MEDICAL 
 
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THE 
 
 PHYSIOLOGY OF THE CIRCULATION 
 
 IN PLANTS, IN THE LOWER ANIMALS, 
 AND IN MAN: 
 
 BEING A COURSE OF LECTURES DELIVERED AT THE SURGEONS' HALL TO THE 
 
 PRESIDENT, FELLOWS, ETC., OF THE ROYAL COLLEGE OF SURGEONS 
 
 OF EDINBURGH, IN THE SUMMER OF 1872. 
 
 BY 
 
 J. BELL PETTIGREW, M.D., F.R.S., F.R.S.E., F.R.C.P.E. 
 
 FELLOW OF THE BOTANICAL, MEDICO-CHIRURGICAL, AND OTHER SOCIETIES; 
 
 LECTURER ON PHYSIOLOGY AT SURGEONS* HALL, EDINBURGH ; 
 
 EXAMINER IN PHYSIOLOGY TO THE ROYAL COLLEGE OF PHYSICIANS, EDINBURGH ; 
 PATHOLOGIST TO THE ROYAL INFIRMARY OF EDINBURGH ; &C., &C., &C. 
 
 EfasttateU bg ne f^tmtiretf attfc JFtftg fEttgrabwgs on 
 
 MACMILLAN AND CO. 
 
 , )-: ;. 1874 
 
OXFORD: 
 Printed by E. Pickard Hall and J. H. Stacy, 
 
 "I I t \ t ER,IN-FRS t ;rp T C HE UNIVERSITY. 
 
\\ r I ui 
 
 PREFACE. 
 
 IN the present volume I have endeavoured to give a 
 comprehensive account of the Circulation and the apparatus 
 by which it is effected in Plants, in the Lower Animals, and 
 in Man. I have discussed the subject in its totality, in the 
 hope that those parts of the circulation which appeared 
 obscure in the higher animals might be simplified by com- 
 paring them with similar parts in the lower animals and 
 in plants. This mode of treatment involves details, but 
 these, I trust, will be found also to add additional interest. 
 I have introduced a large number of drawings in place of 
 the diagrams originally employed in illustrating the Course, 
 in order to efface in some measure the traces of lecturing. 
 I have not, however, found time to recast or alter the 
 Lectures in any way, so that, with the exception of a few 
 verbal corrections, they appear in their original form. This 
 circumstance will not, I trust, detract from their usefulness. 
 
 My best thanks are due to my friend Mr. Archibald 
 Constable for having relieved me of the labour of reading 
 the proofs for press. 
 
 Royal College of Surgeons of Edinburgh, 
 April, 1874- 
 
 f 
 
CONTENTS. 
 
 INTRODUCTION. 
 
 ie Circulation 
 Definition of the Circulation 7 
 
 PAGE 
 Epitome of the History of the Circulation 4 
 
 CIRCULATION IN PLANTS. 
 
 Two Different Systems in Plants 10 
 
 Two Principal Currents in Plants Proof that the Saps ascend and descend 1 1 
 
 Endosmose and Exosmose as Adjuncts of the Circulation . . . 15 
 
 The Vessels of Plants their Function 17 
 
 Points of Resemblance between the Vessels of Plants and Animals . . 20 
 
 Respiration of Plants and Animals . . . . . . . 23 
 Cells of Plants their Nature and Function . . . ... . .24 
 
 The Intracellular Circulation in Plants 28 
 
 The Lactiferous Circulation in Plants 41 
 
 The Forces which produce the Circulation in Plants 42 
 
 The Vessels of Plants in Summer form Syphons * 49 
 
 Intracellular Movements in Plants Probable Explanation of . . .51 
 
 Absorbents of Plants 56 
 
 The Vessels of Plants form a Double System of Syphon Tubes Analogy 
 
 between Leaves and Roots 58 
 
 The Effects produced on the Circulation by the Swaying of Plants in the 
 
 Wind. Mr. Spencer's Views 61 
 
 Epitome of the Forces engaged in the Circulation of Plants .... 64 
 
 Organic Forces a Modification of Inorganic Ones 74 
 
 Motion a Condition of Matter .77 
 
 Circulation in Metals 79 
 
 CIRCULATION IN ANIMALS (!NVERTEBRATA). 
 
 Symmetry of Form in the Organs of Circulation and the Body generally . 80 
 
 Respiration and Assimilation connected with the Circulation . . .82 
 
 Ciliary Currents .... 82 
 
VI CONTENTS. 
 
 PAGE 
 
 Rhythmic Movements Analogy between Involuntary and Voluntary Move- 
 ments 84 
 
 Circulation in the Leech contrasted with that in Plants .... 89 
 
 How the Circulation connects the Organic and Inorganic Kingdoms . . 91 
 
 Digestion and Circulation . . 92 
 
 Cilia their Form and Function 94 
 
 Undefined Forces of the Circulation Slowing and Quickening of the 
 
 Circulation, etc. 96 
 
 Circulation in the Star-fish . 103 
 
 Circulation in the Spider 103 
 
 Circulation in the Insect 103 
 
 Function performed by the Valves of Vessels 106 
 
 Circulation in the Lobster. Position of the Respiratory Apparatus in the 
 
 Lobster, Fish, etc 108 
 
 Circulation in the Brachiopoda and Gasteropoda no 
 
 Circulation in the Cuttle-fish . . . ., in 
 
 CIRCULATION IN ANIMALS (VERTEBRATA.) 
 
 Circulation in the Fish in 
 
 Circulation in the Aquatic Reptiles 117 
 
 Circulation in the Frog 118 
 
 Circulation in the Lacerta Ocellata 121 
 
 Circulation in the Python, Crocodile, etc. Presence of Septum Ventriculorum 122 
 
 FOETAL CIRCULATION. 
 
 Points of Analogy between the Circulation in Reptiles and that of the Human 
 
 Foetus 122 
 
 Circulation in the Body of the Foetus 123 
 
 Circulation in the Placenta .128 
 
 Distribution of the Great Vessels in Reptiles, Birds, and Mammals . .159 
 
 Valves in the Heart of the Bird . 161 
 
 Respiration and Circulation in Birds 162 
 
 The Air-Sacs of Birds, etc 163 
 
 Circulation in the Mammal 164 
 
 Auricles, Ventricles, Valves, Septa, etc. of Mammalian Heart . . . 167 
 
 Right Heart of Mammal . 168 
 
 The Blood urged on by a Wave-Movement; Heart and Vessels Open and 
 
 Close in Parts 169 
 
 Valves of Right Heart of Mammal 175 
 
 Safety- Valve Action of Tricuspid . . 1 76 
 
 Left Heart and Valves of Mammal 177 
 
 Circulation in the Head, Liver, and Erectile Tissues 178 
 
 The Lymphatic and Capillary Vessels of Animals 180 
 
 Structure of the Capillaries, Small Arteries, and Veins : Vessels close and 
 
 elongate, and open apd shorten 182 
 
 Elastic and Vital Properties of Vessels 184 
 
CONTENTS. Vll 
 
 PAGE 
 
 Structure of the large Arteries and Veins . * 187 
 
 Structure of the Heart of the Mammal : the Arrangement of the Muscular 
 
 Fibres in the Auricles and Ventricles . 190 
 
 Analogy between the Muscular Arrangements and Movements of the Hollow 
 
 Viscera (Heart, Stomach, Bladder, Uterus, etc.) and those of the Trunk 
 
 and Extremities of Vertebrates 201 
 
 Structure and Properties of Voluntary and Involuntary Muscles . . .208 
 
 Involuntary Muscle 208 
 
 Voluntary Muscle 208 
 
 Mixed Muscles .211 
 
 Muscles can act in Two Directions ; Sarcous Elements of Muscle ; Peculiar 
 
 Movements of 211 
 
 Muscular Motion as bearing on the Functions performed by the Heart, 
 
 Blood-vessels, Thorax, Extremities, etc 211 
 
 How Muscular Fibres open and close the Vessels, the Compartments of the 
 
 Heart, the Stomach, Bladder, Thorax, Abdomen, etc 224 
 
 Analogy between the Movements of the Thorax, Abdomen, and Heart . 233 
 The Movements of the Mammalian Heart, interrupted and yet continuous. 
 
 How the Heart rests 237 
 
 Size of the Cavities of the Heart (Mammal) 240 
 
 Impulse of the Heart (Mammal) 241 
 
 THE VALVES OF THE VASCULAR SYSTEM. 
 
 Venous Valves their Structure, etc 243 
 
 The Venous Valves in Action 249 
 
 Arterial or Semilunar Valves, their Structure, etc. 251 
 
 The Arterial or Semilunar Valves in Action 259 
 
 Semilunar and other Valves of the Fish, Reptile, Bird, etc 259 
 
 Intricate Structure of the Mitral and Tricuspid Valves in Mammalia ; 
 Relations of the Chordae Tendineae to the Valves and to the Musculi 
 
 Papillares 266 
 
 The Mitral and Tricuspid Valves of the Mammal in Action . . . .273 
 The Mechanical and Vital Theories of the Action of the Mitral and Tricuspid 
 
 Valves considered 276 
 
 The Sounds of the Heart, to what owing , 284 
 
 THE GANGLIA AND NERVES OF THE HEART, AND THEIR 
 CONNEXION WITH THE CEREBRO-SPINAL AND SYMPATHETIC 
 SYSTEMS IN MAMMALIA. 
 
 The Cervical Cardiac Branches 296 
 
 The Thoracic Cardiac Branches 296 
 
 The Superior Cervical Ganglia 297 
 
 The Middle and Inferior Cervical Ganglia . . . . . . . 297 
 
 The Upper Cardiac Nerve 297 
 
 The Middle Cardiac Nerve 297 
 
 The Inferior Cardiac Nerve 298 
 
viii CONTENTS. 
 
 Plexuses formed on the Roots of the Pulmonary Artery and Aorta in the Calf 301 
 
 Plexus formed on the Anterior Coronary Vessels of the Calf . . . 302 
 
 Plexus formed on the Coronary Sinus^of the Calf 302 
 
 Distribution of the Nerves on the Surface and in the Substance of the Auricles 
 
 of the Calf 303 
 
 Distribution of the Nerves on the Surface and in the Substance of the 
 
 Ventricles of the Calf 303 
 
 Distribution of the Nerves on the Right Ventricle ..... 306 
 
 Distribution of the Nerves on the Left Ventricle 307 
 
 Distribution of the Nerves in the Human Heart 309 
 
 Microscopic Appearances presented by the Ganglia found on the Coronary 
 
 Sinus and Cardiac Vessels . . .310 
 
 Why does the Heart act Rhythmically ? 313 
 
 Proofs that the Heart may act independently of the Nerves . . . x . 316 
 Proofs that the Movements of the Heart are regulated and co-ordinated by 
 
 the Nerves 318 
 
 The Theory of Irritability as bearing on the Action of the Heart considered 321 
 
 Concluding Remarks . 329 
 
THE PHYSIOLOGY OF THE CIRCULATION 
 
 IN PLANTS, IN THE LOWER ANIMALS, 
 
 AND IN MAN. 
 
 % 
 
 INTRODUCTION. 
 
 MR. PRESIDENT AND GENTLEMEN, The circulation of 
 the blood forms such an important factor in the animal 
 economy that I feel I need offer no apology for making it 
 the subject of the present lectures. The heart, its nerves, 
 blood-vessels, and valves, supply a theme of unusual interest 
 not only to the anatomist and physiologist, but also to 
 the practitioner, especially since the introduction of the 
 stethoscope. In order to give an intelligible account of the 
 circulation, and the apparatus by which it is effected in man, 
 it will be necessary to avail myself of whatever collateral 
 information is within reach. This will lead me to speak at 
 more or less length of the so-called circulation in plants 
 of the circulation in the lower animals, and in the foetus. 
 
 By adopting this method I hope to be able to lead up to 
 the complex circulation as it exists in man, by a series of 
 steps, which, when taken together, will form a sort of royal 
 road to the goal at which we would ultimately arrive. The 
 time devoted to the journey will not be lost if I succeed 
 in placing before you the links (fearfully and wonderfully 
 made) of a chain, on the integrity of which life itself may be 
 said to depend. In some cases we shall find only one link 
 of the chain present; in others, two; in others, three; and 
 
 B 
 
2, PHYSIOLOGY OF THE CIRCULATION. 
 
 so on until we arrive at a degree of differentiation and com- 
 pleteness which, while it commands the reverence, must elicit 
 the admiration of every one who reflects. In the human 
 circulation nearly all the links are present, and it is only 
 by a knowledge of these, as they exist in the lower grades 
 of life, that we can hope to put them in their proper places, 
 when we come to generalise. In the plant and medusa there 
 is no trace either of a heart or pulsatile vessel. In the insect 
 the heart is absent, but a pulsatile vessel makes its appearance. 
 In the fish a heart, consisting of two cavities, is found. In 
 the serpent those cavities are increased to three ; and in birds 
 and mammals to four. 
 
 The number of the cavities depends to a certain extent on 
 the nature of the respiration, and this in its turn modifies the 
 temperature of the blood. In the fish breathing is effected, 
 and the blood aerated, by the gills ; one cavity (the auricle) 
 receiving the blood from the system ; the other (the ventricle) 
 forcing it directly into the gills, and, through them, indirectly 
 into the system. In the serpent breathing is effected, and 
 the blood aerated, by the aid of lungs ; two cavities (the 
 auricles) receiving the blood from the lungs and from the 
 system ; one cavity (the ventricle) forcing it through the 
 lungs and through the system. In the reptile the circulation is 
 of a mixed character, the arterial and venous blood blending 
 in the ventricle of the heart. In the bird and mammal the 
 heart consists of four cavities two auricles and two ventri- 
 cles ; the auricles receiving the blood from the system and 
 from the lungs ; the ventricles propelling the blood through 
 the lungs and through the system. This object is attained 
 by a cross circulation the right auricle receiving venous or 
 dark blood, the left auricle arterial or bright red blood ; the 
 right ventricle propelling venous or dark blood, the left one 
 arterial or bright blood. The differentiation observable in the 
 cavities of the heart is preceded by a similar differentiation in 
 the channels and vessels through which the nutritious juices 
 flow ; the elaboration of the heart and vessels necessitating 
 the presence of valves, which vary in number according to the 
 complexity of the circulatory apparatus. ' In the lowest or- 
 ganised plants, such as the fungi, algae, etc., and in the lower 
 classes of animals, as the polypi, actiniae, and a great part of 
 
PHYSIOLOGY OF THE CIRCULATION. 3 
 
 the intestinal worms, the nutritious materials are transmitted 
 through their substance, without any distinct canals or tubes ; 
 while in the higher classes of plants, and in the medusae, etc., 
 among animals, vessels are present, but these are unprovided 
 with any pulsatory cavities. In the articulated animals the 
 vessels are still without any pulsatory cavities, but to make 
 up for the deficiency the dorsal vessel itself has a distinct 
 movement of contraction and relaxation V 
 
 With regard to the valves, it may be stated that they are 
 only found in well-formed vessels, and at the orifices of canals 
 or cavities having a definite structure. They are so placed 
 that they compel the circulating fluid always to move in the 
 same direction. They are consequently not found in plants, 
 for in thesej as will be shown presently, the nutritious saps 
 at one period of the year flow from below upwards, and at 
 another, from above downwards. A cross circulation, i. e. a 
 circulation across the stem, and a circulation within the cells 
 of the plant, are likewise to be made out. The valves vary in 
 number and in the complexity of their structure. In the veins 
 they usually consist of from one to four segments. In the 
 arteries, as a rule, they consist of three segments 2 . In the 
 heart they may vary from two to three, and to these as many 
 intermediate segments may be added. The number, however, 
 may greatly exceed this, for in the bulbus arteriosus of the 
 American devil-fish (cephalopterus giorna) we find as many as 
 thirty-six segments. The valves may be placed within com- 
 paratively unyielding structures, as the fibrous rings found at 
 the beginning of the pulmonary artery and aorta of the mam- 
 mal ; or they may be placed within yielding and actively 
 moving structures, as the bulbus arteriosus of the fish, and the 
 base of the ventricles of the bird and mammal. In the former 
 case the structure of the segments is comparatively simple, and 
 their action to a great extent mechanical ; in the latter case 
 the structure of the segments is more complex, the segments 
 
 1 Cyc. of Anat. and Phys., art. Heart.' By Dr. John Reid, p. 577. 
 
 2 The valves of the arteries in the mammalian adult are confined to the origins 
 of the pulmonary artery and aorta. They are termed semilunar from their shape. 
 It happens occasionally that only two segments are present, the number increasing 
 at times to four. In such cases a segment may be absorbed or divided into two by 
 disease. It ought to be observed that rudimentary valves are found in the um- 
 bilical arteries. These are, strictly speaking, foetal structures. 
 
 B 2 
 
4 PHYSIOLOGY OF THE CIRCULATION. 
 
 being provided with tendinous chords which vary in length, 
 strength, and direction. The tendinous chords are necessary 
 to restrain the action of the segments within certain limits, 
 and to co-ordinate the movements of the segments with the 
 movements of the structures within which they are placed 
 the bulbus arteriosus and ventricle opening and closing al- 
 ternately. The forces engaged in carrying on the circulation 
 increase in direct proportion to the number and complexity of 
 the hearts, vessels, and valves, and the number and variety of 
 the tissues to be nourished. It is with a view to reducing 
 those structures and forces to their simplest expression, that I 
 propose to treat the subject of the circulation comparatively. 
 What is true of the particular is necessarily true of the 
 general ; and if we succeed in comprehending a simple struc- 
 ture, and in following a simple action, the knowledge acquired 
 will greatly assist us in comprehending complex structures 
 and combined actions. It is comparatively an easy matter 
 to understand a purely mechanical act. Here the forces and 
 resistances can be appreciated with something like mathe- 
 matical accuracy. It is comparatively a very difficult matter to 
 understand a vito-mechanical act, for in this case we are never 
 exactly sure what is vital and what vito-mechanical. This is 
 especially true of the circulation, where we have on some occa- 
 sions to deal with rigid tubes and cavities, such as exist in plants, 
 and which are incapable of receiving an impulse from without ; 
 while in others, we have to deal with flexible elastic tubes and 
 cavities, such as are found in animals, and which are not only 
 capable of receiving an impulse, but of storing up the impulse 
 or power communicated, and of expending it as required. 
 
 If to the foregoing we add that the action of muscles, which, 
 in animals, are the chief motors in the circulation, is compara- 
 tively unknown, we conclude a list of difficulties which it will 
 require time, patience, and perseverance to overcome. These 
 difficulties were present in force to the ancients, as a brief 
 resume of the history of the circulation will show. 
 
 Epitome of the History of the Circulation. We are in the 
 habit, and very properly, of attributing the discovery of the 
 circulation to the illustrious Harvey. It ought, however, not 
 to be forgotten that there were many pioneers in this field 
 before Harvey. The Chinese, for example, believed that the 
 
PHYSIOLOGY OF THE CIRCULATION. 5 
 
 circulation of the vital heat and radical humours commenced 
 at three o'clock in the morning, reached the lungs in the 
 course of the day, and terminated in the liver at the end of 
 twenty-four hours. This was a very vague and visionary notion 
 of the circulation certainly ; still, it embodied the idea of 
 fluids circulating within the body. The first rational attempt 
 at unravelling this great mystery was made in the time of 
 Hippocrates and Aristotle. It consisted of a description, ap- 
 parently from dissection, of the principal blood-vessels. Galen, 
 towards the end of the second century, described the course 
 of the blood-vessels in many of the lower animals, and appears 
 to have known the structure and uses of the foramen ovale 
 in the foetus, and that the arteries and veins anastomosed. 
 He was also cognizant of the fact that the arteries contained 
 blood, and described them as arising from the heart ; the 
 veins, in his opinion, arising from the liver. He thought that 
 the blood passed through the septum of the heart ; and this is 
 actually true of the heart of the serpent. Neither Hippo- 
 crates, Aristotle, nor Galen, however, was aware that the' 
 blood circulated, i.e, started from one point and returned to 
 the same point after making the circuit of the body. Galen 
 believed that the blood simply oscillated ; and it is a curious 
 circumstance that, in plants and some of the lower animals, 
 this is what actually occurs. 
 
 Mr. Herbert Spencer, for instance, states that in plants the 
 saps ascend and descend in the same vessels, and that their 
 movements are interrupted at irregular intervals. Johannes 
 M tiller, in like manner, affirms that in the leech the blood- 
 vessels on one side of the body contract and force the blood 
 into those of the other and opposite side, and that these in 
 turn contract and force it back again, the blood being made 
 to oscillate transversely across the animal. The celebrated 
 Vesalius examined the subject of the circulation afresh in 
 1542. He pointed out the difference between the arteries and 
 veins, and showed that the veins and the heart contained 
 valves. He also explained that the arterial pulse depended 
 upon the systole of the heart. Here was a decided advance. 
 Servetus, that martyr to science, 1 had, as early as 1 53 1, actually 
 
 1 Servetus fell a victim to religious persecution, and was cruelly burned alive at 
 Geneva in 1553. 
 
6 PHYSIOLOGY OF THE CIRCULATION. 
 
 described a pulmonic circulation. He says, Whereas, In the 
 adult, the vital spirit (blood) cannot pass from the right 
 auricle into the left, because of the imperforate nature of 
 the auricular septum, it must go through the lungs, where 
 it is changed, i.e. undergoes a transformation by coming in 
 contact with the vital spirit which resides in the air, after 
 which it returns to the heart. Servetus expressed his belief 
 that the pulmonary artery and vein had some other function 
 than that of nourishing the lungs an inference deduced from 
 their comparatively large size. 
 
 Caesalpinus, in 1583, described the pulmonic circulation 
 more carefully than Servetus had done, and showed that he 
 had some knowledge of a double circulation. Nor did the 
 foetal circulation, with its several peculiarities, escape the lynx 
 eyes of the anatomists of the sixteenth century. Galen, as 
 has been pointed out, had a knowledge of the foramen ovale. 
 He had also a partial knowledge of the ductus arteriosus. 
 The ductus arteriosus was carefully described by Fallopius, 
 Aranzii, and Vesalius. The last observer likewise discovered 
 the ductus venosus, which was figured by Fabricius and 
 Eustachius. It was reserved however for the immortal 
 Harvey to place the coping-stone on the magnificent edifice 
 of the circulation, and to this philosopher we owe our know- 
 ledge of the circulation in its entirety, and as at present ac- 
 cepted. Harvey was the apt pupil of a celebrated master. 
 He studied under the famous Fabricius of Padua, for the 
 protracted period of six years, viz. from 1596 to 1602. 
 Fabricius, although entirely ignorant of the circulation as 
 subsequently developed and explained by Harvey, had, for- 
 tunately for Harvey, an intimate knowledge of the valves of 
 the veins, of which he published an account in 1603. From 
 Fabricius then the illustrious Harvey derived much of that 
 information which enabled him to astonish the world by his 
 brilliant discovery. Harvey, on his return to England, in- 
 stituted a series of experiments with a view to determine 
 the exact nature and uses of the venous valves. The inquiry 
 was laborious and long ; and it was not till the year 1619, i. e. 
 seventeen years after he left Padua, that he ventured to teach 
 the doctrine of the double circulation publicly. Other nine 
 years elapsed before the Exercitatio Anatomica de Motu 
 
PHYSIOLOGY OF THE CIRCULATION. 7 
 
 Cordis et Sanguinis in Animalibus saw the light. This 
 celebrated work was consequently published in 1628, and, 
 curiously enough, not in England but in Frankfort. It 
 therefore took Harvey some twenty-six years to mature and 
 perfect his views. 
 
 Harvey left little to be done, but that little fell to the lot 
 of a worthy successor, the renowned Malpighi, who, in 1661, 
 by the aid of the microscope, discovered the capillary circula-. 
 tion, -and the presence of blood-globules within the vessels. 
 Harvey's views, thoroughly matured, and sound in warp and 
 woof as they were, met with a determined opposition, and 
 it was only after many an unseemly conflict between really 
 great men, that the blood was allowed to flow quietly in the 
 double channel which he had taken such pains to discover 
 and describe. There is little chance of its changing its course 
 now ; and the task which I set myself in the present lectures 
 is to point out the course which the blood and other nutritious 
 juices pursue, as they meander about in the organic world, 
 now free, now confined ; now checked by the presence of 
 valves, now hurried forward by the pressure of vessels, hearts, 
 and other forces, to which I shall have occasion frequently 
 to allude as the subject becomes more complicated. 
 
 Definition of the Circulation. The term circulation, in the 
 present day, is employed in a double sense. In its wider 
 signification it embraces the course of the nutritious juices 
 through plants and the lower orders of animals ; in its more 
 limited signification, and as applied to man and the higher 
 orders of animated beings, it indicates the course of the blood 
 from the heart to the capillaries, and from these back again to 
 the heart. The word circulation literally means a flowing 
 round a going and returning ; and it is well to bear the 
 original meaning in mind, as we shall find that a single circle 
 aptly represents the circulation in most of the lower animals ; 
 a circle, with one or more accessory loops, representing the 
 circulation in the higher ones. In man, the chief circle 
 represents the systemic circulation two accessory loops re- 
 presenting the pulmonic and portal circulation. The ac- 
 cessory loops may be increased indefinitely to meet the 
 requirements of any particular case. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 CIRCULATION IN PLANTS. 
 
 In plants the circulation is in its most rudimentary form ; 
 in fact it is incomplete as a circulation, i.e. as a continuous 
 flow of nutritious juices in a circle. My meaning will be ob- 
 vious when I remind you, that in trees the sap flows steadily 
 upwards in spring, and steadily downwards in autumn. The 
 chain is, as it were, broken at both ends. There is, in 
 addition to the upward and downward currents, a certain 
 amount of transfusion, i.e. of cross currents running in the 
 direction of the breadth of -the stem ; but the transfusion 
 referred to is trifling when compared with the two principal, 
 and, as regards time, interrupted currents 1 . In order to com- 
 prehend the true nature of this interrupted and, so to speak, 
 disjointed circulation, it is necessary to remember that trees 
 have a season of activity and a season of repose ; that they 
 increase in an upward direction by means of shoots, in a 
 downward direction by means of roots, and laterally by 
 branches 2 . In other words, they increase in every direction; 
 and this holds true of growing animals as well as growing 
 plants. The shoots, by their upward growth, tend to draw 
 up the sap ; the roots, by their downward growth, to draw it 
 down ; and the branches, by their lateral growth, to draw it 
 transversely. Here, then, are the materials for an interrupted 
 or disjointed circulation with a certain degree of oneness 
 about it. Nutrition is a principal factor in the process. The 
 
 1 ' The nutrient fluids in plants follow certain directions according to the struc- 
 ture and arrangement of the tissues, the locality of the sources of nutrition and of 
 growth, or other actions ; and as regards the elaborated fluid, the movement may 
 be (i) from the place of formation to that of consumption ; or (2) to the stem, 
 cells, or reservoirs ; or (3) from the latter to the place of consumption.' Henfrey's 
 Botany, as edited by Dr. Masters, F.R.S., p. 570. 
 
 2 ' The sap will flow to the several parts according to their respective degrees 
 of activity to the leaves while light and heat enable them to discharge their 
 functions, and back to the twigs, branches, stem, and roots when these become 
 active and the leaves inactive, or when their activity dominates over that of the 
 leaves. And this distribution of nutriment, varying with the varying activities 
 of the parts, is just such a distribution as we know must be required to keep up the 
 organic balance.' Principles of Biology, by Herbert Spencer, vol. i. p. 557. 
 
PHYSIOLOGY OF THE CIRCULATION. 9 
 
 idea of a plant or tree increasing in an upward and downward 
 direction and laterally at one and the same time, is consistent 
 with fact. When a seed grows, it extends itself into the 
 ground and into the air ; i. e. it spreads from a centre in an 
 upward and outward direction, and in a downward and out- 
 ward direction 1 . (Figs. 1-3.) 
 
 Fig. i. 
 
 Fig. 2. 
 
 Fig. i. ' A seedling dicotyledonous plant with an ascending and a descending axis." Henfrey. 
 
 Fig. 2. ' Pandanus odoratissimus, the screw-pine, with adventitious roots supporting the trunk.' 
 Henfrey. 
 
 Fig. 3.' Rhizophora mangle, the mangrove-tree, supported as it were upon piles by its numerous 
 roots, which raise up the stem. The plant grows at the muddy mouths of rivers in warm climates.' 
 Balfour. 
 
 If, bearing this fact in mind, you imagine that as the tree grows 
 the central point from which it had its being moves upwards 
 (it must do this if it is to maintain its central position with 
 reference to the tree as a whole), then we are forced to con- 
 clude that the stem of the tree itself is sending off processes 
 in an upward and downward direction, and likewise laterally. 
 That the central or germinal point recedes in an upward 
 direction as the stem grows is rendered almost certain by the 
 researches of Henfrey, who has shown that the root in grow- 
 ing exercises an upward pressure as well as a downward one ; 
 and that if the upper part of the root be relieved from its 
 load of superimposed earth, and the weight of the plant 
 balanced, the root, in virtue of its elongation alone, will cause 
 the whole mass of the plant to rise bodily upwards. . This is 
 particularly well seen in the mangrove-tree and screw-pine, 
 
 1 The hydrogastrum, one of the algae, consists of a single cell, but this cell is so 
 differentiated as to simulate a perfect plant, with roots, stem, bud, and fruit. 
 
10 
 
 PHYSIOLOGY ON THE CIRCULATION. 
 
 where the stems are raised completely out of the ground, and 
 supported as it were upon piles. (Figs. 2, 3.) 
 
 Two^ Different Systems in Plants. The embryo, according 
 to Petit Thouars and Gaudichaud, consists of two portions, a 
 caulinary and radicular ; the one having a tendency to ascend, 
 the other to descend. These portions, which may be taken to 
 represent different systems, have different sets of cells and 
 vessels ; the ascending system in the dicotyledons being con- 
 nected with the medullary sheath, and passing into buds and 
 leaves ; the descending system, which is situated between the 
 sheath and the bark, being connected with the woody tissue 
 
 Fig. s. 
 
 Fig. 4. 
 
 Fig. 6. 
 
 Fig. 4. ' Slip or cutting of root of Madura, showing a number of buds, c, from which proceed radicular 
 fibres, a, which are interposed between the bark, 6, and the fibres of the old wood. The young fibres 
 are traced to the buds, and, in their progress downwards, they remain distinct. This example is brought 
 forward by Gaudichaud as illustrating his vertical theory of wood formation." Balfour. 
 
 Fig. 5. ' Truncated stem of a dracaena after maceration, showing the tracheae, t. t, of the ascending 
 system of the stem and branch. The radicular system of the old stem,./; is seen in the form of fibres, 
 and the radicular woody bundles, r t of the branch are disposed in a grasping manner over those of the 
 old stem. The fibres, according to Petit Thouars and Gaudichaud, come from the bases of the leaves, 
 and belong to the descending system.' Balfour. 
 
 Fig. 6.' Vertical section of the stem of a palm, showing the vascular bundles./z/, curving downwards 
 and interlacing. This peculiar arrangement suggests the idea of roots ramifying.' Balfour. 
 
 sent down from the leaves. The woody fibres of the leaves, 
 aided by the cambium, are developed from above downwards. 
 This belief in a double system in plants is confirmed by 
 numerous facts, and in especial by the vascular bundles in 
 palms, etc. ; these bundles proceeding from the base of the 
 leaves, and interlacing in a curved downward direction, as 
 shown in the accompanying figures. 
 
 It is also confirmed by the development of aerial roots, from 
 different parts of the stems of screw-pines, tree-ferns, vellozias, 
 figs, etc. ; the stem of the screw-pine actually becoming less 
 in proportion to the number of adventitious roots given off. 
 
PHYSIOLOGY OF THE CIRCULATION. II 
 
 (Fig. 2, p. 9.) In some palms, moreover, the descending fibres 
 burst through the stems externally, and appear as roots. If 
 further confirmation of this view were necessary, it is to be 
 found in the fact that occasionally sound wood at a higher 
 level of the stem sends down roots into rotten wood on a 
 lower level. Mr. John Lowe gives a curious example of this 
 in the Salix viminalis, a species of willow. The trunk de- 
 cayed in the centre, and from the sound wood above the 
 decayed part a woody root eighteen inches in circumference 
 descended. It penetrated the rotten mass, and when it reached 
 the sound wood beneath, gave off branches which reached the 
 soil. The radicular stem ultimately produced leaf-buds and 
 leaves. That two distinct, and in some respects opposite, 
 systems exist in plants, is rendered exceedingly probable by 
 the researches of De la Hire, Darwin, Knight, Auber du Petit 
 Thouars, Gaudichaud, and Macaire ; the last observer be- 
 lieving that even the roots of plants have a twofold function, 
 the one to extract moisture from the soil, the other to return 
 excess of moisture to it. The presence of two systems in 
 plants, or what is equivalent thereto, is, in a measure, neces- 
 sary to explain the phenomenon of their general circulation. 
 Without some such arrangement it would be difficult to 
 account for the ascent and descent of the sap, and, at certain 
 periods of the year, the deposit, storage, and subsequent re- 
 moval of starch corpuscles, the simultaneous increase of a 
 tree by shoots, branches, and leaves in the air, and by roots 
 and spongioles in the ground. 
 
 Two Principal Currents in Plants Proof that the Saps 
 ascend and descend. The existence of two principal currents 
 can be readily detected, for it is found that if a tree or its 
 branches be cut in the spring, its sap flows in an upward and 
 outward direction ; whereas if cut in the autumn, the sap 
 flows in a downward and outward direction. The spring and 
 autumn correspond to the bleeding seasons of trees. Walker ] , 
 Burnett'- 2 , and others have shown that in trees there is no 
 descent of sap until after the development of the leaves. This 
 
 1 Walker's Experiments on the Motion of Sap in Trees. Trans. Roy. Soc. 
 Edin. i. 3. 
 
 2 Burnett on the Development of the several Organic Systems of Vegetables. 
 Jour. Roy. Instit. vol. i. 
 

 12 PHYSIOLOGY OF THE CIRCULATION. 
 
 was ascertained by making incisions or notches into the bark 
 and wood of trees in spring and summer. From numerous 
 experiments these investigators came to the conclusion that 
 in all instances the spring sap begins to flow at the root, and 
 that it rises slowly but surely to the very extremity of the 
 tree. This was proved by the tree bleeding at the lowest 
 notch first, and at the under side of the notch before the 
 upper. It was further ascertained that the upward current 
 extends from the stem to the branches. To these interesting 
 experiments Mohl added another of great value. He showed 
 that if a ring of bark be removed, the sap flows up as before 
 the mutilation, but that if a portion of the wood be removed 
 without injury to the bark which covers it, the part of the 
 wood above the wound is no longer supplied with sap, and 
 dries up. 
 
 A converse experiment was performed to prove the descent 
 of the sap in summer. When a ring of bark is removed, the 
 girth of the tree increases in volume above the injury, and 
 remains in statu quo below the injury. If moreover, as 
 Henfrey states, bark be removed in patches, and the surfaces 
 become gradually grown over by new wood, the greater part 
 of the new growth comes from the tipper side \ This shows 
 not only that the crude sap ascends, but that the elaborated 
 sap descends, and that starch granules and other matters are 
 stored up or converted into wood in the part above the 
 injury. If the tree be cut in summer, the nutritious juices, 
 owing to their greater viscidity and other changes, do not flow 
 outwards ; which shows that the nature of the circulation 
 and the material circulated at this period is somewhat dif- 
 ferent from what it is in spring and autumn. In summer the 
 crude sap, which is absorbed by the roots, rises to the leaves, 
 where, by evaporation and other processes, it is elaborated 
 into the succus propritis or proper food of the plant. The 
 
 1 ' In dicotyledons the elaborated sap descends in the nbro-vascular bundles of 
 the cambium layer of the wood and in the internal tissue of the bark. It also passes 
 .inward by lateral transfusion. In dicotyledons the inner layers of wood generally 
 become converted in course of time into heart-wood, the solidity of which obstructs 
 the passage of fluids, which then ascend chiefly in the younger outward layers of 
 the wood which constitute the alburnum or sap-wood.' Hen/rey's Botany, pp. 
 568,569. 
 
PHYSIOLOGY OF THE CIRCULATION. 13 
 
 succus propriuS) which differs in its constitution from the crude 
 sap, subsequently descends into the stem, through which it 
 diffuses itself by a collateral circulation, to be stored up for 
 future wants. M. A. Gris was convinced that the sap ascends 
 and descends from finding that in winter the medullary rays, 
 wood, and pith, are filled with starch grains, which disappear 
 in a great measure during the spring, and are replaced during 
 the summer. He was led to conclude that there are two 
 special movements of the nutritious juices, as illustrated by 
 the formation of starch granules in summer, and their absorp- 
 tion in spring. That the sap ascends there can be no doubt, 
 for the plant derives its nourishment chiefly from the earth ; 
 and that it descends is proved by the experiments referred 
 to. In spring the circulation is mainly concerned with the 
 elongation of the stem and branches, the development of the 
 buds, and the evolution of the leaves, its course being for the 
 most part upwards \ In summer it is chiefly concerned with 
 the functions of the leaf, the elaboration of sap, and the storing 
 up of food for the plant, its course being partly upwards and 
 partly downwards ; while in autumn, owing to excess of 
 moisture, a diminution of temperature, and other changes, the 
 course of the circulation is for the most part from above down- 
 wards ; the circulation having, so to speak, completed its work 
 for the season 2 . Much more sap is taken up than is given off 
 in spring in order to administer to the growth of the plant. 
 In autumn, when the period of growth is over, this process is 
 reversed, more sap being given off by the roots than is taken 
 up by them. The circulation in a tree, as will be seen, is 
 interrupted or non-continuous, and this is accounted for by 
 the tree having periods of greater and less activity. This 
 holds true also, within certain limits, of animals ; the circula- 
 tion in animals being most vigorous when the animal is awake, 
 or when excited ; and least so when it is in a quiescent state, 
 when sleeping or when hibernating. I have attempted to 
 
 1 To the progress of the sap in the direction of the axis in spring Burnett 
 ascribes the early development and vigour of the terminal buds. 
 
 * It may be well to state, that the ascending current of spring is accompanied by 
 a slight downward current, the descending current of autumn being accompanied 
 by a slight upward current, the spring and autumn currents diffusing themselves as 
 they go. This follows because of the share taken by endosmose and exosmose in 
 the circulation. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 convey an idea of the scheme of the circulation in plants by 
 the aid of the subjoined figures. (Figs. 7 and 8.) 
 
 Fig. 7. 
 
 Fig. 
 
 F'ST- 7- Endosmometer, showing endosmotic and exosmotic currents, f, Glass vessel containing 
 water, g, Expanded portion of glass tube bent upon itself at i and k ; its under surfaces being covered 
 by a piece of bladder, k, Column of mercury. The space between the column of mercury and the 
 bladder (g) is filled with syrup at aperture i. Immediately the water and syrup act upon the bladder or 
 interposed membrane, opposite currents are induced, the water rising through the bladder and syrup 
 with great energy, as indicated by the arrows, b, c (endosmosis), the syrup settling down into the water 
 more feebly, as indicated by the arrows a a (exosmosis). The water sets towards the syrup with such 
 force as to elevate the column of mercury k, in the tube /, in the direction e. In addition to the principal 
 currents, indicated by the arrows a and b, there are minor currents which proceed transversely. These 
 are best seen when the bladder is made to project beyond^-, so as to display a certain amount of lateral 
 surface. 
 
 Fig. 8. Diagram, representing the ascending, descending, and transverse currents in the plant. 
 a, Ascending or spring current, b. Descending or autumn current, c. d, Ascending and descending 
 currents of summer ; these being continuous in the direction of the leaves and roots, a, c. Transverse 
 currents. The arrows in this diagram represent the endosmotic currents, the darts the exosmotic ones. 
 
 In contemplating figure 8 we are at once struck with the 
 diversity in the direction of the currents ; one ascends, another 
 descends, or a third runs transversely and at right angles to both. 
 The ascending and descending currents are most strongly 
 pronounced. These currents and it is a remarkable circum- 
 stance are found in all the higher plants and animals up to 
 man himself. The object to be attained is manifest. The 
 circulation is instituted expressly for the purpose of carrying 
 matters of divert kinds to and from the tissues. But to give 
 to and take from implies movements in diametrically opposite 
 directions. In animals with hearts and blood-vessels supplied 
 with valves, we can readily understand why the circulating 
 fluids should pursue two directions, the one current setting 
 from the heart, the other towards it ; but in trees and animals 
 without hearts the explanation is not so obvious. The de- 
 scending current could readily be accounted for by gravitation ; 
 but gravitation can take no part in producing the upward 
 current. 
 
PHYSIOLOGY OF THE CIRCULATION. 15 
 
 Endosmose and Exosmose as Adjuncts of the Circulation. 
 Without a knowledge of the physical forces, the true nature 
 of the ascending and descending currents in plants * would for 
 ever have remained a mystery. Dutrochet 2 , however, made 
 the important discovery, that if a watery or tenuous fluid be 
 placed on one side of a membrane, animal or vegetable, and a 
 thick or mucilaginous fluid on the other (the fluids having an 
 affinity for each other, and for the interposed membrane), two 
 counter or opposite currents are at once established, the thin 
 fluid setting with a strong current in large quantity towards 
 the thicker fluid which it penetrates ; the thicker fluid setting 
 with an equally well-marked but more feeble current, and in 
 smaller quantity, towards the thinner fluid, with which it in 
 turn intermingles. This mingling or diffusion of the fluids 
 through each other occasions a multitude of minor, and what 
 may be regarded as transverse currents. (Fig. 7.) 
 
 In endosmose and exosmose we have physical forces which 
 bear the same relation to each other that the ascending, de- 
 scending, and transverse currents of plants bear to each other. 
 In fact we shall not be overstepping the limits of legitimate 
 inference if we state that the forces of endosmose and exos- 
 mose form important factors in the circulation of plants, and 
 work in the same direction or alongside the vital forces. The 
 probabilities indeed are that the physical and vital forces 
 here referred to are separate manifestations of one and the 
 same force ; the vital forces controlling the physical forces 
 within certain limits to a desired end. From these remarks 
 it will appear that the living plant takes advantage of existing 
 forces when it grows or builds itself up ; that, in fact, the plant 
 has its parts arranged expressly with a view to availing itself 
 of those forces ; the living as it were arising out of the dead, 
 according to fixed laws which govern alike the organic and 
 inorganic kingdoms. It is this circumstance which enables 
 the plant to reciprocate with the external world, and which in 
 some senses fixes its place in nature. Very similar remarks 
 
 1 In animals the currents are ascending and descending only when the creatures 
 assume a vertical position. In animals whose bodies assume a horizontal position, 
 the terms ascending and descending are obviously inapplicable. The great feature 
 in the circulation to be kept constantly in view is that one current goes in one 
 direction, and another in an opposite direction. 
 
 3 Recherches sur 1'Endosmose et 1'Exosmose. Paris, 1828. 
 
i6 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 may be made regarding the circulation in animals, inasmuch 
 as in their ultimate tissues the advancing and receding currents 
 referred to invariably exist. 
 
 Such being the nature and general course of the circulation 
 in plants, we naturally turn our attention to the channels and 
 forces by which the circulation is inaugurated and maintained. 
 
 In the cellular plants, such as the fungi and lichens, and 
 even in the mosses and hepaticae, there are no distinct 
 channels for the transmission of fluids ; the sap passing from 
 
 Fig. 9- 
 
 Fig. 10. 
 
 Fig. ii. Fig. is. Fig. 13. Fig. 14. 
 
 Fig. 15. 
 
 Fig. 16. 
 
 Fig. 17. 
 
 Fig. 18. 
 
 Fig. 19. 
 
 Fig. 9. Cells of the pith of Acanthus ntollis, seen in a vertical section. Magn. 200 diam.' Henfrey. 
 
 Fig. 10. ' Cells of a filament of spirogyra, with spiral green bands. Magn. 200 diam.' Henfrey. 
 
 Fig. ii. ' Cells from the sporangium of -marchantia polymorpha. Magn. 250 diam.' Henfrey. 
 
 Fig. 12. Woody tissue or pleurenchyma, consisting of fusiform or spindle-shaped tubes overlapping 
 each other. The walls of the tubes are thickened by deposits of lignine. 
 
 Fig. 13.' Spiral vessels, consisting of elongated cells which assume a tubular and fusiform shape, and 
 hare a spiral fibre formed on the inside of their walls.' Balfour. 
 
 Figs. 14, 15, and 18. ' Spiral vessels from Sambucus ebulus. Magn. 400 diam.' Henfrey. 
 
 Fig. 16. ' Fragment of a vessel from the stem of a gourd. Magn. 400 diam.' Henfrey. 
 
 Fig. 17. Fragment of the wall of a reticulated vessel of rhubarb. Magn. 400 diam. 
 
 Fig. 19. ' Fragment of the wall of a reticulated vessel of rhubarb. Magn. 400 diam.' Henfrey. 
 
 cell to cell in a more or less complex series by a process 
 of imbibition, much in the same way that water spreads in 
 a piece of blotting-paper. In such cases the currents set 
 most strongly towards those spots where growth is pro- 
 ceeding most rapidly. Precisely the same thing happens in 
 rapidly growing or secreting tissues. Thus the blood is 
 determined to the stag's horn when growing, to the mamma 
 when suckling, and to the stomach when digesting. This 
 constitutes the vis a f route of modern physiologists. 
 
PHYSIOLOGY OF THE CIRCULATION. 1 7 
 
 The Vessels of Plants: their Function. In plants with 
 well-defined stems and branches there are more or less per- 
 fect channels for the circulation of the nutrient material. 
 Thus there are the so-called vascular tissues formed by the 
 fusion of perpendicular rows of variously-constituted cells L . 
 The walls of those cells are in many instances furnished 
 with vertical, annular, spiral 2 , reticulated, or other fibres 3 ; 
 the cells by their union originating the spiral *, annular, re- 
 ticulated, scalariform, and other vessels 5 . (Vide Figs. 9-19 
 inclusive ; and Figs. 20-22, on p. 20. 
 
 1 ' A number of cells permanently combined form the tissues of plants. If the 
 cells entering into the composition of a tissue are essentially alike, they form 
 a simple tissue. The simple tissues are divided into the cellular and vascular 
 tissues. In the former (cellular tissues) the cells, however firmly coherent, are 
 only in contact by their walls, which form a persistent boundary between them. 
 In the latter (vascular tissues) the cells enter into closer relation, becoming con- 
 fluent by the absorption of their contiguous surfaces, and thus converted into 
 more or less extensive tubular bodies, which in their various conditions form what 
 are called the ducts and vessels of plants. The vessels, it will be seen, are in 
 reality compound elementary organs.' Henfrey's Botany, p. 471. 
 
 2 The presence of spiral fibres in cells is most instructive, for in this we see 
 the foundation of a numerous class of structures which were otherwise inexpli- 
 cable. A series of cells with spiral cell-walls originate a vessel with spiral walls ; 
 these vessels may twine in a certain direction and produce a spiral stem the 
 stem itself may twine around another tree in a spiral manner; leaves, flowers, 
 fruit, may all be arranged in spirals of various orders. The spirals of plant 
 structures may be traced to animal structures. The shell of the nautilus is rolled 
 up in a most graceful spiral; the heart (ventricles) of mammals is a double 
 continuous spiral of exquisite beauty. The wings of birds and the extremities 
 of bipeds and quadrupeds are distinctly spiral in their nature, and their movements 
 are curved spiral movements; nay, more, the vertebral column itself is a spiral 
 of very unusual but delightful curve. The soft cell fibres, equally with the bony 
 skeleton, are twisted upon themselves morphologically. This is a point of great 
 interest. It is important physiologically, as spiral continuous structures give 
 rise to spiral continuous movements, as seen in walking, swimming, and flying, 
 and in the movements of the hollow viscera. Dutrochet (Braun sur les Torsions 
 normales dans les Plantes) states that there is a revolving movement in the sum- 
 mits of stems, a spiral rolling of the stems round their supports, a torsion of the 
 stems upon themselves, and a spiral arrangement of leaves all these being, in 
 each plant, in the same direction. These phenomena, he avers, are owing to an 
 internal vital force which causes a revolution round the central axis of the stem. 
 
 3 ' The annular thickenings are less common than the spiral ones, but sometimes 
 occur in the same cell with reticulated ones.' Henfreys Botany, p. 484. 
 
 * The spiral vessels are found in the youngest and most delicate parts of the 
 plant. 
 
 5 ' In the young soft part of the shoot, as in all normal and abnormal growths 
 that have not formed wood, the channels for the passage of sap are the spiral, 
 
 C 
 
1 8 PHYSIOLOGY OF THE CIRCULATION'. 
 
 Doubt has been expressed as to whether the vessels iti 
 question are actually engaged in the transmission of saps, 
 but the preponderance of evidence is in favour of this belief. 
 Mr. Herbert- Spencer has been able to show by recent ex- 
 periments that the passage of fluid through the spiral and 
 other vessels is much more rapid than through the cellular 
 tissue. By soaking young shoots which develop little wood 
 in decoctions of logwood and other dyes, he discovered that 
 the only channels stained by the process were those cor- 
 responding to the spiral, fenestrated, scalariform, and other 
 vessels of the vascular system. Through these vessels con- 
 sequently the coloured fluid must have passed. Nor is it 
 wonderful that the fluid should have preferred open capillary 
 channels, such as those formed by the vessels of the vascular 
 system, to interrupted or non-continuous channels such as 
 are supplied by cellular tissue, or any tissue not differentiated 
 into continuous canals. Mr. Spencer took the precaution to 
 immerse whole plants in his dyes, as well as parts of plants. 
 He obtained the same results in both cases, so that it is 
 natural to conclude the coloured fluids traversed the same 
 channels traversed by the crude and other saps when sub- 
 mitted to the action of the plant. The spiral, annular, and 
 other vessels of the vascular system are most engaged as 
 sap-carriers when new wood is being formed in their vicinity, 
 in which case also they are most porous 1 . 
 
 When new wood is being formed the dye escapes from 
 the vessels of the vascular bundles into the cellular and 
 
 annular, fenestrated, or reticulated vessels. . . . The sap-carrying function 
 is at first discharged entirely by the walls of the medullary sheath, and they cease 
 to discharge this function only as fast as they are relatively incapacitated by their 
 mechanical circumstances. . . . It is not the wood itself, but the more or less 
 continuous canals formed in it, which are the subsequent sap distributors.' 
 Principles of Biology, by Herbert Spencer. Lond. and Edinb. 1867 ; p. 549. 
 
 1 According to Mr. Spencer, there is no direct connexion between the age of a 
 vessel and its porosity ; those vessels being always the most porous around which 
 a formation of wood is taking place. Professor Balfour, on the other hand, 
 states, ' that the tubes forming the wood are pervious to fluids in their young 
 state, but that their walls soon become thickened by deposits of lignine, and in the 
 heart-wood of trees their cavities are obliterated. This filling up of the tube 
 takes place often in a concentric manner, and when it is completed the active life 
 of the cell or tube may be considered as having terminated.' Class-Book of 
 Botany, p. 420. 
 
PHYSIOLOGY OF THE CIRCULATION. 19 
 
 surrounding tissues in such quantity as to lead to the belief 
 that the said tissues and not the vessels transmit the sap. 
 This was the opinion of Hoffmann and linger, who held that 
 in plants possessed of fibre-vascular bundles, the sap in the 
 first instance passes up from the roots chiefly in the paren- 
 chymatous cellular constituents of the bundles, and that these 
 juices do not pass by the spiral vessels themselves 1 . There 
 are many circumstances which induce me to believe that the 
 vessels and intervascular spaces are both engaged in the 
 circulation. 
 
 Mr. Spencer's explanation of the passage of sap through 
 the vascular tissues has been objected to on the ground that 
 the spiral and other vessels of the vascular system frequently 
 contain air. To this he replies, that they only do so during 
 periods of drought, and when they are old their function 
 as sap-carriers having virtually ceased. The canals which 
 ramify through the stag's horn, he observes, contain air after 
 the horn is fully developed, but it is not thereby rendered 
 doubtful whether it is the function of arteries to convey 
 blood 2 . 
 
 It ought moreover not to be overlooked, that while the 
 presence of air in the vessels is fatal to the circulation in 
 animals, it does not of necessity follow that it is so in plants. 
 The conditions are not identical. In animals the walls of 
 the larger vessels are not permeable by fluids, so that air 
 admitted into them has no means of escaping therefrom ; in 
 plants, on the contrary, the walls of the vessels are especially 
 permeable, a free egress being provided by the pitted and 
 other vessels 3 . The presence of air in the vascular bundles 
 of plants is therefore a natural condition at certain periods 
 a plant requiring air as well as sap. 
 
 1 The difference between the cellular and vascular tissues may be briefly indi- 
 cated. In cellular tissues the cells firmly cohere, the cell-walls being persistent. 
 In the vascular tissue, the cells run together by the absorption of their contiguous 
 surfaces to form the tubes, ducts, or vessels known as the vascular tissues. 
 
 2 Principles of Biology, vol. ii. p. 357. 
 
 3 Globes of air in a capillary tube with rigid impervious walls require, as Janin 
 has shown, a pressure of three atmospheres to force them on. As however the 
 walls of the vessels of plants are porous a much smaller force suffices, the air 
 escaping in every direction. 
 
 C 2 
 
20 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 Points of Resemblance between the Vessels of Plants and 
 Animals. Making allowances for difference of opinion as to 
 the function performed by the vessels of plants, there can 
 be no doubt that the vascular tissues of the vegetable king- 
 dom bear a close analogy to those of the animal kingdom. 
 In the vessels of plants we have structures remarkably re- 
 sembling those of the blood-vessels of animals. In an artery, 
 as you are aware, we have straight, annular, and spiral fibres, 
 these being present in variable proportion, according to the 
 thickness of the vessel and its distance from the heart. Thus 
 
 Fig. 20. Fig. 21. 
 
 Fig. 22. 
 
 SP - 
 
 Fig. 20.' Vertical section of an orchis root, highly magnified. The cells, c, gradually pass into 
 dotted cells and vessels,./^, the extremity of the root, called a spongiole, sp.' Balfour, p. 52. 
 
 Fig. 21. ' Magnified representation of two plants of Lemna minor, or lesser duckweed the green 
 mantle of pools showing the extremities of the roots covered by a cellular sheath (spongiole).' Balfour. ' 
 
 Fig. 22. ' Monocotyledonous fibro-vascular bundle (from the spadix of Phoenix dactylifera). Vertical 
 section. /, Parenchyma, in which the bundles lie ; 10 , wood cells ; sv, spiral vessels ; d, reticulated 
 ducts; -vp, -vassa propria ; I, liber cells. Magn. 100 Diam.' Henfrey. 
 
 in the aorta the longitudinal, spiral, and annular fibres are 
 all present ; whereas in the capillaries, fragments of the 
 annular fibres alone appear. Very similar remarks may be 
 made regarding the vessels of plants. In these the spiral 
 vessels are found in the youngest and most delicate parts 
 of the plant, the annular vessels being developed a little later 
 in the same bundles, and in similar situations. The re- 
 ticulated vessels are found in quantity with the spiral and 
 annular kinds in succulent stems, roots, and petioles. The 
 vessels of plants, like those of animals, are usually of a 
 cylindrical form. 
 
 While the vessels of plants and animals may be said to be 
 formed upon a common type, there is this great difference 
 between them, and it is important as far as the circulation 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 is concerned: The vessels of plants, unless when quite 
 young \ are rigid and have no independent movements ; the 
 vessels of animals, on the other hand, are flexible and elastic, 
 and are in many cases endowed with independent motion. 
 This is especially the case in the dorsal vessel of the insect, 
 the veins of the bat's wing, the saphenous veins of the rabbit, 
 the web and mesentery of the frog, the bulbus arteriosus of 
 the fish, and the venae cavae and pulmonic veins of the 
 mammal where they join the heart. There is this further 
 difference, the principal vessels of animals, unless where rete 
 
 Fig. 23. 
 
 Fig. 24. 
 
 Fig- 25. 
 
 Fig. 23. ' Absorbent organ from the leaf of Euphorbia neriifolia. The cluster of fibrous cells formi v* 
 ; one of the terminations of the vascular system is here embedded in a solid parenchyma.' Herbert 
 Spencer. 
 
 Fig. 24 ' A longitudinal section through the axis of an absorbent organ from the root of a turnip, 
 showing its annuli of reticulated cells when cut through. The cellular tissue which fills the interior is 
 supposed to be removed.' Herbert Spencer. 
 
 pjg-. gj. A less developed absorbent, showing its approximate connexion with a duct. In their 
 
 simplest forms these structures consist of only two fenestrated cells, with their ends bent round so as 
 to meet. Such types occur in the central mass of the turnip.' Herbert Spencer. 
 
 mirabile 2 is present, are isolated, /. e. they occur at intervals, 
 with muscular, bony, and other tissues between. The vessels 
 of plants, on the other hand, are in contiguity, and touch 
 each other. (Figs. 2025). 
 
 1 The spiral vessels are found in the youngest and most delicate parts of the 
 plant. As these vessels are formed originally by the confluence of cells which 
 are elastic and flexible, a certain degree of movement may reasonably be claimed 
 for them. 
 
 2 In this remarkable arrangement, the blood-vessels sometimes run parallel to 
 each other, and sometimes interweave in a most perplexing and unaccountable 
 manner. The vessels are so numerous and so close, that they form one continuous 
 mass. I have had opportunities of injecting them in the sloth, spider-monkey, 
 and dolphin. They are found in various animals, their precise functions being 
 at present undetermined. 
 
22 PHYSIOLOGY OF THE CIRCULATION. 
 
 The vessels of animals may be divided into three sets, 
 the arteries, the veins, and the capillaries ; and to these may 
 be added a system of vessels lately discovered, the perivas- 
 cular canals. The arteries conduct from the heart or centre 
 to the periphery ; the veins, from the periphery to the centre ; 
 the capillaries uniting the veins and arteries together. Out- 
 side, or between the capillaries, so to speak, are the perivas- 
 cular canals. In like manner plants may be said to have 
 three sets of vessels, an ascending and a descending set, 
 which, as has been shown, radiate in the embryo from a 
 central point. They have also what may fairly be regarded 
 as a capillary system in their leaves, and also in their 
 stems and branches. (Figs. 23-25, p. 21). Whether, therefore, 
 we compare the actual structure, situation, or functions of 
 the vessels of plants and animals, we shall find they have 
 many things in common. The walls of the vessels in 
 plants are flexible and elastic when young, those of animals 
 being permanently so ; the vessels of plants and the capil- 
 laries of animals are permeable by liquids and gases l . The 
 veins of animals convey impure blood ; corresponding vessels 
 of plants, crude sap. The arteries of animals convey pure 
 blood ; corresponding vessels of plants, elaborated sap. The 
 capillaries of animals expose the impure blood to the in- 
 fluence of the air; the capillaries in the leaves and other 
 parts doing precisely the same thing for the plant. An animal 
 may be said to breathe at every pore 2 , and so of the plant 
 
 1 In the young cells of plants the cell-wall consists apparently of a homo- 
 geneous membrane which is elastic, flexible, and freely permeable by water. When 
 the cells become older the cell-wall becomes firmer, and opposes a greater obstacle 
 to the entrance of water into its substance. This leads me to conclude that the 
 cell-wall is porous a point difficult to determine, as the finest microscope fails to 
 detect the pores. The molecular structure of cell-membranes has been investigated 
 by Nagele. .From a careful examination of the cell-membrane of starch by 
 polarised light, he came to the conclusion that all organic substances are composed 
 of crystalline molecules grouped in a definite manner that these molecules when dry 
 have no interspaces, but that when moist each molecule is surrounded by a thin 
 film of water. The epidermis of the young leaves of the leek, as Garreau has 
 shown, is freely permeable by fluids ; while the epidermis of the older leaves is 
 either not permeable or very sparingly so. Garreau attributed a decided en- 
 dosmotic property to the cuticle, which is greatest in young parts and least in old 
 ones. When leaves are so old as to have lost the power of absorbing water they 
 can still take up carbonic acid. 
 
 2 Spallanzani was the first to point out that the tissues respired. The subject 
 
PHYSIOLOGY OF THE CIRCULATION. 23 
 
 a poisonous atmosphere being destructive to both. In animals 
 it is necessary that the vessels extend to the part to be 
 nourished, in order that the growing portions may absorb 
 or imbibe from the blood what is required, while they return 
 to it whatever is superfluous. In the brain and in bone, this 
 absorption or imbibition takes place through considerable 
 spaces. This is especially true of the so-called non-vascular 
 tissues, as the cornea and lens of the eye, and the articular 
 cartilages. The difference between the vascular and non- 
 vascular tissues is only one of degree. In either case the 
 elementary structures lie outside the vessels, and obtain new 
 material from the blood by imbibition. There is therefore 
 an obvious analogy between the nutrition of plants and 
 animals. In both cases the nutritious juices are presented 
 to the growing tissues, immediately or remotely, by vessels 
 or their representatives. In the capillaries of animals and 
 the cells of plants, the limiting membrane is composed of 
 an exceedingly delicate and apparently homogeneous sub- 
 stance, which greatly facilitates imbibition. 
 
 Respiration of Plants and Animals. By means of the 
 capillaries of the lungs, the blood of animals is aerated, 
 carbonic acid and other matters being given off and oxygen 
 taken in. By means of the capillaries of the system, nutri- 
 tious juices and white blood-corpuscles, also concerned in 
 nutrition, are supplied to the tissues and effete matters taken 
 up. By means of its vessels \ intervascular spaces and leaves, 
 a tree is nourished, grows and breathes ; it gives off oxygen 
 and takes in carbonic acid 2 and other matters. It stores up 
 
 has likewise been investigated by G. Liebig. M. Paul Bert (Le9ons sur la Physio- 
 logic comparee de la Respiration: Paris, 1870) shows that the muscles of 9old- 
 blooded vertebrate animals consume, relatively to their weight, less oxygen and 
 evolve less carbonic acid than muscles of warm-blooded animals; also that the 
 muscles of adult animals absorb much more oxygen and evolve more carbonic acid 
 than those of young animals. He proves that all the tissues of the body absorb 
 oxygen and give off carbonic acid. 
 
 1 Some authors are of opinion that the spiral vessels and their allies are recep- 
 tacles for gaseous matter formed in the course of the movement of the sap within. 
 
 2 'Leaves have the power of absorbing carbonic acid, ammonia, water, and 
 aqueous solutions. They also inhale a certain amount of water, and they give off 
 gaseous matters, especially oxygen. Thus leaves, in the performance of their 
 functions, absorb and inhale watery and gaseous substances.' Class-Book of Botany, 
 by J. H. Balfour, A.M., M.D., F.R.S., etc. 1871 ; p. 451. 
 
24 PHYSIOLOGY OF THE CIRCULATION. 
 
 starch and other compounds, and uses them as occasion 
 demands. The tree, like the animal, may be said to breathe 
 at every pore, by the stomata of its leaves, by the vessels l , 
 intercellular passages and cavities of its stem and branches, 
 vand by its bark, when this is green. There is yet another 
 point of resemblance between the respiration of plants and 
 animals the air given off by both is laden with moisture. 
 The oxygen given off by trees and plants communicates to 
 the atmosphere of the forest its peculiarly exhilarating quali- 
 ties ; the carbonic acid given off by the lungs of animals 
 producing, on the contrary, a depressing effect. 
 
 Cells of Plants -, their Nature and Function. As the cells of 
 plants play a most important part in the general circulation, 
 and have a circulation of their own, it is necessary to direct 
 attention to them at this stage. ' The cell is the elementary 
 organ of a vegetable structure, but is not the smallest or 
 most simple definite form in which organic matter may exist ; 
 it is not to be regarded as the ultimate structural unit, be- 
 cause detached fragments of it are capable of independent 
 existence under certain circumstances,' and a living plant 
 may exist, at least for a time, in the absence of a bounding 
 cell-membrane. 
 
 A vegetable cell may be defined as a closed sac, containing 
 fluid or semi-fluid matter. It may represent an entire plant, 
 or only part of a plant 2 . It contains, or may contain, proto- 
 plasm, a nucleus, a primordial utricle, starch and chlorophyll 
 corpuscles, etc., etc. Here, then, is a mixture of hetero- 
 geneous material, each substance varying in density, and 
 having its own peculiar properties and actions. The cell- 
 
 1 In spring the vessels are found gorged with sap, but later on in the season they 
 usually contain air. The intercellular passages are also filled with air. Professor 
 Passerini, of Parma, has succeeded in showing that gases are exhaled through the 
 stomata. He obtained his results by causing a plant to absorb a solution of 
 sulphate of sodium, and then placing slips of paper saturated with acetate of lead 
 to its leaves. The parts of the paper corresponding to the stomata were coloured 
 dark, clearly showing that a reaction had taken place. 
 
 2 The red snow plant and oscillatoria consist each of single isolated cells, the cell 
 performing the function of nutrition and reproduction. The fungi and sea-weeds 
 the so-called cellular plants are composed of numerous cells, arranged according 
 to a definite order, some of the cells discharging the nutritive and others the 
 reproductive functions. The higher or vascular plants have vessels added to the 
 cells, the organs of nutrition and reproduction being more complicated. 
 
PHYSIOLOGY OF THE CIRCULATION. 2$ 
 
 wall is also of uncertain and varied constitution. It is re- 
 garded by some as originally consisting of a homogeneous 
 membrane, in which spiral, annular, and other fibres are 
 subsequently developed ; others believing that these fibres 
 are present in the cell from the first, and form an integral 
 part of it. Agardh, e.g., is of opinion that the cell-walls are 
 made up of bundles of solid fibres interwoven together. He 
 therefore attributes to the cell-wall a structure resembling 
 that of the blood-vessels and hollow viscera of animals 1 . How- 
 ever this may be, the cell-wall in the young state is elastic, 
 flexible, and freely permeable by water ; and this is im- 
 portant, as rendering the cell liable to all kinds of hygroscopic 
 influences. 
 
 As the cell-wall becomes older it usually thickens and 
 becomes more rigid ; in which case water permeates it with 
 more difficulty. We have therefore in any single cell, or 
 in any combination of cells, the conditions necessary for a 
 great variety of vital, mechanical, and chemical changes ; the 
 presence or absence of heat and moisture accelerating or 
 retarding the changes in question. It may happen that the 
 cell-wall, while thickening, remains soft and flexible, and, if 
 so, it swells up the instant it comes in contact with water. 
 If a unicellular plant be placed in a dense liquid, its contents 
 escape, and it becomes shrivelled ; if, on the other hand, it 
 is put in a thin fluid, it imbibes the fluid and increases in 
 volume. The red blood-globules do the same. These changes 
 are principally due to endosmose and exosmose. The effect 
 which changes of temperature have upon cells is very re- 
 markable. The stomata of the leaves of plants close in 
 dry weather and open in moist, so that the opening or closing 
 of a part, while due in the first instance to the presence or 
 absence of moisture, is due in the second to structural pe- 
 culiarities in the cells themselves. Thus in some species of 
 mesembryanthemum the seed-vessel is closed when dry and 
 open when moistened ; whereas in the spores or germs of 
 
 1 In the cell-walls of Polysiphonia complanata, Conferva melagoniam, and 
 Griffithsia equisetifolia, Agardh has demonstrated numerous bundles of fibres, which 
 cross each other at the joints to form the diaphragm. Between them finer fibres 
 occur, the whole being united by a gelatinous substance. Agardh, De Cellula 
 Vegetabili Fibrillis tenuissimis Contextu. Lundse, 1852. 
 
26 PHYSIOLOGY OF THE CIRCULATION. 
 
 horse-tails (equisetum), the cellular club-shaped filaments 
 which form a part of it are widely expanded when the spore 
 is dry, and closed when it is moistened. This would seem 
 to imply the existence of two forces in plants \ portions of 
 certain plants having the power not only of closing but also 
 of opening. This appears to follow because the presence of 
 moisture in the one case produces the closing, and in the 
 other the opening. The same cause, if I may so phrase it, 
 produces opposite results. A similar phenomenon is wit- 
 nessed in the action of hollow muscles with sphincters, where, 
 apparently under precisely the same conditions, the sphincter 
 opens or expands when the viscus closes. I am inclined to 
 infer from this that heat or dryness, and moisture or wet, 
 do not act as irritants, and that plants and certain parts of 
 animals move without being irritated. If moisture, for ex- 
 ample, acted as an irritant, and caused one plant to close, 
 it could scarcely be regarded as the cause of another opening. 
 Moisture and dryness moreover act upon dead vegetable 
 tissue, where the idea of irritability is inadmissible. Thus 
 a hempen rope shortens when wetted, and elongates when 
 dried. The manner in which cells of wood, liber, etc., swell 
 up on the application of moisture, is deserving of attention. 
 They expand in the direction transverse to their axes, i.e. 
 they shorten in a longitudinal direction as they bulge or swell 
 out laterally 2 . Shortening in one direction is consequently 
 elongation in another. Precisely the same thing takes place 
 in the action of the sarcous elements of a muscle. When 
 a muscle or an elementary muscular fibre contracts, as it 
 is termed, it decreases in the direction of its length, and 
 increases in the direction of its breadth, in fact the decrease 
 in one direction is accompanied by an increase in another 
 and opposite direction, the volume remaining always the 
 same. It is therefore better, when speaking of the move- 
 ments of long muscles, to say they shorten and lengthen, 
 and of hollow muscles that they close and open, than that 
 they contract and relax. The vegetable cell-wall, when dried, 
 
 1 In the hygrometer composed of two pieces of wood, each having different 
 absorbing powers, a certain amount of moisture in the atmosphere produces a curving 
 to the one side, a certain amount of dryness a curving to the opposite side. 
 
 2 Herifrey's Botany, p. 470. 
 
PHYSIOLOGY OF THE CIRCULATION. 27 
 
 becomes smaller, so that the mere application or withdrawal of 
 moisture suffices for conferring certain movements upon it 1 . 
 
 These movements are to be regarded as extraneous, for 
 the presence or absence of moisture may be an accidental 
 circumstance. Cells, however, are living things, and they 
 have living contents endowed in many cases with independent 
 motion. The necessity for such an arrangement is obvious, 
 inasmuch as 'the vital and chemical phenomena exhibited 
 by plants depend in the first instance upon operations which 
 have their seat in the interior of those structures.' Kiihne 
 proved the vitality of cell contents by a very remarkable 
 experiment. He collected a quantity of protoplasm from a 
 living plant, and placed it in a cockchafer's intestine. When 
 he applied the stimulus of galvanism to the intestine so 
 distended, it shortened like a muscle. The protoplasm pos- 
 sesses remarkable properties. In some plants it is endowed 
 with distinct movements, rendered apparent by the granules 
 which float in it. The source of these movements is at 
 present a mystery; some authors contending that the pro- 
 toplasmic mass can change its shape at any moment ; others, 
 that the movements are due to increase or decrease in the 
 amount of protoplasm contained within the cell at any given 
 time 2 . Similar remarkable properties are to be attributed to 
 the primordial utricle which has the power of moulding itself 
 into new external forms. The primordial utricle constitutes an 
 envelope for the zoospore of the algae, when it escapes from 
 the parent cell ; the vitalised contents of the cell establishing 
 a separate existence. The substance of the primordial utricle 
 greatly resembles that of the amoeba and the soft parts of 
 sponges, all three being endowed with independent move- 
 ments. The starch granules of cells are developed from the 
 chlorophyll corpuscles, and these last owe their existence to 
 
 1 ' There is reason to believe that, in some instances, the cell-wall thickens at 
 certain seasons, and becomes thinner at others ; but this appearance may arise from 
 an alternately swollen and contracted state, and not from absorption and re-deposi- 
 tion.' Henfrey's Botany, p. 480. 
 
 1 ' During the time when the protoplasmic contents of young cells are becoming 
 gradually hollowed out into spaces filled with watery cell-sap, a regular movement 
 of this protoplasm takes place, which may be observed very readily in young hairs 
 of phanerogamic plants, and which probably takes place in an early stage in all 
 other structures.' Ibid., p. 551. 
 
28 PHYSIOLOGY OF THE CIRCULATION. 
 
 the elaboration of protoplasm. There is thus a variety of move- 
 ments going on within the cell during the period of growth. 
 
 The Intracellnlar Circulation of Plants. The intracellular 
 circulation, or gyration, as it is called, is most interesting, and 
 in some respects most mysterious. There can be little doubt 
 that it is referable to vital, chemical, and physical changes 
 occuring in the cell-contents ; but the precise nature of those 
 changes is unfortunately at present undetermined. Some 
 investigators believe that the circulation is traceable to the 
 nourishment of the cell, and the commotion consequent on 
 its reproduction ; others to electrical or galvanic agency ; 
 others to the presence of invisible cilia 1 ; and others to en- 
 dosmose and exosmose, depending upon the different densities 
 of the fluids presented from without to the cell-contents. It 
 is therefore referred by one sect to a vital, and by a second 
 to a physical action. Under these circumstances we can only 
 refer to the phenomena as observed ; and it is not a little 
 humiliating to think that at the very threshold of the cir- 
 culation we are confronted with difficulties of such magnitude, 
 and obliged to confess that even in a cell there are hidden 
 powers which neither the microscope, physics, nor chemistry, 
 can as yet explain. From experiments which I have made 
 recently, and which are fully described further on, it ap- 
 pears to me that the intracellular circulation is due in a 
 principal measure to physical causes, such as absorption and 
 evaporation, endosmose and exosmose, capillarity, chemical 
 affinity, etc. 
 
 In many cells a distinct movement of fluids and granules 
 is perceptible ; and Schleiden and Mohl are of opinion that 
 these movements take place in all active formative cells at 
 one period or other of their growth. The intracellular cir- 
 culation is seen to advantage in many aquatic plants. It was 
 discovered by Corti in chara, in i/74 2 . In this plant (chara) 
 
 1 Movements analogous to the intracellular ones occur within the mouth, 
 stomach, and rectum of certain polypes. Dr. Grant was of opinion that these 
 movements were due to the lashing of cilia; and Dr. Sharpey subsequently de- 
 monstrated that cilia actually did exist in the situations indicated. 
 
 2 ' In chara the axis is composed of elongated cells, placed end to end, surrounded 
 by a number of small secondary cells, which take a spiral course round the 
 primary cells from left to right, and which are often encrusted with carbonate of 
 lime.' 
 
PHYSIOLOGY OF THE CIRCULATION. 29 
 
 the movements are of a spiral nature, as indicated by the 
 arrows in Fig. 26. 
 
 It is not a little remarkable that in the stem of the Tubu- 
 laria indivisa, a form of polype, precisely analogous movements 
 occur, as was pointed out by Mr Lister \ (Fig. 27.) 
 
 Fig. 26. 
 
 Fig. 27. 
 
 Fig. 
 
 Fig. 29. 
 
 Fig. 26. ' A small portion of a chara, magnified to show the intracellular circulation. The arrows 
 mark the direction of the fluid and granules in the different cells. The clear spaces are parts where 
 there is no movement. The circulation in each cell is independent of that in the others.' Balfour. 
 
 Fig. 27. Shows the course of the circulation in the stem of the polype (Tubularia. indivisa). 
 a a. Horny tube, containing a soft substance, continuous with stomach (b), and mouth (c). c d, Tenta- 
 cula or arms. The ascending and descending currents in the stem of the polype are indicated by the 
 arrows. They pursue a slightly spiral direction, as indicated by the dotted lines in figure the one set- 
 ting towards the polype, the other away from it. At m and n there were vortices in the tube. The 
 arrows to the right of the figure indicate the continuous nature of the currents within the tube. 
 
 Fig. 28. ' Large internal cell of vallisneria, showing the direction of the currents in intracellular 
 rotation. There is an. occasional nucleus seen in the course of the circulation, along with the chloro- 
 phyll grains.' Balfour. 
 
 Fig. 29 ' Branching and anastomosing tubes of lactiferous vessels. In them there is an evident 
 movement of granules of latex, as represented in some of the tubes in the figure, the arrows marking 
 the direction of the current.' Balfour. 
 
 The movements in - chara are made visible by the presence 
 of granules, which rotate on their own axes, travelling in a 
 spiral direction, up one side of the cell and down the other. 
 Observe, up one side of the cell and down the other, The 
 currents in opposite directions, characteristic of the general 
 circulation, reappear. The same currents are perceptible in 
 our own stomachs during digestion. In the case of Alexis 
 St. Martin, who had his stomach perforated by a gunshot 
 wound, the food, when introduced into the stomach, was seen 
 to circulate first along the greater curvature from left to right, 
 and then along the lesser curvature from right to left. 
 
 1 Movements somewhat resembling the above were found by Dr. Sharpey to 
 occur in the tentacula of the actinia. Cyc. of Anal, and Phys. art. 'Cilia,' p. 615. 
 
30 PHYSIOLOGY OF THE CIRCULATION. 
 
 It may seem far-fetched to trace an analogy between the 
 gyrating of the contents of the human stomach and the 
 gyrating of the contents of a vegetable cell ; but, in some 
 of the lower animals, the contents of the alimentary canal 
 transude through its walls and circulate through the body ; 
 in others (polypes) the gyrating movements occur within the 
 mouth, stomach, and rectum. I am moreover satisfied, from 
 dissection and experiment, that the stomach and heart, even 
 in ourselves, are in some senses identical both in structure 
 and function ; these organs being endowed with a pushing 
 and pulling power, which enables them to manipulate their 
 contents and to propel them in given directions. When the 
 oesophagus is engaged in transmitting food, it pinches on 
 the bolus by opening before and closing behind it simultan- 
 eously the expanding or pulling and pinching or pushing 
 action accompanying the bolus from the time it enters the 
 oesophagus proper until it reaches the stomach. This com- 
 pound movement can transmit fluids with equal dexterity 
 and precision, as is well seen when a horse or other large 
 animal is drinking. Every part of the oesophagus has the 
 power of opening and closing, so that the part which is 
 opened the one instant is closed the next, and vice versa. 
 The opening and closing movements which constitute the 
 oesophageal rhythm, travel, in normal swallowing, in the 
 direction of the stomach ; but the direction of the movement, 
 in abnormal swallowing or vomiting, is reversed ; showing 
 how perfectly the opening and closing power is possessed by 
 the oesophagus. Those animals which ruminate swallow in 
 both directions : first, from the mouth towards the stomach ; 
 second, from the stomach towards the mouth ; and third and 
 finally, from the mouth back again to the stomach. This 
 power is possessed by man himself, some individuals being 
 able to vomit at pleasure, .and others confirming the habit 
 to such an extent as to be actually able to ruminate. The 
 power possessed by the alimentary canal of opening at one 
 part, and closing at another, is well seen in invagination ; 
 the closing portion of gut forcing itself into or within the 
 opening portion the act of expansion assisting the move- 
 ment in virtue of the opening and closing portions travelling 
 in opposite directions. The act of invagination is produced 
 
PHYSIOLOGY OF THE CIRCULATION. 31 
 
 by a double movement, similar to what would be produced 
 in the oesophagus of a ruminating animal if the swallowing 
 and ruminating movements occurred at the same time. This 
 power which the intestine occasionally exerts of shortening 
 its length by invagination is, I apprehend, a power possessed, 
 within certain limits, by all muscles the sarcous elements 
 of a muscle when the muscle shortens tending towards a 
 central point, from which they recede when the muscle elon- 
 gates, very much in the same way as Professor Lister has 
 shown the pigment-cells in the frog's skin converge towards 
 a point at one time and diverge at another. When the 
 sarcous elements of a muscle converge in one direction say 
 in the direction of the length of the muscle they diverge in 
 the opposite direction, viz. in the direction of the breadth 
 of the muscle ; so that, in reality, it is a misnomer to apply 
 the term contraction to a muscle when it shortens the act 
 of shortening in one direction being actual lengthening in an 
 opposite direction. This follows because the sarcous elements 
 of a muscle, or the muscle as a whole when it moves or acts, 
 simply changes shape, the volume of the muscle and the 
 sarcous elements composing it always remaining exactly the 
 same. 
 
 I shall have occasion to return to this subject when I come 
 to speak of the structure and action of the bipod-vessels and 
 heart of animals ; meanwhile I would direct your attention to 
 the fact that the stomach may be regarded as simply an 
 expanded and elaborated portion of the alimentary canal ; 
 and the heart as an expanded and elaborated portion of 
 the vascular system ; the stomach and heart being constructed 
 on precisely the same type and performing analogous 
 functions. Further, the structure and functions of the bladder 
 and uterus closely resemble those of the stomach and heart ; 
 so that the hollow muscles and blood-vessels may be placed 
 in the same category. They all receive fluid, semi-fluid, or 
 solid substances, which they expel at regular intervals. The 
 stomach can cause its contents to gyrate like those of a 
 vegetable cell, and the oesophagus, by the rhythmic movement 
 of its several parts i. e. by the simultaneous opening or 
 widening of one part, and the closing or narrowing of another 
 part (say the part behind that which opens) can seize and 
 
32 PHYSIOLOGY OF THE CIRCULATION. 
 
 dismiss the food, and pass it on in successive waves to the 
 stomach ; just as a blood-vessel with rhythmic movements, or 
 the heart itself, can manipulate or pass on the blood in succes- 
 sive waves, in a given direction. If however one part of the 
 oesophagus closes or narrows while the part beyond expands 
 or widens, the oesophagus in this way foreshadows the move- 
 ments which occur in the stomach where the pyloric sphincter 
 opens, when the stomach closes, and vice versa. I use the 
 terms ' opens ' and ' closes,' in preference to ' relaxes ' and ' con- 
 tracts,' because I regard the opening of the sphincter and the 
 closing of the stomach as equally vital acts. This view is borne 
 out by the structure as well as the action of the parts. In man 
 the stomach has two sphincters a cardiac and a pyloric one. 
 Each of these is composed of two sets of looped symmetrical 
 fibres. The sphincters resemble the valvulae conniventes, 
 and I am disposed to regard them as simply differentiated 
 valvulae conniventes, from finding the two halves of the 
 pyloric sphincter of the dog slightly separated from each other 
 valvulae conniventes, or what is equivalent thereto, being 
 indicated in the oesophagus of the cat. If therefore the 
 stomach be regarded as an expansion of the intestine, and the 
 sphincters as constrictions or partitions which are structurally 
 identical with the other parts of the stomach ; and if, further, 
 the oesophagus and intestines have peristaltic movements, 
 i. e. the power of simultaneously narrowing and widening in 
 parts, then we are bound to conclude that the closing of the 
 stomach and the opening of its sphincters are equally vital 
 acts. But for this co-ordination the movements would be 
 purposeless. The structure of the intestine remarkably re- 
 sembles that of many vessels where we have non-striated 
 longitudinal and circular fibres. But many blood-vessels have 
 distinctly rhythmic movements, so that structurally and func- 
 tionally the intestines and blood-vessels resemble each other. 
 You will therefore, I trust, bear with me, if occasionally, when 
 speaking of the prince of hollow muscles, the heart itself, I 
 refer now and then, for the sake of illustration, to the hollow 
 muscles generally. 
 
 The movements in chara, as has been stated, are made visible 
 by the presence of granules, which rotate on their own axis, 
 travelling in a spiral direction up one side of the cell and down 
 
PHYSIOLOGY OF THE CIRCULATION. 33 
 
 the other. The granules vary in size, and are elaborated in 
 transitu to befit them ultimately for becoming part of the 
 cell-wall. They may therefore be likened to the white blood- 
 corpuscles of animals, which, as recent researches have shown, 
 are also incorporated directly into the tissues. In Vallisneria 
 similar intracellular movements occur. ' Spiral movements 
 of rotation are also seen in the elongated cells forming the 
 hairs of the nettle, loasa, pentstemon, galeopsis, borage, melon, 
 and other plants ; as well as in the separate cells of the 
 staminal hairs of the Virginian spiderwort (Tradescantia 
 Virginica) 1 .' 
 
 The rotations of the protoplasmic contents of cells exhibit 
 a marked resemblance to those of the protozoa ; and many 
 observers are of opinion that the moving bodies owe their 
 power of rotation in part to ciliary processes similar to those 
 which render many of the simpler plants locomotive. This 
 view is entitled to favourable consideration, the more especially 
 as ciliary motion has been discovered by Dr. Sharpey and 
 others in the embryos of infusoria and gasteropoda, while 
 inclosed in the ovum 2 ; and in the ova of the polype, sponge, 
 mollusc, and actinia. Similar gyrating movements have been 
 observed within the stomach of the polype 3 . In all these 
 cases the presence of cilia has been distinctly made out. If 
 cilia could be proved to exist on the lining membrane 
 of the cell-wall of plants, or on the exterior of the moving 
 particles, much of the mystery of gyration would disappear. 
 Until however these are discovered we must fall back upon 
 other forces, and of these I believe absorption on the one hand, 
 resulting in endosmose and exosmose, and evaporation on the 
 other, to be the chief 4 . 
 
 A moderate heat quickens the intracellular circulation, 
 which is arrested if the temperature be elevated above 150. 
 It is also arrested by prussic acid and alcohol, as well as by 
 solutions of acetate of lead, opium, and corrosive sublimate. 
 
 1 Class-Book of Botany, by J. H. Balfour, A.M., M.D., F.R.S., etc., p. 417. 
 
 2 Abhandl. der Akad. der Wiss. zu Berlin fur 1831. 
 
 3 Cyc. of Anat. and Phys., article 'Cilia,' by Dr. Sharpey, p. 610. 
 
 * Rasconi found that when the embryo of the frog was extracted from the ovum 
 it revolved. He attributed this movement to water entering and issuing from the 
 pores of the skin. Sur le Development de la Grenouille Commune. Milan, 1826. 
 
 D 
 
PHYSIOLOGY OF THE CIRCULATION 
 
 Prussia acid, alcohol, and the solutions in question, may destroy 
 the intracellular circulation by poisoning and paralysing the 
 tissues, and by inducing an imperfect osmosis ; for Dutrochet 
 found that all acids, alkalis, soluble salts, alcohol, etc., because 
 of their susceptibility to enter into combination with the per- 
 meable partition of the endosmometer, destroy endosmosis, 
 although they had induced it before their complete combina- 
 tion with the elements of the membrane had taken place ; and 
 it is not until this combination is complete that endosmosis 
 ceases. That the intracellular movements are in a great 
 measure due to osmosis, evaporation, and capillarity, is obvious 
 from experiment, as I have succeeded in producing them 
 
 Fig. 30. 
 
 Fig. 31. 
 
 Fig. 32. 
 
 Figs. 30 and 31 show how the gyration of the cell consents may be produced either by absorption and 
 endosmose, or by evaporation, or by all the three. Fig. 30, a b, cell containing viscous fluid ; c d. ab- 
 sorbing surfaces of cell surrounded by water or other thin fluid (g h) ; x, endosmotic currents, which 
 result in gyration (vide arrows), are thus produced. To the absorbing surfaces, evaporating ones, as at 
 e n,/m, may be added. Fig. 31 shows how gyration may be effected by evaporation alone, a b, cell 
 containing viscous fluid ; cf.de, evaporating surfaces. The arrows (x) indicate the direction in which 
 the evaporation acts. Original. 
 
 Fig. 32 shows how fluids washing the opposite sides of a cell in opposite directions will cause the cell 
 contents to gyrate, c, d. Capillary syphon tubes, the extremities of which communicate with water in 
 the vessels a, b, and with a viscid fluid in the cell h efg; the one syphon enters the cell at e, the other 
 aty; capillary tubes being inserted at g and h to -carry off the superfluous fluid ( z ) The fluid within the 
 cell gyrates, as indicated by the arrows. This is ascertained by introducing powdered charcoal into the 
 fluid contained within the cell. In the present diagram the cell has been placed on a lower level than 
 the water contained in the glasses ; but it might have been placed as high above the water as it is below 
 it, the gyration within the cell not being produced by the gravitation of the water in the vessels acting 
 through the syphon tubes, but by capillarity alone. Original. 
 
 artificially. Thus, if capillary syphon tubes be arranged to 
 act upon opposite points of a glass cell, and supplied with 
 water, they cause the fluid contents of the cell to gyrate 
 (Fig. 32.) Again, if a glass cell be filled with syrup, and en- 
 dosmotic currents induced on opposite sides of the cell above 
 and below, the syrup begins gradually to rotate (Fig. 30.) 
 The same happens when the syrup is allowed to evaporate 
 from opposite points (Fig. 31).. 
 
PHYSIOLOGY OF THE CIRCULATION. 35 
 
 Endosmosis and evaporation may produce gyration by a 
 conjoined action. When endosmosis and evaporation act 
 separately the gyration is in opposite directions (compare 
 arrows of Figs. 30 and 31). While gyration may be induced 
 mechanically by the operation of physical forces, the life of 
 the plant exercises, or may exercise, an influence in its 
 production. 
 
 As a proof that the presence or absence of moisture will not 
 account for all the phenomena witnessed in cells, it may be 
 stated that in the sensitive plant (Mimosa pudica], there is a 
 swelling at the base of the petiole, the cells of which consti- 
 tute, as it were, two springs which act in opposite directions ; 
 so that if from any cause the one be paralysed, the other 
 pushes the leaf in the direction of least resistance. This is 
 exactly what happens in hemiplegia, the tongue when pro- 
 truded being forced by the healthy muscles towards the 
 paralysed side ; muscles, as has been already indicated, having 
 a power of elongating as well as of shortening. If, as univer- 
 sally believed at present, muscles have only the power of 
 shortening, the tongue would be drawn towards the healthy 
 side, which it is not 1 . The springs, if they may so be called, 
 situated at the base of the petiole, are set in motion by the 
 rush of fluid, creating a turgid state of the one set of cells, and 
 an empty state of the other. A kind of rhythmic movement is 
 thus produced. What is it, one naturally inquires, which 
 gorges the one set of cells and empties the other, if it be not 
 a vital power exercised by the plant ? The fluid is present to 
 both sets of cells alike. The same fluid certainly cannot 
 stimulate the one set of cells to shorten and the other to 
 lengthen ; and besides, so far as known, there are no con- 
 tractile tissues present in the plant. Neither can the presence 
 of moisture act as an irritant, moisture being necessary to the 
 life of the plant, and a normal part of it. The only explanation 
 
 1 Sir Thomas Watson, in speaking of hemiplegia, says, ' When the tongue is put 
 out beyond the lips, its point is commonly turned to one side. To which side ? 
 Why, towards the palsied side. For what reason ? Clearly because the muscles 
 that protrude the tongue are powerless on that side, and in full vigour on the 
 other. That half of the tongue which corresponds with the sound side is pushed 
 further out than the other half, and therefore the tongue bends to the palsied side. 
 Such is the usual fact, and such the explanation of it.' Principles and Practice of 
 Physic, 4th ed. vol. i. p. 503. 
 
 D 2 
 
36 PHYSIOLOGY OF THE CIRCULATION. 
 
 that can be given is, that the plant lives, and that it sucks in 
 moisture by the one set of cells, and ejects moisture by the 
 other set, just as one part of the heart sucks in blood while 
 another expels it. The blood is not the stimulus to this act. 
 In the same way the stomach, bladder, rectum, and uterus, 
 close or shorten in one part, and open or lengthen in another, 
 when the proper time arrives for expelling their contents. 
 Here again the contained matters are not to be regarded as 
 irritants, in the ordinary acceptation of the term. If they 
 were, they would be expelled long before they were collected 
 in sufficient quantity. 
 
 Movements greatly resembling those of the petiole of the 
 sensitive plant occur in the cilia of the polygastric infusoria. 
 Ehrenberg showed that each of the cilia in question has a bulb 
 at its root, to which minute muscles are attached. Those 
 muscles shorten and lengthen alternately, and so the cilia are 
 lashed about with a flail-like motion. If the body of one of 
 those curious creatures is fixed, the cilia excite currents in the 
 water in which it is immersed ; if the body be free, they serve 
 as organs of locomotion. In this case there can of course be 
 no doubt as to the vitality of the movements, and the entire 
 absence of anything in the shape of irritation. 
 
 It is most interesting to find in an aggregation of plant- 
 cells movements so obviously analogous to those of muscles. 
 When the one set of cells, Henfrey 1 informs us, is contracted, the 
 other is expanded, and vice versa. According to Mohl 'the ex- 
 pansion of the cellular tissue on the upper side of the articulation 
 of a leaf counteracts a similar expansion of the cellular tissue 
 on the under side ; but if the upper cellular tissue be removed, 
 so that the under cellular tissue is deprived of its antagonist 
 the equilibrium is destroyed, and the leaf is pushed upwards. 
 The reverse of this happens when the under cellular tissue is 
 removed 2 .' Here again we have an illustration of what 
 happens in hemiplegia when the tongue is protruded. The 
 tongue is pushed towards the paralysed side, and if the paralysed 
 half of the organ were removed, the result would be precisely 
 the same as in the plant. The leaf, it will be observed, is kept 
 in a state of equilibrium by the presence of two forces equally 
 
 1 Henfrey's Botany, p. 628. 
 
 2 Anatomy and Physiology of the Vegetable Cell. 
 
PHYSIOLOGY OF THE CIRCULATION. 37 
 
 balanced, and the same may be said of the tongue. The leaf 
 and the tongue are free to vibrate on any slight disturbance 
 of the equilibrium. When the leaf is no longer required for 
 the growth of the plant, it is amputated by a vital process, and 
 not by any vicissitude of temperature ; in fact, the process of 
 disjunction begins with the formation of the leaf-stalk, and is 
 completed when the leaf ceases to be useful. Other vital 
 actions might be cited in this connection which go to prove 
 that plants control their own functions even the roots having 
 a selective power l . The remarks made regarding the move- 
 ments of the hollow muscles and tongue apply equally to the 
 flexors and extensors of the voluntary system ; but, as I shall 
 have occasion to return to this subject, I will merely observe, 
 in passing, that it is not a little remarkable that a mere con- 
 geries of cells devoid of nerves and contractile tissue should 
 have the power, so to speak, of acting rhythmically, and of 
 producing motions in definite directions in the absence of 
 an exciting cause at all events, in the absence of anything 
 which partakes of the nature of irritation. With these facts 
 before our eyes, it is not difficult to understand that volun- 
 tary and involuntary muscles have a centripetal and centri- 
 fugal action ; and by this I mean a power by which long 
 muscles shorten and lengthen, and hollow muscles close and 
 open. 
 
 The intracellular circulation of plants, as a rule, pursues 
 a definite direction. The moving particles, however, occa- 
 sionally stop, reverse their course, and commence de novo. 
 This circumstance inclines me to believe that absorption, 
 evaporation and osmosis play an important part in the 
 gyration of cell contents. That the vitality of the plant is 
 also concerned in the production of the intracellular circulation 
 is rendered all but certain by its occurring only in the active 
 living cells which are engaged in building up the plant, and 
 by its ceasing if the part of the plant in which it occurs is 
 injured 2 . 
 
 1 Desfontaines carried a sensitive plant with him in a coach. At first the jolting 
 caused the plant to close its leaves. When, however, it became accustomed to the 
 movement, it opened them, thus making itself master of the situation. 
 
 2 When a part of a plant is injured, and the membranous cell-walls ruptured, 
 osmosis may be impaired or altogether destroyed. 
 
38 PHYSIOLOGY OF THE CIRCULATION. 
 
 That cells are endowed with vitality, and that this of itself 
 is capable of -setting inert matter in motion, is proved by the 
 fact that some of them in the lower tribes of plants move 
 about in a liquid medium; the oscillatoria advancing with an 
 undulating motion \ Similar moving cells are seen in stepha- 
 nospharae and other genera of volvocineae ; and the cellular 
 spores of many algae are surrounded by cilia or vibratile 
 hairs which, in fluids, move for some time after the spore 
 (zoospore) has been discharged from the plant. 
 
 If we accord the power of motion to an entire cell, we shall 
 have difficulty in resisting the conclusion that it also regulates 
 the movements occurring within itself 2 . Further, in some of 
 the lower plants, as has been stated, the living cell contents 
 actually emerge from their temporary prison in the shape 
 of zoospores, which lead an itinerant life until they find a 
 suitable habitat. 
 
 The primordial utricle has moreover the power of as- 
 suming new shapes ; this remarkable structure, when the cell 
 is dividing, constricting itself, in two or more places, without 
 wrinkling. But I need not pursue the inquiry further ; suffice 
 it to say, that the vital, physical, and chemical phenomena 
 witnessed in plants are due primarily to operations occurring 
 in the interior of cells ; the functions of nutrition, reproduc- 
 tion, etc., necessitating movements in certain directions. In 
 connection with the belief that the process of nutrition results 
 in movements of a more or less definite character, I would 
 here cite the name of one revered in physiology and pa- 
 thology viz. Sir James Paget who gave it as his opinion 
 that the contraction and dilatation of the heart itself is due 
 to the nutrition and growth of the organ. He says, ' But 
 there is another thing common to all rhythmically acting 
 organs, they are all the seats of nutritive processes ; and I 
 believe that their movements are rhythmical, because their 
 
 1 The ova of polypi and sponges also move freely about before they become 
 fixed. This is necessary to spread the individuals of the original community. 
 To this end they are provided with numerous minute cilia on their exteriors, 
 which serve the purposes of locomotion and respiration. 
 
 2 Some authors attribute the contraction occurring in cells to alternate tur- 
 gescence and emptying of certain portions of the protoplasm; but, as has been 
 explained when speaking of the movements of the petiole of the sensitive plant, 
 turgescence, and the absence of it, may be equally traced to vital influence. 
 
PHYSIOLOGY OF THE CIRCULATION. 39 
 
 nutrition is so ; and rhythmic nutrition is, I believe, only a 
 peculiar instance or method of manifestation of a general 
 law of time as concerned in all organic processes. In other 
 words, I believe that rhythmic motion is an issue of rhythmic 
 nutrition, i. e. of a method of nutrition in which the acting 
 parts are, at certain periods, raised with time-regulated pro- 
 gress to a state of instability of composition, from which 
 they then decline, and in their decline may change their 
 shape and move with a definite velocity, or (as nervous 
 centres) may discharge nerve force V 
 
 Certain plants, when vigorous and exposed to a bright 
 light, exhibit rhythmical movements, and notably the Hedy- 
 sarum (Desmodium gyrans\ a native of the East Indies. The 
 leaf in this plant is unequally pinnate, consisting of a larger 
 leaflet at the end of the stalk, and two pairs of leaflets placed 
 laterally. The smaller leaflets come towards and recede from 
 each other with a jerking motion, every three minutes or so. 
 The movements of the heart are certainly not more singular 
 than those of the leaves now referred to. It cannot be the 
 light or heat which produces the movements of the leaflets, 
 for they go on in the dark ; and as they are most regular 
 when the plant is most healthy, we are not entitled to as- 
 sume the presence of stimuli in the shape of extraneous 
 irritation. The movements of the leaflets, in some senses, 
 foreshadow a heart, and are no doubt connected with the 
 nutrition of the plant. They teach us one very important 
 fact, viz. that living organs can come and go, contract 2 , 
 expand, and perform stated motions at stated intervals, 
 without the presence of nerves, muscles, elastic and other 
 tissues ; unless perchance these exist in an undifferentiated 
 form, which is by no means improbable. According to Fee, 
 the fluids drawn to the surface of a plant during light are 
 
 1 Croonian Lecture, ' On the Cause of the Rhythmic Motion of the Heart,' by 
 Sir James Paget, Bart. Proc. Roy. Soc. May 28, 1857. 
 
 2 In the wild lettuce (Lactuca virosa), and in the stings of nettles, the cells, 
 on being touched, contract and exude their fluid contents. The small leaflets 
 of the sensitive mimosas display cellular swellings at the roots, which, when 
 touched, communicate motion to the leaves. Those swellings apparently con- 
 sist of two kinds of cells, the one kind having the power of contracting, the 
 other of dilating. Dutrochet, Sur la Structure Intime des Animaux et Vegetaux t 
 1824. 
 
40 PHYSIOLOGY OF THE CIRCULATION. 
 
 kept in equilibrium by rhythmical evaporation ; the rhythmical 
 movements of the leaves being referable to vital changes in 
 the cell contents and vessels. 
 
 ' Probably the simplest example of rhythmic motions yet 
 known is that detected by the acute researches of Professor 
 Busk in the Volvox globator 1 . At a certain period of the 
 development of this simplest vegetable organism there ap- 
 pear in each zoospore, or in the bands of protoplasm with 
 which the zoospores are connected, vacuoles, spaces, or cavi- 
 ties, of about aa^o of an inch in diameter, which contract 
 with regular rhythm, at intervals of from 38 to 41 seconds, 
 quickly contracting and then more slowly dilating again/ 
 Now, however it may be with the heart, there is no room 
 for doubting that the closing and opening of the vacuoles, 
 spaces, or cavities here spoken of, are equally vital acts ; 
 they close quickly and open slowly, just as in the heart ; 
 and my impression is that the different parts of the heart 
 close and open alternately and independently, the closing 
 of the auricles taking no part in the opening of the 
 ventricles, and vice versa: in other words, the auricles close 
 and open by vital efforts, as do likewise the ventricles ; the 
 movements of the auricles and ventricles being simply co- 
 ordinated for a purpose. Indeed the structure and arrange- 
 ment of the fibres of, the heart forbid any other assumption. 
 If we take the fibres of the ventricles, we find they are ar- 
 ranged in spiral figure-of-8 loops, the fibres being continuous 
 upon each other, and crossing, at various degrees of obliquity, 
 with mathematical precision ; some being vertical, some 
 slightly oblique, some very oblique, and others transverse 
 or circular. When the fibres shorten they likewise thicken ; 
 this shortening and thickening obliterating the ventricular 
 cavities from above downwards, and from without inwards. 
 When the ventricles are closed, all the contained blood is 
 ejected. As the blood, forced on by .the closing of the 
 auricles, cannot obtain admission to the closed ventricles, 
 this fluid cannot mechanically distend the ventricles. They 
 are therefore under the necessity of opening just as they 
 closed. During the systole there is a shortening and thick- 
 
 1 Transactions of the Microscopical Society of London, May 21, 1852. 
 
PHYSIOLOGY OF THE CIRCULATION. 4! 
 
 ening of all the fibres of the ventricles ; during the diastole 
 there is a lengthening and thinning of the fibres. When 
 the fibres of the ventricles shorten and thicken, those of 
 the auricles lengthen and become thinner, and vice versa ; 
 and this is precisely what happens in hollow muscles with 
 sphincters. But for the power which muscles possess of 
 shortening and lengthening, it would be impossible to explain 
 how the pyloric valve of the stomach is firmly closed during 
 the first, stage of digestion, how it partly opens to allow the 
 chyme to pass during the second stage, and how it opens 
 wide to admit of the passage of undigested masses during 
 the third stage. ' The observations of Cohn ] , published 
 about a year later than those of Mr. Busk, but independent 
 of them, discovered similar phenomena in Gonium pectorale 
 and in Chlamydomonas, the vacuoles, like water-vesicles, 
 contracting regularly at intervals of 40 to 45 seconds. The 
 contractions and the dilatations occupy equal periods, as do 
 those of our own heart ventricles ; and in Gonium he has 
 found this singular fact, that when, as commonly happens, 
 two vacuoles exist in one cell, their rhythms are alike and 
 exactly alternate, each contracting once in about 40 seconds, 
 and the contraction of each occurring at exactly mid-distance 
 between two successive contractions of the other. Here 
 then we have examples of perfect and even compound 
 rhythmic contractions in vegetable organisms, in which we 
 can have no suspicion of muscular structure or nervous, or 
 of stimulus (in any reasonable sense of the term), or, in short, 
 of any of those things which we are prone to regard as the 
 mainsprings of rhythmic action in the heart V 
 
 The Lactiferous Circulation in Plants. Scarcely less in- 
 teresting and curious than the intracellular circulation, is 
 that occurring within the lactiferous vessels. The lactiferous 
 vessels of plants have been likened by Carpenter to the 
 capillary vessels of animals ; but they may, I think, with 
 greater propriety be compared to the lacteals and lymph- 
 atics. The lactiferous vessels differ from the other vessels 
 
 1 Untersuchungen uber die Entwickelungsgeschichte der Mikroskopischen Algen 
 und Pilze. Breslau, 4to, 1854. 
 
 2 Croonian Lecture, ' On the Cause of the Rhythmic Motion of the Heart,' by 
 Sir James Paget, Bart. v F.R.S Proc. Roy. Soc. May 28, 1857. 
 
42 PHYSIOLOGY OF THE CIRCULATION. 
 
 of plants by their branching and freely anastomosing with 
 each other. Some authors regard them as cellular canals 
 which are lined with a special membrane. However this 
 may be, they are generally believed to contain the elaborated 
 sap, which has been exposed to the influence of light and air. 
 The movements occurring within the lactiferous vessels are 
 seen to most advantage in plants with milky or coloured 
 juice, as the india-rubber plant, gutta-percha tree, lettuce, and 
 dandelion. 
 
 To the lactiferous movements the name of cyclosis has 
 been given ; and Schultz was of opinion that they are vital 
 in their nature. They are in some cases so rapid as to re- 
 semble the circulation in the web of the frog's foot. They 
 take place in all directions, the currents being usually most 
 vigorous where the plant is developing most rapidly. They 
 are quickened by heat, and retarded by cold and the agency 
 of electricity. It is very difficult to account for them, unless 
 indeed we refer them directly to nutritive changes occur- 
 ring in the plant. The difficulty is increased by the fact 
 that the vessels in which they occur, as far as known at 
 present, are non-contractile. I am disposed to believe that the 
 lactiferous vessels form a complicated series of interlacing 
 syphon tubes (see Fig. 29, p. 29) ; the milky and other juices 
 oscillating in them in obedience to atmospheric and hygro- 
 metric influences the oscillations being regulated within 
 certain limits by vital laws and affinities. I refer at length 
 to this view a little further on. 
 
 The Forces whick produce the Circulation in Plants. In the 
 winter the tree may be said to be in a dormant condition. 
 With the early spring comes fresh life, for then the stem 
 and branches swell and the shoots and young leaves come 
 forth. The warmth of spring inaugurates the circulation ; 
 but evaporation cannot as yet be said to take any very 
 active part in it. The cell tissues of the tree, contracted 
 and dry in winter, are in the best possible condition for re- 
 ceiving sap in the spring. This the roots supply in quantity. 
 Through the roots and through the stem and branches a 
 steady upward stream flows in direct opposition to gravity, 
 and in the absence of any propelling force. . This is a phe- 
 nomenon which can only be explained by a vis a fronte 
 
PHYSIOLOGY OF THE CIRCULATION. 43 
 
 traceable to nutrition and other changes going on in the 
 cells, and to osmotic l and capillary action 2 . 
 
 In the ferns, according to Hoffmann, there are no channels 
 for the descent of fluid, the sap simply ascending and diffus- 
 ing itself in the substance of the plant in its progress. These 
 plants grow by additions to their summits (acrogens), and 
 this fact has much to do with determining the upward 
 current, the leaf-action being virtually one of attraction or 
 suction 3 . 
 
 That nutrition has much to do with the general circulation 
 is proved by the fact that the current always sets most 
 strongly towards those points where growth is proceeding 
 most rapidly : a vine, e.g^ which is being forced by artificial 
 heat, drawing the sap with immense force, although its root 
 is placed outside the forcing-house and not participating in 
 the heat. That osmosis also plays an important part is 
 equally certain, from the fact that the juice presented to 
 the cells by the roots is less dense than that contained in 
 
 1 Dutrochet is of opinion ' that endosmose is due to a state of commixtion 
 within the capillary tubes of the septum, and that the two opposed fluids proceed 
 the one towards the other, with cross but unequal motions.' 
 
 ' M. Poisson and William Power have each in his own way given an 
 analytical explanation of the phenomenon of endosmose, and ascribed it to the 
 action of the capillary canals of the porous septum interposed between the two 
 fluids. In this explanation the phenomenon of the current of exosmosis is set 
 aside, or regarded as occurring merely accidentally. Now this is entirely opposed 
 to the fact ; we have constantly evidence of the simultaneous existence of the two 
 opposite and unequal currents of endosmosis and exosmosis.' Cyc. of Anat. and Phys. 
 article 'Endosmosis,' by Dutrochet, vol. ii. pp. 101, 102. 
 
 2 ' The height to which different fluids rise in capillary tubes depends on a 
 variety of causes, in appearance very different, but which must have some 
 fundamental analogy. Of all fluids, water is that which rises highest; and 
 substances held dissolved in it which increase its density lessen its power of 
 capillary ascent, which is also diminished by increase of temperature : hot water 
 ascends a less way in a capillary tube than cold water. Combustible fluids, 
 such as alcohol and ether, are like dense fluids in regard to power of capillary 
 ascent, so that combustibility acts in the same manner as density in this respect. 
 The matter of which capillary tubes are formed is also -endowed with the power 
 of modifying the capillary ascent of fluids. Thus water at the same tempera- 
 ture will not rise to the same height in a series of equal capillary tubes made 
 of different material/ Ibid. vol. ii. p. 103. 
 
 3 It ought however to be stated, that inasmuch as the upward current is 
 mainly due to endosmose, a certain proportion of downward current, as has 
 been already explained, is under the circumstances unavoidable. This is neces- 
 sary for the growth of the stem. 
 
44 PHYSIOLOGY OF THE CIRCULATION. 
 
 the cells ; the free interchange of fluids of different density 
 through the cell-wall and vascular tissues which are freely 
 permeable being unavoidable. The direction and varying 
 rapidity of the endosmotic and exosmotic currents are 
 exactly suited to the requirements of the circulation. The 
 rapid upward rush of the thin crude sap, and the slow, 
 percolation downwards of the dense elaborated sap, is just 
 what a priori we should expect. The fluid to be elaborated 
 must pass up to the leaves, to be transformed into the succus 
 proprius or true food of the tree, and the more rapidly it 
 does so the better. It is otherwise with the elaborated fluid. 
 This is to be carefully distributed to every part of the plant, 
 nourishing the plant and storing up future nourishment as 
 it goes. A rapid downward movement would be unsuitable 
 for the object to be attained. That capillarity contributes 
 its quota is rendered apparent by the fact that the vascular 
 bundles and interspaces are capillary in their nature, and 
 water will travel through them when detached from the tree ] . 
 The four great factors in the circulation, viz. nutrition, 
 osmosis, capillarity, and evaporation, are intimately asso- 
 ciated and may be considered together. The spongioles of 
 the root imbibe watery sap or moisture, and present it to the 
 cells of the root 2 , which present it to the cells and vessels 
 of the stem ; these in turn presenting it to the branches, 
 shoots, and other growing parts (Fig. 20, p. 20). 
 
 Goodsir philosopher, anatomist, and physiologist in one 
 drew a parallel between the spongioles of the roots and the 
 
 1 ' By far the greater majority of cells in the higher plants originate in forms 
 analogous to those produced by pressure, since they multiply by division, and 
 the septa dividing the newly-formed cells have ordinarily plain surfaces ; a 
 spherical cell forms two hemispherical cells, etc. . . . The cylindrical cells 
 of wood are not uncommonly -^ of an inch in length, liber cells -J^ to \ or of 
 an inch (flax). Hairs composed of one or more cylindrical cells, and the cylindrical 
 cells of some of the Confervae, especially Vaucheria, Bryopsis, and Chara, also 
 attain longitudinal dimensions to be measured in inches, while their diameters are 
 measured in hundredths of an inch.' Henfrey's Botany, pp. 475, 477. 
 
 2 In this they exercise a selective power, for Saussure has shown that if the 
 roots of plants be immersed in a liquid containing equal quantities of different 
 salts, they invariably take up more of the one salt than the other ; some plants 
 preferring one salt, some another. This only happens when the roots are entire. 
 When the roots are cut the two salts are taken up in equal proportions. 
 Recherches Chimiques sur la Vegetation, pp. 247, 261. 
 
PHYSIOLOGY OF THE CIRCULATION. 45 
 
 external layer of cells situated on the club-shaped extremi- 
 ties of the villi of the placenta. He says, these cells are 
 to the ovum what the spongioles are to plants ; they supply 
 it with nourishment from the soil in which it is planted. 
 Thus their action is selective ; and they transmit into the 
 interior of the villus the materials necessary for fcetal growth. 
 The nutritive plasma is then taken up by the internal layers 
 of cells, and by them brought into direct contact with the 
 foetal capillaries. Here a beautiful analogy is established 
 between plants and animals. The processes of nutrition 
 and growth are essentially the same in both cases. The 
 cells of the placental villi, and the spongioles of the plant, 
 exercise a selective power ; they absorb what is beneficial, 
 and reject what is prejudicial. They are imbued with a 
 double function ; they can take in or assimilate new nutri- 
 tious matter, and give off or reject non-nutritious or effete 
 matter. In the plant a thin liquid is drawn from the earth 
 by the spongioles and rootlets, and presented to a thicker 
 liquid of variable constitution found in the cells and vascular 
 tissues. What happens is this : The walls of the cells and 
 vascular canals being freely permeable, the thin fluids rise 
 rapidly into the thicker fluids the latter falling slowly 
 through the thinner ones. Here then we have what virtually 
 amounts to a vigorous upward circulation, and a feeble down- 
 ward one. Precisely the same thing happens in an osmometer 
 (Fig. 7, p. 14). If, e.g.) a dense liquid is confined in a bladder, 
 and the bladder be immersed in a thinner fluid, the thinner 
 fluid rises rapidly through the thicker one the thicker fluid 
 descending slowly into the thinner one. The dense fluid is 
 briskly penetrated by the thinner fluid either from above 
 or from below, according to the position of the latter 
 gravity having no power in the matter. By adding exos- 
 mose as one of the forces of the circulation to endosmose, 
 we are able to explain the reverse currents which we know 
 exist in the circulation of plants ; we are also able to explain 
 how the two currents vary in rapidity how they are more 
 vigorous at certain periods of the year how they are inter- 
 rupted and seem to oscillate at times and how they nearly 
 or altogether cease in winter. In endosmose and exosmose 
 we have two forces which bear a fixed relation to each 
 
46 PHYSIOLOGY OF THE CIRCULATION. 
 
 other 1 . Both operate at the same time. If the one is in- 
 terrupted, so is the other. It is in virtue of this arrangement 
 that the movements of the sap can be quickened in spring, 
 slowed in autumn, and discontinued or stopped in winter. 
 Moisture, heat, and a living plant supply the conditions. 
 If a part of a plant be forced (the other parts of the plant 
 and roots being outside the forcing-house) endosmose and 
 exosmose are at once called into operation in the part forced 
 the saps ascending, descending, and transfusing themselves 
 laterally. If the forcing is suddenly discontinued, the cir- 
 culation is arrested and growth checked. The same thing 
 happens when frost chills a plant in early spring. It is 
 thus that the plant and the circulation of the plant respond 
 to outward influences : the circulation varying at different 
 periods of the year, and of the day and night. 
 
 It is difficult to understand how excess of moisture 
 in the ground can be drawn up into the plant and exhaled 
 by the leaves at one period, and excess of moisture in the 
 atmosphere seized by the plant and discharged by the roots 
 at another. The explanation however is obvious, if we 
 call to our aid the forces of endosmose and exosmose. The 
 tree is always full of tenacious dense saps, and it is a matter 
 of indifference whether a thinner watery fluid be presented 
 to its roots or its leaves. If the thinner fluid be presented to 
 its roots, then the endosmotic or principal current sets rapidly 
 in an upward direction ; if, on the other hand, the thinner 
 fluid be presented to its leaves, the endosmotic or principal 
 current sets rapidly in a downward direction. That two fluids 
 of varying density, such as those situated without and within 
 a plant, will pass through each other in opposite directions, 
 
 1 Dutrochet states that we have constantly evidence of the simultaneous ex- 
 istence of the two opposite and unequal currents of enclosmosis and exosmosis. 
 It is not to be inferred from this that different fluids having the same density 
 act with the same vigour when placed in an endosmometer and placed in water. 
 All that is meant to be conveyed is, that the same fluids differing in density will 
 produce like results when exposed to similar conditions, endosmose being in- 
 variably accompanied by exosmose. Dutrochet, speaking of fluids having the 
 same density but differently constituted, says, ' Sugar-water and gum-water of the 
 same density being put successively into the same endosmometer, which is plunged 
 into pure water, the former produces the endosmosis with a velocity as 1 7, and 
 the latter with a velocity as 8 only.' Dutrochet has made experiments to show 
 that an increase in temperature also increases endosmose. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 47 
 
 whatever their position, may be proved by experiment. If, 
 e.g., I take two tubes, one end of each of which is covered by 
 an animal membrane, and place water in the one and syrup 
 in the other, I find that, when the tube containing syrup is 
 immersed in water, the water rises rapidly through the syrup ; 
 if, on the other hand, the tube containing water is immersed 
 in syrup, the water descends into the syrup ; from which it 
 follows that the thinner fluid passes through the thicker one, 
 either from above or from below. 
 
 Fig- 33- 
 
 Fig. 34- 
 
 Fig 35- 
 
 f/ 
 
 Figs. 33 and 34 explain how endosmose may go on either from above or from below, according as the 
 more tenuous fluid is placed higher or lower than the thicker fluid. In this experiment two tubes of 
 exactly the same calibre are employed, the ends of the tubes (/, g) being covered with an animal or 
 vegetable membrane. The tubes thus prepared are placed in glass vessels also of the same size. The 
 tube i is filled with water until the water reaches the line a ; the tube d being filled with syrup until the 
 syrup reaches the line a; the vessel k (Fig. 34) is filled with syrup until it reaches the line b, the vessel c 
 (Fig. 33) being filled with water until it reaches the line b likewise. When the thick and thin fluids so 
 disposed are left for a short time, the thin fluid in the tube i (Fig. 34) descends by endosmose into the 
 thicker fluid contained in the vessel h, until the thinner fluid reaches the point/, the thicker fluid rising 
 from b to k; in like manner, the thin fluid contained in the vessel c (Fig. 33), ascends by endosmose into 
 the thicker fluid in the tube d until the thicker fluid reaches the point e, the thinner fluid falling from b to/: 
 This experiment proves that a th'.n or watery fluid may be made to pass through the tenacious fluids 
 found in the interior of plants either from above or from below, according as the fluid is absorbed by the 
 leaves or roots. Endosmose, as it were, pushes fluids into the plant ; evaporation, as it were, drawing 
 them out. Original. 
 
 Fig. 35. x large cell with granular contents (r, s) gyrating. This figure shows how two forces may 
 act on opposite sides of a circle or ovoid in opposite directions, and cause the cell or the contents of the 
 cell to gyrate : -vide arrows. Original. 
 
 The force with which osmosis acts is very great, the rush 
 of the thinner fluid into the thicker one being in some cases 
 sufficient to burst the bladder containing the latter. In like 
 manner Hales ascertained that the sap rose with such force 
 in the vine in spring as to counterbalance a column of mer- 
 cury 38 inches in height, which is equal to 43 feet 3J inches 
 of water 1 . 
 
 That endosmose forms an important adjunct to the circu- 
 lation of plants is obvious from the fact that no plant can 
 
 1 Hales, vol. i. p. 124. 
 
48 PHYSIOLOGY OF THE CIRCULATION. 
 
 germinate without moisture, and a process of endosmose must 
 take place before water can be transmitted through the cell- 
 wall. ' Water is required for the solution of the nutritive 
 matter of the seed, as well as for exciting the endosmotic 
 action of the cells : and no circulation nor movement of fluids 
 can take place in the seed until water is taken up.' De Can- 
 dolle states that a French bean weighing 4.5 grains took up 
 6J grains of water during germination. The absorption of this 
 large quantity of fluid is attended with an evolution of force 
 which acts in specific directions according to the structure 
 and condition of the parts at the time. 
 
 In artificial osmosis one membrane and two fluids are 
 usually employed. In natural osmosis a variety of mem- 
 branes and several fluids act and react upon each other 1 . In 
 osmosis there is no visible force at work, gravity being over- 
 come by the thinner fluids nevertheless. In the same way, 
 if a system of dry capillary tubes be arranged vertically in 
 tiers, and have their extreme ends placed in water or other 
 fluid, the fluid will rise more or less quickly into them 2 . Here 
 again, we have a movement of fluids in opposition to gravity, 
 no force being visible. A similar result is obtained if a leash 
 of capillary tubes, or of hair glass or a strip of blotting-paper, 
 be suspended vertically, and their lower extremities placed in 
 water. This result is facilitated if the tubes and hair glass 
 are arranged within a large tube, and if the blotting-paper be 
 placed between slips of glass to prevent lateral evaporation. 
 By keeping down lateral and promoting vertical evaporation, 
 the fluid rises higher. A vis a tergo is therefore not necessary 
 to a flow of sap in an upward direction. It suffices if the sap 
 be supplied to a system of cells and vessels fitted to receive 
 it. While the fluid is proceeding in the stem of the plant 
 from below upwards, it is also disseminating itself laterally. 
 This is necessitated by the porosity of the cells and vessels ; 
 
 1 ' Liquids are diffused throughout the whole plant by the action of cells and 
 vessels having a different chemical constitution and different functions. One cell 
 takes the juice from another, and acts by diffusion on the others. The cells of the 
 rootlets imbibe by endosmose fluid matters which are carried into the stem, and 
 the cells of the leaves by their exhaling functions aid in promoting a general 
 movement of sap throughout the whole system.' Balfour's Botany, p. 507. 
 
 - The fluid rises highest in capillary tubes when they are inclosed within a 
 larger tube. 
 
PHYSIOLOGY OF THE CIRCULATION. 49 
 
 any sap passing along or through them necessarily diffusing 
 itself to a greater or less extent in its passage. It is in this 
 way the transverse or cross circulation is accounted for. Or- 
 dinary capillary tubes form vessels with impermeable walls ; 
 the capillary tubes of nature, on the contrary, form vessels 
 with permeable walls. The cases, although analogous, are not 
 identical. It is necessary that the crude sap taken up from 
 the earth traverse the plant in its length and breadth ; and 
 this, as I have endeavoured to show, can in a great measure 
 be effected by the agency of natural laws, and without effort 
 on the part of the plant or tree itself. From researches just 
 made by Goltz, it would appear that the animal tissues have 
 a similar power of absorbing and spreading a fluid from part 
 to part quite irrespective of the force exercised by the heart 
 in the general circulation. He ascertained this by detaching 
 the heart from the circulation, and presenting strychnia to the 
 tissues. Part of the tissues thus poisoned was administered 
 to healthy frogs as food, and induced in all of them the phe- 
 nomena characteristic of strychnia-poisoning. 
 
 The Vessels of Plants in Summer form Syphons. When 
 the leaves are fully formed in summer the circulation is more 
 complex, but the same forces are at work. The leaves supply 
 a rich anastomosis or network of vessels and structures, which 
 Mr. Herbert Spencer is inclined to regard as absorbents. 
 Similar absorbents are found in the stem and in the roots 
 (see Figs. 23-25, p. 21). They join the vascular vessels to- 
 gether, and in this way, it appears to me, convert them into a 
 system of syphons, the extremities of which are directed alter- 
 nately towards the leaves and roots. If a vigorous process 
 of endosmose goes on in one extremity of the syphon in 
 connexion with the root, a similar process may go on in the 
 other extremity of the syphon, in connexion with the leaf: the 
 direction of the currents will be reversed ; but opposite forces 
 may act on opposite sides of a circle and yet work in harmony. 
 Fig. 35, p. 47, and Fig. 36, p. 50, will illustrate my meaning. 
 
 When the currents are united by loops pointing in oppo- 
 site directions, and the two systems of syphons thus formed 
 anastomose, a movement of the nutritious juices in a circle 
 similar to what occurs in animals may be established. By 
 placing the two systems of syphons together, we get a 
 
 E 
 
SO PHYSIOLOGY OF THE CIRCULATION. 
 
 circulation which is continuous in the direction of the leaves 
 and roots, and which is at the same time interrupted in both 
 these directions. By this means the circulation may be quick- 
 ened or slowed, according to circumstances. 
 
 This explains how the columns of moving fluids may be 
 made to balance each other to oscillate, or move on con- 
 tinuously in one direction for a certain period, and in another 
 and opposite direction at another period. It also shows how 
 
 Fig. 36. 
 
 Fig. 36. Compound syphon, with expanded absorbing and evaporating surfaces covered with animal 
 or vegetable membrane to correspond with the roots and leaves of plants. Through this form of syphon 
 (a, b), which essentially resembles that formed by the vessels (Fig. 29, p. 29) and terminal vascular loops 
 (Figs. 23, 24, and 25 p. 21) of plants, fluids may be transmitted in advancing continuous waves (vide 
 arrows), or made to oscillate. The peculiarity of this syphon consists in its being composed of a number 
 of simple syphons united in such a manner that their free extremities are alternately directed downwards 
 and upwards. The long legs of the simple syphon correspond to the expanded portions of the figure, 
 and represent the leaves and roots of the plant, or, what is the same thing, its absorbing and evaporating 
 surfaces. Any impulse communicated to the expanded portions, whether by absorption or evaporation, 
 occasions a flow of fluid through the syphon, so that the circulation in plants is directly influenced by the 
 presence or absence of moisture, heat, etc. j, h, f, c. Expanded absorbing surfaces covered with 
 vegetable or animal membrane, and surrounded by water (, m, k, I), z, g, e, d, Similar evaporating sur- 
 faces. The absorbing and evaporating surfaces act together. Thus, at j, h, f, and c, absorption and 
 endosmose are taking place (these may be regarded as pushing forces) ; whereas, at i, g, e, d, evapora- 
 tion is going on (this may be regarded as a pulling force). The arrows indicate the direction in which 
 absorption and evaporation act. The different columns of fluid by this arrangement may be made to 
 balance each other, as at s, r, or to flow in the direction b, a. The absorbing surfaces may all .become 
 evaporating surfaces, as in seasons of drought, or the evaporating surfaces may all become absorbing 
 surfaces, as in rainy seasons. In the former case the plant is drained of its juices alike by leaves and 
 roots ; in the latter case the plant is gorged with sap through the same sources. Original. 
 
 the circulation may be influenced throughout its entire extent 
 by a stimulus applied at any part ; how fluids may pervade 
 the plant ; how they may enter by the roots and escape by 
 the leaves, or the reverse ; how, similarly, cross currents may 
 be established ; and, lastly, how the movements occurring 
 in the lactiferous vessels and within individual cells may be 
 explained. 
 
 It is in this way, too, that an excess of moisture in the 
 ground or in the air may be made to pass through the plant 
 in either direction ; the excess of moisture in the ground pass- 
 
PHYSIOLOGY OF THE CIRCULATION. 51 
 
 ing up into the leaves, from which it is exhaled ; the excess 
 of moisture in the atmosphere entering at the leaves and 
 escaping by the roots. There is nothing antagonistic in this 
 arrangement. If an excess of moisture is absorbed by the 
 root, say at / of Fig. 36, it passes in an upward direction, 
 and escapes at e. If an excess of moisture is absorbed by the 
 leaf, say at c of Fig. 36, it passes directly down to the root, 
 as indicated by the arrow, to d. In either case endosmose 
 is at work. When too much sap ascends from the root, it is 
 endosmose acting in an upward direction ; when too much 
 sap descends from the leaf, it is endosmose acting in a down- 
 ward direction. By placing the dense fluid above a less dense 
 one, we get an upward current ; by placing the dense fluid 
 below the less dense one, we get a downward current. But 
 when the currents are once established they may work in 
 harmony ; the upward current acting at / and the downward 
 
 7- Diagram showing how intracellular circulation or gyration may be pro- 
 duced. a, 6, Two vessels, the ends of which are covered with a portion of animal 
 or vegetable membrane (c, d, e, f), to represent the absorbing or evaporating 
 surfaces of plants. Between the vessels two vegetable cells (-, h) are placed. 
 If water (say moisture from the earth) is applied at f to the thicker fluid 
 (crude or other vegetable saps) contained in the vessel b, an endosmotic current 
 sets in an upward direction towards e, as indicated by the arrows. If water (say 
 moisture from the air, as rain or dew) is applied at c to the thicker fluid (crude or 
 other vegetable saps) contained in the vessel a, an endosmotic current sets 
 in a downward direction towards d, as indicated by the arrows. Similar cur- 
 rents'are produced if evaporation goes on at the points e and d; or if absorption 
 goes on at f and c, and evaporation at d and e. In either case the fluids passing 
 through the vessels a and b wash and penetrate the sides of the cells A obliquely, 
 and cause their contents to gyrate (-vide arrows) . A similar result is produced if 
 the cells g, h are bathed with a thinner fluid than that which they contain, the 
 endosmose and exosmose induced, aided by the rounded form of the cells, tending 
 I to rotation of the cell contents. The porosity of the walls of the cells and vessels 
 favours these results. Absorption may be regarded as a pushing force ; evapora- 
 tion as a pulling force. Original. 
 
 one at c, giving a continuous circulation of sap through the 
 plant similar to the circulation in the trunk and other parts 
 of animals. Nor is this all. It may even happen that when 
 an endosmotic current, going in a certain direction, falls in 
 with an exosmotic one having a similar direction, the two may 
 blend and travel together. In this case the fluids fuse more 
 or less completely in transitu an arrangement which ac- 
 counts for every form and variety of movement that can occur 
 in plants. 
 
 Intracellular Movements in Plants^ Probable Explanation 
 of. While the cells inaugurate or commence the general cir- 
 culation, the general circulation in its turn influences the in- 
 tracellular circulation. This follows, because when a current 
 
 E 2, 
 
52, PHYSIOLOGY OF THE CIRCULATION. 
 
 of fluid travels up the one side of a thin porous cell-wall, 
 and another and opposite current travels down the other or 
 opposite side, a certain proportion of the currents pass obliquely 
 through the cell-wall, and cause the fluid contents of the cell to 
 gyrate or move in a circle (Fig. 37, p. 51). The cell contents 
 are made to gyrate, even in the absence of opposing currents 
 outside the cell, if endosmotic and exosmotic currents are 
 induced within it ; or if evaporation or capillarity be made 
 to act at certain points (Figs. 30-32, p. 34). 
 
 The cell and vessel are part of a common stock, and both 
 are influenced by the presence of moisture. The cell and 
 vessel have their long axes running in the same direction, so 
 that fluids entering and escaping from a cell and vessel by 
 endosmose and exosmose produce movements in opposite 
 directions ; these movements, seeing the cell is closed and 
 rounded at either end, being gradually converted into rotatory 
 ones. The same holds true of the general circulation when 
 the vessels are joined in the leaves and roots to form loops. 
 Certain movements (not necessarily those of gyration) occur- 
 ring within the cells inaugurate the general circulation, and, 
 when the general circulation is established, it assists the gyra- 
 tion of the cell contents. 
 
 As the vessel is a differentiation of the cell, so the .general 
 circulation is a differentiation of the intracellular circula- 
 tion 1 . The intracellular and general circulation are referable 
 to the same causes, and always act in harmony ; the gyra- 
 tion of the cell contents within their capsule is equivalent 
 to the gyration of the general circulation, when the vessels 
 are joined by loops in the leaves and roots. The presence 
 of vessels is not necessary to the circulation. This can be 
 carried on in the intervascular spaces, or, indeed, wherever 
 there are cavities or open canals along which fluids can 
 travel 2 . In plants, fluids and air may circulate either 
 
 1 Henfrey is of opinion that intracellular movements take place in all cells at 
 one period or other of their growth. 
 
 2 Rainey was of opinion that the intercellular canals, which are more or less 
 continuous throughout the entire length of the plant, are the channels through 
 which the sap principally ascends; and Tetley was inclined to regard the cells 
 and vessels as secreting organs which operated upon the crude sap in the inter- 
 cellular canals, from which they separated by vito-chemical actions liquid and 
 gaseous matters. The recent experiments of Hoffmann do not support this view. 
 
PHYSIOLOGY OF THE CIRCULATION. 53 
 
 separately or in combination. The syphon arrangement, ex- 
 plained here for the first time, accounts for the upward and 
 downward growth of a plant, and for the fact that a stem may 
 send out of its interior ascending shoots and leaves, and de- 
 scending roots and spongioles the former occasionally assum- 
 ing the function of the latter, and vice versa. A single system 
 of vessels or tubes may act by itself and discharge a double 
 duty, or two systems may combine and discharge a single 
 function. This arrangement supplies a circulation equal to 
 the wants of every form and variety of plant. If the plant 
 is simply cellular, the circulation is diffused, i.e. the fluids 
 enter the plant in all directions, and escape in all directions ; 
 every part of the plant being provided with nutritious juices, 
 and every part being drained of effete matters. If the plant 
 is provided with spiral and other vessels, with intercellular 
 and other spaces, with lactiferous vessels, and with cells having 
 a circulation of their own, the arrangement is equally simple 
 and equally satisfactory as regards the circulation of nutritious 
 juices in the stem and branches, and the absorption and 
 discharge of fluids by the roots and leaves. The circulating 
 forces in a plant are, so to speak, pitted against each other ; 
 the circulation is in equilibria, and anything that disturbs this 
 state of matters causes motion in one direction or another. 
 Too much evaporation or too much absorption in the leaves, 
 or too much moisture taken in or given off by the roots, 
 or growth in a particular direction, may do this. The cir- 
 culation is universal in its nature, and perfect of its kind. It 
 can be made to slow and stop ; to go on languidly or very 
 vigorously; one part of it may be active while another is 
 inactive; it is equal to all the demands made upon it by 
 growth, by reproduction, by heat, by cold, light and dark- 
 ness ; it is equally suited to the simple cellular plant, and the 
 complex fibro-vascular one. 
 
 Rainey was further of opinion that the descent of the elaborated sap was through 
 the vessels, and not through the cells or intercellular spaces. Schultz maintained 
 that the sap descended through the lactiferous vessels, these being compared by 
 Carpenter to the capillaries of animals. Spencer states from experiment that the 
 spiral, annular, scalariform, and other vessels, form the channels not only for the 
 ascent, but also for the descent of the sap, the same vessels sufficing for both. 
 There is thus much difference of opinion as to the precise course pursued by the 
 ascending and descending saps. 
 
54 PHYSIOLOGY OF THE CIRCULATION. 
 
 As the season advances, and the leaves become fully de- 
 veloped, the heat of summer comes into play. Evaporation 
 now begins to take an active part in the circulation \ As the 
 sap rises to the leaves, it is evaporated in quantity from the 
 stomata and other parts ; these, when taken together, con- 
 stituting a vast drying surface. The process which is now 
 inaugurated can be exactly imitated by placing a glass tube 
 in water, the upper end of which is slightly expanded, funnel- 
 fashion, and covered with a layer of moist bladder. As 
 evaporation goes on in the bladder, a continuous upward 
 stream of fluid is furnished. The common spray-producer 
 affords another illustration. In this very useful contrivance 
 a capillary tube, or a tube with a capillary point, is placed 
 in fluid, a corresponding tube being arranged to meet its 
 upper end at right angles. A current of air forced through 
 the second tube causes the fluid to rise in the first tube, an 
 effect favoured by capillary attraction when the tube is small 2 . 
 The sap in summer, from evaporation and the elaboration it 
 undergoes in the leaves, is rendered more tenacious, and 
 
 1 'In the leaves (and green portions of plants generally) the very important 
 phenomenon of evaporation or transpiration of watery vapours occurs, and con- 
 stitutes probably the most important agent of all in causing the supply and diffusion 
 
 of food in plants In the spring, before the expansion of the buds, 
 
 absorption is necessarily greater than transpiration ; the water in such a case is 
 stored in the stem, where it is made available for the expanding buds and growing 
 tissues generally. In the summer, the transpiration is greater than the absorption ; 
 and then the leaves depend for their supply on the stores in the stem, or, failing 
 that, they wither. Even in winter, provided the stem be not absolutely frozen, 
 there is a motion of the juices dependent to a great extent on the temperature of 
 the soil, which is always in that season higher than the air, and it increases in 
 
 amount from the surface downwards The crude sap becomes more 
 
 and more condensed as it ascends in the stem and other organs. In the leaves and 
 other green parts it undergoes a most important transformation, loses by transpira- 
 tion much of its water, and receives a new element in its composition, of the 
 highest importance to it as material for development, viz. carbon, derived from the 
 carbonic acid absorbed by the leaves, and decomposed there in sunlight, with the 
 liberation of oxygen.' Henfrey's Botany, pp. 567-569. 
 
 2 In Professor Lister's spray-producer, the second tube is made to bifurcate one 
 portion descending into the bottle containing the fluid, which it is not allowed to 
 touch ; the other ascending and meeting the point of the first tube at right angles, 
 as before. In this case the current of air introduced into the second tube forces 
 the fluid through the first tube, and breaks it up into spray simultaneously. The 
 cloud of spray produced by this most ingenious instrument is remarkable alike for 
 its great size and the extreme state of division to which its component particles are 
 reduced. 
 
PHYSIOLOGY OF THE CIRCULATION. 55 
 
 adheres with greater force to the vessels and channels through 
 which it passes. As a consequence, there is a slight increase 
 in the amount of capillary action, and a slight diminution of 
 the osmotic action. The vital capillary and osmotic forces 
 vary in intensity, the one being weaker when the other is 
 stronger, and vice versa \ 
 
 The succus proprius, when elaborated, descends into the 
 growing parts of the tree according to demand, and at a 
 varying speed. It goes from a higher to a lower level ; not, 
 however, in obedience to the law of gravity, for it is found 
 that if a branch is bent to the ground, the succus proprius 
 actually ascends prior to descending. Gravity may, under 
 certain circumstances, arrest, instead of cause, the flow of a 
 fluid ; and atmospheric pressure will cause water to flow 
 into an exhausted receiver 2 . Petit Thouars and Gaudichaud, 
 as I have explained, believe that the embryo of plants 
 consists of two systems a caulinary and radicular system ; 
 the former having an ascending circulation, and tending to 
 develop buds and leaves ; the latter having a descending 
 circulation, and tending to develop the stem and roots- each 
 system having cells and vessels peculiar to itself 3 . Many are 
 of opinion that the two systems persist throughout the entire 
 life of the plant. This view is favoured by the growth of plants 
 in an upward direction, and by the presence in screw-pines 
 of adventitious and other roots which grow downwards into the 
 soil (Figs. 2 and 3, p. 9). This growth in opposite directions 
 implies two systems, and a reverse circulation. Mr. Herbert 
 Spencer takes an opposite view. He maintains that the two 
 sets of vessels cannot be demonstrated to exist, and that 
 in reality there is only one set, the fluids oscillating therein 
 in such a manner as at one period to occasion an up- 
 ward circulation to the leaves, and at another, a downward 
 circulation to the roots ; the vessels, according to him, 
 terminating in the leaves and roots in a series of club- 
 
 1 ' The entrance of fluid into a plant may be explained by endosmose and certain 
 vital affinities; the escape by exosmose and certain vital repulsions.' Gyde, On 
 Radical Excretions, Trans. High, and Agric. Soc., Oct. 1843, p. 273. 
 
 2 Grove on the Correlation of Physical Forces, p. 10. 
 
 3 ' In the embryo of a flowering plant it is scarcely possible to define the limits 
 even of the stem itself, which loses itself above in the plumule, and below in the 
 radicle.' Henfrey's Botany, p. 23. 
 
56 PHYSIOLOGY OF THE CIRCULATION. 
 
 shaped expansions, which he was the first to discover and 
 describe (Figs. 23, 24, and 25, p. 21) 1 . 
 
 Absorbents of Plants. The club-shaped expansions referred 
 to consist of masses of irregular and imperfectly-united 
 fibrous cells, such as those out of which the vessels are 
 developed. They do not occur in all leaves, and are found 
 in stems and branches that have assumed the function of 
 leaves. They occupy the intercellular spaces between the 
 ultimate venous network of the leaves, into which network 
 they also open. Some of them, however, open outwards 
 towards the air. The vascular club-shaped expansions are 
 thus brought into immediate contact not only with the veins 
 of the leaf, but also the tissues concerned in assimilation. 
 They are found in a less developed form in the root and 
 body of the turnip. The simplest kinds consist of only 
 fenestrated cells, with their ends bent round so as to meet 2 . 
 By the club-shaped expansions a direct connexion is estab- 
 lished in the leaf between the vascular tubes found in the 
 branches, stems, and roots ; in fact, the free extremities of 
 the tubes may be said to be united in the leaves and roots 
 by a series of vascular expansions resembling the capillary 
 
 1 These structures, when present, form the terminations of the vascular system. 
 They are masses of irregular and imperfectly-united fibrous cells, such as those 
 out of which vessels are developed ; and they are sometimes slender and sometimes 
 bulky usually, however, being more or less club-shaped. Speaking of the club- 
 shaped expansion of the Euphorbia neriifolia, Mr. Spencer says, ' Occupying one 
 of the interspaces of the ultimate venous network, it consists of a spirally-lined 
 duct, or set of ducts, which connects with the neighbouring vein a cluster of 
 half-reticulated half-scalariform cells. These cells have projections, many of them 
 tapering, that insert themselves into the adjacent intercellular spaces, thus pro- 
 ducing an extensive surface of contact between the organ and the embedding 
 tissues. A further trait is that the unsheathing prosenchyma' is either but little 
 developed or wholly absent, and consequently this expanded vascular structure, 
 especially at its end, comes immediately in contact with the tissues concerned in 
 assimilation.' Further on he observes, 'Considering the structure and position 
 of these organs, as well as the nature of the plants possessing them, may we not 
 form a shrewd suspicion as to their function ? Is it not probable that they facilitate 
 absorption of the juices carried back from the leaf for the nutrition of the stem and 
 roots?' Principles of Biology, vol. ii. p. 559. 
 
 2 ' It should be added that, while the expanded free extremities graduate into 
 tapering free extremities, not differing from ordinary vessels, they also pass in- 
 sensibly into the ordinary inosculations. Occasionally, along with numerous free 
 endings, there occur loops, and from such loops there are transitions to the 
 ultimate meshes of the veins.' Ibid., vol. i. p. 559. 
 
PHYSIOLOGY OF THE CIRCULATION. 57 
 
 vessels of animals. If this be so and there is no room for 
 doubt many of the difficulties connected with the circulation 
 in plants disappear, for the presence of a capillary system 
 in the leaves and roots enables us to reconcile the double 
 set of vessels of Petit Thouars and Gaudichaud with the 
 single set of Mr. Spencer. It also enables us to explain 
 the ascending current in spring, the ascending and descending 
 currents in summer, and the descending current in autumn. 
 Further, it shows us how those currents may be inaugurated, 
 how carried on, how interrupted, and how partly or altogether 
 stopped. In the root one set of cells and vessels absorb and 
 another excrete, the excreting vessels, according to Macaire 1 , 
 giving off matters which are detrimental to the soil. In 
 this arrangement we have an indication of two systems 
 and two forces acting in opposite directions (Fig. i, p. 9). 
 
 Whether two distinct systems of vessels exist is immaterial, 
 if, as I have explained, all vessels virtually form syphon 
 tubes. The vessels which convey the sap, as is well known, 
 are arranged in more or less parallel vertical lines. If the 
 vessels are united to each other by a capillary plexus, or, 
 what is equivalent thereto, in the leaves and roots, they are 
 at once, as has been shown, converted into syphon tubes, 
 one set bending upon itself in the leaves, the other set 
 bending upon itself in the roots. As however a certain 
 proportion of the syphon tubes which bend upon themselves 
 in the leaves are porous and virtually open towards the 
 roots ; while a certain proportion of the syphon tubes which 
 bend upon themselves in the roots are porous and virtually 
 open towards the leaves ; it follows that the contents of the 
 syphon tubes may be made to move by an increase or 
 decrease of moisture, heat, etc., either from above or from 
 below. In spring, the vessels may be said to consist of 
 one set, because at this period the leaves and the connecting 
 plexuses which they contain do not exist. All the vessels at 
 this period may therefore be regarded as carrying sap in 
 an upward direction to form shoots, buds, and leaves, part of 
 the sap escaping laterally because of the porosity of the 
 
 1 Macaire-Princeps, Sur les Excretions des Racines, Mdm. de la Soc. Phys. et 
 d'Hist. Nat. de Geneve, torn. v. p. 287. Annales des Sc. Nat., ist series, xxviii. 402. 
 Brugmars, De Mutata Humorum in Regno Organico Indole. 
 
58 PHYSIOLOGY OF THE CIRCULATION. 
 
 vessels. In summer, when the leaves are fully formed, the 
 connecting links are supplied by the capillary vascular ex- 
 pansions formed in them the tubes are, in fact, converted 
 into syphons. As both extremities of the syphons are full 
 of sap in spring and early summer, an upward and a down- 
 ward current is immediately established. When the down- 
 ward current has nourished the plant and stored up its 
 starch granules for the ensuing spring, the leaves fall, the 
 syphon structure and action is interrupted, and all the tubes 
 (they are a second time single tubes) convey moisture from 
 above downwards, as happens in autumn. As the vascular 
 expansions or networks are found also in the stems of plants, 
 it may be taken for granted that certain of the tubes are 
 united in spring, the upward rush of sap being followed by 
 a slight downward current, as happens in endosmose and 
 exosmose. As moreover the spongioles of the root and 
 the leaves are analogous structures, and certain tubes are 
 united in the roots, the downward current in autumn is 
 accompanied by a slight upward current. This accounts for 
 the fact that, at all periods of the year, the upward, 
 downward, and transverse currents exist ; the upward and 
 downward currents being most vigorous in spring and au- 
 tumn, and scarcely perceptible in winter. Furthermore, as 
 some of the vascular expansions in the leaves are free to ab- 
 sorb moisture, etc., in the same way that the spongioles are, 
 it follows that the general circulation may receive an impulse 
 from the leaves, or from the roots, or both together, the 
 circulation going on in a continuous current in certain vessels, 
 as explained (see Fig. 36, p. 50). 
 
 Analogy between Leaves and Roots. That leaves and roots 
 have many points in common was shown by the researches 
 of Bonnet 1 > who found that plants of mercurialis whose 
 leaves were in contact with water absorbed as much, and, 
 for a time, kept nearly as fresh, as those whose roots were 
 immersed 2 . The hairs on the under surface of leaves absorb 
 
 1 Bonnet : Recherches sur 1'Usage des Feuilles dans les Plantes. Getting., 1 754. 
 
 2 ' Leaves proceed from the nodes of the axis, and commence as cellular processes 
 at the extremities of the medullary rays. The extremities of the roots are composed 
 of loose cells, which appear to be the terminal tissues of the radicle, and formed by the 
 elongating root.' Balfour's Botany, pp. 51 and 96. Both leaves and roots are 
 covered by epidermis, and have vessels developed in them. The stomata of the 
 
PHYSIOLOGY OF THE CIRCULATION. 59 
 
 moisture, and seem to act as cellular rootlets. Nor is this 
 all. Hoffmann 1 showed that, after every fall of rain or dew, 
 the leaves absorbed moisture, which passed downwards in 
 the tracheae and enveloping prosenchyma, and displaced for 
 a time the air usually found in the spiral vessels. In pro- 
 portion as the absorption was abundant and rapid, the 
 tendency of the moisture to enter the spiral vessels was 
 increased. Almost precisely the same remarks might be 
 made regarding the spongioles of the root. In seasons of 
 drought they absorb and transmit comparatively little 
 moisture. After a rainfall the spongioles drink greedily, 
 and send on crude sap in abundance. Further, excess of 
 moisture sent up by the roots is exhaled by the leaves ; 
 excess of moisture, sent down by the leaves, escaping by the 
 roots. If the relation existing between the leaves and roots 
 be disturbed, and exhalation prevented, the plant becomes 
 dropsical. If, on the other hand, the exhalation from the 
 leaves be in excess of the moisture absorbed by the roots, 
 the leaves wither and droop. Leaves and roots both give 
 off gases the former, oxygen ; the latter, according to 
 Wiegmann and Polodorff, carbonic acid. In the epiphytes, 
 or air-growing plants, the roots (aerial of course) are of a 
 green colour, like the leaves, and possess stomata. The 
 stomata are wanting in the roots of aquatic plants, but they 
 are also absent in the submerged leaves. The cuttings of 
 many plants give off leaf -buds and roots at the same time. 
 'In the monocotyledons and ferns, the radicle is abortive, 
 and the efficient roots are really lateral organs, comparable 
 in a certain way to the leaves upon the ascending part of the 
 stem V When the branches and leaves are growing rapidly, 
 the roots are also developing their rootlets, and constantly 
 renewing their delicate absorbing extremities. Aerial roots 
 take on the function of leaves, and obtain nourishment from 
 the atmosphere. In this case they lose their fibrils, assume 
 the appearance of stems, and throw out leaf-buds. 
 
 leaves seem to be represented in the roots by hairs. Leaves frequently display 
 hairs, and the stomata are generally absent in submerged leaves. 
 
 1 On the Circulation of the Sap in Plants, in Scientific Memoirs,' Nat. Hist. i. 
 p. 46. 
 
 2 Henfrey's Botany, p. 16. 
 
60 PHYSIOLOGY OF THE CIRCULATION. 
 
 Duhamel proved this ingeniously and very simply. He 
 took a willow and inserted its branches into the soil, where 
 they took root. This done, he pulled up the original root 
 and exposed it to the air. The original root, after a shbrt 
 interval, became transformed into leaf-b earing branches. The 
 fibrous rootlets upon the surface of tuberous taproots, like 
 the carrot, parsnip, etc., appear to be mostly true branches^. 
 Speaking generally, it seems to be a matter of little con- 
 sequence whether the stem be placed in a vertical or pro- 
 cumbent position. In either case the branches and leaves 
 strike upwards the roots and spongioles downwards. Roots, 
 like leaves, are sometimes spirally arranged. Roots may 
 produce buds, as shown in the Anemone japonica, and 
 branches may be made to throw out rootlets. The rhizome 
 of Solomon's-seal throws out a bud from its upper surface, 
 and roots from its under ; and the strawberry, from its 
 runners, sends leaves up and roots down 2 , all which proves 
 very clearly that the spongioles and leaves, and roots and 
 branches, are closely allied both in structure and function 
 the circulation and the forces which produce it being in 
 either case essentially the same. The intimate relation which 
 exists between the roots and the leaves is well expressed 
 by Mulder, who asserts that all the nitrogenous constituents 
 of plants are absorbed by the roots and assimilated there 
 at once, carbon being fixed by the green organs ; that a 
 continual interchange goes on from above and from below 
 between the leaves and roots, the roots supplying protoplasmic 
 material which originates all organic phenomena ; the leaves 
 on their part sending down the ternary compounds (CHO), 
 which supply the material for cell-membranes, starch, etc. 
 The leaves of plants have the power of attracting and con- 
 densing the moisture suspended in the air, and the roots 
 can piimp it up from the soil from considerable depths. A 
 tree has, as it were, open mouths at both ends ; these mouths 
 communicating with open channels, which, in some cases, 
 
 1 Henfrey's Botany, pp. 16-18. 
 
 2 ' The strawberry plant produces in the axils of its leaves, buds, which in the 
 same season expand several of their internodes and form long filiform branches, 
 the buds of which give rise to rosettes of leaves and stock root, and thus form 
 independent plants.' Ibid. p. 33. 
 
PHYSIOLOGY OF THE CIRCULATION. 6l 
 
 traverse the entire length of the tree ; at other times they 
 interlace and form loops, which convert them into syphons 
 directed towards the leaves and roots respectively, as already 
 stated (Fig. 36, p. 50). 
 
 The Effects produced on the Circulation by the Swaying of 
 Plants in the Wind: Mr. Spencer's views. Mr. Herbert 
 Spencer is of opinion that the circulation is influenced to 
 a considerable extent by the swaying of plants and trees 
 in the wind ; this oscillation subjecting certain parts of the 
 tree or plant to lateral and longitudinal strain. The effect 
 of the strain, he remarks, is to bend the tree or plant alter- 
 nately in opposite directions, and from the parts so bent 
 the sap Is driven in an upward and downward direction, a 
 certain amount being forced through the coats of the vessels 
 (which are porous) into the surrounding tissues. According 
 to him, a certain proportion of the propelling power is inter- 
 mittent, confined to no locality, and variable as to intensity. 
 
 To reconcile the idea of an upward and downward circu- 
 lation in a single system of vertical tubes, Mr. Spencer 
 explains, as has been stated, that the vessels of the stem 
 and branches terminate in club-shaped expansions in the 
 leaves ; which expansions act as absorbent organs, and may 
 be compared to the spongioles of the root. If, therefore, 
 the spongioles of the root, Mr. Spencer argues, send up the 
 crude sap, it is not difficult to understand how the spongioles 
 of the leaf (the club-shaped expansions referred to) send 
 down the elaborated sap, one channel sufficing for the transit 
 of both. 
 
 From the foregoing, it will be evident that, in Mr. Spencer's 
 opinion, the upward and downward currents take place in 
 different parts of the same tube, and that when one part 
 of the tube is engaged with the up circulation, the down 
 circulation is prevented, and vice versa 1 . Now, granting 
 
 1 Mr. Spencer observes: 'If, then, returning to the general argument, we 
 conclude that these expanded terminations of the vascular system in leaves are 
 absorbent organs, we find a farther confirmation of the views set forth respect- 
 ing the alternating movement of the sap along the same channels. These 
 spongioles of the leaves, like the spongioles of the root, being appliances by 
 which liquid is taken up to be carried into the mass of the plant, we are obliged 
 to regard the vessels which end in these spongioles of the leaves as being the 
 channels of the down current whenever it is produced. If the elaborated sap is 
 
62 PHYSIOLOGY OF THE CIRCULATION. 
 
 that the upward and downward currents take place in the 
 same tube, it appears to me that both currents may be 
 going on at the same time by a simple process of endosmose 
 and exosmose 1 . I have difficulty in understanding how, in an 
 organised structure, the saps should be driven about in a reck- 
 less manner, at irregular intervals, and as it were by accident. 
 I can, however, readily comprehend how, if a porous vertical 
 tube, or any number of such tubes, containing dense fluids, 
 be arranged in parallel lines, and placed in contact with 
 less dense fluids, that the less dense fluids will penetrate 
 the more dense ones in an upward or downward direction, 
 according as the less dense fluids are placed below or above 
 the more dense fluids ; the more dense fluids penetrating 
 the less dense fluids always in an opposite direction, so as 
 to produce two distinct and opposite currents, which run 
 from below upwards and from above downwards ; the porosity 
 of the vessel occasioning a certain amount of transfusion or 
 lateral circulation. In this we have an arrangement capable 
 of furnishing a steady supply of sap to every part of the 
 tree, quite irrespective of any influence exerted by the wind. 
 In fact, it is necessary to exclude the action of the wind 
 when discussing the question ; for sap ascends, descends, 
 and transudes in trees nailed to walls, in climbing and hot- 
 house plants, where of course the wind is inoperative. Mr. 
 Spencer's argument may be briefly stated. 'If,' he says, 'a 
 trunk, a bough, a shoot, or a petiole is bent by a gust of 
 wind, the substance of its convex side is subject to longi- 
 tudinal tension, the substance of its concave side being at 
 the same time compressed. This is the primary mechanical 
 effect. There is, however, a second mechanical effect, which 
 
 abstracted from the leaves by these absorbents, then we have no alternative but 
 to suppose that, having entered the vascular system, the elaborated sap descends 
 through it. And seeing how, by the help of these special terminations, it be- 
 comes possible for the same vessels to carry back a quality of sap unlike that 
 which they bring up, we are enabled to understand tolerably well how this 
 rhythmical movement produces a downward transfer of materials for growth.' 
 Principles of Biology, vol. ii. p. 561. 
 
 1 Dutrochet believes, that in endosmosis the two opposite fluids pass through 
 the same capillary canal, the one travelling in one direction, the other in a 
 contrary direction; and that the double movement of transmission takes place 
 by a reciprocal penetration of the two fluids. 
 
PHYSIOLOGY OF THE CIRCULATION. 63 
 
 more chiefly concerns us. That bend by which the tissues 
 of the convex side are stretched also produces lateral com- 
 pression of them. It is demonstrable that the tension of 
 the outer layer of a mass made convex by bending, must, 
 by composition of forces, produce at every point a resultant 
 at right angles to the layers beneath it ; that, similarly, the 
 joint tension of these two layers must throw a pressure on 
 the next deeper layer, and so on. Hence, if at some little 
 distance beneath the surface of a stem, twig, or leaf-stalk, 
 there exist longitudinal tubes, these tubes must be squeezed 
 each time the side of the branch they are placed on becomes 
 convex. If, then, the sap-vessels are thus compressed, the 
 sap contained by them will move along the lines of least 
 resistance. Part, and probably the greater part, will escape 
 lengthways from the place of greatest pressure ; some 
 of it being expelled downwards, and some of it upwards. 
 But, at the same time, part of it will be likely to ooze 
 through the walls of the tubes. If these walls are so perfect 
 as to permit the passage of liquid only by osmose, it may 
 still be inferred that the osmose will increase under pressure ; 
 and probably, under recurrent pressure, the places at which 
 the osmotic current passes most readily will become more 
 and more permeable, until they eventually form pores. At 
 any rate, it is manifest that when pores and slits exist, 
 whether thus formed, or formed in any other way,' the escape 
 of sap into the adjacent tissue at each bend will become 
 easy and rapid. The lateral oscillation or strain takes place 
 in stems and branches, a longitudinal strain occurring in roots, 
 the circulation being in part due to a rude pumping process, 
 occasioned by the swinging about of different parts of the 
 tree or plant.' On this doctrine Mr. Spencer founds another, 
 viz. that in the region of the strained part, a profuse exuda- 
 tion of sap takes place ; this sap going to form woody fibre, 
 which strengthens the yielding part. Unfortunately for Mr. 
 Spencer's hypothesis, the upward, downward, and transverse 
 currents, as has been stated, occur in hothouse and other 
 plants, and in roots which are in no way exposed to winds ; 
 wood being formed under these circumstances just as it is 
 out of doors. Indeed, wood is formed in trees nailed firmly 
 to a wall, and in climbing plants which twist themselves 
 
64 PHYSIOLOGY OF THE CIRCULATION. 
 
 around unyielding structures. Nuts and thorns, and other 
 hard structures, in like manner, are formed in the absence 
 of anything in the shape of strains. Mr. Spencer states that 
 in plants with stems, petioles, and leaves, having tolerably 
 constant attitudes, the increasing porosity of the tubes, and 
 consequent deposit of dense tissue, takes place in anticipation 
 of the strains to which the parts of the individual are liable, 
 but takes place at parts which have been habitually subject 
 to such strains in ancestral individuals. If, however, the sap 
 is exuded, and wood formed, before the strain takes place, 
 the strain cannot consistently be regarded as the cause 
 either of the exudation or of the wood. While attaching 
 considerable importance to the effect produced on the cir- 
 culation by the swaying of plants and trees in the wind, 
 it must be stated that Mr. Spencer gives due prominence 
 to the vital, capillary, and osmotic forces. He writes : 
 'The causes of circulation are those actions only which 
 disturb the liquid equilibrium in a plant, by permanently 
 abstracting water or sap from some part of it ; and of these 
 the first is the absorption of materials for the formation of 
 new tissue in growing parts ; the second is the loss by evapo- 
 ration, mainly through adult leaves ; and the third is the 
 loss by extravasation through compressed vessels. Only so 
 far as it produces this last can mechanical strain be regarded 
 as truly a cause of circulation. All the other actions con- 
 cerned must be classed as aids to circulation as facilitating 
 that redistribution of liquid that continually restores the equi- 
 librium continually disturbed ; and of these capillary action 
 may be named as the first, osmose as the second, and the 
 propulsive effect of mechanical strains as the third V 
 
 Epitome of Forces engaged in the Circulation of Plants. 
 Before passing to a consideration of the circulation as it exists 
 in animals, it may be useful to recapitulate very briefly the 
 forces at work in the circulation of plants, and to say a few 
 words with regard to the nature of force generally. Of the 
 forces which produce the circulation in plants, capillarity 
 and osmose undoubtedly play an important part. Capillarity 
 inaugurates, and osmose maintains in a great measure, not 
 only the ascending and descending currents, but also the 
 
 1 Principles of Biology, vol. i. pp. 553, 554. 
 
PHYSIOLOGY OF THE CIRCULATION. 65 
 
 cross currents and the gyration or rotation of the cell con- 
 tents. Capillary action is induced in an upward or downward 
 direction according as the fluid is presented to the top or 
 bottom of the capillary tube. It may go on either within 
 the vessels of the plant, or in the interspaces between the 
 vessels ; and the same may be said of endosmose and exos- 
 mose. Endosmose, as has been explained, acts in conjunction 
 with exosmose. The one implies the other. The endosmotic 
 and capillary actions are modified by vital, chemical, and 
 other changes. They produce a swelling of the cells and 
 entire tissues of the plant, as the fluid absorbed by the 
 roots and leaves must be accommodated within the plant. 
 The fluids imbibed produce pressure of the cell-walls, vessels, 
 etc. these reacting and forcing the fluids in the direction 
 of least resistance. Increase of temperature in the roots, 
 stem, and branches, leads to a similar result ; increase of 
 temperature expanding the air which pervades all parts of 
 plants. The expanded air, like the fluids, naturally escapes 
 in the direction of least resistance. From this it follows 
 that the circulation is most vigorous during the day, and 
 least so during the night. The processes of growth and re- 
 production produce the vacuum into which the fluids urged 
 on by cell, air, and other pressure naturally flow. The pre- 
 sence of sap and air are equally necessary to growing and 
 germinating plants. Growth -or vital change involves chemical 
 change. Starch is to be transformed into sugar, and before 
 this can be done, water must flow to the point where the 
 transformation is to take place ; the demand for water acts as a 
 vis a f route. The leaves exhale from their surfaces, and here, 
 too, a constant evaporation is going on. A fluid abstracted 
 from the leaves by external heat draws on the fluid in the 
 branches ; the fluid in the branches drawing up that in the 
 stem, which, in turn, acts upon that in the roots ; the roots 
 being originally supplied by absorption, capillarity, and 
 osmose. This can be proved by direct experiment. If a 
 system of tubes have their lower extremities placed in water, 
 while a portion of moistened bladder is laid across their 
 upper extremities, expanded to receive it, it is found that 
 the quantity of fluid which passes through the tubes is de- 
 termined by the amount of evaporation. The roots exhale 
 
 F 
 
66 PHYSIOLOGY OF THE CIRCULATION. 
 
 as well as absorb, so that a certain proportion of the fluids 
 are drawn downwards. In other words, the leaves may be 
 said to draw the fluids upwards, while the roots, at stated 
 periods, draw them downwards. The leaves act more espe- 
 cially in conjunction with endosmose, the roots with exosmose. 
 These, again, act in harmony with capillary structures and 
 vito-chemical changes incident to growing plants. 
 
 Lastly, the occasional swaying of petioles, branches, and 
 stems, by the wind, exerts, as Mr. Herbert Spencer has 
 shown, an intermittent pressure, to which he attributes an 
 upward, downward, and lateral thrusting of the sap in the 
 direction of least resistance. The strain to which the dif- 
 ferent parts of the tree are subjected by the swaying in 
 question gives rise, as he explains, to an exudation of sap 
 at the strained point the exuded fluids making room for 
 other fluids, which, being supplied either by the roots or 
 leaves, result in motion. 
 
 I have placed the lateral swaying or pumping process of 
 Mr. Herbert Spencer last, because, as has been already 
 stated, the general and intracellular circulation of plants can 
 go on when no wind is present. 
 
 Considerable diversity of opinion exists as to the channels 
 through which the circulating fluids of plants are conveyed. 
 Hoffmann and Unger maintain that in plants possessed of 
 fibro-vascular bundles, the sap in the first instance passes 
 up from the roots chiefly in the parenchymatous cellular 
 constituents of the bundles, and that these juices do not 
 pass by the spiral vessels themselves. 
 
 Rainey was of opinion that the intercellular canals, which 
 are more or less continuous throughout the entire length 
 of the plant, are the channels through which the sap princi- 
 pally ascends ; and that the descent of the elaborated sap 
 occurs in the vessels, and not in the cells or intercellular 
 spaces. Tetley was inclined to regard the cells and vessels 
 as secreting organs which operated upon the crude sap in 
 the intercellular canals, from which they separated, by vito- 
 chemical actions, liquid and gaseous matters. Schultz main- 
 tained that the sap descends through the lactiferous vessels, 
 these being compared by Carpenter to the capillaries of 
 animals. Spencer states from experiment that the spiral, 
 
PHYSIOLOGY OF THE CIRCULATION. 67 
 
 annular, scalariform, and other vessels, form the channels 
 for the ascent of the sap, and he is disposed to believe that 
 the sap descends in the same vessels in which it ascends. 
 
 Spencer is further of opinion that there is only one system 
 of vessels, the crude and elaborated saps ascending and 
 descending in the same vessels at different times, a result 
 favoured, but not caused, by the swaying of the different 
 parts of the plant or tree in the wind. Mr. Spencer is quite 
 aware that the ascent and descent of the sap is not occasioned 
 by the swaying referred to, for he remarks, ' Whether, there 
 is oscillation or whether there is not, the physiological 
 demands of the different parts of the plant determine the 
 direction of the current V The researches of Petit Thouars, 
 Gaudichaud, De la Hire, Darwin, Knight, and Macaire, favour 
 the idea of a double system of vessels an ascending and a 
 descending set. However authors differ as to the number 
 and direction of the vessels, they are all agreed in this, that 
 the currents ascend, descend, and transude. The question 
 which naturally presents itself at this stage, is, Are vessels 
 necessary to the circulation in plants ? and if so, is there 
 one or two sets of vessels? I pointed out that vessels are 
 not necessary to the circulation, as this goes on in cellular 
 plants where no vessels exist. I also endeavoured to show 
 that when vessels are present, the circulation may go on 
 either within them, or in the intervascular spaces outside of 
 them, provided these, like the vessels, are capillary in their 
 nature. I further attempted to reconcile the views of those 
 who maintain that there is only one set of vessels, with 
 those who believe that two sets are necessary for carrying 
 on the ascending and descending current, by supposing (and 
 we have good warrant for the supposition) that the vessels 
 and intervascular spaces of plants are united in the stem 
 and branches, and at certain periods of the year in the leaves 
 and roots, to form syphons, the free extremities of which 
 are directed alternately in the direction of the leaves and 
 roots. These syphons are infinite in variety and form, and 
 interlace in every conceivable direction. They may be con- 
 fined to the roots, stem, branches, or leaves, or portions of 
 
 1 Principles of Biology, vol. i. p. 557. 
 F 2 
 
68 PHYSIOLOGY OF THE CIRCULATION. 
 
 them, the fluids being sent on by relays; or they may ex- 
 tend throughout the entire length of the plant or tree. They 
 consist of rigid capillary tubes with porous walls, i.e. walls 
 capable of preventing the ingress of air, while they do not 
 prevent the free ingress and egress of fluids, as witnessed 
 in osmose and evaporation. The long legs of the syphons, 
 or what are equivalent thereto, correspond to the evaporat- 
 ing surfaces, and those surfaces in which an active osmosis 
 is established. The leaves and roots form such surfaces, but 
 they are not confined to those portions of the plant, as they 
 exist in every part of it ; the plant breathing and drinking 
 at every pore when it has an opportunity. If you figure to 
 yourselves the vast drying or evaporating surfaces furnished 
 by a tree in full leaf, you will readily comprehend the im- 
 mense tractile power exerted, and the astonishing force with 
 which the fluids are drawn up in the syphon tubes referred to. 
 If, on the other hand, you regard the leaves and roots, not as 
 evaporating surfaces, but as absorbing surfaces (they are both), 
 i.e. surfaces capable of imbibing moisture, you will have no dif- 
 ficulty in understanding that the force exerted by endosmose, 
 which is a pushing force, is equally great. But evaporation and 
 endosmose in other words, the tractile or pulling force, and 
 the propelling or pushing force can, by the syphon arrange- 
 ment, act together; the one operating upon the one leg of 
 the syphon, the other upon the remaining leg, in such a 
 manner as to cause a continuous flow of fluids through the 
 syphon. It is thus that evaporation and absorption can go 
 on together, and that fluids, or fluids and air, may be made 
 to circulate together. The nutritive juices may be said to 
 invade the tissues of the plant by a process of endosmose, 
 the endosmotic action being favoured by evaporation and 
 transpiration ; endosmose pushing and evaporation pulling 
 and giving the fluids right of way through the tissues. No 
 better arrangement can be imagined for the supply of new 
 material and the discharge of effete matter. The tissues are 
 literally irrigated and washed out at the same time. 
 
 Precisely the same remarks may be made regarding the 
 animal tissues. It is an error to suppose that the circula- 
 tion in animals is carried on exclusively by the heart. This 
 is 'an engine employed for carrying the blood to and from 
 
PHYSIOLOGY OF THE CIRCULATION. 69 
 
 the tissues through considerable distances, but the tissues 
 do their own work, or rather the particles of the tissues are 
 so arranged that they permit certain physical forces, such 
 as capillary attraction, osmosis, evaporation, respiration, 
 chemical affinity, etc., to do the work for them. The organic 
 kingdom avails itself of inorganic power. This may account 
 for the great rapidity with which poisons spread in animal 
 organisms, and also for their mode of elimination. The ca- 
 pillary vessels of animals form syphon loops, as in plants, 
 and the animal syphon loops are porous in the same sense 
 that the vegetable syphon loops are porous. They are, there- 
 fore, capable of transmitting a continuous stream of fluid 
 in a given direction, and of absorbing and evaporating at 
 innumerable points the absorption and evaporation, as al- 
 ready explained, greatly facilitating instead of retarding the 
 general circulation. That the tissues respire has been abun- 
 dantly proved by the researches of Spallanzani. He found 
 that all the tissues take in oxygen and give off carbonic acid, as 
 the lungs themselves do. The view here advocated is further 
 favoured by the fact that the circulation of animals does not 
 cease the moment the body dies and the action of the heart 
 fails. On the contrary, the tissues draw on the fluids, these 
 being evaporated as before an arrangement which accounts 
 for the arteries being comparatively void of blood after 
 death, the blood by this process being actually diminished 
 in amount; diminished, because after. the death of the body 
 no new blood is being formed, while the old blood is being 
 circulated and used by the tissues so long as the tissues 
 retain their vitality and heat. That the heart is not neces- 
 sary to the circulation in its widest sense is proved by the 
 fact that it goes on when neither heart nor blood-vessels 
 are present. The heart, therefore, while the major factor 
 in the circulation of animals, may, after all, be regarded as 
 an auxiliary, i. e. a differentiation for a purpose. But to 
 return. I was engaged in discussing the syphons and syphon 
 action in plants. 
 
 The syphons in plants are sometimes simple, sometimes 
 compound. By the term simple, I mean a syphon consist- 
 ing of a tube bent upon itself, the one extremity of which 
 is longer than the other (Fig. 39, r, t, p. 70). By the term com- 
 
70 PHYSIOLOGY OF THE CIRCULATION. 
 
 pound syphon, I mean a syphon consisting of several syphons 
 united to each other, the limbs of which are not necessarily 
 unequal in length. The compound syphon, may be com- 
 posed of rigid non-porous capillary tubes, as shown at Fig. 
 38 ; or of larger tubes with porous walls, as seen at Fig. 39 \ 
 When a series of syphons directed in opposite directions 
 are united and open into each other, the circulation becomes 
 more or less continuous, as in animals. Under these circum- 
 stances a certain proportion of the syphons are open in 
 
 Fig. 38. 
 
 Fig. 39- 
 
 t\\ -ik" 
 
 Fig. 38. Capillary compound syphon, similar to that found in the interior of plants. The capillary 
 syphon differs front the ordinary syphon in this, that the point at which the fluid escapes 'may be mutft 
 higher than that at which it enters. Thus the fluid may enter at a, and escape at c, instead of at d. The 
 instant the end of the syphon b is placed in fluid, the fluid rises and falls, and travels in the direction c, 
 : finally escaping at d. The compound capillary syphon here figured is equally effective when inverted, 
 the fluid being applied from above instead of from beneath. The compound capillary syphon explains 
 within certain limits the circulation as it exists in plants with well-defined vessels and intervascular spaces. 
 Original. 
 
 Fig. 39. Simple and compound syphons perforated at various points ; the perforations being covered 
 with animal or vegetable membrane, to prevent the ingress of air, while they do not prevent the ingress 
 or egress of fluids by absorption and evaporation. 
 
 r. Short leg of simple syphon; t, long leg ditto; s, perforation covered with membrane ; TV, x, fluids 
 escaping through the syphon. 
 
 a Compound syphon, the legs of which are of the same length ; b, c, d, e,f, perforations in compound 
 syphon covered with membrane. By elevating the vessel to the right of the figure, the fluid contained 
 within the syphon is made to pass through it, as indicated by the arrows, into the vessel to the left of the 
 figure. (This process maybe reversed.) Evaporation or absorption occurring at the points b, c, d, e,f, 
 facilitates the transmission of fluids through the syphon. They even generate the movement referred to ; 
 the fluids oscillating now in one direction, now in another, according as one or other prevails. The com- 
 pound syphon may have its legs of the same length, or the one leg long and the other short, as in the 
 simple syphon. The apertures covered with membrane give the unequal pressure required to produce 
 a true syphon action. These apertures correspond to the leaves, roots, and other surfaces of plants, in 
 which absorption, evaporation, and other physical actions go on. Original. 
 
 the direction of the leaves and roots. When I use the 
 term ' open,' I wish it to be understood ' open ' in the sense 
 that they can take in fluids by imbibition or absorption, or 
 give it off by evaporation. 
 
 In such a system of syphons, a true syphon action can be 
 induced and maintained ; the vegetable membrane or aggre- 
 gation of cells, which closes the ends of the syphons, effectually 
 preventing the admission of air from without, but not inter- 
 fering in the slightest with the passage of fluids from with- 
 
 1 The walls in this case may be flexible as well as porous, made of gut, sup- 
 ported with wire. 
 
PHYSIOLOGY OF THE CIRCULATION. 71 
 
 out or from within in other words, with absorption and 
 evaporation. 
 
 In the compound capillary syphon (Fig. 38), I find that the 
 moment the one end of it (a) is immersed, the fluid fills the 
 several loops of which it is composed, and escapes by the ex- 
 tremity not immersed (d). In this case the compound syphon 
 arrangement which I believe exists in plants is nearly but not 
 exactly imitated. The syphons in trees have porous walls in 
 addition to their free open extremities. By porous walls, I 
 mean walls which admit of the passage of fluids through them. 
 
 In the compound syphon represented at Fig. 39, the several 
 conditions found in plants are, I apprehend, exactly repro- 
 duced. Here we have a syphon made of glass tube with 
 numerous apertures in it. These apertures are of large size, 
 and covered with bladder. They admit of a free evaporation 
 or a free absorption at a great many points. As, however, 
 they are covered with an animal membrane, no air is permitted 
 to enter the syphon to disturb its action. 
 
 The syphon action is therefore as perfect as in the syphon 
 in which no apertures are found. In other words, in the novel 
 form of syphon which I have here constructed, fluids and air, 
 if need be, can pass on in rapid and uninterrupted succession ; 
 evaporation taking place, and fluids being added at different 
 portions of the syphon, in such a manner as not only not to 
 interfere with the well-known action of the syphon, but, what 
 is very remarkable, actually to favour it. I showed on a 
 previous occasion that if a capillary tube placed in water be 
 expanded at one end and covered with bladder, the fluid rises 
 in the tube in proportion to the evaporation going on in the 
 bladder. I also drew attention to the fact, that evapora- 
 tion may go on either from above or from below, i.e. in the 
 leaves or roots. When evaporation (as in seasons of drought) 
 goes on at both ends of a plant, the fluids contained within 
 the plant are drawn in opposite directions ; counter currents 
 being thus established which speedily drain the tree of its 
 juices and cause it to exhibit symptoms of collapse to make 
 it droop, in fact (Figs. 40 and 41, p. 72). 
 
 In this case, the presence of heated air, or the condition of 
 dryness, induces opposite currents. But respiring surfaces 
 under certain conditions, say in wet or rainy seasons, may 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 become absorbing surfaces. This is proved by the fact 
 that a thin fluid will pass through an animal or vegetable 
 membrane for which it has an affinity either from above or 
 from below, according as the thin fluid is placed above or 
 below the thicker fluid (Figs. 42 and 43). 
 
 Figs. 40, 
 
 CT7J 
 
 V 
 
 Fig. 40. Tube (<*) with expanded evaporating surface (b) covered with animal or vegetable membrane 
 directed downwards. The expanded portion corresponds to the roots of plants. When evaporation goes 
 on at i>, fluid presented at a is drawn through the tube in the direction of the arrow c. Original. 
 
 Fig. 41. Similar tube with expanded portion directed upward. The expanded portion in this instance 
 corresponds to the leaves of plants. When evaporation occurs at e, the fluid presented at d is drawn 
 through the tube in the direction of the arrowy; Evaporation is to be regarded as a pulling force. 
 Original. 
 
 Fig. 42. Tube (g) with expanded absorbing surface (h) covered with membrane and directed upwards 
 to correspond with the leaves of a plant. When a thin fluid (rain or dew) is presented to the membrane, 
 and to a thicker fluid contained in the tube, it passes by endosmose in a downward direction, as indicated 
 by the arrow i. k, Vessel containing the thinner fluid. Original. 
 
 Fig. 43. Tube (!) with expanded absorbing surface (m) covered with membrane and directed down- 
 wards to correspond with the roots of a plant. When a thin fluid (sap from the earth) o, is presented to 
 the membrane and to a thicker fluid contained in the tube, it passes by endosmose in an upward direc- 
 tion, as indicated by the arrow n. p, Vessel containing the thinner fluid. Endosmose is to be regarded 
 as a pushing force. 
 
 Figs. 42 and 43 show how, in wet seasons, 1 * plants may be gorged with saps both from the leaves and 
 from the roots, and how endosmose occurring in the leaves and roots tends to produce currents in 
 opposite directions. The currents induced by endosmose are always the converse of those induced by 
 evaporation, so that absorption and endosmose may be going on in the leaves, while evaporation is 
 going on in the roots ; the fluids in this case being pushed and drawn through the plant in a down- 
 ward direction : or absorption did endosmose may be going on in the roots, and evaporation in the 
 leaves, in which case the fluids are pushed and drawn through the plant in an upward direction. 
 Original. 
 
 From this it follows that evaporation, or the condition of 
 dryness, draws or sucks the fluids out of the vessels and inter- 
 vascular spaces, while the condition of wetness pushes or pro- 
 pels the fluids into them. Here we have a sucking or pulling 
 force, and a pushing or propelling force ; a vis a fronte and a 
 vis a tergo ; and I am disposed, as already indicated, to claim 
 a like power for certain of the vessels and for the heart. But 
 evaporation and absorption do not as a rule go on at the same 
 surface at the sarne time. When a surface is absorbing it 
 evaporates sparingly, and the converse. A free evaporation 
 and a free absorption may, however, occur at the same time 
 in different surfaces ; and in such cases evaporation and 
 absorption work together and not against each other (Fig. 36, 
 p. 50). Dryness and moisture in this way directly influence 
 the circulation. 
 
PHYSIOLOGY OF THE CIRCULATION. 73 
 
 In the arrangement which I now advocate, evaporation or 
 the withdrawal of fluids, and absorption or the addition of fluids, 
 may take place at an infinite variety of points, and in such a 
 manner as to favour rather than oppose the passage of the 
 fluids in the capillary tubes and syphons. The syphons are 
 set in operation by the presence of fluids, by capillary action, 
 osmosis, evaporation, and by vital and chemical changes 
 occurring in growing parts. 
 
 When the plant is full of fluids, evaporation from the leaves 
 and other parts sucks or draws the fluids up, supplying a 
 vis a f rente ; endosmose pushing on fluids from below, and 
 acting as a vis a tergo. If a superabundance of sap is pre- 
 sented to the roots, and an unusual amount of evaporation is 
 going on in the leaves, the up current is increased in volume 
 and intensity. If these conditions are reversed, the down 
 current is proportionately augmented. The fluid contents of 
 the plant oscillate between either extreme, and the up and 
 down currents are equilibrated when all the forces which 
 operate upon the plant are balanced. 
 
 A plant responds to external conditions as an Aeolian harp 
 responds to the wind. 
 
 The circulation is literally played upon by the elements. 
 I might push the simile further, and apply the remark to 
 ourselves ; for the most exalted natures- are ever the most 
 susceptible susceptible not only to psychical, but also to 
 physical influences. 
 
 While engaged in describing the general circulation in plants, 
 I volunteered an explanation of the intracellular circulation ; 
 the intracellular movements, as I endeavoured to point out, 
 being in all probability due to evaporation ; or to endosmose 
 and exosmose occurring within or outside the cells, the rounded 
 form of the cell converting what would under ordinary cir- 
 cumstances be merely opposite currents into rotatory ones 
 (Figs. 30, 31, 32, p. 34). This led me to infer that certain 
 movements (not necessarily those of gyration) occurring pri- 
 marily within the cell, inaugurate the general circulation, but 
 that when the general circulation is once established, it con- 
 tributes to, and may actually produce, gyration in the cells 
 themselves (Fig. 35, p. 47, and Fig. 37, p. 51). Finally I en- 
 deavoured to show that all the forces engaged in the circulation 
 
74 PHYSIOLOGY OF THE CIRCULATION. 
 
 of plants, whether vital, chemical, or physical, act together to 
 obtain a common result. 
 
 Organic Forces a Modification of Inorganic Forces. I have 
 dwelt upon the subject of the circulation of plants at much 
 greater length than I intended, or than was perhaps desirable 
 under the circumstances; but it is one of extreme interest, since 
 in it we have the germs of many of the arguments advanced to 
 explain the circulation as it exists even in man himself. Thus 
 we are told that the tissues drink out of the blood and draw 
 it onwards, supplying a vis a f rente ; that secreting glands 
 produce a similar effect ; that the column of blood in the 
 arteries is balanced by that in the veins ; that the heart has a 
 sucking and propelling action in other words, that it pulls 
 as well as pushes ; that evaporation assists in determining 
 a flow of blood to the lungs, the movements of respiration 
 assisting the circulation ; that the play of the muscles urges 
 the blood forward, much in the same way that the sap is 
 occasionally urged forward in trees in virtue of their stems 
 and branches swaying in the wind. In discoursing of the 
 circulation in an animal or a plant, we are necessarily dis- 
 coursing of motion as a whole, as it exists in the physical 
 universe. In fact, we are compelled to regard the forces which 
 operate in the inorganic world as essentially the same as 
 those which operate in the organic ; for in all animal and 
 vegetable movements we have ultimately to deal with those 
 of the cells and tissues ; nay, more, with the ultimate particles 
 of matter composing them. The cells and particles of which 
 an organism is composed may be operated upon singly and 
 act individually; or they may be operated upon conjointly 
 and act in masses. In the former case we have motion as a 
 consequence of endosmose and exosmose, capillary and other 
 attractions, vital and chemical, occurring in the ultimate 
 molecules. In the latter case we have motion proceeding from 
 a battery of force, such as that furnished by the heart ; this 
 organ, by its united complex movements, urging on the 
 circulation to a great extent independently. But for the 
 movements primarily occurring in the substance of the heart, 
 the highly differentiated movements representing the diastole 
 and systole of that organ could not take place. The primary 
 molecular movements, if I may so phrase them, always precede 
 
PHYSIOLOGY OF THE CIRCULATION. 75 
 
 those of greater magnitude. In the one we have the par- 
 ticular movement, in the other the general movement ; but 
 nature, with infinite wisdom, has so arranged that the general 
 movement shall harmonise with the particular movement. 
 Thus the heart may act in the circulation of an animal as a 
 vis a tergo, and the demand for nutritious juices in the tissues 
 as SL ms a f rente. They may even act separately. The heart 
 may push forward its blood into an artery occluded by a 
 ligature, and the plant may draw on its juices when no heart 
 exists. As all animals and vegetables may be resolved into 
 inorganic atoms, so the physical and vital forces may be re- 
 ferred to a common source. It is thus that we reconcile the 
 circulation in the plant and lower animals with that of the 
 higher animals, and with certain movements which we know 
 exist in the physical universe. 
 
 When we come to scan the dim border-land on which life 
 and death struggle for pre-eminence, the most cautious 
 observers and the gravest philosophers are often at fault. 
 Indeed the human faculties only enable us to make very 
 partial advances towards a solution of the great problems of 
 life and motion. We are hedged in on all sides by boundaries 
 which apparently we cannot override. If we advance beyond 
 a certain distance, a veil of greater or less density is inter- 
 posed. This arises from the fact that even the greatest minds 
 have a limited range, and that nature is as vast in her littleness 
 as in her greatness. The telescope and the microscope have 
 done much, but just in proportion to what has been done, it 
 becomes apparent that so much the more remains to be done. 
 Our most approved instruments, instead of simplifying matters, 
 have actually complicated them. They have revealed wonder 
 upon wonder, and convinced us that there are points which 
 we must either take for granted or prove by analogy. This 
 becomes very evident when we employ a microscope with a 
 high magnifying power, and attempt to make out an ultimate 
 structure ; or, what is still more difficult, define the nature of 
 certain movements which take place under our eye, but. which 
 we cannot comprehend, as we are at a loss to know whether 
 they are organic or inorganic. Under such circumstances the 
 head becomes confused with thinking and the eye with watch- 
 ing, and all to no purpose. If, for example, we examine a 
 
76 PHYSIOLOGY OF THE CIRCULATION. 
 
 salivary cell, we find apparently deep in its substance a great 
 number of infinitely minute points, each of which is evidently 
 in motion. They are seen after a little careful focussing to 
 quiver and vibrate, and even to rotate. These are the so- 
 called Brunonian movements, and are now regarded as 
 physical in their nature. They afford the first glimmerings of 
 visible motion. If we examine a vegetable or animal infusion 
 after it has stood for a short time, we find a scum or pellicle 
 on its surface. A considerable portion of this scum consists 
 of a molecular mass in which no movement whatever can be 
 detected. In parts of it, however, an aggregation of the 
 molecules has taken place, and when this aggregation occurs, 
 there, of a certainty, movement makes its appearance. The 
 movement is very indistinct, and it requires an experienced 
 eye to detect it. By and by, as the infusion becomes older, 
 the aggregation of molecules becomes more distinct, and the 
 movements exhibited by them more marked. A careful 
 observer will now perceive little dark points and rod-shaped 
 bodies darting about in the field as if by magic. They do not 
 change form, and apparently have no power of contracting 
 and expanding ; nevertheless they advance, recede, pause, 
 advance again, and whirl about with a mad energy which is 
 truly wonderful. 
 
 If the infusion be still older, long pointed bodies are found, 
 which advance with a zig-zag or wavy serpentine motion, but 
 still without any trace of contraction or expansion in any part 
 of their substance. These constitute the so-called vibrios and 
 bacteria, concerning which so much has been said lately. 
 As to their mode of production and real nature, there is still 
 a doubt in the scientific mind. All, or nearly all, are agreed 
 that they are living things a belief favoured by the fact that 
 they increase and multiply. As to their movements there can 
 be no doubt. Still more wonderful, in my opinion, are the 
 movements of the amoeba. This simplest organism consists 
 of a mass of jelly, in which molecules of various sizes are 
 embedded. This transparent creature, which remarkably re- 
 sembles a white blood-corpuscle, and which is in the ordinary 
 acceptation of the term structureless, has nevertheless the 
 power of changing the shape of every part of its body, and of 
 advancing and retiring in whichever direction it pleases. The 
 
PHYSIOLOGY OF THE CIRCULATION. 77 
 
 movements of this most singular creature are like those of 
 water spilt upon the ground ; or the spreading of a drop of 
 fluid in blotting paper. The amoeba causes its body, or a part 
 thereof, to flow out in any direction it pleases. It literally 
 pushes a certain part of its body outwards, and invades a 
 certain portion of territory ; the other parts of its body which 
 are not advancing, remaining stationary. Contraction seems 
 to take no part in this movement. When a part of the body 
 is to be advanced, a transparent portion of it bulges, and into 
 this the granules rush in a continuous stream ; the knuckle or 
 projection of the body advancing as the granules flow into it. 
 There is no constriction, and nothing that can even suggest 
 the idea of contraction. On the contrary, the parts of the body 
 advanced are invariably wedge-shaped. There is change of 
 form but no diminution of volume. The amoeba has the power 
 of changing form apart from contraction a power which I 
 believe is also possessed by the sarcous elements of muscles. 
 I am indebted to my friend Dr. M'Kendrick for an opportunity 
 of studying those movements under unusually favourable con- 
 ditions, and direct attention to them because I am desirous 
 of impressing upon you the necessity, when considering the 
 circulation, of taking into account a large number of vital and 
 a still greater number of physical forces, which all work to- 
 gether to produce it. The tissues have a circulation of their 
 own apart from the heart and blood-vessels, and the presence 
 of a heart, blood-vessels, or indeed of differentiated canals, is 
 not necessary to certain forms of the circulation. Again, the 
 heart, when it exists, impels the blood in virtue of its inherent 
 movements, i.e. the movements which occur in its sarcous 
 elements or ultimate particles ; these in turn being traceable 
 to nutritive and other changes induced by the circulation 
 itself. In fact, in the circulation, we have before us a very 
 involved problem of vital, physical, and chemical reactions. 
 
 Motion a Condition of Matter. It will greatly facilitate our 
 comprehension of the circulation if we bear in mind that 
 motion is a condition of matter l . ' Of absolute rest,' as 
 
 1 Many advanced thinkers are of opinion that there is but one force, and that all 
 the others are but modifications of it. 
 
 Grove, in his work on the Correlation of Physical Forces, says : ' I believe 
 that the same principles and mode of reasoning as have been adopted in this essay 
 
78 PHYSIOLOGY OF THE CIRCULATION. 
 
 Mr. Grove eloquently puts it, ' Nature gives us no evidence. 
 All matter, as far as we can ascertain, is ever in movement, 
 not merely in masses, as with the planetary spheres, but also 
 molecularly, or throughout its most intimate structure 1 .' 
 Force, like matter, cannot be annihilated ; and where we have 
 the one we have the other. ' Thus, matter and force are cor- 
 relates in the strictest sense of the word ; the conception of 
 the existence of the one involves the conception of the exist- 
 ence of the other : the quantity of matter, again, and the 
 degree of force, involve conceptions of space and time.' When 
 motion ceases to be visible, i. e. when moving masses strike 
 against each other and apparently stand still, motion is rede- 
 veloped in the shape of heat, which is invisible motion. In the 
 steam-engine, for example, the piston, and all its concomitant 
 masses of matter are moved by the molecular dilatation of the 
 vapour of the water, the movement of the molecules being 
 imperceptible. If homogeneous substances come together, heat 
 alone is generated ; but if homogeneous and heterogeneous 
 substances come together, electricity is produced ; and some 
 have thought that, whereas the contents of vegetable cells are 
 heterogeneous, and the saps presented to them are nearly if 
 not quite homogeneous, electricity takes part in the circulation. 
 'Motion,' Mr. Grove observes, 'will directly produce heat ; and 
 electricity, being produced by it, will produce magnetism a 
 force which is always developed by electrical currents at right 
 angles to the direction of those currents 2 .' If electricity be 
 permitted to rank as one of the forces in the general i. e. the 
 up-and-down circulation of plants, magnetism would explain 
 why there should be cross cur-rents also. ' If we now take 
 heat as our starting-point, we shall find that the other modes 
 
 might be applied to the organic as well as the inorganic ; and that muscular force, 
 animal and vegetable heat, etc., might, and at some time will, be shown to have 
 
 similar definite correlations From Professor Matteucci's experiment it 
 
 appears that whatever mode of force it be which is propagated along the nervous 
 filaments, this mode of force is definitely affected by currents of electricity. . . . 
 Mosotti has mathematically treated of the identity of gravitation with cohesive 
 attraction, and Plucker has recently succeeded in showing that crystalline bodies 
 are definitely affected by magnetism, and take a position in relation to the lines of 
 magnetic force dependent upon their optical axis or axis of symmetry.' Correlation 
 of Physical Forces, pp. 88, 89. 
 
 1 Grove on the Correlation of Physical Forces, pp. 16, 17, and 104. 
 
 2 Op. cit. p. 23. 
 
PHYSIOLOGY OF THE CIRCULATION. 79 
 
 of force may be readily produced by it V The heat of spring, 
 by creating a demand for sap in the tree may be said to 
 inaugurate the circulation. Heat produces a movement in 
 distant parts, and bodies coming together from a distance 
 produce heat ; inorganic bodies act upon organic ones, and vice 
 versa. What is inorganic now may be organic very shortly. 
 The chemistry of the outer and inner world is essentially the 
 same. It is owing to this circumstance that a living body can 
 assimilate, and maintain its position in the world of matter ; 
 and this principle of force, which pervades both the organic 
 and inorganic kingdoms, shows how an organised being may 
 live in contact with inorganic or dead matter ; how the organic 
 and inorganic may give to and take from each other, may, 
 in fact, reciprocate with positive advantage to both. 
 
 Circulation in Metals. It would sound somewhat curious if 
 I were to speak of a circulation in metals ; but Seebeck has 
 shown, c that when dissimilar metals are made to touch, or are 
 soldered together and heated at the point of contact, a current 
 of electricity flows through the metals, having a definite 
 direction^ according to the metals employed ; which current 
 continues as long as an increasing temperature is gradually 
 pervading the metals, ceases when the temperature is 
 stationary, and flows in a contrary direction with the decre- 
 ment of temperature 2 .' The same words might almost be 
 employed in describing the circulation of plants. In spring, 
 when the temperature increases, there is a steady current of 
 sap in an upward direction ; in autumn, when the tempera- 
 ture decreases, the current is reversed ; in summer, when the 
 temperature may be regarded as stationary, the ascending and 
 descending currents may be said to balance each other or 
 equilibrate. Nor is this all. If a voltaic current be made to 
 act upon electrodes of iron, the molecules of the iron are made 
 to rotate very much in the same way that the cell contents 
 rotate or gyrate in plants. From the foregoing it will be 
 evident that 'heat, electricity, magnetism, chemical affinity, 
 
 1 Grove, op. cit. p. 24. 
 
 2 Hitherto it has been customary to regard the electrical current as consisting 
 either of a single fluid idio-repulsive, but attractive of all matter ; or else one 
 produced by two fluids, each idio-repulsive, but attractive of the other. Grove is 
 inclined to attribute electrical phenomena to a molecular polarisation of ordinary 
 matter, or to matter acting by attraction and repulsion in a definite direction. 
 
80 PHYSIOLOGY OF THE CIRCULATION. 
 
 and motion, are all correlative, or have a reciprocal depend- 
 ence V Animals and plants are especially susceptible to the 
 influence of light ; and it has been supposed, not without 
 reason, that matter of every description is altered by exposure 
 to it. Until, therefore, the organic and inorganic kingdoms 
 are drawn more closely together, both as regards their physical 
 constitution and mode of action, many of the so-called vital 
 forces must remain unexplained. A force can only originate 
 as a transmitted force ; it has no existence as a force per se 2 . 
 Force may be regarded as static or balanced, and dynamic 
 or motive. Static force in the animal and vegetable 
 kingdoms represents rest, or a state of equilibrium in the 
 part. We have this peculiar condition when a flexor and 
 extensor muscle prevent motion in a joint. When this equi- 
 librium is disturbed, dynamic or motive force preponderates 
 over the static or balanced force. When a part is in a state 
 of equilibrium, it is also in a state of tonicity, and ready to act 
 in whichever direction the force preponderates ; and this ex- 
 plains why, in plants, the circulation is now upwards, now 
 downwards, and how, at other times, it oscillates and becomes 
 temporarily suspended. 
 
 CIRCULATION IN ANIMALS (Invertebrate). 
 
 Symmetry of Form in the Organs of Circulation and the 
 Body generally. I now proceed to a consideration of the cir- 
 culation as it exists in animals ; and an attentive examination 
 of the subject not only induces me to believe that there is a 
 striking analogy between the circulation in animals and plants, 
 but that in animals devoid of pulsatile vessels and hearts, it is 
 in some senses identical, and traceable to the operation of the 
 same forces. The direction of the force is determined by 
 influences exerted without or within the animal or plant, or 
 partly the one and partly the other. Uniformity of action 
 implies symmetry of form ; and it appears to me that plants 
 and animals are symmetrically constructed in order that the 
 
 1 Grove on the Correlation of Physical Forces, p. 13. 
 
 2 ' The term " force," although used in very different senses by different authors, 
 in its limited sense may be defined as that which produces or resists motion.' 
 Correlation of Physical Forces, p. 14. 
 
PHYSIOLOGY OF THE CIRCULATION. 8 1 
 
 forces displayed by them may equilibrate or balance each 
 other, and in order that plants and animals as a whole or 
 parts of them may experience moments of repose ; alternate 
 activity and repose culminating in those marvellous rhythmic 
 movements to which I shall have occasion to allude very 
 shortly. Repose implies a balancing power in the structures in 
 which it is manifested, and hence the bilateral symmetry which 
 everywhere obtains in animal organisms, and in organs them- 
 selves. I can instance no more beautiful example than the 
 heart itself. In the ventricles of the mammalian heart, as 
 you are aware, the muscular fibres are arranged in two sym- 
 metrical sets of spiral fibres, so wonderfully and exquisitely 
 convoluted that each individual fibre has a counteracting or 
 opposing fibre ; each region being equilibrated by an opposing 
 region ; the whole forming a minutely reticulated structure, in 
 which the fibres cross with mathematical precision at all 
 conceivable angles, the fibres by their shortening and 
 lengthening producing a motion which is, in some senses, 
 unique in the animal economy. Similar remarks may be 
 made regarding the bilateral nature of the stomach, bladder, 
 and uterus, and indeed of all parts of the body. The flexors 
 and extensors, when in a state of equilibrium, are in a state of 
 rest, and when the flexor shortens the extensor lengthens, and 
 vice versa. The one movement implies the other. In like 
 manner the heart has the power of opening and closing 1 . I 
 employ the terms lengthens and shortens when speaking of 
 long muscles, in preference to relaxes and contracts con- 
 traction literally meaning a diminution of volume, no such 
 diminution occurring in the movements of a muscle. This is 
 proved by causing a muscle to contract in a graduated vessel 
 containing water. The water always remains at the same 
 level. I employ the terms opens and closes^ when speaking 
 of hollow muscles, as involving no theory as to the manner in 
 which a muscle acts. All muscular movements are the result 
 of a vital change of shape in the sarcous elements of which 
 
 1 That the one part of the heart opens while the other closes, is proved by this, 
 that all parts of the heart act, even when they are deprived of blood. When, 
 moreover, the heart is acting slowly, the ventricle or ventricles (if there be two) 
 open before the auricle or auricles, as the case may be, close. I have frequently 
 seen this in the fish and frog. 
 
 G 
 
82 PHYSIOLOGY OF THE CIRCULATION. 
 
 muscles are composed, the volume of the sarcous elements 
 always remaining exactly the same. Such change is not ex- 
 pressed by the terms contracts and relaxes. Contraction is 
 usually regarded as a vital or active movement, relaxation 
 being erroneously regarded as a mechanical or passive one. 
 
 Respiration and Assimilation connected with the Circula- 
 tion. In order to have a just conception of the circulation 
 as it exists in animals, it will be necessary to examine it in 
 connexion with the movements of respiration and nutrition, 
 and the movements of the soft and hard parts generally. 
 
 There is a considerable proportion of the lower animals in 
 which no trace of a circulation has yet been detected, the 
 nutritious fluids in such cases being supposed to pass from 
 the alimentary canal by interstitial transudation throughout 
 the entire body, as the sap passes into the substance of 
 cellular plants. One great obstacle to a proper understanding 
 of the circulation in many of the lower forms of organic 
 animal life, is the difficulty experienced in determining 
 whether the currents observed in inclosed spaces within their 
 bodies belong to the circulation of their blood and nutrient 
 juices, or are a means to a very different end, viz. respiration, 
 locomotion, and other widely dissimilar functions. In sponges, 
 which live and grow in water, this element passes in con- 
 tinuous currents through pores and canals in their substance. 
 These currents enter at one point and issue at another, and 
 are not, as Dr. Grant showed, due to the contraction of 
 the canals. He suggested that they might possibly be due 
 to the action of cilia, and Huxley and Bowerbank have 
 succeeded in demonstrating the presence of those structures. 
 It is only when cilia, blood-vessels, or hearts, are present, 
 that the forces assume a visible form. 
 
 Ciliary Currents. Dr. Sharpey, in his admirable paper ' On 
 Cilia,' shows that definite currents may be produced by 
 ciliary movements. He instances two currents, which he 
 found within the tentacula of the actinia; the one running 
 from the base to the point of the tentaculum, the other in 
 an opposite direction. He observed similar currents in the 
 asterias and echinus ; and those currents, he remarks, curiously 
 enough, continue after the parts which exhibit them are 
 detached from the animal, from which it follows that they 
 
PHYSIOLOGY OF THE CIRCULATION. 83 
 
 are beyond the reach of the will. The peculiarity of the 
 currents referred to consists in this, that they run in opposite 
 directions as in plants. In the polypi, medusae, planaria, 
 and some entozoa, where a circulation is absent or very 
 obscure, the caeca of the alimentary canal is much branched, 
 and evidently assists in carrying nutritious juices to all parts 
 of the body. It thus performs in a great measure the 
 functions of a circulatory apparatus, as well as of an alimen- 
 tary canal. What fluids are not circulated by the caeca are 
 circulated under such circumstances by a transudation or 
 interstitial movement, as in plants. In several of the medusae 
 no distinct organ of circulation can be detected, the alimentary 
 canal in such cases being of large size, and ramifying in 
 every direction on the surface, or in the substance of the 
 animal. Hitherto I have been dealing with the circulation 
 as it exists in plants, and in the lower forms of animals, 
 where neither contractile vessels nor hearts are present. 
 When vessels are present, as in the cestum and beroe, Esch- 
 scholtz has shown that a large loop or ring of vessels surrounds 
 the mouth, from which arteries and veins proceed ; branches 
 passing to the fins, which at once serve for respiration and 
 locomotion; the fins in this respect resembling the growing 
 wings of many insects. It is not quite ascertained whether 
 in the beroe, the circulating fluid, which is of a yellowish 
 colour and contains globules, is actually blood. In the 
 diplozoon (a small entozoa), Nordmann made out, with a 
 high magnifying power, currents moving in opposite directions 
 in two sets of vessels occurring on either side of both limbs 
 of the animal. These vessels terminate posteriorly in a kind of 
 sac, and, according to Nordmann and Ehrenberg, they neither 
 contract nor dilate. We have now, you will observe, got dis- 
 tinct vessels in animals minus contractile power as in plants. 
 
 In the compound ascidiae, as Mr. Lister has shown, the 
 different individuals of the branched animal are united by 
 a polypiferous stem, and have a common circulation. Each 
 individual is furnished with a heart consisting of a single 
 cavity, which pulsates thirty or forty times per minute. In 
 the common stem two distinct currents are traceable, th^ese 
 running in opposite directions (Fig. 27, p. 29). One of the cur- 
 rents enters the ascidia by its peduncle, and goes direct to the 
 
 G 2 
 
84 PHYSIOLOGY OF THE CIRCULATION. 
 
 heart. It proceeds thence to the gills and system generally, 
 which having traversed, it leaves the animal by the peduncle 
 at which it entered, and passes into the common stem, to 
 circulate through another ascidian. The direction of the 
 currents is reversed every two minutes or so ; and Mr. Lister 
 found that if an ascidian was separated from the common 
 stem, the separated individual can set up an independent 
 circulation, consisting of two currents likewise running in 
 opposite directions. The circulation in the ascidiae is very 
 remarkable, and closely resembles that in many plants. It 
 occurs in non-contractile tubes, and in the absence of cilia. 
 It is distinguished by an ascending and descending current, 
 free to enter and leave the animal, as the sap is free to 
 enter and leave the tree. The circulation moreover reverses 
 and oscillates, and it may go on independently in an in- 
 dividual or in a community of individuals. Precisely the 
 same remark may be made of the tree, for in this also the 
 circulation oscillates, and if a portion of a tree, say a vine, 
 be forced, it sets up a circulation of its own, while it at 
 the same time maintains a certain relation with the other 
 parts of the tree which are not forced (compare Fig. 8, p. 14, 
 with Fig. 27, p. 29). 
 
 In the leech, sand-worm, and earth-worm, the circulation is, 
 if possible, more tree-like. In these the blood (which is 
 red in colour) moves slowly forward in the vessels situated 
 on the dorsal surface of the animal, the direction of the 
 current being reversed in the ventral vessels. If the leech, 
 to which my remarks more especially apply, be placed in 
 a vertical position, the currents of course correspond to the 
 ascending and descending currents of plants. Between the 
 dorsal and ventral vessels are numerous transverse vessels, 
 which carry on a lateral or cross circulation, this too being 
 analogous to what is found in plants. (See Fig. 8, p. 14, 
 and compare with Fig. 44, p. 89). 
 
 There are no distinct hearts in the leech, sand-worm, and 
 earth-worm, the circulation being carried on mainly by the 
 closing of the vessels at different points. 
 
 Rhythmic Movements Analogy between Involuntary and 
 Voluntary Movements. If the vessels closed throughout their 
 entire extent, very little if any movement would occur. If, 
 
PHYSIOLOGY OF THE CIRCULATION. 85 
 
 again, the centre of a long vessel closed, the fluid would 
 be driven away from the constricted point in opposite 
 directions. To insure a circulation of the nutritious juices 
 in a particular direction when valves are not present, the 
 vessels must open and close in parts, in a certain order, 
 in a given direction, and at stated intervals ; one part 
 opening while another is closing, and vice versa. This 
 is what virtually takes place in the lashing of cilia. First 
 one moves and then another, to form a progressive wave 
 of movement ; this in its turn forming a progressive wave 
 of fluid. It is this peculiar kind of movement that de- 
 termines the wave of the pulse. The wave movement of 
 cilia has been aptly compared by Dr. Sharpey to the un- 
 dulating motion produced by the wind on a field of corn, 
 and exactly resembles what I myself have seen in the living 
 mammalian heart. The alternation of movements diametri- 
 cally opposed to each other, if they occur at regular intervals, 
 constitute the so-called rhythmic movements. These move- 
 ments are witnessed in the blood-vessels, the heart, the 
 intestines, the stomach, the bladder, and the uterus. They 
 recur at very long intervals in the uterus, but the element 
 of duration or time does not destroy the nature of the 
 movement ; the action of the heart is a rhythmic action, 
 whether the organ beats 50 to the minute or loo 1 . It is 
 the nature of the movement which settles its claim to be 
 regarded as rhythmic or not. Hollow muscles display 
 rhythmic movements when one part of their substance opens 
 and another closes simultaneously ; these movements al- 
 ternating and repeating themselves at longer or shorter 
 periods. Thus the stomach, bladder, rectum, and uterus, 
 close when their sphincters open ; and their sphincters close 
 when the viscera open. Minutes, hours, days, weeks, or 
 
 1 The frequency of the heart's action varies greatly in different animals. 
 According to Burdach (Physiologic, vol. iv. p. 251), the number of pulsations 
 per minute in the shark is 7 ; in the mussel, 15; in the carp, 20; in the eel, 24; 
 in the snake, 34 ; in the horse, 36 ; in the caterpillar, 36 ; in the bullock, 38 ; 
 in the ass, 50 ; in the crab, 50 ; in the butterfly, 60 ; in the goat, 74 ; in the sheep, 
 75; in the hedgehog, 75; in the frog, 77; in the marmot, locust, and ape, 90; 
 in the dormouse, 105; in the cat and duck, no; in the rabbit and monoculus 
 castor, 1 20 ; in the pigeon, 130 : in the guinea-pig, hen, and bremus terrestris, 140; 
 and in the heron and monoculus pulex, 200. 
 
86 PHYSIOLOGY OF THE CIRCULATION. 
 
 months, may elapse between the opening and closing of 
 the parts of a hollow viscus, but when they do open and 
 close, its movements are essentially rhythmic in character. 
 Very similar remarks may be made regarding the voluntary 
 muscles. The voluntary muscles, like the involuntary, are 
 arranged in cycles* the closing of one half of the cycle being 
 accompanied by the opening of the other ; in other words, 
 when the muscle constituting the one half of the cycle 
 shortens, the other elongates. In the involuntary muscles 
 the cycle closes in all its diameters, to expel fluid or other 
 contents. In the voluntary muscles the diameter of the circle 
 remains the same, the object being to cause the jointed bones 
 placed within the cycle to move in specific directions. The 
 motion of the voluntary and involuntary muscles is essentially 
 wave-like in character i.e. it spreads from certain centres, 
 according to a fixed order, and in given directions. Thus the 
 ventricular portion of the heart closes towards the pulmonary 
 artery and aorta ; the stomach towards the pyloric valve ; the 
 rectum towards the sphincters ani ; the bladder towards the 
 urethra ; and the uterus towards the os. It is the same in the 
 movements of the extremities ; the centripetal or converging 
 muscular wave on one side of the bones to be moved, being 
 accompanied by a corresponding centrifugal or diverging wave 
 on the other side ; the bones by this means being moved to a 
 hair's-breadth. The centripetal or converging, and the centri- 
 fugal or diverging waves of force are correlated. The same holds 
 true of the different parts of the body of the serpent when 
 creeping ; of the body of the fish when, swimming ; of the wing 
 of the bird when flying ; and of our own extremities when 
 walking. In all these cases, the moving parts are thrown 
 into curves or waves \ It could not be otherwise. If fluids 
 are to be propelled in certain directions, forces which act 
 in definite directions must be provided. This also holds true 
 of locomotion however performed ; whether by a living un- 
 differentiated mass, i. e. a mass devoid of nerve, muscle, bone, 
 
 1 That an intimate relation exists between the organs of locomotion and the 
 structures which carry on the circulation and the digestion in the higher animals, 
 is rendered exceedingly probable by the fact, that the cilia of the infusoria enable 
 those creatures to move from place to place, and produce the currents which enable 
 them to seize their food and respire. 
 
PHYSIOLOGY OF THE CIRCULATION. 8/ 
 
 etc. ; or by an animal in which all these are present. It may 
 seem out of place to refer to the voluntary muscular move- 
 ments here, seeing I am called upon, strictly speaking, only 
 to deal with the involuntary. It however appears to me, that 
 the two must be studied together : that, in fact, the compound 
 involuntary muscles, such as the heart, stomach, bladder, and 
 uterus, give the cue to the muscular arrangements in the 
 extremities and bodies of animals generally. 
 
 Hitherto it has been the almost invariable custom in teach- 
 ing anatomy, and such parts of physiology as pertain to 
 animal movements, to place much emphasis upon the con- 
 figuration of the bony skeleton as a whole, and the conforma- 
 tion of its several articular surfaces in particular. This is 
 very natural, as the osseous system stands the wear and tear 
 of time, while all around it is in a great measure perishable. 
 It is the link which binds extinct forms to living ones, and we 
 naturally venerate and love what is enduring. It is no marvel 
 that Oken, Goethe, Owen, and others, should have attempted 
 such splendid generalisations with regard to the osseous 
 system should have proved with such cogency of argument 
 that the head is composed of expanded vertebrae. The bony 
 skeleton is a miracle of design very wonderful and very beau- 
 tiful in its way. But when all has been said, the fact remains 
 that the skeleton, when it exists, forms only an adjunct of 
 locomotion and motion generally. All the really important 
 movements of an animal occur in the soft parts. The osseous 
 system is therefore to be regarded as secondary in import- 
 ance to the muscular, of which it may be considered a dif- 
 ferentiation. Instead of regarding the muscles as adapted to 
 the bones, the bones ought to be regarded as adapted to the 
 muscles. Bones have no power either of originating or per- 
 petuating motion. This begins and terminates in the muscles 
 and soft parts. Nor must it be overlooked that bone makes 
 its appearance comparatively late in the scale of being ; that 
 innumerable creatures exist, in which no trace either of an 
 external or internal skeleton is to be found ; that these crea- 
 tures move freely about, digest, circulate their nutritious juices 
 and blood when present, multiply, and perform all the functions 
 incident to life. While the skeleton is to be found in only a 
 certain proportion of the animals existing on our globe, the 
 
88 PHYSIOLOGY OF THE CIRCULATION. 
 
 soft parts are to be met with in all ; and this appears to me 
 an all-sufficient reason for attaching great importance to the 
 movements of soft parts ; to protoplasm, to moving jelly masses, 
 to involuntary muscles such as the oesophagus, stomach, 
 intestine, bladder, uterus, heart, and blood-vessels. It may 
 appear far-fetched to state that the voluntary muscle is a 
 differentiation and further development of the involuntary ; 
 that the movements of the oesophagus, stomach, and intes- 
 tines, prefigure those of the blood-vessels ; that the move- 
 ments of the blood-vessels prefigure those of the heart ; that 
 the movements of the heart prefigure those of the chest and 
 abdomen ; and that the movements of the chest and abdo- 
 men prefigure those of the extremities : but such, I believe, 
 is actually the case 1 . Indeed I hope to be able to show you, 
 before I finish the present course, that if I eliminate the ele- 
 ment of bone from the chest and the extremities, the direc- 
 tion of the muscular fibres of those parts will correspond ex- 
 actly with the direction of the muscular fibres of the ventricles 
 of the mammal ; nay, more, that even the bones of the several 
 regions, especially of the extremities, are twisted upon them- 
 selves in the form of a double spiral, and in a manner re- 
 sembling that in which the fibres of the heart are convoluted. 
 This is especially perceptible if the internal fibres of the left 
 ventricle of the heart be compared with the bones of the 
 bird's wing ; or the bones of the anterior extremity of the 
 elephant ; or the bones of the extremities of any quadruped. 
 
 I hope further to be able to point out that the heart within 
 the thorax is a heart working within a greater heart the 
 thorax itself; the two having a common function, viz. to 
 bring the air and the blood face to face, so as to enable them 
 to reciprocate with the utmost facility and in the most direct 
 way possible 2 . I might make similar observations regarding 
 
 1 The extremities are a differentiation of the trunk. They are not necessary to 
 existence ; they may be lopped off and the trunk live as before. 
 
 2 As the circulatory apparatus adapted to absorb nourishment for the use of 
 the embryo becomes developed, it is necessary that a respiratory apparatus be 
 provided for depurating the blood. This apparatus is termed the allantois. It 
 sprouts from the anterior and lower part of the wall of the belly of the embryo, 
 at first as a little mass of cells, which soon exhibits a cavity so that a vesicle is 
 formed which looks like a diverticulum from the lower part of the digestive 
 cavity. This vesicle in birds has been shown by Vulpian (Journ. de la Physi- 
 ologic, tome i. p. 619 et seq.) to be possessed of a distinct contractile power, and 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 8 9 
 
 Fig. 44. 
 
 the stomach, intestine, bladder, and uterus. These are hollow 
 muscles } situated within the abdomen, a still greater hollow 
 muscle ; and when any of them acts, the abdominal muscles 
 take part in the movement. The hollow muscles and ab- 
 domen may however act separately, just in the same way that 
 the heart may act when cut out of the thorax. I have to 
 apologise for these digressions, but the object of my treating 
 the subject of the circulation comparatively is to bring out 
 contrasts, and to eliminate, if possible, from a mass of detail, 
 some principle or principles. 
 
 Circulation in the Leech contrasted with that in Plants. 
 The circulation in the leech affords a good illustration of 
 what may be done by rhythmic movements 
 acting in a given direction ; the rhythmic 
 movements of the blood-vessels sufficing for 
 carrying on the circulation within the body 
 of the leech ; and, what is not a little curious, 
 the rhythmic movements of the oesophagus 
 of the leech causing the blood of another ani- 
 mal to circulate within its oesophagus and 
 alimentary canal when it feeds 2 . ' In the 
 leech,' Dr. Thompson observes, ( the principal 
 and most highly contractile longitudinal 
 vessels are placed one on each side, and 
 there are also two lesser longitudinal vessels, 
 one superior and the other inferior, all which 
 communicate freely together by small cross 
 branches along the whole body.' (Fig. 44.) 
 According to J. M tiller, for a certain number 
 of pulsations, the middle and the lateral vessel of one side 
 
 soon becomes so large as to extend itself around the yolk-sac, intervening between 
 it and the membrane of the shell, and coming through the latter into relation with 
 the external air ; but in the embryo of mammalia, the allantois, being early super- 
 seded by another provision for the aeration of the blood, seldom attains any 
 considerable dimensions. Carpenters Human Physiology, Lond. 1864, pp. 800, 80 1. 
 
 1 The hollow muscles are adapted for transmitting air, fluids, or solids. Usually 
 they only transmit one of these. The intestine transmits all three. 
 
 2 When speaking of the teeth of the common leech, Mr. Dallas remarks, that 
 immediately the teeth, three in number, have sawed through the skin, they are 
 retracted and the blood pumped from the wound by the alternate dilatation and 
 contraction of the muscular oesophagus. Natural History of the Animal Kingdom, 
 by W. S. Dallas, Esq. F.L.S., p. 95. 
 
 Fig. 44. a, a, Prin- 
 cipal and most highly 
 contractile vessels of 
 leech, a*, minor ves- 
 sels ; e, cross vessels. 
 
90 PHYSIOLOGY OF THE CIRCULATION. 
 
 contract together, and propel the blood into the lateral vessel 
 on the other side ; and then the order is reversed, and the 
 middle vessel acts along with the lateral vessel of the other 
 side, so that one lateral vessel is always dilated, while the 
 median and opposite lateral ones are contracted, and vice versa. 
 
 Some anatomists believe that in the leech there is a simple 
 oscillation of the blood from side to side, or across the animal ; 
 others that there is, in addition, a general progressive move- 
 ment of the blood forwards in the upper vessel, and back- 
 wards in the lower one (vide arrows). The latter view is 
 most probably the correct one, for when a vertical and 
 horizontal system of vessels are united to each other by 
 innumerable capillary loops, a certain proportion of the blood 
 necessarily flows round or gyrates. Indeed it would appear 
 that the blood flows in a circle round the margin of the 
 animal, much in the same way that the granular contents 
 of the cell in many plants gyrate ; that when the upper 
 vessel closes, it forces the blood forwards and laterally ; 
 the lower vessel, when it closes, forcing the blood backwards 
 and laterally. There is nothing contradictory in this sup- 
 position. The principal forces act on opposite sides of a 
 circle in one and the same direction ; the minor forces act- 
 ing transversely. If the vessel on one side of the animal 
 closed throughout its entire length, it would certainly force 
 the blood through the lateral or transverse branches into 
 the vessel on the opposite side ; this again, when it closed, 
 reversing the movement. In this arrangement the circulat- 
 ing fluid would receive a check, i. e. it would have a halt 
 or dead point between each oscillation. There would be 
 this further difficulty : the vessel would close at once through- 
 out its entire length, instead of consecutively and in parts. 
 By adopting the view now suggested, the blood will flow 
 in one continuous round without halt or dead point, and 
 be compelled to do so by a kind of vermicular movement, 
 i. e. by a simultaneous opening and closing of the different 
 parts of the vessel, akin to swallowing ; the wave-like move- 
 ment travelling in one direction, the cause and the effect 
 being equally intelligible. The circulation in the leech re- 
 sembles that in the plant in this, that it consists of an as- 
 cending, descending, and transverse current. (Compare Fig. 8, 
 
PHYSIOLOGY OF THE CIRCULATION. QI 
 
 p. 14, with Fig. 44, p. 89.) There are, however, in addition, 
 well-defined blood-vessels which are endowed with the power 
 of opening and closing for a specific purpose. 
 
 The presence of vessels, as has been already shown, is 
 not necessary to the circulation. In young and abnormal 
 tissues, even in animals, the blood tunnels out channels for 
 itself in determinate directions, and around these channels 
 blood-vessels are ultimately formed l . The direction of the 
 current of the blood and nutritious juices is determined by 
 processes of growth, by capillarity, osmosis, evaporation, and 
 other changes occurring in the animal. It is however quite 
 natural that when the vascular system becomes differentiated 
 the blood-vessels should be laid down in the exact position 
 of the original currents, the existence of which is as necessary 
 to their own formation as that of the tissues generally. 
 
 How the Circulation connects the Organic and Inorganic 
 Kingdoms. In plants and in the lower animals, the distin- 
 guishing feature of the currents constituting the circulation 
 is, that they proceed in the direction of the length of the 
 plant or animal, and transversely the vertical and horizontal 
 currents running at right angles to each other. The cir- 
 culation in plants is essentially an interrupted or disjointed 
 circulation. It occurs within capillary or other syphon tubes 
 or spaces, the syphons being directed alternately towards the 
 leaves and the roots, in which direction the extremities of the 
 syphons are united by vegetable membranes, which pre- 
 vent the ingress of air, and preserve the integrity of the 
 syphon action, while they at the same time facilitate absorption, 
 
 1 The vessels are at first solid cylinders made up of formative cells cohering 
 together. By liquefaction of their substance in the interior, these cylinders be- 
 come tubes, and their central cells thus set free are the primitive blood-corpuscles. 
 Quoin's Anatomy, yth edition, clxxx. In the formation of the Haversian canals 
 in bone, the vessels first pour out the animal matrix, and then deposit in it the bone 
 earth ; thus by degrees they come to be surrounded by their own work. Holden's 
 Human Osteology, p. 32. 
 
 ' We have the fact, that in each plant, and in every new part of each plant, the 
 formation of sap-canals precedes the formation of wood ; that the deposit of woody 
 matter, when it begins, takes place around the sap -canals, and afterwards around 
 the new sap-canals successively developed ; that the formation of wood around the 
 sap-canals takes place when the coats of the canals are demonstrably permeable, and 
 that the amount of wood-formation is proportionate to the permeability.' Prin- 
 ciples of Biology, by Herbert Spencer, vol. ii. p. 564. 
 
92 PHYSIOLOGY OF THE CIRCULATION. 
 
 evaporation, and osmosis. The saps of a plant ascend, descend, 
 advance, and retire, in a series of waves. They rarely gyrate, 
 unless when two systems of alternating syphons unite to 
 form circular spaces, in which case the circulation resembles 
 that within cells or the bodies of animals. Plants grow 
 into the earth and air, or into the water and air. The earth 
 and water operate upon their circulation at one end the 
 air and its vapours at the other. Plants for the most part 
 are fixed. It is otherwise as a rule with animals. These 
 move freely about on the land, or in the water or air. The 
 circulation in animals is, with few exceptions, a closed or 
 complete circulation i. e. the juices flow in a continuous 
 circle. This is necessary because the forces of the circulation 
 in animals are more strictly speaking a part of themselves. 
 
 Digestion and Circulation, The leech, for example, has 
 no roots to dig into the ground, or leaves to spread out in 
 the sunshine, for the purpose of absorbing and giving off 
 moisture. It however does this indirectly by its mucous 
 linings and skin, by its blood-vessels and by its tissues 
 generally, all of which are capable of absorbing and giving 
 off moisture ] . It takes in its food and fluids by the mouth ; 
 these being made to traverse a distinct alimentary canal. 
 The circulation is, so to speak, without, beyond, or cut off 
 from the nutritious juices supplied by the mouth ; these 
 being conveyed to the blood indirectly, and in such a way 
 as would not suffice for carrying on the circulation. In the 
 plant the nutritious juices absorbed by the roots at once 
 suffice for nourishment and for carrying on the circulation. 
 The same holds true of animals very low down in the scale. 
 In the higher animals, however, the food and drink swallowed 
 contribute only indirectly to carrying on the circulation, 
 this being effected by a distinct apparatus specially pro- 
 vided. Indeed between the food as received into the stomach, 
 and the blood as elaborated for nutrition, there is a con- 
 siderable gap the gap being traversed by a distinct set of 
 vessels, the so-called lacteals or chyliferous ducts. Through 
 
 1 Boerhaave says in one place, An animal is a plant which has its roots (inter- 
 nally) in the stomach. Perhaps some other might with equal propriety play upon 
 this idea and and say, A plant is an animal which has its stomach (externally) in 
 its roots. Kant's Lesser Metaphysical Writings. Leipzig, 1838, p. 62. 
 
PHYSIOLOGY OF THE CIRCULATION. 93 
 
 these, and through the capillary blood-vessels, the nutritious 
 portions of the food reach the blood. Between the nutrition 
 as carried on in the plant and animal there are what may be 
 regarded as intermediate systems. Thus in the flustra, a form 
 of polype, the particles taken in by the mouth as food rotate 
 within the stomach and rectum, very much in the same way 
 that the contents of certain plant-cells gyrate. Here the 
 food of the animal circulates in a manner analogous to that 
 in which the pabulum of the plant, or the white and red 
 corpuscles of the blood of the mammal, circulate. This shows 
 how very intimately the functions of the circulation and the 
 digestion are related to each other 1 . Indeed the object and 
 aim of the circulation in every case is to provide nourish- 
 ment for distant parts, and to expose the circulating fluids 
 freely to the air. The circulation connects the plant with 
 the earth and air. It enables it to give to and receive 
 from both, in fact fixes its place in nature. The animate 
 and inanimate kingdoms are by the aid of the circulation 
 enabled to reciprocate. What is said of the plant may also 
 be said of the animal. It is the circulation which more 
 especially connects the animal with the outer world. The 
 pabulum taken in by the mouth of the animal very soon 
 finds its way to the blood, and the circulation insures 
 that the blood duly reciprocates with the air 2 . It is in this 
 way that the peristaltic movements of the stomach and in- 
 testines are related to the rhythmic movements of the heart, 
 blood-vessels, and lungs ; these, in turn, bearing a certain 
 relation to the voluntary muscles. If the voluntary muscles 
 are set violently in motion, as in running or wrestling, these, 
 as is well known, quicken the movements of both lungs 
 and heart. Looking at the circulation in its entirety, 
 
 1 ' The first rudiment of the heart, which is the earliest of the permanent organs 
 of the embryo that comes into functional activity, consists of an aggregation of 
 cells, forming a thickening of the fibrous coat of the anterior portion of the intestinal 
 canal ; the innermost cells of which, becoming detached, float in the newly-formed 
 cavity as the first blood-corpuscles, whilst the outer remain to constitute its walls. 
 For a long time after it has distinctly commenced pulsating, and is obviously 
 exerting a contractile force, its walls obviously retain the cellular character, and 
 only become muscular by a progressive histological transformation.' Carpenter's 
 Human Physiology, 1864, P- 799- 
 
 2 In plants the air and circulating fluids are in many cases mixed, and in insects 
 the whole animal is traversed by innumerable air-tubes, which convey air to every 
 part of the body. 
 
94 PHYSIOLOGY OF THE CIRCULATION. 
 
 we are compelled to take in a wide range of phenomena 
 and forces, the relations of which are as yet imperfectly 
 understood. A more extensive acquaintance with the subject, 
 will, I have no doubt, bring out the interesting fact, that 
 the phenomena and forces are all correlated to each other. 
 It is impossible to speak of the circulation apart from the 
 respiration and the digestion ; and these, in the higher animals, 
 are linked by a silver chain to the nervous system, which, 
 in its turn, reacts upon all the three. 
 
 Cilia, their Form and Function. While it is impossible 
 to fix upon any one force which may be said to carry on the 
 circulation in plants, there are forces at work in the lower 
 animals which would be quite equal to the task. I speak 
 of the forces residing in cilia, and which may be classed as 
 visible forces. Cilia are conical-shaped hair-like processes, 
 semi-transparent, elastic, and apparently homogeneous. They 
 occur in incalculable numbers, and are in some instances in- 
 finitely minute. They are found on the external and internal 
 surfaces of the lower animals ; and on the mucous lining of 
 the nostrils, lungs, Eustachian, Fallopian, and other tubes of 
 the higher. In some cases they are arranged in straight rows, 
 and in others they form circles or spiral lines. Some, ob- 
 servers are of opinion that they contain muscular fibres, or 
 what are equivalent thereto, in their interior ; and Ehrenberg 
 showed that they had muscles attached to their roots. Dr. 
 Grant thought that they were tubular, their movements being 
 due to the absence or presence of water in their interior. They 
 are especially deserving of attention as foreshadowing an in- 
 finite variety of movements in the animal economy. They 
 lash about with a vibratile or reciprocating rhythmical motion, 
 the one after the other, in such a manner as to produce a 
 waved surface, resembling that produced by wind upon water, 
 or, as Dr. Sharpey well put it, wind among corn. Their 
 movements, while they last, are regular and definitely co-ordi- 
 nated ; i. e. they move in certain directions with various de- 
 grees of speed, and produce currents which flow in definite 
 directions 1 . They have thus the power of propelling fluids 
 
 1 In some cases the cilia are flattened out so as to resemble the blade of an oar, 
 the blade in some instances being digitated and resembling the feathers of the 
 wing of a bird. Under these circumstances they are usually employed as organs 
 
PHYSIOLOGY OF THE CIRCULATION. Q5 
 
 in given directions, over any surface on which they are situ- 
 ated. One of the most remarkable motions, essentially ciliary 
 in character, is witnessed in the spermatozoa of the common 
 earth-worm (Lumbricus agricola). Immediately the sperma- 
 tozoa are extruded from the testes, everything in their prox- 
 imity becomes ciliated by them ; one end becoming fixed, the 
 other vibrating free. They thus actually establish ciliary cur- 
 rents on inanimate surfaces ; and if the substance to which 
 they attach themselves is not too large, they drag it about 
 with an undulating motion, and sometimes cause it to gyrate. 
 This is precisely the kind of force which would suffice for car- 
 rying on the circulation, in the absence of a heart and pulsa- 
 tile vessels ; but cilia have not hitherto been found either in 
 the vascular tissues of plants or animals, or on the globules 
 either of the blood or lymph. The function of cilia is very 
 varied. They produce currents outside the animal ; their 
 presence on the interior of the stomach causing its contents 
 to rotate or gyrate. They serve as organs of locomotion, and 
 some are of opinion that they act as lungs and organs of 
 sense. They are, therefore, endowed with this very remark- 
 able property, that they can produce currents in a given direc- 
 tion on any particular surface ; or they can cause the whole 
 animal to move in a line to any given point. They also 
 assist in the processes of digestion and respiration. Here 
 is a multiplicity of function, and it is by regarding such 
 structures that the movements of the blood-vessels and 
 heart are assimilated with those of the intestine, stomach, 
 bladder, and uterus ; and the movements of the intestine, 
 stomach, bladder, and uterus, with those of the voluntary 
 muscles. 
 
 Cilia are endowed with wonderful vital powers ; they live 
 after being separated from the body, and until the parts 
 containing them are on the verge of putrefaction. This 
 shows that they can operate independently of the will. The 
 heart and hollow viscera also act independently of the will, 
 and after being removed from the body, so that both as 
 regards their tenacity of life, their rhythmic movements, and 
 
 of locomotion. In the infusoria the cilia are apparently under the influence of the 
 will. There are, however, numerous cases where they are not, and where they 
 vibrate for protracted periods after having been removed from the body. 
 
96 PHYSIOLOGY OF THE CIRCULATION. 
 
 their involuntary actions, the cilia and heart have many points 
 in common. 
 
 Undefined Forces of the Circulation slowing and quickening 
 of the Circulation, etc. The inference I draw from the fore- 
 going is this : If in nature there are vital forces which can act 
 independently of the will, and produce continuous or inter- 
 rupted currents in definite directions, it is not difficult to 
 understand that a plant or animal, or parts thereof, may 
 exert vital powers in an equally precise and definite manner 
 although unseen. The life of a plant or animal represents 
 the aggregate movements of its structural elements ; and 
 although we cannot trace with the naked eye or microscope 
 the grouping and combined action of its various molecules, or, 
 what is the same thing, the differentiation of its forces, we 
 are, I think, bound to conclude that the life has much to do 
 with the regulation and distribution of those forces in living 
 organisms. The seed has those forces pent up within itself, 
 and when it is placed in proper conditions they manifest 
 themselves. If however the seed is dead, those conditions 
 do not affect it. It is very probable that when the seed is 
 dead its structure is so changed that the physical forces which 
 would come into play in a living seed are inoperative. If the 
 tissues are composed originally of similar elements variously 
 combined, it is difficult to resist the conclusion, that the life 
 has much to do with the production of each. What other 
 than a vital chemistry could transform a mass of protoplasm 
 into the aqueous humour of the eye ; the ivory of the tusks 
 and teeth ; the hard, resisting bone ; and the actively moving 
 muscle ? It was long before the presence of cilia was detected 
 in parts where we now know they exist, and it is quite pos- 
 sible that auxiliary forces, infinitely minute but spread over 
 large surfaces, may assist the heart and blood-vessels in push- 
 ing forward the circulation. There is no absolute necessity 
 for supposing the existence of such forces ; as osmosis, capil- 
 lary attraction, absorption, evaporation, chemical affinity, etc., 
 aided by pulsating hearts and blood-vessels, are of themselves 
 equal to the task. In a living organism, however, where every 
 part helps every other part, and where all is motion, it is 
 scarcely reasonable to suppose that the onus of pushing for- 
 ward a mass of fluid would be delegated entirely either to 
 
PHYSIOLOGY OF THE CIRCULATION. 97 
 
 the heart or the blood-vessels. In plants, as has been ex- 
 plained, fluids can circulate without either the one or the 
 other ; and a portion of skin may be taken from one animal 
 and placed upon an open sore in another, and made to grow ; 
 its connexions with the heart and blood-vessels of the animal 
 from which it was removed being completely destroyed. These 
 facts, coupled with the circumstance that sap is determined 
 to the growing parts of plants and animals, form a strong 
 presumptive proof that in the latter, as in the former, a great 
 variety of hidden or invisible forces are at work. This argu- 
 ment is not demolished by saying that if the heart is removed 
 in an animal the general circulation ceases. It may happen 
 that while the invisible forces are inadequate of themselves 
 to carry on the circulation in an animal, they may neverthe- 
 less afford invaluable assistance. In the cold-blooded animals 
 the capillaries propel the blood for some time after the heart 
 has been removed. The motion proceeds from the smaller 
 to the larger vessels alike in veins and arteries. Haller, who 
 especially investigated this subject, thought that this pheno- 
 menon could not be due to the contraction of the large ves- 
 sels, to capillarity, nor gravitation. He attributed it to some 
 unknown power residing in the solid tissues which attracted 
 the blood, and also to the action of the globules of the blood 
 upon each other. It may in reality be due to a reverse en- 
 dosmotic action ; the blood, during the process of cooling, 
 coagulating and becoming thicker than the serum outside the 
 vessels. What originally passed out of the capillaries by 
 endosmose may in part return to them, the return being 
 favoured by the closing of the capillaries and a diminished, 
 evaporation due to a loss of animal heat. Dr. Alison be- 
 lieved that the capillaries of animals exerted a peculiar pro- 
 pulsive power apart from contractility, and that the globules 
 of the blood were possessed of the power of spontaneous 
 motion. His hypothesis will be regarded by some as extra- 
 vagant, but there is nothing ridiculous in it. The ova of fixed 
 plants, as we have seen, leave the parent and lead an itinerant 
 life, until they find a suitable habitat ; the contents of cells 
 gyrate ; and cilia placed on certain surfaces produce currents 
 in definite directions. 
 
 On watching the circulation in the mesentery of the frog 
 
 H 
 
98 PHYSIOLOGY OF THE CIRCULATION. 
 
 some time ago, with my friend Dr. Wyllie, I found it difficult 
 to believe that the white corpuscles, while they floated in the 
 blood plasma, were not endowed with a certain amount of 
 independent movement. They loitered along the margins of 
 the capillaries, now stopping here, now there, now advancing 
 a little, and now halting resolutely : attaching themselves to 
 the inner surface of the vessels, they forced their way in an 
 outward direction and produced an external bulging, after 
 which, changing their shape, they pushed themselves right 
 through the capillary walls. Once outside the vessels, they 
 reassumed their original form for a brief space, after which 
 they gradually merged into the adjacent tissues, and became 
 undistinguishable from them. The growth of the individual 
 may, in this sense, be regarded as identical with its power 
 of circulation : the one is correlated to the other. The 
 organism lives because it has the power of circulating its 
 nutritious juices. There are many facts which strengthen 
 the hypothesis that the circulation of the blood within the 
 capillaries is not entirely due to the action of the heart. 
 The circulation of the blood may continue in the capil- 
 laries after the heart has ceased to act ; or it may cease 
 in parts, the heart acting vigorously the while. The flow of 
 blood in the capillaries is not regular, which it would be if 
 entirely dependent on the action of the heart. In some in- 
 stances the circulation in certain of the capillaries within a 
 given area is quickened, while in others within the same area 
 it is slowed, and the direction of the current reversed. In 
 cold-blooded animals the circulation within the capillaries 
 goes on after the heart is excised. The arterial system, after 
 most kinds of natural death, is found emptied of blood. In 
 death by yellow fever, the external veins often become so 
 distended, that on puncture the blood gushes forth as from 
 arteries. Secretions depending upon the circulation within 
 the capillaries go on after the heart has ceased to beat. In 
 the early embryo the blood moves in the vascular area before 
 it is subjected to the influence of the heart the movement 
 being towards instead of from the centre. The heart in some 
 cases is absent during the whole of embryonic life the organs 
 being nevertheless well developed, which of course implies a 
 capillary circulation. The circulation in the capillaries may 
 
PHYSIOLOGY OF THE CIRCULATION. 99 
 
 be slowed or stopped by the local application of cold, and by 
 local death or gangrene, which shows plainly enough that 
 there is, as Sir James Paget cautiously puts it, ' some mutual 
 relation between the blood and its vessels, or the parts around 
 them, which, being natural, permits the most easy transit of 
 the blood, but, being disturbed, increases the hindrance to its 
 passage.' -Professor Draper 1 thought that 'if two fluids com- 
 municate with one another in a capillary tube, or in a porous 
 or parenchymatous structure, and have for that tube or struc- 
 ture different chemical affinities, movement will ensue ; that 
 liquid which has the most energetic affinity will move with 
 the greatest velocity, and may even drive the other liquid 
 before it.' The occult forces, if I may so call them, while 
 they are not equal to carrying on the circulation by them- 
 selves, exert, I believe, sufficient power to relieve the heart 
 and blood-vessels from excessive strain. It is, moreover, more 
 natural for the tissues to drink leisurely, and according to 
 desire, than to have blood unceremoniously thrust upon them 
 by a violent vis a tergo. Where the blood has to travel long 
 distances before it is utilised, a perfect system of blood-vessels 
 and a heart are necessary for transmitting it to the scene of 
 its labours. Arrived there, another set of forces comes into 
 play. This is in part proved by the absence of the pulse in 
 the capillaries. I may be here met by the statement that 
 the force of a common injecting syringe can cause a fluid to 
 pass through the arteries and capillaries so as to return by the 
 veins. I have had considerable experience in artificial injec- 
 tions, and have invariably found, that unless extreme care is 
 exercised, the capillaries are ruptured in the process. Nor is 
 this due to coarse particles in the injection blocking up the 
 capillaries, for the same pernicious effects follow when water 
 is employed. It is the force that does the mischief, and this 
 is another reason for believing that the circulation within the 
 capillaries differs materially from that in the main arteries 
 and veins. It could not be expected that the delicate capil- 
 lary vessels, with their thin transparent wiills, could resist 
 without injury the same pressure brp'tight "to'.fyear upon the 
 aorta ; nor are they called upon to do- 36, fte j^ssure being 
 diminished in proportion to the increase" -o^area m the capil- 
 
 1 Treatise on the Forces which produce the Organisation </f Plants, pp 22-4;. 
 
 H 2 
 
IOO PHYSIOLOGY OF THE CIRCULATION. 
 
 laries, as compared with that in the arteries. That the force 
 exerted by the heart is modified as it is transmitted is abun- 
 dantly proved by the greater thinness of the walls of the great 
 veins, as compared with the great arteries. The slowing of 
 the circulation in the arteries in the direction of the capillaries, 
 and the quickening thereof in the veins in the direction of the 
 heart, render it exceedingly probable that the ventricle, or 
 ventricles, exert a propelling power, and that the auricle, or 
 auricles, exert a sucking power. This is what virtually hap- 
 pens in the more simple forms of the circulation, when one 
 surface absorbs and another respires ; fluids entering the tis- 
 sues by endosmose (which may be regarded as a pushing 
 force), passing through them and escaping by evaporation 
 (which may be regarded as a pulling force). The sucking 
 and propelling power, there is reason to believe, is possessed 
 by each compartment of the heart a circumstance due to 
 the fact that the opening and closing of the different parts of 
 the heart are equally vital acts. (They are vital in the same 
 sense that the opening and closing of the medusa, and the 
 vacuoles of such plants as the Volvox globator, Gonium pecto- 
 rale, and Chlamydomonas^ are vital.) Thus the auricle and 
 ventricle, when they close, propel or push the blood ; whereas, 
 when they open, they draw or suck it. As the auricle closes 
 when the ventricle opens, and vice versa, it follows that when 
 the ventricle is pushing, the auricle is pulling ; the auricle 
 pushing when the ventricle is pulling. The two forces, in 
 fact, act together, the object being to cause the blood to flow 
 in a circle. That each compartment of the heart in other 
 words, each pulsating cavity has the power of gently suck- 
 ing in the blood and forcibly ejecting it, seems proved by 
 analogy. If a caoutchouc oval-shaped cylinder furnished 
 with two apertures be compressed by the hand, to exclude 
 the air, and immersed in water, it fills itself when it expands. 
 The water can be extruded by the pressure of the hand, and 
 the operation repeated ad libitum. If the apertures of the 
 cylinder have fitted to them two tubes, one of which is sup- 
 plied with ar ba-l'i-valtfe'as in some forms of enema syringe, 
 water may-b'e pumped 'out of a vessel in a more or less con- 
 tinuous, stream as by' the heart, by immersing that end of the 
 apparatus containing the valve, and applying an interrupted 
 
PHYSIOLOGY OF THE CIRCULATION. IOI 
 
 pressure to the cylinder, by alternately closing and opening 
 the hand in which the cylinder is retained. When the 
 cylinder is forcibly closed, it ejects the water ; and when it 
 spontaneously opens, it draws it in. Precisely the same 
 thing occurs in the heart of the lobster; the heart in this 
 crustacean consisting of a single muscular sac, which gives 
 off and receives numerous tubes (Fig. 48, h, p. 108). This rea- 
 soning is not vitiated by the fact that the vessels proceeding 
 to and from the heart are flexible, for I have ascertained by 
 experiment that the vessels may be as thin as tissue paper 
 and not collapse when suction is applied to them, provided 
 always they be full, or moderately full, of blood blood, like 
 other fluids, being nearly incompressible. If, for example, a 
 piece of gut having a syringe attached to it at either end be 
 immersed, and the gut and one syringe be moderately filled 
 with water, I find that the water in the full syringe can be 
 made to pass to the empty syringe, without in the slightest 
 altering the calibre of the gut. This follows, because the 
 contents of the gut remain always exactly the same. The 
 transference is effected by one operator pushing down the 
 piston of the full syringe, while another draws up the piston 
 of the empty syringe. It is in this way that the vessels are 
 always kept moderately full of blood, and that one compart- 
 ment of the heart always closes and pushes at the same in- 
 stant that another compartment opens and pulls. The blood 
 ejected from the one compartment is received by the other, 
 the vessels being always full ; one compartment of a single 
 heart (heart consisting of an auricle and ventricle), and two 
 compartments of a double heart (heart consisting of two au- 
 ricles and two ventricles), being always empty. From this it 
 appears that two pulsating cavities, one of which opens when 
 the other closes, are capable of carrying on the circulation 
 in the absence of elasticity in the vessels. Nor will this occa- 
 sion surprise. No substance is perfectly elastic ; so that if 
 much power was stored up in the vessels by the heart, a con- 
 siderable proportion of it would be sacrificed. Such vessels as 
 take an active part in the circulation open and close in parts 
 rhythmically, and produce a kind of swallowing movement ; 
 this movement being due less to elasticity than vitality in 
 the parts. The elasticity of the vessels is principally of use 
 
102 PHYSIOLOGY OF THE CIRCULATION. 
 
 in causing the blood to flow in a continuous stream, the 
 elasticity acting when the ventricles have ceased to act (i.e. 
 between the pulsations) in such a manner as definitely to co- 
 ordinate the ventricular movements. Elasticity is also useful 
 in keeping the vessels open, in permitting them to assume 
 various attitudes, and in yielding to and correcting local con- 
 gestions. The blood is most economically circulated by an 
 apparatus which opens and closes spontaneously in parts ; 
 this arrangement reducing friction and conserving energy. 
 Such an apparatus operates upon the blood and not upon 
 itself. It can operate with or in the absence of elasticity, and 
 performs work in whichever direction it moves. The object of 
 the circulatory apparatus is to convey blood to and from the 
 capillaries where the tissues are fed, and this can be done 
 most conveniently by an apparatus which propels fluid in a 
 circle, one half of the apparatus propelling or pushing the 
 fluid round one half of the circle, the fluid , being gradually 
 slowed in its course ; while it sucks or draws it round the 
 other half, the fluid being gradually quickened in its course. 
 By this arrangement no time is lost, the blood being slowed 
 in order to afford the tissues an opportunity of taking from 
 and giving to it, and quickened when these interchanges are 
 not necessary. The blood is slowed as it proceeds from the 
 
 Fig. 45. Diagram representing 1 how the heart pushes and pulls the blood, and how the circulation is 
 slowed and quickened, a, auricle. *, ventricle (pulsating cavities), of exactly the same size ; c, auriculo- 
 ventricular orifice guarded by a mitral valve ; d, artery ; e ,f, capillaries ; g, h, vein. The ventricle () 
 propels or pushes the blood towards the capillaries (e,f ) when it closes ; the auricle (a) sucks or draws 
 it from them when it opens. The auricle always opens when the ventricle closes, and "vice versa (one 
 compartment of the heart being always empty when the other is full). The blood is by this means forced 
 in a circle (vide arrows). It is slowed in the direction b, d, e, and quickened in the direction./; g, h, a. 
 The valves c, g, h, insure that the blood will always flow in the same direction. Original. 
 
 heart, by the breaking up of the arteries into innumerable 
 branches, and from a marked increase in the capillary area ; 
 the friction experienced by the blood in transitu being corre- 
 spondingly increased. It is quickened as it proceeds towards 
 
PHYSIOLOGY OF THE CIRCULATION. 103 
 
 the heart, by the veins converging, and from a marked dimi- 
 nution in the venous area ; the friction experienced by the 
 circulating fluid being correspondingly diminished. (These 
 points are shown in Fig. 45.) 
 
 Circulation in the Star-fish. In the star-fish the intestinal 
 vascular system consists of loops, from which arteries and 
 veins are given off; these being connected with a dilated 
 pulsatile canal, which may be regarded as a -rudimentary 
 heart. Similar remarks are to be made of the holothuria, so 
 that we have at length arrived at what may be regarded as a 
 visible force, viz. a pulsating vessel. It is a remarkable cir- 
 cumstance that in the mammal those veins which are not 
 furnished with valves are largely supplied with non-striated 
 muscular fibres, which run in two directions, viz. across and 
 in the direction of the length of the vessel. This holds true 
 of the inferior vena cava, the renal, azygos, and external iliac 
 veins, and of all the large trunks of the portal venous system, 
 and of the trunks of the hepatic veins ] . These vessels have 
 therefore the power, within certain limits, of opening and 
 closing 2 , and of forcing on the blood independently of valves. 
 Valves are consequently accessory structures and adjuvants 
 to the heart in the higher animals. 
 
 Circulation in the Spider. In the spider a large dorsal 
 vessel makes its appearance, this being dilated posteriorly so 
 as to resemble a heart. The great propelling organ in the 
 circulation of animals is now beginning to assume form. The 
 dorsal vessel gives off lateral branches which ramify through 
 the body ; the venous blood being collected in open spaces 
 or sinuses on the abdominal surface. There is as yet only an 
 arterial system of vessels, the venous one being deficient. The 
 blood is aerated by tracheae or pulmonary cavities. 
 
 Circulation in the Insect. A similar account may be given 
 of the circulation in the insect. Here the dorsal vessel is 
 divided into a series of swellings, each of which is furnished 
 with valves, and endowed with a pulsatile power, as shown at 
 h of Fig. 46, p. 104. The dorsal artery receives lateral currents 
 from various parts of the body, and is widened out posteriorly. 
 
 1 Anatomy, Descriptive and Surgical, by Henry Gray, Esq., F.R.S., p. 401. 
 
 2 Nerves are supplied to the inferior cava and cerebral veins; to the aorta, 
 pulmonary artery, and many other vessels. 
 
104 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 The dorsal vessel opens and closes in parts (one part always 
 opening when the other closes) with a vermicular or wave-like 
 motion this, in conjunction with the valves (^, r\ determin- 
 ing the course pursued by the blood. The blood is returned 
 by two vessels situated on the ventral aspect of the insect (v) ; 
 these, according to Carus and Wagner, being in many cases 
 absent, and their places supplied by open sinuses, as in the 
 spider. The dorsal and ventral vessels are united anteriorly 
 and posteriorly by loops which, in the immature or larval 
 individual, extend into the antennae, fin-shaped caudal pro- 
 cesses, the first joint of each leg, and the immature wing. 
 Under these circumstances the wings, antennae, and caudal 
 appendages, act as respiratory organs. 
 
 Fig. 46. 
 
 Fig. 46 shows the position 'of the vessels in the insect, h, great dorsal vessel, consisting of pulsa- 
 tile swellings which force the blood towards the head. v, vessels situated on the ventral aspect, which 
 collect and transmit the blood in a direction from before backwards. The arrows indicate the direction 
 of the currents in the wings. *, x, r, valves situated in dorsal vessel. Between these the lateral currents 
 enter (vide small curved arrows). The valves are pushed aside and opened by the blood as it travels in 
 the direction of the head (see arrows directed upwards), and forced towards the axis of the vessel, and 
 closed by the blood when it attempts to travel away from the head (see arrows directed downwards). 
 After Thomson. 
 
 In the insect the organs of respiration are also the organs of 
 locomotion. The circulation is most complete, as a rule, in 
 the immature insect. It is however quite perfect in not a 
 few adult insects. Carus found it so in the wings of semblis, 
 developed for flight. In the fully matured insect the circu- 
 lation in many cases becomes circumscribed, the blood being 
 cut off from the several appendages and confined to the body. 
 When the several parts are formed the vessels are either 
 wholly or partly obliterated, as happens in the old vascular 
 bundles of woody tissue in the more central parts of the tree. 
 The insect is by this means rendered stronger and lighter for 
 
PHYSIOLOGY OF THE CIRCULATION. K>5 
 
 the purposes of flight It is by the filling up and obliterating 
 of blood-vessels that organs, such as the branchiae of the frog, 
 and other foetal structures which serve a temporary purpose, 
 are lopped off. As the presence of blood is necessary to the 
 existence of such structures, so its absence results in their 
 destruction. The insect possesses a circulatory apparatus, 
 which compels the blood to flow in given directions. The 
 dorsal vessel of the insect consists virtually of a chain of 
 hearts, which act in unison and in a certain rhythmic order, 
 although they are more or less distinctly cut off from each 
 other by the presence of valves. The caudal heart closes first 
 (that immediately in front of it opening), and so on in regular 
 order, that next the head closing last. The blood is driven 
 forward by a rhythmic wave, or swallowing movement, and 
 the valves are so placed that it must of necessity move in a 
 circle. The peculiarity of the movement consists in the fact, 
 that while one pulsatile cavity closes, another opens ; each 
 cavity opening and closing alternately, and every two cavities 
 reciprocating and co-ordinating to produce a common result. 
 In this way the blood, when expelled by the closing of one 
 chamber, is received by another, which opens for the purpose. 
 The dorsal vessel of the insect thus exerts a pushing and 
 pulling power, similar to that exerted by the oesophagus in 
 swallowing. 
 
 If any one of the pulsating cavities had, when it closed, 
 forcibly to dilate that anterior to it, much power would be 
 lost. The object to be attained by the closing of any one of 
 the cavities is not to dilate that beyond it, but to force on the 
 blood ; and this object is best secured by any two cavities 
 working in unison, the anterior one always opening when that 
 behind it closes. In this way a vis a f route and a vis a tergo 
 is supplied. Each pulsating cavity, when it closes, exerts a 
 pushing power, and, when it opens, a pulling power, so that 
 each bead-like swelling of the dorsal vessel of the insect pos- 
 sesses all the attributes of the most highly differentiated 
 hearts ; in other words, it reverses its movements, so as to 
 work in both directions, at one time acting as a vis a tergo, at 
 another as a vis a fronte. This is a point of very consider- 
 able importance, as it invests pulsating sacs with a double 
 function, literally no power being wasted. In the lobster, 
 
io6 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 Fig- 47- 
 
 where there is only one pulsating sac, the double function is 
 necessary. The arrangement affords a very good example 
 of the conservation of energy in living tissues. 
 
 The heart of the chick greatly resem- 
 bles a segment of the dorsal vessel of the 
 insect. Thus it consists of a tube con- 
 stricted in three portions ; the one por- 
 tion corresponding to the auricle, a second 
 to the ventricle, and a third to the aortic 
 bulb. These have the power of opening 
 and closing rhythmically. The heart of 
 the chick pulsates at a very early period, 
 
 thSy^eventfhourofincubadon! while it is yet B. mass of nucleated cells, 
 SL*TJ*3irV and before muscular fibres are developed 
 
 tion of the heart, c, ventricular 
 ditto, d, bulbus arteriosus. e, e, 
 primitive aortic arches, which sub- 
 sequently unite to [form the de- 
 scending aorta. f,f, omphalo-me- 
 senteric arteries. After Quain. 
 
 in it (Fig. 47). 
 
 Function performed by the Valves. 
 The valves situated between the pulsa- 
 tile sacs of the dorsal vessel of the insect 
 facilitate, as stated, the forward movement, but effectually 
 prevent a retrograde or backward movement. As I shall 
 frequently have occasion to allude to the valves as I proceed 
 with the circulation, it may be as well briefly to refer to them 
 on their first appearance. They consist of crescentic redupli- 
 cations of the lining membrane of the vessels, around the 
 interior of which they are festooned like garlands (Fig. 46, *, 
 X) r, p. 104). They diverge from the interior of the vessel in the 
 direction of its axis, and as they are directed obliquely up- 
 wards and inwards with reference to the axis, they readily 
 admit of the blood passing through them in the one direction, 
 but effectually prevent its return. They may be compared to 
 the folding-doors placed on the floor of a granary, which are 
 opened by each consignment of grain as it is made to pass 
 from a lower to a higher level, but which flap together the 
 instant the grain is elevated to prevent its passing again in a 
 downward direction. They, in fact, permit motion in only 
 one direction. The valves are flexible elastic sluices, which 
 are for the most part opened and closed mechanically by the 
 blood a few being closed partly by muscular movements. 
 The free margins of the valves project into the interior of the 
 vessels to such an extent that when the column of blood is at 
 
PHYSIOLOGY OF THE CIRCULATION. IO/ 
 
 rest, they are more or less in apposition. The slightest reflux 
 therefore instantly and effectually closes them. This action 
 is the more instantaneous from the fact that behind the valves 
 the vessels are scooped out to form sinuses, which contain a 
 large quantity of residual blood ; this, by its mere weight, 
 greatly facilitating the closure. These sinuses I find in both 
 the arteries and veins. They are known in the aorta and 
 pulmonary artery of the human heart as the sinuses of Val- 
 salva (Fig. 49, /, p. 108). The valves are found in infinite variety, 
 and vary as regards the size, shape, number, and structure 
 of their segments in the various orders of animals. As how- 
 ever they all act upon the same principle, and I shall have 
 occasion to describe them minutely hereafter, I shall merely 
 state that, when valves are present, the mystery as to the 
 direction of the current or currents at once disappears ; for 
 it is evident that if a long vessel furnished with valves closes 
 at any given point, the fluid contained in it must move in the 
 direction in which the valves open. ( Vide arrows directed 
 upwards of Fig. 46, * p. 104.) 
 
 The circulation of the insect is remarkable when viewed in 
 connexion with the respiratory system. As you are aware, 
 the body, and indeed every part of the insect, is tunnelled 
 out by an innumerable series of minute elastic tough tubes, 
 the so-called tracheae. By their aid the insect breathes at 
 every pore, very much in the same way that the plant breathes 
 by its vascular and intervascular spaces, when these contain 
 air. This is an interesting circumstance, as it shows the vast 
 importance of constant relays of fresh air for the purposes of 
 the circulation. The presence of air is a sine qua non ; the 
 fish has its gills, the reptiles their branchiae or lungs, and so 
 of the birds and mammals. The respiratory and circulatory 
 systems more immediately connect the living organism with 
 the outer world. In the stems of plants there are large air 
 cavities, and not unfrequently the air and nutritive juices cir- 
 culate together in the vascular bundles. In the lower animals, 
 where the fluids transude, the air enters into combination with 
 them ; and in the higher animals the blood in the lungs and 
 other parts is separated from the air by a membranous film 
 exceedingly delicate in texture. In none of the animals which 
 have hitherto been examined have we met with any one struc- 
 
io8 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 ture which could with propriety be denominated a heart. This, 
 in its simplest form, is to be found in the ascidia, which is 
 provided with a pulsatile sac, consisting of thin membranous 
 walls, apparently devoid of valves. 
 
 Circulation in the Lobster. Position of the Respiratory 
 Apparatus in the Lobster \ Fish, etc. In the lobster a structure 
 is found which may be regarded as a true heart, alike on 
 account of its position and shape, and because of the vessels 
 which proceed from and return to it. The structure in ques- 
 tion is situated below the posterior margin of the thoracic 
 shield, and consists of an oval-shaped cavity or ventricle with 
 muscular walls, as represented at h of Fig. 48. 
 
 4 8. 
 
 Fig. 49- 
 
 Fig. 50. 
 
 Fig. 48 shows the distribution of the blood-vessels in the lobster, a, a, a, a, systemic arteries, 6, b, 
 branchial veins. t>, systemic veins and sinuses, from which the branchial veins arise. /, artery conveying 
 blood to liver and to branchiae. After Thomson. 
 
 Fig. 49. Pulmonic or right side of human heart, e, right auricle, g; right ventricle, a, superior cava. 
 b, inferior cava. c. aorta, d, Pulmonic artery, h, segment of semilunar valve, t. sinus of Valsalva. 
 f, segment of tricuspid valve, j. musculus papillaris. The arrows indicate the direction in which the 
 blood enters and leaves the right or pulmonic heart. After Gray. 
 
 Fig. 50. Heart and vessels of garden -snail, h, auricle, h' ventricle, a, a, arteries, v, -v, -v. veins. 
 b, pulmonary sacs which receive the blood from the veins. After Thomson. 
 
 The heart of the lobster has the power of opening and suck- 
 ing or drawing the blood into it, and of closing and ejecting 
 or pushing the blood out of it. These acts are equally vital 
 in their nature *. It gives off six systemic arteries, these con- 
 
 1 When the heart closes it completely extrudes its contained blood, and is, to 
 all intents and purposes, a solid muscular mass. If it did not open spontaneously, 
 it is obvious that no pressure exerted by the vessels could force the blood into it ; 
 nor must it be overlooked that, in the embryo, the heart acts before it contains 
 blood. The medusa and certain plants, such as the Volvox globator, Gonium pec- 
 torale, and Chlamydomohas, have also the power of opening and closing irrespec- 
 
PHYSIOLOGY OF THE CIRCULATION. 1 09 
 
 veying the blood to the system generally, and to the liver (/). 
 The arterial blood is collected by veins which open into sin- 
 uses situated in the lower or ventral surface of the body. From 
 these the branchial veins, which return the blood which has 
 passed through the gills to the heart, arise. The heart, it will 
 be observed, is a systemic heart, i. e. a heart which forces the 
 blood directly through the arteries, and only indirectly through 
 the veins. It resembles, in some respects, the lymphatic 
 hearts of reptiles and birds. When it closes, the blood is 
 forced from the dorsal to the ventral surface of the lobster, 
 the fluid proceeding simultaneously in the direction of the 
 head and tail. It then flows into sinuses or pouches, from 
 which it passes through the gills on its way back to the -heart. 
 There is as yet no pulmonic heart present, and by this I mean 
 a heart delegated to force the blood directly into the aerating 
 apparatus, whether this takes the form of gills, branchiae, or 
 lungs. The circulation of the lobster, notwithstanding, natu- 
 rally resolves itself into two parts, the presence of gills or 
 aerating structures necessitating this degree of differentiation. 
 The gills or aerating apparatus of the lobster are situated on 
 its ventral surface, and in the track of the venous system, 
 towards its termination ; i. e. they are interposed between the 
 terminal part of the venous system and the heart the blood 
 flowing from the heart towards the system, and from the 
 system towards the gills. The same arrangement obtains in 
 the cephalopoda. In the fish, as I shall show presently, an 
 opposite arrangement prevails, the gills being situated at the 
 beginning of the arterial system ; the blood flowing from the 
 heart (ventricle) towards the gills, and from the gills towards 
 the system. It is therefore a matter of little or no import- 
 ance on what part of the circle representing the circulation 
 the aerating apparatus is situated, so long as it occupies a 
 position favourable to the exposure of the blood to the air. 
 The blood flows in a continuous round, and it suffices if it be 
 aerated at one part of its course, either by the aid of pulmonic 
 sacs, gills, branchiae, or lungs. As the respiratory system be- 
 
 tive of anything they contain. The elasticity of the vessels assists the opening or 
 sucking action of the heart, but does not cause it. When the heart consists of two 
 compartments, one of them closes and pushes while the other opens and pulls, the 
 compartments opening and closing alternately. 
 
IIO PHYSIOLOGY OF THE CIRCULATION. 
 
 comes more differentiated, its connexion with pulsating cavities 
 becomes more intimate. Thus in the bird and mammal the 
 lungs are provided with a heart for themselves the so-called 
 pulmonic or right heart, which consists of two cavities : an 
 auricle which receives the' venous blood fromt he system, and a 
 ventricle which forces the blood directly through the lungs (Fig. 
 49, p. 1 08). The left or systemic heart of the bird and mammal 
 likewise consists of two cavities : an auricle which receives the 
 aerated blood from the lungs, and a ventricle which distri- 
 butes the purified blood to the system. The heart of the 
 bird and mammal consequently each consist of four com- 
 partments. Between the most highly differentiated heart, as 
 found in the bird and mammal and that of the lobster, there 
 is an infinite number of modifications, these mainly depend- 
 ing on the nature of the respiration. Thus in the fish the 
 heart consists of two cavities an auricle and a ventricle ; in 
 the serpent of three two auricles and one ventricle ; in the 
 alligator the cavities virtually amount to four the single 
 ventricle being divided into two by an imperfect septum. It 
 is therefore necessary to bear in mind, when speaking of the 
 heart of animals, that it may consist of one, two, three, or 
 four cavities. 
 
 Circulation in the Brachiopoda and Gasteropoda. The bra- 
 chiopoda have two aortic hearts, i. e. two pulsating cavities 
 situated on the principal artery of the body. The auricle 
 and ventricle of a single complete heart are thus distinctly 
 foreshadowed. Valves are also present. In the gasteropoda 
 and pteropoda, of the former of which the garden-snail may 
 be taken as an example, there is a well-marked auricle and 
 ventricle : the auricle receiving the blood from the pulmonary 
 sacs, which receive it from the veins ; the ventricle forcing 
 it through the arteries (Fig. 50, p. 108). 
 
 In the heart of the garden-snail the movements take place 
 in the same order as in hearts of a higher type. Thus the 
 auricle and ventricle pulsate alternately the auricle closing 
 when the ventricle is opening, and vice versa. The rhythmic 
 peristaltic movement which we beheld in the dorsal vessel 
 of the insect reappears in a slightly modified form, the ver- 
 micular waves of motion being more isolated, and conse- 
 quently more distinct. When a wave movement travels 
 
PHYSIOLOGY OF THE CIRCULATION. Ill 
 
 rapidly forward in a long vessel, it is difficult to say where 
 it begins and where it terminates. This difficulty is in a great 
 measure removed when, as in the present instance, the one 
 cavity is observed to close, and then the other. 
 
 Circidation in the Ciittle-fish. In the cephalopoda, of which 
 the cuttle-fish may be taken as the re- Fi&SI . 
 
 presentative, we find a muscular systemic 
 heart consisting of one cavity. To this 
 may be added two dilated portions in 
 the two vessels which lead to the bran- 
 chiae. These close and open like the 
 heart itself, so that there are virtually 
 two branchial cavities and one systemic 
 one three pulsating cavities in all. The 
 connexion between the circulation and 
 the respiration is now becoming very 
 obvious, and the pulsatile sinuses, sit- 
 uated near the root of the gills, may be 
 
 J Fig. 51. Heart and vessels of 
 
 regarded as harbingers of the pulmonic cuttie-esh. h, heart. <,,<,, Dilated 
 
 * portions of vessels which lead to 
 
 or right heart, as it exists in the bird branchiae. *,*;*, Abranchial v es - 
 
 sels. a, a, arteries, -v, v, veins. 
 
 and mammal (Fig. 51). After 
 
 CIRCULATION IN ANIMALS (Vertebrata). 
 
 Hitherto we have been dealing with the invert ebrata. In 
 my remarks on the circulation of those most interesting and 
 variously-constituted creatures, I have confined myself to no 
 zoological classification, but have picked up a link of the 
 chain wherever I found a suitable one. I have been able to 
 show a gradual development of, and differentiation in, the 
 channels and forces of the circulatory apparatus. 
 
 In the circulation of the vertebrata, to an examination of 
 which I now hasten, I shall be able to show a still higher 
 degree of differentiation not so much of the forces them- 
 selves, as of the organs or instruments by which the forces 
 make themselves manifest. 
 
 Circulation in the Fish. In the fish we find a muscular 
 heart consisting of two cavities, an auricle and a ventricle. 
 The auricle receives the venous blood from the liver and the 
 
112 PHYSIOLOGY OF THE CIRCULATION. 
 
 system generally, the ventricle forcing the blood through 
 the capillaries of the gills (where it is aerated), into a large 
 artery, which may be regarded as the homologue of the de- 
 scending aorta in mammals. The blood contained in the 
 great dorsal artery of the fish is arterial, that in the veins and 
 heart venous (Fig. 52, p. 114). In addition to its general or 
 major circulation, the fish has two special or minor circula- 
 tions ; viz. a circulation through the kidneys, and another 
 through the liver. These minor circulations reappear in the 
 reptiles, and are interesting, the more especially as the portal 
 circulation is also to be found in the mammal. When the 
 major circulation is once determined, any number of minor 
 circulations may be added without greatly increasing the 
 complexity. The major circulation, as has been explained, 
 may be represented by a circle the minor circulation, by 
 one or more loops grafted on the original circle. These 
 loops may be added at any part, and may be increased in- 
 definitely. Thus there may be a capillary circulation, a renal 
 circulation, a portal circulation, a pulmonic circulation, a 
 cephalic circulation, and so on. 
 
 The respiratory apparatus of the fish is placed on the 
 arterial system. In the lobster and cuttle-fish, as has been 
 shown, it is placed on the venous. This however occasions 
 no difficulty. The heart of the fish, while consisting of only 
 two cavities, has accessory structures of considerable import- 
 ance attached to it. Thus the auricle is provided with a 
 great venous sinus, which collects the blood destined to fill 
 the auricle ; while the ventricle is furnished with a muscular 
 pulsatile organ, the so-called bulbus arteriosus, which assists 
 the ventricle in forcing the blood through the gills. These 
 several structures are deserving of separate description. The 
 venous sinus, like its congeners, is a mere irregular dilata- 
 tion or swelling, occasioned for the most part by the con- 
 verging and flowing together of the principal venous trunks 
 of the system. It may be compared to the venae cavae of 
 the mammal. The auricle is a somewhat irregularly shaped 
 oval or angular chamber, having exceedingly thin muscular 
 walls. The muscular fibres entering into its formation pursue 
 no definite direction, but are grouped in such a manner as 
 to secure great strength, and a large degree of pulsatile 
 
PHYSIOLOGY OF THE CIRCULATION. 113 
 
 power. The shape of the ventricle in the most muscular 
 fishes is that of an inverted three-sided pyramid. 
 
 In the heart of the salmon, which I have had an oppor- 
 tunity of dissecting, the ventricular walls are composed of 
 muscular fibres which run in three well-marked directions, 
 viz. vertically, transversely, and from without inwards. The 
 vertical fibres are found on the outside and inside of the 
 ventricle. In addition to being vertical they are also slightly 
 plicate, a certain number of them passing through the wall 
 of the ventricle, in a direction from without inwards or the 
 converse. The vertical fibres, which may be regarded as 
 forming an external and internal layer, are in many cases 
 continuous at the base and apex of the ventricle. The trans- 
 verse fibres occupy a central position in the ventricular wall, 
 and pursue a more or less circular direction. The fish is 
 thus supplied with an organ of great power, capable of open- 
 ing and closing with a steady rhythmic movement. The 
 bulbus arteriosus resembles, in its general appearance, the 
 bulb of a hyacinth. It is muscular, and has a structure in 
 many cases analogous to the ventricle itself. It receives the 
 blood from the heart, and assists in forcing it through the 
 capillaries of the gills, and thence through the system. A 
 careful examination of the movements of the heart and bulbus 
 arteriosus in the living pike, eel, trout, flounder, cod, etc., 
 has convinced me that the ventricle and venous sinus close, 
 when the auricle and bulbus arteriosus open, and vice versa. 
 The auricle supplements, as it were, the movements begun 
 by the veins and venous sinus ; the ventricle, those com- 
 menced by the auricle ; and the bulbus arteriosus, those com- 
 menced by the ventricle. The relation of the auricle, ven- 
 tricle, and aortic bulb to each other is to be inferred from the 
 presence of valves between these structures, an arrangement 
 which provides for combined and independent movements. 
 Nor is this arrangement uncalled for. The close proximity 
 of the gills to the heart would expose the capillaries of the 
 gills to rupture if the ventricle closed with the violence 
 necessary to force the blood through the entire system. This 
 danger is averted by employing a second pulsatile cavity 
 (the bulbus arteriosus), which, closing as it does with less 
 vigour than the ventricle, keeps up but modifies the pressure 
 
 I 
 
114 PHYSIOLOGY OF THE CIRCULATION. 
 
 within the required limits. We have an example of what 
 mischief may be done by a too sudden and too violent closure 
 of a pulsating cavity in the vicinity of capillaries, in cases of 
 hypertrophy of the right ventricle of the human heart, where 
 the pressure exerted not unfrequently produces rupture of 
 the capillaries of the lungs the pulmonary apoplexy of pa- 
 thologists. The branches of the bulbus arteriosus correspond 
 for the most part to the number of gill-plates ; these in the 
 cod-fish amounting to four on either side. The number of the 
 branches vary : thus in the Lophius piscatorius there are only 
 three, in most osseous fishes four, in the skates and sharks 
 five, and in the lampreys six and seven. It is most interest- 
 ing to observe that the arrangement of the vessels at the arterial 
 bulb, and the beginning of the descending aorta, if we may so 
 call it, is the same ; the gills or respiratory system being intro- 
 duced into the circulatory system as it were accidentally, or 
 by the way. Thus, in the cod-fish, there are four main vessels 
 given off from the top of the bulb on either side to the gills, a 
 corresponding number being given off from the gills to consti- 
 tute the first part of what may be regarded as the descending 
 aorta. (Cp. parts marked #, #, , b of branchial plate Fig. 52.) 
 The arterial bulb of the fish is, in some respects, a re- 
 Fig. 5*. markable structure. It is especially so as 
 
 regards the number and nature of the 
 valves contained in its interior. These vary- 
 in number, size, and shape, their segments 
 ranging from two to thirty-two. In fact, 
 in this single structure, every valve in the 
 animal series is either indicated or actually 
 represented. I defer a consideration of 
 them till I come to speak of the valves 
 as a whole. The number of the valves is 
 in some measure necessitated by the pul- 
 sating properties of the bulb, and the pe- 
 5 2.-Heart and vessels cuHar form of the respiration in fishes. 
 
 of the fish (cod), h, ventricle i 
 
 with auricle behind, a', buibus The closins p of the bulb is apt to interfere 
 
 arteriosus. giving off four bran- & 
 
 chiai vessels (*). These con- w ith the perfect action of the valves, and the 
 
 verge to form the first part of 
 
 f & v d s e ^tTmte*etof r ( *' ^' Proximity to the heart of the capillary ves- 
 
 from liver (/). iddneys.etc. SG \ S of the gills predisposes to regurgitation. 
 In either case an increase in the number of valves is demanded. 
 
PHYSIOLOGY OF THE CIRCULATION. 11$ 
 
 The subjoined account of the movements of the heart of 
 the fish, taken from life, may prove interesting. The move- 
 ments are rhythmical in character, and occur as follows : 
 
 The large veins at the base of the heart close slowly and 
 become paler in colour ; the auricle opening and becoming 
 darker in colour. The auricle then closes energetically and 
 suddenly, and changes from a dark purple colour to a reddish 
 hue, the ventricle opening and assuming a dark purple colour. 
 The ventricle now closes suddenly with a vermicular or wave- 
 like motion, and assumes a reddish tinge, the arterial bulb 
 opening and becoming of a purple colour. The bulb when 
 it closes changes from a purple to a bluish or pearly white 
 colour. The change of colour in the parts referred to is due 
 to the presence or absence of blood in their interior. The 
 veins and ventricle close when the auricle and arterial bulb 
 open, and the veins and ventricle open when the auricle 
 and arterial bulb close. The movements of the veins and 
 ventricle co-ordinate those of the auricle and arterial bulb. 
 There are no dead points. Before the veins have ceased to 
 close, the auricle begins to open ; before the auricle has 
 ceased to close, the ventricle begins to open ; before the 
 ventricle has ceased to close, the bulbus arteriosus begins to 
 open ; and so on in regular and uninterrupted succession. 
 It occasionally happens when the heart is more or less de- 
 prived of blood and acting slowly that the auricle opens before 
 the veins close, the ventricle in like manner opening before 
 the auricle closes ; a circumstance which, in my opinion, 
 proves that the opening of the auricle and of the ventricle is a 
 vital act, in the same sense that the closing of each is a vital 
 act. In other words, the opening of the auricle is not due to 
 the closing of the veins, neither is the opening of the ventricle 
 due to the closing of the auricle. The one movement con- 
 tributes to the other, but does not cause it. 
 
 The auricle and ventricle (particularly the latter) open 
 with considerable energy, so much so that the expansile 
 movement may be felt when the heart is grasped between 
 the finger and thumb. 
 
 The veins and arterial bulb shorten when they open, and 
 elongate when they close. The auricle and ventricle, on the 
 -ther hand, elongate when they open and shorten when they 
 
 I 2 
 
Il6 PHYSIOLOGY OF THE CIRCULATION. 
 
 close. This difference is due to an excess of circular fibres 
 in the veins and bulb, as compared with the number of 
 these fibres found in the auricle and ventricle. The veins, 
 auricle, ventricle, and arterial bulb, are highly expansile. 
 They flatten slightly when they open, and become rounded 
 when they close. They increase and decrease by about a 
 third during these movements. The veins act with less 
 energy than the bulb, the bulb than the auricle, and the 
 auricle than the ventricle. The action of the bulb is slow and 
 sustained rather than rapid and violent. The auricle, ven- 
 tricle, and bulb, empty themselves of blood when they close. 
 
 The ventricle when closing rotates and screws slightly in the 
 direction of its length. It also becomes shorter and narrower. 
 The apex of the ventricle describes an ellipse when the 
 ventricle is opening and closing. 
 
 Fig . 53 . I annex a diagram of the ellipse 
 
 as bearing upon the much-disputed 
 question of the impulse of the heart. 
 The letter e (Fig. 53) represents the 
 position assumed by the apex at the 
 time the ventricle is closed and empty 
 of blood. When the ventricle opens 
 and receives the blood from the au- 
 ricle, the apex travels in the direction 
 e, a, and suddenly descends in a 
 
 downward and outward direction, as shown at a, b. When 
 the ventricle closes and ejects its blood, the apex describes 
 the segment of the ellipse b t c, d, e, it being thus drawn out- 
 wards, upwards, and inwards. The apex impinges against the 
 thorax when it is describing the part of the ellipse a, b, c, d, 
 and more particularly at b, c. There is no pause in the 
 action of the ventricle from the time the apex leaves the 
 point e until it returns to it. The ventricle expands between 
 the points e and b. The ventricle as a whole flattens itself 
 at this stage, and recedes from the anterior wall of the thorax, 
 but its apex advances slightly towards it. The auricle closes 
 when the apex of the ventricle is travelling from e to b\ 
 and at this time the ventricle is most full of blood. The 
 ventricle begins to close when the apex reaches b, the clos- 
 ing becoming more complete as the apex travels in the 
 
PHYSIOLOGY OF THE CIRCULATION. 1 1/ 
 
 direction b t c, d, e. At e the closure is perfect and the ven- 
 tricle empty of blood. From this it follows that the impulse 
 of the heart of the fish corresponds neither to the diastole 
 nor the systole of the ventricle, but to the termination of 
 the diastole and the beginning of the systole. Of this I have 
 fully satisfied myself. 
 
 Circulation in the Aquatic Reptiles. I now pass to the 
 circulation in the aquatic reptiles, as it is found in the axolotl, 
 proteus, menobranchus, siren, the larva of the frog, salamander, 
 etc. The gills in the axolotl and allied forms are situated 
 outside the body, and are persistent. The gills of the larva 
 of the frog, on the contrary, become covered as the animal 
 develops, so that they assume the position and function of 
 the gills in the fish. The heart in the protean reptiles con- 
 sists usually of three cavities, viz. two auricles and a ventricle. 
 The great point of interest in these remarkable creatures is 
 the position of the gills, and the mixing of the arterial and 
 venous blood in the ventricle. This is effected in the follow- 
 ing manner : The bulbus arteriosus, which may be compared 
 to the first part of the aorta in mammals, divides into two ; 
 each division giving off three or more branches on either 
 side, which extend along the arches formed by the hyoid 
 bones, and break up into innumerable loops, to form the ex- 
 ternal gills, two branches, when lungs are present, going to 
 them. The lateral vessels pass through the gills in a direction 
 from before backwards, and reunite to form the descending 
 aorta, so that the gills or respiratory apparatus is situated 
 on the arterial or systemic system of vessels, as in the fish. 
 When lungs are present they are furnished with pulmonary 
 veins which proceed direct to the heart. 
 
 The blood is projected from the ventricle into the capil- 
 laries of the gills and lungs. As the vessels from the gills 
 reunite to form the descending aorta, the blood in the de- 
 scending aorta is consequently red or arterialised blood. This 
 pervades the entire body, and is returned to the right auricle 
 by the systemic veins. The blood which circulated through 
 the lungs is returned to the left auricle by the pulmonic 
 veins. When the auricles close, the right one discharges 
 venous blood into the ventricle, the left one arterial blood ; 
 the arterial and venous blood being mixed up in the 
 
Il8 PHYSIOLOGY OF THE CIRCULATION. 
 
 ventricle accordingly. This result is facilitated by the fact 
 that the interior of the ventricle presents a fretted, uneven, 
 or broken surface, which is especially adapted for the tritu- 
 rating or mixing process. In some of the protean reptiles 
 arterial twigs pass directly from the aortic bulb to the de- 
 scending aorta. In such cases the blood is mixed in the 
 descending aorta as well as in the heart ; the blood which 
 circulates through the body being partly arterial and partly 
 venous. (Fig. 54.) 
 
 Fi S- 54- Fig. 55. 
 
 r Fig. 54 Heart and vessels of axolotl. h, ventricle, m, right auricle, receiving venous blood from the 
 system generally (v, -v). n, vessels from gills conveying arterial blood to the left auricle, a (superior), 
 aortic bulb, dividing into eight branches, six of which go to the gills (), and two to the lungs (/, /). 
 a (inferior), descending aorta, formed by the reunion of the vessels which go to the gills. /, veins from, 
 liver. After Thomson. 
 
 Fig. 55. Heart and vessels of frog, h, ventricle with auricles above and behind, a', aortic bulb 
 splitting up into branches to supply the system and lungs. Of these some (a") unite to form the descend- 
 ing aorta (a) ; others (those from the first part of the aortic bulb) going directly to the lungs, v, v, 
 systemic veins. /, u, k, vessels going therefrom to the liver and kidneys. After Thomson. 
 
 Circulation in the Frog. Leaving the aquatic reptiles, 
 which respire principally by gills, I come to speak of those 
 which respire by means of lungs, such, for example, as the 
 chelonia, ophidia, and sauria. The adult frog naturally in- 
 troduces us to this group. In the frog the circulation is very 
 similar to that just described. Here the heart, as in the 
 protean reptiles, consists of three cavities, two auricles and 
 one ventricle. The lungs derive their vessels directly from 
 the first part of the aorta, branches from the aortic arches 
 uniting to form the descending aorta. The venous blood 
 from the system returns to the right auricle, the arterial 
 blood from the pulmonic veins returning to the left. When 
 the auricles close, the blood is mixed in the ventricle as 
 
PHYSIOLOGY OF THE CIRCULATION. 119 
 
 before. The venous blood, while making the circuit of the 
 system, circulates by a special arrangement through the kid- 
 neys and the liver (Fig. 55). 
 
 The following description of the movements of the heart 
 of the frog is taken from notes made during the life of the 
 animal. The observations on which the description is based 
 were made with extreme care on a large healthy frog im- 
 mediately after capture, and before and after the pericardium 
 was removed. The rhythm of the frog's heart essentially 
 consists of four stages, traceable to the movements of the 
 veins at the base of the heart, and to the movements of the 
 auricles, ventricle, and bulbus arteriosus. The movements 
 are essentially wave-like in character, the blood being forced 
 through the structures referred to, by a kind of swallowing 
 movement. The veins, auricles, ventricle, and arterial bulb, 
 act in pairs, as in the beaded dorsal vessel of the insect. 
 Thus when the veins close, the auricles open ; when the 
 auricles close, the ventricle opens ; when the ventricle closes, 
 the aortic bulb opens ; when the aortic bulb closes, the 
 veins open ; and so on in endless succession. These are vital 
 movements, and go on when the heart is deprived of blood. 
 From this it follows that the veins and ventricle open and 
 close together ; the auricles and bulbus arteriosus opening 
 and closing together. As however the auricles open when 
 the veins close, and the ventricle opens when the auricles 
 close, while the arterial bulb opens when the ventricle closes, 
 and the veins open when the aortic bulb closes, the sucking 
 and propelling action of the various chambers through which 
 the blood passes is brought fairly and fully into play. The 
 blood is passed on by a series of definitely co-ordinated 
 movements. When the heart is acting normally, one or other 
 part of it is always moving. The instant the large veins 
 begin to close, the auricles begin to open ; and the moment 
 the auricles begin to close, the ventricle begins to open. 
 When the ventricle begins to close, the aortic bulb begins 
 to open ; and when the aortic bulb begins to close, the veins 
 begin to open ; and so on ad infinitum. It follows from 
 this that the sounds of the heart are more or less continuous. 
 The veins close slowly, the auricles somewhat suddenly ; the 
 ventricle less suddenly than the auricles, and the bulbus 
 
120 PHYSIOLOGY OF THE CIRCULATION. 
 
 arteriosus less suddenly than the ventricle. The closure of 
 the arterial bulb is a slow sustained movement. The veins 
 and auricles open slowly, the ventricle somewhat suddenly ; 
 the aortic bulb opens less suddenly than the ventricle, but 
 more suddenly than the auricles. 
 
 When the veins close they become of a peach colour, the 
 auricles assuming a deep purple colour from the blood which 
 they contain shining through their semi-transparent walls. 
 When the auricles close a dark wave of blood is seen to enter 
 the ventricle, the auricles becoming of a reddish, the ventricle 
 of a purple, colour. When the ventricle closes it becomes pale 
 red, the aortic bulb, when it opens, becoming a pale purple ; 
 when the aortic bulb closes it becomes of a bluish or pearly 
 white colour, the veins at the base of the heart becoming a 
 deep purple,. The colour of the parts referred to depends upon 
 the thickness of their walls and the quantity of blood which 
 they contain at any given time. The veins, auricles, ventricle, 
 and arterial bulb, each reduce themselves by about a third 
 when they close ; they increase by a corresponding amount 
 when they open. The different parts of the heart open and 
 close by progressive wave-movements. The opening move- 
 ment is centrifugal in character, the closing one centripetal. 
 These are the only movements which can increase and diminish 
 hollow chambers. Similar movements, are observed in the 
 opening and closing of the mushroom-shaped disc of the 
 medusa, and the vacuoles or spaces of certain plants ; those, 
 for instance, of the Volvox globator, Gonium pectorale, and 
 Chlamydomonas. The presence of muscular fibres is not 
 necessary to such movements. The ventricle opens more 
 suddenly than it closes ; a remark which also holds true of 
 the bulbus arteriosus. When the ventricle opens it flattens, 
 its long diameter being increased ; when it closes it becomes 
 rounded, its long diameter being diminished. The apex and 
 anterior wall of the ventricle strike the thoracic parietes 
 towards the end of the diastole, and the beginning of the 
 systole, as in the fish. At this period the apex descends and 
 advances towards the thorax. The apex during the diastole 
 and systole describes an ellipse (Fig. 53, p. 116). The ventricle 
 rotates slightly from right to left during the diastole, and from 
 left to right during the systole. 
 
PHYSIOLOGY OF THE CIRCULATION. 121 
 
 The long diameters of the veins and auricles increase when 
 those of the ventricle and bulbus arteriosus decrease, and the 
 converse, the contents of the pericardium remaining nearly 
 always the same. 
 
 The subjoined account of the movements of a snake's heart, 
 written in 1865, is abstracted from my note-book : When the 
 heart is exposed, the auricles and ventricle are observed to 
 open and close alternately. The movements in both cases 
 are exceedingly slow, and apparently of about the same dura- 
 tion. The auricles and ventricle, particularly the latter, close 
 in every direction viz. from above downwards, from below 
 upwards, and from without inwards. When the ventricle closes 
 its anterior wall advances and strikes the internal surface of 
 the thoracic parietes, the impulse being communicated during 
 the ventricular systole. 
 
 The reptiles, which breathe chiefly by lungs, exhibit very 
 considerable variation as to the structure of their hearts, the 
 principal feature in which is the possession by many of a more 
 or less complete septum ventriculorum. In this class the heart 
 has virtually another cavity added to it ; and it will be seen, 
 that in proportion as the septum of the ventricle is rudimentary 
 or complete, the circulation gradually advances from a single 
 or mixed circulation to a double one ; i. e. a systemic and 
 pulmonic. 
 
 Circulation in Lacerta ocellata. In the Lacerta ocellata a 
 rudimentary septum makes its appearance. 
 
 It virtually divides the ventricle into two portions, these 
 corresponding to the right and left ventricles of the bird and 
 mammal. This necessitates a considerable modification in the 
 arrangement of the great vessels at the base of the heart. In 
 the fish, and protean reptiles, only one vessel proceeds from 
 the ventricle, but in the present instance the anterior or right 
 compartment of the ventricle gives off the pulmonic vessels, 
 while the posterior or left compartment gives off the systemic. 
 Provision is thus made to a great extent for a distinct pul- 
 monic and systemic circulation, the right side of the ventricle 
 forcing the blood through the lungs, the left side forcing it 
 through the system generally. Before leaving the heart of the 
 Lacerta ocellata, it is interesting to observe, that while the 
 vessels emanating from the base of the ventricle are modified 
 
122 PHYSIOLOGY OF THE CIRCULATION. 
 
 to suit the requirements of the almost double circulation, they 
 nevertheless present in their groupings the general appearance 
 presented by the branchial vessels of the fish where the circu- 
 lation is single. We have here the remnants of an earlier 
 form. 
 
 Circulation in the Python, Crocodile^ etc. Presence of Septum 
 Ventrictdorum. In the heart of the python the septum ven- 
 triculorum is nearly complete; in fact, the right and left 
 ventricles would be quite distinct but for the existence of a 
 small spiral slit in the septum posteriorly. 
 
 In the heart of the crocodile (Crocodilus Lucius] the septum 
 ventriculorum, as was pointed out by Hentz and Meckel, is 
 fully developed, so that the ventricles of this animal are as 
 perfect as those of either the bird or mammal. The object to 
 be gained by dividing the heart into four distinct compart- 
 ments is obvious. By having two auricles and two ventricles, 
 one auricle and one ventricle can be delegated to receiving the 
 venous blood from the veins and forcing it through the lungs ; 
 the remaining auricle and ventricle receiving the arterial blood 
 from the lungs, and forcing It through the system generally. 
 The lungs on the one hand and the body on the other are 
 each provided with a heart ; hence the epithet double circula- 
 tion, or, what is the same thing, pulmonic and systemic 
 circulation. The peculiarity of the double circulation con- 
 sists in the fact that the arterial and venous blood circulate 
 separately as such, and are not mixed either in the heart or 
 the vessels. This object, of course, can only be attained by 
 increasing the chambers of the heart, and by keeping them 
 separate from each other. 
 
 FOETAL CIRCULATION. 
 
 Points of Analogy between the Circulation in Reptiles and 
 that in the Pluman Foetus. It is not a little curious, that in 
 the foetal life of mammals many of the peculiarities of the 
 reptilian circulation reappear. Thus in the foetus the auricles 
 communicate with each other by means of the foramen ovale, 
 and the great vessels of the ventricles communicate by means 
 of the ductus arteriosus 1 . 
 
 1 These openings occasionally remain pervious in the adult. 
 
PHYSIOLOGY OF THE CIRCULATION. 123 
 
 In the foetus, therefore, the blood in the auricles and great 
 vessels of the ventricles becomes more or less mixed up. As 
 I pointed out on a former occasion, it is a matter of indifference 
 where the respiratory apparatus is situated. It may occur 
 in the venous system, as in the lobster and doris ; or in the 
 arterial system, as in the fish. The respiration of the mam- 
 malian foetus affords a striking illustration of the accuracy of 
 this observation. In the foetus in utero the pulmonary organs 
 perform no function whatever. They are ready for work, but, 
 being in an unexpanded condition, are incapacitated. The 
 arterialisation of the blood is therefore effected indirectly by 
 the placenta, which is a temporary structure. To meet the 
 requirements of such an arrangement, the uterine vessels 
 of the mother, and the vessels of the foetus, are specially 
 modified. 
 
 The foetal circulation naturally resolves itself into two kinds, 
 viz. the circulation within the body of the foetus, carried on 
 principally by the agency of the foetal vessels and heart (these 
 constituting the visible forces) ; and the circulation within the 
 placenta and the tissues of the foetus generally, carried on for 
 the most part by absorption, evaporation, endosmose, exos- 
 mose, capillarity, chemical affinity, nutrition, etc. (these con- 
 stituting the invisible forces). I shall first deal with the visible 
 circulation as it exists within the body of the foetus, after which 
 I shall proceed to examine the invisible circulation as it exists 
 within the placenta. 
 
 Circulation in the Body of the Foetus. The circulation within 
 the body of the foetus is a closed circulation ; i. e. its vessels 
 and capillaries are continued upon themselves in such a manner 
 as to form a series of circles of greater or less magnitude the 
 blood flowing within those circles in one continuous round. 
 The blood is a mixed blood, being partly arterial and partly 
 venous, the mixing taking place in the vessels and within the 
 heart. 
 
 A mixed circulation amply meets the requirements of the 
 foetus, and is a positive advantage, as it places the foetus in the 
 condition of the reptilia, which are very tenacious of life, and 
 endure much hardship without sustaining positive injury 
 qualities of the utmost importance to the foetus in utero, the 
 position of which is being constantly changed. 
 
124 PHYSIOLOGY OF THE CIRCULATION. 
 
 The foetal circulation differs from the reptilian circulation, 
 as to the temperature of the fluid circulated (the one being a 
 cold, the other a warm blood) ; likewise as to the nature of 
 the aerating apparatus, the blood of the foetus not being 
 aerated by branchiae or lungs, but by the placenta, a tem- 
 porary structure, improvised for the purpose. That the 
 placenta performs the office of a lung to the foetus is in great 
 measure proved by the fact that if the umbilical cord be com- 
 pressed before delivery the child makes vigorous efforts to 
 respire by the mouth 1 . The placenta has for its object the 
 close apposition of the capillary vessels of the mother and 
 foetus ; this apposition enabling the foetus to avail itself in- 
 directly of the lungs of the mother. The foetal circulation 
 further differs from the reptilian in the important circumstance 
 that the blood circulated is not produced and nourished by 
 food taken into the alimentary canal, but by material absorbed 
 from without ; this material, in the later stages of pregnancy, 
 being supplied by the blood in the uterine capillary vessels, 
 and by the utricular glands of the mother, and applied 
 indirectly by absorption, osmosis, capillarity, chemical affinity, 
 etc., to the capillary vessels or villous tufts of the foetal portion 
 of the placenta. The foetus in this way indirectly avails itself 
 of the stomach as well as of the lungs of the mother. The 
 placenta consists of two elements ; a maternal element and a 
 foetal element, and the function performed by it is essentially 
 that of an alimentary canal and a lung. Professor Goodsir 
 observes that ' the external cells of the placental villi perform 
 during intra-uterine existence a function for which is sub- 
 stituted, in extra-uterine life, the digestive action of the gastro- 
 intestinal mucous membrane. The internal cells of the pla- 
 cental villi perform during intra-uterine existence a function 
 for which is substituted, in extra-uterine life, the action of 
 the absorbing chyle cells of the intestinal villi. The placenta 
 therefore not only performs, as has been always admitted, the 
 function of a lung, but also the function of an intestinal tube 2 .' 
 
 1 See a remarkable case related by Hecker, and the experiments of Schwartz, etc. 
 Vide Casper's Forensic Medicine (New Sydenham Society's Transactions, vol. ii. 
 p. 1 28, and vol. iii. p. 38). 
 
 2 Structure of the Human Placenta, by John Goodsir, Esq., F.R.S.L. and E., etc. 
 'Anatomical Memoirs,' p. 460; 1845. 
 
PHYSIOLOGY OF THE CIRCULATION. 12$ 
 
 Between the maternal and foetal portions of the placenta 
 there is a line of demarcation, well marked in the earlier stages 
 of pregnancy, but blurred and confused in the later stages ; 
 partly because of the very intimate and accurate apposition of 
 the two parts of the placenta, which in not a few instances 
 gives rise to abnormal adhesions ; and partly because of the 
 serrated nature of the opposing surfaces, and the presence of 
 certain secretions. The line referred to forms at once the 
 natural line of junction and separation between the mother 
 and foetus, and in a perfectly healthy parturition the foetal 
 portion of the placenta parts from the maternal portion in such 
 a manner as not to rupture or destroy to any extent the 
 mucous lining and capillary vessels of the uterus of the mother. 
 On the other hand, the mucous lining and villous tufts of the 
 foetal portion of the placenta likewise remain intact. This 
 accounts for the fact that in the lower animals, and in a per- 
 fectly healthy human female, there is little if any haemorrhage 
 at parturition. The relation which the foetus bears to the 
 mother is that which the plant bears to the ground and the 
 air ; and that which the tissues of the adult animal bear to its 
 alimentary canal and lungs, through which it obtains its 
 nourishment and its breath. The capillary or villous tufts of 
 the foetal portion of the placenta represent the roots of the 
 plant ; the corresponding capillary tufts of the maternal portion 
 of the placenta, the ground and atmosphere on which the 
 plant subsists. The foetus is in this sense to be regarded as 
 a parasite, for it is a living thing living upon another living 
 thing. This explains why a foetus can take root and live 
 upon other mucous surfaces than those supplied by the uterus, 
 as, for example, those of the Fallopian tube ; and I can quite 
 understand that the foetus would thrive on certain portions of 
 the mucous lining of the alimentary canal, if we could only 
 succeed in making a natural transference. 
 
 It is this intimate yet independent existence which enables 
 us to consider the circulation of the foetus as a thing per se. 
 If we examine the foetal portion of the placenta we find that 
 the arteries and vein of the umbilical cord split up into innu- 
 merable capillary tufts, these minute vessels opening into and 
 freely anastomosing with each other. While the capillary 
 vessels of the foetal portion of the placenta communicate with 
 
126 PHYSIOLOGY OF THE CIRCULATION. 
 
 each other, they do not communicate with corresponding 
 vessels in the maternal- portion of the placenta ; so that the 
 foetal blood, impelled by the foetal heart and other forces, 
 flows in a circle and gyrates in the body of the foetus pre- 
 cisely as in the adult. The presence of the umbilical vessels 
 and other foetal structures, and the opening of the chambers 
 of the foetal heart directly and indirectly into each other, do 
 not affect this gyration. We may begin at any part of the 
 circle, but where we begin we must end, if we follow up the 
 course of the blood. The umbilical vein, for example, extends 
 between the placenta and the liver. It conveys arterial blood 
 to the liver 1 , and the ductus venosus (a foetal structure), which 
 opens into the upper part of the vena cava inferior. In this 
 latter situation the arterial blood originally supplied by the 
 umbilical vein is mixed with the venous blood of the vena 
 cava inferior. The vena cava inferior opens directly into the 
 right auricle, and indirectly into the left auricle by the foramen 
 ovale (a foetal aperture). The Eustachian valve is, however, 
 so placed that comparatively little of the blood (some say 
 none) from the inferior cava finds its way into the right 
 auricle, by much the greater portion passing through the 
 foramen ovale into the left auricle. We have now got the 
 mixed blood supplied by the upper portion of the inferior cava 
 in the left auricle. This passes by the left auriculo-ventricular 
 opening into the left ventricle. It proceeds thence into the 
 arch of the aorta, and the right and left carotid and subclavian 
 arteries ; the head and superior extremities of the foetus, which 
 are comparatively very large and well nourished, being supplied 
 by a purer blood than that furnished to the trunk and lower 
 extremities. The blood returns by the jugular and subclavian 
 veins, and vena cava superior, to the right auricle. It then 
 passes through the right auriculo-ventricular opening into the 
 right ventricle. It is impelled thence into the pulmonary 
 artery ; but as the lungs of the foetus are in an unexpanded 
 condition, and only receive so much blood as suffices for their 
 nutrition 2 , the circulation would be stopped in this direction 
 
 1 The arterial blood supplied to the liver is returned to the inferior cava by the 
 hepatic veins. 
 
 2 In the foetus in utero, the pulmonary organs take no part in the aeration of. 
 the blood. They are ready for work, but being unexpanded are incapacitated. 
 
PHYSIOLOGY OF THE CIRCULATION. I2/ 
 
 but for the existence of a temporary canal, the so-called ductus 
 arteriosus, which unites the pulmonary artery and aorta at the 
 aortic arch. Through this canal the more strictly venous 
 blood from the head, superior extremities, and right side of 
 the heart, finds its way. The venous blood from the right 
 side of the heart, and the nearly pure arterial blood from the 
 left side, are thus a second time mixed. (The venous and 
 arterial blood were first mixed in the upper part of the'vena 
 cava inferior.) The blood, doubly diluted as it were, proceeds 
 through the descending aorta and supplies the trunk, viscera, 
 and lower extremities. The passage of the blood through the 
 foetal heart is indicated by the arrows in Fig. 56. It is not 
 
 Fig. 56. 
 
 Fig. 56. Diagram of the course pursued by the blood in the foetal heart, y, superior cava, the blood 
 from which passes into the right auricle ; thence into the right ventricle (q) ; thence into the pulmonary 
 artery (v) ; and thence into the ascending () and descending aorta (m). o, inferior cava, the blood from 
 which passes behind the Eustachian valve (j of Fig. 57, A, p. 129), through the foramen ovale, to the left 
 auricle ; thence to the left ventricle (r) ; and thence to the ascending (u) and descending (m) aorta. 
 u, arch of aorta and its branches. (Compare with similar letters of Fig. 57, A, p. 129.) 
 
 necessary to describe the circulation in the lower extremities 
 at length. All that I wish to impress upon you is, that the 
 foetal circulation is a complete or closed circulation. The 
 aorta at its lower part divides into the common iliac arteries, 
 which subdivide into the external, internal, and hypogastric 
 arteries ; the two former supplying the inferior extremities 
 with blood. The venous blood is returned by the correspond- 
 ing veins to the inferior cava, where it is joined by the arterial 
 blood originally supplied by the umbilical vein. This com- 
 pletes one cycle of the circulation. The other cycle is formed 
 
 The probabilities are that the lungs, towards the full term, perform rhythmic 
 movements -in anticipation of the function to be performed by them after birth, 
 in the same way that the heart pulsates while yet a solid mass, and before it 
 contains blood. 
 
128 PHYSIOLOGY OF THE CIRCULATION. 
 
 by the hypogastric and umbilical arteries and vein, these con- 
 stituting a very remarkable system of temporary canals ; fur- 
 ther proving, if more proof were required, that the chief function 
 of the vessels is to convey the blood and nutritious juices 
 through long distances. Vessels, as has been already shown, 
 are not necessary to the circulation in the tissues. The 
 chief point of interest in the foetal circulation, as far as the 
 heart is concerned, consists in the right and left auricles open- 
 ing directly into each other by the foramen ovale ; the right 
 and left ventricles opening indirectly into each other by the 
 ductus arteriosus, which unites their great vessels together. 
 
 The peculiarities of the circulation within the body of the 
 foetus are shown at Fig. 5 7, A ; those of the circulation within 
 the placenta, at Fig. 57, B (vide arrows). 
 
 Circulation in the Placenta. The foetal circulation thus far 
 is not difficult to comprehend. The really difficult problem, 
 and consequently the really interesting one, is the relation 
 which the foetal circulation bears to the maternal circulation. 
 I have explained that the vessels of the mother and foetus 
 remain quite distinct in the placenta, and that in reality they 
 are merely placed in intimate and accurate apposition. I wish 
 you to bear this fact constantly in mind. To understand this 
 relation it will be necessary to recapitulate shortly, and to 
 point out the relation which the external and internal surfaces 
 of animals i.e. skin and mucous membranes bear to each 
 other, and to corresponding parts of plants. 
 
 On a previous occasion I directed attention to the ana- 
 logy between the branches and leaves and the roots and 
 spongioles of plants, and showed that these parts are es- 
 sentially the same ; roots in some cases giving off branches 
 to produce leaves, and the stems of certain trees giving off 
 branch-like processes which ultimately become roots. I ex- 
 plained that the surfaces exposed by the spongioles and roots, 
 and the leaves and branches, are absorbing, secreting, and 
 evaporating surfaces; the same surfaces at .one time absorb- 
 ing and secreting moisture, and at another, discussing and 
 evaporating it, according to the condition of the plant and 
 the absence or presence of moisture, heat, etc. This arrange- 
 ment facilitates the circulation by favouring endosmose, exos- 
 mose, capillary attraction, and other physical forces, which, we 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 know from experiment, perform an important part in the cir- 
 culation of plants. The nutritious juices, I pointed out, are 
 applied to the leaves and roots, and also, though to a less 
 
 Fig. 57- 
 
 Fig. 57 A. Diagram showing the course of the circulation in the human foetus (vide arrows), g 1 , t\ 
 umbilical vein, conveying arterial blood from the placenta, ft', umbilical arteries, conveying venous 
 blood to the placenta, k, ductus venosus. /, vena portae. o, vena cava inferior, y, vena cava superior. 
 s, Eustachian valve and right auricle, q, right ventricle, v, ductus arteriosus, uniting aorta (u) and pul- 
 monary artery, i, left auricle, r, left ventricle, m, descending aorta, x, common iliac artery, dividing 
 into external and internal iliac arteries, j, hypogastric arteries, continuous with umbilical arteries (A'). 
 
 Fig. 57 B. Diagram illustrating the relation existing between the maternal (m) and foetal (n) portions 
 of the placenta (human). The maternal and foetal surfaces are represented as separated from each other 
 by a certain interval (m, n) to avoid confusion. They are slightly uneven from the projection into them 
 of the maternal and foetal capillary vessels. During pregnancy the two surfaces accommodate themselves 
 so as to dovetail and fit accurately into each other. In the diagram the vessels represented by solid 
 lines contain arterial blood ; those represented by dotted lines venous blood, m, mucous lining of uterus, 
 with nucleated cells on its surface. 6, sub-epithelial, spheroidal, and fusiform corpuscles, embedded in 
 connective tissue, c, d, utricular glands lined with epithelium, and opening on mucous surface of uterus. 
 They pour utricular secretion into utricular space (m, n). This space is mapped off, on the one hand, 
 by the villi and coverings of the maternal portion of the placenta : and on the other, by the villi and 
 coverings of the foetal portion of the placenta. The utricular secretion is necessary to a free osmosis 
 between the maternal and foetal vessels. (Compare space m, n, with similar space at ./"of Fig. 60, p. 132 ; 
 at e of Fig. 64, and at i,foi Fig. 65, p. 134.) n, limiting membrane of foetal portion of placenta covered 
 with nucleated cells, a, sub-epithelial, spheroidal, and fusiform corpuscles embedded in connective 
 tissue. 4, ', anmion. g, umbilical vein, conveying arterial blood to foetus, h, umbilical arteries, conveying 
 venous blood from foetus. The umbilical arteries and vein break up to form the villi of the foetal portion 
 of the placenta ; these being directed towards similar villi (e, f) constituting the maternal portion. The 
 maternal and foetal villi are separated from each other by the utricular space (m, n) containing utricular 
 secretion ; by two layers of cells, by two membranes, and by a certain proportion of connective tissue, 
 spheroidal, fusiform, and other corpuscles (a, b), Goodsir regarded the placental villus as consisting of a 
 maternal and foetal portion ; the maternal portion being composed of a membrane and nucleated cells, 
 and corresponding to m of diagram; the foetal portion being composed of a membrane and nucleated 
 cells, and corresponding to n of diagram. Between the maternal and foetal portions (as he termed 
 them) of a placental villus, he represents a space which corresponds to the space between tn and n 
 of diagram. This space he regarded as the cavity of a secreting follicle (see d of Figs. 61, 62, p. 133). 
 Goodsir has, it appears to me, appropriated the lining membrane of the maternal portion of the placenta 
 (m of diagram) and added it to the limiting or lining membrane of the foetal portion (n of diagram). 
 Original. 
 
 degree, to the stems of plants. I further explained that the 
 animal has no roots to dig into the ground, or leaves to spread 
 out in the sunshine, and that in this case the nutritious fluids 
 
 K 
 
130 PHYSIOLOGY OF THE CIRCULATION. 
 
 and aliments in the majority of instances are applied to an in- 
 voluted portion of the animal's body, to wit, the mucous sur- 
 face of its alimentary canal. But the mucous lining or internal 
 skin of an animal is essentially the same as its external skin ; 
 the two bearing the same relation to each other which the 
 roots and leaves of plants do ; the mucous lining or internal 
 skin of the animal corresponding to the roots of the plant, 
 the external or true skin to the leaves of the plant. When 
 therefore food in a more or less fluid condition is presented to 
 the stomach and intestine, it is absorbed, and passes by osmo- 
 sis, capillary attraction, etc., through the animal in a direction 
 from within outwards, first through the lacteals, and then 
 through the vascular system and tissues of the body generally \ 
 But fluids (in plants and animals) can be transmitted in an 
 opposite direction, viz. from without inwards. This is shown 
 in the case of shipwrecked mariners who immerse their bodies 
 in the sea to slake their thirst, and in the inunction with oil 
 and other nutritious fluids in cases of starvation from disease. 
 The transmission of fluids through the body, both from with- 
 out and from within, is favoured by the respiration of the 
 tissues, and the fact that evaporation goes on both in the 
 mucous lining or internal skin and in the external or true 
 skin, these surfaces, as already stated, being essentially the 
 same. The circulation within the tissues, as I have endea- 
 voured to explain, is in a great measure independent of 
 the heart, and due mainly to the operation of certain phy- 
 sical forces, viz. absorption, endosmose, exosmose, capillary 
 attraction, chemical affinity, evaporation, etc. The heart and 
 blood-vessels, when they exist, are employed for transmitting 
 the nutritious fluids through long distances, in order to bring 
 the blood and other juices face to face with the tissues, the 
 constituent elements of which are so arranged that each takes 
 or one might almost say, has forced upon it, by the physical 
 forces referred to those particular ingredients which are best 
 adapted for its development, maintenance, and reproduction. 
 The object of these remarks is to show that the placental cir- 
 culation of mammals is substantially the same as that of the 
 tissues generally. The ovum is extruded from what may be 
 regarded a mucous surface, viz. the interior of the ovary. It 
 
 1 The lymphatic vessels join the vascular ones the chyle ultimately becoming 
 blood. 
 
PHYSIOLOGY OF THE CIRCULATION. 131 
 
 is grasped by the fimbriated extremity of the Fallopian tube, 
 as by a hand extended to receive it, and conveyed to the in- 
 terior of the uterus, in the mucous lining of which it is literally 
 planted (Fig. 58, .) 
 
 Fig. 58. F g- 59- 
 
 Fig. 58. Impregnated human uterus, showing hypertrophy of the mucous lining ot uterus (the decidua 
 of authors). The mucous lining is represented in black, and the egg (*) is seen at the fundus of the 
 uterus, engaged between two of its projecting convolutions. After Dalian. 
 
 Fig. 59- Human ovum at end of third month, showing placental portion (a) of the chorion fully 
 formed. *, chorion. a, villoas tufts proceeding from chorion. These tufts at an early period completely 
 invest the chorion, hence the epithet ' shaggy chorion.' When the chorion is shaggy the placenta is dif- 
 fuse, as in the mare, f, amnion. x, foetus, i, umbilical vesicle. After, Daltoit. 
 
 The internal surface of the ovum (apparently its external 
 one) is applied to the internal or mucous surface of the uterus ; 
 but the internal surfaces of mother and foetus are similarly 
 constituted and perform analogous functions, the two coming 
 together and blending as naturally as the fingers of the hands 
 pass through and fit into each other. After a certain interval 
 processes equivalent to roots and spongioles are sent out from 
 the internal surface of the foetus (chorion) as seen at a of 
 Fig. 59. Similar processes, which naturally exist in the uterine 
 mucous membrane of the mother, become hypertrophied ar|d ex- 
 hibit a greatly increased activity. These processes of the mother 
 and foetus are at first distinct, a certain interval separating the 
 two (Figs. 57 B, m 9 n, p. 129; 58, b\ and 77,^,^, p. 141). Gra- 
 dually however they approach and interweave until they are 
 accurately adapted to each other ; the foetus being as it were 
 grafted on to the mother. Notwithstanding this very intimate 
 relation, the foetus and mother are essentially distinct. The 
 foetus is in some senses out of, or beyond, the mother, from 
 the first. The arrangement is of a purely temporary character. 
 The internal surface of the foetus, or that part of it which 
 
 K 3 
 
132 PHYSIOLOGY OF THE CIRCULATION. 
 
 constitutes the foetal placental area, is quite distinct from the 
 corresponding internal surface or mucous lining of the uterus 
 which constitutes the maternal placental area. In the rumi- 
 nants this relation is very well seen, the villous tufts which 
 represent the foetal portion of the cotyledon being torn out 
 of corresponding tufts in the mucous lining, representing the 
 maternal portion of the cotyledon, without rupturing the ves- 
 sels, and in such a manner as to occasion no bleeding what- 
 ever. This arises from the fact that the capillary vessels of 
 the foetus and mother are simply laid against each other, i. e. 
 
 Fig. 60. 
 
 Fig. 60. Cotyledon of cow's uterus, a, a, surface of foetal chorion. b, b, blood-vessels of foetal chorion. 
 c, c, surface of uterine mucous membrane, d, d, blood-vessels of uterine mucous membrane. After 
 Dalton. 
 
 f. Secretion from utricular glands (cotyledonous milk) placed between maternal and foetal vessels, and 
 which is necessary to the mutual interchange of gases, nutrient, effete, and other matters, between 
 parent and offspring. Author, 
 
 placed in juxtaposition ; the two sets of vessels and the mu- 
 cous linings investing them remaining essentially distinct. 
 With a view to a natural and easy separation, the maternal 
 and foetal tufts in ruminants are arranged in wedge-shaped 
 masses, the apices of the wedge-shaped capillary masses of 
 the foetus dovetailing into the capillary wedge-shaped masses 
 of the mother, an arrangement which admits of very easy ex- 
 traction. The extraction is further facilitated by the presence 
 of cotyledonous milk between the tufts (Fig. 60). 
 
 In man the relation between the foetal villous tufts and 
 those of the mother is more intimate than in any other animal, 
 
PHYSIOLOGY OF THE CIRCULATION. 133 
 
 the tufts themselves being slightly club-shaped ; but even here 
 I am disposed to believe that the foetal and maternal tufts 
 are radically distinct, and that each is provided with its appro- 
 priate coverings ; that, in fact, an open space exists between 
 the two. This open space or neutral territory occurring be- 
 tween the maternal and foetal placental tufts, I propose to 
 designate the utricular space ^ from the fact that the utricular 
 secretion or cotyledonous milk is poured into it. It corre- 
 sponds, in my opinion, in the human subject, to the space 
 marked d in Figs. 61 and 62, to c of Fig. 63, and to e of Fig. 64. 
 
 Fig. 61. Fig. 62. Fig. 63. 
 
 Fig. 61. The extremity of a placental villus (human), a, the external membrane of. the villus, the 
 lining membrane of the vascular system of the mother, b, the external cells of the villus, cells of the ' 
 central portion of the placental decidua. c, c, germinal centres of the external cells, d, the space be- 
 tween the maternal and foetal portions of the villus. e, the internal membrane of the villus, the ex- 
 ternal membrane of the chorion. /, the internal cells of the chorion. g , the loop of umbilical vessels. 
 ~Goodsir, 1845. 
 
 Fig. 62. This drawing illustrates the same structure as Fig. 61, and has been introduced to show the 
 large space (ct) which occasionally intervenes between the internal membrane and the external cells. It 
 would appear that into this space the matter separated from the maternal blood by the external cells of 
 the villus is cast, before being absorbed through the internal membrane by the internal cells. This space 
 therefore is the cavity of a secreting follicle, the external cells being the secreting epithelia, and the 
 maternal blood-vessel system the capillaries of supply. This maternal portion of the villus and its 
 cavity corresponds to the glandular cotyledons of the ruminants, and the matter thrown into the cavity 
 to the milky secretion of these organs. Goodsir, 1845. 
 
 Fig. 63. Diagram illustrating Dr. John Reid's views of the human placenta, a, curling artery. . 
 b> uterine vein, c, uterine sinus formed by expansion of artery (a) and vein (b). d, foetal tufts or villi, 
 with inner coat (c) of vascular system (a, b) of mother enveloping them. 1841. 
 
 I have represented the utricular space at m t n, of Fig. 576 
 (p. 129), and at e, g, of Fig. 77 (p. 141). Professor Turner has 
 represented a similar space as occurring between the maternal 
 and foetal portions of the placenta of the whale (Orca gladi- 
 ator], seen at i, f, of Fig. 65 (p. 134) ; a corresponding space 
 found in the ox being shown at /of Fig. 60 (p. 132). 
 
 The utricular space is bounded by certain landmarks which 
 it behoves us to study. They are essentially those of two 
 mucous membranes or two portions of skin. The external 
 and internal skin have many features in common. The former 
 consists of innumerable eminences or papillae, the free sur- 
 faces of which display a mass of looped capillary vessels in all 
 
134 PHYSIOLOGY OF THE CIRCULATION. 
 
 respects analogous to the placental villi or tufts. Between 
 the papillae an infinite number of tubes with blind convoluted 
 extremities are found. These tubes open towards the free 
 
 Fig. 64. Fig. 65. 
 
 Fig. 64. Diagrammatic section of human decidua at the termination of pregnancy, a, aronion with 
 epithelium, b, chorion. c, decidua. d, muscular coat. *,<e, line of separation of the membranes of the 
 ovum situated within the cell layer, f, cell layer of decidua. g, glandular layer of the same with ', 
 epithelial cells. F r iedlander, 1870. 
 
 Fig. 65. Diagram illustrating the placental arrangements in the whale (Orca gladiator), c, utricular 
 gland. *, funnel-shaped crypt into which utricular gland opens, a, cup-shaped crypt. f,f, epithelial 
 layer lining crypts, d, fusiform corpuscles, e, e, spheroidal sub-epithelial corpuscles. g r g, close 
 capillary plexus, h, h, foetal villi projecting from chorion. These villi are invested by an epithelial 
 layer (, *). They consist of connective tissue which contains a layer of sub-epithelial corpuscles (k\, of 
 fusiform corpuscles (/), and a close capillary plexus (m, m), derived from the umbilical arteries, which 
 plexus is continued into an extra-villous chorionic network (, ) from which the umbilical vein arises. 
 The foetal and maternal vessels are not in contact, still less continuous with each other, but are separated 
 by the layer of sub-epithelial corpuscles of the villus, the epithelial investment of the villus, the epithe- 
 lial lining of the crypt, and the layer of sub-epithelial corpuscles of the crypt. The space between the 
 two epithelial surfaces is intended to show the interval between the foetal and maternal portions (of the 
 placenta) into which the secretion of the uterine glands is poured. Turner, 1871. 
 
 surface, and correspond to the sweat-glands. They secrete a 
 peculiar fluid which is exhaled when we perspire *. Precisely 
 similar remarks may be made of the internal skin or mucous 
 
 1 The number of sweat glands in the human body is incredibly great. Krause 
 estimated that, on the skin of the cheeks, posterior portion of trunk, thigh and leg, 
 they number 500 to the square inch ; on the forehead, neck, forearm, back of hands 
 and feet, and anterior part of trunk, 1000 to the square inch ; and on the sole of the 
 foot and palm of the hand, 2700 to the square inch. This observer estimated the 
 number of sweat-glands in the body at 2,300,000; the amount of glandular tubing 
 amounting to 153,000 inches, or something like two and a half miles (Kolliker, 
 Handbuch der Gewebelehre; Leipzig, 1852, p. 147). Lavoisier and Seguin estimate 
 the quantity of fluid lost by cutaneous perspiration in twenty-four hours at 13,770 
 grains, nearly two pounds avoirdupois (Robin and Verdeil, op. cit. vol. ii. p. 145). 
 According to Dr. Southwood Smith, labourers engaged in gasworks sometimes lose 
 by cutaneous and pulmonary exhalations as much as three and a half pounds in less 
 than an hour (Philosophy of Health, chap, xiii; London, 1838). The effect pro- 
 duced on the circulation by the extraction of such large quantities of fluid from the 
 system must in such cases be very great. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 135 
 
 lining of the alimentary canal. Here we have a surface con- 
 sisting of minute projections, filled with capillary loops, and 
 studded with a vast array of tubular glands, similar, in many 
 respects, to the sweat-glands and to the utricular glands or 
 follicles of the uterus. The structures constituting the external 
 and internal skin are shown in Figs. 66 to 75. 
 
 Fig. 69. 
 
 a b c 
 
 Fig. 66. 
 
 Fig. 67. 
 
 Fig. 66. Compound papillae from palm of human hand (magnified), a, base of papilla, b, b, c, branches 
 of papillae. (Compare with Figs. 70 and 73.) After Kolliker. 
 
 Fig. 67. Plan of a secreting membrane, a, basement membrane, b, epithelium, composed of secret- 
 ing nucleated cells, c, layer of capillary blood-vessels. (Compare with m, n of Fig. 57 B, p. 129.) Quain. 
 
 Fig. 68. Sweat-gland and duct of human skin, opening upon surface at a (magnified), t, gland sur- 
 rounded by fat. d, duct of gland passing through corium, through lower (c) and upper part (b) of epider- 
 mis. (Compare with Figs. 71 and 72, and with c, d of Fig. 57 B, p. 129.) After Wagner. 
 
 Fig. 69. Ridges on epidermis of human skin, with orifices of sweat-glands (magnified), a, ridge. 
 c, furrow, b. orifice of sweat-gland. (Compare with a of Figs. 74 and 75, p. 136.) After Quain. 
 
 Fig. 70. 
 
 Fig. 71. 
 
 Fig. 72. 
 
 Fig. 70 A. Vertical section of two villi, from intestinal mucous membrane of rabbit ~~T~. a, epithe- 
 lium covering the villi. (Compare with m, n of Fig. 57 B, p. 129.) b, substance of villi, with lymph-cells. 
 c, tubular glands or crypts of Lieberkiihn. (Compare with Fig. 72, and with c, d of Fig. 57 B.) d, e, capil- 
 lary artery and vein forming capillary plexus (/) in villus. (Compare with Figs. 73, p. 136, and 78, p. 143.) 
 g, g, lacteal vessels of villi, joining horizontal lacteal (h, h). t, submucous layer. 
 
 Fig. 70 B. Cross section of three tubular glands more highly magnified. After Frey. 
 
 Fig. 71. Deep portion of pyloric gastric gland, lined with cylindrical epithelium (a, a). From human 
 Stomach (magnified). Kolliker. 
 
 Fig. 72. Utiicular glands from mucous membrane of unimpregnated human uterus (magnified), at. 
 lining of cylindrical epithelium, b, interior of utricular gland, c, orifice of utricular gland. (Compare 
 with Figs. 68 and ^l.)Dateon. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 Here then, I submit, we have the elements but of which the 
 placenta, when it exists, is formed, viz. two pieces of skin, 
 or what is equivalent thereto, displaying innumerable emi- 
 nences and depressions, an inconceivable number of capillary 
 loops, and a vast array of utricular glands corresponding to 
 sweat, gastric, intestinal, and other glands of that type (Fig. 
 57 B, p. 129.) The mucous lining of the uterus displays a re- 
 markably rich network of capillary vessels, looped and directed 
 towards the free surface as in every other part of the body. 
 
 Fig. 73- 
 
 Fig. 73. Blood-vessels of intestinal villi, magnified (human), a. a, arteries, v, v, veins. The artery 
 dnd vein in each villus conducts to an intermediate capillary plexus or network. (Compare with e,f, of 
 Fig. 57 B ; with d, e,f, of Fig. 70 A, p. 129 ; and with Fig. 78 A, C, p. 143.) From Injection by Litter* 
 kithn. 
 
 The capillaries are aggregated in parts like fairy rings in a 
 field, and in the centre of the vascular rings the utricular 
 glands or follicles open (Fig. 74). These glands secrete and 
 
 Fig. 74. 
 
 Fig. 75- 
 
 Fig. 74- Network of capillary vessels (*), with orifices of utricular glands (), as seen on surface of 
 mucous membrane of human uterus (magnified). (Compare with same letters in Fig. 75.) Farre. 
 
 Fig. 7 Network of capillary vessels (*), with orifices of gastric glands (a), as seen on surface of 
 mucous membrane of human stomach (magnified). Ecktr. 
 
 exude an opalescent slightly viscid fluid resembling milk, and 
 which has from this circumstance been designated cotyledo- 
 nous milk. The cotyledonous milk of the uterus supplies 
 during gestation the nourishment afforded at a later period by 
 
PHYSIOLOGY OF THE CIRCULATION. 137 
 
 the mammary glands. It also acts as an osmotic medium to the 
 maternal and foetal blood. The uterus and mammae sym- 
 pathise, and the lacteal fluids which they supply perform 
 analogous functions. 
 
 Goodsir describes in the human subject two membranes 
 and two sets of cells as interposed between the capillary loops 
 of the mother and foetus. These membranes and cells he sepa- 
 rated from each other by a space, indicated at d of Figs. 61 and 
 62, p. 133. Turner has described a somewhat similar arrange- 
 ment in the whale. He represents a foeto-maternal placental 
 space, bounded on the one hand by the vessels and cells of 
 the mother, and on the other by the vessels and cells of the 
 foetus. Thus, proceeding from the space in the direction of 
 the uterus, there is, according to him, 1st, a layer of epithe- 
 lium, and 2nd, a layer of connective tissue, having embedded 
 in it sub-epithelial, spheroidal, and fusiform corpuscles, and a 
 close capillary plexus. Proceeding in the direction of the 
 foetus, a precisely similar arrangement obtains, there being, 
 1st, a layer of epithelium, and 2nd a layer of sub-epithelial, 
 spheroidal, and fusiform corpuscles, in which a close capillary 
 plexus is found (Fig. 65, p. 134). 
 
 Thus far the relation existing between the maternal and 
 foetal capillary vessels and their coverings is quite intelligible. 
 The theories, however, advanced as to the transformations 
 which the vessels and mucous membrane of the uterus un- 
 dergo during the process of gestation have strangely, and, 
 I feel assured, unnecessarily, complicated that relation. 
 
 First as to the mucous membrane of the uterus. There is 
 nothing peculiar in this membrane, other than arises from an 
 increased development and contact with the villous tufts of 
 the chorion ; an ovum evolving as readily in the Fallopian 
 tube as in the uterus. When impregnation takes place the 
 uterine mucous membrane becomes greatly expanded, its com- 
 ponent elements becoming excessively hypertrophied. It has, 
 partly from this circumstance, but chiefly because it was erro- 
 neously supposed to be discharged at parturition, had its name 
 changed from mucous membrane to decidua *. When the ovum 
 
 1 In the posthumous work of Dr. William Hunter (' An Anatomical Description 
 of the Human Gravid Uterus'), edited by Dr. M. Baillie in 1794, the decidua is 
 described as under : ' This membrane is an efflorescence of the internal coat of 
 
138 PHYSIOLOGY OF THE CIRCULATION. 
 
 enters the uterus, Sharpey and Coste believe that the uterine 
 mucous membrane (the decidua of authors) rises up around 
 it in the form of a wall, the free borders of the wall increasing 
 until they unite and form a dome above it; the ovum be- 
 coming completely invested by the maternal lining or mucous 
 membrane of the uterus. 
 
 Dr. Arthur Farre suggests another explanation. He sup- 
 poses that the ovum, on entering the uterus, drops into one 
 of the orifices leading to the utricular follicles, and, in growing 
 there, draws around it the already formed, but soft and spongy, 
 uterine mucous membrane constituting the walls of the cavity 1 . 
 The ovum, according to these views, is buried at conception, 
 and requires to be exhumed at parturition. 
 
 The mucous membrane of the pregnant uterus has for the 
 foregoing reasons been artificially divided into three parts, 
 known as the decidua vera, decidua reflexa, and decidua sero- 
 tina. The decidua vera (also termed parietal) corresponds to 
 that part of the mucous membrane which lines the uterus as a 
 whole ; the decidua reflexa to that part of it which is supposed 
 to grow around and over the ovum ; and the decidua serotina 
 (supposed by some to be a new formation 2 ) to that part of it 
 which corresponds to the foetal portion of the placenta, and 
 with which it is directly or indirectly in contact 3 (Fig. 76). 
 
 These views, I need scarcely add, are hypothetical, and the 
 terms employed in explaining them arbitrary. As there are 
 no sufficient anatomical proofs that the mucous membrane of 
 
 the uterus itself. ... It may be said to be the internal membrane of the uterus. 
 ... It is really the internal lamella of the uterus.' 
 
 1 This hypothesis is based upon what may turn out to be a purely accidental 
 occurrence, viz. the discovery by Bischoff of the presence in the guinea-pig of an 
 ovum in the bottom of a uterine follicle. 
 
 2 ' At the part where the uterine expansion of the decidua is interrupted by the 
 reflexion inwards of the decidua reflexa, and where the ovum entered, the place of 
 the decidua vera is supplied by another layer similar to it, and connected at its 
 margins with it, the decidua serotina.' Kirkes' Physiology, p. 66 1, 3rd edition, 
 1856. 
 
 3 Dr. Arthur Farre is of opinion that the decidua reflexa is in part formed out 
 of the parietal decidua (decidua vera) from the number of orifices of utricular 
 glands seen on its surface. He however admits that much is due to the further 
 development of the elemental decidual tissues, this increase being principally due 
 to the large supply of blood-vessels furnished to the decidua reflexa at an early 
 period. 
 
PHYSIOLOGY OF THE CIRCULATION. 139 
 
 the uterus during pregnancy deports itself as described, I pro- 
 pose abandoning the terms decidua vera, decidua reflexa, and 
 decidua serotina. I will therefore, when speaking of the lining 
 membrane of the uterus, refer to it simply as such, always 
 specifying the portion meant. 
 
 That the uterine mucous membrane does not require to 
 grow around and over the ovum during pregnancy is proved 
 by this, that in extra-uterine foetation the uterine mucous 
 membrane is absent. Similar remarks apply to Fallopian- 
 tube foetation, although here the conditions more closely re- 
 semble those found in the uterus 1 . In pregnancy, whether 
 extra-uterine or intra-uterine, the mucous membrane, capillary 
 
 Fig. 76. 
 
 Pig. 76. -x, Chamber occupied by ovum, b, c, decidua vera. d. decidua reflexa. g, decidua serotina. 
 Compare with same letters in Fig. 77, p. 141. Original. 
 
 vessels, utricular glands, and muscular fibres of the uterus, in- 
 crease in size and activity. We have two admirable specimens 
 of Fallopian-tube pregnancy in the Museum of the Royal Col- 
 lege of Surgeons, Edinburgh, in which the uterine structures 
 have become hypertrophied by sympathy ; the os uteri being 
 curiously enough closed by a plug of mucus. Extra-uterine 
 and Fallopian-tube pregnancies induce me to believe that the 
 ovum brings with it or develops its own membranes 2 ; the 
 
 1 As the Fallopian tube opens into the uterine cavity the two are anatomically 
 continuous. 
 
 2 ' The ovum during its passage along the Fallopian tube acquires a layer of 
 albumen, and this subsequently coalesces with the zona pellucida to form the 
 chorion.' Kirkes' Physiology, p. 676, 3rd edition, 1856. The villi of the chorion 
 consist at first entirely of cells, bounded by an external layer of textureless mem- 
 brane, which gives their form. ^Goodsir.) If a normal placenta be examined after 
 
140 PHYSIOLOGY OF THE CIRCULATION. 
 
 conditions necessary being heat, moisture, and a mucous sur- 
 face, either within or without the uterus. The chick only 
 derives heat from the body of the mother. When the ovum 
 reaches the interior of the uterus, it applies its chorionic (which 
 is in reality its mucous) surface to some portion of the mu- 
 cous surface of the uterus. At first the two mucous surfaces 
 are quite distinct, the relation being that rather of apposition 
 than actual contact. As pregnancy advances the maternal 
 and foetal mucous membranes, and the vessels which underlie 
 them, becorrie developed (particularly in the region which cor- 
 responds to the placental area) ; the membranes and vessels 
 becoming entangled, adhering, and interweaving in a most re- 
 markable manner (Fig. 57 B, p. 129, and Fig. 77, p. 141). 
 
 The advantage of this arrangement consists in the fact that 
 it secures to the mother and foetus an independent and yet a 
 common life the foetus being to the mother in the relation of 
 a parasite. It further secures independence and community 
 of structure. 
 
 Thus the foetus has its mucous lining (d, e of Fig. 77), and 
 the mother her mucous lining (g, b, c of Fig. 77) ; the foetus 
 has its capillary zone, consisting of villous tufts (h, a of Fig. 77), 
 and the mother has a corresponding capillary zone, the capil- 
 laries found on the mucous lining of the uterus (e, f of Fig. 
 57 B, p. 129); the mother has utricular glands (c, d of Fig. 57 B, 
 p. 129) ; the foetus their homologues. The foetus, as partu- 
 rition advances, concentrates and augments its villous tufts 
 and vascular supply (a of Fig. 77, p. 141 ; a of Fig. 59, p. 131 ; 
 z, n of Fig. 576, p. 129) ; the maternal vessels, within the 
 placental area, becoming correspondingly developed (e, f of 
 Fig. 57 B, p. 129), and the blood-supply correspondingly in- 
 creased. This community of structure and of life secures to 
 the ovum and subsequent foetus the fullest opportunities for 
 nourishment and development. In normal pregnancy the 
 ovum, from the time it enters the uterus, is in contact with 
 the uterine mucous lining. It brings with it an independent 
 life and independent structures, and it is the blending of 
 that life and those structures for a certain period with the life 
 
 delivery, a distinct membrane can be traced on its uterine surface ; i. e. the surface 
 corresponding to the uterine placental area. This membrane I am disposed to 
 consider the mucous membrane or lining of the chorion. 
 
PHYSIOLOGY OF THE CIRCULATION. 14 T 
 
 and structures of trie parent, that constitutes the mystery of 
 conception and gestation. 
 
 The mucous membrane of the chorion (the decidua reflexa 
 or decidua ovuli of authors) increases in the same ratio as the 
 ovum, which it incloses and protects. The receptacle con- 
 taining the ovum is a small chamber placed within a larger 
 one, viz. the uterine cavity. Those surfaces of the foetal and 
 maternal chambers which are directed towards each other 
 are each provided with a mucous lining. The walls of the 
 
 Fig. 77- 
 
 Fig. 77. Plan of section of uterus with fully formed ovum (human), g; mucous lining or membrane 
 of uterus, opposite placenta (decidua serotina of authors). *. c, lining membrane on body of uterus 
 (decidua vera of authors), d, lining membrane of foetus (decidua reflexa of authors). This membrane (e) 
 is found on the free surfaces of the chorionic villi (a), being in fact the mucous lining of the chorion. 
 Such parts of it as are not engaged in covering the chorionic villi become thinned away and disappear 
 towards the full term. It may however always be found on the free or uterine surface of a normal 
 placenta, a, chorionic villi constituting foetal portion of placenta. (The maternal portion is formed by 
 capillary vessels found in mucous lining, .) A, chorion, from which the chorionic villi spring, f, amnion. 
 i, umbilical vesicle. _/, Fallopian tube. 
 
 Note, As pregnancy advances the parts marked e, a, f approach each other, and become accurately 
 apposed. The same holds true of the parts marked b and d. This apposition and blending of maternal 
 and foetal structures facilitates the exchange (chiefly by osmosis) of nutritive and effete materials between 
 parent and offspring. Or iginal. 
 
 foetal and maternal chambers are only In apposition at first ; 
 but as development proceeds the foetal chamber becomes 
 fixed to the maternal one, and protrudes from it like a spheri- 
 cal bud. The cavities of the chambers nevertheless remain 
 quite distinct. On the mucous lining of both the foetal and 
 maternal chambers, orifices of utricular glands or their homo- 
 logues can be made out a circumstance of considerable im- 
 portance, as showing that the foetal portion of the placenta is 
 supplied with utricular glands as well as the maternal portion. 
 
142 PHYSIOLOGY OF THE CIRCULATION. 
 
 A large number of vessels, terminating in minute capillary 
 plexuses, are found on the mucous surfaces of both the foetal 
 and maternal chambers. These interdigitate at an early 
 period. The ovum at first lies loose in the foetal chamber, 
 but becomes fixed in it towards the end of the first 
 month. The fixing is effected by the aid of villous processes 
 which project from all parts of the chorion (hence the epithet 
 shaggy chorion). They suspend and fix the ovum in the 
 foetal chamber as a spider is suspended and fixed by its web. 
 The embryo, surrounded by its amnion, chorion, and mucous 
 lining, in this manner becomes securely anchored in a haven 
 of its own forming. Other changes succeed. As the ovum 
 grows, the villi of that part of it which is in contact with the 
 mucous lining of the uterus increase in size, and become more 
 ramified. The villi of the maternal placental area become 
 correspondingly developed. Dissepiments or partitions of 
 mucous membrane also make their appearance, and divide 
 the maternal and foetal villi into groups, producing that lobed 
 appearance so characteristic of the fully formed placenta. The 
 lobes of the human placenta are in reality the homologues of 
 the cotyledons of the ox. 
 
 The ovum brings a certain amount of nourishment with it ; 
 the rest it obtains by imbibition, due to contact with the 
 mucous membrane of the uterus, and the utricular secretion 
 which it there finds. Long before blood-vessels make their 
 appearance in the embryo, a circulation of nutritious juices, 
 similar to that found in plants and the lowest animal or- 
 ganisms, is established. This is effected by osmosis, due to 
 the presence of membranes and fluids of different density. 
 The membranes are seen at Fig. 77, p. 141. They consist of the 
 capillary blood-vessels of the interior of the uterus (e, f of 
 Fig. 57 B, p. 129) the mucous membrane of the uterus (g, b, c 
 of Fig. 77, p. 141) the mucous membrane and capillary blood- 
 vessels of the chorion (e, a, h of Fig. 77), and the amnion (/of 
 Fig. 77). There is every reason to believe that the maternal 
 and foetal membranes when in contact, as in pregnancy, not 
 only act as osmotic media, but also as secreting media. 
 Goodsir attributed a secreting power to the membranes and 
 cells covering the extremities of the placental villi. These, 
 according to him, consist of an external membrane and 
 
PHYSIOLOGY OF THE CIRCULATION. 143 
 
 nucleated cells, and an internal membrane and nucleated cells. 
 Between these a space occurs, which he regards as the cavity 
 of a secreting follicle (Figs. 61 and 62 d, p. 133). The external 
 membrane corresponds to the mucous lining of the uterus, 
 which I believe it really is; the internal membrane to the 
 outer surface of the chorion. This, as explained, I regard as 
 the mucous lining of the chorion. 
 
 The chorion and mucous surface of the uterus are, as a 
 rule, highly vascular. I have succeeded in minutely injecting 
 the arteries and veins of the chorion and amnion of the 
 mare 1 ; and injections of the membranes of the ox, sheep, 
 and other domestic animals, are to be found in nearly all 
 our museums 2 . The mucous membranes of the uterus and 
 
 Fig. 78. 
 
 Fig. 78. A, Extremity of foetal tuft of human placenta. From an injected specimen, magnified lorry 
 diameters. Compare with vessels in Fig. 57 B, p. 129. 
 
 B, Compound villosity of human chorion, with ramified extremity. From a three months' foetus, mag- 
 nified thirty diameters. 
 
 C, Extremity of villosity of chorion more highly magnified, showing the arrangement of the blood- 
 vessels in the interior. After Dalton. 
 
 chorion, with their cells and blood-vessels, may with great 
 propriety be compared to secreting structures composed of a 
 basement membrane, nucleated cells, and capillaries (Fig. 67, 
 p. 135); and it appears to me that they only require to be 
 brought together to inclose a space to enable them to assume 
 the secreting function. 
 
 The desired space is obtained immediately the ovum comes 
 in contact with the mucous lining of the uterus. At first the 
 uterine mucous membrane and utricular glands are more 
 especially engaged in secreting; the product passing by 
 
 1 These and other preparations bearing upon the placenta are to be found in 
 the Hunterian Museum of the Royal College of Surgeons of London. 
 
 2 Particularly fine specimens of placentae and membranes are to be seen in the 
 Anatomical Museum of the University of Edinburgh, the majority of them injected 
 by Goodsir. 
 
144 PHYSIOLOGY OF THE CIRCULATION. 
 
 endosmose and imbibition directly into the ovum ; the ovum 
 returning its peculiar fluids by exosmose. The transference 
 of liquid materials is greatly facilitated by the formation, in 
 the first month of pregnancy, of the shaggy chorion. This 
 structure is composed of an immense number of villous tufts, 
 consisting of a membrane of nucleated cells within which 
 capillary blood-vessels are ultimately developed (Fig. 78, 
 A, B, C, p. 143). 
 
 The villous tufts are at first short club-shaped processes 
 of uniform size. They are not attached to the mucous lining 
 of the uterus, so that the embryo floats freely and obtains its 
 nourishment after the manner of water-plants, viz. by imbibi- 
 tion. The club-shaped villi, as Goodsir pointed out, elongate 
 by additions to their extremities as in the roots of plants; 
 cells passing off from the germinal spots situated on the ends 
 of the villi. Goodsir demonstrated that blood-vessels appear 
 in the chorion and chorionic villi when the allantois reaches 
 and applies itself to a certain part of the internal surface of 
 the chorion. At this stage of development the umbilical 
 vessels communicate with vascular loops in the interior of the 
 villi. The injections of Schroeder van der Kolk showed a 
 profusion of capillary vessels in the chorionic villi as early as 
 the third month ; and at later periods of gestation up to the 
 sixth month, Dr. Arthur Farre succeeded in displaying 
 without difficulty, by the aid of fine injections, a very abun- 
 dant supply of these vessels. At a later period, a large 
 proportion of the fine capillaries within the villi disappear, 
 the long, tortuous, varicose loops described by Goodsir alone 
 remaining. From this it follows that the blood-vessels engaged 
 in nourishing the foetus have a period of development, a 
 period of increased activity, and a period of decay; the 
 period of decay heralding, if not actually producing, parturi- 
 tion. These changes are necessary to inaugurate the cir- 
 culation of the foetus, to unite the circulation of the foetus 
 with that of the mother, and to separate that connexion at 
 the period of parturition. 
 
 The fluids concerned in the nutrition and well-being of the 
 foetus are such as are supplied by the utricular glands and by 
 the various secreting surfaces, maternal and foetal. The 
 utricular glands in the early months of pregnancy supply a 
 
PHYSIOLOGY OF THE CIRCULATION. 145 
 
 milky fluid, nutritive in character, which, as has been ex- 
 plained, acts as an osmotic medium to the fluids contained 
 without and within the foetal chamber. Of the fluids con- 
 tained within the foetal chamber the substance of the embryo 
 imbibes freely. In the later stages of pregnancy, when the 
 placenta is fully formed, the utricular secretion produces an : 
 osmotic action between the blood contained in the placental 
 villi of the foetus and that contained in the capillaries of the 
 placental area of the mother (vide Fig. 79). 
 
 There is reason to believe that, even in advanced preg- 
 nancy, the surface of the foetus imbibes nutritive materials 
 from the fluids in which it is suspended, and by which it is 
 
 Fig. 79. 
 
 Fig. 79. Diagram showing the placental relations of the maternal and foetal capillaries, and the position 
 occupied by the utricular secretion, a, a, a, utricular glands, pouring out utricular secretion (b, b, b). 
 e, e, e, maternal capillary plexuses (with artery and vein) as seen on interior of uterus, d, d, d, foetal 
 capillary plexuses with artery and vein as seen on surface of placenta, directed towards interior of uterus. 
 The maternal and foetal linings and epithelial corpuscles which separate the maternal and foetal villi are 
 not represented. The presence of the utricular secretion (b. b, b) between the maternal and foetal 
 vessels necessitates a free interchange of the ingredients peculiar to each. See also under f of Fig. 60, ' 
 p. 132. Original. 
 
 constantly bathed. This it can readily do, as the external skin 
 of the foetus is so delicate that it in some respects resembles 
 the mucous membrane of the adult. The external skin of the 
 foetus in intra-uterine life in all probability absorbs and 
 exercises a secreting function ; whereas in extra- uterine life 
 it respires and exercises an excreting function. As I showed 
 in plants, certain surfaces may act either as absorbing or 
 respiring surfaces, according as they are exposed to the influ- 
 ence of moisture or air (Figs. 30, 31, p. 34, and Fig. 36, p. 50). 
 
 I have stated thatGoodsir divided the membranes and cells 
 found by him on the extremities of the placental villi into an 
 external and internal set ; and that, in my opinion, the 
 external membrane and cells constitute the. mucous or lining 
 membrane of the uterus. 
 
 Goodsir has, it appears to me, transferred the mucous lining 
 
 L 
 
146 PHYSIOLOGY OF THE CIRCULATION. 
 
 of the uterus to the mucous lining of the chorion ; a not 
 unnatural transference, when it is remembered that, in not 
 a few instances, particularly in highly civilised females, 
 artificial adhesions are formed, and the foetal part of the 
 placenta drags with it at parturition a portion or all of the 
 maternal part. To this circumstance, in all probability, is to 
 be traced the difficulty experienced by anatomists in deter- 
 mining whether the uterus does, or does not, shed its mucous 
 membrane after each parturition l . This would explain why 
 there should be a space between the external and internal 
 membranes covering the extremities of the placental villi, as 
 described by Goodsir; the space being the natural line of 
 junction and separation between the maternal and foetal 
 portions of the placenta 2 . It would also account for the 
 belief entertained by him, by Reid, Ecker, and others, that 
 the maternal blood-vessels (arteries and veins) within the 
 placental area become enormously expanded, and envelop 
 
 1 In man the tissues, as a rule, are more highly elaborated than in animals 
 a circumstance which renders their separation more difficult. Dr. Arthur Farre, in 
 his work On the Uterus and its Appendages,' states that ' in the latter months of 
 pregnancy, the parietal decidua (i.e. the mucous lining of the uterus) becomes 
 thinner, and loses much of its spongy character, except immediately around the 
 placenta, where this is still most distinct. It ultimately becomes blended with the 
 outer surface of the foetal membranes, and is partly thrown off with them in the 
 act of birth, while a part remains, forming a honeycomb layer attached to the 
 uterine muscular coat.' Now it appears from this that the decidua of the placental 
 area admits of division, one part being shed with the placenta at parturition, 
 the other remaining on the interior of the uterus. In reality the placenta takes its 
 own mucous lining with it, the uterus retaining the mucous lining which belonged 
 to it before conception took place. If we examine a normal placenta when thrown 
 off at full term, we find a membrane on its free or uterine surface ; and if we 
 examine the placental area of the uterus which corresponds thereto, we find a 
 similar membrane. This is what we would a priori expect. Why should the 
 placenta at parturition drag off any part of the decidua or mucous lining of the 
 uterus? The maternal and foetal structures are distinct from the first, and so 
 remain. They separate as naturally and with as little inconvenience as they 
 come together. 
 
 2 From the foregoing it will be evident that I do not regard the placenta as 
 structurally united to the uterus, but simply as in apposition and adhering, the 
 union being of the most intimate description, from the fact that the maternal and 
 foetal villi pass through each other so thoroughly that they form with their 
 contained blood a semi-fluid mass. The placenta is to the foetus what the roots 
 are to a parasitic plant (the mistletoe, for example). The foetus, by its placenta, 
 literally plants itself on the inner surface of the uterus, this supplying it with 
 nutritious juices and with air. 
 
PHYSIOLOGY OF THE CIRCULATION. 147 
 
 by bladder-like dilatations the villi of the foetal portion of 
 the placenta (Fig. 63, p. 133, and Fig. 80). If, as I presume, in 
 the specimens examined by Goodsir, Reid, Ecker, and others, 
 the villi of the foetal portion of the placenta dragged with 
 them at parturition the villi of the maternal portion, the 
 result would be exactly that figured and described, viz. a 
 large spongy mass, containing blood sinuses, with occasional 
 villi proceeding from or dipping into them. During pregnancy 
 the vessels of the uterus, particularly the veins, assume gigan- 
 tic proportions, the blood contained within the organ causing 
 it in some respects to resemble a lung ; but the blood-vessels 
 
 Fig. 80. Diagram illustrating the arrangement of the placental decidua (human), a, parietal decidua. 
 b, a venous sinus passing obliquely through k by a valvular opening, c, curling artery passing in the 
 same direction, d, lining membrane of the maternal vascular system, passing in from the artery and 
 vein, lining the bag of the placenta, and covering (e, e) the foetal tufts, passing on 1 to the latter by two 
 routes, first by their stems from the foetal side of the cavity ; and, secondly, by the terminal decidual 
 bars (f,f) from the uterine side, and from one tuft to the other by the lateral bar (g). This membrane 
 is in contact with decidual cells, unless along the stems of the tufts and the foetal side of the placenta. 
 (Compare with Fig. 63, p. 133.) Goodsir, 1845. 
 
 increase in a progressive ratio with the nerves, glands, 
 muscular, mucous, and other tissues, and there are no sufficient 
 grounds, anatomical or physiological, for supposing that during 
 the hypertrophy which occurs during pregnancy, the maternal 
 capillary vessels corresponding to the placental area, cease to 
 exist as such ; in other words, become converted into the 
 bladder-like expansions referred to. Such a metamorphosis 
 would remove the human placenta out of the category of 
 mammalian placentae ; a removal which neither its origin, 
 progress, nor final dehiscence warrants \ 
 
 1 When the human chorion is shaggy, the placenta is diffuse, as in the mare ; 
 and this is a reason why even in its most matured condition, i. e. in its concen- 
 trated and localised form, the human placenta is not to be regarded as a thing per 
 se, but a modification of other placentae, all of which are formed on a common 
 plan. In the mare the villous tufts of the chorion are applied to the mucous lining 
 
 L 2 
 
148 PHYSIOLOGY OF THE CIRCULATION. 
 
 One naturally inquires, when contemplating the enormous 
 maternal vascular expansions represented by Reid (Fig. 63, 
 P- J 33)j Goodsir (Fig. 86, p. 147), and Ecker, where the material 
 comes from which produces them ? The additional material re- 
 quired on the part of the curling arteries and veins of the uterus, 
 to envelop every villous tuft contained in the foetal portion 
 of the placenta, is such as virtually to render the hypothesis 
 untenable. So far as known to me, there is no other example 
 of a modification on a similarly gigantic scale in any natural 
 structure. If the terminal portions of the curling arteries and 
 veins of the uterus were expanded to the extent described, 
 and if, moreover, they embraced and became locked within 
 the villous tufts of the foetal portion of the placenta, as 
 figured, then of necessity the whole of that portion of the 
 interior of the uterus corresponding to the placental area 
 would be converted into an open wound when the placenta 
 was removed ; the wound; exhibiting on its surface an in- 
 credible number of large bleeding vessels, which no degree of 
 contraction on the part of the uterus could either modify or 
 restrain. What however is the real state of things ? During 
 a healthy parturition scarcely any blood is lost, and on 
 examining that portion of the interior of the uterus corre- 
 sponding to the placental area, it is found covered with a 
 mucous membrane somewhat resembling a honeycomb an 
 appearance caused by the apposition and interpenetration of 
 the mucous membrane and yilli of the foetal portion of the 
 placenta. On examining the free or uterine surface of the 
 placenta, a similar membrane is discovered ; the one, in fact, 
 being the counterpart of the other 1 . If a normal full-term 
 placenta is injected with size after its removal, there is little 
 
 of the uterus as a whole. In the tiger a band of villous tufts invests the chorion 
 at its middle ; the villi in this band only being applied to the mucous lining and 
 capillaries of the uterus. In the ox the villous tufts of the chorion are grouped 
 together, and appear as isolated patches, varying from an inch to an inch and a 
 half in diameter. These form so many placentulae. In man the villous tufts of 
 the chorion are ultimately aggregated into one large oval mass, to which the name 
 of placenta has been given. The human placenta is, so to speak, a concentration 
 and higher development of all the other forms. Its great general features are 
 however the same, and the manner of its application to the mucous lining and 
 capillary vessels of the uterus in no respect differs from the others. 
 1 See note i, p. 146. 
 
PHYSIOLOGY OF THE CIRCULATION. 149 
 
 if any extravasation from its free or uterine surface ; plainly 
 showing that it is bounded by its own peculiar mucous 
 membrane. All the difficulties and dangers referred to are 
 avoided by regarding the foetal and maternal portions of 
 the placenta as essentially distinct, not only in the early but 
 also in the later months of pregnancy. The structures in 
 question are simply in temporary apposition (Fig. 57 B, p. 129). 
 This view insures, as stated, an independence and community 
 of structure. It assimilates the human with the placentae of 
 other mammals, It accounts for the fact that a foetus may 
 be developed in the Fallopian tube, or outside the uterus 
 altogether. It in especial explains how the ovum can be 
 applied to the incubating chamber of the mother, and how the 
 foetus may be separated from it, without causing either injury 
 or inconvenience. Lastly, it shows that the maternal and 
 foetal evolutions which constitute a pregnancy are correlated, 
 the one advancing pari passu with the other. 
 
 As a proof that the relation subsisting between the maternal 
 and foetal placental surfaces and vessels in man is not that 
 figured by Reid, Goodsir, Ecker, and others, I may state, 
 that wherever I have had an opportunity of injecting the 
 utero-placental area with the parts in situ i.e. with the 
 placenta adhering to the mucous surface of the uterus I 
 have found an arrangement closely resembling in its general 
 features that found in the mammalia as a class. It is only 
 when the uterus and placenta are partially or altogether 
 separated that the appearances described and figured are 
 observed. In 1863 I destroyed and carefully injected a 
 pregnant monkey, as being likely to throw additional light on 
 this complicated and much disputed question. The monkey 
 was near the parturient period, the foetus being large and 
 well formed. In the monkey the placenta remarkably ac- 
 cords with that found in man. In the present instance I 
 injected the uterus, and then, having ascertained the site of 
 the placenta within the uterus, I made an incision through the 
 uterine wall at a considerable distance from it, through which 
 I pulled the foetus. I then injected the placenta from the 
 umbilical vessels. The placenta consisted of a large oval 
 isolated mass, which might have been taken for a human 
 .placenta at the sixth or seventh month. At a little distance 
 
150 PHYSIOLOGY OF THE CIRCULATION. 
 
 from the placenta proper there was a placentula or little 
 placenta, the vessels from which converged and united with 
 the main vessels of the principal one. The placentula I 
 regarded as an accidental formation. On making micro- 
 scopical sections of the placental area, so as to embrace the 
 maternal and foetal vessels, their coverings, cells, glands, etc., 
 the appearances observed were substantially those represented 
 at Fig. 57 B, p. 129 ; this figure, as already explained, embody- 
 ing my views of the structure and physiological relations of 
 the human placenta. 
 
 I am not therefore disposed to acquiesce in the commonly 
 received opinion that in man the placental foetal tufts are 
 covered by an expansion of the corresponding vessels of the 
 mother. I disagree 1st, Because there is no analogy to 
 support this view. 2nd, Because it is giving to the foetus what 
 I believe in reality belongs to the mother. 3rd, If the vessels 
 of the mother are so expanded, they are necessarily destroyed 
 when the placenta is removed, this relation involving the 
 laceration and destruction of the mucous lining and capillary 
 vessels corresponding to the maternal placental area a pro- 
 ceeding which would expose the mother (notwithstanding the 
 vigorous contraction of the uterus) to serious and probably 
 fatal haemorrhage. 4th, That portion of the mucous lining 
 of the uterus corresponding to the placental area is, as Dr. 
 Matthews Duncan has shown, not removed in parturition. 
 5th, In a healthy parturition there is almost no blood lost, 
 a circumstance which could not occur if the arrangement 
 figured by Reid, Goodsir, Ecker, and others, obtained, as, in 
 this case, not only large vessels, but large sinuses containing 
 blood, would be exposed. 6th, In the lower animals no blood 
 is lost at parturition ; but in these we know the maternal 
 and foetal capillary vessels or tufts are simply placed in 
 apposition, the two separating with the utmost facility. 7th, 
 The blood-sinuses of the uterus (and by these I mean the 
 maternal vascular expansions said to envelop the foetal pla- 
 cental villi) are not necessary to gestation. That these 
 sinuses are not necessary to the evolution of the foetus is 
 abundantly proved by this, that a foetus (as in extra-uterine 
 foetation) can live and thrive where they do not exist. 8th, 
 I have never been able to detect a foetal placental tuft or 
 
PHYSIOLOGY OF THE CIRCULATION. 151 
 
 villus in a uterine maternal sinus (containing maternal blood), 
 where the utero-placental relations were intact, i. e. where the 
 natural line of union between the maternal and foetal portions 
 of the placenta was inviolate. In such cases I have found an 
 occasional foetal villus in a utricular gland whose orifice was 
 dilated ; the uterine gland, as explained, opening on the free 
 or mucous surface of the placental area. Qth, and lastly, 
 Nothing is gained physiologically by the unnatural thinning 
 and dilatation of the maternal vessels for the purpose of 
 investing with bladder-like expansions the placental foetal 
 villi. A moment's reflection will show that such an arrange- 
 ment would not bring the blood of the mother any closer 
 to that of the foetus than it would be if the maternal vessels 
 remained unexpanded and normal. There are good grounds 
 for believing that the placental villi (maternal and foetal) 
 simply fit into each other, and, by a process of interweaving 
 and dovetailing, ultimately form a more or less solid mass. 
 As the maternal and foetal vessels by this arrangement are 
 laid against each other in every conceivable attitude, a more 
 perfect (and I will add a more extensive) osmotic action 
 between the maternal and foetal blood is induced than could 
 otherwise be obtained. The osmotic action is favoured by 
 the presence of a thin layer of utricular secretion between the 
 maternal and foetal villi and their appropriate coverings, as 
 already explained. 
 
 The belief that the maternal uterine vessels do not expand 
 to embrace the foetal placental villi, as recorded by Reid, 
 Goodsir, Ecker, and others, has been recently confirmed by 
 the researches of Dr. Braxton Hicks, the President of the 
 Obstetrical Society of London 1 . This gentleman argues 
 against the existence of blood in the so-called maternal 
 sinus system, and the sinus system itself, from finding that 
 neither are present in extra-uterine foetation. He inveighs 
 against the presence of blood in the sinous system in -normal 
 pregnancy, as he can detect no trace of that fluid when the 
 relations between the placenta and uterus are undisturbed. 
 .By the sinus system is here meant that space (or spaces) 
 
 1 Vide Lancet for i8th May, 1872; also memoir by Dr. Robert Lee 'On the 
 Structure of the Human Placenta and its Connexion with the Uterus/ Phil. 
 Trans. 1832. 
 
152 PHYSIOLOGY OF THE CIRCULATION. 
 
 occurring between the foetal villi of the chorion, which, 
 according to commonly received opinions, is lined by the 
 expanded uterine vessels of the mother. Dr. Hicks Dis- 
 sected four specimens. In two not a trace of blood was 
 found. . In the others there was a trace. In one of them 
 the origin was clearly traced to a small clot extravasated 
 among the villi ; in that which remained to a laceration of 
 the villi themselves. Dr. Hicks adduces further evidence 
 derived from three placentae called 'fatty.' In these the 
 decidual vessels were highly distended with blood, never- 
 theless the intervillal space was absolutely free. 
 
 So much for the vessels of the maternal portion of the 
 placenta. 
 
 With regard to the vessels constituting the foetal portion 
 of the placenta (particularly their coverings), there is con- 
 siderable diversity of opinion. Some say that the foetal 
 vessels and villi are bare ; others that they are covered 
 by a chorionic layer of cells; others that the choriomc 
 cells are covered by a layer of decidual cells ; others that, 
 in addition to all the foregoing, there is a layer derived 
 from the internal membrane of the vascular system of the 
 mother. 
 
 Dr. Arthur Farre holds that the blood of the foetus is 
 separated from the blood of the mother, 1st, by the walls 
 of its own capillaries ; 2nd, by the gelatinous membrane in 
 which these ramify, and 3rd, by the external, non-vascular, 
 nucleated sheath derived from the chorion. With the latter 
 alone, he remarks, the blood of the mother is brought into 
 contact. 
 
 There are, as you observe, grave discrepancies in the ex- 
 planations given both of the maternal and foetal elements 
 of the placenta ; and I cannot help thinking that the truth 
 will be evolved more readily if we discard a certain amount 
 of detail and keep to general principles. Analogy, compara- 
 tive anatomy, and development induce me to believe that 
 the relation of the maternal to the foetal portion of the 
 placenta is not so complicated as authors have laboured to 
 make it, and that the actual relation, as already explained, 
 is that which one portion of skin or mucous lining, furnished 
 with glands, capillary vessels, a limiting membrane, and 
 
PHYSIOLOGY OF THE CIRCULATION. 1 53 
 
 epithelium, bears to another similarly constituted when the 
 two are brought face to face and laid against each other 1 . 
 
 Not less conflicting' are the views advanced as to the 
 manner in which the foetus is nourished and respires. Goodsir 
 is of opinion that the foetal placental villus consists of an 
 external and internal membrane, each provided with nucleated 
 secreting cells, and that between the two membranes there 
 is a space which he regards as the cavity of a secreting 
 follicle. The cells of the external membrane of the placental 
 villus, according to him, secrete from the blood of the mother 
 by means of the uterine capillaries the nutritive matter ab- 
 sorbed through the internal membrane by the internal cells, 
 and conveyed thence to the foetus by the foetal placental 
 tufts or villi. The secretion he compares to the cotyledonous 
 milk of ruminants. 
 
 Ercolani advocates another view. e He admits that the 
 utricular glands do furnish materials for the nutrition of the 
 embryo, but only'in the early period of development; and 
 he strives to prove that, from a transformation and greatly 
 increased growth of the uterine mucous membrane, and of 
 the sub-epithelial connective tissue, a new maternal glandular 
 organ is formed, which in its simplest form consists of secret- 
 ing follicles, arranged side by side and opening on the surface 
 of the mucous membrane. In the human subject, he says, 
 the typical form of the glandular organ is wanting, but the 
 cells of the serotina, which invest the chorionic villi, represent 
 the fundamental portions of the gland organ. Into these 
 new-formed secreting follicles, and not into the utricular 
 glands, the villi of the chorion penetrate, and are bathed 
 by the fluid secretion, which they absorb for the nourish- 
 ment of the foetus 2 .' Ercolani's hypothesis is ingenious, 
 but there is no necessity for supposing that a new maternal 
 glandular organ is formed, as existing structures very slightly 
 modified can perform the work said to be performed by the 
 new structure. Turner does not believe with Ercolani that 
 
 1 See a curious case of ' a placenta partially adherent to a naevus occupying the 
 scalp and dura mater.' Lond. Med. Chir. Soc. Trans, xxii. 1829, pp. 300-309. 
 
 2 Ercolani, as rendered by Turner, in his memoir ' On the Gravid Uterus, and 
 on the Arrangement of the Foetal Membranes in the Cetacea (Orca Va<#<rtor),' 
 Trans. Roy. Soc. of Edin. vol. xxvi. p. 500 (1871). 
 
154 PHYSIOLOGY OF THE CIRCULATION. 
 
 the utricular glands cease to perform their functions at an 
 early period of embryonic life. On the contrary, he states 
 that in the Orca, 'although the foetus had reached an ad- 
 vanced state of development, the vascularity of the glands, 
 their epithelial contents, even the presence of plugs of 
 epithelium or inspissated secretion projecting through the 
 orifices all gave one the impression of structures in a state 
 of active employment. If this be the case, then the secre- 
 tion would be poured out into the crypts, and brought in 
 contact with the villi of the chorion. ... I am disposed, 
 therefore,' he adds, ' to conclude that, in all those forms of 
 placentation in which the utricular glands preserve their 
 structural characters within the placental area, they play 
 an important, if not the whole part, in the nutrition of the 
 foetus, not merely in the early 1 , but throughout the whole 
 period of uterine life 2 .' Turner does not believe that the 
 sub-epithelial corpuscles represented by himself (Fig. 65, , k, 
 p. 1 34) on the uterine and chorionic surfaces of the placenta, 
 and which closely correspond to the external and internal 
 cells of the placental villus of Goodsir (Fig. -61, #, ^, p. 133), 
 have a secreting function. He is inclined to regard them 
 as lymphoid bodies which have wandered out of the adjacent 
 capillaries into the connective tissue, to whose nutrition and 
 growth they adminster. 
 
 According to Goodsir, as has been explained, ' the external 
 
 1 ' When the ovum, with its villous chorion, reaches the uterus, the villi 
 becomes embedded in the secretion poured forth by the enlarged follicular glands 
 of the mucous membrane of that organ ; and from this they doubtless derive 
 the nutriment on which the embryo at first subsists. . . . Coincidently with 
 the increasing size of the follicles, the .quantity of their secretion is augmented, the 
 vessels of the mucous membrane become larger and more numerous, while a sub- 
 stance composed chiefly of nucleated cells fills up the intrafollicular spaces, in 
 which the blood-vessels are contained. The object of this increased development 
 seems to be the production of nutritive materials for the ovum ; for the cavity of 
 the uterus shortly becomes filled with secreted fluid, consisting almost entirely of 
 nucleated cells, in which the villi of the chorion are embedded. . . . After 
 impregnation the glands of those parts of the mucous membrane which come 
 into immediate relation with the ova greatly enlarge, while the extremity of each 
 compound gland, just before it opens on the surface of the uterus, dilates into 
 a pouch or cell, filled with whitish secretion, within which is received a process of 
 the chorion.' Kirkes' Physiology, 3rd ed. 1856. 
 
 2 On the Gravid Uterus, and on the Arrangement of the Foetal Membranes 
 in the Cetacea (Orca gladiator). Trans. Roy, Soc. Edjn. 1871, pp. 501, 502. 
 
PHYSIOLOGY OF THE CIRCULATION. 155 
 
 cells of the foetal placental villi perform, during intra-uterine 
 existence, a function for which is substituted in extra-uterine 
 life the digestive action of the gastro-intestinal mucous 
 membrane. The internal cells of the foetal placenta! villi 
 perform during intra-uterine existence a function for which 
 is substituted in extra-uterine life the action of the absorb- 
 ing chyle-cells of the intestinal villi. The placenta, therefore, 
 not only performs, as has been always admitted, the func- 
 tion of a lung, but also the function of an intestinal tube 1 .' 
 Dr. John Reid, as has been pointed out, believed that the 
 uterine capillary vessels expanded to such an extent that 
 they invested the foetal capillary tufts (Fig. 63, d, p. 133), the 
 foetal villi being bathed by the blood of the mother much 
 in the same way that the gills of aquatic reptiles are bathed 
 by water. The placenta, Dr. Reid observes 2 , is therefore 
 not analogous in structure to the lungs, but to the branchial 
 apparatus of certain aquatic animals 3 . If the views suggested 
 in the text, and illustrated by Fig. 57 B (p. 129), and Fig. 
 77 (p. 141), be adopted, the opinions of Goodsir, Reid, Ecker, 
 Ercolani, Turner, and others, may readily be reconciled, as 
 the utricular glands secrete a fluid which assists in nourish- 
 ing the foetus, while it at the same time acts as an osmotic 
 medium. The membranes and cells found on the surfaces 
 
 1 Anatomical and Pathological Observations, by John Goodsir, Esq., F.R.S.E. 
 etc. ; Edin. 1845, p. 63. 
 
 2 Physiological, Pathological, and Anatomical Researches, by Dr. John Reid, 
 1848, p. 327. Reid's paper On the Blood-vessels of the Mother and Foetus 
 (Human) originally appeared in the Edin. Med. and Surg. Journal (No. 146) for 
 January 1841. 
 
 3 If this analogy be admitted, the following difference is to be noted : The 
 branchiae of the aquatic reptile are in the immediate vicinity of the heart, whereas 
 the placenta is widely removed, not only from the heart, but even the body of 
 the foetus. In this sense the placenta is outside and beyond the foetus ; hence 
 the necessity for that remarkable system of canals which constitute the umbilical 
 cord. This cord might be of any Length, it being a mere tunnel to enable the 
 circulation of the foetus and mother to reciprocate. Similar remarks may be made 
 regarding the principal arteries and veins of all the higher animals. The really 
 effective circulation occurs within the capillaries and tissues, and the large vessels 
 stand in the same relation to the heart as aqueducts to their reservoirs. The 
 longest vessels of all are to be found in trees. The umbilical cord consists of 
 two arteries and one vein ; but it is not to be inferred from this that the arteries 
 and their radicles contain arterial blood, and the vein and its radicles venous blood. 
 On the contrary, the vein contains arterial blood, and the arteries mixed blood. 
 
156 PHYSIOLOGY OF THE CIRCULATION. 
 
 of the maternal and foetal portions of the placenta secrete, 
 by a double process, from the capillaries (maternal and 
 foetal), which they cover, the substances necessary to the 
 well-being alike of parent and child, the placental mem- 
 branes and utricular glands working together. The placental 
 membranes and cells, as I have shown, enclose a space 
 which, from the fact of the glands pouring their secretion 
 into it, I designate the ' utricular space? The space in ques- 
 tion contains the utricular secretion or cotyledonous milk. 
 To this cotyledonous fluid I am disposed to attach con- 
 siderable importance, as it is one of the sources from which 
 the foetus derives its nourishment in the early months of 
 pregnancy, before its blood-vessels are formed, and the 
 medium through which the blood of the mother operates on 
 the blood of the foetus and vice versa, when the maternal 
 and foetal villi are fully developed. In short, I regard the 
 utricular space, with its glandular secretion, as performing at 
 once the office of a stomach, a lung, and an osmotic medium. 
 
 The capillary blood-vessels of the mother and foetus are 
 entirely distinct, and separated, as has been stated, by two 
 membranes and two sets of cells. Here we have the con- 
 ditions necessary for a vigorous osmotic action. Both sets 
 of vessels contain blood, but, as the blood of the mother 
 and foetus are very similarly constituted, they can only act 
 upon each other when a third and thicker fluid is present, 
 on the principle 'ex nihilo nihil fit.' This thicker fluid the 
 utricular glands supply. It is the thinner portions of the 
 maternal and foetal blood which flow out of the vessels by 
 a process of endosmose into the utricular space, where they 
 commingle ; part of the mixed fluid returning by a process 
 of exosmose to the vessels alike of the mother and foetus. 
 By this means a free interchange of nutritious and effete 
 matters is permitted, the mother and foetus participating 
 equally. This would account for the influence exerted by 
 the mother on the foetus, and the converse ; the foetus, as 
 is well known, altering the constitution of the mother, and 
 affecting even her future progeny 1 . The foetal and maternal 
 
 1 When a white mother bears a child to a black father, the future offspring, 
 even if begotten by a white father, is, as rule, coloured. John Hunter relates 
 
PHYSIOLOGY OF THE CIRCULATION. I $7: 
 
 vessels abut against each other in every conceivable posi- 
 tion, and as they are only separated from one another by 
 an osmotic medium and certain membranes and cells, the 
 maternal and foetal blood yield up their peculiar ingredients 
 to each other, gases, especially when in a state of solution,, 
 like fluids, readily passing through certain membranes. The 
 blood of the foetus, there is reason to believe, is by this, 
 means nearly as well aerated as the blood of the mother. 
 
 In a previous lecture I described at length the pecu- 
 liarities of the foetal circulation. On that occasion I ex-, 
 plained that two kinds of forces are employed, viz. the visible 
 and invisible, the visible forces carrying on the circulation 
 within the body of the foetus, the invisible forces carrying 
 on the circulation within the placenta. In the present and 
 subsequent lectures I shall occupy myself solely with the 
 visible forces, and with the machinery, if I may so phrase 
 it, 'in which the visible forces manifest themselves, viz. the 
 heart, blood-vessels, nerves, etc. A consideration of the 
 visible forces necessarily involves details ; but I shall strive 
 to put them in such a way as not to prove irksome. Hitherto 
 we have been dealing with the machinery of the circula- 
 tion as a whole, now it behoves us to become acquainted 
 with the different parts of that machinery. In describing 
 the several structures employed, I must ask your forbear- 
 ance if at times I repeat myself. I only do so because 
 nature repeats herself, and because, in dealing with the 
 highest form of the circulation as it exists in the bird and 
 mammal, I am necessarily dealing with essentially the same 
 materials and forces employed in the lowest. It is this 
 circumstance which makes the comparative anatomy and 
 physiology of the circulation laborious and long ; but the 
 same circumstance, it appears to me, imparts to the circula- 
 tion, as it exists in ourselves, its chief interest. 
 
 In my remarks on the foetal circulation, I directed 
 attention to the fact that the cavities of the heart of the 
 foetus open into each other, the two auricles communi- 
 
 a curious case of an English mare covered by a quagga horse. The offspring 
 displayed the quagga stripes, and these stripes reappeared in the future progeny 
 of the mare when put to English horses. 
 
158 PHYSIOLOGY OF THE CIRCULATION. 
 
 eating directly by the foramen ovale, the two ventricles 
 indirectly by a canal extending between their great vessels, 
 viz. the ductus arteriosus. On a previous occasion I stated 
 that a somewhat similar arrangement obtains in the reptile, 
 where the two auricles open into a single ventricle, 
 this ventricle, in certain cases, being partially divided into 
 two by a rudimentary septum ventriculorum. The circula- 
 tion in the foetus and reptile is from this circumstance 
 a mixed circulation i. e. the blood circulated is partly 
 arterial and partly venous. The reptiles are cold-blooded 
 animals ; and the foetus might be classed under this head- 
 ing also, were it not for the fact that the foetus inherits the 
 temperature of the mother, and the blood of the parent is 
 virtually that of the offspring. To obtain a warm blood, 
 such as is found in the bird and mammal, the chambers 
 of the heart must be walled off from each other, and thus 
 it is that in birds and mammals the cavities of the right 
 and left halves of the heart do not intercommunicate. A 
 warm blood is the result of a complete arterialisation, and 
 this can only be produced where the lungs and breathing 
 apparatus are sufficiently differentiated, and when a complete 
 pulmonic and systemic heart are present. I use the term 
 ' breathing apparatus ' in its widest sense, for we know that the 
 tissues respire, and that the blood is always warmest where 
 its oxidation goes on most vigorously 1 . That the differ- 
 entiation of the heart into four distinct chambers has some- 
 thing to do with maintaining the blood at a certain temperature 
 is proved by this, that in morbus ceruleus, where the cavities 
 of the heart communicate abnormally, the temperature of 
 the body is very considerably reduced. The temperature 
 of the blood bears a fixed relation to the activity of respi- 
 ration ; the respiratory power and temperature being highest 
 in birds, then in mammals, then in reptiles and fishes, and 
 lastly in the invertebrata 2 . Mr. Newport has pointed out 
 
 1 Sir Benjamin Brodie, in the Croonian Lecture for 1810, and in the Philo- 
 sophical Transactions for 1812, cited experiments to show that the maintenance 
 of animal temperature is directly or indirectly under the influence of the nervous 
 system. 
 
 2 In birds, according to Tiedemann and Rudolphi, the average temperature is 
 107; the temperature in the linnet rising to 111-25. In mammalia the average 
 temperature is 101; in the bat (Vespertilio pipestrella) 106; in the narwhal 96. 
 
PHYSIOLOGY OF THE CIRCULATION. 159 
 
 the very interesting fact that the larvae of insects with 
 small respiring organs have a lower temperature than the 
 perfect insect ; and that the flying insects, because of their 
 possessing a large respiratory apparatus, have a higher tem- 
 perature than the non-volant ones. During sleep and hiber- 
 nation the respiration and temperature decrease. 
 
 Distribution of the Great Vessels in Reptiles, Birds, and 
 Mammals. I have alluded to the general distribution of 
 the vessels proceeding from the ventricle or ventricles, as 
 
 Fig. 81. Fig. 82. 
 
 Fig. 81. Anterior aspect of turkey's heart, with right and left ventricles opened to show auriculo- 
 ventricular valves, a, aorta arching to right side and dividing into three branches, two of which (b) go 
 to right side, and one (c) to left side, of, pulmonary artery dividing into two, and sending a branch to 
 right and left lungs, i. muscular or fleshy valve which occludes right auriculo-ventric.ular orifice. 
 j, musculus papillaris of fleshy valve (compare with g). e, portion of septum to which valve is applied 
 when closed, f, left ventricle, v, tendinous valve which occludes left auriculo-ventricular orifice. 
 , musculus papillaris with chordae tendineae attached to tendinous valve Original. 
 
 Fig. 82 shows thej distribution of the great vessels at the base of the human heart, seen anteriorly. 
 Contrast with Fig. 81. u, aorta giving off innominate, left carotid, and left subclavian arteries, nt, de- 
 scending aorta, v, pulmonary artery dividing and giving branches to right'(/') and left (/) lungs, a, 
 trachea bifurcating and dividing in right (/') and left (/ ) lungs y, descending cava. o, ascending cava. 
 s, right auricle, q, right ventricle, t, left auricle, r, left ventricle. 
 
 the case may be, of the reptile, and it is important that 
 I should now direct attention to their arrangement in the 
 heart of the bird, and to the construction of the descending 
 aorta, as this forms one of the connecting links between 
 the circulation of birds and reptiles on the one hand, and 
 birds and mammals on the other. The aorta of birds is 
 very short, and divides into three principal branches almost 
 before it leaves the left ventricle (Fig. 81, a, , c). The 
 aorta of birds arches in the direction of the right bronchus ; 
 
 In reptiles it is 82-5, when the surrounding medium is 75. In fish (the tunny 
 tribe excepted) and in the invertebrata it is the same as the medium in which 
 they live. The mammalia and birds, as Mr. Hunter ascertained, have a certain 
 permanent heat in all atmospheres, while the temperature of the other is variable 
 with every atmosphere. 
 
160 PHYSIOLOGY OF THE CIRCULATION. 
 
 whereas in mammals it arches towards the left bronchus. 
 (Compare b of Fig. .81, with u of Fig. 82, p. 159.) Of the three 
 branches of the aorta in birds, one arches towards the right 
 axilla, and the other to the left, these being analogous to 
 the single arteria innominata of man, the birds having vir- 
 tually two innominates. The pulmonary artery of birds 
 divides into two branches as in the mammal, one going to 
 the right lung, the other to the left. (Fig. 81, d\ compare 
 with i) of Fig. 82, p. 159.) 
 
 In all reptiles the descending aorta is formed by the union 
 of two branches the right and left aortic branches. The right 
 corresponds with the systemic aorta of birds, and arises from 
 the left ventricular compartment. The left arch leads generally 
 from the right ventricular cavity into the descending aorta, 
 and joins the right arch towards the back. The number and 
 distribution of the great vessels proceeding from the heart be- 
 come fewer and less complicated in the mammal. Here the 
 great vessels are reduced to two ; the aorta proceeding from 
 the left ventricle and giving off the innominate, left carotid, 
 and left subclavian arteries, which in conjunction with the 
 descending aorta and branches, convey arterial blood to all 
 parts of the system ; and the pulmonary artery, arising from 
 the right ventricle, which sends blood exclusively to the 
 lungs. Although the great vessels of the mammalian and 
 human heart are reduced to two, it js worthy of remark that 
 the tendency to an arched or branchial arrangement distinctly 
 recurs. Thus the aorta and pulmonary artery are plaited 
 upon each other, the aorta arching from right to left ; the 
 pulmonary artery subdividing and arching equally to right 
 and left (Fig. 82, p. 159). 
 
 In birds and reptiles there are two superior cavae, a similar 
 number being found in the mammalia which approach nearest 
 to the oviparous vertebrata, as the monotremata and mar- 
 supiata, and in some of the rodentia, as for example 
 the porcupine. The heart of the bird, like that of the 
 mammal, consists of four distinct cavities, the cavities 
 being separated from each other by valves and muscular 
 partitions ; the former occurring in the auriculo-ventricular 
 orifices, and isolating the right and left auricles from the 
 
PHYSIOLOGY OF THE CIRCULATION, l6l 
 
 right and left ventricles ; the ' latter separating the right 
 auricle from the left auricle, and the right ventricle from the 
 left ventricle. The right auricle of the bird is compara- 
 tively very large, and the right ventricle highly differentiated; 
 it being supplied with a wonderfully perfect muscular valve 
 (Fig. 8 1, /', p. 159), which takes the place of the tricuspict 
 valve in mammals (Fig. 84, /, p. 174). The elaboration of 
 the right heart of the bird is, no doubt, connected with 
 the very perfect and very extensive respiration of that 
 animal. 
 
 Valves in the Heart of the Bird. The system of valves 
 In the heart of the bird is very complicated and very com- 
 plete. The inferior cava is guarded at its orifice by a semi- 
 lunar valvular fold, which separates it from the orifice 
 of the left superior cava. The orifices of the inferior and 
 left superior cavae are further protected by the large valves 
 which guard the mouth of the coronary sinus. 'In the emu 
 a strong oblique semilunar muscular fold . commences by 
 a band of .muscular fibres running along the upper part of 
 the auricle, and, expanding into a valvular form, extends 
 along the posterior and left side of the sinus, terminating 
 at the lower part of the fossa ovalis. A second semilunar 
 muscular valve of equal size extends parallel with the pre- 
 ceding along the anterior border of the orifice of the sinus, 
 its lower extremity being fixed to the smooth floor of the 
 auricle, its upper extremity being continued into a strong 
 muscular column running parallel to the one first mentioned 
 across the upper and anterior part of the auricle, and giving 
 off from its sides the greater part of the musculi pectinatiV 
 
 The other valves of the bird's heart viz. the aortic, pul- 
 monic, and mitral (Fig. 81, v, p. 159) closely resemble those 
 of the mammal, a description of which will be given further on. 
 The aortic and pulmonic valves of the bird consist of three 
 semilunar cusps or segments the valves which occupy a 
 similar position in the reptiles having only two cusps. The 
 remarkable feature in the valves of the heart of the bird 
 consists in the amount of muscular fibres mixed up with 
 
 1 Comparative Anatomy and Physiology of Vertebrates, by Professor Owen, 
 
 M 
 
1 62 PHYSIOLOGY OF THE CIRCULATION. 
 
 them, some being partly, and others wholly, muscular. The 
 arrangement of the muscular fibres in the heart of the bird 
 closely resembles that in the heart of the mammal, to be 
 described subsequently. 
 
 Respiration and Circulation in Birds. The differentiation 
 perceptible in the cardiac valves of the bird is necessitated by 
 the highly developed condition of the lungs, the lungs being 
 more capacious than in any other class. The increased capa- 
 city of the lungs becomes a sine qua non when it is remem- 
 bered that birds require to make great exertions in launching 
 themselves into the air from a level surface, and also in 
 diving. A bird exerts its greatest power in rising. When 
 fairly launched in space the weight of its body acts upon the 
 twisted inclined planes formed by the wings, and does the 
 principal part of the work \ The air cells and spaces in -birds 
 extend in many cases to every part of the body, not except- 
 ing the bones 2 and muscles ; and a bird can respire for a 
 short time after the trachea is closed if the humerus be per- 
 forated. The great air-sacs in connexion with the lungs of 
 birds, as I have ascertained from artificial injections, have 
 arteries and veins in considerable numbers ramifying on their 
 surface, the arterial and venous blood contained in the vessels 
 being equally exposed to the influence of the air contained in 
 the air-sacs. The air-sacs, which are apparently mere ap- 
 pendages of the lungs, are in reality the harbingers and types 
 of all lungs. They closely resemble, in their rudimentary 
 form, the hollow viscera of vertebrates 3 . The fish has its 
 
 1 'On the Mechanical Appliances by which Flight is attained in the Animal 
 Kingdom,' toy the Author, Trans. Lin. Soc. vol. xxvi. ' On the Physiology of Wings,' 
 by the Author. Trans. JRoy. Soc. Edin. vol. xxvi. 
 
 2 ' In the ;gannet and pelican the air enters all the bones with the exception of 
 the phalanges of the 'toes, mnd in the hombill even these are permeated by air.' 
 Comp. Anat. and Phys. of Vertebrates, by Professor Owen, vol ii. p. 214. 
 
 3 ' In all the air-breathing vertebrata the respiratory membrane is formed by a 
 prolongation of the internal tegumentary or mucous membrane from the upper part 
 of the digestive tube ; and this also holds true in the aquatic vertebrata or the fishes. 
 When the expanded respiratory membrane is placed at some distance from that 
 portion of the mucous membrane of the digestive tube with which it is continuous, 
 as is especially the case in mammalia and birds, this mucous membrane is prolonged 
 to the part where its expansion occurs, in the form of a tube strengthened on the 
 outer surface by elastic textures, to enable it to withstand the atmospheric pressure. 
 Along this tube (trachea) and its branches (bronchi and bronchial tubes) the air 
 
PHYSIOLOGY OF THE CIRCULATION. 163 
 
 swimming bladder a closed sac containing air instead of 
 urine, but which, like the urinary bladder, can open and close. 
 ' In the water-newt, the lungs consist of a pair of elongated 
 sacs, without any internal laminae or folds. In the frogs these 
 membraneous sacs present ridges on their inner surface, espe- 
 cially at the upper part ; and in the lungs of the turtle and 
 crocodile these ridges increase in number and in size, and form 
 partitions dividing the interior of the lungs into numerous 
 cells communicating with each other.' The differentiation is 
 carried still further in the bird and mammal ; and there are 
 grounds for believing that these, like the more simple air- 
 bladder of the fish, have the power of opening and closing 
 within certain limits. 
 
 The Air-sacs of Birds, etc. The air-sacs of birds have nothing 
 whatever to do with flight, as they are found in birds which 
 do not fly, and flight can be performed by the bat in their 
 absence. Sappey enumerates as many as fifteen air-sacs. 
 They open the one into the other, and as they have a peri- 
 staltic action, currents of air are continually passed throughout 
 the entire substance of the body, very much as in the tracheae 
 of insects and in the older vascular bundles of plants. The 
 peristaltic movements of the air-sacs of birds show the in- 
 timate relation existing between the lungs and the heart ; the 
 one circulating air, the other blood. The air-sacs of birds were 
 described by John Hunter as early as 1774. Somewhat anal- 
 ogous membraneous expansions are found in connexion with 
 the lungs of serpents the python, for example ; so that the 
 lungs of birds, which represent the highest development of 
 pulmonary organs, have certain affinities with the lungs of rep- 
 tiles, which are not differentiated to anything like the same 
 extent. 
 
 The only peculiarities in the circulation of birds to which 
 allusion is necessary are to be found in a modification of the 
 portal circulation and the possession of a distinct renal circu- 
 lation. The veins of birds anastomose very freely. One of 
 these anastomosing branches extends between the united 
 caudal, haemorrhoidal, and iliac veins to the vena portae, so 
 that the blood from the viscera and posterior part of the body 
 
 passes to and from the proper respiratory membrane on the inner surface of the 
 lungs.' Cyc. of Anat. and Phys. 'Arterial Respiration,' vol. iv. p. 331. 
 
 M 2, 
 
164 PHYSIOLOGY OF THE CIRCULATION... 
 
 flows either into the vena portae or vena cava inferior. The 
 renal circulation of birds was discovered by Professor Jacob- 
 son. It is venous in character, branches of the inferior cava 
 proceeding to the interior of the kidneys 1 . Other investigators 
 have found what virtually amounts to a renal circulation in 
 reptiles and fishes. 
 
 Circulation in the Mammal. What has been said of the 
 heart of the bird applies, with slight modifications, to the 
 heart of the mammal. This, too, consists of four distinct 
 cavities two auricles and two ventricles ; the auricles and 
 ventricles in the adult being separated from each other by 
 valves and by muscular partitions or septa. In virtue of this 
 arrangement the heart of the mammal is often spoken of as 
 consisting of a right or pulmonic heart composed of the right 
 
 Fig. 83. 
 
 Fig. 83. Heart of dugong seen anteriorly : shows bifid apex, s, right auricle, q, right ventricle, t, left 
 auricle, r, left ventricle, u, aorta giving off innominates, left carotid and left subclavian arteries, -v, pul- 
 monary artery bifurcating and proceeding to right and left lungs. (Compare with human heart, Fig. 82, 
 p. 159.) Owen, 
 
 auricle and ventricle, and a left or systemic heart composed 
 of the left auricle and ventricle. The terms pulmonic and 
 systemic have been employed because the right heart receives 
 the venous blood from the system and forces it into the lungs ; 
 the left heart receiving the arterial blood from the lungs and 
 forcing it into the system. This arrangement provides for 
 what may be regarded a distinct venous circulation, and a 
 distinct arterial circulation ; the two kinds of blood, viz. the 
 arterial and the venous, being no longer mixed either in the 
 vessels or in the heart (Fig. 82, p. 159). 
 
 In the dugong, the systemic and pulmonic hearts are very 
 
 1 I have had opportunities of injecting the kidneys of birds, and the degree of 
 vascularity is in some cases quite remarkable. 
 
PHYSIOLOGY OF THE CIRCULATION. 165 
 
 distinct the right and left ventricles being widely separated 
 from each other at their apices, and only joined towards their 
 bases, as shown at Fig. 83. This virtually divides the organ 
 into a left or systemic, and a right or pulmonic heart. The 
 auricles of the heart of the dugong are of equal size, and the 
 ventricles closely resemble each other in their general con- 
 figuration. The heart of the whales and dolphins more closely 
 resembles that of the other mammals. The arteries of the 
 whale, as John Hunter pointed out, are remarkable for their 
 tortuosity and convoluted arrangement. Vast plexuses of tor- 
 tuous vessels are found under the pleura and between the ribs 
 and their muscles on each side of the spine. Similar plexuses 
 surround the medulla spinalis, more especially where it comes 
 out from the brain. In the porpoise the veins, which are for 
 the most part devoid of valves, display a similar tortuosity, 
 particularly on either side of the spine below the kidneys. 
 When artificially injected the venous plexuses present a very 
 unusual appearance 1 . Hunter was of opinion that the cetacea 
 contain more blood in proportion to their size than other 
 mammals ; and the vast arterial and venous expansions re- 
 ferred to certainly favour this view. He thought the expan- 
 sions had something to do with the habits of the animals 
 the cetacea remaining submerged for long intervals, and de- 
 voting very short periods to breathing and aerating their 
 blood. He thought, in fact, that the plexuses acted as reser- 
 voirs for oxygenated blood, and prevented asphyxia when the 
 animals dived. This may form a partial, but is not the whole 
 explanation ; as I have succeeded in injecting similar arterial 
 and venous plexuses in the arms and legs of the sloth, the 
 arms, legs, and tail of the spider-monkey, and the testicles of 
 the ram where, of course, no such aggregation of oxygenated 
 blood is required 2 . Sir Charles Bell believed that the plexusus 
 and increased vascular supply were necessary to parts per- 
 forming a large amount of work, or undergoing strain ; such 
 parts requiring a more liberal supply of nutritive material* 
 The tortuosity of the vessels quite explains the absence of 
 
 1 In illustration, see specimens prepared by the author, deposited in the Museum 
 of the Royal College of Surgeons, London. 
 
 2 These preparations are deposited in the Hunterian Museum of the Royal 
 College of Surgeons of London, where they may be consulted. 
 
1 66 PHYSIOLOGY OF THE CIRCULATION. 
 
 valves in the veins ; the plexuses of veins in the porpoise re- 
 sembling varicose veins in ourselves, where the valves are 
 diseased or broken down. The circulation in the cetacea is 
 especially remarkable for its magnitude. The enthusiastic 
 and justly-renowned Hunter found in the circulation of the 
 cetacea a subject worthy of his scalpel. He says ' In our 
 examination of particular parts, the size of which is generally 
 regulated by that of the whole animal, if we have only been 
 accustomed to see them in those which are small or middle- 
 sized, we behold them with astonishment in animals so far 
 exceeding the common bulk as the whale. Thus the heart 
 and aorta of the spermaceti whale appeared to be prodigious, 
 being too large to be contained in a wide tub, the aorta mea- 
 suring a foot in diameter. When we consider these as applied 
 to the circulation, and figure to ourselves that probably ten or 
 fifteen gallons of blood are thrown out at one stroke, and moved 
 with an immense velocity through a tube of a foot diameter, 
 the whole idea fills the mind with wonder 1 .' 
 
 In order, as it were, to make the differentiation between the 
 systemic and pulmonic circulation more obvious, the systemic 
 circulation is carried on within vessels termed arteries, and the 
 venous circulation within vessels termed veins. These are 
 separated from each other at the periphery of the body and 
 the organs thereof, by minute plexuses of vessels, which, from 
 their small size, are denominated capillaries. They are sepa- 
 rated at the heart by muscular and valvular septa. The 
 arteries begin at the heart and terminate at the capillaries ; 
 the veins begin at the capillaries and terminate at the heart. 
 Between and around the capillaries, a very minute system 
 of vessels, the hyper-vascular canals, are found. The arteries 
 break up, branch or bifurcate, and become smaller and smaller 
 as they proceed from the heart ; the veins, on the other hand, 
 converge and unite, and become larger as they near the heart. 
 
 The arterial and venous systems may not inaptly be com- 
 pared to a cone, the apex of which is directed towards the 
 heart ; or to a tree, which bifurcates near its roots, and whose 
 stem and spreading branches represent the arterial and venous 
 vessels lying side by side. The arterial system is in some 
 
 1 Phil. Trans. 1787, p. 415. 
 
PHYSIOLOGY OF THE CIRCULATION. l6/ 
 
 respects the converse of the venous. The arteries have thick 
 walls, are elastic in the direction of their length, and breadth, 
 and, if the aortic semilunar valve be excepted, are not furnished 
 with valves. They are also comparatively narrow. The veins 
 have thin walls, are less elastic than the arteries, and are pro- 
 vided with numerous valves which may consist of from one to 
 four or more segments. The veins are, comparatively speak- 
 ing, very wide. The presence of valves in the veins and other 
 structures is to ensure that the circulating fluid shall always 
 proceed in one direction. They are the sluices or floodgates 
 which are thrown open by the advancing tide, but which are 
 closed the instant it attempts to retrogress or recede 1 . 
 
 With the peculiarities of the circulation in the mammal 
 most of you are familiar. I will however take the liberty of 
 briefly adducing the leading facts connected with it, as an 
 enumeration of these will enable me to introduce some new 
 matter which may prove interesting. 
 
 Auricles, Ventricles, Valves, Septa, etc., of Mammalian 
 Heart. The mammalian heart (of which the human may be 
 taken as an example) is a conical-shaped, hollow, muscular 
 mass, slightly twisted upon itself, particularly at the apex 2 . 
 It is divided into four distinct compartments a right auricle 
 and a right ventricle, and a left auricle and a left ventricle. 
 The right auricle is separated from the left auricle by a mus- 
 cular partition, a similar partition running between the right 
 and left ventricles. The right and left auricles are separated 
 from the right and left ventricles by valvular septa (the mitral 
 and tricuspid valves), which, when the heart opens and closes, 
 
 1 ' In man the valves are very numerous in the veins of the extremities, especially 
 the lower ones, these vessels having to conduct the blood against the force of 
 gravity. They are absent in the very small veins, also in the venae cavae, the 
 hepatic vein, portal vein and its branches, the renal, uterine, and ovarian veins. A 
 few valves are found in the spermatic veins, and one also at their point of junction 
 with the renal vein and inferior cava in both sexes. The cerebral and spinal veins, 
 the veins of the cancellated tissue of bone, the pulmonary veins, and the umbilical 
 vein and its branches, are also destitute of valves. They are occasionally found, 
 few in number, in the venae azygos and intercostal veins.' Anatomy, Descriptive and 
 Surgical, by Henry Gray, Esq., F.R.S., etc., p. 401. 
 
 2 In mammalian hearts the apex is slightly notched, the notch varying in dif- 
 ferent animals. In the dugong it is so deep as to separate the right and left 
 ventricles throughout half their extent. The notch in question forms the boun- 
 dary between the apices of the right and left ventricles. (Fig. 83, p. 164.) 
 
1 68 PHYSIOLOGY, OF THE CIRCULATION. 
 
 rise and fall like diaphragms (Figs. 84, /; 85, m, z, n ; p. 174).- 
 ,The cavities of the heart are of nearly the same size, the walls 
 of the right auricle being so thin in parts as to be nearly trans- 
 parent. Those of the left auricle are a little thicker. The walls 
 x)f the right ventricle are about twice the thickness of those of 
 the right auricle ; while those of the left ventricle and septum 
 are nearly twice as thick as those of the right ventricle. The 
 thickness of the walls of the auricles and ventricles is in exact 
 proportion to the work to be performed by them the left 
 ventricle having a greater amount of work to do than the 
 right ventricle, and the left auricle than the right. This is 
 proved by the fact that in the foetus, where there is no dis- 
 tinct pulmonic and systemic circulation, the walls of the 
 ventricles, until quite towards the full term, are of nearly the 
 same thickness. It is also proved by hypertrophy of the right 
 ventricle in cases of disease of the lungs, which, obstructing 
 the passage of the blood through the pulmonic vessels, neces^ 
 sitates an increase of power in the propelling organ. In order 
 to understand the course pursued by the blood in the right or 
 pulmonic and the left or systemic heart of the mammal, it is 
 necessary to be familiar with its entrances and exits. 
 
 Right Heart of Mammal.- The blood enters the right 
 auricle by two principal openings : the one communicating 
 with the superior cava, through which it receives the venous 
 blood from the head and upper extremities ; the other com- 
 municating with the inferior cava, through which it receives 
 the venous blood from the trunk and lower extremities. (Fig. 
 84, a, #, p, 174). These openings are not provided with valves, 
 so that the reflux of the blood when the right auricle closes is 
 prevented in part by atmospheric pressure, by the closing of 
 the valves of the large veins of the upper extremities and 
 neck, and in part by the closure of the cavae themselves, which- 
 are supplied with muscular fibres for this purpose. In addi- 
 tion to the openings of the superior and inferior cavae, there 
 are those of the coronary sinus and foramina Thebesii, through 
 which the venous blood of the heart itself finds its way into 
 the right auricle. These constitute the entrances into the 
 right auricle. There is only one exit. The venous blood 
 passes from the right auricle into the right ventricle by the 
 right auriculo-ventricular orifice, which is guarded by the tri- 
 
PHYSIOLOGY OF THE CIRCULATION. 169 
 
 cuspid valve (/). Once in the right ventricle, the blood is 
 expelled through the funnel-shaped canal known as the in- 
 fundibulum or conus arteriosus into the pulmonary artery (d\ 
 the orifice of which is guarded by the pulmonic semilunar 
 valve (//). It thence finds its way into the lungs, where it 
 is arterialised ; and there we leave it for the present. The 
 right auricle and ventricle form a through route for the venous 
 blood, this being collected in the right auricle, which, when it 
 closes, forces it into the right ventricle, the right ventricle in 
 turn forcing it into the lungs. ( Vide arrows of Fig. 84, p. 174.) 
 
 The Blood urged on by a Wave-Movement ; Heart and 
 Vessels Open and Close in Parts. The blood is projected by 
 a progressive wave-movement, which begins in the cavae and 
 extends to the right auricle, and thence to the right ventricle ; 
 the right auricle opening as the cavae close, and the right 
 ventricle opening as the auricle closes. The blood is thus 
 forced on by a vis a tergo, aided by a sucking or vis a f rente, 
 movement. The vis a tergo or closing movement acts in con- 
 junction with the elasticity of the vessels ; the vis a f rente or 
 sucking movement in conjunction with atmospheric pressure 
 and the demand set up by the tissues for nourishment. If the 
 different parts of the heart have the power of expelling their 
 contents, they should, ceteris paribus, have the power of open- 
 ing to receive a new supply. Dr. Carson believed that the 
 different parts of the heart relaxed after being contracted ; the 
 relaxation being favoured by the distribution of the muscular 
 fibres, by the elasticity of the lungs, and by a diminution of 
 atmospheric pressure on the outer or convex sttrface of the heart, 
 the pressure of blood on the great veins which conduct to the 
 organ, and which act on its inner or concave surface^ being in- 
 creased. In other words, he was of opinion that the relation 
 between the lungs, pleura, heart, and pericardium was such, 
 that the different parts of the organ were opened in a great 
 measure mechanically by a simultaneous withdrawal and in- 
 crease of atmospheric pressure on its outer and inner surfaces 1 . 
 While agreeing with Dr. Carson that the heart exerts a pulling 
 and pushing power, I differ from him as to the modus operandi.. 
 In short, I attribute the opening and closing powers possessed 
 
 1 An Enquiry into the Causes of the Motion of the Blood, by James Carson, 
 M.D., 1815. 
 
I/O PHYSIOLOGY OF THE CIRCULATION. 
 
 by the different parts of the "heart to an inherent vitality. That 
 the movements in question are not due to a rhythmic pressure 
 exerted outside and inside the organ is obvious from this, that 
 the heart acts when it is cut out of the body and deprived of 
 blood, the atmospheric pressure on its outer and inner surfaces 
 being equal. That the heart regulates its movements irre- 
 spective of atmospheric pressure is further apparent from the 
 fact that its different parts move at different times the hearts 
 of some of the lower animals, by the mere vermicular move- 
 ments of their walls, transmitting two kinds of blood through 
 a single chamber. Thus Goodsir 1 observed that there is a slight 
 asynchronism between the movements of the right and left 
 auricles in the heart of the lizard 2 , and that the contraction of 
 the ventricle begins at its right side, in the neighbourhood of 
 the pulmonary artery, and terminates at the left or arterial 
 sinus of the ventricle. Briicke, in his memoir in the Vienna 
 Transactions, has, curiously enough, described a ventricular 
 arrangement by which venous blood only passes into the pul- 
 monary artery in reptiles ; the ventricle beginning to contract 
 on the right side, and afterwards on the left. 
 
 Many are of opinion that the closing of the auricle pro- 
 duces the opening of the ventricle, the closing of the ventricle 
 in turn dilating the auricle. This would be a mere waste of 
 power; and, besides, unless the ventricle opened spontane- 
 ously, the blood from the auricle, which is the distending 
 medium, would be denied admission. The ventricle when it 
 closes becomes a solid mass, to which no fluid, however great 
 the pressure exerted by it, can gain access (Fig. 93, , p. 190) 3 . 
 Nor must it be overlooked that occasionally, when the heart is 
 acting slowly, the ventricle opens before the auricle closes, and 
 the converse. Furthermore, the several parts of the heart 
 open and close when cut out of the body and deprived of 
 blood. There is, therefore, no sufficient ground for believing 
 
 1 Anatomical Memoirs, vol. i. p. 443. 
 
 2 Similar asynchronism was observed in the auricles of the turtle and frog. 
 
 3 In discharging my duties as Pathologist to the Royal Infirmary of Edinburgh, 
 I occasionally open hearts, the ventricular cavities of which are quite obliterated. 
 The extent of centripetal or closing power possessed by the hollow viscera is very 
 remarkable. I have at present in my possession a human stomach, the calibre of 
 the body of which is not greater than that of the small intestine. The patient 
 died of starvation, induced by cancer of the oesophagus. 
 
PHYSIOLOGY OF THE CIRCULATION. 1 71 
 
 that the opening of the ventricle is due to the closing of the 
 auricle, and vice versa. On the contrary, observation and ex- 
 periment tend to prove that the different compartments of the 
 heart open and close spontaneously by vital and independent 
 acts. The probabilities are, that there is no such thing as a 
 violent closing of one part of the circulatory apparatus pro- 
 ducing a violent opening of another part *. That the different 
 parts of the heart and vessels are endowed with the power of 
 opening and closing is in great measure proved by this, that 
 in the lower animals, where there are no hearts, the vessels 
 pulsate and carry on the circulation by themselves. Similar 
 pulsating vessels, as has been already explained, are found 
 when hearts are present ; as in the mesenteric vessels of the 
 frog, the veins of the bat's wing, the caudal vessels of the tail 
 of the eel, the saphenous veins of the rabbit ; and the chances 
 are, that the vessels generally perform an important part in 
 the visible circulation of vertebrates 2 . The caudal vessels of 
 the eel display a sacculation which may be regarded as a 
 venous heart. The power of the vessels to open and close in 
 parts decreases as the elastic properties of the vessels increase. 
 
 1 Dr. Hoggan, in a recent number of the Edinburgh Medical Journal (October, 
 1872), states his belief that the heart dilates or expands in virtue of the blood 
 forced into its parietes at each systole. This doctrine is, I believe, founded in 
 error. The heart in the embryo pulsates while yet it is a solid mass of nucleated 
 cells i. e, before it is supplied with blood-vessels and before cavities are formed 
 in it. In the adult it pulsates after it is removed from the body, its cavities, which 
 contain the blood, and which, according to Dr. Hoggan, indirectly force it into its 
 ventricular walls, being laid open. The presence of blood is moreover not neces- 
 sary to rhythmic movements, as plants and the lower orders of animals, which are 
 devoid of blood, exhibit them. Dr. Hoggan's theory is not more satisfactory when 
 applied to the lungs. If the lungs are expanded by the forcing of blood into their 
 capillary vessels, then the lungs of the foetus should be expanded, as their vessels 
 are pervious, and the foetal heart acts vigorously. Again, in the case of the adult 
 lung, collapsed from fluid or air pressure exerted from without (the carnified lung 
 of pathologists), the heart acts normally, but fails to arrest the mischief. If a 
 lung be deprived of its residual air, it is impossible to inject it. In conclusion, if 
 the blood in the vessels and capillaries of the lungs and heart caused their expan- 
 sion, it is evident that this fluid, which is constant in amount in both, would pre- 
 vent their contraction and destroy their rhythmic movements that is to say, would 
 render the alternate increase and diminution of the volume of the heart and lungs 
 impossible. Dr. Liebermann, of Vienna, who wrote after Dr. Hoggan, but pub- 
 lished before him, virtually endorses Dr. Hoggan's views. 
 
 2 The small vessels are largely furnished with nerves. They diminish their 
 calibre on the application of cold, and increase it on the application of heat. 
 
172 PHYSIOLOGY OF THE CIRCULATION. 
 
 The inferior vena cava, the renal, azygos, and external iliac 
 veins, and the large trunks of the portal venous system and 
 hepatic veins, as Dr. Gray has shown, contain longitudinal and 
 circular non-striated muscular fibres, so that they have a struc- 
 ture resembling that of the intestine, the power of which to 
 transmit solid, semi-solid, or fluid contents is well known. In 
 addition, the inferior cava and the pulmonary artery and aorta 
 at their origins are abundantly supplied with nerves an 
 arrangement which assimilates the great vessels situated at the 
 root of the heart to the bulbus arteriosus of fishes, which, as 
 has been shown, is endowed with rhythmic power. The vessels 
 aid the circulation indirectly by their elasticity and resiliency. 
 By receiving and storing up part of the impulse communicated 
 to the blood by the heart at each systole, and by expending 
 the power thus imparted gradually between the pulsations, 
 they tend to equalise the current, and give continuity of move- 
 ment. That the calibre of the great vessels increases when 
 the ventricles close is proved by placing a ring of metal with 
 a slit in it round the carotid of the horse or other large animal. 
 The slit is widened during the systole, and diminished during 
 the diastole. 
 
 If rigid vessels were compatible with the movements of 
 animals, they would be preferable to elastic ones for carrying 
 on the circulation, as, in this case, the heart would merely 
 require to force on the blood without having to dilate the 
 vessels. If, even with our imperfect knowledge of mechanics, 
 we were asked to transmit fluid from one point to another, we 
 would never dream of employing an elastic tube (a tube which 
 can open and close in parts is quite another matter). Still 
 less would we think of distending the elastic tube with the 
 power which should transmit the fluid, delegating the trans- 
 mission at second hand to the recoil of an elastic apparatus. 
 This, I repeat, with our imperfect knowledge of mechanics, 
 we would not do. Can it be thought, then, that nature, per- 
 fect in every direction, would employ a method to which we, 
 with our limited knowledge and crude methods, would object? 
 The vessels or ducts must of necessity be flexible : they form 
 part of a living, moving mass, and must yield to accommodate 
 themselves to the varying postures and shapes assumed by the 
 organism to which they belong. It does not however follow 
 
PHYSIOLOGY OF THE CIRCULATIONS 173 
 
 from this that they are to be regarded as simply elastic tubes : 
 on the contrary, we know that some of them pulsate i. e. open 
 and close in parts. We know further that all of them are 
 supplied with nerves, and many of them with longitudinal 
 and circular muscular fibres similar to those found in the in- 
 testines ; the intestines exhibiting vermicular movements. Nor 
 must it be forgotten that the presence of nerves and of mus- 
 cular fibres are not necessary to the so-called contraction and 
 relaxation of parts. The heart opens and closes while yet it 
 is a mass of cells (neither cavities nor blood being present) ; 
 and the vacuoles or spaces in many plants open and close with 
 a regular rhythm the closure being rapid and the opening 
 slow, as in the different parts of the heart Here of course 
 neither muscle nor nerves are present. It is therefore exceed- 
 ingly improbable that the blood-vessels take no part in the 
 circulation other than is produced by a mechanical recoil. 
 
 If there is any truth in the theory that living structures 
 accommodate themselves to the conditions in which they are 
 placed, it is reasonable to conclude that the vessels of animals, 
 being opened and allowed to close at brief intervals through 
 innumerable lives (some of them very protracted), come ulti- 
 mately to open and close of themselves, and to act either in- 
 dependently or in conjunction with the heart. If the vessels 
 were rigid and non-resilient, the blood would be forced along 
 them by successive jerks, each jerk corresponding to the closing 
 or systole of the ventricles. This is what actually happens 
 when the heart is acting so feebly that it fails to distend the 
 vessels, and evoke their elastic properties. Under these cir- 
 cumstances a very distinct venous pulse is felt, the elasticity 
 which begets a continuous current being inoperative. The 
 fact that a feeble heart can make its pulsations felt in the 
 veins proves that considerably less power would suffice for 
 carrying on the visible circulation if the vessels were rigid 
 (they are virtually so in this non-distended condition). When 
 the heart is acting normally, the column of blood in the vessels 
 receives during the systole a smart tap, similar to that which 
 a hammer produces when made to strike the end of a column 
 of wood or other rigid material. This follows because fluids 
 are very slightly compressible even under high pressures. The 
 incompressibility of the fluid column of blood accounts for the 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 extreme rapidity with which the pulsation communicated 
 during the systole travels, the impulse at the heart and ex- 
 tremities being nearly synchronous. This rapidity of travel 
 is accounted for by the blood ejected from the ventricles dis- 
 placing that immediately in front of it, this in turn displacing 
 the blood in front of it, and so on ad infinitum^ until the capil- 
 laries are reached by the advancing column on the one hand, 
 and the heart by the receding column on the other. The 
 transmission of the different portions of blood meted out by 
 
 Fig. 84. 
 
 Fig. 85. 
 
 Fig. 87. 
 
 Fig. 84. Pulmonic or right side of human heart, t, right auricle. -, right ventricle, a, superior cava. 
 *, inferior cava. c, aorta, d, pulmonic artery, h, segment of pulmonic semilunar valve, z, sinus of 
 Valsalva. /, segment of tricuspid valve. J. musculus papillaris. The arrows indicate the direction in 
 which the blood enters and leaves the right or pulmonic heart. After Gray. 
 
 Fig. 85. Tricuspid valve in action seen from above (human). The segments are folded and twisted into 
 each other by a screwing wedging motion (vide arrows m, i, n), occasioned by the spiral movements of 
 the ventricles and the spiral impulse communicated to the blood contained within the right ventricle. 
 Original. 
 
 Fig. 6. Semilunar valve of pulmonary artery in action, seen from above (human). Shows how, when 
 the valve is closed the segments rs. so, or, are folded upon themselves, and spirally wedged towards the 
 axis of the vessel (vide arrows'). To produce a perfect closure the margins (a, b) of the segments must 
 flatten against each other, the extent of the flattening increasing as the pressure exerted by the blood is 
 augmented. Original. 
 
 Fig. 87, Diagram showing sectional view of the sinuses of Valsalva (i) in the human pulmonary artery. 
 Shows also the different positions assumed by the segments of the pulmonic semilunar valve when at rest 
 and in action, a, arrow indicating the course taken by the blood on leaving the right ventricle. The 
 blood in its passage pushes aside the segments (/) of the valve, until they assume the positions d and e. 
 d represents the position of the segments when at rest and floating in blood ; e their position when 
 pushed aside by the advancing tide ; and f their position when closed. The arrow b indicates the direc- 
 tion taken by the blood when it retrocedes and closes the valve ; c base of right ventricle (infundibuli- 
 fonn portion). Original. 
 
 the ventricles, at each systole, may be compared to the water 
 and debris contained in the buckets of a dredging-machine, 
 where each bucket is pursued by every other bucket in a con- 
 tinuous round. The all but incompressible nature of the fluid 
 column of blood in the vessels, taken in connexion with the 
 fact that the blood is moved on in relays, enables the heart, as 
 has been stated, to exert a sucking as well as a propelling 
 power. 
 
PHYSIOLOGY OF THE CIRCULATION. 175 
 
 Valves of Right Heart of Mammal. To facilitate the circu- 
 lation of the blood through the heart, the valves, sluices, or 
 gateways of the heart are constructed to open in only one 
 direction ; thus, the tricuspid valve opens towards the right 
 ventricle (Fig* 84, /), and the semilunar one (Fig. 84, k] to- 
 wards the pulmonary artery ; the blood is consequently com- 
 pelled to travel from the right auricle (Fig. 84, a) to the right 
 ventricle (g), and from the right ventricle to the pulmonary 
 artery (d) and lungs. It is only when the valves are diseased 
 and incompetent that even a slight amount of regurgitation 
 is possible, either in the tricuspid (Fig. 85) or semilunar valve 
 (Fig. 86). 
 
 When the blood is being forced from the right ventricle, 
 it is projected as a fluid wedge (the infundibulum is wedge- 
 shaped). The fluid wedge throws the segments of the semi- 
 lunar valves back into the sinuses of Valsalva, as opening 
 folding-doors are forced into recesses formed for their recep- 
 tion (Fig. 87, i}. This has the effect of increasing the orifice 
 of the pulmonary artery very considerably. But the recesses 
 or sinuses of Valsalva (Fig. 87, e) have yet another function. 
 They are large enough always to contain a certain amount 
 of residual blood, which by its mere weight tends to force 
 the segments towards the axis of the pulmonary artery, the 
 instant the systole of the right ventricle ceases. This move- 
 ment is favoured by the sucking power exerted by the right 
 ventricle when it expands (vide arrow b of Fig. 87). The 
 segments of the semilunar valve, in addition, incline towards 
 the axis of the vessel when left to themselves (Fig, 87, d). In 
 virtue of this mechanical adaptation, the margins of the seg- 
 ments are forced towards each other by the slightest reflux ; 
 the reflux, when it increases, producing a folding or wedging 
 of the segments into each other, as shown at Fig. 86. The 
 tricuspid valve acts on the same principle (Fig. 85), but has a 
 more complicated function to perform, from its guarding the 
 right auriculo-ventricular orifice, the size of which varies as 
 the heart opens and closes, and from the fact that it is geared 
 by a series of tendinous bands, the chordae tendineae *, to 
 
 1 In the substance of the pulmonic semilunar valve, similar bands are found ; and 
 in certain cases of disease they are dissected out, and greatly resemble the chordae 
 tendineae of the tricuspid. Both valves are evidently formed on the same type. 
 
1 76 PHYSIOLOGY OF THE CIRCULATION. 
 
 actively-contracting structures, viz. the musculi papillares 
 (//, of Fig. 84, p. 174). 
 
 The action of the tricuspid valve is therefore vito-mechanical, 
 while that of the semilunar is nearly, if not wholly, mechanical. 
 The parts which correspond to the sinuses of Valsalva in the 
 right ventricle are the spaces to the outside of each of the seg- 
 ments of the tricuspid. 
 
 The blood is forced by the right ventricle into the lungs 
 with considerable energy. Much of the force exerted is how- 
 ever dissipated by the rapid bifurcation of the pulmonary 
 arteries, these dividing and subdividing at such short dis- 
 tances as effectually to slow the current before it reaches the 
 delicate capillaries of the lungs. This is a wise provision, for 
 in cases of hypertrophy of the right ventricle, it happens not 
 unfrequently that some of the smaller vessels of the lung are 
 ruptured, and pulmonary apoplexy induced l . 
 
 Safety-valve action of Tricuspid. It has been thought by 
 some 2 , that, in order to prevent injury to the pulmonary 
 organs, the tricuspid valve is never exactly competent, and 
 that, when the right ventricle closes, the blood, which cannot 
 be forced into the lungs without producing mischief, escapes 
 into the right auricle, and thence into the cavae. I am not 
 disposed to look favourably on this argument, as it assumes 
 an imperfection in the circulatory apparatus, which I do not 
 believe exists. In the fish, where there is no reason to suspect 
 a regurgitant action, the gills are situated in close proximity 
 to the heart, but no harm accrues from the proximity, although 
 the ventricle and bulbus arteriosus are both exceedingly power- 
 ful structures 3 . The walls of the right and left ventricles of 
 the mammal, as has been already stated, are of the same 
 thickness in the foetus until quite near the full term. Towards 
 the end of the full term and after birth, when the pulmonic 
 circulation is established, the right ventricular walls thin, while 
 the left ventricular walls thicken. Here is an accommodating 
 process which produces the exact amount of pressure required 
 
 1 Pulmonary apoplexy is usually associated with disease and constriction of the 
 mitral valve, the constriction obstructing the flow of blood into the left ventricle, 
 and damming it up in the lungs. 
 
 2 Mr. T. W. King, in Guy's Hospital Reports for April, 1837, No. IV. 
 
 3 For explanation of the manner in which the ventricle and bulbus arteriosus of 
 the fish act, see under ' Circulation in the Fish,' p. 113. 
 
PHYSIOLOGY OF THE CIRCULATION. 177 
 
 for forcing the blood without danger through the lungs and 
 through the system. If the blood which should be forced into 
 the lungs was allowed to regurgitate into the right auricle, 
 and thence into the cavae, it would tend to disturb the whole 
 circulation, for any impediment at one part would necessarily 
 react upon every other part. We have, moreover, direct proof 
 that the tricuspid valve is competent. If, e.g.> I push a rigid 
 tube past the semilunar valve of the pulmonary artery and fix 
 it firmly in that vessel, and then sink the right heart in water, 
 I find that, by blowing into the tube, the segments of the tri- 
 cuspid are gradually floated up by the water, approximated, 
 and apposed so perfectly that not a single drop of fluid is per- 
 mitted to regurgitate (Fig. 85, p. 174). 
 
 I have repeatedly performed this experiment, and always 
 successfully. If regurgitation is a serious matter in the bicus- 
 pid and semilunar valves, it would be illogical to infer it was 
 harmless in the tricuspid. The express function of the tricus- 
 pid and all other valves is to prevent regurgitation. Not only 
 is the power of the right ventricle exactly suited to the re- 
 quirements of the pulmonic circulation, but the pulmonic 
 vessels are provided with that degree of elasticity and of vital 
 movement which enables them to reciprocate with the utmost 
 nicety. In virtue of this arrangement the blood arrives at the 
 capillaries of the lungs, and the vessels of the entire system, at 
 the speed and in the quantity best suited for each. The slowing 
 of the current is necessary for the purposes of respiration, nu- 
 trition, growth, waste, etc. The slowing of the blood in the 
 delicate capillaries of the lungs increases the opportunities 
 afforded this fluid for taking in oxygen and giving off carbonic 
 acid and other matters. These interchanges effected, the 
 blood is urged on, partly by the closure of the right ventricle, 
 partly by the opening of the left auricle, and partly by atmo- 
 spheric pressure, into the pulmonary veins, which debouch by 
 four openings into the left auricle. 
 
 Left Heart and Valves of Mammal. As there are no tissues 
 to be nourished by the blood in the pulmonary veins, it follows 
 that these can exert no influence in drawing the blood into the 
 left auricle. This function is performed by the closing of the 
 right ventricle, by the vital expansion of the left auricle, aided 
 by atmospheric pressure and by the movements of the lungs 
 
 N 
 
'PHYSIOLOGY OF THE CIRCULATION. 
 
 themselves. Once in the left auricle, the arterial blood is pro- 
 jected thence by the closing of the left auricle through the 
 left auriculo-ventricular opening into the left ventricle, which 
 simultaneously expands to receive it. It is then forced by the 
 closing of the left ventricle through the aorta, and by means 
 of its branches through the whole system. The course of the 
 Current through the left heart is determined as in the right 
 by the presence of two sets of valves, viz. the bicuspid or mitral 
 and the aortic semilunar valve. These valves resemble the tri- 
 cuspid and pulmonic semilunar valves just described so closely, 
 that further allusion to them at this stage is unnecessary. 
 
 Circulation in the Head, Liver > and Erectile Tissues. In 
 mammals the circulation in the head, liver, and erectile tissues 
 is worthy of a separate description. The supply of blood to 
 the brain is comparatively very large \ It is furnished by the 
 two internal carotid and the two vertebral arteries. These 
 spread out on the base of the brain to form the circle of Willis, 
 which may be regarded as a reservoir for providing a regular 
 supply of blood to the arteries of the organ. The arteries 
 break up into an infinite number of minute branches in the 
 pia mater, from whence they betake themselves to the brain- 
 substance. The blood is returned by numerous small veins to 
 the venous sinuses, which are remarkable for their great size, 
 and the fact that they are formed on the one aspect by the tough 
 dura mater, and on the other by the inner table of the cranium, 
 so that their walls may, in a great measure, be regarded as 
 incompressible. This led to the belief that the quantity of 
 blood in the brain is always the same. Dr. Kellie endeavoured 
 to establish this view by experiment. He found that if an 
 animal was bled to death the quantity of blood in the brain 
 remained the same, while the system generally was drained ; 
 but that if the cranium was perforated, and air admitted to 
 the brain before the bleeding took place, the brain and system 
 generally were blanched equally. 
 
 1 Dr. J. Crichton Browne, in a recent and able article On Cranial Injuries and 
 Mental Diseases,' referring to a case where a portion of bone two inches by one 
 had been removed from the upper part of the right frontal region on account of 
 injury, states that the cicatrix pulsated visibly, and that the vascular changes were 
 so rapid and considerable, as to impress him with the idea that the brain in some 
 ,respects resembles erectile tissue. (West Riding Lunatic Asylum Medical Reports, 
 vol. ii. pp. 101, 102 ; 1872.) 
 
PHYSIOLOGY OF THE CIRCULATION. 179 
 
 Dr. Burrows' obtained opposite results, so that the question 
 is still subjudice. The erectile organs are rendered tense by a 
 determination of blood to the very extensive and complicated 
 venous plexuses contained in their interior. Professor Kol- 
 liker is of opinion that the plexuses during the non-erectile 
 state are compressed by the habitual contraction of organic 
 muscular fibres, and that in the erectile state the action of 
 these fibres is suspended by nervous influence, the blood being 
 permitted to distend the plexuses mechanically. It is more 
 natural to suppose that the organic muscular fibres alluded to 
 by Kolliker are not in a state of habitual contraction, i. e. con- 
 stant activity, in the non-erectile state, but resting ; the mus- 
 cles being active and expanding during the erectile state. It 
 is difficult to understand how a muscle should be called upon 
 to perform work constantly, when the same result might be 
 obtained by occasional effort exerted at long intervals. Instead 
 of regarding the muscle as habitually contracted, we have only to 
 imagine that it occasionally expands. These remarks are equally 
 applicable to the class of sphincter muscles. It seems irrational 
 to invest a muscle with the power of contracting or closing, and 
 to divest it of the power of elongating and expanding. 
 
 The venous blood of the principal abdominal viscera passes 
 through the liver on its way to the heart. The following is 
 the arrangement: 'The blood supplied by the cceliac and 
 mesenteric arteries to the abdominal viscera is not returned 
 directly to the heart by their corresponding veins, as occurs 
 in other parts of the body. The veins of the stomach and 
 intestinal canal, of the spleen, pancreas, mesentery, omenta, 
 and gall-bladder, unite together below the liver into one large 
 vessel, the trunk of the vena portae, which branches out again 
 and distributes to the liver by its ramifications the whole of 
 the venous blood coming from the above-mentioned organs. 
 The blood of the vena portae, being joined in the minute 
 branches by that of the hepatic artery, passes into the smallest 
 ramifications of the hepatic veins, by the principal trunks of 
 which the venous and arterial blood circulated through the 
 liver is carried to the inferior vena cava, and thus reaches at 
 last the right side of the heart.' 
 
 The great arteries are important accessories of the circu- 
 lation of the mammal, inasmuch as they transmit the blood 
 
 N 2, 
 
180 . PHYSIOLOGY OF THE CIRCULATION. 
 
 to and from the heart, which is the central engine for its pro- 
 pulsion. They are, however, as has been stated, only acces- 
 sories. The most important functions performed by the 
 vessels are delegated to the capillaries, a mazy labyrinth of 
 minute vessels which ramify and inosculate in every con- 
 ceivable direction. It is within those delicate capillary tubes 
 that the blood meanders and literally irrigates the tissues, 
 each tissue selecting and drawing through the capillary walls 
 whatever it requires ; or what comes very much to the same 
 thing, having forced upon it by an osmotic action those pecu- 
 liar fluids for which it has an affinity, and which are best 
 adapted for its support, nourishment, and decay. The capil- 
 laries are therefore deserving of very particular attention, the 
 more especially as their structure and movements indicate the 
 structure and movements of the larger vessels ; these, again, 
 indicating the structure and movements of the heart, which in 
 its turn curiously enough foreshadows the structure and move- 
 ments of all the other muscles, voluntary and involuntary. 
 
 The Lymphatic and Capillary Vessels of Animals, The 
 capillaries furnish the simplest form of vessel. They may be 
 divided into two kinds, viz. such as convey red blood, and 
 such as convey a pale watery or milky fluid, the lymph or 
 chyle. The lymphatics are intimately connected with the 
 process of digestion in the alimentary canal and tissues gene- 
 rally. ' The lymph' Mr. Huxley observes, ' like the blood, is 
 .'an alkaline fluid, consisting of a plasma and corpuscles, and 
 -coagulates by the separation of fibrine from the plasma. The 
 Jymph differs from the blood in its corpuscles being all of the 
 colourless kind, and in the very small proportion of its solid 
 constituents, which amount to only about five per cent, of its 
 weight. Lymph may, in fact, be regarded as blood minus its 
 red corpuscles and diluted with water, so as to be somewhat 
 less dense than the serum of blood, which contains about eight 
 per cent, of solid matters. A quantity of fluid equal to that 
 of the blood is probably poured into the blood daily from the 
 lymphatic system. This fluid is in great measure the mere 
 overflow of the blood itself plasma which has been exuded 
 from the capillaries into the tissues, and which has not been 
 taken up again into the venous current ; the rest is due to the 
 absorption of chyle. from the alimentary canal.' In reptiles 
 
PHYSIOLOGY OF THE CIRCULATION. l8l 
 
 and birds the lymphatics are provided with pulsating sacs or 
 hearts and valves an arrangement which insures that the 
 lymph shall travel in only one direction, viz. towards the 
 general circulation. The lymph in man is discharged into 
 the general current of the circulation by two apertures situated 
 between the angles of junction of the right and left internal 
 jugular and right and left subclavian veins. The openings by 
 which the lymph is discharged into the general circulation are 
 each provided with a pair of valves to prevent regurgitation 
 of the venous blood. The lymphatic vessels are to be re- 
 garded as the feeders of the vascular vessels, in the same 
 sense that the vessels of the roots of a tree are to be con- 
 sidered the feeders of the vascular vessels in the trunk of 
 the tree. In this respect the sanguineous circulation is to be 
 
 Fig. 88. Fig. 89. Fig. 9- 
 
 Fig. 88. A minute artery (a), ending in (*) larger and (c) smaller capillaries, d, nuclei embedded in 
 the walls of the capillaries. Magnified 200 diameters. 
 
 Fig. 89. A, epithelial cells of the arteries, a, the nucleus. B, muscular fibres of the arteries: the 
 middle one, having been treated with acetic acid, shows more distinctly the nucleus (a). Magnified 300 
 diameters. 
 
 Fig 90 A. a small artery. B, a small vein, both treated with acetic acid ; a fibrous coat ; *, nuclei 
 of the muscular coat ; c, nuclei of the epithelial coat. Magnified 300 diameters. After Huxley. 
 
 looked upon as an evolution or development of the chyliferous. 
 The colourless corpuscles, which are so abundant in the lym- 
 phatic vessels, reappear in the capillaries of the vascular sys- 
 tem, and are known as the white corpuscles of the blood. 
 They are possessed of independent movements and change 
 shape. They have attracted an usual share of attention of 
 late from the power they possess of forcing themselves through 
 the thin walls of the capillaries. The capillaries vary in size 
 from TT Vo- to ^j^ of an inch in diameter, and form an infinite 
 variety of minute loops, being now straight, now slightly waved, 
 and now tortuous. They generally form a network so dense 
 that the point of a pin cannot be introduced without lacerating 
 some of them. The capillaries of the vascular system lie mid- 
 
182 PHYSIOLOGY OF THE. CIRCULATION, 
 
 way between the arteries and veins the arteries conducting to 
 and the veins from them. Around and between the capillaries is 
 a system of still more minute vessels, the hypervascular canals. 
 
 The capillaries form a sort of neutral territory, in which the 
 blood meanders more slowly in order to afford the tissues the 
 fullest opportunity of imbibing nourishment and discharging 
 effete matter. They form a through route for the blood, but 
 one with numerous convenient stages for the interchange of 
 the good and bad things of the economy. The circulation in 
 these minute vessels may not inaptly be compared to a river 
 which carries a blessing wherever it goes, giving freshness and 
 beauty to the country, and purifying the city by removing its 
 sewage. The capillaries of the lymphatic system, so far as 
 known at present, do not form a through route, but begin in 
 the tissues by blind ends, resembling the spongioles of the 
 roots of plants. The lymphatic system would therefore appear 
 to be the precursor of the vascular system, and to form a con- 
 necting link between the vegetable and animal. The lym- 
 phatics are eminently adapted alike for conveying new and 
 old ingredients into the blood. Like the roots of plants they 
 are endowed with selective powers, certain of their terminals 
 taking up new matter, others matter which has been partially 
 used, and others effete or waste matter. 
 
 Structure of the Capillaries and Small Arteries and Veins :' 
 Vessels close and elongate, and open and shorten. The walls 'of 
 the capillaries are composed of a thin, structureless membrane, 
 in which small oval bodies, termed nuclei, are embedded. 
 They bear a considerable resemblance to the walls of the 
 cells and young vascular bundles "of plants. 
 
 The capillaries differ from the small arteries and veins in- 
 being of a uniform calibre, and in having very delicate thin 
 permeable walls. The thin permeable walls permit the fluid 
 contents of the capillaries to escape into the surrounding 
 tissues, ''which are in this manner irrigated and nourished very 
 much in the same manner that' the growing parts of a plant 
 are nourished by the imbibition of saps. In either case, the 
 growing parts, i.e. the ultimate particles of the plant and 
 animal, are outside the vessels 1 . In this sense the foetus is 
 
 ""n 1 - There are portions of the body, such as the nails, hair, teeth, cartilage, epi- 
 
PHYSIOLOGY OF THE CIRCULATION. 183 
 
 also outside the "circulation of the mother. The capillaries 
 further differ from the small arteries and veins in this, that 
 the latter possess a more complex structure and thicker walls. 
 Thus, proceeding from without inwards, the walls of the 
 smaller vessels consist, first, of a sheath of fibrous tissue, the 
 fibres of which pursue a more or less longitudinal direction 1 ; 
 second, of a muscular layer composed of flattened spindle- 
 shaped bands, with elongated nuclei, these bands running 
 transversely or across the vessels 2 ; and, third, of a layer of 
 very delicate, elongated, epithelial cells, the oval nuclei of 
 which are arranged longitudinally or at right angles to those 
 of the muscular fibres 3 . 
 
 This arrangement accounts for the reticulated appearance 
 presented by 'the smaller vessels (Fig. 90, p. 181), and for the 
 fact, first promulgated by John Hunter, that the vessels are 
 extensile and retractile in their length and breadth. As the 
 walls of the vessel become thicker, they lose the permeability 
 which is a distinguishing feature of the capillaries. The 
 vessels, however, have what may be regarded an equivalent 
 added, viz. muscular fibres and nervous twigs, which regulate 
 their calibre and consequently the exact amount of blood 
 supplied to the capillaries and to the tissues. 
 
 When the muscular layer of a small vessel closes in a 
 direction from without inwards, the vessel is lengthened and 
 narrowed, and the fluid contents ejected, from the fact that all 
 muscles, when they shorten in one direction, lengthen in 
 another and opposite direction ; muscular movements being 
 
 thelium, epidermis, etc., which are not supplied with vessels at all. These 
 structures are still further removed from the circulation, but, like the others, they 
 are not beyond the reach of its influence. 
 
 1 The external or areolar fibrous coat consists of areolar tissue and longitudinal- 
 elastic fibres ; it also contains, in some of the larger veins, a longitudinal network 
 of non-striated muscular fibres, as in the whole length of the inferior vena cava, 
 the renal, azygos, and external iliac veins, and in all the large trunks of the portal 
 Venous system, and in the trunks of the hepatic veins. Gray's Anatomy, p. 401. 
 
 2 The middle layer in the larger vessels, according to Gray, consists of numerous 
 alternating layers of muscular and elastic fibres, the fibres of the former running 
 across the vessel, those of the latter in the direction of its length. This layer is 
 thicker in the arteries than in the veins. 
 
 3 The internal layer in the larger vessels consists, in Gray's opinion, of an 
 epithelial lining, supported on several laminae of longitudinal elastic fibres. This 
 layer is less brittle in veins than in arteries. 
 
1 84 PHYSIOLOGY OF THE CIRCULATION. 
 
 due not to any increase or diminution in the volume of 
 muscles, but to a change of shape in their sarcous elements. 
 The fibres of the central or transverse muscular layer of a 
 small vessel are arranged, as explained, at right angles to the 
 fibres composing the external fibrous layer, and the delicate 
 elongated epithelial cells constituting the internal layer. 
 When, therefore, the fibres of the central or transverse mus- 
 cular layer close or shorten, they elongate and stretch the 
 elements composing the external and internal layers ; these, 
 in virtue of their elasticity, the instant the closure ceases, 
 assisting the central layer in regaining its normal dimensions. 
 We have thus two forces at work the muscular force and 
 the elastic force. As however these forces act at right 
 angles to each other, and the structures in which they reside 
 ar geared together, it follows that when the one acts the 
 other must act also. It is thus that muscular and elastic 
 force can act in unison, and by their united efforts produce 
 a common result (Fig. 90, p. 181). 
 
 Elastic and t Vital Properties of Vessels. The influence 
 exerted by the elasticity of vessels in producing a steady 
 continuous flow of blood is well marked. There is however 
 reason to believe that the elastic properties of vessels have 
 been overrated. It must never be overlooked that the 
 movements in vessels have their origin in muscles, either the 
 muscles of the heart, or the muscles of the vessels themselves. 
 Nor must it be forgotten that the muscular layer of even the 
 smallest vessel can by itself increase or diminish the calibre 
 of the vessel, the muscular fibres determining the amount and 
 direction of the movement. This is proved by the fact that a 
 small artery may be made to diminish its circumference by 
 the application of cold, and increase it by the application of 
 heat. That the closing or partial closing and elongating of a 
 small vessel is directly due to the shortening of the muscular 
 fibres comprising the central layer of the vessel, is evident 
 from the direction of the muscular fibres (they are circular, 
 and invest the vessel transversely). That the opening or 
 partial opening of a small vessel is only partly due to the 
 recoil of the fibrous and elastic elements, is apparent from this, 
 that they invest the vessel in the direction of its length. At 
 most, therefore, the elastic elements, when they spring back, 
 
PHYSIOLOGY OF THE CIRCULATION. 185 
 
 shorten the vessel. It remains for the muscular element to 
 elongate, and by its elongation to expand and widen the 
 vessel. The power to increase and diminish the size of 
 the vessel resides chiefly if not exclusively in the mus- 
 cular fibres, these, as already explained, having a centri- 
 fugal and centripetal action. The elastic structures are more 
 developed in the vessels than in the heart and other hollow 
 viscera, these . organs being comparatively inelastic. The 
 voluntary muscles, on the other hand, are less elastic than the 
 involuntary ones. In proportion as the muscular movements 
 become exact the elastic structures disappear. In order to 
 have a perfect co-ordination in muscular movements, all the 
 parts of the muscles involved, whether these be extensors or 
 flexors, pronators or supinators, abductors or adductors, must 
 take part. Nothing is left to chance, and as a consequence 
 elasticity is reduced to a minimum. If a vessel was composed 
 solely of muscular fibres it would not be so strong, neither 
 would its movements be so rapid or continuous, as one com- 
 posed partly of muscular and partly of elastic fibres. A 
 muscle is capable of acting in two directions ; it can first 
 elongate and then shorten itself; but these are opposite 
 movements, and between them a pause or halt (the dead 
 point of engineers) inevitably occurs. Elasticity gets the 
 muscle over this dead point, and decreases the duration of 
 the pause. The value of elasticity in interrupted or rhythmic 
 movements, such as those employed in the circulation, be- 
 comes therefore very obvious. There are many examples to 
 prove that elasticity plays a part not only in involuntary 
 movements, but likewise in voluntary ones. The wing of a 
 bird, for instance, is flexed almost exclusively by the action of 
 powerful elastic ligaments, extending between the shoulder 
 and wrist, and between the elbow and hand. These ligaments 
 gradually close or flex the wing towards the termination of 
 the down-stroke, 1 and are put upon the stretch towards the 
 termination of the up-stroke, by the shortening of the power- 
 ful pectoral and other muscles. Nearly half of the wing 
 movements are therefore performed by a purely mechanical 
 
 1 They are prevented from closing the wing suddenly, after the manner of 
 springs, by the resistance offered by the air to the expanded wing as it descends. 
 
1 86 PHYSIOLOGY" OF THE CIRCULATION.: 
 
 arrangement 1 . Numerous other examples might be cited, 
 but this is a very obvious one. It suffices, when elastic 
 structures are 'present, if the muscles stretch them when they 
 shorten ; the elastic structures, when they shorten, assisting in 
 the elongation of the muscular ones. The elastic and mus- 
 cular structures mutually operate on each other. What would 
 be a purely vital act is by this arrangement rendered more or 
 less mechanical, and no better illustration can be given of the 
 fact that animate, and what may be regarded as inanimate, 
 matter can be made to reciprocate and work in harmony. 
 The difference (but it is an all-important one) between a 
 living vessel and an elastic tube amounts to this : The walls 
 
 Fig 91. 
 
 Fig. g t Diagram showing how the, walls of a vessel or of a hollow viscus may oscillate on either side 
 of a given line, a, position of rest of walls of vessel or heart, b. walls of vessel or heart when expanded, 
 r, ditto when partly closed Original. 
 
 Fig. 92 shows an elementary fibre of the skate in the uncontracted and contracted state. 
 
 A. Fibre in the condition of rest, r, transverse markings or cleavage, s, longitudinal markings or 
 cleavage. 
 
 B. a a a, one side of fibre contracting or shortening. 
 
 C. b b b, both sides of fibre contracting or shortening. All parts of the fibre become involved in suc- 
 cession. Thus the constrictions between bbbotC become the swellings cc of D. After Bowman. 
 
 of a living vessel can oscillate or vibrate on either side of a 
 given line, this line corresponding to their position of rest 2 . 
 An elastic tube, on the other hand, can only be made to 
 vibrate on one side of a given line. In other words, it can be 
 made to open by being artificially distended, but it cannot be 
 made to close. Thus if the circle a of Fig. 91 be made to 
 represent an elastic tube, it may be stretched until it assumes 
 the dimensions b, but it cannot be made to assume the 
 dimensions c. This the living vessel can readily do from the 
 power it possesses of oscillating on either side of the circle a. 
 
 1 ' On the Mechanical Appliances by which Flight is attained in the Animal 
 Kingdom,' by the Author; Trans. Lin. Soc. of London, vol. xxvi. 'On the 
 Physiology of Wings,' by the Author ; Trans. Roy. Soc. of Edinburgh, vol. xxvi. 
 
 2 Precisely similar remarks may be made of the parietes of, the different com- 
 partments of the heart. 
 
PHYSIOLOGY OF THE CIRCULATION.- 187 
 
 All attempts therefore at reproducing by merely elastic 
 tubes and cavities the structure and forces employed in the 
 circulation, are more or less fallacious. Another marked 
 difference between a hollow muscle and an elastic tube is to 
 be noted. An elastic tube, when allowed to return to its 
 position of rest after being put upon the stretch, is active 
 throughout its entire substance at one and the same time. 
 A living muscle, on the contrary, moves in parts its action 
 being a progressive wave action., Bowman is very explicit on 
 this point. He states, 1st, That active contraction never 
 occurs in the whole mass of a muscle at once, nor in the 
 whole of any one elementary fibre, but is always partial at 
 any one instant of time. 2nd, That no active contraction 
 of a muscle, however apparently prolonged, is more than in- 
 stantaneous in any one, of its parts or particles; and there- 
 fore, 3rd, That the sustained active contraction of a muscle is 
 an act compounded of an infinite number of partial and 
 momentary contractions, incessantly changing their place and 
 engaging new parts in succession ; for every portion of the 
 tissue must take its due share in the act. From this it 
 follows that a muscle rests in its sarcous elements or ultimate 
 particles even when it is working. These points are illustrated 
 at Fig. 92. 
 
 Structure of the large Arteries and Veins. As the vessels 
 increase in. size and their walls become thicker and more 
 complex, the structures composing them are arranged at right 
 angles and obliquely, but always in pairs and symmetrically. 
 Regarding the composition of the veins, there is considerable 
 difference of opinion, authorities not being agreed either as to 
 the number or nature of the coats. This may in part be 
 explained by the variation in the thickness of the coats 
 themselves, these, according to John Hunter 1 , becoming 
 thinner and thinner in proportion to the size of the vein, the 
 nearer the vein approaches the heart. In moderate sized 
 veins an external, a middle, and an internal coat are usually 
 described; the first consisting of cellular^ fibrous, and elastic 
 tissue, interlacing in all directions ; the second, of waved 
 filaments of areolar tissue, with a certain admixture of non- 
 
 1 Hunter on the Blood, pp. 180. 181. 
 
1 88 PHYSIOLOGY OF THE CIRCULATION. 
 
 striped muscular fibres, which run circularly, obliquely, or 
 even longitudinally l ; the third, consisting of one or more 
 strata of very fine elastic tissue, minutely reticulated in a 
 longitudinal direction, the innermost stratum (when several 
 are present) being lined by epithelium. Of these layers 
 the second and third, from the fact of their contributing to 
 the formation of the venous valves, are the most important. 
 The coats of the veins, as has been long known, are tough, 
 elastic, and possessed of considerable vital contractility i.e. 
 they have the power of opening and closing within certain 
 limits. Of these qualities, the toughness prevents undue 
 dilatation of the vessel when distended with blood ; the 
 elasticity and the power the vessel possesses of opening and 
 closing assisting the onward flow of that fluid, and tending to 
 approximate the segments of the valves. As the valves of the 
 veins are very ample and very flexible, they readily accom- 
 modate themselves to the varying conditions in which they 
 are placed by the elasticity and vital properties of the vessel, 
 and by the reflux of the blood. 
 
 The coats of the arteries, as is well known, are com- 
 paratively much thicker than those of the veins, while the 
 layers composing them are more numerous. The external 
 coat, according to Henle, consists of an outer layer of areolar 
 tissue in which the fibres run obliquely or diagonally round 
 the vessel, and an internal stratum of elastic tissue ; the 
 middle coat in the largest arteries, according to Raiischel, 
 being divisible into upwards of forty layers. The layers of 
 the middle coat consist of pale, soft, flattened fibres, with an 
 admixture of elastic tissue; the fibres and elastic "tissue being 
 disposed circularly round the vessel. The internal coat is 
 composed of one or more layers of fibres, so delicate that 
 they constitute a transparent film, the film being perforated 
 at intervals, and lined with epithelium. From this account it 
 will be obvious that the large veins and arteries possess a 
 
 1 Dr. Chevers says, that in the deep as well as in some of the superficial, veins of 
 the trunk and neck, the middle coat is composed of several layers of circular fibres, 
 with only here and there a few which take a longitudinal course ; while the middle 
 coat of the superficial and deep veins of the limbs consists of a circular layer, and 
 immediately within this of a strong layer pf longitudinal fibres. Med. Gazette, 
 1845- P- 638- 
 
PHYSIOLOGY OF THE CIRCULATION. 189 
 
 much more complex structure than the smaller vessels 
 these again being more highly differentiated than the capil- 
 laries. The large arteries and veins, in fact, present a structure 
 remarkably resembling that found in the ventricles of the 
 mammalian heart ; thus they have fibres running longitudi- 
 nally, obliquely, very obliquely, and transversely ; the fibres 
 intersecting at a great variety of angles, and arranged with a 
 view to co-ordinating each other. The arteries, as might be 
 expected from their structure, and as was proved by the 
 admirable experiments of John Hunter, whose beautiful 
 preparations I have had an opportunity of examining, possess, 
 in addition to the vital powers peculiar to them, a considerable 
 degree of elasticity, and are extensible and retractile both in 
 their length and breadth ; the power of recovery, according to 
 that author, being greater in proportion as the vessel is nearer 
 the heart. From this it follows that the pulmonary artery 
 and aorta are most liable to change in dimensions. As 
 however any material alteration in the size of the pulmonary 
 artery and aorta at their origins would interfere with the 
 proper function of the semilunar valves situated at their 
 orifices, it is curious to note that the great vessels arise from 
 strong and comparatively unyielding fibrous rings. These 
 rings (particularly the aortic one) are so dense as to be almost 
 cartilaginous in consistence, and Professor Bonders l has lately 
 discovered that they contain stellate corpuscles similar in 
 many respects to those stellate and spicate corpuscles found 
 in many forms of cartilaginous tumours. They have been 
 more or less minutely described by Valsalva 2 , Gerdy :) , Dr. 
 John Reid 4 , and Mr. W. S. Savory 5 , and merit attention 
 because of their important relations to the segments of the 
 semilunar valves. The following description of them has 
 been drawn up chiefly from an examination of a large number 
 of human hearts. Each ring consists, as was shown by Reid, 
 of three convex portions. Each convex portion is directed 
 
 1 ' Onderzoclungen betrekkeligh den bouw van het menchclijke hart,' in Neder- 
 landsch Lancet for March and April 1852. 
 
 2 Opera Valsalvae, torn, i p. 1 29. 
 
 3 Journal Complimentaire. torn. x. 
 
 * Cyc. Anat. and Phys., article ' Heart,' pp 588, 589. London, 1839. 
 5 Paper read before the Royal Society in December 1851. 
 
1 90 PHYSIOLOGY. OF THE CIRCULATION. 
 
 from above downwards, and from without inwards, and as it 
 unites above with that next to it, the two when taken together 
 form a conical-shaped prominence which is adapted to one of 
 the three triangular-shaped interspaces occurring between the 
 segments of the semilunar valves. The ring surrounding the 
 pulmonary artery is broader, but not quite so thick as that 
 surrounding the aorta, and both are admirably adapted for 
 the reception of the large vessels which originate in three 
 festooned borders (Fig. 94). 
 
 Fig. 93. Fig. 94. 
 
 Fiff- 93- Transverse sections of ventricles of heart of deer. - Shows how the right and left ventricles 
 obliterate their cavities during the systole. Fig. 93 A, transverse, section near the base of the ventricles ; 
 i>, left ventricular cavity obliterated by the heads of the musculi papillares ; c, cavity of right ventricle 
 obliterated by the approximation of the right ventricular wall (d) ; e, e, circular fibres of left ventricle ex- 
 ercising their centripetal function. These fibres powerfully contribute to the closing of the left ven- 
 tricular cavity. Fig. 93 B, transverse section near apex of ventricles ; b, e, fibres which form the musculi 
 papillares of left ventricle, curving towards ventricular cavity (b), which they obliterate by a centripetal 
 action. Fig. 93 C, transverse section at apex of ventricles ; b, left ventricular cavity obliterated by the 
 centripetal action of the circular fibres (e, e) and those of th musculi papillares (m, n). Original. 
 
 Fig. 94. Base of ventricles of heart, a, b, Cartilaginous festooned rings, to which pulmonary artery 
 (a) and aorta (b) are attached. Within these the pulmonic and aortic semilunar valves in their closed con- 
 dition are seen, c, fibrous ring partly surrounding right auriculo-ventricular orifice, d, ditto surround- 
 ing left auriculo-ventricular orifice. To these rings the Jricuspid and mitral valves, and a certain number , 
 ' of the superficial fibres of the ventricles are attached. The larger proportion of the fibres of the ventricles 
 are continuous alike at base and apex. Original. 
 
 Structure of the Heart of the Mammal ; the Arrangement of 
 the Muscular Fibres in the Auricles and Ventricles. The 
 auricles of the mammalian heart, as already explained, are 
 two in number, a right and a left They are irregularly shaped 
 muscular pouches or receptacles which collect arterial and 
 venous blood, the right communicating with the ascending 
 and descending cavae, the left with the pulmonary veins. The 
 cavae and pulmonary veins are invested with muscular fibres 
 of considerable strength, which confer on these vessels a cer- 
 tain amount of vermicular movement. The muscular fibres 
 of the auricles are arranged at right angles and obliquely as in 
 the ventricle of the fish and reptile (Figs. 95 and 97, p. 192). 
 The fibres in the auricular appendages are disposed in ridges 
 to form the musculi pectinati. Where most plentiful, they are 
 
PHYSIOLOGY OF THE CIRCULATION. 19! 
 
 arranged in layers. They are circular in some cases, looped 
 in others, and occasionally plicate. They are specially ar- 
 ranged to procure strength, and with a view to opening and 
 closing the auricular cavities, which they do by alternate cen- 
 trifugal and centripetal movements. The auricles when closed 
 contain a certain amount of residual blood, and in this respect 
 they differ from the ventricles, which have the power of com- 
 pletely expelling it (Fig. 93, A, B, C). The auricles serve as 
 reservoirs, and are to be regarded as intermediate structures 
 between the large veins and ventricles. The auricles are ana- 
 tomically distinct from the ventricles, and in boiled hearts the 
 auricles and ventricles may be separated from each other with- 
 out rupturing a single fibre. The auricles are structurally 
 continuous with the large veins (the cavae and pulmonary 
 veins), from which they are not separated by valves as the 
 auricles are separated from the ventricles. From this it fol- 
 lows that when the auricles close, the pressure exerted by them 
 is away from, as well as towards, the ventricles ; an indirect 
 proof that the auricles by their closure do not forcibly dilate 
 the ventricles. It ought however to be stated that the veins 
 are more or less closed at the commencement of the auricular 
 contraction. The great veins and auricles exhibit sponta- 
 neous and rhythmical movements, the veins closing when the 
 auricles open, and vice versa. Analogy favours the belief that 
 the great vessels conducting from the heart (pulmonary artery 
 and aorta), as well as those conducting to it (venae cavae and 
 pulmonary veins), participate in those rhythmical movements. 
 The bulbus arteriosus of fishes and reptiles (the homologues 
 of the first part of the aorta in mammals), as I have already 
 shown, opens and closes like the different parts of the heart 
 itself. The muscular fibres composing the auricles are more 
 plentiful in some regions than in others. In some places they 
 are so sparse as to render the walls of the auricles transparent, 
 while in others they are grouped and superimposed, the walls 
 under these circumstances being quite an eighth of an inch in 
 thickness. (Figs. 95 and 97, p. 192). 
 
 The ventricles of the mammalian heart, like the auricles, are 
 two in number, a right and a left. They form a wedge-shaped 
 hollow muscular mass, which is slightly twisted upon itself, 
 particularly at the apex. The base of the wedge is directed 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 Upwards, and to this portion the auricles are attached, the 
 auricles fitting into the right and left auriculo-ventricular 
 openings as stoppers into the necks of bottles. The auricles 
 adhere to the fibrous rings investing the auriculo-ventricular 
 orifices (Fig. 94, c, d, p. 190), but none of the muscular fibres of 
 the auricles are continuous with those of the ventricles. The 
 arrangement of the muscular fibres in the ventricles is exceed- 
 ingly intricate, and requires careful description. Considered 
 as a muscle, the heart, especially the ventricular portion of it, 
 is peculiar. Being in the strictest acceptation of the term an 
 
 Fig. 95- Fig. 96. Fig. 97. 
 
 Fig. 95. Anterior aspect of the auricles, showing the distribution of the muscular fibres (human). 
 a, pulmonary veins b, vena cava superior. The great vessels (a and b) are invested with muscular fibres, 
 and have distinct movements. After Gerdy. 
 
 Fig. 96.' Ideal transverse section of the ventricles, showing how the septum which divides the right 
 and left ventricles from each other is formed. The heart originally consists of a single tube. At an 
 early period it is divided by a longitudinal and transverse fold into four c mpartments, two auricles and 
 two ventricles. The ventricles (b and c) are separated from each other by the fold (a) passing in an ah- 
 tero-posterior direction until it touches the posterior wall (d) of the ventricles, into which it penetrates 
 and becomes fixed. The two halves of the fold likewise interpenetrate, the septum becoming of nearly 
 the same thickness as the left ventricle, which is the typical ventricle This accounts for the fact that 
 the muscular fibres are continuous on the posterior aspect of the ventricles, and interrupted on the an- 
 terior aspect, and hence the old idea that the ventricles are two muscles enveloped in a third. These 
 po-nts are explained at length in my memoir 'On the Arrangement of the Muscular Fibres in the Ven- 
 tricles of the Vertebrata ;' Phil. Trans. 1864. Original. 
 
 Fig 97. Posterior aspect of the auricles, showing the distribution of the muscular fibres (human). 
 a a. pulmonary veins, c. vena cava inferior. These are surrounded by muscular fibres, and take part 
 in forcing the blood into the auricles. After Gerdy, 
 
 involuntary muscle, its fibres nevertheless possess the dark 
 colour and transverse markings which are characteristic of the 
 voluntary muscles. Unlike the generality of voluntary muscles 
 however, the fibres of the ventricles, as a rule, have neither 
 origin nor insertion ; i. e. they are continuous alike at the apex 
 of the ventricles and at the base. They are further distin- 
 guished by the almost total absence of cellular tissue as a con- 
 necting medium - 1 ; the fibres being held together partly by 
 
 1 The little cellular tissue there is, is found more particularly at the base and 
 
PHYSIOLOGY OF THE CIRCULATION. 193 
 
 splitting up and running into each other, and partly by the 
 minute ramifications of the cardiac vessels and nerves *. 
 
 The manner in which the fibres are attached to each other, 
 while it necessarily secures to the ventricles considerable lati- 
 tude of motion, also furnishes the means whereby the fibres 
 composing them may be successfully unravelled ; for it is found 
 that by the action of certain reagents, and the application of 
 various kinds of heat, as in roasting and boiling 2 , the fibres 
 may be prepared so as readily to separate from each other in 
 layers of greater or lesser thickness. The chief peculiarity 
 consists in the arrangement of the fibres themselves an ar- 
 rangement so unusual and perplexing that it has long been 
 considered as forming a kind of Gordian knot in anatomy. 
 Of the complexity of the arrangement I need not speak ; suf- 
 fice it to say that Vesalius, Albinus, Haller 3 , and De Blain- 
 ville 4 all confessed their inability to unravel it. 
 
 'Having, in the summer of 1858, made numerous dissections 
 
 apex of the ventricles, and is so trifling in quantity as to be altogether, though 
 wrongly, denied by some. 
 
 1 When the vessels of the ventricles are injected in the cold state with some 
 material which will stand heat (as, for example, a mixture of starch and water), 
 and the heart boiled, the larger trunks from either coronary artery are seen to give 
 off a series of minute branches which penetrate the ventricular wall in a direction 
 from without inwards. These branches, when the dissection is conducted to a 
 certain depth, resemble so many bristles transfixing the ventricular wall. As 
 moreover the cardiac nerve-trunks accompany the trunks of the coronary vessels, 
 while the nerve-filaments cross the smaller branches of the vessels and the mus- 
 cular fibres (to both of which they afford a plentiful supply of nerve-twigs), the 
 influence exerted by the vessels and nerves in uniting or binding the muscular 
 fibres to each other is very considerable. Vide Inaugural Prize Dissertation, by 
 the Author, ' On the Arrangement of the Cardiac Nerves, and their connexion with 
 the Cerebro-spinal and Sympathetic Systems in Mammalia,' deposited in the Uni- 
 versity of Edinburgh Library, March, 1861. 
 
 2 Of the various modes recommended for preparing the ventricles prior to dis- 
 section, I prefer that of continued boiling. The time required for the human heart 
 and those of the small quadrupeds, as the sheep, hog, calf, and deer, may vary 
 from four to six hours ; while for the hearts of the larger quadrupeds, as the horse, 
 ox, ass, etc., the boiling should be continued from eight to ten hours ; more than 
 this is unnecessary. A good plan t is to stuff the ventricular cavities loosely with 
 bread-crumbs, bran, or some pliant material before boiling, in order, if possible, to 
 distend without overstretching the muscular fibres. If this method be adopted, 
 and the ventricles soaked for a fortnight or so in alcohol before being dissected, the 
 fibres will be found to separate with great facility. Vaust recommended that the heart 
 should be boiled in a solution of nitre ; but nothing is gained by this procedure. 
 
 8 El. Phys., torn. i. p. 351. * Cours de Physiologic, etc., tom.Ji; p. 359. 
 
 O 
 
IQ4 PHYSIOLOGY OF THE CIRCULATION. 
 
 of the ventricles, upwards of a hundred of which are preserved 
 in the Anatomical Museum of the University of Edinburgh l , 
 I have arrived at results which appear to throw additional light 
 on this complex question, and which seem to point to a law 
 in the arrangement, simple in itself, and apparently compre- 
 hensive as to detail 2 . 
 
 The following are a few of the more salient points demon- 
 strated in connexion with this investigation. 
 
 I. By exercising due care, I ascertained that the fibres con- 
 stituting the ventricles are rolled upon each other in such a 
 manner as readily admits of their being separated by dissec- 
 tion into layers or strata, the fibres of each layer being charac- 
 terised by having a different direction. 
 
 II. These layers, owing to the difference in the direction of 
 their fibres, are well marked, and seven in number viz. three 
 external, a fourth or central, and three internal. 
 
 III. There is a gradational sequence in the direction of the 
 fibres constituting the layers, whereby they are made gradu- 
 ally to change their course from a nearly vertical direction 
 to a horizontal or transverse one, and from the transverse direc- 
 tion back again to a nearly vertical one. Thus, in dissecting 
 the ventricles from without inwards, the fibres of the first layer, 
 which run in a spiral direction from left to right downwards, 
 are more vertical than those of the second layer, the second 
 than those of the third, the third than those of the fourth 
 the fibres of the fourth layer having a transverse direction, 
 and running at nearly right angles to those of the first 
 layer. Passing the fourth layer, which occupies a central posi- 
 tion in the ventricular walls, and forms the boundary between 
 the external and internal layers, the order of arrangement is 
 reversed, and the fibres of the remaining layers, viz. five, six, 
 and seven, gradually return in an opposite direction, and in 
 an inverse order, to the same relation to the vertical as that 
 maintained by the fibres of the first external layer. This re- 
 markable change in the direction of the fibres constituting the 
 
 1 These dissections obtained the Senior Anatomy Gold Medal of the University 
 in the winter of 1859. 
 
 2 On the Arrangement of the Muscular Fibres in the Ventricles of the Verte- 
 brate Heart, with Physiological Remarks/ by the Author ; Philosophical Trans- 
 actions, 1864. 
 
PHYSIOLOGY OF THE CIRCULATION. 195 
 
 several external and internal layers, which is observed to occur 
 in all parts of the ventricular walls, whether they be viewed 
 anteriorly, posteriorly, or septally, has been partially figured 
 by Senac \ and imperfectly described by Reid 2 , but has not 
 hitherto been fully elucidated. It has not had that share of 
 attention bestowed upon it which its importance demands. 
 
 IV. The fibres composing the external and the internal 
 layers are found at different depths from the surface, and from 
 the fact of their pursuing opposite courses cross each other, 
 the fibres of the first external and last internal layers cross- 
 ing with a slight deviation from the vertical, as in the letter 
 X ; the succeeding external and internal layers, until the fourth 
 or central layer, which is transverse, is reached, crossing at 
 successively wider angles, as. may be represented by an X 
 placed horizontally (Figs. 98, 99, and 100). 
 
 Fig. 99. Fig. 100. 
 
 Figs. 98, 99, 100, which are skeleton drawings copied from photographs of my dissections, illustrate the 
 peculiarities in the direction of the fibres of the left ventricle, which I regard as the typical one. 
 
 The solid lines (a) of Fig. 98 represent the external fibres constituting the first layer; the dotted lines 
 (zl of Fig. zoo representing the corresponding internal fibres forming the seventh layer. The interrupted 
 lines (*) of Fig. 98 represent the fibres of the second layer, the interrupted lines (h) of Fig. 100 the fibres 
 of the sixth or corresponding layer. The dotted lines (c) of Fig. 9^ represent the fibres of the third layer, 
 the continuous lines (g) of Fig. 100 the fibres of the fifth or corresponding layer. At d. e of Fig. 99 the 
 fibres constituting the central or fourth layer are seen ; all the fibres to the outside of this layer being ex- 
 ternal, all to the inside of it internal. The fibres are spiral in their nature, and Fig. 99 is particularly 
 interesting as showing the point at which the external fibres reverse their course and become internal. 
 They wind in the direction d, e (vide arrow) round the left apex, and reappear at./: x, left auriculo-ven- 
 tricular opening, y, aortic orifice, with semilunar valve closed. Original. 
 
 V. The fibres composing corresponding external and inter- 
 nal layers, such as layers one and seven, two and six, etc., are 
 continuous in the left ventricle at the left apex (Fig. 102, p. 
 197), and in the right ventricle in the track for the anterior 
 
 1 Trait^ de la Structure du Cceur, de son Action, etc. Paris, 1749. 
 8 Cyc. of Anat. and Phys., art. Heart.' London, 1839. 
 O I 
 
196 PHYSIOLOGY OF THE CIRCULATION. 
 
 coronary artery -, the fibres of both ventricles being for the 
 most part continuous likewise at the base l (Fig. 94, p. 190). 
 
 VI. From this distribution of the fibres it follows that the 
 first and seventh layers embrace in their convolutions those 
 immediately beneath them, while these in turn embrace those 
 next in succession, and so on until the central layer is reached 
 an arrangement which explains alike the rolling movements 
 and powerful action of the ventricles. It also accounts for the 
 spiral shape of the ventricular cavities, and the fact that the 
 blood is literally wrung out of the ventricles during the 
 systole. 
 
 VII. The fibres of the right and left ventricles anteriorly 
 and septally are to a certain extent independent of each other ; 
 whereas posteriorly many of them are common to both ven- 
 tricles ; i.e. the fibres pass from the one ventricle to the other 
 an arrangement which induced Winslow 2 to regard the 
 heart as composed of two muscles enveloped in a third (Fig. 
 96, p. 192). It will be evident from this distribution of the 
 fibres, that while the ventricles are for obvious reasons in- 
 timately united, they nevertheless admit of being readily 
 separated (Fig. 101, p. 197). 
 
 VIII. If the hinge-like mass of fibres (common fibres) which 
 unite the right ventricle to the left posteriorly be cut through, 
 and the right ventricle with its portion of the septum detached, 
 the left ventricle, which consists of four sets of conical-shaped 
 spiral fibres two external and two internal sets will be 
 found to be nearly as complete as it was before the separation 
 took place (Figs. 98, 99, and 100, p. 195). The right ventricle, 
 and its share of the septum, on the other hand, will be found 
 to consist of only conical-shaped spiral fragments of fibres, or 
 at most of flattened rings a circumstance which has induced 
 me to regard the left ventricle as the typical or complete one, 
 the right ventricle being a mere segment or portion nipped 
 off at .some period or other from the left (Fig. 96, c, p. 192). 
 
 1 The late Dr. Duncan, jun., of Edinburgh, was aware of the fibres forming 
 loops at the base, but seems to have had no knowledge of the continuity being 
 occasioned by the union of the fibres of corresponding external and internal layers, 
 or that these basal loops were prolongations of like loops formed by similar corre- 
 sponding external and internal layers at the apex a view which the author believes 
 is here set forth for the first time. 
 
 2 Memoires de 1'Academie Royale des Sciences, 1711, p. 197. 
 
PHYSIOLOGY OF THE CIRCULATION. IQ7 
 
 IX. If the right ventricular walls be cut through im- 
 mediately to the right of the track for the anterior and 
 posterior coronary arteries, so as to detach the right ventricle 
 without disturbing the septum, and the septum be regarded 
 as forming part of the left ventricular wall, it will be found 
 that the fibres from the right side of the septum, at no great 
 depth from the surface, together with the external fibres 
 from the left ventricular wall generally, enter the left apex 
 in two sets (Fig. 102); and if their course in the interior 
 (Fig. 103, m, ri) be traced, they are observed to extend in 
 
 Fig. ror. Fig. 102. Fig. 103. 
 
 Fig. 101. Right and left ventricles of mammal seen posteriorly (human). Shows how the fibres issue 
 from the right and left auriculo-ventricular openings (c, d) ; the fibres from the left opening passing from 
 the left ventricle (e) across septum (f) to the right ventricle (g). Of these some curve in a downward 
 direction and disappear in the left apex ; others curve round anteriorly and disappear in the anterior 
 coronary groove. Compare with Fig. 96, p. 192. b, orifice of pulmonary artery. Original. 
 
 Fig. 102 shows how the two sets of external fibres (ab, cd) of the left ventrical curve round and form 
 a beautiful whorl prior to entering the left apex to become the two sets of internal fibres known as the 
 musculi papillares, seen at m, n of Fig. 103. The fibres twist into each other ajt the .apex in the same 
 way that the segments of the mitral, tricuspid, and semilunar valves twist into each other at the base. 
 Compare with Figs 85 and 86. Original. 
 
 Fig. 103. Musculi papillares (nt, ri), chordae tendineae and mitral valve (v, -v] of left ventricle of deer. 
 Shows how the musculi papillares, which are continuations of corresponding external fibres, are spiral 
 in their nature, and how, when they alternately elongate and shorten, they alternately liberate and drag 
 upon the segments of the mitral valve in a spiral manner; this, in conjunction with the blood, causing 
 the segments to wedge and screw into each other, first in an upward and then in a downward direction 
 (Fig. 85). The segments of the mitral and tricuspid valves rise and fall like diaphragms when the ven- 
 tricles open and close. They alternately increase and diminish the cavities of the ventricles. Similar 
 remarks may be made of the semilunar valves situated at the orifices of the pulmonary artery and aorta. 
 Compare Fig. 85 with Fig. 86. Original. 
 
 the direction of the left auriculo-ventricular opening, also in 
 two sets ; in other words, the left ventricle is bilateral. I wish 
 particularly to direct attention to this bilateral distribution, 
 as it has been hitherto overlooked, and furnishes the clue 
 to the arrangement of the fibres of the left ventricle. 
 
 X. The double entrance of the fibres of the several layers 
 at the left apex, and their exit in two portions from the 
 auriculo-ventricular openings at the base, are regulated with 
 almost mathematical precision ; so that while the one set 
 
198 PHYSIOLOGY OF THE CIRCULATION, 
 
 of fibres invariably enters the apex posteriorly, and issues 
 from the auriculo-ventricular opening anteriorly, the other 
 set as invariably enters the apex anteriorly and escapes from 
 the auriculo-ventricular opening posteriorly. But for this 
 disposition of the fibres, the apex and the base would have 
 been like the barrel of a pen cut slantingly or lop-sided, in- 
 stead of bilaterally symmetrical as they are. 
 
 XI. The two sets of fibres which constitute the superficial 
 or first external layer of the left ventricle, and which enter 
 the left apex in two separate portions or bundles, are for 
 the most part continuous in the interior with the musculi 
 papillares (Fig. 103, m^ #, p. 197), to the free ends of which the 
 chordae tendineae are attached. The musculi papillares, as 
 will be seen from this account, bear an important relation 
 to the segments of the mitral valve (v, v\ to which they are 
 directly connected by tendinous bands. The musculi pa- 
 pillares from this circumstance merit a more particular de- 
 scription than that given of the other fibres. 
 
 On looking at the left auriculo-ventricular opening, the 
 fibres of the first layer are seen to arise from the fibrous ring 
 surrounding the aorta (Fig. 94, #, p. 190), and from the auriculo- 
 ventricular tendinous ring (d) in two divisions : the one division 
 proceeding from the anterior portions of the rings, and winding 
 in a spiral, nearly vertical, direction, from before backwards, to 
 converge and enter the apex posteriorly (Fig. 102, b, p. 197); 
 the other set proceeding from the posterior portions of the 
 ringS) and winding in a spiral direction from behind forwards, 
 to converge and enter the apex anteriorly (Fig. 102, d, p. 197). 
 Having entered the apex, the two sets of external fibres are 
 collected together, and form the musculi papillares and carneae 
 columnae ; the one set, viz. that which proceeded from the 
 auriculo-ventricular orifice anteriorly and entered the apex 
 posteriorly, curving round in a spiral direction from right to 
 left upwards, and forming the anterior musculus papillaris (Fig. 
 103, ;z, p. 197), and the carneae columnae next to it ; the other 
 set, which proceeded from the auriculo-ventricular orifice pos- 
 teriorly, and entered the apex anteriorly, curving round in 
 a corresponding spiral direction, and forming the posterior 
 musculus papillaris (Fig. 103, m, p. 197) and adjoining carneae 
 columnae. As the external fibres converge on nearing the 
 
PHYSIOLOGY OF THE CIRCULATION. 1 99 
 
 apex, so the internal continuations of these fibres radiate 
 towards the base ; and hence the conical shape of the musculi 
 papillares (m, n). I am particular in directing attention to 
 the course and position of the musculi papillares, as they 
 have always, though erroneously, been regarded as simply 
 vertical columns, instead of more or less vertical spiral columns. 
 The necessity for insisting upon this distinction will appear 
 more evident when I come to speak of the influence exerted 
 by these structures on the segments of the bicuspid valve. 
 It is worthy of remark that while the left apex is closed 
 by two sets of spiral fibres (Fig. 102, p. 197), the left auriculo- 
 ventricular orifice is occluded during the systole by the two 
 spiral flaps or segments constituting the bicuspid valve (Fig. 
 105, m, n, p. 200). (Compare with Figs. 85 and 86, p. 174.) 
 The bilateral arrangement, therefore, which obtains in all parts 
 of the left ventricle and in the musculi papillares, extends 
 also to the segments of the bicuspid valve, and hence its name. 
 What has been said of the arrangement of the fibres in the left 
 ventricle applies with slight modifications to the fibres of the 
 right one ; and many are of opinion (and I also incline to the 
 belief) that the tricuspid valve (Fig. 85, p. 1/4) is in reality 
 bicuspid in its nature. It is so in not a few cases, as shown 
 at g, h of Fig. 105, p. 200. The shape of the ventricular 
 cavities of the heart of the mammal greatly influences the 
 movements of the mitral and tricuspid valves, by moulding 
 the blood into certain forms, and causing it to act in certain 
 directions. A precise outline of the ventricular cavities is 
 obtained by filling the ventricles with wax or plaster of 
 Paris, these substances when allowed to harden furnishing 
 an accurate cast of the parts (vide Figs. 104-106, p. 200). 
 
 The form of the left ventricular cavity, which, as already 
 stated, I regard as typical, is that of a double cone twisted 
 upon itself (Fig. 104, p. 200) ; the twist or spiral running from 
 right to left of the spectator, and being especially well marked 
 towards the apex \ The cone tapers towards the apex of the 
 left ventricle (y\ and also towards the base (b) ; and the 
 direction of its spiral corresponds with the direction of the 
 
 1 In this description the heart is supposed to be placed on its apex, with its 
 posterior aspect towards the spectator. 
 

 2OO 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 fibres of the carneae columnae and musculi papillares (Fig. 
 104, x, y). As the two spiral musculi papillares project into 
 the ventricular cavity, it follows that between them two 
 conical-shaped spiral depressions or grooves are found (Fig. 
 I0 4> $/) These grooves, which appear as spiral ridges in 
 the cast, are unequal in size; the smaller one (Fig. 104,7) 
 beginning at the right side of the apex, and winding in an 
 upward spiral direction to terminate at the base of the 
 external or left and smaller segment of the bicuspid valve 
 (Fig. 105, n) ; the larger groove (Fig. 104, q) beginning at the 
 
 Fig. 104. 
 
 Fig. 105. 
 
 Fig. 106. 
 
 Fig. 104. Wax cast of left ventricle (*) and portion of right ventricle (a) of deer. Shows spiral nature 
 of the left ventricular cavity, the spiral courses or tracks of the musculi papillares (x, y) , and how, be- 
 tween the musculi papillares, two spiral grooves (J, q] are found (they are spiral ridges in the cast), 
 which conduct the blood to the segments of the mitral valve in spiral waves. Original. 
 
 Fig. 105. Plaster of Paris cast of right and left ventricles of zebra, seen posteriorly. Shows the mitral 
 (m, n) and tricuspid (f, h) valves in action, and how the blood, when these are closed, assumes a conical 
 form (o) for pushing aside the segments of the semilunar valves, and causing them to fall back upon the 
 sinuses of Valsalva (v. -itf). Italso shows how the right ventricular cavity (c) curves round the left one (*), 
 and how the pulmonary artery (*) and aorta (K) pursue different directions, a, beginning of aorta. 
 /, portion of left ventricle adhering to plaster of Paris, f, ditto of right ventricle, q, spiral groove con- 
 ducting to aorta. Original. 
 
 Fig. 106. Plaster of Paris cast of right and left ventricles of zebra, as seen from the left side. Shows 
 infundibulum or conus arteriosus (*) of right ventricle, and analogous portion of left ventricle (/, a) ; 
 also three prominences on each (d, e, k, r, v], corresponding to the sinuses of Valsalva. It also shows 
 the double cone formed by the left ventricular cavity, the one apex pointing towards the apex of the 
 heart (_/), the other towards the aorta (h). y, portion of anterior musculus papillaris adhering to 
 plaster of Paris, x, portion of posterior musculus papillaris. n, spiral groove between musculi papillares 
 corresponding to q of Fig. 104. c, portion of muscular wall of septum. /, portion of base of left ven- 
 tricle, z, conical space of pulmonary artery where two of the segments of the semilunar valve join each 
 other. TV, point where coronary artery is given off. b, pulmonary artery, h, aorta. Original. 
 
 left side of the apex, and pursuing a similar direction, to 
 terminate at the base of the internal or right and larger 
 segment (Fig. 105, m). 
 
 Running between the grooves in question, and correspond- 
 ing to the septal aspect of the ventricular cavity, is yet 
 another groove, larger than either of the others (Fig. 105, q). 
 The third or remaining groove winds from the interior of the 
 apex posteriorly, and conducts to the aorta (a\ which, as you 
 
PHYSIOLOGY OF THE CIRCULATION. 2OI 
 
 are aware, is situated anteriorly. The importance of these 
 grooves physiologically cannot be over-estimated, for I find 
 that in them the blood is moulded into three spiral columns, 
 and that, during the systole, the blood in the two lesser 
 ones is forced in an upward direction in two spiral streams 
 upon the under surfaces of the segments of the bicuspid 
 valve, which are in this way progressively elevated towards 
 the base, and twisted and wedged into each other, until 
 regurgitation is rendered impossible (Fig. 105, m, ri}. When 
 the bicuspid valve is fairly closed, the blood is directed 
 towards the third and largest groove, which, as has been 
 explained, communicates with the aorta. The spiral action 
 of the mitral valve, and the spiral motion communicated to 
 the blood when projected from the heart, are due to the spiral 
 arrangement of the musculi papillares and fibres composing 
 the ventricle, as well as to the spiral shape of the left ventri- 
 cular cavity. 
 
 What has been said of the conical shape of the left 
 ventricular cavity and aorta applies, with slight alterations, to 
 the right ventricular cavity and pulmonary artery (Figs. 105 
 and 1 06, c, z), the cones formed by the latter being flattened 
 out and applied to or round the left ones. 
 
 Analogy between the Miiscular Arrangements and Move- 
 ments of the Hollow Viscera (Heart, Stomach, Bladder, Uterus^ 
 etc.), and those of the Trunk and Extremities of Vertebrates. 
 The distribution and direction of the muscles and muscular 
 fibres of the trunk and extremities of vertebrates accords in a 
 wonderful manner with that just described in the ventricles of 
 the heart of the mammal ; the arrangement of the muscular 
 fibres in the ventricles closely corresponding with that in the 
 stomach, bladder, and uterus. This is a remarkable circum- 
 stance, and merits the attention of all interested in homologies. 
 If, e.g., the thoracic portion of the human trunk be examined, 
 we find longitudinal, slightly oblique, oblique, and transverse 
 muscles, arranged symmetrically and in pairs as in the 
 ventricles. Thus, in the region of the thorax anteriorly we 
 have the symmetrical muscular masses constituting the 
 pectorals and deltoids, the fibres of which are arranged verti- 
 cally, transversely, and at various degrees of obliquity. The 
 fibres of these muscles if produced would intersect as in the 
 
202 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 ventricles. Beneath the pectorals and deltoids we find the 
 external and internal intercostal muscles running obliquely 
 and crossing each other as in the letter X ; while the serrati 
 muscles run transversely and nearly at right angles to both 
 (Fig. 107). 
 
 In the region of the abdomen this arrangement is repeated. 
 Thus, we have the recti muscles running in the direction of 
 the length of the trunk ; the transversales abdominis running 
 across the trunk or at right angles to the recti ; and the 
 external and internal oblique muscles running diagonally 
 between the recti and transversales and crossing each other 
 (Fig. 109). 
 
 Fig. 107. 
 
 Fig. 108. 
 
 Fig. 109. 
 
 Figs, 107, 108, and 109 show how the muscles of the human chest, arm, forearm, and abdomen run in 
 vertical, slightly oblique, oblique, and transverse directions, as in the heart (left ventricle), and cross, or 
 tend to cross, each other. Compare the letters of these figures with corresponding letters of Figs. 98, 
 99, and 100, p. 195. Original. 
 
 Proceeding to the posterior and lateral aspect of the 
 thoracic region of the trunk a similar arrangement presents 
 itself. Thus, in the trapezii we have the homologues of the 
 pectorals with fibres running in a more or less longitudinal 
 direction, obliquely and transversely, and which would inter- 
 sect if produced. Beneath the trapezii we have the rhomboidei 
 and splenii crossing obliquely as in the letter X. The 
 longitudinal muscles of this region are represented by the 
 levatores anguli scapulae, the accessorii, the longissimi dorsi, 
 spinales dorsi, and semi-spinales dorsi. The slightly oblique 
 muscles are represented by the levatores costarum, the mul- 
 tifidi spinae, the transversales colli, etc. ; and the transverse 
 muscles by the serrati. 
 
PHYSIOLOGY OF THE CIRCULATION. 203 
 
 Proceeding to the loins and the region corresponding to the 
 abdomen behind, the arrangement again repeats itself. In 
 the quadrati lumborum, erectores spinalis, and sacri lumbalis, 
 we have longitudinal muscles ; in the multifidi spinae, slightly 
 oblique muscles ; and in the latissimi dorsi, oblique muscles. 
 If therefore I eliminate the element of bone from the thorax 
 and abdomen, there will remain a muscular mass with fibres 
 running longitudinally, slightly obliquely, obliquely, and 
 transversely ; the longitudinal muscles intersecting the trans- 
 verse muscles at right angles, the slightly oblique muscles 
 intersecting each other at acute angles, and the oblique ones 
 at obtuse angles, symmetrically as in the ventricles of the 
 heart. We have consequently in the thorax and abdomen 
 two hollow muscular masses closely allied to the auricles and 
 ventricles of the heart; the one opening when the other 
 closes, and vice versa. This follows because the bones of the 
 trunk, while they transmit, do not originate movement. Nor 
 does the resemblance stop here. Between the thorax and 
 abdomen there is a movable muscular partition the dia- 
 phragm, which descends when the thorax opens and the 
 abdomen closes. A precisely similar function is performed by 
 the mitral and tricuspid valves of the heart, two tendinous 
 structures situated between the auricles and ventricles. The 
 thoracic and abdominal movements are correlated for the 
 reception and discharge of air, food, urine, faeces, etc., in the 
 same way that the movements of the auricles and ventricles 
 are correlated for the reception and discharge of blood. The 
 thorax may be said to pump and suck air ; the heart blood. 
 In the diaphragm, the muscular fibres are arranged at right 
 angles, slightly obliquely, and obliquely, as in the ventricles, 
 thorax, and abdomen. This curious muscle may consequently 
 be compared to half a heart, half a stomach, or half a bladder. 
 The diaphragm, like the hollow viscera, chest, abdomen, etc., 
 acts by alternately shortening and elongating its fibres. When 
 it elongates its- fibres, it ascends and diminishes the floor of 
 the thorax ; when it shortens them, it descends and enlarges 
 the floor of the thorax. This arrangement provides for the 
 diaphragm oscillating on either side of a given line. The 
 diaphragm ascends when the ribs descend, and vice versa. 
 The ascent of the diaphragm and the descent of the ribs 
 
2O4 PHYSIOLOGY OF THE CIRCULATION. 
 
 diminish the capacity of the thorax, and increase that of the 
 abdomen ; the descent of the diaphragm and the ascent of 
 the ribs increase the capacity of the thorax, and diminish that 
 of the abdomen. When the thorax expands and the abdomen 
 closes, a wave of motion passes from the symphysis pubis in 
 the direction of the ensiform cartilage ; a reverse wave passing 
 from above downwards when the abdomen expands and the 
 thorax closes. The lines representing these waves of motion 
 cross each other figure-of-8 fashion in forced expiration and 
 inspiration. The muscular arrangement described in the 
 hollow viscera and in the human trunk appear in a simpler 
 form in the body of the fish. They are seen to advantage in 
 the body of the manatee, a sea mammal in which the ex- 
 tremities are rudimentary ] . They reappear in the extremities 
 when these are sufficiently developed. Thus, in the human 
 arm the biceps represents the longitudinal fibres, the supinator 
 longus and flexor carpi radialis the slightly oblique fibres, the 
 pronator radii teres and flexor sublimis digitorum the oblique 
 fibres, and the pronator quadratus the transverse fibres 
 (Fig. 1 08, p. 202). 
 
 Stranger than all, the bones of the extremities are twisted 
 upon themselves and correspond to the mould or cast obtained 
 from the cavity of the left ventricle, which shows that the 
 bones mould and adapt themselves to the muscles, and not 
 the converse. The muscles of the extremities are arranged 
 around their bones as the muscles of the ventricles are 
 arranged around their cavities. These points are illustrated 
 at Figs. 110-112, p. 205. 
 
 As the soft tissues precede the hard in the scale of being, 
 I am disposed to tabulate the muscles thus : ist, The heart 
 and hollow muscles, which act independently of bone ; 2nd, 
 The muscles of the trunk, which act in conjunction with bone ; 
 3rd, The muscles of the extremities, also geared to bone. 
 I place the hollow muscles first, because they are found before 
 any trunk proper exists ; the trunk muscles second, because 
 the thorax and abdomen precede the limbs ; and the muscles 
 of the extremities third, because the limbs are differentiations 
 which are only found in the higher animals. 
 
 1 Vide a very splendid memoir on this rare animal by Dr. James Murie, Trans. 
 Zool. Soc. vol. viii. plate 21. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 205 
 
 As bones appear comparatively late in the scale of being, 
 I am inclined to regard the hollow involuntary muscles as 
 typical of the solid voluntary muscles, both as to the direction 
 of their fibres and mode of action. The term solid is here 
 applied to the voluntary muscles from the fact that they 
 invest bones and have no cavities in their interior; the 
 involuntary muscles, on the other hand, surround cavities and 
 have no connexion with bone. The fibres of the ventricles, 
 as explained, are arranged longitudinally, transversely, and at 
 various degrees of obliquity, symmetrically, and with some- 
 thing like mathematical accuracy. The fibres are not to be 
 
 Fig. no. 
 
 Fig. in. 
 
 Fig, 112. 
 
 Fig. no. Photograph of a cast of the left ventricle of the heart of a deer. Shows the spiral nature of 
 the left ventricular cavity. (For further descriptioifsee Fig. 104.) Original. 
 
 Fig. in. Bones of the anterior extremity of the elephant. Shows the spiral arrangement of the bones 
 of the fore leg. (Compare with Fig. no.) q, humerus. x, q', radius and ulna, o, bones of foot 
 Original. 
 
 Fig. ii2. Bones of the wing of a bird. Shows their spiral arrangement. (Compare with Figs, no and 
 in.) ,The bones of the human arm resemble those of the fore-limb of the elephant and the wing of the 
 bird, a, humerus. b, radius and ulna, c, bones of the hand. Original. 
 
 regarded as in any sense antagonistic. Thus the longitudinal 
 fibres do not pull against the transverse, or the various oblique 
 fibres against each other. On the contrary, the fibres act 
 together and consentaneous4y. When the ventricle is to be 
 closed, all the fibres shorten and broaden ; when it is to 
 be opened, they all elongate and narrow. These movements 
 are definitely co-ordinated. The muscles do not exhaust 
 themselves in a suicidal .warfare. The function of the ven- 
 tricles' is .to draw in and eject blood, and this can only be 
 done economically in the. manner explained. In like manner 
 
206 PHYSIOLOGY OF THE CIRCULATION. 
 
 analogy and a variety of circumstances, to be alluded to pre- 
 sently, incline me to believe that the muscular masses found in 
 the thorax, abdomen, and extremities, are not arranged to an- 
 tagonise each other, and that the flexors, pronators, and ab- 
 ductors do not when they shorten forcibly drag out the extensors, 
 supinators, and adductors. On the contrary, I believe that all 
 these movements are co-ordinated as in the heart ; the ex- 
 tensors, supinators, and adductors elongating when the flexors, 
 pronators, and abductors shorten, and vice versa ; there being, 
 in short, no such thing as antagonism in muscular movements. 
 It does not follow that because one muscle is situated upon 
 one aspect of a bone or bones, and a second muscle upon 
 another and opposite aspect of the same bone or bones, that 
 therefore the two muscles antagonise or contend with each 
 other. When a muscle by its shortening is intended to 
 stretch another substance, that substance as a rule is simply 
 elastic, i.e. it has no power of originating movement. We 
 have examples of this in the blood-vessels and the wing of 
 the bird. 
 
 The chief function of the voluntary muscles is to move 
 bones. To move bones effectually and avoid waste there 
 must be conservation of energy. To conserve energy, the 
 muscles of necessity act upon the bones to be moved and not 
 upon each other. The muscles consequently are correlated 
 and their movements co-ordinated. To say one muscle acts 
 against another muscle, is equivalent to saying a muscle acts 
 against itself, and of this we have no proof. In the penniform 
 and other compound muscles, where the fibres meet at a 
 variety of angles and tend to cross, all the fibres shorten and 
 elongate at the same time as in the heart. In the muscular 
 masses investing universal joints, such as are found at the 
 shoulders and pelvis, precisely the same thing happens. The 
 fibres, whatever their length, strength, or direction, act to- 
 gether, and by their united efforts produce an infinite variety 
 of movements. These masses, when acting in conjunction 
 with the muscles of the extremities, can rotate the bones to 
 which they are attached in the same way that the heart can 
 wring out its blood and tilt its apex. 
 
 Before leaving the subject of muscular arrangements, it may 
 be useful to recapitulate very briefly. 
 
PHYSIOLOGY OF THE CIRCULATION. 207 
 
 In the smallest blood-vessels only one set of muscular fibres 
 is present, these running around the vessels. In the larger 
 blood-vessels two sets of muscular fibres are found, these being 
 arranged at right angles to each other ; the one set running 
 across the vessels, and the other in the direction of their 
 length *. The same arrangement obtains in the intestine, the 
 muscular tunic of the wo.rm, and many simple structures. 
 In the ventricles of the heart, the stomach, bladder, uterus, 
 thorax, abdomen, and the extremities, the muscular fibres are 
 arranged at right angles and obliquely, but always sym- 
 metrically and in pairs. The muscles of the tongue afford a 
 good example. In this organ a large proportion of the 
 inherent muscles are arranged in the form of a St. An- 
 drew's cross. Thus there are longitudinal fibres which traverse 
 the tongue from side to side ; others which traverse the tongue 
 from above downwards or vertically. Between these two sets 
 of fibres, which intersect each other at right angles, there are 
 others, which converge towards the axis of the organ, and 
 which intersect or tend to intersect at gradually increasing 
 angles, but always in pairs, as in the heart. To these are to 
 be added a sheath of longitudinal fibres which traverse the 
 tongue in the direction of its length. The universality of the 
 movements of the tongue is well known. The tongue certainly 
 possesses an inherent power of elongating and shortening ; 
 indeed in many of the ruminants it takes the place of a hand. 
 When the tongue elongates, its cross fibres shorten and 
 broaden ; in other words, elongate in the direction of the 
 length of the tongue ; the longitudinal fibres elongating in the 
 
 1 In some of the larger veins, there are two sets of muscular fibres, the one 
 running in the direction of the length of the vessel, the other across it. Thus in 
 addition to the circular fibres always present in the central layers, there are longi- 
 tudinal fibres mixed up with the areolar tissue and longitudinal elastic fibres of 
 the external layer, which extend the whole length of the inferior vena cava, the 
 renal, azygos, and external iliac veins, and in all the large trunks of the portal 
 venous system, and in the trunks of the hepatic veins. Muscular tissue is also 
 abundantly developed in the veins of the gravid uterus, being found in all three 
 coats, and in the venae cavae and pulmonary veins it is prolonged on to them from 
 the auricles of the heart. Muscular tissue is wanting in the veins of the maternal 
 part of the placenta, in most of the cerebral veins and sinuses of the dura mater, in 
 the veins of the retina, in the veins of the cancellous tissue of bones, and in the 
 venous spaces of the corpora cavernosa. Anatomy, Descriptive and Surgical, by 
 Henry Gray, F.R.S. etc.; p. 401. 
 
208 PHYSIOLOGY OF THE CIRCULATION. 
 
 same direction and at the same time. These movements are 
 reversed when the tongue shortens. The muscles situated at 
 the root of the tongue are arranged on a similar principle ; 
 these, when they elongate, pushing out the tongue, and when 
 they shorten drawing it in. This follows because the major 
 portion of the muscles of the tongue are not attached to bone, 
 and therefore have no fixed points. 
 
 Structure and Properties of Voluntary and Involuntary 
 Muscles. The voluntary and involuntary muscular systems at 
 first sight appear to have few things in common. In reality 
 they have many ; the one being a modification or differentia- 
 tion of the other. The common parent of the involuntary 
 and voluntary muscle is the nucleated cell, and to this both 
 may be referred *. 
 
 Involuntary Muscle. The fibres of the involuntary muscles 
 are non -striated or unstriped, i.e. they possess no transverse 
 markings. They consist of elongated spindle-shaped fibre- 
 cells, which are flat, clear, granular, and brittle, so that they 
 break off suddenly, and present a square extremity. Many 
 of them display a rod-shaped nucleus in their interior. They 
 occur in the arteries, lymphatics, stomach, intestine, bladder, 
 the pregnant uterus, the ducts of glands, the gall-bladder, 
 vesiculi seminales, etc. 
 
 Voluntary Muscle. The fibres of foetal voluntary muscle 
 display in their substance the nuclei of the cells from 
 
 1 'The researches of Valentine and Schwann have shown that a muscle 
 (voluntary) consists in the earliest stages of a mass of nucleated cells, which first 
 arrange themselves in a linear series with more or less regularity, and then unite 
 to constitute the elementary fibres. As this process of agglutination of the cells is 
 going forward, a deposit of contractile material gradually takes place within them, 
 commencing on the inner surface and advancing to the centre till the whole is 
 solidified. The deposit occurs in granules, which as they come into view, are seen 
 to be disposed in the utmost order in longitudinal and transverse rows. From the 
 very first period these granules are part of a mass, and not independent of one 
 another. The involuntary fibres are apparently homogeneous in texture. They 
 however, in some cases, present a mottled granular appearance, the granules being 
 arranged in a linear series. This condition Bowman is inclined to regard as an 
 approximation towards the structure of the striped or voluntary fibre ; the granules 
 being of about the same size as those in the voluntary fibres. In the simple' 
 muscles of the lower animals, consisting in some cases of only one or two rows of 
 sarcous elements, a transition from the striped towards the unstriped fibres may be 
 perceived; the transverse markings under these circumstances being irregular, 
 broken, or faintly marked.' 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 209 
 
 which they are developed (Fig. 113 B, a, a); these corre- 
 sponding to the rod-shaped nuclei of the involuntary muscle 
 (Fig. It3 A, a). The striae are very faintly marked (Fig. 
 1136, C). The fibres of the adult voluntary muscles, on the 
 other hand, are distinctly striated or striped, i. e. they display 
 a series of symmetrical, longitudinal, and transverse markings, 
 as shown at Fig. 113 D, E, F, G, H, I. 
 
 A voluntary fibre consequently consists of an aggregation 
 of square particles arranged with great regularity in sym- 
 metrical rows (Figs. 1 1 3 D, H). Each fibre is covered by a thin 
 transparent elastic membrane, the sarcolemma, which isolates 
 the one fibre from the other (Fig. 113 E, a). The involuntary 
 
 Fig. 113. A, Unstriped elementary fibres from human colon ; treated with and without acetic acid. 
 B, elementary fibres from pectoral muscle of foetal calf, two and a half months old, showing corpuscles 
 a, a, magnified 300 diameters. C, elementary fibres from larva of dragon-fly, in aneariy stage of develop- 
 ment, showing central row of corpuscles, magnified 300 diameters. Bo-wman. D, muscular fibrils of pig, 
 magnified 720 diameters, c, single fibril, showing quadrangular outline of component particles, their dark 
 central part and bright margin and their lines of junction crossing the light intervals, b, longitudinal 
 segment of fibre, consisting of a number of fibrils still connected together, a, other smaller collections 
 of fibrils. From a Preparation by Mr. Leatham, after Dr. Sharpey. 
 
 E. Fragment of an elementary fibre of the skate, held together by the untorn and twisted sarcolemma. 
 a, sarcolemma ; b, b, opposite fragments of the fibre. 
 
 F. Fragment of striped elementary fibres, showing transverse cleavage (c, d) of sarcous elements. 
 The longitudinal cleavage is seen at b of I. G, H, appearances presented by the separated single 
 fibrillae. At G the borders are scalloped and the spaces bead-like. At H the borders and transverse 
 lines are all perfect'.y rectilinear, and the included spaces perfectly rectangular. The latter is the more 
 common. After Bowman. 
 
 fibre is not invested with this membrane. The voluntary 
 differs from the involuntary fibre in being of a cylindrical 
 shape. 
 
 Much confusion unfortunately exists as to the utimate 
 composition of the voluntary muscles, and the nature of the 
 striation. Some are of opinion that the elementary particles 
 of which a fibrilla is composed consist of rows of corpuscles 
 or discs connected by a homogeneous transparent material ; 
 others believing that they consist of little masses of pellucid 
 
 P 
 
2IO PHYSIOLOGY OF THE CIRCULATION. 
 
 substance, possibly nucleated cells, which because of the 
 pressure to which they are subjected, present a rectangular 
 outline, and appear dark in the centre. Bowman, who has 
 devoted much attention to this subject, describes and figures 
 a longitudinal and transverse cleavage (Fig. 113 I, F, p. 209). 
 He says, ' Sometimes the fibre will split into discs only (Fig. 
 113 F, , </, p. 209), more often into fibrillae only (Fig. 113!, 
 #, p. 209) ; but there are always present in it the transverse 
 and the longitudinal lines which mark the two cleavages' 
 (Fig. 113 I, a, p. 209). He delineates two fibrillae, in one 
 of which the borders and transverse lines are all perfectly 
 rectilinear, and the enclosed spaces perfectly rectangular (Fig. 
 113 H, p. 209) ; in the other, the borders are scalloped, and 
 the spaces are bead-like (Fig. 113 G, p. 209). When most 
 distinct and definite the fibrilla presents the former of those 
 appearances. The ultimate particles, or sarcous elements, 
 as they have been termed, are merely indicated when the 
 fibre is entire ; the dark and light squares being blended 
 together and forming a continuous structure. It is only 
 when the fibre is injured, and partly disintegrated, that the 
 alternate squares can be seen to advantage (Fig. 116, p. 218). 
 The squares in question exist under all circumstances ; their 
 number and form being imprinted in the very structure of the 
 fibre in its perfect state. In virtue of the longitudinal and 
 transverse cleavage which takes place, a muscle may be 
 separated into its longitudinal fibrillae and transverse discs. 
 * To detach a fibrilla entire is to remove a particle from every 
 disc, and to take away a disc is to abstract a particle of every 
 fibrilla.' The dark and light markings are due not to an 
 actual difference in colour in the sarcous elements, but to 
 unequal refracting power. This can be shown by altering the 
 focus of the microscope ; the dark and light lines being by 
 this means made to change places. Some aver that in living 
 muscle no lines are visible ; but the fact that the dead muscle 
 coagulates and disintegrates, or breaks up into square patches, 
 tends to prove that the sarcous elements differ in some way 
 from the material which connects them, and that there are at 
 least two substances in an ultimate muscular fibre. I direct 
 attention to the sarcous elements so admirably described and 
 figured by Bowman, because I think they furnish us with 
 
PHYSIOLOGY OF THE CIRCULATION. 211 
 
 a means of explaining the manner in which voluntary and 
 involuntary muscles shorten and lengthen. 
 
 Mixed Muscles. Between the involuntary and voluntary 
 muscles are a mixed class which run the one into the other 
 by gentle gradations. Thus the mammalian heart, the lym- 
 phatic hearts of reptiles and birds, the stomach and intestines 
 of some fish, and the upper part of the oesophagus, are all 
 involuntary muscles, and yet they possess the transverse 
 markings distinctive of the voluntary muscles. The move- 
 ments of the voluntary and involuntary muscles likewise run 
 into each other. Thus 'many involuntary movements are 
 performed by muscles which are subject to the will ; and 
 many muscles that are commonly independent of the will are 
 liable to be affected by it or by other acts of the mind. More 
 than all, whether a muscle is involuntary or not, depends not 
 on itself, but on the nervous system ; for if the brain be 
 removed or inactive, all the muscles become involuntary ones.' 
 
 Muscles can act in Two Directions ; Sarcous Elements of 
 Muscle Peculiar Movements of. The first fact to be fixed 
 in the mind when attempting to comprehend the action of 
 a muscle, is the remarkable one, that when a muscle con- 
 tracts or shortens, it bulges out laterally, and elongates 
 transversely. This follows, because when a muscle acts, its 
 volume remains always the same. 
 
 In order that a muscle may shorten in the direction of 
 its length and elongate in the direction of its breadth, and 
 the converse, its ultimate particles, whatever their shape, 
 must have the power of acting in two directions, viz. in the 
 direction of the length of the muscle, and across it. 
 
 Muscular Motion as bearing on the Functions performed by 
 the Heart, Blood-vessels, Thorax, Extremities, etc. With a 
 view to forming a just estimate of the manner in which 
 muscles act, it is necessary to take a wide survey of those 
 substances which we know are capable of changing shape, 
 and which take part in locomotion and other vital manifesta- 
 tions. This becomes especially necessary when we remember 
 that some physiologists maintain that even the striation in 
 voluntary muscles is due not to the presence of two sub- 
 stances, but simply to unequal refraction and the play of light. 
 The advocates of this view regard the substance of voluntary 
 
 P 2 
 
212 PHYSIOLOGY OF THE CIRCULATION. 
 
 muscle as homogeneous ; the dark and light sarcous elements 
 or squares constituting the longitudinal and transverse striae 
 being in their opinion all of the same colour. The striae, 
 as stated, are absent in involuntary muscles, and very faintly 
 indicated in young voluntary muscles, so that we must not 
 lay too much stress on the transverse markings, which may, 
 after all, be an optical delusion. When I employ the term 
 sarcous element, cube, or square, I wish it to represent 
 a definite portion of the muscular mass having that par- 
 ticular form. The dark and light sarcous elements may or 
 may not have exactly the same chemical constitution, but 
 this does not interfere with the property which both possess 
 of changing shape, and this it is which distinguishes mus- 
 cular and all other forms of movement occurring in the 
 tissues. The movements of the voluntary and involuntary 
 muscles are in some senses identical. As voluntary muscle 
 is a development and differentiation of involuntary muscle, 
 so voluntary movements are to be regarded as higher mani- 
 festations of involuntary movements. In the involuntary 
 muscle there is a recognisable structure (Fig. 113, A, p. 209), and 
 in the voluntary muscle that structure apparently becomes 
 more elaborate (Fig. 113, D, p. 209) ; but movements definitely 
 co-ordinated, and very precise in their nature, can occur in 
 tissues which are structureless or homogeneous ; and this is 
 a point not to be overlooked when studying the movements 
 of the voluntary and involuntary muscles, for it shows that 
 structure, in the ordinary acceptation of the term, is not 
 necessary to motion. Thus, the amoeba, which consists of 
 a soft jelly mass, can change its shape in any direction it 
 pleases. It can, as I have ascertained from actual observa- 
 tion, push out or draw in a knuckle of any part of its 
 body. These movements are not due to contraction in the 
 ordinary sense of the term, for the portion of the body 
 protruded is wedge-shaped ; no trace of constriction being 
 anywhere visible. They are doubtless referable to a cen- 
 tripetal and centrifugal power inhering in the protoplasmic 
 mass which enables the creature to advance or elongate, 
 and withdraw or shorten, any part of its body. At times 
 the amoeba elongates its entire body by a wave-like move- 
 ment, after which it sends out lateral processes which 
 
PHYSIOLOGY OF THE CIRCULATION. 213 
 
 exactly correspond with the bulgings produced on a mus- 
 cular fibre when it is made to contract or shorten under 
 the microscope. When it sends out the lateral processes 
 or elongates in the direction of its breadth, the body of 
 the animal is shortened. When the lateral processes are 
 shortened, the body of the animal is elongated. The analogy 
 between the movements of an amoeba and those of a mus- 
 cular fibre, or a portion thereof, is therefore complete. 
 Indeed there is every reason to believe that the movements 
 of the amoeba and the sarcous elements of a muscle are 
 identical. Both can change their form, elongation in one 
 direction entailing shortening in another and opposite direc- 
 tion. In either case change of form does not involve 
 change of volume, this always remaining exactly the same. 
 Similar properties are possessed by the mushroom-shaped 
 disc of the medusa. This consists of a jelly mass devoid 
 of muscular fibre. The animal advances by a deliberate 
 opening and closing of its disc ; these movements, as I have 
 fully satisfied myself from an attentive examination of 
 living specimens, being quite independent of each other. 
 The disc opens slowly and closes rapidly, as in the heart ; 
 the disc when it closes forcing itself from the surface of 
 a fluid wedge with considerable energy. Here the cen- 
 tripetal and centrifugal power which I am disposed to claim 
 for muscle, and especially for hollow muscles such as the 
 heart, stomach, bladder, uterus, blood-vessels, etc., is seen 
 to perfection. When the disc closes, the substance of the 
 animal converges and seeks the centre ; when the disc 
 opens, its substance diverges and avoids the centre. The 
 closing movement is the result of a vital converging, closing, 
 or shortening of all the particles composing the body ; the 
 opening movement being the result of a vital diverging, ex- 
 panding, or elongating of the same particles. This follows 
 because the fluid in which the medusa is immersed can 
 take no part either in the closing or opening of the disc. 
 The movements of the Salpa cristata still more closely re- 
 semble those of the heart (Fig. 114, p. 214). The salpa may 
 very properly be compared to the left ventricle. Thus it is 
 a conical-shaped bag supplied with two apertures ; one of 
 which, situated at the extremity of the animal (b\ corre- 
 
214 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 spends to the auriculo-ventricular orifice ; the other, situated 
 at the mouth (a), to the orifice of the aorta. The orifice 
 corresponding to the auriculo-ventricular 
 opening is supplied with a valve (c) 
 which may be compared to the mitral 
 valve. When the animal wishes to ad- 
 vance it expands, and draws or sucks 
 water into its body by the aperture 
 furnished with the valve. It then by 
 a centripetal movement closes its body 
 and the valve, and by so doing forces 
 the water out of its interior at the 
 aperture which corresponds to the orifice 
 of the aorta. By this expedient the 
 salpa confers on its body a retrograde 
 movement. The fact to be attended 
 to in the movements of this simple 
 creature is the power it possesses of 
 expanding and drawing water into its 
 interior, which it subsequently forcibly 
 ejects. It thus exerts a pulling and 
 pushing power, similar to that exercised 
 by the left ventricle or any other com- 
 partment of the heart. 
 
 The centripetal and centrifugal movements adverted to 
 are not confined to animals, and we must descend still 
 further in the scale of being if we would see them in their 
 most rudimentary forms. They occur in such plants as the 
 Volvox globator and Chlamydomonas, the vacuoles of 
 which open and close with time-regulated beat 1 . They 
 are the same which cause the leaves and flowers of certain 
 orders of plants to open and close at various periods of the 
 day and night. If therefore structureless masses have the 
 power of opening and closing, or, what is the same thing, 
 
 1 That a jelly-like mass, apparently devoid of structure, is capable of shorten- 
 ing and elongating, is proved by a very remarkable experiment made by Kuhne. 
 This distinguished physiologist took the intestine of a cockchafer and stuffed it 
 with living protoplasm from a living plant. He applied electricity to the gut so 
 prepared, and found, to his surprise, that it exhibited all the phenomena peculiar to 
 to muscle when artificially stimulated the intestine shortening suddenly when 
 the stimulus was applied, and elongating slowly after it was withdrawn. 
 
 Fig. 114. Salpa cristata. a, 
 orifice at mouth. 6, orifice cor- 
 responding in situation to anal 
 aperture, c, valve guarding 
 orifice *, which permits water 
 to enter in the direction of the 
 
PHYSIOLOGY OF THE CIRCULATION. 215 
 
 of elongating and shortening, it is not too much to claim 
 a similar power for a muscular fibre and the sarcous elements 
 of which it is composed ; the more especially as we know 
 from observation and experiment that the muscular fibre 
 when it shortens in one direction elongates in another 
 direction, the fibre and its component particles possessing 
 the power of abandoning and returning to their original 
 form. If it be true that when a muscle shortens it elon- 
 gates in the direction of its breadth, and if further it be 
 true that when a muscle elongates it shortens in the direc- 
 tion of its breadth, it follows that all the particles in the 
 mass obey the same laws. Thus when a muscle shortens in 
 the direction of its length, all its particles, whatever be their 
 composition, colour, or original form, elongate in the direction 
 of the breadth of the muscle. When, on the other hand, a 
 muscle elongates in the direction of its length, all its particles 
 shorten in the direction of the breadth of the muscle. But 
 the particles of a muscle are free to change shape in any 
 direction, for it is well known that if a long muscle be 
 artificially stimulated it shortens and after a while regains 
 its original dimensions, so that by repeating the stimulus 
 it may be made to shorten a second time. This happens 
 even when the long muscle is cut away from its connexions, 
 and when it is removed from the influence supposed to be 
 exerted upon it by what is termed its antagonist muscle. 
 This tends to prove that the power which all muscles possess 
 of alternately shortening and elongating inheres in their 
 substance or sarcous elements, the movements being essen- 
 tially vital in their nature, and independent of each other. 
 That a muscle or fibre, or their component particles, are 
 endowed with universality of motion, is apparent from the 
 fact that when a muscle or a muscular fibre shortens, it is 
 thrown into rugae or swellings, the long axes of the par- 
 ticles of the swelled portions being arranged at right angles 
 to the long axes of the particles representing the constric- 
 tions or narrow parts. But those parts of the muscle or 
 fibre which form the constrictions the one instant become 
 the swellings the next, the direction of the long axes of the 
 particles or sarcous elements of the muscle or fibre being 
 in this case reversed. Muscular movements are therefore 
 
2l6 PHYSIOLOGY OF THE CIRCULATION. 
 
 the result of a rhythmic motion in their ultimate particles, 
 in all respects analogous to the rhythmic movements of the 
 heart. The movements of muscles are characterised by two 
 forces acting at right angles to each other; the one force 
 flying a fixed point, while the other seeks it (Fig. 115). 
 
 Fig. 115 shows an elementary fibre of the skate in the uncontracted and contracted state. 
 
 A. Fibre in the condition of rest, r, transverse markings or cleavage, s, longitudinal markings or 
 cleavage. 
 
 B. a, a, a, one side of fibre contracting or shortening. 
 
 C. b, b, b, both sides of fibre contracting or shortening. All parts of the fibre become involved in 
 succession. Thus, the constrictions between b, b, b of C become the swellings c, c of D. After 
 Bowman. 
 
 In reality the ultimate particles or sarcous elements of a 
 muscle are correlated and definitely co-ordinated, neighbouring 
 particles or groups of particles exercising a centrifugal and cen- 
 tripetal power which causes one set of particles to advance in 
 one direction, while a corresponding set recede in an opposite 
 direction. This is what virtually happens in the voluntary 
 system of muscles. When one muscle shortens on one side 
 of a bone, that on the opposite side elongates. By assign- 
 ing a centrifugal and centripetal power to a moving mass, 
 we can readily understand how structureless tissues open 
 and close. Without such a power even elaborate tissues 
 would have difficulty in moving. From the foregoing it 
 follows, that from the time the particles of a muscle leave 
 their position of rest and begin to change their form until 
 they return to their original position and assume their original 
 shape, they are in a state of activity. This is proved by 
 the fact that when a muscle or sarcous element shortens 
 in the direction of its length, it broadens or lengthens in 
 the direction of its breadth, and vice versa. If we assign 
 to muscles, or their sarcous elements, the power of changing 
 form in one direction, it is unphilosophic to assume that 
 they have not the power of changing form in another and 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 opposite direction. Even structureless masses of protoplasm 
 are endowed with this power, and the amoeba, which may 
 be regarded as an aggregation of such masses, can elongate 
 and shorten its body with equal facility, can contract or 
 close in one direction and expand or open in another can 
 make a temporary cavity in its substance to serve the pur- 
 pose of a temporary stomach, and then obliterate it. Similar 
 attributes inhere in the white blood corpuscle. The majority 
 of physiologists of the present day deny that muscles are 
 endowed with the power of elongating. They say that 
 muscles can only contract or shorten, and that when they 
 elongate their elongation is due to elasticity, or they are 
 drawn out by antagonist muscles ; a flexor drawing out its 
 extensor the one instant, the extensor drawing out the 
 flexor the next. If this were so, the muscles, as already 
 indicated, would act upon and against each other, instead 
 of upon the bones they are intended to move. The waste 
 of muscular energy under such circumstances would be in- 
 ordinate. The prevailing theory of muscular action is thus 
 stated by Bowman : * The contraction of a muscle will be 
 permanent if no force from without be exerted to obliterate 
 it by stretching, for a contracted muscle has no power of 
 extending itself.' Much of the obscurity regarding mus- 
 cular movements is, I believe, traceable to the employment 
 of the terms contraction and relaxation, contraction primarily 
 signifying a shrinkage or diminution in volume, which does 
 not occur in muscular movements ; relaxation, an abandon- 
 ment of the contracted state. An example may be useful. 
 According to prevailing opinions a flexor, when it contracts 
 or shortens, drags out or elongates its extensor ; the flexor 
 being active, the extensor passive. Another way of putting 
 it is this : When the flexor contracts the extensor relaxes, 
 i. e. offers no opposition to being drawn out by the flexor. 
 This however is avoiding the difficulty by taking refuge in 
 terms. Either a muscle (or parts thereof) is or is not active. 
 When it is not in a state of activity, it is in the condition 
 of rest, so that the phrase passive contraction, so frequently 
 employed, has no meaning. I propose therefore for these 
 and other reasons to abandon the terms contraction and 
 relaxation, as being inapplicable to muscular movements, 
 
218 PHYSIOLOGY OF THE CIRCULATION. 
 
 and to substitute for them the more simple ones of shortening 
 and elongating, as applied to long muscles ; and closing and 
 opening, as applied to hollow muscles. By the shortening 
 or closing of a muscle, I mean its centripetal action, that 
 action by which its particles converge and crowd towards a 
 certain point ; by the elongating or opening of a muscle, 
 I mean its centrifugal action, that action by which its par- 
 ticles diverge or escape from a certain point. These move- 
 ments are not equally rapid, but they are equally independent 
 and vital in their nature 1 . My meaning will be obvious 
 from the annexed woodcuts. 
 
 Fig. 116. Fig. 117. 
 
 Fig. 116. Elementary fibres from leg of newly-born rabbit after having been exposed to the action of 
 spirit. Shows longitudinal and transverse cleavage, and the manner in which the sarcous elements or 
 cubes (a, a) may become detached. After Bowman. 
 
 Fig. 117. A, sarcous element or cube capable of changing shape in any direction (vide arrows). 
 B, same element when elongated vertically. C, ditto when elongated horizontally. The position of rest, 
 and the form of B and C when at rest, is that represented at A. Original. 
 
 At Fig. 117 A, a sarcous cube or integral portion of a 
 muscle is represented. This cube, like the amoeba, is en- 
 
 1 Dr. Martin Barry endeavoured to explain muscular actions by assuming that 
 the sarcous elements were arranged as in a spiral spring ; but neither the dis- 
 position of the dark and light squares, nor their mode of action, favours this view. 
 The late Professor Alison attributed the contraction and relaxation of muscle to 
 the attraction and repulsion of its ultimate particles. Thus he states that con- 
 traction essentially consists in a greatly increased attraction among the particles, 
 or globules constituting the muscular fibres, and alteration in the direction in 
 which the attraction acts, rapidly communicating from one particle to another, 
 both along the same fibre and among adjacent fibres, and rapidly succeeded by 
 repulsion or return to the previous state of cohesive attraction existing among 
 those particles; and Dr. C. B. Radcliffe (Nature, Jan. 2, 1872) expresses a belief 
 ' that living muscle is kept in a state of elongation by the presence of an electrical 
 charge, and that contraction is nothing more than the action of the fibres, by 
 virtue of their elasticity, when liberated by discharge from the charge which kept 
 them elongated previously.' Matteucci had come to a similar conclusion at an 
 anterior date, and expressed his belief that muscular action is accompanied by 
 a discharge of electricity analogous to that of a torpedo. This view, Dr. Radcliffe 
 adds, has received confirmation from the new quadrant electrometer. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 dowed with universality of motion. Thus it can, by a 
 conjoined centripetal and centrifugal movement (see solid 
 arrows), assume the shape represented at B ; or it can by 
 a similar but opposite movement (vide dotted arrows) assume 
 the shape represented at C. In the case of the open or ex- 
 panded heart, the long axes of the sarcous elements of the 
 more vertical fibres are arranged as at B, those of the more 
 transverse fibres as at C. When the heart closes, the sarcous 
 elements of the more vertical and transverse fibres assume 
 the shape A. In the case of an open hollow muscle with 
 a closed sphincter, the long axes of the sarcous elements 
 of the nearly vertical and horizontal fibres forming the body 
 of the muscle are arranged as at B and C, the sarcous elements 
 of the fibres forming the sphincter having the shape indicated 
 at A. When the hollow muscle closes, the sarcous elements 
 of the vertical and horizontal fibres assume the shape A, those 
 of the sphincter assuming the shape C (see Fig. 128, p. 231). 
 The same arrangement obtains in the voluntary muscles. 
 When a flexor and extensor muscle are at rest, their sarcous 
 elements or cubes assume the form figured at A. When the 
 flexor shortens, its sarcous elements take the form C ; the 
 sarcous elements of the extensor, when it elongates, taking the 
 form B. When the extensor shortens, its particles assume 
 the form C ; the particles of the flexor, when it elongates, 
 assuming the form B. The change of shape in the sarcous 
 elements is necessary to produce the shortening of the flexor 
 and the elongation of the extensor, and the converse ; the 
 one muscle, as explained, always shortening when the other 
 elongates, and vice versa. The particles of the muscle, like 
 the muscles themselves, as already stated, are co-ordinated. 
 They work together and not against each other. The cube 
 figured at A consequently not only represents the position 
 of rest for the sarcous elements of both flexor and extensor 
 muscles, but also the line on either side of which they oscillate 
 or vibrate when the muscles are in action. The shape of 
 the sarcous elements, as seen in the biceps and triceps in 
 flexion of the arm, is shown at Fig. 118, p. 220. 
 
 That muscles possess a centripetal and centrifugal power 
 /. e. a power by which they alternately shorten and elon- 
 gate and that one set of muscles is never employed for 
 
220 PHYSIOLOGY OF THE CIRCULATION. 
 
 violently pulling or drawing out another set, is abundantly 
 proved by the action of the heart and the hollow muscles 
 with sphincters, such as the stomach, bladder, rectum, uterus, 
 etc. The heart pulsates in the embryo while yet a mass 
 of cells, and before it is provided either with cavities, blood, or 
 muscular fibres. The different compartments of the heart 
 open and close after the organ is cut out of the body, and 
 when it is deprived of blood ; but the deprivation of blood 
 prevents the auricles acting upon the ventricles, and the 
 converse. The auricles and ventricles are to be regarded as 
 anatomically and functionally distinct. That the auricles 
 when they close do not forcibly distend or open the ven- 
 tricles, is evident from the fact that the ventricles open 
 
 Fig. 118. 
 
 Tig. 118 illustrates how the forearm is fixed or folded on the arm by the combined action of the biceps 1 
 and triceps. When the biceps (a) shortens and the triceps (*) lengthens, flexion is produced. When 
 the triceps shortens and the biceps lengthens, extension is produced. In flexion the long axes of the 
 sarcous elements of the biceps muscle (a) are directed transversely ; those of the triceps (} longitudinally. 
 ; These conditions are reversed in extension. At a the centripetal action of muscle is seen (vide arrows 
 marked f) ; at its centrifugal action (vide arrows marked/). (Compare with arrows of Fig. 130.) d, 
 coracoid process of scapula from which the short head of the biceps arises, e, insertion of the biceps 
 into the radius. /, long head of the triceps, g, insertion of triceps into the olecranon of the ulna. 
 h, hand. Original. 
 
 and close spontaneously when the auricles are removed. 
 Further it occasionally happens when the heart is intact, in 
 situ, and acting slowly, that the ventricles open before the 
 auricles close. Finally the ventricles, which are very power- 
 ful structures, obliterate their cavities when they close, so 
 that the auricles, which are very feeble structures, have not 
 the requisite power to force the blood which they contain 
 into the solid muscular mass formed by the ventricles at 
 the termination of the systole. That the ventricles do ob- 
 literate their cavities when they close is a matter of 
 observation. Ever and anon, when making post-mortem 
 examinations at the Royal Infirmary of Edinburgh, I find 
 
PHYSIOLOGY OF THE CIRCULATION. 221 
 
 the ventricles rolled together in the form of a solid ball. 
 Even the stomach is endowed with the power of all but 
 obliterating its cavity, and I have at present in my posses- 
 sion a human stomach, the body of which has a diameter 
 not greater than that of the small intestine \ The movements 
 of the hollow muscles with sphincters also support the view that 
 muscles have the power of elongating as well as shortening ; 
 in other words, have a centrifugal and centripetal action. 
 When the stomach, bladder, or rectum close, their sphincters 
 open, and vice versa. But the closing of the stomach, 
 bladder, and rectum, is occasioned by the simultaneous 
 closing, shortening, and broadening of all the fibres com- 
 posing the bodies of the viscera ; the opening of the sphincters 
 being occasioned by the simultaneous opening, elongating, 
 and narrowing of all the fibres which go to form the 
 sphincters. As the sphincters are powerful structures which 
 guard narrow apertures, and the bodies of the viscera 
 are comparatively feeble, it follows that no effort, on the 
 part of the bodies of the viscera, acting upon their fluid 
 contents, could force a passage. Such force is not required, 
 as the sphincters open spontaneously when the bodies of 
 the viscera close. The movements are co-ordinated in the 
 same way that the movements of the different parts of the 
 heart or those of the flexor and extensor muscles are co- 
 ordinated. These movements are however only possible in 
 structures which alternately open or elongate, and close or 
 shorten; i.e. exert a centrifugal and centripetal power. 
 They occur in muscular and other tissues. 
 
 The opening and closing of the rectum and its sphincters 
 are represented at Figures 119 and 120,, p. 222. 
 
 Another element calculated to introduce confusion into our 
 ideas of muscular movements is the arrangement of the 
 muscular fibres,- and the muscles themselves. Hitherto, and 
 by common consent, it has been believed that whereas a 
 flexor muscle is situated on one aspect of a limb, and its 
 corresponding extensor on the other aspect, these two muscles 
 must be opposed to, and antagonise each other must, in 
 
 1 The patient to which this stomach belonged died of inanition, occasioned by 
 stricture of the oesophagus. The stomach itself is quite healthy. 
 
222 PHYSIOLOGY OF THE CIRCULATION. 
 
 fact, work against each other. Now there can be no greater 
 fallacy than this. Nature never works against herself. The 
 voluntary muscles whether flexors and extensors, or ab- 
 ductors and adductors, or pronators and supinators form 
 cycles, one segment of the cycle being placed on one side of 
 the bone to be moved, the remaining segment of the cycle on 
 the opposite side of the bone. When the one side of the 
 cycle closes or shortens, the opposite side of the cycle opens 
 or elongates (vide Fig. 118, p. 220). Muscular energy is thus 
 conserved to the utmost, and the bones are made to vibrate 
 
 Fig. 119. 
 
 Fig. 119 shows how the rectum closes and the sphincters open to discharge the faeces. In the act of 
 defecation the rectum closes, and narrows in the direction a, a and elongates in the direction b, b ; the 
 sphincters opening and widening in the direction c, c. The arrows indicate the direction in which the 
 forces engaged in discharging the faeces operate. The assistance derived from the co-operation of the 
 abdominal muscles is not estimated. Original. 
 
 Fig. 120 shows how the rectum opens to receive the faeces, and how the sphincters close to prevent 
 their escape. In this case the rectum opens in the direction d, d, and shortens in the direction e, e ; the 
 sphincters closing in the direction/;/: Here the arrows indicate the direction in which the forces act to 
 retain the faeces. Original. 
 
 within their muscular cycles with marvellous precision and 
 exactitude. But for this arrangement the delicate mani- 
 pulations required in the manufacture of watches, philoso- 
 phical instruments, etc., could not be performed. The opening 
 and closing, say of the flexor and extensor arcs of the cycles, 
 are in all respects analogous to the opening and closing 
 movements which occur in the different parts of the heart and 
 in the hollow muscles with sphincters. It is thus that the 
 movements of the voluntary and involuntary muscles may be 
 assimilated and referred to a common source. 
 
 The involuntary hollow muscles supply the type or pattern 
 on which the voluntary muscles are formed. Nor is this all. 
 In idiots whose nervous system is deranged, the involuntary 
 movements return in the voluntary muscles ; and it is by no 
 means an uncommon thing to see in our large lunatic asylums 
 poor demented creatures exhibiting rhythmic movements in 
 
PHYSIOLOGY OF THE CIRCULATION. 223 
 
 different parts of their persons. Thus you will find a con- 
 siderable number of patients who for hours together move 
 their head, trunk, or limbs, backwards and forwards, or 
 laterally, with a steady see-saw motion, automatically and 
 unconsciously. I was particularly struck with these rhythmic 
 movements in voluntary muscles on a recent visit to the 
 West Riding Lunatic Asylum, where owing to the courtesy 
 of my distinguished friend, Dr. J. Crichton Browne, the 
 medical superintendent of the institution, I had an opportunity 
 of studying them under unusually favourable conditions. 
 
 I am well aware that elasticity is assigned a high place 
 in muscular movements by modern physiologists, but there 
 are grounds for believing that its power has been greatly 
 over-rated ; the sarcous elements, of which muscles are com- 
 posed, being arranged to act either with or without elastic 
 substances *. 
 
 Elasticity is to be regarded as an auxiliary of muscular 
 manifestations, a modification to confer continuity of move- 
 ment. All muscular movements are interrupted movements 
 i.e. muscles act first in one direction, and then in another. 
 In order that muscles may reverse their movements, they are 
 endowed with a certain amount of elasticity to assist them 
 over their dead points. That however elasticity is quite a 
 secondary matter is evident from this : elasticity cannot 
 generate a movement, muscular movements beginning and 
 terminating in the muscles themselves. Elasticity is to a 
 prime mover (such as a muscle) what an echo is to a sound. 
 It repeats, or tends to repeat, movements generated without 
 or beyond the substance in which it inheres. The blood- 
 vessels are endowed with a greater share of elasticity than the 
 hollow muscles and -involuntary muscles generally, the in- 
 voluntary muscles having a greater share than the voluntary 
 ones. In proportion as muscles become differentiated, and 
 their movements exact, their elastic properties disappear. By 
 assigning a centripetal and centrifugal action to muscles, 
 as apart from elasticity and antagonism, we secure to the 
 
 1 When the sarcous elements have departed as far as they can from their original 
 shape and position of rest, elasticity assists the particles in reversing their forces, 
 and gives continuity of motion. The elementary particles may be said to vibrate, 
 and elasticity is calculated to help them over their dead points. 
 
224 PHYSIOLOGY OF THE CIRCULATION. 
 
 muscles, and the sarcous elements composing them, absolute 
 rest when they are not engaged in shortening or lengthening. 
 There is no necessity for supposing, as hitherto, ' that muscles 
 are kept upon the stretch by the nature of their position and 
 attachments, and by a state of passive contraction which 
 opposes their elongation by antagonists.' It is more natural 
 to assume that the muscles which form opposite sides of 
 muscular cycles, instead of maintaining their relative positions 
 by a state of passive contraction, as it is termed, are simply 
 in a state of inaction. By assigning, as I have done, to the 
 muscles and their sarcous elements the power of acting in 
 two directions at right angles to each other, we get rid of 
 the passive contraction of authors, and the necessity for one 
 muscle or sarcous element, when it shortens, dragging out 
 another muscle or element which has been regarded as its 
 antagonist, but which in reality is its correlate. It is impos- 
 sible to understand how a muscle can be resting in a state of 
 even passive contraction. A healthy muscle is firm in 
 absolute inaction, but its hardness is not due to contraction. 
 A muscle enjoys a greater degree of repose than is usually 
 imagined. It is in a state of absolute rest when not shortening 
 or elongating. But the sarcous elements of a muscle, even 
 when shortening and elongating, have intervals of repose, 
 from the fact that they do not all act at once, but alternately 
 and successively. As a muscle moves in its ultimate ele- 
 ments, so it rests therein. This explains how the heart can 
 go on without pausing as long as life lasts ; how a muscle 
 during its action produces a sound, the so-called susurrus ; 
 and how it develops heat, the ultimate particles triturating 
 each other as they advance or recede. 
 
 How Musctdar Fibres open and close the Vessels, the 
 Compartments of the Heart, the Stomach, Bladder, Thorax, 
 Abdomen, etc. In the smallest capillary vessels no muscular 
 fibres are to be detected. In the larger capillaries faint 
 traces of circular fibres make their appearance. It is only 
 in the smaller arteries and veins that a circular layer of 
 muscular fibres becomes well marked. Every vessel furnished 
 with circular muscular fibres can open and close. When the 
 circular muscular fibres shorten, they elongate the vessel and 
 diminish its calibre. When they elongate, they shorten the 
 
PHYSIOLOGY OF THE CIRCULATION. 225 
 
 vessel and increase its calibre. This follows because the 
 circular fibres form closing rings, and any change in their 
 shape produces either an elongation and narrowing of the 
 vessel, or a shortening and widening thereof (Fig. 124, p. 331). 
 The circular fibres are capable of acting by themselves, or in 
 conjunction with elastic structures arranged in the direction 
 of the length of the vessel. When elastic structures are 
 present they are stretched when the circular fibres shorten. 
 As elastic structures tend to regain their original form when 
 the force which extended them has ceased to act, they assist 
 the circular fibres in elongating. They confer rapidity and 
 continuity of movement by assisting the muscle over its dead 
 points : muscle, of necessity, acting first in one direction and 
 then in another. 
 
 In the larger vessels a longitudinal layer of muscular fibres 
 is added to the circular one. Under these circumstances, 
 the two sets of fibres are arranged at right angles, and work 
 together. When the vessel is to be narrowed and elongated, 
 the circular fibres shorten and the longitudinal ones lengthen ; 
 when it is to.be widened and shortened, the circular fibres 
 lengthen and the longitudinal ones shorten. The two sets of 
 fibres take part in both movements, and do not antagonise 
 or act against each other (Fig. 125, p. 231). The same thing 
 happens in, the vermicular movements of the intestine and the 
 creeping of the earthworm (Lumbricus agricola), to which they 
 are likened. The muscular tunics of the intestine and worm 
 are composed of longitudinal and circular fibres, so that they 
 exactly resemble certain of the blood-vessels. ' I have studied 
 the movements of the worm with considerable -attention, as 
 being likely to throw some light upon similar movements in 
 the vessels. Prior to moving, the earthworm draws itself 
 together, and shortens and thickens its whole body (Fig. 121 
 A, p. 226). It then elongates and narrows, telescopic fashion, 
 the first inch or so (Fig. 121 B, a, p. 226). In this movement 
 the rings representing the circular fibres are separated from each 
 other and thickened, the part moving being of a paler colour 
 than the rest of the body. This shows that while the circular 
 fibres shorten and broaden, the longitudinal ones lengthen and 
 narrow, both sets of fibres taking a nearly equal share in the 
 work. The power possessed by the worm of elongating a 
 
 Q 
 
226 PHYSIOLOGY OF THE CIRCULATION. 
 
 part of its body is undoubted. When the first instalment of 
 the body is sent forward, it is corrugated or gathered together 
 (Fig. 121 C, a), and securely fixed on the ground by the 
 assistance of the setae or hairs situated on the ventral aspect 
 of the animal. A second inch or so is now elongated, 
 telescopic fashion, and sent on precisely as in the first instance 
 (Fig. 121 C, b). The second instalment is not drawn forward, 
 as is generally believed, but pushed forward as described. 
 When the second instalment is gathered to the first, and both 
 fixed to the ground by the setae, a third instalment is sent on, 
 the worm not beginning a second step until the tail instal- 
 
 F'lg. 121. 
 
 Pig. tax. A represents the worm as drawn together prior to commencing a step, and divided into 
 four equal portions, a, 6, c, d. Ortgmai. 
 
 B shows the first part of the worm as elongated or pushed out (a) ; the parts b, c, d acting as fulcra. 
 Original. 
 
 C shows the first part of the worm lf<t) shortened, corrugated, and fixed on the ground, the second 
 part of the worm (b) being elongated or pushed out ; the parts c and d acting as fulcra. Or iginal. 
 
 ment is forwarded and added to the body. The worm 
 advances by a peristaltic or wave movement. It pushes 
 itself forward upon the ground, and in this respect resembles 
 all other animals with terrestrial habits. If the worm had not 
 the power of elongating and pushing its body forward, it is 
 evident that it could never begin a step (Fig. 121 B, a]. 
 
 The movements of the worm are exceedingly interesting, 
 as showing that a muscular mass composed of circular and 
 longitudinal fibres (each set continuous upon itself) has the 
 power of elongating even in the absence of fixed points. 
 The locomotion of the worm is performed by two forces, 
 which always act at right angles to each other. Thus when 
 
PHYSIOLOGY OF THE CIRCULATION. 22/ 
 
 the first part of the body is sent forward, the circular fibres 
 exert their centripetal power, the longitudinal ones their 
 centrifugal power. When this portion of the body is short- 
 ened and corrugated prior to being fixed on the ground by 
 the setae, the circular fibres exert their centrifugal power, and 
 the longitudinal ones their centripetal power. The sarcous 
 elements of the circular and longitudinal fibres alternately 
 seek and fly the centre of the moving parts. It follows from 
 this that the part of the worm which is corrugating and 
 broadening may be compared to a sphincter muscle which is 
 opening ; while that part of the worm which is elongating and 
 narrowing may be compared to a hollow muscle closing. In 
 these two movements, both of which are necessary to the 
 locomotion of the worm, the elongating and shortening power 
 possessed by muscle is clearly shown. One part of the worm 
 elongates while another part shortens, and but for this con- 
 sentaneous double movement (which is a co-ordinated rhyth- 
 mic movement) no locomotion can take place. The same 
 holds true of the voluntary muscles. When bones are to be 
 moved, one part of the muscular cycle must shorten when the 
 other elongates, and vice versa. If any part of the worm 
 attempted to shorten and lengthen at the same instant, it is 
 evident that no locomotion would ensue. In like manner, 
 if the voluntary muscles situated on one aspect of a bone 
 or bones acted against the muscles situated on the opposite 
 aspect, the bones would remain in statu quo. The commonly- 
 received opinion, that muscles have only the power of 
 shortening, and cannot elongate, is, I believe, founded in error. 
 The belief is no doubt traceable in a great measure to the 
 incautious use of artificial stimuli. If, e.g., electricity is 
 applied to the first part of the worm when in the act of 
 elongating, it instantly shortens. This however is no proof 
 against the elongating power of muscle. It is simply the 
 sudden substitution of an abnormal for a normal movement. 
 If artificial stimuli produced natural movements they would, 
 when applied to a muscle in the act of elongating, cause it to 
 elongate more rapidly ; in other words, they would quicken 
 its movements, and in no instance check or reverse them. 
 Muscle is not the only substance which shrinks or retires 
 within itself on being assailed by a troublesome neighbour. 
 
 Q2 
 
228 PHYSIOLOGY OF THE CIRCULATION; 
 
 The sensitive plant does the same \ The worm elongates its 
 body on the withdrawal of the stimulus, and the sensitive 
 plant regains its original shape. The return movements are 
 therefore vital and normal. In the same way a muscle, when 
 cut out of the body and made to shorten by an irritant, 
 regains its original shape when the irritant is withdrawn, and 
 may be made to shorten many times in succession. When 
 the muscle returns to its original shape it elongates, the 
 elongation being necessary to a repetition of the muscular 
 movement. A long muscle when it shortens virtually re- 
 produces the movements observed in the body of the worm 
 when creeping, one part of the muscle swelling out or 
 broadening by a centrifugal movement, while another portion 
 thins or narrows by a centripetal movement. This accounts 
 for a long muscle being thrown into ampullae when it shortens 
 (Fig. 115 G, D, p. 216). 
 
 Similar movements to those described in the worm occur in 
 the tentacles of the gasteropoda. In murex, the tentacles are 
 thick solid fleshy stems, composed of various strata of circular, 
 longitudinal, and oblique muscular fibres. These are elongated 
 and retracted at pleasure (Fig. 122, p. 229). In the garden-snail 
 (Helix pomatid], the tentacles are hollow tubes, composed of 
 circular bands of muscle. Within each tentacle is a long 
 muscular slip (Fig. 123, c y d, p. 229), extending between its 
 free extremity and the common retractive muscles of the foot. 
 When the muscular slip (c) shortens, the circular muscular 
 fibres elongate, and the tentacle is invaginated (a). The 
 same thing happens in invagination of the intestine. A 
 reverse action takes place when the tentacle is protruded (#), 
 the enclosed muscular slip (d) elongating, and the circular 
 fibres shortening. That the evagination or protrusion of the 
 tentacle is not due to the contraction or shortening of the 
 circular fibres alone, is evident from this. If the tentacle, is 
 half invaginated (a), the shortening or closing of the circular 
 fibres by themselves tends rather to invagination than evagina- 
 tion. To complete the process the longitudinal muscular 
 slip (c) must elongate and push slightly. 
 
 1 Desfontaines once carried a sensitive plant with him in a coach, with the 
 following curious result. The jolting of the machine caused it at first to curl up its 
 leaves. When however it became accustomed to the movement, it expanded them. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 When a garden-snail elongates its tentacles, we feel that 
 the act is a voluntary and a vital one. The moment however 
 they touch a foreign body, they shrink l . The alarm passes 
 away, and again the tentacles are cautiously elongated. The 
 same thing happens in the sea-anemone. When this mag- 
 nificent creature expands its tentacles like a gorgeous flower 
 opening to the sunlight, it pushes them out with exquisite 
 grace like so many microscopic telescopes. If, however, 
 foreign matter be dropped into the water upon the anemone, 
 
 Fig. 122. Fig. 123. 
 
 Fig. 122 shows tentacles of murex (a, b) in elongated state. Adapted. 
 
 Fig. 123 shows the four tentacles of garden snail (a, b, e,f), one of which (a) is invaginated, and its 
 muscle (c) shortened; a second one (b) being evaginated or pushed out, and its muscle (d) elongated. 
 Adapted. 
 
 the tentacles instantly retreat into the interior of the animal. 
 The power of elongating and shortening possessed by the 
 tentacles is, I believe, possessed by every muscle, by every one 
 of its fibres, and by every one of its sarcous elements. If we 
 grant to muscles the power of alternately shortening and 
 elongating, we have an explanation of the multifarious move- 
 ments which we behold in our own bodies. We can compre- 
 hend how the heart, blood-vessels, and hollow viscera act ; 
 how we are capable of migrating from one place to another ; 
 
 1 In phthisical patients, as Dr. Stokes has shown, a smart tap on a muscular 
 part is followed by a contraction and swelling of the part struck. The part struck 
 is surprised, and contracts or rolls itself together. 
 
230 PHYSIOLOGY OF THE CIRCULATION. 
 
 and how the hand is supplied with its cunning. All are vital 
 manifestations. The elongation and shortening of the ten- 
 tacles are analogous to the opening and closing of the heart, 
 the extending or flexing of the arm, or the protruding and 
 retracting of the tongue. 
 
 To take another example : the mouth of the gasteropoda 
 in most instances presents the appearance of a prehensile 
 and retractile proboscis. This remark, I may observe, ap- 
 plies to the mouth and lips of a great many animals, the 
 oval aperture and lips being pushed out and retracted at 
 pleasure. 
 
 In the gasteropoda, which have no jaw or masticating 
 apparatus, the moveable proboscis consists of a muscular 
 tube composed of longitudinal and circular fibres as in the 
 intestine. By means of this simple structure, every possible 
 kind of movement is effected, the tube seizing the food, 
 and, by alternately opening and closing, forcing it into and 
 along the alimentary canal, just as the blood is forced along 
 a vessel endowed with rhythmical movements. The re- 
 traction of the proboscis is occasioned by the shortening of 
 the longitudinal fibres, and the expansion or elongation of 
 the circular ones ; the elongation being effected by a counter 
 and contrary movement. The tongue, as has been stated, 
 is also endowed with the power of elongating and shorten- 
 ing ; the organ being employed by the ox for seizing the 
 grass, and by the chameleon for securing insects. 
 
 By investing the sarcous elements of muscle with the 
 power of shortening and elongating, longitudinal and cir- 
 cular fibres can be made to act by themselves or in com- 
 bination, and so of every form of oblique fibres. If circular 
 fibres are to act by themselves and diminish the calibre of 
 a vessel, they shorten in the direction of the breadth of the 
 vessel. If the same function is to be performed by longi- 
 tudinal and circular fibres arranged at right angles, the 
 circular fibres shorten in the direction of the breadth of the 
 vessel, the longitudinal fibres elongating in the direction of 
 its length. These movements are reversed if the vessel is 
 to be widened. If a cavity is to be obliterated by longi- 
 tudinal and circular fibres, the fibres shorten longitudinally 
 and transversely. If it is to be opened, they elongate. If 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 2 3 r 
 
 oblique fibres are present, they are accessories, and deport 
 themselves in exactly the same way as the others. In 
 hollow muscles the fibres require to be continuous upon 
 themselves, and this accounts for the fact that in the heart, 
 stomach, bladder and uterus, the fibres have neither origin 
 nor insertion. (Vide Figs. 124 130.) 
 
 Fig. 124. Fig. 12-. Fig. 126. Fig. 127. 
 
 Fie. 120. 
 
 Fig. 130. 
 
 Fig. 124. Vessel supplied with circular or transverse fibres (a), capable of increasing or decreasing its 
 calibre, and of shortening or elongating it. Original, 
 
 Fig. 125. Vessel supplied with circular (a) and longitudinal (*) fibres, capable of increasing or diminish- 
 ing its calibre, and of shortening or elongating it. Original. 
 
 Fig. 126. Hollow muscle provided with circular (a, and longitudinal {b\ fibres capable of increasing : 
 and diminishing its cavity so as to take in and eject fluid. Original. 
 
 Fig 127. Hollow muscle provided with circular iaj, longitudinal (b), and oblique (c, d) fibres, capable 
 of opening and closing, and of taking in and ejecting fluid. In this case the opening and closing, be- 
 cause of the presence of the oblique fibres, is more perfect than in Fig. izd.^Original. 
 
 Fig. 128. Hollow muscle (human bladder) provided with circular (a). lon.,'itudinal (6), and oblique (c,d) 
 spiral fibres, continuous at base (b) and apex (<?), in which latter situation they form a sphincter. When 
 the fibres constituting the body of the muscle close, the continuations of those fibres which forni its 
 sphincter open, and vice versa. Such a muscle can receive, contain, and eject fluid. Original. 
 
 Fig. 129. Hollow muscle (left ventricle of heart of mamma.) provided with circular (a), longitudinal (b), 
 and oblique (c, d) spiral fibres, continuous at apex (<) and base (b). These fibres, by their united efforts, 
 can open or close the muscle, and can cause it to suck in and eject the b.ood alternately. (Cpmpare 
 with Figs. 98, 99, 100, p. 195.) Original, 
 
 Fig. 130. Transverse section of left ventricle of heart (mammal), showing it in the open and closed 
 condition, v, ventricle when open. TV, ventricle when closed, and cavity (j) obliterated, x, imaginary 
 line, on either side of which the walls of the ventricle vibrate when the ventricle closes and opens, and 
 when the ventricular fibres e-ercise their centripetal (/, n) and centrifugal (o, /) act., n. Original. 
 
 The heart differs slightly from the blood-vessels, inasmuch 
 as when it closes, all its diameters are shortened ; whereas, 
 when it expands, all its diameters are elongated. In the 
 opening and closing of the different compartments of the 
 heart we have two diametrically opposite conditions. To 
 produce this apparently impossible result in the ventricles, 
 
23 1 PHYSIOLOGY OF THE CIRCULATION. 
 
 the fibres and the sarcous particles of the fibres are arranged 
 vertically, transversely, and obliquely, in continuous spirals, as 
 shown at Fig. 129, p. 231. Fig. 130, p. 231, v, shows a trans- 
 verse section of the left ventricle of the heart in the expanded or 
 dilated condition ; w, of the same figure, showing a transverse 
 section of the left ventricle when its cavity is obliterated. The 
 arrows m ;z, op of Fig. 130, p. 231, indicate the centripetal and 
 centrifugal force possessed by the heart, in virtue of which 
 it acts as a sucking and propelling organ. The heart has 
 the power of forcibly expanding itself, as it has of forcibly 
 closing itself. It can therefore in virtue of its rhythmic 
 movements alternately suck in and eject blood the auricles 
 attracting it while the ventricles are repelling it, and vice 
 versa. When the walls of the ventricle travel beyond the 
 circle represented by x of Fig. 130, p. 231, in an inward direc- 
 tion, they push the blood out of the ventricular cavity ; when 
 they travel beyond the same circle in an outward direction, 
 they suck the blood into it. A common caoutchouc bag, 
 if immersed in water and squeezed at intervals, will do the 
 same. The order in which the closure occurs in the vessels 
 and hearts of the lower animals and in the heart of the 
 mammal favours this view. In the. cold-blooded animals 
 the large veins (even to the venae hepaticae) close first ; 
 then the auricle or auricles, as the case may be ; then 
 the ventricle ; and lastly the bulbus arteriosus. In the 
 warm-blooded animals the terminations of the pulmonary 
 veins and cavae (superior and inferior) close first ; then the 
 auricles, then the ventricles, and then the large vessels in 
 the vicinity of the heart ; these vessels, as already pointed 
 out, being supplied with an elaborate plexus of nerves. The 
 blood is, as it were, manipulated while it is being transmitted. 
 Thus, it is drawn into and seized by the large veins leading 
 to the heart; then by the auricles, then by the ventricles, 
 and then by the large arteries leading from the heart. No 
 sooner, however, is it seized than it is dismissed, the seizure 
 and the dismissal being alike necessary to the circulation. 
 The blood is not permitted to wander about at pleasure in 
 the cavities of the circulatory apparatus. On the contrary, 
 it is made to flow in a continuous onward stream, by a series 
 of very wonderful peristaltic movements, very much in the 
 
PHYSIOLOGY OF THE CIRCULATION. 233 
 
 same way that the blood is forced into the alimentary canal 
 of the leech by the simultaneous opening and closing in 
 regular succession of the different portions of its muscular 
 oesophagus. Nay more, it is made to open and close the 
 doors which lead to and conduct from the chambers through 
 which it passes. It is customary, when speaking of the 
 action of the heart, to refer only to the closure of the organ, 
 its opening being regarded as comparatively unimportant 
 and depending indirectly on the closing. The opening of 
 the heart however is as necessary to the circulation as its 
 closing ; and but for the fact that one part of the heart 
 opens while the other closes, the blood could not be made 
 to perform its endless round without quite an extravagant 
 waste of power. The blood, like other fluids, is nearly in- 
 compressible, and if it is ejected from one place it must be 
 received in another of nearly, I might safely say of exactly, 
 the same dimensions. These are but so many proofs of 
 arrangement and design. When the veins close, the auricles 
 open ; when the auricles close, the ventricles open ; when 
 the ventricles close, the arteries and veins open, and so on 
 ad infinitum. The blood is alternately pushed and pulled. 
 That the vessels may take a part in and modify the circula- 
 tion is evident from the researches of Marey and Garrod, 
 who show that any obstruction or narrowing in the small 
 vessels slows the action of the heart. 
 
 Analogy between the Movements of the Thorax, Abdomen, 
 and Heart. The primary function of the thorax is alter- 
 nately to suck in and eject air; but it has a second function, 
 it attracts or determines blood to the heart. In fact, the 
 movements of the chest and heart are essentially the same, 
 the object of both being to bring relays of air and blood 
 into intimate contact within a given area. In breathing 
 the air does not simply rush into the lungs : it is drawn 
 in by a vital act. It is likewise expelled by a vital act. 
 In like manner the blood is drawn into the auricles and 
 forced out of the ventricles by vital acts. This follows 
 because the chest and heart have the power of alternately 
 opening and closing. If the air rushed into the lungs me- 
 chanically, and was expelled thence by the mere elasticity 
 of the lungs, we could not regulate the supply of air admitted 
 
234 PHYSIOLOGY OF THE CIRCULATION. 
 
 into and sent from the lungs in inspiration and expiration. 
 There would moreover be an absence of the rhythm which 
 characterises the chest movements. We can arrest both 
 the inspiration "and expiration, which shows that these 
 actions are voluntary and vital as well as involuntary and 
 mechanical. That an intimate relation exists between the 
 thorax and heart appears from this : by arresting the re- 
 spiration, we can also arrest the circulation. M. Groux, who 
 had a congenital fissure of the sternum, could arrest the 
 pulsation of his subclavian and rodial arteries by making 
 a full inspiration, and then by holding his breath for a short 
 interval. If he held his breath for a few moments after 
 a full expiration, the pulsating tumour which appeared at the 
 cleft sternum became larger, apparently from the heart 
 becoming unusually distended with blood. 
 
 During inspiration the great veins entering and contained 
 in the chest viz. the subclavian, jugular, and superior and 
 inferior cavae are full of blood, the blood being attracted 
 by inspiratory effort. During expiration the vessels are 
 comparatively flaccid. These changes are not confined to the 
 chest ; thus the radial pulse is weaker and less voluminous 
 during inspiration, and stronger and more voluminous during 
 expiration. The pulse is weakened during inspiration, from 
 the fact that when air is inspired a large mass of blcod is 
 attracted to the chest, which has the effect of relieving the 
 plethora of the arterial system the blood being as it were 
 dammed up in the arteries during expiration. The inspira- 
 tory and expiratory acts affect all the vessels of the body, 
 the respiratory influence being most marked in the vessels 
 of the head, chest, and trunk, and least in those of the ex- 
 tremities. This is rendered obvious by the fact that when 
 the brain, which contains a Very large number of vessels, 
 is exposed, it is seen to shrink and recede during inspira- 
 tion, and to swell out or expand during expiration. The 
 attraction of the blood to the chest, and the consequent 
 draining of the capillaries of the brain, sufficiently account 
 for the diminution of its volume during inspiration ; the 
 absence of that attraction and the gorging of the capillaries 
 accounting for the opposite condition during expiration. 
 The rise and fall of the brain here referred to is not to be 
 
PHYSIOLOGY OF THE CIRCULATION. 235 
 
 confounded with similar but minor changes induced by the 
 action of the heart itself, as the two sets of phenomena 
 occur at different periods. The celebrated Hales made this 
 a matter of experiment. By causing the blood of horses 
 and dogs to enter a vertical graduated tube, he found that 
 with each beat of the pulse the haemostatic column rose 
 and fell two, three, or four inches ; but that when the animals 
 respired deeply or struggled, it rose and fell from twelve 
 to fourteen inches. Here again the principal rise and fall 
 of the column coincided exactly with the inspiratory and 
 expiratory acts, the column being lowest during inspiration, 
 and highest during expiration. Another proof that the in- 
 spiratory act draws the blood towards the chest is to be 
 found in the fact that when a wound is made in a vein 
 anywhere in the vicinity of the thorax, the air is most apt 
 to enter during sighing, or when deep inspirations are made. 
 
 Dr. Buchanan, of Glasgow 1 , attaches great importance to 
 respiration as an auxiliary of the circulation, and states his 
 conviction that asphyxia is less due to the poisoning of the 
 blood than to the fact that, when the breathing ceases, the 
 heart is unable to carry on the circulation by itself 2 . I 
 am not disposed to go thus far; for while admitting that 
 respiration forms one of the forces of the circulation in the 
 mammal, I cannot overlook the fact that in some of the 
 lower animals the circulation is carried on where no re- 
 spiration proper exists. The respiration may be divided into 
 three kinds viz. (a) the respiration due to the action of 
 the chest and laryngeal muscles ; (b) that due to the action 
 of cilia, situated on the trachea and bronchial tubes ; and 
 (c) that occasioned by the diffusion of gases. The two former 
 correspond to the visible vascular circulation ; the latter to 
 the invisible. The diffusion of gases in the lungs is analogous 
 to the diffusion of fluids in the tissues. The chest and lungs 
 
 1 The Forces which carry on the Circulation of the Blood, by Andrew Buchanan, 
 M D., etc., Professor of Physiology, University of Glasgow. 
 
 2 Professor Alison is of opinion that the effects of asphyxia first show themselves 
 in the lungs, that the arterialisation of the blood has the power of attracting that 
 fluid to the lungs, and of drawing it on through the capillaries, and that when this 
 auxiliary to the circulation is cut off, the blood stagnates in the lungs. He assigns 
 to the absorption and exhalation which goes on in the lungs in a state of health 
 a power similar to that claimed by most physiologists for the tissues. 
 
236 PHYSIOLOGY OF THE CIRCULATION. 
 
 form an apparatus for supplying fresh relays of air, just as 
 the heart and blood-vessels form an apparatus for supplying 
 fresh relays of blood. When once the air is inside the lungs 
 it is manipulated, and caused to pass in two directions, by 
 the pulmonary cilia, and the tendency which the carbonic 
 acid and the oxygen in the lungs have to diffuse or pass 
 through each other. The ciliary movements produce currents 
 within the air-passages and lungs akin to those produced 
 within a bee-hive by the fanning of the wings of the bees 
 at the entrance. The ciliary movements and passage of 
 gases in opposite directions produce the primary circulation 
 of air as it exists in the lowest animals ; and it is not a 
 little curious to find that, as the circulation of the blood 
 becomes differentiated, so the breathing apparatus becomes 
 complicated. Thus, to the ciliary movements and the me- 
 chanical diffusion of gases found in the lower animals, there 
 are added in the higher a complex muscular and bony 
 apparatus. 
 
 The movements of the chest, like those of the heart, are 
 said to be active and passive ; the expansion or opening of 
 the chest and glottis being due, it is stated, to the contraction 
 of the diaphragm, the intercostal muscles, and the crico- 
 arytenoid muscles ; the diminution or closing of the chest and 
 glottis being due to the relaxation of these muscles, to the 
 resiliency of the costal cartilages, and the elasticity of the 
 pulmonic substance and vocal chords. Dalton states that the 
 movement of expiration is entirely a passive one. I am 
 however disposed to regard the movement of expiration as 
 well as that of inspiration as vito-mechanical. Dalton evi- 
 dently experiences a difficulty in regarding expiration as a 
 purely passive act ; for he says, in expiration the muscles of 
 both chest and glottis are relaxed, while the elasticity of the 
 tissues, by a kind of passive contraction (observe, passive 
 contraction), restores the parts to their original condition 1 . 
 If contraction is active in inspiration, it must also be active in 
 expiration, otherwise there is a contradiction in terms. It is 
 worthy of remark that, according to current views, a vital act 
 opens the chest, while it closes the heart. But why this 
 
 1 Dalton's Treatise on Human Physiology, p. 206. 
 
PHYSIOLOGY OF THE CIRCULATION. 237 
 
 discrepancy, seeing the movements of the thorax and heart 
 are involuntary and rhythmic in character, and in this sense 
 identical l ? There is plainly a difficulty here, which requires 
 to be cleared up, and which only disappears when the opening 
 and closing of the thorax and heart are regarded as vital in 
 their nature. The presence of cartilage and bone in the 
 thorax may be thought by some to afford a sufficient ex- 
 planation, but these need not be taken into account, as the 
 muscles of the thorax are arranged in such a manner as 
 would enable them to open and close the chest even in the 
 absence of the hard parts. Nor must it be forgotten that the 
 movements of the thorax are muscular movements, and that 
 whatever change is induced in the hard parts is referable to 
 prior change in the soft parts 2 . If we attend to the inspiratory 
 and expiratory movements in our own persons, and convert 
 what are naturally involuntary movements into voluntary 
 ones, we find that in inspiration we draw in the air by a vital 
 act, and that in expiration we expel it by a vital act. This 
 is proved by the fact that if we interfere either with inspira- 
 tion or expiration, the movements are arrested. If we make 
 a forcible inspiration, we must also, if we would avoid dis- 
 comfort, make a forcible expiration. 
 
 The Movements of the Mammalian Heart, interrupted and 
 yet continuous. How the Heart rests. Having described the 
 direction and distribution of the muscular fibres composing 
 the heart of the mammal, the order in which the several 
 compartments of the heart act, and the change of shape 
 induced in all muscles, whether voluntary or involuntary, in 
 a state of activity, we are now in a position to speak of the 
 general and particular movements of the heart. The following 
 are the appearances observed in the living heart of a puppy 
 one day old. The large veins at the base of the heart close 
 in the direction of the auricles, and the auricles slowly open. 
 The auricles then close in the direction of the ventricles with 
 
 1 Inspiration corresponds to the opening of the heart ; expiration to its closing. 
 The former act is performed more slowly than the latter. 
 
 2 Since the above was written, Dr. Arthur Ransome has assigned an outward, 
 forward, or pushing movement to the chest in inspiration ; and an inward, back- 
 ward, or pulling movement in expiration. These movements are seen to most 
 advantage in women and children, where the ribs and costal cartilages are soft- 
 est. Proceedings of the Royal Society, November 21, 1872. 
 
238 PHYSIOLOGY OF THE CIRCULATION. 
 
 a vermicular wavy movement, somewhat suddenly, the ven- 
 tricles opening meanwhile. Finally, the ventricles close 
 suddenly and with great energy, a wave movement travelling 
 in spiral lines from the apex to the base, and then from the 
 base in the direction of the apex. When the heart is in 
 motion it rotates on its long axis alternately to right and 
 left, the extent of the rotation being rather more than a 
 quarter of a turn either way. When the ventricles open, the 
 left apex is elongated and pushed downwards by a peculiar 
 screwing motion, similar to that witnessed when a screw is 
 being forced into wood. When the ventricles close, the left 
 apex is shortened and elevated by a remarkable screwing 
 motion, which exactly corresponds with that observed when a 
 screw is being extracted from wood. The left apex, while 
 this screwing motion is taking place, describes an irregular 
 ellipse ; the apex impinging against the thorax, particularly 
 towards the termination of the systole, when it gives a sudden 
 bound in an upward and forward direction as if from recoil ! . 
 The auricles close simultaneously, and so of the ventricles ; 
 the auricles always opening when the ventricles close, and 
 vice versa. These structures increase and diminish by about 
 a third when they open and close. They also change colour 
 slightly. This is due to a diminution or increase in the 
 quantity of blood in the walls of the heart and within its 
 cavities at any given time. It is trifling when compared with 
 that observed in the heart of the frog or fish. The ventricles 
 completely empty themselves during the systole. Of this 
 there can be no doubt, as the ventricles are occasionally found 
 so firmly closed after death that their internal or endocardial 
 surfaces are in contact throughout. Analogy also favours 
 this view ; the ventricles of the fish and frog completely 
 emptying itself of blood and becoming pale during the 
 systole. When the heart is beating normally, one or other 
 part of it is always moving. When the veins cease to close 
 and the auricles to open, the auricles begin to close and the 
 ventricles to open, and so on in endless succession. In order 
 to admit of these changes, the auriculo-ventricular valves, as 
 has been stated, rise and fall like the diaphragm in respira- 
 
 1 In the fish and frog the impulse of the heart, as has been explained, cor- 
 responds with the termination of the diastole and the beginning of the systole. 
 
PHYSIOLOGY OF THE CIRCULATION. 239. 
 
 tion ; the valves protruding now into the auricular cavities 
 and now into the ventricular ones. There is in reality no 
 pause in the heart's action. The one movement glides into 
 the other as a snake glides into grass. All that the eye can 
 detect is a quickening of the gliding movements at stated and 
 very short intervals. A careful examination of the sounds of 
 the heart shows that the sounds like the movements glide 
 into each other. There is no actual cessation of sound when 
 the heart is in action. There are periods when the sounds 
 are very faint, and when only a sharp or an educated ear can 
 detect them, and there are other periods when the sounds are 
 so distinct that even a dull person must hear : but the sounds 
 and this is the point to be attended to merge into each 
 other by slow or sudden transitions. It would be more 
 accurate, when speaking of the movements and sounds of the 
 heart, to say they are only faintly indicated at one time, and 
 strongly emphasized at another, but that neither ever alto- 
 gether ceases. 
 
 If however the heart is acting more or less vigorously as a 
 whole, the question which naturally presents itself is, How is 
 the heart rested ? There can be little doubt it rests as it 
 acts, viz. in parts. The centripetal and centrifugal wave 
 movements pass through the sarcous elements of the different 
 portions of the heart very much as the wind passes through 
 leaves : its particles are stirred in rapid succession, but never 
 at exactly the same instant ; the heart is moving as a whole, 
 but its particles are only moving at regular and stated 
 intervals; the periods of repose, there is every reason to 
 believe, greatly exceeding the periods of activity* The 
 nourishment, life, and movements of the heart are in this 
 sense synonymous. That the different parts of the heart act 
 consecutively and in regular order was proved by Mr. Maiden. 
 He found that if a part of the ventricle of a frog or turtle was 
 irritated exteriorly, it instantly contracted, the contraction 
 spreading from the irritated point in every direction. He 
 found moreover that before the contractile wave had spread 
 over the entire ventricle, the part originally irritated, and 
 which contracted first, expanded or bulged out to form a 
 sacculation ; thus showing that the act of dilatation is as 
 much a vital movement as the act of contraction. In proof 
 
240 PHYSIOLOGY OF THE CIRCULATION. 
 
 of this, some poisons apparently kill the heart by destroying 
 its expanding power, the organ in such cases being found 
 firmly contracted after death. The older observers, as 
 Pechlin, Perrault, Hamberger, and more recently Bichat and 
 Dumas, expressed their belief that the dilatation or expansion 
 of the heart is a vital act in the same sense that its contraction 
 is a vital act ; and it appears to me that modern physiologists 
 have fallen into a grave error in stating that the contraction 
 of the heart represents its only period of activity ; the heart 
 being passive when it expands, or, as they term it, relaxes. 
 The heart no doubt must rest like every other part of the 
 body, and the most convenient explanation of the phenomenon 
 is to suppose that when the heart is contracting and forcing 
 out the blood it is active, but that when it is receiving the 
 blood it is passive, i. e. resting. This however, as I have 
 endeavoured to show, is not the real explanation, the heart 
 performing work not only when it closes, but also when it 
 opens. The heart cannot be said to be resting when -it is 
 returning to its position of rest, for if the sarcous elements 
 are doing work from the time they leave their position of rest, 
 it is obvious that they must be doing work until they return 
 to it. The position of rest moreover of the ventricular walls 
 does not correspond to that assumed by them during their 
 diastole or opening, any more than to that assumed by them 
 during their systole or closing. It corresponds to a line 
 midway between both, as shown at x of Fig. 130, p. 231. In 
 like manner the position of rest of the voluntary muscles is 
 semi-flexion or semi-extension ; the muscles being in a state 
 of activity in complete flexion and complete extension. During 
 repose the limbs are always slightly bent. 
 
 Size of the Cavities of the Heart (Mammal). The auricles 
 and ventricles increase in all their diameters when they open, 
 and decrease when they close. As however the auricles are 
 always closing when the ventricles are opening, and the 
 contrary, the actual contents of the pericardium fluctuate very 
 little. This circumstance renders it somewhat difficult to 
 determine whether the long diameter of the heart as a whole 
 varies. This was a question keenly debated by the Mont- 
 pellier and Parisian anatomists and physiologists, but is 
 practically of little importance. There are several subjects 
 
PHYSIOLOGY OF THE CIRCULATION. 24! 
 
 which hinge on the degree of opening and closing which 
 occurs in the heart. One of these is the comparative size 
 of the auricular and ventricular cavities. Winslow, Senac, 
 Haller, and Lieutaud, maintain that the disparity in the size 
 of the auricles and ventricles is considerable ; Laennec, Bouil- 
 laud, Meckel, and Portal, that it is trifling ; Lower, Sabatier, 
 and Andral, that there is no difference whatever. The latter 
 is most probably the correct opinion, as it is natural to suppose 
 that the auricles contain the exact quantity of blood to be 
 injected into the ventricles ; these forcing out into the large 
 arteries (aorta and pulmonary artery) a corresponding amount, 
 which in due time is returned to the auricles by the large 
 veins (venae cavae and pulmonary veins) . This opinion is in 
 a great measure corroborated by the practically incompressible 
 nature of the blood. If a certain quantity of blood is forced 
 out of one chamber, it is natural to suppose (seeing fluids are 
 virtually incompressible) that a chamber of exactly the same 
 size is prepared to receive it. A contrary supposition would 
 tend to disturb the even tenor of the circulation. It is quite 
 impossible, as I know from experience, to determine the size 
 of the cavities of the heart after death, and there is no means 
 of accurately ascertaining it during life. The parietes of the 
 heart after death yield to such an extent that they may 
 be distended at pleasure ; a uniform pressure giving anything 
 but a uniform expansion, as the ventricular walls, because 
 of their varying thickness, become unequally stretched. 
 
 Impulse of the Heart (Mammal). Another subject arising 
 out of the degree of opening and closing occurring in the 
 living heart is the impulse or beat of the organ against the 
 anterior wall of the chest. Is this due to the closing or 
 opening of the heart? The heart during the diastole has 
 its apex pushed deeper into the chest ; and if to this cir- 
 cumstance be added the fact that at this particular period 
 the organ is enlarged, we a priori arrive at the conclusion 
 that the heart is impelled against the thorax during the 
 diastole of the ventricles. Pigeaux, Burdach, and Beau, 
 entertain this belief. There can be no doubt, however, that 
 the impulse in the mammal is communicated, not during 
 the diastole of the ventricles, but during the systole. The 
 illustrious Harvey found it so in man when the heart was 
 
 R 
 
242 PHYSIOLOGY OF THE CIRCULATION. 
 
 exposed by disease. I have not had an opportunity of 
 examining the human heart thus disclosed, but I have made 
 observations on an anaesthetised living monkey, in which 
 the pericardium was opened sufficiently to enable, me to 
 witness without disturbing the cardiac movements. The 
 heart in this case beat with great regularity and apparently 
 quite normally. The heart when it opened and closed, ro- 
 tated on its long axis in opposite directions, to the extent 
 of nearly a quarter of a turn either way. The ventricles 
 elongated themselves during the diastole, and shortened 
 themselves during the systole ; a spiral wave of -motion 
 travelling from the apex towards the base, and from the 
 base towards the apex. The left apex had a distinct 
 screwing motion. The left apex and the middle third of 
 the right ventricle impinged against the thorax during the 
 systole : the former structure describing an ellipse, as in the 
 fish and frog. " Senac stated correctly enough that the im- 
 pulse is communicated during the systole, and endeavoured 
 to prove his position by averring that the heart is suspended 
 from two curved tubes, viz. the pulmonary artery and aorta ; 
 these tubes, when the blood is forced through them by the 
 closing of the ventricles, endeavouring to straighten them- 
 selves, and causing the apex of the heart to impinge against 
 the thorax. This is the principle on which the steam- 
 gauges at present employed for registering steam-pressure 
 are constructed. The explanation is ingenious, but the large 
 vessels, as Shebeare and Corrigan have shown, curve in 
 such a manner that their recoil would not force the apex of 
 the heart in the direction indicated, but just the opposite. 
 There is this further objection, the ventricles are shortened 
 in their long diameter during the systole. Senac seems to 
 have been aware of this difficulty, for he endeavoured to 
 strengthen his position by adding that the impulse was 
 partly due to the expansion of the left auricle, which, be- 
 cause of its situation between the spine and the left ventricle, 
 tended to force the apex of the heart outwards. The heart, 
 however, tilts forwards when the large vessels are cut through, 
 and it is altogether removed from the body ; in which case, 
 of course, neither the straightening of the vessels nor the 
 swelling of the blood within the left auricle could produce 
 

 PHYSIOLOGY OF THE CIRCULATION. 243 
 
 any effect. The true explanation is, I believe, to be found 
 in the shape of the ventricles, and in the distribution and 
 direction of their muscular fibres. The ventricles form a 
 twisted cone, which is flattened posteriorly and truncated 
 obliquely in this direction at its base. The anterior fibres 
 of the ventricles are consequently much longer than the 
 posterior fibres; and as muscular fibres shorten in propor- 
 tion to their length, this accounts for the heart tilting when 
 removed from the body the apex, as stated, describing 
 a more or less perfect ellipse. A similar explanation was 
 suggested by Professor Alison, and accepted by Mr. Carlisle 
 and Dr. John Reid. 
 
 The Valves of the Vascular System. 
 
 Before proceeding to a consideration of the sounds of the 
 heart, it will be necessary to describe somewhat minutely 
 the structure and movements of the cardiac valves. 
 
 These are important and interesting, in a medical point 
 of view, from the fact that they are frequently the seat of 
 morbid lesions which inaugurate a long list of painful com- 
 plaints, very bewildering to the physician, and especially 
 dangerous to the patient. In order fully to comprehend the 
 nature and uses of the highly elaborated cardiac valves as 
 they exist in man, a knowledge of the relations, structure, 
 and functions of the more rudimentary valves found in the 
 veins of mammals and in the hearts of the lower animals 
 is necessary 1 . 
 
 Venous Valves their Structure, etc. The valves of the 
 veins vary as regards the number of the segments com- 
 posing them. In the smallest veins, and where small veins 
 enter larger ones, one segment only is present. In the 
 middle-sized veins of the extremities two segments are 
 usually met with ; while in the larger veins, as the internal 
 jugulars of the horse, three and even four segments are by 
 no means uncommon. (Fig. 131 A J, p. 244.) 
 
 The segments, whatever their number, are semilunar in 
 
 1 Vide Memoir On the Valves of the Vascular System in Vertebrata,' by the 
 Author; Transactions of the Royal Society of Edinburgh, vol. xxiii. part iii., 1864. 
 The preparations on which this investigation is based are preserved in the Hunterian 
 Museum of the Royal College of Surgeons of London. 
 
 R 2 
 
244 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 shape (Fig. 131 A, B, C, H), the convex borders being at- 
 tached to the wall of the vessel ; the crescentic or concave 
 margins, which are free and directed towards the heart, 
 projecting into it. When a valve is composed of one seg- 
 ment, the segment is placed obliquely in the vessel, its 
 attached convex border occupying rather more than a half 
 of the interior. When the segment occurs at the junction 
 of a smaller with a larger vein (Fig. 131 H), its convex border 
 (a) is attached to a half or more of the orifice of the smaller 
 
 Fig. 131. 
 
 Fig. 131 A. "External jugular vein of horse inverted. Shows valve, consisting of three (r, s, f) seg- 
 ments. Original. 
 
 B. Section of external jugular vein of horse. Shows valve consisting of two segments (a, b), with 
 dilatations (g, h) corresponding to the sinuses of Valsalva in the arteries. Original. 
 
 C. External jugular vein of horse opened, to show the relations of the segments (a, b) where they 
 come together (e), and are united by fibrous tissue (r). The free margin of one of the segments is seen 
 at c, the attached margin at a. Original. 
 
 D. Portion of femoral vein distended with plaster of Paris. Shows dilatations (h, g) in the vessel 
 behind the valve ; a, b, segments of valve ; e, point where the segments come together when the valve is 
 acting. Original, 
 
 E. Shows venous valve, consisting of two segments (a, b) in action ; h, g, bulgings corresponding to 
 sinuses of Valsalva ; e, line formed by the margins of the segments flattening against each other. 
 Original. 
 
 F. The same, not in action. 
 
 G. Venous valve from external jugular of horse, consisting of three segments (r, s,t). Original. 
 
 H. Venous valve of one segment situated at the confluence of a small with a large vein, a, attached 
 convex border; b, free crescentic border. Original. 
 
 I. Venous sinus from the auricle of a sturgeon, a, b, muscular walls of sinus ; c, d, muscular fasciculi 
 which assist in opening and closing the sinus Original. 
 
 ]. Femoral vein distended with plaster of Paris. Shows two sets of venous valves in action ; the one 
 set (upper a, b) where a small vein enters a larger one ; the other (lower a, b) in the principal vessel ; 
 <?, line of junction between the segments of the venous valves. The segments are flattened when they 
 come in contact, so that, if forcibly separated, they display a smooth crescentic surface, represented at 
 E, e of Fig. 132. Original. 
 
 one where it joins the larger, its free margin (b) running 
 transversely to the larger trunk. In such cases the seg- 
 ment acts as a moveable partition or septum, common alike 
 to both vessels ; but its position and relations are such, 
 that while it readily permits the blood from the smaller 
 vein to enter the larger one, it effectually prevents its return. 
 
 When the valve consists of two segments they are semi- 
 lunar in shape, and very ample, the vertical measurement 
 of each being not unfrequently nearly twice that of the 
 
PHYSIOLOGY OF THE CIRCULATION. 245 
 
 diameter of the vessel. 'In such cases both segments are 
 usually of the same size, so that they divide the vessel into 
 two equal parts (Fig. 131 B, C, F). They are placed across 
 the vessel, their free margins being inclined towards the heart 
 and the mesial plane of the vessel. The free margins, when 
 the vessel is placed in fluid, run parallel with each other 
 (Fig. 131 E, ; Fig. 132 E, e, p. 248). The attached margins, on 
 the other hand, diverge to form festoons in the interior of 
 the vessel (Fig. 131 A, r, s, t). This is necessary, as the 
 attached margins must accommodate themselves to the in- 
 terior of the vessel, which is more or less circular. The 
 free margins of the segments, like the attached ones, start 
 from a common point (Fig. 131 C, r) ; but the shape of 
 the segments, and the angle at which they are placed with 
 regard to each other and the mesial plane of the vessel, 
 are such that the free margins do not diverge to the same 
 extent as the attached ones, but run in a nearly straight 
 line across the vessel. I was much struck, on injecting 
 the external saphenous vein of the human subject from 
 the dorsum of the foot, to find, on dissection, that- the 
 free margins of the segments of some of the valves, were 
 in contact throughout ; clearly showing that when the seg- 
 ments are allowed to float in a fluid, they are more or 
 less parallel, and so projected against each other that even 
 the slightest reflux instantly closes them. This relation, of 
 the segments is in part accounted for by the presence of a 
 fibrous structure (Fig. 131 C, r), which extends from the 
 wall of the vessel into the interior, and supports them at a 
 certain distance from the sides of the vessel. The fibrous 
 structure referred to is well seen in the semilunar valves of 
 the pulmonary artery and aorta (Fig. 133 A, b> p. 252), and 
 seems to have escaped observation. In a line corresponding to 
 the attached border of each of the segments, the middle 
 and internal coats of the vein are thickened, as may be 
 ascertained by a vertical section, or by introducing coloured 
 plaster of Paris into the vessel ] . I particularly direct atten- 
 
 1 I have derived much information from the employment of this material ; its 
 use having enabled me to determine with accuracy the relation of the segments 
 of the valves to each other when in action, and other points connected with the 
 physiology of the heart. 
 
246 PHYSIOLOGY OF THE CIRCULATION. 
 
 tion to this circumstance, as the thickenings referred to 
 form fibrous zones which extend for a short distance into 
 the substance of the segments, and afford them a considerable 
 degree of support (Fig. 131 E, h ; C, r,p. 244). They further 
 assist in preserving the shape of the segments, and in enabling 
 them to maintain the proper angle of inclination, the said 
 angle inclining the segments towards each other in the mesial 
 plane of the vessel (Fig. 131 E, e, p. 244). When a valve con- 
 sisting of two segments is situated at the junction of a smaller 
 with a larger vein, one of the segments is usually placed 
 between the two vessels at the point of juncture (Fig. 131 J, 
 upper #, p. 244), the other on the wall of the smaller vein 
 (upper a). The position of the segments in such instances varies, 
 their long diameter sometimes running parallel with the larger 
 vessel, sometimes obliquely, but more commonly transversely. 
 When the valve consists of three segments (Fig. 131 A and 
 G, p. 244), the segments, as a rule, are unequal in size, one of 
 them being generally a little larger (t) than either of the other 
 two (r, s). They are semilunar in shape, as in the smaller 
 and middle-sized veins, and differ from the latter in being 
 less capacious. The tri-semilunar valves in the veins may 
 therefore be regarded as intermediate between the fully 
 developed bi-semilunar valves found in the veins of the ex- 
 tremities and the fully developed tri-semilunar valves which 
 occur at the origins of the pulmonary artery and aorta. The 
 existence of valves in the veins is indicated externally by 
 a dilatation or enlargement of the vessel (Fig. 131 D, h, g t 
 p. 244; Fig. 132 A, k, g, p. 248), the dilatation consisting of 
 one, two, or three swellings, according as the valve is com- 
 posed of one, two, or three segments. These dilatations or 
 swellings are analogous to the sinuses of Valsalva in the 
 arteries (Fig. 1 33 A, B, d, p. 252). They form, with the segments 
 to which they belong, open sinuses or pouches which look 
 towards the heart, and as they extend nearly as far in an 
 outward direction as the segments project inwardly, they 
 give a very good idea of the size and shape of the segments 
 themselves. The object of the swellings is evidently two- 
 fold, firstly, to cause the blood to act on the segments of 
 the valve from without inwards, z, e. in the direction of the 
 mesial plane, or of the axis of the vessel, according as there are 
 
PHYSIOLOGY OF THE CIRCULATION. 247 
 
 two or three segments present ; and secondly, to increase the 
 area over which the pressure exerted by the reflux of the 
 blood extends^* 
 
 The segments of the venous valves are exceedingly flexible, 
 and so delicate as to be semi-transparent. They possess 
 great strength and a considerable degree of elasticity 1 . 
 Usually they are described as consisting of a reduplication 
 of the fine membrane lining the vessel, strengthened by 
 some included fibro-cellular tissue, the whole being covered 
 with epithelium. This description, however, is much too 
 general to convey an accurate impression of their real struc- 
 ture, and the following, drawn up from the examination of 
 a large number of specimens taken from man, the horse, 
 ox, sheep, and other animals, may prove useful. 
 
 When one of the segments of a well-formed bi-semilunar 
 valve removed from the human femoral vein is stained with 
 carmine, fixed between two glasses, and examined micro- 
 scopically, I find the following : 
 
 i st, The lining membrane of the vessel which forms the invest- 
 ing sheath of the segment, and which is covered with epithelium. 
 
 2nd, Large quantities of white fibrous tissue mixed up 
 with areolar and yellow elastic tissue, and a certain amount 
 of non-striped muscular fibres from the middle coats of the 
 vessel. The distribution of the fibres is represented at B, C, 
 D of Fig. 132, p. 248. 
 
 Thus running along the concave or free margin of the seg- 
 ment (Fig. 132 B, a, p. 248), as likewise on the body, especially 
 where the segments join each other (b\ is a series of very 
 delicate fibres, consisting principally of yellow elastic tissue. 
 These fibres proceed in the direction of the long diameter of 
 the segment, but transversely to the course of the vessel, and 
 may be denominated the horizontal fibres* 
 
 Running in a precisely opposite direction, and confining 
 themselves principally to the body of the segment, is a 
 series of equally delicate fibres (c\ having a like composition, 
 and which, for the sake of distinction, may be described as 
 
 1 Hunter denies the elasticity of the segments, on the ground that the valvular 
 membrane is not formed of a reduplication of the lining membrane of the vessel 
 an opinion at variance with recent investigation. Treatise on the Blood, pp. 181, 
 182. 
 
248 PHYSIOLOGY OF THE CIRCULATION. 
 
 the vertical series. These two sets of fibres are superficial, 
 and to be seen properly a power magnifying from 200 to 250 
 diameters is required. 
 
 Radiating from the centre of the segment (Fig. 132 C, e\ 
 towards its attached border (t t f), and seen through the more 
 delicate horizontal and vertical ones, is a series of stronger 
 and deeper fibres, composed of white fibrous and yellow 
 elastic tissue, the former predominating. Still stronger and 
 deeper than either of the fibres described, and proceeding 
 from the attached border of the segment (Fig. 132 D, s, t\ 
 is a series of oblique fibres, continuous in many instances 
 with corresponding fibres in the middle coat of the vessel. 
 These fibres cross each other with great regularity, and form 
 the principal portion of the segments. They are most 
 
 Fif. 132. 
 
 Fig. 132 A. Vertical section of vein distended with plaster of Paris. ; Shows the nature of the union 
 between the segments (e). h.g, pouches behind the segments (a, V). Original. 
 
 E. The same, the section being carried between (e) instead of across or through the segments, e, por- 
 tion of segment flattened against corresponding segment, which in this case is removed, b, portion of 
 segment not flattened by pressure, g, bulging of wall of vein behind segment. Original. 
 
 B, C, D, show the structure of the venous valves. Original. 
 
 strongly marked at the margin of the convex border of the 
 segment, where they form a fibrous zone or ring, which, as 
 has been explained, supports the segment, and carries it 
 away from the sides of the vessel into the interior. I have 
 also detected, in the vicinity of the attached border of the 
 segment, some non-striped muscular fibres. The segment of 
 a venous valve, it will be observed, is a highly symmetrical 
 and complex structure, the fibrous tissues composing it being 
 arranged in at least three well-marked directions ; viz. hori- 
 zontally, vertically, and obliquely. The great strength which 
 such an arrangement is calculated to impart to the segment 
 is readily understood. 
 
 The segment is thinnest at its free margin, and thickest 
 towards its attached border. This follows because the free 
 
PHYSIOLOGY OF THE CIRCULATION. 249 
 
 margins of the segments support each other when the valve 
 is in action the strain falling more upon the attached 
 borders. 
 
 The Venous Valves in Action. The manner in which the 
 venous valves act is well seen when a vein is suspended per- 
 pendicularly overhead, and water, oil, glycerine, or liquid 
 plaster of Paris, poured into it by an assistant from above. 
 In order to witness this experiment properly, that part of 
 the vein beneath the valve should be cut away, the better to 
 expose the segments to the view of the spectator. When 
 the valve consists of one segment only, the fluid is observed 
 to force it obliquely across the vessel^ and to apply its free 
 crescentic margin to the interior or concave surface of the 
 vessel with such accuracy as to prevent even the slightest 
 reflux. When two segments occur in the course of a vein 
 they are forced by the fluid simultaneously towards each other 
 in tJie mesial plane of the vessel (Fig. 1 3 1 E, e ; J, , p. 244), 
 the sinuses behind the segments becoming distended, and 
 directing the current and regulating to a certain extent the 
 amount of pressure. The closure in this instance is almost 
 instantaneous, and so perfect that not a single drop escapes. 
 It is effected by the free margins of the segments^ and a large 
 portion of the sides coming into accurate contact, the amount 
 of contact increasing in a direct ratio to the pressure ap- 
 plied. If liquid plaster of Paris be employed for distending 
 the vein, and the specimen is examined after the plaster has 
 set, one is struck with the great precision with which the seg- 
 ments act (Fig. 131 E, a, b ; J, a, b, p. 244 ; Fig. 132 A, a, d, 
 p. 248), these coming together so symmetrically that they form 
 by their union a perpendicular wall or septum (Fig. 132 A, e) of 
 a beautifully crescentic shape^ (E, e). This fact is significant, 
 as it clearly proves that the free margins of the segments 
 and a considerable proportion of the sides are pressed against 
 each other when the valve is in action, a circumstance dif- 
 ficult to comprehend, when it is remembered that the attached 
 
 1 In order to see the perpendicular wall formed by the flattening of the sides 
 of the segments against each other when the valve is in action, the vein and 
 the plaster should be cut across immediately above the valve, and the segments 
 forcibly separated by introducing a thin knife between them. In Fig. 132 E one 
 of the segments has been so removed. 
 
250 PHYSIOLOGY OF THE CIRCULATION. 
 
 borders are applied obliquely to the walls of the vessel, and 
 that the segments, when not in action, incline towards each 
 other at a considerable angle. When three segments are 
 present, as .happens in the larger venous trunks, the closure 
 is effected as in the semilunar valves of the pulmonary artery 
 and aorta. The fluid employed, in virtue of the direction 
 given to it by the venous sinuses, causes each of the segments 
 (Fig. 131 G, r, s, t, p. 244) to fold or double upon itself at an angle 
 of something like 120 ; the three lines formed by the folding 
 and union of the three segments dividing the circle corre- 
 sponding to the wall of the vessel into three nearly equal 
 parts. (Compare with Fig. 86, p. 174). In the folding of the 
 segments upon themselves, each segment regulates the amount 
 of folding which takes place, in that next to it, and as the 
 free margins of the segments so bent advance synchronously 
 towards the axis of the vessel, they mutually act upon and 
 support each other. As the three segments are attached 
 obliquely to the wall of the vessel, while the free margins, 
 after the folding has taken place, are inclined towards and 
 run parallel with each other, they form a dome, the convexity 
 of which is always inclined towards the heart. The dome 
 consists of three nearly equal parts, the margins of the seg- 
 ments, and a certain portion of the sides, when the pressure of 
 the refluent blood is applied, flattening themselves against each 
 other to form three crescentic partitions or septa 1 , which run 
 from the axis of the vessel towards the circumference. (Com- 
 pare with r s t, v w x, of Fig. 134, p. 253.) 
 
 The tri-semilunar valve, as will be seen from the foregoing 
 description, is closed in a somewhat different manner from 
 the bi-semilunar one. The occlusion of the vessel, however, is 
 not the less complete ; the segments, when three are present, 
 being wedged into each other from without inwards and away 
 from the heart. As the apices of the wedges formed by the 
 doubling of the segments whilst in action are composed 
 principally of the flexible and free crescentic margins, and 
 are at liberty to move until the wedging process is completed, 
 a careful examination has satisfied me that they rotate to a 
 
 1 The crescentic partitions, as they occur in the semilunar valves of the 
 pulmonary artery and aorta, are shown at Fig. 133 C, b, p. 252. 
 
PHYSIOLOGY OF THE CIRCULATION. 251 
 
 greater or less extent before the valve is finally closed. This 
 spiral movement, which is simply indicated in the venous 
 valves, is more strongly marked in the semilunar ones of the 
 pulmonary artery and aorta (Fig. 134, r s t, v w x, p. 253), and 
 attains, as will be shown subsequently, a maximum in the 
 auriculo-ventricular valves of the mammal (Figs. 140143, 
 pp. 268, 28i)7 
 
 By whatever power the blood in the veins advances 
 whether impelled by the heart alone, or aided by the shorten- 
 ing and lengthening of muscles in different parts of the body, 
 or by rhythmic movements which take place in the vessels 
 themselves, or by respiratory efforts, or by atmospheric pres- 
 sure, or by combinations of all of these, there can be no 
 doubt that this fluid, in its backward or retrograde movement, 
 acts mechanically on the valves as described. It ought how- 
 ever to be borne in mind that the veins and the valves are 
 vital structures, and that, although a perfect closure may be 
 effected by purely mechanical means in the dead vein, it 
 is more than probable that, in the living one, the coats of 
 the vessel, with their included nerves, exercise a regulating 
 influence. 
 
 Arterial or Semilunar Valves^ their Stricture, etc, The 
 arterial valves may be regarded as occupying an intermediate 
 position between the venous valves on the one hand, and the 
 auriculo-ventricular valves on the other. The segments com- 
 posing them are three in number, and resemble the segments 
 of the venous valves in their shape, position, mode of attach- 
 ment, and movements ; whereas structurally they are more 
 nearly allied to the segments of the auriculo-ventricular, i.e. 
 the mitral and tricuspid, valves. Like the venous valves, 
 the arterial occupy the interior of vessels, and are crescentic 
 in shape. Thus the segments have a free crescentic thin 
 margin, and a thicker convex attached margin. The convex 
 margin is firmly secured to the scalloped aortic and pulmonic 
 fibrous rings already described (Fig. 94, <z, b, p. 190). The seg- 
 ments are surrounded by a fibrous framework, which enables 
 them to maintain their shape and relative position to each other. 
 This framework carries the segments away from the interior 
 of the vessel, and inclines their free margins towards its axis, 
 so that if the vessel, with its semilunar valve, be submerged, 
 
252 PHYSIOLOGY OF THE CIRCULATION. 
 
 the free margins of the segments are naturally more or less 
 in contact an arrangement which insures the immediate 
 closure of the valve the instant the blood regurgitates. The 
 great vessels are thickened where the segments approach each 
 other (Fig. 133 A, b), and thinned and dilated behind each 
 segment (B, i), to form three large cavities or sinuses, known 
 as the sinuses of Valsalva (B, d). These sinuses contain a 
 considerable amount of residual blood, which by its weight 
 and pressure assists in closing and wedging the segments 
 together during the diastole. They are also the receptacles 
 which receive the segments during the systole an arrange- 
 
 Fig. 133 A. Section of pulmonary artery and right ventricle of human heart between the segments of 
 the semilunar valve. Shows the variation in the thickness of the vessel (a, 6), and how it bifurcates (r) at 
 its origin, s, segment of valve, c, b, t, f, fibrous framework surrounding it. d, sinus of Valsalva. e, 
 pulmonic fibrous ring, v, ventricle. Original. 
 
 B. Similar section carried through pulmonary artery (a, 6) and middle of segment (s). Shows the 
 thinning of the vessel in this situation (z). c, portion of fibrous framework, d, sinus of Valsalva. c, pul- 
 monic fibrous ring, v, ventricle. Original. 
 
 C. Human semilunar valve distended with plaster of Paris, and one of the segments (g) removed to 
 show the shape of the lunulae or opposing surfaces which come together when fluid pressure is applied 
 to the segments, n, aorta, m, flattened portion of segment. This flattening increases with the pres- 
 sure, as at b. The flattening represents the degree of contact between the segments. It is much greater 
 than is usually supposed. Original. 
 
 D. Shows how the segments of the semilunar valve are folded, flattened, and spirally wedged into each 
 other when the valve is closed, v -w x, direction in which the blood flows down upon the segments to 
 fold them, or s, line of union between the segments, cab, nature and amount of flattening occurring 
 along the free margins of the segments. Original. 
 
 ment which increases the diameter of the great vessels at 
 their origins at this particular period (Fig. 87, e, p. 174). When 
 the reflux of the blood occurs, the segments of the semilunar 
 valves fold or bend at their central portions in such a manner 
 that their free crescentic margins become accurately applied 
 to and flattened against each other, the flattening increasing 
 according to the pressure. This arrangement effectually pre- 
 vents regurgitation in healthy valves. (Fig. 133 A, B, C, D.) 
 The sinuses of Valsalva are not disposed in the same plane. 
 They are moreover unequal in size. The highest and 
 smallest is placed anteriorly, that which is intermediate in 
 
PHYSIOLOGY OF THE CIRCULATION. 253 
 
 size posteriorly, the lowest and largest being directed towards 
 the septum. They correspond in situation and dimensions to 
 the segments behind which they are found, and differ from 
 the venous sinuses in being more capacious, a section of the 
 sinus and its segment (which is likewise very ample) giving 
 a sweep of nearly half a circle. As a result of this amplitude, 
 those portions of the segments which project into the vessel 
 are, during the action of the valve, closely applied to each 
 other throughout a considerable part of their extent (Fig. 133 
 C, b ; D, a, $, c), the great size of the sinuses furnishing an 
 increased quantity of blood for pressing the segments from 
 above downwards, and from without inwards, or in the direc- 
 tion of the axis of the vessel. The sinuses of Valsalva curve 
 
 Fig. 134- 
 
 Fig. 134. Base of heart, with right and left ventricles removed to show the pulmonic, aortic, and mitral 
 valves. The pulmonic and aortic valves (r s t, -v TV x) have been closed by pouring liquid plaster of 
 Paris into them. The mitral valve (<:) is open, it always happening that when the semilunar valves are 
 closed, the auriculo-ventricular ones are open. The segments of the pulmonic and aortic valves (vide 
 arrows r s t, -v TV x) are spirally wedged into each other, a, b, right and left musculi papillares of left 
 entricle. c, aortic segment of mitral valve. From photograph. Original. 
 
 towards each other in a spiral direction ; and this ought to be 
 attended to in speaking of the action of the semilunar valves, 
 as the sinuses direct the blood spirally on the mesial line of 
 each segment (Fig. 133 D, v t w, x), and cause the segments 
 to twist and wedge into each other, as shown at r s t, v w #, 
 of Fig. 134. In order to determine this point, I procured 
 a fresh pulmonary artery and aorta, and after putting the 
 valves in position with water, caused an assistant to drop 
 liquid plaster of Paris into the vessels. The greater density 
 of the plaster gradually displaced the water, and I was in this 
 way furnished with accurate casts of the sinuses and of the 
 valves. The segments of the semilunar valves are unequal 
 in size, and consist of a reduplication of the fine membrane 
 
254 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 lining the pulmonary artery and aorta, strengthened by cer- 
 tain tendinous bands, and, as was first satisfactorily demon- 
 strated by Mr. W. S. Savory, of a considerable quantity of 
 yellow elastic tissue 1 . Some of the older anatomists, among 
 whom may be mentioned Lancisci 2 , Senac 3 , Morgagni 4 , Win- 
 
 . 135- 
 
 ttg. 135 A. Segment of human semilunar valve (pulmonic) suspended) from fibrous band (a, a'). 
 x, r, lunulae which, when the valve is in action, become accurately applied: to corresponding lunulae in 
 the two remaining segments, c, portion of segment usually thickened in old people. The thickening is 
 absent in young healthy valves. z, thickened convex border attached to fibrous ring of pulmonary 
 artery, o, thinner portion of segment, s, s', fibrous bands which split up in the mesial line of the seg- 
 ment, in order to support and strengthen it. These structures are better seen at E, which represents the 
 terminal portion of the aorta of a whale with a half segment of one of the semilunar valves attached. 
 a, b, c, thickened portion of aorta, e, thinned portion, a, n, fibrous ring attaching segment of valve to ' 
 aorta, r, free margin or delicate lunula of segment, o, thicker portion of segment, v, s, s', s'', thickest 
 portion of segment, consisting of fibrous bands which break up into brush-shaped expansions, and at 
 once strengthen and support the segment. A scheme of the arrangement of these bands is given at C. ; 
 r, s, mesial line of segment, a, band splitting up into b and c. d, band splitting up into e and/T At B a 
 semilunar segment (v) is shown, where the bands which split up (s, t) are separated by a very delicate 
 membrane (r), and so resemble chordae tendineae. This segment is abnormally thickened and presents 
 a well-marked corpus Arantii (d). At D a segment (b) is shown with its free crescentic borders (e) 
 thickened. This too presents a corpus Arantii (d). Original. 
 
 slow 5 , and Cooper 6 , believed that they had detected the 
 presence of carneous or muscular fibres ; but Haller 7 , and 
 many since his time, have gravely doubted the accuracy of 
 their observations. Mr. Moore 8 has figured two sets of mus- 
 
 1 Purkinge and Rauschel had detected elastic tissue in the corpora Arantii, 
 but knew nothing of its existence throughout the other portions of the valves. 
 Of its presence I have frequently satisfied myself. 
 
 2 De Motu Cordis. 
 
 3 Traite de la Structure du Coeur. Livre i. 
 * Adversaria Anatomica Omnia, 
 
 8 Exposition Anat. de la Structure du Corps Humain, p. 592. 
 
 6 Myotomia Reformata. 
 
 7 Elementa Physiologiae. Liber iv. sect. 10. 
 
 8 Med. Gazette, March 8, 1850. 
 
PHYSIOLOGY OF THE CIRCULATION. 255 
 
 cular fibres, which he has termed, according to their supposed 
 action, dilators and retractors ; and Dr. Monneret l has de- 
 scribed two similar sets, which, for like reasons, he has named 
 elevators and depressors. I have sought in vain for the 
 muscular fibres in question, and am inclined to think that 
 when found, they have been mistaken for the tendinous bands 
 accidentally stained with blood. The tendinous bands have 
 hitherto been regarded as following three principal directions, 
 one band being said to occupy the free margin, and to be 
 divided into two equal parts by the nodulus or corpus Arantii, 
 otherwise called corpusculum Morgagni, and corpus sesamoi- 
 deum ; a second band, proceeding from points a little above 
 the middle of the segment, and curving in an upward direc- 
 tion towards the corpus Arantii ; the third band, which is 
 the thickest, surrounding the attached border of the segment. 
 A careful examination of a large number of mammalian 
 hearts, particularly those of man, has induced me to assign 
 to the semilunar valves a more intricate structure. (Fig. 135 
 A-E.) 
 
 In a healthy human semilunar valve 2 taken from the 
 pulmonary artery, the following seems to be the arrange- 
 ment. Proceeding from the attached extremities of the seg- 
 ment above, and running along its free margin, is a delicate 
 tendinous band, which gives off still more delicate slips (Fig. 
 135 A, ^r, r\ to radiate in a downward and inward direction, i. e. 
 in the direction of the mesial line and body of the segment. 
 These fine slips interdigitate in the mesial line, and are 
 attached below to the uppermost of a series of very strong 
 fibrous bands which occupy the body of the segment (s, s). 
 In the interspaces between the slips the valve is so thin as 
 to be almost transparent. Those portions of the segments 
 included within the delicate fibrous band, running along the 
 free margin and the uppermost of the stronger bands occu- 
 pying the body, are somewhat crescentic in shape (r\ and 
 have, from this circumstance, been termed lunulae. They do 
 
 1 Lancet, Dec. 29, 1850. 
 
 2 It is comparatively a difficult matter to get a perfectly healthy human aortic 
 semilunar valve, especially if the patient is at all advanced in years. Out of 
 twenty adult hearts examined by me, nearly half of that number had the valves 
 abnormally thickened. 
 
256 PHYSIOLOGY OF THE CIRCULATION. 
 
 not form the perfect crescents usually represented in books, 
 the horns of the crescents directed towards the mesial line 
 of the segment being much broader than those directed 
 towards the extremities, or where the segments unite above. 
 The object of this arrangement is obvious. The broader 
 portions of the crescents are those which, when the segment 
 is folded upon itself during the action of the valve, are 
 accurately applied to corresponding and similar portions of the 
 two remaining segments (Fig. 133 C, b ; D, a y b, r, p. 252). If 
 however the lunulae had been symmetrical in other words, 
 if they had terminated in well-defined horns towards the 
 mesial line, or where the segments fold upon themselves 
 then the union between the segments in the axis of the vessel 
 (Fig. 133 D), where great strength is required, would have 
 been partial, and consequently imperfect. 
 
 Proceeding from the attached extremities of the segments 
 at points a little below the origins of the marginal band, and 
 curving in a downward and inward direction, is the first of 
 the stronger bands (Fig. 135 A, b, p. 254). The band referred to 
 splits up into brush-shaped expansions as it approaches the 
 mesial line (c), where it interdigitates and becomes strongly 
 embraced. Other and similar bands, to the extent of three 
 or four (s\ usually the latter number, are met with, and as 
 they all curve in a downward and inward direction, and have 
 finer bands running between them in a nearly vertical direc- 
 tion, they suspend the body of the segment ; so that when 
 blood or water is directed upon it, the various parts of which 
 it is composed radiate from the attached or convex border 
 (#, s) like a fan, each band dragging upon that above it ; the 
 whole deriving support from the thickened convex margin. 
 The bands, which are thus from five to six in number, are 
 best seen on that aspect of the segments which is directed 
 towards the sinuses of Valsalva. The surfaces of the segments 
 directed towards the axis of the vessel are perfectly smooth, 
 and so facilitate the onward flow of the blood. The bands 
 are thickest at their attached extremities, where they interlace 
 slightly, and are mixed up to a greater or less extent with 
 the pale soft flattened fibres and elastic tissue of the central 
 layer of the vessel. The several points alluded to are well 
 seen in Fig. 135 E, p. 254. 
 
PHYSIOLOGY OF THE CIRCULATION. 257 
 
 As the bands under consideration are exceedingly strong 
 when compared with those occurring in other portions of the 
 segments, and project in an inward direction, or towards the 
 axis of the vessel, when the preparation is sunk in water, their 
 function, as ascertained from numerous experiments on the 
 semilunar valves of a whale (Physalus antiquorum, Gray), 
 seems to be the following : 
 
 ist, They carry the bodies of the segments away from the 
 sides of the vessel, and incline their free margins towards each 
 other at such an angle as necessitates the free margins of 
 neighbouring segments being always more or less in apposition. 
 In this they are assisted by the thickened portion of the pul- 
 monary artery which projects between the segments, where 
 they unite above, and by the fibrous zones which correspond 
 to the convex border of each segment. 
 
 2nd, The stronger fibres suspend the bodies of the segments 
 from above, and permit the reflux of blood to act more imme- 
 diately upon the mesial line of each segment where thinnest 
 and where least supported, to occasion that characteristic fold- 
 ing of the segments upon themselves when the valve is in 
 action. The closure of the valve is in part due to the weight 
 of the blood, in part to the sucking action of the right ven- 
 tricle when opening, and in part to the elastic properties of the 
 artery. 
 
 From the foregoing it will be perceived that the segments 
 of a semilunar valve are bilaterally symmetrical, and con- 
 structed on a plan which secures the greatest amount of 
 strength with the least possible material (Fig. 135 C, p. 254). 
 
 On some occasions the tendinous bands proceeding from 
 the marginal one are abnormally thickened (Fig. 1 35 B, s, t\ 
 and terminate in brush-shaped expansions in the body of 
 the segment (v) ; the body under such circumstances pro- 
 jecting in an upward direction towards the corpus Arantii 
 (d). In such cases, those portions of the valve which occur 
 between the thickened bands proceeding from the marginal 
 one, are exceedingly thin, and in some diseased conditions 
 altogether awanting (r), so that the segment very much 
 resembles one of the segments of the mitral or tricuspid 
 valve, with its chordae tendinae. That there is an analogy 
 between the semilunar and the mitral and tricuspid valves, 
 
 S 
 
2 5 8 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 and that the tendinous chords are a further development, 
 seems probable from the fact that in the bulbus arteriosus 
 of certain fishes, as the gray and basking sharks, lepidosteus, 
 etc., the semilunar valves are furnished with what may be 
 regarded as rudimentary chordae tendineae (Figs. 137 and 
 138, 3); the auriculo-ventricular valves of fishes, which have 
 hitherto been regarded as semilunar, exhibiting tendinous 
 chords in various stages of development (Fig. 136, c). 
 
 Fig. 136. 
 
 Fig. 137. 
 
 Fig. 138. 
 
 Fig. 136. Bulbus arteriosus and ventricle of sturgeon ; the former (a.) displaying five rows of serai- 
 lunar valves (b), the latter an auriculo-ventricular valve (c), with numerous tendinous bands running into 
 it. Original. 
 
 Fig. I37- Bulbus arteriosus and portion of ventricle of lepidosteus. Shows the great thickness of the 
 bulb (a), and of the valves (b), between which tendinous bands run. Original. ' 
 
 Fig. 138. Portion of bulbus arteriosus of basking shark. Shows the great thickness of the bulb (a) and 
 of the valves (b), and how the latter support each other. Original. 
 
 The corpus Arantii is never present in a perfectly healthy 
 semilunar segment ; nor will its absence occasion surprise, 
 when it is remembered that its presence materially interferes 
 with the folding of the segments upon themselves when the 
 valve is in action. That its existence is not necessary to the 
 perfect closure of a semilunar valve, is proved by its complete 
 absence in the segments of the human pulmonic valve, in the 
 segments of the pulmonic and aortic semilunar valves of the 
 lower animals, and in all veins. In the semilunar valve of 
 the whale, where one would have naturally expected the 
 corpus Arantii in perfection, I could not detect even a trace 
 of it. I am therefore disposed to regard it as a morbid con- 
 dition, due to irritation and subsequent deposit. 
 
 What has been said of the semilunar valves of the pul- 
 monary artery may with equal propriety be said of those 
 of the aorta ; the only difference being that the segments 
 of the aorta are stronger and more opaque, to harmonise with 
 the greater strength of the left ventricle. 
 
PHYSIOLOGY OF THE CIRCULATION. 259 
 
 The Arterial or Semilunar Valves in Action. As the 
 manner in which the semilunar valves are closed does not 
 seem to be well understood, an account of some experiments 
 conducted by me some time ago with various fluids and liquid 
 plaster of Paris may prove interesting : 
 
 When the aorta is cut across an inch or so above the aortic 
 semilunar valve, and water introduced, the segments, if 
 watched from beneath, are seen to act with great alacrity, 
 the smallest segment, which is situated highest, descending 
 with a spiral swoop, and first falling into position ; the 
 middle-sized segment, which is placed a little lower, descend- 
 ing in like manner, and fixing the first segment by one of 
 its lunulae or crescentic surfaces ; the third and largest 
 segment, which occupies a lower position than either of the 
 others, descending spirally upon the crescentic margins of 
 the other two, and wedging and screwing them more and 
 more tightly into each other. The spiral movement, as has 
 been already explained, is occasioned by the direction of the 
 sinuses of Valsalva, which curve towards each other, and 
 direct the blood in spiral waves upon the mesial line of each 
 segment (Fig. 133 D, v w x, p. 252 ; Fig. 134, v w x, p. 253). 
 
 From the foregoing description of the venous and arterial 
 semilunar valves in mammalia, it will be evident that there is 
 nothing either in their structure or relations to betoken any 
 great degree of activity on their part. That these structures 
 are, on the contrary, to a great extent passive, seems certain 
 from the fact that a stream of water or other fluid directed 
 upon them from above as recommended at once closes the 
 orifices which they guard. Thus far my remarks have been 
 confined to the so-called venous and arterial semilunar valves 
 of the mammal. I will now say a few w r ords regarding 
 similar structures in the fish, reptile, and bird. 
 
 Semilunar and other Valves of the Fish, Reptile -, Bird> etc. 
 The semilunar valves in the bulbus arteriosus of the fish, 
 and the auriculo-ventricular valves in the fish and reptile, 
 differ from the venous and arterial semilunar valves of the 
 mammal in being, for the most part, exposed, either directly 
 or indirectly, to the influence of muscular movements. The 
 bulbus arteriosus is a muscular structure which opens and 
 closes like the other parts of the heart. As a consequence, 
 
 S 2, 
 
260 PHYSIOLOGY OF THE CIRCULATION. 
 
 the valves situated in its interior are opened and closed by 
 vito-mechanical movements. The segments vary as regards 
 number, size, and shape, apparently with a view to meeting 
 the requirements of the structure in which they occur. Thus, 
 in the frog-fish (Lopkius piscatorius) , the origin of the bulbus 
 arteriosus is guarded by a semilunar valve, consisting of two 
 ample and very delicate segments, resembling those found in 
 the middle-sized veins ; while in the sun-fish (Orthagoriscus 
 mola, Schneider) the same aperture is guarded by a semilunar 
 valve consisting of three- segments, the segments being 
 analogous in every respect to those found in the largest veins, 
 and in the pulmonary artery and aorta. As the valve in 
 these cases is situated between the actively moving bulbus 
 arteriosus and ventricle, it is surrounded by a fibrous ring 
 similar to that occurring at the origin of the pulmonary artery 
 and aorta in 'man. The movements of the valve are conse- 
 quently not affected by the movements of the bulbus arteriosus 
 and ventricle to any great extent. The semilunar valves in the 
 frog-fish and sun-fish are to be regarded as connecting 'links 
 between the venous and arterial ones in the bird and mammal, 
 and that more complex system of analogous valves which is 
 found in the bulbus arteriosus of fishes generally. In the 
 bulbus arteriosus of the skate (Raia batis\ the segments 
 occupy the whole of the interior of the bulb, and are arranged 
 in three pyramidal rows of five each. As the segments in 
 this instance are very small, and cannot obliterate the cavity 
 of the arterial bulb, they must be looked upon as being useful 
 only in supporting the column of blood ; it being reserved for 
 the segments at the termination of the bulb, which are larger 
 and more fully developed, to effect the closure. The action 
 of the segments in the bulbus arteriosus of the skate is 
 rendered more perfect by the pressure from without, caused 
 by the closure of the bulb itself. In the bulbus arteriosus 
 of the sturgeon (Accipenser sturio), the segments are arranged 
 in four rows of eight each (Fig. 136, b, p. 258). They are more 
 delicate, and less perfectly formed than in the skate. In the 
 bulbus arteriosus of the American devil-fish (Cephalopterus 
 giorna), the segments increase to thirty-six, are more im- 
 perfect than in any of the others, and are supported by three 
 longitudinal angular muscular columns. As the segment- 
 
PHYSIOLOGY OF THE CIRCULATION. 26 1 
 
 bearing columns, from their shape, project into the cavity 
 of the bulb, and almost obliterate it when the bulb closes, 
 they in this way bring the free margins of the segments 
 together. The orifice of the bulbus arteriosus, however, is not 
 closed by the imperfect segments referred to ; this being 
 guarded by two well-formed and fully-developed trisemilunar 
 valves, the one of which is situated at the beginning, trie other 
 at the termination, of the bulb. In the bulbus arteriosus of 
 the gray shark (Galeus communis], we have a slightly different 
 arrangement, the two rows of segments of which the valve 
 is composed being connected with each other by means of 
 tendinous bands, resembling chordae tendineae. In the bulbus 
 arteriosus of the lepidosteus (Fig. 137, b, p. 258), and that of 
 the basking shark (Fig. 138, b, ib.), the same arrangement pre- 
 vails ; the segments being stronger and less mobile, and the 
 tendinous bands which bind the one segment to the other 
 more strongly marked. As the tendinous bands referred to 
 are not in contact with the wall of the bulbus arteriosus, 
 but simply run between the segments, and are in some 
 instances, as in the basking shark, very powerful, they must 
 be regarded in the light of sustaining or supporting structures ; 
 their function being probably to prevent eversion of the 
 segments. Other examples might be cited, but sufficient have 
 been adduced to show that the form, as well as the number 
 and arrangement, of the segments is adapted to the peculiar 
 wants of the structure in which the segments are situated ; 
 and it ought not to be overlooked, that when a multiplicity of 
 segments is met with in an actively moving organ, the muscles 
 and valves act together. 
 
 If we now direct our attention to the auriculo-ventricular 
 valves of the fish and reptile, similar modifications as regards 
 the number of the segments, and the presence or absence of 
 chordae tendineae and analogous structures, present them- 
 selves. Thus, in the heart of the serpent (Python tigris\ the 
 two crescentic apertures by which the blood enters the pos- 
 terior or aortic division of the ventricle are each provided 
 with a single semilunar valve. The same may be said of 
 the aperture of communication between the left auricle and 
 ventricle of the crocodile (Crocodilus acutus] and of the 
 sturgeon (Accipenser sturio, Linn.). In the heart of the Indian 
 
262 PHYSIOLOGY OF THE CIRCULATION. 
 
 tortoise (Testudo Indica, Vosmaer), the left auriculo-ventri- 
 cular orifice is guarded by a single membranous fold, the right 
 orifice having in addition a slightly projecting semihmar ridge, 
 which extends from the right ventricular wall, and may be 
 regarded as the rudiment of the fleshy valve which guards 
 the same aperture in birds (Fig. 139, i,j, p. 264). In the heart 
 of the bulinus, frog-fish, American devil-fish, gray shark, and 
 crocodile, the auriculo-ventricular orifice is guarded by a 
 semilunar valve consisting of two cusps or segments ; while in 
 the sturgeon, sun-fish, and others, it is guarded by four, two 
 larger and two smaller. 
 
 So much for the number of the segments constituting the 
 auriculo-ventricular valves in fishes and reptiles ; but there 
 are other modifications which are not less interesting physio- 
 logically. In the bulinus, frog-fish, and crocodile, the seg- 
 ments of the valves are attached to the auriculo-ventricular 
 tendinous ring, and to the sides of the ventricle, and have no 
 chordae tendineae. In the sun-fish the valve is likewise 
 destitute of chordae tendineae ; but in this instance the 
 muscular fibres are arranged in the direction of the free 
 margins of the segments of the valve, and no doubt exercise 
 an influence upon them. In the gray shark the membranous 
 folds forming the segments are elongated at the parts where 
 they are attached to the ventricular walls, these elongated 
 attachments being more or less split up, so as to resemble 
 chordae tendineae. 
 
 In the American devil-fish the auriculo-ventricular valve 
 consists of two strong well-developed membranous folds, 
 which, like the preceding, are attached by elongated pro- 
 cesses to the interior of the ventricular wall ; these processes 
 consisting of distinct tendinous slips, which are attached to 
 rudimentary musculi papillares. 
 
 In the sturgeon three tendinous chords from rudimentary 
 musculi papillares are seen to extend into the half of each 
 of the segments ; while in the left ventricle of the dugong, 
 six chords proceeding from tolerably well-formed musculi 
 papillares are distributed to the back, and six to the margins 
 of each of the segments. It is however in the bird and 
 mammal, particularly the latter, that the musculi papillares 
 are most fully developed, and the chordae tendineae most 
 
PHYSIOLOGY OF THE CIRCULATION. 263 
 
 numerous the number of tendinous chords inserted into 
 each of the segments amounting to eighteen or more. As 
 the chordae tendineae of the auriculo-ventricular valves are 
 attached either to the interior of the ventricle, or to the 
 musculi papillares or carneae columnae, it is evident that the 
 closure of the ventricle must influence both valves and chords 
 to a greater or less extent That, however, the presence of 
 muscular substance does not impair the efficiency of the 
 valves appears from this that some valves are partly muscular 
 and partly tendinous, a few being altogether muscular. Thus, 
 in the heart of the cassowary, the right auriculo-ventricular 
 orifice is occluded by a valve, which is partly muscular and 
 partly tendinous ; the muscular part, which is a continuation 
 of two tolerably well-formed musculi papillares, extending 
 into the tendinous substance of the valve where it gradually 
 loses itself. In the right ventricle of the crocodile, a muscular 
 valve, resembling that found in, v the right ventricle of birds, 
 exists. 
 
 In some birds the right auriculo-ventricular valve is alto- 
 gether muscular. It is usually described as consisting of 
 two parts, from the fact of its dependent or free margin 
 being divided into two portions by a spindle-shaped muscular 
 band, which connects it with the right ventricular wall. As 
 however the valve consists of one continuous fold towards the 
 base, and the two portions into which its free margin are 
 divided are applied during the systole not to each other but 
 to the septum, the valve in reality consists of a singular 
 muscular flap or fold, as shown at i of Fig. 139, p. 264. 
 
 The muscular flap or fold extends from the edge and upper 
 third of the septum posteriorly to the fleshy pons anteriorly. 
 It opens towards the interior of the ventricle in a direction 
 from above downwards, and is deepest at the edge of the 
 septum posteriorly. As it gradually narrows anteriorly (i), 
 it is somewhat triangular in shape, its dependent and free 
 margin describing a spiral which winds from behind forwards, 
 and from below upwards. The valve, from its shape and 
 structure, might not inappropriately be termed the musculo- 
 spiral valve. It is well seen in the right ventricle of the 
 emu, swan, turkey, capercailzie, and eagle. The muscular 
 valve of the bird is composed of the fibres entering into the 
 
264 PHYSIOLOGY OF THE CIRCULATION. 
 
 formation of the several layers of the right ventricular wall 
 (the ventricular wall in fact bifurcates or splits up towards 
 its base) ; the external layers forming the outer wall of the 
 valve, the internal layers, which are slightly modified, forming 
 the inner. If the muscular valve be regarded as an in- 
 dependent formation, which it can scarcely be, it will be best 
 described as a structure composed of fibrous loops, these 
 loops being of three kinds, and directed towards the base 
 the first series consisting of spiral, nearly vertical fibres, 
 forming a somewhat acute curve ; the second series consisting 
 of slightly oblique spiral fibres, forming a larger or wider 
 curve; and the third series consisting of still more oblique 
 fibres, and forming a still greater curve. As the fibres 
 composing the different loops act directly upon each other 
 
 Fig- 139- 
 
 Fig. 139-. Anterior aspect of turkey's heart, with right ami left ventricles open to show auriculo ven- 
 tricular valves, a, aorta arching to 1 right side and dividing into three branches, two of which' (b) go to 
 right side, and one (c) to left side, d, pulmonary artery dividing into two, and sending a branch to right 
 and left lungs. *', muscular or fleshy valve which occludes right auriculo-ventricular orifice, j, nvusculus 
 papillaris of fleshy valve (compare with g). e, portion of septum to which valve is applied when closed. 
 f, left ventricle, v, tendinous valve which occludes left auriculo-ventricular orifice, g, musculus papil- 
 laris with chordae tendineae attached to tendinous valve. Original. 
 
 when the ventricles close, the object of the arrangement is 
 obviously to supply a movable partition or septum which 
 shall occlude the right auriculo-ventricular opening during 
 the systole. The manner in which the several loops act is 
 determined by their direction. Thus, the more vertical ones, 
 in virtue of their shortening from above downwards, have the 
 effect of flattening or opening out the valvular fold, and in 
 this way cause its dependent or free margin to approach 
 the septum. The slightly oblique fibres, which shorten 
 partially from above downwards, but principally from before 
 backwards, assist in this movement by diminishing the size of 
 
PHYSIOLOGY OF THE CIRCULATION. 265 
 
 the right auriculo-ventricular orifice in an antero-posterior 
 direction, it remaining for the very oblique and transverse 
 fibres, which shorten from before backwards and from with- 
 out inwards, to complete the movement by pressing the inner 
 leaf of the fold directly against the septum an act in which 
 the blood plays an important part, from its position within 
 the valve ; this fluid, according to hydrostatic principles, 
 distending equally in all directions, and acting more im- 
 mediately on the dependent or free margin of the valve, which 
 is very thin and remarkably flexible. When a vertical section 
 of the fold forming the right auriculo-ventricular valve of the 
 bird is made, that portion of it which hangs free in the right 
 ventricular cavity is found to be somewhat conical in shape, 
 the thickest part being directed towards the base, where it 
 has to resist the greatest amount of pressure ; the thinnest 
 corresponding to its dependent and free margin, where it 
 is applied to and supported by the septum. The upper 
 border of the fold is finely rounded, and in this respect 
 resembles the convex border which limits the right ventricle 
 of the mammal towards the base. 
 
 The spindle-shaped muscular band (Fig. 139,7, P- 264), which 
 from its connexion may be said to command the upper and 
 lower portions of the right ventricle interiorly, is obviously 
 for the purpose of co-ordinating the movements of the mus- 
 cular valvular fold (/) ; and as its position and direction nearly 
 correspond with the position and direction of the musculus 
 papillaris situated on the right ventricular wall of the mam- 
 mal, it is more than probable that it forms the homologue of 
 this structure. Indeed this seems almost certain from the 
 fact that if the ventricles of the bird be opened anteriorly and 
 the band referred to (/) contrasted with the anterior musculus 
 papillaris of the left ventricle (g), both are found to occupy a 
 similar position. The fleshy band is therefore to the muscular 
 valve of the right ventricle, what the anterior musculus 
 papillaris and its chordae tendineae are to the segments of 
 the mitral valve. Compared with the tricuspid valve of the 
 mammal, the muscular valve of the right ventricle of the bird 
 is of great strength. As, moreover, it applies itself with 
 unerring precision to the septum (e), which is slightly promi- 
 nent in its course, its efficiency is commensurate with its 
 
2,66 PHYSIOLOGY OF THE CIRCULATION. 
 
 strength. The prominence on the septum alluded to is very 
 slight, and might escape observation, were it not that im- 
 mediately below the prominence the septum is hollowed out 
 to form a spiral groove of large dimensions. This groove, 
 like the valve, runs in a spiral direction from behind forwards 
 and from below upwards, and when the valve is applied to 
 the septum during the systole, converts the right ventricular 
 cavity into a spiral tunnel, through which the blood is forced, 
 on its way to the pulmonary artery. The efficiency of the 
 right auriculo-ventricular muscular valve in birds, clearly 
 shows that large apertures may be occluded by purely 
 muscular arrangements and by vital movements ; and it is 
 important to bear this fact in mind, as it shows how the 
 musculi papillares in mammals, by their elongating and 
 shortening, may take part in the opening and closing of the 
 mitral and tricuspid valves. In addition to the muscular 
 valve of the bird described, it may be well to state that in 
 the serpent the opening between the right and left ventricles 
 occurs as a spiral slit in the septum. It is guarded by two 
 projecting muscular surfaces, which are rounded off for the 
 purpose. The orifices of many of the venous sinuses are closed 
 by purely muscular adaptations ; the fibres in such instances 
 running parallel with the slit-like opening (Fig. 131 I, a, b), 
 and being continuous with two or more bundles of fibres 
 (c, d\ which supply the place of musculi papillares. From 
 the great variety in the shape and structure of the auriculo- 
 ventricular valves, and from the existence in almost all of 
 tendinous chords, which connect them with actively moving 
 structures, there can, I think, be no doubt that these valves 
 possess an adaptive power traceable in a great measure to 
 the centripetal and centrifugal power residing in muscle. S 
 
 As it would obviously occupy too much time to give a 
 detailed account of the numerous auriculo-ventricular valves, 
 to which allusion has been made, I have selected for descrip- 
 tion the auriculo-ventricular valves of the mammal, and those 
 of man more particularly. 
 
 Intricate Structure of the Mitral and Tricuspid Valves in 
 Mammalia ; Relations of the Chordae Tendineae to the Valves 
 and to the Musculi Papillares. The auriculo-ventricular 
 valves, known as the mitral or bicuspid and tricuspid valves, 
 
PHYSIOLOGY OF THE CIRCULATION. 267 
 
 are composed of segments which differ in size, and are more 
 or less triangular in shape. They are much stronger than 
 the segments composing the aortic and pulmonic semilunar 
 valves, which in some respects they resemble in structure 
 as well as function. The segments of the mitral and tricuspid 
 valves are very dense, and quite opaque, unless at the margins 
 and apices, where they are frequently remarkably thin. They 
 unite at the base where thickest, to form tendinous zones, which 
 are attached to one or other of the fibrous rings surround- 
 ing the auriculo- ventricular orifices (Fig. 94, c, d, p. 190). The 
 auriculo-ventricular fibrous rings have been variously described, 
 the majority of investigators regarding them as strongly 
 pronounced structures, which afford attachment, not only to 
 the valves, but to all the muscular fibres of the auricles and 
 ventricles. A careful examination of these rings in boiled 
 hearts has led me to a different conclusion. They afford 
 attachment to the muscular fibres of the auricles and to the 
 valves, but to almost none of the muscular fibres of the ventricles. 
 They are most fully developed anteriorly, and on the septum, 
 where they form a dense fibrous investment. The left ring, like 
 everything else pertaining to the left ventricle, is more fully 
 developed than the right ; but neither the one nor the other can 
 compare in breadth or thickness with the pulmonic or aortic 
 fibrous rings (Fig. 94, a, b, p. 190). The influence exerted 
 by the auriculo-ventricular fibrous rings in conferring rigidity 
 on the auriculo-ventricular orifices is consequently immaterial. 
 The position of the segments of the mitral and tricuspid 
 valves in the auriculo-ventricular orifices, and their relation to 
 the musculi papillares, is deserving of attention. The left 
 auriculo-ventricular orifice is provided with a valve consisting 
 of two major or principal segments, and two minor or smaller 
 segments which are placed between the principal ones. The 
 major segments are unequal in size and form ; their shape 
 and depending position resembling a bishop's mitre inverted, 
 hence the epithet mitral or bicuspid applied to this valve. 
 The larger of the major segments is suspended obliquely 
 between the left auriculo-ventricular and aortic openings, and 
 occupies a somewhat internal and anterior position ; the 
 smaller one, which runs parallel to it, occupying a more 
 external and posterior position. The right auriculo-ventricular 
 
268 PHYSIOLOGY OF THE CIRCULATION. 
 
 orifice, on the other hand, is supplied with a valve composed 
 of three major or principal segments, and three minor or 
 smaller intermediate segments. From this it follows that the 
 right auriculo-ventricular valve has been denominated tricuspid 
 to distinguish it from the mitral or bicuspid one. The three 
 principal segments forming the tricuspid valve vary in size, 
 the smallest running parallel with the septum ; the largest 
 being placed anteriorly and inclined to the right side ; the 
 one which is intermediate in size occupying a more posterior 
 position. The segments, whatever their size, are attached by 
 their bases to the auriculo-ventricular fibrous rings, and by 
 their margins and apices (by means of the chordae tendineae) 
 to the spiral musculi papillares. 
 
 Fig. 140. 
 
 Fig. 140. Anterior segment of human mitral valve. Shows the threefold distribution of the chordae 
 tendineae from above downwards, and from the mesial line towards the margins of the segment, z, base 
 of segment, x, apex ditto, r r', s s', chordae tendineae from anterior portions (a, c) of right and left 
 musculi papillares, bifurcating and losing themselves in margins of segment, b, d, posterior portions of 
 right and left musculi papillares, which send chordae tendineae to posterior segment of mitral valve. 
 Original. 
 
 The segments of the mitral valve, to which the following 
 description, drawn from an extensive examination of mam- 
 malian hearts ', more particularly applies, consist of a redu- 
 plication of the endocardium, or lining membrane of the 
 heart, containing within its fold large quantities of white 
 fibrous tissue, and, as was pointed out by Mr. W. S. Savory, 
 
 1 Of the hearts examined, those of man, the elephant, camel, whale (Physalus 
 antiqnorum, Gray), mysticetus, horse, ox, ass, deer, sheep, seal, hog, porpoise, 
 monkey, rabbit, and hedgehog, may be mentioned. 
 
PHYSIOLOGY OF THE CIRCULATION. 269 
 
 and after him by Professor Bonders 1 , of a moderate amount 
 of yellow elastic tissue. The white fibrous tissue greatly 
 preponderates, and is derived principally from the chordae 
 tendineae, which split up into a vast number of brush-shaped 
 expansions, prior to being inserted into the segments. The 
 fibrous expansions, which assume the form of bands, may con- 
 sequently be regarded as prolongations of the chordae ten- 
 dineae. They are analogous, in many respects, to similar 
 bands in the semilunar valves (Fig. 1 35 B, s, t, p. 254) ; the only 
 difference being, that in the semilunar valves, the bands re- 
 ferred to, instead of being free, as in the present instance (Fig. 
 140, r /, s /, p. 268), are involved in the valvular substance. 
 
 As each of the segments composing the bicuspid or mitral 
 valve, like the left ventricle itself, is bilaterally symmetrical, 
 it will be convenient, when speaking of these structures, to 
 describe in the first instance only the half of one of the 
 segments ; and in order to do this the more effectually, 
 it will be necessary to consider each musculus papillaris as 
 essentially consisting of two portions 2 , an anterior portion 
 (Fig. 140, c, p. 268), which gives off two (more commonly three) 
 chordae tendineae (r, r) to that half of the anterior segment 
 of the mitral valve which is next to it ; and a posterior portion 
 (d), which also gives off three tendinous chords, these being 
 inserted into the adjacent half of the posterior segment. The 
 three tendinous chords which proceed from the anterior 
 portion subdivide, and are inserted by brush-shaped expan- 
 sions into the half of the anterior segment in nine different 
 places 3 . Of these, three are inserted into the mesial line of 
 the segment, viz. into the base, central portion, and apex ; 
 three into the basal, central, and apicial portion of the free 
 margin ; and three into intermediate points between the 
 mesial line and the margin. On some occasions, as in the 
 mitral valve of the whale, a slightly different arrangement 
 prevails ; three chordae tendineae being inserted into the 
 
 1 Professor Donders describes the yellow elastic tissue as being most abundant 
 in the upper surface of the segments. 
 
 2 The musculi papillares in the human and other hearts either bifurcate or show 
 a disposition to bifurcate at their free extremities, so that the division of the 
 chordae tendineae into two sets is by no means an arbitrary one. 
 
 3 The number .of insertions varies in particular instances. In typical hearts, 
 however, it is remarkably uniform. 
 
2/O PHYSIOLOGY OF THE CIRCULATION. 
 
 mesial line of the segment at the base, at the centre, and 
 at the apex ; an additional chord going to the free margin 
 near the apex ; three into intermediate points between the 
 mesial line and the margin ; a second additional chord going 
 to the central portion of the margin. A third and independent 
 chord goes to the base of the margin. In the whale, as will 
 be observed, the arrangement is virtually the same as that 
 first given ; the insertions being nine in number, three into 
 the mesial line, three into the free margin, and three into 
 intermediate points. The tendinous chords pursue different 
 directions prior to insertion ; the three which are inserted 
 into the mesial line of the segment (r\ and are the longest 
 and strongest, being less vertical than those which are in- 
 serted nearer the margin (/) ; these in turn being less vertical 
 than the ones inserted into the margin, which are the shortest 
 and most delicate. The basal chord of each set (z), on the 
 contrary, is more vertical than that beneath it, or nearer 
 the apex (x) ; the apicial chords being more or less horizontal. 
 As there is a disposition on the part of the higher and more 
 central chordae tendineae to overlap, by their terminal brush- 
 shaped expansions, those below and to the outside of them, 
 the segment is found to diminish in thickness from the base 
 (z) towards the apex (x), and from the mesial line towards the 
 periphery or margin ; the basal and central portions of the 
 segment being comparatively very thick, the apicial and 
 marginal portions very thin ; so thin, indeed, that in some 
 hearts, particularly in the right ventricle, they present a 
 cobwebbed appearance. As the marginal portions form the 
 counterparts of the lunulae in the semilunar valves, and are 
 those parts of the segments which come into accurate ap- 
 position when the valve is in action, they are from this 
 circumstance entitled to consideration. When a perfectly 
 healthy mitral valve from an adult, or still better, from a 
 foetus at the full time or soon after birth, is examined, the 
 portions referred to are found to be of a more or less cres- 
 centic shape (vide that part of the mitral valve to which the 
 chordae tendineae marked r', Fig. 140, p. 268, are distributed), 
 and so extremely thin, that the slightest current in the fluid in 
 which they are examined causes them to move like cilia. The 
 physiological value of this delicacy of structure, and con- 
 
PHYSIOLOGY OF THE CIRCULATION. 271 
 
 sequent mobility, is very great ; as the most trifling impulse 
 causes the marginal parts of the segments, which are naturally 
 in juxtaposition, to approach towards or recede from each 
 other. The half of one of the segments of the mitral valve, 
 it will be seen, consists of a reduplication of the endocardium 
 or lining membrane of the heart, supported or strengthened 
 in all directions by nine or more tendinous brush-shaped 
 expansions ; these expansions being arranged in three vertical 
 rows of three each, with much precision, and according to a 
 principle which is seldom deviated from. In addition to the 
 reduplication of the lining membrane and the tendinous 
 expansions described, Lancisi 1 , Senac 2 , and Kiirschner 3 have 
 ascertained that there is a slight admixture of true muscular 
 fibres 4 . When a segment of the mitral valve is examined by 
 being held against the light, or by the aid of a dissecting lens, 
 it is found to consist of tendinous striae running transversely, 
 obliquely, and more or less vertically ; the striae of opposite 
 sides being so disposed that they mutually act upon and 
 support each other an arrangement productive of great 
 strength, and one which secures that the segments shall be 
 at once tightened or loosened by the slightest shortening or 
 lengthening of the musculi papillares. The minor or accessory 
 segments of the mitral valve resemble the principal ones 
 in structure and general configuration. They are, com- 
 paratively speaking, very thin ; and the chordae tendineae 
 inserted into them differ from those inserted into the principal 
 segments, in having a more vertical direction, and in being 
 longer and more feeble. The description given of the bicuspid 
 valve applies, with trifling alterations in particular instances, 
 to the tricuspid, if allowance be made for an additional large 
 segment, and three or more accessory segments. With regard 
 to the smallest of the three large segments forming the 
 tricuspid, I have to observe that, in all probability, it is 
 simply an over-developed accessory segment ; the so-called 
 tricuspid valve being in reality a bicuspid one. Nor is this to 
 
 1 De Motu Cordis. 
 
 2 Traite de la Structure du Coeur, livre i. p. 76. 
 
 3 Wagner's Handworterbuch, art. ' Herzthatigkeit.' 
 
 * According to Mr. Savory's observations the muscular fibre is found more 
 particularly at the upper or attached border of the valves. 
 
2/2 PHYSIOLOGY OF THE CIRCULATION. 
 
 be wondered at, when I remind you that the right ventricle 
 is a segmented portion of the left, and partakes of its bilateral 
 symmetry even in matters of detail. The opinion here 
 advanced is by no means new, but it appears to me that the 
 point has not been sufficiently investigated, and we are in 
 want of statistics regarding it. In ten human hearts which I 
 examined for this purpose, no less than four had well-marked 
 bicuspid valves in both ventricles (Fig. 144, p. 281): and on 
 looking over a large collection of miscellaneous hearts in the 
 Museum of the Royal College of Surgeons of England, I found 
 that nearly a third of them had the peculiarity adverted to ; 
 if indeed that can be called peculiar, which seems to me to be 
 typical. When two principal segments, with two or more 
 accessory segments, occlude the right auriculo - ventricular 
 orifice, the chordae tendineae are arranged as in the segments 
 of the bicuspid valve already described. When there are 
 three principal segments, with as many or more accessory 
 segments, the distribution is varied to meet the exigencies of 
 the case : there being a tendency in each of the chordae 
 tendineae to divide into three ; one of the chords so divided 
 being inserted by one of its slips into the mesial line of the 
 segment at the base ; by another into the margin of the 
 segment, likewise at the base ; and by the remaining slip 
 into a point intermediate between the mesial line and the 
 margin. Other chords, similarly divided, are inserted at 
 intervals in a direction from above downwards, or from base 
 to apex, the insertions in each case proceeding from the 
 mesial line towards the margin. The segments of the tri- 
 cuspid valve are thinner than those of the bicuspid. This is 
 traceable to the fact that the right heart is more feeble, and 
 has less work to perform, than the left one. As the chordae 
 tendineae are inserted into every portion of the bicuspid and 
 tricuspid valves, and freely decussate with each other in all 
 directions, by means of their terminal brush-shaped expan- 
 sions ; as, moreover, the chordae tendineae are of infinite 
 variety as regards length and strength, those at the base of 
 each segment being long and exceedingly strong, while those 
 at the margins and towards the apices are short, and in some 
 instances as delicate as hairs, it follows that every part of the 
 mitral and tricuspid valves is under the control of the conical- 
 
PHYSIOLOGY OF THE CIRCULATION. 2/3 
 
 shaped spiral musculi papillares, whose power to shorten and 
 lengthen is now well established 1 . There can be little doubt, 
 therefore, that the chordae tendineae are to be regarded as 
 the satellites of the constantly moving musculi papillares, 
 under whose guidance they have to perform, not only a very 
 important, but a very delicate function, and one which could 
 not by any possibility be accomplished by a simply mechanical 
 arrangement. 
 
 The Mitral and Tricuspid Valves of the Mammal in 
 Action. The theories which have long divided the attention 
 of physiologists as to the action of the mitral and tricuspid 
 valves are two in number; one sect maintaining that the 
 valves are acted itpon mechanically by the blood, as if they were 
 composed of inanimate matter ; the other believing that they 
 form part of a living system, their movements being traceable 
 to their connexion with the musculi papillares, which, as 
 explained, have the power of elongating and shortening. 
 
 According to the mechanical theory, the segments of the 
 valves are supposed to be passively floated up by the blood, 
 which acts upon them from beneath during the systole, and 
 brings their edges or free margins into such accurate apposi- 
 tion as enables the segments completely to occlude the 
 auriculo-ventricular orifices. In these movements the musculi 
 papillares and carneae columnae are said to take no part ; the 
 chordae tendineae acting mechanically, like so many stays, 
 to prevent eversion of the segments in the direction of the 
 auricles. 
 
 According to the vital theory, the segments of the valves 
 are supposed to be from the first under the control of the 
 musculi papillares ; these structures, when they shorten, draw- 
 ing the lips or free margins of the segments closely together 
 in the axes of the auriculo-ventricular openings to form two 
 impervious cones, the apices of which project downwards into 
 the ventricular cavities. 
 
 1 Dr. John Reid states from experiment, that the carneae columnae act simul- 
 taneously with the other muscular fibres of the heart, and that the musculi 
 papillares are proportionally more shortened during their contraction than the 
 heart itself taken as a whole. He attributes this to the more vertical direction of 
 the musculi papillares, and to their being free towards the base and in the 
 direction of the ventricular cavities. 
 
 T 
 
274 PHYSIOLOGY OF THE CIRCULATION. 
 
 In these movements, it is said, the blood takes no part, the 
 chordae tendineae, which are regarded as the proper tendons 
 of the musculi papillares, acting as adjusters or adapters of 
 the segments, a function which their varying length and 
 strength readily enables them to perform. 
 
 I need scarcely add that these theories are diametrically 
 opposed to each other. 
 
 In the valvular controversy, as in most others, a certain 
 amount of truth is to be found on either side ; and I have 
 to express my conviction that both theories (conflicting 
 though they appear) are virtually correct so far as they go, 
 but that neither the one nor the other is sufficient of itself to 
 explain the gradual, and to a certain extent self-regulating, 
 process by which the auriculo-ventricular valves are closed 
 and kept closed. On the contrary, I believe that the closure 
 is effected partly by mechanical and partly by vital means. 
 In other words, that the blood towards the end of the diastole 
 and the beginning of the systole forces the segments in an 
 upward direction, and causes their margins and apices to be 
 so accurately applied to each other as to prevent even the 
 slightest regurgitation ; whereas during the systole, and to- 
 wards the termination of that act, the valves are, by the 
 shortening of the musculi papillares, dragged down by the 
 chordae tendineae into the ventricular cavities to form two 
 dependent spiral cones. 
 
 Granting that my explanation is correct, there is yet another 
 point as to the manner of the closure ', to which I am particularly 
 anxious to direct attention, as it is of primary importance, 
 and appears to have hitherto escaped observation. I refer to 
 the spiral form assumed by the blood in the ventricular 
 cavities, which, as has been already explained, causes it, 
 towards the end of the diastole and the beginning of the 
 systole, to act in spiral waves (Fig. 104,7', & P- 2O ) mechanically 
 on the under surface of the segments, with the effect of twisting 
 and wedging them into each other in a spiral upward direction 
 (Figs. 142, 143, min^r s, p. 281). The segments of the aortic 
 and pulmonic valves are twisted and wedged into each other by 
 the refluent blood in a direction from above downwards (Fig. 
 141, v wx, rst,p. 281). I allude also to the spiral course pursued 
 by the musculi papillares (Fig. 103, m n, p. 197); these structures 
 
PHYSIOLOGY OF THE CIRCULATION. 2/5 
 
 as the systole advances shortening in such a manner as occasions 
 the spiral descent of the segments into the ventricular cavities 
 (Fig. 141, m n, r s, p. 28 1) , to form two spiral dependent cones, the 
 apices of which are directed towards the apices of the ven- 
 tricles. As the decrease of the blood in the ventricles is 
 followed, as has been stated, by a corresponding increase in 
 the auricles, the blood in the auricles assists in keeping the 
 free margins and apices of the segments from being everted 
 by the uniform pressure exercised on them by the blood 
 in the ventricles during the systole. From this account of 
 the closure of the auriculo-ventricular valves it will be evident 
 that the bicuspid and tricuspid valves form two movable 
 partitions or septa, which rise and fall during the diastole and 
 systole of the heart, in the same way that the diaphragm 
 rises and falls during expiration and inspiration. The advan- 
 tage of such an arrangement is obvious. When the ventricles 
 are full of blood, and the auricles empty, or comparatively so, 
 the valvular septa are convex towards the base of the heart, 
 and protrude into the auricular cavities (Figs. 143, 144, p. 281). 
 When, on the other hand, the auricles are full of blood, and the 
 ventricles all but drained of it, the valvular septa are dragged 
 downwards into the ventricular cavities to form inverted cones 
 (Fig. 141, p. 281). Certain portions therefore of the auriculo-ven- 
 tricular cavities are common alike to the auricles and to the 
 ventricles ; and it is important to note this fact, as the valvular 
 septa, by their rising and falling, at one time increase the 
 size of the ventricular cavities, while they diminish the 
 auricular ones, and vice versa. The principal object gained 
 by the descent of the segments into the ventricles is the 
 diminution of the ventricular cavities towards the base ; the 
 dependent cones formed by the valves fitting accurately into 
 the conical-shaped interspaces situated between the slanting 
 heads of the musculi papillares and the auriculo-ventricular 
 fibrous rings. As the musculi papillares, when the ventricles 
 close, mutually embrace and twine round each other, the 
 obliteration of the ventricular cavities is readily effected. 
 
 An important inference to be deduced from the spiral 
 nature of the ventricular fibres and ventricular cavities and 
 the undoubted spiral action of the auriculo-ventricular valves, 
 is the effect produced on the blood as it leaves the ventricles, 
 
 T 2 
 
2/6 PHYSIOLOGY OF THE CIRCULATION. 
 
 that fluid being projected by a wringing or twisting movement, 
 which communicates to it a gliding spiral motion. This view 
 is favoured by the spiral inclination of the sinuses of Valsalva 
 to each other, these structures as has been already explained 
 gradually introducing the blood so projected into the vessels. 
 The phrase ' wringing the heart's blood ' is consequently true 
 in fact. It is not a little curious that other hollow viscera 
 besides the heart, as the bladder and uterus, also expel their 
 contents spirally. 
 
 The Mechanical and Vital Theories of the Action of the 
 Mitral and Tricuspid Valves considered. That the theory 
 which attributes the closure of the auriculo-ventricular valves 
 to the mechanical floating up of the segments from beneath 
 by the blood, forced by the auricles ] into the ventricles, 
 distending equally in all directions 2 , is of itself inadequate to 
 explain all the phenomena, is, I think, probable from analogy 
 and the nature of things ; for if a merely mechanical arrange- 
 ment of parts was sufficient for the closure of the auriculo- 
 ventricular orifices, then it may be asked, why were these 
 apertures in birds and mammals not furnished with sigmoid 
 or semilunar valves similar in all respects to those met with 
 in the veins and arteries ? The answer to this question is no 
 doubt to be found in the nature of the structures in which 
 the valves are situated, as well as in the circulation itself. 
 In the veins, as is well known, the movements of the blood are 
 sluggish the closure of the vessels being feeble, and not 
 consequently calculated to interfere to any great extent with 
 the closing of the valves. In the arteries, where the circulation 
 is more vigorous, and the closure of the vessels more decided, 
 the valves are surrounded by dense fibrous rings, which 
 protect them from the opening and closing alike of the 
 ventricles and vessels. No such fibrous rings occur in the 
 bulbus arteriosus of fishes, and as a consequence the valves 
 are exposed to the influence of muscular movements. To 
 
 1 According to Harvey, Lower, Senac, Haller, and others, the auricles contract 
 with a very considerable degree of energy. 
 
 2 ' In a quantity of fluid submitted to compression, the whole mass is equally 
 affected and similarly in all directions.' Hydrostatic Law. Dr. George Brit ton 
 Halford attributes the closure of the auriculo-ventricular valves entirely to the 
 pressure exercised by the auricles on the blood forced by them into the ventricles. 
 That however this is not the sole cause, will be shown further on. 
 
PHYSIOLOGY OF THE CIRCULATION. 27; 
 
 obviate this difficulty the segments of the valves are not only 
 increased in number^ but chordae tendineae, in the shape of 
 tendinous bands, begin to make their appearance. In the 
 auriculo-ventricular valves of fishes and reptiles, chordae ten- 
 dineae in various stages of development are discovered, these 
 being attached to the interior of the ventricle to more or 
 less fully developed musculi papillar es. The musculi papillares 
 in fishes and reptiles are in no instance so well marked as in 
 birds and mammals. As we rise in the scale of being, and 
 the requirements of the circulation become greater, it will be 
 observed that the relation of the segments to actively moving 
 structures becomes more and more denned. In the ventricle 
 of the fish, as I pointed out, the fibres proceed in wavy lines 
 from base to apex, and from apex to base, from without 
 inwards and circularly ; so that the organ closes and opens 
 very much as one would shut and open the hand. In the 
 reptilia the external and internal fibres pursue a slightly spiral 
 direction the ventricles rotating more or less when in action. 
 In the cold-blooded animals moreover, as every one is aware, 
 the circulation is languid or slow, so that an arrangement of 
 valves similar in some respects, though more complex than 
 that which exists in the veins and venous sinuses and in the 
 arteries, amply suffices. In the hearts however of the warm- 
 blooded animals, where the ventricles are composed entirely 
 of spiral fibres, and where the circulation, on account of the 
 sudden twisting and untwisting of the fibres, is rapid, a system 
 of valves which will act with greater alacrity and precision 
 is absolutely necessary. But functional precision implies 
 structural excellence ; and hence that exquisite arrangement 
 of parts in the auriculo-ventricular valves of mammals, where- 
 by every portion of every segment (by reason of the ever- 
 varying length and strength of the chordae tendineae) bears a 
 graduated relation to the musculi papillares and carneae 
 columnae. Although the partial closing of the valves during 
 the diastole is occasioned by the uniform expansion of the 
 blood owing to the force exercised upon it by the closure of 
 the auricles, still it must be evident to all who reflect, that 
 this cause is not of itself adequate to the complete closure, 
 and for a very obvious reason. The blood which is the 
 expanding force, enters the ventricular cavities by the 
 
278 PHYSIOLOGY OF THE CIRCULATION. 
 
 auriculo-ventricular orifices. Once in the ventricles, however, 
 the blood has no inherent expansive power by which it can of 
 its own accord entirely shut off or close the apertures by 
 which it entered. This act requires for its consummation the 
 force exercised by the closure of the ventricles at the com- 
 mencement of the systole. Admitting however that the 
 expansion of the blood was adequate to the closure of the 
 auriculo-ventricular valves at one period, say at the end of 
 the ventricular diastole, when the ventricles are full of blood 
 and the auriculo-ventricular orifices widest, it is scarcely 
 possible that it could keep them closed towards the end of the 
 systole, when the auriculo-ventricular orifices are greatly 
 diminished in size and the blood itself all but -ejected. A 
 regulating and motor power therefore, in addition to the 
 blood, for adapting the different portions of the segments 
 of the valves to the varying conditions of the auriculo-ven- 
 tricular orifices and cavities during the systole, seems requisite. 
 Such a power, in my opinion, resides in the conical-shaped 
 spiral musculi papillares with their proper tendons, the 
 chordae tendineae. 
 
 That the theory which ascribes the closing of the auriculo- 
 ventricular valves entirely * to the contraction of the musculi 
 papillares,' is likewise of itself insufficient, appears for the 
 following reasons : 
 
 1st, If the valves which, at the commencement of the ven- 
 tricular diastole, are floated mechanically upwards, and have 
 their edges approximated by the blood towards the ter- 
 mination of the diastole, were dragged upon at the beginning 
 of the systole from above downwards, or in an opposite direc- 
 tion to that in which the force by which they were brought 
 together acts, the segments of the valves, instead of being 
 further approximated, would inevitably be drawn asunder, and 
 regurgitation to a fatal extent supervene. 
 
 2nd, By such an arrangement as Dr. Halford has satisfac- 
 torily shown, the cavities of the ventricles would not only be 
 materially diminished at a very inconvenient time 1 , but a 
 
 1 Dr. Halford states his belief, ' that the segments of the valves are forced even 
 beyond the level of the auriculo-ventricular orifices, and in this way become con- 
 vex towards the auricles, and deeply concave towards the ventricles.' On the Time 
 and Manner of Closure of the Auriculo-ventricular Valves. Churchill, London, 1861. 
 In his zeal for the enlarged accommodation of the ventricles, Dr. Halford forgets 
 
PHYSIOLOGY OF THE CIRCULATION. 279 
 
 certain amount of the force required for the expulsion of the 
 blood from the ventricular cavities would be expended in 
 closing the valves. 
 
 The auriculo-ventricular valves are so constructed and so 
 placed that they equally obey the impulses communicated 
 by the blood and by the musculi papillares. Thus, as the 
 blood finds its way into the ventricular cavities, the segments 
 of the valves are floated upwards upon its surface like the 
 leaves of water-plants. This floating upwards brings the 
 delicate margins of the segments into such accurate ap- 
 position, that they are closed the instant the ventricles begin 
 to contract, an arrangement which effectually prevents re- 
 gurgitation. The sudden closure of the ventricles upon their 
 contained blood has the effect of momentarily forcing the 
 valves in an upward direction into the auricular cavities a 
 movement limited by the chordae tendineae, which effectually 
 prevent eversion. The upward movement is gradually checked 
 as the systole advances and the musculi papillares shorten ; 
 the valves being made to descend upon the blood rapidly 
 disappearing from the ventricular cavities. In this move- 
 ment the valves form depending cones, the sides of which 
 fit accurately into the conical spaces formed at the base of 
 the heart by the slanting heads of the musculi papillares. 
 The ventricular cavities are diminished towards the base 
 of the heart by the depending position of the segments of 
 the mitral and tricuspid valves towards the end of the 
 systole. If to this be added the fact that, at this particular 
 period, the musculi papillares twine into and around each 
 other so as to become strongly embraced, and the ventricles 
 are greatly diminished from below upwards and from without 
 inwards, it will not be difficult to understand how the ven- 
 tricular cavities are drained of blood during the systole. 
 
 that the auricles are equally entitled to consideration, and that it is unfair to give 
 to the one and take from the other ; for if, as he argues, the segments of the valves 
 form convex partitions, whose convexities throughout the entire systole of the ven- 
 tricles point in the direction of the auricles, the space beyond the level of the 
 auriculo-ventricular orifices is appropriated from the auricles without compensation. 
 As, however, such an arrangement could not fail materially to inconvenience the 
 auricles when they are fullest of blood, we naturally turn to the ventricles for 
 redress. The additional space required is, as I have already shown, supplied by 
 the descent of the segments of the bicuspid and tricuspid valves towards the end of 
 the systole, when the ventricles are almost draiaed of blood. 
 
28O PHYSIOLOGY OF THE CIRCULATION. 
 
 It therefore appears to me that the auriculo-ventricular 
 valves are alternately active and passive, there being a brief 
 period when they are neither the one nor the other. 
 
 The passive state corresponds to the diastole or opening 
 of the ventricles ; the active state, to the systole or closing ; 
 and the neutral or intermediate state, to that short interval 
 which embraces the termination of the diastole and the 
 commencement of the systole. In speaking of the closure 
 of the valves, it is of great importance to remember that the 
 action, although very rapid, is a strictly progressive one, and 
 necessarily consists of stages. In this however, as in many 
 other vital acts, it is often very difficult, if not indeed im- 
 possible, to say precisely where the one stage terminates ancl 
 the other begins. As the action of the valves is, to a cer- 
 tain extent, dependent upon and induced by the action of 
 the auricles and ventricles, the following slight differences 
 as regards time are to be noted. The passive state of the 
 valves corresponds to that period in which their segments are 
 floated mechanically upwards, and their margins partially ap- 
 proximated by the blood forced by the auricles into the 
 ventricles ; the .neutral state, to that almost inappreciable 
 interval which succeeds the sudden closure of the ventricles, 
 in which the blood set in motion is arranged in spiral 
 columns, and acts in such a way as not only instantly closes 
 the valves, but screws and wedges the segments thereof into 
 each other 1 , in an upward spiral direction. The active state 
 corresponds to the period occupied by the progressive closing 
 of the ventricles. During this period the valves are dragged 
 forcibly downwards by the shortening of the musculi papillares, 
 in an opposite direction to that by ivhich they ascended ; and 
 are twisted into or round each other to form spiral dependent 
 cones. In the active stage, as in the neutral, the blood acts 
 from beneath, and keeps the delicate margins and apices 
 of the segments of the valves in accurate contact. The 
 appearances presented are represented at Figs. 141 144, 
 p. 281. 
 
 1 This act takes place just before the blood finds its way into the aorta and 
 pulmonary artery, the amount of pressure required for shutting and screwing home 
 the auriculo-ventricular valves being less than that required for raising the semi- 
 lunar ones. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 28l 
 
 That the foregoing is the true explanation of the gradual 
 approximation and continued closure of the auriculo-ven- 
 tricular valves, there can, I think, be little doubt, both from 
 the disposition and structure of the parts, and from experi- 
 
 Fig. 141. 
 
 Figs. 141, 142 and 143 show the mitral (r s) and tricuspid (m in) valves in action (human) : how the seg- 
 ments, acted upon by the spiral columns of blood, roll up from beneath towards the end of the diastole 
 (Fig. 141) ; how, at the beginning of the systole, they are wedged and twisted into each other, on a level 
 with the auriculo-ventricular orifices (Fig. 142) ; and how, if the pressure exerted be great, they project 
 into the auricular cavities (Fig. 143). When the mitral and tricuspid valves (Fig. 141 r s, m n) are open, 
 the aortic and pulmonic semilunar valves (v TV x, r s t) are closed. When, on the other hand, the mitral 
 and tricuspid valves are closed (Figs. 142, 143- and 144. r s, m i n), the aortic and pulmonic semilunar 
 ones (vwx,rst) are open. To this there is no exception. Original. 
 
 Fig. 143- 
 
 Fig. 144 shows a human heart with a true mitral valve in both ventricles as seen in action at the com- 
 mencement of the systole. The letters are the same as in Figs. 141, 142, U3- Original. 
 
 Note. The spiral downward movement of the mitral and tricuspid valves (Fig. 141) has onlybeen partly 
 shown, from the difficulty experienced in representing spiral cavities. 
 
 ment. If, c.g.^ the coagula be carefully removed from per- 
 fectly fresh ventricles, and two tubes of appropriate calibre 
 be cautiously introduced past the semilunar valves, and se- 
 curely fixed in the aorta and pulmonary artery 1 , and the 
 
 1 Strictly speaking, the tubes should be introduced into the auriculo-ventricular 
 orifices, as it is through these apertures that the blood passes during the dilatation 
 
282 PHYSIOLOGY OF THE CIRCULATION. 
 
 preparation be sunk in water until the ventricular cavities 
 fill, it will be found, when one of the tubes 1 , say that fixed 
 in the aorta, is carefully blown into, that the segments of 
 the bicuspid valve roll up from beneath in a spiral direction 
 (Fig. 141, rs, p. 281), in a progressive and gradual manner ; each 
 of the two larger or major segments, by folding upon itself, 
 more or less completely, in a direction from within outwards, 
 forming itself into a provisional or temporary cone, the apex 
 of which is directed towards the apex of the left ventricle 
 (first stage in which the crescentic margins and apices of the 
 segments are slowly approximated by the uniform expansion 
 of tJie blood forced into the ventricle by the auricle}. As the 
 pressure exerted by the air is gradually increased, and the 
 action of the valve is further evolved, the segments, folded 
 upon themselves as described, are gradually elevated^ until they 
 are on the same plane with the auriculo-ventricular fibrotts 
 ring, where they are found to be wedged and screwed into each 
 other, and present a level surface above (Fig. 142, r s, p. 281). 
 At this, the second stage of the closure, the crescentic 
 margins of the segments are observed to be accurately ap- 
 plied to each other, to form two perpendicular crescentic walls, 
 which accord in a wonderful manner with similar walls formed 
 by the union of the semilunar valves (Fig. 133 C, b, p. 252) ; 
 in fact the manner of closure is, to a certain extent, the 
 same in both ; the segments in either case being folded upon 
 themselves by the blood, and presenting delicate crescentic 
 margins, which are flattened against each other in proportion 
 to the amount of pressure employed. When the crescentic 
 margins of the segments are so accurately applied to each 
 other as to become perfectly unyielding, and the distending 
 process is carried beyond a certain point, the bodies or 
 central portions of the segments bulge in an upward or 
 downward direction respectively, the segments of the mitral 
 valve protruding into the auricle (Fig. 143, r s, p. 281) ; those of 
 
 of the ventricles. As, however, the insertion of tubes, however small, into the 
 auriculo-ventricular openings would necessarily prevent the complete closure of the 
 valves, that is one good reason for adopting the plan recommended in the text. 
 
 1 Thin metallic tubes with unyielding parietes are best adapted for this purpose, 
 as they can be readily fixed in the vessels, and the amount of pressure exercised by 
 the breath on the valves easily ascertained. 
 
PHYSIOLOGY OF THE CIRCULATION. 283 
 
 the semilunar ones into the ventricle (Fig. 134, p. 253, and 
 Fig. 141, v w x t r s t> p. 281). Compare Figs. 85 and 86, 
 
 P- 174. , 
 
 This completes the first and second stages of the process 
 by which the mitral or bicuspid valve is closed ; but the 
 more important, as being the more active and difficult, is 
 yet to come. This consists in adapting the segments of the 
 valve to the gradually diminishing auriculo-ventricular orifice ; 
 and in dragging them down into the left ventricular cavity^ 
 to diminish the ventricle towards the base. By this act, 
 the segments, as has been shown, are made to form a spiral 
 dependent cone, an arrangement which renders the oblitera- 
 tion of the left ventricular cavity towards the base a matter 
 of certainty. 
 
 The third stage of the closure of the mitral valve entirely 
 differs from the first and second stages, inasmuch as the 
 chordae tendineae, when the musculi papillares shorten, 
 drag the segments in a downward direction, to adapt them 
 to the altered conditions of the auriculo-ventricular orifice 
 and ventricular cavity. That this downward movement 
 actually takes place, is proved as follows: If a portion of 
 the fluid be withdrawn by applying the mouth to the tube 
 in the aorta, so as to create a certain amount of suction, 
 the segments of the bicuspid valve are found gradually to 
 descend in a spiral direction (Fig. 141,7/2, n, p. 281), forming as 
 they do so a spiral cone, whose apex becomes more and 
 more defined in proportion as the suction is increased ; the 
 water in the interior keeping the margins of the seg- 
 ments accurately in apposition, and thereby preserving the 
 symmetry of the cone. If, again, the musculi papillares be 
 cut out of the ventricular walls and made to act in the di- 
 rection of their fibres, i. e. in a spiral direction from left to 
 right downwards, they will be found, in virtue of being 
 connected by the chordae tendineae more or less diagonally 
 to either segment of the bicuspid valve, to act simultaneously 
 on that side of the segment which is next to them ; the 
 anterior musculus papillaris acting spirally on the margin 
 and apex of the larger or anterior segment ; the posterior 
 musculus papillaris acting spirally on the margin and apex 
 of the smaller or posterior segment, in a precisely opposite 
 
284 . PHYSIOLOGY OF THE CIRCULATION. 
 
 direction. The effect of these apparently incongruous move- 
 ments on the segments is very striking. 
 
 The space which naturally exists between the segments 
 is gradually but surely diminished, and the segments twisted 
 into or round each other to form the spiral dependent cone 
 referred to. 
 
 This arrangement, I may observe, while it facilitates the 
 spiral movement, absolutely forbids any other. 
 
 The closure is rendered perfect by the pressure exercised 
 on the delicate margins of the segments by the spiral columns 
 of blood, as already explained. 
 
 By the time the blood is ejected from the left ventricle, 
 and the segments of the mitral valve have formed the spiral 
 dependent cone, the left auricle is distended ; and due ad- 
 vantage being taken of the extra space afforded by the 
 descent of the mitral valve, the blood assumes a spiral wedge- 
 shaped form, which is the best possible for pushing the 
 segments of the mitral valve in an outward direction, these 
 being in the most favourable position for falling away from 
 the ventricular axis towards the ventricular walls. The same 
 phenomena are repeated, with unerring regularity, with each 
 succeeding action of the heart. What has been said of the 
 manner of closure of the mitral or bicuspid valve applies, 
 I need scarcely add, with slight modifications to the tricuspid. 
 
 The Sounds of the Heart ; to what owing. With regard 
 to the sounds of the heart and their mode of production, 
 there is much discrepancy of opinion. Harvey was aware of 
 their existence, and compared them to the sounds produced 
 by the passage of fluids along the oesophagus of the horse 
 when drinking. Laennec was the first strongly to direct 
 attention to them. He described their character, the order 
 of their succession, and showed how a knowledge of them 
 would enable us to detect many cardiac lesions. He has 
 therefore laid the profession under lasting obligations. The 
 sounds have been divided for convenience into two, a first 
 and second sound. The first sound is dull, deep, and pro- 
 longed ; and the second, which follows immediately after 
 the first, is quick, sharp, and more superficial l . The second 
 
 1 These sounds have also been called inferior and superior, long and short, dull 
 and sharp, systolic and diastolic. 
 
PHYSIOLOGY OF THE CIRCULATION. 285 
 
 sound was compared by Laennec to the flapping of a valve 
 or the lapping of a dog; the first and second sounds being 
 likened by Dr. Williams to the syllables ' lupp, dupp.' The 
 first sound immediately precedes the radial pulse, and cor- 
 responds with the impulse of the heart against the thorax, 
 the closure and susurrus of the ventricles, the rush of the 
 blood through the aortic and pulmonic valves, and the 
 closing and tightening of the auriculo-ventricular valves and 
 chordae tendineae. The second sound coincides with the 
 closure and susurrus of the auricles, the rush of the blood 
 through the auriculo-ventricular orifices into the ventricular 
 cavities, the opening of the auriculo-ventricular valves, and 
 the closing of the aortic and pulmonic valves. As the 
 different substances set in motion by the action of the heart, 
 such as the blood, valves, muscular fibres, etc., are all capable 
 of causing sound, it is reasonable to conclude that the several 
 structures and substances moving at the time the sound is 
 heard are one and all concerned in its production. It is 
 this circumstance, combined with the fact that sound once 
 propagated repeats itself or echoes sounds of different in- 
 tensity running into each other which makes it so ex- 
 ceedingly difficult to determine what actually produces the 
 sounds under consideration. What I mean will be understood 
 when I state, that at the same instant the ventricles are 
 closing and striking the chest, and while they are forcing 
 their blood through the pulmonary artery and aorta, opening 
 the aortic and pulmonic valves, and closing the mitral and 
 tricuspid ones at this same instant the heart is rolling 
 within the pericardium, and the venae cavae and the pul- 
 monic veins are closing, and forcing their blood into the 
 auricles, which are actively dilating to receive it. The sounds 
 produced by the latter movements are therefore, on our 
 part, unconsciously mixed up with the sounds produced by 
 the former movements, and must be added to them. When 
 again the auricles are closing and forcing their blood into 
 the ventricular cavities, when the auriculo-ventricular valves 
 are being pushed aside and opened, and the aortic and 
 pulmonic valves closed, at that same instant the ventricles, 
 the venae cavae, and pulmonic veins are actively dilating. 
 The sounds which one hears are consequently numerous 
 
286 PHYSIOLOGY OF THE CIRCULATION. 
 
 and of a mixed character, as regards intensity and duration ; 
 and to make matters worse, they run into each other by 
 insensible gradations, sometimes slowly, sometimes suddenly. 
 The sounds in fact merge into each other precisely in the 
 same way that the movements of the different parts of the 
 heart merge into each other. They have their points of 
 maximum and minimum intensity, and it is upon these the 
 physiologist and physician fixes when he attempts to define 
 their nature and duration. Such definitions I need scarcely add 
 are more or less arbitrary. The first and second sounds 
 are followed by apparent pauses the pauses corresponding 
 to the brief intervals which* follow the closing of the ven- 
 tricles and auricles respectively. Thus the dull, deep, pro- 
 longed, or first sound is followed by a short pause, while the 
 sharp, short, or second sound is followed by another and longer 
 pause. The sounds and the pauses which occur between 
 them follow in regular order, and when taken in connexion 
 with the closing and opening of the different parts of the 
 heart to which they owe their origin, constitute the rhythm 
 of the heart. They occasionally vary in duration, just as 
 the pulse varies in frequency, and in certain cardiac affec- 
 tions the sounds are increased in number, while the pauses 
 are decreased in duration. When the movements and sounds 
 of the heart are very irregular, the condition is expressed 
 by the term ' tumultuous.' Various attempts have been made 
 to represent the duration of the sounds and pauses in figures. 
 Thus some authors state that if the number 9 be made to 
 represent one complete pulsation, the first sound occupies 
 a third, the short pause a sixth, the second sound a sixth, 
 and the long pause a third. Others aver that if we divide 
 one entire action of the heart into four parts, the two first 
 will be occupied by the first sound, the third by the second 
 sound, and the fourth by the pause ; all which proves very 
 conclusively that the sounds and pauses run into each other 
 and cannot be separated with any degree of accuracy. When 
 so many causes exist it is exceedingly difficult, perhaps 
 dangerous, to particularise. There are however many cir- 
 cumstances which induce me to believe that the susurrus, 
 or sound produced by the opening and closing of the auricles 
 and ventricles, and the rushing of the fluid blood against 
 
PHYSIOLOGY OF THE CIRCULATION. 287 
 
 the valves and into the cavities and vessels of the heart, 
 constitute the major factors, the opening and closing of the 
 valves the minor. 
 
 The Dublin committee, appointed to investigate this matter, 
 concluded that the first sound is produced either by the 
 rapid passage of the blood over the irregular internal surface 
 of the ventricles on its way towards the mouth of the arteries, 
 or by the bruit musculaire (susurrus) of the ventricles, or 
 probably by both of these causes. The London committee, 
 appointed for a like purpose, came to similar conclusions. 
 It found that the sound produced by the contraction (shorten- 
 ing) of the abdominal muscles, as heard through a flexible 
 tube, resembles the systolic sound, and that the impulse of 
 the heart against the chest in certain positions of the body 
 intensified this sound. M. Marc D'Espine maintained that 
 both the first and second sounds depend on muscular move- 
 ments the first sound upon the systole and the second 
 upon the diastole of the ventricles. D'Espine, it will be 
 observed, attributes sound both to the diastole or opening 
 of the ventricles, and to the systole or closing of them, and 
 in this I think he is perfectly correct the opening and 
 closing of the different parts of the heart, as I have en- 
 deavoured to show, being equally vital movements. That 
 muscle invariably produces sound during its action is well 
 known ; and that a powerful compound muscle like the heart, 
 with fibres interlacing in every direction, should, when closing 
 and opening in hollow cavities such as the pericardium and 
 thorax, produce audible and characteristic sounds, is what 
 we would a priori expect. That sound may be produced 
 by the impinging of fluids against animal tissues, or by 
 the trituration of the particles of the fluid itself, can be 
 proved by direct experiment. Valentin, e.g., showed that 
 if a portion of a horse's intestine be tied at one end, and 
 moderately distended with water without any admixture of 
 air, and a syringe containing water be fixed into the other 
 end, by pressing the piston of the syringe down, and forcing 
 in more water, the first sound is exactly imitated. When, 
 on the other hand, the aortic or pulmonic valves are diseased, 
 their surfaces roughened, and the apertures which they guard 
 diminished, the character of the first sound is altered. 
 
288 PHYSIOLOGY OF THE CIRCULATION. 
 
 Laennec and Dr. C. J. B. Williams regard the susurrus or 
 noise produced by the contracting (closing) ventricles as the 
 exclusive cause of the first sound ; and the latter endeavoured 
 to prove the point by cutting away the aorta and pulmonic 
 vessels, and by placing the fingers in the auriculo-ventricular 
 orifices, so as to exclude the blood. He found under these 
 circumstances that the sound was still produced. I cannot 
 however agree with Laennec and Dr. Williams when they 
 state that the contraction (closure) of the ventricles is the 
 sole cause ; for, in cases of hypertrophy of the heart, the in- 
 tensity of the first sound, instead of being increased, which 
 it would be if solely due to the closing of the ventricles, is 
 diminished. An attempt has been made to clear away this 
 difficulty by saying that in such cases the susurrus of the 
 superficial fibres alone is heard. That the first sound is in 
 part due to the ventricular susurrus must, I think, be con- 
 ceded, but that it is also due to the attrition of the blood 
 against the great vessels and valves seems proved, 1st, by 
 the experiment of Valentin with the piece of intestine already 
 quoted ; 2nd, by cases of anaemia, where the character of the 
 sound is changed, although the valves and vessels are healthy ; 
 and 3rd, by cases of diseased valves and vessels where the 
 character of the sound is altered, the blood being normal. 
 Rouanet, Billing, and Bryan referred the first sound to the 
 rapid approximation of the auriculo-ventricular valves during 
 the contraction (closure) of the ventricles. This however 
 cannot be the sole cause ; for, as I pointed out when ex- 
 plaining the action of these valves, their movements are not 
 sudden but gradual and progressive. The auriculo-ventri- 
 cular valves, in fact, move up and down like diaphragms as 
 the systole proceeds. Thus they are elevated at the begin- 
 ning of the systole, and drawn down or lowered towards the 
 end of it. Bouillaud attributes the first sound partly to the 
 closing of the auriculo-ventricular valves, and partly to the 
 sudden opening of the pulmonic and aortic valves ; while 
 Mr. Carlisle refers it to the rush of blood along the pulmonary 
 artery and aorta, occasioned by the contraction (closure) of 
 the ventricles. The first sound, there are good grounds for 
 believing, is referable, ist, to the ventricular susurrus ; 2nd, to 
 the impinging of the blood against the auriculo-ventricular 
 
PHYSIOLOGY OF THE CIRCULATION. 289 
 
 and semilunar valves; 3rd, to the closing of the auriculo- 
 ventricular valves and the opening of the semilunar ones ; 
 4th, to the impulse of the heart ; 5th, to the flow of blood 
 into the auricles, caused by the closing of the cavae and 
 pulmonic veins ; and 6th, to the rolling of the heart within 
 the pericardium, 
 
 As Laennec attributed the first sound to the contraction 
 (closure) of the ventricles, so in like manner he referred the 
 second sound to the contraction (closure) of the auricles* 
 The susurrus of the auricles no doubt contributes to this 
 result, but the walls of the auricles are so thin that the share 
 they take in the production of the sound must be trifling. 
 
 M. Rouanet, Billing, Bryan, Carlisle, Bouillaud, and Dr. 
 Elliot have attributed the second sound principally to the 
 regurgitation of the blood in the aorta and pulmonary artery, 
 and the flapping together, closure, and tightening of the semi- 
 lunar valves ] . 
 
 Dr. C. J. B. Williams endeavoured to prove this by actual 
 experiment on the ass. He passed a common dissecting 
 hook through a segment of the pulmonic valve, with the 
 effect of weakening the normal sound and producing a hiss- 
 ing one. He then passed a curved shoemaker's awl through 
 a segment of the aortic valve, and the second sound ceased, 
 a hissing sound being substituted. This author states that 
 the second sound is loudest over the great vessels, and that 
 it is suspended if these are artificially occluded and the aurir 
 cles laid open. It must be admitted that the experiments 
 referred to are not of a delicate or exact character. By- 
 opening the auricles those structures lose the power they 
 possess of injecting the blood into the ventricular cavities: 
 the characteristic sounds produced by the impinging of the 
 blood against the auriculo-ventricular valves, chordae ten- 
 dineae, carneae columnae, and musculi papillares being re- 
 moved. By occluding the great vessels the sound resulting 
 from the flow or oscillation of the blood within them, as 
 apart from the effect produced on the valves, is destroyed 
 In healthy semilunar valves there is little, if any, regurgitation, 
 
 1 These valves are closed with considerable energy, partly because of the elasticity 
 of the great vessels, and partly because of the sucking action exerted by the ven- 
 tricles during the diastole. 
 
 U 
 
2QO PHYSIOLOGY OF THE CIRCULATION. 
 
 the segments, from their being more or less in contact at 
 the end of the systole, being closed by the slightest reflux, 
 and with almost no noise. By transfixing by hooks two of 
 the six segments composing the aortic and pulmonic semi- 
 lunar valves, an abnormal element is introduced which renders 
 the experiment of little value. The substitution of one sound 
 for another proves nothing, and if the second sound is de- 
 stroyed there is some fallacy, as only two of the six segments 
 which were supposed to produce it were restrained. I am 
 therefore disposed to put a different construction on the 
 results obtained by Dr. Williams, and to attribute the second 
 sound partly to the closure and susurrus of the auricles, but 
 mainly to the rush of blood into the ventricular cavities, and 
 against the auriculo-ventricular valves, chordae tendineae, 
 carneae columnae, and musculi papillares. To this is to be 
 added the flapping together of the semilunar valves, a slight 
 degree of regurgitation, and the susurrus produced by the 
 dilatation of the ventricles, venae cavae, and pulmonic veins. 
 
 As an illustration of the extreme difficulty experienced by 
 investigators in determining the precise nature of the move- 
 ments and sounds of the heart, I may cite the case of M. 
 Groux, who exhibited in his person an almost unique example 
 of congenital fissure of the sternum. Here we had the parts 
 in the vicinity of the heart opened up as it were for inspection. 
 M. Groux visited the principal schools on the Continent, in 
 America, Russia, and Britain, and was examined by upwards 
 of 2000 physicians, many of them eminently distinguished. 
 The discrepancy of opinion is quite remarkable. In M. 
 Groux's case, the fissure extended the whole length of the 
 sternum, and presented a Y-shaped appearance. In natural 
 respiration, the fissure was depressed to variable depths, and 
 had a transverse measurement at its upper boundary of one 
 inch and a quarter ; this increasing at the central part on a 
 level with the third and fourth ribs to an inch and a half, 
 and decreasing at the lower boundary of the fissure to a 
 quarter of an inch. Through the action of the pectoral 
 muscles, the hands being joined and pulling upon each 
 other, the fissure could be dilated to the width of about 
 two and a half inches. The fissure could be , increased 
 by forced expiration and decreased by forced inspiration. 
 
PHYSIOLOGY OF THE CIRCULATION. 2QI 
 
 About the middle of the fissure, on a level with the fourth 
 rib, a large pulsating tumour could be seen and felt. In 
 a vertical line with the principal tumour were two smaller 
 ones, the one above, which could be felt ; the other below, 
 which could, like the large one, be seen and felt. I examined 
 the pulsating tumours with others interested in the heart 
 when M. Groux was in Edinburgh, and at first sight it 
 appeared as if no great difficulty would be experienced in 
 determining which parts of the heart produced the pulsations 
 and sounds. A closer examination however revealed in- 
 numerable difficulties, all traceable to the circumstances 
 already adverted to viz. that the movements and sounds of 
 the heart merge into each other by slow and sudden transi- 
 tions. This case, simple as it appeared, has baffled the most 
 expert physiologists and stethoscopists in all countries, so 
 that instead of a few valuable facts we have a mass of con- 
 flicting evidence of comparatively little value. By some the 
 large tumour has been supposed to be the aorta, by, others 
 the right auricle, by others the right ventricle, by others 
 the infundibulum or conus arteriosus, and by others the 
 arteria innominata. I have taken the pains to tabulate some 
 of those opinions. Professor Hamernjck (Prague), Dr. Wil- 
 helm Reil (Halle), Professor Baumgartner (Friburg), Professor 
 Forget (Strasburg), M. Jules Biclard, M. Aran, M. Piorry, 
 M. Pouchet (Rouen), Dr. Ernst (Zurich), Dr. R W. Pavy 
 (London), Dr. C. Radcliffe Hall (Torquay), and Dr. Robert 
 D. Lyons (Dublin), thought the pulsating tumour was the 
 right auricle; Sir James Paget, Dr. George Burrows, Dn 
 William Baly (London), and Dr. Traube (Berlin), that it was 
 the right ventricle ; Dr. Lionel S. Beale (London), Dr. John 
 Hughes Bennett (Edinburgh), and Dr. Charles C. King 
 (Galway), that it was the right auricle and ventricle; Dr. 
 Lombard (Liege), and Dr. Francis Sibson (London), that 
 it was the aorta and right auricle ; M. Boillaud and M. Marc 
 d'Espine (Geneva), that it was the aorta ; Professor Virchow, 
 that it was the right ventricle and conus arteriosus; Dr. 
 Carlisle (Belfast), that it was the ascending aorta and pul- 
 monary artery ; Dr. P. Redfern (Aberdeen), that it was the 
 aorta, right auricle, and ventricle ; Professor W. T. Gairdner 
 (Glasgow), that it was the right auricular appendage, aorta, and 
 
 U 3 
 
2Q2 PHYSIOLOGY OF THE CIRCULATION. 
 
 right ventricle ; and Dr. C. J. B. Williams (London), that it 
 was the right auricle, ventricle, pulmonary artery, and aorta. 
 
 The account given by Drs. Pavy and Williams of M. 
 Groux's pulsating tumour are very interesting. Dr. Pavy, 
 who believed it to be the right auricle, states that it rises 
 rapidly and suddenly, and instantaneously after falls with 
 that peculiar thrill, wave, or vermicular movement, proceeding 
 from above to below, which he pointed out as, at this period 
 of the heart's action, running through the parietes of the 
 auricle of the dog. Dr. Pavy, it will be observed, character- 
 ises the action of the auricle as progressive,--- the auricle 
 contracting (closing) with a peculiar thrill, wave, or vermicular 
 movement, proceeding from above to below. Dr. Williams, 
 who thought the pulsation corresponded with the right auricle, 
 states that the closing of the auricle immediately precedes 
 the closing of the ventricle ; the wave of motion, in slow 
 pulsations, beginning with the auricle, and rapidly passing 
 downwards to the ventricle. 
 
 In quick pulsations the closing of the auricle and the 
 closing of the ventricle appear synchronous (mark how the 
 auricular and ventricular movements glide into each other, 
 and with what rapidity). Dr. Williams goes on to say that, 
 by the aid of a small flexible ear-tube, with a narrow pectoral 
 end, he heard a distinct sound accompanying the commence- 
 ment of the auricular contraction or closure. It is faint, short, 
 or flapping, and ends in the less abrupt and more distinct 
 sound of the ventricular contraction or closure. When the 
 stethoscope is placed over the ventricle the flapping sound 
 of the auricle is not heard, but the vessel swells or rolls out 
 its peculiar sound, till it ends with the sharp clack of the 
 diastolic or valvular sound. Dr. Williams concludes from 
 this that each movement of the heart has its proper sound, 
 and that the reason why the auricular sound is not usually 
 heard is, that it is too faint to pass through the intervening 
 lung. Dr. RadclifTe Hall thought there were three distinct 
 degrees of distance of sound, indicating as many distinct 
 sources ; the sound in the presumed auricle being far more 
 superficial and bell-like than that produced by the aorta 
 above, or the right ventricle below. Dr. Williams thought he 
 made out two distinct valvular sounds. By placing the stetho- 
 
PHYSIOLOGY OF THE CIRCULATION. 293 
 
 scope over the aorta/he detected a simple sound (lubb-dup); 
 but when he placed it partly over the aorta, and partly over 
 the pulmonary artery, he obtained a double sound (lubb- 
 darrup) from the valves not closing at exactly the same 
 instant. This want of synchronism in the action of the aortic 
 and pulmonic valves occurs principally in disease ; but it 
 is also found in health, and tends to show that the closure 
 of the right and left ventricles is progressive, which is just 
 what we would expect when we remember that muscular 
 movements originate in. the sarCous elements and diffuse 
 themselves. 
 
 The nerves of the heart, from the influence they exert 
 upon its movements, come next to be considered. 
 
 The Ganglia and Nerves of the Heart, and their connexion with 
 the Cerebro-spinal and Sympathetic Systems in Mammalia. 
 
 The movements of the heart and the circulation generally 
 are directly and indirectly influenced by the nervous system. 
 This is sufficiently proved by the division and irritation of 
 such nerves as send filaments to the organ ; these experiments 
 being attended in some cases with a slowing of the heart's 
 action, and in others by quickening. Similar results are 
 obtained by the administration of certain active substances, 
 some of which paralyse and others stimulate the nerves 
 conducting to and from the heart The movements of the 
 heart, as is well known, cannot be controlled by efforts of 
 the will ; they are nevertheless influenced by certain mental 
 conditions, sudden joy being calculated to render the move^ 
 ments of the organ tumultuous ; and protracted grief and 
 watching to impede rather than quicken them. The intimate 
 connexion between the head and heart induced the ancients 
 to regard the heart as the seat of the affections a view which 
 is adopted in popular discourse. 
 
 The nerves of the heart are derived from two sources, viz; 
 the pneumogastric (nervus vagus, par vagum) and the sym- 
 pathetic (nerve of organic life, Bichat). 
 
 The pneumogastric and sympathetic nerves are compound 
 in their nature; i.e. they contain afferent or sensory and 
 efferent or motor nerve-filaments. 
 
2Q4 PHYSIOLOGY OF THE CIRCULATION. 
 
 The pneumogastric nerve has its origin within the cranium, 
 while the sympathetic lies outside the spinal chord. Both 
 however are connected by nerve-filaments to each other and 
 to the cranial and spinal nerves, an arrangement which in 
 part accounts for the involuntary rhythmic movements of the 
 heart, and for the influence exerted upon those movements by 
 certain mental states. Considerable difference of opinion 
 exists as to the exact nature of the so-called sympathetic and 
 cerebro-spinal nerves. There are two leading views : ' Ac- 
 cording to the one, which is of old date, but which has lately 
 been revived and ably advocated by Valentin, the sympathetic 
 nerve is a mere dependency, offset, or embranchment of the 
 cerebro-spinal system of nerves, containing no fibres but such 
 as centre in the brain and cord, although it is held that these 
 fibres are modified in their motor and sensory properties, 
 in passing through the ganglia in their way to and from the 
 viscera and involuntary organs. According to the other, the 
 sympathetic nerve (commonly so called) not only contains 
 fibres derived from the brain and cord, but also proper or 
 intrinsic fibres which take their rise in the ganglia ; and in its 
 communications with the spinal and cranial nerves, not only 
 receives from these nerves cerebro-spinal fibres, but imparts 
 to them a share of its own proper ganglionic fibres, to be 
 incorporated in their branches and distributed peripherally 
 with them. Therefore, according to this latter view, the 
 sympathetic nerve, commonly so called, though not a mere 
 offset of the cerebro-spinal nerves, yet receiving as it does a 
 share of their fibres, is not wholly independent, and for a like 
 reason the cerebro-spinal nerves (as commonly understood) 
 cannot be considered as constituted independently of the 
 sympathetic; in short, both the cerebro-spinal and sym- 
 pathetic are mixed nerves ; that is, the branches of either 
 system consist of two sets of fibres of different and inde- 
 pendent origin, one connected centrally with the brain and 
 cord, the other with the ganglia.' 
 
 In order to comprehend the relation existing between the 
 heart and the cerebro-spinal and sympathetic systems of 
 nerves, it will be necessary to speak first of the pneumogastric 
 and those branches which it sends to the heart ; second, of 
 such parts of the sympathetic as supply filaments to the 
 
PHYSIOLOGY OF THE CIRCULATION. 2Q5 
 
 organ ; and third, of those nervous extensions which connect 
 the pneumogastric, sympathetic, and cerebro-spinal nerves 
 together. This done, we shall then be in a position to 
 describe the meshes or plexuses formed by the splitting up 
 and mingling of the several nerves referred to at the base of 
 the heart, their distribution on the surface and in the sub- 
 stance of the organ, and the nature of the ganglionic en- 
 largements which characterise the cardiac nerve reticulations. 
 
 In man the pneumogastric nerve springs from that part of 
 the cerebro-spinal axis known as the medulla oblongata. It 
 issues from the jugular foramen, an aperture at the base of 
 the skull, and courses down the neck and chest to supply 
 filaments to the organs of voice, respiration, the alimentary 
 canal as far as the stomach, and to the heart. It is the 
 longest of the cranial nerves, and displays two ganglionic 
 enlargements or swellings, the one designated the ganglion of 
 the root of the pneumogastric, situated within the jugular 
 foramen ; the other the ganglion of the trunk of the pneumo- 
 gastric, situated half an inch or so below that opening. 
 
 The upper ganglion, viz. that of the root, is somewhat 
 spherical in shape, two lines in diameter, and of a grayish 
 colour ; the lower ganglion, viz. that of the trunk, being of a 
 flattened cylindrical form, ten lines in length, two in breadth, 
 and reddish in colour. In the neck the ganglion of the root 
 (upper ganglion) is connected by nerve-filaments with the 
 facial, the glosso-pharyngeal, spinal-accessory, and sympa- 
 thetic nerves ; the ganglion of the trunk (lower ganglion) being 
 connected in the same region with the hypo-glossal, spinal, 
 and sympathetic nerves. 
 
 In the thorax the branches of the right and left pneumo- 
 gastric nerves pursue somewhat different courses : the re- 
 current laryngeal branch on the right side curving backwards 
 and upwards round the first part of the right subclavian 
 artery, the recurrent laryngeal branch on the left side curving 
 backwards and upwards round the arch of the aorta. The 
 recurrent nerves send branches to the so-called deep cardiac 
 plexus, placed behind the pulmonary artery and aorta. The 
 pneumogastric nerves (right and left) supply branches to the 
 ear, pharynx, larynx, lungs, the oesophagus, stomach, spleen, 
 liver, and other organs. They also furnish two sets of nerves 
 
296 PHYSIOLOGY OF THE CIRCULATION. 
 
 to the heart a cervical and thoracic set : with these alone 
 we have to deal in the present instance/ 
 
 The cervical cardiac branches are given off by the pneumo- 
 gastric at the upper and lower portions of the neck. The 
 upper branches unite with the cardiac nerves of the sympa- 
 thetic, are few in number, and small. There is only one 
 lower branch. This, in the left side, crosses the arch of the 
 aorta, and terminates in what is called the superficial cardiac 
 plexus, situated in front of the pulmonary artery and aorta. 
 On the right side it unites with one of the cardiac nerves 
 and takes part in the formation of the deep cardiac plexus, 
 located, as explained, behind the pulmonary artery and aorta. 
 The nerves constituting the superficial and deep cardiac 
 plexuses are continuous with each other, and completely 
 envelop the great vessels (pulmonary artery and aorta) at 
 their origins. 
 
 The thoracic cardiac branches on the right side proceed from 
 the first part of the right recurrent laryngeal nerve, and the 
 trunk of the right pneumogastric nerve, where it is in contact 
 with the trachea; those on the left side proceeding from the 
 left recurrent laryngeal nerve. The thoracic branches assist in 
 the formation of the deep cardiac plexus. The pneumogastric 
 nerves, as will be seen from the foregoing account, are con- 
 nected with the cranfal nerves issuing from the head, with 
 the spinal nerves issuing from the spinal cord, and with the 
 sympathetic nerves lying in front of the spinal cord. 
 
 The sympathetic system supplies the major portion of the 
 nerves to the heart. It also sends branches to the lungs and 
 stomach, the upper part of the alimentary canal, the bladder, 
 uterus, and the coats of the blood-vessels. 
 
 The nerves of the sympathetic system consist of a com- 
 plicated series of ganglia, cords, and plexuses ; the ganglia 
 and the cords which extend between them being arranged 
 in a double row on either side of the spine, and corresponding 
 for the most part in situation with the bodies of the cervical, 
 dorsal, and lumbar vertebrae. There are, however, only three 
 ganglionic enlargements in the neck in man to seven verte- 
 brae, there being even fewer in some of the lower animals. 
 This state of matters is probably due to the ganglia in the 
 neck having at some period approximated >and coalesced. 
 
PHYSIOLOGY OF THE CIRCULATION'. 297 
 
 The sympathetic cervical ganglia in man are designated 
 superior, middle, and inferior, from their respective positions ; 
 one being placed at the base of the skull, a second at the root 
 of the neck, and the third above the head of the first rib. 
 They are united to the spinal nerves in their immediate 
 vicinity by short cords composed of white and gray matter ; 
 the white matter, it is believed, proceeding from the spinal 
 nerves to the ganglia, the gray matter from the ganglia to 
 the spinal nerves. The cords' extending between the ganglia 
 are similarly constituted. 
 
 The superior cervical ganglia are connected with certain of 
 the cranial nerves as well as with the spinal nerves. Thus 
 small twigs unite the superior cervical ganglion with the first 
 four spinal nerves, with the first and second ganglia of the 
 pneumogastric, with the ninth cranial nerve, and with the 
 petrosal ganglion of the glosso-pharyngeal nerve. Besides the 
 branches which it gives off to the spinal and cranial nerves, 
 the superior cervical ganglion supplies branches to the pharynx, 
 blood-vessels, and heart. 
 
 The middle and inferior cervical ganglia likewise supply 
 branches to the heart. 
 
 The branches given off by the three cervical ganglia of the 
 sympathetic are named respectively the superior, middle, and 
 inferior cardiac branches. 
 
 The cardiac branches vary in size, and also in their distri- 
 bution on the right and left sides. 
 
 The upper cardiac nerve of the right side proceeds from two 
 or more branches of the superior cervical ganglion, with occa- 
 sionally a branch from the main cord which connects the supe- 
 rior and middle cervical ganglia. In its passage down the neck 
 it is joined by filaments from the external laryngeal and the- 
 trunk of the pneumogastric, and as it enters the chest it unites 
 with the recurrent laryngeal. It contributes to the formation 
 of the deep cardiac plexus. On the left side the upper cardiac 
 nerve runs parallel with the left carotid artery until it reaches 
 the arch of the aorta, where it breaks up to assist in forming 
 the superficial or deep cardiac plexus according as it passes 
 in front of or behind that vessel. 
 
 The middle cardiac nerve on the right side communicates 
 with the upper cardiac nerve and the recurrent branch of the 
 
298 PHYSIOLOGY OF THE CIRCULATION. 
 
 pneumogastric. It sends filaments to the deep cardiac plexus. 
 The middle cardiac nerve on the left side also sends branches 
 to the deep plexus. 
 
 The inferior cardiac nerve on the right side communicates 
 with the middle cardiac and recurrent laryngeal nerves, and 
 terminates in the cardiac plexus at the arch of the aorta. On 
 the left side it unites with the middle cardiac nerve and ends 
 in the deep cardiac plexus. 
 
 The superficial and deep cardiac plexuses, as already stated, 
 are continuous with each other. They receive filaments from 
 the recurrent, lower cervical, and thoracic branches of the 
 right and left pneumogastric trunks ; and from the superior, 
 middle, and inferior cardiac nerves of the right and left 
 sympathetic trunks. They envelop the origins of the pulmo- 
 nary artery and aorta In a meshwork, after which they resolve 
 themselves on the anterior and posterior surfaces of the heart. 
 
 Thus the superficial cardiac plexus sends branches to the 
 anterior and right coronary arteries, and to the anterior portions 
 of the right and left auricles and ventricles ; the deep cardiac 
 plexus sending branches to the coronary sinus and left 
 coronary artery, and the posterior surface of the right and 
 left auricles and ventricles. A few of the branches forming 
 the superficial cardiac plexus pass backwards and appear on 
 the posterior surface of the heart ; a certain number of the 
 branches from the deep cardiac plexus passing forwards to 
 appear on the anterior surface of the heart. It is quite 
 correct to say that the surface and substance of the auricles 
 and ventricles are enveloped in a more or less uniform plexus. 
 The superficial and deep cardiac plexuses and their prolonga- 
 tions on the surface and in the substance of the heart display 
 numerous ganglionic enlargements, to be described presently. 
 
 The branches supplied by the pneumogastric and sympa- 
 thetic nerves to the heart on the right side of the human 
 subject are represented at Fig. 145. This figure also shows 
 the interlacing of the nervous filaments which forms the various 
 plexuses described, as well as the ganglionic enlargements, 
 which are a distinguishing feature of the plexuses. 
 
 In the lower animals the relations of the pneumogastric 
 and sympathetic nerves are less complicated than in man, and 
 if time had permitted it would have been interesting to trace 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 299 
 
 Fig. I4S- 
 
 Fig. 145 shows the nerve-filaments supplied to the heart by the pneumogastric and sympathetic nerves 
 on the right side in man (after Hirschfeld and Leveille). c, trunk of right pneumogastric nerve in neck. 
 * ganglion of trunk of right pneumogastric nerve, d trunk of great sympathetic aerve in neck, h, ditto 
 at root of neck, j, ditto in thorax, a, superior cervical ganglion of sympathetic nerve, f, middle cer- 
 vical ganglion of sympathetic. /', inferior cervical ganglion of sympathetic, e, superior cardiac nerve. 
 g, middle cardiac nerve, o, nerve from middle cervical ganglion of sympathetic proceeding to right re- 
 current laryngeal nerve (/). k, intercostal nerves. /, intercostal vein, m, intercostal artery furnished 
 with nerve from ganglion of sympathetic. , intercostal nerve receiving branch from trunk of sympa- 
 thetic, q, innominate artery, r, trachea with nerves proceeding to deep cardiac plexus, s, arch of 
 aorta with nerve-plexus, dragged forward by a hook. /, posterior or deep cardiac plexus with ganglion. 
 u, pulmonary artery with nerve-plexus, v, superior cava cut across. ?v, right auricle with nerve-plexus. 
 r, right ventricle with nerve-plexus, y, plexus of nerves investing the vessels occupying the horizontal, 
 or right auriculo-ventricular groove, z, a similar plexus investing the vessels occupying the vertical ven- 
 tricular groove anteriorly. 
 
3 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 the gradations through which the nerves furnished to the 
 heart by the pneumogastric and sympathetic in some of the 
 lower animals pass. I have dissected them in the cat, rabbit, 
 and calf, and find that, while the branches supplied by the 
 pneumogastric nerves are tolerably constant, those furnished 
 by the ganglia of the sympathetic and the ganglia themselves 
 vary. Thus, in the cat, according to my dissections, only four 
 
 Fig. 146. 
 
 Fig. 147. 
 
 Fig. 146. Nerves and ganglia on anterior surface of calf's heart, a, fi, pulmonary artery and aorta 
 with nerve-plexuses and ganglia, i", descending cava with nerve-plexus and ganglia, c, right auricle, d, 
 left auricle, e. Nerves and ganglia distributed on right side of heart, f, ditto on left side, g, anterior 
 coronary vessels covered with nerve-plexuses and gang i-. Original. 
 
 Fig. 147. Nerves and ganglia on posterior surface of calf's heart, i, descending cava. c, nerves and 
 ganglia on right auricle, d, ditto on left. e. nerves and ganglia on right ventricle, f, ditto on left. 
 j, great nerve-plexus and ganglia covering coronary sinus (>) and extending itself on the right (h), left 
 (/), and posterior coronary vessels, and the right (e) and left (f) ventricles generally. The ganglia in 
 this case are very numerous, particularly on the coronary sinus (r). Original. 
 
 ganglia (two on the right side and two on the left) send 
 branches to the heart ; whereas in the rabbit, the ganglia 
 supplying branches are increased to six, and in the calf to 
 eight. The number of nerves found on the surface and in 
 the substance of the calfs heart is greater than in any heart 
 which I have examined, a circumstance which has induced 
 me to select it for description 1 . 
 
 1 My cardiac nerve dissections, fifty in number, are deposited in the Anatomical 
 Museum of the University of Edinburgh, where they may .be consulted. They 
 
PHYSIOLOGY OF THE CIRCULATION. 30* 
 
 Plexuses formed on the Roots of tie Pulmonary Artery and 
 Aorta in the Calf. These plexuses are virtually three in 
 number. 
 
 First, That found on the ascending aorta (Fig. 146 b, p. 300) 
 and superior cava (/), composed of branches from the superior 
 or first dorsal ganglion of either side, and from the pneumo- 
 gastric of the right side. 
 
 Secondly ', That situated on the pulmonary artery (a\ and 
 between that vessel and the left auricle (d), composed of 
 branches from the first dorsal 'ganglion of the left side, left 
 pneumogastric, and left recurrent laryngeal. 
 
 Thirdly, That formed on the coronary sinus (Fig. 147, /, r, 
 p. 300), composed almost exclusively of branches from the 
 second and third dorsal ganglia of the sympathetic of the left 
 side. The aortic plexus supplies branches to that surface of 
 the right auricle (Fig. 146 r, p. 300) directed towards the 
 aorta, and likewise to the right ventricle (e) and right coronary 
 vessels (Fig. 149 //, p. 304). These plexuses, as well as the 
 distribution of the nerves on the anterior and posterior surfaces 
 of the heart generally, are seen at Figs. 146 and 147, p. 300. 
 
 Plexus formed on the Anterior Coronary Vessels of the Calf. 
 Those branches of the first dorsal ganglion which do not 
 expend themselves on the ascending aorta, descend behind 
 the pulmonary artery to supply branches to the anterior as- 
 pect of the left auricle (Fig. 146 </, p. 300). They then appear 
 between the left auricle and pulmonary artery, and form an 
 elaborate plexus on the anterior coronary vessels (g) and the 
 anterior surface of the ventricles generally (e,f). This plexus is 
 well seen in the human heart (Fig. 145, p. 299) and that of the 
 horse (Fig. 148 A, a, b, c, d, e, p. 302), and if the nerves com- 
 posing it be carefully examined they will be found to display 
 a great number of ganglionic enlargements and spindle-shaped 
 swellings, particularly where they cross vessels, and where they 
 split up to change their direction and enter the substance of 
 the heart. Some of these ganglia are of large size, and com- 
 municate with as many as four, six, and eight nerve-filaments^ 
 
 embrace specimens of the cardiac nerves of man. the horse, calf, sheep, cat, rabbit, etc. 
 For descriptions of the dissections vide Gold-Medal Inaugural Dissertation ' On 
 the Ganglia and Nerves of the Heart,' deposited in the Library of the University 
 of Edinburgh in 1861. 
 
302 
 
 PHYSIOLOGY OF THE CIRCULATION. 
 
 Plexus formed on the Coronary Sinus of the Calf. This 
 plexus, which is either altogether omitted or very imperfectly 
 represented in works on the nerves of the heart, is composed 
 almost exclusively of branches from the second and third 
 dorsal ganglia of the sympathetic on the left side (Fig. 147,7, r * 
 p. 300, and Fig. 148 C, /, r). It affords the chief supply to 
 the left ventricle, which it occasionally envelops in a beautiful 
 
 Fig. 148, A. Nerves and ganglia on horse's heart, a, large quadrangular ganglion communicating 
 with five branches. Three of these branches form ampullae or spindle-shaped swellings where they 
 cross the coronary artery. Similar swellings are observed where the nerves cross the vessels occupying 
 the anterior ventricular groove (d, e). Original. 
 
 B. Apex of left ventricle of calf's heart. Shows that the muscular fibres of the ventricle pursue a 
 spiral direction from left to right downwards (fi) ; the nerves pursuing a spiral direction from right to 
 left downwards (a), and always crossing the muscular fibres at nearly right angles. Several ganglia are 
 to be observed on the nerves as they approach the apex (c). Original. 
 
 C. Nerve-plexus and ganglia on coronary sinus (j) and base of left ventricle (/) of calf's heart. The 
 ganglia (r) in this situation are for the most part quadrangular and triangular in shape, and stand boldly 
 out. They consist of a superficial and a deep set 0r4'i>a/. 
 
 network of delicate nerves, as shown at /of Figs. 147, p. 300, 
 and 1 50, p. 304. The nerves forming the coronary plexus are in 
 many cases so fragile that it is impossible to preserve them. In 
 one specimen, which I showed Professor Goodsir, the sinus was 
 completely covered with nerve-filaments, so that it would 
 have been difficult to insert the head of a pin between them. 
 In other specimens (Fig. 147, r, p. 300 ; Fig. 148 C, r) the nerves 
 are stronger and not so plentiful, the meshes or spaces between 
 
PHYSIOLOGY OF THE CIRCULATION. 303 
 
 the nerve-filaments being somewhat greater. In every case 
 the nerves on the coronary sinus and posterior surface of the 
 heart display a vast number of ganglionic enlargements and 
 spindle-shaped swellings, some of them so large as readily 
 to be detected by the naked eye ; others requiring the aid 
 of a pocket lens and a good light. The ganglia vary in shape 
 as well as size. Thus in one of my dissections a stellate- 
 shaped ganglion with seven branches is found on the coronary 
 sinus ; another with five branches is seen in a second dis- 
 section on the left coronary artery posteriorly ; a large 
 triangular mass, with numerous nerve-filaments, is detected 
 in a third, where the coronary sinus receives the left coronary 
 vein. In a fourth, several irregularly-shaped ganglionic 
 masses of large size occupy the coronary sinus. In a fifth, 
 a triangular-shaped ganglion is found on the left coronary 
 artery below the sinus ; while in a sixth a well-marked 
 ganglionic enlargement, situated on the sinus and having five 
 branches, is readily recognised. 
 
 The cardiac plexuses have been more or less accurately 
 represented by Scarpa, Remak, Swan, Lee, and others. 
 
 Distribution of the Nerves on the Surface and in the 
 Substance of the Auricles of the Calf. The nerves supplied 
 to the right auricle are as a rule very delicate, and proceed 
 from the right pneumogastric, from the first dorsal ganglion 
 of the sympathetic on the right side, and from the coronary 
 plexus. 
 
 Those supplied to the left auricle are derived principally 
 from the coronary plexus, some offsets being sent from the 
 left pneumogastric, and the first dorsal ganglion of the sym- 
 pathetic on the left side. The nerves, on reaching the surface 
 of the auricles, break up and spread out to form a nervous 
 reticulation or network. Ganglia may be detected in numbers 
 where the nerves split up, where they encounter vessels, and 
 where they dip into the substance of the auricles. Of the 
 nerves which enter the substance of the auricles not a few pass 
 through the auricular walls. The nerves supplied to the 
 auricles are not quite so numerous as those supplied to the 
 ventricles. 
 
 Distribution of the Nerves on the Surface and in the 
 Substance of the Ventricles of the Calf. The nerves on the 
 
304 PHYSIOLOGY OF THE CIRCULATION. 
 
 surface of the ventricles, if allowance be made for their break- 
 ing up slightly to form meshes, follow a common course ; i. e. 
 they run in spiral lines from right to left downwards. The 
 direction pursued by the nerves is precisely the opposite of 
 that pursued by the muscular fibres ; in other words, the 
 muscular fibres form left-handed spirals, whereas the nerves 
 form right-handed spirals. I mention this, because although 
 it has been noted that the nerves cross the muscular fibres 
 
 Fig. 149. Fig. 150. 
 
 Fig. 149. Nerves and ganglia on. right ventricle of calf's heart, a, pulmonary artery. *, aorta. 
 
 c, right auricle. A, plexus of nerves on right coronary vessels, e, nerves and ganglia on right ventricle. 
 f, left ventricle, g, anterior coronary vessels, k, large gangjion- with' numerous nerves proceeding to 
 and from it. A large number of similar but smaller and more delicate ganglia are seen on a close ex- 
 animation. Original, ..., 
 
 Fig. 150. Nerves and ganglia on left ventricle of calf's .heart, a, pulmonary artery, c, right aurirle. 
 
 d, left ditto, e, ganglia and perves on right ventricle, f, ditto on left, j, ganglia and nerves on coronary 
 sinus, which extends to left coronary vessel (z') and left ventricle (/), both of which it envelopsJn a beau- 
 tiful network of nerves and. ganglia. The ganglia are well seen on the left, coronary artery ,(') and one 
 
 ,'. ; , . of .the branches () of the anterior coronary artery. The swellings or enlargements of the nerves as they . 
 cross the vessels are represented more especially at n, but they are observed wherever vessels occur. 
 Original. 
 
 obliquely from base to apex, no allusion is made to the com- 
 plete spirals formed by them, particularly as they near the 
 apex. These points are illustrated at Figs. 146, 147, p. 300, 
 148 B, p. 302, 149 and 150. 
 
 The nerves, from the fact of their crossing the muscular 
 fibres and blood-vessels at a great many different points, are 
 in a position to stimulate or intercept stimulus, ^o that one 
 
PHYSIOLOGY OF THE CIRCULATION. 305 
 
 can readily understand how the nerves regulate not only the 
 movements but also the nourishment of the ventricles. The 
 blood-vessels, as is well known, occupy the anterior and pos- 
 terior coronary grooves ; i. e. the vertical sulci or furrows 
 which separate the right and left ventricles from each other. 
 They also occupy the transverse or horizontal grooves which 
 separate the right and left auricles from the right and left 
 ventricles. As the manner in which the coronary vessels break 
 up to nourish the heart is not well understood, I may state that 
 the branches are given off from the main trunks very ob- 
 liquely, and in such a manner that their course corresponds 
 exactly with that of the muscular fibres. When they have 
 proceeded a certain distance they dip into the substance of 
 the ventricles and branch or bifurcate ; the smallest branches 
 penetrating the muscular walls in a direction from without 
 inwards. The anterior and posterior coronary vessels con- 
 sequently have the same direction as the nerves ; whereas 
 the branches of those vessels have the same direction as the 
 muscular fibres, and a contrary direction to that of the nerves 
 (Figs. 146, 147 and 150, pp. 300, 304). The smallest vessels, as 
 stated, penetrate the substance of the ventricles from without 
 inwards. From this it follows that the nerves intersect the 
 larger branches of the coronary vessels and muscular fibres 
 always at nearly right angles. That the nerves bear an 
 important relation to the blood-vessels will appear from this. 
 The nerves invariably form plexuses on the vessels, and the 
 ganglionic enlargements and spindle-shaped swellings are 
 always most numerous where the nerves come in contact 
 with or cross them (Fig. 146 g, p. 300 ; Fig. 147 j r r, /, k, 
 p. 300; Fig. 148 A, a, b, c, d, e\ C, j\ r, /, p. 302; Fig. 
 H9 h> > P- 304; and Fig. 1507, i, n,g, p. 304). The nerves 
 occasionally even swerve from their original course to intersect 
 and accompany certain vessels. They likewise form nervous 
 rings or loops on such vessels as are embedded in the sub- 
 stance of the ventricles but accidentally rise to the surface. 
 In a word, the nerves not only constantly intersect the vessels, 
 but they in many instances send off fine filaments to run in 
 the direction of the length of the vessels, a triangular enlarge- 
 ment or ganglion being found where the nerves divide. As 
 a rule the nerves are thickened and flattened where they cross 
 
 X 
 
30(5 PHYSIOLOGY OF THE CIRCULATION. 
 
 the vessels, the nerves at these points presenting a spindle- 
 shaped characteristic appearance (Fig. 148 A, a, b, c 9 d, e, 
 p. 302 ; and Fig. 150 n, p. 304). These ampullae or swellings 
 on the nerves where they cross the vessels were described by 
 Lee as ganglia, although on what grounds he does not state. 
 He is quite correct in so regarding them, as I find they con- 
 tain numerous unipolar with a few bipolar nerve-cells. Similar 
 remarks may be made regarding the stellate-shaped ganglionic 
 enlargements everywhere perceptible on the surface of the 
 heart (Figs. 146, 147, 148, A, B, C, 149 and 150, pp. 300, 302, 
 304). To these allusion is made further on. 
 
 Distribution of the Nerves on the Right Ventricle. As a 
 proof that some purpose is served by the spiral distribution of 
 the nerves on the ventricles, I may refer to the arrangement 
 on the right ventricle (Fig. 149, p. 304). This ventricle, it will 
 be remembered, is supplied by the nerve-plexus formed on 
 the aorta, and between that vessel and the pulmonary artery 
 (&). As, however, the plexus in question is situated behind 
 the pulmonary artery and the infundibulum or conus arte- 
 rwsus 1 , it follows that if the nerves were at once to proceed 
 on their downward course, not only would the infundibulum 
 be left destitute of nerves, but their direction would nearly 
 correspond with that of the muscular fibres. In order, there- 
 fore, to enable the nerves to run in a contrary direction to 
 that of the muscular fibres, they at first proceed in a forward 
 direction so as to cross the infundibulum and supply the 
 vessels thereon, after which (and mark this) they suddenly 
 bend upon themselves at nearly right angles in order fairly 
 to intersect the muscular fibres in spiral lines in a direction 
 from left to right downwards. 
 
 The points to be more particularly attended to in the dis- 
 tribution of the nerves on the right ventricle are the follow- 
 'ing : They are derived from the plexus which invests the 
 aorta, and extends between that vessel and the pulmonary 
 artery. They receive, as was formerly stated, a few branches 
 from the plexus on the anterior coronary vessels. They run 
 in a spiral direction from before backwards and downwards ; 
 a course the opposite of that pursued by the muscular fibres 
 
 1 The comis arteriosus corresponds to the conical-shaped portion of the right 
 ; ventricle from which the pulmonary artery springs. 
 
PHYSIOLOGY OF THE CIRCULATION. 307 
 
 and the branches of the cardiac vessels. Generally, they 
 split up from time to time, the branches maintaining a certain 
 parallelism and becoming finer and finer as they reach the 
 posterior of the ventricle (Fig. 149 *?, p. 304). Occasionally the 
 nerves coalesce or run together, and under these circumstances 
 there is a marked increase of nerve-substance at the point of 
 junction. This is particularly the case in the large ganglion 
 represented at k of Fig. 149, p. 304. When the nerves reach 
 the posterior surface of the ventricle (e), they unite with others 
 from the plexus on the coronary sinus to form stellate-shaped 
 expansions or ganglia well seen at e of Fig. 147, p. 300. The 
 expansions referred to display, on microscopic examination, 
 numerous unipolar and bipolar nerve-cells. The plexus 
 formed on the right coronary artery (Fig. 149 ^, p. 304), when 
 examined with a lens in a good light, is found to be very 
 complex. The nerves on the right ventricle (Figs. 147 and 
 149 ^, pp. 300, 304) are fewer in number than those on the 
 left ventricle (Fig. 150 /, p. 304). Posteriorly, there is usually 
 a part of the right ventricle comparatively unprovided for, 
 where the terminal nerve-filaments of the right ventricle unite 
 with similar terminal nerve-filaments from the plexus on the 
 coronary sinus. 
 
 Distribution of the Nerves on the Left Ventricle. This 
 ventricle derives its nervous supply almost exclusively from 
 the plexus situated on the coronary sinus (Fig. 1477, ^ P- 3 j 
 Fig. 148 C, j, r, p. 302 ; Fig. 150 /, p. 304). It exhibits still 
 more clearly than the right the spiral course pursued by the 
 nerves. As a rule, the nerves on the posterior surface of the 
 left ventricle proceed in almost parallel lines (Fig. 147 /, p. 300), 
 subdividing and becoming more attenuated as they near the 
 apex. On the lateral and anterior aspect of the ventricle the 
 arrangement is more irregular, i.e. it assumes to a certain 
 extent the plexiform character (Fig. 150 f, g^ p. 304). In 
 one of my dissections it is altogether plexiform, and the 
 nerves, by alternately dividing, subdividing, and reuniting, pro- 
 duce a beautiful network of nerves which envelops the ven- 
 tricle from base to apex. In examining this network I find 
 that sometimes as many as three branches unite when cross- 
 ing a vessel, after which they separate and reunite when 
 another vessel is to be crossed (n). The plexus formed on the 
 
 X 2 
 
308 PHYSIOLOGY OF THE CIRCULATION. 
 
 left coronary vessels (Fig. 147 /, p. 300) is an extension of 
 that formed on the sinus (j\ r). It is very intricate, and when 
 patiently examined with a lens in a good light numerous 
 ganglia and spindle-shaped enlargements are discovered (Fig. 
 148 C, p. 302). The spindle-shaped enlargements occurring 
 on the general surface of the left ventricle are usually 
 met with where the nerves cross the vessels, as was correctly 
 described and figured by Lee. Lee, however, it appears 
 to me, has slightly exaggerated the number and size of the 
 enlargements, as well as the number of branches with which 
 they communicate. The enlargements in many cases are ap- 
 parently produced by a mere flattening of the nerves on the 
 projecting rounded surface of the vessels (Fig. 150 ;/, p. 304). 
 The appearance of the enlargements (they are spindle-shaped) 
 suggests this idea. I am, however, satisfied that there is an 
 actual increase of nerve-substance ; a view favoured by the 
 fact that they contain a large number of nerve-cells, and not 
 a few of them give off one or more delicate nerve-filaments 
 to the vessels they cross. In this respect they resemble the 
 typical stellate-shaped ganglia found on the coronary sinus 
 (Fig. 147 j, r, p. 300 ; and Fig. 148 C, /, r, p. 302). In the 
 heart of a camel which I had the good fortune to obtain 
 through the kindness of Professor Goodsir, the increase of 
 nerve-substance was very marked, the enlargements in this 
 instance having a somewhat quadrangular shape, and sending 
 branches to the vessels and other nerves. 
 
 The number of nerves which dip into the substance of the 
 left ventricle is considerable. Large and small branches 
 disappear separately or together without apparently following 
 any order. Generally speaking, they take advantage of a 
 vessel entering the substance and accompany it, or they seek 
 one of the openings occurring between the muscular fasciculi. 
 In a dissection which I made of the horse's heart, three 
 branches were observed to enter the posterior wall of the left 
 ventricle within a few lines of each other. The distribution 
 of the nerves in the substance of the right ventricle is similar 
 in all respects to that described in the left. The arrangement 
 of the nerves in the substance of the heart is essentially the 
 same as on its surface. Thus, the nerves run slantingly, and 
 so come in contact with the vessels and muscular fibres. 
 
PHYSIOLOGY OF THE CIRCULATION. 309 
 
 Ganglia are found on the deep nerves as on the more super- 
 ficial ones, although not to the same extent. 
 
 Distribution of the Nerves in the Human Heart. The 
 number of nerves is slightly fewer in the human heart than in 
 that of the calf and some of the lower animals (Fig. 145. p. 299). 
 The nerves are also more delicate, the aggregate of the nerve- 
 filaments as compared with the aggregate of the muscular 
 fibres being less. The distribution and arrangement are as 
 nearly as may be identical with that described in the calf. 
 It is somewhat difficult to get a good view of the nerves of 
 the human heart, partly from the greatly thickened condition 
 of the exocardium or outer covering of the heart, and partly 
 from the excessive quantity of fat which usually invests it, 
 particularly in the vertical and horizontal coronary grooves. 
 By a diligent search extending over several years, I have 
 secured some very fine specimens, the best of which have 
 been obtained from young or emaciated patients, or those 
 who died from dropsy, in which case an excess of pericardial 
 fluid had softened and rendered the exocardium more or less 
 transparent. The nervous supply to the posterior surface of 
 the human heart is, comparatively speaking, very scanty ; a 
 deficiency observed in the hearts of many of the lower 
 animals, though not to the same extent. As regards the 
 actual number of nerves on the ventricles of the human heart, 
 authorities differ. According to Scarpa and what I myself 
 have seen, the nerves are fewer and more delicate than in the 
 lower animals. Of this I think there can be little doubt, 
 as I have examined some hundreds of human hearts more or 
 less carefully. Lee nevertheless affirms that the nerves of 
 the human heart are quite as numerous as those of the heart 
 of the heifer. He corroborates his statement by drawings 
 of the nerves as seen on the heart of a child nine years of age, 
 and on the adult human heart hypertrophied 1 . Lee's pre- 
 parations are deposited in the Museum of St. George's 
 Hospital, London, and I am disposed to believe, from an 
 inspection of them, that he has to some extent been misled 
 by his not having injected the minute cardiac vessels, and by 
 his manner of dissection (he teases the nerves out by the aid 
 
 1 Dr. Robert Lee ' On the Ganglia and Nerves of the Heart,' Plates I and 5. 
 Phil. Trans. 1849.) 
 
3IO PHYSIOLOGY OF THE CIRCULATION. 
 
 of needles a procedure which displaces the nerves, and 
 causes shreds of the exocardium or fibrous membrane invest- 
 ing the heart greatly to resemble nerves). In my own dis- 
 sections, deposited in the Anatomical Museum of the Uni- 
 versity of Edinburgh, I have endeavoured to avoid this 
 source of error by careful injections of the cardiac arteries 
 and veins with two colours, and from dissecting everything 
 away from the nerves, without dragging or pulling upon the 
 nerves themselves. The nerves in my dissections are con- 
 sequently all in sitU) and their relations to the cardiac vessels 
 and muscular fibres undisturbed. The ganglionic enlarge- 
 ments found on the nerves of the human heart have been 
 partially figured by Scarpa and more fully by Lee. I have 
 shown them at Fig. 145, p. 299. They are not so distinct as 
 those found on the nerves of the heart of the calf, neither are 
 they so numerous ; nevertheless, they are sufficiently numerous 
 and well-marked to attract attention. 
 
 The arrangement of the nerves in the heart of the camel, 
 alpaca, panther, seal, and all the other mammals which I 
 have examined, is in every respect similar to that already 
 described in the calf. 
 
 Microscopic Appearances presented by the Ganglia found on 
 the Coronary Sinus and Cardiac Vessels. 
 
 The ganglia of the heart, as already explained, vary greatly 
 in size, some being so minute that a pocket lens or microscope 
 is required to detect them ; others being so large as to be 
 readily recognised by the unaided eye even at a distance. 
 In every case they are characterised by an increase of nerve- 
 substance, the aggregate of any one ganglion being greater 
 than the aggregate of the nerves which enter and leave it. 
 The increase in bulk is due for the most part to the presence 
 of an infinite number of unipolar nerve-cells mixed with a few 
 bipolar ones 1 . The ganglia also vary in form. Thus some, 
 as has been stated, are stellate-shaped, others quadrangular, 
 others oblong, others triangular, and others spindle-shaped. 
 
 1 Similar ganglia are found in the stomach, intestines, bladder, uterus, and certain 
 of the blood-vessels ; and it is worthy of remark, that the structures here enumerated 
 are endowed with more or less typical rhythmical movements. 
 
PHYSIOLOGY OF THE CIRCULATION. 311 
 
 The form depends in a great measure on the number of 
 nerve-filaments which conduct to and from the ganglion. 
 Thus, if a ganglion is connected with eight nerve-filaments, 
 it is stellate-shaped ; if with four, quadrangular or oblong ; 
 if with three, triangular ; and if with only two, spindle-shaped. 
 The spindle-shaped ganglia are found where the nerves cross 
 the smaller vessels; the others on the coronary sinus and 
 larger vessels, and on the surface, and in the substance of the 
 heart generally, particularly where the nerves bifurcate and 
 break up with a view to changing their direction. The gan- 
 glia consist for the most part of irregular aggregations of 
 nerve-cells, with nerve-filaments proceeding to and from them 
 (Fig. 151 C, p. 312). This is the character of the irregular- 
 shaped ganglia found on the coronary sinus. In other cases, 
 the aggregation of nerve-cells assume an oval form, the nerves 
 proceeding to and from the cells being arranged in two sets, 
 as witness the spindle-shaped ganglia found on the nerves as 
 they cross the smaller vessels (Fig. 151 B, p. 3 1 2). In other cases 
 the nerve-cells are disposed in the form of a bulb, the nerves 
 conducting to and from the nerve-cells being arranged in a 
 fasciculus^ the ganglion with its leash of nerves resembling a 
 hyacinth bulb with its leaves (Fig. 1 5 1 A, p. 3 1 2) . Wherever a 
 large terminal ganglion is found, one or more smaller ones, 
 apparently in process of formation, may be detected. The 
 following is the arrangement as ascertained by me in 1861 : 
 ' The bundles of nerve-filaments on entering the clump (termi- 
 nal ganglion) resolve themselves into their component nerve- 
 fibres, and each fibre selects and becomes connected with a 
 nerve-cell 1 .' 
 
 In order to see the nerve-cells to advantage, the best plan 
 is to take a fresh heart and remove one of the ganglia from 
 its surface in such a manner as not to injure or compress it in 
 any way. This done, the ganglion is placed in an ammoniacal 
 solution of carmine for a short time. The unequal staining 
 produced by this pigment differentiates the nerve-cells and 
 nerve-filaments. The ganglion is then transferred to a glass 
 slide and a little glycerine added with a view to examination 
 with a low power. A cursory examination at once reveals 
 
 1 Inaugural Dissertation by the Author, ' On the Ganglia and Nerves of the 
 Heart/ p. 36. University of Edinburgh Library, 1861. 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 the dark central mass of the nerve-centre and the lighter 
 nerve-filaments in connexion therewith. A keen eye may 
 also detect traces of the nerve-cells, which appear as dark 
 rounded masses. To see the nerve-cells properly, the ganglion, 
 if large, must be broken up with needles ; if small, a thin 
 covering-glass should be employed, and pressure applied with 
 a view to flattening and even squashing it. A microscope, 
 
 Fig. 151. 
 
 Fig. 151 A. Large and small terminal ganglia with nerve-cells and nerve-fibres proceeding to and from 
 them, a, bundle of nerve-filaments in connexion with large ganglion (b). A similar bundle is connected 
 with small ganglion (<r). Original. 
 
 B. Ganglionic enlargement or swelling of nerve as it crosses a vessel, a, b, nerve-filaments proceeding 
 to and from the ganglion and nerve-cells (c). d, nerve-substance surrounding and investing ganglion (c). 
 Original. 
 
 C. Large ganglion crowded with nerve-cells from coronary sinus of calf, a, b, c, d, e,f,g, h, nerver 
 filaments proceeding to and from the ganglion and nerve-cells. The nerve-cells contain a nucleus and 
 one or more nucleoli. They are for the most part unipolar in character. A few bipolar nerve-cells are 
 also found. Original. 
 
 D. Unipolar (a) and bipolar (b) nerve-cells from cardiac ganglion, displaying nucleus and nucleolus. 
 Original. 
 
 E. Terminal ganglion or aggregation of cells in a nerve as it crosses a vessel, a, nerve-filaments pro- 
 ceeding to and from the nerve-cells of the terminal ganglion (b). Original. 
 
 magnifying from 300 to 400 diameters, will reveal the nerve- 
 cells as represented at Fig. 1 5 1 A, B, C, D, E. These figures 
 are copied from my Inaugural Dissertation, deposited in the 
 Library of the University of Edinburgh in 1861, and it will 
 be observed that they remarkably accord with analogous 
 figures representing the ganglia and nerve-cells in the heart 
 of the frog, published by Dr. Beale in 1863. 
 
PHYSIOLOGY OF THE CIRCULATION. 313 
 
 The cells, as has been already pointed out, are for the most 
 part unipolar, with a sprinkling of bipolar ones (Fig. 1 5 i D, 
 p. 312). They contain a nucleus and one or more nucleoli 
 (A, B, C, D). In some cases and under certain conditions 
 they present a granular appearance (E). Analogy inclines 
 me to believe that the ganglia and nerve-cells just described 
 are to be regarded as nerve-centres or diminutive brains. In 
 this I agree with Winslow, Winterl, Johnstone, Unger, Lecat, 
 and Peffingers. They assist in regulating and co-ordinating 
 the movements of the heart, and preside over its nutrition. 
 This view, if taken in connexion with the vital properties 
 inhering in involuntary muscles, in part accounts for the 
 rhythmic movements of the heart when the organ is cut out 
 of the body, when it is severed from its nervous connexions, 
 and when it is deprived of blood, unless such as is found 
 within its walls. It is the blood within the muscular parietes 
 of the heart which keeps it alive and enables it to move 
 rhythmically. 
 
 Why does the Heart act Rhythmically '? 
 
 To this question no satisfactory reply can be given in the 
 present state of science. The older observers attributed the 
 phenomenon to various and extraordinary causes. Stahl, e.g. 
 declared the movements of the heart to be under the guidance 
 of the anima or soul. Sylvius, the head of the chemical sect, 
 traced them to an effervescence caused by a mixture of the 
 old and alkaline blood with the acid chyle and acid pancreatic 
 juice ; while Descartes referred them to a succession of 
 explosions occurring within the heart due to a generation 
 of steam. Willis, with a greater show of reason, attributed 
 the movements of the heart to the cerebellum and the eighth 
 pair of nerves. To these Boerhaave added two additional 
 causes, viz. the action of the blood of the arteries on its fibres, 
 and of the venous blood on the surface of its cavities. The 
 hypothesis of Willis explained how the heart is subject to 
 the storm of the passions, but it did not explain how the 
 heart beat in the anencephalous foetus (foetus devoid of brain 
 and spinal cord), or in animals whose brain and spinal cord 
 were crushed or removed. Still less did it explain how the 
 
314 PHYSIOLOGY OF THE CIRCULATION. 
 
 heart moved with a regular rhythm, when cut out of the body, 
 deprived of its blood, and placed in an exhausted receiver 
 with a view to excluding the air which was supposed to act 
 as an irritant. This difficulty induced Haller to deny that 
 the heart owed its movements to its nerves, and led him 
 ultimately to declare that the movements of the heart are due 
 to irritability inhering in the muscular fibres (vis insita) as 
 apart from its nerves. Haller's theory failed to account for 
 the presence of nerves on the surface and in the substance 
 of the heart, and for the connexion which is known to exist 
 between that organ and the head. Some of his followers, 
 Soemmering and Behrends for instance, endeavoured to evade 
 this difficulty by supposing that the cardiac nerves were 
 distributed only to the vessels of the heart ; a view which, 
 in the present state of the subject, is untenable. Stannius, in 
 recent times, has made experiments to show that the rhythm 
 of the heart is referrible to its ganglia, which he regards as 
 automatic nerve-centres ; and Sir James Paget has argued 
 with much ability to the effect that it is due to rhythmic 
 nutrition. There are no sufficient grounds for believing that 
 the nerves actually produce the movements of the heart. 
 These in all probability originate in the sarcous elements 
 composing the muscular fibres of the heart, as is partially 
 demonstrated by the following experiment : When the 
 nerves proceeding to a muscle are poisoned by certain sub- 
 stances, such as woorara, so that stimulation of the nerves 
 fails to produce shortening or contraction of the muscle, 
 the muscle may nevertheless be made to shorten by applying 
 the stimulus to its fibres directly. Furthermore, Bowman 
 asserts from observation, that a muscular fibre destitute of 
 nerves may be made to contract. The heart acts rhythmically 
 for protracted periods after it is cut out of the body and its 
 nerves divided l , a circumstance which compels us to conclude 
 either that the rhythmic movements inhere in the muscular 
 substance or are referrible to the ganglia which are found in 
 great numbers on the surface and in the substance of the 
 heart generally. But, as has been stated, the nerves may be 
 poisoned, and still the heart contract under stimulation. The 
 
 1 The heart of the frog, if supplied with fresh serum, will pulsate for several 
 days after removal. 
 
PHYSIOLOGY OF THE CIRCULATION. 31$ 
 
 will exercises no influence upon the movements of the heart 
 under ordinary circumstances, and the brain and spinal cord 
 may be crushed without interfering with them even in a 
 remote degree. In the anencephalous foetus, where the brain 
 and spinal cord are absent, the heart acts rhythmically and 
 regularly. On the other hand, it is well known that certain 
 mental states (joy, grief, etc.) affect the heart, and that division 
 of the pneumogastric nerves is followed by a quickening of 
 the heart's action, while irritation of the cut ends of these 
 nerves is accompanied by slowing of the heart's action. 
 Division of the nerves tends to prove the regulating influence 
 of the nervous system ; the cause of the rhythm of the heart 
 remaining still unexplained. Sir James Paget, whose phi- 
 losophic utterances have necessarily great weight, is disposed, 
 as already stated, to attribute the rhythm of the heart to 
 rhythmic nutrition. This however cannot be accepted as the 
 final explanation ; for one naturally inquires, Why should the 
 nutrition of the heart be rhythmic, seeing it is only a muscle, 
 and there are innumerable other muscles equally well nourished 
 whose movements are not rhythmic ? 
 
 There is a further difficulty as to whether nutrition is to be 
 accredited with the movements, for cilia vibrate rhythmically 
 when removed from the body, and even when on the verge of 
 putrefaction. Granting however that the rhythmic nutrition 
 of the heart produces its rhythmic movements, the question 
 still remains (and it is equally hard of solution), What causes 
 the rhythmic nutrition? The rhythmic nutrition hypothesis 
 only removes the difficulty one step further back ; it cannot 
 be accepted as a final explanation. All nutrition is not 
 rhythmic, and when it is, there must be laws to regulate it. 
 Those laws are as yet undiscovered, and are probably only to be 
 recognised by their effects. For reasons to be stated presently 
 I am disposed to believe that the rhythm of the adult heart is 
 due partly to a healthy nutrition, partly to the inherent 
 vitality or power of moving residing in muscles, and partly to 
 the influence exerted on the cardiac movements by the ganglia 
 and nerves situated on the surface and in the substance of the 
 heart and other parts of the body. There can be no doubt 
 that the nervous system presides over the nutrition of the 
 circulatory apparatus as a whole, and it is equally evident 
 
3l6 PHYSIOLOGY OF THE CIRCULATION. 
 
 that the movements of the heart and blood-vessels, and the 
 degree of vascular tension or pressure, are modified by the 
 condition of certain nerves and nerve-centres. With a view 
 to simplifying our comprehension of this very involved but 
 highly interesting problem, I propose to arrange existing 
 materials under two heads : 
 
 I. Proofs that the heart can move independently of the 
 nerves. 
 
 II. Proofs that the movements of the heart are regulated 
 and co-ordinated by the nerves. 
 
 Proofs that the Heart may act independently of the Nerves. 
 Analogy favours this view. 
 
 (a.) Certain plants when vigorous and exposed to a bright 
 light, such as the Hedysarum (Desmodium gyrans\ exhibit 
 rhythmical movements. 
 
 (b.} Professor Busk showed that at a certain period of the 
 development of the Volvox globator (a very simple vegetable 
 organism), there appear in each zoospore, or in the bands 
 of protoplasm with which the zoospores are connected, va- 
 cuoles, spaces or cavities, of about ^ ^ of an inch in diameter, 
 which contract with regular rhythm at intervals of from 38 
 to 41 seconds, quickly contracting and then more slowly 
 dilating again, as in the heart. 
 
 (c.) Similar phenomena were observed by Cohn to occur 
 in Gonium pectorale and Chlamydomonas^ the vacuoles or 
 water vesicles contracting regularly at intervals of from 40 
 to 45 seconds. Here, of course, neither nerve nor muscle, 
 nor blood, nor any kind of stimulus, or anything in the 
 shape of irritation, is present. Sir James Paget attributes 
 the rhythmic movements in plants to rhythmic nutrition. 
 This, however, can only be accepted as a partial explanation. 
 All nutrition is not rhythmic. Only certain plants exhibit 
 rhythmic movements, but all plants are equally nourished. 
 
 (d.} Rhythmic movements occur in cilia, these, so far as 
 known at present, not being supplied with nerves. That 
 ciliary movements, at least, are not due to rhythmic nutri- 
 tion appears from this, that cilia vibrate rhythmically when 
 removed from the body, and even when on the verge of 
 putrefaction. 
 
 (e.) The amoeba, which consists of an undifferentiated mass 
 
PHYSIOLOGY OF THE CIRCULATION. 317 
 
 equally devoid of nerve and muscle, can change shape in 
 every direction, and can open and close any part of its body 
 to produce a temporary stomach. 
 
 (/.) The heart pulsates while yet a mass of nucleated cells, 
 i. e. before it is furnished with either muscular fibres, nerves, 
 or blood. 
 
 (g.) Bowman showed that a muscular fibrilla on or in which 
 no nerve can be detected may be made to contract artificially. 
 
 (h.} The brain and spinal cord may be gradually crushed 
 without in the slightest disturbing the movements of the heart 
 (Marshall Hall). 
 
 (z.) The branches of the pneumogastric nerves which supply 
 filaments to the heart have little or no sensibility, and the 
 filaments supplied to the organ by the sympathetic trunks 
 only act upon it after being stimulated a short time previously. 
 
 (/.) The great sympathetic nerves which furnish the prin- 
 cipal nervous supply to the heart in the mammal are par- 
 ticularly sluggish in their action, and when stimulated affect 
 the movements of the heart only after a considerable interval ; 
 the effect produced not ceasing when the stimulation is dis- 
 continued. 
 
 (/.) When woorara poison has been administered to an 
 animal, it completely paralyses the motor nerves, leaving 
 the sensory nerves and muscular irritability intact. Under 
 these circumstances the muscular fibres may be made to 
 contract by the direct application of a stimulus, showing 
 that movement inheres in the sarcous elements of the mus- 
 cular fibres of the heart. This power of moving on the 
 application of a stimulus which inheres in muscle was desig- 
 nated by Haller the vis insita. 
 
 (/.) When an animal is poisoned by woorara, and the 
 rhythm of the heart maintained by artificial respiration, the 
 galvanisation of both pneumogastric nerves does not affect 
 its movements. If the pneumogastrics be powerfully gal- 
 vanised the heart is stopped for a short period, but resumes 
 its functions as soon as the motor filaments are temporarily 
 exhausted and deprived of what is termed their inhibitory 
 or slowing power (Bernard). 
 
 (m.) In birds, according to Bernard, galvanisation of the 
 pneumogastric nerves does not affect the heart. 
 
318 PHYSIOLOGY OF THE CIRCULATION. 
 
 (;*.) The heart may be cut out of the body and deprived 
 of blood, and still beat regularly. This experiment shows 
 either that the movements of the heart are independent of 
 the nerves as a whole, or are referable to the nerves and 
 ganglia situated on its surface and in its substance ; but, as 
 has been already explained, the nerves of the heart may be 
 paralysed by woorara poison in such a manner that they do 
 not respond to stimuli ; the muscular fibres, on the other 
 hand, responding to the stimuli as if no poison had been 
 administered. The latter fact inclines to the belief that the 
 motor power of the heart resides in its muscular fibres. 
 
 (0.) Many physiologists maintain that the rhythmical move- 
 ments of the heart continue not only in the heart as a whole 
 when its cerebro - spinal and sympathetic connexions are 
 severed, and when it is removed from the body and deprived 
 of blood, but also in fragments of the muscular substance 
 in which no ganglia or nerve-centres can be discovered. 
 Those who oppose this view aver that nerve-cells can, as a 
 rule, be detected in the pulsating shreds, whereas they are 
 absent in the non-pulsating shreds. This, however, does not 
 always hold true. 
 
 Proofs that the Movements of the Heart are Regulated and 
 Co-ordinated by the Nerves. 
 
 (a.) That the movements of the heart are regulated and 
 co-ordinated by the nerves, is proved indirectly by their pre- 
 sence on the organ and by the fact that the nerves exercise 
 a marked influence on the movements of voluntary muscles ; 
 the voluntary muscles, as has been shown, being a differen- 
 tiation and development of the involuntary. 
 
 (&.) Mental excitement arising from sudden joy, etc., quick- 
 ens the movements of the heart. 
 
 (c.) The heart may be stopped indirectly by a voluntary 
 effort. This is effected, first, by distending the lungs, stop- 
 ping the mouth and nose, and making a strong expiratory 
 effort ; and, second, by partially emptying the lungs, stopping 
 the mouth and nose, and making a strong inspiratory effort. 
 These are dangerous experiments. 
 
 (d.} The direct action of the pneumogastric nerves upon 
 .the heart is through their motor filaments, as shown by di- 
 vision of the , nerves in the neck. Galvanisation of their 
 
PHYSIOLOGY OF THE CIRCULATION. 319 
 
 central ends does not affect the heart, while stimulation of 
 their peripheral ends stops it. Some experimenters, how- 
 ever, aver that if the nerves be divided and their peripheral 
 ends feebly stimulated by galvanism, the action of the heart 
 is quickened. These contradictory statements show that the 
 division and irritation of nerves may yield fallacious results. 
 
 (e.) The motor filaments of the pneumogastric nerves which 
 act directly on the heart are derived from the communicating 
 branch of the spinal accessory (Waller). 
 
 (/.) When one of the pneumogastric nerves is divided in 
 the neck of the dog, the number of pulsations is slightly 
 increased, and the cardiac pressure, as indicated by the 
 cardiometer fixed in the carotid artery, slightly diminished. 
 When both pneumogastrics are divided, the beats of the 
 heart are doubled in frequency, but are weak and tremulous. 
 A similar result is produced if the afferent nerves of the 
 sympathetic which are united to the pneumogastrics are di- 
 vided. The acceleration in the latter case is produced by a 
 reflex act. 
 
 (<") When the pneumogastric nerves in the neck are gal- 
 vanised the action of the heart is slowed, and if the galvanism 
 be sufficiently powerful it is arrested (The brothers Weber). 
 The action of the pneumogastrics is therefore supposed to be 
 inhibitory. 
 
 (k.} The heart may be stopped for a few moments by 
 pressure on the right pneumogastric at a certain point in the 
 neck (Czermak). 
 
 (z.) If the action of the heart is arrested by galvanisation 
 of the medulla oblongata, the action is resumed if both 
 pneumogastrics be divided (Longet). 
 
 (/.) If the pneumogastric nerves be divided in the neck, 
 galvanism of their central ends modifies the movements of 
 the heart, by modifying the respirations, the latter being 
 diminished in frequency (Traube and Bernard). 
 
 (k.} If the central extremities of the divided depressor 
 nerves 1 be galvanised, the heart is slowed, and the arterial 
 
 1 The depressor nerve in the rabbit arises in the neck by two roots, one con- 
 nected with the trunk of the pneumogastric, the other with the superior laryngeal 
 branch. It passes down the neck, and when it reaches the chest receives filaments 
 from the sympathetic. The nerve thus augmented passes by numerous short 
 
32O PHYSIOLOGY OF THE CIRCULATION. 
 
 pressure in the arteries diminished by a reflex action. The 
 diminution of arterial pressure is not due to the slowing of 
 the heart, for it occurs even when both pneumogastrics are 
 divided in the neck and the action of the heart quickened 
 (Cyon and Ludwig). These experiments are calculated to 
 show that the depressor nerves exert a twofold influence ; 
 viz. on the heart and on the blood-vessels. 
 
 (/.) If the spinal cord be divided immediately below the 
 medulla oblongata and the cord stimulated by electricity, 
 the arterial pressure is increased and the movements of the 
 heart quickened (Ludwig and Thiry). The nerves by the 
 .instrumentality of which those changes are produced, pass 
 through the lower cervical ganglion, and are known as the 
 ' accelerator nerves' They are regarded as the antagonists of 
 the pneumogastric nerves, whose function, as stated, is sup- 
 posed to be * inhibitory? 
 
 (m.) The filaments of the sympathetic nerves everywhere 
 invest the heart and blood-vessels. These they supply with 
 innumerable nerve-plexuses and ganglia, the nerves to the 
 smaller vessels being in some cases excessively minute. 
 
 (n.) Division of the sympathetic produces vascular conges- 
 tion and widening of the vessels supplied by the portion of 
 the sympathetic divided. The congestion is removed by 
 irritating by electricity the portion of the nerve supplied to 
 the tissues (Bernard). 
 
 (<?.) Excitation of the spinal cord of the frog by electricity 
 causes contraction or narrowing of the arteries of the web of 
 the frog's foot, and if the excitement is kept up, the circu- 
 lation in the arteries is stopped. 
 
 (/.) Direct excitation of a vaso-motor nerve causes contrac- 
 tion of the arteries to which it sends nerve-filaments. Division 
 of a vaso-motor nerve, on the other hand, produces dilatation. 
 
 (q.} Division of the sympathetic in the neck of the rabbit, 
 causes dilatation of the central artery of the ear ; but if 
 the peripheral end of the nerve be excited, the artery con- 
 tracts (Brown-Sequard). 
 
 (r.) If one of the splanchnic nerves be divided in the rabbit, 
 
 branches to the heart between the origins of the great vessels (pulmonary artery 
 and aorta). Cyon finds the homologue of the depressor nerves of the rabbit in the 
 horse. (Brit, and For. Med.-Chir. Rev. Lond. 1*71. No xcvi. p. 540. 
 
PHYSIOLOGY OF THE CIRCULATION. 321 
 
 the arterial pressure is reduced; but if the divided nerve be 
 stimulated by electricity, it is increased. 
 
 (s.) If a portion of the base of a frog's heart be removed 
 with a sharp knife or scissors, it acts rhythmically ; whereas a 
 portion removed from the apex does not, as a rule, act rhyth- 
 mically. This does not always hold true, but when it does, 
 it is supposed to be due to an increase in the ganglia and 
 nerves at the base of the heart as compared with the apex. 
 
 (/.) If a ligature be adjusted so as to enclose or map off 
 the sinus venosus of the frog's heart, it is found that when 
 the ligature is tightened the sinus continues to pulsate, 
 whereas the ventricle after a few beats is arrested in diastole. 
 After a short interval the ventricle also begins to pulsate, 
 but the pulsations of the sinus venosus and ventricle are no 
 longer synchronous (Stannius). This experiment is supposed 
 to prove that the sinus venosus contains an automatic nerve- 
 centre, i. e. a ganglion in which nerve energy is accumulated 
 and discharged at stated intervals or rhythmically. As, how- 
 ever, the automatic motor centre has not been demonstrated 
 to exist anatomically, the statement must be received with 
 caution. Admitting, however, that the automatic motor 
 centre really exists, the rhythm of the heart is still unex- 
 plained. The mystery of the movement confronts us as 
 before. The question, then, comes to be, What causes the 
 automatic motor centre to act rhythmically? The answer 
 to this question will probably bring us face to face with the 
 hidden springs of life itself ; and the why and the wherefore 
 of existence, there is reason to believe, will for ever remain 
 a sealed book. 
 
 The theory of Irritability as bearing on the Action of the 
 Heart, considered. The voluntary muscles, according to 
 Haller, are alone under the influence of the nerves ; the 
 hollow muscles, such as the heart, stomach, bladder, and 
 "uterus, not being stimulated by their nerves but by their 
 contents. In Haller's opinion, the blood is the stimulus to 
 the heart. Dr. John Reid also adopted this view. He says, 
 ' The ordinary and natural stimulus of the heart is the blood 
 which is constantly flowing into its cavities. The greater 
 irritability of the inner surface over the outer is evidently 
 connected with the manner in which the stimulus is habitually 
 
 Y 
 
322 PHYSIOLOGY OF THE CIRCULATION. 
 
 applied. When the blood is forced on more rapidly towards 
 the heart, as in exercise, its contractions become propor- 
 tionally more frequent ; and when the current moves on more 
 slowly, as in a state of rest, its frequency becomes propor- 
 tionally diminished. If the contractions of the heart were 
 not dependent upon the blood, and their number regulated 
 by the quantity flowing into its cavities, very serious and 
 inevitably fatal disturbances in the circulation would soon 
 take place.' If, however, the impinging of the blood against 
 the inside of the heart is the cause of the heart's move- 
 ments, it is natural to suppose the heart would close the 
 instant the blood enters its cavities, without waiting until 
 those cavities are full. If exception be taken to this state- 
 ment, and it is asserted that the blood only becomes a 
 stimulus when a certain quantity has been collected, then 
 we are equally entitled to assume that the heart has become 
 accustomed to the stimulus up to a certain point. But if 
 so, seeing the heart is always receiving blood, why does it 
 not become altogether accustomed to the presence of blood, 
 and the blood cease to act as a stimulus? I will go further, 
 and ask, how can the blood possibly act as a stimulus to 
 the dilating ventricles ? When the ventricles have closed, 
 every drop of blood is literally wrung out of them. The 
 ventricles, in fact, at the end of the systole, form a solid 
 mass ; the auricles have no power to force blood into a solid 
 mass ; and, if the blood be not present, it cannot act as a 
 stimulus. The heart, moreover, closes and opens when re- 
 moved from the body and placed in an exhausted receiver, 
 and when neither blood nor air are present. I have on 
 many occasions made transverse sections of the human and 
 other hearts when in the contracted state, and have satisfied 
 myself that the ventricles can completely obliterate their 
 cavities l . 
 
 1 The ventricles of the heart obliterate their cavities in the following manner : 
 Towards the ends of the systole, the walls of the ventricle thicken to a marked 
 extent; the ventricles become shorter; the musculi papillares shorten and twist 
 and plait into each other, and the auriculo-ventricular valves are dragged down 
 into the ventricular cavities to form two dependent twisted cones, The thickening 
 of the ventricular walls from without inwards, aided by the shortening of the more 
 oblique spiral fibres, tends to diminish the ventricular cavities from side to side ; 
 while the shortening of the more longitudinal spiral fibres and spiral musculi 
 
PHYSIOLOGY OF THE CIRCULATION. 323 
 
 That no blood is contained in the ventricular cavities at 
 the termination of the systole, is. proved by the fact that in 
 animals bled to death the ventricular cavities are, for the 
 most part, completely obliterated. This arises from the sur- 
 faces of the ventricular walls, which are directed towards 
 the axes of the cavities, being closely and accurately applied 
 to each other throughout. 
 
 In the frog and other animals with semi-transparent hearts, 
 the ventricle is blanched at the end of the systole an ap- 
 pearance due, not, as was thought, to the absence of blood 
 in its walls, but in its interior. The impinging of the blood 
 against the endocardium cannot therefore be regarded as 
 the prime mover of the heart. As well might we say that 
 the presence of the pericardial fluid and the impinging of 
 the exocardium or outer surface of the heart against the 
 pericardium was the source of its activity. This would be 
 an equally if not a more satisfactory explanation, the more 
 especially as there is, as has been shown, a superabundant 
 supply of nerves and ganglia on the external surface of the 
 heart. 
 
 That the doctrine of irritability has elements of fallacy in 
 it is, I think, proved by the movements in plants, cilia, the 
 worm, the tentacles of the snail, sea anemone, and allied 
 structures, already described. It seems also proved by the 
 movements of the hollow viscera as a class. If the contents 
 of the hollow viscera acted as stimuli to them, these organs 
 could not consistently be employed as receptacles either 
 for living or dead matter. If the blood formed the stimulus 
 for the heart, the food for the stomach, the urine for the 
 
 papillares, aided by the descent of the auriculo-ventricular valves, diminishes the 
 cavities from above downwards. The apices of the ventricles are closed by the 
 shortening and thickening of the spiral fibres in those regions ; the spiral fibres, 
 particularly of the left apex, forming a whorl or vortex of great beauty. The 
 spiral fibres, by their shortening and thickening, press the walls of the apices 
 forcibly together, in a direction from without inwards and from below upwards, 
 and so convert them into a solid mass. This is necessary, because the apices are 
 the weakest portions of the ventricular walls the left apex of even the horse's 
 heart being something like i-8th of an inch in thickness ; that of the human heart 
 being little over i-i6th of an inch. The tenuity of the ventricular walls at the 
 apices enables the several orders of spiral fibres to coil and uncoil with great 
 facility during the systole and diastole, when the fibres of the heart screw home 
 and then unscrew. 
 
 Y '2 
 
324 PHYSIOLOGY OF THE CIRCULATION. 
 
 bladder, the faeces for the rectum, and the foetus for the 
 uterus, these organs would eject their contents, not at stated 
 intervals, but whenever the stimulus was applied to them. 
 It would be impossible, I apprehend, to apply the stimulus 
 of electricity to any one of them, without producing violent 
 closure of their muscular walls ; nor would this state of 
 matters be improved by keeping up the electricity with a 
 view to familiarising them with it, as this would result in 
 paralysis. The hollow viscera are living muscles ; they open 
 out, to receive the substances prepared for them, and when 
 they have received the full measure thereof, they close and 
 expel them according to fixed laws, and independently of 
 irritation. If the closing of the hollow viscera was due simply 
 to irritation, our bodies would be much more uncomfortable 
 habitations than they are. I am disposed to believe that a 
 living organism has the power in all its parts of avoiding or re- 
 jecting and selecting and appropriating whatever it chooses. 
 It is this power which makes it superior to the outer world in 
 which it lives, moves, and has a being. It is more rational 
 to suppose that a living creature, or a part thereof, controls 
 or avoids the inanimate matter by which it is surrounded, 
 than that the inanimate matter inaugurates and controls its 
 movements. For my own part, I cannot for a moment 
 imagine that the presence of the urine and the faeces in 
 the bladder and rectum act as irritating stimuli. I can still 
 less believe that the blood and foetus act as such to the heart 
 and uterus. This view will no doubt be met by the old objec- 
 tion, viz. that we may have an irritable stomach, bladder, or 
 rectum, and that under these circumstances the viscera close as 
 soon as anything is placed within them. If this argument 
 proves anything, it proves that, in a normal or healthy con- 
 dition, the contents of the hollow viscera do not act as irritants. 
 I am aware that those who hold the doctrine of irritability in 
 its entirety, assert that, when a call is made to pass faeces or 
 urine, and the call is not attended to, the uneasy feeling passes 
 away, because the viscus becomes accustomed to the irritant 
 which is stimulating it. Would, let me ask, the viscus become 
 accustomed to the presence of a coil of wire in its interior 
 conveying electricity ? The fact that the uneasy feelings do 
 pass away when the call is not attended to, proves conclu- 
 
PHYSIOLOGY OF THE CIRCULATION. 325 
 
 sively that the contained matter is not an irritant in the 
 ordinary acceptation of the term. It is very difficult, I 
 believe impossible, to reconcile the theory of irritability with 
 vital manifestations in a healthy organism. The effects pro- 
 duced by artificial stimuli are, I strongly suspect, calculated 
 to mislead. Even the amoeba, which is a mere protoplasmic 
 jelly-like mass, has the power of taking in, containing, and 
 ejecting at will, the dead or living matter on which it de- 
 pends for support ; and it will take no great stretch of the 
 imagination to believe that the hollow viscera are provided 
 with a like power, the more especially as they are abun- 
 dantly supplied with blood, and provided with innumerable 
 nerve-plexuses and ganglia. The oesophagus seizes and 
 transmits the food intended for the stomach, the muscular 
 walls of this tube closing or contracting behind the bolus, 
 and expanding or dilating in front of it a fact inconsistent 
 with the doctrine of irritability ; for in that case the oeso- 
 phagus would close before the bolus, and not behind it. 
 The stomach, when it has received the food which consti- 
 tutes a meal, immediately sets to work upon it, and causes 
 it to travel in certain determinate directions in its interior, 
 until, in conjunction with the gastric and other secretions, 
 it reduces it to a pulp. This done, it opens its pyloric valve, 
 and causes the more fluid portions of the mass to pass into 
 the duodenum. The pyloric valve is then closed, and the con- 
 tents of the stomach rolled about as before. The pyloric valve 
 is a second time opened, and the more pultaceous portions of 
 the digesting mass ejected. The pyloric valve is a second 
 time closed, and the contents of the stomach again rolled 
 about and manipulated as by an intelligent agent. The 
 pyloric valve is opened a third time, and the entire contents 
 of the stomach ejected l . Now, it will be observed that it 
 cannot be the irritation produced by the food which causes 
 the movements of the stomach ; for in that case, the food 
 would be expelled immediately it came in contact with the 
 lining membrane of the stomach, which it is not. If more- 
 over, the food be regarded as the irritant which causes the 
 body of the stomach to close or contract, it cannot con- 
 
 1 In the case of Alexis St. Martin, who had the anterior portion of his stomach 
 removed by a gunshot wound, these movements could be seen. 
 
326 PHYSIOLOGY OF THE CIRCULATION. 
 
 sistently be regarded as the irritant which causes the pyloric 
 valve or sphincter of the stomach to open, as these are op- 
 posite acts, and the sphincter lies beyond the source of the 
 irritation. What is said of the stomach applies equally to 
 the heart, the bladder, the rectum, and the uterus. All 
 these have a common structure and a common nervous sup- 
 ply, and their movements are, strictly speaking, rhythmic 
 in character. The heart acts rhythmically when deprived 
 of blood, both before and after it is removed from the body, 
 and M. Chauveau has introduced caoutchouc bags into the 
 ventricles of the heart, when full of blood and acting nor- 
 mally, without in the slightest degree disturbing their action. 
 The bladder in a healthy subject acts from four to six times 
 in the twenty-four hours, i. e. it contains a fluid for six hours 
 at a time, without causing the slightest inconvenience to the 
 patient. During that period the urine certainly does not act 
 as an irritant in the common acceptation of the term, yet this 
 same fluid at the end of the sixth hour is said to occasion 
 its own expulsion. It could only do so by being suddenly 
 transformed into a highly irritating fluid, which its presence 
 in the bladder for six hours proves it not to be. But grant- 
 ing that the irritating nature of the fluid at the sixth hour 
 caused the body of the bladder to contract, it could not 
 cause the sphincter of the bladder to open, as this is an 
 opposite act, and the sphincter is placed beyond the reach 
 of the irritating medium. If I am here met by the argu- 
 ment, that it is the irritation produced by the increased 
 pressure of the urine at the sixth hour, I reply that this 
 cause cannot operate in the case of the stomach the sto- 
 mach and bladder, as has been pointed out, having a common 
 structure and a common nervous supply. Similar remarks may 
 be made of the rectum and its sphincters. The rectum in a 
 condition of health receives faeces for twenty-four hours, at 
 the expiry of which period it closes by a rhythmic movement 
 and expels its contents. The closing of the body of the 
 rectum is accompanied by the opening of its sphincters, but 
 the former act does not produce the latter, both being equally 
 vital in their nature. The uterus in the human subject 
 retains its contents for nine months. During this long period 
 (and the term is greatly exceeded in the case of the ele- 
 
PHYSIOLOGY OF THE CIRCULATION. 327 
 
 phant), the foetus, notwithstanding its vigorous movements 
 and ever-varying position, occasions little or no inconvenience 
 to the mother. It is assuredly not to be regarded as an 
 irritant. After a few incipient contractions of the uterus 
 (the false pains of obstetricians), occurring at intervals during 
 the period of gestation, and a few vigorous contractions (the 
 true pains of obstetricians), towards the. full term, the foetus 
 is thrown off or expelled. While the body of the uterus is 
 contracting or closing, the sphincter of the uterus is ex- 
 panding or opening. These acts are independent and sepa- 
 rate, and constitute the rhythm of the organ. 
 
 But to return to the heart. 
 
 The heart beats, because its elementary particles i. e. its 
 ultimate or sarcous elements live. If a potent poison is 
 introduced into the substance of the heart, the particles die, 
 and the heart ceases to act both within and without the body. 
 If, moreover, the nerve-plexuses of the heart be suddenly 
 destroyed, and the nutrition of the heart impaired, the action 
 of the organ becomes irregular, or altogether ceases. The 
 blood within the substance of the heart, and not within its 
 cavities, is the cause of its movements, and these movements 
 are not due to irritation, but to a healthy nutrition and as- 
 similation, which go on so long as the body lives and the 
 heart beats. That the movements of the heart are not due 
 to the blood which it contains in its several cavities acting 
 as a stimulus is, I think, apparent from Reid's own writings. 
 In his admirable paper on the ' Heart,' he states that in ex- 
 tensive injuries to the central organs of the nervous system, 
 such as concussion of the brain, severe mechanical injuries, 
 the shock after operations, extensive burns, peritonitis, etc., 
 the quantity of the blood entering the heart is reduced, the 
 action of the heart quickened 1 , and its contractility lessened. 
 If, however,' the blood contained within the cavities of the 
 heart stimulate the organ to contract, how, it may reasonably 
 be asked, are the contractions more frequent when the supply 
 
 1 The frequency of the heart's action in man varies at different periods of life. 
 Thus, in the human foetus, the heart beats 140 times per minute ; at birth, 130 ; 
 second year after birth, 100 ; third year, 90 ; fourteenth year, 80 ; middle age, 70 ; 
 old age, 60, or even less. The variations in the frequency of the beat of the heart 
 in the lower animals is still more remarkable. 
 
328 PHYSIOLOGY OF THE CIRCULATION. 
 
 of blood is reduced, and the contractile power of the organ 
 diminished ? The heart, as I have already pointed out, does 
 not, in a state of health, contract the instant the blood 
 touches its interior ; on the contrary, its several parts do 
 not begin contracting until they have received all the blood 
 they are capable of containing. If, however, the heart, under 
 certain circumstances, contracts more frequently when it 
 contains a small quantity of blood and its irritability is di- 
 minished, than when there is a full supply of blood and its 
 irritability is greatest, then we are, I think, entitled to con- 
 clude the blood contained within the cavities is not the 
 cause of the movements of the heart. Furthermore, it is 
 known that arterial tension or fulness retards rather than 
 increases the heart's action ; the pulsations being fewest 
 when the blood is as it were dammed up in the heart. If, 
 e.g. the aorta is compressed, the pulse rate is at once di- 
 minished. The injuries to which Reid alludes most probably 
 change the character of the heart's action by paralysing or 
 otherwise impairing the function of the nerves which regu- 
 late its nutrition. The rapid feeble pulse in the cases re- 
 ferred to is rather to be attributed to the fact that the 
 vitality of the heart is temporarily lowered, and that it only 
 admits a minimum quantity of blood as it has not the power 
 to expel the maximum quantity. In the same way, in certain 
 chest complaints, the respiratory efforts are increased in 
 frequency the inspiratory and expiratory acts being decreased 
 in duration. Dr. Kay furnishes a direct proof that the pre- 
 sence of blood within the cavities of the heart is not the 
 cause of the movements of the heart. In his experiments 
 on asphyxia, he describes how the left side of the heart 
 dies. He says, 'A smaller quantity of blood is received 
 into its cavities and expelled vigorously into the arteries. 
 The ventricle, meanwhile, diminishes in size as the quantity 
 of 'blood supplied becomes less, until at length, although 
 spontaneous contractions still occur in its fibres, no blood 
 issues from the divided artery, and the ventricle, by con- 
 traction, has obliterated its cavity.' As a further proof that the 
 heart does not depend for its movements on the blood it con- 
 tains, the following experiment may be cited : If a frog be 
 slightly curarized and its spinal cord destroyed, it is found on 
 
PHYSIOLOGY OF THE CIRCULATION. 329 
 
 exposing the heart that the sinus venosus, vena cava inferior, 
 the auricles and ventricle, are quite destitute of blood, and 
 yet the organ beats normally and with the utmost regularity. 
 The heart also beats normally when cut out of the body, 
 deprived of blood, and placed under a bell-jar. Furthermore, 
 the interior of the heart, as M. Chauveau has shown, is al- 
 most devoid of sensibility. He proved this by introducing 
 small caoutchouc bags (cardiac sounds) into the cavities of 
 the ventricles of the horse, without causing the animal either 
 pain or inconvenience. 
 
 Concluding Remarks. 
 
 In bringing the present lectures to a close, I have to ex- 
 press my gratitude for the kindly spirit in which they have 
 been received. I am no stranger to their defects, but, like 
 others discharging a variety of duties, have to plead 'Time 
 stolen by snatches.' To the more advanced, some of the 
 lectures may savour of redundancy ; while to the novice they 
 may even appear fragmentary. My having had to address 
 a mixed audience affords an explanation of this circum- 
 stance. I have aimed at producing a comprehensive view 
 of the circulation as it exists in the lowest vegetable and 
 highest animal forms ; and in carrying out this design have 
 been compelled to expunge much that is old and introduce 
 much that is new. How far I have been right in doing so, 
 time and an advanced Physiology will determine. I will 
 not attempt a recapitulation; suffice it to say, I have en- 
 deavoured to prove by a variety of arguments that the cir- 
 culation, whenever and wherever found, differs less in kind 
 than in degree ; that fluids may move in living tissues with 
 or without vessels and hearts ; that the circulation in an 
 aggregation of vegetable cells is essentially the same as that 
 which occurs in the tissues of our own bodies. As a chain 
 is composed of links, all of which are formed on a common 
 type and fit into each other, so the circulation in the lowest 
 vegetables and animals gradually develops into that of the 
 higher, until we reach man himself ; the circulation in the one 
 being relatively as perfect as in the other. 
 
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 realize this design, the copious use of experimental illustrations was 
 necessary. The apparatus used in the Lectures and figured in the 
 volume has been principally built up from Professor Willis 's most 
 admirable system. In the selection of the subjects, the question of 
 practical utility has in many cases been regarded as the one of para- 
 mount importance, and it is believed that the mode of treatment 
 which is adopted is more or less original. This is especially 
 the case in the Lectures relating to friction, to the mechanical 
 pmvers, to the strength of timber and structures, to the laws of 
 motion, and to the pendulum. The illustrations, drawn from 
 the apparatus, are nearly all original and are beautifully exe- 
 cuted. "Jn our reading we have not met with any book of the sort 
 in English." Mechanics' Magazine. 
 
 Bayma. THE ELEMENTS OF MOLECULAR MECHA- 
 NICS. By JOSEPH BAYMA, S.J., Professor of Philosophy, 
 Stonyhurst College. Demy 8vo. cloth. ios. 6d. 
 
 Of the twelve Books into which this treatise is divided, the first 
 and second give the demonstration of the principles which bear 
 directly on the constitution and the properties of matter. The next 
 A 2 
 
SCIENTIFIC CATALOGUE. 
 
 three books contain a series of theorems and of problems on the laws 
 of motion of elementary substances. In the sixth and seventh, the 
 mechanical constitution of molecules is investigated and determined: 
 and by it the general properties of bodies are explained. The eighth 
 book treats of luminiferous ether. The ninth explains some special 
 properties of bodies. The tenth and eleventh contain a radical and 
 lengthy investigation of chemical principles and relations, which 
 may lead to practical results of high importance. The twelfth and 
 last book treats of molecular masses, distances, and powers. 
 
 Boole. Works by G. BOOLE, D.C.L, F.R.S., Professor of 
 Mathematics in the Queen's University, Ireland : 
 
 A TREATISE ON DIFFERENTIAL EQUATIONS. Third 
 Edition. Edited by I. TODHUNTER. Crown 8vo. cloth. 14^. 
 Professor Boole has endeavoured in this treatise to convey as complete 
 an account of the present state of knowledge on the subject of Dif- 
 ferential Equations, as was consistent with the idea of a work in- 
 tended, primarily, for elementary instruction. The earlier sections 
 of each chapter contain that kind of matter which has usually been 
 thought suitable for the beginner, while the latter ones are devoted 
 either to an account of recent discovery, or the discussion of such 
 deeper questions of principle as are likely to present themselves to the 
 reflective student in Connection with the methods and processes of his 
 previotis course. ' ' A treatise incomparably superior to any other 
 elementary book on the subject with which we are acquainted^ 
 Philosophical Magazine. 
 
 A TREATISE ON DIFFERENTIAL EQUATIONS. Supple- 
 mentary Volume. Edited by I. TODHUNTER. Crown 8vo. cloth. 
 &r. 6d. 
 
 This volume contains all that Professor Boole wrote for the purpose 
 of enlarging his treatise on Differential Equations. 
 
 THE CALCULUS OF FINITE DIFFERENCES. Crown 8vo. 
 
 cloth. IOJ-. 6d. New Edition revised. 
 
 In this exposition of the Calculus of Finite Differences, particular 
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 involves far more than a merely formal analogy. The work is in 
 some measure designed as a sequel to Professor Boolfs Treatise on 
 Differential Equa-tions, 
 
MATHEMATICS. 
 
 Brook-Smith (J.) - ARITHMETIC IN THEORY AND 
 PRACTICE. By J. BROOK-SMITH, M.A., LL.B., St. John's 
 College, Cambridge; Barrister-at-Law ; one of the Masters of 
 Cheltenham College. Crown Svo. 4^. 6d. 
 
 Writers on Arithmetic at the present day feel the necessity of expla iniiig 
 the principles on which the rules of the subject are based, but few as 
 yet feel the necessity of making these explanations strict and complete ; 
 or, failing that, of distinctly pointing out their defective character. 
 If the science of Arithmetic is to be made an effective instrument in 
 developing and strengthening the mental powers, it ought to be 
 worked out rationally and conclusively ; and in this %vork the 
 aiithor has endeavoured to reason out in a clear and accurate 
 manner the leading propositions of the science, and to illustrate and 
 apply those propositions in practice. In the practical part of the 
 subject he has advanced somewhat beyond the majority of preceding 
 writers; particularly in Division, in Greatest Common Measure, 
 in Cube Root, in the chapters on Decimal Money and the Metric 
 System, and more especially in the application of Decimals to Per- 
 centages and cognate stibjects. Copious examples, original ahd 
 selected, are given. 
 
 Cambridge Senate-House Problems and Riders, 
 
 WITH SOLUTIONS : 
 
 1848-1851. PROBLEMS. By FERRERS and JACKSON. Svo. 
 cloth. 15^. 6d. 
 
 1848-1851. RIDERS. By JAMESON. Svo. 'cloth. >]s. 6d. 
 
 1854. PROBLEMS AND RIDERS. By WALTON and 
 MACKENZIE. Svo. cloth. IQJ. 6</. 
 
 1857. PROBLEMS AND RIDERS. By CAMPION- and 
 WALTON. Svo. cloth. &s:-6& 
 
 1860. PROBLEMS AND RIDERS. By WATSON and ROUTH. 
 Crown Svo. cloth. 7-r. ()d. 
 
 1864. PROBLEMS AND RIDERS. By WALTON and WIL- 
 KINSON. Svo. cloth. io>. 6d. 
 
 These volumes will be found of great value to Teachers and Students, 
 as indicating the style ^and range of mathematical study in the 
 University of Cambridge. 
 
 Cambridge and Dublin Mathematical Journal. 
 
 The Complete Work, in 'Nine Vob. Svb. cloth. io/. los. 
 
SCIENTIFIC CATALOGUE. 
 
 Only a. few copies remain on hand. Among contributors to this 
 work will be found Sir W. Thomson, Stokes, Adams, Boole, Sir 
 W. R. Hamilton, De Morgan, Cayley, Sylvester, Jellet, and other 
 distinguished mathematicians. 
 
 Cheyne. Works by C. H. H. CHEYNE, M.A., F.R.A.S.: 
 
 AN ELEMENTARY TREATISE ON THE PLANETARY 
 THEORY. With a Collection of Problems. Second Edition. 
 Crown 8vo. cloth. 6s. 6d. 
 
 In this volume, an attempt has been made to produce a treatise on the 
 Planetary theory, which, being elementary in character, should be 
 so far complete as to contain all that is usually required by students 
 in the University of Cambridge. This Edition has been carefully 
 revised. The stability of the Planetary System has been more fully 
 treated, and an elegant geometrical explanation of the formula for 
 the secular variation j}f the node and indinatioti has been in- 
 troduced. 
 
 THE EARTH'S MOTION OF ROTATION. Crown 8vo. 
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 The first part of this work consists of an application of the method of 
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 case of the earth. 
 
 Childe. -THE SINGULAR PROPERTIES OF THE ELLIP- 
 SOID AND ASSOCIATED SURFACES OF THE NTH 
 DEGREE. By the Rev. G. F. CHILDE, M.A., Author of 
 " Ray Surfaces," " Related Caustics," &c. 8vo. IDJ-. 6d. 
 
 The object of this volume is to develop peculiarities in the Ellipsoid ; 
 and, further, to establish analogous properties in the unlimited con- 
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 DodgSOn. AN ELEMENTARY TREATISE ON DETER- 
 MINANTS, with their Application to Simultaneous Linear 
 Equations and Algebraical Geometry. By CHARLES L. DODGSON, 
 M.A., Student and Mathematical Lecturer of Christ Church, 
 Oxford. Small 4to. cloth. ioj. 6d. 
 
MA THEM A TICS. 
 
 The object of the author is to present the subject as a continuous 
 chain of argument, separated from all accessories of explanation 
 or illustration. All stick explanation and illustration as seemed 
 necessary for a beginner are introduced either in the form of 
 foot-notes, or, where that would have occupied too much room, of 
 Appendices. f 
 
 Earnshaw (S., M. A.) PARTIAL DIFFERENTIAL 
 
 EQUATIONS. An Essay towards an entirely New Method of 
 
 Integrating them. By S. EARNSHAW, M.A., of St. John's 
 
 College, Cambridge. Crown 8vo. $s. 
 
 The peculiarity of the system expounded in this work is, that in every 
 equation, whatever be the number of original independent variables, 
 the work of integration is at once reduced to the use of one indepen- 
 dent variable only. The author's object is merely to render his 
 method thoroughly intelligible. The various steps of the investiga- 
 tion are all obedient to one general principle : and thotigh in some 
 degree novel, are not really difficult, but on the contrary, easy when 
 the eye has become accustomed to the novelties of the notation. Many 
 of the results of the integrations are far more general than they were 
 in the shape in which they appeared informer Treatises, and many 
 Equations will be found in this Essay integrated with ease infinite 
 terms, which were never so integrated before. 
 
 Ferrers. AN ELEMENTARY TREATISE ON TRILINEAR 
 CO-ORDINATES, the Method of Reciprocal Polars, and the 
 Theory of Projectors. By the Rev. N. M. FERRERS, M. A., Fellow 
 and Tutor of Gonville and Caius College, Cambridge. Second 
 Edition. Crown 8vo. 6s. 6d. 
 
 The object of the author in writing on this subject has mainly been to 
 place it on a basis altogether independent of the ordinary Cartesian 
 system, instead of regarding it as only a special form of Abridged 
 Notation. A short chapter on Determinants has been introduced. 
 
 Frost. Works by PERCIVAL FROST, M.A., late Fellow of St. 
 John's College, Mathematical Lecturer of King's College, Cam- 
 bridge : 
 
 THE FIRST THREE SECTIONS OF NEWTON'S PRIN- 
 CIPIA. With Notes and Illustrations. Also a Collection of 
 Problems, principally intended as Examples of Newton's Methods. 
 Second Edition. 8vo. cloth, icxr. 6d. 
 
8 SCIENTIFIC CATALOGUE. 
 
 FrOS t continued. 
 
 The author s principal intention is to explain dijjiculties which may le 
 encountered by the student on first reading the Principia, and to 
 illustrate the advantages of a careful study of the methods employed 
 oy Neivton, by shcnving the extent to which they may be applied in 
 the solution of problems y he has also endeavoured to give assistance 
 to the student ^vJlo is engaged in the study of the higher branches of 
 mathematics, by representing in a geometrical form several of the 
 processes employed in the Differential and Integral Calculus, and in 
 the analytical investigations of Dynamics. 
 AN ELEMENTARY TREATISE ON CURVE TRACING. 
 
 8VO. I2J. 
 
 The author has written this book under the conviction that the skill 
 and power of the young mathematical student, in order w be 
 thoroughly available afterwards, ought to be developed in all possible 
 directions. The subject which he has chosen presents so many faces t 
 pointing in directions towards which the mind of the intended 
 mathematician has to radiate, that it would be difficult to find 
 another which, with a- very limited extent of reading, combines, to 
 the same extent, so many valuable hints of methods of calculations 
 to be employed hereafter, with so much pleasure in its prtseni use. 
 In order to understand the work it is not necessary to have much 
 knowledge of what is called Higher Algebra, nor of Algebraical 
 Geometry of a higher kind than that which simply relates to the 
 - : Conic Sections. From the study of a work like this, it is believed 
 that the student will derive many advantages. Especially he will 
 become skilled- in- making correct approximations to the values of 
 quantities, which cannot be found exactly, to any degree of accuracy 
 which may be required. 
 
 Frost and Wolstenholme. A TREATISE ON SOLID 
 
 GEOMETRY. By PERCIVAL FROST, M.A., and the Rev. J. 
 
 WOLSTENHOLME, M.A., Fellow and Assistant Tutor of Christ's 
 
 College. 8 vo. cloth. i8.y. 
 
 Intending, to make the subject accessible, at least in the earlier portion *, 
 to all classes of students, the authors have endeavoured to explain 
 completely all the processes which are most useful in dealing with 
 ordinary theorems and problems, thus directing the student to the 
 selection of methods which are best adapted to the exigencies of each 
 problem. In the more difficult portions of the subject, they have 
 e&ntidered themselves to be addressing a higher class of students ; 
 
MA THE MA TICS. 
 
 and they have there tried to lay a good foundation on which to 
 build, if any reader should wish to purstie the science beyond the 
 limits to which the work extends. 
 
 Godf ray. Works by HUGH GODFRAY, M.A., Mathematical 
 Lecturer at Pembroke College, Cambridge : 
 
 A TREATISE ON ASTRONOMY, for the Use of Colleges and 
 Schools. Svo. cloth. i2j. 6d. 
 
 This book embraces all those branches of Astronomy which have, from 
 time to time, been recommended by the Cambridge Board of Mathe- 
 matical Studies : but by far the larger and easier portion, adapted 
 to the first three days of the Examination for Honours, may be read 
 by the more advanced pupils in many of our schools. The author's 
 aim has been to convey clear and distinct ideas of the celestial phe- 
 nomena. "It is a working book," says the Guardian, "taking 
 Astronomy in its proper place in the Mathematical Sciences. . . . 
 It is a book which is not likely to be got up unintelligently ." 
 
 AN ELEMENTARY TREATISE ON THE LUNAR 
 
 THEORY, with a Brief Sketch of the Problem up to the time of 
 
 Newton. Second Edition, revised. Crown Svo. cloth. 5^. 6d. 
 
 These pages will, it is hoped, form an introduction to more recondite 
 
 works. Difficulties have been discussed at considerable length. The 
 
 selection of the method followed with regard to analytical solutions, 
 
 which is the same as that of Airy, Herschel, etc. , was made on 
 
 account of its simplicity ; it is, moreover, the method which has 
 
 obtained in the University of Cambridge. "As an elementary 
 
 treatise and introduction to the subject, we think it may justly claim 
 
 to supersede all former ones.' 1 '' London, Edinburgh, and Dublin 
 
 Phil. Magazine. 
 
 Green (George). MATHEMATICAL PAPERS OF THE 
 
 LATE GEORGE GREEN, Fellow of Gonville and Caius 
 
 College, Cambridge. Edited by N. M. FERRERS, M.A., Fellow 
 
 and Tutor of Gonville and Caius College. Svo. 15^. 
 
 The publication of this book may be opportune at present, as several 
 
 of the subjects with which they are directly or indirectly concerned 
 
 have recently been introduced into the course of mathematical 
 
 study at Cambridge. They have -also an interest as being the work 
 
 of an almost entirely self-taught mathematical genius. The Papers 
 
io SCIENTIFIC CATALOGUE. 
 
 comprise the following : An Essay on the application of Mathe~ 
 matical Analysis to the Theories of Electricity and Magnetism 
 On the Laws of the Equilibrium of Fluids analogous to the Electric 
 Fluid On the Determination of the Attractions of Ellipsoids of 
 variable Densities On the Motion of Waves in a variable Canal 
 of small depth and width On the Reflection and Refraction of 
 Sound On the Reflection and Refraction of Light at the Common 
 Surface of two Non- Crystallized Media On the Propagation of 
 Light in Crystallized Media Researches on the Vibrations of Pen- 
 dulums in Fluid Media. "It has been for some time recognized 
 that Green's writings are amongst the most valuable mathematical 
 productions we possess. " Athenoeum. 
 
 Hemming. AN ELEMENTARY TREATISE ON THE 
 
 DIFFERENTIAL AND INTEGRAL CALCULUS. For the 
 Use of Colleges and Schools. By G. W. HEMMING, M.A., 
 Fellow of St. John's College, Cambridge. Second Edition, with 
 Corrections and Additions. 8vo. cloth. 9^. 
 
 " There is no book in common use from which so clear and exact a 
 knowledge of the principles of the Calculus can be so readily ob- 
 tained.' 1 '' Literary Gazette. 
 
 Jackson. GEOMETRICAL CONIC SECTIONS. An Ele- 
 mentary Treatise in which the Conic Sections are denned as the 
 Plane Sections of a Cone, and treated by the Method of Projections. 
 By J. STUART JACKSON, M. A., late Fellow of Gonville and Caius 
 College. Crown 8vo. 4*. 6d. 
 
 This work has been written with a view to give the student the benefit 
 of the Method of Projections as applied to the Ellipse and Hyper- 
 bola. When this method is admitted into the treatment of Conic 
 Sections there are many reasons why they should be defined, not 
 with reference to the focus and directrix, but according to the 
 original definition from which they have their name, as Plane 
 Sections of a Cone. This method is calculated to produce a material 
 simplification in the treatment of these curves and to make the proof 
 cj their properties more easily understood in the first instance and 
 more easily remembered. It is also a powerful instrument in the 
 sohition of a large class of problems relating to these curves. 
 
MA THE MA TICS. 1 1 
 
 Morgan. A COLLECTION OF PROBLEMS AND EXAM- 
 PLES IN MATHEMATICS. With Answers. By H. A. 
 MORGAN, M.A., Sadlerian and Mathematical Lecturer of Jesus 
 College, Cambridge. Crown 8vo. cloth. 6s. 6d. 
 
 This book contains a number of problems, chiefly elementary, in the 
 Mathematical subjects usually read at Cambridge. They have been 
 selected from the Papers set during late years at Jesus College. Very 
 few of them are to be met with in other collections, and by far the 
 larger number are due to some of the most distinguished Mathe- 
 maticians in the University. 
 
 Newton's Principia. 4 to. cloth. 31*. 6</. 
 
 It is a sufficient guarantee of the reliability of this complete edition of 
 Newtoris Principia that it has been printed for and under the care 
 of Professor Sir William Thomson and Professor Blackburn, of 
 Glasgow University. The following notice is prefixed : ' { Finding 
 that all the editions of the Principia are now out of print, we have 
 been induced to reprint New ton's last edition [of 1 726] without note 
 or comment, only introducing the ' Corrigenda ' of the old copy and 
 correcting typographical errors." The book is of a handsome size, 
 with large type, fine thick paper, and cleanly-cut figures, and is 
 the only recent edition containing the whole of Newtoris great 
 work. 
 
 Parkinson. Works by S. PARKINSON, D.D., F.R.S., Fellow 
 and Tutor of St. John's College, Cambridge : 
 
 AN ELEMENTARY TREATISE ON MECHANICS. For the 
 Use of the Junior Classes at the University and the Higher Classes 
 in Schools. With a Collection of Examples. Fourth Edition, 
 revised. Crown 8vo. cloth. 9^. 6d. 
 
 In preparing a fourth edition of this work the author has kept the 
 same object in view as he had in the former editions namely, to in- 
 clude in it such portions of Theoretical Mechanics as can be con- 
 veniently investigated without the use of the Differential Calculus, 
 and so render it suitable as a manual for the junior classes in the 
 University and the higher classes in Schools. With one or tivo short 
 exceptions, the student is not presumed to require a knowledge of any 
 
12 SCIENTIFIC CATALOGUE. 
 
 Parkin s on continued. 
 
 branches of Mathematics beyond the elements of Algebra, Geometry, 
 and Trigonometry, Several additional propositions have been in- 
 corporated in the work for the purpose of rendering it more complete, 
 and the collection of Examples and Problems has been largely in- 
 creased. 
 
 A TREATISE ON OPTICS. Third Edition, revised and en- 
 larged. Crown 8vo. cloth. los. 6d. 
 
 A collection of Examples and Problems has been appended to this work, 
 which are sufficiently numerous and varied in character to afford 
 useful exercise for the student. For the greater part of them, re- 
 course has been had to the Examination Papers set in the University 
 and the several Colleges during the last twenty years. 
 
 Phear. ELEMENTARY HYDROSTATICS, with Numerous 
 
 Examples. By J. B. PHEAR, M. A., Fellow and late Assistant 
 Tutor of Clare College, Cambridge. Fourth Edition. Crown 8vo. 
 cloth. 5.$-. 6d. 
 
 This edition has been carefully revised throughout, and many neiv 
 Illustrations and Examples, added, which it is hoped will increase 
 its usefulness to students at the Universities and in Schools. In ac- 
 cordance ^vith suggestions from many engaged in tuition, answers to 
 all the Examples have been given at the end of the book. 
 
 Pratt. A TREATISE ON ATTRACTIONS, LAPLACE'S 
 FUNCTIONS, AND THE FIGURE OF THE EARTH. 
 By JOHN H. PRATT, M.A., Archdeacon of Calcutta, Author of 
 "The Mathematical Principles of Mechanical Philosophy. " Fourth 
 Edition. Crown 8vo. cloth. 6s. 6t/. 
 
 The authors chief design in this treatise is to give an ansiver to the 
 question, f ' Has the Earth acquired its present form from being 
 originally in a fluid state?" This edition is a complete revision of 
 the former ones. 
 
 Puckle. AN ELEMENTARY TREATISE ON CONIC SEC- 
 TIONS AND ALGEBRAIC GEOMETRY. With ntftnerous 
 
MA THE MA TICS. 1 3 
 
 Examples and Hints for their Solution ; especially designed for the 
 Use of Beginners. By G. H. PUCKLE, M.A. New Edition, 
 revised and enlarged. Crown 8vo. cloth. Js. 6d. 
 
 This work is recommended by the Syndicate of the Cambridge Local 
 Examinations. The Athenaeum says the author " displays an 
 intimate acquaintance with the difficulties likely to be felt, together 
 with a singular aptitude in removing them" 
 
 Routh. AN ELEMENTARY TREATISE ON THE DYNA- 
 MICS OF THE SYSTEM OF RIGID BODIES. With 
 numerous Examples. By EDWARD JOHN ROUTH, M.A., late 
 Fellow and Assistant Tutor of St. Peter's College, Cambridge ; 
 Examiner in the University of London. Second Edition, enlarged. 
 Crown 8vo. cloth. 14^. 
 
 In this edition the author has made several aa ditions to each chapter : 
 he has tried, even at the risk of some little repetition, to make each 
 chapter, as far as possible, complete in itself, so that all that relates 
 to any one part of the subject may be found in tlie same place. This 
 arrangement will enable every student to select his own order in 
 which to read the stibject. The Examples which will be found at 
 the end of each chapter have been chiefly selected from the Examina- 
 tion Papers which have been set in the University and the Colleges 
 in the last few years, 
 
 Smith's (Barnard) Works. See EDUCATIONAL CATA- 
 LOGUE. 
 
 Snowball. THE ELEMENTS OF PLANE AND SPHERI- 
 CAL TRIGONOMETRY ; with the Construction and Use of 
 Tables of Logarithms. By J. C. SNOWBALL, M.A. Tenth 
 Edition. Crown 8vo. cloth. 7-r. 6d. 
 
 In preparing the present edition for the press, the text has been sub- 
 jected to a careful revision ; the proofs of some of the more import- 
 ant propositions have been rendered more strict and general ; and 
 a considerable addition of more than two hundred examples, taken 
 principally from the questions set of late years in the public exami- 
 nations of the University and of individual Colleges, has been made 
 to the collection of Examples and Problems for practice, 
 
SCIENTIFIC CATALOGUE. 
 
 Tait and Steele. DYNAMICS OF A PARTICLE, with 
 
 numerous Examples. By Professor TAIT and Mr. STEELE. New- 
 Edition. Crown 8vo. cloth. IOT. 6d. 
 
 In this treatise will be found all the ordinary propositions, connected 
 with the Dynamics of Particles, which can be conveniently deducea 
 without the use of D' Alembert's Principle. Throughout the book 
 will be found a number of illustrative examples introduced in the 
 text, and for the most part completely worked out ; others with occa- 
 sional solutions or hints to assist the student are appended to each 
 chapter. For by far the greater portion of these, the Cambridge 
 Senate-House and College Examination Papers have been applied to. 
 
 Taylor. GEOMETRICAL CONICS; including An harmonic 
 Ratio and Projection, with numerous Examples. By C. TAYLOR, 
 B.A., Scholar of St. John's College, Cambridge. Crown 8vo. 
 cloth. 7-r. 6d. 
 
 This work contains elementary proofs of the principal properties of 
 Conic Sections, together with chapters on Projection and Anharmonic 
 Ratio. 
 
 Todhunter. Works by I. TODHUNTER, M.A., F.R.S., of 
 
 St. John's College, Cambridge : 
 
 "Perspicuous language, vigorous investigations, scrutiny of difficulties, 
 
 and methodical treatment, characterize Mr. Todhunter's works" 
 Civil Engineer. 
 
 THE ELEMENTS OF EUCLID; MENSURATION FOR 
 BEGINNERS ; ALGEBRA FOR BEGINNERS ; TRIGO- 
 NOMETRY FOR BEGINNERS; MECHANICS FOR 
 BEGINNERS. See EDUCATIONAL CATALOGUE. 
 
 ALGEBRA. For the Use of Colleges and Schools. Sixth Edition. 
 Crown 8vo. cloth. 7-y. 6d. 
 
 This work contains all the propositions which are usiially included in 
 elementary treatises on Algebra, and a large number of Examples 
 for Exercise. The author has sought to render the work easily in- 
 telligible to students, without impairing the accuracy of the demon- 
 strations, or contracting the limits of the subject. The Examples, 
 about Sixteen hundred and fifty in number, have been selected with 
 
MATHEMATICS. 
 
 Todhunter (I.) continued. 
 
 a vieiv to illustrate every part of the subject. The work will be 
 found peculiarly adapted to the wants of students who are without 
 the aid of a teacher. The Answers to the Examples, ^uith hints 
 for the sohition of some in which assistance may be needed, are 
 given at the end of the book. In the present edition two Neiv 
 Chapters and Three hundred miscellaneous Examples have been 
 added. "It has merits which unquestionably place it first in the 
 class to which it belongs." Educator. 
 
 KEY TO ALGEBRA FOR THE USE OF COLLEGES AND 
 SCHOOLS. Crown 8vo. icxr. 6d. 
 
 AN ELEMENTARY TREATISE ON THE THEORY OF 
 EQUATIONS. Second Edition, revised. Crown 8vo. cloth. 
 7s. 6d. 
 
 This treatise contains all the propositions which are usually included 
 in elementary treatises on the theory of Equations, together with 
 Examples for exercise. These have been selected from the College 
 and University Examination Papers, and the results have been 
 given when it appeared necessary. In order to exhibit a compre- 
 hensive view of the subject, the treatise includes investigations which 
 are not found in all the preceding elementary treatises, and also 
 some investigations which are not to be found in any of them. For 
 the second edition the work has been revised and some additions 
 have been made, the most important being an account of the 
 Researches of Professor Sylvester respecting Newtorfs Rule. l ' A 
 thoroughly trustworthy, complete, and yet not too elaborate treatise." 
 Philosophical Magazine. 
 
 PLANE TRIGONOMETRY. For Schools and Colleges. Fourth 
 Edition. Crown 8vo. cloth. 5^. 
 
 The design of this work has been to render the subject intelligible 
 to beginners, and at the same time to afford the student the oppor- 
 tunity of obtaining all the information ^vhich he will require on 
 this branch of Mathematics. Each chapter is follcnved by a set 
 of Examples : those which are entitled Miscellaneous Examples, 
 together with a few in some of the other sets, may be advantageously 
 reserved by the student for exercise after he has made some progress 
 in the subject. In the Second Edition the hints for the solution of 
 the Examples have been considerably increased. 
 
i6 SCIENTIFIC CATALOGUE. 
 
 Todhunter (I.} continued. 
 
 A TREATISE ON SPHERICAL TRIGONOMETRY. Third 
 
 Edition, enlarged. Crown 8vo. cloth. 4-r. 6d. 
 
 The present work is constructed on the same plan as the treatise on 
 Plane Trigonometry ', to which it is intended as a sequel. In the 
 account of Napier's Rules of circular parts, an explanation has 
 been given of a method of proof devised by Napier, which seems to 
 have been overlooked by most modern writers on the subject. Con- 
 siderable labour has been bestowed on the text in order to render it 
 comprehensive and accurate, and the Examples (selected chiefly 
 from College Examination Papers) have all been carefully verified. 
 "For educational purposes this work seems to be superior to any 
 others on the subject." Critic. 
 
 PLANE CO-ORDINATE GEOMETRY, as applied to the Straight 
 Line and the Conic Sections. With numerous Examples. Fourth 
 Edition, revised and enlarged. Crown 8vo. cloth. 7^. 6d. 
 
 The author has here endeavoured to exhibit the subject in a simple 
 manner for the benefit of beginners, and at the same time to include 
 in one volume all that students usually require. In addition, 
 therefore, to the propositions which have ahoays appeared in such 
 treatises, he has introduced the methods of abridged notation, 
 which are of more recent origin : these methods, which are of a 
 less elementary character than the rest of the work, are placed in 
 separate chapters, and may be omitted by the student at first. 
 
 A TREATISE ON THE DIFFERENTIAL CALCULUS. 
 With numerous Examples. Sixth Edition. Crown 8vo. cloth. 
 los. 6d. 
 
 The author has endeavoured in the present work to exhibit a compre- 
 hensive view of the Differential Calculus on the method of limits. 
 In the more elementary portions he has entered into considerable 
 detail in the explanations, with the hope that a reader who is without 
 the assistance of a tutor may be enabled to acquire a competent ac- 
 quaintance with the subject. The method adopted is that of Dif- 
 ferential Coefficients. To the different chapters are appended 
 Examples sufficiently numerous to render another book unnecessary; 
 these Examples bdng mostly selected from College Examination 
 Papers. This and the following work have been translated into 
 
MATHEMATICS. 17 
 
 Todhunter (I.) continued. 
 
 Italian by Professor Battaglini, who in his Preface speaks thus : 
 "In publishing this translation of the Differential and Integral 
 Calculus of Mr. Todhunter, we have had no other object than to 
 add to the books which are in the hands of the students of our Uni- 
 versities, a work remarkable for the clearness of the exposition, the 
 rigour of the demonstrations, the just proportion in the parts, and 
 the rich store of examples which offer a large field for usejul 
 exercise" 
 
 A TREATISE ON THE INTEGRAL CALCULUS AND ITS 
 APPLICATIONS. With numerous Examples. Third Edition, 
 revised and enlarged. Crown 8vo. cloth. los. 6d. 
 This is designed' as a work at once elementary and complete, adapted 
 for the use of beginners, and sufficient for the wants of advanced 
 students. In the selection of the propositions, and in the mode jf 
 establishing them, it has been sought to exhibit the principles clearly, 
 and to illustrate all their most important results. The process of 
 summation has been repeatedly brought forward, with the view 
 of securing the attention of the student to the notions which form the 
 true foundation of the Calculus itself, as well as of its most 
 valuable applications. Every attempt has been made to explain those 
 difficulties which usually perplex beginners, especially with reference 
 to the limits of integrations. A new method has been adopted in 
 regard to the transformation of multiple integrals. The last chapter 
 deals with the Calculus of Variations. A large collection of Exer- 
 cises, selected from College Examination Papers, has been appended 
 to the several chapters. 
 
 EXAMPLES OF ANALYTICAL GEOMETRY OF THREE 
 DIMENSIONS. Third Edition, revised. Crown 8vo. cloth. 4.$-. 
 
 A TREATISE ON ANALYTICAL STATICS. With numerous 
 Examples. Third Edition, revised and enlarged. Grown 8v o . 
 cloth. IOJ-. 6d. 
 
 In this work on Statics (treating of the laws of the equilibrium of 
 bodies) will be found all the propositions which usually appear in 
 treatises on Theoretical Statics. To the different chapters Examphs 
 are appended, which have been principally selected from University 
 Examination Papers. In the Third Edition many additions have 
 been made, in order to illustrate the application of the principles of 
 the siibject to the solution of problems. 
 
i8 SCIENTIFIC CATALOGUE. 
 
 Todhunter (I.} continued. 
 
 A HISTORY OF THE MATHEMATICAL THEORY OF 
 PROBABILITY, from the Time of Pascal to that of Laplace. 
 8vo. i8j. 
 
 The subject of this work has high claims to consideration on account 
 of the subtle problems -which it involves, the valuable contributions 
 to analysis which it has produced, its important practical applica- 
 tions, and the eminence of those who have cultivated it ; nearly 
 every great mathematician within the range of a century and 
 a half comes under consideration in the course of the history. The 
 author has endeavoured to be quite accurate in his statements, and 
 to reproduce the essential elements of the original works which he 
 has analysed. Besides being a history, the work may claim the title 
 of a comprehensive treatise on the Theory of Probability, for it 
 asstimes in the reader only so much knowledge as can be gained from 
 an elementary book on Algebra, and introduces him to almost every 
 process and every special problem which the literature of the subject 
 can furnish. 
 
 RESEARCHES IN THE CALCULUS OF VARIATIONS, 
 Principally on the Theory of Discontinuous Solutions : An Essay 
 to which the Adams' Prize was awarded in the University of 
 Cambridge in 1871. 8vo. 6.y. 
 
 The subject of this Essay was prescribed in the following terms by the 
 Examiners : "A determination of the circumstances under which 
 discontinuity of any kind presents itself in the solution of a problem 
 of maximum or minimum in the Calculus of Variations, and 
 applications to particular instances. It is expected that the discus- 
 sion of the instances should be exemplified as far as possible geo- 
 metrically, and that attention be especially directed to cases of real or 
 supposed failure of the Calculus." While the Essay is thus mainly 
 devoted to the consideration of discontinuous solutions, various 
 other questions in the Calculus of Variations are examined and 
 elucidated ; and the author hopes he has definitely contributed to the 
 extension and improvement of our knnvledge oftku refined depart- 
 ment of analysis. 
 
 A HISTORY OF THE MATHEMATICAL THEORIES OF 
 ATTRACTION, and the Figure of the Earth, from the time of 
 Newton to that of Laplace. Two vols. 8vo. 245-. 
 
MATHEMATICS. 19 
 
 Wilson (W. P.) A TREATISE ON DYNAMICS. By 
 W. P. WILSON, M.A., Fellow of St. John's College, Cambridge, 
 and Professor of Mathematics in Queen's College, Belfast. 8vo. 
 9-r. 6d. 
 
 Wolstenholme. A BOOK OF MATHEMATICAL 
 PROBLEMS, on Subjects included in the Cambridge Course. 
 By JOSEPH WOLSTENHOLME, Fellow of Christ's College, some 
 time Fellow of St. John's College, and lately Lecturer in Mathe- 
 matics at Christ's College. Crown 8vo. cloth. 8s. 6d. 
 
 CONTENTS : Geometry (Euclid) Algebra Plane Trigonometry 
 Geometrical Conic Sections Analytical Conic Sections Theoiy of 
 Equations Differential Calculus Integral Calculus Solid Geo~ 
 metry Statics Elementary Dynamics Newton Dynamics of a 
 Point Dynamics of a Rigid Body Hydrostatics Geometrical 
 Optics Spherical Trigonometry and Plane Astronomy. In some 
 cases the author has prefixed to certain classes of problems frag' 
 mentary notes on the mathematical subjects to ^vhich they relate. 
 "Judicious, symmetrical, and well arranged." Guardian. 
 
 B 2 
 
20 SCIENTIFIC CATALOGUE. 
 
 PHYSICAL SCIENCE. 
 
 Airy (G. B.) POPULAR ASTRONOMY. With Illustrations. 
 By Sir G. B. AIRY, K.C.B., Astronomer Royal. Seventh and 
 cheaper Edition. i8mo. cloth. 4,5-. 6d. 
 
 This work consists of Six Lectures, which are intended ' ' to explain 
 to intelligent persons the principles on which the instruments of an 
 Observatory are constructed (omitting all details, so far as they are 
 merely subsidiary), and the principles on which the observations 
 made with these instruments are treated for deduction of the distances 
 and weights of the bodies of the Solar System, and of a few stars, 
 omitting all minutice of formula, and all troublesome details of 
 calculation." The speciality of this volume is the direct reference of 
 every step to the Observatory, and the full description of the methods 
 and instruments of observation. 
 
 Bastian. Works by H. CHARLTON BASTIAN, M.D., F.R.S., 
 Professor of Pathological Anatomy in University College, London, 
 etc. : 
 
 THE MODES OF ORIGIN OF LOWEST ORGANISMS : 
 Including a Discussion of the Experiments of M. Pasteur, and a 
 Reply to some Statements by Professors Huxley and Tyndall. 
 Crown 8vo. 4^. 6d. 
 
 The present volume contains a fragment of the evidence which will be 
 embodied in a much larger work now almost completed relating to 
 the nature and origin of living matter, and in favour of what is 
 termed the Physical Doctrine of Life. " It is a work worthy of the 
 highest respect, and places its author in the very first class of scientific 
 physicians. . . . It would be difficult to name an instance in which 
 skill, knowledge, perseverance, and great reasoning power have been 
 more happily applied to the investigation of a complex biological 
 problem." British Medical Journal. 
 
PHYSICAL SCIENCE. 
 
 Bastian (H. C.) continued. 
 
 THE BEGINNINGS OF LIFE: Being some Account of the 
 Nature, Modes of Origin, and Transformations of Lower Organ- 
 isms. In Two Volumes. With upwards of loo Illustrations, 
 Crown 8vo. 2%s. 
 
 These "volumes contain the results of several years' investigation on the 
 Origin of Life, and it was only after the author had proceeded 
 some length with his observations and experiments that he was 
 compelled, to change the opinions he started with for those announced 
 in the present work the most important of which is that in favour 
 of " spontaneous generation " the theory that life has never ceased 
 to be actually originated. The First Part of the work is intended 
 to show the general reader, more especially, that the logical conse- 
 quences of the now commonly accepted doctrines concerning tJ,e 
 " Conservation of Energy " and the " Correlation of the Vital and 
 Physical Forces " are wholly favourable to the possibility of the in- 
 dependent origin of "living" matter. It also contains a view of 
 the " Cellular Theory of Organisation." In the Second Part of 
 the work, under the head " Archebiosis," the question as to the 
 present occurrence or non-occurrence of " spontaneous generation " 
 is considered. "It is a book that cannot be ignored, and must 
 inevitably lead to renewed discussions and repeated observations, and 
 through these to the establishment of truth" A. R. WALLACE in 
 Nature. 
 
 Birks (T. R.) ON MATTER AND ETHER ;*or, The Secret 
 Laws of Physical Change. By THOMAS RAWSON BIRKS, M.A., 
 Professor of Moral Philosophy in the University of Cambridge. 
 Crown 8vo. $s. 6d. 
 
 The author believes that the hypothesis of the existence of, besides matter, 
 a luminous ether, of immense elastic force, supplies the true and suf- 
 ficient key to the remaining secrets of inorganic matter, of the phe- 
 nomena of light, electricity, etc. In this treatise the author endea- 
 vours first to form a clear and definite conception with regard to the 
 real nature both of matter and ether, and the laws of mutual action 
 which must be supposed to exist between them. He then endeavours 
 to trace out the main consequences of the fundamental hypothesis, 
 and their correspondence with the known phenomena of physical 
 change. 
 
22 SCIENTIFIC CATALOGUE. 
 
 Blanford (W. T.) GEOLOGY AND ZOOLOGY OF 
 
 ABYSSINIA. By W. T. BLANFORD. 8vo. 2is. 
 
 This work contains an account of the Geological and Zoological Obser- 
 vations made by the author in Abyssinia, -when accompanying the 
 British Army on its march to Magdala and back in 1868, and 
 during a short journey in Northern Abyssinia, after the departure 
 of the troops. Part I. Personal Narrative; Part II. Geology; 
 Part III. Zoology. With Coloured Illustrations and Geological 
 Map. "The result of his labours" the Academy says, "is an 
 important contribution to the natural history of the country. " 
 
 Clodd. THE CHILDHOOD OF THE WORLD : a Simple 
 Account of Man in Early Times. By EDWARD CLODD, F.R.A.S. 
 Second Edition. Globe 8vo. 3-r. 
 
 " Likely, we think, to prove acceptable to a large and growing class of 
 readers." Pall Mall Gazette. 
 
 PROFESSOR MAX MULLER, in a letter to the Author, says : " I read 
 your book with great pleasure. I have no doubt it will do good, 
 and I hope you will continue your work. Nothing spoils our temper 
 so much as having to unlearn in youth, manhood, and even old 
 age, so many things which we were taught as children. A book 
 like yours will prepare afar better soil in the child's mind, and I 
 was delighted to have it to read to my children." 
 
 Cooke (Josiah P., Jun.) FIRST PRINCIPLES OF 
 
 CHEMICAL PHILOSOPHY. By JOSIAH P. COOKE, Jun., 
 Ervine Professor of Chemistry and Mineralogy in Harvard College. 
 Crown 8vo. 12s. 
 
 The object of the author in this book is to present the philosophy of 
 Chemistry in such a form that it can be made with profit the subject 
 of College recitations, and furnish the teacher with the means of 
 testing the student's faithfulness and ability. With this view the 
 subject has been developed in a logical order, and the principles of 
 the science are taught independently of the experimental evidence on 
 tihich they rest. 
 
 Cooke (M. C.) HANDBOOK OF BRITISH FUNGI, 
 with full descriptions of all the Species, and Illustrations of the 
 Genera. By M. C. COOKE, M.A. Two vols. crown 8vo. 24?. 
 
PHYSICAL SCIENCE. 23 
 
 During the thirty-five years that have elapsed since the appearance of 
 the last complete Mycologic Flora no attempt has been made to revise 
 it, to incorporate species since discovered, and to bring it up to the 
 standard of modern science. No apology, therefore, is necessary for 
 the present effort, since all will admit that the want of such a 
 manual has long been felt, and this work makes its appearance 
 under the advantage that it seeks to occupy a place which has long 
 been vacant. No effort has been spared to make the work worthy 
 of confidence, and, by the publication of an occasional supplement, 
 it is hoped to maintain it for many years as the "Handbook" 
 for every student of British Fungi. Appended is a complete alpha- 
 betical Index of all the divisions and subdivisions of the Fungi 
 noticed in the text. The book contains 400 figures. " Will main- 
 tain its place as the standard English book, on the subject of which 
 it treats , for many years to come" Standard. 
 
 Dawkins, CAVE-HUNTING: Researches on the Evidence of 
 Caves respecting the Early Inhabitants of Europe. By W. BOYD 
 DAWKINS, F. R.S. Illustrated. 8vo. [In the Press. 
 
 Dawson (J. W.) ACADIAN GEOLOGY. The Geologic 
 
 Structure, Organic Remains, and Mineral Resources of Nova 
 Scotia, New Brunswick, and Prince Edward Island. By JOHN 
 WILLIAM DAWSON, M.A., LL.D., F.R.S., F.G.S., Principal and 
 Vice-Chancellor of M'Gill College and University, Montreal, &c. 
 Second Edition, revised and enlarged. With a Geological Map 
 and numerous Illustrations. 8vo. iSs. 
 
 The object of the first edition of this work zuas to place within the 
 reach of the people of the districts to which it relates, a popular 
 account of the more recent discoveries in the geology and mineral 
 resources of their country, and at the same time to give to geologists 
 in other countries a connected view of the structure of a very in- 
 teresting portion of the American Continent, in its relation to 
 general and theoretical Geology. In the present edition, it is hoped this 
 design is still more completely fulfilled, with reference to the present 
 more advanced condition of knowledge. The author has endea- 
 voured to convey a knowledge of the structure and fossils of the 
 region in such a manner as to be intelligible to ordinary readers, 
 and has devoted much attention to all questions relating to the nature 
 and present or prospective value of deposits of tiseful minerals. 
 
24 SCIENTIFIC CATALOGUE. 
 
 Besides a large coloured Geological Map of the district, the work 
 is illustrated by upwards of 260 cuts of sections, fossils, animals, 
 etc. ' ' The book will doubtless find a place in the library, not only 
 of the scientific geologist, but also of all who are desirous of the in- 
 dustrial progress and commercial prosperity of the Acadian pro- 
 vinces." Mining Journal. ' l A style at once popular and scientific. 
 . . . A valuable addition to our store of geological kncnvledge." 
 Guardian. 
 
 Flower (W. H.) AN INTRODUCTION TO THE OSTE- 
 OLOGY OF THE MAMMALIA. Being the substance of the 
 Course of Lectures delivered at the Royal College of Surgeons 
 of England in 1870. By W. H. FLOWER, F.R.S., F.R.C.S., 
 Hunterian Professor of Comparative Anatomy and Physiology. 
 With numerous Illustrations. Globe 8vo. Js. 6d. 
 
 Although the present work contains the substance of a Course of Lectures, 
 the form has been changed, so as the better to adapt it as a hand- 
 book for students. Theoretical views have been almost entirely ex- 
 cluded: and while it is impossible in a scientific treatise to avoid the 
 employment of technical terms, it has been the author's endeavour to 
 use no more than absolutely necessary, and to exercise due care in 
 selecting only those that seem most appropriate, or which have re- 
 ceived the sanction of general adoption. IVith a very few excep- 
 tions the illustrations have been drawn expressly for this work from 
 specimens in the Museum of the Royal College of Surgeons. 
 
 Galton. Works by FRANCIS GALTON, F.R.S. : 
 
 METEOROGRAPHICA, or Methods of Mapping the Weather. 
 Illustrated by upwards of 600 Printed Lithographic Diagrams. 
 4to. 9-r. 
 
 As Mr. Galton entertains strong views on the necessity of Meteorolo- 
 gical Charts and Maps, he determined, as a practical proof of what 
 could be done, to chart the entire area of Europe, so far as meteorological 
 stations extend, during one month, viz. the month of December, 1861. 
 Mr. Galton got his data from authorities in every part of Britain 
 and the Continent, and on the basis of these has here drawn up 
 nearly a hundred different Maps and Charts, showing the state of 
 the weather all over Europe during the above period. " If the 
 various Governments and scientific bodies would perform for the 
 
PHYSICAL SCIENCE. 25 
 
 G al t o n continued. 
 
 whole world for two or three years what, at a great cost and labour, 
 Mr. Galton has done for a part of Europe for one month, Meteoro- 
 logy would soon cease to be made a joke of." Spectator. 
 
 HEREDITARY GENIUS : An Inquiry into its Laws and Con- 
 sequences. Demy 8vo. I2s. 
 
 " I propose" the author says, "A? show in this book that a man's 
 nat^lral abilities are derived by inheritance, under exactly the same 
 limitations as are the form and physical features of the whole organic 
 ^uorld. I shall shcnv that social agencies of an ordinary character, 
 whose influences are little suspected, are at this moment working 
 towards the degradation of human nature, and that others are 
 working towards its improvement. The general plan of my argu- 
 ment is to show that high reputation is a pretty accurate test of high 
 ability ; next, to discuss the relationships of a large body of fairly 
 eminent men, and to obtain from these a general survey of the laws 
 of heredity in respect of genius. Then will follow a short chapter, 
 by way of comparison, on the hereditary transmission of physical 
 gifts, as deduced from the relationships of certain classes of oarsmen 
 and wrestlers. Lastly, I shall collate my results and draw conclu- 
 sions." The Times calls it "a most able and most interesting 
 book;" and My. Darwin, in his " Descent of Man" (vol. \. p. ill), 
 says, " We kncnv, through the admirable labours of Mr. Galton, 
 that Genius tends to be inherited." 
 
 Geikie (A.) SCENERY OF SCOTLAND, Viewed in Connec- 
 tion with its Physical Geography. With Illustrations and a new 
 Geological Map. By ARCHIBALD GEIKIE, Professor of Geology 
 in the University of Edinburgh. Crown 8vo. los. 6d. 
 
 " We can confidently recommend Mr. Geikte's ivork to those who wish 
 to look below the surface and read the physical history of the Scenery 
 of Scotland by the light of modern science" Saturday Review. 
 " Amusing, picturesque, and instructive." Times. 
 
 Guillemin. THE FORCES OF NATURE: A Popular Intro- 
 duction to the Study of Physical Phenomena. By AM^DBE 
 GUILLEMIN. Translated from the French by MRS. NORMAN 
 LOCKYER ; and Edited, with Additions and Notes, by J. NORMAN 
 
2.6 SCIENTIFIC CATALOGUE. 
 
 LOCKYER, F.R.S. Illustrated by n Coloured Plates and 455 
 Woodcuts. Second Edition. Imperial 8vo. cloth, extra gilt. 
 
 M. Guillemin is already zvetl known in this country as a most success- 
 ful populariser of the results of accurate scientific research, his 
 works, while eloquent, intelligible, and interesting to the general 
 reader, being thoroughly trustworthy and up to date. The present 
 work consists of Seven Books, each divided into a number of 
 Chapters, the Books treating respectively of Gravity, Sound, 
 Light, Heat, Magnetism, Electricity, and Atmospheric Meteors. 
 The programme of the work has not been confined to a simple 
 explanation of the facts : but an attempt has been made to grasp 
 their relative bearings, or, in other words, their laws, and that 
 too without taking for granted that the reader is acquainted 
 with mathematics. " The author* s aim has been to smooth the way 
 for those who desire to extend their studies, and likewise to present 
 to general readers a sufficiently exact and just idea of this branch of 
 science." Daily News. " Translator and Editor have done 
 justice to their trust. The text has all the force and flow of original 
 writing, combining faithfulness to the author s meaning with 
 purity and independence in regard to idiom ; while the historical 
 precision and accuracy pervading the work throughout, speak of the 
 watchful editorial supervision which has been given to every scientific 
 detail. Nothing can well exceed the clearness and delicacy of the 
 illustrative woodcuts, borrowed from the French edition, or the 
 purity and chromatic truth of the coloured plates. Altogether, the 
 work may be said to have no parallel, either in point of fulness or 
 attraction, as a popular manual of physical science. .... 
 What we feel, however, bound to say, and %vhat we say with 
 pleasure, is, that among works of its class no publication can stand 
 comparison either in literary completeness or in artistic grace with 
 if." Saturday Review. 
 
 Henslow. THE THEORY OF EVOLUTION OF LIVING 
 THINGS, and the Principles of Evolution applied to Religion 
 considered as Illustrative of the Wisdom and Beneficence of the 
 Almighty. By the Rev. GEORGE HENSLOW, M.A., F.R.S. 
 Crown 8vo. 6s. 
 
PHYSICAL SCIENCE. 27 
 
 Hooker (Dr.) THE STUDENT'S FLORA OF THE 
 BRITISH ISLANDS. By J. D. HOOKER, C.B., F.R.S., 
 M.D., D.C.L., Director of the Royal Gardens, Kew. Globe 8vo. 
 los. bd. 
 
 The object of this work is to supply students and field-botanists "with a 
 fuller account of the Plants of the British Islands than the manuals 
 hitherto in use aim at giving. The Ordinal, Generic, and Specific 
 characters have been re-written, and are to a great extent original, 
 and drawn from living or dried specimens, or both. ' ' Cannot fail to 
 perfectly fulfil the purpose for which it is intended." Land and 
 Water. " Containing the fullest and most accurate manual of the 
 kind that has yet appeared.' 11 Pall Mall Gazette. 
 
 Huxley (Professor). LAY SERMONS, ADDRESSES, 
 
 AND REVIEWS. By T. H. HUXLEY, LL.D., F.R.S. New 
 and Cheaper Edition. Crown 8vo. Js. 6d. 
 
 Fourteen Discourses on the following subjects: (i) On the Advisable^ 
 ness of Improving Natural Knowledge: (2) Emancipation 
 Black and White : (3) A Liberal Education, and where to find 
 it: (4) Scientific Education: (5) On the Educational Value of 
 the Natural History Sciences: (6) On the Study of Zoology: 
 (7) On the Physical Basis of Life: (8) The Scientific Aspects oj 
 Positivism: (9) On a Piece of Chalk: (10) Geological Contem- 
 poraneity and Persistent Types of Life : (n) Geological Reform: 
 (12) The Origin of Species: (13) Criticisms on the "Origin of 
 Species: 1 ' (14) On Descartes' " Discourse touching the Method of 
 using One's Reason rightly and of seeking Scientific Truth." Tht 
 momentous influence exercised by Mr. Huxley's writings on physical, 
 mental, and social science is universally acknowledged ; his ^vorks 
 must be studied by all who would comprehend the various drifts of 
 modern thought. 
 
 ESSAYS SELECTED FROM LAY SERMONS, ADDRESSES, 
 AND REVIEWS. Crown 8vo. u. 
 
 This volume includes Numbers I, 3, 4, 7, 8, and 14, of the above. 
 
 CRITIQUES AND ADDRESSES. 8vo. ior. 6d. 
 
 These " Critiques and Addresses,' 1 like the " Lay Sermons," etc., pub- 
 lished three years ago, deal c hie fty with educational, scientific, and 
 
28 SCIENTIFIC CATALOGUE. 
 
 Huxley (Professor) continued. 
 
 philosophical stibjects ; and, in fact, as the author says, "indicate 
 the high-water mark of the various tides of occupation by which 1 
 have been carried along since the beginning of the year 1870." The 
 following is the list of Contents: I. Administrative Nihilism. 
 
 2. The School Boards: what they can do, and what they may do. 
 
 3. On Medical Education. 4. Yeast. 5. On the Formation of 
 Coal. 6. On Coral and Coral Reefs. 7. On the Methods and 
 Results of Ethnology. 8. On some Fixed Points in British Eth- 
 nology. 9. Paleontology and the Doctrine of Evolution. 10. 
 Biogenesis and Abiogenesis. 1 1. Mr. Darwirfs Critics. 12. The 
 Genealogy of Animals. 13. Bishop Berkely on the Metaphysics of 
 Sensation. 
 
 LESSONS IN ELEMENTARY PHYSIOLOGY. With numerous 
 Illustrations. New Edition. i8mo. cloth. 4*. 6d. 
 
 This book describes and explains, in a series of graduated lessons, the 
 principles of Human Physiology, or the Structure and Functions 
 of the Human Body. The first lesson supplies a general view of 
 the subject. This is followed by sections on the Vascular or Venous 
 System, and the Circulation ; the Blood and the Lymph ; Respira- 
 tion : Sources of Loss and of Gain to the Blood ; the Function of 
 Alimentation; Motion and Locomotion; Sensations and Sensory 
 Organs ; the Organ of Sight ; the Coalescence of Sensations with 
 one another and with other States of Consciousness ; the Nervous 
 System and Innervation ; Histology, or the Minute Structure of 
 the Tissues. A Table of Anatomical and Physiological Constants 
 is appended. The lessons are fully illustrated by numerous en- 
 gravings. The new edition has been thoroughly revised, and a con- 
 siderable number of new illustrations added : several of these have 
 been taken from the Rabbit, theSheep,the Dog, and the Frog, in order 
 to aid those who attempt to make their knowledge real, by acquiring 
 some practical acquaintance with the facts of Anatomy and Physi- 
 ology. " Pure gold throughout" Guardian. "Unquestionably 
 the clearest and most complete elementary treatise on this subject 
 that we possess in any language." Westminster Review. 
 
 Jellet (John H., B.D.) A TREATISE ON THE 
 THEORY OF FRICTION. By JOHN H. JELLET, B.D., 
 
PHYSICAL SCIENCE. 29 
 
 Senior Fellow of Trinity College, Dublin ; President of the Royal 
 Irish Academy. 8vo. 8>r. 6d. 
 
 The Theory of Friction, considered as a part of National Mechanics, 
 has not, the author thinks, received the attention which it deserves. 
 On this account many students have been probably led to regard 
 the discussion of this force as scarcely belonging to Rational 
 Mechanics at all ; whereas the theory of friction is as truly a part 
 of that subject as the theory of gravitation. The force with which 
 this theory is concerned is subject to laws as definite, and as fully 
 susceptible of mathematical expression, as the force of gravity. 
 This book is taken up with a special investigation of the laws of 
 friction ; and some of the principles contained in it are believed to 
 be here enunciated for the first time. The work consists of eight 
 Chapters as follows : I. Definitions and Principles. //. Equili- 
 brium with Frictions. III. Extreme Positions of Equilibrium. 
 IV. Movement of a Particle or System of Particles. V. Motion 
 of a Solid Body. VI. Necessary and Possible Equilibrium,. VII. 
 Determination of the Actual Value of the Acting Force of Friction. 
 VlIL Miscellaneous Problems \. Problem of the Top. 2. Friction 
 Wheels and Locomotives. 3. Questions for Exercise. " The book 
 supplies a want which has hitherto existed in the science of pure 
 mechanics. " Engineer. 
 
 Jones. THE OWENS COLLEGE JUNIOR COURSE OF 
 PRACTICAL CHEMISTRY. By FRANCIS JONES, Chemical 
 Master in the Grammar School, Manchester. With Preface by 
 Professor ROSCOE. i8mo. with Illustrations. 2s, 6d. 
 
 Kingsley. GLAUCUS : OR, THE WONDERS OF THE 
 SHORE. By CHARLES KINGSLEY, Canon of Westminster. 
 New Edition, revised and corrected, with numerous Coloured 
 Plates. Crown 8vo. 5-r. 
 
 Kirchhoff (G.) RESEARCHES ON THE SOLAR SPEC- 
 TRUM, and the Spectra of the Chemical Elements. By G. 
 KIRCHHOFF, Professor of Physics in the University of Heidelberg. 
 Second Part. Translated, with the Author's Sanction, from the 
 Transactions of the Berlin Academy for 1862, by HENRY R. 
 ROSCOE, B.A., Ph.D., F.R.S., Professor of Chemistry in Owens 
 College, Manchester. Part II. 4to. 5-f. 
 
30 SCIENTIFIC CATALOGUE. 
 
 "It is to Kirchhoff^ve are indebted for by far the best and most accurate 
 observations of these phenomena.' 1 '' Edin. Review. " This memoir 
 seems almost indispensable to every Spectrum observer" Philo- 
 sophical Magazine. 
 
 Lockyer (J. N.) Works by J. NORMAN LOCKYER, F.R.S. 
 ELEMENTARY LESSONS IN ASTRONOMY. With mi- 
 merous Illustrations. New Edition. i8mo. $s. 6d. 
 The author has here aimed to give a connected view of the whole subject, 
 and to supply facts, and ideas founded on the facts, to serve as a basis 
 for subsequent study and discussion. The chapters treat of the 
 Stars and Nebula ; the Sun; the Solar System ; Apparent Move- 
 ments of the Heavenly Bodies ; the Measurement of Time; Light ; 
 the Telescope and Spectroscope; Apparent Places of the Heavenly 
 Bodies ; the Real Distances and Dimensions ; Universal Gravitation. 
 The most recent Astronomical Discoveries are incorporated. Mr. 
 Lockyer's work supplements that of the Astronomer Royal. ' ' Tkf 
 book is full, clear, sound, and worthy of attention, not only as a 
 popular exposition, but as a scientific ' Index S " Athenaeum. 
 "The most fascinating of elementary books on the Sciences. "- 
 Nonconformist. 
 
 THE SPECTROSCOPE AND ITS APPLICATIONS. By J. 
 NORMAN LOCKYER, F. R.S. With Coloured Plate and numerous 
 Illustrations. Second Edition. Crown 8vo. $s. 6d. 
 
 This forms Volume One of" Nature Series," a series of popular 
 Scientific Works now in course of publication, consisting of popular 
 and instructive works, on particular scientific subjects Scientific 
 Discovery, Applications, History, Biography by some of the 
 most eminent scientific men of the day. They will be so written as 
 to be interesting and intelligible even to non-scientific readers. Mr. 
 Lockyer's work in Spectrum Analysis is widely known. In the 
 present short treatise will be found an exposition of the principles 
 on which Spectrum Analysis rests, a description of the various 
 kinds of Spectroscopes, and an account of what has already been 
 done with the instrument, as well as of what may yet be done both 
 in science and in the industrial art. 
 
 CONTRIBUTIONS TO SOLAR PHYSICS. With numerous 
 Illustrations. Royal 8vo., uniform with Roscoe's " Spectrum 
 Analysis," Thompson's " Depths of the Sea," and Ball's "Me- 
 chanics." u. 6d. 
 
PHYSICAL SCIENCE. 31 
 
 Macmillan (Rev. Hugh). For other Works by the same 
 Author, see THEOLOGICAL CATALOGUE. 
 
 HOLIDAYS ON HIGH LANDS ; or, Rambles and Incidents in 
 search of Alpine Plants. Crown 8vo. cloth. 6s. 
 
 The aim of this book is to impart a general idea of the origin, cha- 
 racter, and distribution of those rare and beautiful Alpine plants 
 which occur on the British hills, and ivhich are found almost every- 
 where on the lofty mountain chains of Europe, Asia, Africa, and 
 America. In the first three chapters the peculiar vegetation of the 
 Highland mountains is fully described ; while in the remaining 
 chapters this vegetation is traced to its northern cradle in the moun- 
 tains of Norway, and to its southern European termination in t'he 
 Alps of Switzerland. The information the author has to give is 
 conveyed in a setting of personal adventure. "One of the most 
 charming books of its kind ever written" Literary Churchman. 
 " Mr. M.'s glowing pictures of Scandinavian scenery" Saturday 
 Review. 
 
 FOOT-NOTES FROM THE PAGE OF NATURE. With 
 numerous Illustrations. Fcap. 8vo. $s. 
 
 " Those who have derived pleasure and profit from the stttdy of flowers 
 and ferns subjects, it is pleasing to find, now everywhere popular 
 by descending lower into the arcana of the vegetable kingdom, 
 will find a still more interesting and delightful field of research in 
 the objects brought under review in the following pages :" Preface. 
 '* The naturalist and the botanist will delight in this volume, and 
 those who understand little of the scientific parts of the work will 
 linger over the mysterious page of nature here unfolded to their 
 vieiv." John Bull. 
 
 Mansfield (C. B.) A THEORY OF SALTS. A Treatise 
 on the Constitution of Bipolar (two-membered) Chemical Com- 
 pounds. By the late CHARLES BLACHFORD MANSFIELD. Crown 
 8vo. 145-. 
 
 " Mansfield" says the editor, "wrote this book to defend the prin- 
 ciple that the fact of voltaic decomposition afforded the true indi- 
 cation^ if properly interpreted, of the nature of the saline structure, 
 and of the atomicity of the elements that built it up. No chemist 
 
32 SCIENTIFIC CATALOGUE. 
 
 "will peruse this book without feeling that he is in the presence of an 
 original thinker, whose pages are continually suggestive, even 
 though their general argument may not be entirely concurrent in 
 direction with that of modern chemical thought." 
 
 Miller. THE ROMANCE OF ASTRONOMY. By R. KALLEY 
 
 MILLER, M.A., Fellow and Assistant Tutor of St. Peter's Col- 
 lege, Cambridge. Crown 8vo. $s. 6d. 
 
 " On the whole, the information contained is of a trustworthy cha- 
 racter, and we cordially recommend it to the perusal of those who, 
 without being in possession of the knowledge requisite for discussing 
 astronomical theories, or the means by which they are arrived at, 
 are yet desirous of becoming acquainted with some of the most 
 interesting of astronomical conclusions^ Athenaeum. 
 
 Mivart (St. George). Works by ST. GEORGE MIVART, F.R.S. 
 etc., Lecturer in Comparative Anatomy at St. Mary's Hospital: 
 
 ON THE GENESIS OF SPECIES. Crown 8vo. Second 
 Edition, to which notes have been added in reference and reply to 
 Darwin's "Descent of Man." With numerous Illustrations, pp. 
 xv. 296. 9-r. 
 
 The aim of the author is to support the doctrine that the various 
 species have been evolved by ordinary natural laws (for the most 
 part unknown) controlled by the subordinate action of "natural 
 selection" and at the same time to remind some that there is and 
 can be absolutely nothing in physical science which forbids them to 
 regard those natural laws as acting with the Divine concurrence, 
 and in obedience to a creative fiat originally imposed on the primeval 
 cosmos, "in the beginning" by its Creator, its Upholder, and its 
 Lord. Nearly fifty woodcuts illustrate the letter -press, and a com- 
 plete index makes all references extremely easy. Canon Kingsley, 
 in his address to the " Devonshire Association," says, "Let me re- 
 commend earnestly to you, as a specimen of what can be said on the 
 other side, the ' Genesis of Species? by Mr. St. Geffrge Mivart, 
 F.R.S., a book which I am happy to say has been received elsewhere 
 as it has deserved, and, I trust, will be received so among you." 
 "In no work in the English language has this great controversy 
 been treated at once with the same broad and vigorous grasp of 
 facts, and the same liberal and candid temper." Saturday Review. 
 
PHYSICAL SCIENCE. 33 
 
 Mivart (St. George) continued. 
 
 LESSONS IN ELEMENTARY ANATOMY. With upwards of 
 400 Illustrations. i8mo. 6s. 6d. 
 
 This volume is intended to form one of the series of Elementary Class- 
 Books of Science, and the Lessons are intended in the first place for 
 teachers and for earnest students of both sexes, not already acquainted 
 with human anatomy. The author has endeavoured, secondly, by 
 certain additions and by the mode of treatment, to fit them for 
 students in medicine, and generally for those acquainted with 
 human anatomy, but desirous of learning its more significant rela- 
 tions to the structure of other animals: the author therefore hopes 
 his volume may serve as a hand-book of Human Morphology. The 
 book is amply illustrated with carefully drawn woodcuts. 
 
 Murphy. Works by JOSEPH JOHN MURPHY: 
 
 HABIT AND INTELLIGENCE, in Connection with the Laws of 
 Matter and Force : A Series of Scientific Essays. Two Vols. 
 8vo. i6j-. 
 
 The author's chief purpose in this work has been to state and to dis- 
 cuss what he regards as the special and characteristic principles of 
 life. The most important part of the work treats of those vital 
 principles which belong to the inner domain of life itself, as dis- 
 tinguished from the Principles which belong to the border-land 
 where life comes into contact with inorganic matter and force. In 
 the inner domain of ife we find two principles, which- are, the 
 author believes, coextensive with life and peculiar to it : these are 
 Habit and Intelligence. He has made as full a statement as 
 possible of the laws under which habits form, disappear, alter under 
 altered circumstances, and vary spontaneously. He discusses that 
 most important of all questions, whether intelligence is an ultimate 
 fact, incapable of being resolved into any other, or only a resultant 
 from the laws of habit. The latter part of the first volume is 
 occupied with the discussion of the question of the Origin of Species. 
 The first part of the second volume is occupied with an inquiry 
 into the process of mental growth and development, and the nature 
 of mental intelligence. In the chapter that follows, the author dis- 
 cusses the science of history, and the three concluding chapters 
 contain some ideas on the classification, the history, and the logic, of 
 the sciences. The author's aim has been to make the subjects treated 
 of intelligible to any ordinary intelligent man. "We are pleased 
 C 
 
34 SCIENTIFIC CATALOGUE. 
 
 Murphy continued. 
 
 to listen" says the Saturday Review, "to a writer who has so firm 
 a foothold upon the ground within the scope of his immediate 
 survey, and who can enunciate with so much clearness and force 
 propositions which come within his grasp" 
 
 THE SCIENTIFIC BASES OF FAITH. 8vo. 14*. 
 
 Nature. A WEEKLY ILLUSTRATED JOURNAL OF 
 
 SCIENCE. Published every Thursday. Price 4^. Monthly 
 
 Parts, is. ^d. and is. %d. ; Half-yearly Volumes, los. 6d. Cases for 
 
 binding Vols. is. 6d. 
 
 " Backed by many of the best names among English philosophers ; and 
 by a fau equally valuable supporters in America and on the Conti- 
 nent of Europe" Saturday Review. " This able and well-edited 
 Journal, which posts up the srience of the day promptly, and 
 promises to be of signal service to students and savants" British 
 Quarterly Review. 
 
 Oliver Works by DANIEL OLIVER, F.R.S., F.L.S., Professor of 
 Botany in University College, London, and Keeper of the Herba- 
 rium and Library of the Royal Gardens, Kew : 
 
 LESSONS IN ELEMENTARY BOTANY. With nearly Two 
 Hundred Illustrations. New Edition. i8mo cloth. 4^. 6d. 
 
 This book is designed <to teach the elements of Botany on Professor 
 Henslorv *s plan of selected Types and by the use of Schedules. The 
 earlier chapters, embracing the elements of Structitral and Physio- 
 logical Botany, introduce us to the methodical study of the Ordinal 
 Types. The concluding chapters are entitled, " flcnu to Dry 
 Plants " and "How to Describe Plants." A valuable Glossary is 
 appended to the volume. In the preparation of this work free use 
 has been made of the manuscript materials of the late Professor 
 Hensloru. 
 
 FIRST BOOK OF INDIAN BOTANY. With numerous 
 Illustrations. Extra fcap. 8vo. 6s. 6d. 
 
 This manual is, in substance, the author's " Lessons in Elementary 
 Botany" adapted for ttse in India, In preparing it he has had in 
 view the want, often felt, of some handy resume of Indian Botany ', 
 
PHYSICAL SCIENCE. 35 
 
 ivhich might be serviceable not only to residents of India, but also 
 to anyone about to proceed thitJier, desirous of getting some pre- 
 liminary idea of the botany of the country. It contains a well- 
 digested summary of all essential knowledge pertaining to Indian 
 Botany, wrought out in accordance with the best principles of 
 scientific arrangement '." Allen's Indian Mail. 
 
 Penrose (F. C.) ON A METHOD OF PREDICTING BY 
 
 GRAPHICAL CONSTRUCTION, OCCULTATIONS OF 
 STARS BY THE MOON, AND SOLAR ECLIPSES FOR 
 ANY GIVEN PLACE. Together with more rigorous methods 
 for the Accurate Calculation of Longitude. By F. C. PENROSE, 
 F.R.A.S. With Charts, Tables, etc. 410. 12s. 
 
 The author believes that if , by a graphic method, the prediction of 
 occultations can be rendered more inviting, as well as more expedi^ 
 tious, than by the method of calculation^ it may prove acceptable to 
 the nautical profession as well as to scientific travellers or amateurs. 
 The author has endeavoured to make the whole process as intelli- 
 gible as possible, so that the beginner, instead of merely having to 
 Jollow directions imperfectly understood, may readily comprehend 
 the meaning of each step, and be able to illustrate the practice by the 
 theory. Besides all necessary charts and tables, the work contains 
 a large number of skeleton forms for working out cases in 
 practice. 
 
 Roscoe. Works by HENRY E. ROSCOE, F.R.S., Professor o 
 Chemistry in Owens College, Manchester : 
 
 LESSONS IN ELEMENTARY CHEMISTRY, INORGANIC 
 AND ORGANIC. With numerous Illustrations and C.hromo- 
 litho of the Solar Spectrum, and of the Alkalies and Alkaline 
 Earths. New Edition. i8mo. cloth. 4^. 6d. 
 
 It has been the endeavour of the author to arrange the most important 
 facts and principles of Modern Chemistry in a plain but concise 
 and scientific form, suited to the present requirements of elementary 
 instruction. For the purpose of facilitating the attainment of 
 exactitude in the knowledge of the subject, a series of exercises and 
 questions upon the lessons have been added. The metric system of 
 weights and measures, and the centigrade thermometric scale, are 
 C 2 
 
36 SCIENTIFIC CATALOGUE. 
 
 ROSCOC continued. 
 
 used throughout this work. The new edition, besides new wood- 
 cuts, contains many additions and improvements, and includes the 
 most important of the latest discoveries. " We unhesitatingly pro- 
 nounce it the best of all our elementary treatises on Chemistry." 
 Medical Times. 
 
 SPECTRUM ANALYSIS. Six Lectures, with Appendices, En- 
 gravings, Maps, and Chromolithographs. Royal 8vo. 2is. 
 
 A Third Edition of these popular Lectures, containing all the most 
 recent discoveries and several additional illustrations. "In six 
 lectures he has given the history of the discovery and set forth the 
 facts relating to the analysis of light in such a way that any reader 
 of ordinary intelligence and information will be able to understand 
 what 'Spectrum Analysis' is, and what are its claims to rank 
 among the most signal triumphs of science" Nonconformist. 
 ' ' The lectures themselves furnish a most admirable elementary 
 treatise on the subject, whilst by the insertion in appendices to each 
 lecture of extracts from the most important published memoirs, the 
 author has rendered it equally valuable as a text-book for advanced 
 students. " Westminster Review. 
 
 Stewart (B.) LESSONS IN ELEMENTARY PHYSICS, 
 By BALFOUR STEWART, F.R.S., Professor of Natural Philosophy 
 in Owens College, Manchester. With numerous Illustrations and 
 Chromolithos of the Spectra of the Sun, Stars, and Nebulas. New 
 Edition. i8mo. 4^. 6d. 
 
 A description, in an elementary manner, of the most important of 
 those laws which regulate the phenomena of nature. The actii'c 
 agents, heat,' light, electricity, etc., are regarded as varieties of 
 enei'gy, and the work is so arranged that their relation to one 
 another, looked at in this light, and the paramount importance of 
 the laws of energy, are clearly brought out. The volume contains 
 all the necessary illustrations. The Educational Times calls this 
 "the beau-ideal of a scientific text-book, clear, accurate, and 
 thorough." 
 
 Taylor. SOUND AND MUSIC : A Non-Mathematical Trea- 
 tise rn the Physical Constitution of Musical Sounds and Harmony, 
 
PHYSICAL SCIENCE. 37 
 
 including the Chief Acoustical Discoveries of Professor Helm- 
 holtz. By SEDLEY TAYLOR, M.A., late Fellow of Trinity Col- 
 ledge, Cambridge. Large crown 8vo. Ss. 6J, 
 
 This treatise aims at placing before persons unacquainted with 
 Mathematics an intelligible and succinct account of that part of 
 the Theory of Sound which constittites the physical basis of the 
 Art of Music. No preliminary knowledge, save of Arithmetic 
 and of the musical notation in common use, is assumed to be pos- 
 sessed by the reader. The importance of combining theoretical and 
 experimental modes of treatment has been kept steadily in vieiv 
 throughout. Though the author has incorporated the chief acous- 
 tical discoveries of Professor H^lmholtz, the present volume is not a 
 mere epitome of his work, but the result of independent study. 
 
 Thomson. THE DEPTHS OF THE SEA : An Account of the 
 
 General Results of the Dredging Cruises of H.M.SS. " Porcupine '' 
 and "Lightning" during the Summers of 1868-69 and 70, under 
 the scientific direction of Dr. Carpenter, F.R.S., J. Gwyn Jeffreys, 
 F.R.S., and Dr. Wyville Thomson, F.R.S. By Dr. WYVILLE 
 THOMSON, Director of the Scientific Staff of the "Challenger" 
 Expedition. With nearly 100 Illustrations and 8 coloured Maps 
 and Plans. Second Edition. Royal 8vo. cloth, gilt. %is. 6d. 
 
 If was the important and interesting results recorded in this volume 
 that induced the Government to send out the great Expedition n<nv 
 launched under the scientific guidance of Dr. Wyville Thomson. 
 The Athenaeum says, * ' Professor \ Thomson's book is full of in- 
 teresting matter, and is written by a master of the art of popular 
 exposition. It is excellently illustrated, both coloured maps and 
 woodcuts possessing high merit. Those who have already become 
 interested in dredging operations will of course make a point of 
 reading this work ; those who wish to be pleasantly introduced to the 
 subject, and rightly to appreciate the news which arrives from time 
 to time from the " Challenger,' 1 ' 1 should not fail to seek instruction 
 from Professor Thomson." 
 
 Thornton. OLD-FASHIONED ETHICS, AND COMMON- 
 SENSE METAPHYSICS, with some of their Applications. By 
 WILLIAM THOMAS THORNTON, Author of "A Treatise on Labour." 
 8vo. loj. 6d. 
 
38 SCIENTIFIC CATALOGUE. 
 
 The present volume deals "with problems which are agitating the 
 minds of all thoughtful men. The following are the Contents : 
 /. Ante-Utilitarianism. II. History's Scientific Pretensions. III. 
 David Hume as a Metaphysician. IV. Htixleyism. V. Recent 
 Phases of Scientific Atheism. VI. Limits of Demonstrable Theism. 
 
 Thudichum and Dupre. A TREATISE ON THE 
 ORIGIN, NATURE, AND VARIETIES OF WINE. 
 Being a Complete Manual of Viticulture and CEnology. By J. L. 
 W. THUDICHUM, M.D., and AUGUST DUPRE, Ph.D., Lecturer on 
 Chemistry at Westminster Hospital. Medium 8vo. cloth gilt. 25^. 
 
 In this elaborate work the subject of the mamtfacture of wine is 
 treated scientifically in minute detail, from every point of vieiv. A 
 chapter is devoted to the Origin and Physiology of Vines, two to the 
 Principles of Viticulture; while other chapters treat of Vintage and 
 Vinification, the Chemistry of Alcohol, the Acids, Ether, Sugars, 
 and other matters occurring in wine. This introductory matter 
 occupies the first nine chapters, the remaining seventeen chapters 
 biing occupied with a detailed account of the Viticulture and the 
 Wines- of the various countries of Europe, of the Atlantic Islands, 
 of Asia, of Africa, of America, and of Australia. Besides a 
 number of Analytical and Statistical Tables, the work is enriched 
 with eighty -five illustrative woodcuts. "A treatise almost unique 
 for its usefulness either to the wine-grower, the vendor, or the con- 
 sumer of wine. The analyses of wine are the most complete we 
 have yet seen, exhibiting at a glance the constituent principles of 
 nearly all the wines known in this country-." Wine Trade Review. 
 
 Wallace (A. R.) CONTRIBUTIONS TO THE THEORY 
 
 OF NATURAL SELECTION. A Series of Essays. By 
 ALFRED RUSSEL WALLACE, Author of " The Malay Archipelago," 
 etc. Second Edition, with Corrections and Additions. Crown 
 8vo. Ss. 6d. (For other Works by the same Author, see CATA- 
 LOGUE OF HISTORY AND TRAVELS.) 
 
 Mr. Wallace has good claims to be considei-ed as an independent 
 originator of the theory of natural selection. Dr. Hookej-, in 
 his address to the British Association, spoke thus of the author : 
 " Of Mr. Wallace and his many contributions to philosophical 
 it is not easy to speak without enthusiasm; for, putting 
 
PHYSICAL SCIENCE. 39 
 
 aside their great merits, he, throughout .his -writings, with a 
 modesty as rare as I believe it to be unconsciou-s, forgets his otvti 
 unquestioned claim to the honour of having originated indepen- 
 dently of Mr. Darwin, the theories which he so ably defends. ' ' 
 The Saturday Review says : "He has combined an abundance of 
 fresh and original facts with a liveliness and sagacity of reasoning 
 which are not often displayed so effectively on so small a scale." 
 The Essays in this volume arc : /. "On the Law which has regii- 
 lated the introduction of Neiv Species. '' //. ' ' On the Tendencies 
 of Varieties to debar t indefinitely from the Original Type" III. 
 "Mimicry, and other Protective Resemblances among Animals." 
 IV. " The Malayan Papilionidce, as illustrative of the Theory 
 of Natural Selection" V. " On Instinct in Man and Animals." 
 VI. " The Philosophy of Birds' Nests." VII. " A Theory of 
 Birds' 1 Nests." VIII. " Creation by Law." IX. " The Develop- 
 ment of Human Races under the Law of Natural Selection." 
 X. " The Limits of Natural Selection as applied to Man." 
 
 Warington. THE WEEK OF CREATION ; OR, THE 
 
 COSMOGONY OF GENESIS CONSIDERED IN ITS 
 RELATION TO MODERN SCIENCE. By GEORGE WAR- 
 INGTON, Author of "The Historic Character of the Pentateuch 
 Vindicated." Crown 8vo. \s. 6d. 
 
 The greater part of this work it taken up with the teaching of the 
 Cosmogony. Its purpose is also investigated, and a chapter is 
 devoted to the consideration of the passage in which the difficzdties 
 occur. ' 'A very able vindication of the Mosaic Cosmogony, by a 
 writer who unites the advantages of a critical knowledge of the 
 Hebrew text and of distinguished scientific attainments." 
 Spectator. 
 
 Wilson. Works by the late GEORGE WILSON, M.D., F.R.S.E., 
 Regius Professor of Technology in the University of Edinburgh : 
 
 RELIGIO CHEMICI. With a Vignette beautifully engraved after 
 a design by Sir NOEL PATON. Crown 8vo. 8s.-6rf.- 
 
 "George Wilson," says the Preface to this volume, "Jiadit in his heart 
 for many years to write a book corresponding to the Religio Medici 
 of Sir Thomas Browne, with the title Religio Chemici. Several 
 of the Essays in this volume were intended to form chapters of it. 
 
40 SCIENTIFIC CATALOGUE. 
 
 Wilson 
 
 These fragments being in most cases like finished gems waiting to be 
 set, some of them are now given in a collected form to his friends 
 and the public. In living remembrance of his purpose, the name 
 chosen by himself has been adopted, although the original design 
 can be but very faintly represented." The Contents of the volume 
 are: " Chemistry and Natural Theology." " The Chemistry of 
 the Stars; an Argument touching the Stars and their Inhabitants." 
 ' ' Chemical Final Causes ; as illustrated by the presence of Phos- 
 phorus, Nitrogen, and Iron in the Higher Sentient Organisms" 
 1 ' Robert Boyle. " " Wollaston. " ' 'Life and Discoveries of Dalton . : ' 
 " Thoughts on the Resurrection; an Address to Medical Students" 
 "A more fascinating volume," the Spectator says, "has seldom 
 fallen into our hands." The Freeman says: "These papers are all 
 valuable and deeply interesting. The production of a profound 
 thinker, a suggestive and eloquent write)', and a man whose piety 
 and genius went hand in hand" 
 
 THE PROGRESS OF THE TELEGRAPH. Fcap. 8vo. I*. 
 
 " While a complete view of the progress of the greatest of human 
 inventions is obtained, all its suggestions are brought out with a 
 rare thoughtfulness, a genial humour, and an exceeding beauty of 
 ^^tterance. " Nonconformist. 
 
 Wilson (Daniel.) CALIBAN : THE MISSING LINK. By 
 DANIEL WILSON, LL.D., Professor of History and English Litera- 
 ture in University College, Toronto. 8vo, IOT. 6d. 
 
 In the present state of the controversy as to the Origin of Man, this 
 work of a competent scholar and critic, in which the Monster 
 Caliban is studied from varwus points of view, will be of consider- 
 able interest. Besides ' ( Caliban, " the work treats oj various other 
 matters of Shakespearian interest, as " The Supernatural," " Ghosts 
 and Witches," " Fairy Folk-Lore," "The Commentators," "The 
 Folios." The two last chapters contain notes on " The Tempest," 
 and " A Midsummer Night's Dream" 
 
 Win Slow. FORCE AND NATURE : ATTRACTION AND 
 REPULSION. The Radical Principles of Energy graphically 
 
PHYSICAL SCIENCE. 41 
 
 discussed in their Relations to Physical and Morphological De- 
 velopment. By C. F. WINSLOW, M.D. 8vo. 14^. 
 
 The author having for long investigated Nature in many directions, 
 has ever felt unsatisfied with the physical foundations upon which 
 some branches of science have been so long compelled to rest. The 
 question, he believes, must have occurred to many astronomers and 
 physicists whether some subtle principle antagonistic to attraction 
 does not also exist as an all-pervading element in nature, and so 
 operate as in some way to disturb the action of what is generally 
 considered by the scientific world a unique force. The aim of the 
 present work is to set forth this subject in its broadest aspects, and 
 in such a manner as to invite thereto the attention of the learned. 
 The subjects of the eleven chapters are : /. "Space." II. "Matter." 
 III. "Inertia, Force, and Mind." IV. "Molecules." V. 
 " Molecular Force." VI. "Union and Inseparability of Mattel' 
 and Force" VII. and VIII. " Nature and Action of Force 
 Attraction Repulsion" IX. " Cosmical Repulsion" X." Me- 
 chanical Force." XI. "Central Forces and Celestial Physics." 
 "Deserves thoughtful and conscientious study." Saturday Review. 
 
 Wurtz. A HISTORY OF CHEMICAL THEORY, from the 
 Age of Lavoisier down to the present time. By AD. WURTZ. 
 Translated by HENRY WATTS, F.R.S. Crown 8vo. 6s. 
 
 " The discourse, as a resume of chemical theory and research, unites 
 singular luminousness and grasp. A few judicious notes are added 
 by the translator." Pall Mall Gazette. " The treatment of the 
 subject is admirable, and the translator has evidently done his diity 
 most efficiently." Westminster Review. 
 
 Young. SIMPLE PRACTICAL METHODS OF CALCU- 
 LATING STRAINS ON GIRDERS, ARCHES, AND 
 TRUSSES ; with a Supplementary Essay on Economy in Sus- 
 
 ; pension Bridges. By E. W. YOUNG, Member of the Institution 
 of Civil Engineers. 8vo. JS. 6d. 
 
42 SCIENTIFIC CATALOGUE. 
 
 WORKS IN PHYSIOLOGY, ANATOMY, AND 
 MEDICAL WORKS GENERALLY. 
 
 Allbutt (T. C.) ON THE USE OF THE OPHTHALMO- 
 SCOPE in Diseases of the Nervous System and of the Kidneys ; 
 also in certain other General Disorders. By THOMAS CLIFFORD 
 ALLBUTT, M.A., M.D. Cantab., Physician to the Leeds General 
 Infirmary, Lecturer on Practical Medicine, etc. etc. 8vo. 15^. 
 
 The Ophthalmoscope has been found of the highest value in the inves- 
 tigation of nervous diseases. But it is not easy for physicians who 
 have left the schools, and are engaged in practice, to take up a new 
 instrument which requires much skill in using; it is therefore 
 hoped that by such the present volume, containing the results of the 
 author's extensive use of the instrument in diseases of the nervous 
 system, ivill be found of service ; and that to all students it may 
 prove a usejul hand-book. After four introductory chapters on the, 
 history and value of the Ophthalmoscope, and the manner of investi- 
 gating the states of the optic nerve and retina, the author treats of 
 the various diseases "with which optic changes are associated, and 
 describes the way in which such associations take place. Besides 
 the cases referred to throughout the volume, the Appendix con- 
 tains details of 12^-cases illustrative of the subjects discussed in the 
 text, and a series of tabulated cases to show the Ophthalmoscopic 
 appearances of the eye in Insanity, Mania, Dementia, Melancholia 
 and Monomania, Idiotcy, and General Paralysis. The volume is 
 illustrated with two coloured plates of morbid appearances of the 
 eye under the Ophthalmoscope. 
 
 THE EFFECTS OF OVERWORK AND STRAIN ON THE 
 HEART AND GREAT BLOOD-VESSELS. (Reprinted from 
 St. George's Hospital Reports.) 2s. 6d. 
 
 Anderson. ON THE TREATMENT OF DISEASES OF 
 
 THE SKIN : with an Analysis of Eleven Thousand Consecutive 
 
ANATOMY, ETC. 43 
 
 Cases. By Dr. McCALL ANDERSON, Professor of Practice of 
 Medicine in Anderson's University, Physician to the Dispensary for 
 Skin Diseases, etc., Glasgow. Crown 8vo. cloth. 5.5-. 
 
 The first part of this work consists of a carefully tabulated and critical 
 analysis of n,ooo cases of skin disease, 1,000 of these having 
 occurred in the author 1 s private practice, and the rest in his hos- 
 pital practice. These cases are all classified under certain distinct 
 heads, according to the nattire and cause of the disease, while a 
 number of the more interesting cases are alluded to in detail. The 
 second part of the work treats of the Therapeutics of Diseases of 
 the Skin, and will be found to contain many hints, the results of a 
 long and extensive experience, as to the most successful method of 
 treating their multitudinous forms. 
 
 Anstie (F. E.) NEURALGIA, AND DISEASES WHICH 
 
 RESEMBLE IT. By FRANCIS E. ANSTIE, M D., M.R.C.P., 
 Senior Assistant Physician to Westminster Hospital. 8vo. los. 6d. 
 
 The present treatise is the result of many years' independent scientific 
 investigation into the nature and proper treatment of this most 
 painful disease. The author has had abundant means of studying 
 the subject both in his own person and in the hundreds of patients 
 that have resorted to him for treatment. The Introduction treats 
 briefly of Pain in General, and contains some ideas as to its nature 
 and in reference to sensation generally. 
 
 Barwell. THE CAUSES AND TREATMENT OF LATERAL 
 
 CURVATURE OF THE SPINE. Enlarged from Lectures 
 published in the Lancet. By RICHARD BARWELL, F.R.C.S., 
 Surgeon to and Lecturer on Anatomy at the Charing Cross Hospital. 
 Second Edition. Crown 8vo. 4,!-. 6d. 
 
 Having failed to find in books a satisfactory theory of those conditions 
 which produce lateral curvature, Mr. Barwell resolved to investi- 
 gate the subject for himself ab initio. The present work is the 
 result of long study of Spines, normal and abnormal. He 
 believes the views which he has been led to form account for those 
 essential characteristics which have hitherto been left unexplained ; 
 and the treatment which he advocates is certainly less irksome, and 
 will be found more efficacious than that which has hitherto been 
 pursued. Indeed, the mode in which the first edition has been 
 
44 SCIENTIFIC CATALOGUE. 
 
 received by the profession is a gratifying sign that Mr. BarweWs 
 principles have made their value and their weight felt. Many 
 pages and a number of woodcuts have been added to the Second 
 Edition. 
 
 Corfield (Professor W. H.) A DIGEST OF FACTS 
 
 RELATING TO THE TREATMENT AND UTILIZATION 
 OF SEWAGE. By W. H. CORFIELD, M.A., B.A., Professor 
 of Hygiene and Public Health at University College, London. 
 Svo. icxr. 6d. Second Edition, corrected and enlarged. 
 
 The author in the Second Edition has revised and corrected the entire 
 work, and made many important additions. The headings of the 
 eleven chapters are as follow : /. "Early Systems: Midden- Heaps 
 and Cesspools." II. "Filth and Disease Cause and Effect." 
 III. "Improved Midden- Pits and Cesspools; Midden- Closets, Pail- 
 Closets, etc." IV. "The Dry-Closet Systems." V. "Water- Closets." 
 VI. "Sewerage." VII. " Sanitary Aspects of the Water- Carrying 
 System." VIII. " Value of Seivage ; Injury to Rivers." IX. 
 " Town Sewage; Attempts at Utilization" X. ''''Filtration and 
 Irrigation" XI. "Influence of Sewage Farming on the Public 
 Health." An abridged account of the more recently published 
 researches on the subject will be found in the Appendices, while 
 the Summary contains a concise statement of the views which the 
 author himself has been led to adopt: references have been inserted 
 throughout to show from what sources the numerous quotations have 
 been derived, and an Index has been added. "Mr. Corfield" s work 
 is entitled to rank as a standard authority, no less than a con- 
 venient handbook, in all matters relating to sewage. " Athenreum. 
 
 Elam (C.) A PHYSICIAN'S PROBLEMS. By CHARLES 
 ELAM, M.D., M.R.C.P. Crown Svo. 9*. 
 
 CONTENTS : " Natural Heritage." " On Degeneration in Man." 
 ' ' On Moral and Criminal Epidemics. " ' 'Body v. Mind. " " Il- 
 lusions an. i Hallucinations." " On Somnambulism " " Reverie 
 and Abstraction." These Essays are intended as a contribution U 
 the Natural History of those outlying regions of Thought and 
 Action whose domain is the debatable ground of Brain, Nerve, 
 and Mind. They are designed also to indicate the origin and mode 
 of perpetuation of those varieties of organization, intelligence, and 
 general tendencies twvards vice or virtue, which seem to be so 
 
PHYSIOLOGY, ANATOMY, ETC. 45 
 
 capriciously developed among mankind. They also point to causes 
 for the infinitely varied forms of disorder of nerve and brain 
 organic and functional far deeper and more recondite than those 
 generally believed in. " The book is one which all statesmen, 
 magistrates, clergymen, medical men, and parents should study and 
 inwardly digest." Examiner. 
 
 FOX. Works by WILSON Fox, M.D. Lond., F.R.C.P., F.R.S., 
 Holme Professor of Clinical Medicine, University College, London, 
 Physician Extraordinary to her Majesty the Queen, etc. : 
 
 DISEASES OF THE STOMACH : being a new and revised 
 Edition of "THE DIAGNOSIS AND TREATMENT OF THE 
 VARIETIES OF DYSPEPSIA." 8vo. 8s. 6d. 
 
 ON THE ARTIFICIAL PRODUCTION OF TUBERCLE IN 
 THE LOWER ANIMALS, With Coloured Plates. 4to. $s. 6d. 
 
 In this Lecture Dr. Fox describes in minute detail a large number of 
 experiments made by him on guinea-pigs and rabbits for the pur- 
 pose of inquiring into the origin of Tubercle by the agency of direct 
 irritation or by septic matters. The work is illustrated by three 
 plates, containing a number of coloured illustrations from nature. 
 
 ON THE TREATMENT OF HYPERPYREXIA, as Illustrated 
 in Acute Articular Rheumatism by means of the External Applica- 
 tion of Cold. 8vo. 2s. 6d. 
 
 The object of this work is to show that the class of cases included under 
 the title, and which have hitherto been invariably fatal, may, by 
 the use of the cold bath, be brought to a favourable termination. 
 Details are given of the successful treatment by this method of two 
 patients by the author, followed by a Commentary on the cases, in 
 which the merits of this mode of treatment are discussed and com- 
 pared with those of other methods. Appended are tables of the 
 observations made on the tempei'ature during the treatment ; a table 
 showing the effect of the immersion of the patients in the baths em- 
 ployed, in order to exhibit the rate at which the temperature was 
 lowei'ed in each case; a table of the chief details of twenty-iwc 
 cases of this class recently published, and which are referred to in 
 various parts of the Commentary. Two Charts are also introduced, 
 
46 SCIENTIFIC CATALOGUE. 
 
 giving a connected vieiv of the progress of the two successful cases, 
 and a series of sphygmographic tracings of the pulses of the two 
 patients. ' ' A clinical study of rare value. Should be read by 
 everyone" Medical Press and Circular. 
 
 Galton (D.) AN ADDRESS ON THE GENERAL PRIN- 
 CIPLES WHICH SHOULD BE OBSERVED IN THE 
 CONSTRUCTION OF HOSPITALS. Delivered to the British 
 Medical Association at Leeds, July 1869. By DOUGLAS GALTON, 
 C.B.,F.R.S. Crown 8vo. 3*. 6</. 
 
 In this Address the author endeavours to enunciate what are those 
 principles which seem to him to form the starting-point from which 
 all architects should proceed in the construction of hospitals. Be- 
 sides Mr. Galtoris paper the book contains the opinions expressed in 
 the subsequent discussion by several eminent medical men, suck as 
 Dr. Kennedy, Sir James Y. Simpson, Dr. Hughes Sennet, and 
 others. The work is illustrated by a number of plans, sections, and 
 other cuts. ll An admirable exposition of those conditions of struc- 
 ture which most conduce to cleanliness, economy, and convenience." 
 Times. 
 
 Harley ( J.) THE OLD VEGETABLE NEUROTICS, Hem- 
 lock, Opium, Belladonna, and Henbane ; their Physiological 
 Action and Therapeutical Use, alone and in combination. Being 
 the Gulstonian Lectures of 1868 extended, and including a Complete 
 Examination of the Active Constituents of Opium. By JOHN 
 HARLEY, M.D. Lond., F.R.C.P., F.L.S., etc. 8vo. i2j. 
 
 The author's object throughout the investigations and experiments on 
 which this -volume is foiinded has been to ascertain, clearly and 
 definitely, the action of the drugs employed on the healthy body in 
 medicinal doses, from the smallest to the largest ; to deduce simple 
 practical conclusions from the facts observed ; and then to apply the 
 drug to the relief of the particular conditions to which its action 
 appeared suited. Many experiments have been made by the author 
 both on men and the lower animals ; and the author's endeavour 
 has been to present to the mind, as far as words may do, impres- 
 sions of the actual condition of the individual subjected to the 
 drug. 
 
PHYSIOLOGY, ANATOMY, ETC. 47 
 
 Hood (Wharton). ON BONE-SETTING (so called), and 
 its Relation to the Treatment of Joints Crippled by Injury, Rheu- 
 matism, Inflammation, etc. etc. By WHARTON P. HOOD, 
 M.D., M.R.C.S. Crown 8vo. 4J-. 6d. 
 
 The author for a period attended the London practice of the late Mr. 
 Hutton, the famous and successful bone-setter, by whom he was 
 initiated into the mystery of the art and practice. Thus he is 
 amply qualified to write on the subject from the practical point of 
 view, while his professional education enables him to consider it in 
 its scientific and surgical bearings. In the present work he gives a 
 brief account of the salient features of a bone-setter's method of pro- 
 cedure in the treatment of damaged joints, of the results of that treat- 
 ment, and of the class of cases in which he has seen it prove successful. 
 The author's aim is to give the rationale of the bone-setter 's practice, 
 -to reduce it to something like a scientific method, to show when force 
 should be resorted to and when it should not, and to initiate 
 surgeons into the .secret of Mr. Huttoris successful manipulation. 
 Throughout the work a great number of authentic instances of 
 successful treatment aw given, with the details of the method of 
 cure; and the Chapters on Manipulations and Affections of the 
 Spine are illustrated by a number of appropriate cuts. 
 
 Humphry. Works by G.M. HUMPHRY, M.D., F.R.S., Professoi 
 of Anatomy in the University of Cambridge, and Honorary Fellow 
 of Downing College : 
 
 THE HUMAN SKELETON (including the Joints). With 260 
 Illustrations, drawn from nature. Medium 8vo. 28-r. 
 In lecturing on the Skeleton it has been the author 1 s practice, instead 
 of giving a detailed account of the several parts, to request his 
 students to get up the descriptive anatomy of certain bones, with the 
 aid of some work on osteology. He afterwards tested their acquire- 
 ments by examination, endeavouring to supply deficiencies and 
 correct errors, adding also such information physical, physiologi- 
 cal, pathological, and practical as he had gathered from his own 
 observation and researches, and rvhich was likely to be useful and 
 excite an interest in the subject. This additional information 
 forms, in great part, the material of this volume, which is intended 
 to be supplementary to existing works on anatomy. Considerable 
 space has been devoted to. the description of the joints, because it is 
 less fully given in other works, and because an accurate knoivledge^ 
 
48 SCIENTIFIC CA TALOG UE. 
 
 H U m p h ry continued, 
 
 of the structure and peculiar form of the joints is essential to a 
 correct knowledge of their movements. The numerous illustrations 
 were all drawn upon stone from nature ; and in most instances 
 from specimens prepared for the purpose by the author himself, 
 
 OBSERVATIONS IN MYOLOGY. 8vo. 6s. 
 
 This work includes the Myology of Cryptobranch, Lepidosiren, Dog- 
 Fish, Ceratodus, and Pseudopus Pallasii^ with the Nerves of Crypto- 
 branch and Lepidosiren and the Disposition of Muscles in Vertebrate 
 Animals. The volume contains a large number of illustrations, 
 
 Huxley's Physiology. See p. 27, preceding. 
 
 Journal of Anatomy and Physiology. 
 
 Conducted by Professors HUMPHRY and NEWTON, and Mr. CLARK 
 of Cambridge, Professor TURNER of Edinburgh, and Dr. 
 WRIGHT of Dublin. Published twice a year. Old Series, Parts 
 I. and II., price 7-r. 6d. each. Vol. I. containing Parts I. and II., 
 Royal 8vo., i6s. New Series, Parts I. to IX. 6s. each, or yearly 
 Vols. 1 2s. &d. each. 
 
 Leishman. A SYSTEM OF MIDWIFERY, including the 
 Diseases of Pregnancy and the Puerperal State. By WILLIAM 
 LEISHMAN, M. D. , Regius Professor of Midwifery in the Univer- 
 sity of Glasgow ; Physician to the University Lying-in Hospital ; 
 Fellow and late Vice-President of the Obstetrical Society of 
 London, etc. etc. 8vo. Illustrated. 30^. 
 
 The author's object' Jn this work has been to furnish to students and 
 practitioners a complete system of the Midwifery of the present 
 day. There exists no text-book in English which can be compared 
 ruith those of Cazeaux and Scauzoni ; this want the author has 
 endeavoured to supply by the publication of the present work, 
 in writing which he has availed himself of all the most recent 
 researches. The work is profusely illustrated. 
 
 Lankester. COMPARATIVE LONGEVITY IN MAN AND 
 THE LOWER ANIMALS. By E. RAY LANKESTER, B.A. 
 Crown 8vo. ^s. 6d. 
 
PHYSIOLOGY, ANATOMY, ETC. 49 
 
 This Essay gained the prize offered by the University of Oxford for 
 the best Paper on the subject of ivhich it treats. This interesting 
 subject is here treated in a thorough manner, both scientifically and 
 statistically. 
 
 Maclaren TRAINING, IN THEORY AND PRACTICE. 
 
 By ARCHIBALD MACLAREN, the Gymnasium, Oxford. 8vo. 
 Handsomely bound in cloth, 'js. 6d. 
 
 The ordinary agents of health are Exercise, Diet, Sleep, Air, Bath- 
 ing, and Clothing. In this work the author examines each of 
 these agents in detail, and from two different points of view. First, 
 as to the manner in ^vhich it is, or should be, administered under 
 ordinary circumstances : and secondly, in what manner and to 
 what extent this mode of administration is, or should be, altered for 
 purposes of training ; the object of "training," according to the 
 aiithor, being " to put the body, with extreme and exceptional care, 
 under the influence of all the agents which promote its health and 
 strength, in order to enable it to meet extreme and exceptional de- 
 mands upon its energies." Appended are various diagrams and 
 tables relating to boat-racing, and tables connected with diet and 
 training. " The philosophy of human health has seldom received 
 so apt an exposition." Globe. "After all the nonsense that has 
 been written about training, it is a comfort to gtt hold of a 
 thoroughly sensible book at last. " John Bull. 
 
 Macpherson. Works by JOHN MACPHERSON, M.D. : 
 
 THE BATHS AND WELLS OF EUROPE; Their Action and 
 Uses. With Notices of Climatic Resorts and Diet Cures. With 
 a Map. New Edition, revised and enlarged. Extra fcap. 8vo. 
 i 6s. (yd. 
 
 This work is intended to supply information which zvill ajford aid in 
 the selection of such Spas as are suited for particular cases. It 
 exhibits a sketch of the present condition of our knowledge on the 
 subject of the operation of mineral waters, gathered from the 
 author's personal observation, and from every other available 
 source of information. It is divided into four books, and each 
 book into several chapters : Book I. Elements of Treatment, in 
 which, among other matters, the external and internal uses of water 
 are treated of. II: Bathing, treating of the various kinds of baths. 
 III. Wells, treating of the various kinds of mineral waters. 
 D 
 
50 SCIENTIFIC CATALOGUE. 
 
 Macpherson (} .^-continued. 
 
 TV. Diet Cures, in which various vegetable, milk, and other 
 <( cures " are discussed. Appended is an Index of Diseases noticed, 
 and one of places named. Prefixed is a sketch map of the principal 
 baths and places of health-resort in Europe. "2)r. Macpherson 
 has given the kind of information which every medical practitioner 
 ought to possess." The Lancet. " Whoever wants to know the 
 real character of any health-resort must read Dr. Macpherson 's 
 book." Medical Times. 
 
 OUR BATHS AND WELLS : The Mineral Waters of the British 
 Islands, with a List of Sea-bathing Places. Extra fcap. 8vo. 
 pp. xv. 205. 3-r. 6d. 
 
 Dr. Macpherson has divided his work into five parts. He begins by 
 a few introductory observations on bath life, its circumstances, uses, 
 and pleasures ; he then explains in detail the composition of the 
 various mineral waters, and points out the special curative p)-o- 
 perties of each class. A chapter on "The History of British 
 Wells " from the earliest period to the present time forms the 
 natural transition to the second part of this volume, which treats of 
 the different kinds of mineral waters in England, whether pure, 
 thermal and earthy, saline, chalybeate, or sulphur. Wales, Scot- 
 land, and Ireland supply the materials for distinct sections. An 
 Index of mineral watei's, one of sea-bathing places, and a third of 
 wells of pure or nearly pure water, terminate the book. ' ' 7 his little 
 volume forms a very available handbook for a large class of 
 invalids" Nonconformist. 
 
 Maudsley. Works by HENRY MAUDSLEY, M.D., Professor of 
 Medical Jurisprudence in University College, London : 
 
 BODY AND MIND : An Inquiry into their Connection and 
 Mutual Influence, specially in reference to Mental Disorders ; being 
 the Gulstonian Lectures for 1870. Delivered before the Royal 
 College of Physicians. Crown 8vo. $s. New Edition, with 
 Psychological Essays added. Crown 8vo. 6j-. 6d. 
 
 The volume consists of three Lectures and two long Appendices, the 
 general plan of the whole being to bring Man, both in his physical 
 and mental relations, as much as possible under the scope of scientific 
 inquiry. The first Lecture is devoted to an exposition of the physical 
 
PHYSIOLOGY, ANATOMY, ETC. 
 
 Maudsley (H.) continued. 
 
 conditions of mental function in health. In the second Lecture are 
 sketched the features of some forms of degeneracy of mind, as exhibited 
 in morbid varieties of the human kind, with the purpose of bringing 
 prominently into notice the operation of physical causes from 
 generation to generation, and the relationship of mental to other 
 diseases of the nervous system. In the third Lecture are displayed 
 the relations of morbid states of the body and disordered mental 
 function. Appendix I. is a criticism of the Archbishop of York's 
 address on " The Limits of Philosophical Inquiry.' 1 '' Appendix II. 
 deals with, the "Theory of Vitality ;" in which the author en- 
 deavours to set forth the reflections which facts seem to warrant. 
 
 THE PHYSIOLOGY AND PATHOLOGY OF MIND. 
 
 Second Edition, Revised. 8vo. 16.?. 
 
 This work is the restilt of an endeavour on the author's part to arrive 
 at some definite conviction with regard to the physical conditions of 
 mental function, and the relation of the phenomena of sound and 
 unsound mind. The author's aim throughout has been twofold : 
 I. To treat of mental phenomena from a physiological rather than 
 from a metaphysical point of view. II. To bring the manifold 
 instructive instances presented by the unsound mind to bear upon 
 the interpretation of the obscure problems of mental science. 
 
 Morgan. UNIVERSITY OARS: Being a Critical Enquiry 
 into the After-health of the Men who rowed in the Oxford and 
 Cambridge Boat-Race, from the year 182910 1869, based upon the 
 personal experience of the Rowers themselves. By JOHN E. 
 MORGAN. M.D., M.A. Oxon., F.R.C.P., late Captain of the 
 John rf (Coll. Univ.), Physician to the Manchester Royal 
 Infirmary, author of " The Deterioration of Races," etc. Crown 
 8vo. IOJ-. 6d. 
 
 " Dr. Morgans book presents in a most admirable manner full a'na 
 accurate statistics of the duration of life, and of the causes of 
 death, of all the men who have rowed in Oxford and Cambridge 
 boats from 1829 to 1869, and also gives letters addressed to the 
 author by nearly every individual of the number. " Daily News. 
 
SCIENTIFIC CATALOGUE. 
 
 Practitioner (The). A Monthly Journal of Therapeutics 
 and Public Health. Edited by FRANCIS E. ANSTIE, M. D. 
 8vo. Price is. 6d. Half-yearly vols., 8vo. cloth. IQJ-. 6d. each. 
 
 Radcliffe. DYNAMICS OF NERVE AND MUSCLE. By 
 CHARLES BLAND RADCLIFFE, M.D., F.R.C.P., Physician to the 
 Westminster Hospital, and to the National Hospital for the 
 Paralysed and Epileptic. Crown 8vo. 8s. 6c*. 
 
 This work contains the result of the author's long investigations into 
 the Dynamics of Nerve and Muscle, as connected with Animal Elec- 
 tricity. He endeavours to show from these researches that the state 
 of action in nerve and muscle, instead of being a manifestation of 
 vitality, must be brought under the domain of physical law in order 
 to be intelligible, and that a different meaning, also based upon pure 
 physics, must be attached to the state of rest. 
 
 Reynolds (J. R.) A SYSTEM OF MEDICINE. Vol. i. 
 
 Edited by J. RUSSELL REYNOLDS, M.D., F.R.C.P. London. 
 
 Second Edition. 8vo. 25^. 
 
 ' ' // is the best Cyclopedia of medicine of the time" Medical Press. 
 
 Part I. General Diseases, or Affections of the Whole System. 
 /. Those determined by agents operating from ^mthout, such as 
 the exanthemata, malarial diseases, and their allies. //. Those 
 determined by conditions existing within the body, such as Gout, 
 Rheumatism, Rickets, etc. f Part II. Local Diseases, or Affections 
 of particular Systems. /. Diseases of the Skin. 
 
 A SYSTEM OF MEDICINE. Vol. II. Second Edition. 8vo. 
 
 25^. 
 
 Part II. Local Diseases (continued). 7. Diseases of the Nervous 
 System. A. General Nervous Diseases. B. Partial Diseases of 
 the Nervous System. I. Diseases of the Head. 2. Diseases of the 
 Spinal Column. 3. Diseases of the Nerves. //. Diseases of 
 the Digestive System. A. Diseases of 'the Stomach < 
 
 A SYSTEM OF MEDICINE. Vol. III. 8vo. 25*. 
 
 Part II. Local Diseases (continued). //. Diseases of the Digestive 
 System (continued). B. Diseases of the Mouth. C. Diseases oj 
 
PHYSIOLOGY, ANATOMY, ETC. 53 
 
 the Fauces, Pharynx, and (Esophagus. D. Diseases of the In- 
 testines. E. Diseases of the Peritoneum. F. Diseases of the 
 Liver. G. Diseases of the Pancreas. ///. Diseases of the 
 Respiratory System. A. Diseases of the Larynx. B. Diseases of 
 the Thoracic Organs, 
 
 Reynolds (O.) SEWER GAS, AND HOW TO KEEP IT 
 OUT OF HOUSES. A Handbook on House Drainage. By 
 OSBORNE REYNOLDS, M.A., Professor of Engineering at Owens 
 College, Manchester, Fellow of Queen's College, Cambridge. 
 Second Edition. Crown 8vo. cloth, is. 6d. 
 
 The author's chief object in writing on this subject is to suggest a plan 
 for preventing the evil which has been causing so much alarm since 
 the recent illness of the Prince of Wales viz. the back-fioiv of gas 
 into our houses. Of the plan he here suggests, he has nwv had 
 four years' experience, and has, without exception, found it to answer 
 perfectly. He applied it to his own house, a house of the ordinary 
 type drained into a foul sewer, at a cost of about fifty shillings. 
 Before the introduction of the new plan it was never free from smells; 
 while since, there has been no annoyance of the kind, nor have the 
 drains required any attention -whatever. The plan is very simple 
 and can be applied to any house without requiring the inside drains 
 to be disturbed. Besides fully explaining the plan and showing its 
 application by means of illustrations, the author throws out sug- 
 gestions with regard to drainage generally which many will find 
 to be very valuable. "Professor Reynolds' admirable pamphlet will 
 a thousand times over repay its cost and the reader's most attentive 
 perusal." Mechanics' Magazine. 
 
 Rolleston. THE HARVEIAN ORATION, 1873. By GEORGE 
 
 ROLLESTON, M.D., F.R.S., Linacre Professor of Anatomy and 
 | Physiology, and Fellow of Merton College, in the University of 
 Oxford. Crown 8vo. 2s. 6d. 
 
 In this Lecture the author expounds certain advances recently made 
 in our knowledge of the anatomy and physiology of the circulatory 
 organs, and gives the as yet unrecorded history of one of the many 
 attempts to rob Harvey of the glory of the great discovery. 
 
54 SCIENTIFIC CATALOGUE. 
 
 Seaton. A HANDBOOK OF VACCINATION. By EDWARD 
 C. SEATON, M.D., Medical Inspector to the Privy Council. Extra 
 fcap. 8vo. 8s. 6d. 
 
 The author's object in putting forth this work is twojold : First, to 
 provide a text-book on the' science and practice of Vaccination for 
 the use of younger practitioners and of medical students ; secondly } 
 to give what assistance he could to those engaged in the administra- 
 tion of the system of Public Vaccination established in England. 
 For many years past, from the nature of his office, Dr. Seaton has 
 had constant intercourse in reference to the subject of Vaccination, 
 -with medical men who are interested in it, and especially with that 
 large part of the profession who are engaged as Public Vacci- 
 nators. All the varieties of pocks, both in men and the lower 
 animals, are treated of in detail, and much valuable information 
 given on all points connected with lymph, and minute instructions 
 as to the niceties and cautions which so greatly influence success 
 in Vaccination. The administrative sections of the work will be 
 of. interest and value, not only to medical practitioners, but to 
 many others to whom a right understanding of the principles on ' 
 which a system of Public Vaccination should be based is indis- 
 pensable. 
 
 Symonds (J. A., M.D.) MISCELLANIES. By JOHN 
 ALDINGTON SYMONDS, M.D. Selected and Edited, with an 
 Introductory Memoir, by his Son. 8vo. 7^- 6< 
 
 The late Dr. Symonds of Bristol was a man of a singularly versatile 
 and elegant as well as powerful and scientific intellect. In order 
 to make this selection from his many works generally interesting, 
 the editor has confined himself to works of pure literature, and to 
 s.uch scientific studies as had a general philosophical or social 
 interest. Among the general subjects are articles on l( the Principles 
 of Beauty" on "Knowledge," and a " Life of Dr. Prichard ;" 
 among the Scientific Studies are papers on ' 'Sleep and Dreams," 
 "Apparitions," "the Relations between Mind and Muscle," 
 "Habit" etc.; there are several papers on "the Social and 
 Political Aspects of Medicine ; " and a few Poems and Transla- 
 tions selected from a great number of equal merit. "A collection of 
 graceful essays on general and scientific subjects, by a very accom- 
 plished physician." Graphic. 
 
MENTAL AND MORAL PHILOSOPHY, ETC. 55 
 
 WORKS ON MENTAL AND MORAL 
 PHILOSOPHY, AND ALLIED SUBJECTS. 
 
 Aristotle. AN INTRODUCTION TO ARISTOTLE'S 
 
 RHETORIC. With Analysis, Notes, and Appendices. By E. 
 M. COPE, Trinity College, Cambridge. 8vo. 14^. 
 
 This work is introductory to an edition of the Greek Text of Aristotle' 's 
 Rhetoric, "which is in course of preparation. Its object is to render 
 that treatise thoroughly intelligible. The author has aimed to 
 illustrate, as preparatory to the detailed explanation of the work, the 
 general bearings and relations of the Art of Rhetoric in itself, as 
 well as the special mode of treating it adopted by Aristotle in his 
 peculiar system. The evidence ttpon obscure or doubtful questions 
 connected with the subject is examined; and the relations which 
 Rhetoric bears, in Aristotle's mew, to the kindred art of Logic are 
 fully considered. A connected Analysis of the work is given, and 
 a few important matters are separately discussed in Appendices. 
 There is added, as a general Appendix, by way of specimen of the 
 antagonistic system of Isocrates and others, a complete analysis of 
 the treatise called 'P^ropix^ "^pos 'AAe^cw'Spoy, with a discussion of 
 its authorship and of the probable results of its teaching. 
 
 ARISTOTLE ON FALLACIES; OR, THE SOPHISTICI 
 ELENCHI. With a Translation and Notes by EDWARD POSTE, 
 M.A., Fellow of Oriel College, Oxford. 8vo. Ss. 6d. 
 
 Besides the doctrine of Fallacies, Aristotle offers, either in this treatise 
 or in other passages quoted in the Commentary, various glances 
 over the world of science and opinion, various suggestions or pro- 
 blems which are still agitated, and a vivid picture of the ancient 
 system of dialectics, which it is hoped may be found both interesting 
 
56 SCIENTIFIC CATALOGUE. 
 
 and instructive. "It will be an assistance to genuine students sf 
 Aristotle" Guardian. "It is indeed a work of great skill.''' - 
 Saturday Review. 
 
 Birks. FIRST PRINCIPLES OF MORAL SCIENCE; Or, 
 a First Course of Lectures delivered in the University of Cam- 
 bridge. By the Rev. T. R. BIRKS, Professor of Moral Philosophy. 
 Crown 8vo. 8s. 6d. 
 
 Boole. AN INVESTIGATION OF THE LAWS OF 
 THOUGHT, ON WHICH ARE FOUNDED THE 
 MATHEMATICAL THEORIES OF LOGIC AND PRO- 
 BABILITIES. By GEORGE BOOLE, LL.D., Professor of 
 Mathematics in the Queen's University, Ireland, &c. 8vo. i^s. 
 
 The design of this treatise is to investigate the fundamental laws cf 
 those operations of the mind by which reasoning is performed ; to 
 give expression to them in the symbolical language of a Calculus, 
 and upon this foundation to establish the science of Logic and con- 
 struct its method / to make that method itself the basis of a general 
 method for the application of the mathematical doctrine of Proba- 
 bilities / and, finally, to collect from the various elements of truth 
 brought to view in the course of these inquiries some probable inti- 
 mations concerning the nature and construction of the human 
 mind. The problem is one of the highest interest, and no one is 
 better able than Professor Boole to treat of this side of it at any rate. 
 
 Butler (W. A.) y Late Professor of Moral Philosophy in the 
 University of Dublin : 
 
 LECTURES ON THE HISTORY OF ANCIENT PHILO- 
 SOPHY. Edited from the Author's MSS., with Notes, by 
 WILLIAM HEPWORTH THOMPSON, M.A., Master of Trinity 
 College, and Regius Professor of Greek in the University of 
 Cambridge. Two Volumes. 8vo. I/. $s. 
 
 These Lectures consist of an Introductory Series on the Science of Mind 
 generally, and Jive other Series on Ancient Philosophy, the greater 
 part of which treat of Plato and the Platonists, the Fifth Series 
 being an unfinished course on the Psychology of Aristotle, contain- 
 ing an able Analysis of the well kncnvn though by no means u'dl 
 
MENTAL AND MORAL PHILOSOPH Y, ETC. 57 
 
 Butler (W. A..) continued. 
 
 understood Treatise, irepl tyvxfjs. These Lectures are the result of 
 patient and conscientious examination of the original documents, 
 and may be considered as a perfectly independent contribution to our 
 knowledge of the great master of Grecian wisdom. The author's 
 intimate familiarity with the metaphysical writings of the last 
 century, and especially with the English and Scotch School of 
 Psychologists, has enabled him to illustrate the subtle speculations 
 of which he treats in a manner calculated to render them mart 
 intelligible to the English mind than they can be by writers trained 
 solely in the technicalities of modern German schools. The editor 
 has verified all the references, and added valuable Notes, in which 
 he points out sources of more complete information. The Lectures 
 constitute a History of the Platonic Philosophy its seed-time, 
 maturity, and decay. 
 
 SERMONS AND LETTERS ON ROMANISM. See THEO- 
 LOGICAL CATALOGUE. 
 
 Calderwood. Works by the Rev. HENRY CALDERWOOD, M.A., 
 LL.D., Professor of Moral Philosophy in the University of Edin- 
 burgh : 
 
 PHILOSOPHY OF THE INFINITE: A Treatise on Man's 
 Knowledge of the Infinite Being, in answer to Sir W. Hamilton 
 and Dr. Mansel. Cheaper Edition. 8vo. *js. 6d. 
 
 The purpose of this volume is, by a careful analysis of consciousness, 
 to prove, in opposition to Sir W. Hamilton and Mr. Mansel, that 
 man possesses a notion of an Infinite Being, and to ascertain the 
 peculiar nature of the conception and the particular relations in 
 which it is found to arise. The province of Faith as related to that 
 of Knowledge, and the characteristics of Knowledge and Though! 
 as bearing on this subject, are examined; and separate chapters are 
 devoted to the consideration of our knowledge of the Infinite as 
 First Cause, as Moral Governor, and as the Object of Worship. 
 "A book of great ability .... written in a clear style, and may 
 be easily understood by even those who are not versed in such 
 discussions" British Quarterly Review. 
 
 A HANDBOOK OF MORAL PHILOSOPHY. Second Edition. 
 Crown 8vo. 6s. 
 
58 SCIENTIFIC CATALOGUE. 
 
 "ft if, we feel convinced, the best handbook on the subject, intellectually 
 and morally, and does infinite credit to its author." Standard. 
 
 Elam. A PHYSICIAN'S PROBLEMS. See MEDICAL 
 CATALOGUE, preceding. 
 
 Galton (Francis). HEREDITARY GENIUS : An Inquiry 
 into its Laws and Consequences. See PHYSICAL SCIENCE 
 CATALOGUE, preceding. 
 
 Green (J. H.) SPIRITUAL PHILOSOPHY: Founded on 
 the Teaching of the late SAMUEL TAYLOR COLERIDGE. By die 
 late JOSEPH HENRY GREEN, F.R.S., D.C.L. Edited, with a 
 Memoir of the Author's Life, by JOHN SIMON, F.R.S., Medical 
 Officer of Her Majesty's Privy Council, and Surgeon to St. 
 Thomas's Hospital. Two Vols. 8vo. 2$s. 
 
 The late Mr. Green, the eminent surgeon, was for many years the 
 intimate friend and disciple of Coleridge, and an ardent student of 
 philosophy. The language of Coleridge's will imposed on Mr. 
 Green the obligation of devoting, so far as necessary, the remainder 
 of his life to the one task of systematising. developing, and establish- 
 ing the doctrines of the Coleridgian philosophy. With the assist- 
 ance of Coleridge's manuscripts, but especially from the knoivledge 
 he possessed of Coleridge's doctrines, and independent study of at least 
 the basal principles and metaphysics of the sciences and oj all the 
 phenomena of human life, he proceeded logically to work out a 
 system of universal philosophy such as he deemed woidd in the main 
 accord with his master's aspirations. After many years of pre- 
 paratory labour he resolved to complete in a compendious form a 
 work which should give in system the doctrines most distinctly 
 Coleridgian. The resiilt is these two volumes. The first volume 
 is devoted to the general principles of philosophy ; the second aims at 
 vindicating a priori (on principles for which the first volume has 
 contended) the essential doctrines of Christianity. The work is 
 divided into four parts: I. "On the Intellectual Faculties and 
 processes which are concei'ned in the Investigation of Truth." 
 II. "Of First Principles in Philosophy.'" III. " Truths of 
 Religion." IV. " The Idea of Christianity in relation to Con- 
 troversial Philosophy. " 
 
MENTAL AND MORAL PHILOSOPHY, ETC. 59 
 
 Huxley (Professor.) LAY SERMONS, ADDRESSES, 
 AND REVIEWS. See PHYSICAL SCIENCE CATALOGUE, 
 preceding. 
 
 Jevons. Works by W. STANLEY JEVONS, M.A., Professor of 
 Logic in Owens College, Manchester : 
 
 THE SUBSTITUTION OF SIMILARS, the True Principle of 
 Reasoning. Derived from a Modification of Aristotle's Dictum. 
 Fcap. 8vo. 2s. 6d. 
 
 "All acts of reasoning" the author says, "seem to me to be dif- 
 ferent cases of one uniform process, which may perhaps be best 
 described as the substitution of similars. This phrase clearly 
 expresses that familiar mode in which we continually argtie by 
 analogy from like to like, and take one thing as a representative 
 of another. The chief difficulty consists in showing that all the 
 forms of the old logic, as well as the fundamental rules of mathe- 
 matical reasoning, may be explained upon the same principle / and 
 it is to this difficult task I have devoted the most attention. Should 
 my notion be true, a vast mass of technicalities may be swept from 
 our logical text-books and yet the small remaining part of logical 
 doctrine will prove far more useful than all the learning of the 
 Schoolmen" Prefixed is a plan of a new reasoning machine, the 
 Logical Abacus, the construction and working of which is fully 
 explained in the text and Appendix. ' ' Mr. Jevons 1 book is very 
 clear and intelligible, and quite worth consulting." Guardian. 
 
 MaCCOll. THE GREEK SCEPTICS, from Pyrrho to Sextus- 
 An Essay which obtained the Hare Prize in the year 1868. By 
 NORMAN MACCOLL, B.A., Scholar of Downing College, Cam- 
 bridge. Crown 8vo. 3-y. 6d. 
 
 This Essay consists of five parts: I. "Introduction." II. "Pyrrho 
 and Timon." III. "The New Academy." IV. "The Later 
 Sceptics" V. " The Pyrrhoneans and New Academy con- 
 trasted." "Mr. Maccoll has produced a monograph which merits 
 the gratitude of all students of philosophy. His style is clear and 
 vigorous ; he has mastered the authorities, and criticises them in a 
 modest but independent spirit " Pall Mall Gazette. 
 
60 SCIENTIFIC CATALOGUE. 
 
 M'Cosh. Works by JAMES M'Cosn, LL.D., President of Princeton 
 College, New Jersey, U.S. 
 
 " He certainly shows himself skilful in that application of logic ta 
 psychology, in that inductive science of the human mind which is 
 the fine side of English philosophy. His philosophy as a whole is 
 worthy of attention." Revue de Deux Mondes. 
 
 THE METHOD OF THE DIVINE GOVERNMENT, Physical 
 and Moral. Tenth Edition. 8vo. los. 6d. 
 
 This vvork is divided into four books. The first presents a general 
 view of the Divine Government as fitted to throw light on the 
 character of God; the second deals with the method of the Divine 
 Government in the physical world; the third treats of the principles 
 of the human mind through which God governs mankind; and the 
 fourth is on Pastoral and Revealed Religion, and the Restoration 
 of Man. An Appendix, consisting of seven articles, investigates 
 the fundamental principles which underlie the speculations of the 
 treatise. " This work is distinguished from other similar ones by 
 its being based upon a thorough study of physical science, and an 
 accurate knowledge of its present condition, and by its entering in a 
 deeper and more unfettered manner than its predecessors upon the dis- 
 cussion of the appropriate psychological, ethical, and theological ques- 
 tions. The author keeps aloof at once from the a priori idealism and 
 dreaminess of German speculation since Sc helling, and from the 
 onesidedness and narrowness of the empiricism and positivism 
 which have so prevailed in England." Dr. Ulrici, in "Zeitschrift 
 fur Philosophic." 
 
 THE INTUITIONS OF THE MIND. A New Edition. 8vo. 
 cloth. ioj. 6d. 
 
 The object of this treatise is to determine the true nature of Intuition, 
 and to investigate its laws. It starts with a general view of 
 intuitive convictions, their character and the method in which they 
 are employed, and passes on to a more detailed examination of 
 them, treating them under the various heads of "Primitive Cogni- 
 tions," " Primitive Beliefs," " Primitive Judgments," and "Moral 
 Convictions." Their relations to the various sciences, mental and 
 physical, are then examined. Collateral criticisms are thrown 
 into preliminary and supplementary chapters and sections. ' ' The 
 undertaking to adjust the claims of the sensational and intuitional 
 
MENTAL AND MORAL PHILOSOPHY, ETC. 6 r 
 
 M'Cosh (J.) continued. 
 
 philosophies, and of the a posteriori and a priori methods, is 
 accomplished in this work with a great amount of success." 
 Westminster Review. "7" value it for its large acquaintance 
 with English Philosophy, which has not led him to neglect the 
 qreat German works. I admire the moderation and clearness, as 
 well as comprehensiveness, of the author's vieivs. " Dr. Dorner, of 
 Berlin. 
 
 AN EXAMINATION OF MR. J. S. MILL'S PHILOSOPHY: 
 Being a Defence of Fundamental Truth. Crown 8vo. 7-y. 6d. 
 
 This volume is not put forth by its author as a special reply to Mr. 
 Mill's "Examination of Sir William Hamilton's Philosophy." 
 In that work Mr. Mill has furnished the means of thoroughly 
 estimating his theory of mind, of which he had only givtn hints 
 and glimpses in his logical treatise. It is this theory which Dr. 
 M'Cosh professes to examine in this volume; his aim is simply to 
 defend a portion of primary truth which has been assailed by an 
 acute thinker who has extensive influence in England. "In 
 such points as Mr. Mill's notions of intuitions and necessity, he 
 will have the voice of mankind with him." Athenaeum. "Suc/i 
 a work greatly needed to be done, and the author was the man to 
 do it. This volume is important, not merely in reference to the 
 views of Mr. Mill, but of the whole school of writers, past and 
 present, British and Continental, he so ably represents" Princeton 
 Review. 
 
 THE LAWS OF DISCURSIVE THOUGHT : Being a Text- 
 book of Formal Logic. Crown 8vo. $s. 
 
 The main feature of this Logical Treatise is to be found in the more 
 thorough investigation of the nature of the notion, in regard to 
 which the views of the school of Locke and Whately are regarded 
 by the author as very defective, and the views of the school of Kant 
 and Hamilton altogether erroneous. The author believes that 
 errors spring far more frequently from obscure, inadequate, indis- 
 tinct, and confused Notions, and from not placing the Notions in 
 their proper relation in judgment, than from Ratiocination. In 
 this treatise, therefore, the Notion (with the term, and the Relation 
 af Thought to Language) will be found to occupy a larger relative 
 place than in any logical work written since the time of the famous 
 
62 SCIENTIFIC CATALOGUE. 
 
 M'Cosh (J.) continued. 
 
 Art of Thinking. "The amount of summarized information 
 which it contains is very great; and it is the only work on the very 
 important subject -with which it deals. Never was such a work 
 so much needed as in the present day." London Quarterly 
 Review. 
 
 CHRISTIANITY AND POSITIVISM : A Series of Lectures to 
 the Times on Natural Theology and Apologetics. Crown 8vo. 
 7s. 6d. 
 
 These Lectures "were delivered in New York, by appointment, in the 
 beginning of 1871, as the second course on the foundation of 
 the Union Theological Seminary. There are ten Lectures in all, 
 divided into three series : 7. ' ' Christianity and Physical Science" 
 (three lectures). II. "Christianity and Mental Science" (four 
 lectures). III. " Christianity and Historical Investigation" (three 
 lectures). The Appendix contains articles on "Gaps in the Theory 
 of Development;^ "Darwin's Descent of Man ;" "Principles 
 of Herbert Spencer's Philosophy" In the course of the Lectures 
 Dr. M'Cosh discusses all the most important scientific problems 
 which are supposed to affect Christianity. 
 
 Masson. RECENT BRITISH PHILOSOPHY : A Review, 
 
 with Criticisms ; including some Comments on Mr. Mill's Answer 
 to Sir William Hamilton. By DAVID MASSON, M.A., Professor 
 of Rhetoric and English Literature in the University of Edinburgh. 
 Crown 8vo. 6s. 
 
 The author, in his usual graphic and forcible manner, reviews in 
 considerable detail, and points out the drifts of the philosophical 
 speculations of the previous thirty years, bringing under notice the 
 work of all the principal philosophers who have been at work during 
 that period on the highest problems which concern humanity. The 
 four chapters are thus titled: /. "A Survey of Thirty Years." 
 II. "The Traditional Differences: how repeated in Carlyle, 
 Hamilton, and Mill" III. " Efftcts of Recent Scientific Con- 
 ceptions on Philosophy" IV. "Latest Drifts and Groupings." 
 The last seventy-six pages are devoted to a Review of Mr. Mill's 
 criticism of Sir William Hamilton's Philosophy. " We can 
 nowhere point to a work ichick gives so clear an exposition of 
 
MENTAL AND MORAL PHILOSOPHY, ETC. 63 
 
 the course of philosophical speculation in Britain during the past 
 centttry, or which indicates so instructively the mutual influences of 
 philosophic and scientific thought" Fortnightly Review. 
 
 Maurice. Works by the Rev. FREDERICK DENISON MAURICE, 
 M.A., Professor of Moral Philosophy in the University of Cam- 
 bridge. (For other Works by the same Author, see THEOLOGICAL 
 CATALOGUE.) 
 
 SOCIAL MORALITY. Twenty-one Lectures delivered in the 
 University of Cambridge. New and Cheaper Edition. Crown 8vo. 
 los. 6d. 
 
 In this series of Lectures, Professor Maurice considers, historically 
 and critically, Social Morality in its three main aspects : I, " The 
 Relations which spring from the Family Domestic Morality.'''' 
 II. " The Relations which subsist among the various constituents 
 of a Nation National Morality." III. "As it concerns Uni- 
 versal Humanity Universal Morality." Appended to each series 
 is a chapter on " Worship : " first, "Family Worship; " second, 
 "National Worship;" third, "Universal Worship." " Whilst 
 reading it we are charmed by the freedom from exclusiveness and 
 prejudice, the large charity, the loftiness of thought, the eagerness to 
 recognize and appreciate whatever there is of real worth extant in 
 the world, which animates it from one end to the other. We gain 
 new thoughts and new ways of viewing things, even more, perhaps, 
 from being brought for a time under the influence of so noble and 
 spiritual a mind" Athenaeum, 
 
 THE CONSCIENCE : Lectures on Casuistry, delivered in the 
 University of Cambridge. New and Cheaper Edition. Crown 
 8vo. 5-r. 
 
 In this series of nine Lectures, Professor Maurice, with his wonted 
 force and breadth and freshness, endeavours to settle what is meant 
 by the word ' ' Conscience, " and discusses the most important 
 questions immediately connected with the subject. Taking "Casu- 
 istry " in its old sense as being the "study of cases of Conscience," 
 he endeavours to show in what way it may be brought to bear at 
 the present day upon the acts and thoughts of our ordinary 
 existence. He shows that Conscience asks for laivs, not rules ; 
 for freedom, not chains ; for education, not suppression. He 
 
64 SCIENTIFIC CATALOGUE. 
 
 Maurice (F. D.) continued. 
 
 has abstained from the use of philosophical terms, and has touched 
 on philosophical systems only when he fancied "they were inter- 
 fering ^uith the rights and duties of wayfarers." The Saturday 
 Review says : ' ' We rise from them with detestation of all that is 
 selfish and mean, and with a living impression that there is such a 
 thing as goodness after all. n 
 
 MORAL AND METAPHYSICAL PHILOSOPHY. New 
 Edition and Preface. Vol. I. Ancient Philosophy and the First to 
 the Thirteenth Centuries ; Vol. II. the Fourteenth Century and the 
 French Revolution, with a glimpse into the Nineteenth Century. 
 New Edition. 2 Vols. 8vo. 25^. 
 
 This is an Edition in two volumes of Professor Maurice's History of 
 Philosophy from the earliest period to the present time. It was 
 formerly scattered throughout a number of separate volumes, and it 
 is believed that all admirers of the author and all students of 
 philosophy will welcome this compact Edition. The subject is one 
 of the highest importance, and it is treated here with fulness and 
 candour, and in a clear and interesting manner. In a long intro- 
 duction to this Edition, in the form of a dialogue, Professor Matirice 
 justifies some of his own peculiar views, and touches upon some of 
 the most important topics of the lime. 
 
 Murphy, THE SCIENTIFIC BASES OF FAITH. By 
 JOSEPH JOHN MURPHY, Author of " Habit and Intelligence." 
 8vo. 14-r. 
 
 " The book is not without substantial value ; the writer continues the 
 work of the best apologists of the last century, it may be with less 
 force and clearness, but still with commendable persuasiveness and 
 tact ; and with an intelligent feeling for the changed conditions of 
 the problem. " Academy. 
 
 PictOn. THE MYSTERY OF MATTER AND OTHER 
 ESSAYS. By J. ALLANSON PICTON, Author of " New Theories 
 and the Old Faith." Crown 8vo. t IQJ. 6d. 
 
 CONTENTS: The Mystery of Matter The Philosophy of Igno- 
 rance The Antithesis of Faith and Sight The Essential Natttre 
 of Religion Christian Pantheism. 
 
MENTAL AND MORAL PHILOSOPHY, ETC. 65 
 
 Thring (E., M. A.) THOUGHTS ON LIFE-SCIENCE. 
 By EDWARD THRING, M.A. (Benjamin Place), Head Master of 
 Uppingham School. New Edition, enlarged and revised. 
 Crown 8vo. Js. 6d. 
 
 In this volume are discussed in a familiar manner some of the most 
 interesting problems between Science and Religion, Reason and 
 Feeling. "Lea rning a nd Science, ' ' says the author, * ' are claiming 
 the right of building lip and pulling down everything, especially 
 the latter. It has seemed to me no useless task to look steadily at 
 what has happened, to take stock as it were of men's gains, and to 
 endeavour amidst new circumstances to arrive at some rational 
 estimate of the bearings of things, so that the limits of what is 
 possible at all events may be clearly marked out for ordinary 
 
 readers This book is an endeavoiir to bring out some of the 
 
 main facts of the world." 
 
 Venn. THE LOGIC OF CHANCE : An Essay on the Founda- 
 tions and Province of the Theory of Probability, with especial 
 reference to its application to Moral and Social Science. By JOHN 
 VENN, M.A., Fellow of Gonville and Caius College, Cambridge. 
 Fcap. 8vo. 7-y. 6d. 
 
 This Essay is in no sense mathematical. Probability, the author 
 thinks, may be considered to be a portion of the province of Logic 
 regarded from the material point of view. The principal objects of 
 this Essay are to ascertain how great a portion it comprises, where 
 we are to dra^v the boundary between it and the contiguous branches 
 of the general science of evidence, what are the ultimate foundations 
 upon which its rules rest, what the nature of the evidence they are 
 capable of affording, and to what class of subjects they may most 
 fitly be applied. The general design of the Essay, as a special 
 treatise on Probability, is quite original, the author believing that 
 erroneous notions as to the real nature of the subject are disastrously 
 prevalent. "Exceedingly well thought and well written," says the 
 Westminster Review. The Nonconformist calls it a "masterly 
 book," 
 
 LONDON : K. CLAY, SONS, AND TAYLOR, PRINTERS, BREAD STREET HILL. 
 
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