. — This originally extended from the anterior abdom- inal wall to the lesser curvature of the stomach and to the beginning of the duo- denum. It is subdivided into two portions by the liver, which develops within ii The anterior part is the falciform ligament, between the abdominal wall and the liver ; the posterior part is the gastro-hepatic omentum, between the liver and the stomach. ' Waldeyer : Journal of Anatomy and Physiology, vol. xxxii., 1898. THE PERITONEUM. 1745 The falciform ligament (llRBmentam falcifonne hepatte) makes the fourth fold which has been mentioned as leaving the umbilicus. Seen from the side, .t is a Ikle-shaped fold attached to the anterior wall above the umbilicus and later to the dtaDhraKiT as far back as the top of the fissure of the ductus venosus on the pos- SHurface of the liver (Fig. 1441 )• In its free inferior border runs the round .Jament once the umbilical vein, from the umbilicus to the notch in the liver, and hence in its own fissure on the under surface until it reaches the portal figure, where the falciform ligament ends. The latter divides the "PP^'^^P*';* ^^ ),h^dome of the abdomen into two chambers, one on either side of which the left one is the kwer There is but little areolar tissue in the folds of the falciform ligament. SnnU'veins run along the round ligament, connecting the hepatic system with that of "he abdominal walls. AlthoMgh in the embryo the fold starts from the navel, in the adult it does not leave the abdominal wall for an inch or more above it The superior surface of the liver is covered with peritoneum from either side of the falciform ligament, which at the top of the posterior surface is reflected onto the under side of the dia- ^^^ phragm. At the edge of the right lobe, which has a considerable posterior sur- face uncovered by jjerito- neum and attached to the diaphragm, the layers cov- ering the upper and lower surfaces meet to form the right triangular ligament, which is attached for a short distance beyond the liver to the diaphragm and has a sharp, free edge. There is a similar arrange- ment on the upper surface of the left lobe, but the left triangular ligament is longer, and passes to the diaphragm on the left of the rvfte ?pl^" Pl«"g around the border of the right lobe of the liver the peri- toneum irSds over the inferior surface of that lobe as well as of the quadrate coy enW the gall-bladder which lies in a hollow between them. Exceptionallythe gall- bkdder is entirely surrounded, and is attached to the liver merely by a narrow old. The pJr^toneum i continued over the cystic duct to the edge of thelesser omentum to be^pSTtW described. The entire under surface of the left obe is also covered Ly perTtreum^ continuous with the preceding. The parage of the finger o^^^^^^^^ surface to the right is interrupted at the front by the end of the falcifonn hgamen* b^fw^n it and ?he quadrate W. At the back farther progress to the nght is stopped by the lesser omentum in the fissure of the due us venosus. All the peri- toneal covering of the liver has thus been accounted for. excepting that of the caudate lobe and of the lobe of Spigelius. „„„„*„„ The postro-hePatic or lesser omentum (liRamentum hepatogastrium, omentum minus) is that part of the original anterior mesentery '^""''"ting the stomach and the beginning of the duodenum with the liver. It must, theoretically, have been origin^y a median antero-posterior fold, but it is now so twisted in consequence o thJ^change in position of the stomach as to be chiefly nearly transverae Its line of attachment to the stomach is along the lesser curvature from the gullet past he pylorus, continued onto the first part of the duodenum, where it crosses from the Top to the left of the gut, until it passes the common bile-duct (by .^hicji 'he duct, of the liver originally grew out of the.gut) with its companions, the hepatic artery andThe porul vein It is formed by the union of the peritoneal layers covering ?«p«Sively the front and back of the stomach and the sides of the duodenum con- no icnm showing «»rly «rtmnf«i»nt ol P«rl«««l "ncl. vi.ceril pCTlto- _ ^ue p«rietar;>-ellow, right side, red, left iideolvnceral. /..liver; !5, stomach ' 5, spleen ; P. pancreas ; *■. kidney. Uia neom. 1746 HUMAN ANATOMY. 1 Ji \r Pio. tinuous with them. The two layers join at the bundle of vessels just mentioned, thus forming a fold which is the termination of the lesser omentum on the right, known as the duodtno-hepatic omentum (ligamentum hepatodnodenale). The lesser omentum is sometimes described as prolonged across the first part of the duodenum to the transverse colon, fusing with the greater omentum. This is only an acci- dental modification, although a very common one. An accessory fold, the duodeno- cystic ligament, is prolonged to the right from the front of the lesser omentum, around the cystic duct from the gall-bladder. The hepatic attachment of the lesser omentum is to the transverse fissure of the liver and from its left end to the fissure fA the ductus venosus. From the point at which the latter reaches the diaphragm the two layers diverge, the '*'*• left one passing to the lower side of the left lobe and the right one to the lobe of Spigelius. The structure of the lesser omentum is dense and fibrous at the right. It is very delicate in the middle, but somewhat thicker at the left end. The fold siround the vessels at the free edge (Fig. 1473) forms the anterior border of xiat foramen of Winslow (foramen epiploicum), a nar- row part of the peritoneal cavity by which the general cavity communicates with that behind the stomach which has been formed by the rotation of that organ and the inordinate growth of the mescw^trium. The Of the three vessels in I>iagnin showing cbannd relation of vifccral peritoneum in consequence of twisting, so that oriKinal right and left sides of mesentery of small intes- tine and of part of colon have exchanged places. The detached portion which is twisted is supposed to be attached :it a higher level. D, duode- nunij C, C. ascending and descending colon ; y, amallintestine j K, kidney ; D, C t are being displaced towards posterior wall. foramen is circular, with a diameter of from 2-3 cm. the fold forming its anterior border, the portal vein is the posterior at the point of entrance into the liver, with the hepatic artery in front on the left and the hepatic duct in front on the right. The cystic duct is really in an accessory fold. The hepatic artery, which passes along the left side of the duodenum and turns upward, is the vessel that most definitely bounds the foramen in front. The duo- denum lies below the foramen, but its loteer border is often formed, not by the gut, but by a fold of serous membrane arising from it. The foramen is bounded behind by the vena cava and ahove by the caudate lobe of the liver, which is covered by peritoneum. The Posterior Mesentery : Part I. — The posterior mesentery arises from the spine, with the aorta between its folds. The first part is the mesogastrium, in which run the branches of the coeliac axis. It will be remembered that, except at the fundus, this is attached to the greater curvature of the stomach, which was originally the posterior border, but which has turned to the left. The spleen and most of the pancreas are developed in this fold, which grows inordinately. We must trace it both m a horizontal and m a sagittal plane. To understand the horizontal arrangement, it is sufficient to remember that the original mesentery, which ran straight forward from the spine to the stomach, in its subsequent excessive growth describes a loop to the left (Fig. 1470), so that the original left side of the mesentery near its root faces backward, and later, after the bend of the loop, forward, ultimately covering the an- terior wall of the stomach. This fold forms a great pouch behind and below the stomach called the lesser cavity of the peritoneum (bursa omentalis), which, of course, is continuous with the general cavity. The mesothelium of the left side of the mes- entery nearly to the spleen fuses with that of the posterior wall o* the abdomen, so that the splenic vessels and the pancreas which are in it come to lie behind the per- i. THE PERITONEUM. 1747 manent serous covering of the posterior abdominal wall, which here is that o the SS right side of the mesogastrium. The spleen, and perhaps he tail of he S2rL. Tie free, surrounded by peritoneum. If the hand be introduced into he K^ondriuk,. it slides along the wall behind the sp^een^o the pomt at^whjch F,o 147a. posterior ill and pass in a fold, tht . If no-renal liga- ment, to the hilum of the spleen. From this position tiie hand can be carried arounvl the spleen to the front of the vessels at the hilum and thence tf) the right along the continua- tion of the mesHgastrium to the greater curvature of the stomach, where its layers separate to coat the front and back of that organ. The part of the mesogas- trium between the stomach and the spleen is the^oi/ro- spUnic omtntum. The right layer of peritoneum of the mesogastrium, lining first the hind wall of the abdo- Diaimm showinu later sUije where secondary tneKntery is Ipmvrf and men and then the back of the stomach, bounds the lesser cavity of the pentoneunL TZzastr^phr^nic ligament is a small vertical fold, usuaUy found extending fom the Irfforthe end of the oesophagus to the top of the stomach. Near it is often 'anoth , the ..S^li' ligalJof the spleen, "^enjng from the diaph-gm to the too of that onran, of which it may enclose a small part. It marks the upper oart o?the hne ofTeflection of the mesogastrium from the posterior abdominal waU ^C^phr^Tolicfold, also derived from the mesogastrium, is a horizontal shell with a free anterior semi- lunar edge forming the floor ""• "♦"• of a niche for the spleen. It extends from about the eleventh rib inward onto the upper surface of the trans- verse colon. That this liga- ment is really a part of the mesogastrFum, and not a lig- ament of the colon, is shown by development, as well by its existence (as in the mon- key) when the descending colon is unattached to the wall. The Greater Omentum. We are now to trace the mesogastrium in a sagittal plane downward from the greater curvature of th" stomach. On opening t abdomen the first tb'ng that . , ^ \ ™t,;^», u appears below the stomach b the greater amentum (omentum "»>"^)- ^'''^'J « spread like an apron over the intestines. It is that part of the mesogastrium :Ch ITILJ in front. The terms ^-'--'"-.^"^'^-'^Lt^he '^^^^ are but names for different parts of this structure. It extends from the greater Diagrammatic action pawinK through level of f"™"*" »' y^^}"^^ winB^elalions of parietal an?! visceral perUnneum««^ mc USUiiH CM Rastrtihepalic omentum, contammK I""^"" «'" Z^^?" ^Uc knen^ ( //)^n.l bile^uct ( /?);«. stomach ; 6.S, «lsln«.plenic omen- tum ; LK. lieno-renal omentum ; f'C A. vena cava an.l aorta. 1748 HUMAN ANATOMY. curvature of the stomach, where it is continuous on the left with the double layer coming from the spleen and on the right with that coming from the inferior sur- face of the first part of the duodenum ; from this broad origin the greater omentum hangs down over the intestines to near the pubes, where it turns upon itself and ascends posteriorly. Often it does not descend so far, but may be folded uf>on itself to almost any degree and in almost any position. F"or purposes of description it is supposed to lie spread out smoothly, and to consist of an anterior and a jjos- Fio. 1474. Ensiionn cartilage Liver- Uall4>laddcr. Ascendinjc colon Carcuifi DescendJtiK colon iginoid tiL'Xurb l*rulisturht:d abdominal viscera of t) subject ; liver and stomach abnormally large, hence the exaggerated , ip.ireiit tniiiH\erse iN>stti<>n of stomach. terior fold ( Fijj. 1467). The former passes down over the transverse colon, but with- out adhering to it. The peritoneum on its anterior surface faces forward into the greater peritoneal cavity, while that on its posterior surface looks into the lesser one. On turning backward upon itself, it runs up to the transverse colon. If this were literally tnic, it is evident th.it the lesser cavity would extend from behind the stomach over the colon down into this fold (recessus inferior omentalis) of the greater omen- tum, and in fact this is actually the case in the fuetus (Fig. 1439) and exceptionally m THE PERITONEUM. 1749 in the adult ; but generally, except iuj J-'-^^'^-t'^^^^^^^^^^^ In the adult, when the returning «°W f^.^^"? J^^,^^ and re"niti"K ^^"^ "• '" ^ composing it seem to diverge to «"'^>°*1,'J^ '"'!^""^„^^"running across the back of cont&upw^d^ t^ej«n-«e n--t"ai ext';::iry'and apparently con- the abdomen, to be a»cnDea ater. i m ^ggogastrium, or mesentery i>f the tradictory arrangement by which a Pf" ot the mesoga^ ^ explanation stomach, has become also »»»^ "'"^"'/"^^y •"i.^'^" °' em^^ is very different. In is furnished by embryology, since 'f ^^/"«"!* .^^^^ef omentum pSses up in front the foetus (Fig. 1439) «»>^'-^*"Tlnl tt lowe^r Srder of the ,>a)^eas. The pos- of the colon to the posterior wal f l°"g t»^f J°*^; ^,Xer of the original mesogas- terior layer of the greater omentum s '" *f » f ^ '^" '^l^\ „„( „i,h^,he pancreas, trium, which we should be ab e to fdlow to die^orta. ^^^^J^^ J ^ -^j, ,he Xl^llwC tt^^Hg^t l"nThig?:nXLt "^^nSe^^^ear thespleen it Joins. from the vessels that course through ,t. f^^'l ^ ^^^^^nJ^^Lt is found al)out tissue which supports the m^'»;^''"'^,„;"^^!: ^a^ed wTth it The two lavers..f the vessels, and in some cases »he jmen urn is oaded w«n n^ ^^ ^ serous membrane are sometimes »^|""*"yJ='"^2s'orthe omentum atrophy and double origin can be recognized Sometnnw parts 01 t^ k ^^^^ disappear, leaving ^^^"dows, or /.«../r^^^^^^^^ .Series at arteries are long and very slender. T^^«y*"!*'™7aiifht downward to the folded colon, it. continuation from bdow the !»»=«»»■ ,„ ,,,' dZrio,i„„ of the fold, colon « the posteriorUyer ol >Kf «"" ~'°'" „„';cS.nr3^t£ aSUion. to of the adnlt in a aigitul plane it wa. "«^7; ,?li'S,°into the stomach tack ,,,e™e,heno,Tn.lc™,»a^.of*Y^^™^^^^^^^^ the median vertical \o\A—piica gastro-pancremuu ,. ' ■ . j^ card a. On and extending upward behind the lobe of f P'Kr:"\^;^\^o„fof the peritoneum over pocket behind the liver (recessus superior) a.-^V* /?hrE,rvenosus which meet is: left of the .inferior vena cava and th^^^^^^^^^^ I750 HUMAN ANATOMY. I ' i 4 ri Ih over onto the right side against the right of the spinal column, to the peritoneal covering of which it has grown with the transformation into connective tissue of the right serous covering of its mesentery. The second or descending portion of the duodenum lies against the right of the column under the permanent parietal peri- toneum, derived from the mesocolon, as is shown later. The great difficulty of un- derstanding the lesser cavity is that in man the duodenum rises to so near the liver that the entrance to the vestibule at the foramen of Winslow is very small. If, as in many animals, these parts were more distant, it would be evident that this is a pouch- Fio. 1 475. Hepatic artery Gaitro-hepatic omentam Accidental peritoneal (old Pylonia Firvt (tart of duooeniun Foramen of Winslow Gaitro- pancreatic fold Stomach Peritoneum lining posterior wall of lesser sac Transverse coloa Greater omentum, cut Spleen Pancreas Folds of greater omentum Gastro-splenic omentum The subject. King on its back, is seen from the left side ; the stomach, except fundus, is turned over. The greater omentum has been cut below the greater curvature of the stomach so as to open the lesser sac to show the foramen of Winslow from the left side. I'' I III' ■ S< like formation, the mouth of which is behind the edge of the lesser omentum. The relations to the mesogastrium of three branches of its artery, the coeliac axis, are as follows. The splenic artery, in the adult condition, lies entirely behind the perma- nent peritoneum to near the hilum of the spleen, where the mesogastrium is no longer attached to the wall. It then sends its terminal branches to the spleen, the gastro-epiploica sinistr.i to the gre.iter curv.iture of the stomach, and the vasa brevia to the fundus. The gastric artery, originally in the mesentery of the duodenum, reaches the cardiac end of the stomach through the piica gastro-pancreatica, and then runs between the layers of the lesser omentum along the lesser curvature. H THE PERITONEUM. 1751 Til. henatie Mterv reaches the duodenum through its mesentery, and crowesthe S .iWthrS? to^lS it gives branches f hence it ru.« in or near the edge d ^leMer omenium at the foramen of VVinslow to the portal fissure. Fio. I476- Ga!itri>-iiam'rcatic fold Vettibulc o( Icuer uc Lcsiser or (astro-bepaiic oiii«tituin. |.ieii<>-renal fold J> Lcswr Site uf |>cril»iiieum Cutro-iplcnk omcntUBi Greater omcntttm ^Sf^^ denum {D) at floor of toP'""""' Wm»^°S' 'f?^l, ™»?'>I^^i^^^^^^ «l." h lies to left of .orta. The Posterior Mesentery: Part II.-This is that part of the peritoneum derivL from the%riginal mesente^ of the Jejuno-ileum. t^e -cum pd the a^^^^^^^ in«r and transverse colon. Its artery is the supenor mesenteric. I the t"nsverse ciorwith the «^ter omentum be turned upward and the sma 1 mtest.ne to he r^ht the TefTside of^e mesentery of the jejuno-ileum is seen running from the left of the too o the body of the second lumbar vertebra to the nght sacro-ihac joint. At the beginninTthis is attached to the lower side of the gut where it -"akes a sharp flexure at the origin of the jejunum from the end of the duodenum. This flexure fiesTrectly b fX of the iJrta. which usually Ues covered w th P-ntoneum at the STck of the abdomen, with the fourth part of the duodenum to the righ of « (Tlus relation is more fully described with the duodenum (page 1647)- The line ot attach mlrof rresentLy (Fig .477) descends over »!- ^-^^^^^,^^1^, J^^^^^ crossing the third part and the inferior vena cava. The greatest breaatn o! ine mes OTW the free border is from ^23 cm. (8-^ in.). It reaches its full breadth S S once after its origin. Usually it becomes very r^-"?;^-^^^''P'£y,l^^^^. —at its termination ; but this varies much, as does also the point of that terniina ;^n ThJTonnectiv; tissue between the layers is thickest and the lymph-nodes mc«t numerLs near the attached part. Except in very fat subjects, \he« « »f ^^'*^"e the layers of peritoneum besides the vessels, within an inch or so of the gut^ The surJrK)r mesenteric artery can be felt at the top, entering it from under the lower Kr of the pLnTreS The peritoneum can bi^followed at. any point across from the left to the ^ght side of the mesentery. From the latter it is fol owed along he Ste or wall tl the kidney and the ascending colon, lying on the front of the K where they are in contact. The membrane crosses the ascending colon Sg itsVsterbr surface without covering attached to the parts behind it, and Ste? ^velops the caecum, passing on the left into the mesenten^ Very S?he>ritoneum is carried for an inch or two behind the lower pa^ of the Mcending ^lon. It then passes into the left flank and the pelvis without incident^ Developmen shows that this is a departure from the original condition, in which the 175* HUMAN ANATOMY. liil nil attachment of this mesentery was exceedingly short, merely broad enough to contain the superior mesenteric artery. The so-called ptrmantnl mesentery is caused by the fallii;g over to the right of the fold of mesentery for the ascending colon, twisting the membrane, and the downward growth uf that part of the gut which brings the caK:um down from under the liver to the right iliac fussa. The twist having occurred, and the ascending colon having fallen against the abdominal wall, the fold ))caring the ascending and transverse colon becomes fused with the peritoneum of the pos- terior right abdominal wall on the right of a line from the b^inning of the jejunum Right lupim- muu body Venacavm Porul vein FlO. 1477- Duodcni Splenic flexure ol colon Jejunum Showing relations and attachments of mesentery of small and targe intestines ; greater part of transverse colon, of sigmoid flexure and of jejuno-ileum has been removed, the latter by cutting through the mesentery near its posterior attachment. to the end of the ileum, the part bearing the small intestine remaining free. This oblique line of attachment becomes the permanent mesenter}*. The peritoneum to the right of it, as far as the ascending colon, forms the permanent parietal perito- neum, having fused with the original parietal layer behind it. When the colon under the liver becomes the transverse, the fwrt nearest to the latter continues free and hangs down as a transverse fold, on which the >ifreater omentum lies, and sub- sequently fuses, as already described. The transverse colon is attached by the transverse mesocolon (also a secondary adhesion) to the front of the right kidney and to the posterior wall across the second part of the duodenum and the head of THE PERITONEUM. I75i ,1... nancreas alone the lower border ol that gland to the left kidney ( Fig. I477> !» ieaC b^dthb wme five or .ix inches. (For a fuller description, «... ,H.r.toneal greatest »>'^«f5"" *! """^ "J . . jh^ breadth oJ the transverse mcsoc..l„n is from 7inrm (S^TnT.' I^the adit ilu. fu^ with the greater omentum as already d^S. The superior mesenteric artery enters thin mc.sentcry u.uler t ho ,«ncre;« SgwSfromi.|t<.conj.x^ »'^Ke'.LirTnd\L^^^^ I" «he adult the rChtcdic artery runs behind the permanent posterior parietal ,jeritoncuin. STnSrrS-un"?^^^^^^^^^^ abdominal wall, over Fio. 1478. CKvnm S"«>" Intntinc \ — ■ Treiitveric cokm AtccndiriK colon Lower end of ileum Mnentery Duodrnum Dncniiliiix lolon MesenUry Poaterior wall ol abdomen _i Bladder I 1.11.1 „i ihrM. von • the usual relations would be restored by bringinis upper dotted line Mesenterium commune in child ol three year. . «J«^;^^ ^J^^ lower. the lower oart of the left kidney, and over the descending colon which, although S^ching'th^t^o^'rglnriies chiefly^ external to it The P-tX^:^s^^h' t'Jhe'^^r" freedom of the fold, from that point to the middle °' ''^I^Xl; Wei the rectum is chief forms are described on page 167..) Be>°"*L'»'^ '*' ^' ^Lmy diverging parUy uncovered behind, where the mesentery ceases, and its gradually aivergmg «754 HUMAN ANATOMY. : l- h 1ft m ;i lines uaa> onto its sides, leaving the termination ol the gut without any peritoneal covenng. The branches of the inferior mesenteric artery in thit* region are the lift colica sinistra, which runs behind the |>ermanent parietal peritoneum ; the sigmoid, which does the same until it reaches the part of the mesentery which is free : and the superior hemorrhoidals, which descend m the lower part ol the original mesentery until they reach the retroperitoneal area behind the rectum. PRACTICAL CONSIDERATIONS : THE PERITONEUM. The development, topography, and relations of the i)eritoneum have already been sufficiently described It remains to consider its diseased conditions and those in which it is an important or controlling factor in the production of disease in so far as they are influenced by anatomical circumstances. PerHonUis is the most common and the most serious of peritoneal diseases. The separate consideration of wounds of the peritoneum is not necessary, as traumatism, unassociated with infection, produces merely hyperemia and exudation. The pro- cess is for convenience known as plastic or reparative |)eritonitis, a term also applied to those forms of true ( infective) peritonitis in which the bactericidal and absor})tive powers of the membrane itself and of its serum have resulted in the destruction or thf isolation of the invading oacteria. The anatomical routes by which bacteria may reach the peritoneum are : 1. From without, as through an accidental or operative wound. 2. Prom within, as from an escape of the micro-or^nisms through intestinal walls leaky as a result of strangulation (as in intestinal hen.ias or volvulus or intussuscep- tion) or of inflammation (as in appendicitis) ; or through an actual i)erforat' .n, as in gastric ulcer, typhoid fever, or intestinal cancer. 3. Through the blood- or lymph-channels, as in many cases of tuberculous peritonitis and possibly in so-called rheumatic, nephritic, and other clinical forms of peritonitis, in some of which the infecting organism is still unknown. 4. Through the Fallopian tubes. The peritoneum is not equally susceptible to traumatism or to infection on b...h its surfaces or in all its parts. The exterr.al, areolar, or "wrong" side (page 1740 ) may be extensively separated from the subjacent structures (as in the extraperi- toneal approach to the ureter or to the common iliac artery), or may be in contact for a long time with an inflamed or a suppurating surface (as in perirenal or other retroperitoneal abscess) without damage to the mesothelisil or free surface of the membrane, and with but littie risk of the supervention of peritonitis. On the other hand, a small penetrating wound made with a dirty instrument will probably set up a diffuse and perhaps a fatal inflammation. The difference in results is due to the delicacy and vulneribility of the mesothe- lial as compared with the fibrous surfar , to the great absorbent power of the former (vide infra), the area of which is about equal to that of the cutaneous surface of the body, favoring toxemia if the bacteria and their toxins are not destroyed or encap- sulated ; to the excellent culture material supplied by blood-dot or by the injured or necrotic epithelial surface ; and to the involvement in diffuse or spreading cases of the peritoneal covering of the neighboring viscera, particularly the intestines. These facts determine the surgical rule that in doubtful cases of bullet and stab wounds of the abdominal wall it is well — under aseptic conditions — to enlarge the wound, ascertain the presence or absence of penetration, and cleanse or drain if necessary. Not only are the two sides of the peritoneum thus unlike in susceptibiliiy to m- fection, but a similar difference exists between the parietal peritoneum and that cover- ing the viscera. The former, applied by a layer of fat-containing connective tissue to the relatively immobile muscular layer of the abdominal wall, is less easily inflamed, or if inflamed develops a less diffused and less quickly spreading form of peritonitis than does the thinner, more sensitive, and more vulnerable visceral peritoneum, especially that covering the most mobile of the abdominal viscera, the small intestine. So, too, peritonitis originating in certain regions is, by reason of the facility with which they may be shut off by adhesions, less threatening in its course and PRACTICAL CONSIDERATIONS. THK I'F.RITONEUM. 1755 Pelvic jierit"- aml subhf|»atic more amenable to .urgical treatment than that beRinninK tlsewhere. nitis uara-appcndioil and iMracolic i.eritonitw. »ubdiaphrajrmatic SoSitb,i^ peritonitis limit«l to tL l«»er. fH.ritonc;al «c iv,d.- '«/-)»"„;'' V'^^ S« that are l«» danRerous than i» peritonitis beRmnm^ am-.n^ the »hiftmK coil* "•""Se'Somical «<.urc« of peritoneal infection may therefore be arranged ap- nroximLteirin The order uf their Rravity. as follows : ( « ) ,H.rioratKms or wounds of The Sr m « ineV(*) ixrriorations or wounds of the stomach or larjce mtest.m. : U) Sor^S or 'wounds .>f other viscera, including kidneys, »«t-^. »'»^;^^'«^,^; P;"', irias and bile-passanes ; {d) entrance of l«cteria by contmuous «row h throuKh a^g=«rlC^nal walls; (.) bacterial migrat on through stra.«uU^^ tineT(/) infection through the Fallopian tubes ; (g) wounds of the aNlommal **" ThriSnuement is based upon two factors : the number and virulence of the bacteria wSare likely t.. gain ^trance, and the op,x,rtunity wh.ch w.ll j.rolMbly SSdtXXe form'Ltion of limiting adhesions. The latter factor ^"uc l|e co ; Sdered from the anatomical stand-point. ;is the variations in the intensity of tht in flamimtion due to varving forms and doses of the invading bactena arc influenced by fhe sTe Ta wLnd or'other traumatism, or of an ulcerative or "'^^'^if^-Vr.ti Y^„.».;nri vi«^a For example and for reasons already indicated, pe tratmg tS^boveXlevel of^eTim^ less likely to pr-xluce fataT: M.on.tis rCn a?e tK n the low.r half of the abdomen. The differences in this res,3ect be- hT^^nwoun^ or perforations of the stomach, of the different portions of the M.iall St^dne? and oTthTe lar^e intestine have been described in relauon to the an.Uomy ..f '''^T^e^SltWe^irutTinfection is usually in direct proportion to the nor^LTy^f its mesotiielial coat, which is les- ed by all forms of traumatism "eluding handling or sponging, or irrigation with strong antiseptics. To a ceru n exter'KnstKTeness of he^toneum and the rapidity with which it responds to Son isTcon^^^ive proc^. The prompt exud m wh.ch follows either injury rSon ohen'Ses t'he affected are'a Uprevonts a fatal 'f-r--y^^;;^^Zl tion The ereat absorptive power of the peritoneum— which should be studied als.> n SnnecAionSthVly^pha^' system-may be alluded to here as it aids materially ^iSng the danger from infection. It has been demonstrated expenmentolly that^m V to 8 per cent, of the body weight in fluid can be taken up by the pen- toneum from witWn its cavity in one hour, which is equ valent to fe total body weiehTin TenTy-four hours ( Wegner ). The current of this process of absorption of Soneal 3 has been shown to set normally from the peritoneal cavity towards Ae di^pS and to be much hastened by elevation of the pelvis and lower abdo- men SmTiUrticles (carmine, bacteria, etc. ) are carried through the 'ntercellular Ses in the^aphragmatic peritoneum-" the openings made by the retracUon o KdothelUim" (Kdly)-iluo the lymph-spaces beneath, then into the medmstinal ymph-Saces and glands, and then into the blood-current (Muscatello)^ This pro- c^ go^ on much more rapidly in this direction-towards the diaphragm and m«l.- SrSand^than does the similar process beginning m the v>sceral int^tina^ peritoneum and associated with the mesenrenc lymph-nodes,-an additional ana- lomical explanation of the greater fatality of visceral pentonitis The dose relation of the nerves of the peritoneum and of the abdomina^ viscera to tho nerves supplying the abdominal and the lower intercostal muscles has l^n mentioned in reir^on to appendicitis and other intra-abdominal lesions (pag«. V8. T683), and is of the high^t importance in connection with the mimical symptoms of peritonitis. Hilton comparer the peritoneum and the muscles of fje aMomen to the synovial membrane and the muscles moving a joint. The "P* X '''«5 '°"' ^^ inflammation in either case is due to the reflex muscular spasm resulting from the correlation of the nerve-supply. Thus the six lower intercostals supplying tje com-- spondinK intercostal muse!.-, and pAssing through thed.aphragm, to which they send twigs, are I tributed to the skin over most of the abdomen, and to the rectus ex- erS i.-^ eternal oblique, and transversalis muscles. Through the splanchnics they join . in the innervation of the peritoneum and of the abdominal viscera. In 1756 HUMAN ANATOMY. a case of injury to the abdominal wall, therefore, the impression is barely made upon the skin before the muscles contract and an attempt at protection is made. In a case of visceral lesion or of beginning peritonitis the rigid contraction of the muscles in closest nerve relation to the area involved will constitute a valuable diagnostic symp- tom. In general peritonitis the board-like, tender abdomen, the fi.xed diaphragm, and the thoracic breathing (to lessen movement of the abdominal viscera) are all phenomena to be understood only by recalling the correlation of the nerves involved. The flexion of the thighs (to remove pressure from the tender surface and to relax the muscles as much as possible) is a secondary symptom due to the same cause. The condition is in strong contrast with that seen in intestinal spasm (co/ic), in which, although the patient may be doubled up with pain, pressure gives relief and the loose, relaxed abdominal muscles may be moved easily and freely over the un- derlying viscera. The intestinal distention and paresis of peritonitis are due partly to the involvement of the nerve-plexuses of the gut and partly to the extension of in- flammation to its muscular walls. They are increased by later vasomotor paralysis and by fermentative decomposition of intestinal contents. Other phenomena common to many abdominal lesions, but especially to those affecting the peritoneum, are due to the relation of the nerves of the latter to the great abdominal nerve-plexuses. They have been grouped by Giibler under the term peritonism, are indejjendent of toxaemia, and are essentially the symptoms of " shock, ' — subnormal temperature, a running pulse, pallor or lividity, quick, shallow breathing, and great mental and physical depression. The more distinctive peritoneal symptoms are vomiting (although that is not uncommon in many forms of shock ) and generalized abdominal pain becoming epigastric or umbilical, and later— if peri- tonitis develops — associated with tenderness. In illustration of this relation of nerves and nerve-centres, Treves says, very truly, that almost all acute troubles within the abdomen begin with the same group of symptoms, and that until some hours ha\e elapsed it is often impossible tc say whether a violent abdominal crisis is due to the perforation of an appendix or other portion of the intestine, the bursting of a pyo- salpinx, the strangulation of a loop of gut, the passage of a gall-stone, the rupture of a hydatid cyst, an acute infection of the pancreas, the twisting of the pedicle of an ovarian tumor, or a sudden intraperitoneal hemorrhage. The later symptoms of peritonitis — the board-like rigidity of the abdominal mus- cles, the tenderness, the meteorism, the intestinal paresis or paralysis, and the ascitic dulness in the flanks — require no further anatomical explanation. The factors already described, plus the existence of profound tox£emia, sufficiently account for them. Chronic peritonitis oi the proliferative type (said to be found frequently in the subjects of chronic alcoholism) is attended by great thickening followed by fibroid contraction, which, in accordance with the locality chiefly involved, may cause (a) constriction of the gastro-hepatic omentum with pressure on the portal vein and re- sulting serous effusion ; ib) diminution in the volume of the liver from perihepatitis ; (c) thickening of the omentum, which forms a hardened roll lying transversely between the colon and the stomach : (d ) shortening of the mesentery so that the intestines are drawn into a rounded mass, situated in the mid-line and feeling like a solid tumor ; (e) thickening and contraction of the intestinal walls, the mucous mem- brane being thrown m* 'olds like the valviilae conniventes ; (/) the formation of cicatricial bands attacht : their ends to intestine and parietes or to two portions of the gut, and under which other coils of intestine may jjass and become strangulated. Tuberculous peritonitis is the most common chronic form of the disease. The infection — especially in children and males — usually proceeds from the digestive tract through the retroperitoneal lymphatics ; or from the lung or pleura and bronchial lymph-nodes by the same route ; or, less frequently, directly from ulcers within the intestine ; in women it often enters through the Fallopian tubes. It may be con- veyed by the blood. Of the conditions described as due to chronic peritonitis, the omental thickening and the retraction and thickening of intestinal coils are frequently present. Agglu- tination of these coils is apt to occur and to contribute to the sense of resistance which may l>e erroneously interpreled as indicating the presence of a tumor. In addition there are apt to be (a) a sacculated exudation in which the effusion is limited and PRACTICAL CONSIDERATIONS: THE PERITONEUM. 1757 ronfined by adhesions between the coils of gut. the parietal peritoneum, the mesen- te,!y! !nd the abdominal or pelvic organs (Osier) ; and (*) enlargement at the '"'^Th'TexSSe of a superficial periumbilical area of redness and thickening is said .o be a symptom of this variety of peritonitis (Fagge), and is even thought to Ik; ^thn^nomonic ( Henry ). It may follow adhesion of intestme to the mner ,«r.etes, ^ X protebly Is due to exten^sion of the inflammation of the partetal per.toneum tilAno- the track of the obliterated umbilical vessels. /• i . „.i ^^^SJdperitonitis should be briefly considered from the topographical sund- ^'"^'Peh'k fienloniiis, usually due to infection by way of the uterus and Fallopian tubes is ofV^CSy essened danger <.n account of (a. 'he fact that the so-irce of ElSriLl supply is not large, the endometrium possessing a high degree of uul e- Stance and its'^secretion rendering its cavity in most instances sterile ( ^V a basse) fl, the comparatively low virulence of the bacteria most frequently found in tuKil nfiction Te Konococcus and bacillus tuberculosis ; and (O the opf>ortun.tv usually S^ (by the thickness and immobility of the subperitoneal tissues iny<.iv«l) fur the£iKcompetent adhesive barriers, including those.wh.ch seal the openn^g of the tX and conf^Ae the infection to the latter and its vicinity (Fowler . Pue^i^ral peritonitis is much more serious, owing to the anatomical contl . ms associaed with pregnancy-chiefly the vastly greater size and vascularity of the mer^fand S el^ement of its ijmph-channels-and to the minor traumaUsms to the endometrium which occur even in physiological parturition. These oHtr an OD Jrturyforlncreased dosage of bac-teria and of their toxins. The 'linger is TnSed by the fact that the invading organism is apt to be a streptococcus and by the usual Dost-partum diminution of vital resistance. .u i, i Subd^hmgmatic peritonitis may be confined to the space between the arch of the d^aoKm and the upper surface of the liver to the right or left of the suspen- sory iSmen It is apt to assume a suppurative form. It may follow (or prececk) rpleuralor pulmonary^ infection. It is commonly mistaken for an empyema. 1 he fnfectbn is of course at its onset within the greater cavity of the peritoneum but is o" en ^n shut off by adhesions. When it has followed a perforation of the stomach or duXum the abscess usually contains air (pyo-pneumothorax subphrenicus Ae Sragm may be pushed up to the level of the second or third nb. the liver is feprSd fh^rriJ bul|ing of the right thorax, and the physical signs are those of P"'Thf SyTsibdiaphragmatic peritonitis which involves the 'esserJ>erito^ «r.//r may orfgLte in gastric, duodenal, or colic perforations, in pancreatic dlseast^ or in Xer ways The communication with the greater peritoneum is soon cut off by Ldhiive rnflammation of the edges of the gastro-hepatic omentum at the foramen *** ^^Sention of the lesser sac with serum or with pus follows and first causes an enieastric swelling extending by gravity to the umbilical region ; on account of the E re^istlnSer'ed by ifs left boundary-the lieno-renal ligament-as compar^ whh th^ of the gastro-hepatic omentum, and because the lesser sac extends farther Towards that side the swelling may appear later in the leh hypochondriac reg on. As The flo^r of the space is formed by the upper layer of the transverse mes,>cc^on, The colon UdepreLset and never lies in front of or above the enlargement, as it A<^ nc^ of renal tumor. As the space lies below and behind the stomach, distention of thTfatter Tf w th liquid, will render the swelling less palpable, but may apparent v increase its area of dulness : if with air, will convert the dulness into resonance and ^^^^'?L;;^Srev:;:;S:rS^X^ abs«^ n.y -^e place into any S diaphragm or, more circuitously, through the weakened intervals between the sternal costal, and vertebral portions of that muscle. Ihl appendicular and st'^hepatic varieties of localized penton.t.s have been sufti- ciently described in connection with the organs involved. 1758 HUMAN ANATOMY. Cancer of the peritoneum is occasionally primary, b«t is usually due to exten- sion from the stomach, uterus, ovaries, liver, or other organs. The irregular mass of a carcinomatous omentum cannot be distinguished by touch from the similar tumor due to chronic peritonitis. lYve peritoneal cavity as a whole — the interval betivi:»n adjacent visceral surfaces or between such surfaces and the parietes — may be scarcely more than a pote.itial space, containing enough serous fluid for pur{>oses of lubrication, or may be more or less distended by an eflusion of the same fluid, — ascites. Such eflusion may result from (a) infection followed by chronic inflammation ; {b) abdominal tumors, causing irritation and pressure ; (f ) obstruction of the portal circulation, either terminal, as in hepatic cirrhosis, or by pressure on the vein itself in the gastro-hepatic omen- tum, as from certain pancreatic or duodenal growths, aneurism, or the exudate of a chronic peritonitis (^vide supra); or {d) from conditions producing a general dropsy (of which the ascites is but a part), such as cardiac or renal disease, chronic empyema, or pulmonary sclerosis. Ascites is recognized by (a) a flat abdomen bulging at the flanks, with prominent umbilicus ; {b) dulness in the flanks varying with change of posture ; (f) resonance over the uppermost part of the abdomen in either dorsal or lateral decubitus (from floating upward of the intestine) ; {d) flue tuation. Sudden withdrawal of ascitic fluid may cause syncope in persons with pre-existing cardiac lesions by diminishing intra-abdominal pressure, permitting a dilatation of the deep circumflex iliac, the deep epigastric, the lumbar and other deep abdominal veins, and thus suddenly lessening cardiac blood-pressure. The difference between the peritoneal cavity and the abdominal cavity should not be overlooked by the student. A number of the abdominal viscera are not intra- peritoneal, but lie more or less completely behind that membrane. Thus the kidney and pancreas and certain aspects of the ascending and descending colon and duode- num may be wounded, or may be the subject of infectious disease, without involve- ment of the peritoneum, while similar wounds or infections of the liver, spleen, stom- ach, or small intestine would necessarily include it to some extent. The parietal peritoneum, the least sensitive portion of the membrane (vide supra), is thickest below and posteriorly, and is there connected loosely with the abdominal wall by relatively abundant subperitoneal cellular tissue containing fat. This loose connection permits it to be stripped forward, as in some operations on the kidneys or ureters or on the iliac vessels. About the umbilicus and along the mid-line of the abdomen it adheres much more closely. It is strong, bearing a weight of fifty pounds (Huschke) ; distensible, as shown by the gradual stretch- ing it undergoes in ascites, during pregnancy, or in a hernial sac ; and elastic, as in such cases it returns to its normal dimensions when the distending cause is removed. It may be ruptured by sudden force without injury being done to the underlying viscera. From Its superficial position, the greater omentum is often involved in penetrating wounds of the abdominal wall. Wounds of the omentum are not in themselves seri- ous, except from hemorrhage. The rapid adhesive inflammation which follows injury to the omentum, as to other parts of the peritoneum, may act beneficially by leading to the closure of an intestinal wound or perforation before extravasation occurs, or by favoring the localization of an area of infection. It is sometimes utilized by the sur- geon to reinforce an intestinal suture or to cover intestinal defects, especially in the cjecum (E. Senn) ; or to protect the general peritoneal cavity, as in some operations on the bile-diK ts. Through inflammatory adhesions, portions of the omentum may act as bands beneath which a loop of gut may be strangulated, or such a loop may pass through an aperture in the omentum itself and become strangulated. The omentum is constantly found in sacs of ordinary hernia or may constitute their only contents (epiplocele), especially in umbilical and frequently in femoral herniw. It almost always contracts adhesions to the neck or other portion of a hernial sac, if the hernia is not kept permanently reduced. It then prevents reduction. It is found oftener in left-sided herniae, because it was developed from the mesogastrium and inclines somewhat towards that side. It is very vascular, and has — through acci- dental adhesions — maintained the blood-supply of an ovarian tunwr the pedicle of which has been twisted so as to occlude its vessels. Its vascularity and rapid adhe- PRACTICAL CONSIDERATIONS: ABDOMINAL HERNIA. .750 sion to other peritoneal surfaces have been utilized in an operation for the relief of the ^^^T^^^£^ o! ^^^^^^^ is of in,..ance -t^£B ^si^iJ^ !=^lS:;r 1^'^n r i^LS hemorrhage takes P>^«=!,'° V^ '^^^ ? i^."^^^^ be more common in the ri^ht than m the left liac tossa. '^\;" ' ... coneenital defects in the mesentery, holes due to injury, there are others which ^'^^°"f "'^^j . ^^ {„ jhe lower ileum ; and has called attention to the fact that ^"^^^^["^"Sic^Lch of the su,K.rior are surrounded by an f "^»7° \'=. f^f'^.^Xrterie^ tha t^ area is often the seat mesenteric artery and the l'^' ° j]'; 'f ^S and glands are absent. ?SeSrWnr£Tgi.rtJrS^^^^^^^^^^^ area of mJ^ntery could occur with -7;-»-^,f ^^„,ery as a means of recognition of a particular portion of gut ^"^^h^^SXeLlTofThe^A"^^^^^^ ^ -^'^-^ '" ''^ section on hernia (page 1765). PRACTICAL CONSIDERATIONS: ABDOMINAL HERNIA, and ileum) and of the o"l^"™™' " 7" however in which a portion of the mtestin.- ""'°°/r? wXS -tS" gene^l condition. .I»t prriispose to o, actually |.to.l..cj e,..,Sd.aS^io««so?i.ted»i.h (■) inctc^d in,„-abdo,n»0 prc«,o,.- and *"' 1'"Sl',t"o™e°'s?»rd"r;iiS «) oc„p.ti„„, that „cc.».itate n,uch ^'°^? 'S^&TeSS^ttSrabdominal wall may be due to (a) debili- 2. Decreased resisianc j gd distention (ascites, abdominal tumor, tatmg f -^^'^ (*>^i°'^(f)"'e44irco.|ulence, or (.) emaciation. The last two repea' ■' ir« Intercolumnar fascia. anificUlly distended Inner pillar of external rinjC Uutos, cut cdg« Branch of internal cutaneous Dcrvf Internal saphenous vein Superficial dissection of inguinal region; spermatic cord is seen issuing from external abdomitia) ring; intercolumnar fascia has been artificially distended by injection ol fluid; saphenous opening is closed by cribriform fascia. Fig. 1480. external nMiquc. cut edge Internal oblique muscle Aponeurosis of external obll.)ue. cut edifc Anterior superior «r'n« '>' '''"' PoupartA liKaitiefit AtUchtnent irf deep layer »>f su[ierfictal fascia of abdomen to fnscia laU Transversalis muscle Spermatic cord Fascia lata Eitrmal pillar - Anlcritif sui*rk>r t\^w of lllutii Internal fd TnnsveivaUi £uKia Crrmasttoric fiwcU, cut edije ^ Conjoined tendon -^' Anterior tniral nerve—-" Falciform procew of faicla Ian L'rural hranchof ijenlto-crural nerve — hrtnoral art. within femoral cheath Femoral c*nal.*rtificially distended — Femoral vein wMiln fnnoral sheath batcmal pUUr of external rtBt[, turned down ln»crtiou of crenuulcr A|> *'f ntemal i>Ui«iue, t.ut eilKC Inlemal rftli-iue. . "t edtje Tmn-iversali* mii* Ir TrlaniEular f^s. la Spermatic t>)u circumflex iliac ar^ |irp()ep*ip«tt ■ Internal aWion. Pmii«rt'< li«a Infundibuliform fascia, artiflc distendedl Anterior crural net e Femoral sheath' Saitorius Fascia lata Femoral artery Fascial ^ej^um between artery an.l vein Feninml vein Se|)titiii l»el« een vein and femoral < anal l-'einoral canal External pillar o( external rina, tumcl neur(>«iH «f external oUk)ue, cut eittfc ^Transversalis frscia Conjoined tendon TriannuUrfr'Scia S|iemtatie run! . XremasteriL &scia reflecWd fro« si>erni4lic rord uwTr .irt ol mascl. r.n.ov«l .nd posterior wall of »h«lh «p««l. Ill 1762 HUMAN ANATOMY. . r\ developmental defects ; (6) the presence in the abdomen of portions of the pelvic organs increiising intra-abdominal pressure ; ( c) the habitual flexion of the thighs on the abdomen in infants, relaxing the tissues about the hernial orifices ; ( nenU of external abdominal henita. »>4: Anterior superior iliac spine Poupart's lii{«nicni Falciform process- Iliac portion of fascia lata^ ' Femoral ring — Femoral artery — Femoral vtin Aponeurosis o« extenial oblique — Intercolumnar ,ibres External aNIominal ring — Kxternal pillar Internal pillar ^Gimliemat's ligament Internal saplielious vein I'liliii poriioti i>f fascia lata -^Spermatic coril Scrotum Dissection o. ri«h. inguinal region, showing -xtern.-.l ah.lominnl ring an.l saphenous opening in fascia lata. ically by considering its mode of production when /«) .-«;a'l'rect ^«-':"'t "' Z^;:;"^ dcvdutmiental defcrt it is pr.-sent at or s..on after birth ; (b) the hernial sac being p™ congenSv, the hernia follows some increase- ..f intra-alxlomina pressure; or r") as a^onsec'iuence of a less mark«l-or less complete-original defect or oJ 1764 HUMAN ANATOMY. an acquired delect (vide supra), the hernia develops in the presence of causative factors (page 1759)- ...... n j •. 11 Acquaintance with the changes in the abdominal wail and peritoneum involved in the descent of the testis is necessary to an understanding of the anatomy of inguinal hernia. Although these changes are described with the development of the testicle (page 2040), the chief features of the process may be noted here with advantage. By the end of the second fcetal month the developing testicle lies behind the peritoneum at the side of the upper lumbar vertebrie, the epididymis and later the testicle being attached to a fibro- muscular band, the frenito-inguinal ligament, which stretches from the sexual gland to the lower part of the anterior abdominal wall. During the third month, guided by this attachment, the testicle migrates from its primary location to a position which later corresponds to the internal abdominal ring. About this time the muscular, fascial, and peritoneal layers of the abdominal wall show a protrusion in the inguinal region which results in the production of a sac, the inguinal bursa ; this deepens and extends into the scrotal fold, which meanwhile is formed independently as an integumentary fold. The genito-inguinal ligament. Fio. 1485. •n: internal ohiiqi rrenuster mosilt Apniwurusia of extenuil_A oMiqur. turned outward SapheniHU opening <°ut edge of i(ianeuro>i> of external oblique .Sheath uf rectus Tranaver^alis fascia Conjoined tendon .Triangular faM-ia Spermatic cord l>i»!iection of right inguinal canal ; aponeurosis of external oblique has been cut and tum«l outward. being attached to the structures undergoing evagination, extends into the inguinal bursa. The muscular tissue within the wall of the latter is derived from the interna oblique and transversalis and constitutes the cremaster. The lining of the inguinal bursa is obviously the direct continuation of the general serous membrane of the- abdominal cavity and later constitutes the processus vagina/is peritonei. Thicken- ing of the lower end of the genito-inguinal ligament produces an elevation of the floor of the bursa known as the inguinal conus, a structure, however, that in man is very feebly developed as compared with that found in some lower animals. Subse- quently, during th-e seventh and eighth months, the inguinal conus and tbe attached testicle are drawn downward into and through the inguinal canal until, shortly before birth, the sexual gland gains its permanent position in the scrotum. The rudimentary conus and the genito-inguinal ligament, which together correspond to the structure usually described as the giibernaculum testis, Ijecome progressively shorter and smaller as the testicle descends, their remains constituting the scrotal ligament, the subserous band which permanently attiches the tunica vaginalis and the testicle to the surrounding tissue of the walls of the scrotum. The original retroperitoneal position of the testicle is always retained, this organ and the accompanying constituents of the spermatic cord descending outside the PRACTICAL CONSIDERATIONS : ABDOMINAL HERNIA. i7r..S prntun>si> ni inttrnal <>lilU|UV, i'ut eflK«-* Inti-rnal ulMlomimtl riiiii; — loiil ojvere*! I»> inluii'iih- ulittirm laiK'ia — Traiit»rni.»lis (•.•Mi.uvt'.tk -^i-t) -t\>iiit>itittl UMitlmi TriuHKiiIar fa^t ia DUs«.i.m ..( riKh. h,,«in.. >»na.; «..n,a. .n.l internal obliqu. c„, an., r,flc...l. e„K.i„K .n.n,v,r«..,, n.n^-l,. versalis fascia ■ 1 %) cremaster fibns, irom the transversalis and internal oblique_mus- clTSend^ by areolar tissue into the cremasteric fascia ; (4) intrrfolumnar fasaa, f mm the a?o, e,m«is of the external oblique. In a.ldition to thes.- covennRS from the aSoiS «'ill. the envelopes forming the sorot.nn proper contribute (5) the mo.l£d rU W fascia or tunica darios and ( 6 ) the ski,,. Unusual attachments rfLniKa^lum below to the tulx-r ischii and sphincter an. account for some of "he form^^ tt^ticular ectopia (q.v. ). Attachments above to the peritoneum of Jf ci^nTr ileum or of the siRmoid. or to the l.H.sely attach«l ,K.r.toneum hnm^ the TxcZZ account in part f..rNhe formation of the s=»c in i„/antilc hem.a ( v,dc ,„/ra ». ThT^treuRth of the attachments of the ^.ubernacula t<> the testes and to the dart.« is shown bv the fact that in cases of elephantiasis scroti. althouKh the enormously thicken^ skin and dartos may form a tumor reaching to the knee, the testicles w.ll iwnaltv he found ne-ar its lower extremitv. .... The nex step in the anatomical' study of inguinal hem.a should oms.s. .n a survey of the innir surface of *e alKlo.uinal cavitv in the ...gu.nal, .l.ac and hyi^v cistric regions (Fie. 14«7 >• This will show that the space bet^^en the lateral wall o Ihe Smen and the mid-line-marked by the pentoneal fold over the urachu. IV HUMAN ANATOMY. (plica Mrachi)—i» divided on each side into two shal'ow depressions by a slight eleya- Uon of the peritoneum over the deep tpiKastric artery (p/ica epij^as/rua ) ninnmg from a little internal to the middle of Pcjupart's liRament to a i>omt on the outer edge of the rectus muscle abijut one-third the distance between the level of the symphysis pubis and that of the umbilicus. The outer of these depressions is called the exUrnai inguinal fossa (hernial fos-sa). The inner contains a triangular spiice known as Hesselbach's triangle, bounded by the plica epigasirica, the outer edge of the rectus, and Poupart's ligament. The whole inner region— extended to the mid-line — is further subdivided by a line corresponding to the peritoneal fold over the obliterated hypogastric artery (plica h^pogasUica) into two other fossa;, the internal inguinal and the supravesical, which are of use as aids to the descnption of hernia, but, viewed as mechanical factors, have little bearing on its production. The external inguinal fossa is deepened just to the outer side of the epigastnc artery into a slight pouch (Fig. 1487), which marks the point of exit of the sper- matic cord from the abdomen, and therefore the site of the internal abdominal nng and of the mouth of or. .• form of inguinal hernia,— the external, oblique, or indirect. On the external surface of the abdomen this pouch corresponds to an area about three- quarters of an inch in circumference, situated a linger* s-breadth above the middle of Poupart's ligament. To the inner side of the epigastric artery are two other and Fio. 1487. I"' Peritoneal iiirfice Plica epij(astnca_ Hesselbach's triangle - Vas deferens. External iliac arter- External iliac vein Plica hypogastrica. ( )uter edge of rectus nuacle Supiavesical fossa 'uter inguinal fossa Inner inguinal fossa Bladiler, somewhat distended Median umbilical ligament Posterior surface of anterior abdominal wall of fonnalin subject. still slighter depres-sions corresponding approximately in position to the outer part of the posterior wall of the .-anal and to the external abdominal nng (page 1771) and the lower fifth of the inguinal canal. When viscera make their way outward from either of these depressions as the point of departure, the resulting hernia is known as direct because it does not pass through the entire length of the inguinal canal but takes a shorter route, or internal because it hes to the inner side ot the epigastric artery. A further examination of the structures (already described on pages 52^ 524) which are related to the production of inguinal hernia will serve to ex- plain its occurrence in certain localities and in certain forms that may now be considered separately in theif simpler varieties, the rarer and more complicated being merely mentioned or altogether omitted as unessential to the anatomical study of nemia Oblique, external, or indirect inguinal hernia, which makes its exit from the abdo- men at the internal ring, is incomplete if it remains in the inguinal canal, complete if it emerges at the external ring, and scrotal if it descends into the scrotum. In frequency it bears about the same relation to the other form of inguinal hernia— the direct— as inguinal hernis do to all other forms of hernia in males,— viz., from 95-97 per cent. This frequency depends upon the following anatomical conditions, (a) The descent of the testicle from behind the peritoneum (page 2040), carrying with it a process (vaginal) of peritoneum, a portion of the transversalis fascia (infundibuliform fascia). r-1; PRACTICAL CONSIOKRATIONS : ABIK1MINAI. IIKRNIA. I7f'7 and of the transversalis and internal nbliciue muscles ( cremiister muscle ) . nialces its rSon oJ exit fr..m the aUlomen-/.... of its entrance into the mKumal can I- he ir^a in he abdo.ninal wall l^-st a.lapte.1 l.y reason o ,ts weakness and ts sha k t f , ?K.V ..vit ..I visceri {b) This s|K)t is s tuate.l near the lowi'St level of the So':. :':;th:;^a;:;ty.^:<-. at a'level at which, when thesi.eof .1,ecavr^« IXr temi«jrarily decreasetl (as during cou^hin^; or stra.nin«i. or r.lam.y decrJased US when the upper z..ne is compressctl by t.^ht la.m^;.. or actually tc^^ as bv intra-alxlominal fat, or by a tu„,or or ascitc-s ,, the outward thrust o^ the^bdominai viscera is addeil to bv their suiK-nncunilK-nt wei^h ( r i I he per - U neum ove^the 1 wer ,«rt ..f the anterior alxlominal wall is th.n an.l .«>sely attached TtC kis unable to offer much effective resistance to distention by pressure fro, , wit£ Such distention is favored by the funnel-sha.jed d^l.--'''" ;'« '''^ l^t i^rii^r fSa^iSr=eL;^ts :.5r^f ^^^ d^n of he tendon which is derived from the internal oblique has generally a less mViSef^acrKidy) The thinnest and least protected ,x,rtion of the inner-posterior ™w^U of the 3 s therefore that adjacent to the inner edge of the '^t-m^d abclomina "iwhT It should bv.' noted that Treves is inclined to consider the resistant Zer o the normtaMominal ^^1 as less over Hesselbtch' s triangle than .wer the ^ternaVinBuinal fossa ; but even if this is true, the existence of the internal ring and of the canal more than compensates for it in favoring hernia. . TWfa^rsufficiently explain the frequency of oblique inguinal hernia of the ocauirTio^iv^dein/ral-le., the form in which the congenital dehc.enc.es or SeS pat^logS changes next to be mentioned are not demonstrable, although itt not Sikely that some original or acquired defect of the abdominal wall in the nerehtorhoK the hernial orifices is present in the great majonty of cases of herma ofd^flsofaU varieties. (/) The not infrequent total or part.al patency of he IdnaUroce^ givefri^ to a number of subvarieties of inguinal hern.a icon^en'lal LS/f/Sar). all of which are oblique.-/.... enter the .ngu.nal canal at t^ Sal riir nd to he outer side of the epigastric artery. These herniae, depend- 5 on anoma.S in the closure of the proces.sus vaginalis, h- been -r„^sly s«h^ divided and defined, often w th unnecessary complexity. It will sutt.ce ntre to s..y d^Itr7«r"i/a/ hernia (Fig. 1488) is due to complete patency of the v^ag.nal prcKess thfcavXofvhich is directly continuous with the cavity of the abdomen, the sac of the £n°a Jndosi..^ .th its visceral contents and the testicle, which lie in con- uct Sough the ^..ndition leading to the formation of this Jerma's truly con- genital the hernia itself is very rarely in existence at the ime of birth but ''^ -ipt " ™ in early He when intri-abdominal pressure is either habitual y or suddenly ™ased It should be remembered that, although a true congenital herma neces- S depends upon a patent processus vaginalis, i>atency of the P';??^'? '"^'y ,'^"'?* SoutTernia A foW of ^ritoneum at the edge of the '"'""'l*"''*"™ f*f '^ Sy scrSg the abdominal opening of such a process has been descri^ and h^bLen tl^ought to aid in nrevenling hernia (Macready) In wonjen Potency of fh^ S of Nuck acts similariy as a predisposing cause of congenita herma. wh.ch is however of ereat rarity, on account of the narrowness of the canal .tself, the i.ict Thaf it^b^l frifice is s^ill smaller. - ^TXf i^Se mTof th'e^'SS larger size and greater distinctness in the female than in the male ot tne pcriionta. -_j u^rvx\ fold coverin"- the entrance to the ran.il. . MfnuThemlam^. 1489) results from occlusion of the processus vaginalis at the internal ring^ly the visceral pressure, aided by the attachments of the guber- nac^SmtesdL above described, carrying this septum and the ne.ghbonng pento- 1768 HIMAN ANATOMY. ncum downward tu cunstitute a stac that d«»tcendii behind the tunica vaginalis, esiMx'ially if the latter is capacious, as it is apt to be when its upper limit is at the in- ternal rinx. A hernia of this variety has, therefore, between the skin and the con- tents three layers of serous membrane, two of the tunica vajfinalis and one of peri- toneum ( its own sac) connected with one another at the neck. Not uncommonly, however, — as might be expected from the tendency of serous membranes to adhesive Fio. 1488. Fiii. 14S9. -lUllIaiiilb^U UlnudhxU Hernial lac Tunica vmginali* IHaKfam of crHti^nital hernia, ahowinn relation ot hrnilal Mai- to (lerittmeuni. DiaKram of Infant 1e hernia, showing relation of hernial aac to tunica vaginalis. inflammation,— the posterior la •r of the tunica vaginalis is intimately blended with the front wall of the sac. Infant- • ^'ernia, while due, like the congenital variety, t<. anomaly in development, is even ; r s apt to e.xist at birth and, in fact, Ls rarely seen in infancv. A variety of infantilt hernia known as the encysted (Fig. 1490) is de- scrilied. in which the intestine depresses the septum at the internal ring, making a stc which |)asses into instead of behind the processus vaginalis, so that the hernia has in frt)nt of it a layer of tunica vaginalis and a layer of septum (sac). This hernia is very properly described (Lockwood, Macready) as "a figment of the- imagination." When, after occlusion of the process at the internal ring only, the septum gives way suddenly during some unusual intra-abdominal pressure, the intes- tine may descend at once into instead of behind the tunica vaginalis and lie in con- tact with the testicle,— a form of "congenital" hernia that appears in adult life. Fig. 1490. Prritoneum Siienitatio cotd Skin and IhKia IMaicmm of so-called enc\-ste tunica vafcinalis elation of Funicular hernia ( Fig. 1491 ) is a sequence of the closure of the vaginal process at the iiitper end nf the epididymis "nlv. the short pouch of peritoneum remaining in communication with the peritoneal cavity. The contents of such a hernia are separated from the testicle bv the septum formed at the point of closure. Interparietal ( intraparictal. interstitial) hernia is so usually a \ariety of oblique inguinal hernia, and is so commonly associated in the male with anomalies of the |'--*t- ' PRACTICAL CONSI DERATIONS: ABDOMINAL HKRNIA. i7'-> dominal */"• ^ ' * > ^^t Lcia Z\ the trunsvcrsiili. musclf. or amonj; tht- hhrc-n '^"' While the exact mechanism of the formation ..f these herniie is still unknown and .KarSts Sclg theoric.-althou«h of grjrat i-^^r:^tT^ Tei be set forth, it is perhaps ^-^^V^^^ ^X' ^^E^r^^ n^h;Vl.r.! tion It'rvT,;' p^^batll^^lrS^e'^m^^^^^ which ft ,«L. and with which it is so .n- ^^eT^s found in the extraperitoneal connective tissue that precedes the s.»c and r ^,;! orthe coverinirs of nearly all abdominal hernije, but this is more than the scrotum^ ,hV testicle where it mav be ajjain arrested-often permanent v—by I770 HUMAN ANATOMY. usefulness as denoting the route of the hernU, and are occasiondly of value as land- marks during herniotomies or operations for the radical cure of hernia. The sac of a complete oblique inguinal hernia (Fig. 1492) wo^'a «rry with il (I) a layer of extraperitoneal connective tissue ; (2) that portion of the transversalis fascia known as the infundibuli/orm fascia ; (3) the muscular fibres derived from the transversalis and internal oblique muscles, and called the crcmaskr muscle ; (4) the fibres from the external oblique aponeurosis that aid in strengthening the external "ring," especially the upper angle.— the Mercolumnar fascia ; (5) the superjicial /'ai«(j,— in the scrotum the k;ia' KascU ami bkin' .Deep t-pigmstric artery Diagram showing lovenngs of complete direct inKuiiial hernia relation to the inguinal canal as have oblique herniae, although when the peritoneal pouch first forms, and before the resistance of the aponeurosis at the external nnj- has been overcome, they usually enter the lower part of the canal, as the resistance in that direction is less than it is inward, towards the rectus. They are never con- genital and have no definite pre- existing path. They are there- Fio. 1494- fore hernije of slow development, usuallyseen in adult life.especially if the local weakness of the ab- dominal wall is emphasized by its laxity from general muscular atrophy, or by increased intra- abdominal pressure from accu- mulation of fat. They are usually small, globular in shape (by rea- son of the shortness of the neck ), . .. . j .u do not, as a rule, descend into the scrotum, but remain above the crest of the tjubes, and when reduced go directly backward into the abdomen. The orihce m the abdominal wall is easily felt, the outer edge of the rectus to its inner side, the crest of the pubes below. The epigastric artery is to the outer side of this aperture, but its pulsation can rarely, if ever, be felt Macready says • the opening m the posterior wall of the inguinal canal through which a direct hernia comes is much more accessible to examination in the living than the internal abdominal ring so that it is duite possible, in the majority of cases, to explore the conjoined tendon with the finger and ascertain the shape and size of the opening as well as the extent to which the posterior wall has suffered. When a hernia is oblique, the posterior wall of the canal is felt as a plane surface by the finger passed into the external ring, and its attachment along the pubes can be traced. The finger is prevented from entering the abdomen till it reaches the internal ring But in direct hernia, when fully devel- oped the finger at once passes into the belly over the bare pubes, and can feel the hack of that bone and of the rectus muscle. No trace of the posterior wall o the canal is felt nor the margin of an opening in it. All that remains is a narrow layer of membrane which just fills the angle between the pubes and the rectus ; it seems as if the triangular ligament had alone withstood the distending force of the hernia. In * . these cases, in which the pro- trusion has done its worst, all the posterior wall of the canal between the rectus and epigastric artery has gone, and the large opening has a triangular figure coinciding with the triangle of Hessel- Imch. If strangulation occurs, it is apt to be at the exter- nal ring, and the incision for relief of the constriction should be upward with a slight inclination inward. Large oblique herniae (scrotal), especially when of long standing and in old persons with relaxed abdom- inal walls, may have the in- ternal ring displaced so far towards the median line by the weight of the hernia that it occupies almost exactly the usual site of exit of a direct hernia. The epigastric artery will, of course, -till lie to its inner ■i\t\c, hut cannot be felt. M a rule, how- ever, a sufficient portion of the jx)sterior wall of the inguinal canal will be left to pre- serve some obliquity of the neck ( Macready ), by which the hernia may be recognized. Fir. 1495. .Plica hypoKastrica I'lica epigastrtcH — Oblique inguinal hcinia (exlernalfoi-sai Direct ingutiinl hernia (internal fofsa J Femoral hernia Obturator hernia riica urachi Supravesical fossa Semidiagrammatic view of povn-rior «urface of anterior abdominal wall. Nhowitig relative potiittonN of \arious forms of hernias. tAftrr Sfftkft. \ Fig. 1496. PRACTICAL CONSIDERATIONS: ABDOMINAL HERNIA. 1773 Femoral hernia is more common in females than in males for reasons already ^«ition in the abdomen and the thigh. .J^is smcc tnt ^^ ^'j ,^. h'*r='s:'*srLaz;iS;o,\L-;S»vS^^ ^^^^'y and the iliac fascia pos- teriorly. This sheath does not embrace the vessels closely until it descends from one-half to three-quarters of an inch below the rela- tively unyielding Pou- part's ligament, about opposite the upper margin of the saphe- nous opening, — /. f. , to a point at which, in the movements of flex- ion and extension of the thigh on the abdomen, the vessels are less lia- ble to injurious traction or compression. It is therefore infundibuli- form, and at its begin- II -ac (asc I'eclincal fascia Vascular space External abdominal 'rinK Outer |)illar Pubic spine i:imbemat's lixament Deep di^ction of right half of ,«lvis. showing attachments of iliac fa«i.. 1774 HUMAN ANATOMY. Femoral artery Femoral vein Hernial sac pro- truding through saphenous open- ing hood is relatively undeveloped ; its outer edge and the vein may then almost touch. It is strengthened by the conjoined tendon and Colles's ligament, while some hl)res of the iliac portion of the fascia lata and of the deep femoral arch {vide injra) also contribute to the formation of the inner boundary. On the outer side is the femoral vein. Behind lies the horizontal ramus of the pubes covered by the origin of the pectineus muscle and its fascia. In front are Poupart's ligament and the strong band of fibres running along its deep surface from the anterior superior iliac spine to the pubic spine, and known as the deep femoral arch. At the point at which the sheath of the vessels closely unbraces them— the lowest limit of the femoral canal —the saphenous opening in the fascia lata (described on page 635) has somewhat the same relation to a femoral hernia that the external abdominal ring has to an in- guinal hernia. After emerging from these openings neither hernia is further arrested in its progress bv any strong aponeurotic barrier, and they are both therefore more ^ ' likely to increase in size ; but in femoral hernia the change in direction of the a.xis of the fundus as compared with that of the neck is much more marked. In its etiology femoral hernia conforms to the general laws already enumerated ( page 1 759 ). As the knuckle of gut involved presses the peritoneum before it into the femoral ring and down through the femoral canal, it car- ries before it ( i ) the extraperilotieal tissue ; (2) the septum crurale, when that constitutes a distinct layer ; (3) ^^ femoral sheath, some- times described as transversalis fascia because the anterior layer of the sheath is derived from that structure; (4) the cribriform fascia ; (s,) ihc superficial fascia ; (6) the i*i«. As the transverse axis of the femoral ring —parallel with that of Gimbernat's ligament — is, in the erect posture, neariy horizontal, a femoral hernia first descends aJmost perpen- dicularly. After it reaches the point of close adhesion of the sheath to the femoral vessels it takes the direction of least resistance and protrudes through the saphenous opening. Its neck is, of course, the porUon of the sac between the femoral ring and the bottom of the femoral canal. The body is apt to be small and globular or hemispherical in shape. The following anatomical relations of the latter will be found of great importance in distinguishing between femoral and incomplete inguinal hernia. («) The upper edge of a femoral hernia does not, as a rule, pass above the inguinal furrow (page 670), although it may reach it,— «>., the hernia will be below a line drawn from the anterior superior spine of the ilium to the spine of the pubes. This may usually be determined by inspection. Exceptionally, on account of the stronger attachment of the cribriform fascia to the lower edge of the saphenous opening, the hernia nnds its direction of least resistance after emergence from that opening to be upward, when this sign will be fallacious, {b , The neck of a femoral hernia is external to the pubic spine, that of an inguinal hernia internal to it. The already described methods for locating that process (page 349) may fail in very fat persons, especially m females. In that ca.se the lower crease that in such persons crosses the abdomen (page 530. and which in the mid-line rests upon the symphysis pubis, will be a reliable guide to the latter point ; the bone may thence be traced outward to the pubic spine. In the reduction of a femoral hernia— apt to be difficult on account of the nar- rowness of the channel of exit— the position of the patient should be that already descrilied as appropriate when the hernia is inguinal. The thigh should be in a posi- tion of inward rotation, flexion, and adduction, to relax the fascia lata and relieve ten- sion about the saphenous opening. After the hernia— the axis uf the body of which is nearlv at right angles with the axis of the neck— is drawn downward so that the axes correspond, it is gradually pushed backward and then upward. Superficial dissection of left femoral hernia pro- truding through saphenous upenmg. PRACTICAL CONSIDERATIONS: ABDOMINAL HERNIA. I775 It should be noted that in this form of hernia the density of the ^ix^neuroses i^iliiSllgpii Fio. 1498. Anlerior superior iliac spine - Iliacus muscle - Deep circumflex iliac arter>- ^Artery External iliac < > I Vein^ Obturator ner\' Rounil lixament Obturator canal '"^ Pubic branch of obturator artery- Pouitart's ligament Transversalis muscle Rectus muscle epigastric vessels emoral ring imbemat's ligament jurator artery from deep epigastric lymphysis Bisection of ,«rt of left half of pelvis and adiac.,,. b.Mly-w.n. showing obturator artery arising from deep DIaicclion 01 iiaii epigastric and crossmg femoral nng. Umbilical hernia is most conveniendy divided from either a clinical or an the antS abdominal wall fiilinR to close in the region of the "^vel AnaloKOUS nmarkedcases the condition resembles an eventration (fissura a^'d^mmahs) rather S p^enWum'^som'ttimS present. These layers are rarely separately demon- ^^t thl^^trhiS.'riy'^a'^e^^rmrwUle of gut or a d.vertict„u.n i. involved (he^at the r^t of t'he corT) there may be merely tbickenmg ..r enlarge- 1776 HUMAN ANATOMY. ment at that point. If this is overlooked and the cord is tied within the limits of this enlargement, the intestine, if not previously replaced, may be included. Acquired Umbilical Hernia. — Usually, although the cord is tied at a short dis- tance from the abdominal wall, the stump separates on a level with Uie latter on account of the contraction of the elastic fibrous tissue around the umbilicus. This cuts off the urachus and the vessels passing through the ring, — ^the two allantoic or hyiMjgastric arteries and the umbilical vein. Viewed from within, the fibrous cords representing these obliterated vessels would be seen converging to the puckered umbilical scar, the vein from above, the urachus and the arteries from below. As the usu.il contraction of fibrous tissue takes place, and as the abdomen grows, the traction of these cords depresses the umbilicus so that anteriorly it lies a litde below the surrounding surface of the abdomen. The larger amount of tissue represented by the urachus and the two arteries and their close attachment to the lower edge cause that portion of the umbilicus to become the stronger, the umbilical vein being less closely connected to the upper edge of the ring. In infantile umbilical hernia these changes are not complete, but when a knuckle of gut protrudes through the umbilicus during infancy, as a result of increased intra-abdominal pressure, it usually escapes between the vein and the upper margin of the ring on account of their loose attachment. The coverings are peri- toneum, transversalis fascia, and skin. These hemiae are usually small, and are often cured spontaneously by the contraction of the umbilical and periumbilical scar tissue. Their occurrence is favored by tight phimosis or by constipation, causing straining, or by improper feeding, causing flatulence. After infancy umbilical hernia is rare until adult life. The umbilical hernia of adults is far more common in women than in men (73 per cent.), and is especially favored by obesity — with accumulation of fat in the omentum and mesentery — and by repeated pregnancies. The coverings of such a hernia are peritoneum, transversalis fascia, superficial fascia, the fibrous tissue of the umbilical scar and the linea alba, and skin. For the reasons above given, it appears usually at the upper semicircumference of the umbilical ring and often involves the linea alba immediately above it, — a form of ventral hernia. Such hemise are very apt to contain omentum — the growth of fat in which often makes them irreducible — and portions of the colon, and, on account of the readiness with which fecal obstruction may be caused in the large intestine, they are prone to incarceration. Ventral herniae protrude through the abdominal parietes at other points than the umbilicus or groin, or than those weakened by the passage of vessels and nerves from within outward. The most common are in the linea alba, between the umbilicus and a point midway between it and the ensiform cartils^e {epigastric hernia). Above that they are very rare, as the effect of gravity is lacking and the contiguous viscera are less mobile. Immediately below the umbilicus they are not uncommon, as the linea alba has still an appreciable width. Lower, where it has become a mere raphe, they are very rare. They are often associated with subserous lipomata, and may be caused by them. The protrusion of fat from the subserous tissue is thought to draw the peritoneum out into a diverticulum which readily becomes a hernial pouch when intra-abdominal pressure is great enough. The linea semilunaris, especially below the level of the umbilicus, is a not uncommon site of ventral hemiae. It has been suggested that their position is de- termined by the fold of Douglas (page 522), —the semilunar lower margin of the posterior layer of the internal oblique aponeurosis, which fuses with the transversalis aponeurosis to form the posterior sheath of the rectus muscle, which ends about half-way between the umbilicus and the pubes. Below that all the aponeuroses pass in front of the rectus, leaving the posterior surface of the inferior portion of that muscle separated from the abdominal contents only by the transversalis fascia and pcritnnc\im. Ventral hernia of the linea semilunaris near its lowest portion and direct hernia issuing through the internal inguinal fossa (page 1770) are indistinguishable, if not practically identical. PRACTICAL CONSIDERATIONS: ABDOMINAL HERNIA .777 has not been demonstrated by "act dissec lo^ _Grynfelt and Lesshaffs Above Petit's triangle is another triangular space, orynieii *■ FlO. I409. Latinimin dor»i, cot edge- Xll rib- Fanciallrianiile - Quadralus lumborum— Intrnial iibliuue- (PetilslrialiRfc) Vertebnl aponeurosis. •Cut digiution ol laliMimus dorai External oblique Iliac crast Oi-ectlono. pcter^late™. ^^'^^^^5.^^^^!,'^^ po-erlor bou»U„ aponeurosis of the latissimus dorsi lacking on both sides in a case in w hernia existed on one side. „Kt„ratnr r-inal which runs downward, Obturator hernia escapes through the obturator canaO^ ^^^"^ internal hernial •orward, and inward below the horizontal ramus of |he^ pubes-^ J^e mte^^ ^^^^^^^^^ Fio. 1500- Entrance ol hernia orilice IS ai iiic iiaaui- ." — - --- internus muscle which permits of the pas- sage of the vessels and nerve. A hernia starting there passes through the opening between the upper edge of the obturator membrane and the lower surface of the pubic ramus (Fig. 1500), and usually descends between the obturator externus I^Wtfll^^^^^KJKI' and pectineus muscles to lie beneath the \^M^^^^^^H|K latter muscle and the adductor loiigus. ^IHP^^^^Bf It is therefore to be looked or felt for \ * "^IK ^^^^HT: ^,^^ j^p pybes and the inner end <>f Poupart's ligament, but at a point both low 1 and more internal than the site of femoral hernia. The thigh should be flexed, adducted, and rotated outw.vd to relax the pectineus, adductor longus, and obturator externus. As this hernia occurs most «requef y in ^Weri^^ '^He well to note that the inner orifice of the '^f "?,»^ ^.^^ '^^^^ J^J^..^^^^^^^^ Z^resTaklt-^^-ir^^^^^^ 112 Hernia seen Ihrongh obturator membrane Right obturator hernia, seen from within 1778 HUMAN ANATOMY. value. The obturator nerve, which is in close relation with the vessel and the track of the hernia, supplies the hip- and knee-joints and the adductor muscles and aids in furnishing sensation to the inner side of the thigh as low as the knee, and sometimes to the middle of the leg. Pain in these joints and in that region not otherwise explicable, and especially if associated with mtestinal symptoms, should therefore suggest a careful examination of the obturator region. Sciatic herniee include all the herniiu that emerge from the pelvis through one or other of the sciatic foramina, — that is, (I) through the great siicro-sciatic foramen alongside of the gluteal artery (above the pyr if ormis) ; (2) through the same fora- men alongside of the sciatic nerve and artery (below the pyriforniis) ; (3; thrt)ugh the lesser sacro-.sciatic foramen (Sultan). They are all very rare. The peKic fascia forms one of the coverings of the sac. Within the pelvis the hernia is anterior to the pyriformis muscle and sciatic nerve. On entering the thigh the sac crosses over the nerve to its posterior surface, and is covered by the gluteus maximus. As the rupture enlarges, it emerges from beneath the lower border of the gluteus and descends the thigh, or may pass forward above the trochanter towards the groin. When the hernia is small and makes no obvious swelling in the buttock, it is found at the sjxjt where the sciatic artery is tied just outside the pelvis. A line is drawn from the posterior superior iliac spine to the trochanter major rotated inward, and about half an inch below the junction of the upper with the middle third of this line the hernia enters the buttock (Macready). Perineal herniae include those which pass through the outlet of the pelvis and its muscular floor. The boundaries of the former are the glutei maximi and coccyx posteriorly, the pubo-ischiatic arch anteriorly, and the great sacro-sciatic ligaments con- necting the coccyx and the tuberosities of the ischium (Fig. 1423). The coccygeus and levator ani muscles form the floor of this space, which is perforated by the rectum and urethra and vagina, and extends from the outer walls of these structures to the inner walls of the pelvis (Fig. 1424). It might be supposed that the comparatively yielding nature of the parts which close the lower opening of the pelvis would favor the production of herniae, but, as Macready has shown, hernia through muscular planes is everywhere very infrequent. The normal oblique inclination of the pelvic floor and its elasticity are doubtless factors in preventing the occurrence of perineal herniae. A hernia starting at the upper surface of the pelvic diaphragm must pass between the coccygeus and levator ani or between the fibres of the latter muscle, and will descend into the ischio-rectal space (Fig. 1423), where it may cause a protrusion of the skin of the perineum, or may advance towards the rectum {rectal hernia), the vagina {vaginal hernia), or the posterior portion of the labium majus {pudendal hernia). The development of perineal hernia is believed by Ebner to depend upon an abnormally low descent of the recto-uterine peritoneal fold which occupies Douglas's pouch in the female or of the recto-vesical fold in the male. In the presence of such a fold, intra-abdominal pressure is able to carry a peritoneal pouch, with or without included intestinal coils, to the right or left (its progress in the mid-line being arrested by the firm septum between the rectum and vagina or the rectum and urethra), so that it rests on the levator ani muscle, the fibres of which are often separated at places (Henle descril)es it as three muscles). Its subsequent downward progress has been noted ( vide supra). A form of perineal hernia known as inguino-perincal has been described (Coley) in which the hernial sac accompanied — or followed — the misplaced testicle (ectopia perinwalis ) into thft perineum. Diaphragmatic hernia are usually congenital and 779 or in abnormal pc-r.tonea [;;'---4;^"*'"«„^ • l,,^ ^'^^.n.fr.h.M^.iv to indu.le all The classification ailoptcd » y ^"'^*" .';•.*, V\"'\,,ri..tL can 1^ clifferentiattd : herniae coming under ^he aU'^^i^;;J,";" 'V, hJ „ia rth'.lu-leno-K-junal recess ;;! SoftllTrluiri/lJli:?:-^.! -esses, U) hernia o. the inters-K-noul cavity, which may be regarded as •■' P;^^'-''. ^"«, J^J^/X.-s that eit thenkrrownessof the o,,enmK(i.a!ie 1/46 .■md.^^^^^^^^^ ^^ ^^^. ^,,,,,,^ :;;2Si?;:s.:;t^=;^^ar:'^^^ ^^^ Fio. I5«>«- Jeiunom ; Ouodeoum Superior dllod«ni>-Wun«l fasu .Branch ol l»'t colii- an«ry Inferior \\«. '^' ;","",ie,iKm.«d artery, and i. ab»ul r^":e''Jt'"ur\rrrvir''TLVn Jc^pied „y coil, „i »naU 1780 HUMAN ANATOMY. jfravity, or by their own vermicular movement, intestines may be forced into a cavity or space either actually or potentially pre-existing, in which, under lessened pressure- as compared with that at the orifice, the bulk of the hernia may increase, with the Fig. 1502. -^ Ileum l\ £ -J^ --/- iieo-«ppcndicular ^ fold Hairf W / ^1 ^i Inferior ileo-i-iL-cal IP f 1 fowu !i fold Ponterior lavcr of 4. / vm meMtitery Retrociccal foMta w V I ■ Peritoneal fosflv of Meo-csecal rvKion, necum beitiK drawn fnrwiird and upward, {/otineseo'i. constant danger of incarceration (stoppage of the fecal current) or strangulation (cutting off the supply of blood). The symptoms of internal hemise are therefore always those of intestinal disturbances and very often those of complete intestinal obstruction. ■ L i * THK SPLEEN. 1781 ACCESSORY ORGANS OF NUTRITION. In this kjroup .nav Ik- indu.lcnl the ./>Av«. ihv thyroid bodv.xh^- parathyroids, the tainlv n^Xncr h" amc is unfortunate. To certain men,lH.Ts o the above «r..u,,. ing according to the organ mvolvetl. THE SPLEEN. The spleen i« essentially a lymphatic orpn. It is of a l'"^P"'*|' ,^"'";,'*"f '*' verv riable structure, and is situatc^l in the left hypo; hon.lnum U-hnul the -t.mia h The Sht rexces;ively variable, changing with the state of chgestmn. ami h. lie to imnS increase in certain diseases, as well as to slighter mod.ha.t.ons .„ oth rs. ^«^v Xes the average weight in ten men as 195 gm- (approximately 7 <>/ • S'^iclficgrav^ty is va'riously'stated between .037 and 1 060. The length accord- ing to Sapi>ey, in the same ten men was 12.3 cm. (4?^ m. >• Posterior border loUnMdiate bordi Kenal (urface Splenic artery Splenic vein Internal hiisal angle. Gastric !Hir(a< e Anterior bonier. uo1i1k-<1 t*nt |ieritot.euni snrrounding iiilum Anterior basal anxle Posterior basal angle Basal surface Visceral aspect of spleen hardened in ttlu T,e Shape of this ^^at^;^ hasten ^^..ntjy^-;^^ determined. We follow Cunnmgham .n d^^"^"f a^'3"'£^des this there are lower end. although it is by no means =Jway^ o be recogn.z^^ Bes _^^^ three distinct surfaces, -the /A^^/»., the rcna,, and the gastnc, at a rounded point at the top of the organ. ^^^^^ ^„j The 1783 HUMAN ANATOMY. outline of this surface is that of a Ioziiikc ciKlosetl by an anterior and a pfwterior l)oriler, one jxiint lK"injj afxrte and iR-hind, the other IkIow and in front. Thus in the main the lnds to the course of the lower rilw, which sometinus make impressions on this con\ex surface. The anterior border, fortnerly the marj^o cnnatus, separatin>j this surface from the gastric, is sharp, esi)ecially Ih-Iow. It shows one or more notches in 9.^ (ht cent.' of the aiscs. They are most com nion in the lower jwrt of the iM)rder, which is st>metimc-s (juite scallo|)earatin); the phrenic surface from the renal, is nuich k'ss prominent. Parsons found notches in it in ,^2 j)er cent. ; hut the general apjiearance of this fxirder is very different from the preceding, lx-in>j in the main solid and uniform. The jjhrenic surface occ;i.sionally ( 20 per cent. ) presents a sharp fissure, rarely more than one. It usually starts from a notch in the posterior border and runs some distance across this surface, forward and upward. I-ess fre- qucndy it starts from the Fic. 1504. anterior border, or lies en- tirely in the convexity, reaching neither lx)rder. The renal surface, facing inward, does not extend so high as the pre- ceding. It is eiiclosetl by the |K)sterior fjorder, the internal or intermediate border, which separates it from the gastric surface, and by one side ct the ba- s.\l surface. In the upper third this surface is nearly plane, resting against the suprarenal capsule, and in the lower two-thirds dis- tinctly concave, where it is mouldeil o\er the upper part of the left kidney. The end of the pancreas, if that organ be short, may rest against the anterior part of this surface. The gastric surface, considerably larger than the preceding, -i bounded by the intermediate and anterior borders and, be- low, by another side of the base. It is concave, being for the most part moulded over the stomach. It contains the hihim. a fissure some inch and a half long, running parallel to the iiitirmediate border and about one-half inch distant from it, which receives the \criHs. The part of this surface which is not against the stomach is at the lower end, and r. sts against the splenic flexure of the colon. In .some ca.ses, when the stomach is cvintr.icted and the colon distended, the relative areas of the two may be reversed Moreover, the omenluni may reach the spleen between them. The tail of the panciea- may touch the right part of this surface or, if long, lie against the spleen just abo\ >• the colon. The basal surface is a triangular area, much smaller than the other surfaces. It is enclose i by the lower part of the posterior border of Vic spleen and !-.y two lines diverging from the lower end of the intermediate border. One of these separates the basal surface from the gastric and the other from the renal surface. One or Ixjth of these lines may be so rudimentary that the base may seem a part of either the ' Parsons : Journal of Anatomy and Physiolc^y, vol. xxxv., 1901. Postero-Iateral wall of fntmalin siihjerl ha-i fc«ti removed to show relations of spleen hardeneti in situ. THi: SPI.KKN. I7»3 ««tric or renal surface, n.on- uftc-n tlu- w.rnu. ..r it may appir simply as a km.1. at EuKr siSf the lower en.l. This k...l. the ,>0r,^. /«^vl>tiliiT tralH-i ulu mill vein .Sfilcntc |iulp Interlobular vci MalpighianbiM Splenic put] S«.io.. of spl«,i under very low maKniftca.ion, ,h„«mK Kener..! arrangement of splcnu .is.ue. hut freelv communicate, since the interveninR trabeculae form only inromjjlete paiti- Snl The ~ wkhin the fibrous framework are filled with the highly vascular lymphoid tissue constituting the splenic pulp. accordine to The relation of the blood-vessels to the lobules of the spleen is. a«orciing to Mall very definite. The branches of the splenic artery, after entering at the hilum knd mnning f<- ^^^ distance within the trabecule break up '"'<' 7=^"f J.^'^' each of which enters the pro.ximal end of the lobule, through the middle of which it Ssse^ giving off lateral twigs, one for each pritnary compartment .,f the Jobu c. Th^vmphoid tissue occupying the compartment is arranged as ?nf '""^"''/"K ^y''"' drica^^^^^ the /*«//» W.. Within thVlatter course the terminal branch.^ of the J en c aTerie,. w&^outside and between the cords lies the plexus of venous space, from which the more defini'.- chann.ls. the intralobular vetns anse. The terminal tromwncntnL mo ^^ ^ g,„^, branches w'-.ch terminate in ^:^^£^^mpu^of Tkon,a The latter communica, -h ^^^ -- spaces surrounding the pulp-cords, so thn' nely dn ,ded substance^ .. a^ metallic . Johns Hopkins Hospital BuH aift i nurphol. u. Anthro, , Bd. .... 190a 1784 HUMAN ANATOMY. pigments, when injected into the arteries, pass into tlie veins. The walb of the ampulla: are very thin and, towards the junction with the venous radicles, imper- fect, being here composed of the reticulum of the surrounding pulp-tissue. The channels, however, are sufficiendy definite to prevent the escape of the blood-cells under normal conditions, although the plasma constantly passes into the intercellular spaces of the pulp (Mai., The walls of the venous spaces are even more pervious than those of the ampullse, and, like the latter, possess only an incomplete endothelial lining, supported externally by a mesh of circularly disposed elastic fibres. The endo- theUum consists of narrow, elongated spindle-cells instead of the usual plate-like ele- ments which line the larger splenic blood-vessels. The round or oval nuclei project into the lumen of the venous s()ace beyond the level of the protoplasm of the cell, which often presents a distinct striation. The venous spaces between the pulp-cords are the beginnings of more definite channels, the intralobular veins, which pass from the primary compartments towards Fio. 1 506. Capsule Primary compartmcot Interlobular trabecula Intralobular trabecula Interlobular vein Malpighian body .Splenic artery 1; Diagram showing architecture of splenic unit ; splenic pulp is rci>resenl«l in only one compartment. t,^lfr Mall.-, the trabecula between the lobules to become tributaries of the larger interlobular veins occupying the periphery of the lobules within the boundary septa. These veins follow the larger trabecule until, finally, they emerge at the hilum to form the splenic vein. ■ 1 i_ 1 1. In their journey through the lobule, shortly after leaving the trabecula, the branches of the splenic artery present marked local accumulations of lymphoid tissue within their adventitia. These aggregations constitute the Malpighian bodies, or splenic nodules. When seen in transverse section, they appear as conspicuous oval areas of dense lymph-tissue surrounding the artery, which usually occupies a somewhat eccentric position. Longitudinally sectioned, the splenic nodules appear as cylinders. They correspond in structure with true lymph-nodes, possessing germ-centres. Sur- rounding the Malpighian bodies, the spleen-tissue presents the usual arrangement of the pulp-cords. The splenic pulp consists of a delicate stipporting reticulum, continuous with the terminal ramifications of the intralobular trabecule, and the cells contained within THE SPLEEN. 1785 and supported by the mesh-«ork. Thepu/p-a/s mclude a vanety of Jj^enU *he mit instant of which are : (a . small "mononuclear lymphocyte (*)leuc2«^ Se mononuclear and polymorphonuclear types ; (O red blood-cells . (d ) nuclcatea red blood-cells; (e) large phagocytic cells contammg ""• ' ' disintegrating red blood-cells, or pigment particles derived from the destruction of the same; (/) giant cells with large composite nuclei, chiefly in young animals. In addi- tion a variable amount of free pigment is present, probably from the broken-down red blood-cells. During embry- onic life and later, in response to unusual demands for addi- tional red blood-cells, as after severe hemorrhage, the spleen is the birthplace of new red corpuscles ; these are at first nucleated, but soon lose their Venous space Arteriole' Reticulum. Pulp-cords .Venous space Arteriole .Cell cnntainiiiK pigment Section of spleen, showhiK details ot pulp-iissuc Hi/on/r omfMhim which extends forward to the greater curvature and above to the teck ofThTSndurof the stomach. These two folds, stretching respectively tack- ^rf and fori^ard from the hilum, bound a part of the le«cr cavity of the pentonetim. 1786 HUMAN ANATOMY. The suspensory ligament of the spleen is an inconstant fold belonging to the lieno- phrenic ligament, extending from near the oesoph^eal opening in the diaphragm to the top of the spleen. It contains connective tissue between its layers, which connects a triangular retroperitoneal area of the spleen with the diaphr^^m. The phreno-colic ligament is a sheU-like fold, .lerived from the greater omentum, stretched with its free edge forward from the abdominal wall in the region of the eleventh rib to the transverse colon so as to form the floor of a niche in which the spleen rests. . , The Vessels.— 7)1* Arteries.— I^t splenic artery is a large, tortuous vessel, a branch of the coeliac axis. It is remarkable not only for its large size in propor- tion to the organ, but for the thickness of its walls. About an inch from the spleen it breaks up into six or more branches which enter the hilum one above another, in Fio. 150.^. Eniifonn cmrtilagc Diaphragm Left li>be oj liver ^. vV; •. ■. CEsophaciu (•astrfvhepatic .^ omentum Lobe o( Spigelius Inferior ^ vena cava Vena azygoa major Aorta Vena ai>'go5 minor Diaphragm Lung Lung GaMro-aplenIc omcntam Left half of froKB Kction acnw body at level of eleventh thoracic intervertebral disk ; under aide of section. the main anterior to the veins, with which they travel along the fibrous walls of the interior. No arterial branch has any anastomosis with the others. Soon after its origin the splenic artery gives off a branch which runs above the main trunk, supplies some twigs to the stomach, and, breaking up into smaller branches, enters the spleen near the top.' ... .1 The veins ramify in the spleen in company with the arteries, and leave it in about the same number of branches, which unite to form the splenic vein behind and below the arterv. , , , •. u 1. The lymphatics are chiefly deep ones emerging from the hilum, but there are ' Haberer : Archiv fur Anat. und Phys., Anat. Abtheil., 19M. PRACTICAL CONSIDERATIONS: THli Sl'LEEN. 1787 They empty into a little group of lymph-inxles at the also a few superficial ones. '"" m'll^^'eMrom the solar plexus, enter the hilum with the vc^b. Develooment and Growth.-The splenic anlaue appears about the fifth , I fS We L a Siirht condensation of the mes».l.lastic tissue of the meso- SS^Th^SiSkn bodies %pear relatively late as accumulations of young ?h7spi^v:£r o-H7Xr hand.^— ^^^ ^^::ii^:i £ spleen more regular t^anm later hfe l-^^ Ji^ur ^^^ ^^^^ ,„be Ircl^a^Vi^Tthr^ieeZ^^^^^^^^^ capsule nearly or quite "•" ArciUo;;'l;ie1n'»'^^^^^^^ common, but they .-. not all ofthe same signifi- mmtmm """^ ■ MndonThe spleen near the hilu'm are due to the fusion c^such accessory - tto has seen twenty-three accessory spleens in one body. They are ;ice Anaiomy!-The relations of the spk.n to other organs have been de .but itXuld'^ be stated that the phrenic surface 1 es beneath the ninth tenth and ereventh ribe (sometimes the eighth also), and that .to long '^''^ » .'^f «' !r.L^,nf these ribs It is important to note that the spleen is situated behind the A line from the top of the sternum to the tip of the eleventh rib should be enureiy anterior to the spleen. PRACTICAL CONSIDERATIONS: THE SPLEEN. The SDleen may be congenitally absent, or it may be of extremely small size - no Jeer tC wafnut ; or there may be supernumerary spleens connected with he manfland or There may be mu/iifi^e spleens entirely separate and lying m the foWs Tthe'^eaier omentum, the gastro-splenic omentum, or 'J^^ t'-nsverse m«o^ colon It is conceivable but unlikely that these anomalies may lead to mistaken diagnoses^ of the normal spleen is difficult of accurate determination by either pal Jion or percuss on because («) it is covered in front by the stomach thecardjac 33 whkh-if the stomach is distended-completely overiaps it ; (*) 1>«« «i«;y ft is cov*r^ at ts lower portion by the diaphragm and by the tenth «nd eleventh Ste and ;?e thick musciroverlving them, and »»» '^.K'n^/.TintriorlyTtTs muscles the diaphragm, the ninth rib, the pleura, and the lung , < f ) '"'f """X, " '" r^nuct intem^ally with the upper end and part of the outer edge of the ^ft W^-y^ and externally with the splenic flexure of the colon ; (d) the upper part 01 ine Dhrenksurface ^occasionally in contact with the leh lobe of the hver ( Quain ) ;(e) &he r^S viiable in both shape and size of all the abdominal viscera ; (/) .t ' Archivf. mikro. Aiwt., IW. Ivi., ig«J. . • Consult articles by Parsons and by Haberer. just noted. sio'- s- ' U! de 1788 HUMAN ANATOMY. changes in position with the movements of the stomach, having its longest diameter vertical when the latter is contracted and horizontal when it is distended. These relations sufficiently explain the difficulty not only in determining the size of the normal spleen, but also in distinguishing by percussion its abnorma. enlargement from cases of colonic fecal impaction, of tumors of the left kidney, of large plastic exudate at the base of the left pleura or lung, of hypertrophic cirrhosis mvolving the left lobe of the liver, and of certain growths of the stomacli or omentum. In cases of hypertrophy or of swelling of the spleen, as in malaria ( ' ' ague-cake" ), palpation is often of more value than percussion, the sharp creitated anterior border being recognizable below the tenth costal cartilage. Physiological increase in size occurs during d^^iution, but pathological enlargement may follow portal congestion, leukaemia, mala;i i. typhoid, or other infectious di.sease, including most forms of general sepsis, or may result from infection of the splenic substance. It may — as in some malarial and leuksemic cases — so enlarge as to occupj^ most of the abdominal cavity. It is then closely applied to the parietes, and is not, like renal tumors, covered ante- riorly by the intestines. Enlargement of the spleen in infants is often due t -. inherited syphilis, and if it occurs at the age of two or three months is usually of that character. It is of more diagnostic value than enlargt.Tient of the liver, because that organ is normally dispro- portionately large in infancy, and hecause other causes than congenital syphilis lead to its enlargement. In all forms of enlargement of the spleen in children there is said to be more relative encroachment upon the thoracic cavity than in adults, owing to the firmer support of the phreno-colic ligament in young persons (Treves). Whenever it is greatly enlarged, at any age, it is apt to push upward the diaphragm and compress injuriously the base of the left lung and the heart. In splenic tumors, therefore, irregular cardiac action and dyspnoea are often present fc mechanical reasons as well as on account of the associated anaemia. The normal movements of the spleen are not so much affected by respiration as are those of the liver, which is more closely and extensively connected with the dia- phragm. It rises slightly in expiration and descends during inspiration. It is pushed down in emphysema and in left-sided empyema, haemothorax, or pneumo- thorax. It is pushed up by ascites or by intra-abdominal new growths. Its relations explain why abscesses of the spleen (usually due to septic emboli, as in pyamia or septicaemia, typhoid fever, or ulcerative endocarditis) open spontaneously in the following directions: (i) Into the general peritoneal cavity (the most fre- quent). (2) On the cutaneous surface below the costal margin anterioriy or poste- rioriy. (3) Into the large intestine. (4) Into the left pleural cavity. (5) Into the left kidney. Afox'ablr spleen {dislocated , floating , wandering spleen) occurs only in adult*, and is especially found associated with some degree of splenic enlargement — in- creasing its weight — in persons with relaxed or flabby abdominal walls. It is, there- fore, often found in anemic multiparae, as it is held in position normally not only by the phreno-splenic and phreno-colic ligaments, but also by the pressure of the other abdominal viscera due to the general tonicity of the abdominal muscles. In such cases, after elongation of the phreno-splenic ligament, the spleen falls forward, lies horizontally with the hilum directed upward, and is sustained only by the gastro-splenic attachments and the vessels, thus drawing the stomach downward and causing serious gastro-intestinal disturbance, or possibly, if the vessels are twistetl and obliterated, a fatal peritonitis (Shattuck). In exceptional cases a movable spleen may reach the pelvis. From a movable kidney a wandering spleen may be distinguished by the super- ficial position of the latter, its shape, the disappearance of the spleen from its normal position, and the absence of urinary symptoms. Wounds of the spleen, if posterior, usually involve the diaphragm and the base of the left pleural cavity, or, if higher, the lung itself ; if anterior, the stomach may be penetrated. In gunshot wounds the kidney, colon, or pancreas may likewise he involved. THE THYROID BODY. 1789 In fractures of the ninth, tenth, or eleventh nb the fragments may lacerate the 1 Jn OrTaccount of its great vascularity, wounds of the spleen are serious and '& necSitote oJeStion,^but occasionily, after small stab wounds or gu.«hot '*''^^^1M^llet^o? small calibre spontaneous recovery ukes place, and has been Tllff^ /rr^vSto r contSity^of the muscular tiLue of the splenic capsule. Sn1r^ow7 the\-ordrcKna^les it to retain the blood-clot, and thus stops '^" '^TKte'i.v", a wound of the spleen is usually bright red. In wounds of ssjS-ssrss£:-r=sss ''' Tn"S^rr«. on the spleen it may be approached. through incision either at the ''"^'innS^^S:^^- --- ^ t£ t'^t^l^'j^mature tearing or di^^ion of th^" ^^"^{Y^^^^^ "^'''"^rltC'Sfberea ftbylSbgth^^^ the spleen, and some- Tes twTen)^ P^lHnTthTspIeen dfwn from beneath the diaphragm and turning '''Textio hemorrhage, the chief risk is that arising from damage to acjoining viscera during trS^aradon of adhesions, and the relations of the stomach, pan- crS colon? and kidney should therefore be c. -fully borne m mmd. THE THYROID BODY. 1790 HUMAN ANATOMY. antero-extemal surfaces of the lateral lobes. The isthmus varies much m sizt . and is often more or less incorjwrated in one of the lobes. In lo |)er cent, it i> absent ' An upward projection, the pyramida/ process, rising from either the isthniii> or one of the lateral lobes, and usually rejjarded as a remnant of the median anlam ot the thyroid, is found more or less developed in probably half the cases. A typical one reaches the hyoid bone, to the body of which the process is generally attachtil either by muscle or ligament. It is rarely quite median, being more frequently found on the left. Statements as to its frequency vary greatiy. Streckeisen ' says it i> wholly wanting in only alxmi Fig. isio- ■EpiKlottis uperior cornu of ttiyroid cartilage .Occasional foramen ■Thyroid cartilage .Crico-thyroid membrane .frjco-thyroid muscle ■Cricoid cartilage ■Suspensory ligament -Pyramidal process ■Isthmus ■Lobule Thvn.iil IhhIv /» siiu , anterior aspect. 20 j)er cent. ; but, since goitre is common in Switzerland, his sources of information are not of the best. Zuckerkandl, however, puts the occurrence of the process at 74 per ctiit. timber, in Russia, found it in only 40 per cent., and Mar- shall, in England, in 43 per cent. We incline to believe that these latter figures rep- resent the more common pro- portion. The thyroid lies beneath the group of infrahyoid mus- cles, from which it is separated by the middle layer of the cervical fascia. The sterno- mastoid muscle crosses the lower part of the lateral lobes. The inner surface lies against the trachea, the cricoid carti- lage, and the lower posterior part of the wings of the thy- roid cartilage. It reaches back to the oesophagus, which it touches on the left, and some- times on the right also. It may touch the lower part of the pharyn.x on both sides. The sheath of the carotid lies against the posterior surface at its outer border and is in part external to the organ. The common carotid is usually be- hind the thyroid and the inter- nal jugular vein beyond it. This explains how an enlarged gland insinuates itself between these vessels Frozen sections show that often the carotid is external rather than posterior to tM organ, but still in close relation to it. Internal to the carotid sheath it rests behind against the prevertebral fascia. The inferior thyroid arter-es enter the lateral lobes from the inner side and the superior thyroid arteries from the antero-cxternal. The middle cer\ ical sympathetic ganglion is behind. The infenor lar\-ngeal ner\es lie at its inner surface, the left one being in actual contact with the thyroid and the right one at least very close to it. The sheath connects the thyroid body verv closely to ncighl«>ring parts. It is so firmly bound to the trachea as to foUow its' movements. Median bands to the cricoid and thyroid c.irtilages have been ' M.ir-hall : Journal of Anatomy and Physiology, vol. xxix., 1S95. ' Virchow's Archiv, lid. ciii.. 1886. THE THYROID BODY. 1 79 1 Histineuished as suspensory ligaments. A lateral ligament from the 'nner side of the fateKbTis tolerawTwdl defined. It pas-Ses backward and upward to the first nng of the tr^hea, to the cricoid, and perhaps to the inferu.r horn of the thyroid. Ihe VTJ^andula: thvroide^ is a small muscle often fotnid jxi^sinR down from the hyo.d toMtothe capsule. It may or may not be connected with the pyramidal process. Sterno-lhyroid musi-Ie Fio. 1 51 1. Stermi-hyoid muscle ^ KiRht internal Left internal JUKUlar vein / ~'St^^'i.?r^.t^'^^'j^^^Bi^^\'^'/'i0pf^,\ \ juKuL-ir \ tin Uft pneumouBstric nerve /^^^ISSV^^^^SSSk^^LeSSX'^f^'^ PneumoRastric nerve ' ijSjTCfl -^MMMnBt J _C r ' Richt common carotid artery Left common carotid artery ^^^T^^^^^Sc!^^^ Inferior larynKeal nerve / •^'SJStBBF '^ 1 „ Inferior thyroid arter^ TTT^*^ Inferior laniig««> "«""= Prevertebral fascia 1 Trachea CEsophaKua Anterior part kA froien section across neck, shawing relation* of thyroid body. Structure.— Although in principle corresponding in its development with other compound alveolar glands, the thyroid body pos-sesses no excretory ducts and pre^ sentT peculiarities in the structure of its terminal compartments. The hbro-elastic f«/)*«/rinvesting the gland gives off septa which subdivide the organ into the chief lobules, the latter being composed of smaller compartments separated by thin parti- tions of connective tissue. These subdivisions, or primary lobules, from .5-1 mm. Fig. 1513. Interlobular, connective-tis- sue septum Colloid mas! within acinus Section of thyroid body, showiuK acini in v.irious degrees of distention. in diameter, contain a variable and usually large number of tenninal vesicles r f lli _ cles which c-rrespond to the alveoli or acini of ordinary glands. The delu-.tt and highly vasci..ar framework supporting the follicles consists essentially of hbrot.s r,m- nective tissue, elastic fibres being few or entirely absent. The «r/»/ vary greatly in size (.050-. 200 mm.), depending upon the amount 1792 HUMAN ANATOMY. of secretion and the distention of the acini. Their hning consists of a single layer of fairly regular polygonal cells, about .010 mm. m diameter, the height of the cells varying with tlie dotation of the follicle. In young subjects, in whom the acini arc Kenerally less completely filled than in older ones, the epithelium of the follicles ipproaches the columnar type. A similar condition is often to be noted in certain acmi even in thyroids in which the usual distention affects the majonty of follicles. A distinct basement membrane is wanting, the cells resting directly upon a somewhat condensed stratum of the surrounding connective tissue. Since the epithelia lining is the source of the peculiar colloid secretion of the gland, the cells ordinarily con- tain a variable number of highly refracting granules, particularly m the «one next the sac The peculiar substance or colloid commonly found within the follicles ot the adult organ is regarded as a proteid, although its exact chemical characteristics are still uncertain. The consistence of this substancs vanes being more fluid m young than in old glands. Its varying appearance within the follicles, as vacuo- lated reticular, or shrunken, is referable to the action of reagents, in is natural condition the secretion being homogeneous and entirely filling the foUice. the differentiation of the epithelial lining of the acini into chief and colloid cells ^Lang- endorff). as represenUng disUnct elements, is doubdul. since specific difference. probably do not exist. . . , , Vessels.— The blood-supply is very generous, coming from two pairs ol rela- tively large aHeries, the superior thyroids from the --'^^^^S^^^^i^X'^ I, _, subclavians. The superior '■'° '*'^" descend to the top of the lateral lobes and ramify over the front of the organ, sending branches to the interior, and sometimes meeting on the isthmus. The inferior arteries pass upward behind and enter the organ on its inner sur- face. Their relations to the inferior laryngeal ner^'e are of practical impor- tance. In 437 observa- tions' the artery was found in front of the nerve on the right in about 41 per cent, and on the left in 63 per cent. In over 10 per cent, of the cases the branches were so inter- laced that the relation was uncertain. It is evident that in enlargement of the thyroid body, with conse- ouent enlargement of the arteries, the number of such indefinite relations would be verv much fncTLed, as very minute branches would then spring into importance^ AnlnTrge^ tortiou; artery tends to curi around the nerve. There was no artery on £ rkht^in one case and' none on the left in five cases of th« series. An aW.;,^ ihvrofdea ima springing from the arch of the aorta and ascending in the median line is Sonal y seen. From the rich superficial arterial plexus numerous branches pass aS"he interlobular septa, following the ramifications of ^he atter « the^fo^^^^^^^^ where the arterioles break up into capillaries. These surround the fo"'^'^-_^^' f, ^'^ meshetl net-works, which are often common to the adjacent sacs, rcscmbh.ig the caoillarv net-works around the pulmonary alveoli. •^ The m«* are very numerous. Emerging from the organ, they form a large ' Dwight: Anatom. AnzeiKer, Bd. x.. 1895. '^Acinui Interlobular vewcis Acinus con- taining col- loid Section of injected thyroid body. X 4*. THE THYROID BODY. 1/9.^ Irom Ih. d«per part of .he '«." »™ j''™ » "'>■ t"n.«"V.n. ,.«,. .hi- M. in- ferior thyroid veins can be injfcted from bcU.w. . , ly^ph-s.^ces ; from constitute a sunerhmlpexus from ^'l^f , .^^\ > ^^'^fro^^ of the larynx, some r:. Edir ; : :s ^l-dral'^^h':^n^^^^ -d .j. .rom the Sm^rand^U parts S.];n.a^^^^^^^^ ^^^,^_ ,, Sin::i%r/r;»l'£>i^^^^ end around the foUid. median and two lateral The -''''''?'' «'XJ^^«^^^^^^ pharynx 3-4 mm. as an ep.thelial °"'Sr°«^VThmrtSoTen close relation with the fn the region o the second v'^-^arch^therefore m c^^^^ ^^^ evagination posterior part of the tongue. At hrst P??*™ ?L ^V ^.hjch for a short time is L>n loses its cavity and becomes a -I'd ^^^^^^ *^„d. Usually the latter connected with the pharyngeal wall by a dehca e ^^V^^^lia^^ra j J increases soon disappears and the isolated median » Y' / tho ttera^tnbees The position ..f as a bilotid mass, pa^ to the lower level «« ^J^ '^^^'„''J'X^ /.ra- the primary -^'h^Xi^/rthe V^-row of Ercumvallate pa'pUte. Occa- mrn cacum, just behind the -^pex oi !"« ^ . (hvro-ghssal duct, a narrow tube sionally the evagination persists, and thf";°""^^f Sds the thyroid body. The extening for a -^able d.sunce f^om f„% -^Tut^^^^^^ the venLl wall lateral anlage appears on each side a^" an epiineu » becoming trans- of the fourth pharyngeal furrow (F'K/S^O.the «"'""»« I^''"^^^ .^^ rudi- formed into a sac. ^^icW ^ V '^f.XS aLSm. . join to form^he definitive mentsgrowventtBlly, and later. '"^^.^'X^^/^r^X medikn anlage contributes the thyroid -Ht^Sd SvroidbLdy tomparati"embryolo|y emphasizes the most important part of the thyroia '^5'y- . J^ . . '^^ . indeed, all participation of significance of the median anlage as the t'^^^^'V^Xanimairis denWl (Verdun). numerous cyhndncal epithelial '^«™!, •[°'"Jj/;'i^ ^^^^rds into a net-work the meshes second stage witnesses the «"«'X,''**SblSt£ue During the third foetal month of which are occupied by vascular mesoHast.ctis.u^^^ ^^^^.^j^ ^, ^^^ the epithelial reticulum breaks up into masses "^P^l^""'"*^ ,, become arranged and behind and sometimes below it. 1 hey are remnam thvro-glossal duct. Uculum from the pri|nit.ve phaO^nx. somet.^^^^^^ This ,«^d onginally '"J™"* "' Those behind and below the hyoid are probably SrSS'aru^a7d »ownwar?g^wThU the primary diverticulum. "3 1794 HUMAN ANATOMY. PRACTICAL CONSIDERATIONS: THE THYROID BODY Congenital absence of the thyroid body, or its atrophy with loss of function, occurring at any time before puberty, is apt to be followed by the interference with nii trition and with normal mental and physical development that produces the condition known as cretinism. Similar atrophic changes occurring later in life cause myxu- dema, and the same condition — also known as cathexia strumipriva — may be brought about by the complete excfaion of the gland. Calcification of the gland may take place in old age. The isthmus may be congenitally absent and two separate lobes lie present, representing the originally distinct embryonic lateral anlages of the organ. Accessory thyroids may undergo hypertrophy and form large masses occupying the pleural or the mediastinal cavity (Osier- Packard) ; or they may develop at the base of the tongue, — lingual goitre ; or, on account of their embryonic relation to the thyro-glossal duct (which passes behind the hyoid bone), they may be found in the median line of the neck below or behind the hyoid, and may be mistaken for growths of a different character (page 554). The thyroid gland may be temporarily enlarged in women during menstruation. Hypertrophy oi the thyroid gland (goitre) may be (a) parenchymatous when it results from a general hyperplasia of the gland- tissue ; (*) vascular, due to a great increase in the size and number of the blood-vessels ; {c) cystic, characterized b^ the formation of walled-off cavities within the already enlarged gland ; (rf ) fibrinov the connective-tissue elements being in excess ; (^) exophthalmic (Graves's disease in which the thyroid enlargement is associated with exophthalmos and function. . derangement of the vascular system ; (/) adenomatous, the hypertrophy affecting one or more lobules or the isthmus. This last form appears as a one-sided or asym- metrical swelling, is common, and is often classified with tumors of the thyroid, rarer forms of which are the cancerous and sarcomatous. It may be noted that the gland is relatively larger in females, and that the right lobe is larger than the left. This has been thought to explain the greater frequency of goitre on the right side, and in women. Inflammation of the thyroid is rare, and usually occurs dunng typhoid or other infections, although it is favored by -'•evious thyroid disease or overgrowth. The tumefaction which it produces may cf e acutely many of the symptoms brought on more slowly by the chronic forms of enlargement. These symptoms, so far as they have any anatomical bearing, are : (i) The swelling rises and falls with the latp^nx during deglutition. This is due to the attachment of the thyroid gland to the cricoid cartilage by the upward prolongations of its capsule known as the suspensory liga- ments and to the subjacent larynx and trachea by connective tissue. (2) Dyspnaa. The gland is covered and its growth anteriorly resisted by the sterno-hyoid and stemo-thyroid muscles (Fig. 545), and, to a less degree, by the omo-hyoid and the anterior border of the stemo-mastoid. Its forward progress is also resisted by the pretracheal layer of the cervical fascia. Its close relation to the trachea, therefore, renders the latter subject to direct pressure, especially in the firmer forms of bilateral enlargement, or in those adenomata which begin in the isthmus or lie between the trachea and the sternum. In the unilateral forms the trachea may be displaced to one side. (3) Headache, vertigo, cyanosis, and epistaxis. The relation of the outer border of the thyroid to the carotid sheath explains the disturbance of the cir- culation in the carotid and internal jugular (either through direct pressure or by deflection of the vessels outward) and accounts for these phenomena. (4) Dys- phagia is relatively rare, but may occur as the result of pressure upon the upper end of the gullet or the lower portion of the pharynx. It is more common in left- sided goitres, owing to the curvation of the oesophagus towards the left. As a great rarity the isthmus of the gland is found between the trachea and oesophagus ( Burns). (5) Dysphonia, or aphonia, due to pressure upon the recurrent laryngeal ner\es. ( 6) Pulsation or bruit. These may be apparent, and caused by the close relation of the enlargement to the common carotid artery, or — much more rarely — real, and due to the relatively enormous blood-supply of the vascular form of goitre, the thyroid with its four constant arteries and occasional fifth one (the thyroidea ima, — 10 per THE PARATHYROID BODIES. "795 . ^ raaMt beiiMT normally one of the most vascular structures ol the body. ^Ir ^ ^ cSon in th/ exophthalmic form. (7 ) The trrmor, lacky""«- °Ln-'' p^bly in the medulla" (Treves)-have been invoked to explain the phe- "'"'S^IS. ^hyrolfen^^^^^^^^^ vary with the character of the latter. iTthe adenomatous and cystic varieties, after division of the capsule o the '" 'Texdsi'oSr'the skin platysma and cervical fascia should be freely divided and the ieSToids and th?roiL retracted or divided : after '".-'^ founrfix'd b^en wdl exposed the growth is first loosened externally. -:« it will »* «ound hxeU o^vP hv fhi^rior thyroid vessels, below by the inferior thyroids, and internally above *'.y ^''"'^"h/vS setiaratcly ligated. great care being taken to avoid the structures, and the growth removed. THE PARATHYROID BODIES. Thi-^e organs the ebilhelial bodUi of many authors, are small elliptical m.isses situaSTearThe thjrdd^hich formerly were Mistaken either for accessory thyroids or for lymphatic nodules. They arise from the posterior wall of the third and fourth pharvngeal pouches, and thus diHer from the thyroid body in origin as wrll as in stnicture. 1 hey are 6 or 7 mm. long. 3 or 4 mm. brrud. and 1.50' 2 "^m- 'hick^ The leneth may be as much as 15 mm. They are always separated from the thyroid ' y the ca,«ule. Most frequenriv theparathyroids exist as two p-iirs on each side; their disposi- tion however, may be asy nnietrical, in some «^^ "J='"y as four, in others none, lying on one side. The position of the stiPerwr pair is the more constant and, according to >\ elsh coVrespoAds about with the level of the lower edge of the cricoid cartilage. They usually lie against the P<»'*^7«""r^^^^^^ of the lateral thyroid lobes, between the middle and the inner border of this surface. The inferior pair is lower and more anterior than the superior, their position being less constant. Sometimes they lie against the side of the t;^^»;«;» "'^•'[.;^^;; ends of the rings, under cov.r of the lower part of the th>rod lobes; sometimes thev are found in a corresfK.nding relation o the windpipe, but much lower, so as to have "" /^'f "" ^^."'^ the thyroid ; occasionally they lie on the front "t^e trachea ^__^ below the thyroid. The surest means «« '«^?,""K. ^f^^'^ "f^ ^^:S^:^JS^^^^t bodies are the minute parathyroid artenes, small tw igs chietiy f^. ^r. ".^^^ ,^,,, . „, ^^^. Tmlhe inferior thyroTds. to each one of which a parathyroid r.o^.Hv™--V,,i---, body is attached It is evident, therefore, that these organs „„„ (c.«»».al epithelial celU, aUiut .010 mm in diiimeter, varyin>{ly disjxRied as c< u.i'Uinis my, is c; im|M '-ctly separatwl <«.riN ami alveoli. The cells ptjssess rouno nu. !< i *|ii. v.iitain chromalin r«licula. Ihi cells are surroundiil bv a honey -comb «. 'lelioiU' n • mbrafie». rttirous tissue ap|)ear in>{ only in the immediate vidnity of th' larger i l....puM-d ai acini, &onic oi which ^ distinct organs, as now established by both anatomical and physiolo>,'ical investiga- tions,' opinions differ as to their histological relations. Schaper' and others incline to the view ad\anced by Sandstroem, that the parathyroids corresjmnd in structure to the immature and undeveloped thyroid. Welsh, on the contrary, denies this resemblance and points out the close similarity to th< anterior lobe of the pituitary body, in both organs colloid-containing alveoli being occasionally present. ' The arteries distributed to the parathyroids are deri\ ed from the branches sup- plying the thyroid body. Regarding the lymphatics and the nerves little is known ; the latter are chiefly sympathetic fibres destined for the walls of the hh .od-vessels. THE THYMUS BODY. The thymus is apparendy an organ of ser^ice to the nutrition — - >ssibly blood- formation— of the foetus and'infant, since it usually reaches its grea >t size a about the end of the second year, having grown since birth fairiy in pr fx>rtion to the body. It continues for some years to enl.irye in certain directions at -1 t=^ dwindle in others; coincidendy deposits of fat appeal <1 it gradually degenerates When m its prime it is moderately firm and of a pmki.sh color ; later it 1j. . - nes very friable and resembles fat and areolar tissue. Shape and Relations. — The api'^arame of the thymu - tl organ. It is surrounded by a fibrous capsul which svnds pro, sya lobules. It is situited beneath the upper pan of the sternum, n 11 periiaps 2 cm. into the neck, descending to alniit 'he fourth cost, tionally as far as the diaphragm. The organ is thickest above, w pericardium, and descends in front of the latter in two flattened K distinct, which grow thinner and sometimes diverge lielow. Thes. a layer of fibrous tis-sue which enters oblitjuely from the front i' above the left lobe overlaps the other. The lobes are generally 01 u leqi •^^ left one being more often the larger. Sometimes '-■ lobes are fused, and be a thinl one between then:, such vari-itions merely -imiilying irregul-ir; fibrous septa. The thymus lies in front of and above he pericardium, ai ' A critical review of the relations of the tpithelial onf: is derived from the pbar)-ngi.il pouches is given by Kohii in Merkel and Bonnets ErRebnissc, Btl. i.x., 1899. ' Archiv f. mikru. Anat. u. Entwick., Bd. xlvi., 1895. of a glandii.ar •i,.. ■ ns amor . wher ' irtilapt e it p - s, morr :e separa !(■' • Wil .nth ■- le THK Tl VMIS BODY >797 I-* in Mirfa' ■'/ — — , , its hi Uest jmrt luav r< t on tht- ir.ictiia ippeiir« ■>« thf Ult of t " former. It txi, iwtwifn tho ptri.anJiu and the i>lvura w.ntal scxtion in thw r. . cm Hhows the th> becomes thinntr a- the . xan atn.i it-s. Fio. i> latt-r.i - thi- . .IS .1 •hiiMl til (»n eatli -iMlf into th»' intt rval • of it* liitwt -i/x', a ! >ri .^ cresc- (Fix. i.siH), «'"*' ery toj i the sternum its Common carotid arli Pneiimn||Kf(tTtc nrr\ nit-rnal V filial- — -cm tl..;:.!: Rlf lobr Luii( eni'ar- iliutn Dissection of new-born child, sliowing th ind II. ■»«» bodies IH s^m. line on section is roughly quadrilateral ^^-;^^'^':^;:;:^f ^S! botly to the capsule of the thymus ar- ■-.wmmt as t«- suxpeniurj, >, internal mammary vessels run in front rt. ^^,^^ , jj^frag" w-^itlit of the Weight and Change8.-Accor s^,,,,ev thvmusatbirthis 13.75 gjn- : the ^"^<='"'"'^^;^™^^„ ' ;^,^.,f' .^^^^ " VVi^n hcavi- tri;rinK ? em. and Testut. from twentv o.^rr- al^ms. an ^''^^'^f 5 J.m^ Xtrophv S^ aL'u^ puberty according to Hamm.r, .. '--^^J^'^^^^;- ^^,% X-' and the replacement of thymus tissue bv fat - m while gr.mtn m iLngxi h 1798 HUMAN ANATOMY. Groove for left innominate vein Kressing ; this increase is said to continue even after puberty, the organ, how- fv^ bicoming thinner and softer. Although later almost completely replaced by adip^ and connective tissue, the thymus never entire y disappears, remains of it. autpv/<». tissue being present even in extremr Fjo. 1 517. old age (Waldeyer). Until abt le%el o( fourth thor«clc vertebra ; from child of about one year In ..ddition to the usual elements, eosinophilic cells .»[^f«""'*.';!;;°"£*'"' '^,^ cortex Jarticularly in the neighborhofKi of the capillaries. Accoiding to J. Saffer the cortex of the thymus contains nucleated and other developmental THE THYMUS BODY. I7» Fio. isip- Lobalr, Blood- vesMls, inlccted CorpuMlC' of itauaU Corte: Medulla Tr.n.«r« ««ion o. Ihymu. body of child, .hewing g«,e«l .rr.n,«n«.i o. lobol». X aj. ,„„^,_.jj**,n. - cj«^yJ^o™ .h^o;j^ -Sfl- r '^'i tion of tie cortical and medullary zonM T^^.y^^^JJ^ The rrm between the lary net-work, the medulla being relatively P°"7^"PP^^he larger trunks carrying lobules, which chiefly dram the *=='P'"^':f-""''^fectb^, the most important being the blood from the organ. These run l""^^. «'^^\'°"'; '^i numerous, and empty tribuury to the left innominate. The Wf^'^^^^" n erior of the organ, the lym- sinuses, has not been established. i8oo HUMAN ANATOMY. Cortex The nerves are small and come from the sympathetic and the vagus. They are traceable along the arteries and connective-tissue septa, and end chiefly in the walls of the blood-vessels. Bovero has described terminal filaments which pass from the interlobular plexuses into Fjo- ^S'o. the medulla. Development. — The thymus proper originates from a jjaired anlage (Fig. 1521) which appears as an epithelial outgrowth from the ventral wall of the third pharyngeal pouch. From this results a long cylindrical mass of closely packed epithelial cells which grows downward and en- closes a narrow lumen. The lower end of this mass in- creases in size by the formation of solid acinous outgrowths resembling those of an im- mature tubo-alveolar gland. Coincident with the downward extension of the organ, the upper cylindrical portion grad- ually assumes the alveolar con- dition until the entire thymus acquires a lobulated character. During these changes histo- logical .tltcrations take place, the epithelial masses becoming invaded by ingrowing lym- phoid tissue and blood-vessels and broken up into irregular islands. The latter become smaller and less conspicu- ous as the lymphoid character of the thymus becomes more predominant. The cor- puscles of Hassall represent derivatives of the primary epithelial elements. For a time the two originally distinct anlages develop independendy ; later they come into close contact in the mid-line, and form the single irregular organ the bilateral Section of thymm body Corpuscles of Hauall within medulla •howine details o( cortical and mdullary subfttanre. .« 300. Fio. ts>t. ReconHtrurtinna of ilevelopjnK thvrnid. thvmuit, and |>arathyroi(l hodien in embryt« of 14 mm. ( .-f t und of 26 mm. tfti. mt. mefljan thyroid; //, lateral thyroid: /v, thvmua; /, tliyroid; ^1,/^, superior and inferior parathyroids; i-f. \ftia cava su^wrior ; a, aorta. ( Toumritx and I 'frdnn. ) derivation of which is indicated by the connective tis.sue separating the right and left divisions. The upper ends of the latter are often continued as far as the thyroid as lateral processes. Subsequent to the second year regression sets in, and the THE SUPRARENAL BODIES. 1801 .Thymus thymus structure is largely replaced by fibrous and adipose tissue, vestiges «{ the '^•^^iS^^'tSSaS'Sl^i.-Hi^dVyngeal pouch, a rudimenury ^h-ere^iarwTo/Te fourth one, external to the origin of the lateral thyroid. According to Groschufl,' this anlage may persist in man as iheparaihymus, a small body which occurs in close association, or even encloses, the para- thyroid derived from the dorsal wall of the fourth pouch. The lat- ter, therefo-', corre- sponds to the third pharyngeal pouch in giving rise to both a parathyroid and a thy- mus ; in addition it pro- duces the lateral thy- roid anlage. According to Beard, Prenaut, Bell and others, the transfor- Thymus tissue Section of thvmas body of man of Iwenty-eiRht. showlnj invasion nn.l rrplace- meiu of thymus liasiic by fat. > ». mSon of the tWmus into a lymphoid organ occurs as the direct conversion ..fits nrSi c-i'V'-lial elements into lymphocytes and not by invasion of pre-exisling wTphoid'dis. While accepting such origi.i for the reticulum, Hammar' regards the lymphocytes as entering from without. THE SUPRARENAL BODIES. These are a pair of cocked-hat-shaped bcKlies situated at the back of the alxlo- Tfht inn^ asuect of the upper ends of the kidneys. F^nch has a f>ase, or S surface Tr^L^Sg to theT^tom... the hat. and a'n anfenor .ud ^ postrnor ^.r^fhl^^dersof which are concave and look outward and downward. Thte kre an^?i?^nd " loweV angle at either end of the base. The inner convex Srder :nds,"^^cially in the right^ capsule, to present ^ ^^ermor" c^Jsc'^^ c^ the middle Thus the right one is more triangular and the left more crescentic Thev mavbe 6or 7 cm. long and about half as broad. The thickness doe. not orotabTv often exce^ 2 cm. The base is concave, adapted to the kidney of which ft ov^rhani "he a^rior surface. The lower end is much thicker than the upper. The conca^tv deeiLns above into almost a hirrow filled by areolar tissue. The an- J^'L^rPlirrs^a deep fissure, the „i/un,, in the "^^-J>l"^^,^'^J^^^,' ^1 dividing it into two approximately equal regions. T'^^. ^'^'^T ^^r „ve^ siderably smaller than the anterior, owing to the orojecton "^^ J^^ »»"" ^ff J^^, front of the kidney. It also presents a f^NSure nearly parallel with the base-line. Dut ndther extending the whole length of the organ nor so deep as the front one. I^cdor he suprarenalsa?eof a dirty yelluwish brown and more or less p.g- mpntMl Thev weieh 6 or 7 gm. The left one is usually the larger. ReUtioM.-The W W«r« are on the kidneys. The post.nor surfaces are as^iS "he diaphragm. The anUnor surface of the right capsule has its l<.«.r Tne^^^rtUtlnffe inferior vena cava. The part of t^eow^r end near, his mav he behind the duodenum. The remainder is in contact with the liver. Ihe hii,nest ' Anatom. AnzeiRer, Btl. xvii., • Ibid., Bd. xxvii., 1905. ll^UU. :i:M: i8oa HUMAN ANATOMY. part is between the non-peritoneal posterior surface of the liver and the abdominal .vail. This, of course, like the two preceding areas, has no peritoneum. The rest lies in contact with the lower surface of the liver, and is coated by the peritoneum ol the posterior abdominal wall. The anterior surface of the left capsule is neariy or quite peritoneal, resting against the stomach, the spleen, and the tail of the pancreas. Structure. — The suprarenal body is invested by a thin, but fairly strong, fibrous capsule. Section across the thicker parts of the organ displays an outer zonf, or cortex (. 25-1. 20 mm. in thickness ), which surrounds the central medulla. Where thinnest, as towards the borders, the medulla !;< reduced to a narrow zone and may he entirely wanting ; where best developed, as in the middle of the organ, it may attain a thickness of over 3 mm. The cortex is usually of a dirty yellow color, presenting Fio. 1513. Crura of dtephragm Captular vein in groove, for vena cava Hepatic surface' Peritoneal surface- Inferior vena cavn. Riglit liidiiey Ctzliac artery Superior mesenteric artery .Capsular vein cmerginK from hilum Lett kidney Anterior aspect of suprarenal bodies liardened in situ. Fio. 1534 Diaphragmatic surface -^H|. ^^^^^Diaphragmatic suHace Renal surface ^H V^^^^^r„»i surface I.eft RiKht Posterior aspect of suprarenal bodies siiown in preceding figure. ne.xt the medulla a narrow darker zone of varying shades of brown. The medulla is of a grayish tint and generally lighter in color than the cortex. Its exact tint, how- ever, varies with' the amount and condition of the containef cells. The zona fasciculata forms the chief part of the cortex, and maintains the radial dispositic n of the cell-columns. The zona reticularis, next the THE SUPRARENAL BODIES. 1803 Capiale rdJi eSelS «Us from O20-.o,6 mm. in diameter; in addition there are numer- spaces. The cells of the medulla are ^^^ more prone to undergo post-mortem change than those of the corte-x. Veisels.— The chief artfru. supplying the organ are the three sui^rarenal or capsular arteries,— the middle from the aorta and the su- perior and inferior from the phrenic and renal aiteries respectively. They break up into a dozen or more fine branches before reaching the organ, which they enter at various points, some penetrating direcdy into the medulla, others terminating m the cortex. The latter form a superficial capillary net-work within the cap- sule, from which continuations pass between the cortical cell-columns, around which they constitute capil- lary net-works. The medulla is di- rectly supplied by arteries destined for the interior of the organ. These soon break up into capillaries which surround the medullary cords and pass over into an unusually rich plMUS of veins. The latter claim as tributaries the venous radicles of the zona reticularis and impart to the medulla in general a spongy charac- ter. The veins form a rich plexus about the organ, communicating freely with those of the kidney. The deeper lyn^ajsmthe^^^^ «-m the solar and renal Dlexu^ The num^7of meduMed fibres would imply that many come throu^i, mwimmmm Section ot ,upram«l body •"'''"»'■'« «?J"3^S^°' "a""' i8o4 HUMAN ANATOMY. ments ; but in all cases they exhibit the characteristics of sympathetic cells. Indeed so numerous are the latter that the suprarenal is regarded by some anatomists as ai organ accessory to the sympathetic nervous system. Development and Growth. — ^The genesis of the suprarenal body has been the subject of much discussion and uncertainty, especially as to the origin of tht medulla. Comparative and embryological studies clearly indicate that the mam malian suprarenal body consists of two separate and distinct organs, which, although intimately united as cortex and medulla, possess a different origin and function.' According to the investigations oi Pio. 1536. '^ Capiule Aichel,' the suprarenal in the highei- mammals first appears in close rela tion to the Wolffian body, the anla^i arising from the proliferation of meso- blastic cells at the ends of invaginations of the mesothelium lining the body- cavity. The individual cell-groups thus arising with the several invagina- tions fuse into the general anlage of the suprarenal. The primary close asso- ciation of. the latter with the Wolffian body is later lost, the subsequent mi- gration of the organ bringing it into secondary relation with the j>ermanent kidney. Regarding the origin of the me- dulla two views obtain. According to the one now widely accepted, the medullary portions are developed from cells which are derived from the ad- jacent embryonic sympathetic gan- glia, the chief support of this opinion Ix'ing found in the close correspond- ence of the medullary cells with the chromaffin elements of sympathetic ori- gin occurring in other localities, such cells wherever found exhibiting an especial affinity for chromium salts. When fully developed, the medullary- cells may be regarded as highly special- ized cells which elaborate a powerful stimulant that passes into the l)lf)od (Vincent). The other view, supported by Janosik, V'alenti, and Aichel, attri- butes the origin of the medullary cells to the same mesoblastic anlage that produces the cortical cords of which those of the medulla are only speciali- zations. The differentiation of the su- prarenal into cortex and medulla occurs comparatively late and long after the primitive oi^n has become sharply de- fined from the surrounding tis.sue. For a time the entire organ consists of cells which are identical in appearance. During the third month this common tissue differenti- ates into cortex and medulla, in consequence of the breaking up of the enter zone into columnar ma-sses by the ad\ent t'f connective-tissue trabeculae from which delicate lil)iillie arise, ioiiiiiiig the inner boundary of the corte.\. Within the central part of the organ thus defined numerous venous capillaries appear and break up the tissue Capillar)- Znnn nrticularis Medulla iif suprarenal IxkIv. shiiwiiiK details of superficial and deep portions of cortex. X 225. ' X'incent : • Archiv f. Joiimal of Anatomy anrl PhysioloRy, vol. xxxviii., 1903. mikro. Anat., Bd. Ivi., 1900. THE SUPRARENAL BODIES. 1805 rich supply o{ ner^•e-fibres and KanR)'''^ F,o. .5,8. cells distinRUisKing the medulla. Ihese orirans are proportionally very large in the foetus (Fig. 1529)- At birth the intero-posterior diameter is i cm. and the greatest transverse diameter at the base is Fio i5»7- Ceninil vein SKlioii oi suprarenal body. showinK portions of cortex and medulla. X 225. •wiinn of injected suprarwial IkxIv; the ve«^V.??o«er th'ud of 6^5.. are chi.fl> tr.bu- Uries to the centml vein- v 'S- Fig. i5»9- Suprarenal Kidney Suprarenal ..5 cm.; the length '- the apex to the ~^^^^^^^ srs;^"Mr:ar,ie?;.:ri:^x^^^^^^ to resemble the kidneys ; at term, however, the lobulation has nearly disappeared. Accessory Suprarenals.— These are mostlv very small, rarely surpassing a pea in size, they mav be found near the su- prarenal lx)dy. in the kidney, in the liveT, in the solar and renal ple.vuses, or beside the testis or the ovary. The accessory su- prarenal situated within the broad ligament m the vicinity of the ovary is regarded by Marchand and others as a normal ami almost constant organ. The latter under- goes compensatory hypertrophy after re- moval of the chief suprarenal. The in- vestigations of Aichel empha-size that the organs included under the designation "accessory suprarenals" comprise two groups of structures of different origin and morphological significance. Those asso- uidnev or liver, are derived sr^-pTJ?:; ««-*p:?"=™- r^-rnr^ftsri *» »p„™.. .^. rreier . allopian tube Round liKament Bladder Fi Dissection of three months female (.rtus. show- ing h^^ suprareiuite. lobed kidneys, and «.x..:.l i8o6 HUMAN ANATOMY. therefore, are supernumerary. The bodies, on the contrary, situated within thf broad ligament, or in intimate relations with the epididymis, are probably developed from the atrophic tubules of the Wolffian body, and hence must be regarded as inde- pendent structures. It is said that the suprarenal bodies are sometimes wanting. PRACTICAL CONSIDERATIONS : THE SUPRARENAL BODY. Hemorrhage into the suprarenal body in new-born infants has been obser\'ed (post mortem) in a number of cases. Various opinions as to its cause have been expressed. They have been summed up (Hamill) as follows : (i) weakness of the vessel-walls, normal or abnormal; (2) traumatism, especially during labor, from pressure of the hands in making traction in delivery by the lower pole, and from the frictions and flagellations used to resuscitate the apparently dead-bom ; ( 3 ) asphyxia from delay in the establishment of respiration at birth ; (4) acute fatty degeneration of the vessel-walls ; (5) fatty degeneration of the tissues of the organ : (6) firm contraction of the uterine muscles, the resistance of the parts traversed, and consequent compression of the inferior vena cava between the liver and the vertebral column, thereby producing congestion and hemorrhage into the non- resistant tissues of the suprarenal gland; (7) convulsions; (8) syphilis; (9) cen- tral vasomotor influence from cerebral lesions ; ( 10) mechanical squeezing of blood into the part during the process of labor ; ( 1 1 ) too early ligation of the cord ; (12) arrest of the circulation through the umbilical artery from compression of the cord or separation of the placenta; (13) thrombosis of the renal vein or inferior vena cava ; ( 14) infection. , . , , Hamill concludes that the first of these seems to be the fundamental anatomical element favoring the occurrence of hemorrhage, that in still-born children prolonged and difficult labor is the exciting cause, and that in those dying later some form of infection is responsible. , .. . . . In cases of tumor of the suprarenal body the foUowmg sj mptoms have been noted (Mayo Robson) : («) shoulder-tip pain, probably explained by the fact that a small branch of the phrenic nerve passes to the semilunar ganglia ; (*) pain radi- ating from the tumor across the abdomen and to the back, not along the genito-crural nerve ; ic) marked loss of flesh ; (rf) nervous depression with loss of strength ; (f) digestive disturbance, flatulence and vomiting ; (/) presence of a tumor beneath the costal margin, right or left, at first movable with respiration, but soon becommg fixed ; it can be carried into the costo- vertebral angle posteriorly, and can be pushed forward into the hollow of the palpating hand in front of the abdomen. Bronzing of the skin is not usual unless both suprarenals are affected. THE ANTERIOR LOBE OF THE PITUITARY BODY. The pituitary body (hypophysis), although usually described in connection with the brain, to the base of which it is attached by a stalk continued from the infun- dibiilum (Fig. 976), consists of two entirely distinct parts which differ both in their genesis and structure. These a,e the so-called anterior and posterior lobes. The latter, being derived from the diencephalon, is appropriately described with the brain (page 1 130) ; the former, derived as an outgrowth from the roof of the primitive oral cavity, in view of its probable function as an organ of intertial secretion, may be here considered, since in certain respects it resembles the thyroid body. The anterioi* lobe, which constitutes the major part of the entire hypophysis, is kidney-shaped and receives the infundibular process in a hilum-like depression on its (XJSterior surface. It increases in size until about the thirtieth year, when it meas- ures in the transverse direction about 1 2 mm. , in the sagittal about 7 mm. , and in the vertical 5 mm. The anterior lobe of the hypophysis is light grayish red in color, the posterior appearing grayish white. It is surrounded by a well-marked fibrous capsule which forms, even where the two lobes are in contact, a distinct investment. In the anterior part of the lobe, on either side of the mid-line, a con- densation of the connective tissue marks the position of large blood-vessels. Fine processes extend from the capsule inward and form a delicate net-work, rich in capil- THE ANTERIOR LOBE OF THE PITUITARY BODY. i«o7 lori«L the meshes of which arc occupied by spherical or cord-like masses of cuboidid ir^veonTShhelial cells. The latter are apparently of two k.n< Is.-the smalle ^rt?hUy sSing ckUf ceUs, from .003-004 mm. in diameter, and the larger and FlO. IS3°- Iiitttlotarxploni Conn«ctive4iM« tnbecula _Cap»ulr Tnin.«™e action o( pituitary bod,, .howing retatioo o( .nt«lor (oral, and po.lcrtor (crcbral* lob«. x ^. def-ply staining chromophile cells (.005-008 mm. ), so called because of their mark«l Sty for certain dyes The two varieties of cells seem to be mtermmRlwl w.thout S tVa^ngement' .ud are regarded by some as the "P-'f-'T "L^^^mim; pending upon merely functional changes, the two kmds of cells bemg e^ntuilly "^^"tS .i^grt^ations of the cells, cord-like or spherical in form and usually without distinct luS^.r lie in very close relation to the wide capillary blood-vessels that Fio. 153'- Chief cells.. Chiet cella Capillar)' Colloid Capillary Cbromoptaile cella Section of anterior lobe of pituitary body ; th-ee acini contain colloid material ramify bet^vee^ th...n, supported by the delicate connective-tissue 'l^jf- "^J^ ;\"'' there however, the glandular epithelium surrounds a lumen which ma> contain Soid material: thus riembling the acini of the thyroid body. The colloid-contain- l8o8 HUMAN ANATOMY. ing acini lie chiefly against the posterior lobe, in which location a number of siicli spaces (Fig. 1531), of moderate si«e and lined with cuboidal epithelium, are usually normally present, although colloid vesicles may be absent in other parts of the antf rior lobe ( Schocnemann ). The absence of excretory ducts, the activity of the epithelial cells as excretory elements, and their intimate relation to the blood-vessels all support the view that Fig Wall ct rhombencephalon. Pituitary cvaKinalion from diciicev»al<><> Pituitary evaKination from Dial cavitv .Communication with oral cavity Wall oi oral cavity Portion of sagittal section oJ rabbit embryo, ihowinK early aUge ol development ot pituitary body. X 80. the anterior pituitary lobe is to be regarded as an organ engaged in internal secre- tion. Its assumed function as direcriy concerned with somatic growth, suggested by the enlargement of the pituiury body observed in giants and in cases of acromegaly, needs further confirmation, since, as pointed out by Thom,' such changes are by no means con.-^ant. . . Development.— ,As above stated, the two lobes of the pituitary t)ody are de- veloped from entirely different sources. While the posterior lobe originates as a tubular e.xtension of the Fig. isii diencephalo cavity of the interbrain (diencephalon), the an- terior lobe is derivetl from an ectoblastic outgrowth from the pri- mary oral cavity which appears during the fourth week. The cere- bral end of this evagina- tion {Ralhke's pouch) soon expands into the hypophysial pouch, which remains con- nected with the mouth for a considerable time, until the formation of the base of the primi- tive skull leads to sev- erance of the tubular communication, the hy- pophysial anlage then lying within the cranium against the lower surface of the interbrain. In very exceptional ca-ses a canal in the sphenoid bone, leading from the sella turcica to the ba.se of the skull, contains a prolongation of the hypophysis, and ' Archiv f. mikro. Anat., B<1. Ivii., iqi.i Wall III. rhombcncephalun agination Piirii.iii lit MKlttal section of rabbit embryo, showinit development of pituitary body. >' Ho. THE ANTERIOR I.OBF. OF THE PITUITARY BODY. 1809 thus represents the condition existinR in s.)mc animals, in which the pituitary stalk persists during We. passing through a .anal in the l«se of the skull and connecting Uh the oral epithelium. During the latter half of the second month the hypo- physial sac sends jubular out- ^.^ _ ^^^ growths into the surrounding vas- cular mesoblastic tissue. l^ter these tubules become separated from the main pouch, until the Utter finally becomes entirely con- verted into a mass of small, tor- tuous tubules or acini which in large part lose their narrow lumen and become solid masses sejxuated by septa of vascular connective tissue. The anterior lolx- thus formed becomes pressed .»,'ain!.t the under surface of the brain-lolx' with which it is closely bound. The posterior pituitary lobe is developed from the tubular outgrowth from the diencephalon and retains its connection with the brain through the infundibulum. The primary lumen, however, be- comes obliterated and the organ converted into a solid mass com- posed of tissue which resembles neuroglia and contains few or no rouVe'j:™^.'' irlrX'rluiirconcerning the posterior lobe are given in connection with the brain (page 1130). .W>ll III - cell-mass. In ^nsiderat.on of this association a.u the constant presence of the distinctive chromaffine cells it is highly probable tl^ the aortic b.^ies .ire to l,e regarded, along with the medullary portion of he suprarenal and the carotid Ixnlies, as appendages or paraganglia of the sympathetic. ' Verhaiidluniten der Anatom. Hesellschaft, 1901. RAR- Aortic IwdlM of new-born child : KAB LAB. right >nd Icfl aortic bodlcn ; a. aorta . im. inferior "!'"«"- liric artery : hi. left common iliac ; ir. inferior cava ; /,T, left renal vein ; a(. aortic nympatheUc pleius ; n, ureter. ■ l. (^«r><-i*.i»rf/.l THE ORGANS OF RESPIRATION. This tract includes the organs by which an interchange of gases ^kcs pla^ between the blood and the air. It consists of ihUarynx, the Ir^ira «r *;ndp'^. ^d it* subdivisions, the Sronchi, the /««^* and the serov* ^•^•"branes the/^r«r^. which surround them. Morphologically thb tract is an outgrowth from the fore- L 4he l^nx is a specialized apparatus for the production of the vo.ce situated S^tiie beginning of the windpipe, of sufficient importance to be consulered by itself. THE LARYNX. The larynx consists of a number of cartiUges which, by their relative changes of ix«"tion modify the approximation and tension of two folds of "lucous mem- biJSrrer'fiKs tissue, known as the vocal cords, on either side of the cleft through S ^he air enters the windpipe. The larynx is in the neck, being suspended from The toid tone an^l^ding to the trachea. It is practically subcutaneous in front. Its upe^or orifice fs tehind the base of the tongue, and can be seen in life only by a m.iror The artilatres are connected by joints and ligaments, moved by muscles and covered Jy mSS^membrane, the foldVof which iorm important morphological parts ..f the '*^"''' THE CARTILAGES. JOINTS. AND LIGAMENTS. The cartilages which form the framework of the h^nx are three single ones : the cricoid \Sy^id. ^nd the. pigMiis; and three pairs: tht apifn<»dcarMa,res,thecor. ZtX/a^^is or cartilages 0/ Santorim, and the cunfi/cm, cartilages or those of W^J^rrL^^V^^^'"^^^^ determining well-defined swellings of the mucous S^ne are very small : indeed, the cartilage is not always to be found There are othTr Sr^^te of cartilage to be mentioned with the structures m which they ocaar The StiS the upper part of the cartilages of Santonni, those of Wnsherg, and the endLonh? vS and apical^proces-ses of the arytenoids consist of elastic cartilage the ^th^« h^ni^of h^ine cartilage. The cricoid and arytenoid cartilages are derivations Sht^rachea a'S reprSnnhe more primitive form of larynx. The thyroid and the cp£ott1s"pp^ar in mammals. In monotremes the epiglottis is of hyaUne cartilage. P* The Cricoid Cartilage—This is the foundation of the larynx, being a nng on tl« top o the trachea. It is nearly circular, the diameter m the male being .9 mm (Lu^hka). It is narrow in front, being from J-H mm., usually alx.at .s mm. broad, and some four or five times as much behind. The height at the back is approxi- mately 25 mm. in the ni >!•• and from 16-23 mm in the female. The cricoid is 3 or 4 mm. thick in the lower part and in the upper as much as 5 or 6 mm. The posterior aspect is somewhat quaJrilateral, the upper lx>rder de- scending very steeply at the sides. Internally the cricoid is perfectlv smooth. The lower border presents a slight median descent in front Fio. 15.18. Articular face* (or nrylelioid cartilaiT Atticxlar fai-rt for thyroid cirtilaRt fricoid cartilanc, i^lhl lateral a«p«' t t8i4 HUMAN ANATOMY. Fio. ■S39. Cartilage of Santori PoAterior surface for arytclioideus Potterior crico- arytenoid ligament Muscular proc Posterior ridge oa cricoid cartilage Depression for crico-arytcnoideua posticus Cricoid and ar>'tenoid cartilaees from behind. extremely variable in all its details. A median ridge divides the posterior surface u\ the cricoid cartilage into two symmetrical depressions for the origin of the jX)sterior crico-arytenoid muscles. Each loUercl surface of the cricoid, below the middle, and nearer the back than the front, bears an oval articular facet for the crico-thyroid joint, its long diameter extending upward, backward, and inward. The facet, which is nearly plane, faces chiefly outward, but also somewhat upward and a littie backward. The long diameter b about 5 mm. and the cress one nearly as great. A ridge connecting it with the superior articular facet bounds the posterior sur- face of the cartilage. The anterior surface of the cricoid b somewhat convex vertically, si' as to resemble an over-large tracheal ring. The Thyroid Cartilage. — Thb, tht shield-shaped cartilage, consbts of two quadri- lateral plates, the alie, broader than high, which meet in front and are widely apart behind. The posterior border of each is prolonged upward and downward into two horns, or comua, some- what flattened from side to side. The lower pair rest on the inferior articular facets of the cricoid and the upper are attached by ligaments to the ....... • ends of the greater horns of the hyoid bone. Being thus open behind, the thyroid cartilage b complementary to the cricoid upon which it rests. The thyroid notch (indsura thyroldea) b a deep median depression of the upper border in front, extend- ing nearly or quite half-way down. The plates are strongly everted (especially m the male) at the sides of the notch, thus causing most of the prominence known as Adam's apple (protuberanUa laryngea). The resulting median ridge ends shortly below the notch, and at the lower border the front of the thyroid is smooth and convex. The upper border b slightly convex on either side, and usually presents a small notch just in front of the root of each superior horn. The superior tubercle is a little prominence on the outer surface, just below and anterior to this notch. The lower border b alternately convex and concave. There is a moderate median con- vexity followed by a hollow, external to which b a marked prominence, the inferior tubercle, between which and the inferior horn is a deep notch. The posterior border is dightly concave in the middle. The oblique line is a ridge running downward and forward from the upper tubercle to the lower. It marks the intemiption of the mus- cular layer out «)f which the sterno- thyroid and the thyro-hyoid mus- cles ari.se. The inferior constrictor of the pharynx is inserted behind it. The superior horns, usually longer and more flexible than the inferior, run upward, backward, and inward. They become more cylindrical and have blunt rounded ends. The in- ferior horns, liroader than thick, run downwarii and slightly inward, with a turn forward at the ends. In- ternally each presents near the tip a round articular surface of indefi- nite .shajK- for lh«- inferior articular surface of i.ie cricoid. The dimensions of the alae vary w ith the sex : in man the height is >,o mm. and the breadth 38 mm. ; in woman, 2^ and 28 mm respectively The prominence and sharpness of the angle are male characteristics, in man the avcrt^n- lH.ing i)o° and in woman 120°. It b chiefly through the thyroid cartil ige that the male larynx acquires its relatively large size. -Epiglottis Ohlique line, end- ing in tHl»erclei* ;ilM)ve and below Infvrior coniu - Thyroid cartilagi' with ipiKloitis. riKhi aiilero-Uteral aspeit THE LARYNX. iftiS C Wirchildhood ; subsequently it becomes less and less du^tmct. V.rUtl««..-U is not rare to find a foramen "-/ »he .jpper outer an^^^^^^^^^^^^ superior tubercle, which transmits fh^.'J^P^^VneTve^ A^^mTnrtharth^^ developed of the external branch of the superior '-'Onueal n"^. ^^^^^'^^"h^and fifth branchial bars, ft is as above stated, the foramen represents a ^«" ^'r, Th ,n tte Xr and not verv rare for one to ra^n^S;:? e1^^e:;'n^r:!tL%L^ror ?sTnt^^^^^^ the absence more common on the left side. and is nearly plane, but either par- ticipant of the joint may be the contained one. The capsule is lax, although somewhat strength- ened by two by no means con- stant ligamentous bands. An an- terior one extends downward and forward from the front of the lower horn ; a posterior one ex- tends upward and hac'-.ward from the back of the same. The motion fa usually described as rotation on a transverse axis passing through both joints, but in fact a great deal of irregular sliding is possible. The crico-thyroid mem- brane, although connecting the cartil^es in front, has no direct attachment to the thyroid at the sides, and consists of a central anterior and a lateral part. The anterior part, a\so known as the conoid ligament, is triangular in shape, with its base attached to the upper edge of the cricoid car- tilage and its tnincatetl aijc.x to the lower border of the thyroid. Fig. I54'- EpiRMti* Ar>t<*>o>eco.nc-s directly blende.l tached. The upper l«.rder of this V'^^^f.^^^J^^Z^^^^^ „,^. Uuter being practically and continuous with tlic inferior \»^y;°;!^y X iri^ h^^ *»"'^'' '" '^'^ the thickened and free superior '^^'l^'^ '"' '^'^..^^'^.^^J^.S cord. The lateral crico- sense, becomes the sup,M.rting framework or the t^^ ^^ ^^_^_, ^^^ Slir^;:f';;^S-r'^r^:^cSthe l^ter^, covered by the laryngeal mucous mcinbrane. „,mhrane is one continuous sheet of fibrous I8i6 HUMAN ANATOMY. Criitt arcoat*. Aitkabir ikcci Articular facci A, antero- rior horns of the thyroid and the tips of the greater horns of the hyoid. They may be artificially dissected to resemble cords (ligamcnta thyreohyoldea lateralta), although in faa they are continuous, not only with the rest of the membrane, but with its expansion which mingles with the fascise of the neck. As a rule, a little nodule {eoriilago triticea) is tound in the middle of this lateral thickening (Fig. 1 541). .^ cording to Gegenbeur, it is the remnant of a closer connection between the third md fourth branchial bars. The more membranous part of the ligament extends from the superior border and the inner side of the superior horns of the thyroid to the upper border of the body of the hyoid and its greater horn. A bursa, extending under the body of the hyoid, lies on the anterior surface of this membrane, which is denser beneath it , , .. . The Arytenoid CartiUge*.— These are a pair of very irregular four-sided pyramids (one side being the base) perched on the superior articular facets of the cricoid. The vocal cords extend between them and the entering angle of the thyroid. Besides the base, there is ?i posterior, an internal, and an antero-extemal surface, sep- arated by tolerably distinct borders. A section near the base is semilunar, the bound- ary between the posterior and internal surfaces being effaced. The two remaining angles are each prolonged (F«. 1542). The anterior, extending forward as the vocal process for the attachment Fio. 1543. of the true vocal cord, is •^ * long and slender ; the ex- ternal or muscular process, short and thick, projects out- ward and backward. The base is chiefly occupied by an oval articular cavity rest- ing on that of the cricoid. The long axis of this articu- lar facet, which does not much surpass its transverse one, extends in the main for- ward, crossing that of the opposed facet. The concavity is nearly at right angles to the long axis. The posterior surface is well defined and deeply concave, bein^ filled by the arytenoid muscle. The internal surface is nearly plane, offering nothing for description. The antero-extemal surface is triangular. A ridge, the crista arcuata, sUrts from the vocal process and runs backward and upward, ultimately describing nearly a circle around a hollow, the foi'ea triangularis, which is quite as often oval. This litde hollow is filled by a mass of glands, and is overlooked unless the cartilage be cleaned very carehilly. The false vocal cord is attached to a little tubercle on this ridge either above or behind the fovea. The borders meet above at a blunt apex. The Crico-Arytenoid Joint. — From the foregoing description of the two opposed articular surfaces it is evident that in consequ»?nce of the crossing of their long axes the whole of one is not in contact with the whole of the other. The joint is surrounded by a lax capsule, strengthened behind by straight vertical fibres, which have been calleed plate of ela.stic cartilage which, inserted by its stalk into the angle of the thyroid, rises above the hyoid bone and guards the entranre into the larynx. The length is some 3. 5 cm. The epiglottis expands trans- versely and uiiris forward over the root of the tongue. Its posterior surface is entirely free, but less th;m the upper half of the anterior surface is exiiosed. Begin- ning at the free border, which is bent forward towards the tongue, the posterior surface is convex, slightly concave, and finally convex again, owing to a prominence, calletl the tubercle, which its root forms in the larynx. The free edge is rounded transversely and the jxwterior surface in the main concave across. The st.nlk, when well develcipetl, is triangtilar on section, fitting into the angle of the thyroid. The Richt ar>'tenaid cactllaiK. capped by caftila|c of Santorini. lateral aapcct ; B, paatefo-aiadlal aapcct. x |. THE LARYNX. 1817 DeprtMioitK lor glumls -a.«n™.« stroma is lull of pits, or even perforations, conuining glands. The 2Sn^Sr« atSed t^ it very closeir- that in dissecting the cartilage .t in that direction. It is continuous with the septum of tne '**"^7» hrh""' I8l8 HUMAN ANATOMY. The inferior thyro-arytenoid ligaments (liKamenta vocalla) are a pair of bands of tibrous tissue, chiefly elastic, supporting the free edges of the true votal cords, extending from the angle of the thyroid a little below the false ones to tho vocal processes of the arytenoids. These ligaments are continuous with the lateral parts of the crico-thyroid membrane, as the thickened and modified upper Ixirdirs of which they may be regarded (Fig. 1544). Each band is triangular on section. having the free edge at that of the Fio. 1544. . -. Kpiglottis, bent forward Thyroid cartilajec left ala Superior coniu. 01 thyroid car* tilagc cord. There may be a mmi'tc nodule of cartilage in the ligament just in front of its {wsterior attach- ment. Anicu'ar facet fur inferior thyroid coniu Riirht thyroid ala (cut) Lateral |iart of crico-lh>rold mem- rane attached to vucal process Afedian mrt of crico- thyroid membrane .Cricoid cartilage Trachea Ouification of the L4U]mx. — The proces.s, befnnninK as it does at ab«>ut twenty, is a normal change. Chievitz ' found some iissiticatiun m every male larynx of over twenty and in every fe- maJe one of over twenty-two. it ap- pears at about the same time in tine cricoid and thyroid, — namely, at alxiut the bef^nniuK of the twentieth vear. — and in the arytenoid at about tfie mid- dle of the twenties in man and nearer the thirtitM in woman. r/ie Cricoid. - The first nucleus appears on each side at the l)ack of the facet for the arytenoid, and almost at the same time another appears at its front. These are shortly lollowed b^- one at the joint for the thyroid. These three unite, forming a lateral ossification which spreads across the back. One or more ixjints apfiear in front near the iipix-r border of the arch, which is thus ossified and joins with the sides. After these various unions the entire lower liorder of the cricoid is still cartilaKimitis. The younjtest man otiserved by Chievitz with complete ossification was forty-four and the vouuRest woman seventv-six. 'thf Thyroid.— The prix-ess l)eKins near the posterior inferior an^le and invades the in- ferior honi. It appears next near the lower part of the anterior aiijtle, and these two centres on e.ich side join by spreading alon^ the inferior border. The sti|>«-rior horn then ossifies either by a sejKtrate centre or by extension along the hind Ixjrder. Kinallv a tongue-like process, starting near the inferior tut)ercle. extends upward and forward across the ala to meet the ossi- fication which has spread along the su|)erior Ixirder, leaving More and behind it places which are the last to ossifv. This tongue-like process is i>eculiar to the male ; in the female ossifica- tion advances chiefly from the [josterior f)order. The youngest man with complete ossification of the thyroid w.is fifty and the youngest woman seventy-six. The .IrylfNoids. -The pnK-ess tiegins in the b.xse.' In man the starting-|Miint is the mus- cular nrocess, but in woman it is less certain. The youngest man in whom the process was complete was Sfventy-live ami the vmingt^t woman efghty-five. The larti/ago triUtra. when present, also tends to ossify. Lateral view of larynx after removal of greater part of right thyroid ala. Hhowing attachment of crico-thyruid membrane to ar\teiioid cartilage. The free bt>nicr of the mcmhraue constitutes the tliyrit-arytenoiil ligament and the framework of the vocal cord. Tin: FORM OF TlIK L.'VKYNX AND IT.S MiaH'.S MEMBRANE. The shajie of the laryn.x depends not only on the cartilajjis. but also on folds of miKous membrane stretched over bands of connective tissue .md over muscles. The cavity of the larynx is subdivided into three parts : the SHpragloHic, the glottif. and the infragloitic. The supragiottic region ( vestibulum larynsis) Ix-gins with the entrance to the larynx, an oval (or rather a he.irt -shaped ) plane, which, owing to the height and the iMisition of the larynx, faces nearly backward. It is Ixmnded bv the free Ixirder of the epiglottis in front and by the aryrpif^loltic fold which pa.sses from this on either side hick over the top of the arytenoid cartil.iges, Ft is interniptetl in the meilian line in-hind by a notch. On either side of this the fold presents a sm.ill swelling ( tulK'tddnni corniculatum), caused by the cartilage >;lott.s. and ,lecp "^,'^[^^r'7J' he tubercle. The mucous tnembrane is very closclv attached meeting l^V.tr.nu Im. tlfin k,t he straw coL.r of the cartilage is seen through it. to the epiglottis •'"';*;.'" \'^;';,"'Vhe pits lor the glands in its substance can also TrnKr^ Thetterr:X" thl re^^ion. which^s separate.1 fron. the front by Fio. I54S' ronKUC Cushiiin of cplKli'llis Cuiu'ifinin lutn-Klt TulK-ri li; i>l Saliuiri.ii. HtHrterior .;rii<>-*rslfiH>iil_ miucW I'riiiiiil lartilaRi- Furamcn arcum RiKht fauiial tonsil Mclia« I ,;,,„^„.,„^u,„|, ,,,1,1 l..-iti'ral I Superior !i>oiil lormi Superior thvroiil cormi .SiiiUR pyi> (iloUi* Ph«r>ine»l wall (EM>phaKus mix ous pourhCT rnihratiH' t \ 111 m»KOlt> R-.. itif'talit ,!a. creiso inclines inward, and iK^-conies llu fold of nui.ous tncnbrane k.ioun ^ the Wse^^TuS Farther luck a shallow gr.H.vc, the/*,//r««., nu.s u.n. in. . .r- tJn.:;:!. the tuberdes .;<^-tonni and .. WnsU^g^ |^^;- ^ ^,,,, ,,.. „j . f .1, .i. ..f tin thvroid and the t ivr.)-livoid nunibrane l)etween them. It is llilenul'b^aliro/t^ier' "l^o'g'l'^ passing fron, the thyro-hyoid mem- brane, which it i)eii..rates. to the l;nynx pro|)er. ifiiitJii; .;Jt,\ l820 HUMAN ANATOMY. The glottic region extends from the free edges of the false cords above u< those of the true ones belov The narrowest part of the larynx, the rima glottidis or eki*k of the larynx, is the interval between the true cords in front and the arytenoid Fio. 154& Areolar Macoui mrmbiane covcriiiK cpi(liAtii FiMore bctwetn cmnifaigca of Santorinl Canilan o( epiglotU* tusiw Cattlluc o( Santorini tubtn-le Slenio-hyoid Ttayro-h>oid Sinui pvrlfonnii Suprrior conitt a< hyoid (cnli Siemo-mastoid Prevcitcbnl muscles Founli cervical veitebfB ArytaMMpiclottk ioM (cut) Poatarior wall of pharynx Anterior part of Mctioa acroaa neck at Icrcl of fourth cervical vertebra, pawinc through upper part of (uperior aperture of laryax. cartilages behind. The false vocal cords (plicae ventriculares) are folds of mucous memb-ane continuous with the sides of the supraglottic space. They are attached in front to the inner side of the angle of the thyroid, above its middle, and behind to the antero-e.\temal surface of the arytenoids. They are soft folds of mucous mem- brane containing connective tissue (out di which a skilful dissector can manufacture Fio. IS47- Body of hyoid Imnic Crico-lhvroid. membrane Cricoid cartilage,, anterior arch Traihi Superior hyoid rotenoidi^u5 Glottil Vocal cord Median ugiltal wction ol larvin; riifhl side seen from withiii. I.ar^■nx ha» tv«n partly rut acrrws at 1«t1 Iviween false and true vikhI iurlw vocal cord Vocal cord Vtntricic oi tarynz Arytenoid cartilacc Thyroid cartilage PlO. 1549 ocd u Sterno-hyoi«i Ventricle o( lanT« Buna Thyro-hyoiJ Phar>ns ,Onio-hvoid Stcmcniaatoid Internal' Jupilar vein ,Stcmtd Paettmognitric nerve , Carotid artery ralatu-pliarynsena ^ , . , Prevertehial faicia i \ ThynxrytenoideiM I Inferior pharyn(ea> conilrictor ArytemMdeiu Anterior part o( ^ucn across neck at level o. ..l.e vocal cord. ; on I, ft .Me ventrtel. o. larynx i» ..,«-«•. median cartilaeinou nodule, o. from one for each cord, the disunce between them membrane The^ubstancc- is chiefly muscular tissue from the thyro-^rytenoid. which Fia. 1550. « CH tvn^\M Epiglottlt- Voc»l cord- ArytMH>-«p(clottic Mrf— ' Cunrifbrtn tuhcrilc TulXTtU of Sutorini'— — I »leral yjloiso — Mnlian i{b>-.»i) •l>i|[lu«1tt 6>I>1 l'3l«« voial lortt Vcxal lord Riina ittottiili* X■un«^^«'"■ tul>rrvl« .\ixal [tT'Ktts of SAIlloTtat Interior of Unnx ... »ec„ «i.h larvn^-^ope. A. rim. ,.ottidi, .ideh opr„ : «. rim. .Icttidi, clo«d. J . .u ^,1 r.rn/-.««Ps a Considerable part of the chink of the glottis is Selengrhof £ chink in the male is 23 mm., of which the vocal part is .5.5 .nm. > Archiv f. Anat. u. Phys Anat Abth., 1889. • Uull. de I'Acatl. tie >Kdecir,r. ^ans, 1879. l822 Hl'MAN ANATOMY. and the respiratory 7.5 mm. In the female the lenjith is 17 mm. , and the respectn. parts measure 11.5 mm. and 5.5 mm. The elasticity oJ the voc.il part, however sJlows it to stretch. The shape of the rima Klo«'d«» vanes with the position of tlu arytenoids, and the theoretically straight lines of its borders may both be approxi mated and drawn asunder, and, moreover, may be bent at the juncUon of the tw.. The ventride or laryngeal sinus ( ventriculus lar)n)il») is a pouch, lined with mucous membrane, opening into the laryn.x between the true and false cords of eaili side The horizontal elliptical opening has a breadth (vertically) of from 3-6 mm As has been stoted, the upper surface of the true cord slants downward and outwar.l but the ventricle is partly under cover of the false cord, around which it ascends. The ascent may be due to an appendix of the ventricle (Fig. 1551). which may be an almost separate cavity connected with the front of the ventride by a slit or an irregular Pio. 1551. Glandl FmIrc \ iKal cord Lymph(>i(l tissue Vtxiil cord Thyro-arNlenoiil miuclc Thyroid cartilagr EpIclMtii .jL>inphaid tiasiK Fat ,Glands .Ventricle Point at whicli s<|uaim>us epitlie- liuin ends ,l.ater ;t 1 ICO ar>i -ty.id ni iscle CMcoid cani'an* . Fronul section ol lar>-nx. abont middle ol vocal cords. X3. opening. Not rarely, however, it is ■ ithout separation from the rest of the ventricle. It may a.scend to a height of 15 mm. irom the bottom of the ventricle. These cavi- ties are compressed laterally, and situated in the thickness of the wall of the arynx proper, internal to the fossa pyriformis. According to Rudinger, the ventricle? arc relatively much larger in the male. Occasionally cases of great over-development ot the ventricles are met with. They may even periorate the thyro-hyoid membr.we. This is analogous to the sacs of the anthropoid apes. Brosike' has seen a median pouch perforating the thyroid in the region of the vocal cords. A similar structure occurs in the horse, ass, and mule. The function of the true cords is to change the size and shape of the glottis both during respiration and phonation, and to cause sound by their vibrations, which depend in part on their tension. When drawn into ' Virchow's Archiv, Bd. xcviii., 1884. THE LARYNX. i>>^ region, which is broadest between them. . j^ , ,^,^„„, Fio. i55»- Glands Vortl corJs Thyro-arytenoid Ventricle Fibres o{ Ihvro- :ir\'tenoid perhal* ;^. ins»-rt«nl liilo votal ' Tj. proccMi 1 jiteral crico- arytciiui«l carlilage .CricoW cartila«« Fronul »«llon of lar>-nx IhrouRh vocal proc««« of arytenoid crtll.f«. X 3. grrniins of serous elements. ... . , 11., „Uc--,.«r) ,,n the D" >•*'»'<■''>'■ ^'\ymphmd tissue, as distinct .u.Uul« is occasiomdly observed .m tne p-^_. 1834 HUMAN ANATOMY. surface of the epiglottis and the side and back walls of the larynx, its most usual position being the ventricle (Fig. 1551). Within the laryngeal pouch the lymphoid tissue is so constant and plentiful that laryngeal tonsil has been suggested (Fraenkel) as an appropriate name for these collections. THE MUSCLES OF THE LARYNX. The extrinsic muscles of the larynx should include those going to the hyoid bone, which is physiologically a part of this apparatus. These have been described in the systematic consideration of the Muscular System (page 543). The intrinsic muscles are the crico-thyroid, t\ie posterior crico-arytenoid, the lateral crico-arytenoid, the thyro- arytenoid, and the arytenoid. All of these, except the last, are in pairs. From a physiological stand-point these muscles may be divided into three groups : the con- strictors, including both the adductors of the cords and those which draw together the supraglottic portion of the larynx ; the dilators, which abduct the cords ; and those which modify the tension of the cords without necessarily approaching or separating them. The constrictors are the lateral crico-arytenoids, the thyro-arytenoids, and the arytenoid. The dilators are the posterior crico-arytenoids. Those modifying the tension of the cords are the i:rico-thyroids, which stretch them, and a part o' the thyro-arytenoids, which relax Fio. 1553. them. Moreover, many of these muscles, even antagonistic ones, when acting together may be con- sidered as parts of a sphincter. The laryngeal muscles are ex- tremely variable, especially the thyro-arytenoid, detached fibres of which have been described as the thyro-epiglottideus. The cnco-thyroid muscle (Fig. 1 5 10) is well defined, pass- ing upward and outward from the anterior ring of the cricoid to the under border and the inferior horns of the thyroid. The origin is from the whole of the anterior surface of the arch, except for a slight interval between the mus- cles. The internal fibres are nearly vertical and the lateral ones nearly horizontal. The insertion is into the lower border of the thyroid cartilage from a point a few milli- metres in front of the inferior tubercle to all the rest of the lower border and the front of the inferior horn. It often extends a little onto the posterior surface of the ala. The muscle is frequently divided into a superficial and a deep part. The distinction may be very striking, and also not to be seen. The superficial is the more internal vertical f)art, which conceals a little of the origin of the deeper. The crico-thyroid may be continuous by some fibres with the inferior constrictor of the pharynx. It may descend to the first ring of the trachea, and it may give off fibres to the capsule of the thyroid body. Occasionally the muscles of the two sides are connected at the lower border of the cricoid. In extre. ;e cases each may cross the median line. Action. — This muscle is a tensor of the vocal cords by. separating their points of attachment on the thyroid cartilage from those on the arytenoids. Although the conventional names of origin and insertion have been used, the more movable of the two cartilages is the cricoid, and the action of the muscles is to raise its anterior arch, thereby tipping the posterior plate with the arytenoids backward, and so stretching the cords. While the thyroid can he held fixed by manv muscles, tht only extrinsic one .attached to the cricoid is a part of the inferior constrictor of the pharynx, so that CartilaKotriticca- Thyro-hyoid- membrane Ar> t-pislotticus Arytetioideus, oblique portion ArytenoideUB,- transverse por- tion Crico-' arytenoideus posticus Epiglottis, dorsal surface Superior comu of llyoid bone Superior thyroid cornu 'uneifurm tubercle 'artilaffe of Santurini Posterior marjciii of thyroid car- tilage Inferior thyroid comu ricojd cartilage .Trachea Muscles of larynx from behind. m THE LARYNX. 1835 upon the cricoid cartilage devolves the whole, or nearly the whole of the movement. Although the movement is generally described as rotation on a transverse axis pass- ing through the two cricothyroid joints, the articulation is of so vague a character that a great deal of sliding occurs. The posterior crico-arytenoid muscle (Fig. 1554) »* very distmct and occupies the hollow on either side of the median ridge on the back of the cricoid cartil^e It is triangular, with rounded angles at the base, which is at the ridge, and the third sh^p angle at the posterior border and upper aspect of the muscular process of the arytenoid. The origin is not from the whole of the fossa on the cri- coid, but chiefly from the region of the ridge whence it springs by tendinous fibres. It arises also from the lower part of the cricoid, but not from the part near the arytenoid. It passes over the capsule of the joint, with which it is intimately fused, and is inserted as above stated, some of its fibres becoming tendinous. Action.— It pulls the muscular process downward and inward, thus raising and everting the vocal process and conseqn .lUy enlarging the cleft of the glottis. Two occasional small muscles in the neighborhood of the inferior horn of the thyroid are orobabtv aberrant bundles of the posterior crico-arytenoid. One, the poslertorcrtco-Myroia, SSKiverSr^ from the lower eitemal fibres, runs from the back of the cncoid upward and oitwafd to^ interna! aspect of the inferior horn of the thyroid. The other, the postertor th}fro- fl^/^W. runs from the liwer horn upward to be inserted with the posterior cnco-arytenoid mto the muscular process. The lateral crico-arytenoid muscle (Fig. 1554), of an elongated triangular form, arises from the upper border of the lateral part of the cricoid and froni the ascending edge of the plate as tar as the arytenoid joint. It also may have fibres springing from the cnco-thyroid membrane. \x 'ts, inserted xtAq i>c\t Fio. 1554. front of the muscular process. This muscle is less well defined than the posterior crico-thyroid, and may be more or less fused with the thyro-arytenoid, on the one hand, and the crico-thyroid, on the other. Action. — It pulls the muscular process forward, thereby bringing the vocal cord nearer to its fellow. The thyro-arytenoid mus- cle (Fig. 1554) arises from the inner suriace of the thyroid, just outside the entering angle, from the level of the true cord to the lower border. At the side it arises from a part of the crico-thyroid membrane, and may there be con- tinuous with the lateral crico-ary- tenoid. It runs backward and is inserted into the upper surface of the vocal process of the arytenoid and into the antero-external sur- . , . , , . 1 ... face of that cartilage. It is convenient to speak of an internal and an external p;irt. but there is no separation between them. The internal portion (m. tbyreoarjtae- noideus vocalis) is a prismatic ma.ss, triangular on sect .on (Fig. 1551). forming the bulk of the true cord, with one of its angles against the ligament m the free edge. I.udwig taught that fibres diverged from the body of this muscle to be inserted suc- cessively into the ligamentous band of the vocd cord, which thus resembled the tendon of a muscle receiving oblique fibres along its side. These were supposed to modify its tension indefinitely by pulling upon it at various points. This view' has been denied by Luschka. and the point remains undecided. Jacobson found on 'Archivf, mikro. Anat., Bd. xxix., 1887. ii5 Suiierior thyroid comu Aoepiglouicus _ An-tenoideus Criro-arj1enoideiis lateralis Crico.ar>1enoid»ii» posticus Cricoid carlilagv .L.ar>-nKcal t>ou€-h RiRht thyroid ala (cut) Thyro-arytciioidcus extern lis .Crico-lhyroideua (cnti Tr«ch«a Muscles of larynx lateral view alter |iartial removal of right thyroid ala. 1826 HUMAN ANATOMY. Body of hyoid bone (cut) Epif;loltis Mass of fat microscopic sections that fibres were often inserted obliquely into the cord and into the end of the vocal process. There was, however, much variation, and in some cases no such fibres were found. Our own observations incline us to look upon such fibres as possible, but probably in the ordinary larynx they are few and far between. The external portion (Fig. 1554) is a thin membrane on the outer side of the ven- tricle, with its fibres spreading upward and backward towards the aryepiglottic fold. Some few fibres are, or may be, found in the false cord, and some occasionally arch over the ventricle. The external portion is very irregular and inclined to give off aberrant bundles. The superior thyro-arytenoid is a common one. It arises from the inner side of the ala of the thyroid, near the top, a little outside of the notch, and runs downward and backward to the top and .t terior aspect of the vocal process, resting on the outer side of the external part > the thyro-arytenoid and crossing it at right angles. It consists of long parallel .bres and varies much in size. Tht thyro-epiglottic muscle is simply fibres of th< -.ystem of the thyro-arytenoid that pass upward to the side of the epiglottis. We incline to consider the aryepiglol'-' muscle (Pig. 1554) — a little L^ndle ex- tending from the side of the arytenoid to thf epiglottis in the edge of the fold — a part of this same system. Action. — That of the in- ternal part of the thyro-aryte- noid is to relax the vocal cords by approximating their ends ; if, however, the fibres inserted into the cords be worth consid- ering, this action must be modi- fied by the stretching of parts of the cords while others are relaxed. The irregularity of this arrangement is quite in har- mony with the endless variations of the human voice. The shape of the walls below the true cords must also be modified by the swelling of the contracting mus- cle. The action of the outer portion of this muscle must be in the main that of a constrictor of the supraglottic region. It is possible that when the cords are abducted some of the fibres inserted into the muscular processes may act as adductors. The arytenoid muscle (m. interarjtaenoideus) is a mass of fibres running trans- versely between the hollows on the posterior surfaces of the arytenoid cartilages, which it fills (Fig. 1553). There is usually a superficial oblique part of this muscle which, when well developed, is formed by two bands crossing each other like the arms of an X placed on its side. Each arm starts from the muscular process of the arytenoid and crosses to the summit of the arytenoid of the opposite side. Here it may end or be continuous with the fibres of the aryepiglottic muscle, which ascend to the epiglottis. One or both arms may be wanting, and this part may be more or less fused with the deeper transverse fibres. Action. — It draws the arytenoid cartilages together, and is, moreover, an im- portant part of the sphincter-like arrangement. Vessels. — The arteries are the superior laryngeal and the crico-thyroid from the superior thyroid artery and the inferior laryngeal from the inferior thyroid artery, he superior laryngeal pierces the thyro-hyoid membrane some 5 mm. from the superior horn of the thyroid and about midway lx;tween the top and the bottom. After givir- of! an epiglottic branch, which on its way supplies the areolar tissue anterior to the epiglottis, the vessel runs downward and backward under cover of the ala of the thyroid to its distril^ution in the upper part of the larynx. The crico- False vocal cord Thyroid cartilage. True vocal cord Thyro-arytenoideus. intemus Crtco-thyroidens Anterior arch of cricoid cartilage Tracheal cartilages Greater hyotd coniu Superior thyroid cornu Ventricle of larynx Arytenoid cartilage Crico-arytenoideus lateralis ■Posterior arch of cricoid cartilage Line of cut mucosa Sagittal section of larynx from within ; mucous membrane has been removed from vocal cord to lower level of cricoid cartilage. THK LARYNX. 1827 Fio. 1556. thyroid branch meets its fellow so xs to form an arch across the median line and sends (leriorating branches into the larynx through the crico-thyroid membrane. The inferior laryngeal from the inferior thyroid reaches the region of the Iwck of the larynx from the side. It anastomoses with the su|H?rior laryngeal and sometimes sends branches through or into the arytenoid muscle. The vocal cords |x)sse89 relatively few blood-vessels. The veins correspond in the main to the arteries, but, owing to their greater size and freer anastomoses, they seem in more immediate relation with thosi- < if the thyroid body. Moreover, they tend to form a median descending vessel in the front of the neck. There is a plexus on the pharyngeal side of the biick of the larynx which communicates through the folds at the sides of the entrance with the veins of the dorsum of the tongue. The inferior laryngeal vein empties into the inferior thyroid through a circular plexus around the entrance of the trachea. The lymphatics of each side empty into two chief ves.sels, of which the superior pierces the thyro hyoid membrane, carrying the lymph from the supraglottic region to the nodes under or near the stemo-mastoid. The inferior vessel descends under the mucous membrane outward and backward to the ntKles along the posterior sur- face of the trachea. It may, however, open into an inconstant node in front of the crico-thyroid membrane. This node occurs in 44 per cent, of adults and in 57 per cent, of children. It may be double.' Nerves. — ^These are the superior and the inferior laryngeal nerves, both from the vagus. The sujiericr, on reaching the thyro-hyoid membrane, divides into an exter- nal and an internal branch. The external continues down- ward and forward to the crico-thyroid muscle, which it supplies. It is in relation with the pharyngeal plexus and the superior sympiathetic ganglion. The internal branch pierces the membrane together with the superior laryngeal artery, and supplies the greater part of the mucous mem- brane. Its ramifications are in two groups : ascending ones to the epiglottis, the region just before it, and to the aryepiglottic folds ; others passing to the mucous mem- brane within the larynx and to that of the posterior surface looking towards the pharynx. The inferior laryngeal, as- cending by the side of the back of the trachea, divides into two branches. The branch nearer the median line inner- vates the posterior crico-arytenoid and the arytenoid mus- cles. Its fibres, in j)art sensory, enter into communication with those of the superior laryngeal. The other branch of the inferior laryngeal goes to the other intrinsic muscles of the pharynx. Thus the superior laryngeal divides into a motor branch that ends in one muscle, and a sensory division which plays the greater part in supplying the mucous membrane. The inferior laryngeal is also a mixed nerve, but chiefly motor. It supplies all the other muscles and helps to sup- ply the mucous membrane. A remarkable peculiarity of the sensory nerves is a tendency to cross the median line, so that certain regions are reached from both sides. The general teaching by English anatomists has been that the superior laryngeal is as above stated and that the inferior is purely motor. Exner ' made obser\ations, in jjart confirmed and in part disputed, to the effect th?i both nerves are mixed, supplying both muscles and mucous membrane (the superior supplying, in part at least, certain muscles within the larv-nx), and that both motor and sensory fibres cross the median line, so that some muscles receive the corresjjonding nerve of l)oth sides. Moreover, he found in some animals a middle laryngeal nerve from the pharyngeal branch of the vagus, of which the analogue exists in man, in whom it goes, together with the superior laryngeal, to the cricothyroid muscle of both side's. ' Nicolas in Poirier's Trait<5 d'Anatomie Humaine. ' Vienna AkRd. SitrtmRxN-richf, iS-S.}. VrsUbule !'alse vcxral cord Ventricle .Vocal cord Trachea Cast c»( cavity of larynx and •d)acenl part of trachea ; anterior aspect. mm 1828 HUMAN ANATOMY. In the above description we coincide with Onodi,' who denies entirely the existence of the middle laryngeal in man. The endings of the numerous sensory nerves in the mucous membrane, as def "ribed by Retzius, Fusari, Ploschko, and others, include free terminations between th' epithelial cells and subepithelial end-arborizations. According to Ploschko, special end-organs, composed of columnar cells surrounded by delicate nerve-fibrilla;, exist within the true vocal cords. Taste-buds occur not only on the posterior sur- face of the epiglottis, but also within the laryngeal mucous membrane in the vicinity of the ary^moid cartilages. Position and Relations of the Larynx. — ^The larynx forms a part of the anterior wall of the pharynx and rests, therefore, against its posterior widl. In the adult male the tip of the epiglottis is opposite the lower border of the third cervical vertebra and the lower end of the cricoid opposite some part of the seventh vertebra. Thus in man it covers about four vertebral bodies, with the intervening disks. It is small in the female and rather higher. Mehriert ' believes that in the living body in the upright position the cricoid is about one vertebra lower than it is after death in the recumbent position. Individual variation is marked, as is shown by the results compiled from the researches of Taguki.' Thus in thirty-five men the lower border of the cricoid was opposite or below the seventh vertebra twenty-nine times, but in thirty-three women only twenty-one times. It was above it six times in men and twelve times in women ; in one case (male) it was as high as the fifth vertebra. Anteriorly the larynx lies beneath the middle layer of the cervical fascia. The lobes of the thyroid rest on either side against the cricoid and thyroid. The larynx as a whole can be raised and depressed by muscles, and changes its position with the movements of the spine. Thus, when the neck is bent, it falls i cm, , and rises 3 cm. when the neck is extended. When the head is turned to one side, the hyoid is twisted less than the head, but more than the larynx, although the latter and the trachea may share in the movement. The larynx may be displaced sideways by external pressure. Changes with Age and Sexual Differences. — At birth the larynx is very small, but may be said to be relatively larger than later. The sharp angle of the thy- roid cartilage is entirely wanting. The larynx grows gradually up to puberty, when it takes on a sudden expansion, which occurs in both sexes, but is much more marked in the male. According to Luschka, it doubles in man and increases by less than half in woman. The most marked sexual difference is the size and prominence of the thyroid cartilage in the male. The duration of the process by which the larynx of a child changes into that of an adult may, according to F. Merkel, be as much as two years, and, in fact, changes may occur throughout growth. In the foetus the position of the larynx is very high. At birth the lower border of the cricoid is oppo- site the lower border of the fourth vertebra. Symington found it at six years at the lower border of the fifth and a* thirteen at the top of the seventh. Probably it reaches what may be called its permanent position at about puberty. Mehnert, however, finds from his observations on the living that the descent continues till about thirty, when there is a great retardation, or even a suspension, of the process till about sixty, when it goes on again with renewed activity. According to him, the cricoid n>ay ultimately reach the second or even the third thoracic vertebra. It is to be noted that, while the earlier descent is a physiological process, that of old age is a degenerative one, depending in part on changes in the spine and on the loss of elasticity of the tissues. PRACTICAL CONSIDER.\TIONS : THE LARYNX. The Air-Passages. — The Avoid done is closely contiguous to the opening of the larynx, and as its injuries derive their chief surgical importance from that rela- tion, they are considered here. Fracture of 'he hyoid results from compression by the gr.isp of a hand, by the rope in cases of inging, or from a direct blow. It usually occurs near the junction of the greater C' rnu with the body of the bone. Displacement is not apt to be ' Die Anatomie und Physiolojtie der Kehlkopfnerven, Berlin, 1902. ' Ueber topograpliLsche Altersvcraiiderungeii des Atniungsapparates, 1901. • Arcliiv f. Anat. u. Phys., Anat. Abth., 1889. PRACTICA!- CONSIDERATIONS. THK LARYNX. I8i9 marked, because the great horn is held above by the digastric aponeurosis and thi- hyo-glossus muscle and below by the thyro-hyoid ligament and muscle. Kxcep- tionally the middle constrictor of the pharynx may draw it somewhat backward and inward. The attachments to the hyoid of the constrictor and of the hyo-glossus and genio-hyo-glossus invariably make deglutition and speech jjainful after this fracture, while the genio-hyoid and digastric, by their contraction, cause pain on opening the mouth, the associated swelling may involve the epiglottic mucous membrane and. spreading thence, give rise to serious dyspnoea. The thyro-hyoid tnembrane, springing from the posterior upper margm of the hyoid bone and attached to the upper border of the thyroid cartilage, has inter|K>sed between its anterior surface and the posterior face of the body of the hyoul a bursa which descends below the lower border of that bone, and when enlarged forms a cystic swelling situated in the median line of the neck, just beneath the hyoid. Thyro-lingual cysts are sometimes found in the same situation. A similar cystic swelling, lined with columnar epithelium and occupying the same region, is referable to the persistence of the foeUl thyro-lingual duct. At the upper end of that duct such a cyst would lie in the mid-line of the tongue between the two genio-hyo-glossi muscles. At the lower end it would lie over the thyroid or the cricoid cartilage. The sinuses formed by the bursting of such cysts, or ongmally by the persistence of jwrtions of the thyro-lingual duct, are obstinate, and, on account of their epithelial lining, must be dissected out completely to secure healing. The lower portion of the thyro-hyoid membrane is covered in the mid-hne by cervical fascia and skin, laterally by the sterno-hyoid and thyro-hyoid muscles. Cut-throat wounds of the neck, especially if suicidal, are apt to pass through this membrane, which is made tense when the head is thrown l>ackward, and, if they are deep, will divide the inferior constrictor, open the pharynx, and possibly wound or sever the epiglottis near its base, first passing through the cellulo-adipose tissue that inter\'enes. If the wound is not immediately beneath the lower border of the hyoid, it may divide the internal branches of the superior laryngeal nerve, leading ultimately to a pneumonia from the inspiration of foreign matter. In infrahyoid pharyngotomv such a transverse wound, hugging the lower edge of the hyoid, gives access to the base of the pharynx and the supraglottideal region. Above the hyoid a cut-throat wound would divide the tongue muscles and enter the mouth. Below the thyroid it would pass through the crico-thyroid membrane and open the larynx. Still lower the trachea would be incised or severed. The great vessels often escape in suicidal wounds, as the usual position of the head in extreme extension increases the projection of the laryngeal apparatus and therefore the depth of the vessels from the surface. One reason for their escape when the air-passages below the glottis are opened may be that the sudden rush of air from the lungs and consequent collapse of the chest-walls deprive the muscles running from the thorax to the humerus of their fixed point of support, and that the arm necessarily drops (Hilton). Death may be caused, however, by hemor- rhage from the superior thvroid or the lingual artery, or even from the crico-thyroid if the blood enters the larynx or trachea ; or may result from suffocation produced by the dropping backward of the tongue after division of the genio-hyoid, hyo- glossus, and genio-hyo-glossus muscles, or by the occlusion of the glottis by a partly divided epiglottis or arytenoid. Fracture of the thvroid or cricoid cartilage may occur from the same causes that produce fracture of the hyoid bone. The thyroid, on account of its greater prom- inence, suffers more frequently. Fractures of the thyroid are seen oftener in males tha in females, because (a) in the former it is relatively more prominent ; (b) the process of ossification — ^which, in common with other hyaline cartilages, it undergoes after adult life has been reached — is more complete in them ; and (f ) males are oftener exposed to violence. The symptoms depend for their gravity chiefly upon the degree of invoh ement of the laryngeal mucous membrane. If that is wounded, bloody expectoration, aphonia, and dyspnoea arc present, and tracheotomy may be urgently indicated. In any event, deglutition is painful. The voice is usually altered, and there is apt to be some ex- ternal deformity. Crepitus may be present, but should be distinguished from the 1830 HUMAN ANATOMY. sound produced by moving the normal larynx laterally, and caused by the friction be- tween the somewhat irregular anterior surface of the vertebral column and the posterior border of the thyroid, the corresponding surface of the cricoid, and the lower part of the pharynx, which move together. This normal crepitus disappears in retropharyn- geal abscess, but persists in retrolaryngeal abscess (Allen ). It should be remembered that the superior cornua of the thyroid are sometimes found separate from the body. The cricoid and, much more rarely, the thyroid and arytenoid cartilages may be the subject of perichondritis secondary to ulceration (typhoidal, cancerous, syphi- litic, or tuberculous) of the interior of the larynx. In the case of the cricoid it is asserted that the condition may result from the pressure of the posterior aspect of the cartilage against the spine in very debilitated subjects, or from the traumatism caused by the frequent passage of an (Esophageal bougie (Pearce Gould). The origin of the inferior constrictor from the cricoid accounts for the pharyngeal s[>asm and dysphagia said to accompany disease of this cartilage (Gibbs). Allen says that the cricoid is elatively more prominent in women than in men, and that it is often the site to which abnormal sensations originating in the pharynx are referred, because in such conditions deglutition is [jainful, and since the cricoid lies at the lower part of the pharynx, its motions determine a greater amount of dbtress than do the corresponding motions at any other p.>rt of the throat. The epiglottis is not infrequently affected by syphilis, and is also, although more rarely, the seat of tuberculous lesions, and may be extensively ulcerated or may become necrotic. The danger of such cases results usually from the accompanying oedema {vide infra), but in rare instances a sloughing and wholly or partially separated epi- glottis may directly occlude the laryngeal aperture. Infection originating in disease of the epiglottis may involve the cellulo-adipose tissue between its base and the thyro-hyoid membrane, giving rise to a thyro-hyoid abscess which may extend towards the mouth and project in the groove between the root of the tongue and the epiglottis. Such an atscess may also follow primary infection of either the tongue or the thyroid. It is very apt to cause adema of the glottis. The condition known by this name may occur in any form of laryngitis, or by extension of inflammation from the mouth, tongue, or pharynx, or as a result of trauma or of wound, scald, or the application of local irritants. It involves the glottis only secondarily. The thin mucous membrane covering the true vocal cords and the arytenoids is so closely applied to them, and the subcutaneous connective tissue is so scanty, that there is no opportunity for much exudation. But in the supraglottidean region the mucosa is thick and the submucosa plentiful, especially over the aryteno-epiglottidean folds, and almost equally so in the ventricles and over the false cords and the posterior surface of the epiglottis. Effusion of serum and swelling are thus favored and, according to their degree, will produce hoarseness, aphonia, dyspnoea, cyanosis, or positive suffocation. In some cases of oedematous laryngitis the swelling affects chiefly the region below the glottis {subglottic oedema) and causes the same symptoms. This is rarer and is attended by less effusion on account of the relatively closer association of the mucosa and the cricoid cartil^e. The mucous glands of the laryn.x which supply the moisture needed in normal phonation are sometimes inflamed as an indirect result of the over-use of the voice, — as in clergymen, costermongers, public speakers, etc. The increased volume of air taken in through the mouth dries up the mucous surface of the larynx, and the effort to compensate for this may result in such irritation of the glands and mucosa as to cause a form of chronic laryngitis, — " clergyman's sore throat." The rima glottidis, — the aperture of the glottis, — the narrowest portion of the air-passages, measures a little less than one inch antero-posteriorly in the adult male. Its transverse diameter at its widest portion is about one-third of an inch. In the male before puberty, and in the female, these measurements are about one-fourth less. They are important in reference to the introduction of instruments and the arrest of foreign bodies (vide infra). The level of the glottis — i.e., of the true vocal cords — is a little above the middle of the anterior margin of the thyroid cartilage. The shape vA the aperture varies. It is linear when a high note is produced in speaking or singing, triangular (with the apex forward, equal sides and a narrow mmmmm PRACTICAL CONSIDERATIONS: THE LARYNX. IS.^I base) during quiet respiration, and diamond- shaped (with the posterior angle cut of!) in forced breathing. As various forms of ulceration (.tuberculous, syphilitic, diphtheritic) may affect the mucous membrane covering the true vocal corik, or the cords themselves, or the structures in their immediate vicinity (( r^pecially the aryteno- epiglottidean and interarytenoid folds and the ventricular bands), and as cicatrization with subsequent contraction of scar tissue may follow, diminution of the calibre of the rima ghttidis (stricture) is not uncommon. Polyps, warty growths, and other benign tumors are found in the vicinity of the vocal cords, and if they cannot be removed by intralaryngeal operation, may neces- sitate thyrotomy. Subglottic tumors are relatively infretjuent. They often spring from the inferior surface of the vocal cords, intraglottic growths from thi free border of the anterior part of the vocal cords, and supraglottic growths from the epiglottis and the aryteno-epiglottic folds (Dclavan). Spasm of the glottis (laryngismus stridulus) may occur, especially in infancy, from reflex irritation, and may cause great dyspncea or may even result fatally. The irritation is conveyed chiefly to the inferior laryngeal nerves through the pneumo- gastrics, if the cause is undigested food ; through the trifacial, if the irritation is asso- ciated with dentition ; or through the spinal accessory, if vertebral disease is present. The different forms of laryngeal paralysis should be studied in connection with the p^ ''">" of phonation. Some of the chief anatomical considerations may lie indie 'oUowing classification, which is, however, necessarily incomplete, as f.".' .'ds the central causes of paralysis — as in bulbar palsy — and those due ' the post-diphtheritic. ^ to direct or indirect involvement of the superior laryngeal nerves. (<. ^ 'ry and thyro-epiglottic — or aryepiglottic— paralysis, characterized by a tendency of food or liquids to enter the larynx, by dysphagia, by immobility of the epiglottis, and by diminished sensation in both the pharyngeal and laryngeal mucous membranes, would suggest especial implication of the internal branch. (*) Crico-thyroid and thyro-arytenoid paralysis, causing loss of tension in the vocal cords, inability to regulate and control the voice, and with evidence of the want of action of the crico-thyroids detected by the finger placed on either side of the crico-thyroid interval externally during phonation ( Agnew), may, in some cases, be referred anatomically to the external branch. 2. Those dite to involvement of the inferior laryngeal nerves. (a) Lateral crico-arytenoid paralysis, causing separation of the vocal cords, with more or less complete aphonia, may be due to implication of the external branch. In many cases there will be evidence of the existence of innominate or aortic aneurism, thyroid or bronchial glandular enlargement, carcinoma of the oesoph- agus, or some other condition competent to produce pressure on the nerve. The paralysis may be unilateral and attended only by hoarseness and partial loss of voice. (3) In posterior crico-arytenoid paralysis (abductor paralysis) the loss oi power in the abductors permits the lateral crico-arytenoid muscles to narrow the glottis into a mere fissure, so that inspiration becomes stridulous and dyspnoea is marked ; the voice is not materially interfered with. The condition may be due to intra- or extralaryngeal growths, or to inflammatory conditions, possibly causing pressure on the inner branch. It may be unilateral and due to aneurism. It should be understood that the relation of these paralyses to the external and internal branches of the superior and inferior laryngeal nerves cannot be demonstrated clinically with definiteness. Pressure on the main trunk of either nc; e, tabes, hysteria, toxsemia, and other central or general causes may produce any of these forms of paralysis. In intubation of t' larynx (employed in some forms of acute stenosis, as in diphtheria or oedematous laryngitis) an irregular cylindrical tube with a fusiform enlargement and an expanded upper extremity — so that it may rest on the ven- tricular bands — is carried into place by an " introducer' ' and is guided by the left forefinger of the surgeon, which is passed over the dorsum of the tongue to the epiglottis and made to recognize the laryngeal opening. Thyrotomy is sometimes done for the removal of intralaryngeal tumors. The incision extends from the thyro-hyoid space to the top of the cricoid cartilage, is mm 1832 HUMAN ANATOMY. directly in the median line, and divides skin, superficial and deep fascia, the iuncli^n of the alse of the thyroid, and the mucous membrane of the larynx. Laryngotomy (through the crico thyroid membrane) may be indicated in adults for impemUng suffocation from any form of obstruction of the glottis. In children the space is too small. A median incision beginning over the thyroid cartilage is r;>Tied to half an inch below the cricoid cartilage. The skin and fascia? having been uivided, the crico-thyroid membrane is exposed between the two cri< o-thy roid muscles, which sometimes require separation. 1 he crico-thyroid arteries ma\ be exception- ally large, and in any event should usually be ligated, although in cases of great emergency that step may be postponed until the membrane has been divitled. This may be done by a transverse incision to minimize the risk of hemorrhage. The nearness of the vocal cords to the opening renders this operation unsuitable to cases in which a tracheotomy tube must be worn for some time. Excision of the larynx, occasionally done for malignant disease, necessitates the separation of the larynx from the sterno-thyroid and thyro-hyoid muscles latemll) , from the inferior constrictor and the hyoid bone above, from the trachea below, and from the pharynx and cesophagus posteriorly. The superior and inferior thyroid arte- ries, or their branches, and the superior and inferior laryngeal nerves will be divided. For landmarks of the neck, see page 554. THE SUBDIVISIONS OF THE THORAX. As the entire respiratory apparatus, with the excepdon of the larynx and a \yaxx of the trachea, is within the thorax, it is advisable to describe the subdivisions of that Fio. ISS7. (EsophaKii^ Innominate arter\ Left iiinominale vein Arch of aorta — Traclie* IV thoracic vertebra .Right pulmonary artery ■ft auricle thagus .Inferior vena cava Sternum Ascendin]; aorta RiKht ventricle Right auricle- t>iaphniKni \ SpiKelian lube Median sagittal smtion of formalin subject ; relative position of mediastinal spaces outlined in red. cavity. The lungs, enveloped in their serous coverings, the pleurae, fill the greater part of the sides of the chest external to planes passing forward from the sides of the ^ep ^HHPVH mmm^F ^^^m^m^ FRACTICAI. CONSIDKRATIONS : THK MKDIASI INIM. ««.v; bodies of the vertebrx to the sides of the stterniiin. The median space iMftweeii tlu- pleurx is called the pmediastinal state, and is subdivided into four |Kirts called medi- astina. The aliove statement of the lateral boundaries of the mediastinal s|>ace is only a general one, for in the middle the mediastinal space expands lieytmd them and in front is ri-stricted by the advance of the pleura- beneath the sternum. The superior mediastinum is that part of the space above a plane passing from the disk lielow the fourth thoracic veaebra to the junction of the first and secontl pieces t>f the sternum. This is occupied by the upper part of the thymus, the arch of the aorta and the vessels rising from it, the innominate veins, and the sujierior vena cava. It is traversed by the trachea and uesophagus, the thoracic duct, the pneumogastric, the phrenic, and the sympathetic ner>'es. Th ■ region below the absterior compartment. The middle mediastinum is occupied by the heart within the peri- cardium. The roots of the lungs are partly in this and in the »u|)eric>r mediastinum. The shallow anterior mediastinum is between the middle one anti the sternum. It contains the lower part of the thymus, a few lymph-nodes, fat, ami areolar tisstue. The posterior mediastinum, between the spine ynd the middle mediiistinum, contains the oesophagus, the aorta, the thoracic duct, the ozygos veins, the pneumogastric and sympathetic nerves PRACTICAL CONSIDERATIONS; THE MEDIASTINIM. Wounds {lenetrating the mediastinum, even when they do not involve the air- passages, may, in consequence of air being drawn into the space by respiratory movements, be followed by general emphysema or by mediastinal emphysema. This condition is not infrequent sdter tracheotomy, the conditions favoring its production being free division of the deep fascia, continued obstruction of the air-passages, and labored inspiration. If there is hemorrhage into the mediastinal space, or if abscess results from infec- tion of a clot, or from extension of tuberculous disea.se of the bronchial glands, or as a sequel of typhoid fever, the anatomical symptoms will be those of pressure ( vide infra). In the presence of a large abscess, pus may perforate the sternum by ero- sion or may find its way out through the little circular openings sometimes found as a result of developmental failuri ixtge i68). It may also be evacuated through an intercostal space or into the trachea or oesophagus. Tumors may be malignant or benign (lymphomata, dermoids, hydatids, fibro- mata), the order of mention being that of their relative frequency. The chief symp- toms are those due to intrathoracic pressure, which is, of course, not uniform, and varies with the origin, extent, and density of the tumor, but in its effects upon the separate structures contained within the mediastinum affords a reasonably accurate basis for an anatomical classification of the clinical phenomena of these growths. 1. Compression of veins, (a; The suf)erior vena cava : cyanosis or lividity of the face ; dilatation of the superficial veins of the neck, face, and head ; oedema of the same region ; epistaxis ; disturbances of vision or amaurosis ; tinnitus aurium or total deafness ; cerebral effusion or hemorrhage ; oedema of one or both arms, {b) The greater azygos vein : dilatation first of the right and later of the left intercostal veins ; oedema of the upper part of the chest-wall ; right-sided hydrothorax with secondary or later effusion into the left pleura (Stengel); pericardial effusion ; medi- astinal effusion, (f) The pulmonary vein : oedema of the lung ; hiemoptysis. 2. Compression of arteries (much rarer than of venous channels), (a) The aorta : inequality in the radial pulses ; engorgement of the left side of the heart ; pulsation of the growth, if it is visible or palpable (as the suprasternal notch or over the sternal ends of the clavicles); pallor ; giddiness ; anginose pains, (b) The pulmonary arter)- : distention of the right heart ; dyspnoea ; ultimately — as a sec- ondary result of the cardiac condition — ascites ; oedema of the lower extremities ; general anasarca. 3. Compression of nerves, (a ) The psieumogastric : irregular heart action with marked rapidity or slowness ; syncofie ; vomiting ; hiccough ; pharyngeal or laryngeal spasm or paralysis ; dysphagia ; spasmodic cough. (*) The inferior laryn- l834 HUMAN ANATOMY. eeal nerve ; posterior crico-arytenoid paralysis with rtridoi and inspiratory dytpnoa ( pajre 1 273). (r) The sympathetic : various disturbances of vision ; irregular pupUs. 4. Compression of the thoracic duct Emaciation ; chylo-thorax ; chylous ascites ; mediastinal effusion of chyle. . . j 5. Compression of the air-passajfes. (a) The trachea: stridor; dyspnaa. (d) The bronchi: feeble breath-sounds; dyspnoea; recess'on of ihc suprasternal and supraclavicular fowa and base of chest ; cough. ( e) The lungs and pleura : dyspncea ; collapse of the lungs ; pleural eflusion. , . u 6. Compression of the heart and pericardium. Displacement of the heart ; peri- cardial effusion ; irregular heart action. 7. Compression of the oesophagus. Dysphagia. _ . 8. Outward pressure upon the walls of the mediastinal space. Widening ot inter- costal spaces ; bulging of the sternum ; increase of the circumference of the chest on •^ "* one side ; weakness or Fio. 153*' Thyroid cmrtilafc absence of vocal fremi- tus ; increased area of transmission of heart- ■ounds. Of course, all of these symptoms are not present in any given case of mediastinal growth, but some of them are sure to be and can be more readily understood if referred to their ana- tomical causes. The phenomena ref- erable to the separate subdivisions of the me- diastinum can be classi- fied only in a very gen- eral way. It may be said, however, that: ( i ) The anterior mediasti- num is the most fre- quent seat of abscess ; that its growths usually begin in the thymus ; and that the chief symp- toms are apt to be those of pressure upon the .su- perior vena cava, inva- sion of the suprasternal fossa, involvement of the cervical glands, bulging or erosion of the ster- num, and dyspnoea. (2) Growths of the poste- rior and middle mediastinum are apt to originate in the lymph-nodes, and the chief symptoms are those of pressure upon the pneumogastric, recurrent laryngeal or sym- pathetic nerves, the greater azygos vein, the oesophagus, and the air-passages. The urgent dyspnoea and troublesome r'^ . are out of all proportion to the physical signs (Osier). THE TRACHEA. The trachea or windpipe (Fig. 1558) is a tube, composed of cartilage and mem- brane, extending from the cricoid cartil^e to a point opposite the disk below the fourth thoracic vertebra, corresponding to the level of the junction of the first and Trachea «nd bronchW Inw, »nlerlor upKt. com bronchus Icft'ipkarbronchuV'di'vidlnlTi'nto'ventrai (o) and doreal (o') branch« itinuatlon of main bronchus ; *, *'. ventral and dorial branch: K, I., rJKht and left bronchus; c, cardiac ■nSHIMi mmm im mmmfi mm mm THK TRACHEA. iHm Tunica pruprU a«».-und pieces ol the sternum, where it divides into the twi> bronchi. The jxjint ol division is usually on the rijjht ol the median line : sonutinies s«j far as to lie behind the ri^ht edj{e of the sternum. The trache; is a cylindrical tube, flattened behind. The convexity is <.ue to the so-calle<' 'ings, ' iiich represent only alH)Ut three-i)iwrter» ol a circle. The lonKth is difficult (•> .cterr ne with accuracy on acctmnt of the eUis- ticity ol the or^an as well a.s of its variaf- .. It nwy be said to be, on the average, Irorn 10.5-12 cm. (4-4^4 i". ) in man and Irom 9-11 cm. (3^j-4'j in. 1 in woman. The isolated trachea can lje stretched and comprcsscil to a surprisim xtent, and even in life the changes are considerable. The aiu«ro-postirior and .u- transverse diameters are not very different, e.xcept iii-.t at the lower end. where the trachea enlarges transversely. It is very plausibly stated by I.ejars' that in life the windpi|ie is more or less constricted by the tonic ctmtraction of its muscles. J'"^- '559- According to him, it grows con- -« Epithelium tinually smaller from alxjvc down- ward. Braune and Stahel' be- lieved that after death it w largest in the middle. We have no doubt whatever that, as a rule, the dead trachea is enlarged transversely at ti.e lower end. Abey* gives the following measurements for the upjier and lower ends : upjier transverse diameter 1 3. 1 mm. , sagittal 16 mm. ; lower transverse diameter 20.7 mm., sagi"^l 19. i mm. The frameworU jI the trachea is so light that its shape may be influencerl by neighbor- ing organs, such as the thyroid body and the arch of the aorta. Structure. — The frame- work of the anterior and lateral walls of the trachea consists of the so-called rings of hyaline car- tilage, which form some three- quarters of a circle. In the great majority of cases there are from sixteen to nineteen rings. It is not rare to find twenty, but very rare to find more. The rings are from 2-5 mm. broad, usually measuring 3 or 4 mm. They are plane externally and convex in- ternally, becoming pointed at the ends. They are very irregular in many respects. Sometimes one end bifurcates, the rings above and below ending prematurely. Occasionally bifurcation of the oppo- site ends of alternate rings is observed. Rarely both ends of the same ring may divide. The first ring, which is broader than the others, is occasionally fused with the cricoid cartilage. A highly elastic fibrous sheath, continuous with the peri- chondrium of the rings, envelops them, connects their posterior ends, and completes the tube. The distance between the rings is less than their eadth, at times only half as much. Involuntary muscular fibres of the treuhtalis muscle lie between the fibrous sheath and the lining mucous membrane. They are in the main disposed transversely, some of them connecting the ends of the rings ; some bundles, however, run longitudinally. ' kevue de Chirurgie. iSgi. ' Archiv f. Anat. u. Phys.. An.it. Abth., 1886. *Der Bronchialbaum der Menschen, u. s. w., i88a Canilaic Perichondrium Fibnnu lunlc ' V— Transverse section o( trachea, ihowinx general arrannement of its wall. X Ho. 1836 HUMAN ANATOMY. muscle A layer of connective tissue, representing a submucosa, separates the cartilage and muscle from the mucous lining of the trachea. The submucosa contains small ^gregations of fat-cells and the tracheal glands. The latter, tubulo-alveolar mucous in type, are most numerous and largest between the rings of cartilage, especially towards the lower end of the trachea. Over the cartilages they are small and often wanting. Their ducts pierce the mucosa to gain the free suiiEace of the latter. The mucous membrane, smooth and atUched with considerable firmness to the underlying tissues, is clothed with stratified ciliated columnar epithelium. Many of the surface cells contain mucus and are of the goblet variety. The stroma of the mucosa is rich in fine elastic fibres, which, in the lower part of the trachea, are con- densed into a distinct elastic lamella separating the mucous membrane from the sub- mucosa. Lymphoid cells are constantly found in the mucosa, in places, particularly around the openings of the ducts of the tracheal glands, being aggregated into small collections which suggest lymph-nodules. Vessels. — ^The arteries, which .ire insiirnificant, are branches of the inferior laryngeal from the inferior thyroid, and tend to form a series of horizontal arches between the rings. They anastomose below with the bronchial arteries and with the internal mammaries Fig. 1560. through the anterior mediastinal twigs. The veins, arranged like the arteries, belong to the system of the inferior laryngeals. They com- municate with those of the oesophagus, with the thyroid ple.\us, and, according to Luschka. with the azygos. The lymphatics, which are very numerous, are also disposed in horizontal curves. Leaving the windpifie at the sides of the membranous portion, they open into small tracheal lymph- nodes and communi- cate with the bronchial nodes also. The nerves are from the pneumogas- tric and sympathetic nerves. Their ultimate distribution, in addition to the supply for the muscular tissue and the walls of the blood-vessels, includes sensory endings within the mucous membrane which, accord- ing to Ploschko, are similar to those of the larynx. The Relations of the Trachea.— The oesophagus, beginning at the lower border of the cricoid cartilage, lies at first behind the trachea, to which it is con- nected by areolar tissue ; but almost at once it is, relatively to the trachea, displaced to the left, to be pushed over again by the arch of the aorta, where this vessel lies on the left of the trachea. The gullet always lies behind the origin of the left bron- chus. Behind the first piece of t'.ie sternum the arch of the aorta passes in front of the trachea, which is placed almost symmetrically in the fork made by the innomi- nate and left carotid arteries. The isthmus of the thyroid crosses usually the second and third rings, its lobes resting on tht sides of the trachea. The inferior thyroid veins constitute a vascular layer before the lower part of the cervical portion of the trachea. The recurrent laryngeal nerves run up at the back of either side of the Cart Ha ice Traniverae section of trachra and tesophaKUS of child, seen from below. THE TRACHEA. 1837 trachea, the left one being the first to reach this position. The inferior laryngeal artery and veins are near them. The relations of the artery and nerve are given with the relations of the thyroid. The remains of the thymus lie in front of the trachea within the thorax. Owing to the forward inclination of the sternum, the trachea is more deeply placed as it descends. A lymph-node or, more frequently, a group of them is constandy found under the bifurcation. Tillaux ' found the dis- tance of the cricoid cartilage above the sternum (in a small series) to range in the male from 4.5-8.5 cm., with an average of 6.5 cm.; and in the female from 5-7.5 cm., with an average of 6.4 cm. This distance, however, may be modified by other factors than the length of the trachea. Growth and Subsequent Changes. — In the infant the trachea measures from 4-5 cm. in length, b^ns at a higher point in the neck, as has been shown for the larynx, and divides at a higher point in the thorax. The level of this division \aries very much in the foetus, but at birth is generally opposite the third thoracic vertebra. The lowest position is opposite the fourth and the range extends over two vertebra. There are comparatively few records of the changes durine childhood.' We have found it opposite the lower part of the fourth thoracic vertebra in a child whose age was estimated at about three. Symington* has found it at the top of the fifth in two children of six and oppo- site the fourth in one of thirteen. In the young adult it is opposite the disk between the fourth and fifth thoracic vertebrjE, which is its normal position, although it is not abnormal for it to be opposite the fifth. I^te in life it descends to the lower border of the fifth and even to the seventh vertebra.' The trachea of the infant appears almost round, the rings forming a relatively larger part, perhaps five-sixths of the periphery. According to several authorities, the transverse diameter much exceeds the sagittal ; but, although we have seen this condition, we are not inclined to agree that it is normal in the infant, unless, perhaps, at the lower end. The size of the transverse section of the trachea is, for many reasons, hard to determine. Merkel ' thinks we may accept the following statement of the diameter of the upper part of the trachea without fear of being much out of the way in particular instances : from six to eighteen months, 5 mm.; from two to three years, 6 mm. ; from four to five, 7 mm.; from five to ten, 8 mm.; from ten to fifteen, lo-u mm. Ossification of the rings begins deadedly later than in the larynx. The earliest appearances of it obser^•ed bv Chievitz were at about forty in man and about sixtj- in woman. His youngest case of complete ossification was at fifty in man and seventy-eight in woman. The deposit is first seen in the upper rings, but not in the first one, the points being irregularly distributed along the borders. They come next in the lower rings, and here at the posterior ends. As the process spreads, there is left a median unossified tract along the trachea, which probably is usually invaded from below. THE BIFURCATION OF THE TRACHEA AND THE ROOTS OF THE LUNGS. The carina trachea (Fig. 1561) is a prominent semilunar ridge running antero- postetiorly across the bottom of the trachea between the origin of the two bronchi. It usually starts from a larger anterior triangular space and ends at a smaller pos- terior one. Heller and v. Schrotter' found the framework of the spur cartilaginous in 56 per cent. , membranous in 33 per cent. , and mixed in 1 1 per cent. The spur, when cartilaginous, is derived in various wajrs : from a tracheal ring, from the first ring of either bronchus, or from a combination of these sources. The height of this ridge, especially when membranous, is difficult to measure, but these authors believe that it may reach 6 mm. According to Luschka, the free edge of the spur is 15 mm. from the apprent lowest point of the windpipe, seen from without. This great distance should m part be accounted for by the interbrmichial ligament, a col- lection of fibres running transversely in the angle between the bronchi. This band is, however, very variable in development and nut constant, so that Luschka' s estimate of the distance is probably excessive for most cases. Heller and v. Schrotter found ' Anatomic Topographique, tme Wit., i88j. • Dwight : Frozen Sections of a Child, 1881. * Anatomy of the Child, 1887. ♦ Mehnert : Ueber topographische Altersveranderungen des Atmungsapparates, 1901. » Handburh der Topograph. Anat.. Bd. ii.. 1899. • Denkschrift der Acad. Vienna, 1897. 1838 HTTMAN ANATOMY. Fio. 1561. Anterior surface Carina, anterior triangle CartilaRe the spur on the left of the middle of the trachea in 57 per cent. , in the middle in 42 per cent., and on the right of it in the remainder." Semon, in 100 tjxaminations of the living, found it on the left in 59, at the middle in 35, and on the right in 6. The roots of the lungs consist of the bronchi (the right one giving off a branch before entering the lung), the pulmonary artery and vein, the bronchial arteries and veins, the lymphatic vessels and nodes, and the nerves. The bronchi (Fig 1562) are the two tubes into which the windpipe divides, one running downward and outward to each lung. Until they enter the lungs, their shape and structure are precisely those of the trachea, the membranous por- tion being still posterior. This applies also to the branch that springs from the right bronchus before it enters the lung. While treating of the root of the lung we shall consider only the extrapulmonary part of the bronchi. According to modern usage, the term "bronchus" is applied to the whole of the chief tube that runs through each lung ; formerly it was restricted to the part from the trachea to the first branch. As the left bronchus gives off no branch before entering the lung, it was described as much longer than the right one. The length of the left bronchus to its first branch is about 5 cm. (2 in.), that of the right is rarely more, and often less, than 2 cm. (^4 in.). There are some eight or ten rings in the left bronchus before the branch, while in the right one there are three, often two, and sometimes four. The right bronchus, which is the more direct con- tinuation of the trachea, is the larger. The diameter of the bronchi at their origin is greater from above downward than from before backward. The dimensions are very differentiy given. According to Aeby, the transverse diameter of the right bronchus is from 13. 5-21 mm. and that of the left Left bronctiiu Carina tracheae Origin of apical bronchus Continuation of right main bronchus Bifurcation of trachea, seen from above after section of windpipe just above carina. Flc. I 563. Membranous part of tra- cheal wall from 1 2. 5-1 7 mm. Braune and Stahel found that the calibre of the right one is to that of the left as 100:77.9. The extreme ratios of the series were 100 : 71.6 and 100 : 83.3. We have deduced from Heller and v. Schrotter's tables that in some 10 per cent, the calibres are equal. It was formerly taught that the larger right bronchus is more nearly horizontal than the left, but that the contrary is true is easily proved by a glance down the trachea in a frozen section (Frg. 1561). The cause of the error is that, if it be not recognized that after the apparent splitting of the right bronchus the lower division is the main trunk, the eye is apt to follow the upper border of the primitive bron- chus, which carries it along the upper branch. It is very difficult to determine the angles at the origin of the bronchi, for the parts are so flexible that obsea-a- tions on non-hardened subjects are of little value, and it is not easv accurately to measure even good preparations, on account of the irregularity of the outline. One fact which adds to the difficultv of taking satisfac- tory measurements, and which also tends to make the right bronchus the more direct continuation of the trachea, is the inclination of the latter to the right as it descends. ' They st.itc th.it this rcm.iindur consists of 3 cnscs, but as their series comprised 125, it would seem that there must he a misprint. l.eft bronchus Hifutc.-ition i>f trachea Inid open after incision along an teriur wall of trachea and bronchi. THE TRACHEA. 1839 We have made measurements on two casts from frozen sections of the adult, and one from a section of a child thought to be of about three years, and have calculated the angles between the prolongation of the axis of the terminal part of the windpipe and that of each bronchus. An attempt was also made to measure the angles from a skiagraph made by HIake ' aftiT injecting fusible metal into the trachea of a hardened body. Two observations on adults by Kobler and V. Hovorka ' are included for comparison. It seems that ^Jnesubtracheal angle, that of divergence of the bronchi, is about 70°. We have found it precisely that in another specimen. Kobler and v. Hovorka measured the lateral angles in the hardened bodies of sixteen new-bom infants. The average was right 25.6, |r.it 48.9. The variations ranged on the right from 10 to 35 and on the left from 30 to 65. A'e found their average angle of divergence 74.5. This shows that, contrary to the general im- pression, the bronchi are not more nearly vertical in the infant than subsetjuently. Aeby gives the angles of divergence of two new-bom children as 33 and 61 ; Mettenheimer " as 50 and 63. Vessels. — The pulmonary artery at its bifurcation is anterior to the bronchi and at a lower plane. Each branch of the artery rises over the bronchus and comes to lie more or less external to it. This ap}Kirent crossing of the bronchus by the artery occurs on the right just after the origin of the first secondary bronchus. The usual teaching, following Aeby, that the artery actually arches over the cxtrapul- Fio. 1563. Stenium Pulmonary laniluiiar valve L.eft lun^ Leh pulmonary -1 veini> Left bronchua Aorta Superior vena cava / Parietal pleura Visceral pleura Reflection of viscernl onto mediastinal pleura III rib RiEbt bronchus ^ Rigbt lunK Fimnre / Thoracic aorta / ""^V »' vertebra (EsopbaKua Kiltiit pulmonary artery Transverse section of thorax at level of fifth thoracic vertebra. Spine of scapula Superior fissure tnonary bronchus and lies behind it, is incorrect. The artery divides before enter- ing the lung, one branch entering through the upper and the other through the lower part of the hilum. The pulmonary veins are usually two on each side. The superior lie in front of and below the artery. The inferior are the lowest of the large vessels of the lung- root, passing from behind under the bronchus into the heart. The bronchial arteries follow the bronchi along their posterior surfaces. The bronchial veins Mc hoth anterior and posterior. On the right side lK)th open into the larger azygos vein. The left posterior ones often receive the anterior and open into the superior hemiazygos. There may be various anastomoses with mediastinal, pericardial, and tracheal veins. The lymphatics run fii\ided. The proximity of the great azygos vein on the right side, and of the arch of the aorta, the descending aorta, the oesophagus, and the left auricle on the left, must be remembered. It is more difficult to retract the pleura on the right side so as to expose the bronchus. Bryant has called attention to the following anatomical points bearing upon this operation, whether it is under- taken for the removal of a foreign body from a bronchus or the oesophagus, or for posterior mediastinal tumors or abscess, or for the relief of pressure from enlarged bronchial glands : the lower portion of the fourth dorsal vertebra is the boundary line between the posterior mediastinum and the lower part of the superior medias- THE LUNGS. i»43 tinum ; the spinous process of any dorsal vertebra, with the exception of the first, eleventh, and twelfth, denotes the situation o the posterior extremity of the rib articulating with the transverse process of the vertebra immediately below ; the tips of the spinous processes of the tirst, eleventh, and twelfth dorsal vertebra? are above rather than opposite the transverse processes of the vertebr* immediately below ; the space between the ends of the transverse processes and the angles of the rilw varies from one to two and a half inches, according to the numerical position of the rib ; the incomplete rings of the bronchi render those tubes easily recognizable by touch ; they are found about an inch and a hall anterior to the opening in the thoracic wall. THE LUNGS. The lungs are a pair of conical organs, each envelofied in a serous nembrane, — the pleura, — occupying the greater part of the cavity of the thorax, and >oparated from each other by the contents of the mediastina. Although in general conical, the lung diflers in many respects from a true cone. The base is concave, moulded over the con- vexity of the diaphragm, and descending farther at the back and side than at the front and internally. The apex is not over the middle of the base, but much to the inner and p<»terior side of it, so that the back and inner side of the lung descend much more directly than the rest. The right lung is the larger on account of the greater encroachment of the heart on the left. The surfaces of the lungs are the base, the external surface (which is the mantle of the cone from apex to base, and embraces all the periphery from tht- front of the mediastinal space around the wall of the thorax to nearly opposite the front of the vertebral column), and the interna! or mediastinal surface. The borders are the inferior, which surrounds the base, and the anterior and posterior, which bound respectively the back and front of the internal surface. The external surface (facies costalis), much the largest, is closely applied to the portion of the wall of the pleural cavity formed by the ribs and the intercostal muscles. The region of the apex is a part of this surface. It rises slightly — possibly I cm. — above the oblique plajie of the first rib, which indents it towards the front. The apex itself is in the internal and posterior part of this region. It rests closely against the firm fibrous structures that roof in this region, and is grooved trans- versely by the subclavian artery, more anteriorly on the right lung than on the left. A slight groove made by the subclavian vein may be found in front of the arterial one. The rest of the external surface is smooth, except where it may be slightly depressed beneath the individual ribs. It should be noted that a part of what is termed the external surface faces inward against the vertebral column and the first part of the ribs as they pass backward. The external surface descends lowest at the back and at the side. The internal surface (facies mediastinalis) is approximately plane, except for the cardiac fossa, which is much deeper on the left than on the right, and extends as far as the lower surface. The left lung presents a shelf-like projection from behind under this fossa. The other chief feature of the internal surface is the hilum for the entrance of the structures composing the root of the lung. It is situated nearer the back than the front and below the middle, being behind and above the cardiac fossa. The outline of the hilum in the left lung is approximately oval, with the lower end sharpened and the long diameter vertical. It is more triangular in the left lung, as the root expands forward near the top. The position of the bronchi and the chief vessels as they enter the lungs differs on the two sides. Right lung : the chief bron- chus enters at the middle or lower part and its first branch near the top, both being at the back of the hilum ; the pulmonary artery, generally in two branches, enters one branch in front of the main bronchus and the other in front of the secondary bronchus, but at a higher level ; the superior pulmonary vein is high and in front of the higher arterial branch ; the inferior, often subdivided, is near the lower end of the hilum ; one branch may be in front of the bronchus and one below it. Left lung : the bronchus enters the back of the hilum rather above the middle ; the pulmonary artery is at the top, sometimes in two divisions ; the superior pulmonary vein is high up in front, . J844 HUMAN ANATOMY. Groove lor •ubclaviau artery Groove lur Innominate vein Right lung, hardened m tUu iddic lobe Inferior lobe antero-lateral aipect. causing the expansion which makes the outline triangular, the inferior vein being •" jhe lower angle. The inner surfaces are also marked by certain adjacent structures which require a separate account for each lung. The right lung presents a vertical groove above and in front for the superior vena cava, and one for the vena azygos major, which is distinct behind the upper part of the hilum and above it where this vein runs forward to the cava. The r^ht subclavian artery, owing to its high origin from the innominate, indents but little of the internal surface. A more or less marked vertical groove for the oesophagus is seen behind the hilum and below that for the azygos. There is aiso a groove below on the inner surface where the in- ferior vena cava turns forward to enter the heart A slight impression made by the trachea may also be present near the apex. The inner surface of the left lung is deeply grooved by the aorta arching over the root and descending behind it, the imprint growing faint and disappear- ing at the lower end. The left carotid and subclavian arteries make distinct impressions at the upper part divei^ng h-om the aortic groove. The baae (fadfs diaphragmatica) is concave, that of the right one being ... . .. » rather the more so. Both are semilunar in outlme, owmg to the part cut out of them by the heart ; since this encroachment is greater on the left, the base of that lung is a narrower Fio. 1165. crescent. The inferior border surrounds the base. The latter forms about a right angle with the internal sur- face, but at the periphery, especially at the back and at the side, a sharp edge of lung is prolongred down into the narrow space be- tween the diaphr^;m and the thoracic walls. The anterior border is sharp and somewhat irregular, often presenting a series of convexities. Starting near the apex, it descends on both lungs with a forward curve, which is most promi- nent in the upper part, so that the lungs nearly or quite meet behind the ma- nubrium. The anterior bor- der of the right lung then inclines downward and out- ward so as to meet the inferior border in a gradual curve. On the left this convex- ity is changed into a sharp concavity where the border curves outward around the Groove fur innominate artery Groove for riftht' innominate vein Groove for vena cava superior- Secondary, bronchus Blanches of. pulmonary artery Cardiac impression Infrrior pul- muiiary vein Groove for •ena azygoa major lain bronchus Diaphragmatic surface Preceding lung ; median asfwft THE LUNGS. »845 Fio Groove lor -~ ■ubdtvisn anery Groove for hmumUiate vein Inferior Bom Left liini, hardened m tilm ; antero-lateral aspect. heart. As this concavity ends in front, the anterior and inferior borders enclose a prolongation of the lung towards the median line, known as the linguia. The pos- terior border is vanously described. Often the term is applied to the thick mass of lung that fills the region of the thorax along the sides of the vertebrse and the part of the ribs running back- ward. Properlv, it is a ridge starting on the inner side of the apex, growing sharp as it descends, but becoming vague and effaced at the lower end. The position of this line is not the same on both sides, nor is it probably always dependent on the same causes. On the le/l it is more regular, beginning as the posterior bor- der of the groove for the siibi'lavian ar- tery, and continuing as that oi iIh aortic impression until it is lost near the lower border of the lung. Sometimes the be- ginning has no relation to the subclavian groove, but appears posterior to it, the lung-tissue forming^ a ridge which enters a little into the space between the front of the spine and the cesopliagus, which is here deflected to the left The line behind the aortic groove lies on the side of the vertebrie, and consequently is the farther back the more the aorta is on the side of the column. On the right the posterior border is farther forward, being about opposite the anterior surface of the spine. It may begin as the posterior bor- der of the subclavian groove, or more posteriorly, and continues as a ridge tending to insinuate itself between the spine and the contents of the posterior mediastinum. From just above the root of the lung it is for a short distance continued as the t>ack of the groove for the major azygos vein, below which it tends to pass between the cesophag^s and the pericar- dium, and finally disappears a little above the lower border. The Lobes and Fis- sures. — The lungs are di- vided into lobes by deep fissures. The chief fissure starts on the inner aspect of the lung, behind the upper part of the hilum, and as- cends to the posterior sur- face, which it may reach at the same level on both sides, or, as is perhaps more frequent, the right fissure may be one intercostal space lower. The fissure then descends obliquely along the otitcr aspect of the lung, and reaches the inferior border, where it ends somewhat sooner on the right side than on the left. In the right lung this occurs at the front of the lateral a.spect, while it is likely to Pio. 1567. Iroove (or left rabclavten artery Groove (or left 'common carotid artery Superior pulmo- nary vein Subcardiac shelf ,LinKula Diaphraitmatlc surface PrecedinK Inne ; median a«i is thus divided into a superior and an inferior lobe. In the right lung a middle lob7\a cut off from the superior by a secondary Jissure, which starts from the main fissure far back on the lateral aspect and runs forward, either straight or with an upward or a downward inclination. The foregoing description applies to the course ofthese fissures as seen on the suriace ; but the chief fissure is. moreover, very deep, penetrating to the main bronchus, and completely dividing the lung into a part above iTand one below it. The depth from the suriace of an inflated lung to the bronchus at the bottom of the fissure (uken at the point of origin of the secondary hssure on the right and at a corresp«.nding point on the left) is from 7-8 cm on the right and about I cm. less on the left. The secondary fissure is much less deep and may end prematurely, or even be wanting, so that the middle lobe Is a very irreguUu- structure. The left superior lobe comprises the apex and the entire front of the lung, while the inferior takes in most of the l>ack and all of the base, unl«s the lingula be re- garded as constituting its anterior border. In the right lung the middle lobe forms a varying part of the front and one-fourth or one-third of the base. The volume o the upper and lower lobes of the left lung is about equal. In the right l«."«/''f "' the inferior is about equal to that of the other two. We consider the middle lobe simply as a piece cut off from the upper, so that the right upper and middle lobes correspond to the left uppei one. Variation* of the Lobaa and Fiaaurea.— Were it not for the ereat difficulty m properly examining the lunes, their marked tendency to variation would doubtless be more fuIW appre- ciated. Schaffner" has shown that an accessory in/enor lode is very freauently found on the under surface, extending up onto the inner surface In front of the broad ligament. Ihis lone may be merely indicated by shallow fissures or sharply cut off from the rest. It may present a toninie-like projection inward or may comprise the entire mner portion of the liase. It usu- ally represents, when present, from one-fifth to one-third of the base. It may occur on either sitfe or on both, but is larger and more frequently well defined on the nght. On the other hand, it is present, or at least indicated, rather more often on the left. Schaffner found it in 47. i |)er cent of 210 lungs. The lobe of the right lung represents the siihcardtac lobe of many mam- mals, that of the left being evidently its fellow. The irregularity and occasional absence of the fissure marking off the middle lobe have been mentioned. An irregular fissure may subdivide the left lung into three lobes, and both lungs may exceptionally bestil further subdiv-ided, espe- cially the right one. A little process of the right lung just above the base, behind the termina- tion of the inferior vena cava, may very rarely become more or less isolated as the lobus cava. The azygos major vein may be displaced outward, so that, instead of curving over the root of the lung, it may make a deep fissure in the upper |>art of the right lung, marking off an extra lobe. External Appearance and Physical Characteristics.— The adult lung is bluish gray, more or less molded with black. At birth the lung-tissue proper is nearly white, but the blood gives it a pinkish or even a red color. It grows darker with age, jiartiy, perhaps chiefly, by the absorption of dirt, but also by the greater quantity of pigment. Before middle age the lungs become decidedly dark by the presence of black substance (be it dirt or pigment), arranged so as to bound irregular polygons from 1-2.5 cm. in diameter, which are the lobules. At first, while the black is scanty, the lines seem to enclose considerably larger spaces, but when more of the lobules appear, owing to a greater deposit of the pigment in the areolar tissue and lymphatics marking them off, it is clear that their diameter rarely much e.xceeds 1.5 cm. Some, however, are relatively long and narrow. It is re- markable that the deposit of pigment is much greater in certain places than in others. Thus the rounded posterior parts of the lungs are darker than the anterior portions. In general the external surface is much darker than the mediastinal or the base, while the surface within the fissures is the. lightest of all. Moreover, the pigment on the external surface, before the coloration has become general, is often m stripes corre- sponding to the intercostal spaces, as if there were more pigment in the places most accessible to light. The lungs being filled with air, after respiration has begun, are soft and crack- ling on pressure. They are extremely elastic, so as to collapse to perhaps a third of their size when the chest is op>ened. ' Yirchow's Archiv, Bd. clii., 1898. THE LUNGS. 1847 Fio. 1 56*. Extcrmil turiace of tuiiK, thowlng polyimnal areas corresponding to lobuks ma|>prtl out by deposits d pigmented particles within cuiiuec-tivc tissue. The weight (A the Iudk is difficult to determine, owin^ to the imiMMtsibility of quite excluding fluids. Sappey puts it at 60 or 65 urn. lor the (ti'tus at term, and at 94 gm. on the average for the new-bom infant that has breathetl (thii.s show- ing cunvinciiiKly the worthlessness of the method ). Kniuse gives the athilt weight as 1.^00 gm. in the male and loa;^ gm. in the female. According to Rraune and Stahcl, the weight of the right lung is to that of the left as 100 : 85. The specific gravity of the lung be- fore breathing is greater than that of water, so that the lung sinks in it. VVilmiirt ' has recently stated it as 1068, which i.« the same as Sappey' s statement and grc.iter than that of Krause (1045-1056). After breathing it may be as little as ,^42, but may go as high as 746. Probably figures like the latter represent either diseawd or congested lungs. The dimensions are necessarily nf lit- tle value. According to Krause, the length in man is 37.1 cm. on the right and 39.8 cm. on the left. In woman these dimen- sions are 31.6 cm. and 23 cm. resp-.ctively. There is little difference in length between the lungs, but such as there may b« is in favor of the left. The other dimensions are probably more variable. According to Sappey, the antero-posterior diameter, which increases from above downward, finally reaches 16 or 17 cm. Krause gives the transverse diameter at the base in man as 13.5 cm. on tlie right and 13.9 cm. on the left, and in woman as 1 3. 3 cm. and 10.8 cm. respectively. Fio. The average capacity of the lungs of a powerful man, after an ordinary inspiration, is stated at from 3400-3700 cc. The vital capacity, which is the greatest amount of air that can be expelled in life after a forced inspiration, is from 3300-3700 cc. for men and 2500 cc. for women. The Bronchial Tree.— The plan of the bronchi of the human lung (Fig^ 1558) is as follows. The two primary bronchi, resulting from the bifurcation of the trachea, run down- ward and outward into the lowest lateral part of the lungs, the right one descending more steeply. Their course has been variously described. That of the right one has been said to resemble a C with the concavity inward, and that of the left an S; but both comparisons are very forced. On their way they give off secondary bronchi, which are divided into ven- tral and dorsal branches. The ven- tral might more properly be called lateral, since they spring from the outer aspect of the primary bronchus. They are much the larger, and supply all the lung, e.\cept the apex and the posterior portion lying along the spine ; the latter is supplied by the * La Clinique, 1897. Relations of bronchial tree to anterior thoracic wall, as shown by X-rays. K^lrr Blakr.) m iM HUMAN ANATOMY. donal branches, which are tnull and inwular. There are usually four large and weli- nurked ventral secondary bronchi, besir Bronchialbaum der SSugethiere und des Menschen, i88a » Verhandl. d. Anat. Gesellschaft, 189a. ' Annals of the New York Acidemy of Sciences, 1898. Rctatloiu of bronchiil trw to pouerlor thoracic wall, m ahown by X-ny*. (A/trr Blakr.) iiM THE Ll'NGS 1849 depwturc from it one with tymmetrical eparterial bronchi. The type found in man ii» the mutt cummun among nMmnwIs. Huntington would do away entirely with the ttrm-* enaiterial and ••hyparterid," except «or purposes a< topography. Cetiainly there is n<> need «,< them m human anatomy ax a special study ; whether or not the arterial relation!* should, an Narath main- Uins. be absolutely di-scarded in comparative anatomy, we must leave undetermined.' It must be admitted that were our knowledge derived solely m the human lung it would be impossible to make out this plan. We shall now describe what is actually to be seen. EHMribution of tlM BroncU.— In the rigki Immg the apical brunthus, with a diameter of about 10 mm., arises about a cm. from the trachea (often nearer and rarely farther), and, entering the top of the hilum, divides as described above. The diameter of the mam trunk, after giving off the apical branch. Is 12 mm. The first right ventral branch arises irom its outer side, about 5 or 6 cm. from the bifurcation of the Uachea, and runs downward, outward, and for- ward. It is about 8 mm. in diameter. The apical branch and the first ventral supply the supe- rior lobe, of which the middle lobe is really a part Shortly after the origin of the first ventral branch the chief bronchus seems to break up into a bundle of branches runnmg m«»tly in the same general direction, but diverging. It is usually not prawible to determine which is the main trunk, but the subcardiac branch may sometimes be distinguished. In the le/l lung the first branch is the first ventral, with a diameter of la mm., arising some 40 mm. from the bihirca- tion It lives off the apical, 7 or 8 mm. in diameter, after which the diameter of the mam branch J» la mm. It presently breaks up like the right one. <)n this side the first ventral sup- plies the upper lobe. A branch from the second ventral goes tc the accessoiy kibe, ■{. there be one. The branches of the left bronchus are very apt to rive the appeararice of being divided into an upper and a fower set, the former, consisting of the first ventral branch, bearing the apical and supplying the superior lobe, while the lower sheaf of branches supplies the inferior. The secondary bronchi give off branches oi 4 or s mm. in diameter, whic iverge at acute angles from the parent trunk, and in turn give off smaller branches at continu '.> greater angles. THe branches 'o the lobules are probably the fourth or fifth branches They are about i mm. in diameter and arise by the subdivision of the preceding branch. In the larger lubts the ramification is clearly from the side, but in the smaller ones it is more sui^gestive of a splitting. His • Minot,' and more recently Justesen* defend the theory that the onpfin of the bronchi is throughout by bifurcation, with subsequent unequal growth of the subdtvisioii until we come to the smallest. Aeby gives the following table of diameters of the mam bronchus above the ongin of the chief branches, the nomeiKlature being his. Right. tcft. Above the epartetial branch »a.8 mm. . • Above the fit &i hyparterial branch 9.6 mm. 10.1mm. Above the second hyparterial branch ... 7.2 mm. 7.7 mm. Above the third hyportcrial branch 5-8 mm. 6.4 mm. Above the fourth hyparterial branch 4-6 mm. 5.3 mm. The varUtioBS of the bronchial tree are very numerous. Very rarely indeed the right aoical branch does not spring from the primary bronchus, so that the disposition of the two sides is symmetrical. The origin of the left apical from the pnmary bronchus has been observed in two or three cases of infants, which also makes the arrangement symmetncar Chiari' has seen several cases in which the right apical bronchus is double, the duplication being apparently due to the springing of one of its branches from the mam bronchus. The right apiS bronchus may spnng from the trachea, as in *« »heep and other mamrnaK U e hlvesichan instance in wfiich it is separated rom the chief bronchus by ttie ^SK^^J": The dorsal secondary bronchi are particularly likely to be reduced in number. The ventral ones may also be reduced by two having a common origin or by one becoming merely tne branch of another. The number may be apparently increased by the separate origin from the parent stem of what are normally branches of branches. The Lung Lobule.— The surface of the lung is covered with lines of con- nective tissue containing blood-vessels and lymphatics, with pigment either within the latter or free, the lines marking of! little polygons (Fig. 1568), which are the bases of pyramidal masses of pulmonary tissue known as the /o6u/es. The shape of the latter within the depths of the lungs is not accurately known ; those at the sharp borders are modifications of the typical ones at the surface. The bases of the pyiamids at the surface are bounded by four, five, or si.x sides, the laiger diameter varying from 10-25 mm- and the smaller from 7-12 mm. If the base be assumed to be square, the average breadth would be 12.57 mm.* The average height is 13 mm. The lobules are separated from one another by a layer of connective tissue containing * The latest and most elaborate work on this subject is Narath'S Der Bronchialbaum der Saugethiere und de«: Menschen, Stuttgart. 1901. » Archiv f. Anat. u. Phys., Anat. Abth , 1887- * ! ''iman EmbrN'olofO', 189a. * K:-hivf. mikro. Anat., Bd. Ivi., 1900. ' .> 'schrift fiir Heilkiinde, Prag., Bd. x., 1890. ■ luiiographie Anatomique. 1898. 1850 HUMAN ANATOMY. 1 1 Diagram showiiif; relations of terminal suh- diviHiuns of air-tuhes. B, bronchiole eiidinK in terminal bronchi iTB); latter divide into atria M). each of which communicates with several air-sacs {s) into which open the alveoli (a); PA, branch of pulmonar)' arteo' follows bron- chiole; PK pulmonary vein at periphery of lung-unit ( /V'"' Miller. ) vessels. Each lobule is entered by an intralobular bronchus (.5-1 mm. in diam- eter), accompanied by its artery, — not quite at the apex of the pyramid, but slightly to one side of it. The bronchus divides into two, at an angle of from go'-ioo", a little above the middle of the lobule, having previously given of! two or three col- lateral branches to its upper part. In the third quarter of the lobule the two subdivisions (2-3 Fio. 1571. mm. in length) again split, with about the same degree of divergence as the parent stems, but in a plane at right angles to that of the previous splitting. This is repeated in three or four suc- cessive bifurcations, a varying number of col- lateral branches being given off. Thus the num- ber of branches in the third quarter is much in- creased ; but it is in the last quarter and towards the periphery of the lobule throughout that the tubes break up into the great number of truly ultimate bronchi. The various collaterals, spread- ing and even reascending, undergo subdivision also. Laguesse and d' Hardiviller ' estimate the number of terminal bronchi (ductuli alveolares) within a single lobule at from fifty to one hun- dred or e > en more. The slightiy dilated distal ex- tremity of the terminal bronchus communicates with from three to six spherical cavities, the atria of Miller' (so named by him from the resemblance to the arrangement of an ancient Roman house). The atria, in turn, communicate with a group of larger and irregular cavities or air-sacs ( sacculi alveolares), into which directly vyen the ultimate air-spaces, the alveoli or air-cells ( alveoli pulmonis) . The latter open not only into the air-sacs, but also into the atria, the dilated distal part of the terminal bronchus being likewise beset with scattered alveoli. Miller holds that the terminal bronchus, the air-chambers connected with it, together with the vessels and Fig. 157a. nerves, is the true lung-unit, and calls it the lobule. We cordially agree that this is the true lung-unit, and pro- pose that name for it, retain- mg the term "lobule" for the above-described more or less isolated pwrtion of the lung which is surrounded by connective tissue and vessels and receives a single intra- lobular bronchus and artery. In some animals the lobules are perfectly distinct ; they may be isolated in the infant, and can be in the main easily made out in the adult. The lung-unit, on the other hand, . minute bronchus » not surroundcd by areolar e, alveoli. ■ 8. tissue, and its limits can be determined only by recon- struction from microscopical sections ; hence, apart from its minuteness, it is practi- cally too much of an abstraction to deserve the name almost universally applied to something tangible. > BibliuKraphicf Analomique, 1S9& •Journal of Morphology, 1893. Archiv f. Anat. u. Phys., Anat. Abth., 1900. Corrosion-preparation of lung, showing lung-units. 1 ending in terminal bronchi ib,f>)\ r, atria; - arter>'. X 35- The intralobular bronchus is accompanied by some areolar tissue, and certain fibrous prolongations extend into the lobule from the connective tissue disixiseil about its- surface. Although superficially these appear to divide the lobule into from four to twelve parts, they penetrate but a short dis- tance. They are not real partitions, and the sub- divisions they suggest have no morphological significance. Structure. — As far as their entrance into the lungs, the bronchi pos- sess essentially the same structure as the trachea. After the division of the bronchus within the lung, the cartilage-rings are replaced by irregu- lar angular plates, which appear at longer and longer . intervals until they finally cease, the last nodules usually marking the points of bifurcation of the bronchi. Within the walls of bronchioles of a diameter of i mm. or less cartilage is seldom present. As the cartilage disappears the unstriped muscle broadens into a continuous layer, which, however, gradually becomes thinner as the air-tube diminishes, and extends only as far as the terminal bronchi. Around the circular openings, by which the latter communicate with the atna, the muscle is arranged as a sphincter-like band _ (Miller). "*■ The walls of bronchi of medium size consist of three coats, which from without in are : ( i ) an exter- nal fibro-elastic tunic which encloses the cartilage and blends with the surrounding lung-tissue ; (2) a usu- ally incomplete layer of involuntary muscle composed of circularly dis- posed elements ; (3) the mucosa, consisting of a stratum of compact elastic fibres next the muscle, the fibro-elastic stroma and the cili- ated columnar epithelium. Mucous glands, similar to those of the trachea, are present, decreasing in number and size until the bronchus approaches i mm. in diameter, when they disappear. Their chief location is outside the muscular layer, which is pierced by the ducts. In addition to diffused cells within the mucosa, more definite aggre- gations of lymphoid tissue occur as minute lymph-nodules along the bronchi, tfie points of bifurcation of the latter being their favorite »e.its. The epithelium lining the air-tubes retains the ciliated columnar type, with many Epithelium K>blctM:ell KihroHs ttssuf * Alvet>lar wall Cartilage Portion of wall of small bronchus. X iSo. 1852 HUMAN ANATOMY. goblet-cells, as far as the smaller bronchi. Within these the riliated cells are replaced by simple columnar elements which, in turn, give place to Vv cuboidal cells within the proximal part of the terminal bronchi. Towards the termination of the latter, transition into a simple squamous epithelium takes place. The walls of the air-spaces — the atria, the air-sacs, and the alveoli — have es- sentially the same structuri-, consisting of a delicate ■hro-elastic framework wh'ch supports the blood-vessels and the epithelium. Within the adult lung the latter is simple and is represented by two varieties of cells, the large, flat, plate-like elements (.020-.045 mm. ) and the small nucleated polygonal cells (.007-.015 mm.) occurring singly or in limited groups between the plates. Before respiration and the conse- quent expansion of the air-spaces take place, the cells lining these cavities are small and probably of one kind. The groups of the smaller cells are larger, more numer- ous, and more uniformly distributed in young animals than in old ones, in which they are often represented by single cells irregularly disposed. The adjacent alveoli share in common the interposed wall, which consists of the two layers of delicate elastic membrane beneath the epithelium lining the alveoli and Pio. 157S- Air^nc Passage from atrium into air-sa* Alvcolui Trnninal bronchus Pulmonary aitcry. Bronchiole- -Atrium -Alveolus Air-sact Section of lung, showing general relations of divisions of air-tubes. X so. the intervening capillary net-work, supported by a delicate framework of elastic fibres. The capillary net-work is noteworthy on account of the closeness of its meshes, which are often of less width than the diameter of the component capillaries. The latter are not confined to a single plane, but pursue a sinuojis course, projecting first into one alveolus and then into the one on the opposite side of the interalveolar septum. The capill.nries are, therefore, excluded from the interior of the air-cells by practically only the attenuated respiratory epithelium, the large plate-like cells lying over the blood-vessels wliile the small cells cover the intercapillary areas. Distinct intercellu- lar apertures or stomata, formerly described as affording direct entrance from the alveoli into definite lymphatics, probably do not exist. That, however, inspired foreign particles may pass between the epithelial cells into lymph-spaces within the alveolar wall and thence into lymphatics, to be transported to more or less dis- tant points, is shown by the gradual accumulation of carbonaceous and other parti- cles within the interlobular tissue and the lymph-nodules along the course of the lymphatic vessels. .Such accumulations may acquire conspicuous proportions, the entire interlobular septum appearing almost black. In view of the very frequent presence of pigment-loaded leucocytes within the alveoli, as well as outside the alve- THE LUNGS. 1853 CapllUiry. net'Work Branch of pulmonar)' vein Portion of injected *nd inflated lung. X 80. olar walls, it is highly probable that such cells are important agents in transporting the particles of inspired carbon through the walls of the air-cells. Additional par- ticles, however, usually occupy the cement-substance between the alveolar epithelial cells, sometimes lying appar- Pio. 1576. ently within the cytoplasm of the latti r. Blood-Vessels of the Lung. — The pulmonary artery, serving not for the nutrition of the lung but for the aeration of the blood, is very large, — at first larger than the bronchus, which it follows very closely throughout its ramifications to the terminal bronchi. Situated at first anterior to the bronchus, it passes onto its superior and then onto its outer side, and in most cases twists aroimd the bronchus, so as finally, when deep in the lung, to reach its dorsal aspect. This is very dif- ferent from .At '. y's alleged cross- ing of the main bronchus. The arterial branches accompanying the apical bronchus are in the main anterior to the tubes in the right lung and behind them in the left. According to Narath, the genera' course of the artery along the main bronchus is between the ventral and dorsal branches ; but, as he states, this is not constant. We Fig. 1577. have found certain ventral bronchi in the lower part of the lung with the artery before them. An in- tralobular branch en- ters each lobule near the apex with the bronchus, and follows its ramifications until the ultimate bronchi have ended in the air- chambers of the lung- unit. The terminal arterioles are in its in*" 'or until they ^k up into capil- laries in the walls of the alveoli. Side branches, interlobu- lar arteries, run in the connective tissue between the lobules. It is from these, ac- cording to Miller, that the subpleural net-work is filled ; held to be supplied by the bronchial arteries. The pulmonary veins, which return the aerated blood to the left auricle, are als.^ large when they leave the hilum, — two on each side, one near the top and the other Smaller cell! Larger cella Epithelium lining al- veoli Section o( lung, showing collections n( particles »■( tissue. X 140. i-.irimn in |terivascular connective formerly the latter was 1 854 HUMAN ANATOMY. I i Portion of in] vessels to bronchi inK bronchi (white) of lobule. X a ilccted lung, showing relation of bloo»' l; pulmonao' arteries (blue) accomfiany- pulmonary veins (red) at periphery near the bottom. They arise from the capillaries in the walls of the air-chambers, running first on the outside of the lung-units, unite with others, and ramify in the connective tissue about the lobules, so that, first in the lung-units and then in the lobules, the circulation is from the centre towards the periphery. As they ascend to the hilum they unite with others and form trunks that accompany the bronchi, lying Fio. 1578. in the main lower and to the inner side of the latter. Corrosion preparations (Fig. 1578) show very clearly that the small arteries travel in close comjiany with the bronchi, while the veins course by themselves. The bronchial arteries carry the blood for the nutrition of the lungs, es- pecially that of the air-tubes, the lymph- nodes, the walls of the blood-vessels, and the areolar tissue about them ; hence they follow the course of the bronchi. They are in communication with the interlobular system of the pulmonary arteries. The bronchial veins are very irreg- ular. Both anterior and jxjsterior are described. The former carry the blood back from the bronchi and the tissues about them, becoming perceptible at the bronchi of the third order {ie., the branches of the first branches) and running to the hilum anterior to the bronchi, two with each. The posterior bronchial veins appear at the back of the hilum and, without any close connection with the bronchi, anastomose with other veins at the back of the roots of the lungs. Anastomoses between the Fio. 1579. Pulmonary and the Bron- Pleura chial Systems. — Not only do ■^.'■'-'-'^ — . — the capillaries at some places drain into either system of veins, but important com- munications occur between both the arteries and the veins. (a) The bronchial arteries as they enter the lungs give off occasional branches which, running for some distance beneath the pleura, suddenly plunge into the lung to anastomose with an interlobular artery. Such a branch may arise from an oesophageal artery. There are also deep connections between the arteries of the two systems on or near the secondary bronchi and their br.inches. (^) The com- munications between the two systems of veins are very extensive. Apparently all the blotxl from the smallest branches of the bronchial arteries returns by the pul- monary veins ; and, moreover, the bronchial veins about the larger bronchi have free communication with those of the pulmonary system. According to Zucker- Pulmonary vein Lymph-vessel jnierted lun>c- showing lymphatit^ accompanying peripheral branch of pulmonary vein, v 60. {MiUrr.) ■I * THE LUNGS. 1S55 kandl, ' the pulmonary veins anastomose freely with those of the orgjan'* of the pos- terior mediastinum, and even of the portal system. The lymphatics of the lung are very numerous. The deejier ones probably begin as lymph-spaces within the interalveolar septa, distal to the terminal bronchi, distinct lymphatics being found only along the arteries and veins. These commu- nicate with the subpteural lymphatic plexus. Surrounding the walls of the terminal bronchi Miller found usually three lymph-vessels. The latter increase in size and number as the calibre of the air-tubes enlarges. On reaching the bronchi the lym- phatics form plexuses along them which ultimately open into the lymphatic nodes, which are numerous in the hilum and in the roots of the lungs. According to Miller, where cartilage-rings are present a double net-work exists, one on each side of the cartilage, the inner lying within the submucosa. The lymph-nodes of the lungs are deeply pigmented, owing to the colored particles of foreign substances inspired. Nerves. — The nerves of the lungs, from the pneumogastrics and sympathetics, form the very rich anterior and posterior pulmonary plexuses about the roots, whence they enter the iungs, running adong the branches of the bronchial arteries and the bronchi to their ultimate distribution in the septa between the alveoli ( Retzius, Berk- ley). The nerves are destined chiefly for the walls of the blood-vessels and of the air- tubes. Berkley describes interepithelial end-arborizations within the smaller bronchi. THE RELATIONS OF THE LUNGS TO THE THORACIC WALLS. The relations of the median and diaphragmatic surfaces of the lungs have been given (page 1844). The apex rises vertically about 3 cm. above the level of the upper border of the first costal cartilage and about i cm. above the level of the cla\icle. These ul:;iances are to be reckoned on a vertical plane, not on the slanting surface of the root of the neck. They vary extremely, depending, as they do, on the formation of the body. Thus a sunken chest, which means a very oblique first rib, would have more lung above the cartilage than a full chest with a more nearly horizontal first rib. In extreme cases the lung may rise as much as 5 cm., or as little as i cm., above the first cartilage. The plane of the inlet of the chest is made by the oblique first ribs. The fibrous parts enclosing it are dome-like, the roof of the cavity, to which the lung is closely applied, swelling upward perhaps i cm. above this oblique plane ; the top of the lung, however, is never above the level of the neck of the first rib. It was formerly taught that the right lung rises higher than the left. As a rule, there is no appreciable difference between the two sides. The most that can be said for the old view is that, if there be some trifling difference, it is probably rather more often in favor of the right. The anterior borders of the lungs descend obliquely behind the stemo-clavicular joints, knd cur\'e forward so as to nearly, or quite, meet in the median line on the level of the junction of the manubrium and body of the sternum. Below this the ' "u lung extends a little across the median line and the left recedes slightly fron he right border leaves the ste.num at the sixth right costal carti- lage, to whit i gradually cur-, .'d, runs along that same cartilage, or a little above it, to its June. vith the sixth n' hen crosses the ribs, passsing the eighth at about the axillary line, and reaches the spine at the eleventh rib or a little higher, the guide being the spine of the tenth thoracic vertebra. The lowest part of the lung is on the side at the axillary line or behind it, but the line thence along the back, although rising a litde, is very nearly horizontal. The course of the border of the left lung is essentially the same, except that, leaving the sternum at the fourth cartilage, or at the space above it, the border describes a curve with an outward convexity, exposing a large piece of the pericardium, and turns forward to end as the lingula opposite the sixth cartilage, some distance to the left of the sternum. As this point depends on the development of the lingula. it cannot be stated accurately. It may be said in general to be 3 or 4 cm. to the left of the median line. The greatest depth of this curve is in the fourth intercostal space, about 5 cm. from the median line. The course of the inferior border along the side and back is practically that of the right one. although, perhaps, the left lung may descend a trifle lower at the si to thoracic wall; anterior aspect. extreme expiration the lower borders of the lungs rise in the axillary lines to 13 cm. on the right and 14 cm. on the left above the lower border of the chest. He states also that the anterior borders may withdraw to the parasternal lines (vertical lines dropjjed from the inner third of the clavicles), which to us appears excessive. In our opinion, the great factor in the expansion of the li'n^ is the increase in the vari- ous diameters of the chest rather than the changes of relation of the borders of the lungs to the walls. The re/a/ions of the fissures to the surface are rather variable. The chief ones ascend from the hila and reach the posterior surface at the sides of the vertebral col- umn, generally at different levels, the right being the lower. We must, therefore, 'Die Formen des inenschlichen Korpers und die Formanderungen bei der Athmung, jena, 1888 and 1890. THE LUNGS, 1857 trace the course of each fissure separately. The fissure of the right luns leaves the vertebral column either at the fifth rib or at the interspace above or below it The fissure tends to follow the fifth rib, being in the axillary line still, either beneath it or beneath an adjacent intercostal space. Towards the front the fissure gets relatively lower, ending in most cases either at the fifth space or beneath the sixth rib, near the junction of the bone and cartilage, from 5-10 cm. from the median line. The secondary fissure of the right lung leaves the chief one somewhat behind the axillary line, and, running about horizontally forward, ends at a very uncertain point Rochard, in his small series of twelve observations, found it at the third intercostal space seven times. Once it was higher and four times lower. The fissure of the left lung leaves the side of the spine at a less definite point, ranging in most cases from beneath the third rib to the upper border of the fifth, and being sometimes even Fio. 1 581. N SetnlHiflffntmmfttic reconslriution. showinfc relations <»f pleural sacs (bluel and lungs (red) to body-w-all; ptMterior as|>et't. lower. At the axillary line it is at the fifth rib a little more often than at any other particular point, but it is almost as often at the fourth and more often somewhere below the fifth. Its termination is more constant than its course, being beneath the sixth rib, or the space above or below it, usually from 6-1 1 cm. from the median line.' The relations of the bronchi to the chest-wall have not been studied on a suffi- cient number of bodies for satisfactory conclusions. Blake' has had X-ray photo- graphs taken of an adult body hardened with formalin, the bronchi being injected with an opaque substance. The bifurcation was normally placed. We attach the ■Gazette des HApitaux, 1892. Our description is almost wholly a synopsis of Rochard's work. • American Journal of the Medical Sciences, 1899. >i7 , i ; 1858 HUMAN ANATOMY. most importance to the course of the main bronchus : "On the posterior w^l the course of the left bronchus is from a point to the right of the fourth thoracic spine to a point on the eighth rib three inches to the left of the spine. The course of the right bronchus is from the same point above to a point on the eighth rib two inches to the right of the spine. On the anterior wall the course of the left bronchus is from the lower part of the second right sterno-chondral articulation to a point on the fifth rib just internal to the mammiilary, and of the right bronchus from the same point above to the intersection of the fifth rib with the parasternal line." The hilum is opposite the bodies d the sixth and seventh thoracic vertebrx and a part of the adjacent ones. (Figs. 1569 and 1570.) (The changes of the relations of the lungs during growth and in old age are considered with those of the pleurae. ) :' !!! in !i i It 'I i iif Fio. t58a. THE PLEURA. The pleurse are a pair of serous membranes disposed one over each lung and then reflected so as to line the walls of the cavity containing it, thus forming a distinct clewed sac about each lung ; hence the pleura is divided into a viscera/ and a parietal layer. The latter is subdivided according to its situation into a mediastinal, a costal, a cervical, and a diaphragmatic part. The visceral layer closely invests the lung, following the surface into the depth of the fissures. It leaves the lung at the borders of the hilum and invests the root for a short distance (1-2 cm.), when it leaves the latter and spreads out as the mediastinal pleura, which is applied, back to back, to the pericardium, thus form- ing on each side a vertical antero- posterior septum between the lungs and the contents of the mediastina. The prolongation over the root is not quite tubular, since a triangular fron- tal fold extends from beneath the root to the inner side of the lung, growing narrower as it descends, to end at or near the lower borders. This is the broad ligament of the lung ( ligamen- tam latum pulmonis ). Its line of at- tachment to the lung often slants backward. The mediastinal pleura, besides being applied to the side of the pericardium, lies also against some of the structures of the other medi- astina. Above it is in contact with the thymus on both sides, the superior vena cava on the right and the arch of the aorta on the left. The phrenic nerve descends on each side between it and the pericardium in front of the root of the lung. In the posterior mediastinum it lies against the left side of the descending aorta and the right of the upper part of the greater azygos vein. It is in contact with nearly the whole of the oesophagus on the right, and just before the latter pas.ses through the diaphragm on the left also. It covers the gangliated cord of the sympathetic on both sides as it passes into the costal pleura, and is here stretched so tightly across the terminations of the intercostal veins as to keep their walls distended. Anteriorly it crosses the areolar tissue of the anterior mediastinum below the remnants of the thymus. It Semidiarrammalic recoiistruition. showinif relations of right pleurafsac (blue) and lung (red) to thoracic wall ; lateral aspect. THE PLKURiC. »«59 is continued outward, both before and behind, to become the costal pleura, and is continuous above with the cervical pleura which lines the dome in the concavity of the first rib. It |>asses lielow into the diaphragmatic pleura which invests the upper surface of the diaphrat^m. Laterally, and still more behind, it follows for a certain distance the vertical fibres of the diaphragm, and then is reflected onto the thoracic wall so as to line a ]x>tential cavity between the two layers which, except (or some litde serous fluid, are here in apposition. Villous projections occur alont; the borders of the lun^, especially at the inferior border, where they form a dense, but very minute fringe, not over i mm. broad. Relations of the Pleurc to the Surface.— In some places the lun^s and the pleura; are always in the same relation ; in others the |)leuru; extend a certain distance beyond the lungs, which fill them in complete inspiration so that their out- lines correspond ; in other places the pleurae extend so much beyond the lungs ''°- '5*3- that even in the most extreme inspira- tion the latter do not reach the limits of the former. At the apices the relations of the lungs and pleurie are constantly the same, both being in contact. All that has been said of the relation of one to the body-walls is true of the other. Behind the first piece of the sternum the relations are nearly the .>.ime, but below this level a space exists in the pleiir»- into which the lungs enter during deep inspiration. This is notably the case at the left halt of the body of the sternum. The pleurae present inferiorly at the sides and behind a merely potential cavity between the diaphragm and the chest- wells, to the bottom of which ( probably at the sides and certainly behind) the lungs can never descend. The pleurae, however, never approach closely the lower border of the chest at the sides, for the diaphragm arising from the inner surface of the frame of the thorax takes up a certain amount of space, and above it the connective tissue fills the cleft so that the pleura* do not descend to within 3 cm. of the lower border. In the sub- ject used by Ha?se the space in the ax- illary line below the reflection of the pleurae to the origin of the diaphragm (the lower border of the chest) was 5.5 cm. on the right and 4 cm. on the left. The outlines of the pleura are as follows. Beginning at the apex, about 3 cm. vertically above the cartilage of the first ribs, the anterior borders descend behind the stemo-clavicular joints to meet at the median line at the level of the second cartilage. They then descend together, or nearly so, behind the left half of the body of the sternum. Half-way down the body of the sternum the left pleura tends to diverge to the left, pa.ssing from behind the sternum usually at about the junction *ith the sixth cartilage. The right pleura descends more nearly in a straight line and turns suddenly outward at the level of the seventh cartilage. Laterally the pleurae run pretty close to the cartilages of the sixth rib on the left and the seventh on the right, but both cross the eighth rib at or near the junction of bone and cartilage. In the axillary line, or a little behind it, the pleura crosses the tenth rib at about the same place on both sides, and usually endr, posteriorly opposite the lower part of the twelfth thoracic vertebra, the right one being often the lower (Tanja). While such is the general outline, there are considerable and important variations both anteriorly and pos- SemidlatframmaUc rtrcun»tructiun, showing relatione of left pleural sac (blue) and lung (red) to thoracic wall; lateral aspect. I l^f i860 HUMAN ANATOMY. Fio. 1584. tertoriy. The former teaching, according to which the left (deuia describes at the front a curve somewhat similar to that of the left lung, is auite wrong. However, the point at which it leaves the sternum, the extent to which it is in contact with the right pleura, and the distance the latter advances under the sternum are all very uncertain. The roost important point is the extent to which the pleura covers the peticardium. According to Side's' observations on twenty-three bodies of adults, the reflection of the left pleura at the fifth cartilage was in seventeen either behind the sternum or just at its border ; thus it left the sternum at a higher point only six times. At the sixth cartilage the pleura was ten times behind the sternum and less than I cm. from it in six. At the seventh cartilage it was five times at the border of the sternum or behind it and Ave times not over t cm. external to it. It left the sternum close to the seventh cartilage five times. Tanja,* however, found the left pleura leaving the sternum at the fourth cartilage in four of fourteen bodies ranging from eight years upward. The left pleura may ex- ceptionally cross the median line, and, it is said, mav not extend forward as far as the sternum ; but such a condition must be very exceptional. There is con- siderable variation as to the depth of the descent posteriorly. Tanja never found the lower fold at the back in the adult higher than the middle of the last thoracic vertebra. It may descend to the first lumbar and even to the second. Structure. — The pleura, like other serous mem- branes, consists of a stroma-layer composed of bun- dles of fibrous tissue intermingled with numerous elastic fibres. The general disposition of the con- nective-tissue bundles is parallel to the free surface, although the bundles cross one another in various directions. The free surface of the pleura is covered with a single layer of nucleated endothelial cells (from .020-.045 mm. in diameter), which rest upon a delicate elastic limiting membrane differentiated from the stroma-layer. The existence of definite openings, or stomata, between the endothelial plates, leading into the numerous lymphatics of the pleura, is doubtful. The subserous layer is very thin over the lung where it is continuous with the elastic interlobular tissue. In the mediastinum it has a firm fibrous backing so as to make a strong and dense membrane. The cervical pleura is extremely thick and resistant, being strengthened by fibrous or muscular bands from the system of the scaleni muscles spreading into it from behind, as well as by expmsions from the areolar tissue about the trachea, oesopha- gus, and subclavian vessels. The costal pleura has a subserous layer, known as the fascia endothoracica, through which it is attached to the thoracic walls less closely than elsewhere. This fascia is thickest near the top. The ribs show clearly through the pleura of the opened thorax, appearing light in contrast to the congested inter- costal spaces. The subserous layer is hardly existent beneath the diaphragmatic pleura, but at the sides of the thorax there is a considerable space below the reflection of the pleura from the diaphragm, occupied by areolar tissue connecting the dia- phragm and walls. Blood-Vessels. — The arteries of the visceral pleurae have been shown by Miller to come from the system of the pulmonary arteries instead of from that of the bronchial, as previously believed. They form a tine net-work over the lung. Those of the parietal pleurae come from the aortic and superior intercostals. the in- ternal mammaries, the mediastinal, the oesophageal, the bronchial, and the phrenic arteries. ' Archiv f. .Anat. n. Phys., Anat. Abth., 1885. • Morphol. Jahrhiich, 1891. Endothelium or free siirfat-e iiiiective-UMUe stroma of pleura Strrtiun throujtih free cdfte of Iuiik. show- ing visi-er«l pleura, v ly). THE PI,EUR/F.. 1H61 Injrctcfl IvmphiilU-ii nl plcun, acm from turticc. . 7,1. iMillrr.) The veiMt of the visceral pleurx are tribuUry to the pulmonary system ; those of the parietal pleurae open into the veins correspondinK to the arteries. It » important to note that the intercostal spaces have many veins and that the pleura over the libs lias but lew, these chiefly communicating with the veins above and below them. Owin^; to the arrangement by which the intercostal veins are kept open, the venous circulation of the |)arietsd pleurae is under the influence of the suction power both of respiration and of the heart. The lymphatics are numerous over the lungs and also in the intercostal spaces. Those of the parietes open into both inter- costal and substernal lymph-nodes. Nervet. — The nerves of the visceral picurx are from the pulmonary plexuses, con- taining both pneumogastric and sympathetic fibres ; those of the parietal pleura are from the intercostal, the phrenic, the sympathetic, and the pneumogastric nerves. Development of the Respiratory Tract. — The respiratory tract develops as an outgrowth from the primitive digestive tube. Early in the third week, in embryos of little over j, mm. in length, a longitudinal groove appears on the ventral wall of the fore-gut, extending from the primitive pharynx above well towards the stomach below. This groove becomes deeper, constricted, and finally separated from the fore-gut as a distinct tube, the differen- tiation resulting in the production of two canals, — the respiratory tube in front anha- gus and air-tube open. The cephalic end of the latter becomes enlarged and forms the larynx, the adjoining portion correspond- ing to the trachea. The Lungs. — The distal extremity of the primary respiratory tube soon enlarges and becomes bilobed, pouching out on each side into a lateral diverticulum which rep- resent- the primitive bronchus and lung. These . ulmonary diverticula elongate and subdivide, the right one, which is somewhat the larger, breaking up into three secondary divisions and the left into two, thus early foreshauowing tK liter asymmetry of the lung-lobes. Sii. j the primary air-tube lies medially in the dorsal attachment of the sep- tum transversum, the pulmonary buds extend laterally and backward into the dorsal parie- tal recesses (later the pleural cavities), carry- ing before them a covering of mesoblast. The primary lobes increase in size and complexity as additional outgrowths arise by the division of the enlarged terminal part of each diverticulum. The resulting divisions, or new bronchi, are at first equal, but soon grow at an unequal rate, the one elongating most rapidly becoming so placed as to continue the main air-tube, while the less rapidly elongating division becomes a lateral branch. The repeated bifurcation in this manner results in the production of a chief bronchus, traversing the entire length of the lung, into which open numerous lateral tubes or secondary bronchi. Fio. Prinilive oropharynx M»lian th>r(iii(' aiilagc CEsophag^!'. Lung-tutx' Part of sagittal Mction o( rabbit einbr> o. »haratively solid and re- sembles in many ways a racemose gland. With the expansion following the establishment of respiration, the epithelial celb lining the ultimate air-spaces undergo stretching, a majority of the small polygonal elements becoming converted into the flat plate-like cells seen in the functionating lung. The Larynx. — The pharyngeal end of the pri- mary respiratory tract is surrounded in front and later- ally by a U-shaped ridge, known as the/urcu/a, anterior to which lies the paired posterior aniage of the tongue. The anterior portion of this ridge forms a median ele- vation from which is formed the epiglottis ; the lateral portions cotistitute the arytenoid ridges which bound the laryngeal aperture at the sides. During the fourth month a furrow on the median side of the arytenoid ridges marks the first appearance of the ventricle of the larynx, the margins o! the groove later becoming the vocal cords. About the eighth week the cartilaginous framework is indicated by mesoblastic condensations. The thyroid cartilage consists for a time of two separate lateral mesoblastic plates, in each of which cartilage is formed from two centres. These are regarded as representing the cartilages of the fourth and fifth branchial arches. As development proceeds the cartilages formed at these centres fuse and extend vcntrally until they unite anterioriy in the mid-line. Chondrification is completed comparatively late, and when incomplete or faulty may result in the production of an aperture,— the thyroid foramen. The aiilages of the cricoid .ind arytenoid cartilages are at first continuous, but later become differentiated bv the appearance of a centre of chondrification for each arytenoid and an incomplete ring, for a time open behind, for the cricoid. The latter thus resembles in development a tracheal ring, with which it probably morphologically corresponds. The cartilages Reconstructions of developing bronchial tree. A, fourth week ; K, heKinninf( of 6fth week ; C. close ol fiftliweek. (His-Mtrktl.) THE PLF.UR.f:. i86.^ of WrisherK (cuneiform) and o( Santorini (curnicula laryngw) are formed from •mall portions sc(>arated from the epi|{lottiit and the arytenoids respectively. The Nt«ral canal ll|4ral raril SpiiMl nnrilion Pio. ISS& *,-V«t«bf» Cardhal vdi Rifht lun(«> Right bronchus Diaphrmitm luiehur vena cava Left bronchua Lhrer Poitinn o( tranavcnc aertion of rabbit enibr>o. showinf drvelopinR lunip. v js. ep^lottis and the cricoid possibly represent rudiments of the cirtilages of the sixth and seventh branchial arches. Fio. 1589. Changes in the Relations of the Lungs and Pleura to the Chest-Walls. — At birth the thorax is small, relatively very narrow, with the lower part undeveloped and with more horizontal ribs. The costal car- tila(;es are relatively lonjj to the ribs proper. Nevertheless, at birth and in childhood the borders of the lungs have very nearly the same relations to the chest-walls that they have in the adult, excepting in front. Here they do not extend so far forward, and conse- quently the pericardium is at first less covered by the left lung. The course of the pleur* is much less certain. Tanja found much variation in that of the lower borders of the pleurae, the latter crossing all the costal cartilages fourteen times in twenty-four bodies of children under two years and not a single time in the adult. In eleven of the same series the pleurae did not meet behind the sternum, and in nine the left pleura did not reach it. He found neither of these conditions even once in the adult. According to Mehnert, there is a very slight progressive sinking of Secliuii of fuKal Iuhk. sIu'winK t«i"iiavl ct.anii:tcr oi unin- flated pulni<>nar>' liasiw. X Joo. 1864 HUMAN ANATOMY. the lower border of the lung during the period preceding old age, which is more rapid than the senile increase of the declination of the ribs. -r '' PRACTICAL CONSIDERATIONS: THE LUNGS AND PLEURA. The Lungs and Pleurc — Many of the most important practical questions arising in cases of injury or disease of the lungs and pleurae can be answered only after a physical examination, the value of which will depend primarily upon com- plete knowledge of the normal phenomena associated with respiration. Such knowledge must be based upon acquaintance with the structural conditions that influence the sounds caused by a current of air entering and leaving the normal air- passages and with the chief modifications caused by disease. Only a few of even the most elementary facts bearing upon this subject can here be mentioned, but their consideration at a time when the pulmonary system is being studied can scarcely fail to be of practical value, and is necessary to an understanding of those symptoms of pulmonary or pleural injury or disease which have the most obvious anatomical bearing. Anatomical Basis for Varied Character of Breath-Sounds. — The normal sounds of respiration vary with the situation of the air-passages examined. Their loudness is in direct proportion to their nearness to the larynx, so that laryngeal, tracheal, bronchial, and vesicular breathing sounds are here mentioned in the order that indi- cates progressively increasing softness. Those terms acquire pathological significance when breathing of one type is heard in a portion of the chest where it should not be heard. The nearness of the larynx to the surface and its inclusion of air, as if within a hollow box (West;, make laryngeal sounds loud and noisy on both expiration and inspiration. In the trachea, part of which is deeper, and a portion of the walls of which is of soft muscular and fibrous tissue, both these sounds, as heard over the suprasternal notch, or over the lower cervical or upper dorsal vertebrae, while still loud, are softer and are raised in tone. Over the bronchi, heard best between the scapulae (page 1842), they are both audible and are harsh, but have still further diminished in loudness. Over the pulmonary tissue inspiration has become soft and blowing and expinition can scarcely be heard. The reasons for these differences are as follows. The sounds of breathing are produced chiefly at or about the glottis, therefore distance from the larynx accounts for the diminution in loudness. The decrease in the diameter of the air-tubes accounts for the rise in pitch of the respiratory note. The entrance of the air into compartments of various sizes within the pulmonary tissue breaks up the air-column which carries the sound and distributes the vibrations, so that the sounds are mufiied and soft (West). If the bronchial tubes or tubules are obstructed, as from hyperaemia of the mucosa, or the presence of viscid secretion, the exit of air will be interfered with, and there will be " prolonged expiration." In a broad way, it may be said that in cases in which vesicular breathing is dimin- ished or absent the cause should be sought : (i) In obstruction (pseudo-membrane or fibrinous exudate). (2) In compression (aneurism, glandular swellings, medias- tinal tumors). (3) In immobilization of the chest-wall on the affected side (fracture of rib, intercostal neuralgia, pleurisy or pleuritic adhesions). (4) In distention of the pleura by liquids or air (pneumothorax, empyema). If as a result of disease the vesicular structure is occupied by an exudate (as in pneumonia), the vibrations are conveyed more directly to the ear, expiration becomes audible, and, as consolidation increases, the sounds, first of the smaller bronchioles and then of the larger bronchi, replace the normal blowing sound, and "bronchial breathing" Is established. If the cavity of the pleura is distended with air {pneumothorax), which separates the lung- tissue from the thoracic wall and conducts sound vibrations much less effectively than do solids, the breath-sounds will be feeble and disUnt or absent. If the pleural cttvi;.y is so filled with either air or fluid {empyema) that the lung is collapsed or compressed against the spine, the breath-sounds may be feebh or distant or entirely wa^Iing over the front and sides of the chest, but bronchial breathing can be heard o\'e) the back. In exceptional cases of pleural effusion such breathing is also heard PRACTICAL CONSIP-V / TIONS : THE LUNGS AND PLEUR/E. 1865 over the sides and front, and it has been suggested that this is due to contact hetwi-en a bronchus and a rib, the latter conveying the breath-sounds directly to the . If the larynx or trachea is narrowed, the air has to pass through a constricted aperture, must do so at a greater rate, and will make a louder noise, — stridor. R&les are caused by changes in the mucous and epithelial lining and contents of the air-passages. Like the normal breath-sounds, they are louder and noisier the nearer they are to the larynx or the larger the tubes in which they are produced. Mucous r&les are moist, are thought to be produced by the bursting of air- bubbles in viscid c- watery mucus occupying the larger air-passages, as in bronchitis, and vary in character (i.e., in fineness or coarseness, or in loudness) in accordance with the size of the tube that they occupy. The bubbling of air through the ac- cumulating mucus in the larynx, trachea, and bronchi of a moribund person — the " death-rattle" — is an example of the larger kind of mucous riles. Crepitant r&les arc dry r&les, due, it is thought, to the gluing together of the opposing surfaces of a number of air-vesicles by an exudate, the entrance of air on inspiration then causing a fine crackling sound, ' ' like that which is heard when a small bunch of hair near the ear is rolled backward and forward between the tips of the finger and thumb" (Owen). If a similar condition affects the lumen of a tube, \* may produce larger riles, still dry, known as rhonchi (%nox'm^~) ox sibili (hissing). Other factors enter into the production of riles, but the chief underlying anatom- ical conditions have been mentioned. Air entering a cavity (pulmonary vomicig, bronchiectasis) causes a sound re- sembling that produced by blowing into an empty bottle, — amphoric. A peculiar sound heard often in pneumothorax, and caused by the air from the fistulous com- munication with the lung entering the pleural cavity and producing a bubbling sound at the orifice, is described as metallic tinkling. It is also thought to be due to the dropping of liquid into an accumulation of fluid at the base of the pneumo- thorax. Voice-sounds, like breath-sounds, are louder over the laryngeal, tracheal, antl bronchial regions. When the voice seems very close and loud to the ear placed over other regions (^pectoriloquy, bronchophony), it indicates increased power of conduction, — i.e., consolidation of lung- tissue. If the tremor from the vibration of the vocal cords in speaking (vocal fremitus) is transmitted with increased distinctness to the hands placed on the surface of the thorax, it has the same significance. If it is absent, it usually indicates the interpo- sition of some relatively non-conducting substance, as air (pneumothorax), or pus ' (empyetna), or blood (hamothorax). Percussion-sounds vary with the region and the condition of the lungs and pleurae. Normally, during quiet breathing, the resonance is increasingly clear from the supraclavicular region downward over the front of the chest to about the fifth rib on the right side — where the pulmonary tissue begins to decrease in thickness on account of the presence of the liver — and to the sixth rib on the left side. It is less above the clavicle and over it, on account of the comparatively small amount of lung- tissue in the apices ; and over the upper part of the back, on account of the interpo- sition ol the scapulae and of thick muscular masses. It becomes diminished in the presence of moderate effusion, as in oedema ; dull if there is consolidation of lung- tissue ; and is absent (flat) if there is either plastic exudate or fluid effusion in the pleural cavity. In pneumothorax, or over a cavity in the pulmonary tissue, especially if it is superficial, the percussion-note is tympanitic. Injuries. — Contusions of the lung may occur without fracture of the bones of the thorax or obvious lesion of the parietes. They are thought to be due to suddenly applied elastic compression when — the glottis being closed — the lung or the lung and pleura are ruptured as one may burst an inflated paper bag between the hands. The consequences are interlobular emphysema, the air having escaped from the ruptured air-cells into the connective-tissue spaces of the lung (vide infra); gerurcU emphysema, the air reaching the subcutaneous cellular tissue of the neck and trunk through a ruptured pleura, or, the pleura being unbroken, passing from the root of the lung into the mediastinum and thence to the base of the neck ; pneumo- t866 HUMAN ANATOMY. ;i^ il thorax, the air entering the pleural cavity ; in traumatic interlobular emphysema, or pneumothorax, the chest on the affected side will be hyper-resonant, the vesicular murmur will be feeble or absent, and in the latter there may be amphoric breathing and — if there is a coincident effusion — metallic tinkling ; hetmoptysis, not an invaria- ble symptom in either these injuries or lacerations by fractured ribs, probably because they are usually on the external lung surface and remote from the larger bronchi ( Bennett) ; htemoihorax, indicated by percussion dulness gradually extending upward, by weakness or absence of respiratory murmur, by bronchial breathing over the compressed lung, and by absence of vocal fremitus. Penetrating wounds of the lung will have many of these signs plus the escape of blood from the external wound. In the absence of haemoptysis, the possibility of a wound of the costal pleura and of an intercostal or internal mammary artery causing hsemothorax, dyspnoea (from pressure), and hemorrhage, apparently in- fluenced by respiration, should be borne in mind. Wounds of the pleura without involvement of the lungs are rare, the visceral pleura being closely adherent to the lung suriace and the two pleural layers in close contact with each other. At the base of the pleura, where a potential cavity (page iS.sq) — costo-phrenic sinus — exists between the costal and diaphrs^^matic layers, a wound could penetrate both layers and the diaphragm and open the abdominal cavity and involve the liver or spleen (page 1788) without implicating the lung, which even in forced inspiration does not descend to the bottom of this sinus. Wounds of the pleura are apt to be followed by pneumothorax and by collapse of the lung, which is partly driven back towards its root and the vertebral column by the atmospheric pressure from without, and partly drawr there by its own elasticity even when the pressure within and without IS equal. In operations for empyema this collapse of the lung i.iay take place, but is infrequent because the pulmonary tissue has often already undei^one considerable compression, and because the atmospheric pressure is resisted by preformed pleural adhesions. General emphysema is often associated with wounds of the lu.igs and pleura. It may be due to (a) escape of air from a pneumothorax into the subcutaneous tissue during respiratory movements, or (^) escape of air direct from injured lung-tissue when pleural adhesions about the wound prevent the formation of a pneumothorax. Its occasional occurrence in laceration of the lung without external wound and without involvement of the pleura has been explained (vide supra). It may follow a non-penetrating wound of the chest if the opening happens to be valvular, so that the air drawn in during respiratory movements cannot make its exit by the same channel. Pneumocele — hernia of the lung — is rare as a result of thoracic wounds because the elasticity of the lung-tissue and atmospheric pressure tend to cause collapse and retraction of the lung rather than protrusion. When it is primary it therefore follows (a) a limited and oblique wound through which air cannot freely enter the pleural cavity, although the egress of the lung under the pressure of muscular effort or the strain of coughing is unopposed ; or (b~) a very large wound when the lung escapes at the moment of injury (Bennett). Treves says that these recent hemiae are most common at the anterior part of the chest where the lungs are most movable, and that the injuries that cause them are often associated at the time with violent respiratory efforts. Pneumocele is more apt to follow the rare wounds that divide only the costal pleura, as a wound of the lung itself tends to the production of a pneumothorax — which would lead to collapse of the lung — and instantly lessens the pressure of air con- tained in the lungs and trachea, one of the forces favoring protrusion. Diseases of the pleurse and lungs can here be very briefly summarized only with reference to the anatomical factors. Pleurisy is at first attended by a "friction-sound" due to the roughening of the opposed surfaces of the visceral and parietal pleurae by fibrinous exudate. Later it may be lost by rea.son of (a) the temporary disappearance of the roughness, (^) the formation of adhesions between the surfaces, or (f ) their separation by effusion. It is tost njomentarily when the patient holds his breath, which will serve to differ- entiate it from a pericardial friction-sound. As the costal pleura, the intercostal PRACTICAL CONSIDERATIONS : THE LUNGS AND PLEURA. 1867 muscles, and the abdominal muscles are all supplied by the lower intercostal ner\-fs, the respiratory movements on the affected side are painful and are therefore greatly limited. Accordingly there will be hurried, shallow breathing with a weak vesicular murmur on the affected side and exaggerated respiratory sound;- on the opposite side. Pain and tenderness in the epigastrium may result from implication of the trunks of the lower intercostal nerves when the pleurisy is near the Ixise of the chest. When it is higher the pain may be felt in the a.xilla and down the iniK-r side of the arm from involvement of the intercosto-humeral nerve, or in the skin over the seat of disease through the lateral cutaneous branches of the upper intercostals ( Hilton). In diaphragmatic pleurisy the pain may be intensified by pressure over the point of insertion of the diaphragm into the tenth rib (Osier). Pleural effusion (hydrothorax , empyema), in addition to the sif'ns already described {vide supra), causes, when it is of sufficient amount, additional symptoms, as bulging of the side of the chest with obliteration of the intercostal spact-s, disten- tion of the net- work of superficial veins (from pressure on the vena cava or greater azygos vein), and displacement of other viscera. If the fluid occupies the left pleura, as its weight depresses the diaphragm, the pericardium, which is attached to the central tendon, d< 's also, and with it the apex of the heart. At the same time the heart is pusi -^rds the right so that the ape.x beat may be felt in the epigastrium (Owen). An empyema m. v / . and discharge itself spontaneously, in which case it often does so at about itte fifth intersjjace just beneath and external to the chondro- costal junction (Marshall). At this place the chest- wall is exceptionally thin, as the region is internal to the origin of the serratus magnus, external to the insertion of the rectus, and above the origin of the external oblique (McLachlan). Evacuation of the fluid may be effected by paracenteses — in pleurisy with serous effusion — through the sixth or seventh intercostal space in the mid-axillary line, or through the eighth or ninth space just anterior to the angle of the scapula. The same regions are selected for thoracotomy — incision and drainage — in empyema. The former site is usually preferred for anatomical reasons already given (page 170). Pneumonia is often limited to one lobe of a lung, usually the lower. The fis- sure between the two lobes of the narrower left lung runs from the third rib behind, or from about the third dorsal spinous process or the inner end of the spine of the scapula, to the base in front. The fissure between the two lobes of the right lung begins at about the same level behind and extends to the base of the lung anteriorly. Where it crosses the posterior axillary line a second fissure springs from it which passes horizontally forward to the fourth chondro-costal junction making the middle lobe. Both lower lobes are posterior to the anterior lobes, and on both sides the fissures run from the level of the inner end of the spine of the scapula behind to the base in front. Therefore the dulness, crepitant rales, bronchial breathing, and increased vocal fremitus of a lobar pneumonia affecting the base would often be below that line posteriorly and would be less marked in front ; while the flatness, prolonged expiration, and other physical signs of a tuberculous infection (which affects by preference the upper lobe) would be above the spine of the scapula posteriorly, and lower would be more marked anteriorly. The relations of the lungs to the thoracic walls have been described in detail (page 1855). The congestion and oedema which precede the so-called ' ' hypostatic pneumonia' ' are very apt to begin in the thick lower and posterior jiortions of the lower lobes in weak or aged persons kept long in the supine position. Tuberculous infection of the lungs is found oftenest in the apices, probably because of the relatively defective expansion in that region which exists in all persons, and particularly in those of the so-called phthisical type, with round shoulders, long necks (page 143), and flat chests ; possibly also because of the greater exposure to changes of external temperature ; and perhaps somewhat owing to the short distance intervening between the outside atmosphere and the ultimate bronchioles where tuberculous pulmonary disease usually has its inception. The physical signs are those indicating consolidation followed by softening or the formation of a cavity {vide supra). ■i iM8 HUMAN ANATOMY. II b Surface Landmarks of Thorax. — The most important of the bony points have already been described in connection with the spine, thorax, clavicle, and scapula. The relations of the thoracic viscera to the surface have likewise been given (page 1855). Inspection or palftation of the front of the chest will show (a) the oblique eleva- tions of the ribs and the intercostal depressions ; (^) the curved arch of the costal cartilages ; (/r) the sternal groove ; (age 579). KlG. 1590. Infraclavicular (ofwa ^^ A£|K' Coracoid |»rocMs^^r-A'^- ^5%^ '^ W^' (Groove between deltott) and {lectoraliH nia>>r SuprR!«lemal notch .Clavkle criiuiii -ALTumion Deltoid KiiHifurm cartilaK« Surface Uindinark^ oz. ) in the male, slightly less in the female, and measures about 11.5 cm. (4>4 in.) in length, 6 cm. (aj^ in.) in width, and 3.5 cm. ( I J4 in. ) in thicknes-s. The left kidney is usually somewhat longer, narrower, and thicker, and slightly uavier than the right. Individual variations, especially as to length, are responsible in some cases for organs unusually long (15 cm.), in others for those relatively short. Each kidney presents two surfaces, a convex anterior or visceral, when the organ is in place directed forward and outward, and a posterior or parietal, some- what flattened and looking backward and inward ; two rounded ends, or poles, of which the upper is usually the blunter and bulkier ; and two margins, the external, marking the convex lateral outline of the organ, and the straighter internal. The latter is interrupted by a slit-like opening, the hilum (hilus renalis), bounded by rounded edges, which leads into a more extended but narrow space, the sinus (sinus renalis), enclosed by the surrounding renal tissue. The capsule is continued from the exterior of the kidney through the hilum into the sinui., wMeh it partly lines. In addition to the blood-vessels, lymphatics, and nerves passing to rnd from the kid- ney through the hilum, the sinus contains the expanded upper cud of the renal duct 1X69 1 1 iSro HUMAN ANATOMY. or ureter, which also emerges at the hilum. The interspaces between these structures are filled with loose areolar tissue, in which lie accumulations of fat continuous with the perirenal tunica adiposa. Position. — The kidneys lie behind the peritoneum, embedded within the sub- peritoneal tissue, so placed against the side of the vertebral column and the posterior abdominal wall that they occupy an oblique plane, their anterior surfaces looking forward and outward. The long axes of the organs are not parallel, but oblique to the spine, in consequence of which disposition the upper ends of the two organs are closer (8.5 cm. ; than the lower extremities ( 1 1 cm. ), the planes of the inner margins Hepatic veiiu Fig. 1 59 1. M' RiKht supnireMal^'^-\ body Vctia cava -\ Right renal vein Riirht kidney 1,' Right ureter Right spermatic- vein Right s|K.'rniatic artery Externa) iliac artery Vas deferens Spermatic cord Cteliai- axis Oesophagus y^ Superior mesenteric artery X y^ y^ ^^ Left suprarenal ^' • body Left renal vein Left kidney Left renal artery Rectum (cut) Vas deferens Kladder Dissection of abdomen, showing kidneys tn position and course and relations of ureters. being anterior to those of the external. The greater part of lx)th kidneys lies within the epigastric region, but their outer margins reach within the hypochondriac areas and their lower ends ordinarily encroach to a limited and varial^Ie extent upon the umbilical and lumbar regions. The intersection of the plane of the transverse infra- costal line and that of the vertical Poupart line usually passes through the lower pole of the kidney, falling, as a rule, somewhat higher in the right than in the left organ. Approximately the kidneys may be said to lie opposite the last thoracic and the upper two lumbar vertebrae, reaching to within from 2.5-3.5 cm. (i-ij4 in.) of the highest part of the iliac crest. The exact level of the kidneys, however, is subject i THE KIDNEYS. 1871 to considerable individual variation, as v-oii as usually differing on the two sides in the same subject. The right organ corimunly lies somewhat lower than the left, in consequence chiefly of the greater permanent volume of the right lobe of the liver. Not infrequently the kidneys occupy the same level, and in exceptional cases the ordinary relations may be reversed, the right lying a trifle higher than the left. Addison ' found that in 30 per cent, of the subjects examined by him the right kidney lay as high or higher than the left. According to Helm,' in women the kid- neys lie, as a rule, about one-half of a lumbar vertebra lower than in men, this differ- ence depending upon the smaller size of the vertebra and the greater curvature of the lumbar spine in the female subject. As a rule, the right kidney extends from the upper border of the last thoracic to the middle of the third lumbar vertebra, or somewhat lx;low the lower border of the third lumbar transverse process. While always obliquely cros.sed by the twelfth rib, the outer margin of the right kidney usually falls short of the eleventh rib. Fig. 1593. Aorta Pancroi! ro-hrpatic omentum Superior meiieiiterit: artery Hepatic arter> Portal vein Left Icidney Perirenal Ut.' ^-~-^iaphraxni Kight Miprarviial bocly 'Right kuliivy AHceiKling colon Psoas muiale : ^ I Posuri.ir a»|>e-»all has bet'ti also |iarts of pleural sacs and diaphragni. been removed, as have the support of which organ it materially contributes. Although everywhere sepa- rated from the fibrous tunic of the kidney by the intervening layer of fat (tunica adiposa), the renal fa.scia is attached to the renal capsule proper by bands of con- nective tissue, which are especially strong at the lower pole, thus directly affording support to the organ. Ikhind, the posterior layer of the renal fascia is likew|ise attached to the transA'ersalis fascia by means of areolar tissue, between the connecting bands of which a \'ariable amount of fat is usually present. Above, beyond the suprarenal body, the renal fascia fades away over the diaphragm ; below, it passes into and is lost within the fatty subperitoneal tissue of the iliac fossa. The fixation of the left kidney is firmer than that of the right, greater security being gained for the left organ in consequence of its more extensive relations to the THE KIDNEYS. 1873 Xll rib- Dill phraKm I.IVCT RiKht Hupraretial bu fusion which takes place during the development (page 1704) of the large intestine between the original parietal peritoneum and that covering the applied surface of the primary mesentery of the descending colon ; in consequence, the left kidney is mveated anteriorly with a subperitoneal layer of exceptional strength, \yhen, for various reasons, the tonicity of the tissues supporting the kidney becomes impaired and these structures become abnormally lengthened, the organ may acquire undue mobility and suffer displacement. Relations. — The position of the kidneys being wholly retroperitoneal, the posterior relations of both organs are chiefly muscular, since they lie closely applied to the diaphragm, psoas magnus, quadratus lumborum, and the posterior aponeurosis of the transversalis, the jiarietal fascia and iK-rirenal areolar tissue alone intervening. The inequalities in the supporting structures produce corresponding modelling of the opposed renal surfaces, which is clearly distinguishable on organs hardened in situ. In specimens hardened in formalin, the psoas area appears as a nar- row, slightly di'prcsseritonral) Suprarenal area (non-periloneal) tIepaUc area 'peritoneal) Colic area (non-peritoneal) Jejunal area ijieritoneal) Pancreatic area (non-peritoneal) Duodenal area (non-peritoneal) Ri(hl renal dud Colic area (non-peritoneal) Jejunal area (peritoneal) Left renal duct (ureter) Inferior vena ca\-a Anterior auriace of kidneys ol formalin-hardened suD)eci, snowint viacerai areaa, blood-vessels, and renal ducts. by areolar tissue ; its area is therefore non-serous. The upper two-thirds of the outer border and the adjacent part of the anterior surface of the kidney are covered by the spleen, the peritoneum intervening, except within the narrow attachment of the layei^ of the lieno-renal ligament. Below the splenic area the kidney is covered to a variable extent by the splenic flexure of the colon, this non-peritoneal area usually including the outer half of the lower pole. The pancreas lies in front of the hilum and approximately the middle third of the kidney, frequently reaching as far as the outer border. Above this non-peritoneal area, between the latter and the suprarenal and splenic surfaces, lies the small triangular serous area which the stomach touches, while below the pancreatic zone, internal to that for the splenic flexure, the kidney presents a triangular peritoneal area over which the coils of the jejunum glide. From the foregoing it is evident that each kidney rests within a depression, the "renal fcssa," formed by the structures with which it comes into contact above, behind, at the sides, and below. The fossae are deeper and narrower in the male than in the female, owing chiefly to the greater development of the muscles against which the kidneys lie. The Renal Sinus. — ^The longitudinal, slit-like hilum, occupying somewhat less than the middle third of the inner border of the kidney, opens into a more extensive but shallow C-shaped space, the renal sinus, which, surrounded by the kidney-dssue, THE KIDNEYS. 1875 takes in approximately the median half of the interior of the organ. The ifreatest dimension of the sinus corresponds with the long axis of the kidney, the shortest with the distance between the anttrior and posterior walls. The space — most extended vertically — is compressed from before backward, while its greatest depth ( 2. 5-3. 5 cm. ) is just above the upper border of the hilum. The sinus is occupied in large measure by the dilated upper end of the ureter, the rcna/ pelvis, and its subdivisions, the calyces; the remaming space accommodates the blood-vessels, lymphatics, and nerves that pass through the hilum and the intervening cushion of areolar and adipose tissue tx>ntinuous with the perirenal fatty capsule. The fibrous cipsule of the kidney covers the rounded lips of the hilum and is continued into the sinus, to which it furnishes a partial lining. In contrast to the even external surface of the ki'iiiey, the walls of the sinus are beset with conical elevations, the renal papilla, which are well seen, however, only after removal of the contents and the fibrous lining of the sinus. The i)apill.-e mark the apices of the pyramidal masses of kidney-tissue of which the organ i.s composed. The individual cones, from 7 to 10 mm. in height, are in many instances somewhat com- pressed, so that their bases are elliptical in section instead of circular. Adjacent ones may undergo more or less complete fusion, the resulting compound papillae being often grooved and irregular in form. Usually from eight to ten papilla; are present in each kid- ney, but their number varies greatly, as few as four and as many as eighteen having been observed (Henle). The walls of the sinus between the bases of the papillcC are broken up into elevations and depressed areas, the latter marking the localities at which the blood-vessels and nerves enter and leave the renal substance. The apex of each papilla is pierced by a number of minute openings, barely recognizable with the unaided eye, which mark the terminal orifices (foramina papiliaria) of the uriniferous tubules from which the urine escapes from the renal tissue into the receptacles formed by the '"alyces which surround the papillae and are attached to their bases. The number of uriniferous tu- bules opening at the apex of a single papilla — the field in which the pores open being the area cribrosa — varies with the size of the cone, from eighteen to twenty-four being the usual complement for a simple papilla. When the latter is compound and of large size, more than twice as many orifices may be present. Architecture of the Kidney — The entire organ — a conspicuous example of a compound tubular gland— is made up of a number of divisions which in the mature condition are so closely blended as to giv? little evidence of the striking lobulation marking the foetal kidney. The external surface of the latter (Fig. 1597) is broken up by furrows into a number of irregular polygonal areas, each representing the base of a pyramidal mass of renal tissue, the kidney lobe or renculus, which, sep- arated from its neighbors by an envelope of connective tissue includes the entire tiiickness of the organ between its exterior and the sinus, a renal papilla being the apex. For a short time after birth the lobulation is evident, but later the de- marcations gradually disappear from the surface, which becomes smooth, and ti\c interlobular connective-tissue septa within the organ disap{>ear, the pyramids alone indicating the original lobulation. Rnul vein Renal pel- vis, luwcr part Anterior turface o( ilsht kidney from which fibrous capsule has been partly rctnnvr less marked decree, tht reiwl lobules o< the aquatic mammals bein|f unuNually distiiKt. In some mammals ( rodents, insectivora ) the entire kidney correspunds to a Hinxle papilla, while in others lelephant, horsej no distinct papilla: exist. On making a lunKitudinal section of the fresh kidney, from its convex border throu^rh the sinus, the papillae will l>e seen to form the free apices of conical masses, the renal pyramidi, the broKres!tively less numerous but larger, in consequence of repeated juncture, until, as the wide excretory duets, they end at the summit of the papilla. The relations of the pyramids to the papilhir are less simple than foni ; recognized, since, instead of each of the latter embracing Ixit one of the former, Maresch ' hiut shown tlutt a single prinih the papillary apex. Structure of the Kid- ney. — The fundamental coni|X)nents of the verte- brate excretory organ, both in the fcctal and mature con- dition, include (i) a tuft of arterial vessels derive*! more or less directly from the aorta, ( 2 ) tubules lined with secretory epithelium, and ( .•? ) a duct for the convey- ance of the excretory pro- ducts. These constituents are represented in the kid- ney of man and the higher animals by ( i ) the glomeru- lus, ( 2 ) the convoluted uri- niferous tubules, and ( y, ) the collecting tulies, pelvis, and ureter. Since, in a general way, to the epithelium lining the tubules may be ascribed the function of taking from the circulation the more solid constituents of the urine, and to the glomerulus the secretion of its watery parts, obviously the most favora- ble arrangement to secure the removal of the excretory products is one insuring flushing of the entire tubule with the fluid secreted by the glomerulus. Such ar- rangement implies the loca- tion of the vascular tuft at the very beginning of the tubule, — a disposition which in fact is found in the kidneys of all higher animals. The numt«r of the glomeruli, therefore, corresponds with that of the uriniferous tubules, each of which begins in close relation with the vascular tuft. The kidney-substance consists of an intricate but definitely arranged complex of uriniferous tubules, supported by the interstitial connective-tissue stroma, which ha\e their commencement in the cortex and their termination at the apict - of the papillae, their intervening course l)eing marked by many and conspicuous > .liiatioiis in the character, ^i/ie, and din iion oi the tubules. The uriniferous tubule begins as a greatly expanded •' extremity, the capsule (i), which surrounds the vase r ttift >r glomerulus, x vo together con- stituting the Ji!i^»^A/a« * vith hp labyrinth. *',. leaving the Mal- ;er, Bd. xii., i8q6. I-cHipof Heiile PapnUir> tlurt^ Papilla Diagram showiiiK course >f uriniferous tubule. i87« HUMAN ANATOMY. pighian body the tubule becomes very tortuous and a»ches towards the free surfoce as the proximal convoluted tubuU (2) ; this, after a course of considerable length, usually leaves the labyrinth and Fig. 1600. enters the medullary ray, which it 'Capiuie traverses, somewhat reduced in diameter and slighdy winding in course, as the spiral tubule (3) and piasses into the medulla. Immedi- ately upon gaining the latter, the tubule suffers marked decrease in size, penetrates the renal pyramid for a variable distance towards the papilla, then bends sharply upon Itself and retraces its course to once more enter the labyrinth. Its ex- cursion into the medulla includes the descending limb (4) and as- cending limb (5) of the loop of Henle. The ascending limb— the longer and wider of the parallel limbs of the loop— rises within the labyrinth to the immediate vicinity of the corresponding Malpighian body, the neck of which it crosses, and then, after arching over the cor- puscle, gives place to the distal convoluted or intermediate tubule (6), a segment which, marked by increased diameter and tortuosity, crosses the general course of the convoluted tubule and is succeeded by the narrower and arching con- necting tubule (7). The latter enters the medullary ray and, join- ing with similar canals, forms the ^XiMghX. collecting tubule (%), which, progressively increasing in size by junction with others, traverses the remaining length of the medullary ray and enters the renal pyramid. Within the deeper part of the latter the collecting tubules fuse into larger and larger canals until, as the relatively wide papillary ducts (9), they terminate on the apex of the papilla at the orifices {fora- mina papillaria) which open into the calyces. The relations between the various segments of the uriniferous tubules and the subdivisions of the kidney are, therefore, as follows : Blood, vessels ■Ht f%^ ^}1%JV Section of cortex, showing relation ol labyrinth and medullary rays. X Jo. Cortex Labyrinth Medullary ray Medulla Malpighian body, — capsule and glomerulus Proximal convoluted tubule Ascending limb of Henle' s loop Distal convoluted or intermediate tubule Connecting tubule (beginning) Connecting tubule (termination) Spiral tubule Collecting tubule I Descending limb and Ascending limb of Henle's loop Collecting tubule Papillary ducts THE KIDNEYS. »«79 .Caiwule Injected (loinerulas, «ho« ng tffercnt mm) eflerem vesnels «nd continuation into intertubular capilUrie*. X J50. Althoup^h as a matter of convenienre the entire canal, from its commencement in tlie Malpigiiian body to its termination on the papilla, has been described as the uriniferous tubule, both geneti- cally and functionally two dis- P««*- '*«'• tinct parts must be recognized. These are the unbranched uri- niferous tubule proper, which includes all divisions from the Malpighian body to the termi- nation of the intermediate tu- bule, and the duct-tube, which, when traced from the papilla towards the cortex, undergoes refieated division until from a single stem the number of con- necting tubules is sufficient to provide each uriniferous tubule proper with its own excretory canal. ^'-^t^lKF" ~^V&'.irlflH^IKiBBI^^~ — -■ latenubular ^^■& '^K^fr^l^^BHl^V!Qft capillaries I. The Malpighian Body.— This structure, spherical in form and from .OI2-.030 mm. in diameter, consists of two parts, the glomeruius and the capsule. The former is an ajisi'ega- ion of tortuous capillary blood-ves- sels into which break up the lateral terminal twig;s given of! from the arteries as these pass between the cortical lobules towards the free surface of the kidney. The lateral branches— very short, often arched, and only .002-.004 mm. in diameter— spring at vary- ing angles from all sides of the interlobular arteriole and enter the Malpighian body as the yas afferens. On entering the glomerulus, the afferent vessel divides into from four to six twigs, each of which breaks up into capillaries. These may anastomose and form a vascular complex that may be filled from any branch ; not infrequently, however, such communication does not exist, each terminal twig Fio. i6ot. then giving rise to an iso- lated capillary territory, the entire glomerulus con- sisting of vascular lobules, each drained by its own radicle. Sooner or later all the channels of exit unite to form the single ifos efferens, through which the blood from the en- tire glomerulus escapes. The efferent ves.sel as it emerges from the Mal- pighian body is close to the vas afferens, both usu- ally lying on the side op- posite to that occupied by the neck of the capsule from which the uriniferous tubule Is continued. In consequence of the short course and manner of ori- gin of the twigs from the interlobular arteries, the glomeruli are disposed in rows, somewhat like berries attached to a straight common stalk. The capsule of Bowman, the dilated beginning of the uriniferous tubule, almost com- pletely iriVests the glomerulus uith a double layer derived from the wall of the tubule, which seemingly has suffered invagination by the vascular tuft. Such pushing in, however, is only Capule Section of renal cortex, ihowinc details of Malpighian body . surrounded by capaule whicn {xuaes into obliquely cut neck. glomerulus is X joo. i88o HUMAN ANATOMY. Fi8. i6oj. i ' BInocl-VCSKi Convoluted tabuln. cut transveriely and ob- liquclv, showing character of epithelial lining. X 400. apparent, since the close relations oJ glomerulus and capsule result from the (jrowth of the latter around the vascular tuft and not from invagination of the dilated tubule. The capsule consists of a distinct membrana propria and a liniiig; composed of a single layer of flat, plate-like cells, the modified epithelium of the uriniferous tubule. In sections pa.ss- ing through the afferent vessel and the neck the lumen of the capsule appears crescentic in outline, since the space between its otfter and inner walls is widest at the neck and reduced to a mere slit where the two layers are continuous around the narrow stalk tra- versed by the afferent and efferent ves-sels. The inner or " visceral" layer of the capsule, the thicker of the two, is firmly attached to the glomerulus by the deli- cate intervening connective tissue, the entire complex appearing rich in nuclei which belong to the epithe- lium of the capsule, the endothelium of the capillaries, and the ronnective-tissue cells. i. The Proximal Convoluted Tubule. — After un- dergoing !he conspicuous constriction marking the neck of the capsule, the uriniferous tubule abruptly enlarges into the convoluted segment which forms ap- proximately one-fifth of the length of the entire canal and has a diameter of from .040-.060 mm. In com- mon with other parts of the tubale, its wall consists of a membrana propria, apparently structureless, but com- posed of a delicate reticulum and intervening homoge- neous substance and a single layer of epithelial cells. Although the histological details of the latter vary in different, but not constant, parts of the convo- luted segment, the lining cells present certain charac- teristics, chief among which is the differentiation of the cytopla.sm of the cells into a broader outer and a narrow inner zone. The former exhibits coarse radial striations, the so-called " rods," pro- duced by rows of granules within the vertically di.sposed threads of spongioplasm (Rothstein) which occupy approximately the pe- ripheral half of the cell extending Fio. 1604. from the membrana propria towards the inner zone. The latter, next the lumen, usually appears as a well- defined narrow border whkh, when successfully preserved, presents a fine vertical striation ("bristle bor- der") that depends not upon rows of ;/ranules, as do the rods of the outer zone, but upon the disposition of the threads of the spongioplasm. In consequence of maceration and other post-mortem changes, the inner zone may undergo partial disintegration and break up into short hair-like rods which have been mistaken for cilia. Although the spherical nuclei (.005- .007 mm.) of the epithelium of the convoluted tubule are sharply de- fined, the demarcations between the individual cells are obscure and often wanting, the tubule being lined by a seemingly continuous nucleated layer or syncytium. The lumen is not uniform throughout the convoluted tubule, in some places being wide and In others reduced to mere clefts ; these differences depend chiefly upon the varying height of the epithelial Ittlins. 3. The Spiral Tubule.— Following the tortuous path of the convoluted tubule, the canal is usually continued into the medullary ray by a segment whkrh, while comparatively straight, de- flecting tubule Blood-vessel Portion t f medullan' rmy. showing spiral and collectinit tubules. Y 400. . THE KIDNEYS. 1881 scribes a wavy or spiral course in its descent to the pyramid. This, the spiral nibule of Schachowa, differs from the preceding in the graduat reduction of its diameter (.35-.040 nmi. ) and in the thiclcness of the epithelial lining, the cells of which, although retaining the general character of those of the convoluted tubule, exhibit a distinct demarcation from one another and a narrow homogeneous inner zone. The spiral tubules are distinguishable from the surrounding collecting tubules by the lighter sharply defined cuboidal lining cells of the latter. Just before pa.ssing into the medulla to become the descending limb of Henle's loop, the spiral tubule diminishes in width and in consequence ends as a canal of conical form. 4. The Loop of Henle.— The descending limb of this I -like segnient is distinguishetl not only by the coaspicuous reduction in its diameter (.012-015 mm.), being the narrowest iNirt of the entire uriniferous tubule, but also by the altered character of its epithelium. The latter consists of low elements, so thin that the oval nuclei cause distinct elev-itions in the cells which project beyond the general level of the epithelium. Since the nuci . . usually do not lie exactly Fio. 1605. Fio. 1606. Henle's loop" Collectiin tutnile ' L.ongitudina1 section of medulla passing throuKh Henle's loop. ^ 400. Ascending liml Longitudinal section o( medulla, showing pans of limbs of Henle's loop. X 40a. opposite each other, the projections on one wall alternate with those of the other, in consequence of which dispo- sition the lumen appears wavy and irregular, although not much reduced below the diameter of that of the pre- ceding spiral segment and generous in proportion to the entire width of the tubule. The flattened cells consist of clear, slightly granular cytopla.sm, in which is embedded a distinct elliptical nucleus of relatively large size. The ascending limb differs from the descending in its increased diameter (.024-.038 mm. ), which depends upon sudden augmented thickness of the walls and not upon the width of the lumen, the darker and striated appearance of its epithelium, and its extension from the medulla into the cortex. The outlines of the individual lining cells are not sharply defined in well-pre- served organs, although the readiness with which these elements undergo post-mortem change often results in their artificial separation. The cells are often irregular in height, the lumen, in consequence, varying and in places, especially within the cortex, being almost obliterated. The nuclei often occupy a clear area, and are separated by striations of unusual length. Although the cells exhibit a differentiation into an outer rodded zone, a finely striated inner border, as seen in the epithelium of the convoluted tubules, is wanting ; where an inner zone is represented, it as.sumes a variable vesicular rather than a striated character. The length of the loop of Henle is influenced by the level of the corresponding Malpighian body within the cortex— the nearer the latter lies to the medulla the greater the descent of the loop towards the papilla, and vice versa, this relation probablv depending upon the intimate association between the termination of the ascending limb and the Malpighian body. According to the reconstructions of Huber,' > Amer. Joum. of Anatomy, vol. iv., Supplement, 1905, 1 883 HUMAN ANATOMY. %K^: Fio. 1607. on gaining the Malpighian corpuscle the ascending limb crosses the neck in close proximity to the glomerulus, with which it is connected by twigs from the vas efferens (Hamburger'), and then arches over the corpuscle to end in the succeeding connecting tubule. The position of the sudden transition from the narrow into the wider tube of Henle's loop varies, the change exceptionally occurring after the turn is reached, sometimes within the loop itself, but most fre- quently within the descending limb a short distance above the loop. 5. The Distal Convoluted Tubule— On gaining the level of the corresponding Malpighian body, the ascending limb gradually widens into the distal convoluted or intermediate tubule, a canal approximating the diameter (.o4o-.a45 mm.) of the surrounding convoluted tubules, but differing from the latter in its wider lumen and in the character of its epithelium. This consists of well-defined cuboidcl cells, with spherical nuclei, the cytopla.sm oi which, while granular, is comparatively clear and devoid of stria- tions. The moderately tortuous path of the intermediate tubule is marked by a number of abrupt changes in direction, but in general lies for a time enclosed by the arch described by the corresponding convoluted segment (Schweiger-Seidel), which it finally crosses (Huber). 6. The Connecting Tubule. — This portioi of the tubule ( .023-.0J5 mm. in diameter) resembles the preceding seg- ment in its clear epithelium, the lining cells, however, being lower, with a cor- responding increased lumen. After a short and usually arched course, the con- necting tubule enters the medullary ray and, uniting with similar canals, joins in forming the collecting tubule. 7. The CoUecting Tubule.— This first lies within the medullary ray, where it form: .he beginning of the system of straight duct-tubes that culminates in the canals opening upon the papilla, and then passes into the renal pyramid. During their course through the medul- lar}' ray the collecting tubules repeatedly unite to produce stems, which, while in- creasing four- or fivefold in diameter, are diminishing in number. In consequence of this fusion within the pyramid, the col- lecting tubules are disposed in groups (Fig. 1609), each of which corresponds to the tubules prolonged from a single medullar}' ray and is surrounded by the limbs of the loops of Henle. On enter- ing the renal pyramid, the groups of col- lecting tubules at first are separated by the intervening bundles of straight blood- ves.sels {vasa recta) that are given off from the larger twigs within the boun- dary zone for the supply of the medulla. After pas.sing to within about 5 mm. of the apex of the papilla, towards which they converge, the large collecting canals undergo repeated junction, increa.sing in diameter but rapidly dimin- ishing in number, to form the wide papillary ducts. The epithelium lining the collecting tubules — the larger as well as the smaller — consists of c'«;ar cuboidal or low columnar cells, sharply defined from one another and provided with spherical nuclei. The light-colored cytoplasm and distinct demarcation of these elements render the collecting tubules conspicuous and their recognition easy. 8. The Papillary Ducts.- These, the final segments of the kidney tubules, number from ten to eighteen for each sinj,-le papilla, at the apex of which they end. Each is formed by the junction of from ten to thirty of the larger collecting tubules (.050-.060 mm.) and attains a diameter of from .2-. 5 mm. The lining epithelium is composed rif mnspimous, clear columnar cells, about .oao mm. in height and one-third as much in width, which rest upon a distinct > Archiv /. .'Vnat. u. Entwick., Suppl. Bd., 1890. I.onptudinal ocction of renal medulla, showing Henle'i loops and collectinjc tubules. X 45. THE KIDNEYS. 1883 Blood-vrad I >encendinx limb ul loop membrana propria almost as far as the termination of the canal. At this point the membrane fades away and the epithelium of the duct becomes continuous with that clothing the surface of the papilla and lining the pelvis of the kidney. ^"»- '*»*• It is evident that the num- ber of Malpighian bodies and uri- niferous tubu'es proper is greatly in excess o* the larger collecting tubes, ead) papillary duct repre- senting the termination of an elab- orate system of dividing canals as far as the connecting tubules, from which point the true uriniferous tu- bules complete their tortuous path without further subdivision. The Supporting Tiiaue. — The interstitial stroma holding in place the tubules and the blood- vessels consists of a net-work of modified connective tissue, or re- ticulum, which has been shown by Mall to withstand pancreatic digestion and to form a continu- ous framework throughout the kidney. The stroma is most abun- dant along the paths of the in- terlobular and the larger blood- vessels, from the adventitia of which delicate trabecule extend in all directions to form the meshes lodging the tubules, smaller ves- sels, and capillaries. Within the cortex the supporting tissue is meagre, being best developed akMig the interlobular ves.sel' and around the Malpighian bodies. According to Mall, the membrana propria of the tub ilts is resolvable into delicate net-works of reticulum directly continuous with the surrounding ■ .>ma, the general arrangement of which corresponds to the disposition of the tubules. Within the medulla the interstitial tissue is much more abundant than in the cortex, its amount increasing towards the apex of the papilla, in which location considerable tracts of comparatively coarse stroma-fibres separate the papillary ducts. At the surfaces of the divisions of the renal substance AscetutiriK limb of loop Section of medulla acrou renal pvramld. •howinK large collecting tubules, limbs d Henle's loops, blood-vessels, and stroma. X 130. Fio. 1 610. Space for blood-vesael Fig. 1609. Blood -- vessels Uriniferous. tubules .*. »•- a • • -^^ ,• V SP ^^^%v Section across upper part of renal p>Tii- mid, showing Rroujis of blood-vessels sur- rounded by uriniferous tubules. X so. SupportiiiK ntroma-timue of kidney after pancreatic dijceAtlon ; spaces lodged tubules and blood-vessels. X no. the interstitial tissue is continuous with the investing fibrous capsule, the interlobar septa, or the lining of the pelvis, as the case may be. Not only the blood-vessels, but likewise the nerve- trunks and the lymphatics are provided with sheaths of the renal stroma. 1 884 HUMAN ANATOMY. Fio. 1611. Two calyces Blood-Vt»ne\9.—^rierifs. — ^The renal arteries— usually one to each kidney, but not infrequently two, and in exceptional cases three or even four — are of unequal length, the right one being the longer in consequence of the parent stem, the aorta, lying to the left of the mid-line. Embedded within the subperitoneal tissue and covered by the renal fascia (ps^e 1872), they pass laterally, accompnied and more or less masked by the renal veins, to the hilum of the kidney, dunng their course giving of! small twigs to the capsula adiposa as well as to the suprarenal bodies. Just before entering the kidney, or within the hilum, the renal artery divides into an anterior (ventral) and a posterior (dorsal) branch, each of which embraces the pel- vis and divides into four or five twigs that hug their respective wall of the sinus. Preparatory to entering the kidney, each twig breaks up into from three to five smaller divisions which enter the renal substance through the vascu- lar foramina surrounding the pa- pilla:. On entering, they piss along the sides of the papillae, their course corresponding in position to the original tracts of connective tis- sue that separate the primary di- visions of the foetal kidney (page 1876) ; they are therefore appro- priately designated interlobar ar- teries. The general expansion of the branches derived from the an- terior and posterior arteries is par- allel to the corresponding ventral and dorsal surfaces of the kidney ; the intervening zone along the convex border of the organ con- tains few, if any, of the larger ves- sels and, in consequence, ap[>ears lighter in color, constituting the white line of Brodel. The vessels supplying the kidney do not anas- tomose, each such "end" artery providing for a particular area of renal substance. On reaching the level of the bases of the renal pyramids, each interlobar artery breaks up into a tree-like bundle of twigs, some of which pursue an arched course across the bases of the pyramids, thereby producing the impression of a series of arcades at the junction of the medulla and cortex. From these vessels two series of terminal branches arise, one for the supply of the cortex, the other for that of the medulla. Inferior divialon of pelvis preparation of injected rirht kidney , from beliind, sliowinff relations of oranchen of renal arter>- to divisions of renal pelvis. The cortical arterioles pursue a course Renerally perpendicular to the free surface, towards which they run between the cortical lobules, ftiving off short lateral twigs that end as the vasa afferentia in the glomeruli of the .Malpighian bodies. The latter are arranged in columns in correspondence with the path of the interlobular cortical arterioles. Some of these, however, do not give off vasa afferentia, but ascend to the kidney capsule, for the supply of which they provide in conjunction with the direct branches from the renal artery. After traversing the capillary complex, the blood is carried from the glomerulus by the vas efferens, which, smaller than the vas afferens, on its exit immediately breaks up into the cortical capillaries that form net-works enclosing the tubules within the labyrinth, and, continuing, surround those within the medullary ray, in the latter situation the meshes being relatively longer and more open and containing blood that has already supplied the proper urniferous tubules. The medullary arterioles, derived from the arching terminal branches of the interlobar stems at the ba.ses of the pyramids, descend within the latter as bundles of .adially disposed THE KIDNEYS. 1885 straight twigs (arleriola recta) that at first surround the groups of collecting tubules and then break up to take part in forming the capillar>' net-work of the medulla. From these meshes the blood Is collected by the straight venous radicles that accompany the arterioles and, with the latter, constitute the vasa recttr, owing to whose presence the darker stris of the medulla are due. In consequence of numerous anastomoses the va.scular supply of the medulla is less independ- ent of that of the cortex, than was formerly supposed (Huber). Veins. — The veins of the kidney are also disposed as cortical and medullary branches which empty into larger stems {vena arci/ormes) that cross the ba.ses of the pyramids as a senes of communicating venous arcades. The blood within the cortkal capillaries escapes by three paths : ( i ) through numerous small veins that traverse the outer third of the cortex towards the capsule, beneath which they empty into larger stems running parallel to the free surface of the kidney. From three to five of these horizontal ves- Fin i6i*. sels converge towards a com- nion point and thereby pro- duce a star-like figure (vena stellala), which is the begin- ning of the inlerlobular vein that, in company with the cor- responding arteriole, passes through the cortex to become tributary to the venous arcade at the base of the pyramid ; (3) through small venous branches that empty directly into the interlobular veins at various levels ; (3) through the deep cortical veins that traverse the inner third of the cortex and are tributaries of the venae ardformes. The medulla is drained by the ven- ula recta, straight vessels •hat begin in the medullary capillary net-work and empty into the arciform veins. The latter terminate in the larger interlobar veins that accom- pany the arteries along the sides of the pyramids and emerge into the sinus around the papills. The further course of the relatively large and valveless venous trunks corresponds with that of the arteries ; the veins draining each half of the kidney unite into a single stem, the two stellate vein Connecting vein EnBient vessel Medullary Capillar)- net -work- Papilla Diagram allowing arrangement of blood-vcsielt of kidney. (After Ditsr.) thus derived joining to form the renal vein. The latter usually lies anterior to the renal artery in its path to the vena cava, the left vein being longer than the right in consequence of the position of the cava on the right of the spine. The lymphatics of the kidney occur as a superficial and a deeper net-work. According to the investigations of Stahr' and of Cunfe,' the superfia 'iphatics comprise a delicate subcapsular mesh-work from which two systems jilecting trunks arise ; the one passes into the kidney to join the deeper lyn., 'atics within the renal substance, the other pierces the capsule to unite with the perirenal lymphatics within the capsula adiposa. The deep lymphatics arise within the cortex from deli- cate interlobular net-works, the general path of the more definite stems being that of the blc d- vessels. On leaving the hilum, the larger collecting trunks — from four to ' Archiv f. Anat. u. Entwick., 1900. » Bull. d. Soc. Anat., F6v. 1902. 1886 HUMAN ANATOMY. seven in number — follow the renal artery and vein, especially the latter, which they surround. The lymphatics of the kidney end chiefly in the nodes lying at the sides or in front of the aorta ; small lymph-nodes frequently occur in the vicinity of the hilum. The nerves of the kidney are derived from the renal plexus formed by contri- butions from the solar and aortic plexuses and the least splanchnic nerve. The Pio. 1 613. StaUatevcia Glomenilui ol Malpixhian body Interlobular aitcrjr Interlobular vein O^tUlary net-work in labyrintli Capillary nc mcduuar)' net-work in rray Large blood-vcaaels at Junction o( cortex and medulla Longitudinal lectlon ol Injected kidney of dog, •howinK xenenl arrangement o< blood-veuels of cortex and adjacent mcdulu. X 40. plexus accompanies the renal artery, which it surrounds with its mesh-work, into the sinus ; within the latter is formed a well-marked perivascular net-work from which a number of twigs are given off to supply the walls of the pelvis and ureter, while the majority accompany the vessels into the kidney. The investigations of Retzius, Kolliker, Disse, Berkley, and especially of Smimow,' have shown that all the renal blood-vessels are generously provided with fibres for the supply of the muscular > Anatom. Anzeiger, Rd. xix., 1901 PRACTICAL CONSIDERATIONS: THE KIDNEYS 1887 tissue of their walls. In continuation the nerve-fibres pass between •' e urinife/ous tubules and form plexuses surrounding the membrana propria. S.jirnow traced the ultimate fibrillae within the tubules, their free endings lying between the epithelial cells. The vessels and tubules of the medulla are provided with similar but less closely disposed nervous filaments which are destined chiefly for the muscular tissue. According to the last-named investigator, the nerves of the kidney include some sensory and both meduUated and non-medullated fibres. The fibrous capsule also possesses a rich nervous supply. Variations. — More or less conspicuous furrows are frequently seen on the surface of the adult kidney j these represent a persistence of the lobulation normally present in the hcUis and the young child. In addition to variations in size, a marked deficiency on one side t>eing usually compensated by a large organ on the other, the Icidneys often present difTerent degrees of union depending upon abnormal approximation or fusion of the primary renal aniages. The connection may consist of a band, chiefly of fibrous tissue, that unites otherwise normal organs ; or it may tie formed by an istnmwt of renal tissue that extends between the approximated lower |M>les ; or the two organs may form one continuous (J-shaped mass across the spine, then constituting a " horseshoe " kidney. Extreme displacement .ind fusion may produce a single irregular orvan whose primary double anlage is indicated by the presence of two renal ducts that descencTon different sides of the pelvis to terminate normally in the bladder. Absence of one kidney occasionally occurs, the organ present usual I y being correspondingly enlarged. Complete absence of both kidneys has been observed as a rare congenital malformation. PRACTICAL CONSIDERATIONS : THE KIDNEYS. Congenital abnormalities of the kidneys may affect (a) their shapie, size, and numlier ; (6) their position ; and kidneys that are abnormal in one of these respects are apt to be so in others. The matter is of practical importance in relation to the diagnosis of intra-abdominal swellings and to the many operations now undertaken for the relief of various renal conditions. (a) Anomalies as to Shape, Size, or Number. — One kidney may be congenitally absent or gready atrophied ; may be constricted so as to a.ssume an hour-glass shape ; or lobulated, as in the foetal condition ; or the two kidneys may be fused so that ( I ) their inferior portions are united by a band of tissue — glandular or fibrous — that crosses the vertebral column, usually in the lumbar region ("horseshoe kidney") ; or (2) they may form an irregularly bilobed mass, one side of which is much larger than the other, or become one single "disk-like" kidney lying in the mid-line on the lumbar spine, on the sacral promontory, or in the hollow of the sacrum (Rokitansky, Morris). Of these conditions the rarest is the true congenital absence, or extreme atrophy of a kidney ( i in 2650) ; horseshoe kidneys are more than twice as common ( i in 1000) ; while one-sided renal atrophy associated with post-natal disease is relatively frequent (i in 138) (Morris). Both kidneys have been absent in many still-bom children and acephalous monsters. In a very few cases a sufiemumerary kidney has been found. Anomalies affecting the blood-supply to the kidney occur in nearly 50 pier cent, of cases. The renal arteries are usually increased in number, or divide at once — before reaching the hilum — into several branches, foetal conditions in the human species that are permanent in many birds and reptiles. Accessory or supernumerary veins are much more rarely found. {b) Anomalies of Position. — Congenital displacement — apart from the horseshoe kidney — usually affects one kidney, which is apt to be found in the vicinity of the sacral promontory or the sacro-iliac joint, but may be either higher or lower, and may, by its malposition, pve rise to serious or even fatal error in diagnosis or treat- ment It would seem proper to include here those rare temporary displacements that are due to the congenital presence of a mesonephron, which — as the usual support given by the peritoneum is lacking, and as the contained blood-vessels are in such cases of abnormal length — permits mobility of the kidney beyond the physiological limits (floating kidney). 1888 HUMAN ANATOMY. Movable Kidney. — The extent vk the normal kidney movement— of ascent during expiration or while Tying supine, and of descent during inspiration or while standing erect — does not, on an avenge, much exceed an inch in the vertical direction. There may also be a slight lateral movement. When this limit is distinctly and greatly overpassed the condition known as ' ' movable kidney' ' results. The normal kidney is usually not palpable below the costal arch. Occasionally the lower end of the right kidney may be felt there just external to the rectus muscle. In emaciation the lower ends of both kidneys may be palpable. Three degrees of abnormal mobility have been arbitrarily but usefully agreed upon fur purposes of description : ( i ) The lower half may be felt by bimanual pal- pation — the fingers of one hand being pressed into the ilio-costal sf>ace posteriorly, and of the other, into the subcostal region anteriorly— during deep mspiration. (3) The greater part of the kidney or the whole organ may be felt during deep inspiration, but ascends under cover of the ribs and liver during expiration. (3) The whole kidney descends and can be retained between or below the examiner's fingers during the respiratory movements (Morris). The most important factors in holding the kidney in its normal position in the renal fossa ((Kige 1874) are : (a) the perirenal fascia, which through its attachment to the transversalis fascia and to the perinephric fat, in conjunction with (^) the peri- toneum, where that covering exists, prevents any undue mobility; (c) the renal vesse' . which must correspond in length to the radius of the circle of movement of the kidn - and, to an extent, resist elongation ; (soas and quadratus lumborum. A careful study of the body-form in its relation to movable kidney seemed to show ( Harris) that a relative diminution in the capacity of the middle zone or area of the body-cavity (containing the liver, stomach, spleen, pancreas, and larger por- tion ot each kidney), either original or acquired (as from tight lacing), acts by forcing the liver and spleen downward upon the kidneys, and at the same time depriving them of the support afforded by the narrowest or most constricted portion of the parietes of this zone, which narrow portion is then above the centre of the kidney instead of below it, as it should be normally. Consideration of the above-mentioned anatomical factors makes clear the greater frequency (80 per cent.) of movable kidney in women than in men. It should be added that in women the renal fossae are normally shallower and less narrowed at the lower ends than in men, the depth and the narrowing def)ending, as has been said, upon muscular development. It will be understood, too, why among the women who suffer from this condition is found a so considerable proportion who are thin and round-shouldered, with long, curved spines and flattening and adduction of the lower ribs, or who have had several children, or one difficult labor, or an exhausting illness attended by emaciation, or have been addicted to tight lacing. In both sexes the history of a violent fall or of a chronic cough is not infrequent. Movable kidney is thirteen times more frequent on the right side than on the PRACTICAL CONSIDERATIONS: THE KIDNEYS. 1H89 left, because of the foUuwing conditions, which are ol varying relative importance in different cajes : (a) the left perirenal fascia is sUengthened by some fibrous bandh, remnants of the fusion of the descending mesocoU)i» with the primitive |)arietal jK-ri- toneum (MoiUlin), the Idt kidney being thus more firmly bound to the descending colon than is the right to the ascending colon ; (d) the greater size, weight, and density of the liver as compared with the spleen, and its more intimate association with respiratory movements, making the impact of the former on the upper surface of the right kidney both more frequent and more potent than the similar conuct of the spleen with the left kidney ; (c) the greater length of the right renal artery, which has to cross the mid-line to reach the kidney ; although the right vein issimilariy shorter than the left vein, it offers less resistance to elongation than does the left renal artery ; (rf) the right kidney is usually lower than the left kidney (page 1871), and therefore more easily loses the support of the parietes at the region where that support is most effective (vuU supra) ; {e) the connection of the left suprarenal capsular vein with the left renal vein gives some fixation to the left kidney, as the capsule remains in position and does not follow the kidney in its abnormal movements (Morris, Cru- veiUiier) ; (/ ) the right renal fossa is more cylindrical — i.e., less narrowed at its lower end — than the left, especially in women, owing to a slight torsion of the lumbar spine (Moullin), or perhaps to the greater width and development of the right side of the pelvis. From an anatomical stand-point, the symptoms caused by excessive mobility are : 1. Those due to traction upon and irritation of the nerves ; as, for example, pain, felt in the loins and often referred to the lower abdomen or genitalia, owing to the association of the renal plexus with the spermatic or ovarian plexus ; the same association gives to the pain produced by pressure upon a movable kidney the sick- ening quality peculiar to testicular nausea (page 1951); nausea and vomiting, due to a similar connection with the solar plexus and pneumogastrics ; neurasthenia, which may be either a result of movable kidney — through nerve irritation — or a c^use, when it has produced emaciation and muscular weakness. 2. Those due to traction upon the gastro- intestinal tract, especially upon the duodenum and bile-ducts, as digestive disturbance, flatulence, constipation, and even jaundice. As the second portion of the duodenum is dragged upon throiigh its areolar-tissue connection with the right kidney, its lack of mesentery prevents it from moving downward, it is stretched so that its lumen is diminished, and interference with the digestive current and secondary dilatation of the stomach follow (Bartels) ; at the same time the bile-ducts are elongated and narrowed and the passage of bile through them is interfered with (page 1731). On the left side similar disturbance of digestion may follow the pull of the kidney on the stomach and colon. 3. Those due t traction upon the vessels, resulting — as the compressible vein is more readily affected — in congestion of the kidney, sometimes so marked as to give rise to a temporary haematuria. 4. Those due to traction upon or angulation or twisting of the ureter, causing an acute hydronephrosis, at first intermittent. Tuffier has shown that the bending or kinking of the ureter when a kidney is displaced occurs in more than 50 p^r cent, of cases at a jxjint a few centimetres below the pelvis, where it is held again.st the abdominal wall by strong connective tissue and cannot follow the moving kidney (Landau). In some cases, as a result of ureteral stenosis at the point of obstruc- tion, secondary changes occur in the kidney which consist essentially in (a) an atrophy of the renal structure most directly exposed to pressure from the retained urine (Virchow) ; and (*) interstitial degeneration resulting from interference with nutrition, due to the facts that distention of the pelvis of the kidney takes the direc- tion of least resistance, which is forward, and that the pelvis b placed behind the vessels where they enter the hilum, so that as it distends it stretches, flattens, and obstructs them (Griffiths). As Morris has pointed out. the increased resonance and diminished resistance in the loin, described as indicating the absence of the kidney from its nn in.J position, are of little value because (a) the ilio-costal space in some positions ^\ the trunk and thigh is somewhat hollow ; (Jb) the thickness of the loin muscles and of the fat makes the percussion-note dull even when the kidney is displaced ; and (r) in its normal 119 1890 HUMAN ANAiC'MY. position the kidney is so overlappe<- ' ptionally- oblique insertion of the ureter into the pelvis (Virchow), or i)rought ,1 ^ut by distention of the pelvis (Simon >, or aggravated by liwelling oi the peUu .auc<>»a (Kiister, Cabot; — or ob- structive disease of any part of the louer urinary tr.n.' ojay al»i result in a hydrone- phrosis which, if infection occurs, — as it often does, — becomes a pyonephrosis. Either a purulent collection thus formed or an abscess originatHi^ in the renal structure (pyogenic or tuberculous infection) may find its way iiii^ the fatt and connective tissue of the loin, — perinephric tissue,— or suppuration may reach that rejjiun from other sources or may occur there primarily. Perinephric abscess is characterized by certain symptoms which should be studied in connection with the anatomy of the region, as (^a) pain, radiating to the lower ab- domen, genitalia, or thigh, — i.e., in the distribution of the iliu-hypogastrir ilit) ingui- nal, anterior crural, obturator, and othfcr branches of the lumbar plexus ; bj flexion and adduction of the thi^h, from irritation of the motor filami nts of the same nerves, especially if the abscess is about the lower pol*- of the kidney, -md therefore in inti- mate relation with the third and fourth lumbar nerves, from which the supply of the flexors and adductors is chiefly ' derived ; (r ) bending of the body towards the afiected side, towards which the concavity of a lateral lumbar curve in the spine is directed, — a symptom which, like 6, may be due either to muscular spasm or to an instinctive effort to increase the loin space; (d) intestinal disturbance from the proximity of the abscess to the colon, into which it may ■ ;>en. Such abscess may also penetrate the lumbar aponeurosis and the quadratus lumb« rum muscle and ap- pear in the loin at the outer border of the erector spinae between the latissimus dorsi and external oblique (the lower part of which interval is Petit's triangle, q. v. ), or mav descend by gravity into the pelvis, or may — very exceptionally— open into the peri- toneal cavity. Abscess of the kidney which penetrates the renal capsule to reach the perirenal region usually docs so at a non-peritoneal area of the kidney surface, but does not necessarily reach the loin. As reference to the relations of the kidney (page 1873) will show, the pus may be evacuated directly into the colon or duodenum, or more fre^ such as is afforded by the X-rays — depend for their interpretation 11 j - of the renal reflexes, — i.e., of the association of the small and lesser the tenth to twelhh dorsal and first Uimhar spinal segments with the .enso^^' and motor nerves derived from the same segmeri's. These sympton;-- are, 111 part, pain radiating to the genitalia, vesical irritability, nausea and vomiting, -rtil tenesmus. and retraction of the testicle. The last-named symptom is m- '■■ mi- and young jiersons, in whom the gland is "ften drawn up '.\y even into the inguinal canal. After pubertj' is the testis increases cremaster grows feebler with age. the retraction becomes less obvi ^i It has been suggested that occasionally the sudden exacerbw ring at night when the patient is at rest may be due to the passa the colon that presses against the kidney (Jacobson . The aching pain beginning at the lower edge of the last rib, in it and the spine, and extending along the edge of the rectus mus. i. of the umbilicus, is probably reflected along tht last dorsal nerve, certainly relieved by uperatioiis in which that ner\ e is divided, but the st - is found (Lucas). Disease of the kidney, when non-suppurative, has >ut little obvious an;- m: bearing. It may be noted, however, that the time-h mored practice of aDplying counter-irritants and heat to the loin in renal congestions has a scientific bas- in the 'hose described and which — > nee of i' stone, rn a knowledge : 'anchnics and Ked in cbikiv^Ti ' xtemal t _ 'ft weight a ht - (Lucc n of p.-i of flatu •ccui rlon= ang-le l)et»et >tki«i the \fv*- I PRACTICAL CONSIDERATIONS: THl KIDNK S. 1891 free ^nastonn>-.i» between the low ■ the par><-tt3> oi the loin, aiut i«i>nv part of the " suhperitontal arteri;' by a tiinilar v( '>ua anaMlotnattis. or countcr-irrit;! ts to the loin may v«9!iels an<) with= rawing blood fron' In son. -whai the «ime line of i, intercottal and upper lumbar arteries, supplying tr. nal branrheaol the renal artery. Tni! iiJlexir*" • ihus the u-t at If u^ht, to the bi ts ?hat 1 •■ capsuU nd pelv is o« tht reni»i pain, u,{ 1- :>endent iitfectioii, or on the Irrit. pla< nent, .suall means im caaed t sion ; that great gesuufl is theteforr dten e\ptnenced a tcr nephrotomies Turner) — is accompanied, of murse, ,f>lication of cups 1 'r hot fomentation!! tempffrar !v by cnlarginv -iU' rficial ixl kidney. >n, attention mil called he seniutive |)ort, ns ; that 11 of a calculus, < r on lis- liel of both jwin ., ud c<.n- at are merely expl- iratorv. or infl (.onR. idney 1 .if .., the to chronic n-A ) , and e\\ i£rav rena, congestion ,iay d ito evacuation and the accompanying siwlden relief from habitual pressure just as . ((.'.lows some cases of catheterization of habituall , distewle.' iiladders i Belheld : ar. 1 th.it occasional cures of various forms of acute or siib:uut. nephritis, of of "albuminuria associated with kidney tension ' 1 Harrison i-. be«>n obtauivf? m rely by itiiitg the kidney capsule with or w hout pii kidney r"«lf. The i.iore rece it attempt (Israel) to :inply tl'.. m< ' nttihriti vith sevt or .iangcrous symptoms (especial colic and j th« still more r. I ent ntrmiuction ( Edebohls) of bilateral deco- ali' tion — in chronu nephniis without such symptoms, have not at is tii their value. T v a ;> of mii < interest, however, in relation ject of tension i the nidi y ' '>f the effects of nvxlification The l-^ nclicial resnitr of relie tension in swellings of thf- tes: )r o! the eye (acute glaucoii .ue pointed out as illusti itio which splitting the --apsule benents some forms of nephritis rortiCBtf Ml is sup; >sed to act by removing a barrier — th aitaWkhp ' nt of coilati li circulation, promoting a fref- sup] p viousi' impoverished by reason of the inadetjuar' >f it ab- Hjftioi exce* tvt interstitial connecti\e tissu he thf-lium. an e removal ot injurious pressure ujx)n the The probl. 1.: pres- "ted have so distinct an anatonn here does M' «?m ppropriate. The rici. nl-supply of the kidney, — an amount of tJood equal in weight to that of the or^ ' 1 itsdf flowing through it each minute during full functional activity (Tilden Brown), -while it favors congestive conditions nakes total embolic necrosis — such as occurs in other glands confined within dense < salivary gland as a secondary result in angina Ludwig^ii cle in some cases of torsion with complete venoe (Gerster) — very rare, only one case (Friedlander i Subparietal injuries to the kidney are conm .1. visceral lesions resulting from contusions of the abdomen or loin. Rupture of the kidney by abdominal or lumbar contusion has been experimentally shown (Kiister) to depend upon the effect of a force (hydraulic) acting: through the full vessels and the pelvis and causing the kidney to burst, usually along the lines radiating from the hilum in the direction of the tubules, — i.f., transverse to the lonv - of the kid- ney, towards the point of maximum impact of the lowpr ribs, the opp«>- ^ of which the tatal kidney is composed. As the ribs in immediate rel. •-'■■ n - l • k»*«»ey ..re the eleventh and twelfth, which are rarely fractured, lacer<«s«'« br *rect mepae* of brokes n\x is relatively uncommon, although it does ewxm Ruptures may much more raretv l»r jwrxiiice^ « muscular action alone, but in such cases the violent muscuiar effort tha' usually at«»«ct» the ribs .< forces them against the kidney and towanis the spite is almost .dways associat. with forward or lateral bending of the vertebral column Forcible anterior tiexion >: the spine, as sub- pjy. s) in le- ts Cii lie the >lood ; th-- kidney ■els, and favoring the tion of renal epi- ou,s -iiles ( Exlebohls ) . iring that their mention tiles, .«s in the si hmaxillary 'c 553) and in the testi- rtial arterial obstruction g t.>een reported constituting 34 per cent, of 1892 HUMAN ANATOMY. from a wei^jht falling on the shoulders, may cause compression of the kidney between the lower ribs and the ilium, and is, therefore, not infrequently followed by hsema- turia, indicating some degree of rupture of kidney-substance. The rupture may be (a) incomplete, — i.e., may involve the parenchyma alone, the symptoms in these relatively rare cases being those of excessive renal tension {vide supra), the constitutional signs of hcmorrh^e and of toxaemia (usually due to urinary extravasation or to perinephric cellulitis) being moderate or lacking : {b) complete internally, — into the pelvis of the kidney, — a more common condition, in which haematuria, acute hydronephrosis, from blocking of the ureter with blood- dot, and vesical irritability are prominent symptoms, and the constitutional signs of hemorrhage and toxaemia are more marked ; (f) complete externally, ^-exltadmfi, through the fibrous capsule, — in which, in addition to the immediate indications of hemorrhage and the later symptoms of sepsis, the usually free urino-sanguineous effusion into the loin produces marked lumbar swelling and tenderness ; or (d) com- plete, — running from the pelvis to and through the capsule, — in which, with a com- mingling of the above symptoms, there is often profound shock which may terminate fatally. Rupture of the kidney extending through its outer surface may be (^) transperi- toneal, in which case hemorrhage is apt to be very free, as there is no surrounding pressure to resist and limit the extravasation, and fatal peritonitis will almost surely follow unless the escaped urine is normal, acid, and sterile, and unless both it and the blood-clots are speedily evacuated. When, in addition to the laceration of the kidney, a single intraperitoneal organ is also injured, it is always on the same side as the injured kidney (Watson). The liver, for example, or the ascending colon, may be involved in a case of sutoarietal rupture of the right kidney, but never the spleen or the descending colon. Inis will readily be understood from a consideration of the frequency with which the cause of rupture is a forcible forward bending of the vertebral column, the kidney being caught in the angle of the bend, any lateral deviation of which may determine the side on which the injury occurs and the involvement of liver or spleen respectively. Transperitoneal rupture of the kidney is relatively far more common in children than in adults. Until the age of eight or ten years is reached the kidney lacks its covering of perinephric fat, and its anterior suriace lies in contact with, and is closely connected to, the ]>eritoneum. A rupture involving that surface is therefore practi- cally certain to open the peritoneal cavity and is likely to be followed by excessive hemorrhage and septic infection. In children under ten years of age 85 per cent, of subparietal ruptures of the kidney have proved fatal (Maas). Wounds of the kidney must, of course, involve the capsule and external surface, so that hemorrhage into the perinephric tissues is an almost constant symptom. If the wound has reached the calyces or the pelvis, urine will be commingled with the blood. Vesical haematuria may be prevented by the presence of a clot in the ureter, or by the actual severance of that tube. If large vessels have been opened, the blood, in addition to reaching the bladder or the perinephric space or the peritoneal cavity, may pass upward to the diaphragm, downward to the iliac fossa, or along the spermatic vessels to the external abdominal ring, or outside of the ureter to the perivesical space, or forward between the two layers of the mesocolon. In a reported case of gunshot wound in which the missile reached the kidney from above downward, injuring pleura and diaphragm en route, the concomitant injury to the lower intercostal nerves caused rigidity and tenderness of the anterior abdominal wall and gave rise to the unfounded suspicion that the wound was transpteritoneal. Anuria due to' reflex effect upon the normal kidney may follow a rupture or wound or even calculous irritation of the other kidney, although, as a rule, calculous anuria indicates a bilateral lesion. Both kidneys are, of course, supplied from the same segments — the tenth, eleventh, and twelfth dorsal and first lumbar — of the spinal cord. Excessive tension from compensatory hyperaemia has been thought to explain this form of anuria, and the theory is supported by the facts that the condi- tion sometimes follows a nephrectomy, the remaming kidney being normal, and that, whatever its cause, it is often relieved by nephrotomy of the hitherto sound kidney. The susreptibility of the kidney to reflex stimulation or inhibition must be admitted, PRACTICAL CONSIDERATIONS: THE KIDNEYS. «893 however, as cases of both polyuria and threatened suppression have followed the f/entle and partial insertion of the ureteral catheter (Tilden Brown). Tumors of the kidney have, as a class, die following disUncUve anatonucal characters, which have been well summarized by Morris : ..... (a) The large intestine is in front of the tumor. NormaUy the right kidney, unless enlarged, lies a little way from the lateral wall of the abdomen, behind and to the inner side of the ascending colon ; not in close contact with the abdominal wall and outside the ascending colon, as the liver does. When the kidney is enlanjed, the ascending colon is usually placed in front of and towards the inner side of the tumor. On the left side the descending colon is in front of, and inclines towards the outer side of, the kidney below ; in some cases coib of small intestine may overlie either right or left tumor if the enlargement is not sufficient to bring the kidney into direct contact with the fro it abdominal wall. When the colon is empty or non-resonant, it can be felt as a roil on the front surface of the tumor. Bowel is not thus found in front of splenic tumors and very rarely in front of a tumor of the liver. (*) There b no line of reson^mce between the kidney dulness and the vertebral spine, and no space between the kidney and the spinal groove into which the fingere can be dipped with but little relative resbtance, as there is between the spleen and the spine. ,..,,, i. • j (r) While a renal tumor fills up the "hollow of the back somewhat, it does not often protrude or project backward. Marked posterior projection usually indi- cates perinephric swelling, as from an abscess or a urino-sanguineous effusion. (rf) A kidney tumor can sometimes be recognized by its proneness to maintain an oudine resembling that of the normal kidney. .... {e) A kidney swelling, if inflammatory in origin, descends less m inspiration than does a splenic, hepatic, or adrenal swelling; this symptom in a case of new growth is not very valuable, as the renal Mmor may have a considerable degree of movement. ... (/) As a rule, kidney tumors do not reach the mid-line, do not invade the bony pelvis, and are separated from the hepatic dulness by a line of resonance. If large enough, the tumor may reach the anterior abdominal parietes about the level of the umbilicus, but external to it ..... .- {g) In large renal tumors varicocele, from compression or distortion and dis- tention of the spermatic vein, has been noticed in a number of instances. Optraiwns upon the kidney for its xation (nephrorrhaphy, nephropexy), for drainage or relief of tension (nephrotomy), for the extraction of a calculus (nephro- lithotomy), or for the establishment of collateral circulation (decortication), are almost invariably done through the loin. The vertical inasion— on a line about an inch posterior to the middle of the crest of the ilium and running from that level to the twelfth rib — does not, as a rule, give sufficient room, divides the last dorsal and the lumbar vessels and nerves, and hence jeofwundizes the subsequent integrity of the ilio-costal wall. The oblique incision begins about a half inch below the twelfth rib and at the outer border of the erector spinse. It is well to count the ribs from above downward, as when the twelfth rib is rudimentary it may not project beyond the edge of the erector spinse and may be mistaken for the transverse process of the first lumbar vertebra. In such circumstances the incision, having by error been made close to the edge of the eleventh rib, has, in reported cases, opened the pleura. The oblique incision ii extended forward for three or four inches parallel with the twelfth rib, — i.e., with the vessels and nerves of the region. The skin and super- ficial fascia, the latissimus dorsi, and the external and internal oblique muscles having been divided and the lumbar aponeurosis and the transversalis fascia severed, a layer of fat will then appear or will bulge into the incision (perirenal or transversalis fat). As this is cut through or separated with fingers or forceps, a layer of con- nective tissue may be recognized — the posterior layer of the perirenal fascia — and then a second layer of fat ({>erinephric fat, capsula adiposa), which is sometimes finer in texture and more distinctly yellowish (Morris), and which, if it is incised or torn through and drawn into the wound, will present a funnel-sh.-iped opening leading down directly to the kidney (Gerota), which can then often be isolated by blunt Li 1894 HUMAN ANATOMY. dissection with the finger, and either stitched in place, decapsulated, or opened, in accordance with the indications. It may be noted that bleeding from the separation of the capsule is comparatively trifling; and that if the kidney itself is to be incised, the fact that its blood-supply is naturally divisible into two independent segments — anterior and posterior — which are completely separated by the renal pelvis, and the vessels of which are given ofi from the main trunk of the renal artery (Hyrtl), indicates, as the line of safety, the convex posterior or outer border. When the pelvis of the kidney is distended wiUj fluid, a white line on that border (Brodel's line) is said to indicate the relatively avas- cular area. The anterior vascular division is said to carry three-fourths of the arterial blood-supply and the posterior divii.ion the remaining fourth (Brodel), so that in the majority of cases the posterior surface of the kidney would furnish the lesser quantity of blood. For removal of the kidney (nephrectomy) the oblique incision may be prolonged forward, the peritoneum being detached and pushed in that direction ; or a vertical incision running downward from it may be added ; or, if the nephrectomy is to be done for the removal of an exceptionally large tumor, the anterior or transperitoneal route may be adopted and the incision made in either the linea semilunaris or the linea alba, the outer layer of the mesocolon being opened to gain access to the retro- peritoneal space. The nerves and vessels, as they enter the hilum of the kidney, the vein lying in front, constitute the " pedicle." The ureter lies more posteriorly and on a slighdy lower plane. The irregularities in the division, distribution, and points of entrance of the renal artery should be remembered, as should also — on the right side — the proximity of the vena cava during the separation of close adhesions. In all the lumbar operations ufton the kidney the colon may present in the wound after the transversalis fascia has been opened, and should be looked for and displaced antero-extemally to avoid danger rA wounding it. THE RENAL DUCTS. The duct of the kidney — the canal which receives the urine as it escapes from the kidney and conveys it to the bladder — consists of a short dilated and sub- divided upper segment, the rentU pelvis, and a long, narrow, tubular lower segment, the ureter. Since not only Fio. 1614. these but also the papillary ducts of the kidney are de- veloped from a common out- growth from the Wolffian duct, the renal duct stands in most intimate relations with the renal substance. The pelvis of the kidney (pelTis renalls), al- though bq^inning and lying chiefly within the sinus, ex- tends beyond the latter, passing downward to be- come continuous with the ureter. Its widest part, just within the hilum, presents an unbroken convex postero- mesial surface, its opposite side, directed towards the renal substance, being inter- rupted by the subdivisions of the pelvis. These include the divisions of the pelvis into an upper and a Itmer segment (calyces majeres), extending towards .the respective poles of the kidney. Each of these segments rev.eive8 a group of from four to six smaller conical passages, the calyces or infun- Casts obtain^ by corrosion, showing two forms Die Samenbtasen der Menschen, Berlin, 1901. Ureter Sagittal Mction through sinus of child's kidney, showing lower part of pelvis and commencement of ureter, X lo. THE RENAL DUCTS. 1897 more or less blendeu, a distinct submucosa being wanting. The mucous membrane is clothed with "transitional" epithelium consisting of several strata of cells, the su- perficial elements being plate-like and the deepest ones irregularly columnar. The tunica propria constitutes a subepithelial layer of fibro-elastic tissue which blends with the subjacent muscular tunic. Within the ureter the mucous membrane is usually thrown into longitudinal folds, and in consequence in transverse section the lumen of the canal appears stellate. Neither well-marked papillae nor true glands are pres- ent, although in places the subepithelial tissue invades the epithelium and subdivides the latter into nest-like groups of cells. Occasional aggregations of lymphoid cells occur, which in the vicmity of the calyces sometimes form distinct minute lymph- nodules with I the mucosa (Toldt). On the papilla the epithelium lining the renal duct passes uninterrupted into that of the papillury canals, while the underlying tunica propria becomes continuous with the intertubular renal stroma. The muscular tunic consists of bundles of the involuntary variety disposed as a thin inner longitudinal and a chief external circular !iyer. Within the renal pelvis and its larger subdivisions both layers are well represented, but are reduced on the calyces ; at the junction of the latter with the kidney the circular muscle increases and surrounds the papilla with a minute sphincter-like bundle (Henle). Except in the upper part of the renal F10. 1616. Epithetium Macon coat, thrown _ ^ : into longitudinal (olds Outer lonKitudiiial muscular bundles Inner longitudinal '^ muscular bundles Circalar muscular bundles Transverse section of ureter, y 15. duct, an additional imperfect outer longitudinal layer of muscle is represented by irregularly scattered bundles. The fibrous coat, or tunica adventitia, composed of bundles of fibrous and elastic tissue, invests the renal duct as its outer tunic and con- nects it with the surrounding areolar tissue. At the kidney the outer coat of the renal duct blends with the tunica fibrosa that invests the renal substance between the calyces. beginning several centimetres above the bladder, the adventitia of the ureter is strengthened and thickened by robust longitudinal bundles of involuntary muscle that follow the duct to its vesical orifice and, in conjunction with the fibrous tissue in which they are embedded, form the ureteral sheath (Waldeyer). Accord- ing to Disse, this muscle belongs to the wall of the ureter and is distinct from the musculature of the bladder. Vessels. — The arteries supplying the different segments of the renal duct are derived from several .sources. Those distributed to the pelvis and the adjoining part of the ureter are small branches from the renal artery, the abdominal portion of the canal being additionally supplied by twigs given off from the spermatic (ovarian) artery as the latter crosses the duct and by a special vessel (a tiretcrica) prnceefli ig from the internal or common iliac artery or from the aorta (Krause). The pelvic portion receives branches from the middle hemorrhoidal or the inferior vesical arteries. The 1898 HUMAN ANATOMY. vessels from these several sources anastomose and produce a net-work that encloses the canal and sends twigs that break up into capillaries that supply the coats com- posing its wall. The veins begin within the mucosa, beneath which they form an in- ternal plexus that communicates with a wider-meshed outer plexus withm the fibrous coat, from which tributaries pass to the internal or common iliac and the spermatic veins. The lymphatics withm the mucous membrane and submucosa, according to Sakata,' are not demonstrable as distinct net-works, but as such are seen within the muscular tissue and on the surface. The lymph-trunks from the middle third of the ureter, which are the most numerous, pass to the lumbar nodes ; those from the lower segment are tributary to the internal iliac nodes or communicate with the lymphatics of the bladder ; while those of the upper part either empty into the aortic nodes or join the renal lymphatics. The nerves of the renal duct, derived from the sympathetic system, accompany the arteries and come from the renal, spermatic, and hypogastric plexuses. Within the adventitia they form a plexus containing numerous microscopic ganglia, the largest of which are at the upper and lower ends of the duct. In addition to the fibres sup- plying the blood-vessels, both meduUated and non-meduUated fibres pass to the mus- cular and mucous coats. Vaiiationa. — These consist most often in more or less complete doubling of the canal on one or both sides. While subdivision of the pelvis into an unusual number « tubular calyces is rare, its cleavaf!^ into two separate compartments, either alone or in correspondence with doubling of the ureter, is relatively common. The division may be so complete that the two resulting; ducts open into the bladder by separate orifices. The termination of the ureter in the semmal vesicle — a malformalion occasionally encountered — depends upon the close embryo- logical relations (page 2039) which exist between the two structures. While congenital absence of the kidney is not necessarily associated with entire absence of the ureter, faihire of the latter to develop implies incompleteness or absence of the kidney, since a part of the duct- system of the latter is derived from the primitive ureter (page 1937). PRACTICAL CONSIDERATIONS: THE URETERS. The ureters may be multiple from a fused kidney, or two or more ureters may spring from the pelvis of a single kidney, indicating a defect in the development of the primary foetal ureter. The separate ureters may unite at any point between the kidney and the bladder or may remain distinct throughout. Marked obliquity of insertion of the ureter into the pelvis (page 1896) may leave on a lower level than the ureteral origin a pouch of the pelvis — corresponding to the lowest of its original subdivisions — which, when it fills with urine, compresses the upper end of the ureter, narrows its lumen, and favors the production of hydro- nephrosis. This condition may also occur in either the second or third of the fol- lowing variations in the upper end of the ureter thus described by Hyrtl : (a) there is no pelvis, but the ureter divides into two branches without dilatation at the point of division, each branch having a calibre a little larger than that of the ureter ; (*) there is a pelvis, — that is, a funnel-shapeil dilatation at the point of division ; the upper portion is the smaller, and terminates in three short calyces ; the lower and more voluminous portion terminates in four or five calyces ; (<■) there is only half a pelvis, — that is, the lower branch divides and is funnel-shaped, forming a narrow pelvis, which terminates in one, two, or three short calyces; while the upper is not dilated, and extends to the upper portion of the kidney as a continuation of the ureter (Fenger). The lower end of the ureter may in the male, as a rare anomaly, open within the boundaries of the sphincter vesicae, or into the prostatic urethra, or into the seminal vesicle, ejaculatory duct, or vas deferens. As the opening is never anterior to the compressor urethra, incontinence of urine does not result, but interference with its free exit causes ureteral dilatation and hydronephrosis. In the female the ureter may open into the urethra, v:igina, or vestibule. There may be incontinence of urine, or again such obstruction as to cause uretero- renal dilatation. ' Archiv f. Anat. u. Kntwick., 1903. PRACTICAL CONSIDERATIONS : THE URETERS. These anomalies are readily understood by reference to the embryology of thie ureter (page 1937). Ureteral calculus is most often arrested (tf.) at a pomt from 4-6.5 cm. (i>4- 2ji in.) from the renal pelvis ; (*) at the point where the ureter crosses the iliac artery; (V) at the junction of the pelvic and vesical portions; (d) at its vesical orifice. At these places normal narrowings are found in the majority of subjects. The symptoms of calculus impacted in the ureter are difficult of distinction from those of stone occupying or engaging in the pelvis of the kidney, but it may be said that if. after the usual phenomena erf renal colic, vesical symptoms are marked and per- sistent, and especially if they are associated with slight hsematuria and no calculus is detected in the bladder, the existence of stone in the ureter should be strongly suspected. The bladder-symptoms— irritability, frequent urination, tenesmus— will be more marked the nearer the situation of the stone to the lower end of the ureter. The relations of thf nerve-supply of the ureter with that of the bladder and the geni- ulia and with the great intra-abdominal plexuses sufficiently explain the chief sub- jective symptoms of calculus. Complete and sudden blocking of the ureter by a calculus often produces an acute hydronephrosis, the symptoms of which may overshadow those direcriy referri- ble to the region of impaction. The muscular walb of the ureter are capable of strong contraction, and, indeed, the painful "colicky" symptoms attending the passage of a stone along the ureter would better be described as " ureteral" rather than "renal." ..,,.. . j -.u At present the diagnosis of ureteral stone and its localization are to be made with much ceruinty by the X-rays. In an effort to find tenderness which, in the presence of the above symptoms, might locate a stone, or might determine the region of rupture or other ureteral injury, or might confirm a diagnosis of ureteritis or of tuberculous infiltration {jas, a result of ascending or descending infection), it should be noted that the beginning of the ureter, the lower extremity of the kidney, and the level of origin of the spermatic or ovarian artery are all approximately defined byToumeur's point, which is situated at the intersection of a transverse line between the tips of the twelfth ribs, with a vertical line drawn upward from the junction of the inner and middle thirds of Poupart's ligament ; the course of the abdominal portion of the ureter corresponds to the same vertical line. Toumeur considers its direction vertical from the border of the kidney down to the pelvic brim, over which it passes 4j4 cm. (2 in.) from the median line. The exact location of this point is 'he intersection of a horizontal line drawn between the anterior superior iliac spinc;^ and a vertical line passing through the pubic spine. Morris thinks that this point would usually be too low and too far inward, and that the junction of the upper and middle thirds f-f the line for the iliac arteries (page 819) better indicates the point of crossing of the ureter over the artery. At this point, under favorable circumstances, a dilated or tender ureter may be felt by gende, steady pressure backward upon the abdominal wall until the resistant brim of the pelvis is reached. The vesical portion of the ureter can be palpated in man through the rectum. Guyon has caU«l attention to the exquisite sensitiveness of this portion of the ureter upon rectal exploration in cases of stone, even when the calculus is located high up. In woman vaginal examination permits the palpation of the ureter to an extent of two or even three inches, as it runs beneath the broad ligament in close relation to the antero-lateral wall of the vagina (Cabot, Fenger). Morris gives the following directions for palpating the lower extremity of the ureter : . , , (rt) Vaginal Palpation. — The part of the ureter which is capable of being felt through the vaginal wall is about three inches or a little less, or, roughly speaking, about a quarter of the whole length of the duct. It is that part which extends from the vesical orifice of the ureter backward, outward, and upward to the base of the iH-oad ligament .-ind towards the lateral wall of the true pelvis. It is in the superior third of the anterior and lateral wall of the vagina that the examination must be made, and it is at the part fietween the level of the internal orifice of the urethra and the anterior fornix, where the tissues are very lax, that the I90O HUMAN ANATOMY. ureter will be most readily felt. The examination should be made very gently, and the finger should be pa^ed comparatively lightly over, not pressed firmly against, the vaginal surface. The ureter courses about midway between the cervix uteri and the wall of the pelvis, and by hard pressure the ureter is displaced before the finger in a direction towards the pelvic wsdl. The uterine artery or the muscular fibres of the obturator intemus or levator ani (Sanger) should not be mistaken for the ureter. {6) RecUil Palpation. — ^The lower extremity of the ureter, when occupied by a foreign body or in a state of disease, can be felt through the rectum in the male, but less readily than through the vagina in the female. A calculus impacted in the lower end of the ureter has ^n located and removed through the rectum. It is through the antero-lateral wall of the bowel and a little higher than the level of the base of the vesicula seminalis that we feel for the ureter. The pulp of the finger should be directed towards the back of the bladder and pushed as far as possible beyond the upper edge of the prostate ; afterwards the finger-pulp should be turned towards the lateral wall of the pelvis, and whilst still pushed as Sas as possible, it should traverse the wall of the rectum forward and backward. The examination is difficult, and if the prostate is much enlarged the detection of the ureter is impossible. The normal ureter b not likely to be distinguished, even if the perineum be thin and the prostate normal. (f ) Vesical palpation — through the dilated urethra of the female — may disclose, dilatation, oedema, prolapse, or infiltration, inflammatory or tuberctilous, of the vesical end or orifice of the ureter, or may reveal the presence of an impacted calculus. Wounds or subparietal injuries of the ureter, unassociated with other intra- abdominal lesions, are rarer than similar injuries of the kidney, decrease in frequency from above downward, and, on account of the bony protection afforded it, are very uncommon in the pelvic portion of the ureter. The upper portion may be crushed against the transverse process of the first lumbar vertebra (Tuffier), or so stretched as to tear or sevei 't (Fenger). Unless the escape of urine from an external wound occurs, the symptoms are merely those of ureteral irritation, usually with slight transient haematuria and the evidence of slow urinary extravasation superadded. After extraperitoneal rupture or wound the swelling due to extravasated urine and subsequent cellulitis might be recognized in the loin or detected by rectal or vaginal examination in the pelvis. Longitudinal wounds gape less (and therefore h^ more readily) than transverse \\ unds, on account of the longitudinal disposition of the thicker internal layer of muscular fibres. Tumors of the ureters are almost unknown as primary conditions, but consider- ation of the relations of the ureter (page 1895) will show that it may be pressed upon by growths or involved in inflammatory processes originating in the caecum or in the ascending or descending colon. Its pelvic portion is more exfxjsed to pressure than is the abdominal on account of the counter-resistance of the pelvic walls, and here it may be compressed by fecal masses in the sigmoid or rectum, by iliac aneurism, or by growths of the uterus, ovary, or Fallopian tube, or may become involved in dis- ease of the appendix when it occupies a pelvic position, or of the bladder or seminal vesicles. The tough, resistant character of the walls of the tube, the laxity of the con- nective tissue in which it lies, the layer of loose fat that, in part of its course, surrounds and protects it in well-nourished individuals (Luschka), and its rich vas- cular supply (from the renal, spermatic or ovarian, and vesical arteries) enable it to resist or avoid injury or to undergo speedy repair. It is thus possible to separate it extensively from surrounding structures during operations with little or no risk of necrosis. The oblique course of the ureter through the vesical wall subjects it to pressure when the bladder contracts, or when it becomes rigid from arterio-sclerotic disease. Frequency of urination alone has been thought competent — by the constandy recur- ring obstruction to the entrance of urine into the bladder — to produce ureteral dila- tation and hydronephrosis. As its obliquity leaves it on the inner asftect covered by mucous membrane only, and as the outer aspect is covered by the muscular layer of THE BLADDER. 1901 the bladder- wall, it can be understood that incision of the mucosa over the intra- parieul part of the ureter, for the purpose of extracting a calculus, involves little risk of pelvic cellulitis from extravasation of urine. It cannot be said that there is no risk, as in one case a peritoneal fistula and death resultetl (Thornton). (^rations upon the ureter are frequent for the extraction of a calculus (uretero- lithotomy); or the extirpation (ureterectomy) of an infected ureter ( tuljerculous or pyogenic) either at the same time with its kidney (nephro-uretcrectomy ) or at a later period; or f.r the closure of wounds or iistul^e, or the relief of stricture, or the implantation of the distal end of the ureter — after removal of a diseased, injured, or obliterated portion — into the bladder, rectum, or elsewhere. The anatomical factors relating to these operations cannot here be described, but it may be said generally that whenever it is possible the extraperitoneal route is selected to lessen the danger of peritonitis, and that the oblique lumbar incision employed to reach the kidney (page 1893) will, if prolonged downward and forward parallel to Poupart's ligament and to the outer edge of the rectus, give access to the whole abdominal ureter and to the upper part of its pelvic portion. Cabot has shown that the ureter is bound to the external— or under — surface of the peritoneum by fibrous bands, and that wh6n that membrane is stripped up from the posterior abdominal wall the ureter accompanies it. He found that the relation of the ureter to that part of the peritoneum which becomes adherent to the spine is, within a slight range of variation, feurly constant, the ureter lying just outside the line of adhesion. Hence, if the sui^eon has stripped up the peritoneum and has come down to that point where it refuses to separate readily from the spinal column, he will find the ureter upon the slripped-up peritoneum at a short distance outside of this point. On the left side the distance from the adherent point to the ureter is from one-half an inch to an inch, while on the right side it is somewhat greater, owing to the ureter being displaced to the outside by the interposition of the vena cava between it and the spine. It should be remembered that the peritoneum adherent to the abdominal portion of the ureter is very thin and may be torn in an attempt to separate it Aft':r the ureter dips down into the true pelvis it is less easily located because it has no tixed relation to a bony landmark. Cabot has suggested that osteoplastic resection of the sacrum would give access to this lower pelvic portion of the ureter. In women it can often be reached through the vagina. The ureter is, of course, accessible transperitoneally through its whole route. THE BLADDER. The bladder (vesica urinaria) — ^the reservoir in which the urine is received from the renal ducts and retained until discharged through the urethra — is a muscular sac, lined with mucous membrane, situated in the anterior part of the pelvic cavity imme- diately behind the symphysis pubis. Its form and size, and likewise to a considerable extent its relations, vary with the degree of distention, so that in describing the organ the condition of expansion must be taken into account. When containing little fluid and hardened in situ, the general shape of the bladder is pyriform, presenting a free, slightly convex superior surjuce, covered with peritoneum and projecting into the [)elvic cavity, and a distinctly convex non-peritoneal inferior surface, attached I'y areolar tissue to the pubic symphysis and the pelvic floor upon which it rests. The urethra, surrounded by the prostate, emerges from the most dependent portion of the lower surface, behind which point the latter ascends to join the upper surface along the indistinct posterior border. The part of the bladder between the urethra and the posterior border constitutes the fundus or base (fundus vesicae), which in the male is in relation with the seminal ducts and vesicles and the recto-vesical pouch and is directed towards the rectum, and in the female is attached to the anterior vaginal wall. In the empty oiyan the superior and inferior surfaces blend along the sides in the convex lateral borders ; anterioriy these meet at the apex or summit (vertex vesicae), from which a median fibrous band (lixamentam umbllicale medium) that rep- resents the urachus — the obliterated segment of the intra-embryonic part of the allan- toi»— extends to the umbilicus along the abdominal wall. The body (corpus vesicae) I903 HUMAN ANATOMY. mpulla Seminal ve* .Ic Uriurv bladder, slightly dlatended and hardened n ii/k, ■ Irom formalin subject ; viewed from above. includes the uncertain part of the bladder between the apex and the fundus. The term neck is sometimes applied to the region immediately surrounding the urethral orifice, although a distinct neck in the usual sense does not exist. The intersections of the lateral and posterior bor- Fio. 1617. ders mark approximately the points at which the ureters enter the vesical wall. As pointed out by Dixon,' the attachments of the ureters correspond to the lat- eral angles of the trigonal figure that the empty bladder resembles when viewed from above, the apex being the anterior angle. The cavity of the strongly con- tracted bladder, as seen in sagittal sections iA organs hardened in situ, is little more than a cleft bounded above and below by the thick vesi- cal walls and below continuous with the urethra ; in the vicinity of the ureteral orifices, however, the lumen broadens Into the lateral recesses which are never entirely effaced (Luschka). Themodificatkinsof the lumen sometimes seen, more frequently in women and especially in organs not hardened in situ, in which the superior surface is more or less sunken and in consequence the vesical cavity is crescentic or V-shaped in mesial section, are to be rejjarded as the result of post-mortem change and not as representing conditions existing during life, since normal contractions of the muscular vesical sac are little calculated to produce such forms. The empty bladder measures in length from 5-6 cm. (1-2% in.), in breadth from 4-5 cm. (i)i-jin.), and in thickness from a-a.scm. (?^-i in.) (Waldeyer). In the distended bladder the demarcation between the surfaces above described is gradually effaced urtil, in extreme expansion, the organ assumes a general ovoid form in which the supe- rior and inferior surfaces and the fundus are uninterruptedly continuous and all indication of the borders is completely obliterated. Such extreme changes, however, accompany only exces- sive and unusual distention, the alterations taking place under normal conditions, with a prob- able maximum capacity of from 250-300 cc. (7)i-9ft. oz. , Ijeing much less radical. "O. x6x8. When the bladtl. ' begins to fill, the region first to be affectetl is the posterior and lower lateral portions of the organ, expansion oc- curring more rapidly in the transverse than in the longitudinal axis (Delbet), which for • a time ret.iins a g^ aerally horizontal direc- tion. Willi increasing distention the blad- der invades the paravesical fossae at its sides, behind is prts.sed against the seminal vesi- cles, which in the empty condition of the bladder extend laterally as transverse wings and tou"h the vesical wall only with their inner ends, anil encroaches upon the recto- vesical pouch and the rectum. The con- dition of the latter also influences the direc- tion of the vesical expansion, since the filled rectum decreases the available space behind and forces the bladder upward and forward. Not until the distention has progres.sed to a cnnKiderahle ilpgree does the antero-inferior segment lengthen and undergo upward displacem-nt and the apex rise much above the pubic symphysis ; and only after the distention greatly . v-eeds physiological limits and becomes very excessive does the bladder altogether lose its pyriform contour and become symmetrically ovoid. The highest point of the greatly enlarged organ no longer corresponds with the attachment of ■ ' Anatom. Anzeiger, Bd. xv., iS<>o Vaia defemitia Superior surface Apex Cut edge of peritoneum Lalero-inlerior surface Prostate gland, lateral surface PrecedinK preparation viewed from side, showinK relations of Madder, auociated ducts, and proetate. THE BLADDER. »90i tha urachiw, but lies farther abovt- and behind, since the antero-infcrior wall always remains •horter than the postero-superior. The condition of the rectum ami tlie pressure exerted by the abdominal viscera influence in no sliRht degree the form and (MMition of the distended bladder, since, when these factors are both unfavorable to unham|>eretl expansion, the inferior surface and fundus are depressed to a jfreater degree than when the Ixjwcl is empty and the superior surface is little impressed by the ovetlyinK organs, the entire bladder aHsummg a more vertical position and the ovoid form being modified { Merkel ). I'nder pathological conditions the bladder may suffer such enormous expansion that it reaches as high as or even above the umbilictLS and occupies a large part of the abdominal cavity. Owing to its intimate attachment, the part of the inferior surface united to the prostote and the pelvic floor undergoes least change both as to form and relations. Pio 1A19. External iliac artery Extemml iHac- vein Deep epig*itric. •rtery Spennatic vcMels Internal abdominal - Tins OMiti h^'pogauric artery Urachu*. Suspemory ligament of pcni Internal urethral orii Ureter, enlerint bladder Fatty tiasi containing veint Pectinate se|iti Spongy urcthi Navicalar Seminal vrsicle Rectum EJaculatury duct Proiitatic urethra and utiide ProMate Membranous urethra Bulb o( cavernous body Balbouf urethn Scrotum Dlaaection of sagitially cut pelvis, showing relations of organs after fixation by formalin injection. The capacity of the bladder during life so obviously depends upon individual peculiarities and habit that it is impossible to more than indicate approximately the quantity of fluid that ordinarily induces a desire for the evacuation of the vesical contents. This quantity — the physiological capacity of the bladder — may perhaps be said to vary from 175-^50 cc. (6-9 fl. oz. ), 700 cc. (24 fl. oz. ) representing the maximum for the normal organ (Disse). Under pathological conditions, as in paralysis of the vesical wall, the bladder may contain from 3-4 litres without rupture. As a means of determining its capacity during life, estimates based upon artificial distention of the bladder after death are worthless, since the maximum resistance 1904 HUMAN ANATOMY. without rupture of the dead vesical wall is much less than *hr.' of the living organ. The bladder in the female has d smaller capacity than in the malt . The interior of the bladder varies in i^piiearancc according to the condition of the mucous membrane. The latter is Ijxwely attached to the muscular tunic by iiiibniucous areolar tissue, and hence in the contracted state of the organ is thrown into conspicuous, mostly longitudinal plications ; when the bladder is Ailed these folds are efiaced and the inner surface appears smooth. With e.xcesslve distention, the interlacing bundles of the muscular wall may be stretched so far apart that the submucous tissue and the mucosa may occupy the interstices so formed, an irregular pitting or pouching of the mucous linmg resulting. A triangular area, the trigonum rtsiitf, included between the urethral orihce in ironi and the ureteral oixnings ^hind, is distinguished by its smoothness under all decrees of contraction, even in the empty Madder bemg only indistinctly wrinkletl. Over the trigone (Fig. 1620) the .>iubmucosa is absent and the mucous membrane rests directly upon a compact muscular stratum in which the closely plac««l transverse bundles of the vesical wall are reinforced by radiating fibres continued from the ureteral sheath (page 1897). ^}** slighdy cur>-ed posterior border or base of the trigonum ii> marked by a bond-like elevation, the p/ica ureterica, or torus urelefiau of Waldeyer, that unites the open- ings of the renal ducts. This ridge, best marked at its outer ends, is less evident and often interrupted near the mid-line, and is subject to much individual variati(Mi. Its production depends upon the eleva- Pio. t6to. tion of the mucosa and muscular tissue in consequence of the oblique path of the ureters through the vesicsu wall. The margins of the trigonum — lateral as well as posterior — are raised and its central area is somewhat depressed towards the urethral opening. The lat- ter (orlfidna urcthrac internum) occu- pies the apex of the trigonum, and is usually not circular, but crescentic, owing to the projection of its posterior border as a small median elevation, the vesical crest (uvula vesicae), that ex- tends from the apical end of the trigone into the urethra to become continuous with the urethral crest in the prostatic part of the canal. The vesical crest consists of a thickening of the mucous membrane enclosing bundles of muscular tissue. When hypertrophied, as it not infrequently is in aged subjects, this fold may form a valvular mass that occludes the urethral orifice. The anterior wall of the latter is commonly marked by low converging folds continuous with the longi- tudinal plications of the urethral mucous membrane. The ureteral orifices are usually slit-like in form (4-5 mm. long), obliquely trans- verse in direction, but may be oval, round, or punctiform (Disse). The lateral bor- der of the opening is guarded by a valve-like projection (valvuia ureteris) that forms part of the nodular elevation that is produced by the wall of the ureter. The median margin of the opening is embedded in the interureteral plica. The urethral and the two ureteral openings mark the angles of an approximately equilateral triangle, the sides of which, in the contracted condition of the bladder, measure from 2-2.5 ""•; when the organ is expanded, this distance increases to from 3. 5-5 cm. or even more. The urethral orifice lies from 1.75-2.2 cm. in front of the base of the trigone when the latter is contracted. Immediately behind the vesical triangle the posterior bladder- wall presents a slight depre»ion, the retrotrigonal fossa or fovea retroureterica (Waldeyer), that corresponds to the "bas-fond" of the French writers. When abnormally enlarged and pouch-like, as it often is in advanced life when associated with an enlarged prostate, this fossa becomes of practical importance (page 1981). Peritoneal Relations.— -The superior surface of the empty or but slightly filled bladder is completely covered by peritoneum as far as the lateral and posterior Opcningm of untcra bimdder, 'aecmcnt ', viewed fnwi above and behind. bwdera. On each iide the »er.m» commmm ip— iwrtunm tfce orfan lo JMC the p«a- vesical ioMa, the »ickle-ahapeit the |)elvic wall or, passing over the pelvi<: tiriirt, tiMnuids th«? ini«mu»l alMti«minal nnj>. Dixon ' found the fold well represented in the nwte tortus, awl inclines to tli«- view tlwt iu production is connected w«h a drag on t»»e jKiritoneuin iwident to th*- formation oi the ii^uinal pouches. Behind the peritoseiwi passe* front the posit.-rtor b«»rder ol the emotv bladder over the upper end of tb. wsminal v.-^iicl*-^ and the vasu* de^erentia, to form .. horiiontal crescentic shelf-like loki pUca nctotcsicaliK ) fruin 1-1.5 cm. wide, that extends from the bladder backward, embracing tb*- rectum and ending at the !s.'crum on either side of the gut the ut«frc>-!iacral folds in the (emoie f,,!" :•. r-i'jpicuous behind the empW' bladder, - ,;•. .>■,» cuHiKS the lowest part of the jwritoneal receairdie rtcto-vesital fossa, tliat inter*' .aa ;i«ii.cec t«e rectum and the seminal vesrcles and ainpullz of the vasa deferentia, and towards whkh the fundw) of the bladder is directed. In recoicnition of these relations, the anterior wall o* this recess beinK i.i direct relation with the seminal tract-, the authors last mentioned propose to call this deprcs,sion the rectfy^rnual fossa. —a term alike applicable to both sexes, since the relations of the rectwm to the uterus m the pouch of Douglas in the female are similar All other parts ot the bladder, including the postero-inferior (fundus) and the antert>-inferior surfaces, are entirely de%'oid of peritoneal coverinK- In the female the serous membrane puses from the posterior border of the bladder onto the anterior uterine wall, the shall-vesical fos.sa, along with the shelf-like fold, and the elevation of the line of peritoneal .oflection at the sides, so that the lateral false ligaments no longer reach the pelvic Boor, Iwt pa- •- from the lateral wall of the pelvis directly to the superior surf^ice of the bladder, from which thtr , lica transversa has disappeared. Anteriorly the relations of the serous covering are also affected, since with the rise of the bladder above the level of the symphysis the peritoneum is carried upward and a suprapubic non-peritoneal area becomes progressively more extensive until, in extreme distention, a space measuring vertically from 8-9 cm., or about 3V in., may be uncovered. Fixation. — The attachments of an organ so subject to ». .isiderable alteratioiu in size and form as is the bladder must obviously provide for such changes as well as the maintenance of a more or less definite piosition. The ' ' ligaments ' ' of the bladder are conventionally described as true and false, under the latter being included the peritoneal folds Cabove describi-d) that pass from the organ to the adjacent ab- dominal and pelvic walb. The sacro-genital folds were formerly sometimes called the posterior faise ligaments. From the manifest instability of the relations and attachments of the peritoneum incident to distention and contraction, it is evident that such peritoneal folds can contribute little to the definite support or fixation of the bladder ; hence those parts of the organ possessing a serous covering are movable. The inferior surface, on the contrary, is comparatively fixed on account of its close relations to the pelvic floor ^and in the male to the prostate") and the presence of fascial bands or true ligaments. The latter are derived from the pelvic fascia, which in the vicinity ok the bladder presents a stout, glistening, band-like thickening (arcns tendincns) that on each side stretches from the posterior suriace of the symphysis, a ' Journal of Anatomy and Physiology, vol. xxxiv., 190a 'Journal of Anatomy and Physiology, vol. xxxvi., 1903. l9o6 HUMAN ANATOMY. short distance above its lower border, backward to the ischial spine (pi^e 1899). On either side of the mid-line the anterior ends of these tendinous arches pass aa strong fascial bands, the pubo-prosttUic ligaments, from the symphysis to the prostate, blendtne with its capsule, and thence continue to the inferior surface of the bladder, where they are lost m the outer fibrous coat of the vesical wall. In the female these fascial bands pas^ direcdy to the bladder as the atUerior true ligaments. After leaving the symphysis, the tendinous arches send expansions — the lateral true ligaments — to Jie side of the bladder, which materially assist in fixing the organ. The cleft left between the medial borders of the two levator ani muscles is occupied in the male by the rectum and prostate and in the female by the rectum, vagina, and urethra, over some of which organs (rectum, vagina, and prostate) the pelvic fascia covering the upper sur- face of the levator ani muscles (foida dUphragma ptivli mpcrivr) sends more or less extensive investments and thus binds them to the pelvic floor. Additional support is afforded by more or less definite processes of muscular tissue pro- longed from the bladder to adjacent structures ; those passing within the arcus tendineus to be attached on either side to the back of the symphysis constitute the pMbo-vesical muscles, while Otliers, the rtcto-vesical muscles, extend backward to blend with the rectal wall. Pubovesical tpace. cloned out. Ftlvic line. Arcns tendtneu* faaciic pelvis VthWc linf ji fsrcus tendineus m Icvatorisani) Syiiiph>'sis pubis Pubo-vesicsl ligament Arcus tendineus Levator ani muscle ;urator canal y. Wbite line Bladder, partly distended Anterior part of pelvis of female, viewed from above and behind, showina relations of bladder to pelvic fascia ; bladder has been partly distended and pulled Iwckward Between the lateral pubo-prostatic ligaments, the symphysis, and the bladder lies a deep recess (fovea pubovtsicalis), traversed by the dorsal veir. of the penis and filled with fatty areolar tissue, the floor of which is formed by the fusion of the pelvic fascia with the transverse ligament of the perineum. Above the level of the pubo-prostatit ligaments lies the prevesical space, or space of Retzius, which is bounded in front by the anterior wall of the pelvis below and the transversali!! fascia above, and behind by a thin membranous condensation of areolar tissue, the fascia umbilico-veticaiis (Farabeuf), that passes from the pelvic floor over the prostate and bladder to the abdominal wall, to fuse with the transversalis fascia at a variable distance below the UiTibillcus. Laterally the boundaries of this space, filled with areolar tis-siie loaded with fat, are uncertain, since when distended, as when the seat of an abscess, It may embrace the sides of the bladder below and extend above as far as the obliterated h>'pog.xstric arteries. Under usual conditions, however, the space may be regarded as confined chiefly between the antero-inferior surface of the bladder and the adjacent anterior pelvic wall. » Relations. — When empty, or containing only a small quantity of fluid, the bladder possesses t^vo general surfaces, a superior and an inferior. The anterior two- thirds of the the latter rests upon the prostate and the pelvic floor, and, according to Dixon.' when hardened in situ presents a rounded niedian ridge which, together with the ureters, outlines two forward, upward, and outward sloping infero-lateral areas. These rest upon the pehic floor and the posterior surface of the pubis, separated ' Journal of Anatomy and Physiology, vol. xxxiv., 1900. THE BLADDER. 19&7 from th» latter by the retropubic pad of fat from .5-1 cm. thick. The fundus — the posterior part of the inferior surface included between the urciliral opening and the posterior border — is in contact with the median ends of the seminal vesicles and of the ampullae of the seminal ducts, by which structures and their musculo-adipose bed the bladder is separated from the anterior wall of the recto-vesical fossa. The internal orifice of the urethra lies immediately above the prostate, usually from 1.2-2.5 cm.( J^i in. ) above the plane passing through the lower border of the symphysis and the lower end of the sacrum ; the distance from the upper border of the symphysis to the orifice measures from 5-6 cm. (2-2J4 in.) ; in the horizontal Clane it lies from 2.5-3 cm. behind the symphysis, its nearest point on the latter eing about 2 cm. (Disse). These measurements are influenced by changes in the position of the inferior surface, being shortest when the empty bladder b pushed upward. Fio. 163*. L'rrtCT- Suipenaory. ligament ol ovary Fallopian tube- Kound liKamcnt. Ovary, OhMteralirt. hypogastric artery Symphyaia putW' Uretlii External urethral, orifice in veallbule Utcnvaacral foM Rectum External oa uteil Bottom of recto- nterine pouch .Vagina Perineal body Sagitul aection of female pelvis of formalin «nl>(ect. Laterally the paravesital fosstg intervene between the empty bladder and the sides of the pelvis. In the contracted condition the superior surface usually lies below the plane of the pelvic inlet, the entire bladder being within the anterior third of the pelvis and close to the pelvic floor. This upper surface, covered with peri- toneum, is in contact with coils of small intestine which, when the rectum is empty, may occupy a [lart of the recto-vesical fossa. In the diitcndcd bladdn the relatinnw the level of the urethral orifice, which does not come into relation with the pelvic floor. In the new-bom female child the uterus is situated rela- tively high and comes into contact with the bladder, while the vagina does not, only touching the urethra. The reflection .iis pubii Urethra Sagillal wrtion throiirh pelrii of nrw-bom female child, hardened in fomulin, showing infantile fonn and (uprapubic position of bladder. Stinicture. — The hlaiJder consists esscntialiy of a muscular sac lined with mucous mcmbi.inc and covered cin its upper surface with peritoneum, a layer f>f connective tis- sue l«x»sely uniting the ntticoiis and muscular coats. From within outward, four coats ' Anatomisrhe Hefte, Ud. i., 1891. iaffnaiiiiii mm THE BLADDER. 1909 Epithcliunt are distinguishable.— the mucous, the submucous, the muscular, and the incomolete **'** T"he mueous coat varies in thickness with both location and the d^ee of con- traction Over the vesical trigone, where always comparatively smooth, it is thin, nLsuring only about . i mm. ; where strongly wrinkletl by contracuon it may attain a thicknL of over 2 mm. The mucosa '««»"«, /^'^^'X^'^'^S^'^SX^^^^ ^l^^ consisting of a fibro-elastic tunica propria covered with transitional epithelium. The latter includes several strata of cells, the deepest of which are columnar, the middle ^Sularly polygonal or club-shaped, and the inner pU»te-hke, their deeper surface fitUSg over and'^between the underiying elements. Although glands may be con- sider^ as absent, tubular depressions are occasionally found m |he vicinity of the ttigone which are regarded by some (Kalischer. Brunn) as true glands. Waldeyer S suggested thatTese structures may be interpreted as representing in a sense urethrd glands displaced during the development of the vesical trigone. Th^ submucous coat, loose and elastic, perr.uts free gliding of the mucous over the muscular tunic when readjustment becomes necessary during contracuon. Com- S«ed of bundles of fibrous tissue interwoven with elastic fibr«, it supports the blood-vessels and nerve-plexuses, and contains numerous bundles of involuntary muscle. It is not sharply defined _ Fio. ««»4- from the adjoin- ing coats, but blends with the stroma of the mu- cosa on the one side and extends between the tracts of the mus- cular coat on the other. Beneath the trigonum a distinct submu- cous layer is wanting or re- placed by a sheet of muscular tis- sue. The muscu- lar coat, thicker than the mucosa and compara- tively robust, va- [£ Stion o?the bladder, being thin during distention and verv thick in strong contSn when it may measure :« much as 1.5 cm. The bundfes of mvoluntary muile are arranged in two fairiy distinct chief layers.-a thin outer longitudinal and rS inner circular. Inside the latter, an|| virtually within the submucosa, hes an Incomplete additional layer. The longitudinal bundles, best developed on the upper a"id Wr surfaces, do not constitute a continuous sheet, hut interface, leaving inter- h.scicuTar intervals which are occupied by connective tissue. In the vicin. v of he pTSe extensions <,f the outer layer are attached to the antenor pelvic waH as he Sute vesical muscles ; others pass Kickward to blend with the intestinal wall as the K- •« cal muscles, while from the apex bundles are prolonged into the urachus The circular layer, although more robust and uniform than the ou er. js «'e..k and imlrfect over the trigond region, and in both sexes is well developed only aft^r Sing the level of the internal ureteral orifices (DisseV T. vards tiie apex of rf,e b adder^he bundles of the circular layer .ssume an obli.,ue and >««,;;^'»» ^^ 3: sition. The innermost laver-that within the submucosa-.s represented by .so ated and indefinite muscular bundles that are blended with the connective tissue. « >ver 'Og// Section o( wall oJ bl«dd«r, under very low maicnification, showinn itenenil duponitlon of roats. K i>. I9IO HUMAN ANATOMY. I i the vesical trigone, however, this layer becomes condensed and forms a compact transverse muscular sheet that is closely united to the overlying mucous membnme and, m conjunction with the muscular tissue of the urethra, surrounds the beginninir of that canal with a constrictor-like tract the interned vesical sphincter. The outer ^brous coat of the vesical wall is strongest over the inferior surface where it ro cives reflections from the pelvic fascia; towards the apex and beneath the peritonei- it is less definite and often intermingled with adipose tissue. Over the postero-inierior surface in the male it is fused with the fibrous tissue surrounding the seminal vesicles and ducts, and in the female is blended with the anterior vaginal wall . , VesMls.— The arteries supplying the bladder are chiefly the superior and mfenor vesical, from the anterior division of the internal iliac ; these ar^ reinforced by branches from the middle hemorrhoidal, as well as by small twigs from the internal pudic and the obturator arteries. The superior vesical supplies the upper segment of the bladder and sends small branches along the urachus. The inferior vesical divides into two or more branches which are distributed to the infero-Iateral and postero-inferior surfaces. In addition to twigs to the region of the trigone, others pass to the prostate, seminal vesicles, and ducts. On gaining the bladder, the vesical branches anastomose and enclose that oi^an in an arterial net-work from which twigs enter the muscular coat and break up into capillaries for its supply. Others penetrate the muscular tunic and within the submucosa form a net-work from which arterioles pass inward for the supply of the mucous membrane. The veins do not accompany the arteries, but form a submucous plexus that drains the mucous membrane and empties into a muscular plexus which, in turn, is received by an external subperitoneal plexus. From the latter the blood from the entire oi^n passes into the large prostatico-vesical plexus at the sides of the bladder and thence into the tributaries of the internal iliac veins. With the exception of the smaller ones on the inferior surface, all the vesical veins possess valves (Fenwick). The lymphatics of the bladder begin as a dose-meshed net-work within the mus- cular coat, according to Geroto,' being absent within the mucous membrane. Out- side the muscular coat they form a wide-meshed subperitoneal plexus, those from the apex and body coursing downward and laterally and those from the fundus upward Leaving the sides of the bladder, the efferent channeb, chiefly in company with the arteries, pass to the internal iliac lymph-nodes and to those situated at the bifurca- 'l*^"!-?' J j^ ^""^ ^'*'"^ **** P*^** °' '•" lymphatics on the antero-inferior surface of the bladder Gerota describes one or two very small nodes as usually present. The nerves of the bladder include both sympathetic and spinal fibres. The former, distributed chiefly to the muscular tissue, are from the vesical plexuses, which as subordinate divisions of the pelvic plexuses, lie at the sides of the bladder The sympathetic fibres accompany the arteries and are joined by the vesical branches from the sacral plexus derived from the third and fourth, possibly also the second, sacral spinal ner\'es. The principal trunks reach the bladder in the vicinity of the ureters, the trigonal region receiving the most generous nerve-supply and the apical segment the fewest fibres. Within the outer fibrous coat the larger nen'es divide into smaller branches that are connected with ganglia, especially in the neighborhood of the ureters, from which twigs enter the muscular tunic and'break up into smaller ones bearing terminal microscopic ganglia before ending in the muscle. Other branches penetrate the submucosa, where they form plexiform enlargements contain- ing numerous minute ganglia, from which fine twigs proceed to the mucosa to end, according to Retzius, between the epithelial cells. In general the sensibility of the normal bladder is comparatively slight, the trigonal region, especially at the ureteral openings, being its most sensitive area. PRACTICAL CONSIDERATIONS: THE BLADDER. Absence of the bladder is a very rare abnormality, but in more than one case has proved to be consistent with prolonged life, the dilated ureters— opening into the urethra— having acted as reser\'oirs for the urine and the muscle-fibres at their con- stricted orifices having taken on sphincteric action and prevented urinary incon- ' Anatom. Anzeifcer, Bd. xii., i8q6. PRACTICAL CONSIDERATIONS: THE BLADDER. 191 1 tinence. In other less fortunate cases in which the ureteral openings were on the surface of the body, implantation of the ureters into the intestinal tract (page 1901; has been done with varying degrees of success. Extroversion (exstrophy) of the bladder, the most frequent congenital ab- normality of this organ, is associated with failure of the ventral plates formmg the abdominal wall to unite in the mid-line. In this condition, which occurs m males »•> from 80 to 90 per cent, of cases, the symphysis pubis and the anterior wall of the bladder frequently are also lacking, and the posterior vesical wall— protruded by intra-abdominal pressure— forms a rounded prominence, deep red m color, from chronic congestion. The ureteral orifices are often plainly visible. Cryptorchism, bifid scrotum, inguinal hernia, and epispadias are frequently present. Although the opinions regarding the causes and factors leatling to these malformations are various and conflicting, it is certain that these defects depend upon faulty development at a very early period of foetal life, probably in connection with abnormalities of the allantois and of the cloacal region of the embryo, and that the suggested explana- tions on a mechanical basis, as over-distention of the allantois or unusual shortness or location of the umbilical cord, are entirely inadequate to account for malformations which often so profoundly affect the entire lower segment of the anterior body-wall and the associated organs. • u .u Occasionally a vesico-abdominal fissure occurs without extroversion, when the posterior wall of the bladder will be concave instead of convex and partially covered by the imperfect abdominal wall. ... The posterior wall of the bladder and the anterior wall of the rectum or vagina may be defective at birth, resulting in a congenital vesico-rectal or vesico-vaginal The foetal communication between the extra- and intra-abdominal portions of the aV.. ntoic sac may remain pervious, so that the urachus, instead of becoming a fibrous cord extending from the umbilicus to the summit of the bladder, is patent and constitutes a channel by means of which urine is discharged at the navel. Cysiocele.—K portion of the bladder may be found either alone or together with intestine or omentum in the sac of an inguinal or femoral hernia, or more rarely it may be part of an obturator or perineal or ventral hernia. The ordinary causes of abdominal hernia (page 1759) tavor the production asm of the anal sphincter may be caused by vesical irritation. Other referred pains in vesical disease are to the lumbo-sacral region, through the communication between the second, third, and fourth sacral nerves and the hypo- gastric plexus ; to the kidney, by the junction in the sf>ermatic plexus of filaments frcm the vesical and renal plexuses ; and to the lower limb, occasionally to the foot (pododynia), through the sacral nerves which enter into the sacral plexus and the lumbo-sacral cord, gi\'ing off the great sciatic nerve, and also mto the pelvic plexuses. The important muscular element in the vesical, as in the ureteral, walls gives the "colicky" chara^er to the symptoms of irritation and, in the case of the in- flamed bladder, causes the violent tenesmus accor. ,)anying the discharge of the last drops of urine, when the muscles in the vicinity of the sensitive trigonum contract si>asmodically. -^^CTTTT^TM PRACTICAL CONSIDERATIONS: MALIC I'LRINEIM. 1915 The same symptom*— frequent micturition, referred |win!', tenesmus— arc caiwttj \w a vesical eaiaui'smd have the same anatomical basis. They are most marked if the atone is small, rough, and movable, so that in the erert (Kisition 11 falls ujion the trigonal surface. Such a stone may roll or be forced by the stream of urine into the vesical outlet and produce sudden interruption of micturition. This symptom is seen most often in young male children, in whom the relatively vertical MMition of the bladder, the marked tenesmus caused by the presciicu of the stone, and the small size of the vesical oriJice favor its production. The tcmsmiis in children is often so excessixe as to result in prolapse of the rectum, which is aliected by and participates in the straining expulsive efforts. ,•..,•,. in a sacculated bladder a very lai^e stone may he in a pouch with but little ot its surface presenting towards the' bladder-cavity (encystwl stone) and give nsc to almost no subjective symptoms. , j.u. Perineal lithotomy is much less frequently done than formerly, on account of the application of Bigelow's operation of lilholapaxy to the great majority ..f calculi, and of the revival of suprapubic lithotomy and its use in a considerable propt>rtior. ot the remainder. A description of the parts involved in this operation ser\cs, however, as Treves has said, to give a proper conception of their important anatomical re- lationships. . , 1 • I The Male Perineum.— This region— a fissure when the thighs are approxi- mated— becomes an ample lozenge-shaped space when the legs and thi^jhs are flc.x^d Pia. i6t5. TnbcrlacliU- -TutwrUcbli - Anns -MiU-m. r.eout tihros o( sphinc- ter ani extemtia .TipoC coccy» DItMction of perineum ; skin lia» been removed, leaving nuperfirial favia undiaturbed Sound has been paaaed through urethra into bladder and scrotum drawn forward. and the latter are strongly abducted,— the lithotomy position. It corresponds to the outlet of the pelvis. On the surface it is bounded roughly by 'he scrotum anteriorly, the buttocks posteriorly, and the upper limits of the inner as{>ects of the thighs laterally. More deeply the' boundaries are the symphy.si.-. pubis and subptibic ligament anteriorly, the coccyx posteriorly, and the greater sacro-sciatic ligaments, the I9i6 HUMAN ANATOMY. iidual tubiTositiesand rami, and the pubic rami laterally (Fig. it-27). It is divided into two lateral Rymmetrical halves by a dense cutaneous ridge, the raphe, across which, as it represents the junction ck the two foetal halves of the perineum, no blood- vesseb pass from one side to the other ; and into two unsvmmetncal antero- posterior triangular portions by an imaginary transverse line drawn between the anterior borders of the ischial tuberosities and running in front of the anus. The posterior of these two divisions — the portion of the outlet of the pelvis which contains the rectum and anus — is the recUU triangle (anal perineum). Its practical relations have been sufficiently dealt with in the article on the rectum and anus (page 1693). The anterior division, the Mro-genital Mangle (urethral perineum), has for its deep boundaries : posteriorly the deep layer of the superficial fascia (fascia of Colles) as it passes behind the transverse perineal muscles to become continuous with the inferior layer of the triangular ligament (page 563); laterally the rami of the pubes Fif» i6a6 Internal per- ineal nerve Inferior - puflendal nerve Int. itutlir artrrv- I'udii nerve- Anal faKcia- Inferior hcmc»r-|- rhulilul at1er\ I Inferior hrmnr ) . rhoidal nrrv-i'* \ Colles'i laacia Sphincter ani extern UK Tuber iacliii Tip o( coco'X Disseclinn of peiineum, shnwinK luperfkial an') hemorrhoiilal hranchea of internal pudfc artery and uf pudic nerves on right aide ; CoUes's faacia exposed on left. and ischia : anteriorly the pubic arch. Over the uro-genital triangle the superficial fascia is separable into two distinct layers, the superficial and the deep. The su|)<;r- ficial layer contains a considerable an >iint of fat, and is continuous with the corre- sponding l.-iyer over the thighs and butuxks and with the masses of fatty tis.sue that fill the ischio-rtotal fosike. The d«H"p layer, or fascia of Colles, is membranous and free from fat, and is not only applied closely to the lower edges of the transveise erineal muscles and attached to the base of the inferior layer of the triangular lij;a- iiijnt, but is also attached to the external mar^'in of the rami of the pubis and ischium. Anteriorly it is continuous with the defep layer of superficial fa.scia of the scrotum (dartos), penis, and spermatic cords, and with the f.iscia of Scaipa (page 515) on the front of the abdomen. When it is divided, a definite space, the superficicl perineal interspace, is opened, which is bounded below by CoUes's fascia, above by the inferior layer of the triangular ligament, laterally by the attachments of the fascia PRACTICAL CONSIDERATIONS: MALE PERINEUM. 1917 • and the ligament to the pubo-ischiatic rami, and behind by the union ol the iasoa with the ba»e of the ligament Thia space or pouch conuins the bulb and the crura of the penw and the muacles covering them, the superficial transverse perineal muscles, the superficial perineal nerves and vessels, and the long pudendal nerves ; in its anterior part the mteriial pudic artery divides into iu terminal branches, the dorsal artery ol the penis and the artery to the corpus cavernosum. It is very imporunt in its relations to wounds and ruptures of the urethra (y.r.). In the uro-genital triangle, hall-way between the centre ol the anus and the perineo-scroul junction, is the so-called " perineal centre," where the bulbo-caver- nosus, the sphincter ani, and the superficial transverse perineal muscles meet, and which corresponds to the middle of the posterior edge of the fibrous shelf formed by the union of the two layers of the triangular ligament. These structures are exposed when Colles's iascia is turned back, and on either side a triangular »|)ace is Fig. 1627. BuliMHomnMNt auKla CrmpvBU ColtM'i fMcU. n^Ktfd - Trianffula* I'g.. inf. U>«r - Isi hii)-caTCTmoftt», Mump* Tr»o«^t«. periBtt niu»tU~ Tut^TlwMl' Sphincter a il citcti M— l^v alOT anl - rudlr ncT^ t - ■ ■MffHAl pudk afMry ' Gf«at«r ucn-tclstk llg. - Clultus ■uximitt llcMo.cat»nw«u* mukh — ln(«fiul pvTtnMl Mr*» - ^^— E«lrfii*l |i*Ho«l««f»« Supvrti. ul prriaekl art«ry TraMvvnut paftMl nut. Aulb«l> — GfcalCff urro^rUtk llg. . „|Bf . licnia«Tlia4d«l Bcrv* - -I»». » ■nucli of bwtk ••. nl ■«r«« .Btu>hij'er of trianiniiar iigam^t and inner wall of ischio-rertal fossa partially ex(>osed. (fascia trii;oni urosenitalis inferior) ; (d ) compressor urethrse muscle ; (e) superior or deep layer of the triangular ligament (fascia trlKoni urogenitalis superior (/) levator ani muscle ; ( j^) prostatic fascia (sheath). Landmarks. — With the patient in the lithotomy position : ( i ) The pubis, coccyx, tuberosities, ischio-pubic rami, and greater sacro-sciatic ligaments may be felt. (2) The transverse diameter, between the tuberosities, is 9 cm. (3J4 in.) ; the antero-posterior diameter, from the coccyx to the pubis, is also 9 cm. (^'/i in.) on the skeleton, 10 cm. (4 in.) as measured on the living person. (3) The centre of the anus is about 4 cm. ( i ';! in. ) from the tip of the coccyx, and is on a line drawn between the tips of the ischial tuberosities. (4) The perineal centre is approxi- mately 4 cm. ( 1 li in. ) in front of the anus. (5) The bulb (and its artery) are just anierior to this ; its position .may be indicated by a slight median surface elevation : the artery passes inward between the layers of the triangular lisjament about a half mMPP PRACTICAL CONSIDERATIONS: MALE PERINEUM. 1919 inch above the base of the latter,— />.. about one and a half inches from the anus. (6) Measured in the mid-line from the symphysis to the centre of its base, the tri- angular ligament extends backward about one and a half inches. (7J The mem- branous urethra, lying between the two layers of the triangular ligament, is a little below the middle of this line,— />. , a litde less than an inch below the symphysis and from one-half to three-quarters of an inch above the anus. It measures from one- half to three-quarters of an inch in length. (8) The dorsal vein passes above the triangular ligament a little less than a half inch below the lower margin of the sym- physis ; the pudic artery and nerve pierce the superficial layer of the triangular hga- ment a litde lower. (9) The distance from the surface of the perineum to the pelvic floor is about one inch near the symphysis and from two tu three inches posteriorly and laterally. ( 10) The vesical orifice is on a horizontal anteroposterior line drawn through a point a litde below the middle of the symphysis, is about an inch to an inch and a quarter behind it, and is from two and a half to three inches above the Fig. Z639, Corpus spongtotun, cut I'rcthra Colics 's hida^—- Crus penii PoitfoB of bull^- - Cowper's ifUnd— - - Posterior edifc ot-~- trian|£uUr ligameDt Tuber Ischil- lotenutl pudic artery— — ^Crw penli — Dorsal arfery of peals — Ischio-cavcrnosus mutcle — lArterjf of corpus i avrrausum — Dorsal nerve of p«nis --CoTn|)ressor urethr.r muscle -Artery of bulh Deep transverse perineal niuSi le Dorsal nerve t>f i-enia —Internal pudic artery __SphincteT ani Perineal tttvtiion of idk nervr .^Lcvalur ani ^Greater sacro-tciatlr: liicament "-:r:_. .X Coccyx Dissection of perineum, in whicli inferior layer of trianicnlar linament and corpus spongiosum have been par- tially removed, exposing uretlira covered by compressor uretiirte muscle and Cowper's gland. perineal surface. ( 1 1 ) The prostate is about three-quarters of an inch below the symphysis. (12) The pudic artery, as it lies in Alcock's canal, is about one and a half inches above the lower inarjrin of the ischial tuberosity. These measurements are, of course, approximate, and viry with the size of the pelvis and its outlet and the amount of subcutaneous fat, which, in the lithotomy position, may much increase the normal antero- posterior convexity of the perineal surface. Lateral Lithotomy. — It will now be understood that in openinfj the bladder through one side of the perineum the incision must not extend too far forward, as it might involve the artery of the bulb, which lies a little anterior to the ' ' perineal centre" (Fig. 1629) ; or too much externally, as the pudic might be wounded where it lies on the ramus of the ischium ; or too far posteriorly, as, after dividing the layer of the superficial perineal fascia covering the rectal triangle, and thus opening up the ischio-rectal space, it might open the rectum itself. In the deeper parts of the wound it will be seen that if it is too extensive, or carried too far upward, it might pass completely through the left lobe of the prostate and divide the visceral layer of I920 HUMAN ANATOMY. t.ie pelvic fascia (which is reflected from the gland near its upper end), favoring the development of pelvic cellulitis from urinary infiltration (page 1933) ; or it might divide the neck of the bladder and open up the recto-vesical fossa with the same results ; or, if the prostatic incision were too extensive and too vertical, it might wound the ejaculatory ducts or seminal vesicles. The incision — which is made after a grooved staff has been introduced into the bladder, and while it is held in place by an assistant — accordingly begins at a point a little to the left of the raphe and a litde posterior to the perineal centre — i.e., about one to one and a quarter inches in front of the anus — and, opening the left ischio-rectal fossa, ends at the junction of the outer and middle thirds of a line drawn between the posterior margin of the anus and the ischial tuberosity. This incision should be d^ epest near its upper end — not far, at its upper and deepest portion, from the apex ■ : the " |>erineal triangle" — and should become shallower as it passes into the iscb >-rectal space. It divides skin, Fig. 163a Sectional surface of corpus spongiosum CoTpiis cav- ernosum, cut Adductor brevis Corpus cavemosum, cut Urethn Subpubic ligament i*rostatc Greater sacro- sciatic ligament' Coccygeus Gluteus- maximtts, cut Tuber ischii — Obturator intemus Greater sacro- sciatic ligament Gluteus maximus Coccyx Deep dissection of perineum. In which root of penis has been removed, showing urethra emerging from prostate, which is partly exposed between levatores am. both layers of superficial fascia, the superficial transverse perineal muscle, artery, and nerve, the lower edge of the superficial layer of the triangular ligament, and, as it crosses the ischio-rectal fos.sa, the inferior hemorrhoidal vessels and nerves. The left forefinger of the operator now guides the knife into the groove of the staff, and the incision is deepened with the knife-blade inclined laterally and pushed onward into the bladder, dividing the compressor urethrae muscle, the membranous urethra, the superior layer of the triangular ligament, a few median fibres of the leva- tor ani, the prostatic urethra, and a portion of the left lobe of the prostate. he neck of the bladder should be dilated with the finger rather than incised, an will, without serious laceration, permit the extraction of a stone of the diameter of an inch to a' 'nch and a quarter. In children the following facts should be borne in mind : (a) the relative nar- rowness of the pelvis, limiting the operative space ; (^) the undeveloped condition PRACTICAL CONSIDERATIONS. MALE PERINEUM. i92« of the prostate, necessitating the division of more of the vesical neck and incrcMing the risk of opening up the pelvic fascia ; (c) the greater mobility of the bladder (the neck of which in the adult is largely fi.xed by its connection with the base of the prostate), so that it has been pushed before the finger and torn from the urethra ; (d)the situation of the bladder above rather than in the pelvis, the neck, therefore, being relatively higher than in the adult ; (e) the looseness and delicacy of the recto-vesical fascia, permitting the easy separation of the bladder and rectum and forming a cavity which the linger may mistake for that of the bladder ; (/) the relatively low level of the recto- vesical fold of peritoneum, exposing it to injury if the wound is unduly prolonged upward. .... Median lithotomy involves the division, through the median raphe of the jjeri- neum, of the skin, superficial fascia, sphincter ani and portions of the other struc- Fio. I 63 I. Cecpu* fpongiofum, cut Grcftter tacio-tclatiC' IlKftnMBt Gluteus mftxinus, Deep dissection of perineuir. in which pelvic floor has heen partly removed. enposinK Madder, seminal vesicles, sp«.rmatic ducts, and prostate ; rectum has hcen turned baclc. tures entering into the "perineal centre," the lower portion of the superficial layer of the triangular ligament, the compressor urethrae muscle, the membranous urethra, and the apex of the prostate. The bladder is entered by dilating with the finger the prostatic urethra and vesical neck. The advantages claimed for it are :_ (a) dimin- ished hemorrhage on account of the relatively slight vascularity of the mid-line : {b') lessened risk of opening the jjelvic fascia ; (<•) lessened risk of wounding the ejacu- laiory ducts or seminal vesicles. The disadvantages are : i ij ) the narrow space between the rectum and the deep urethra, exposing the bulb and its artery to danger anteriorly and the rectum posteriorly ; (^) the lack of space for the extrac- tion of even moderately large calculi ; (f) the increased risk of pushing the bladder before the finger and tearing it from the urethra. All these objections are much greater in the case of children. Suprapubic lithotomy is done by means of an incisijn in the mid-line, imme- diately above the symphysis, dividing skin, superficial fascia, transversalis fascia 1923 HUMAN ANATOMY. (there is no distinct linea alba at this point), and prevesical fatty connective tissue in the space of Retzius. Sometimes this fat can be gently pushed or sponged upward and carries the peritoneum with it. The method of securmg a non-peritoneal area of bladder and abdominal wall for this operation (as for others involving a suprap 'lie cystotomy; has been sufficiently described. TiK/ema/e bladder is less capacious than the male bladder. Its longest diame- ter is transverse, as posteriorly the pelvic space it occupied by the uterus and vagina, and as the female pelvis is relatively wider than that of the male. The lesser depth of the pubic symphysis in the female and the absence of the prostate result in a relatively lower vesical oudet and a short, direct, distensible urethra, the dilatability of which (also on account of the absence of the prostate) extends to and includes the vesical neck. As these conditions favor easy and full evacuation of the bladder, cystitis and stone are comparatively uncommon ; and as they facilitate intravesical exploration or operation per urethram, cystotomy in the female is rarely called for. Foreign bodies introduced by the urethra are relatively common in the female bladder. The utero-vesical jxjuch of peritoneum does not descend so low as the recto- vesical pouch in the male. Below it the close relations between the bladder and the cervix uteri and the upper h:ilf of the vagina lead to the involvement of the bladder in many of the diseases originating in these structures. The latter relation permits of the recognition by vaginal touch of calculi impacted in the lower ends of the ureters, the orifices of which are about opposite the middle of the vagina. THE URETHRA. The urethra — the canal conveying the urine from the bladder to the exterior of th« body — differs in the two sexes, since in the male, in addition to its primary com- mon function of conducting the urine, it serves for the escape of the secretions of the testicles, seminal vesicles, prostate, Cowper's glands, and urethral glands. It is of interest to note that in the lowest mammals, the monotremes, in which the urethra and intestine open into a common space, the cloaca, the seminal duct is prolonged to the end of the penis as a separate canal. Embryologically the male urethra consists of two parts, a posterior segment — homologous with the canal in the female — beginning at the bladder and ending at the openings of the ejaculatory ducts, and an anterior segment including the remainder of the canal. With regard to the regions of the body in which they lie, the urethra may be considered as being composed of a pel- vic, a perineal, and a penile portion. It is more usual, however, to describe the male urethra as consisting of the prostatic, membranous, and spongy portions, — a division based upon more or less definite anatomical relations of structures through which it passes. The prostatic portion (par. prostatica), from 2-^ cm. (H-1% in.) in length, descends with a slight cur\-e, but almost \'ertically, from the internal urethral orifice of the urethra to the superior layer of the triangular ligament. Beyond the vesical wall, which embraces Its commencement (pars intramuralis o\ Waldeyer), it is en- tirely surrounded by the prostate, which it pierces from base to apex (Fig. 1619). Notwithstanding, this part of the urethra admits of considerable dilatation, althougli ordinarily its lumen is more or less obliterated by the apposition of the anterior and posterior walls. At the two ends of this division the lumen is narrower than in the inten'ening part, although this spindle-form dilatation is reduced by the encroach- ment of a fusiform elevation, the urethral crest (crista urethralis) or venimontanum, that extends along the dorsal wall from the ridge (uvula) on the vesical trigone above to the membranous urethra below, into the folds of which it fades, usually by diverging ridges (frenula cristae urethralis). On transverse section (Fig. 1681), the lumen of this part of the urettra appears crescentic in outline in consequence of the projection of the crest. The m ^t prominent and expanded part of the latter (colliculns semi- nalis) is occupied by le slit-like opening of the prostatic utricle (utriculus prostaticus) or sinus pocularis, a t ibular diverticulum, usually from 6-8 mm. in length, but some- times much longer, that leads upward and backward into the substance of the pros- tate and represents the fused lower ends of the Miillerian ducts of the embryo ; the IBPI! THE URETHRA. 1923 sinus is, therefore, regarded as the morpholoRical equivalent of the vagina and uterus. On the lateral lips of this recess lie the small orifices of the ejaculatory ducts, while those of the prostatic tubules open into the groove-like depressions on either side of the urethral crest. The internal urethral orifice lies appro.ximately on a horizontal plane passing through the middle of the symphysis, about 2. 5 cm. ( i in. ) behind the latter and an eqi^ distance from its lower border. The membranous portion (parsmenbranacea) curves downward and forward from the apex of the prostate to the bulb of the corpus six>ngiosum, which it enters somewliat (about i cm.) in advance of its posterior extremity. In its course the membranous urethra pierces both layers of the triangular ligament and is surrounded by the fibres of the compressor urethrjc muscle ; behind it, on either side of the mid-line, lie the glands of Cowper. This part of the canal measures only about i cm. in length, and is the shortest, narrowest, and least distensible of the segments. When empty, its mucous membrane is thrown into longitudinal folds, and on cross- section its lumen is stellate. In consequence of its curved course, pio. 163J. the anterior wall is shorter than the posterior, which ni»rks the most dependent point of the subpubic curve that lies about 18 mm. (3^ in.) below and behind the lower border and in the plane of the sym- physis. Since almost the entire membranous portion lies between the layers of the triangular liga- ment, its mobility is much less than that of the other parts of the urethra. The short terminal part of the membranous urethra that lies below the triangular ligament and above and in front of the bulb as it enters the corpus spongiosum (pars praetrigonalls) is, however, not only wider and thin-walled, but much more movable, — charac- teristics that increase the difficulty of guiding instruments into the narrow and fixed intratrigonal seg- ment beyond. The spongy portion (pars cavernosa) includes the remainder of the canal and terminates at the external urethral orifice. Its ^ length varies with the size and ' condition of the penis, but averages about 14 cm. (s% in.). In the flaccid condi- tion of the penis it presents a double cur\'e (Fig. 1619), the fixed proximal part of which continues the subpubic cur\'e forward and slightly upward through the peri- neum to a point corresponding aporoximately with the attachment of the suspensory ligament to the dorsum of the penis, while the freely movable distal part, or prepubic curve, follows the pendent penis. Throughout its course this part of the urethra is surroundf ^ by the corpus spongiosum, at first embedded near its upper border, then about in the middle, and at the termination near its lower margin covered by the thick cap of spongy substance forming the glans. The lumen of the spongy [xirtion is variable both in size and form ; at its two ends, where surrounded by the bulb and the glans, it presents fusiform dilatations, the intermediate pirt being of more uniform calibre. The first of these dilatations (fossa buibi) occupies the bulb of the corpus spongiosum for about 2 cm. , beginning about half that distance in front of its posterior extremity. Abruptly narrowing behind, towards the pars membranacea, in front the fossa gradually diminishes into the ordinary lumen of the canal. The ducts of Cow- Ejaculatory duct Prostatic dui'ts-^ Membranous urethra Rulbus. sponKiosutn SpofiRV urethra. Opening vi duct ol Cowper's gland — —Corpus cavcrnostim. cut and turned out Part o( bladder and male uielhra. exposed by openinR and tumhiK aside anterior wall, showinK (Kjstenor surface of prostatic, membranous, and beginning of spongy portions of urethra. 1934 HUMAN ANATOMY. per's glands open by slit-like orifices on the posterior wall or floor of this part of the urethra. The terminal dilatation, the navicular fossa (foua naTlcnlarls nrcthrac), occurs at the extreme distal end of the canal within the glans and opens onto the surface by a vertical slit-like aperture, the external urethral orifice (orifiduiii nrctlirac eztcrnam) or meatus, the most contracted and least distensible part of the entire pas- sage. Since the lateral walls of the navicular fossa are in apposition except during the passage of fluid, its lumen appears as a vertical slit on crosa-section ( Fig. 1674) ; beyond the fossa, however, the anterior and posterior walls come into contact, and hence the lumen is here represented by a transverse cleft ( Fig. 1674, 6"), which in the region of the bulb is replaced'by one of irregularly stellate outline. The female urethra — about 3.5 cm. (i^ in. ) in length — is much shorter than the canal in the male and embryologically corresponds to the portion of the latter that lies between the internal urethral orifice and the openings of the ejaculatory ducts. Except at its beginning, the canal is firmly united behind with the anterior vaginal wall, the downward and forward curvr of which it closely follows until near its termi- nation, where it turns more sharply forward (Fig. 1623). In consequence, the lower I>art of the urethro-vaginal septum is somewhat thicker below than above. With the exception of a slight spindle-form dilatation about the middle of its course, the lumen of the female urethra a fairly uniform, with a dian">ter of about 7.5 mm. during physiological distention ; except during the passage of fluid, however, its walls are in contact and the mucous membrane is thrown into slight longitudinal folds. One of these on the upper half of the posterior wall, known as the urethral crest, is more conspicuous, ineflaceable, and continuous with the apex of the vesical trigone ; it cor- responds, therefore, with the similar ridge in the male urethra. The position of its termination below, on the roof of the vestibule, is marked by a low, corrugated, coni- cal elevation or papilla which surrounds the external urethral orifice and lies from 1.5-3 cm. below the subpubic border. The urethral orifice, usually a small sagittal slit about S mm. in length, is subject to much variation in size and shape, being at times triangular, crescentic, cruciate, or stellate in form. On the papilla, on either side of the mid-line and close to the posterior margin of the urethral orifice, lie the minute openings of the paraurethral ducts, or tubes of Skene, from i-a cm. long, which are the excretory passages of small groups of tubular glands situated without the wall of the urethra. These ducts, regarded as the homologues of the prostatic ducts that open into the grooves at the sides of the urethral crest, sometimes open directly onto the posterior urethral wall just within the orificium externum. Structure. — The Male Urethra. — The wall of this canal consists of a mucous membrane containing a rich venous plexus and supplemented in the prostatic and membranous portions by considerable tracts of muscular tissue. The mucous mem- brane, which [Kissesses an unusual amount of fine elastic fibres, is clothed with an epithelium that varies in different parts of the canal. Throughout the upper two- thirds of the prostatic portion it resembles that of the bladder, belonging to the transitional vanety ; on approaching the pars membranacea the epithelium becomes columnar in type, usually being simple, but in places suggesting a stratified arrange- ment on account of the presence of small reserve cells ' between the outer ends of tht chief epithelial elements. This variety is continued through the cavernous portion as far as the navicular fossa, where the epithelium becomes stratified squamous in type, and at the external orifice is directly continuous with the epidermis covering the glans. The deeper parts of the mucosa contain a rich venous plexus, and in places, notably in the urethral crest, assume the character of erectile tissue. The constriction of the external orifice is due to a ring of fibro-elastic tissue prolonged from the envelope and septa of the cavernous tissue of the glans. The muscular tissue associated with the male urethra includes intrinsic and ex- trinsic fibres, the former being involuntary in character and directly incorporated with the wall of the canal and the latter being accessory bands of striped muscle de- rived from structures surrounding the duct. The intrinsic musculature consists of an inner longitudinal and an outer circular layer, of which the former is thinner but more widely distributed, extending from the internal urethral orifice (where it is con- tinuous with the superficial layer of the muscle of the vesical trigone) as far forward as ' Herzog: Archiv f. mikro. Anal. u. Entwick., Bd. Ixiii., 1904. THE URETHRA. 1935 ^Bvrlac* cpittKlium Section ol mucoui memhtane ol proMatIc nrethra, ibowinc (land-Uke crypu in mucoM. X 45- the orifices ol the ducts ol Cowper' s gUnds. The circular fibres, outside the longittidi- nal. are best developed at the internal orifice, where they form a layer three or four times as thick as the longitudinal, which they accompany as a dtstmct, although di- minishing, stratum as far forv trd as the termination ol the membranous ure- thra, disappearing first on the lower and last on the upper wall of the fossa bulbi. Beyond the pos- terior third ot the pars spongiosum the intrinsic musde is wanting, the muscular tissue surround- ing the remaining parts belonging to the erectile tissue ol the corous spon- giosum (Zuckerkandl). The inter. 9I vesical sphincter . . the commence) e- thra is d« 'i^ deeper laj thlTmuS o! u.e -^S^t vesical wall does not direcdy take part in its production (Kalischer). ^^ ^^^^^ ^^^ ^^^^^^ .^ encircled by bundles ol striped muscle known as thrextemal vesical sphincter. Higher up th«e bundles he entirely in front ol the urethra in close relation with the lower border ol the mvoluntary sph'ncter, n Iront of which they extend. Below, the external sphincter ,s continuous with the compressor urethr* muscle, as an upward prolongation of which it 3 be r^arded ( Hoin As it passes between the two layers ol the tnangubr ligament, the mem- viiuiiy- f branous portion of the Fio. 1634. urethra is enclosed by stout annular bundles of the compressor urethra muscle, which when stim- ulated to contraction, as by the presence of an in- strument in the canal, may tightly embrace ihe urethra and embarrass the passage of the cathe- ter. These fibres are continued forward for some distance beyond the lower layer of the trian- gular ligament. Since they affi t the canal, although not in intimate relation with its wall, the fibres of the bulbo-cavemosus muscle may also be included in the extrinsic urethral Section of wall of urethra in sponfo' portion, showing crypts miis/'iilntiiri' in mucosa and numerous venous spaces. X 35. iiiuM-umiuic , The urethral glands, or glands of Littri, embrace two groups — those within the mucous membraiie and those within the submucous tissue — the ducts of which are seen with a magnifying- Suiface epithelium 1926 HUMAN ANATOMY. glass as minute openings on the muams membrane. The former, the intramuctms glands, are simple in structure, consisting usually of a single alveolus, less frequently of two or three, from .070-. 100 mm. in diameter. They are lined with cylindrical epithelium and occur in all parts of the urethra, being mi.st numerous in the sjxjngy portion (Herzog). The submucous glands, although small, are larger than those limitid to the mucosa, but are less widely distributed, being absent in the distal half of the pars membranacea and the proximal third of the spongy portion. They are most abundant and best developed on the upper wall of the spongy poitioi.. anterior to the openings of the ducts of Cowper's glands ( Herzogj. Their ducts often e.xtend several millimetres obliquely backward, more or less pardlel to the urethra, and divide into two or more slightly e.\|>anded terminal tubules which are lined with cylindrical epithelium. Where surrounded by the corjjus spongiosum, the submucous glands lie embedded within the fibrous tissue of the albuginea ; in the pars membranacea the glands are surrounded by the bundles of the compressor urethra muscle. In addition to the foregoing true, although small glands, the urethral mucous membrane is beset, along its upper wall and near the mid-line, with small diverticula (lacunae urctbralcs) which are little more than tubular depressions within the lining of the canal and cannot be regarded as glands, although they often receive the ducts of submucous glands that Fio 1635. open into them. One of exceptional size ( from 4- ' 1 2 mm. in length 1 is com- monly found on the roof of the navicular fossa, its orifice being guarded by a fold of mucous mem- brane (valvula fossae na- vicnlaris). The Female Urethra. — As in the male, the wall of this canal consists es- sentially of a mucous membrane supplemented by an outer muscular tu- nic. The mucous mem- brane, thrown into longi- tudinal folds when the canal is closed, is composed of a tunica propria, rich in elastic fibres, covered with stratified squamous epithelium that above resembles the vesical type and below that of the vestibule. In the female the urethral glands are represented by small groups of tubular alveoli that open by minute orifices on the mucous surface and correspond to Littr6's glands in the male. They are most plentiful in the upper part of the ure- thra, and often, especially in aged subjects, contain concretions resembling those found in the prostatic tubules (Luschkai. The mucosa is also beset with small pit- like depressions, similar in character to the lacuns in the male, into which the ducts of the glands frequently of)en. The muscular tissue of the female urethra comprises intrinsic unstriped fibres forming part of the wall and extrinsic striated tissue outside of the canal. The former aie represented by an inner layer of longitudinally disposed fibres and an outer one of circular bundles, the two being separated by an intervening stratum of areolar tissue on which a rich venous plexus confers the character of erectile tissue. At the internal orifice the circular fibres, in conjunction witli those from the trigone, form the internal vesical sphincter. Between the layers of the triangular ligament the canal is surrounded by bundles of the compressor ur.. .hrse, fibres of which are pro- longed into the anterior vaginal wall. The lower end of the urethra is embraced by the anterior fibres of the sphincter vaginae muscle (Lesshaft). Vessels.— The arteries supplying the urethra are from several sources, since those distributed to the canal are usually branches derived from the vessels passing to the surrounding organs. The pars prostatica receives twigs from the middle hem- Circular muscle IxmgUudinal section of wall of female urethra, x 50. PRACTICAL CONSIDERATIONS: MALE URETHRA. i<)27 orrhoidal and the interior vesical ; the membranous jM.nion from the inferior hem- orrhoidal and the M.,K;rhcial perineal: md the spongy portion from the bulbar, cavernous, and dors.U arteries from the internal pudic. /« thejanak the ure hra « supplied by branches from the inferior vesi.al. the uterine, and the n.ternal pudic lor the upi)er, middle, ai.d lower thirds resi>ectively. , ;.. .u. The veins, which form a rich plexus beneath the mucous membrane, n. the proximal part are tributary to the vesical and pr.«tatic vcms, and n. the si>..ngy |wr. rionTthl dorsal vein of the penis and the inter.u pud.c veins. In the Jauak tl e veins empty into the vesico-vaginal and pudenda^ ple.xus Below hey communicate with the venous siwces of the clitoris and the bulbus vestibuli (, W aldc> er ; . The numerous lymbhatus within the mucous n. -nbrane form a proximal and a distal set The former pass backward to join the lymphatics of the vesical trigone, the later course forward and unite with those of the glans. The lymph-lracts from the sponiry and membranous portions of the urethra communicate with the internal or pubic group of inguinal lymph-nodes ; those from the prostatic portion are aflcr- ents to the internal iliac nodes. In the femalt the lymphatics from the upper part of the canal pass to the internal iliac nodes ; below they empty into the lymph-vessels of the labia minora and communicate with the inguinal mxies. The nerves are frjm the pudic, which conveys sensory fibres to the mucous nembrane and motor fibres to the striped muscle, and from the hypogastric plexus of the sympathetic by -vay of the prostatic and cavernous plexuses. PRACTICAL CONSIDERATIONS: THE MALE I'RETHRA. Coneenital abnormalities of the urethra are not common. Absence of the urethra usually a) affects both prognosis and treatment (page 1931). (^) The ^x^rf portion of the urethra includes the prostatic and the membranous portions and a little — from one to one and a half inches — of the posterior part of the spongy portion. It may be said to extenu from the neck of the bladder to the posterior margin of the suspensory ligament of the penis, about two and a half inches anterior to the inferior layer of the triangular ligament Of this relatively fixed portion the membranous urethra is the only part that has practically n.. mobility. The pros- tatic portion may be moved slightly within the limits alk.weU ../ the pubo-prostatic ligaments and by the connection of its capule with the .uperio;- layer of the triangular ligament in front and the recto-vesical fascia and rectum beneath and above. The posterior part of the spongy urethra, the "bulbous" portion, has even more motion both laterally and inferiorly, as its movement in those directions is not opposed by any strong membranous or ligair ^^ntous structure. Of course, anterior to the suspen- sory ligament the spongy urethra moves with the corresponding portion of the penis. This division, like the one following, is of great practical importance in urethral or vesical instrumentation. (f) The terms curved and straight, as applied to the urethra, are purely rela- tive. With the penis flaccid and pendent there is almost no straight portion, and the urethra presents a reversed, irregular, S-shapcd curve, the upper segment of which begins a little anterior to the vesical orifice and is nearly vertical, with its concavity forward in the erect position of the subject, while the lower and longer segment is less vertical, is convex anteriorly, and ends at the meatus. The whole urethra may be divided, as to its cur\es, into ( i ) a comparatively fixed subpubic curve, including most of the prostatic urethra, all of the membranous urethra, and that portion of the spongy urethra posterior to the suspensory ligament ; and (2) a prepubic curve, including the remainder. The former, or fixed, curve is, for convenience, described as that part of a circle of three and one-quarter inches diameter which is subtended by a cord two and three-quarters inches long. Practically it varies greatly from this stand- ard. It maybe flattened out by downward pressure (the patient being supine) with a finger on each side of the root of the penis, thus elongating somewhat the slightly elastic suspensory ligament and depressing th^ anterior limb of the curve ; it can temporarily be obliterated, as in passing *' ^h it a straight instrument or the straight shaft of an instrument •vith a tern, ^i curve. The two ends of the curve are approximately on the level of a line drawn through the under surface of the symphysis at right angles to its vertical axis. The summit of the curve — the lowest point with the subject erect — is on a line prolonging the vertical axis of the sym- physis, and is at the centre of the membranous urethra and about an inch behind and below the subpubic ligament. ice of ..lal cali- PRACTICAL CONSIDERATIONS : MALE URET ^A. 1929 The prepubic curve can be ttraightencd by erecting or raisinR up the penis as is done during the uie of urethral instruments. «<« of which, esjHrcially wunds and catheters, are made u> « to correspond in their c-. v«. to the theoretical hxed curve above deicribed. The catheters employ .• -n cer «n conditions, esjH^cially pr.«tatic hy^rtroThy. are elongated and given a I., ger r ve to correspond with tKc elonga- tioroftfie prostatic urethra and the greater .urve given it by the elevation of the vesicaUeck (^p^e .98^.). ^^^^ ^^^ ^^^^^^^ ^^ p.^^^ instrumenu. is a mere valvular slit, the walls lying m contact, it has to be stu.lied as "owiM^narr^Hfss by various methods of dilatation during life and of injection rpTn he caXver. The^esult of such studies demonstrates that the narrow and K tSrt^ns of the urethra alternate as follow, : the external meatus (the nar- Tow^fr thHowa navicularis. the spongy urethra, the bulbous portion, the mem- branous urethra, the prostatic urethra, the vesical onlit»>. ... U) a1 to xs dilatatility,-i.e., its suscepHbiUly todistfnl.cn by instruments - the m«.t« is the least distensible, and then, in order, follow t^e membranous, sp^ngyr. bulbous, and prostatic portions, the latter being the «"o?\*««tfn«»^''^:. . •^ A definite n;tio (nine to fouV) has been thought to ex ( Otis) betwee he cir- cumference of the flaccid penb and that of the distended uretn.a. A ceitai tionate rel-Mionship in size between the calibre of the urethral and the nrcum the penU does undoubtedly exist, but neither is it so dehnite nor is the- iiret. bre so laree as the above figures would indicate. . f n At the point at which the prostatic urethra enters th- bladder it is sur- rounded by the internal vesical sphincter, a muscle mat! u. of imstriii. l h^rcs ; antenor to this a double layer of unstriped muscular fibres an. >'■. glandular tructure of the prostate surround the urethr At the apex ..f the pio.ute lies the external vesical sohincter, made up chiefly of voluntary muscular fibres. . The discharge of urine from the bladder is prevent«l by the tonic contrartion of the muscular apparatus of the membranous and prostatic urethra. As the bladder becomes distended, the internal vesical sphincter yields and the unne enters the pos- terior part of the prostatic urethra, causing a desire to urinate, which is resiste.1 by the artion of the voluntary fibres of the external vesical sphincter and the compressor urethne On passing a catheter when the bladder is full, the urethra seems about an inch shorter thknit does immediately after micturition ; this is owing to the particir«- tion of the posterior portion of the prostatic urethra in the retentive hinction of the ^'*'^ The compressor urethr* muscle is readily excited to reflex spasm. Ordinarily. on the passage of instruments, a moderate degree of resistance cr^n be detected due to the contraction of this muscle. In irritable conditions of th- mucous membrane there mav be excited a spasm so violent that it will be impossible to introduce a soft instrument. Such spasm may also be excited by irritation of the prostatic urethra either from distention of the bladder or from any other cause. Thus it is often found extremely difficult to evacuate the bladder when the desire to urinate has been re- sisted for many hours, and acute inflammation of the posterior urethra not infrequently reauires the use of catheters to overcome the tight muscular contraction of the com- oressor urethra which prevents micturition. Not only the introduction of sounds, hut even the injection of bland liquids will cause contraction of the compres.sor urethrje muscle and hence prevent such injection from reaching the membranous or the pros- tatic urethra. Any inflammation in these portions of the urethra will also cause the tonic contraction of the sphincter muscles to be accentuated. Hence inflammatory discharge from the membranous or the prostatic urethra wi» ten-* to flow, not for- ward but into the bladder, and injections intended to reach the de.p urethra will, it driven in at the meatus, extend no farther back than the infenor layer of the trian- ^"Thw^^s'^m then, to be good grounds, both from a physiological and from a clinical stand-point, for dividing the urethra into an anterior erectile part and a pos- terior muscular part. • . .l 1: (£■■) The penile urethra terminates at the antenor margin of the suspensor>- 1 ga- ment f the/^r/wfl/ urethra includes the bulbous (with the so-called pretngonal or I930 HUMAN ANATOMY. prediaphragmatic portion) and membranous urethra ; the prostatic ureihn, of course extends thence to the bladder. All of these terms are in constant use, and a consid- eration of the urethra from the stand-points suggested by its subdivisions as above described cannot fail to be useful in relation to its injuries and diseases. Subcutaneous rupture of the urethra is rarelv seen in its penile portion In the great majonty of cases (92 per cent. ) it affects t»>e perineal portion (80 per cent, from falls astnde, 12 per cent, from perineal blows), and in the majority of these the bul- bous urethra sutlers most severely. The mechanism of rupture varies with the size and shape of the vulnerating body, but the urethra is usually crushed against either •he transverse ligament or subpubic arch, the anterior face of the pubis (which is placed at an ang e of only 30 degrees with the horizon), or the ischiatic or pubic rami. In cases of fracture of the pelvis or temporary or permanent disjunction of the pubic symphysis, the membranous urethra may be lacerated by the fragments or may be torn partly or completely across by the drag upon it of the triangular ligament. 1 he rupture may be complete or incomplete, the former being more common in the membranous urethra on account of (a) its fi.xity ; (^Uhe density of the triangular ligament ; (c) its proximity to the pubes and ischium ; ( d) the relative thinness of its walls ; and (f ) the absence of the protection afforded by erectile tissue which is present m only a scanty layer. The symptoms are hemorrhage from the meatus or into the bladder, or both ; difficult or painful urination, or retention of urine ; swelling usually in the penneum or at the perineo-scrotal junction ; and later extravasation of urine, which will be guided in certain definite directions in accordance with the locality of the rupture {vide infra). ' Urethritis, almost always due to gonococcus infection, but sometimes caused by the ordinary pyogenic organisms aided by congestion from trauma (catheter urethritis) may from the anatomical stand-point best be divided into anterior and posterior Anlertor urethritis affects that portion of the urethra in front of the compressor urethrae muscle ; the following characteristic symptoms and complications are due to Its situation : (a) free discharge from the meatus ; (b) ardor urinee, due partly to the mechanical disturbance of the flow of the stream of urine (converting the urethral sht into a suitable channel and separating the apposed walls), but chiefly to the con- tact of the acid and salme urine with the inflamed mucosa ; {c) frequent and painful erection due (1) to irritation of the lumbar centre, causing increased blood-supply through the dorsal arteries and the arteries to the bulb and corpora cavem.isa (2) to the compression of the dorsal vein of the penis by clonic contraction of the com- pressor urethra? and bulbo-cavemosus muscles, and to the compression of the penis Itself against the pubic arch by similar contraction of the ischio-cavemosus also obstructing the return current ; (3) to the loss of elasticity by the congested, infil- trated mucous membrane and submucous connective tissue, which are not able to stretch as they normally do when the cavernous bodies become engorged with blood • (d) chordee, a cur\ation of the penis due to the fact that the inflammation extends to the submi cous connective tissue, and thence to the trabecule of the erectile tissue of the sponp body. The exudation of lymph consequent upon this fills up the intertra- becular spaces, which by engorgement ftirnish the ordinary mechanical element ot normal erection. When the organ becomes erect the corpora cavernosa are fully engorged with venous blood. The infiltrated portion of the corpus spongiosum how- ever remains ngid and undilatable, the blood being unable to find its way into the partially obliterated spaces. If the inflammation extends to the corpora cavernosa erections will be equally painful : but in this case the cur^•e will be upward. If only one cavernous body is involved, the cur\'e, of course, will be towards the affected side ; (e) follicular or peri-ttrelhral abscess, due to involvement of the urethral folli- cles and to occlusion of their mouths by swelling of the mucosa, preventing drainage into the urethra ; (/) lymphangitis and bubo, usually associated with retention of discharge and inflammation between the prepuce and glans, the infection extending by the superficial lymphatics and reaching one of the superficial nodes lying just below Poupart s ligament, embedded in the subcutaneous cellular tissue and above the fascia lata. The lymphatics more directly connected with the urethra itself belong to the deeper set. and run beneath the pubic arch to join the deep pelvic lymphatics and to terminate in the lumbar nodes. PRACTICAL CONSIDERATIONS. MALE URETHRA. «93» A rare complication {Cowperitis) may result from infection of the bulbo- urethral glands through their ducts which r.npty into the bulbous urethra. The first symptom usually developed is pain ii' the perineum, much increasetl by press- ure, and rendering sitting or walking markedly painful. Tiie inrianunatory swell- ing of the glands is resisted by the two layers of the triangular ligament between which they arc situated and by the deep perineal fascia, and this resistance, associ- ated with the determination of blood to the part by gravitation, imparts, as in other inflammations where the same conditions exist, a throbbing element to the pain which renders it peculiarly distressing. Posterior Urethritis. — Although it is true that the compressor urethra muscle constitutes a sphincter which, by its tonic contraction, keeps the membranous part of the canal constantly closed against injections forced through the meatus, the gonococcus, as it passes backward in the deeper layers of the epithelium, is not arrested by this muscle, but with few exceptions invades the posterior urethra, from which region it can readily extend to the prostatic ducts, the seminal vesicles, the vas and epididymis, and, much more exceptionally, to Cowper's glands and to the bladder. To some or all of the above symptoms may then be added : {a) frequent and _ urgent urination, as the normal slight desire to urinate, felt when the bladder is moderately distended, the internal vesical sphincter dilates, and the urine comes in contact with the prostatic urethra, is transformed into an uncontrollable dc-sire when the prostatic mucosa is inflamed and hypersensitive ; (b) tenesmus from spasm of the internal sphincter transmitted to the detrusors and due to the same excitation in the neighborhood of the vesical neck ; (c) cystitis (page 1914) may follow direct extension of the infection by way of the mucosa ; (d) prostatitis (page igSo) from its spread along the prostatic ducts or into the prostatic follicles ; (<■) epididymitis (page 1952); or (/) vesiculitis (page i960), from its following the vas deferens or the seminal ducts. Chronic urethritis is apt to follow an acute attack because : (a) the canal affords periodical passage to a secretion, the urine, which is liable, by reason of changes in its constitution, to become an actual irritant; (^) it is exposed, at times of erection, to intense congestion of all its vessels, and the converse is also true, a congested or irritated spot along the urethra pretlisposing to erection ; (f ) gravitation, the propor- tionately excessive supply of blood to the region, and the absence of extravascular resistance due to the loose character of the spongy tissue, all favor the persistence of any congestion left after a first attack of urethritis ; (n of urine may occur early and suddenly from an acute increase of the congestion ot the mucous membrane of the strictured region, or it may be a late symptom and dependent on the great obstruction offered by the stricture. Ardor urinae, change in the character of the stream, diminution of expulsive power, vesical tenesmus, and urethral discharge may occur, but are not constant, and require no explanation from an anatomical stand-point. (d) Extravasation of urine is one of the most serious of the late results of stricture. The localizing symptoms — those which indicate the point at which the urethra has given way — depend upon the course taken by the urine. In all that part from the meatus to the scrotal curve, extravasation is accompanied by a swelling of the penis, greatest in the immediate neighborhood of the point of escape. In the region included between the attachment of the scrotum and the posterior part of the bulb the course of extravasated urine is governed by the attachments of the deep layer of the superficial fascia, or the fascia of Colles. Extravasation of urine occurring through a solution of continuity in this region of the urethra will first follow the space enclosed by this fascia in front and below and by the inferior layer of the triangular ligament posteriorly, and as it cannot reach the ischio-rectal space on account of the attachment of the fascia to the base of the ligament, and cannot reach the thighs on account of the attachment of the fascia to the ischio-pubic line, it is directed into the scrotal tissues, and thence up between the pubic spine and symphysis until it reaches the abdomen. PRACTICAL CONSIDERATIONS: MALE URETHRA. 1933 When it escapes from the membranous urethra, extravasated urine is confined to the region included between the layers of the triangular ligament, and only gains access to the other parts after suppuration and sloughing have given it an outlet, the consecutive symptoms then depending upon the portion of the aponeurotic wall which first gave way. If the opening is situated behind the superior layer of the triangular ligament, — i.e., in the prostatic urethra, — the urine may either follow the course of the rectum, making its appearance in the anal perineum, or, as it is separated from the pelvis only by the thin pelvic fascia, it may make its way through the latter near the pubo-prostaUc ligament, and may spread rapidly through the subperitoneal con- nective tissue. . , , ,, (ir) The bladder, ureteral, and kidney changes are similar to those that follow obstruction from any other cause, and cystitis, sacculated bladder, ureteral dilatation, and pyonephritis are not uncommonly terminal conditions in cases of stricture. Catheterism is one of the most important of the minor operations of surgery. For its proper performance, even in the normal urethra, an acquaintance with the differences in direction, mobility, dilatability, and contractility of that canal is essen- tial (,vide supra), as is familiarity with its relations to such structures and o-gans as the triangular ligament, the prostate, and the rectum {q.v.). The following points are worthy of mention here in their relation to the anatomy of the urethra, (a) The penis is gently stretched, the dorsum facing the abdominal wall to avoid folds or twists in the mobile anterior urethra. (*) In persons with protuberant bellies the shaft of the catheter is at first kept parallel with the line of the groin ; if this is not done, the point of the instrument may be made to catch in the upper wall, at the tri- angular ligament, owing to the elevation of the handle necessitated bjr the protrusion of the abdomen ; the handle should, in any event, be kept low until the tip of the instrument is about to enter the membranous urethra, (f ) The penis is drawn up with the left hand while the instrument is gradually pushed onward, the handle being finally swept around to the median line, the shaft being kept parallel to the anterior plane of the body and nearly touchin^f the integument. The instrument is now pressed downward towards the feet, while the left hand still steadies the penis and makes slight upward traction. After four or five inches of the shaft have disappeared within the urethra, it will be found that the downward motion of the instrument is arrested, (rf) The fingers of the left hand are then shifted to the perineum and used as a fulcrum, while the handle is lifted*from its close relation with the anterior abdomi- nal wall and swept gendy over in the median line, describing the arc of a circle, {e) After the shaft has reached and passed the perpendicular, the handle should be taken in the left hand and the index and middle fingers of the right hand should be placed one on either side of the root of the penis, making downward pressure (to straighten the anterior limb of the subpubic curve, vide supra), while the left hand, depressing the handle, carries the point of the instrument through the membranous and prostatic urethra into the bladder. The entrance into that organ will be recognized by the free motion that can be given the tip of the instrument when the handle is rotated, and by the latter remaining exactly in the median line and pointing away from the pubes when the hold upon it is relaxed. In urethral instrumentation it should never be forgotten that the elasticity or extensibility of the urethra resides for the most part in the spongy portion, as is clearly demonstrated by erection, and this elasticity belongs in the greatest degree to the inferior wall, which permits of easy distention or elongation, and changes its dimen- sions and form with notable facility ; while the superior wall yields with much more reluctance, and offers a certain resistance to all agents tending to depress or elongate it. This difference increases with age, and obtains especially in senile urethra-. The extensibility of the inferior wall is brought into play even by a moderate force, and the surgeon cannot count on its resistance. It glides before an instrument, and cannot serve to guide it ; it cannot be incised with arty accuracy or precision : it lacerates or ruptures when surprised by distention ; and it yields rapidly and ea^ \- to mechanical pressure testing its extensibility. It should be noted, too, that this elongation of the canal is chiefly at the expense of the anterior urethra. Again, the sptong)' portion docs not yield equally in all its parts, since it has been shown that of the different regions the perineo-bulbar is the most distensible. The inferior wall of 1934 HUMAN ANATOMY. the urethra can then be considered as normally longer than the superior surface. The term "surgical wall," proposed for the upper wall by Guyon, would seem to be merited, because it offers the shortest route to the bladder, is the most regular and constant as to form and direction, presents the smoothest and firmest surface, is the less capable of gliding before an instrument or being modified by mechanical pressure, offers the greatest resistance to rupture and penetration, is less intimately connected with important structures, and is the less vascular of the two walls. As to the calibre and distensibility of the urethra, enough has already been said ; but it should not be forgotten that there are three relatively constricted parts, the internal or vesical mea- tus, the external meatus, and the membranous regions ; and three dilatations, the fossa navicularis, the bulbar cul-de-sac, and the prostatic depression, the last two dila- tations presenting numerous individual variations , and in this connection it is impor- tant to remark that all three of these dilatations are excavated at the expense of the inferior wall of the canal. The urethral curve only remaining regular in the superior wall, it results that the more pronounced the curve the more accentuated are the bul- bar and prostatic depressions ; and as a certain degree of lengthening of the urethra always corresponds to the greatest curve, — since these are both produced by bulbar and prostatic augmentation of volume,— one can reasonably conclude that urethra of the greatest curves present at the same time the greatest length. With a knowledge of these facts, the instrumental exploration of the urethra becomes a matter of much accuracy and precision (Morrow). The anatomy of the various forms of urethrotomy and other operations on the urethra is sufficiently dealt with in the foregoing and in the practical considerations relative to the bladder, male perineum, and prostate {f.t:). DEVELOPMENT OF THE URINARY ORGANS. The development of the essential parts of the urinary tract — the kidney and its duct — is so intimately related with the foetal excretory organ, the Wolffian body, that a brief account of the latter and of the f)rinciples underlying its genesis is a necessary introduction to the intelligent consideration of the subject here to be presented. The excretory apparatus of amniotic vertebrates, even in the highest mammals and man, includes three structures which, although a^ functionating organs existing in no single animal, stand in genealogical sequence. These are the pronephros, the meso- nephros or Wolffian body, and the tnetanephros or definitive kidney. The Pronephroi. — The first of these, the pronephros, sometimes called the "head-kidney" on account of its anterior position in its primary condition, in all higher forms is at best a rudi- mentary and functionless organ ; nevertheless, it is of extreme interest as indicating the funda- FlG. 1636. Neural tube IntermeHiale mass Ectoblast Parietal tneaobtast / Body' division of mesoblast into somite, intermediate mass, and parietal and vift* ceral layers. X 100. Fio. 1637, Neural tube Somite '\nl3Ke of nephric duct Parietal mesoblast BodvKiavity Visceral mesoblast Remains of intermediate mass Section of sllKhtly older embryo, show. ine differentiation of duct-anlaj^ and mass in which tubules develop. X 100, mental plan upon which, in a modified form, the later Wolffian body is developed. Although, so far as known, existing as a permanent organ alone in the hag fishes ( Ah.rinidtr), as a temporary stnictiire the pronephros attains ron<:idcrahIc developtnent in many fishes .ind .-imphihi.-ms ; in the higher animals, even as aii embryonal organ, it remains very rudimentary and transient. When adequately represented, the pronephros consists of a more or less extensive series of DEVELOPMENT OF THE URINARY ORGANS. 1935 sliehtly transverse Mmles within the posterolateral body-wall that intertjally communicate with the body-cavity or calom. the openings beinR known ius nephrostomata, and externally join a common canal, \\\e pronephric duel, wTiich extends caudally and empties mto the dilated terminal segment of the intestinal tube, the cloaca. In relation with the inner end of each tubule, but projecting freely into the body-cavity, lies a group of convoluted WcHKl-vessels. the glomerulus, supplied by branches of the aorta. These liree parts of the pr itive excretory Fig. jOji. Neural tube. Somitic cavity. iw>1ated- Malpiffhlan hody of mesonephros, Mesonephric tubule Mooncphric duct. Parieul perJtoneuni- BoQy.cnvity^ Nephrostome'' Sexual gland Suprarenal body^ Integument Cavity of somite continuous with cixlom Notochord Nephrostome Pronephric tubule Gut-tube Pronephric duct Mooblast ul body-wall , BodyKavity (coelom ) N^ Glomerului of pronephroa •v Aorta Visceral peritoneum Diagram showing fundamental rrlations ot pronephros (on right side) and of roeaonephroa or Wolffian body (on left side of figure). {Uudersktim.) Fio. 1639. organ provide for the essential requirements of the most elaborate urinary apparatus,— the pro- duction of the watery constituents, the excretion of the wa.ste products, and the conveyance of the excretion so elaborated. The pronephros is fundamentally a segmental organ, the tubules being so arranged that each corresponds to a single body-segment or metamere, although by no means every such division contains a tubule. It may be assumed that the tubules of the pronephros represent the segmental ducts which in ancestral forms extended from the body-cavity directly onto the external surface of the 1 ody and thus carried off the fluids accumulated within the ccelom. In consequence of the closure of this direct communication with the exterior, which may be accepted as having occurred during the evolution of a more elaborate excretory system, the necessity for a new path of exit is met by the formation of the common pronephric diict into which the tubules open, and which, by its prolongation to and termination in the end-gut, insures the escape of the excretions. The development of the pronephros is closely associated with the mesoblastic somites. A transverse section of an early mammalian embryo ( Fig. 1636) shows the paraxial mesoblast, be- tween the neural canal and the cleavage of the lateral mesoblast into the somatic and visceral plates, to comprise two parts, the mesial forming the somite and the lateral or inlennediate cell-mass. It may be assumed that in the higher types the solid somite and the intermediate cell- mass have arisen by fusion of the primarily distinct dorsal and ventral mesoblastic plates (Fig. 163S). The inter- mediate cell-mass soon separates into a small duct-anlage, situated dorsally and in close relation with the ectoblast, and a larger ventral tract comprising the remainder of the intermediate cel'-mass. Within this ventral area the tu- bules shortly appear, and later the glomeruli. Although reaching a comparatively hijfh development in certain fishes and amphibians (especially in Ichthyophis df'icribed bv Se- mon), in mammals the pronephros consists of a few tuBules connected with the duct, and even as an organ of embryonic life never attains more than a feeble and transient exist- ence. In the human embry-o of 3 mm. length, studied by janosik, it was represented by two rudimentary tubules that extended from the mesothelial lining; of the bodyked upon as the continuation .ind mor- phological persistence of the pronephric duct. In tlieir development these tubules and duct bear a similar relation to the intermediate cell-ma.ss as do those of the pronephros, onlv the body- segments involved lie farther tailward and the strict segmental arrangement of the tubules is lost owing to their multiplication and, as in mammals, precocious development. In contrast to the Body^avity Lonf{itudin.il section of \nunK t mHr\-o, showing early stage of Wolffiaii hody ; tu- bules are joining duct. X y> >936 HUMAN ANATOMY. — AotU nidimentary character of the pronephros, the Wolffian body not only serves for a time as the chief excretory or^an of the embrjo, but in many lower vertebrates continues to functionate during life. The anlage of the Wolffian duct first appears as bud-like outgrowths from the dor- sal side of the intermediate cell-mass ; these fuse into a strand which, separating from the cell- mass, lies as a solid cord beneath Fir 1640. the ectoblast The latter takes no part in the formation of the duct, which is entirely of mesoblastic origin, th*; appearances leading to the assumption by certain authori- ties of its derivation from the outer germ-layer depending upon the temporary apposition or attach- ment that the duct effects in con- sequence, probably, of its inher- ited inclination, since in ancestral forms the tubules opened on the free ectoblastic surface. At first solid, the Wolffian duct later pos- sesses a lumen which gradually follows the tailward ^owth of the strand until, finally, it opens into the dilated end-gut or cloaca. In mammals the Wolffian tubules are developed within the ventral division of the intermedi- ate cell-mass as solid cords that later acquire a lumen and an at- tachment to the Wolffian duct. Although in the lower vertebrates (fishes, amphibians) retain- ing a communication with the coelom by means of a nephrostome, in mammals this connection is Tost and the expanded inner end of each tubule comes in close relation with the convoluted vascular tuft, the glomerulus, which now, however, no longer projects freely into the body- cavity. As in the kidney, the glomerulus is supplied by an afferent twig from a branch of the aorta, and is drained by an efferent ves.sel that breaks up into a capillary net-work surrounding the convoluted tubule and eventually Fio. 1641. Wolffian duct Mesot helium' Wolffian Aortic branch to glomerulus sloping capsule Part of transverse section of embr>'o, showing commencing develop- ment of Malpighian corpuscle in Woifnan body. X 150. Capsule of Malpighian '' twdy becomes tributary to the cardinal vein. The first apjiearance of the Wolffian body in the human embryo occurs very early (2.4 mm. length) and at a time when the remains of the pronephros are still present. The duct precedes the tubules and opens into the cloaca in em- bryos of 4.2 mm. length (Keibel), the tubules, which develop independently, establishing communication with the duct shortly before. The development of the glomeruli is relatively tardy, since these bodies are not found until the human embryo has attained a length of about 7 mm. Their formation and growth continue during the first and second months until the embryo meas- ures 22 mm. in length, when their great- est perfection is reached (Nagel). When fully developed, about the end of the second month, the Wolffian body appears as an elongated organ (Fig. 1720) which extends along almost the entire length of the posterior wall of the bodyovity, on either side of the mid-line, from behind the lung-anlage to the lower end of the gut-tube. Ah- it the eighth week, the Wolffian bo0' canals of the sexual Klands. In the male the Wolffian duct and tubules jwr st chiefly as the Vi>s deferens and the epididymis ; in the female, in whom the atrophy is more complete, these remains are represented principally by the epoophoron and Gartner's duct. In both sexes certam ad- ditional rudimentary- organs— the paradidy- mis in the male and the paroophoron in the female— are derived from the tubules of the sexual seKment of the Wolffian Ixxly. A more detailed account of these transformations is given in connection with the development of the reproductive organs (page 20,^7 and Fig. 1 719). ■Stroma The Metanephrca or Kidney.— The development of the definitive kidney in mammals begins as a i)ouch-like out- growth from the posterior wall of the Wolffian duct, a Short distance alwve its termination into the cloaca. In man the renal diverticulum makes its appearance during the fourth week, at which time the embryo measures from 6-7 mm. in length. At first short and wide, the stalk of the pyriform sac soon becomes tubu- lar, growing upward and backward into the mesoblast of the posterior body-wall. This stalk rapidly elongates, and termi- nates above in a blind club-shaped ex- tremity which after a time lies behind the upper atrophic segment of the Wolffian body. The tubular duct becomes the ureter and its dilated end-segment the renal pelvis. The latter is surrounded by a sharplv defined oval area of compact mesoblast that is intimately concerned in the prcnluction of the convo- Fio. 1643. Ampullarv terminations of prim.iry collecting: tubules .Primar>' collrctinic tuhuleH olH-ninK into liubitivtaioiw of pelvis Renal pelvii Malpif;hian txxly MalpiKfiian corpu-Hcle of atrophJL- Wolffian body Lonxitudinal section throiiith devflopine kidney ; por- tion of atrophic Wolffian body is seen below. X 35. Devrloping Maipi^nian IxmIu's Primar>' collecting tube LatKC col- lectiuK duct Section of developing kidney, showing formation of urinifer- ous tubules and collectings canals. X 100. luted kidney-tubules (of which as yet no trace is present), and hence is termed ^crenal blastema. From the \entral and dorsal walls of the primi- tive pelvis, which is com- prtssed from before back- ward, a number of hollow sprouts grow into the surrounding mesoblastic stroma. Each is a short cylinder that terminates in a slight dilatation. At first few, these sprouts in- cre.tse rapidly in number as well as in length, and by repeated dichotonious division give rise to a sys- tem of branching canals that later are represented by the straight collecting tubules of the kidney. Concerning the ori- gin of the remaining portions of the uriniferous tubules two opposed views obtain. According to the one, all parts of these canals develop as direct continuations of the 19.18 HUMAN ANATOMY. RiRht umbilu'ul artery. Fio. 1644. Gut-tube outgrowths from the primitive renal pelvis ; according to the other, the convoluted tubules (from their beginning in the capsule to their termination ifr the collecting tubules within the medullary ray) arise inde{}endently within the renal blastema, and, secondarily, unite with the duct-system from the |x:lvis to complete the canals. The careful studies and reconstructions of Huber ' leave little doubt as to the cor- rectness of the latter view, which, moreover, accords with the prin- ciple observed in the develop- ment of the pronephros and the Wolffian bo-o of twenty-six days (6.5 mm. length) ; Wolffian duct opens into ventral segment of cloaca. X 75. ( Drawn from Keibet model. ) Cloacal membrane Preceding model viewed from right side, show- ing beginning division of cloaca into ventral ( uro- genital) and dorsal (intestinal) segment by longi- tudinal septal fold. (Drawn from Keibet modetTj investigations of Keibel, Retterer, and Nagel, upon whose conclusions the following account is based. A sagittal section through the r.iiidal pole of an f-arly human embryo of 6.5 mm., about the beginning of the fourth week (Fig. 1645"), exhibits 'American Journal of Anatomy, vol. iv.. Supplement, 1905. DEVELOPMENT OF THE URINARY ORGANS. »9.W Fig. 1647. N'ciia luva Allmntotc iliict Brlty-italk- T»il . , , Ureter \ \ NotiKlionl Rixlum Wolffian duct Krnal (irlvis ReconMniction of cinaral region ol human embryo of thirty-lhre* davs (MS mm. lent^h) ; cloaia now incompleti'ly wiiarated mti> uro- genital and intestinal aegmeiiU. X ly {Drawn /ram Kettel modrl.) the end-segment of the gut dilated into an elongated chamber, the cloaca, from the upper end of which the allantois passes forward and on the sides of which ojn-n the Wolffian ducts. The ventral wall of this space is thin, and consists of the i>p|M)sed outer and inner germ-layers alone, no mesoblast intervening. This crti>-entol>!astic septum is the cloacal mem- brane. During the fourth week the subdivision of the cloaca into a ventral and a dorsal compartment begins by the for- mation of a frontal fold that projects downward from the angle between the gut and the allantois. Subsequently this partition is supplemented by two lateral folds that appear on the side walls of the cloaca and are continuous above with the frontil fold (Fig. 1646). By the union of these three plicae, above and from the sides, a septum is formed that gradu- ally grows caudally and sub- divides the cloaca into a ventral ... ' allantoic and a dorsal intestinal chamber. This partition, however, for a time is incom- plete below, communication between the two spaces being thus maintained. During these changes the short canals common to the Wolffian ducts and the primitive ureters are drawn into the ventral chamber, the four tubes thereafter open- ing independently, but in close proximity, on the posterior wall of the ventral cloaco- allantoic space. This undergoes further differentiation into an upper (vesical) and a lower (genital) segment, the latter gradually narrowing into a tubular space, closed below by the fore part of the cloacal membrane, which becomes the uro-genilal stmts and, after rupture of the membranous floor, communicates with the exterior. For a time the orifices of the Wolffian ducts and the ureters are closely grouped, those of the former, how- Pio. 1648 ever, lying nearer the mid-line and slightly higher than the more widely sef>arated ureteral ojjenings. During the second month an important modification of these relations occurs, associ- ated with elongation and expansion of the upper part of the vesical seg- ment, by which the ure- ters are drawn upward and the Wolffian ducts downward. The inter- vening tract corresponds to the lower segment of a spindle-shaped sac that extends upward and is continued towards the umbilicus by the allantois. The upper part of this sac, which is the dilated allantois, forms the l)ody and summit oi the bladder and the urachus ; the lower part, into which the ureters open (Fig. 1649") and which is derived from both allantois and cloaca, differentiates into the vesical trigone and the urethra as far as the openings (A Allantoic duct^ r.enital eminence >^- Epitl knc Notochord Wnlffian duct T'reter Reconstruction of cloacal reRJon of human embno of thirty-seven davs (14 mm. lenxth); ureter now opens indei>endently into uro-Renital siniis, which above contributes lower sefonent of bladder and below is now almost separated from gut-tube. X 17. {Drawn/rom Keibei model.) «inui, which i> com- pletely iiepanileil from intatine. X lo. { Drawn from Keibtt mmitl.) upper part being from the allantois alone, while in the formation of the trigonal region both allantois and cloaca take part. The remaining portions of the urethra in the male are formed by the extension of the uro-genital sinus along the under surface of the coqxira cavernosa of the developing penis (page 2044"). I THK TKSTES. 1941 THE MALE REPRODUCTIVE ORGANS. This group comprises the sexual glands (the testes), the ducts (^vasa dt/frentia) and their appendages (the seminal vesicles), the copulative organ (the penis), and certain accessory glands (the prostate and Cowper s glands). Although at first situated within the abdominal cavity, the testes migrate through the inguinal canal into the scrotum, which sac they usually gain shortly btfore birth. In their descent they are accompanied by blood-vessels, lymphatics, nerves and their ducts, which structures, with the supporting and investing tissue, constitute the spermatic cord that extends from the internal abdominal ring through the abdominal wall to the scrotum. THE TESTES. As often employed, the term " testicle" includes two essentially different larts, the testis — the true sexual gland — and the epididymis, the highly convoluted begin- ning of the spermatic duct. The testes, or testicles proper, the glands producing the seminal elements, are two slightly compressed ellipsoidal bodies so suspended within the scrotum — the left lower Fio. 1650. Tunica vaginalis communis, cut Tunica vaginalis l.ower vihI 6k spermatic ci>nl, with xtramls of crcmaster mUMie" Tunica vaginalis communis- Diiptal. fossil Epididymii Reflection i>l tunica vaginali covering scrotal lifcament Tunica vagina lit "^1 I'dobuH ma)or of t^ididytnis Aftpendiii epididymidix " — Appendix tetlis ^KjF - Sac u( tunica vaKinalift Right testis Serous iao~^^^| Reflect ioi of s<.'nju.s A, antero-lateral view of right testicle after enveloping membranes liave been cut atul turnett aside ; B, antero-median view of same. than the right — that their long axes are not verticil, but directed somewhat forward and outward. Each testis measures from 4-4.5 cm. (I'/j-i^^ in. ) in length, .ibout 2. 5 cm. in breadth, and 2 cm. in thickness, and presents a lateral and a medial sur- face, separated by an anterior and a posterior border, and an upper and a lower pole. The lateral surface looks outward and backward, and the flatter medial one inward and forward. Both surfaces, as well as the anterior border, are completely covered with serous membrane (the visceral layer of the tunica vaginalis) and are, therefore, smooth. The rounded anterior border is free and most convex, the much less arched posterior border, covered by the epididymis and attached to the sjjermatic cord, being devoid of serous membrane and corresponding to the hiluiu. In consequence of the obliquity of the long axis of the organ, the upper pole, capped by the head of the epididymis, lies farther outward and forward than the more pointed lower one, which is related to the tail of the epididymis and attached to the scrotal ligament ("page I 1942 HUMAN ANATOMY. FlO. 3043). The testis is of a whitish color, and, although readily yiddinii;, imparts a characteristic impression {>f resilience when compressetl between the tinkers. Architecture of the Teitit. — The framework of the testicle pr(>|>er consists of a .Htout capsule, the luni:a albuginta. a dense libro-elastic envelope from .4-. 6 mm. in thickness, that (;ives form to the organ and protects the subjacent soft glundular tissue. Along the posterior border of the testis the capsule is greatly thickened and projects forward as the mediastinum testis or corpus Highmori, a wedge-shaped body (from 2.5-3 cm. 'i length ), from which radiate a number of membranous septa that piiss to the inner surface of the tunica albuginea. In this manner the space within the capsule is subdivided into pyramidal compartments, the bases of which lie at the periphery and the apices at the mediastinum. These spaces contain from 150 to 200 pynform masses of glandular tissue, more or less completely separated from one another, that correspond to lobules (lobnli testis). Each of the latter is made up of from one to three greatly convoluted seminiferous tubules, held together by delicate vascular intertubular connt .-live tissue. The seminiferous tubules — from .15-. 25 mm. in diameter and from 25-70 cm. ( 10-28 in. ) in length — begin as blind canals, which are moderately branched and very tortuous ( tubuli contorti) throughout their course until they converge at the apex of the lobule, where they pass over, either directly or after junction with another canal, into the narrow, straight tubules (tubuli recti) that enter the mediastinum and unite into a close net-work, the rete testis. The latter extends almost the entire length of the mediastinum, and consists of a system of irregular inter- communicating channels, the cuboid epithelial lining of which rests directly uj)on the en- sheathing fibrous tissue of the mediastinum. With these passages the canals of the testicle proper end, the immediate continuation of the spermatic tract being formed by from fifteen to twenty tubules, the ductuli efferentes, that pierce the tunica albuginea along the posterior border and near the upjier pole of the testis and, forming the coni vasculosis connect the sexual gland with the tube of the epididymis. Structure. — In contrast to the dense fibrf)-elastic tissue that composes the frame- work of the testis, — ;' e capsule, mediastinum, and interlobular septa, — the con- nective tissue occupying the spaces between the seminiferous tubules is loose in texture and arrangement, consisting of delicace bundles of white fibrous tissue in which elastic fibres are few or absent. In addition to the plate-like cells, leucocytes, and eosinophiles that occur in varying numbers within the meshes of this tissue in conjunction with blood-vessels and nerves, groups or cord-like masses of peculiar polygonal elements, the interstitial cells, also occupy the intertubular stroma, especi- ally in the vicinity of the mediastinum. These cells (Fig. 1654), from .015-.020 mm. .'.- diameter, possess relatively small round or oval eccentrically placed nuclei and a finely granular protoplasm that usually contains numerous brownish droplets, pigment particles, and, sometimes, crystalloid bodies in the form of minute needles or rods. In some animals, notably in the hog, the deeply colored interstitial cellr form conspicuous tracts that impart a dark tint to the testicle in section. Their significance is obscure, but they are probably modified connective-tissue elements deriveti from the niesoblast of the germinal ridge (Allen, Whitehead). The wall of the convoluted seminiferous tubules consists of a delicate tunica propria, composed of an inner elastic lamella strengthened externally by circularly disposed fibres, within which are several layers of epithelial cells. The latter vary not only before and after the attainment of sexual maturity, but subsequently with functional activity or rest ; in man, however, the variations depending upon these 1651. GU>bui Rujor of epiilid)-r«b •Vi» deferrn< Cntll VHM-'Ulosl Ductus epitlidymidi* -Ourluli effereiitn Tubulj recti .Retr testis in mediastinum Tubuli conturti Vat abeirans Durtus rpididymidis Globus minor Septum Tunica albufinea Dtaftam showing^ relaliuna of secretory- tubules ana system oit ducts. THE TESTES. «943 causes are much less marked than in animalst, in which sexual activity is limited to dehnitc periods. Seen in sections of the mature human testicle (Fiy;. 1656 ), the epi- thelium lining the seminiferous tubules includes two chief kinds of cells, the support- ing and the sptrmatogenelic. The former— the cells of Ar/o/i— take no active piirt in the production of the spermatozoa, but serve chieHy as temporary sup|)orts for the more essential elements during certain stages of spermatogenesis. 1 hey are elongated elements of irregularly pyramidal form that rest by cxi>anclc«l biises «|K)n the nu-m- brana propria, and project towards the lumen ol the tubule between the layers of the Fio. 163*. BpldM)inli ConvolutioM o( duct u< cpMidymto in ilobiu mi)ur (-'(Hii vaKulonl icinivolutloiis ol cfivrrnt ducts i DiKttll ScnHu rartacc oi toll* T«tlt Interlobular septum Tunica albuginea Effcmu ducts 'Sections f^ tluct of cpitlHlvmis Blood' vnseli R*lc leatit in mediastinum ■Lx}bu1es of (land-tissue •Convolutions of duct of epididymis in xlobus minor Sagittal section of testicle of child, 5howin(t ceneral arrangement of framework and Kland-lissuc and of canals connectmg epididymis witli testis, v lo. surrounding spermatogenetic cells. The large oval nuclei of the Sertoli cells are con- spicuously meagre in chromatin, and lie towards the middle of the cell at some distance from its base. Th«. outer part of the protoplasm contains fat-droplets, the inner zone being granular or often longitudinally striated. Where the tubuli contorti pass into the straight tubules the supportini; cells bemme reduced in height and form a layer of simple colu-nnar cells continuous with the low cuboidal epithelium lining the rete testis. , . , , • , The S}> •*. f'ogenetic cells include three forms that stand in the relation of .suc- ceeding gent, loiis to one another, those representing the oldest lying nearest the 1944 HUMAN ANATOMY. membrana propria, and the youngest, from which the spermatic filaments are directly derived, next the lumen of the tubule. The first generation, the spermatogones, lie at the periphery between the cells of Sertoli, and, although small round elements, Fio. Z653. Seminiferous tubule, cut obliquely Tunicm albu^ni Seminiferous tubule,x^ cut transversely -■ '.'.roup of interstitial cells Tunici. vaginalis vesKi Blood'Vessel Portion of cross-section of testis, showine dense fibrous envelope and adjacent seminiferous tubules, X y>, possess nuclei exceedingly rich in chr matin. The division of these cells results in two cells, of which one retains the position of the parent cell, which it replaces as a new spermatogone destined for a succeeding division, while the other passes inward, enlarges, and becomes a mother cell or primary spermatocyte of the second genera- tion. This element, conspicuous by reason of its size and large nucleus, undergoes mitotic division and gives rise to daughter cells or secondary spermatocytes. The latter almost immediately divide and produce smaller cells, the spermatids, by the transformation of which the spermatic filaments are directly produced. It is impor- tant to note that the spermatids Fio. 1654 contain only one-half of the num- ber of chromosomes normal for the ordinary (somatic) cells, a like reduction (pa^ji- 18} occur- ring in the matured ovum. Spermatogenesis. — The cytological cycle resulting in the production of the spermatozoa from the epithelial cells lining the seminiferous tubules comjirises four principal stages : (i ) divi- sion of the spermat{)gones into spermatocytes ; ( 2 ) division of the latter into spermatids; (3) transformation of spermatids into .spermatozoa ; (4 ) completed dif- ferentiation and iilx;ration of sper- matozoa. The changes incident to the first and second of these stages have been outlined ; a brief account of the subsequent changes may here be •iddcd. The -spermatids, at first small cells with rouiul nuclei, elongate, their nuclei coincidendy becoming oval and smaller, but rich in chromatin, and shifdng to the ;g| L S i Intertuhular ,vSi/^' ton nect i vc ' ■ " tissue «T ''©^ Tunica propria of tuhule Group of interstitial cells lying within intertuhular stroma. X .vk>. THE TESTES. •945 end of the cell most removed from the lumen. The modified spermatids now become closely related with a Sertoli cell, with the protoplasm of which they fuse. The structure thus formed, known as the sperma- toblast, consists of an irrejijular nucleated conical protophis- mic mass (Fig. 1657, 27). with the inner end of which the radiating clusters of partially fused spermatids are blended. The succeeding changes in- clude the transformation of the elongated nucleus of the sper- matid into the head and of its centrosome into the middle- piece of the spermatic filament, while from the protoplasm of the spermatid, possibly in con- junction with that of the sper- matoblast, the flagellate tail- filament is derived. As the spermatozoa become more and more differentiated, they appear as fan-shaped groups in which the heads are always buried within the spermato- blast and the tails directed to- wards the lumen of the canal. After separation, which subse- quently takes place, the liber- ated spermatozoa occupy the centre of the tubule as masses which often occlude its lumen and in which the seminal fila- ments are disposed in peculiar whorl-like groups. Their com- plete development, however, is deferred until they reach the tube of the epididymis, during the passage through which highly tortuous path they attain maturity and lose the protoplasmic remains of the spermatids that usually for a time adhere to the middle- piece. The spermatogenetic process docs not involve uni- formly all parts of the seminif- erous tubulo, but is manifested with wave -like periodicity; consequently sections taken through the same tubule a few millimetres apart exhibit dif- ferent stages of the cycle, al- though the cells are never all of one phase. Fio. 1655. Dilatol rtuct Bloo 75. Fig. 1656. Tunica propria Secondary spermatocyte Spermatids Spermatitis Iwiiiff transformetl itito spermatozoa t^'\ SecoiKiary spermattRV^e -^Jv: Spermato/on InntT- lameDa Sertoli cell ' r~^~^^tS,\ Resting si)ermat(>Ktnie Dividing s|iermatii>ii celU in various stages of spermatogenesis. X 350- 1946 HUMAN ANATOMY. The spermatic filaments or spermatozoa, the essential male reproductive elements, are, hke the ova, direct derivations of epithelial cells that ire dracendants Flo. 1657. niaKiam illiMtratinr phaan of one romplete cycle of spermatogenesis. Sequence of fieures shows in det.-i.l Krowth ( 1-6) and division (7-S) of siKrSiatoKone ; growth and .Tivision ofprimary spermat^vte (^li^ 1110 secmdary sr*rmatoc>1es ; division of latter ( 1.JI21 ) into siK^rmati.ls (22-24 1: fusion of th\^ wrth^rtoircel to (onn siKrrmatoblast (25-26); digeremiation (27-Ji ( and final liberation (32) of spermatc.zia(^/,rA'«i.,^) of the primary indifferent sexual elements. Unlike the ova, however, which are rela- tively large and often absolutely huge, and, apart from size and minor distinctions, p fairly similar in all vertebrates, the sper- 5 matic filaments present great diversity in form and detail and represent a high degree of specialization. The human spermatic filament is small, and consists of an ovoid Aead, a cylindrical middle- piece of uncertain extent, and a gready attenuated and prolonged tail, — the propelling organ of the flagellated cell. The mature element measures about .050 mm. in its entire length, of which only about .005 mm. is contributed by the head, prolxibly about the same by the middle-piece, and from .040-.045 mm. by the tail. The head, somewhat flattened in front and hence pyriform in profile, although rich in chromatin, appears homogeneous, since the chro- matin is uniformly distributed and not Tt,„ „»„ » 1 u • t .. arranged as threads or mesh -works, structural basis .■ the remaining parts of th.' spermatic element is a delicate axial Jihre that extends Ironi the head to the tip of the tail (Fig. 12) and is in- Human spermatic filaments seen from the hroad sur- faif. except a. which is in profile. • hoo THE EPIDIDYMIS. <947 vested by a delicate envelope, with the exception of the last .005-006 mm. that con- tinues uncovered as the attenuated end-piece. In front a mmute spherical thicken- ing the end-knob, marks the termination of the axial fibre, where it joins, but does not penetrate, the head, and probably represents the centrosome of the spermatid. Within the middle uiece the envelope surrounding the axial hbre, after the action of certain stains, exhibits markings that suggest the presence of a spirally arranged filament of great ' elicacy. THE EPIDIDYMIS. The epididymis, the gready convoluted beginning of the seminal duct, is a crescentic body, triangular in section, that covers the entire posterior border and the adiacent pait of the outer surface of the testis. Its enlarged upper end or globus maior (caput epididymldis) covers the superior pole of the sexual gland and is attached to the latter not only by connective tissue and serous membrane (as is the globus minor) but by the efferent ducts that establish communication between the testis and its excretory canal. The succeeding part, the body, gradually tapers as it descends to the lower pole, at which point the epididymis presents a second and less conspicuous enlargement, the globus minor (cauda epididymidis), that bends backward to liecome the vas deferens. The latter passes upward along the median side of '''°- ' so- the posterior border of the epidid- ymis to ascend in the spermatic cord. Where attached to sur- rounding structures, as at its two ends where in contact with the tes- ticle and along its posterior border where blended with the spermatic cord, the epididymis is devoid of serous covering ; in other places it is completely invested by the tunica vaginalis, a deep recess, the digital fossa (s.nus epididymidis) intervening between the body of the epididymis and the adjacent surface of the testis. The bulk of the globus major depends upon the aggregation of from twelve to fifteen conical masses (lobuli epi- didymidis) formed by the effenni ducts and their tortuosities, the coni lasculosi, that pass from the upper end of the testis and connect the rete testis with the canal 0/ the epididymis. The latter (ductus epididymi- dis) bepi"^- ing in the globus major, receives the efferent ducts and becomes greatly convol' .., the extraordinary windings of the single tube contributing the chief bulk of the body and the tail of the epididymis. When unravelled, the canal measures from 5-5.5 m. ( 18-20 ft. ) in length, its remarkable convolutions sufficing to pack awav this long duct within the small volume of the epididymis. Structure.— The conical lobules of the globus major are enclosed by a fibrous envelope resembling but less robust than the tunica altniginea testis, within which the convolutions of a single tubule are held together by delicate vascular connective tissue. The transition of the channels of the rete testis into the efferent ducts is marked by an abrupt change in the character of the lining epithelium, the low cuboidal cells of the former giving place to irregularly ciliated columnar elements within the latter. .e tubules— from .i-.5 mm. in diameter— present .m irregular lumrn, owing to the inconstant thickness and pitted surface of their epithelium. Just before terminating Kflerent ducts •Rete testis Glohu minor Pyramidal lobules of gland-tissue (seminiferous tubules) Dissection of testicle alter tubules have been filled with quick- silver; testis has been separated into the component lobules. 1948 HUMAN ANATOMY. Fibrous envelope VaH aberrans in the canal of the epididymis, the tubules become narrowed and surrounded by a thin layer of circularly disposed involuntary muscle. The cana/ of the epididymis — from .4-5 mm. in diameter — is lined throughout by a double layer of tall and slender columnar cells, the free ends of which bear groups of cilia of exceptional length that adhere and form pointed tufts surmounting the cells. A noteworthy feature of the wall of the canal is the layer of involuntary muscle, from .01 5-. 030 mm. in thickness, that encircles the membrana propria and, especially in the globus minor, almost entirely replaces the stroma Fio. 1660. „f ti,g mucous membrane. Exter- nally the muscle fades into the con- nective tissue holding toj; 'ler the convolutions of the canal. Vessels of the Testis and Epididymis. — The arteries sup- plying these organs are the sper- matic and the deferential, the former being distributed especially to the testis and the latter to the epi- didymis. An additional source is provided by anastomoses with the cremasteric artery. The spermatic artery (a. testicularls)— a slender branch from the abdominal aorta arising a short distance below the renal — is distinguished by its long course necessitated by the migra- tion of the sexual gland from the lumbar region into the scrotum. On reaching the posterior surface of the testicle, it divides into three or four branches that enter the medi- astinum and break up into super- ficial and deep twigs, which follow the tunica albuginea and the septa respectively and form the rich ca- pillary net-works surrounding the seminiferous tubules. One or more branches pass to the head of the epididymis and anastomose with the artery of the vas. The latter (a. defercntialis), from the inferior or superior vesical, accompanies the spermatic duct and supplies chiefly the body and tail o* vhe epididy- mis, by its connections with the spermatic artery establishing an anastomosis that may become of importance in maintaining the nutrition of the testicle. The veins, superficial and deep, emerge from the testis and, joining with thos^ from the globus major, form several stems of considerable size that ascend within the spermatic cord in front of the vas deferens, while those from the body and tail of the epididymis unite into a smaller (xjsterior group that accompany the canal (page i960). The lymphatics of the testicle, beginning in the walls of the tubules and the sur- rounding connective tissue, follow in general the coiirse of the veins as a superficial and a deep set, and emerge as a half-dozen or more relativelv large trunks to which the lymphatics of the epididymis are tributary. Within the spermatic cord they ac- comp.-iny the groups of veins, and finally empty into the lumbar lymph-nodes. The nerves of the testis and epididymis, chiefly sympathetic fibres destined for the walls of the blood-vessels, accompany the latter as the spermatic and the deferential plexuses that surround the corresponding arteries. Medullated fibres, probably conveying sensor)' impressions, occur among the inure usual pale ones. The relations between the terminations of the nerves and the tubules are uncertain, Letzerich and .Sclavunos describing intercellular filaments within the canals in addition VaF deferens Section across lower part of epididymis, THE APPENDAGES OF THE TESTICLE. 1949 Epididymis ApiwiKlix testis THE APPENDAGES OF THE TESTICLE. Under this heading are ...eluded --J^'ti"S^::,Se:^i;j.ed\: variable period, some throughout Ufe as mor^ "J^'^^^Z <" ly on account oC their the testis or to the epididymis J'^^'^X t nee they may become the seat of .teresting ^'''^trJicL cKgl-s Th^n «riS^^^ the appe.JJ.v I^X S Ta^^^^^t^'^: (3! the parajJyn^s, and (4) the .asa a^-r- ''"""^u o«n..ndix testis often called the totsta.'Jked or scssi/e hydatid, is a small form is irregular. Its free end often f.g.66.. presents a shallow, funnel-hke de- pression surrounded by a denuted margi.1, the whole suggest.ng the fimbriated end of the oviduct m minia- ture, a resemblance supported by the embryological significance o! the ap- pendage as the remains of the cranial end of the Miillerian duct (page ^o^8) overgrown and enclosed by connective tissue. In structure the appendage consists of a vascular con- nective-tissue stroma m which lies embedded a minute canal, of variable size and extent, lined with columnar epithelium. Usually the canal ends blindly, but in exceptional cases it may open on the free surface. Inconspicuous additional appen- dages of the rete testis have been described by Roth and by Poiner, which consist of blind tubules that extend from the testicle into the lower end of the globus major, either lying SSI^tScW "^ "SS^s on the fVee surface Thev probal.ly represent tSremarns oTw^lh ales that faile-' -. retain their connection with the canal of the f .^''iy^li^^^jy^"'' idid^^ or stalked hydatid, much less constant than the •i ??^noI cent ace -rdinsi to Toldt), apt^ars as a small pyriiorm »«dy ( .n.m n mnrin iL'gth ataXed to'tLe upper polT of the globus major < Fig- .650). '^"''■According to Toldt. an additional minute body (louy A':?''^:"'7'\^';'|S*ihe &'"'o'r":rrtly ^disconSd This tube is frequently the seat of cysts which,- SsKltUl section ot appendix testis. V as- I I950 HUMAN ANATOMY. when the canal retains its connection with the epididymis or testis, may contain spermatozoa. The paradidymis, or organ of Giraldis, consists of an irregular group of blind tubules (from 5-6 mm. in extent) that lie within the lower end of the spermatic cord, above but close to the globus major and always in front of the venous plexus. This organ {upper paradidymis of Toldt) is regarded as representing a partial per- sistence of the rudimentary tubules of the Wolffian body (page 1936) and is, there- fore, the homologue of the paroophoron. It is essentially a fcEtal structure, usually entirely disappearing after the first few years of childhood. The tubules (from . i-. 2 mm. in diameter and lined with ciliated epithelium) rarely give rise to cysts. The vasa aberrantia (ductuli abcrrantes) include tubular appendages — usually two, but sometimes only one — that extend for a variable distance within the epididymis and end blindly. The upper and shorter one is attached to the rete testis and pur- sues a downward course within the epididymis. The /ower and larger one, often ,^0 cm. (12 in. ) or more in length, passes upward from the lower part of the canal of the epididymis and consists of one or more convoluted tubes of considerable size. Both are to be regarded as probably originating from the Wolffian tubules. PRACTICAL CONSIDERATIONS: THE TESTICLES. Monorchism — the absence of one testicle (not to be confounded with cryptor- chism, vide infra) — has been shown at autopsies to occur occasionally. It is attended by no symptoms. Anarchism — the absence of both testicles — may be inferred when the scrotum is also absent or incompletely developed, and there is a rudimentary condition of the external genitalia ; impotence, sterility, and the physical and mental attributes of eunuchism appear later. Arrest of descent of one or both testicles (page 2040) may occur at any point between the lower border of the kidney and the bottom of the scrotum. The chief forms are: (a) Abdominal Retention (cryptorchism, unilateral or bilateral) : the testicle may be applied to the posterior abdominal wall in close relation to the lower, outer border of the kidney ; it may be provided with a long mesorchiiim, allowing it to move freely in the abdominal cavity, or it may lie in the iliac fossa close to the internal ring ; (^) Inguinal Retention : the testicle may be arrested at the internal ring, in the inguinal canal, or at the external ring. It is usually extremely mobile until subject to repeated attacks of inflammation and fixed by adhesion, (f) Cruro- Scrotal Retention : the testicle may pass through the external abdominal ring, but fail to descend completely, lying in close relation to the ring or at a varying distance bflow it. Of these, inguinal retention is the most common. Adhesions from prenatal peritonitis in a, small size of the external ring in i>. and undue shortness of the cord or of one of its constituents in c have been thought to explain some of these cases. Aberrant descent (ectopy), in which the testicle leaves its normal route, may occur in one of several forms, (a) \\\ peno-pubic ectopy the testicle is found beneath the skin of the abdomen al)ove the root of the penis, (b) In perineal ectopy the testicle is felt as a freely movable, ovoid turr:<^r, sensitive to pressure, lying on one side of the central raphe, and placed in front of the anus ; the cord can often be traced from the tumor to the external abdominal ring. The overlying skin some- times exhibits ruga», and the corresponding side of the scrotum is often atrophied. ic) Femoral ectopy appears as a movable tumor exhibiting the physical character- istics of the testicle and the peculiar sensitiveness. Its position is that of complete femoral hernia or of the inflammatory swellings which so commonly affect the glands overlying the saphenous opening. Of these, perineal ectopv is the usual form. Irregular de\'elopment of the gubernaculum may explain a and c, as certain of the fibres of the genito-inguinal ligament run to the pubic, lower inguinal, and inguino-femoral regions, and their over-development might draw the testicle in front of the pubes or into the femoral canal. Exceptional attachments (which have been shown to exist) of the guber- jiaculum below to the tuber ischii or sphincter ani may account for at least some of the cases included in b. PRACTICAL CONSIDERATIONS: THE TESTICLES. lysi In its bearing on the development and course of hernia and inrtammatit)n the relation of inisplacwl testicle to the peritoneal pt.uch, which accompana-s it, is of treat imporfcince. This pouch may remain oin-n. conmunicatniK freely with the gen- eral peritoneal cavity, thus enhancing the probability of the formation of hernia (.r of the extension of inflammation ; it may be closed above but oi>en below the testicle, favoring the development of hydrocele ; it may be obliterated. Kxceptionally. csi)e- ciallv when the testicle is retained but the vas has jxirtly or completely descended, the funicular process of the peritoneum may e.xtend as an open iM.uch to the lK)ttoni of the scrotum, thus allowing a hernia to pass far lieyond the position of the retained **^" Occasionally the testicle is found in the front of the scrotum (the epididymis anterior and the vas deferens in front of the other constituents of the cord ) as it it had made a semi-revolution on its vertical axis {inversion of the testicle ). 1 he pos- sibility of the existence of this anomaly emphasizes the propriety o deterimninK by palpation and by the test of translucency the position ot the twticle before tapping for hydrocele ; or, if these fail, of evacuating the fluid by incision instead of with a ^'"^""'■hrsion (axial rotation) of the testicle, including the sperniatic c'lrd,— also on its longitudinal axis,— is an accident which usually affects imperfectly descended tes- ticles but is not confined to them. The cause is probably a congenital malformation^ since as Owen has pointed out, a testis property placed m the scrotum and possessed of a normal mesorchium cannot be twisted. The twist may be in either direction,— to the right or to the left,— and in accordance with its extent and the degree of con- striction to which the vessels are subject the symptoms are slight or severe. In slight cases the epididymis alone becomes infiltrated. In severe cases the entire gland with the epididymis becomes gangrenous. .... i, t :,u,.r Orchitis— as distinguished from epididymo-orchitis— is rare as a result of eithir trauma or infection, owing to the firm support the gland receives fr.m the tunica allni- irinea and to the free movement of the testicle, not only within its serous tunic, but also within the .crotum, and, on the other hand, to the fact that septic organisms eaining access to the ejaculatory duct, or brought to the gland in the general circula- tion, are in either case arrested and given the opportunity to multiply in the neigh- borhood of the epididymis. . , • . • i . The intimate investment of the testicle by the tunica vaginalis, which is complete except at the point of entry and emergence of the vessels at its posterior border, but which leaves the whole hinder aspect of the epididymis without a serous covering, determines the frequency with which serous effusion (acute hydrocele) occurs in contusions or inflammations of the testicle proper as compared with those of the epi '^y^'^^-^^.j^^ ^^^^ investment of the former by the tunica albuginea accounts for the relatively greater pain and slower swelling in orchitis. It also brings about, when by ulceration a communication with the cutaneous surface has been established, the slow protrusion of the swollen and infected testicular substance, known as hernia tn fungus testis, analogous to hernia or fungus cerebri, the physical conditions--enclo- sure of peculiarly soft and yielding tissue within a dense and resisting membrane— being similar in the two instances. The sickening pain following contusion of the tes- ticle or often associated with orchitis, is due to pressure upon or irritation of testicu- lar nerves which, by way of the spermatic plexus, communicate with the aortic and solar sympathetic plexuses. A similar communication with the renal plexus explains the testicular pain and retraction accompanying the passage of a renal calculus 1 he primary development of the testicle in the vicinity of the tenth dorsal vertebra has determined its chief inner%'ation from the tenth dorsal segment of the cord (Head) and thus its relation to the posterior divisions of the lower dorsal and the lumbar nerves which causes the " backache" so commonly felt in orchitis, in the presence of a solid tumor of the testicle, or after injecting the sac of a hydrocele. The epididy- mis derives its nerve-supply chiefly from the pelvic plexus, which also supplies the vas deferens and the seminal vesicles. As it communicates with the spermatic plexus, the same symptoms may be associated with an epididymitis ; but as swdling is less resisted and pressure is therefore less, and as the communication with the great «952 HUMAN ANATOMY. abdominal plexuses is more indirect, ' ' testicular nausea' ' is less pronounced and is (if ten absent ^ididymo-orchitis is usually of infectious origin, the gonococcus and the bacillus tuberculosis being the micro-organisms most often found, although the inflammation may occur in the course of any infectious disease, as scarlatina, mumps, or typhoid fever. The direct channel offered by the vas deferens explains the localization of the gonorrhuL-al infection (page 1954); the division of the spermatic artery at the epidid- ymis, and the fact that the arteries of the epididymis are smaller and more tortuous than those of the vas or of the testicle, and the consequent slowing up of the blood- current (favoring bacterial growth), may account for the preference shown the epidid- ymis by the general infections. Syphilis more often affects the testicle itself because syphilitic orchitis is usually a late manifestation ; the disease at this stage shows its customary predilection for fibrous and connective-tis.sue structures, and, beginning, as it often does, as a cellular infiltration of the tunica albuginea, it follows the trabecule into the interior of the gland. When syphilis affects the testicle during the second- ary stage, it behaves like other infections and is, at least at first, Iodized in the epididymis. A certain numl)er of cases of epididymo-orchitis follow strain, there having been no known infectious cause and no direct trauma. They have the usual symp- toms, — apt to be slight at first, — and occur with much greater frequency on the left than on the right side. Two of various theories as to their production are inter- esting from the anatomical stand-point. («) Violent contraction of the cremaster muscle, which, by suddenly jerking the testicle against the pillars of the external ring, causes bruising of the gland-tissue and the epididymis. The cremaster is cer- tainly capable of vigorous contraction. Thus it is not rarely observed that direct trauma of the testicle is followed by marked retraction of the organ, so that it may Ih; drawn into the inguinal canal or even into the abilominal cavity. Even in severe pain, such as that which accompanies renal colic, the testicles are frequently found in close apposition to the external ring, while any one can observe the contraction of the cremaster by noticing the motion of one or both testicles during the passage of a catheter. Certain cases of chorea of the testicle are at times observed when this organ is moved by the cremaster with considerable rapidity and violence. (teni*l iliac- artery External il vein Deep epiicaMrie artery Spermatic vessels Internal abdominal ring Obliterated hypogastric artery Urachufl- Suspensory ligament uf peniS' Internal urethral orifice Fatty tissi containing veins Pectinate septum- Spongv- urethra- Navicular fossa ■Ureter, entering bladder .Ejaculatory duct 'rostfttic urethra anft utricle restate -Membranous ur .hra Bulb of cavernous body -Bulbous urethra Scrotum Dissection of sagittally cut (>elvis, showing; ret.ttions of organs after fixation by formalin infection. of larger and more uniform size (3 mm. ) .is it enters the sj)ermatic cord. Although the apparent entire length of the canal is about 30 cm. (12 in.), its actual extent is some 45 cm. C18 in.) on account of the tortuosity of its first part. Within the spermatic cord (pars funicularis), accompanied by the deferential artery and the postrrinr plexus of veins (Fig. i6S2\ the vas ncrnpies .i position behind the other constituents of the cord, and may be recognized by the hard, cord- like feel imparted by its thick fibro-muscular wall. The duct ascends almost verti- cally to the pubic spine, and on gaining the abdominal wall pas.ses through the external abdominal ring, traverses the inguinal canal, and completes its passage of the body- THE SPERMATIC DUCTS. 1955 ^*^-^J«S^^^* Net- work of rut rtil|{t-H •Mucoux coat .• L „„ ,Kr.,...,h the internal abdominal rin^- Alter emerging Irom the laiur wall by KotnK thjouRh he '"^'^^ » , ^^^^^ „^„ ^^,^ ,.^i„„ai and ix«tcr...r it parts comi^iny ^'J^ '^^^P^^^"*^ l'^^ obliquely the external iliac vessels and suriace of the *'«--*^l' .'^'>[f *"if S' "i™! From its entrance at the inter.wl ri..>- t I^^L'Sirtt'^XroJ/Jrue^-.n-li-'y b^-neath the ..ntoneum. through which it may usually be traced. ^ j ,■ ^^t xi^^ ^^^„^ the lateral , ••'"Tdl^Jt'StcWwa'^ nWhtly i-rd ^--^^'^ ^^^ ^^ f'"^- ^"'=^-'"« pelvic wall, directed nacKwaru a.. . ,P / .' ,^ ^^j^ic artery, the obturator nerve t. their inner or m^d^ms^yhe^^^^^^^^^^^ J^ .„ ^„ ^,^ and vessels, the vesical \^*?' ■*"" ,harulv downward and nward and traverses inner side of the ureter, the duct "["^. J;^ J^^^^^ ^* ^h the vicinity ol the seminal the subperitoneal "ri'^^iTTCter^uir luri^e if the bladder and the rectum. rirlTi; -"^^^^^^^^^^^ mm'^^tn'itsVJst ^idth. that p.^. in front and then along p^^ ,^5^ the median side of the seminal vesicle in its descent to the pros- tate gland. Thecott- tour of the ampulla is uneven and humpy, especially alter re- moval ol the invest- ing fibrous tissue, due to the sacculations and tortuosity ol the canal (Fig. 1666) and the short diverticula that pass off Irom the main duct at various angles, thus antici- patingin simpler lorm the arrangement seen in the seminal vesicle. Just before reach- ing the latter t! vas rrvt'dirfcre^'^l^cktard and outward (Fig. .469) and occupies the cresce"tic rec^^ vcJcal sacro-geniuil ) peritoneal fold. At the lower end of the ampu la the v as l<«,es ks Scutadons nd again becomes a narrow tv.tn. which, joining with the {.ass;ige m^the sLm"nal vesick. ...ntinued as the ejaculatory duct that traverses the sub- mce of r pros a"e gland and terminates in the urethra at the su e ol he pros- tik utricle. The ampullar ol the two sides converge as they descend, so that the r g«er ends are almost in contact where the spermatic duct .ecen^es th- seminal vesi- cle The intimacy of the relation between the vasa deferentia and the bladder Ses w th the condition of the latter organ. VVith the increased volume •ncuient to Tte dLtTntion. the posterior surface of the bladder is preyed against the spermaUc |£cte on th; otheVhand, when the bladder is empty, only the lower parts of these structures are in close relation with the vesical wall. . r ,i,„ strucmresae ^^^^^ ejacnlatorius). the terminal segment of the spermatL canal and apparently formed by the imion ol the duct of the correspondmg seS vesicle and the vas deferens, is really the morphological continuation ol the ,"™n;om which the seminal vesicle is developed a.s a secondary outgrowth. Be- Snn ng wTth a dia.neter of from 1.5-2 mm., the e aculatory 'l""^^"^':^,"^ »^1'*="^^ ginning *"" " ,p. .^. defining the ower limit of the middle lobe, and XrrcouS^Cr,8^ro'mm.^Lut H i^) in length, ends in the urethra by a £ute dlipTcaropening situated on the crest at the side of the orihce ol the prostatic "^^.^O^ CFWM-settion of ampulla of spermatic duct. Circular muscle -Longitudinal muscle 1956 HUMAN ANATOMY, Fihroiu coat Lumen ~^ Utricle (Fig. 1634J. In rare ca^t^ the ductn of the two sides may juin before reucli- in^r the urethra and communicate with the latter by a common aperture, ur they may o|M*n inde]K-ndently into the prostatic utricle. In the desicent of the duct the lumen of iut up|)er and middle thirds is modiheil by a series of four or live diverticula of de- crea.sint; size (Felix). At such levels the usual oblique oval outline of the canal is amplified by the irregular dilatations. Structure of the Spermatic Duct. — The tas deftrem is distinguished by the conspicuous thickness of its wall (from 1-1.5 mm. ) that encloses a relatively narrow lumen ( . 5-. 7 mm. ) and confers upon the canal its characteristic hard, cord-like feel. The wall consists c)f three coats, the mucous, muscular, and fibrous ( Fig. 1664). The mucous coat is clothed with Kic. 1664. epithelium which in the vi- cmity of the testicle and for an uncertain disUtnce lieyond resembles that lining the duct of the epididymis, consist- ing of an imperfect double layer of tall, columnar cili- ated cells. Throughout the greater part of the duct, how- ever, the cells are lower and without cilia and contain numerous particles of pijj- ment. The tunica propria possesses a dense felt-work of elastic fibres intermingled with bundlesof fibrous tissue. The robust muscular coat (from .8-1.2 mm. in thick- ness ) constitutes approxi- mately four-fifths of the en- tire wall, and consists of f>ale fibres arranged as an outer longitudinal, a middle circu- lar, and an inner longitudinal layer, the latter being less well developed than the outer and middle strata. The external fibrous coat that in\ ests the muscular tunic is thin and serves to connect the spermatic duct with the .surrounding structures. In its general structure the ampulla corresponds with the vas deferens, the walls of this part of the duct, however, possessing a much thinner mu.scular coat, in which "le inner longitudinal layer is wanting, and a mucosii modelled by numerous ridges and depressions (Fig. 1663) and covered with a single layer of low, columnar, non- ciliated epithelial cells. The ejaculaton' duct likewise possesses a structure es.sentially the same as in other parts of the spermatic canal. Its walls, however are thinner than those of the ampulla, this reduction lx"ing due to the diminished thickness and incompleteness of the muscular coat, which on nearing the urethra fjecomes attenuated and mingled with fibrous tissue. In some places the epithelium of the duct consists of a single and in others of a double laver of columnar cells until within a short distance from the termi- nation of the canal, Where it assumes the transitional character of the epithelium lining the prostatic urethra. Outst totiKitmlinal- muHclc Circular^ muitcle Inner lonKttiulinal' innsrlf Mucoiu mcmhranr rros»-!wrtton of v\% deferens. THE SEMINAL VESICLES. The seminal vesicles ( vesiculac seminales ) are two sacculated appendages of the \asa deferentia that lie behind the bladder and in front of the rectum. F"lattencd from t)cfore backward, their general shape is pyriform, with the larger ends, or bases, directed upward and outward, the long axes converging towards the mid-line as the . THK SEMINAL VESICLES. |'>.S7 Hadilrr, loiiKi- -lutlinal niu-Hlf Va* ilrfctiiis I'rHri - AmiiulU Seminal vnitlv Rjaculatury dui't Mcmbraiiouk uiclhra Cf>wpcr'» Klamli Ditarcllon ahowinc aemlnal duiia and vt-Mcl«, prortatc and Cowpir^ gland»; viewed Irom behiml. onrans taper, olten abruptly, at their lower ends to join the spermatic ducU. Liwally fri!in 4-5 cm. in length, sometimes much longer ami relatively slender and at others sh«)rt and broad, the seminal vesicles vary Kri:M\y in size and in the detail of arranut nient of their com|x>ncnt jwrts and not infrequently are markedly icsyminetrical. the right one bein^ often, but not in- variably, the lar^ r. Divested of the tibro-muscular tissue that invests the or^an as its capsu/e ani\ blends its divisions into a tuberculateti common mass, each vesicle may be resolved into a c^if/ duel and diverticula. The former —from IO-I2 cm. (4-5 in.) in length^^nds blindly after a more or less tortuous course, its terminal part often describing a sharp hook- like returninjj curve ( Fig. 1667). From the main canal an unti-rtain number (from four to eight or more ' ) of blind tubular diverticula branch at varying angles and in different directions and by their tortuosities add to the complexity of outline. The lumen of the chief duct, as seen in section, is irregu- lar, constrictions and dilatations foil Jwing one another with little regularity. The opening of the duct into the lateral wall of the vas , 1 u deferens is large in comparison with the terminal lumen of the ejaculatory duct, thus favoring the entrance of the secretions temporarily stored within the ampulla into the sacculated vesicle. The latter contains a fluid of light brownish color in which sjier- matozoa are nearly always found during the period of sexual activity. Relationa.— The seminal vesicles, together with the ampulla-, lie emlxKlded within a dense fibro-muscular layer, so that their position remains relatively lixeth the vesical and rectal wall, sur- rounded by numerous veins that continue the prostatic and vesi- cal plexuses. The lower half of the seminal vesicles and the ampulhe lie behind the fundus of the bladder, their axes ap- proximately corresponding with the sides of the vesical trigone and embracing the retrotireteric fossa, which part of the bladder- wall, when distended, m.ay pro- ject between and even displace laterally the seminal ducts and vesicles. In passing from the slightly expanded bladder onto the rectum, the peritoneum covers the upjXT fourth of the seminal vesicles and the adjoining part of the ampullae. I he ' Pallin : .Archiv f. Anat. u. Entwick., 190I. SeniitLiI vesicle Ejaculatorv ducts Cast ol anipulUe and seminal vesicles, shouitiK wind- ings and sacculations of lumen. (Paiim.\ i . 1958 HUMAN ANATOMY. bWb DiaKram showing course of msin canal in preceding preparalio a, ampulla; r. seminal vesicle; ^, ejaculatory duct, {rallm.) extent of this investment, however, varies with the depth of the recto-vesical pouch, which in turn dejjcnds upon the degree of distention of the Ixjunding organs, the bladder and the rectum. Structure. — In their general make-up the seminal vesicles closely resemble the ampulla, possessing a robust muscular wall composed oi an inner circular and an outer longitudinal layer of involun- FiG. 1 667. tary muscle. The mucous mem- brane is conspicuously modelled by numerous ridges and pits, so that the free surface appears honey-combed (Fig. 1668). The epithelial covering consists of a single or imperfect double layer of low columnar cells, many of which present changes indicating secretory activity. Although true glands are wanting within the seminal vesicles, the minute di- verticula within the epithelium containing goblet-cells may be re- garded as concerned in producing the peculiar fluid found within these sacs, which is of importance probably not only in diluting the secretion of the testicle and supplying a medium favorable for the motility of the spermatic fila- ments, but also in completing the volume of fluid necessary for efficient ejaculation (VValdeyer). Vessels of the Seminal Ducts and Vesicles. — The arteries supplying the spermatic duct are derived chiefly from the deferential, a vessel of small size but long ct)urse that arises either directly from the internal iliac or from its Fio. 1668 vesical branches. On reaching the duct, just above the ampulla, the artery divides into a smaller de- scending and a larger ascending division. The former, in conjunc- tion with accessory twigs from the middle hemorrhoidal and the in- ferior vesical arteries, generously provides for the ampulla, and the latter accompanies and supplies the vas deferens throughout its long course, finally, in the vicinity of the testicle, anastomosing with branches from the spermatic, — a communica- tion of importance for collateral cir- culation. The twigs passing to the spermatic duct enter its wall and break up into capillary net-works within the mu.scular and mucous layers. The rich arterial supply for the seminal vesicle includes anterior and upper and lower branches, con- tributed by the deferential, the in ferior vesical, :>.ik1 the superior and middle hemorrhoidal ,\rteries. The minute (listribulion is effected by capillary net-works to the muscular ind mucous coats. The I'-'iiii fii.-.i iullow the spermatic duct as the deferential plexus^ and within the spermatic cord -ommunicate with the pampiniform plexus, increase in size and Muscular coat Pits nf ma- cous coat Cross-section of seminal \esic1e. showing modelling of mucous surface. X l6. Partition st| jratiiiK adjacfiil diverticula Epithelium PRACTICAL CONSIDERi*r!(>NS : SEM'NAL VESICLES. i959 number as they approach the bladder and seminal vesicle ; in the vicinity of the latter thev communicate with the seminal plexui and empty with the trunks ot the posterior bladder-wall into the vesico-prostatic plexus. The posterior and lateral surfaces ol the seminal vesicle are covered with a net-work of large veins (plexus vcnosus scmi- aalis) that become tributary to the vesico-prostatic plexus. The lymthalks of the seminal ducts anil vesicles are numerous and arranKed as deeper and superficial sets which form afferent trunks that pass to the internal iliac lymph-nodes. Those from the lower part F«o. 1669. of the seminal vesi- cles join the vesical lymphatics. The nerves sup- plying the spermatic duct are derived from the hypog;i.stric plexus of the sympa- thetic and consist chiefly of pale fibres destined for Lhe in- voluntary muscle, some medullated fibres, however, be- ing present. They accompany the greater part of the duct as the deferen- tial plexus and have been traced into the muscular tissue and the mucosa. Within ., , . c- 1 1 i the former they form the Atrnx plexus myospermatiais described by Sclavunos, anti are fairly plentiful within the mucous coat (Timofeew ')• The nervi>8 distributetl to the seminal vesicles are very numerous and are derived in part directly from the hypogastric plexus (Fraenkel'), or through prolongations of the latter as secondary plexuses that follow the vesical and middle hemorrhoidal arteries. ■Mucous cuflt ■Fibrous coat Portion of wall ol seminal vesicle in lonRitudinal section, showtiiK piUiiiK t>* mucous coal. X 45- PRACTICAL CONSIDERATIONS. THE SEMINAL VESICLES. The seminal vesicles are rarely injured. The two forms of infection that are most common are the gonorrhccal and the tuberculous, although vesiculitis vcas h^ due to the ordinary staphylococci or to the colon bacillus. The channels of infection are comparable to those which convey disease to the epididymis: the ejaculatory ducts are continuous with the vas deferens and the vesicular duct, and the inferior vesical and middle hemorrhoidal arteries replace the spermatic artery. The tuber- culous disease is, however, usually secondary to similar infection of the prostate or of the epididymis. ... /^n .u The anatomical relations of the vesicles to (a) the vesical trigonum, (*) the prostate and prostatic urethra, and (c) the rectum sufficiently explain the usual symptoms of acute vesiculitis : (n) frequent, painful, straining urination, hypogastric pain • (*) priapism, painful emissions of blood-stained semen, occasionally epididy- mitis as a complication ; (f) painful defecation, rectal tenesmus, perineal and anal Rectal exploration (page 1692) will usually establish the diagnosis, as it will n tuberculous vesiculitis, in which condition, as in other forms— acute and chronic— of vesiculitis, there are apt to be pains referred to the loins, the hypogastrium, the ' Anatom. Anzeiger, Bd. ix., 1894. ' Anatom. Anzeieer. Bd. ix., 1894- • Zeitsch. f. Morph. u. Anthrop., Bd. v., 1903. i960 HUMAN ANATOMY. anus and perineum, the hip-joint and sacro-iliac articulation of the affected side and the other side of the thigh, due to the association of the vesical, prostate, and pelvic plexuses with the lumbar and sacral nerves and their plexuses. Vesiculitis may be a very serious condition, as it may result in abscess with per- foration into the bladder within the limits of the peritoneal covering, or directly into the peritoneal cavity by way of the recto-vesical cul-de-sac. Cases of both these acci- dents have been reported. Pyamia has also been known to follow a septic phlebitis of the adjacent venous plexuses; pelvic cellulitis with diffuse suppuration has resulted ; and various troublesome abscesses burrowing between the bladder and rectum, and leaving fistulous tracts very slow to heal, have had their origin in suppurative vesicu- litis. The chronic form may be associated with persistent vesical irritability, with some pain on emission of semen, with sexual excitability accompanied by premature ejacu- lation, and with persistent urethral discharge often mistaken for an ordinary gleet. In chronic cases " massage" through the rectum has been advised and practised with some benefit in comparatively rare cases. The contents of the vesicles can sometimes be pressed through the ejaculatory ducts into the prostatic urethra and so evacuated. A similar expression of the normal secretion of the vesicles by fecal masses at stool is a fertile source of sexual hypochondriasis in young male neuras- thenics, who, in consequence, imagine that they are afflicted with ' ' spermatorrhoea. ' * Fio. THE SPERMATIC CORD. In consequence of its migration from the abdominal cavity into the scrotal sac, the testicle is followed by its duct, vessels, and nerves through the abdominal wall into the scrotum. These structures, held together by connective tissue anil invested by certain coverings acquired in their descent, form a cylindrical mass, known as the spermatic cord (fuaicnlns spennaticus), that extends from the internal abdominal ring obliquely along the inguinal canal, emerging at the external ring, and thence descends vertically, beneath the integument, into the scrotum to end at the posterior border of the testicle. Most constant within the inguinal canal, where its diameter is about 15 mm. Cfi in.), the thickness and length of the spermatic cord vary with the con- traction of the cremasteric muscular fibres that ' *70' control the position of the testicle. Poncrior veins The Constituents of the spermatic cord are numerous and fall under four groups. f__^. -^JKT ' • The vas deferens with its accompanying jKgJ^^^^v, deferential artery and plexuses of veins, lym- ._ '?'JRB!faicik^>. phatics, and nerves. The vas, surrounded by Its artery and a venous plexus, occupies the posterior part of the spermatic cord, and is readily distinguished as a hard, round cord, from 2-3 mm. in diameter, by virtue of its unusually firm walls. 2. The spermatic artery, veins, lymphatics, and nerves belonging to the testicle projjer. In contrast to the artery, the veins are particu- larly large and numerous and form the conspicuous pampiniform plexus which con- tributes in no small measure to the bulk of the cord. 3. The coverings with their blood-vessels and nerves. The coverings proper of the spermatic cord, contributed by the layers of the abdominal wall, correspond to those of the testicle, with the exception of the serous coat, which is wanting after closure of the processus vaginalis. From within outward they are : (a ) the infundib- uliform fascia (tunica vasinalis cnmmunis), a distinct layer continued from the trans- versalis fascia ; (b) the cremasteric fascia, consisting of the muscular fibres prolonged from the internal oblique and transversalis, blended together by connective tissue. The muscular fibres descend as loops along the spermatic cord, especially on the posterior surface as far as the testicle, over the coverings of which they spread out in festoons and net-works ; and (r) the intercolumnar fascia, a delicate sheet derived from the aponeurosis of the external oblique at the margin of the external alxiominal Veins of painpitij- form plexus ■S[)ennatic arter> Tunica vat^inalis C'lmmums trema-steric fascia Section across left spermatic conl hardcneH in formatin, showiuK |K>sitiuti of vas deferens. M THE SCROTUM. 196 1 ring, is most distinct above, becoming thinner as it descends, until over the testicle it loses its identity as a distinct investment. ^ ,., , , c u: «„ »u„ The coverings of the spermatic cord receive their blood-supply from chieHy the cremasteric branch of the deep epigastric artery ; additional cremasteric tuigs from the spermatic artery are distributed to the upper part of the cord, anastomosing with those from the first-named source. The ner^'es include the genital branch of the genito-crural and usually a twig along the front of the cord from the terminal branch of the ilio-inguinal. . , , • r »u „„,., 4 The rudimentary structures, the remains of the processus vaginalis, the para- didymis, and sometimes the vas aberrans. After closure of the communication between the serous pouch and the peritoneal cavity, the processus vaginalis is represented by a delicate fibrous band (ligamentuni vaginale) that may be traced, under favorable con- ditions from the internal abdominal ring above through the spermatic cord as tar .a the upper margin of the tunica vaginalis below. The paradidymis (page 1950) lies within the lower end of the spermatic cord, immediately above the epididymis, or behind its upper pole, and in front of the venous ple.xus. Occasionally, when unusu- ally developed, the vas aberrans (page 1950) may also extend into the lower end of * *P* ■ ■■ • ' • ' >rings proper, the spermatic cord is enveloped > -p laver of the superficial fascia. The deep tinuous above with thefascia on the abdomen with CoUes's fascia in the perineum. 'e, In addition to the foregoi by the skin, the superficial an layer of the latter is important, and below, after investing the tesi PRACTICAL CONSIDERATIONS: THE SPERMATIC CORD. The most frequent pathological condition associated with the cord (and not else- where described) is varicocele, an enlargement— with dilatation and lengthening— of the veins of the cord, occurring most frequently in young unmarried adults (fifteenth to twenty-fifth year) and on the left side (90 per cent, of cases). The veins composing the spermatic plexus can be ranged in three groups, the most anterior of which has in its midst the spermatic artery, the middle the vas def- erens and the posterior is compos-ed of those veins which pass upward from tlie tail of the epididymis. The anterior group is the one first affected, or. if the dilatation affects all the veins, is most extensively involved. It is thought that varicocele often depends upon a congenital predisposition but many anatomical reasons have been given to account («) for its occurrence and (b) for its greater frequency on the left side, (a) i. The relative length and the vertical course of the veins. 2. The lax tissue surrounding them so that (as with the long saphenous vein) they derive littie support and their blood-current receives no aid from the presence or contraction of surrounding muscles. 3. Their large size as compared with the corresponding artery, so that the vis a tergo mu.st be reduced to a minimum (Treves). 4. Their tortuosity, frequent anastomosis, and few anrt imper- fect valves 5. The pressure exerted upon them as they pass through the inguinal canal not altogether unlike that experienced by the hemorrhoidal veins m their passage through the walls of the rectum, (b) i. The veins in the left cord arc much larger than those in the right. 2. The left tey'-'cle hangs lower than the right, so that the column of blood in the left veins is longer. 3- The left spermatic vein empties into the left renal vein at a right angle, whereas the right spermatic vein empties into the vena cava at an acute angle. 4- The left spermatic vein running behind the sigmoid flexure of the colon is constantly subjected to pressure from accumulation of fitces in the liowel. , . ... , ^, In the operation for varicocele by excision of the pampiniform plexus the sper- matic artery is often included, but gangrene of the testicle does not follow because of the escape of the deferential arter>' and of its free anastomosis with the spermatic and scrotal vessels. THE SCROTUM. The scrotum, the more or less pendulous sac of integument that contains the testicles and the associated structures and the lower part of the spcrmatie cords, is attached to the under surface of the penis in front and to the perineum behind, b lat- • If 1963 HUMAN ANATOMY. tened in front above, where atUched to the penis and receiving the spermatic cords, its general form is pear-shaped and somewhat asymmetrical, since the left of the two oval swellings produced by the enclosed testicles and separated by a shallow longi- tudinal furrow is lower than the right owing to the position of the corresponding sexual gland. The scrotum vari' ,, however, in form and appearance, even in the s;»me individual, with the condition of the subcutaneous muscular tissue. When the latter is contracted, as after the influence of cold, the scrotum is drawn up and com- pact and its surface corrugated by numerous transversely cur\ed folds ; when relaxed, it becomes smooth, flaccid, and penduloiw. Indications of its formation from two distinct parts are seen externally in the longitudinal raphe, which marks the line of fusion of the original halves and extends longitudinally from the urethral surface of the penis over the scrotum onto the peri- FiG. 1671. Ape recounted as a dis- tinct layer, but so closely att;iched to the integument as to lonu practical y a part of t At Ihe raphe, while ime fibres follow the skin and remain superhcial. the majority enter the septum, being especially well vlevelo,K.-d in the lower part, and at the attached up4r border pals over into the dartos of the penis and the perineum. The numerous bundles of elastic tissue within the tunica dartos. m the upper am anterior ,wrt of he scrotum become condensed into robust bands which efhciently aid m supp..rtin« e scrotal sac since they are continued laterally at the sides of the penis and over the spLrmauTcords into the superficial fascia of the abdomen, and m the mid-iine blend w^h the suspensory ligament of the penis. Those on the posterior surface are attached over the pubic and ischial rami. . _t i Enumerated from without inward, the layers interposed iK^tween the suriace of the scrotum and the serous cavity surrounding the tc^stis are : ( i ) the skm 2 ) the modified superficial fascia or tunica dartos, ( 7, ) the intercolumnar fasca, ( 4 • the crc^ masteric fascii (5)" the infundibuliform fascia, and (6) x\.^ tumcava^.nahs. Of Tesf he first two alone," strictly considered, are contributed by the scrotum the remaining layers being derived from the deeper structures o the abdominal wall and associated wfth the descent of the testicle. The connection b^^w- V'^'i' 'd bv\ Wse and the underlying intercolumnar fascia is by no means firm, being eflected b\ a loose kyer of areolar tissue, devoid of fat. that penni^ a ready separation. Part'ci'larly m front, between the external scrotiil envelope and the coyerings proper of the teMis. Beneath the posterior surface of the scrotum the connection is firmer ( Disse ). I his fep^ation. h^ever. is arrested at the lower part of the scrotum owm,^ \° l''U?Tower of the scrotal liga,ne,it (Fig. 1723). a mass of fibrous tissue that anchors the lower end of the tunica vaginalis and the testicle to the external envelopes. With the exception of the serous coat, the tunica vaginalis, these con erings have been considered in connection with the spermatic cord (page i960) : it remains, there- foTe to describe more fullv the serous coat to which incidental reference has been made rpa^'e 1041) i" its relations to the testis and the epididymis. ^ . „ , , ^ The production of an isolated, closed serous sac within each half of the scro urn results from partial obliteration of the serous pouch, the processus vaginalis, that during foetal life extends from the general peritoneal cavity into the scrotum in an- ticipation of the descent of the sexual gland. _ The tunica vaginalis (tunica vaRinalis propria testis), m correspondence with other serous membranes, consists of a parietal and a visceral portion, the latter pro, V ding an extensive but incomplete investment for the testis and the ep-d'c >"";• a"d the former lining the serous cavity into which these organs thus covered, project. With the exception of small spacer caused by the elevation of the epididymis, espe-- ciaSy of the globus major, these two layers are practically in contact and separa ed by only a capUlary cleft. Whatever space exists is filled by a clear straw-colored '^''''TiSition to walling the c v ity. the parietal layerjny^t^ the spermatic cord for abou 12 mm. above the testicle and the blood-vessels behind, and then '^ continued fnto the visceral layer along the line of reflection th;it passes over he back of the tSs to i^'ower pole on the one side and along the posterior surface of the epi- didymis on the other, thus leaving an intervening uncovered strip as a passage-way for the duct, vessels, and nerves. . .u . .: . From the line of reflection the thin visceral layer completely invests the testis and the epididymis, adhering intimately with the tunica albuginea, a"<\dipping deeply between these organs to form the digital fossa ( sinus epididymidis) This Set (F g 1650), the entrance to which is narrowed by two transverse folds (liga- S^ntoepidiS-nidis superior rt inferior), may be so deep that the serous membrane at its bottom i/ in contact with that reflected from the median side of the e.ticle. Nu- merous bundles of involuntary muscle-the m. cremaster aUernus oi "^'"^'^-•^d'ate h^om theTrotal ligament at the lower part of the scrotum to spread out between the |,- 1964 HUMAN ANATOMY. parietal layer of the tunica vaginalis and the infundibuliform fascia, extending upward into the spermatic cord. Vessels. — The arteries supplying the scrotum, — ^as distinguished from those des- tined for the sf>ermatic cord and the sexual gland and associated structures, — although of small size, are derived from different sources. Those distributed to the front and sides are the anterior scrotal branches from the deep external pudics, supplemented above by twigs from the superficial external pudirs. The back of the scrotum and the septum are supplied by the posterior scrotal arteries, superficial branches from the internal pudics. Free communication exists not only between the vessels of the two sides across the mid-line, but also between the anterior and posterior branches at the sides. The scrotal arteries anastomose with twigs from the obturator and internal circumflex, as well as with those from the cremasteric artery. The veins, numerous and plexiform in arrangement, form tnmks that follow the general course of the chief arteries, becoming tributary to the external saphenous or the femoral and the internal pudic veins. They anastomose freely with the adjoining venous paths of the penis, jierineum, and pubic region. Fio. 1672. Vdn Vas deferens St)ermatir %-eins 'rmatic arteries Blood-vesflels -^ -^ififflBmWM ^'n '^ I S^S^ — MediaMiiiuni te>tift ♦.—- ^j — Visceral tiiiiira vaKitialis Parietal tunica vKxinalis Ltibules of left testis Sac of tunica vaginalis Tunica vaijinalis'^ , '" y"- Cremasteric fasciu | Skin and dartos t Septum of scrotum Obliquely cut vas deferens Section across formalin-hardened scrotum, sliowinir lower end of spermatic cords and testes in section. The lymphatics of the scrotum are very numerous and form a superior and an inferior group of vessels, all of which lead to the median group of superficial inguinal lymph-nodes. Frequent communications occur with those of the penis and perineum, but only sparingly with the deep lymph-tracts within the spermatic cords. The nerves supplying the scrotum are derived from both the lumbar and sacral plexuses. Those from the foiner source are distributed to the front and sides of the scrotum and include cutaneous twigs from the genital branch of the genito-crural nerve, usually reinforced by twigs from the ilio-inguinal that end in the integument in the vicinity of the root of the scrotum. Those from the sacral plexus supply the posterior surface of the scrotum and are from the perineal or inferior pudendal branches of the small sciatic nerves and the anterior or external superficial perineal branches of the pudic nerves. Sympathetic fibres accompany the cutaneous ner\-es for the dartos muscle. PRACTICAL CONSIDERATIONS: THE SCROTUM. The .scrotum, from a practical stand-point, may be studied as if composed of two layers, an external, made up of the skin and dartos, and an internal, consisting of the three coverings — fascial, muscular, and afmneurotic — derived from the abdomi- nal wall, the infundibuliform, cremasteric, and intercolumnar. As the testes are safer from injury in a loose pouch, in which they can readily glide away from threatened trauma, the scrotum is redundant (more so on the left THE PENIS. "965 side on account of the greater length of the left spenvaiic cord ) and lax. Advantage of these facts is taken in certain operative priKedure.,, as in making the rtajw in Roux s operation for vesical exstrophy, or excising a ptjrtion of the scrotum ( to secure (inner support for the vascular structures of the cord ) in varicocele. , , , , The redundancy, thinness, and elasticity of the skin and the laxity of the falles.s areolar tissue connecting the internal and external layers combine to favor : ( <« ) marked discoloration and great extravasation of bUxKl in cases of hemorrhage from the ves-sels lietween the two layers ; hence in orchitis leeches are applied, not over the scrotum, but in the line of the cord in the groin ; (d) extreme distention, as in large scrota hernia in hydrocele, in bulky testicular tumors; (c) extensive o-dema 111 general anasarca as a result of pelvic venous thrombosis, or accomiwnying an infectious cellu- litis or an extravasation of urine, which, when it proceeds from a s. bodv. distal part; /■:. boily proxmal part, rc^orpus lawr- no.um; rifcorpi. suonxioSum ; rffl. dorsal artery ;rfrf... deep dorsal vein ; '• fi^.^';"*. '■";^f "Pf, ,'' : ""^'^ tissue o( i{Uns;/,frenum;//. fibrous tissue; j, fibrous septum; n/v, auperficial donal vem; i/, super- ficial faacia ; st, skin ; la, tunica albuginea ; n, urethra. spongiosum. Farther forward, in the vicinity of the penile angle, the corixsra caver- nosa press against each other with their median surfaces, the opposed flattened cap- sules blending to form a median partition (septum penis). Lower the latter becomes imperfect and replaced by a series of vertical bands, and hence is often designated the pediniform septum, the intervening slit-like apertures permitting commu nication between the blood-spaces of the two cavernous bodies as well ;is the passage of anastomotic branches of their arteries, 'n certain mammals, especially the rnivora and some marsupials, a bone (os penis) is de- veloped within the fibrous septum. On approaching the corona, the cor- pora cavernosa again become discrete and rapidly taper to blunt-pointi d ends that are separated externally by a slight furrow and cappeU by the over- lying glaas. The dorsal and under surfaces common to the closely ap- plied cavernous bodies are marked by longitudinal grooves ; that along the former surface lodges ihe dorsal ves- sels of the penis, while the under fur- row is filled by the spongy body. The corpus spongiosum (cor- pus cavernosum urethrat: ), the third and much smaller, although longer (alx)ut Fig. 1675. Dorsal vein, now .iouble Pubic bor Crus Deep artery ii corpus cavenntsum r ret bra' lscbi» wave! nosus muscle Bulh Bulbo.ravemos US- muscle Colles's fascia Frontal section throunh pubic arch and root ot penis. l^ cm. or b% in.), cylinder of erectile tis.sue, occupies the groove along the under surface of the cavernous bodies. The two ends of this cylinder are enlarged, the 1968 HUMAN ANATOMY. upper expanding into a pyriform mass of erectile tissue, the urethral bulb ( bulbvH nrethrae), and the lower broadening into a conical cap of erectile tissue that covers the ends of the corpora cavernosa and contributes the bulk of the glans. With the exception of the bulb, the major jwrt of which lies behind the canal, the coq)us spon- giosum is traversetl by the urethra, the cavernous tissue completely surrounding the urinary tube. The bulb, attached by its upper surface to the inferior layer of the triangular ligament and covered below by the bulbo-Givemosus muscle, presents a slight median furrow (sulcus bnibi) that suggests a division into the so-called hemi- spheres. Internally an imperfect median septum bulbi partially subdivides the erectile tissue below and behind. The glans penis consists almost entirely of erectile tissue (corpus cavernosum glandis) directly continuous with that of the ; -^ body. Its upper surface is holli>wed out to receive the pointed extreni'tie the corpora cavernosa, so that a section across the upper part of the glans shows the erectile tissue of the cavernous bodies surrounded by an overhanging crescent of the cavernous tissue of the glans (Fig. 1674, C). Along the frenum the fibrous envelope of the glans is prolonged inward towards the urethra as a fibro-elastic band ( ligamentnm medianum glandis) which, in conjunction with a similar band connecting the ends of the cavernous bodies with the upper urethral wall, forms a median partition, the septum glandis, that in- completely divides the erectile Fig. 1676. Krertilf tiiwue nf corpus Turi'i'a albuKUica cavi-nMnutn broken u]> Prepuce by ptxtttltfomi septum l-^rectile tissue of Klans' Anterior I'Xtremityol corpus lav- eriiosum External urethral orifice Navicular lossa' Frenum Erectile I'relhni tisHUe of corpus sjKiitKiosum Mesial lonKittidinal section of end of penis. tissue of the glans and sur- rounds the terminal part of the urethra. The penile portion of the urethra is descnbed with the other parts of the urinary tract in the male (page 1923). Beneath the skin and sub- cutaneous tissue the cylinders of erectile tissue, enclosed and united by their albuginea, are enveloped by the superficial fascia (Fig. 1674, E). The latter, directly continuous with that of the perineum (Colics' fascia ) behind and of the ab- domen (Scarpji's fascia) above, invests the penis as far as the neck, where it becomes blended with the prepuce. This fibro-elastic sheath is often called the faseia penis. In addition to the attachment of the crura of the corpora cavernosa to the peri- osteum of the pubic arch and of the bulb of the spongy body to the triangular liga- ment, the penis is supported by fibrous bands that extend from the abdominal wall and pubes to the dorsum penis. This triangular sheet, the suspensory ligament, in- cludes a superficial and a deeper portion. The former ( ligamentum fundiforme penis) begins at the linea alba, from 4-5 cm. ( i J4-2 in. ) above the symphysis, and consists of elastic bundles prolonged from the deep layer of the superficial fascia downward to the dorsum of the penis (Fig. 1671) at the so-called angle, where it divides into two arms that embrace the penis and, after uniting on the urethral surface, are continued into the septum scroti. The deeper portion ( liKameatum suspensorium penis) contains compact fibrous bands that (mss from the symphysis to the corjxira cavernosa, just in advance of their separation into the diverging crura, to blend with the dense albuginea. Structure. — Each of the component cylinders of erectile tissue is enclosed in a robust sheath, the tunica albuginea, composed of dense white fibrous tissue, inter- mingled with relatively few elastic fibres and no muscle. The sheath surrounding the corpora cavernosa, which in places attains a thickness of 2 mm. and is much stronger than that enclosing the ^^pongy body, is imperfect along the opposed median surfaces of the two cylinders, where it forms the pectiniform septum. From the inner surface of the tunica albuginea septa and trabecule are given off which constitute the framework supporting the vessels and nerves and enclosing the characteristic blood-spaces of the erectile tissue. Numerous bundles of involuntary THE I'ENIS. 1969 Fio. 1677, Deep domi vein Snhcutanrou* tiMUe Skin- Septum^ ■M Tunica ilbiixinc* :mS'' l.M\'XiS\ UCorpu* 1 cKverfKMum muscle, rircularly, lonRitudinally, and obliquely disposed, occupy the connective-tiMue trabecula- and plates se|>aratin>{ the venous lacuna-, arounenis give of! short, tortuous branchw {arterie helicinte), about a mm. in length, that project into the blongy body. The corpora cavernosa are supplied chiefly by the deep arteries of the penis, supplemented by twigs from the dorsal arteries that pierce the albu- Fio. 1678. _ . . Ceiilral bluod-spactra Inner perlpbenil ipaces Outrr prriphcral Bpacc* gmea. Entering the cavern- ous bodies about where the crura unite, the deep arteries of the penis traverse the cyl- inders somewhat eccentri- cally, to the median side of their axes. Communication between the vessels of the two bodies is established by anastomotic twigs that i)ass through the apertures in the median septum, as well as by the terminal loop. The dorsal arterii>. the longest branches of the internal pudics. pass along the dor- sum between the fascia and the albuginea, in company with the dorsal nerves and vein, and, in addition to the twigs distributed to the cov- erings, the cavernous Ixidies, and the corpus sjwngiosum, supply the erectile tissue of the glans. The anastomoses between the various vessels supplying the penis are very free, not only between the corresponding and other branches of the two sides, but also between those of the superficial and deep sets. The jeins of the penis, like the arteries, constitute a superficial and a deep group which freely communicate and carry off the blood from the < iv .lopes and from the erectile tissue respectively. The superficial veins for the most p.in .ire tributary to a subcutaneous trunk f v. dorsalis penis superficialls ) that passes upward along the dorsum beneath the skin to the pubes and terminates either by dividiiitr i"t<. I. ranches that empty into the internal saphenous or the femoral veins on litlicr side or by joining the deep dorsiil vein ; both modes of ending, however, may exist. .A number of vessels from the integument covering the posterior part of the urethral surface are collected by the anterior scn^tal veins. The deep vein^, which begin by tributaries from the erectile ssue that they drain, to a large extent discharge their contents into the deep dorsal vein (v. dorsalis penis profunda ) that lies beneath the fascia and occupies the groove on the dorsum as far as the suspensory ligament, between the superficial and deep parts of which it Trabecular Bundles ot muscle Denite fibrous ttiisue r tunica albUKtiiea Transverse section throuKh peripher>' of corpus cavernosum. X 50. . THE iKNIS. 19" < fr passes. C.mtinuinK betwtt-n the subpubic a.,.t tr.insverse liKamonts and nierc »,« he XxuH IWinninK aU.ve the corona by tho union of two stems that collet brunches from the ulans and the prepuce, the rtant tributaric-s of the mternal ,..k1.c ve ns St acco,^p.my th.- corrc-spondin^ arteric-s. The corpus s,K.n«..«um .s 'Ir-u^-^^l'V anterior brinchc-s that conXy the bUnxl to the dorsal ven. by jonunR tj- ' '^>^' "f-'' or other veins from the corp.racavern.««. ami by ,K«.tenor stems (»v. ufithrales) hat pass upward and backward' and empty i«rtly into the prcmtat.c plexus and partly no The intS pudic veins, the veins from' the urethral bulbhavm^ a sm.Uar destuwt.o. . Numerous aLtomoses betwcH..n the cutaneous veins and those from the erect.le tissue establish free communication l)etween the suiK-rticial and deep vessels. The /v,nphalus are numerous and dispos-xl .ns su,>erfic.al p.v- -U.-p vessels The former are tnbutary chiefly to a su,>erficial dors;il stem that »c.on,.>an.es the t r- T^'Jnl x"in and begins by the'confluence of pkxiform K n ; . aUcs w.thm the SuS of the prepuce and frenum. Duriujj its course the dor*il trunk recevc-s ynSics from thL adjacent territory as well as others '^'^'he under surhice that K^ the dorsum bv following the circumflex veins around the ber lymph.-itics are StkuSy numerous in the periphery ..f the glans. .around the meatus commum- Sg Sh the urethral and preputial plexuses. Trunks are formed which occupy the retroglandular sulcus and unite into a deep dorsal lymph-stem, sometime^ double, that accompanies the corresponding vein beneath the fascia and terminatc>s. when sinirle in the median inguinal nodes of the left side (Marchant). The nerves of the penis include both spinal and sym,>athetic fibres the former from the ilio-inguinal and the pudic nerxes. and the latter 'f^l" j'^^. ''>'P*'«''''\"^ plexus The integument around the r.wt of the penis is supplied by the cuUmet, us Ranches of the ilio' inguinal and the inferior P^^enclal nerves while that .J h^ l,ody and the prepuce is provided with the cutaneous branches of the dorsal nerves. I he cv nderTof' cavernLs tis.sue also receive twigs from the pud.c -rv-. the bulba branches of which pass to the bulbus urethra- an.l in addition supply th^" •" ''""^ membrane of the urethra. Kach corpus cavem.jsum rece.vc-s a deep 'l™";;'; '";^™ dorsal nerve which is given off as the latter lies between the layers of the triangular Hgament. The sympathetic fibres destined for the blcKH^-^ essels and muscle o the erecdle tissue are continued from the hypogastric plexus through the pn^tat.c plexus U> the plexus c-ivernosus, where, joining the don«.l ner%es of the penis twigs ( ncr^i «vern-i ^nis minores) are sent to the posterior part and the crur:. f f^'" corp-.ra cavernosa'^while others (nervi cavernosi penis majores) are d.stnbv.te bod> C net-works of n.,n-m«lullated fibres have been traced withm the bundles o.inoN untarv muscle of the blo.Kl-ves.sels and tralKCul.T of the erectile tissue. Certain cerebro-spinal fibres (nervi eri«entes) suppos.-d to Ix. especially "'""^^'J,;".,^^!.' "" are conveyed, in company with the sym,«itlKt.c fibres, along the paths of the cavernous ^^^""in addition t.-. n gcnermw ^-.i .-nlv of the more nsnal nerve-terminati. ns th-- skin of the glans and the prepuce is provided with special nerve-endings, the tactile ^L a the genital corpuscles o{ Krause (p... .0.7 'y"!.: -thm th. ^-e and the Pacinian corpuscles within the -'• •'--' n^tur The paths of >ens,.ry impressions lie within the dorsal . 1972 HUMAN ANATOMY. VuiatioiM.— Apart from the unimportant individual differences due to age, growth, and sexual activity, the variations of the penis are for the most part referable to imperfect develop- ment and are reccwnized as malformations rather than as anatomical deviations. The explana- tion of many of these conditions is cupplied by the developmental history of the structures mvulved (p^ 2044) ■ PRACTICAL CO> ^DERATIONS : THE PENIS. The size of the penis bears less constant relation to general physical develop- ment than does any other organ of the body. The normal average size of the flaccid penis of the adult is about three inches in circumference and from three and a half to four inches in length, measured from the suspensory ligament. When erect, this length increases to about six and a half inches and the circumference to three and a half or more. Absence of the penis may occur, but is rare unassociated with other anomalies. Apparent absence (concealed penis) may be due to the subcutaneous situation of an atrophic or undeveloped organ which may be palpated through the skin and revealed by an incision. Micropenis (infantile penis) is not uncommon, and varies in degree from a mere failure to attain quite the average size (annoying chiefly to sexual neurasthenics) to a retention throughout life of the dimensions and development normal in early childhood or infancy. Occasionally in such cases, after puberty and following physiological activity of the organ, rapid growth takes place and conditions approximating normal- ity may result. Afegalopenis. — As has already been observed, the size of the organ bears no constant relation to the size or strength of the individual. In congenital imbeciles it is often of unusual size, and in dwarfs and hunchbacks it is not uncommonly devel- oped, not only out of proportion to the other parts of the organism, but beyond even the average for individuals of normal growth. Hypertrophy of the penis is at times an inconvenience, and may even be a source of danger, since an excessive develop- ment predisposes to abrasions and fissures through which inoculation with venereal disea.ses may occur. Double penis has been recorded in a few instances, in at least two of which each organ was functionally perfect. The skin of the penis is thin and delicate (to maintain the sensitiveness of the organ), and is lax and elastic (to permit of its changes in size). On account of these qualities abrasions are not unusual, and through them syphilitic infection frequendy takes place. The loose, plentiful layer of subcutaneous connective tissue permits of enormous oedematous swelling as a result of ordinary staphylococcic or streptococcic (pyogenic or erysipelatous) infection; its abundance in conjunction with the elasticity of the skin, accounts for the disappearance of the penis in cases of very large scrotal hernia, in hydroceles of similar size, and in elephantiasis scroti. Anterior to the corona the skin is modified and resembles a mucous mem- brane, at the meatus becoming continuous with the mucosa oi the urethra. The line of demarcation between the ordinary and modified cutaneous surfaces is not, however, so distinct as on the lips or the nostrils, the passage of one surface into the other more closely resembling that which takes place at the margin of the anus. On the proxi- mal face of the corona the subcutaneous tissue is still abundant. Over the glans it practically disappears and the modified integument closely embraces the erectile tissue of the expanded anterior extremity of the corpus spongiosum. Chancres anterior to the corona (except at the frenum) are apt to exhibit the variety of induration known as "laminated" or "parchment-like." corresponding to a sclerosis limited to the papillary layer of the derma and to the vascular net-work of the papill.-e. At the frenum, corona, or cerxix. where the cellular ti-ssue is abundant, " nodular" induration — a sclerosis of the whole thickness of the derma, of thesubder- moid areolar tissue, and of the a.ssociated vascular net-work, which is much larger than the superficial or papillary supply — is apt to occur, and is, as the name indicates, deeper, thicker, and harder. On the skin of the penis chancres are apt to be exten: sive in area, but are limited in depth by the firm, resistant fascia penis. PRACTICAL CONSIDERATIONS: THE PENIS. •973 At birth the prepuce is normally adherent to ihe glans, its moderate retraction barely exposing the meatus. Continued retraction everts the hps of the meatus and then separates the epithelial adhesions between glans and prepuce, ultimately exposmg a congested surface and causing punctate hemorrhages. This separation should normally take place during mfancy or early childhood, either spontaneously as a result of erections and of the growth of the organ or because of gradual mechanical retraction by nurse or mother. When it fails to do this, the condition of i»A/»«t»«> -inability to retract the prepuce— follows, and is due partly to the persistent adhesions and partly to a frequently associated narrowing of the preputial orifice. . , . . .• ■ Both these factors may be the result of disease, and acquired phimosis may occur at any time of life and follow any form of inflammation of the skin covenng the glans (balanitis), of the inner surface and cellular tis.sue of the prepuce (poslAilis), or of both (balano-posthUis), the last named being the most common. Following phimosis there may be, (a) as a result of retention of secretion and of urine in the subpreputial space, balanitic or herpetic ulceration, or the development of papillomata (venereal warts) • (*) as a result of obstruction to the flow of urine and the consequent strain- ing vesical irritability, dilatation of the bladder, ureters, and kidneys, hemorrhoids, and hernia (62 per cent, of cases of congenital phimosis) (Kempe, quoted by Jacob- son) ; (f) as a result of nerve irritation (the region having an unusually rich nene- supply), spastic palsies, reflex joint pains and muscular spasm (simulated coxalgia), or even general convulsions. These complications are most apt to occur in infants and very young children, and their frequency has been exaggerated. As a result of phimosis, even when the preputial orifice is ample, there may be a contracted or "pin-point" meatus, which may give rise to the same train of symp- toms and will require to be divided (meaMomv) by a linear incision directed towards the frenum, and kept open during the process of healing. Circumcision, whether done for phimosis or to meet other indications, requires for its successhil performance attention to the following anatomical points : (a) the laxity of the skin, permitting it easily to be drawn so far in front of the glans that when it is severed at that point so much may be removed that the remainder retracts quite to the root of the organ, which is left denuded ; {b) the close attachment of the inner or mucous layer of the prepuce to the corona, so that the length of the portion of that layer that is allowed to remain will determine the distance of the operative scar (at the muco-cutaneous juncrion) from the meatus ; if this stump i.-i not exces- sive, it will thus effectually prevent the mortifying but not infrequent accident of re- formation of a phimosis after a circumcision ; (r) the loose, abundant cellular tissue and rich vascular supply in the frenal region, which, together with the dependent position of the part, may determine an excess of exudate that will result in an objec- tionable fibrous mass in that region if full hsemostasis is not secured or if any redun- dant tissue is left there. When a relatively small preputial orifice is drawn behind the corona it causes marked constriction at that point, especially if it is not only small but also inelastic as a result of chronic inflammation. If the constriction remains \mnY\e\eA, paraphimo- sis results ; the glans becomes distinctly enlarged, increa.sing the constriction, purplish in color, and glossy. It is often partially concealed by a thick collar of shiny, o-'dem- atous skin, behind which there is a deep, excoriated sulcus, and back of this sulcus there is usually a second oedematous band less marked than the one lying immediately behind the coronary sulcus. The penis seems to have a distinct upward kink or bend just behind the glans. This appearance is due to the deep notch caused by the margin of the retroverted orifice of the prepuce and to the oedematous swelling which is particularly marked about the ptwition of the frenum. In some cases, where the tense, inelastic edge of the orifice exerts a more than usual amount of constriction, circulation is markedly interfered with, and ulceration and even sloughing involving both the foreskin and the head of the penis may take place. This complication would undoubtedly be more frequent were it not for the rich blood-supply to the glans and the anastomosis between its vessels .ind those of the corpora cavernosa, The ulceration usually involves the foreskin only. «974 HUMAN ANATOMY. When the swelling consequent upon paraphimosis is well developed there is en- countered first a furrow, the coronary sulcus, which is normally found behind the corona ; in these cases it appears deeper because it is intensified by the cedematous swelling. Covering this furrow, and even overlapping the glans somewhat, is the portion of the prepuce which is normally in contact with the posterior face and border of the corona. Behind this swollen fold is found a second deep, often ulcerated fur- row indicating the position of the preputial muco-cutaneous margin ; this is the actual seat of constriction, and behind it is placed yet another ridge of swollen integument. The /asda penis (page 1968) gives the organ some of its most im|x>rtant physical characteristics. The tensile strength of the [>enis, because of its tough fibrous invest- ments, is sufiicient to bear the entire weight of the body. That portion of this fibrous investment which covers the blunt extremities of the two cavernous bodies where they are capped by the glans, delays, and sometimes prevents, the backward extension of inflammatory or infiltrating processes, particularly cane- : us infiltration, which pri- marily involve the glans. This fibrous sheath, being a ci iitinuation of the deep layer of the superficial fascia, also limits the forward extension of urinary and purulent infiltra- tions beneath this fascia, such infiltrations leaving the glans untnvolved. The free blood-supply to the penis and its rich innervation insure rapid healing in case of wounds, and justify conservative treatment even although the organ has been nearly severed or extensively crushed. Contusion of the penis is often followed — owing to the laxity of the skin — ^by such rapid and pronounced ecchymosis and oedema as to simulate gangrene. When the vessels of the cavernous bodies are involved there is free subcutaneous bleeding, giving rise to a circumscribed fluctuating tumor, most prominent during erection. This tumor is somewhat slow in formmg, and occasionally suppurates. Under conservative treatment it usually disappears. When injury has. not only occa- sioned extensive extravasation of blood, but has lacerated the urethral canal, the inflammatory phenomena observed after rupture of the urethra quickly develop. Moreover, there is immediately bleeding from the meatus, which should lead to prompt diagnosis and appropriate treatment. Wounds, if involving the erectile tissue, bleed freely, and, if transverse and ex- tensive, may be followed by loss of erectile power in the region anterior to the wound. Fracture, in a literal sense, is possible only when the orijan has undergone calcifica- tion or ossification (vide infra), but the term is applied to injuries that result when, during vigorous erection, the penis is subjected to a sudden twist or bend. The resulting condition is not unlike that caused by contusion, but the subcutaneous effusion is apt to be lacking. The chief lesion is usually in the corpora cavernosa, or in one of them, and is apt, as a result of obliteration of erectile spaces, to leave a flail-''ke organ, erection anterior to the break being impossible. Chronic induration (ossification, calcification, chronic inflammation) of the sheath and erectile tissue, especially of the corpora cavernosa, is marked by the formation of fibrous, calcareous, or bt>ny thickenings or plates, which fonn usually in middle- aged or elderly men of gouty diathesis. They cause but little pain, are easily recog nized by palpatio", and are accompanied by bending of the pienis to the affected side during erection, which is incomplete in the region anterior to the induration. The condition is unknown before forty or forty-fi\'e, and is probably analogous to the thickening ind toughening of the palmar fascia, which goes by the name of Dupuy- tren's contnction, and which we recognize as partly due to gout and partly to some constant irritation. Thus they may he met with in both the penis and the hands of the same gouty person (Jacobson). It has been suggested (Metchnikoff) that in their osseous form they represent reversions to the condition existing in many mam- mals and e\en in the anthropoid apes, in whom an os penis is i>resent. Lymphangitis may follow peripheral inflammation of any type, but is usually of venereal origin. The diagnosis between lymphangitis and phlebitis of the dorsal vein is based upon the much smaller size of the lymphatic \essels as compared with the \ein ; upon the fart that the former \psspIs do nnt pass vipward in the middle line, but are directed into the groins ; and finally upon the ability to lift the indurated vessel up from the deeper {larts, this not being possible in the case of the vein, since it is placed in a THE PROSTATE GLAND. 1975 furrow between the two cavernous bodies. Phlebitis occasions much more marked ^"EMhelioma of the penis is not uncommon. It usually follows prolonged subpre- putial frritation. It involves ultimately bpth the inguinal and the deep pelvic nodes. Amputation of the entire penis may be required for the relief of malignant dis- ease The following description (Treves) should be studied in connccUon with the anatomy of the penis and of the urethra. The patient is placed in the lithotomy pos._ tion and the skin of the scrotum is incised along the whole length ot the raphe VV ith the finKcr and the handle of the scalpel the halves of the scrotum are separated down to the corpus spongiosum. A full-sized metal catheter is passed as far as the tnan- Kular liuament. and a knife is inserted transversely between the corpora r ernosa and the corpus spongiosum. The catheter is withdrawn, the urethra is cut across, and its deep end is detached from the penis back to the triangular hgament. An incision is made around the root of the penis continuous with that in the median line. Ihe suspensory ligament is divided and the penis is separated, except at the attachment to the crus The knife is then laid aside, and with a stout penosteal elevator or rugine each crus is detached from the pubic arch. The two arteries of the corijora cavernosa and the two dorsal arteries require ligature. The urethra and corpus spongiosum are split up for about half an inch, and the edges of the cut ? stitched to the back part of the incision in the scrotum. The scrotal incision is closed by sutures, and if drain- age is used, the tube is m placed in the deep part of the wound that its end can be brought out in front and behind. No catheter is retained in the urethra. THE PROSTATE GLAND. Altho- ; *• developed as an appendage of the urinary tract, and not directly as part of *^ 'lal apparatus, the prostate is functionally so closely related to the gen- erativ ■. ■ ^^ lat it may appropriately be regarded as one of the accessory glands, the others ''\ .e glands of Cowper. ... ^ • i i j 1 ^ ate is complex in both its make-up and relations, being partly glandu- lar and '. , muscular and traversed by the urethra and the ejaculatory ducts. In general form it resembles an inverted Spanish chestnut, having the base Fic. 1679. applied to the under surface of the bladder and the small end, or apex, directed downward. Additional an- terior, lateral, and posterior surfaces are recognized. Grayish red in color and of firm consistence, the adult prosUte varies considerably within physiological limits in size and weight. The former includes a length, from apex to base, of from 2. 5-3. 5 cm. ( I to I ^ in. ) , a breadth or transverse diameter of from 3. 5- 4.5 cm. {i%i-i}i in.), and a thick- ness of from 2-2.5 cm. (f-i in.). Its average weight is about 22 gm. (3^ oz. ). Marked increase in size and weight is common in elderly subjects. The oblique upper surface or ,,,111 base (baste prostatae. fades veslcallfi) is applied to the under surface of the bladder, with which it is inseparably blended by muscular tissue surrounding the urethral ori- fice and is pierced by the urethra usually slightiy in advance of the middle. Ihe base is outlined by free rounded borders, so that its limits are separate.1 from the vesical wall by a groove. The posterior surface ( facics posterior ), directed backward and towards the rectum, is defined literally by prominent rouiuk-d l>orders that extend from the base to the apex and enclose a flattened cordiform or triangular area Blight icroove produced by symphysiA Inferior lurface St'miiial vehicle SliKhtlv distendett tilnddir. liardeniKl in ji/k, "ihiiw iiiK prmlate, wminal vwiclea.and seminal ducts ; viewid from below and behind. tr- * ■ it .il: 1976 HUMAN ANATOMY. ■Semiiial vesicle Ampnlla Inferior wall of bladder Intenial urethral orifice I'rethfBl crest Prostatic urethra FrofiUte, middle icbe Ejaculatory duct Portion of sagittal section showing prostate and related stmctum. that ohen presents a shallow concavity. The junction of the upper and posterior surfaces is marked by a transverse crescentic slit (incisiira prostatae) into which sink the ejaculatory ducts in their course to the urethra. The imperfecdy defined wedge- sttaped mass bounded by Fio. 1680. the urethra in front, the ejac- ulatory ducts at the sides and behind, constitutes the so-called middle lobe (lobus medius), the base of which lies beneath the v.-isical tri- gone. The prominent por- tions of the prostate lying external to the ejaculatory ducts are known as the lat- eral lobes, which, however, superficially are not dis- tinctly marked off. The prominent convex lateral surfaces, dnected outward, downward, and forward, and behind, limited by rounded borders, in front pass insen- sibly into the narrow con- vex anterior surface (fades anterior) that is approximately vertical and faces the symphysis. The urethra traverses the prostate with a vertically placed curve, the concavity looking forward, that above begins slightly in advance of the middle of the base, and below ends on the anterior surface just in front and above the apex. The posterior wall of the prostatic urethra is marked by a longitudinal median nA%^. the urethral crest, on the most exjjanded and elevated part of which (colliculus seminaiis) are situ- ated the o()enings of the pros- tatic utricle (ntriculus prostati- Fio- 1681. cus) and of the ejaculatory ducts fpage 1955). In the grooves or recesses on either side of the crest, open the mi- nute orifices of the prostatic tu- bules, some twenty in number, that discharge the products of the glandular tissue. Owing to the continuity of the muscular tissue with the surrounding structures in front, above, and below, the outlines of the prostate in places lack definition. Except over its base, apex, and lower anterior surface, the prostate is enclosed by a fibrous envel- ope or capsule, the extension of the visceral layer of the pel- vic fascia in conjunction with the investment of the bladder and the seminal vesicles. The caps..', is best oeveloped on the posterior surface, where it separates the prostate from the rectum and constitutes a part of the recto-vcsiral fascia in its restricted sense. Relatiotis. — Lodged between the bladder and the pelvic floor, the prostate is in relation 'vith a number of important structures. Above, its base is intimately Folds of mucous membrane 'Urethnl mucous membrane Urethral crest Prostatic utricle Ejaculatory ducts Section across prostatic urrihni above entrance of e)acala- lory ducts, showinK crescentic form of urethral lumen pro- duced by encroacliment of urethral crest. Y lo. THE PROSTATE (".LAND. 1977 attached to the lower surface of the bladder, lying beneath the vesical trigone. SL' Jts apex rests upon the superior layer of the triansular hgament. surrounded by fibes of the com/lressor ureVhr* muscle that constitute th- external v^l sphincter (page 1925) In front, the rounded anterior surface is directed touarc^ tLpubL symphysis^ from which it is separates! by an interveninK w«lKe-sha,>ed space occupied by loose areolar tissue containing p.rt of the prostatic plexus of veins aKt The pubo-prostatic ligaments (the continuations of the arcus tendincus of the two sides) stretch t .nween the symphysis and the prostate and contain muscular tissue prolonged from the latter and the bladder. At the stdes, the prostate ^-^^^^^ by the levator ani muscles, the prostatic venous plexuses, '^'^Yl .aIaV^. reflections of the pelvic fa.scia that here constitute the capsule of the gland inter- venS Behind, ihe prostate is in relation with the ampulla of the vasa deferent.a and the seminal vesicte above and with the lower part of the rectum below, separated from the latter by the dense capsule and the overiying layer of areolar tis.ue^ The p^ition of the prUate is not constant, since it is affected by movements of the vesi- S^wall, with which the prostate is intimately united, incident to marked distention and contraction of ^^^ i^g, the bladder. On the other hand, the at- tachments of the prostate to the trian- gular ligament and pelvic fascia indi- rectly confer upon the lower segment of the bladder its most efficient means of fixation. The pros- tate is further influ- enced by changes in the anterior wall of the rectum, under- going compression and displacement forward when the bowel is distended. Structure. — The prostate is a gland of the tubo- alveolar type and is made up of three Tcnninal duct opening into alveoli Involuntmry muscle. Alveoli Blood-vesael Portion of cross-section of prostate Ktand. X 75- chief components,— the connective-tissue framework, involuntary muscle, and the glan- dular tissue. Of these the latter constitutes usually a little more than one-half of the entire orc-in, and the connective tissue and muscle each somewhat less than one-quarter. The connective-tissue //-aw^ror/t consists of an external investing fibro-elastic en- velope the capsule proper, and a median septum, which encloses and blonds with the wallsof the urethra. Between these denser lamellpe numer-is partitions radiate and subdivide the organ into from thirty to forty pyramidal lobules occupied by the glandu- lar tissue The involuntary muscle, embedded within the capsule and ramihcations of the connective-tissue framework, surrounds the gland-substance as a superficial layer from which a median septum, about 2 mm. in width, extends ventro-dorsallv, enclosing the urethra in an annular thickening. In consequence, the interior of the prostate is occupied by a dense fibro-muscular nucleus, in which the glandular tissue IS represented by only the narrow prostatic ducts passing towards the urethra. The muscle is not limited, however, to the foregoing positions, but extends also between the ultimate divisions of the gland-tissue, the interalveolar septa in places consisting largely of the v.trionslv disposed muscle-bundles. The glandular tissue consists of twenty or more distinct tube-systems, each drained by an independent duct that opens into the urethra in the groove on either side 1978 HUMAN ANATOMY. Muiclc cell ill concrrtion of the colliculus. Bej^nning at their narrow orifices, these excretory tubules (dnctnii prostatic! ) pass outward into the lobules, and after a course of about i cm. divide into tubules that repeatedly branch and exfiand into the terminal alveoli. Throughout the greater part of their course the wavy ducts are beset with saccular and tubular diver- ticula, simple or com(x>und, that give the canal an irregular lumen and constitute what have been termed the duct alveoli as distinguished from the terminal alveoli. The latter form a series of irregularly branched tubular and saccular spaces lined with a single or imperfect double layer of columnar epithelial cells, — the secreting elements of the gland. In places the alveoli intercommunicate and form net-works of spaces of variable lumen. The epithelium in the ducts and their diverticula corresponds with that lining the more deeply situated alveoli, the change into the transitional variety of the prostatic urethra not talcing place until very near the termination of the ducts. Peculiar concretions ( ' ' amyloid bodies' ' or " prostatic calculi' ' ) are almost con- stantly present within some of the tubules of the adult organ, especially in advanced life. These bodies (Fig. 1683), round or oval in outline and very variable in size (from .2-1 mm. and more in diameter), usually exhibit a faint concentric striation and a light brownish color. Their nature is uncertain, but they probably consist of a colloid substance giving the reactions of albumen. The secretion of the prostate gland {succus prostalicus) is milky in ap- pearance, thin in consist- ence, slightly alkaline in reaction, and possesses a characteristic odor (Fiir- bringer ) . It is discharged into the urethra and min- gled with the fluid enter- ing by the seminal ducts during ejaculation, and probably serves an impor- tant purpose in facilitating and {>erhaps stimulating the motility of the sper- matozoa. The "sperm crystals" formed in semen after standing, and attributed to the products of the prostate, are not found in the secretion of the living subject (although frequently present in the gland after death) until after the addition of ammonium sulphate (Fiirbringer). Vessels. — The arteries supplying the prostate are small branches from the inferior vesical and middle hemorrhoidal. They enter the periphery of the gland at various points, particularly in company with the ejaculatory ducts, and break up into capillary net-works that surround the alveoli. The veins are exceedingly numer- ous, forming close mesh-works within the glandular tissue and around the ducts. They leave the organ on either side and unite into a plexus within the capsule, which, receiving the deep dorsal veins of the penis and communicating with trunks from the bladder, seminal vesicles, and rectum, is continued as the prostatico-vesical plexus, tributary to the internal iliac veins. The lymphatics are numerous and form a net- work on the lower and posterior surface of the organ from which on either side pass two trunks, a superior and a lateral. The upper and smaller trunks are afferent to the obturator lymph-nodes of the pelvic wall, and the lateral and larger terminate in the internal iliac nodes ( Sappey). The nerves of the prostate are chiefly sympathetic fibres derived from the hypogastric plexus, numerous minute ganglia being included along their course. Peripherally situated Pacinian corpuscles are said to be connected with the sensory fibres (Griffiths). Blood-venel Portion of Mction of proatate gland, showing details of alveoli. X rja. M.ir<^? PRACTICAL CONSIDERATIONS : PROSTATE GLAND. '979 Development.-At about the third month of fcetal life the wall of the primitive urethra undergoes thickening, leading to the 1'^"^"*^"??/;'^'" ^"""/'';; "1?^^^ Xm blastic tissue that surrounds the lower ends of the Wolffian and MuUerun Uucts Ser the ejaculatory ducts and the prostatic utricle respectively) and subsequently Kmes differentiated largely into unstriped muscle. Into this penetrate solid epi- S^^urgrowTs, from the lining of the ut^ethra. which e.xpand into branched cylinder Eliveriletothe pro.static glandular tissue. These »"^«^7%\^'-V™«^^^^^ three groups (Pallin). a ventral, an upper and a lower dorsal J»«-;'-\f ^^^^^J^^^^^^ irives rise to the glandular tissue in front ok the urethra, which at hrst is ri.lati\tly fbundLnt but sc^n suffers reduction, and in the adult organ is often almost wanUng. The S «oups produce the imporUnt glands of the median and lateral lobes. For a Se'^he btterarearranged'^as two separate lobes, but afterward beaje consoliS by the capsule and broken up by the invasion of the fibro-muscular ^'''^t birth the prostate measures about '2 mm. in its transverse dimension and remah^s small until puberty, when it begins to rapidly enlarge, acquiring its fuU pro- [«rrions with the esublishment of sexual activity. With the approach of old age. [he prosul; usually undergoes increase in size.-an augmenUUon often resulung in pathological conditions. V«i.tion..-Apart from abnormalities in size, the .pn»tote U subject to few var^^ Amone theUtter have been persistence of the original independence of the lateral '"bes ab- Among tne laiier nave uc^ i^ 1^ I j^ Variat ons m the relations and mode ^endi of ™e$c2"a1o',?d?^tei^ imoasingle canal or termination in the PJ-tatic utricle or bv a Tu^cial caral Wow the crest) or in the prostatic utricle (absence, enlarged size, or un- ZZ oi^S) aTprop^riy referred to deviations in the development of the generative tract PRACTICAL CONSIDERATIONS: THE PROSTATE GLAND. The prostate gland is a portion of the male generative system. The prostatic utricle, or sinus pocularis, is the homologue of the sinus genitalis in the female,— the uterine and vaginal cavities,— since it represents the persistent part of the fused Mul- lerian ducts (page 2039). Alhough the prostate and the uterus cannot be rtjgardetl as homologous organs, they are similar in structure, and would be strikingly alike if the tubular glands found in the inner walb of the uterus were prolonged into its muscular substance. . • 1 During infancy and childhood the prostate is still immature ; at puberty it enlarges coincidently with the enlargement of the testicles. In eunuchs and after castration in man and other animals it is atrophied. The seminal vesicles are in close relation to it and the eiaculatory ducts penetrate it (page 1955). Its size and perfection of struc- ture in animals rise and fall with the breeding season (Hunter, Owen. Grithths). These facts sufiiciendy demonstrate the essential relation of the prostate to the gen- erative system. It. however, affords passage to the prostatic urethra, its unstriped muscle-fibres are continuous with the vesical muscle at the trigonum and with the circular fibres of the bladder, and both the anatomical and subjective effects of the more common pathological changes in the prostate are observed in relation to the urinary system, with which, therefore, it is most intimately associated. Injuries of the prostate are rare on account of its protected position, and usually involve also the rectum or the bladder. Hemorrhage from the prostato-vesical plexus may be dangerous in amount ; and if a wound extend upward into the neck of the bladder, that organ may become distended with blood and form a tense, globu- lar hypogastric tumor. Infihration of urine following a prostatic wound may, in accordance with the situation of the latter, reach the hypogastrium from the pre- vesical space, the ischio-recul region or the perineum from coincident division oi the fascia of Colles, or the recto-vesical space and the pelvis from similar division of the recto-vesical fascia. _ , . , . j. Disease of the prostate, if infectious, is usually gonorrhceal in origin. It is often due tu the use of • nclcan urethral or vesic.nl instruments. It tends to suppuration on account of the •. dry imperfect drainage of the products of inflammation from the numerous follicles. .r m 1980 HUMAN ANATOMY. Prostatitis is attended by (a) much swelling, owing to the vascularity and spongy structure of the gland. As the forward enlargement of the prostate is pre- vented by the resistance of the dense pubo-prostatic ligaments, the subpubic liga- ment, and the firm superior layer of the triangular ligament, the swelling is greatest in the posterior two-thirds of the gland. Its downward extension is evidenced by (*) a sense of weight and uneasiness in the perineum and (c) rectiil irritation and tenesmus. Its upward and backward spread is shown hy id) interference with mic- tuntion, due to compression of the prostadc urethra and elevation of the vesical out- let. The symptoms of (<•) painful and ffequent micturition and (/) vesical tenesmus are due in part to the mechanical obstruction, but chiefly to the extension of the inflammation to the trigonal region and to the obstruction by pressure of the pros- tatic venous plexus into which the vesical plexus empties, causing intense conges- tion of the vesical mucosa. The unyielding character of the prostatic sheath pro' change in the bladder necessitating a compensatory hypertrophy of the prostate (Harrison); (r) a growth analogous to uterine fibro- myoma (Thompson) ; (rf) the persistence, in an adjunct sexual organ, of physiological activity intended for the control and determination of the ma.sculine characteristics after the need for such activity had disappeared (White); (<■) an attempt to com- pensate quantitatively for a qualitative deterioration in the prostatic secretion, whose function (Purbringer) is to facilitate the mobility and vitality of the spermatozoa (Rovsmg); and, recently, (/) infecnon (most often by the gonococcus), aggravating a senile degenerative process (Crandon). The enlargement may affect chiefly any of the separate components of the pros- tate, and may thus be adenomatous, myomatous, or fibrous in its character, although usually the glandular element predominates. It may involve particulariy the lateral obes, or may affect almost exclusively the so-called median portion placed at the lower posterior part of the gland, between the ejacislatory ducts. This portion is direcUy beneath the vesical neck. The degree of hypertrophy is extremely variable, the prostate being increased from Its normal weight of between four and six drachms to a weight of many ounces, and, of course, correspondingly increased in size. It is not possible here to do more than call attention to these varieties of hyper- trophy, but Its usual and general effects may be considered with reference to their anatomical causation. I. The direction of greatest resistance to enlargement is forward (vide supra) and next downward (towards the rectum). Hence the growth usually takes place in an upward and t«ckward direction, although the resistance offered by the recto- vesical layer of fascia does not prevent marked extension in that direction in many cases. As a direct result of this enlargement there follow : (o) compression, flatten- PRACTICAL CONSIDERATIONS : PROSTATE GLAND. 1981 inij and elongation of the prostatic urethra, or lateral deviation of that canal (if one lobe greatly exceeds the other in size); (*) elevation of the vesical neck and outM which are carried up by reason of their intimate connection with the prostate, especially with iu median lobe, the base of the bladder remainmg relaUvely un- affected ; (c) the formation in this manner of a pouch or pocket (post-prostotic pouch) in the bladder at a lower level than the vesical outlet. The indirect results of these conditions are the changes in the bladder occasioned by (a) the mechanical obstruction which the enLvged prostate offers to the ready and complete evacuation of its contente, (*) the circulatory disturbance incident to pressure on the prostatic veins into which the blood from the vesical veins passes, and (f ) septic infection. . . , • « .l As a result of the narrowing or deflecuon of the urethra, the elevation of the vesical outlet, and the formation of the post-prosutic pouch, the bladder is not entirely emptied at each act of micturition, a certain amount of residual urine remain- ing behind This may gradually increase as the obstruction becomes more marked, ultimately causing dilatation 0/ the bladder, with atonv consequent on partial de- generation of its muscular walls, or, in consequence of the more vigorous bladder contraction required to empty the bladder, the trabeculae may become enormously hypertrophied, the inner layers forming pronounced ridges. These by their con- traction exert a powerhil pressure upon the vesical contents, which, escaping very slowly, transmit the pressure in all directions and occasion bulgmgs or sacculations in such weak parts of the bUdder-walls as are not supporlec. by muscular bands or by strong investing fasd*. The hypertrophy and sacculation are hirther encouraged by the vesical irritability incident to venous congestion at the neck of the bladder, which, as the prostatic veins become more obstructed, keeps up a condition of passive hyperiemia and erethism more potent than residual urine alone to occasion the fre- quenriy recurring desire to urinate and the muscular spasm of the sphincter at the beginning of the act, which calk for such strong and repeated efforts on the part of the detrusor muscles. ... Septic infection of a healthy mucous membrane by the pyogenic microbes caus- ing acute or chronic cystitis b not possible, even although such bacteria are present in the urine; when, however, the vesical mucous membrane is congested in conse- quence of obstruction to venous return, and of distention of the viscus and frequently recurring contractions of the detrusor muscles, it offers but slight resistance to the microbic invasion. The pyogenic microbes are generally carried to the bladder by dirty instruments, or, if these are rendered sterile, through failure to cleanse the anterior urethra before the instrument is introduced into the bladder. Often cystitis develops independently of the use of instruments, probably as a result of infection conveyed by way of the urethral mucous membrane. 2. The subjective symptoms brought about by these conditions may be briefly summarized and will be readily understood by reference to the foregoing and to the article on the bladder, (a) Frequent urination, due partly to the inability completely to empty the bladder, but chiefly to the venous congestion about the trigonum. (b) Difficulty in starting urination, due to muscular spasm of the external vesical sphinc- ter, which, excited by reflexes from the hypersesthetic prostatic urethra and neck of the bladder, is not fully under the control of the will. A temporary reflex inhibition of the detrusor muscles may also delay the act of urination, {c) Feeble unnatton, due to the weakness, atony, or paresis of the overstretched detrusors, (rf) Inter- rupted urination, due usually to spasmodic contraction of the external vesical sphinc- ter and compressor urethra muscles, reflexly excited by urethro-cystitis ; occasionally the result of intermittent contraction of the detrusors, often (as in many cases of cardiac palpitation) a sign of beginning muscular atony. The physiology of micturi- tion requires continuous contraction of the detrusor muscles and relaxation of the sphincter >r a brief interval only. When there is sufficient obstruction to triple or quadruple the time normally required fully to empty the bladder, the detrusor mus- cles, exhausted by their effort, may relax, whereupon the sphincter miLscles, relieved of the vis a tergo, promptly contract. After some seconds or minutes the detrusors recover sufficiendy to make hirther efforts at evacuation. (*) Incontinence of urine, which may always be taken as a symptom of retention with overflow, the intravesical H ri 19^3 HUMAN ANATOMY. tension of the overfull bladder being sufficient to overcome the resistance offered by the tonic contraction of the sphincter muscle plus that due to the prostatic enlar);e ment. (/*) Complete retention of urine, due either to an aggravation of the chronic congestion of the urethro-vesical mucosa or to the completion of an atrophic process which has finally destroyed all power of contraction in the bladder. (^) Referred pains, similar to those noted as occurring in acute prostatic swelling (^vide supra), (h) Constitutional disturbance, due to septicsemia or urxmia, or both. Operationa. — Prostatotomy. — Incision or puncture of the prostate for the evac- uation of an abscess may be made through the rectum or by a median perineal incision. The same name is applied to an o|)eration which consists in opening the urethra at the apex of the prostate by a median perineal incision, and dividing the obstructing portion of the gland by means of a probe-pointed bistoury, cutting from within outward. The channel may be further enlarged by divulsion with the finger. The anatomy and relations of the parts involved have already been described (f>age 1921). Of the various operative procedures to which the prostate is subjected, prostatec- tomy is, however, by far the most important. Under this name operations have been described which consist of the removal of the enlarged median lobe, or of portions of one or both lateral lobes, or of the whole prostate, by either perineal or suprapubic routes. In suprapubic prostatectomy the prostate is approached by means of a supra- pubic cystotomy (page 1921). The mucous membrane over the most prominent portion of the intravesical protuberance is scratched through and, as a rule, the growths or the prostate removed by enucleation with the finger. The possibility of total removal of the prostate, and especially of such removal without coincident injury or removal of the prostatic urethra and ejaculatory ducts, ha-, been vigorously discussed. It has been complicated by confusion as to the struc- tures described as the " capsule" and as the "sheath." The views of Freyer appear at present to explain most satisfactorily the actual anatomical conditions found at operation, and are thus summarized by him : The prostate is in reality composed of twin organs, which in some of the lower animals remain distinct and separate throughout life, as they exist in the human male during the first four months of foetal existence. After tl ■ period, in the human foetus, they approach each other, and their inner aspects bet ..e agglutinated, except along the course of the urethra, which they envelop in their embrace. These two glandular organs, which constitute the lateral lobes of the prostate, although welded together, as it were, to form one mass, remain, so far as their secreting sutetance and functions are concerned, practically as distinct as the testes, their respective gland ducts open- ing into the urethra in the depression on either side of the urethral crest. Elach of these two glandular bodies, or prostates, is enveloped by a thin, strong, fibrous capsule ; and it is these capsules — less those portions of them that dip inward, cover- ing the opposing aspects of the glandular bodies or lobes, and thus disappear from view, being embedded in the sulwtance of the prostatic mass — that constitute the trut capsule of the prostate regarded as a whole. This capsule extends over the entire organ except along the upper and lower commissures, or bridges of tissue, that unite the lateral lobes alxive and below the urethra, thus filling in the gaps between them. This true capsule is intimately connected with the prostatic mass and incapable of being removed from it save by dissection. The urethra, accompanied by its surrounding structures, — viz., its longitudinal and circular coats of muscles continued forward from the liladder, its vessels and nerves, — passes forward and upward between the inner aspects of the two glands or lobes and is embraced by them. The ejaculatory ducts enter the prostatic mass close together, in an interlobular depression at the lower part of its posterior aspect, each coursing along the inner surface of the corresponding lobe. They do not penetrate the (-ipstilcs of the lobes, bnt p.iss forward in the interlobular ti.ssue, to open into the urethra. The prostate, thus constituted and enveloped by its true capsule, is further encased in a second capsule or sheath, formed by the visceral division of the pelvic fascia, numerous connecting bands passing, however, between the two (Thompson). PRACTICAL CONSIDERATIONS : PROSTATE GLAND. 1983 Between these two capsules, or rather mainly embedded in the outer one. «« the prostatic plexus of veins, most marked in front and on the sides of the prostate. 1 he larKer arteries also lie between the true capsule and the sheath numerous small branches passing from them through the true cipsule for the supply of the prostatic substance. , , • i a Freyer illustrates his view by imagining the edible portion of an oninRe comjioseU of two Kgments only, instead of several, with the aeptum between them placed vertically, and says that the thin, strong, fibrous tissue which covirs the segments of the orange, and which is intimately connected with the pulp would then represent the true capsule of the prostate, the two segments or halves of the orange being rep- resented by the two lobes of the prostate. Further, the rind of the orange wou d represent the outer capsule or prostatic sheath, contributetl by the jk^Ivic fascia. In the method of suprapubic prostatectomy now known by his name, it is the true cap- sule as above described that is removed, the sheath bemg left behind, thus pre- ventine infiltration of i-rine into the cellular tissues of the pelvis. In most cases of hypertrophy of the prostate the overgrowth is adenomatous in chara .-r, numerous encapsuled adenomatous tumors being found embedded within the substance of the lobes and frequently protruding on their surfaces. They s..me- times assume the form of polypoid outgrowths, which however, are invariably en- closed within the true capsule, which is pushed before them. As the lobes enlarge they bulge out and have a tendency, each enclcwed within its own capsule, to become more defined and isolated, thus recalling their separate existence in early foeul life. They become more loosely attached along their com- missures (particularly the upper one), which in the normal prostate unite them above and below the urethra. And in the course of this change the urethra, with its accompanying structures, is loosenetl from its close attachment to the inner sur- faces of the lob«, thus facilitating its being detached and left behind uninjured in the removal of the prostate. ... . • u In the earlier stages of the adenomatous overgrowth the enlargement _ P'O''/'- blv entirely extravesical. Its expansion in this position is. however, limited by the pubic arch above, the triangular ligament in front, and the sacrum below. As the enlareement progresses, it advances in the direction of least resistance.— namely, into the bladder. The sheath, which at the posterior aspect of the prostate is least de- finetl becomes gradually thinner as the enlargement in this direction pr.)gresses. till eventually the prostate has burst through it, and is then merely covered by the mucous membraneof the bladder (Freyer). ,,.••... , It has been asserted that what \^^& here been called capsule is in the normal prostate reallv only a thin outer nat:-glandular portion— cortex— containing both muscular and fibrous tissue (Shatt, cl:), and that the envelope formed from the pros- tate by the expansion of adenomata represents more than the " cortex and contains glandular tissue derived from the stretched and compressed outer portion of the prostate (Wallace). ... ■ 1 • .. t .u However this question may ultimately be settled, the anatomical views set forth above explain the separability of the mass of the prostate from fa) the prostatic plexus of veins (avoiding hemorrhage), (b) the under surface of the recto-vesical fascia (avoiding urinary infiltration), and (f) the prostatic urethra .ind cjaculatory ducts (minimizing interference with micturition and with potency), which separa- bility has been shown to be at least occasionally possible during operation. Perineal prostatectomy is done, with the patient in the lithotomy position, by means of a semilunar incision in front of the anus carried down through the successive structures of the urethral perineum until the sheath of the prostate is reached. After division of the sheath on either side in a direction parallel with the medial ""jes of the levator ani, the prostate in its capsule— or portions of it— may be enucleated with the finger The gland mav be made more accessible by downward pressure tnfo'lB" the space of Retzius (by means of a suprapubic incision) or through the bladder itself (after a preliminary suprapubic cystotomy). It may iie reaLlitd by a latr.a. incision half enrircling the anus. It should be remembered that it is separated -i nn the ischio-rectal fossa only by the levator ani muscle, with the visceral layer of the pelvic fascia on its upper and the anal fascia on its lower surface. I9M HL'MAN ANATOMY THE GLANDS OF (»VVPER. Cowper's glands (glaodulac bulbeurcthraies i >'<- tv.o «,.i u void bodies situated alon{f the under surface of tf»e membranous porti" n erf tht vi 'hra ( Fij; 1632), one on either side of and close to the mid-line. In jjen' al forni ,111 I si/c (frf>»n 5-8 mm. in diameter) they resv mWe a pea, although their .-ont-jiir is ii ftT^l ir and ^rmiewhat knobl)eetween the two layers of the triangui.'ir tii|[]iment em- bedded within the fibres of the compressor urethr.i> muscle. The duf/s of the glands — atxiut 1.5 mm. in diameter and In n 3-4 cm. in length — nm forward and medially, at first between the bulbus spongiosum and the membranous urethra, then within the bulb itself, and, finally, for alxiut 2 cm. be- neath the urethral mucous membrane to opin by small slit-like orifices on the lower wall of the bulbus urethra near the mid-line. The position of these inconspicuous openin^j-^ is s Tifice. Structure. — These glands are mucous tubo-alveolar in tyj)e, thi r terminal divisions ending, after more or less branching, in irreguLirly sacculated - ompart- ments. In places the latter communicate by means of a retic\ilum of connecting canals (Braus). The alveoli are lined with low columnar or pyriform epithelial cells, among which mucus-secreting cells are plentiful. The cuboida! epithelium that clothes the smaller ducts and the dilatations connected with them gives place to clear columnar cells within the larger excretory canals. The divisions of the gland arc united by interlobular connective tis.sue and investetl in a gener.il filirous en- velope in which a consider ;ble quantity of unstriped muscle occurs. The secretion of Cowper's glands, clear and viscid and of alkaline reaction, is probably of ser\ice in maintaining favorable conditions for the spermatozoa by neutralizing acidity of the urethral canal due to pa.s.sage of urine ( Eberth). In addition to their recognized homology with the glands of Bartholin in the female, the observed histological changes incident to sexual excitation warrant the grouping of these glands as acces- sory sexual organs. Vessels. — The arteries supplying Cowper's glands are twigs given off from the arteries of the bulb as they course between the two lavers of the triangular liga- ment. The veins are tributary to those returning the blood from the bulbus sponvji- osum which empty into the internal pudic. The lymphatics are afHerents to the internal iliac lymph-nodes. The nerves are derived from the pudic. Development. — The bulbo-urethral glands appear about the end of the tl rd month of foetal life as solid outgrowths from the entohlastic lining of the uro- genital sinus. With the elongation of the latter incident to the formation of the male urethra and the penis (page 2044), the glands issume a lower position ^m! their ducts are correspondingly lengthened. During first ten or twelve - .-ais the glands undergo only small increase in volume, bvit iietween the sixteenth antl eighteenth years they attain their full size. In aged subjects they atroph\ an" are frequently so small that their recognition is difficult Variations. — In addition to abnormalities in size, the two gl'tids may be fused into .> izle mass, or one or b«lvis and abo- iif p' :l(H>r, . : and b* 1<>' the triuJigular i, irnent a jones, *;i >. and inteuumvnt. Thi ,-s, whith \, oduce • ova, the ovidu. ^xual ^ellh the Mi us, and the vagi Htemal situ- ; the exitmal, supported by Ternal organs or Fallopinn the passage vis, eixbraces the ! >wer end of the uterus above, Ixh ithin the e lernal genital cleft. The Fallo- The reproductive ortjans ated for the most part w iihin ; embraced by the subpubc arc: attachmenu to the surrout.dinj; are the sexual gl ds, th« ota, lubes, the canals fivi-yinji tlu which, beffinninj within the ji nierres tht- pelvii rt(M)r, aiv! et>', .ri „- - i i i pian cubes uterus, and v.«ma repr. o the excretory canals of the- sexual glands which in ll. . mbryo, as tlu .Mulleri.«a ducts, for a time are separate. After fusion of their lower , -gments tias takvn pla .-. the unpaired tube thus formed b^omes the vagina and the ut. .n- tht- latter !-m.; sperialized for the recepUon and r ention o' the fertilized ovum - rmggesutii Hi ... , , ^ , . . The e^ienwl otj^tas, oftei. <.nm--l colltH:tively the vulva (pwlt lum muhcb! include the elUds, the /«*/ the enclosed vesHMe AnA vagtHu. Mfi,' id glands of Bartholin, in a -en, i .1 «ay these parts represent structures ho .log . w h the i)enis and scrotum, i .: a less a vanced and specialued stage of f-vel p- n nt. THE 0\ lES. ^ he ovary (ofanua), ■•?»* on either side . i the body, is the sexual gl. W! and f->m whi. h ire dev» oped and liberated the mature maternal tb - va i " asohu .lody, rc^cm' img in forma large almond, and lies a^'atnst or ear to ^ 'w lateral pelvic wall invested by peritonei ^ co the .«terior suiiu-e o tS* broir! ligament of the uterus Ev.^ sei organ pre- "its constdeni'- • indu dual \ mations in size, its averaj; m. 36 mm. ( \ in. ) in lenc t8 m^' ( ^ in. ) in breadth, and i a mm. new. \.. nations in ^\f clud length of from 2.5-5 cm. (1-2 from I vj cm. (H-«'« ■*"J » thickness of from .6-1.5 cr. , according to German auth. =.i.e8. The right ovary is frequently somewhat larger thar the left. The adult organ weighs about 7 grm. {% oz.). Acer the cesMtion di n ,.-4truation, about the forty -fifth year, the ovary decreases m si? ind wtight. m <^ u Hnen being reduced to one-half or less of its normal proportio ibp ovary presents two turfaces— a »m'soiy ament of the ovary and usuaHy to the fimbriated extremity of the Fallopian t^^b*- id a lower (extremltas uterina), pointed and attached to the uterus by a hbw. uscular band, the utero-ovarian ligament. The portion of fhe .ittachrd anten^ >rder through which the vessels and nerves enter and emerge is knowi) as tbe :lum (hllns ovarii). The surfaces of the mature ovw' »t* '«« even, as in eariy iife, but modelled by rounded elevations of uncertair Hnh«f ^ae and W irregu- lar pits and scars. The elevations are produced H \inrter .i^ Graahaf follicles in different stages of growth, while the irregul ) .. «' w as* iad tcate the^sitioti of corpora lutea of varying age and develop it. « 'oelamd the attachment of the mesov-irium and parallel to the hilnm. the M.Hac* M the t w)^'-«a ry are c-«^ by a narrow stripe of lighter color, straight or < urved iw! often i%i*ii/ raised, i ms band, the while line of Farre, marks the tran»«>..n n the usual f#entoneal endotb' lium into the cylindrical germinal epithelium thai cfjvers the exterior of the at^f' and appears dull and lacking in the lustre charactenstit of serous surfaces. ii5 ^.cr cell^ adui I'd from , '. the sioii- -ew^ . ) in ihick- a width of '4-5.i in.), 1986 HUMAN ANATOMY. Position and Fix ation.— Although subject to deviations due to the -nfluence of other organs, especially the pull of the uterus, and of pregnancy, the long axis of the normally placed ovary, in the erect pbsture, is approximately vertical (Fig. 1684). The margin attached to the broad ligament of the uterus is directed forward and slighdy outward and the free convex tx>rder backward and inward. The outer sur- face usually lies in contact with the peritoneum covering the lateral pelvic wall within a more or less well-marked depression, the ovarian fossa (fossa ovarica). This recess, triangular in its general outline and variable in depth, is included within the angle formed by the diverging peritoneal folds covering the external and internal iliac vessels. In favorable subjects, in which the amount of subperitonral fat is small and the em- bedded structures, therefore, not masked, the ureter and the uterine artery will be seen forming the immediate boundary of the ovarian fossa behind, while above and in front extends the remains of the obliterated hypogastric artery. Below, where its Fig. 1684. Intenul iliac aitery Fimbriated end of Fallopian tube, pulled fonnrd Suspensory ligament of ovary External iliac vessels Round ligament Deep epigastric- artery Mesosalpinx Oblitersted h>-pogastric artery Fallopian tube Bladder Symphysis pubis Itoaeum, cat cd(« Ureltr Right ovary, median surface Ligament of ovary .Utero-sacral ligament Rectum Recto-uterine pouch ~^Utems, pulled to the left Right lateral wall of pelvis, showing ovary in position ; Fallopian tube has been pulled forward and uterus to the left. boundary is indistinct and uncertain, it fades into the pelvic floor, often without demarcation. The floor of the fossa is obliquely crossed by the obturator vessels and nerve. Within this depression the ovary lies, hidden to a considerable extent beneath the oviduct, which arches over the upper pole and largely covers the median surface with its expanded fimbriated end. The upper or tuba', pole reaches almost to the level of the external iliac vein and the peUic brim, and is overhung by the inner edge of the psoas muscle. The lower pole rests upon the upper ( posterior) sur- face of the broad ligament and nearly touches the pelvic floor — about 2 cm. above and in front of the upper border of the pyriformis muscle and the trunk of the greater sciatic nerve (Rieffel). The vertical position of the ovary is maintained by the suspensory ligament (liKamentum suspensorium), also called in/undibulo-pehic li/fament, which is a trian- eiilar band of ftbro-mtisculnr tismip, attached to the upper tubal pole of the ovary and mvested by a peritoneal fold continued from the upper and outer corner of the broad THE OVARIES. 1987 Fig. 1685. lieament. It passes outward across the external Miac vessete in front of the sacro-iliac articulation anri is lost in the fascia covering the psoas muscle. Embedded w.thm the enclosed fibro-muscular tissue lie the ovarian vessels and nerves, which thus gam the broad ligament in their passage to the ovary. • . i .u- The anterior margin of the ovary is attached to the posterior surface of the broad ligament by a short but broad band— the «i^f^..ar.««i— covered on both sides by peritoneum, that conveys the ovarian vessels proper and the nerves to the hilum through which they enter and emerge from the organ. The somewhat pointed lower end 0? the ovary is connected with the posterior border of the uterus, between the oviduct and the round ligament, by a cord-like band. \\i^uUro-ovartan ligament or ligament of the ovary (ligamentum ovarii proprlum). This band, from 3-4 mm. thick, lies within the posterior layer of the broad ligament beneath the peritoneum, through which it is seen as a distii-~t cord. ... . .: Since the uterus and its broau Sigament are subject to continual changes of posi- tion, the attachment of the ovary to these structures often produces deviaUons from its typical location. These in- fluences affect particularly the lower pole, the upper enjoying s„rf,^. greater fixation from the support epithelium ' afforded by the suspensory liga- ment Asymmetry in the po- sition of the two ovaries is usual, as the fundus of the uterus seldom lies stricdy in the mid-line, and hence the lower pole of the ovary of the opposite side is dragged medially. The long axis of the ovary, under such conditions, is oblique on the side opposite to that towards which the uterus is deflected. Conversely, relaxa- tion of the ligaments occurs on the side towards which the uterus tends and thus favors the reten- tion of the vertical position of the ovary. Notwithstanding the lati- tude of movement possible, the „,„,„,„. position of the normal ovary is tranuimum ■ fairly constant, the close relation of the oviduct to the median surface, aided by the pressure exerted by other organs within the pelvis, materially assisting in retaining the ovary within its . fossa. The stretching and subsequent relaxation of the suspensory ligament incident to pregnancy are predisposing causes of disnlacement of the ovary due to insufficient fixation. Structure. — The ovary consists of two principal parts, the cortex (lona parenchymatosa) — ^a narrow superficial Lone, from 2-3 mm. thick, that forms the entire periphery of the organ beyond the white line ; and the medulla ( zona vascn- losa,) that embraces the deeper and more central remaining portion of the gland. The cortex alone contains the characteristic Graafian follicles and the ova, while the medulla is distinguished by the number at)d size of the blood-ves-sels. especially the veins. The cortex, as seen in vertical sections of the functionally active organ, con- sists chiefly of the compact ovarian stroma that is composed of peculiar spindle- shaped connective tissue-cells, from .01 5-. 030 mm. in length and alwut one-fifth as mitrh in width, and fibrillar intercellular substance. The xtrotna-cells, which some- what resemble the elements of involuntary muscle in appearance, are arranged in Ovarian atroma Immatara primary follicle Follicle beginning to grow Stnttura Theca Section of cortex of ovary of voung woman, nhowinn primary and growing folliclea within ovarian stroma, a I'jo. n 1988 HUMAN ANATOMY. bundles that extend in all directions (chiefly, however, obliquely vertical to the surface) and are seen cut in different planes. Immediately beneath the germinal epithelium covering the surface, the stroma-elements are disposed with greater reg- ularity and form a compact superficial stratum, the tunica albuginea. Embedded within the stroma lie the most characteristic components of the cortex, the egg-sacs or Graafian follicles. These are seen in different stages of development, but for the most part are small, inconspicuous, and immature, in the human ovary being much fewer and less prominent than in many other mammals. Corresponding with their stages of development the egg-sacs may be divided mXo primary, grcnving, and ma- turing follicles. In general, the youngest lie nearest the surface, the more advanced deeper and towards the Fig. i68«. medulla, while those ap- proaching maturity ap- pear as huge vesicles that occupy not only the entire thickness of the cortex, but often produce marked eleva- tion of the free surface. The medulla, the vascular zone of the ovary, consists of loosely disposed bundles of fibro-elastic tissue sup- porting the blood-ves- sels, lymphatics, and nerves. In the mature organ, with the excep- tion of the encroaching ripening Graafian folli- cles, egg-sacs are not found within the me- dulla. The larger ves- seb are accompanied by bundles of involuntar}' muscle prolonged from Blood-veucI Connective- tissue stroma Muscle Section of medulla of ovary, showinK nnmeroin blood- venaels and fibro-muscular atroina. x 7S. iiiu3\.ic piuiuiigt^u irom the utero-ovarian ligament through the mesovarium and the hilum into the medulla. The veins are particularly large and appear in sections as huge blood spaces of irregu- lar outline in consequence of their tortuosity and plexiform arrangement. PoUidet and Ova.— The aaxanXwK primary follicles (folliculi oopbori primaril) arc micro- scopic in size (from .04-.06 mm. in diameter) and var>- greatly in number, the estimate for the two ovaries of young adults being placed at approximately 35,000 (Bonnet). Each follicle consists of the centrally situated young egg (ovalam) surrounded by a single layer of flat- tened epithelium or mantle cells (Fig. 1685). Immediately outside the latter lies the stroma, in the interstices of which the young <;gg-sacs are lodged. The primary ova are approximately spherical and mea.sure from .035-.045 mm. in diameter in ordinary sections, but a third more in the fresh unshnmken condition (Nagel). They possess a finely granular cytoplasm, a centrally placed spherical nucleus, about .oiC mm. in diameter, and a nucleolus. The primary ova may remain for years, sometimes from early infancy to advanced age, practically unchanged, until they undergo either atrophy, as do most of them, or further growth leading, under favorable conditions, to the development of the mature sexual cell. Of the thousands of primary eggs contained in the ovaries just before puberty, only comparatively few attain perfection. Sooner or later, but at some uncertain time, the primary follicles enclosing ova destined for complete development enter upon a period of active growth, the eartiest indication of which is the con- version of the flat mantle celts of the egg-sac into a single layer of cuboid epithelium. In addition to increasing size, the growing follicles are distinguished by rapid prolifera- tion of the cuboid epithelium, which results in the production of a stratified follicular epUhe- Hum that surrounds the ovum. Outside these polygonal elements the stroma becomes con- densed into a connective-tissue envelope or theea (thcca follinli). Increasing in thickness, the latter is subsequently differentiated into two layers, an outer (taaica txuna), consisting of con- THF OVARIES. 1989 centric,.., '^r^r''^irn^Tr;^:fc:^i^i^ 'usTr'^^i^c^'^^Lr:^ ^'f^'t^^S":^^^^7^^^S^^ proceeding unUorm.y and affecting parauvely early and ong ^'"j '"V" invested with a protecting envelope-, the zona 5^S^er^^^£^^^ vac.o,r„':^r.iSk£=^''™ resulting clefu '.^"^ "^^^ » XXth^^TsupJ.'^ Wrc^nri;:^Li%roil.eration. vacuolation, accumulatmgflmd the/w«^^/^'^^«^^»'^^ ,„„ ,he surrounding blood-vesseU. "i'^n^^C.'t^unTlo ^Hch'L extent that U ««n occupies the greater part o. the and rel^^ ^^T^^^^U^J^^^^^ li-hich M St^« finTruptuC^atins a diameter o. .rem .-. cm. ormore. and appears on the Fig. 1687. Surface epitbeliimi— Prinuiry lollicli Then of follicle Zona pcllucida Ovum Section of ov»r>, sliowinK partially dev«lof»l Gnallan follicle. Cavity filletl hy liquor folliculi free surface of the ovary as a tense rounded elevation. After liberation of the ovum, the folli- cle is converted into the conspicuous corpus lutetim (page 1990). r „■ ,^ ^„„=i... Sin section, the wall of the ripe follicle, now known as *e (7r<»a;fa»>//.r/^, cons.ste of a wenT^.qped capsu.e or theca (from ..4-20 mm. in thickness) of which the outer ayer UaUmXtedXous^mbrane, and the inner tunic i''. «>'"P««^ "' '°^.' 7"""^, ^^ "3 contaWng numerous peculiar large i-ells which, as maturity approaches, exhibit J^aniUar^d a fSeflowish color Next the inntr layer of the caps.ite lies a delicate '"[^Xttl^; ^ganst theTnnersuriaceof which is applied the stratum granulosum, composed of the outer "E of the follicular epithelium that hound externally the fhi.d-spa« of the vesicle. A totve S always opposite the place where the follicle n.pt.,res (stigma), the stratum granulosum is S«d nto r^uncurated spherical mass of epithelial cells that projects mto the cavrty SK Uie li^r folliculi. This mass (n.ulu. -ph.™.) contains the egg and m. sect on SiT as a nx^K (discus proligerus) that encircles the zona pelluc.da and the enclosed ovt^in an^co^sUts of Two or thrT^yers of epithelial cells. Those next the .ona are elongate! with ?he rends directed towards the ovum pointed and prolonged into delicate Processes that ai^ auS toT^netrate within the zona pfllucida. The latter, from .007-J31 . mm. •" thickness, fs theWluct of the surrounding follicular cells and does not form a part of the ovum pr^r. ?te radW ^n° tions which the envelope sometimes exhibits (hence the name, z^« r«nieter of from .16-. 20 mm. Its cytoplasm, or vitellui, exhibits differ- entiation into a peripheral protoplasmic and a central deutoplasmic zone. According to Nagel, within the former are to be distinguished a narrow slight superficial marginal layer, apparently Fio. 1688. homogeneous and free from yoik-partides, and a finely granular zone containing mi- nut<> and scattered deutoplas- mic granules. The dark or central deutoplasmic zone is conspicuous on account of the irregular refraction of the enclosed yolk-particles that represent the important nutri- tive materials for the embryo contained in the eggs of birds and reptiles, but which in the mammalian ovum, especially in that of man, have been for the most part lost during the evolution of the higher types. Beyond a slight condensation of the surface, the presence of a distinct cell-wall, or vi- telline membrane, in the mam- malian ovum is doubtful. In the fresh condition the egg- cytoplasm is usually closely applied to the zona pellucida (Ebner), the narrow inter- vening cleft that is sometimes seen being the perivitelline space. Embedded within the deutoplasmic zone, and always eccentrically placed, lies the spherical germinal vesicle, as the egg-nucleus is termed. The vesicle measures from .030-.045 mm. in diameter, is bounded by a sharply defined double-contoured nuclear membrane, and contains xhe germinal spot or nucleolus (from .004-. 008 mm.) and the nuclear reticulum. Corpus LuteuRi. — The causes leading to the final rupture of the Graafian follicle are still uncertainly^ known, although in the light of later researches the older view, attributing the bursting of the ripe vesicle to mechan- ical overdistention induced by accumulation of the liquor folliculi, is inadequate. According to Nagel, when the follicle approaches maturity the inner layer of the theca becomes the seat of great activity. The blood-vessels in- crease in size and number and the cells undergo not only rapid proliferation, but extraordinary growth, the enlarged elements becoming filled with a peculiar yellowish sub- stance and transformed into lutein cells. In consequence of this activity, the formerly smooth theca becomes thickened and wavy and projects into the cavity of the follicle as vascular papilla and ridges. The encroachment thus effected gradually forces the contents of the vesicle towards the surface and that part of the dis- tended follicular wall possessing least vitality and resist- ance, until, finally, rupture takes place. Coincidently with the proliferation of the lutein cells, the follicular epithelium undergoes fatty change which results in the breaking down of the cumulus and the setting free oi the ovum, encircled with the cells of the discus proligerus, into the cavity of the ej^-sac. When rupture of the follicle occurs, the expulsion of the egg and the epithelial cells immediately surrounding it is followed by hemorrhage Almost mature human ovnm taken from fresh ovar\'. Ovum, with K«rmmal vesicle and spot, is encircled by clear xona pellucida, which is surroundetl by cells of the follicular epithelium. X 300. ( WaUryer.) Fig. 1689. -Corpus luteum :ament ovary Ovary has been laid open by lonaitudinat incision, exposlnx follicles and corpus luteum. THE OVARIES. 1991 .Central connective tiuuc into the cavity of the former egg-sac, which now becomes converted into a corpus The latter long known as the corpus luteum verum when associated with preg- nancy grows to huge dimensions and forms a conspicuous oval mass that may approid 3 cm. in length and occupy a considerable part of the entire cortex. When impregnation does not toke place, the yellow body (now called the ayrput luteum s^rtum) is smaller, seldom exceeding 1.5-2 cm. m diameter. The classic distinction of "true" and "false," apart from difference of size, has no anatomical basis since both foiros possess identical structure. The a.ssumption that the presence of a 'large corpus luteum is positive proof of the existence of pregnancy must be accepted with caution, ince yellow bodies of unusual size are sometimes obser%ed in °^*":^ortly"!§ter the rupture of the follicle and the replacement of its contents by blood, the opening in the wall of the egg-sac is closed. The rapid proliferation and growth of the lutein cells pro- duces an irregularly plicated ^''G- '<»9o. wall of increasing thickness z^JirMi that encloses the remains of the degenerating follicular epithe- lium (granulosa) and invades the hemorrhagic mass. The latter is gradually absorbed until, finally, the encroaching projections of lutein ceUs and connective tissue meet and the cavity of the follicle obliter- ated, its former position being subsequently indicated by a central core of connective tis- sue. The cells of the stratum granulosum, the original epi- thelial lining of the egg-sac, entirely disappear and take no direct part in the formation of the corpus luteum, their function during the develop- ment of the Graafian follicle having been to contribute the liquor foUiculi (Schottlaender). Along with the proliferating masses of lutein cells, strands of connective tissue are car- ried inward from the theca, whereby, after a time, the yel Blood-vesKis Section of human corpus luteum. X To. wnereoy, ;uier a iimc, mc yti- .. , , » i »!,«;.. low body becomes broken up by numerous radially disposed vascular septa and their prolongations. With the production of a solid corpus luteum and the absorption o! the blood (evidences ot which latter for a long time remain as hematoidin crystals), the active rdU of the lutein cells is finished. These elements now lose their distinc- tive vellow pigment {lutein), undergo fatty metamorphosis, and finally entirely tlis- appeai . With the subsequent shrinking and decrease in the vascularity of the corpus luteum, the connective tissue, which now constitutes the entire mass {corpus fibro- sum), undergoes hyaline change, becoming clear and non-fibrillar. In consequence the ating corpus luteum loses its former appearance and is transformed into an irreg- ular body, light in color and sinuous in outline, sometimes known as the corpus albicans (Fig. I691). This gradually suffers absorption, but remains for a consider- able time, especially when associated with pregnancy, as a conspicuous hght corru- galed area within the cortex, the last traces of its scar-like tissue hnally disappearing in the ovarian stroma. The greatly increased vascularity, within the wall o the ripe Graafian follicle and later around the corpus luteum, subsides as the ye.low .xiay if "^ \\\\ 1992 HUMAN ANATOMY. underg^oes regression, until all the new vessels concerned in its nutrition have disap- peared and the circulation of that particular part of the ovary is permanently reduced. The function usually ascribed to the corpus luteum is that of filling the empty follicles and thus restonng the eq^uilibnum of circulation and tension. Clark ' regards the corpus luteum as a preserver of the circulation, since, when performing its hinctions most perfectly (durine the eariier years of menstrual life), it effects the elimination of the eflete follicle and tl4 superifuous blood-vessels without leaving dense and disturbing scars. Later in life, however, when the oyanan stroma becomes denser, die corpora lutea are less efficient and are incompletely absorbed, their remains impainng the circulation until, finally, the follicles are no longer matured anJ ovulation ceases. The origin of the lutein celk has long been a subject of discussion, and even at present two opposed views ^re the support of eminent anatomists. According to the older theory, advanced by Baer, diese celU are modified connective-tissue elements, derived from die pro- Fic. 1691. Corpora lutes ^ of corpora lulca Sectiona of Fallopian tube Cron-Mction throuKh ovary, ovidact, and part o» broad ligament. X 6. hferation of die cells of the inner layer of the theca folliculi. The other view, formulated bv Bischoff, rtwards die lutein cells as modified follicular epithelium. In the foregoine sketch 0I the corpus liiteum, the lutein cells are ascribed to die dieca, a conclusion based up^n the con- vincing observations of Nagel, RabI, and Clark, and confirmed by the writer's bwn studies .sobotta, on the odier hand, is most positive in his support of the follicular origin of the lutein ceMs, oaseu upon an exhaustive investigation on the ovaries of the mouse and rabbit The not be otS chafl'"'"*^ corpora lutea in the earliest stages places the conclusions as to man Vessels.— The arteries supplying the ovary are four or five branches that arise from the anastomosis of the ovarian artery with the ovarian branch of the uterine. The trunks {aa. ovarica propria) given dflf from this anastomotic arch pass to the ovary between the layers of the mesovarium and, entering through the hilum as closely grouped tortuous vessels, reach the medulla. According to Clark,' whose descnption is here followed (Fig. 1692), immediately after gainii^ the medulla each stem divides into two branches, the medullary or parallel arteries, that proceed in a threct course towards the opposite free margin of the organ, lying just beneath the corte.\, to which they distribute cortical branches at regular inter\'als. In their course to the periphery the cortical branches, losing the characteristic corkscrew-like twist- '"<^i, 1 parent stems, supply hundreds oi follicular twigs to the e^-sacs, each of the latter being provided with a rich vascular net-work anastomosing with irwo or more follicular branches— an arrangement of great importance in assuring an adequate blood-supply for the growth of the follicle (Clark). At the penpherv, the cortical arterioles pass into the veins through an intervening capillary net-work. .'.■^'^''i^'- '^"**- "• Physlolog., Anat. Abth., 1898. 'Welch Anniversary Contributions, 190a THE OVARIES. 1993 Fig. 1691. Superficial •naMoffloM* The vrins follow the general arrangement of the arteries within the cortex and m«lulla • the oairs of parallel veins, however, do not unite into single stems, but Il"g^fmm th^Sum ^independent tortuous trunks Within the nK-sovari«m they a^ [nterwoven with the bundles of involuntary muscle, and when distended present a conSuous venous complex (bulbus nditterent germinal ridge which is early formed on the median surface of '^e Wolffian b^^^^ (page 2038) Whether, as usually accepted, the ova in common ^1*^ /^e folhcular SeUum are direcdy derived from the modified mesothelium (germinal epithelium) covering the sexual ridge, or are the descendants of germ-cells eariy set apart from the somatic cells for the special r61e of reproduction, remains to be decided, al- though evidence in support of this latter hypothesis— the continuity of the germ- cells— is accumulating from obser\'ations on the lower animals, in which the origin ol the orimordial sex-cells is less obscured. . 1 • j Kiman embryos of 12 mm. in length, among the cells of the germinal ridge certain elements are already distinguished by their ««PV«"»';i!;t*"^;^!;«^' ^'X nuclei. These are the primary sexual cells, ihi^prtmordtal ova ( F g. «7i7). "dually regarded as originating from the transformation of the germinal epithelium At fiTthe latter and the subjacent stroma of the Wolffian body are well d««e.^n tiated from each other. This demarcation is soon lost in consequence of the a^^tive inter- growth which takes place between the proliferating germinal epithelium and the in- growing vascular a.Lective tissue of the Wolflfon body-the two chief factors in the histogenesis of the ovar) . u 1 ,.., K„ th^ mn- As the mass of epithelial elements increases, it becomes broken up by the con nective-tissue strands into large tracts, composed of the primary ova surrounded Dy Arteria propfia Oiarian artery Ovarian veins Diagram iUuatraiinganangernentuf blood- vcMelsof ovar>-. (Ciart.) I" 1994 HUMAN ANATOMY. IT. .7titudes of the smaller and less specialized cells of the germinal epithelium. The larger tracts are subdivided into smaller spherical cell-segregations (the egg-balls of Waldeyer) by the continued intergrowth and mutual invasion of the tissues, and the " e^-balls, ' in turn, are broken up by the same process until the final division results m the isolation of the ultimate groups, the primary follicles, that include the primary ova surrounded by a single layer of flattened germinal epithelium. In places the larger compartments are cylindrical and attached to the germinal epithe- lium, appearing as solid outgrowths connected with the surface ; to them Pfliiger gave the name ' ' egg-tubes' ' and attributed an aggressive invasion. Since the con- nective tissue of the Wolffian stroma first invades the deeper'stratum of the germinal epithelium, this region, the fu- FiG. 1693. ture medulla of the ovary, is Gcimimi epiuwiiom subdivided into the ultimate Mmordiaiovnm groups of cells, the primary fol- licles, earlier than the more su- perficial and younger layers, this genetic relation being seen in the fully developed ovary, in which the youngest and least mature follicles always occupy the peripheral zone. The most superficial stratum of the ger- minal ridge remains as the ger- minal epithelium that covers the exterior of the ovary and replaces the usual peritoneal mesothelium plates. The details of the trans- formation of the prir, ary folli- cles, consisting of the ovum and the investing single layer of mantel-cells, into the ripening Graafian follicles have been de- scribed (page 1988). Of the thousands of primary follicles within the young ovary (over- estimated by Waldeyer at 100,000 in the two ovaries of the new-born child) very few reach maturity, and by advanced life nearly all have disappeared. This reduction begins during intrauterine life and first affects the fol- licles situated within the deeper parts of the ovary destined to become the medulla, from which the ova are later entirely absent. The remains of these early follicles probably account for certain of the minute epithelial bodies occasionally seen in the medulla of young adults. Section of developinif ovaty from hummn embo'Oj ersp-owth netween srerm ■ stroma tissue Jerivetl from Wolntaii bfKly siiowinfc interernwth I Tmmal epithelium and Numbers of follicles within the cortex also are continually undergoing destruction. This affects especially thu primary follicles while they lie naked within the stroma, and are unpro- vided with a theca, thi; ovum undergoing hyaline degeneration and, along with the mantcl- cflls, finally entirely disappearing within the ovarian stroma. Beginning in the young ovary long Ijefore puberty, as well as throughout the period of sexual maturity, certain egg-sacs are continually transformed, moie or less fully, into Graafian follicles that develop to a certain stage .ind are then arreste,e Vound iuament (the homoloRue upon the ,»oasma«nus muscle; VX*^ e wee^K SL"pa%^^^^^^^^^ through the ofthe eenito- ngumal hgamen u the "^KP»K^,=^>^S„Pf-S rtie aclult are commonly a.^- ||^Sib£S^eb^«%rch^ont?^-r^^^^^^^ PRACTICAL CONSIDERATIONS: THE OVARY. Since the ovaries project below the Fallopian tubes from the V°^f^\ s"rf»<^^ ^ the bSl K^ments. in s^king for them in abdominal operations the hand should be Jl^sed outSlrom the posterior surface of the uterus along the broad ligament, on *^'^i?Us usual position the long axis of the ovary is approximately vertical its externalTurface lybg against the pelvic wall close to the obturator vessels and nerve. TJiP iiretfr and uterine artery lie behind and below it. .,.,•£. SA of he ovary 4urs most freq. ■ .dy as the result of subinvolution after labor tColution is in any way arrest^ or rendered i-^^P''*-^' J^ofX ^^^ favorable f ^r prolapse of the ovary will be present. -increased weight of the ovary and relaxac")n and lengthening of its attachments. .... -, „„...„,ii„ The left ovary is more frequently prolapsed than the right, because .t normally become! more enkrged durinrpregnancy. and therefore suffers more from subinvolu- l^n and b<^ui X arrangement of the veins on the left side is such that venous ™donr"e^ liable to^'occur (Penrose). An analogous anatomical condition exEo that which, in the male, favors left-sided varicocele, the eft ovarian vem emptying into the r^nal vein at a right angle, wi.^le the right ov^nan vein empties '"" fn\rpi:«;roCrth" :r^n te'^ouglas^s pouch Het.v.en the rectum and the p^ten^? vaginal ^W. There is apt to be pain on walking, because the ovarv is SenCmpressed between the cervix and the sacrum, and on coitus or defecation. 1996 HUMAN ANATOMY. because of direct trauma. The pain is often nauseating and may be felt in the breast on the same side. In spite of its small size the ovary gives origin to a great variety of tumors and cysts which may grow to enormous proportions, filling and distending the abdomen. As they grow they at first crowd the uterus and other pelvic structures towards the opposite side ; later they ascend into the abdomen, drawing the attached structures upward with them in their pedicles. The pedicle is the base of attachment, and consists of the same anator' Sixinoid flexure -Rectum I'lero-sacral liKament -Left ovary -Liltament of ovary -Oviduct t -.Round IJKamenl -I'leru^. fundus Bladder'^ Pelvic orpins of youni^ woman, viewed from above and in front; hardened in situ and un' laterally, in relation to the inner surface of which it ends after numerous windings. The entire length of the tube is about 11.5 cm. ('4,'/^ in.), although variations from 6-20 cm. (^2^-77/^ in.") have been observed. Emerging from the lateral angle of the fundus uteri, in the immediate vicinity and just above the uterine attachments of the utero-ovarian and round ligaments, the first part of the tube is narrow and THE FALLOPfAN TUBES. 1997 comparatively straieht and constitutes the hfimus {Mhmm tubaeuterinae), about .35 cm ( I *i in. ) in length and from 3-4 mm. in diameter. Throughout the succeeding 8 cm U^ in. ) of the tube, known as the ampu//a (anpiilla tubae uteriaae), the diameter Kradually increases (from 6-H mm. ) until the canal suddenly expands mto the terminal trumpet-shaped infundibulum. The margins of the latter are prolonged and slit up into long, irregular processes. the/tmM>, from 10-15 mm. m length, the resulting fimbriated extremitv of the tube resembling, when exammecl m fluid, an ex- panded sea-anemone (Nagel). One of the fimbria: ( fimbria ovarica) is usually longer than the others, attached to the free border of the mesosalpinx and stretches towards the ovary, the tubal pole of which it often, but by no means always, reaches, llie lumen of the oviduct varies greatly at different points. Beginning at the lateral angle of th- uterine cavity as a minute, inconspicuous opening (.ostium uterinum tubae), commonly i>bscurcd by mucus and about i mm. in diameter the canal traverses the uterine wall fpars uUrlna) and gains in size and longitudinal folds so that on crosa. section the isthmus presents a stellate lumen. Within the ampulla the plications of the mucous membrane become progressively more markwl, appearing in transverse sections as a complex figure of primary and secondary folds ( Hg. 1695) »/'*» Rf^")' encroach upon the calibre of the tube. The folds are continued mto the infundibulum and onto the inner side of the fimbria. The outer or ovanan end of the oviduct opens direcUy into the peritoneal cavity by a small aperture (ostium abdomlnale tubae). 2 mm. or less in diameter, that lies at the bottom of the infundibulum and is produced by local contraction of the muscular tissu • of the wall of the tube, a special sphincter, however, not being demonstrable. The mucous lining of the oviduct is continued from the infundibulum onto the fimbria, the line of transiUon into the pen- toneum following the bases and outer sides of the fringes. The excepUonal relation of the tubal lining to the serous membrane, this being the only place in the body where a mucous tract opening onto the exterior communicates with a closed serous sac, b referrible to the similar original relation of the embryonal Mullenan duct from which the Fallopian tube is directiy derived (page 2038). Course aiid Relation*.— Since each Fallopian tube occupies the free border ol the broad ligament, changes in the position of the uterus affect the course of the oviduct. From the upper angle of the uterus the tube may. therefore, first pass out- ward towards the ovary in a strictly transverse direction, or describe a gentle forward or backward curve, depending upon the position of the fundus uteri, this part of the tube, however, never being tortuous. On gaining the uterine or lower pole of thie ovary, it there bends upward and winds obliquely, from below upward and backward, across the median surface of the ovary, close to the antenor border and tub^ pole, to the convex posterior margin, where the tube bends sharply downward, its fimbriated end being in relation with the lower and back part of the median surface. When in its usual position, the ovary is, thus, partly covered not only by the tortuous oviduct itself, but also necessarily by the mesos^pinx in which the tube lies, so that when viewed from above the ovary is often entirely hidden by the Fallopian t ibe and the attached portion of the broad ligament. In consequence of this arrangement, the ovary is partly surrounded by a hood of serous-membrane and lies within a pocket, known as the bursa ovarii, which may facilitate the entrance of the hberatwi ova into the FaUopian tube. In its course from the uterus to the ovary the oviduct lies in front of and generally parallel with the utero-ovarian ligament and is overlaid by the coils of the small intestine. As the tube ascends and arches over the ovary, tlie intestinal coils cover its medial surface, the sigmoid colon also occasionally being m relation on the left side. In formalin-hardened subjects, with otherwise normal pel vie contente, we have so often found the termination of the Fallopian tube lying away from the ovary, that Merkel's suggestion, that the assumed constant close relation between the fimbriated extremity and the ovary may sometimes, at least temporarily, be wanting during life, seems well founded. Structure— The wall proper of the Fallopian tube, consisting of the mucous and muscular coats, lies embedded within the loose connective tissue of the oroad ligament {tunica odvenHtia) surrounded by the peritoneum, which completely invests the tube with the exception of the narrow interval through which the tubal vessels and nerves pass. The wall is thickest and firmest in the isthmus, less so in the i 13 199« HUMAN ANATOMY. Epilbcliam ampulla, and thinnest and most relaxed in the infundibulum and fimbr!^. The mucous membrane is thrown into longitudinal folds, which increase from 5-15 low rid(res in the commencement of the isthmus to double the number in the ampulla, where they attain a much greater height as well an complexity of arranf^ement, the main folds bcin^ supplemented by secondary and tertiary ones, so that in transverse section the lumen ap|iears almost occluded by branching villus-like projections. The surface of the mucosa is covered with a single layer of columnar epithelium (from .015-.020 mm. in height; provided with cilia that produce a current directed from the infundibulum towards the uterus, and thus, while facilitating the progress of the ova -long the tul>e, retard the ascent of the spermatoroa. Thf elaborate plications and receswes within the outer jiart of the ampulla favor the temporary retention of the sexual cells and thereby promote the chance of their meeting, fertilization usually taking place within this part of the tube. The vascular connective-tissue stroma of the folds, which in the Fio. 1695. chief plications may reach a thickness of . 3 mm. , within the acces- sory folds is reduced to a narrow interepi- thelial layer in places measuring less than the height of the covering cells. The tunica pro- pria of the mucosa is directly continuous with the intermuscular connective tissue, and, with the exception of a few bundles prolonged into the deepest part of the mucous mem- brane, does not contain muscular tissue. The muscular coal, most robust towards the uterus and thinnest at the infundibulum (therefore the reverse of the arrangement of the mucosa), includes an inner circular and an outer longitudinal layer of involuntary muscle. At the isthmus, where the firmness of the tubal wall depends chiefly upon the muscular coat, the circular layer is the thicker (from .5-1 mm.) and the hmgitudinal one repre- sented by an incomplete stratum of mu.scle-bundles. Towards the infundibulum, on tiie contrarj-, the longitudinal layer is beiicr developed, the circular-muscle being reduced to . 2 mm. or less in thickness. The surrounding fibrous tissue, sometimes retfardef oviduct near iiutrr md of ampulla, y 35 PRACTICAL CONSIDERATIONS. FiiLi TIBES I9«W formed numerous twig» are Kiven off to the wall of tiw- ull..,)ii«i tuU- *wd to iIh- mesosalpinx Those distributed to the .ividuct jiain tb^ -.i^ aU.nn; ii^ n..TOt>«nt«.i»eaf tract between the iM.Titoneal reflecti.>n and. piercing the *a»i break «p iwt.. capiUary net-works within the muscular and mucous cf«it^ H.- «»- « lnc^ beRin within tne walla ol the tube, especially between the mutcukr layrrs ..n») =*« a sul^^rous net-wortc. follow the uteries and become tribuUry to Ixrth the ui.-m:- iml ovanan trunks. The lymphatia, alter emerjnnK frvmi th.- wall , .Ik- i-.nn threr „r i.mr stems that accompany the blood-vessels and pa.* in i r tl.* attaclH^ U««l.r ..f the ovary. For the most part they follow th.- n ariar ,-»»ph»i..H thr..iiKh ;.»• sus- nensorv Wament to become finally tribuUr% to the lumwar ivmph-.i.«i» sun-^wiidii^ ihe aorta It is probable that !«>me of the lymphatics .irf tl»- tube co«m«nicat«- with those of the fundus uteri (Poiricr, Bruhns). , , j u The nerves supplying the Fallopian tube, numen .« ,\v\ chirtly >vmpaThetic fibres follow the arten and. therefore, reach the oviduct ir<«n lx>th the .narian and the uterine plexus. Within the subserous tissue they form .i pttntu^l pu-xus ivnm which twigs penetite the wall of thf caiwl antl are diwril»«ed ,)nnci|«i«y to the ~ '^_ . ci ^ .„!.:„.. ..-.r* ;« tlw r . I. •on ol a subepUhelutl ptexui ill. t of the oviducw is '11 c!i:'j> (|K»ge 2o.^S), the • i:ir III ! ■! abdominal open- V tic^Av ..vity or ccelom ^ is ..e fifth foetal month. muscular tissue, soi. '■ filaments uking p;irt in the j within the mucous mt Hrane (Jacques). Development aud Change*.— The earl) directly associai-^d with that of the embryonal Mu unfused portions of which the tubes rei)reseni. Thv ing (the persistent original evagination from the p at first cushion-like, but soon exhibits indent;..ioBT > .- , ^ ■ . develop into distinct fimbria. At birth, while smal er, the latter possess their charac- teristic appearance and are lined by ciliaten of the MiiHerian ducts. Retention of the fcetal tortuosity, stunted lU , elopment . r entire absence ni.iy affect one or iM.tn tubes Complete doublinR of the oviducts m.n , giving rise to a.n,rt.>pic gestation (tubal pregnancy ). Such pregnancy ma\ occur in the ampulla,— th<- most usual place. — in the infundibulum ( tubo-ovarian pregnancy \ or in the intra-mural portion of the tube, — i.e., that part traversing the wall of the uterus. ^1 3000 HUMAN ANATOMY. The chief causes of tubal pregnancy are pathological or abnormal conditions of the tube. The more important of these are: (a) congenital, such as exaggerated con- volutions, diverticula, and atresias ; {6) sagging and attachments by adhesions dis- torting the tube ; (c) pressure from surrounding structures ; (d ) thickening of the tubal walls, interfering with peristalsis ; and (e) destruction of the cilia or narrowing of the tube following salpingids. Complete occlusion of the tubes of both sides would result in sterility. The great danger of ectopic gestation is that of hemorrh^e following rupture of the tube by the growing fcetus. This will occur some time prior to the fourth month, and may be intraperitoneal, — i.e., direcdy into the pentoneal cavity ; or extraperitoneal, — ' e., downward, cleaving the layers of the broad ligament, and finally rupturing the tube within the layers of the ligament ; or, in case the pregnancy is "mterstitial," the rupture may be intrauterine. The intraperitoneal rupture usually takes place before the seventh week ; the extraperitoned usually from the seventh to the twelfth week. If the foetus should survive the primary rupture in the extraperitoneal variety, secondary rupture into the general peritoneal cavity may occur later, and the ovum may go on to full term within the abdominal cavity. The Fallopian tube offers a passagewav in the opposite direction for the entrance of infections, especially gonorrhoeal, from the vap;ina and uterus into the peritoneal cavity. When inflammation involves the tube, it is followed soon by a closure of the fimbriated extremity, the fimbriae adhering to each other, to the ovary, or to some adjacent peritoneal surface. Later the uterine end of the tube also closes, and the pus which results from the infection now accumulates within the tube {pyo- salpinx) and may gready distend it. If the infection is gonorrhoeal, such a pus-tube without rupture is frequently unaccompanied by acute symptoms. Slight ruptures with leakage into the peritoneal cavity followed by sharp attacks of localized pelvic peritonitis often occur. A large rupture may give rise to a diffuse septic peritonitis, although the danger of this result in a case of chronic pyosalpinx, even if of enormous size, is far less than after acute gangrene of the appendix with escape of a relatively minute portion of its contents. In the former case a certain degree of immunity has probably been esublished during the slow formation of the pyoulpinx (Binnie) ; and moreover, in many such cases (6i per cent, Penrose) the contained pus has become sterile. When the inflammation 's of a mild grade the accumulation may be of a serous cliaracter {hydrosalpinx), and may become so large as to reach half-way to the umbilicus. If hemorrhage occurs mto the tube it is called an hamalosalpinx. The proximity of the right Fallopian tube to the appendix should be recalled, as salpingitis on that side has not infrequently been misUken for appendicitis, and rice t-ersa. The right ovary is often connected with the meso-appendix by a fold of peri- toneum, — the appendiculo-ovarian ligament ; and it is stated that the fact that this fold often contams a small artery which gives an additional blood-supply to the ap- pendix helps to account for the relative infrequency of appendicitis in females. RUDIMENTARY ORGANS REPRESENTING FCETAL REMAINS. The development of the reproductive organs (page 204J) emphasizes the fact that whereas, in the male, the Wolffian body and its due; play a very imporUnt r61e in the production of the excretory canals for the sexual gland, and the Miiilerian duct remains rudimentary; in the female, the converse is true, the Mullerian ducts forming the excretory can^s — the tubes, the uterus, and the vagina — while the Wolffian structures arc secondary in importance and give rise to only rudimentary and (unc- tionless organs, situated chiefly m the vicinity of the ovary and Fallopian tube between the layers of the broad ligament. These ffetal remains include the epoophoron, Gartner s duct, \\\^ paroophoron, and the vesicular appendages, which may be appro- priately described in this place. The Epoophoron. — This riidimentary organ, parovarium or or^an of Kosenmiiller, lies tx-tween the layers of the broad ligantent (mesosalpinx) m front of the ovarian vessels, in the aresi bounded by the ampulla of the oviduct, the ovarian fimbria and the tubal pole of the ovary. It is quite flat, triangular, or RUDIMENTARY ORGANS. MOI tnoezoidal in outline, and measures from 2-2.5 cm. in length and about 1.75 cm. STS h ^nsb^ of from 8-20 narrow wavy canals, which beg.nn.ng with d<^ Mid diKhUy expanded ends, diverge from the vicnity of the Tnlum of the nv^a^ ioin dmostTrieht angte, a common chief duct that lies close and paraUel to rfTeT^duSan'STriXe sLuer tubules the relation of the backof a comb to i^ t^ The transverse tubules (ductali transver^l). the remams of the sexual mbSd the WoE body, may extend as far as the hilum. or. as m the young SSd evcn^netStVbto the medulla of the ovary and be continuous with the rudi- Sk^meSX^ tubes therein found, since the latter, as well as the transve«e ^n^them»dv«. are vestiges of the same embryonic structures. The common onritud^SS^ (d^.epoo?hori iongitudiiuiUs), cfosed at both ends. « a pen«stent Sn ofArK>l£nudr From iS embryological relations it « evident that the KSpSi^on U homdious with the epididymis (the transverse tubules corresponding n.e durtuU efieren^ and the coni vasculosi. '"^ »he long.tud.^ *act to th^ ^ of the epididymis), since both are direct derivaUons from the Wolffian tubiUoi ^dCct iSe ^rectVture, when in its normal position ^f" .jJ'^r^PS the longitudinal duct is ^proximately vertical and hes paraUel with the FaBopian Epoopborun U« Miu-t OMiam abdominmlc Licai uT u Flu. 1696 LtKament Cavity of olovao utcTUa Oviduct laid open Epoophorun InluDdibiilum Hydatid nf MoripiKn' Flmbrte Fimbi;! ovaries R.Hind liKamcM RiKht o>.iry Rouiiil liKam.ol Broad linamcnt VaKin* tube, while the transverse tubules are horizontally disposed. The chief duct may be interrupted and connected with the secondary tubules in groups, or on the other hand, it may be prolonged as Gartner's duct (page 2043) ^.r beyond its usual length In the child, the transverse tubules, from .3-4 mm. In diameter, usually possess a lumen throughout their entire lengtl,. but later in life the minute canals niay undergo partial or complete occlusion and may be the seat of cystic dilatations. T»^*^ *^'* ™ ihe tubules and duct consist ot :>. fibrous coat, which sometimes contains bundles of involuntary muscle, lined by a single layer of epithelial cells ^jj^ /'»«> 1" '«"". "^^^ low cuboid to columnar, and in places, or occasionally in the adult "^n^ frequently in the child, bear cilia. The epoophoron is most satisfactorily demonstrated by ho.ding tht stretched mesosalpinx against the light : it is more conspicuous in the broad li|^- nicnt of the young child on account of its development and the greater transparency of the overlying tissues. In common with the sexual organs, the epoophoron 'ncreasw during the years leading to sexual maturity and atrophies in advanced age. Uuring preenancy It is said to lie unusually vascular (Merkel). Oartner'8 duct results from the more or less extensive persistence of portions of the Wolffian duct that usually disappear by the en.l of foetal ife and is. therefore, a continuation, direct or interrupted, of the longitudinal canal of the epoopnoron. Although by no means consUnt and often tepresented by only a short atrophic 126 11 I 3003 HUMAN ANATOMY. segment, the duct is present in about twenty per cent. (Merkel) of adult subjects, in children being relatively better developed. When complete, as it exceptionally is, the duct continues from the epoophoron along the Fallopian tube to the hindus of the uterus, then descends within the lateral border of the uterus, between the vessels, and sooner or later (usually in the lower part of the body) enters the uterine muscle. As it traverses the cenix, the duct becomes more and more medially placed until, in the supravaginal segment, it approaches the mucosa. The duct then assumes a more lateral course, and in the vagina descends within the muscular coat, at first along the side and lower more on the anterior wall, to end blindly in the vicinity of the hymen (R. Meyer). Such complete persistence is, however, very unusual, Gartner's duct being most frequently represented in the lower part of the body and the upper part of the cervix, less oftfen in the cervical segment alone (Maudach). The canal is lined by a single layer of columnar epithelium and beset with lateral diverticula, uncertain in number and form, which in the lower part of the duct are often short-branched tubules that resemble glands. Accumulations of secretion within the tubules or the duct may lead to the production of cysts. The Paroophoron. — Under this name Waldeyer described an inconspicuous rudimentary organ, distinct at birth, but usually disappearing, and only exceptionally reUined after the second year, that lies between the layers of the mesosalpinx medially to the epoophoron and, therefore, nearer the uterus. It consists of a small, flat, irregularly round group of blind canals, which represent the remains of Wolffian tubules. The accuracy of Waldeyer's assumption that this organ is homologous with tiie paradidymis (page 1950) has been challenged by later mvestigators (Aschoff, R. Meyer), who have discovered similar groups of rudimentary tubules within the lateral part of the mesosalpinx near the division of the ovarian artery, in a position corresponding to that of the paradidymis. It is to this group, therefore, that the term, paroophoron, may be applied with greater propriety, although there can be little doubt that both sets of tubules are deviations from those of the Wolffian body. The tubules are blind, lined with columnar epithelium, and in places resemble the tortuous canals of the Wolffian body. Apart from their interesting morphological relations, they may become of importance as the seat of cysts. Vesicular Appendages. — Under this heading are included the little vesicles or hydatids (appendices vesiculosi ) attached to the broad ligament by longer or shorter pedicle.;. Tii»!se structures present two general groups, the first including the con- s;)icuGU..!i)n;f -stalked hydatids of Morjjagni, and the second the smaller vesicles, vary- ing in f,)nr. and size, conni cted by short steins. The hydatid of Morgagni, present on one or both sides in tilty \tcx cent, or over of all female subjects, is a spherical or pyrifomi thin-walled sac, that contains a ciear fluid, and usually measures from 4-8 mm. in diameter, but sometimes much more, and is attached by a slender stalk (from 1.5-4 cm. '" length) to the anterior surface of the broad ligament. Traced towards the latter, the stalk crosses the ovarian or other fimbria- without being attached and sinks into the mesosalpinx about i cm. from its free border, from which point it may be followed through the broad ligament to the upper end of the main or longitiid-nal duct of the ejx)o|)horon, as the continuation of which it may be identified (Watson). In structure the hydatid consists of a fibrous coat, lined by a layer of columnar epithelium and c<- vered extem.-illy with a d.^licate prolong.itioii of the peri- toneum. The smalli-r vesicles, present in aix)ut twenty |«.'r cent. ( Ros.s;i), often num- fier two or thrci on each side, and are attached to the anterior surface of the mesosal- pin.x, usually over the epoophoron. They are fouml at birth and even in the foetus, as well as later in life, in advaucetl age undergoing atrophy The origin and mor- phological si^ni(i<'ance of the vesicular afipendages have occasione'--«lf -/^^^.^irdr ' 1^^^ it. thir-lcnpss iboiit 2 ■; cm (I n. ). In women who have borne chinir».n, me uierus Sdom'^quTe rSHmsM its virgin size, but shows a permanent ""^^^ f,*^^"'^^,-- in its various dimensions, except in the cervix, which is relatively shorter than before. The convex upper extremity of the organ, above the level of the entrance of the Fallopian tubes, is known as \.\ic fundus (fundus uteri), which in front and behind passes into the anterior and posterior surfaces and at the sides into the lat- eral borders (margo laterales). Of the two sur- faces, the anterior (fades Ttaicalbi) is the more flattened and less convex and only partially cov- ered with peritoneum, while the more rounded and projecting posterior surface (fades intesti- nalls) is completely invested with serous mem- brane. The lower end of the cylindrical cervi.x. flattened somewhat from before backward and slighdy tapering downward, is divided by the attachment of the sui rounding vagin.il wall, which it seemingly pierces, into a free lower seg- ment (portlo vaginalis), that projects into the vault of the vagina, and an upper one above the ring of attachment (portio supravaginaHs). Be- low, the vaginal segment of the cervix termi- nates in thick, rounded, and prominent lips that bound a sunken opening, the external os (ori- fidum exteruum uteri) that marks the lower liinit of the cervical canal and is directed towards the posterior vaginal wall. Owing to the horizontal position °* f^.*; "7^.- '^^'^ . m^^^^^ anterior /,>> (labium anterius cervids) is shorter and somewhat lower than the oxer hanging posterior lip (labium posterius cervids ). ,„-.mmes ( 1 '^- The weight of the virgin uterus vanes between forty and fifty gnimme^ ( 1 3 i^i oz. ). that of the organ after pregnancy being about twenty grammes ( .7 oz. ) """"The ravitv of the uterus is small in com,x..-ison with the size of the organ and the thickness of its walls, and differs i.i form according to the pUtne of ''•'c Uo v In L'gi tal section, it is little more than a narrow cleft separating the oppc>sed .m enor and posterior walls, and mea.s„res atx>ut 6 cm. (2-^ in. ). "'j'^lf^ .^5 c hr n out belongs to the cervix. In frontal section, the cavity of the bodv .s ""^"^^ ""^ "^ '^^J. line (Fig. 1A98), the apex l^^ing below, where the up,>er end of the «* ^''V '' J;^^,^.^' vix passes into that of' the ImkIv, and the has. above, '-'t^^een the tubal ..rihc^ which mark the iater.al angles. The sid« of the triangle are not straight »^" ^''-^^^^^^'^J^^ to the itnvard curve of the thick projecting uterine walls. The greatest transNtrse width ..f the cavity of the b^Kly, just below the tubal openings, is ^^^xnit 2 S cm_ The canal of the cerx'ix (canalis cervids uteri ), as the lower segment o t..^ uterine cavity is called, is fusiform in longitudinal sections, In^in^^ widest mulwav ^-tY,?," ^^ external os below ami the somewhat smaller and more circular '"t«;f"f' ^, '""J^^^^^ internum uteri) above, where the contracted lumen of the virgin uterus expands into Vagina nerll* lal.l open bv raiciltal.Kecti.m. nhowing r»vil> ami relation* of labia to vaitina. 11 '• 'J I'll l|ti 3O04 HUMAN ANATOMY. Ovidnct the cavity of the body. In cross-section the canal appears as a markedly compressed oval. The position of the internal os corresponds with the slight external constriction (iitfraiui uteri) that uncertainly marks the neck from the body of the utenis. In contrast to the smooth mucous surface of the body, that of the anterior and posterior walls of the cervical canal is marked by conspicuous ridges (plicae palmatae) — the arbor vitie tUerinte of the (V ivr writers — consisting of a chief median longitudinal fold from which numerous sec' I'lary rugae divert upward and outward on each wall. Attachments and Peritoneal Relations. — In addition to the Fallopian tubes that embryologically are direct continuations of the component Miillerian ducts by the fusion of which the uterus is formed, the uterus is connected with the ovaries, the abdominal wall, the lateral and posterior walls and the floor of the pelvis, the vagina, the bladder, and the rectum by fibro-elastic tissue, muscular bands, and peri- toneal folds. Most of these attach- Fic. 1 698. ments, or so-called ligaments, however, have little influence m supporting the uterus, but, owing to the intimate con- nection of the cervix with the vagina, and thus with the pelvic floor, and with the sacrum by fibro-muscular bands, the lower segment enjoys a relatively fixed f>osition ; the body, on the con- trary, being freely movable. The Broad Ligament.— ^'nYi the exception of a narrow strip along the sides betAveen the layers of the broad ligaments, the body of the uterus is completely invested by peritoneum. The cervix, on the contrary, possesses a serous covering only behind and at the sides above the attachment of the vagina. From each lateral border of the uterus this serous investment is reflected to the pelvic wall and floor as a conspicuous transverse duplicature of peritoneum, the broad ligament {\i%% amcatum latum), that passes across the pelvis and encloses between its layers the round and ovarian ligaments, the Fallopian tube, the epoophoron and the paroophoron, together with the associated vessels and ner\'es. Although enclosed by a peritoneal duplicature continued from its posterior surface, the ovary is attached to, rather than lies within, the broad ligament. When detached from the pelvic wall and floor and spread out ( Fig. 1699), the broad ligament is wing-like in form and has four borders, of which the median or uterine is vertical, the upper or tubal is horizontal, longest, and free, the lateral short and approximately vertical to correspond with the plane of the pelvic wall, and the lower sloping downward and inward in agreement with the direction of the pelvic floor. Within the body, the plane of the median portion of the fold depends upwn the position of the uterus, in the erect posture usually extend- ing more or less horizontally, so that the posterior surface presents upward and ba( kward, and the anterior downward and forward : when the uterus assumes an upright position, the fold likewise becomes erect. On ncaring its lateral attachment, the upper border of broad ligament becomes not f)nly more vertical, but also parallel with the pelvic wall in consequence of the support afforded by the suspensory liga- ment of the ovary. From their attachment to the pelvic walls and floor the two serous layers of the broad lijj.imeiit pass in opposite directions and are continuous with the general peritoneal lining of the pelvis. Along the pelvic floor their diviTsiencc leaves a non-pcritoiieal interval through which the vessels and ncr\'es and the ureter gain the si(le of tho uterus. The free border of the broad ligament is occupied by the Fallopian tube, the course of which it follows as far as the outer end of the infundibulum, and thence passes to the pelvic wall to become continuous with the suspensory ligament of the -55^ ~^Exlrmal uft Vagina rteru** Imiil open by (mntal settton. showing torm of iavilvof body and i-trrvis. THE UTERUS. 2005 ««.rv As the tube crosses the medial surface of the latter organ the broad li^- r.^i, d«in over it sTthat the ovary lies partly within a pentoneal pocket the !£.i;r ikte^lir^^^^ ^^low.'Wmes continuous with the general subserous layer '^n^^touriJ Lvam.ni.-ln addition to the Fallopian tube and the Uga^e"; °' the or^, a^ady Lcribed (page .987). a third band, the round hgament Hi,.. Fig. 1699. Fmllopiaii Kibt, ampulla UKametit ot ovary w,..Jj^, I M«Ki«lpin« I hallopiai. lube Alxlomiiial u|>riiinK u( Kallof>iaii luht: K|ioophoroii Hy.u){las!' iwuih- / VaKina Uleru, and a,*e...l.«e, «n Iron, "f h'";! ^ i™l|lSS ""** oviduct have been stretched out to show mewMalplna. mcfltniB structure This 5 ^ni- um™.wSl"Xl..^ll>cKic ,v,ll.«l.icl, Ure»ch™ near the fl,»r Thence .1 SI in™™?o Viu:« beneathV pert™.,™ l™rf »^^ r5:ih^,&:L^nireT,VL&s^^^^^^^^^^ he iubic sc^ne. In its median third the rotmd liRament contains /"»'"«» 'f'^°' nvoCarV muscle prolonged from the superficial layers of the uterus but LeNond tremuiuTar tissue disappears, and in its lower part the ban.l «-"f' ?. ^^"^^ '>' ";1 ^^^^ ItetTcTssue. During its passage through the inguinal canal, the l'R»"^5"t«'" \^;« baccompaned. along^ts upper border, by small, short bundles of striped muscle if aoo6 HUMAN ANATOMY. derived from the internal oblique and transversrJis, which represent a feebly developed cremaster muscle. Alter gaining the pelvic wall, the round ligament pursues a course very similar to that of the vas deferens ; morphologically, it corresponds to the genito-inguinal ligament (p^e204o). In the fcetus the round ligament is preceded by a small peritoneal diverticulum representing the larger processus vaginalis peri- tonxi in the male ; usually this disappears, but may persist as a distinct serous pouch, the canal of Nuck, that accompanies the round ligament for a short distance within the inguinal canal. In exceptional cases it may extend throughout the entire length of the canal into the labium majiis. The peritoneal relations of the two surfaces of the uterus (P'ig. 1700; are dif- ferent, the anterior surface being covered with serous mt -nbrane only as far as the Fio. 1700. Urn Suspensory, lixammt ai oviry Fallopian tube. Round IJKiinient Ovary. Ohlitciai^.'d. hypogastric artery I'tcn Symphyan pubii Urethra External urethral orifice in vestibule .rtero-aacral fold Kectum Eiiemal o» uteri Bottom o( recto- uterine |joucb .Vagina rerin*':»I b SaKittal lection of pelvlH of female. junction of the body and cervi.x, from which line the peritoneum pas-ses on to the bladder a.s the uteroveska/ fold And lines the shallow utero-vesical pouch (ezcavatio vesicouterina ). Below the reflection of the peritoneum and as far as its attachment to the vagina, the anterior surface of the cervi.x is connected by areolar tissue with the adjacent pt«terior wall of the bladder. As far as the attachment of the vaginal wall, the posterior surface of the vitenis is coveretl with peritoneiini, which then -ontinues downward for about 2.5 cm. over the tipper part of the back wall of the vagina before being reflected onto the rectum a.s the agino-rfctal fold. The latter forms the bot- tom of the ^w\iSf:\v,\\^ pouch of Douglas ieicavatio rcctouterina) that lies between the uterus in front and the rectum behind. The lateral boundaries of the opening into this pouch are formed by the two crescentic utero- rectal folds (pliciie rectoutcrina ) that curve from the hind surface of the cervix liackward to the posterior pelvic wall at the THE UTERUS. 2007 siden of the rectum. Between the layers of these folds robust bundles of fibrous and smooth muscular tissue extend from the uterus to be insetted partly in the rectum, there constituting the uUr^rectal musek, and parJy mto the front of the sacrum as the utero-sacral ligament. The latter structure contributes eflicjent aid m supporting the cervical segment of the uterus, which is thus enabled to maintain Us powtion indeoendently, to a certain degree, of that of the body. • , „ j l>08ition and Relations.— The attachment of the cervix to the vaginal walls and utero-sacral liRaments give to the lower uterine segment a more definite position than that enjoyed by the body, which, being little restrained by Us lateral atuchments. « e^eck^ly affected by the condition of the bladder and rectum. When these organs "rbTslighdy distended, the uterus normally, in the erect posture, hes tilted for- ward (anteverted). with the body resting upon the upper veJical surface. Since under th«^ conditions, the cervi.x is comp^iratively fixed and directed backward and the tody^ore or less bent forward (antiflexed). the uterine axis exhibits a marked flexure at the beginning of the cervical segment. This angle vanes conUnually with "he posiUon of the hindus, which, receiving little support from «ts peritoneal and otherattachments, is influenced by the changing condition of the Madder. When the latter is contracted and the uterus strongly anteflexed, the angle » !"«^« F©- nounced than when the upper vesical wall, and consequenUv the fundus, l'« y er With increasing distention of the bladder the angle gradually disappears and the uterine axis becomes straight : in exc.-ssive vesical expansion, a.s.sociated with an empty rectum, the entire uterus may be tilted backward (retroverted), its axis then cor^iponding with that of the vagina. When both bladder and rectum are d s- tendetl the entire uterus may be pushed up above the level of the symphysis. UsualW the fundus does not lie strictly in the mid-line but to one side, pro.baWy more frequently to the left (Waldeyer, Merkel). This deflection may also affect the axis of the ovary of the opp*«ite side, which, in consequence of the pull thus exerted, then lies more obliciuely than on the side on which the utero-ovanan li^^- ment is relaxed. The anterior surface of the uterus following the changes of the upper vesical wall upon which it lies, the utero-vesical fossa very seldom co;^ains in- t^tinal coils, which, on the contrary, frequently occupy the i>ouch o Douglas. The posterior (upper) surface of the uterus is overlaid by coils of the small intestine, and may also be in contact with the i)elvic and sigmoid colon. Antenoriy. below the reflection of the utero-vesical fold, the lower segment of the uterus is connected with the posterior bladder-wall by l.Kwe connective tissue ; posteriorly, it is sepa- rated from the rectum by the intervcninjj peritoneal pouch of po.igla.s ; laienUly it is crossed bv the ureters, which, opposite the middle of the cervix, he alxiut 2 cm from the uterine wall. In the erect i)osition, the level of the external os corresponds ap- proximately with that of die upper margin of th.- symphysis, and m »"? antero- posterior axis lies slightly behind a frontal plane paiwmg *'ough the ischial spines ^Structure.— The uterine walls, thickest in the fundus and posterior wall of the body where they measure fn.m 1-1.5 cm., and somewhat thinner (fro.n K-9 mm.) at the entrance of the tulles and in the cer\'ix, comprise three coats, the mucous, muscular, and serous. The mucous coal, or endometrium, of a light red-lish coU.r. soft, and friable, and from .5-1 mm. thick, consists of a connective-tissue stroni;.^ loose in te.xture but rich in cells and resembling the ti.nica propria of the intcstmai mucous, and the surface epithelium. The latter is a single lay.-r of covunnar i ells. about .028 mm. high, that in their typical cmdition pos.sess cih:i l)y < li«:h a dovvn- ward current is established towards the external os. It is irobable. h..«e' er, ihat the cilia are neither always present, nor uniformly distribut -d since 'he. u- lost during the disturbances incident to menstruation, and are often present only in patches (Gage) The ulerine glands are simple tubular, or slightly bifurcated, wavy invaginations of the mucosa, said to be lined with a single layer of ciliated col- umnar cc'ls resembling those covering the interior of the uterus. 1 hey are dis- trit)uted at falrlv regular interxals and extend the entire thickness of the mucosa their tortuous, blind extremities in many cases being lodged between the adjacent muscular bun.iles, since a distinct submucom is wanting. In the vicinity of the orihces of the Fallopian tubes, the uterine mucos;> becomes thinner, the epitheUum lower. If n 3008 HUMAN ANATOMY. Gbnd opcuinx on mucous tur- tac«. and the elands shorter and fewer, until they finally disappear, glands being absent in the tubal mucous membrane. The cen'ical mucosa differs from that i; ?ing the iiody in being somewhat denser, owing to the greater amount of fibrous tissue withm its stroma, and in possessing a taller epithdium, a single layer of columnar cells from .040-.060 mm. in height, and larger mucous glands. The latter (glandulac ccrvicales uteri), from i-i.,j mm. long and .5 mm. wide, are branched and often reach with their blind ends between the muscle bimdies. The mucus secreted by these glands is peculiar, being clear and exceeding tenacious, and sometimes is .seen as a plug protruding from the external os. Not infrequendy the orifices of the cer\icaf glands become blocked, which condition results in Fic. 1701. the production of retention cysts that appear as minute vesicles between the folds of the plicae palmatx. These bodies were formerly de- scribed as the ovules of Na- both i^ovula Nabothi). The transition of the cylindrical epithelium of the cervical canal into the squamous cells covering the vaginal portion of the uterus takes place ab- ruptly at the inner border of the external os. At the inner OS, where the cervical mu- cosa passes into that lining the body, the change is so gradual and inconspicuous that no sharp demarcation exists. The muscular coat, or myometrium, although com- jjosed cf bundles of inv-olun- tary muscle arranged with little individual regularity, may be resolved into a robust inner layer, in which the bundles possess a general circular disposition, and a thin, imperfect outer layer in which their course is for the most part longitudinal. The longitudinal musrie bundles of the f«-eble outer layer, which is present only over the fundus and body, are con- tinued beytjnd the uterus onto the tubes and into the broad, round, ovarian and utern-sacral ligaments. The thick inner layer, the chief compoi ent of the myome- trium, is distinguished by the number and size of the blood-vessels that traverse the intermuscular connective tissue and, hence, is known as the stratum vasculare ( Kreit- zer). The bundles of this layer are confined to the uterus, exrept below, where they become continuous with the mu.scle of the vaginal walls. At the three angles i)f the body, corrcspf>nding to the two tubal orifices and the internal os, the dispo- sition of the bundles surrounding these openings suggests the existence of distinct sphincters. Ir other places the innermost bundles are less regularly disposed and are oblique or even longitudinal Within the cervix the outer longitudinal layer is unrepresented, the musculature of this segment consisting chieflv of circular and oblique bundles. Intermingled with a considerable amount of dense i.brous and elastic tissue that confer upon the cer\'ix greater resistance and hardness. The component fibre-cells of the uterine muscle vary in form, being in some places short and broad Sfclion of endometrium, fthowinic utetiii« glandi rut in varous planes. ^ 40. THE UTERUS. 3009 and in othus long and spindle form. During pregnancy their usual length (horn .O40-.o6t. mm. ) may increase tfc> old. „ , . ■. 1 :„,.„., The serous foot, or perimefrium, continuous laterally with the peritoneal invest- ment of the broad ligament, is so closely adherent to the utenne nuisck over the Kus and adjacent ^irts of the anterior and posterior surface that .t '^",7;,"' with d;ffic-.lty. I-oweT the presence of the mterxemng loose connective tissue { />flr«- ■««/«■«»») renders the attachment less intimate. ■ u u. .^k VeMeU.-The arteries supplying the uterus are the two uterine, each a branch of the interr.il iliac that accompanies the ureter along tlie |)elvic wall. Ix-hiPd and Wow the^^riai. fossa, to the a««ched border of the br.«d ligament iK-nea ii wh.rh U^Sm« in its course to the uterus. On gaining a point about a jm from the cei^nd on a level with the internal os (Merkel) the uterine artery bends med.allv and crosses the ureter obliquely and in front. It then traverses ilensc •<.nnccU%e tteue^on appiS^chhig^e Uteral wall of the cervix bends sharply "pward ^. ^^ b^een °he layers of the broad ligament along the lateral Ix.rders of the r^. r^ as the lateral angle. Imm^iately below the ovarian ligament the frll Fig. 170*. .Xntvrior nurface Longitiuliiial muscle ^ Blood -vesaeU Attachment of bnad //•/«■ Hnment en' «^^ closinK l«r* metrium Muco-m (endomelriu.'n) Ixincitudlnal mmclt -Circular niUMie T^toneum ((xrimflrium) Poitcrlor raffece TraiMvcTK section ol utenw throngh body. X »• uterine artery divides into if terminal branches dirtrihuted to the fundus^ Fallo- -jian tube, and ovary. In addition to a small branch lo the ureter just Ix tore bending upward it gives off the vaginal artery that P^^*^ ,^"«-7;f;'' .;^":' .^T^e in supplying the cervix and the vagina. As it ascends along the sid.^ of he uten,s^Vom%-.o mm. removed and surrounded b>' a '^^"'"^ Pl""=; '^^ ^'^J^ very tortuous uterine artery sends numerous b«t variable branches t"^^^ '^^'•\\Xe body, as well as to the broad ligament, those distributed to t^e pmtenor surtace being somewhat larger than those to the anterior i Robinson) 1 "^^ !"^"^'"*'' ![-^^^^^ passing to the fundus framus fundi) is especially strong and freely ^"^^^^'^^^ .'^ the corresponding vessel from the opposite arter>-. thus insuring ""P^^jl'j^^^" larity to that part of the uterus in which the placenta is usually •-\^t»'=»'«' 'jS^^L of Twi^ also accomptny the ovarian and round ligaments. After the establ^hmcnt of the Junction bet^^een the ovarian artery and its ovanan branch, the utenne arter> plays an important part in maintaining the nutrition of the ov.-uy. "" ^^ ""? '"^ muLular cc^t the ikrger branches divide into vessels that penetrate he o U-Ma> er of the myometrium and within the inner muscular ayer break "P '"*" "'"^If'"^^ minute twigs that confer upon this stratum its highly vn-'ular character. Witnm 90I0 HUMAN ANATOMY. the mucosa the capillaries s > ound the glands and form a superficial net-work beneath the epithelium. The vrtHs, already of considerable size within the inner muscular layer, emertje from the myometrium and form a dense plexus of thin-walled vessels that surround the uterine artery at the sides of the uterus between the layers of the broad ligament. The veins are arranged as an upper, middle, and lower group. The first of these includes the veins from the fundus and upper part of the body, which become tribu- tary to trunks that join the ovarian veins and leave the pelvis by way of the sus- pensory ligament. The middle group comprises the venous radicles from the lower half of the body and upper part of the cervix that unite into one or two main stems that accompany the uterine artery. The lower group is formed by the veins from the most dependent part of the uterus, the anterior vaginal wall, and the posterior surface of the bladder. These unite into robust ascending stems that become tribu- tary to the trunks following the uterine artery. The middle and lower groups freely anastomose with the vesical plexus and also communicate with the hemorrhoidal plexus. The lymphaHcs, within the mucosa not demonstrable as definite vessels but only as uncertain clefts, constitute an intermuscular net-work of which the larger trunks follow the blood-vessels and establish communication between the cervical lymphatics and those of the body. On emerging from the myometrium a suj)erfici.-il (subserous) jile.xus is formed, especially over the posterior surface in the vicinity of the lateral .ingles ; large trunks also accompany the blo«xl-vessels along the sides of the uterus. The lymphatics from the cervix, usually t^vo or thret stems, pass to th< lytiiph-nodes occupying the angle between the external and internal iliac arteries. According to Bruhns,' those from the remaining parts of the uterus follow different paths : one set, from the body, goes likewise to the iliac nodes ; another, from the fundus, courses towards the ovary, and in company with the trunks from the latter oi^jan follows the ovarian artery to terminate in the lumbar nodes. A third set, also from the fundus, eventually gains the limibar glands after joining the lymphatics of the Fallopian tul)e, while a fourth jjroup di\ergcs from the fundus along the round liga- ment to become alferents of the inguinal lymph-nodes. In addition to free anasto- mosis among theniscKi-s, the uterine lymphatics communicate with those of the vairina, n-ituni, ovaries. Fallopian tubes, and broad ligament. The nerves of the uterus, being ciiiefly destined for the involuntary muscle, are numerous and of large size to corrcspoiul *ith the highly developed myome- tr uni. Thev are derived not only fiom the sympathetic system from the utero- va.vnn.il .sutwlivision of the ikI, ic plexus (the continuation from ihe liypogastric), but also (lir from tlie second, third, and fourth sacra! spinal nerves. According to the classic description of FVankenhaiuser, the iitero-vag:nal plexus divides into two p;irts, the smaller of which is distributt*d to ihe posterior and lattral parts of the uterus, while the larger includes a chain of minute ganglia along the cervix and vaginal vault. One of these, the cenical ganglion, is esj)ecially large, and lies behind the upper p.irt of the vagin i, receiving, in addition to the svmiwthetic, spinal fibres from the sacral nerves and giving off twigs to the uterus. These latter pass to the titerine walls between th- Livers of the br.ad lig.iment, p.irticularly at the sides in company with the blood- .essek, antl penetrate the myometri'im, to the fibre-cells of which the ner\e-filamcnts are chiefly distributed ; others pass mto the mucosa to end beneath the epithelium. Development and Cbange;;. — In consequence -f the medial rotation of the ventral border of the Wolffian hotly, the relations of tlie Miillerian to the Wolfl[ian duct change. Instead of lying laterally to the Wolffian duct, as it does above, the Miillerian duct gains the inner side of that tul)e as they pass into the urogenital fold (page 2038) wh.. h prolongs the lower end of the Wolffian body into a median strand known as the genital cord. Within the latter, formed by the fusion of the plic.-e urogenitales. the two Miillerian ducts lie next the mid-line, side by side and in contact with the Wolffian duct on either hand. Beginning about the eighth w^ek, the opposed surfaces become imited, the intervening septum disappears and the two Miillerian ducts are converted into a single tube from which the uterus is derived. ' Archiv f. Anat. u. Phys., 1898. THE UTERUS. 30II For a time this tube ends blindly and is conUnued to the urogenital »in.». with which it Jnttes M a solid cyUnder of Urgcr cells ; thi=. lumenless seRment r,f the fused MmSn ductTrepSents the anV «! the vapna. The extent ^^ "h.ch he Md erian ducts undergo fusion is early indicated by a sharp inward bend of t.*^ tubes VuTt below the lower and medial ends of the Wolffi;in bodies, the flexure on eaMe co««,H,nd ing to the atUchment of t.hrc-H that pass to the antenor aWom- fnal wSl an""ter frcnn the round ligament. Ihe portions ..f the Mulleruin duett Ltove this r^int rem^un se,«rate and ununite.1 and become the ovducts. th.«e below undereo fusion and produce the uterus and vi^tl^a. i „ /k„ Aher the vaginal portion of the united Miillerian ducts acquires a lumen (bv the end d the fourth m^th), the uterine and vaginal segments of the tube are d.f- tenSat^ by the U,T cylindrical and the larger o.boi.lal epithelial cells that line he two^rtions respectively. The transition zone, which Incomes progressively mL^red c" rr^Ss to the position where later the cylindrical utenne epithe- hum c^g^ into the s.,uamous vig.nal cells at the '""" -''«7 ^ ^ nuTcal's Soon the distinction between the uterine and vaginal portions of t^egenit..! canal is addhionallv emphasized by the forward curNe of the onner and the Mraightcr downS ccuZ- .^ the latter. The more definite division of the utenis from the vaJinrTs ef^S by the appearance of crescentic thickenings of the anterior and S erio' w;Sk oTthe canal wWh mark the beginnings of the corres,«nding lips of Ih^ cervix Distinction between the Ixxly and cervix is earlv suggested by the 'uterine eJitheHum the cells lining the lower portion being talfer. -o-j^jy^^d"-! aid numerous than th.^e of the bcxly ^he connectiveand muacu ar ti^ue of he uterine wall are differentiated from the condensed mesoderm that surrounds tnt : rdialtJb: Distinct muscle is not distinguishable before the .Jh --th. abou which time the cervical glands also make their appearance ' Nagel). thus anticipa ting bv some weeks the development of the glands in the corpus lUeri At birth the uterus mciisiires about ^ cm. in length of which the c^rvi^ c n tribu es more than half, and is thicker and denser than the thm-walled and riaccid 3v The characteristic arched form of the hmdus is lacking and the lateral aSL a "prolonged int> the tubc-s, often recalling a b.coniate conditi.m. The ?r,SoA,!inaliss inconspicuous and projects to only a slight degree. .Jthough the K.«lnati are^vcllde^^ limited, ;is they later are, to the cervical £ 'burSfend through<,ut the uterine cavity. Since at this time the "nternal os is Su mmature. the division of the uterine cavity into an upper and a lower segment U onlv sucir^teil. The general position of the utems is higher than later, it, o«re£r wfthX bladder, lying al^ve the level of the pelvic hnm. with the fundus oTposite h 'u the fifth lumLr vertebra ( Merkel). With the increasing capacity of the^oelvis th ■ uterus sinks, so that by the end of the sixth year the external .« « inle'wgher han In the adult ( SyminU)- Ar«rt from the Rradua^^devxlopment of the glands and the disappearance ..f the folds of the mucosa w thin the U^> durine childhood the uterus grows slowly until near puberty, «hen the body Sen. leiKthens, and acquires the arched c.ntours of its mature form. In its e ative V long cerv x and slightly prominent fundus, the uterus of the virgin retains hecharuSt."of early childh^xl. The repeated ' »^-«- l^f "» »V„,^ "^u"^ Itl^l cycle, produce gradual thickening of the utenne wall, and e">=»'-K^'"«"^,"' /l^^ lumen.^o that, even independendy of pregnancy, the wtrus increases somewhat in size and weight during the years of se.xual activity. After the cessation of menstruation, between the forty-fifth and fiftieth >ea,rs, the uterus suffers gradual atrophv ( inx olution ). This first affects the cer^•lx. which £annc" smaller .tnd more sir.ul.r, the entire organ '" . -"X'-\. ^J^^l more pronounced pyriform outline. The general reduction in the size and prom nence oT"he vaginal portion is accompanieecome thinner an< lZsTes^"uJh ..trophy cl tin- n.Lular tissue and decreased vasculanty. and hTnce^le^ color, of the mucosal, lor a time the uterine cavity is enlarged, but. later sCng in the general atrophv and not inconsiderable dnn.nut.on in sMze of he organ, the lL..n likewise undergoes reduction and. in some cases, suffers obliteration in the vi-ir,ity -! the internal os. w 30I3 HUMAN ANATOMY. Cbanf e« during Mcnttruation and Pregnancy — AlthouKh liberation of a mature ovum may occur at any time, such independence is exceptional, and in the vast majority of cases ovulation and menstruation are synchronous processes, the uterine changes occurring regularly, every twenty-eight days, only when the ovaries are functionally active. In anticipation of the possible reception of a fertilized ovum, the uterine mucous membrane becomes .swollen, exces- sively vascular and hypertrophied, with conspicuous enlargement of the subepithelial blood- vessels and the glands. The resulting thickened and modified mucosa, now from 3-6 mm. in thickness, offers a soft velvety surface favorable for the implantation of the embr>o-sac. Should this purpose be realized, the hypertrophy proceeds, and the lining of the uterus is con- verted into the decidua; and ukes an important part in the formation of the placenta and at- tached membranes (page 44). If, on the contrary, fertilization does not occur, the proliferative proces.ses are arrested and the hypertrophied mucosa (now called the decidua meMs/rua/is) enters upon regression. Incidental to the latter are subepithelial extravasation and rupture and partial dest.-uction of the epithelium, followed by the characteristic discharge of blood. While usually the destruction of the mucosa is limited to the epithelium, it is probable that at times the superficial layer of the subjacent tissue is involved. During pregnancy the most conspicuous changes are occasioned by the growth necessary to accommodate the rapidly augmenting volume of the uterine contents, by the provision of an adequate source of nutrition and protection for the foetus, and by the development of an efficient contractile apparatus for the expulsion of the same. From an organ ordinarily weighing about 45 grams (i^ oz.), measuring 7 cm. in length and possessing a capacity of from 3-5 cc, by the close of pregnancy the uterus has expanded into a rouiided or oval sac about 36 cm. ( 14 in. ) in its greatest length, from 900-1000 grm. (about 2 lbs. ) in weight and with a capacity of 5000 cc. ( 169 fi. oz. ) or more. This enormous increa.se depends especially upon the hypertrophy of the muscular coat of the organ, which during the first half of pregnancy becomes greatly thickened, but later thinner and membranous owing to stretching. The increase in this coat results from both the growth of the previously existing muscle-cells and, during the first half of pregnancy, the development of new muscle elements. The individual cells may increase tenfold in length and measure between .4-.5 mm. Although the cervix actually almost doubles in size, its growth is overshadowed by that of the body, since it remains relatively passive. During the first five months, the mucous membrane of the body of the uterus also becomes greatly hypertrophied, in places attaining a thickness from 7-10 mm. The glands and blood-vessels, particulariy the arteries, enlarge and, within the specialized area, are concerned in the formation of the placenta (page 48). The cervical mucosa takes no direct part in the formation of the decidus, although it thickens and is the seat of enlarged glands that secrete the plug of mucus that for a time occludes the mouth of the uterus. After the tennination of pregnancy, the uterus enters upon a (leriod of involution and repair, the excessive muscular tissue undergoing degeneration and absorption and the lacerated mucosa regeneration, the latter process being completed in from five to six weeks ( Minot). In sympathy with the growth of the myometrium, the round ligaments enlarge and also show marked augmentation of their muscular tis.sue. The peritoneal relations are disturbed by the excessive bulk of the uterus, so that at the sides the layers of the broad ligament become separated. Variations. — The chief anomalous conditions of the uterus depend upon defective devel- opment or imperfect fusion of the Miillerian ducts by the union of which the normal organ is formed. Arrested development of the lower part of these ftetal canals accounts for entire ab- sence of the uterus and vagina. Depending upon the extent to w hich failure of fusion occurs, all degrees of doubling are produced. In the most pronourccd cases, in which the Miillerian ducts remain separate throughout their entire length, two completely distinct uteri and vaginx may result, each pair being capable of performing the functions of the normal organs. (Jn the other hand, slight indentation of the fundus may be the only evidence of imperfect union. Be- tween these extremes all gradations occur ; the body may be completely cleft (uterms bicomis). with or without divided cervix ; or the duplicity may be partial and limited to branching of the fundus ; or the faulty fusion may he manifested by only a partition, more or less complete, that divides the uterine cavity into two compartments (u/frus septus), although the external form of the organ is almost or quite normal. When, in conjunction with any of the foregoing variations, one of the component Miillerian ducts fails to keep pace in its gi-owth, all degrees of asymmet- rical development may result, from complete suppression of one of the tuVies in a bicomate uterus to merelv unilateral diminution of the fimdus. Subsequent arrest of what to a certain stage was a normal development may result in permanent retention of the foetal or infantile type of uterus. PRACTICAL CONSIDERATIONS : ITERUS AND ITS ATTACHMENTS. In the female the pelvis is subdivided into two compartments by a fold of peri- toneum reflected from the floor and sides of the cavity. This fold passes from one side to the other and includes between its layers in the median line the uterus. On each side of the uterus it is known as the broad ligament, and encloses the uterine PRACTICAL CONSIDERATIONS: THE UTERUS. 3013 api>endages, their blood-vessels, together with their nerves and their enveloping connective tissue. This transverse fold of peritoneum is analogous to the mesentery of the small intestine, serving the same purpose for the uterus and its appendages— / e to hold them in position and to transmit their blood-vessels and nerves. ' The posterior compartment of the pelvis, the recto-utertne, is the larger and deeper of the two. The lower portion of it, included between the two recto-uterine folds of the peritoneum, is the pouch of Douglas, or recto-vaginal pouch, because it lies between the rectum and the upper fourth of the vagina, from which it is separated onlv by subperitoneal connective tissue. The rectum, bulging forward the ix>sterior wall and the ovaries, hanging from the anterior wall, tend to till this compartment, the remaining space being occupied by small intestine and a portion of the sigmoid Abnormally it may be encroached upon by a retroposed uterus, which tends to drag downward and backward its appendages, the tubes and ovaries, towards Douglas's pouch, where they may be palpated by the fin^' through the vagina. Because of the greater depth of the posterior compartment .md because of the fact that abscess and other pelvic operative conditions arc usually situated in it, it must almost always be drained, if drain^e is necessary after operation in this region. The anterior or vesico-uterine compartment of the pelvis extends below only to the isthmus of the uterus. The remaining supravaginal portion of the cervix is in close relation to the bladder, but the loose intervening layer of subperitonea tissue permits a ready separation of the two in the operation for the removal of the uterus (hysterectomy). Since the body of the uterus inclines forward, nor- mally, touching the bladder, the space in this compartment is slight. It excep- tionally contains a few coils of small intestine, and may lodge also a part of the sigmoid flexure. . •.• A tumor or pregnant uterus filling the pelvis may press upon the iliac veins, producing cedema and varicose veins of the lower extremities, of the vulva, and of the rectum (hemorrhoids) ; upon the lumbar and sacral nerves, causing cramps, neuralgia, or paralysis ; upon the bladder, with resulting vesical irritability and pain : upon the rectum, inducing constipation and hemorrhoids ; upon the ureters, giving rise to hydronephrosis ; or upon the renal veins and kidney, pro.lucing albummuna and piossiblv uraemia. . The uterus is held in position between the bladder and the rectum by its liga- ments, and is kept from dropping to a lower level (prolapse) mainly by the support received from atmospheric pressure acting through the floor of the pelvis. The broad or lateral ligaments attach it and its appendages— the Fallopian tubes and ovanes to the sides of the pelvis. The round ligaments act chiefly in tending to prevent retro-displacements. The musculo-fibrous utero-sacral ligaments and the anterior and posterior reflections of peritoneum materially steady the cer^•ix, which is also fixed by its attachments to the bladder and vagina. Moreover, the intra-abdominal pressure applied through the intestinal convolutions that are normally in contact with its jjosterior surface aids in holding it in position. The body of the uterus is more freely movable than the cervix, and in spite of its supports the uterus, as a whole, is one of the most mobile of the viscera. The cervix, for example, may easily be made, through traction by means of a tenaculum, to present at the orifice of the vagina, in such operations as amputation of the cervix, repair of lacerations, or dilatation and :urettement. On account of its mobility, its intrapelvic situation, and the elastic sui)port received from the bladder, and indirectly from the levator ani muscles, the uterus is very rarely injured by blows on the abdomen. If upon examination it is found to be tixed. or not easily movable, some abnormal cause should 1k' sought for, such as pelvic inflammations or tumors. The essential conditions in the production of Vi prolapsed uterus obtain when the uterus is the seat of subinvolution from any cause, especially a puerperal infection, and the pelvic floor is relaxed or torn. The stretching of the pelvic lijjaments has then not been fully overcome by later contraction, and the atmospheric supjM)rt ( dependent upon a' tightly closed vaginal outlet) is lacking because of the weak- ened jjcrineal floor. As the uterus reaches a lower level its ligaments become truly ' ' suspensory" ' and resist its further downward progress as soon as their uterine attach- 30I4 HUMAN ANATOMY. ments are bel w their pelvic attachments. Normally their insertions and origins lie approximately in the same horizontal plane when the woman is erect (Penrose). The integrity of the levator ani muscle, ensuring a well-closed vaginal outlet, b the most important factor in supporting the uterus within the pelvis. It keeps the outlet forward under the pubic arch out of the line of abdominal pressure, gives it the form of a narrow slit, preventing the protrusion of the pelvic viscera, and directs the axis of the vaginal canal forward instead of directly downward, so that the intra- abdominal pressure strikes the pelvic floor at a right angle ; and by aiding in main- taining the vagina in its normal condition of a closed slit with its walls in contact, it prevents disturbance of the forces which hold the uterus in place. If a laceration of the perineum converts the vagina into an open air-containing tube, the equilibrium of these forces is destroyed and prolapse often follows. In severe c -es of prolapse the ureters are so stretched that, at their vesical ends, their luri- a is narrowed and ureteral dilatation or hydronephrosis may result. Anterior and posterior jiexions of the uterus occur at thi isthmus, which is the weakest point and is the junction of the larger and more movable portion — the body — with the smaller and more fixed portion — the cervix. On account of the normal anteflexion of the uterus, it is not always easy to decide in a given case whether the degree of anteflexion is normal or abnormal. When it is abnormal the most imfKtrtant symptom is dysmenorrhcea, from obstruc- tion of the canal by the flexion ; if irritability of the bladder occurs, it is probably reflex in its origin. Anything which weakens the support of the uterus, or increases its weight, tends not only to cause prolapse, but also to the production of retroflexion or retro- version of the uterus, the first degree of prolapse being associated with some retro- displacement. The uterus then loses its normal anteversion, and the intra-abdominal pressure is brought to bear on its anterior surface, es()ecially if the patient is either confined too long in the supine position after labor, with the abdomen too tightly bandaged, or if she leaves her bed too soon or undertakes any physical work. The uterus is larger and heavier than normal, as a result of imperfect involution ; the uterine ligaments are lax ; the vagina and the vaginal orifice are relaxed, and the support of the pelvic floor is consequently deficient ; the abdominal walls are flabby and the retentive power of the abdomen is diminished. These are also the causes that favor prolapse of the uterus ; in fact, a slight degree of uterine prolapse usually accompanies such cases of retrodisplacement. A certain amount of retro- version must always exist before the uterus can pass along the vagina. It must turn backward, so that its axis becomes parallel to the axis of the vagina (Penrose). In the purely retroverted positions the uterus revolves on the isthmus as on a pivot, so that as the fundus goes in one direction the cervix passes in the other. Therefore, as the cer\ix is turned forward against the base of the bladder, the fundus presses backward on the rectum, often producing reflex symptoms. The uterus may be found inclined to one side — more usually the fundus to the left, and the cer\-ix, on account of the presence of the sigmoid and rectum on the left side, to the right. Unless extreme, such inclination is not to be regarded as patho- logical. Between the layers of the broad ligaments is a quantity of loose adipose cellu- lar tiissue, the parametrium, separating the contained structures — those of the most importance being the tubes and ovaries with their vessels and ner\'es — from one another an ficium vaginae) is contracted, and in the virgin is still further narrowed by a duplicature of mucous mem- brane, the hymen, of variable form but usually cre- scentic in outline, that stretches from the posterior wall forward and occludes more or less the vaginal entrance. After rupture the hymen is for a time represented by a series of irregular or fimbriated pro- jections that become the caruncula hymenales. These surround the of>ening of the vagina and undergo re- duction and partial efl?rement after childbirth. The anterior and posterior walls of the main and widest part of the canal (corpus vaginae) are modelled by median elevations (coluninae rugarum), from which numerous oblique folds diverge laterally. These markings, most r onounced in the lower half of the vagina, are particularly conspicuous on the front wall. Here the anterior column is beset with close V-like ridgf' s and ends below in a crest-like elevation — the carina urethralis — that lies behind the urethral orifice. Relations. — With the exception of the triangular area, from 1.5-2 cm. long, over the uppennost part of the posterior wall, where the bottom of the recto-uterine pouch reaches the canal, the vagina is devoid of peritoneum, being attached to the surrounf «-all oi bladder Urethra Veaico-vaginal venous plexus Rectum Uchio-recUl fossa vaginal plexus that above surrounds the ureter and the vaginal branches of the uterine artwy^ vaginal walls, from 2-3 mm. thick, include a mucous and a muscular^coat, supplemented externally by an indefinite fibrous tunic. The mucous Z^consSs of a tunica propria, exceptionally rich in elastic fibres and veins, he SrrS of which is teset with numerous conical papiU* that encroach upon the over ying epithelium, but do not model the free surface. The epithelium fom o 15^. 20 mm. thick, is stratified squamous in type and possesses ^ superficial stratum of olate-like cells (.020-. 030 mm. in diameter) that resemble the epidermal ele- ments of the skin and are constantiy undergoing maceration and *b/=»«'°";„^^Jthou^h normally moistened bv a thin mucous secretion of acid reaction, the vagina is devoid "rtme gSand probably derives its lubricating flui.i for the most part from the u teSe glands, the laline Lretion becoming modified^ Small nodules of lymphoid dssue a7e scattered within the mucosa, especially ...the upper P^rt of the canaL The duplicature of the mucous membrane forming the hymen corresponds in structure with that lin"ng other parts of the canal. The muscular coat, which directly sup- norts the mucoia without the intervention of a submucous tunic, consists of bundles S^ involuntary ...uscle that arc arranged, although not w.th Prf^"''""-^'^ ^«" '""^^^ circular and an outer longitudinal layer. The Tatter is best developed over the "7 01 Hi 30l8 HUMAN ANATOMY. Fio. '70S. Tunica propria of mucosa anterior vaginal wall, from which bundles of muscular tissue are continued into the urethro-vagmal stptum ; behind, bundles pass into the recto-vaginal partition. Above, the vaginal muscle is directiy continuous with that of the uterus and below penetrates the perineal body. Within, the conspicuous columme rugarum, the muscular coat, as well as the mucous, is thickened, the elevations acquiring the character of erectile tissue owing to the great num- ber of veins intermingled with the irregularly disposed mus- cle bundles. After piercing the superior layer of the tri- angular ligament and in the vicinity of the orifice, the vagi- nal walls receive strands of striated fibres derived from the middle part of the com- pressor uretnrae (m. urethro- vaginalis) and the bulbo-cav- emosus muscles. Vessels.— The arteries supplying the vagina, all de- rived from the internal iliac, reach the organ by various routes. The upper part of the vagina is supplied by twigs continued from the cervical branch of the uterine arteries, that descend along the sides of the canal and communicate with the branches from the middle hemorrhoidal and vagi- nal (vesico- vaginal), that are distributed to the middle and lower portions of the vagina respectively. Those from the vaginal, of the two sides, form encircling anastomoses from which an unpaired ves.sel (a. azygos vagina) fre- quently is given off on the posterior, and sometimes anterior, wall. Additional branches pass to the lower part of the vagina from the arteries to the bulbus vestibuli from the internal pudics. Free anastomosis exists b'Ttween the vessels derived from these various sources. The veins, numerous and large, after emerging from the mus- cular tunic unite on each side to form the rich vaginal plexus that extends along the sides of the genital canal and communicates with the vesical and uterine plexuses. It receives tributaries from the external generative organs and is drained by a trunk, the vaginal vein, that passes from its upper part to the internal iliac vein. The lymphatics \\'\\\\\x\ the mucous membrane form a close net-work that commu- nicates with the lymph-vessels of the muscular coat. The collecting trunks pass from the upper and middle thirds of the vagina, in company with those from the cervix uteri, chiefly to the lymph-notles along the internal iliac artery. Additional stems from the posterior vaginal wall encircle the bowel and terminate either in the rectal or the lumbar nodes (Bruhns). The lymphatics from the vicinity of the vagi- nal orifice pass chiefly to 'the ujiper median group of inguinal nodes ; some, however, join the lynij)h-paths from the upper segments. The nerves are derived from the hvpogastric sympathetic plexus, through the pelvic, and from the second, third, and fourth sacral ner\'es. The immediate source of the sympathetic tihres is the cervical ganglion, at the side of the neck of the uterus, from which, in association with the sacral branches, twigs pass to form, on each side, the vaginal plexus that embraces the vagina and provides filaments chiefly for the in\()luntary muscle of its walls and b!ood-\cssels. The sensorv- fibres supplying the mucous miMnhrane i.f the iijijmt p.irt of the vagina are me.igre, since, under norma! conditions, this part of the canal possesses sensibility in only very moderate degree. Towards the orifice the vagina receives fibres from the pudic nerves which endow Section of wall o( vagini. X So. PRACTICAL CONSIDERATIONS: THE VAGINA. 3019 V .. >„- «f th.. lower third with treater sensibility and send motor fila- ':::rri^T£^^i^^VZnouM.Z i^^.nu.n... ScnLy ncr^ccndings o. of th?MiuS ducts Alter union of the latter with the iK.ster.or wall o the uro- s 1 in r^nd th. iDoearance of a lumen, which at first is wanUng. he gcmlal genual smus f 'I. ^V ; P^f "^""p;rture later the orificium vagina;, that lies between r/SruStS-^rthrWoCd'cts. The utter sul^^uenUy atrophy a.ul ana cioseiy uimcu « „,:„„_i na>u-i iM>rs st to a ercater or less extent as (.jart- disappear but may .nex^^^^^^^^^^^^ i^Jr^'agina is^early guarded by an annular E.TS. ™^l.icb^e» at birth i. sliBMly com.B.tcd. In con».-quejcc .. I« the fifth month. ^^j j^^ ^^,5 j^, comparatively At birth, the vagma . -n^ r .^ .^; . ^^^^ ^^^ ^^^^ '^'^b::u^Tu^"'''°^l^t . .dverdcal but after the tenth year grows liSlv t^increSwidTh ^... :;eductionTn the rug*, which from now on are s£i^Ss^t2ini=yea;js^c£^n^ ticity and undergoes atrophy. V.ri.tion..-The most -PO"ft variations depend up^^^^^^^ perfect fusion of the ^X^enV^e tub^ M tore^^h ^he ur^en" ai sinus, the v.nRina en.ls anomalies of the uterus. When these tubes }^";^^° J^"^'^ ^e^y^nted, the vagina (and often blindly above the vestibule ; or when their lower seRmentt are «^^^^ ^^ uterus') maybe ^"''^«'y "^"""{^in.KucT' The doul^^rry'^not'exlend tl'.roughout the separate or imperfectly fusedMullenan ducts ,„ imnerfect and partial septum, isolateil tends, lelTgth of the v»«ina but may be repj^esented b>^^ ^^ ^^^ ^^^^ charges occurs. PRACTICAL CONSIDER.\TIONS : THE VAGINA. Congenital malformations of the vagina, such as absence of the vagina, rudi- mentary vadna, or vaginal septa, are usually associated with corresponding errors b developr^rnt of the uterus. While other malformations due to faulty union of the \m lerianTrts occur, the more common is a uterus bicornis, or a double "Jerus and vSa Tl ev are not incompatible with pregnancy, labor and 'l^^, P^-'-P^""^ ^f^*^" pSg w thout unusual incident ; indeed, this condition is usually r«<^«K"'^!^J y Sent, since no external evidence is seen. Conception may occur on one or both "d^rsimultaneously. A vaginal septum > ^ich interfered with t^^ P-^^-f^" ^^'^^^ head should be divided. From imperfect development of one side , ! ■''>'"' "^^e uterus, pregnancy may lead to great danger of rupture of the weak utenne wall, or to a failure to expel the child. . , , ,. .• « »u„ uuAA,.r ivhpn the While varying within normal limits with the distention of the bladder, "henjhe latter is empty the axis of the fundus of the ulcus lies at alKOUt a right ^'"r!'' ^.th the v4ina The inner or uterine end of the broad ligament is, except at its ba.e. ao2o HUMAN ANATOMY. more nearly horizontal than vertical in direction. As a result oi this position of the uterus, it will be seen that the lower surface of 'the cervix presents aeainst the pos- terior vaginal wall, and that, therefore, this wall of the vagina must he longer than the anterior. The posterior wall is usually about three and a half inches long ; and the anterior about two and a half to three inches. The length of the ordinary Anger is about three inches ; it can, therefore, reach the anterior fornix of the vagina and anterior lip of the cer 'x. To explore the posterior fornix of the vagina considerable pressure is required. To palpate structures in Douglas's cul-de-sac the bimanual method of examination will be necessary, and a relaxed abdominal wall, to obtain which a general anaesthetic may exceptionally be required. An empty bladder facili- tates a bimanual examination. In the knee-chest posture the vagina becomes dis- tended with air, permitting a more thorough visual examination of its walls. The rectum posteriorly, and the base of the bladder and the urethra anteriorly, are within reach of the finger in the vagina. Calculi, either in the lower ends of the ureters {vide supra) or in the bladder, can be removed through the anterior vaginal wall (page 2015). The intravaginal portion of the cervix uteri can, with little or no pain, be grasped by a tenaculum and drawn down towards the vaginal orifice so that local applications can be made. It is so insensitive that such applications, even when strong and irri- tating, do not necessitate the use of an anaesthetic. Since it is the part of the cervix most exposed to traumatism and infection, it is the most frequent seat of pathological lesions, such as the so-called "erosions." Persistent — i.e., unhealed — lacerations are often sources of irritation, of reflex pains, and of some forms of dysmenorrhoea. Much of the pelvic pain, associated with them, is probably due to pelvic lymphangitis or lyn.phadenitis (Penrose). These lacerations seem to invite the development of cancer. Primary involvement of the body of the uterus is comparatively rare, the great majority of cancers of the uterus beginning in the cervix. As a result of the relations and contiguity of the cervix to surrocnding important structures, such as the bladder, ureters, and rectum, the prognosis of cancer of the cervix is less favorable than that of the body of the uterus, where infiltration of neighboring stiactures does not occur so early. As a rule, dissemination by lymphatic channels from carcinoma of the cervix, affects first the sacral or the iliac glands; carcinoma of the body of the uterus is more likely to involve the lumbar glands surrounding t' .• common iliacs, the aorta, and the vena cava. Pressure on the last-named v jel may result in cedematous swelling of the lower e.xtremities or in ascites. An hypertrophied cer\'ix shows as an increased projection into the vagina and a deepening of the vaginal fomices. This condition may be a cause of sterility. The vagina is most roomy in its upper portion, and is narrowest at its lower end, where it passes through the triangular ligament and is surrounded by the con- strictor vaginae muscle. This favors the retention of blood-dots within the vagina during the menstrual period and after labor. Spasmodic contraction of this muscle (vaginismus) is described as being sometimes strong enough to prevent coitus and to call for surgical treatment, though such cases, if they exist at all, are due to reflex irritation, such as from urethral caruncle. The dilatation of the vagina seems to be limited only by the pelvic wall. In nullipara the rugosity of its mucous membrane — necessitated by its great changes in diameter — is marked. The transverse folds favor retention of secretions and of discharges resulting from infection and render sterilization of the vagina difficult. Vaginitis may be followed by endometritis, as the uterine and vaginal mucoste are directly continuous. The hymen rarely may have no opening, when it will require incision to relieve the obstructed first menstrual flow. The exact importance to be attached to the presence or absence of the hymen in medical jurisprudence is still undetermined. While it is usually broken at the first coitus, it may remain intact until the first parturition. Therefore its presence does not prove virginity. Its original perfora- tion may have been large enough to leave little or no evidence of the membrane, so that its absence does not prove that coitus has taken place. Fislulte between the bladder and vagina (vesico- vaginal), between the urethra and vagina (urethro-vaginal), between the rectum and vagina (recto-vaginal), and between the cervical canal and the bladder futero- vesical), may occur. THE Labia and the vestibule. 302I openini! into .he Wadte. " " '"^X. to a ttoi ottraditig lotw.rd through the y„lt>-Mn^ li«.il« '^.'?H,?"irf 1^ Jong tte ctvioJ cnJ. The S.^fe.'''KKr^n'T,£'r£.»rt:r.e .K.n h... . .;... ulero-vaginal fistula. ^ , e, ^nd of the vagiiw. ^^'^--^-f' fi!t"S/;*irfr^^^^^ «t^nsion of an epithelioma o? the 1 V FEMALE EXTERNAL GENITAL ORGANS. The external gen«.tive organs oMheJ^^^ ductive apparatus that he below ^^^^^ ^^^] * J"^„ ^bove and the urogen- pubic arcli. They are '^fJ^/J.^ZraTnymPha, Ja the enclosed vesHbuU, the italcU/t between them. *« f^.* *"!f C" ^^He^AiW* o/^ Bartholin ; within the clitoris and the bulbus *f '*«' ' ^!^^d d the vS Of these structures, col- s^avTrubr»sr3,ftitotrvr^rirHhi„.^.-^»>««- THE LABIA AND THE VESTIBULE. The Ubia m.ior (labia major. P-^-u^TTcr HntS Td" S T^uZ folds, the homologueof *e scrotum about 7-5 cm ^m^^^^^^^ that extend backward from Je jnons pub« and endo^^ beUveen ^^^ ^^^^^^^^ ^ ^^,^. the urogenital cleft (rinuumdeodi). .Above^he*' >nnf ^ g j^j^j^^ missura labiorum anterior) «^,^^„ J^ '^^.^j^S^^^^ by a trans- where their upenng ends blend with the P?'^*"'?; "V^.. ^^ ^^^ sometimes verse fold (commissara {f**'"™" P^^^f^^J,!,^^^^^ Their outer surface is wanting, that crossw the "ud-line "'*^^ *"J ^set with hairs, in varying profusion, covered with thick, dark-hued mtegument ^n** .'^^ "^yj.^S, and may extend as that encroach for a limited zone on the '""^^^ »^^f ^^^'^Ih^ arl few and'^ minute, is far as the anus. The med.al ^"fXatP textlre thTt at the bottom of the nympho- clothed with skin of much more del«c^e Je'tture that «^»«^ j^j^j^^ ^^ ^^^ skin, labial furrow passes onto the outer «"£^!^°* ^J^ f^f^fi^een which and the integu- each labium consists of » J.f ^J f^.«"*'"!,*^^nf inVStT^ muscle (tunica darto- ment in the posterior l"*!'-*/*^'" **™^""'°', '"L perineum and represents the labialis) is continued «^-^^d from the dlartos of the pemeu ^^ ^^^^ ^^P^^^ .^ ^^^ -ci;?^^7S;rS;:=^^^ IrStxX^'tr^^:^^ ^ :SL'Sin^r llbium n,^^ sweat .nd 's^LrisglSaJe numerous within '1- int^^^o ,t^^^^^^^^^^ above the ^^^.^^:^:^^^^^^^ covered with hair. The subcutaneous fatty layer. usuaii> irom •, i \\\ 3033 HUMAN ANATOMY. Gtanl clitoridii PKpuiium clitoridii Frmulum clitoridii •omctinies as much as 8 cm. «>r more, » supported by connective-tusue septa that pajw from the underlying peri. ,teum to the skm, whereby the tension of the L ter is maintained. , ,. ' ''* ,'■*»'■ «n»nor«. or nymphs (tabia oiinora padendi), are two thin folds of delicate skin that, for the most part, lie concealed between the larger labia unless the latter are separated, and enckwe the vestibule. Their length is from 2.K--1 s cm their width about half as much, and their thickness from 3-5 mm. Near its anterior end, each labium divides into a lateral and a medial limb ; the lateral divisions of the two sides unite above the free end of the clitoris, which they enclose with a hood the p-epu/tum clitoridu, while the medial limbs join at a.i acute angle on the under side of the ditoris to form its/r<-««« (freaulum clitoridis). Behind, the nympha grad- ually fade away by joining the inner surface of the labia m.ijora. In the vifgin? and when well developed, the medial border of the posterior ends of the nymphas are usu- ally connected by a slight Fio 1706. transverse crescentic fold, the /tenum or fourchetlt (frtanlam labionim ptidendi) that marks the posterior lx>undary of the sliallow navicular fossa (Fig. 1706). Both surfacesof the nymphae are covered with delicate skin, which, on account of the protection afforded by the greater labia and con- stan. contact with the vagi- nal secretions, remains moist and soft and assumes the color and appearance of a mucous membtane. The entire absence cf mucous glands and the presence of numerous sebaceous folli- cles, on the inner as well as on the outer surface, to- gether with the develop- ment of the nymphae from the margin of the doacal fossa, establish their cuta- neous character. The skin covering the nymphae ex- ternally is continuous with that of the labia majora at I .1 , ,. , the bottom of the interlabial turrow ; internally the line of transition into the mucous membrane lining the vesti- bule follow.s the medial attachment of the folds which overlie the vestibular bulb In addition to the two cutaneous layers, the nymphae consist of an intermediate stratum of loose connective tissue, rich in blood-vessels, and containing many bundles of in- voluntary muscles that possess the character of erectile tissue. Hairs and fat are entirely wanting in the labia minora, but sebaceous and sweat glands are present the (WebstTr) '^^'te''^ ^'U' "lost plentiful in the anterior part and in the prepuce The vestibule (vestibnium vaginae) is the elliptical space enclosed between the labia minora, extending from the clitoris in front to the cr ntic frenuin behind When the nympha- are separated, the vestibule resembles i .nond in outline beine pointed in front and broader behind. In the roof (as usually examined the 9ioc^T^ of tins space arc seen the urethral and vaginal orifices and the minute openings of the paraurethral ducts and of the canals of Bartholin's glands. The urethral orMce occu- pies a more or less conspicuous corrugated elevation (papilla urethralis) that lies about External Kenital organs of virgin : lahia haw been iwpinilcd to txtxKx vt-stibule and vaginal orifice. mpp THE LABIA AND THE VESTIBULE. JOJ3 papilla to the frcnum of the clitoris. „,„,u„ ,-j th^t of ... vaeina is subject to ^^ The.vea between the ont,ce..f the urehra ana hat .^^^^^^^^^^^^ i„ the extent considerable inlividual va"?*'"" '"^"^^fj'^i^^'^^rt^ encroaches to which the lower ^nd of the «^tenor v^irul^^^ ^^^ ^^ ^ ^„, upon the vestibule. After rupture ot ^^^/^^^ "^^^^,„^ that turm the caruntu/o' is surrounded by a series d irregular h^^"!^'^^. 'KsXuous nodules. InchuU-d kym.na/.s which, alter l^^^^^' ^Xm^n and he iTkwardly directed arching fold ^r rich^r.^'tr/;rVa'«^^^^ r.'hl.low. crescent^. po.-Uet-,iWe depres- Fio. 1707' CmtrmI tol-body Labium matus Labium minut Ip-tr ftiirfacc Sebaceous glands on exi cutaneous suriacea Intcrlabial (roovc Section acTOM the labia oi veiy young child. X 18. sion This recess is best marked in the virgin, when the nymph* are well developed. .„ais^usu^ly.^-dafjr^^^^^^^^^ posterior labial branches '-m the external and in^^r^^^^^^ ^^^ ^all twig from the »"?«'■««» .^^^^^ Seen ^ anterior commissure ; several ^^^'^.J^™/? tuppS by the posterior labial twigs half of the labium, while the posterior haU '* *"P;P"7;,3i'^ di^^artery. Additional from the superficial Pe"«.^*l branch from thy ntemapud^^^^^^ o the vestibule. The arteries trom tnese varioy. . • '{ tj,e labia ma ora in another as well as with adjacent vessels Wh.le the ^^,«^^^^^^^^^ neighboring general follow the con.esp»ndmg arter.^^^^^^^^^ ,„„,! ThI systems, particularly with t]^?^"^;*'^^;"^ 'e present a pkxiform arrangement, ;tX tSl^ac^rtS^^^^^^^^^^ The collecting stems .■ ( i ma 1 1 3034 HUMAN ANATOMY. join those of the labia niajora, as well as communicate with the veins ol the clitoris and bulb. The lymphatics of the labia are very numerous, noubly in the more superficial parts of the folds, a half dozen or more trunks passing to the upper and medial group of inguinal lymph-nodes. The lymphatics from the nympha, also venr numerous, join the afierents from the labia majora and end in the same inguinal nodes. Communications sometimes exist with the nodes of the opposite sides (Bruhns). The nerves supplymg the anterior half of the labia majora are derived from the ilio-inguinal and the genital branch of the genito-crural, while the posterior part of the labia receive filaments from the perineal branches of the pudic and the small sciatic trunks. The nymphse are highly sensitive and receive branches from the superficial perineal nerves upon which special sensory endings are found within the subepithelial tissue. THE CLITORIS. The clitoris, the homologue of the penis, repeats in reduced size and modified form the chief components of the organ of the male. Morphologically considered, it consists of two corpora cavernosa, united in front into the body and separated behind into the crura attached to the pubic arch, and the imperfectly developed and cleft corpus spongiosum— known as the bulbus vestibuli and usually described as an inde- pendent organ. The clitoris lies so buried within the subcutaneous tissue and beneath the labia that only its small conical anterior end, called the glans clitoridis, and the low verti- FiG. 1708. lorpus clitoridit — Glans clitoridit Pan intermedia Urethral orificC' Bulbui vestibuli Vaginal orifice Inferior layer ot- triansular ligament ■Cms clitoridis curved by ischio"«^Xof he un^T^ s-^ructure in the male. Each bulb half corresponding to a semAm b of ^^ ™ . ^ody. narrow in front and broad regarding the organ as paired, is » rf^^^J?*^ ;„ length, where broadest from a^ rounded behind, that measures from 3 4 cm.j^ ^^^ -^ ^ests against the ,-,.5 cm. in width, and leM »»»»" ' ^m 'y^^^^T^^rgin, somewhat medially di- inferior layer of the trmgular J^e^^^ Sb um ^jus and the nympha. Behind reeled, being covered by the base of the 'aDwmmaj ^ entrance, and Ae m^ial surface is closely /«»^»?2;«J^^ '^"g Jthe posterior wall of the vagina, when well developed may "^"^ Jf ^.S^^urethra^nd joU the under surface of the In front, the bulb pa»« at ^e s de of the uretnra a ) bulbo-cavemosus mus- spongiosum, although 1«8 ^«fi""* '" in^the'ditoris and vestibular bulb correspond ^ Vessels.-The arUrifs supp ymg the ciiioris a ^^^^^^ ^^^ withThose dismbuted to the homologous ^^J^"* J^^^^^j^e (s V artery of the bulb As in the male, the fijf^t branch to the^vemo ^^^ ^^^ ^ ^ short and (a. bttlbl VBitibuU). winch enters that PP^V [^^J^ . ^ ^^ the bulb from the deep J^mparatively strong vessel and ]o.n«wrAa ^L ^^^^ ihe free blood-supply in the horned cattle. Because of ^he 'axity 01 n e ^ ^^^^^^ vest.buli «s labia majora >?r«e h^rnatomata ^^ t^^^'^J;, 7;:i^d\oose tissue in this region, opened. Again. heca"«e of the free "^^ JP V hemorrhage is free, but ord.- plastic operations are ^o?^^"^^^'^ ere/t^ tissue of the clitoris or its continuations narily stops spontaneously unlesa tne erecuie i.» backward, the bulbus vest.buh. « r'""^^^^ ^„ .^e groin, thus explaining the en- The/j/«Ma/^^andr«»«oftheWva^^^^^ nguinal nodes, such as ih-'S. 'a^Snls- S-t^. ;^Vlr;elf ' About L oHfice of the vagina is a zone in which the two sete '"J^'-^'^i^^^^^ .^^etion within the glands Cysls of the vulvaare '^o"™'"^" y,f "^ *? 5^'Hach SdeTthe vaginal orifice, and of Bartholin. They occupy the P«*7;°r,\^'"* ""Jn^^fs^^^^^^ These glands are project more from the mucous f^jT^^^ ST^hJ^orrhe^\M.c6ou. The often the seat of abscess, almost. 'J "f ^^ ^ ' j^^ if is nearest to the vaginal female urethra, running '^^^^^^'i^XiS "c** ^^'^'^' '^'^"''^'^ '""'''' *''^^''' wall in its upper P<>rt'°"T« T ^Jf^^: bHttSrof such density-much more and-as it is not surrounded at ''^ P^'^^^^y/^^^^^^^ j^, shortness, its width, the direc- dilatable than the male urethra '" '=°"^"^'^f„„ ^^ serving as a passage for urine, tion of its course and the l>™t*»'°" "^ 'f„S l^Veq^ andits inflammation ,t is, as compared with the jna^e uretfi^. '"I^jf^^/;,^,^^ >o treatment, and gives ,s associated with less severe ^y"?*"™^' JTiiLVre for example, being very rare, rise to fewer complications a«dseguel^-^tnm^^^ ? exploration As a result of its d«latab.lity it may be u^ SlcuU or pedunculated tumors, if THE MAMMARY GLANDS. 3038 HUMAN ANATOMY. and separate glands, opening by independent ducts, that collectively constitute the true secreting organ (corpas mammae), as distinguished from the enveloping layer of tat and areolar tissue. As seen in the young, well-developed subject, before the occurrence of preg- nancy, the mammae form two hemispherical projections that lie upon the thoracic wall, one on either side of the sternum, extendmg from the outer margin of the latter to the axillary border and from the level of the second to that of the sixth rib. The oudine of the organ is not quite circular but elliptical, the horizontal diameter, from IO-I2 cm. (4-4^ in.), being about one centimetre more than the vertical. The height of the projection measures about 5.5 cm. The rounded contour of the breast depends chiefly upon the fat that forms a complete envelope for the glandular tissue KiG. 1710. Areolii Lohiile oi gland-tissue Fxrretory duct Nipple Ampulla l.actiferous duct Lift mamma drawn from living subjct ; ilucls and jclandular tissue have lie.ii drawn (roni ilisseilimi. except beneath the nipple and, in places, on the deep muscular surface. In the young subject, in whom the gland has ne\er enlarged in consequence of pregnancy, the secre- ttiry tissue is relatix ely small in amount and masked by the fat that penetrates between the lobules. The approximate summit of each breast, when firm and non-pendulous as in young women, is marked by the conical or wart-like >upp/e (papilla mammae), which lies opposite the lower border of the fourth rib and is pierced by the excretory canals, or lactiferous ducts, from the lobes. The nipple, about 1 cm. high, and marked by numerous shallow furrows, is surrounded by the areola, a cutaneous zone about 4. 5 cm. in diameter that is modelled bv minute low elevations produced hv the small subcutaneous areolar glands, or glands of \fontgomery, which represent isolated accessory portions of secretory tissue. Although varying with the complexion, the THE MAMMARY GLANDS. 2039 which not Fig. »;««• Siupen' faai PectonI muK SSc, the oolor ol tl»« part. » "f."^ C-m^ t,. lJ~.. i" varying .hade, ol isrjl;rrir;/,h?J-" e'.Siy-'ss^.rs. b„.w™» te™,„™n, '"'■"Tt1,2X''.£nirr»i.hi„ .he ...pcrtida. la«U o, .he ,«, only forms a general investment for the or- gan, but also sends into it septa that mate- & aid in supporting the fat and glandular issue. Local Spheral th.ckenmgs of he fascia occur above and below and assume the character of suspensory bands those above being known as the ItgofMnis of ^r^ Although for the most part separated fmrn the underlying muscle by a layer of fascia U«t permits of shifting of the mamma. «ts deepest lobules may occupy recesses between the fas- ciculi of the pectoralis major. Structure.— The corpus mammae con- sists of from 15-20 or more flj"e"ed pyrami- dal lobes (lobi mammae), each of which ma distinct gland measuring from 1.5-2 cm. 1 he lobes are radially disposed, the groups of al- veoli or lobules lying towards the periphery and the excretory ducts converging towards the nipple, upon which they open. When enlarged, as during lactation the lobes pro- duce irregularities in the outline and on the surface d the gland-mass that may be felt through the covering of adipose tissue, bach lobe B subdivided by connecUve tissue mto several lobules (lobuH mammae), which in turn are made up of the ultimate divisions of the s^reting tissue or alveoli. The latter are sacular compartments, the walls of which con- sist of a well-defined membrana propna, or basement membrane, lined, •" the resting con- dition, by a double layer of cells. Those next the membrana propna are probably to be regarded as muscular in nature (Lacroix, Benda), thus emphasizing the resemblance ^r^" ^^uTTe'^rW elfment^are cuboid or low columnar, from .005- i„,erveni,/con„ecti.e feue com»pond„,8ly ■jf^u? often r^^U^.hi'^^rS ti' ffin=rcoSsi,ThrSc"Sni ss. -; £.|.<^^- °* ^^e - ^^^^XrJt^t-L tSr etSfTo which .he aWeoU open. never borne children ; hardene.1 in lormalin. 2030 HUMAN ANATOMY. 'Excretoiyduct Involuntao' musck- Section of mammary gland before lactation, x 170. At first tiiey are small and much like the terminal compartments of the eland and imed with a thm stratum of longitudinally disposed involuntary muscle, upon which reste a smgle layer of cuboid epithelial cells. The latter give place to cells of col- umnar type within the lactiferous i-io. i7it. ^„^/j jjjgj g^p formed by the junction of the smaller canals. On approaching the base of the nipple, beneath the areola, each milk-duct presents a spindle-form enhrgement or ampulla (sinus lactiferus), from 10-12 mm. long and about half as wide, that serves as a temporary reservoir for the secretion of the gland. Beyond the ampulla the duct narrows to a calibre of little over 2 mm., passes into the nipple, and ends, after traversing the lat- ter paiallel with the other ducts, in a minute orifice from .5-. 7 mm. in diameter, at the summit of the papilla. On gaining the last-named point, the lining epi- thelium of the duct assumes the stratilied squamous type of the adjacent epidermis. Embedded ,..,., within the de'xate but more or less pigmented skm that covers their exterior, the areola and nippl' contain well- marked bundles of involuntary muscle, by the contraction of which the nipple becomes erect and prominent, as after the application of mechanical stimulus. Within the areola this contractile tissue forms a layer, in places almost 2 mm. thick, that encircles the base of the nipple and is continued into its substance as a net-work of bundles, between which the lactiferous ducts pass. Deeper longitudinal strands of unstriped muscle occupy the axial portions of the nipple. Over both areola and nipple the skin is provided with large sebaceous glands, the secretion of which is increased during lactation and designed Fig. 1713. II ir protection while nursing. . Sweat-glands are absent over -"^ ' " "■ the nipple, but large and modi- fied in the vicinity of the perijih- ery of the areola. The .surface of the latter is modelled, esjiecially towariis the close of pregnancy, by low rounded elevations thiit indicate the positions of the sub- cutaneous areolar or Montgom- ery s glands. The latter are rudimentary accessory masses of glandular tissue, from 1-4 mm. in diameter, that correspond in their general structure with that of the mammary glands. Their ducts open by minute orifices on the surface of the areola. Milk. —The fully estab- lished .secretion of the mammary gland ( lac fcmininum) is an emulsion, the fattv milk- globules being suspended in a clear, colorless, and waterv plasma, the variations in tint— from bluish to yellowish-white— depending upon the amount of fat. The Section of mamman- fland durini^ lactation. shnwinR tlistendcd aJvpiiii lintMl with fat-lK-arins cells. ■: 170. THE MAMMARY GLANDS. 2031 composition of human n.uic includes over 86 per c.nu o«jate .^^"' \t*S m^ subsmces, 5.3 of fat. 5 of sugar. «^d J;^,;'^i"^Jj;^/S d Jpl^t?^ from the phological constituents dm.lk are the mMo^^^^^ ^^^ ^^.^^^ alveolar cells), that vary m sixe from the «"«•""*"";« jP"*" ^^j^^ ^ „uch. Their diameter of from ooj-.^os mm^and exc^P^^^^^^^^^ ^B^„,,^. r^jnroni;i^Str 1^^^^^^^ 2^ •-. the ce.. already emulsiiie*U The arteries supplying the mamma are pnncipuuy n^ . deeper ones surround the gtoups ol aheoU as =''»X„ ,h„ idn the tieh sutareolar £f^"T&e^1,r^«=tfc*^^^^^ w»k. that drain the integument covering the n.ppic and areola. With the e«eept.o» ' 11 \{\ lllr, 2032 HUMAN ANATOMY. of a few trunks that follow the perforating arteries and become afierents of the lymph- nodes lying along the internal mammary artery, all the lymphatics of the breast join to form two or three large trunks that pass from the lower and lateral border of the organ through the subcutaneous tissue towards the axilla to empty, sometimes united into a single stem, into the lymph-node that lies upon the serratus magnus over the third rib. The nerves supplying the glandular tissue are from the fourth, fifth, and sixth intercostals, the accompanying sympathetic fibres passing by way of the rami com- municantes from the thoracic portion of the gangliated cord. Their ultimate distri- bution may be traced to the plexuses upon the t«sement membrane surrounding the alveoli and, according to Arnstein, even between the secretory cells. The cutaneous nerves are derived from both the supraclavicular branches of the cervical plexus and the anterior and lateral cutaneous branches of the second to the fifth intercostals. Development. — The arrangement of the several pairs of mammarv glands possessed by a majority of the lower animals in two longitudinal rows is foreshadowed m the earliest stage of the development of these organs, so characteristic of the highest class of vertebrates (mammalia). A linear thickening of the ectoblast, known as the milk-ridge, appears as a low elevation that extends obliquely from the base of the fore to the inguinal region. Along this ridge a series of enlargements, later sepa- rated by absorption of the intervening portions of the ridge, indicates the anlage for a corresponding number of mammae. The occurrence of a definite milk-ridge in the human embryo is uncertain, although its presence has been observed (Kallius), and the {x>sition of supernumerary mammse suggests its influence. In man a knob-like thickening of the ectoblast appears during the second month n! foetal life. This thickening sinks into the underlying mesoblastic tissue, which undergoes proliferation and condensation and forms an mvestment for the growing epithelial mass. From this envelope the fibrous and muscular tissue of the areola and nipple are derived, while the subjacent mesoblast produces the connective-tissue stroma. The ectoblastic ingrowth represents a sunken area of integument that in principle corresponds to the marsupial pouch of the lowest mammals (.tnonotremes). Solid epithelial sprouts grow out from the sides of the coniral or flask-shaped epidermal plug and are the first anlages of the true mammary gland, later becoming the excretory ducts. Subsequently the central part of the ectoblastic ingrowth undergoes degeneration and destruction, and what at first was an elevation now becomes a depression of the surface. From the middle of this depressed area there appears, shortly before or immediately succeeding (Basch) birth, an elevation that later becomes the nipple. Meanwhile, the epithelial duct-outgrowths penetrate the surrounding condensed mesoblastic stroma, in(!rease in length, subdivide, and acquire a lumen at their expanded distal ends, thus giving rise to the system of ducts and the lobules of imm^nre gland-tissue. With the further development of the latter, the surrounding m' .oblastic stroma is broken up into the interlobular septa and fibrous framework of the corpus mammx. At birth the gland is represented by the lactiferous ducts with their ampullae, the smaller ducts, and the immature alveoli. Quite commonly the mammary glands in both sexes are the seat of temporary activity during the first few days after birth, the breasts yielding a secretion resembling colostrum, popularly known as "witch-milk." The mammae remain rudimentary during childhood until the approach of sexual maturity, when they increase in size and rotundity in consequence chiefly of the deposition of fat. The full development of the true gland is deferred until the occur- rence of pregnancy, when active proliferation and increase in the gland-tissue take place in pre[>aration for its functional activity as a milk-producing organ. After lacta- tion has ended, the mammae undergo regression or involution, the glandular tissue being reduced in amount and returning to a condition resembling that existing before pregnancy. With the recurrence of the latter, the gland again enters upon a period of renewed growth and preparation, to be followed in time by return to the resting condition, in which the .imount of glandular tissue is incon-spicuous. After cessation of menstruation the mammary gland gradually decreases in size, and in advanced years the corpus mammz may be reduced to a fibrous disc in which gland-tissue is almost entirely wanting. PRACTICAL CONSIDERATIONS: MAMMARY GLANDS. 1 ^1 t..!* Uai 2033 SSTof DolvthelU inJnen. a* •nn«»«4fi^.5fTte o^Jlirrence of rudimentary supe™""*'*! PRACTICAL CONSIDERATIONS: THE MAMMARY GLANDS. The sUin coveHn. the ^^^^'^ t^t^^t'^^^^'rft^^^^ mary region. The frequent °5f "f^^^^e .^^^o tSrt that most mothers, being larger. « said ( WiUi^™) P'o^ably to t« d^^^^ ^.^ ^^ ^ „„ ^„ ^^er- ri^t-handed. sucVde ?»"«f V /'^^t^'VitSe pdvic sexual organs, more prone- a|e heavier, more >«;t"»»»^L"?^ S The sSt of carcinoma or other neoplasms, tf hyP«^°P»'yu'"f jrS^^lL u^n the^eath of the pectoralb major muscle. The greater part o the br«st li« "P°" » ; ^^^^^^ tissue being extremely ax. on which it is «r« y ™o^"fi howevtf extends beyond and below the axillary About one-third of the gland. •»°**=X''' r,;!" ;„ .u ' axilla with the serratus mag- Sorderof the pectondis nuj>r. and « m ^dat^n^^^^^^^ ^^l nus and, when large, *"V^ °"f " ^' J^'S miLle. it al*> moves slighdy with the normal breast "loyes fr^Y «ver *«^?„«4 J^3:tio„ of the breast, or ^er it when the muscle « «>nt^~;j ^^mu^le should be kept at rest by bmdmg operation up«n .t or ^r tttremov^. ^^^^^ ^^^^^^^ of the breast to the pec- the arm to the side. In «'^"«£'bS^in the direction of the fibres of the pecto- Su S'" Wrf rovrt'n.S:S^^lo them, it may carry the relaxed muscle ^t'hS no diminution of ability wJlb^nuW^^^^ ., ^^ ^ In examining for PO*'*" °* Jr^'^J' w and may be mistaken for tumors. enlarged, may be felt ^ro^K^j^'t^^St^ wU^^^^^^^ hLd. which should gently To avoid th.s, the gland should be pa pated ^^^^^ ^^ p, comp -ssit agamst *« ^^^'^^J'"^^ "J'" resistant and more promment than the may i recogn zed, <« *7>*=^,'^^,tnhouW?^ thus examined at the same time, normal gland t«sue. . J'^^ V^o^'^J^^g^tence, or sensitiveness may be detected, so that any difference m their ?^^' "'""'^^^^^ j^ found over the fourth intercostal The nipple va men and ^^y«"^^f J.'JJ^^ers of an inch external to the costo- space, or over the fifth 7^' *^"; ' ;.f o^itfon is not constant, and, of course, it chondral junction. In "^^l ^X"emenriaxn^^ and pendency that follow preg- ^ rd\£ a^r^cTmln tntor^of-tn^pical lands and in negresses and women of other of the lower ra<«s. arrested at the stage when the central • Anatom. Anzeiner. Bd. vii., i^jt. -^ Ergebrisse d. Anat. n. Entwidc.. ' An intetesung review of the suDjeci is given uy Bd. ii., 189a. „8 w ao34 HUMAN ANATOMY. exists towards the bottom of which the ducts of the mamma converge. In such casa die depression persists ; in others the areola is present, but the nipple absent In both, while lacution may be normal, the suckling of children is impossible. The nipple may be absent or defective as a result of trauma or of disease— wouiub, burns, ulcers, abscesses — during uifancy. The normal nipples of virgins or nullipara: may be almost on a level with the areola, whde those of multipara are often greatly elongated from the traction u[x>n them. Temporary elongation or erecbon of the nipple may be caused by reflex stunulation of the unstnped muscular tissue of the skin of the nipple and areola. "^"^ Infection of the nipple is common, because, on the one hand, of the many folds of Its delicate cutaneous covering, containing a number of sebaceous glands and closely connected to the underlying structures ; and, on the other, of its frequent exposure during suckling to irntotion from unhealthy discharges from the child's mouth, leading to epidermic maceration and to painful erosions, fissures, and ulceis. Atrophy of the mammary glandular elements is of normal occurrence after the menopause, the fibrous and fatty structure being also affected in many instances of noticeable withenng of the breasts. In early life this condition may result from disease, or from removal of the ovaries, and become a true deformity. l[yP'^'^'^^y o* ^« breast consbts in an overgrowth of both the glandular and the fibrous elements, the latter predominating, an<] tccurs usually between 14 and 30 years of age— the period of greatest sexual activity. Amenorrhoea and pregnancy are frequently associated with it. •II ^'*/'^*^ *•' ***' breast is usually carried through either the lymphatics or the milk ducts, most commonly during the early period of lactation ; more rarely it appears during the other notable periods of mammary physiological excitement— f.r, in the newly bom— the "witch-milk" period {vide *ir™P'S^^^'nf th^ seSuVmagnus ^arising from the third or anterior) overlying U»e tation age 1833). 5. The free communication in the sub.4reolar plexus between the glandular lymphatics, deep and superficial, (paramammary) and the subcutaneous and thoracic lymphatics, together with the connection established between the periglandular tissue below and the skin above by the ligaments of Cooper (suspensory ligaments), explains the frequency with which mammary carcinoma extends to the overlying sicm. As a result of its infiltration the latter bee imes dense, inelastic, brawny, dusky, and adherent. It cannot be picked up betw :en the thumb and finger in a fold; and often quite early and before it has become adherent, and as a result of con- traction of the growth pulling on the fibrous bands uniting it to the deeper parts, it is drawn into a number of little depressions or dimples like those on the skin of an nrange. When such infiltration is diffuse and spreads largely through the subcu- taneous net-work of lymph vessels, the condition known as cancer en cuiraste is pro- duced. In the later stages ulceration, infection, hemorrhage, and foul discharge are frequent results of the cutaneous involvement. 6. If the growth is central it may extend to the lactiferous ducts or to the peri- acinous tissue continuous with that surrounding the ducts, and through its own or their cicatricial contraction it may depress or retract the nipple or puU it so that it deviates from its normal direction. This is not so valuable a symptom as the dim- pling of the skin above described, as it may be caused by injury or by chronic disease, such as abscess, tubercle, or mastitis. Moreover, it may not' be present if the growth is peripheral. 7. The carcinoma may extend through the lymph communications between the gland and the underlying connective tissue and pectoral fascia and muscle, so as to become fixed to or incorporated with those structures, the breast losing much of its mobility, especially in a direction parallel with the pectoralis major fibres. It may thence continue through the thoracic wall ^nd invade the pleural or mediastinal cavity directly. 8. Through the intercommunication of the lymph system of the two breasts through the subcutaneous thoracic lymphatics, cancer of one breast may extend to the other (Moore), or to the glands of the opposite axilla (Volkmann, Stiles), or to the glands of both axillae (Scarpa, Cooper ; quoted by Williams). 9. General dissemination of the cancerous disease may also take place through detached cells or particles (emboli) from the primary growth entering the blood stream. The liver is the organ most frequently affected by metastasis in cases of breast cancer. The bones, the lungs, and the pleurae come next, but almost no organ or structure of the body is exempt. In removal of the breast the following anatomical points should be borne in mind : (o) The intimate connection between the skin and the gland itself by means of lymph- and blood-vessels, by the suspensory ligaments, and by glandular processes accom- panying or contained within these ligaments (Stiles), shows the necessity for free sacrifice of the skin overlying the breast. (b) The irregular shape of the breast, which has two extensions that frequently reach into the axilla, and one that reaches to or overlaps the border of the sternum, and not uncommonly similar processes that spring from other parts of the surface of DEVELOPMENT OF THE REPRODUCTIVE ORGANS. »37 eued glandular tiwue. „trcMrlandutar lattv envelope. brinninR the glandu- (f) The usual detect in the «\W™""'^^^ and muscle ( Hcidenham). ,ar lobile. into in^^X^^/^'K. if that <^ -U^^^ a^lndicates the Iree removal ol laciliutes extenwon o« the disease in m-i the pectoralis major in most <^^: . „^_,, auBolies the same indication as to V ) The lymphatic distribution [^^\J^^'^^ to the le«Ksr pectoral a^so. removal o{ the greater P«^°r*> f ^IrJLnSorTh^Kh cleaning out of the axilla. It. of cour... poinu -^"^^^ove Uie cS^ohJ^^^^^^ no«:les: (a) .«''"* "^"AS is so ^t^^^ the axillary vem. and when this is so m inc y^ 7 s ^^^ ^^^jj ^e inner side these glands ^°" ^ remau^hmd . UM g^^;,, . j^j^ ^-ith their rt'a::?ed'To^; c:;*:^- ^^^^^^^^ --»« ^^^'' ^ --^'^ '"' -^^ removed separately (Leal). dancer during the operation is the (,) The most '«'l^'^4"»,*'^e^^Lre^;^^^^ axillary vein (page 888), '«.*''_f ,?""^^^ .^-^j ^nd the head of the humerus is made and the brachial P»«"*rf '^J^i^Tru^tC^r^^orm^^ lie on the ..ter waU of the to pro ect into the «^;,T^f^_*""^;, of cancerous tissue as to be difficult of axilla, but may be so «nbejf ed jna ^^ «' j ^j,^ subscapular v-^ls and (in recognition. On the P°?»*"°^ .^P^ °; Se long subscapular nerve supplying the close proximity to the '"b^fP"^' ^^ The inner (thoracic) wall of the axilla latissimus doni{ mu^le »^^^^^f^^ Jcondi^ted with the greatest freedom 18 the region in which the a»»«?tion may "^ ., ^ ^^^d in close contact with the posterior thon^ac "«-^~«J-^' ^sf LXch it is distributed. The the outer surface of *'. r?^|"X murse of the operation are (1) the pectoral arteries met with or divided in the "="""f "^j' thoracic; (3) the long thoracic branches of the »"°'«'»».'i^'?"^^' u^' ^^^ (external --2,> ,~he S^th^aS f^^^^^^ intel^tal arteries : and (5) (4) lateral branches from tne seco ^^ artery, emerging at the second. some during operation. DEVELOPMENT OF THE REPRODUCTIVE ORGANS. and temporary stoj^eo^ the p^u^oyh<^g^a ^^^^ ^^ ^ '^^k^^S^tt^IcL^tn'^^^o^lA two additional^^canals-the Miillenan •^-Vrences to the ^^^.^^^ ^ ^Zftl^'^l^^^'^^^^'^^o t\:::^:^Z^LS:lT^:ttXr, that the Wolfhan tubules comprise an anterior sexual and a po?t, , r excretory group. 2038 HUMAN ANATOMY. '^= ^jaiX7"o»X^* •""» a secondary outgrowth, the seminal vesicle. I he cauaai group oi i" i ^rfrepr Jnted^in both sexes by ^dime"^^^,^;,^"^ The epidiiymiT.t sUlkS paradidymis and the vasa aberrantia. The appendix of the epiamym hydatid, probably also owes its origin to the NVolffian duct ^ Although, L is evident from the forgoing. ^»>«.^°;5,Hn the m»»" ^^^^^^^^^ largely concerned in the development of the generative '^act m he male the M ierfan'^duct is not without representation, ''•"-.f ^^^^X^thf tS and tSe upper (after migration lower) end remains as he a pe^^^^^^ .^^^^ lower, fused with its fellow, is seen as the Prostatic titricie.wm^. ^^ ^here it ho. .ologue of the vagina and. possibly, tiie uterus. In exceptional cases, where 3040 HUMAN ANATOMY. persists, the intervening portion of the Miillerian duct is represented by Rathke's duct. Since the prostate gland arises as an outgrowth from the urogenital sini.s (page 1979), it has no genetic relation with the seminal ducts. Descent of the Testes. — ^The development of the sexual glands, in both sexes, is attended with conspicuous migration from their original position on either side of the upper two lumbar vertebrae, opposite the lower pole of the kidney. In the case of the testis, this migration is so extensive that by birth the organ usually has passed through the abdominal wall and entered the scrotum, having completed Its so-called descent. Certain peritoneal folds (mesenteries) and fibro-muscular bands (ligaments) merit brief description, since they are more or less concerned in the migration of the sexual glands. The Wolffian body is enclosed and attached to the posterior body-wall by a fold {mesonephridium), of which the upper elongated end is continued to the Fig. 1719, C BG Diagrams illustrating differentiation of two sexes from indifferent type. A. Indifferent: G. sexual Kland; WD, Wolffian duct; WT. WT. groups of Wolffian tubules; MD, Miillerian duct; RD, renal diverticulum ; C. cloaca; G, gut; A, allantois. *, Male: T. testicle; VE. vasa efferentia; GM. globus major; VD, vas deferens; Pa, para- didymis; VA, vas aberrans ; SV, seminal vesicle ; AT. appendix testis ; AE. appendix epididymidis ; P, bladder ; PU, prosutic utricle; Pr. prostate; Ur, urethra; CG. Cowper's gland ; CC, coipus cavemosum ; R. rectum; RD, rvnai duct; K, kidney. C />»ni/^.- O, ovar>- ; Ov, oviduct ; F, fimbria ; U, uterus ; V, vagina ; DEp, duct of epoophoron ; TEp, tubules of epoophoron ; Po, paroophoron ; HM, hydatid of Morgagni ; GD Oirtner's duct ; BG, Bartholin's gland; C, clitoris; K, kidney; R, rectum. (Moiijied/rmm Wiedershetm?) diaphragm (plica phrenico-mesonephricd) and the lower to the abdominal wall in the inguinal region {plica inguino-mesonephricci). The eariy sexual gland is also provided with a mesentery (mesorchium or mesovarium), that above and below is continuous with folds that pass from the upper and lower poles of the gland to the mesentery of the mesonephros. Within the inferior plica, of the two much the better marked, lies a (ibro-musciilar strand (the ligament of the testis or ovary), that below is attached at first to both the Wolffian and Miillerian ducts. Later, owing to the atrophy of the one or the other of these ducts, according to sex, the ligament of the testes remains connected with the Wolffian duct and the ligament of the ovary with the Miillerian duct. A second band of muscular tissue appears within the lower part of the inguino- mesonephric fold, and has its upper attachment also to the Wolffian and Miillerian ducts at a pcint about \vhcrc they receive the insertion of the ligament of the testes or ovary. The lower end of the band blends with the subperitoneal tissue of the anterior abdominal wall in the vicinity of the future abdominal ring. This hand, the genito- Sexual gland DEVELOPMENT OF THE REPRODUCTIVE ORGANS. 2041 sponding to the origin Pi^, j^^^ of the vas deferens from the epididymis. The testicle begins its descent during the second foetal month, coincidendy with com- mencing atrophy of the Wolffian body, and, under the influence and guidance of the genito- inguinal ligament, by the end of the third month reaches the an- terior abdominal wall in the vicinity of the later internal abdomi- nal ring. This position it retains until the close of the sixth month, when it enters upon its final descent. Meanwhile, the musculo-fascia layers Plicm phrenico- nKsonefihricm Sexual glaiid Wolffian btxly Mesentery al_ (land Wolffian dud Onilo-inguinal liKament I'lica inguino-- niewnephnca / LiKament of gland ^ Umbilical arteries>^ Allantnic duct Umbilical vein wolffian bodie, and ^1 ^^^^Tl^tH::^ "'^'" ifltClll*» •■■■"J musculo-fascia layers .^.^^nation resulting in the production of a shallow of the abdomina wall unde go evagnation r«u g v^^ processus vapnafts pouch, the inguinal bursa, '"^o ^-^l-- J^ genUo-inguinal ligament. The mgumal ^tends, together wuh the ck«elya^c.ated^^^^^^ ^g independently dev_el- bursa. in turn, smks mto the '•*'»'|°*J[/^f j^Vbursa conte^^^ master, and surround feFem^-mgumal ligament ^^^^ ^ .light elevation appears Owing to the thickenmg «l *^^ '"r^^^^in , becomes pushed up towards the on the floor of the bursa which l^us^eem^Y^^^ ^^^^^^^ testis to form the rudiment «\„^^^^^'"Xrv, remains insignificant. In consequence tion, the c^us inguabs, but in man »'*^y?^ "^^^^^ f^ displaced upward and its of these changes, during the fourth month the testis «^^^^^^ temporarily inter- Fig. i7»»- Epididymis Testis Vas deferens Dttv epigMtric »«si€l» Peritoneal cavity Im obi. ind 0»««™» nii»cl«-^ Roi tiis muscle rupted. . . , About the lieginmnj; o the seventh month, the tinal descent of the testicle is in- augurated with dcepenmg of the bursa and downward extension of the peritoneal pouch, accompanied by the now thickened and short- ened geiiito-inguinal liga- ment. Although shorten- ing of the latter, together ij,.gT«n. ~.w-...» .-.., — ^.\^\^ the pull exerted by the ing from the ^ th and expansion "« th?Pf J'^ of the s^ otal Ic in advance of the The processus vaginalis reaches the bottom ot tne scrui- ApoMurolU of eiMIMl oHIque Pentoneun' Genito-inRuinal ligamei.i — Transversalls fascia Cremasler muscle Intercolumnar fascia Integumenury scroUl pouch Processus va(finalis \ AMmcbm«nl of llg«m«nt to J ihUkmed Hoot uf liiiulosl -^ ^,^^ buna Diagram showing early sUg. in descent of testicle. (.-.//- «'««-«) 3042 HUMAN ANATOMY. Peritoneum y Vas deferens Deep cpiKBStric vessels Sac of processus vaginalis Peritoneum Tunica vaginal communis Cremaster Intercolumnar fascia Skin and dartM Diagram showing relations of descended testicle to tcessus vaginalis, which peritoneal sac of abdomen. processus vaginalis, which still freely communicates with (Aft" WaUcyer.) testicle, which, drawn from its mesentery (mesorchium), descends outside and behind the peritoneal pouch that later constitutes its partial serous investment, the tunica vaginalis. After the descent is completed, usually shortiy before birth, but some- times not until afterward, the tubular Fig. 17a a. upper segment of the peritoneal sac closes normally during the early months of childhood. This closure takes place first in the vicinity of the internal ab- dominal ring and in the middle of the tube, passing upward towards the ring and downward to within a short distance of the sexual gland. The occluded portion of the vaginal process is later represented by a small fibrous band (lig- amentum vagina/e) that extends from the internal abdominal ring above, through the inguinal canal and for a variable dis- tance down the spermatic cord, some- times, although not commonly, as far as the tunica vaginalis. When the pro- cessus v^;inalis fails to close, as it oc- casionally does in man and always in certain animals, as the rat, in which de- scent and retraction of the testis periodically occur, the serous sac surrounding the tes- ticle communicates throughout life with the peritoneal cavity, a condition favorable to the production of hernia. With the obliteration of the lumen of the processus vaginalis, an inguinal canal, in the sense of a distinct tube, disappears, the spermatic duct and associated vessels and nerves, that necessarily share in the migration of the sexual gland into the scrotum, passing between the muscular and fascial layers of the abdominal wall embedded in connective tissue. The remains of the shrunken genito-inguinal liga- ment, or gubemaculum, are represented by a fibro-muscular band, the scrotal liga- ment, that connects the lower end of the epididymis to the scrotal wall (Fig. 1687). Descent of the testicle may be imperfectly accomplished, so that the gland, failing to reach the bottom of the scrotal sac, may be arrested within the inguinal canal or spermatic cord, or permanently retained within the abdomen, a condition known as cryptorchism, usually leading to atrophy of the gland. Associated with faulty descent may be anomalous situation, the testis lying beneath the integument near the external abdominal ring, in the tliigh, or in the perineum. After descent the axis of the testicle may be abnormally di- rected, the gland assuming a transverse, rotated, or even inverted position. Differentiation of the Female Type. — Development of female internal reproductive organs proceeds along the same lines as in the male, the ovary being differentiated from the indifferent sexual gland and the genital canals from the Miillerian and Wolffian ducts. Differentiation of the ovary has been described in connection with that organ (page 1993). That of the Fallopian tubes, uterus, and vagina results from further growth, fusion, and modification of the Miillerian ducts. Lower segments Fig. iraj. Peritoneum Vas deferens Deep epigastric vessels Closed portion of, processus vaginalis Cremaster loAindlbulifomi bscU Sac of tunics vs^sslla Visceml layer- ParieUI laver skin and dartoS' Diagram showing relations of testicle to serous mem- brane after upper part of processusvaKinalis has closed, its lower part |>ersisting as tunica vaginalis. of the latter, below the attachment of the ligament of the ovary (p^e 2040), undergo fusion and form the uterus and vagina. Their upper segments remain uufused and be- come Fallopian tubes. Details of these changes are given under the respective organs. DEVELOPMENT OF THE REPRODUCTIVE ORGANS. »43 I„ ,h. ic^Je the Wolto ...buta and due, <''y'^^;'IT^^„:^;^'t^. ,„ lorn radimenHr, organ., Ihe •P<»Pl!»"",k"^rrt^.i;t»« S^ S>0. ^c t --£SH£^s.r^d.c£°^' S'.rK! ill ^^ cremaster muscle. The gland fails to reach the internal abdominal ring and remains until birth at the brim of the pelvis in consequence of the large size of the uterus in relation to the small pelvis. When the growth and expan- sion of the latter have pro- vided additional capacity, as the uterus sinks to its definite position, the ovaries, attached by their ligaments and ovi- ducts, follow into the pelvis. The genito-inguinal liga- ment becomes the round ligament of the uterus, the lower end of which is attached to the subcutaneous tissue of the labium majus at the exter- nal abdominal ring. These relations are foreshadowed by the close association of the lower end of the fcetal liga- ment to the bottom of the ing-jinal bursa and the wall of the processus vaginalis. The lumen of the latter usually disappears, but in exceptional cases may persist as the canal of Nuck (page 2015). Asso- ciated with this condition, occasion.' of the testicle by passing into or ever Suprarenft) body Kidney Ureter Oviduct Round ligament Bladder Suprarenal body Kidney .1 .,.»... ol female talus of third month . showing ovariea ^*"" "i;!?! undJ^nded and bicomate uterus. X 2. ovary more closely imiutes I'^e descent gh the inguin-' .-mal. DEVELOPMENT OF THE EXTERNAL ORGANS. The external genital organs d-lopj^m an ^^^^^^,;^^^^^ beginning of the third month do not exhibU^ne a«g^^^^^ .^ ^^^^^ =nui:r,s?n,fcrEsr'H^33E4s!or^^^ bordering the external cloacal fossa m '^?n;j™J^V°r: ^ differentiates into adisul the ;e-«..W tui^cU. The latter rapidly ^creases in «'^^4"f/Xicji Vcomes divided knob-like end and a bulbous genual expar^on at .t^^^^^^^ ^^^^^^ ^^^ ^.^ by a groove that ««"ds along Uieunde^^^^^^^^ g^^ ^.^^ ^j ^^^ ^^^^^ i„t„ of this groove elongate into the genttai/oias inai nc !! iiij 2044 HUMAN ANATOMY. Surface nurkinf^a of cloacal region of human embn-o o< seventeen days (Fi(. 1644)- X i>. (Keibel.) Fig. t7>6. Genital tubercle Ctoacal membrane Lower limb Caudal process the urogenital sinus that appears when the cloacal membrane ruptures. Somewhat later, about the ninth week, a pair of thick crescentic swellingrs, the outer genital, or !abio-scrotal folds, make their appearance on either side of the genital tubercle. In the female, in which the original relations are largely retained, the genital tubercle grows slowly and is converted into the glans and body of the clitoris, while the inner genital folds become the nymphse and the outer ones the labia majora. The urogenital sinus remains as the vestibule and its opening as the vulvar deft. The wedge of tissue between the posterior margin of the latter and the anus becomet the perineal body. A description of the development of the glands of Bartholin is given in connec- tion with the consideration of these organs (page 2036). In the male the modifications lead- Fig. i7»s- ing to the fully differentiated external f organs are more pronounced in conse- quence of the formation of the urethra. The genital tubercle rapidly increases loacai membrane '" *'^*' ^comes somewhat conical and differentiated into the glans and shaft of the penis. The parts of the outer genital folds behind the penis soon become en- larged, rounded, approach each other, and, finally, unite along a line afterward indicated by the median raphe, so that in embryos of 45 mm. length the scrotum is already well defined. According to Her- 20g,' the development of the urethra pro- ceeds from an epithelial ridge that appears on the cloacal membrane and extends for- ward along the under surface of the geni- tal tubercle towards its distal end. This ridge sinks into the mesoblastic tissue of the elongating genital tubercle as a nar- row longitudinal strand (urethral septum), and later becomes partially divided by a superficial furrow, the urethral groove, the lips of which correspond to the inner geni- tal folds. In consequence of the cleavage of the posterior third of the epithelial ridge, the cloacal membrane is ruptured and communication established with the urogenital sinus by means of a small canal that opens into the urethral groove. As the latter grows farther forward towards the glans, approximation and fusion of its edges occur beh'nd, whereby the groove is gradually converted into the urethral canal. In this manner the distal opening of the urethra is carried forward until its definite pt)sition on the glans is reached. Arrested development or fusion of the edges of the urethral groove results in defec- tive closure of the canal, a condition known as hypospadias (page 1927 ■). The formation of the prepuce begins as a thickening and ingrowth of the surface epithelium at the bottom of an annular groove that separates the glans from the body of the penis. From this thickening the epithelium grows backward, invading the young connective tissue as a narrow wedge-shaped mass that encircles the glans, except below, where it is incomplete and the frenum later appears. In this manner an annular fold, the prepuce, is defined around the base of the glans that later, just before or shortly after birth, becomes free by the partial solution of the intervening solid epithelial stratum and its conversion into the preputial sac. 'Archivf. mikros. Anatom., Bd. Ixiii., 1904. External genitals of human embr>-o of about twenty seven days. (AW/monm.) Fig. 17*7. Labio-scrotal folds ipenin^ of urogenital sinus Anal groove Coccygeal eminence Indifferent stage of external genitals of human embryo of thirty-three days (Fig. 1647). x 8. (Keibfl.) DEVELOPMENT OF THE REPRODUCTIVE ORGANS. ao45 Male. Fio. i7»8. Fbmale. Gbuu Urethral groove. Scroul lolil — Anal gnxiv- Coccyg«»l— eminence w .__GI«n»clUoridit kLmhium maius t-Nymph« -UfogeniUl slnuj Anu> -Coccygeal eminence Seven and a half week.. («frw«^) Clans Urethral groove doling Raphe Scrotum- Nine weeks. {KtiM.) Clans clitoridis •Nymph« Lahium majus Vaginal orifice Eleven weelts. (A5i.«»«^«inLl"i^ii '^'») -r the abdomen. GlanB ilitoridi* Suix:rfiii«l— — laKia Labia minor*"" Vulvar fiMure"^" Labia majtif* CoUm's fascia— EilKc ol cut akin— • Ceccys — Interior pudcnilal nerve — Faacia laUk oi thifh Inferior . pudendal nerve -Tuber iachii t uttaMUl l«ftBchM -..dnttnul*'"'!""'- Dsl p«fi»e»l ■«T»«* From iiuemal (lerineal ner>e — ur b«inoffhot» ^^^^J^J^ t cCp^r S^ '^^^ ^'''^°' ^^ muscular aheet that <:«":«P?"*^ ^''^h^^ Xri^«s. into the deep transverae of this sheet is differentiated. ^'^'VX ftiTtK)5ities. pass behind the vagina perineal muscles which, ansing fronri the ^^^ sheet, collectively much le» to the perineal centre. The "i^J"^'"'"^ ^^^ urShr^ in the male. U continued developed than the sphincter-like ~"?P''^' ,„ "{^closely encircles the vagina. rC^arrfrom the perineal centre as ^^^J'^/^f^^; fr^^of the urethra in the and in front either surrounds he ^'^'l^\^^i (Kalischer). In recognjuon LTtiriSr totlhThe T4S SSri^canals. ^this muscular sheet has been appropriately called the urogenital sphtncUr^ . INDEX. Abdomen, examination of. •B«ton..-«l rela- tiona. S36 faacia, iuperficiftl of. 515^ , Undmarlu and topography of. S3« lymphatici of, 07 a iymph-nodea of. 974 muKleaof. 515 pract. coniiid.. 5»6 ventral aponeuroM of, s»« Abdominal cavity, 161$ aorta, 794 regions, 1615 hernia. i7S9 , incisi'o' s anatomy of, 535 ting, exiemal, 514 internal, 5*4 walU. lymphatics of. 976 poatenor surface of, 5»5 Acervulus, JUS Acetabulum, 336 Acoustic area, 1097 strise. laS" , Acromio-clavicuUr articulation, a6a pract. consid.. ao4 Acromion process, a 50 Adamantoblasts. 1561 Adipose tissue, 79 - , chemical composition of, 83 After-birth, SS Sr^A Kll'nd. (Peyer's patches), .64. Air-cells, ethmoidal, i4a4 pract. consjd.. i4a9 Air-sacs of lung, 1850 Air-spaces, accessory, 14?] pract. consid., 1436 Ala cinerea, 1097 Albinism, 1461 Alcock's canal, 817 Alimentary canal, 1 538 tract, development of. 1694 Alis{>>ienoids, .86 Allatitois, 33 arteries of, 33 human, 3 s stalk of, 33 veins of, 33 Alveoli of lung, iSi'o Ameloblasts, 1561 Amitosis, 14 .\mnion. 30 false, 31 folds of, 30 human, 35 cavity of, 35 fluid of, 4> liquor of. 31 suture of, 31 Amniota, 30 .\mphiarthrosis, 107 Anal canal, it)73 Analogue, 4 Anamnia, 30 Anaphases of mitosis, 13 Anastomoses, of ophthalmic veins, 880 THIS VOLUME CONTA Angulus Ludovici. i6« Ankle, landmarks of, 67 a muscles and fasciae of, pract. . onsid.. «>66 Ankle-joint. 43* movements of, 440 prai.t. consid . 45" Annuli tibroei, of heart, 698 Annulus ovalis, 695 tymjpanicus, 1493 of Vieusaens, 695 Anorchism, «95o . .. Anthropology of skull. asS Anthropotomy, i Antihehx, 1484 Antitragus, 1484 Anlruin. J27 of Highmore, M^' pract. consid., i4a» pylori. 1618 of superior maxilla, aoi Anus. 1673 formation of, 1095 muscles and fasc^a^ of. 167 s pract. consid., 1689 Aorta, abdominal, 794 ^ . . . . branches of, pract. consid., »o6 plan of branches, 796 pract. consid., 796 dorsal, 7a J pulmonary, 7aa segmental arteries of, 847 systemic, 723 thoracic. 791 prac. consid., 730 valves of, 700 ventral, 7a 1 Aortic arch, ^l^ pract. consid., 7ao variations of, 734 bodies, tSia bows, 847 septum. 707 Aponeurosis. 468 abdominal, ventral, 5a» epicranial, 48a (fascia) plantar, 659 i)almar, 606 Appendages,vesicular,of broad ligament,aoo3 Appendices epiploic*. 1660 Appendix epididymidis, 1949 testis, 1949 vermiform, 1664 blood-vessels of, 1667 development and growth of, mesentery of, 1665 orifice of, 1 66a peritoneal relations of, 1665 pract. consid., i68i Aquteductus cochleae, 1514 vestibuli, 15' a Aqueduct of Fallopius, 1496 Sylvian, 1108 Aqueous humor, 1476 chamber, anterior of. 1668 INS PAGES 9»6 TO THE 1476 J05.I END. 2052 INDEX. Aqueous humor, chamber, pocterior of, 147 pract. consid., 1476 Arachnoid, of brain, 1 203 of spinal cord, loaz Aranttus, nodules of, 700 Archenteron, aj Arches, visceral, 59 fifth or third branchial, 61 first or mandibular, 60 fourth or second branchial, 61 second or hyoid, 60 third or first branchial, 61 Arcuate nerve-fibres, 107 1 Area acustica, 1097 embryonic, 23 parolfactory, 1 1 53 pellucida, 35 Areola, aoaS Arm, lymphatics, deep, of, 965 superficial, of, 963 muscles and fascia of, pract. consid., 589 Arnold's ganglion, 1 346 Arrectores pilorum, 1394 Arterial system, general plan of, 730 Artery or arteries, 7 1 o aberrant, of brachial, 775 allantoic, 33 alveolar, 741 of internal maxillary, 741 anastomoses around the elbow, 778 anastomotica magna, of brachial, 77S of femoral, 831 angular, 738 of facial, 738 aorta, systemic, 733 articular, of popliteal, 833 auditory, internal, 759 auricular, anterior, of temporal, 745 deep, 740 of internal maxillary, 740 of occipital, 744 posterior, 744 axillary, 767 pract. consid., 769 azygos, of vaginal, 813 basilar, 758 brachial, 773 pract. consid., 776 brachialis superficialis, 775 bronchial, 793 buccal, 741 of internal maxillary, 741 to bulb (bulbi urethrx), 817 calcaneal, external, 838 internal, 839 of external plantar, 840 calcarine, 760 carotid, common, 730 pract. consid., 731 external, 733 pract. consid., 733 internal, 746 pract. consid., 747 system, anastomoses of, 753 carpal, of anterior radial, 788 of anterior ulnar, 783 arch, posterior, 789 of posterior radial, 788 of posterior ulnar, 783 reta, anterior, 791 centralis retinje. 749 cerebellar, inferior, anterior, 755 posterior, 759 Artery or arteries, cerebellar, superior, 759 cerebral, anterior, 753 middle, 753 posterior, 760 cervical, ascending, of inferior thyroid, 766 of transverse cervical, 767 deep, 764 superficial, 766 transverse, 767 choroid, anterior, 751 ciliary, 749 anterior, 749 posterior, 749 circle of Willis, 760 circumflex, anterior, 773 external, of deep femoral, 838 internal, of deep femoral, 838 posterior, 773 circumpatellar anastomosis, 834 coccygeal, of sciatic, 815 coeliac axis, 797 colic, left, 803 right, 803 comes nervi ischiadici, 815 communicating, anterior, 753 of peroneal, 838 posterior, 751 of posterior tibial, 839 coronary, inferior, 738 of facial, 738 left, 738 right, 738 superior, 738 of facial, 738 of corpus cavemosum, 817 cremasteric, of deep epigastric, 830 of spermatic, 805 crico-thyroid, 734 of superior thyroid, 734 cystic, of nepatic, 799 dental, anterior, of mtemal maxillary, 741 inferior, 740 development of, 846 of lower limb, 848 of upper limb, 848 digital, collateral, of ulnar, 784 of ulnar, 784 dorsal, of foot, 845 of penis (clitoris), 817 dorsalis hallucis, 846 indicis, 789 pedis, 845 pollicis, 789 epigastric, deep, 830 superficial, 8a6 superior, 763 ethmoidal, 749 anterior, 750 posterior, 749 facial, 737 anastomoses of, 738 glandular branches of, 737 pract. consid., 738 transverse, 745 femoral, 831 anastomoses of, 83 1 deep, 838 development of, 833 pract. consid., 834 fibular, supenor, of anterior tibial, 844 frontal, of ascending middle cerebral, 753 TH!« VOLUME CONTAINS PAGES 986 TO THE tND. INDEX. 2053 Artery or arterie.. frontal, of inferior middle cerebral, 753 internal, anterior, 753 middle, 753 posterior, 753 of otmthalmic. 75° . , ,,„ GasserUr of middle menmgeal. 740 gastric, 798 . short, of splenic, 800 gastro-duodenal, 799 gastro-epiploic, left, 801 right, 799 glandular, of facial, 737 gluteal, 811 pract. consid., 014 hemorrhoidal, inferior, 817 middle, 813 superior, 803 hepatic, 799 hyaloidea, i474 hypogastric axis, 808 obliterated, 808 ileo-colic, 80 a iliac, circumflex, deep, 8ai superficial, 826 common, 807 pract. consid., 807 external, 8i8 anastomoses of, 8a i pract. consid.. 819 of ilio-lumbar, 810 internal, 808 , „ . anastomoses of, 81 » pract consid., 810 ilio-lumbar, 810 infrahyoid, of superior thyroid, 734 infraorbital, 741 of internal maxillary, 74' innominate, 729 pract. consid., 729 . , intercostal, of anterior internal mam- mary, 763 aortic, 79a of internal mammary, 765 superior, 764 ., ^ internal mammary, pract. consid., 764 interosseous, anterior, 781 common, 781 dorsal, 846 posterior, 78a . intestinal, of superior mesenteric, 80a labial, inferior, 738 of facial, 738 of internal maxillary, 74' lachrymal, 749. laryngeal, inferior, 766 superior, of superior thyroid, 734 lateral cutaneous, of aortic intercostals. lenticulo-striate, of middle cerebral, 75a lingual, 735 , ^ anastomoses of. 730 dorsal, 736 pra^t. consid., 736 lumbar, 80 j of ilio-lumbar, 810 malleolar, external, 844 internal, of anterior tibial, 844 of posterior tibial, 839 mammary, of aortic intercostals, 793 internal, 763 lateral interna], 764 masseteric, 740 Artery or arteries, mi^sse.^.- 0, of facial, 738 of internal maxillary, 740 mastoid, of occipital. 744 maxillary, internal, 739, anastomoses of. 74a development of, 74a median. 781 , mediastinal, of internal mammary, 703 of thoracic aorta, 79a meningeal, anterior, 748 ofascending pharyngeal, 743 middle, 740 of internal maxillary, 74© posterior, of otiipital, 744 of vertebral, 758 small, 740 mesenteric, inferior, 80a superior, 801 metacarpal, dorsal. 789 metatarsal, of foot, 84S middle, colic, 80a musculo-phrenic, 763 nasal, lateral, 738 of facial, 738 of ophthalmic, 750 naso-palatine, of internal maxillary, 74a nutrient, of brachial. 774 of peroneal. 838 of posterior tibial, 838 of ulnar, 781 obturator, 813 . from deep epigastnc, 814 occipital. 743 pract. consid., 744 cesophageal, of gastric, 798 of thoracic aorta. 79a omphalomesenteric, 31 ophthalmic, 748 anastomoses of, 7 50 orbital, of middle meningeal. 740 of temporal, 745 ov.irian, 805 of uterine, 813 palatine, ascending. 737 of facial, 737 descending, 741 of internal maxillary, 74' palmar arch, deep, 785 superficial, 784 deep, 78a intero8S.TOus, 790 palpebral, of internal maxillary, 741 of ophthalmic, 7 50 pancreatic, of splenic, 800 pancreatico-duodenal, inferior, 802 superior. 799 parietal, of middle cerebral, 753 parieto-occipital, 760 temporal, 753 parotid, of temporal, 74.S. , __ perforating, of anterior internal mam- mary, 763 of deep femoral, 828 posterior, of external planti.r, 840 of radial, 70' perineal, superficial, 817 transverse, 817 peroneal, anterior, 838 posterior, 838 of posterior tibial, 838 petrosal, of middle meningeal, 740 pharyngeal, ascending. 743 I of ascending pharyngeal, 743 THIS VOLUME CONTAINS PAGES 996 TO THE END. 2054 INDEX. Artety or arteries, phrenic, inferior, 804 superior, 763 plantar arch, 840 digital, 840 external, 840 internal, 839 interosseous, 840 popliteal, 831 pract. consid., 833 posterior choroidal, 760 ininceps cervicis, 744 hallucis, 841 poUicis, 789 profunda, inferior, 777 superior, 777 prostatic, 81 a pterygoid, 740 of internal maxillary, 740 pterygo-palatine, 742 of internal maxillary, 743 pubic, of deep epigastric, 810 of obturator, 813 pudic, external, deep, 828 superficial, 826 internal, 815 accessory, 8t8 pulmonary, 723 valves of, 700 pyloric, of hepatic, 799 radial, 785 development of, 786 pract. consid., 786 recurrent, 787 radialis indicis. 790 superficialis, 775 ranine, 736 recurrent, of palm, 791 of posterior interosseous, 782 renal, 804 sacral, lateral, 810 middle, 806 scapular, dorsal, 773 posterior, 767 sciatic, 815 septal, of nose, 738 sigmoid, 803 spermatic, 805 spheno-palatine, 743 of internal maxillary, 742 spinal, anterior, of vertebral, 759 posterior, of vertebral, 758 splenic, 800 stemo-mastoid, of external carotid, 743 of occipital, 744 of superior thyroid, 734 striate, external, of middle cerebral, 752 internal, of middle cerebral, 752 structure of, 675 stylo-mastoid, 745 subclavian, 753 pract. consid., 756 subcostal, 792 sublingual, 736 submental, 737 of facial, 737 subscapular, 77a suprahyoid, 736 supraorbital, j\g suprarenal, 804 inferior .Hn.} suprascapular. 767 tarsal, external, 845 internal, 845 Artery or arteries, temporal, anterior, ol vertebral, 760 deep, 740 of internal maxillary, 740 middle, 74s posterior, of vertebral, 760 superficial, 745 pract. consid., 745 thoracic, acromial, 771 alar, 773 long, 772 superior, 771 thyroid axis, 765 pract. consid., 766 inferior, 766 superior, 734 pract. consid., 735 tibial, anterior, 842 anastomoses of, 844 pract. consid., 843 posterior, 834 anastomoses of, 841 development of, 836 pract. consid., 836 recurrent, anterior, 844 posterior, 844 tonsillar, 737 of facial, 737 tubal, of ovarian, 805 of uterine, 813 tympanic, of internal carotid, 748 of internal maxillary, 740 of middle meningeal, 740 ulnar, 778 accessory, 776 development of, 779 pract. consid., 780 recurrent, anterior, 781 posterior, 781 umbilical, 54 ureteral, of ovarian, 805 of renal, 804 of spermatic, 805 of uterine, 813 urethral, 817 uterine, 813 vaginal, 813 vertebral, 758 pract. consid., 761 vesical, inferior, 81 1 middle. 811 of obturator, 813 superior, 81 1 vesiculo-deferential, 81 a Vidian, 742 vitelline 33 volar, superficial, 788 Arthrodia, 113 Articulation or articulations, acromio-clavio ular, pract. consid , 364 carpo-metacarpal, 325 movements of, 336 costo-vertebral, 160 of ethmoid, 194 of foot, 440 of frontal bone, 197 of inferior turbinate bone, 308 of lachrymal bone, 307 of malar bone, 310 metacarpo- phalangeal. 327 movements ot, 338 of nasal bone, 309 of occipital bone, atlas, and axis, 135 THIS VOLUME CONTAINS PAGES 996 TO THE END. INDEX. 2055 ArUcutation or articulatioM. of palate bone 205 of parietal bone, 199 sacro-iliac, 338 scapulo-clavicular, aoj of sphenoid bone, 190 stemo-clavicular, a6i pract. consid., 263 of superior maxilla, »oi of temporal bone, 184 temporo-mandibular, 214 development of, 215 movements of, 215 thoracic anterior, 1 58 of thorax, IS7 of thumb, 3»6 , . ^ tibio-fibular, inferior, 390 superior, 396 of vertebral column, 132 of vomer, 206 Arytenoid cartilages, 1810 Asterion, 228 Astragalus, 4«3 , development 01, 4*5 Astrocytes, 1003 Atlas, 130 development of, 131 variations of, 120 Atria of lung, 1850 Auditory canal, external, 1407 „ blood-vessels of, 1489 nerves of, 1490 pract. consid., 1491 internal, 1514 ossicles, 1496 path, 1258 Auerbach, plexus of, 1643 Auricle or auricles, 1484 antihelix of, 1484 antitragus of, 1484 blood-vessels of, 1480 cartilage of, 148 s concha of, 1484 of heart, 693 helix of, 1484 ligamenU of, i486 lobule of, 1484 muscles of, i486 nerves of, 1487 pract. consid., 1490 structure of, 1485 tragus of, 1484 Auricular canal, 70s ,u „^ ■,„, Auriculo- ventricular bundle of heart, 701 ^"'muiJlU and fascia of, pract. consid., 579 Axis, 121 Axis-cylinder, looi Axones, of neurones, 997 Azygos system of veins, 893 Bartholki, glands of, 2026 Basion, 228 , Bell, external respiratory nerve of, 1295 Bertin, bones of, 191 columns of, 1876 Bicuspid teeth, 154S Bile-capillaries, 1715 Bile-duct, common, 1720 opening of, 1720 pract. consid., 1731 interlobular, 1717 lymphatics of, 981 Biliary apparatus, 17 18 Bladder, lymphatics of, 985 urinary, 1901 capacity of, 1903 development of, 1938 in female, 1908 fixation of, 1905 infantile, 1908 interior of, 1904 nerves of, 191 o peritoneal relations of, 1904 pract. consid., 1910 relations of, 1906 structure of, i9°8 trigone of, 1904 vessels of, 19 10 Blastoderm, 32 bilaminar, 23 trilaminar, 23 Blastodermic layers, 22 derivatives of, 24 vesicle, stage of, 56 Blastomeres, 21 Blast - 2S Bla. Blor Bio jlored, 681 .„c, 684 development of, 687 Blood-crystals, 681 lakes of dural sinuses, 85* plaques, 685 Blood-vascular system, 673 Blood-vessels of auricle, i486 of bone, 93 of brain, uo6 capillary, 678 of cartilage, 81 development of, 686 of duodenum, 1649 of Eustachian tube, 1 504 of external auditory canal, 1489 of eyelids, 1445 of glands, 1535 of hair-follicles, 1394 of kidney, 1884 of liver, 1 709 lobular, of liver, 17 13 of lung, 1853 . ^ . .. ,.. of membranous labynnth, 1522 of nasal fossa, 1425 , of non-striated muscle, 456 of nose, 1407 of pericardium, 716 of pleura, i860 of rectum, 1679 of retina, 1467 of sk=- 1387 of smaU intestine, 1642 of spinal cord, 1047 of stomach, 1627 of striated muscle, 464 structure of, 673 of sweat glands, 1400 vasa vasorum, 674 Body-cavity, differentiation of, 1 700 Body-form, general development of, 56 Body-stalk, 37 Bone or bones, 84 age of, 106 astragalus, 423 of Bertin, 191 blood-vessels of, 93 THIS VOLUME CONTAINS PAGES 996 TO THE END. 2056 INDEX. middle, 41; development of, 94 Bone or bones, calcaneum, 4 1 9 canaliculi of, 86 cancellated, 85 carpus, 309 cells of, 89 chemical composition of, 84 clavicle, 257 • compact, 86 development of, 100 cranium, 172 cuboid, 423 cuneiform, 310 external, 428 internal, 426 of, I endochondral, 94 intramembranous, 98 diaphysis of, 104 elasticity of, 105 ethmoid, 191 femur, 352 fibula, 390 frontal, 194 general considerations of, 1 04 growth 01, 10 1 Haversian canals of, 88 system of, 86 humerus, 265 hyoid, 216 ihum, 332 inferior turbinate, 308 innominate, 332 intramembranous, loi ischium, 336 lachrymal, 207 lacunx of, 86 lamells of, circumferential, 86 Hav rsian, 86 int( stitial, 86 lymphatics cf, 93 malar, 209 maxilla, inferior, 211 superior, 199 mechanics of, 105 metacarpal, 314 metatarsal, 428 nasal, 209 nerves of, 94 number of, 107 occipital, 172 OS magnum, 312 palate, 204 parietal, 197 parts of, 106 patella, 398 periosteum of, 89 phalanges of foot, 431 of nand, 317 physical properties of, 85 pisiform, 311 pubes, 334 radius, 287 relation of to figure, 107 ribs, 149 scaphoid, 309 of foot, 425 scapula, 248 semilunar, 310 sesamoid. 104 sex of, 106 shapes of, 104 Sharpey's fibres of, 87 Bone or bones, of shoulder -girdle, 248 skull, 17a sphenoid, 186 sphenoidal, turbinate, 191 sternum, 155 structure of, 85 subperiosteal, 98 tarsal, 419 temporal, 176 of thorax, 149 tibia, 383 trapezium, 311 trapezoid, 311 ulna, 281 imciform, 312 variations of, 107 Volkrnann's canals of, 89 vomer, 205 Bone-marrow, 90 cells of, 92 giant cells of, 92 nucleated red cells of, 92 erythroblasts, 93 normoblasts, 93 primary, 95 red, 90 yellow, 93 ' Bowman, glands of, 1415 membrane of, 1451 Brachium, inferior, 1107 internal structure of, mo superior, 1107 Brain, 10S5 blood-vessels of, 1 206 general development of, lojS lymphatics of, 948 measurements of, 1195 membranes of, 1197 pract. consid., 1307 weight of, 1 196 Brain-sand (acervulus), 1135 Brain-stem, 1056 Brain- vesicles, primary, 1059 secondary, 1061 Branchial arches, derivatives of, 847 Bregma, 328 Bronchial tree, 1847 variations of , 1849 Bronchus or bronchi, 1838 homologies of, 1848 Sract. consid., 1840 , membrane of, 1456 Brunner, glands of, 1639 Buccal fat-pad, 489 Bulb, 1063 of internal jugular vein, 8A1 olfactory, 11 51 urethral, 1968 Bulbo-tecto-thalamic strands, 11 16 Bulbus vestibuli, 2025 Bulla, of ethmoid, 194 Bums, space of, 543 Bursa or burss, 1 1 1 acromial, $86 around ankle. 648 bicipito-radial, 586 iliopectineal, 623 of biceps femoris, 636 of gluteal region, 630 of knee-joint. 406 of m. obturat. int., 630 of m. pyriformis, 561 olecranal, 586 THIS VOLUME CONTAINS PAGES C96 TO THE END. INDEX. 3057 Bursa or bursa, subdeltoid, 578 subscapular, 57* Ca-vum, 1660 blood-vessels of, io*7 interior of. 1661 . ,(.. peritoneal relations of, 1665 position of. 1 66a pract. consid., 1680 structure of, 1663 Calamus scriptorius, 1096 Calcaneum, 419 Camper's fascia, Ji 5 ,, . . Canal or canate, Alcock s, 817 alimentary, 1538 anal, 1673 auditory, external, i4»7 auricular of heart, 705 carotid, 184 central, of spinal cord, 1030 of Cloquet (Stilling), i474 crural, 625 . » „. ethmoidal (foramina), 19* facial, 184 femoral, 6a S,^ Haversian, of bone, »» Hunters, 6a8 hyaloid, 147 4 incisive, I4'3 inguinal, 523 naso-lachrymal, i479 neural, a6 neurenteric, as of Nuck, aoo6 palatine, anterior, aoi posterior, ao4 of Petit, 1476 pterygo-palatine, 305 reuniens, 1515 of Scarpa, aoi of Schlemm, i45» semicircular membranous, 151 5 osseous, 151a structure of, 1516 of Stenson, aoi of Stilling, 1474 VidUn, 180 Volkmann s, of bone, 89 Canaliculi, of bone, 86 lachrymal, 1478 Canine teeth, 1 544 Canthi of eye, i44» ,„ CapiteUum of humerus, a68 Capsule, extemfil, ii7» of Glisson, 1708 internal, ii73 ^ , „ Suprarenal (body), 1801 of Tenon, 504 Caput medusae, 534 Cardiac muscle, 46a Cardinal system of veins, 854 Carina tracheae, 1837 urethralis, aoi 6 Carotid body (gland), 1809 chromaffine cells of, 1010 sheath, 543 Carpo-metacarpal articulations, 335 Carpus, 309 pract. consid., 319 Cartilage or cartilages, 80 Cartilage or cartiUges, articular, 81 arytenoid, 1816 of auricle, 1485 blood-vessels of, 81 capsule of, 80 chemical composition of, 83 costel, 153 cricoid, 181 3 cuneiform of Wnsberg, 181 7 development of, 8a elastic, 81 hbrous, 8 a hyaline, 80 lacunae of, 80 lateral, of nose, 1405 matrix of, 80 of nasal septum, 1405 uf nose, 1404 perichondrium of. 81 of Santorini, 181 7 thyroid, 1814 triangular, of nasal septum, aa4 vomerine, 1406 Cartilage-cells, 80 CaruncuUe hymenales, aoi 6 salivares, 1581 Caruncle, lachrymal, 1443 . Cauda equina of spinal cord, loas Cavity, abdominal, 161 5 tiasal, a 33 pneumatic accessory, aa6 segmentation, aa synovial, of foot, 447 tympanic, I49» of tympanum. 183 Cell or cells, animal, 6 of bone, 89 of connective tissues, 73 decidual, 47 gustatory, 143 5 mastoid, 1504 of Rauber, 33 spermatogenetic, 1943 tactile, of Merkel, 1016 Cell-division, 10 direct, 14 indirect, u reduction division, 18 Cell-mass, inner, 33 intermediate, 39 Cementoblasts, 1563 Cementum, 155a formation of, 1 563 Centrosome, 9 Cephalic flexure, 1061 Cerei'sUar peduncle, fibre-tracts of, 1093 inferior, 1067 inferior, fibre-tracts of, 1093 middle, fibre-tracts of, 1094 superior, fibre-tracts of, 1094 Cerebellun., io8a architecture of, 1088 cortex of, ioqo histogenesis of, 1 105 development of, 11 03 flocculus of, 1085 hemispheres of, 108 a lobus cacumicis of, 1085 centralis of, 1084 divi of, 1085 culminis of, 1084 lineulx of, 1084 noduli of, 1085 THIS VOLUME CONTAINS PAGES 996 TO THE END. iOjS INDEX. (-.';-' Cerebellam, lobus pyramidis of, 1086 tuberis uf, 1087 uvuls of, iod6 medullary substance of, 1093 nuclei, internal of, 108S nucleus, dentate of, 10S8 einboliformis (embolus) of, 1089 fastigii of, 1089 globosus of, 1089 Purkmje cells of, 1090 tonsil (a.mygd»la) of, 1086 worm of, 108] Cerebral commissures, development of, 1194 convolutions (gyri), 1135 fissures (sulci), 1135 hemispheres, 1133 architecture of, 1155 longitudinal fiisure of, 1133 lobes, 1 135 localization, mo peduncles, 1107 Cerebro-spinal fluid, 1033 Cerumen, 1489 Cervical flexure, 1063 Cheeks, 1538 lymphatics of, 951 pract. consid., 1594 Choanse, 1413 (bony), 334 primitive, 1439 Chorda dorsalis, 37 Chordae tendines, of heart, 697 Choriocapillaris, 1456 Chorion, 33 allantoic, 33 epithelium of, 49 frondosum, 38 human, 41 laeve. 38 primitive, 31 syncytium of, 49 villi of, 49 Choroid, 1455 development of, 1483 plexus of fourth ventricle, 1 1 00 of third ventricle, 1131 pract. consid., 1459 structure of, 1456 Chromaffine cells of carotid body, 1810 Chromatin, 9 Cilia, 70 Ciliary body, 1457 ganglion, 1336 muscle, 1458 processes, 1457 ring, 1457 Circulation, foetal, 939 general plan of, 719 Cistemu magna, 1303 Claustnim, 1 173 Clava, 1066 Clavicle, 357 development of, 358 fracture of, 359 landmarks of, 360 pract. consid., 358 sexual differences, 358 surface anatomy of, 358 Clinoid process, anterior, 189 processes, middle, 186 posterior, 186 Qitoris, 3034 glans of, 3014 Clitoris, nerves of, 2015 prepuce of, 3034 vessels of, 3035 Cloaca, 1696 Cloquet, canal of, 1474 lymph-nodes of, 993 Coccygeal body, 1810 Coccyx, 137 development of, 131 Cochlea, membranous, i5>7 nerves of, 1531 or^an of Corti of, 15 19 Reissner's membrane of, 151 7 structure of, 15 18 osseous, 1513 Coeliac plexus, lymphatic, 973 Coelom, 38 pericardial, 1700 pleural, 1700 Cohnheim's fields of striated muscle-fibre, 4O1 Collagen, 83 Colles, fascia of, 563 ligament of, 533 CoUiculi inferiores, 1107 superiores, 1107 Colliculus, inferior, internal structure of, IIIO superior, internal structure of, mo Colon, 1668 ascending. 1668 blood- vessels of, 1673 descending, 1669 flexure, hepatic of, 166S splenic of, 1668 lymphatics of, 1673 nerves of, 1672 peritoneal relations of, 1670 pract. consid., 1685 relations of, 1668 transverse, i668 Colostrum, 3031 corpuscles, 3031 Columnae camese, of heart, 697 Column, spinal, 114 Columns, anterior, of spinal cord, 1037 lateral, of spinal cord, 1037 of Morgagni, 1674 posterior, of spinal cord. 1037 Commissura habenulae, 1 1 34 hippocampi, 1158 hypothalamica, 11 28 Commissure, anterior, 1185 of Meynert, 1115 middle, 11 19 pnsterior, 1135 Concha, 1484 Condylarthrosis, 113 Conjunctiva, 1441 bulbar, 1445 palpebral, 1445 pract. consid., 1447 Connective substances, chemical composi- tion of, 83 tissues, 73 cells of, 73 fixed, 74 typical, 74 wandering, 74 chemical ccmposition of, 83 granule-cells of 74 ^ound-substance of, 7 5 mtercellular constituents of, 74 pigment-cells of, 74 1 THIS VOLUME CONTAINS PAGES 996 TO THE END. ■ in INDEX. 2059 Construction, general plan o^t Conus meduUari., of »P'"al {^°[f 1, "" ' Convolutions (gyn) cerebral, ii35 Cooper, Ugaments of, aoag Cord, spermatic, i960 Corium, 1383 Cornea, 1450 pract. consid., 1453 structure of, I45> ComiculiE laryngjs, 1817 Comua sphenoidalia, 19' Corona radiata, it85 Coronoid process. °f "!"»•. '*' .6 Corpora cavernosa of pems 1966 SnammiUaria (albicantia), ii»S quadrigemina, 1106 Corpus albicans, i99' Arantii, 7°° callosum, 1155 ciliare, I457 dentatum, 1088 tibrosum, i99' Highmori, i94» luteum, 1990 , . ,., spongiosum, of penis, 196? striatum, 1169 , ,,, connections of, 1172 development of , 1193 structure of, 1 1 7 ' subthalamicum, 1128 trapezoides, 1079 Corpuscles, corneal, 14 5» genital, 10 17 of Grandry, 1016 of Hassall, I799 of Herbst, 1019 of Meissner, 1017 of Ruflfini, 1017 Vater-Pacinian, ioi» Cortex of cerebellum, logo cerebral, histogenesis of , ..9. local variations in, 1180 nerve-cells of. 1176 nerve-fibres of, "79 structure of, 11 75 Corti, ganglion of, "57 membrane, 15*' organ of, I5'9 Costal cartilage, 153 Cotyledons of placenta, 5° Cowper, glands of, 1984 Cranial capacity, 23° nerves, 1319 abducent (6th), H49 auditory (8th), 1J56 develooment of, 1376 facial (7th), i»5o Blosso-pharyngeal (9th). n6o Hypoglossal (nth), i»75 oculomotor (3rd), uaS olfactory (ist). mo optic (»nd), 1223 pract. consid., mo spinal-accessory (nth), ineeminal (5th), 1230 trochlear (4th), m8 vagus (loth), 1265 Cranio-cerebral topography, 12 14 Cranium, 172 architecture of, 220 exterior of, 218 fossa, anterior, 220 middle of, 220 1274 Cranium, fossa, posterior of, aao fractures of, 238 iSStdYascia., prac-.. consid.. 489 pract. consid., 235 vault of, 320 Cretinism, 1794 Cricoid cartilage, 1813 Crista gain, of ethmoid. 191 Crura of penis, 1967 Crusta. Ill 5 Cuboid bone. 422 Cumulus Oophorus. 1989 Cuneate nucleus, 1069 tubercle, 1067 Cuneiform bone, 310 extemal, 428 internal, 426 middle, 427 Cuticle, 1385 , „ Cuvier. duets of, 854 Cystic duct, 1720 pract. consid., 173' Cytoplasm, structure of, 7 Dacrvon, 328 Darwin, tubercle of, 1404 Decidua, 44 capsularis, 46 I cells of, 47 placentalis. 48 retlexa, 45 serotina, 48 vera, 46 . . ,. Decussation of pyramids, 1064 sensory, 1070 Deiters. cells of , 1521 nucleus, 1076 Demours, membrane of, i45» Dendrites, of neurones, 997 Dental formula, 1 543 papilla. 1558 Dentine. 1550 , formation of, 15 59 . , Dentition, first and second, 1 564 Derma, 1383 , ,^,, Descemet s membrane, 1452 S^^JlfimTntoUlimentary tract, .694 of atlas, 131 of auditory nerves, 1535 of axis, 131 of bone, 94 of carpus, 3 1 3 of cartilage, 83 of cerebeUum, 1103 of clavicle, 358 of coccyx, 131 of cranial nerves, 1376 of ear. 1523 early, IS of elastic tissue, 77 of ethmoid bone, 194 of extemal ear, 1526 of extemal genital organs, 2043 of eye. 1 480 of face, 62 of Fallopian tube. 1999 of femur, 359 of fibrous tissue, 76 of fibula, 393 of frontal Done, 197 of ganglia. 1012 THIS VOLUME CONTAINS PAGES 996 TO THE END. 9o6o INDEX. Development, general, of brain, 1058 of general Dody-form, 56 of glands, 1537 uf hairs, 1401 of heart, 705 of humerus, 269 of hyoid bone, a 16 of inferior turbinate bone, 208 of innominate bone, 337 of internal ear, 1 523 of kidney, 1937 of liver, 1723 of lungs, 1 86 1 of lymphatic vessels, 939 of lymph-nodes, 940 of malar bone, 2 1 o of mammaiy glands, 2032 of maxilla, inferior, 213 of maxilla, superior, 202 of medulla oblongata, 1 101 of mesencephalon, 1 1 1 7 of middle ear, 1 52 s of muscle, non-striated, 457 of muscle, striated, 465 of nails, 1403 of nasa! bone, 209 of nerves, 1375 of nervous tissues, 1009 of nose, 1429 of occipital bone, 175 ol oral cavity, 62 glands, 1589 of ovary, 1 993 of palate bone, 205 of pancreas, 1737 of parietal tx>ne, 199 of patella, 400 of pelvis, 344 of peripheral nerves, loii of peritoneum, 1 70^ of pharynx, 1603 of pituitary body, 1808 of pons Varolii, 1 103 of prostate gland, 1979 of radius, 293 of reproductive organs, 2037 of respiratory tract, 1861 of ribs, 1 53 of sacrum. 1 39 of scapula, 253 of skin, 1 400 of sphenoid bone, 190 of spinal cord, 1049 of spleen, 1787 of sternum, 157 of suprarenal bodies, 1804 of sweat glands, 1404 of sympathetic system, 1013 of teeth, 1556 of temporal bone, 184 of thymus body, 1800 of thyroid body, 1 793 of tibia, 387 of ulna, 385 of urethra, 1938 of urinary bladder, 1938 organs, 1934 of uterus. 2010 of vagina, 2019 of veins, 926 of vertebrae, 128 of vomer, 206 Diaphragm, ^56 lymphatics of, 970 of pelvis, 1676 Diaphra^a sella, 1 200 Diaphysis, of bone, 104 Diarthrosis, 107 Diencephalon, 11 18 Diverticulum of Meckel, 44 Dorsum selke, 1 86 Douglas, fold of, 532 JS'7 pouch of, 1741 Duct or ducts, cochlear, of Bartholin, 1 585 bile, 1730 of Cuvier, 854 cystic, 1730 eiaculatory, 1955 Gartner's, 3001 hepatic, 1718 lactiferous, 3028 lymphatic, right, 945 Mfllterian, 3031 nasal (naso-lachrymal) 1479 pancreatic, 1736 paraurethral, 1924 parotid, 1583 of Rathke, 2040 renal, 1894 of Rivinus, 1585 of Santorini, 1 736 spermatic, 1953 of Stenson, 1583 sublingual, 1585 Submaxillary, 1584 thoracic, 941 thyro-glossal, 1793 vitelline, 32 of Wharton, 1584 of Wirsung, 1736 Wolffian. 1935 Ductus arteriosus (Botalli), 733 endolymphaticus, 15 14 venosus (Aarantii), 939 Duodenal glands, 1639 Duodeno-hepatic ligament. 1644 Duodeno- jejunal flexure, 1645 fosss, 1647 Duodenum, 1644 interior of, 1648 Dupuytren's contraction, 616 Dura mater of brain, 1198 of spinal cord, 1033 Ear, 1483 development of, 1 533 e>:temal, 1484 pract. consid., 1490 internal, 1510 membranous labyrinth of, 1514 osseous labyrinth of, 1 5 1 1 perilymph of, 15 14 lymphatics of, 950 middle, 1493 antrum of. 1508 Eustachian tube, 1501 mastoid cells, 1 504 pract. consid., 1504 suprameatal triangle, i5?o suprameatic spine, 1 508 tympanum of, 1493 Ear- point, 1484 Ectoblast, 33 THIS VOLUME CONTAINS PAGES S96 TO THE END. INDEX. 3061 \ EKK-nucleu», 16 lUstic tiMue, 76 development of, 77 Elastin, 83 Elbow-joint, 301 landmarks of, 308 movements of, 303 pract. consid., 305 Embryo, stage of, 56. Emincntia hypoglossi. 1098 teres, 1097 Enamel, 1548 , , formation of, 1 50* Enamel-cells, 1561 Enamel-cuticle, 1550 Enamel-organ, 1560 Enarthrosis, 1x3 Encephalon, lojS , End-bulbs of Krause, 1016 fiSd-knobs of free «»nsory nerve-endmgs, 1015 Endocardium, 702 »,.,,:„,», jua Endolymph of membranous labyrinth. i5«4 Endometrium, 2007 Endomysium, 45* Endoneurium, 1006 Endothelium, 7« Enophthalmos, i439 ^ _ .,« Ensilform cartilage of sternum, 156 Entoblast, 23 Entoskeleton, 84 Ependymal cells, 1004 Epicardium, 70* Epidermis, 1385 Epididymis, 1947 appendix of, 1949 canal of, 1948 digital fossa of, 1947 globvis major of, 1947 minor of, 1947 nerves of, 1948 structure of, 1947 vasa abherrantia of, 1950 vessels of, 194* Epiglottis, 1816 ligaments of. 181 7 movements of, 1817 Epimysium, 458 Epineurium, 1006 Epiphysis. iU4 ossification of, 98 Epispadias, 1928 Epithalamus, 1H3. Epithelium of chorion, 49 columnar, 69 glandular, 70 modified, 70 pigmented, 70 specialized, 70 squamous, 68 stratified, 68 transitional, 69 Epitrichium, 1401 Eponychium, 1403 Epoophoron, jooo Erythroblasts, 9» Ervthrocytes, 681 development of, 687 Ethmoid htme, 191 articulations of, 194 bulla of, 194 cells of, 192 development of, 194 Ethmoid turses of, I457 cornea of, 14J0 fovea centralis of, 1466 iris of, 1459 lens, crysUUine of, 147 « macula lutea of, 1466 movements of, 505 optic nerve of, 1469 ora serrata of, 1467 pract. consid., 1449 retina of, 1462 sclera of, i449 , vascular tunic of. 14 54 vitreous body of, i473 Eye-lashes. i44> Eyelids, 1441 . , blood-vessels of, 144 5 development of, 1 483 lymphatics of, 1445 nerves of, 1446 pract. consid., i44<» structure of, i443 Face, 222 architecture of, 228 development of, 62 landmarks of. 246 muscles and fascia, pract. consid., 49* pract. consid., 242 FalcSorm ligament, i745 Fallopian tube. 1996 changes in, 1999 course of, J997 development of. 1999 fimbriae of, i997 infundibulum of, 1997 isthmus of, 1997 lymphatics of, 988 nerves of, 1999 pract. consid., 1999 relations of, 1997 structure of, 199 7 vessels of, 1998 THIS VOLUME CONTAINS PAGES 996 TO THE END, 3063 INDEX. Fall yi\u. aatieduct of, iSi Falx cerebelli, iioo cerebri, 1199 Faacia or fascitE, 470 of abdomen, 515 anal, 1678 of ankle, pract. coniid., 666 antibrachial, 591 of anus, 1675 of arm, pract. consid., 589 of axilla and shoulder, pract. consid., 579 axillary, 574 (if back, 508 bicipital (semilunar), 586 brachial, 585 bucco-pharyngeal, 488 of buttocks, pract. consid., 641 of Camper, 5 1 5 cervical. 543 of Colles, 56a of cranium, pract. consid., 489 cremasteric, i960 cribriform, 635 crural, 647 dentata, 11 66 of face, pract. consid., 49a of foot, pract. consid., 666 of hand, 606 of hip and thigh, pract. consid., 643 iliac, 634 infundibuliform, 534 intercolumnar (external spermatic), 534 of knee, pract. consid., 645 lata, 633 of leg, pract. consid., 665 obturator, 559 of orbit, 504 palmar, 606 palpebral, 1438 parotido-masseteric, 474 pectoral, 568 pelvic, S58 perineal, superficial, 56a plantar, 659 prevertebral, 543 rectal, 1678 recto- vesical, 1678 of rectum, 1675 of scalp, pract. consid., 489 of Scarpa, 5 1 5 temporal, 475 transversalis, 530 Fasciculus, auriculo- ventricular of heart, 701 posterior longitudinal, 11 16 retroflexus, 1 134 solitarius, 1074 Fat, orbital, 1437 Fat-cells, 79 Fauces, isthmus of, 1 569 pillars of. 1 569 Femoral canal, 635 ring, 635 Femur, 353 development of, 359 landmarks of, 366 pract. consid., 361 surface anatomy, 360 variations, sexual and individual, 3 so Fertilization, 18 Fibres, intercolumnar, 534 Fibrin, canalized, of chorion, 49 Fibro-cartilage, 83 Fibrous tissue, 74 Fibrous tissue, development of, 76 Fibula, 300 development of, 393 pract. consid., 393 Fillet, decussation of, 1070 median, 1 1 1 5 Fimbria, 1 1 59 hippocampi, 1165 Fissure, calcanne, 1 1 46 calloso-marginal, 1 1 39 central, of cerebrum, 1137 collateral, 1 139 ethmoidal, 1 4 1 1 of Glaser, 1 78 palpebral, 1441 paneto-occipital, 113.? portal, of liver, 1 708 ptr .yeo-maxillary, jo.[ of Rolando, 1137 sphenoidal, 188 Speno-maxillary, 33a (sulci) cerebral, 1135 of Sylvius, 1 136 Fistula, cervical, 61 Flexure, cephalic, 58 cervical, of embryo, 59 dorsal, of embryo, 59 sacral, of embryo, 59 Flocculus, 1085 1" :.tus, membranes of, 30 stage of, 63 eighth month, 66 week, 64 fifth month, 66 week, 63 fourth month, 65 ninth month, 66 seventh month, 66 week, 64 sixth month, 66 week, 63 third month, 65 Follicles, Graafian, 1988 Fontana, spaces of, 1453 Fontanelles, 331 Foot, articulations of, 440 as whole, 447 bones of, 41Q landmarks of, 437 pract. consid., 436 joints of, landmarks of, 453 landmarks of, 673 muscles of, 659 and fascise of, pract. consid., surface anatomy, 449 synovial cavities of, 447 Foramen or foramina, csecum, 1574 ethmoidal, anterior, 193 posterior, 193 jugular, 330 of Luschka, 11 00 of Magendie, 1 1 00 mastoid, 180 of Monro, 1131 optic, 189 ovale, 188 of heart, 695 pterygo-spinosum, 190 rotundum, 187 sacro-sciatic, great, 341 lesser, 341 sphenoidal, 187 spheno-palatine, 304 666 THIS VOLUME CONTAINS PAGES 996 TO THE END. INDEX. 3063 Foramen or (oramina. tpinoaum. iM »tyto-ma»toid, i8> thvroid (obturator), 337 of -vena cava, of diaphragm. 557 of Vesiiliui, 188 Forearm, 381 as whole, »QQ , intrinsic movements 01, 199 motion of on humerus. 303 pract. consid.. 603 Fore-brain, 105Q Formiitio rcticulans. 1070 reticularis alba, 1076 grisea. 1074 Fornix. 11 58 . ..,„ pillars of , antenor, i»S9 posterior, ii59 Fossa or fossa, , , . duodeno-jejunal. J047 glenoid, 178 hyaloidea, I473 ileo-caecal. 1666 infraspinous. a 5° inguinal, inner, 5'<> lateral. i743 median. i74» outer, 5^6 interpeduncjilar, "07 intersigmoid, 1671 ischio-rectal, 1078 jugular, i8j nasal. 1409, ., ._.. navicular of urethra. 19*4 ovalis. 695 ovarian. 1986 pararectal. i744 paravesical. i744 perica^cal, 1666 pineal, no* pituitary, 186 retro-colic. 1667 of Rosenmiiller, 1 59° spheno-maxillary, a»7 subscapular, 349 supraspinous. 350 supratonsillar, 1600 supravesical. 536 Sylvii, "37 temporal, 318 zygomatic, 337 Fourchetie, 3033 Fourth ventricle. 1096 choroid plexus of. i too floor of, 1096 roof of, 1099 Fovea centralis. 1466 vagi. 1098 , . Frenulum of Giacommi. 11 66 Frenum of prepuce. 1966 of tongue, 1 573 Frontal bone. 194 , articulations of, 197 development of, 197 lobe, 1 139 ^ _ , sinus, 1433. 326 (bony) Fuudamental cmbryologjcal proceMe«, 30 Funiculus cv.neatus, 1066 gracilis, 1066 of Rolando, 1067 Furrows, visceral, 59 external, 61 Furrows, inner. 61 inner, second, 6j innet, third. 6a Galen, vein of, 856 Gall-bladder, 17 '9 cystic duct of, i7'0 fossa of, 1708 lymphatics of, 981 nerves of, 1730 pract. consid., 1739 vessels of, 1719 Ganglion or ganglia, 1007 Arnolds, 1346 t«"iM.l inferior (sympathetic) 136* middle (sympathetic), 1^63 superior (sympathetic), 1359 ^cygeal^mpar), sympathetic, 1367 development of, lois of Froriep, 13*0 Gasserian, 133a geniculate. 1353 habenulae. 1133 impar, 1367 interpeduncular, 1134 jugular, of glosso-pharyngeal. 1363 of vagus, 1 367 lenticular. 1336 Meckel's, 1340 . mesenteric, inferior, 1373 superior, 137 a nodosum of vagus, i a68 ophthalmic. 1336 ™troiu*of glosso-pharyngeal, H64 semilunar, sympathetic, 1369 spheno-palatine, 1340 spinal, 1379 spiral. 1357 spiraleof cochlea, 15a a splanchnic, great, sympathetic, 1365 submaxillary. 1347 sympathetic, 1009 of sympathetic system. 1356 vestibular, 1359 Ganglion-crest, 1013 Gartner's duct. 3001 Gasserian gangUon. 133 a Gastric glands, 1633 Gastro-pulmonary system. iS»7 Gastrula, 35 Gelatin, 83 Geniculate bodies, lateral, H07 """^ Onteroal) internal structure of, . . 10 I ganglion, 1353 I Genital cord. 3038 oiins^e^xtemal, development of, 304J female. 3031 pract. consid., 2037 ridge, 3038 tubercle, 3043 Genu of corpus callosum, H5S Germinal spot. i6 Gestation, ectopic, 199? Giacomini, frenulum of, 1106 Gianuzzi. crescents oi. iS34 Gimbernat. ligament of, 533 Ginglymus, 113 , Giraldes. organ of. 1950 Glabella, 338 external, 01 -..ur- rtan THIS VOLUME CONTAINS PAGES 996 TO THE END. ao64 INDEX. '<>: GUdiolui of itemutn, 135 Gland or sUnds, 1 511 alveolar (tacc-ular) compound, 1535 (saccular) timpla, 1535 anal, 1674 areolar, loaS of Bartholin, joi6 of Blandin, 1577 blood-veuelt of , 153 s of Bowman, 141 5 of Brunner, 1639 cardiac of stomach, 1614 carotid, 1809 ceruminous, 1489 ciliary, 1400 circumanal, 1400 ixiccygeal, 1810 of Cowper, 1984 cutaneous, 1397 gastric, 1623 uf Henle, 1445 of intestines, 1637 of Krause, 1445 lachrymal, 1477 aucts of, 1477 of Lieberkuhn, 1637 of Luschka, 1810 lymphatics of, 1 536 mammary, 1027 Meibomian (tarsal), 1444 of Moll, 1444 of Montgomer>-, 2028 mucous, 1534 nerves of, 1536 of Nuhn, 1577 parotid, 1582 prostate. 1975 pyloric, 1624 salivary, 1582 sebaceous, 1397 serous, 1534 sexual, development of, 2038 sublingual, 1585 submaxillary, 1583 sweat, 1398 duct of, 1399 structure of, 1399 of tongue, 1575 tubo-alveolar, 1533 tubular, compound, 153 a simple, 1532 of Tyson, 1966 unicellular, 1531 of Zeiss, 1444 Clans of clitoris, 3024 penis, 1968 Glaser, fissure of, 178 Glisson's capsule of liver. 1 708 Globus pallidus, 1 1 70 Go'olet-cells, 70 Golgi-Mazzoni corpiiscles. 10 19 Gonion, 228 Graafian follicle!:. ig8S Grandry, corput. les of, 1016 Growth, 6 of bone, loi Gudden, inferior commis-siire of, 11 10 Gums. I r.6y pract. consid., 1590 Gustatory cells, 1435 Gyrus or gyri, callosal (fomicatus), 1 1 50 (convolutions) cerebral, 1 135 dentate, 11 66 Gyrus or gyri, development of, 1 190 hippocampal, 11 51 Hair-cells (auditory) inner, 1 510 outer, 1520 Hair-follicle, 1302 blood-veaaels of, 1394 nerves of, 1394 Hairs, 1389 arrangement of, 1391 development of, 1401 growth of, 140a structure of, 1391 whorls of, 1 39 1 Hair-shaft, 1391 Hamular process of inner pterygoid plate, 1 89 Hamulus of bony cochlea. 1514 Hand, 309 deep fascia of, 606 landmarks of, 320 lymphatics of, 964 muscles of, 606 pract. consid., 613 surface anatomy of, 328 Harelip, 1589 Hassall, corpuscles of, 1 799 Haversian canals of bone, 88 system of bone, 86 Head, movements of, 14a Heart, annuli fibrosi of, 698 annulus ovalis, 695 of Vieussens, 695 architecture of walls, 700 auricles of, 693 blood- vessels of, 703 canal auricular of, 705 chambers of, 693 chordte tendtnec of, 697 columns cames of, 697 development of, 705 endocardium of, 70a epicardium of, 702 faacicttlus atiriculo-ventricular, 701 foramen ovale of, 695 foua ovalis of, 695 feneral description of, 68n lis's bundle, 701 lymphatics, 703 muscle of, 462 muscles, pectinate of, 695 nerve-endings in, 1015 nerves of, 704 position of, 693 practical considerations, 710 relations of, 693 septum, aortic, 707 auricular of, 694 intermedium, 706 interventricular of, 696 primum, 706 secundum, 708 spurium, 707 Thebesian veins of, 694 tubercle of Lower, 695 valves. Eustachian, ^4 auriculo-ventricular, 699 mitral, 699 position of, 69 a structure of, 703 Thebesian, 695 tricuspid, 699 x-ein, oblique of, 695 ventricles of, 696 THIS VOLUME CONTAINS PAGES 996 TO THE END. INDEX. 3065 Het*< ifamilttiiM o(. 1534 Heltcotrama, 15M KliTuptait.. «oci.Uon fibre, of. >.8. ofc««beUum. io8j »«4 lobMof, IIJ9 , ...» proiaction fibre* of. 1 186 whiU centre of . h8j Henle, gUnde of. i44S loop of. 1881 Henien. node of, »S Herbal, corpvactee of, 1019 Homiit, abdominal. 17 59 diaphragmatic, «77» femoral, 17 73 funicular, 17*8 infantile, 1767 inguinal, 1763 direct, «77o inte,iSa"o«t«-^««««"» retroperito- ««'>• '",' ». interpaneUl. tyo» labial, 1769 lumbar, i777 obturator, i777 perineal, 1778 •ciatic, 1778 ■crotal, 1769 umbilical, i77S . acquired, 1770 congenital, 1775 ventral, 177* Hesselbach, ligament of, S»$ triangle ot, 5'*^ Hiatus, aortic, of diaphragm, 557 Pallopii, 181 ULi. .phageal, of diaphragm, 557 semilunaris, of nasal cavity. 194 of nose. 14" Highmore. antrum of. i4»» Hind-brain. 1061 Hio. landmarVM of. 669 -a a., ^muscles and fasci« of. pract. consid.. 64a Hip-joint. 367 movemcts of. 373 pract. consid.. 374 synovial membrane of, 37' Hippocampis. i«65 His's bundle, of heart, 70' Histogenesis of neuroglia, loio of neurones, 10 11 Homologue. 4. , „ Homer, muscle of, 484 Howship, lacuna of, 97 Humerus, 265 development of, 109 pract. consid., 170 sexual differences, 269 structure of. 269 surfacvi anatomy, 270 Humor, aqueous. 1476 Hunter's canal, 628 Hyaloid canal. 1474 Hyaloplasm, 8 Hydatid of Morgagni, 200a Hydramnion. 4a Hymen, aoi6 Hyoid bone, 216 development of, 216 Hyomandibular cleft, 61 THIS VOLUMe CONTAINS Hypogastric lymiihatic pluxus. Hypophysis, 1806 Hyiusiudias, 1917 Hypothalamus, 1117 Hypothonar eminence. 607 Ileo-cBcal fossK, 1666 valve, 1661 llio-femoral ligament, 369 liio-pcctineal line, 334 llio-tibial hand, 634 Ihum, 3 j Implantatio... 35 Impregnation. 18 Incisor teeth. 1 543 Incus, >497 . . . ■ Inferior caval system of veins, 898 Infundibulum, 1 1 29 of nasal cavity, nu of nose, I4>i Inguinal canal, 523 lymphatic plexus, 991 Inion, 228 inion, x Labia major, 30a i minora, ao33 nerves of, 3034 vessels of, 3033 Labyrinth, membranous, 1514 blood-vessels of , 1533 canalis reuniens of, 151 5 cochlea of, 1517 ductus endolymphaticus of, 1514 endolymph m, 1514 macuue acusticc of, 1516 saccule of, 1515 semicircular canals of, 151 5 utricle of, 1 514 osseous, 1511 cochlea of, 1513 semicircular canals of. 151a vestibule of, 151 1 Lachrymal apparatus. 1477 pract. consid., 1479 bone, 307 articulations of, aoj development of, ao7 canaliculi, 1478 caruncle, 1443 gland, 1477 ike. 1443 papiils, 1478 puncta, 1478 sac, 1478 Lactation, 3039 Lacteals, 1643 Lacunae, of bone, 86 of cartila^. 80 of Howship. 97 Lambda, 338 Lamina cinerea (terminalis), 1130 fusca, 1450 suprachoroidea. 1456 Landmarks, of abdomen, 53 1 of ankte and foot, 673 of bones of foot, 437 of buttocks and hip, 669 of clavicle, 260 of elbow-joint, 308 THIS VOLUME CONTAINS PAGES 996 TO THE END. INDEX. ao67 I; 14 Landmarks, of face, 146 of femur, 366 of fibula, 396 of hand, 330 of ioints of foot, 453 ofkmM, 671 of knee-joint, 416 of leg, 671 of lower extremity, 669 of male perineum, 1918 of neck, 554 of pelvis, 349 of radius, 296 of scapula, 35^ of shoulder-joint, a 80 of skull, 140 of spine, 146 . of surface of thorax, 1868 of thigh, 670 of thorax, 1 70 of tibia, 390 of ulna, 387 of upper extremity, 61S of wnst-joint, 330 Langerhans, islands of, 173s Lanugo, 66 Laryngo-pharynx, 1598 larynx, 1813 . - _ age changes of, i8a8 arytenoid cartilages of, 1816 comicute laryngis, 1817 cricoid cartilage of, 18 13 cuneiform cartilages of, 181 7 development of, i86a elastic sheath of, 1817 epiglottis, 1816 form of, 1818 lymphatics of. 958 mucous membrane of, 1833 muscles of, 1824 n-rves of, 1827 ossification of, 1 81 8 position and relations of, i8a8 pract. consid., i8a8 region, glottic of, i8ao infraglottic of, 1823 supraglottic of, 1818 sexual differences of, t8a8 thyroid cartilage of, 181 4 ventricle (sinus) of, i8aa vesseU of, i8a6 vocal cords, false of, 1820 true of, 1820 ligaments of, 181 8 Leg, bones of, as one apparatus, 397 surface anatomy, 397 framework of, 38a landmarks of, 671 lymphatics, deep of, 994 superficial of, 993 muscles and fascite of, pract. consid., Lens, crystalline, 147 « , development of, 1481 . oract. consid., 1473 suspensory apparatiM of, 1475 Leptorhines, 1404 Leucocytes, 684 development of, 688 varieties of, 685 Lieberkuhn, glands of, 1637 Lieno-phrenic fold, 1785 Ligament or ligaments, iia alar, of knee-joint, 40$ 665 Ligament or ligaments, anterior annular, of ' ankle, 647 of wrist, 335 arcuate, external, 557 internal, 557 atlanto-axial, anterior, 137 atlanto-axial, posterior, 137 of auricle, i486 broad, of uterus, 3004 broad, vesicular appendages of, aooa check, of orbit, 1438 of CoUes, 533 . - _;_ common anterior and posterior, of spine, coraco-acromial, 256 coraco-clavicular, 363 conoid part, a6a trapezoid part, 363 coronary, of liver, >7*' . . costo-clavicular or rhomboid, a6a cotyloid, of hip-joint, 367 crucial, of knee-joint, 404 cruciform, of axis, 136 deltoid (lat. int.) of ankle-joint, 439 denticulate, of spinal cord, 1033 dorsal, of foot, 443 duodeno-hepatic, 1644 of epiglottis, 1817 external check, of eyeball. 505 falciform, 1745 gastro-phrenic, 1747 of Gimbemat, 533 of Hesselbach. 535 • ilio-femoral, 369 ilio-lumbar, 339 interarticular of ribs, 160 interclavicular, a 6a interosseous, of foot, 441 interspinous, 134 intertransverse, 135 ischio-femoral, 370 of lamiiUE and processes of vertebrte, 133 lieno-renal, 1747 of liver, 1731 metacarpal, superficial transverse, 607 nucr«, 134 occipito-atlantal. accessory, 137 anterior, 137 posterior, 137 occi{nto-axial, 137 odontoid, or check, 136 orbicular, of radius, 397 of ovary, 1987 palpebral, 1441 internal, 484 patellae, 4°° pectinate of iris, 145a of pelvis, J37 of pericardium, 716 plantar, 444 posterior annular, of wrist, 335 of Poupart, 533 pterygo-mandibular, 488 radio-ulnar, 397 round, of hip-joint, 370 of liver, 1731 of uterus, 3005 sacro-iliac, posterior, 338 sacro-sdatic, 339 Ct or posterior, 339 T or anterior, 341 of scapula, 356 of shoulder-joint, 274 THIS VOLUME CONTAINS PAGES 996 TO THE END. 2£: ao68 INDEX. rtii)/ Ligament or UnmenU, ipino-glenoid, 257 stylo-manaibular, 475 subflavs, 133 suprascapular or transverse, 356 supraspinous, 133 suspensory, of lens, 1475 of orbit, 1438 of ovary, 1986 thyro-arytenoid, inferior, t8i8 superior, 181 7 thyro-hyoid, 181 5 transverse, of atlas, 136 triangular, of liver, 1721 of perineum, 563 of verteoral bodies, 133 of Winslow, of knee-joint, 401 of wrist and metacar, s, 330 Limb, lower, muscles of, 633 Limbic lobe, 1 1 50 Linea alba, 533 semilunaris, of abdomen, 533 transversa, of abdomen, 533 Linin, g Lips, 1538 lymphatics of, 951 muscles of, 1 540 nerves of, 1543 pract. consid., 1590 vessels of, 1543 Liquor amnii, 3 1 pericardii, 714 Littr^, glands of, 1925 Liver, 1705 bile-capillaries of, 1 71 5 biliary apparatus, 17 18 blood-vessels of, 1709 borders of, 1707 caudate lobe of, 1709 cells of KupfTer, 1717 common bile-duct, 1730 cystic duct of, 1730 development and growth of, 1733 fissure of ductus venosus of. 1 707 fossa for eall-bladder of, 1 708 gall-bladder of, 1719 rlisson's capsule of, 1708 hepatic artery of, 171 1 ducts of, 1 7 18 veins of, 17 10 impression, oesophageal of, . 708 renal of, 1 709 intralobular connective tissue of, 1717 bile-ducts of, 1 7 1 7 veins of, 17 10 ligaments of, 1731 coronary, 1731 falciform, 1731 round, 1731 triangular, 1731 lobes of, 1706 lobular blood-vessels of, 17 13 lobules of, 1713 lymphatics of, 17x1 nerves of, 1 7 1 1 non-peritoneal area of, 1 707 peritoneal relations of, 1731 portal (transverse) fissure of, 1 708 vein of, 1709 position of, 1733 praot, consid., 1736 quadrate lobe of, 1 709 size of, 1706 Spigelian lobe of, 1707 Liver, structure of, 1713 sublobular veins of, 17 10 surfaces of, 1707 tuber omentale of, 1 709 umbilical fissiue of, 1 708 notch of, 1707 weight of, 1706 Liver-cells, 1714 Liobe or lobes, cerebral, 1135 frontal, 1139 of hemispheres, 1 139 limbic, 1 1 50 occipital, 1 145 olfactory, 1151 parietal, 11 43 temporal, 1147 Lobule of auricle, 1484 Loin, pract. consid., 530 Lordosis, 144 Liunbar plexus, lymphatic, 973 Lumbo-sacral coitl, 1331 Lung or lungs, 1843 air-sacs of, 1850 alveoli of, 1850 atria of, 1 8 so blood-vessels of, 1853 borders of, 1843 development of, 186 1 external appearance of, 1846 fissures of, 1845 ligament broad of, 1858 l(»>es of, 184$ lobule of, 1849 nerves of , 1855 physical characteristics of, 184C1 pract. consid., 1864 relations to chest-walls, changes in, 1803 to thoracic walls, 1855 roots of, 18^8 dimensions of, 1840 nerves of, 1839 relations of, 1840 structure of, 1851 surfaces of, 1843 vessels of, 1839 Lunula, of nail, 1395 Luschka, foramina of, 1 100 ^land of, 1 810 Lutein cells, 1990 Luys, nucleus of, 11 38 Lymphatic or lymphatics, of abdomen, 97s of abdominal walls, 976 of arm, deep, 965 superficial, 963 of bile-duct, 981 of bladder, 985 of bone, 93 of brain, 948 of brain and meninges, 948 broncho-mediastinal trunk, 968 capillaries, 933 of cervical skin and muscles, 958 of cheeks, 951 of diaphragm, 970 duct, right, 945 of ear, 950 of eye and orbit, 949 of eyelids, 1445 of Fallopian tubes, 988 of gall-bladder. 981 of glands, 1536 of gums, 9SI of hand, 964 THIS VOLUME CONTAINS PAGES 996 TO THE END. INDEX. 3069 Lymphatic or lymphatics, of the head, 045 of heart, 970 hemolymph nodes, 936 intercostal, 969 of intestine, large, 978 small, 977 jugular trunk, 958 of Kidney, 982 lacteals. 931 of lar^mx, 958 of leg, deep, 994 supernciai, 993 of lips, 951 of liver, 980 of lower extremity, 991 mammary gland, 968 of meninges, 948 of muscle, non-striated, 456 of nasal fossa, 1416 region, 951 nodes, 935 of nose, 1 407 of oesophagus, 971 of palate, 954 of pancreas, 979 of pelvis, 083 of pericardium, 716 of perineum, 987 of pharynx, 954 of prostate gland, 985 of rectum, 1 680 of reproductive organs, external, male, 987 external, male, 98 internal, femt' internal, ma) >: of retina, 1468 of scalp, 948 of semmal vesicles, 98t of skin, 1388 of small intestine, 1643 of spleen, 982 of stomach, 976 of striated muscle, 464 subclavian trunk, 963 of suprarenal body, 983 system, 931 of teeth, 951 of testis, 987 thoracic duct. 941 pract. consid., 944 of thorax, 966 cutaneous, 968 of thyroid gland, 959 of tongue, 95* of tonsils, 954 of trachea, 958 of upper extremity, 961 of ureter, 981 of urethra, 986 of uterus, 989 of vagina. 989 of vas deferens, 988 vessels, development of, 939 Lymph-corpuscles, 031 Lymph-nooes of abdomen, pract. consid. abdominal, visceral, 974 ano-rectal, 976 ant"!rior auricular, 946 aj.,x:ndicular. 975 of arm, pract. consid., 965 of axilla, pract. consid., 965 axillary, 961 fe- Lymph-nodes, brachial, deep, 9*' superficial, 961 bronchial, 967 buccinator, 947 cervical, deep, inferior, 958 superior, 957 of Cloquet, 99a coeliac, 973 delto-pectoral, 961 development of, 940 epigastric, 973 cpitrochlear, 961 facial, 947 gastric, 974 of head, pract. consid., 955 hepatic, 975 hypogastric, 984 iliac, circumflex, 972 internal, 984 inguinal, 991 intercostal. 966 of intestine, 1640 jugular plexus, 956 of leg, piract. consid., 994 lingual, 947 mammary, internal, 966 mandibular, 947 mastoid, 945 maxillary, 947 mediastinal, anterior, 967 posterior, 967 mesenteric, 975 mesocolic, 976 of neck, 956 pract. consid., 950 (Kciintal. 945 pancreatico-splenic, 975 parotid, 946 pectoral, 962 of pelvis, pract. consid., 990 popliteal, 992 posterior auricular, 945 retro-pharyngeal, 948 of RosenmttUer, 992 sternal, 966 structure of, 937 submaxillary, 94'> submental, 946 subscapular, 962 superficial cervical, 056 thorax, pract. consid., 971 tibial, anterior, 993 tracheal nodes, 967 umbilical, 972 Lvmph-nodules, 936 Lymphocytes. 031 varieties of, 685 L>'mphotd structures of pharynx, 1 599 tissue, structure of, 936 L>Tnph-space«, 931 Lymph-vessels, 934 Lyra, 11 58 990 Macula lutea, 146* Maculte acusticte, 1516 Magendie, foramen of, iioo Malar bone, 20a articulations of, 210 Malleus, i497 ,. , , , Malpighian bodies of spleen, 1 784 Mammary glands, iai; development of, 203* lymphatics, 968 THIS VOLUME CONTAINS PAGES 996 TO THE END- L aoffo INDEX. Mammary glanda, nerves of, 2033 pract. consid., 2033 structure of, 1029 variations of, 3033 vessels of, 2031 Mandible, 11 1 Manubrium of sternum, 155 Marrow of bone, go Mast-cells of connective tissue, 74 Mastoid cells, 1 504 pract. consid., ijoS process, pract. consid., 1508 Maturation of ovum, 16 Maxilla, inferior, 211 development of, 213 structure of, 313 superior, 199 antrum of, 301 articulations of, 202 development of, 303 Maxillary sinus, 1433 Meatus, auditory, internal, 181 inferior, of nose, 14 12 middle, of nose, 141 1 superior, of nose, 141 1 Meckel, divertic-'um of, 44 Mediastinum, auverior, 1833 middle, 1833 posterior, 1833 pract. consid., 1833 superior, 1833 Medulla oblongata, 1063 central gray matter of, 1073 development of, iioi internal struct tire of, 1068 Medullary folds, 36 , groove, 26 sheath, looi velum, inferior, 1099 superior, 1099 Medullated fibres, 1003 Megakaryocytes, 689 Meux>mian (tarsal) glands, 1444 Meissner, corpuscles of, i o 1 7 plexus 01, 1643 Membi^ne or membranes. Bowman's, 1451 of Bruch, 1456 cloacal, 1939 costo-coracoid, 568 crico-thyroid, 1815 of Demours, 1452 Descemet's, 1452 fenestrated, 77 foetal, 30 human, 35 hyaloid, 1474 interosseous, of tibia and fibula, 396 mucous, 1528 obturator, 341 olfactory (Schneiderian), pharyngeal, 1694 pleuro-pericardial, 1700 pleuro-peritoneal, 1700 of Reissner. 1517 of Ruysch, 1456 of spinal cord, 1022 synovial, of joint, no tectoria, 1521 Ihyro-hyoid, 1815 of tympanum, 1494 vitelline, 15 vitrea, 1456 1414 Meninges of brain, pract. consid., 1208 lymphatics of, 948 Menstruation, 2013 Merkel, tactile cells of, 10 16 Mesencephalon, 1105 development of, 1 1 1 7 internal structure of, 1 109 . Mesenteries, 1741 Mesenterium commune, 1697 Mesentery, anterior, 1744 of appendix, 1665 of jejtmo-ileum, 1650 of large intestine, 1670 permanent, 1752 posterirr, pprt 1st, 1746 pr. t 3nd, 1751 p.-,ii 3rd, 1753 pmutive, 1697 Meso-appendix, 1665 Mesocolcn, 1670 development of, 1 704 Mesoblast, 33 lateral ^tes of, 39 paraxial, 39 parietal layer, 29 visceral layer, 29 , Mesogastrium, 1697 Mesognathism, 229 Mesometrium, 2005 Mesonephros, 1935 Mesorarium, 2040 Mtsorchium, 2040 Mesorhines, 1404 Mesosal]nnx, 1996 Mesotendons, 471 Mesothelium, 71 Mesovarium, 1987 Metabolism, 6 Metacarpal bones, 314 Metacarpo-phalangeal articulations, 327 Metacarpus, pract. consid., 319 Metanephros (kidney), 1937 Metaphase of mitosis, 1 2 Metaplasm, 8 Metatarsal bones, 428 Metathalamus, 11 36 Mevnert, commissure of, 1 1 1 5 Mia -brain, 1061 Milk, 2030 Milk-ridge, 2033 Mitosis, II anaphases of, 13 metaphase of, 13 prophases of, 1 3 telophases of, 13 Molar teeth, 1546 Moll, glands of, 1444 Monorchism, 1950 Monroe, foramen of, 1131 Mons pubis, 2031 veneris, 3021 Montgomery, glands of, 2038 Morgagni, columns of, 1674 hydatid of, 3002 sinus of, 497 valves of, 1674 Morula, 22 Mouth, 1538 floor of, pract. consid., 1593 formation of, 1094 pract. consid., 1589 roof of, 238 pract. consid., 1593 THIS VOLUME CONTAINS PAGES 996 TO THE END. INDEX. 3071 Mouth, vestibule of, 1 538 Mucoid, 83 Mucous membranes, 1518 structure of, ts>8 MoUerian duct, 1038 Muscle or muscles, abdominal. 515 abductor ballucis, 66 1 minimi digiti, 608 minimi, of foot, 66s pollicis, 608 adductor brevii, 6a6 hallucis, 663 longus, 6a6 magnus, 6a8 polucis, 610 anconeus, 589 of ankle, pract. consid., 666 antibrachial, $91 post-axial, 598 t pre-axial, 592 of anus, 1675 appendicular, 566 of arm, pract. consid., 589 arytenoid, i8a6 of auricle, i486 auricularis anterior, 483 posterior, 483 superior, 483 axial, 50a of axilla and shoulder, pract. consid., azygos uvuue, 496 biceps, 586 femoris, 636 brachial, 58; post-axial, 588 pre-axial, 586 brachialis anticus, 586 brachio-radialis, 598 branchiomeric, 474 buccinator, 488 bulbo-cavemosus, 565 of buttocks, pract. consid., 641 cardiac, 46a cervical, 54 a chondro-glossus, 1578 ciliary, 145* coccygeus, 561, 1676 compound pinnate, 469 compressor urethne, 565 constrictor inferior of pharynx, 1606 middle of pharynx, 1605 pharyngis inferior, 499 medius, 498 superior, 497 superior of pharynx, 1604 coraco-Drachialis, 575 of cranium, pract. consid., 489 cremaster, 519 crico-arytenoid lateral, i8as posterior, i8as crico-thyroid, i8a4 crural, 647 post-axial, 6sS fffe-axial, 648 crureus, 640 dartos, 1963 deltoideus, 578 depressor anguli oris, 487 labii inferioris, 485 diaphragma, 556 digastricus, 477 diuttor pupilUe, I4te Muscle or muscles, dorsal, of trunk, 507 of Eustachian tube, 1 503 extensor brevis digitorum, 66$ pollicis, 60a carpi radialis brevior, 598 longior, 598 ulnaris, 601 communis digitorum, 599 indicis, 603 longus digitorum, 655 longus biulucis, 656 pollicis, 603 minimi digiti, 600 ossis metacar^x pollicis, 60a of face, pract. consid., 49a facial, 479 femoral, 633 post-axial, 638 pre-axial, 636 flexor accessorius, 654 brevis digitorum, of foot, 660 hallucis, 66o_ minimi digiti, 609 digiti of foot, 664 pollicis, 608 carpi radialis, 593 radialis brevis, 597 ulnaris, 594 ' longus digitorum, 651 hallucis, 651 pollicis, 596 profundus digitorum, 595 sublimis digitorum, 595 of foot, 659 post-axial, 665 pract. consid., 666 pre-axial, 659 gastrocnemius, 649 gemelli, 630 genio-elossus, 1578 genio-hyoid, 1578 genio-hyoideus, 545 gluteus maximus, 630 medius, 631 minimus, 633 gracilis, 616 of hand, 606 pre-axial, 607 of hip and thigh, pract. c-wsmL, 64s hypoglossal, 506 hyo-glossus, 1578 hyoidean, 480 variations of, 480 iliacus, 634 ilio-costalis, 508 infraspinatus, 576 intercostales extern!, 538 intemi. 539 interossei dorsales of foot, 664 of hand, 613 plantares, 663 volares, 61 a interspinales, 513 intertransversaWs, S'S anteriores, 547 laterales, 511 intratympanic, 1499 involuntary, arrectores pilorum, 1394 nerve-endings of, 1015 ischio-cavemoeus, 564 of knee, pract. consid., 645 of larynx, 1814 latisstmus dorsi, 574 THI*^ VOLUME CONTAINS PAGES 996 TO THE Et O. iHiM m 3073 INDEX. m Muide or luuKlet, of leg. pract. coniid., 66s levator anguli orii, 487 ■capuUe, 571 ani, 560, 167J labii auperioni, 487 labii superiori* alcqne nasi, 485 tnenti (luperbiu), 485 palati, 496, 1571 palpebts luperioris, 50a levatoret coataruin, 540 linguali*, 1579 ofBpa, 1540 longinimus, 510 longua colli, 548 of lower limb, 613 liunbricales, of hand, 610 of foot, 661 masseter, 474 of mastication, 474 variations of, 477 metameric, 503 multifidus, 51a mylo-hyoideus, 477 nasalis, 486 non-striated, blood-vessels of, 456 development of, 457 (involuntary), 454 lymphatics of, 456 nerves of, 456 structure of, 455 obliquus capitis inferior, 514 superior, 514 extemus, 517 . inferior, 504 intemus, 517 superior, 504 obturator extemus, 619 intemus, 629 occipito-frontalis, 48a omo-hyoideus, 544 opponens minimi digiti, 608 pollicis, 608 orbicularis oris, 486 palpebrarum, 484 orbital, 502 of palate and pharynx, 495 palato-glowus, 497, 1579 palato-pharyngeus, 497, 1571 palmans brevis, 607 longus, 593 pectinate, of heart, 695 pectineus, 63^ pectoralis major, 569 minor, 570 pelvic, 559 perineal, c63 peroneus brevis, 658 lon^, 657 tertius, 656 of pharynx, 1604 pinnate, 469 plantaris, A49 platysma, 481 popliteus, 655 pronator quadratus, 597 radii teres, 593 psoas magnus, 633 parvus (minor), 614 pter^goideus extemus, 476 intemus, 476 pyloric sphincter, 1636 pyramidalis, 517 » Muscle or muaclet, pyriformte, s't quadratus femoris, 639 lumborum, 531 quadriceps femoris, 639 of rectum, 1675 rectus abdctmnis, 516 capitis anticus major, 549 capitis anticus minor, 550 lateralis, 547 posticus major, 513 posticus minor, 514 extemus, 503 femoris, 639 inferior, 503 intemus, 503 superior, 503 rhomboide«u major, 371 minor, 573 risorius, 487 rotatores, of back, 513 sacro-spinalis, 508 lalpingo-pharyngeus, 1606 iartoniis, 638 scalene, variations of, 547 scalenus anticus, 546 medius, 546 posticus, 547 of scalp, pract. consid., 489 semimembranosus, 438 semi-pinnate, 469 semispinalis, 5 1 1 semitendinusus, 638 serratus magnus, (71 posticus inferior, 541 posticus superior, 541 of soft palate, 1570 soleus, 649 sphincter ani, external, 1676 extemus, 563 internal, 1677 pu|>ills, 1460 vesical, external, 1935 internal, 1935 spinalis, 511 splenitis, 510 stapedius, 480, 1499 stemalis, 570 stemo-cleido-mastoideus, 499 stemo-hyoideus, 543 stemo-thyroideus, 545 striated, attachments of, 468 blood-vessels of, 464 burse of, 471 classification of, 471 development of, 465 form of, 469 general considerations of, 468 lymphatics of, 464 nerves of, 464 nerve-supply, general, 473 structure, general of, 458 variations, 461 (voluntary), 457 stylo-glossus, 1579 stylo-hyoideus, 480 Etylo-pharyngeus, 495, 1606 subclavius, 570 subcostal, 539 subcrureiw. 640 submental, 477 subscapularis, 578 supinator, 601 BUpraspinatus, 575 THIS VOLUME CONTAINS PAGES 996 TO THE END. 4 *..\>*»-^ :",j INDEX. 2073 Ifuacle or muiclea. temporalU, 475 tensor fasciz laUe, 631 palati, 479, 1570 tympani, 479, 1499 teres major, 577 minor, 576 thoracic, 538 thyro-arytenoid, 1815 thyro-hyoideus, 545 tibialis anticus, 65 s posticus, 654 of tongue, 1 577 trachealis. 1835 transversalis, 510 transverso-costaf tract, 508 transverso-spinal tract, 511 transvemus perinei profundus, s^S superficialis, 564 of tongue, 1579 trapezius, 500 tn^ngularis stemi, 540 triceps, 588 trigeminal, 474 palatal, 479 tympanic, 479 of tnmk, J07 of upper limb, 568 vago-acct.*ory, 495 vastus externus, 640 internus, 640 ventral, of trunk, 515 voluntary, motor nerve-endings of, 10 14 zygomaticus major, 485 minor, 485 Muscle-fibre, structure of, 459 Muscular system, 454 tissue, general, 454 Myelin, looi Myelocytes, of bone-marrow, q» Myeloplaxes, of bone-marrow, 9a Myometrium, 3008 Myotome, 30 Myxoedema, 1794 Naboth, ovules of, a 008 Nail, structure of, 1395 Nail-bed, 1396 Nail-plate, 1395 N«ils, 1394 development of, 1403 Nares, anterior, 1404 posterior, 14 13 Nasal bone, aoo articulations of, ao9 development of, aog cavities, pract. consid., 141 7 cavity, a 23 hiatus semilunaris of, 194 infundibulum of, 194 meatus inferior of, aas middle of, aas superior of, aas chamber, aa4 fossa, blood-vessels of, 1425 floor of, 1413 lymphatics of, 1436 nerves of, 1436 roof of, T4ia fosStP, 1409 index, 1404 mu( JUS membrane, 141 3 septum, 333, 1410 triangular cartilage of, 334 Nasion, 338 Nasmyth, membrane of, 1550 Na£o-lachr>-mal duct, 1479 Naso-optic groove, 63 Naso-pnarynx, 1598 Navel, 37 Neck, landmarks of, $54 pract. consid., 550 triangles of, 547 Nephrotome, 30 Nerve or nerves, abdominal, of vagus, 137a abducent, 1349 development of, 1379 aortic (sympathetic), 1364 auditory, 1356 development of, 1379 of auricle, 1487 auricular, ^;rea' 386 posterior, 01 facial, 1354 of vagiel*of, i57» Pall T.'.i, developrnent of, 1189 Palti. .r aponeurosis, 606 fascia, 606 Pancreas, 1731 body of, 1733 development of, 1737 ducts of, 1736 head of, 1731 interalvoolar cell-areas of , 1735 islands of Langerhans of, 1735 lymphatics of, 979 nerves of, 1737 pract. consid., 1738 relations to peritoneum of, 1736 structure of, 1734 vessels of, 1736 Panniculus adiposus, 1384 Papilla or papillae, circumvallate, 1575 dental, 1558 of duodenum, 1720 filiform, 1575 fungiform, 1575 lachrymal, 1478 optic, 146a renal, 1875 Paradidymis, 1950 Parametrium, jooj Parathyroid bodies, 1795 structure of, 1795 Parietal bone, 197 articulations of, 199 impressions, 199 lobe, 1 1 43 Paroophoron, aooa Parotid duct, 1 583 gland, 1582 nerves of, 1 583 relations of, 1 583 structure of, 1 586 vessels of, 1 583 Parovarium, aooo Patella, 398 development of, 400 movements of, 409 10A7 350 Patella, pract. consid., ^lA Peduncle, cerebellar, inferior, cerebral, 1107 Pelvic girdle, 33 a Pelvis, 33 a development of, 344 diameters of, 34a diaphragm of, $$i) index of, 343 jointB of, 337 pract. consid. of kidnev. 1894 landmarks of, 349 ligaments of. 337 lymphatics of, 983 position of. 14a pract. consid., 345 sexual differences, 343 surface anatomy of. 345 white lines of, 559 as a whole, 341 Penis, 1965 corpora cavemtjsa of, 1966 corptis spongiosum of, 1967 crura of, 1967 glans of, 1968 nerves of, 197 1 pract. consid., 1971 prepuce of, 1966 structure of, 1968 vessels of, 1970 Pericecal fosss, 1666 Pericardium, 714 blood- veaaels of, 716 ligaments of, 716 lymphatics of . 716 nerves of, 716 pract. consid.. Perichondrium, 81 Pericranium, 489 Perilymph of internal ear, Perimetrium, aooy Perimysium, 458 Perineal body, 3046 Perineum, female, 3046 lymphatics of, 987 male, 191s land, narks of, i g 1 8 triangular ligament of, 563 Perineurium. i.>o6 Periosteum. 89 alveolar, 1553 Peritoneum, 1740 cavity, lesser of, 1749 development of, 170a of large intestine, 1670 parietal, anterior, 1743 folds of. 174a fosss of, 1743 pract. consid., 1754 Perivascular lymph-spaces, 931 Pes anserinus, 1 352 hippocampi, 1165 Petit, triangle of, 574 Petro-mastoid portion I7Q Petrous ganglion, of 1364 subdivision, of petro-mastoid 181 Peyer's patches, 1641 Phalanges of foot, 433 of nand, 317 71ft 'S"4 of temporal lM)ne, glosso-pharyngeal, bone, n THIS VOLUME CONTAINS PAGES 996 TO THE END. S078 INDEX. PhalanfM of hand, davalopamt of, jil peculMritiM, 318 IKmct. Gonaid., ji o VMiationtof, J19 Pharyiifval pouchea, 1695 Pharynx, 1596 development of, i6oj growth of, 160J urynso-, 1398 lymi^Btict of, 954 lymphoid atructures 01, 1599 muaclea of, 1604 naao-, 1598 nervea of, 1606 oro-, 1598 pract. conaid., 1606 primitive, 1694 reUtiona of, 1601 ainua pyriformia of, 1598 veaaela of, 1606 Philtrum of lipa, 1 540 Pia mater, of otain, laoa of aptnal cord, loaa Picment-cells of connective tiiaue, 74 Pillara of faucea, 1569 Pineal body, 1114 Pinna, 1484 Piaiform bone, 311 Pituitary body, anterior lobe of, 1806 development of, 1 808 (hypophyaia), 1139 Placenta, 49 baaal plate of, 51 cotyledona of, 50 diacoidal, 34 foetal portion, 50 ^ant cella of, 51 mtervilloua apacea of, 51 marginal ainua of, 53 maternal portion, 51 multiple, 34 aepta of, 51 vitelline, 31 zonular, 33 Placentalia, 34 Plane, frontal, 3 aagittal, 3 transverse, 3 Plasma-cella of connective tiaaue, 74 Plaamosome, 9 Plates, tarsal, 1444 Platyrhines, 1404 Pleura or pleurse, 1858 blood-vessels of, 1 860 nervea of, 1861 outlines of, 1859 pract. consid., 1864 relations to chest-walls, changes in, 1863 of to surface, 1859 structure of, i860 Plexus or plexuses, aortic, 1373 of Auerbach, 1643 brachial, 1293 branches, infraclavicular of, 1297 supraclavicular of, 1295 constitution and plan of, 1193 pract. consid., 1294 cardiac, 13^7 carotid (sympathetic), 1360 cavernous, of penis, 1374 (sympathetic), 1361 cervical, 1285 branches of, 1285 Plexus or plnuMS, cervical, br I.ea. communicating O' t s^ daep, of, isSo . deacanding of, 1 28M muacular uf, 1289 auparficial of, 1286 aupraikcromial of, 1 389 aupraclavicular of, 128b aupraatemal uf, ia8S pract. ronaid , 129a coccygeal, 1352 caliac, 1370 lymphatic, 973 coronary, 1368 gaatric, 1370 hemorrhoidal, 1374 hepatic, 1370 hypogaatnc, 1373 lymphatic, 984 iliac, lymphatic, 983 inguinal, lymphJatic, 991 lumbar, 1119 lymphatic, 973 muacular branchea of, 1310 of Meiaaner, 1 64 1 meaenteric infenor, 1373 auperior, 1372 ' oeaophageal, 127* ovarian, 1371 pampiniform, i960 parotid, 1252 pelvic, 1374 phreni'-. 1371 pract. consid., 1330 proatatic, 1374 pudendal, 1345 branch^, muscular of, 1346 viaceral of, 1346 pulmonary, anterior, 1272 poatenor, 1272 renal, 1371 aacral. 133 1 branchea, articular of, 1334 collateral of, 1332 muacular of , 1333 terminal of, 1334 lymphatic, 984 poaterior, 1282 pract. consid., 1352 solar, 1368 spermatic, 13 71 aplenic, 1370 suprarenal, 13 71 of sympathetic nerves, 1367 tympanic, 1264 utero-vaginal, 1374 vesical, 1374 Plica fimbriata, 1 573 semilunaria, of eye, 1 443 aubUngualis, 1573 Polar body, first, 16 aecond, 16 Pona Varolii, 1077 development of, 1103 internal atructure of, 1078 Pontine flexure, 1063 nucbus, 1078 Portal system M veins, 519 Postaxial, 4 Pouch of I>ouglas, 1743 pharyngeal, 61 recto-uterine '1743 recto- vesical, 1743 THIS VOLUME CONTAINS PAGES 996 TO THE END. I INDEX. ao79 \i> PDapart, iigktnent o<, j-ij Pl*«xial. 4 Pragnai v, joia Prapui'c of jiriiU, i<)66 Primitivo streak, 34 »ignjti>an. o(, »i Proceu of prcK-esBw*. ciliary, 1457 fronto-nasai. 6a mandibular, &a maxillary, 6a naaal, mesial, 6a lateral, 6j styloid, of petrous oone, 183 uncinate of ethmoid, 193 Processus cochleariformis, 18a vaeinalis, ao4i PriKtodieum, 1695 Prognathism, aa(; Pronephros, 19,^1 Pronucleus, femai 16 mate, ao Prophases of mitosU, 1 2 Prosencephalon, loscj Prostate eland, 1975 development of . kit} lymphatics of, uAs nerves of, 1978 pract. consid., 11179 relations of, 197' stnu-ture of, 19 7 vessfla of 1978 Proteins, 8 Protoplasm. 7 Protovertel>r», m Psalteritmi. i ' '^ PseudostomHtJ ?» Pterion. ia8 Pterygoid plait- inner, iSg ou iSq process.. jI' -phenoid l».ne, t Fube«, 33 1 , „ Pulmonary svs em of veins, 35; Pulp of teeth, i =;54 Pulvinar, 11 19 Puncta, lachryi 1478 Pupil, 1459 Purlcinje cells of rebellur dqo Putamen, 1 1 70 Pyramid, 1065 Pyramidal trait m mt- 'iU''= '5 Pyramid? dec issition 1, renal 18-'' Pvronin, • Radius, a: ; devefc .pwe' landm. pract. I . structure iurUice an. Rai a coinmunii •r, nodes 01. iec Re-; •rils of, a3 ■ — ne pouch a! pouch. 672 '.t-ssels of, hof, 1680 phatics of, 16S0 iscles and fascite of, 1675 ,;rves of, 1680 (jeritoneal relations of, 1679 <43 '743 T679 Kectiim, pract. consid., i68<,i »i ructure of, ■ 674 V .tlveaof. 167 i KeductKm division 18 Keil, island of, 1 M'i liti 'ting sulcus of, iijij Keissm- s libre, 10 jo mc: brane, of i ochlea, 1 1 7 Kemak. ibres of, 1005 Rtual di t, I 894 Ke)>rodu: ion, 6 KefTitdut ve or^." develojm>ent ol. . .'ct«rTial, K' tie, h .jhatus of, <)8 , male lymphatics ' 986 1. ->ials, ! ::•- ^ miemii n nale, lymphiitics of, yU maid, ivmtrfMtic* of, 087 mala, it^i lUapiratiun, otk^hh uf. 1813 Respiratory res;- "i of nose, 1415 tract, di pment of, 1861 Kesttform body, 1067 Kete Mal]nt!hi, 1 {86 Retifiilar t!««r, 75 Ruticuhn. » ; Retina, '46-' b|< 1-v. -uieU of, . iSy dev .iopi'ient (, 1 ' lym{*atics ol. 14' pars i.pti- a of, 14< fwact. consid.. 146; F- 'ucture of. 1463 Retru-coli fossa. 1667 K«txius. t^evesiial space of, sas space uf , I sio6 veins of. 934 Rhi: -ncepl' loo, i ' ^! ieveUij snent < ; 1 193 R"! beiK»»!.halon, derivatives of, 1 Rib 149 'fm,: . 50 i. I'lg. ISO praci consid., 109 stem-il, 150 variations of, 1 53 Right lymphatic duct, 945 Rima glottidis. i8ao Ring, abdominal, external, 584 I internal, 524 femoral (cTural), 1773 . ! Riolan, muscle of, 484 i Rivinus, ducts of. 1 585 I notch of, 1493 ! Rolando, fissure of, 1137 i funiculus of. 1067 I Rosenmflller, fossa of, 1 598 lymph-nodes of, 992 organ of, 2000 Rostrum, of corpus callosum, M56 of sphenoid bone, 1S7 Ruflfini. corpuscles of. 1017 Ruysch, membmne of. MS* Sac, conjunctival, 1443 lachrymal. 1478 vitelline, 32 Saccule, is'S structure of, 1 5 1 ft Sacral lymphatic plex»t«. 0X4 Sacro-iliac articulaticm. 338 1063 THIS VOLUME CONTAINS PAGES 996 TO THE END. aoSo INDEX. ■ ^\-": 8acto-«ciatic ligamenU, 339 Sacrum, 134 development of, lao sexual difference* 01, 137 variations of, 137 Salivary glands, 1581 structure of, 1585 Santorini, cartilages of, 1817 duct of, 1 7^6 Saphenous opening, 635 Sarcolemma, 459 Sarcous (muscular) substance, 459 Scala tympani, 15 14 vestibuli, 1514 Scalp, lymphatics of, ^4$ muscles and fascue, pract. consid., 489 Scaphoid, 309 bone of i.jOt, 435 development of, 436 Scapula, 348 development of, 353 landmarks of, 355 ligaments of, 356 pract. consid., 353 sexual differences, 353 structure of, 3 a Scapulo-clavicular articulation, 36a Scarpa, canals of, 301 fascia of, 515 ganglion of, 1359 triangle of, 639 Schlemm,' canal of, 1453 Schwann, sheath of, looi Sclera, 1449 develojxnent of, 1483 pract. consid., 1453 structure of, 1450 Scleiotome, 30 Scoliosis, 144 Scrotum, 1961 dart-- muscle of, 1963 nerves of, t<)64 pract. consid., 1964 raphe of, 1963 tunica vaginalis of, 1963 vessels of, 1964 Segmentation, 31 complete, 33 * eq'ial, 33 partial, 33 Sella turcica, 1S6 Semilunar bone, 310 cartilages of knee-jcint, 403 valves, 700 Seminal vehicles, 1956 lymphatics of, g88 pract. consid., 1959 relations of, 1957 structure of, 1958 vessels of, 1958 Seminiferous tubules, i>>43 Sense, organs of, 1381 Septum or septa, aortic, 707 auricular, 694 crurale (femorale), 635 intermedium, 706 intermuscular, 470 interventricular, 696 lucidum, 1 1 59 median, posterior, of spinal cord, 1037 nasal, 1410 cartilage of, 1405 placental, 51 Septuii or septa, primum, 706 aei;undum, 708 spuiium, 707 transversum, 1701 Serosa, 31 Sertoli, cells of, 1943 , Sesamoid bones, 104 of foot, 433 of hand, 318 Sharpey's hbr^ of bone, 8 L Shoulder, miucles and fascia of, pnct consid., ^79 Shoulder-girale, 348 surface anatomy of, 363 Shoulder-joint, 374 burste of, 377 dislocation of, 583 landmarks of, 380 ligaments of, 374 movements of, 377 pract. consid., 378 Shrapnell's membrane, 1494 Sigmoid cavity, greater, of ulna, sSi lesser, of ulna, 381 flexure, 1669 peritoneal relations of, 1671 pract. connd., 1685 , Sinus or sinuses, basilar, 874 pract. consid., 874 cavernous, 873 prrxt. consid., 873 circular, 873 confluence of, 868 of dura mater, 867 frontal, 1433; 336 (bony) development of, 1433 pract. consid., 1437 intercavernous, 873 lactiferus, 3030 lateral, 867 pract. consid., 869 longitudinal, inferior, 871 superior, 870 pract. consid., 870 marginal, 873 of placenta, 53 maxillary, 1433; 30 (bony) development of, 1431 pract. consid., 1438 of Morgagni, 497 occipital, 873 palatal, 1435 petrosal, inferior, 874 superior, 874 pocularis, 1933 prjecervicalis. 61 pyriformis of pharynx, 1598 renal, 1874 reuniens, 707 sigmoid, 868 sphenoidal, 143 j pract. consid., 1438 spheno-parietal, 874 straight, 873 uro-genital, 1939 of Valsalva, 700 venosus, 705 Skeleton, 103 appendicular, 104 axial, 103 Skene, tubes of, 1934 Skin, blood-vessels of, 1387 development of, 1400 THIS VOLUME CONTAINS PAGES S9« TO THE END. mmta mik 1^ INDEX. 3081 Skin, end-bulbs of Krauio, 1389 end-organs of Ruffini, 1389 genital corpuscles, 1389 Golgi-mazzoni corpuscles, 1389 lymphatics of, 1388 Meissner's corpuscles, 138') nerves of, 1389 pigmentation of, 1387 stratum comeum.of, 1387 germinativum of, 1385 granulosum of, 1 386 lucidumof, 1386 8truct»ire of, 1381 Vater-Pacinian corpuscles, 1389 Skull, i7» . , o alveolar point of, a»» anthropology of, tiS asymmetry, 230 auricular point of, m8 capacity of, iao changes in old age, 233 chordal portion, 38 dimensions of, 329 fontanelles of , 331 glenoid point of, »38 growth and age of, 330 index, cephalic of, 329 facial of, 339 of height of. 329 nasal of, 239 orbiul of, 339 palatal of, 339 landmarks of, 340 malar point of, 328 mental point of, 338 occipital point of, 338 pract. consid., 335 prechordal portion, 28 sexual differences, 234 shape of, 229 ■ubnasal point of, 339 surface anatomy, 334 weight of, 333 M whde, 216 Smegma. 19M SoUUry nodules of Intestme, Somatopleura, 29 Somites, 29 , _ Space or space*, of Bums, 543 of Fontana, 1452 perforated, anterior, J153 posterior, 1107 quadrangular, of w of Retiius, 1906 . , _, „,, subarachnoid, of spinal cord, 1022 subdural, of sjrinal cord, 1022 sublingual, ijSi of Tenon, 1437 „- triangular, ot m. teres major, 578 Spermatic cord, i960 , constituents of , 1060 pampiniform jdexus of, i960 pract. consid., 1961 ducts, 1953 . nerves of, 19 59 structure of, loS^ vessels of, 195^ filaments, 1946 Spermatids, 1944 Spermatocytes, primary secondary, 1944 Spermatogenesis, 1944 Spermatogones, 1944 1411 lOjC , 1640 [ m. teres major. 1944 Spermatosoa, 1946 Spemiatosoon, 16 Sperm-nucleus, 30 Spheno-ethmoidal recess. Sphenoid bone, 186 articulations of , 190 development of, 190 great wings of , 187 fesser wings of, 188 pterygoid procssae* of. 189 Sphenoidal sinus, 1425 Spheno-palatine ganglion, 1240 Spigelius, lobe of, 1707 Spinal column, 114 Spinal cord, 103 1 anterior horn, nerve-cells M, arachnoid of, 1032 blood-vessels of, 1047 Cauda equina of, 103$ central canal of, 1030 columns of, 1037 anterior, 1037 lateral, 1037 posterior, 1027 commissure, gray of, io»8 white, anterior of, 1038 conus meauUaris, io3t denticulate ligaments of, 1023 development of, 1049 dura mater of, 1033 enlargement, cervical, of, 1036 lumbar of, 1036 fibre-tracts of white mattor, 1038 fissure, median anterior of, 1017 form of, 1036 gray matter of, 1028 nerve-fibres of, 1036 neuroglia of, 1035 ground-bundle, anterior, 1046 lateral, 104J horn, anterior of, 1029 lateral of, 1029 posterior of, 1029 membranes of, 1032 microscopical structure of, 1030 nerve-cells, grow ig of, 1032 pia mater of, 102* posterior horn, nerve-cells of, 1033 pract. consid., 1051 root-line, ventral of, 1037 segments of, 1024 septum, median posterior of, losT substantia gelatmosa Rotandi ol, 1029 , , sulcus postero-lateral of, ]on tract, anterior pyranwdal (direct), 1046 of Burdach, 1039 direct cerebellar, 1044 of GoU, 1039 of Gower, 1044 . . , ,. lateral (crossed pyramidal), 1043 of Lissauer, 1042 white matter of. T036 ganglia, 1279 nerves, 1278 constitution of, 1278 divisions, primary, anterior, 01, 1 204 posterior, of, 1279 number of, 1279 sice of, 1379 typical. 1284 I THIS VOLUME CONTAINS PAGES 996 TO THE END. A ifir^if alglfC 3083 INDEX. Spiiisi nerves, ventral (motor) root* of, 1179 Spine, 114 articulations of, 131 aspect, anterior 01, 138 lateral of, 138 posterior of, 138 curves of, 138 dimensions and proportions of, 141 landmarks of , 146 lateral curvature of, 144 ligaments of, 13 a movaments of, 14a practical considerations, 143 sprains of, 144 as whole, 138 Sfdanchnopleura, 19 Splanchnoskeleton, 84 Spleen, 1781 development and growth of, 1787 lymphatics of, 98 a movable, 1788 nerves of, 178T nodules (Malphighian bodies) of, 1784 peritoneal relations of, 1785 pract. consid., 1787 pulp of, 1783 structure of, 1 783 surface anatomy of, 1787 basal, 178a gastric, 178a phrenic, 1781 renal, 1783 suspensory hgament of, 1 786 vessels of,' 1 786 Spleens, accessoiy, 1 787 S(denium, of corpus callosum, 1 1 56 Spongioblasts 10 10 Spongioplasm, 8 Sprains, of spine, 144 Squamous portion of temporal bone, 177 Stapes, 1498 Stenson, canals of, aoi duct, 1583 Stephanion, 339 Stemo-clavicular articulation, a6i pract. consid., 363 Sternum, 155 developmient of, 157 pract. consid., 168 sexual differences of 1 56 variations of, 156 Stigmata, 72 Stilling, canal of, 1474 Stomach, 161 7 blood-vessels of, 1637 ctirvature greater of , 1617 curvature lesser of, 1617 fundus of, 1 61 8 glands of, 1633 growth of, 1639 lymphatics of, 976. 1638 nerves of, 1638 peritoneal relations of, 1619 position and relations of, i6ig pract. consid., T639 pylorus, 1 61 8 shape of, 1618 structure of, i6ai variations of, 1639 weight and dimensions of, 1619 Stomata, 73 Stomodeum, 1694 Strabismus, 1440 Stratum sonale, of thalamus, iisj Stria medullsrif, 11 19 Stris, acoustic, 1096 Structure, elements of, 5 Styloid process of ulna, 285 Sublingual ducts, 1585 gland, 1585 nerves of, 1585 structure of, 1587 vessels of, 1 585 space, 1 58 1 Submaxillary duct, 1 584 ganglion, 1347 gland, 1583 nerves of, 1385 structure of, 1 58/ vessels of, 1 585 Subpatellar fat, 405 Subperiocteal bone, 98 Sub-peritoneal tissue, 174a Substantia nigra, itoq Sulci, development of, 1 190 fissures, cerebral, 1135 Sulcus hypothalamicus, 11 19 Suprarenal bodies, 1801 accessory, 1805 development of, 1804 ^ growth of, 1804 nerves of, 1803 pract. consid., 1806 relations of, 1801 structure of, t8o3 vessels of, 1803 body, lymphatics cf, 983 Suture or sutures, 107 amniotic, 31 coronal, 316 cranial, 3t6 dostuie of, 333 lambdoidal, 317 sagittal, a 16 Sylvian aqueduct, 1 108 gray matter, 11 09 Sylvius, fissure of, 1136 Sympathetic ner\-es, plexuses of, 1367 Sympathetic system, 1353 aortic nerves, 1364 association cords of, 1357 constitution of, 1355 ganglia of. 1356 gangliated cord of, 1355 gangliated cord, cervico-cephalic portion, 1358 lumbar portion, 1366 sacral portion, 1367 thoracic portion, 1364 nerve-fibres of, 1356 plexus, aortic, 1373 cardiac, 1367 carotid, 1360 cavernous, 1361 cavernous, of penis, 1374 coeliac, 1370 gastric, 1370 nemorrhoioal, 1374 hepatic, 1^70 hypogastric, 1374 mesenteric, inferior, 1373 superior, 1373 ovarian, 137a pelvic, 1374 phrenic, 1371 prostatic, 1374 THIS VOLUME CONTAINS PAGES 996 TO THE END. % tg^m WU I- .^ / INDEX. 30S3 .» Sympathetic aystem, plexiia, renal, 1371 •oUr, 1368 •pennatic, 137 a ■plenic, 1370 •uprarema, 137 1 utero-vaginal, 1374 vesical, 1374 plexuiet of, 1356 pract. consid., 1375 pulmonary nerves, 1364 rami communicantes of, 1356 •fdanchnic afferent fibres of, 1357 efferent fibres of, 1357 nerves, 1364 Symphvsis, 108 pubis. 339 Synarthrosis, 107 Synchondrosis, 108 Syncytium of chorion, 49 Syndesmosis, 108 System, gastro-pulmonary, 1597 muscular, 454 nervous, 906 uro-genital, 1869 Tsnia chorioidea, 1164 coli, 1660 fomicis, 1 1 63 semicircularis, ti6a thalami, iiig Tapetum, 1157 Tanal bones, 419 plates, 1444 Tarsus, 419 Taste, organ of, 1433 Taste-buds, 1433 development of, 1436 nerves of, 1435 structure of, 1431 Teeth, 154; alveolar periosteum, 1553 bicuspids (premolars), 1545 canines, 1544 milk, 1545 cementum of, 1552 dentine of, 1550 development of, 1556 enamel of, 1 548 homologies of, 1 566 implantation and relations of, incisors, 1543 milk, 1 544 lymphatics of, 951 milk, eruption of, 1 564 «S54 (temporary), 154* molars, 1546 milk, 1547 neck of, 154a permanent, 1541 development of. 1 564 eruption of, 1565 relations of, 1554 pract. consid., 1591 pulp of, 1 554 pulp-cavity of, 1542 temporary, relations of, 1556 variations of, 1 566 Tegmen tympani, 1496 Tegmentum, ma Tela chorioidea, 1097 subcutanea, 1384 Telencephalon, 1131 Tdophaaes of mitosis, 13 Temporal bone, 176 articulations of, 184 cavities and passages, 1S3 development of, 184 portion, petro-mastoid, 179 squamous, 177 tympanic, 179 lobe, 1 147 Tempoto-mandibular articulation, a 14 Tenoo oculi, 484 Tendon, 77, 468 conjoined, 518 Tendon-cells, 78 Tendon-sheaths, 470 Tenon, capsule of, 304 space of, 1437 Tentorium cerebeiU, 1199 Terms, descriptive, 3 Testis or testes, 1941 appendages of, 1949 architecture of, 194a descent of, ao4o lymphatics of, 087 mediastinum of, 194a nerves of, 1948 pract. consid., 1950 structure of, 194a tubules seminiferous of, 1949 tunica albuginea of, 194a vessels of, 1948 Thalamic radiation, 112a Thalamus, it 18 connections of, 11 ai structure of, 11 30 Thebesian valve, 695 veins, 694 Theca foUiculi, of hair, 139a Thenar eminence, 607 Thigh, landmarks of, 670 muscles and fascise of, pract. consid. 64 a Third ventricle, 1131 choroid plexus of, 113 1 Thorax, 149 artictUations of, i<;7 in infancy and childhood, 164 landmarks of. 170 lymphatics of, 966 movements of, 165 pract. consid., 167 sexual differences, 104 subdivisions of, 1832 surface anatomy 166 landmarks of, 1868 as whole, 163 Thumb, articulation of, 336 Thymus body, 1 796 changes of, 1797 development of, tSoo nerves of, t8oo shape and relations of, 1796 structure of, 1 798 vessels of, 17^9 weight of, 1797 Thyroid bodies, accessory, 1793 Thyroid body, 1789 development of, 1793 nerves of, 1 793 pract. consid., 1794 shape and relations of, 1789 structure of, 1791 vessels of, 179a cartilage, 181 4 THIS VOLUME CONTAINS PAGES 996 TO THE END. HP ' 9084 Thyroid t\rvilage, development of, vrowtn of, 181 5 gland, lymphatics of, 959 TIblt., i»2 development of, 387 landmarks of, 390 pract. consid., 387 Ktnicture of, 387 variations of, 383 Tibio-fibular articulation, mfenor, 396 superior, 396 Tissue or tissues, adipose, 79 connective, 73 elastic, 76 elementary, 67 epithelial, 67 fibrous, 74 muscular, general, 454 nervous, 997 osseous, 84 reticular, 75 Tongue, 1573 foramen csecum of, 1574 frenum of, 1573 glands of, 1575 growth and changes of, 1 580 lymphatics of, 952 muscles of, 1577 nerves of, 1 580 papillse, circumvallate of, 157S filiform of, 1575 fungiform of, 1575 ptact. consid., 1 594 vessels of, 1 580 Tonsil or tonsils (amygdala), of cerebellum, 1086 faucial, 1600 faucial, relations of, 1603 lingual, 1575 lymphatics of, 054 pharyngeal, 1601 pract. consid., 1608 tubal, 1503 Tooth-sac, 156a Tooth-structure, 1548 Topography, of abdomen, 531 cranio-cerebral, 1114 Trachea, 1834 bifurcation of, 1837 carina of, 1837 growth of, 1837 lymphatics of, 958 nerves of, 1836 pract. consid., 1840 relations of, 1836 structure of, 1835 vessels of, 1836 , Tract or tracts, (fibre) nibro-spmal, 1114 habenulo-peduncular, it»4 mammillo-thalamic, im of mesial fillet, 1076 olfactory. 115* thalamocipetal, lower, ii»» Tragus, 1484 Trapezium. 311 Tra peloid bone, 311 Trerts, muscle of, 558 Triangle of Hesselbach, saft rectal, 191 6 uro-genital, 191 6 Triangles of neck, 547 INDEX. Trigone of bladder, urinary. 1904 Trigonum acustici, 1097 habenuUe, 11 23 hypoglossi, 1097 lemnisci, 1108 uro^nitale, 563 vagi, 1097 Trochanter, greater, of femur, 35a lesser, of femur, 353 Trochlea of humerus, a 68 of orbit, 504 Trochoides, 113 Trophoblast, 46 . , Truncus bronchomediastmalis, lympnatw 968 Eubclavius, lymphatic, 963 Tube, Eustachian, 1501 Tuber cinereum, 1129 Tubercle of Lower, 695 Tuberculum acusticum, 1097 olfactoritmi, 11 53 Tubes, Fallopian, 1996 Tunica vaginalis of scrottmi, 1963 Turbinate bone, inferior, 208 articulations of, io8 development of, 308 middle, of ethmoid, 193 superior, of ethmoid, 193 ' Tympanic portion of temporal bone, 17Q Tympanum, 149a attic of, 1 500 cavity of, 183 contents of, 1496 membrane of, 1404 pract. consid., ijos mucous membrane of, 1500 oval window of, 149 5 pract. consid., 1 504 promonotory of, 149S pyramid of, 1496 round window of, 149 5 secondary membrane of, 1495 tegmen of, 1496 Tyson, glands of, 1966 Ulna, a8i development of, a85 landmarks of, a 87 pract. consid., a8s structure of, 385 surface anatomy, 300 Umbilical cord, 53 . allantoic duct of, $4 amniotic sheath of, 54 blood-vessels of, 54 furcate insertion of, 55 jelly of Wharton of, 54 marginal insertion of, 5 s velamentous insertion of, SS fissure of liver, 1708 hernia, 1775 notch of liver, 1707 vesicle, 4» Umbilicus, 37 Unciform bone, 31a Uncus, 11S4 , , ,, Upper limb, muscles of, 568 Urachus, 535 Ureter or ureters, 1895 femals, 1896 lymphatics of, 983 ner^'es of, 1898 pract. consid., t»9» THIS VOUUWr CONTA'.NS PAGES 996 TO THE END. ittmirii 2o86 Vein or vein*, cervical, deep, 859 middle, 884 chord* WiUitei, 870 choroid, 877 ciUary. antenor, 879 posterior, 879 circulation, foetal, 9 '9 circumflex, iliac, deep. 910 superfitial, 917 of leg;, 9>4 claMification of, 851 clitoris, 909 colic, middle, 981 INDEX. right. 931 condyloid, antenor, 874 863 confluence of the sinuses coronary, of {»"?••.** 5 inferior, of facial, 865 left, 85s right. 856 of corpus callosum. antenor, 87S posterior, 877 cavemosum, 907 striatum, 877 ^^th?pi2:'orsuperior thyroid. 867 d^p'^do^l of penis (clitoris), 909 of forearm, 886 of hand, 886 dental, inferior. 883 superior. 883 development of, 926 diploic. 874 anterior. 875 occipital, 875 pract. consid.. 875 | temporal, antenor. 873 | posterior. 875 ] dorsal, of foot. Qio j interosseous, 886 I ductus Arantii. 929 ! arteriosus, 930 ' Botalli. 930 ' venosus, 920 . j-..^ emissaries of foramen lacerum medium, 876 emissary. 875 condyloid, antenor. 870 posterior, 876 of foramen ovale. 876 of Vesalius, 876 mastoid, 876 occipital. 876 parietal. 876 pract. consid., 876 epigastric, deep. 901) superficial, qi 7 superior, of internal mammary, 860 ethmoidal. 879 facial. 864 common. 864 deep. 865 pract. consid.. fiCu transverse, 882 fernoral. deep. 01 i rrart. consid., oiS circulation, 929 of foot. deep, qio superficial. 914 foramen lacerum medium, 876 frontal, of facial. 865 of Galen, 856 Vein or vein*, gMtrlc, 9»3 short, 931 gMtro-«piploic, left, 9*1 right, 921 gluteal, 905 hemiacygoa, 895 acceuorv, 80s . hemorrhoidal, infcnor, 907 middle, 908 plexus, 908 superior, 9a* hepatic, 90* pract. consid., 904 hepatica communis, 900 ileo-colic, 931 iliac, common, 905 pract. consid., 917 external, 909 pract. consid., 918 internal, 905 pract. consid., 910 ilio-lumbar, 906 inferior cava, pract. consid., 900 caval system, 898 innominate, 858 development of, 859 pract. consid., 859 intercapitular of hand, 889 > intercostal, 896 ^^„^ riso anterior, of internal mammary. 8O0 superior. 896 ; accessory left, 896 intervertebral, 898 jugular, anterior, 884 external, 880 posterior, 884 pract. consid.. 88f internal, 861 bult>» of. 86 1 prac. consid., 863 labial, inferior, of facial, 865 superior, 865 lacunae of dural sinuses, 851 laryngeal, inferior. 861 superior, of superior thyroid, 867 of leg, deep, 9". , pract. consid.. 918 of limbs, development of, 939 lingual, deep, of facial, 867 of facial, 867 lumbar, 901 ascending, 901 mammary, external. 888 internal. 860 marginal, right. 856 marginalis sinistra, 855 of Marshall, 856 masseteric, of facial. 866 mastoid emissary, 869 maxillary, internal, 881 . . a^, internal, antenor, of facial. 865 median, 890 deep, 886 mediastinal, anterior. 861 meduUi-spinal. 898 meningeal, middle, 883 mesenteric, inferior, qii superior. 931 metacarpal, dorsal. 889 , nasal, lateral, of facial, 865 oblique, of heart, 69s of left auricle, 856 obturator. 907 Wirsung, duct of, 1736 Wisdom-tooth, 1546 Wolffian body, 1935 duct, 193 s Womb, 2003 Worm of cerebellum, 1082 Wrist, anterior annular ligament, 607 movements of, 336 pract. consid., 613 surface anatomy of, 328 Wrist-joint, landmarks of, 330 pract. consid., 329 Xiphoid process of sternum, 156 Volk-stalk, 37 Zeiss, glands of. 1 444 Zinn, annulus of, 503 zonula of, 147 5 Zona pellucida, 1 5 radiata, i s Zonula of Zinn, 1475 Zuckerkandl, bodies of, 1812 Zygomatic process of temporal bone, 178 THIS VOLUME CONTAINS PAGES 996 TO THE END. llkWiiittaiAi