le pea Lett eat el Sy? pe ie ees priicinibe ALBERT R. MANN LIBRARY New York STATE COLLEGES OF AGRICULTURE AND HoME ECONOMICS AT CORNELL UNIVERSITY wang - ANATOMY OF THE CAT ' BY , JACOB REIGHARD Professor of Zoology in the University of Michigan AND H. S. JENNINGS Instnittor in Zoology in the University of Michigan WITH ONE HUNDRED AND SEVENTY-THREE ORIGINAL FIGURES DRAWN BY LOUISE BURRIDGE JENNINGS NEW YORK HENRY HOLT AND COMPANY 1901 Copyright, 1901, BY HENRY HOLT & CO. ROBERT DRUMMOND. PRINTER, NEW YORK. PREFACE. ALTHOUGH the cat has long been in common use for the practical study of mammalian anatomy, a clear, correct, not too voluminous account of its structure, such as should be in the hands of students in the laboratory, has remained a desideratum. A number of works have been published on the cat, some of them of much value, yet there is none which fulfils exactly the conditions mentioned. The books which have appeared on this subject are the following: 1. Strauss-Durckheim, H. Anatomie descriptive et com- parative du Chat. 2 vols. Paris, 1845. 2. Mivart, St. George. The Cat: an Introduction to the Study of Back-boned Animals, especially Mammals. New York, 1881. 3. Wilder, Burt G., and Gage, Simon H. Anatomical Technology as applied to the Domestic Cat. New York, 1882. 4. Gorham, F. P., and Tower, R. W. A _ Laboratory Guide for the Dissection of the Cat. New York, 1895. 5. Jayne, H. Mammalian Anatomy. Vol. I. Phila- delphia, 1898. The first of these works treats only of the muscles and bones, and is not available for American students. Its excel- lent plates (or Williams's outline reproductions of the same) should be in every laboratory. The second book named is written in such general terms that its descriptions are not readily applicable to the actual structures found in the dissection of the cat, and experience has shown that it is not fitted for a laboratory handbook. It contains, in addition to a general account of the anatomy of the cat, also a discussion of its embryology, psychology, paleontology, and classification. iii lv . PREFACE. The book by Wilder and Gage professedly uses the cat as a means of illustrating technical methods and a special system of nomenclature. While of much value in many ways, it does not undertake to give a complete account of the anatomy of the animal. The fourth work is a brief laboratory guide. The elaborate treatise by Jayne, now in course of publica- tion, is a monumental work, which will be invaluable for refer- ence, but is too voluminous to place in the hands of students. At present only the volume on the bones has been published. As appears from the above brief characterization, none of these books gives a complete description of the anatomy of the cat in moderate volume and without extraneous matter. This is what the present work aims to do. In the year 1891-92, Professor Reighard prepared a partial account of the anatomy of the cat, which has since been in use, in typewritten form, in University of Michigan classes. It has been used also at the Universities of Illinois, Nebraska, and West Virginia, and in Dartmouth College, and has proven so useful for college work in Mammalian Anatomy that it was decided to complete it and prepare it for publication. This has been done by Dr. Jennings. The figures, which are throughout original, are direct re- productions of ink drawings, made under the direction of Dr. Jennings by Mrs. Jennings. The book is limited to a description of the normal anatomy of the cat. The direct linear action of each muscle taken alone has been given in the description of muscles; other matters belonging to the realm of physiology, as well as all histological matter, have been excluded. It was felt that the monumental work of Jayne on the anatomy of the cat, now in course of publication, forms the best repository for a description of varia- tions and abnormalities, so that these have been mentioned in the present volume only when they are so frequent as to be of much practical importance. Except where the contrary is stated, the descriptions are based throughout on our own dissections and observations and are in no sense a compilation. For this reason we have not PREFACE. v thought it necessary to collect the scattered references to the anatomy of the cat that may occur in the literature. A collection of such references may be found in Wilder and Gage’s Anatomical Technology. In addition to the works already referred to, we have of course made use of the standard works on human and veterinary anatomy. Among these should be mentioned as especially useful the Axatomie des Hundes by Ellenberger and Baum. Other publications which have been of service in the preparation of the work are Windle and Parson’s paper Ox the Myology of the Terrestrial Carniv- ora, in the Proceedings of the Zoological Society of London for 1897 and 1898, T. B. Stowell’s papers on the nervous system of the cat in the Proceedings of the American Philo- sophical Society (1881, 1886, 1888) and in the Journal of Comparative Neurology (vol. I.), and F. Clasen’s Die Muskeln und Nerven des proximalen Abschnitts der vorderen Extremti- tat der Katze, in Nova Acta der Ksl. Leop-Carol. Deutschen Akademie der Naturforscher, Bd. 64. Nomenclature.—The question of nomenclature has been ene of difficulty. What is desired is a uniform set of anatomical names,—a system that shall be generally used by anatomists. At present the greatest diversity prevails as to the names to be applied to the different structures of the body. The only set of terms which at the present time seems to have any chance of general acceptance is that proposed by the German Anatomical Society at their meeting in Basel in 1895, and generally designated by the abbreviation BNA. This system has therefore been adopted, in its main features, for use in the present work. It seems impossible at the present time, however, to impose any one set of terms absolutely upon anatomists of all nations, and we have felt it necessary to use for certain familiar structures, in place of the BNA terms, names that have come to have a fixed place in English anatomy, and may almost be considered component parts of the English language. The German anatomists have expressly recognized the fact that this would be to a greater or less degree necessary among anatomists of different nations, and have characterized their list as for the present tentative, and vi PREFACE. capable of farther development. The only purpose of a name is that it shall furnish a key to a common understanding; where the BNA name does not furnish such a key to English readers, and where there is a term in established English usage that does serve this purpose and seems unlikely to be sup- planted, we have used the latter. But we have endeavored to make the number of these exceptions as small as possible, and in such cases we have usually cited at the same time the term proposed by the German society, followed by the abbreviation BNA. When, on the other hand, we have adopted a BNA term for which there is also a commonly used English equiva- lent, the latter has likewise usually been cited in parenthesis. In deciding whether or not to use in a given case the BNA term many difficult cases arose. Will the common English name zanominate bone (os innominatum) be replaced by the BNA term os cox@ or coxal bone? We have held this to be highly improbable, and have therefore used the term zznomz- nate bone, merely citing os core (BNA) as a synonym. In the same way we have used centrum as a designation of a part of a vertebra, in place of corpus (BNA); premaxillary bone or pre- maxilla in place of os zncisitvum (BNA); malar bone in place of os zygomaticum (BNA); trapezoid as a name of one of the bones of the carpus, in place of os multangulum minus (BNA), etc. In other cases where it has seemed probable that the BNA term would come into common use, though now un- familiar, this and the more common English expression are both used or used alternatively; such has been the case, for example, with the Gasserian ganglion or semilunar ganglion (BNA). In naming the cerebral sulci and gyri the system in use for man is not well fitted for bringing out the plan of those in the brain of the cat, so that it was necessary to reject the BNA names for these structures. As to the use of the Latin terms and their equivalents in English form, we have made a practice of employing in the text sometimes one, sometimes the other; this has the advan- tage of giving variety, and of impressing the interchangeability of the Latin and English forms on the mind of the student. Where a given structure is called by two equally well-known PREFACE. vii names, we have used both, holding that the student should become familiar with each and recognize their identity of meaning. In general we have maintained the principle that the primary purpose of such a work as the present is not to illus- trate or defend any particular system of nomenclature, but to aid in obtaining a knowledge of the structures themselves. With this end in view, we have used such terms as would in our judgment best subserve this purpose, making the BNA system, as the one most likely to prevail, our basis. In apply- ing the system we have had to keep in mind a number of sometimes conflicting principles. In some cases the judgment of other anatomists will doubtless differ from our own; but this we feel to be inevitable. The matter of an absolutely uniform nomenclature is not ripe for settlement at the present time. Some further explanation is needed in regard to the topo- graphical terms, or terms of direction, used in the present work. We have adopted the BNA terms in this matter also. The terms superior, inferior, anterior, and posterior have been avoided, as these terms do not convey the same meaning in the case of the cat as they do in man, owing to the difference in the posture of the body. In place of these terms are used dorsal and ventral, cranial and caudal. As terms of direction these, of course, must have an absolutely fixed meaning, sig- nifying always the same advection without necessary reference to any given structure. For example, crvanzal means not merely toward the cranzum, but refers to the direction which is indicated by movement along a line from the middle of the body, toward the cranium; after the head or cranium is reached, the term still continues in force for structures even beyond the cranium. Thus the tip of the nose is’ considered to be crantad of the cranium itself. Lateral signifies away from the middle plane; medzal toward it. Juner and outer or internal and external are used only with reference to the struc- ture of separate organs, not with reference to the median plane of the body. In describing the limbs the convexity of the joint (the elbow or knee) is considered as dorsal, the concavity being therefore viii PREFACE. ventral. Medial refers to that side of the limb which in th normal position is toward the middle of the body; lateral t the outer side. Terms of direction which are derived only fror the structure of the limb itself are in some cases more conven ient than the usual ones. In the fore limbs the terms radi (referring to the side on which the radius lies) and ulna (referring to the side on which the ulna lies) are used; in th hind limbs the terms ial and fibular are used in a simila manner. Dzstal means toward the free end of a limb or othe projecting structure; proxzmal, toward the attached end. For all these terms an adverbial form ending in -ad ha been employed. Experience has shown this to be very usefi in practice, and while not expressly recommended by the BNA it is not condemned. Terms ending in -a@/ are therefor adjectives; those ending in -ad are adverbs. In compounding these terms of direction, the hyphen ha been omitted in accordance with the usage recommended b the Standard Dictionary. Thus dorsoventral is written i place of dorso-ventral, etc. The student will perhaps b assisted in understanding these compounds if he notes th the first component always ends in -o, so that the letter o prac tically serves the purpose of a hyphen in determining how th word is to be divided. In one particular the BNA nomenclature is not entirel consistent. While recommending or at least permitting th use of the general terms dorsal and ventral in place of th human fosterior and anterior, and cranial and caudal in plac of supertor and inferzor, it retains the words anterior, posterior superior, and inferior as parts of the names of definite organ: For example, we have the muscle serratus anterior in plac of serratus ventralis; serratus posterior inferior in place « serratus dorsalis caudalis. This is very unfortunate, from comparative standpoint, but we have felt it necessary to retai the BNA terms in order that the structures of the cat ma receive the same names as the corresponding structures < man. In the matter of orthography we have endeavored to follo: the best English anatomical usage, as exemplified in Gray PREFACE. ix Human Anatomy,—therefore writing peroneus in place of peroneus, pyriformis in place of piriformis, etc. ‘ The book is designed for use in the laboratory, to accom- pany the dissection and study of the structures themselves. Anatomy cannot be learned from a book alone, and no one should attempt to use the present work without at the same time carefully dissecting the cat. On the other hand, anatomy can scarcely be learned without descriptions and figures of the structures laid bare in dissection, so that this or some similar work should be in the hands of any one attempting to gain a knowledge of anatomy through the dissection of the cat. The figures have all been drawn from actual dissections, and have been carefully selected with a view to furnishing the most direct assistance to the dissector. It is hoped that no figures are lacking that are required for giving the students the necessary points of departure for an intelligent dissection of any part of the body. The fore limb is illustrated somewhat more fully than the hind limb, because it was thought that the fore limb would usually be dissected first; the hind limb will be easily dissected, with the aid of the figures given, after the experience gained in dissecting the fore limb. As the book is designed to accompany the dissection of the specimen in the laboratory, it was deemed best to give succinct specific directions for the dissection of the different systems of organs, together with suggestions as to methods of preserving and handling the material. These are included in an appen- dix. CONTENTS. PAGE THE SKELETON OF THE CAT.......00..-- cee eeceeees ee Re niece se HORS. eave oreo I I. The Vertebral Column... .........2. cece eee eees sats earls raw ges asi I Thoracic Vertebrotig..03 ege0ess ie eneemnaes geen eenes aa ales eto oT Lumbar Vertebrae.. 1... 0... cece cee eee ear yranerae areata ne 4 ces 7 Sacral Vertebree : Sacrum......... cus sig sary sl wean tecaa te) ieee 18 Caudal Vertebrae ...........6...-6- os Stacia yep adnan ibanoxaye\ans elatere discars's II Cervical Vertebra............ asec eis ners Si scavaanese saaiisesiaisinie fvaisceve avesa IL Ligaments of the Vertebral Column.......... a WENNER TREES 16 IL. The Ribs... 06 seeses scctehtstteloesteta tieia a (eee EEE sas Y 18 III. The Sternum........ euareetavensetieYepestech aa arate tare guetchatmuene euerpeieale ses 20 JV. ‘Ther Skull. c .-<.:0:0 exaceaisicicete pro seeress oaaievatg Spaseseelers ihviersreisiete ss I2E Occipital Bone....... savaindaeuaee tates ikongraresten gti aaasalcgiaardya e seuaertne ecvne 122 IMPS rPATIStah scvisiere ese:a: a: saie-oiereieiaiane wieedroisveraye! Hea @ enceinlacat ice suktouasders Seeburg 25 Sphenoid.......... TR aT ets Ke PN he TRE HAMAD BSc 25 Presphenoid.......... .cceee eee ANE EEL RETS RM OMI ia snnaverincns 29 Temporal. ccansuss sors acewsmeeenweniiins sveacnerates ce eee 30 Parietal.........++- Gi ghWapei meats uasteacerareieiarelery ais eins Samim we uete 2 oars 36 Frontal... ....-+-.6+ See ieretery ats er Sealsereg 37 Maxi anyiiscecnnescvasetevere\operoarn sia naaeniaaeinoutunvn bares ea Gnaaog sigyecene oposecevege, 230) Premaxillary........... adeadeiisoxarere wi ativppariecepstas wee e ener tee ence ees 41 INASAls cicorsnastec:3 SR Scei shee Ba titios WR eee nan Ree ere aaa Acesicsare 42 Ethmoids..cs<..... saa ieatan cde ee 232 3s BHsophagus cc cccccces ceeseensceen Thewuben aes bee 234 4; Stomach ios cisse swinn sens suuriswicas ereueisaiweacrmeeests 234 5. Small Intestine.......... ste iecessiaios never ash au dheraiigca era wishes ai etahareSetatoiens 236 6. Large Intestine. ........... eee ee a Ssasetereceacavavele wiaigen sgaegueinnn 287, 7. Liver, Pancreas, and Spleen..........ceeeee severe aserasialauavein 239 Hi. ac ie ORGANS .:sieaispccs ns SRR R RR eeaer aT FRE Sen 243 - Nasal Cavity....... ERAS SAAD SENR OSES HOV ONS TRAST + 243 2: LaryiX. cs cseveanseges ne ee ee ee 246 Cartilages of the Larynx,........ slasctaioheiotalahede aa to gases sacsigg, AT Muscles: of the Larynxiss sis: ss-se scigigie ig ee settee arerace nia e eraiarg Sisal any 249 Ba MACH CA a vareave dhinarauivacst eraser code le needa ayo mane atab baron Skids 251 Ge TUDES ese essa ters ewido narsies Saleen cocoate fe ere asap ait be eee Sutiiad auoeraee 252 Thyroid Gland. ....... cece cece ee ete e een ce eee eeteetenees 254 Thymus Gland ...........-055 Sestlasan Ries mucins ta senna ae 254 IV. Urogenital System. .... cece sec cece teeter c cece nacenaneaane 255 1s Exerétory OrgansSwcivese csi sss accuses oredr sayecernas as 255 Kidneys ..... seueiuewees sie niaearerwea eww Gdyetsto- cavover pores wiatels 255 UUreter snewsiinsinreeadailnesingons evarmmenaneanamnadmaets «. 256 Bladder ............ Pls tava avenegraseroranoravei ele LisjaclaiG Sta vayeyeomutaaagas ouatavaraes 256 (Suprarenal Bodies)..........02.. sees eee eeeees Seine Baasseree ar08 257 2. Genital Organs... ...... cece cece eee ener ee nee eee ereeceereee 257 A. Male..........eeeee Stee wae Cnet 257 Be FEMALE: 10:68 oes AAs DRED ERO NE RR OE ir eee. 263 Muscles of the Urogenital Orsansy Rectum, andl pene ee 268 a. Muscles Common to the Male and Female....... dilenTae 268 6. Muscles Peculiar to the Male...........-. eee eee eee eee 271 r XiV CONTENTS. PAGE c. Muscles Peculiar to the Female........ ON RATA EAOES 272 THE CIRCULATORY SYSTEM.......0.0-. 0000s Jew E GRIME ReT ate ae +. 274 I. The Heart ..............- siueinloiaterend sears eee er aeseeeees scat aholavereiei ste 274 I; PhevArteries)s....co.pr si ainacnyrracagigergeneereag dgieistsoualranmaisavaeias, 1290 1. Pulmonary Artery ......... 0c cee cen cece eene afatareswgyaeratowansy's/aiecs 280 Bi, NOV Bia: vover crave soca cca. s0cou6 eee enayecasivens ace bionayanntads igisGeuayasdate asdhat nae iohs 281 A. Thoracic Aorta and its Branches..........-002.ece ee eee 281 Common Carotid Artery........ SPY assess OTLB RED Gere 283 Subclavian Artery........0.0005 slerewinsuneelatne.« wanves 290 8. Abdominal Aorta and its Branches.............. erase eins 301 External Iliac Artery and its Branches ................ 309 J, “Dhe: Veins: aiceictnearr nen car aaa cgracoeneuwewsicinee we veins sisiavetarereinjecea: 355 a. Veins of the Heart.... 0.0... cece cece eee eeee pnckelonarah aVerstaeer gr vig 315 2. Vena Cava Superior and its Branches........0..eeeeeeseeeeeee 316 Veins of the Brain and Spinal Cord.......... Sdssouisaaisicuetwsevecob ace 324 3. Vena Cava Inferior and its Branches..........- BORO RSPR os Sree 325 Portal. Veit. ss scswexcwasvaeews oem JRE EERE 326 IV. Lymphatic System.......... \alesuginlah ais ayer jireeee EMG OEOiSalew 330 1. Lymphatics of the Head.............000eeeees aeeeesee beara 331 2. Lymphatics of the Neck ..........0eecueeee ace sejalateverigndghMes ares 332 3. Lymphatics of the Thoracic Limbs........:.0..csceceeeeenees 332 4. Lymphatics of the Thorax and Abdomen...........+.0.0.. wierd BSR 5. Lymphatics of the Pelvic Limbs ...... GE RORLR TES sie ROS is A 334 THE NERVOUS SYSTEM... 2.060 cece e cece eee nenneeee emcdeamG Rees 335 I. The Central Nervous System..... 00.6... ceeecee eee cen eceeeeeeeees 336 1. Spinal Cord...... SUUISAMRA ES Ue Deeks ane ReRATEaTE 336 2. The Brain........... KU NRAE SEW Rian Serle wuaeeeeEten 339 (1) Myelencephalon............0. 00.065 prereren Spokara eit ateieey 344 (2) Metencephalon....... idavbvawa, Shavetlvaond aeusetorasivale eee 347 (3) Mesencephalon...... .....+.4 te nerees eee e ene eee + 351 (4) Diencephalon .......... weennmetesceaieeenk stacnncesee 352 (5) Telencephalon .......... acacia aCe S Aa eenteenias genie 357 Il. The Peripheral Nervous System,........+.eeseres Lautioireseeyeows 369 tu. Cranial Nerves: cagsunecnsseguewrs saues sbesaiarene siesremmernquaiesste 369 I. Olfactory Nerve............00. idea degayerivt aaa nskpeanesia derreyert are 369 Il. Optic Nerve....... sraronersnscersste a oye ceveibualatarmcavannressecaue sane 369 III. Oculomotor Nerve. ...........0eeeee sueisereydkoneare'aeale a ietaseeuts 369 IV. Trochlear Nerve... 0... cesses cece cece ees cece eenes 370 V. Trigeminal Nerve........eeeeeeeeeeeeee aise eR ts RIN +. 370 VI. Abducens ....... teaseeee seteiainye Riis ROTA OROR. ACER 375 VII. Facial Nerve...... senRraaa ae ATER OTST eS ORES 375 VIII. Auditory Nerve.......... SUeasis ea Caw be espeureGeew ee eisai 377 IX. Glossopharyngeal Nerve... escesececenenseteres dense 378 X. Vagus Nerve ........+. sh ska! 6.e4:e'e Sans sataaxonayovavayeraxaxevanoieis Gaedoriie 378 XI. Accessory Nerve........ shaiaelous ene eanansongniegsareteneys sche Shaye doienthae GOD XII. Hypoglossal Nerve ........seeceee cnet eceeccen es eeceees 383 2. Spinal Nerves......... MNES TER oe BREE SPST Es wine ace 383 A. Cervical Nerves....... EMA RISAT SAT RH RAMAO ere weess 383 The Brachial Plexus.............-4 Sa Separate waar 386 CONTENTS. xv PAGE Bz Thoracic Nerves... c0.00 2566 ce edin itis seein seeerrewensars 393 Cy Lumbar Nerveseecucuxnsxaceaae bees end swweieeeeeewen: BOR Lumbar Plexus............. iRGEA ROO NOR ERRKERR RRS 395 D. Sacral Nerves and Sacral Plexus mae ee ies sertinasieeee angen BOO i, Nervemof the Tally sceneescanye cya ee nage unas Sp eiitoi sa axa M04. 3. Sympathetic System..............0 ce eee eee sivecaiaseierdsswieie cess OG. SENSE ORGANS AND INTEGUMENT.........-0008 A seiovacsosk Anat Sik eae omen enOa 409 Te TRE YG ocx acisvsueue ere adios Machin ania areicaieg Ske ee EO Cite CRP + 409 es TRE Bary, iit eae ida anette oc eae BNeitele devaaty aes eRe ena 415 III. Olfactory Organ ......... 2. cess ee eee mavens wees Xe waeenbienan 426 IV. Organ of Taste: «scwsscwewercsew sso esa we mneuemmneenuiies vee be eee 426 Vi IUntegumentenssiaiaiv ees edisciessisialeguninis biog cigiele see cinta egisisnegieee sores 427 APPENDIX: PRACTICAL DIRECTIONS......ccceececeerccescrcesecsrsecene 429 LIST OF ILLUSTRATIONS. FIG. PAGE 1. Skeleton...............- Bisiack seeds ase baat aan avantyarenerens acaigboeurinsicnsesss 2 2. Fourth Thoracic Vertebra.......... Bibsereiaess ainfayeiuarsigenaeseys scenececsces 3 3p 5% ae ee shivers aise sd eae eave dadinarecoea Hualscemieie se GiaGepen: 33 4. Thoracic Vertebrae............... al ite se Sera halts ie gvdioiese aie sims 5 5. Lumbar Vertebre........ see U Tae S eee aEeras ie supa MOREE toe 7 6. Sacrum............eee Sidhge ac shig tate Un 4 nn Sia ls se nacotaceniatons ss are eeetors we art seen Q 7: UO actress aN alate Bestia i aei Gree Tain/eheraeg dt Ga Seiad oe eigen 9 8. Caudal Vertebra.......... sciaietavisyaraiinwslone gear ova 0d snag phacatny shierarapad sisitavawiake’y Il 9. ig BUS pte Wicepacss a atara sea: elgs Susie etevacorevestussakos atanaviante ralauswuds whe AaNwate vans IL to. Cervical Vertebrae........ eC so MOE ari. BBuvsanscBetenacerave Sree. forasude ai 12 ri. Sixth; Cervical! Vertebra.. .sioicx saspreis ¢ soe wea aawdaviee seed ee sists oie 13 12; Atlas: icoscarsisien mara sv emwemaneens ot J Save Se ose nsw dy wean Seay ATF 13. AXIS iw, ces, Sapmanvarcy aimar gongs: as eoiee sae ss hee ew eases Saye, 15 14. Ligaments of the Odontoid Process............. dca newer cara aeialak 18 TGs TRAD cese:sicase-siecassisvavatesep e evesacnrenarortver a ics aiebieaesecalie Seay mbalaraver naiehavarlwnminra cd diacels 19 TOs: ‘SUSHI s.55 cach icra ei ead wid BR ain eu aya senBataver Sh dicie Ses id ee ce whe Gnaeeverauecmianiod ce 20 17 ‘Occipital Bone x xs. 2 wniarwiamnans kw 025 8 55004 MORSE ORI ews Riss wre 22 18. es SO awe ek MENS WORSE ENO eo we eo ewee EN aa eee 22 19: Interpartetal s:jiiso ose ene wetwinsee sean awe be ee Pee mesa ne eirete tsann 2S 20; SPHENOId isis, ogaiaeigtey age sseres qeninnindue gigs oy 4 @ Sat angie Buarwiangenne Gates. 8 « 25 ZT. PrésphenOidiniesioiieccwisinis rueyawandaniueeds CA senepse lade veteran seer Wee alesis Bien: 29 22. Temporal....,.....- icanavagusvans tall aan anda asneeaneen acy al oveisiuesel ag Mace adhe 31 23. He had iit betel est ean ctah ibe BaP R wiese Sareea i anaes Mises tarasenspras acta Atal 31 24. Tympanic Bulla............. ee cece eee eee a Sanat PEG TAT Cavan 33 25 Petrous Bones «os: sacssquaasoeoee rs ces 4 wa slaatawa’s sama Kae to Va 34 26: Frontaloagc css seernsisteiqunerdeen niu ts os aR dawees wOK Hem HOR BRM 37 27. Maxillary Bone) je cvsciac:2 vieisiss saistog areca ieee Vale ae edegsae des BAe Sane 39 28. “ Be a tate: « Gekee eiauldctic den Sana stead ecanas eae NOS nena 39 Do. Prema lla ry 2 opsaaicsvs stevens, avosaerasiecaueat d astuoracqvaraes aus dada unedeannarwia alareiaion & 41 BO. ANGSAl or avccesis.0:8-siposseniren toad Vis Saha asece eMC GED sais AER Gas Ardbere a win ae 42 i> Ethmoid and. VonierssO Ventral “ « sh et a Bisiavn sears aniareteeetwvotareiacs seeeee 352 Longitudinal Section of Brain...... Oreste aus einaricunee seas seeseee 356 Lateral View of Brain...... SEGRE eGiaaiereeneteig aiadhae wa euaksare veee 358 Diagram of Sulci and Gyri........ aretaoiainiees avevavshaysroesss siassnayuideaiarennce sees 359 a sissaciessteee shepiaianasde . 361 Corpus Callosum...........05. Re ee Session » 363 Fornix, Hippocampus, and Corpus Striatum................. eee aeters + 364 Transverse Section of Brain........ Sra aia eMereeb tears eeateseientoneye ++ 366 se CC EE ES sememenete akakeouse celeb steraj shave auanauaneusieennataheraysreys 366 “ ir) MS a ceca cotenaes Si a AGO Ors Bw RG WreeMaraaTe vee 366 ee HE CREE EB a oe sas storavarslecng erase GiatesSieag aby tgstertdetors 367 ““ TH BE aca aicheaneeeia as ero Bloholan aside seees 367 Cranial Nerves...........-0000 ierarcnemcecrnnas aiaiccdbentectancdsponavoeins wees 374 Nerves Of Fac€icacedeccte env ee etsn ces Sit, oe o We RIG panes Rueiciess 376 Cranial Nerves in the Neck ...........-see00.- MCI wi aaitsess. 399 Sympathetic and Vagus in the Thorax...... eo ero 381 Nerves of the Neck......... Heitee enews tisaneeees winmeaneleerereetara ose 384 Brachial Plexus...... eats Vale eatees aidtezdicieratcinis aeons lista dara feaecossvolotagnsiete 387 Nerves and Vessels of Axilla...... seoisiaeretertiaiy cidlgraneeblend geucusivacgueratendnanaratee G80 Nerves and Vessels of Forearm,......0..e+005 eee eee eee eee e ones 391 Lumbar and Sacral Nerves...... snivaeaearevanaiieaev Salesian a ovesalisaausiafesonduavesere? GOO! Great Sciatic Nerve... 2.0... eee eeee hs pia avid Gilg its eels eda scovezigendyavepsiiene «nn GOL Sympathetic and Vagus in Abaoiten,.. aaachrate asehdaine spb odes ee Rosutharwrs wees 407 Nictitating Membrane............ cseiaceveeeawhelse ioreceaelie caver siesssevajare-aydve 410) Muscles of Eyeball........ tists oe eee SWiMen teem gIl Diagram of Eye...... Se aea SRS oIS means a Ree Tees ws ehtseceraeieereiet G13) Cartilage of External Ear.......... Leieiarenys wee eRe sarees GIT Muscles of External Ear.......ccceccesccccsscccccusccceescceceses G1Q Tympanic Membrane.......... sia Delos) ainialeiaiern Way creel esata Gils ois oseieseiee see 422 Malleus and Incus........ Dna Taie een ake ere wa wee See woes 423 Stapes...........0 cee is Shinya tes airoacbiahs, wie to svaseiievaveusRopeseielaiasa rarevnaee sae atenigivven G24 Membranous Labyrinth.......ccssecccccccssccceetcceceecenseseces G25 ANATOMY OF THE CAT. THE SKELETON OF THE CAT. THE skeleton of the cat consists of 230 to 247 bones ex- clusive of the sesamoid bones (44) and the chevron bones (8). These are divided as follows: head 35-40, vertebral column 52-53, ribs 26, sternum 1-8, pelvis 2-8, upper extremities 62, lower extremities 54-56. The number of bones varies with the age of the individual, being fewer in the old than in the young animal, owing to the fact that in an old animal some bones that were originally separate have united. I. THE VERTEBRAL COLUMN. COLUMNA VERTEBRALIS. The vertebral column, spinal column, or back-bone, consists of a varying number of separate bones, the vertebre. At its cranial end are seven vertebrz (cervical, Fig. 1, c) which are without ribs and support the head; caudad of these are thirteen rib- bearing vertebre (thoracic, Fig. 1, 7); caudad of these are seven that are again without ribs (lumbar, Fig. 1, 0); these are followed by three vertebre (sacral, Fig. 1, +) which are united into a single bone, the sacrum, which supports the pelvic arch. Following the sacral vertebre are twenty-two or twenty-three small ribless vertebra which support the tail (caudal, Fig. 1, ). Thoracic Vertebre. Vertebre thoracales (Fig. 4).—The thoracic vertebre are most typical, and the fourth one of these may therefore be first described (Figs. 2 and 3). It forms an oval ring which has numerous processes and surrounds an opening which is the vertebral foramen (a). The ventral one- THE SKELETON OF THE CAT. ‘wiqoyiaa pepnes ‘f tumioses tr Ssonurjryd ‘ez tsnsivzeyour ‘a tsnsaey 92 feiqn 7 fernqy ‘s teppayed %¢ tamuayz ‘J !sauog ayeururouur ‘Yt aeaqayiaa avquiny$ ‘o tsqia ‘ve feaqayiaa D19v410y} ‘2 isaBuryeyd 7 ‘sndivovjaut ‘y fsndivo ‘7 teupn & tsnipea cy tsnaaumy oF fumureys */ sendvos +7 saporavpo (p Saztqayea [eoTALed ‘9 tprody ‘g sypnys ‘2 ‘LVD AO NOLITINS—'I “DIY THE VERTEBRAL COLUMN. 3 third of this ring is much thickened and forms the centrum or body (corpus) (4) of the vertebra. The centrum is a semi- cylinder, the plane face of which bounds the vertebral canal, while the curved surface is concave longitudinally and is directed ventrad. The dorsal plane surface of the centrum is marked by a median longitudinal ridge on either side of which Fic. 2,—FourRTH THORACIC VERTE- Fic. 3.—FourRTH THORACIC VERTE- BRA, CRANIAL END. BRA, SIDE VIEW. a, vertebral foramen; 4, centrum; ¢, caudal, and d, cranial, costal demifacets; e, radix or pedicle; f lamina; g, transverse process; 4, cranial articular facet; 7, caudal articular facet; 7, caudal articular process; 4, spinous process. is an opening (nutrient foramen) for a blood-vessel. The ends are nearly plane, the caudal being slightly concave; they are harder and smoother than the other surfaces. They may be easily separated in a young specimen as thin plates of bone known as epiphyses. At the caudal end of the centrum, at its dorsolateral angle, is a smooth area on each side continuous with the surface of the epiphysis and bounded dorsolaterally by a sharp ridge of bone (c). It isa costal demifacet. In corresponding positions at the cranial end of the centrum are two demifacets not limited by bony ridges (@). When the centra of two contiguous thoracic vertebre are placed together in the natural position the cranial costal demifacets of one together with the caudal demi- facets of the other form two costal facets (Fig. 4, ¢), one on each side, and each receives the head of a rib. The dorsal two-thirds of the vertebral ring forms the verte- bral arch which is continued dorsally into the long, bluntly pointed spinous process (Figs. 2 and 3, #) for attachment of muscles. 4 THE SKELETON OF THE CAT. The vertebral arch (each half of which is sometimes called a neurapophysis) rises on each side from the cranial two-thirds of the dorsolateral angle of the centrum, as a thickened por- tion, the radix or pedicle (Figs. 2 and 3, ¢), which forms the ventral half of the lateral boundary of the vertebral canal. From the dorsal end of each radix a flat plate of bone, the lamina (/), extends caudomediad to join its fellow of the opposite side and form the vertebral arch. Owing to the fact that the radix rises from only the cranial two-thirds of the centrum there is left in the caudal border of the vertebral arch a notch bounded by the radix, the lamina, and the centrum. There is also a slight excavation of the cranial border of the radix. When the vertebre are articulated in the natural posi- tion, these notches form the intervertebral foramina (Fig. 4, ad), for the exit of the spinal nerves. At the junction of radix and lamina the arch is produced craniolaterad into a short process, the transverse process (¢), knobbed at the end. On the ventral face of its free end the transverse process bears a smooth facet, the transverse costal facet or tubercular facet (Fig. 4, ¢), for articulation with the tubercle of a rib. On the dorsal face ‘of each lamina at its cranial border is a smooth oval area, the cranial articular facet (superior articular facet of human anatomy) (Figs. 2 and 3, #). Its long axis is oblique and it looks dorsolaterad. The slight projections of the cranial edge of the laminz on which the facets are situated are the inconspicuous cranial articular processes (prezyga- pophyses). On the ventral surface of each lamina at the caudal border, near the middle line is a similar area, the caudal articular facet (inferior articular facet of human anatomy) (7); these occupy the ventral surfaces of two projections which form the caudal (inferior) articular processes (postzygapophyses) (/). These are separated by a median notch. When the vertebra are in their natural position the caudal articular facets lie dorsad of the cranial facets and fit against them. They thus strengthen the joint between contiguous vertebre, while permitting slight rotary motion. THE VERTEBRAL COLUMN. 5 Differential Characters of the Thoracic Vertebre (Fig. 4). —Following the thoracic vertebrz caudad there is to be seen a gradual increase in the size of the centra brought about by an increase in their craniocaudal and transverse measurements. ; 4, caudal articular pro- ¢, transverse costal facets; d, intervertebral Fic. 4,—THORACIC VERTEBR&, SIDE VIEW. : 6, cranial articular processes; ; f; accessory processes; g, mammillary processes S processes costal facets a, spinow foramina; e, cesses. The dorsoventral measurements remain nearly the same. The costal facets (Fig. 4, ¢) shift caudad so that on the eleventh, twelfth, and thirteenth thoracic vertebre each lies entirely on the cranial end of its centrum, while the caudal end 6 THE SKELETON OF THE CAT. of the centrum immediately preceding is not marked by any part of it. In the eleventh thoracic vertebra each costal facet is usually still confluent with the smooth cranial end of the centrum. In the twelfth vertebra the facets are separated by smooth ridges from the cranial end of the vertebra, while in the thirteenth vertebra they are separated by rough ridges. The spinous processes (a) of the first four are of about the same length. They then decrease in length to the twelfth, while the twelfth and thirteenth are slightly longer than the eleventh. The first ten slope more or less caudad, while the spinous process of the tenth (anticlinal) vertebra is vertical and those of the eleventh, twelfth, and thirteenth point craniad. Each of the transverse processes of the seventh thoracic vertebra shows a tendency to divide into three tubercles; one of these is directed craniad, the mammillary process (or meta- pophysis), one caudad, the accessory process (or anapophysis), while the third (transverse process proper) looks ventrad and bears the transverse costal facet. This division becomes more prominent in the succeeding vertebre, being most marked in the ninth and tenth. In the eleventh, twelfth, and thirteenth vertebre the mammillary (g) and accessory (/) processes are very. pronounced, while the transverse costal facet and that part of the transverse process which bears it have disappeared. The ribs of the eleventh, twelfth, and thirteenth vertebrze are thus attached to their respective centra by their heads alone. The cranial articular processes (0) are prominent on the first two thoracic vertebra; back of these they are very small as far as the eleventh, so that the articular facets seem to be borne merely upon the dorsal surface of the cranial edge of the laminz. In the eleventh, twelfth, and thirteenth the cranial articular processes are large, bearing the articular facets on their medial surfaces, while the mammillary processes appear as tubercles on the lateral surfaces of the articular processes. The caudal articular processes (/) are prominent in the first thoracic, then smaller until the tenth is reached; in the tenth, eleventh, twelfth, and thirteenth they are large and their facets are borne laterally, so as to face the corresponding cranial THE VERTEBRAL COLUMN. 7 facets. Thus from the tenth to the thirteenth thoracic vertebra rotary motion is very limited, owing to the interlocking of the articular processes. The Lumbar Vertebre. Vertebre lumbales (Fig. 5).— The last thoracic vertebre form the transition to the typical lumbar vertebra. These are larger than the thoracic vertebra. ¥ Fic. 5.—LuMBAR VERTEBRA. a, cranial articular processes; 4, mammillary processes; ¢, caudal articular processes; @, accessory processes; ¢, transverse processes; /, spinous processes. {“ The centra are of the form of the centra of the thoracic vertebrz, and increase in length to the sixth, but the seventh is about. the length of the first. They increase in breadth to the last.. 8 THE SKELETON OF THE CAT. The cranial articular processes (Fig. 5, @) are prominent and directed craniodorsad; they have the facets on their medial surfaces, while their dorsolateral surfaces bear the mammillary processes (4) as prominent tubercles. The caudal articular processes (c) are likewise large; their facets look laterad. When the vertebrz are articulated they are received between the medially directed cranial processes. The accessory processes (@) are well developed on the first vertebra, diminish in size to the fifth or sixth, and are absent on the seventh and sometimes on the sixth. The transverse processes (more properly pseudo-transverse processes) (¢) arise from the lateral surface of the centra; are flat and are directed ventrocraniolaterad. The first is small, and they increase in length and breadth from the first to the sixth, those of the last being slightly smaller than in the sixth. The free ends of the last four are curved craniad. The spinous processes (/) are flat and directed cranio- dorsad. They increase in length to the fifth and then decrease. The first five are knobbed at the end. In a dorsal view the spinous process and cranial articular processes of each vertebra are seen to interlock with the caudal articular processes and accessory processes of the preceding vertebra in such a way as to prevent rotary motion, and this arrangement may be traced craniad as far as the eleventh thoracic vertebra. Sacral Vertebre. Vertebre sacrales (Figs. 6 and 7).— The three sacral vertebree are united in the adult into a single bone, the os sacrum, or sacrum. Ina kitten the three verte- bre are separate, while in an animal almost mature the first two are united and the third is still separate. The sacrum lies between the last lumbar and the first caudal vertebrze and articulates laterally with the two innominate bones. It is pyramidal, with the base of the pyramid directed craniad, and is perforated by a depressed longitudinal canal, the sacral canal, which is a continuation of the vertebral canal, and by four large foramina dorsally and four ventrally. It may be described as having a cranial end or base and a caudal end or apex, a dorsal, a ventral, and two lateral surfaces. "The base is slightly oblique and presents a smooth trans- THE VERTEBRAL COLUMN. 9 versely oval articular facet (the cranial end of the centrum of the first sacral vertebra), for articulation with the centrum of the last lumbar vertebra. Dorsad of this is the sacral canal, more depressed than the vertebral arch craniad of it. It sup- ports a spinous process (Fig. 6, 2) which is directed dorsad. At the junction of its lamina and radix is seen the prominent Fic. 6.—Sacrum, Dorsa SuRFACE. Fic. 7.—SACRUM, VENTRAL SURFACE. Fig. 6.—1, 2, 3, the three sacral vertebrae. «, a’, spinous processes; 4, cranial articular process of first sacral vertebra; ¢, expanded transverse process of first sacral vetebra; d@, caudal articular processes of third sacral vertebra; e, transverse processes of third sacral vertebra; 7, tubercles formed by fused articular processes of the vertebrze; g, dorsal (or posterior) sacral foramina. Fig. 7.1, 2, 3, the three sacral vertebrae. a, the transverse ridges formed by the union of the centra; 4, cranial articular processes of first vertebra; c, transverse process of first vertebra; @, caudal articular processes of third vertebra; ¢, trans- verse processes of third sacral vertebra; 7, 7’, ventral (or anterior) sacral foramina; g, notch which helps to form third ventral sacral foramen. cranial articular process (4) with sometimes slight indications of a mammillary process on its lateral surface. Laterad of the articular facet is seen the cranial face of the expanded ‘‘ pseudo- transverse process’’ (c) of the first sacral vertebra. The ventral border of the base is concave ventrad, forming an arc of about 120 degrees. The apex shows the caudal end of the last sacral centrum. Dorsad of this are the vertebral arch with a very short spinous process (a@’), and the caudal articular processes (@:). Laterad of the centrum appears the laterally directed thin transverse process (¢). The ventral or pelvic surface (Fig. 7) is smooth, concave craniad, convex caudad, and crossed by two transverse ridges (a) along which are seen the ossified remains of the interverte- bral fibro-cartilages. At the ends of the first ridge is a pair of nearly circular ventral (or anterior) sacral foramina (/) for 10 THE SKELETON OF THE CAT. the passage of sacral nerves. At the end of the second ridge is a pair of ventral sacral foramina (/’), smaller than the first pair and continued laterocaudad into shallow grooves for the ventral rami of the sacral nerves. That portion of the bone lying laterad of a line joining the medial borders of these two pairs of foramina is known as the lateral mass of the sacrum and is composed of the fused transverse processes of the sacral vertebra. At the caudal margin of the ventral surface there is a notch between the lateral mass and the centrum (g). When the caudal vertebre are articulated, this notch helps to form a foramen for the third sacral nerve. The dorsal surface (Fig. 6) is narrower at its cranial end than is the ventral surface. Its cranial border bears laterally a pair of cranial articular processes (4) with their medially directed facets and between them it is concave, so that a large dorsal opening is left into the vertebral canal between the last lumbar vertebra and the sacrum. Caudad of the articular processes are two pairs of tubercles (/). These are the fused ° cranial and caudal articular processes of the sacral vertebra. Caudad of them are the caudal articular processes of the last sacral vertebra (d). Craniolaterad of the middle and cranial tubercles are dorsal (posterior) sacral foramina (g) for the transmission of the dorsal rami of the sacral nerves. Three spinous processes (a) appear between these rows of tubercles. They decrease in height caudad. That part of the surface in- cluded between the ‘spinous process and the tubercles is made up of the fused laminz of the sacral vertebra. That part between the tubercles and a line joining the lateral margins of the dorsal (posterior) sacral foramina is formed by the fused radices of the sacral vertebre. The lateral surface may be divided into two parts. Craniad is a large rough triangular area with equal sides and with one of its angles directed ventrocraniad. It is the lateral face of the pseudo-transverse process of the first sacral vertebra (Fig. 6, ¢). A smooth curved surface (the auricular facet) along its ventral edge articulates with the ilium, while the dorsal por- tion is rough for attachment of ligaments. Caudad is the narrow longitudinal triangular area of the lateral faces of THE VERTEBRAL COLUMN. 11 the fused transverse processes of the second and third sacral vertebre. Caudal Vertebre. Vertebre caudales (Fig. 1, y, and Figs. 8 and 9).—The caudal vertebre (21-23 in number) decrease gradually in size to the last one. Caudad they become longer and more slender and lose the character of verte- bre. They become finally re- duced to mere centra,—-slender rods of bone knobbed or enlarged i at their two ends (Fig. 8). The irs 781 ii last one is more pointed than the Fig. 8.—Caudal Vertebra, from near others and bears at its caudal end the caudal end of the tail. ‘ . Fig. 9.—Fourth Caudal Vertebra, a small separate conical piece, ventral view. a, transverse processes; the rudiment of an additional] % cranial articular processes; c, hamal processes; @, chevron bone. vertebra. The parts of a typical vertebra—vertebral arch, transverse processes, cranial and caudal articular processes—may be recognized in the vertebre as far back as the eighth or ninth. The transverse processes (Fig. 9, a) are directed caudad and decrease rapidly in length. They are very small on the ninth vertebra, but may be recognized for a considerable distance back of this. The spinous process disappears at about the fourth caudal vertebra, and the vertebral canal becomes gradually smaller caudad, until on the eighth or ninth vertebra it becomes merely a groove open dorsad. Caudad of the third vertebra for a considerable distance, each centrum bears on each lateral face at its cranial end a short anterior transverse process, and on its ventral face at its cranial end a pair of rounded tubercles, hamal processes (c), which articulate with a small pyramidal chevron bone (d@) so as to enclose a canal. These structures disappear caudad. Cervical Vertebre. Vertebre cervicales (Fig. 10).—The cervical vertebrze number seven. The first two of these are so peculiar as to require a separate description, so that the last five may be first considered. Passing craniad from the fourth thoracic vertebra to the third cervical there is a gradual transition. The centra of the 12 THE SKELETON OF THE CAT cervical vertebrze are broader and thinner than those of the thoracic vertebre, while the vertebral arches and vertebral canal are larger (Fig. 11). The caudal end of each centrum is concave and looks dorsocaudad when the centrum is held with its long axis horizontal. The cranial end of the centrum is convex and looks ventrocraniad when the centrum is hori- zontal. These peculiarities are more marked in the third vertebra than in the seventh. The spinous’ processes grow Fic. 10.—CERVICAL VERTEBRA, SIDE VIEW. a, spinous processes; 4, cranial articular processes; ¢, caudal articular facet; d, intervertebral foramina; ¢, transverse process proper; /, processus costarius: & wing of the atlas; 4, dorsal arch of the atlas; z, atlantal foramen. rapidly shorter as we pass craniad; the fifth, sixth, and seventh are directed dorsocraniad, the third and fourth dorsad. The caudal articular processes are situated at the junction of the radices and lamine; their facets (Fig. 10, ¢) look ventrocaudolaterad. The cranial articular processes also become more prominent than is the rule in the thoracic verte- bras; they are borne at the junction of radix and lamina and have their facets (Fig. 11, 4) directed dorsomediad. The cranial and caudal articular processes of each side are joined by a prominent ridge which is most pronounced in the third, fourth, and fifth vertebre. The characteristic feature of the cervical vertebre is their transverse process, so called. In each of them it arises by two roots, one from the centrum and one from the arch. THE VERTEBRAL COLUMN. 13 These two roots, which are broad and thin, converge and unite so as to enclose a canal or foramen, the foramen transver- sarium (Fig. 11, g), for the vertebral artery. Laterad of the foramen the two parts of the process are, in the third cervical, almost completely united, the dorsal part being, however, dis- tinguishable as a tubercle at the caudolateral angle of the thin plate formed by the process as a whole. This dorsal compo- nent is the transverse process proper (Figs. 10 and 11, e), while the ventral portion represents a rib, and is hence known as the processus costarius (7). The expanded plate formed by the union of these two processes is directed nearly ventrad and somewhat craniad in the third, fourth, and fifth vertebra. The two components of the process gradually separate as we Fic. 11.—S1IxTH CERVICAL VERTE- Fic. 12.—ATLAS, VENTRAL VIEW. BRA, CRANIAL END. Fig. 11.—a, spinous process; 4, cranial articular facet; c, lamina; d, radix or pedicle; e, transverse process proper; /, /’, processus costarius; g, foramen trans- versarium; 4, centrum; 2, vertebral canal. Fig. 12.—a, ventral arch; 4, tuberculum anterius; ¢, lateral masses; .d, trans- verse processes; ¢, cranial articular facets; 7, groove connecting the foramen trans- versarium with the atlantal foramen; g, atlantal foramen; 4%, caudal articular facets. pass caudad; in the fourth and fifth vertebre the part which represents the transverse process proper forms a very prominent tubercle at the caudolateral angle of the plate formed by the processus costarius. In the sixth (Fig. 11) the two parts are almost completely separated ; the dorsal part forms (¢) a slender knobbed process, while the processus costarius is divided into two portions (f and /’) by a broad lateral notch. In the seventh the ventral part (processus costarius) is usually quite lacking, though sometimes represented by a slender spicule of bone. In the former case the foramen transversarium is of course likewise lacking. 14 THE SKELETON OF THE CAT. The Atlas (Fig. 10, 1; Fig. 12).—The first cervical verte- bra or atlas has somewhat the form of a seal ring. The centrum is absent; it has united with the second vertebra to form the odontoid process or dens. Its place is taken in the atlas by a narrow flat arch of bone, narrower at the ends than in the middle, the ventral arch (Fig. 12, a) of the atlas. This connects the lateral, thicker portions of the ring ventrally and bears on its caudal margin a blunt tubercle (tuberculum anterius, Fig. 12, 4). Laterally the ring is thickened, forming thus the lateral masses (c) which are continued into the broad thin transverse processes (Fig. 10, g; Fig. 12, d@). Each lateral mass bears at its cranial end on its medial surface a concave, pear-shaped facet, cranial (or superior) articular facet, (Fig. 12, ¢) for articulation with the condyles of the skull. These facets look craniomediad. Dorsad of each is a foramen, the atlantal foramen (Fig. 10, 7; Fig. 12, g). which pierces the dorsal arch at its junction with the lateral mass. Caudal to the facet, on the medial face of each lateral mass, within the vertebral canal, is a tubercle. To the two tubercles are attached the transverse ligament (Fig. 14, 6) which holds in place the odontoid process (dens) of the axis. That part of the lateral mass which bears the articular facet projects craniad of the dorsal arch and is separated by a deep triangular notch from the transverse process. Along the bottom of this notch runs a groove (Fig. 12, 7), convex craniad, which connects the cranial end of the foramen trans- versarium and the atlantal foramen. The vertebral artery passes along it. The foramen transversarium is circular. It is bounded laterally by the lateral masses, and dorsally by the dorsal arch. The dorsal arch (Fig. 10, %) is two to three times as broad as the ventral, has a thick convex cranial border with a median notch, and a thin concave caudal border. The caudal articular facets (Fig. 12, #) are borne by the caudal ends of the lateral masses. They are slightly concave, triangular, and look caudomediad, so that their dorsal borders form with the caudal border of the dorsal arch nearly a semi- circle. The transverse processes are flat and directed laterad. THE VERTEBRAL COLUMN. 15 The attached margin of each is about two-thirds the length of the thinner free margin. The somewhat thicker caudal end of the transverse process projects further caudad than any other part of the vertebra and is separated by a slight notch from the caudal articular facet. From the bottom of this notch the foramen transversarium extends craniad and opens at the middle of the ventral face of the transverse process. Epistropheus or Axis (Fig. 10, 2; Fig. 13).—The second cervical vertebra (epistropheus or axis) is not so wide as the atlas but is much longer. Craniad the centrum is continued into a slender conical, toothlike projec- tion, the dens or odontoid process (Fig. 13, @) which represents the centrum of the atlas. The dens is smooth below for articulation with the ventral arch of the atlas. It is rougher above. Laterad of the dens the centrum bears a pair of large Fic. 13.—Axis or Epis- crania] articular facets (6) which look T#OFHEUS, Sipe View. craniolaterad. These have each the form seg: seo iger ah of a right-angled triangle with rounded co a Tete tnee angles, one side of the triangle being «, transverse process; /, nearly horizontal. Each is separated from ‘r#men transversarium, the articular face of the dens by a roughened groove. The spinous process (c) runs the length of the vertebral arch. It extends craniad of the vertebral arch nearly as far as the dens, as a flat rounded projection. Caudad of the vertebral arch it projects for a short distance as a stout triangular spine. The caudal articular facets (2) are borne on thickenings of the caudolateral portions of the arch; they face almost directly ventrad. The transverse process (¢) is slender and triangular and directed nearly caudad. Its apex reaches no farther than the caudal or articular face of the centrum. Its base is traversed by the foramen transversarium (/). Differential Characters of the Cervical Vertebre.—It is possible to identify each of the cervical vertebra: The first by the absence of the centrum. The second by the dens or odontoid process. The third by the small spinous process and slightly marked 16 THE SKELETON OF THE CAT. tubercle of the transverse process, and by a median tubercle on the cranial border of the vertebral arch. The fourth by the spinous process directed dorsad, and the short thick tubercle of the transverse process not trifid. The fifth by the spinous process directed craniad, and the more slender spine-like tubercle of the transverse process not trifid. The sixth by the trifid transverse process. The seventh by the long spinous process and the slender -simple transverse process, and by the usual absence of the foramen transversarium. LIGAMENTS OF THE VERTEBRAL COLUMN. Fibro-cartilagines intervertebrales.—The separate verte- bre (except the atlas and axis) are united by the disk-shaped intervertebral fibro-cartilages, which are situated between the centra of the vertebree. Each consists of a central pulpy por- tion and a fibrous outer portion, covered by strong intercross- ing tendinous fibers which unite with the periosteum of the vertebre. Ligamentum longitudinale anterius.—On the ventral face of the centra of the vertebrae, from the atlas to the sacrum, lies a longitudinal ligament, the anterior longitudinal ligament. It is very small, almost rudimentary, in the cervi- cal region: large and strong in the thoracic and lumbar regions. Ligamentum longitudinale posterius (Fig. 14, a).—A corresponding ligament (posterior longitudinal ligament) lies on the dorsal surface of the centra (therefore within the verte- bral canal). It is enlarged between each pair of vertebrz and closely united to the intervertebral fibro-cartilages. Ligamentum supraspinale.— Between the tips of the spinous processes of the thoracic and lumbar vertebrz extend ligamentous fibers. They are not united to form a distinct band, and can hardly be distinguished from the numerous tendinous fibers of the supraspinous muscles. Together they represent the supraspinous ligament. From the tip of the spinous process of the first thoracic vertebra to the caudal end of the spine of the axis extends a slender strand representing THE VERTEBRAL COLUMN. 17 the ligamentum nuche or cervical supraspinous ligament.. It is imbedded in the superficial muscles of this region, some of which take origin from it. Ligamentous fibers are also present’ between the spinous processes of the vertebre (ligamenta interspinalia): between the transverse processes (ligamenta intertransversaria), and between the vertebral arches (ligamenta flava). Capsule articulares.—The joints between the articular processes are furnished with articular capsules attached about the edges of the articular surfaces. These are larger and looser in the cervical region. Atlanto-occipital Articulation.—The joint between the atlas and the occipital condyles has a single articular capsule, which is attached about the borders of the articular surfaces of the two bones. This capsule is of course widest laterally, forming indeed two partially separated sacs, which are, how- ever, continuous by a narrow portion across the ventral middle line. This capsule communicates with that which covers the articular surface of the dens, and through this with the capsule between the atlas andaxis. That portion of the capsule which covers the space between the ventral arch of the atlas and the occipital bone represents the anterior atlanto-occipital mem- brane ; it is strengthened by a slender median ligamentous strand. The posterior atlanto-occipital membrane covers in the same way the space between the dorsal arch of the atlas and the dorsal edge of the foramen magnum. In it a number of different sets of fibers, with regard to direction and to degree of development, may be distinguished; these have sometimes been considered separate ligaments. The lateral ligaments of the atlas begin at the lateral angle of the cranial margin of the atlas, at about the junction of its dorsal and ventral arches, and pass cranioventrad to the jugular processes. Articulation between the Axis and Atlas.—The articular capsule is large and loose, being attached to dorsal and ventral borders of the atlas, about the articular surfaces of the axis, and to the cranial projection of the spine of the atlas. It also passes craniad along the ventral side of the dens and communi- 18 THE SKELETON OF THE CAT. cates here with the capsule of the atlanto-occipital articulation. In the dorsal part of the capsule a short strong ligamentous strand is developed, connecting the caudal border of the dorsal , arch of the atlas with the tip of the ‘“2)\ cranial projection of the spinous process t of the axis. The dens or odontoid process is held in place by the transverse liga- ment (Fig. 14, 4) of the atlas, which passes across the process as it lies with- in the vertebral canal of the atlas. The transverse ligament is attached at its Fic. 14.—LIGAMENTS OF THE ODONTOID PROCESS or DENs. two ends to the medial surface of the First three cervical ver- .; i tebrseand bassof theskull, sides of the atlas at about the region with dorsal surface re- where the dorsal and ventral arches of moved. a, ligamentum : longitudinale posterius; 4, the atlas unite. transverse ligament of the From the cranial end of the odontoid atlas; ¢, ligamenta alaria; li i h d, odontoid process; ¢, oc. Process the two ligamenta alaria (Fig. cipital condyles; 1, 2, 3, 14, c) diverge craniolaterad to the rou the first three cervical ver- 4, ¢) ; 8 rough tebrz; 4, basal portion of ventromedial angle of the condyles of sheinrerpial bone: the occipital bone. II. RIBS. COSTA. (Figs. 1 and 15.) The cat has thirteen pairs of ribs. One of the fifth pair (Fig. 15) may be taken as typical. It is a curved flattened rod of bone attached at its dorsal end to the vertebral column, and at its ventral end to a cartilage (costal cartilage, Fig. 15, f) which serves to unite it to the sternum. The most convex portion of the bone is known as the angle (e). Each rib presents a convex lateral and a con- cave medial surface, a cranial and a caudal border. The borders are broad dorsad and narrow ventrad, while the sur- faces are narrow dorsad and broad ventrad. The rib has thus the appearance of having been twisted. The rib ends dorsad in a globular head or capitulum (a), by which it articulates with the costal demifacets of two con- tiguous thoracic vertebra. Between the capitulum and angle RIBS. 19 on the lateral surface is an elevated area, the tubercle, marked by the smooth tubercular facet (c) for articulation with the transverse process of a_ vertebra. The constricted portion between the head and tubercle is known as the neck (collum) (7). The angle is marked by a projecting process (¢) (angular process) on its lateral bor- der, for attachment of a ligament. The ribs increase in length to the ninth (the ninth and tenth are of the same length) and then de- crease to the last. They decrease iil | in breadth behind the fifth. The |i first is nearly in a dorsoventral Ui plane, while the others have their | dorsal ends inclined slightly craniad. The tubercles become less promi- nent as we pass caudad and are absent on the last two or three ribs, which do not articulate with the transverse process. Sing, CRANIAL VIEW. The first nine ribs (true ribs or 4, head; 4, tubercle; «, tuber- cular facet; d, neck; ¢, angle, coste vere) are attached separately with angular process; f, carti- to the sternum by their costal carti- lage. lages. The last four (false ribs or coste spuriz) are not attached separately to the sternum. The costal cartilages of the tenth, eleventh, and twelfth are united to one another at their sternal ends. They may be united also to the ninth costal cartilage or to the sternum by a common cartilage of insertion, or they may be quite free from the sternum. The thirteenth costal cartilages are free (floating ribs). Ligaments of the Ribs.—The articular surfaces between the head of the rib and the centra, and between the tubercle and the transverse process of the vertebra, have each an articular capsule. There are also a number of small liga- mentous bands from the tuberosity and the neck of the rib to the transverse process of the vertebra. 20 Fic. 16.—Srer- NUM, VENTRAL VIEW. a, manubrium; 4, the separate pieces forming the body; ¢, bony part of the xi- phoid process (the expanded cartilaginous por- tion not being shown); d, facet for attachment of first rib. THE SKELETON OF THE CAT. Ill. STERNUM. (Fig. 16.) The sternum consists of three portions, a cranial piece or manubrium (a), a caudal piece or xiphoid process (c), and a middle portion or body (corpus), which is divided into a number of segments (4). To the sternum are united the ventral ends of the first nine ribs. It thus forms the median. ventral boundary of the thorax. Since the thorax decreases in dorsoventral measurement craniad, the long axis of the sternum is inclined from its caudal end dorsocraniad, and if con- tinued would strike the vertebral column in the region of the first cervical vertebra. The manubrium (a) makes up about one-fifth the whole length of the sternum and projects craniad of the first rib. It has the form of a dagger and presents a dorsal surface and two lateral surfaces, the latter uniting ventrad to form asharpangle. In the middle of the lateral surface near the dorsal margin is an oval articu- lar surface (7) borne on a triangular projection. It looks caudodorsad and is for the first costal cartilage. The caudal end articulates with the body by a synchondrosis and presents a slightly marked oval facet on each side for the second costal cartilage. The body consists of six cylindrical pieces (4) enlarged at their ends and movably united by synchondroses. They increase in breadth from the first, and decrease slightly in length and thickness. At the caudal end of each near its ventral border there is a pair of facets looking caudolaterad. They are for the costal carti- lages. The xiphoid process (c) is a broad thin plate of cartilage at its caudal end; bony and cylin- THE SKULL, 21 drical at its cranial end. It is attached by its base to the last segment of the body by a considerable cartilaginous in- terval, while the opposite end is free and directed caudo- ventrad. i The cartilage of the ninth rib is attached to the lateral face of the cartilage between the xiphoid and the body, and just caudad of this the common cartilage of insertion of the: tenth, eleventh, and twelfth costal cartilages is attached, if present. IV. THE SKULL. The bones of the head consist of the skull proper together with a number of separate bones forming part of the visceral skeleton; these are the lower jaw, the hyoid, and the ear- bones. The skull proper is considered as divided into cranial and facial portions. The former includes all the bones which take part in bounding the cranial cavity or cavity of the brain; the latter includes the bones which support the face. The cranial portion of the skull includes all that part enclosing the large cavity which contains the brain. For con- venience this portion may be considered as made up of three segments, each of which forms a ring surrounding a part of the cranial cavity. The first or caudal segment or ring consists of the occipital bone (with the interparietal) surrounding the foramen magnum. The second segment consists of the sphenoid ventrad, the parietals laterad and dorsad. Between the first and second segments are intercalated laterally the temporal bones containing the auditory organ. The third segment or ring consists of the presphenoid ventrad, of the frontals laterad and dorsad. The cranial opening of this ring is closed by the lamina cribrosa of the ethmoid. The cranial portion of the skull therefore contains eleven separate bones: one occipital, one interparietal, two temporals, one sphenoid, two parietals, one presphenoid, two frontals, and one ethmoid. The facial portion of the skull is much smaller than the 22 THE SKELETON OF THE CAT. cranial, and lies craniad of the latter; it encloses the nasal cavity. It contains the following thirteen bones: two pala- tines, one vomer, two maxillaries, two lachrymals, two pre- maxillaries, two nasals, two malar or zygomatic bones. The two halves of the mandible or lower jaw are frequently included in the facial portion of the skull, making in all fifteen separate bones in this part of the skull. In the following the bones of the skull are first described separately, then an account is given of the skull as a whole. Occipital Bone. Os occipitale (Figs. 17 and 18).—The occipital bone forms the most caudal portion of the cranium, entering into the formation of its caudal wall and of its base. It connects the cranium with the vertebral column and surrounds a large opening, the foramen magnum (@), by means of which the cranial cavity communicates with the vertebral canal. Ke a Fic, 17.—OccirPITAL Bong, CAUDAL Fic. 18.—OccrpiraL Bong, INNER OR OUTER SURFACE. SURFACE. a, basilar portion; 4, lateral portions; ¢c, squamous portion; ¢, foramen mag- num; ¢, occipital condyles; /, jugular processes; g, jugular notch; 4, lambdoidal ridge; z, external occipital crest; 7, external occipital protuberance. In young kittens four portions may be distinguished in this bone. These are, a basal portion (the basioccipital bone), two lateral portions (the exoccipital bones), and a dorsal por- tion (the supraoccipital bone). These four bones remain separate through life in many lower vertebrates. In the adult cat they are completely united into a single bone, but it is convenient to describe this bone as made up of four parts: a basal portion (a) (pars basilare), corresponding to the basi- occipital, two lateral portions (4) (partes laterales), corre- sponding to the exoccipitals, and a squamous portion (¢) squama occipitalis) corresponding to the supraoccipital. THE SKULL, 23 The basilar portion (a2) as seen from the dorsal or ventral surface is oblong and flattened. It is broadest at the junction of its middle and last thirds, and tapers toward both ends. It presents a cranial end and a caudal end, a dorsal, a ventral, and two lateral surfaces. Its caudal end, which helps to form the ventral boundary of the foramen magnum, is concave from side to side. The cranial end is transversely elongate, about five times as broad as high, pointed laterally and roughened for attachment to the caudal end of the body of the sphenoid, which has a corresponding form. The joint is a synchondrosis. The dorsal surface is concave from side to side, forming a longitudinal groove in which rest the pons and medulla. The concavity is more pronounced caudad, where the bone is thinner at its middle. The ventral surface is marked by three parallel longitudinal ridges. One of them is median and expands caudad into a smooth triangular elevated area which extends to the foramen magnum. The other two ridges run near the lateral edges of the bone. Between them and the median ridge the surface is smooth and is depressed caudad. Laterad of each lateral ridge is a rough triangular surface overlaid in the natural state by the medial edge of the tympanic bulla. The lateral surfaces are smooth and sharp and abut against the petrous portion of the temporal bone. They pass into the lateral portions of the occipital caudad. The lateral portions (4) of the occipital arise from the caudal margin of the basilar portion in the transverse plane; a short distance laterad of the line of junction they turn dorsad at an angle of nearly ninety degrees. They form the lateral boundaries of the foramen magnum and pass dorsally into the squamous portion. The external surface of each presents an elongated elevated spirally curved surface, the occipital condyle (¢), for articula- tion with the atlas. A small part of each condyle is formed from the basal portion. The two condyles are separated from one another ventrally by a narrow notch, and each extends (laterad) along the border of the foramen magnum to a point slightly dorsad of the transverse diameter of the latter. 24 THE SKELETON OF THE CAT. Laterad of each condyle the bone is elevated into a blunt triangular projection, the jugular process (7), which covers the caudal end of the tympanic bulla. Between the jugular process and the condyle is a deep depression. : The internal surface (Fig. 18) is concave dorsoventrally, following the outline of the foramen magnum. It is convex from side to side. It is smooth except at its outer margin, which is rough for articulation with the mastoid portion of the temporal bone. The cranial face of the jugular process (/) shows a rough concavity for the reception of the bulla tympani. Mediad of the jugular process is a notch (jugular notch) (¢) which when the bones are articulated forms part of the bound- ary of the jugular foramen. Mediad of this notch is a foramen which forms one end of the hypoglossal canal. It passes dorso- caudad into the cranial cavity and transmits the hypoglossal nerve. Dorsad of the hypoglossal canal is the cranial opening of the condyloid canal, which passes caudad and opens just craniad of the dorsal end of the condyle. It transmits a vein. The outer border of this portion is rough for articulation with the petrous and mastoid portions of the temporal. The squamous portion (c) has the form of a sector of a circle whose arc is a little more than ninety degrees. The central angle of the sector is truncated and bounds the foramen magnum dorsally. The arc of the sector forms the dorsal margin of the bone, while along the radii it passes into the lateral portions. Its dorsal portion is thick and porous; its ventral portion near the foramen magnum is thin and compact. The external surface (Fig. 17) is marked by a prominent ridge, the lambdoidal ridge (4), parallel with the dorsal border and near to it. The narrow portion of the outer surface that lies dorsad of the ridge forms an angle of about ninety degrees with the ‘remainder’ of the surface. A median crest (2) extends ventrad from the middle of the lambdoidal ridge toward the foramen magnum; this~ is the external occipital crest. At its junction with the lambdoidal ridge it is elevated into a tubercle, the external occipital protuberance (7). THE SKULL. 25 The inner surface (Fig. 18) presents depressions for the convolutions of the cerebellum. The dorsal border is thick and rough for articulation with the parietals and interparietal. The ventral border abuts on the foramen magnum and is thin and smooth. Interparietal Bone. Os interparietale (Fig. 19).—This is a small triangular bone lying between the parietals, with its apex directed craniad, and its base in contact with the squamous portion of the occipital. Its dorsal surface is arrow-shaped and has its posterior border notched. It is marked by a median crest (part of the sagittal crest) which is continued craniad from the middle of the lambdoidal crest. The ventral surface is irregularly triangular, smooth, and concave. The three borders are rough for articulation with the parietals and occipital. 2 é Fic. 19. —INTERPARIETAL FIG. 20.-- SPHENOID Bong, DorsaL oR Bone, OUTER SURFACE. INTERNAL SURFACE. Fig. 19, showing the sagittal crest rane craniocaudad across its middle. Fig. 20.—a, body; 4, wings; ¢, pterygoid process; d@, tuberculum sellz; e, dor- sum sellz; 7, sella turcica; g, notch which aids in forming the foramen lacerum; A, longitudinal groove of alisphenoid; 7, notch which aids in forming the orbital fissure; 7, foramen rotundum; 4, foramen ovale. Sphenoid Bone. Os sphenoidale (Fig. 20).—The sphe- noid bone of man is represented in the cat by two entirely distinct bones,——one cranial, the other caudal. The cranial portion may be designated as the presphenoid (Fig. 21); the caudal part will be described as the sphenoid (proper) (Fig. 20). an sphenoid bone in the kitten is in three parts: a central, portion, the basisphenoid, and two lateral portions, the ali- sphenoids. In many lower vertebrates these three bones are permanently distinct, but in the adult cat they are united to form the sphenoid bone. To these there is added a fourth element, separate in many vertebrates as the pterygoid bone. 26 THE SKELETON OF THE CAT. The sphenoid may thus be described as composed of a central portion, the body (a) (basisphenoid), and of two thin expanded wings (4) (alisphenoids, ala magne of the human sphenoid); each of which has arising from it a thin curved process, the pterygoid process (c), directed craniad and largely made up of the pterygoid bone. The body of the sphenoid (a) lies in the middle line of the base of the skull. It is wedge-shaped, with the converging sides of the wedge directed laterad and its apex pointed craniad. ‘ It has six surfaces, of which the dorsal and a part of the laterals look into the cranial cavity. The cranial end articu- lates with the body of the presphenoid, and the caudal with the body of the occipital. The dorsal surface is triangular, with one apex of the tri- angle truncated, elevated, and directed craniad. This eleva- tion is the tuberculum selle (7). Just caudad of the middle the surface presents a rectangular elevation with rounded angles, the dorsum sell (¢). The cranial end of the dorsum sella presents at each dorsolateral angle a very small smooth tubercle which represents one of the posterior clinoid processes of man. Between this elevation and the elevated cranial end of this surface there is a deep excavation, the sella turcica (/), in which in the natural state is lodged the hypophysis. Near the cranial end of the sella is a small foramen, probably nutrient. At the caudal end of the body a slight notch (jg) separates it from the wing: this notch forms a part of the foramen lacerum. Against this notch fits the apex of the petrous bone, and from it a groove (carotid groove) is con- tinued mediocraniad to the sella turcica. The ventral surface (Fig. 41, 3) is triangular, smooth, and nearly flat; it is marked by a median ridge which is the con- tinuation craniad of the ridge on the ventral face of the basilar portion of the occipital. | Its caudal angles are separated from the rest of the bone by sharp triangular elevations, laterad of which are rough triangular areas, overlaid when the bones are articulated by a triangular spine “ the tympanic bulla. THE SKULL. 27 Its lateral surfaces are mostly covered by the wings. They appear at the sides of the elevated cranial end of the dorsal surface as triangular areas. The caudal end is concave, rough, and has the form of the cranial end of the basilar part of the occipital. The cranial end is nearly square and rough for articulation with the body of the presphenoid. The Wing (alisphenoid ; ala magna of the human sphenoid) (Fig. 20, 6).—This is a thin quadrilateral plate of bone attached by its medial border to nearly the whole of the lateral surface of the body. Its middle portion lies nearly in the same plane as the body, but its ends are curved dorsad so that its internal surface is concave and its external surface is convex. The curvature is most pronounced near the long lateral border, so that this border forms nearly a semicircle. The internal surface supports the occipital lobe of the cere- brum. It is marked by a rounded groove (/) which is parallel with the lateral surface of the body. The dorsal margin of the groove projects mediad in the form of a sharp ridge which is broadest caudad, where it often reaches nearly to the posterior clinoid process. The groove passes craniad into three fora- mina. The first (cranial) of these, the orbital fissure (2), is large and lies between the wing, the body, and the pterygoid process. It is incomplete, but is completed by the presphenoid. The second foramen is small and rounded; it is the foramen rotundum (7). The third, foramen ovale (4), is larger and oval and penetrates the wing through about the middle of its longitudinal axis. Another minute foramen penetrates the sphenoid between the wing and the body of the bone, just laterad of the tuberculum sella. This foramen is continuous craniad with a groove on the dorsal surface of the pterygoid process; the groove and foramen constitute the pterygoid canal. It transmits a nerve. The external surface shows the orbital fissure, the foramen rotundum and the foramen ovale, bounded ventrally by a sharp ridge, which is continued onto the pterygoid process. Between this ridge and the body the surface is longitudinally erenees for the tuba auditiva or Eustachian tube. 28 THE SKELETON OF THE CAT. The semicircular margin of the bone articulates with the squamous portion of the temporal. At the junction of its caudal and middle third there is sometimes a toothlike projec- tion which underlies the root of the zygoma. The whole of the cranial margin, except the lateral end, articulates with the wing of the presphenoid. At this end the angle formed by the junction of lateral and cranial borders is produced into a flat process, which passes dorsocaudad between the squamous portion of the temporal and the frontal, and articulates by the roughened internal surface of its free end with a similar process from the parietal. The caudal margin laterad of the groove is bevelled and roughened at the expense of the dorsal surface and is overlaid by the ventral end of the tentorium. Mediad of the groove it projects caudad as a slender point, the lingula of the sphenoid. This is received into a narrow cleft between the apex of the petrous bone and the bulla tympani. The pterygoid process (¢) is a nearly square, thin plate of bone. The medial surface is smooth and concave, the lateral face is convex and marked by two parallel ridges. The medial one of these is continued craniad from the bony septum which separates the orbital fissure from the foramen rotundum, and the lateral one from the septum which separates the foramen rotundum from the foramen ovale. A sharp triangular spine projects laterad from near the caudal end of the lateral ridge. The two ridges and that part of the lateral surface of the bone included between them form a part of the sphenoid bone known as the pterygoid process of the sphenoid bone, in those cases where the pterygoid is a separate bone. The remainder of the process is equivalent to the pterygoid bone of other vertebrates. Between the caudal margin of this bone and the lateral of the two ridges, i.e., between the pterygoid bone and the pterygoid process of the sphenoid, is a long deep fossa, the internal pterygoid fossa (Fig. 40, s). . The laterocaudal margin of the pterygoid process projects caudad, as a curved triangular spine, the hamulus or hamular process (Fig. 40, 7; Fig. 43, 2 THE SKULL. 29 The Presphenoid Bone. Os presphenoidale (Fig. 21).— In a young cat this bone is in three pieces, a basal portion (presphenoid) and two wings (orbitosphenoid bones). These bones remain distinct throughout life in many lower vertebrates, but in the adult cat they fuse to form a single bone. We may nevertheless 4, conveniently describe this bone as made up of “& ae4 a body (a) (the basisphenoid), and two wings Fic. 21, —PRE- (0), the orbitosphenoids (the ala parve of the fuimolp sacle human sphenoid). a, body; 5, wings; The body (a) lies in the base of the skull in % optic foramina. the median line, craniad of the basisphenoid. It has the form of a rectangular prism about twice as long as broad. It is hollow, and the cavity is divided by a median longitudinal par- tition into two cavities (sphenoidal sinuses, Fig. 43, 7). The sphenoidal sinuses are continued craniad into'the cavities of the ethmoid. The body has six surfaces: The dorsal or internal surface (Fig. 42, 2) looks into the cranial cavity and is continuous with the dorsal surface of: the wings. The caudal end of the body is depressed, and when united to the basisphenoid aids in forming the cranial wall of the sella turcica. At each caudolateral angle is a short spine, the anterior clinoid process. At about one-third the length of the bone’ from the caudal end is a transverse groove (chias- matic groove, Fig. 42, m) for the optic chiasma. Its ends lead into two round foramina (the optic foramina, Fig. 42, /; Fig. 21, ¢) whith pass craniolaterad between the body and the wings of the presphenoid and transmit the optic nerve and the ophthalmic artery. The ventral surface (Fig. 21) is hour-glass-shaped and marked by a smooth median ridge, continuous with the ridge on the basisphenoid and overlaid at its cranial end by the vomer. The caudal end presents a rough triangular area on each side, for articulation with the pterygoid process of the sphenoid bone, while the cranial end has ‘similar areas overlaid by the nasal portion of the palatine bones. The lateral surface looks towards the orbitotemporal fossa. It is notched near the caudal end by the ventral border of the 30 THE SKELETON OF THE CAT. optic foramen (c). Caudad of this foramen the surface presents an oblique groove which forms in the natural condition the medial boundary of the orbital fissure. Craniad of the optic foramen the surface is smooth and marked near its ventral border by a longitudinal ridge which forms part of the dorsal boundary of a fossa, the external ptery- goid fossa (Fig. 40, f). The caudal end presents ventrally a quadrangular rough . surface for articulation with the body of the sphenoid. The cranial end presents the two apheanical = sinuses separated by a median partition. The median partition articulates by its free border with the lamina perpendicularis of the ethmoid. At its ventral end is the abruptly truncate end of the median ridge of the ventral surface, which is continuous with the ventral cartilaginous por- tion of the lamina perpendicularis. The lateral walls of the sphenoidal sinuses are continued craniad of the dorsal and ven- tral walls and of the median partition, and articulate ventrally with the nasal portion of the palatine bones, and dorsally with the orbital plate of the frontal. Between them is received the caudal ends of the labyrinths of the ethmoid in the middle, while between their dorsal edges is received the caudal end of the cribriform plate, and between their ventral edges the expanded end of the vomer. The wings (6) arise each from nearly the whale of the dorsolateral angle of the body. They form prominent nearly horizontal triangular projections over the optic foramina. The dorsal and ventral surfaces are smooth and continuous respectively with the dorsal and lateral surfaces of the body. The dorsal surface looks into the cranial cavity, while the ven- tral looks into the orbitotemporal fossa. Craniad of the apex of the wing its border articulates with the ventral edge of the orbital portion of the frontal bone. Caudad of the apex the border articulates with the cranial border of the wing of the sphenoid. Temporal Bone. Os temporale (Figs. 22 and 23).—This forms a part of the lateral wall of the cranium, filling the gap between the occipital and the sphenoidal segments. It is made THE SKULL, 3r up of three portions which are distinct in kittens but somewhat firmly united in adult cats. In lower vertebrates these portions are distinct bones called the Squamous, the Petrous, and the Tympanic bones. In the cat-they may be described as the squamous (a), petrous (4), and tympanic (c) portions of the temporal bone. Fic. 22,-TEMPORAL BONE, EXTERNAL Fic. 23.—TEMPORAL BonE, INTERNAL SURFACE. SURFACE. a, squamous portion; 4, petrous portion; ¢, ¢, tympanic portion (c, entotym- panic; ¢’, ectotympanic); d@, zygomatic process; e, mastoid portion of the petrous; Jj, mandibular fossa; g, postmandibular process; #, tuberculum articulare; 7, ex- ternal auditory meatus; 7, stylomastoid foramen; %, pit for tympanohyal bone; 2, mastoid process; #, grooves bounding the jugular foramen; , internal auditory meatus; v, appendicular fossa; Z, hiatus facialis; g, styliform process of tympanic bulla. The squamous portion (2) (squama temporalis) is thin and oval or has the form of an equilateral triangle with rounded angles, with a curved process, the zygomatic process (2), arising from its ventral border. Its outer surface (Fig. 22) is convex and smooth and gives origin to part of the temporal muscle. Its inner surface (Fig. 23) is concave and smooth except near the margins, where it is bevelledand rough. The roughened border is broader dorsad and caudad. The ventral margin of the bone is turned mediad at its cranial end so that the lateral face of the inverted portion looks ventrad. By this portion of its lateral face the squamous rests upon the tympanic bulla, and its edge articulates with the tentorium and the wing of the sphenoid. The remaining (caudal) portion of the ventral border overlies the mastoid portion (¢) of the petrous. By the remainder of its border the bone articulates with the parietal dorsad and with the wing of the sphenoid craniad. The 32 THE SKELETON OF THE CAT. roughened portion of its inner surface overlies the margins of both these bones. The zygomatic process (d) is formed by the confluence of two roots. One of these starts from the ventral end of the. lambdoidal ridge and passes along the ventral margin of the squama dorsad of the external auditory meatus. The other arises abruptly from the cranioventral angle of the bone. The process thus formed is at first broad and passes horizontally laterad and slightly craniad. It soon grows more slender and turns gradually craniad, while at the same time it twists so that the surface which is dorsal at the base becomes medial at the tip; the posterior root which is continuous with the caudal border at the base is continuous with the dorsal border at the apex. On the ventral surface of the base is a transversely elongated concave articular surface, the mandibular fossa (f), for the condyloid process of the lower jaw. Caudad of this is a sharp transverse ridge, the postmandibular or postglenoid process (g), and craniad of the lateral end of the fossa a slight tubercle, the tuberculum articulare (Z). Near its apex the zygomatic process is more slender and its ventral border is bevelled for articulation with the malar or zygomatic bone. The tympanic (Figs. 22 and 23, c; Fig. 24) is expanded into a large hollow olive-shaped ‘bone which is known as the auditory bulla and encloses the tympanic cavity. Its sub- stance is very compact. Unlike the tympanic of most other mammals it is developed from two bones, known as the ecto- tympanic (Fig. 22, c’) and entotympanic (c). These are strongly marked in young kittens, and can usually be easily distinguished in adult cats. The entotympanic (Figs. 22 and 23, ¢) forms the larger part of the bulla, constituting its ventral and medial surfaces; it is thin, smooth, and transparent. The ectotympanic (Fig. 22, c’) surrounds the external auditory meatus: it is thicker and more opaque than the entotympanic. The bulla lies ventrad of the squamous, and in an external view conceals a large part of the petrous. On its lateral surface it presents near the dorsal border an irregular oval opening, that of the external auditory meatus (Fig. 22, 2), which leads into the tympanic cavity. Caudad of THE SKULL. 33 the external auditory meatus is a nearly dorsoventral groove, which, when the bone is articulated, forms a part of the boundary of the stylomastoid foramen (Fig. 22, 7); just ventrad of this groove is a pit (£) which lodges the tip of the tympanohyal bone. : Craniad the bone is produced into a short spine, the styli- form process (¢), which lies in a horizontal groove in the ventral surface of the basisphenoid. Laterad of this spine is a groove for the tuba auditiva or Eustachian tube. The medial surface (Fig. 24) presents in the middle near its ventral margin a short triangular spine which lies in the natural state against the ventral surface of the basilar portion of the occipital. Caudad of this spine the surface is marked by two or three vertical parallel grooves (Fig. 23, mm). They indicate the portion of the bone which bounds the jugu- |, ca : : . IG, 24. — TYMPANIC lar foramen, and are possibly impressions of Butta, IsoLaTeD, the ninth, tenth, and eleventh nerves. MEDIAL SURFACE. — f ‘ a, inner end of audi- The dorsal two-thirds of the medial tory meatus; 4, partition surface is lacking in the disarticulated bulla dividing tympanic cav- : _ ity; ¢, styliform process, (Fig. 24), so that the cavity of the bone is exposed. This opening is in the natural state closed by the petrous bone. The caudal end is rough where it is overlaid by the jugular process. On the inner surface of the tympanic bulla is seen the thick- ened margin of the inner end of the auditory meatus (Fig. 24, a). To it is attached the membrana tympana. In the median dorsal line this margin is notched for the reception of the incus and head of the malleus. From the lateral wall of the cavity at the line of junction of the ectotympanic and ento- tympanic a thin bony partition (4) rises. It runs almost directly mediad; is concave dorsally and divides the tympanic cavity into two chambers. The Petrous Portion (Fig. 23, 4, and Fig. 25).—This con- sists of two parts, a very dense part (the petrous portion proper, Fig. 25), which has the form of a triangular pyramid and encloses the auditory labyrinth, and a less dense part, the 34 THE SKELETON OF THE CAT. mastoid portion (Figs. 22 and 23, e), which is flattened and triangular and is attached by its base to the base of the pyramid. The petrous portion may be described as having a base and three sides, lateral, dorsal, and medial. It completes the medial wall of the tympanic bulla, so that it is not possible to see it from the exterior of a skull except through the auditory meatus (Fig. 22, 7). When the bones of the skull are articulated its dor- sal surface is covered by the tentorium and alisphenoid. Its lateral face looks Fic. 25.—Petrous Bonz or into the tympanic cavity, while the RIGHT SIDE, LATERAL medial face looks into the cranial cavity. SURFACE, ENLARGED. : “ a, fenestra cochleze; 4, pro- Its lateral face (Fig. 25) (medial tet ee eee a wall of the tympanic cavity) presents tympani muscle; ¢, fossa for Just ventrad of the middle of its base a incus and malleus; /, fossa large circular foramen, the fenestra continuous with stylomastoid foramen; g, foramen leading cochlee (a) (or fenestra rotunda), which tostscraLieanals looks caudolaterad; it leads into the cochlea. The fenestra cochlew lies at the summit of a nipple- like elevation, the promontory (4), which is continued toward the apex of the bone as a gradually diminishing semicylindrical ridge, due to the presence within it of the bony cochlea. Dorsad of the fenestra cochlez is the much smaller fenestra vestibuli (c) (or ovalis) which leads into the vestibule. It is occupied in the natural condition by the base of the stapes. Dorsocraniad of the fenestra vestibuli is a large fossa (@) which contains the tensor tympani muscle. Dorsocaudad of this, partly bounded by the squamous portion of the temporal, is another large fossa (¢), the cranial end of which is occupied by the incus, while its caudal end is occupied by the head of the malleus. Nearly caudad of this fossa and separated from it by an oblique bony septum is a third fossa (/) which is narrow and curved. It is continuous with a notch in the mastoid portion of the bone. When the tympanic is articulated the notch is converted into a foramen (stylomastoid foramen, Fig. 22, 7) THE SKULL. 35 for the exit of the seventh nerve. The fossa gives passage to the seventh nerve and also lodges the stapedius muscle. A groove may be traced from the stylomastoid foramen to the caudal border of the fossa for the tensor tympani muscle, where it passes into a canal (g). The groove and canal are parts of the canalis facialis or facial canal (aqueductus Fallopii) for the passage of the seventh nerve through the petrous bone. The medial surface (Fig. 23, 6) of the petrous portion shows near its middle a fossa, the internal auditory meatus (vz). This is divided by a partition of bone into a dorsal and ventral part. The dorsal portion is the beginning of the facial canal (aqueductus Fallopii) by which the seventh nerve passes through the petrous bone to emerge at the stylomastoid foramen. The ventral portion shows at its bottom several small foramina for the auditory nerve. Dorsocaudad of the internal auditory meatus is a deep fossa (0) for a small lobe, the so-called appendicular lobe, of the cerebellum. This may be called the appendicular fossa. The dorsal surface is triangular and presents near its apex a foramen—the hiatus facialis (~), the opening of a canal which joins the canalis facialis and transmits the superficial petrosal branch of the nerve of the pterygoid canal (Vidian nerve). That part of the dorsal surface which lies caudad of the hiatus facialis is known as the tegmen tympani. The base of the petrous is attached to the mastoid portion (Fig. 23, @). (For an account of the structures within the petrous bone and the. tympanic cavity, see the description of the internal and middle ear.) The mastoid portion (Figs. 22 and 23, ¢) is attached by its base to the pyramidal petrous portion, with which it forms an angle of about 120 degrees. It appears in the lateral wall of the skull between the parietal bone and the occipital (Fig. 40, 2). The lambdoidal ridge is continued on its outer surface to the caudal border of the external auditory meatus. Caudad of the stylomastoid foramen it forms a slight nipple-like eminence, the mastoid process (Fig. 22, 7). Its inner face looks into the cranial cavity. 36 THE SKELETON OF THE CAT. Parietal Bone. Os parietale (Figs. 39, 40, and 43, 3).— The parietal bones form the larger part of the lateral and dorsal boundary of the cranial cavity. Each is a thin rectangular bone, compact and curved and with a deeply notched shelf of bone, the tentorium (Fig. 42, ¢, and Fig. 43, /), projecting inward from near the caudal margin. The outer surface is smooth and convex. The highest part of the convexity, a little caudad of the middle of the bone, is known as the parietal tubercle or eminence (Fig. 39, @); it marks the point of beginning ossification. An obscure curved ridge (Fig. 39, ¢), running from the caudodorsal angle or a point craniad of it craniolaterad, indicates the boundary of the origin of the temporal muscle. Near the ventral border the surface is roughened and is covered in the natural state by a part of the squamous portion of the temporal bone. The inner surface (Fig. 43, 3 and 8) is smooth and marked by ridges and grooves for the convolutions of the cerebrum. Near the medial border is a ridge which, when the bone is articulated with that of the opposite side, forms a shallow groove for the superior sagittal sinus. Beginning near the middle of the ventral margin and passing dorsad is a groove for the middle meningeal artery. The tentorium (Fig. 43, /) arises from the inner surface near its caudal margin and projects mediad as a thin curved or notched shelf of bone which separates the cerebellar fossa (Fig. 43, /) of the cranium from the cerebral fossa (Fig. 43, //). When the parietals are articulated there is left between the tentoria a large foramen by means of which the two fosse communicate. The. foramen is bounded laterally and dorsally by the free margins of the tentoria, while the ventral end of each tentorium articulates with the alisphenoid, and its dorsal end with the opposite ten- torium. The medial border is straight and is united by suture to the opposite bone. ; The cranial border is bevelled at the expense of the inner surface and articulates with the frontal. Just ventrad of the middle of the border projects a sharp spine which fits into a corresponding notch in the caudal border of the frontal. THE SKULL. 37 The ventral border is concave, sharp, and bevelled at the expense of the outer surface, for articulation with the squamous portion of the temporal, except near the cranial end, where it articulates with the wing of the sphenoid. The caudal border is thick and porous medially, but thin laterally, and bevelled at the expense of the inner surface for. articulation with the interparietal and mastoid portion of the temporal. Frontal Bone. Os frontale (Figs. 39, 40, and 41, 5; Fig. 43, 8; Fig. 26).—The frontal bones meet one another in the median dorsal line so as to form the roof of the skull between the parietal and nasal bones. A part extends also ventrad, forming a large part of the medial wall of the orbit and a part of the temporal fossa. The bone may be divided into two portions, a plate forming the cranial portion of the roof of the skull and a part of the roof of the nasal cavity, the frontal plate (Fig. 40, 5), and a part descending into the orbit, the orbital plate (Fig. 40, 5’). The frontal plate (Fig. 40, 5) isa right-angled triangle with the hypothenuse lateral. Its dorsal surface is convex and smooth. The cranial two-thirds : of its lateral border is separated from the orbital fossa by a ridge, the supraorbital arch or mar- gin (Fig. 39, 2; Fig. 40, 0); the caudal third passes gradually into the temporal fossa. At its cranial angle isa triangular pro- Fic. 26,—FrontaL Bons, MEDIAL jection, the frontal spine or ates ais ee nasal spine (Fig. 26, a), which C, Thee ariel to the sthineide a fits into a space between the vertical plate of medial border. nasal and maxillary bones. The ventral surface is concave and smooth over its caudal one-half and helps to form the cranial part of the brain-case. It presents slight ridges and depressions for convolutions of the cerebrum. At its narrowed middle region the ventral surface is marked by a thick transverse ridge (Fig. 26, 4). Caudally the ridge descends by a gentle slope to the level of the ventral 38 THE SKELETON OF THE CAT. surface of the bone. The cranial end of the ridge is pierced by an oval foramen through which the frontal sinus (Fig. 43, m, m'), which lies within the ridge, communicates with the spaces in the ethmoid bone (nasal cavity). Craniad of the ridge the surface (Fig. 26, c) is rough and, together with the raised medial border of the bone and the orbital plate, encloses a rectangular space which in the natural state receives a portion of the labyrinth of the ethmoid. ‘The ventral surface is marked at its medial edge by a thin longitudinal ridge which, when the bones are articulated, is continuous with one of the vertical lamellz of the ethmoid. The medial border forms a vertical plate (Z), broadest craniad and roughened for articulation with its fellow of the opposite side except at its cranial end, where it articulates with the border of the nasal bone. The caudal border is roughened, bevelled at the expense of the outer surface, and articulated with the parietal bone except at its ventral end, where it articulates with the alisphe- - noid. The lateral border is smooth, and it is here that the orbital plate is joined to the frontal plate at right angles. Along its cranial two-thirds this union is marked by a sharp ridge, the supraorbital margin (Fig. 40, 0) or arch. This ridge extends caudolaterad as a triangular projection, the zygomatic (or postorbital) process (Fig. 40, ), which is flattened on its cranioventral face near its extremity and forms part of the boundary of the orbital fossa. At its cranial end the lateral border articulates with the nasal and maxillary bones. ‘The orbital plate (Fig. 40, 5’) arises from the ventral surface of the lateral border of the frontal plate. It is directed ventrad, is smooth and concave on its outer surface, and forms the dorsal portion of the medial wall of the orbital fossa. Near its ventral border it bears the small ethmoidal foramen, for the artery of the same name. On the caudal one-half of its inner surface (Fig. 26) it assists the caudal part of the dorsal plate in forming the brain- case. The cranial one-half of its inner surface is marked off from the remainder of the surface by a sharp irregular ridge THE SKULL. 39 which is for articulation with the cribriform plate of the ethmoid. Craniad of this the surface is marked by ridges and looks into the nasal cavity. The cranial margin is produced dorsally in the form of a blunt triangular spine. Mediad of this spine the bone articu- lates with the lachrymal bone. The ventral border articulates by its cranial one-third with the orbital plate of the palatine, and by its caudal two-thirds with the body and wing of the presphenoid. Maxillary Bone. Maxilla (Figs. 27 and 28).—The maxillary bone forms the cranial and lateral portions of the roof of the mouth. The bones of opposite sides meet craniad, but diverge caudad to enclose the palatal plates of the palatine bones. Each consists of a thick prismatic ventral portion or Fic. 27,—MAXILLARY BONE, Fic. 28.—MAXILLARY BONE, LATERAL SURFACE. MEDIAL SURFACE. a, body: 4, frontal process; c, infraorbital foramen; d, elevation for root of canine tooth; ¢, canine tooth; /, first premolar; g, second premolar; 4, third pre- molar; z, molar tooth; 7, zygomatic process; &, beginning of lachrymal canal; /, ridge to which the ventral nasal concha is attached; m, nasal crest of palatine process. body (a) and a thin flat plate, the frontal process (4), extending dorsad from the cranial part of the bone. The body (a) has the form of a triangular prism whose broader dorsal face looks into the nasal cavity and orbit, while the ventral face looks into the mouth, and the lateral face toward the cheek. From the junction of the dorsal and lateral surfaces at the cranial end the large flat curved frontal process (6) passes dorsad, while the teeth are implanted along the border, alveolar border or process, formed by the junction of the ventral and lateral surfaces. 40 THE SKELETON OF THE CAT. The lateral surface is continuous with the lateral surface of the frontal process and shows at the base of the frontal process on its caudal border the large infraorbital foramen (Fig. 27, ¢), for the vessels and nerves of the same name. Near the medial end of the surface is a cylindrical elevation (@) for the root of the canine tooth (e). The ventral surface is smooth and looks into the roof of the mouth. On the dorsal surface caudal and cranial halves may be dis- tinguished. The caudal one-half enters into the floor of the orbit. The lateral edge of this portion is divided into two laminz, between which is received the end of the malar bone. Caudad this edge is prolonged into the short dorsally directed zygomatic process (7). The cranial half of the dorsal surface looks into the nasal cavity and is separated from the caudal half by a sharp vertical lamina of bone which runs caudo- mediad from the base of the nasal process. To the dorsal edge of this lamina are articulated the lachrymal bone and a part of the palatine. At the point where the lamina joins the base of the nasal process a foramen is seen leading into a canal, the nasolachrymal canal (4). Craniad of the lamina the surface is concave. Where it becomes continuous with the inner edge of the frontal process there is attached to it a thin bone, the ventral nasal concha (or maxilloturbinal), which is rolled into an irregular spiral. The nasolachrymal canal opens ventrad of its cranial end. The cranial third of this part of the bone projects further mediad than does the rest of the medial border, forming thus the broad palatine process. This is rough on its medial edge for articulation with the premaxillary and the palatine process of the opposite bone. This medial edge rises also dorsally into a low ridge, the nasal crest (7), which is roughened for artic- ulation with the vomer. The caudal two-thirds of the medial edge articulates with the palatine bone. The cranial end of the bone articulates with the premaxilla. The caudal end is smooth. The frontal process (4) presents on its inner surface, which looks into the nasal cavity, certain transverse ridges which are THE SKULL. 41 in relation with the ethmoid bone. Its outer surface is smooth. By its cranial border it articulates with the nasal bone dorsally and with the premaxillary bone ventrally. Its dorsal end articulates medially with the nasal spine of the frontal bone, and caudally with the orbital plate of the same bone. Premaxillary Bone. (Os incisivum BNA.) Premaxilla (Fig. 29).—The premaxillary bones bear the incisor teeth and form the cranial portion of the roof of the mouth. Each consists of an irregular, horizontal palatal portion (4) and of a perpendicular nasal process (c) which forms part of the lateral boundary of the nares and enters into the formation of the lateral wall of the nasal cavity. The palatal portion has in its caudal border a deep notch for the foramen incisivum or anterior palatine canal, which lies between it and the rye, 29, — pre. maxillary and transmits blood-vessels and nerves. Serena see It articulates with the maxillary bone by this iquery Cra- border. eee The medial border is raised into a thin crest a, the three in. of bone which, besides forming the medial wall of SOB saree * the foramen incisivum or anterior palatine canal, the bone; ¢, nasal articulates by its medial border with the bone of P™°°*** the opposite side, forming a sort of median trough (sulcus pala- tinus) which projects dorsad into the nasal cavity and receives the ventral border of the nasal septum. The caudal end of this border articulates laterad with the maxilla, dorsad with the vomer. Its craniolateral border bears the incisor teeth (a). The nasal process (c) presents three surfaces, all elongated and triangular; one, the medial surface, is smooth and concave and looks into the nasal cavity. Its dorsal border is rough for articulation with the nasal bone dorsad, and smooth ventrad where it aids in forming the nares. The lateral surface is smooth. The caudal surface is rough for articulation with the maxil- lary bone. 42 THE SKELETON OF THE CAT. Nasal Bone. Os nasale (Fig. 30).—The nasal bones {fill the space between the nasal process of the premaxillary, the frontal process of the maxillary, and the nasal spine of the frontal bone (Fig. 39,7). They thus form part of the dorsal wall of the nasal cavity near the middle line. Each may be described as consisting of two elongated triangular lamellz, one vertical, the other ; horizontal. The vertical lamella is curved slightly ig Fis. 30° ventrad and has its apex directed craniad. It is ASAL BONE, : ‘ i Doxrsau applied by its medial surface against the vertical SEs lamella of the opposite bone, the two thus forming a median vertical partition, the nasal crest (Fig. 43, 12), which extends ventrad into the nasal cavity and, by joining the dorsal edge of the lamina perpendicularis, helps to form the internasal septum. The horizontal lamella is attached to the dorsal margin of the vertical lamella in such a way that its apex lies opposite the base of the vertical lamella. It helps to roof in the nasal cavity, and by its base forms a part of the dorsal boundary of the narial opening. By its lateral margin it articulates with the nasal spine of the frontal at its caudal end, with the frontal process of the maxillary at its middle, and with the nasal process of the premaxilla at its cranial end. The lateral angle of its base projects in a curved line which forms the dorsal part of the lateral boundary of the narial opening. From the lateral border of the horizontal lamella a bony plate curves ventrad and mediad, enclosing a narrow fossa which receives a part of the ethmoid. This is the concha nasalis superior (nasoturbinal bone). Ethmoid Bone. Os ethmoidale (Figs. 31 and 32).—The ethmoid bone closes in the cranial cavity at its cranial end and extends forward into the nasal cavity, which it largely fills. It consists of a median vertical portion, the lamina perpen- dicularis (Fig. 43, ~; Fig. 42, #), forming a part of the nasal septum, of two lateral portions made of thin sheets of bone variously folded and united—the labyrinths (or ethmotur- binals), which fill the greater part of the nasal cavity; and of. THE SKULL. 43 a transverse perforated plate, the cribriform plate (lamina cribrosa), attached to the caudal end of the lamina perpendicu- laris and the labyrinths. The lamina perpendicularis (Fig. 43, ; Fig. 42, p) is a flat four-sided bone. By its caudal margin it is continuous with the cribriform plate; by its ventral margin it is enclosed by the halves of the vomer; by its dorsal margin it unites with the crest formed by the vertical portion of the nasal bone craniad and with the vertical lamina of the medial margin of the frontal caudad, while its cranial margin is continued into the septal cartilage of the nose. Its lateral faces are smooth and free. The lamina cribrosa or cribriform plate (Fig. 42, 0) is elongated heart-shaped, with the apex of the heart ventrad. Its caudal face is concave and looks into the cranial cavity. It presents three irregular longitudinal rows of holes, one median and two lateral, for the passage of the olfactory fibres from the cranial cavity into the nasal cavity. Its cranial face is continuous along the medial line with the lamina perpendic- ularis, and at the sides with the labyrinths. The notch in the heart is directed dorsad and receives the vertical lamina of the medial border of the frontal bone. The Fic, 31 —-ETHMOID AND VOMER, Fic. 32.—ETHMOID AND VoMER, SIDE VIEW. VENTRAL VIEW. a, vomer; 4, vertical cells of the labyrinth of the ethmoid; ¢, horizontal cell of the same; ¢@, part of the ethmoid that forms the lamina papyracea; e, edge of cribri- form plate. apex of the heart articulates with the cranial end of the dorsal surface of the presphenoid. Its lateral margins are articulated with the ethmoidal ridges on the medial surface of the frontal bone. The labyrinths (Figs. 31 and 32) are attached to the cranial face of the lamina cribrosa, one on each side of the lamina perpendicularis. Each is made of thin bony plates irregularly 44 THE SKELETON OF THE CAT. folded so as to enclose spaces, the ethmoid cells. In each may be distinguished a cranial portion (4), in which the cells are nearly vertical, and a caudal portion (c), in which the cells are nearly horizontal. : The medial surfaces are separated by a space from the lamina perpendicularis. This space is broadest along the junction of-the horizontal and vertical portions of the labyrinth. There are thus formed two passageways which correspond to the superior meati of human anatomy. The lateral surfaces come into contact with the frontal process of the maxillary and the orbital plate of the frontal bone. On the lateral surface of each labyrinth there is a thin irregular lamina of bone lying in a dorsoventral longitudinal plane and closing in some of the ethmoid cells laterally (¢). A small part of this lamina, situated near the caudoventral angle of the bone, appears in the orbital fossa on the external surface of the skull between the presphenoid, palatine, and frontal bones or between the lachrymal, palatine, and frontal bones. Sometimes in the entire skull two such pieces may be seen, one in each of these positions. This corresponds to the lamina papyracea of human anatomy. The dorsocaudal angle of each bone is received into the space between the orbital plate of the frontal and the vertical lamina of the medial border of the frontal. Its ventrocaudal angle is received between the cranial extensions of the lateral walls of the presphenoid, while its ventral surface is overlaid caudally by the expanded portion of the vomer, to which it is attached at its caudolateral angles. Vomer (Figs. 31 and 32, @).—The vomer consists of two thin lamine of bone which ensheath the ventral margin of the lamina perpendicularis (or the cartilaginous plate which con- tinues ventrad from this margin) and unite ventrad of it; the two thus form a trough open dorsad. - Each becomes horizontal near its caudal end and at the same time expands. The expanded portion lies ventrad of the labyrinth of the ethmoid, closing in some of its cells: its lateral angles are united with the labyrinths. At its caudal end the bone articulates with the body of the THE SKULL. 45 presphenoid, and each half of it is produced caudad near the middle line into a triangular spine which lies ventrad of the body of the presphenoid. The horizontal portion of the bone helps to separate the olfactory and respiratory passages of the nasal chamber, while its vertical portion contributes to the formation of the nasal septum. The ventral margin formed by the junction of the two halves of the bone is smooth and free caudad, but at its cranial end is broad and rough for articulation with the palatal processes of the maxille. Palatine Bone. Os palatinum (Fig. 33).—The palate bone or palatine bone consists of two portions, a horizontal or palatal portion (2) and a perpendicular or nasal portion (4), uniting at an angle of about forty-five degrees. The horizontal portions (a) of the two bones are received between the maxillary bones and form the caudal and medial part of the roof of the mouth. Each is irregularly quadrilateral in form, with the caudolateral angle produced caudad into a long process which is continuous with the perpendicular portion of the bone. The lateral margin of the horizontal por- tion articulates over its cranial half with the maxillary bone. At about its middle a short thick % maxillary spine (c) projects caudolaterad. The Fic. 33.—Para- remainder of the lateral margin is directly con- ae tinuous with the perpendicular plate of the bone. a, __ horizontal The medial margin is rough for articulation with Portion; 4 per- . i ; pendicular _por- the corresponding margin of the opposite pala- tion; eae tine; the caudal angle of this margin projects aL ae caudad as the short posterior nasal spine (2). sphenupslatin : 7 or. 2 4; 5 The caudal margin forms a free edge which gap Sn at bounds the choanz; it passes laterally into the Cle palatine canal. perpendicular portion. The ventral surface (Fig. 41, 8) looks into the mouth. Near the middle of its craniolateral margin are two or more small foramina (Fig. 41, g) which form the cranial temination of the posterior palatine canal. The dorsal surface is smooth and looks into the nasal cavity. 46 THE SKELETON OF THE CAT. The perpendicular or nasal portion (Fig. 33, 4) of the palatine is thin and irregularly quadrilateral in form. It is attached by its cranial two-thirds to the dorsal surface of the horizontal portion. The outer surface is concave and looks into the orbital fossa. The inner surface is convex and looks into the nasal cavity. The perpendicular portion is marked by two formaina just craniad of the middle. The larger dorsal oval foramen is the sphenopalatine foramen (¢). The smaller ventral foramen is the caudal opening of the posterior palatine canal (f). From this opening the canal passes craniomediad, lying in the sub- stance of the palatine bone; it opens on the ventral surface of the horizontal portion at the small openings previously described (Fig. 41, @). By its cranial margin it articulates with the lachrymal bone. By its dorsal margin it articulates craniad with the orbital plate of the frontal: with the lamina papyracea at its middle, and with the body of the presphenoid caudad. The caudal half of the dorsal margin is partially divided into two lamelle with a rough surface between them: this rough surface lies against the ventral surface of the presphenoid. The caudal margin articulates with the pterygoid portion of the sphenoid. Lachrymal Bone. Os lachrymale (Fig. 34; Fig. 39, 10). ~The lachrymal bone is a thin pentagonal scale of bone filling Fic. 34.—LACHRYMAL BONE OF Fic. 35.—MALar Bone oF RIGHT SIDE, Lert SIDE, EXTERNAL SURFACE. LATERAL SURFACE, Fig. 34.—@, notch forming the beginning of the lachrymal canal. Fig. 35.—2, ridge for origin of the masseter muscle; 4, frontal process; ¢, zygo- matic process. the interval between the horizontal plate of the palatine, the maxillary, and the orbital plate of the frontal. Its outer surface looks into the orbit, its inner surface into the nasal cavity. THE SKULL. , 47 Near the middle of its cranial border it is notched obliquely by a foramen (a), the beginning of the nasolachrymal canal. Malar Bone. Jugal Bone. Os zygomaticum (Fig. 35). —The malar or zygomatic bone is a flat curved plate of bone which forms the lateral wall of the orbit and together with the zygomatic process of the temporal forms the zygomatic arch. Its outer surface is smooth and marked by a longitudinal ridge (a) for attachment of the masseter muscle. At its caudal end the bone is continued into two processes: one, the frontal process or orbital process (4), is a triangular spine of bone directed caudomediad; when the bones are articulated it lies opposite the zygomatic process of the frontal to which it is joined by a ligament (orbital ligament). ‘Che other, zygomatic process (c) of the malar bone, extends ven- trocaudad and articulates with a similar process from the tem- poral to form the zygomatic arch above mentioned. Its inner surface is smooth and looks into the orbit, except that of the zygomatic process, which looks into the temporal fossa. Its cranial border is roughened at the expense of both sur- faces and articulates with the maxillary bone. Its other borders are smooth except the dorsal border of the zygomatic, process, which is roughened for attachment to the zygomatic process of the temporal. The Mandible. Mandibula (Figs. 36 and 37).—The mandible (or inferior maxillary bone) is composed of two halves which come together at the cranial end and form the lower jaw. At its caudal end each half articulates with the temporal bone at the mandibular fossa, and at its cranial end it joins the opposite bone, the suture being known as the sym- physis of the jaw (symphysis menti) (Fig. 37, 2). Each half consists of a horizontal portion, the body (4), bearing teeth on one of its borders (the alveolar border), and of a vertical portion, the ramus (c). The body (0) has the form of a flattened cylinder and has two surfaces and two borders. The lateral surface (Fig. 36) is smooth and presents near its cranial end a foramen (or sometimes two), the mental foramen (@), forming the cranial 48 THE SKELETON OF THE CAT. termination of the mandibular canal. At its caudal end is a deep fossa continuing on to the ramus, the coronoid fossa, or masseteric fossa (¢). The medial surface (Fig. 37) is smooth and has near its caudal end a foramen, the mandibular foramen (/), which Fic, 37-—MANDIBLE, MEDIAL SURFACE. a, symphysis; 4, body; ¢, ramus; @, mental foramina; ¢, coronoid fossa; 7, man- dibular foramen; g, angular process; 4, coronoid process; 2, condyloid process; I, 2, 3, the three incisor teeth; 4, the canine tooth; 5, 6, the premolars; 7, the molar tooth. communicates with the mandibular canal leading lengthwise through the bone to the mental foramen. The cranial end is roughened for attachment to the bone of the opposite side. The ventral border is smooth and rounded; it ends caudally in a blunt point, the angular process (¢). The dorsal (alveolar) border is slightly curved and bears the sockets (alveoli) for the teeth. It is continuous with the cranial margin of the coronoid process. The ramus is divided into two portions, the coronoid process (2) and the condyloid process (2). The coronoid process (4) extends dorsocaudad as a thin plate of bone with smooth sur- faces and borders. Its outer surface is partly occupied by the coronoid fossa (¢). The condyloid process (z) has the form of THE SKULL. 49 a semicylindrical transverse piece of bone attached to the caudal margin of the coronoid process. It articulates with the mandibular fossa of the temporal bone. Hyoid Bone. Os hyoideum (Fig. 38 and Fig. 104).— The hyoid bene forms the support for the tongue and gives origin to muscles passing to the Z tongue and larynx. It also supports the thyroid cartilage (Fig. 104, 1). It consists of a transverse bony bar, the body (Fig. 38, a) 4 and of two cornua or horns yy, 38.—Hyorp Bong, Dorsat View. attached to each end of the az, body; 4, ¢, d, e, cranial cornu; /, caudal cornu; 4, ceratohyal; ‘, epihyal; body. d, stylohyal; e, ‘tympanohyal; f, thyro- The cranial cornu (lesser hyal. cornu of human anatomy) i is the longer (Fig. 38, d-e). Each arises from the cranial face of the body at its lateral end, curves laterad, and then caudodorsad. It consists of four bony pieces movably united by cartilage. The terminal piece is the tympanohyal (¢); it is imbedded in the tympanic bulla just ventrad of the stylomastoid foramen. It is not therefore seen attached to the cornu after the latter has been separated from the skull. The other pieces become successively shorter toward the body, and are called stylohyal (d), epihyal (c), and ceratohyal (2). The caudal cornua (/) (greater cornua of human anatomy) arise from the ends of the body. Each consists of a single piece of bone, the thyrohyal (/), which passes caudolaterad ; its free end is united to a process of the thyroid cartilage (Fig. 104, 1). The Skull as a Whole.—In the following description of the skull as a whole the mandible, hyoid, and ear-bones are not included. The skull forms a bony box which contains the brain and is produced craniad into the facial portion which encloses the nasal cavity and forms the framework of the face. In dorsal view (Fig. 39) the skull presents a smooth con- vex surface, broadest caudad, with the two zygomatic arches 50 THE SKELETON OF THE CAT. (g) curving out some distance laterally. The following bones are visible in dorsal view: the occipital (1), interparietal (2), parietals (3), temporals (4), frontals (5), malar or zygomatic . Fic. 39.—SKULL, DoRSAL SURFACE, I, occipital bone; 2, interparietal bone; 3, parietal bones; 4, temporal; 5, frontal; 6, malar; 7, nasal; 8, maxillary; 9, premaxillary; 10, lachrymal. a@, lambdoidal ridge; 4, external occipital tubercle; ¢, sagittal crest; ¢, parietal eminence; ¢, line which forms the dorsal boundary of the temporal fossa; /, zygomatic process of the frontal; g, zygomatic arch; 4, frontal process of the malar; z, supraorbital arch; 7, nares; 2, foramen incisivum or anterior palatine foramen; /, sphenopalatine foramen; m, zygomatic process of the temporal; 7, infraorbital foramen; 0, opening of lach- rymal duct. bones (6), nasals (7), maxillaries (8), premaxillaries (9), and lachrymals (10). The caudal boundary of the dorsal surface is marked by the prominent lambdoidal ridge (a) which passes from the middle cranioventrad along each side to the root of the zygomatic arch: it is borne by the occipital and temporal bones. From the middle of the lambdoidal ridge a second ridge, the sagittal THE SKULL. 51 crest (c), passes craniad in the middle line across the inter- parietal bone: it varies greatly in extent, reaching ina very old and muscular cat to the cranial border of the parietals, while in kittens it does not exist. The most prominent portions of the skull in this region, just craniad of the middle of the parie- tal bones, are known as the parietal tubercles or eminences (¢@). A faint curved line (¢) runs from the cranial end of the sagittal crest craniolaterad to the base of the zygomatic process of the frontal: it marks the dorsal boundary of the origin of the tem- poral muscle, and may therefore be considered the dorsal boundary of the temporal fossa. This fossa extends from its dorsal boundary as far laterad and caudad as the lambdoidal ridge (a), and as far craniad as a line connecting the tip of the zygomatic process of the frontal (/) with the frontal process of the malar (2). The temporal muscle takes origin from its surface. The middle portion of the dorsal surface is formed by the frontals (5). Each frontal presents laterally a prominent zygomatic process (/), extending ventrolaterad toward a cor- responding (frontal) process (4) of the malar bone. These two processes mark the boundary between the orbital fossa (craniad) and the temporal fossa (caudad). Craniad of the zygomatic process of the frontal a sharp margin separates the dorsal sur- face of the skull from the wall of the orbital fossa: this is the supraorbital arch or margin (2). The cranial portion of the dorsal surface is formed by the maxillary (8), nasal (7), and premaxillary bones (9). Just craniad of the nasals, bounded ventrad and craniad by the premaxillaries, appears the large opening of tne nares (4), leading into the nasal cavity. The zygomatic arch (.g) is formed by the zygomatic process of the temporal (7) and the malar or zygomatic bone (6). Each presents near its middle a prominent dorsocaudally directed process, the frontal process (2) of the malar bone. The zygomatic arch forms the lateral boundary of the temporal and orbital fosse, which are separated by a line connecting the frontal process of the malar (Z) and the zygomatic process of the frontal (/). 52 THE SKELETON OF THE CAT. A portion of the floor of the orbit and the opening of the lachrymal canal (0) may also be seen in dorsal view; they are described in connection with the lateral surface. The caudal surface of the skull is formed largely by the occipital bone (Fig. 17), surrounding the foramen magnum (Fig. 17, 2). At the sides of the foramen magnum are the two prominent curved occipital condyles (¢) for articulation with the atlas. Craniolaterad of the condyles, separated from them by a deep notch, are the jugular processes (/) of the occipital, closely applied to the caudal ends of the tympanic bulla. Dorsad of the foramen magnum are faint indications of a median ridge running dorsad, the external occipital crest (Fig. 17,2); this rises at its junction with the lambdoidal ridge to form the prominent external occipital tubercle (Fig. 39, 4). The dorsal and dorsolateral boundaries of the posterior surface are formed by the lambdoidal ridge (Fig. 17, 4; Fig. 39, a). The lateral surface of the skull (Fig. 40) is much more complicated than the dorsal and posterior surfaces. Caudally the occipital condyles (a) and external occipital crest (4) are visible; dorsocaudad the sagittal crest (c). Extending from the caudal end of the sagittal crest the lambdoidal ridge (d@) is seen passing ventrocraniad to the tym- panic bulla, thence craniad to the root of the zygomatic arch. In the ventral part of the caudal region the tympanic bulla (e) is visible with the jugular process (/) of the occipital pressed close against its caudal end. Just craniad of the jugular process the mastoid process (g) of the temporal rests against the side of the bulla. Beneath the cranial edge of this process is the opening of the stylomastoid foramen (/) for the seventh nerve, while just ventrad of the foramen is the small pit (2) in the tympanic bulla for the reception of the tympanohyal bone. Craniad of the stylomastoid foramen is the large opening of the external auditory meatus (7), leading into the middle ear. Immediately dorsocraniad of the external auditory meatus the zygomatic arch begins as the zygomatic process_(£) of the temporal bone. On the cranial surface of the base of this process is the deep mandibular fossa (/) for the condyle of the THE SKULL. 53 mandible. This fossa is bounded caudally by the prominent postmandibular process (7). All that portion of the lateral surface of the skull which lies craniodorsad of the lambdoidal ridge may be divided (exclud- ing the zygomatic arch) into three main parts, the temporal fossa, the orbital fossa, and the face. The boundaries of the temporal fossa have been given. The orbital fossa is bounded Fic. 40,—SKULL, SIDE VIEW. 1, occipital bone; 2, interparietal; 3, parietal; 4, temporal; 5, 5’, frontal; 6, malar; 7, sphenoid; 8, palatine; 9, presphenoid; 10, maxillary; 11, nasal; 12, pre- maxillary; 13, incisor teeth; 14, canine; 15, 16, 17, premolars; 18, molar. a, oc- cipital condyle; 4, external occipital crest; c, sagittal crest; ¢, lambdoidal ridge; e, tympanic bulla; 7, jugular process; g, mastoid process; 4, stylo-mastoid foramen; , pit for tympanohyal bone; 7, external auditory meatus; 2, zygomatic process of tem- poral bone; /, mandibular fossa; m, postmandibular process; #, zygomatic process of the frontal; 0, supraorbital margin; 2, external pterygoid fossa; g, sphenopalatine foramen; 7, orbital fissure; s, internal pterygoid fossa; z, hamulus; #, foramen ovale; v, foramen rotundum; w, optic foramen; +, opening of lachrymal canal; y, infraorbital foramen, externally by a prominent semicircular ridge formed chiefly by the zygomatic arch, the zygomatic process of the frontal (z), ’ and the supraorbital arch (0) of the frontal, which may be traced to the cranial root of the zygomatic arch. The orbital fossa may be considered to end caudally and ventrally at the level of the optic foramen (z); ventrad of it are certain smaller fosse. Immediately ventrad is the long external pterygoid fossa (/), from which arises part of the external pterygoid muscle. This fossa begins at the sphenopalatine foramen (¢) and extends caudad to the orbital fissure (7); it is separated by a ridge from the orbital fossa. Caudoventrad of the external 54 THE SKELETON OF THE CAT. pterygoid fossa and separated from it by a sharp ridge is the small narrow internal pterygoid fossa (s), which extends ven- trad without interruption on to the surface of the hamulus (s) and caudad to within two or three millimeters of the tympanic bulla. From it the internal pterygoid muscle takes origin, The hamulus (¢) projects caudoventrad in this region, forming a prominent feature in a lateral view. Four foramina leading into the cranial cavity are visible in a lateral view of the skull, craniad of the tympanic bulla. The one nearest the bulla is the foramen ovale (z) for the third division of the fifth nerve; next craniad of this is the foramen rotundum (v) for the second division of the fifth nerve. These two foramina pierce the alisphenoid: just craniad of them, between the alisphenoid and the orbitosphenoid, is the large orbital fissure (7) (foramen lacerum anterius), which transmits the third, fourth, and sixth cranial nerves and the first division of the fifth. Dorsocraniad of the orbital fissure is the optic foramen (w), for the optic nerve. Ventrad of the cranial portion of the orbit is the large sphenopalatine foramen (¢), for the nerves and arteries of the same name. Just craniad of this is the small caudal opening of the posterior palatine canal, which passes through the sub- stance of the palatine bone and opens on its ventral surface near its cranial margin. Just dorsad of the cranial root of the zygomatic arch is the opening of the lachrymal canal (+), while the root of the arch is pierced by the large infraorbital foramen (7), which transmits the infraorbital nerves and artery from the orbit. The teeth (13-18), implanted along the alveolar border of the maxillary and premaxillary, form a prominent feature in a lateral view: they are described in the account of the alimen- tary canal. The ventral surface of the skull (Fig. 41) is very complex. It is separated by the orbits into a caudal and a cranial portion, united by a narrow median trough-like part. Laterad of this trough-like part are visible parts of the orbit and the zygomatic arches, which do not properly belong to the ventral surface and have already been described. THE SKULL. 55 Caudally there appear in the ventral view the foramen magnum (qa), occipital condyles (4), and jugular processes (c). In front of the jugular processes the two tympanic bull (2) form prominent features, with the mastoid process (¢), the stylomastoid foramen (f), and the external auditory meatus Fic, 41.—SKULL, VENTRAL VIEW. I, occipital bone; 2, temporal; 3, sphenoid; 4, presphenoid; 5, frontal; 6, malar; 7, vomer; 8, palatine; 9, maxillary; 10, premaxillary, @, foramen magnum; 4, occipital condyles; ¢, jugular process; @, tympanic bulla; e, mastoid process; /, stylo- mastoid foramen; g, external auditory meatus; 4, jugular foramen; 7, styliform proc- ess; 7, groove for Eustachian tube; 2, foramen ovale: 7, foramen rotundum; #2, pterygoid process of sphenoid; 7, perpendicular plate of palatine; v, choanz or pos- terior nares; ~, zygomatic arch; g. cranial end of posterior palatine canal; 7, pala- tine grooves; s, foramina incisiva or anterior palatine foramina; /, opening of ptery- goid canal. (g) on their lateral surfaces. All these structures have been described. The tympanic bullz (d) are placed with long axes directed craniomediad, so that they converge toward their cranial ends. At the caudomedial angle of each bulla is the 56 THE SKELETON OF THE CAT. large jugular foramen (/), for the ninth, tenth, and eleventh nerves. Opening into the mediocaudal margin of the jugular foramen is the smaller hypoglossal foramen, for the twelfth nerve. The craniomedial end of the tympanic bulla projects craniad as the styliform process (2). Just laterad of this process is the opening (/) into the tympanic bulla by which the tuba auditiva or Eustachian tube passes into the middle ear. A faint groove for the tube passes craniomediad from this opening, on the sur- face of the sphenoid. Craniolaterad of the opening for the tuba auditiva is the foramen ovale (4); craniad of this the foramen rotundum (/) is faintly indicated. On the surface of the sphenoid just craniad of the styliform process of the bulla tym- pani is the minute opening of the pterygoid canal (¢). The orbital fissure and optic foramen are not seen in the ventral view. The middle region of the ventral surface is narrow: it is formed by a trough-like fossa which is bounded laterally by the pterygoid processes (77) of the sphenoid and the perpendicular plates of the palatines (w). Ventrad of this lies, in the natural condition, the soft palate, converting the fossa.into the nasal portion of the pharynx or nasopharynx. Craniad this fossa is bounded by the free caudal edges of the palatines; beneath which the fossa communicates with the nasal cavity by the two choane (0). lLaterad of this median fossa are visible in the ventral view parts of the temporal and orbital fosse, bounded laterally by the zygomatic arches (f). The cranial part of the ventral surface is a somewhat tri- angular plane area formed by the palatal portions of the pala- tines (8), maxillari2s (9), and premaxillaries (10), which together constitute the hard palate (palatum durum). Laterad and craniad this area is bounded by the alveolar borders of the maxillaries and premaxillaries bearing the teeth. The hard palate is marked near the cranial border of the palatine bones with two or more foramina which form the cranial termination of the posterior palatine canal (7). Two faint grooves pass from these foramina a short distance craniad, gradually con- verging: these are known as the palatine grooves (7) (sulci THE SKULL. 57 palatini). Near the cranial end of the hard palate are two large openings close together near the middle line: these are the foramina incisiva (or anterior palatine foramina) (s). Cavities of the Skull (Figs. 42 and 43).—The bones of the cranial portion of the skull enclose the cranial cavity for Fic. 42.—-SKULL, WITH DorsAL SURFACE REMOVED, SHOWING THE CRANIAL AND NASAL CAVITIES, a, foramen magnum; 4, caudal end of hypoglossal canal; ¢, jugular foramen; @, internal auditory meatus; ¢, tentorium, forming the cranial boundary of the cerebellar fossa; 7, dorsum sellz; g, sella turcica; 4, anterior clinoid processes; 2, foramen ovale; 7, foramen rotundum; 4, orbital fissure; 7, optic foramen; , chiasmatic groove; 2, presphenoid bone; 9, cribriform plate: J, lamina perpendicularis of eth- moid; g, labyrinths of ethmoid; 7, nares; s, foramina incisiva or anterior palatine foramina; ¢, infraorbital foramen; #, opening of the lachrymal canal; v, caudal opening of posterior palatine canal; w, sphenopalatine foramen; .r, frontal process of the malar; y, zygomatic process of the temporal; z, appendicular fossa, in the pe- trous bone. the brain; the facial bones enclose the nasal cavity, for the olfactory organ. The cranial cavity is divisible into three principal fossx: the cerebellar fossa (Fig. 43, 7) caudad, for the cerebellum; 58 THE SKELETON OF THE CAT. the cerebral fossa (//) in the middle, for the cerebrum; the small olfactory fossa (///) at the cranial end for the olfactory bulb of the brain. The cerebellar fossa (/) is bounded caudally by the occipital bone enclosing the foramen magnum (Fig. 42, 2). Its ventral surface is formed by the basilar portion of the occipital and the petrous portions of the temporals; its lateral surface by the mastoid portions of the temporals and parts of the parietals and occipital. Its roof is formed by the parietals and interparietal. Craniad the cerebellar fossa is partly separated from the cere- bral fossa by the tentorium (Fig. 42, ¢; Fig. 43, /) formed by the two parietals: this encloses a quadrangular opening by which the two fosse communicate. The caudal, dorsal, and lateral walls of the cerebellar fossa are deeply marked by fosse for the lobes of the cerebellum; the small appendicular fossa .(Fig. 43, ¢), forming a deep indentation in the petrous bone near its dorsocaudal end, is particularly noticeable. The following openings are found in the walls of the cere- bellar fossa. Caudad is the large foramen magnum (Fig. 42, a) by which the brain-cavity communicates with the vertebral canal. Near the caudal margin of the foramen magnum, on its lateral side, just mediad of the dorsal end of the occipital condyle, is the caudal opening of the condyloid canal (Fig. 43, 2) which passes craniad through the substance of the occipital bone to open just caudad of the petrous: it transmits a vein. The condyloid canal varies greatly in size in different speci- mens. A few millimeters craniad of the edge of the foramen magnum on the floor of the fossa is the small opening of the hypoglossal canal (Figs. 42 and 43, 4), for the twelfth nerve. Just craniad of this, at the caudomedial border of the petrous, is the large jugular foramen (c). On the petrous itself, near the middle, is the internal auditory meatus (@) divided into the dorsal facial canal for the seventh nerve, and a ventral passage for the eighth nerve. At the cranial end of the cerebellar fossa is the large opening bounded by the free edges of the tentorium. . The cerebral fossa forms much the largest part of the cranial cavity, It is bounded by the parietals (Fig. 43, 3°), THE SKULL, 59 squamous portions of the temporals (4), frontals (8), the sphenoid (5), and presphenoid (6). A slight rounded ridge on its lateral wall at about the position of the suture between the frontals and parietals separates a smaller cranial portion sometimes called the anterior fossa, from a larger caudal por- tion sometimes known as the middle fossa of the cranial cavity. The walls of the cerebral cavity are marked with numerous ridges and shallow furrows for the cerebral convolutions. The floor of the cerebral cavity is bounded caudad by the prominent dorsum selle (Fig. 42, 7; Fig. 43, g), just craniad of which is the rounded depression known as the sella turcica (Fig. 42, ¢; Fig. 43, 4), for lodgment of the hypophysis. A number of foramina pierce the floor of the cavity in this region. Just ventrad of the cranial tip of the petrous portion of the temporal is the small foramen lacerum (medius). Craniad and laterad of this is a row of four foramina: the caudal one is the foramen ovale (Fig. 42, 7); then come in order the foramen rotundum (7), the orbital fissure (£), and the optic foramen (Fig. 42, 2; Fig. 43, &). The two optic foramina are connected by the shallow transverse chiasmatic groove (Fig. 42, 7), for the optic chiasma. Another small foramen continues caudad from a groove on the floor of the orbital fissure; this opens on the ventral surface of the sphenoid, between the wing and the body of the bone. The groove and foramen constitute the pterygoid canal, which transmits a nerve,—the nerve of the pterygoid canal, or Vidian nerve. The cranial cavity narrows at its cranial end to form the small olfactory fossa (Fig. 43, //7) which lodges the olfactory bulbs. This is bounded by the frontals and the lamina cribrosa (Fig. 42, 0) of the ethmoid; caudad it opens directly into the cerebral fossa. Numerous openings through the lamina cribrosa for the olfactory fibres connect the olfactory fossa with the nasal cavity. The roof of the fossa is marked by a promi- nent median crest from the united edges of the frontals. The nasal cavity is almest completely filled by the ethmoid and vomer and the conche nasales. Its roof is formed by the nasal bones and portions of the frontals; its sides by the frontals, lachrymals, maxillaries, premaxillaries, and palatine 60 THE SKELETON OF THE CAT. bones; its floor by the horizontal plates of the palatines, maxillaries, and premaxillaries. _ The nasal cavity opens craniad by the large nares (Fig. 39, J; Fig. 42, 7), which are bounded by the premaxillary and Fic. 43.—SKULL, MEDIAN LONGITUDINAL SECTION, SHOWING THE CAVITIES. J, cerebellar fossa; //, cerebral fossa; ///, olfactory fossa. 1, occipital bone; 2, interpariétal; 3, 3’, parietal; 4, temporal (4, squamous portion; 4’, petrous portion; 4”, tympanic portion); 5, sphenoid; 6, presphenoid; 7, palatine; 8, frontal; 9, max- illary; 10, premaxillary; 11, ethmoid; 12, nasal; 13, incisor teeth; 14, canine; 15, 16, 17, premolars; 18, molar. «@, tondyloid canal; 4, hypoglossal canal; ¢, jugular foramen; @, internal auditory meatus; ¢, appendicular fossa; /, tentorium; g, dorsum sellze; 4, sella turcica; 7, hamular process; 7, pterygoid process of sphenoid; , optic foramen; /, presphenoid sinus; , m', frontal sinus; 2, lamina perpendicu- laris of the ethmoid (broken at cranial edge). nasal bones. In the natural condition this opening is divided by a median cartilage which is continuous with the lamina per- pendicularis (Fig. 43, 2) of the ethmoid, thus forming a parti- tion which divides the nasal cavity into two separate halves. From the floor of the cranial part of the cavity rises a ridge formed of the nasal crests of the maxillaries and premaxillaries, and the cranial portion of the vomer. Farther caudad the vomer spreads out in a horizontal plane and separates from the floor of the cavity, so that the nasal cavity is thereby divided by a horizontal partition into dorsal and ventral portions. The ventral portion is small, forming the inferior meatus of the nose; it ends caudally at the choanz (posterior nares, Fig. 41, 0) which lead into the nasopharynx. That portion. of the nasal cavity lying dorsad of the vomer is almost com- THE SKULL. 61 pletely filled by the ethmoid and the conche nasales, superior and inferior. It is bounded caudally by the lamina cribrosa of the ethmoid (Fig. 42, 0). The nasal cavity communicates with the cranial cavity by the foramina for the olfactory fibres in the lamina cribrosa; with the nasopharynx by the choane; with the exterior of the body by the nares; with the mouth-cavity by the foramina incisiva or anterior palatine foramina (Fig. 42, s); with the orbit by the sphenopalatine foramen and the naso- lachrymal canal. It communicates directly also with the frontal sinuses (Fig. 43, mz, 2’), the sphenoidal sinuses (Fig. 43, 2), and with the cells of the labyrinths of the ethmoid. JOINTS AND LIGAMENTS OF THE SKULL. Sutures of the Skull.—The bones of the skull join each other by means of immovable articulations known as sutures. These sutures are designated by combining the names of the bones between which they are situated: as, sphenofrontal suture (sutura sphenofrontalis), between the sphenoid and frontal; nasomaxillary suture (sutura nasomaxillaris), between the nasal and maxillary bones. When a suture joins the two corresponding bones of opposite sides the prefix inter is used, as the intermaxillary suture (sutura intermaxillaris) between the maxillaries. The sutures bounding the parietals have, however, received special names not derived in this manner. The suture caudad of the parietals, separating them from the occipital and interparietal, is known as the lambdoidal suture; that between the two parietals is the sagittal suture; that separating the parietals and squamous portions of the temporals is the squamous suture; that between the parietals and frontals is the coronal suture. The suture separating the two frontals also is known as the frontal suture, in place of interfrontal. Articulations of the Mandible.—In man the two halves of the mandible are united craniad, so as to form a single bone. In the cat the two halves are separate, but articulate closely at the symphysis menti by a thin interarticular cartilage. The articulation of the mandible at the mandibular fossa of the temporal is covered with a close articular capsule. The 62 THE SKELETON OF THE CAT. mandibular fossa is lined with cartilage. A slender ligament passes from the angular process of the mandible caudad to the external auditory meatus, being attached to the latter about 8 millimeters from its medial end. This is the stylomandib- ular ligament. V. BONES OF THE THORACIC EXTREMITIES, Scapula (Figs. 44 and 45).—The scapula may be described as a flat triangular bone with one angle rounded. It lies Fic. 44.—ScaPuLa, LATERAL SURFACE. Fic. 45.—SCAPULA, MEDIAL SURFACE. J, fossa supraspinata; //, fossa infraspinata; 7//, fossa subscapularis; /V, fossa for teres major. @, vertebral border; 4, coracoid border; ¢, glenoid border; ¢, glen- oid angle and fossa; ¢, coracovertebral angle; /, glenovertebral angle; g, spine; 4, tuberosity of the spine; 7, metacromion; 7, acromion; 4, supraglenoidal tubercle; 4, incisura scapulze; 7, coracoid process; #, groove indicating portion of spine; 2, 0’, ridges for attachment of muscle-fibres. beneath the muscles on the lateral face of the thorax near its cranial end. From its lateral surface there projects a flat ridge (Fig. 44, g), the spine of the scapula. The ventral end of the ridge is free as a curved process, the acromion process (Fig. The ventral angle of the scapula (2), the glenoid angle THORACIC LIMBS. 63 (lateral angle of human anatomy), is much heavier than the others and bears a concave, pear-shaped articular facet, the glenoid fossa, for articulation with the humerus. The border with which this angle is more nearly continuous may be called the glenoid border (c) (axillary border of human anatomy). Near the narrower cranial end of the glenoid fossa is a small curved projection of the bone, the coracoid process (Fig. 45, m). The border upon which it lies is the coracoid border (6) (superior border of human anatomy). The third border is turned toward the vertebral column and is the vertebral border (a). The angle between the glenoid and vertebral borders is the glenovertebral angle (/) (inferior angle of human anatomy), and that between the coracoid and vertebral borders the coracovertebral angle (¢) (medial angle of human anatomy). The medial or costal surface (Fig. 45) is smooth and nearly flat. A shallow furrow (7) marks the position of the spine of the scapula. Between the furrow and the coracoid border are two oblique parallel ridges (@ and o’) for the insertion of muscle- fibres. Near the glenoid border is a well-marked ridge sepa- rating the subscapular fossa (///), comprising the greater part of the medial surface of the scapula, from the fossa in which the teres major muscle has origin (/V). The surface presents several nutrient foramina usually directed toward the glenoid angle. The lateral surface (dorsal surface of human anatomy) (Fig. 44) is divided by the spine (g) into two portions. The portion of the scapula craniad of the spine and the cranial surface of the spine bound the supraspinous fossa (fossa supra- spinata) (/), while the surface caudad of the spine and the caudal portion of the spine bound the infraspinous fossa (fossa infraspinata) (//). The spine (g) begins as a triangular elevated area in the middle of the vertebral margin and runs toward the glenoid angle. It rises gradually for about two-fifths of its length and then the margin becomes broader and the spine remains of the same height to its glenoid end. There is a rough thickening, the tuberosity (Z) of the spine, situated on its free border about 64 THE SKELETON OF THE CAT. midway between the tip of the acromion and the vertebral end of the spine. The spine is inclined toward the glenoid margin so as to form an angle of about 60 degrees with the caudal half of the lateral surface. At the base of the acromion process (7) the margin of the spine presents a flat triangular projection, the metacromion (;), directed toward the glenoid border. The acromion (7) continues in the direction of the spine. It is thicker than the spine, smooth and rounded on both its surfaces and both its borders, and its apex is connected by fibrous tissue to the clavicle. The coracoid border (4) presents a slight rounded notch, the incisura scapule or suprascapular notch (Z), just dorsad of the glenoid angle, and at its ventral end bears the coracoid process (7) which is directed ventromediad. The glenoid angle (d) is the only one requiring special mention. Between the root of the coracoid process and the glenoid cavity it presents a tubercle, the supraglenoidal or bicipital tubercle (£), for the tendon of origin of the biceps muscle. The glenoid angle is separated by a contracted neck. from the rest of the bone. Between this angle and the inner margin of the acromion there is left a deep notch, the great scapular notch. Clavicle. Clavicula (Fig. 46).—The clavicle in the cat is greatly reduced. It is a slender curved rod b= a of bone imbedded in the muscles of the Fic. 46.—Cravicre. Shoulder and connected by fibrous tissue to a, medial end; 4, lat- the apex of the acromion process. The eral enh lateral end (0) is slightly enlarged. Humerus (Figs.. 47 and 48).—The humerus forms the sup- port of the upper arm and articulates by its proximal end with the scapula at the glenoid cavity, and by its distal end with the radius and ulna, the bones of the lower arm. It is a nearly cylindrical bone with enlarged ends, and is so curved that its dorsal and ventral borders are hooked at the opposite ends so that it has the form of an Italic f. The proximal end of the bone bears on its dorsomedial portion a thickening, the head of the humerus (a), which bears THORACIC LIMBS, 65 a smooth ovoid articular facet by which the bone articulates with the glenoid cavity of the scapula. The head is not separated from the body by a distinct anatomical neck as in the human humerus. Along the lateral border of the proximal end of the shaft is a high rough ridge semicircular in side view, the great tuberosity (4). It gives attachment to muscles and is marked Fic. 47.—HUMERUS, VENTRAL SIDE. Fic. 48.—Humervs, MEDIAL SIDE, a, head; 4, greater tuberosity; ¢, lesser tuberosity; ¢@, bicipital groove; ¢, pectoral ridge; /, deltoid ridge; g, rough area for insertion of latissimus dorsi and teres major; A, nutrient foramen; 2, capitulum; 7, trochlea; 4, coronoid fossa; 72, radial fossa; 7, medial epicondyle; 9, lateral epicondyle; 7, supracondyloid foramen. on its dorsal border by a deep depression for the tendon of the infraspinatus muscle. On the medial margin of the proximal end closely associated with the head is a smaller elevation, the lesser tuberosity (c), also for muscular attachment. Between the greater and lesser tuberosities on the ventral 66 THE SKELETON OF THE CAT. surface is seen a broad groove, the sulcus intertubercularis or bicipital groove (@), which passes distad onto the surface of the shaft. In the natural state it is converted into a canal by overlying tendons and lodges the tendon of the biceps muscle. The shaft is nearly cylindrical at its middle, but its dorso- ventral diameter is slightly greater than its mediolateral diameter. Its proximal end is flattened mediolaterad, while its distal end is flattened dorsoventrad. From the ventral margin of the greater tuberosity a ridge, the pectoral ridge (¢), is continued onto the surface of the shaft, and from the dorsal margin another ridge, the deltoid ridge (/), passes distad and ventrad so as to meet the pectoral ridge near the middle of the ventral surface of the bone. On the medial margin of the bone near the junction of the first and second fourths is a roughened area (g) for the attachment of the ten- dons of the latissimus dorsi and teres major muscles, and on the same surface near the junction of the second and last thirds is a nutrient foramen (Z). The distal end ‘of the bone presents a smooth saddle-shaped articular surface, which, in well-marked bones, is divided, when seen from the ventral surface, by a slight nearly median ridge into two unequal portions, lateral and medial (¢ and 7). The lateral half is rounded and is called the capitulum (z). It is broader ventrad than dorsad, and is not continued onto the dorsal surface of the bone. It is for articulation with the proximal end of the radius. The medial half of the surface, the trochlea (7), is concave and passes directly into the capitular surface laterad, but is limited mediad by a sharp ridge. It is continued onto the dorsal surface of the bone, where it is limited also laterad by a ridge. It articulates with the semilunar notch of the ulna. Proximad of the trochlea the dorsal surface presents a deep fossa, the olecranon fossa, which receives the olecranon of the ulna when the arm is straightened. On the ventral surface (Fig. 47) are two shallower fosse separated by a longitudinal ridge. The one over the trochlea receives the coronoid process: of the ulna when the arm is bent, and is called thence the coronoid fossa (/). The one over the capitulum, the radial THORACIC LIMBS. 67 fossa (7), receives a triangular facet on the proximal end of the radius at the same time. Between the radial and coronoid fossze on one side and the olecranon fossa on the other is only a thin plate of bone. On the medial surface of the distal end is a considerable roughened elevation, the medial epicondyle (z) (epitrochlea). It gives origin to flexor muscles and to the ulnar collateral ligaments of the elbow-joint. Opposite the medial epicondyle over the capitulum is the lateral epicondyle (0) for the origin of extensor muscles of the forearm and of the radial collateral ligaments of the elbow-joint. From the lateral epicondyle a ridge, the lateral supracondyloid ridge (f), con- tinues proximad, curving onto the dorsal surface of the bone and ending about opposite the junction of the deltoid and pectoral ridges. Proximad of the medial epicondyle the bone is pierced near its medial margin by an oblique oval foramen, the supracondy- loid foramen (¢). Radius (/, Figs. 49 and 50).—In the usual position the radius lies with its proximal end on the lateral side of the arm, articulating with the capitulum of the humerus. The proximal end is thus laterad of the proximal end of the ulna. _ Its distal end, however, lies on the medial side of the distal end of the ulna, so that the radius in the natural position crosses ventrad of the ulna. The radius is a curved bone slightly flattened dorsoven- trally, with enlarged ends. It may be described as consisting of a shaft and of a proximal and a distal end. Its proximal end presents on the ventral surface a tuberosity, the bicipital tuberosity (c), for the insertion of the tendon of the biceps muscle. Proximad of this the bone is contracted to form a neck (4) which is surmounted by a head (a). The head has on its proximal surface a depressed oval facet by which it articulates with the capitulum, and on its ulnar border a long narrow facet, the articular circumference (7), for articulation with the radial notch of the ulna; also a triangular facet (e), which fits into the radial fossa of the humerus. The shaft is convex dorsad and concave ventrad. The distal end is somewhat pyramidal. From its medial or radial 68 THE SKELETON OF THE CAT. side a wedge-shaped process, the styloid process (/), extends distad. The distal surface of the end together with the lateral surface of the styloid process form a concave articular cavity (g) which fits against the scapholunar bone. . ee Fic. 49.—Rapius AND ULNA, Dorso- Fic. 50.—RapDIUS AND ULNA, VENTRO- LATERAL VIEW. MEDIAL VIEW. JZ, radius; 7/7, ulna. a, head of radius; 4, neck; ¢, bicipital tuberosity; 4, articular circumference; ¢, facet for radial fossa of humerus; /, styloid process of radius; g, facet for articulation of scapholunar bone; 4, semilunar (or great sigmoid) notch of ulna; 2, coronoid process; 7, olecranon; &, area for insertion of brachialis and clavobrachial muscles; /, rough area for attachment of interosseous membrane; m, styloid process of ulna. . The dorsal surface of the distal end is marked by longi- tudinal grooves for tendons, and its lateral or ulnar surface bears a concave facet for articulation with the ulna. Ulna (//7, Figs. 49 and 50).—The ulna is a long slender THORACIC LIMBS. 69 bone, flattened mediolaterad. It is enlarged at its proximal end and becomes gradually smaller toward the distal end. The proximal end is marked ventrally by a deep excava- tion, the semilunar notch, or great sigmoid cavity (2). By the saddle-shaped articular surface of the semilunar notch it articulates with the trochlea. This articular surface is divided into two parts by a transverse non-articular area. The distal boundary of the semilunar notch is a blunt process, the coro- noid process (2), which bears on its lateral surface a concave facet, the radial notch, for the head of the radius. The portion of the bone proximad of the semilunar notch is called the olecranon (7). It fits into the olecranon fossa of the humerus when the arm is straightened, and is rough at its end for the insertion of tendons. The body of the ulna becomes triangular distad. The distal end is slightly larger than the shaft just proximad of it, and bears on its radioventral side a hemispherical head for articulation with the radius. Distad of the head the bone con- tinues as the flattened styloid process (7), which projects distad from its dorsolateral side and is smooth on the medial side of its apex, for articulation with the cuneiform bone of the wrist. Carpus (Fig. 51).—The carpus (wrist) consists of seven bones arranged in two rows, three in the proximal row and four in*the distal row. Beginning on the medial side of the hand (thumb or radial side), the first bone in the proximal row is the scapholunar (a) (equal to the scaphoid or navicular and lunar of the human hand). It articulates with the radius. The next is the cuneiform (4), articulating with the styloid process of the ulna, and the next, which is attached to the cuneiform and projects freely ventrad, is the pisiform (c). In the distal row the bone on the radial side is the trapezium (d); the next is the trapezoid (¢), the next the os magnum (/), and the last the unciform (g). The distal row articulates with the metacarpals or bones of the palm of the hand (1-5). In the kitten the scapholunar is represented by three bones, the scaphoid or navicular, on the radial side, the lunare, be- tween the scaphoid and the cuneiform, and a centrale, which lies distad of the other two. 7° THE SKELETON OF THE CAT. _ Scapholunar Bone. Os scapholunaris (Fig. 51, a).—The scapholunar is a quadrangular bone with the ventroradial angle produced into a blunt process.. Its proximal surface is smooth and articulates with the distal end of the radius. The distal end is marked by oblique ridges and articulates with the unci- form, os magnum, trapezoid, and trapezium. The ulnar surface articulates with the cuneiform, and the dorsal surface of the ventroradial process with the radial sesamoid. Cuneiform Bone. (Os triguetrum BNA) (Fig. 51, 6).— The cuneiform bone has the form of a flattened pyramid. Its base articulates with the unciform, its proximoulnar surface with the pisiform except at its dorsal margin, where it articulates with the styloid process of the ulna. On its proximoradial sur- face is a smooth facet for articulation with the scapholunar. Pistform Bone. Os pistforme (Fig. 51, c).—The pisiform bone is about twice as long as broad, with enlarged ends. Its dorsal end articu- lates with the cuneiform, and on its proximal surface, separated from the above by a smooth ridge, is a &mooth facet for articulation with the styloid process of the ulna. Unciform Bone. (Os hamatum BNA) (Fig. 51, g).—The unciform is a wedge-shaped bone with the apex Fic. 51.—Carpus, MeEta- : / : CARPUS, AND PuALANcEs, of the wedge directed proximad, and nee GEE smooth for articulation with the a, scapholunar bone; 4, cuneiform; ¢, pisiform; d, trape- scapholunar. By a part of its ulnar zium; ¢, trapezoid; /, os mag- surface it articulates with the cunei- num; g, unciform; 4, radial : : : sesamoid ; 7, proximal phalanges; form, and by its radial surface with the J, second phalanges; #, distal 45 macnum. Its distal end articulates phalanges; I, 2, 3, 4, 5, meta. : carpals in order from the radial with the fourth and fifth metacarpals. es Os magnum. (Os capitatum BNA) (Fig. 51, f).—The os magnum may be described as an THORACIC LIMBS. 71 oblong plate bearing on its proximal surface a semicircular ridge which crosses it diagonally. The proximal end of the bone articulates with the scapholunar. Its distal end articulates with the third metacarpal except near its ventroulnar angle, where it articulates with the fourth metacarpal. Its ulnar sur- face articulates with the unciform. Its radial border articulates with the trapezoid, the third metacarpal, and, by two facets, with the second metacarpal. Trapezord. (Os multangulum minus BNA) (Fig. 51, e).— The trapezoid is somewhat wedge-shaped, with the apex of the wedge pointing ventrad. Its proximal side articulates with the scapholunar, its distal side with the second metacarpal, its ulnar side with the os magnum, and its radial side with the trapezium. Trapezium. (Os multangulunt majus BNA.) (Fig. 51, @). —The trapezium has the form of a triangular prism curved into a semicircle. The convex face looks proximad and articulates by its ventral half with the scapholunar. The ulnar surface articulates with the second metacarpal dorsally, and ventrally with the trapezoid. Its radial surface articulates with the first metacarpal. Bones of the Hand or Manus (Fig. 51, 1-5).—The Meta- carpals. Metacarpus.—The metacarpals are the five bones of the palm of the hand; they are numbered from one to five, beginning with the thumb. They are cylindical elongated bones with enlarged ends. The distal end is called the head, and the proximal end the base. Each head bears a hemispherical articular facet which is marked over its ventral half by a prominent smooth ridge. The surface dorsad of the ridge articulates with the proximal head of a phalanx. The ridge and the surface at its sides are for a pair of sesamoid bones. The first metacarpal (1) is the shortest. Its head is oblique, and it articulates by the ulnar half of its proximal surface with the trapezium (d); by the radial half with the radial sesa- moid (). The second metacarpal (2) is marked on the proximal part of its dorsal surface by an oblique groove passing from the radial side distad to the ulnar side. The base articulates with the trapezoid (e). The ulnar surface of the proximal end 72 THE SKELETON OF THE CAT. articulates with the os magnum (/) and third metacarpal, while the radial surface articulates with the trapezium (d). The third metacarpal (3) is the longest, and its base is rhomboidal with a projecting dorsoradial angle separated by a groove from the rhomboid surface. The proximal end articu- lates with the os magnum (/) and second metacarpal; the radial surface of the proximal end with the second, and the ulnar surface with the fourth, metacarpal. The fourth metacarpal (4) has a base similar in form to that of the third, and when placed in position with the fifth the two form a hemispherical facet which articulates with the unciform (g) and os magnum (/). The fourth metacarpal articulates by its radial side with the third, and by its ulnar side with the fifth. The fifth metacarpal (5) articulates by its proximal end with the unciform (g), and by the radial side of its proximal end with the fourth metacarpal. Digits (Fig. 51).—The first digit of the hand is called the pollex (thumb), the second the index, the third the medius, the fourth the annularis, the fifth the minimus. The first digit has two phalanges, each of the others three phalanges. Phalanges (Fig. 51, 2, 7, 2).—The phalanges of the proxi- mal row (2) are elongated, flattened dorsoventrally and curved so as to be longitudinally convex dorsad. All have thickened ends. The proximal end is notched, and its proximal surface looks dorsad and is concave for the head of the metacarpal. The distal end is pulley-shaped, and the pulley surface extends farther on to the ventral than on to the dorsal surface, and serves for articulation with the middle phalanx. The phalanges of the middle row (/) are like those of the proximal row, but shorter. The proximal surface is triangular and marked by a median facetted ridge. The whole surface is smooth and adapted to the distal end of the phalanx of the first row. The distal end is transversely elongated, so as to be cylindrical, and projects more toward the ulnar than toward the radial side. The distal phalanx (&) articulates with this: cylinder so that when it is fully extended it lies on the ulnar side of the middle phalanx. THORACIC LIMBS. 73 The distal phalanx (4) has the form of a quadrangular prism. It is excavated on its proximal surface for articulation with the middle phalanx. Its distal surface presents dorsad a deep excavation from the bottom of which arises a compressed plate of bone having the form of a bird's beak. The depression receives the base of a claw, and the beak-like projection sup- ports the claw. Sesamoid Bones of the Hand. Ossa sesamoidea.—The hand contains, in addition to those already described, eleven small bones that are developed in tendons. One of these, the radial sesamoid (Fig. 51, 4), is closely applied to the radial end of the scapholunar bone. It is developed in the tendon of the extensor brevis pollicis muscle. The other ten occur in pairs as small flattened curved bones on the ventral side of the joint between each metacarpal and the phalanx with which it articulates. JOINTS AND LIGAMENTS OF THE THORACIC LIMBS. The shoulder-joint is an arthrodial or ball-and-socket joint. The bones entering into its formation are the scapula and the ‘*humerus. The capsular ligament or articular capsule is very ample and allows for extended movement of the humerus. It is attached to the edge of the glenoid fossa of the scapula and passing distad covers the head of the humerus and is inserted at the line of junction of the shaft and the epiphysis which forms the head of the bone. On the lateral side of the ventral sur- face of the humerus the attachment continues distad about two centimeters along the lateral edge of the bicipital groove. On the medial side the insertion passes over the proximal end of the lesser tuberosity. A strong transverse band passes from the greater tuberosity to the lesser tuberosity and bridges the bicipital groove, converting it into a canal. The lateral and medial parts of the capsule are strengthened by thicker bands of fibres, the more prominent medial one of which passes from the coracoid process of the scapula to the lesser tuberosity. To the capsule are closely united parts of the supraspinatus, 74 THE SKELETON OF THE CAT. infraspinatus, coracobrachialis, and subscapularis muscles. A synovial membrane lines the capsule within and forms a sheath around the biceps tendon, so that the latter does not actually enter the synovial capsule. The elbow-joint (Figs. 52 and 53) is a ginglymus or hinge-joint. The bones which enter into it are the humerus, radius, and ulna. The capsule of the joint forms a sac, with the following attachments to the bones: (1) To the humerus it is attached at the proximal edge of the coronoid and radial fosse; to the sides of the capitulum and trochlea distad of the two epicon- dyles, and to the distal edge of the olecranon fossa. (2) To the ulna it is attached at the edges of the radial and semilunar Fic. 52.—-LIGAMENTS OF ELBOW- Fic. 53.—ELBow-JOINT, LATERAL JOINT, MEpIAL SIDE. VIEW. Fig. 52.—1, humerus; 2, ulna; 3, radius. @ and 4, the two medial collateral ligaments. Fig. 53.—1, humerus; 2, radius; 3, ulna. «, dorsal collateral ligament; 4, ven- tral collateral ligament; ¢, annular ligament. notches; (3) to the radius around the articular facet, two or three centimeters distad of the border. Many of the muscles of this region are closely attached to the capsule. Closely connected with the capsule of the joint are the collateral ligaments. The two medial collateral ligaments (Fig. 52) arise from the medial epicondyle. One (4) passes distad and laterad to the interval between the radius and ulna; here it divides, one branch going to the head of the radius, while the other is attached to the lateral surface of the ulna at the edge of the semilunar notch. The second medial ligament (a) lies dorsad of the first; it passes to the medial surface of the ulna, at the distal edge of the semilunar notch. THORACIC LIMBS. 75 The two collateral ligaments on the lateral side (Fig. 53) arise from the lateral epicondyle. The ventral one (4) passes almost directly distad and is inserted into the lateral surface of the proximal end of the radius about one centimeter from the articular surface; its inner surface is partly united to the annu- lar ligament (c) of the radius. The dorsal one (a) is attached to the lateral border of the semilunar notch of the ulna. Articulations of Radius and Ulna.—The proximal radio- ulnar articulation (Fig. 53) is by a pivot-joint or trochoid. The two bones are held in place by the annular ligament (Fig. 53, ¢). This is attached on the lateral side to the dorsal border of the radial notch of the ulna, passes around the head of the radius, receiving some ligamentous fibres which come from the lateral epicondyle, and is attached to the coronoid process of the ulna. The annular ligament is closely united with the capsule of the joint. The radius and ulna are united for about their middle third by the thin interosseous membrane, which fills the interosseous space between their adjacent edges. The Wrist.— At the wrist or carpus there are in reality three joints, the first between the radius and ulna proximad and the first row of carpals distad, the second between the two rows of carpal bones, the third between the distal row of carpals and the metacarpals. The first two are movable joints; the third is not. Each of these three joints has a capsule, and the bones entering into the joints are interconnected by numer- ous ligaments. These ligaments are named by combining the names of the two bones which they interconnect. Ligaments which interconnect bones of the same row in the carpus are sometimes distinguished as interosseous ligaments, as con- trasted with intercarpal ligaments, which connect together bones of different rows. According to their position the liga- ments may also be distinguished as dorsal, ventral, and lateral. Detailed descriptions and figures of all these ligaments are given by Strauss-Durckheim. Metacarpals.—The joint between the carpals and meta- carpals has been described. At the distal end of the meta- carpals the articulations with the phalanges have each a 76 THE SKELETON OF THE CAT capsule. The joint is further strengthened by a double lateral ligament on each side. The two sesamoid bones at each joint are interconnected by a strong transverse ligament, and each is connected with the head of the metacarpal and the base of the first phalanx by a lateral ligament. Phalanges.—Between the phalanges the joints possess cap- sules, and each has a radial and an ulnar lateral ligament. VI. BONES OF THE PELVIC EXTREMITIES. Innominate Bones. Ossa innominata. (Os coxe BNA) (Figs. 54 and 55).—The two innominate bones articulate with the sacrum and extend thence caudoventrad and finally turn mediad and unite in the middle line, forming the symphy- sis pubis. They thus form an arch, the pelvic arch, pelvic girdle or pelvis, which is closed dorsad by the sacrum. In the middle of the lateral surface of each bone is a hemispherical depression, the acetabulum (Fig. 55, @), which receives the head of the femur. In the kitten each innominate bone is composed of three principal parts united by. sutures (Fig. 54). From the sacrum to the acetabulum is a’single bar, the ilium (J/). Weck ee Innomr. Caudad of the acetabulum are two bars. NATE Bone oF Kir- The dorsal one of these is the ischium (//), ae oo and the ventral one is the pubis (///). The /, ilium; Z/, ischium; ischium enters into the formation of the ane a re acetabulum (a), but the pubis does not. ulum; 4, obturator fora- The two bones, however, are in contact at ne the ventral edge of the acetabulum. .From this point they diverge, but unite with one another again near the middle line and thus enclose an oval foramen, the obtura- tor foramen (4). Wedged between the ilium, ischium, and pubis at their point of junction and helping to form the ace- tabulum is a small irregular bone, the acetabular bone (/1’). In the adult cat these four parts are united into a single bone which is nevertheless usually described, ignoring the acetabular PELVIC LIMBS. 77 piece, as made up of ilium (Fig. 55, /), ischium (//), and pubis (///). The ilium (/) is somewhat contracted at the middle and broader at its ends. One end enters into the acetabulum (Fig. 55, @) and forms about one-fifth the articular surface. This end is also the thickest part of the bone. The lateral surface of the ilium is concave for the attachment of muscles. The me- dial surface is smooth over its acetabular half and rough over its sacral half. The rough portion is marked at its junction with the smooth portion by the ear-shaped auricular impression by which the bone articulates directly with the sacrum. The caudal half of that part of the medial surface craniad of the auricular impression gives attachment to the ilio-sacral ligaments which bind the ilium to the sacrum. The dorsal border is straight at its cranial end and Fic. 55.—INNOMINATE BONE OF concave and rounded at its caudal - aoe Cat, VENTROLATERAL end. Between the two portions /, ilium; Z/, ischium; Z7/, pubis. and at the dorsal edge of the @, crest of the ilium; 4, posterior in- i . ferior spine; ¢, great sciatic notch; d, auricular surface is a protuberance acetabulum; @’, incisura acetabuli: ¢, ; ‘ spine of the ischium; /, lesser sciatic eee onding ad the posterior rakes g tuberosity & the ischium; inferior spine (Fig. 55, 4) of the 2, ramus of the ischium; 2, ramus of 1s P the pubis; 7, obturator foramen; &. human ilium. The concavity of pubic tubercle; ¢. iliopectineal line: the dorsal border (c) corresponds t, ilio-pectineal eminence; #2, anterior to the great sciatic notch of the *“P°mO" Process. human ilium. At its caudal end is the short spine of the ischium (c), whichis nota part oftheilium. The ventral border of the ilium is broad caudad, becoming narrower craniad. The g lateral margin of the ventral border is continued to a tuberosit g$ y at the edge of the acetabulum; its medial margin is called the WAN mw WAN 78 THE SKELETON OF THE CAT. iliopectineal line (/) and extends on the pubis to the symphysts. An eminence, the iliopectineal eminence (/’), on the iliopec- tineal line, lies opposite to the acetabulum at about the junction of the ilium and pubis. The cranial end of the bone is thick- ened, forming the crest (@) of the ilium. At the junction of the crest with the ventral border is a projection, the anterior superior process (#7) of human anatomy. The pubis (///) (including the acetabular bone) enters into the formation of the acetabulum (@) constituting about one- sixth the circumference, but less than one-sixth its area. It may be described as a flat, curved bone, contracted at the middle and expanded at the ends. The dorsal end enters into the acetabulum; the ventral end unites with the opposite bone at the symphysis pubis and sends caudad a projection, the ramus (2) of the pubis, which unites with the ramus of the opposite bone to form about two-thirds of the entire symphysis. At the sides of the symphysis a slightly marked angle projects craniad from each of the pubic bones; these two together con- stitute the pubic tubercle (4), for the origin of the rectus abdominis muscle. The surfaces of the ramus are smooth. One of its borders is concave and enters into the formation of the obturator foramen (7). Another of its borders is the ilio- pectineal line (7). Its third border is rough for the symphysis. The ischium (//) has the form of a triangular prism con- tracted at the middle. Its cranial end forms nearly two-thirds of the acetabulum. Its caudal end bears dorsad a rough thickening, the tuberosity of the ischium (g). From the caudal half of the ventral border of the bone a sickle-shaped process, the ramus (/) of the ischium, curves medioventrad and then craniad and joins the ramus of the pubis. Its medial border is rough and enters into the symphysis, forming the caudal one-third. The lateral angle of the bone is rounded. Its dorsal angle is marked near the cranial end by the spine (c) of the ischium. The concavity between this spine and the tuberosity corresponds to the lesser sciatic notch (/) of human anatomy. The acetabulum (d@) is cup-shaped. The ventral one-sixth of its border is deficient and a broad groove extends from the PELVIC LIMBS. 79 defi¢iency to the bottom of the cup. The deficiency, incisura acetabuli, or acetabular notch (a’), is closed naturally by a ligament, and the groove gives origin to the ligament (liga- mentum teres) which attaches the head of the femur. Femur (Fig. 56).—The femur is the proximal bone of the posterior extremity. It consists of enlarged proximal and distal ends connected by a nearly cylin- drical shaft. The proximal end presents on its medial side a hemispherical head (2) which fits into the acetabulum. It is supported by a neck (4) which is con- tracted near the head and expanded dorso- ventrally where it joins the remainder of the bone. The medial surface of the head presents near its ventral border a depres- sion (¢) for the insertion of the round liga- ment of the femur. Ventrad the articular surface of the head extends as an acute projection onto the shaft, so that the whole articular surface appears somewhat pear- shaped. On the lateral side of the proxi- mal end opposite the head is a projecting mass, the great trochanter (@), forming the end of the shaft. On the medial side of the great trochanter at its junction with the neck is a deep fossa, the trochanteric ( fossa or digital fossa (e) for the insertion Ss of muscles. From the ventral surface of P!% so TEFL Femur, the great trochanter a ridge, the imter- u, head; 4, neck; ¢, de- trochanteric line (7), is continued distad, ee Cee ending in a pyramidal projection, the 4, trochanteric fossa; /, lesser trochanter (g), which serves for jwcrrochanteric line; gi lesser trochanter; 4, linea the insertion of muscles. A second ridge aspera; 7, medial condyle; : : J, lateral condyle; 4, inter- is continued to the lesser trochanter from ‘ondyloid fossa; '7, lateral the neck. A slight but well-marked ¢Picondyle. ridge, the spiral ridge or line, runs round two sides of the neck parallel to the second ridge. ’ 80 THE SKELETON OF THE CAT. The shaft is nearly straight and cylindrical. A roughfline is continued along its ventral surface from the lesser trochanter, and a similar line along its lateral surface from the greater trochanter; these unite ventrad to form the linea aspera (2). On its ventral surface is a nutrient foramen, directed proximad. The shaft gradually widens distad and ends in two condyles (¢@ and 7) which are continuous dorsad but separated ventrad by a deep notch, the intercondyloid fossa (2). The distal surface of the shaft and condyles is articular. This articular surface is larger on the lateral condyle (7). The part of the articular surface on the end of the shaft (patellar surface) is for the patella; that part of it on the condyles and separated by the notch is for the tibia. On the lateral surface of the lateral condyle is a slight prominence, the lateral epicondyle (/), and on the medial sur- face of the medial condyle is another prominence, the medial epicondyle; both are for the attachment of ligaments. Patella (Fig. 1, ~).—The patella is a small flat bone with a pear-shaped outline, having its apex distad. It lies against the articular surface at the lower end of the shaft of the femur. It thus covers the knee-joint. The inner surface is smooth and convex from side to side, but concave in a proximodistal line. It fits against the lower end of the femur. Its outer surface is rough and concave. It is a sesamoid bone inserted in the tendon of the quadriceps femoris muscle. Three other sesamoid bones are found in the region of the knee (see Fig. 61, p. 89). Two are in the tendons of the gastrocnemius muscle, proximad of the two condyles of the femur. The third is in the tendon of the popliteus muscle, just laterad of the lateral condyle of the femur. Tibia (/, Fig. 57).—The tibia is the longer of the two bones of the leg between the knee and the ankle, and is the longest bone of the body. It has a triangular shaft and enlarged proximal and distal ends. The proximal end is curved ventrad and projects into two prominences, the tuberosities, on either side. Each tuberosity bears on its proximal end an articular facet for the condyles of the femur; these are known respectively as the lateral and PELVIC LIMBS. medial condyles (a and 4) of the tibia. The condyles are oval, convex dorsoventrad, and concave from side to side. The two con- dyles are separated at the middle of their contiguous margins by a bicuspid projection, the spine of the tibia (c). They are con- tinuous dorsad, but separated ventrad by a deep notch between the tuberosities, the popliteal notch. On the distal side of the lateral condyle is an elongated tacet for the proximal end of the fibula. The shaft is triangular, smallest at about its middle and enlarged at both ends. It presents dorsal, medial, and lateral borders, and medial, lateral, and ventral surfaces. The lateral surface is concave proximad. The medial surface is convex. The two are continuous at the distal end. At their proximal ends the border separating them is raised into a prominent ridge, the crest (d) of the tibia, the proximal end of which contributes to increase the proximal sur- face of the bone, and presents an oblong tubercle (¢) for the insertion of the liga- mentum patellz (ligament of the quadri- ceps femoris muscle). The ventral surface is concave proximad where it abuts upon the tuberosities. Its proximal half is crossed by two rough parallel lines, the distal one of which crosses in a spiral course from the lateral to the medial border; near its begin- ning is a nutrient foramen. The distal end extends farther distad on its medial side. The extension is the medial malleolus (7). The malleolus presents two grooves on its medial surface for the tendons of muscles. On the lateral side of the distal 81 Fic. 57.—TIBIA AND Fisuta oF Lerr Lec, DorsaL View. /, tibia; Z7, fibula. a, medial condyle of the tibia; 4, lateral con- dyle; ¢, spine of the tibia; d@, crest of the tibia; e¢, tubercle for at- tachment of the patellar ligament; /, medial malleolus; g, projection of dorsal surface of the tibia; 2, head of fibula; z, lateral malleolus. end is an oblique triangular facet for the distal end of the 82 THE SKELETON OF THE CAT. fibula. The ventral surface of the distal end presents an ob- lique border which passes from the apex of the malleolus proximolaterad. The dorsal surface extends into a V-shaped projection (g) between the malleolus and the fibular facet. The distal end presents an oblique ridge running from the apex of the V-shaped extension of the dorsal surface to near the base of the medial malleolus. The ridge and the con- cavities on either side of it, the medial one of which is deeper, fit against the proximal trochlear surface of the astragalus. Fibula (//, Fig. 57).—The fibula lies at the lateral side of the tibia in the shank. It is a slender triangular-bone with enlarged proximal and distal ends. The proximal end or head (4)is flattened. It bears a facet on its proximomedial surface for articulation with the tibia, and is longitudinally grooved on the outer surface. The shaft has a very sharp medial border. This border is turned toward the tibia and gives attachment to the interosseous membrane, which runs between the tibia and fibula. The distal end is expanded to form the lateral malleolus (7). This bears a facet on the proximal portion of its medial surface near its dorsal margin, for the tibia, and distad of this is a second facet for the astragalus. The ventral and lateral sur- faces are grooved for tendons. Tarsus (Fig. 58).—The tarsus consists of seven bones. The longest of these, lying on the lateral side of the foot and forming the support of the heel, is the calcaneus or os calcis (a). It articulates distad with a bone, the cuboid (c), which bears the fourth and fifth metatarsals. Lying between the calcaneus and the tibia is the astragalus or talus (4), the distal end of which. articulates with the boat-shaped navicular or scaphoid (d). The scaphoid bears on its distal surface the three cunei- form bones, lateral (¢), medial (g), and intermediate, bearing the rudiment of the first metatarsal and the second and third metatarsals. Astragalus. (Talus BNA) (Fig. 58, 6).—The astragalus may be divided into body, neck, and head. The body is marked on its proximal surface by a deep pulley-like groove for the articulation with the distal end of the tibia, and on its META- AND PHALANGES oF LeFT Foot, VENTRAL View. Fic. TARSUS, 58. — Tarsus, a, calcaneus; 4. astragalus, ¢, cuboid; d, scaphoid; ¢, lat- eral cuneiform; g, medial cuneiform; #, peroneal groove, for the tendon of the peroneus longus muscle; 7, proximal phalanges; 7, second row of phalanges; 4, distal phalanges; Z, sesamoid bones, 1, rudi- mentary first (medial) meta- tarsal; 2, 3, 4, 5) the other metatarsals. PELVIC LIMBS. 83 lateral and medial surfaces by curved facets for articulation with the malleoli of the tibia and fibula. | This entire surface for articulation with the bones of the leg is known as the trochlea. The lower surface is marked by two facets separated by a groove; these are for articulation with corresponding facets on the calcaneus. Distally the bone contracts to form the neck and enlarges at the end, forming the head, which is smooth on its distal surface for articulation with the navicular or sca- phoid. Calcaneus (Fig. 58, @, and Fig. 59). —The calcaneus (os calcis) is the largest bone of the foot and forms the heel. It is two or three times as long as broad and has six surfaces: dorsal, ventral, medial, lateral, proximal, and distal. The proximal one-half of the dorsal surface (Fig. 59) is smooth, while the distal half is broadened and bears two facets which are separated by a groove. These articulate with the corresponding facets on the astragalus. The medial Fic. 59. —CaALCANEUS OF RIGHT Foot, DorsaL VIEW. a, distal facet for cuboid; 4, proximal end with groove for tendon of Achilles; ¢, sustentacu- lum tali; ¢, peroneal tubercle. 84 THE SKELETON OF THE CAT. facet is borne on a projection of the bone, the sustentaculum tali (c). Distad of the facets the surface is rough. The ventral surface is smooth. The proximal end (4) is grooved for the tendon of Achilles. The lateral surface is smooth and marked by a grooved tubercle, the peroneal tubercle (2), near the distal end. The medial surface is marked by part of the articular facet for the astragalus, and also by the grooved sustentaculum tali. The distal end (a) articulates with the cuboid. Cubord. Os cuboideum (Fig. 58, c).—The cuboid has somewhat the form of a cube and articulates by its proximal end with the calcaneus (a), and by its distal end with the fourth and fifth metatarsals. Its medial surface articulates with the scaphoid (@) and lateral cuneiform (¢). The ventral surface is marked near its distal end by an oblique ridge, distad of which is a deep groove, the peroneal groove (%), for the tendon of the peroneus longus muscle. Scaphoid. (Os naviculare pedis BNA) (Fig. 58, @).— The scaphoid is a boat-shaped bone. Its proximal surface is marked by a concave facet for the head of the astragalus (0), and its distal surface has three facets for the lateral (¢), ‘inter- mediate and medial (g) cuneiform bones. At the junction of the ventral with the medial surface is a prominent tubercle. The lateral surface bears two linear facets for articulation with the calcaneus (a) and cuboid (c). Lateral Cunetform. LEctocunetform. Os cunetforme ter- tium BNA (Fig. 58, ¢).—The lateral cuneiform is a wedge- shaped bone with a hooked process extending from the ventral sharp angle of the bone. It articulates by its proximal end with the scaphoid (¢@), and by its digtal end with the third metatarsal. The medial surface bears near its distal end two facets for the second metatarsal, and on its proximal end a facet for the intermediate cuneiform. The caudal surface has a facet on its proximal end for the cuboid (c). Intermediate Cuneiform. Mesocunetform. Os cunetforme secundum BNA.—The intermediate cuneiform is small and wedge-shaped, with the base of the wedge dorsad. It lies between the lateral cuneiform and the medial cuneiform, articu- lates by its proximal end with the middle facet of the scaphoid, PELVIC LIMBS. 85 and bears on its distal end the second metatarsal. It is not visible in ventral view. Medial Cunetform. Entocunetform. Os cuneiforme primum BNA (Fig. 58, ¢).—The medial cuneiform lies on the medial side of the foot. It is a flat triangular bone about twice as long as broad, and broader at its proximal end than at the distal end. It bears on its distal end the rudimentary first meta- tarsal. The proximal end is oblique and bears a concave facet for the lateral distal facet of the scaphoid (¢). The lateral surface has a concave facet at its proximal end for the inter- mediate cuneiform, while the distal portion is applied against the medial surface of the second metatarsal. Bones of the Foot or Pes (Fig. 58).—Metatarsals. Meta- tarsus (Fig. 58, 1-5).—The metatarsals are five in number. They bear a close resemblance to the metacarpals, but they may be distinguished by their bases. The first metacarpal (1) is rudimentary and conical. Its base has a facet for the distal end of the medial cuneiform (g), while the outer surface fits into a depression on the inner sur- face of the base of the second metatarsal. The second (2). The proximal surface of the base is tri- angular, corresponding to the distal end of the intermediate cuneiform. The medial surface is marked by two concavities, one along the proximal border for the distal end of the medial cuneiform, and one distad of this for the first metatarsal. The lateral surface bears on the proximal margin an oblique tri- angular facet dorsad and a similar facet ventrad, both for the lateral cuneiform (¢). Distad of these facets is a rough ridge. The third (3). The proximal end of its base is a triangular facet with the apex directed ventrad and the sides excavated. It is for the distal end of the lateral cuneiform (¢). Its medial surface presents a depression which receives the ridge of the second metatarsal. On the lateral surface a short distance distad of the proximal border is a triangular concave facet, and near the proximal border ventrad a second concave facet. Both are for the fourth metatarsal. The fourth (4). The proximal end is convex, notched medially and facetted for the cuboid (¢). Its medial surface 86 THE SKELETON OF THE CAT. bears dorsad, a short distance from its proximal end, a smooth tubercle, and ventrad a small convex facet. Both articulate with facets on the lateral surface of the third metatarsal. The lateral surface has a sinuous facet along its dorsal border, and ventrad of this a depression. There is a second facet along the ventral border. Both facets are for the fifth metatarsal, and the depression is for ligaments. The ji/th (5) has its base flattened and expanded so as to be wedge-shaped, with the apex of the wedge directed proxi- mad. Its dorsal end extends into atubercle. It thus presents only lateral and medial surfaces. The medial surface shows two tubercles, one distad of the other. The distal tubercle and the distal half of the proximal tubercle are facetted and fit into the sinuous facet on the fourth metatarsal. A narrow facet on the ventral border of the surface articulates with the facet on the ventral border of the lateral surface of the fourth metatarsal. The proximal half of the distal tubercle is facetted for the cuboid (c). The lateral surface is smooth, non-articular, and obliquely grooved. Phalanges (Fig. 58, 2, 7, &).—There are three phalanges in each of the four digits, and these are almost identical with those described for the manus. Sesamoid Bones. Ossa sesamoidea (Fig. 58, /).—The sesamoid bones are found at the joints between the metatarsals and phalanges, and are in all respects like those of the manus. JOINTS AND LIGAMENTS OF THE PELVIC LIMBS. Ligaments of the Pelvis.—The ilium and sacrum are articu- lated at the auricular facet of the ilium and the corresponding rough surface ofthe sacrum. The joint is an amphiarthrosis, per- mitting very little movement. Ze oe ——— SSH ee Fic. 70.—MUuSCLE3 ON THE DorRSAL SIDE OF THE VERTEBRAL COLUMN IN THE LUMBAR, SACRAL, AND CAuU- DAL REGIONS. Both sheets of the lumbodorsal fascia have been removed, the deep layer (c) being cut where it passes into the longis- simus dorsi. 1, crest of ilium; 4-7, tips of spinous processes of the fourth to seventh lumbar vertebre, / //, tips of spinous processes of first two sacral ver- tebree. a, 4, M. longissimi dorsi (a, medial portion; 4, lateral portion; 6’, portion taking origin from the lumbo- dorsal fascia); ¢, cut edge of deep layer of lumbodorsal fascia; @, M. multifidus spine; ¢, M. extensor caudz medialis; J, M. extensor caudz lateralis, g, M. abductor caudz externus, of the vertebral arches. In the thoracic region (Fig. 69, 7’) 128 THE MUSCLES most of the fibres.are inserted in separate bundles by small tendons on the transverse processes of the vertebre, while some of the medial fibres unite with tendinous strands which become attached to the laminz and articular processes of the vertebra. At the region of the eighth or ninth thoracic verte- bra the spinalis dorsi (Fig. 69, g) begins to be separated off on the medial side, the separation becoming complete only some distance farther craniad; the longissimus dorsi then con- tinues into the cervical region (/’’). Bundles of fibres become attached in the manner above described to transverse processes of all the thoracic vertebra. In the cervical region (/’’) the muscle spreads out and becomes thinner, and bundles of fibres become attached to the transverse ‘processes of the cervical vertebre as far forward as the second. In the more cranial portion of its extent the muscle receives fibres having origin on the articular processes and laminz of the cervical and a few of the more cranial thoracic vertebre. The portion of the muscle which is inserted on the cervical transverse processes (/”) is sometimes distinguished as the longissimus cervicis; it is not well separated from the rest of the muscle in the cat. The longissimus capitis (Fig. 69, ¢; Fig. 73, g) is to be considered a differentiated cranial portion of this muscle. Relations.—Outer surface with the: following, beginning with the caudal end: the sartorius (Fig. 68, 7), the latissimus dorsi (Fig. 68, 7), the lumbodorsal fascia (Fig. 68, y), the serratus posterior inferior (Fig. 73, ~) and superior (Fig. 73, 2), and the levator scapule (Fig. 73, 2). Lateral margin with the abdominal muscles, the iliocostal (Fig. 69, 4), and the levator scapule (Fig. 73, %). Medial side with the multi- fidus spine (Fig. 70, @), the spinous processes of the thoracic vertebrae, the spinalis dorsi (Fig. 69, g), the complexus (Fig. 69, 4), the biventer cervicis (Fig. 69, 2), and the longissimus capitis (Fig. 69, ¢). Action.—Extends the vertebral column. M. iliocostalis (Fig. 69, %).—This is a muscle about 14 to 2 centimeters wide, lying on the dorsal portion of the ribs, laterad of the longissimus dorsi (/’). It is composed of many MUSCLES OF THE BODY. 129 partly separated bundles, each with an oblique tendon. The muscle begins at the last or next to the last rib, where it is connected with the longissimus by a rather small bundle of fibres. The rest of the muscle-fibres take origin in bundles from the lateral surface of the ribs, at about the angles, or from thin tendons connecting the angles, of the ribs; they pass obliquely craniad and are inserted, usually by tendons, on the lateral surface of the third or fourth rib craniad of the one on which the given bundle has origin. The insertions on any given rib lie ventrad of the origins on the same rib, In the cat this muscle is confined to the thoracic region. Relations.—Outer surface with the serratus posterior inferior (Fig. 73, 2) and superior (Fig. 73, 7), and the levator scapulz (Fig. 73, #). Inner surface with the dorsal surface of the ribs, the external intercostals (Fig. 69, 2), and craniad with the levatores costarum. Medial edge in contact with the longissi- mus dorsi (Fig. 69, 7’). Action. —Draws the ribs together. M. spinalis dorsi (Fig. 69, g).—A muscle interconnecting the spinous processes of vertebrze some distance apart, in the thoracic and cervical regions. It lies on the medial side of the longissimus dorsi (/’). Origin by strong tendons from the tips of the spinous pro- cesses of the tenth to the thirteenth thoracic vertebrae. These tendons represent the cranial portion of the deep layer of the lumbodorsal fascia, and give origin also to many fibres of the longissimus dorsi, so that the two muscles are completely united at the origin of the spinalis. They become separated at about the level of the sixth thoracic vertebra, the spinalis form- ing a strong separate bundle passing into the neck region close against the sides of the spinous processes. The insertion is by fleshy bundles into the sides of the spinous processes of the first nine or ten thoracic vertebrz and of the cervical vertebra as far forward as the second. Some of the fibres of this muscle pass craniad into the biventer cervicis (Fig. 69, a). Relations. —Outer surface with the tendons of the serratus posterior inferior (Fig. 73, 2) and serratus posterior superior (Fig. 73, 7), and with the splenius (Fig. 73, 4), biventer 130 THE MUSCLES. cervicis (Fig. 69, a), and complexus (Fig. 69, 4). Lateral and ventral surface with the longissimus dorsi (/’); medial surface with the spinous processes and the multifidus spine. Action. —Extensor of the vertebral column. M. multifidus spinz.—This consists of bundles of fibres which have origin on the transverse processes or neighboring parts, pass craniodorsad across one or more vertebre, and are inserted into the spinous processes of vertebre lying some dis- tance craniad of the origin. They lie deeper than the muscles previously described. The muscle is most strongly developed in the lumbar region (Fig. 70, @), where it forms a thick inter- woven mass in which it is difficult to distinguish separate bundles. The fibres in this region have origin on the accessory or mammillary processes and usually pass over more than one vertebra between origin and insertion; their insertions reach the dorsal ends of the spinous processes, so that part of the muscle lies immediately beneath the lumbar fascia. In other regions the multifidus is covered by other muscles. In the thoracic region the separate bands are more distinct, and usually pass in their course over but one intervening vertebra. In the cervical region the bands are interconnected, forming a fairly distinct single muscle, which is described separately below as the semispinalis cervicis (Fig. 71, c). The portion of this muscle attached to the head (semispinalis capitis) forms the biventer cervicis (Fig. 69, a) and complexus (6). Caudad this muscle passes onto the tail as the extensor caude medialis (Fig. 70, e). Relations.—Outer and lateral surface in the lumbar region with the longissimus dorsi (Fig. 69, 7) and the lumbodorsal fascia (Fig. 68, y); in the thoracic region with the longissimus dorsi (Fig. 69, 7’) and spinalis dorsi (g). Inner surface with the arches, articular processes, and spinous processes of the vertebra. Action.—Extends the back when the muscles of both sides work together. Turns the vertebral column obliquely side- ways when one set acts alone. The deepest layer of the multifidus forms what is sometimes MUSCLES OF THE BODY. 131 distinguished as the Mm. rotatores; no separate layer of this sort is to be made out in the cat. Mm. interspinales.—Muscle-bundles passing from the spinous process of one vertebra to that of the vertebra imme- diately craniad or caudad of it. They are best developed in the lumbar region. Mm. intertransversarii.— Muscle-fibres interconnecting the transverse processes. In the lumbar region the inter- transversarii mediales connect the accessory and mammillary processes; the intertransversarii laterales lying between the transverse processes. In other regions only one set of the intertransversarii is to be distinguished. (0) Dorsal Muscles of the Cervical Region.—The clavotra- pezius (Fig. 68, @) and occipitoscapularis (Fig. 73, @) have been described in connection with the muscles of the shoulder. The remaining muscles of this region may be considered as differentiations of the general vertebral musculature (M. ex- tensor dorsi communis). M. splenius (Fig. 73, .)—A large sheet of muscle cover- ing the dorsal part of the side of the neck, beneath the trapezii. Origin from the whole cervical ligament and from the fascia covering the deeper muscles along a line which extends from the first thoracic spinous process caudolaterad for about two centimeters. Jnsertion by a thin tendon into the whole lambdoidal ridge. Laterad the tendon may be fused with that of the longissimus capitis (Fig. 73, ¢). Relations.—Outer surface with the sternomastoid (Fig. 68, c), occipitoscapularis (Fig. 73, @), clavotrapezius (Fig. 68, @), rhomboideus, tendon of the serratus posterior superior (Fig. 73, 2), and the levator scapule (Fig. 73, 7). Lateral edge closely united with the longissimus capitis (Fig. 73, g). Inner surface with the longissimus capitis, complexus (Fig. 69, 0), and biventer cervicis (Fig. 69, a). Action.—Lateral flexor of the head. The two together elevate the head. M. longissimus capitis (trachelomastoideus) (Fig. 73, g; Fig. 69, e).—This is a slender muscle lying close against the 132 THE MUSCLES. lateral border of the splenius (Fig. 73, 4), and sometimes fused with the splenius at its craniad end.. It is a cranial continua- tion of the longissimus dorsi (Fig. 69, 7’). Origin by five slips which are attached by strong tendons to the anterior articular processes of the last four cervical vertebre. The tendons are common to this muscle and the complexus. The five slips unite to form a flat belly which has its Insertion by a strong rounded tendon into the mastoid process of the temporal bone. The tendon may be closely united to that of the splenius. Relations.—Lateral surface with the sternomastoid (Fig. 68, c), the levator scapule (Fig. 73, 2), and longissimus dorsi (Fig. 69, 7’). Medial surface with the splenius (Fig. 73, 4) (to which it is partly united), the complexus (Fig. 69, 4), and the longus atlantis (Fig. 69, @). Action. —Lateral flexor of the head. M. biventer cervicis (Fig. 69, a) (medial portion of ‘M. semispinalis cervicis et capitis).—The biventer cervicis is a flat muscle which lies beneath the splenius (Fig. 73, 4), next the median line of the neck, with its fibres longitudinal. Origin in three or four slips from the surface of the three or four aponeurotic arches which take origin from the tips of the spinous processes of the last cervical and the first three thoracic vertebrze and pass laterad and caudad to the anterior processes of the second, third, fourth, and fifth thoracic verte- bre. These arches are deviated from their straight course by four aponeurotic bands which pass.from them obliquely caudad and dorsad to the sides of the spinous processes.of the vertebrz into which the arches are inserted. The arches form the ‘beginning of the sheet of fascia which passes outside of the longitudinal supraspinous muscles, and the anchoring bands form the beginning of a similar sheet which passes within the longitudinal supraspinous muscles. An additional slip may take origin from the cervical ligament between the last cervical and the first thoracic vertebrae. The fibres form a flat band divided by two or three oblique tendinous intersections. It adheres closely to the cervical supraspinous ligament. MUSCLES OF THE BODY. 133 Insertion by a strong tendon into the medial part of the lambdoidal crest. Relations.—Outer surface with the splenius (Fig. 73, 4) and at the caudal end with the longissimus dorsi (Fig. 69, 7”). Inner surface with the spinalis dorsi (Fig. 69, g), the semi- spinalis cervicis (Fig. 71, c), and the rectus capitis posterior major (Fig. 71, a). Medial edge with the muscle of the oppo- site side; lateral edge with the complexus (Fig. 69, 4). Action.—Raises the snout. M. complexus (Fig. 69, 4) (lateral portion of M. semi- spinalis cervicis et capitis).—The complexus is closely asso- ciated with the biventer cervicis (a) and lies on its lateral side beneath the splenius (Fig. 73, 4). Origin by tendinous bands from the anterior articular processes of the last five or six cervical and the first one, two, or three thoracic vertebrae. The same bands give origin externally to the fibres of the longissimus capitis (Fig. 69, ¢), and internally to those of deeper muscles of the neck. The six or more muscular slips continued from these tendons unite to form a flat band, the Insertion of which is by a flat tendon into the medial third of the lambdoidal crest some distance ventrad of the free edge of the crest. Near the insertion the lateral border of the muscle is connected by an aponeurotic band to the lateral border of the transverse process of the atlas. Relations. —Outer surface at the dorsal border with the biventer cervicis (Fig. 69, 2); at the middle with the splenius (Fig. 73, 4); at the ventral border with the longissimus capitis (Fig. 69, ¢) and the longissimus dorsi (Fig. 69, f). Inner surface with the cervical portion of the spinalis dorsi, with the semispinalis cervicis (Fig. 71, c), the obliquus capitis inferior (Fig. 71, 4), the rectus capitis posterior major (Fig. 71, a), and the obliquus superior (Fig. 71, ¢). Action.—Raises the head. M. spinalis dorsi extends into the cervical region; it has been described. M. semispinalis cervicis (Fig. 71, c).—This represents that portion of the multifidus spine which extends into the 134 THE. MUSCLES. cervical region. It is not composed of distinct bundles, like the multifidus of the thoracic region, but all the fibres are united into a fairly well-defined muscle. Origin from the articular processes of the last five cervical vertebre. dnsertion into the spinous processes of the cervical vertebre up to the second, the largest part of the muscle being inserted into the caudal end of the spine of the atlas. Relations.—Outer surface with the spinalis dorsi (Fig. 69, g) and the complexus (Fig. 69, 4). Inner surface with the vertebra. Action.—Extends the neck. M. longissimus dorsi extends into the cervical region, where it is often distinguished as the longissimus cervicis (Fig. 69, 7”). It has been described. M. longus atlantis (Fig. 71, f; Fig. 69, d).—This repre- sents a differentiated portion of the longissimus dorsi. Origin from the transverse process and the side of the vertebral arch of the third cervical vertebra. Insertion into the caudolateral angle of the wing of the atlas. Relations.—Dorsal surface with the complexus (Fig. 69, 4), the longissimus capitis (Fig. 69, ¢), and the obliquus inferior (Fig. 71, 4). Ventral surface with the scalenus (Fig. 71, g), longissimus dorsi (Fig. 69, 7”), and levator scapula (Fig. 71, h). Action. —Extends the neck and turns the head sideways. M. rectus capitis posterior major (Fig. 71, @). Origin.—The whole length of the spinous process (or crest) of the axis, or its caudal part only. It is united by a raphe to the opposite muscle. The muscle passes craniad and laterad to its Insertion into an area ventrad of the medial part of the lambdoidal crest beneath the insertion of the complexus (Fig. 69, 4) and the biventer cervicis (Fig. 69, a). Relations.—Dorsal surface with the biventer cervicis (Fig. 69, a). Ventral surface with the rectus capitis posterior medius (Fig. 71, @) and the obliquus capitis inferior. MUSCLES OF THE BODY. 135 Action.—Raises the snout. M. rectus capitis posterior medius (Fig. 71, 2): (This is in man a part of the rectus capitis posterior major.)—It lies beneath the rectus capitis posterior major (Fig. 71, a). Fic. 71.—-Drrp MuscLEs OF THE NECK, AFTER THE REMOVAL OF MM. BIVENTER CERVICIS AND COMPLEXUS. a, M. rectus capitis posterior major; 4, M. obliquus capitis inferior; ¢, M. semi- spinalis cervicis; d, M. rectus capitis posterior medius;¢, M. obliquus capitis superior; J; M. longus atlantis; g, M. scalenus (part of cervical portion); 2, cut end of M. levator scapule. Origin from the cranial end of the axial spine. It forms a triangular prismatic mass which passes craniad and has its (nsertion into an elongated area on the occipital bone, ventrad of the median half of the lambdoidal crest. Relations.—Dorsal surface with the rectus capitis posterior major (Fig. 71, @). Ventral surface with the atlas and the rectus capitis posterior minor. lction.—Assists the rectus capitis posterior major. M. rectus capitis posterior minor.—A small triangular muscle beneath the rectus capitis posterior medius (Fig. 71, 2). Origin by the apex of the triangle from the cranial border of the dorsal arch ot the atlas for about two millimeters laterad of the median line. The muscle passes over the ligament which connects the atlas to the occiput and adheres to it. Insertion into an elongated area on the occipital bone, \ 136 THE MUSCLES. ventrad of the insertion of the rectus capitis posterior medius for about five millimeters next to the median line. Relations.—Dorsal surface with the rectus capitis posterior medius. Ventral surface with the posterior atlanto-occipital membrane. Action.—Assists the rectus capitis posterior major. M. obliquus inferior (Fig. 71, 4). Origin from the whole lateral surface of the spine of the axis. The parallel fibres form a thick mass which passes laterad and craniad. fnsertion into the dorsal surface of the transverse process of the atlas along a narrow area near its lateral margin. Relations. —Outer surface with the rectus capitis posterior major (Fig. 71, @), the complexus (Fig. 69, 4), and the obliquus superior (Fig. 71, ¢). Inner surface with the axis. Action.—Rotates the head. M. obliquus capitis superior (Fig. 71, ¢; Fig. 72, e).— This is a triangular muscle passing from the outer border of the atlas laterad of the recti capitis posteriores to the occiput. Origin from the lateral border of the transverse process of the atlas on its ventral margin. The fibres pass craniad and diverge. Insertion into the caudal side of the mastoid process of the temporal bone and into a line parallel with the lambdoidal ridge and ventrad' of it, from the mastoid process to within one centimeter of the median line. Relations.—Outer surface with the splenius (Fig. 73, 4), complexus (Fig. 69, 4), and longissimus capitis (Fig. 73, g). Inner surface with the obliquus inferior (Fig. 71, 4), the wing of the atlas, and the rectus lateralis (Fig. 72, d). Ventral border with the cleidomastoid (Fig. 73, @) and one head of the levator scapule ventralis (Fig. 72, c’). Action.—Flexes the head laterally. Mm. interspinales and intertransversarii are found in the neck region also; they are described with the muscles of the back. C. MUSCLES OF THE TAIL.—M. extensor caude medialis (Fig. 70, ¢).—This is a continuation caudad of the multifidus MUSCLES OF THE BODY. 137 spine (Fig. 70, d); it lies next to the dorsal median line, the muscles of right and left side touching one another in the middle line. Origin by numerous fleshy bundles from the spinous processes of the sacral and first caudal vertebre. The fibres pass caudad and are inserted by tendons into the articular processes and the dorsal surface of the caudal vertebre. Action. Extends (raises) the tail. M. extensor caude lateralis (Fig. 70, /).—This is a con- tinuation caudad of the medial portion of the longissimus dorsi (Fig. 70, a); it lies just laterad of the extensor caude medialis (Fig. 70, é). Origin in many fleshy bundles from the articular processes of the sacral vertebra, and the transverse processes of the caudal vertebrae. The fibres curve dorsocaudad and are inserted by many long slender tendons on the dorsal surfaces of the caudal vertebra. The muscle grows continually smaller as it passes caudad. Action.— Raises the tail. M. abductor caude (coccygis) externus (Fig. 68, w; Fig. 70, ¢).—A rounded muscle on the lateral surface of the cranial part of the tail. Origin from the medial side of the dorsal border of the ilium, and from the dorsal surface of the sacrum. The muscle passes caudad, lying just ventrad of the extensor lateralis, and is znserted into the transverse processes and lateral surfaces of the caudal vertebre, as far back as the eighth or ninth. Action.—Bends the tail sideways. M. abductor caude internus (or M. coccygeus).—A large flat muscle, having origin on the spine of the ischium. The muscle passes dorsomediad, spreading out, and is inserted into the transverse processes of the second to the fourth caudal vertebre. - Relations.—Lateral surface with the caudofemoralis (Fig. 68, s), gluteus maximus, and pyriformis. Medial surface with the iliocaudalis and the flexor caude longus (Fig. 68, +). M. iliocaudalis (Str.-D.) (Fig. 162, 1”, page 398).—This represents a portion of the levator ani of man, and in some 138 THE MUSCLES. specimens is united with that muscle (Fig. 162, 11) in the cat. Origin along the ventral half of the medial surface of the ilium, caudad of the sacrum. The fibres pass caudad and are anserted by a flat tendon into the ventral surface of the caudal vertebrz, from the second or third to about the seventh. Relations.—Lateral surface with the gluteus maximus and abductor caude internus (Fig. 68, w). Medial surface with the levator ani (Fig. 162, 11), with which this muscle may be partly united. Action.—The two muscles together flex the tail. M. flexor caude longus (Fig. 162, 12; Fig. 113, ¢, page 270). Origin on the ventral surface of the last lumbar vertebra, of the sacrum, and of the transverse processes of the caudal vertebre. Caudad the muscle forms long, strong tendons which are zzserted on the ventral surface of the tail. Relations.—Lateral surface with the ilium, the gluteus maximus, the abductor caudz internus, the iliocaudalis, and the skin of the tail. Dorsally it touches in the caudal region the abductor caudz externus (Fig. 68, w), medially the flexor caudze brevis (Fig. 162, 13). Action.—Flexes the tail. M. flexor caude brevis (Fig. 162, 13). Origin on the ventral surface of the caudal vertebrz, from the first to the seventh or eighth. The principal head comes from the first vertebra. The bundles thus formed pass caudad and are inserted each into the ventral surface of a vertebra some distance caudad of the origin. The muscle extends to about the tenth caudal vertebra, and its most caudal parts are closely interconnected with the flexor caudz longus. Relations—Lateral edge with the flexor caude longus. Medial edge in the sacral region with the levator ani (Fig. 162, 11) and the iliocaudalis (Fig. 162, 11’); in the caudal region with the muscle of the opposite side. Action.—Flexes the tail. 2. Muscles on the Ventral Side of the Vertebral Column. A. LUMBAR AND THORACIC REGIONS.—The iliopsoas (Fig. MUSCLES OF THE BODY. 139 162, 8) belongs in this group, but since it moves the leg it is described with the muscles of the pelvic limbs. M. psoas minor (Fig. 162, 9, page 398).—This muscle lies along the ventral surface of the vertebral column, next to the peritoneum, and extends from the thoracic vertebrz to the ilium. Origin usually by five heads, from the caudal border of the centra of the last two (or one) thoracic and first three (or four) lumbar vertebrae. These heads also serve as origin for a part of the iliopsoas, and are closely united at their origin with the quadratus lumborum. They unite to form an, at first, rather large flat muscle, which rapidly becomes smaller caudad, finally forming a slender tendon which is zzserted on the ilio- pectineal line, just craniad of the acetabulum. Relations.—Dorsolateral surface with the quadratus lum- borum and iliopsoas (Fig. 162, 8). Ventral surface with the pleura and diaphragm near the origin; with the peritoneum caudad. Action.—Flexes the back in the lumbar region. : M. quadratus lumborum.—A flat muscle lying on the ventral surface of the transverse processes of the lumbar verte- bre. Craniad it has origin on the ventral surface of the ‘last two thoracic vertebrz, and by a few fibres from the last rib. The muscle passes caudad, lying on the lateral side of the psoas minor (Fig. 162, 9), and becomes attached to each of the transverse processes of the lumbar vertebra. Caudad the muscle passes into a strong flat tendon which is inserted into the anterior inferior spine of the ilium. Relations.—Dorsal surface with the transverse processes and the intertransverse muscles. Ventral and medial surfaces with the psoas minor (Fig. 162, 9) and iliopsoas (Fig. 162, 8). Action.—Bends the vertebral column sideways. _ B. MUSCLES ON THE VENTRAL SIDE OF THE NECK (Fig. 65, page 109).—M. sternomastoideus (Fig. 65, g; Fig. 68, ¢).—The sternomastoid (sternal portion of the human sternocleidomastoid) is a flat band one to three centimeters wide extending from the cranial end of the manubrium and the midventral line craniad of it to the lambdoidal ridge. 140 THE MUSCLES. The origin extends from the cranial end of the manubrium along the midventral line as far as the caudal border of the cricoid cartilage, and is in two parts. The caudal portion arises from the lateral surface of the manubrium along the dorsal half of its cranial end, and from the median raphe for about one centimeter craniad of the manubrium. Its fibres are parallel and tend to diverge into two layers. The cranial portion arises by means of fibres which cover the median line and interdigitate with the fibres of the opposite muscle between the cricoid cartilage and a point a few millimeters craniad of the manubrium. Its caudal border is thus overlaid by the caudal portion. Its. fibres converge and join those of the caudal portion. The muscle passes dorsocraniad and is Inserted by means of a flat tendon into the lateral half of the lambdoidal ridge and into a continuation of the ridge onto the mastoid portion of the temporal bone as far as the mastoid process. The thickest part of the tendon is inserted into the mastoid process. Relations.—Outer surface at the caudal end with the pec- toralis major (Fig. 65, 7); in the middle part with the platysma, the depressor conche (Fig. 64, 6), and with the external jugu- lar vein (Fig. 65, 5), which crosses it obliquely; at the cranial end with the submaxillary (Fig. 65, 2) and parotid (1) glands. Inner surface with the sternohyoid (Fig. 65, ¢), sternothyroid (g), internal jugular vein, longus capitis muscle, the cleido- mastoid (4), levator scapule ventralis (2), a large lymphatic gland ventrad of the ear, and the splenius (Fig. 73, 4). Action.—One muscle turns the head and depresses the snout. Both together depress the snout. M. sternohyoideus (Fig. 65, ¢).—A slender muscle on the midventral line of the neck close to the opposite muscle. Origin from the cranial border of the first costal cartilage. The muscle passes craniad closely united near its caudal end to the sternothyroid (g’). Insertion (Fig. 67, m) into the outer half of the ventral sur- face of the body of the hyoid bone caudad of the origin of the geniohyoid (Fig. 67, 2). Relations.—Outer surface with the sternomastoid (Fig.. MUSCLES OF THE BODY. 14! 65, ¢). Inner surface with the thyrohyoid (Fig. 65, f; Fig. 67, p), the trachea (Fig. 67, 4), and the larynx. Action.—Draws the hyoid caudad. Raises the ribs and sternum when the hyoid is fixed. M. sternothyreoideus (Fig. 65, ¢’).—The sternothyroid lies beneath the sternohyoid and is connected with it at its caudal end. Origin from the first costal cartilage beneath the sterno- hyoid. : Insertion (Fig. 67, 0) into the lateral part of the caudal border of the thyroid cartilage of the larynx. Relations. —Outer surface with the sternohyoid (Fig. 65, ¢) and laterally with the sternomastoid (Fig. 65, ¢). Inner sur- face with the trachea (Fig. 67, 4), and at the lateral edge with the thyroid gland (Fig. 67, 6). Action.—Pulls the larynx caudad. M. scalenus (Fig. 73, 7/’’).—This is a large and com- plex muscle lying on the ventral side of the neck and the lateral surface of the thorax. It might equally well be classified with the muscles of the thorax. It is divisible into a consider- able number of interconnected bundles which are sometimes described as separate muscles. The largest, middle portion (scalenus medius) (/’) takes origin by thin tendons from the sixth, seventh, eighth, and ninth ribs, just dorsad of their junction with the cartilages; these tendons unite near their origins to form a flat band which becomes fleshy at about the fifth rib, passes craniad, and unites just craniad of the first rib with the other parts of the muscle. The dorsal portion (scalenus posterior) (/’’) has origin by a very slender tendon from about the middle of the outer surface of the third or fourth rib; it extends craniad as a narrow band which passes laterad between the heads of the serratus anterior (7) that are attached to the second and third (or third and fourth) ribs, and unites with the other heads. The ventral head (part of scalenus anterior) (/’”) arises by one or two minute tendons from the cartilages of the second and third ribs; they are partly united with the transversus costarum (7). This ventral head passes craniad and unites with the other heads. 142 THE MUSCLES. These three divisions unite just craniad of the first rib with each other and with the cervical portion of the muscle (/): (part of scalenus anterior). This consists of a number of small bundles of fibres which arise from the first rib and the transverse processes of the first thoracic and the last six cervical vertebre. The zzsertzon is onto the transverse processes of all the cervi- cal vertebre, including the axisandatlas. According to Strauss- Durckheim the fibres from any given transverse process are insert- ed into the transverse processes of all the vertebrz craniad of it. The muscle is partly continuous craniad with the longus capitis (¢). The cervical nerves pass out between the bundles of the cervical portion. Relations.—Outer (lateral) surface in the thoracic region with the external oblique (Fig. 68, #), the pectoralis minor (Fig. 65, 0), and in part with the serratus anterior (Fig. 73, 2); in the cervical region with the sternomastoid (Fig. 65, g). Inner (medial) surface with the serratus anterior (Fig. 73, 2), the levator scapula (Fig. 73, 2), the longus atlantis, the trans- verse processes of the cervical vertebrx, and the longus capitis (Fig. 73, @). Action.—Flexes the neck and draws the ribs craniad. M. longus capitis (or rectus capitis anterior major) (Fig. 72, a; Fig. 73, ¢).—This is a long muscle lying on the ventral aspect of the cervical vertebre. With the muscle of the opposite side and the underlying longus colli (Fig. 72, g’) it forms a trough: in which lie the cesophagus, pharynx, and trachea. Origin by five (or six) heads from the ventral margins of the transverse processes: of the cervical vertebre from the second to the sixth inclusive. The heads unite into a common belly, the lateral border of which is united with the levator scapulz ventralis (Fig. 72, c’’) near its insertion. Insertion into the body of the sphenoid bone between the bulla and the middle line. The insertion extends craniad onto the basisphenoid. Relations. —Ventral surface with the sternomastoid (Fig. 65, g) and the large lymphatic gland ventrad of the external MUSCLES OF ear. with the levator scapule ven- tralis (Fig. 72, c-c’). Medial surface with the carotid artery, the trachea, cesophagus, and pharynx. Dorsal edge with the vertebrze, the longus colli (Fig. 72, g’), and the rectus ca- pitis anterior minor (Fig. 72,0). Action.—Lowers the snout. M. rectus capitis anterior minor (Fig. 72, 6).—This is a flat band beneath (dorsad of) the longus capitis (a). Origin from the ventral sur- face of the inferior arch (body) of the atlas (3) for about five millimeters laterad of the mid- dle line. Insertion into a deep depres- sion on the basioccipital caudad of the insertion of the longus capitis (2) and between the caudal end of the bulla (1) and the median line. Relations.—Ventral surface with the longus capitis (qa). Dorsal surface with the anterior (ventral) atlanto-occipital mem- brane (2). Action. — Depresses snout. M. rectus capitis lateralis (Fig. 72, @).—This lies ventrad of the obliquus superior (¢) on the ventral face of the transverse process of the atlas and at first the THE BODY. 143 Lateral surface with the scalenus (Fig.72, 4) and craniad Fic. 72,—MuscLEs ON THE VENTRAL SURFACE OF THE CERVICAL VER- TEBRA. On the left side the longus capitis and one head of the levator scapulz ventralis have been cut, in order to show the rec- tus capitis anterior minor. @, M. longus capitis; 4, M. rectus capitis anterior minor; ¢, M. levator scapulz ventralis (c’, its atlantal head; -", its occipital head); @, M. rectus capitis lateralis; ¢, M. obliquus capitis superior; 7, M. longis- simus capitis; g, M. longus colli (g’, its cervical portion; g”, its thoracic por- tion); 4, part of M. scalenus. 1, bulla tympani; 2, ventral atlanto-occipital membrane; 3, ventral arch of atlas; 4, first rib. appears to be a part of the obliquus superior. 144 THE MUSCLES. Origin from the median half of the ventral surface of the, transverse process of the atlas. The fibres form a cylindrical mass which passes craniad and slightly laterad. /nsertion into the fossa laterad of the condyle of the occipi- tal bone. Relations.—Ventral surface with the digastric (Fig. 65, 6) and the lymphatic gland ventrad of the ear. Dorsal surface with the wing of the atlas. Action.—Flexes the head laterally. M. longus colli (Fig. 65, 2’, g’’).—A long, rather slender muscle lying on the ventral surface of the cervical and first six thoracic vertebrzee. It consists of many separate bundles, and is divisible into a thoracic and a cervical portion. The thoracic portion (g’’) has origin by six heads from the ventral surface of the first six thoracic vertebra. The separate heads join to form a band which passes craniad and is inserted for the most part into the processus costarius of the sixth cervical vertebra; a portion of it joins the cervical division of the muscle. The cervical portion (g’) is a continuation craniad of the thoracic portion. It arises in small bundles from the transverse processes and sides of the ventral surfaces of the centra of the cervical vertebre. These bundles pass craniomediad, so that those from the muscles of opposite sides meet and are inserted on the centra of the vertebre in the middle line, each pair of bundles forming a V opening caudad. The most cranial insertion is into the tubercle on the middle of the ventral sur- face of the ventral arch of the atlas (3). Relations.—Dorsal surface with the centra of the vertebrz. Ventral surface in the thorax with the trachea; in the neck with the cesophagus. Medial edge with the muscle of the opposite side. Lateral margin in the cervical region with the longus capitis (a). Action.—Bends the neck. 3. Muscles of the Thorax.—A. BREAST-MUSCLES (con- necting the arm and thorax) (Fig. 65, page 109). The muscles connecting the arm with the sternum, corre- sponding to the pectoralis muscles of man, fall into a consider- MUSCLES OF THE BODY. 145 able number of not always clearly separated bundles in the cat. We shall distinguish by name four such bundles; these might be, and frequently are, further subdivided. M. pectoantibrachialis (Fig. 65, #).—This is a small flat bundle about one or two centimeters wide, forming the most superficial portion of the pectoralis group. Origin on the lateral surface of the manubrium. The muscle passes laterad onto the arm and is zuserted by a flat tendon into the superficial fascia of the dorsal border of the forearm, near the eblow-joint. The tendon is continuous craniad with the border of the clavobrachial (£), so that a bundle of fibres may pass from this muscle to be inserted with the clavobrachial, or a bundle from the clavobrachial to be inserted with this. The tendon is continuous caudad with that of the epitrochlearis (7). The fascia of insertion may be traced to an attachment into the dorsal border of the ulna. This muscle usually receives near its insertion a slip, sometimes called its caudal division, from the deep layer of the pectoralis major. Relations.—Outer surface with the integument. Inner sur- face with both divisions of the pectoralis major (7) on its medial two-thirds, and with the biceps () and bicipital arch (¢’) in its lateral one-third. The cranial border is closely applied to that of the clavobrachial (£), except at the two ends. Action.—Draws the arm mediad. M. pectoralis major, or ectopectoralis (Fig. 65, /, /').— In this it is usually possible to distinguish a superficial and a deep layer. The superficial (/’) layer is a flat band of fibres one or two centimeters wide. Origin from a raphe in the midventral line, along the cranial half of the manubrium and for five to ten millimeters craniad of it. Insertion (Fig. 81, f).—The pectoral ridge of the middle third of the shaft of the humerus, slightly dorsad of the line of insertion of the deep portion. Relations. — Outer surface with the clavobrachial (Fig. 65, #) and integument, the medial end caudally with the pectoantibrachialis (m), and the distal end with the brachialis 146 THE MUSCLES. (v). Inner surface with the deep portion (/), the fibres of which it crosses obliquely. The deep portion (/) is a flat band of parallel fibres about three times as broad as the superficial portion. Origin.—The ventral surface of the manubrium and of the first three divisions of the sternum, and the median raphe for about one centimeter craniad of the manubrium. It passes directly laterad. Insertion (Fig. 81, ¢) along a line which begins at the infraspinatus fossa of the great tuberosity, and runs parallel to the deltoid ridge until it reaches the pectoral ridge at the junc- tion of the second and third fourths of the humerus and then continues in the direction of the pectoral ridge as far as the junction of the third and fourth fourths of the humerus. Some of its fibres may pass caudad of the biceps and be inserted with the epitrochlearis. Into the part of the line which is parallel to the deltoid ridge the muscle is inserted by a flat tendon; into the remainder of the line it is usually inserted directly by muscle-fibres, though at its caudal end its insertion may again be tendinous. Relations.—Outer surface with the cutaneus maximus, the outer layer of the pectoralis major (Fig. 65, 7’), the pectoanti- brachialis (7), and the clavobrachial (2). Inner surface with the pectoralis minor (0), the proximal end of the humerus, the coracobrachialis (Fig. 77, f), and the supraspinatus (Fig. 77, d) at the insertion of the latter. At the cranial part of its origin it touches the sternomastoid (Fig. 65, ¢) and sternohyoid (Fig. 65, ¢). Action.—Draws the arm mediad and turns the foot forward. M. pectoralis minor, or entopectoralis (Fig. 65, 0).—This is a fan-shaped mass of fibres, flat but thicker than the pec- toralis major. , Origin from the lateral half of the first six divisions of the body of the sternum and sometimes from the xiphoid process. The fibres are divisible into several bundles which vary in extent and distinctness and are sometimes described as separate muscles. They pass craniolaterad and converge so that the line of insertion is about one-half as long as that of the origin. MUSCLES OF THE BODY. 147 Insertion (Fig. 81, @) into the humerus along.a line which forms the ventral border of the bicipital groove at the proximal end of the bone, passes thence onto the pectoral ridge and continues in the direction of the pectoral ridge nearly as far as the middle of the length of the humerus. The cranial and caudal fibres are inserted by means of a thin tendon; the middle fibres directly. The cranial border of the tendon of insertion is continued as a thin tendon to the coracoid process; it is closely united with the insertion of the supraspinatus. Relations.—By its outer surface with the pectoralis major (Fig. 65, 7) over its cranial half; with the cutaneus maximus, latissimus dorsi (Fig. 65, g), and integument over its caudal half. By its inner surface with the xiphihumeralis (Fig. 65, J), rectus abdominis (Fig. 73, £), and a mass of fat in the axilla. The tendon of the xiphihumeralis is also connected with its inner surface near its insertion. Its cranial border is free. Its caudal border is in relation at its medial end with the xiphi- humeralis, at its lateral end with the tendon of the latissimus dorsi (Fig. 65, ¢). Action.—Draws the arm toward the middle line. M. xiphihumeralis (Fig. 65, 7).—A long, thin, narrow muscle which may be considered as part of the pectoralis minor. Origin a median raphe along the xiphoid process or at an angle to the median line on the rectus abdominis muscle. It passes craniad, becoming gradually smaller, and about two centimeters from its insertion ends in a thin tendon. /nsertion.—lIt ends in a flat tendon which in passing is con- nected by a strong fascia with the tendon of the latissimus (Fig. 65, ¢). It passes along the inner surface of the pectoralis minor (0) to be inserted with its cranial fibres near the ventral border of the bicipital groove. Relations.—Outer surface with the cutaneus maximus at its medial end, with the pectoralis minor (¢) at its distal end. Inner surface with the external oblique (Fig. 68, #), the rectus abdominis (Fig. 73, £), and a mass of fat in the axilla. Borders free. Some of the fibres of the cutaneus maximus are attached to its outer surface. 148 THE MUSCLES. Action.—Assists the pectoralis minor. B. MUSCLES OF THE WALL OF THE THORAX.—M. ser- tatus posterior superior (Fig. 73, /).—A thin sheet of muscle and tendon beneath the serratus anterior (2) on the dorsal part of the thorax and neck. Origin by fleshy slips from the outer surfaces of the first nine ribs just ventrad of their angles. The origin may extend as far as the tenth or eleventh ribs. The first slip is usually delicate. The fibres are directed dorsad and craniad and unite to form a continuous sheet. This ends along a longitudinal line opposite the vertebral transverse processes in the aponeuro- sis which covers the longissimus dorsi and other muscles in this region. Its insertion is into. the median dorsal raphe between the axial spinous process and the tenth thoracic spinous process. Relations.—Outer surface with the serratus anterior (7), the latissimus dorsi (Fig. 68, #), and the rhomboideus. Inner surface with the external intercostals (Fig. 73, 2), the iliocos- tal (Fig. 69, 2), the longissimus dorsi (Fig. 69, /), the spinalis dorsi (Fig. 69, g), and the splenius (Fig. 73, 4). Action.—Draws the ribs craniad. M. serratus posterior inferior (Fig. 73, ).—The serratus posterior inferior is a thin muscle lying caudad of the serratus posterior superior (7) and sometimes overlying the caudal end of the latter. . Origin by four or five heads from the last four or five ribs. In some specimens only three heads may be present. The separate bundles pass dorsocaudad and unite to form a contin- uous sheet which ends in a continuation of the aponeurosis of the serratus posterior superior (/). Insertion into the lumbar spinous processes and the inter- vening interspinous ligaments. Relations.—Outer surface with the latissimus dorsi (Fig. 68, #), and at the origins with the intercostales externi (Fig. 73, m). Inner surface with the intercostales interni (Fig. 69, 4) at the origin and with the intercostales externi (Fig. 69, 7), iliocostal (Fig. 69, 4), longissimus dorsi (Fig. 69, 7), and the caudal end of the spinalis dorsi (Fig. 69, g). 149 MUSCLES OF THE BODY. “elosey [estopoquiny ‘¢ ‘snusajut sturmopqe snnbiqqo “yl fe ‘oLayat Jolaysod snyeias “wy {ruzayxe sapeysoosrajzUl “JA ‘we ‘aoradns Jouajsod snjyeues “(7 ‘(uopuay si ‘y) slurmopqe snjoar “W ‘y ‘umiejsoo snsiaasuey) ‘ ‘f ‘(jno) 1owajue snyesias “WH “2 $(qno) eepndeos toyeaat “WwW ‘y ismideo snumsstSuoy yw ‘5 ‘(uonsod yeotaras (f ‘uoisiarp [equaa © f ‘woIstatp yesiop |,, f SUOIsIAIP e[PPiu Cf) snuapeos “TW ‘f isnides sn8uo] ‘yy ‘2 ‘(jno) sneploysemoprap “yw ‘py '(3nd) stjeajuaa zyndeos soyeaay “yy ‘2 ‘sntuayds “yy ‘g +(n9) suendeosofidioso “yl ‘v ‘99 “DIY NI NMOHS SHTOSN SHL GNV AWITYOY AHL JO TVAOWAY UALAV CasodXxa saTOSAW Agog—'EL ‘91g 150 THE MUSCLES. Action.—Assists the serratus posterior superior. M. transversus costarum, or sternocostalis externus (Fig. 73, 7).—This is a thin muscle applied to. the cranial part of the side of the thorax, covering the cranial end of the rectus abdominis (£). Origin by tendon from the side of the sternum between the attachments of the third and sixth ribs. The muscle passes dorsocraniad to its Jnsertion on the first rib and the lateral portion of its costal cartilage. : Relations. —Outer surface with the pectoralis minor (Fig. 65, 0). Inner surface with the scalenus (Fig. 73, /’”), the rectus abdominis (Fig. 73, %), and the intercostales externi (Fig. 73, m). Atits insertion it is united with a portion of the scalenus (Fig. 73, 7’). Action.—Draws the sternum forward. Mm. levatores costarum.— Small muscles having origin on the transverse processes of the thoracic vertebra, passing caudoventrad, and ‘becoming zzserted on the angle of the rib lying immediately caudad of the origin. They are continuous with the external intercostals. Relations.—Outer surface with the longissimus dorsi (Fig. 69, 7), and craniad with the iliocostal (Fig. 69, 2). Inner surface with the internal intercostals (Fig. 69, &). Action.—Pull the ribs dorsocraniad. Mm. intercostales externi (Fig. 73, ; Fig. 69, 7).—The external intercostals are placed in the outer portion of the intercostal spaces. They are composed of bundles of fibres attached by their ends to the adjacent borders of the ribs and having in general the direction of the external oblique muscle, i.e., they pass from their cranial ends caudoventrad. They occupy the intercostal spaces between the true ribs and extend even caudad into the spaces between the false ribs. They are lacking between the ventral ends of the costal cartilages of the first six to eight ribs, so that the internal intercostals (Fig. 69, #) are here exposed. The more caudal external intercos- tals are more nearly craniocaudal in direction. Relations. — Outer surface with obliquus abdominis externus MUSCLES OF THE BODY. 15! (Fig. 68, f), latissimus dorsi (Fig. 68, #), serratus posterior inferior (Fig. 73, 2) and superior (Fig. 73, 7), serratus anterior (Fig. 73, 2), scalenus (Fig. 73, 7), and iliocostal (Fig. 69, 4). Inner surface with the internal intercostals (Fig. 69, £). Actton. —Protractors of the ribs. Mm. intercostales interni (Fig. 69, #).—The internal intercostals are similar to the external intercostals, beneath which they lie. Their fibres pass between the ribs at nearly right angles to those of the external intercostals and have nearly the direction of the fibres of the internal oblique. They occupy all the intercostal spaces from the first to the thirteenth ribs. Relations.—Outer surface with the external intercostals (Fig. 69, z), and ventrad with the scalenus (Fig. 73, /), trans- versus costarum (Fig. 73, 7), and rectus abdominis (Fig. 73, &). Inner surface with the pleura and the transversus thoracis. Action.—Retractors of the ribs. M. transversus thoracis (triangularis sterni; sternocostalis internus).—This represents a thoracic portion of the transversus abdominis. It consists of five or six flat muscular bands lying on the inner surface of the thoracic wall. Origin on the lateral borders of the dorsal face of the sternum, opposite the attachments of the cartilages of the third to the eighth ribs. The six bands thus formed, each about one centimeter wide, pass laterad and are zzserted into the cartilages. of the ribs near their junction with the ribs, and into the fascia which covers the inner surface of the internal intercostals in this region. Relations. —Outer surface with the internal intercostals and the cartilages of the ribs. Inner surface with the pleura. Diaphragma (Fig. 74).—The diaphragm consists of a cen- tral so-called semilunar tendon (ce) and of muscular fibres which pass radially from the body wall to the tendon. It forms a complete oblique partition between the abdominal and thoracic cavities. The dorsal end is farther caudad than the ventral. The central tendon (e) is thin and irregularly crescent- shaped, with the convexity ventrad and the horns of the cres- cent prolonged as two tendinous bands (¢’) which end in two 152 THE MUSCLES. triangular membranous portions (¢) of the diaphragm, one on each side of the spinal column. It is pierced by an opening for the vena cava (/). Fic. 74,—DIAPHRAGM, CAUDAL SURFACE SEEN OBLIQUELY FROM THE RIGHT. a, right crus; 4, left crus; ¢, ¢’, sternocoslal part of diaphragm; d@, @’, membra- nous portions of the diaphragm; ¢, central tendon; e’, prolongations of central ten- don; 7, opening for posterior vena cava; g, cesophagus; %, aorta; 7, M. transversus abdominis. The muscular portion is in two parts: (a) The vertebral portion (a, 4) arises by a single tendon from the ventral surface of the second, third, and fourth lumbar centra. The tendon diverges into two, the right one (a) of which is much stronger, and from each of the two arise muscle-fibres. Each mass of fibres is one of the two crura (sing. crus) ofthe diaphragm. The aorta (/#) enters the abdomen between the crura dorsally. The fibres of each crus diverge to be inserted into the’central tendon and the dorsal continuation of its horn. The two sets of fibres unite ventrad of the opening of the aorta. Between this open- ing and the central tendon is another opening for the cesopha- MUSCLES OF THE BODY. 153 gus (g); this lies entirely in that part of the diaphragm which arises from the right crus (#2). The fibres are again united ventrad of the cesophageal opening. (2) The sternocostal part (c, c’) takes origin from the xiphoid process and the last five ribs, by fleshy bundles which interdigitate with those of the transversus abdominis (7). The fibres converge to the central tendon (¢)., Between the crus of each side and the most dorsal of the costal fibres is the membranous interval (7) mentioned above. 4. Abdominal Muscles. M. obliquus abdominis externus (Fig. 68, 2).—A large, thin sheet of muscle covering the whole abdomen and part of the thorax ventrally. Origin. —(a) From the last nine or ten ribs by means of as many tendons, which are interconnected to form arches that span the slips of the serratus anterior. The muscle-fibres arise from these tendons and from their intervening arches. (2) From the lumbodorsal aponeurosis common to it and the internal oblique. The cranial fibres pass nearly ventrad, the caudal fibres caudad, arid the intervening fibres take an inter- mediate course. The fibres end in a thin aponeurosis of inser- tion along a curved line which passes at first caudad and then laterodorsad. The aponeurosis fibres continue in the direction of the muscle-fibres to the Insertion into the median raphe ventrad of the sternum from the insertion of the seventh costal cartilage to the xiphoid process, into the linea alba from the sternum to the pubic tubercle, and into the turbercle and the cranial border of the pubis. Caudad of the xiphoid process the aponeurosis is closely united to the superficial layer of the internal oblique, where it forms the outer layer of the sheath of the rectus abdominis. Laterad of the pubic tubercle the tendon is perforated by the inguinal canal. In the cat neither the caudal part of the muscle nor its tendon is attached to the ilium, as it is in man and the dog, so that no Poupart’s ligament, or inguinal ligament, is formed. Relations. —Outer surface with the cutaneus maximus, the integument, and near the origin with the latissimus dorsi (Fig. 68, #). Inner surface with the obliquus internus (Fig, 154 THE MUSCLES. 73, 0), the rectus abdominis (Fig. 73, #), the intercostales ex- terni (Fig. 73, #), a small part of the serratus posterior inferior (Fig. 73, 2), and by its dorsal tendon with the longissimus dorsi (Fig. 69, /). Action.—Constrictor of the abdomen. M. obliquus abdominis internus (Fig. 73, 0).—A thin sheet similar to the preceding but of less extent. Its fibres cross those of the external oblique nearly at right angles and lie beneath them. Origin.—(1) Between the fourth and seventh lumbar verte- brze from the lumbar aponeurosis which is common to it and the external oblique. The lumbar aponeurosis takes origin from the lumbar spinous processes and the interspinous ligaments, and is continuous craniad with the aponeurosis of the serratus posterior inferior. Laterad it splits into three sheets, two for the above-named muscles and a third which passes to the vertebral transverse processes and forms the fascia covering the supraspinous muscles of the lumbar region. (2) By a similar. aponeurosis from “the ventral half of the iliac crest. (3) By fleshy fibres from the three crural arches. These are three delicate ligamentous arches which stretch from the crest of the ilium to the pubic spine. The dorsal one gives exit to the iliopsoas muscle, the middle to the femoral vessels, and the ventral to the spermatic cord. In the female the middle and ventral arches may fuse. The pillar between the dorsal and middle arches is attached to the iliopectineal eminence. Jnsertion.—The fibres pass cranioventrad and end along a longitudinal line in a thin aponeurosis of insertion, which is united in the linea alba to those of the external oblique and transversus. At the caudal end of the aponeurosis all its fibres pass outside of the rectus abdominis (Fig. 73, #). At its cranial end the fibres divide into two sheets or lamine, one of which passes outside of the rectus and the other inside. The outer lamina uhites with the aponeurosis of the external oblique, while the inner lamina unites with that of the trans- versus. There is thus formed a sheath for the cranial part of the rectus muscle. Relations. —Outer surface with the obliquus externus (Fig. MUSCLES OF THE BODY. £55 68, ~). Inner surface with the transversus abdominis (Fig. 69, 7), and by its ventral tendon with the rectus. Action.—Compressor of the abdomen. M. transversus abdominis (Fig. 69, /).—A thin sheet covering the whole surface of the abdomen and lying beneath the internal oblique. Its fibres are nearly transverse. Origin. —(1) By fleshy fibres or by a thin aponeurosis from the cartilages of all the false and floating ribs, by interdigitation with the fibres of the diaphragm. (2) From the tips of all the lumbar transverse processes. (3) From the ventral border of the ilium. (4) From the dorsal and middle of the three crural arches, where it may blend partly with the internal oblique. The muscle is continuous craniad with the transversus thoracis muscle. Near the lateral border of the rectus abdominis the muscle ends in a thin aponeurosis of insertion which is con- tinued (its fibres having the direction of the muscle-fibres) to the /nsertion in the linea alba. Relations.—Outer surface with the internal oblique (Fig. 73, 0) and the rectus abdominis (Fig. 73, #), dorsad also with the longissimis dorsi (Fig. 69, f). Inner surface with a thin fascia covering the peritoneum and ventrocaudad with the rectus (Fig. 73, #). The dorsal edge of the muscle touches the iliopsoas and longissimus dorsi; the ventral edge touches the muscle of the opposite side. Action.—Constrictor of the abdomen. M. rectus abdominis (Fig. 73, 4).—A rather thick, flat muscle which lies near the median ventral line separated by the linea alba from its fellow of the opposite side and stretching from the pubis to the first costal cartilage. Opposite the first lumbar vertebra it is approximately four centimeters wide. It narrows at both ends. Origin by a strong tendon from the tubercle of the pubis. The muscle passes craniad at first between the peritoneal fascia and the transversus aponeurosis, then in the sheath formed by the internal and external oblique and the transversus aponeuro- sis. It emerges from the sheath opposite the xiphoid process and passes ventrad of the costal cartilages. Between the third 156 THE MUSCLES. and fourth costal cartilages it ends in a thin tendon which passes beneath the transversus costarum and is Luserted into the first costal cartilage near its middle, into the second costal cartilage near its sternal end, and into the sternum between the first and fourth cartilages. Relations.—Outer surface of the cranial part of the muscle and its tendon with the pectoralis minor (Fig. 68, 0) and the transversus costarum (Fig. 73,7); caudad the muscle is covered by the outer layer of the rectus sheath. Lateral edge with the obliquus externus (Fig. 68, ), obliquus internus (Fig. 73, 0), and transversus abdominis (Fig. 69, 7). Medial edge with the muscle of the opposite side. Inner surface with the internal intercostals (Fig. 69, £) and the rib cartilages; the inner layer of the rectus sheath and the peritoneum. Action.—Retracts the ribs and sternum and compresses the abdomen. , IV. MUSCLES OF THE THORACIC LIMBS. The muscles connecting the thoracic limbs with the rest of the body have been described. 1. Muscles of the Shoulder. A. MUSCLES ON THE LATERAL SURFACE OF THE SHOULDER. M. deltoideus.—The deltoid muscle of the cat is divided into two (or three) portions which are together equivalent to the human deltoid. These are the spinodeltoid, the acro- miodeltoid, and possibly the clavobrachial, which is frequently called clavodeltoid. M. spinodeltoideus (Fig. 75, ¢; Fig. 68, 2).—A rather thick, flat muscle between the scapular spine and the deltoid ridge of the humerus. It forms a chord of the angle between the glenoid border of the scapula and the humerus. Origin by short tendon-fibres from the glenoid border of somewhat more than the middle third of the spine of the scapula (Fig. 76, g), and from a tendinous raphe between the spinotrapezius (Fig. 68, 7), acromiotrapezius (Fig. 68, /), and MUSCLES OF THE THORACIC LIMBS. 157 infraspinatus (Fig. 75, ¢). The origin may pass toward the vertebral border of the scapula onto the infraspinatus muscle (Fig. 75, c). . Lusertion (Fig. 81, #) by a flat tendon upon the deltoid ridge of the humerus, nearly parallel to that of the pectoralis major. Relations.—Outer surface -with the integument and at the insertion with the acromiodeltoideus (Fig. 75, 7). Inner sur- face with the infraspinatus (c), teres minor (Fig. 80, c), caput laterale (Fig. 75, 4%), and caput longum (Fig. 75, g) of the triceps muscle. ‘ Action.—Flexes the humerus and rotates it outward. M. acromiodeltoideus (Fig. 75, /; Fig. 68, g).—A flat muscle which overlies the distal end of the spinodeltoideus (Fig. 75, ¢). It connects the acromion with the humerus. Origin (Fig. 76, d@).—From the glenoid border of the acromion, and sometimes the adjacent metacromion as far as the tip. Lnsertion.—Mostly upon the outer surface of the spinodel- toideus (Fig. 75, ¢). The outer fibres are continued to the bone, especially at the lateral border of the muscle, and are inserted along a line ventrad of the line of insertion of the spinodeltoideus, and extending farther distally (Fig. 81, ¢). Some of the outer fibres pass into the brachialis (Fig. 80, %). Relations.—Outer surface with the integument and the clavobrachial (Fig. 68, ¢). Inner surface with the infraspinatus (Fig. 75, ¢), teres minor (Fig. 80, ¢), spinodeltoid (Fig. 75, ¢), and caput laterale of the triceps (Fig. 75, 4). Action.—Like that of the spinodeltoid. M. clavobrachialis (Fig. 65, 4; Fig. 68, ¢).—A flat, tri- angular muscle on the cranial surface of the shoulder, forming a direct continuation of the clavotrapezius (Fig. 68, @). These two are frequently described as constituting a single muscle, the cephalohumeral or cephalobrachial. (The clavobrachial is frequently given the name clavodeltoid; as its homology with the human clavodeltoid appears doubtful, it seems well to use the’ name clavobrachial, as proposed by Clasen.) Origin. —Its superficial fibres are continuations of the THE MUSCLES. Fic. 75..-MUSCLES ON THE LATERAL SURFACE OF THE ARM. a, M. supraspinatus; 4, part of insertion of M. rhom- boideus; ¢, M. infraspinatus; d, M. teres major; ¢, M. spi- nodeltoideus; 7, M. acromio- deltoideus; g, caput longum of M. triceps brachii; 2, caput laterale of M. triceps brachii; z,M. brachialis; 7, M. biceps; &, M. brachioradialis; 4, M. extensor carpi radialis lon- gus; m, M. extensor com- munis digitorum (’, tendon of same); 2, M. extensor la- teralis digitorum; (#’ tendon 4 of same); o, M. extensor carpi ulnaris (o', tendon of same); 2, M. extensor indicis proprius; ¢, fifth head of M. flexor profundus digitorum; r,m. flexor carpi ulnaris. 1, vertebral border of the scap- ula; 2, spine of the scapula; 3, greater tuberosity of the humerus; 4, olecranon; 5, transverse ligament of the wrist. MUSCLES OF THE THORACIC LIMBS. 159 clavotrapezius (Fig. 68, @); other fibres have origin from the clavicle and from a raphe laterad of the clavicle which is com- mon to this muscle and the clavotrapezius. It passes distad along the cranial surface of the arm, growing narrower as it appreaches the convexity of the elbow. dnsertion.—Eight to ten millimeters from the ulna it joins the brachialis muscle (Fig. 79, 7) to be inserted with it by a flat tendon (Fig. 79, 7; Fig. 87, c) upon a rough area on the medial surface of the ulna just distad of the semilunar notch, and about midway between the dorsal and ventral borders. Relations. — Outer surface with the integument. Inner surface with the pectoralis major (Fig. 65, 7), biceps (Fig. 77, £), lateral head of the triceps (Fig. 75, 4), acromiodeltoid (Fig. 75, f), and brachialis (Fig. 80, 2). Medial border with the pectoantibrachialis (Fig. 65, #). Lateral border free except near the insertion, where it is in relation with the brachialis. Action.—Flexor of the antibrachium. M. supraspinatus (Fig. 75, @) occupies the whole of the supraspinatus fossa of the scapula. It is covered by strong fascia which stretches from the free edge of the spine to the coracoid border of the scapula and to the coracoid half of its vertebral border. Origin (Fig. 76, 4) by fleshy fibres from the whole surface of the supraspinatus fossa, from the above-mentioned fascia, and from the subscapularis (Fig. 77, @) craniad of the coracoid border of the scapula. Insertion (Fig. 83, @).—It passes over the capsule of the shoulder-joint, to which it is closely attached, and is inserted into the free border of the great tuberosity ventrad (or proxi- mad) of the fossa for the infraspinatus (Fig. 83, ¢). Relations.—Outer surface with the spinotrapezius (Fig. 68, 7), acromiotrapezius (Fig. 68, ”), levator scapule ventralis (Fig. 68, f), clavotrapezius (Fig. 68, @), and cleidomastoid (Fig. 65, 2). Inner surface with the scapula. The distal end of the coracoid border is closely related to the pectoralis minor (Fig. 79, f). The glenoid border is related to the origin of the deltoidei. 160 THE MUSCLES. Action. —Extends the humerus after it has been flexed on the scapula. M. infraspinatus (Fig. 75, c).—This fills the infraspinatus fossa, its fibres converging to the insertion on the great tuber- osity of the humerus. Origin (Fig. 76, a).—By fleshy fibres from the whole infra- spinatus fossa, and by a raphe between it and the teres major Fic, 76.—LATERAL SURFACE OF THE SCAPULA, WITH THE AREAS OF ATTACH- MENT OF MUSCLES. «, M. infraspinatus; 4, M, supraspinatus; c, origin of M. biceps; ¢, M. acromio- deltoideus; ¢, M. teres minor: 7, M. levator scapulz ventralis; g, M. spinodeltoideus; h, M. acromiotrapezius; 7, M. rhomboideus; 7, M. teres major; 4-4, line of insertion of M. spinotrapezius. (Fig. 75, @), and sometimes by fibres from the teres minor (Fig. 80, ¢), triceps, spinodeltoideus (Fig. 75, ¢), spinotrapezius . (Fig. 68, 7), and subscapularis (Fig. 77, a). Insertion (Fig. 83, c).—By a flat tendon which passes over the capsule of the joint, into the ventral half of the infraspinatus fossa on the great tuberosity of the humerus. (The dorsal half of the fossa is covered by a synovial bursa.) Relations.—Outer surface with the spinotrapezius (Fig. 68, 7), spinodeltoid (Fig. 68, 7), acromiodeltoid (Fig. 68, g), teres major (Fig. 75, @), and levator scapule ventralis (Fig. MUSCLES OF THE THORACIC LIMBS. 161 68, f). Inner surface with the scapula. Glenoid border with the teres minor (Fig. 80, c), the teres major (Fig. 75, 2), and the long head of the triceps (Fig. 75, g). . Action.—Rotates the humerus outward. M. teres minor (Fig. 80, c).—A small muscle from the glenoid border of the scapula to the proximal end of the humerus. Origin (Fig. 76, ¢) by a sheet of tendinous fibres from the glenoid border of the scapula beginning about one-fifth the length of the border from the glenoid fossa and extending to its middle. It is often attached to the infraspinatus (Fig. 80, 6) and the caput longum of the triceps (Fig. 75, g). Insertion (Fig. 83, @) by a short tendon into the tubercle just distad of the infraspinatus fossa on the great tuberosity of the humerus. Relations.— Outer surface with the spinodeltoideus (Fig. 75, e), acromiodeltoideus (Fig. 75, /), and the infraspinatus (Fig. 80, 6). Inner surface with the lateral (Fig. 75, 4) and long (Fig. 75, ) heads of the triceps and the capsule of the joint. Action.—Assists the infraspinatus to rotate the humerus outward. B. MUSCLES ON THE MEDIAL SURFACE OF THE SHOULDER. (Fig. 77.) M. subscapularis (Fig. 77, @).—A triangular mass from the subscapular fossa to the lesser tuberosity of the humerus. Origin (Fig. 78, a@).—From the whole subscapular fossa except along the fusiform area for the attachment of the levator scapulze and the serratus anterior near the vertebral border, and except over a quadrangular area about one centimeter long near the glenoid angle. The origin is-by fleshy fibres directly from the periosteum except along two or three lines marked by oblique ridges. To these lines are attached tendinous fibres. At the glenoid border the area of origin sometimes occupies part or the whole of the surface of the fossa for the origin of the teres major, so that the teres arises from the fascia on the sur- face of the subscapularis. At the coracoid border some of the fibres may take origin from the adjacent fascia of the supra- spinatus (Fig. 77, @). 162 THE MUSCLES. Insertion (Fig. 82, 6\.—The fibres converge to the glenoid : border, and the insertion is by a strong, flat tendon into the dorsal border of the lesser tuberosity of the humerus. \ Relations. — Lateral ly surface with the scapula and the capsule of the shoulder-joint. Medial surface with the levator scapule (Fig. 73, 2), ser- ratus anterior (Fig. 73, 2), part of the scalenus (Fig. 73, f), the transversus cos- tarum (Fig. 73, 7), and the coracobrachialis (Fig. 77, /). Cranial border with the supraspina- tus (Fig. 77, @). Caudal border Fic. 77..—-MuscLes ON THE MEDIAL SIDE OF THE ARM. M. epitrochlearis, M. clavobrachialis, and the breast-muscles have been removed. u, M. subscapularis; 4, insertion of M. levator scapulze and of M. serratus anterior; c, M. teres major; d, M. supraspinatus; e, M. latissimus dorsi (¢’, cut edge of that part which becomes united with the bicipital arch); 4, M. coracobrachialis; g, M. biceps brachii (the capsule of the joint has been laid open to show its tendon); 4, cut insertions of pectoralis muscles; z, caput longum of M. tri- ceps brachii; 7, long portion of caput mediale of M. triceps brachii; 2, intermediate portion of caput mediale of M. triceps brachii; 4, short por- tion of caput mediale of M. triceps brachii; 7, cut end of M. clavobrachialis; ~, M. brachiora- dialis; 0, M. extensor carpi radialis longus: J, M. extensor carpi radialis brevis; 7, M. pro- nator teres; 7, M. flexor carpi radialis; », M. palmaris longus (s‘, its tendons); ¢, M. flexor carpi ulnaris (¢, ulnar head; 2’, humeral head); 2, third head of M. flexor profundus digitorum; «’, fifth head of M. flexor profundus digitorum; z’’, one of the tendons of M. flexor profundus digitorum; v, M. pronator quadratus; w, M. abductor brevis pollicis; «, ulnar part of M. flexor sublimis digi- torum, I, transverse ligament of the wrist. MUSCLES OF THE THORACIC LIMBS. 163 with the teres major (Fig. 77, ¢) and infraspinatus (Fig. 75, €). Action.—Pulls the humerus inward (mediad). M. teres major (Fig. 75, d; Fig. 77, c).—A thick muscle, triangular in cross-section, lying parallel with the glenoid border of the scapula. Origin (Fig. 76, 7; Fig. 78, 6) from the vertebral one-third of the glenoid border of the scapula, and from fascia covering the subscapularis (Fig. 77, @) and the infraspinatus (Fig. 75, ¢) over a small area near the gleno- vertebral angle of the scapula. It may touch the insertion of the rhomboideus. ps: Insertion (Fig. 82, f) by a AN tendon common to it and the latissimus dorsi (Fig. 79, @’), as already described. Relations. — Outer surface with the caput longum (Fig. 75, g) and the long portion (Fig. 80, 7) of the caput mediale of the triceps, the latissimus dorsi (Fig. 77, e), and the cutaneus maximus. Inner surface with the serratus anterior (Fig. 73, 2), Fic. 78.—MEDIAL SURFACE OF THE the scalenus (Fig. 735 SJ), the SCAPULA WITH THE AREAS OF transversus costarum (Fig. 73,7), ATTACHMENT oF MuscLes. ss : a, M. subscapularis; 4, M. teres major; and the biceps (Fig. 77) &): c, M serratus anterior; d, M. levator Dorsal border with the subscapu- scapule; s M. pera Mi oc- - A : - cipitoscapularis; g, M. biceps; M. laris (Fig. 77> a) and infraspina- coracobrachialis; z, caput longum of M. tus (Fig. 75, c). triceps. Action.—Rotates the humerus inward and flexes it in oppo- sition to the infraspinatus, teres minor, and. the deltoidei. 164 THE MUSCLES 2. Muscles of the Brachium or Upper Arm. M. clavobrachialis and the pectoralis group (Fig. 65, page 109) lie partly in this region; they have been described. M. coracobrachialis (Fig. 77, £; Fig. 79, c).—A very short muscle covering the inner (medial) surface of the capsule of the shoulder-joint. It extends from the coracoid process to the proximal end of the humerus. Origin (Fig. 78, 2).—By a round tendon from the tip of the coracoid process. Insertion (Fig. 82, ¢) usually by fleshy fibres on an area five to eight millimeters long and about half as wide, which lies on the medial side of the humerus parallel with the ridge which runs from the dorsal end of the lesser tuberosity to the shaft and close to it. The proximal end of the area is about one centimeter from the proximal end of the head of the humerus. Relations. —Medial surface with the biceps (Fig. 77, g), pectoralis minor (Fig. 65, 0), and teres major (Fig. 77, ¢). Lateral surface with the capsule of the shoulder-joint. Dorsal border with the subscapularis (Fig. 77, 2) and the long portion of the caput mediale of the triceps (Fig. 77, 7). Action.—Adducts the humerus. The part of the coracobrachialis just described is known as the short head. ¢). nner surtace wi € ¢, M, extensor carpi radius and ulna, and distad with the tendons ulnaris; 7, M. extensor indicis; aot supina- of the two extensores carpi radiales (Fig. tor; . extensor brevis pollicis; i, M. 84, € and /). . pronator teres; 7, M. Action.—Extends and abducts the pol- flexor profundus digi- 1 torum; 4, M. biceps. /€X- MUSCLES OF THE THORACIC LIMBS. 179 B. MUSCLES ON THE RADIAL AND VENTRAL SIDE OF THE FOREARM (flexors and pronators). M. pronator teres (Fig. 77, ¢). Origin (Fig. 82, 2) by a short strong tendon from the extremity of the medial epicondyle of the humerus. Insertion (Fig. 86, 2) by fleshy fibres and short tendinous fibres along the medial border of the radius, at its middle. The radial edge of the muscle is continuous with the strong deep layer of the antibrachial fascia. Relations.—-Outer surface with the superficial fascia. Radial border with the tendon of the biceps (Fig. 79, 7’), with the extensor carpi radialis brevis (Fig. 77, p), and the supinator (Fig. 85, 2). Ulnar border with the flexor carpi radialis (Fig. 77, r) and part of the flexor profundus digitorum (Fig. 77, Ut). Action.—Pronates the hand by rotating the radius. M. flexor carpi radialis (Fig. 77, ~).—A slender fusiform muscle. Origin (Fig. 82, #) from the tip of the medial epicondyle of the humerus. Insertion.—The slender tendon passes through a deep groove between the os magnum and the first metacarpal. The groove is converted into a canal by the overlying tendons and muscles. The tendon is finally inserted into the bases of the second and third metacarpals. Relations.—Outer surface with the pronator teres (Fig. 77, q), the superficial fascia, and the third head of the flexor profundus (#). Radial border with the pronator teres (gq). Ulnar border with the third and fourth heads of the flexor pro- fundus. Inner surface with the ulna proximad and the fifth head of the flexor profundus (z’) distad. Action indicated by the name. M. palmaris longus (Fig. 77, s).—A flat fusiform muscle beneath the fascia on the medial border of the forearm. Origin (Fig. 82, p) bya short flat tendon from the distal part of the medial surface of the medial epicondyle of the humerus. About one centimeter from the wrist the muscle ends in a flat tendon which passes through the transverse ligament and divides on the hand into four or five (or sometimes only three) 180 THE MUSCLES. tendons (Fig. 77, s’) which diverge to the insertions. The ulnar portion of the flexor sublimis digitorum (Fig. 77, +) takes origin from the common tendon before its division. Jnsertion.—Each tendon except the first gives off a branch which spreads out in the trilobed pad inthe palm. The middle two of these may be traced to the integument covering the pad. The tendon is then inserted (Fig. 88, a) near the base of the first phalanx onto the outer surface of the perforated portion of the flexor sublimis tendon (0, 0’) at its side, except that to the thumb, which divides near its distal end into two which are inserted into the sesamoid bones at the base of the first phalanx. The tendons of insertion are closely united to the fibrous pulley- ring at the base of the first phalanx, and each may send a slip to the base of the phalanx at either side of the ring. Relations.—Outer surface with the superficial fascia and one head of the flexor sublimis (Fig. 77, +). Radial border with the flexor carpi radialis. Ulnar border with the flexor carpi ulnaris and a part of the flexor profundus digitorum. Inner surface with the flexor carpi radialis (7), the flexor carpi ulnaris (2), the flexor profundus digitorum (z), and the radial head of the flexor sublimis digitorum. Action.—Flexor of the first phalanx of each of the digits. M. flexor carpi ulnaris (Fig. 77, ¢, 7’). Origin. —There are two heads. The first or humeral head (¢’) takes origin in common with the second part of the flexor profundus from the median surface of the distal end of the humerus just distad of the medial epicondyle (Fig. 82, g). The second or ulnar head (¢) takes origin by fleshy fibres from the lateral surface of the olecranon and from the dorsal border of the ulna from the olecranon to a point distad of the semilunar notch (Fig 87, /). The two heads join proximad of the middle of the forearm. The muscle passes obliquely across the ven- tral surface of the forearm to its Insertion by fleshy and tendinous fibres into the proximal surface of the pisiform bone. Relations. —Outer surface with the integument and the palmaris longus (Fig. 77, s). Inner surface and ulnar border with the flexor profundus digitorum. MUSCLES OF THE THORACIC LIMBS. 181 Action indicated by the name. M. flexor sublimis digitorum (or perforatus).—-This muscle is in two parts, which are given a common name only because of the similar structure and insertions of their tendons. The ulnar part (Fig. 77, x) is a conical muscle taking origin from the outer surface of the tendon and muscle of the palmaris longus and from the adjacent ligament. It gives rise to two or three tendons (Fig. 88, 4) which arise from distinct slips of the muscle; these pass to the ulnar two or three digits: That passing to the fourth or fifth digit receives an accessory slip from a small mass of fibres attached to the transverse liga- ment on the radial side of the palmaris tendon. The radial part is a small flat triangular muscle which takes origin from the outer surface of the tendon formed by the junction of the tendons of the first and second parts of the flexor profundus. It divides into two slips, each giving rise to a tendon. These tendons (Fig. 88, 4') pass to the second and third digits. That to the third digit may divide into two, one of which goes to the fourth digit. Each of the four tendons (Fig. 88, 4 and 6’) is perforated by a tendon of the flexor profundus (Fig. 88, c) as it passes through the fibrous pulley-ring at the base of the first phalanx. It. then continues beneath the flexor profundus tendon through the second pulley-ring (2) and is inserted into the base of the second phalanx. Relations.—Outer surface of the ulnar part with the integu- ment; inner surface with the palmaris longus (Fig. 77, 5). Outer surface of the radial part with the palmaris longus; inner surface with the flexor profundus. Action.—Flexor of the second phalanx of digits 2-5. -M. flexor profundus digitorum (or perforans).—This arises by five heads, the tendons of which join one another at the wrist to make the strongest and deepest of the flexor tendons. The first or ulnar head has origin (Fig. 87, g) from the dor- sal half of the medial (radial) surface of the ulna from the proximal lip of the semilunar notch to within a centimeter of the styloid process. Its fibres converge to a large flat tendon which forms the lateral (ulnar) and superficial part of the common tendon. T82 Fic. 87,.-RADIUS AND ULNA, Medial or Flexor Side, with M. pronator quadratus and the Areas of Attachment of Other Muscles. a, M. pronator quadratus; 4, tendon of M. biceps; ¢, conjoined tendon of M. brachialis and M. clavobrachialis; @, insertion of caput longum of M. triceps; e, insertion of short portion of caput mediale of M. triceps; /, origin of M. flexor carpi ulnaris; g, origin of first head of M. flexor profundus digitorum; 4, origin of fifth head of M. flexor profun- dus digitorum; 7, intermediate portion of caput mediale of M. triceps. THE MUSCLES. The second head has origin (Fig. 82, 2) from the distal end of the medial epicondyle of the humerus between the flexor ulnaris and the third and fourth heads of the profun- dus. It may be very closely attached to these muscles at their origins. Its tendon joins the radial border of the tendon of the first head. From this junction the radial part of the flexor sublimis arises. The third head (Fig. 77, u) has origin (Fig. 82, 0) by a strong tendon from the media] epicondyle of the humerus, between the palmaris (/) and flexor radialis (#). Its tendon forms the radial part of the common tendon. The fourth head has origin by a strong tendon from the medial epicon- dyle of the humerus just ventrad of the origin of the second head and the flexor ulnaris, to which many of its fibres are attached. Its tendon forms the middle and superficial part of the common tendon. The fifth‘or radial head (Fig. 75, q; Fig. 77, u’) has origzn (Fig. 87, 2) from the middle third of the ventral. surface of the shaft of the radius over an area limited by two oblique bony ridges; from the adjacent parts of the interosseous membrane; and from the ventral part of the medial surface of the shaft of the ulna between a point about two centimeters distad of the semi- lunar notch and the junction of the middle and distal thirds of the shaft. MUSCLES OF THE THORACIC LIMBS. 183 Its very thick tendon forms the middle and deep part of the common tendon. The common tendon (Fig. 88, c’) covers the carpus and metacarpus ven- trally. It divides into five tendons (c) which pass to the five digits and are zz- serted into the bases of the terminal phalanges. Those of the first four digits perforate the tendon of the flexor sublimis (2) at the base of the first phalanx of each digit. At the same place each passes through a fibrous pulley-ring attached to the base of the phalanx. Each then passes through a second pulley-ring (2) near the head of the phalanx and is finally inserted into the base of the terminal phalanx. Relations. —Outer surface with the pronator teres (Fig. 77, ¢), flexor carpi radialis (Fig. 77, 7), palmaris longus (s), flexor carpi ulnaris (¢), integument, and extensor carpi ulnaris (Fig. 75, 0). Inner surface with the radius, ulna, interosseous membrane and pronator quadratus (Fig. 87, a). Action.—Flexor of all the digits. M. pronator quadratus (Fig. 87, a). —A thick quadrangular muscle whose fibres run obliquely between the distal ends of the ulna and radius. Origin by fleshy fibres from about the distal half of the ventral (flexor) surface or border of the ulna and from the interos- seous membrane adjacent to the area. The fibres pass obliquely distad toward the radial side to their Insertion by fleshy fibres into the ven- tral (flexor) surface of the radius distad of Fic, 88.—ARRANGEMENT OF THE TENDONS of M. palmaris longus, M. flexor sublimis digito- rum, and M, flexor pro- fundus digitorum, with Mm. lumbricales. The integument, fibrous pads, and the palmaris longus (except the ends of its tendons) have been re- moved; the flexor sublimis has been cut. a, cut ends of tendons of M. palmaris longus; 4, tendons of M. flexor sublimis digitorum, ulnar division; 4’, radial part of M. flexor sublimis digitorum; c¢, tendons of M. flexor profundus digi- torum (¢, the common ten- don); @, M. abductor digi- ti quinti; e, M. flexor brevis digiti quinti; 7, Mm. lum- bricales (/’, their tendons). I, transverse ligament of wrist; 2, annular ligaments. the area of origin of the fifth head of the profundus. 184 THE MUSCLES. Relations.-Outer surface with the flexor profundus. Inner surface with the radius, ulna, and interosseous membrane. Action as indicated by the name. 4. Muscles of the Hand. A. BETWEEN THE TENDONS.—Mm. lumbricales (Fig. 88, f, /’).—Four small muscle in the palm of the hand. Origin by fleshy fibres from the outer (palmar) surface of the tendon common to the ulnar four parts of the profundus (c’). Insertion (f').—TVhe four slips are flat at their origin. Each becomes cylindrical and curves about the base of one of the four ulnar digits and is inserted into the radial side of the base of the first phalanx close to its ventral border. Action.—Bend the digits toward the radial side. B. MUSCLES OF THE THUMB.—M. abductor brevis pollicis (Fig. 77, w) (in- cludes also the opponens pollicis of man). —A very minute, probably rudimentary muscle. Tie, Bole Beene Origin from the transverse ligament oF THE PALM oF THE (1) which connects the prominent fibrous, HAND, __.. hairless projection that lies over the pisi- a, M. flexor brevis polli- F : cis; 6, M. adductor pollicis; form bone with the radial border of the Sat. Hiexec teevie digi head of the radius. The muscle passes secundi); d, M. adductor radiodistad and ends in a very slender gigi Geena diet tendon, the insertion of which is into the M. interosseus of fourth base of the first phalanx of the thumb. at recoaator M. flexor brevis pollicis (Fig. 89, 2). fifth digit (M. flexor brevis Origin by fleshy fibres from the ad- diee ae pei Z jacent borders of the os magnum and sca- the digits in order. pholunar bones and from the fascia which bridges the intervening groove for the flexor carpi radialis. Insertion by a short tendon into the base of the first phalanx of the pollex. Action.—Flexor of the thumb. MUSCLES OF THE THORACIC LIMBS. 185 M. adductor pollicis (Fig. 89, 4). Origin by fleshy fibres from the ventral border of the os magnum. It curves about the base of the first metacarpal on its ulnar side to its insertion. Insertion by fleshy fibres into the base of the first phalanx of the pollex on its ulnar side. C. MuscLes LYING BETWEEN THE METACARPALS.— Mm. interossei (Fig. 89).—Small stout muscles lying on the palmar surfaces of the metacarpals of the second, third, fourth, and fifth digits. Origin by fleshy fibres from the ventral or lateral surfaces of the bases of the metacarpals. Near the distal end of the metacarpal each divides into two masses which pass onto the lateral surfaces of the metacarpal, so as to leave the ventral surface of the distal end exposed. Insertion partly onto the lateral surfaces of the base of the first phalanx and its sesamoids, and partly by a slender tendon (Fig. 84, %) which is continued dorsad to join the extensor tendon of the digit. D. SPECIAL MUSCLES OF THE SEGOND DIGIT (THE INDEX).—M. flexor brevis digiti secundi (or indicis).—This name may be applied to M. interosseus of the second digit (Fig. 89, c). M. abductor digiti secundi.—This name might be applied to a portion of the interosseus of the second digit which is sometimes differentiated from the remainder. Origin from the radial and ventral surfaces of the base of the second metacarpal, and from the ventral surface of the trapezium. Insertion into the radial side of the base of the first phalanx of the second digit and into its sesamoid. M. adductor digiti secundi (Fig. 89, 2). Origin from the ventral surface of the os magnum. Insertion into the ulnar side of the base of the first phalanx of the second digit. , E. SPECIAL MUSCLES OF THE FIFTH DIGIT.—M. ab- ductor digiti quinti (Fig. 89, z).—A thick, small, conical bundle. 186 THE MUSCLES. Origin from the distal surface of the pisiform bone and from the transverse ligament on the ulnar side of the pisiform. It ends in a slender tendon which runs along the ulnar side of the fifth metacarpal to its Insertion into the ulnar side of the base of the first phalanx of the fifth digit. M. flexor brevis digiti quinti (Fig. 89, 2; Fig. 88, ¢).— This covers the ventral surface of the fifth metacarpal, and is really the interosseus of this digit. Origin by fleshy fibres from the ventral surface of the base of the fifth metacarpal; from the ventral process of the unci- form bone, and from the transverse ligament proximad of the fifth metacarpal. Insertion by fleshy fibres into the ventral border of the proximal end of the first phalanx of the fifth digit. M. opponens (adductor) digiti quinti (Fig. 89, g). Origin by a flat tendon from the ventral surface of the os magnum on the ulnar side of the adductor pollicis (4). It passes toward the ulnar side and distad, the fibres diverging to their Insertion (1) into nearly the whole of the radial surface of the fifth metacarpal, (2) into the base of its first phalanx. V. MUSCLES OF THE PELVIC LIMBS. 1. Muscles of the Hip. A. ON THE LATERAL SURFACE OF THE HIp. Fascia of the Thigh.—After the removal of the superficial fascia with its fat and blood-vessels, there is seen a strong glistening fascia, the fascia lata (Fig. 68, 2, page 117), cover- ing the vastus lateralis muscle over the dorsal half of the thigh. Ventrally it dips between the vastus lateralis and the biceps femoris and, becoming gradually thinner, is lost on the surface of the former muscle. Passing over the dorsal border of the thigh, it extends beneath the sartorius and is attached to the dorsal border of the vastus medialis. Toward its distal end the fascia is continuous with the tendon of the biceps femoris and dorsad with the border of the sartorius muscle, while MUSCLES OF THE PELVIC LIMBS. 187 between these points it is united with the tendon of the vastus lateralis ; it thus gains insertion into the patella. At its proxi- mal end the fascia receives the insertion of the tensor fascie late (Fig. 68, 7). M. tensor fascia late (Fig. 68, 7, page 117; Fig. 92, a). —The tensor fascia late is a thick triangular muscle which may be recognized by its insertion into the proximal end of the fascia lata (Fig. 68, 2; Fig. 92, a’). Origin by fleshy fibres as a thick triangular prism from the outer margin of the ventral border of the ilium craniad of the auricular impression and from the fascia covering the ventral border of the gluteus medius (Fig. 90, 0) over its cranial half. The caudal border of the muscle may be continuous with the cranial border of the gluteus maximus. The muscle spreads out in a fan-like manner, covering the proximal third of the dorsal surface of the thigh. The cranial fibres pass farther distad than the others. /nusertion into the fascia lata (Fig. 68, 2) along an irregular line which begins caudad at the base of the great trochanter and ends on the cranial side of the thigh at the junction of the first and second thirds. Relations. —Outer surface with the cutaneus maximus (Fig. 62, 46, page 94) and craniad with the sartorius (Fig. 68, g). Cranial border with the sartorius (g); caudodorsal border with the gluteus medius (Fig. 90, 4). Inner surface with the gluteus medius, the rectus femoris (Fig. 92, 0), and the vastus lateralis (Fig. 90, @). Action indicated by the name. It also assists the quad- riceps femoris in extending the leg. M. gluteus maximus.—The gluteus maximus is a rather small quadrangular muscle in the angle between the gluteus medius (Fig. 90, 4) and the caudal vertebre. Origin (Fig. 163, 8, page 401) by fleshy fibres from the tips of the transverse processes of the last sacral and the first caudal vertebra, from the fascia covering the spinous muscles dorsad of the transverse processes of these vertebre, and from the fascia covering the gluteus medius. The muscle passes laterad and slightly caudad to its 188 THE MUSCLES. Lnusertzon by tendon and muscle-fibres into a tubercle on the caudal side of the great trochanter at the middle of its distal end, and for a few millimeters into the ridge which continues distad from this tubercle. Relations. —Outer surface with the caudofemoralis (Fig. 68, s, page 117), the superficial fascia, and a few fibres of the cutaneus maximus. Inner surface with the abductor caude internus, the tenuissimus (Fig. 90, g), the great sciatic nerve (Fig. 163, a), the obturator internus (Fig. 90, ¢), the gluteus medius (Fig. 90, 4), the gemellus superior, and the pyriformis (Fig. 163, 7). Cranial border with the gluteus medius and the tensor fasciz late. Caudal border with the caudofemoralis (Fig. 68, s). Action. —Abducts the thigh. M. gluteus medius (Fig. 90, 4).—The gluteus medius is a very large triangular muscle which connects the ilium and the sacrum with the great trochanter (1). Origin by fleshy fibres (1) from the superficial sacral fascia; (2) from the lateral surface of the fascia which covers the sur- face of the supraspinous extensor muscles of the tail; (3) from the fascia intervening between it and the tensor fascie# late; (4) by tendon fibres from the dorsal half of the crest of the ilium and its dorsal border, and the dorsal half of the lateral surface craniad of the auricular impression; and (5) from the tips of the transverse processes of the last sacral and the first caudal vertebrz. The fibres converge to.a strong internal tendon. Insertion into the proximal end of the great trochanter. &elations.—Outer surface with the gluteus maximus and tensor fasciz lata, and between these with the strong fascia lying beneath the cutaneus maximus muscle. Inner surface with the gluteus minimus, the pyriformis, and’ the gemellus superior. Cranial border with the tensor fasciz late. Caudal border with the gluteus maximus. Action.—Abducts the thigh. M. pyriformis (Fig. 163, 7).—The pyriformis is a triangu- lar muscle covered by the gluteus maximus and the gluteus medius (Fig. 90, 4) and overlying the gemellus superior (Fig. 163, 6). MUSCLES OF THE PELVIC LIMBS 189 Origin by fleshy fibres from the tips of the transverse processes of the last two sacral and the first caudal vertebre. The muscle passes laterad through the great sciatic notch to its Insertion by a flat tendon into an elongated area on the proximal border of the great trochanter just outside (caudad) of the insertion of the gemellus superior. Relations.—Outer surface with the gluteus medius (Fig. go. 4) and the gluteus maximus. Inner surface with the gemellus superior (Fig. 163, 6), the great sciatic nerve (Fig. 163, a), and the flexor caudz longus (Fig. 68, 1). Action:—Abductor of the thigh. M. gemellus superior (Fig. 163, 6).—-The gemellus superior is a triangular muscle lying beneath the pyriformis (Fig. 163, 7). It is broader than the pyriformis, so that it projects beyond its borders both caudad and craniad. It is closely united craniad with the gluteus minimus, so that the limits of the two are definable only with difficulty. Its caudal border is closely united to the gemellus inferior. Origin by fleshy fibres from an elongated area on the dorsal border of the ilium and ischium. The area is narrowed craniad. It does not quite reach the posterior inferior iliac spine in the one direction nor. the spine of the ischium in the other direction. The fibres converge to a strong tendon the Insertion of which is into a triangular area dorsad of the tip of the great trochanter. Relations. —Outer surface with the gluteus medius (Fig. 90, 4), the pyriformis (Fig. 163, 7), the great sciatic nerve (Fig. 163, a), and the gluteus maximus. Inner surface with the ilium, ischium, the capsularis, the caudal edge of ‘the gluteus minimus (Fig. 163, 5), and the cranial edge of the obturator internus (Fig. 90, ¢). Action.—Rotates the femur and abducts it so as to carry the foot outward. M. gluteus minimus (Fig. 163, 5).—The gluteus minimus is a long triangular muscle beneath the middle of the gluteus medius (Fig. 90, 4) and with its caudal border against or covering the cranial border of the gemellus superior (Fig. 163, 6), to which it is frequently closely. united. 190 THE MUSCLES. Origin from the ventral half of the ilium, from near its cranial end to a point midway between the posterior iliac spine and the spine of the ischium. The muscle ends in a strong flat tendon. . insertion into an oval facet at the base of the dorsal surface of the great trochanter on its lateral side. Relations.—Outer surface with the gluteus medius (Fig. 90, &) and at the caudal border with the gemellus superior (Fig. 163, 6). Inner surface with the capsularis and rectus ‘femoris (Fig. 92, @). Action.—Rotates the femur so as to carry the foot out. M. capsularis (gluteus quartus, or epimeralis).—The cap- sularis is a small flat bundle of muscle-fibres which lies obliquely beneath the gluteus minimus (Fig. 163, 5) and gemellus superior (6) on the lateral or outer surface of the ilium. Origin by fleshy fibres from the surface of the ilium over a triangular area between the origin of the rectus femoris (Fig. 92, 4) ventrad, the gemellus superior (Fig. 163, 6) dorsad, and of the gluteus minimus (Fig. 163, 5) craniad and the aceta- bulum caudad. The muscle passes over the smooth surface of the ilium and the pubis ventrad of the acetabulum and then over the capsule of the joint. Insertion by fleshy fibres for about one centimeter in the middle line on the dorsal surface of the femur distad of the great trochanter. Relations.—Outer surface with the gluteus minimus (Fig. 163, 5), the gemellus superior (6), and the vastus lateralis (Fig. go, @). Inner surface with the ilium, the rectus femoris (Fig. 92, 8), the capsule of the joint, and the vastus medialis (Fig. 92, ¢). Action.—Rotates the thigh so as to carry the foot inward, hence antagonizes the iliopsoas. M. gemellus inferior.—The gemellus inferior is a flat tri- angular muscle situated just caudad of the gemellus superior and beneath the obturator internus (Fig. 90, ¢), so that it is seen on reflecting the latter Origin from the dorsal one-half of the whole lateral surface of the ischium between the ischial spine and the ischial tuber- MUSCLES OF THE PELVIC LIMBS. I9gt osity. The fibres converge toward its insertion. The inner surface of the muscle is covered by a strong tendon. Insertion into the inner surface of the tendon of the obturator internus (Fig. 90, ¢) by tendon- and muscle-fibres. Some of the muscle-fibres are inserted into the capsule of the joint. Relations.—Outer surface with the obturator internus (Fig. 90, ¢). Medial surface with the ischium. Caudal border with the quadratus femoris (Fig. 90, 7). Cranial border with the gemellus superior. Action.—Abductor of the thigh. The muscle may be con- sidered as a separate head of the obturator internus (Fig. gO, 2). M. quadratus femoris (Fig. 90, £).—The quadratus femoris isa short thick muscle connecting the ischial tuberosity (2) and the proximal end of the femur. It lies just caudad of the obturator internus (¢) beneath the proximal end of the biceps femoris (Fig. 68, 2). The origin is by fleshy fibres from a considerable triangular area on the lateral surface of the ischium near the tuberosity. The area lies between the origin areas of the gemellus inferior, biceps, semimembranosus, and the obturator externus. Insertion into the distal two-thirds of the ventral border of the great trochanter and about half the adjacent surface of the lesser trochanter. Relations. —Outer surface with the tenuissimus (Fig. 90, ¢), the biceps (Fig. 68, 7), the semitendinosus (Fig. 90, 7), and the great sciatic nerve (Fig. 163, @). Caudal border with the semimembranosus (Fig. 90, 7). Ventral border with the adductor femoris (Fig. 90, 2); dorsal border with the obturator internus (Fig. 90, ¢) and gemellus inferior. Action. —Extensor of the thigh and rotator of the femur so as to carry the foot inward. M. obturator externus.—The obturator externus is a flat triangular muscle beneath the adductor femoris (Fig. 92, g). Origin by fleshy fibres from the median lip of the obturator foramen and from both dorsal and ventral surfaces of the rami of the pubis and ischium adjacent to the lip. Also from the 192 THE MUSCLES. outer surface of the ramus of the ischium as far as the area for the quadratus femoris (Fig. 90, /). The fibres converge to a strong flat tendon. /nsertion into the proximal por- tion of the bottom of the tro- chanteric fossa. Relations.—Ventral _ sur- face with the adductor fem- oris (Fig. 92, g). Dorsal surface with the pubis and ischium. Caudal border with the quad- ratus femoris (Fig. 90, /). Action. — Assists the iliopsoas. B. MUSCLES ON THE MEDIAL SurR- FACE OF THE Hip.— M. obturator internus (Fig. 90, ¢).—The obtura- tor internus appears as a tri- angular muscle caudad of the ge- mellus superior. Fic. 90.—MuscLES ON THE LATERAL SIDE OF THE LEG, AFTER REMOVAL OF THE MUSCLES SHOWN IN Fic. 68 (Biceps, TENSOR FASCI4 LAT, Cauno- FEMORALIS, AND GLUTEUS MAXIMUS). a, M. sartorius; 4, M. gluteus medius; ¢, M. rectus femoris; @, M. vastus lateralis: e, M. obturator internus; J, M. quadratus femoris; g, M. tenuissimus; 4, M. ad- ductor femoris; z, M. semimembranosus; 7, M. semi- tendinosus; 4, M. vastus intermedius; 7, M. plantaris; m, m', m!', M. gastrocnemius, outer head (#, part from the external sesamoid bone; 7’, from the plantaris; m”, from the superficial fascia); 7, M. tibialis anterior; o, M. soleus; 2, M. extensor longus digitorum; g. M. peroneus longus; 7, M. peroneus tertius (7' its tendon); s, M. peroneus brevis; 7, tendon of Achilles; #, M. extensor brevis digitorum. 1, great trochanter of femur; 2, tuberosity of ischium, with cut origin of M. biceps oi femoris; 3, patella; 4, calcaneus; 5, transverse liga- Lip ments; 6, lateral malleolus. : MUSCLES OF THE PELVIC LIMBS. 193 Origin by numerous small separate heads from the dorsal surface of the ramus of the ischium along its symphysis and following its medial border from the symphysis nearly to the tuberosity. The fibres form a flat muscle which narrows and passes through the lesser sciatic notch, turns ventrad and ends in a strong flat tendon whose Jusertion is into the bottom of the trochanteric fossa of the femur. The tendon is continued proximad on the inner surface of the muscle and forms a smooth firm surface by which the muscle glides over the dorsal border of the ischium. Into the inner surface of this tendon near its insertion the tendon of the gemellus inferior is inserted. Relations.—Medial surface within the pelvis with a mass of fat:separating it from the pelvic organs. Dorsal or outer sur- face with the biceps femoris, the tenuissimus, the caudofemora- lis, and the great sciatic nerve. Inner surface with the ischium and the great sciatic nerve. Caudal (or ventral) border with the quadratus femoris. Action.—Abductor of the thigh. M. iliopsoas (Fig. 162, 8; Fig. 91, c).—The iliopsoas (equivalent to the human psoas and iliacus) is a conical muscle emerging from the abdominal cavity onto the medial surface of the femur. Origin.—(a) The portion corresponding to the human psoas (Fig. 162, 8) arises by ten vertebral heads. The first five of these come from the five cranial tendons of origin of the psoas minor (Fig. 162, 9); the sixth from a tendinous expansion which passes from the tendon of the first head over the ventral longitudinal muscles to. the transverse process of the fifth lumbar vertebra. The seventh, eighth, ninth, and tenth heads arise by fleshy fibres from the ventral surfaces of the centra of the last four lumbar vertebre. (6) The portion corresponding to the human iliacus arises by fleshy fibres from the ventral border of the ilium, from opposite the auricular impression to the iliopectineal eminence. The portions of the muscle all converge to form a conical mass which ends in a strong tendon lying on its outer sur- face. . ‘ty a 194 THE MUSCLES. Insertion by tendon and fleshy fibres into the apex of the lesser trochanter of the femur. Relations.—Dorsal surface with the quadratus lumborum (with which this muscle is partly united), the rectus femoris (Fig. 91, @), and, by the iliac head, with the gluteus minimus. Ventral and medial surface with the psoas minor (Fig. 162, 9) and the peritoneum. Lateral edge with the transversus abdominis (Fig. 162, 4). _Action.——Rotates the thigh so as to carry the foot out; also flexes the thigh. 2. Muscles of the Thigh. M. biceps femoris (Fig. 68, ¢, page 117).—A very large flat muscle covering about two-thirds of the lateral side of the thigh. Origin (Fig. 90, 2).—From the ventral surface of the tuberosity of the ischium by tendon- and muscle-fibres. The fibres diverge, and near the knee the mass has spread out, end- ing in a fascia. The dorsal border of the muscle and -the common fascia are continuous dorsad with the superficial fascia of the thigh and with the tendon of the caudofemoralis (Fig. 68, s). Ventrad it is continuous with the superficial fascia of the shank. Insertion into rather more than the proximal one-third of the dorsal border of the tibia along its lateral margin and into the lateral margin of the patella. In passing over the knee- joint it is closely united to the underlying ligaments and tendons. Relations.—Outer surface with the superficial fascia and with a few of the most caudal fibres of the cutaneus maximus (Fig. 62, 4, page 94). Cranial (or dorsal) edge with the caudofemoralis (Fig. 68, s) and the vastus lateralis (Fig. 90, @). Caudal border with the semitendinosus (Fig. 68, ~) and a mass of fat. Inner surface with the caudofemoralis (Fig. 68, s), the tenuissimus (Fig. 90, g), the obturator internus (Fig. 90, ¢), the quadratus femoris (Fig. 90, /), the semitendinosus (Fig. 68, z), the semimembranosus (Fig. 90, 2), the adductor femoris (Fig. 90, %), the great sciatic nerve (Fig. 163, a), and distad MUSCLES OF THE PELVIC LIMBS. 195 with the following muscles of the lower leg: the tibialis anterior (Fig. 90, 7), the extensor longus digitorum (Fig. 90, £), the peroneus longus (Fig. 90, g), and the lateral head of the gastrocnemius (Fig. go, #7). Action.—Abductor of the thigh, and flexor of the shank. M. tenuissimus or M. abductor cruris (Fig. 90, g).—A very slender muscle, only three or four millimeters wide. Origtx from the tip of the transverse process of the second caudal vertebra, in common with the caudofemoralis (Fig. 68, s) or gluteus maximus. It passes obliquely beneath the biceps femoris (Fig. 68, 2) distad and ventrad, to the distal end of the ventral border of that muscle. Here it becomes con- tinuous with the ventral border of the biceps, ending in a con- tinuation of the same fascia into which the biceps is inserted. Relations.—Outer surface with the caudofemoralis (Fig. 68, s) and the biceps femoris (Fig. 68, #); distad with the integument. Inner surface with the obturator internus (Fig. go, ¢), quadratus femoris (/), semitendinosus (7), adductor femoris (4), semimembranosus (2), and distad with the muscles of the lower leg. M. caudofemoralis (parameralis, Strauss-Durckheim) (Fig. 68, s, page 117). Origin by a flat tendon from the transverse processes of the second and third caudal vertebra. The muscle forms a flat band which passes distad along the middle of the lateral side of the thigh over the pelvis and caudad of the great trochanter. At the middle of the thigh it ends in a very thin tendon. The tendon passes distad along the medial surface of the biceps femoris (Fig. 68, 7), pierces the fascia lata near the knee, and passes to its , Insertion into the middle of the lateral border of the patella. Relations. —Outer surface with the superficial fascia and a few fibres of the cutaneus maximus; distad with the biceps femoris (Fig. 68, 2). Cranial border with the gluteus maxi- mus; caudal border with the biceps femoris. Inner surface with the tenuissimus (Fig. 90, g), the gluteus maximus, the abductor caudz internus, and with the obturator internus (Fig. 90, ¢); distad with the vastus lateralis. 196 THE MUSCLES. Action.—Abducts the thigh and helps to extend the shank. M. semitendinosus (Fig. 90, 7).—A long slender muscle on the ventral (caudal) border of the thigh, between the semi- membranosus (2) and the biceps femoris (Fig. 68, 2). Origin from the apex of the tuberosity of the ischium beneath the origin of the biceps femoris. The muscle passes to the medial side of the shank and ends in a thin but strong tendon (Fig. 92, 2’) about five millimeters broad. The tendon curves proximad and passes beneath the gracilis tendon (Fig. gl, 8) to its Insertion into the crest (dorsal border) of the tibia one or two centimeters from its proximal end. Relations.—Lateral surface with the biceps femoris (Fig. 68, 2), the integument, a mass of fat, and distad with the gas- trocnemius (Fig. 92, 7) and popliteus (Fig. 92, #). Caudal surface with the integument. Medial surface with the semi- membranosus (Fig. 90, z) and distad with the integument of the lower leg. Action.—Flexor of the shank. M. semimembranosus (Figs. 90 and 91, z; Fig. 92, 2).— A thick prismatic muscle lying along the ventral (or caudal) side of the thigh between the semitendinosus (7) and the gracilis (Fig. 91, 4). — Origin by short tendon-fibres from the caudal border of the tuberosity and the ramus of the ischium. The muscle mass is divided throughout most of its length into two portions (Fig. 92, # and h’), one of which (2’) lies laterad and caudad of the other. The two portions pass to the medial side of the knee. ‘The caudal portion (Z’) ends in a strong flat tendon five milli- meters broad, the Insertion of which is into the medial surface of the femur on the medial epicondyle, at the middle of its distal border and into the adjacent medial surface of the tibia behind the lateral ligament. The dorsal part has its zzser¢éon into the distal one and one-half to two centimeters of the ridge which is continued from the medial epicondyle of the femur onto the shaft; and nto the sesamoid bone of the medial epicondyle. MUSCLES OF THE PELVIC LIMBS. 197 Relations.—Lateral surface with the semitendinosus (Fig. 90, 7), the biceps femoris (Fig. 68, 2), and distad with a small part of the adductor femoris (Fig. 92, g),and with the gas- trocnemius (Fig. 92, 7). Medial 7 surface with the gracilis (Fig. gI, 4) and distad with the sartorius (Fig. g1,’@). Cra- nial (or dorsal) border at the origin with the quad- ratus femoris (Fig. go, J); for the remainder of its length with the adductor femoris (Fig. go, #). Caudal bor- der with the integu- ment proximad. Action. — Extensor of the thigh. M. sartorius (Fig. g1, a; Fig. 68, 7).—A large flat muscle along the medial side of the thigh near its cranial (dorsal) border. Origin from the ventral half of the crest of the ilium and from the medial half of its ventral border craniad of the auricular impression. The caudal third of the origin is by a thin tendon, the rest by fleshy fibres. Fic. 91.—MuscLEes ON THE MEDIAL SIDE OF THE LEG. a, M. sartorius; 6. M. gracilis; c, M. iliopsoas; d, M. rectus femoris; ¢, M. vastus medialis; 7, M. pectineus; g, M. adductor longus; 4, M. adductor femoris; 7, M. semimembranosus; 7, M. semitendinosus; 4, medial head of M. gastrocnemius; /, M, plantaris; 7, M. flexor longus hallucis (#’, its tendon); 2, M. flexor longus digitorum; (’, its tendon); 0, M. tibialis posterior; Z, M. tibialis anterior; g, M. interosseus of second digit. I, patella; 2, calcaneus; 3, medial malleolus; 4, second metatarsal; 5, transverse ligament of the lower leg. 198 THE MUSCLES. Jusertion on a long S-shaped line which begins on the dorsal border of the tibial shaft about two centimeters from its proximal end, passes thence to the middle of the proximal end of the medial surface of the tibia, thence across the ligaments of the knee-joint and the medial surface of the medial epicondyle to the patella, crosses the patella obliquely to the middle of its proximal end, and may be continued for some distance proximad along the middle line on the fascia. Relations.—Medial surface with the integument and proxi- mad with the internal oblique muscle (Fig. 68, f). Lateral (inner) surface with the tensor fascie late (Fig. 68, 7), the vastus lateralis (Fig. 90, @), the superficial fascia, the vastus medialis (Fig. 92, c), the rectus femoris (Fig. 92, 4), and the distal end of the semimembranosus (Fig. 92, 4’). Action.—Adducts and rotates the femur and extends the tibia. ; M. gracilis (Fig. 91, 4).—The gracilis is a flat, thin, sub- cutaneous muscle occupying the ventral half of the medial sur- face of the thigh. Origin by a strong tendon from the caudal three-fourths of the symphysis of the ischium and pubis. The tendon may extend caudad of the symphysis in the middle line to the level of the tuberosity of the ischium. For about its first centimeter the tendon is common to the two muscles of opposite sides and gives origin on two sides to the fibres of the adductor femoris. The common tendon divides into two which pass laterad, each ending in a convex border from which the muscle-fibres spring. Insertion.—It ends in a thin aponeurosis, part of which is continuous with that of the sartorius. The aponeurosis is finally inserted into the medial surface of the tibia near its proximal end, while distally it is continuous with the fascia. Relations.—Outer (medial) surface with the integument. Inner (lateral) surface with the semimembranosus (Fig. 91, 7) and the adductor femoris (Fig. 91, /). Action.—Adducts the leg and draws it caudad. M. adductor femoris (magnus et brevis) (Fig. 92, ¢; Fig. 90, 4). —The adductor femoris lies between the semimembrano- MUSCLES OF THE PELVIC LIMBS. 199 sus (Fig. 92, “) and the femur. Its proximal part is covered by the semimembranosus, while its distal part lies outside of it. Origin by muscle-fibres from the rami of the pubis and the ischium along the whole of the length of the symphysis; from the ramus of the ischium between the symphysis and the tuberosity, and from the tendon of origin common to the two gracilis muscles. Jnsertion into nearly the whole of the ventral surface of the shaft of the femur. The area begins at the base of the great trochanter opposite the proximal end and the insertion area of the gluteus maximus. It extends thence distad along the caudal border of the surface as an area about one millimeter ' wide. At the junction of the first and second thirds of the shaft the area expands and occupies the whole of the ventral surface of the bone, ending at the intercondyloid fossa. Relations. —Lateral surface with the biceps (Fig. 68, z), the great sciatic nerve (Fig. 163, a), the tenuissimus (Fig. 90, g), and the semimembranosus (Fig. 92, %); dorsolateral border in contact with the vastus lateralis (Fig. 92, c). Dorsal surface with the quadratus femoris (Fig. 90, /) and obturator externus (Fig. 90, ¢). Caudal surface with the semimembranosus (Fig. 92, #). Medial surface with the gracilis (Fig. 91, 4), adductor longus (Fig. 92, /), pectineus (Fig. 92, ¢), vastus medialis (Fig. 92, ¢), and distad with the medial head of the gastroc- nemius (Fig. 92, 7). Action.—An extensor of the thigh. M. adductor longus (Fig. 91, ¢; Fig. 92, 7/).—A thin muscle which covers the dorsal half of the medial surface of the adductor femoris (Fig. 92, g)- Origin by muscle-fibres from the median three-fourths of the cranial border of the pubis, the line of origin forming a medial continuation of that of the pectineus (Fig. 92, ¢). Insertion by a thin aponeurosis into the external linea aspera of the femur along the second and third fifths of the bone. Relations. —With its medial or cranial surface the adductor longus forms part of the boundary of a depression among the muscles at the proximal end of the medial side of the leg. 200 THE MUSCLES. This depression is called the iliopectineal fossa; it contains the femoral vein and artery and saphenous nerve imbedded in fat (Fig. 127). The medial edge of the adductor longus is in relation with the integument; the lateral edge with the pec- Wp Fic. 92.—SEcoND LAYER OF MUSCLES ON THE MEDIAL SIDE OF THE THIGH, a, M. tensor fascize late; a’, fascia lata; 5, M. rectus femoris; c, M. vastus medi- alis; d, M. iliopsoas (cut); ¢, M. pectineus; 7, M. adductor longus; g, M. adductor femoris; 4, 2’, M. semimembranosus; 7, M. semitendinosus (2’, its teridon); 7, medial head of M. gastrocnemius; 2, M. popliteus; 2, M. flexor longus digitorum. 1, patellar ligament; 2, ligamentum collaterale tibiale. Inner or caudal surface with the adductor A tineus (Fig. 92, ¢). femoris (Fig. 92, g). Action.—Adductor of the thigh. M. pectineus (Fig. 92, ¢).—A flat band of fibres closely united with the adductor longus (/), of which it appears to be a lateral continuation. Origin by fleshy fibres from the lateral one-fourth of the cranial border of the pubis. The muscle passes over the smooth outer surface of the pubis between its origin area and MUSCLES OF THE PELVIC LIMBS. 201 the acetabulum, crosses the iliopsoas (@) obliquely and has its Insertion by muscle-fibres into an elongated area (five milli- meters in length) on the shaft of the femur just distad of the lesser trochanter and between the insertion of the adductor femoris (g) and that of the vastus medialis (c). Relations.—The ¢ranial edge forms part of the floor of the iliopectineal fossa. Lateral surface in relation with the iliopsoas (2) and vastus medialis (¢); medial surface with the adductor longus (/) and adductor femoris (g). Action.—Adductor of the thigh. M. quadriceps femoris.—The quadriceps femoris is a very powerful extensor muscle on the front of the thigh. It consists of four muscles which unite to form the great extensor of the shank. It is inserted into the patella and through it, by the ligamentum patelle, into the tibia. It may be compared to the triceps brachii. The parts are: (1) M. rectus femoris (Fig. 92, 4; Fig. 90, c). Origin by strong tendon from an elongated triangular area which has its base at the acetabulum and its apex about five to seven millimeters craniad of the acetabulum, along the ven- tral border of the ilium. The area is between that for the capsularis and that for the iliopsoas. The muscle is flat near its origin, but soon becomes a triangular prismatic mass which is united to the dorsal border of the vastus lateralis (Fig. go, @) at the junction of the middle and last thirds of the thigh. Insertion into the oblique area on the outer surface of the patella near its proximal border in connection with the vastus lateralis. Relations.—Outer or lateral surface at the origin with the gluteus minimus, the edge of the capsularis, the gluteus medius (Fig. 90, 4), and farther distad with the vastus lateralis (Fig. 90, @). Medial surface with the tensor fascie late (Fig. 92, a), sartorius (Fig. 90, a), and vastus medialis (Fig. 92, c). Inner (caudal) surface with the vastus intermedius. (2) M. vastus lateralis (Fig. 90, d).—A flat triangular prismatic mass joined distally to the preceding. It covers the dorsal part of the lateral surface of the thigh. Origin from a triangular area on the dorsal and lateral sur- 202 THE MUSCLES. faces of the shaft and the great trochanter of the femur. The base of the area is at the great trochanter, and its apex is at the junction of the second and third fifths of the shaft on the linea aspera. The linea aspera forms the ventral boundary of the triangle, while its dorsal boundary is formed by a line drawn frorn its apex to the dorsomedial angle of the great trochanter. The mass unites with the rectus femoris (c) by its dorsal border at the junction of the middle and distal thirds of the thigh. fusertion into the oblique area on the outer surface of the patella near its lateral border in connection with the rectus femoris. (3) M. vastus medialis (Fig. 92, ¢) lies on the medial side of the thigh. Origin by fleshy fibres over a diamond-shaped area on the shaft of the femur lying between the medial branch of the linea aspera and the area for the vastus lateralis. Proximad the area is bounded by the spiral line, and distad it is bounded by a line parallel to the spiral line and having its proximal end at about the junction of the first and second thirds of the bone. ‘The muscle forms a triangular, prismatic mass. It ends ina thin aponeurosis which is continuous dorsad with the border of the rectus femoris (Fig. 92, 4), and ventrad sometimes with the tendon of the gracilis (Fig. 91, 4). Insertion into the medial border of the patella and the liga- mentum patella. The insertion may extend onto the head of the tibia. The adjacent surfaces of the vastus lateralis and the vastus medialis are connected over their distal thirds by an aponeuro- sis which passes transversely beneath the rectus femoris. The distal end of the aponeurosis is inserted into the proximal border of the patella. Its proximal end receives the insertion of some muscle-fibres which form a part of the vastus medialis as here described. This mass of fibres is described by Strauss- Durckheim as the crural muscle. Sometimes the transverse aponeurosis is continuous with only one of the two vasti and sometimes with neither, so that the insertion of the crural of Strauss-Durckheim becomes more or less independent. Relations of the vastus medialis. Outer (medial) surface MUSCLES OF THE PELVIC LIMBS. ‘ 203 with the sartorius (Fig. 91, a) and the structures in the ilio- pectineal fossa. Cranial (or dorsal) surface with the rectus femoris (Fig. 92, 4) and vastus intermedius. Caudal (ventral) surface with the pectineus (lig. 92, ¢), adductor longus (Fig. 92, f), adductor femoris (Fig. 92, g), and semimembranosus (Fig. 92, #2). (4) M. vastus intermedius.—A flat mass of muscle which lies beneath the rectus femoris. Origin from nearly the whole of the dorsal surface of the shaft of the femur between the areas for the vastus medialis and vastus lateralis. The area of origin extends distad to an oblique line the middle of which is about one and one-half centimeters from the patellar surface, the lateral border of the area being longer than the medial border. Jusertion by muscle-fibres into the capsule of the joint. The central fibres are inserted about one centimeter proximad of the patella, while the lateral mass ‘passes to the level of the proximal end. Relations.—Outer surface with the rectus femoris (Fig. g2, 6); borders with the vastus medialis (Fig. 92, c) and vastus lateralis (Fig. 90, @); inner surface with the femur. Action.—The quadriceps extensor is an extensor of the shank. The vastus intermedius acting separately is a tensor of the capsule of the knee-joint. 3. Muscles of the Lower Leg (Crus). A. ON THE VENTRAL SIDE. —M. gastrocnemius.—This is the great muscular mass of the calf. It arises by two heads, the caput laterale or lateral head (Fig. 90, #), and the caput mediale or medial head (Fig. 91, £), of the gastrocnemius. Caput laterale (Fig. 90, ™, m’', n’’).—The origin of the lateral head is in four portions: (1) From the tendon of origin of the plantaris which comes from the middle of the lateral border of the patella. The ten- don ends in a small conical mass of fibres (7) which joins the ventral part of the common head. (2) By a slender flat tendon, distad of the first, from the 204 THE MUSCLES. superficial fascia of the shank (#’’). The tendon ends in a conical mass which joins the dorsal border of the common head. (3) By a strong tendon and by muscle-fibres from the distal border of the lateral sesamoid bone (Fig. 61, 8) of the femur. These fibres (7) form the middle and outer part of the common head. : (4) By muscle-fibres from the middle of the outer surface of the aponeurosis covering the plantaris (Fig. 90, 7) along rather more than the proximal half of the tibia. The lateral head thus formed is flat and fusiform in section. Caput mediale (Fig. 91, 4; Fig. 92, 7).—The medial head resembles the lateral head closely. Origin by a strong tendon from the medial sesamoid bone of the femur (Fig. 61, 4) and by muscle-fibres from the surface of the shaft for a short distance proximad of this. The two heads unite by their contiguous borders at the junction of the first and second thirds of the tibia. The common muscle narrows rapidly and ends in a flat tendon which joins the tendon of the soleus to form the so-called ten- don of Achilles (tendo calcaneus) (Fig. 90, 7). This has its Insertion into the proximal end of the calcaneus (Fig. 90, 4) near its ventral border. This tendon together with that of the soleus (Fig. 90, 0) and the fascia of the shank forms a tubular sheath for the tendon of the plantaris. Relations.—(1) Of the lateral head. Lateral (outer) surface with the biceps femoris (Fig. 68, 7) and the superficial fascia. Medial (inner) surface with the popliteus (Fig. 92, #), the plantaris (Fig. 90, 7) (to which it is closely united), the medial head of the gastrocnemius (Fig. 91, 2), the soleus (Fig. go, 0), and the peroneus longus (Fig. 90, g). (2) Of the medial head. Medial (outer) surface with the superficial fascia and the tendons of the gracilis (Fig. 91, 4), semimembranosus (Fig. 92, 4’), and semitendinosus (Fig. 92, 7). Lateral (inner) surface at the origin with the adductor femoris (Fig. 92, g), then with the plantaris (Fig. 91, 7), the popliteus (Fig. 92, £), flexor longus digitorum (Fig. 91, 2), and the lateral head of the gastroc- nemius (Fig. 90, 72). Action.—Extensor of the foot. (It is to be noted that what MUSCLES OF THE PELVIC LIMBS. 205 is called extension in the foot is analogous to what is called flexion in the hand, so that the extensors of the foot are most readily to be compared with the flexors of the hand.) M. plantaris (Fig. 90, 7; Fig. 91, /).—A fusiform muscle covered distally by the gastrocnemius, but appearing between the two heads of the gastrocnemius at their proximal ends (Fig. go, 7). Origin by a strong tendon from the middle of the lateral border of the patella and by fleshy fibres from the ventral border of the lateral sesamoid. The patellar tendon ends in a flattened head which passes ventrad over the lateral epicondyle of the femur and then curves distad; it is closely united with the lateral head of the gastrocnemius. The muscle ends in a thick tendon which passes through a sheath formed by the tendons of the gastroc- nemius and soleus, and the fascia of the shank. The tendon passes over the grooved proximal end of the calcaneus onto its ventral surface. It is held in place against the groove by two sheets of aponeurosis, which leave the tendon on either side for a distance of more than.a centimeter and are attached to the lateral surfaces of the calcaneus at its proximal end. Lateral motion is thus hindered, while longitudinal motion is permitted. Between this tendon and the tendon of Achilles is a synovial bursa which aids the gliding movement of the tendon. In the sole of the foot opposite the distal end of the calcaneus the tendon broadens and ends in the flexor brevis digitorum (pedis perforatus) muscle, which might also be considered as a second part of the plantaris. In man the plantaris is inserted into the calcaneus along with the gastrocnemius. Relations. —The muscle is covered throughout by the two heads of the gastrocnemius (Fig. 90, #; Fig. 91, £), except at, the proximal end (Fig. go, 2), where it is in contact with the integument. Inner surface in relation with the popliteus (Fig. 92, #), the soleus (Fig. 90, 9), the flexor longus digitorum (Fig. 91, 2), and flexor longus hallucis (Fig. 91, 7). M. soleus (Fig. 90, 0).—A flat fusiform muscle lying beneath the plantaris. Origin by muscle-fibres from the lateral surface of the head 206 THE MUSCLES. of the fibula, and by tendon-fibres from the proximal two-fifths of its ventral border. Lnsertion.—The muscle ends in a slender tendon which joins the lateral border of the gastrocnemius tendon to form the tendon of Achilles (Fig. 90, 2), which forms the sheath of the plantaris tendon. Relations.—-Outer surface with the gastrocnemius (Fig. go, m) and plantaris (Fig. 90, 7). Inner surface with the peroneus longus (Fig. 90, g), peroneus tertius (Fig. 90, v), and flexor hallucis (Fig. 91, 72). Action.—Assists the gastrocnemius to extend the foot. M. triceps sure.—The gastrocnemius and the soleus are sometimes considered as forming a single muscle, with three heads, under the name triceps sure. M. popliteus (Fig. 92, #).—A triangular muscle passing from the femur obliquely toward the medial side over the ven- tral surface of the proximal end of the tibia. Origin by a strong tendon from the popliteal groove on the surface of the lateral epicondyle of the femur. In the tendon is a sesamoid bone, the popliteal bone (Fig. 61, 5, page 89), which glides over the ventral part of the lateral articular facet on the proximal end of the tibia. As the muscle passes over the joint it is closely attached to the joint capsule. From the popliteal bone, which with the tendon lies within the capsule of the knee-joint, the muscle-fibres diverge to their Insertion into the proximal end of the ventral surface of the tibial shaft on the medial side of the medial oblique ridge. The area of insertion extends slightly onto the medial surface of the bone. Relations.—-Outer surface with the gastrocnemius (Fig. 92,7) and plantaris (Fig. 91, 7), and with the tendon of the semitendinosus (Fig. 92, 7). Distal border with the origins of the soleus and flexor longus digitorum. Inner surface with the capsule of the knee-joint and the tibia. Action.—Rotates the thigh so as to turn the toes inward. The three following deep muscles on the ventral surface of the shank are covered by a deep fascia (the deep crural fascia) MUSCLES OF THE PELVIC LIMBS. 207 which separates them from the overlying muscles. This fascia stretches from the dorsal border of the tibia about the ventral side of the shank to the medial border of the tibia. It sends a slip beneath the border of the fibula. M. flexor longus digitorum (Fig. 91, # and ).—Owing to the reduction of the first digit in the cat the tendon of the flexor longus hallucis (7) has become united to that of the flexor longus digitorum (7), so that the two might be considered separate heads of a single muscle. The head corresponding to the flexor longus hallucis (m) is much larger than that corre- sponding to the flexor longus digitorum (z). The two heads will be described separately. (1) M. flexor longus hallucis (Fig. 91, m).—This lies against the ventral surface of the tibia and fibula beneath the popliteus (Fig. 92, £) and soleus (Fig. 90, 2). Origin by fleshy fibres, (1) from the sheet of deep crural fascia which dips between it and the tibialis posterior (Fig. 91, 0) and the flexor longus digitorum (7). (2) From the ven- tral surface of the tibia distad of the lateral oblique line to within one to three centimeters of the distal end of the shaft. (3) From the medial surface of the shaft and head of the fibula and from the whole interosseous ligament. On the fibular side the origin may extend onto the tendon of the popliteus and the fascia of the peroneus longus. The fibres form a flat fusiform mass ending one centimeter from the heel in a strong flat tendon (m’') which passes over the groove on the distal surface of the astragalus and over the groove on the sustentaculum tali. The two grooves are converted into a continuous canal. by strong transverse ligaments, and the canal is lined by an extension of the synovial bursa of the ankle-joint. Emerging from the canal the tendon broadens and receives on its medial side the insertion of the tendon of the flexor longus digitorum (z). The tendon gives origin on its outer surface to the lumbricales and to the common plantar ligament. The tendon continues to broaden until it reaches the middle of the length of the meta- carpals; here it divides into four tendons which pass to the terminal phalanges of the digits. Insertion.—The relations of the four tendons and their 208 THE MUSCLES. insertions are identical with those of the flexor profundus digi- torum of the hand. Relations. —Outer surface with the soleus (Fig. 90, 0) and plantaris (Fig. 91, 7). Lateral border with the soleus, the peroneus tertius (Fig. 90, v), and peroneus brevis (Fig. 90, s). Medial border with the tibialis posterior (Fig. 91, 0) and flexor longus digitorum (Fig. 91, 2). Action.—Flexor of the phalanges. (2) M. flexor longus digitorum (Fig. 91, 7). Origin by muscle- and tendon-fibres from the ventral sur- face of the tibia over its proximal half between the oblique ridges; by fleshy fibres from an aponeurosis between it and the tibialis posterior (Fig. 91, 0), and by tendon from the medial surface of the head of the fibula. At the junction of the middle and distal thirds of the bone the muscle ends in a slender ten- don which passes through the ventral groove on the medial surface of the tibia and, curving onto the sole of the foot, becomes attached to the medial border of the common tendon described under the last. Relations.—Outer surface with the medial head of the gas- trocnemius (Fig. 91, &) and with the superficial fascia. Inner surface with the tibialis posterior (Fig. 91, 0). Medial border at the proximal end with the popliteus (Fig. 92, £), lateral border with the tibialis posterior (Fig. 91, 0), and flexor longus hallucis (Fig. 91, #2). Action.—F lexor of the phalanges. M. tibialis posterior (Fig. 91, 0).—A slender flat fusiform muscle beneath the flexor longus digitorum and between it and the flexor longus hallucis. Origin by fleshy fibres from nearly the whole medial surface of the head of the fibula, from the inner surface of the apo- neurosis between it and the flexor longus digitorum (x), and by a few fleshy fibres from the ventral surface of the tibia between the oblique ridges. Some fibres may also arise from the outer surface of the aponeurosis covering the flexor longus hallucis (m). The muscle ends at about the middle of the tibia in a slender flat tendon which passes parallel to the tendon of the flexor longus digitorum (z) through the dorsal groove on the MUSCLES OF THE PELVIC LIMBS. 209 medial surface of the distal end of the tibia. This groove is converted into a canal by a transverse ligament. Beyond the canal the tendon turns onto the plantar surface of the foot and passes through a groove on the ventral surface of the scaphoid bone. It then divides. Insertion into the outer tuberosity on the surface of the scaphoid, and onto the proximal end of the ventral surface of the medial cuneiform. Relations. —Outer and medial surface with the flexor longus digitorum (z). Lateral surface with the flexor longus hallucis (#2). Action. —Extensor of the foot. B. MUSCLES ON THE DORSAL AND LATERAL SURFACES OF THE LOWER LEG.—M. peroneus longus (Fig. 90, g).— A slender, fusiform muscle lying superficially on the lateral side of the leg, dorsad of the soleus. Origin by tendon-fibres from the lateral surface of the head of the fibula and from the proximal half of the lateral surface of its shaft. At the junction of the middle and distal thirds of the lower leg the muscle ends in a slender tendon which passes through the groove on the lateral surface of the lateral malleolus. This groove is converted into a canal by a transverse ligament. The tendon passes through the groove on the peroneal tubercle of the calcaneus, then turns onto the sole of the foot and passes through the peroneal groove on the cuboid bone. It then turns mediad and passes through the groove between the ventral processes of the lateral cuneiform and the metatarsal until it reaches the first metatarsal. The entire groove is converted into a canal by the overlying ligaments. Insertion into (1) the base of the fifth metatarsal, and (2) the outer side of the base of the first metatarsal, and (3) by slender branches into the bases of the other metatarsals. Relations. —Outer (lateral) surface with the superficial fascia and the tendon of the biceps femoris. Inner surface with the peroneus tertius (7) and peroneus brevis (s), and with the extensor longus digitorum (f). At the proximal end the dorsal border touches the tibialis anterior (#). Action. —Flexor of the foot. 210 THE MUSCLES. M. peroneus tertius (Fig. 90, 7).—A slender fusiform muscle beneath the peroneus longus (g). Origin by fleshy fibres from about the second quarter of the lateral surface of the fibula. The muscle ends in a slender tendon (r’), which passes with that of the peroneus brevis (s) through the groove on the ventral border of the lateral mal- leolus. The groove is converted into a canal by a transverse ligament. Emerging from it, the tendon turns and passes along the outer margin of the foot. In passing the sesamoid at the base of the first phalanx of the fifth digit it is united to it by a band which passes from the sesamoid to the tendon. The zzserton is finally into the lateral border of the extensor tendon of the fifth digit as it passes from the first to the second phalanx. Relations. —Outer surface with the peroneus longus (g), the soleus (0), and the superficial fascia. Ventral border with the soleus (¢) and flexor longus hallucis (Fig. 91, 7). Inner sur- face with the peroneus brevis (Fig. 90, s). Action. —Extensor and abductor of the fifth digit and flexor of the foot. M. peroneus brevis (Fig. 90, s) lies beneath the other peronei. Origin by fleshy fibres from the distal half of the surface of the fibula, which it embraces. At the lateral malleolus the muscle ends in a thick tendon which passes through the canal on the ventral surface of the malleolus. In the canal it is enlarged and surrounded by a synovial bursa. It then turns onto the foot and passes over the dorsal surface of the calcaneus on its lateral side and has its Insertion into the tubercle on the lateral side of the base of the fifth metatarsal. Relations. —Outer surface with the peronei longus (g) and tertius (7). Inner surface with the bone. Action. —Extensor of the foot. M. extensor digitorum longus (Fig. 90, ).—A fusiform muscle which lies beneath the tibialis anterior (), against the interosseous membrane, and between the tibialis anterior and the peronei. MUSCLES OF THE PELVIC LIMBS. 21T Origin by a thin flat tendon from the lateral surface of the lateral epicondyle of the femur just dorsad of the origin of the popliteus. The tendon becomes narrower and thicker and passes through the capsule of the knee-joint and over a slight: groove on the tibia just dorsad of the head of the fibula. The belly of the muscle extends the entire length of the tibia, pass- ing beneath the transverse ligament (5) along with the tendon of the tibialis anterior (z). At the ankle it runs through a fibrous loop which is attached to the dorsal surface of the calcaneus (the annular ligament of the calcaneus); it then turns and passes onto the dorsum of the foot. The muscle ends in four slender tendons, the two middle of which begin at the transverse ligament, while the others begin at the fibrous loop. The tendons diverge to the four digits. Each tendon is con- nected with the fibrous sheath surrounding the base of the first phalanx, and each has a synovial bursa beneath it at this point. Near the distal end of the first phalanx the tendon is united on the, lateral side to the conjoined tendon of the extensor brevis digitorum and an interosseus muscle, and on the medial side to the tendon of the interosseus. The lateral side of the most lateral tendon is not thus united, but is joined on the outer side by the tendon of the peroneus tertius. Insertion.—The tendon thus formed on the dorsum of each phalanx by the junction of the two or three tendons above mentioned is firmly attached to the base of the second phalanx at its proximal end in the middle of its dorsal surface. In crossing the joint between the first and second phalanges the tendon forms a fibrous pad which protects the dorsum of the joint and glides over it. It then continues to be inserted into the base of the terminal phalanx. Relations. —Outer surface with the tibialis anterior (7) and the superficial fascia; Inner surface with a part of the tibialis anterior, with the bones, the interosseous membrane, and the peroneus brevis (s). Action.—Extensor of the phalanges. M. tibialis anterior (Fig. 90, ~).—This is the superficial muscle covering the lateral side of the tibia. Origin by fleshy fibres from the proximal one-sixth of the 212 THE MUSCLES. lateral surface of the shaft of the tibia, from the proximal third of the medial border of the shaft and head of the fibula, and from the intervening interosseous ligament. The triangular body of the muscle covers the lateral surface of the tibia and the outer surface of the extensor longus digitorum (f). Near the malleolus it ends in a strong tendon which passes beneath the transverse ligament along with the tendon of the extensor longus (~). The tendon crosses the dorsal surface of the foot obliquely toward its medial side. Insertion into the outer surface of the first metatarsal. Relations.—Outer surface with the superficial fascia and the tendon of the biceps femoris. Inner surface with the extensor longus (/), the tibia, and the interosseous membrane. Action.—Flexor of the foot. 4. Muscles of the Foot. A. MUSCLES ON THE DORSUM OF THE FOOT.—M. ex- tensor brevis digitorum (Fig. 90, ~).—A broad thin muscle covering the tarsus and part of the metatarsus on the lateral side of the dorsum of the foot. It may be divided into three slips. Origin from the distal border of nearly the whole calcaneal annular ligament (5), and from the proximal end of the dorsal surface of the three lateral metatarsals. At the middle of the metatarsals the muscle ends in three flat tendons which pass into the three interspaces between the four tendons of the ex- tensor longus. Each tendon is divided into two branches. Insertion.—The lateral branch of each tendon is inserted into the cartilaginous plate which lies in the metatarsophalan- geal articulation of the digit on the outer side. The medial branch joins the lateral side of the extensor longus tendon on the dorsum of the first phalanx. Action.—Extensor of the digits. B. MUSCLES OF THE SOLE OF THE FooT.—M. flexor brevis digitorum (pedis perforatus).—This is the direct con- tinuation of the tendon of the plantaris. It lies immediately beneath the superficial plantar fascia. The flat belly of the muscle has its medial border attached by an oblique tendinous MUSCLES OF THE PELVIC LIMBS. 213 band to the medial surface of the scaphoid and the medial cuneiform. It divides into four slips which diverge to the four toes, each ending ina flat tendon. The slips decrease in size from the lateral to the medial side. The three lateral ones overlap one another proximally. fusertion.—Each tendon expands at the distal end of the metatarsal and is wrapped about the tendon of the deep flexor which perforates it. The two halves unite beneath the perforat- ing tendon and pass together with the perforating tendon through fibrous rings, the annular ligaments. One of these is attached to the sesamoids at the base of the phalanx. The other is attached to the head of the first phalanx. The tendons are finally inserted into the bases of the second phalanges. The two annular ligaments are connected by fascia so as .to form a continuous canal for the tendons. This canal is lined by a synovial membrane. Covering this canal is a more super- ficial layer of fascia. Before passing into the proximal annular ligament the two middle tendons unite each with the tendon of the corresponding lumbrical muscle. Each also gives off a branch, the lateral one on its lateral side and the medial one on its medial side. These branches, like those of the two middle ones, are inserted into the common phalangeal fascia. Actton.—Flexor of the second phalanges of the digits. M. quadratus plante (called also the plantar head of the flexor longus digitorum) is a thin flat muscle which takes origin from the dorsal part of the lateral surface of the cal- caneus and the cuboid. Its fibres converge to a flat tendon which passes transversely across the flexor longus digitorum and beneath the flexor brevis digitorum and calcaneometatar- sal. Iusertion.—Into the medial part of the outer surface of the tendon of the flexor longus digitorum. Action.—It holds the flexor longus tendon in place. Mm. lumbricales.—These are six. Origin.—The three larger ones have origin from the outer surface of the expanded portion of the flexor longus digitorum on its distal half. Each ends in a slender tendon. Insertions. —The tendons unite with the divisions of the 214 THE MUSCLES. tendon of the flexor brevis which pass to the three lateral digits, at their entrance to the first annular ligament. The one to the fifth digit is sometimes absent. The other three, have orzgiu from the tendon of the flexor longus digitorum at the point where it divides. Each occupies one of the three intervals between the four divisions, and its fibres originate from the proximal ends of the two tendons which bound its interval. Insertion by a very slender tendon into the medial side of the first phalanges of the third, fourth, and fifth digits near their bases. Action.—Move the third, fourth, and fifth digits toward the medial side. : Mm. interossei.—The interosseus of the second digit forms five portions, which cover the ventral surface of the digit. Origin.—(1) By two tendons from the ventral process of the lateral cuneiform. The muscle divides into four parts, three of which pass to the medial side of the digit and act as abductors. They are called the long, short, and middle abductors (abductor longus, brevis, and intermedius digiti secundi). JInsertions.—The short head into the medial sesamoid of the metatarsophalangeal joint, the middle into the medial side of the base of the first phalanx, and the long into the extensor communis tendon near the distal end of the first phalanx. The names long, short, and middle refer to the lengths of the tendons as determined by their points of insertion. The fourth portion which comes from the lateral cuneiform has its zzsertion into the lateral side of the extensor tendon near the distal end of the first phalanx. It is therefore an adductor longus digiti secundi. In some cases there is an adductor brevis from this same head. (2) The fifth part of the interosseus of the second digit has origin from the middle of the ligament covering the peroneal canal, along with the middle adductor of the fifth digit. The two muscles diverge. J/nsertion into the outer side of the base of the first phalanx of the second digit. It is an adductor medius digiti secundi. MUSCLES OF THE PELVIC LIMBS. 215 The interossei of the third and fourth digits are alike. Origin from the ventral surface of the base of the metatar- sal. The muscles cover the ventral surface of the shaft. At the head each divides and passes onto the sides of the metatarsal. ‘nsertion.—Each half of the muscle shows a tendency to divide into two parts. One of these, the more superficial and ventral, ends in a tendon which joins the extensor tendon near the distal end of the first phalanx. The other part is inserted by short tendon- and muscle-fibres into the side of the base of the first phalanx; one of the parts is therefore a middle, and the other a long, adductor or abductor, the adductores and abduc- tores digiti tertii and quarti. The fifth digit has five short muscles. M. abductor medius digiti quinti. Origin from the ventral surface of the calcaneus and from the fifth metatarsal. J/usertion by a slender tendon into the lateral side of the base of the first phalanx of the fifth digit. M. adductor medius digiti quinti. Origin with the adductor medius digiti secundi. /nsertion on the inner side of the base of the phalanx of the fifth digit. M. opponens digiti quinti. Origin by a flat tendon from the middle of the ligament which covers the peroneal canal. It passes obliquely outward parallel to the last. Jusertion on the inner side of the shaft of the fifth metatar- sal. The two remaining muscles of the fifth digit take origzz from the outer part of the ligament covering the peroneal canal. They cover the ventral surface of the shaft. Jnsertion.—The lateral one is inserted into the lateral sesa- moid and is therefore an abductor brevis. The medial one is inserted into the extensor tendon and is therefore an adductor longus. C. MUSCLES OF THE TARSUS.—M. calcaneometatarsalis (part of M. adductor minimi digiti ?).—A weak muscle made up 216 THE MUSCLES. largely of tendon-fibres, some of which pass directly from origin to insertion. It may be regarded as a ligament. Origin, the lateral and ventral surface of the calcaneus near the proximal end. It passes distad and slightly laterad outside of the quadratus plante. Insertion, the lateral side of the base of the fifth metatarsal, and the adjacent surfaces of the cuboid and calcaneus. Action.—Probably causes slight motion of the cuboid on the head of the calcaneus. M. scaphocuneiformis.—A small muscle lying on the sole of the foot in the depression between the lateral cuneiform, medial cuneiform, and the lateral tubercle of the scaphoid. It is hidden by the overlying ligaments. Origin, the lateral tubercle of the scaphoid bone. It passes distad and laterad. Insertion, the lateral surface of the medial cuneiform. Action.—Rotates the medial cuneiform on the scaphoid and would thus act as an opponens of the great toe if the great toe were present. THE VISCERA. I. THE BODY CAVITY. The greater part of the viscera are situated in the body cavity or cceelom. This is divided by the diaphragm into two parts, the thoracic cavity and the abdominal cavity. Each is lined by a serous membrane, in which the part covering the outer wall of the cavity is distinguished as the parietal layer from the part covering the viscera, which is known as the visceral layer. The thoracic cavity is bounded by the thoracic vertebre, the ribs, the sternum, and the diaphragm. The cranial open- ing of the cavity is filled by the trachea and cesophagus as they enter from the neck region. The thoracic cavity is lined by two thin layers of tissue, the outer one of which is the fascia endothoracica, while the inner is the pleura. The fascia endothoracica is a sheet of connective tissue which lines the entire inner surface of the thoracic cavity, descending from the dorsal median line to the heart, and passing into the fibrous layer of the pericardium. The pleura is a thin membrane covering the fascia endothoracica and corresponding to the. peritoneum of the abdominal cavity. It forms two sacs, the pleure, lining respectively the right and left halves of the thoracic cavity. Each of these two sacs is closed, the viscera being suspended within them by folds of the membrane, so that the cavity is everywhere separated from the viscera by a sheet of the pleura. That portion of the pleura which lines the thoracic wall is known as the parietal layer; it may be divided into that covering the ribs (costal pleura), and that covering the diaphragm. That portion which covers the viscera is the visceral layer, or, since it covers chiefly the lungs, it may be 217 218 THE VISCERA. distinguished as the pulmonary pleura. The medial walls of the two pleural sacs come in contact in the median plane, forming a median vertical partition passing lengthwise of the thoracic cavity. This partition is known as the mediastinal septum. The space between the two layers which make up the mediastinal septum is known as the mediastinum, or mediastinal cavity; it contains numerous organs of the thorax. Three parts are usually distinguished in this cavity: a ventral mediastinal cavity, containing chiefly blood-vessels and the thymus gland; a middle mediastinal cavity, enclosing the heart and the anterior and posterior venz cavz; and a dorsal medi- astinal cavity, containing the trachea, the cesophagus, and the aorta. , The abdominal cavity lies caudad of the diaphragm; in it are sometimes distinguished the abdominal cavity proper, extending as far caudad as the cranial edge of the pubis, and the pelvic cavity, lying caudad of this, in the region surrounded by the innominate bones and the sacrum. The two cavities are not distinctly marked off, so that it is convenient to con- sider the abdominal cavity as undivided. Both parts are lined by the peritoneum. The peritoneum is a thin transparent sheet of connective tissue supporting on its surface a layer of flattened epithelial cells, the peritoneal epithelium. It forms a sac which lines the entire abdominal cavity. This sac is closed in the male; in the female, however, it communicates with the exterior through the uterine (or Fallopian) tubes and uteri. All the organs of the abdominal cavity are outside the sac. In the course of their development these organs have encroached on the peritoneal sac. Each has grown against the outer wall of the sac to a greater or less extent and has forced a part of this wall ahead of it into the cavity. In some cases the encroachment has gone so far that the organ in question lies apparently within the peritoneal cavity, suspended from the wall of the sac by a fold of that wall. The wall may thus be divided into three portions. One of these, the parietal layer, lines the wall of the body cavity. The second (the mesentery in case of the alimentary canal, or a ligament in the case of another organ) THE BODY CAVITY. 219 suspends the organ from the body wall. Between the layers of each inesentery or ligament blood-vessels may pass to the organs. The third portion or visceral layer covers the organ in question, forming its serous covering. The reflections of the peritoneum to form the mesenteries and ligaments may be thus described : Caudally the peritoneum covers the whole surface of the bladder and is reflected from its ventral wall to the linea alba as the suspensory ligament of the bladder. Farther craniad the peritoneum suspends the rectum and colon from the mid- dorsal line, forming the mesorectum and mesocolon.. The mesocolon continues craniad to the level of the caudal end of the right kidney and is broadest at its cranial end. At this end the mesocolon passes into the mesentery proper, which suspends the small intestine and is very broad and much folded. Its dorsal border is attached to the median line opposite the caudal end of the kidneys and is very short compared to its very long ventral or intestinal border. Toward the cranial end the mesentery of the jejunum passes gradually into the very much shorter duodenal mesentery. This is drawn out at the caudal end of the duodenum into a fold, the duodenorenal liga- ment which attaches the duodenum to the kidney. The mesogastrium or peritoneal fold for the stomach passes from that part of the median dorsal line lying between the kidneys and the diaphragm, to the greater curvature of the stomach. It does not pass directly to the stomach, but passes first ventrad of the small intestine as far as the pelvis. Thence it turns craniad to reach the greater curvature of the stomach. The fold thus formed is called the great omentum. It forms the dorsal and ventral walls of a sac, the omental sac, the cavity of which is called the lesser peritoneal cavity. The descending limb of the fold forms the dorsal wall of the sac, and its ascending limb forms the ventral wall. Each of these walls is double like a mesentery, so that the great omentum consists of four sheets of peritoneum. Between the two sheets forming the descending limb lies the left half of the pancreas, which passes thence to the right into the duodenal mesentery. A transverse fold passes from the descending limb of the 220 THE VISCERA. omentum along the cranial border of the pancreas to the duodenal mesentery. Farther to the right the descending limb of the omentum, which is here shorter, encloses the spleen and holds it in position parallel to the greater curvature of the stomach and about one centimeter from it. This part of the great omentum is sometimes called the gastrosplenic or gastrolienal omentum. The great omental sac communicates with the peritoneal sac by an opening, the foramen epiploicum or foramen of Winslow. This opening lies caudad and dextrad of the caudate lobe of the liver. This lobe itself lies within the sac. Along the ventral border of the foramen epiploicum pass the common bile-duct from the liver and the portal vein to the liver. The size of the great omental sac is increased by the lesser omentum. This is a double sheet of peritoneum which stretches horizontally from the liver to the duodenum and the lesser curvature of the stomach. It covers ventrad the caudate lobe of the liver. Its right border is at the foramen epiploicum. The part of it which stretches to the duodenum is called the duodenohepatic ligament and contains the bile-ducts and the portal vein. The part that stretches to the stomach is called the gastrohepatic ligament. The peritoneum covers the caudal and cranial surfaces of the liver and is reflected to the adjacent parts to form the ligaments of the liver. The suspensory ligament of the liver passes from the caudal surface of the diaphragm and the median ventral line for about one or two centimeters caudad of the diaphragm, to the liver, and extends between its two halves. The ligamentum teres or round ligament is the thickened free caudal border of the suspensory ligament. It is the remains of the fcetal umbili- cal vein. From the dorsal border of the liver the peritoneum which covers its cranial surface turns ventrad onto the caudal surface of the diaphragm, while that which covers its caudal surface turns dorsad onto the caudal surface of the diaphragm to reach the dorsal body wall. Between these two sheets a small linear part of the surface of the liver is closely applied to the diaphragm without intervening peritoneum. The two THE ALIMENTARY CANAL. 221 sheets which bound this area constitute the coronary ligament of the liver. This ligament is broader where it passes from the left lateral lobe to the diaphragm and is called the triangular ligament. (There is perhaps a corresponding right trangular ligament, from the cranial division of the right lateral lobe.) The caudal division of the right lateral lobe is held to the kidney of that side by the hepatorenal ligament. II, THE ALIMENTARY CANAL, APPARATUS DIGESTORIUS. The alimentary canal may be divided into mouth, pharynx, cesophagus, stomach, small intestine, and large intestine. With thesé are associated certain accessory structures,—the salivary glands, the liver, and the pancreas. The spleen, though not belonging to the digestive system, is usually described in connection with it. The respiratory organs are almost throughout in close relation with the organs of the digestive system. 1. The Mouth. Cavum oris.—The mouth cavity extends from the lips to the pharynx. It is narrower toward the lips, broadens caudad as far back as’ the last teeth, then becomes narrowed to form the isthmus faucium, by which it communi- cates with the’ pharynx. The mouth cavity is divisible into the vestibule of the mouth (vestibulum oris), which comprises that part outside the jaws proper, bounded externally by the lips and cheeks, and the mouth cavity proper (cavum oris proprium), which lies within the teeth. That portion of the vestibule which is bounded by the cheeks is sometimes farther distinguished as the buccal cavity. The entire mouth cavity (except the teeth) is lined by the mucous membrane or mucosa. The lips (labia oris) are thick folds of skin bounding the entrance to the mouth cavity. The outer surface is covered with hair; the inner surface is covered with the mucous mem- brane. The upper lip is marked in the median line by a deep external groove which extends upward to the septum of the nose. Along the inner surface of this groove the lip is closely united to the jaw by a thick fold, the frenulum of the upper lip. For some distance on each side of the frenulum the inner 222 THE VISCERA. surface of the lip bears numerous large papillz. The lower lip is also united to the jaw by a frenulum in the median line; it is again united to the jaw just caudad of the canine tooth, in the space between the latter and the first premolar. Caudad the two lips pass into each other (forming the commissura labiorum), and unite with the cheek. The muscles of the lips have been described (page 105). The cheeks (bucce) in the cat are comparatively thin and small, extending from the lips caudad to the ramus of the mandible. The outer surface is covered with hair; the inner surface is smooth and somewhat folded. The buccal cavity is rather small. On the inner surface of the cheek open the duct of the parotid (Steno’s duct), the ducts of the molar gland, and that of the infraorbital gland. The roof of the mouth cavity is formed by the hard and soft palates. The hard palate (palatum durum) forms the cranial part of the roof; it is supported by the palatal plates of the maxillary and palatine bones. The mucosa of the hard palate is elevated to form seven or eight curved transverse ridges, which are concave caudad. Between the ridges are rows of papillz. In front of the most cranial ridge is a papilla in the middle line, and at each side of the papilla is the open- ing of a small duct (the incisive duct or Stenson’s duct), which leads dorsad through the incisive foramen to the vomeronasal organ (or organ of Jacobson), which lies on the floor of the nasal cavity. Caudad of the hard palate the roof of the mouth is formed by the soft palate or velum palatinum, described below. The floor of the mouth cavity is formed chiefly by the tongue, which extends as far caudad as the isthmus faucium. Ventrad of the free edge of the tongue the mucosa forms a prominent median vertical fold which unites the tongue with the floor of the mouth beneath it; this fold is the frenulum linguz. On each side of the median line at the cranial border of the floor of the mouth is a prominent papilla, at the apex of which open the ducts of the submaxillary and sublingual glands, the former on the lateral side of the apex, the latter on the medial side. THF ALIMENTARY CANAL. 223 The sides of the mouth cavity are formed by the teeth and the gums, covering the alveolar borders of the mandible, maxillaries, and premaxillaries. The mouth cavity presents further for examination the glands, the teeth, the tongue, and the soft palate. THE GLANDS OF THE MOUTH (GLANDUL ORIS).— There are five pairs of salivary glands which open into the mouth cavity. 1. The parotid gland (glandula parotis) (Fig. 65, 1; Fig. 131, 10) is flattened, rather finely lobulated, and lies ventrad of the external auditory meatus and beneath the dermal muscles. Its cranial border follows the caudal border of the masseter muscle and overlies it somewhat; its caudal border is about three centimeters caudad of the border of the masseter. Its borders are unevenly lobed. The parotid duct (ductus paro- tideus: frequently called Stenon’s or Steno’s duct) is formed by the union of several smaller ducts near the ventral end of the cranial border of the gland. It passes craniad imbedded in the fascia covering the masseter. At the cranial border of the masseter it turns inward and lies close against the mucous membrane of the mouth, so that from the inside of the mouth it appears as a white ridge on the mucosa. It opens on the inside of the cheek opposite the most prominent cusp of the last premolar tooth. Along the course of the parotid duct in some cases one or more small accessory parotid glands are found. 2. The submaxillary gland (glandula submaxillaris) (Fig. 65, 2, page 109, and Fig. 131, 11) is approximately kid- ney-shaped. Its surface is nearly smooth, the lobulations not being apparent externally. It lies ventrad of the parotid, at the caudal edge of the masseter muscle, just caudad of the angular process of the mandible. The posterior facial vein (Fig. 131, 6) crosses its outer surface, and its cranioventral border is hidden by two lymphatic glands (Fig. 131, 12) lying at the sides of the anterior facial vein. The submaxillary duct (ductus submaxillaris, frequently called Wharton’s duct) leaves the inner surface of the gland and passes beneath the digastric and mylohyoid muscles and against the outer surface of the styloglossus. From the point where the styloglossus 224 THE VISCERA. passes into the tongue the duct continues craniad close against the oral mucosa and parallel to the mandibula. It is accom- panied by the duct of the sublingual, which lies at first dorsad of it and then mediad. It opens at the apex of the prominent papilla which lies at the side of the middle line at the cranial end of the floor of the mouth. 3. The sublingual gland is elongated and ne in form, with its base against the submaxillary, of which it appears to be a continuation. It stretches along the submaxillary duct for about one and one-half centimeters, lying between the masseter and digastric muscles. The sublingual duct leaves its ventral side, passes close to the submaxillary duct, at first dorsad and then mediad of it, and opens on the medial side of the apex of the same papilla with the submaxillary duct. 4. The molar gland (glandula molaris) (Fig. 65, 9) lies between the orbicularis oris and the mucosa of the lower lip. It stretches from the cranial border of the masseter to a point between the first premolar and the canine. It is flat, broad caudad, and ends in a point craniad. It has several ducts which pass straight through the cheek and open on the mucous surface of the mouth. 5. The infraorbital (or orbital) gland lies in the lateral part of the orbit on its ventral floor. It is ovoid and about one and one-half centimeters long and one-third as thick. Its ventral end rests against the mucosa of the mouth just caudad of the molar tooth. .Its duct leaves the ventral end and opens into the mouth at a point about three millimeters caudad of the molar tooth. THE TEETH. DENTES.—The adult cat has thirty teeth, fourteen in the lower jaw and sixteen in the upper jaw. There are twelve incisors, four canines, ten premolars, and four molars. The tooth formula for the cat is then gas et ine, ou fea! Sp arg 2—2 I—I The teeth are implanted in the alveolar borders of the premaxillaries, maxillaries, and mandible. In each tooth can be distinguished the root, imbedded in the socket of the bone, THE ALIMENTARY CANAL 225 the crown, which projects above the gums, and a narrow neck connecting the two. The root is composed of one or more separate fangs; the crown bears one or more points or cusps. At the cranial end of each jaw are six incisor teeth (Figs. 93 and 94, a). These are imbedded in the alveolar borders of the premaxillaries and the man- dible. The incisor teeth are small, with a crown bearing a sharp edge which is notched so as to form three minute cusps. The root of each has a single fang. The lateral inciscrs are the largest in each jaw, and those of the upper jaw are larger Fic. a Weer J ave, sia Boor than those of the lower. a, incisors; 6, canine; ¢, an pre- Caudad of the incisors, and molar; d, second premolar; ¢, third pre- in the upper jaw separated from ™l@": 4 molar. them by a slight interval, are the canines (4), two in each jaw. These are long, strong, pointed teeth, deeply imbedded in the mandible and maxillaries, their large sockets causing a rounded swelling on the external surface of the bones. Each has a single fang and a single cusp. When the mouth is closed the upper canines lie laterocaudad of the lower ones. Caudad of the canines there is in each jaw a considerable interval free from teeth: this is called the diastema. Caudad of the diastema are the premolar teeth, three pairs (¢, d, ¢) in the upper jaw and two pairs (c, d) in the lower jaw. These teeth are compressed sideways, and those of the lower jaw fit inside of those of the upper jaw. In the upper jaw (Fig. 93) the first premolar (c) is small and usually has but a single cusp and asingle fang, though occasionally there is a small supple- mentary cusp and fang. The second premolar is larger (2); it has a large central cusp, with a single smaller cranial cusp and two small caudal cusps, making four in all. This tooth has two fangs. The third premolar (¢) is the largest tooth in the jaws; it has three large cusps in longitudinal series and a small cusp lying on the medial side of the first one in the row. Its root has three fangs. The molar tooth (/) of the upper 226 THE VISCERA. jaw is small and lies caudomediad of the last premolar. It has two small cusps and two fangs. Fic. 94.—-MANDIBLE, WITH ROOTS OF THE TEETH LAID BARE. 4, incisors; 4, canine; ¢, first premolar; d, second premolar; /, molar. - In the lower jaw (Fig. 94) the two premolars (¢ and @) are similar, the caudal one being a little larger. Each has four cusps; a single large one, a small one craniad of this, and two small ones ‘caudad of it. Each has two fangs. The single molar (/) is the largest tooth of the lower jaw; it has two large cusps and two fangs. The Deciduous Teeth.—At birth the cat has no teeth. There appears later a set of twenty-six teeth: twelve incisors, four canines, and ten molars (six in the upper jaw and four in the lower). These teeth are later replaced by the permanent ones above described. The deciduous teeth of the cat are fully described by Jayne (‘‘ Mammalian Anatomy,’’ vol. I. p. 319), where also an account is given of the order of appearance of the teeth. THE TONGUE. LINGUA (Fig. 95).—The tongue is a muscular organ covered with mucous membrane; in life it is very mobile. It is an elongated organ, flat above, broadest in the middle, and very slightly narrowed at each end. It extends from the incisor teeth to the isthmus faucium and nearly fills the mouth cavity: The caudal third of the tongue forms the floor of the mouth cavity, so that the tongue has here no ventral surface, but is directly continuous with underlying organs. It is in this region that the extrinsic muscles of the tongue (except the genioglossus) enter it. The cranial two- thirds of the tongue is partly or entirely free from the floor of the mouth, the cranial one-third being completely free and movable. In about the middle third the ventral surface of the THE ALIMENTARY CANAL. 227 tongue is held to the floor of the mouth by the fold known as the frenulum lingua. The frenulum contains parts of the two genioglossus muscles, which enter the tongue through it. The ventral surface and lateral borders of the tongue are smooth, soft, and free from papille. The dorsal surface is raised into papillze of various kinds, and has a‘slight median longitudinal furrow. The caudal part of the dorsal surface is softer, redder, and marked with papilla of a different kind from those of the rest of the tongue. From the caudal end a small median vertical fold, the frenulum (or plica) glossoepiglottica passes from the dorsal surface of the tongue to the cranial surface of the epiglottis. The papille of the tongue are of three kinds. 1. The very num- erous filiform papilla (a) (pap- ill filiformes); many of them are horny and tooth-like, with ~ points turned caudad. These are most numerous at the middle of the free end of the tongue. 2. The fungiform papille (4) (papille fungiformes) are found scattered 4 over the surface of the middle of Fic. 95. = tencar: EPIGLOTTIS, the tongue caudad of the large “ND OPENING oF Larynx. : : @, filiform papille; 4, fungiform filiform papilla. They are en- papille: 3’, very large papille at the larged at their free ends. “There #3 of the tongue; ¢, circumvallate : 5 papille; tonsils; e, epiglottis; 7, is a prominent row of very lar ge plica aryepiglottica: & arytenoid car- ones (6') opposite the circumval- Sages. (Cored with mucosa) late papillz at the borders of the vocal cords. tongue. 3. The circumvallate papille (c) (papille vallate) are blunt and each is surrounded by a trench which is bounded in turn bya raised wall. They are in two rows of two or three 228 THE VISCERA. each, which converge near the base of the tongue so as to form a V with the apex directed caudad. MUSCLES OF THE TONGUE (Fig. 96).—M. genioglossus (/) passes from the symphysis of the lower jaw into the tongue and lies beneath (dorsad of) the geniohyoid (g). Origin from the medial surface of the mandible near the symphysis and dorsad of the origin of the geniohyoid. Insertion. —The fibres pass dorsad, diverging in a fan-like manner and forming a flat vertical plate closely applied to the muscle of the opposite side. This plate extends along the caudal three-fourths of the tongue, i.e. as far as it is attached. The cranial fibres arch craniad to the tip of the tongue, the caudal fibres arch caudad to the root of the tongue. Dorsad the muscle is confounded with the muscle of the opposite side. Action.—Draws the root of the tongue forward and the tip backward. M. hyoglossus (4).—From the body of the hyoid bone to the tongue. Origin.—(1) From the ventral surface of the body of the hyoid laterad of the geniohyoid (g), and (2) by a second head from the ceratohyal. /nsertion.—Both heads penetrate into the tongue between the styloglossus (¢) and the genioglossus (/). The fibres intermingle with those of the styloglossus (¢) and thus help to form the lateral parts of the tongue. They finally end in the integument on the dorsum of the tongue at the sides. Action.~ Retracts the tongue and depresses it. M. styloglossus (¢).—From the stylohyal bone to the tongue. Origin from the mastoid process of the temporal bone, from the stylomandibular ligament (2) (which connects the border of the external auditory meatus with the angular process of the mandible) and from the proximal cartilaginous portion of the cranial cornu of the hyoid bone. The fibres pass mediad, diverging between those of the digastric and hyoglossus (4) into the lateral part of the tongue. Insertion.—The fibres pass toward the tip of the tongue, where the mass finally ends in a point, the superficial ones THE ALIMENTARY CANAL. 229 gaining insertion into the integument at the sides’ of the tongue. Relations. —Outer surface with the digastric (Fig. 65, 4) and mylohyoid (Fig. 65, c). Inner surface with the ptery- Fic. 96.—Muscies oF Toncugz, Hyorp Bong, AND PHARYNX. a, M. tragicus lateralis; 4, M. jugulohyoideus; c, M. pterygoideus externus; d, partially cut surface of M. pterygoideus internus; ¢, M. styloglossus; 7, M. genio- glossus; g, M. geniohyoideus; 2, M. hyoglossus; z, M. glossopharyngeus; 7, M. con- strictor pharyngis medius; 4, M. constrictor pharyngis inferior; 7, M. stylopharyngeus; m, M. sternohyoideus (cut); 7, M. cricothyreoideus; 0, M. sternothyreoideus (cut); 2p, M. thyreohyoideus. 1, mandible; 1’, angular process of mandible; 2, stylo- mandibular ligament; 3, bulla tympani; 4, trachea; 5, cesophagus; 6, thyroid gland; 7, isthmus of the thyroid gland. e goideus internus (Fig. 96, @), the cranial cornu of the hyoid, and the tympanic bulla. Action.—Retracts the tongue and raises it. The intrinsic muscles of the tongue (those entirely within it) are attached to its integument at both their ends. There are three sets of fibres: a longitudinal, a transverse, and a ver- tical one. These are seen most readily in cross-sections. The SoFT PALATE. VELUM PALATINUM (Fig. 66, page 230 THE VISCERA. 112).—The soft palate is the free curtain-like structure which forms the caudal part of the roof of the mouth. It is attached to the caudal border of the palatal plates and the ventral border of the perpendicular plates, of the palatine, and to the pterygoid processes and hamuli of the sphenoid, and extends some dis- tance caudad of the hamuli. It thus forms a rather long and narrow curtain separating the caudal part of the nasal cavity from the mouth. Caudad it ends in a free arched border (Fig. 66, 4) which is at about the level of the epiglottis, and may lie against the cranial or the caudal surface of the latter. The narrowed passage bounded by the margin of the velum palat- inum dorsad and the tongue ventrad is the isthmus faucium. From the sides. of the velum a short distance from the caudal border a fold of mucosa passes ventrad to the side of the tongue; a short distance caudad of this a similar fold passes to the floor of the pharynx. These folds form the cranial and caudal pillars of the fauces. Between these folds is a shallow pocket, from the bottom of which there arises a prominent pro- jection or swelling which is one of the two tonsils (Fig. 95, 2). Each tonsil is a reddish, lobulated gland, lymphoid in the adult, nearly a centimeter in length, and about one-third as long as broad, with its long axis craniocaudad. The velum palatinum consists of two layers of mucous membrane, oral and nasal, with intervening muscular and con-. nective tissue. The muscles of the soft palate in the cat are as follows: M. tensor veli palatini (Fig. 66, d, d’, page 112). Origin from the ventral surface of the body of the sphenoid between the foramen ovale and the groove for the Eustachian tube. The muscle ends in a flat tendon which passes over the hamular process (8) of the pterygoid bone. Insertion by spreading out in the soft palate into an aponeurosis which joins the aponeurosis, of the opposite muscle and lies between the mucous membrane of the mouth and that of the nose. Action.—Stretches the palate. M. levator veli palatini (Fig. 66, ¢, ¢’).—A flat triangular muscle which lies within the tensor. THE ALIMENTARY CANAL. 231 Origin from the surface of the body of the sphenoid mediad of the groove for the Eustachian tube, from the styliform process of the bulla tympani, and in part from the Eustachian tube. The muscle passes caudad, and its fibres then diverge into the velum palatinum. lusertion into the velum palatinum, some of the fibres meeting in the middle line. .4ction indicated by the name. A number of other muscles have been described in the soft palate of the cat; they are, however, poorly developed and not easily distinguished. For an account of these, see Stowell, Proceedings of the Am. Soc. of Microscopists, 1889. 2. The Pharynx.—At the caudal end of the mouth cavity the passage for the food and that for the air cross; at the cranial end the food-passage (mouth) is ventral, the respiratory passage (nasal cavity) dorsal. Farther caudad the food-passage (cesophagus) is dorsal, while the respiratory passage (larynx and trachea) is ventral. In the region of crossing there is therefore for a certain distance a common passageway for food and air, and this is known as the pharynx. It extends from the isthmus faucium, at the free caudal margin of the soft palate, to: the beginning of the cesophagus, at the dorsal or caudal margin of the opening of the larynx. The dorsal wall of the pharynx is separated from the base of the skull and the centra of the cervical vertebre only by intervening muscles (longus capitis, levator scapule ventralis, and longus colli, Fig. 72, page 143). Its lateral and ventral walls are supported by the hyoid bone and the cartilages of the larynx. Craniad the pharynx continues, usually, without break nto the cavity lying dorsad of the soft palate. But at the time of swallowing the free edge of the soft palate is pushed dorsad against the dorsal wall of the pharynx, while the caudal part of the pharynx is drawn craniad, so as to form a cavity con- tinuous with that of the mouth. In this way the cavity above the soft palate is completely separated at the time of swallow- ing from the rest of the pharynx. This separated portion is known as the nasopharynx: it is strictly a portion of the respiratory passage, as the food does not pass into it. The 232 THE VISCERA. nasopharynx is continuous craniad by the choanez with the nasal cavity; it forms a horizontal tube between and ventrad of the perpendicular plates of the palatine bones, and has the same craniocaudal extent as the soft palate. Its dorsal wall lies against the basis cranii and the longus capitis muscles; its lateral walls against the pterygoid muscles and the perpendic- ular plates of the palatine bones; its ventral wall is the soft palate. At the middle of its length, at the junction of its dorsal and lateral wall, are two longitudinal slits about three millimeters long. These are the medial openings of the Eustachian tubes, by which the nasopharynx communicates with the tympanic cavity. The pharynx proper, situated caudad of the nasopharynx, is smaller than the latter. It is bounded craniad by the epiglottis and the margin of the soft palate, and is continuous between the two, by the isthmus faucium, with the mouth cavity. Its floor is formed by the cranial end of the larynx. At its caudal end it passes dorsally into the cesophagus, while ventrally it communicates with the larynx. Its walls are muscular. MUSCLES OF THE PHARYNX (Fig. 96).—M. glossopharyn- geus (z). Origin.—Some fibres on the ventral and lateral part of the genioglossus (/) leave that muscle near its caudal end. They form a thin band of diverging fibres which pass outside of the cranial horn of the hyoid.