L.ITELY PUBLISHED Bi CAREY? LEA & BLANCHARD, PHILADELPHIA. A TREATISE ON PULMONARY CONSUMPTION, Comprehending' an Inquiry into the Cause, Nature, Prevention, and Treatment of TUBERCULOUS and SCROFULOUS DISEASES in general. By James Clark, M. D., F. R. S., &c. In 1 vol. 8vo. " Dr. Clark's Treatise on Consumption is the best that has yet been published in this coun- try, or on the continent. It shows an intimate knowledge of the approved methods of diag- nosis, and of the morbid anatomy so successfully investigated by the continental pathologists, and by Professor Carswell; while it displays an acquaintance with the resources of the sys- tem, and the power of the therapeutic agents, only possessed in this country and in Germa- ny."—Lancet, August, 1835. DUNGLISON ON HYGIENE. On the Influence of Atmosphere and Locality; Change of Air and Climate, Sea- sons, Food, Clothing, Bathing, Exercise, Sleep, Corporeal and Intellectual Pursuits, &c. on Human Health, constituting Elements of HygieYie. By Rob- let Dcnglison, M. D., Professor of Materia Medica, Therapeutics, Hygiene, and Medical Jurisprudence in the University of Maryland, &c. In 1 vol. 8vo. "The want of a precise and practical compendium of the principles of hygiene, has long been felt in this country, especially by the younger members of the profession, who from the deficiency of elementary treatises, and still more, of a proper course of instruction on this im- portant subject, are in a great measure obliged to rest content with the general views of the operations of external agents on the human organization, which they acquire whilst pursuing the general routine of their medical studies."— American Medical Journal for February. " We can recommend this work to the public with the utmost confidence, as one oft lie best treatises on the subject we possess."—Ibid. DENTAL SURGERY. A SYSTEM OF DENTAL SURGERY, In three Parts. I. Dental Surgery as a Science. II. Operative Dental Surgery. III. Pharmacy connected with Dental Surgery. By S. S. Fitch, M. D. Se- cond edition. In 1 vol. 8vo. With numerous copperplate engravings. ANIMAL AND VEGETABLE PHYSIOLOGY, Considered with reference to Natural Theology. By Peter Mark Roget, M. D. Illustrated with nearly 500 wood cuts. In 2 vols. 8vo. Being a part of the Bridge water Treatises. THE HISTORY, HABITS, AND INSTINCTS OF ANIMALS. By the Kev. William Kirbt, M. A., F. R. S. In 1 vol. 8vo. Illustrated by numerous en- gravings on copper. Being a part of the Bridgewater Treatises. THE PRACTICE OF PHYSIC. By W. P. Dewees, M. D., Adjunct Professor of Midwifery, in the University of Pennsylvania. New edition, greatly en- larged. Complete in 1 vol. 8vo. " We have no hesitation in recommending it as decidedly one of the bes*«ystems of medi- ■-ine extant. The tenor of the work, in general, reflects the highest honour on Dr. Dewees's, talents, industry, and capacity for the execution of the arduous task which he had undertaken. It is one of the most able and satisfactory works which modern times have produced, and will be a standard authority."—London Mai. and Surg. Journ. Aug. 1830. 2 DEWEES ON THE DISEASES OF CHILDREN. Sixth edition. In 1 vol. 8vo. The objects of this work are, 1st, to teach those who have the charge of children, either as parent or guardian, the most approved methods of securing and improving their physical pow- ers. This is attempted by pointing out the duties which the parent or the guardian owes for this purpose, to this interesting, but helpless class of beings, and the manner by which their duties shall be fulfilled. And, 2dly, to render available a long experience to these objects of our affection when they become diseased. In attempting this, the author has avoided as much as possible, "technicality;" and has given, if he does not flatter himself too much, to each dis- ease of which he treats, its appropriate and designating characters, with a fidelity that will prevent any two being confounded together, with the best mode of treating them, that either his own experience or that of others has suggested. DEWEES ON THE DISEASES OF FEMALES. Fifth edition, with Addi- tions. In 1 vol. 8vo. A COMPENDIOUS SYSTEM OF MIDWIFERY; chiefly designed to facili- tate the Inquiries of those who may be pursuing this Branch of Study. By W. P. Dewees, M. D. In 1 vol. 8vo. with 13 plates. Seventh edition, cor- rected and enlarged. A NEW EDITION OF GIBSON'S SURGERY. THE INSTITUTES AND PRACTICE OF SURGERY; being the Outlines of a Course of Lectures. By William Gibson, M. D., Professor of Surgery in the University of Pennsylvania, &c. &c. Fourth edition, greatly enlarged. In 2 vols. 8vo. With thirty plates, several of which are coloured. " The author has endeavoured to make this edition as complete as possible, by adapting it to the present condition of surgery, and to supply the deficiencies of former editions by add- ing chapters and sections on subjects not hitherto treated of. And, moreover, the arrangement of the work has been altered by transposing parts of the second volume to the first, and by changing entirely the order of the subject in the second volume. This has been done for the purpose of making the surgical course in the university correspond with the anatomical lec- tures, so that the account of surgical diseases may follow immediately the anatomy of the parts." DUNGLISON'S PHYSIOLOGY. HUMAN PHYSIOLOGY; illustrated by numerous Engravings. By Roblet Dunglison, M. 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" A work, like this, so abounding in important facts, so correct in its principles and so free from errors arising from a prejudice to favourite opinions, will be cordially received and ex- tensively consulted by the profession, and by all who are desirous of a knowledge of the func- tions of the human body, and those who are the best qualified to judge of its merits will nro nounce it the best work of the kind in the English language."—Silliman. ' ' "This is a work of no common standing; it is characterized by much learning and research contains a vast amount of important matter, and is written*y a man of taste. We are in- clined to think that it will be placed by general consent at the head of the systems of Physio- logy now extant in the English language. Nor are we prepared to say, that all things consi- dered, its superior exists in any language. It has a character of its own, and is a trueAnelo- American production, unsophisticated by garnish forcignism."— TYansylvania Jtumal TREATISE ON SPECIAL. AND GENERAL ANATOMY. BY WILLIAM E. HORNER, M. D. ROFESSOR OF ANATOMY IN THE UNIVERSITY OF PENNSYLVANIA—MEMBER OF THE IMPERIAL MEfilCO-CHIROROlCAL ACADEMY OF ST. PETERSBURG—OF THE AMERICAN PHILOSOPHICAL SOCIETY, &C. Multum adhuc.restat operis, multumque restabit, nee ulli nato, post mille sscula prscluditur occasio aliquid adjiciendi. SENECA, EPIST. IN TWO VOLUMES. VOL.. II. iFOURTH EDITION, REVISED AND IMPROVED, CAREY, LEA & BLANCHARD. * 1836. ,* v, 2, Eastern District of Pennsylvania, to wit: BE IT REMEMBERED, that, on the seventeenth day of October, in the fifty-first year of the Independence of the United States of America, A. D. 1826, Wilham E. Horner, of the said district, hath deposited in this office the title of a book, the right whereof he claims $s. Author, in the words follow- ing, to wit:— "A Treatise on Special and General Anatomy. By William E. Horner, M. D., Adjunct Professor of Anatomy in the University of Pennsylvania—Member of the American Philosophical Society—Surgeon at the Philadelphia Alms House, &c. ' Multum adhuc restat operis, multumque restabit, nee ulli nato, post mille saecula praecluditur occasio aliquid adjiciendi.' Seneca, Epist. In Two volumes. Vol. II." In conformity to the Act of the Congress of the United States, entitled, " An Xct for the Encouragement of Learning, by securing the Copies of Maps, Charts, and Books, to the Authors and Proprietors of such Copies, during the times therein mentioned"—And also to the Act, entitled, "An Act supplemen- tary to an Act, entitled, ' An Act for the Encouragement of Learning, by se- curing the Copies of Maps, Charts, and Books, to the Authors and Proprietors of such Copies, during the times therein mentioned,' and extending the bene- fits thereof to the arts of designing, engraving, and etching Historical and other Prints." D. CALDWELL, Clerk of the Eastern District of Pennsylvania. A I TREATISE ON ANATOMY. BOOK IV. \i PART II. Organs of Assimilation. t CHAPTER I. OF THE ABDOMEN GENERALLY. The cavity of the abdomen occupies the space between the inferior surface of the diaphragm and the outlet of the pelvis; a considerable part of it is, therefore, within the periphery of the lower ribs above, and of the pelvis below. It is completely se- parated from the cavity of the thorax by the diaphragm, with the exception of the foramina in the latter, for transmitting the aorto, the ascending cava, and the oesophagus. It is bounded below, by the iliaci interni, the psoae, and the levatores ani mus- cles; on the front and sides by the five pairs of muscles called abdominal; and behind by the lesser muscle of the diaphragm, the Quadrati Lumborum, the lumbar vertebrae, and the sacrum. The figure of this cavity is, therefore, too irregular to admit of a very rigid comparison with any of the common objects of life; but a little reflection, on the course of its parietes, will make it perfectly understood. It should be borne in mind, that the very great projection of the lumbar vertebrae forms for it a partial vertical septum behind; which, in thin subjects, is almost in con- tact with the lihea alba in front, and may be easily distinguished Vol. II.—2 / 6 ORGANS OF DIGESTION. through the parietes of the abdomen', when the intestines are empty. The abdominal cavity varies only, inconsiderably, in its ver- tical diameter, owing to the resistance of the diaphragm above, and of the pelvis below; neither does it change behind, owing to the resistance of the spine, the ribs, and the muscles there. But as the introduction of food, the development of gaseous sub- stances during digestion, the evolution of the foetus, and many other conditions, require some provision for its undergoing an easy augmentation of volume; the latter occurs principally for- wards and laterally, by the yielding of the muscles and by the extension of their aponeuroses. The diaphragm and the abdo- minal muscles, for the most part, act alternately; as the former descends in inspiration, the latter relax and give way to the con- tents of the abdomen: but in expiration, the abdominal muscles contract, and the diaphragm is pushed upwards by the viscera. In attempts at the expulsion of faeces, and in parturition, these muscles contracting, and the diaphragm being fixed all at the same moment, the cavity of the abdomen is actually much di- minished. The viscera contained in the cavity of the abdomen are of three kinds. One kind is engaged in digestion and assimilation; another in the secretion and excretion of urine; and the third in generation. As these viscera are numerous, and it is of great im- portance to determine with precision their position and relative situation, anatomists are agreed to divide the cavity of the ab- domen into several arbitrary regions. This is the more advan- tageous, as the bony prominences bounding the abdomen are not sufficiently numerous and distinct, to afford those obvious points of relation to the viscera which they furnish in other sec- tions of the body. To obtain these regions, consider a line or plane as extending across the abdomen, about two inches below the umbilicus, from the superior part of the crista of one ilium, as it appears through the skin, to the corresponding point of the other side. Strike on each side a line perpendicular to the pre- ceding, by commencing at the lower end of the anterior inferior spinous process of the ilium, and carrying it up to the dia- phragm. Extend a fourth line across the abdomen parallel with the first, and intersecting the two last where they come upon OP THE ABDOMEN. 1 the cartilages of the false ribs. It is evident that these four lines or planes, two horizontal and two vertical, will, with the assistance of the parietes of the abdomen, furnish nine regions: three above; three in the middle, and three below. The cen- tral region above, is the Epigastric; and on its sides are the right and the left Hypochondriac.. The central region in the middle, surrounding the navel, is the Umbilical; and on its sides are the right and the left Lumbar. The central region below, is the Hypogastric; and on its sides are the right and the left Iliac. There are also some subordinate divisions; for example, the hollow in the epigastric region, around the ensiform car- tilage, is called the pit of the stomach, or Scrobiculis Cordis; and for an inch or two around the symphysis pubis, is the re- gion of the pubes, (Regio Pubis.) Anatomists differ among themselves about the points of de- parture and the position of the lines, or rather planes, separating the regions. Some fix them at arbitrary distances from the umbilicus, and others assume the points of the skeleton. The umbilicus is the most fallacious mark, because its elevation va- ries considerably, according to the state of distention of the ab- domen, it being comparatively higher when the abdomen is tumid than when it is not. Neither does it answer to take the anterior ends of the last ribs as the points for the upper horizon- tal line to pass through; as they, sometimes, are almost as low down as the umbilicus itself. The superior anterior spinous processes are also objectionable as the points of departure for the vertical lines; as they leave too much room for the central regions of the abdomen, and too little for the lateral: I have, therefore, after some hesitation, thought proper to substitute the anterior inferior spinous processes; and, especially, as the posi- tion of the viscera, as almost universally described, is more in accordance with this rule. General Situation of the Viscera of the Abdomen. When the abdomen is so opened as to leave its viscera in their natural position, they will be found as follows:— 1. The Liver, the largest gland of the body, is in the right 8 ORGANS OF DIGESTION. upper part of the abdomen, immediately below the diaphragm. It occupies nearly the whole of the right hypochondriac region; the upper half of the epigastric; and the right superior part of the left hypochondriac. The anterior extremity of the gall- bladder projects beyond its anterior margin. 2. The Spleen is situated in the posterior part of the left hy- pochondriac region. 3. The Stomach, in a moderate condition of distention, occu- pies the lower half of the epigastric region, and the right infe- rior portion of the left hypochondriac. 4. The Smaller Intestine, when moderately distended by flatus, occupies the umbilical region, the hypogastric, portions of the iliac on each side, and also the upper part of the cavity of the pelvis, when the viscera of the latter are empty. 5. The Large Intestine traverses the cavity of the abdomen in such manner as to perform almost the entire circuit of it. It begins in the right iliac region by receiving the lower extre- mity of the small intestine; it then ascends through the right lumbar and the right hypochondriac, passes into the lower part of the epigastric, or into the upper of the umbilical, according to the state of distention of the stomach; thence it gets into the left hypochondriac, being fixed higher up there than in the cor- responding region of the other side; afterwards it goes down into the left lumbar and into the left iliac; thence it passes into the pelvis, and, descending in front of the sacrum, terminates in the orifice called anus. 6. The Caul, or Omentum, is a membrane, of various densi- ties, in different individuals, and lies in front of the intestines. Sometimes it is found spread over the latter like an apron, but on other occasions is drawn up into the umbilical region, form- ing a ridge across it. 7. The Pancreas lies transversely in the lower back part of the epigastric region. It extends from the left hypochondriac OF THE ABDOMEN. 9 region to the right side of the spine, and is placed behind the stomach, so as to be covered by it. 8. The Kidneys and the Capsular Renales, two in number each, are placed in the posterior part of the lumbar region on the side of the spine. 9. The Urinary Bladder and the Rectum, in the male, occupy the cavity of the pelvis, and in the female between them are placed the uterus, the ovaries, and the vagina. As, in the dissection of the abdominal viscera, the subject is commonly placed on its back, so the preceding description is made out with a strict reference to that position. Some modi- fication in the shape of the abdomen, as well as in the situation of its contents, occurs in standing upright. The front of the abdomen becomes more protuberant, the lumbar vertebra? make a greater projection forwards. The pelvis is so adjusted, in order to bring the acetabula directly in the line of support to the spine, that the convexity of the sacrum presents almost up- wards, and the superior straight looks forwards and upwards towards the navel, so that much of the weight of the viscera is thrown upon the pubes. In this attitude most of the viscera descend, but more obviously the liver, from its weight, size, and solidity. Portal has verified this descent by comparing the thrusts of poniards into the liver in the erect, with those inflict- ed in the horizontal position. He also asserts that the same may be ascertained in the living body by applying the fingers under the false ribs, and then directing the person to change from the recumbent into the vertical position. The spleen af- fords the same results when it is slightly enlarged, and the de- scent of the liver and spleen will of course ensure that of the stomach and intestines. According to Winslow, the pain and faintness which are felt after a long abstinence, come from the vacuity of the stomach and intestines, which thereby withdraw their support from the liver, and permit it to drag upon the diaphragm. The presence of flatus in the stomach and intestinal canal, seems to be entirely natural to them; for it is comparatively 10 ORGANS OF DIGESTION. rare to find them destitute of it, even when they contain no food or fasces. The large intestine is, however, more frequent- ly found contracted or empty than the small. Owing to the flexible character of a considerable portion of the abdominal pa- rietes, the latter, by their own contraction, as well as by atmo- spheric pressure, are kept in close contact with the viscera; and the viscera again, by the same influence, are kept in close con- tact with one another; so that, notwithstanding the irregularity of their forms and the fluctuating size of the hollow ones, there is no unoccupied space in the cavity of the belly. Several instances are reported by anatomists, in which a to- tal transposition of the abdominal viscera has occurred, so that those which belonged to the right side were placed in the left.* They are, however, exceedingly rare: in probably more than fifteen hundred observations, or more, I have never met with one instance of it. CHAPTER II. OF THE PERITONEUM, AND SEROUS MEMBRANES, GENERALLY. SECT. I.--OF THE PERITONEUM. The sides of the abdomen are lined, and its viscera are co- vered by a membrane called Peritoneum.f As the reflections of this membrane, by being thrown over the periphery of almost every viscus of the abdomen, consequently, assume the same shape; and as it lines, without exception, the interior surface of every part of theabdomen, its form is extremely complicated, and can only be judged of accurately after the study of the viscera is completed. For the present it will only be neces- sary to give the outline of it, leaving the details to each appro- priate occasion. * Portal, Haller, Sandifort, &c. f From Trsefttma-Bu quod est circumquaque extendi. OF THE PERITONEUM. 11 In man, it is a complete sac, having no hole in it; but in wo- man, its cavity communicates externally through the Fallopian tubes. It has a double use: In consequence of covering the viscera, it is so reflected from them to the sides of the abdomen, that its processes keep the viscera in their proper places, and, therefore, answer as ligaments: again, its internal surface being smooth, indeed, highly polished, and continually lubricated by a thin, albuminous fluid, corresponding with the synovial mem- brane of the joints, the motions which the viscera have upon each other in exercise, and in the peristaltic movements of the bowels, are much facilitated. The manner in which a double night-cap is applied to the head, will afford the easiest conception of the reflections of the peritoneum. If there were only one viscus in the belly, and that of a somewhat regular outline, as the spleen, the comparison would be rigid, and perfectly appreciable. One part of the cap is close to the head, and compares with the peritoneal coat of the spleen; the other is loose, and is equivalent to the peritoneum, where it is in contact with the parietes of the belly. It is also evident from this, that none of the viscera can be said to be within the cavity of the peritoneum; that they are all on its out- side; and that a viscus, in getting a coat from the peritoneum, merely makes a protrusion into its cavity. Starting with this simple proposition, it is easy to conceive of a second, a third body, and so on, deriving an external coat from a protrusion into the same sac. Admitting these bodies to be spheres, the proposition is immediately intelligible; and, as a last step from it, the idea is not rendered much more complex by substituting any bodies even the most irregular in form,, for these spheres. Such, then, is the fact in regard to the stomach, intestines, &.c; they all, with exceptions to be stated, derive an external coat from the peritoneum. The Peritoneum is, for the most part, smoothly spread upon the interior surface of the abdominal muscles. It adheres to them with considerable firmness by means of intervening cellular substance: this adhesion, where it closes the posterior opening of the umbilicus, is unusually strong. Below, the uniformity of the membrane as it descends from the navel to the pelvis is inter- rupted by its being reflected over the urachus, and over the re- 12 ORGANS OF DIGESTION. mains of the umbilical artery on each side. Where the urachus is, it forms an oblong prominent ridge, reaching to the upper ex- tremity of the bladder; and, as regards each umbilical artery, the duplicature is of variable breadths in different individuals; but always forms a well marked falciform process, reaching from near the umbilicus to the lower side of the bladder, and di- viding the inguinal region into two parts or fossae, one nex't to the.pubes, and the other nearer to the ilium. In the undistended state of the bladder the peritoneum reaches to the pubes, is re- flected from the latter to the upper, and then goes over the pos- terior surface of the bladder. In the male, it goes from the pos- terior lower end of the bladder to the rectum, but, in the female, it does not descend so low there, and passes from the bladder to the vagina and uterus, and afterwards to the rectum. In the concavity of the ilium, and in the lumbar region, the peritoneum is attached by long loose cellular substance, which permits it to be stripped off easily, simply by tearing. In these several regions it encounters the colon, over which it is reflected, and thereby forms the Mesocolon; thence it passes in front of the kidneys, but separated from them by a thick layer of cellu- lar and adipose matter, and immediately afterward it is thrown into a long duplicature, extending obliquely across the lumbar vertebrae from above, downwards, and to the right side. This duplicature includes the small intestine, and is the Mesentery. In the highest regions of the abdomen, the peritoneum is in the greater part of its extent uniformly reflected over the concave surface of the diaphragm, and adheres so closely to it, as to re- quire a cautious and protracted dissection for its entire removal. As the remains of the umbilical vein of the foetus are still found. but in a ligamentous condition, going from the navel to the under surface of the liver, their existence gives rise to a broad falciform duplicature of peritoneum, which passes from the upper half of the linea alba and from the middle line of the diaphragm to the liver. Another line of attachment, or of reflection, of this mem- brane to the liver, is found all along the posterior margin of the latter. In the same region, it is also reflected from the diaphragm to the spleen and to the stomach. Such is the general account of the course of the peritoneum. Each of the duplications has a distinct name, and some peculiarity of organization or of relation, OF THE OMENTA. 13 which will require a specific description and a frequent allusion bit. It is proved, from what has been said, that the peritoneum is a single and complete sac, and that, with the exception stated of the Fallopian tubes, there is no hole in it either for the passing of blood vessels, nerves, or viscera. And that it is so folded over the abdominal viscera, that with patience and sufficient address, one might remove it from their surface and extract them, with- out even laying open its cavity: an experiment said to have been successfully accomplished by Nicholas Massa,* and some other anatomists. SECT. II.—OF THE OMENTA. There are four processes of the peritoneum, each of which is designated under the term Omentum, Epiploon, or Caul. 1. The Omentum Minus or the Hepatico-Gastricum, extends, as its name imports, between the liver and the stomach. It be- gins at the transverse fissure of the liver, and proceeds from it, from the right side of the lobulus spigelii, the front of which it conceals, and from the inferior posterior face of the tendinous centre of the diaphragm; it is attached to the lesser curvature of the stomach in all the space between the cardiac and the pylo- ric orifices. Its right margin reaches beyond the pylorus to the duodenum, and includes the vessels going to the liver, and the biliary ducts; in consequence of which, this margin is called the Capsule nf Glisson. The»capsule is, however, more properly the condensed cellular substance within. The two laminae which compose it are thin and transparent, and have but little fat in them; in approaching the stomach they become very distinct from each other, and receive between them the superior coronary vessels of the stomach. One lamina then goes before the stomach and the other behind, in the form of a peritoneal covering. These laminae, having covered in that way the anterior and the posterior surface of the stomach, unite again on the greater curvature of the latter, to form the beginning of the omentum majus. • Anat. Liber. Introduct. an. 1539. Portal. Vol. II.—3 14 ORGANS OF DIGESTION. 2. The Omentum Majus or Gastro-Colicum, as indicated by its name, is connected at one end all along the greater curvature of the stomach, and by the other along the transverse part of the colon. As it commences by two laminae, so it is continued throughout in the same way. It is commonly found more or less spread on the front surface of the small intestines, but occasion- ally it is tucked up in the epigastric region. When fairly spread out, either naturally or artificially, its course will be found as fol- lows : It first of all descends from the stomach to the pelvis; it then turns upwards, so as to reverse its course, and continues to ascend till it reaches the colon. Its two laminae then separate and receive the colon between them, so that, in this respect, the ar- rangement is entirely cornformable to what happens to the sto- mach. The subsequent continuation of these laniinae is the mesocolon, which will be more particularly described. As the omentum majus consists of two laminae in its whole ex- tent, it is clear that it resembles a flattened bag lined by another bag; so that in its whole thickness, when held between the fin- gers, there are four laminae. It is an irregular quadrilateral membrane, which, in corpulent subjects, is interspersed with a great deal of fat; but in such as are emaciated, it is wholly des- titute of the latter; and instead of being entire in its parietes is a delicate reticulated membrane, so that the rule about the integ- rity of the peritoneum is not fully accurate as applied to this sec- tion of it. On the right side it is continuous with the omentum colicum, and on the left with the omentum gastro-splenicum. 3. The Omentum Colicum may be considered as a continuation of the omentum majus along the ascending and a part of the transverse colon. In some rare cases, (for in my own observa- tions I have not met with the arrangement,) its origin is conti- nued downwards to the ccecum, and at its left margin is extended along the transverse colon to the spleen. Much more commonly it is, as stated, simply an appendage of the great omentum, or its right flank, advancing for a short distance along the ascending colon. It consists of but two laminae in all, commonly containing fat, but in this respect subject to the same rule as the omentum majus. OF THE OMENTA. 15 4. The Omentum Gastro-Splenicum is the left flank or mar- gin of the omentum majus, extended from the great end of the stomach to the spleen. It of course consists of but two laminae, which contain between them the splenic vessels and the vasa brevia. By looking for the posterior end of the gall-bladder, and then passing a finger under the right margin of the hepatico-gastric omentum, or, in other words, under the capsule of Glisson, where it extends from the liver to the duodenum, the finger will be found to have insinuated itself behind the stomach, and, by be- ing directed downwards, will be thrust into the sac or cavity of the great omentum. In children, where the latter is less reticu- lated than in adults, and consequently more entire, a large blow- pipe introduced at the same point will enable one to inflate this cavity, and to separate its anterior from its posterior wall. This aperture, called the foramen of Winslow, is the route by which the internal or lining lamina of the omentum majus is introduced, so as to make this process of peritoneum double throughout its whole parietes. Though this fact of duplicity is generally conceded, no author heretofore, to my knowledge, has pointed out satisfactorily the means; and for the suggestion of it, I am indebted to a learned and zealous member of the profession, now Professor Hodge of the University. Struck, at,an early pe- riod of his studies, with the difficulty of tracing a double sac to the omentum majus, out of a single membrane of the peritoneum, this suggestion was happily made by him to remove the difficul- ties of other explanations. An attempt at a diagram formed upon any other principle I have invariably seen to fail. If the reader has conceived the idea, the inference will be plain, that the lining lamina of the omentum majus is continued as a com- mon peritoneal covering over the posterior face of the stomach, and then forms the posterior lamina of the hepatico-gastric omen^ turn. It wall also be plain that the same lamina, having reached the colon in its return, continues afterwards as the upper lamina of the transverse mesocolon. From what has been said concerning the general qualities of the peritoneum, it is to be understood that though it enjoys much power of gradual extension, nevertheless this quality is not suf- 16 ORGANS OF DIGESTION. ficient to enable it to endure, without a special provision, the sudden and extensive dilatations to which the stomach and bow- els are exposed, from the introduction of food and from the evo- lution of gases during digestion. Of all the coats of these organs, it is the least extensible and contractile; its rupture, therefore, is guarded against by one invariable rule. For example: as the muscular and other coats of the stomach dilate, the perito- neum is drawn from the omentum minus and majus to cover the stomach; therefore, as the stomach enlarges, the omenta dimi- nish: and as the stomach decreases, the omenta, by the restora- tion of peritoneum, resume their primitive size. In this way the uterus, notwithstanding its great augmentation in the progress of pregnancy, still keeps itself covered by peritoneum, from the ability of the latter, as mentioned, to slide from one part and to apply itself to another. The true intention, then, of the appa- rently useless length of many processes of the peritoneum, is explained, by their being a provision for the augmentation of the hollow viscera of the abdomen, in the discharge of their na- tural functions. Adopting this explanation as the basis of our observations, we shall find that according to the probable or even possible augmentation of a viscus, so are its peritoneal at- tachments. The stomach, which next to the uterus enlarges more than any other viscus, gets its subsidiary supply of perito- neum from the length of the omentum minus and majus; the colon, which is next in order, is supplied from the length of its mesocolon; the small intestines, which are next, from the length of the mesentery. The latter, however, would be too long for that simple purpose; but the objection is removed by recollect- ing that the mesentery has also to accommodate numerous chains of lacteal glands, through which the chyle must pass in its elaboration, before it is fit to enter into the general circula- tion. The liver, being of a size almost stationary, has its peri- toneal attachments proportionally short; and its peritoneal co- vering, from the shortness of the connecting cellular substance, is disqualified from sliding. The spleen is in the same predica- ment with the liver, except that its size is not stationary; but, in this case, the peritoneum presents a phenomenon entirely re- markable : it wrinkles upon the contraction of the spleen. If this mode of reasoning, derived from an arrangement of OF THE OMENTA. 17 parts which no one denies, be correct, it follows that physiolo- gists have erred sadly in the supposed uses of the omentum ma- jus. That this organ is, in fact, only subsidiary to the enlarge- ment of the stomach and colon, so as to prevent the rupture of their peritoneal coat, and that it is neither intended to keep the belly warm, as so learned a naturalist as M. G. Cuvier has sug- gested;* nor is it a special store-house for the wants of the sys- tem during the destitution of other aliment, farther than adipose matter in other parts of the body is.t In regard to the first theo- ry, it does not appear that the inhabitants of cold climates are better furnished with, an omentum majus than those of the torrid zone: that it is better developed in winter than it is in summer; that it is tucked up in warm weather to cool the intestines, or spread out in cold weather to make them more comfortable. On the contrary, it is ascertained that its position is variable at all seasons; that in the coldest of weather it is as often found col- lected in the epigastric region, or to one side of the abdomen, as it is in the warmest; consequently, its position is the result of whatever motions may, for the time, have been impressed upon it by the distention of the stomach, and by the peristaltic move- ments of the bowels. In regard to the theory of Dr. Rush, the objection is insurmountable, that children, who are equally, if not more exposed to starvation and sickness than adults, never have fat, except in very small quantities, in the omentum, and that only along the course of its vessels. The fat is, therefore, not to be viewed as an essential circumstance in the structure of the omentum, as all children and many adults have it only very sparingly; for the omentum being wanted as a membrane of reserve to the stomach and colon, the deposite of fat in it, is in obedience to one of the general laws of the system, whereby the cellular substance beneath the serous membranes is disposed to secrete fat as the individual advances in life; which is exempli- fied on the heart and in the pleura. Another argument is, that in the ruminating animals, where there are four stomachs, and from the vegetable nature of their aliment these stomachs must, in the course of digestion, be very much distended, the great omentum is of proportionate magnitude. J ' XXII. Lecon D'Anat. Comp. j- An Inquiry into the Uses of the Omentum, by James Rush, Philad. 1809. t Cuvier, XXII. Legon, loc. cit. 18 ORGANS OF DIGESTION. As occurs in other parts of the body, also, the fat of the omen- tum accumulates in animals that take but little exercise, while it is very deficient in such as lead an active life. I am induced to believe that the hard knots felt in the abdo- men of such persons as suffer from abdominal affections, fre- quently depend upon the accumulations of the omentum majus at particular but variable points. SECT. III.—GENERAL ANATOMY OF THE SEROUS MEMBRANES. As the peritoneum presents one of the best examples of a nu- merous class of membranes, called Serous, it will be useful at this point to inquire into their general condition and properties. They are, for the most part, thin, and strongly resemble com- pressed cellular membrane; having been, indeed, by some ana- tomists, considered as such. They invariably assume the form of perfect sacs, and as they are found in all parts of the body, they are kept distinct from each other. The arachnoid mem- brane of the brain, the pericardium, the pleura, the synovial, membranes of the joints, the bursae mucosae of tendons, the peri- toneum, and the tunica vaginalis testis, belong to this class. They are not all of the same thickness, as some are much more dense than others; they adhere to neighbouring parts by a la- mina of cellular substance, which is also of variable thickness and ductility; indeed, on some occasions, it is not entirely dis- tinct, from its extreme shortness and tenuity. As the serous membranes are only displayed over the surface of the organs which they cover, after the manner of a double night-cap drawn over the head; their cavity always remains en- tire, notwithstanding it is variously modified by the shape of the organs protruded into it; and has its parietes in contact, owing to external compression. They are entirely distinct from the essential structure of the organs covered, and are displayed over those of the most dissimilar functions, as, for example, the intes- tines and the liver. A sac of this description, then, is of infinite importance in establishing between organs which border upon one another a strong partition : and, consequently, in wardino- off any injurious influence which their dissimilar natures would ANATOMY OF SEROUS MEMBRANES. 19 otherwise cause them to have upon each other. Important or- gans are, therefore, invariably thus insulated, so that whether in a healthy or in a diseased state, their actions are carried on within themselves; and not only so, but it is even possible, and, indeed, is found in morbid dissections, every day, that an organ may be diseased while its serous covering is unaffected; or the reverse. Thus, we have large suppurations in the liver, while its peritoneal coat is healthy; large accumulations of water in the tunica vaginalis testis, while the testicle itself is sound; in the thorax, with sound lungs and heart; in the abdomen, with vis- cera generally sound; in the joints, without an affection of the bones. Nothing is more common than to see partial adhesions, the result of inflammation, causing the opposite sides of these sacs to adhere, without any evident constitutional or visceral derangement; and some of our plans of cure, as in the hydro- cele, are founded upon this well established fact. The serous membranes are throughout thin, transparent, and white: in some points their tenuity is so extreme that they seem to consist simply in a smooth, polished surface, spread over parts; this is strikingly the case on the interior face of the dura mater, on the ventricles of the brain, and on the cartilages of the joints. The evidence of 'their extension there, is conse- quently derived principally from induction; and from morbid alteration, in which they become thickened. Their internal surface, in a natural state, is always smooth, highly polished, shining; and, being also lubricated by its peculiar unctuous se- cretion, the opposite parietes, when they come into contact, glide freely upon each other; a circumstance indispensable to the free action of the joints, and to the peristaltic motion of the bowels. Bordeu has asserted, that these remarkable characters of the serous membranes depend upon the compression and the friction to which they are continually exposed: but to this opi- nion the argument of Bichat is unanswerable, that in their ear- liest observable period in the foetus they have the same polish. The fluid secreted from the serous membranes resembles, strongly, the serosity of the blood. It is poured out continually by the exhalent orifices, and in a short time afterwards is taken up by the absorbents; so that in a natural state there is seldom more than sufficient to lubricate the surfaces of the membrane. 20 ORGANS OF DIGESTION. When the abdomen of an animal recently killed is exposed to the air, this fluid rises in the form of a vapour. The several experi- ments, as the application of heat, mineral acids, and so on, which prove the abundance of albumen in the serum of the blood, pro- duce the same results when applied to the secretion from the se- rous membranes. The system of serous membranes has been considered by Bi- chat, and others, as only a modification of cellular membrane, for the following reasons. The inflation of air into the cellular tis- sue subjacent to them, reduces them to the form of cellular sub- stance. Protracted maceration produces the same effects with more certainty and precision. When cellular membrane is in- flated, the parietes of the distended cells resemble strongly the finest parts of the serous system, as the arachnoid membrane. There is an identity of functions and of affections, for they are both continually engaged in the great work of exhalation and ab- sorption, and suffer in the same way from dropsical effusion, with the only difference that the latter is more amassed in the one than in the other. My own experience goes to prove, that drop- sy very seldom manifests itself, to any extent, in the cellular tis- sue without also going to the serous cavities, and the reverse. The serous membranes are also of a uniform texture, like cellular substance, and present no appearance of fibres. The serous membranes are furnished with a great abundance of exhalent pores, and of absorbents, which carry on their func- tions with great activity. They, when healthy, receive only the colourless part of the blood, whence the uniform transparency of these membranes. The existence of exhalent pores, is proved by strangulating a piece of intestine with a ligature for thirty-six or forty-eight hours, when they become evident, by dilating them- selves so as to receive red blood. A fine coloured injection pro- duces the same result; and also moistens, by the escape of its wa- tery particles, the surface of the intestine, by a very fine halitus or dew. The intestine of a living animal, if wiped perfectly dry, will, after the same way, soon present another coat of serosity on its surface. The existence of absorbents to a great extent in them, may also be equally well proved, as they very readily re- ceive a mercurial injection, which diffuses itself over their whole surface, and causes them to have the appearance of being formed ANATOMY OF SEROUS MEMBRANES. 21 entirely of such vessels. The readiness with which fluid effused into their cavities is taken up, is another proof of the same. Bi- chat once saw them distended with air in a man who had be- come emphysematous from poisoning. Mascagni has frequently found them distended with the fluid, of dropsical collections, which he recognised by its colour. It happened to the same anatomist to find in two bodies, where there had been an effusion of blood into the thorax, the absorbents of the lungs gorged with blood. This faculty of absorption may sometimes be proved to continue for some hours after death, by keeping an animal in a warm bath. Mascagni asserts, that he has witnessed its continuance for fifteen, thirty, and even for forty-eight hours; it is not impro- bable, however, that there was some illusion in these instances. It is more than probable that the serous membranes are en- tirely deprived of red blood vessels; the latter unquestionably ex- ist, in great numbers, on the exterior surface, where they creep through the cellular substance, but they may be removed with a scalpel without affecting the continuity of these membranes. Again, where these membranes are free and unconnected on both surfaces, as in some parts of the tunica arachnoidea, there is no appearance of red blood vessels. In hernial protrusions, where there is a considerable prolapse of peritoneum, the blood vessels which are found abundantly about the neck of the sac do not fol- low the course of the protrusion. Unquestionably some commu- nication exists between the arterial system and the serous mem- branes, as proved by exhalation and morbid phenomena, but the mode is not well ascertained. In common hernia and in dropsy, the serous membranes be- come more thick: from my dissections I am inclined to think, that this change is not so great as is generally allowed; for most fre- quently, by a careful removal of the exterior cellular substance, they have been restored to their primitive condition. In other cases, as in large umbilical herniae, they are so much attenuated as to be found with difficulty. The power of extension which these membranes possess, is strikingly marked in dropsical effusions, in the development of tu- mours, and in pregnancy; but much of this apparent quality is derived from their mode of attachment to adjacent parts, where- by they are drawn from one surface to cover another. This hap- Vol. II.—4 22 ORGANS OF DIGESTION. pens daily where the peritoneum is drawn from the lower part of the abdomen to cover the bladder in the distentions of the lat- ter ; in pregnancy, where it is drawn upon the growing uterus from all the neighbouring parts; and in the distentions of the sto- mach by food or flatus, where it is drawn up from the omenta. The serous membranes have also a power of contraction equal to that of their extension; but it should not be confounded with that condition where they are simply restored by the connecting cel- lular substance, to the surfaces to which they originally belonged. The sensibility of the serous membranes, from the want of nerves in them, is extremely obscure in a natural state, and only affords an imperfect sensation of touch. This is proved by the impunity with which they may be irritated on living animals. But, when the condition of inflammation is once established, they feel the most acute and distressing pain. Though they resist most frequently, and for a long time, disease in adjacent parts, yet it not unfrequently is extended to them at last. In such cases, it is generally a local instead of a universal affection, which is communicated to them: Thus, in the cancer and scirrhus of the uterus; in disease of the spleen, and so on; the portion of pe- ritoneum nearest the affected organ manifests the marks of the disease by preternatural adhesions and by disorganization, with- out the whole membrane being involved. As the serous system consists in many species of sacs, so each of them has some peculiarity of organization, of attachment, and of vital properties, which is stated elsewhere in the account of the species themselves. CHAPTER III. OF THE CHYLOPOIETIC VISCERA. SECT. I.--OF THE STOMACH. The Stomach {Ventriculus, Stomachus) is a hollow viscus situated in the epigastric region, intended to receive at one end THE STOMACH. 23 alimentary matters from the oesophagus, and to transmit them, at its other extremity, after digestion, into the intestinal tube, where the nutritious part of the food is absorbed into the circu- lation. It is a sort of conoidal sac, curved considerably up- wards, and presents two Faces, two Orifices, two Curvature?, and two Extremities. The Faces of the stomach are, from their position, named anterior and posterior, or, one presents to the spine and the other towards the linea alba. The flat configuration is rendered more obvious when the organ is empty; for when distended it is rounded, and the anterior face is caused to look forwards and upwards from the resistance of the spine behind. In other respects they do not present any thing worthy of particular at- tention.* The two Orifices of the stomach are named Cardia and Py- lorus. The first is at the left and most superior part, but re- moved to the distance of two inches or more from the left ex- tremity. It is generally considered a smooth uninterrupted continuation of the oesophagus into the stomach, immediately after the oesophagus has passed through the diaphragm into the abdomen. But in a preparation by me,t of this organ, made by drying, and now in the anatomical cabinet, a circular round- ed pad is very perceptible at the cardiac orifice; being elevated two lines or more all around, so that it makes a perfect ring of from eight to twelve lines broad at its base. This pad seems to be composed of a cellular substance, which is almost per* fectly white, elastic, and consists of the finest filaments, resem- bling carded cotton: it is placed between the lining membrane of the cardiac orifice and the adjoining coat. The pylorus, when viewed externally, seems like a smooth continuation of the stomach into the duodenum; but when felt, there is a mani- fest thickening of the part, depending upon a structure to be presently explained. It points upwards and to the left side, but is, by the whole thickness of the liver, lower down than the cardia. The two Curvatures are designated the great and small, or * In some cases the posterior face of the stomach is concave to accommodate it to the spine: this is best seen on inflation and drying. f Made December, 1828. 24 ORGANS OF DIGESTION. the upper and the lower. The first, forming the upper margin of the stomach, is bounded at its extremities by the orifices, and is very concave; its curvature is maintained both by a na- tural configuration and by the small omentum. The great cur- vature forms the whole inferior periphery of the organ, extend- ing also from one orifice to the other. When the stomach is flattened, these curvatures form very evident boundaries to the anterior and the posterior faces. The Extremities of this organ are singularly disproportionate in size. That on the left forms the base of the cone, or the large extremity, and projects considerably beyond the cardia towards the spleen. It is a rounded cul-de-sac, or tuberosity, the dimensions of which will, of course, vary according to the state of distention. The right extremity, on tho contrary, is produced by a gradual diminution of the organ from its middle to the duodenum. When the stomach has approached within an inch or two of the latter, it suffers a sort of constriction, which gives to the right end a more cylindrical shape. This part is sometimes called the little cul-de-sac, or the antrum pylori. Where the stomach has been kept empty for some time pre- viously to death, it is found not much larger than an intestine; its variable magnitude, therefore, prevents any very rigid rule of dimension from being applied to it; most commonly, how- ever, we find it between the capaciousness of a pint and a quart measure. It is retained in its situation by its continuity with the oeso- phagus and duodenum; also by the hepatico-gastric, and the gastro-splenic omentum. It is in contact above, at its lesser curvature, with the diaphragm, the left lobe of the liver, and the lobulus spigelii; at its great extremity with the spleen, at its posterior face with the pancreas, and at its greater curvature with the colon and the mesocolon. The stomach is formed by four laminae of a character essen- tially differing from each other: The Peritoneal, the Muscular, the Nervous, and the Mucous. The Peritoneal Coat envelops the stomach completely, and adheres closely, except at the curvatures, where, as has been THE STOMACH. 25 mentioned, a provision is made for the distention of the organ, by the looseness and the separability of the attachment of the two laminae of the omentum minus and majus. An uncovered space will, consequently, be found between the laminae at these places, along which the vessels run that furnish the stomach. The peritoneal coat is very thin, and is attached to the subjacent muscular, by very fine cellular substance, which permits it to be raised from the muscular by a careful dissection. The Muscular Coat is intermediate in thickness to that of the intestines and of the oesophagus, but its fibres are pale, are col- lected into flattened fasciculi, and go in three directions. The most superficial are a continuation of the longitudinal fibres of the oesophagus, and are less numerous and less uniform in their distribution than the circular fibres. The greater part of them form a flattened broad fasciculus, which extends along the lesser curvature of the stomach, from the cardiac to the pyloric ori- fice. A thinner and less distinct fasciculus may be "traced over the great cul-de-sac, and, somewhat indistinctly, along the great- er curvature, and a few others may be seen on the anterior and posterior faces of the stomach. The second Series consists in a lamina of circular fibres distinctly covering the whole surface of the organ. They are not so numerous near the cardia, but become more abundant as they are examined towards the pylo- rus, in the vicinity of which they are multiplied so as to form a lamina of two lines or more in thickness. The circular fibres are parallel with each other, and, when the stomach is much distended, their fasciculi separate so as to leave interstices be- tween them in many places. ' The individual fibres do not sur- round entirely the stomach, but are rather segments of circles. The third and deepest series of fibres may be called oblique, and are arranged into two broad flattened fasciculi, one of which is placed to the left side of the cardia, and is prolonged over the anterior and the posterior faces of the stomach; while the other, being to the right of the same orifice, is extended over the anterior and the posterior faces of the cul-de-sac, where it supplies the want of transverse or circular fibres: they are con- sidered as a continuation of the circular fibres of the oesophagus. The Nervous or Cellular Coat connects the muscular with the mucous. It is formed from a compact, thick, and short cellular 26 ORGANS OF DIGESTION. substance, which contributes much to the general strength of the organ, and serves to conduct the blood vessels and the nerves to the mucous coat. The Mucous or Villous Coat is the most internal, is not quite a line in thickness, and can be readily raised up by dissection. In an undistended state of the stomach it is arranged into a number of wrinkles, which are very irregular in their form, size, and direction, but disappear immediately on distention, or at least leave but very faint traces. It is continuous with the internal membrane of the oesophagus and of the duodenum, but presents a surface differing from either of them, and which is rendered very apparent by floating it in water. The epidermis, which is continued along the internal face of the oesophagus, ceases around the cardiac orifice, and, by a slight maceration, may be raised up and demonstrated to terminate there. This membrane or coat, the office of which is to secrete the gastric juice for the digestion of articles of food, presents a sur- face that resembles very much common velvet, from whence the term villous was applied to it. It is common to find it, if examined a short time after death, having, particularly along the smaller curvature and at the great end, a pink and some- times a deeper colour, produced by an accumulation of blood in its veins. The texture of this membrane is soft, loose, and easily lace- rated. When floated in water and examined with a magnify- ing glass, it is found to have a superficial honey-comb arrange- ment, and to be studded with a multitude of small follicles or orifices. In the vicinity of the cardiac and of the pyloric ori- fices, the same arrangement is more obvious, and conducts to some small muciparous glands, which are more or less apparent, and called the glands of Brunner. At the junction of the' lesser extremity of the stomach with the duodenum, the internal membrane is thrown into a circular duplicature constituting the pyloric valve, and abridging the size of the orifice. It is seen most favourably in the distended and dried state, and then presents a sort of septum not unlike the form of the iris. Around, the external periphery of this ring, the circular muscular fibres have a sudden augmentation of number, which gives them, when viewed from the duodenum, INTESTINAL CANAL. 27 the appearance of a distinct circular muscle, occasionally called the muscle of the pylorus, but it does not exist in a state so se- parate as this name indicates. The opening of the valve is ge- nerally circular, but sometimes ovoidal, and it is sometimes to one side. It is very common to find the stomach divided as it were into two compartments, by a contraction of its middle, resembling that of an hour glass. It is said that this occurs habitually during digestion; in my personal observations, however, I have seen the stomach more frequently in this state when it contained nothing, not even air, than when articles of aliment were in it. The stomach is extremely vascular. Its arteries, being branches of the Coeliac, are the Gastric, the Right, and the Left Gastro-Epiploic, and the Vasa Brevia. The first goes along its lesser curvature, the second and the third along its greater cur- vature, and the last, from four to six in number, go to its great cul-de-sac. They all approach it between the laminae of its omenta, and undergo many divisions and subdivisions in the cellular coat; they at length terminate by forming a very fine and delicate vascular arrangement in the substance of the mu- cous membrane, and by being successfully injected give to the latter a thorough tinge of red. The veins follow the course of the arteries, and like them have frequent anastomoses, but are larger; they terminate either directly or indirectly in the trunk of the Vena Portarum. The nerves of the stomach come from the Par Vagum, and from the semi-lunar ganglion of the Sym- pathetic. Its lymphatics arise from both the external and the internal surfaces, and their trunks having to pass first of all to the lymphatic glands, situated along the curvatures, afterwards empty into the thoracic duct. SECT. II.--OF THE INTESTINAL CANAL. * The Intestinal Canal is from thirty to thirty-five feet in length, and extends from the pylorus to the anus. Owing principally to a well marked difference in magnitude, it is divided by ana- tomists into the Small and into the Large intestine. 28 ORGANS OF DIGESTION. Of the Small Intestine. The Small Intestine (Intesiinum Tenue) commences at the pylorus; and terminates in the right iliac region by a lateral aperture into the large intestine. It is four-fifths of the length of the whole canal, and measures from twenty-four to twenty- eight feet* When moderately distended its diameter is about one inch. It retains from one end to the other an uninterrupt- ed cylindrical shape, with the exception that if the two ends be compared, the upper will be found larger than what is stated as the medium measurement, and the lower smaller; or, in other words, the intestine decreases- successively from above down- wards, and, as a whole, is slightly conoidal, though this diminu- tion is so gradual that it is not perceptible at any given point. The Small Intestine, like the stomach, consists of four dis- tinct coats, the peritoneal, the muscular, the cellular, and the mucous. The Peritoneal Coat is complete, and forms the external sur- face. It is continued afterwards in two laminae from the intes- tine to the lumbar vertebrae, thereby constituting the Mesente- ry. The two laminae, where they depart from the intestine, are loosely connected with each other, for the purpose of allowing room for the dilatation of the intestine, on the same principle which is exemplified in regard to the stomach. The Muscular Coat is next to the peritoneal. Its fibres are pale, and form a lamina not so thick as common writing paper. The superficial ones are longitudinal, not very distinct, and too much separated to form a perfect coat. . The others all run in a circular direction, approaching to the spiral, and are sufficiently numerous to form a perfect coat; none of them perform a com- plete circuit of the intestine, but are rather segments of circles. • This is th* generally received opinion of anatomists: it would appear, how- ever, to be applicable only when the intestine is left attached to the mesentery; for if it be cut off and straightened, it will measure thirty-four feet, which, added to eight feet of large intestine treated in the same way, will amount in all to forty- two feet. If to the estimate of this length we add what is lost by the doublings of the mucous coat, the entire length of surface must amount to nearly sixty feet, at least, in many subjects. INTESTINAL CANAL. 29 This coat is united to the peritoneal by a thin scattered cellular substance. The Cellular Coat of the small intestine, also called the ner- vous, like that of the stomach, is only a lamina of condensed cellular substance, which serves as a medium of connexion be- tween the muscular and the mucous coat; and also conducts to the latter the blood vessels, nerves, and lacteals. The Mucous Coat is the most internal, and when it has been cleaned by maceration, exhibits an opaque pearly colour. It is remarkable for having its extent very considerably augmented beyond that of the other coats; by being thrown into a great number of permanent folds, or duplicatures, which lie one upon another successively, like the shingles upon the roof of a house. These duplicatures are the Valvulae Conniventes, and are for the most part about three lines in breadth. They are either placed in the direction of the circumference of the intestine, or are very slightly oblique; generally they go all around, but some of them are segments of circles, and by being arranged successively, their ends pass one another, or are connected by slight elevations. They are more numerous and broad in the upper than in the lower half of the intestinum tenue, and are evidently intended to retard the progress downwards of alimen- tary matter, and to increase the surface for absorption and for exhalation. The mucous membrane, on the side which it presents to the cavity of the intestine, is furnished with a great number of de- licate cylindrical projections, resembling the down on the skin of an unripe peach, and called Villi, from whence the term vil- lous has also been applied to this coat. These villi are to be found in abundance everywhere; but in the upper half of the intestinum tenue they are so numerous as to stud its whole sur- face, and to be in contact with each other. They are from one- fourth of, to a line in length; and some of them, when examined with a microscope, appear flattened and fungiform. According to the estimate of Meckel,* where they are thickest, every square inch of intestine furnishes about four thousand of them, and by extending this computation, with a proper allowance for * Manuel D'Anat. Vol. II.—5 30 ORGANS OF DIGESTION. diminished numbers below, their aggregate amount is about one million. Each Villus is composed of an artery, a vein, and a lympha- tic; all united by cellular substance. From the extreme vascu- larity of the mucous membrane, the blood vessels readily re- ceive a fine injection and thereby become evident, forming a very delicate vascular net-work in each of the villi. It is ascer- tained that the lymphatic opens on its surface, but whether by one or more orifices is yet unsettled. According to the cele- brated Lieberkuhn, there is commonly but one orifice at the end of each villus, and very rarely two: this assertion he considered himself as having established by passing a current of air through the villus till it was dried, and then slitting it open. Hewson, Cruikshank, and W. Hunter, on the contrary, are said to have found many more, amounting even to twenty, on such villi as were gorged with chyle. The subject has been fruitful with controversy to anatomists, and ranks many distinguished cham- pions on each side; but as from the minuteness of the parts un- der discussion and the consequent necessity of microscopical observations, it is exposed to much fallacy and illusion; it can- not be satisfactorily settled, though the general analogies of papillary structure are in favour of the latter authorities. The more important fact, however, is ascertained by the admission of all, that there is a branch of the lymphatic system in every villus; which has, for its function, the absorption of chyle from the cavity of the intestine. An abundance of Mucous Glands is found deposited in the cellular coat of the small intestine, between the muscular and the villous; the ducts of which open upon the internal surface of the latter, in the interstices of the villi, and from their smallness require the intestine to be floated in water, and examined with a magnifying glass, before they can be recognised. In order to see the glands themselves, the intestine must be cleaned by soaking it in water; it is then to be slit open longitudinally, and held between the eye and the light, in which case the glands appear like little points or spots in the thickness of the intestine. They are more abundant in the beginning of the latter, decrease about its middle, and increase again towards its termination. INTESTINAL CANAL. 31 Their structure is very simple, as they consist in a congeries of blood vessels, terminating in short canals secreting mucus.* Some of these glands are microscopical, and are called cryptae; others are to be found from that size to a line in diameter, and flattened. They are either alone or in clusters. The former (Glandulos SoUtarice, Brunneri) are found principally about the duodenum and the neighbouring portion of the small intestine. The latter (Glandules Agminatce, Peyeri) exist principally in the lower part of the small intestine, and are collected into clusters varying from a few lines to three or four inches in length, but seldom more than from eight to twelve lines broad. They are for the most part in elliptical patches, which in a healthy state may be recognised rather by a slight discoloration, than by the more ordinary means, and are generally situated some distance from the mesentery. There are about thirty of these clusters, of all sizes, in the ileum, and they are placed nearer and nearer to one another, in approaching the ileo-colic junction. All of these muciparous glands are too much flattened to project sensibly into the cavity of the intestine, and when they do, there is reason to believe that they are in a diseased state, at least in the adult: for the most part, in children, the glands of Brunner may be seen in the whole length of the small intestine. The mucous coat of the small intestine is extremely vascular. The Small Intestine, though an uninterrupted tube from one end to the other, is divided by anatomists into Duodenum, Jeju- num, and Ileum. There is some reason for the first name, but the two latter may be very conveniently blended, as has been done by some, under the term Mesenteric Portion of the intes- tinal canal. The Duodenum, named from its being about twelve inches, or twelve fingers' breadth in length, is nearest to the stomach; or, in other words, is the commencement of the canal. It is larger than either of the others, and is, moreover, susceptible of great dilatation, whence it has also been called Ventriculus Succentu- * Soemmering, de Corp. Hum. Fabrics. 32 ORGANS OF DIGESTION. natus. Its direction is much varied: beginning at the pylorus, it first of all passes upwards and to the right side, till it reaches the neck of the gall-bladder; it then turns downwards, so as to form a right angle with itself, and descends in front of the right kidney to the third lumbar vertebra, being there placed behind the superior lamina of the transverse mesocolon. It then forms a round elbow, crosses the spine obliquely, under the junction of the mesentery and mesocolon, in ascending from right to left; and making its appearance to the left of the second lumbar ver- tebra, is there continued into the mesenteric portion of intestine. The beginning of the duodenum is moveable, and has a pe- ritoneal coat continued from the lesser omentum; the descend- ing and the transverse portions have no proper peritoneal coat, but are only loosely fixed between the laminae of the mesocolon; the termination is both moveable and has a peritoneal covering, from being at the commencement of the mesentery. From the course assigned to the duodenum, it is evident that it forms the segment of a circle, the concavity of which looks to the left side. This concavity is occupied by the head of the pancreas. The transverse portion crosses the spine below the latter, and is separated from it by the superior mesenteric artery and by the vena portarum: behind it are the crura of the dia- phragm, the ascending cava, and the aorta. The organization of the duodenum is the same with that of other portions of the intestinum tenue. Its peculiarities consist only in a partial deficiency of peritoneal coat, and in its aug- mented size. Its internal or mucous coat is very much tinged with bile, abounds in valvulae conniventes, and about four inches from the pylorus is marked by a small tubercle or elevation, in- dicative of the orifice of the biliary and of the pancreatic ducts. The Glands of Brunner are very conspicuous in this intestine, and are so numerous near the pyloric orifice, as to form with some a perfect layer. The Jejunum and Ileum form the remaining length of the small intestine, and have no external marks of difference from each other. They are strung along the mesentery, and, in con- sequence of their great length, are thrown into folds or^ convolu- tions, which give to them a complicated appearance. There is, however, no difficulty in tracing them regularly from one end to INTESTINAL CANAL. 33 the other. They occupy the umbilical, the hypogastric, and a part of the iliac regions, and are surrounded by the circuit of the colon. The upper two-fifths is the jejunum, and the lower three-fifths, the ileum. This distinction, originally introduced by Galen,* from a supposition that the jejunum was more fre- quently found empty than any other intestine, has no rigid ana- tomical support. The only difference between the two is, that the valvulae conniventes, abundant in the whole length of the je- junum, become less so at the upper part of the ileum, and finally disappear entirely towards its lower extremity. The distinction has, therefore, been rejected by the most approved modern au- thorities, such as Haller, Soemmering, Meckel, and so on. It sometimes happens, that the intestinum tenue has one or more blind pouches appended to its sides and opening into its cavity. « The small intestine is supplied with blood from the superior mesenteric artery; its nerves come from the sympathetic. The Mesentery (Mesenterium) is a process of peritoneum which serves, as mentioned, to connect the intestinum tenue to the posterior parietes of the abdomen, and extends its connex- ions from the left side of the second lumbar vertebra to the right iliac fossa. This attachment, called the root, is about six inches in length; whereas its lower circumference, which encloses the small intestine by giving it a peritoneal coat, is, of course, the whole length of the bowel, (duodenum excepted,) and, conse- quently, from twenty-three to twenty-seven feet in length. This expansion becomes intelligible the moment that the arrangement of the part is inspected, and is somewhat after the manner of a ruffle, except that it is not puckered at the root. The two laminae of peritoneum which form the mesentery, contain between them the superior mesenteric artery, and the corresponding portion of the superior mesenteric vein; an abun- dance of lymphatic or lacteal glands and vessels; ramifications from the solar plexus of the sympathetic nerve; and a considera- ble quantity of cellular and of adipose tissue. The superior la- mina is continued directly into the mesocolon, and at the place of junction the transverse part of the duodenum is very percep- tible beneath. The lower lamina descends along the posterior • Portal, Anat. Med. 34 ORGANS OF DIGESTION. parietes of* the abdomen, concealing the large blood vessels there and the ureters. Of the Large Intestine. The Large Intestine (Intestinum Crassum) receives the effete matter from the small, and is supposed also to have some pecu- liar secretion of fcecal matter from the internal surface. It ex- ceeds much in its diameter the small intestine, and differs also from it in not being by any means so regularly cylindrical. It commences at the inferior end of the small intestine, and termi- nates at the anus, describing in this course, as mentioned, a cir- cle which surrounds two-thirds of the abdomen, and embraces the intestinum tenue. Like the latter, though only a continuous tube, it is divided into three parts; the commencement of it, which is below the insertion of the ileum, and about two inches in length, is the Ccecum, or Caput Coli; the remaining portion, which occupies almost its whole length, is called the Colon, until it reaches the pelvis, when the name is converted into Rectum. The Mesocolon is a reflection or duplication of peritoneum, that fixes the large intestine to the posterior parietes of the abdo- men. This duplicature is not of a breadth so uniform as the mesentery, but allows to the middle of the large intestine very considerable motion, up and down, according to the distention of the stomach, while the lateral portions are very much confined. For example, in the right iliac fossa the mesocolon is so short that the posterior surface of the gut is in contact with the iliac fascia, and adheres to it by loose cellular substance; in the right and left lumbar regions the bowel is immoveably fixed in front of the kidneys, but in the space between these two points, that is to say, where the bowel traverses the hypochondriac and the epigastric or umbilical regions, the peritoneal attachment, here called, from its situation, the transverse mesocolon, is so long and loose that it forms a complete and moveable septum between the small intestine and the stomach. In the left iliac region, again, the large intestine, after having been bound down to the left lumbar, is suddenly loosened by an increased breadth of the INTESTINAL CANAL. 35 mesocolon, which permits it to form a large convolution, called its sigmoid flexure. The mesocolon is then continued into the pelvis in front of the sacrum, first of all a little to the left of the middle line of the latter, and, as it descends, it gets directly in front of the middle^ line. The portion of it in the pelvis is called mesorectum, after the gut which it serves to attach. The composition of the mesocolon is precisely the same with that of the mesentery, though it be not so thick: it, therefore, consists in two laminae of peritoneum, which contain between them some adipose and cellular matter, along with the arteries, the veins, the nerves, and the lymphatic vessels and glands be- longing to the large intestine. When the large intestine is inflated, it is rendered very ob- vious that it decreases in size from its commencement to the lower part of the sigmoid flexure, it then increases again in size just above the anus. Its surface is arranged into three series or longitudinal rows of projections, separated by transverse depres- sions, the whole corresponding with an internal cellular arrange- ment, by the latter surface being the reverse of the former. Its coats, like the small intestine, are four in number; the pe- ritoneal, the muscular, the cellular, and the mucous. The Peritoneal Coat prevails in its whole extent, with the exception of the lower part of the rectum: on the ascending and the descending portions of the colon, however, where the latter comes in contact with the parietes of the abdomen, the perito- neum does not invest it entirely; but the transverse portion or the arch, as it is called, and the sigmoid flexure, are completely surrounded. The surface of this intestine is studded with small projections of various lengths, called Appendices Epiploicae, which are small duplicatures of peritoneum containing fat. The Muscular Coat is thin, like that of the small intestine, and consists in two orders of fibres, the longitudinal, and the trans- verse or circular. The longitudinal fibres have the peculiarity of being collected into three equidistant, flattened fasciculi or bands, of about half 36 ORGANS OF DIGESTION. an inch in breadth, which begin by a common point at the ex- tremity of the coecum, and extend to the upper end of the rec- tum. One of them is along the line of junction with the meso- colon, another anterior, and the third inferior. These fibres, being shorter than the other coats of the gut, have the effect of puckering them into the internal cellular condition alluded to; for, when they are cut through, the intestine is much elongated, and its cells disappear. It occasionally happens that the longi- tudinal fibres, instead of being confined to the bands alluded to, exist in considerable quantity over the intermediate spaces; in this case the cellular arrangement is restricted, and in some in- stances entirely dispensed with; of the latter, an example is in the Anatomical Museum. The circular muscular fibres form a thin semi-transparent la- mina beneath the last, and do not present any peculiarity of in- terest. The Cellular Coat is a condensed thin lamina of cellular sub- stance, serving to connect the muscular with the mucous coat, and to conduct the blood vessels and nerves to their terminations on the latter. The Mucous Coat lines smoothly the internal face of the cel- lular, and has no doublings or folds, exclusively in it, like the valvulae conniventes of the small intestine.* The transverse projections which it makes between the longitudinal bands, into the cavity of the gut, and which separate the cells of the large intestine from each other, are not mere duplicatures of it alone, but are also constituted by the other coats. Near its commencement this coat has the fungous appearance of the stomach, but about the sigmoid flexure it has a plane, smooth, and, to a degree, a polished surface. It has but few villi, such as exist in the small intestine; indeed, by some anato- mists it is denied that it has any. Its muciparous glands and follicles are numerous, and the former, when somewhat enlarged, project; they are unusually conspicuous about the sigmoid flexure, and in the rectum. Its lacteals are not abundant. • This may be considered as the general rule: if it be examined, however, in its whole length, here and there narrow ones may be found.' INTESTINAL CANAL. 37 The mucous coat of the large intestine is very vascular, but not so much so as that of the small intestine. Each division of the large intestine has some peculiari- ties of structure and connexion; which may now be attend- ed to. The Coecum, or Caput Coli, is generally from an inch and a * half to "two inches long, has a rounded termination below and somewhat to the left, from which proceeds an intestinal pro- cess, the Appendicula Vermiformis. The latter is from three to four inches long, is cylindrical, has a diameter of two or three lines, and consists also of the same number of coats, having the same structure with other portions of the intestinal canal; its base is the point from which the three longitudinal bands start. It is attached by a narrow duplicature of peritoneum, a process of the mesentery, which permits it to float loosely in the abdo- men. It seldom contains faeces, but it is kept distended by flatus. The coecum, as mentioned, is for the most part confined to the right iliac fossa, but we very frequently see it with a length of peritoneal attachment permitting it to descend for a short distance into the pelvis. The Ileo-colic Valve (Valvula Bauhini) is formed at the junction of the ileum with the caput coli. This valve, destined to prevent the return of faecal matter from the large into the small intestine, consists in a transverse elliptical opening, or slit, whose lips become approximated in the distentions of the colon. The ileum runs into the left wall of the large intestine, and continues its cellular and mucous coats into the correspond- ing coats of the latter. The circular muscular fibres of the large intestine separate to a certain degree to permit this introduction, but their farther separation is restrained at each commissure or corner of the lips, by a blending of the structure, aided by a few ligamentous fibres, designated as the retinacula of Bauhin or of Morgagni; which, however, are frequently not very dis- tinct. This separation is also restrained by the two longitudinal bands between which they are inserted, one of which is at the posterior commissure and the other only a short distance off Vol. II.—6 38 ORGANS OF DIGESTION. from the anterior. The lips themselves, formed principally by the" mucous membrane, approach one another after the man- ner of the ship dock or canal gate; the superior is somewhat broader than the inferior. Their power, as well as their existence depend entirely on the tension which is kept up by the natural connexions of the parts; for a very slight dissection causes them to become almost effaced, and instead of forming an elliptical transverse opening, to be converted into a round patulous one. The Colon, properly speaking, has some regional distinctions which are serviceable to accurate description. The right lumbar colon, which is bordered in front by the small intestine, and behind, by the right kidney, extends from the ileo-colic valve, to the margin of the false ribs of the corresponding side. The transverse colon, bordered above by the stomach, and below by the small intestine, goes from one hypochondriac region to the other. It is generally found more distended than the other portions. The left lumbar colon descends from the hypo- chondriac region of the left side to the sigmoid flexure, being bordered behind by the left kidney, and in front by the small intestine. The sigmoid flexure, placed in the left iliac fossa, forms a convolution, but is very indifferently described by the term applied to it. It is occasionally very long and loose, and terminates at the left sacro-iliac symphysis. It is not unfre- quently found destitute of the partitions which prevail in other parts. The Rectum begins at the left sacro-iliac symphysis, and passes obliquely downwards to the centre of the sacrum, thence in front of the middle line of the sacrum, and of the coccyx, to terminate at the point of the latter. It is not regularly cylin- drical, but, just above the anus, is dilated into a wide pouch, flattened from before backwards by the pressure of the bladder, and very distinguishable upon the introduction of the finger, for it is but seldom in a contracted state. It, of course, has a flexure by adapting itself to the concavity of the sacrum, and is bound- ed in front by the bladder, the prostate gland and the vesiculae seminales of the male, and by the vagina and the uterus of the female. INTESTINAL CANAL. 39 The peritoneum covers only the superior two-thirds of the rectum, and attaches it by the short duplicature, called the me- sorectum, to the front of the sacrum. A small pouch, passing down between the vesiculae seminales almost to the base of the prostate, is formed, as mentioned previous^, by the peritoneum in its course from the rectum to the bladder. The muscular coat of the rectum has a thickness and redness surpassing much that of any other intestine, and is divided very clearly into two laminae, the external of which consists in lon- gitudinal and the internal in circular fibres. The external forms in itself a complete coat continuous with the longitudinal bands of the colon, but is much increased by additional fibres. The circular fibres also form a complete coat, and, just below the pouch of the rectum, are multiplied so much for eight or ten lines as to be a perfect internal sphincter muscle, bearing a strong analogy with the pyloric muscle of the stomach. At the anus, an arrangement of the muscular coat prevails, which, as far as I know, has not been heretofore attended to by anato- mists. The longitudinal fibres, having got to the lower margin of the internal sphincter, turn under this margin between it and the external sphincter, and then ascend upwards for an inch or two in contact with the mucous coat, into which they are final- ly inserted by fasciculi which form the base of the columns of the rectum; many of the fibres, however, terminate also between the fasciculi of the circular fibres. This connexion must have obviously much influence in the protrusions of the mucous coat, which sometimes take place. The mucous coat of the rectum is thick, red, and fungous, j and abounds in mucous lacunae and glands. It is smoothly laid above, but below it is thrown into superficial longitudinal folds called columns. At the lower ends of the wrinkles, between the columns, are small pouches of from two to four lines in depth, the orifices of which point upwards; they are occasional- ly the seat of disease, and produce, when enlarged, a painful itching. An original observation of Dr. Physick, on the nature of this affection, and the remedy for which consists in slitting them open or removing them, induced me to look for the ordi- nary natural structure, which I have, found to be as now de- 40 ORGANS OF DIGESTION. scribed.* The wrinkling of the anus is from the influence of the external sphincter ani muscle. In some subjects, large cells are formed in the cavity of the rectum by transverse -doublings of the mucous coat only, resembling the valvulae con- niventes of the small intestine; this, however, is not the most frequent arrangement, though deserving of notice. The large intestine is supplied with blood from a part of the superior mesenteric, from the whole of the inferior mesenteric, and from the internal pudic artery. Its veins empty into the vena portarum. Its nerves are derived from the solar and the hypogastric plexus of the sympathetic. SECT. III.--ON THE MINUTE ANATOMY OF THE MUCOUS COAT OF THE ALIMENTARY CANAL. In the preceding account of the mucous coat of the stomach and bowels, I have admitted the most generally received opi- nions, as it is in every way proper for medical men to be aware of them. Having been, however, much occupied, a short time ago, in ascertaining the pathology of Asiatic cholera by dissec- tions, the observations which I then made upon the healthy and diseased structure have induced me to modify very much my former views, as will be seen in the following pages.f The mucous coat of the alimentary canal, in a healthy state, and successfully injected, appears to consist almost entirely of a cribriform intertexture of veins; these veins being commonly empty at death present themselves as a soft spongy structure, which gives rise to the ordinary description of its sensible con- dition as a velvety layer. The most minute injection of the ar- teries scarcely makes itself visible among these veins when they are properly injected, a straggling branch only here and there exhibiting itself. The arborescence of the arteries is confined to the level beneath the venous intertexture, and is there deve- * See an interesting paper on Fistula in ano, by M. Ribes, in Mem. de la So- ciety D'EmuIation, vol. 9, 1826; where the influence of this structure is al- luded to.—It appears that Glisson and Ruysch first described them as valves. Also, an elaborate and excellent article by Dr. Reynell Coates, in the Cyclopaedia of Pract. Med. and Surgery, Philada. 1835, under the term anus. X Amer. Journ. Med. Sciences for 1835. ANATOMY OF THE MUCOUS COAT. 41 loped to an extreme degree of minuteness, being intermixed with corresponding venous ramuscles, generally larger and more numerous than the arteries themselves. The fine venous trunks of this deeper layer have their originating extremities bent ver- tically towards the cavity of the gut, and by that means receive the blood of the first venous intertexture or layer, as the petrous sinuses join the cavernous, or the veins of the penis arise from its spongy structure. The meshes of the first venous intertex- ture are exceedingly minute, and vary in a characteristic man- ner in the stomach, small intestines and colon. This intertex- ture is very different in its looks from a common vascular anas- tomosis, and produces in the colon an appearance resembling a plate of metal pierced with round holes closely bordering upon each other; these holes constitute, in fact, follicles or gaping ori- fices, the edges of which are rounded off, and,, their depth is that of the thickness of the venous anastomosis being bounded be- low by the arterial venous layer, and by the cellular coat of the part. Nothing short of an entirely successful injection will exhibit this venous anastomosis as described; and it may be seen either by injecting a vein or an artery, provided the injection passes from the artery into the veins, but the latter process is the least desirable, because we lose the benefit of a distinction of colour between the two sets of vessels. Ordinary modes of examination give no evidence of the exis- tence in the alimentary canal, from the cardiac orifice of the stomach to near the anus, of an epidermis; on the contrary, they rather lead to a belief of its being absent, in consequence of the softness, tenuity, and transparency of the mucous membrane; but that it is really present, may be proved by the following process:—Tear off the peritoneal coat—invert the part and in- flate it to an emphysematous condition; the epidermis will then be raised as a very thin pellicle, and may be dried in that state; but as this pellicle retains the air, we hence infer that it lines the follicles, and is uninterrupted by any perforations. This epidermis, if the part be previously injected perfectly, shows dots of injecting matter, but no arborescence if it be inflated up from the veins. In so doing the villi disappear, are in fact un- folded. The villi cannot be seen to any advantage except they be 42 ORGANS OF DIGESTION. erected by an injection, in which case those of the upper part of the small intestines are found to run into each other very much like the convolutions of the cerebrum, and to press upon each other's sides in the same way. Some of them, however, are merely semi-oval plates, the transverse diameter of which exceeds the length. At the lower end of the small intestine they become simply conical projections, somewhat curved, with the edges bent in, and they retain this mechanism until they entirely disappear near the ileo-colic valve. In the whole length of intestine there is, however, every variety of shape, from oblong curved and serpentine ridges, to the flattened cone standing on its base; the first condition changing gradually to the last in the descent of the bowel. Conformably to this de- finition of villi, none exist either in the stomach or colon, for there we have only the venous mesh. The villi of the jejunum are about the thirtieth of an inch high, and those of the ileum about one-sixtieth. The superficial venous layer has great regularity in the ileum, and the conical villi stand out beautifully from its partitions, or in equivalent language, from the divisions of the follicles. In the upper part of the small intestine the follicles are in equal number to what they are in the ileum; the regularity of their arrangement being interrupted by the long serpentine and oval villi; but invariably the same venous intertexture exists and forms in both the chief bulk of the villi, by passing into them. In the stomach the follicles vary much in size, and there is an arrangement whereby many of the smaller ones are seen to open into the larger: on an average about two hundred and twenty-five are found upon every eighth of an inch square, which would give of course to an inch square sixty-four times that amount, or fourteen thousand four hundred follicles; and conceding*"the whole stomach to present an area of ninety inches, which is probably below the mark when this organ is moderately distended,as exhibited in the preparation upon which this calculation is founded, the entire number of follicles is one million tioo hundred and ninety-six thousand. The great uniformity of size of these follicles in the colon, and its even surface, enable us to count them with more cer- tainty, and they appear to exist at the beginning of this gut at ANATOMY OF THE MUCOUS COAT. 43 the rate of about four hundred for every eighth of an inch square, but in the sigmoid flexure at the rate of about two hun- dred to the same area; they become, in fact, both smaller and less numerous in descending towards the anus. Admitting the entire area of the colon to be five hundred inches, and nineteen thousand two hundred of these follicles, on an average, to exist on every inch square, the aggregate number will be nine mil- lions six hundred and twenty thousand. Again, estimating the whole area of the mucous coat of the small intestines at fourteen hundred and forty inches, and al- lowing for interruptions occasioned by villi, about twenty-five thousand follicles are found upon every square inch, and the two numbers muftiplied, produce thirty-six millions. The entire number of follicles in the whole alimentary canal is, by the preceding estimates, forty-six millions nine hundred thousand, and upwards. I am very far from pretending to have counted them all, but have made an approximation to the actual number by observing sections of different portions of the same subject, and verifying the observations upon other subjects. The external surface of the cutis vera presents, as it were, in outline the same arrangement; the venous reticular intertexture appearing broader, not quite so perfect, and more shallow, and forming the papillae; but as additional experiments are wanting, it ma}^ be passed over with this transient notice; perhaps, indeed, a more skilful hand in adopting the hint may perfect the details. In the stomach, the largest of these follicles is about -g^th of an inch in diameter, and the smallest about T-|oth. In the co- lon the largest is about alsth of an inch in diameter, and the smallest about -j^oth.v In the small intestines their size varies in about the same ratio as in the colon, but they are much more irregular in shape, being scattered more in grodpPin conse- quence of the villi intervening: some of them penetrate oblique- ly towards the foundations of the villi; hence, when examined from the exterior, their distribution is more regular, and they are seen lodged in the cellular coat of the gut. I have endeavoured to keep the estimate of the number of follicles below what other calculators would make it upon an observation of my preparations, and a fair measurement of the 44 ORGANS OF DIGESTION. area of the alimentary canal, lest the number may seem exces- sive and incredible; I have therefore the most reasonable as- surance of being within bounds on that point. I may now ask their use; is it to secrete or absorb? If they are simply se- cernents of mucus, the number, one would think, much greater than so limited a secretion requires—moreover, why is it that they become smaller and less numerous towards the lower end of the large intestine, where greater lubrication is required for hardened faeces; in addition, are not the glands of Brunner, (so- lit arise,) and of Peyer, (agminatse,) amply sufficient to furnish the required mucus? Again, after most sedulous observations upon the villi of all kinds, finely erected by my injections, and placed under most accurate, simple, and compound microscopes, I find invariably a polished reflecting surface, uninterrupted by foramina, either at their ends or sides, while many of these fol- licles are found passing obliquely into their bases. An excel- lent Woollaston's doublet, which makes the villi of the ileum appear an inch long, exhibits them with a polished translucent surface, without foramina, except where a villus from accident has been broken, a contingency readily recognised by one in the habit of viewing them. Finally, if the lacteal foramina of Lieberkuhn and others, do exist in fact, why is it that the raising of the intestinal epidermis by inflation does not exhibit these foramina by the air escaping through them, but on the contrary, admits of a dried preparation in that slate, the villi being completely effaced. In these and other microscopical observations, I have been much assisted by my young friend, Dr. Paul Beck Goddard, who has acquired an accuracy and skill in such matters deserving of confidence. Taking into consideration these several objections to the theo- ry of the foITicles being secreting orifices, it appears to me that a better idea of their use is called for, which suggestion is sub- mitted to the profession, with the hope that a more capable per- son will remove the difficulty by additional confirmation of pre- ceding theories, or by the invention of a new one: for my own part, I am much inclined to adopt the opinion of their absorb- ing faculties. It is generally conceded that the erection and pre- hension of the Fallopian tube is produced by a vascular tur- ANATOMY OF THE MUCOUS COAT. 45 gescence, in which the veins, from their number, must execute an important part; in like manner as these follicles are formed in the midst of veins, their orifices only become erect and pa- tulous by the distention of those veins, and cannot be seen, especially in the small intestine, unless an injection has suc- ceeded fully; but the erection of these veins during digestion puts the follicles in a similar condition; there is therefore some ground of inference, that the act of the Fallopian tube in con- veying a germ, and of a follicle in conveying into the thick- ness of an intestine congenial matter, may be analogous. Notwithstanding the facility with which I can detect these follicles, I have failed entirely under various means of exami- nation, in finding any orifices to Peyer's glands, in the dried intestine; they appear to be merely small lenticular excavations in its substance, and wherever a cluster of them exists, it dis- turbs the arrangement of the villi, and gives to them a scatter- ing unequal distribution. I would also suggest very respecful- ly to anatomists whether our knowledge in regard to them is sufficiently exact to render farther inquiry useless? for my own part it appears that this subject requires some additional attention. The above view, relative to the structure of mucous membrane, presents at least a degree of novelty, by determining, with some precision, the whole number of the Gastroenteric Follicles of the human body, and how they are in every instance formed by meshes of veins, while the arteries enter only inconsiderably into their composition, to an amount in some measure comparable to the presence of the arteries in other erectile tissues, as the corpus spongiosum and cavernosum penis. In the latter it is familiar to every practised anatomist, that the branches of the arteries are but small, as they terminate in the cells of the penis, which are to be considered as only a modification of the incipient stage of venous trunks. If the corpus spongiosum were in fact spread out into a thin membrane, so as to line a hollow viscus, it would present no very exaggerated representation of what I have de- nominated the superficial venous layer of the alimentry canal; it being also admitted that within the circuit of every anasto- mosis a follicle was formed. Viewed on the preparations of the mucous membrane of the small and large intestines which I have, these follicles appear like puncta lachrymalia disseminated Vol. II.—7 46 ORGANS OF DIGESTION. by thousands over every inch square, and existing so invariably upon every part that, as I have stated, the smallest calculation of their numbers puts them at from forty to fifty millions. It is now to be borne in mind, that it is the whole of this vascular and follicular structure, endowed with the vital actions the most important to life, and presenting in the aggreate an area of about thirteen square feet, the size of a small breakfast table; whose morbid derangements constitute the essential features of cholera. It has been shown in some of my dissections, that this ap- paratus in the progress of cholera is detached entirely from the stomach and colon, in consequence of the excessive actions go- ing on in them. The small intestines also, in some of my pre- parations, exhibit in patches a similar phenomena; but as the entire observation has been presented to me in its true light only since the disappearance of the disease, I have no means of ascertaining the extent to which they suffer in this way. The anatomy of the muciparous system of the alimentary ca- nal unquestionably requires a more exact attention than has been heretofore bostowed upon it, especially so as to distinguish be- tween that part which is really glandular, and the foramina or follicles now under consideration. The following extract will explain the difficulty which still exists in regard to a proper conception of the latter. "The mucous glands, called also follicles or cryptae mucosas, are to the membranes of that name what the sebaceous follicles are to the skin; that is to say, folds of the mucous mftmbrane in form of a cul-de-sac, whose orifices open upon that mem- brane. These follicles have not yet been discovered over the whole surface of the mucous membrane; but here, as with the skin, analogy leads us to admit them. It is not long since they have been discovered in the pituitary membrane, where their existence had been denied. Be this as it may, we shall use the same observation upon these glands that was made on the seba- ceous, viz. the impossibility of making an exact dissection of the capillary tissues does not allow us to discover all the forms of animal matter; but wherever a particular humour is found in a tis- sue, we are forced to conclude that this latter is organized in such a manner as to be able to produce it, and when in place of one humour we meet with many, we must acknowledge that the ANATOMY OF THE MUCOUS COAT. 47 tissue is complex. Such is precisely the case with the mucous membrane of the digestive canal, and especially of the stomach, which could have a form of animal matter calculated to furnish digestive juices, although no gland destined to that purpose is discoverable."* This desideratum of positive evidence, instead of the induc- tive, is clearly supplied to M. Broussais by my preparations. In infancy, especially, the glands have a sensible thickness, which enables us to see them, but the smallest of them require the aid of a microscope, and appear to have been described by Galeati.t As the paper is not to be had in any of the public libraries of this city, I can only quote from it on the current authority of anatomical works. In a note to the anatomy of the human body by Sir Charles Bell, article Intestine, it is stated as follows:—"It has been supposed that the fluids excreted from the surface of the intestines were furnished by very minute fo- ramina, (which are visible by particular preparations,) in the interstices of the villi. See the letter of Majpighi to the Royal Society of London on the pores of the stomach, and the paper by M. Galeati in the Bologna Transactions, on the inner coat, which he calls the cribriform coat. The pores, according to Ga- leati, are visible through the whole tract of the canal, and par- ticularly in the great intestines." Meckel designates these as glandular bodies under the name of glandulae mucosae, cryptse minimse. Another order of glands are those of Brunner. J They are readily found in the duodenum at all ages; and particularly well in infancy, as low down as the ileo-colic valve. The third order are the glands of Peyer, discovered in 1677.§ The cele- brated Ruysch appears also to have understood the existence of the follicles of the stomach, and Swammerdam to have had some idea of those of the small intestines,|| and he calls them tubuli glandulosi intestinorum interiores. I may here remark, that the account of the villi of the small intestines given by Hedwig, * Broussais'Physiology. First American edition, p. 419. j- De cornea ventriculi et intestinorum tunica. Comm Bonon. 1745. $ Glandulx intestini duodeni vel pancreas secundarius; discovered in 1715. See Mangetus, Theat. Anat. where this paper is introduced with the plates illus- trative of it. § See also Mangetus for the description from Peyer, with his plates. || Mangetus Theat. Anat. Vol. I. p. 310. 48 ORGANS OF DIGESTION. in his Disquisit. Ampullarum, &c. 1797, and which appears, from its introduction into Caldani'sand M. Jul. Cloquet's Anato- my, to have a classical value, is, judging from my own prepara- tions, too much a work of the imagination, executed under pro- bably some fallacious views of the part itself: a cluster of cylin- drical villi, with holes at the ends, would be an anomaly, for those of the upper part of the intestines are either serpentine folds, as represented in my plates, with branches running into contiguous folds, or semi-oval laminae; while those lower down are of a flattened conical shape, somewhat bent, but in every in- stance they are destitute of what has been termed by Lieberkuhn an ampulla, and to my eye have uniformly polished surfaces, uninterrupted by foramina. Mascagni has also introduced views of a good kind in regard to the follicular structure of the stomach and colon.* But it is to Sir Everard Home, that we are indebted for one of the best papers on the glandular structure of the stomach of different animals.t As, the real muciparous glands have an orifice leading into each by the admission of anatomists, the follicles described commonly by them, are of this description, and are not compa- rable in number to the follicles found in the venous meshes. The highest estimate of the number of the former, as made by M. Lelut, fixes them about forty-two thousand.J In consult- ing many of the distinguished modern authorities on this sub- ject, there seems to be scarcely any trying in the anatomy of the intestinal canal which is presented in a more indefinite way; especially in regard to the small intestines, than the difference between the follicles, properly speaking, and the glands; and none of them, so far as I know, have undertaken to approximate the entire number of the follicles. SECT. IV.--OF THE GENERAL ANATOMY OF THE MUCOUS MEMBRANES. The extent of the mucous coat of the alimentary canal, and the important and varied sympathies which it has with most other parts of the body, render useful some remarks on mem- * Prodromo delta grande anatomia. Tab. xiii. X Phil. Trans. 1807 and 1817: and also his Comparative Anatomy. t Bouillaud, Traite" du Chole'ra, p. 256. GENERAL ANATOMY OF THE MUCOUS MEMBRANES. 49 branes of this kind generally. Mucous Membranes are so called from the nature of the secretion which they furnish: and the term having been first applied to the lining coat of the nose, a similitude of character has caused its extension to that of other organs. The celebrated Bichat, the founder of the science of general anatomy, was the first to adopt fully, and to perceive the value of this classification; since which it has been almost universally received by anatomists. As the skin forms an external covering to the body, so mu- cous membrane lines the internal surface of the hollow viscera. When it is recollected that this membrane forms an internal in- tegument to the whole alimentary canal, from the mouth to the anus; to all of the urinary and genital apparatus; to the whole respiratory system, from the nose down the trachea and through- out the lungs; it will be admitted that its extension exceeds much that of the skin. A mucous membrane presents two surfaces, one of which ad- heres to the contiguous parts, and the other is free by being in- ternal. The adherent surface is attached by a cellular structure somewhat condensed. This cellular structure is principally re- markable for its want of disposition to secrete fat into its inter- stices ; a property of immense importance, as without it, ob- structions would be continually occurring to the destruction of life : it is pervaded by a multitude of fine vessels and nerves, run- ning forward to be spent upon the mucous membrane; and has been unfortunately named nervous coat, by anatomists of high au- thority. The strength of attachment which it furnishes is some- what varied; for example, in the small intestinal canal I have often seen the mucous membrane caught at one end and entirely withdrawn from the other coats, an experiment which alone can give rigid ideas of its greater length, as by it all the duplicatures or valvulae conniventes are stretched out. The experiment suc- ceeds much more certainly by the regular pressure of a column of water between the tunics of the intestine. The mucous mem- brane of most organs is arranged into wrinkles and duplicatures, for the purpose of augmenting its extent. This arrangement pre- vails in the pose, and, as mentioned, in the oesophagus, in the stomach and intestines; to say nothing of many other instances which are noticed in the description of each organ. In some 50 ORGANS OF DIGESTION. examples, they are permanent, and, in others, depend on the state of contraction of an exterior muscular coat. The interior face of the mucous membranes, allowance being made for the inequalities just stated, moreover, presents, when closely viewed, an abundance of more minute depressions and of elevations, causing it to resemble velvet. Some of these depressions are so large as to give it a cellular appearance, as in many parts of the intestinal canal, and the gall-bladder, and have been particularly described by Sir Everard Home. In reo-ard to organization, the mucous membranes are of a soft, spongy consistence; easily yield to mechanical violence; and depend for their strength upon the surrounding cellular coat They are not of a uniform thickness; for example, they are much thinner in the urinary and genital apparatus, than in the alimen- tary canal; they also present some varieties of consistence. They yield very readily to putrefaction, and are quickly reduced to a pulpy state by the action of the mineral acids. Caustics of all kinds act more promptly on them than on the skin, owing to the protection of the latter by a dry epidermis; Bichat states, that in the practice of the Hotel Dieu, this effect is frequently exempli- fied, by the administration of lunar caustic among the common people for the purpose of poisoning. The nitric acid leaving the silver, quickly applies itself to the mucous membrane of the sto- mach, and disorganizing it, forms a whitish eschar, which, if life be preserved long enough, is finally detached in a membranous form. One of the remarkable properties of the mucous surfaces of the stomach and intestines is, that of coagulating milk. According to the experiments of Spallanzani, the gastric juice, in the living state, assists in this change; but it is perfectly well known in do- mestic affairs, that the dried stomach of a calf, where the juices have been completely evaporated, is also productive of it. The observations of the same author led him to conclude, that the peritoneal and the muscular tunics of the stomach are insufficient to produce this effect. The internal surface of all the mucous membranes is furnished with small projecting points or spiculae, called papillae or villi. They are particularly conspicuous and numerous, as mentioned, on the upper surface of the tongue and in the small intestine, GENERAL ANATOMY OF THE MUCOUS MEMBRANES. 5] and bear an analogy of function and organization with the very fine papillae which are seen invariably on the surface of the cutis vera. These papillae are invariably furnished with ner- vous filaments, giving them a high degree of sensibility; and with an abundance of blood vessels. The term papillae has been more exclusively applied to the projections on the surface of the tongue, from their greater size; they are there also more distinctly covered with an epidermis, frequently called epithelium, or peri- glottis. The villi, from their connexion with the process of di- gestion, have been emphatically denominated the roots of ani- mals. According to M. Beclard,* who has examined them upon a plan of his own contrivance well suited to accurate microsco- pal observations, they are presented under a diversity of shapes. Those of the pyloric half of the stomach, and of the duodenum being broader than they are long, are composed of very small thin laminae, having a tufted arrangement. Those of the jeju- num are long and narrow, having more the form commonly assigned to them, while in the lower part of the ileum and in the colon they again become laminated. It should be observed that notwithstanding the assertion of Lewenhoeck, Hewson, Hunter, and others, the fact is still called in question, by two of the most distinguished anatomists of the present time, MM. Beclard and J. F. Meckel, whether the orifices of the lacteals are, under any circumstances, visible on the sur- face of the villi. Admitting that they do not open as stated, the power of interstitial absorption in the mucous membrane will still account for the chyle finally getting into the lacteals, as well as for fluids passing into the circulation from the stomach, when its continuity with the intestinal canal has been interrupted.t The Epidermis or Epithelium of mucous membranes is very distinct at their external orifices, but becomes less and less ap- parent towards the interior of the body, until finally it cannot be distinguished; and anatomists generally consider that it is entirely deficient, notwithstanding the assertion of Haller to the contrary. It is a matter of common observation, that when the interior of mucous membranes is exposed by an eversion for a long time, to * Anat. Gen. p. 253. X Should the suggestion of the absorbing powers of the gastro-enteric follicles which I have proposed in Section third, be correct, it will dispose of the diflv culties and opposing opinions alluded to in this paragraph. 52 ORGANS OF DIGESTION. the action of the atmosphere; they take on more of the structure of skin, and become evidently covered with a cuticle which pro- tects them and diminishes their secretion. This is exemplified in eversion of the vagina from prolapsed uterus, in elongated and tumid labia interna, and in other ways: restore the parts to then- natural situation, and they are brought back to their original structure. In the partial prolapse of the mucous membrane of the rectum, from piles, corresponding circumstances occur. From this we infer, that the full development of cuticle depends very much upon the degree of exposure which any surface of the body has to undergo. The reverse also takes place: shut up or close any surface of the skin so that it is put in the condition of an interior cavity, and it immediately begins to assimilate it- self to a mucous membrane. This is proved by the tendency in voung children to a detachment of the cuticle, or excoriation of the opposed surfaces of the deep wrinkles about their thighs and in their perineum; a tendency obviated by the practice of nurses of covering these surfaces with powdered starch. It is also manifested frequently in the dressing of wounds with sticking plaster, where an incautious approximation of the contiguous surfaces of the skin, not only is followed by excoriation, but even by ulceration; a fact, the importance of which was formerly set in proper relief by Dr. Physick in his surgical lectures, and of which I have seen an example in a case of extirpated female mamma. The state of this question is, in fine, such that I think we may safely admit the existence of a very thin epidermis on the alimentary canal, but so pulpy that it cannot be distinguished except by the process alluded to in Section third of this Chapter. The mucous membranes vary in colour from a very light pink to a deep red, which is owing to the blood that circulates in them. In cases of suffocation, they become almost brown from the congestion of blood in them, while in fainting they turn white from the desertion of the latter. These vessels after having pe- netrated the thickness of the membrane, ramify with extreme minuteness on its surface. In consequence of this superficial si- tuation, the vessels being unsupported on one side, are exposed to rupture from slight concussions; in this way hemorrhage is produced in the lungs from coughing, and bleeding at the nose from blows upon the head. GENERAL ANATOMY OF THE MUCOUS MEMBRANES. 53 Exhalent orifices exist in great numbers in the mucous mem- branes: this is especially the case in the lungs, where the pul- monary perspiration, as it is called, is very obvious to common observation. Elsewhere, this discharge is so much blended with the mucus of the part, that it is difficult to appreciate its quantity. From the superficial situation of the blood vessels, it is clear that the exhalent orifices or pores, have but a short course to run. This is considered by Bichat as a satisfactory reason for the tendency of the blood to escape through them, or to ooze out where there is no rupture. Absorbents exist also in great numbers, as proved by the ab- sorption of chyle, of watery drinks from the intestinal canal, and by the inhalation of the vapour of spirits of turpentine into the lungs, rapidly communicating the particular smell of this article to the urine. There are, moreover, cases recorded of obstructed urethra, where the urine has been almost entirely absorbed by the mucous coat of the bladder. In regard to nerves, the mucous membranes are well furnished with them. Bichat has remarked that wherever these mem- branes are situated near the surface of the body and enjoy com- mon sensibility, they are almost wholly furnished from the cen- tral portions of the nervous system, as the brain and spinal marrow: this is exemplified in the conjunctiva, the pituitary membrane, the palate, the glans penis, &c. On the contrary, the sympathetic nerve furnishes the intestines, the bladder, and the excretory tubes generally. Mucous Glands, as they are called, exist throughout the sys- tem of mucous membranes, being situated either under them or in their thicknesses. From them is derived the mucilaginous fluid which lubricates so abundantly their interior surfaces, so as to facilitate the passage of extraneous bodies, and, at the same time, to protect the membrane from mechanical violence. These glands are of various sizes, from that of the tonsils and the muciparous glands on the lips, cheeks, and root of the tongue, to the almost imperceptible cryptae of the bladder and urethra. Their shape is either lenticular, rounded, or that of a pouch. The two former have their parietes of a sensible thickness, but the last are too thin to be distinguished from the mucous mem- brane itself. For the most part, the excretory duct of these Vol. II.—8 54 ORGANS OF DIGESTION. glands is short and patulous, so as to lead directly into the sub- stance of the gland. This is remarkably the case with the ton- sils, which consist in a congeries of these follicles; and with the glands on the root of the tongue. In some animals they are so numerous as to form almost a distinct lamina to the intestines; after the manner of the human subject, on the palate and parietes of the mouth. - The Mucosity discharged from these glands is one of the prin- ciples of animals, and, as is well known, exists also to a great extent in some vegetables. When perfectly pure and fluid, it is white, transparent, inodorous, and insipid. It is insoluble in al- cohol, but soluble in acids. Water forms more than nine-tenths of it, the remainder is mucus, properly speaking, blended with some neutral salts of soda and potash. The mucous membranes are exposed to a multitude of mor- bid alterations, such as polypus, scirrhus, cancer, phlegmor- rhagiae or serous fluxes, blennorrhagiae or mucous fluxes, inflam- mation in all its forms, gangrene, ulcerations, and congestions. CHAPTER IV. OF THE ASSISTANT CHYI.OPOIETIC VISCERA. r SECT. I.--OF THE LIVER. The Liver (Hepar, Jecur) secretes the Bile, and is the largest glandular body in the human frame. It, as mentioned, occupies the whole of the right hypochondriac region, the upper half of the epigastric, and, as it becomes tninner in going towards the left side, it occupies a small space in the right superior part of the left hypochondriac region. Its whole superior face is in contact with the diaphragm; on the left it is bounded by the spleen, and below by the stomach and the transverse colon; be- hind it, are the vertebral column and the ascending cava. The shape of the liver is like one half of an ovoidal body cut into two in the direction of its long diameter, and having the thick end turned to the right side. It is about ten inches in THE LIVER. 55 length by six or seven wide, and weighs from four to five pounds in the adult. Its colour is a reddish brown, generally; though, on its under surface and about its edges, broad, blue or black patches are constantly met with, which do not indicate any morbid derangement. Its upper surface is of a uniform convexity, rather more pro- minent at the right posterior part than elsewhere; adjusts itself accurately into the concavity made by the under surface of the diaphragm; and is unequally divided from before backwards by the suspensory ligament. The anterior margin is thin, and is notched where the suspensory ligament begins; the posterior margin is much thicker, and has near its middle a broad de- pression, to fit it to the projection of the vertebral column. The ascending vena cava forms a superficial sulcus upon this mar- gin, and frequently there is a complete canal through the sub- stance of the liver for transmitting it. The right extremity is very thick, and almost fills the hypochondriac region of that side, while the left extremity is reduced to a thin, tapering, and flexible edge. The under surface of the liver is much more irregular than the upper; it is traversed in an antero posterior direction, in a line corresponding with the attachment above of the suspensory ligament, by the umbilical fissure, (Sulcus Umbilicalis) which extends from the notch in the front edge to the depression be: hind, and obtains its name from having accommodated in the fcetal state, the umbilical vein, now converted into a round liga- mentous cord. In the posterior part of this fissure is likewise to be seen, in the same condition, what remains of the ductus ve- nosus. The anterior portion of the umbilical fissure is not un- frequently converted into a complete canal, by a-portion of he- patic substance crossing it like a small bridge. The transverse fissure (Sulcus Transversus, Intermedins) is situated in the middle of the under surface of the liver, and extends along a third or fourth of the long diameter of the latter. It begins somewhat to the left of the umbilical fissure, and crossing it at right angles, proceeds towards the right extremity. It contains the vena por- tarum, the hepatic artery, and the hepatic duct; all of which are bound to each other by a close cellular substance. The suspensory ligament above, and the umbilical fissure be- 56 ORGANS OF DIGESTION. low, give occasion to divide the liver into Lobes; right and left; of which the right is by much the largest, and accommodates almost entirely the transverse fissure, having also on its under surface some subordinate elevations, to wit, the Lobulus Spigelii and the Lobulus Quartus, together with the Gall-Bladder. The Lobulus Spigelii is placed between the transverse fissure and the posterior margin of the liver, to the right of the poste- rior end of the umbilical fissure. Its shape is somewhat prisma- tic, bifurcating in front; one of the elongations is a papilla over- hanging the transverse fissure, and is, therefore, considered as one side of the gateway (porta) opened for the vena portarum; the other elongation is a small ridge, sometimes called Lobulus Caudatus, and is lost gradually on the under surface of the great lobe, by inclining to the right. The Lobulus Quartus, or Anonymus, is not by any means so elevated as the last, but having a flattened surface, is placed in front of the transverse fissure, between the fore end of the um- bilical fissure and the gall-bladder; its posterior extremity is the second porta of the Liver, and is just opposite to that furnished by the Lobulus Spigelii. The liver, from being completely enveloped in peritoneum, has a smooth glossy appearance. The reflections of this membrane, from it to the parietes of the abdomen, form the ligaments, as they, are called, which consist each of two laminae. The Fal- ciform Ligament, or Suspensory, containing in its anterior mar- gin the remains of the umbilical vein, now called Ligamen- tum Teres, begins at the umbilicus, extends from it along the linea alba and the middle line of the diaphragm, and, as men- tioned, is reflected to the upper surface of the liver, from the an- terior to the posterior margin. The Right Lateral Ligament is situated behind, and departs from the back part of the diaphragm to the posterior margin of the right lobe. The Left Lateral Li- gament also goes from the back part of the diaphragm, and is attached along the posterior margin of the left lobe. Where the suspensory ligament inclines on each side into the lateral, it passes with so much obliquity as to leave some portion of the posterior margin of the liver uncovered by peritoneum; the lat- ter, where it describes the periphery of this space, has been ra- ther unnecessarily designated as the Coronary Ligament. THE LIVER. 57 In addition to the peritoneal coat, the liver has another, con- necting it with the peritoneum, and seeming to be only condensed cellular substance, which also penetrates into the substance of the gland, and holds its constituent parts together. It is parti- cularly well seen within the circle of the coronary ligament. Of the Organization of the Liver. The Liver is made extremely vascular by the ramifications of three kinds of blood vessels, the vena portarum, the Hepatic Arte- ry, and the Hepatic Veins. The two first convey the blood to it, and the third removes it again, into the general circulation, by emptying into the ascending vena cava. There are also branches of the hepatic duct, lymphatic vessels, and nerves. The glandular substance is fragile and easily lacerated; when torn it assumes the appearance of a congeries of spherical or po- lyhedrical grains, called acini from their resemblance to small ber- ries : they are united in mass by the elongations of the cellular coat, and traversed by the trunks of the blood vessels. Each of these granulations is about the size of a millet seed, and is a re- presentative of the entire gland, as its structure is complete in itself; being formed by the terminations of the blood vessels, and by the origin of a branch of the hepatic duct, called the porus biliarius. When examined with a microscope, it is said that these acini are composed of a yellow and of a brown-looking sub- stance ; it lias not, however, occurred to me to see the distinction in a very satisfactory way, though it is recognised by anatomists of high authority.* The Vena Portarum having arisen from the junction of all the veins of the stomach, intestines', pancreas and spleen, is about three inches in length when it reaches the transverse fis- sure, by going over the duodenum and under the pancreas. It immediately divides into two branches, called collectively the Sinus Venae Portarum, which is at right angles with the trunk of the vein; the right branch being the shortest and largest, is distributed by radiating trunks to the right lobe of the liver; • Bichat, Meckel, &c. 58 ORGANS OF DIGESTION. the left branch is distributed, after the same manner, to the left lobe, to the lobulus spigelii, and to the lobulus quartus. Some of its branches anastomose with the hepatic veins, which ac- counts for the etise with which an injection will pass from one to the other. Other branches of a smaller description anasto- mose with the pori biliarii, but with less freedom than in the preceding case; and lastly, the most delicate ramifications are spent upon the cortical or yellow matter of the acini, without penetrating to the brown.* The Hepatic Artery is a branch of the coeliac, and in ap- proaching the transverse fissure divides into three or more branches, that penetrate the substance of the liver, between the sinus portarum and the ducts as they come out; one branch goes to the right lobe, another to the left, and a third to the lobulus spigelii. There is some variety in regard to the precise mode of distribution, and their division into subordinate rami- fications frequently occurs before they get fairly into the sub- stance of the liver. When there, they seem to be intended for the nourishment of this organ, according to the observations of several able anatomists: and follow.the ramifications of the vena portarum and of the biliary ducts, forming upon them a very delicate and complicated tissue of anastomosing vessels; some of which, probably the vasa vasorum, communicate with the vena portarum. The Biliary Pores (Pori Biliarii) or the commencing rami- fications of the biliary duct, take their origin in the acini; and, as is said, upon the boundary between the two kinds of matter, avoiding1 the brown and passing through the cortical.t The larger branches converge into their respective trunks succes- sively or in pairs; while the primordial, or most minute ones, converge several of them to the same point, giving a penicillous appearance. It is asserted that a fine injection passes more readily from them into the lymphatics than into any other order of vessels; which may account for the promptitude of jaundice upon an obstruction of the hepatic duct. * Mappes, I. F. Meckel, loc. cit. f I. F. Meckel, loc. cit. THE LIVER. 59 The Hepatic Veins arise in the acini from the capillary ter- minations of the vena portarum and the hepatic artery. Their branches are sucessively accumulated into three large trunks, the collective area of which vastly exceeds that of the vessels bringing the blood to the liver. Two of these trunks come from the right lobe and one from the left, to empty into the ascending cava, while it is still in contact with the liver, im- mediately below the diaphragm; just below the preceding trunks there are five or six, sometimes more, small hepatic veins, coming from the posterior margin of the liver, and from the lobulus spigelii. The hepatic veins are destitute of valves, and remarkable for the thinness of their parietes. An injection passes readily from them into the other systems of vessels. They may be recognised by their insulated course, by their consisting in trunks which converge from the periphery of the liver to the vena cava, while all the other vessels diverge from the transverse fissure to the periphery, and consequently cross the course of the hepatic veins. At the bottom of the transverse fissure of the liver is to be found a condensed cellular fibrous tissue, which invests the vena portarum, the hepatic artery, and the biliary ducts; and, as they all keep together in their ramifications, this tissue follows them throughout the substance of the liver, and thereby forms sheaths for them. It may be considered as continuous with the processes sent in from the cellular coat; and, contrary to the opinion of Glisson, whose capsule it has been called, it is devoid of muscu- lar structure.* Of the Gall Bladder. The Gall Bladder (Cistis Fellea) is a reservoir for the bile se- creted by the liver. It is fixed on the under surface of the great lobe, to the right of the umbilical fissure, and removed fr,om the latter by the lobulus quartus.t It is an oblong pyriform sac, * An elaborate work on the minute anatomy of the liver has lately appeared, from the English press, by Francis Kiernan, Esq. R. C. Surgeons, London, 1833, in which there are some peculiar notions of structure. It is highly creditable to the zeal of the author and well worthy of perusal. X 1 have seen an instance where it was to the left of the umbilical fissure, on the small lobe. The latter was much longer than common. Dec. 1830. 60 ORGANS OF DIGESTION. having its anterior extremity or fundus projecting somewhat be- yond the anterior margin of the liver, while the posterior end reaches to the transverse fissure. Its long diameter inclines slightly to the right side, so that it is not precisely in an ante- roposterior line. It varies in its shape in different subjects, be- ing much more spheroidal in some than in others. Its fundus is rounded and obtuse, while the posterior end is gradually re- duced to a narrow neck, which is bent up on itself, so as to re- tard the flow of a fluid through it. Its upper surface is in con- tact with the substance of the liver, and is received into a broad shallow fossa, while the lower surface is projecting, and by coming in contact with the transverse colon, tinges it with bile, by transudation after death. The Gall Bladder has three coats, a peritoneal, a cellular, and a mucous one. The Peritoneal Coat is not complete, but only covers that part of the sac not received into the fossa on the under surface of the liver; it is, therefore, a continuation of the peritoneal coat of the latter; sometimes, however, the gall bladder is so loosely at- tached to the liver that it almost hangs off from it, in which case the peritoneal coat is nearly complete. The second coat is condensed cellular membrane. Through it ramifies a great number of lymphatics, and blood vessels; be- low, it attaches the peritoneal to the mucous coat, and above, the latter to the liver. The Mucous Coat is always tinged of a deep green or yellow, by the bile which it contains percolating after death; for it is said to be, before that, of a light colour. This coat is thrown into irregular tortuous folds or wrinkles of extreme delicacy, in the intervals of which are many round or polyhedrous cells, causing it to look, when floated in water, like a fine honey comb; such as are about the fundus of the sac are superficial, and not so distinct; but those near its middle and about the neck, are a line or a line and a half deep. In the neck or apex, and in the beginning of the cystic duct, are from three to seven, sometimes twelve, semilunar duplicatures of the internal membrane, which also retard the flux and afflux of any fluid, though they do not afford so much resistance to the ingress as to the egress of it. THE LIVER. 61 These duplicatures are sometimes arranged into a spiral valve, projecting from the inside of the duct, and forming two or three turns.* Very small mucous follicles exist over the internal face of this membrane, the discharge of which fills the gall bladder when the secretion of bile has been interrupted by diseased ac- tion, as in yellow fever, or by scirrhus of the liver. The artery of the gall bladder is a branch of the hepatic. Its veins empty into the vena portarum. Its nerves come from the sympathetic, and its lymphatics join those of the liver. Of the Biliary Ducts. A succession of very fine branches having arisen from the aci- ni of the liver, these branches are united into three or four trunks by the time they reach the transverse fissure. These trunks then coalesce into a single one, the Hepatic, of eighteen or twenty lines in length, and about the diameter of a writing-quill. The Hepatic Duct is then joined at a very acute angle with the duct from the gall-bladder, which is somewhat shorter and smaller; the union of the two forms the Common Duct, (Ductus Commu- nis Choledochus.) The latter is larger than either of the others singly, and is three or three and a half inches long; it descends behind the right extremity of the pancreas through its substance, passes for an inch, obliquely, between the coats of the duodenum, becoming at the same time diminished in diameter; and, finally, ends by an orifice still more contracted, on the internal face of this gut, on its second turn, and about three or four inches from the stomach. The orifice is marked by a small surrounding tu- bercle somewhat obscured by the valvulas conniventes. The Biliary Ducts are situated, as mentioned, along the right margin of the lesser omentum, and have the vena portarum and the hepatic artery to their left. The bile ducts are formed by two coats; the external is a fibrous, lamellated, and very extensible membrane, while the in- ternal is mucous, having the same structure with that of the gall bladder, of which it is in direct continuation. In the Cystic Duct, * Discovered latterly by M. Amussat of Paris. M. Amussat has also detected muscular fibres in the gall bladder and biliary ducts, in which we see an analogy with other hollow viscera.—Am. Med. Jour. vol. ii. p. 193. Vol. II.—9 92 ORGANS OF DIGESTION. and at the lower part of the Common Duct, are several longitu- dinal folds. The Common Duct sometimes receives, just before it empties into the duodenum, the Pancreatic Duct. Of the Bile. This secretion from the liver, is of a deep yellow, sometimes green cojour: when recent, it is thin and fluid; but after it has been conveyed to the gall bladder, and permitted to remain there for some time, it becomes as thick as molasses, and increases also in the intensity of its colour and in bitterness. Some anatomists have believed that there was a more direct communication be- tween the liver and the gall bladder than that through the hepa- tic and the cystic duct; but repeated and close observations have proved the opinion to be erroneous, or, at least, destitute of pro- per proof: it is, therefore, clear, that the difference between the hepatic and the cystic bile, depends upon the watery particles being removed from the latter by the absorbing power of the in- ternal coat of the gall bladder. According to Berzelius, the chemical analysis of bile furnishes about eighty parts of water, eight of a particular substance which assumes a resinous condition on the application of an acid: three of mucus; and nine of saline matters; of which soda is a princi- pal constituent. SECT. II.--OF THE SPLEEN. The Spleen (Lien. Splen) is situated deeply in the posterior part of the left hypochondriac region, and is bounded above by the diaphragm, below by the colon, and on the right by the great end of the stomach, and by the pancreas. It is not ascertained that it secretes any thing. Its colour varies from a deep blue to a dark brown. In shape it resembles the longitudinal section of an oval, being flat or very slightly concave on the surface next to the stomach, and convex on that contiguous to the diaphragm. Occasionally its margins are notched, but this is not invariably the case. Its flat surface is slightly depressed longitudinally in the centre, where the blood vessels enter it by six or eight foramina. THE SPLEEN. G3 Several spleens sometimes exist in the same individual, in which case the supernumerary ones are not larger than nutmegs. The common size of this organ is about four and a half inches long, by two and a half or three wide, in which case it has a solid firm feel; but it very often exceeds these dimensions; its transi- tion and varieties of magnitude are so frequent, that no settled rule can be established. In its inordinate enlargements I have seen it only slightly smaller than the liver, its texture in this case is soft and easily lacerated. It is fixed in its place by three lines of reflection or processes of peritoneum, whose names indicate sufficiently their places of attachment. They are the Gastro-Splenic Ligament or Omen- tum, in which are the vasa brevia of the stomach; the Splenico- Phrenic; and the Splenico-Colic. These reflections, by being continued over the spleen, give it a complete peritoneal coat, which is raised up with more difficulty than the corresponding membrane of any other viscus of the abdomen, and is common- ly thrown into very small inequalities or wrinkles, The internal or proper coat of the spleen is a grayish, com- pact, extensible, and elastic membrane, the use of which is evi- dently to sustain the natural shape of the organ, and to support its parenchymatous structure. It sends in processes to accom- pany the blood vessels, and from its internal face there proceeds a multitude of lamellae and of fibres, which traverse its cavity in every direction, and reduce it into a cellular condition, not unlike the spongy structure of bones. The spleen, in proportion to its size, is furnished to a remark- able degree with blood. The largest branch of the coeliac artery runs to it along the superior margin of the pancreas, forming numerous serpentine flexures, and distinguished for its thickness; it divides into several trunks for penetrating into the spleen, and enters by the foramina in the fissure. The veins come out by a number of trunks equal to what the artery is divided into; they assemble then into a single trunk, which attends the artery along the pancreas, and is remarkable for the tenuity and ex- tensibility of its coats. The splenic vein is destitute of valves, and empties into the vena portarum. The spleen has also lym- phatic vessels; and is furnished with nerves from the solar plexus. I 64 ORGANS OF DIGESTION. Of the Intimate Structure of the Spleen.—The Splenic artery having penetrated into this organ, is divided and subdivided into a radiating succession of very fine branches, which, according to the injections of Ruysch, do not anastomose with each other; in consequence of which, one part is sometimes finely injected and not another, of which, in my own observations, 1 have had an example. The veins, on the contrary, do anastomose, not only as regards the collateral branches of the same primitive trunk, but also by the collateral branches of different trunks. These anastomoses are not large. The arteries terminate freely in the veins, as may be proved by fine injections, and by the microscope. The mass of the spleen, upon superficial examination, seems to consist in a dark brown pulp, which is contained in the cells dividing the cavity of the internal coat, and may be easily de- monstrated by tearing the spleen, and scraping it with a knife handle. MM. Assolont and Meckel believe, that blood, besides being in the arteries and veins, is placed in a state of particular combination and of intimate union with the other organic- ele- ments of this viscus, and with a large quantity of albumen; and that this combination of the blood forms the dark brown pulp alluded to. The great quantity of albumen in the pulp, is rea- dily proved by the hard coagulum which it forms, when steeped in alcohol. But a question has arisen whether the pulp be ex- travasated in the cells which contain it, or whether it be still re- tained in the extremities of the blood vessels. Superficial exa- mination is in favour of the first, but M. Marjolin denies it on the following grounds: that injections, cautiously made, pass immediately from the arteries into the veins; and that the spleen, when successfully injected and frozen, does not exhibit ice in the interstices of its vessels, while their capillary ramifi- cations, distended by the injected fluid, are distinctly seen. From these he concludes that the glandular structure of the spleen is formed essentially of arterial and venous capillary ves- sels with very delicate and extensible coats, and that they com- municate with one another without the intermedium of anv cell; that the extreme tenuity of these vessels, and their extensibility in every direction, are sufficient to explain the augmentation of THE SPLEEN. 65 volume of the spleen, under certain circumstances, as well as the promptitude of its diminution under others. In addition to this pulp, many observers have met in the spleen with an abundance of rounded corpuscles, varying in size from an almost imperceptible magnitude to a line or more in dia- meter.* They are of a gelatinous consistence, soft, grayish, and semi-transparent, and either cluster together, or are widely sepa- rated. By Malpighi, they were considered glandular, and, by Ruysch,t as convoluted vessels. Professor Soemmering, from the following paragraph, seems to join in the opinion of the latter: " Qui nonnunquam occurrunt, acini vel glomeruli, microscopii ope accuratissime explorati nihil sunt, nisi vasorum fasciculi, vel teretes penicilli aut cirri vasculosi." According to the observa- tions of Sir Everard Home, they swell considerably after an ani- mal has finished drinking. The spleen, from having no excretory duct, and, consequently, from our inability to ascertain whether it secretes, has its nature and uses shrouded in mystery. No single theory concerning it has ever been generally adopted, for speculations have multiplied in proportion to the obscurity of the subject. The idea, howe- ver, on the use of this body, which to me is most reasonable, is, that it acts a subsidiary part to the liver. It would seem, indeed, as a general rule in regard to glandular structures and such other highly vascular organs of the body as have an intermittent func- tion, that the blood which is sent to them during their state of activity, should be passed off through a different channel, while they are in a state of repose. This does a double service, it pre- vents superfluous secretions, and it also keeps up the vascular equilibrium of the body, as there must be always in readiness a quantity of blood sufficient for the supply of any secretion which may be wanted for the time. This proposition will derive some additional illustrations from the foetal state. The kidneys being then inactive the glandulae renales take off their blood, and thereby prevent what would otherwise be a very inconvenient secretion of urine; again, the lungs being also then inactive, the circulation through them is proportionately reduced, and the superabundant blood is con- * Malpighi, Ruysch, Hewson, Home, Dupuytren, Meckel, &c. f Epist. Anat. IV. 66 ORGANS OF DIGESTION. ducted through the thymus gland. But as the full functions of the lungs and of the kidneys are established upon birth, and con- tinue uninterrupted during life, their supplementary organs, the thymus gland, and the capsulae renales, are not wanted, and they wither away after the early period of infantile existence is passed. In regard to the liver, its functions also suspended during the foetal state, are of an intermittent kind throughout life, the spleen may, therefore, be considered a vicarious organ for it during the whole period of existence, receiving its blood during the continu- ation of uterine life, and, in the intermission of action, during common life. The spleen is, therefore, an organ useful to the foetal and to the perfect state, and we, consequently, never see it in the collapsed and dwindled condition 'of the thymus gland, and renal capsule. The same reasoning which applies to the spleen will also ap- ply to the Thyroid Gland, for the latter may be considered as ex- ecuting for the salivary glands during fcetal and perfect existence, what the spleen does for the liver. For it is ascertained, that the salivary glands are inactive during fcetal existence, have only an intermittent action during perfect life, and, therefore, proba- bly stand in need of a supplementary organ during their periods of inactivity. SECT. III.—OF THE PANCREAS. The Pancreas (Pancreas) secretes saliva, and is the largest of the salivary glands. It is fixed in the lower back part of the epi- gastric region; and extends horizontally across the spine, being separated from it by the lesser muscle of the diaphragm. It is connected to the spleen on the left; at its right extremity is sur- rounded by the curvature of the duodenum; is bounded in front by the stomach, which conceals it; and is placed between two laminae of the mesocolon. The pancreas is about six or seven inches long, two wide, and flattened before and behind. Its figure would be represented by a parallelogram, were it not that its right extremity is enlarged considerably into a head or tuber, to which Winslow gave the name of the Lesser Pancreas. The anterior face of this organ is turned obliquely upwards, and is covered by the superior lamina THE PANCREAS. 67 of the mesocolon. The posterior face looks obliquely downwards, and is in contact with the aorta, the vena cava ascendens, the superior mesenteric vessels, and several nerves: along the supe- rior margin of this face exists a long superficial fossa, occupied by the splenic artery and vein. With the exception of the loose covering given by the mesoco- lon, the pancreas has no peritoneal coat; neither has it an appropriate tunic, unless we consider as such the lamina of con- densed cellular membrane which envelops it, and sends in pro- cesses between its lobules, as in the case of the salivary glands in the neck. Of the Minute Structure of the Pancreas.—This body, like the other glands, which discharge saliva, is of a light gray or pink colour. It consists in lobules of various forms and sizes, united by an intermediate cellular tissue, and having their interstices oc- cupied by numerous blood vessels. These lobules, by a slight maceration, may be separated and resolved into small granular masses, constituting integral portions of the gland. The arteries of the pancreas come principally from the splenic, as it cruises along the superior margin. The veins empty into the splenic, and thus, finally, into the vena portarum. It is fur- nished with nerves from the solar plexus, and has lymphatics. The excretory duct of this gland (Ductus Wirsungii) arises, by very fine roots or tubes, from each of the small granular masses. These tubes coalesce into larger ones, which run transversely from the periphery towards the centre of the gland, inclining slightly, at the same time, towards the right. These secondary tubes finally discharge successively into a single one, which runs the whole length of the gland nearly in its middle. The single tube, by these additions, enlarges continually from left to right, being small where it begins at the splenic extremity of the pan- creas, and about the size of a crow-quill at the duodenal. At the latter place, it is joined by the duct of the lesser pancreas, which is derived after the same rule as itself. The pancreatic duct, al- most immediately afterwards, empties into the ductus communis choledochus, or runs at the side of the latter, and makes a dis- tinct opening near it into the duodenum, at the posterior part of the second curvature. BOOK V. OF THE URINARY ORGANS. The Urinary Organs, (Organa Uropoietica,) being destined to secrete and convey the urine out of the body, consist in the Kidneys, the Renal Capsules, the Ureters, the Bladder and the Urethra. Of the Kidneys. The Kidneys (Renes) are two glandular bodies for the secre- tion of the urine, fixed one on either side of the spine. They are in the back part of the lumbar regions, have their internal edges inclining very slightly forwards, and extend from the upper margin of the eleventh dorsal to the lower margin of the second lumbar vertebra; the right, however, is ten or twelve lines lower than the left, owing to the thick posterior margin of the right lobe of the liver, which presses it downwards. The kidneys are covered in front by the peritoneum and the lumbar portions of the large intestine, but in such a manner as to be separated from them, in corpulent subjects, by a surrounding layer of fat; behind, they repose upon the lower part of the great muscle of the diaphragm, upon the quadrati lumborum, and upon the upper end of the psoae magni muscles. The kidney is a hard solid body, of a brown colour; in shape it is a compressed ovoid, excavated on the margin which it presents to the spine, and bears a very strong resemblance to the common kidney bean. Its flat surfaces present forwards Vol. II.—10 70 URINARY ORGANS. and backwards, and the broad end of the ovoid is above. Its periphery is smooth, so that one does not see from an external examination the lobules or internal divisions. The excavation of the kidney, called its fissure, (hilum renale) occupies about one-third of its long diameter, is bevelled in front, and leads to the very interior of the gland; conducting its blood vessels and excretory duct, which have to pass through a quantity of cellular and adipose matter. The kidneys are generally of equal size, being about four inches long, and two wide; and each one weighs three or four ounces. They have no ligaments for keeping them in position, but depend for the latter upon the adjacent cellular adhesions and blood vessels. The kidney being destitute of a peritoneal coat, has a well marked capsule which envelops it entirely and penetrates into its fissure for some depth, where it is perforated with foramina for transmitting the blood vessels and the ureter. This capsule is white, semi-transparent, fibrous, strong, and elastic: it adheres to the surface of the kidney by delicate cellular and vascular filaments, which are so weak that they permit it to be stripped off without difficulty, and when so removed, some indications of the original lobulated condition of the organ are seen. The kidney receives from the aorta one or more branches, called the renal or emulgent arteries, which divide as they ap- proach the fissure; and having got into the substance of the gland are distributed by innumerable twigs to all parts of it. Some terminate in veins, others in the substance of the organ, and others, again, in the excretory tubes. The veins equal in number the arteries, and are somewhat larger. When both, or even one, of these systems of blood vessels is injected with wax and corroded, its branches are so abundant as to retain the form of the gland. In engaging in the fissure of the kidney, the arterial ramifications are in front, the veins in the middle, and the commencement of the ureter behind.* The artery on the right side is longer than that on the left. The reverse is the case with the emulgent veins, as they empty into the vena cava ascendens. This arrangement is owing to the relative • This rule is subject to frequent variations. THE KIDNEYS. 71 position of the aorta and the vena cava ascendens, as the first is on the left side of the spine, and the last on the right side. The nerves come from the solar plexus of the sympathetic, and adhering to the arteries cannot be traced very far through the glandular structure. The quantity of lymphatics is consi- derable. Of the Minute Structure of the Kidney.—When the kidney is cut open longitudinally, it obviously consists of two kinds of substance, differing in their situations, colour, consistence and texture. The one nearest to the periphery of the gland is called from its position Cortical, (Substantia Corticalis, Glandulosa,) while the other, being more internal, is designated as the Me- dullary or Tubular, (Substantia Medullaris; Tubulosa: Fi- brosa.) The Cortical or Secretory Substance forms the whole circum- ference of the kidney, and, on an average, is about two lines in thickness: but it is thicker at some points; as from its internal face processes converge towards the centre of the gland, which separate the tubular part into as many distinct portions of a conoidal shape. It is composed principally of arteries and veins ramifying, among small graniform corpuscles that secrete the urine, and are very distinct when viewed with a microscope. It tears with facility, thereby presenting this granular appearance, and is of a dark, or reddish brown colour, varying considerably, however, according to the cause of death. The granular corpuscles which form the mass of the cortical or secretory substance, are, individually, imperfectly visible to the naked eye, and appear like rounded points. The celebrated Ruysch, who was distinguished for the suc- cess of his injections, and for the acuteness of hi? vision, de- clared that they consisted wholly in the very fine extremities of arteries and veins having a penicillous arrangement; while Malpighi and Schumlansky viewed them as purses or small sacs of a glandular character, specifically suited to secrete urine, and upon whose parietes the blood vessels ramified. From these granuli or acini the incipient extremities of the tubuli uriniferi take their rise. 72 URtNARY ORGANS. The Tubular or Conoidal portion, consists in from twelve to eighteen eonoidal fasciculi (Pyramides Malpighiana) present- ing their rounded bases towards the cortical matter, and en- closed in it, while their apices converge to the central cavity of the kidney, the surface of which they form. The bodies of these pyramids, as just mentioned, are separated by processes of the cortical matter; but their apices are free, and project from the internal surface of the kidney so as to resemble as many small nipples, whence they are called Papillae Renales. Fre- quently two of the pyramids coalesce so as to form but one papilla together; in such case the latter generally preserves a duplicate appearance. The papillae are arranged into three ver- tical rows, one before, one in the middle, and another behind; those of the foremost row are turned backwards; those of the middle look inwards; and those behind look forwards. Not un- frequently there is a small depression (foveola) on the very summit of the papilla. The tubular part is of a lighter colour and harder than the cortical, but the difference in these respects is not always manifest. The conoidal fasciculi may each be considered, along with its appertaining cortex, as a sort of distinct gland, or at least as a lobe; for upon them depend the tabulated appearance of the kidneys of a foetus, and of animals. Each cone, when analyzed, is found to consist in a collection of tubes (Ductus Uriniferi Bellini) converging from the circumference of the kidney to the apex of the papilla. These tubes are more numerous near the base, in consequence of their successive junction in approach- ing the apex:* their terminating orifices,'on the latter, appear likt small pores, from which the urine can be squeezed in little drops. In the early part of the course of the ductus uriniferi, while they are still in the cortical matter, they are wound up in a very serpentine and tortuous manner, and are distinguished by the name of Conical Canals, (Ductus Ferrenii.X) They com- monly go alone, winding their way in the cortical substance until they reach its most, interior face; they then become straight, * Schumlansky, Dis. de Struct. Renum, Strasburg, 1788. | A. Eerrein; sur la Structure des reins et du foie. Mem. de Paris, 1749. THE KIDNEYS. 73 form the medullary substance, and have the name of the con- duits of Bellini.* Some of the calculations on this subject are not a little curious. It was ascertained by Ferrein that in each of the conoidal fas- ciculi (Pyramides Malpighianse) there were, at least seven hun- dred subordinate cones or pyramids; and as the number of co- noidal fasciculi is generally about fifteen, these pyramids would amount to ten thousand five hundred. Again, each of the sub- ordinate pyramids (Pyramides Ferrenii) is composed of many hundred uriniferous tubes, and, by the observations of Eysen- hardt,| each of these tubes consist of twenty smaller ones. The arteries of the kidneys, in ramifying minutely through its structure, adopt the following arrangement. They first of all pass through the processes sent inwards from the cortical matter between the Pyramids of Malpighi, or large cones, and, having got into the cortical matter, they divide into very fine twigs, which form arcades around the bases of the pyramids of Ferrein, and pass between them.J These arcades have but few anastomoses with each other, and their branches go almost exclusively to the cortical substance, very few of them being found on the tubular. Their branches radiate from the con- vexities of the arches so as to surround the base of each cone, and to penetrate to the surface of the kidney. Some of these branches terminate in corresponding veins, and others on the granular corpuscles, or acini. The connexion between the cor- puscles and the arteries, has been compared to that between grapes and the stems on which they grow, so as to form a bunch. The veins penetrate the substance of the kidney, and have a similar distribution; but they are much larger than the arteries and have free, large and numerous anastomoses. A connexion of the corpuscles with the veins is not quite evident, and, even if it does exist, remains yet to be proved; at least, in the opinion of some anatomists: the fact, however, is well established, that fine injections will readily pass from the veins into the tubuli uriniferi. In one instance, I found in a young female subject one of the * L. Bellini, de Structura Renum. Florence, 1662. f De Struct. Renum. Obs. Micros. Berlin, 1818. $ Schumlanskv. 74 URINARY ORGANS. kidneys in the pelvis in front of the rectum. A similar case has been seen by Professor Hensinger;* and I have met with several instances of a coalition across the spine, of the two kidneys, so as to present the appearance of a bilobed organ. Of the Excretory Duct of the Kidney, or the Ureter. The Ureter is a canal which conveys the urine from the kid- ney to the bladder. It commences in the centre of the kidney by an enlargement called pelvis, which branches off into three or four portions, (calices) one above, one below, and one or two intermediate. Each of these calices is divided, at its free ex- tremity, into three or four short funnel-shaped terminations, (Infundibula.) Each of these terminations embraces by its expanded orifice, the base of a papilla, so as to permit the latter to project into it, and thereby to distil its urine there. Very frequently the number of papillae exceeds that of the infundi- bula, in which case two of the former project into one of the latter. The pelvis of the kidney having emerged at the fissure be- hind the vessels, from being expanded and somewhat conoidal in shape is reduced to a cylindrical canal, which, properly speaking, is the ureter: the latter is about the size of a goose- quill and descends through the lumbar region, between the pe- ritoneum, and the psoas magnus muscle. It dips into the pelvis by crossing in front of the primitive iliac vessels and the in- ternal iliac, crosses the vas deferens at the back of the bladder, and penetrating obliquely the coats of the latter, terminates in an orifice ten or twelve lines behind that of the neck of the bladder. The excretory duct of the kidney is formed by two coats. The external is a condensed, fibrous, and cellular tissue, but is destitute of any thing like muscle. The internal is a thin mu- cous lamina, which can be raised up without much difficulty, and is continuous, at its lower end, with the internal coat of the bladder; at the upper end, it is supposed by some anatomists to be reflected over the papillae, and even to pass for some distance • Am. Med. Jour. Vol. iii. p. 442. THE KIDNEYS. 75 into the tubuli uriniferi. This duct has considerable powers of extension, as manifested by its transmitting large calculi from the kidney, and also, by its general enlargement in some cases of obstructed urethra; its sensibility is exquisite when irritated by a calculus passing down it. Of the Renal Capsules. The Renal Capsules (Capsulas Renales, Renes Succentu- riati,) are two small bodies, one on either side, placed upon the upper end of the kidney. They are of a yellowish brown colour tinged with red, have no excretory ducts, and are more distinctly developed and softer in the perfect foetus than in the adult; whence they are ranked among those organs, as the thy- mus gland, and others; which, having some peculiar value in fcetal existence, are perhaps unnecessary to that of the adult.* They are of a triangular pyramidal shape, flattened before and behind, and rest by a concave base upon the kidney; they are about fifteen lines high and as many wide. They are surrounded by a proper coat of lamellated con- densed cellular tissue, which, by detaching inwards its prolon- gations, keeps the parts of these bodies together, and marks out their divisions. In the centre of the renal capsule, a cavity may, from time to time, be found; but, according to my own observations, nothing is less certain than its existence; and, in the opinion of Meckel, when found, it is the result of cadaverous decomposition. In the foetus it contains a reddish viscid fluid^ which seems to consist in a large share of albumen, as it coagu- lates with alcohol; in children, this fluid becomes yellow; in adults it is dark brown; and in old people it is either entirely deficient, or in a remarkably small quantity. Of the Minute Structure of the Capsulx Renales.—The arteries of these bodies come from the emulgents, from the phrenics, and from the aorta. The veins of the right one ter^ minate in the cava ascendens, and of the left in the emulgent. Each one is divisible into lobes, and by a slight maceration • This opinion has recently been confirmed in a dissection of a foetus, where I found the capsulx renales, though the kidneys were absent, 76 URINARY ORGANS. may be reduced into lobules and small granulations. The ex- ternal part is rather more consistent and yellow than the in- ternal. The granulations seem to have an intimate connexion with the veins, as they are easily penetrated by fluid injections from the latter. Reputed excretory ducts for these bodies have been found going to the testicles, to the pelvis of the kidneys, and to the thoracic duct, but no weight is now attached to such assertions. Of the Bladder. The Bladder (Vesica Urinaria,) is the reservoir for the urine, and is placed in the pelvis, just behind the symphysis of the pubes. When pressed upon, as it commonly is, by the ad- jacent viscera, it is flattened somewhat before and behind; but removed from the body and inflated, it is an elongated sphere or an oval; the greatest diameter of which is vertical, in regard to the linea ileo-pectinea. The superior end of the bladder is called the upper fundus, and the lower end the inferior fundus; the latter is rather more obtuse than the other; and between the two is the body. The neck of the bladder is its place of junction with the urethra. The form of the bladder is influ- enced by age and by sex; in very young infants it is cylindroid, and owing to the smallness of the pelvis, rises up almost wholly into the abdomen. In the adult woman, who has frequently borne children, it is nearly spherical, has its greatest diameter transverse,* and is more capacious than in man. The bladder is bounded in front by the pubes, above by the small intestine, behind by the rectum, and berow by the pro- state gland and the vesicular seminales. From its superior end there proceeds to the umbilicus a long conical ligament, the urachus, which is placed between the linea alba and the perito- neum, and produces a slight elevation or doubling of the latter. In mankind, the urachus is solid; some very rare cases, how- ever, are reported, in which it has been hollow, so as to permit the urine to flow through it from the bladder. This vicious conformation has generally been attended with a congenital ob- struction of the urethra.t When the anterior parietes of the ab- * H. Cloquet, Anat. Descrip. f Sabatier, Anat. vol. iii. p. 19. THE BLADDER. 77 domen are put upon the stretch, a semi-lunar fold of the peri- toneum, as formerly mentioned, is seen to proceed, on either side of the urachus, from the lateral surface of the bladder al- most to the umbilicus. These folds contain, in their loose edge, the fibrous remains of the umbilical arteries of the foetus, called, subsequently to uterine life, the Round Ligaments of the blad- der, though they have little or no influence on its position. The bladder is also fixed in its situation by the pelvic aponeu- rosis, a membrane elsewhere described with the organs of ge- neration. The bladder consists of four coats: the Peritoneal, the Mus- cular, the Cellular, and the Mucous. The Peritoneal Coat is very imperfect, and is derived from the part of the peritoneum which descends from the anterior parietes of the abdomen into the pelvis. It covers the upper and the posterior face of the bladder, and then passes to the rectum, by sinking down between these two organs, so as to form the small pouch beneath the lower fundus of the bladder; the apex of this pouch reaches within an inch of the base of the prostate. The upper margin of this pouch next to the bladder, forms a strong horizontal doubling, stretching across the pelvis, when the rectum is empty, and is on a level with the posterior end of the vesicular seminales. Being connected to the subja- cent muscular coat by a thin lamina of loose cellular membrane, the peritoneum may be dissected off without difficulty. In con- siderable distentions of the bladder, it is reflected from the up- per end of the latter to the abdominal muscles in a line much above the pubes; whereby a good opportunity is afforded of reaching", with an instrument, the cavity of the bladder without injuring the peritoneum. The Muscular Coat is of a thickness intermediate to thatof the stomach and of the oesophagus, and its fibres are pale. They pass in very varied directions,* and are collected into flattened fasciculi, leaving interstices between them, through which the internal coat is occasionally caused to protrude, in strictures and other obstructions of the urethra. These fasci- * Santoiini, Septemd. Tabid. Vol. II.—11 7S URINARY ORGANS. culi, for the most part, arise about the neck of the bladder, and ascending upwards, before, behind, and laterally, terminate at the superior fundus in the base of the urachus. Within these, which may be considered as the longitudinal fibres of the blad- der, there are others forming a thinner lamina, whose course is transverse, or oblique: they serve to connect the preceding. As the muscular fibres are collected at the neck of the bladder, and at the urachus, there is, of course, an increased thickness at these points. The Cellular Coat consists in a close, dense, lamellated, and filamentous tissue, very extensible and difficult to tear. It is impervious to water, adheres closely to the muscular coat with- out, and to the mucous within, so as to form a strong bond of union between them. It is pervaded by many vessels and nerves, which it conveys to the mucous coat. The Mucous Coat is also called the villous, but is much more smooth than the corresponding one of the stomach. It is white, with a slight tinge of red, and abounds with mucous follicles, which, though small and scarcely discernible in a natural state, are rendered very obvious by disease. It stretches with much facility, but, like other mucous membranes, does not restore itself readily, and is rather thrown, in the contracted state of the bladder, into wrinkles or folds, having a diversified course, and of a fugitive character, as they disappear again upon the next distention. It is very vascular. The intepnal faee of this coat presents, at its inferior part, the following appearances: 1. The Vesical Triangle (Trigonus Lieutaudi, Trigone Ve- sicale) is placed immediately behind and below the neck of the bladder, occupying the space between it and the orifices of the ureters. It is an equilateral triangle of an inch in length, its surface is smooth, is not affected materially in extent either by the dilatation or the contraction of the bladder, and is elevated so as to be sufficiently distinct and well defined. 2. The anterior angle of the triangle looks into the orifice of the urethra, and is generally so elevated that it has obtained the name of Uvula Vesicae; it is, however, simply a projection THE BLADDER. 79 of the mucous membrane depending upon the subjacent third lobe of the prostate; which, at this point, is not unfrequently much enlarged in the aged, and then presents a great difficulty in the introduction of a catheter. 3. The Orifices of the ureters form the posterior angles of the triangle, and are contracted somewhat below the size of the ca- nals themselves. They are said, by Mr. Charles Bell,* to be furnished each one with a small fasciculus of muscular fibres, which runs backwards from the orifice of the urethra, just be- neath the lateral margins of the triangle, and, in its contraction, will stretch the orifice of the ureter, so as to permit an easy pas- sage of the urine into the bladder. The retrogradation of the urine is prevented by the ureter passing obliquely, for six or eight lines, between the muscular and mucous coat; there is something also in the obliquity of the orifice itself which as- sists in this effect; as I have ascertained by removing the mus- cular coat entirely, at this point, and dissecting up the ureter, notwithstanding which, the bladder, when inflated, still retained its contents. Where the ureter penetrates the muscular coat, I have in several instances found a layer of longitudinal muscular fibres enveloping it for half an inch, or an inch. 4. The Inferior Fundus of the bladder (bas-fond of the French) is a depression of the general concavity of the bladder, of about six lines in depth, placed between the base of the triangle and the posterior side of the bladder. In the erect position, calcu- lus, when one has it, lodges there. 5. The Internal Orifice of the neck of the bladder resembles strongly that of a Florence flask, modified, however, by the projection of the uvula vesicas, which makes is somewhat cres- centic below. The neck of the bladder penetrates the prostate gland, but, at its commencement, is surrounded by loose cellu- lar tissue containing a very large and abundant plexus of veins.t The internal layer of muscular fibres is here transverse; and they cross and intermix with each other in different directions, * Med. Chir. Trans. Vol. iii. X Mascagni, Anat. Univ. Str. Prim. Tab. Spec. Fig. V. 80 URINARY ORGANS. forming a close compact tissue, which has the effect of a parti- cular apparatus for retaining the urine, and is called Muscu- lus Sphincter Vesicas Urinaria?. Generally, anatomists have not considered this structure as distinct from the muscular coat at large; but Mr. Charles Bell, of London, whose reputation as an anatomist is well established, gives the following account of it:— "Begin the dissection by taking off the inner membrane of the bladder from around the orifice of the urethra. A set of fibres will be discovered on the lower half of the orifice, which, being carefully dissected, will be found to run in a semicircular form round the urethra. These fibres make a band of about half an inch in breadth, particularly strong on the lower part of the opening, and, having mounted a little above the orifice, on each side, they dispose of a portion of their fibres in the substance of the bladder. A smaller and somewhat weaker set of fibres will be seen to complete their course, surrounding the orifice on the upper part; to these sphincter fibres a bridle is joined, which comes from the union of the muscles of the ure- ters,"* After repeated observations on this point, I have come to the conclusion that Mr. Bell has indicated a real structure; but my own dissections have resulted as follows: The inferior semi- circumference of the neck of the bladder is surrounded by a thick fasciculus of muscular fibre, half an inch wide, running in a transverse direction, and having its ends attached to the lateral lobes of the Prostate Gland, being above the third lobe of the latter. This fasciculus is perfectly distinct from the or- dinary muscular fibre of the bladder, and resembles in its tex- ture the musculo-fibrous coat of the arteries. The superior se- micircumference is also surrounded by a thin layer of muscular fibres of an ordinary kind, forming a broad, thin band of a cre- scentic shape, the lower ends of which are insensibly lost in the adjacent muscular coat of the bladder by being spread out. And, lastly, beneath the mucous membrane of the vesical triangle there is a triangular muscle of the same size as the triangle with elongated angles, the anterior angle of which may be traced to * Diseases of the Urethra, &c. p. 10. Lond. 1820. THE BLADDER. 81 the posterior part of the caput gallinaginis, and the posterior angles to the orifices of the ureters and the adjacent part of the bladder. The texture of this muscle is, also, like that of the musculo-fibrous coat of the arteries. When a bladder is recent, this detail of structure is made out with difficulty: it requires to be previously hardened in spirits of wine. That a power exists in the neck of the bladder of retaining completely the urine, has been satisfactorily demonstrated to me in a case of fistula in perineo, which was presented to the notice of Dr. Physick and myself, a few years ago.* Occasionally there ex- ists on each side of the neck of the bladder, passing from it to the pubes, a muscle of half an inch in breadth, the effect of which is to draw the neck of the bladder towards the symphysis pubis. As the urethra of the male performs the double office of con- ducting both semen and urine, it will be described more pro- perly along with the organs of generation. The urine has a considerable number of constituents, the pro- portion of which varies according to age, health, and other cir- cumstances. Water forms about nihe-tenths of it, the remainder is an animal matter insoluble in alcohol; uric and lactic acids; lactate of ammonia; sulphate of potash and of soda; hydrochlo- rate of soda and of ammonia; phosphate of soda and of lime; and fluate of lime. • Chapman's Med. and Phys. Journ. 1824. BOOK VI. Organs of Generation. CHAPTER I. OF THE ORGANS OF GENERATION IN THE MALE. The Male Organs of Generation consist in the Testicles and in the Penis, with their appendages; or, in the language of some anatomists, in the Formative and in the Copulative Organs; which distinction has been applied to both sexes. SECT. I.—OF THE PENIS. The Penis, (Membrum Virile, Menlula,) from performing the two offices, one of which is the conducting of urine from the bladder, and the other the projection of semen into the female, has, accordingly, a peculiarity of structure, which allows it to assume a state of collapse or of erection. Its shape is almost cylindrical, but terminating in front by an obtusely pointed ex- tremity, named Glans. It adheres by its posterior end or root to the bones of the pelvis, at and below the symphysis pubis. It is formed by common integuments, by condensed cellular tissue, by the Corpus Cavernosum, and by the Corpus Spon- giosum. The skin on the penis is more thin and delicate than it is on most other parts of. the body, and is furnished with a considera- ble number of sebaceous follicles or glands about the root of the organ, with hairs growing from the centre of them. This same 84 ORGANS OF GENERATION. skin, in passing to the abdomen over the pubes, is somewhat pro- truded by a subjacent deposite of fat and cellular matter, causing an ap'pearance corresponding with the mons veneris of the fe- male; and is also generally thickly covered with short curly hair, which, as the individual advances in life, proceeds in a pointed direction to the umbilicus. The skin of the penis is but loosely connected to the organ, so that it slides readily back- wards and forwards, and by its elasticity is well suited to the varying states of erection and collapse. At the anterior ex- tremity it is thrown into a duplicature or fold; the Prepuce, (Preputium,) the internal lamina of which being fixed circularly to the penis, some distance back from the point, permits a con- siderable portion of that extremity of the penis, called the Glans, to remain uncovered when the prepuce is drawn back. The under middle part of the prepuce is attached to the extremity of the glans by^a vertical longitudinal duplicature, called the Frae- num, which extends to the orifice of the urethra. The skin does not actually stop at the circumference of the glans, but is continued smoothly over it, modified, however, so , much in its structure, as to be much more adherent, soft, deli- cate, vascular, and sentient: its cuticle there is a thin epithelium, readily separated by maceration. The projecting circular and oblique shoulder of the glans, behind which the skin becomes firmly joined to the penis, is called the Crown, (Corona Glandis.) The contracted portion, behind the corona, is the neck, (Collurn.) On the surface of the neck and the posterior face of the corona, the skin is furnished with an abundance of small glandular masses or follicles, (Glanduloz Odoriferce Tysonii,) which secrete the thick white sebaceous matter, (Smegma praputei',) that accumulates when personal cleanliness is not attended to. The penis, in addition to other modes of attachment to the bones of the pelvis, is fixed by the Ligamentum Suspensorium. The latter is a triangular vertical fibrous lamina, which proceeds downwards from the symphysis pubis to the dorsum of the penis; and, according to Mr. Colles, envelops this organ to the glans, forming its cellular coat, and being continued into the fascia su- perficialis abdominis. Posteriorly, it is lost insensibly on the fascia of the thighs, covering the adductor muscles. At its ori- THE PENIS. 85 gin it is occasionally furnished with muscular fibres; one strongly marked instance of which has been presented to me in my own dissections. The Corpus Cavernosum of the penis, forms by much the most considerable portion of the whole organ. Externally, it is a white fibrous membrane, of a dense structure, enjoying extensi- bility and an extreme degree of contractility. Its external fibres pass, for the most part, longitudinally, except about the root, where they are blended with the periosteum of the bone, and with the tendons of the muscles.' This coat of the penis is occasionally called its elastic ligament. It arises by two conical crura, from the internal face of the crura of the pubes and ischia, to within a little distance of the anterior part of the tuber ischii. At the lower part of the symphysis pubis these crura join and form a body; which, when stripped of its connexions, resembles two cylinders lying along side of each other, united; and which terminate in couimon, anteriorly, by a truncated cone, covered obliquely by the glans. At the posterior part of the corpus ca- vernosum, in its centre, there is a septum, almost complete, also of the same elastic substance, which separates the two halves from each other; but, anteriorly, this septum is more imperfect, having an arrangement like the teeth of a comb, whence the term Septum Pectiniforme has been given it. This septum is continued at its margins into a layer of circular fibres, consti- tuting the internal coat of the corpus cavernosum. In the middle of the corpus cavernosum, above, is a longitudi- nal depression for lodging the veins of the penis, and, in the same manner, there is another below, for the corpus spongiosum ure- thra?. The cavity of this membrane is filled by a spongy tissue, that arises from its internal face, and is formed of filaments and little laminae; they, by crossing each other, make a multitude of cells, which have a perfectly free communication with one an- other, and generally are somewhat occupied by blood. A fine injection through the artery of the corpus cavernosum will fill these cells and return through the veins; from which cause the cells may be considered as intermediate to the two orders of vessels. This opinion is the more probable from the cells being lined by a thin membrane like the internal one of the veins, and Vol. II.—12 86 ORGANS QF GENERATION. which is easily seen near the septum by tearing the spongy part from it The Corpus Spongiosum Urethras extends from ten or twelve lines behind the junction of the crura of the corpus cavernosum, to the anterior extremity of the penis. Externally, it has a coat resembling that of the corpus cavernosum, except that it is thin- ner, and in its centre is the canal for the passage of urine. Be- tween the canal and the coat is a spongy structure, much finer than that of the corpus cavernosum, and though the cells com- municate freely, still they have the appearance of convoluted veins. The corpus spongiosum is not of equal diameter in its whole course, for its commencement in the perineum, where it is pendulous, is enlarged into what is termed the Bulb; from this it diminishes gradually to the anterior end, where it is again en- larged into the glans penis. The Urethra is a canal, whose length varies according to the degree of erection in the penis, and extends from the neck of the bladder to the extremity of the glans. It is curved, and receives in its course the ductus ejaculatorii, the excretory ducts of Cou- per's glands, and the mucous lacunae of its own internal mem- brane. The first part of this canal which traverses the prostate gland is from fifteen to eighteen lines in length, and is called the Prostatic Portion: it is well supported by this body, although its own sides are very thin. On its inferior surface is a doubling which constitutes the Verumontanum or Caput Gallinaginis. On either side of the caput gallinaginis the canal of the urethra is depressed into something like a cul-de-sac, where are to be found the lacunae of the prostate gland. Between the Prostate and the Bulb is the membranous part of the urethra, about eight or ten lines long; it is unprotected, except by a soft covering, which seems in some measure to be a mixture of gelatinous matter and muscular fibre. The former was considered by Littre as a glandular body which secreted a viscid humour into the interior of the canal; the latter, probably, is the part described by Winslow as the inferior prostatic mus- cle ; which, arising on each side of the membranous part of the urethra, goes to be inserted into the corresponding branch of the THE PENIS. 87 pubes near the symphysis. The membranous part of the urethra does not get into the end of the bulb, but penetrates it from above, half an inch or more occasionally, from its extremity, just below the junction of the crura of the corpus cavernosum. The canal varies in its dimensions: at its commencement, which is synonomous with the neck of the bladder, it is large; it then contracts at the back of the caput gallinaginis, and imme- diately enlarges in the fore part of the prostate, at the sides of the caput. The membranous part is small; the canal then en- larges in the bulb. In the body of the penis the canal is suc- cessively diminished, till it comes almost to the glans, when it is so remarkably enlarged again as to get the name of Fossa Na- vicularis; it terminates, finally, by a short vertical slit at the extremity of the glans. In the whole length of the canal there are two whitish middle lines, one above, and the other below; and in the membranous and spongy portions, excepting the fossa navicularis, longitudinal folds of the lining membrane exist, which are effaced by disten- tion. In the upper part of the canal there are a great many mucous lacunae ;* Loder has marked about sixty-five: there is one particularly large in the upper surface of the fossa navicu- laris, which, it is said, has stopped the point of a bougie, and been mistaken for stricture.t Mr. Shaw has described a set of vessels immediately on the outside of the internal membrane* of the urethra; which, when empty, are very similar in appearance to muscular fibres. He says, he has discovered that these vessels form an internal spongy body, which passes down to the membranous part of the urethra, and forms even a small bulb there.J His preparation, being a quicksilver injection of the part, is certainly a very sa- tisfactory demonstration of its existence; yet, in my own obser- vations, where the blow-pipe has been resorted to, it has rather appeared to me to be the cellular membrane connecting the canal of the urethra with the corpus spongiosum. • Tabula Anat. ■j- Sir Everard Home has lately communicated to the Royal Society a highly interesting paper on the structure of the lining membrane of the urethra. From his microscopical observations he is induced to think that it is muscular. t Med. Chir. Trans, vol. x. 88 ORGANS OF GENERATION. The arteries of the penis come from the internal pudic; some of its veins follow the course of the arteries, and others collect into the two venae dorsales penis; the nerves come from the in- ternal and external pudics. SECT. II.--OF THE MUCOUS GLANDS AND APPARATUS. The Seminal Vesicles (Vesicidm Seminales) are two convoluted tubes, one on each side, two inches in length, placed on the lower fundus of the bladder, between it and the rectum, and be- hind the prostate gland. At their anterior extremities they ap- proach very nearly to each other, being only separated by the intervention of the vasa deferentia. They are fixed to the blad- der, and surrounded by a thick mass of adipose and cellular matter, with many blood vessels, principally Veins, passing through it. When inflated and dried, they present the semblance of cells, but are, in fact, long tubes; which, by being convoluted, are reduced to the apparent dimensions mentioned. When dissected and stretched out, they are four or five inches long, by three lines in diameter. There are also several pouches on each side of the long tube which increase the number of cells. The convolutions are pre- served by the intermediate cellular tissue. These bodies consist of two coats: an external, which is fibrous and cellular; and an internal, which is mucous, being a continuation of the lining membrane of the urethra. They are commonly filled by a drab- coloured thick fluid, supposed to be a mixture of the semen, with their own proper secretion, though, of this, Mr. Hunter doubted.* The excretory duct of each vesicle is about a line and a half long, when it joins in the substance of the prostate with the vas deferens of the same side; a common canal (ductus ejaculatorius) is thus formed, which runs parallel with its fellow, below the ure- thra.f * Observations on the Animal fficonomy. f Lately, in a dissection executed at the university by Dr. Togno, a muscle was found on the inferior surface of the seminal vesicles arising from the pros- tate gland, and inserted into them. This is said to be a common arrangement in some animals. MUCOUS GLANDS. 89 The Ductus Ejaculatorius is about eight or ten lines long, and opens by an oblong orifice, at the lateral anterior face of the Caput Gallinaginis: it is larger behind than before, which gives it a conical shape, and allows fluids injected to pass freely from the vas deferens to the vesicula, and the reverse. The Prostate Gland (Glandula Parastata*) is a body about the size and form of a horse chestnut, fixed on the neck of the bladder, and penetrated by the urethra, which traverses it much nearer its superior than its inferior surface. The base of it is turned backwards, and the point forwards; its inferior surface rests upon the rectum; it is rendered concave by that circum- stance, and its sides, in the distentions of this organ by faeces, are overlapped by it. The Prostate has, posteriorly, a notch in its centre, which divides it into two lateral lobes, and by raising the Vesiculae Seminales, we see where their excretory ducts pe- netrate the gland, and separate from the body of it, the little tu- bercle, to which Sir Everard Homef has particularly called the attention of the profession, and considered as a Third Lobe; it being certain that it is frequently the seat of disease and tume- faction. On the under surface of the canal formed in the prostate, by the urethra, is the oblong elevation called the Verumontanum, or Caput Gallinaginis. It commences a little in front of the uvula vesicae, and, being broader and higher behind, comes to a point very gradually before; it is about eight or ten lines long. Along the posterior part of this ridge is a long cleft, being the orifice of a lacuna, first observed by Morgagni; and in front of it are the orifices, bordering upon each other, of the ductus ejaculatorii. The prostate consists in a condensed, white, extensible, though easily lacerated fibrous cellular tissue, within which are placed a great number of mucous follicles, that have from eight to twelve ducts, or, according to Loder, from thirty-two to forty-four, pass- ing obliquely forwards, and terminating in the urethra, as seated, at the sides of the urethral crest, or caput gallinaginis. The fluid secreted is thick, ropy, white, and semi-transparent, in a healthy state. The prostate is surrounded by a fibrous capsule, to be described. * From 'im/ui, sto. X Diseases of Prostate. 90 ORGANS OF GENERATION. The lacunas of the third lobe penetrate the coats of the blad- der, behind the caput gallinaginis. Of the Glands of Couper.—These glands are also intended for the secretion of mucus, or a fluid very much like it, into the ca- nal of the urethra. They are two in number, one on each side, and are situated in advance of the prostate, between the laminas of the triangular ligament, at the point where the bulb of the urethra adheres to it. Commonly, they are about the size of a garden pea, but not unfrequently much smaller, and, in some in- stances, cannot be found at all, which induced Hiester to declare, that he had searched for them fruitlessly. They are yellowish, hard, and consist of several lobules united together. Each one has an excretory duct that receives readily a bristle, and passes obliquely forwards, between the corpus spongiosum and the ca- nal of the urethra, to terminate in an oblique orifice in the latter, about, an inch distant from the gland. One or more glands, of the same description, and discovered by Littre, are occasionally found just in front of Couper's. They also discharge their secretion into the adjacent part of the ure- thra. In my own dissections I have not met with them. SECT. III.--OF THE TESTICLES. The Testicles (Testes, Didymi) are two in number, one for each side of the scrotum. Being the seat of the secretion of sperm or the male prolific liquor, their function is of the first im- portance in the act of generation. They are of an oblong oval form, somewhat compressed laterally; and present their edges forwards and backwards. From being suspended near the mid- dle of their posterior edge by the spermatic chord, the upper end points somewhat forwards, while the lower one is directed in the same degree backwards. They are about an inch and a half long, by one inch in breadth, and eight or nine lines in thick- ness. They are of equal size generally, but in case of a diffe- rence it is in favour of the right; the latter is also remarkable for being suspended higher than the left, a feature in ancient statuary so universal, as to prove the vigilance and accuracy of the sculptors of those days, in regard to the proportions and THE TESTICLES. 91 peculiarities of the human form. "Two obvious advantages attend this arrangement: one, that of the testicles passing each other without collision when the thighs are brought together; and another, the facility of keeping the penis to one side, instead of straight forward in the middle line of the body."* The testicle is enveloped by several tunics; they are the Scrotum, the Dartos, the Tunica Vaginalis, and the Tunica Al- buginea. The Scrotum is merely a continuation of the common skin from the.inner side of the thighs, the perineum, and the penis, and is common to the two testicles. It is a symmetrical bag, and the two halves are marked off from each other by a middle line or elevation of the skin, called the Raphe, which begins in the perineum at the anus, and, winding around the scrotum, is continued along the under surface of the penis to the prepuce. The skin of the scrotum is thin, darker than elsewhere, but has a thick, strong epidermis; it has many sebaceous follicles in it, and is sparingly furnished with hair. It is very extensible, as manifested in fatigue, and by hydrocele ; and may be contracted again so as to draw the testicles close under the pubes, though for the latter power it principally depends upon the subjacent coat. Its surface is covered with wrinkles, for the most part transverse, and ending at the raphe: they are effaced during its great distentions in hernia and dropsy, and then it has a smooth shining surface. The Dartos is placed within the scrotum, and forms two dis- tinct sacs or tunics, one for each testicle. It arises from the inferior margins of the crura of the ischia and of the pubes, and lines the scrotum till it reaches the raphe; it is then reflected upwards to form the partition between the testicles, (septum scroti,) and terminates at the corpus spongiosum urethras. This membrane, according to the observations of MM. Chaussier, Lobstein, and Breschet,t does not exist in the scrotum till the descent of the testicle, and then appears to be an expansion of the gubernaculum testis. * Sir A. Cooper on the Testis. 1830. f Dictionnaire des Sciences Med. tome viii. 92 ORGANS OF GENERATION. It receives a considerable number of blood vessels, which, owing to the thinness of the skin, may be seen in the living body, ramifying through its substance: its general appearance is, therefore, reddish. It is destitute of fat, and consists in long fibres much matted together, and passing in every direction: they are easily separated by distention with air or water, and by slight maceration. Its powers of contraction are exceeding- ly well marked upon the application of cold to the scrotum, from which cause it has been considered by many anatomists as muscular: the only distinct evidences, however, which I have met with of a resemblance to the latter, have been found gene- rally on its posterior face, near the perineum.* From its equi- vocal character, J. F. Meckel has very ingeniously suggested that it forms the transition from cellular to muscular tissue, and that there exists between it and other muscles the same relation that there is between the muscles of the superior and of the in- ferior orders of animals. Among the latter, the fibrous structure is indistinctly marked, and is masked by gelatine; an element of the cellular tissue which envelops and conceals the fibrine, an element of the muscular tissue. The fibres of the cremaster muscle, which are next in order, form a very imperfect covering to the testicle, and belong rather to the spermatic chord: what remains to be said concerning them will be more properly introduced into the account of the latter. The cellular substance that connects the dartos and the cremaster with the tunica vaginalis forms a compact and perfect lamina, sometimes spoken of as the Tunica Vaginalis Communis Testis. There is one for each testicle, which it surrounds en- tirely, as well as its chord, and connects the chord to the mar- gins of the abdominal rings, as stated in the account of them. At its upper end it is continuous with the cellular substance that unites the peritoneum to the parietes of the abdomen, as may be proved by inflating it, when the air will penetrate according- ly through the abdominal canal. The Peritestis, or Tunica Vaginalis, was originally a process * Since the first edition, I have dissected one subject, (January, 1830,) where " the fibres were evidently muscular, though interwoven. THE TESTICLES. 93 of peritoneum, communicating with the cavity of the latter through the abdominal canal; but in the adult, it appears as a complete and distinct sac. As it is very rigidly comparable to a double night-cap drawn over the head, we accordingly find that the tes- ticle, along with the epididymis, is pushed into it from bcjhind. That portion of the tunica vaginalis which is in contact with the testicle, or rather with the tunica albuginea, adheres so closely that it cannot be separated, except very partially, and in shreds; but it may be detached easily from the epididymis, with the con- volutions of which it is in immediate contact. This sac is longer and larger than the testicle itself, from which cause it ascends for several lines above the superior end of the gland, and the " free part hangs loosely about it. Its cavity may, with but little force, be injected so as to hold an ounce or two of fluid. This membrane is smooth and polished on the surface forming its cavity, and contains a small quantity of serous halitus, which allows the opposed surfaces to glide freely upon one another. Its exterior connexion with the dartos is so slight that it may be withdrawn without dissection, with the exception of an adhesion at the lower end of the testis arising from the remains of the gu- bernaculum: in such case, however, it still continues to be in- vested by the tunica vaginalis communis, from which it can only be removed by a special dissection. The Tunica Albuginea is the proper coat of the testicle, is in immediate contact with its glandular structure, and serves to maintain its shape, as well as to protect it from pressure. From its internal surface proceed many membranous, horizontal fibres, which form partial partitions of its cavity (Septula Testis) and incline towards its posterior part, where they terminate in a lon- gitudinal projection, called Corpus Highmorianum. The latter is of a prismatic shape, somewhat broader above than below, and is of but little consequence, except that it was once errone- ously supposed to be a sinus, into which the seminiferous tubes dis- charged. Sir Astley Cooper proposes to call this the mediastinum testis, and considers the Corpus Highmorianum as being'formed by an inflection of the tunica albuginea. The Septula? Testis, he asserts, really envelop the seminiferous tubes, by forming bags which support, confine, protect, and nourish the tubular struc- Vol. II.—13 94 ORGANS OF GENERATION. ture of the testis.* The albuginea is perforated by several fo- ramina along its posterior margin, where there is a deficiency of tunica vaginalis, for the passing of excretory ducts and blood vessels. This membrane is dense, strong, white, and fibrous, resem- bling in structure the tunica sclerotica of the eye, and the dura mater of the brain. Sir A. Cooper considers the tunica albugi- nea as consisting of two layers which can be readily separated by dissection, excepting in front; the outer layer is the fibrous one, while the internal one, which he calls Tunica Vasculosa, has the spermatic arteries and veins ramifying upon it. They are rendered very distinct from each other by a minute injec- tion.t Of the Minute Structure of the Testicle.%—The glandular por- tion of the testicles consists in a congeries of convoluted tubes (Tubuli Seminiferi) amounting to 300, according to Dr. Munro; and whose aggregate length is 5208 feet. The diameter of each one does not exceed one two-hundredth part of an inch, and its length is somewhat short of seventeen and a half feet. These tubes form convolutions or hanks, the threads of which are ser- pentine, very much like the thread of a ravelled stocking; and are held together by a delicate cellular substance easily softened by maceration. Each tube forms of itself a hank or lobule, which is kept distinct from the adjacent ones by the septulae or parti- tions of the albuginea, and may be easily picked out from them. Their extreme tenuity and delicacy of structure cause them, when well macerated, drawn out with a pin, and then suspended in water, to resemble a tangled skein of fine silk. The tubuli seminiferi finally terminate in straight tubes, called the Vasa Recta, which unite near the centre, of the testicle in a somewhat complicated arrangement, obtaining the name of the Rete Vasculosum Testis. From the latter there proceed from twelve to eighteen ducts (Vasa Efferentia) which go upwards and * Observations, &c. on the Testis, p. 14. London, 1830. f Id. \ Hunter, Med. Comment, p. 1, 1777. Albinus, Acad. Annot. Lib. ii. Loder, Tab. Anat. Ruysch, Thes. Anat iv. Haller, Op. Min. tom. ii. Alex. Munro, de Testibus, Ed. 1755. THE TESTICLES. 95 backwards to penetrate the corpus Highmorianum and the tunica albuginea. Each of these vasa efferentia is then convoluted upon itself into a conical body, called Conus Vasculosus, which pre- sents its base backwards. Each cone, at its base, has its tube entering successively into the tube of which the Epididymis is formed. Notwithstanding the extreme tenuity of these several arrange- ments in the excretory ducts of the testicle, they may be entirely filled with quicksilver from the vas deferens; but the task is one of great difficulty, and rarely succeeds. The epididymis is the prismatic arch which rests vertically on the back of the testicle, and adheres to it by the reflection of the tunica vaginalis. It is enlarged at both ends, the upper of which being formed by the Coni Vasculosi, is called the Globus Major, and the lower enlargement is the Globus Minor. It is formed of a single convoluted tube, of the fourth of a line in diameter. After this tube has got to the lower end of the globus minor it becomes less convoluted, enlarges, turns upwards on the inner side of the epididymis, and obtains the name of Vas Deferens. Before it reaches the top of the epididymis it has become per- fectly straight, or almost so. There is a blind duct which be- gins at the top of the epididymis and terminates below; the ob- ject of it is not understood. Of the Spermatic Chord. The Spermatic Chord is a fasciculus of about half an inch in diameter, which may be felt very readily through the skin of the scrotum, passing from the upper end of the testicle to the exter- nal abdominal ring. It is formed by the Vas Deferens; the Sper- matic Artery and Veins; the Lymphatics of the Testicle; and the Nerves; all being covered in by the Tunica Vaginalis Com- munis, and by the Cremaster Muscle. The Cremaster Muscle, also called the tunica elythroides,* be- ing derived from the internal oblique and the transverse muscle of the abdomen,! forms a very complete envelope to the chord from • EKulpv, a sheath. f See Abdominal Muscles. 96 ORGANS OF GENERATION. the abdominal ring to the testicle. But when it reaches the lat- ter its fibres spread out and become indistinct upon the tunica vaginalis communis, as they there consist in small, pale, scat- tered fasciculi; many of which terminate insensibly, while others form on the front of the tunica vaginalis loops, having their convexities downwards. This muscle draws the testicle up- wards, an action very different from the corrugation of the scrotum. The Vas Deferens, or the proper excretory duct of the testicle, is a white tube of about a line and a half in diameter, and has a cartilaginous feel. Its parietes are thick, as its cavity will not receive a body larger than a bristle, without being put upon the stretch. It traverses a long space, and in doing so, first passes at the back of the chord from its commencement to the internal abdominal ring: having reached the latter, it then abandons the spermatic artery and vein, and dipping into the pelvis, by the side of the bladder, goes between the lower fundus of the latter and the ureter. It then converges towards its fellow, along the under extremity of the bladder, at the inner margin of the vesi- cula seminalis, of the same side, and finally terminates in the ure- thra near the neck of the bladder, by forming the Ductus Ejacu- latorius with the assistance of the duct of the adjoining vesicula seminalis. About two and a half inches from its termination, it enlarges and becomes somewhat tortuous. This duct consists of two coats: the external one is hard, com- pact, and, occasionally, fibres are seen in it; but its structure is not very evident, and is peculiar. The internal is a mucous membrane. For the description of the remaining portions of the chord, see Spermatic Artery, Vein, Lymphatics, and Plexus of Nerves. The Testicles undergo a remarkable change in their position, from the earliest development of their rudiments to the perfect fcetal state. They are not formed in the scrotum, but in the ab- domen just below the kidneys; from which position they are gradually transferred. About the middle of the third month of gestation they are two lines long, and placed behind the perito- neum, to which they loosely adhere. The vas deferens then, in- MUSCLES AND FASCIA OF THE PERINEUM. 97 stead of rising up on the side of the epididymis, goes straight down into the pelvis. At this period may be seen the guberna- culum testis, discovered by J. Hunter,* which becomes more dis- tinct in a few weeks afterwards, and assumes a triangular appear- ance. This gubernaculum has the office of drawing the testicle down into the scrotum; its point commences in the upper part of the latter, somewhat below the external abdominal ring; it passes through the abdominal canal, ascends upon the iliac us internus muscle, and is attached by its base to the inferior end of the tes- ticle. In front of the gubernaculum, a process, or small pouch of peritoneum, passes through the abdominal canal to the upper part of the scrotum. By the contraction of the gubernaculum, the testicle is brought, about the seventh or eighth month, into the scrotum, by sliding down behind the pouch. The lower end of the pouch, at which the testicle is finally arrested, becomes the tunica vaginalis testis. As soon as the testicle has reached the scrotum, the neck of the pouch has a tendency to close and to become obliterated, which is commonly accomplished at the period of birth; yet it sometimes remains open for a longer time, and becomes the oc- casion of congenital hernia. Very generally, at birth, the orifice of the pouch will receive the end of a probe to the depth of a line or two; but all below is perfectly closed, and has its structure so condensed and altered, that no one, from a view of it alone, would suppose that the cavity of the tunica vaginalis had ever communicated with that of the peritoneum.t SECT. IV.--OF THE MUSCLES AND FASCIA OF THE PERINEUM. Perineal Fascia. The Perineal Fascia is placed just beneath the skin of the peri- * Med. Comment. Lond. 1777. f The explanations and anatomy of this process have been treated at large in the following works : Ginirdi, Tabul. II. adj. Septemd. Tab. Santorini. Hunter, Observations on certain parts of the Anim^HEconomy. W. Hunter, Med. Commentaries. Edwardi Sandlfort, Opusc. Anat. Wrisberg Comment. Medic. Physiolog. &c. 98 ORGANS OF GENERATION. neum, and covers the muscles. It occupies nearly all the space between the anus and the posterior margin of the scrotum, and between the rami of the pubes and the ischia on each side: it is very firmly fixed to these bones, and is gradually blended with the cellular substance of the posterior part of the scrotum. This fascia is rather thin, but, in case of a rupture of the posterior part of the urethra, prevents the urine from showing itself in the peri- neum, and drives it into the cellular structure of the scrotum.— In abscesses of the perineum, it also prevents the fluctuation from being very evident. The Musculus Erector Penis, Is so situated, as to cover the whole of the crus of the penis which is not in contact with the bony margin of the pelvis. It arises, therefore, tendinous and fleshy, from the anterior part of the tuber ischii; its fleshy fibres adhere to the internal and exter- nal margins of the ramus of the ischium, and of the pubes, and proceed upwards: just before the union of the crura of the pe- nis, they end in a flat tendon which is lost on the side of the corpus cavernosum of the penis.* Its use is not well understood. The Musculus Accelerator Urinoz, XT- Lies on the bulb and back part of the corpus spongiosum ure- thras : it is a thin muscle, consisting of oblique fibres. It arises by a pointed production from the side of the body of the penis; its origin is continued obliquely across the inferior sur- face of the crus penis, where the latter begins to form the body of the penis. It arises, also, for an inch from the inner side of the ramus of the pubes, between the crus penis and the triangu- lar ligament of the urethra. The muscles of the opposite sides are inserted into one another by a white line, which marks the middle of the bulb of the urethra; and by a point, into the ante- rior extremity of the sphincter ani, where they are joined by the transversi perinei. * The late Dr. Lawrence informed me that he had frequently found muscular fibres between the bone and the crus penis. MUSCLES OF THE FASCIA AND PERINF.UM. 99 In order to see the origin of these muscles very distinctly, se- parate them from each other in the middle line, and dissect them from the corpus spongiosum. Cut transversely through the cor- pus spongiosum about three inches before the triangular liga- ment, and dissect it clearly from the corpus cavernosum, turning it downwards so that it may hang by the membranous part of the urethra. By putting the two acceleratores on the stretch, it will be seen that besides the origins mentioned, they arise, also, from each other by a tendinous membrane that is interposed be- tween the corpus spongiosum and cavernosum; so that they lite- rally surround the back part of the urethra, constituting a com- plete sphincter muscle for it. This account of the accelerator urinae being peculiar to myself, is adopted from a strong analogy between it and the sphincter vaginae. The two muscles are considered by M. Chaussier as forming but one: in that case its origin will be reversed, and commence in the middle line of the perineum instead of terminating there. As this muscle, and the erector penis, touch by their contiguous faces, it is difficult to get into the membranous part of the ure- thra in lithotomy without cutting through the muscular fibres of one or the other. It propels the urine and semen forward. The Musculus Transversus Perinei, As its name implies, passes directly across the perineum; it arises from the inner side of the ischium, just at the origin of the erector penis, and is inserted where the sphincter ani and acce- leratores join. I have observed tha,t when the lower part of the accelerator was extended much below its usual line, and strongly developed, that the transversus was very irregular in its origin and course; consisting frequently of a few fibres which did not deserve the name of a distinct muscle, and lying almost unappropriated in the adipose matter of the part. Occasionally, a fasciculus of muscular fibres exists, called, by Albinus, Transversus Perinei Alter, which arises in front of the transversus: it seems generally to be a fasciculus loosened of 100 ORGANS OF GENERATION. the accelerator urinae muscle, and is inserted into the perineal junction just behind it. The use of these muscles seems to be to contribute to fix the bulb of the urethra. The Musculus Sphincter Ani, Consists in a plane an inch thick, of elliptical fibres immediate- ly beneath the skin of the anus, and which surrounds the latter in order to keep it closed. The long diameter of the ellipsis is extended from the coccyx towards the symphysis pubis, and has its angles very much elongated: the anterior may be traced terminating insensibly in the posterior face of the scrotum. It has two fixed points, the last bone of the os coccygis behind, and the perineal union of the other muscles in front; its lateral dia- meter occupies about one-half of the space between the tuberosi- ties of the ischia, and it is in the middle of this space. Besides closing the orifice of the rectum it will draw the bulb of the urethra backwards, or the point of the os coccygis for- wards. The Musculus Coccygeus, Belongs to the interior of the pelvis. It arises by a small, tendinous, and fleshy beginning, from the spine of the ischium, and, lying on the anterior face of the anterior sacro-sciatic liga- ment, it is inserted into the side of the last bone of the sacrum, and of all those of the os coccygis. It draws the os coccygis forwards. It frequently happens that there is on each side a small fasci- culus of muscle arising from the inferior bone of the sacrum in front, and inserted into the bones est the coccyx; it is called Sacro-Coccygeus. A large quantity of adipose and cellular matter exists on the side of the rectum, between it and the parietes of the pelvis, con- cealing the perineal surface of the levatores ani muscles. MUSCLES AND FASCIA OF THE PERINEUM. 101 The Musculus Levator Ani, Arises, fleshy, from the back of the pubes near its symphysis, and from near the superior margin of the foramen thyroideum above the obturator internus muscle. It also arises from the aponeurosis pelvica, where this membrane is extended as a thickened semi-lunar chord from the superior margin of the thy- roid foramen towards the spinous process of the os ischium. This second part of the origin of the levator ani is defectively described in most books on anatomy. It is then seen to cross obliquely,, as far as the spine of the ischium, that portion of the obturator internus which arises from the plane of the ischium* From this extensive origin the fibres converge and descend backwards, and have three distinct places of insertion; the pos- terior fibres are inserted into the two last bones of the os coccy- gis ; the middle, and by far the greater number, are inserted into the semi-circumference of the rectum between its longitu- dinal fibres and the circular fibres of the sphincter ani; and, finally, the most anterior fibres pass obliquely downwards and backwards on the side of the vesical end of the membranous part of the urethra, and on the side of the prostate gland, and are inserted into the common place of junction of the perineal muscles. The Triangular Ligament of the Urethra, Is a membrane which fills up the space below the symphysis of the pubes, and answers there as a septum between the peri- neum and the pelvis: when closely examined, it is seen to con- nect itself to the internal edges of the rami of the pubes and ischia on the inner posterior sides of the crura penis as far down as the beginning of the latter. At its lower edge its ligamentous character is not so well defined. On its anterior surface is the bulb of the urethra, and just at the extremity of the latter, en- closed by the ligament, and adhering to. it, are Couper's Glands. In contact with it behind, and adhering, is the prostate gland, covered by its fibrous capsule, which is a continuation of the pelvic aponeurosis over it. A perforation exists in it, througli. Vol. II.—14 102 ORGANS OF GENERATION. which passes the membranous part of the urethra. This open- ing is not very apparent, in consequence of its edges being con- tinued a little distance on the canal; but by detaching them the whole becomes well defined. The relative situation of the bulb and of the membranous part of the urethra is such, that the former goes towards the anus, while the latter passes upwards towards the neck of the bladder; they, consequently, form a considerable angle with each other. The membranous part of the urethra is much the deepest, the recollection of which is all-important in lithotomy, as it teaches us to avoid the one, and to cut into the other. It may also be observed, -that the hole in the triangular ligament is an inch be- low the symphysis pubis. By removing the upper corner of the triangular ligament, we are made acquainted with another just behind it, which is total- ly distinct. This ligament is half an inch broad, is thick and strong, particularly at its lower edge, and is very firmly attached laterally to each of the pubes, just below the symphysis: it is a continuation of the ligamentous union of the symphysis pubis. Mr. Colles calls it pubic ligament, with great propriety. I would suggest, as somewhat more expressive, the term Inter-Pubic Li- gament;* as it serves to distinguish it from another called Pubic, which is above the pubes, and described in the account of the recti abdominis muscles. The breadth of this having been stated at half an inch, it is obvious that the hole in the triangu- lar ligament is half an inch below its lower edge. Pelvic Fascia. The Pelvic Fascia (Aponeurosis Pelvica) connects the bladder to the sides of the pelvis. " This fascia descends from the ileo- pectineal line to about midway in the depth of the pelvis; here it is reflected from the surface of the muscle, (the Levator Ani,) and applies itself to the prostate gland and bladder on the body of which it is ultimately lost. At the angle of its reflection, this fascia appears particularly strong.and white, but becomes more weak and thin as it lines the muscle and covers the bladder. In * See Symphysis Pubis. MUSCLES AND FASCIAE OF THE PERINEUM. 103 tracing this membrane it will be seen that from the pubes just below the symphysis, a pointed production of it, constituting its anterior margin, is fixed into the side of the neck of the bladder. This pointed production on each side is called, by most anato- mists, the anterior ligaments of the bladder. Between them, just beneath the symphysis of the pubes, a pouch large enough to receive the end of the finger, is formed by the union of the fasciae of the two sides: this pouch connects the middle anterior part of the neck of the bladder to the lower margin of the sym- physis pubis."* This fascia adheres closely to the periosteum of the pubes, between the upper margin of the thyroid foramen and the crista of the pubes; about the middle third of the linea innominata it is obviously a continuous membrane with the iliac fascia which covers the iliacus internus muscle; but behind this, again, it arises from the remaining third of the linea innominata. The portion of this fascia which Mr. Colles speaks of as par- ticularly strong and white, forms a bow, the concavity of which looks upwards, one end of the bow being fastened to the pubes above the foramen thyroideum, and the other end to the ischium above its spine. The perineal surface of this bow is an impor- tant point of the origin of the levator ani. Above the bow this fascia is very thin, for the fibres of the obturator internus can be readily seen through it. At the bow the fascia divides into two laminae; one pursuing its course to the bladder and rectum, the other covers the lower part of the obturator internus muscle, and thereby constitutes the obturator fascia. The levator ani is interposed between the two laminae. The aponeurosis pelvica also forms a bow or se- mi-lunar edge in front of the sacral nerves. The triangular li- gament and this fascia are so identified in forming the capsule of the prostate, that the latter, in description, may be referred either to the one or the other, or to both, according to the fancy of the describer. * Colles' Surgical Anatomy. 104 ORGANS OF GENERATION. CHAPTER II. OF THE ORGANS OF GENERATION IN THE FEMALE. The Copulative Organs in the female are, the Vulva and the Vagina; the Generative are the Uterus and the Ovaria. SECT. I.—OF THE VULVA. The term Vulva is applied to the most superficial of the co- pulative organs, and consists in the Mons Veneris, the Labia Externa, the Labia Interna, the Clitoris, the Vestibulum, the Orificium Urethrae, the Fourchette, and the Fossa Navicularis. The Mons Veneris is the protuberance on the fore part of the pubes. Its size varies considerably, according to the state of obesity of the subject, in consequence of its being formed by a deposite of fat between the skin and the bone: in corpulent women it is very large and prominent, whereas, in such as are much emaciated, it simply describes the outline of the bones. The skin, there, is abundantly furnished with sebaceous glands, seated in the cellular texture beneath it, and about the size and shape of millet seed. At the age of puberty a growth of hair takes place upon it, which is not so long as the correspondent growth upon men, and is not so much disposed to spread itself over the lower {jart of the abdomen as life advances. In wo- men who have abused coition, it is said that these hairs become much curled. The Labia Externa are a continuation of the mons veneris downwards in the form of an oblong eminence on either side. Their elevation is produced in the same way by a deposite of fat beneath the skin. They are somewhat broader and more prominent above than below. On the side which is next to the thigh, the integument is common skin, sparingly covered with hair; but on the other face it is a mucous membrane, being a continuation of that of the vagina. The skin here, as well as THE VULVA. 105 at the commencement of every mucous membrane, is insensi- bly changed into the latter. They have many sebaceous glands externally, and mucous glands internally, upon them. Much cellular membrane, like that of the scrotum, is found in their interior structure; whereby they enjoy great extensibi- lity in order to favour the dilatation of the parts in parturition. The rima which exists between them is the Fissura Vulvae of authors, and is about twice the length of the orifice of the vagi- na; this arrangement of it gives increased facility to the expul- sion of the foetus. The Fourehette or Frenulum Vulvas, is situated at the poste- rior commissure of the labia externa, and is a thin, narrow transverse duplicature of skin; which, owing to its weakness, is most frequently ruptured at the first act of parturition, and then disappears. The Clitoris bears, in some respects, a resemblance to the penis of the male, but is by no means so large. It is situated imme- diately below the symphysis pubis, and consists in a cylindrical body of three or four lines in diameter, with two crura. The body is an inch long; the crura are likewise of the same length, and arising from the internal face of the crura of the pubes, unite beneath the symphysis so as to form the body. The body is not straight, but has the anterior half bent downwards and forwards. The exterior covering, or capsule of the clitoris, in its texture, resembles the elastic ligamentous membrane of the corpus cavernosum penis; and is, moreover, filled within by a similar cavernous or cellular structure, which is divided into two equal parts by a septum pectiniforme, and is susceptible of distention during sexual excitement. The clitoris is supplied also with blood vessels and nerves like the penis, and is held up to the under part of the symphysis pubis by a suspensory ligament. The anterior extremity of the body of the clitoris is found in the rima or fissura vulvas, about an inch below the upper com- missure of the labia externa. It projects somewhat, and bears a general resemblance in shape with the end of the penis, whence its name of glans clitoridis; but it has not the same'or 106 ORGANS OF GENERATION. ganization, excepting the delicacy, the extreme sensibility, and" the vascularity of the skin which covers it. The clitoris has no corpus spongiosum, neither is it concerned, like the penis, in conveying the urine from the bladder. Its glans is covered by a doubling of skin called the prepuce, and is likewise furnished with the glandulae Tysoni, from which is discharged a smegna, or sebaceous fluid, as in the male. The prepuce does not fur- nish a regular well defined fraenum. The ^rector Clitoridis muscle corresponds with the erector penis. It arises from the ascending ramus of the ischium, and, covering the inferior face of the crus clitoridis, runs as far for- wards as the commencement of the body. The Labia Interna, or Nymphae, are two duplicatures of the mucous membrane of the vulva, which pass down, one on each side, from the clitoris. The prepuce of the latter terminates, on either side, in the labia; while the latter are continued up- wards, by a narrow process, to the under surface of the glans clitoris. They arise, all along their base, from the internal sides of the labia externa, or majora; and being wider in the middle than elsewhere, they terminate insensibly about half-way down the orifice of the vagina. Between the laminae of each one is placed a vascular cellular substance, susceptible of distention and of partial erection during sexual excitement. In young sub- jects, their vascularity communicates a vermilion tinge, which is lost and becomes brownish in the progress of life. As they are effaced during parturition, their chief use seems to be a pro- vision for the great distention of the vulva, which then occurs. The labia interna are about half an inch broad in the natural state, and do not project obviously beyond the labia externa ex- cept in cases of extreme emaciation, where the prominence of the latter has been destroyed by a removal of its fat. They are, however, very subject, as the individual becomes old, to a pointed elongation, increasing their breadth to an inch, or an inch and a half; and to become thickened and indurated. A tribe of Hottentots, the Boschismans, living near the Cape of Good Hope, are uniformly subject to this enlargement; which, for a long time, was represented, by travellers, as an organ su- peradded to what is common in the human species. ' f* THE VAGINA. 107 The Vestibulum is a depression of twelve or fifteen lines long, between the labia interna; it is bounded above by the cli- toris, and below by the orifice of the vagina. It is abundantly furnished with mucous lacunae. The Urethra of the female has its external orifice (Orificium Urethra) in the inferior part of the vestibulum, about one inch below the glans clitoridis, and is generally marked by a slight rising, which is easily distinguished by the sensation of touch alone; its margin is often bounded by a little caruncle on each side. The urethra itself is an inch long, larger and much more dilatable than that of the male, its course is obliquely down- wards and forwards from the neck of the bladder; passing under the symphysis of the pubes, and being slightly curved from that cause. It consists of two membranes, a lining and an external one. The lining membrane is a continuation of that of the bladder; it is thrown into several longitudinal folds, and has many mucous follicles in it. The external coat of the urethra consists of condensed laminated cellular membrane, having a strong affinity with muscular fibre: the principal direction of the fibres is transverse, forming a cylindrical body of half an inch in its transverse diameter, and which has given the idea of the existence of a prostate gland in the female: the lower and lateral surfaces of this cylinder are in contact with the vagina, forming a protuberance into its cavity; and the upper surface is firmly connected to the triangular ligament of the pubes. Im- mediately behind the neck of the bladder, we find the vesical triangle with its muscle, as in the male, excepting that the an- terior angle of it goes to the anterior end of the urethra. The Fossa Navicularis is that portion of the rima vulvae which is below the vestibulum, and anterior to the orifice of the vagina. SECT. II.--OF THE VAGINA. The Vagina is a thin membranous canal which leads from the vulva to the uterus. It is from four to six inches in length, dif- fering according to age and pregnancy, and being much shorter 108 ORGANS OF GENERATION. in women who have borne children than in virgins. It is placed between the bladder in front, and the rectum behind, being flattened by them so as to bring its anterior and posterior sur- faces into contact. Its anterior extremity is the smallest of the two; and presents its greatest diameter vertically, while that of the posterior is transverse. As it follows accurately the central line of the pelvis, it is, consequently, curved with its concavity forwards. Its anterior parietes are shorter than the posterior, both from the smaller depth of the pelvis in this direction, and from the mode of connexion with the uterus. The vagina is formed by two tunics; a fibrous and a mucous one. The first is external, of a light red colour, highly elastic, and seems to consist of condensed cellular membrane, the fibres of which are much intermixed, and pass in every direction. It is vascular, and immediately adjacent to the large venous sinuses of the pelvis. The mucous membrane being a continuation of that of the vulva, is at and near its anterior orifice of a vermi- lion tinge; while, posteriorly, it is grayish and frequently spotted, so as to give it a marbled appearance: its thickness di- minishes as it recedes from the external orifice; and upon be- ing floated in water many mucous lacunae are observable upon it. The internal surface of the vagina is commonly covered with the mucus which comes from its lacunae. On the anterior or pubic portion, it is divided longitudinally by a middle ridge, which commences by a sort of tubercle just below the orifice of the urethra, and proceeds backwards, becoming indistinct as it approaches the uterus. Transverse ridges formed in the same way by folds of the mucous membrane, arise from the sides of the last at its anterior portion, and give a roughness to that part of the vagina. The inferior side, or that next to the rectum, has the same kind of arrangement of the mucous membrane, but not so distinct. In a majority of subjects, the uterine half of the vagina is perfectly smooth, but the rule does not always hold. The Corpus Spongiosum Vagina; is an erectile tissue, like that of the penis, and closely resembles in structure the corpus spongiosum urethras. It is placed at the anterior end of the va- THE VAGINA. 109 gina, on its outer circumference, just below the clitoris, and at the base of the labia minora or interna. It is an inch broad, and a line or two thick, adheres closely to the fibrous coat of the vagina, and extends around the superior semi-circumference of the orifice, but not around the inferior. It is frequently called Plexus Retiformis. The Sphincter Vaginas Muscle surrounds the anterior orifice of the vagina, and covers the plexus retiformis. It is about an inch and a quarter wide, and arising from the body of the clito- ris and the crus of the pubes, behind the crus of the clitoris, passes backwards and downwards to be inserted into the dense, white substance, in the centre of the perineum, common to these muscles, the tranversi perinei and the anterior point of the sphincter ani. There is a strong analogy between it and the accelerator urinas of the male. The Transversus Perinei of the female, has the same circum- stances of origin and insertion as in the male, but is not quite so strong. On each side of the orifice of the vagina, near its middle, is frequently found a mucous gland, the size of a garden pea: it corresponds with Couper's gland of the male subject. The Hymen,* one of the attributes of the virgin state, is placed at the anterior orifice of the vagina for the purpose of closing it, and commonly remains until it is ruptured by vio- lence. In all cases, except where there is an unnatural adhesion, it leaves a small' orifice for the passage of mucus and of men- strual blood. In my own observations, I have found it most frequently crescentic, the convexity of the crescent presenting downwards, and the horns upwards; but in some cases, it is to one side. Next in frequency to the lunated is the circular shape, where it surrounds completely the orifice and leaves a hole in its own centre. There are some other varieties, such as its be- ing fleshy, fasciculated, unequally divided into two portions, and * J. G. Tolber. Diss, de Variet. Hymen. Haller, Icon. Anat. Fasc. i. Albin. Acad. Annot. Lib. iv. Santorini, Septemd. Tab. Vol. II—15 110 ORGANS OF GENERATION. so on, which are narrated by different writers. Being simply a duplicature of the mucous membrane, it is generally so weak as to be ruptured at the first act of copulation, or even from slighter causes during infancy; but occasionally, it becomes thickened, and so strong as to require division with the knife. After the rupture of the hymen, its place is indicated in subse- quent life by from two to six small tubercles, called Carunculas Myrtiformes, which are its remains. The peritoneum, in descending from the uterus, anteriorly, touches the top of the vagina for a little distance, and is then reflected to the bladder, but posteriorly, almost the Upper half of the vagina has a peritoneal coat before this membrane is re- flected to the rectum. The attachment of the vagina to the bladder is strong and close just about the urethra, but its con- nexion with the rectum is by rather loose cellular substance. SECT. III.—OF THE UTERUS, AND ITS APPENDAGES. The Uterus, or Womb, is a compressed pyriform body, the larger end of which stands upwards, while the lower is directed downwards, and is attached to the vagina. Unimpregnated, it is two and a half inches long, and one and a half in diameter at its widest part. The posterior face is very convex, while the anterior is almost flat, or very slightly convex. It is about one inch in thickness. It is diviCnsd by anatomists into fundus, body, and neck. The fundus is formed by its superior ex- tremity, and comprises the space between the orifices of the Fallopian tubes; the neck is the lower cylindrical portion, of about an inch in length; and the body is the part intermediate to the two. On the exterior circumference of the uterus there are no marks or lines distinguishing these several portions from each other. The uterus, being destined to lodge the fcetus from a short period after conception to the moment of birth, has a cavity ready for its reception. The shape of this cavity bears some general, but not a rigid resemblance to that of the organ itself, and is so much flattened as to have its anterior and posterior parietes in contact, or nearly so. The cavity of the body is an equilateral triangle of eight or ten lines in diameter; the sides UTERUS, AND ITS APPENDAGES. Ill of the triangle are bent inwards in parabolic curves, in such a way as to present their convexities to the cavity of the uterus: this, of course, occasions an apparent elongation of the angles. The inferior angle is continued into the cavity of the neck, while the two superior run into their respective Fallopian tubes. From this arrangement it happens that, the parietes of the uterus are only two or three lines thick on the angles of the triangular cavity, while at the middle they are from four to six lines. The cavity of the, neck has not its anterior and posterior sides so near together as that of the body; and is rather cylindrical, being smaller, however, at the upper and lower ends than in the middle. This arrangement gives to its sides a paraboloid curvature which presents its convexity outwards, differing in that respect from the corresponding curvature in the cavity of the body. The cavity of the neck terminates in the vagina by an orifice about the size of a small writing-quill, but ovoidal, and pre- senting its long diameter transversely. This orifice is the Os Tineas, or Orificium Externum Uteri; frequently, without ap- parent disease, I have seen it conoidal, with its base, half an inch in diameter, presenting downwards. The upper orifice, where- by the cavity of the neck communicates with that of the body, is not subject to such fluctuations in size: it is occasionally called Orificium Internum Uteri, and is generally somewhat larger than a small writing-quill. The os tineas is bounded before and behind by the lips of the uterus, formed by the projection of the neck into the vagina. For the most part the anterior side of the vagina is directly continuous with the anterior lip; so that its projection is very inconsiderable, and, indeed, not ap- preciable to the finger: at the same time, this lip is rather thicker than the posterior. The projection of the latter, on the contrary, is always well marked, because the vagina, instead of being inserted into its ridge, is joined to the posterior surface of its base. The cavity of the uterus is lined by a very thin mucous mem- brane, a continuation of that of the vagina. This membrane is of a light pink colour, which changes to a vermilion during the period of menstruation; it is furnished with villosities, which, though seen with difficulty in the usual way, may be rendered 112 ORGANS OF GENERATION. apparent, by floating the uterus in water; and it adheres so closely to the substance of the uterus, that it seems to form an inseparable portion of it, which can neither be dissected nor ma- cerated off entirely, as in the case of other mucous membranes. This membrane is smoothly laid upon the cavity of the body, and gives it a polished shining surface. On the cavity of the neck, it is wrinkled along the anterior and the posterior parts; there being a longitudinal line running along the centre, and on each side of this line transverse or oblique elevations or dupli- catures. This arrangement presents an arborescent appearance, technically called the arbor vitas. In the interstices of these duplicatures there are some small mucous glands or lacunas, which, as their orifices are exposed to obliteration from inflam- mation or some other irritation, become distended,into small spherical sacs by the accumulation of their habitual secretion. Naboth, from seeing them in this state, mistook them for eggs, or the rudiments of the foetus, and the error has been comme- morated by their being called Ovula Nabothi. The uterus is covered completely by the peritoneum; in the reflection of the latter, from the rectum to the bladder, it ad- heres to the uterus by a subjacent cellular substance, which al- lows it to be dissected off without difficulty. The same dupli- cature of peritoneum which encloses the uterus, is also reflected from each of its lateral margins, by their whole length, to the corresponding side of the lesser pelvis, and forms the Lateral or the Broad Ligament, (Ligamenta Lateralia, Lata.) The peritoneum, in passing from the uterus forwards to the bladder, forms, on each side, a duplicature, not very distinct, and de- pending, in a measure, upon the state of the bladder; this con- stitutes the Anterior Ligament. The same membrane, in passing from the back of the uterus to the rectum, and in co- vering the posterior superior end of the vagina, also forms, on each side, a duplicature, denominated the Posterior Li°-ament: they are always better seen than the anterior. Muscular fibres are said to be found, occasionally, between the laminae of these several duplicatures, running in the direction of the latter:* * J. F. Meckel, vol. ii. p. 605. UTERUS, AND ITS APPENDAGES. 113 they have not been presented to me in such a way as to arrest my attention. The broad ligaments, along with the uterus, form a transverse septum, passing from one side of the pelvis to the other; and contain, between their laminae, the arteries and the veins which belong to the uterus and ovaries. Resides the duplicatures of peritoneum, the uterus is retained in its position by the Ligamenta Rotunda, one on each side. These round ligaments arise from the sides of the uterus, a lit- tle below the insertion of the Fallopian tubes, and going between the laminae of the broad ligament, reach, finally, the internal abdominal ring: they then traverse the abdominal canal and the external ring after the manner precisely of the spermatic chord, and terminate by several fasciculi in the fatty cellular matter of the mons veneris and of the labia majora. The round ligaments are rather smaller in the middle than at either extremity: they con- sist of a condensed cellular or fibrous structure, and have many blood vessels in them. It has been asserted,* that they con- tain strongly marked muscular fibres; some of which come from the uterus, and others from the broad muscles of the abdomen. No evidence of this fact has as yet been presented to me, though I do not deny it; and, indeed, I think it probable, that such fibres may be developed there during gestation. The texture of the uterus is very compact, and of a cartila- ginous feel; it is composed of fibrous matter, intermixed with a great many blood vessels. In regard to its fibrous structure, there is no subject in anatomy on which opinions are more di- vided, or more authoritative and numerous on both sides of the question. Some deny its existence at any period, while others admit it as a constant condition: others, again, limit its duration only to the period of pregnancy. Without dwelling on the value of the several doctrines, and the means and obser- vations tending to support them, it may be sufficient here to mention that the structure of the uterus takes on very impor- tant and strongly marked changes, in passing from the unim- pregnated state to that of advanced gestation. In the first the fibres look ligamentous and pass in every direction, but so as to • J. F. Meckel, loc. cit. 114 ORGANS OF GENERATION. permit the uterus to be lacerated more readily from the cir- cumference to the centre than in any other course: it, indeed, manifests an indisposition to be torn in a laminated manner. The fibres, moreover, break off short, are separated by the blood vessels, and seem to contain, in their interstices, something like fibrine. In the impregnated state, on the contrary, the vessels become immensely increased in size, the laminated structure becomes very evident, and submits readily to the tearing of one layer from the other: these lamina consist of fibres, which are princi- pally parallel with each other. The muscular nature of these fibres seems to be sufficiently" proved, by their powerful con- traction in the expulsion of the foetus, and on being irritated by the introduction of the hand. They are, however, not red like other muscles, but of a very light colour as those of the bladder and intestines; and are collected into fasciculi of peculiar flatness and looseness. The development of this muscular structure is not, however, limited to the pregnant state, but it is disposed to manifest itself on all occasions which produce an increased size in the uterus. This fapt was first excmplied to me in a small scirrhus of a virgin uterus, presented by Dr. Hugh L. Hodge,* and has been still farther confirmed in a case, where the scirrhus was five or six inches in diameter; also in a virgin uterus, very much enlarged from scirrhus, presented by Dr. Charles D. Meigs. A similar fact has been noticed by Lobstein, of Stras- burg, where the tumour was also steatomatous. The fibres of the uterus, examined near the term of pregnan- cy, consist in two planes separated by the large blood vessels; one within and the other without. These layers are readily divisible into subordinate laminae, intermixed with one another, but yet to a considerable extent separable. The external layer is thicker than the internal, and both have an increased thick- ness at the fundus; while they are much diminished, and in- deed indistinct, at the cervix. The fibres generally are either circular or longitudinal, but many of them are oblique. The exterior surface of the exter- nal plane, is composed principally of longitudinal fibres, within * Now Professor of Midwifery in the University of Pennsylvania. UTERUS, AND ITS APPENDAGES. 115 which are the circular. The inner plane, on the contrary, has the circular fibres external, and the longitudinal internal. In both planes the circular fibres are more abundant at the fundus, and the longitudinal upon the body of the uterus; but, generally speaking, there are collectively more longitudinal than circular fibres. Of the Fallopian Tubes. The Fallopian tubes (Tubse Fallopianas) are two membranous canals, one on either side, fixed in the superior margin of the broad ligaments of the uterus. They serve to conduct the ru- diments of the embryo from the ovarium into the uterus. They are about four inches long, and extend from the upper angle of the uterine cavity to the side of the pelvis: their outer extre- mity is loose, and hangs upon the posterior face of the broad ligament over the ovarium, consequently, inclines downwards, thereby forming an angle with the other portion. At their uterine extremities the Fallopian tubes are about the size of the vas deferens, resemble it strongly, and scarcely ad- mit a hog's bristle; but having proceeded about one-half of their length, they begin to enlarge, and continue to do so rapidly for an inch, until they reach the size of a writing-quill; they then contract again somewhat, and immediately afterwards expand into a broad trumpet-shaped mouth. The latter has an oblique orifice, the edge of which is extremely irregular, by being re- solved into a number of ragged fringe-like processes, of unequal size and length; and which, as a whole, are called Corpus Fim- briatum or Morsus Diaboli. One of the longest of these pro- cesses adheres to the external end of the ovarium. The Fallopian tube is covered by the peritoneum, and con- sists of two coats: the external is fibrous, and bears sufficient resemblance to the structure of the uterus to be considered a continuation of it; the internal is mucous, and is likewise a con- tinuation of the corresponding one of the uterus. The external end of the tube, which is called Pavilion by the French anato- mists, is flaccid, thin, and generally in a collapsed state, as it is formed solely by the mucous membrane, assisted by the peri- toneum, neither of which furnishes resistance sufficient to keep 116 ORGANS OF GENERATION. * it expanded; but, as many blood vessels enter into its composi- tion, their turgescence, in sexual excitement, probably commu- nicates a certain degree of erection. Of the Ovaries. The Ovaries, (Ovaria, Testes Muliebres,) two in number, one on either side, are situated on the posterior face of the broad ligaments, by a duplicature of which they are surrounded, and are twelve or fifteen lines below the Fallopian tubes. Their shape is that of a compressed ovoid, about half the size of the male testicle; their long diameter is horizontal; they are sus- pended from the broad ligament rather by the edge than by the flat surface, so that they project, and are to a considerable de- gree pendulous. Their distance from the uterus varies from an inch to an inch and a half, and from the internal end of each one, there proceeds a small vascular fibrous chord, the Liga- ment of the Ovarium, which is inserted into the uterus, some- what below the origin of the Fallopian tube. From their being the seat of conception, they have, in the youthful and healthy female, a pliancy and succulency, indi- cative of their state of preparation for the act; but in advanced life they diminish much in volume and become hard and dry. Their surface, originally smooth or slightly embossed, is sub- sequently rendered uneven, by repeated acts of conception, leaving on it a number of cicatrices or small stellated fis- sures. They are of a light pink colour. Within the peritoneal coat is another, the Tunica Albuginea, of a strong, compact, fibrous texture, like the same coat of the testicle, and sending inwards many processes. The structure of the ovarium is not ascertained with entire satisfaction, though the grosser arrangement of it is known. But few females, of such as are presented in our dissecting rooms, have these parts in a state fit for study, owing to age, disease, or excessive sexuaL indulgence: my best opportuni- ties have been derived from post mortem examinations, in pri- vate, of individuals of from fourjteen to twenty, where the virgin state had been preserved. When an ovarium of the latter kind THE OVARIES. 117 can be got, by cutting through the tunica albuginea simply, and then tearing open the organ, it will be found to consist of a spongy tissue, abundantly furnished with blood vessels from the spermatic artery and vein. In this spongy tissue are from fifteen to twenty spherical vesicles (Ovula Graafiana) varying in size from half a line to three lines in diameter; the larger ones are nearer the surface, and from having caused the absorp- tion of the tunica albuginea, may sometimes be seen through the peritoneal coat, and give to the surface of the ovarium its embossed condition. The vesicles contain a transparent fluid supposed to be, or to have within it, the rudiments of the em- bryo. As the vesicles are evolved they advance from the centre to the circumference. Their parietes are thin, transparent, and have creeping through them minute arterial and venous ramifications.* The Organs of Generation in the female are supplied with blood principally from the internal pudic and other branches of the hypogastric artery: their veins run into the hypogastric. Their nerves come from the sacral and from the hypogastric plexus. * The Bladder and the Rectum, with unimportant exceptions, are the same in both sexes. The Levator Ani, the Coccygeus, and the Sphincter Ani, are also similar. The pelvic aponeu- rosis in the female, besides connecting the bladder to the sides of the pelvis, is attached to the anterior part of the vagina. The triangular ligament of the urethra also exists, but under circum- stances somewhat modified by the close connexion of the urethra with the vagina. • In an ovary exhibited to me by Dr. Hopkinson, there were thirty-six ve- sicles. Vol. II.—16 118 ORGANS OF GENERATION. CHAPTER III. OF THE LACTIFEROUS GLANDS, OR BREASTS. The Breasts (Mammae) of the female, are intended for the secretion of milk, and thereby to maintain the connexion be- tween mother and infant, for some time after the uterine life of the latter is passed. All mammiferous animals exercise this function: in birds there is a sort of substitute for it, in the changes which take place in the first stomach or crop during incubation. In the male subject, there is, also, a small glandular body on each side, which has the same organization as in the female, but is in miniature, and always remains in a collapsed state, with some rare exceptions, when it has been known to expand in volume, and to furnish a secretion, as in the female.* The Breasts are two in number, one on either side; they are situated on the same level, in front of the pectoralis major mus- cle, and between the arm-pit and the sternum. They are he- mispherical, and have their base united to the muscle by a thin lamina of loose, extensible, cellular substance, containing, even in corpulent women, but little fat. The skin which covers the front of this gland is very fine and thin, so that the blood which circulates in its veins may be readily seen. Between the skin and the front surface of the gland, there is a considerable thick- ness of cellular adipose matter, which, from its superabundance * In a male patient, now resident in the Philadelphia Alms House, the pheno- menon of a full evolution of the glandular structure in both breasts is manifested. The individual (James Mclntyre) is forty-five years of age, the breasts are as large as those of a nursing woman, but the nipples are not proportionately evolved Though his frame is robust, and well set, the voice is feminine; his external or- gans of generation are about the size of those of a boy of fourteen or fifteen. Thinking that there might be an internal state approaching to hermaphrodism, he informed me, on inquiring, that in earlier life he had the common'inclinations for the female. He also informed me that this unusual development took place seven or eight years ago, owing to an excessive salivation; but as he has a reserve on the subject, this statement may, probably, be received with some qualifications. I have also seen a second case, in which the voice is weak and feminine, but the genital organs have not been examined.—July, 1826. LACTIFEROUS GLANDS. 119 in certain individuals, gives to them an appearance of having the glands enormously enlarged. There is, however, a great variety in the size of the glandular structure itself; for in fe- males who are youthful and giving suck, they are much larger than in such as have passed the period of child-bearing, and whose health is impaired. When all the.fatty matter has been removed from a breast, and it is permitted to repose upon a ta- ble, its hemispherical shape disappears, and it then seems rather a flattened circular disk, of from four to five inches in diameter. The mamma is of a very light pink colour; and though very flaccid and yielding on being handled, its texture is actually ex- tremely tough, and is cut only by much force. With the ex- ception of bone, it dulls the knife sooner than any other tissue of the body. Its grosser arrangement consists in lobes of dif- ferent sizes, united in such a way by cellular texture, that, though they can be pulled somewhat apart, they cannot be entirely se- parated without injury. These lobes, when examined through the skin, give to the gland a knotted feel, and are sometimes partially affected by inflammation, so as to become still more distinct. The Lobes are composed of Lobuli, which are resol- vable by maceration and particular modes of treatment, into small graniform masses (acini) about the size of millet seed, and which contain the ultimate glandular arrangement. The acini themselves consist of very small oblong vesicles, united by cellular substance, and by the common blood vesels; and are said to be very apparent by the aid of a microscope in a lac- tescent gland.* Excretory Ducts (Ductus Galactophori, Lactiferi) of this gland are numerous.f They are of an arborescent shape, and be- gin by very fine extremities or ramuscles in the acini; the ramus- cles from several acini coalesce into a larger branch; several branches unite to form one still larger, and so on, successively, until a lactiferous duct, constituting, as it were, the body of the tree, is formed by this assemblage. These trunks vary considera- bly in size, according to the number of tributary branches, and having got towards the centre of the gland near the nipple, from * Marjolin, Manual D'Anat. J. F. Meckel, Manual D'Anat. X Alex. Kolpin, Diss. Inaug. de Struct. Mam. Cuboli, Append, ad Septemd. Tab. Santorini. Girardi, Append, ad Septemd. Tab. Santorini. 120 ORGANS OF GENERATION. two to four of them, according to Cuboli, run into a common stock or root, called a Lactiferous Sinus. These Sinuses are in all about fifteen: they are only a few lines long, and differ in size; some not being larger than a lactiferous duct, while others have a diameter of from two to three lines. The sinus at the end next to the nipple terminates in a sort of rounded cul-de-sac; but from the extremity of the sac a conoidal tube arises which runs through the nipple, and conducts the milk: the point of this tube is very fine, and ends on the top of the nipple. This tube, from its shape, is suited to the retention of milk; in addition to which, it is sometimes dilated in the middle, is curved when the nipple is not in a state of erection or stretched out, and terminates by an external ori- fice, which is so small as to be seen with difficulty by the naked eye. The excretory ducts of the breast, under which term may be comprehended the lactiferous ducts, the sinuses, and the conoi- dal tubes in the nipple, are formed by a soft, thin, and semi-trans- parent membrane, very capable of extension and of contraction. The trunks generally go deeply through the substance of the gland, and are tortuous, but do not anastomose laterally with one another; whence it happens that the lobes and lobules of the gland are arranged into sections, each of which has its ap- propriate excretory duct. In order to make a complete injec- tion of the gland, each sinus must be separately injected through its conoidal tube. This rule is not, however, of universal ap- plication, as in some experiments performed by the elder Meckel upon women advanced in pregnancy and during lactation, he succeeded in forcing mercury through one sinus, by its ramifi- cations, into those of another: this route was supposed to have been through the finest extremities of the ducts. The whole gland itself may, however, from the infrequency of this circum- stance, and from the difficulties and partial condition of these anastomoses, rather be considered as a congeries of smaller glands kept distinct by the interposition of cellular substance be- tween their lobes; but joined, in one respect, by having the ter- minations of their excretory tubes collected into one bunch in the nipple. This latter circumstance seems to be only a provi- sion for the more convenient sucking of the infant. LACTIFEROUS GLANDS. 121 The excretory ducts are no where furnished with valves, which accounts for the facility with which they may be injected backwards from the nipple. An opinion was entertained by Haller," and by other anatomists after him, that some of these ducts originated in the surrounding cellular substance, but this has been refuted by the researches of Cuboli. Some anatomists have thought that there is a direct communication between the ends of the lactiferous tubes and the arteries, veins, and lym- phatics. Mascagni, after a very successful injection of the gland, whereby its vesicles were filled with quicksilver, not meeting with such an occurrence, was induced to think that when the communication did happen, it was produced by rupture. The Areola, In virgins is a rose-coloured circle, which surrounds the base of the papilla or nipple. In women who have borne children, or in those whose age is advanced, it becomes of a dark brown. The skin of the areola is extremely delicate, and on its surface, particularly in pregnant or nursing females, there are from four to ten tubercles, which sometimes form a regular circle near its circumference, and in other subjects are irregularly distributed. Each of these tubercles has near its summit three or four fora- mina, which are the orifices of the excretory ducts of a little gland forming the tubercle. The areola consists of a spongy tissue beneath which there is no fat; it is susceptible of disten- tion during lactation, or from particular excitement. The greater number of anatomists have considered these tu- bercles as intended only for the secretion of an unctuous fluid which lubricates the areola and nipple, and protects them from excoriation by the sucking of the infant. It is said, however,* that when some time has elapsed after a repast, or when there has been a long interval to the nursing of the child, milk flows from them abundantly; but that in inverse circumstances a transparent, limpid fluid is distilled in small drops: all of which would tend to prove that they are of the same nature with the * J. F. Meckel. 122 ORGANS OF GENERATION. mammas themselves, being only smaller. In addition to them, it is said, that the areola and the nipple are furnished with a great number of sebaceous glands, which do not elevate them- selves above the surface, and which may be found on and near the tubercles. The Papilla, Is the truncated cone in the centre of the mamma, of the same colour with the areola, and surrounded by it. The lactiferous tubes terminate on its extremity. It is collapsed and in a very pliable state for the most part, but when excited it swells, be- comes more prominent, and of a deeper colour. Its skin is rough, and provided with numerous and very small papillas. Its internal structure consists of the extremities of the lactiferous tubes united by condensed cellular membrane. The mamma is supplied with blood from the external thoracic, intercostal, and the internal mammary arteries. Its veins attend their respective arteries. The nerves come from the axillary plexus and from the intercostals. The lymphatics run into the internal mammary, intercostal, and axillary trunks. BOOK VII. Of the Organs of Respiration. The Organs of Respiration are the Larynx, the Trachea, and the Lungs. CHAPTER I. OF THE LARYNX. The Larynx is an irregular cartilaginous tube that forms the upper extremity of the windpipe. It is situated immediately be- low the os hyoides and the root of the tongue, where it may be felt readily through the integuments, and by its prominence con- tributes to the outline of the neck. Its position is such, that it is bounded behind by the pharynx, which is interposed between it and the vertebras of the neck; and laterally by the primitive ca- rotid arteries and the internal jugular veins. It gives passage to the air which is inhaled into the lungs or exhaled from them, and also contributes essentially to the production of the voice. Its special use, on the latter occasion, has induced some anato- mists to give it a description apart from that of the other organs of respiration; but as the function of voice is subordinate to that of respiration, I have preferred an observance of its most natu- ral and local connexions. Five distinct cartilages form the skeleton of this structure: the 124 ORGANS OF RESPIRATION. os hyoides, which is common to it and to the root of the tongue, also contributes to its superior part, in a manner which will be presently mentioned. The cartilages are one Thyroid, one Cri- coid, one Epiglottis, and two Arytenoid. The Thyroid Cartilage (Cartilago Thyroidea) is the largest of the five, and being placed about one inch below the os hyoides, produces in the upper part of the neck the prominence called Pomum Adami. It consists in two lateral halves, which in most individuals are perfectly symmetrical, and are continuous with each other on the middle line of the body. These two sides form at their line of junction an angle projecting forwards, and resembling that of the canal or hydraulic gate: the superior part of the angle is more prominent than the inferior; particu- larly in the male subject. The sides of this body lean outwards, by which its transverse diameter above is increased. The angle is terminated above by a deep notch, from which the superior margin begins to form a curvature, on either side, like the letter S; the inferior margin is also somewhat curved, but to a smaller degree. The posterior margin of each half is nearly straight, but is elongated above, with the aid of the upper margin, into a long process, the Cornu Majus; and below with the aid of the inferior margin, into another process not so long, Cornu Minus. By the latter, the thyroid cartilage is articulated by ligamentous fibres called the lateral crico-thyroid ligament, to the side of the cricoid cartilage, which thereby becomes the ful- crum of many of its motions. The internal surface of each half of the thyroid cartilage is flat; but the exterior surface is slightly marked by the sterno- thyroid and the thyreo-hyoid muscles. The Cricoid Cartilage (Cartilago Cricoidea) is placed below the thyroid, and is the base of the larynx. It is an oval ring, of an unequal thickness and breadth. Its inferior margin is nearly straight and horizontal, and is connected to the first ring of the trachea; it is also thinner than the superior: the latter is very oblique, and rises from before backwards and upwards so abruptly, that the breadth of the cri- coid cartilage behind becomes three times as great as it is in THE LARYNX. 125 front, under the inferior margin, of the thyroid cartilage. The superior margin has on each side, behind, a little head, or con- vexity, which receives the base of the corresponding arytenoid cartilage, and forms with it a ball and socket joint. The interior surface of the cricoid cartilage is smooth, and covered by the lining membrane of the larynx. lis exterior surface is flattened on each side behind, by the posterior crico- arytenoid muscles; it is marked also laterally by other muscles, and by the inferior cornu of the thyroid carl i lane. The cricoid cartilage is embraced by the inferior margin of tlie thyroid, but in such a way that a triangular interval is left in front between the two cartilages This interval is filled by a ligament adhering to its margins called the middle Crico-Thyroid, to distinguish it from the li- gamentous junction between the inferior cornua of the thyroid, and the sides of the cricoid. The middle ligament has some small apertures in it for the passage of blood vessels and of nerves. It is the part commonly cul in the operation of laryn- gotomy. The Arytenoid Cartilages (Carlilagines Arytanoidea) re- semble triangular pyramids curved backwards, and about six lines long. They are placed on the upper margin of the cri- coid cartilage behind. The anterior face of each is uneven, and divided into two concavities; the posterior face forms a single cylindrical concavity; and the internal face, by which it approx- imates its fellow, is nearly flat. When joined together, the two cartilages resemble the mouth or spout of a pitcher, from whence their name. Their bases are hollowed into a small gle- noid cavity, for articulating with the cricoid cartilage. A synovial capsule is reflected over the articulation, between the arytenoid and the cricoid cartilage: this capsule is strength- ened by a few scattered ligamentous fibres. The Epiglottis Cartilage (Epiglottis) is situated on the pos- terior face of the base of the os hyoides, being enclosed partial- ly by the two sides of the thyroid cartilage. Its general form is that of an oval disk; the upper margin of it is thin and round- Vol. II.—17 126 ORGANS OF RESPIRATION. ed, and the lower part is elongated into a pedicle which adheres to the entering angle of the thyroid cartilage. Its surfaces, though nearly flat, are not fully so; for, anterior- ly, it forms a cylindrical convexity, and posteriorly, a cylindri- cal concavity, from side to side. When nicely stripped of its covering, a number of very small foramina are seen to exist in it, which give passage principally to the ducts of muciparous glands. Its connexions, aided by its natural elasticity, keep it in a vertical attitude behind the base of the tongue; its round- ed margin is elevated above the latter, and overlooks it. In addition to the preceding cartilages, there are always two, and sometimes four others. On the top of each arytenoid is to be found one, (Corniculum Laryngis:) it is somewhat trian- gular and elongated; its inferior face is attached by a few liga- mentous fibres to the end of the arytenoid; it is included in the soft parts, and is very moveable. The others, when they exist, are found on the margin of the glottis, in the duplicature of the membrane which is extended from the side of the epiglottis to the tip of the arytenoid cartilage. From the whole superior margin of the thyroid cartilage in- cluded between its greater cornua, there proceeds upwards a thin lamina of somewhat condensed cellular substance, which is attached to the inner margin of the base and of the cornua of the os hyoides their whole length. It fills completely the space between the os hyoides and the thyroid cartilage. This mem- brane is called the middle Thyreo-hyoid Ligament, (Ligament. Thyreo-Hyoid. Medium,) though its ligamentous character is by no means well developed. It completes the periphery of the larynx in the space alluded to, and, from its thin yielding nature, presents no obstacle to the motions of the os hyoides and of the thyroid cartilage upon each other. The posterior margin of this membrane, on each side, is bounded by a long, rounded, fibrous chord, the Lateral Thyreo- Hyoid Ligament, (Ligamentum Thyreo-Hyoideum Laterale.) The latter is extended from the cornu major of the thyroid car- tilage to the tuberculated extremity of the os hyoides, and fre- quently contains, about its centre, a small, oval cartilage or THE LARYNX. 187 bone, (Cartilago-Triticea,) not quite so large as a grain of wheat. Immediately under the body of the os hyoides, between its concave face and the middle thyreo-hyoid ligament, is a small sac or cell formed between the laminae of the ligament, and fre- quently extending itself downwards as far as the notch of the thyroid cartilage; it is flat about four or five lines in its trans- verse diameter, and presents a shining surface. I have never seen a fluid in it in the natural state; its secretion, however, sometimes becomes excessive, and it is then elongated down- wards over the front of the thyroid and of the cricoid cartilage, as far as the isthmus of the thyroid gland. In this state it fre- quently forms a small fistulous opening, at its lower end, through the skin, which is marked by a fold of the latter across the neck. The true pathology of the disease was first pointed out by Dr. Physick, who cures it, in some cases, by the introduc- tion of lunar caustic, and in others by extirpation. The Thyreo-Arytenoid Ligaments are two in number, on each side of the larynx; one above the other, at the distance of three lines. The inferior is extended from the anterior angle of the base of the arytenoid cartilage to the inferior part of the entering angle of the thyroid, and, by converging towards its fellow, is inserted there in contact with it. Its fibrous structure is very distinct. It also bears the name of Ligamentum Vo- cale, from its bordering the rima glottidis. The superior thy- reo-arytenoid ligament arises from the middle of the anterior edge of the arytenoid cartilage, and is also inserted into the en- tering angle of the thyroid; it is more distant from its fellow than the lower one, and goes almost parallel with it; so that the opening between the two is both larger and more like an ob- long. Its fibrous structure is less distinct than that of the lower. Both the upper and the lower ligaments are covered by a re- flection of the lining membrane of the larynx, and are small, round fibrous threads, which are rendered more or less tense by the action of the small muscles of the larynx. The superior thyreo-arytenoid ligament is attached, in its whole length, by a triangular fibro-muscular layer to the pedi- cle of the epiglottis: the posterior margin of this layer is dis- 128 ORGANS OF RESPIRATION. tinctly muscular, and must have the effect of drawing the liga- ment upwards. There are several pairs of muscles belonging to the larynx. 1. The Thyreo-Hyoideus, as observed in the former account of this muscle, looks like a continuation of the sterno-thyroideus. It arises, obliquely, from the side of the thyroid cartilage by the ridge, there; and running upwards, it is inserted into a part of the base, and into nearly all the cornu of the os hyoides. When the thyroid cartilage is fixed, it draws down the os hyoides; but when the latter is fixed, it draws up the thyroid cartilage. 2. The Crico-Thyroideus arises, tendinous and fleshy, from the the anterior lateral surface of the cricoid cartilage, and passes upwards and backwards, to be inserted into the inferior cornu of the thyroid cartilage, and the adjacent part of its inferior edge. Use, to draw these cartilages obliquely together. 3. The Crico-Arytenoideus Posticus arises from the back of the cricoid cartilage, occupying its excavation, and is inserted into the posterior part of the base of the arytenoid cartilage. It draws the arytenoid backwards, and makes the ligaments tense. 4. The Crico-Arytenoideus Lateralis arises from the side of the cricoid cartilage, and is inserted into the side of the base of the arytenoid. Use, to draw the latter outwards, and open the chink of the glottis. 5. The Thyreo-Arytenoideus arises from the posterior face of the thyroid cartilage, near its angle, and the middle crico- thyroid ligament, and is inserted into the anterior edge of the arytenoid cartilage. Use, to relax the ligaments of the glottis. THE LARYNX. 129 6. The Arytenoideus Obliquus arises from the base of one arytenoid cartilage, and is inserted into the tip of the other. It is a very small fasciculus, and sometimes only one muscle exists. Use, to close the chink of the glottis. 7. The Arytenoideus Transversus is always a single muscle, which arises posteriorly from the whole length of one arytenoid cartilage, excepting a little part of the tip, and is inserted, in a corresponding manner, into the other. It fills up the cylindri- cal concavity of the arytenoid cartilages. Use, to close the chink of the glottis. 8. The Thyreo-Epiglottideus consists in a few fibres, and arises from the posterior face of the thyroid cartilage near its entering angle. It is inserted into the side of the epiglottis. Use, to draw the epiglottis downwards. 9. The Aryteno-Epiglottideus consists also in a few indis- tinct fibres, and arises from the^superior lateral parts of the ary- tenoid cartilage. It is inserted into the side of the epiglottis. Use, to draw the epiglottis downwards. These two last muscles are generally so small and undefined, that they cannot be satisfactorily distinguished from the adja- cent soft parts. On the posterior face of the thyroid cartilage, of the middle thyreo-hyoid ligament; and on each side of the epiglottis carti- lage, surrounding its lower part with the exception of its poste- rior face, there is an accumulation of cellular and adipose sub- stance. In the lower part of this substance there are several small glandular bodies, sometimes insulated and sometimes col- lected together, which detach their prolongations into the fora- mina of the epiglottis cartilage, and seem to open thereby on its laryngeal surface: they are mucous glands. The Arytenoid Gland, which is also muciparous, is situated in front of the arytenoid cartilage, in the duplicature of the mu- 130 ORGANS OF RESPIRATION. cous membrane which passes from the side of the epiglottis car- tilage to the arytenoid. It is a small body of a grayish colour, resembling the letter L, and consists in distinct grains: it is supposed to have its excretory ducts opening into the larynx. It is frequently wanting. The Interior Face of the Larynx is lined by a mucous mem- brane, continuous above with that of the mouth and pharynx, and below with that of the trachea. Where it is reflected from the base of the tongue to the epiglottis cartilage, it forms, as described, a well marked vertical fold or fraenum in front of the middle of the latter, and on each side of this middle fold there is another, not so distinct, but varying in different sub- jects. Beneath the middle fold is the strong fibro-muscular connexion with the root of the tongue.* The three folds form two pouches in front of the epiglottis, in which food is some- times lodged. The mucous membrane also forms the duplica- ture on each side already alluded to, which passes from the la- teral part of the epiglottis cartilage to the arytenoid of the same side of the body. This duplicature forms the superior boundary of the cavity of the larynx, and is very soft and extensible, per- mitting freely the epiglottis to be depressed and to rise again into its vertical position. The duplications of the two sides, taken together, form an oblong oval opening into the larynx, passing very obliquely upwards and forwards to the epiglottis, and terminated behind by a notch between the cornicula laryn- gis. At the latter place the mucous membrane is wrinkled and loose, so as to permit, by its extensibility, free motion to the arytenoid cartilages. * A muscle of a triangular shape has lately been observed by the English ana- tomists,! situated in front of the epiglottis, passing to it from the base of the os hyoides: it is called Hyo-Epiglottideus. The observations on its existence have not yet been repeated sufficiently often to determine whether it belongs to the normal structure of the body or not; and in my own dissections, for the purpose of ascertaining its existence, it has not occurred. Albinus, Soemmering, and others, speak of the occasional existence of muscular fibres there. A strong mus- cle is found there in the lower animals, as stated in the description of the tongue, vol. 1st. t Am. Med. Jour. vol. v. p. 475. THE LARYNX. 131 After adopting the preceding arrangement, the lining mem- brane of the larynx passes downwards; it covers smoothly the posterior face of the epiglottis, adhering closely to.it; but, when it reaches the thyreo-arytenoid ligaments, it is tucked in be- tween the upper and the lower one, so as to form, on either side, an oblong pouch, the bottom of which is broader than its ori- fice between the ligaments. This pouch is the ventricle of Galen, or of Morgagni, or of the larynx; it projects into the fatty glandular matter on the posterior face of the thyroid car- tilage, and has its base resting on the thyreo-arytenoid muscle. Its superior end reaches almost as high as the upper margin of the thyroid cartilage, and it has some small fasciculi of muscular fibres on its interior which seem appropriated to its use. The continuation of the membrane afterwards lines smoothly the cricoid cartilage, and abounds there in mucous follicles. That portion of the larynx which is formed by the thyreo- arytenoid ligaments, and the pouches between them, is the structure essential to the formation of voice. The opening be- tween the two lower ligaments is the Rima Glottidis, and the space between the upper ligaments and the duplicature of the mucous membrane passing from the arytenoids to the epiglottis cartilage, may be termed the Glottis. The Epiglottis Cartilage is principally useful in preventing articles of food from falling info the glottis, either in swallow- ing or in vomiting. The strength of its muscles, however, does not seem to be sufficient to draw it down over the glottis, as many physiologists suppose; on the contrary, I am induced to believe that the glottis is rather drawn upwards to it. If, on any occasion, it be depressed or bent down over the glottis, the position must be caused by mechanical pressure from the bulk of the article swallowed. But the latter explanation is not suf- ficient to account for the swallowing of fluids, or of a verv small body, as a pill or a crumb of bread. Impressed with these objections, and unsatisfied with the common theory, I had an opportunity, in a dissection a few years ago, of witnessing a position of these parts which afforded a satisfactory explanation. The subject was a robust, muscular man, who had died suddenly. The upper orifice of the glottis was closed and protected, but by an arrangement precisely the 132 ORGANS OF RESPIRATION. reverse of the received opinion; for the epiglottis, retaining its naturally erect position, with a slight inclination backwards, had the opening of the glottis drawn up so as to come in contact with its posterior face. The cricoid cartilage, as has been men- tioned, slopes on its superior margin upwards and backwards; the front surfaces of the arytenoid cartilages, in their natural position, are nearly on a line with this slope, or a continuation of it; the whole may, therefore, be considered in the light of an oblique plane, rising up behind the epiglottis cartilage. By a very slight additional elevation of this plane along with the rotatory motion of the thyroid cartilage upon its lesser cornua, the plane is caused to come in contact with the posterior face of the epiglottis, and thereby to close the upper opening of the glottis. The principal agents in this motion are the thyreo-hyoid mus- cles, the contraction of which, causing the larynx to ascend, the opening of the glottis is brought up behind the epiglottis, and thereby secured from the introduction of food into it. Whether the food be passed from the mouth into the stomach, as in swallowing, or from the stomach into the mouth, as in vomiting, is^equally unimportant; and the security is the same, whether the article be small or large, fluid or solid. Several years ago, I dissected a gentleman who had symptoms of sore throat with swelling of the neck, superadded to those of pulmonary con- sumption: during the existence of his sore throat, in addition to the usual difficulty of swallowing, he was frequently affected in the act, with strangulation to an alarming and distressing de- gree. In the dissection, it was found that an abscess, of con- siderable extent, existed between the os hyoides and the thyroid cartilage, and involved the thyreo-hyoid muscles. Without knowing at the time the value of this observation, I am now persuaded that the strangulation arose from the inactivity of the thyreo-hyoid muscles. In some ulcerations of the epiglottis cartilage, which I have had an opportunity of seeing, the up- per circular portion, which projects above the root of the tongue has been lost; if the accident be confined to that extent only, deglutition is not much impaired, because still enough of the epiglottis is left to perform the office assigned to it, as the up- per part is less essential. The cases of its reputed loss by wounds. THE TRACHEA. 133 must be considered as applying themselves to this upper portion only, because a wound low enough to remove the whole body, would cause such a destruction of the rima glottidis, as to produce an embarrassment of respiration, incompatible with life. It is probable that the inferior constrictors of the pharynx, as well as the stylo-pharyngeal muscles, assist in this use of the thyreo-hyoidei. There is a well marked difference in the larynx of the two sexes. In the female, it is generally smaller by one-third than it is in the male; the thyroid cartilage is also less prominent, in consequence of its two halves uniting at an angle more obtuse, the pomum Adami is, therefore, seldom conspicuous. The rima glottidis is also smaller in women. The nerves of the larynx come principally from the superior and the inferior laryngeal branches of the par vagum. CHAPTER II. OF THE TRACHEA, AND THE GLANDS BORDERING UPON IT. SECT. I.—THE TRACHEA. The Trachea, or Aspera Arteria, is a cylindrical canal of four or five inches in length and about nine lines in diameter, com- municating with the lungs for the transmission of air. It opens into the larynx above, by being attached to the inferior mar- gin of the cricoid cartilage, and terminates in the thorax oppo- site the third dorsal vertebra, by two ramifications called Bron- chiae. In this course it is situated over the middle line of the neck, beneath the sterno-thyroid muscles, and separated from them by the deep-seated fascia of the neck and the adipose mat- ter beneath it. It is placed in front of the oesophagus, between the primitive carotid arteries and the internal jugular veins. When it has got into the thorax, it inclines slightly to the rieht Vol. II.—18 6 134 ORGANS OF RESPIRATION. side as it passes behind the curvature of the aorta. Of its two branches, the right bronchia is larger than the other; it is also less slanting, and an inch long before it divides; it sinks below the right pulmonary artery, to penetrate the lung about the fourth dorsal vertebra. The left bronchia being an inch longer, sinks into the lung of the left side, below the corresponding pulmonary artery, and opposite the fifth dorsal vertebra. The bronchiae then'divide and subdivide very minutely through the lungs. Very dissimilar structures enter into the composition of the trachea; they are cartilage, ligamentous fibre, muscle and a mu- cous membrane. The Cartilage preserves the cylindrical shape of the trachea, and consists in from sixteen to twenty distinct rings, which are deficient in the posterior third of their circumference. Each ring is about two lines broad, and half a line thick, and is kept apart from the one above and below it by a small interstice; sometimes, however, they run into each other. There is an almost uniform similitude between these rings; the principal departure from which is observed in the first being ra- ther broader in front than the others, and in the last ring, which, by its corset-like shape in front, contributes to the beginning of each bronchia. The rings of the Bronchias are, like those of the trachea, defi- cient in their posterior third, and the same arrangement holds during their primitive ramifications in the lungs. But as they sub- divide more and more, the cartilages do not succeed each other so closely, and are smaller segments of circles, they are not re- gularly deficient at the posterior third; but, in place of the latter, the whole periphery of the bronchial ramification is cartilage, and the latter consists in several pieces put end to end. The pieces become, after awhile, more and more scattered and small- er, till they finally disappear, and the bronchia is simply mem- branous. At the orifice of each branch of the bronchia, there is a semi-lunar cartilage, forming rather more than one half of its circumference, and having its concave edge upwards. The whole arrangement resembles somewhat the pasteboard to an eared bonnet, and is evidently to keep the orifice open. THE TRACHEA. 135 The Ligamentous Structure of the trachea and of the bron- chiee is very evident between the proximate margins of the car- tilaginous rings, and fills up the intervals between them so as to make the tube perfect. This tissue may be traced over the sur- faces of the rings, forming their perichondrium, so that they may be considered as embedded in it, It does not exist, satisfactorily, in the human subject, in the interval behind, where a third of the ring is defective, its place being supplied by a condensed cel- lular substance; but in the bullock it is there also. In the small- er ramifications of the bronchias, where a complete circle is formed by the juxta-position of the several little cartilaginous seg- ments, it is probable that this tissue contributes to the whole pe- riphery of the ramification. It possesses great elasticity, which is manifested by the rapid shortening of the trachea, when its two extremities are stretched apart and then suddenly let loose. And it is the continuance of this quality of elasticity, in the minute ramifications of the bron- chias, which proves the existence of this tissue there, even when it cannot be very distinctly seen. The Muscular Structure of the trachea exists at the cartilagi- nous deficiency in its posterior third, and consists in a thin mus- cular plane whose fibres pass transversely between the interrupt- ed extremities of the cartilaginous rings of the trachea and of the bronchias. These transverse fibres begin at the first ring, and exist all the way down to the lungs: they rise from the internal faces of the rings, and the intermediate elastic ligamentous tis- sue ; about a line beyond their extremities. Anteriorly, they are covered by the lining membrane of the trachea, and posteriorly, by the cellular tissue just spoken of. In the lungs, where the cartilages become scattered and irre- gular, the muscular fibres are said, by J. F. Meckel, and by M. Reisseissen,* to perform the whole circuit of the bronchial rami- • De Fabrica Pulmonis. Berlin, 1822. M. Laennec says (Traite, de 1'Ausculta- tion, Paris, 1826, vol. ii. p. 189,) that he has sought in vain to verify these obser- vations of Reisseissen, but that the manifest existence of circular fibres upon branches of a middling size and the phenomena of many kinds of asthma, induce him to view, as a thing well established, the temporary occlusion of the small bronchial ramifications, by a spasmodic contraction of their parietes. 136 ORGANS OP RESPIRATION. fication, and to be visible even beyond the existence of the carti- laginous pieces. Soemmering expresses a doubt of this arrange- ment* It is very difficult in such minute structure to arrive at a satisfactory conclusion; careful observations, latterly made, have, however, induced me to adopt the same conviction as Reis- seissen. Longitudinal fibres are also said by Portal to exist be- tween the contiguous margins of the cartilaginous rings, but the fact is far from being ascertained.t The use of this muscular tissue has been pointed out, by Dr. Physick, as follows:—" In expectoration, it diminishes the caliber of the air tubes, so that the air having to pass out with increased rapidity through them, its momentum will "bring up the inspissated fluid which may be in its way." This very ingenious theory has subsequently been advanced by M. Cruveilheir, of Paris, possibly without a knowledge of his having been anticipated; but cer- tainly not without the claims of the eminent individual to whom we owe it, having been established by its publication/]; The Mucous Membrane of the trachea lines its whole interior periphery, from the larynx to the bronchias, and is continued, un- der the same circumstances, through the latter to their minute divisions. It adheres very closely to the contiguous structure, and is continued, in the substance of the lungs, beyond the traces of any of the other tissues which compose the trachea; it indeed terminates in the air cells. It is very vascular, like other mu- cous membranes; and also, like them, the venous appears to pre- vail over the arterial vascularity. A successful minute injection makes it look as if it consisted of a tissue of blood vessels; thin and red, it presents an abundance of slightly elevated longitudi- nal folds: one of the latter, conspicuous for its greater size, ex- ists at the commencement of the left bronchia, and is yet more developed in the still-born infant. The exterior circumference of the mucous membrane is stud- • Extimst autem vel posticx ejus fibrx per longitudinem, a cartilagine cricoi- dea ad pulmones usque descendunt ac, vel in ipsis tracheae ramis haud parum conspicui sunt.—De Corp. Hum. Fabrica. f Anat. Med. * Wistar's Anatomy, 3d edition, vol. ii. p. 64. Phil. 1821. THE THYROID GLAND. 137 ded with muciparous glands, about the size of millet seed. These glands are particularly conspicuous and abundant on the poste- rior part of the trachea and of the bronchias, where the deficien- cy of the cartilaginous rings is supplied by the membranous struc- ture only; and more of them exist at the lower part of the tra- chea and upon the roots of the bronchias than elsewhere. They are placed behind the muscular layer, which their excretory ducts have to penetrate. Besides occupying these situations, they are found in the interstices between the cartilaginous rings, but here they are much smaller. The mucous membrane abounds so much in the orifices made by their excretory ducts, that it looks cribriform, which appearance is increased by floating it in water. About the origins of the bronchias, there is a considerable num- ber of black coloured lymphatic glands, called Bronchial, which it is easy to distinguish from the preceding by their colour and much greater size. There are two more glands of a different character, which, though they do not enter into the composition of the trachea, yet, from their locality, are most conveniently studied at this time: they are the Thyroid and the Thymus. SECT. II.--OF THE THYROID GLAND. The Thyroid Gland (Glandula Thyroidea) is placed on the first and second rings of the trachea, and on the sides of the larynx. It consists in a middle portion, which is thin, of variable mag- nitude in different individuals, sometimes entirely wanting, and which, being stretched across the upper part of the trachea just below the larynx, is called its isthmus; and of two lobes, one on each side, which, being flattened and ovoidal, are extended up- wards on the side of the larynx, and downwards on the side of the trachea and of the oesophagus. Frequently from the superior part of the isthmus, and most commonly on its left side, a small pyramidal process runs upwards in front of the cricoid and of the thyroid cartilage, and is attached, by ligamentous fibres to 138 ORGANS OP RESPIRATION. the os hyoides; this process, however, varies much in size and length: I have never seen it double. According to Morgagni and Meckel, its existence is much more common than its ab- sence, which corresponds with my own observations. The thy- roid gland, when extended, measures about three inches from side to side. It is covered in front by the sterno-hyoid and thyroid muscles, and laterally by the omo-hyoid and the sterno-mastoid. Em- bracing the trachea and the sides of the larynx, its lobes repose upon the primitive carotids, and the internal jugular veins. The thyroid gland has a capsule which is not very easily raised up, but serves to give it a polish; it is also invested by the con- densed cellular membrane of the part called fascia profunda colli. Its surface is smooth and uniform. It is of a dark brown colour. When cut into or torn, it is seen to consist of several lobules adhering to each other: but this arrangement is not very distinct, except in an enlarged or diseased state; and may be traced most easily by following the course of the large blood ves- sels, which pass in the interstices between the lobules. The lat- ter contain many small vesicles, or cells, filled with a transparent or yellowish and somewhat unctuous fluid; the cells are fre- quently in a collapsed state, which prevents them from being ma- nifest to the naked eye. There are four considerable arteries which supply this body, two on each side, one coming from the external carotid and the other from the subclavian. The veins follow the course of the arteries for the most part. Bichat has made a very interesting remark on the subject of its blood vessels; that, notwithstanding their size and number, and minute ramifications in it, much less blood remains in its capillary system than in that of the liver or kidney, as is proved by the quantity of water it tinges in mace- ration ; he, therefore, infers that the capillary system is less abun- dant. Anatomists have sought in vain for one or more excretory ducts to this body, and some have imagined that they had found them terminating in the trachea, or in the larynx. Santorini con- sidered the pyramidal process from the isthmus as the desired duct The emphysema with which the gland has sometimes been affected, was supposed to be a proof of its communicating THE THYMUS GLAND. 139 with the trachea by excretory tubes; but it is more probable that the air was forced into the cellular substance, uniting its lobules, and not into the structure itself of the gland. The settled opi- nion now seems to be, that whatever fluid it secretes is conveyed away by the lymphatic vessels. Meckel has suggested, that as this gland is more voluminous proportionately in early infancy, particularly its pyramidal process, possibly the duct may be ob- literated when the gland begins to be restrained- in its growth; but if this were the case, the duct ought to have been found during the period indicated. The probability is, that it is a di- verticulum of blood from the salivary glands during the inter- in ittence of their action; and from the marked sympathy between it and the brain in goitre, it may exercise a corresponding func- tion on this organ during its intervals of repose. Duverney* has described a small azygous muscle on the mid- dle line of the body, coming from the under margin of the base of the os hyoides, and running over the middle of the thyroid cartilage, to be inserted into the upper margin of the isthmus of the thyroid gland. Soemmering calls it Levator Glandulas Thy- roideas, and speaks of it as being fodhd more frequently on the left side, and about half of the breadth of the thyreo-hyoideus. After many special examinations for it I have found it in but few instances; I, therefore, consider it rare; though without a close attention to structure, the pyramidal process of the isthmus of the gland may, from the similitude of colour and position, be very readily mistaken for it, which I have reason to believe is frequently the case.f Some few fibres are often found going to the isthmus of the gland from the crico-thyroid, and the thyreo- hyoid muscles, or from the thyroid cartilage. SECT. III.--OF THE THYMUS GLAND. This body'(Glans Thymus) is placed between the trachea and • Essai D'Anatomie en tableux imprimes, pi. IV. Paris, 1745. f The unassisted eye, in a strong light, is generally sufficient to determine the structure; but in case of doubt, by boiling the gland, if there be muscular fibres along this process, their longitudinal and parallel direction will become evident: they also may then be torn asunder, so as to be made still more distinct; whereas, the vesicular structure of the gland is not susceptible of division into fibres. 140 ORGANS OF RESPIRATION. the upper extremity of the sternum. It is irregularly triangular, its broadest part being above, and the narrower below. In the adult, it is in a collapsed and shrivelled state, and scarcely pre- sents a vestige of what it once was; it is, therefore, only in the infant that it can be satisfactorily studied. At birth, it is much larger, not relatively, but actually, than it is in the adult, and extends from the body of the heart up to the thyroid gland. It is of a very soft consistence and of a pink co- lour. It is surrounded by a capsule of cellular substance, which, when removed, permits the gland to be resolved into two lobes, one on either side, which adhere to each other. These lobes may be separated with facility into lobules, and contain a whitish fluid. A good Essay on the structure of this gland, has latterly been published by the distinguished British surgeon and anatomist, Sir Astley Cooper,* illustrated by excellent plates. From this it ap- pears that the lobules of the gland are formed of vesicles of va- rious sizes, all discharging into a duct which runs from one end of the gland to the other, the consistence of which duct is ex- tremely feeble. This duc\ and the vesicles may be filled with an injection, by means of a pipe introduced into the substance of the gland. A large lymphatic trunk passes from the gland, on each side, into the transverse vein. Sir Astley thinks, or,' rather, asks, whether this gland does not prepare a fluid fpr fcetal nourishment, in the absence of proper chylification, during foetal life? inasmuch as all the elements of theblood are upon chemical analysis, found in the fluid contained in its cavities. It is visible in the third month of gestation, and continues to grow till the end of the second year of extra-uterine life. It then collapses, and its structure is effaced about the twelfth year; its remains are scarcely distinguishable subsequently from the sur- rounding cellular substance. No excretory duct has been found for it, unless we may consider as such the lymphatic trunk al- luded to by Sir Astley Cooper, and, though it clearly belongs to fcetal and infantile existence, its use is problematical. The pro- bability is, that it is a diverticulum of blood from the lungs * London, 1832. THE LUNGS. 141 during their state of quiescence in foetal life, and until their struc- ture becomes confirmed and proportionately evolved. CHAPTER III. OF THE LUNGS. The Lungs (Pulmones) are the essential seat of the process of respiration, and occupy the greater part of the cavity of the thorax, as formed by the ribs and the intercostal muscles on the sides, by the sternum and its cartilages in front, by the dorsal vertebras behind, and by the diaphragm below. They are two bodies, placed one on either side of the thorax, and se- parated from each other by the heart and its great vessels. As the heart is the only organ of much volume which is also in- cluded in the cavity of the thorax, the size of the lungs is in a direct relation with the capacity of the latter; and may, therefore, be known by external indications in the living body. It is probable that there is no void, or only a very small one, be- tween the sides of the lungs and the sides of the thorax. Each lung forms an irregular cone, the apex of which is above, and the base below; the latter, from resting upon the diaphragm, is, consequently, oblique from before backwards and downwards, and is also concave. The surface which reposes against the pe- riphery of the side of the thorax, is uniformly rounded, but that which looks towards its fellow, is concave, from beino- pressed in by the heart. From the oblique direction of the diaphragm, the vertical diameter of the lung behind, when it is fully dis- tended, goes from the first to the last rib,, and is, consequently, much more considerable than the vertical diameter in front, which extends only from the first rib to the inferior end of the second bone of the sternum, or, in other words, to a level with the tendinous centre of the diaphragm. The left lung is divided into two lobes by a deep fissure, Vol. II.—19 142 ORGANS OF RESPIRATION. which begins behind, on a level with the fourth dorsal vertebra, and runs obliquely downwards and forwards to the anterior margin of its base. A deep fissure in a nearly similar situation is observed on the right lung; but from it another fissure branches out forwards, by which the right lung is divided into three lobes. The internal face of the left lung is also rather more concave than that of the right, from the side of the heart projecting into it. The right lung is more voluminous than the left, which corresponds with the greater size of the bronchia on this side, but its vertical diameter is not so great, from the pressure of the liver from below. Near the middle of the internal face of each lung are to be seen the points of connexion with the bronchia, and with the pulmonary vessels. Before these the anterior margin is thin, and more or less winding where the lung is introduced between the heart and the front parietes of the thorax. When the lungs are fully inflated, only a very small portion of the pericardium can be seen here between them. The posterior margin is thick, and rounded where it rests against the vertebral column. The whole rounded circumference of the lung as well as its base, though they are in contact with the parietes of the thorax, do not adhere at any point to them. The connexion of the lung, constituting its root, as it is called, and by which it is maintained in its situation, is entirely on the side of its concave face, where the pulmonary vessels and bronchia enter, and though other attachments are frequently found springing from different points of the thorax, they are purely the results of disease. Of the Texture of the Lungs. Each lobe of the lungs is divided into a great many distinct lobules, which adhere together by intermediate cellular tissue. The marks of these divisions are apparent on the surface by lines running in different directions, but they are made still more distinct by tearing them asunder. The Lobules are sub- divided into very fine air vesicles or cells, which may be con- sidered as the terminations of the ultimate branches of the bronchia. The opinion is generally held, that the cells do not THE LUNGS. 143 communicate laterally with one another, as the cells of the bones, but only with the ramifications of the bronchia, to which they respectively belong. Recent preparations, however, have in- duced me to abandon this idea, and to conclude that the cells of the lobules individually communicate, but not those of dif- ferent lobules. I have succeeded in proving this by distending the air cells with tallow, and, after the lung was dried, by re- moving the tallow with spirits of turpentine. This process shows the cells of their natural size, and communicating freely. In tracing the terminations of the bronchias, in the substance of the lungs, the parietes of these canals are observed to become very thin, and especially after the cartilaginous structure has ceased. The ramifications seem then to be composed almost entirely of muscular fibres, and a lining of mucous membrane: the latter is smooth, polished, and so thin that it is a mere film, about the thickness and transparency of the peritoneum, where it covers a small intestine. Longitudinal folds may still be traced in the length of the mucous membrane, and, with the aid of a lens, mucous follicles are very perceptible, in innumerable quantities all over it. It may also be remarked, that the bronchias do not end by a regular succession of proportionately finer and finer branches; but that a bronchial trunk, of some lines in diameter, sends off in different directions to the contiguous lo- bules, branches about the size of a bristle, which are followed with much difficulty, owing to their collapsing; the probability is, however, that each one of these branches belongs to a lobule, and discharges into its cells, in a manner resembling a blow- pipe fixed to the side of a small piece of sponge. In my pre- parations, these terminating tubes of the bronchias, the size of bristles, are seen very distinctly; but there is no appearance of the penicillous arrangement, which would be apparent if each air cell had its own specific branch of the bronchia running to it. Besides the ramifications of the bronchias, the substance of the lungs is composed of numerous blood vessels and lymphatics, and is well supplied with nerves. The blood vessels are of two kinds, the pulmonary and the bronchial. The pulmonary artery, coming from the right ven- tricle of the heart, divides under the arch of the aorta into two 144 ORGANS OF RESPIRATION. large brafiches-: one for the right lung, and the other for the left. The right branch is larger than the left. Each of these branches having reached the upper part of the root of its respective lung, begins there to distribute itself in large trunks, which divide and subdivide throughout the substance of the lung. The terminating branches finally become capillary, and ramify in the parietes of the fine cells, where the blood which they carry, from being dark- coloured and venous, is so altered as to have the arterial quali- ties restored to it, and to become of a bright red. From the ul- timate branches of the pulmonary artery, arise the first branches of the pulmonary veins. These are -successively accumulated into two large trunks on each side, which, issuing at the lower ;part of the root of the lung, go to open into the left auricle of the heart. It has been remarked by Mr. Boyer, that the two pulmonary veins are less capacious than the pulmonary artery of the same side, in which they manifest a peculiarity of blood ves- sels, differing from what exists in other parts of the body. The pulmonary artery and veins are distributed in company with the bronchias. From the observations of Professor Mayer, it ap- pears that valves exist in the pulmonary veins, contrary to the general opinion of anatomists. They are found where smaller trunks join the larger ones, at an acute angle, but there are none when they join at a right angle.* The second order of blood vessels, being the bronchial, also consists in arteries and in veins, and are for the nourishment of the lungs. They, too, attend the branches of the bronchias. The arteries pervade the substance of the lung by innumerable fine branches, and anastomose with the pulmonary arteries. The bronchial veins also anastomose with the pulmonary veins, but, finally, come out in small trunks from the root of the lung, and empty into the vena azygos. The Lymphatics of the lungs are numerous; after traversing the black bronchial glands, those of the left side empty into the thoracic duct, and those of the right into the large lymphatic trunk coming from the right upper extremity. The nerves come principally from the par vagum. Some of them are distributed with the bronchia, and may be traced easi- • Am. Med. Jour. vol. iii. page 186. THE LUNGS. 145 ly far along its branches, forming beautiful anastomoses around them: their texture there resembles much that of the sympathe- tic : they are thought to be, finally, spent upon the mucous mem- brane : others seem to be more specifically appropriated to the vessels. It will now be understood that the root of each lung is formed by the pulmonary artery, the two pulmonary veins, and the bron- chia*, covered by the pleura, where the latter extends from the lung to the pericardium. The relative situation is such that the pulmonary artery is above, the bronchia in the centre and be- hind, and the pulmonary veins below. The lung of the adult is of a light pink colour, with specks or patches of black: in early life there is much less of the latter, and in advanced life it becomes more abundant. The texture of the lung is so light and spongy after an animal has once breathed, that its weight is very inconsiderable when compared with its volume. Its cells are left much distended, even when the animal is dead; and, notwithstanding from its unusual elasticity, it expels a great quantity of air when the tho- rax is opened, and is thereby reduced to a third of its size during life ,* yet it retains enough air to make it float in water, or even in spirits of wine. The quantity of air which the lungs contain differs very considerably in different individuals, depending en- tirely on the capaciousness of the thorax. Its medium amount is computed at one hundred and forty-five cubic inches;' thir- ty cubic inches of which are changed at every act of respira- tion. Of tl\£ Pleura. Each lung has a perfect covering, called Pleura, to which it is indebted for its shining surface. This membrane is also re- flected from the internal surface of the lung to. the adjacent side of the pericardium, and is then spread over the interior periphery of that half of the thorax to which it belongs, by linino- the ribs and intercostal muscles, and covering the convex face of the diaphragm. There are, therefore, two pleurae, each of which is confined to its appropriate half of the thorax, so as to line its cavity and to cover its lung. The pleura, as other serous mem- branes, is a thin membranous sac. Its circumference is entire, 146 ORGANS OF RESPIRATION. like that of an inflated bladder; there is, therefore, no point or line at which one may exclusively begin an account of its course and attachments. To commence, however, at the sternum; the pleura goes thence outwardly to line the lateral parietes of the thorax, as formed by the cartilages of the ribs, the ribs them- selves, and the intercostal muscles. In this way it may be traced around to the dorsal vertebras, and over the convex sur- face of the diaphragm. In proceeding along the first rib, which is very oblique, it forms a sort of bulging bag, which projects towards the trachea, lines the lower part of the scalenus an- ticus muscle, and receives the upper extremity of the lung. The pleura, having reached the dorsal vertebrae from the ribs, passes from their sides forwards to the posterior part of the pe- ricardium, a very small portion of which it covers. It then goes upon the posterior face of the pulmonary vessels and of the bronchia to the lung; and applies itself closely to the latter. It then covers the part of the lung posterior to the pulmonary vessels, and continues to advance along the rounded surface of the lung, to its anterior margin: it then passes over the internal surface of the lung, which is anterior to the pulmonary vessels. It afterwards covers the front of the pulmonary vessels and of the bronchia, and gets in a very short space to the pericar- dium. It then passes forwards on the side of the latter, and having got near its middle line, goes from it to the sternum, and reaches the line from which the description of its course com- menced. There is no important difference between the two pleuras either in their mode of reflection or in the organs to which they are attached, so that the description of one will apply to the other. The portion of each pleura covering the lung is called Pleura Pulmonalis, and that portion which lines the thorax is the Pleura Costalis. A duplicature of the pleura commences at the inferior margin of the pulmonary veins, and descending as far as the diaphragm, attaches the inferior portion of the poste- rior margin of each lung to the side of the pericardium in front of of the vertebras. This duplicature is the Ligamentum Pulmo- nis. It is longer on the left lung than on the right, by reason of the greater vertical diameter of the former. From what has been said it will now be readily understood, THE LUNGS. 147 that the whole cavity of the thorax is divided vertically into two halves, by that portion of the two pleurae which advances from the spine towards the sternum. This septum is called the Mediastinum, and the heart, enveloped by the pericardium, is placed in its centre, and separates the two pleurae widely apart. It has been found useful by anatomists, for descriptive purposes, to subdivide the mediastinum into three portions or regions. One, passing from the front of the pericardium to the posterior face of the middle line of the sternum, is the Anterior Medias- tinum; another, passing from the posterior face of the pericar- dium to the dorsal vertebrae, is the Posterior Mediastinum; and a third, which is within the circuit of the first ribs, is the Supe- rior Mediastinum. This division, though evidently arbitrary", is indispensable to a correct account 6f the relative situation of very important organs placed between the two pleurae. 1. The Anterior Mediastinum is less important than the other two; the portions of the two pleurae of which it consists are al- most in contact, and contain between them some loose cellular substance by which they adhere together, and by cutting through which, after a longitudinal section of the sternum, they are easily separated from one another. The upper part of this sep- tum contains the remains of the thymus gland; its lower part leaves the middle line of the sternum, and inclines to the left side; and when the sternum is narrow below, it is attached to the anterior ends of the cartilages of the lower true ribs. 2. The Posterior Mediastinum, where it leaves the vertebras to reach the pericardium, passes off from a line nearer the heads of the ribs on the left side, than on the right. The descending portion of the thoracic aorta is contained within this septum, on the left side of the dorsal vertebras. The oesophagus is in its middle in front of the vertebras above, but, in descending, it crosses in front of the aorta, and inclines to the left side of the dorsal vertebras. The vena azygos occupies the right side of this mediastinum, and, after ascending, forms an arch over the root of the right lung, and terminates by joining the descending cava. The thoracic duct, after entering the thorax between the crura of the diaphragm, ascends in front of the dorsal vertebras 148 ORGANS OF RESPIRATION. between the aorta and the vena azygos, and behind the oesopha- gus, till it reaches the third dorsal vertebra; it then inclines to the left side, and mounting into the root of the neck near the vertebra, it, finally, forms an arch, which, by advancing for- wards, terminates in the angle formed by the junction of the left internal jugular and subclavian veins. The par vagum nerve, of both sides, is also in the posterior mediastinum. 3. The Superior Mediastinum is bounded in front by the up- per part of the sternum, behind by the upper dorsal vertebras, and laterally by the first ribs. The cavity is conoidal, with the base upwards, but is too peculiar to admit of a rigid comparison with any thing else. The pleurae are reflected downwards from the internal edge of the first ribs, not abruptly, but in a round- ed bulging manner, receiving there, as mentioned, the tip or apex of the lungs. In order to understand well the position of the pleurae, it must be borne in mind that the. upper rib is placed very obliquely downwards and forwards, at an angle of about forty-five degrees with the spine; consequently, the pleura, on being reflected from its whole internal edge, is much higher at the head of the rib than it is at the anterior extremity of the same. This cavity is continuous, of course, with that of the an- terior mediastinum in front,.and also with that of the posterior mediastinum behind. The remains of the thymus gland are where this cavity joins the anterior mediastinum: a part of the gland is, indeed, in each of these cavities just below the transverse vein. In contact with the right pleura is the descending Vena Cava. The com- mon trunk of the Left Subclavian, and Internal Jugular, called the Transverse Vein, or Vena Innominata, after crossing in an oblique descent behind the upper portion of the sternum, joins the descending cava an inch above the place where the latter penetrates into the pericardium. Behind the transverse vein are the top of the arch of the aorta, the arteria innominata, the left carotid, and the left subclavian. The trachea, with the oeso- phagus behind it, descends along the middle line in front of the spinal column. The arteria innominata crosses the front of the trachea from left to right in ascending; it is in contact with the transverse vein, and more superficial than either of the other THE LUNGS. 149 arteries. The phrenic nerve, passing at the internal edge of the scalenus anticus, between the subclavian artery and vein, de- scends vertically in contact with the pleura. The par vagum passes along the side of the trachea, and afterwards behind the corresponding bronchia, having got into the superior mediasti- num between the subclavian vein and artery: its inferior laryn- geal branch encircles the subclavian artery on the right side, and the arch of the aorta on the left. The internal surface of the pleura is smooth and polished, and is moistened and kept lubricated by an unctuous serum, the na- tural quantity of which is merely sufficient to allow the parts to slide freely upon each other. In dropsy of the chest, it is aug- mented frequently to such an amount as to cause the collapse of the lung by pressing upon it. In the cellular tissue, between the pleura and pericardium, as well as on the diaphragm, adipose matter, in considerable abun- dance, is found in corpulent persons advanced in age. The blood vessels of the pleura costalis are derived from those which supply the parietes of the thorax, as the intercostals and phrenics. They ramify in the subjacent cellular substance, and end by exhalent orifices on the internal face of the pleura, from which a minute injection is poured out very copiously. Vol. II.—20 BOOK VIII. OF THE CIRCULATORY SYSTEM. PART I, Of the General Anatomy of the Circulatory System. CHAPTER I. GENERAL CONSIDERATIONS. The Circulatory or the Vascular System, consists in a conge- ries of tubes, or cylindrical canals, which convey the blood to and from every part of an animal body, and therefore, enter into the texture or composition of almost every portion of it. In all animals there seems to be a necessity for the alternate reception and discharge of alimentary materials; in the higher orders, this is effected through the agency of the vascular system; but in the most simple animals this system does not exist, and their whole fabric being soft and permeable, nutritious matter is introduced by a direct absorption, or a species of capillary attraction, after the manner of a sponge, or any other porous body, and is dis- charged by a process equally simple.* It is probable that there are some parts of the human body whose mode of nutrition is analogous to the latter; as, for example, the articular cartilages, the hair, nails, and so on; for many observations tend to prove that all these organs have an interstitial circulation. • Hunter on the Blood. Biclard, Anat. Gen. 152 CIRCULATORY SYSTEM. In many animals, the blood is propelled from a central point, called the heart, to all parts of the body, and then returns again to the heart. The first movement is executed through canals called arteries, and the second through veins. It is the most simple scheme by which a circulation can be carried on through a sanguiferous system, and requires a heart with only two cavi- ties ; one for propelling blood into the arteries, or departing tubes, and another as a reservoir for receiving the blood of the return- ing tubes, or the veins. The two cavities must be near each other, and have a valvular opening between them, which will permit the blood to pass from the venous into the arterial reser- voir ; but not from the arterial into the venous. A circulation of this simple cast is found in fish, and in animals generally whose respiration is effected on the surface of the body; but in man, and in other warm-blooded animals, where respiration is carried on interiorly by means of the lungs, their circulatory apparatus is double; one part being for the lungs, and the other part for the body generally. In man, the heart consists of four cavities: two auricles, or re- servoirs of venous blood, and two ventricles, into which the ve- nous blood is transmitted, and which, in their functions, may be compared to the forcing-pump of a fire-engine. The circulation is effected in the following manner: The blood contained in the right auricle of the heart flows into the right ventricle, and from the latter it is forced through the pulmonary artery into the lungs. It returns from the lungs through the four pulmonary veins, and is received into the left auricle of the heart; from the latter it flows into the left ventricle, and is propelled from it into the aorta. The aorta then distributes it through the whole body by an infinitude of small branches; from the latter it is collected, by corresponding veins, into two trunks, the Ascending and the Descending Cava. The ascending vena cava brings the blood from the lower extremities and from the abdomen; the descend- ing vena cava brings the blood from the head and neck, the up- per extremities, and the parietes of the thorax. These two trunks finally discharge the blood into the cavity from which it started, to wit, the right auricle. The same round is then renewed, and continues to be repeated during the whole course of life. It is GENERAL CONSIDERATIONS. 153 customary for anatomists to call the route of blood from the right ventricle, through the lungs, to the left auricle inclusively, the lesser or the pulmonary circulation; and that which begins at the left ventricle, goes through the whole body, and ends in the right auricle, the greater circulation. The blood contained in the veins of the greater circulation, in the right auricle and ventricle, and in the pulmonary artery, is of a dark brown or reddish colour; while that contained in the pulmonary veins, in the left auricle and ventricle, and in the aorta and its ramifications, is, from being vivified by respira- tion, of a carmine or vermilion complexion. The celebrated Bichat has, upon this difference of colour, founded his division of the whole circulating system into two parts; qne containing black blood, " Systeme vasculaire a sang noire;" the other red blood, " Systeme vasculaire a sang rouge." This division having general physiology for its object, affords a well marked distinction, suited to such discussions. The lymphatics also are a part of the circulatory system, but as they do not commonly convey red blood, the consideration of them will be introduced subsequently. " They take a very active part in the animal economy, whether natural or diseased, and seem, in many actions, to be the antagonists of the arteries; while the veins are much more passive, being principally em- ployed in returning the blood to the heart."* The largest vascular trunks are situated near the centre of the body and limbs, on the side upon which flexion is accomplished, while those near the surface are generally small. Most com- monly there are one artery, one or two veins, and several lym- phatics, all together. The arterial system in its external configuration may be com- pared to a tree, the trunk of which is attached to the heart, and which by a continued succession of divisions and subdivisions reaches to every part of the body. There are no means of esti- mating rigidly the collective area of the branches in proportion to that of the trunk, but a little observation on the size of the primitive branches will satisfy one of a great excess on the part of the latter; and as the rule is maintained throughout, there * Hunter, loc. cit. 154 CIRCULATORY SYSTEM. must finally be an immense disproportion. We have then rea- son to believe, that if all the branches were assembled into a single cavity, this cavity would be scunewhat like a cone, the apex of which would be next to the heart. The same rule holds in regard to the venous system, it being observed, how- ever, that the latter has two trunks connected with the heart in- stead of one. The general rule is, therefore, established through- out the vascular system, that the collective area of the branches is always greater than that of the trunk from which they pro- ceed.* By the same rule the circulation in the branches must * I am indebted to a scientific friend, Mr. Erskine Hazard, for the following computation, by actual measurement, of the arteries, from which it appears that in many of them, at least, the area of the trunks is greater than that of the branches near them. The Left Carotid at the Aorta is.......42 Its diameter at the branching is ------ .43 Increase of diameter......01 Its square at the Aorta is --.....1764 Bach Carotid branch measures .28, and the sum of their squares is - -.........1568 The difference of the areas of the Carotid and its branches is 122 per cent. in favour of the Carotid. Diameter of Aorta near the Uiacs - - - - - .64 Its square --......4995 Diameter of Left Iliac......_4Q Its square ----,__ ^goO Diameter of Right Iliac.....37 Its square.......1369 Sum of their squares -.--__ 2969 Aorta largest by nearly 38 per cent., or - - - . . 1127 Square of Right Iliac, as above, ----_. 1369 Ditto External Iliac...... qqq Ditto Internal do. .- - . . . . 729 ---- 1629 GENERAL CONSIDERATIONS. 155 be more languid than in the parent trunks, as this circulation is retarded both by additional friction and by having to fill up a Branches largest by nearly 19 per cent., or 260 Square of Left Iliac, as above,.......1600 Ditto Internal Iliac.......961 Ditto External do. - -......900 ---- 1861 Branches largest by above 16 per cent., or .... 261 Great Sinus of Valsalva.......- 13456 Innominata ------- 2601 Carotid.......1444 Subclavian - - - - - - - 1024 Aorta beyond......3600 ---- 8669 Sinus greater than all, by.......4787 or 55 per cent. Comparison of the areas of the Iliac Arteries, with that of the Aorta, half an inch above them, in decimals of an inch. Left Iliac. Aorta. Right Iliac. Greatest diameters - - .354 .556 .390 Least do. - - .290 .410 .290 Sum of diameters - - .644 .966 .680 Mean diameters - - - .322 .483 .340 Their squares - - - 103684 233289 115600 103684 Sum of the squares of the Iliacs ----- 219284 Square of the Aorta - - - - - 233289 Aorta larger than the Iliacs......14005 or nearly 6^ per cent. As the areas of circles are to each other as the squares of their diameters, it follows that the aorta will contain, in a given length, nearly 6^ per cent, more than the two iliacs; and, consequently, the blood must flow that much faster 156 CIRCULATORY SYSTEM. larger canal.* The course of rivers exemplifies this continual- ly; while confined to narrow channels, they rush tumultuously through them, but when they begin to expand themselves into capacious basins, or to be divided into a multitude of smaller channels, the current becomes slower, and in some cases imper- ceptible, though the fact is clear, that an equal volume of wa- ter is every where descending in the same period of time. The moisture conferred upon all parts by the circulation of the blood, bears a sufficient analogy to the effects of irrigation upon ground. The water may be conducted to the latter by a canal, which is finally divided into an infinitude of streamlets, which ramify every where, and from the porosity of their beds percolate laterally, so that the whole field, even to its most minute atom, is kept moistened. The streamlets, afterwards, successively assemble again into a single canal, which bears off their superabundant water. From the nature of the particles of blood, many of them are confined to their proper channels, and can never pass off by percolation into the tissue, through which the blood vessels ramify. This may be proved by the fact that the red globules of blood have a diameter of from the two- thousandth to the five-thousandth part of an inch, a size incon- siderable as it is, yet too large to permit their flowing through elementary fibres or atoms; whereas serum, or the water of the blood, may, from the extreme fineness of the particles, be ab- sorbed by any tissue whatever; a circumstance entirely un- questionable, both from daily observation, as, for example, in soaking a piece of dried meat or a bone; and from the reflec- throsgh the iliacs than through the aorta, as the same blood has to be disposed of in both in the same time. By this means the power of the heart is continued much farther through the system, as each artery is large enough to supply its branches with but little friction. The interior surfaces of the above iliacs are, together, 2.0806 inches, while that of the aorta is but 1.518 inches, or only three- fourths of the rubbing surface. Independently of this circumstance, it is found that there is a greater difference in the quantities of fluids passing through aper- tures of different sizes than there is in the areas of the respective apertures. This is accounted for by there being less friction between the particles of fluids than there is between these particles and a solid,- and, in the larger apertures, a smaller proportion of the particles comes in contact with the solid. * It is computed that the blood moves 5233 times slower in the capillaries than in the aorta. GENERAL CONSIDERATIONS. 157 tion, that the air itself will hold a certain quantity of water in solution. A question then arises whether the moisture of parts not sup- plied with red globules of blood, comes in the living body ex- clusively from infiltration or from a peculiar set of vessels called exhalents, often talked of, but as yet never seen? That the lateral porosities of blood vessels are large enough to allow watery,fluids to exude, is readily proved by injecting water into the blood vessels of a limb, or of any other part, when the latter invariably becomes oedematous. It is in this way even possible to inundate a living animal, as I have seen accomplished by M. Magendie, in Paris. This moisture requires a change, and by continued additions would become superabundant: as it has been thrown out of the common current of the circulation and could not be removed in any other way, the lymphatic sys- tem has, therefore, been added for the purpose. In the lower orders of animals, who are destitute of the blood vessels, the interstitial change of moisture goes on without lymphatics. No part of the human body is exempt from moisture, but it is furnished by smaller streams, and is also less abundant in some textures than in others; for example, though blood vessels susceptible of conveying red blood do ramify through tendons and ligaments, yet they are not numerous, apparently; not more so, indeed, than what is sufficient to keep up by a de- posite of serum, the flexibility of those parts. The vascularity of apart during life may be ascertained by a*simple process after death, the most vascular always lose proportionately of their bulk by drying; for example, a muscle shrinks more than a tendon, a gland more than a muscle. Besides the operation of the lymphatics, much of the super- abundant moisture is carried off by insensible perspiration and evaporation from the surface of the body: the latter process, however, is much restrained by the peculiar character of the cuticle, without which it would become excessive, probably so much so as to exceed any supply of fluid through the stomach. The red globules of the blood, besides their less obvious uses, Vol. II.—21 158 CIRCULATORY SYSTEM. Unquestionably serve to inspissate the serous or watery part, by an intimate mixture with it, and thereby put a certain re- straint upon its extravasation. They also, from their size, serve to keep open the channels through which the blood circulates. So much associated is the existence of red globules with regular bloodvessels, that there are but few examples of animals having the former, without also having the latter; whereas, in animals whose circulating fluid has not red globules, but is a mere serum, the entire destitution of regular blood vessels is very common, ■and their circulation, if the name be deserved, consists simply in the transmission of moisture from one pore to another, as oc- curs in a rag or in a sponge, by mere capillary attraction. Such animals form a numerous class in the chain of organized beings, and have a gelatinous consistence. A remarkable feature in the vascular system, both arteries and veins, is the disposition of trunks to run into one another; or, in other words, to form an anastomosis, whereby, if the blood should be cut off by one route, it may still be supplied through another. These communications are frequent in the head, in the neck, in the thorax, in the abdomen, and in the extremities; they exist, indeed, wherever the blood vessels do, and become more numerous as the blood vessels are smaller, or more removed from the centre of the circulation. It is unne- cessary here to specify instances, as the more remarkable ones will be mentioned at a proper time. But some estimate may be made of their importance, and of the facility of communica- tion established by them, when it is remembered that cases have occurred of obstructed aorta, without the circulation ceasing in the parts of the body beyond it: the same has occurred to the venae cavae, and to the thoracic duct also.* The extreme vascular ramifications are called Capillaries, {Vasa Capillaria,) and they form the connexion between the arteries and veins; or, by being intermediate to the two, they are the ultimate terminations of the arteries, and the commencing roots of the veins. From the extreme tenuity of these vessels, it is * Beclard, Anat. Gen. GENERAL CONSIDERATIONS. 159 t impossible to indicate where the arteries terminate and the veins begin; yet their continuity with the capillary system has been repeatedly demonstrated, by throwing injections from the one into the other system, and by microscopical observations made on the transparent parts of living animals, as the mesentery and web foot of frogs, and the tail of fishes. These facts are suffi- ciently substantiated by the observations of Malpighi, Lewen- hoeck, Prochaska, and a crowd of others; yet there are anatomists who hold a contrary doctrine, and admit the parenchyma of the ancients (an indefinable something, conceived, however, to be spongy) as a point of termination for the arteries, and of com- mencement for the veins. Though the capillaries are all too fine to be seen distinctly without the microscope, yet they are found to have several gra- dations of size. The largest of them are those which only escape the naked eye, experience successive divisions, whereby their diameters are reduced from admitting a file of several globules of blood to the caliber of one globule only.* The capillaries have also frequent anastomoses with one another. Sometimes the artery is simply doubled on itself, and immediately becomes a vein: on other occasions, several capillary arteries run into the same vein. When these communications are unduly en- larged, they constitute what has been called by Mr. John Bell the aneurism from anastomosis, a frequent mark in young chil- dren, and which, when it has developed itself fully, has a spon- gy structure resembling the erectile tissues, as the corpus caver- nosum penis, &c. As there is a double circulation, so there is a double capillary system, one for the lungs and the other for the body generally: to these may be added a third, which exists in the liver, between the hepatic extremities of the vena porta- rum and the hepatic veins. The texture of the capillary vessels is too fine to admit of much scrutiny, but they appear as simple cylindrical excavations in the substance of the part to which they belong. It is not improbable, that they may be uninterrupted continuations of the internal coat of the arteries into that of the veins. They have striking powers of extension and of contraction, and are easily • Beclard, loc. cit. 160 CIRCULATORY SYSTEM. irritated. An emotion of the mind, as a sentiment of shame or a feeling of resentment, quickly causes those of the face to become turgid with blood. Local stimuli cause congestions in them. Cold, the application of a weak acid, or fear, causes them to con- tract; though, under the influence of the heart, they are less so than larger vessels. Their innumerable channels cause a compa- paratively languid circulation of the blood in them, for reasons mentioned; and by furnishing it with more places of contact with their parietes, put it more under nervous influence than it is elsewhere. These vessels are not equally abundant in all the textures of the body. Their quantity may be ascertained by the redness which a part acquires by inflammation, as well as by fine injec- tions: the latter proof is preferable, as, in the former, it is diffi- cult to distinguish them from the extravasations which also oc- cur at the same time. The celebrated injections of Ruysch, from their unusual minuteness, induced him to think that every solid portion of the body was vascular, yet he admitted that some portions were more vascular than others, thereby con- ceding to his antagonists, that some points at least were not formed by blood vessels. In the microscopical examinations on living animals, for example, the frog, it is seen that in their feet the smallest capillaries are separated by distinct intervals, while in the mucous membrane of the lungs the finest needle cannot have its point inserted without opening several of them.* The younger an animal is, the more vascular are its parts: but, on the contrary, as it advances in age, the proportion of parts not susceptible of injection increases, while the capillaries dimi- nish in number. In cold-blooded animals, it is very evident that some of these capillaries, or arterio-venous communications, are large enough to admit a file of several red globules abreast, while others allow a single file only. As a general rule, their diameter may be stated at from one to five globules of red blood.t The nutrition of the body depends upon an alternation of ex- halation and of absorption} but it is still undetermined, whether * Beclard, Anat. Gen. f Beclard, loc. cit. GENERAL CONSIDERATIONS. 161 there be any vessels whatever whose especial office is that of exhalation, and which produce the several secretions and ex- halations. If there be such, they are generally designated by the term exhalents, and their diameters are too small to transmit the red globules of blood; their function is, consequently, to give passage to the serous particles only. This subject has been much agitated by anatomists, and marshals the best authorities on both sides. Among the distinguished advocates in the affir- mative, are Boerhaave, Haller, and Bichat; and opposed to them, are Prochaska, Mascagni, and Richerand. The leading facts of the former are; The microscopical observations of Lewenhoeck, who speaks of vessels admitting only serous globules; the phe- nomena of inflammation, which render red, parts naturally white and transparent; the difficulty of conceiving how the nourishment of certain parts can be maintained, whose capillary system of red blood is so limited, in proportion to points not susceptible of it. The opinion of Mascagni and others to the contrary, is: That those exhalents, if they existed, should be seen readily, inasmuch as they are within the range of a mi- croscope, whose powers enable one to examine a body'much smaller than a red globule of blood; that injections should pe- netrate them, instead of being limited to vessels whose existence is sufficiently confirmed by examination in the living state; that if during inflammation they do seem to be injected with red blood, the appearance is delusive, and depends upon the exist- ing capillaries being dilated so as to receive more red blood than usual, upon the formation of new vessels, and upon san- guineous infiltration; and, as to membranes naturally white, as the conjunctiva, the colour depends upon the capillaries,- while in a healthy state, being so small that they do not admit the red globules in a file sufficiently numerous to be perceived by the eye, the globules being, probably, then conducted in a series of one only, or in a single file, like a string of beads. It is, there- fore, much more reasonable not to admit the existence of ves- sels which it is very doubtful whether any one has seen. When a watery injection is pushed into a blood vessel, it in a little time shows itself as a fine dew upon the surface of the serous and mucous membranes; in the cellular membrane, and elsewhere. According to many anatomists, it has gone through 162 CIRCULATORY SYSTEM. the system of exhalents, and, indeed, presents itself to sight in very much the same way that exhalation occurs in the living state. From the view which has just been taken, it becomes more probable, that this perspiration is executed through the interstices or pores of the vessels. In the dead state it is merely a mechanical result, a simple straining of the fluid; whereas, in the living body it is a vital function, continually modified by the peculiar vital powers of the organ or membrane where it occu/s; and, therefore, presents itself under the form of the dif- ferent secretions. The question of the exhalents being a dis- tinct set of vessels, does not, however, appear to be one of much consequence; because, if they do exist, they must be very short and very small; and the assumption of their existence does not throw any light upon the function of secretion. For the latter is still an incomprehensible vital process, and as far as we have any idea about it, it is quite as easy to conceive of its being performed in the parietes of the capillaries, as in the mouths of a distinct set of vessels, whose length is too short to admit of an estimate. Besides the supposed existence of a general system of exha- lent vessels, some anatomists have thought that there was a spe- cies of them acting particularly as nutritive vessels. According to Boerhaave, every part must, therefore, be vascular. Mascag- ni thought that the extreme arterial ramifications are not only furnished with exhaling, but also with nutritive porosities; and that there are every where orifices of absorbing vessels, to con- tain the nutritive molecules. The theories of Bichat and of Prochaska, do not differ materially from the latter. Whatever may be the mode of existence, and the route of nutriment to the several parts of the body, the operations involved are entirely too subtle even for microscopic observation. We, therefore, can only understand, in a general way, that the blood vessels deposite, and the lymphatics absorb, by invisible avenues in the cellular substance, the molecules of composition and of decom- position in our organs.* It is to this power that the name of vital force has been given, and especially that of the force of formation, (nisus formalivus.) The arteries, though commonly said to be cylindrical canals, * Beclard, loc. cit. GENERAL CONSIDERATIONS. 163 are not exactly so, but, as they recede from the heart, increase somewhat in diameter, even where they do not send off any branches. In this way the arteries of the umbilical chord are evidently larger as they get nearer the placenta; and the sper- matic arteries of a bull as they get nearer to the testicle. Ob- servations made on the carotid arteries of the camel, and of the swan, by Mr. Hunter,* tend to prove the same disposition in them. It is probable that the rule extends to all arteries through- out the system, but it cannot be ascertained with so much cer- tainty, because of the close succession of branches which they send off Arteries have within themselves a power of increase connect- ed with the exigencies of the part to which they go: thus, the uterine arteries increase much in their capacity during pregnan- cy, while the hypogastric, from which they are derived, aug- ment inconsiderably, and the primitive iliacs not in an appre- ciable manner. In animals of the deer kind, whose horns are deciduous, the same augmentation of arterial trunks occurs while the horn is growing. Tumours are supplied in the same way. But in all these cases, after the exigency is passed, the vessels diminish to their primitive size. With the exception of the semi-lunar valves at the orifice of the pulmonary artery and of the aorta, there are no others in the whole arterial system. These valves permit the blood to pass in the direction of the circulation, but not backwards, as they are closed immediately upon the cessation of the contrac- tion of the ventricles. The tricuspid valve of the heart, and the semi-lunar of the pulmonary artery, are naturally not so per- fect in their closure as those on the other side of the heart, but permit a small quantity of blood to retrograde.t As life ad- vances, the valves of the aorta are much disposed to ossifica- tions and derangements of different kinds, which render them much less perfect than those of the pulmonary artery. * On the Blood and Inflammation. -J- Hunter, loc. cit. 1G4 CIRCULATORY SYSTEM. CHAPTER II. OF THE TEXTURE OF THE ARTERIES. The arteries are composed of three coats; an external, a mid- dle, and an internal. The External Coat, also called Cellular, is, in fact, condensed cellular substance formed into a cylinder. Its fibres run in eve- ry direction, so as to be perfectly interwoven with one another. The exterior periphery of this coat is continued into the adja- cent cellular substance, but its internal face is united more close- ly to the middle coat; not, however, so tightly as to prevent a slight sliding of the one upon the other, and to forbid their easy separation by a knife. Scarpa is not disposed to admit this as one of the coats of arteries, and says that it only serves as an exterior envelope, and retains them in their places. This coat manifests its fibrous character in not being disposed to secrete fat, and is more distinct in the large arterial trunks. It has con- siderable strength and elasticity, both circularly and longitudi- nally, and is remarkable for its whiteness. If an artery be sur- rounded by a tightly drawn ligature, the middle and the internal coats will be completely cut through by it, while the exteinal coat remains entire. This coat, then, answers the purpose of a strong investing fascia,* in which respect it may be considered as a sheath to the proper arterial structure, though the term sheath is commonly applied to the cellular membrane on its outer side. The Middle Coat of the arteries is called the Muscular, the Proper, the Tendinous, and so on. It is of a light yellowish tinge, and decreases continually in thickness, with but few ex- ceptions, from the heart to the ends of the*arteries; it is, how- ever, proportionately thicker in the small arteries than in the large ones. Its fibres are circular, but do not individually per- form the circuit of the vessel. They are parallel to each other. * Jones on Hemorrhage. TEXTURE OF THE ARTERIES. 165 and adhere laterally by very slender ties. In the larger arte- ries, this coat may be divided into several laminae, though the division is entirely artificial. There are no longitudinal fibres whatever in it; the consequence of which is, that an artery di- vested of its external coat, yields more readily in the direction of its length than of its circumference. The middle coat has a firmness, whereby, even when an ar- tery is emptied, the cylindrical shape is still retained. Its cha- racter seems to be the result of a mixture of elastic and of mus- cular properties derived from a state of tissue entirely peculiar; but which some anatomists have been very desirous of ranging under the head of muscles, others under that of ligaments, and a third, under both united. The celebrated John Hunter, whose observations were generally made with the most scrupulous at- tention to perfect exactitude, were often repeated, so as to make one confirm another; and who has received that sanction of greatness in which one's posthumous reputation becomes more exalted than the living; bestowed much attention on this sub- ject. He was induced to believe that this middle coat was formed by a muscular lamina internally, and an elastic one ex- ternally ; which distinction might be rendered evident by cutting a contracted artery through transversely, when the muscular coat would be found projecting beyond the other. He acknow- ledges, however, that he never could discover the direction of the muscular fibres: though he supposed them to be oblique, be- cause their degree of contraction was greater than a straight muscle could produce. The elastic contraction of an artery, is manifested both in the direction of its length and of its circumference; for, when put upon the stretch in either way, it has the ability of returning to its original dimensions after the distending force ceases. The Muscular contraction, however, only occurs in the circumference, and not at all in the length: by it the caliber of arteries is re- duced to a very small diameter, if an animal be slowly bled to death. If, in this contracted condition, an artery be slit open longitudinally, the elastic coat will, at the cut margin, project beyond the other, which Mr. Hunter considers as another way of ascertaining the existence of the two tunics. But if this same artery be then stretched transversely, the muscular coat will Vol. II.—22 166 CIRCULATORY SVSTEM. project beyond the other; for the reason, that if a muscle, after death, be elongated by force, it has no power of returning from that state, but will remain precisely as it is: whereas, elasticity being a property of matter enjoyed quite as fully in the dead as in the living state, the elastic coat of the artery returns to the medium condition. Mr. Hunter, with a view of satisfying himself on these several points, had a horse bled to death, so as to obtain the vessels at their minimum of contraction. A circular section of the aorta measured, at first, five inches and a half, and, on being stretched, it lengthened to ten inches and a half; being let alone, it con- tracted to six inches, at which it remained stationary; the dif- ference between six inches and ten and a half was then the amount of its elastic power, while only half an inch of contrac- tion was due to the muscular stratum, or, in other words, an eleventh of the whole. A section of the iliac artery, measuring two inches in circum- ference, on being allowed to contract after stretching, measured two and one-third inches; it, therefore, gained one-sixth the amount of its muscular contraction. A section of the axillary artery gained one-eighth—of the carotid, two-thirds—of the ra- dial artery, doubled its primitive extent. From all which the inference was drawn, that the power of recovery in a vessel is greater, in proportion as it is nearer the heart, but lessens as the distance increases, which shows the decrease of elastic, and the increase of muscular power. The elastic coat gives a middle state to an artery, or has a continued tendency to it; if, therefore, the artery be too much dilated, it contracts it, and if it be too much contracted, it dilates it, all of which is readily exemplified by a cylinder of gum elastic, which, whether compressed or dilated, has only one state of re- pose, to which it immediately returns on being left to itself. Mr. Hunter supposed, that a certain degree of elasticity is con- tinued to the very end of every artery, from this quality being better suited to sustain a permanent resistance than muscular power; as a pipe of lead, from its want of elasticity, finally becomes stretched and useless under the pressure of a column of water, whereas, one of iron, from being elastic, always re- acts efficiently. It is this elasticity in the arteries, which TEXTURE OF THE ARTERIES. 167 causes the blood, at a little distance from the heart, to flow through them in a continued jetting stream when they are opened, although it is supplied to the aorta by interrupted strokes. In this way, as the artery is more distant from the heart, the stream becomes proportionately regular. " The muscular power of an artery renders a smaller force of the heart sufficient for the purposes of circulation; for the heart need only act with such force as to carry the blood, through the larger arteries, and then the muscular power of the arteries takes it up, and, as it were, removes the load of blood while the heart is dilating. In confirmation of this remark, it is observa- ble in animals whose arteries are very muscular, that the heart is proportionably weaker, so that the muscular power of the ves- sels becomes a second part to the heart, acting where the power of the heart begins to fail, and increasing in strength as that de- creases in power."* The Internal Coat of the arteries is designated by the terms Nervous and Arachnoid. It is continued from the ventricles of the heart, in the left one of which it is of unusual thickness. It is the duplication of this membrane with some fibres interposed, that composes the semi-lunar valves of the aorta and of the pul- monary artery. Its internal face is smooth, polished, and mojst- ened wfth a kind of humidity which permits the blood to flow through with diminished friction. In the larger arterial trunks, some small longitudinal wrinkles are observable in it; and when an artery has been cut through, as in amputation, it is disposed to retract in small transverse wrinkles. It is, therefore, not very extensible, but has, according to the experiments of Sir Everard Home,t a considerable degree of solidity and strength. Ossifications of this membrane are very frequent after the age of sixty. In addition to the tunics mentioned, cellular substance, vessels, and nerves enter into the structure of arteries. The Cellular Substance is not abundant, and serves principally * Hunter, loc. cit. f Transactions for the Improvement of Medical and Surgical Knowledge, vol. i. 168 CIRCULATORY SYSTEM. to unite the sides of the circular fibres to one another, and to join the internal to the middle coat. The Vessels (Vasa Arteriarum) consist both in arteries and in veins, and come from the adjacent trunks, instead of from those on which they ramify. They may be made very distinct by a fine injection, or by laying them bare in the living body; when in a little time after exposure, they begin evidently to carry red blood, and to grow turgid as in inflammation. The difference in the colour of the blood distinguishes these arteries from the same kind of veins. Both arteries and veins may be traced very well into the middle coat, but not upon the internal, though the changes which occur in the latter, from disease and upon the application of ligatures, prove clearly that exhalation and ab- sorption are continually going on there. For in inflamed arte- ries, an exhalation is seen upon their internal surface, and when a coagulum has been produced by ligature, it is finally, ab- sorbed. The Nerves of the arteries, according to Wrisberg and Be- clard, are numerous and considerable, form around them a plex- us resembling that of the par vagum around the oesophagus, and follow them into the interior of our organs, with the exception of the brain; which has them only to its surface. They are proportionately more abundant in the aortic than in the pulmo- nary system; also upon the smaller than upon the larger arte- ries. The arteries of the head, of the neck, of the thorax, and of the abdomen, are supplied from the sympathetic nerve, while those of the extremities are supplied from the nerves of the spi- nal marrow. The passing of the blood through the arteries is accompanied with a pulsating motion, which, for the most part, is exactly synchronous with the contraction of the left ventricle, and de- pends upon an increased quantity of blood thrown into them at the moment. The dilatation of the artery may be both seen and felt: " but were we to judge of the real increase of the artery by this, we should deceive ourselves; for when covered by in- teguments, the apparent effect is much greater than it really is in the artery itself; for in laying such an artery bare, the nearer we come to it, the less visible is its pulsation; and, when laid en- tirely bare, its motion is hardly either to be seen or felt. This TEXTURE OF THE VEINS. 169 % apparent diastole of the artery is augmented in proportion to the solid matter covering it, whence tumours over large arteries have considerable motion given to them, and have often been supposed to be aneurismal. Arteries, in fact, during their dias- tole or dilatation, increase much more in length than in width, and are thrown into a serpentine course: instead, therefore, of the term diastole, it should rather be called the elongated state."* Mr. Parry, of Bath,t has denied that the arteries dilate at all during their diastole: his opinion, however, is peculiar, though, in an experiment performed some years ago upon the carotid artery of a calf, its correctness appeared to me then to be fully proved. There is no part of the human body which presents more fre- quent varieties, in different individuals, than the arteries. These varieties are found, in their place and manner of origin, in posi- tion, and in the number of their ramifications. They are com- paratively rare in the trunks of the first order, more common in those of the second, and still more usual in those of the third and fourth. From these causes, discrepancies are continually found in the descriptions of the most approved authorities, and must last so long as writers repose upon a partial experience, instead of referring to what has been most generally observed. CHAPTER III. OF THE TEXTURE OF THE VEINS. The veins, from their duty of receiving the blood in all parts of the body from the extreme arteries, and returning it to the heart, by successively collecting it into the two venae cavae, may be more appropriately compared to the roots of a tree, than to its branches. The variations in them as well as their anasto- moses, are more frequent than in the arteries. They are more numerous than the arteries; for, in addition to * J. Hunter, loc. cit. f Experimental Inquiry on the Pulse, 1816~-1819. 170 CIRCULATORY SYSTEM. two venous trunks attending each artery wherever the structure of the part is intended for locomotion, as in the extremities, and in some places upon the trunk of the body, there is a very abun- dant class of veins which are superficial or subcutaneous, and which, when filled properly with injecting matter, form a fine vascular network over the whole surface of the body.* These su- perficial veins, in some places, form trunks even larger than such as attend the arteries, and especially in the extremities. Besides the excess in number, the veins which attend the arteries (Vena Comites) have a capaciousness which, in many cases, is double that of the latter. From these several circumstances, it results that the area of the venous system vastly exceeds that of the ar- terial. In some cases the veins follow precisely the course of the ar- teries, one for one, as in the greater number of the viscera of the abdomen, where they have common points of entering and departure. Sometimes two arteries discharge into one vein, as in the penis, the clitoris, and the umbilical chord; sometimes they pursue a course entirely different from the arteries, as in the pia mater. For the most part they are less tortuous than the arteries. The veins, when injected, assume a cylindrical shape, yet they differ materially from the arteries, in having much thinner coats, and in being so pliable that they collapse by their own weight. ' In the lower extremities, however, near the feet and upon them, as the veins sustain the pressure of a long column of blood; they have additional thickness and strength, so as to ap- proximate them more to the arterial structure. This provision will be found occurring in most places where they have much duty to perform. " They are similar to the arteries in their structure, being com- posed of an elastic and muscular substance: the elasticity pre- serves them in some degree in a middle state, although not so perfectly as it does in the arteries. The muscular power adapts the veins to the various circumstances, which require the area to be within the middle state, and assists the blood in its motion to- wards the heart."t * Pauli Mascagni Anatom. Univers. Pisis, 1823. X Hunter, loc. cit. TEXTURE OF THE VEINS. 171 The External Coat is thinner and not so strong as that of the arteries; in other respects, the resemblance is sufficiently close not to require any particular comment. The Middle Coat, near the entrance of the larger veins into the heart, is distinctly muscular.* It is formed of soft extensible fibres, many of which, when the vein is held up to the light, ap- pear longitudinal, while the most internal are circular: there are difficulties, however, in the separation of these fibres, which pre- vent their course from being accurately ascertained. Bichat and Meckel assert, that the whole of them are longitudinal, and that there are none circular. This coat, in the human subject, is much thicker in the system of the ascending than of the descending cava; it is also thicker in the superficial than in the deep-seated veins. In some sub- jects it is much better developed than in others. In certain parts of the body it is entirely deficient, as in the sinuses of the dura mater, and has its place supplied by this membrane; the same deficiency exists in the sinuses of the bones. The Internal Coat is more delicate and extensible than the corresponding one of the arteries, is less liable to rupture, and less disposed to ossification. It is thrown into a considerable number of duplications, forming valves. Each valve is of a se- micircular shape; is connected by its convex edge to the vein, while the straight edge is loose, and turned towards the heart. When the veins are injected backwards, these valves may be forced in the larger, trunks, and give them a knotted appearance. The valves arc commonly in pairs, but in certain veins, as the crural and the iliac, there are three of them together; very rare- ly do they amount to four. In some instances there is but a single one; this arrangement is more frequent at venous orifices, as the great coronary vein of the heart, the vena cava ascen- dens, the vena azygos. They are frequently found reticulated as if they had been lacerated, whence it has been supposed that the fibres which cross the sinuses of the dura mater are an elemen- tary approach to them. * Beclard, loc. cit. 172 CIRCULATORY SYSTEM. The valves are more abundant in the superficial than in the deep-seated veins, but they do not exist every where. There are none in the branches of the vena portarum, excepting the vasa brevia: none in the spine, in the umbilical vein, the cervical veins, the kidneys, womb, ascending and descending cava, or in the median vein. The valves are proportionately more abundant in the lower extremities. From the tenuity of the parietes of the veins, the blood may be readily distinguished circulating through them. Their coats, like those of the arteries, are vascular, or have the vasa vaso- rum. The arteries come from the nearest small trunks, while the corresponding veins do not empty immediately, but second- arily, into the trunk, whose parietes they supply. They are well furnished with veins. Their elasticity, both transversely and longitudinally, is well marked; but they are not so extensible in the latter direction as the arteries, while they are more so transversely. There can be no doubt of their spontaneous powers of contraction, for it is abundantly proved by their diminishing much in volume upon the application of cold; moreover, when a venous trunk, dis- tended with blood, is intercepted by two ligatures, and then punc- tured, it empties itself entirely and rapidly. The circulation in the veins is produced, in a principal degree, by the contraction of the heart; their own contraction may also favour this motion, as well as lateral pressure from contiguous parts. As the movement of the blood in the smaller arteries is so uniform as to be almost without pulsation, so the latter disap- pears entirely in the veins. It is not clear that this circumstance depends exclusively on the friction experienced by the blood in passing through the capillaries, but is probably rather owing, as Mr. Hunter has suggested, to the veins receiving their blood from different arteries, some of whose channels are more circuitous than others, and, consequently, their blood arrives at different times. The momentum of the heart, then, even if it did impinge upon those channels, would not be synchronous upon the venous trunk, but would be divided in such a way as to produce a tre- mour or confused motion. The larger veins, however, have near the heart a pulsatidn during the contraction of the auricles, THE BLOOD. 173 arising from the arrest of their circulation at the moment. During inspiration, the vacuum created in the thorax hurries on the blood to the heart, but in expiration it is somewhat im- peded.* It has sometimes happened, that a large vein near the heart being opened by an accident or an operation, a strong inspira- tion has caused the introduction of air, which, being carried to the heart, has produced instant death. It lately occurred in Pa- ris to the celebrated surgeon Dupuytren. CHAPTER IV. OF THE BLOOD. The Blood, in the human subject, and in many animals, is of a red colour. It is about the consistence of thin size, has a pe- culiar smell, a nauseous and slightly saline taste, and is some- what heavier than water; its specific gravity being about 105) and its temperature in the living body is from 96 to 98° of Fah- renheit. Its quantity is variously estimated at from eight to one hundred pounds, so that there would seem to be no very exact means of ascertaining this point. So long as it continues to circulate, or while it is still flowing from an opened vessel, it has, to common inspection, the appear- ance of a homogeneous fluid; yet, after it has been drawn a few minutes, and permitted to remain at rest, it assumes a thick ge- latinous condition, expressed by the term coagulation, and by * This ancient observation has lately been renewed, with additional interest and details, by M. Barry of Paris. See a Report of MM. Cuvier and Dumeril, con- cerning the Influence of the Atmosphere on the Circulation of the Blood, in the Philadelphia Journal of the Medical and Physical Sciences, July, 1826. M. Bar- ry has probably assigned too much importance to this influence, as it is certain that the circulation may go on very well where no vacuum is produced at inter- vals in the thorax; for example, in the foetus, in incubation, and in fish. Vol. II.—23 174 CIRCULATORY SYSTEM. which it ceases to be any longer fluid. The coagulation begins on the surface of the mass, and by a thin pellicle, which shows itself in three or four minutes; commonly at the end of twenty minutes the coagulation is complete throughout, but this rule varies according to the state of the body at the moment; and the coagulation is more protracted when the quantity of blood is large and has been drawn through a large orifice, than where it is small, and has been evacuated through a small orifice. This change has scarcely taken place, when a spontaneous separa- tion follows, whereby it is resolved into a watery part called Se- rum, and into a thick condensed mass called Cruor or Crassa- mentum. The serum first shows itself on the surface of the co- agulum, in small drops, which quickly increasing in number and size, finally run together, and form a mass of fluid exceeding considerably that of the crassamentum. The separation into se- rum and crassamentum, though sufficiently evident after a few hours, yet requires some days for its complete accomplishment; for the coagulum still continuing to contract, expels more and more of the serum. The peculiar complexion of the blood depends upon a red co- louring matter consisting in globules. This matter does not seem to be an indispensable constituent, as many animals are entirely deprived of it, and such as naturally are possessed of it, may have its quantity very much reduced by repeated bleedings. The colouring matter is generally ah ingredient of the crassamentum, so that the whole of the latter has a red appearance; yet there are some conditions of the body in which a spontaneous separa- tion of it takes place, more or less completely. For example, in inflammatory diseases the blood does not coagulate so soon as in health; and the red globules, from being naturally heavier than the other constituents of the crassamentum, subside to its bottom and leave it of a white semi-transparent colour. It is this white part upon which depends the whole property of coagulating, and which has been called coagulating lymph. We have, therefore, three constituents of blood manifested by its own spontaneous changes; the serum, the red globules, and the coagulating lymph. Coagulation, contrary to popular opinion, is not assisted by cold, but rather retarded by it: heat assists it.* If the heat be raised * Hunter on the Blood. Hewson. THE BLOOD. 175 to 120°, blood will coagulate five minutes sooner than if left at its natural standard, and even sooner than if its temperature be reduced to 50°. If blood be frozen quickly, before it has time to coagulate, on being thawed it returns to the fluid state, and will coagulate afterwards. The contact of air does not produce coagulation. Dr. Physick, in order to ascertain this point con- clusively, took a glass tube, which had a stop cock at each end, and attached one of its ends to the vein of a dog. A current of blood was then conducted through the tube, and while it was flowing, the far stop cock was closed, and im- mediately afterwards the other; thus, a column of blood was obtained which had not touched the air. After permitting it to remain a proper time, the tube was broken asunder, and the blood found coagulated as usual. Rest is not indispensa- ble to the process, for blood, if shaken in a vial, will still co- agulate. The division of the blood into small masses expe- dites coagulation. Therefore, when it flows slowly from the blood vessels, falls from some height, or runs for a distance over the surface of a dish, it coagulates sooner than under op- posite circumstances. The latter are then auxiliary to the blood manifesting the sizy coat, one of the concomitants of inflam- mation ; because, if the coagulation be very rapid, it will pre- vent the constituents of the crassamentum from separating from one another, by entangling the red globules, in the coagulating lymph. After death the blood is coagulated in the veins, though not so perfectly or generally as is supposed, for there are no sub- jects which do not bleed from their large veins, when the latter are opened. There are many modes of death which prevent entirely the coagulation of the blood in the vessels, for example, where life is destroyed by a paroxysm of excessive anger; by electricity; by lightning; by a blow upon the stomach; by certain fevers of a typhoid character. Many chemical articles prevent its co- agulation on being mixed with it. - 176 CIRCULATORY SYSTEM. SECT. I.—OF THE SERUM OF THE BLOOD. Serum is common to the blood of all animals, and is consi- dered, by Mr. Hunter, to be more abundant in such as have red globules. It is, generally ^ of a lighter specific gravity than the crassamentum. I have, however, often seen the latter floating in it, which shows the contrary in some instances. Though its separation commonly depends upon the coagulation of the latter, yet that process is not indispensably necessary, as was once witnessed, by Mr. Hunter, in a lady, in whom the serum was disengaged from the crassamentum, while the latter was yet in a fluid state. The phenomena of dropsy, also, prove the same point. Serum, though very fluid, is not so much so as water. It is a light yellow or straw colour, varying, somewhat, in different subjects. It contains a large quantity of albumen, or matter re- sembling the white of an egg. It also consists of water, of soda uncombined, and of some of the salts of soda, the presence of all which may be manifested in several ways. For example, when exposed to a heat of 140 degrees of Fahrenheit, it becomes opaque, and at 160 or 165 coagulates firmly. During this pro- cess, a great deal of air is disengaged from it. It is also coagu- lated by spirits of wine, by all the mineral acids, by corrosive sublimate, and by many other articles, all of which prove the presence of albumen. Mr. Brande considers this liquid albumen as an albuminate of soda, with an excess of its base, and that its fluidity depends on the excess of soda; when, therefore, the lat- ter is removed or neutralized by an acid, the albumen coagu- lates. Under the action of the Galvanic pile, like the influence of heat, the soda produces mucus, by blending with a part of the albumen; and the remainder of the latter, not being able to retain its fluidity after the abduction of the soda, coagulates. This mucus is, probably, the part which Mr. Hunter speaks of as retaining its fluidity when other portions of the serum are coagulated by heat. It is observed in meat either roasted or boiled, and comes from it as a thin, limpid fluid, somewhat tinged with the red globules. The older the animal is, the greater is its comparative quantity: in lamb, there is scarcely COAGULATING LYMPH OF THE BLOOD. 177 any of it, whereas, in mutton five or six years old, it is abun- dant ; the same rule seems to hold in regard to the human sub- ject. This serosity, or mucus, is coagulable by Gourlard's Ex- tract* The serum is not always transparent, but sometimes wheyish and thin: when it settles, it often throws up a white scum like cream. This more frequently occurs in pregnant women, though it is not confined exclusively to either sex, or to any known con- dition of body. The specific gravity of the globules composing this scum varies; for though it generally floats on the surface of the serum, it does not always: it also sometimes swims, and, on other occasions, sinks in water. It has been erroneously considered as chyle not yet assimilated, or as absorbed fat or oil. It is, probably, this substance which presents itself under the form of microscopic globules in the coagulum of serum; and, when serum has been kept for several days, is deposited in the form of globules at its bottom. These globules present a singular motion of ascent and descent in the serum; upon the application of heat to it by holding it in the hand. It is said that albumen, coagulated, presents a very close resemblance to fibrine.f The presence of soda uncombined in the serum, is readily as- certained by an infusion of red cabbage, (Brassica oleracea,) or the juice of the flag, (iris versicolor,) which are both made green by it. Sulphur combined with ammonia, is also found in it. Owing to the presence of sulphur, serum has the effect of black- ening silver when left in it, and also has its power of dissolving the oxydes of mercury, iron, copper, and other metallic prepa- rations. SECT. II.--OF THE COAGULATING LYMPH OF THE BLOOD. Coagulating lymph, or fibrine, when circumstances are suita- ble for collecting it, freed from the red globules, offers the ap- pearance of a semi-transparent body of a very light drab colour; it is elastic and strong, and, when subjected to the microscope, has the appearance of muscular fibres, by being composed of * Hunter, loc. cit. f Beclard, loc. cit. 178 CIRCULATORY SYSTEM. colourless globules. Like muscle, it also, when macerated in water, resolves itself into those globules before it putrefies. If the blood, while flowing from an animal, be collected, and, at the same moment, stirred round and round with a rough stick, the fibrine will gather upon the latter in a fibrous form, so as to resemble a mass of entangled and knotted packthread. The fibrine may be afterwards washed almost white, and, at any rate, so as to clear it entirely from the red globules. The fibrine, when dried, loses greatly in its bulk and weight, by the evaporation of the serum from it, so that the proportion which it seems to bear to the whole mass of blood is much less considerable than one would suppose from seeing it in the sim- ple coagulated state. The coagulating lymph of the blood being common, probably, to all animals, while the red particles are not, we must suppose it from this alone to be the most essential part; and, as we find it capable of undergoing, in certain circumstances, spontane- ous changes, which are necessary to the growth, continuance, and preservation of the animal; while to the other parts we can- not assign any such uses, we have still more reason to suppose it the most essential part of the blood in every animal."* SECT. III.--OF THE RED GLOBULES OF THE BLOOD. The particles of blood upon which its red colour depends are, by a majority of observers, considered to be globular, and while the blood circulates they float about in the lymph and serum. They are of the same size in animals of the same species, and have no tendency to run into each other, as globules of mercury would. They are plastic, by which they can assume an ellip- tical shape when they circulate through vessels of a very small size. According to the microscopical observations of Mr. Bauer, each globule is one two-thousandth part of an inch in diameter, but Capt. Kater does not consider it to exceed one five thou- sandth part of an inch.t There seems, however, to be a great • Hunter, loc. cit. f Phil Trans. 1818. RED GLOBULES OF THE BLOOD. 179 uncertainty in these estimates of form and of size, inasmuch as different observers do not agree among themselves. Father Delia Torre considered them as flat circles or rings, with a perforation in the centre, while Mr. Hewson, in ascribing the same shape, represented them as hollow or vesicular, with a red dot in the middle. Mr. Bauer, on the contrary, considers that the dot, or colouring matter of the globule, is placed upon its periphery. As the colour is supposed to depend upon particles of iron, Dr. John Mason Good has wittily suggested, that, ac- cording to Mr. Hewson, we have the wheels of life moving upon iron axles, whereas, according to Mr. Bauer, they only have iron tiers.* It has .been observed that the red globules are the heaviest part of the mass of blood, and are, therefore, always disposed to subside to the bottom of the crassamentum, though, from the quick coagulation of the latter, they can seldom do it before they become entangled in it, and thereby fixed to a certain place- They do not invariably retain their form, but are readily dis- solved in water. They are, of course, insoluble in serum. Urine does not dissolve them; neither does a solution of muriate of soda, of sal ammoniac, Epsom salts, nitre, diluted sulphuric or muria- tic acid: the latter, however, deprives them of colour. The solution of red globules in water is manifested by the mix- ture becoming of a fine transparent red, and the process takes place almost immediately. On the contrary, when the globules refuse to be dissolved, a muddy mixture is formed. When they are dried in serum, and afterwards soaked again in it, they do not resume the globular form. They have more substance than the coagulating lymph, for they do not lose so much of their bulk by drying. Notwithstanding the doubts that have been raised on the sub- ject, it seems now to be very well ascertained, that iron is the colouring principle of the red globules of the blood, though it cannot be detached in the coloured state, owing to the absolute necessity of using strong heat, or concentrated acids to destroy the substance with which it is combined. The iron is an oxide with a small quantity of the sub-phosphate, but a knowledge of * Study of Medicine, vol. ii. p. 25. 180 CIRCULATORY SYSTEM. this fact does not enable the chemist to imitate red globules by mixing these chemical substances with albumen. The process by which Berzelius obtains iron from the blood, consists in placing a clot of the latter upon blotting paper, whereby its se- rum is absorbed. The clot being afterwards put into water, its colouring matter is dissolved, while the lymph remains entire; by removing then the lymph, and evaporating the water, the co- louring matter is obtained, which, on being reduced to ashes, renders about one to two-hundredth part of its weight in iron. The chemists also inform us, that fibrine, albumen, and the co- louring matter, all resemble one another so closely, that they are only modifications of one and the same substance; and that each of them yields, upon decomposition, phosphate and carbonate of lime, though these ingredients cannot be detected by tests ap- plied to the entire mass of blood. " It is difficult to determine by what means the iron, or the sulphur, or the elementary principles of calcarious earth, obtain an existence in the blood. If these materials were equally dif- fused throughout the surface of the earth, we might easily con- ceive that they were introduced through the medium of food. But as this is not the case, as some regions, like New South Wales, at least, on this side the Blue Mountains, contain no lime- stone whatever, and others, no iron or sulphur, while all these are capable of being obtained apparently as freely from the blood of the inhabitants of such regions, as from that of those who live in quarters where such materials enter largely into the natu- ral products of the soil; it is, perhaps, most reasonable to con- clude that they are generated in the laboratory of the animal system itself, by the all-controlling influence of the living prin- ciple."* The red globules, according to the opinion of Mr. Hunter, from not being pushed into the extreme arteries, where the coagulating lymph reaches, and from not being found in all ani- mals, do not contribute to the growth and to the repair of the system. But they seem to be connected with strength, in such animals as have them, as the strength acquired by exercise in- * Good, loc. cit. RED GLOBULES OF THE BLOOD. 181 creases their proportion and occasions them to be carried abun- dantly into parts which previously, from a debilitated state, re- ceived them but partially, if at all. This fact is well known to graziers, who keep their quantityin certain animals, as veal, re- duced by quietude and frequent bleeding. Their source is not understood, though many conjectures on the subject have been hazarded. Mr. Hunter's opinion was, that they do not appear to be formed in those parts of the blood already produced, but rather to rise up in the surrounding parts; as, in the incubated egg, they exist in the form of a zone, com- posed of dots, previously to the formation of vessels. This fact ought to quiet all speculations about their coming from the spleen, thymus gland, and so on. Vol. II—24 BOOK VIII. PART II. Of the Special Jinatomy of the Circulatory System. CHAPTER I. OF THE HEART AND PERICARDIUM. The Heart, (Cor,) the centre of the circulation, is situated in the thorax, between the sternum and the spine; being bounded on its sides by the lungs, and below by the tendinous centre of the diaphragm. It is a hollow muscular organ. The heart is of a conoidal shape, but flattened on the surface which lies upon the diaphragm. This flat surface is on a hori- zontal line with the lower end of the second bone of the ster- num; the base of the cone is towards the vertebrae, and looks obliquely backwards to the right side, while the apex is about the junction of the left fifth rib with its cartilage. Being placed between the right and the left pleura, in the mediastinum, it is surrounded by its own proper capsule called the pericardium. Its common weight is about six ounces. Its greatest length, to wit, that from- the apex to the base, is about five and a half inches, four of which are taken up by the ventricles: its base is about three and a half inches in diameter. The heart is divided into four cavities; two auricles and two ventricles: the places where the'partitions are placed between these cavities are marked on the surface of the heart by fissures, sufficiently distinct to be immediately recognised. The two auricles form the base of the heart, the ventricles constitute its 184 CIRCULATORY SYSTEM. body, and the anterior end of the left ventricle, by being ex- tended somewhat beyond the right, forms the apex. The right auricle and the right ventricle are the two cavities which are nearest to the right side of the body, while the left auricle and the'left ventricle are the two cavities nearest to the left side. It will, however, be understood, from the general observations already made, that the relative situation of these cavities is such that the right ones are in front of the others, and present ob- liquely forwards to the right side, while those on the left side look obliquely backwards to the left side. This position of the heart makes it encroach more upon the left cavity of the thorax than it does on the right; from which cause its pulsations may be very easily distinguished where the left ribs join their carti- lages, while on the right side of the sternum there is scarcely ever a perceptible pulsation. The Pericardium is covered on its sides by the pleurae, and reposes on the tendinous centre of the diaphragm, to which it adheres by close compact cellular substance, particularly at its periphery. When the latter attachment is cut through, a sepa- ration of the remainder is easily effected. Behind, the pericar- dium is opposed to the bronchiae and the oesophagus. The pericardium does not adhere to the heart, except at the base of the latter; it is, therefore, a loose capsule in, by far, the greater part of its extent. It not only surrounds the heart, but also the roots of the large arteries and veins connected with it. Thus, it includes the aorta, as high up as the great vessels pro- ceeding from its arch; from the latter, it passes to the trunk of the pulmonary artery, and also includes it, causing the aorta and the pulmonary artery to lie close together. The posterior face of these vessels is not covered so high up as the anterior face. The pericardium also invests the descending vena cava for an inch above its junction with the right auricle: it likewise in- vests the trunks of the pulmonary veins, and the ascending cava as it rises above the diaphragm. The pouches which it forms at the base of the heart, in passing from one of these vessels to another, are the cornua of some anatomists. It cannot be con- sidered as pierced for the passage of these vessels, but is lost in- sensibly on their parietes; being continued into the cellular co- THE HEART. 185 vering of the arteries, in accompanying them to a great dis- tance.* The pericardium is a double membrane, or consists of two layers, an internal and an external one. The external mem- brane, to which the preceding description is especially applica ble, resembles strongly the dura matter, but is thinner; it is, therefore, white, semi-transparent, fibrous, and inelastic. Its thickness is greater on the sides than below, where it rests upon the diaphragm, or above, where it goes along the great' vessels: its fibres are irregularly disposed and interwoven, but many may be traced longitudinally. The internal membrane lines the external, and gives the po- lish to its cardiac surface; it is then conducted along the sur- face of the several vessels that have been mentioned, to the heart, over the whole of which it is spread, and adheres to it by cellular substance, frequently containing much adipose mat- ter: it also causes the heart to have a smooth shining surface. This is a very delicate thin serous membrane; and secretes a fluid, transparent and somewhat unctuous, like that of the joints, but not so consistent; which lubricates the surface of the heart and permits it to play freely within its pericardium. This fluid, in a natural state, seldom exceeds a tea-spoonful, though two ounces, or a little more, are not considered sufficient evidence of a pathological state: its augmentation constitutes a dropsy. After death, we find the pericardium lying loosely upon the heart, from the vacuity, and consequently diminished bulk of the latter; but while the circulation is going on, the heart fills and distends it. A striking resemblance is observable between the condition of the pericardium and the moveable articulations. Its external membrane corresponds with the strong fibrous cap- sule that passes from one bone to the other; while the internal is the synovial bag, which scarcely assists in the strength of the apparatus, but secretes a fluid to render motion easy. Several instances are on record of a total absence of pericardium. The Right Auricle (Auricula Dextra, anterior) is an oblong cuboidal cavity. It is joined at its posterior superior angle by * Sabatier, Trait. d'Anat. vol. ii. p. 284. 18G CIRCULATORY SYSTEM. the descending vena cava, and at its posterior inferior angle by the ascending vena cava. The structure of the auricle, between these two points, seems to be only a continuation of that of the veins. These veins enter with a direction slightly forwards, so that their columns of blood are not directly opposed to each other. In front of this continuation of the two veins, the auri- cle is dilated into a pouch called its sinus; the upper extremity of the latter, just in front of the descending cava, is elongated into a process with indented edges, that hangs loose, and has some general resemblance to the ear of an animal, from which it is probable that the term Auricle has been derived. The exterior surface of this cavity is smooth and uniform, but its internal surface is varied at several places. About midway between the orifices of the two cava? is found a transverse pro- minence, the Tuberculum Loweri, which is occasioned by the continuous structure of the veins meeting at an obtuse angle. This cavity is separated from the left auricle only by a thin sep- tum, which is common to the two auricles. On the septum, below its middle, is a superficial circular depression, the Fossa Ovalis; it is more distinct above than below, and varies much in its dimensions. It is surrounded by an elevated margin, com- posed of muscular fibres, and called its Annulus, or the Isthmus of Vieussens. The septum of the auricles is thinner at the fos- sa ovalis than elsewhere, and is frequently perforated by one or more foramina. I have, in several instances, seen a hole there, large enough to transmit the finger. On similar, occasions, from the valvular arrangement of the opening, it is probable that the blood of the two auricles is still kept distinct. The fossa ovalis always presents this foramen in the foetal state. Just below the fossa ovalis is found the Eustachian valve, consisting in a duplication of the lining membrane of the auri- cle. It is crescentic, but varies much in its dimensions and shape. Its left extremity commences at the left inferior mar- gin of the annulus ovalis; it then extends itself along the front of the orifice of the ascending cava, where the latter is con- nected with the auricle, but never to an extent sufficient to ar- rest the circulation there. Sometimes it is reticulated at its margin, and half an inch wide; on other occasions, it is scarcely THE HEART. 187 developed. Its loose edge looks upwards, and to the right side. Its office in the foetus is clearly, according to the opinion of Sa- batier, to direct the blood of the ascending cava through the fo- ramen ovale. In the adult, it may, on the general principle of venous valves, oppose itself to the introduction of refluent blood into the ascending cava; but this office cannot be very impor- tant, as the valve is frequently scarcely visible at that age. At the lower part of the right auricle, just to the left of the Eustachian valve and very near it, is the orifice of the large co- ronary vein of the heart: it is protected by a small semi-lunar valve, (Valvula Thebesii,) formed also by a duplication of the lining membrane of the auricle. This orifice will admit a quill of common size very readily. Between the right auricle and ventricle is a round hole, of more than an inch in diameter, for the passage of the blood; it is the Ostium Venosum. Its margin, on the auricular side, is smooth and rounded. The parietes of the right auricle are formed by muscular fibres. On the sinus these fibres are collected into small trans- verse fasciculi, called Musculi Pectinati, from their resembling the teeth of a comb. These fasciculi, though slightly united by other fibres, yet leave between them deep interstices, by which the external and the internal membrane of the heart come into contact. The parietes of the auricle are about one line in thickness. Its muscular structure is continued for a short dis- tance, on the two venas cavae. There are several orifices of small veins on the internal surface of this cavity, and in greater abundance around the fossa ovalis; they belong to the system of coronary vessels, and are the foramina Thebesii. The right Ventricle (Ventriculus Dexter, anterior.) The general form of this cavity, which receives the blood from the right auricle, is that of a triangular pyramid, curved somewhat backwards, and having its base downwards. It forms the great- er part of the anterior surface of the heart, and is about three lines in thickness. It is bounded on its posterior face by the left ventricle, from which it is completely separated by a thick septum. The internal surface of this cavity is covered by muscular fasci- 188 CIRCULATORY SYSTEM. culi, of very irregular shapes and dimensions, designated under the term of Columnar Carneae: some of the latter go from one side to the other; others contribute to the mechanism of the valvu- lar apparatus between it and the right auricle; but the greater portion is employed in forming a complicated reticular texture over the internal face of the ventricle. Those connected with the valve vary from four to eight in number: they are rounded, of different lengths and sizes, and detach from their projecting extremities several small rounded tendinous chords, (chordae tendineae,) which are inserted into the floating edge of the valve. These chords sometimes form an intertexture among them- selves. The Valve, between the ventricle and the auricle, consists in a duplicature of the lining membrane of the ventricle, arising uninterruptedly from around the ostium venosum, at the left margin, which is there somewhat tendinous. This Valve is called the Tricuspid, (Valvula Tricuspis, Triglochis,) because its loose margin is divided into three points or processes. One of these points, which is at the anterior external margin of the orifice, is much larger than the other two and more distinct in its boundaries. The edges of these processes form a sort of re- ticulated work along with the adjoining ends of the tendinous chords: by this arrangement they are always kept expanded and in the cavity of the ventricle. The opening for the pulmonary artery is placed above the ostium venosum; at this point, the cavity of the ventricle, in- stead of being reticulated, is made smooth, for the more ready transmission of blood. The orifice of the pulmonary artery is round, and about twelve lines in diameter; it is furnished with three valves, called from their shape Semi-lunar or Sigmoid. Each valve is a semicircular plane, formed from the lining membrane of the artery, and attached to the latter by its semi- circumference. The diameter of the plane is loose, and, instead of being straight, has each semi-diameter of a curved or fes- tooned shape: in the centre of its edge is a small cartilaginous body, the Corpusculum Aurantii, which, when the valve is thrown down by the reaction of the artery, comes in contact with the corresponding bodies of the other valves, so that they serve as mutual abutments. Between the outer face of each THE HEART. 189 valve and the artery there is a pouch, attended with a slight dilatation of the artery, and called the Sinus Valsalva. Between the coats of each valve there is an additional fibrous substance, for the purpose of strengthening it. The Pulmonary Artery, immediately after its origin, goes upwards and backwards to the under part of the curvature of the aorta, and there divides into two trunks, one for each lung. These trunks separate widely, and from the middle of their fork proceeds a ligamentous substance, the remains of the Ductus Arteriosus of the foetus, to the aorta posteriorly to the origin of the left subclavian artery. The right Pulmonary artery is both longer and larger than the left, and passing transversely behind the aorta and the descending cava, then penetrates the substance of the lung to be distributed as mentioned. The left pulmonary artery passes to the lung in front of the descending aorta. Though the pulmonary artery is quite as large as the aorta, its parietes are thinner. The left Auricle, (Auricula Sinistra, posterior,) in the na- tural situation of the heart, is concealed by the right auricle and the ventricles. Its figure is more regularly quadrangular, or square, than that of the right, and into each of its angles is introduced a pulmonary vein, their being two on each side. Sometimes, however, the latter join together previously, so that the two have but a common orifice. Its tip, or ear-like portion, is situated at the left side of the pulmonary artery, and is longer, narrower, more crooked, and more notched at its margins than the corresponding portion of the right auricle. The parietes of this cavity are muscular, and somewhat thicker than those of the right; they are smooth and uniform, both externally and internally, with the exception of its ap- pendix or ear-like portion, in which the musculi pectinati pre- vail. The term sinus venosus or sinus pulmonalis of anato- mists, only means that part of the cavity into which the pul- monary veins empty. The septum between the auricles, when viewed on this side, has the place of the fossa ovalis marked out principally by its diaphanous condition. Occasionally, there is some appearance of the valve which once existed there. Vol. II.—25 190 CIRCULATORY SYSTEM. At the inferior part of the anterior side of this cavity is found the opening between it and the left ventricle, also called Ostium Venosum; it is circular, and rather more than an inch in dia- meter, resembling strongly the corresponding orifice of the right side of the heart. The Left Ventricle (Ventriculus Sinister,posterior) in the shape of its cavity resembles a long ovoidal or conical body. Its parietes are generally three times as thick as those of the right ventricle, amounting to about eight lines: it is thicker, however, at its inferior than at its superior part, as it gradually decreases.in approaching the aorta. Its internal surface is arranged on the same principle with that of the right ventricle, being roughened by the presence of numerous fleshy columns (Columnae Carneae) some of which are connected with the valvular apparatus between it and the left auricle; others form an intricate reticular texture on its sides, and a few pass from one side to the other. As this sur- face approaches the orifice of the aorta, it becomes smooth, so that no impediment may be afforded to the passage of the blood. The Ostium Venosum, on the side of this cavity, has its mar- gin looking tendinous, and furnished with a duplicature of the lining membrane that surrounds it. This duplication, by being severed on its loose edge into two divisions, obtains the name of Mitral Valve, (Valvula Mitralis.) Its margin is secured from being pushed into the left auricle by several chordae ten- dineae, which are attached by their other extremities to four or five columnae carneae projecting from the surface of the ven- tricle. The whole internal arrangement of this cavity indicates a great increase of strength over that of the right side: in the robustness of its fleshy columns, the number and size of its ten- dinous chords, and the greater thickness of its valve. The upper division of the mitral valve is placed immediately below the orifice of the aorta, and is considerably broader than the other, so that when it opens to admit blood, it is in some mea- sure thrown over the aortic orifice. There is less of an in- tertexture among the tendinous chords here than on the right THE HEART. 191 side of the heart: they cluster more, and, owing to the breadth of the extremities of the fleshy columns, are more pa- rallel. The Septum of the Ventricles is of considerable thickness, being formed almost exclusively by the continuation of the fibres of the left ventricle. Where the large columnae carneae elevate themselves on its surface, its thickness is increased. Its shape is somewhat triangular. It forms a round projection into the right ventricle, while its other surface, which presents to the left, is concave to the same degree. It is rather thinner as is approaches the auricular septum than elsewhere. Its fibres near the apex are less closely connected to each other. The Orifice of the Aorta is furnished with three semi-lunar Valves, which, in the mode of their arrangement, correspond precisely with those of the pulmonary artery. They are, how- ever, thicker, and the Corpuscula Aurantii are larger. The Sinuses of Valsalva, attended with a slight dilatation of the ar- tery, exist in the same way. Just beyond the margins of the right and of the left valves are observed the orifices of the two coronary arteries. The orifice of the aorta is somewhat tendi- nous, which marks out the distinction of structure between it and the ventricle.* Of the Texture of the Heart. The Heart, with the exception of the membrane which lines * Mr. Erskine Hazard has furnished me with the following1 estimate on the action of these valves:— If the diameter of the artery be put = 10, the length of the superior edge of the valve will also be 10. The arc occupied by the valve will be 10.47= 120° of the circle. The valves, when open, will either assume the form at B, or that of the double chord of 60°, as at A. In either case, being .47 shorter than the arc, they cannot come in contact with it, and must, therefore, leave room for the blood to get behind them, and depress the valves. For the same reason, they cannot close the orifice of the coronary arteries. The chord of 120° would be 8.67. 192 CIRCULATORY SYSTEM. its cavities, and of the serous lamina of pericardium which co- vers its surface, consists entirely of muscular fibres. The sides of the auricles, as stated, are much thinner than those of the ventricles. In the right auricle, the stratum of muscular fibres is uniform in its venous portion, but on the sinus is arranged into the parallel fasciculi called the Musculi Pectinati; a circular fasciculus surrounds the orifice of the de- scending cava. In the left auricle, the stratum of muscular fibres forms a uniform layer, and is also thicker than on the right side. These fasciculi commence on the pulmonary veins and run transversely across the auricle, with the exception of the more deeply seated, which are irregular, and crossed upon each other. The septum of the auricles is also formed by a muscular stratum. In the ventricles, the superficial fasciculi observe a spiral course, and many of those belonging to the left ventricle may be traced over the right; as the fibres are more deeply situated, they become shorter and more interwoven. In the septum, between the ventricles, the fibres of the two cavities are much interlocked; but, with some trouble, may be partially separated. The fibres of the columnae carneae are too irregular in their course to admit even of a general description. It would appear, however, that they are a continuation of the superficial spiral fibres of the ventricles which penetrate into the interior of the heart at its apex, and leave there a small foramen which is closed only by the pericardium, externally, and the lining membrane of the heart. M. Gerdy asserts, that all the fibres of the heart arise from, and are inserted into, the tendinous rings forming the ostia venosa and the orifices of the arteries; having in the mean time traversed the course which is peculiar to the several fasciculi, according to their being superficial, in the middle or deep-seated.* All the cavities of the heart are lined by a serous membrane, resembling that of the blood vessels. * For a very detailed exposition of the Structure of the Heart, see Wolff Act. Acad. Petrop. 1781; and Gerdy, Journal Complementaire du Diet, des Sc. Med. vol. x. p. 97. THE HEART. 193 Of the Blood Vessels of the Heart. The Heart is furnished with both arteries and veins, which be- long to its nutritious system. The arteries, called Coronary, arise, as observed, from the trunk of the aorta, somewhat above the margins of the semi-lu- nar valves; so that when the latter are applied against the aorta, the orifices of these arteries are still visible. The Right Coronary Artery begins above the anterior valve, and passes to the right, beneath the pulmonary artery; it then shows itself in the upper part of the fissure, between the right au- ricle and right ventricle, and follows the course of this fissure to the flat side of the heart. It detaches, as it goes along, several small branches, which come off at right angles from it. One set of these branches is distributed upon the right ventricle, and ano- ther set upon the right auricle. Small branches are also sent from it to the root of the pulmonary artery, and to that of the aorta. The Left Coronary Artery begins above the left semi-lunar ■ valve. While its root is still obscured by the pulmonary artery, it divides into two principal branches, of which the anterior runs in the fissure on the upper part of the septum of the ventricles to the apex of the heart, and in this course distributes branches to the right and left ventricles: those to the right anastomose with the branches of the right coronary artery, which go to the same ventricle. The other branch goes along the groove, on the sep- tum, between the left auricle and left ventricle, and reaches the under surface of the heart; and in this course distributes many branches -to the left auricle and left ventricle, both on their upper and under surfaces. It anastomoses freely with the branches of the trunk that run along the upper part of the septum. In consequence of the frequency of the anastomoses between the two coronary arteries, injecting matter thrown into one very readily finds its way into the other. 194 CIRCULATORY SYSTEM. The Coronary Veins receive the blood, which is distributed by the coronary arteries through the substance of the heart. The Great Coronary Vein ( Vena Coronaria Maxima Cordis) is formed by the union of several trunks, which run from the apex towards the base of the heart. One of them begins at the apex, goes along the superior fissure of the septum of the ventricles, and then winds to the left side, between the left auricle, and the left ventricle: while in the latter position, it is joined by several trunks coming from the left ventricle and the left auricle: it, finally, empties into the lower part of the right auricle, just in front, as mentioned, of the orifice of the ascending cava; being there covered by its own valve. The Lesser Coronary Vein (Vena Coron. Minor Cordis) lies in the inferior fissure of the septum of the ventricles. It begins at the apex, and, going backwards, collects the blood from the flat surface of the heart, principally on the right ventricle. It dis- charges into the great coronary vein, just before the latter ter- minates in the auricle. Besides the preceding veins, some of a! smaller size exist on the right ventricle, and about the root of the aorta and pul- monary artery, and, empty by several orifices into the right au- ricle. There are also some veins of a still smaller size, which open into all the cavities of the heart by little orifices, called the Foramina of Thebesius: by Mr. Abernethy they are considered as being larger when the lungs are diseased.* The Nerves of the Heart come principally from the cervical ganglions of the sympathetic, and follow the course of the coro- nary arteries. It has been doubted whether these nerves are actually distributed in the substance of the heart, from the pre- sumption, that as they cannot be traced beyond the third order of branches of the coronary arteries, they are limited to them. But, as the ramifications of the sympathetic are bestowed exclu- sively upon the branches of the circulatory system, Meckel has • London Philosophical Transactions, 1798. BRANCHES FROM THE ARCH OF THE AORTA. 195 very properly suggested, that the heart being also supplied with nerves from the same source, it follows that there can be no de- parture from the general rule, as the heart is nothing more than the fibrous portion of the blood vessels more completely deve- loped. While the circulation continues, as both auricles contract at the same instant, whereby the blood is thrown into the ventri- cles, and as immediately afterwards the ventricles contract si- multaneously also, whereby the blood is forced into the aorta and the pulmonary artery, so it is the contraction of the ventricles which causes the heart to strike against the parietes of the tho- rax. For, as was first pointed out by Dr. W. Hunter, the blood which is forced through the large arteries, by extending them diminishes their curvature, or brings them more into a straight line, in which effort the heart bounds up from the tendinous cen- tre of the diaphragm. The filling of the auricles, while this is going on, also assists in protruding the heart forwards. The French anatomists assert, that during the contraction of the ven- tricles, their extremity is elevated or bent upwards on the body of the heart, which will also increase the momentum of the stroke against the thorax. CHAPTER II. OF THE ARTERIES. SECT. I.--THE AORTA AND THE BRANCHES FROM ITS CURVATURE- The Aorta is the trunk of the arterial system. Having arisen from the superior posterior end of the left ventricle, its root passes beneath the pulmonary artery, and is entirely concealed in front by it. Keeping to the right, it emerges from' the base of the heart, between the right auricle and the trunk of the pulmo- nary artery, being bounded on the right side by the descending # 196 CIRCULATORY SYSTEM. cava. Continuing its ascent, it forms a curvature with the con- vexity upwards, and the summit of which rises to within eight or twelve lines of the superior edge of the sternum. This cur- vature is in front of the third and fourth dorsal vertebrae, and its direction is nearly marked out by a line drawn from the anterior extremity of the third right rib, to the posterior end or tubercle of the third one on the left side. In this course, therefore, the aorta passes over the right pulmonary artery, across the left bronchia, and applies itself to the left side of the spine, about the third or fourth dorsal vertebra. It is this curvature which ob- tains the name of the Arch of the Aorta, (Arcus Aorta.) Near its origin, where the aorta is still within the pericardium, it has very commonly, especially in persons advanced in age, a dilatation, which is called the great sinus to distinguish it from the lesser sinuses, or those of Valsalva. This dilatation is use- ful in diminishing the resistance arising from the curvature of the aorta, to the current of blood, or rather it is a provision for doing away with the effects of this friction, whereby a larger current of blood becomes a compensation for diminished velo- city. The ascending portion of the arch is to the right of the vertebral column, the descending portion to the left, and the mid- dle or horizontal part goes in front of the trachea. The aorta, in its descent down the thorax, is placed in the posterior mediastinum, and is covered on one side by the left pleura, while the other side is in contact with the left surface of the bodies of the dorsal vertebrae. At the lower part of the tho- rax it inclines towards the middle line of the vertebras, in order to reach the hiatus aorticus of the diaphragm, through which it penetrates to the abdomen. In the abdomen it descends in front of the lumbar vertebrae, somewhat inclined to their left side; and at the intervertebral space between the fourth and fifth vertebrae of the loins, or somewhat above it, it ceases, by being divided into two large trunks, the Primitive Iliacs; one for each lower extremity, and the corresponding side of the pelvis. In this course of the aorta, from the heart to the loins, it first gives off the branches which supply the head and the superior extremities: then, those which supply the sides of the thorax; af- terwards, in the abdomen, it detaches the trunks which supply the viscera and the sides of the latter cavity. * BRANCHES FROM THE ARCH OF THE AORTA. 197 . The Coronary Arteries are, strictly speaking, the first branches of the aorta, but as they belong especially to. the heart, their de- scription is associated with it. In all the space between them and the superior convexity of the aortic arch no branches are given off; but as the aorta is crossing the trachea three conside- rable trunks arise from it, which are distributed upon the head and the upper extremities principally. They are, the Arteria Innominata, the Left Primitive Carotid, and the Left Subcla- vian. The Arteria Innominata is first in its origin: in ascending from left to right in front of the trachea, and behind the transverse vein, it crosses the trachea very obliquely; is from an inch to an inch and a half, and sometimes, though rarely, two inches long, when it divides into the right subclavian and the right pri- mitive carotid. The left primitive carotid arises from the aorta, close upon the left border of the innominata; frequently, indeed, from a part of it. The left subclavian, though at its origin, near the left carotid, generally leaves a distinct interval of one, two, or three lines. The relative situation of these trunks is particu- larly alluded to in the account of the superior mediastinum. The two last are, of course, longer than the corresponding trunks of the right side, by the whole length of the arteria innominata. With the exceptions connected with their mode of origin, the ar- terial trunks of the two sides are exactly alike, and have the same mode of distribution. The Common Carotid Artery (Carotis Primitiva) being a branch of the innominata on the right side, and of the aorta on the left, goes up the neck to terminate just below the cornu of the os hy- oides. In the early part of its course, the right one is more in- clined outwardly than the left, owing to its origin from the arte- ria innominata in front of, and to the right side of the trachea; whereas, the left ascends almost vertically. At the lower part of the neck, just above the sternum and the clavicle, the carotid is covered by the sterno-hyoid and thyroid muscles, and by the sternal portion of the sterno-cleido-mastoid. It is crossed obliquely on a line with the lower part of the thy- Vol. II.—26 198 CIRCULATORY SYSTEM. roid cartilage or of the larynx, by the omo-hyoid muscle. It lies at the side of the thyroid gland, the trachea, the larynx, the oeso- phagus, and pharynx, in front of the transverse processes of the cervical vertebrae, and the longus colli muscle; having on it3 outer margin, but somewhat in front the internal jugular vein, and the pneumogastric nerve enclosed in the same sheath, and the sympathetic nerve behind. At the side of the larynx, the carotid is very superficial, and, with the exception of being crossed by the omo-hyoideus muscle, it is only covered by the platysma myodes and the integuments. The Carotid having got as high as the space between the os hyoides and the thyroid cartilage, but varying slightly in differ- ent subjects, there divides into two large trunks, the Internal Carotid, which goes to the brain and to the eye, and the Exter- nal Carotid, which is principally distributed upon the more su- perficial parts of the head and neck. The first of these trunks is placed behind the other, and bends outwardly at its root: it is generally the largest in infancy, on account of the proportionate volume of the brain at that age; it is also swollen at its root, so as to form a sinus there, resembling an incipient aneurism. No branch, except in the abnormous cases, is given off from the ca- rotid between its origin and bifurcation. SECT. II.--OF THE CAROTIDS, AND THEIR BRANCHES. The Internal Carotid, (Arteria Carotis Interna,) in the adult, is smaller than the external, and extends from the larynx to the sella turcica. It ascends between the external carotid and the vertebrae of the neck, being in front of the internal jugular vein, and having the pneumogastric nerve at its outer margin: as it gets on a level with the base of the lower jaw, it is crossed ex- ternally by the digastric and the stylo-hyoid muscles: it is im- mediately afterwards concealed in the subsequent part of its ascent by the ramus of the lower jaw. Having gone along the most internal or deeply seated margin of the parotid gland and the styloid process of the temporal bone, at the side of the supe- CAROTIDS, AND THEIR BRANCHES. 199 rior constrictor of the pharynx, it then penetrates into the crani- um through the carotid canal of the temporal bone. It is slightly flexed between its origin and the carotid canal: just before it reaches the latter it curves upwards and forwards. The first part of its course through the canal is vertical, after- wards it goes horizontally forwards; and to escape from the ca- nal it has once more to ascend almost vertically, which brings it to the posterior extremity of the Sella Turcica. On the side of the Sella Turcica it again passes horizontally forwards through the cavernous sinus; and at the anterior clinoid process it once more ascends, and having penetrated the dura mater, it reaches the brain. In this passage, through the carotid canal, it is attended by the upper extremity of the sympathetic nerve, and gives one or more small branches to the petrous bone; it also gives a few branches to the dura mater and to the nerves about the caver- nous sinus. But for the full exposition of the distribution of the internal carotid, see the articles Brain and Eye. The External Carotid Artery (Carotis Externa) extends from the termination of the primitive carotid, to the neck of the lower jaw. In the early part of its course, where it is situated in front of the internal carotid, and between the pharynx and the sterno- mastoid muscle, it is comparatively superficial, being only enve- loped by its sheath, and covered by the platysma myodes and the skin. Just above this place it is crossed externally by the hy- poglossal nerve, which detaches the descending branch along the front of its sheath and of that of the primitive carotid. Some- what above this nerve, it is also crossed externally by the digas- tric and the stylo-hyoid muscle, and lies there on the side of the superior constrictor muscle of the pharynx, near the tonsil gland. About its middle, it is crossed internally by the stylo-glossus and the stylo-pharyngeus muscle; it then ascends through the sub- stance of the parotid gland, between the ramus of the lower jaw and the ear, to its termination. Several very important branches are given off from the ex- ternal carotid; they are as follow: The Superior Thyroid Artery (Art. Thyroidea Superior) arises 200 CIRCULATORY SYSTEM. from the external carotid, about a line above its root, and is dis- tributed to the larynx and to the thyroid gland. It goes at first inwards and forwards on the side of the larynx, being covered by the omo-hyoideus muscle, and by the platysma myodes; it then descends under the sterno-thyroideus to the upper margin of the lobe of the thyroid gland. In this course, it performs several flexuosities, of considerable variety in different indivi- duals. The Laryngeal Branch comes from it near the superior margin of the thyroid cartilage; this branch glides in between the thyreo- hyoid muscle and the middle membrane or ligament of the same name; after a short course, it penetrates the latter, and is then distributed in a great number of small twigs to the muscles and to the lining membrane of the larynx. A small trunk, either from the laryngeal branch, or from the thyroid artery itself, is spent upon the crico-thyroid muscle, and traversing the front surface of the middle crico-thyroid ligament, anatomoses with its fellow: small twigs from this branch penetrate to the interior of the larynx through the middle crico-thyroid ligament. Some- times this crico-thyroid ramus - is superior in size to the one above, in which case, it principally supplies the interior of the larynx. The Thyroid Branch is the continuation of the principal trunk: it penetrates into the substance of the thyroid gland, and divides into two ramuscles, one of which goes along the posterior face of the lobe of the gland, and anastomoses with the inferior thy- roid; the other goes along the upper margin of the gland, and anastomoses with its congener of the opposite side. The thy- roidal artery is split up into a great many branches in the sub- stance of the gland, it also sends small branches to the pharynx, cesophagus, and the little muscles on the front of the neck. The Lingual Artery (Art. Lingualis) comes from the external carotid at the distance of from six to twelve lines above the su- perior thyroid, and goes to the tongue. It is concealed in the early part of its course by the digastric and the stylo-hyoid mus- cles; it then penetrates the hyo-glossus muscle just above the cornu of the os hyoides, or goes between it and the middle con- strictor of the pharynx; it then ascends between the hyo-glossus CAROTIDS, AND THEIR BRANCHES. 201 and the genio-hyo-glossus muscle; advancing forwards, it is placed between the latter and the sublingual gland, and, finally, reaches the tip of the tongue. The, lingual artery sends off the following branches. At the root of the tongue one or more trunks arise from it (Dorsales Lingua) which go to the base of this organ, the tonsils, the palate, and the epiglottis. A little farther on, this artery detaches an- other branch, (Ramus Sublingualis,) which, advancing between the mylo-hyoid and the genio-hyo-glossus muscles, and above the sublingual gland, detaches a great many ramifications to these parts and to the lining membrane of the mouth; it is some- times a branch of the facial. The Ramus Raninus, is the con- tinuation of the lingual; it advances between the lingualis and the genio-hyo-glossus muscle, to the tip of the tongue, distributing continually its twigs on each margin, and ends there by anasto- mosing with the corresponding artery of the other side. The Facial Artery (Arteria Facialis, Maxillaris Externa) arises from the external carotid two or three lines above the lingual, and is spent principally on the side of the face below the eye. It is of considerable size, and very tortuous; its root is concealed by the stylo-hyoid and the digastric muscles, and it is traversed externally by the hypo-glossal nerve. It goes forward within the angle of the lower jaw, and above the submaxillary gland, but very much connected with it: it then mounts over the base of the maxilla inferior, at the anterior margin of the masseter muscle, and afterwards shapes its course, in a serpentine manner, to the internal canthus of the eye, passing between the muscles and the integuments of the face. In this course, the fascial artery sends off the following branches. As it passes by the submaxillary gland it sends several twigs to it: previously it also sends several little branches to the con- tiguous muscles, as the internal pterygoid, digastric, and so on; but they are too small to be of much consequence. The Submental branch arises, then, on a level with the base of the lower jaw; it advances forwards under the origin of the mylo-hyoides, and above the anterior belly of the digastricus. It sends several ramuscles to these muscles, some of which anastomose with the ranine artery; behind the symphysis of the 202 CIRCULATORY SYSTEM. jaw it anastomoses with its fellow, it then mounts over the chin, to which and to the lower lip it is distributed, anastomosing there with the inferior coronary artery of the mouth, and with the inferior maxillary which comes out from the anterior men- tal foramen in the lower jaw. When the fascial artery has got upon the face, it sends back- wards a small branch to the lower part of the masseter muscle. Somewhat above this it sends forwards a branch called the In- ferior Labial, which is distributed upon the middle of the chin. When it gets on a level with the corner of the mouth, but some- times lower down, it sends forward, under the depressor anguli oris, the Inferior Coronary Artery, to the lower lip, which fre- quently supplies the place of the inferior labial entirely; but when the latter is large, the coronary is small in proportion: a few lines higher up the fascial sends forward a third branch, the Superior Coronary, which goes to the upper lip. These coro- nary arteries are very tortuous, and are distributed by many branches in the substance of the lips: by anastomosing with their congeners of the other side, they surround the mouth com- pletely. The superior coronary artery, as it passes under the nose, sends upwards one or more small branches to the integu- ments of its orifice and septum. After this, the facial artery, in ascending towards the internal canthus of the eye, sends a branch to the ala nasi, and another to anastomose with the infra-orbitar artery. It, finally, termi- nates at the internal canthus of the eye by anastomosing with the branches of the ophthalmic, which come out there upon the side of the root of the nose. Several ramuscles, which are too small to merit special description, are given by the fascial to the integuments and muscles of the face, and to the lower eyelid. The Inferior Pharyngeal Artery (Art. Pharyngea Inferior, as- cendens) is one of the smallest of the original branches of the ex- ternal carotid, and generally arises opposite to the lingual; but there is much variety in the latter respect, it being sometimes higher up or lower down, and not unfrequently a branch of one of the other arteries, instead of being an original trunk. It ascends on the side of the pharynx, between the external and CAROTIDS, AND THEIR BRANCHES. 203 the internal carotid, and is covered by the stylo-pharyngeus muscle. It is principally distributed on the constrictor muscles of the pharynx, and upon their lining membrane. But one of its branches, called the Posterior Meningeal Artery, ascends through the posterior foramen lacerum of the cranium, between the jugu- lar vein and the pneumo-gastric nerve, and is distributed on the contiguous dura mater. The Occipital Artery (Arteria Occipitalis) is a very considera- ble trunk, which comes from the external carotid, generally op- posite to the facial, and is spent upon the integuments, on the back part of the head. At its root, it is deeply situated in the side of the neck, below the parotid gland, and has the internal jugular vein and the par vagum on its inside. It goes obliquely backwards, in ascending along the posterior belly of the digastricus between the trans- verse process of the atlas and the mastoid portion of the tempo- ral bone, being covered by the several muscles which are in- serted into the latter, as the sterno-mastoid, the splenius, and the trachelo-mastoid. It is covered, for some distance, by the in- sertion of the splenius capitis, and becomes at length superficial at the posterior margin of this muscle. The occipital artery is distributed as follows: Shortly after its origin, it sends branches to the digastric muscle behind, to the upper part of the sterno-mastoid and to the lymphatic glands of the upper part of the neck. While en- closed by the muscles on the back of the neck, it also sends branches to them, and anastomoses thereby with the vertebral artery; occasionally, one of these branches is of considerable magnitude, and has been found descending very low on the back, between the splenius and the complexus muscles. It also sends a small branch to the dura mater, through the mastoid foramen generally, but sometimes through the posterior foramen lacerum. When the stylo-mastoid artery is wanting, it also detaches a branch through the stylo-mastoid foramen to the internal parts of the ear. The occipital artery, having become superficial at the inter- nal margin of the splenius on the occiput, ascends on the latter bone towards the vertex in a tortuous manner, sending off, on 204 CIRCULATORY SYSTEM. each side, many small ramifications. It ends by anastomosing with the posterior temporal artery. The Posterior Auricular Artery (Art. Auricularis Posterior) arises a little above the last, at the lower edge of the parotid gland, from the external carotid, and is one of its smallest branches. It ascends backwards enclosed by the parotid gland, and afterwards between the meatus auditorius externus and the mastoid bone: at the latter place, it sends a ramification to the internal side of the external ear; it then ascends and is distri- buted, by small branches, on the contiguous integuments of the side of the head.' While still involved in the parotid gland, it sends some small ramifications through the meatus externus to its lining membrane and the membrana tympani. It then de- taches a branch through the stylo-mastoid foramen, from which the whole artery is also named Stylo-Mastoid; but this branch, as stated, sometimes comes from the occipital. The stylo-mas- toid passes 'along the aqueduct of Fallopius, detaching its arte- riole to the typanum and to the labyrinth. The External Carotid having given off these trunks, pene- trates vertically through the inner margin of the parotid gland, and gives to it several small twigs. When it arrives on a line with the neck of the lower jaw, it divides into two large trunks; one of them, the Internal Maxillary, goes to the parts within the ramus of the lower jaw; the other, being smaller, is the Tem- poral Artery. The Temporal Artery (Arteria Temporalis) continues to as- cend through the substance of the parotid, but becomes super- ficial in front of the meatus externus, in mounting over the root of the zygoma; it is then distributed to the integuments on the side of the head. It frequently sends off one or two ramifications, of but little volume, to the masseter muscle. Just above its root, and while surrounded by the parotid, a branch of some importance, the Transverse Facial, (Transversalis Faciei,) leaves it, and crosses, horizontally, the masseter muscle, just below the parotid duct, sometimes above it. This branch is distributed to the adjacent integuments and muscles, and terminates in front by anasto- mosing with the facial and the infra-orbitar artery. CAROTIDS, AND THEIR BRANCHES. 205 A little below the zygoma, the Middle Temporal Artery (Art. Temp. Media) comes off from the Temporal, and, ascending with the parent trunk, perforates the temporal fascia at the upper margin of the zygoma, and is distributed to the temporal muscle by many ramifications, which anastomose with the deep-seated temporal arteries. After this, some small twigs, called Auri- cular, go to the external ear from the trunk of the temporal artery. The temporal artery, having ascended for an inch or so be- tween the aponeurosis of the temporal muscle and the skin, it di- vides into an Anterior and a Posterior Branch. The former as- cends towards the side of the os frontis, and is distributed in ramuscles to the orbicularis palpebrarum, the belly of the occi- pito-frontalis, and the integuments of the front of the cranium, anastomosing with the frontal artery and the temporal of the other side. The posterior branch is distributed on the integu- ments of the middle of the side of the cranium, anastomosing with the anterior branch, with its fellow of the other side, and with the occipital artery. The Internal Maxillary Artery (Arteria Maxillaris Inter- na) winds around the neck of the lower jaw, and, passing be- tween the pterygoid muscles, proceeds in a tortuous manner to the deepest points of the zygomatic fossa. The first part of its course is horizontally inwards; it then ascends in front of the pterygoideus externus to the bottom of the temporal bone, or the spinous process of the sphenoidal; it then passes for- wards, within the temporal muscle, to the upper part of the pterygo-maxillary fossa. It sends off several branches, and commonly in the following ' order:— 1. The Arteria Tympanica, to the tympanum, through the glenoid fissure. 2. The Arteria Meningea Parva, to the dura mater, through the. foramen ovale. It is most frequently a branch of the next. ' 3. The Arteria Meningea Magna, or Media, to the dura ma- Vol. II.—27 206 CIRCULATORY SYSTEM. ter, through the foramen spinale. This branch having entered the cranium, is distributed upon the dura mater in the manner marked off by the furrows upon the internal face of the tempo- ral, the parietal, and the frontal bones. One of its branches en- ters the aqueduct of Fallopius, through the Vidian Foramen, and is distributed upon the internal parts of the organ of hear- ing, anastomosing with the stylo-mastoid artery. 4. The Arteria Maxillaris, or Dentalis Inferior, descends along the internal face of the ramus of the lower jaw, and having sent off some ramifications of small size to the contigu- ous muscles and the lining membrane of the mouth, it enters the posterior mental foramen with the inferior dental nerve. Going along the canal in the substance of the lower jaw, it-de- taches successively from its superior margin ramifications to the teeth. At the anterior mental foramen a trunk is sent for- ward as far as the symphysis, which supplies in its course the canine and incisor teeth; the remainder of the inferior maxilla- ry artery comes out at the foramen, and supplies the chin, anas- tomosing with the facial artery. 5. The Arterise Temporales Profundae are two in number. The first of them, called Posterior, arises next to the inferior maxillary. It is concealed between the external pterygoid and the temporal muscle for some distance; it then ascends in the posterior part of the temporal fossa, beneath the temporal mus- cle and is minutely distributed upon it. The anterior deep temporal artery is separated from the posterior, in its origin from the internal maxillary, by the pterygoid and the buccal arteries. It arises near the pterygo-maxillary fossa; and, as- cending between the temporal muscle and the fore part of the corresponding fossa, it is minutely distributed upon the former, anastomosing with the posterior deep, and with the middle tem- poral artery. 6. The Arteriae Pterygoideae arise after the posterior deep temporal. They vary considerably in regard to number, size, and origin, and are distributed upon the pterygoid muscles, as their name implies. One of their branches, which is sometimes CAROTIDS, AND THEIR BRANCHES. 207 an independent trunk from the internal maxillary, goes between • the posterior margin of the temporal muscle and of the neck of the lower jaw, in front of the latter, to be distributed upon the internal face of the masseter muscle. 7. The Arteria Buccalis, sometimes a branch of the internal maxillary, but frequently coming from one of its trunks, either the alveolar or the anterior temporal, passes along the external face of the upper jaw, and distributes its branches to the bucci- nator and zygomatic muscles, and to the lining membrane of the mouth. 8. The Arteria Maxillaris Superior, or Alveolaris, proceeds downwards and forwards in winding around the tuber of the upper jaw bone. It first sends some ramifications through the bone to the roots of the great and small molar teeth, and to the lining membrane of the maxillary sinus; it then passes forwards along the gums, near the buccinator, and gives ramifications to . them and to the contiguous muscles. 9. The Arteria Infra-orbitalis comes from the internal maxil- lary, at the upper part of the pterygo-maxillary fossa; it sends some inconsiderable ramifications to the fat and the periosteum of the orbit, through the spheno-maxillary fissure. It then en- ters the infra-orbitary canal, and passes through it with the in- fra-orbitary nerve. On arriving near the anterior orifice of the canal, it detaches downwards a branch which goes to the canine and the incisor teeth, and to the lining membrane of the an- trum. It then gets to the face below the origin of the levator labii superioris muscle, and is distributed upon the muscles in front of the upper maxilIa,»anastomosing with the facial and with the ophthalmic artery. 10. The Arteria Palatina Superior descends through the pos- terior palatine canal, and, having reached the mouth, leaves some ramifications with the soft palate: it then advances be- tween the bones and the lining membrane of the roof of the mouth, and disperses itself in several small twigs; one of which passes through the foramen incisivum into the nostril. 208 CIRCULATORY SYSTEM. 11. The Arteria Pharyngea Superior is sometimes a branch of the last, and is spent upon that portion of the pharynx bor- dering on the pterygoid processes. 12. The Arteria Spheno-Palatina is the terminating trunk of the internal maxillary; it enters the nose through the spheno- palatine foramen, and divides into two branches, which are minutely distributed over the Schneiderian membrane. One of them descends along the septum narium; the other along the external margin of the posterior naris, and divides into two principal ramuscles, one of which is dispersed along the mid- dle turbinated, and the other along the inferior turbinated bone. SECT. III.—-OF THE SUBCLAVIAN ARTERY, AND ITS BRANCHES. The Subclavian Artery (Arteria Subclavia) of the right side having arisen from the innominata, and that of the left from the aorta, they each go over the first rib of their respective sides, adhering closely to it, in the bottom of the interval between the scalenus anticus and medius muscles. The right subclavian is much shorter, and more superficial than the left, from its origin to the scaleni muscles. Near the latter they are each covered in front by the sternal end of the clavicle, by the sterno-hyoid and thyroid muscles, and by the subclavian vein of the corre- sponding side; behind they are separated from the vertebral co- lumn by the longus colli muscle; belovv them is the pleura, the left artery being in contact with it for its whole passage in the thorax; and on their internal side is the primitive carotid. The subclavian of the right side is crossed near the scalenus anticus by the par vagum; the phrenic nerve also goes in front of it, but on the internal edge of the scalenus. The subclavian of the left side having a course almost vertical from its origin to the interval of the scaleni muscles, is nearly parallel with, and be- hind, the primitive carotid of that side; the phrenic nerve has the same relative position with it as on the right side; but the par vagum goes parallel with, and in front of the subclavian ar- tery, for some distance along the root of the latter. At the inner margin of the Scaleni Muscles the Subclavian SUBCLAVIAN, AND ITS BRANCHES. 209 gives off a cluster of trunks; to wit. the Vertebral; the Inferior Thyroidal; the Superior Intercostal; the Internal Mammary; and the Cervical Artery. They sometimes arise distinctly, and after the order mentioned; but there is too great a diversity in subjects to establish any rule on these points. 1. The Vertebral Artery (Arteria Vertebralis) is the most voluminous of the branches of the Subclavian. Immediately af- ter its origin it ascends on the side of the spine, and enters the canal of the transverse processes of the neck at the sixth ver- tebra. Pursuing this course, it gets into the cavitv of the cra- nium through the foramen magnum occipitis, and is distributed to the brain in the manner mentioned in the description of that organ. ■. . . ' While in the canal of the transverse processes, it sends off several branches to the heads of the contiguous muscles, and to the medulla spinalis of the neck. 2. The Inferior Thyroid Artery (Arteria Thyroidea Infe- rior) arises from the upper face of the subclavian, and goes to the thyroid gland. It ascends at first on the internal margin of the scalenus medius muscle, and then turns suddenlv inwards be- tween the vertebrae and the great vessels of the neck. • In this course several unimportant twigs are sent from it to the contiguous parts. Near its root it detaches the Anterior, or the Ascending Cervical Artery, which going up the neck is spent upon the heads of the muscles arising from the transverse processes, as the scaleni, the longus colli, and so on. The infe- rior thyroidal then gets to the thyroid gland, and is very mi- nutely distributed to it, anastomosing with the other arteries which supply the same organ. 3. The Superior Intercostal Artery, (Arteria Intercostalis Superior,) arising from the under surface of the subclavian op- posite the inferior thyroid, descends across the neck of the first rib, and divides into two branches, which supply the two upper intercostal spaces: each of them also sends backwards near the vertebra a small trunk to the muscles of the back. 210 CIRCULATORY SYSTEM. 4. The Internal Mammary Artery (Arteria Mammaria In- terna, Thoracica) descends at first along the internal margin of the scalenus anticus; having then got fairly into the cavity of the thorax, it continues to descend across the posterior face of the costal cartilages, parallel with, and about nine lines from, the outer edge of the sternum, between the triangularis sterni and the intercostal muscles. In this course, besides some distinct twigs to the anterior me- diastinum, it sends a branch (Phrenica Superior) which accom- panying the phrenic nerve between the pleura and the pericar- dium, reaches finally the diaphragm, and is spent upon it. At each intercostal space which it crosses, the internal mammary sends outwards a branch, which is spent upon the fore part of the intercostal muscles, and anastomoses with the correspond- ing intercostal artery: other branches also leave it at each space, which getting forwards near the sternum, are distributed upon the pectoralis major, and upon the contiguous muscles. The last of these branches, according to M. H. Cloquet, goes trans- versely over the ensiform cartilage, and, having anastomosed with its fellow, descends between the peritoneum and the linea alba to the suspensory ligament of the liver. On a line generally with the anterior extremity of the fifth rib, the internal mammary divides into two principal branches; the most exterior of which, descending along the cartilaginous margin of the thorax, is distributed in small twigs to the origin there of the diaphragm and of the transverse muscle of the ab- domen. The interna] branch reaches the posterior face of the rectus abdominis muscle, and is dispersed upon it: some of its branches go as low as the umbilicus, to anastomose there with the epigastric artery. 5. The posterior Cervical Artery (Arteria Cervicalis Pos- terior, Transversa) is of a very unsettled origin, but comes most frequently either from the subclavian itself, or from the inferior thyroid. It is but small in some subjects, owing to its place being supplied by branches from the adjoining arteries. It crosses horizontally the root of the neck on the outer face of the scaleni muscles above- the subclavian artery. It gets SUBCLAVIAN, AND ITS BRANCHES. 211 under the anterior margin of the trapezius, and is there divided into two principal branches; the ascending one is spent upon the trapezius and the levator scapulae; the other descends along the base of the scapula, and is spent in ramifications upon the rhomboidei and the serratus magnus muscles. Several branches of minor size and importance are sent off from the posterior cervical artery to the muscles on the back of the neck and thorax. The Subclavian Artery having sent off the preceding branches, then escapes from the thorax between the scaleni muscles, and gets to the arm-pit between the first rib and the subclavius muscle. The trunk of it is then continued downwards through the axilla, and at the inner side of the arm to the elbow joint. From the scaleni muscles to the elbow its relative position is as follows: When it first appears between the scaleni, it is bounded above and behind by the collected fasciculi of the ax- illary plexus of nerves. In front it is separated from the sub- clavian vein by the insertion of the scalenus anticus. It is placed at the bottom of the depression between the sterno-ma- stoideus and the trapezius, being covered by the skin, the pla- tysma myodes, and some loose cellular substance below the latter. It then descends between the first rib and the subcla- vius; escaping from below the latter, it is covered in front by the outer margin of the pectoralis major until it reaches the lower part of the axilla; and in this course it has the following relation to other parts: it passes under the shoulder joint, then under the insertion of the pectoralis minor, then along the in- ternal face of the coraco-brachialis muscle; it has the axillary vein in front of it, and the axillary nerves plaited around it as far down as the coracoid process, when they begin to disperse. This artery in emerging from the axilla is placed upon the an- terior face of the insertion of the latissimus dorsi: it then runs out the length of the coraco-brachialis, and is afterwards conducted along the inner margin of .the biceps flexor cubiti and its tendinous termination: it lies upon the anterior face of the brachialis internus; and goes beneath the aponeurosis at the bend of the arm, coming from the tendon of the biceps. In the arm it is concealed only by the integuments and fascia, 212 CIRCULATORY SYSTEM. and is bordered internally by the brachial vein and the median nerve. This great trunk of the upper extremity loses the name of subclavian, to be called Axillary Artery, (Art. Axillaris,) from the subclavian muscle to the lower margin of the arm-pit: and from the latter place to the elbow joint, it is named Brachial Artery, (Art. Brachialis.) It sends off many interesting branches to the thorax, to the shoulder, and to the arm; and, finally, terminates a little below or at the elbow joint by bifur- cating. Of the Branches of the Axillary Artery. 1. The Superior Scapular Artery (Art. Dorsalis Superior Scapula) varies considerably in its origin. Sometimes it is a branch of the subclavian, sometimes of the inferior thyroid, and it frequently comes from the upper part of the axillary; so that it cannot be referred, with strict propriety, to any determined origin. When it comes from the axillary, it, is very tortuous, and has to ascend to its destination, which removes it entirely from any interference with the course of the subclavian over the first rib, and over the upper head of the serratus magnus muscle. But in the other cases,' it goes transversely backwards and outwards, somewhat belovv the posterior cervical, and along the posterior inferior margin of the clavicle, being covered by the sterno-mastoideus, the platysma myodes, and the trapezius; consequently, it is just in the way of the incisions which are made for reaching the subclavian artery, from above the clar vicle. It reaches the superior costa of the scapula near the root of the coracoid process, and passing through the notch there, is distributed, by one large branch, upon the supra-spinatus muscle; and by another, which goes across the anterior margin of the spine of the scapula, to the infra-spinatus muscle. In its course, it sends off several small ramifications to contiguous parts. 2. The External Mammary Arteries (Art. Mammaria seu Tho- racica Externa) arise from the axillary, between the subclavius SUBCLAVIAN, AND ITS BRANCHES. 213 and the pectoralis minor muscle. They are four principal trunks, which go uniformly to certain parts, but vary considera- bly in their origin; for sometimes the latter is distinct in the case of each artery, but frequently otherwise. Their distribu- tion is as follows: a. The Thoracica Superior is distributed to the upper part of the pectoralis major muscle, and to the pectoralis minor. Some of its branches reach the mamma in the female, and anastomose with the internal mammary and with the intercostals. b. The Thoracica Longa descends along the posterior face of the pectoralis major, between it arid the serratus magnus. It gives many branches to the lower part of the pectoralis major, to the integuments, and, in the female, to the mamma; anasto- mosing likewise with the internal mammary and with the inter- costals. c. The Thoracica Acromialis, immediately after its origin, makes for the fissure between the deltoid and the great pectoral muscle, and divides there into an ascending and a descending branch. The former reaches the clavicle, and is partly distri- buted superficially along it, partly to the contiguous muscles, and to the shoulder articulation. The other branch follows the cephalic vein along the interstice between the deltoides and pec- toralis major, and is, finally, distributed to these muscles and to the integuments. d. The Thoracica Axillaris is irregular, both in regard to the number of its branches and to their origin. Instead of a distinct origin by one or more trunks from the axillary artery, the branches belonging to the name of thoracica axillaris, are some- times derived from the other thoracic arteries. They are ge- nerally distributed only to the fat and the lymphatic glands in the axilla. They occasionally exist primitively as a large trunk, which runs on the scapular face of the serratus magnus the whole length.of the scapula, and is distributed to the adjacent muscles, and to the fat and glands of the axilla. 3. The Scapular Artery (Arteria Scapularis communis, Sub- scapulars) arises from the axillary below the shoulder joint, at or near the anterior margin of the subscapularis muscle. Giving Vol. II.—28 . 214 CIRCULATORY SYSTEM. off some inconsiderable branches to the lymphatic glands of the arm-pit, it descends along the anterior margin of the subscapu- laris, and is distributed to it, to the latissimus dorsi, and to the teres major and minor muscles. A little below the neck of the scapula, it detaches a largp trunk, the Dorsalis Inferior Scapulae, which, winding around the inferior costa of the bone over the anterior margin of the sub- scapularis and the teres minor, reaches the fossa infra-spinata. This trunk then divides into two branches: one of which is dis- tributed superficially between the aponeurosis and the infra-spi- natus, and the other more deeply near the dorsum of the bone: one of the ramuscles of the latter ascends beneath the neck of the acromion to anastomose with the Dorsalis Superior Sca- pulae. 4. The Anterior Circumflex Artery (Art. Circumflexa Anterior^ Articularis Anterior) is about the size of a crow quill, and arises from the axillary just above the tendon of the teres major and of the latissimus dorsi. It adheres closely to, and surrounds the front of the neck of the os humeri, passing between it, the cora- co-brachialis, and the short head of the biceps. It then divides into several branches, some of which go to the deltoides, and anastomose therewith the posterior circumflex; others go imme- diately to the articulation, and either terminate on it or ascend to the muscles on the dorsum of the scapula, where they anasto- mose with the scapular arteries. The Posterior Circumflex Artery (Art. Circumflexa Posterior) is much larger than the last, and arises from the axillary somewhat below it. It surrounds the posterior face of the neck of the os hu- meri, passing between it and the long head of the triceps muscle, below the insertion of the teres minor. Many of its ramifica- tions go to the capsular ligament of the articulation and to the muscles adhering to it. But this artery is principally intended for the deltoid muscle, to the internal face of which- the most of its branches go. It anastomoses with the anterior circumflex, and with the scapular arteries. In some cases, the posterior circumflex arises from the axil- lary below, instead of above the tendinous insertion of the latis- simus dorsi: when this happens, it commonly gives off the arte- SUBCLAVIAN, AND ITS BRANCHES. 215 ria profunda major of the arm, and afterwards ascends on the posterior face of the tendon to its appropriate destination. Of the Brandies of the Brachial Artery. 1. The Profound Artery (Arteria Profunda Major Humeri, Spiralis) arises from the brachial, a little below the tendinous insertion of the latissimus dorsi; and having passed downwards, for a short distance, it enters the interstice between the first and the third head of the triceps muscle, and winds spirally down- wards around the os humeri in company with the radial nerve. On the outer side of the arm, it becomes superficial between the margins of the triceps and of the brachialis internus, and then directs its course between the latter and the supinator longus to the external condyle. In this course, the artery sends several branches to the triceps muscle, to which, indeed, it is principally destined. Near the external condyle, it supplies the brachialis internus and the heads of the extensor muscles of the fore arm, and anastomoses with the recurrent branch of the radial artery. 2. The Small Profound Artery (Art. Profunda Minor) comes from the brachial, two or three inches below the profunda ma- jor, but frequently it is only a branch of the latter, and is gene- rally much smaller. It is distributed superficially on the internal face of the triceps at its lower part, and has its terminating branches reaching as far as the internal condyle. 3. The Nutritious Artery (Art. JVutritia) is the next in order from the brachial; and arises from it near the medullary fora- men of the os humeri, through which it penetrates, and is distri- buted to the lining membrane of the bone. It is not larger than a knitting needle. 4. The Anastomotic Artery (Arteria Anastomotica) arises from the brachial below the last, and is larger than it. It lies upon the lower internal part of the brachialis internus muscle, and crosses the ridge leading to the internal condyle in order to 216 f CIRCULATORY SYSTEM. reach the depression between the latter and the olecranon, where it anastomoses with the ulnar recurrent artery. The preceding is a common arrangement of the branches proceeding from the brachial artery, yet deviations from it are continually met with, in a deficiency or in a redundancy of these collateral trunks, and in their mode of origin. An account of all the varieties which are observed here would be almost end- less, as every subject has some peculiarity. Several small ar- teries are also sent from the brachial to the coraco-brachialis, the biceps, the brachialis internus, and to the triceps muscles. They, for the most part, are, simply, muscular branches, which are too small and irregular to deserve specifying. A division of the brachial artery into two trunks, the Radial and the Ulnar, will be found in a majority of subjects in front of the brachialis internus muscle on a line with the elbow joint: sometimes it occurs nearer the root of the coronoid process. It is, however, by no means rare to see this bifurcation much above the elbow. Examples of it have been witnessed at every point between the latter and the arm-pit; in such cases, the course of the radial artery down the fore arm is generally much more superficial than usual, as it is placed immediately below the skin. Of the Radial Artery. The Radial Artery (Arteria Radialis) is smaller than the ulnar, and extends from the elbowr to the hand. In the upper half of the fore arm it is placed at the bottom of the fissure between the supinator, radii longus and the pronator teres muscle. Having crossed the insertion of the latter, it runs in front of the radius -between the tendon of the supinator and of the flexor carpi ra- dialis. Below the styloid process of the radius it runs between the outer end of the carpus and the extensor muscles of the thumb; it then penetrates to the palm of the hand between the root of the metacarpal bone of the thumb and of the fore fino-er, above the abductor indicis muscle. The following branches are sent from the Radial Artery.- SUBCLAVIAN, AND ITS BRANCHED. 217 1. The Recurrens Radialis arises at the neck of the radius. It winds, externally, around the joint between the external con- dyle and the muscles coming from it, and anastomoses with the spiralis of the humeral artery, being distributed in many colla- teral branches, to the joint and to the contiguous muscles. 2. Several small and irregular muscular branches arise from the radial artery, in its progress to the wrist: they have no ap- propriate names. 3. The Superficialis Volae arises from the radial about the in- ferior margin of the pronator quadratus muscle. It passes su- perficially over the process of the trapezium to the muscles of the ball of the thumb, and one of its terminating branches joins the arcus sublimis. Sometimes the superficialis volae is the prin- cipal branch of the radial. 4. The Dorsalis Carpi arises from the radial at the carpus, runs across the back of the latter below the extensor tendons, and detaches the posterior interosseous arteries of the back of the hand. They anastomose with branches from the ulnar and interosseous arteries of the fore arm. 5. The Magna Pollicis, a terminating branch of the radial, comes from it in the palm of the hand just at the root of the me- tacarpal bone of the thumb. It runs beneath the abductor indi- cis, and at the head of the metacarpal bone divides into two branches which run along the sides of the thumb to its extremity, where they anastomose and terminate. 6. The Radialis Indicia, arising at the same place with the latter, runs along the metacarpal bone of the fore finger, and along the radial side of the same finger to its extremity. 7. The Palmaris Profunda is the third terminating branch of the radial artery. It arises near the same place with the two last, crosses the hand between the metacarpal bones and the flexor tendons; thus forming the Arcus Profundus, from which branches proceed to the interossei muscles, and which ends on 218 CIRCULATORY SYSTEM. the ulnar side of the palm of the hand by a branch to the Arcus Superficialis. Of the Ulnar Artery. The Ulnar Artery, (Arteria Ulnaris,) one of the forks of the brachial at the elbow, passes more in a line with it than the ra- dial artery does. It goes, immediately after its origin, under se- veral of the muscles of the internal condyle, to wit: the pronator teres, flexor radialis, flexor sublimis, and palmaris longus, and between the flexor sublimis and profundus digitorum, being deep- ly seated; getting from beneath the flexor sublimis, it afterwards runs parallel with the ulna, or nearly so, lying on the flexor pro- fundus between the flexor ulnaris and the ulnar margin of the flexor sublimis, and concealed two-thirds of the way down the fore arm by the overlapping of these muscles. At the thin part of the fore arm, commonly called the wrist, it is superficial, and may be felt pulsating in the living body at the radial margin of the tendon of the flexor ulnaris. The ulnar artery, at the carpus, takes a very different course from the radial, for it passes over the anterior annular ligament of the carpus just at the radial side of the os pisiforme, to which it is held by a small ligamentous noose; it then proceeds to the palm of the hand. Between the aponeurosis palmaris and the flexor tendons it forms that curve from the ulnar to the radial side of the hand called the Arcus Sublimis. This curve com- monly begins a little beyond the anterior margin of the annular ligament, and presenting its convexity forwards, terminates about the middle of the ball of the thumb at its inner margin. The branches sent from the ulnar artery are as follow:__ 1. The Recurrens Ulnaris arises from the ulnar about the lower part of the tubercle of the radius, and, winding upwards, is distributed in small branches to the muscles of the internal condyle. One of its ramuscles goes between the internal con- dyle and the olecranon process to anastomose with the arteria anastomotica of the humeral. 2. The Interossea arises from the ulnar, just below the other. SUBCLAVIAN, AND ITS BRANCHES. 219 It is a large trunk, and proceeds but a little distance when it di- vides into two principal branches, called anterior and posterior interosseal arteries. a. The Interossea Anterior is much the larger; it runs in con- tact with the interosseous ligament to the upper margin of the pronator quadratus, giving off branches to the deep-seated mus- cles of the fore arm in its course. Under the pronator it per- forates the interosseous ligament, and distributes branches to the back of the carpus and of the hand, which anastomose with branches of the radial and posterior interosseal. b. The Interossea Posterior is sometimes a separate trunk, arising from the ulnar just above the former. In either case it soon perforates the interosseous ligament to get to the back of the fore arm. Here it sends backwards a Recurrent Branch (Recurrens Interossea) to the back of the elbow, which anasto- moses with the recurrens ulnaris and radialis. It then proceeds downwards, being deeply seated and distributed to the different muscles on the back of the fore arm. Some of its branches reach the wrist, and anastomose with the carpal arteries. 3. The ulnar artery, in its descent on the fore arm, sends off many small and irregular muscular branches, called by Pro- fessor Chaussier, Cubito-muscularis: they do not require descrip- tion. 4. The Dorsalis Manus leaves the ulnar at the lower end of the fore arm, and passes under the tendon of the flexor ulnaris to the back of the hand. It there meets ramuscles of the radial and interosseous, and conjointly they supply with very small branches the back of the wrist, of the metacarpus, and of the fingers. 5. As the Arcus Sublimis is about beginning, the ulnar arte- ry sends superficial but small branches to the integuments of the palm; and a little farther on, a considerable branch, which dives into the bottom of the palm, through the muscles of the little finger, and joins the ulnar extremity of the arcus profundus: this is the Cubitalis Manus Profunda of Haller. 220 CIRCULATORY SYSTEM. 6. The Arcus Sublimis then sends a branch to the ulnar side of the little finger. Afterwards in succession three digital branches are sent off, which, arriving at the interstices between the heads of the metacarpal bones, each divides into two branches to supply the sides of the fingers which are opposite to each other; one branch is called Digito-radial, the other Di- gito-ulnar, according to the side of the finger on which the ar- tery may be placed. The digital arteries, before they divide, receive each a small branch from the arcus profundus. The digito-radial, and the digito-ulnar arteries, pass along the sides of the fingers in front to their extremities: at the joints and extremities, anastomoses between the arteries of the two sides of the same finger fre- quently occur. The arcus sublimis terminates on the radial side of the palm by a branch which joins the inner branch of the Arteria Magna Pollicis of the Radial. The most frequent distribution of the arteries of the hand is what has just been described: anatomists are, however, not all agreed on frhis point. It would probably be more just to say, that this occurs more frequently than any other single arrange- ment. The varieties, in fact, are so great, that before a hand is opened, it is not possible to know in what manner its arteries will be distributed. Sometimes the Radial Artery furnishes one half of the arcus sublimis, and the Ulnar the other half. On other occasions, the interosseous artery or the superficialis volae is continued as a large trunk over the ligament of the wrist, and crosses the root of the thumb, to join the arcus sub- limis. SECT. IV.--BRANCHES OF THE DESCENDING THORACIC AORTA. The Aorta, in its course from the lower part of its curvature to the crura of the Diaphragm, gives off several branches to the viscera and to the parietes of the thorax. The Bronchial Arteries (Arterias Bronchiales) are the SUBCLAVIAN, AND ITS BRANCHES. 221 tritious vessels of the lungs. There is commonly one for each lung, but sometimes two or more. The right arises frequently from the superior aortic intercostal artery, instead of from the aorta, while the left comes from the latter: occasionally they have a common root. On either side they follow the course of the bronchia into the substance of the lung; and are distributed along with it, by ra- mifications which become successively finer and finer, and anastomose with the pulmonary artery; after the manner men- tioned in the description of the lungs. Before they enter the latter, they send some small ramifications to the posterior me- diastinum, to the pericardium, and to the black bronchial glands. The (Esophageal Arteries (Arteriae GSsophagea) are gene- rally five or six small twigs which come successively from the descending thoracic aorta. They ramify minutely in the sub- stance of the oesophagus, communicating freely with each other: the lowest of them also anastomoses around the cardia with the superior coronary artery of the stomach. The Posterior Arteries of the Mediastinum, (Arteriae Me- diastinales Posteriores,) are numerous and small; they come from the anterior face of the aorta, as well as from the branches last mentioned; and are spent upon the posterior mediastinum, and upon its contents. The Intercostal Arteries (Arteria Intercostales Inferiores Aortica) of the aorta supply the ten lower intercostal spaces on eacK side, as the two upper ones are supplied by the subclavian artery. There is commonly an intercostal artery arising dis- tinctly from the aorta for each space, but sometimes two of them arise from a common trunk. Those for the right side having to cross the spine behind the oesophagus and the vena azygos, are, of course, longer than such as belong to the left. The upper ones on either side have to ascend, in order to reach their destination. Each artery joins the rib near its tubercle, and goes along the groove in its lower margin, between the external and the inter- nal intercostal muscles, for two-thirds of the length of the rib. Vol. II.—20 222 CIRCULATORY SYSTEM. It then abandons the groove, and divides into several branches, which go to the intercostal muscles and contiguous parts, and anastomose in front with the internal mammary artery. As each intercostal artery passes the head of the rib, it sends a branch backwards, (ramus dorsalis}) between the transverse processes of the adjoining vertebrae, which penetrates to the posterior face of the trunk, and is distributed to the muscles and skin on the side of the spine. A ramification from this branch enters the intervertebral foramen, and is spent upon the medulla spinalis and its membranes. Each intercostal artery also gives off, about the middle of the rib, a branch, (ramus costalis inferior,) much smaller than the trunk. This branch advances along the upper margin of the rib below, and gives ramifications to its periosteum and to the adjacent intercostal muscles. The last intercostal artery is remarkable for its size. Its ori- gin is concealed by the small muscle of the diaphragm, to which it gives some ramifications: it then passes, at the under margin of the rib, behind the upper end of the quadratus lumborum muscle, where it divides into three branches; one of which goes transversely to the broad muscles of the abdomen; while the other two descend between the oblique and transverse muscles towards the crest of the ilium, where they anastomose with the lumbar arteries, and with the circumflexa ilii. SECT. V.—OF THE BRANCHES OF THE ABDOMINAL AORTA. The Phrenic Arteries (Arteria Phrenica) are two in num- ber, one for the right and the other for the left side of the dia- phragm. They arise singly, but sometimes by a common trunk, from the front of the aorta, immediately on the latter showing itself in the abdomen, between the crura of the diaphragm; con- sequently, just below the crossing of the muscular fibres, which takes place between the foramen for the aorta and that for the oesophagus. The phrenic arteries ascend along the lesser muscle of the diaphragm, and give some ramifications to it and to the capsulae renales. They then divide each' into two leading trunks, which are distributed over the diaphragm, principally on its concave BRANCHES OF THE ABDOMINAL AORTA. 223 surface. Some small ramifications from them go to the liver and to the lower part of the oesophagus. The two phrenic arteries anastomose with each other: also, with the superior phrenics, coming from the internal mammary; and with the intercostals. Sometimes one or both of them come from the coeliac artery, or its branches. The Cceliac Artery (Arteria Cozliaca) is the next branch of the abdominal aorta, and arises immediately below the phrenics, between Ihe pillars of the diaphragm, opposite the junction of the last dorsal with the first lumbar vertebra. It is a very large trunk, and goes off at right angles, being placed between the left lobe of the liver and the superior margin of the pancreas. When it is only half an inch long, it is split into three trunks,- the Gastric, the Hepatic and the Splenic; this division is the Tripus Halleri. The Gastric Artery (Arteria Gastrica, Coronaria Ventri- culi) is the smallest of the three trunks, and frequently arises from one of the others. It advances forwards and towards the left, in order to reach the small curvature of the stomach, the course of which it pursues to the pylorus, between the two lami- nae of the little omentum. It gives off the following branches:— a. Ramifications to the oesophagus, some of which ascend along it into the posterior mediastinum, and anastomose there with the similar branches coming from the aorta; others go trans- versely, so as to surround the cardia, reach the greater end of the stomach, and anastomose with the vasa brevia. b. The ramifications to the stomach are abundant, but of an indeterminate number, and arising along its lesser curvature, are distributed in winding branches to the anterior and the posterior surfaces of this viscus, between its membranes. c. Not unfrequently the artery which supplies the left lobe of the liver is a branch from the gastric, in which case the lat- ter is much larger than usual. 2. The Hepatic Artery (Arteria Hepatica) is generally con- siderably larger than the gastric, and inclines towards the right side, in order to reach the liver, which it does through the cap- sule of Glisson. It send off the following branches:— 224 CIRCULATORY SYSTEM. a. The Right Gastric or Gastro-Epiploic Artery (Arteria Gastrica Dcxtra) comes from it near the pylorus, and descend- ing between the duodenum and pancreas, reaches the great- er curvature of the stomach, to the right half of which, and to the corresponding part of the great omentum, it is distributed. In the early part of its course, the right gastric detaches some small ramifications to the pylorus (arteria pylorica;) also, to the duodenum and to the pancreas (art. pancrealico duode- nales.) The latter communicate, by very free anastomoses, with the superior mesenteric artery. After having sent off this branch, the hepatic artery advances to the transverse fissure of the liver, in front of and to the left of the vena portarum. It then divides into a right and a left branch. The former sends off a ramification to the gall-bladder, (art. Cystica,) which first reaches its neck, and is distributed, by many arterioles, upon the parietes of this reservoir; the right branch then penetrates deeply into the transverse fissure, and is distributed, by many ramifications, throughout the right lobe of the liver. The left branch of the hepatic artery is distributed, in the same manner, throughout the left lobe of the liver. -3. The Splenic Artery (Arteria Splenica) is larger in the adult than either of the other two branches of the cceliac, and goes to the spleen along the superior margin of the pancreas, performing, in this course, several considerable flexuosities. It gives off the following branches:— a. The Pancreatic Arteries (Art. Pancreatica Media el Sinis- tra) come successive^ from its inferior margin, as it goes along the pancreas. Their number and size are variable, but com- monly they are not bigger than a knitting needle: they pene- trate perpendicularly into the pancreas, and then subdivide mi- nutely in furnishing its structure. b. The Left Gastric Artery (Art. Gastrica Sinistra, Gasiro- epiploica Sinistra) comes from the left extremity of the splenic, and is about the same size with the right gastric artery, but some- times larger. It attaches itself to the left extremity of the sto- mach, and goes along the left half of its greater curvature, ter- minating by an anastomosis with the right gastric artery. In this course, it detaches ramifications to the front and to the back of the stomach, and to the omentum majus. .BRANCHES OF THE ABDOMINAL AORTA. 225 c. The Short Vessels (Vasa Brevia, Art. Gastrica Breves) come from the splenic, immediately before it enters the spleen, and after it has subdivided for that purpose. They are five or six in number, and are distributed upon the greater extremity of the stomach, between the cardia and the left gastric artery. The anastomoses between the several arteries of the stomach are so free, that a fine injection pushed into one, readily finds its way into all the others. The splenic artery, when it gets to the left end of the pan- creas, is divided into a cluster of branches, and in that condition enters the fissure of the spleen, throughout the interior of which it is divided into an infinitude of ramifications. The Superior Mesenteric Artery (Arteria Mesenlerica Su- perior) arises from the aorta, while the latter is still engaged, between the crura of the diaphragm. It is about the same size as the coeliac, and comes off half an inch below it. It is distri- buted to all the small intestine and to the right side of the large one after the following manner: it first passes behind the pan- creas, and then in front of the duodenum, to reach the root of the mesentery, between the two laminae of which it divides and subdivides into several series of arches, one after another: they become successively smaller and more numerous till they reach the margin of the intestine, where they cease by sending a great many small parallel branches. The trunk of the superior mesenteric artery, in descending between the laminae of the mesentery, describes a considerable curvature, the convexity of which is to the left side and down- wards, while its concavity is in a contrary direction. It is from the convexity of this trunk, that from fifteen to twenty large branches are sent off successively to form the roots of the first row of arterial arches. These branches are shorter, and gene- rally somewhat smaller, the lower down they arise; and their origins very closely succeed each other. Besides the preceding branches, the superior mesenteric ar- tery sends off the following: Near its root several small ramifications arise, which go to the duodenum and to the pancreas, and anastomose there with other arteries supplying the same organs. aA0 CIRCULATORY SYSTEM. From about the middle of the concavity of the superior me- senteric artery, arise the three Colic arteries called Ileo-colica, Colica Dextra, and Colica Media: the first supplies a cluster of branches to the lower part of the ileum and to the head of the colon, anastomosing; on the left with the last of the small in- testinal arteries and on the right with the colica dextra: the Colica Dextra is smaller than either of the other two branches, and going between the laminae of the mesocolon, supplies the ascending portion of the colon by dividing into two principal branches, one of which anastomoses with the ileo-colic artery, and the other with the colica media: the Colica Media, situated between the laminae of the transverse mesocolon, and arising higher up than the colica dextra, advances forwards and divides into two principal trunks; one of which supplies that part of the colon in the right hypochondriac region, and the other the remainder of its transverse portion, forming an anastomosis with the colica superior of the inferior mesenteric artery. The arteries which supply the colon differ from those supplying the small intestines, in forming but one row of arches; which, in fact, are produced by the anastomoses spoken of, and have, there- fore, extremely large meshes. From the convexity of these arches, many parallel branches run out to supply the colon, and are very minutely distributed to it. The Capsular Arteries, the Emulgents, and the Spermatics, arise from the aorta, between the superior and the inferior me- senteries. But they will be described^fter the inferior mesen- teric, so as to keep together the account of the arteries of the intestines. The Inferior Mesenteric, Artery (Art. Mesenlerica Inferior) generally arises about one inch above the division of the aorta into the two primitive iliacs, and is much smaller than the su- perior Mesenteric. It inclines downwards to the left side, and gets between the laminae of the mesocolon; it then divides into three branches, called the Left Colic Arteries, from their dis- tribution to the left side of the colon. From their relative si- tuation to each other, they are distinguished into the Superior, the Middle, and the Inferior; sometimes, however, there are but two of these trunks. BRANCHES OF THE ABDOMINAL AORTA. 227 The Superior Colic (Art. Colica Sinistra Superior) goes ho- rizontally towards the colon in the left lumbar region; having got near the intestine it divides into two branches, one of which ascends to the transverse colon to form the anastomosis with the Colica Media of the upper mesenteric, while the other, de- scends to unite with the colica media sinistra. The middje Colic Artery (Art. Colica Sinistra Media) is sometimes a branch of the superior, and is occasionally wanting; it goes to- wards the upper part of the sigmoid flexure of the colon, and then bifurcates; one branch ascends to form by anastomosis an arch with the superior colic, while the other branch descends to join the lower colic artery. The Inferior Colic Artery (Art. Colica Sinistra Inferior) goes towards the middle of the sig- moid flexure of the colon, and there, like the preceding, divides into two branches; one anastomoses with the artery above, while the other joins with the arteries which go to the rectum from the inferior mesenteric. The Superior Haemorrhoidal Artery (Art. Ilamorrhoidea Supe- rior, Interna) is the lowest and the last branch of the inferior me- senteric. It descends between the laminae of the mesorectum, and is divided into two symmetrical trunks, which radiate by dividing and subdividing on the side of the rectum, and are dis- persed in very fine and numerous branches throughout its sub- stance : and anastomose with the middle and the inferior hae- morrhoidal arteries, also with the lateral sacral. The Capsular Arteries (Art. Capsulares) arise frequently from the aorta just below the superior mesenteric; but quite as often, if not more so, from the emulgents. They are not larger than a crow's quill, and vary from one to three on either side, gene- rally, however, not exceeding one: when they do, they are pro- portionably small. Passing horizontally outwards, they divide into several small ramifications, which terminate in the capsuke renales. Some of their branches go to the lesser muscle of the diaphragm. The Emulgent Arteries (Art. Emulgentes, Renales) are two in number, one for each kidney, but sometimes more. They are large and short, arise from the side of the aorta immediately be- 228 CIRCULATORY SYSTEM. low the superior mesenteric, and pass outwardly in a horizontal direction. The right one is longer than the left, somewhat lower down, and passes behind the ascending cava. They are both, in their course, from the aorta to the kidney, covered in front by the emulgent vein, and have to pass through a mass of adipose matter. The emulgent sends off some fine ramifications to the adipose matter, which surrounds it, and before it reaches the fissure of the kidney divides into three or four branches, preparatory to its introduction into this gland; upon the structure of which it is ul- timately distributed by very fine branches. The Spermatic Arteries (Arteria Spermalica, Seminales) arise from the aorta somewhat below the emulgents, but in some cases from the latter themselves. They are two in number, one on each side, and are about the size of a crow quill in the male subject, but smaller in the female. One comes off generally higher up than the other; they then descend on the sides of the vertebral column before the psoae muscles, and cross in front of the ureters, being in all this course behind the peritoneum. They are tortuous, and shortly after their origin begin to adhere to the spermatic veins, which adhesion is continued to the testicle. The branches that the spermatic artery sends off in the abdo- men are inconsiderable, consisting in very fine twigs to the adja- cent adipose matter, to the lymphatic glands, to the ureter, and to the peritoneum. In the male subject, it passes with the vas deferens, through the abdominal canal, and reaching the testicle divides into branches which supply the body of this gland and the epididymis. In descending from the external ring to the tes- tis, some small ramifications, to the adjacent parts leave it. In the female, the spermatic artery does not leave the cavity of the abdomen, but descending into the pelvis, gets between the lami- nae of the broad ligament to the ovarium, and is spent principally upon the latter. Some of its branches go to the Fallopian Tube, to the Round Ligament of the uterus, and to the sides of the lat- ter, where they anastomose with the uterine arteries. The Lumbar Arteries (Arteria Lumbares) are commonly five in number on either side, but seldom less than three, and, in their course outwards, correspond with the intercostal arteries. They BRANCHES OF THE ABDOMINAL AORTA. 229 are much larger than the latter. They arise in pairs, from the posterior external face of the aorta, at a point corresponding with the middle of the bodies of the four upper lumbar vertebrae; and pass outwards between the fasciculi of the psoas magnus muscle, to which, to the quadratus lumborum, and the bodies of the vertebrae, they distribute several branches. Sometimes each pair arises by a common trunk from the posterior face of the aorta. As the latter terminates at the fourth lumbar vertebra, the fifth lumbar artery is a branch from the fourth in most in- stances. At the base of the transyerse process each artery di- vides into two branches, a posterior or dorsal one, and an ante- rior or lumbar. The dorsal branch, which is smaller than the other, detaches a ramification through the intervertebral foramen to the lower part of the medulla spinalis and to the cauda equina: it then gets to the back, where it is spent upon the muscles near the spine. The anterior lumbar branch advances between the broad mus- cles of the abdomen, to which it is distributed; and runs for- wards far enough to anastomose with the epigastric artery. The first lumbar artery is small, and sometimes comes from the last intercostal; it goes a little below the inferior margin of the last rib, and then descends almost vertically between the pe- ritoneum and the transversus abdominis muscle. The lower lum- bar arteries anastomose with the circumflexa ilii, and with the superficial branches of the gluteal. The Middle Sacral Artery (Arteria Sacra Media) is generally not so large as a lumbar; it arises from the centre of the bifur- cation of the aorta into the two primitive iliacs, or else a line or two above it, behind. It descends, in front of the middle line of the fifth lumbar vertebra and of the sacrum, to the coccyx, adhering to the surface of these bones, and performing some flexuosities. , It sometimes happens that the last pair of mmbar arteries come from it, or at least one, according to Meckel, more com- monly the left: in which case the sacral is of unusual size. The sacral afterwards sends off, to the right and left, a pair of branches for each pair of sacral foramina. They run across the sacrum, send branches to it, anastomose with the lateral sacral Vol. II.—30 230 CIRCULATORY SYSTEM. arteries, and then penetrate to the cauda equina. The middle sacral artery is lost at the inferior end of the coccyx, in the fat and cellular tissue of the part. SECT. VI.—OF THE PRIMITIVE ILIAC ARTERIES, AND THEIR BRANCHES. The Primitive Iliac Arteries, (Art. lliaca Primitiva, communes,) one on each side, are, as mentioned, the terminating trunks of the abdominal aorta. They extend from the lower part of the fourth lumbar vertebra to the sacro-iliac junction, or near it, where they divide into two trunks, the Internal and the External Iliac. The primitive iliac is bounded on the outer side by the psoas magnus muscle, and behind by the primitive iliac vein; it is crossed at its lower part by the ureter. No branches deserving of especial notice are sent from it before it bifurcates ; such as exist are very small, and go simply to the parts immediately con- tiguous. The right artery crosses in front of the root of the left iliac vein. SECT. VII.—OF THE INTERNAL ILIAC ARTERY, AND ITS BRANCHES. The Internal Iliac Artery (Art. lliaca Interna, Hypogastrica) descends from the front upper part of the sacro-iliac junction, to the lower part of the same articulation. In this descent, it is bounded behind by the sacral plexus of nerves, and gives off se- veral arterial trunks; but the manner by which the last is ac- complished is much varied in different subjects. For the most part, it is an inch or more long before any important branches leave it; it is then frequently divided into two principal trunks, an anterior and a posterior, from which proceed the several branches that supply the internal and the external parts of the pelvis. The rule of origin of the secondary trunks from these two principal ones, even when the latter exist, is not fixed, for sometimes they ajise from one, sometimes from the other, and then again from the trunk of the hypogastric itself. The Ilio-Lumbar Artery (Art. Mo-Lumbar is) is commonly the INTERNAL ILIAC ARTERY, AND ITS BRANCHES. 231 first branch of the hypogastric, or of its posterior trunk. It as- cends outwards and backwards behind the psoas magnus mus- cle, and there divides into two branches, a superior and an in- ferior. The former continues to ascend between the psoas magnus and the iliacus internus muscles, to which, and to the quadratus lumborum, it distributes branches: it also sends rami- fications into the spinal cavity, and anastomoses with the lower lumbar arteries; sometimes it supplies the place of the last lum- bar entirely. The inferior branch, going outwardly, is divided into two orders of ramifications which supply the iliacus inter- nus muscle, on its surface and more deeply; also the os ilium by a ramuscle which penetrates the nutritious foramen of the latter. The inferior branch anastomoses with the circumflexa ilii of the external iliac. The Lateral Sacral Arteries (Arteria Sacra Laterales) arise next, either from the hypogastric or from its posterior trunk: their number is commonly equal to that of the foramina on the side of the sacrum in front, though they come from only one or two roots. They cross the front of the sacrum, and divide into branches, some of which anastomose with the middle sacral artery, while others enter the foramina of the sacrum, to be spent on the lower part of the cauda equina. The Obturator Artery (Arteria Obturatoria) comes commonly from the hypogastric or from one of its principal trunks; in some cases it arises from the epigastric or from the external iliac, near Poupart's ligament. In the first cases it passes forwards parallel with the brim of the pelvis, and in the latter cases it de- scends behind the superior ramus of the pubes. Whatever may be the condition of its organ, it gets from the pelvis through the upper part of the thyroid foramen over the superior margin of the obturator internus muscle, having previously sent off some inconsiderable ramifications to the periosteum and the contiguous muscles. It emerges from the pelvis on the upper margin of the obtu- rator externus muscle, and then divides into two principal trunks. The posterior descends along the external margin of the obtu- rator externus muscle, to which it gives ramifications; it like- 232 CIRCULATORY SYSTEM. wise sends some branches to the heads of the muscles coming from the tuber of the ischium, and thereby anastomoses with the sciatic artery; other branches are spent upon the hip joint, one of which gets into the cavity of the latter through the notch at the lower part of the acetabulum, and is spent upon the adipose matter in its bottom. The anterior branch goes to the heads of the adductor muscles, to the pectineus, to the obturator externus, and to the integuments of the upper internal part of the thigh. Near its origin this branch sends a ramification along the inter- nal margin of the thyroid foramen to anastomose with the pos- terior branch, so that the foramen is surrounded by an arterial circle. The Middle Haemorrhoidal Artery (Art. Hamorrhoidea Media) varies in its origin, being sometimes from the hypogastric itself, and, on other occasions, from one of its branches, as the gluteal, ischiatic, &c. It descends on the fore part of the rectum, op- posite the lower fundus of the bladder in the male, and is distri- buted by branches to the rectum, to the vesiculae seminales, and to the prostate gland. In the female it dispenses branches to the vagina. It is called middle, from its position between the upper and the lower haemorrhoidal arteries. In both sexes, the branches which it sends to other parts be- sides the rectum, frequently arise from other arteries, and in a manner which causes them to have distinct appellations, as va- ginal, &c. The Vesical Arteries (Arteria Vesicales) consist in several ra- mifications, coming from what was the umbilical artery of the foetus, but which, in the adult, with the exception of a short space near its origin, is converted into a ligamentous chord. These branches ramify upon the parietes of the bladder; one of them, more voluminous than any other, and called, by M. Chaussier, vesico-prostatic, gains the lower fundus of the bladder; sends branches to it, to the prostate, to the vesiculae seminales, and to the commencement of the urethra. The Uterine Artery (Arteria Uterina) arises from the hypogas- tric, or one of its branches, near the vesical, sometimes before, INTERNAL ILIAC ARTERY, AND ITS BRANCHES. 233 and on other occasions subsequent to them. Being peculiar to the female sex, its size varies according to the individual, being in a state of pregnancy or not: in the latter stages of gestation it is as large as any other branch of the hypogastric. It goes inwards towards the superior part of the vagina, to which it gives some ramifications; it then ascends between the laminae of the broad ligament, in a tortuous manner along the side of the uterus, and divides into many branches which are distributed through the tissue of this organ. It anastomoses with the corresponding arteries of the other side, apd with the branches of the spermatic artery which go to the Fallopian tube and to the ovarium. Besides the preceding, the hypogastric artery sends off two large branches, the Gluteal and the Ischiatic, which terminate it. In many subjects they are the direct continuation of the two pri- mitive trunks, into which the hypogastric is frequently originally divided. The Gluteal Artery, (Arteria Glutea,) shortly after its origin, issues from the pelvis above the pyriformis muscle, at the upper part of the ischiatic foramen, where it adheres closely to the edo-e of the bone. When it first gets to the dorsum of the ilium, it is covered by the gluteus maximus muscle, and lies at the poste- rior margin of the gluteus minimus, precisely under a line drawn from the posterior superior spinous process to the top of the tro- chanter major. It almost immediately afterwards divides into two principal trunks. One of these trunks, the more superficial, advances between the gluteus medius and the maximus, and distributes branches to them; also, to the posterior margin of the maximus, where it comes from the posterior sacro-sciatic ligament. The more deeply-seated trunk goes forwards between the gluteus medius and minimus, and subdivides into three orders of branches for their supply. One set follows the superior margin of the gluteus minimus towards the anterior superior spinous process; another set passes nearer the middle of the gluteus minimus; and the third set still lower down upon the dorsum of the ilium, above the acetabulum; some of the ramifications go to the capsular li- 234 CIRCULATORY SYSTEM. gament of the joint, where they anastomose with branches from the femoral artery. The Ischiatic Artery (Arteria Ischiadica) is somewhat smaller than the gluteal, but looks rather more like the continuation of the hypogastric. It descends between the rectum and the pyri- formis muscle, and issues under the lower margin of the latter, out of the pelvis, being there placed in front of the sciatic nerve. It goes downwards on the back of the thigh, between the tro- chanter major and the tuberosity of the ischium, being at the in- ternal edge of the sciatic nerve, and on the posterior face of the small rotator muscles of the thigh. It sends off in the pelvis the Internal Pudic Artery, and also some inconstant branches, of small size, to the viscera within the pelvis; when it has emerged from the latter, it detaches some considerable branches to the ori- gin and to the inferior margin of the gluteus magnus muscle, and to the small rotator muscles. The branch which may be consi- dered as the continued trunk of the ischiatic, descending on the posterior face of the thigh, along with the sciatic nerve, under the hamstring muscles, is lost in ramifications to them, and by anastomoses with the perforating arteries. The Internal Pudic Artery, (Arteria Pudica Interna,) though a branch of the ischiatic, is only in a slight degree smaller. It arises a little above the spinous process of the ischium, in the pelvis, in front of the sciatic plexus, and getting from the pelvis "between the anterior sacro-sciatic ligament and the inferior margin of the pyriformis muscle, it passes over the posterior face of the anterior sacro-sciatic ligament, at the spinous process of the ischium. It immediately afterwards returns into the ca- vity of the pelvis, between the two sacro-sciatic ligaments, at the place where the obturator internus muscle winds over the ischium; it then winds along the internal face of the latter bone and of its ascending ramus, at the inferior margin of the obtu- rator internus muscle; and continues on the internal face of the ramus of the pubes, between the two laminae of the triangular ligament, above the crus of the penis to the symphysis of the pubes. INTERNAL ILIAC ARTERY, AND ITS BRANCHES. 235 In this course the Internal Pudic Artery detaches, several im- portant branches, in the following order:— a. A ramification along the inferior margin of the piriformis, to this muscle and to the parts on the posterior face of the neck of the os femoris, where it anastomoses with the other arteries of this region. b. The Lower Haemorrhoidal Artery (Art. Hamorrhoidea In- ferior Externa) to the inferior part of the rectum, and to the external sphincter ani muscle. This artery arises after the inter- nal pudic has returned within the pelvis, and consists sometimes in several branches. c. The Perineal Artery (Art. Perinea, Transversa Perinei) has its root near the origin of the transversus perinei muscle, and advancing obliquely forwards is distributed in several ramifica- tions to the muscles and integuments of the perineum, and to the posterior part of the scrotum. It is unavoidably cut in the late- ral operation for the stone. In the female it goes to the sphinc- ter vaginae and to the labium externum. d. When the internal pudic has got beyond the transversus perinei muscle near the beginning of the crus penis, it detaches to the bulb of the urethra, along the posterior margin of the tri- angular ligament, a branch which penetrates to the corpus spon- giosum, and is minutely distributed upon it, some of its ramifica- tions reaching to the corpus cavernosum. This branch is called, by M. Chaussier, Urethro-bulbar, and instead of being always distinct, it on some occasions comes from the Perineal. e. At the under part of the symphysis pubis, between it and the back of the penis, the internal pudic sends forwards, on the dorsum of the penis, a superficial branch, (Ramus Superficialis Dorsi Penis.) It advances to the end of the penis, under the skin, being parallel with its fellow of the other side, and near to it: sometimes the two unite after a short course. They are dis- persed in branches to the integuments, and to the elastic liga- ment of the penis. / The Cavernous Artery of the Penis (Art. Cavernosa Profun- da Penis) may be considered as the terminating trunk of the in- ternal pudic. It penetrates the corpus cavernosum, beneath the symphysis of the pubes, and quickly divides into many ramifica- tions. The latter advance, and continue to subdivide upon the 236 CIRCULATORY SYSTEM. cells of the corpus cavernosum, to which they are principally distributed: some of them reach the corpus spongiosum urethrae, and others anastomose with the corresponding arteries of the other side. SECT. VIII.--OF THE EXTERNAL ILIAC ARTERY, AND ITS BRANCHES. The External Iliac Artery (Arteria lliaca Externa) extends from the bifurcation of the primitive iliac to Poupart's ligament, where it is continued to the lower extremity under the name of the femoral artery. It looks like the continuation of the primi- tive iliac, and descends at the superior strait of the pelvis along the internal margin of the psoas magnus muscle. In the early part of its course, it is anterior to the external iliac vein; it then, as it approaches Poupart's ligament, gets to its outer margin. It is covered by the peritoneum in front. Where it passes be- neath Poupart's ligament to the thigh, it is about half way be- tween the anterior superior spinous process of the ilium and the symphysis pubis, having the vein at its pubic margin and the anterior crural nerve, half an inch from its iliac margin. No branches of consequence arise before it reaches the crural arch; it then sends off two, the Epigastric and the Circumflex of the ilium. The Epigastric Artery (Arteria Epigastrica) arises somewhat above the crural arch, at the line where the peritoneum is re- flected from the fascia transversalis upon the iliac fascia. It at first passes horizontally inwards, then rises obliquely upwards and inwards, behind the spermatic chord, at the pubic margin of the internal abdominal ring. Afterwards it reaches the ex- ternal margin of the rectus abdominis muscle, two or three inches above the pubes: ascending along it for a short distance, it then passes to its posterior face, and continues ascending above the umbilicus; where being divided into several branches, it terminates by anastomosing with the lower ramifications of the internal mammary artery. This artery is almost entirely spent upon the anterior parietes of the abdomen, in ramifications, which anastomose with the last intercostal and with the lumbar arteries. One of its small EXTERNAL ILIAC ARTERY, AND ITS BRANCHES. 237 twigs, following the course of the spermatic chord, or of the round ligament, is distributed upon the cremaster, the tunica vaginalis, and the scrotum of the male, and upon the mons ve- neris of the female. In some cases it gives off the obturator artery. The Circumflex Iliac Artery (Arteria Circumflexa Mi) is of the same size with the epigastric, and comes from the external iliac, sometimes on a level with it, and on other occasions lower down, even below the crural arch. It ascends outwardly towards the anterior superior spinous process of the ilium, along the posterior margin of the crural arch, and following afterwards the direc- tion of the crista of the ilium, it anastomoses with the corre- sponding branch of the ilio-lumbar artery. The following branches come from it. In the early part of its course some unimportant twigs are sent to the adjacent mus- cles, as the sartorius, iliacus internus, and so on. At the ante- rior superior spinous process, it divides into two branches, the smaller ascends between the internal oblique and the transversa- lis muscle, and is distributed upon them; the other branch, which is the continuation of the main trunk along the crista of the ilium at the margin of the iliacus internus muscle, sends ra- mifications to the latter, and also to the posterior part of the broad muscles of the abdomen, where it anastomoses with the other arteries of this region. Of the Femoral Artery. The Femoral Artery (Arteria Femoralis, Cruralis) the continu- ation of the external iliac, extends from the crural arch to the perforation for its passage through the abductor magnus, which is commonly one-third of the whole length of the os femoris, above the knee joint. This great trunk, immediately below Poupart's ligament is very superficial, and may be felt pulsating where it passes over the pubes. It is there covered only by the common integuments and the fascia femoris, which is thin; it is bounded internally by the femoral vein, externally by the crural nerve, is half-way between the anterior superior spinous process and the symphysis of the pubes, and lies upon the internal face Vol. II.—31 238 CIRCULATORY SYSTEM. of the psoas magnus over the interstice between it and the pec- tineus. In the upper third of its course the femoral artery is at the inner edge of the rectus femoris, and at a short distance from it; it then inclines inwards, and occupies the angle formed by the adhesion of the vastus internus to the adductor longus. The sartorius, at first, is remote at its outside, but this muscle inclining inwards in its descent gets to the exterior margin of the artery, and afterwards covers it completely for the remainder of its course. The femoral artery is in front of the femoral vein when it has descended three or four inches below the crural arch; be- hind the two is the arteria profunda. When the femoral artery and vein reach the angle formed by the vastus internus and the adductor longus, they are covered by a strong interlacement of tendinous fibres from these muscles. The femoral artery sends off these branches:— 1. The Superficial Artery of the Abdomen (Art. ad Cutem Ab- dominis) is small, and arises at the lower margin of Poupart's ligament; it goes upwards towards the umbilicus, lies beneath the fascia superficialis abdominis, and is distributed to the in- teguments of this region. One of its ramifications goes to the inguinal glands. 2. The External Pudic Arteries (Art. Pudenda Externa) come from the femoral at the same point, and are two or even three in number; they are of small size. One of them inclines inwards along the groin, between the skin and the fascia femoris, and is distributed to the integuments of the pubes—to those of the penis,—and to the scrotum, or to the labium externum of the fe- male. The second, and the third when it exists, are rather lower down, and are dispersed upon very much the same parts. The lymphatic glands of the groin also derive their supply of blood from these external pudic arteries. 3. The Profound Artery, (Arteria Profunda Femoris,) the great muscular artery of the thigh, is but slightly inferior in size to the femoral itself, and comes from the latter at the distance of from one to two inches below the crural arch. It lies behind the fe- moral artery, and descends in that situation between the inser- EXTERNAL ILIAC ARTERY, AND ITS BRANCHES. 239 tion of the adductor brevis and the vastus internus muscle, to the upper part of the insertion of the adductor longus. In this course, its size is much diminished, by the origin from it of seve- ral considerable trunks, as follows:— a. The External Circumflex, (Arteria Circumflexa Externa,) though most frequently a branch of the profunda, sometimes comes from the femoral above or below it a short distance. It goes immediately outwards between the rectus femoris muscle and the cruralis, giving off some inconsiderable ramifications. While between these muscles it divides into two branches, one of which ascends, and the other descends; the former is distri- buted to the anterior margins of the gluteus medius and minimus, to the capsule of the joint, and the parts about the trochanter major, anastomosing with the gluteal and the ischiatic. It is said by Meckel, that these anastomoses have been found much dilated where the externa] iliac artery has been taken up. The descending branch is about the size of a crow quill, or even larger; it first passes obliquely downwards between the rectus femoris and the cruralis, it then descends vertically under the anterior margin of the vastus externus, between it and the cru- ralis, to terminate at the knee, where it becomes superficial and anastomoses with the articular arteries. It is, however, princi- pally distributed to the vastus externus and to the cruralis. b. The Internal Circumflex Artery (Arteria Circumflexa In- terna) arises from the profunda, near the external circum- flex, generally below it, but sometimes the reverse; in some cases, it comes from the femoral artery itself, near the crural arch. It passes transversely inwards, and dips into the inter- stice between the pectineus and the psoas magnus, after having given off some small twigs to the heads of the adjoining ad- ductors. It then winds under the neck of the os femoris and divides into two branches; the upper one goes to the capsular ligament of the joint, to the obturator externus muscle, anasto- moses with the obturator artery, and sends a branch behind the adductor brevis to the upper part of the adductor magnus: the inferior branch is larger than the other; it descends behind the adductor magnus and is distributed in branches to it, to the gra- cilis, and to the hamstring muscles, sending upwards some rami- fications (rami trochanterici) to the parts about the trochanter 240 CIRCULATORY SYSTEM. major, where they anastomose with the external circumflex ar- tery. c. Muscular branches of inconstant origin, and of inconsider- able size, are sent from the profunda to supply the anterior face of the adductor muscles. d. The Perforating Arteries (Rami Profundi Perforantes) ob- tain the name from their perforating the adductor magnus, which they do near the linea aspera, so as to get to the back of the thigh. They commonly are four in number, and as they come off successively from the profunda, they are designated numeri- cally. In some cases, however, they are reduced to one, by be- ing concentrated in a common trunk, which, penetrating high up the adductor magnus, and afterwards descending on its posterior face, is dispersed upon the muscles on the back of the thigh. The First Perforating Artery arises somewhat below the tro- chanter minor, and penetrates the adductor magnus a little be- low its superior margin. One of its branches ascends towards the trochanter major, where it anastomoses with the external circumflex and with the gluteal, while another descending is spent upon the heads of the flexor muscles of the leg. The Second Perforating Artery gets to the back of the thigh, at the lower margin of the insertion of the gluteus maximus into the linea aspera, being distributed in that region, and to the cor- responding portion of the long head of the biceps flexor cruris. The Third Perforating Artery penetrates the Adductor mag- nus somewhat below the commencement of the short head of the biceps, and is dispersed upon the adductor and the adjacent portion of the flexor muscles. The Fourth Perforating Artery penetrates the insertion of the adductor magnus an inch and a half above the opening in it, for the femoral artery; it, in the same way, supplies the posterior face of the adductor and the adjacent muscles. As a summary, it will be readily understood that the profunda is, in this way, through the external and the internal circumflex, and through the perforating arteries, distributed upon all the large muscles of the thigh. After the origin of the profunda, the Femoral Artery gives POPLITEAL ARTERY, AND ITS BRANCHES. 241 off, at different points of its course to the opening of the ad- ductor magnus; several twigs the size of a large knitting needle, which go to the sartorius, the gracilis, the adductors, and the extensors on the front of the thigh; but they are too inconstant to require more particular description. The Anastomosing Artery (Arteria Anastomotica) is the last branch of the femoral, and arises just before it perforates the adductor magnus. It descends to the knee, in front of the ten- don of the latter, concealed by the internal margins of the vastus internus muscle. It sends off many small twigs to the adjacent muscles, and terminates below by anastomosing with the inter- nal articular arteries. It is about the size of a crow-quill. The Popliteal Artery (Arteria Poplitaa) is the continuation of the femoral, after the latter has passed through the tendinous insertion of the adductor magnus, and extends from this point to the opening in the interosseous ligament of the leg, just below the head of the tibia. It, first of all, passes from the internal margin of the os femoris, to the notch between the condyles; being there placed in the middle between the internal and the external hamstring muscles, and surrounded by a mass of adi- pose matter which fills up the hollow of the ham. It is in con- tact, anteriorly, with the knee joint, and a little below the latter with the popliteus muscle, descending there between the heads of the gastrocnemius. It is covered, in the greater part of its extent, posteriorly, by the popliteal vein, and by the sciatic nerve, the latter being more superficial than the vein. The popliteal artery sends off some small branches to the hamstring muscles, and to the parts contained between the lat- ter, which are too irregular and inconstant for description. The following arteries, also, come from it:— 1. The Superior Internal Articular Artery (Art. Articularis Superior Interna) arises at or above the internal condyle, and frequently consists in two trunks. It passes through the ten- don of the adductor magnus, just above the condyle; it then be- gins to distribute itself in branches, some of which are spent 242 CIRCULATORY SYSTEM. upon the lower part of the vastus internus muscle, and others upon the superior internal part of the knee joint. 2. The Superior External Articulating Artery (Art. Arlicu- laris Superior Externa) arises from the popliteal, somewhat above the external condyle of the os femoris. It winds, hori- zontally, above the external condyle, around the bone, between it and the lower part of the biceps flexor cruris, and is then dis- tributed, also, in two orders of branches, some of which supply the lower part of the vastus externus muscle, and others the superior external portion of the knee joint. 3. The Middle Articular Artery (Art. Articularis Media) is smaller than either of the above, and sometimes comes from one of them, but generally from the popliteal, on a line with the articulation of the knee. It is distributed to the posterior part of the capsular ligament, to the crucial ligaments, and to the corresponding adipose matter. 4. The Inferior Internal Articular Artery (Art. Articularis In- ferior Interna) arises on a line with the inferior part of the inter- nal condyle, sometimes lower down. Its origin is very much concealed by the internal head of the gastrocnemius; it passes beneath the latter, and then between the internal lateral liga- ment of the knee and the head of the tibia; consequently, it is covered by the internal hamstring muscles. It afterwards as- cends towards the patella, and is distributed in numerous branches to the inferior internal part of the knee joint, and to the adjacent portion of the tibia. 5. The Inferior External Articular Artery (Art. Articularis Inferior Externa) arises near the last, below the external condyle, being concealed by the belly of the plantaris. It passes, hori- zontally, or nearly so, between the popliteus and the outer head of the gastrocnemius, and afterwards beneath the tendon of the biceps and the external lateral ligament of the joint, around the external face of the head of the tibia. It gives small branches to these several parts, and is then distributed, by two orders of EXTERNAL ILIAC ARTERY, AND ITS BRANCHES. 243 ramification's, to the superficial and to the more deeply seated parts at the external inferior portion of the knee joint. These several articular arteries anastomose freely with each other, and are minutely ramified on the knee joint and the con- tiguous structure. They also anastomose with the long de- scending Branch of the external circumflex of the thigh, with the anastomotica of the femoral, and with the tibial recurrent. 6. The Gastrocnemial Arteries (Arteria Gemella) are two in number, one for each head of the gastrocnemius. They arise commonly between the superior and the inferior articular arte- ries, and are about the same size. They penetrate into the muscle, and supply it with blood, terminating their course near the lower part of its bellies. Moreover, some small branches, which go to the contiguous muscles, are frequently observed here; also, the nutritious ar- tery of the tibia. But their number and condition are very in- constant. Near the head of the fibula, branches go from the popliteal artery to the upper end of the soleus muscle. Generally, on a level with the aperture in the upper part of the interosseous ligament, but sometimes an inch or two higher up, the popliteal artery terminates by dividing into two large trunks, the Anterior and the posterior Tibial. The Anterior Tibial Artery (Art. Tibialis Anterior) passes forwards through the foramen of the interosseous ligament, just below the head of the fibula, and runs down the front of the leg and foot, as far as the base of the metatarsal bone of the great toe. In this course, its relative situation is as follows: It rests upon the front of the interosseous ligament of the leg, on a line drawn from the middle anterior part of the head of the fibula to the middle of the ankle joint. Superiorly, it is bounded on the tibial side by the tibialis anticus muscle, and on the other by the extensor longus digitorum: lower down on the leg, the place of the latter is supplied by the extensor pollicis pedis. Somewhat above the ankle joint the artery, leaving the inter- osseous ligament, rests upon the front of the tibia, and then gets- to the top of the foot, between the Gangliis Nervorum. Leipsick, 1772. f Legallois on the Principle of Life. $ Observ. and Exper. on the Nervous System, by W. E. Horner. See Chap- man's -Med. and Phys. Journal, vol. i. p. 285. GENERAL ANATOMY OF THE NERVOUS SYSTEM. 321 nervous system, seems proved by the fact, that where there has been a congenital deficiency of all the limbs, or an ac- cidental one, which, of course, removes a very considerable portion of the peripheral part of the nervous system, animal life and the intellectual operations have still gone on vigo- rously. The following are some of the physical functions over which -the nervous system seems to preside. Digestion; the whole alimentary canal, from the mouth to the anus, is under this influence: first of all in mastication, then in swallowing, afterwards in digestion and the absorption of chyle, and, finally, in the passing of the effete matter out of the body. It has been sufficiently proved, by the experiments of several physiologists, that the section of the par vagum destroys the faculty of digestion. Respiration; the mechanical act of this process, that by which the cavity of the thorax is enlarged so as to admit of the intro- duction of air, evidently depends upon the phrenic and the in- tercostal nerves. If the nerves which supply the structure of the lungs be alone intercepted, as the par vagum, either by liga- ture or section, the changes on the blood produced by respiration cease, and the animal dies. Secretion, exhalation, absorption, and animal heat, seem also to be dependent upon the integrity and the activity of nervous influence. The action of the heart, sensation and voluntary mo- tion, are in the same predicament. The manner in which these several kinds of innervation is produced, is unintelligible. One has supposed it to consist in a vibration of the elementary fibres of the nerves; another in an agitation of its elastic globules; another in the transmission of an imponderable fluid, as ether, magnetism, electricity, and Galva- nism. Reil has proposed, on this subject, what has been termed a chemico-vital hypothesis: according to him, the genera] action of parts depends upon their form and composition ; consequently, when the two latter vary, the first does also. M. Beclard* in- clines to the opinion, that " the nervous system is the elaborator and conductor of an imponderable agent; and, like electricity • Anat. Gen. 322 NERVOUS SYSTEM. or magnetism, that by it we can explain all the phenomena of innervation:—The relation between the benumbing influence of electric fish and Galvanic phenomena on one part, and ordinary nervous action on the other;—The practicability of causing Galvanic phenomena by the nerves and muscles alone;—The possibility of producing muscular contraction, the chymifiant ac- tion of the stomach, the respiratory action of the lung, &c, in substituting a Galvanic for a nervous influence;—The existence of a nervous atmosphere, acting at a distance around the nerves and muscles, and between the ends of divided nerves;—The wrinkling of muscular fibres in contraction, and the relation of the finest transverse nervous fibres with those wrinkles, are phe- nomena of innervation which nearly approach certain electro- magnetical ones." This subtile fluid, according to M. Beclard, seems to be formed every where, but principally in places where there is much vas- cularity along with the ash-coloured substance. It impregnates all the humours and organs. The blood seems to be especially endowed with it, and owes to it the properties which distinguish it during life. In consequence of which, life is essentially con- nected to the reciprocal action of the blood upon the nervous substance, and of the nervous substance upon the blood.* Mr. Charles Bell, of London, has lately presented, in a very in- teresting light, certain functions of the nervous system:! by his researches it appears, that besides the nerves^ of vision, smell, and hearing, there are four other systems, having different func- tions, and extended through the whole frame. Those of Sensa- tion ; of Voluntary Motion; of Respiratory Motion; and nerves, which give unity to the body in harmonizing the functions of nutrition, growth, and decay, or whatever else is indispensable to animal existence. * M. Rolando (Saggio sulla vera struttura del cervello, e sopra le funzioni del sistema nervoso, 1809, Beclard, p. 622,) has been so much taken with the Gal- vanic manifestations of the nervous system, that in the laminated arrangement of the cerebellum, he has only seen a modification of the Voltaic pile. In the con- volutions of the cerebrum, he, no doubt, would have recognised an acquaintance with that powerful instrument, the Spiral Calorimotor of Professor Hare of this University. ■J- Exposition of the Natural System of the Nerves of the Human Body. Philad. 1825. GENERAL ANATOMY OF THE NERVOUS SYSTEM. 323 According to this theory, the several filaments of a nerve exercise one or the other function, but only the one; these dis- similar filaments being bound up in the same fasciculus, con- stitute a nerve or fascis, and they never exchange power with one another: their anatomical differences, however, are such, as not to make obvious one kind of filaments from the others. Se- veral columns of nervous matter form the spinal marrow, six in all, three on each side; the anterior for voluntary motion, the posterior for sensation, and the middle for respiration; and it is probable that still more may be found out. The first and the third ascend into the brain, and the middle stops short in the medulla oblongata; hence, the function of respiration goes on so long as the medulla oblongata remains entire. These few prin- ciples, supported by several experiments, have 'enabled Mr. Bell to bring forward a system of no small importance on the anatomy and physiology of the nervous system.* The development of the nervous system is amongst the earliest processes in the distinct evolution of the fcetal organs.t At the end of the first month, when the head is a mere swelling of one end of the small maggot-like being, the brain and the spinal marrow are not by any means distinct, but the parts being trans- parent, a limped fluid holds their place. About the fifth or sixth week, the embryo having acquired a length of five or six lines, the rudiments of the brain appear as vesicles containing a whitish and almost diaphanous fluid, while the spinal marrow represents a long canal containing the same, and communicating with the cerebral vesicles. In the early part of the third month, the brain and spinal mar- row show very distinctly the rudiments of the several cavities, elevations, and fasciculi, which mark their subsequent mechanical arrangement of surface; and from this period it is no longer dif- ficult to trace the successive development of each part to the degree of perfection which it has at the time of birth. • The same subject has been taken up, in an inaugural thesis, by a zealous and intelligent graduate of the University; and, by a series of ingenious experiments, seems to have been generally proved and illustrated. Chapman's Med. and Phys: Journal, 1823, vol. vi. p. 240. Remarks on some of the Nervous Func- tions, by J. P. Hopkinson, M. D. f Anat. du Cerveau, par F. Tiedemann, traduit par Jourdan, Paris, 1823. Anat. Comp. du Cerveau, par E. R. A. Serres, Paris, 1824. 324 NERVOUS SYSTEM. From the many observations made by Tiedemann on these points, he has deduced the conclusion, that the brain is produced by the superior part of the spinal marrow; that is to say, by the medulla oblongata, which grows and is developed for the pur- pose. That this is proved, in the extension upwards and for- wards of the two principal fasciculi of the spinal marrow, and by a canal which is found in the spinal marrow of the foetus, being extended to the fourth, and even to the third ventricle; also, by the cerebellum proceeding evidently from the medulla spinalis, since its two crura may be traced growing from it, and subsequently uniting over the fourth ventricle, so as to form the especial structure of the cerebellum; also, by the tubercula quadrigemina being derived from the corpora olivaria of the me- dulla oblongata, and by the thalami and the corpora striata pro- ceeding from the corpora pyramidalia, and, finally, forming the hemispheres of the cerebrum. In addition to the preceding proofs, comparative anatomy fur- nishes other illustrations. The brain becomes more and more complex as one ascends from fish to reptiles, from the latter to birds, and then to mammiferous animals. The spinal marrow is very voluminous in the inferior animals, while the brain only forms an appendix to it; whereas, if the spinal marrow were an appendix to the brain, we ought to find the last of a prior forma- tion in foetuses, and also in a perfect state in the lower animals, before a medulla spinalis could be found.* * Tiedemann, loc. cit. p. 157. BOOK IX. PART II. On the Special Anatomy of the Central portion of the Nervous System. CHAPTER I. OF THE SPINAL MARROW AND ITS MEMBRANES. The Spinal Marrow, (Medulla Spinalis) though commonly described after the brain, as a continuation or appendage of it, has precedence, as seen, both in the period of its formation in the embryo, and in its importance to the functions of the ani- mal system; it will, consequently, be useful to give it that prio- rity in description to which its natural rank entitles it. SECT. I.—OF THE SPINAL MARROW. It is placed within the vertebral cavity, and extends from the first vertebra of the neck to the first or second vertebra of the loins, inclusively. It is surrounded by three membranes, of which the Dura Mater is external, the Pia Mater internal, and the Tunica Arachnoidea, between the other two. Its general form is cylindrical, yet it has slightly the appearance of being flattened both behind and before. It departs also from the strict cylindrical shape, by being enlarged or swollen at particular points. One of these enlargements occurs in the neck, where the canal is formed by the five lower cervical vertebrae, and the axillary plexus of nerves is given off. The enlargement is in Vol. II.—42 326 NERVOUS SYSTEM. the transverse direction or axis of the spinal marrow, but not so much in its thickness, and terminates gradually both above and below. The medulla spinalis afterwards continues small, with very slight undulations or nodosities, until within three or four inches of its lower extremity, when it again enlarges. The enlargement here, though sufficiently obvious, is not equal in actual magnitude to that in the neck, and is the place from which all the lumbar nerves and the three superior sacral pro- ceed. It is then brought gradually to a point somewhat blunt- ed, which most commonly does not descend below the first lum- bar vertebra. The point is, in some rare cases, bifurcated, and by a transverse fissure converted into a tubercle. The spinal marrow, besides terminating so much above the lower end of the spinal canal, is much smaller in its diameter, even with the addition of its membranes, than the canal. This circumstance prevails, especially in the neck, and in the loins, where much motion is experienced; and, consequently, a provi- sion is thus made against any injury to it from pressure. The Medulla Spinalis is marked off, longitudinally, into two symmetrical parts, by one fissure in front and another behind, both of which extend its whole length, and are placed exactly in its middle. The contiguous edges or surfaces of each of these fissures adhere so, that it requires a slight maceration or dissec- tion to render them evident. The posterior fissure is decidedly deeper, especially at its upper part, than the anterior; but the latter, in return, is somewhat broader. The difference in depth, however, is unimportant, as subjects are frequently met with in which it is not appreciable. Moreover, on each side of the medulla spinalis there is a la- teral fissure. It is not precisely in the middle, but somewhat posterior, and penetrates inwards and forwards. In many in- stances it is merely a simple superficial depression, much less deep than either of the former. It does not run the whole length of the medulla spinalis, but terminates somewhere in the upper part of its thoracic portion by joining with its fellow after having converged regularly towards'it.* The different opinions of ana- * Meckel, Manuel D'Anatomie. SPINAL MARROW. 327 tomists on the existence of this fissure may be accounted for by its being readily found in early life, while it is obliterated or very indistinct in old age. This lateral fissure should be care- fully distinguished from two others, one before and the other behind it, which extend the whole length of the medulla spina- lis, and consist in a series of little depressions, running into each other and transmitting the filaments which form the roots of the spinal nerves. * The posterior, of the last named lateral fissures, is deeper than the anterior, and penetrates in the same direction with the lateral fissures first mentioned; it also, in like manner, joins its fellow, but only after having proceeded to within a few lines of the inferior end of the medulla spinalis. The substance of the spinal marrow being of two kinds, ci- neritious and medullary, the order of their position is reversed from what occurs in the brain; for the cineritious is included or enveloped by the other. On making a transverse section the cineritious will be found much less abundant than the other, and consisting of a thin transverse part in or near the centre of the medulla. This part is joined at either end to a portion somewhat crescentic, whose concavity is outwards, and the con- vexity inwards. The transverse part does not run into the middle of the crescent, but somewhat anterior to the middle? so that the anterior horn is shorter than the other, and i>s also thicker and obviously more obtuse. The cineritious jr grayish substance is more abundant at the lower part o^ the medulla spinalis than it is above. In the fcetus, at the *nd of gestation, it predominates below, occasionally, to the entire exclusion of the other. The medullary or white substance is more abundant laterally than elsewhere, and has its two symmetrical sides joined together by a thin lamina at Ae bottom of the anterior and of the posterior fissure. Each half or symmetrical sid/of the medulla spinalis is itself divided into two chords, marked off from each other by the pos- terior horn of the cineritious crescent, and by the first described lateral fissure. Of these chords the anterior is, consequently, much the larger; it is 0'so longer and forms the inferior extre- mity or the point of tfe medulla spinalis. The posterior chord, though so much smaller and narrower than the anterior, is it- 328 NERVOUS SYSTEM. self subdivided into two, by a slight but well marked split; of the two last chords, the one next to the posterior middle fissure of the medulla is smaller than the other. These arrangements, according to Meckel, are much more obvious in the early life of the human subject, than afterwards, and are particularly con- spicuous in the brute creation. The thin white laminae by which the two sides of the spi- nal marrow adhere to each other at the bottom of the middle fissures, are called, by modern anatomists, Anterior and Poste- rior Commissures. Their precise arrangement is not yet fully ascertained, but it is stated by Grail and Spurzheim,* that the Anterior Commissure is formed by transverse fibres or filaments, which adhere to one another from the opposite sides like a su- ture, or after a serrated fashion; whereas, the Posterior Com- missure is formed by a band of longitudinal fibres. There is also another Commissure, called Middle or Cortical, from its position,.and from its being formed out of the transverse part of the grayish or cineritious substance. The chords which form each half of the medulla are different- ly disposed: the posterior continues on the side to which it specially belongs, while the anterior having got within the cir- cumference of the first cervical vertebra, crosses over to the op- posite side by decussating with its fellow. This decussation occupies the space of four or five lines, and interrupts, for that distance, thb middle fissure in front of the medulla. It is not effected by tht chords passing in mass from one side to the other, but each chord sends off four or five fasciculi, which are interwoven with tluir congeners, like the fingers of the two hands when interlocked .obliquely. It is to be observed that the whole mass of the an»erior chords is not subjected to such distribution; for the fascicuK just described come from their an- terior and from their posterior faces, while the intermediate part is permitted to pursue its course straight upwards. This decussation, upon which so much interesting physiological spe- culation depends, though known for tVe last century, and spoken of by Mistichelli and Petit, has been tf.rangely overlooked by many anatomists, and is even positively dtnied by some. There * Recherches sur le Syst. Nerv. etsur celui du Cerveau. Paris, 1809. SPINAL MARROW. 329 are other places where the fasciculi of the spinal marrow seem to cross from one side to the other, but the fact is not yet veri- fied sufficiently. The existence of canals in the spinal marrow has been from time to time announced;* though authors differ much in the ac- counts of their position and extent. When such an appearance is presented, it is supposed, by some, to be either the result of disease or of accident, with the exception of a small one of eight or nine lines long, which communicates at one end with the fourth ventricle, and is shut up at the other.f The Spinal Marrow sends out from its sides thirty pairs of nerves, which, like the vertebrae, are arranged into cervical, dor- sal or thoracic, lumbar, and sacral. Of these there are eight cervical, one of which, from its escaping between the occiput and the first vertebra, is most usually designated as sub-occipital, and, therefore, the number of the cervical nerves is reduced to the same with that of the vertebrae, to wit, seven. There are twelve pairs of dorsal nerves, five of lumbar, and five of sacral. Occasionally, there is a sixth sacral nerve on each side, which augments the number of spinal nerves to thirty-one pairs. Every spinal nerve is formed from two roots on the same level, one before and the other behind, and each root consists in several fasciculi of nervous matter. The front root arises from the anterior chord of the medulla spinalis, and the other from the posterior chord. The posterior root is larger than the ante- rior, but has fewer fasciculi in its composition, and is not so fila- mentous. The two roots are kept asunder by the Ligamentum Denticulatum. The fasciculi of each are slightly connected by a loose delicate cellular substance, and as they are about pene- trating the dura mater, each fasciculus collects into a single chord, which passes the dura mater through its appropriate fo- ramen. In this way the anterior and posterior roots are kept distinct till they have got to the outside of the membrane men- tioned ; but the foramina, through which they pass, border close- ly upon one another. The posterior root, then forms a ganglion • Gall, Portal, Morgagni. X Meckel, p. 605, vol. ii. Bichat, vol. iii. p. 128. 330 NERVOUS SYSTEM. of a round or oval shape; from whose external extremity there proceeds a single nervous trunk, which is joined immediately at its commencement by the anterior root. With the exception of the ganglions of the sacrum, which are in the spinal cavity of that bone, these bodies are placed in the intervertebral foramina. The size of the ganglion is not proportionate to that of the nerve from which it proceeds; for some of the dorsal ganglions are the largest, while those of the sacrum are smaller than any others. The two nerves of the same pair, though generally symme- trical, or precisely resembling, are not invariably so; sometimes one is placed higher than another, and the number of the fasci- culi may be greater or smaller. The roots of the nerves are much nearer, or cluster more at the extremities of the spinal marrow, than in its middle. The lumbar and sacral nerves are, indeed, so close together and so much in a bunch, that the ar- rangement is designated by the term Cauda Equina. The Cervical Pairs of Nerves are nearly horizontal in their course from the medulla spinalis to the foramina in the dura mater.' The first one, or the sub-occipital, is strictly so; the others incline very gradually more and more downwards. They have, therefore, but a very short passage before they reach the intervertebral foramina. Their roots are so pyramidal, that the bases nearly touch each other, and, for the most part, are con- nected by an anastomosing filament, which goes from the upper margin of the root below to the lower margin of the root above. These anastomoses are found connecting the upper with the lower fasciculi, both on the anterior and posterior chords of the medulla, but more uniformly as regards the latter. Modifica- tions of this arrangement, which it is unnecessary to specify, are met with in different subjects. The Dorsal, or Thoracic Pairs, are much inferior in size to any other nerves, except the inferior sacral. Anastomosing filaments do not generally prevail, yet they are found occasion- ally, as in the neck, upon the two or three upper pairs. The first one has the broad pyramidal or triangular root of a cervi- MEMBRANES OF THE SFINAL MARROW. 331 cal nerve, and resembles it also in volume. The second is the smallest of any: they then go on increasing in size to the low- est, but not in an uniform gradation. They are successively more oblique, and consequently longer from their bases to their passage through the dura mater. The Lumbar and the Sacral Pairs arise closely upon each other, indeed in absolute contact successively, from the lower end of the medulla spinalis. As their place of origin is within the precincts of the first lumbar vertebra and the two or three last dorsal, they all observe a very oblique course in their de- scent to the vertebral foramina, and the lower ones are almost vertical. Notwithstanding they are in contact, and adhere by a loose cellular substance, yet there are no anastomosing fila- ments between the adjacent roots. From the sacral gangli- ons presenting the peculiarity of being situated in the spinal cavity of the sacrum, instead of in the foramina, the single nerve formed from the ganglion and the anterior fasciculus, has to proceed a distance more or less considerable in the spinal cavi- ty before it can escape from it. SECT. II.--MEMBRANES OF THE SPINAL MARROW. Of the Dura Mater of the Medulla Spinalis. This membrane, forming the exterior envelope of the spinal marrow, extends from one end of the spinal canal to the other, being continuous above with the dura mater of the brain, and terminating below in a cul-de-sac, or closed extremity. It does not adhere to the surface of the spinal canal, but lies looseJy at- tached to it, with the exception of the first cervical vertebra, to- which it is closely fastened. Between it, and the ligaments and periosteum on this surface of the bones of the spine, is a long, loose, and spare cellular substance, generally somewhat watery, and containing in the lumbar and sacral regions, a reddish adi- pose matter. This membrane is so much larger than the medulla, that it invests it very loosely and always presents a collapsed appear- ance. Where the nerves penetrate, it furnishes to each one, a 332 NERVOUS SYSTEM. sheath as far as the intervertebral foramen. Those sheaths are longer for the cauda equina than elsewhere, and, of course, ob- serve the same successive obliquity with the nerves to which they belong. Having reached the intervertebral foramina, they enlarge so as to enclose the ganglions, adhere by cellular sub- stance to the contiguous periosteum, and are then insensibly lost in the tunics of the nervous trunks. The internal surface of the dura mater is smooth and shining, which is probably owing to the tunica arachnoidea being reflected over it. This membrane has a fibrous texture, and, with inconsiderable ex- ceptions, is like that of the brain. Of the Tunica Arachnoidea of the Medulla Spinalis. This membrane is next to the dura mater, and is easily dis- tinguished by its extreme delicacy, thinness, and almost perfect transparency. It is destitute of red blood vessels. It forms, also, a complete envelope for the medulla spinalis, and adheres to it only very loosely by means of long, slender, and scattered filaments of cellular substance. If the dura mater be slit up its whole length before and behind, and a blow-pipe be introduced at one end of the medulla, between the pia mater and the arach- noidea; inflation will cause the latter to rise, and to present itself as a long capacious tube, detaching on each side processes which surround the roots of the nerves. These processes having reached the points where the nerves penetrate the dura mater, are then reflected upon its internal face, and are supposed to give it the glistening appearance. The processes enclosing the fasciculi of the spinal nerves, are particularly conspicuous about the Cauda Equina. Of the Pia Mater of the Medulla Spinalis. This third envelope of the spinal marrow forms also a com- plete investment of the latter, and adheres very closely to it. Its external face is smooth, and is in contact with the arachnoi- dea, from which it may be readily separated by inflating the latter. But from the middle of its internal face both anteriorly and posteriorly, a process or partition penetrates into the middle MEMBRANES OF THE SPINAL MARROW. 333 fissures of the medulla spinalis, and reaches to their bottoms. From these partitions there proceed a great number of small vascular canals, that pass in various directions through the me- dulla, and anastomose freely with each other. This arrangement is rendered sufficiently obvious by injecting and then destroying the medulla in an alkaline solution; or if the medulla be hardened by neutral salts or acids, it splits into longitudinal radiated la- minae, divisible into chords, whereby the arrangement is made equally manifest. A fact of some consequence is thus estab- lished, to wit, the similitude between the structure of a nerve and of the medulla spinalis. At the inferior end of the medulla the pia mater becomes a single chord, which is continued among the cluster of nerves to the lower end of the tube formed by the dura mater, and there it joins with the latter. As a membrane, the pia mater is much more complete than the corresponding one of the brain, has more strength, but is not so vascular. Its thickness in- creases in its descent. It is of a yellowish-white colour. It seems to hold the medulla somewhat in a state of compression, for when a puncture is made through it, the medullary substance protrudes like a hernia. It goes from the medulla to the fasci- culi of nerves and forms their neurileme or sheath. Of the Ligamenta Denticula. These bodies are narrow semi-transparent bands, and very thin, which are placed one on either side of the medulla spina- lis, between the pia mater and the tunica arachnoidea. They commence at the occipital foramen, and descending between the anterior and the posterior fasciculi of nerves, terminate somewhat above the inferior extremity of the medulla. Each one is, at its commencement, in front of the accessory nerve, and in descending is rather nearer to the posterior than to the anterior fasciculi. By its internal margin it adheres with uniformity to the pia mater, but the external margin has a very different arrangement; for it sends off at intervals from twelve to twenty-four serrated or denticulated processes, which for the most part are placed between the fasciculi of cervical and of dorsal nerves. The extremities of these teeth are small, Vol. II.—43 334 NERVOUS SYSTEM. rounded, and strong, are surrounded by the arachnoidea, and adhere very firmly to the dura mater, being pointed down- wards. The position and connexions of each ligamentum den- ticulatum are such, as to make it serve as a fastening; which use is additionally indicated by its fibrous texture, and by the ne- cessity that the medulla has for such fastening, in consideration of its being so deficient in filling up the vertebral canal. It is taught by many anatomists, that the ligamenta denticu- lata, from the opposite sides, join at the lower end of the spinal marrow to form the single cylindrical chord, just mentioned, that passes thence to the lower end of the spirfal cavity, and has been described as an emanation from the pia mater. I am, however, induced to think with Meckel and others, that gene- ral analogy is in favour of the latter. SECT. III.--OF THE BLOOD VESSELS OF THE MEDULLA SPINALIS. The Arteries of the Spinal Marrow are derived from the Vertebrals, Intercostals, Lumbar, and Sacral Arteries. 1. The Posterior Spinal Artery (Arteria Spinalis Posterior) is the lowest branch of the vertebral, given off in the cavity of the cranium. It reaches, soon after its origin, the posterior face of the Medulla Spinalis, and runs to the lower extremity of the latter, on the side of its posterior fissure. Its course is parallel with its fellow, and very serpentine. In its descent it is con- tinually re-enforced by the small branches which get into the spinal cavity through each of the intervertebral foramina. 2. The Anterior Spinal Artery (Arteria Spinalis Anterior) arises above the last from the vertebral. Shortly after its ori- gin it unites with its fellow into a common trunk, which de- scends alono- the anterior fissure of the medulla spinalis, but is subject to interruptions. It also is re-enforced by twigs from the arteries that pass into the spinal cavity through the inter- vertebral foramina. In its whole course it sends off branches from each side to the medulla spinalis. The Cauda Equina is supplied by arteries from the Lumbar THE ENCEPHALON. 335 and from the Sacral Arteries, which reach, it through the fora- mina, between the vertebras and in the sacrum. The Veins of the Spinal Marrow are very abundant. A large one, called the Sinus Columnae Vertebralis, is situated in the spinal cavity, on the posterior face of the bodies of the vertebrae, between their ligamentous covering and the dura mater. One of these veins exists on each side of the middle line. They detach a considerable number of branches, which run trans- versely, and anastomose with one another on the body of each vertebra, so that each vertebra has its little system of anasto- mosing branches, called Circelli Venosi. These anastomoses communicate with the intercostal veins, and, indeed, with all such as are on the outside of the spinal column, by means of small branches that get out by the intervertebral foramina. They receive the veins from the bodies of the vertebrae, and from the dura mater of the spine. The two sinuses may be traced as low down as the inferior end of the sacrum, where they arise by small trunks from the fatty matter which surrounds the lower end of the cauda equina. When their size is, somewhat augmented by their ascent, they communicate by a large transverse branch. The superior end of each sinus terminates by several anastomoses with the verte- bral vein, and with the anterior occipital sinus; through the latter of which its blood is, finally, carried into the lateral sinus. For a farther account, see Sinus Vertebrales. CHAPTER II. OF THE ENCEPHALON, OR BRAIN. By this term is designated that section of the central portion of the nervous system, which is contained within the bones of the cranium. In its general configuration it differs materially from the medulla spinalis in being spheroidal or oval. It is 336 NERVOUS SYSTEM. surrounded by the same membranes; to wit, the Dura Mater, externally, the Tunica Arachnoidea next, and the Pia Mater, internally. The Encephalon is formed by cineritious and medullary matter, and, as a mass, consists of four distinct portions. The Medulla Oblongata, which is a continuation of the spinal mar- row, or its superior part; the Protuberantia Annularis, or Pons Varolii, which is placed at the upper extremity of the Medulla Oblongata; the Cerebrum, which occupies six or seven-eighths of the cavity of the cranium; and the Cerebellum, which lies upon the posterior fossae of the base of the cranium. As the brain is a double organ, each of these parts is symmetrical, or consists in right and left halves perfectly alike. SECT. I.—OF THE MEMBRANES OF THE BRAIN, OR ENCEPHALON. Of the Dura Mater. This membrane, the most exterior of the three belonging to the encephalon, lines the whole internal face of the cavity of the cranium, and is attached with great tenacity to it, particu- larly in early life, from which cause it is also considered as an internal periosteum. Its external surface has a rough and unequal appearance, and adheres much more strongly where the sutures exist than else- where, owing to its detaching many large filaments, which pe- netrate into the sutures and reach to the pericranium. The adhesion to the surface generally of the bones is accomplished by fine filaments of fibres, and by very numerous and small blood vessels which become evident from the dots of blood collected upon its surface, when tho bones are torn up, as in the usual manner of examining the head. To the base of the cranium, its adhesion is still stronger, owing to the abundance of the foramina and fissures there; to the margin of each one of which it is fixed with extreme compactness, and may be con- sidered as continuous with the adjacent pericranium. The external surface is marked by the arteries and veins which creep and ramify through it, and make, as mentioned elsewhere, corresponding furrows in the bones. MEMBRANES OF THE BRAIN. 337 The Dura Mater consists of two laminae, one within the other; they, however, are attached so closely in the greater part of their extent, that it requires the knife, or strong artificial force, to separate them. Sometimes, in tearing off the skull- cap of a middle-aged person, the external lamina is brought away with the bone. Several processes arise by a duplicature of the internal la- mina of the dura mater, and extend from the circumference to- wards the centre of the cavity of the cranium. They are as follow:— The Falx Cerebri separates the hemispheres of the brain, and is, consequently, precisely under the middle line of the head. Its shape is well indicated by its name. It commences by a small point from the middle of the body of the sphenoid bone, and continues to arise along the crista galli, the spine, and middle line of the frontal bone, the sagittal suture and the up- per limb of the occipital cross, till it reaches the internal occi- pital protuberance. It is about an inch broad in front, where it begins, but it increases continually, though gradually, in breadth till its termination, where it is two or two and a half inches wide. It is strongly fastened along the crista galli, and at the foramen ccecum, and being also fastened behind to the tentorium, (with which it is continuous,) as well as along the intermediate points of bone, it is kept in a state of strict tension, which does not admit of its wavering to one side or to the other. Its inferior margin is very concave, and goes to within a small distance of the corpus callosum. There are sometimes conside- rable apertures in it, through which the flat surfaces of the he- mispheres come in contact. The Tentorium Cerebelli, another process of the dura mater, is placed transversely across the posterior part of the cranium, and separates the cerebellum from the posterior lobes of the cerebrum. It is continuous with the posterior end of the falx major, whereby these two processes exercise a mutual tension. The tentorium is, therefore, kept convex above and concave below. 338 NERVOUS SYSTEM. Its form is crescentic; its outer circumference is extended along the horizontal limbs of the occipital cross, and along the superior corner or margin of the petrous bones to the posterior clinoid process. The internal circumference is much smaller and unattached, and being placed immediately behind the sella turcica, it leaves an opening (the Foramen Ovale) which is near- ly of the same size with, and occupied by the tuber annulare, and the crura cerebri. The anterior extremities of the crescent are continued from the posterior clinoid process to the anterior on each side, so that a deep depression is formed for lodging the pituitary gland. The Falx Cerebelli is a small triangular process of the dura mater, which extends in the middle line from the under surface of the tentorium to the posterior margin of the occipital fora- men. Its base is above, and its point below: the latter termi- nates by a small bifurcation. It adheres by its posterior mar- gin to the middle inferior limb of the occipital cross; the ante- rior margin is free, and serves to separate the two hemispheres of the cerebellum." The Dura Mater is essentially fibrous, as is sufficiently evi- dent at whatever point it may be examined. These fibres have no settled course, but cross each other in every direction. It is white, sufficiently transparent for the vessels of the pia ma- ter to be imperfectly seen through it, and almost inelastic. Its internal face is smooth and polished, and is covered or lined by the tunica arachnoidea, the halitus from which gives it a slip- pery feel. It is insensible to common excitants, such as cutting, or even cauterizing it; from which circumstance, together with the common inability of anatomists to trace nerves into its struc- ture, it is supposed, by many, to be entirely destitute of them. The venerable Chaussier, however, takes a different position in regard to these points, and says, that it has sensibility, and that though none of the cerebral nerves can be traced into it, yet, by attentive examination, it is found, that filaments from the sympathetic nerve follow the ramifications of its middle or great artery.* * Exposition de L'Encephale, p. 29. y MEMBRANES OF THE BRAIN. 339 It is well supplied with blood vessels, both arteries and veins. The former are derived principally from the branches of the in- ternal maxillary of either side, which get into the cranium through the foramen spinale and ovale. There are branches also from the aethmoidal, the inferior pharyngeal, and the ver- tebral. The branch of the internal maxillary called meningea magna, divides into two, of which the anterior being the more considerable, gains the anterior and inferior angle of the parie- tal bone; but the other is directed backwards to the squamous portion of the temporal. Each of these branches is subdivided into a considerable number of smaller ones, which for the most part incline backwards. Their capillary terminations are sup- posed by Bichat to be in small number comparatively, and to be limited principally to those of nutrition. Some of the veins accompany the arteries, as in other parts of the body, and empty into the sinuses about the base of the cranium. In the case of both arteries and veins, there is, how- ever, a very considerable anastomosis with the blood vessels of the diploic structure of the cranium, and with those of the in- teguments. Of the Sinuses of the Dura Mater.—The sinuses are large cavities placed between the two laminae of the dura mater, and receive the blood from the veins of the pia mater. They are formed by the separation of these laminae, and are lined by a membrane corresponding with the internal coat of the veins. 1. The Sinus Longitudinalis Superior extends along the whole base of the falx cerebri, from the ethmoid bone to the tentori- um, where it terminates in the lateral sinuses. It begins at the foramen coecum in a small pointed manner, and, according to some anatomists, by a small vein, which passes from the nose through this foramen; it is successively increased in size from before backwards, and is of a prismatic shape. One side of the prism is upwards, and, of course, is formed by the external la- mina of the dura mater; while the other two parietes are late- ral, and are formed by the duplicature of the internal lamina. Its cavity presents a number of small cords, round or flattened. 1 340 NERVOUS SYSTEM. passing from one side to the other; they are called Chordae Wil- lisii or Trabecular, and prevail principally at its back part. The longitudinal sinus receives on each side from ten to twelve large veins, which bring the blood from the pia mater. Those from the convex surface of the brain are joined just before enter- ing the sinus by such as belong to the flat side of the hemispheres. These veins enter the sinus, for the most part, obliquely forwards, or in a manner opposed to its circulation. The most posterior ones previously glide eight or ten lines between the laminae of the dura mater, and are somewhat tortuous; they are also furnished with valves, which circumstance, besides their oblique entrance into the sinus, is a provision against their being filled by the regurgitating blood. This sinus also receives several veins from the bones, and some from the scalp, which traverse the bones at different places: among the largest of them are those that come through the parietal foramina. The dura mater itself sends some of its veins into this sinus. In the longitudinal sinus, towards its posterior part, are found a considerable but variable number of small granular bodies; some in clusters, others insulated; and from the size of a pin's head to a line or more in diameter. They are the Glanduke Pacchioni; they have no excretory ducts that have been dis- covered, and it is entirely uncertain whether any specific fluid is secreted from them. These bodies are also to be found on the surface of the dura mater near this sinus; some of them, in- deed, make foramina through the dura mater, and corresponding depressions in the skull. One on each side, larger than usual, and near the parietal foramen, is remarkable for this. 2. The Sinus Laterales, one on each side, are situated in the base of the tentorium, and follow its course along the grooves of the occipital and parietal bones. They then leave the tentorium and go along the groove in the mastoid portion of* the temporal bone to reach the posterior foramen lacerum, where they ter- minate in the internal jugular veins. Their shape is ovoidal, instead of prismatic, as the longitudinal sinus is; they are also larger than it. The sinus of the right side is very frequently larger than that of the left, and seems to be more a continuation of the superior MEMBRANES OF THE BRAIN. 345 longitudinal sinus. In some rare cases one of these sinuses is deficient. The lateral and inferior veins of the cerebrum, and the inferior veins of the cerebellum run into the lateral sinuses. 3. The Sinus Longitudinalis Inferior is situated in the falx cerebri just above its concave edge. It is much smaller than the superior, and terminates behind in the sinus quartus. It re- ceives the veins of the falx, and sometimes a few from the cor- responding parts of the hemispheres. 4. The Sinus Quartus, or Rectus, is situated in the tentorium, where the latter is joined by the falx major or cerebri. It is triangular or prismatic, and runs from the anterior margin of the tentorium to the posterior, where it terminates in the extre- mity of the longitudinal sinus. The general union which is there found between the longitudinal, the fourth, and the lateral sinuses, constitutes the Torcular Hierophili. The anterior extremity of the fourth sinus, besides receiving the inferior longitudinal, is joined by the Vena Galeni, a single trunk, formed by the junction of the two veins of the middle of the velum interpositum, and extending from the posterior margin of the fornix to the beginning of the fourth sinus. The latter, in its course, also receives the superior veins of the cerebellum, with the exception of the most anterior ones, which terminate in the Vena Galeni. 5. The Sinus Petrosi are small cylindrical cavities, and are so called from being situated on the petrous bone. There are two on each side; one above and the other below. The former is the Superior, and runs from the cavernous sinus along the su- perior margin of the petrous bone to join the lateral sinus, where the latter quits the tentorium to descend towards the base of the cranium. The other Petrous Sinus is the Inferior. It is larger than the superior, and arises, also, from the cavernous sinus by its posterior margin. It then runs along the fissure be- tween the occipital and the petrous bone, leaving its mark on the margin of these bones, but principally on the former, and then terminates in the lateral sinus just above the posterior fora-, men lacerum. Vol. II.—44 342 NERVOUS SYSTEM. 6. The Sinus Cavernosi, one on each side, are also formed by a separation of the two laminae of the dura mater, though their shape is so different from that of the others. They are situated at the sides of the sella turcica, and on the body of the sphenoid bone. Their cavity is very irregular, and is furnished with a number of filaments, which cross in every direction, and give it a cellular arrangement. The internal carotid artery and the sixth nerve traverse it, but are protected by its lining membrane being reflected over them. The cavernous sinus anastomoses in front with the circular sinus, and behind with the two petrous sinuses and the anterior occipital. It receives, in front, the ophthalmic veins; fromabove, •the anterior and inferior cerebral veins; and on the sides, some veins from the dura mater. 7. The Sinus Circularis is placed in the sella turcica, and sur- rounds the pituitary gland. It is a small cavity which receives the veins of this gland, and, as just mentioned, communicates with the cavernous sinus. 8. In the posterior part of the base of the cranium, there are also some other sinuses, called, from their position, Occipital. One of these is upon the basilar process of the os occipitis, and extends itself directly across the bone, from the hind part of one Cavernous sinus to the corresponding point of the other; and is, therefore, a means of communication between these two cavities. Another of these sinuses extends from the region of the torcular hierophili, or the upper extremity of the lateral sinuses, along the base of the falx cerebelli, to the posterior margin of the oc- cipital foramen, where it bifurcates, and then goes along the margin of this foramen to discharge itself into the lateral sinus at the posterior foramen lacerum. The smaller sinuses about the base of the cranium, besides the outlets mentioned, have collateral ones, which pass at dif- ferent places through the base of the cranium, and run into the branches of the internal jugular vein. These communications, as mentioned in the account of the veins, were known to San- torini, and are called his Emissaries. MEMBRANES OF THE BRAIN. 343 Of the Tunica Arachnoidea. This membrane is the second of the envelopes of the brain, and is spread over the surface of the pia mater, adhering to it close- ly in the greater part of its extent. It is so diaphanous and thin as its name implies, that it is distinguished with some difficulty, wherever it adheres to the pia mater; which it does all over, with the exception of some few places on the basis of the brain, as, for example, just in front of the tuber annulare, and behind the medulla oblongata. There this membrane may be seen stretched from one prominence to another, and separated con- siderably from the pia mater. It does not follow the anfrac- tuosities of the brain, but goes directly across them, from the ridge of one convolution to that of the adjacent, so that it is en- tirely smooth and uniform in its distribution. Notwithstanding the general closeness of its cennexion with the pia mater, it may yet be separated from it by careful dissection, by slight maceration, or by the use of the blow-pipe; dropsical effusions frequently make out the distinction between the two membranes; also the deposite of coagulating lymph. Considering this membrane as a single layer, we have to speak of the dura mater, as lying loosely upon it. But the au- thority of Bichat, sanctioned by the testimony of many other anatomists, has assigned to it a much more considerable extent. For it seems to be well ascertained, both by analogy and by ob- servation, that it is a sac; which*, besides covering the external surface of the pia mater, is reflected over the internal surface of the dura mater, and gives to the latter its smooth shining appearance. This lining is on the same principle that the se- rous lamina of the pericardium lines its fibrous lamina, or that the synovial membrane lines the ligamentous attachments of an articulation. In the early periods of life, it may be sepa- rated from the dura mater, by dissection. Vicq. D'Azyr has related a case in which it was detached by a collection of pus. Its places of reflection to the dura mater are on the basis of the cranium, where the blood vessels and nerves pass into the sheaths formed by the dura mater, and along the blood vessels 344 NERVOUS SYSTEM. entering into the sinuses. This membrane is continuous with the tunica arachnoidea of the medulla spinalis. The tunica arachnoidea passes into the ventricles of the brain by the same apertures that the pia mater does, but it is much less manifest there than elsewhere. The texture of this membrane is exceedingly delicate and fine. It is always found, in health, in a transparent state, and is furnished with neither red blood vessels nor nerves. It se- cretes a sort of halitus, or synovia, which facilitates the motions of the brain, and prevents it from adhering. Occasionally, this secretion is so much augmented 'as to constitute a genuine dropsy. Of the Pia Mater, The Pia Mater, or Tunica Cerebri Vasculosa, is in contact with the substance of the brain. It also is extremely delicate, but, unlike the last, is furnished with an immense number of blood vessels which go to or return from the brain, and are, in most subjects, so abundant that they give a florid appearance, at a little distance, to the whole membrane. Its external face appears entirely smooth, owing to its being covered, and its processes cemented together by the tunica arachnoidea; but its internal face exhibits these processes as following precisely the anfractuosities of the brain; consequently, it is very un- equal. The pia mater presents, along the course of the longitudinal sinus, an abundance of those small graniform bodies, existing also in this sinus, and called Glandulae Pacchioni. They beset the veins as they enter into the longitudinal sinus, and even follow them there, so that there is a chain of them from the surface of the pia mater, into the sinus. They are frequently so abundant on the superior part of the hemispheres, near the great fissure, that they cause the dura and pia mater to adhere, as if from inflammation. It is the larger of this kind which frequently produce an absorption of the dura mater, and of the internal table of the skull. These bodies are also found, along with the pia mater, in the ventricles of the brain, as at the ex- MEMBRANES OF THE BRAIN. 345 ternal margin of the plexus choroides, around the pineal gland, and at the bottom of the fourth ventricle. The Glandulae Pacchioni, wherever found, present a similar appearance and structure, varying much in size: they are ge- nerally in clusters, which repose on common bases. Anato- mists differ much in their opinion concerning them. Bichat acknowledges his complete ignorance on the subject; Portal says that they are only congeries, of vessels or of cellular bo- dies filled with fat. Meckel states, that as they are found es- pecially in the latter periods of life, and never before birth; as they never exist in very great abundance, except in persons who have often experienced diseases of the head; and are not observed in any animal: that we are forced to consider them as morbific productions, and not, as Pacchioni conceived, glands whose excretory ducts opened into the ventricles of the brain. The Pia Mater covers the upper surface of the cerebrum with such uniformity as not to require a detailed description of it; where it sinks into the great fissure of the hemispheres, it ad- heres from the two sides just above the corpus callosum. On the basis of the brain, it penetrates deeply into the anterior fissure,. or the Fissura Sylvii; is reflected over the inequalities, but never in such a way as to leave them; and closes up the bottom of the third and of the fourth ventricle. The distribution of the pia mater, over the ventricles of the brain, is more complicated than that over its periphery, and it may be remarked, that this portion is called, by some anato- mists, the Internal Pia Mater; that its texture is much more de- licate, and net-like, and that it adheres more closely to the sub- jacent parts. Being extended from the superior surface of the cerebellum and of the tuber annulare, it enters into the third ventricle, under the posterior margin of the fornix, by the large transverse fissure between the latter and the tubercula quadrige- mina. By its course between the fornix and thalami, it consti- tutes the Velum Interpositum, or the Tela Choroidea of Vicq.. D'Azyr. The pia mater is also introduced into the inferior cor- nu of the lateral ventricles along the internal margin of the hip- pocampus major, at the side of the pons-varolii; and into the fourth ventricle from its bottom part. 346 NERVOUS SYSTEM. The several plexuses of vessels found in the ventricles of the brain have for their basis the pia mater; which is there ar- ranged into a great number of folds, some of them being lon- gitudinal and others crossed. Their formation, according to the new views which have been taken of the development and growth of the brain, by Tiedemann, depends upon the internal membrane of the brain contracting itself as it finishes the depo- site of medullary matter called Centrum Ovale. The vessels of the plexuses are the arteries, which are spent upon the surface of the ventricles, and the veins derived from the same; the lat- ter are much more numerous than the first. Of the Structure of the Pia Mater.—The pia mater is com- monly spoken of as a complete membrane, yet its structure is different from that of membranes generally, inasmuch as it is a net-work, the meshes of which are formed by arteries and veins, and the interstices filled up by a loose, weak cellular substance. Bichat has very justly observed, that the union with the tunica arachnoidea is solely on the part of this cellular substance; whereas, the union with the cerebrum is confined to the ves- sels, which are extremely numerous and very small before they penetrate it, and appear as bloody points when we cut into the substance of the brain. The principal arterial trunks of the pia mater are at the basis of the brain; these trunks divide into smaller branches, in the anfractuosities and fissures. The pri- mary divisions again divide and subdivide into tubes not much exceeding the size of the capillary vessels. In this last state they enter the brain and may be seen very readily, either by a fine injection or by tearing up the pia mater. SECT. II.--OF THE &EDULLA OBLONGATA. According to the usage of the best authorities of the present day, who follow in the description of the central parts of the nervous system, the order of their development in the human subject, and also of their appearance in animals, I shall describe the encephalon from below upwards instead of from above down- wards. The preference thus shown is, perhaps, principally ser- viceable in fixing upon the mind the order of growth and ap- THE MEDULLA OBLONGATA. 347 pearance, which, according to well established experiments, are exactly in the order of importance to life. The Medulla Oblongata, also called Bulbus Rachidicus, ex- lends from the superior margin of the first cervical vertebra to the middle of the basilar process of the os occipitis. It becomes gradually larger as it ascends, and is about an inch in length, and eight lines wide at its base. It is by no means so cylin- droid as the medulla spinalis, but presents several risings and depressions on its surface. The under surface of the Medulla Oblongata is divided lon- gitudinally by the middle fissure, a continuation of that on the front of the Medulla Spinalis. The fissure is two or three lines deep, which is rendered manifest by removing the pia mater. The Corpora Pyramidalia are placed one on either side of it, and are oblong bodies; being a continuation of the chords that decussate from the opposite sides of the spinal marrow. These bodies occupy the whole length of the Medulla Oblongata, in- crease in breadth as well as in elevation during their ascent, and are, lastly, somewhat constricted or diminished abruptly, where they join the Protuberantia Annularis or Cerebralis. Precisely at the latter point, between their bases, is a deep tri- angular pit, into which penetrates the pia mater. J. F. Meckel says, that they are united at their lower extremities by a small transverse medullary.Commissure of a line and a half in breadth. This junction is above the decussation of the chords from which the Corpora Pyramidalia arise. The Eminentiae Olivares are two bodies; one on either side, at the external margin of the corpus pyramidale. They are about seven lines long: two and a half wide, and are elevated to the height of one line. The elevation ceases somewhat short of the annular protuberance, but their interior structure is continued into the latter, and may be traced into the thalamus nervi optici. Like the pyramidalia, those bodies are medullary externally; but within,, there is a nucleus of cineritious matter, called, from the irregularities of its margin, Corpus Fimbriatum, and which encloses some medullary matter. The jcorpus fimbriatum is 348 NERVOUS SYSTEM. open at the inner circumference, and has the medullary matter which it contains, continuous there with the substance of the corpus pyramidale. Below, its circumference is continuous with the cineritious matter of the medulla spinalis. In the slight depression between the corpus pyramidale and the emi- nentia olivaris, are the roots of the hypoglossal nerve. The Corpora Restiformia, also one on either side, are placed at the lateral posterior margins of the medulla oblongata, just posterior to the olivares; and are readily brought into view by elevating the contiguous parts of the cerebellum. They are el- liptical risings of an inch in length; their lower extremities are in contact, and project where they begin to arise from frhe bor- ders of the posterior fissure of the medulla oblongata; they then diverge, and advance forwards and upwards to terminate above in the cerebellum. The corpus restiforme is formed of medullary matter, and is a continuation of the posterior cord of the medulla spinalis. From its superior posterior margin a thin medullary lamina of about three lines square arises, and being sustained by the pia mater, advances to meet its fellow, but does not absolutely touch it.* From the anterior margin of each corpus restiforme there departs a second process of medullary matter, larger and more thick than the preceding, and being covered by the roots of the pneumogastric and glosso-pharyngeal nerves, adheres to the plexus Choroides of the fourth ventricle. The superior face of the medulla oblongata is excavated be- tween the corpora restiformia, in such a way as to present the outline of a writing pen, and is, therefore, called Calamus Scriptorius; which forms a considerable part of the floor of the fourth ventricle of the Brain, or the sinus rhomboideus. The fissure, in its middle, corresponds with the slit of a pen, the nib being downwards; and the fissure extends from the poste- rior fissure of the medulla spinalis the whole length of the me- dulla oblongata. The calamus scriptorius is marked by several streaks of medul- lary matter, which extend themselves transversely with a very * Called Pons Sinus Rhomboidei by J. F. Meckel. THE MEDULLA OBLONGATA. 349 slight degree of obliquity upwards, and reach the external mar- gin of the corpus restiforme of the corresponding side. These medullary striae present some varieties in regard to their vo- lume, number, and arrangement. Sometimes they are slightly elevated narrow lines, which are perfectly distinct from each other, and from one to fourteen in number. On other occa- sions their volume is greater, but they are not so numerous. They generally extend, either one or all, from the middle fis- sure to the commencement of the auditory nerve, and are thereby a part of its origin. Sometimes the anterior ones are directed towards the origin of the trigeminus nerve, but their union with it is not yet ascertained;' the posterior ones are some- times blended with the radical filaments of the pneumogastric nerve. The striae themselves, are sometimes interwoven or blended, and pass the boundary of the middle fissure to join with those of the other side. Their roots may be traced occa- sionally along the middle fissure, almost to the front or under surface of the medulla oblongata. Meckel, whose observations on this subject are highly interesting, is disposed to consider the striae not only as forming the roots of the auditory nerve, but as also related closely to the trigeminus and to the pneu- mogastric. On this surface, also, of the fourth ventricle, or sinus rhom- boideus, but in advance of the preceding striae, there is another, on each side, still larger, which may be distinguished by its al- ways beginning at some distance from the middle fissure. Its direction is transverse, and it passes just above the anterior ex- tremity of the corpus restiforme, to run into, or to assist in forming, the root of the auditory nerve. Its existence is much more constant than that of the others. It is considered as an assistant ganglion to the auditory nerve, and in cases of deaf- ness has been deficient. Being principally cineritious, it is called Fasciola Cinerea. In tracing the continuation of the structure of the medulla spinalis, into that of the medulla oblongata,' we find that each of the anterior cords of the medulla spinalis, besides crossing with some of its fasciculi at the place mentioned, to wit, at the decussation of Mistichelli, and continuing its course upwards Vol. II.—45 350 NERVOUS SYSTEM. to form the corpus pyramidale, sends off a larger fasciculus, which ascends behind theeminentia olivaris, and forms the floor of the sinus rhomboideus. There is a third fasciculus of white matter between the other two, into which the anterior column of the medulla spinalis is divided. It is described by Rosen- thal, who says, that it touches the eminentia olivaris, surrounds it, and, after having traversed the annular protuberance, termi- nates in the tubercula quadrigemina. The posterior cords of the Spinal marrow, being continued into the corpora restiformia, become still more evidently di- vided into two fasciculi, from an increase of their volume, than they were in the vertebral canal. The internal of these fasci- culi stops, by a pointed termination, near the borders of the sinus rhomboideus; while the external is continued on through the annular protuberance to the cerebellum. SECT. JII.--PROTUBERANTIA ANNULARIS. The Annular Protuberance (Protuberantia Annularis, No- dus Cerebri, Pons Varolii) is the large projecting body, placed near the centre of the base of the encephalon, at the top of the medulla oblongata, and upon the junction of the body of the sphenoid bone with the basilar process of the os occipitis. It is convex, and about an inch in diameter, its transverse mea- surement being a line or two larger than the other. It is di- vided by a superficial fossa into two symmetrical halves, right and left. When the pia mater is removed from the Protuberantia An- nularis, the under surface of the latter is seen to be formed by transverse medullary fibres which come from the crura cere- belli. When these, which are commonly one or two lines in depth, are removed by scraping or cutting, a cineritious matter is exposed, which is traversed by numerous layers of medullary matter, also going jin a transverse direction. About two lines ' deep from the surface of the protuberance, near the middle of each of its halves, are found some longitudinal medullary fibres connected with cineritious matter, and which may be fairly traced as a continuation of the filamentous structure of the py- » THE CEREBELLUM. 351 ramids. These fasciculi, or filaments, passing on through the protuberance, are continued so as to form the under surface of the crura of the cerebrum. Lying still deeper than the medullary fibres alluded to, there is an accumulation of cineritious matter, intermixed with per- pendicular medullary layers situated one behind the other. Be- hind (or above when we stand erect) this intertexture, a small fasciculus (the cord described by Rosenthal) of medullary mat- ter exists, which is a continuation of the intermediate fascicu- lus of the anterior medullary cord of the medulla oblongata, and may be traced afterwards to the superior face of the crus cere- bri, where it terminates, as alleged by Rosenthal, in the Tuber- cula Quadrigemina. SECT. IV.—OF THE CEREBELLUM. The Cerebellum, being placed in the posterior-fossae of the cranium, is separated by the tentorium from the posterior lobes of the cerebrum, beneath which it lies. It is connected with the Pons Varolii by a trunk of medullary matter on each side, called the crus of the cerebellum; which is a root of the medullary matter entering into the composition of the latter. It is of a rounded form, and well fitted to the cavity in which it reposes. It is convex above and below; measures about four inches in its transverse diameter, two and a half in thickness, and about the same from before backwards. The upper sur- face is divided into two equal parts or halves, by a middle ridge, while the lower surface is divided in the same way by a fossa. These halves are called hemispheres; their surface is marked by many horizontal fissures, the edges of which are kept closed by the adhesion of the pia mater. The fissures are interposed between the laminae or convolu- tions of the cerebellum, which, for the most part, are concen- tric; the larger are behind, while the shortest are in front, near the annular protuberance. The pia mater penetrates to the bot- tom of these fissures, some of which, when exposed fully by its removal, are found to extend to the depth of an inch or more. 00/i NERVOUS SYSTEM. One of these fissures, which exists on the superior surface of . the cerebellum, half an inch distant from the posterior and ex- ternal margin of the latter, has a circular course, and is so well marked by its size and depth, that it is called the Sulcus Supe- rior Cerebelli. Another, situated under similar circumstances on the inferior surface of the cerebellum, is called the Sulcus Inferior Cerebelli. On the latter surface, also, there are two or three more of a middle size, situated between the sulcus infe- rior and the tuber annulare. These larger sulci have given oc- casion to anatomists to multiply most unreasonably the number of lobes of which the cerebellum consists. Bichat's mode of description is preferable: he says, that by cutting (vertically) through one of the hemispheres of the cerebellum, so as to ex- pose the thickest part of its medullary matter, that six or seven principal fissures will be seen, which, by penetrating to a con- siderable depth, divide the cineritious portion into as many con- verging parts. In the interior of these fissures there are much smaller ones, which pass at right angles to them. On the sur- face or periphery of the cerebellum, in the intervals of the larger fissures, there are many small ones, which, though near- ly horizontal, terminate in each other by acute angles. The superior middle ridge of the cerebellum, from its shape and position, is called, by Vicq. D'Azyr, Vermis Superior; the anterior extremity of which, from its elevation, is the Monti- culus Cerebelli. The middle inferior part of the cerebellum, which presents the deep sulcus running longitudinally and forming the divi- sion into hemispheres, has a long ridge occupying the sulcus. This ridge is the Vermis Inferior of Vicq. D'Azyr, and is so concealed by the adjacent portions of the hemispheres, that a good view of it can be got only by removing the pia mater and pushing the hemispheres aside. The transverse fissures which penetrate it, and its general irregularity of surface, will then be sufficiently distinct. The pia mater passes from the fore part of this body to the medulla oblongata, and thus assists in form- ing the floor of the fourth ventricle; which, without this reflec- tion would be exposed. The central part of the cerebellum as formed by the vermis superior and *by the vermis inferior, is the Fundamental Portion of Gall and Spurzheim. THE CEREBELLUM. 353 The Valve of Vieussens (Velum Medullare, Valvula Cerebri) arises from the cerebellum, just under the anterior part of the base of the monticulus, and runs obliquely upwards to terminate in the testes. Sometimes it is marked, in its middle, by a lon- gitudinal line or slight fissure, from either side of which proceed small lateral ones. It is principally medullary, and has a small quantity of cineritious matter at its extremities. It is thinner in the middle than at either of its margins. At the root of the crus cerebelli are two small protuberances; the one below it, in the erect position, is the Lobulus Amygda- loides, and the other the Lobulus Nervi Pneumogastrici. The substance of the cerebellum is formed of cineritious mat- ter externally, and of medullary matter internally. When a vertical section of it is made through the middle of one of its hemispheres, the medullary matter puts on the appearance of the thuya or arbor vitae, the roots and ramifications of whose limbs, even to their smallest extremities, are surrounded by ci- neritious matter. In this view, there appears to be more cineri- tious than white matter; but when a horizontal cut is made from the periphery to the centre, parallel with one of the deep concentric fissures, the proportion of medullary matter seems to to be much more considerable; and the arbor vitae arrange- ment is proved to depend upon the laminae of medullary matter radiating from the centre, or, in other words, from the massive medullary trunk in the interior of the hemisphere of the cerebel- lum. Each of these radiations commences by a root of consi- derable size, which divides and subdivides into branches. Each primitive radiation, as well as its branches, is covered by its own layer of cineritious matter about one line in thickness, and is kept perfectly distinct from the contiguous ones by the fissures which extend internally from the periphery of the cerebellum. In the middle of the trunk of the arbor vitae, exists the Corpus Rhomboideum, or Dentatum. It is an oblong rounded body, and jagged and cineritious in its circumference, but medullary within. Its configuration resembles that of the corresponding body in the eminentia olivaris, with the addition of its being larger, and having its outline better marked. It is the ganglion of the cerebellum of Gall and Spurzheim. 354 NERVOUS SYSTEM. The Centra] or Fundamental Portion of the Cerebellum ex- hibits also very clearly the arborescent arrangement, and is fur- nished with about seven primitive radiations, coming from a medullary trunk. The proportion of medullary matter to corti- cal, is less in it than in the hemispheres of the cerebellum. Each of the primitive radiations may be traced to some particu- lar point or prominence on the surface of the fundamental por- tion, thus forming its basis; but this study is more curious than useful, though several anatomists have pursued it. Three medullary fasciculi, on each side, have now been traced to the cerebellum; one of these is the continuation of the corpus restiforme of the medulla oblongata; a second is the valvula cerebri; and the third, the Crus Cerebelli, which joins the annu- lar protuberance. The two first fasciculi belong to the middle or fundamental portion of the cerebellum; they are, consequent- ly, situated more internally, and are partially concealed by the crus cerebelli, and have interposed between them and the latter, the Corpus Rhomboideum, or Dentatum. SECT. V.—OF THE CEREBRUM. The Cerebrum weighs about three pounds, and is seven times as heavy as the cerebellum. It is ovoidal, and measures about six inches in its antero-posterior diameter, five inches in its great- est breadth, which is behind, and four or five in depth. It is separated above by a deep fissure, (Fissura Longitudinalis,) into two equal parts, called Hemispheres. At the bottom of this fis- sure, by separating the contiguous surfaces of it, is to be seen a broad lamina of medullary matter, passing from side to side, and called the Corpus Callosum, which connects the two hemi- spheres together. The under surface of each hemisphere is subdivided into three lobes; Anterior, Middle, and Posterior. The anterior lobes are placed upon the anterior fossae of the base of the cranium; the Middle, upon the middle fossae of the same; and the Posterior Lobes rest upon the tentorium. The two anterior lobes are completely separated by the Fissura Longitudinalis, which extends between them to the base of the THE CEREBRUM. 355 cranium; the same is the case with the posterior lobes; the middle lobes have interposed between them the annular protu- berance and the crura cerebri. When the pia mater is removed, the anterior lobe is seen to be marked off from the middle lobe by a deep sulcus, the fissure of Sylvius, in the under surface of the cerebrum, corresponding, in its position, with the posterior margin of the Lesser Sphenoidal Wing. The boundary between the middle and the posterior lobe is, by no means, well defined on the basis of the brain, but it is agreed to consider as posterior lobe, all that part of the hemisphere which rests upon the tento- rium. The periphery of the cerebrum is formed into convolutions, (Gyri,) which give it an unequal tortuous surface, resembling the intestines of a small child. These convolutions are sepa- rated by fissures (Sulci) of depths varying from an inch to two inches or more. The convolutions proceed in diversified and complicated courses, which never correspond in different indi- viduals, and seldom on the two hemispheres of the same brain. Though their summit is generally convex, yet some of them have it depressed slightly, which is considered a proof of each convolution being divisible into two halves or layers, placed side by side. Some of the convolutions are short, others long; they present numerous varieties in the manner of joining each other. Owing to the narrowness of the fissures between them, they are closely packed together, so that the lateral surfaces of each one are suited to such as are contiguous: occasionally, there is a departure from this rule. The surface of the convolution, by which we mean not only the most exterior periphery of the cerebrum, but also the surface formed by the fissures to their very bottom, is covered by cine- ritious matter of about one line in thickness. Within the periphery of the cerebrum, the mass of medullary matter is very considerable, and is of an ovoidal shape. This ovoid is called the Centrum Ovale of Vieussens, and is brought fairly into view by making a horizontal cut through the hemi- spheres, two inches below their summit. In proceeding with the anatomy of the cerebrum from its base upwards, the following is the order or succession of parts 356 NERVOUS SYSTEM. in its structure: In advance of the pons varolii, and springing from it, there are two divergent medullary trunks, one on each side, which run forwards, and are lost in the medullary sub- stance of the cerebrum. These trunks are the crura cerebri, upon the upper surface of which are two protuberances: the pos- terior is the thalamus nervi optici, and the anterior is the corpus striatum. Each crus cerebri, having penetrated into the sub- stance of its respective hemisphere, expands by a multiplication of the filaments composing it, so as to constitute the principal bulk of the hemisphere. These filaments may, indeed, be traced very satisfactorily in almost every direction towards the peri- phery of the cerebrum, where they terminate in the convolu- tions, their extremities being covered by the cineritious matter there. The arrangement is best seen by scraping with a knife along the base of the brain, especially when the latter has been hardened in spirits of wine, and it is constituted by what are called, by MM. Gall and Spurzheim, the diverging fibres of the brain. The point is not, indeed, entirely settled that the diverging filaments end in the convolutions, or do not rather afterwards inflect or double on themselves, and pass inwards again to the middle line of the brain, forming, by their convergence, the cor- pus callosum. At all events, the fact is quite demonstrable, that as the under and lateral portions of the hemisphere consist in diverging filaments, arising in and from the crus cerebri, so the upper portion and the corpus callosum, consist in filaments which arise in the adjoining convolutions, and collect towards the mid- dle line of the corpus callosum, where they adhere to the con- generic filaments of the other side. The arrangement, in the most simple conception and illustra- tion of it, would be exemplified by folding a strip of cloth double on itself, so as to convert it into a loop; the under part of the loop would then represent the diverging fibres of the cerebrum and the upper part the converging fibres, or corpus callosum; it being at the same time borne in mind that the continuation of the two orders of fibres into one another in the brain is not so fully ascertained as it would be represented by this model. Between the two orders of fibres there is a horizontal cleft or interval. This interval is the lateral ventricle of the hemisphere, THE CEREBRUM. 357 which may be got into under the posterior margin of the corpus callosum, from its being open there, or rather only closed by an adhesion of the membranes, which is easily lacerated. The preceding is intended as a mere outline upon which to form the base of the descriptive anatomy of the cerebrum. The following, therefore, may be considered as the detailed account:— The Crura Cerebri are rounded below; are about eight lines long, and increase in their transverse diameter as they advance; their vertical diameter is about ten lines. They mutually di- verge, beginning from their roots, and are separated by a deep fissure, considered as a continuation of that on the front of the medulla oblongata. This fissure is the third ventricle of the brain. Their surface is marked by superficial furrows, running longitudinally; and about two lines before the tuber annulare, by a transverse fasciculus of medullary matter, very slightly elevated: the optic nerves also cross them obliquely at their fore part. In regard to texture, the crus cerebri presents, on its under surface, a medullary layer of two lines in thickness; to this suc- ceeds a parcel of cineritious matter, which, on being removed, is* followed by a mixture of both cineritious and white matter, more abundant than either of the preceding. The Eminentiae Mammillares, or Corpora ynhicantia, are two small bodies, one on each side, about the ^'ie °f a French pea. They are situated near the anterior extremities of the crura ce- rebri, on their internal faces, and aAnost in contact with each other. Their texture is medullar/ without, and cortical within. The Infundibulum is pla^d immediately before the eminen- tiae mammillares. It is a flattened conoidal body, half an inch long, with its base upwards, and its apex going downwards and forwards. It is formed of cineritious matter. Most generally its base is hollo^ and opens into the third ventricle, but its point is closed. J &• Meckel, however, asserts that a communication exists entirely through it, from the pituitary gland to the third ventricle, and that he has [frequently proved it by passing air or Vol. II.—46 §58 Nervous system. liquids from this gland, though the experiment does not succeed when he attempts the injection from the third ventricle. The Pituitary Gland (Glandula Pituitaria) is situated in the Sella Turcica, and is covered so completely by the dura mater, that only a small aperture is left for the point of the infundibu- lum to pass through and to adhere to it. It is an ovoidal body, the greatest diameter of which is transverse, and amounts to six lines. It is partially divided, so as to give the appearance of two lobes, of which the anterior is much the larger. It is hard and cineritious, with a small quantity of medullary matter within. In either side of it there is a depression from wdiich leads a small canal towards the place where the infundibulum joins it: the two canals are, in the latter place, united into one. In some very rare cases, gritty matter has been found in it, as there is in the pineal gland. It is also surrounded by pia mater. The Tuber Cinereum, or Pons Tarini, is a portion of the un- d^r surface of the crura cerebri, at the floor of the third ventri* cle. It is continuous in front with the anterior margin of the corpus e<»llosum. In front of the infundibulum the optic nerves unite, after ^aving crossed obliquely the crura cerebri from without in ward.? and forwards. In this passage, where they reach the middle of the\rura, and at the internal border of the same, they come in contacfvith the tuber cinereum, from which they get a few filaments; but vf this, more hereafter. The Thalami Optici, called,Hy Gall, the Posterior Ganglions of the brain, (Ga?iglia Poslica,)^re amongst the most conspi- cuous parts of the internal structun. 0f the cerebrum, and are two in number, one for either side. They are situated on the superior face of the crura cerebri, are abow; an inch and a half long from behind forwards, and about eight nr ten lines broad and deep. The thalami are convex above and internally. A.t the junc- tion of these two surfaces is observed a medullary line, de- scribed under the name of peduncle of the pineal gland. Their posterior extremity is likewise convex, and is divided into three THE CEREBRUM. 359 rounded prominences; one is above the other two, and is the Tuberculum Posterius Superius; the second is below and with- in, (Corpus Geniculatum Internum,) and the third is below and external, (Corpus Geniculatum Externum.) There is a fourth tubercle (Tuberculum Anterius) which is situated on the upper convex surface of the thalamus; it is produced by the fan-like termination of a large medullary fasciculus which comes from the eminentia mammillaris. The thalami are somewhat flattened on the middle of their convex internal surface, and adhere there to each other by a layer of cineritious substance, called Commissura Mollis. When the brain is very slightly advanced in putrefaction, or has been made soft by dropsy, this junction scarcely seems to exist at all. The thalami are medullary on the surface presented to the ventricles of the brain, but within they are a mixture of cineri- tious with medullary matter. The fibres of the medullary are very intimately blended with the crura cerebri, and radiate from within towards the circumference of the brain: some of them are placed in layers, and are. connected with the tuhercula quad- rigemina. The Corpora Striata, or the Ganglia Cerebri Antica,. also two in number, one for each side or hemisphere of the brain, are situated before the thalami optici, at the bottom of the lateral ventricles. They are about two and a half inches long, convex on their upper surface, and eight lines broad at their front part, but taper very gradually to a point behind. They are about four lines apart in front, and are separated there by the septum lu- cidum, but their posterior extremities diverge from each other, so as to admit the thalami optici between them. The surface of the corpus striatum is cineritious, but within it consists of cineritious and of medullary matter, placed in lay- ers which alternate with each other. These layers are arranged in a crescentic manner, so as to present the convexity upwards and the concavity downwards. The medullary substance is a continuation of that of the crus cerebri and of the optic thala^ mus. It enters at the posterior inferior part of the corpus stri- atum, and immediately divides into three layers, placed one above the other, and of which the two inferior are more narrow 360 NERVOUS SYSTEM. and short than the superior. The upper layer, in its progress forwards, is interrupted by a body of cineritious substance, which occasions it to divide into a multitude of distinct radiated fibres. The same circumstance attends the other layers, but in a more limited degree. The medullary matter of the corpus striatum may then be traced, in all directions, into the hemisphere of the brain. The cineritious substance of the corpus striatum is abun- dant, and is divided by some anatomists into two kinds, one of a light gray, and another of a darker colour. The first forms the middle and inferior part of the corpus striatum; the second is in greater quantity, and is found principally above and be- tween the two upper layers. Such is the general plan of the structure of the corpus striatum; but, it should also be under- stood, that a close intertexture exists between its medullary and cineritious matter. The most satisfactory way of unravelling the structure of the corpus striatum, is to scrape away its under surface, in tracing its medullary matter from the crus of the brain, and through the optic thalamus. It will then be seen, that the medullary substance of the crus reaches the posterior inferior part of the corpus striatum, and is immediately invested in the greater part of its circumference with cineritious matter, it then begins to expand after the manner of a fan into filaments. These fila- ments or fasciculi penetrate the cineritious matter in various directions, besides those just detailed. A particular exposition of them is given by Gall and Spurzheim, in their anatomy of the brain. The Taenia Striata is placed in the angle formed between the internal margin of the Corpus Striatum, and the external one of the Thalamus Opticus, where these two bodies are in contact and continuous with one another. It is a small medul- lary band, not a line in breadth, commencing near the anterior crus of the fornix, with which it is connected frequently by fila- ments; and observing the curved course of the fissure in which it is placed, it goes to the posterior end of the corpus striatum, and even beyond it in most cases, by uniting itself to the top of the Cornu Ammonis. The Corpus Callosum. When the fissure between the he- THE CEREBRUM. 361 mispheres of the cerebrum is widely separated, or when the su- perior part of the hemisphere is cut away on a level with the bottom of the fissure, the Corpus Callosum, a medullary layer, is brought fully into view. This body unites the medullary mass of the two hemispheres, and is a large commissure. It occupies about two-fifths of the long diameter of the brain, be- ing nearer to its anterior than to its posterior end, and is about eight lines broad; increasing, however, somewhat in breadth posteriorly. The lateral half of it, on either side, is concealed by the hemisphere overlapping it, but is prevented from ad- hering by a horizontal fissure which extends from one end to the other. It has an arched form, being convex above and concave below. Its thickness is uniformly about three lines, with the exception of its anterior and its posterior margins, which are more. The middle line of its upper surface is marked out from one end to the other by a very slight depression, the Raphe; on each side of which there is a very small linear elevation of the same extent, but slightly curved inwards towards its fellow. From these longitudinal lines there proceed outwardly trans- verse ones, having a fibrous appearance. At the anterior and posterior ends of the corpus callosum, the latter are somewhat curved and radiated towards the periphery of the brain. Other longitudinal lines also exist on the surface of the corpus callo- sum, but they are not seen with equal facility. The anterior extremity of the corpus callosum is rounded off, and bent down- wards towards the basis of the brain, in such a manner as to present backwards its concavity; which thus embraces the fore part of the corpora striata, and closes the lateral ventricles at this point. The posterior end of the corpus callosum is rounded, also, and continuous with the fornix and with the cornu ammonis. By examining the Corpus Callosum from belovv, or by look- ing at its relative situation and shape on a hemisphere which is accurately separated from its fellow in the middle line, it will be seen that its lower surface is very concave, being highly arched from before backwards; that it forms the roof of the la- teral ventricles, and that this surface of it is about two inches in its transverse diameter, and, therefore, more than twice as broad as the upper surface. 362 NERVOUS SYSTEM. The Fornix (Trigone Cerebral, of the French) is placed im- mediately below the corpus callosum. It is a triangular body of the medullary matter, the base of which is behind and the apex in front. It is about an inch and a half long in its body, and one inch wide at its base. It is the latter part, which, ly- ing immediately beneath the posterior end of the corpus callo- sum, is continuous with it, and causes the fornix to be consi- dered as a part of the same structure with the corpus callosum. These two bodies, which may be compared to a sheet of me- dullary matter doubled on itself, have their surfaces in contact for a short distance behind, the fornix afterwards, by advancing and keeping itself in close contact with the thalami nervorum opticorum, which are just belovv it, diverges more and more from the under surface of the corpus callosum. It conceals all the upper surface of the thalami except their external margins, and, having reached their anterior extremities, its apex de- scends towards the basis of the brain. The body of the fornix is about a line thick, but, at its ante- rior extremity, it becomes somewhat cylindrical, and is divided into two columns, called Crura Fornicis Anteriora. Each of these crura, in descending adheres to the anterior extremity of the thalamus of that side, and, getting finally below it into the floor of the third ventricle, it, after a course slightly curved, joins the cortical substance of the FJminentiae Mammillares. Santorini, aware of this junction, considered the eminentiae as a part of the fornix, and, therefore, called them Bulbi For- nicis. The fornix has other attachments of a more complex descrip- tion, which the anatomist should attend to, as they serve to indicate the modes of intercourse between the several parts of the cerebrum. Its fibres having reached, and probably formed, the eminentiae mammillares: one fasciculus of them ascends from thence along the internal face of the optic thalamus, in- vested by the cineritious matter of the latter, and spreads it- self above like a fan, and forms the tuberculum anterius: a se- cond fasciculus from the same point, having divided into two, after going a short distance, sends one division backwards along the upper internal face of the optic thalamus, to join THE CEREBRUM. 363 the peduncle of the pineal gland, and the other division, which is more anterior, runs to join the taenia striata; a third fasci- culus from the eminentia mammillaris, being covered by the optic nerve, goes outwards and backwards to terminate in the thalamus. The posterior margin, or the base of the fornix, besides run- ning into the corpus callosum, has the angle on each side elon- gated so as to rest upon and to join the upper end of the cornu ammonis. The angle, being continued, then follows the wind- ing course of the latter, adhering to its posterior margin, but hanging loosely over the anterior. This loose edge or continu- ation of the external margin of the fornix is the Taenia Hippo- campi, or Corpus Fimbriatum of the Lateral Ventricle. The elongations of the posterior angles are called Crura Posteriora Fornicis. In the brains of individuals who have suffered from general dropsy, one frequently finds the fornix narrower than usual, and in its middle a fissure which separates almost com- pletely its two halves. As the fornix is fitted to the upper surface of the optic tha- lami, it is of course concave below and convex above, or resem- bles a triangular arch resting upon its three points or angles. Owing to some misunderstanding of the original Greek word iexxlhi, which, according to the interpretation of Sabatier, means a vault, and thereby expresses the whole body, anato- mists, with the exception of him, have generally supposed the striated under surface of the fornix to be meant by it, and have called the surface Lyra, in which mistake one has followed another. The Septum Lucidum is a partition placed vertically in the middle line of the brain, and extends from the corpus callosum above to the fornix belovv. It is of a triangular shape, but ir- regularly so, being much broader before than it is behind, and having its edges so incurvated as to fit the bodies against which it is applied. The septum lucidum is formed by two laminae placed side to ^ide, but not adhering to each other, and leaving, therefore, an interval between them, called the Ventriculus Septi, or the fifth ventricle. Each of these laminae eonsists of two lasers; the 364 NERVOUS SYSTEM. internal is medullary substance, continuous with that of the cor* pus callosum and of the fornix; and the external is a layer of cineritious substance. The cavity is about an inch and a half long by a line wide, and is narrower in the middle than at either extremity. It is lined by a delicate serous membrane, which becomes manifest when the halitus that naturally covers its sur- face is accumulated into a body of water. It is generally sup- posed to be insulated or completely shut up, yet occasionally it has been found elongated in front, towards the space between the anterior commissure and the anterior crura fornicis, and to •communicate there with the third ventricle.* The Pineal Gland (Glandula Pinealis, Conarium) is placed beneath the posterior margin of the fornix, upon the superior of the tuberculaquadrigemina, or the nates. It is an oblong conoi- dal body, the long diameter of which is transverse, and amounts to three or four lines, while the short diameter is about three lines. These diameters are, however, sometimes reversed. The substance of the pineal gland is cineritious, and of a reddish co- lour. At its inferior part there is a small cavity, sometimes lined with medullary matter, and the orifice of which looks to- wards the third ventricle. This body is connected to the adjacent parts by several cords. From its bottom there proceeds, on each side, the long medul- lary filament, called its peduncle, which runs along the upper internal face of the thalamus opticus, and, as observed, joins, or is continuous with, one of the filamentous processes from the Eminentia Mammillaris. From its base there proceeds a trans- verse lamina of medullary matter, called the Posterior Commis- sure of the brain, which first advances forwards, and then re- cedes, so as to be in some measure doubled on itself. This la- mina, at either end, is united to the upper posterior part of the corresponding optic thalamus, and by its lower margin runs into the superior edge of the tubercula quadrigemina. Frequently, within the pineal gland, and sometimes on its surface, there is an accumulation of calcarious matter, the Acer- vulus Cerebri, that appears about the sixth year of life, and con- * J. F. Meckel. THE CEREBRUM. 365 tinues for ever afterwards. It is variable both in quantity and in its mode of concretion, for sometimes there are only a few atoms of grit, scarcely distinguishable by the feel; while, on other occasions, it is collected into a body of irregular shape, and more than a line in diameter. The pieces of which the acervulus consists are sometimes united by cellular substance, and enclosed in a sac. The chemical analysis presents phos- phate of lime in large proportion, carbonate of lime, and ani- mal matter. A reflection of pia mater, called the Velum Interpositum, se- parates the pineal gland from the fornix, and the fornix from the thalami nervorum opticorum. The Tubercula Quadrigemina (or the Nates et Testes) are situated on the superior face of the crura cerebri, and just be- hind the thalami nervorum opticorum. A very complete view of them is obtained by separating the posterior lobes of the ce- rebrum, and by paring off the vermis superior cerebelli. Though the name implies four distinct prominences, yet they are formed from a common mass of nine or ten lines square, on the poste- rior surface of which these prominences arise. They are in pairs, and are separated from one another by a crucial depres- sion. The largest, or upper pair, is the Nates, the lower pair the Testes. The external surface of these bodies is medullary, and within they are cineritious. From the Nates there pro- ceeds a considerable medullary fasciculus, which runs forward to join the Corpus Geniculatum Internum on the internal pos- terior face of the thalamus nervi optici; there proceeds also from them a second fasciculus, which either joins the optic nerve itself, or the contiguous part of its thalamus. The Testes receive, at their lower end, the valve of the brain; and there also proceeds from them a large fasciculus of medullary matter, which joins the Corpus Geniculatum Externum of the optic thalamus. Vol. II.—47 366 NERVOUS SYSTEM. Of the Ventricles of the Brain. These cavities are four in number: two, called lateral, are placed one in either hemisphere of the cerebrum, a third is be- tween the two thalami, and the fourth under the cerebellum. They have all been alluded to, but only incidentally. The two Lateral Ventricles (Ventriculi Laterales) are horizon- tal cavities, or fissures, of an extremely irregular shape, in the very centre of the hemispheres, being the interval between the diverging and converging filaments of the cerebrum. They are separated from each other only by the septum lucidum; are co- vered over by the corpus callosum, and have the fornix, thalami optici, and corpora striata for a floor. Each one consists in a body or principal cavity, and three processes, called cornua. The body has been sufficiently described in speaking of the parts which constitute its parietes; but the processes are yet to be considered. The Cornua, from their position, are named Anterior, Poste- rior, and Lateral or Inferior. The Anterior is a very small space between the anterior extremity of the corpus striatum and the opposite surface of the hemisphere, and has nothing in it particularly deserving of notice. The Posterior Cornu extends from the base of the fornix to the distance of an inch or more in the substance of the posterior lobe of the cerebrum. Its cavity is conoidal, somewhat curved, with its convexity outwards, and of six or seven lines in diameter at its base. Its internal side is furnished with an oblong eminence called Hippocampus Minor, or Ergot, from its resemblance to a cock's spur, but its size and form are somewhat variable. When this eminence is cut through transversely, it is easy to see that it is formed by a convolution of the posterior lobe projecting into the posterior cornu. The convolution is covered by medullary matter on the side of the ventricle, and of course by cineritious on the side of the peri- phery of the brain, and is the bottom of an anfractuosity. The Inferior, Middle, or Lateral Cornu, of the Lateral ven- tricles is situated in the middle lobe of the cerebrum. It com- THE CEREBRUM. 367 mences at the posterior angle of the fornix, and winds down- wards and forwards in a semicircle towards the fissure of Sylvius, presenting its convexity outwards, and its concavity within. Its floor is furnished in its whole length with an ele- vated ridge, the surface of which is semi-cylindrical. This ridge is the Cornu Ammonis, or Hippocampus Major, and increases somewhat, .both in breadth and elevation, as it winds down the process of the ventricle. Its lower or anterior extremity is ter- minated by two or three small tubercles, and is the Pes Hip- pocampi. Occasionally the Hippocampus Major is marked off by a middle longitudinal fissure into two elevations, of which the external is the smaller. On its concave side there is the thin edge of medullary matter, continuous with the external margin of the fornix. The extremity of a knife handle may be insinuated for a short distance between this edge and the Hippocampus; it ceases about half way down the latter, and in the natural state of the parts is concealed by the plexus choroides. This edge is, as mentioned in the account of the fornix, the Taenia Hippocampi or Corpus Fimbriatum. Beneath the latter, and partially covered by it, there is another body, which presents itself in the form of a small chord of cineritious matter, is not quite so long as the Taenia, and is called Fascia Dentata, from being divided into several sections by transverse fissures, which give it an undu- lating appearance. A transverse incision of the Hippocampus Major shows that it is a body of cineritious matter, covered on its surface by a thin layer of medullary substance. The Third Ventricle, (Ventriculus Tertius.) When the fornix is separated from its anterior crura and turned over backwards, the process of pia mater, called Velum Interpositum, is found between it and the optic thalami. This process is of a triangu- lar shape, resembling the fornix, and is about the same size; it is insinuated into this place from the surface of the brain, under the posterior margin of the corpus callosum. Its lateral margins, which project'beyond the corresponding ones of the fornix, are formed by a congeries of convoluted vessels, constituting the plexus choroides. The plexus, indeed, may be traced from the Hippocampi along the corpus fimbriatum to its position on the 368 NERVOUS SYSTEM. margin of the velum interpositum; and insinuates itself from the bottom of the cerebrum between the pons varolii and the convolution forming the Hippocampus Major; but when it reaches the anterior end of the fornix its convoluted character ceases, and it terminates, on each side, in a single vein, (Vena Galeni,) which runs from before backwards, in a straight line, near the middle of the velum interpositum. The vein, finally, unites with its fellow to form a single trunk, which runs into the fourth sinus of the dura mater. The Velum Interpositum, or Tela Choroidea, adheres very strongly to the fornix, by means of small vessels: it may be raised with less difficulty from the thalami, though it serves to keep the third ventricle closed above, with the exception of the part just behind the crura of the fornix, where the third and the lateral ventricle communicate by the foramen of Monro. The pineal gland is entangled in its posterior part, being placed be- low it, and is generally torn from its peduncles when the tela is raised up. It is at this point that the tunica arachnoidea may be traced into the cavity of the lateral ventricles, according to Bichat* The Plexus Choroides, which was stated to bound the tela choroidea on each side, and to descend along the Hippocampus Major to the fissure of Sylvius, or rather to ascend from this point, and to terminate in the vein on the side of the middle line of the tela, is narrow at its termination, but increases continually in breadth as it is traced towards its commencement. The middle part, however, where it makes its turn, is an exception to this rule, for there it is larger in every way than elsewhere: its vessels being more capacious and more tortuous. Precisely at this point a vesicle or more is very frequently found, consi- dered by some as a hydatid of the brain; in some cases it is filled with calcarious matter instead of with water. The Glan- dulae Pacchioni, as stated, also prevail at this margin. On the under surface of the tela choroidea, adhering to it, there is on each side a small venous plexus which goes from be- • Some doubts may be reasonably raised on this point of anatomy, as the evi- dence is seldom or never satisfactory to the full extent, and as such an arrange- ment would be contradictory to that of the tunica arachnoidea on the surface of the brain, as it never dips into fissures. THE CEREBRUM. 369 fore backwards, and terminates in the vena galeni, near its junc- tion with its fellow. It receives the blood of the third and of the fourth ventricle.* There is also the same sort of plexus in the fourth ventricle. Upon the removal of the Velum Interpositum, or its elevation, the whole upper surface of the thalami optici is exposed. The third ventricle is also brought into view, being placed imme- diately between the thalami optici. It is a narrow oblong cavi- ty, bounded below by the pons tarini, crura cerebri and the eminentiae mammillares, and above by the velum interposi- tum, and the fornix. The anterior crura of the fornix are at its fore part, and just before them is the anterior commissure (Com- missura Anterior.) This body is a transverse fasciculus of medullary matter, which passes from one hemisphere to the other through the anterior margins of the thalami optici. Its middle part is rounded and free, but its extremities penetrate into the substance of the anterior inferior portion of the corpus striatum, and spreading out gradually, describe a curve with its convexity forwards, which terminates on each side in the Taenia Hippocampi of the inferior cornu of the lateral ventricle. This fasciculus, in penetrating the corpus striatum, does not mix with its substance, but, in the early part of its course, goes in a canal formed in the latter. In order to see this arrangement, a part of the corpus striatum must be removed. The anterior commis- sure resembles a nerve in its structure, as it is surrounded by a very delicate sheath, and is divided into fasciculi of fibres. It will now be understood that three commissures are found in the third ventricle, the anterior Commissure—the posterior, which is just in front of the Pineal Gland,t and soft Commissure, being a cineritious adhesion of the Thalami.J Just behind and below the anterior commissure, the base of the infundibulum opens into the third ventricle; this place is the Iter ad Infundibulum. At the posterior extremity of the third ventricle, just below the posterior commissure, which has been described as a process of the pineal gland, the communication exists with the fourth ventricle. This passage is the Aqueduct * Meckel, Manuel D'Anatomie. X See Pineal Gland. $ See Thalami. 370 NERVOUS SYSTEM. of Sylvius, and leads obliquely downwards and backwards under the valve of the brain. The third ventricle communicates freely with the lateral ven- tricle through the aperture called the Foramen of Monro, which is situated precisely at the place where the plexus choroides ter- minates; that is to say, under the anterior crus of the fornix. Doubts have, from time to time, been suggested in regard to the natural existence of this communication; it only requires a mo- derate degree of accurate observation to dispel them: they have arisen, probably, from the aperture being shut up by the occa- sional adhesion of the plexus choroides to the contiguous surface of the brain. The Fourth Ventricle (Ventriculus Quartus, Cerebelli) has been, in a great degree, described in the account of the- neigh- bouring parts; it will, therefore, be very readily understood on the present occasion. It is an irregular triangular cavity, the base of which is downwards. It is bounded in front by the tuber annulare, and the medulla oblongata, behind by the fundamental portion of the cerebellum, and above by the valve of the brain and the tubercula quadrigemina; it is under the latter that the •communication between it and the third ventricle is found. Its lateral parietes are formed by the medullary prolongations from the cerebellum to the tubercula quadrigemina. This cavity, as stated, is open below, when that portion of pia mater is removed, which passes from the cerebellum to the medulla oblongata. From what has now been said of the connexion of the pia mater with the ventricles, it will be understood that as their sur- faces are covered by pia mater, and the removal of it exposes their cavities, they are, in fact, continuations of the external sur- face of the brain. SECT. VI.—OF THE NERVES OF THE ENCEPHALON.* These nerves are designated numerically, from before back- wards, and, also, by some peculiarity of distribution or function. * The more improved observations of modern anatomists having pointed out the fallacy of considering the brain as the source of the spinal marrow, instead of NERVES OP THE ENCEPHALON. 371 The Olfactory Nerve or First Part (JVervus Olfactorius, Par Primum,) is situated on the under surface of the anterior lobes of the brain, near the fissure that separates the hemispheres. It goes forwards from its root, and also converges gradually to- wards its fellow, so as to reach the cribriform plate of the ethmoid bone, through the perforations of which it passes out. In its course, it is lodged in a small furrow, by which pressure upon it is prevented. This nerve arises by three medullary fasciculi, or roots, from the basis of the brain at the corpus striatum, in the fissure of Sylvius, where the anterior and middle lobes join each other: these roots are from eight to twelve lines on the outer side of the infundibulum. The roots are placed, in regard to each other, diverging; one is within, another in the middle, and the third external. The external root is the longest, and arises from the extreme posterior margin of the anterior lobe by its last convo- lution. It has a curved course from without inwards, the con- cavity of which is forwards, and the convexity backwards. The internal root is concealed by the chiasm of the optic nerves, and arises from the adjacent surface of the anterior lobe. The middle root comes from the posterior margin of the anterior lobe by the cribriform surface, which is between the other two roots. These origins unite to form a single prismatic cord, which increases in size as it advances forwards, and consists of medullary and ci- neritious longitudinal fibres mixed together. The anterior extremity of the olfactory nerve is swollen out into what is called the Bulb, (Bitlbus,) and sends from its under surface filaments, which, surrounding themselves with a tunic from the dura mater, penetrate into the nose, and spread themselves on the Schneiderian membrane. In its whole length it is exceedingly soft and pulpy, till it gets out of the cranium. The Optic Nerve or Second Pair (Nervus Opticus, Par Se- ttle reverse; it follows, that the proper order of describing the nerves of the en- cephalon, is successively from the spinal marrow. I had adopted this plan, for- merly, but certain considerations of facility in study, have induced me to abandon it after some years of experience. 372 NERVOUS SYSTEM. cundum) is about the same size with the trigeminus. It arises by a broad flattened root, one portion of which comes from the posterior end of the thalamus opticus, and another from the testis through the means of a medullary band that passes from the latter towards the thalamus of the same side. From this point the optic nerve winds forwards under the crus cerebri, adhering to it, and inclining inwards towards its fellow. Its adhesion to the crus is considered by many anatomists as an- other of its origins. The Optic Nerve, having reached the under anterior part of the third ventricle, adheres so closely to its fellow that the two seem fused together, in such a way that there is no line of separation between them. This junction receives, above, from the third ventricle, some medullary filaments, which Meckel feels authorized to consider as another origin. The junction presents the form of the letter X, and is called the chiasm or crossing of the optic nerves. The most distinguished anato- mists, however, have laboured in vain to settle the question of the mode of junction; some believing that there was only a la- teral union, others that the nerve of one side crossed over to the other side, and others, again, that the decussation occurred only with some of the fibres, but not all. Observations, in comparative anatomy, on blindness, and indeed on every con- ceived mode of elucidation, have been resorted to without producing a solution of the problem; but the discussion of their merits would require too much space for the present work. The Optic Nerves as they approach their chiasm become more cylindrical, and, continuing so afterwards, penetrate into the orbits through the foramina optica. It is only in front of their junction that they are invested by a neurileme; which, having considerable firmness, penetrates into their interior, and divides them into distinct canals. The Nervus Motor Oculi, or Third Pair (Par Tertium,) arises from the internal face of the crus cerebri, about two lines in advance of the anterior margin of the tuber annulare. Its roots come, in great part, from the cineritious matter which is found on the surface of the crus, and may be traced for some NERVES OP THE ENCEPHALON. 373 distance opwards and backwards along the parietes of the third Ventricle. The nerves of the opposite sides are in contact for some distance by the internal faces of their roots, but do not adhere. The Nervus Motor Oculi proceeds from its origin towards the external margin of the cavernous sinus, and, penetrating into the orbit through the sphenoidal foramen, it is distributed to most of the muscles of the eye-ball. The Pathetic N^erve, or Fourth Pair (Nervus Patheticus, Par Cerebrate Quartum,) is the smallest which comes from the encephalon, and is not larger than a sewing thread. It arises by two filaments, or roots, from the upper anterior face of the valve of the brain, just below the testes. This origin is soft, and easily broken, from the want of a neurileme; but the latter is soon afterwards furnished. The Nervus Patheticus appears on the base of the brain, be- tween the cerebellum and the posterior lobes of the cerebrum, at the external margin of the tuber annulare. It then goes for some distance along the margin of the tentorium till it comes near the posterior clinoid process: it then penetrates into a ca- nal of the dura mater, and reaches the orbit of the eye through the sphenoidal foramen, to be distributed on the superior oblique muscle. The Nervus Trigeminus, or Fifth Pair, also called Trifacial, (Par Quintum) is one of the largest among those that proceed from the basis of the brain, and emerges from the side of the pons varolii, just where it is continuous with the crus cerebelli. It is composed of three roots: an anterior, a posterior, and a mid- dle' ;* of which the latter is much the largest. The middle root is about a line and a half in breadth, and has a passage made for it by the very obvious splitting of the super- ficial fibres of the pons varolii. It is composed of thirty or forty fasciculi, which are divisible into a hundred or more fibres. These fasciculi may be traced into the substance of the tuber '* Santorini, Observ. Anat. Venitia, 1724. Soemmering, de Corp. Hum. Fab- rica, tom. iv. Gall and Spurzheim, Anat. du Cerv. / Vol. II.—48 374 NERVOUS SYSTEM. annulare, (but intersected by the transverse fibres of the latter,) in the direction of the fourth ventricle. When they have come near the latter, they may be traced thence into the medulla ob- longata, towards the fissure that exists between the corpus oli- vare and restiforme. It is at this point, that the greater num- ber of the fibres arise; some from the corpus olivare, and others from the fissure. The commencement of this root is pulpy and destitute of fibres, and is surrounded by grayish substance; but when it has ad- vanced into the pons, it is surrounded by a fine membrane, and is very evidently fibrous. There is a successive increase in its size, from its commencement till it is ready to emerge from the pons, when it becomes somewhat contracted, and immediately afterwards increases again considerably in size. It then enters a canal of the dura mater at the fore part of the petrous por- tion of the temporal bone, and just behind the cavernous sinus. This canal sets but loosely about it at first, but afterwards it ad- heres to the surface of the nerve. The middle root of the nervus trigeminus, in the upper part of the canal of the dura mater, preserves its fasciculated ap- pearance, and many small filaments are interchanged between the fasciculi, so as to make a complex net-work. But, at the lower part of this canal, it is converted into a ganglion of a semi-lunar shape, with its concavity upwards, being about six or eight lines in length, and one and a half in breadth. This body, called the Ganglion of Gasser, (Ganglion Semi-lunare, Plexus Gangliformis,) is compact, and has its fibres very much matted above, but below they assemble into larger and more distinct fasciculi, which are afterwards arranged into three prin- cipal trunks, departing from the cranium through different fora- mina ; to wit, through the sphenoidal foramen, the foramen ro- tundum, and the foramen ovale. J. F. Meckel asserts that the filaments of the plexus above the ganglion, for the most part terminate in a gutter formed in the superior margin of the ganglion, and that there are but very few of them which can be traced into the trunks below. The trunks below, consequently, arise from the circumference of the gan- glion. The two smaller roots of the nervus trigeminus proceed out NERVES OF THE ENCEPHALON. 375 of the tuber annulare at different points, from that of the large root, and each one has its appropriate fissure for that purpose. One, from its situation, is called Anterior, and the other Poste- rior. Each may be traced into the posterior cord of the me- dulla oblongata, but not so far as the large middle root, and is formed by several fasciculi of medullary fibres. The anterior and the posterior roots, after going separately for six or eight lines, unite to form a single cord. This cord does not merge it- self in the semi-lunar ganglion, but continues distinct from it,* with the exception of sending off to it a few fasciculi; it after- wards gets from the cranium through the foramen rotundum, and is distributed to some of the muscles of mastication, as the the temporal and buccinator. The general distribution of the fifth pair of nerves, or the tri- geminus, is to the orbit, to the face, and to the tongue. The Motor Oculi Externus, or Sixth Pair of Nerves (Par Sex- tum) is found four or five lines distant from the facial nerve, and at its internal side. It arises from the base or upper extremity of the corpus pyramidale, under the posterior margin of the tuber annulare: when the latter is broader than usual, some of the fibres seem to come from it; but the appearance is deceptious, as they only penetrate it. The fibres are assembled into two roots, of which the internal is three or four times as large as the other. These roots, before they penetrate the dura mater, most com- monly unite into a single trunk, which goes almost directly for- wards, and is enveloped in a neurileme. Passing through the cavernous sinus, it gets into the orbit by the sphenoidal foramen, and is spent upon the abductor oculi muscle. The Seventh Pair of Nerves is composed of the Facial and the Auditory. The Facial Nerve (Nervus Facialis, Porlio Dura Septimi, Par Septimum) is placed in front of and above the auditory nerve, It arises.by two branches, which are perfectly distinct from. * In this respect the fifth pair resembles one of the spinal nerves.. 376 NERVOUS SYSTEM. each other, and differ much in their size. The larger one, which is placed within and above the other, arises from the me- dulla oblongata at the most superior part of the corpus resti- forme, where the latter joins the tuber annulare. The origin of the nerve is sometimes overlapped by the latter, so that some few of its fibres appear to come from the annular protuberance, while they only pass through it, in their course from the medul- la oblongata. The second branch, which is much smaller than the other, arises, by three or four filaments, from that portion of the medulla oblongata which is placed between the first branch and the auditory nerve. The two branches of the facial nerve are kept distinct for the distance of several lines before they unite. Proceeding outwards and backwards, they reach the meatus auditorius internus, and then proceed, as a single cylindrical trunk, through the aqueduct of Fallopius, to emerge at the stylo-mastoid foramen, for the purpose of being distributed upon the muscles and skin of the head. The Auditory Nerve (Nervus Auditorius, Acusticus, Portio Mol- lis Septimi) arises, in part, from the medullary striae on the sur- face of the calamus scriptorius, and partly from the corpus res- tiforme^ between the glosso-pharyngeal nerve and the tuber annulare. At its origin it is so extremely soft as not to bear handling, and is too pulpy to present the appearance of fibres; but, becoming more distant from the medulla oblongata, it is harder and more fibrous. This nerve is impressed on its internal face by a longitudinal furrow for the reception of the facial nerve. It passes obliquely forwards and outwards beneath the crus cerebelli, and penetrates into the meatus auditorius internus. It adheres somewhat near its root to the under anterior margin of the cerebellum, just be- hind the crus of the latter: the circumstance is considered by J. F. Meckel, as a proof of its having there another origin, where-' by an analogy is established between it and the two other nerves of the senses; to wit, the optic and the olfactory. The distribution of this nerve is confined to the labyrinth of the ear. NERVES OF THE ENCEPHALON. 377 The Eighth Pair of Nerves is composed of the Glossopharyn- geal, the Pneumogastric and the Spinal Accessory. The Glossopharyngeal Nerve (Nervus Glosso-Pharyngeus, of Eighth Pair,) arises from the posterior cord of the medulla ob- longata, just above, and somewhat anterior to the superior fila- ments of the next nerve, with which it is very closely connected. Its filaments, which are five or six in number, spring, therefore* from the anterior margin of the corpus restiforme, or from the fissure separating it from the corpus olivare, under the posterior margin of the tuber annulare. Its filaments soon collect into a round cord, and anastomose, even in the cavity of the cranium, by a considerable branch with the pneumogastric. It runs outwards and backwards to the foramen lacerum posterius, and goes through the same divi- sion of it that the pneumogastric does, but in its own canal of the dura mater. About half an inch from this canal it en- larges within the cranium, into a small oblong ganglion of five or six lines long, which extends itself as far as the foramen lace- rum.* Its general distribution is to the tongue and to the pharynx, as its name implies. The Pneumogastric Nerve (Nervus Pneumogastricus or Vagus> of Eighth Pair,) arises from the corpus restiforme of the medulla oblongata, just behind, or on the borders of the fissure separating it from the corpus 'olivare, somewhat above, and posterior to the highest root of the accessory nerve. It commences by a num- ber of parallel filaments, varying in number from ten to fifteen, which are placed very near each other, so as to form two or three flattened fasciculi of half an inch or more in length. The fasciculi below adhere to the spinal accessory, and those above to the glosso-pharyngeal nerve. The fasciculi, finally, collect into a single flattened cord of one and a half lines in breadth. This cord goes outwards and backwards to the foramen lace- rum posterius, and gets through it in front of the internal jugular * This ganglion is described by Andersech and by Huber, but its existence is questioned by Bichat. 378 NERVOUS SYSTEM. vein, being separated from the latter by the small spine which arises from the pars petrosa of the temporal bone. It passes through its own canal in the dura mater, being thus kept distinct from the glosso-pharyngeal, and from the accessory nerve, and in this canal the fasciculi which form it are collected into a single cylindrical trunk. After getting through the canal it then ad- heres by a close, strong, cellular substance, to the glosso-pharyn- geal and to the accessory. The general plan of distribution of the pneumogastric nerve is, as its name implies, to the organs of respiration, and to the stomach. The Accessory Nerve (Nervus Accessorius, of Eighth Pair,) arises from the posterior fasciculus of the medulla oblongata, just behind the nervus hypoglossus, and also from the posterior fasci- culus of the medulla spinalis, sometimes as low down as the seventh cervical nerve. There are six or seven roots from the medulla spinalis, and about three or four from the medul- la oblongata: the former are single, and run, successively, into the same trunk; but the latter are each composed of two branches, consisting respectively of two filaments. These ropts are, successively, larger and longer, as they ascend to join the common trunk. The latter goes up between the posterior fasci- culi of spinal nerves and the ligamentum denticulatum, and gets into the cavity of the cranium, behind the vertebral artery, through the foramen magnum occipitis. This nerve varies in respect to the number of its roots, and the mode of their origin. In all cases, the trunk, thus formed, passes from the cranium through the foramen lacerum posterius, traversing there the dura mater, either in a sheath common to it and to the pneumo-gastric nerve, or in its own particular open- ing behind that of the latter. Its general distribution is to the muscles and to the integu- ments of the neck. The Hypoglossal Nerve, (Nervus Hypoglossus, or Ninth Pair,) arises from the medulla oblongata, by several fasciculi placed one above the other. The roots of these fasciculi spring from the fissure which separates the corpus pyramidale from the cor- ARTERIES OF THE BRAIN. 379 pus olivare. The fasciculi are from four to eight in number, be- ing subject to vary in different individuals. They unite into two or three trunks, which coalesce into one, after penetrating the dura mater by distinct openings; and then proceed through the anterior condyloid foramen of the occipital bone. The general distribution of this nerve is to the muscles of the tongue. SECT. VII.--OF THE ARTERIES OF THE BRAIN, The arteries of the brain, or pia mater, are derived from the two internal carotids, and from the two vertebrals. The Internal Carotid Artery (Carotis Interna) gets into the ca- vity of the cranium through the carotid canal of the temporal bone, conforming itself of course to the curvature of this canal, and is brought by it to the posterior part of the body of the sphenoidal bone. In escaping from the' petrous bone it has to ascend, and also to advance somewhat, by which it is brought to the posterior part of the sella turcica. From this point it goes horizontally forwards through the cavernous sinus; and reaching its fore part, it then ascends again, and towards the fis- sure of Sylvius. While in the carotid canal, it gives a small branch to the tympanum of the ear, and as it lies on the side of the sella turcica it gives off the anterior and the posterior arte- ries of the cavernous sinus. When it reaches the anterior cli- noid process it sends off a large branch through the optic fora- men to the parts contained within the orbit of the eye. This branch is the ophthalmic artery, and what remains of the inter- nal carotid is then distributed to the brain after the following order:— There are, first of all, some small branches sent to the adja- cent parts; as the pituitary gland, the infundibulum, and the lower part of the third ventricle. The Arteria Communicans Posterior is directed backwards and inwards, and runs into the corresponding trunk of the basi- 3S0 NERVOUS SYSTEM.* lar artery Called the posterior cerebral. There are some varie- ties in regard to the size and precise point of origin of this trunk, which it would be needless to mention particularly. Besides the important anastomosis formed by it, it detaches several ramus- cles to the adjacent parts of the pia mater. The Arteria Choroidea is the next branch from the internal carotid. It goes outwards and backwards, and after detaching some minor branches, it penetrates into the inferior cornu of the lateral ventricle, by the side of the Pons Varolii, and expends it- self in ramifications upon the plexus choroides. The Arteria Callosa, or Ariferior Cerebri, is detached from the internal carotid, opposite the last. It advances in front of the union of the optic nerves, converging rapidly at the same time towards its fellow. Just before the chiasm of the optic nerves, a transverse branch passes between it and its fellow. This branch, the Arteria Communicans Anterior, is of variable length and size in different subjects, being sometimes a line, and on other occasions three or four lines long. The arteria callosa then keeps near its fellow on the under surface of the hemisphere, giving out small branches; and having got on a line with the anterior margin of the corpus callosum, it Ascends on the flat side of the hemisphere; and divides into anterior and into posterior twigs. The former supply the fore flat part of the hemisphere; the latter the corpus callosum and the adjacent surface of the brain. These several branches of the arteria anterior reach as far as the upper convex surface of the brain, and there anastomose with other arteries. The Internal Carotid may now be considered to have lost its name, and the trunk is continued as Arteria Cerebri Media. It is directed outwards, and engages in the fissure of Sylvius; while there it detaches a great number of branches to the ad- joining surfaces of the anterior and of the middle lobe. Some of these branches are of considerable magnitude, and winding along the convolutions of the brain, they at length ascend to the upper surface of the hemisphere, and anastomose with the branches of the anterior and of the posterior cerebral artery. "The Vertebral Artery (Arteria Vertebralis) is a branch of ARTERIES OP THE BRAIN. SSI the subclavian. In order to reach the cavity of the cranium it has to traverse the foramina of the transverse processes of the six upper vertebrae of the neck. It ascends in a straight line till it reaches the second vertebra, but there, in order to pass through the transverse process, it takes a direction upwards and outwards. It then ascends vertically again till it has passed through the transverse process of the first vertebra. After which it takes a horizontal course, winding around the posterior face of the upper oblique process of the same vertebra, in a depres- sion for the purpose, and having reached the internal extremi- ty of this process, it ascends upwards and inwards through the occipital foramen into the cavity of the cranium: perforating the dura mater just above the condyle of the occipital bone. Having got into the cranium, it is first on the side and the^i on the under surface of the medulla oblongata, and continues to ap- proach its fellow till it reaches the posterior margin of the tu- ber annulare. At this point the two vertebral arteries coalesce, and from their union results the basilar artery. The vertebral artery in this course, from its origin to its ter- mination, detaches several arterioles to the heads of the adjoin- ing muscles, to the membranes of the spinal marrow, and to the nerves as they come out of the intervertebral foramina: they are generally too small and irregular to deserve a special de- scription. At its upper extremity, however, it sends off three branches of some consequence: the Spinalis Posterior, the Spi- nalis Anterior;* and the Inferior Cerebelli. The Arteria Inferior Cerebelli divides shortly after its ori- gin, or otherwise is double from the beginning. The most pos- terior trunk is distributed about the bottom of the fourth ven- tricle, on the fundamental portion of the cerebellum, and the contiguous faces of the two hemispheres or lobes of the latter. The other trunk of this artery is distributed on the under surface of the cerebellum. The Basilar Artery (Arteria Basilaris) is on the middle line of the tuber annulare, and extends from its posterior to its an- terior margin. In this course it detaches some arterioles to the * See Arteries of Medulla Spinalis. Vol. II.—49 3S2 NERVOUS SYSTEM. tuber; others to the meatus auditorius internus, (Arteriae Audi- tivae Internae,) which are spent upon the labryinth, and anas- tomose with twigs from the internal and external carotids. At its anterior extremity it detaches on each side two considerable trunks; first the superior artery of the cerebellum, and imme- diately afterwards the posterior artery of the cerebrum. The Arteria Superior Cerebelli goes outwardly from its ori- gin just behind the anterior edge of the tuber annulare, until it gains-the front margin of the cerebellum. It then divides into several branches, some of which are distributed on the upper surface of the cerebellum and run to its posterior margin, where they anastomose with the branches of the arteria inferior: others are spent upon the substance of the cerebellum near its anterior edge. The Posterior Artery of the Cerebrum, (Arteria Cerebri Posterior,)~ one on each side, is the termination of the basilar artery. It proceeds abruptly outwards, and has gone but a few lines when it receives the arteria communicans posterior of the internal carotid. It then continues outwardly parallel with the anterior margin of the tuber annulare, and near it crosses the crus cerebri, and is then distributed, on the inferior*and on the posterior part of the hemisphere and of the corpus callosum. As mentioned, its branches anastomose with those of the ante- rior and of the middle arteries of the cerebrum. It will now be understood, that an arterial circle or link en- closes the chiasm of the optic nerves and the corpora albicantia. The fore and lateral parts of the circle are formed by the inter- nal carotids and their branches; while the hind part is formed by the Basilar Artery and its bifurcation. This is the circle of Willis, and establishes a very free communication between the vessels of the two sides of the brain. The veins of the Brain have been sufficiently alluded to in the account of the Pia Mater, and of the sinuses of the Dura Mater. BOOK IX. PART III. Senses. To the peripheral portion of the nervous system, belong all the nerves which are sent off from the Medulla Spinalis and Encephalon, as well as the Sympathetic. Some of these nerves have a special apparatus attached to their external extremities, for the purpose of augmenting and facilitating their appropriate powers of sensation; of this class are the Olfactory, the Optic, and the Auditory. Others of them, as the nerves of the tongue and of the skin, though they .are the means of special sensations, yet the apparatus upon which they are spread is applied to many purposes, more striking and useful, than that of indicating the presence of surrounding bodies. And, lastly, the remaining nerves, being by far the most numerous and large, are distri- buted to the muscles and to the viscera. CHAPTER I. OF THE ORGAN OF SMELLING, OR THE NOSE. The two succeeding senses are so insulated in their offices, that there can be no doubt of the propriety of considering them 384 NERVOUS SYSTEM. as belonging to the peripheral portion of the nervous system: but the nose being, in the human subject, though not in all animals, associated with the function of respiration, its allo- cation is less exceptionable. Without detailing the considera- tions which have induced me to put its description under this head, I will only mention that I have been principally actuated by its office of smelling and by its position. In common language, the term nose is applied to the part of the organ of smelling which manifests itself externally; but a very extensive cavity of the same vertical diameter, and divided into two equal compartments, exists behind it, the form of which has been described in the account of the bones of the nose. This cavity extends from the bottom of the cranium to the roof of the mouth, and backwards to within an inch and a quarter of the vertebrae of the neck. The nose, externally, is generally pyramidal, and has its base below; what is technically called the root of the nose is the part contiguous to the fore- head. The base, on each side, is marked from the cheek, by a semicircular depression; which becoming more and more shallow at its upper extremity, and increasing its breadth, is insensibly lost upon the side and point of the nose. The ala nasi is the swell of the posterior part of the base, being bounded behind by the depression. The base of the nose offers on each side an oblong oval orifice, looking downwards and having its long diameter forwards and slightly inwards. These openings are commonly about two lines below the floor of the nose, but there is a diversity in this respect. The Nasus Cartilagineus, or the cartilaginous portion of the nose, is placed wholly at its anterior extremity, and serves to elongate the cavity in that direction. It presents a vertical cartilage, which is in continuation of the bony septum: on each side of this, there is an oval cartilage, and behind and below the latter, several distinct and small pieces of cartilage, which preserve the form of the alae nasi, and, in fact, constitute them. The Vertical Cartilage, or Cartilaginous Septum (Septum Cartilagineum) is placed in the middle line of the nose, and ORGAN OP SMELLING. 385 has its anterior angle projecting beyond the bony orifice of the anterior nares. Occasionally, from a faulty conformation, it inclines more to one side than to the other. It adheres, by its superior margin, to the nasal lamella of the ethmoid and to the middle nasal suture, and behind to the anterior margin of the vomer. The inferior margin is free in the greater part of its extent, but adheres behind to the suture between the maxillary bones. The anterior margin sends out, on each side, a trian- gular plate, the upper edge of which adheres to the inferior margin of the nasal bone, and of the nasal process of the upper maxillary. These plates form the upper part of the cartilagi- nous nose, and from their ligamentous attachment to the bones, admit of a slight motion from side to side. The Oval Cartilages, one on each side, are a species of ellip- tical ring, but deficient or open at their posterior end. The external side of the ring, is an oblong oval plate, which is di- rected upwards and backwards. The internal half of the ring is much narrower, and proceeds backwards from the preceding part at a very acute angle: its superior margin is in contact with the septum; its inferior margin reaches below the latter, and its anterior extremity is in contact with its fellow, owing to the cartilaginous septum not reaching so far forwards. The place of contact of the two oval cartilages to each other, forms the tip of the nose and the columna nasi, and gives the apparent thickness, before dissection, to the lower part of the septum narium. The Alae Nasi, or the convexities on each side of the base of the nose, it has been said, owe their shape to the presence of several small pieces of cartilage, whose form, size, and num- ber are too variable to admit of a standard description: occasion- ally they are all collected into but one cartilage. They serve a similar purpose with the oval cartilage, and with it are the means by which the orifice of the nose is kept patulous. They are deposited in, and held together by a ligamentous membrane. This membrane attaches them to the lateral margin of the an- terior bony nares, and also unites the upper edge of the ex- ternal plate of the oval cartilage to the inferior margin of the triangular plate of the cartilaginous septum. It is the length and looseness of this ligament which permits such free motion 386 NERVOUS SYSTEM. to the end of the nose. In addition there exists a small liga- ment described by Caldani, which goes from the posterior end of the columna nasi to the anterior inferior margin of the bony nares. The skin which covers the upper half of the nose is loosely attached, by cellular substance, to the subjacent parts, but it adheres very closely to the surface of the cartilaginous and li- gamentous structure, and is abundantly furnished with seba- ceous glands and follicles. The exterior orifices of the latter are apparent, and are often filled with their appropriate fluid in an inspissated state, which, when forced out by pressure, as- sumes the form of small worms, the blackness of the end of which is only dirt. There are several muscles destined to move the cartilaginous structure of the nose, which have been described among those belonging to the face. The Levator Labii Superioris Alaeque Nasi, which lies upon the side of the nose and comes from the superior part of the nasal process and body of the upper maxillary bone, is, besides its insertion into the upper lip, connected with the ala nasi, and will draw the latter upwards. The Compressor Naris, arising from the ala nasi by a small pointed beginning, is spread out upon the upper edge of the cartilage and upon the triangular plate, so as to cover it, and is inserted into its fellow on the middle line. The Depressor Labii Superioris Alaeque Nasi, by arising from the roots of the alveolar processes of the incisor and canine teeth of the upper jaw, and going to be inserted into "the ala nasi, as well as into the upper lip, will draw the ala nasi down- wards. The Nasalis Labii Superioris, or Depressor Narium, which is the pointed production from the orbicularis oris, going into the columna nasi, will draw the latter downwards and back- wards. The Mucous Membrane of the Nose (Membrana Pituitaria, Schneideriana) lines the whole of each side of the nose, pene- trates into the several sinuses and cavities communicating with ORGAN OP SMELLING. 3S7 it, and is continuous, at the orifice of the nostrils, with the skin, and at the posterior nares, with the mucous membrane of the pharynx. It is not of essential importance to trace its course from any particular point, but for the sake of perspicuity,'we may begin at the floor of the nostril, which it covers in a smooth even manner. From this it ascends on the septum narium, which it covers also smoothly without forming any fold or duplicature, and adheres so loosely that it may be detached with great fa- cility. Behind, it covers the body of the sphenoid bone, and lines its cell; in front, it covers smoothly the os nasi and nasal process of the upper maxillary bone, and also the cartilaginous nose. Above, it is reflected upon the cribriform plate of the ethmoid bone, and blocks up all its foramina. At this point, the olfactory nerves seem to terminate on its surface and ad- here very closely to it. From the cribriform plate, the Schneiderian membrane passes to the cellular part of the ethmoid, and covers smoothly its an- terior half. But behind, as it passes over the upper spongy bone, a pendulous duplicature is formed along its inferior mar- gin, and is continued beyond the bone, backwards as far as the spheno-palatine foramen. It then lines the upper meatus and the posterior cells of the ethmoid, and is extended upon the convex surface of the middle spongy bone. At the inferior margin of the latter, it forms another loose and somewhat pen- dulous duplication, which does not go beyond the posterior ex- tremity of the bone. The membrane is then reflected into the middle meatus of the nose, and penetrates into the maxillary sinus which it lines completely. The orifice through which it enters, is about the size of a crow-quill ;'is variable in its situa- tion, being sometimes in the middle of the meatus, sometimes more forward, and on other occasions higher up and concealed by irregularities, in the conformation of the ethmoid. This ori- fice, which was found to be so large and jagged in the dried bone, is reduced to its present size entirely by the mode of re- flection of the mucous membrane over its margins. In front of the latter orifice, beneath the anterior margin of the middle tur- binated bone, the mucous membrane is reflected into the ante- 388 NERVOUS SYSTEM. rior ethmoidal cells by one or more foramina, and through the most anterior of these cells into the frontal sinus. From the middle meatus, this membrane passes upon the lower turbinated bone so as to cover it, and also to form a loose duplication along its inferior margin; it then lines the inferior meatus of the nose, and is continued on its floor into the part from which its description commenced. Under the anterior part of the inferior spongy bone, this membrane is continued into the lining membrane of the lachrymal sac, and there forms a fold, frequently resembling a valve. Along the posterior mar- gin of the vomer„the membrane of the nostril is continued into the corresponding one of the other side, whose arrangement is in all respects the same. The pituitary membrane, in its structure and appearance, re- sembles other mucous membranes; its colour, however, is na- turally of a deeper red. It consists of two laminae, which can- not be readily separated: the one next to the cavity of the nos- tril has the mucous structure; the exterior one is fibrous, and resembles the periosteum of other parts of the body. This composition is best seen on the part belonging to the septum narium. By floating the pituitary membrane in water its mucous la- mina is made to exhibit, very satisfactorily, the villous and spongy appearance. This is particularly evident on the turbi- nated bones. Its whole surface is studded with pits or folli- cles of various sizes, irregularly arranged and resembling pricks made into a plastic substance with the point of a pin. From these cavities or cryptae proceeds the mucus of the nose. In the thickness of the pituitary membrane, there exist numerous and thickly set glands, of a size so small that they escape common observation, but their existence is generally admitted, both on the authority of anatomists who have described them,* and on the principle of their being always the concomitants of mucous membranes.f It is owing to the great abundance of blood vessels in this membrane, to their very superficial course, and to the habitual * Ruyschii, Epist. Anat. Probl. vii. Mayer. X Bichat, Anat. Descrip. ORGAN OP SMELLING. 389 residence of blood in them, that it always presents a deep red colour in the living state. These blood vessels bleed very freely from slight mechanical causes, and are also disposed to congestions, which are relieved by the blood being poured out through their exhalent orifices, without laceration or any solu- tion of continuity. Though the description just given corresponds with the tex- ture, generally, of the pituitary membrane, yet there are modi- fications of the latter at particular points which it does not fully suit. For example, at the anterior orifice of the nostril it is insensibly changed into a thin skin, furnished in the male adult with stiff hairs (Vibrissas;) and in all the sinuses it is more thin and white than elsewhere, being also smooth and shining, and not presenting clearly the little pits which are so distinct in the nose. The surface which adheres to the sides of the sinuses, is destitute of a fibrous structure, and is so loosely attached that it peels off with a very inconsiderable force. When the mem- brane of the sinuses is inflamed, it then thickens, admits more red blood, and is thus brought to resemble the pituitary else- where. It is extremely difficult to assign a proper use to the sinuses bordering on and entering into the nose; for, according to Des- sault, the sensation of smell does not exist in them. Bichat be- lieved that they, by being filled with air charged with odorous particles, were reservoirs of the latter, serving to prolong the sensation of smell, which would have been too fugitive if it had depended only on the passage of air during respiration. Ano- ther problem in regard to these cavities, is the manner in which they discharge the mucus which they secrete. Perfectly rigid and unyielding, and so situated that the most frequent attitudes of the head would rather serve to retain, than to discharge the contents of most of them by gravitation, we yet seldom see more than their surface smeared with mucus, and accumulations of it are quite uncommon, except in the diseased state. The se- cretion in them, it is to be observed, is much les§ abundant than it is in the nose. Vol. II.—50 390 NERVOUS SYSTEM. Of the Nerves of the Pituitary Membrane.* The pituitary membrane is furnished with nerves from two sources; from the olfactory, and from the fifth pair. The Olfactory Nerve having formed its bulb, which reposes in the ethmoidal fossa, sends off from the under surface of the bulb, the succession bf filaments which penetrate to the nose through the cribriform plate of the ethmoidal bone. The lat- ter, when examined from the upper surface, has its foramina ar- ranged into two rows, one next to the crista galli, and the other next to the cellular portion of the ethmoid. Each row consists of about six or eight foramina, and between these rows there are other foramina, smaller, and not so much in a line with each other. The same cribriform foramina, when examined from the cavity of the nose, are more numerous, especially those be- longing to the two first rows, in consequence of the latter branching out below into several canals, which may be seen very distinctly on the side of the base of the nasal lamella, and on that of the cellular portion of the ethmoid. The distribution of the olfactory nerve corresponds with this arrangement of the cribriform plate, for it has three rows of branches proceeding from the under surface of its bulb, each branch going through its appropriate foramen, and subdividing in it, but sometimes two filaments pass through the same fora- men. In a short space after their origin, they become invested by sheaths of the dura mater, which are extended a considera- ble distance, and which, by a close adhesion to the nerves, make them appear much larger below than they are at the roots. When the nerves reach the cavity of the nose they anastomose together, and descending between the bone and the pituitary membrane, they ramify into an infinitude of small branches, the terminating filaments of which reach the nasal surface of the membrane. The Internal Branches, or those next to the crista galli, di- verge from the cribriform plate, and pass downward between • Antonii Scarpa, Anatom. Annotationes, Lib. ii. ORGAN OP SMELLING. 391 the septum and the pituitary membrane: where they first appear in the nose, there are some few adhesions or anastomoses be- tween them; but their filaments afterwards keep perfectly dis- tinct, and, spreading themselves out on the pituitary membrane of the septum, make an appearance resembling a flat camel's- hair pencil. The middle ones are the longest, and may be traced almost to the floor of the nose; the anterior are shorter somewhat; the posterior do not reach obviously below the middle of the septum. The External Branches have a very different mode of distri- bution. While still in their canals they divide into many fila- ments, which anastomose frequently with each other, and when they have fairly got into the cavity of the nose, the same fre- quency of anastomosis continues, so that they form a net-work of numerous and small meshes, which prevails from the cribriform plate to the inferior margin of the middle turbinated bone. Their filaments cannot be traced below the latter line, and, therefore, do not descend so low as the filaments of the internal row, nei- ther are they so close to each other. They do not penetrate to the ethmoidal cells. The posterior ones are very abundant, on the upper turbinated bone, and incline backwards in their de- scent ; the anterior are also abundant on the flat anterior half of the ethmoid, and when they get below the line of the upper meatus, they extend backwards to the posterior end of the mid- dle turbinated bone, and to its inferior margin. On this bone they are less abundant than above it; their meshes are larger, and their distribution is confined to the Schneiderian membrane covering its convex surface. The filaments of the middle row associate themselves indis- criminately with those of the external and of the internal row, according to local convenience. The other nerves of the Pituitary Membrane come from the first and from the second branch of the Trigeminus. The first branch gives off from its nasal branch the nerve called Internal Nasal, which penetrates from the orbit into the cavity of the cranium, through the anterior internal orbitary foramen, and lies covered by the dura mater, at the side of the crista galli; thence 392 NERVOUS SYSTEM. it passes into the cavity of the nose through the most anterior foramen of the cribriform plate. This Internal Nasal Nerve (Nasalis Internus) having got into the nose, divides into two fasciculi, an internal and an external. The internal descends along the anterior margin of the septum, between the mucous membrane and the bone, and, after a short course, is divided into two filaments, one of which, applying it- self to the posterior face of the os nasi, terminates by smaller filaments in the integuments of the lower part of the nose; the other filament continues along the margin of the septum to the lower part of the latter, where it terminates by smaller filaments. The external fasciculus of the Nasalis Internus gives off early a filament, which descends along a groove on the posterior face of the nasal bone, and winding over the lower edge of the latter, or passing through a foramen in it, is lost upon the integuments of the corresponding part of the nose. Other filaments from the external fasciculus descend upon the mucous membrane, along the external anterior part of the nose, or that which cor- responds with the nasal process of the upper maxilla, and ter- minate near the anterior extremity of the inferior spongy bone: they are three or four in number. The internal nasal nerve is also said to send one or more filaments to the frontal sinuses, but they are so fine that doubts of their existence are entertained by Bichat, though they are admitted by J. F. Meckel. The Spheno-Palatine' Ganglion, a part of the second branch of the Trigeminus, detaches to the nose, through the spheno-palatine foramen, several filaments. One of these, discovered by Cotun- nius, and admirably delineated by Scarpa and by John Hunter, called the Naso Palatinus, runs across the front of the sphenoidal sinus to the upper posterior part of the septum narium, beneath the mucous membrane. It then descends obliquely along the septum to the foramen incisivum, and passes through it to the roof of the mouth. In many cases, however, a distinct foramen is formed in the middle palate suture for it, anterior to the fora- men incisivum. The nerve of the left side is anterior to that on the right. When the two reach the roof of the mouth, or are near it, they unite to form a little swelling, called the naso-pa- ORGAN OF SMELLING. 393 latine ganglion,* from which several filaments arise and are spent upon the membranous caruncle at this point, and upon the contiguous part of the palatine membrane. The spheno-palatine ganglion sends several filaments to the mucous membrane of the upper spongy bone and of the upper meatus, and to that of the posterior end of the middle spongy bone. The palatine nerve, one of its largest branches, in de- scending along the posterior palatine canal to the soft palate of the mouth, also contributes to the supply of nerves to the nose. Shortly after it has arisen from the ganglion, it sends one or more filaments to the middle spongy bone, and to the superior part of the lower spongy bone, and when it has got, in its descent, on a level with the posterior end of the latter, it detaches another filament, which supplies the mucous membrane, along the infe- rior margin of this bone. ! * An opinion advanced by Mery about the close of the seven- teenth century, has lately been revived by M. Magendie, of Paris, that the olfactory nerves are not those which communicate the impressions of odorous bodies. In contradiction, however, to his experiments, it should be stated, that several respectable anatomists have seen cases where the privation of the sense of smell during life, was found, upon examination after death, to be attended with the absence of the olfactory nerves. Of the Blood Vessels of the Nose. The extreme vascularity of the Schneiderian Membrane is derived from several sources. The Internal Maxillary Artery sends through the Spheno-Palatine Foramen a large branch, which is distributed upon the septum and upon the spongy bones. The palatine artery also supplies this membrane with one or more small branches. The Ophthalmic also sends the anterior and the posterior ethmoidal branches to it, from the orbit of the eye. The infra-orbitar artery likewise contributes to its vas- cularity by one or more branches, sent off in its course through the infra-orbitar canal. * J. Cloquet, Anat, 394 NERVOUS SYSTEM. The veins follow the course and distribution of the arteries. Some of them, however, unite with the trunks called emissaries of Santorini, which reach the sinuses of the brain through the foramen ovale and rotundum of the sphenoid bone. CHAPTER II. OF THE EYE, AND ITS DEPENDENCIES. The organ of vision which depends upon the optic nerve for its usefulness, is formed by the Ball of the Eye and many Depen- dencies or Auxiliary parts, all of which are situated within the orbit, and fill up its cavity. SECT. I.--OF THE AUXILIARY PARTS OF THE EYE. The Eyelids (Palpebra) are placed at the anterior orifice of the orbit, and serve to shut out the light from the eye, by their closing; and also, by their frequent motions, to sweep the front of the eyeball, so as to remove, from its transparent part, moats and dust. They are distinguished into upper and lower, and the place at each end, where the horizontal fissure between them ceases, is called their Commissure, Angle or Canthus. The angle next to the nose, or the internal, is called the Great one, and the other, the Little one. The Internal Canthus is united to the nasal process of the su- perior maxillary bone by a rounded tendon, (Ligamentum Palpe- brale Internum,) which passes horizontally inwards, and is nearly half an inch in length. It throws the skin into a small ridge, which may be distinctly seen and felt at this point. The Exter- nal Canthus is held in place by its general attachments of cellu- lar substance and by the external palpebral ligament. The upper eyelid is somewhat larger than the lower, but the structure of both is the same, for each one is formed by skin ex- THE EYE. 395 ternally; next to it a plane of muscular fibres, being the orbicu- laris palpebrarum; then a plate of cartilage; and, lastly, a thin membrane uniting it to the eyeball. There is nothing in the texture of the skin of the eyelid which needs description in a more particular manner, than that of stating its fineness, its thinness, the looseness of its attachment to the muscle beneath by long yielding cellular substance, and the deficiency of adipose matter. It is rendered prominent at the superior margin of the orbit, both by the projection of the bone there, and by the presence of the corrugator supercilii muscle at its internal extremity. This prominence is furnished with an arched cluster of hairs, (SuperciUa,) which have their loose ends inclined horizontally outwards, and are rather more abundant at the root of the nose than externally. The superciUa of the two sides are separated commonly by a small bare space called Glabella, the existence of which adds much to the calm and in- tellectual expression of the human countenance; whereas, the junction of the two eyebrows, by the hairs filling up this space, gives a gloomy, and, occasionally, a ferocious appearance. The margins of the eyelids are also furnished with hairs, (Cilia,) the roots of which are insinuated between the skin and the tarsus cartilage: the most deeply seated seem, indeed, to pe- netrate the latter. The hairs of the upper lid are longer and more numerous than those of the lower; they are concave up- wards, while the latter are concave downwards, so that the con- vexities of the two ranges of hairs come in contact when the eyelids are closed. The hairs of each cilium are disposed into three or four rows, by which a long brush is formed, the central hairs of which are longer and larger than any others. The hairs of the superciUa and of the cilia resemble one ano- ther strongly, for, when examined closely, each one will be found to have a bulbous soft root, just beyond which there is a narrow part. The middle of the hair is swollen, and its external extre- mity is brought to a fine point. These hairs correspond in co- lour with the hairs of the head. When the orbicularis muscle is removed, a ligamentous or fibrous membrane is found passing from the external margin of the orbit to the corresponding margin of the palpebral cartilages, 396 NERVOUS SYSTEM. and separating the eyelids from the parts contained within the orbit. There is a partial decussation of the fibres of this mem- brane, from the external commissure of the cartilages to the ex- ternal edge of the orbit; it has more firmness than any other part of the membrane, and is the external palpebral ligament, (Ligamentum Palpebrale Externum.) On the side of the internal canthus of the orbit there is no corresponding ligamentous ex- pansion, but a few irregular fibres, which allow the masses of fat beneath to project forwards between their fasciculi. The Palpebral Cartilages (Tarsi) are two in number, one at the margin of each eyelid, to which they communicate a smooth, even surface, from the internal to the external commissure. They are between the orbicularis muscle and the tunica conjunc- tiva. The upper one is larger than the lower, resembles an oval cut in half in its long diameter, and is about six lines broad in its middle: the lower one is of a breadth, nearly uniform, of about two lines. Their internal extremities cease just before they reach the puncta lachrymalia, and are attached to the in- ternal palpebral ligament, which has been described as one of the origins of the orbicularis oculi muscle, at the nasal process of the upper maxillary bone; their external extremities cease just before their commissure, and are firmly attached to the external palpebral ligament. These cartilages are thicker where they form the margin of the eyelids, and have there a slope or bevel, by which, when in contact, a small groove is formed on their posterior surface. From their resistance to the concentric contractions of the or- bicularis, they keep the eyelid smooth, and favour its sliding upon the eyeball. Certain animals, being destitute of these car- tilages, when they wink, the skin, by the contraction of the or- bicularis, is drawn up like the mouth of a purse. Conjunctiva.—Below the palpebral cartilage is the fourth layer of the eyelid, the conjunctiva. It is a white, thin, and diapha- nous membrane, in the uninflamed state. Beginning at the roots of the cilia, where it is continuous with the skin, it covers the posterior face of each eyelid, is reflected for eight or ten lines towards the bottom of the orbit, and then passes to the eyeball, THE EYE. v 397 of which it covers the anterior half, not excepting the cornea. It penetrates into the lachrymal passages, to be continuous with the lining membrane of the lachrymal sac. From this description, it is evident that the tunica conjunctiva has one surface presented against itself when the eyelids are closed; this surface is lubricated and very smooth, so as to per- mit a free motion of the lids and ball of the eye. The other surface is connected in its anterior half by cellular substance to the eyelids, and in its remaining part to the ball of the eye, by the same means. It is united rather loosely to the sclerotica till it gets near the margin of the cornea; but to the latter it ad- heres so firmly, and changes there so much its texture, that it seems like a portion of the cornea. This membrane, from its continuity with the skin and the lining membrane of the nose, from its sympathies with them, from the nature of the discharge from it, and from its extreme >sensibility, is ranked by Bichat among the mucous membranes. It has, however, some peculiarities in its structure, for it is en- tirely deficient in villosities, and though most abundantly fur- nished with capillary vessels, they do not obviously admit red blood, but in a state of irritation. Glandula Palpebrarum.—These bodies, also called the glands of Meibomius, from an anatomist who has described them par- ticularly, are situated at the margin of each eyelid, between its cartilage and the conjunctiva. They are about two or three lines long, and appear like small, white, serpentine threads, run- ning at right angles to the margin of the lid, near to, and paral- lel with one another. They are more abundant on the upper than on the lower lid. They terminate by a row of small ori- fices in the margin of the lid, just behind the cilium. For prevent- ing the overflowing of the tears, and the sticking together of the eyelids, they discharge an unctuous fluid, which may be made manifest by squeezing them. Their secretion is occasionally much augmented, and then has a large quantity of serum and glutinous matter in it: in this case the evaporation of the serum makes it adhesive, and causes the eyelids to adhere after they have been closed for some time, as in sleep. Vol. II.—51 398 NERVOUS SYSTEM. Muscles. The Musculus Levator Palpebrae Superioris is placed in the superior part of the orbit. It arises by a small round tendon from the upper margin of the optic foramen, and, becoming fleshy, it expands itself into a long thin triangle, of which the base is in front. It covers the rectus superior muscle. Terminating in front by a thin tendinous expansion, it is in- serted into the superior margin of the upper palpebral cartilage; but some of its fibres continue on between the latter and the or- bicularis to the lower edge of the cartilage. It raises the upper lid, by drawing it towards the bottom of the orbit. There are six muscles concerned in moving the eyeball, four of which, from their direction, are said to be straight; and the other two, for the same reason, are called oblique. With the exception of the inferior oblique, they all arise from the bottom of the orbit. 1. The Rectus Oculi Superior, being placed immediately be- low the levator palpebrae, arises from the superior margin of the optic foramen. It runs forward, increasing somewhat in breadth, and is inserted by a broad thin tendon into the sclerotica, two lines from the cornea. It turns the eye upwards. 2. The Rectus Oculi Externus arises from the external mar- gin of the optic foramen. It then advances along the middle of the external wall of the orbit, near the periosteum, to which it adheres slightly, and is, finally, inserted, by a thin broad tendon, into the external side of the sclerotica, about two or three lines from the cornea. It abducts the eye, or turns its outwards. 3. The Rectus Oculi Inferior arises also from the optic fora- men, at its inferior margin, and, lying upon the floor of the orbit THE EYE. 399 as it advances forwards; it is inserted, tendinous, into the under surface of the sclerotica, two lines from the cornea. It depresses the eye, or turns it downwards. 4. The Rectus Oculi Internus arises from the internal margin of the optic foramen, and goes forwards along the internal wall of the orbit, being separated from it by a layer of adipose mat- ter. It is inserted, by a tendinous expansion, into the inner side of the sclerotica, two or three lines from the cornea. It adducts the eye, or turns it inwards. 5. The Obliquus Oculi Superior is placed along the upper in- ternal angle of the orbit. It arises from the corresponding mar- gin of the optic foramen, by a small round tendon; it then ad- vances forwards, and when it has got near the margin of the orbit, it is converted into a long round tendon. The tendon passes through a cartilaginous loop which is formed for it, just at the inner margin of the supra orbitary fo- ramen, and is connected to the loop by long loose cellular sub- stance, which permits it to play freely backwards and forwards. The tendon from this point changes its direction by going back- wards and outwards: it also becomes more flat, and is then in- serted into the upper face of the sclerotica near its middle, just beneath the internal margin of the rectus superior muscle. This muscle is the longest, but the most delicate of those be- longing to the eyeball. According to Soemmering, it draws the eyeball forwards, and towards the internal canthus, and directs the pupil towards the cheek. By the aid of the inferior oblique, it draws the eyeball towards the nose: it expresses pride: it ap- pears to be greatly excited in anger.* The preceding muscles are all connected, either directly or indirectly, with the theca of the optic nerve. 6. The Obliquus Oculi Inferior is at the bottom of the orbit * Bulbum in priora et angulum internum versus movet; pupillam deorsum ad genam dirigit; juvante musculo obliquuo inferiore bulbum nasum versus trahitj animi fastum exprimit; ira valde commoveri videtur. 400 NERVOUS SYSTEM. It arises, by a small tendinous beginning, from the os maxillare siiperius at the side of the os unguis, and, increasing in size, it goes below the rectus inferior outwards and backwards, and gets between the eyeball and the rectus externus. It is then in- serted into the outer face of the sclerotica, about half way be- tween the optic nerve and the cornea. It causes the eye to revolve on its axis, and turns the cornea towards the nose. Its action, however, is much modified by that of the other muscles. As one axis of the eye is a line passing from the centre of the optic nerve, forwards and outwards, it will be found that each of the oblique muscles is inserted, at right angles, to this line; consequently, their simple and un- modified action is to produce a revolution of the eye, on its axis, in the line of their insertion, the first making the eye roll in- wards, and the latter outwards, on the two poles: they, there- fore, are strictly antagonists. Of the Lachrymal Apparatus. The apparatus for the tears (Organa Lachrymalia, via Lachry- males) consists in the Lachrymal Gland, the Lachrymal Ducts, the Lachrymal Sac, and a few other parts. The Lachrymal Gland (Glandula Lachrymalis) is situated in the orbit, immediately below and within the external angular process of the os frontis. It secretes the moisture that lubri- cates the eyelids and eyeball, and which, when it becomes abun- dant, is called the Tears. It is a flattened oblong or oval, con- vex above and concave below, of ten lines in length, six in width, and about two lines at its thickest part, for its edges are somewhat bevelled. It may be considered as divided into two parts or lobes, of which the superior is the larger and occupies the depression attributed to it in the frontal bone, while the in- ferior, being the smaller, is placed at the anterior margin of the depression.* It is lined below by the conjunctiva, and is pro- tected in front by the margin of the orbit which it touches. This gland resembles much a salivary gland in its light pink colour, and in its consisting in a congeries of lobules united by * These lobes are frequently marked off by a ligamentous band passing from between them to the external angular process. THE EYE. 401 cellular substance. Unless we are to consider the latter as such, it has no regular capsule. From the lachrymal gland there pro- ceed six or seven excretory canals, extremely fine, and found with so much difficulty that many distinguished anatomists have sought for them in vain.*. The orifices of these ducts have been laid down, by Soemmering, as equi-distant; forming in the con- junctiva, a row half an inch long, and parallel with the superior margin of the upper tarsus cartilage, beginning a quarter of an inch above its external end and going inwards. By squeezing the gland, small drops like tears, will appear on the nearest sur- face of the conjunctiva, but not in the regular order laid down by anatomists for the lachrymal orifices. The Lachrymal Ducts (Canaliculi Lachrymales) are situated immediately beneath the skin, at the internal commissure of the eyelids, in their posterior margin, and behind the orbicularis muscle. There is one for each eyelid. They are about half an inch long, though the lower one is rather longer than the upper. The lachrymal ducts commence at a small elevation of the margin of each eyelid, bordering immediately upon the internal end of the tarsus cartilage, but perfectly distinct from it. This elevation is conical, has a vermicular motion during life, and points towards the ball of the eye; in its centre is a very small foramen, called the Punctum Lachrymale, which is the begin- ning of the lachrymal duct. The punctum is about a line in length; and enlarging in its course, it runs at right angles to the duct into which it empties, of which it may be called the Orbital Orifice: the upper one will, therefore, ascend, and the lower one descend. The lachrymal ducts are much larger than the puncta, and are in their whole course about one line in diameter. At their * These are Morgagni, Haller, Zinn, and Durverney. Meckel, Soemmering, and many others, speak with all confidence concerning them. Bichat admite that he only acknowledges their existence inductively. Dr. Monro, of Edinburgh, claims to have discovered them by plunging the eye into a coloured fluid which was absorbed by them. Dr. W. Hunter seems to have a prior claim to Dr. Monro. See Med. Comment, p. 54. Mascagni also acknowledges their exist- ence :—Prodtomo della Grande Anatomia, vol. i. p. 60. 402 NERVOUS SYSTEM. orbital extremities, they go rather beyond the puncta, so as to form a small cul-de-sac. These canals converge, and having got to the internal angle of the eyelid, they are there placed be- hind the internal palpebral ligament. They then discharge, by distinct orifices, but very near each other, into the lachrymal sac at its external anterior part, where they form a small round pro- jection into the interior of its cavity, and are overlapped, some- times, by a small duplicature of its lining membrane. When the eyelids are closed, the lachrymal ducts are horizontal and nearly parallel, but when the eye is open the upper duct is elevated, and thereby becomes oblique; it is hence more proper for the introduction of the instruments into the lachrymal sac. The Lachrymal Caruncle (Caruncula Lachrymalis) is placed in the angle formed by the internal junction of the eyelids. It is a red-coloured tubercle, differing in size in different individuals, but commonly as large as a grain of wheat. It is conical, and obtains its redness from the conjunctiva being reflected over it: when accurately examined, it will be found to consist in a group of sebaceous glands; of which, according to some anatomists, there are seven ranged two in a row, and one on the top of the others. The surface of this body is beset with very fine hairs, and the orifices in it are distinguishable with a glass. The Semilunar Valve, or Fold, (Plica Semilunaris,) is situated immediately at the outer margin of the caruncle. It has the form of a triangle, the point of which runs into the caruncle, and the base, which is somewhat crescentic, is directed towards the ♦ eye. It is a duplicature of the conjunctiva, becomes very mani- fest from behind, and, in some cases, has its base furnished with a very small strip of cartilage.* I have seen several cases of the kind very well marked; they occur more frequently in the African, according to my personal experience. Between the base and the caruncle it is formed into a number of loose wrin- kles, which disappear when the eye is very much abducted. This body, in the human subject, is evidently intended to per- mit to the eye a great freedom of abduction. Its analogy, how- • Meckel. THE EYE. 403 ever, with the third eyelid of animals is very striking, and the difference is rather in the full development of the latter, than in the organization. It is very properly remarked by J. F. Meckel, that in descending the scale of animals, the third eyelid is al- ways in an inverse ratio to the other two, till it ends by being a complete substitute for them. Surrounding the caruncle, may be observed a depression. on the adjoining part of the plica semilunaris. Into this depression the puncta lachrymalia are directed, and there play up and down: the tears accumulate in it; from which cause the depres- sion is called Lacus Lachrymalis. The Lachrymal Sac (Saccus Lachrymalis) is placed at the in- ternal canthus of the orbit; in the depression of the os unguis, and of the nasal process of the upper maxillary bone. It is an ob- long cylindroid cavity; and extends from the transverse facial suture to the anterior extremity of the inferior meatus of the nose; being concealed there by the anterior part of the inferior turbinated bone. It is crossed at its front part by the tendon of the orbicularis, which, with a few fibres of this muscle, adheres to it. The course of the lachrymal sac, is, at first, slightly forwards in the descent to the nose; but when it reaches the lower part of the orbit, it is afterwards slightly backwards: so that it may be considered as forming an obtuse angle forwards. It also de- creases somewhat in size from above downwards, and at its lower orifice is flattened from side to side. The lachrymal sac consists in two membranes, an exterior fibrous one continuous with the periosteum of the contiguous bones; and an interior mucous one, which is thick, villous, of a red colour, from the abundance of its blood vessels, and abound- ing in mucous follicles. The interior is continuous above with the lachrymal ducts, and below with the Schneiderian membrane. On a line with the floor of the orbit, this internal membrane is thrown into a circular duplicature, considered by some anatomists, as forming the proper boundary of the lachrymal sac: all below this is called by them nasal canal. The distinction is rather arbitrary, and, in some degree, hurtful to clearness of descrip- tion : a much better plan is to call the part above the valve, the 404 NERVOUS SYSTEM. orbital portion of the sac; and the part below the valve, its nasal portion. Sometimes there is a second valve about three lines below the first, and generally another at the nasal orifice, formed by a duplication of the Schneiderian membrane. The Tensor Tarsi is a small muscle on the orbital face of the lachrymal sac, of which I gave a detailed account some few years ago.* It arises from the posterior superior part of the os un- guis, just in advance of the vertical suture between the os pla- num and the os unguis. Having advanced three lines, it bifur- cates; one bifurcation is inserted along the upper lachrymal duct, and terminates at its punctum, or near it; and the lower bifurcation has the same relation to the lower lachrymal duct. The base of the caruncula lachrymalis is placed in the angle of the bifurcation. The superior and the inferior margins of the muscle touch the corresponding fibres of the orbicularis palpebrarum, where the latter is connected with the margin of the internal canthus of the orbit, but may be readily dis- tinguished by their horizontal course. The nasal face of this muscle adheres very closely to that portion of the sac which it covers, and also to the lachrymal ducts. The lachrymal sac rises about a line above its superior margin, and extends in the orbit four lines below its inferior margin. The orbital face of the muscle is covered by a lamina of cellular membrane, and between this lamina and the ball of the eye are placed the val- vula semilunaris, and a considerable quantity of adipose matter. As the bifurcated extremities of the muscle follow the course of the ducts, they are covered by the tunica conjunctiva. When this muscle is examined from behind, the eyelids being in situ, it becomes obvious that it is concave on its orbital surface, and, consequently, convex on the nasal; that the muscle is an oblong body, half an inch in length, and about three lines wide, bifur- cated atone end: and that it arises much deeper from the orbit than any acknowedged origin of the orbicularis. The superior fork, however, has a few of its fibres blended with the orbicu- laris. In regard to the use of this muscle: its attachment to the posterior face of the sac is such, that it draws the orbital parts * Philadelphia Journal of Med. and Phys. Sciences, 1824. THE EYE. 405 of the sac away from the nasal, and dilates the sac, from the na- sal face of the latter being fixed to the bones. As this mus- cle is cylindrically concave on its orbital side, it is evident that when it contracts, the fibres become straight, or nearly so, like the fibres of the diaphragm, and the cavity of the sac is enlarged after the same manner as the cavity of the thorax. A tendency to a vacuum being thus produced by it, the valves or folds of the internal membrane of the sac permit the vacuum to be filled more readily through the puncta than from the nose; and the puncta being continually bathed in the tears of the lacus lachry- malis, both in the waking and in the sleeping state, the tears are constantly propelled through them by atmospheric pressure. The evacuation of the sac is no doubt accomplished by its own elasticity, and by the contraction of the orbicularis; probably in a chief degree by the latter, because in persons who have epiphora, or a tendency to obstruction in the nasal duct, the ac- cumulation of tears and matter principally takes place at nighf, when the action of the orbicularis is suspended by sleep. For these reasons, we should argue that this little muscle is active at all times, both night and day. To Dr. Physick I am indebt- ed for suggesting another use for it; to wit, that of keeping the lids in contact with the ball of the eye. Some persons posess unusual voluntary power over this muscle, of which I have seen several examples. In each instance the individual could short- en so much the internal angle of the eyelids, as to conceal it, along with the puncta, in the internal canthus of the orbit.* * Having laboured, first of all, to convince the profession of the existence of this muscle, the next step, as is usual on such occasions, was to vindicate my own pretensions to its discovery, and to attempt to remove such objections us re- quired attention. For the arguments on this subject, I refer to the Philadelphia Journal of Medical and Physical Sciences, of Nov. 1824, edited by Professor Chap- man. My claims have been unequivocally admitted by Messrs. Breschet and Jourdan, of Paris, anatomists of unusual distinction, in the translation which they have made of J. F. Meckel's Manual of Anatomy, vol. iii. p. 219; by Gery, in the Melanges de Chirurgie etrangere, Geneva, 1824, p. 415; and by Professor Giu- seppe Trasmondi, in the Arcadica Journal of Rome, vol. xix. p. 1, 1823. Vol. II.—52 406 NERVOUS SYSTEM. Of the Nerves of the Orbit. In addition to the optic nerve, there are several belonging to the eye and to its auxiliary parts; they are derived from the Motor Oculi or third pair; from the Trochlearis, or fourth pair; from the first branch of the Trigeminus, or fifth pair; and from the Motor Oculi Externus or sixth pair. For an account of which, see Nerves. Of the Arteries of the Orbit. The Eyeball, and its auxiliary parts, are principally supplied by the Ophthalmic Artery, which, as was mentioned in the ac- count of the Brain, is a considerable branch given off by the In- ternal Carotid at the fore part of the Sella Turcica. This branch gets into the orbit on the outer side of the optic nerve through the optic foramen, and, after a short course, crosses obliquely above the optic nerve, so as to pass to the internal side of the orbit. It sends off a great many small trunks, which are very inconstant both in their size and origin; they are as follow:— 1. Arteria Lachrymalis arises, commonly, soon after the oph- thalmic has got into the orbit: it goes forwards between the rec- tus superior and the rectus externus muscle, to which it dis- tributes arterioles; it then reaches the lachrymal gland, and having left branches with it, what remains issues out at the ex- ternal angle of the eye, so as to supply the contiguous part of the upper eyelid. 2. Arteriae Ciliares. According to Soemmering, before the origin of the lachrymal artery, the ophthalmic detaches from one to three ciliary, which penetrate into the ball of the eye near the optic nerve. Other arteries" of the same class arise subt sequently from the ophthalmic, and, occasionally some of them from the lachrymal itself. They go to the choroid coat of the eyeball and to the iris. THE EYE. 407 3. The Arteria Centralis Retinae arises from among the clus- ter of ciliary arteries, and, like them, has no invariable root. It penetrates the optic nerve about the middle of its orbitar por- tion, and, going in its centre, gets into the eye through the crib- riform part of the sclerotica. It is then distributed by ramus- cles to the retina, to the tunica hyaloidea, and to the capsule of the lens. 4. The Arteria Ethmoidea Posterior is inconstant in exist- ence, and comes at one time from the trunk, at another from a branch of the ophthalmic. It passes over the superior oblique muscle, and penetrating through the posterior orbitary foramen, is spent by arterioles upon the neighbouring part of the dura mater, and upon the posterior ethmoidal cells, where it anasto- moses upon the Schneiderian membrane, with branches from the internal maxillary. 5. Arteriae Musculares. Of these there are two; one of them^ the inferior, sends branches to the rectus internus, rectus infe- rior, and obliquus inferior oculi; also to the lachrymal sac, and to the parts about the bottom of the orbit. It occasionally de- taches some of the ciliary arteries. The superior muscular branch is also called the supra orbitar. It supplies the muscles of the superior part of the orbit, and then issuing through the supra orbitary foramen, it is spent in arterioles, upon the os frontis and its periosteum, and upon the orbicularis oculi, cor- rugator supercilii, and occipito-frontalis. It anastomoses there with other branches of the ophthalmic* and with the temporal artery. It is usual for the anterior ciliary arteries to come from the muscular branches. The Ophthalmic Artery, after having detached atf the afore- said branches, is much diminished in volume, pnd, advancing along the internal parts of the orbit, its next branch is— 6. The Arteria Ethmoidea Anterior, which dips into the an- terior internal orbitary foramen, and is divided into small branches, some of which are spent upon the adjacent portion of 408 NERVOUS SYSTEM. the dura mater, others upon the frontal sinus and the anterior ethmoidal cells. Some of these branches penetrate from the cranium through the cribriform bone into the nose, and, rami- fying upon the Schneiderian membrane, anastomose with the internal maxillary. 7. The Arteriae Palpebrales are two in number: they come sometimes from a common trunk, and on other occasions arise separately. One is the Superior, and the other the Inferior. The latter arises first, and is distributed to the conjunctiva, the caruncuta lachrymalis, lachrymal sac; and finishes by many small branches to the lower eyelid, that anastomose with the infra-orbital artery, so as to form the lower tarsal arch. It also anastomoses with the lachrymal artery by its extreme branches. The Superior Palpebral Artery also distributes branches to the conjunctiva, sac, and caruncle; it then emerges above the inner palpebral ligament, around the margin of the superior eye- lid, and forms, along with the lachrymal and the supra orbital artery, the superior tarsal arch, which distributes small branches, in great profusion, to the orbicularis muscle, and to the struc- ture, generally, of the lid. It anastomoses, externally, with the lower palpebral artery. 8. The Arleria Nasalis is sometimes a well marked continu- ation of the ophthalmic. It passes out of the orbit at its inter- nal canthus, above the internal palpebral ligament, an'd anas- tomoses at the root of the nose with the facial artery. It is distributed to the side of the nose, and to the lower part of the forehead. Its chief contribution to the eyelids is at the in- ternal end of the orbicularis, where it anastomoses with the pal- pebral arteries. 9. The Arteiia Frontalis passes out of the orbit, at the supra orbitary foramen. It is quickly divided into branches, which go to the orbicularis and corrugator muscles, to the occipito- frontalis, and to the frontal sinus. THE EYE. 409 Of the Veins of the Orbit. The blood distributed to the eyeball and to its auxiliary parts* has two routes for returning to the heart, one through the ca- vernous sinus, and the other by the superficial veins of the face. As a general rule, all the branches of the ophthalmic artery which reach the eyelids, or become otherwise superficial, return their blood by the latter route; and those whose distribution is to the ball of the eye and to the parts deeply seated in the orbit, re- turn their blood by the sinus. When the veins are well injected, a very considerable num- ber is manifested in both eyelids. They form a handsome net- work, the meshes of which are small and numerous, and com- mence by small roots at the margin of the eyelids. The vessels of this net-work becoming, successively, larger from the centre to the circumference of the orbicularis, cover the whole surface of the latter, and from the thinness of the skin are readily seen be- neath it. The veins of the lower eyelid are discharged into the facial vein, where it borders on the orbicularis; and the veins of the upper lid, being bordered along the superior mar- gin of' the orbicularis by a horizontal branch of the temporal vein, discharge themselves into it. The Ophthalmic Vein (Sinus Ophthalmicus) is the large trunk within the orbit which receives, successively, the remain- ing blood of the eye, and, passing along the internal parts of the orbit, crosses over the optic nerve, and penetrates through the optic foramen into the cavity of the cranium, where it termi- nates in the cavernous sinus. It may be considered as com- mencing by an anastomosis with the facial vein at the internal canthus; it then receives the following branches:^- 1. The nasal, which arises from the parts about the internal canthus of the eye. 2. The anterior ethmoidal, which comes from the nose and frontal sinus. 3. Branches from the recti and obliqui muscles. 410 NERVOUS SYSTEM. 4. The lachrymal vein, from the lachrymal gland and leva- tor palpebrae muscle. 5. Posterior ethmoidal vein, from the nose. 6. The ciliary veins, or those of the choroid coat, which are very numerous. 7. The central vein of the retina, which is collected from three or four principal branches, and follows the course of the artery of the same name, through the cribriform part of the sclerotic coat, and through the centre of the optic nerve. The trunks of this vein anastomose, at the anterior margin of the retina, with those of the Ciliary Body. There are, of course, frequent anastomoses between the veins of the eyelids and the primitive branches of the ophthalmic vein. SECT. II.--OF THE BALL OP THE EYE. The Eyeball (Bulbus Oculi) is situated within the anterior half of the orbit, from which it is kept separated by its auxili- iary parts, and by a large quantity of adipose matter which fills up their interstices. It is very nearly spherical, but not so much so as to prevent its antero-posterior diameter, which is about an inch long, from exceeding in measurement every other. Such, at least, is the general opinion of anatomists: but from some recent experiments, made by distending the eye with mer- cury, I have been induced to doubt its correctness, and especial- ly in the African; for, in the latter, I found the transverse dia- meter to exceed the antero-posterior by a line or more. The Eyeball is also somewhat flattened at the insertion of each of the straight muscles. It is formed by a series of concentric tunics, one investing the other, and by humours contained within those tunics. Of the former, the Sclerotica and the Cornea are external, the Cho- roidea and the Iris next, and the Retina is internal: of the lat- ter, the Vitreous Humour is, by far, the most abundant, and constitutes a principal part of the eyeball; the Crystalline Hu- mour is in front of the vitreous; and the Aqueous is placed be- tween the crystalline and the cornea. THE BALL OP THE EYE. 411 Tunics, or Membranes of the Eyeball. The Sclerotic Coat (Tunica Sclerotica, Albuginea) forms about five-sixths of the exterior investment of the eyeball, the remaining sixth of which is obtained from the cornea. At its posterior part it is joined by the optic nerve: this junction does not occur precisely at its axis or centre, but at the inner side of it. When the optic nerve is detached at this junction, a small round hole is perceptible in the sclerotica, or, rather, it is more frequently perceived as a thin cribriform lamella, through the holes of which the pulpy part of the optic nerve passes, so as to get within the eye. This cribriform lamella, or the appear- ance of it, is no doubt produced artificially by the nerve being commonly cut through very near the eye; and, as Mr. Jacobs, of Dublin, very properly suggests, should be considered as the most anterior termination, or the point of the optic nerve in- stead of as a portion of the sclerotica. The neurileme of the optic nerve, is so arranged, that small round longitudinal canals are left, which contain the nervous matter: from this cause it happens that a thin section of the optic nerve in any part of its course in the orbit, will, if held up to the light, manifest the same cribriform arrangement with the part alluded to. This part of the structure of the optic nerve will be readily under- stood by the American student, in comparing it with the pith of the Indian corn-stalk, which, being traversed longitudinally, by many fibres, upon the drawing of them out, an equal num-^ ber of longitudinal canals is left in their places. At its fore part, the edge of the sclerotica is bevelled all around for its junction with the cornea; and though nearly cir- cular, is not completely so, from its horizontal diameter being somewhat greater than any other. There are several orifices of inconsiderable size scattered over the sclerotica, some of which are oblique and others direct: they transmit the blood vessels and nerves. The Sclerotica is nearly a line in thick- ness at its back part, from which it gradually becomes reduced to half that thickness in front, where it is strengthened by the tendinous insertions of the recti muscles. Its internal surface 412 NERVOUS SYSTEM. is smooth and somewhat shining, being loosely attached to the cellular substance intervening between it and the choroid coat; but the external surface is rough, and more obviously fibrous^ and is attached somewhat strongly to all the adjoining parts. This membrane is of a white colour, and consists of a single layer, whose structure is essentially fibrous. The fibres are very closely compacted, and compose an intertexture which can- not be unravelled. It is so closely united to the dura mater co- vering of the optic nerve, that many anatomists, notwithstand- ing its greater thickness, are disposed to speak of it as a conti- nuation of the same. Its strength and its want of elasticity suit it remarkably to maintain the form of the eye, and to resist in- juries. Out of the many blood vessels that penetrate it, but few ramify in its structure, and the existence of nerves in it is by no means evident. The tunica arachnoidea follows the course of the optic nerve, within its' coat of dura mater, and forms, in the eye, just around the cribriform plate, or foramen of the sclerotica, a circular pad: it is then reflected on the internal face of the sclerotica, as far as its anterior edge. It is this which causes the inter- nal face of the sclerotica to be smooth and shining, and there- by to correspond with that of the dura mater.* This circum- stance is more readily proved in a very young eye, than in the adult one. The Cornea, as mentioned, fills up the aperture at the fore part of the sclerotica, and, of course, has the same diameters, measuring thereby more transversely than in any other direc- tion. It is a segment of a smaller sphere than the sclerotica, and is, consequently, more convex than it. Its thickness is uniform, and commonly exceeds that of the sclerotica at the fore part of the latter. Its circumference adheres very closely to the sclerotica, and presents^ bevelled or oblique edge, which is inserted into the corresponding bevel of the sclerotica, so that the latter includes the former. The closeness of this junction induced the older anatomists to consider these membranes as one and the same, * J. F. Meckel. Zinn supposed this surface to be derived from the pia ma- ter. THE BALL OF THE EYE. 413 notwithstanding their obvious difference of structure and of pro- perties. Their adhesion yields to protracted maceration. The cornea is covered in front by a continuation of the tunica con- junctiva, which unites the eyeball to the eyelids. This may be proved by dissection, by maceration, and by its sloughing off entirely along with the epidermis of animals that are subject to this process, as the locust, snakes, and others. On its posterior face, it is covered by the membrane of the aqueous humour, which may be rendered evident by steeping it in spirits of wine; whereby the latter membrane is made more hard, and may be torn off. The cornea, in a natural state, is perfectly transparent, and readily transmits the rays of light. It consists of an indefi- nite number of laminae, which are placed one againt the other like the leaves of a book, and are united by a delicate trans- parent cellular substance which permits the laminae to slide upon each other. These laminae are kept moist and pellucid by an interstitial secretion of a fluid equally pellucid with them- selves, the abundance of which in health gives to the eye its brilliancy, and the deficiency of it in illness and in death causes the eye to look dim and somewhat opaque. Its evaporation, which no doubt is continually occurring, is as constantly sup- plied by a fresh and abundant secretion. The motion of the eyelids sweeps the residuum, after the evaporation of its wa- tery particles, from the surface of the cornea: without this pro- cess, the residuum appears as a thin layer or film of albuminous matter spread over the cornea, when the eye is kept open without winking for a considerable time. The cornea has not the fibrous structure of the sclerotica, yet the application of mechanical force to the eyeball shows that it is stronger. Neither has it vessels, conveying red blood naturally, yet, in a state of inflammation, its capillaries dilate so as to admit red blood, and deposite coagulating lymph be- tween its layers. It is common for anatomists to attribute a want of sensibility to it in a natural state: as a general rule, this is fallacious; for many persons, where the eyes are not in- flamed, suffer extremely from its being cut in cataract, and some- times faint from the pain, while others are truly unconscious of the incisions made through it. Of this opinion, I have a full Vol. II.—53 414 NERVOUS SYSTEM. assurance from repeated observations on the practice of Dr. Physick, as well as in instances in my own hands. The Choroid Coat (Tunica Choroidea, Vasculosa,) is placed immediately within the circumference of the sclerotica, and is of equal extent. At its posterior part it furnishes, for the pas- sage of the optic nerve, a singular annular opening, the margin of which is somewhat thickened, and perfectly distinct from the pia mater investment of the nerve, from which some anato- mists have desired to trace this coat. The anterior opening of the choroid is bounded by the ciliary ligament and by the iris. On its outer side may be seen an abundance of loose flocculent cellular substance which joins it to the sclerotica. Internally, it is spread over the retina, but does not adhere to it. The choroid coat is closely fastened, at its anterior margin, to the corresponding part of the sclerotica, by a ring which surrounds it, of a short, compact cellular tissue. This ring, called the Ciliary Ligament, (Ligamentum Ciliare, Orbiculus Ciliaris,) is from a line to two lines in breadth, and may be readily distinguished by its whiteness, contrasted with the dark colour of the choroid. It is intimately united to the latter, and seems to form a part of its structure, whereby it is caused to detach itself entirely from the sclerotica, and to adhere, by pre- ference, to the choroid when these two membranes are sepa- rated.* The iris is set in the front margin of the ciliary liga- ment, so that the sclerotica and the cornea may be peeled from the choroidea and iris, without impairing the continuity of the two latter. Just beyond the junction of the two last, the liga- ment presents a small ridge or elevation all around, which is fitted into a corresponding fossa at the circumference of the posterior face of the cornea. The internal face of the choroid coat, as well as its anterior margin, undergo a very remarkable change from the general plan of this tunic, by forming what is called the Ciliary Body, (Corpus Ciliare, Corona Ciliaris.) In order to see this in * Fontana asserted that a circular canal was to be found in this ligament; manv examiners have failed in finding it, and its existence is denied. THE BALL OP THE EYE. 415 the most favourable manner, the eye should be laid on the cor- nea, and its posterior half cut away. It will then be evident, that just behind the iris, and within the circumference of the ciliary ligament, the internal face of the choroid coat forms a considerable number of radiated folds or little ridges, which converge from behind forwards and inwards. These folds commence by striae, almost imperceptible to the naked eye, which are in contact with the fore part of the vitreous humour, and with the canal of Petit, and thereby not only impress the neighbouring portion of the tunica hyaloidea with their shape, but even leave upon it the black pigment with which they themselves are covered. These folds, when they get near the circumference of the iris, coalesce one with another, and ter- minate in a considerable number (from fifty to sixty, accord- ing to Soemmering,) of processes, (Processus Ciliares,) the central extremities of which are loose, and float in the aqueous humour. Some of these processes are longer than others. As a whole, the ciliary processes constitute a ring of radiating fila- ments, which are a line or more in length, placed along side of, and in contact with, one another; the external periphery of the ring adheres to the ciliary ligament, and through it to the greater circumference of the iris, so that the ring appears, but falla- ciously, to be continuous with the iris. In certain animals, as the sheep, the radiated appearance of the iris, on its posterior face, favours this notion still more. The internal periphery of the ring presents the central ends of the filaments detached from one another, and of a downy appearance; with the handle of a knife they may be readily pushed backwards and forwards. Generally speaking, the ciliary processes are so much con- cealed by the iris, that they cannot be seen in the living body through the cornea: in cases, however, of extreme dilatation of the pupil by narcotic applications, their central extremities are brought into view. The choroid coat always appears, when uninfected, of a very dark brown or black colour, arising from a black paint (Pig- menlum Nigrum) being very thickly spread over the whole of that surface of it which is adjacent to the retina, and being also diffused through its thickness. This paint is more abun- dant near the iris than posteriorly, being laid on there in flakes, 416 NERVOUS SYSTEM. in the intervals between the ciliary striae, and tinging also the ciliary processes. It may be removed in a considerable degree, indeed almost entirely, by maceration, or by careful washing with a camel's-hair pencil. It is supposed to be an exhalation from the vessels. Its particular colour is of a most durable kind. According to the observations of Bichat, the long-con- tinued action of light upon it, when this pigment is transferred from the choroid to a piece of paper, does not affect it; neither is it changed by being submitted to very strong chemical agents, as sulphuric, muriatic, or nitric acid, alcohol, or caustic potash. This degree of indestructibility of colour is an invaluable pro- perty, and almost singular; for it is well known to the keepers of medicinal articles, that the colours of all of them yield to the continued influence of light, and that they also become weaker by the same cause. In regard to structure, the choroid coat is thin, soft, and easily lacerated: when cleared of its pigment by maceration, it is semi- transparent, and is then seen evidently to consist of but one la- mina; unless we may be disposed to consider as a second one the pigment, naturally on its internal face. It has no appear- ance of fibres in its composition, but, when injected, seems to consist almost wholly of arteries and of veins. The arteries are branches of the ophthalmic, and are called ciliary. There are two Long Ciliary Arteries, which pene- trate the sclerotic coat not far from the optic nerve, and pass, one of them, on the external and superior part of the choroides, and the other on its inferior and nasal side, to the front of the eye. In this course, they do not send off any branches of con- sequence till they reach the iris, on which they are distributed. The Short Ciliary Arteries are much more numerous than the others, and also smaller; their number sometimes amounts to twenty; the most of them penetrate the sclerotica from behind, near the optic nerve also.* They quickly divide into a great number of branches, which depart at very acute angles, and have frequent anastomoses with one another. These branches run forwards, nearly parallel, and, at the fore part of the cho- * Soemmering, Icones Oculi Humani. THE BALL OP THE EYE. 417 roides, form a very intricate intertexture, which is continued upon the ciliary processes, and communicates with the vessels of the iris.* The veins of the choroid coat are also extremely abundant. They run from before backwards, and the branches which con- cur to form them, being adjacent with, and parallel to each other, for the most part, form large curves, the convexity of which is forwards; they, moreover, anastomose freely, and thereby pro- duce a vascular sort of net-work, filling up the concavity of some of the curves. These veins, called the Vasa Vorticosa, are nearer the external surface of the choroides than the arteries, and are assembled into twelve or fourteen trunks, which, en- gaging in the sclerotica, near its middle, run for some distance in its substance, and then, by their junction, are reduced to four or five in number. The latter, disengaging themselves from the eye, join, subsequently, the ophthalmic vein. In addition to the veins mentioned, the long ciliary arteries have their venae comites, which take a course parallel to and ad- joining them. These veins do not observe the vortical arrange- ment of the others; they bring back the blood of the iris, and terminate in the larger trunks of the others. This structure has been most cautiously explored by the ce- lebrated Soemmering, and his observations have tended very much to determine the opinions of anatomists concerning many parts of the eye. A curious remark of his is, that " the human eye may be distinguished from that of animals by a form of this vascular net-work, entirely peculiar; for example, in the eye of the ape, its vascular tissue differs not only from that of the hu- man subject, but also from that of the dog, and still more evi- dently from that of the calf. From which cause, it would be as easy to distinguish with a microscope, the choroides, well in- jected, of different animals, even a piece of only the forty- eighth part of an inch in extent, as it is easy to distinguish a poplar stripped of its leaves from an oak, a pear tree, an apple tree, or any other tree, by the arrangement of its trunk and branches." * Icones Oculi Humani. 418 NERVOUS SYSTEM. The choroides, on its internal face, is not smooth, but velvety, which becomes still more conspicuous when the eye is finely injected and examined with a microscope. Meckel considers the appearance to depend upon its very fine tissue of vessels. This surface is called Tapetum, in the bullock, and some other animals, at a particular part, it presents a shining, silvery ap- pearance, and may be torn off from the external surface. Ruysch attributed two laminae to the membrane in the human subject, the internal of which was called after his name, but the distinction is now generally abandoned. The Iris is a circular plane placed at the front of the cho- roides, and having, in its centre, a round opening called the pu- pil (pupilla.) Its external circumference is attached to the ci- liary ligament, and by it to the choroid coat, and is exactly at the junction of the cornea with the sclerotica. Professor Soem- mering has bestowed much attention in ascertaining whether this membrane is perfectly flat or somewhat convex in front, and, by repeated observations, carefully made, has assured him self that it is flat.* My own observations and preparations have induced me to believe that in many cases it will be found slight- ly convex in front, as Petit asserted more than a century ago. In a moderate state of dilatation, its nasal or internal border is somewhat narrower than its external or temporal. With the exception of its external circumference, every part of the iris is free from any attachment; by which arrangement it moves free- ly in the aqueous humour, so as to contract or dilate its pupil, according to the quantity of light admitted upon the eye. The iris, with the exception of its central or pupillary cir- cumference, where it is thinner than elsewhere, is much thick- er than the choroid coat. The posterior face of the iris, some- times called uvea, is covered in great abundance with pigmen- tum nigrum. When this is removed by maceration, which may be readily done, the membrane becomes semi-transparent. Its anterior surface is the seat of the colour, which characterizes every individual's eyes. There are but two of these colours, light blue and orange, the predominance of one or the other of * Icones Oculi Humani. THE BALL OF THE EYE. 419 which, assisted by the dark ground on the back of the iris, gives the cast of hue to the eye. The front surface, when examined on the living eye with the microscope, is seen to be downy or flocculent, and is traversed by filaments forming an intertex- ture, some of which are circular, others oblique; and others ra- diated. This arrangement is remarkably distinct in the eye of the seal. The power which the iris has of dilating the pupil when there is but little light, and of contracting it when there is much, has induced many anatomists to think that it is formed of mus- cular radiated fibres, which by their contraction produce the first motion, and of circular ones which produce the last. Among these anatomists may be mentioned, Ruysch, Morgagni, Zinn, Sabatier. Ruysch asserted that the radiated fibres extended from the greater circumference of the iris to the pupil, and were fixed there by very delicate tendons. The late Doctor Monro, of Edinburgh, has described particularly the circular fibres, and a preparation of the bullock's eye which belonged to him is still exhibited there, where these fibres are seen around the margin of the pupil. The several fibres can only be seen distinctly, when the pigmentum nigrum is washed away. Demours and Meckel deny the existence of the radiated fibres. The late distinguished Professor Wistar taught that the contraction of the pupil was produced by circular fibres, and the dilatation of it by its elas- ticity. In objection to this, Dr. Physick remarks, that as elas- ticity is as much a property of dead as of living matter; in death, therefore, we should always find the pupil dilated from the want of active contraction in the circular fibres; also, in cases of con- cussion of the brain, where there is a sudden loss of sensibility and of muscular motion, the pupil should be invariably dilated; but the fact is, that the pupil remains just in the same state that it was at the moment of the accident* Notwithstanding the extreme sensibility and mobility of the iris on the admission of light, one is occasionally astonished to find it not contracting when instruments are applied to it, as I * It would appear that the question of the muscularity of the iris has been settled almost conclusively by Mr. Bauer. See Ph. Trans, for 1822. 420 NERVOUS SYSTEM. have had an opportunity of twice observing, upon the removal of a considerable portion of it, in making an artificial pupil for opacity of the cornea. In these cases, upon the letting out of the aqueous humour, it became quite as flaccid as we are accus- tomed to see it in our dissections. The same remark has been made by Mr. now Sir Charles Bell. The Blood Vessels of the Iris are principally branches of the Long Ciliary, which have been alluded to. Each of the two Long Ciliary Arteries having gained the greater circumference of the iris, bifurcates; the bifurcations run along this circumference, meet, and join with the corresponding ones of the other arterial trunk. From the circle thus formed there proceed radiated branches, that run towards the pupil, and form around its mar- gin, by their frequent anastomoses, a fine vascular net-work. The radiated branches themselves give off collateral branches, which supply the intermediate spaces of the iris.* The veins of the iris are also numerous, but cannot be quite so distinctly seen: they enter into the long ciliary veins, and also into the vasa vorticosa. The nerves of the Iris belong, in part, also to the choroid coat, and are classed under the term Ciliary, (Nervi Ciliares.) They arise from the ophthalmic ganglion, and from the trunks contri- buting thereto, and are about twenty in number. They penetrate the posterior part of the sclerotica obliquely, and then run for- wards between it and the choroides. Having reached the pos- terior part of the ciliary ligament, they penetrate it, and distri- bute their filaments in its substance, after the same fashion that the trigeminus nerve is divided in its glanglion. This cir- cumstance has given occasion to Soemmering to consider the ligament as a true ganglion, and to call it Annulus Gangliformis. The nerves then get to the front of the iris, and are there dis- tributed as white radiating filaments; in the course of which may be observed small nodes, supposed by Meckel to be Ganglions. The trunks of the ciliary nerves depart from the common form of such bodies, by being flattened instead of cylindrical: they are small, and resemble sewing threads. From their num- ber, the iris is probably more abundantly supplied with nerves than any other organ of the body. • Soemmering, Icones Oculi Humani. THE BALL OF THE EYE. 421 The Retina forms the third coat of the eye, and lines the in- ternal face of the choroides almost in its whole extent. The optic nerve having passed through the sclerotica, terminates on its inner side by a bulb or button-like end, from the circumfe- rence of which the retina begins to expand, and may be traced satisfactorily as far as the commencement of the ciliary plaits of the choroid coat, where it terminates by a straight edge, some- what thickened. Just at the edge, the retina adheres to the vitreous humour, and is supposed, erroneously by some anato- mists, as Bichat and Monro, to be continued on to the circum- ference of the lens. Repeated dissections, and the substantial testimony of Soemmering,* have satisfied me that the retina cannot be fairly traced beyond the greater circumference of the impressions made on the vitreous humour by the ciliary striae of the Choroidea. When the eye is slightly macerated, the re- tina always parts from the vitreous humour at this line; more- over, when its structure is still more slightly changed by freezing and then thawing, the retina manifests a decided pre- ference to separate there, and, under the most careful dissec- tion, it is very difficult to prevent it. In addition to these con- siderations, these is a well marked change of colour at the line mentioned: in front of this line, the surface is transparent when cleaned from thepigmentum nigrum; whereas, if it were retina, it should be the colour of ground glass, as is usual in the dead body: also the veins of the retina never trespass beyond this line, but are seen to cruise along it. Most anatomists teach that the retina is an expansion of the optic nerve. Bichat believed that the latter terminated at the bulb, and that the retina was another part of the structure, but still consisting of the same sort of nervous matter. Thelatter opinion is probably the more strictly correct, because there is more pulpy matter in a section of the retina than can be found in the same length of the optic nerve; also, if the retina were simply an expansion of the nerve without any addition of mat- ter to it, it should, from its hollow globular shape, be thinner in the middle, where it is most expanded, than it is where the: expansion first begins at the bulb of the optic nerve. * Icones Oculi Humani. Vol. II.—54 422 NERVOUS SYSTEM. The retina does not adhere to the choroid coat, neither to the vitreous humour which it encloses, except at the line mentioned: when this line of attachment is broken, the retina quickly col- lapses. The texture of the retina is extremely soft and pulpy; in the living state, it is probably perfectly transparent, but this can only be conjectured from the readiness with which the vessels of the choroid coat can be seen in animals destitute of pigmen- tum nigrum. It is composed of two laminae, of which the ex- ternal is medullary, and the internal, or that next to the vitre- ous humour, is formed of a fine reticulated cellular membrane with blood vessels running through it. The external lamina may be removed by a camel's hair-pencil, or by slight putrefac- tion and washing, so as to leave the internal entire. The cele- brated John Hunter succeeded, however, in separating the two laminae fairly from each other, and preserving them, so as to show their difference. This specimen may be considered unique, and every way deserving of the source from which it proceeded.* Exactly in the axis of the eye, or at its centre, posteriorly, consequently, about a line and a half from the outer side of the bulb of the optic nerve, Soemmering discovered, in 1791, a yellow spot of a line in diameter, with a small hole in its middle, made by a deficiency of medullary matter. From the optic nerve there goes, towards the foramen, a small fold of the retina, pointed at its internal end, and obtuse or bifurcated externally. Unless the eye be fresh, these things cannot be seen distinctly, for the evaporation of the aqueous humour causes a collapse or wrinkling of the retina, which obscures them. But, in a per- fectly fresh eye, which is well managed, they may be seen both from before and behind. It was thought, for some time, that the yellow spot and the foramen were peculiar attributes of the human being: more extended and successful observation has corrected this mistake, by detecting them in several classes of animals. In the centre of the optic nerve, where it enters the eye, is * The fact was communicated to me by Dr. Physick, who studied under Mr. Hunter, and frequently saw the preparation. THE BALL OP THE EYE. 423 a foramen for the passage of the artery and vem belonging to the retina. These vessels ramify, by a few branches, on the internal surface of the membrane, and form a sort of circle sur- rounding the yellow spot. Neither the branches of the ar- teries nor of the veins communicate with those of the cho- roides; and, as observed, never go beyond what we just con- sidered as the anterior margin of the retina, but rather run along it. Interposed between the retina and the choroides, is a most delicate serous membrane, lately discovered by Mr. Jacobs, Demonstrator of Anatomy in Trinity College, Dublin. By preparing the retina in the usual way, and then floating the eye in a saucer of water, this membrane may be turned down with the-handle of a knife from the optic nerve to the termi- nation of the retina. It is supposed to be the seat of the ossi- fications which are sometimes met with in the eye. Humours of the Eyeball. The Vitreous Humour (Humor Vitrtus, Corpus Vilreum,) occupies, with the exception of a very small part just behind the iris, the whole of the space posterior to the latter. It is, therefore, very nearly globular; is in contact the greater part of its extent with the retina, at least as far as the latter mem- brane proceeds; in front it is in contact with the crystalline humour, and from the margin of the retina to the circumference of the lens it is in contact with the ciliary body, meaning there- by the ciliary striae and processes of the choroides. Two parts compose the vitreous humour,—the hyaloid mem- brane and a thin fluid. In a natural state they are perfectly transparent, and, therefore, cannot be readily distinguished from each other; but by immersion in spirits of wine the mem- branous portion is brought to the colour of ground glass, and may then be studied very advantageously. The membrane, though extremely delicate, is generally strong enough to permit the whole vitreous body to'be suspended in the air by a thread passed through it, and it may also be momentarily held up with a pair of forceps. 424 NERVOUS SYSTEM. The Tunica Hyaloidea may be traced as a complete capsule, forming the periphery of the vitreous humour; and from the internal face of this capsule there proceeds a great number of partitions dividing the whole cavity into cells of various mag- nitudes and forms. Some anatomists, who have frozen the eye, and then picked out the pieces of ice from the cells, have got the idea of their being all cuneiform, and of their edges pointing forwards. Our preparations in the anatomical cabinet are per- fectly satisfactory in exhibiting the existence of an arrange- ment of cells, but do not manifest a regular cuneiform shape in them. When the capsule of the tunica hyaloidea has got to the dis- tance of two lines, or thereabouts, from the circumference of the lens, it divides into two laminae, which reunite at the cir- cumference of the lens. They then divide again, and one goes before the capsule of the lens, and the other behind it. The space between the two layers, around the circumference of the lens, is the canal of Petit, and is that part of the tunica hya- loidea which is impressed by'the ciliary striae and ridges of the choroides. At intervals, passing in a radiated manner from the exterior to the interior circumference of the canal, there is a sort of shortening or constriction of it, producing partial septa in its cavity; so that when the canal is inflated, it seems to consist of a series of small cells, arranged circularly. The cells of the colon will give some idea of this arrangement, though they are produced in an entirely different manner. The fluid part of the vitreous humour, by analysis, gives out 98.40 water, .16 albumen, and the remainder is saline. In con- sequence of the very small quantity of albumen in it, neither acids nor heat coagulate it to a striking degree. The vitreous humour is supplied with a branch from the cen- tral artery of the retina. This branch does not convey red blood, but only serum, except in the foetal eye. It may be in- jected, at almost any age, with size, coloured with vermilion; but is then, of course, put very much on the stretch. It has been well described by Zinn. It penetrates the vitreous hu- mour near the optic nerve, and is disseminated by very fine branches on the periphery, and on the internal cellular struc- ture of the tunica hyaloidea. M. J. Cloquet has described par- THE BALL OP THE EYE. 425 ticularly one branch, which, running through the centre of the vitreous humour, in an appropriate canal, is spent by small ra- mifications upon the posterior part of the capsule of the lens. Some anatomists* speak of a fluid between the tunica hyaloi- dea and the retina: when it does exist, it in all probability is the fluid of the vitreous humour, which has strained through the tunica hyaloidea after death. The Lens (Lens Crystallina) or the Crystalline Humour, as it is very generally called, is placed immediately behind the pupil, in a depression on the front of the vitreous humour. Its shape is that of a doubly convex lens, of which the posterior convexity is greatest, being the section of a sphere whose dia- meter is from four to five lines, while the anterior convexity is in the proportion of a sphere of from six to nine lines. The usual breadth of the lens is about three and a half lines. It, however, varies its shape in a remarkable degree at the differ- ent periods of life; immediately after birth it is spheroidal, in about six years afterwards its lenticular shape is well marked, and, subsequently, it becomes more flat and thin. The Tens naturally is perfectly transparent. In the greater part of its thickness it has the consistence of half dissolved glue, but its centre is much more solid; this change, however, is ef- fected successively. When it is subjected to the mineral acids, to heat, to alcohol, and several other agents, it becomes much more solid throughout; it may then be separated, like an onion, into a series of concentric lamellae, subdivisible into longitu- dinal fibres. Besides these, there are fibres more or less ob- lique which hold the lamellae together. These arrangements prevail from the centre to the circumference of the lens; and between its laminae there is a diaphanous humour resembling that between it and its capsule.t The lens is invested by a capsule which is a complete sac, having exactly its shape, but separated from it, to a very in- considerable extent, by the transparent humour just alluded to called the Liquor Morgagni. The capsule is covered in front by a layer of the tunica hyaloidea adhering very closely * Bichat, Anat. Descrip. ■J- J. F. Meckel. 426 NERVOUS SYSTEM. to it, but which, in one instance, I was enabled to peel off par- tially in the eye of a sheep, from one sicbe to the other. The capsule is covered, in like manner, on its posterior face by the tunica hyaloidea; but the two may be separated there more ea- sily, according to the observations of Bichat. Some of the most distinguished continental anatomists are decidedly in fa- vour of the capsule of the crystalline being a complete bag; but it is rather unsettled whether the exterior margin of the capsule bounds the lesser circumference of the canal of Petit, or whether the two layers of the tunica hyaloidea unite previously at the circumference of the capsule. The latter seems to be the opi- nion of M. J. Cloquet. Dr. Physick, in some cases of mem- branous cataract, has succeeded in drawing out the capsule en- tire, so as to exhibit its whole extent when floated in water. The capsule in front of the lens is much thicker than the tu- nica hyaloidea, and its difference of character from the latter appears to me to be very strongly marked. For, notwithstand- ing its immersion in spirits of wine, it retains its transparency; it is hard and elastic, and when clipped with the scissors, gives nearly the same sensation as the thin paring of a finger nail would; or, as has been observed by Haller, it, in this "respect, resembles the cornea. The analogy with the cornea ceases, however, at this point: for the cornea has always so much albu- minous matter in it as to be rendered turbid when it is immersed in alcohol. The posterior section of the capsule of the lens, is not so well marked either by its thickness or specific characters as the anterior, yet our preparations in the University demon- strate its existence equally as conclusively. It is more assimi- lated to the nature of the tunica hyaloidea. In the injected fcetal eye, the artery of the tunica hyaloidea which comes from the central one of the retina, is seen to fur- nish several minute ramifications to the posterior face of the lenticular capsule; some of its branches also go to the front of the capsule, but the latter part is furnished principally by arte- rioles from the ciliary body of the choroides. The two sets of arteries anastomose with each other; some of the latter are also spent upon the membrana pupillaris. The point is yet doubtful whether any of these arteries pene- trate into the body itself of the crystalline humour. Ruysch, THE BALL OF THE EYE. 427 Albinus, and Haller, assert the fact of their having seen and in- jected them in the tiuman species and in animals, and J. F. Meckel admits their testimony. Yet there are not many ana- tomists who can corroborate it by their personal observations. It is sufficiently reasonable to admit it; for without, we cannot conveniently account for the growth and nutrition of the lens, as well as the morbid changes which occur in it. It should be observed that if this vascular connexion do exist, it is a very weak one: for the lens seems to be simply surrounded by its capsule without adhering to it. Some veins which discharge into the veins of the choroid coat, have been observed by Walter* on the posterior part of the capsule. It should be continually borne in mind that nei- ther the arteries nor veins of the healthy crystalline, nor of its capsule convey red blood: in which respect they correspond with the hyaloidea; for if this were the case, vision would be very much disordered by it. It may be that the moats or speck seen in ophthalmia arise from the grosser particles of the blood, getting into these serous vessels by the dilatation of the latter. The Lens and its Capsule are devoid of nerves, at least none have been as yet traced into them. The Aqueous Humour (Humor Aquosus) occupies the space which is between the anterior face of the crystalline capsule, and the posterior face of the cornea. This space is unequally divided by the iris into two chambers, of which the anterior is in front of the latter membrane, and the posterior behind it. In consequence of the convexity of the lens, the posterior cham- ber has but very little depth just behind the pupil; but its space is augmented at the circumference of the crystalline, so as to leave room for the floating of the ciliary processes and for the motions of the iris. The posterior chamber is, therefore, a circular vacuity; the centre of which, from the projection of the centre of the crystalline, has scarcely any appreciable depth. The anterior chamber, in its shape resembles the segment of a sphere: its depth depends essentially on the size and the projec- tion of the cornea. * De Oculis. Berlin, 1778. 428 NERVOUS SYSTEM. The aqueous humour is perfectly transparent, and almost as fluid as water. The analysis of Berzeliu% exhibits 98 parts of water, 1 of hydrochlorate and lactate of lime, .75 of some ani- mal matter soluble in water, and a very small quantity of albu- men. From the latter circumstance it will be understood how this fluid refuses to coagulate on the addition of alcohol or of mineral acids to it, and is only rendered in a very slight de- gree turbid by them. The rapidity of the exhalation of this fluid is remarkable; when the whole of it is lost in the opera- tion for cataract, it is regenerated in from twenty-four to thirty- six hours. Its source has been sought for in supposititious canals and glands, but the more probable opinion is, that it may come from any or all of the exhalent arteries of the chambers of the eye. Like the other two humours of the Eye, the aqueous is fur- nished with a capsule, but whether it is complete or not is yet undetermined. By immersing the eye in hot water, or in al- cohol, this capsule may be readily detected on the posterior face of the cornea, and to the greater circumference of the iris; it may even be traced for some distance on the front surface of the latter. Some of the French anatomists, as Demours,* De- scemet, and J. Cloquet, have asserted that it continued also through the pupil to line the posterior chamber. An opinion like this, from the extreme tenuity of the part, must be rather the result of conjecture than of accurate observation; it has, therefore, never found its way with full force into the writings of anatomists. The condition of the pigmentum nigrum on the posterior face of the iris, and on the ciliary processes, would seem to be an objection to the existence of this capsule in the posterior chamber of the eye. But if it really does exist there, as is pretended by M. Portal, who supposes it to be derived from the tunica hyaloidea, its structure is incomparably more delicate than that part on the cornea, and, indeed, is merely glutinous. The Chambers of the Eye, till the seventh month of fcetal existence, and sometimes later, are perfectly separated from each other by the Membrana Pupillaris, called so from its po- • Demours, Lettre, 1767. THE BALL OP THE EYE. 429 sition in the pupil of the iris. It was discovered in 1740, by Wachendorf, and is sometimes called after his name. It is a thin, delicate, and transparent membrane, which is stretched across the pupil from its circular margin, and may, by its co- lour, be readily distinguished from the iris, when it has been made somewhat turbid by alcohol. The Membrana Pupillaris consists, according to M. J. Clo- quet,* of two laminae placed back to back, of which the fore- most is a continuation of the membrane which lines the ante- rior chamber of the eye, and the hindmost of that which lines the posterior chamber. According to this, it may be noted that each chamber has its distinct capsule. This membrane is very vascular; some of its arteries are those which subsequently form the internal arterial circle of the iris, and they radiate from the circumference to the centre of the membrane; others come directly from the long ciliary arteries, and others again from the arteries of the crystalline capsule. These several vessels are found principally on its posterior face. Its veins have not not been observed. This membrane first shows itself about the third month of foetal existence, and is most perfect at the seventh; from the latter period it begins to decline, by disappearing from the cen- tre to the circumference. At the ninth month it consists only in a few loose flocculent masses adhering to the pupil. M. J. Cloquet has ascertained that its vessels do not participate in its destruction, but that the arches which they form are retracted to the margin of the pupil, and there form the lesser arterial circle of the iris. From the observations of Drs. Jacob and Tiedemann, it appears that traces of the membrana pupillaris exist for ten or fifteen days after birth. The latter, in one case, injected its vessels in a foetus at full term.t * Journal Universelle des Sc. Med. Paris, 1818. Mem. sur la Memb. PupilL Paris, 1818. X Am. Med. Jour. vol. i. p. 192. Vol. II.—55 430 NERVOUS SYSTEM. CHAPTER III. OF THE EAR. The ear, the organ of hearing, is placed principally within the petrous portion of the temporal bone, and consists in the Ex- ternal Ear, the Tympanum, and the Labyrinth. SECT. I.--OF THE EXTERNAL EAR. The position of this portion of the organ is familiar to every one. It is useful in collecting the rays of sound, and in convey- ing them to the more internal parts. It is formed by the struc- ture, exterior to the petrous bone, called, in common language, the Ear; and by a bony canal which leads internally to the tym- panum. The basis of the first portion is cartilaginous, on which circumstance it depends for the permanency of its shape. The ear, of common language, is divided into two parts, Pin- na* and Lobus: the former is the most extensive, as it compre- hends all the cartilaginous portion: the latter is attached to the inferior margin of the former, and, having no cartilage in its composition, is soft and pendulous. In the centre of the external ear is a deep depression called the Concha; in the bottom of it is the orifice of the canal lead- ing to the tympanum, and called Meatus Auditorius Externus. The circumference of the pinna is convoluted into a scroll called the Helix, and commences just above the meatus by a ridge. This ridge divides the concha into two unequal cavities, of which the lower is the larger. The scroll becomes gradually less pro- minent, till it terminates at the posterior inferior part of the pin- na, in the lobus, The Antihelix is the slightly curved and vertical eminence in * From some resemblance to a certain shell fish. THE EXTERNAL EAR. 431 the middle of the pinna; its lower part forms the posterior boun- dary of the concha, and its upper part bifurcates into two small ridges, between which there is a depression called the Seapha. Between the antihelix and the posterior half of the helix, is an oblong depression called the Fossa Innominata. The Tragus is a cartilaginous elevation of the pinna placed in front of the concha, and inclining somewhat over it; opposite to it, at the inferior part of the concha, is the Antitragus. The cartilaginous plate upon which the external ear depends for its shape is of a thickness very nearly uniform; of course, the ridges and depressions on its exterior surface have correspond- ing depressions and ridges on the side next to the head. It is interrupted at several places by fissures; for example, there is one of considerable size filled up with ligamentous matter, which separates the upper margin of the tragus from the beginning of the helix: there is another between the lower extremity of the antihelix and the antitragus. In the tragus, there are two and sometimes three small narrow ones, said, by Santorini, to be filled with muscular fibres; but the latter assertion does not cor- respond with the observations of subsequent anatomists, as the matter appears fibrous. The external ear is united to the side of the head by three ligaments. The anterior arises from the root of the zygomatic process above the articulation of the lower jaw, and is inserted into the pointed production of cartilage on the fore part of the helix. The posterior arises from the swell of the temporal bone, which runs into the front margin of the base of the mastoid pro- cess, and is inserted into the convex side of the concha, at the beginning of the meatus auditorius. The superior arises from the temporal aponeurosis, and is inserted into the upper part of the concha. These ligaments lie immediately below the muscles destined to move the ear. The Meatus Auditorius Externus, is, in the adult, an inch in length, reckoning from its external orifice to the membrane of the tympanum, which closes it inwardly. It is about three lines in diameter, is rather oval than cylindrical, and somewhat smaller in the middle than at either of its extremities. It runs inwards, 432 NERVOUS SYSTEM. with a slight inclination forwards; the exterior half is formed by the cartilage of the pinna, and the internal half by the temporal bone: it departs from the horizontal course, in being curved at its middle where the two sections join. This curvature has its convexity upwards, so that when we wish to look to the bottom of the canal, the external ear must be pulled upwards and back- wards. The cartilaginous portion of the meatus auditorius, is formed by a triangular piece springing from the base of the tragus and from the inferior anterior part of the concha. This portion is nearly a tube, but is interrupted above and behind by the in- tervention of a dense fibrous tissue, continuous with, and indeed the same with that which joins the helix and the tragus. The internal margin of the cartilaginous meatus forms a point below; and adheres by ligament very closely to the asperities on the margin of the bony meatus. If there were no fissures in the ex- ternal ear, it would, therefore, be almost immoveable. The skin covering the external ear, is more delicate than in most other parts of the surface of the body. Its sebaceous glands or follicles are very abundant, and in infants secrete free- ly their peculiar fluid. When a slight inflammation occurs, this discharge is frequently purulent without erosion. A duplication of the skin, containing a delicate granulated adeps with some fibrous matter, constitutes the lobe of the ear. The skin, after lining the concha, descends into the meatus auditorius, and lines it also as well as the external face of the membrane of the tympanum. It adheres moderately to the cartilaginous part of the tube, and more tenaciously to its fibrous portions: between it and the latter, are found many small reddish bodies, generally oval, the Glandulae Ceruminosae,* from which proceeds the earwax. The skin is extremely thin in the bony meatus, adheres closely to its periosteum, and is highly sensible: where it forms the exterior layer of the membrane of the tym- panum, it may be detached from the latter with the slightest force, and seems to be converted almost entirely into cuticle. * Duverney, CEuvres Anatomiqnes. THE EXTERNAL EAR. 433 A slight maceration or incipient putrefaction frequently enables one to draw the cuticle out entire from the meatus, so that it looks in shape like the finger of a small glove. The dermoid lining of the meatus is studded with fine hairs, which serve to keep out small bodies that may be floating in the air. A considerable number of small pores are also seen in it, which are the orifices of the ducts of the ceruminous glands. The discharge of the latter, when first secreted, is thin and white: by evaporation, it becomes thick and yellow, and by ac- cumulating obstructs the passage. < There are several small muscles situated on the external ear, which are for the most part so feebly developed that they cannot always be found, and when they do exist they seem more like the rudiments of what is well marked in animals, than intended for a special purpose in the human body. 1. The Helicis Major is an oblong fasciculus, situated on the front of the helix. By its lower end it is attached to the point of cartilage on the front of the helix, and its other extremity ex- tends to the top of the latter. 2. The Helicis- Minor is a small square fasciculus, also on the front of the helix, between the folded margin of the latter and the inferior half of the helicis major. 3. The Tragicus is a square fasciculus, on the front surface of the tragus, near its margin: its upper extremity sometimes runs into the helicis major. 4. The Antitragicus is a small oblong fasciculus, which arises from the upper extremity of the antitragus, and going upwards it is inserted into the inferior extremity of the anti- helix. 5. The Transversus Auriculae is on the internal surface of the pinna. It arises from the prominence of the concha, and is in- serted into the hollow dorsum of the antihelix. 434 NERVOUS SYSTEM. There are some other muscles which may be uniformly found and are intended to move the external ear upon the side of the head, though from the want of exercise there are very few in- dividuals capable of making them contract. They are as fol- low:— 1. The Attollens Auriculae is placed on the side of the head beneath the integuments: it is a broad, thin, and somewhat tri- angular muscle, which arises from the inferior margin of the tendon of the occipito-frontalis, and from the temporal aponeu- rosis. It becomes narrower in its descent, and is inserted ten- dinous into the upper end of the pinna by the elevation corre- sponding with the scapha. Its name implies its action to be that of raising the pinna. 2. The Retrahens Auriculae, consists in two or three oblong fasciculi, placed parallel, and one above the other. It arises from the mastoid portion of the temporal bone, above the mas- toid process, and is inserted tendinous into the convex side of the concha near the meatus auditorius. It draws the pinna backwards. 3. The Anterior Auriculae is a small quadrangular slip, just above the root of the zygomatic process. It arises from the temporal fascia, and is inserted tendinous into the fore part of the helix just above its beginning. It draws the pinna forwards and upwards. SECT. II.—OF THE TYMPANUM. The Tympanum is the middle portion of the organ of hear- ing, being interposed between the meatus auditorius and the labyrinth. Its depth is about three lines, its antero-posterior di- ameter about six, and its vertical diameter rather more, though from the general inequality of the cavity, and its communication with adjoining cavities, it is not easy to fix upon very precise measurements. THE TYMPANUM. 435 The Membrana. Tympani, is a complete membranous septum, interposed between the meatus externus and the tympanum. It is placed very obliquely, so that its upper edge inclines outwards, and its under edge inwards; the latter, therefore, forms a very acute entering angle with the inferior part or floor of the meatus, and gives to that portion of the meatus an additional length, which renders it difficult to see to its bottom. The membrane of the tympanum is nearly circular, and has its circumference adhering very closely to the external orifice of the tympanum. It is slightly tense, and has its middle drawn inwards by being attached to the handle of the malleus. The membrana tympani consists of four laminae; the two ex- terior of which, being the cuticle and the cutis vera, which fine the meatus auditorius, are easily detached, as mentioned before, and seem scarcely to adhere to the layer below. The third layer is the proper membrane, and is distinguished by its dryness and by its transparency. Sir Everard Home was enabled to de- tect radiated muscular fibres, forming it in the elephant.* In the human subject, its fibrous character is best seen on its inter- nal face, but the radiated arrangement is not so distinct. Cal- dani considers it as formed by filaments, decussating each other at right angles, and intermixed with blood vessels.t The inter- nal layer is a continuation of the lining membrane of the tym- panum; it is separated with some difficulty, owing to its tenuity. The proper membrane of the tympanum, when successfully injected, exhibits a high degree of vascularity ;J though, in its natural state, but very few red blood vessels are seen in it. The floor of the tympanum, or the side next to the labyrinth, presents an unequal surface. In its middle is a well marked rising, the Promontory, (Promontorium,) formed by one end of the labyrinth. Just above the superior margin of this promi- nence, near its centre, is an oval opening, called, from its sliape, Foramen Ovale, or Fenestra Ovalis; having its long diameter horizontal, its superior margin rounded or concave, and its infe- rior straight. At the posterior inferior part of the promontory * Philosophical Transactions, for 1800. London. f Plate XCVIII. Anat. $ Ruyschii, Epist. Anat. Probl. viii. Anatomical Museum. 436 NERVOUS SYSTEM. is another opening, which, though somewhat triangular, is called the Foramen Rotundum, or Fenestra Rotunda, and in the dried bone leads to the cochlea, but is naturally stopped by the lining membrane of the tympanum. According to M. Ribes, this membranous plug has also two other layers, an internal one, the continuation of what lines the cochlea, and a middle ope, which is peculiar. In these respects, there is a correspondence with the membrana tympani. The Eminentia Pyramidalis is a small conical eminence pro- jecting from the posterior part of the tympanum, on a line with the fenestra ovalis. It is hollow, contains a muscle, and com- municates at the other end with the Canal of Fallopius. Lower down, and more externally, there is a small orifice, (Aperlura Chorda,) through which the nerve called Chorda Tympani passes. The Mastoid Portion of the Temporal bone, in the adult, abounds in large cells or sinuses, which communicate freely with one another. They are distinct from the diploic structure of the bone, as they contain no meditullium, and are lined by a continuation of the internal membrane of the tympanum, which is extremely thin upon them. The orifice of communication be- tween these cells and the tympanum, is placed at the superior posterior part of the latter: it is rough and irregular, and par- tially occupied by the short leg of the incus. Just in front of this opening, the cavity of the tympanum is extended vertically, for the purpose of accommodating the body of the malleus and of the incus, whereby they are in a great degree concealed, unless the corresponding margin of the tympanum be cut away. At the fore part of the tympanum is the Eustachian Tube, which runs for six or eight lines in the substance of the petrous bone, near its exterior margin; and then terminates in a carti- laginous and membranous portion, which communicates with the pharynx at the posterior naris. The latter extremity of the Eustachian Tube is placed on a line with the posterior end of the inferior spongy bone. Its orifice is rounded or oval, is large enough to admit the tip of the little finger, and reposes against THE TYMPANUM. 437 the side of the internal pterygoid process of the sphenoid bone.- Though almost within the precincts of the posterior naris, this orifice is to be considered as opening into the pharynx. This canal, in its whole length, measures nearly two inches, and, with the exception of the portion in the petrous bone, is cartilaginous and membranous. The cartilage is a single, thick, triangular plate, flat, and adhering by one of its edges to the pterygoid process. The under part of the tube is membranous, thin, and affords attachment to some of the muscles of the soft palate. Its course is nearly horizontally, backward and out- ward. It is lined in its whole extent, by a very fine mucous mem- brane continuous with that of the pharynx and of the tympanum. This membrane is thickened at its anterior extremity by the mucous glands beneath it, which assist in giving the marked elevation to its orifice. The canal diminishes as it goes back- ward, so as to receive with difficulty a small probe. Parallel with the bony part of this canal, but above it, and se- parated by a very thin partition of bone, is another canal which lodges a muscle of the malleus. On the outer side of the Eusta- chian tube is the glenoid foramen, by which, in the dried bone, the tympanum communicates with the glenoid cavity; in the re- cent state the foramen receives the long process of the malleus and its muscle, and transmits the chorda tympani. There are four bones in the tympanum, which, being succes- sively articulated with each other, form a chain, one end of which is fastened to the membrana tympani, and the other end rests upon the foramen ovale. They are the Malleus; the Incus; the Orbiculare; and the Stapes. ft The Malleus forms the fore part of the chain, and is placed almost vertically. Its superior extremity is the head, which is rounded, with the exception of the posterior face, where a small concavo-convex surface is observable, for its articulation with the incus. Its lower extremity is long and tapering, inclines in- wardly, terminates by a little knob, and forms an angle with the part above; this portion is the manubrium, and adheres its whole Vol. II.—56 438 NERVOUS SYSTEMS length to the membrana tympani, commencing at the superior margin of the latter, and insinuating itself between the internal and the proper layer, as far as the centre of the membrane. It is this adhesion with the inclination inwards of the manubrium, that causes the membrane to be depressed in its centre. Between the head and the manubrium is a short portion called the neck. From the superior external extremity of the manu- brium there proceeds outwardly the short process, (Processus Brevis;) and from the front of the neck, there proceeds the long and very delicate process, concave externally and convex inter- nally, which is insinuated into the glenoid foramen, and is the Processus Longus, or Gracilis. The Incus is behind the malleus, and is also upright. It con- sists in a body and two branches, Which diverge very conside- rably, and has a general resemblance to a molar tooth. The body presents, on its fore part, a deep concavity, which articu- lates with the convex head of the malleus. The branch which arises from the back part of the body is horizontal, looks into the orifice of the mastoid cells, and is much shorter than the other. The inferior branch is long, upright, tapering, and near- ly parallel with the manubrium of the malleus, but somewhat within it The Orbicularis a very small flattened sphere of bone, which articulates with the lower end of the long process of the incus, and in adult life is most generally fused into it, so as to lose its distinctive character: the latter change sometimes occurs even in early infancy. The Stapes is the last of the chain. It resembles very strong- ly the common stirrup iron, from whence its name, and is placed horizontally at right angles to the incus, being separated from the extremity of the long process of the latter by the os orbicu- lare, and being directed inwards to the foramen ovale. It is composed of a head, two crura, and a base. The head is oblong and flattened: it has a slight depression where it joins the orbiculare. The crura are slightly curved, with the concavities towards each other: the anterior is some- THE TYMPANUM. 4^9 what straighter than the posterior, and is also shorter. They are both excavated, longitudinally, on their concave surfaces, and between them is stretched a process of the lining membrane of the tympanum. The base is precisely adapted to the fenestra ovalis, and is connected to it by the lining membrane of the tympanum, but not so closely as to prevent it from executing slight vibratory movements. Between the malleus and the incus there is a moveable arti- culation with a synovial membrane, but the other joints of the chain are simply ligamentous. This chain of bones is moved by several muscles, which in- fluence the degree of tension of the membrana tympani. 1. The Laxator Tympani arises from the posterior end of the spinous process of the sphenoid bone, and passing behind the articulation of the lower jaw into the glenoid foramen, is in- serted, tendinous, along the processus gracilis of the malleus. It draws the malleus forwards and outwards, so as to relax the membrana tympani. 2. The Tensor Tympani is placed in the canal just above the Eustachian tube. It arises from the posterior extremity of the cartilaginous portion of the latter, and having got into the tym- panum, is changed into a small tendon, which, going outwardly, is inserted into the neck of the malleus, just below its processus gracilis. It draws the malleus inwardly; consequently makes tense the membrana tympani, and drives the stapes into the fenestra ovalis.. 3. The Stapedius arises from the bottom of the cavity in the pyramid, and terminates in a small round tendon, which, going through the apex of the latter, is inserted into the head of the stapes. It draws the stapes backwards, and perhaps fixes it more firmly by its contractions. 4. There is a fourth muscle mentioned by anatomists, the ex- 440 NERVOUS SYSTEM. istence of which is more equivocal; it is called the Laxator Tympani Minor. It arises from the superior margin of the ori- fice of the tympanum, and is inserted into the processus brevis of the malleus. It is by some considered only as a ligament, to which opinion I am inclined. Of the Lining Membrane of the Tympanum. This membrane is a continuation of the lining membrane of the pharynx, being introduced into the tympanum through the Eustachian tube. It covers completely the surface of the tym- panum, and is reflected over its little bones so as to give them a covering also: in addition to which, it lines such of the mastoid cells as communicate with the tympanum. This membrane is extremely delicate: on its, surface, adja- cent to the bones, it is somewhat fibrous, and thereby resembles periosteum; but the other surface has the characters of the mu- cous membranes generally, in the nature of its secretion, and in its vascularity, which is very strongly marked in inflammations, and by fine injections. Bichat mentions, that in certain catar- rhal affections its mucous secretion is so abundant as to fill the whole cavity of the tympanum, and that without ulceration. Sometimes, in such cases, the membrane of the tympanum is ruptured, and the discharge finds its way out through the mea- tus externus, presenting itself under a purulent form, as if an abscess had formed in the ear. SECT. HI.--OF THE LABYRINTH.* The Labyrinth (Labyrinthus) is placed on the inner side of the tympanum, in the thickness of the petrous bone. Its ex- terior parietes are bone, but internally there is a membranous structure, having, in many respects, the same shape. It is got at with great difficulty in the adult, owing to the compactness of the petrous bone which envelops it; but in the foetus of the full period, where it is almost as large as in the adult, the sur- rounding bone is of a softer and more spongy texture, and may be pared away with a pen-knife without much trouble. In the * Antonio Scarpa, Disquisit. de Auditu et Olfacto. THE LABYRINTH. 441 latter case, the parietes of the bony labyrinth remain about the thickness of an egg-shell, and have very much the same de- gree of consistency and strength. The bony labyrinth consists of three portions: the Vestibu- lum, the Semicircular Canals, and the Cochlea. The Vestibulum is the cavity to which the foramen ovale leads; it, with the cochlea, occasions the protuberance into the tympanum, known as the promontory. It is an irregular round- ed excavation, the surface of which is impressed by its contents; thus, at the superior posterior and external part, next to the semicircular canals, there is a superficial Fossa, called, from its shape, Semi-Elliptica, and at its anterior and inferior part, nearer the cochlea, another, called Fossa Hemi-spherica. These fossae are marked off from each other by a ridge of bone, at the lower end of which there is a third fossa between the other two, called, by Soemmering, Cavitas Sulciformis. There are seven orifices belonging to the vestibulum besides the foramen ovale; five at its posterior part leading into the se- micircular canals; one anteriorly leading into the upper scala of the cochlea: and the last placed in its internal paries is the aque- duct of the vestibule. In addition to these orifices, the parietes of this cavity are cribriform in the fossa semi-elliptica and near the foramen rotundum.* The Semicircular Canals (Canales Semicirculares) are at the posterior extremity of the vestibulum. They are three in num- ber, and are named from their relative situation, Superior or An- terior, Posterior or Inferior, and External. Each one forms rather more than the half of a semicircle, and has its cavity,. about half a line in diameter: their orifices are somewhat dilated beyond this measurement. The apparent thickness of their pa- rietes is greater in the adult than in the infant. The Superior Canal runs from without inwards and backwards. Its anterior orifice is above the fenestra ovalis, and is enlarged into an ampulla or elliptical cavity. At its posterior extremity, * Ant. Scarpa, loc. cit. 442 NERVOUS SYSTEM. it joins the upper extremity of the inferior canal, so that a com- mon trunk is thus formed, the orifice of which is at the internal posterior part of the vestibulum, and is dilated into the shape of a funnel.* The Posterior or Inferior Canal is nearly vertical; has its concavity in front, and its convexity behind, and joins, as just remarked, with the superior; its inferior orifice, which is near the foramen rotundum, is also enlarged into an ampulla or ellip- tical eavity. It is the longest of the three canals, and has its branches nearer together. The External Canal is nearly horizontal, and is placed in the space left by the divergence of the other two. It is the shortest and the largest of the three. Its exterior orifice is also enlarged into an ampulla or elliptical cavity, and is just behind the fora- men ovale, or below the ampulla of the upper canal; the inter- nal orifice is below the common opening of the other two ca- nals. It is the union of the superior and of the posterior canals at one of their extremities, which reduces the number of openings into the vestibulum, from the semicircular canals to five instead of six. The Cochlea forms the fore part of the labyrinth, and resem- bles very strongly the shell of the common snail. Its base is the bottom of the meatus auditorius internus, and its apex is di- rected towards the cavity of the tympanum, so that the axis of the cochlea is turned downwards and outwards. It consists in a conoidal tube wound spirally twice and a half around a co- lumn of bone termed the Modiolus. The tube then of course diminishes in size from the base to the apex of the cochlea. " This conical tube is divided in its length by a plate called Lamina Spiralis. Of the two compartments thus formed, one is above the other. The inferior is the larger, and communi- cates at its base, through the foramen rotundum, with the tym- panum; it is, therefore, called Scala Tympani. The other com- partment communicates at its base with the vestibulum, and is, therefore, called Scala Vestibuli. ' Scarpa, loc. cit. THE LABYRINTH, 443 The Modiolus is of a conical shape and cribriform: one canal, larger than the others, runs from its base to its sum- mit. This canal is surrounded by many others, which dimi- nish successively as they advance towards the apex, and ter- minate in orifices upon the lamina spiralis. This cribriform arrangement of the modiolus is the Tractus Spiralis Foramina^ losus. The base of the modiolus is towards the meatus audi- torius internus, and its point does not go to the apex of the cochlea, but stops short of it, and is expanded into a cavity called the infundibulum, the base of which is towards the apex of the cochlea. That portion of the apex of the cochlea which covers over the.infundibulum, is the Cupola. It was just mentioned that the lamina spiralis divides the cochlea into two tubes; the septum thus formed, does not, how- ever, run their whole length, for it ceases in the infundibulum by a small crooked process of bone, called the Hamulus Coch- leae. The lamina, when examined by strong glasses, is seen to consist of four distinct structures called its Zones. 1. The Zona Ossea is next to the modiolus, and is composed of two bony laminae, with an intermediate diploic structure, in which are the canals for transmitting the filaments of the portio mollis or auditory nerve. 2. The Zona Coriacea, on the outer side of this, the structure of which is cartilaginous. 3. The Zona Vesicularis, said to contain in its cells a pellucid fluid. 4. The Zona Membranacea, which is probably only the lining mem- brane of the cochlea, and completes the lamina spiralis on its edge next to the periphery of the cochlea. Some very re- spectable anatomists pass over this minute distinction in the structure of the septum, and merely divide it into Zona Ossea, and into Zona Mollis. Of the Membranous Labyrinth. The whole internal face of the bony Labyrinth is lined by a very delicate and vascular membrane, which is more distinct during the early periods of intra uterine life. Besides this, there is a membranous labyrinth, consisting in three semicir- cular canals, nearly filling up the cavities, and having the same shape and general arrangement of the bony canals; and in two sacs contained in the vestibule. 444 NERVOUS SYSTEM. The Semicircular Membranous Canals have also at their ends the elliptical enlargements called ampullae; they termi- nate by both extremities in the sac of the superior part of the vestibule. This sac is generally called, from its shape, Sac- culus Ellipticus; and by Scarpa, from its function, the Alveils Communis. In front of the Sacculus Ellipticus, nearer the cochlea, and opposite the foramen ovale, is the Sacculus Sphe- ricus; it is a complete bag, having no communication with the other, or with the membranous canals. Both of the sacs adhere to the vestibulum at their posterior parietes. The sacs of the vestibule and the membranous semicircular canals are filled with a very fluid transparent liquid. Accord- ing to the observations of M. Ribes^ it is not necessary to the function of hearing that this fluid should be so abundant as to distend the membranous labyrinth, inasmuch as in his dissec- tions he met with individuals in whom the latter was only half filled, and yet they had heard very well. He also met with similar cases in which the fluid was abundant in the vestibulum, but deficient in the canals, and the reverse. Corresponding observations have been made by M. Brugnone, of Turin,* where he had adopted the precaution of previously freezing the bone, so that none of the fluid could be said to have been lost by ac- cident. From the frequency with which this deficiency was observed, his opinion seems to be well founded, that it is the most natural state of the labyrinth. The parietes of the membranous labyrinth are very thin and transparent; there is a very loose cellular tissue between them and the bone, and they are susceptible of being highly coloured by injection. A fluid of the same character with the preceding also fills the scalae of the cochlea, and extends itself into the bony vestibu- lum and the bony semicircular canals upon the outer surface of the membranous labyrinth. * Mem. de Turin, 1805—1808. LABYRINTH. 445 Of the Aqueducts of the Ear. T'he Aqueducts (Aquaeductus) of Cotunnius, as they are called, are two small canals which go through the petrous bone from the labyrinth. There is one for the vestibule, and ano- ther for the cochlea. The Aqueduct of the Vestibulum, commences in the latter cavity, somewhat in advance of the common orifice of the two semicircular canals; it goes inwards and opens on the posterior face of the petrous bone, behind the meatus internus. It en- larges gradually in its course, which causes it to have somewhat of a triangular shape, and it is lined by a continuation of the dura mater. It is about four lines long. The Aqueduct of the Cochlea commences in the Scala Tym- pani, near the foramen rotundum, and, enlarging in its course, terminates on the under surface of the petrous bone, in the in- ternal margin of the jugular fossa, at the root of the little spine which separates the eighth pair of nerves from the jugu- lar vein. The anatomist* from whom these canals were named, and who first described them, was under an impression that the fluid of the labyrinth always filled it completely; and that without a sort of waste gate for it on an occasion, the vibration of the stapes would be prevented from putting it in motion, conse- quently, hearing must cease. These canals, the existence of which is sufficiently obvious in many subjects, were, therefore, considered by him as the desired avenues for the discharge of the superabundant fluid, and his theory and descriptions were very generally adopted. Of late years, the investigation of this subject has been renewed by MM. Ribes and Brugnone, and their observations are considered by the French anatomists, to have proved conclusively, the error into which Cotunnius and others have fallen. In regard to the aqueduct of the vestibule, M. Ribes has found it only in three instances emptying into the vestibule; for most • Dominici Cotunnii, Anat. Dissert, de Aquaeduct. Naples, 1761. Vol. II.—57 446 NERVOUS SYSTEM. commonly it leads, after a course somewhat tortuous, into the spongy structure of the petrous bone, at the posterior part of the vestibule, and smaller canals diverge from it in different di- rections. In the cases where it was connected with the laby- rinth, it was so by several orifices leading into the vestibule, and into the posterior semicircular canal. He has not found this canal in the foetus nor till some time after birth, and from his injections he believes that, in all cases, it and its branches are only intended to convey blood vessels throughout the pe- trous bone and to the labyrinth. In regard to the supposed aqueduct of the cochlea, M. Ribes has also found it diverging into collateral branches, and occupied by blood vessels, which are distributed to the spongy structure of the petrous bone, and to the tympanum. In my own researches on this point, on the dried bones, the canals, as described by Cotunnius, were closed at the labyrinth, in the case of subjects advanced in life; but, in the middle aged, and in infantile specimens, 1 have been more successful in tracing them fairly into the labyrinth, and have the prepara- tions in the Wistar Museum. At the same time, I think it much more probable that they only contained blood vessels, and that Cotunnius was in error. Besides these vascular ca- nals, M. Ribes has described some others having the same use. "SECT. IV.--OF THE NERVES OP THE ORGANS OP HEARING. The Nerves which pass through the petrous bone, and are either wholly or partially spent upon the organ of hearing, come from three sources. 1. The Auditory Nerve; 2. The Portio Dura; 3. The Trigeminus, or Fifth Pair. The Meatus Auditorius Internus conducts the two first, and has its bottom divided by a ridge into two fossae, of which the upper one is the smaller. This bottom, it has been observed cor-> responds with the base of the modiolus, and is cribriform. One foramen, larger than any of the others, and in the superior fossa, transmits the portio dura or facial nerve: all the others are oc- cupied by the filaments of the auditory nerve. NERVES OP THE ORGANS OF HEARING. 447 1. The Auditory Nerve divides at the bottom of the meatus into fasciculi of filaments; one of which penetrates into the ves- tibulum through the foramina behind that for the portio dura, and is distributed upon the sacculus ellipticus, and upon the am- pulla of the superior and of the exterior membranous canal; other filaments get to the sacculus sphericus; and a third fasci- culus of filaments is distributed to the ampulla of the posterior membranous canal. These several filaments are said to preserve, when they first penetrate into the bony labyrinth, a fibrous ap- pearance, and are interlaced; they also penetrate the parietes of the membranous labyrinth, and have their extremities bathed in its fluid, in which place they are converted into soft pulp, resem- bling mucus, or the retina. Another very considerable fasciculus of filaments penetrates into the canals of the modiolus, and enters through them into the cavity of the cochlea, along the Zona Ossea, and between its tables; they terminate also by a soft pulp on the internal face of the lining membrane of the cochlea. One of these filaments, conspicuous for its size, goes through the central canal of the modiolus and terminates in the infundibulum.* 2. The Facial Nerve, or Portio Dura, is only connected to the organ of hearing by sending a few filaments to the muscles of the bones of the tympanum. The canal of the petrous bone, through which it passes, is very crooked; beginning at the larger orifice of the meatus internus in its upper fossa, it passes outwards until it nearly reaches the Vidian foramen, on the front of the petrous bone; it then turns very abruptly backwards, form- ing an angle, and is continued in a circuit around the superior and % the posterior parietes of the tympanum, till it terminates in the stylo-mastoid foramen. Its course is marked by a ridge pro- jecting into the tympanum, above the foramen ovale, and pass- ing between the semicircular canals and the cochlea. This canal has been very much misnamed by the calling of it the aqueduct of Fallopius, as its only use is to conduct nerves and blood vessels. It is lined by a delicate fibrous membrane, between which, and * For a knowledge of the minute distribution of the auditory nerve, the pro- fession is signally indebted to the distinguished Scarpa, in his Disquisitiones de Auditu et Olfactu. 44S NERVOUS SYSTEM. its contained parts, there is so little adhesion, that the latter may be drawn out entire. The facial nerve is joined at the Vidian foramen by the Vi- dian nerve, shortly after which it sends a filament to the tensor tympani muscle.* As it passes the base of the pyramid it de- taches another filament, which supplies the stapedius muscle. Shortly after this, it is abandoned by the Vidian nerve, and does not give off any more branches till it escapes from the sty- lo-mastoid foramen, when it sends off a branch, the posterior auricular (Auricularis Posterior?) which is distributed by filaments, some of which run into the mastoid process; other branches mount on the side of this process, to the skin which covers it, and to the occipital muscle: others go to the concha of the ear, being spent upon its skin, upon the posterior auricular muscle, and some of them, penetrating the pinna, are lost upon the in- teguments of the meatus externus. The triink of the fascial then goes to its destination on the face. 4. The Chorda Tympani or Superficial Petrous Nerve, is a branch of the Pterygoid branch of the Trigeminus, and leaves it near the anterior part of the carotid canal of the petrous bone. It, as just mentioned, under the name of Vidian nerve, joins the facial nerve at the angle of the canal of Fallopius, and continues to adhere closely to it, almost to the styloid foramen; it then abandons the facial nerve at a very acute angle, and running upwards and forwards, gets into the cavity of the tympanum, on a level with, but a line or two exterior to the pyramid. It then crosses the tympanum nearly horizontally, between the long crus of the incus and the handle of the malleus, adhering to the latter so as to be affected by its vibrations. At the fore part of the tympanum, it anastomoses with some other filaments of the fifth pair, by which its size is augmented, but it gives no branches to the parts contained in the tympanum. It then is- sues from the latter cavity through the glenoid foramen, and descending a short but somewhat variable distance along the ramus of the lower jaw, terminates by anastomosing at an acute angle with the lingual branch of the trigeminus. * The tensor tympani is also supplied by a nerve from the Third Branch of the Trigeminus. NERVES OF THE ORGAN OF HEARING. 449 To Mr. John Hunter is due the merit of having traced the continuity and identity of the Vidian nerve with the chorda tympani. The continental European anatomists, for the most part, seem ignorant of his observations, and give a very differ- ent account of the matter. Some consider it to arise from the facial at its angle, and to anastomose at the other end with the pterygoid, or the reverse; and they very generally agree in re- garding the chorda tympani as a filament from the facial, just before the latter gets out of the stylo-mastoid foramen. The Vidian Nerve, or Superficial Petrous, also traverses the tympanum in another place. Just below the posterior extre- mity of the Eustachian Canal, there is a small foramen, which leads upwards to the superior surface of the petrous bone, and downwards to a small gutter upon the promontory: this gutter is converted into a canal that opens upon the under surface of the petrous bone, between the carotid canal and the jugular fossa. Through the course indicated, passes a filament from the superficial petrous nerve: this filament is joined by another detached from the sympathetic while in the carotid canal, and the two communicate at the base of the cranium with the gang- lion of the glosso-pharyngeal nerve.* These filaments were discovered by Professor Jacobson of Copenhagen. • Meckel, Man. D'Anat."vol. iii. p. 174. Jacobson, Supplemata Act.Hafn„ vol. v. p. 292. An. 1818. BOOK IX. PART IV. Special Anatomy of the Nerves. CHAPTER I. OF THE NERVES OF THE ENCEPHALON. SECT. I. The course and distribution of the first pair, or the olfactory nerves, have been described fully in the account of the brain and nose. SECT. II.--NERVUS OPTICUS. The Optic Nerve, as mentioned in the account of the basis of the brain, gets into the orbit by the optic foramen, and is there entirely surrounded by the origins of the muscles of the eyeball. It then describes a slight curvature, of which the con- vexity is outwards, and runs forwards for an inch, when it pe- netrates into the ball of the eye, where it gives origin to or ex- pands into the retina. Between the muscles and it, except at their origins, there is a mass of adipose matter. 452 NERVOUS SYSTEM. SECT. III.—NERVUS MOTOR OCULI. The Nervus Motor Oculi, or third pair, having reached from the basis of the brain to the external side of the cavernous si- nus, is placed there within and above the optic nerve and the sixth pair; it then changes its direction, and penetrates through the sphenoidal fissure into the orbit, on the outer side of these nerves, and below them. The motor oculi divides, in the sphenoidal fissure, into two branches, one above the other. The first crosses over the op- tic nerve and the nasal branch of the ophthalmic, having some anastomoses with the latter, and then distributes its filaments upon the rectus superior muscle: some of them also penetrate the latter to get to the levator palpebrae. The second branch is much larger than the first. It passes between the optic nerve and the rectus inferior muscle, and is subdivided into three fasciculi: one for the rectus internus muscle; another for the rectus inferior; and a third, which is the longest and the small- est, for the obliquus inferior muscle. The latter fasciculus, not far from its root, gives off a filament, which, going along the external margin of the optic nerve, runs into the posterior mar- gin of the lenticular or ophthalmie ganglion, and is its short root. The Lenticular Ganglion is situated on the outer side of the optic nerve, in the orbit of the eye, and is about a line in dia- meter, being flattened. Two nerves concur to form it: the branch just alluded to, from the motor oculi, and one from the "ophthalmic branch of the trigeminus. From this ganglion arise the most of the ciliary nerves; which, as stated, are about twen- ty in number, and go to the choroid coat of the eye and to the iris. SECT. IV.--NERVUS TROCHLEARIS. The Nervus Trochlearis, or fourth pair, having got into its canal in the cavernous sinus, as it goes along the internal mar- gin of the ophthalmic nerve, receives there a small filament from NERVUS TRIGEMINUS. 453 it* It then rises a little, and enters the orbit at the internal extremity of the sphenoidal fissure; and, going forwards, next to the periosteum of the upper part of the orbit, it enters into the superior oblique muscle of the eye, near its middle, and is distributed upon it. This nerve augments in volume as it ad- vances towards its destination. SECT. V.--OF THE NERVUS MOTOR EXTERNUS. The Nervus Motor Externus, or sixth pair, having got into the cavernous sinus, is placed there at the external side of the internal carotid artery, and adheres closely to it. It there sends off one or more filaments, which follow the internal carotid artery through its canal, and anastomose in their descent with a branch of the pterygoid nerve: the junction of these two forms the upper end of the great sympathetic nerve, and runs down to the superior cervical ganglion of the sympathetic in two or more filaments generally. The sixth nerve enters the orbit through the sphenoid fissure, and is there closely connected with the nervus motor oculi and the nasal nerve. It penetrates into the substance of the rectus externus muscle, and is entirely distributed upon it; with the exception that sometimes it sends a filament to the ophthalmic ganglion. SECT. VI.--OF THE NERVUS TRIGEMINUS. This nerve, having formed the ganglion of Gasser, (Plexus Gang lifor mis,) on the side of the petrous bone, then divides, as mentioned, into three large trunks, the foremost of which is the Ophthalmic Nerve: the second fasciculus is the Superior Maxillary; and the third the Inferior Maxillary Nerve. The Ophthalmic Nerve, or the first branch of the trigeminus, is smaller than either of the other two branches, and comes from the superior part of the plexus gangliformis. It passes along the external border of the cavernous sinus, and penetrates * Soemmering, Icones Oculi Humani. Vol. II.—58 454 NERVOUS SYSTEM. the orbit through the sphenoidal fissure, on the outer side of, and near the motor oculi. In its whole course it is united to Ihe trochlearis nerve by close cellular membrane, and does not give off any ramifications before it reaches the orbit, with the exception of the filament sent to the trochlearis nerve. While engaged in the sphenoi- dal fissure it divides into three branches; the nasal, the lachry- mal, and the frontal. The Nasal branch of the ophthalmic, is between the other two in size. ( It ascends obliquely above the optic nerve to gain the internal face of the orbit of the eye, and then passes forwards just below the superior oblique muscle, involved in a quantity of adipose matter. Shortly after its origin the nasal nerve de- taches a branch (the ramus ciliaris) which, situated at the ex- ternal margin of the optic nerve, runs into the ophthalmic or lenticular ganglion, and constitutes the long root; it then sends- off one or more filaments, which, without communicating with this ganglion, penetrate into the eyeball, and are amongst the ciliary nerves which have been described. The nasal nerve, continuing to pass forward along the inter- nal paries of the orbit, when it reaches the anterior internal or- bitary foramen, detaches through it the internal nasal or eth- moidal branch, which, thus getting into the cavity of the cra- nium, goes along side of the crista galli, and then passes into the nose through the foremost hole of the cribriform plate. It then descends along the anterior part of the nose, on the outer side of the Schneiderian membrane, and is spent by ramifi- cations upon the contiguous portions of the latter.. Some of its terminating branches reach the tip of the nose and the alae.* The nasal nerve, after this branch is sent off, is frequent- ly called external nasal, or nervus infra-trochlearis. It con- tinues to advance along the under margin of the trochlearis muscle and gets to the trochlea, near which it divides into an upper and an under ramuscle; from them filaments pro- ceed to the upper and under eyelids, to the lachrymal sac, • See Nerves of Nose. NERVUS TRIGEMINUS. 455 the caruncle, the tunica conjunctiva, and the muscles on the root of the nose. These filaments anastomose with the ter- minating branches of the frontal nerve, the facial, and the in- fra-orbitary. According to Dr. G. Trasmondi,* of Rome, two filaments may be traced very distinctly from the external na- sal nerve to the tensor tarsi muscle of the lachrymal sac. They adhere to the muscle by means of cellular structure, and pass on to its bifurcated extremities and to the puncta lachryma- lia. The Frontal Nerve is the largest of the three branches of the ophthalmic. It proceeds forward between the levator pal- pebrae superioris and the contiguous part of the orbit, and in this course is divided into two branches, the internal and the external frontal nerve. The former approaches the trochlea of the upper oblique muscle, and detaches a filament to join with one from the nasal nerve. Other filaments are detached to the upper eyelid, some of which anastomose with filaments from the lachrymal nerve. The internal branch of the frontal then issues from the orbit just by the trochlea, and, in ascend- ing, is lost upon the occipito-frontalis, the corrugator super- cilii, and the orbicularis. The external branch of the frontal issues from the orbit, through the supra-orbitary foramen. It quickly detaches a filament, which goes outwardly to anasto- mose with the facial; the remaining part of the nerve is distri- buted to the occipito-frontalis, to the corrugator supercilii, to the integuments of the forehead, and to the scalp. This dis- tribution, according to Bichat, is best followed by detaching the skin, muscles, and periosteum from the cranium, from be- hind forwards as far as the orbit. The Lachrymal Branch of the ophthalmic nerve goes for- wards along the external side of the orbit near the superior margin of the rectus externus muscle. In this course it sends off a filament through the spheno-maxillary fissure which unites with one from the second branch of the fifth pair; it afterwards • Intorno la scoperta di due nervi del Occhio umano ragguaglio del Dr. Giu- seppe Trasmondi, Professore di Anatomia Practica nel ven. ospidale della Con- solazione. Roma, 1823. 456 NERVOUS SYSTEM. sends off another filament, which, passing through a foramen in the malar bone, anastomoses with a filament of the facial nerve. What remains of the lachrymal nerve is then distri- buted by several filaments upon the lachrymal gland, the upper eyelid, and some of them reach the conjunctiva. Second Branch of the Trigeminus. The Second Branch of the Fifth Pair, (Nervus Maxillaris Superior,) arising from the middle of the plexus gangliformis, or ganglion of Gasser, and also, in part, from the common trunk formed from the anterior and posterior roots of the tri- geminus, gets from the cranium through the foramen rotundum of the sphenoid bone. While still in the cranium, it sometimes forms an anastomosis, described by Laumonier with the begin- ning of the sympathetic nerve, but generally it does not detach any filament till it reaches the pterygo-maxillary fossa. At a short distance after its exit from the cranium, it gives off a small filament, the Nervus Subcutaneous Malae, which ascends into the orbit through the spheno-maxillary fissure, and then divides. One of the branches, the malar, anasto- moses with the lachrymal nerve, and leaves filaments with the lachrymal gland; it then gets, by one or more filaments, through the holes of the malar bone to the face, and termi- nates on the orbicularis muscle and the skin of the cheek, anas- tomosing with the extremities of the facial nerve. The other branch, the temporal, gets into the temporal fossa by pene- trating the internal part of the malar bone, and, having anas- tomosed with a branch of the inferior maxillary nerve, it goes outwards and backwards, becomes superficial by penetrating the temporal aponeurosis, and terminates on the integuments of the temple, anastomosing there with the branches of the facial nerve. The superior maxillary then divides into two trunks much larger than the preceding, and of a volume nearly equal; the Infra-Orbital and the Pterygo-Palatine. The Infra-Orbital (Nervus Infra-Orbitalis) passes forwards, with a slight ascent, to the posterior part of the orbit, and en- NERVOUS TRIGEMINUS. 457 ters the infra-orbitar canal. As it is about engaging in the lat- ter, it detaches a considerable branch, the Posterior Dental. This branch descends a little distance, externally, along the poste- rior paries of the maxillary sinus, then penetrates into the cavi- ty of the latter. It terminates by filaments, some of which supply the lining membrane of the antrum; others pass through the little canals leading to the three large grinders, and enter the roots of the latter; others go to the corresponding gums. One branch goes along the outer side of the sinus to anastomose with the anterior dental nerve. The posterior dental, before it enters the bone, also detaches a branch of some size, which winds around the tuberosity of the maxillary bone, and is spent upon the buc- cinator muscle and upon the gums. The infra-orbitary nerve afterwards, in its course through the canal, sends off the anterior dental nerves from one or more roots. Some of them detach fibres to the mucous membrane of the nose, where it covers the anterior part of the inferior turbinated bone. With this exception, they are distributed, through their appropriate canals in the bone, to the incisor and canine teeth, and to the corresponding gums. The small mo- lar teeth are most frequently supplied by a union of filaments, from the anterior and posterior dental nerves. The infra-orbitar nerve, on issuing from the infra-orbitar fo- ramen, is most frequently found already divided into several fasciculi, which may be classed into superior and into inferior. The former, called Palpebral, radiate, externally and internal- ly, into filaments which supply the lower eyelid. One of these filaments may be traced to the end of the nose, where it anasto- moses with the internal nasal branch of the ophthalmic; another, which terminates about the internal angle of the eye, anasto- moses there with the external nasal nerve. Others of its termi- nating filaments, anastomose with the extremities of the facial nerve on the eyelid. The inferior fasciculi are more numerous and large than the superior. They descend upon the face co- vered by the levator muscles of the upper lip, and from their distribution are called Labial. The most internal of these fas- ciculi terminate on the skin, the muscles, and the beginning of the mucous membrane of the nose, where they anastomose with the extremities of the internal nasal nerve. The middle fasci- 458 NERVOUS SYSTEM. culi go to the muscles of the upper lip and the skin of the lat- ter, and to its mucous glands. The external fasciculi go to the zygomatic muscles and to the contiguous skin. All the fore- going branches of the infra-orbitar nerve anastomose with the extremities of the facial, and are so minutely distributed to the skin and muscles of the face, that it would require a very pro- tracted description to point them out particularly. The Pterygo-palatine Nerve (Nervus Plerygo-palalinus) de- scends, as a single or a double trunk, from its root to the out- side of the spheno-palatine foramen, and there forms the gang- lion of Meckel,* or the spheno-palatine ganglion, the existence of which is not constant. From this ganglion, or from the nerve itself proceed several branches. A filament, described by Bock, is detached from it, which enters into the sphenoidal sinus to be distributed on its lining membrane, and sometimes to anastomose with the motor exter- nus oculi. Then arise the spheno-palatine branches, which enter the nose through the spheno-palatine foramen, and are distributed upon the mucous membrane of its septum and turbinated portions, after the manner described in the account of the nose. The Vidian, or Pterygoid Nerve (Nervus Vidianus, recurrens, pterygoideus) arises from the inferior part of the ganglion, and is a recurrent branch, which goes backwards through the pterygoid foramen of the sphenoid bone. From it there arise some fila- ments, which get to the mucous membrane about the anterior orifice of the Eustachian Tube, either through the spheno-pala- tine foramen, or by small foramina in the pterygoid process of the sphenoid bone. They are sometimes united into a single trunk, called pharyngeal, by Bock. The Vidian nerve, while still in its canal, then divides into two trunks, the superficial, and the deep petrous. The Superficial Petrous (Nervus Petrosus Superficialis) tra- verses the cartilaginous matter at the point of the petrous bone in the anterior foramen lacerum of the basis of the cranium, • Discovered by Meckel, 1749. NERVUS TRIGEMINUS. 459 gets there into the cavity of the latter, continues its progress backwards on the superior face of the petrous bone, in a gutter marked on the bone, and disappears through the Vidian fora- men. It, in a short space, reaches the aqueduct of Fallopius, and then continues to adhere to the facial nerve till the latter almost reaches the stylo-mastoid foramen: it then abandons the facial nerve, and, as mentioned in the account of the ear, traverses the tympanum under the name of chorda tympani; and, finally, emerging at the glenoid foramen, it runs to asso- ciate itself with the lingual branch of the trigeminus. The su- perficial petrous, in the early part of its course, at the point of the petrous bone, detaches one or more filaments to the sym- pathetic in the carotid canal. The Deep Petrous (Nervus Petrosus Profundus) is larger than the other. It also penetrates through the cartiraginous matter at the point of the petrous bone, and enters the cavity of the cranium under the dura mater. It then advances to the internal carotid artery, and anastomoses there with a filament from the motor externus. This anastomosis is commonly called the beginning of the sympathetic nerve. The Palatine Nerve (Nervus Palatinus) proceeds from the inferior part of the ganglion of Meckel, and gets to the soft palate of the mouth through the posterior palatine foramen. In this course, it detaches several filaments to the Schneiderian membrane, which reach it either through the spheno-palatine foramen, or by perforating the nasal lamella of the palate bone. These are described in the account of the nose. The trunk of the palatine nerve, having reached the roof of the mouth, bends forwards, and is divided into many filaments, some of which are distributed along the gums of the upper jaw, others are distributed on the lining membrana of the hard pa- late and upon its mucous glands. There are two other nerves, which arise either immediately from the palatine, or from the ganglion of Meckel, and go to supply the soft palate. They are called the smaller palatine. One of them, having proceeded for a short distance in the pos- 460 NERVOUS SYSTEM. terior palatine canal, departs from it in a little canal of its own, which opens behind the hook of the internal pterygoid process. It then radiates into filaments, which supply the tonsil gland and the muscular and membranous structure of the soft palate. The other smaller palatine also traverses, after the same man- ner, its own canal, and is likewise distributed to the tonsil gland and to the soft palate. Third Branch of the Trigeminus. The Third Branch of the Trigeminus (Nervus Inframaxil- laris) is the largest of the three. It arises from the posterior inferior part of the ganglion of Gasser, and having anastomosed with the cavernous ganglion of the sympathetic nerve by fila- ments, which are not constant, it emerges from the cranium through the foramen ovale of the sphenoid bone. A portion of this branch, as mentioned, does not enter into the composi- tion of the ganglion of Gasser, but proceeds immediately from the, pons varolii. The inferior maxillary nerve, at its exit from the foramen ovale, is covered by the pterygoideus externus muscle, and commonly divides there into two branches, one anterior and the other posterior. The anterior branch, which is much smaller than the other, radiates into five fasciculi; the masseter nerve; the two tem- poral; the buccal; and the pterygoid. a. The Masseter Nerve is directed horizontally outwards and backwards, along the external margin of the pterygoideus externus, and in front of the temporo-maxillary articulation: it leaves some filaments with the latter, and then passing be- tween the insertion of the temporal and of the external ptery- goid muscle, over the concave edge of the bone, between the condyle and the coronoid process of the lower jaw, it passes into the substance of the masseter muscle, and is distributed through it. b. The two Temporal branches arise by a common fascicu- lus, but sometimes differently. They pass outwards, horizon- tally, between the external pterygoid muscle and zygomatic NERVUS TRIGEMINUS. 461 fossa. They then ascend on the side of the temporal bone, be- tween it and the temporal muscle, and are distributed through the latter by a great number of filaments. Some of these fila- ments penetrate the aponeurosis, to anastomose with the super- ficial temporal nerves. And one of them anastomoses with that branch of the superior maxillary which sends filaments to the lachrymal gland, and afterwards escapes from the orbit, through the foramina in the malar bone, into the temporal fos- sa. It is at the latter place that the anastomosis occurs. c. The Buccal Branch is the largest of the five. It advances between the pterygoid muscles, to which it furnishes a few fila- ments, and then descends between the temporal and external pterygoid muscle to the posterior part of the buccinator. It is principally distributed on the latter, upon the buccal glands, and the corresponding part of the lining membrane of the mouth. Some of its branches advance under the integuments of the face, as far as the commissure of the lips to the muscles there, and anastomose with the facial nerve. d. The Pterygoid Branch is the smallest, and is distributed principally on the internal pterygoid muscle. The posterior branch of the inferior maxillary nerve is so large, that it looks like a continuation of the trunk. It is di- vided into the superficial temporal, the inferior dental, and the lingual nerve. a. The Superficial Temporal Branch is formed by a union of two fasciculi, between which passes the middle artery of the dura mater; the inferior of these fasciculi comes from the infe- rior dental nerve. The nerve is directed outwardly, and winds horizontally around the posterior face of the neck of the con- dyle of the lower jaw, between it and the meatus auditorius ex- ternus. It is there divided into several small fasciculi, two or three of which penetrate into the substance of the parotid gland, and anastomose with the facial nerve or its ramifications; one or two others go backwards, penetrate between the bony and the cartilaginous meatus to the auditory canal, and are dispersed by fine filaments upon the concha, and the meatus externus. According to Bock, one of these filaments supplies the mem- brane of the tympanum, and also anastomoses with the chorda Vol. II.—59 462 NERVOUS SYSTEM. tympani. Another branch of the superficial temporal, which is the largest of any, traverses the parotid gland, and thereby becomes superficial, just in front of the external ear. It then divides into filaments, which follow the course of the superfi- cial temporal artery, and thereby supply the middle part of the integuments on the side of the head. It anastomoses with the filaments of the frontal nerve, and with those of the occi- pital. b. The Inferior Dental Nerve is placed between the other two branches, and exceeds them in size. It descends between the two pterygoid muscles, towards the posterior mental fora- men. Just above the latter it detaches a small branch, the mylo- hyoid, which occupies the small gutter on the bone leading downward from the posterior mental foramen. This branch sends a filament to the submaxillary gland, then passes between the anterior belly of the digastric muscle and the mylo-hyoi- deus, to both of which it gives filaments, and finally winding over the base of the lower jaw in front, it is lost upon the mus- cles of the chin. The inferior dental nerve then enters the posterior mental foramen, and divides into two branches, which run parallel with one another, through the canal in the middle of thcspongy structure of the bone, and send a great number of anastomotic filaments to each other. One of the branches, the dental, properly speaking, as it passes along the ends of the roots of the teeth, detaches a filament to each root, from the last grinder to the first incisor tooth inclusively: it also sends a filament to the gum intermediate to every two teeth. All of these filaments arise from the denial nerve, at places behind the points of destina- tion; so that they have, before reaching the latter, to run for- wards and upwards through little canals in the cellular struc- ture of the bone. The other branch of the inferior dental nerve is the mental; it does not advance so far forward in the bone as the preceding, but issues from it at the anterior mental foramen, and immedi- ately is divided into two fasciculi, the inferior labial nerves. The internal fasciculus is distributed by filaments upon the muscles of the chin and lower lip, the contiguous lining mem- brane of the mouth and the labial glands. The external fas- NERVUS TRIGEMINUS. 463 ciculus rises upwards and is distributed on the muscular struc- ture, about the under part of the commissure of the lip, and to the contiguous lining membrane and glands of the mouth. c. The Lingual Nerve descends in company with the infe- rior dental, but in advance of it, and diverging slightly. While between the two pterygoid muscles it receives the chorda tym- pani at a very acute angle. It then passes towards the side of the root of the tongue, deeply concealed by the angle of the lower jaw, and above the submaxillary gland, to which it gives some considerable filaments. Occasionally, however, a gan- glion, called the maxillary, is formed here by one or more fila- ments of the lingual nerve, and from this ganglion proceed fila- ments to the submaxillary gland. The lingual nerve then proceeds forwards betwee i the mylo- hyoideus and the hyo-glossus muscle, and between the sublin- gual gland and the latter, having in front of it the excretory duct of the submaxillary gland. It anastomoses frequently with the hypoglossal nerve, sends several filaments to the lining membrane of the mouth, below the tongue, and to the sublin- gual gland. It then divides, or radiates, into seven or eight fasciculi, which run upwards and forwards on the side of the stylo-glossus muscle, and the genio-hyo-glossus, and are finally spent by very fine filaments penetrating into the structure of the papillae, on the upper surface of the tongue. The third branch of the trigeminus, according to Dr. Arnold, forms, by several filaments, a ganglion near the foramen ovale. This ganglion is below the spinous process of the sphenoid bone, and sends off several filaments: one contributes to the ner- vous anastomosis of Jacobson,* which connects the pterygoid, sympathetic, and glosso-pharyngeal nerves: the other filament passes to the tensor tympani, and is distributed upon it. Other filaments join the superficial temporal nerve; that part of it which supplies the membrana tympani. There is also an anas- tomosis with the portio mollis.t * This nervous anastomosis is described, page 449, article Vidian Nerve. X Am. Med. Jour. vol. v. p. 192. 404 NERVOUS SYSTEM. SECT. VII.—NERVUS FACIALIS. The Facial Nerve (Nervus Facialis; portio dura septimi; par sepiimum) having gained the meatus auditorius internus, passes in front of the auditory nerve into the canal of Fallopius, and winding through it, around the tympanum, it emerges at the stylo-mastoid foramen, having sent in this course one or more filaments to the muscles of the little bones of the tym- panum. Afterwards, the facial nerve gives off several branches, which are distributed as follows:— a. The Posterior Auricular (Auricularis Posterior) arises near the stylo-mastoid foramen, as stated in the account of the Nerves of the Ear; and having sent several filaments into the mastoid process, it winds over the anterior face of the base of the latter, and divides into two fasciculi. The anterior is dis- tributed in filaments upon the back of the external ear, the car- tilaginous meatus, and the posterior auris muscle; the posterior ascends upon the mastoid portion of the temporal bone to the posterior belly of the occipito-frontalis muscle, and is spent by filaments to the latter, and to the corresponding integu- ments, anastomosing likewise with ramifications of the occipi- tal nerve. b. The facial nerve then detaches filaments to the muscles of the styloid process, and to the posterior belly of the digas- tric muscle. It also sends filaments of anastomosis to the su- perior part of the sympathetic nerve; to the cutaneous cervical; and to ramifications of the glosso-pharyngeal, of the pneumo- gastric, and of the accessory. The facial nerve, having given off the foregoing filaments and branches, penetrates downwards and forwards into the substance of the parotid gland, where it is divided info a number of branches, varying from two to five, which form a plexus by their anastomosis. This plexus is re-enforced, as mentioned, by branches from the superficial temporal of the inferior max- illary, which wind around the neck of the lower jaw. It is NERVUS FACIALIS. 465 then distributed to the side of the face in radiating clusters or columns of filaments, called the temporo-facial, the buccal, and the cervico-facial. The Temporo-Facial Nerves, or Branches, are hid, for some distance, in the upper part of the parotid gland, which they traverse below the neck of the lower jaw. They divide into filaments, some of which go to the temple, and others to the cheek. The temporal branches are commonly two or three in number; they leave filaments with the parotid gland, mount over the zygoma, and are distributed to the anterior auris mus- cle, to the outer section of the orbicularis palpebrarum, and to the integuments of the temple; they anastomose in their distri- bution with each other, with the superficial and deep temporal branches of the inferior maxillary nerve, and with the frontal and lachrymal branches of the ophthalmic. The malar branches are primitively, also, two or three in number: they cross the malar bone, dividing, subdividing, and anastomosing again, and are spent upon the integuments and muscles of this part of the face. They also anastomose with filaments of the lachrymal nerve, and with those of the infra-orbitar nerve. The Buccal Branches are three in number, sometimes two only; and pass across the masseter muscle under the skin. The superior anastomoses with the temporo-facial, and the inferior with the cervico-facial. The buccal branches supply the skin and muscles of the face intermediate to the eye and to the low- er lip. The numerous filaments into which they divide anas- tomose frequently with eaeh other, and with the branches of the fifth pair, which appear about the same parts, as the exter- nal and internal nasal nerve, the infra-orbitar, and so on. The middle buccal is parallel with the duct of the parotid gland, and adheres to it. The Cervico-Facial Branch descends in the substance of the parotid gland, behind the ramus of the lower jaw; when it reaches the angle of the latter it goes obliquely forwards, be- neath the platysma myodes muscle. Though it sends off many fasciculi, they may be referred to two divisions, a superior and an inferior. The first crosses the inferior part of the masseter muscle, and may be traced in its numerous distribution of fila- ments, to the integuments and muscles lying upon the body of 466 NERVOUS SYSTEM. the lower jaw. These filaments anastomose with each other, and with the mental branches of the inferior dental nerve. The inferior division supplies the skin and the platysma myodes muscle on the upper part of the neck along the base of the lower jaw. Its filaments are joined by several coming from the anterior fasciculus of the third cervical nerve. The anastomoses of the facial nerve, derived from its own branches and from those of the trigeminus, which reach the face, are entirely too numerous for a detailed description of them; it, indeed, appears unnecessary to extend the latter beyond a certain point.- The most satisfactory account has been pub- lished by Meckel.* SECT. VIII.—NERVUS HYPOGLOSSUS. The Hypoglossal Nerve, (Nervus Hypoglossus, Lingualis,) having arisen from the medulla oblongata, and escaped from the cranium through the anterior condyloid foramen, adheres closely for an inch to the pneumogastric nerve. It descends between the external carotid artery and the internal jugular vein, the latter being behind the other; and then winds over the carotid, externally, just below the origin of the occipital ar- tery. It is there covered by the posterior belly of the digas- tricus and by the stylo-hyoideus. It then passes forwards be- neath the external jugular vein, and lower down somewhat than the tendon of the digastric muscle, and, finally, ascends to the tongue, being covered or concealed by the mylo-hyoideus mus- cle. The nerve in this course, from the external carotid to the tongue, forms a remarkable curve, the convexity of which is downwards. The Hypoglossal, while adhering to the par vagum, com- monly leaves a few filaments with it. As it crosses the ex- ternal carotid, it detaches a large branch, the Ramus Descen- dens Noni, which goes down the neck, along the sheath of the carotid artery and the internal jugular vein, in front of the latter. • J. F. Meckel, de Nervis Faciei, Mem. de l'Acad. des S. de Berlin, 1751, Caldani, Tab. 247. NERVUS HYPOGLOSSUS. 467 The ramus descendens has been beautifully figured by Scar- pa, in his Plates of the Nerves. According to him. when it has got about half way down the neck, but still resting on the sheath of the vessels, it detaches, in front, two filaments, which, after the course of an inch forwards, unite, and then separate again to be distributed to the upper ends of the omo-hyoid and sterno-hyoid muscles. The descendens noni then forms, an inch lower down, a small gangliform plexus, resting upon the sheath of the great vessels of the neck, under the omo-hyoid muscle. This plexus is joined by two fasciculi, which descend from the first and second cervical nerves, and from it pro- ceed downwards and backwards, two filaments, which join the phrenic nerve; also, one to the lower part of the omo-hyoid muscle; and three or more, which are divided and distributed upon the sterno-hyoid and thyroid muscles, and upon the mus- cles of the larynx. Meckel states, that some of these ramifica- tions, on the left side principally, penetrate to the thorax, and reach the pericardium. The hypoglossal nerve, having sent off the ramus descendens, reaches the external face of the hyo-glossus muscle, and is there concealed by the mylo-hyoideus, where it gives filaments to the muscles of the larynx, to the hyo-glossus, genio-hyoideus, and genio-hyo-glossus. These filaments anastomose frequently with each other, and in two or three places at the anterior part of the tongue with the lingual branch of the nervus trigeminus. Af- ter these branches are given off, the trunk of the hypoglossal nerve penetrates into the substance of the genio-hyo-glossus muscle, and extends itself near its fellow, and not far from the middle line of the tongue to the point of the latter. It first dis- tributes filaments near the posterior part of the tongue, and then, successively, as far as its anterior extremity. They can- not be traced to the papillae, but are lost upon the muscular structure. It is a general opinion among anatomists that the hypo-glos- sal nerve is only intended to excite the muscular movements of the tongue. The opinion is founded upon the circumstance of its filaments not reaching the papillae, whereas those of the lingual branch of the trigeminus do. Colombo narrates a case, •468 NERVOUS SYSTEM. in which there was a congenital privation of taste, where the lingual branch of the trigeminus was distributed upon the occi- put instead of upon the tongue, which goes far to prove the dif- ference of function in the two nerves. SECT. IX.—NERVUS ACCESSORIUS. The Accessory Nerve, (Nervus Accessorius, IVillisii,) having arisen, as described, from the cervical medulla and the medulla oblongata, is directed outwards to the posterior foramen lace- rum, in company with the pneumogastric or par vagum. Some- times it is separated from it in its passage through the base of the cranium, by a thin partition of dura mater; on other occa- sions merely by a fold of the tunica arachnoidea: but at the in- ferior part of this foramen it adheres so closely to the par va- gum that the two look like but one nerve. Near its exit it is divided into two fasciculi. The most in- ternal gives off one or two filaments, which, joining a branch of the par vagum, forms the superior pharyngeal nerve; the internal branch then descends, and being divided into several branches, they, successively, join the upper part of the par vagum. The external fasciculus descends for two inches be- hind the internal jugular vein, being placed first of all between it and the occipital artery, but subsequently between the vein and the sterno-mastoid muscle. It then pierces this muscle about one-third of the length of the latter from its superior extremity, and leaves filaments in it which anastomose with some from the third cervical nerve. In continuing its descent, it is re-enforced and augmented considerably in volume, by branches from the second and third cervical. Having reached the anterior margin of the trapezius muscle, it then distributes itself to the latter, by internal and by external branches. SECT. X.—NERVUS GLOSSO-PHARYNGEUS. The Glosso-Pharyngeal Nerve (Nervus Glosso-Pharyngeus,) though commonly considered as distinct from the pneumogas- NERVUS ACCESSORIUS. 469 trie, has so many connexions with it, both at its root, in its course through the posterior foramen lacerum, and, in its dis- tribution, that it seems like a part or branch of the same. At the base of the cranium in front of the pneumogastric, it forms, according to some anatomists,* a ganglion of five or six lines in length, the existence of which was denied by Bichat. From this ganglion proceeds a filament,t which penetrates into the tympanum and divides into two branches; one of them ascends along the promontory, having detached a filament to the mem- brane of the foramen rotundum: it then penetrates the petrous bone; and anastomoses or joins with the superficial petrous nerve. The other branch passes below the bony Eustachian Tube, and, gaining the carotid eanal, anastomoses there with the Sympathetic Nerve. This is part of the anastomosis of Jacob- son, and is also described in the account of the Vidian Nerve. The ganglion also gives off other filaments, which traverse the canal of the dura mater, to join the pneumogastric nerve, the accessory and the sympathetic. On issuing from the posterior foramen lacerum, the glosso- pharyngeal is separated from the pneumogastric by the internal jugular vein. It is then directed downwards and forwards be- tween the internal carotid and the stylo-pharyngeus muscle; afterwards between the latter and the stylo-glossus; it fol- lows the direction of the latter to the side of the root of the tongue. In this course, it sends off many filaments. Shortly after leaving the cranium, it detaches one backwards to the digas- tric branch of the facial, and another to the pneumogastric. It then sends off two filaments, which descend along the internal and the common carotid, and are divided into several branches, some of which anastomose with the pharyngeal branch of the pneumogastric, others descend on the common carotid with filaments from the pharyngeal branch, and being joined by two or three small twigs from the superior cervical ganglion, tfcey reach the lower part of the neck, and concur in the forming * Andersach and Huber. This ganglion is considered by some as commencing before the nerve penetrates the foramen lacerum. X Rosenmuller, Jacobson, Lobstein. Vol. II.—60 470 NERVOUS SYSTEM. of the superficial cardiac nerve. Farther down after the origin of these branches the glosso-pharyngeal detaches two or three filaments to the stylo-pharyngeus muscle, as well as some to the upper and middle constrictors of the pharynx, to the pharyngeal plexus of the sympathetic and pneumogastric, and to the pos- terior lateral and superficial part of the tongue. The glosso-pharyngeal nerve having got between the stylo and hyo-glossus muscles, is placed intermediately to the lingual branch of the fifth pair and hypo-glossal nerve. Some of its branches then go to the integuments of the base of the tongue, to its mucous glands, large papillae, and may be traced to the mucous membrane of the soft palate, to the amygdalae, and to the covering membrane of the epiglottis. Others go into the muscles of the tongue, and others may be traced along the ex- ternal margin of the tongue, beneath its'mucous membrane for some distance. Scarpa has delineated a remarkable plexus, which he denominates Circulus Tonsillaris Anderschii or Anas- tomosis Plexuosa, formed by these several filaments and by branches of the lingual, on the side of the root of the tongue, at the base of the tonsil gland. SECT. XI.--NERVUS PNEUMOGASTRICUS. The Pneumogastric Nerve (Nervus Pneumogastricus, Vagus, Par Octavum, Decimum of Andersech) at its exit from the cra- nium through the posterior foramen lacerum, in front of the in- ternal jugular vein, is closely united to the hypo-glossal, glosso- pharyngeal, and accessory nerves, by compact cellular substance. It is first placed in front of the hypo-glossal nerve, but, in a short space, gets behind it, and is also separated from the glosso-pha- ryngeal by the internal jugular vein. Opposite the transverse process of the atlas, it leaves the hypo-glossal nerve, and as- sies a position between the internal carotid and the internal jugular, on the vertebral side of these vessels, and is enveloped in their sheath of dense cellular substance. It maintains this relativeNposition along the common carotid to the root of the neck. x At the latter place, the pneumogastric of the right side goes in front of the Subclavian artery, near its root, but on the left PNEUMOGASTRIC NERVE. 471 side it crosses the root of the left subclavian artery, and the arch of the aorta to the left of the origin of the left carotid. In get- ting fairly into the cavity of the thorax, it is directed backwards and downwards from these points, towards the posterior face of the bronchia, between it and the pleura. It then abandons the bronchia, and applies itself to the oesophagus, and follows it through the diaphragm to the stomach. The nerve of the left side, in its course along the oesophagus, is on the front surface of the latter, and the nerve of the right side, on its posterior surface. The pneumogastric anastomoses with the accessory while passing through the foramen lacerum posterius. Somewhat lower down, it also anastomoses with the glosso-pharyngeal and with the superior cervical ganglion of the sympathetic. The branches which it afterwards sends off, go to the neck to the viscera of the thorax, and to those of the abdomen, after the fol- lowing manner:— A. Cervical Branches. The Superior Pharyngeal Nerve (Ramus Pharyngeus) arises just below the preceding anastomo- sis. It is directed downwards on the internal face of the inter- nal carotid, and having sent an anastomotic filament to the glos- so-pharyngeal nerve, it forms on the middle constrictor of the pharynx, the pharyngeal plexus which is re-enforced by fila- ments from the superior cervical ganglion of the sympathetic, from the glosso-pharyngeal, and from the superior laryngeal nerve. The filaments departing from this plexus, are spent principally upon the middle constrictor, but a few of them also go to the superior constrictor; and others, descending along the primitive carotid, anastomose with ramifications from the glos- so-pharyngeal, and from the superficial cardiac nerve. A fila- ment, called the inferior pharyngeal, sometimes proceeds from the pneumogastric a little below the other, and also is spent upon the pharynx. The pneumogastric, at the place where it detaches these pha- ryngeal branches, or a little above them, becomes softened in its texture, enlarges somewhat, and has the fasciculi which compose it moderately separated by a sort of red gelatinous substance interposed between them. This portion is its gang- 472 NERVOUS SYSTEM. liform plexus, and into it is joined one or more branches from the accessory nerve. The Superior Laryngeal Nerve (Nervus Laryngeus Supe- rior) arises from the gangliform plexus. It descends between the internal carotid and the superior cervical ganglion, anasto- mosing on the way with the latter, with the pharyngeal plexus, and the hypo-glossal nerve; it then divides into an external and an internal laryngeal branch. The former sends its filaments to the muscles situated on the fore part of the thyroid cartilage; to the thyroid gland; and some of them penetrate through the crico-thyroid membrane to the lining membrane of the larynx. The internal laryngeal branch is placed above the other; it is directed towards the thyreo-hyoid membrane, which it pene- trates and then begins to ramify. Some of the branches go to the epiglottis cartilage, its covering membrane, and the adjacent portion of the lining membrane of the pharynx. Other branches are distributed to the small muscles which move the arytenoid cartilages, and to the lining membrane of the larynx. The fila- ments which go to the epiglottis have an arrangement indicated by Bichat; that of going into the foramina which perforate it, but they cannot be traced farther. The pneumogastric afterwards does not send off any regular branches till it reaches the lower part of the neck. It then detaches two or three filaments, (rami cardiaci,) which, on the right side, have their roots about, an inch above the subclavian artery, and on the left side, an inch lower down. On the right side, they descend along the subclavian and the arteria innomi- nata, on the left along the left carotid; they reach the arch of the aorta, and in their course, as well as there, anastomose very freely with the superficial cardiac nerve. The rami cardiaci are frequently more abundant on the right side than on the left. The Inferior Laryngeal Nerve (Nervus Laryngeus Inferior, Recurrens) is a considerable branch of the pneumogastric, which comes off next to the cardiac. On the right side it arises im- mediately after the trunk has passed between the subclavian artery and the subclavian vein. It then winds around the sub- clavian artery so as to retain the latter in its loop; having thus PNEUMOGASTRIC NERVE. 473 got behind the artery, it then ascends towards the larynx, on the side of the trachea, covered by the common carotid and by the inferior thyroid artery. In this course the inferior laryngeal nerve detaches the fol- lowing branches: 1. From the convexity of its loop it sends filaments to the assistance of the cardiac branches just spoken of, arising from the pneumogastric, and to those coming from the inferior cervical ganglion of the sympathetic. 2. It de- taches the pulmonary branches, the origin of which is compli- cated with the plexus of nerves existing about their roots; these descend in front of the trachea, reach the pulmonary artery, and follow its ramifications into the lungs; some of the fila- ments, however, go to the cardiac plexus. 3. The inferior laryngeal then sends many filaments to the oesophagus; 4. Branches which go to the inferior part of the thyroid gland; 5. Filaments to the trachea, some of which penetrate the mem- brane on its posterior part, others go between the cartilages; they are then distributed to the lining membrane and to the mucous glands of the part. 6. The inferior laryngeal nerve is then distributed in branches to the inferior constrictor of the pharynx and its lining membrane, but the most of its termi- nating filaments penetrate to the larynx, between the thyroid and the cricoid cartilage, and are lost upon the lining membrane of the larynx, and upon the small muscles which move the ary- tenoid cartilages. These terminating filaments anastomose with such as come from the superior laryngeal nerve. It is generally stated by anatomists that the distribution of the inferior laryngeal nerve to the larynx, is confined to the thyreo-arytenoid, and posterior and lateral crico-arytenoid mus- cles. Mr. G. Rainy, states, in the London Medical Gazette, that he has repeatedly traced its filaments, also, to the trans- verse and oblique arytenoid.* The recurrent of the left side forms a much larger loop than the other, and arises lower down, inasmuch as it has to wind around the arch of the aorta, at the origin of the left subclavian artery; with some inconsiderable exceptions, its course and distribution afterwards are precisely the same with those of the nerve of the right side. * Am. Med. Joum. vol. iv. p. 198. 474 NERVOUS SYSTEM. B. The Thoracic Branches of the pneumogastric are as fol- low: The inferior tracheal nerves come from it just below the recurrent: they are five or six in number; some of them go in front of the trachea and bronchia, and others behind them. They are complicated by anastomoses with the branches of the recurrent nerve, and with those of the inferior cervical ganglion, and form a small plexus, denominated the anterior pulmonary, which lies upon the front of the root of the lung, and has its filaments following the branches of the pulmonary artery through the lung. The posterior filaments supply the structure of the bronchia by penetrating it, and some of them go to join the posterior pulmonary plexus. As the pneumogastric gets behind the trachea and the bron- chia, it is sensibly enlarged and somewhat flattened, the cohe- sion of its fasciculi being somewhat looser. Several filaments depart there from it, which form an intertexture with each other; some of them pass inwards, to be distributed on the bronchia, trachea, and oesophagus. Others, which are given off as the nerve lies upon the posterior face of the root of the lung, amounting to six or seven in number, but being of various sizes, run transversely outwards, and form an intertexture with one another. The latter are joined by filaments from the infe- rior cervical and the first dorsal ganglion of the sympathetic, and thus constitute the posterior pulmonary plexus. The fila- ments from this plexus follow the distribution of the bronchia, and, according to Bichat, are all destined to the mucous mem- brane and the mucous glands of the lung; as they may be traced piercing successively the ramifications of the bronchia, in order to reach its lining membrane. On the right side, the par vagum, while furnishing the pul- monary plexus, and for some distance lower down, is divided into from four to six considerable fasciculi, which form with each other a plexus or series of anastomoses, having very large meshes, and from which proceed many filaments to the oesopha- gus. Afterwards these fasciculi are assembled into a single chord, which proceeds on the posterior face of the oesophagus, along with it into the abdomen. On the left side, the par vagum, after forming the posterior pulmonary plexus, is split into two or three fasciculi; which SYMPATHETIC NERVE. 475 likewise furnish branches to the oesophagus, and unite to form a single chord, which proceeds on the front surface of the oeso- phagus, along with it into the abdomen. The two nerves, while descending in this way, send frequent anastomotic filaments to each other, and to the oesophagus. C. In the Abdomen the par vagum is distributed as follows: Filaments are sent from each nerve, which form a plexus around the cardiac orifice of the stomach. The right nerve is then divided into many branches; some are distributed on the poste- rior face.of the stomach; others go along the lesser curvature of this viscus, and reach thereby the pylorus, where they anas- tomose with filaments from the left nerve, and from the gastric plexus of the sympathetic; others go behind the stomach to join the solar plexus, and are blended with the latter in its distribu- tion to the liver, vena portarum, duodenum, and pancreas. The left par vagum, being placed in front of the cardia, is resolved into several radiating filaments or fasciculi, some of which sup- ply the anterior face of the stomach, others go along its lesser curvature to the pylorus, to anastomose with the right nerve and the gastric branches of the sympathetic, and are finally blended, after the same manner as the preceding, with the so- lar plexus. CHAPTER II. OF THE SYMPATHETIC NERVE. • The Sympathetic Nerve (Nervus Sympatheticus Magnus, Intercostalis Maximus, Gangliosus,) differs, in a great num- ber of respects, from every other nerve of the body; and if we were actuated only by its peculiarities, with Bichat, Meckel, and others, we might with great propriety, set it apart as some- • Anton. Scarpa, Tabul. Neurolog. 476 NERVOUS SYSTEM. thing having a claim to an insulated description and location. The dissection of it, however, is so much ^blended with that of the par vagum, that the descriptions of the two go best hand in hand; and are, therefore, most conveniently studied together. This nerve consists in a series or chain of ganglions, extend- ing from the base of the cranium to the lower end of the sac- rum. They are placed on the lateral part of the bodies of the vertebrae, are united to each other by intermediate nervous chords, and send off continually filaments to the adjacent organs. With the exception of the neck, there is a ganglion for each intervertebral space, both of the true vertebrae and sacrum. Be- sides these ganglions, there are others which are situated around the trunks of some of the large vessels of the abdomen. The superior extremity of the sympathetic nerve, opposite to the transverse process of the second cervical vertebra, and behind the internal carotid artery, forms a ganglion, which, for the purpose of description, may be considered as the first of the series. This ganglion is the superior cervical. The nervus motor externus oculi, in passing through the cavernous sinus, and the Vidian nerve, in passing by the point of the petrous bone, both send a filament downwards through the carotid canal; which two filaments unite to form a single chord, that runs into the superior extremity of this ganglion. The filament from the Vidian nerve is, as mentioned, the deep petrous nerve. The common view taken by anatomists' of this nervous con- nexion is, that it is the beginning of the sympathetic, though by Bichat it is described as the termination, or one of its ex- tremities. The distinction, though important physiologically, is less so when the object is simply to describe the course and anatomical relations of this nerve, as they may be equally un- derstood by either mode of description. The branch from the motor externus most frequently forms, on the external face of the internal carotid, in the cavernous sinus, a ganglion, (Ganglion Cavernosum, Caroticum,) dis- covered by Laumonier, which is sometimes made by several filaments, from the motor externus, instead of one. M. Lob- c SYMPATHETIC NERVE. 477 stein, in his Essay on the Sympathetic, has attributed this ganglion to the deep petrous nerve, in which I think he is mistaken.* From the ganglion cavernosum, it has, of late, been ascertained that filaments may be traced to the ganglion of Gasser, (Plexus Gangliformis,) of the trigeminus, to the pituitary gland, to the infundibulum; and, moreover, a fasciculus which, according to H. Cloquet, forms a plexus around the ophthalmic artery, and may be traeed along all its branches, even the central artery of the retina. This plexus anastomoses with the lenticular ganglion, and consequently establishes a di- rect nervous communication between the sympathetic, the mo- tor externus oculi, and first branch of the fifth pair. The know- ledge of this connexion has caused anatomists to locate the len- ticular ganglion and the ciliary nerves in the ganglionic system of the sympathetic, as forming a part of the latter. The sympathetic, in descending the neck, is placed behind the carotid artery and internal jugular vein. It is common- ly said to be enclosed in the sheath of these great vessels, but the statement is loose and inaccurate, as it is fastened to the front surface of the longus colli muscle by cellular substance distinct from the sheath, as may be manifested by pushing a knife handle between them and raising up the sheath. The chord which comes down from the carotid canal is close to the pneumogastric and hypoglossal nerves. Having formed the first cervical ganglion, it descends as mentioned; and, op- posite to the space between the fifth and sixth cervical ver- tebrae, it is again enlarged into the Middle Cervical Ganglion, which is much smaller and more irregular than the first. The sympathetic is then traced with some difficulty, in con- sequence of the numerous branches coming from it; but, with attention, a trunk may be found as the continuation of it. This trunk passes to the interval betAveen the head of the first rib and the transverse process of the last cervical vertebra, and there enlarges into another ganglion, called Inferior Cervical, or First Dorsal. To understand well the connexions of the sympathetic in the * De Nerv. Sympathetic. Paris, 1823. Vol. II.—61 47S . NERVOUS SYSTEM. neck, each of the cervical ganglions must be studied particu- larly. 1st. The Superior Cervical Ganglion varies considerably in its extent; commencing very generally opposite to the second cervical vertebra, it is sometimes elongated to the lower part of the third and even of the fourth. In cases of unusual elon- gation, it is smaller than in others. It sends off, from its external margin, several filaments, about four, which cross the anterior face of the rectus anticus major muscle, and terminate by anastomosing with the anterior fasci- culi of the occipital nerve and of the three first cervical: when the ganglion is short, the two lower filaments come from the sympathetic below it, instead of from the ganglion. Several filaments also proceed from this ganglion to the con- tiguous muscles on the vertebral column, to the pharynx, to the larynx, and to the thyroid gland. This ganglion also sends off what are called its Anterior branches, which are peculiar for their reddish colour and for their softness; the latter quality has obtained for them the name of Nervi Molles. They may be referred, by their position, to three orders. The superior ascends to anastomose with the pneumogastric, hypoglossal, and facial nerves, near their exit from the cranium. The middle are two or three in number, but immediately divide into many filaments, forming the caro- tid plexus by assistance from the pneumogastric, glosso-pha- ryngeal, and facial nerves. Some of the branches of this plex- us descend behind the primitive carotid, at the place of its bi- furcation, and accompany it to its origin, continually interlacing with each other. Others surround, after the same manner, the external carotid, and subdivide into a plexus for each of its branches, so that very fine filaments may be traced along the superior thyroidal, the lingual, facial, occipital, and temporal arteries. These nerves are, for the most part, difficult to trace from their extreme tenuity. The primitive branches, from which these plexuses come, are sometimes previously united into a small ganglion, which serves as a common centre to all these nervous irradiations. The third order of anterior branches, amounting to from four to six, come either from the ganglion THE SYMPATHETIC NERVE. 479 or from the sympathetic just below it. The chord formed by their union, called the Superficial Cardiac Nerve, descends on the external side of the primitive carotid, anastomosing with filaments from the pneumogastric and from the descendens noni. It gives small ramifications to the contiguous parts, as to the pharynx, oesophagus, the sterno-hyoid and thyroid muscles. It terminates in the lower part of the neck, by detaching anasto- mosing branches to the branches of the recurrent nerve; some of them also go along the inferior thyroid artery to the thy- roid gland. What remains of it is lost in the middle cardi- ac nerve; for it cannot be traced, in an insulated and distinct manner, to the heart; from which cause, its appellation is ob- jectionable. 2. The Middle Cervical Ganglion, placed intermediately to the fifth and sixth cervical vertebrae, upon the longus colli mus- cle, is there concealed by the common carotid, the internal ju- gular vein, and the pneumogastric nerve. It is sometimes de- ficient: according to Meckel, in the proportion of once in three times. In my own dissections I have always found it, though under various circumstances of size and form. It is more flat- tened than the preceding, and never so long. Sometimes it is double. Like the preceding, it has a great many filaments at- tached to, or emanating from it. The external filaments, amounting to about three in number, pass from it to the anterior fasciculi of the fourth, fifth, and sixth cervical nerves, between the origins of the scaleni muscles. Some of its filaments accompany the inferior thyroid artery, and, along with the superficial cardiac, form a plexus around it, which reaches to the thyroid gland. The Middle Cardiac Nerve is formed by several of the ante- rior branches, collecting into a single chord. The latter de- scends along the external side of the primitive carotid, crosses, on the right side of the body, the root of the subclavian artery, and then going along the posterior face of the arteria innomina- ta, it gets between the aorta and the bifurcation of the trachea, where it is merged in the commencement of the cardiac plexus of nerves. On the left side, the middle cardiac nerve is formed by an assemblage of filaments from the middle and inferior cer- 480 NERVOUS SYSTEM. vical ganglions, which descend along the left subclavian artery to the aorta, and are joined, on the front of the latter, by the su- perficial cardiac nerve. On both sides, these cardiac nerves form intricate anastomoses with the pneumogastric nerve and its recurrent branch. 3. The Inferior Cervical Ganglion, situated as mentioned, near the head of the first rib, like the others, is subject to vari- ations in its form and size. Several filaments may be traced between it and the middle cervical ganglion. One penetrates into the canal of the transverse processesalong with the verte- bral artery, and, forming a plexus around it, may be traced dis- tributing^ branches to the heads of the contiguous muscles, as high up as the second cervical vertebra. The external branches of -the inferior cervical ganglion are numerous and small. Some of them anastomose with the ante- rior fasciculi of the two or; three inferior cervical and the first dorsal nerve. Others form a plexus around the subclavian ar- tery, and follow the latter, in its distribution, to the upper ex- tremity and to the shoulder. The anterior branches of this ganglion concur, after some anastomoses with each other, to form a single chord, the Infe- rior Cardiac Nerve, which goes, on the right side, along the ar- teria innominata, to be blended with the cardiac plexus. On the left side, it is not so distinct, but is blended with the mid-' die cardiac nerve, and forms its inferior root. Of the Cardiac Plexus of the Sympathetic. The Cardiac Plexus (Plexus Cardiacus) is situated between the arch of the aorta, and the lower part of the trachea and the bronchiae, and extends from the division of the pulmonary ar- tery to the commencement of the arteria innominata. It is formed, almost wholly, from the branches sent by the three cervical ganglions of the sympathetic of each side, and prin- cipally from that of the middle one, or the middle cardiac nerve. The filaments which come from the recurrent nerve and the THE SYMPATHETIC NERVE. 481 par vagum are blended into the cardiac plexus in such a man- ner that they cannot be traced immediately to the "heart. It is worthy of remark, that the three cardiac nerves of the right side are more constantly found than the same number on the left, in consequence of the lower one of the latter soon merging itself, after its origin into the middle cardiac nerve of that side. The cardiac plexus is formed by the common assemblage of the nerves from the two sides of the neck, and is therefore single. From this plexus-arise all the nerves which go to the heart, so that in tracing them the distinction between right and left is confounded. Scarpa, has pointed out, in this circum- stance, an analogy between them and the nerves which supply the abdominal viscera. The cardiac plexus is distinguished by the softness of its tex- turt. For the purpose of description, its branches may be di- vided into Anterior, Posterior, and Inferior. The Anterior Branches are but few. They are found on the front of the arch of the aorta. One of them crosses it on the right side of the arteria innominata; others cross it from the root of the left carotid and subclavian, downwards. In both cases, se- veral of the terminating filaments run into the anterior corona- ry plexus.* The Posterior Branches are more numerous; but run only a short course, when they are merged in the anterior pulmonary plexus formed by the par vagum. The Inferior Branches are the largest and the most abundant. Some of them follow the pulmonary artery until its entrance into the lungs, others are distributed upon the pulmonary veins; but the greater number of them are arranged into two plexuses called Coronary, from their observing the course of the corona- ry arteries. The posterior coronary plexus is larger than the other. It reaches the base of the heart, along the pulmonary artery,-and has its filaments distributed principally to the left • Scarpa. 482 NERVOUS SYSTEM. auricle and left ventricle, observing the course of the left coro- nary artery and of its branches. The anterior coronary plexus gets in front of the heart, between the aorta and the pulmonary artery. It anastomoses freely at its superior part with the other, and is then distributed to the right auricle and ventricle, along the course of the right coronary artery and of its branches. Of the Thoracic Ganglions of the Sympathetic. These ganglions are twelve in number, and are placed on or near the heads of the ribs, at the commencement of each inter- costal space, and are only covered by the pleura. Their shape is irregular, and they differ also in size, being always smaller than the cervical ganglions. The chord of the sympathetic is continued, successively, from one ganglion to another, so that they form a complete chain by their connexion with each other. From each ganglion there proceeds one or more external branches which go outwards to anastomose with the intercostal nerve of the corresponding part. Each ganglion also detaches one or more internal branches or filaments to the adjacent parts lying on the vertebral column: some go to the cellular substance, others to the longus colli muscle, others to the aorta, others to the cardiac and to the pulmonary plexuses. Among these in- ternal branches there are several which concur to form the Splanchnic Nerves, of which there are two; the Great and the Small. The Great Splanchnic Nerve arises, by filaments, from the sixth to the ninth or tenth thoracic ganglions, inclusively; one or more filaments coming from each ganglion. They are di- rected downwards and forwards on the sides of the dorsal ver- tebrae, covered by the pleura, and unite, successively, into a trunk about the eleventh dorsal vertebra. This trunk penetrates into the cavity of the abdomen, between the middle and the in- ternal head of the lesser muscle of the diaphragm, and some- times by the opening for the aorta. Having got into the abdomen, the great splanchnic divides into several fasciculi, which diverging from each other, are con- cealed on the right side by the liver, and on the left by the sto- THE SYMPATHETIC NERVE. 483 mach. On each side of the aorta there is a large ganglion formed by an assemblage of several smaller ones; it is called the Semi-lunar. Into it terminate, for the most part, these fasciculi: some of them, however, go immediately into the solar plexus, which emanates from the semi-lunar ganglion. The Small Splanchnic Nerve is derived, by filaments, from the tenth and the eleventh thoracic ganglions. Having united, they penetrate the crus of the diaphragm, and, reaching the ab- domen, the trunk is divided into two branches, of which the uppermost ascends to join the great splanchnic before its divi- sion, and the lower descends to join the renal plexus. Besides these two splanchnic nerves, it frequently happens that there are others which come from the eleventh and twelfth thoracic ganglions,and from the communicating branch between the last thoracic and the first lumbar. They unite into a trunk which goes to the renal plexus, and have been called, by Walter, the Posterior Renal Nerves. Of the Solar Plexus. The Semi-lunar Ganglion, situated, as mentioned, on the side of the aorta, is somewhat semicircular or oval, and is about an inch long; its form, however, is much diversified in different subjects. The several ganglions of which it is composed, are frequently fused into a single one. That of the right side is more voluminous than the other, and is placed between the as- cending vena cava and the crus of the diaphragm, somewhat above the right renal artery. That of the left is situated upon the left crus of the diaphragm, somewhat below the splenic ar- tery. Between their inferior extremities, there are generally two or three smaller ganglions. These several ganglions are united by numerous filaments, which send out many ramifications, and anastomose freely with each other. The preceding arrangement may be considered as the root of the solar plexus, which extends from the coeliac artery to the lower margin of the emulgents, and as it is common to the ganglions of the two sides, it is an inch and a half or two inches 484 NERVOUS SYSTEM. wide. Bichat has very properly remarked, that this plexus seems to exist for the aorta, as all the divisions which it sends out follow so exactly the branches of this artery, that we are forced to adopt the latter as the basis of the description. The intertexture and the number of the branches emanating from the solar plexus are so complicated, that a description of individual branches would be almost endless, as well as unintelligible;, ana- tomists are, therefore, generally agreed to describe the plexus according to the order of the arteries which its detachments ad- here to and surround. 1. The Diaphragmatic Plexus consists of a few filaments coming from the superior part of the solar, and following the course of the phrenic arteries. Some of them anastomose with the terminating filaments of the phrenic nerve, in the thickness of the diaphragm. 2. The Plexus ivhich surrounds the Coeliac Artery, like it, is quickly disposed into three divisions, which follow the branches of this artery. a. The Superior Coronary Plexus of the stomach, is the smallest of the three. It attends the corresponding artery along the lesser curvature of the stomach to the pylorus, sup- plying the stomach continually with very fine filaments. In its course, it anastomoses with the par vagum, and sends fila- ments to the hepatic plexus. b. The Hepatic Plexus is the largest of the three. It sur- rounds the hepatic artery and the vena portarum, and, in its course, detaches branches which go with the right gastro-epi- ploic artery to the great curvature of the stomach, and constitute the inferior coronary plexus. Branches are also sent to the pan- creas and to the duodenum. The hepatic plexus then enters the transverse fissure of the liver, and its branches may be traced to the several lobes and to the gall-bladder. c. The Splenic Plexus is but small, and surrounds the sple- nic artery. The few branches of which it is composed, anasto- SYMPATHETIC NERVE. 485 mose but rarely with each other. Some of them are distri- buted upon the pancreas, along with the pancreatic branches of the splenic artery; others go with the left gastro-epiploic ar- tery to the left extremity and to the greater curvature of the stomach; the remainder penetrate into the substance of the spleen, through its fissure, along with the branches of the sple- nic artery. 3. The Superior Mesenteric Plexus is derived from the so- lar, near the superior mesenteric artery; it descends some short distance on the aorta, before it reaches the latter. It passes with the artery between the pancreas and the duodenum, and is then included between the two laminae of mesentery; it is then distributed, by very numerous filaments, along with the branches of the artery, to the whole of the small intestines, to the coecum, and to the ascending and transverse colon. 4. The Renal Plexus, one on each side, is derived from the lower lateral part of the solar. Two or three ganglions, on the root of the renal artery, contribute to it, and it is also re-en- forced by an addition from the lesser splanchnic nerve. The branches which form this plexus do not anastomose much, till they get near the kidney; they then penetrate into its substance, through the fissure. Some filaments from this plexus go to the capsule renales: others follow the course of the spermatic arte- ry, and constitute the spermatic plexus which goes to the testi- cle in the male, and to the ovarium in the female. 5. The Inferior Mesenteric Plexus is a continuation of the solar, on the anterior face of the abdominal aorta. It is much smaller than the superior mesenteric plexus, though it receives continually, in its descent, filaments from the lumbar gangli- ons of the sympathetic. It forms frequent anastomoses around the root of the inferior mesenteric artery, and near the superior strait of the pelvis, is resolved into two columns of fibres. One column is distributed along with the artery to the rectum, to the sigmoid flexure of the colon, and to the left section of the latter, thereby anastomosing with the colic branches of the su- Vol. II.—62 486 NERVOUS SYSTEM. perior mesenteric plexus. The other column descends into the pelvis, in front of the sacrum, and contributes to form the hy- pogastric plexus, but several of its branches also follow the ex- ternal and the internal iliac arteries. Of the Lumbar Ganglions of the Sympathetic. These ganglions are five in number, on either side, and are placed anteriorly on the sides of the bodies of the lumbar ver- tebrae, near the anterior margin of the psoas magnus muscle. Their form is irregular; they are smaller than the cervical gan- glions, but larger than the dorsal. The last thoracic ganglion is united to the first lumbar by a small branch, which may be considered as the continuation of the sympathetic. A deficiency of this branch has, however, been several times observed by anatomists; also a deficiency in the connecting nervous chord of the ganglions below. The gan- glions themselves are inconstant in their number, being some- times less than five; they vary likewise in their situation. It is to be understood, however, that in a majority of subjects, the sympathetic goes on uninterruptedly from one ganglion to ano- ther, sometimes by one branch; on other occasions, by two or three. Each lumbar ganglion sends outwards one or more external branches, which applying themselves to the body of the conti- guous vertebra, reach the corresponding intervertebral foramen of the loins, and join with the anterior branch of the corre- sponding lumbar nerve. Some of these external branches are spent upon the quadratus lumborum muscle. Each lumbar ganglion, or the intermediate chord of the sym- pathetic, also detaches branches internally, which are very small, and more or less interwoven with each other. These branches get to the abdominal aorta, and, joining the inferior mesenteric plexus upon it, are distributed along with the latter. THE SYMPATHETIC NERVE. 487 Of the Sacral Ganglions of the Sympathetic. There are generally three of these ganglions which may be readily found: sometimes four or five. They are situated in a line, on the anterior face of the sacrum, near the correspond- ing foramina for the transmission of the sacral nerves; and are united with each other by intermediate fibres, from one to three in number, which are the continuation of the sympathetic nerve. Bichat asserts, that frequently the first of these ganglions is not united to the last of the lumbar by an intermediate nerve, so that there the continuity of the sympathetic is interrupted. Each ganglion sends off, externally, one or more filaments, by which it is united to the corresponding sacral nerve: it also detaches filaments in this direction to the pyriformis and the levator ani muscles. Each ganglion likewise detaches, from its internal margin, ramifications, which go obliquely downwards on the front of the sacrum, and anastomose with corresponding filaments from the opposite side. From these ganglions many branches pass forwards to the hypogastric plexus; which is formed by them, by the inferior mesenteric plexus, and by a great many filaments from the lower sacral nerves, principally the third. This plexus is distributed upon the rectum, the bladder, vesiculae seminales, and prostate of the male; and, in place of the two latter in the female, upon the vagina and the uterus. The last sacral ganglion detaches downwards one or more filaments, which lie upon the front of, the os coccygis, and anastomose with the corresponding filaments from the other side, to form a sort of arch, the convexity of which is down- wards. In this manner, terminates the chord of the sympa- thetic nerve. 488 NERVOUS SYSTEM. CHAPTER III. OF THE NERVES OF THE MEDULLA SPINALIS. The nerves of the medulla spinalis, with the exception of the first, which, from its position, is generally called the Sub- occipital by anatomists, are arranged into cervical, dorsal, lum- bar, and sacral, according to the order of the inter-vertebral foramina, through which they pass out: but a much better division would be Cervical,* Thoracic, and Abdominal. Their mode of origin, and the ganglions formed by them, have been pointed out in the account of the medulla spinalis. SECT. I.—OF THE UPPER NINE SPINAL NERVES. These are spent upon the neck, upon the upper extremities, and upon the diaphragm. They consist in the Sub-occipital Nerve, the Cervical, and the First Dorsal. Of the Sub-occipital Nerve. The Sub-occipital Nerve (Nervus Infra-occipitalis, decimus cerebri) is one of the smallest that proceeds from the medulla spinalis. It has the peculiarity, generally, of arising by a single root, which comes from the anterior chord of the medulla spi- nalis, between the occiput and the first cervical vertebra. This root consists of from two to six or seven fasciculi, situated one above another. When the posterior root exists, it is very small, is composed of from one to three fasciculi, and anasto- moses with the accessory nerve. The trunk of this nerve passes from the vertebral cavity through the foramen formed in the dura mater by the vertebral * In this case, the term Cervical would include the first eight. UPPER NINE SPINAL NERVES. 4S9 artery; it goes out below the latter, and between the occiput and the first vertebra, behind its superior oblique process. It there forms a small long ganglion, like the other spinal nerves, and then divides into an anterior and a posterior fasciculus. The anterior fasciculus is the smaller of the two; it follows, in some measure, the course of the vertebral artery, and going forwards to the front of the transverse process, is then divided into several fine filaments, some of which go to the contiguous muscles on the front of the vertebrae; others join themselves to the pneumogastric and hypoglossal nerves, and to the supe- rior cervical ganglion of the sympathetic; others anastomose with the first cervical nerve. The posterior fasciculus runs backwards, and is distributed to the recti and the obliqui muscles on the back of the neck and to the complexus. Of the Cervical Nerves. These are seven in number: the first one gets from the spinal cavity between the atlas and the dentata, and the last between the seventh cervical and the first dorsal vertebra. After the ganglion is formed upon the posterior fasciculus of each, the trunk, made by the union of the two fasciculi, di- vides almost immediately again into an anterior and a posterior trunk. Of the First Cervical Nerve. The posterior trunk is the largest, and goes directly back- wards. It has its filaments distributed to many of the mus- cles on the upper posterior part of the cervical vertebrae, and to the integuments of the part. Some of the branches ascend through the muscles, near the occiput; and, rising up on the latter, are distributed upon its integuments, and upon the occi- pito-frontalis muscle. The anterior trunk is directed forwards under the inferior oblique muscle of the neck, and then divides into two branches: the superior joins the anterior branch of the sub-occipital nerve, and anastomoses with the first cervical ganglion of the sym- 490 NERVOUS SYSTEM. pathetic, and with the par vagum and the hypoglossal nerve; the inferior joins the anterior branch of the second cervical nerve. Of the Second Cervical Nerve. This nerve issues between the second and the third cervical vertebra. Its posterior trunk is spent upon the trapezius, com- plexus, and other muscles on the back of the neck, and upon the integuments of the latter; it also anastomoses with the pos- terior trunk of the nerve above and below. The anterior branch or trunk detaches, first of all, some small filaments to the muscles on the front of the cervical vertebrae; it then divides into two principal fasciculi, one of which ascends and the other descends. The ascending branch goes upwards and backwards, and early in its course anastomoses with the first cervical nerve, thereby forming with it a nervous noose; it then mounts upon the occiput, and is distributed upon the parts on the latter region, anterior to the occipital branches of the preceding nerve. The descending branch turns over the posterior, margin of the sterno-cleido mastoideus muscle, and gives filaments to it. It is distributed afterwards by branches, some of which go to the integuments of the middle and inferior parts of the neck, (nervi subcutanei colli medii et inferiores;) others go to the integuments of the neck upon the angle and the base of the lower jaw, (nervi subcutanei superiores;) and one to the ex- ternal ear, (nervus auricularus cervicalis.) From the anterior fasciculus of the second cervical nerve there proceeds a filament downwards, which is the upper root of the phrenic nerve; another filament from it joins the superior cervical ganglion of the sympathetic. Of the Third Cervical Nerve. This nerve comes out between the third and the fourth cer vical vertebra. Its posterior fasciculus is distributed to the mus- UPPER NINE SPINAL NERVES. 491 cles on the back of the cervical vertebrae, and to the integu- ments of the part; anastomosing, by its branches, with the nerve above and below. The anterior fasciculus is larger than the posterior, and goes obliquely downwards and outwards at first; it sends anastomo- tic branches to the nerve above and below; it also anastomoses with the superior cervical ganglion of the sympathetic and with the descendens noni. One of its branches, being joined by the branch just spoken of, from the second cervical nerve, consti- tutes the root of the phrenic nerve. But the principal number of its branches are distributed to the integuments along the cla- vicle, (nervi supra-claviculares,) the upper part of the sternum, and the shoulder; some of them going into the contiguous mus- cles, as the trapezius, subclavius, &c. Several anastomoses exist between the branches of this nerve and the terminating branches of the nervus accessorius. The three preceding cervical nerves form, by their anasto- moses with each other, a plexus, consisting in a number of large loops or arches, which lie upon the sides of the muscles con- nected with the transverse processes of the cervical vertebrae. There are commonly two series of anastomoses: the branches of the first, form the second series, and from the latter proceed, for the most part, the several branches which have been de- scribed. These anastomoses are covered by the upper half of the sterno-cleido mastoid muscle, are involved in the cellular membrane surrounding the great vessels of the neck, and are covered by the lympathetic glands. Their intertexture and dis- tribution are such, that no adequate idea of them can be con- veyed without dissection. From this plexus several branches go to the sterno-mastoid muscle, and it is united above to the sub-occipital nerve and below to the fourth cervical. Of the Phrenic Nerve. The Phrenic Nerve (Nervus Phrenicus, Diaphragmaticus) arises, in the manner stated above, from the anterior fasciculus of the second and of the third cervical, and is assisted generally by two or three filaments from the upper part of the brachial 492 NERVOUS SYSTEM. plexus. It descends, vertically, on the humeral side of the in- ternal jugular vein, but removed a considerable distance from it, and is attached, by cellular substance, to the front of the scale- nus anticus muscle. Getting, in its descent, to the internal mar- gin of the latter, it passes into the thorax, at the inner margin of the first rib, between the subclavian artery and the subclavian vein, the latter being before it. It then goes along the superior mediastinum to the pericardium, to the side of which it adheres in front of the root of the lung, being between the pericardium and the corresponding portion of the pleura; it finally reaches the diaphragm, to which it is distributed. Just before the phrenic nerve reaches the diaphragm, it radi- ates into several branches, which interchange filaments. Some of the branches are distributed to the convex surface of the dia- phragm; others penetrate the muscle, and are distributed in its thickness and upon its concave surface. On the right side some of these branches pass through the opening for the ascending vena cava, and, thus getting into the abdomen, anastomose with the solar plexus, and with the pneumogastric nerve. The phrenic nerve of the left side is nearer to the root of the lung'than that of the right, in consequence of the projection of the apex of the heart on that side. Its distribution in other re- spects does not present any remarkable difference from the other; its branches radiate in the same way to the diaphragm, and sup- ply its thickness, as well as its upper and under surfaces. It sends some filaments to the lower part of the oesophagus. The phrenic gives off in the neck a few filaments to the sca- lenus anticus, and'the rectus anticus major muscle. It also com- municates there, with filaments from the inferior cervical gang- lion, and sometines from the superior cervical. Of the Four Inferior Cervical Nerves. The trunks of these nerves, on issuing from the intervertebral foramina, have one general mode of distribution, which permits them to be described together or in Common. The posterior branches are much smaller than those of the preceding cervical nerves; they go backwards between the UPPER AND LOWER SPINAL NERVE. 493 complexus and the transversalis colli, and leave filaments in their passage with them; they then reach the splenius and the trapezius, to which and to the integuments of the neck they are distributed. The anterior branches are large; they appear on the side of the neck, between the scalenus anticus and medius muscle; some- times perforating the substance of one or the other of these mus- cles. They each detach filaments to the sympathetic. The fourth, also, commonly sends one to the phrenic. They then form the Brachial Plexus. Of the Brachial Plexus and the Nerves of the Upper Extremity. The Brachial or the Axillary Plexus is formed by the junction and the intertexture of the four inferior cervical nerves, and the first dorsal or thoracic. It extends from the scaleni muscles to the axilla, on a level with the neck of the os humeri. The nerves at first converge, and are situated somewhat behind the subcla- vian artery where it passes over the first rib; but are at various heights above it, according to their origin, with the exception of the first dorsal nerve, which has to ascend in order to pass out of the thorax. The plexus is formed in the following manner. The fourth and the fifth cervical nerves unite near the scaleni muscles into a single trunk, which runs a short distance downwards, and then splits into two. The seventh cervical and the first dorsal do the same. The sixth cervical is the central nerve of the plexus, and after going downwards two or three inches, it bi- furcates also. Combinations of these primary divisions are formed, which'are dissolved, and then reformed, in such a way that a thorough intertexture of the original nerves takes place. This intertexture surrounds the axillary artery somewhat like the braids of a whip-cord, from the clavicle to the os humeri below its head. In this course the axillary plexus passes along with the artery between the subclavius muscle and the first rib, lies in contact with the superior part of the serratus major anticus muscle, and immediately below the articulation of the shoulder joint. The axillary vein is in front of it. Vol. II.—63 494 NERVOUS SYSTEM. The nerves which proceed from the axillary plexus are the Scapular; the Thoracic; the Axillary; the two Cutaneous; the Radial; the Ulnar; and the Median. They supply the superior extremity, including the shoulder and the axilla. 1. The Nervus Scapularis is a small branch coming common- ly from the upper part of the plexus, as formed by the fourth cervical nerve. It goes backwards in company with the arte- ria dorsalis superior scapulae, through the notch or foramen of the upper costa of the scapula; and having thus got to the pos- terior face of the latter, it gives filaments to the supra spinatus muscle; continuing its course then on the posterior face of the cervix scapulae, it is lost in filaments upon the infra-spinatus and teres minor muscles. 2. The Nervi Subscapulares of Bichat present some varieties in their origin; occasionally they come from the same trunk, but commonly each one has its peculiar root from the central parts of the axillary plexus. They are generally three of them. One of them descends behind the axillary vessels, between the sub- scapularis and the serratus major anticus; it crosses the teres major, and is lost upon the contiguous part of the latissimus dor- si. Another is distributed upon the subscapularis muscle. The third descends along the anterior margin of the subscapularis for a short distance, and distributes filaments to it, to the teres mi- nor and major muscles. 3. The Nervi Thoracici are primarily two or three in number, and proceed from about the middle of the plexus. The fascicu- li into which they are resolved, may be distinguished as anterior and posterior. The former are distributed, by filaments, to the subclavian muscle, to the pectoralis minor and major, and to the integuments covering the latter. The posterior thoracic has its origin somewhat concealed by the scalenus anticus muscle. It descends into the axilla, adhering to the serratus major muscle for some distance, and is then distributed by many filaments to this muscle. 4. The Nervus Axillaris, or Circumjlexus, comes from the infe- UPPER NINE SPINAL NERVES. 495 rior part of the plexus. Immediately after its origin, it goes downwards and outwards over the upper extremity of the sub- scapularis muscle. It then winds around the os humeri, between the teres minor and major muscles, observing the course of the posterior circumflex artery, and, finally, terminates on the under surface of the deltoid muscle. This nerve sometimes gives off the subscapular, and, indeed, it is usual for anatomists to include the description of the latter in it. As it turns around the bone, it divides into two principal trunks; the superior goes to the inferior margin of the infra-spi- natus, and to the posterior margin of the deltoides; the inferior is distributed principally in the substance of the deltoid muscle, but some of its filaments, by perforating the latter, reach the skin, and constitute the nervus cutaneus humeri. Filaments go from the nervus axillaris, in the early part of its course, to the subsca- pularis and the two teres muscles. 5. The Nervus Cutaneus Internus* arises from the lower part of the axillary plexus, and is one of the smallest of those which go to the arm. It is situated between the median and the ulnar nerve, and adheres almost as far as the elbow, to the basilic vein. In its descent, this nerve detaches several small filaments, which, perforating the fascia of the arm, are distributed to the integuments of the biceps muscle, and to those on the internal face of the triceps. Somewhat above the bend of the elbow, at the place where the median basilic vein joins the basilic, but occasionally some inches higher up, the internal cutaneous becomes superficial, and splits into two branches of nearly equal magnitude, which di- verge but little from each other at first. The branch nearest the internal condyle of the os humeri, lies in front of the basilic vein, as it passes over the elbow joint; and continues in this position for two or three inches: it goes down the front of the fore arm on its ulnar side, but inclines continually to the back of the fore arm. In this course, it detaches small ramifications to the inte- guments about the internal condyle, and about the heads of the flexor muscles; it also detaches continually, from its sides, small * Antonius and Caldani, Tabul. CCLV1II. 496 NERVOUS SYSTEM. filaments to the integuments of the ulnar side of the fore .arm both anteriorly and posteriorly, some of which reach to the hand. The other, or the external branch of the internal cutaneous, which is nearer the radius, passes beneath the median basilic * vein, about six lines from the basilic; but, just before it does so, it detaches a very superficial cutaneous filament, which crosses in front of the median basilic vein about its middle, and is lost a little below the bend of the arm. The outer branch of the in- ternal cutaneous having got from beneath the median basilic vein, goes superficially as far as the middle of the fore arm without sending off any filaments of note; it is then divided suc- cessively into several, which diverge to supply the skin down to the wrist. 6. The Nervus Musculo-Culaneous, or Cutaneous Externus, is somewhat larger than the preceding, and arises from about the middle of the brachial plexus. It descends a short distance, and then perforates obliquely the upper part of the coraco-brachialis , muscle. Having passed through this muscle, it continues its course obliquely, between the brachialic internus and the bi- ceps flexor, and, finally, makes its appearance superficially on the outer side of the tendon of the latter. In this course, it distributes filaments to the several muscles with which it is con- nected. It afterwards passes the elbow joint under the median cepha- lic vein near its middle, and descends between the skin and the fascia of the fore arm, near the outer margin of the me- dian vein, to the hand: in this course, it is parallel with and on the front of the supinator radii longus. It distributes many filaments to the corresponding integuments on the radial side of the fore arm, and, having at length got near the lower end of the radius, it divides into two orders of fibres, one of which is distributed to the integuments on the dorsal, and the other to those on the palmar side of the hand, about the root of the thumb. 7. The Nervus Radialis, or Musculo Spiralis, arises from the upper portion of the brachial plexus, but in such a way, that filaments from almost every part of the latter run into it. NERVES OP THE UPPER EXTREMITY. 497 It is a large trunk which winds spirally around the os humeri^ between the triceps muscle and the bone, entering the fissure between the first and the third head of the triceps. It appears on the outside of theos humeri, between the brachialis internus and the triceps muscle; running for some inches in contact with their intermuscular ligament. While beneath the triceps, it sends several branches to its heads. There are three principal trunks afterwards from this nerve. a. The Ramus Superficialis Dorsalis is sent from it on a line with the point of the deltoid muscle. This branch then goes just below the skin, parallel with and over the external ridge of the os humeri; it, of course, crosses the origin of the mus- cles of the external condyle. It continues superficial on the posterior external edge of the supinator radii longus muscle, and terminates in the integuments on the back of the hand. The continued trunk of the muscular spiral goes in the inter- stice between the extensor muscles and the brachialis inter- nus, and, at the external condyle, divides into the other two branches, from which filaments proceed to the contiguous heads of the muscles. b. The Ramus Profundus Dorsalis perforates the supinator brevis muscle, getting beneath the radial extensors to the back of the fore-arm; it is then distributed in numerous filaments to the muscles on the back of the fore arm, some of its branches reaching to the wrist. c. The Ramus Superficialis Anterior seems to be a continua- tion of the main trunk of the nerve, and descending at the an- terior margin of the supinator radii longus muscle, it joins with the radial artery and continues in its company to a short distance below the middle of the radius. Here it crosses the bone obliquely beneath the tendon of the supinator longus, and then divides into a palmar and a dorsal ramuscle; the first being distributed to the muscles and integuments of the thumb, the second terminating so as to supply the back of the hand, of the thumb, fore, middle, and ring fingers to their extremities. 8. The Nervus Medianus descends the arm at the inner edge of the biceps muscle; along the anterior surface of the 498 NERVOUS SYSTEM. brachial artery, adhering firmly to it, and the deep-seated veins, by cellular substance. As far as the elbow, it sends off no branch of importance. There it lies at the side of the biceps tendon, crosses the lower part of the brachialis internus, and is beneath the aponeurosis of the biceps. It then perforates the pronator teres and gets between the flexor sublimis digito- rum, and the flexor longus pollicis, and enters the palm of the hand under the ligament of the wrist, at the radial edge of the tendons of the flexor sublimis. In the palm it is situ- ated beneath the aponeourosis pulmaris and the arcus sublimis of the arteries. The median nerve dispenses the following branches:—At the bend of the arm, it furnishes filaments to the heads of the first layer of muscles of the fore arm; and a little below, it de- taches the nervus interosseous, which supplies filaments to the flexor longus pollicis and flexor profundus digitorum. The in- terosseous nerve then descends with the interosseous artery in front of the interosseous ligament, and terminates in the prona- tor quadratus. Before the median nerve reaches the wrist, it sends a branch which supplies with filaments the muscles and integuments of the ball of the thumb. In the palm of the hand, it divides and subdivides so as to send a branch to each side of the thumb, of the fore, and of the middle finger, and to one side of the ring finger. • These branches go along with the arteries to the ends of the fingers and thumb. 9. The Nervus Ulnaris comes from the lowest section of the brachial plexus. It descends along the internal anterior part of the triceps muscle, in a groove formed between it, and the intermuscular ligament; it diverges, in this course, gradu- ally from the median nerve till it reaches the elbow, when it is at its greatest point of separation. At the elbow, it is behind the internal condyle, in the groove between it and the olecra- non, and separates the two heads of the flexor ulnaris mus- cle. It then gets to the fore arm between this muscle and the flexor profundus digitorum, and continues between them to within two inches of the wrist joint, when it detaches the Ramus Dorsalis. NERVES OF THE UPPER EXTREMITY. 499 The Ramus Dorsalis dips between the ulna and the tendon of the flexor ulnaris, runs along the internal margin of the ulna to the carpus; it then divides into ramuscles, which supply the ulnar side of the integuments on the back of the hand, and on the backs of the two last fingers. At the interval behind, be- tween the heads of the metacarpal bones of the middle and ring fingers, a considerable ramuscle joins one from the branch of the muscular spiral nerve which attended the radial ar- tery. The Ulnar Nerve, having given off this dorsal branch, de- scends along the radial margin of the tendon of the flexor ul- naris and the os pisiforme, above the annular ligament, to the palm of the hand. Getting beneath the aponeurosis, it there detaches first a deep-seated branch, which penetrates the mus- cles of the little finger to supply them, the interossei, and the short flexor of the thumb. The ulnar nerve then furnishes a superficial branch, and afterwards divides into three; one for the ulnar side of the little finger, another for the opposing sides of the little and ring finger, and a third which joins the most internal digital branch of the median nerve. SECT. II.--OF THE THORACIC SPINAL NERVES. The Dorsal or Thoracic Spinal Nerves (Nervi Thoracici, Dorsales) consist in twelve pairs, the first pair goes through the intervertebral foramina, between the first and the second dorsal vertebra, and the twelfth pair between the last dor- sal and the first lumbar vertebra. The common trunk, formed after the ganglion of each nerve, goes but a short distance when it divides into an anterior and a posterior branch. The Posterior Branch (Ramus Dorsalis) of each nerve., goes backwards between the transverse process of the corre- sponding vertebrae, and, having got beneath the multifidus spinas, is commonly subdivided into internal and external ramuscles. The internal are the smaller, and are distributed upon the mus- cles lying upon the spine, as the multifidus, the sacro-lumbalis, 500 NERVOUS SYSTEM. longissimus dorsi, and so on: their terminating filaments reach the skin. The external branches descend obliquely outwards beneath the longissimus dorsi, and then issue between the latter and the sacro-lumbalis, to both of which they dispense filaments: they afterwards are divided into branches, which go to the tra- pezius, latissimus dorsi, rhomboideus and to the corresponding integuments. The Anterior Branches of the Dorsal Nerves (Rami Sub- coslales) correspond with the intercostal spaces of the ribs. Each one, in a short course after its origin, applies itself to the rib just above it, and accompanies the intercostal vessels in the groove, formed in the under margin of each rib. After it pro- ceeds about two-thirds of the length of the rib, it separates gra- dually from it, and goes nearer the middle of the intercostal space and the superior margin of the rib below. To the angle of the rib, each nerve is only covered in front by the pleura, but afterwards it goes between the intercostal muscles. Near the sternum, the branches become superficial by escaping from between the intercostal muscles, and are distributed upon the pectoral muscles, and the adjacent skin. These terminating branches of the five or six inferior dorsal nerves go to the upper portions of the abdominal muscles and their integuments. Not far from its origin, each dorsal nerve anastomoses with the gang- lion or chord of the sympathetic, after the manner described in the account of the latter nerve. There are some differences between the thoracic nerves in their manner of distribution. The anterior fasciculus of the first, as mentioned, forms the lower part of the axillary plexus by joining itself to the se- venth cervical. It sends out, however, a subcostal branch which goes along the inferior face of the first rib, supplying the intercostal muscles and having the general distribution al- luded to. The Second Subcostal Branch, besides the common distribu- tion, detaches a fasciculus, which, penetrating between the ribs, gets into the axilla and is augmented by a branch from the i. THORACIC SPINAL NERVES. 501 internal cutaneous nerve of the upper extremity. It then de- scends along the internal posterior face of the arm to the elbow, and in this course detaches several fine filaments to the integu- ments. The Third Subcostal Branch in like manner detaches an axillary fasciculus which goes to the inferior part of the arm- pit, to the integuments of which, and to those on the internal face of the arm, it is distributed. It does not descend quite so low as the preceding. These two nerves are called Intercosto- Humeral, and from their origin and course, are supposed to account for the numbness of the arm, in cases of angina pec- toris. The Fourth, Fifth, Sixth, and Seventh Subcostal Branches of the Dorsal or Thoracic Nerves, about the middle of the ribs to which they respectively belong, are all divided into two branches. One of them, which is properly speaking the in- tercostal, continues in the intercostal space, giving filaments to its muscles and to the triangularis sterni; it then emerges near the sternum to terminate upon the great pectoral muscle, the mamma, and the integuments of the front of the thorax. The other branch is the external pectoral: it extricates itself earlier from the intercostal space, and is distributed upon the muscles and the integuments on the side of the thorax. The remaining subcostal branches, to the eleventh inclu- sively, have very much the same principle of distribution. Their intercostal fasciculi, having reached the anterior ends of the intercostal spaces, pass on to the abdominal parietes, be- tween the transversalis muscle and the internal oblique, to both of which they give filaments. They reach the external margin of the rectus abdominis muscle, and then divide into filaments, some of which go to this muscle, others pierce the fore part of its sheath and are ramified upon the integuments of the front of the abdomen. The Twelfth Subcostal Branch of the Dorsal Nerves, sends first a branch downwards, which joins with the first lumbar nerve. It then crosses in front of the quadratus lumborum muscle, to which it gives filaments as well as to the adjoining portion of the diaphragm. It afterwards divides into two branches, the superior of which goes for some distance between Vol. II.—64 502 NERVOUS SYSTEM. the two oblique muscles of the abdomen, detaching filaments to them, and finally terminates on the integuments of the ab- domen; the other branch goes between the transversalis and the internal oblique, and is extended to the lower part of the rectus, and to the pyramidalis muscle, to all of which it distri- butes filaments. SECT. III.—OF THE ABDOMINAL SPINAL NERVES. There are five lumbar, and five, sometimes six, sacral nerves on each side; the first of them passes out of the intervertebral foramen, between the first and the second lumbar vertebra; and the remaining lumbar and sacral nerves go, successively, through the foramina in the loins and in the sacrum. The anterior fasciculi of these nerves, form a plexus which extends from the upper part of the loins to the lower part of the sacrum; it is designated under the general term of Plexus Cruralis. The posterior fasciculi are much smaller. Those of the loins go backwards between the transverse processes, and are distributed upon the sacro-lumbalis, the longissimus dorsi, the multifidus spina?, and the corresponding integuments. The pos- terior fasciculi of the sacral nerves are not so large, generally, as those of the lumbar: they get out through the foramina, on the posterior face of the sacrum, are distributed to the same muscles; to the origin of the glutaeus magnus, and to the inte- guments of the sacrum, and of the adjoining portion of the but- tocks. The Plexus Cruralis, for the purpose of description, has been divided by anatomists into the Plexus Lumbalis, formed by the four superior lumbar nerves, and the Plexus Ischiadicus, formed by the last lumbar and the sacral nerves. The Lumbar Plexus (Plexus Lumbalis) is concealed by the psoas magnus muscle, and is placed between it, the lumbar ver- tebrae, and the quadratus lumborum: frequently the roots of the nerves forming this plexus penetrate through the substance of the psoas magnus, and form their unions in it. The plexus is narrow and pointed above, where it commences by the fasci- culus of the last dorsal nerve joining the first lumbar; but it in- ABDOMINAL SPINAL NERVES. 503 creases continually afterwards in breadth, owing to the nerves composing it, successively anastomosing farther and farther from the spinal column. From this plexus proceed three principal trunks: the upper one (Cruralis Anterior) is of considerable size; and goes to the skin and the muscles on the front of the lower extremity; the middle (Nervus Obturator) is not so large as the preceding, and goes through the obturator foramen to the adductor muscles of the thigh; the inferior, formed by the whole of the fifth and a fasciculus from the fourth lumbar nerve, joins the upper part of the sciatic plexus in the pelvis. Besides these, there are several branches of smaller size and of less im- portance, proceeding from the lumbar plexus. The Abdomino Crural Branches, according to Bichat, are most commonly three in number, and come from the two upper lumbar nerves. The first of them goes obliquely downwards and outwards, in front of the quadratus lumborum, to the posterior part of the spine of the ilium, and runs for a short distance along the crista of the bone: it gives filaments to the iliacus internus, and to the abdominal muscles, where they border on this part of the bone. Some of the filaments become cutaneous, but the main trunk of the nerve reaches the anterior superior spinous process, by going between the transversalis and the internal ob- lique muscle; it then follows the inguinal arch to the external ring, through which it passes, and is distributed in filaments upon the groin, the pubes, and the scrotum. The second or middle branch arises from the plexus near the preceding; it descends along the external margin of the psoas magnus, and crosses the ilia- cus internus, covered by the peritoneum; near the anterior superior spinous process, it gets between the lower margins of the abdominal muscles, and is distributed upon them there: some of its ramifications get also through the external ring, and may be traced to the scrotum. The third, or the inferior branch, arises from the plexus still lower down, and, after having tra- versed the front of the iliacus internus, it emerges from the pel- vis beneath Poupart's ligament, near the anterior superior spi- nous process; it then divides into filaments which penetrate to the skin through the femoral fascia, and are distributed along the external anterior face of the thigh. 504 NERVOUS SYSTEM. The Spermaticus Externus arises from the upper part of the plexus, by a fasciculus from the first lumbar nerve, which is increased by one from the second lumbar. It descends at first in the body of the psoas magnus muscle and then in front of it: it crosses the iliacus internus, somewhat above Poupart's Ligament, by directing its course towards the anterior superior spinous process of the ilium. Here, it involves itself in the edge of the abdominal muscles, and goes on the posterior face of Poupart's ligament; at the internal abdominal ring it joins the spermatic chord of the male, or the round ligament of the uterus of the female. In the first case, it is distributed to the spermatic chord and scrotum; in the second, to the labium ex- ternum and mons veneris. The Cutaneus Externus arises from the lumbar plexus be- low the external spermatic. It passes across the iliacus in- ternus towards the anterior superior spinous process, about an inch below the spermaticus externus, and crosses the latter nerve just at that process. Emerging from the abdomen, by penetrating the commencement of Poupart's ligament, it is dis- tributed in several branches to the integuments of the vastus externus muscle, and along the edge of the rectus femoris: one of the latter extends to the patella. The Cutaneus Medius is detached from the anterior crural, an inch or so above Poupart's ligament. It arises among the cluster of branches, which come off there to be distributed to the iliacus internus muscle, and to the muscles of the thigh. It appears, superficially, on the thigh, for the first time, by pene- trating the sartorius muscle, about the internal edge of the rec- tus femoris: it descends then along the same edge of the latter muscle, and is distributed to its integuments. It does not de- scend so low as the external cutaneous. The Cutaneus Anterior arises, also, from the crural nerve. It is on the inner side of the cutaneus medius, emerges from the fascia of the thigh, and crosses the sartorius muscle two or three inches below the cutaneus medius. It is distributed on the in- teguments of the vastus internus muscle, and some of its branches extend to the internal edge of the patella. ABDOMINAL SPINAL NERVES. 505 The Cutaneus Internus arises from the anterior crural nerve, among the same cluster, above Poupart's ligament. It divides into four or five branches of different lengths, and is distributed to the integuments of the adductor muscles, and along the inner front side of the thigh. One branch observes very much the course of the tendon of the adductor magnus, and reaches as far down as the inner side of the knee. The Cruralis Anterior arises from the middle of the lum- bar plexus; at first, it is beneath the psoas magnus muscle; it then gets to its outside, and passes from the abdomen, under Poupart's ligament, about half an inch from the outside of the femoral artery. Before it reaches Poupart's ligament, it gives off a cluster of nerves, several of which go to the iliacus inter- nus muscle; others form the superficial or cutaneous nerves of the thigh just mentioned; and others, the deep-seated or mus- cular branches, which supply the adductor muscles, the four extensors, the pectineus, the sartorius, and the gracilis. One of the branches of the anterior crural nerve is seen to accompany the femoral artery, till the artery penetrates the adductor magnus; it then runs along the front margin of the tendon of the adductors in a theca formed by this tendon and the origin of the vastus internus. The nerve alluded to is the Saphenus; it passes afterwards between the internal condyle of the os femoris and the sartorius muscle, attaches itself to the saphena vein, and is distributed to the integuments of the inner side of the leg, and of the upper internal parts of the foot. The Nervus Obturatorius is derived from the middle of the lumbar plexus, also; and has very much the same position, in regard to the psoas magnus, as the anterior crural nerve. It descends into the pelvis from beneath the psoas magnus, near the sacro-iliac articulation; and passes forwards and downwards to the obturator foramen; having got through which it divides into an anterior and posterior branch. The first is distributed to the head of the adductor longus and brevis, and to the gra- cilis and integuments. The second terminates in the obturator externus, and the adductor magnus. 506 NERVOUS SYSTEM. The Sciatic Plexus (Plexus Ischiadicus) is fbrmed by the union of the last lumbar with the four upper sacral nerves; the last lumbar, before it joins the plexus, receiving the branch of the fourth lumbar nerve, which is left after the lumbar plex- us is formed. This plexus is situated at the side of the rectum before the pyriformis muscle. The volume of the posterior branches of the Sacral Nerves increases till the fourth; but the fifth and the sixth are much smaller, in fact only fibrillae. The anterior branches of the sacral nerves are much larger than the posterior. The four first communicate with the sacral ganglions of the great sympathetic, besides forming the ischi- atic plexus. The third and the fourth, assisted by the sympa- thetic, form the hypogastric plexus. The fifth, and the sixth, when it exists, are distributed to the coccygeus, sphincter, and levator ani.* The following small branches go from the Sciatic Plexus, f a. Nervi Glutaei: one passes through the upper part of the sciatic notch along with the artery, to the glutaeus medius and minimus; another below the pyriformis muscle to the glutaeus magnus. b. Nervus Pudendalis Longus Inferior, passes under the tuber of the ischium to the glutaeus magnus; perineal mus- cles; urethra and integuments of the penis and scrotum in men; and to the inferior parts of the labium externum in wo- men. c. Ramus Femora lis Cutaneus Posterior. This nerve is placed between the integuments of the thigh and the muscles which arise from the tuberosity of the ischium. It sends many branches, successively, to the skin on the back of the thigh; one of its branches, longer than the others, goes down to the ham, • This is only given as the most frequent arrangement of the sciatic plexus, and of the branches of nerves which proceed from it? other arrangements will often be met with in the cavity of the pelvis, in which not so many sacral nerves are sent to the plexus ischiadicus, and the several branches proceeding from it, depart in a different manner. f They sometimes come from a common trunk called, in such case, the Small Sciatic. ABDOMINAL SPTNAL NERVES. 507 and there divides into several filaments, which are distributed to the integuments on the back of the leg. The Nervus Pudendalis Longus Superior comes from the third and fourth sacral. It goes in company with the internal pudic artery between the sacro-sciatic ligaments, and then di- vides into two branches; the inferior is distributed to the in- teguments and muscles of the perineum, to the urethra and scrotum; the superior passing along the ramus of the ischium and pubes with the trunk of the internal pudic artery, is dis- tributed to the obturator internus, accelerator urinae, urethra, and afterwards, getting between the symphysis of the pubes and the penis, terminates on its integuments and the glans penis. The Nervus Ischiadicus, or the Great Sciatic, is the com- mon trunk, formed from the sciatic plexus; it is much the largest nerve in the body, and passes from the pelvis between the pyriformis and the geminus superior. It crosses, vertical- ly, the small rotator muscles of the thigh, being concealed by the inferior edge of the glutaeus magnus; it is there about half- way between the tuberosity of the ischium and the trochanter major. Thence it descends on the back of the adductor mag- nus, at the outer edge of the long head of the biceps flexor cru- ris. About half way down the thigh, sometimes a little lower, the Sciatic Nerve divides into the Popliteal, or Posterior Tibi- al, and Peroneal. Occasionally this division takes place as high as the exit of the nerve from the pelvis; but in this case the fasciculi are parallel with each other as far as the middle of the thigh. From the trochanter minor to its usual place of division, this nerve is parallel with, and on the back of the thigh bone; afterwards the two branches begin to diverge. The popliteal nerve continues straight downwards to the back and middle of the knee-joint, and to the interstice between the heads of the gastrocnemius muscle; whereas the peroneal nerve goes along the inner posterior edge of the biceps flexor cruris, and passes between its tendinous insertion and the external head of the gastrocnemius muscle. In this course, the following branches are sent from the seia- 50S NERVOUS SYSTEM. tic.—Twigs to the little rotator muscles of the thigh.—The Cu- taneus Internus Superior, which arises near the upper part of the thigh, and is distributed to the skin of the corresponding part.—The Cutaneus Internus Inferior, which arises just below the last, and, descending upon the inner head of the gastrocne- mius, is distributed to the integuments of the calf of the leg.— A large trunk, and sometimes, instead of it, distinct branches, which go to the Adductor Magnus, Semi-membranosus, Biceps, and Semi-tendinosus. The Peroneal Nerve (Nervus Peroneus) divides at the head of the fibula into two branches, the Peroneus Externus and the Tibialis Anterior; but, before this division, it sends a small branch to the external parts of the knee-joint, and two cutane- ous branches called Peroneo-Cutaneous. The Internal Pero- neo-Cutaneous descends behind the external head of the gas- trocnemius, and, at the bottom of the leg, is united to a division of the posterior tibial called the External Saphenus, or Commu- nicans Tibiae. The External Peroneo-Cutaneous is distributed to the skin, along the fibula. The External Peroneal Nerve (Peroneus Externus) gets between the head of the peroneus longus and the fibula, then between the peroneus longus and the extensor longus digito- rum. It descends, at the outer edge of the last muscle, to the inferior third of the leg, giving out, in the mean time, many muscular branches. Here it penetrates the aponeurosis, and divides into cutaneous branches, which supply the lower part of the leg, and the upper surface of the foot and toes. This nerve is called, by the French, the Musculo-Cutaneous of the leg. The Anterior Tibial Nerve (Tibialis Anterior) gets oblique- ly between the fibula, the peroneus longus, and the extensor longus digitorum, to the front of the interosseous ligament, where it accompanies the anterior tibial artery. It passes, with the artery, under the annular ligament of the ankle, and has its terminating filaments going to the muscles and integuments of the upper surface of the foot, as far as the end of the two first ABDOMINAL SPINAL NERVES. 509 toes. One of its branches sinks down with the anterior tibial artery to the sole of the foot. High up in the leg it gives fila- ments to the knee-joint, and, in its course downwards, it fur- nishes the muscles on the front of the leg. The Posterior Tibial, or Popliteal Nerve, (Nervus Popli- teus,) having the direction mentioned, is placed between the skin and the popliteal vein. It gets between the heads of the gastrocnemius muscle, and perforates the origin of the soleus; going with the posterior tibial artery, between this muscle and the flexor longus digitorum, to the bottom of the leg. It gives off the following branches:— a. The External Saphenus, (Saphenus Externus, or Com- municans Tibiae?) which arises above the knee-joint, and, de- scending between the skin and the gastrocnemius, turns out- wardly, and anastomoses with the cutaneous branch, alluded to, of the peroneal nerve. The common trunk, thus formed, passes behind the external ankle, along the external margin of the foot, and terminates on the last toes, having given off a great number of cutaneous branches. b. Branches to the heads of the gastrocnemius^ soleus, plan- taris, and popliteus. c. Branches to the flexor longus digitorum, tibialis posticus, and to the flexor longus pollicis pedis. d. A branch through the interosseous ligament, above, to the tibialis anticus. e. At the inferior part of the leg many cutaneous filaments, one of which gets to the sole of the foot. The Posterior Tibial Nerve, having given off these branches, divides, in the hollow of the os calcis, into Internal and Exter- nal Plantar Nerves. The Internal Plantar (Plantaris Internus) proceeds along- side of the tendon of the flexor longus muscle of the great toe, and the flexor longus digitorum, and gives filaments to the con- tiguous muscles. It then divides in such a way as to furnish Vol. II.—65 510 NERVOUS SYSTEM. the two sides of the three first toes and4he internal side of the fourth. The External Plantar (Plantaris Externus) proceeds with the artery of the same name to the outer edge of the foot, be- tween the flexor brevis digitorum and the flexor accessorius. It is distributed to the two sides of the little toe, and to the ex- ternal side of the fourth toe. One branch penetrates to the in- terosseous muscles and to the transversalis pedis. A branch of considerable size is detached, near the heel, to the muscles and integuments connected with the os calcis. INDEX TO VOL. It. Abdomen, generally, ♦ ' General Situation of the Viscera of, . Veins of, . • * Abdominal Aorta, Branches of, » Absorbent Glands of the Abdomen, Head and Neck, Lower Extremity, . Upper Extremity, Thorax, . Absorbents of the Pelvis, Head and Neck, . , • Upper Extremities, and the Contiguous Parts of the Trunk of the Bodys Inferior Extremities, and the Contigu- ous Parts of the Trunk of the Body, Organs of Digestion, Parietes of the Trunk, Viscera of the Thorax, Absorbent System, Special Anatomy of, General Anatomy of, Accelerator Urinae, Aorta, and the Branches from its Curvature, Aqueous Humour, Aqueducts of Ear, Arachnoidea, • » Areola, • • • Arcus Sublimis, - Arteries, Texture of, Arteria Basilaris, • . ad Cutem Abdominis, Alveolaris Superior, Anastomotica, (Arm,) Anastomotica, (Thigh,) . • Articularis Superior Interna, lhign, Articularis Superior Externa, *« Articularis Media, . Axillaris, Page 5 264 222 303 292 296 294 310 297 290 293 295 299 307 305 290 281 98 195 427 445 343 121 219 195 164 381 238 207 215 241 241 242 242 212 512 INDEX. Arteria Articularis Inferior Externa, Thigh, Articularis Inferior Interna, Auricularis Posterior, Brachialis, . . Buccalis, Callosa, Carotis Primitiva, Carotis Interna, Carotis Externa, Cavernosa Profunda Penis, Coeliaca, . Cerebri Posterior, Cervicalis Posterior, Choroidea, Ciliaris, Circumflexa Anterior of Axillaris, Circumflexa Posterior, Circumflexa Externa, Circumflexa Interna, Circumflexa Ilii, Colica Sinistra Superior, . Colica Sinistra Media, Colica Sinistra Inferior Communicans Posterior of Brain, Dentalis Inferior, Dorsalis Carpi, Dorsalis Hallucis, Dorsalis Manus, Epigastrica, Facialis, . Femoralis, Frontalis, . Gastrocnemea Gastrica, . Gastrica Dextra, Gastrica Sinistra, Glutea, Haemorrhoidea Inferior Externa, Haemorrhoidea Media, Haemorrhoidea Superior Interna, Hepatica, lliaca Interna,. lliaca Externa, llio-Lumbaris, Innominata, Intercostalis Superior, Interossea Anterior, Interossea Posterior, Infra-Orbitalis, Inferior Cerebelli, Ischiadica, INDEX. 513 Arteria Lachrymalis, Lingualis, Magna Pollicis, Mammaria Externa, Mammaria Interna, . Maxillaris Interna, Malleolaris Externa, Malleolaris Interna, Mesenterica Inferior, Mesenterica Superior, Metatarsea, Meningea Parva, Meningea Magna Muscularis of Orbit, Nutritia, Brachialis, Nasalis, Obturatoria, Occipitalis, GSthmoidea, Palatina Superior, Palmaris Profunda, Palpebralis, Peronea, . Pedioea, Perinea, . Pharyngea Inferior, Pharyngea Superior, Plantaris Interna, Plantaris Externa, Poplitea, Profunda Femoris, Profunda Major Humeri, Profunda Minor, " Pterygoidea, Pudica Interna, Radialis, Radialis Indicis, . Recurrens Radialis, Recurrens Ulnaris, Sacra Media, . Scapularis, Superior Scapulae, Spheno-Palatina, Superficialis Volae, Superior Cerebelli, Splenica, Subclaviana, Tarsea, Temporalis, Thyroidea Inferior, Thyroidea Superior, 199 514 INDEX, Arteria Thoracica Longa, Thoracica Acromialis, Thoracica Axillaris, . Transversalis Faciei, Temporalis Media, Temporalis Profunda, Aorta, Thoracic Branches of, Thoracica Superior, Tibialis Anterior, Tibialis Postica, Tibialis Recurrens, . Tympanica, Ulnaris, Uterina, Vertebralis, Arteriae Bronchiales, OEsophageae, Capsulares, Emulgentes, Gastricae Breves, Gemellae, . Intercostales Inferiores Aorticae Iliacae Primitivae, Lumbares, Mediastinales Posteriores, , Pancreaticae Mediae et Sinistrae, Phrenicae, Profundae Perforantes Femoris, Pudendae Externae, Sacrae Laterales, Spermaticae, Vesicales, Arytenoid Cartilages, Aryteno-Epiglottideus, Arytenoideus Obliquus, Transversus, Auditory Nerve, . Axillary Artery, Branches of Biliary Ducts, Bile, Bladder, Structure of, Blood, . Coagulating Lymph of, Red Globules of, Serum of, Bones of Tympanum, Brachial Artery, Branches of, Broad Ligaments of the Uterus, Brain, INDEX. 515 Brain, Veins of, Carotids, Branches of, . Capillaries, Capsule of Glisson, Caul, Situation of, Coecum, Cerebellum, Cerebrum, Chambers of Eye, . Choroidea, Chorda Tympani, . Chylopoietic Viscera, • Assistant, Cilia, . Circulation of the Foetus, Peculiarities of, Peculiarities of, connected its Nourishment, Circulatory System, with General Anatomy Considerations on of, . Special Anatomy of Clitoris, Coccygeus, Muscle, Cochlea, Colon, Commissura Anterior, Conjunctiva, . Corona Glandis, . Cornea, Corpus, Callosum, Cavernosum, Ciliare, Dentatum, Fimbriatum, Spongiosum, Spongiosum Vaginae, Corpora Striata, Crura Cerebri, Couper's Glands, Coronary Arteries, Veins, Cremaster Muscle, Cricoid Cartilage, Crico-Arytenoideus Posticus, Lateralis, Crico-Thyroideus, Dartos Muscle, Ductus Ejaculatorius, of, . General Anatomy Page 382 198 158 13 8 37 351 354 428 414 448 22 54 395 271 276 151 151 151 183 105 100 442 38 369 396 84 412 360 85 414 353 115 86 108 359 357 90 193, 197 194 95 124 128 128 128 91 516 INDEX. Ductus Lactiferi, . Duodenum, . Dura Mater, . Sinuses of, Ductus Wirsungii, Ear, Eminentiae Mammillares, Olivares, Epididymis, Epiglottis, Erector Clitoridis, Penis, Eustachian Valve, . Tube, External Iliac Artery, Branches of, Eye, Eyeball, Eyelids, . Fallopian Tubes, . Foetus, Peculiarities of, arising from want of Respiration, Fornix, . Fossa Navicularis, Ovalis, Fourchette, . Fourth Ventricle, Fraenum Penis, Frontal Nerve, Fundamental Portion of Cerebellum, Ganglion Cavernous, Cervical, Lumbar, Lenticular, Spheno-Palatine, . Sacral, Thoracic, Gall Bladder, Glandulae Odoriferae Tysonii, Pacchioni, Palpebrarum, Glandula Pituitaria, Pinealis, Globus Major, Minor, Glands of Brunner, Peyer, . Head and Neck, Veins of, Heart, . Right Auricle of, Right Ventricle of, INDEX. Heart, Left Auricle of, Left Ventricle of, Blood Vessels of, Texture of, Hymen, Ileo-Colic Valve, Ileum, . Incus, ... Internal Iliac Artery, Branches of, Inguinal Glands, Intestinal Canal, . Intestine, Small, • ^ • Large, . Small, Situation of, Large, Situation of, Iris, Jejunum, Kidneys, Situation of, Minute Structure of, Labia Interna, Externa, Labyrinth, Lachrymal Apparatus, . Caruncle, Ducts, Gland, Nerve, Sac, • Larynx, Lateral Ventricles, Levator Ani, Lens, . • Ligamentum Ciliare, Denticulatum, Palpebrale Internum, Externum, Liver, • . • Organization or, Situation of, Lower Extremity, Veins of, . Lungs, . Texture ot, Lymphatic Glands, Mesocolon, Malleus, Meatus Externus, . Vol. II.—66 518 INDEX. Mediastinum Anterior,. Page 147 Posterior, 147 Superior, . * 148 Medulla Oblongata, 346 Spinalis, Nerves of, 325, 488 Membrana Pupillaris, 429 Tympani, . 435 Membranous Labyrinth, 443 Mesentery, .... 33 Mitral Valve, . . 190 Mons Veneris, 104 Mucous Glands, and Apparatus, 88 Membranes, General Anatomy of, . 48 Musculus Anterior Auriculae, 434 Antitragicus, 433 Attollens Auriculae, 434 Helicis, Major et Minor, 433 Laxator Tympani, 439 Levator, Palpebrae Superioris, 398 Obliquus Oculi Superior, Obliquus Oculi Inferior, 399 399 Rectus Oculi Superior, 398 Rectus Oculi Externus, 398 Rectus Oculi Inferior, 398 Rectus Oculi Internus, . , 399 Retrahens Auriculae, 433 Stapedius, 439 Tensor Tarsi, 404 Tensor Tympani, 439 Tragicus, 433 Transversus Auriculae, 433 Mucous Coat, minute Anatomy of, 40 Nervous System, 315 General Anatomy of, 315 Nasal Nerve, 454 Nerves of Encephalon, 370 Ear, Nervus Abdomino Cruralis, 446 503 502 Abdominal Spinal, Accessorius, Auditorius, 378, 468 376 464 489 494 505 496 495 504 504 505 Auricularis, Cervical es, Circumflexus, Cruralis Anterior, Cutaneus Externus, Cutaneus Internus, Cutaneus Femoris Externus, . Cutaneus Medius, Cutaneus Femoris Internus, . INDEX. 510 Nervus Cutaneus Anterior, Cutaneus Femoris Posterior, Descendens Noni, Facialis, Glosso-Pharyngeus, Glutei, . Hypoglossus, .' Infra Maxillaris, Infra Orbitalis, Ischiadicus, Laryngeus Inferior, Laryngeus Superior, Maxillaris Superior, Medianus, Motor Externus, Motor Oculi, Nasalis Internus, Naso-Palatinus, Obturatorius, . Olfactorius, Opticus, . -. Patheticus, Palatinus, Peroneus, Petrosus Superficialis Petrosus Profundus, Pharyngeus Superior, Phrenicus, Plantaris Externus, Plantaris Internus, Pneumogastricus, Portio Dura, Portio Mollis, . Popliteus, . Pudendalis Superior, Pudendalis Inferior, Pterygo-Palatinus, Radialis, . Scapularis, Saphenus Externus, Spermaticus Externus Splanchnic us, Spiralis, Subcostales, Suboccipitalis, . Subscapularis, Sympatheticus, . • Trigeminus, Thoracici, Tibialis Anterior, Trochlearis, 520 INDEX. Page Nervus Ulnaris, . 498 Vidianus, . . . . 449, 458 Neurilemma of Nerves, . 317 Nose, . ' A ' Blood vessels of, . 383 393 Nerves of, 390 Omenta, . 13 Omentum Colicum, . . . . 14 Omentum Gastro Splenicum, 15 Majus, or Gastro Colicum, . . 14 Minus, or Hepatico Gastricum, 13 Ophthalmic Nerve,. .... 453 Optic Nerve, . 371 Orbit, Arteries of, . 406 Nerves of, . 406 Veins of, . 409 Orbiculare, os, . 438 Organs of Assimilation, 4 Generation, . 83 Generation in the Male, 83 Generation in the Female, . 104 Respiration, .... 123 Os Tincae, . 111 Ostium Venosum, .... 187, 190 Ovaries, .... 116 Pancreas, . 66 Situation of, . 8 Minute Structure of, 67 Papilla Mammae, .... 118 Pelvic Fascia, . • . 102 Penis, ..... 83 Pericardium, . 184 Perineal Fascia, . . . 93 Perineum, Muscles and Fascia of, 97 Peritoneum, ..... 10 Pia Mater, .... 344 Pigmentum Nigrum, of Eye, 415 Pituitary Gland, .... 358 Membrane, «... 386 Pleurae, .... 145 Plexus Brachialis, . 493 Cardiacus, . 480 Choroides, 368 484 Coeliacus, .... Coronarius, 484 484 506 502 Hepaticus, Ischiadicus, Lumbalis, .... Mesentericus Inferior, 485 Mesentericus Superior, 485 INDEX. 521 Plexus Diaphragmaticus, Renalis, Solaris, Splenicus Plica Semilunaris, Pori Biliarii, Prepuce, Primitive Iliac Artery, Branches of, Processus Ciliaris, Prostate Gland, Protuberantia Annularis, Pulmonary Artery, Rectum, Renal Capsules, Minute Structure of, Situation of, Retina, . Round Ligaments of the Uterus, . Sacculus Ellipticus, Sphericus, Sclerotica, Scrotum, Semicircular Canals, . Seminal Vesicles, Senses, . Serous Membranes, generally, General Anatomy Septum Lucidum, Sinuses of Valsalva, the Vertebral Column, Sinus Cavernosus, Circularis, Laterales, Longitudinalis, Inferior, Longitudinalis, Superior, Occipitalis, Petrosi, Quartus, Scemmering's Foramen, Spermatic Chord, Sphincter Ani, Vaginae, Spinal Marrow, Membranes of, . Nerves of, . Vessels of, Spleen, . Situation of, Intimate Structure of, of, 522 INDEX. Stapes, Stomach, Situation of, . Subclavian Artery, Branches of, Tarsi, Taenia Striata, Tela Choroidea, Testicles, Minute Structure of, Thalami Optici, Third Ventricle, Thymus Gland, Thyreo-Arytenoideus, Muscle, Epiglottideus, Hyoideus, Thyroid Gland, . Cartilage, Thoracic Aorta, Descending Branches Ducts, Trachea, Transversus Perinei, (Male,) (Female,) Triangular Ligament of the Urethra, Tubuli Seminiferi, Tuber Cinereum, Tubercula Quadrigemina, Tunica Albuginea, Hyaloidea, Vaginalis, Tympanum, Umbilical Artery, Vein, Upper Extremity, Nerves of, Veins of, Ureter, Urethra, (Male,) . (Female,) Urinary Organs, . Uterus, and its Appendages, Vagina, . Valve of Vieussens, Vasa Arteriarum, . Efferentia, Recta, Vorticosa, Vas Deferens, Vena Azygos, Axillaris, Basilica, of, Page 438 22 8 208 396 360 345 90 94 358 367 139 128 129 128 137 124 220 310 133 99 109 101 94 358 365 93 424 92 434 277 276 493 258 74 86 107 69 110 107 353 168 94 94 417 96 256 261 260 INDEX. 523 Vena Cava Inferior, Cava Superior, . Cephalica, Choroidea, Facialis, . Femoralis, Hypogastrica, Hemiazygos, lliaca Externa, lliaca Interna, . lliaca Primitiva, Innominata, Intercostalis Superior, Jugularis Externa, Jugularis Interna, Lingualis, Mammaria Interna, . Maxillaris Interna, Mediana, . Meseraica Inferior, Meseraica Superior,. Occipitalis, Ophthalmica, Palatina Inferior, Pharyngea, Poph-tea, Portarum, Ranina, Sacra Media, Saphena Minor Externa, Saphena Magna Interna, Splenica, Subclavia, Submentalis, Temporalis, Temporalis Superficialis, Thyroidea Inferior, . Thyroidea Superior, Vertebralis, Veins, Texture of, Venae Capsulares, Diploicae, Emulgentes, Hepaticae, Lumbal es, Phrenicae Inferiores, Spermaticae, Ventricles of the Brain, Verumontanum, . Vesical Triangle, Vestibulum of Vulva, •I 524 INDEX. Page Vestibulum, Ear, . . . .441 Vitreous Humour, .... 423 Vulva,. . ... 104 Willis, Circle of, .... 382 Winslow, Foramen of, . . . .15 THE END. A NEW WORK. CAREY, LEA & BLANCHARD, Philadelphia, HAVE JUST PUBLISHED, POPULAR MEDICINE; OK, FAMILY ADVISER: CONSISTING OF OUTLINES OF ANATOMY, PHYSIOLOGY AND HYGIENE, WITH SUCH HINTS ON THE PRACTICE OF PHYSIC, SURGERY, AND THE DISEASES OF WOMEN AND CHILDREN, AS MAV PROVE USEFUL IN FAMILIES WHEN REGULAR PHYSICIANS CANNOT BE PROCURED: BEING A COMPANION AND GUIDE FOR INTELLIGENT PRINCIPALS OF MANUFACTORIES, PLAN- TATIONS, AND BOARDING SCHOOLS, HEADS OF FAMILIES, MASTERS OF VESSELS, MISSIONARIES, OR TRAVELLERS ; AND A USEFUL SKETCH FOR YOUNG MEN ABOUT COMMENCING THE STUDY OF MEDICINE. By REYNELL COATES, M. D., Fellow of the College of Physicians of Philadelphia—Honorary Member of the Philadel- phia Medical Society—Correspondent of the Lyceum of Natural History of New York__Member of the Academy of Natural Sciences of Philadelphia—P'ormerly Resi- dent Surgeon of the Pennsylvania Hospital, &c.—Assisted by several Medical Friends. IN ONE VOLUME, OCTAVO. 2 EXTRACTS FROM THE PREFACE. "An incalculable advantage which results from the extension of cor- rect medical knowledge beyond the limits of the profession, is the diffi- culty which it throws in the way of the ignorant pretender, by enabling the public to judge more correctly of medical information. For, although the writer contemns the arrogance of those who have ventured, in simi- lar works, to persuade their readers that all opinions differing from their own are the offspring of ignorance or folly, yet he believes that the principles laid down, and the practical directions given, in the following pages, will be found generally in accordance with received doctrines. They will therefore enable the patient, or his friends, so to direct their questions to the practitioner, and to comprehend the replies, as to dis- tinguish between the mere empiric, and the man who has really studied his professions an advantage of immense value to both parties, in situ ations distant from large cities. Among the strongest proofs of the propriety of the present undertak' ing, are the constant demand for a popular medical guide of some kind, and the circumstance that the very few works of this character now extant, which can be considered as adapted to the present state of the science, have their subject matter arranged in alphabetical order:—an arrangement which precludes the possibility of preserving the recollec- tion of the mutual relations of facts, and destroys that system which is best calculated to aid the memory, facilitate reference, and impress cor- rect principles. In executing his task, the author has endeavoured conscientiously to inculcate such caution as is calculated to secure his readers against a rash dependence upon their own partially enlightened endeavours, when other and more efficient assistance is at hand, while he has exerted himself to communicate, in a form as much condensed as possible, whatever information he considers likely to aid the cause of humanity under less favourable circumstances. Theso explanations are due to the practitioners of an honourable pro- fession. To those who propose to commence the study of that profes- sion, it may be stated that, under the present organization of our universities and medical colleges, the pupil, at the moment of entering upon his career, is overwhelmed by the quantity of scientific matter forced upon his attention by the number and variety of the lectures he is called upon to attend. These lectures treat of a variety of sciences, the very terminology of which is unknown to him; and much of the value of his first year of study is usually lost in obtaining a few general ideas, laboriously gleaned from a great mass of more profound, but, to him, unintelligible learning. Some weeks spent in perusing and reflect- ing upon the contents of the first three chapters of the present work, 3 will communicate, it is confidently believed, such broad views and im- pressions on anatomical, physiological, and hygienic subjects, as will enable him to listen with pleasure and advantage to the first course of medical instruction;—that tedious, and, to many, almost intolerable portion of the labour of a student. The best advice that can be given to an individual actually suffering under disease, or desirous of pursuing such a course of diet, exercise, &c. as is likely to promote his health, and invigorate and preserve the force of his constitution, is, most unquestionably, to recommend a consultation with some deservedly eminent physician. But the directions and rea- sonings of a physician are better understood by a patient who has him- self some knowledge of the first principles of medicine. This knowledge is also a protection against the machinations of wonder-working empi- rics; for who, that has the slightest idea of the structure of the most complicate of all the works of nature, would confide the management of such a delicate machine to the hands of an ignorant pretender. It is not always possible to obtain the desired assistance in due time, and in many situations it is altogether impracticable to obtain it at all. There is, therefore, no intelligent man who may not find his own com- fort consulted, and his sphere of usefulness increased, by studying the first principles of physiology, hygiene, practical medicine, and surgery. To heads of families, principals of large manufactories, seminaries, and landed estates, missionaries on foreign stations, and the captains of vessels, such knowledge is still more important. The " Family Adviser" being designed not to supersede the family physician, but merely to supply his place, when inaccessible, it will be found that the practical part of the work dwells chiefly on diseases of an acute character, and that when chronic complaints are mentioned, directions for the management of the earlier stages have received more attention than the after treatment. Those diseases which are incurable in their nature, or which defy domestic treatment at any stage, are omit- ted, or but lightly touched upon; and when such remedies or operations as are employed only by the profession become the subject of remark, they are introduced merely to gratify the natural curiosity of the reader. When, in the current of a case, the requisite treatment becomes danger- ous, or demands superior skill, the subject is generally fore-closed by referring the reader to competent medical advisers. The work is divided into two parts; of which the first is descriptive and theoretical, the second practical. It is desirable that all who would qualify themselves for rightly comprehending the practical part should peruse, previously and attentively, the first four chapters, which may be regarded as introductory. An Appendix contains a list of many of the simple medicines and compound prescriptions recommended in the work, with the mode of preparing the latter. It is remarked, that the most experienced prac- titioners generally employ the smallest number of remedies, as the most able mechanic often uses but few implements. Instead, then, of follow- ing the example of his predecessors, by perplexing the minds of his readers with a history of a great multitude of medicines, the writer has confined his attention to those of established reputation, and named in the body of the work." 4 CONTENTS OF THE VOLUME. PART FIRST. 3UTLINES OF ANATOMY, PHYSIO- LOGV AND HYGIENE. CHAPTER I. 3RELIMINARY REMARKS ON THE ORGANIZATION OF ANIMALS. CHAPTER II. STRUCTURE OF THE HUMAN BODY. )f the cellular tissue. )f fat, or adipose tissue. )f the bones, or osseous system. If the skeleton. )f the muscles or muscular system, anato- n the digestive apparatus. )f the stomach. )f the duodenum. )f the liver. )f the pancreas. )f the small intestine. )f the great intestine. )f the circulation. )f the circulating fluids. )f the route of circulation. )f the portal vessels. )f the capillaries. )f the function of nutrition. )f the function of absorption. )f respiration. )f the apparatus of respiration. )f secretions. )f the urinary apparatus. )f the urine. )f the skin or integument. )f the nerves. )f the brain. )n the duplicature of certain organs. CHAPTER III. PHYSIOLOGICAL REMARKS. )f assimilation and nutrition. )f the reproduction of parts, as displayed in the healing of wounds. Of symptomatic fever. Of irritation and hyper-nutrition, inflamma- tion, physiological. Of capillary irritation. Of nervous irritation. Of the balance of vital action and reaction. Of vicarious discharges and transformations of tissues. CHAPTER IV. REMARKS ON HYGIENE. Of food. Of clothing. Of air and moisture. Of exercise. Of the food and exercise of children. Errors of female school discipline. Of matrimony. PART SECOND. PRACTICAL DIRECTIONS FOR THE TREATMENT OF MEDICAL AND SURGICAL DISEASES. CHAPTER I. OF SURGICAL ACCIDENTS AND DISEASES. Sect.1. Of wounds and contusions. Of incised wounds. Of incised wounds of the scalp. Of incised wounds of the neck and throat. Of incised wounds of the chest. Of incised wounds of the abdomen. Of incised wounds of the joints. Of lacerated wounds. Of contused wounds. Of contusions. Of injuries of the head. Concussion of the brain, Fractures of the skull. Of contusions in the cavity of the spine. Of fractures, dislocations, and sprains of the spine. 5 Of concussions of the spine. Of contusions of the chest. Of contusions of the abdomen. Of contusions of the pelvis and perineum. Fractures of the pelvis. Of contusions or sprains in the joints. Of punctured wounds. Sect. 2. On the dilation of natural passages, and its consequences. Dilation of the anus. Of dilated or varicose veins. Of varicocele. Of piles, or hemorrhoids. Of dilatations of the heart and arteries. Of aneurisms. Of aneurismal varix and varicose aneurism, Of mother-spots, or aneurism from anasto mosis. Of hernia, or rupture. * Sect. 3. On deformities from imperfect nutrition of the osseous and muscular systems. Of curvatures of the spine. Of club foot. Sect. 4. Of fractures. Fractures of the clavicle. Fractures of the shoulder blade. Fractures about the shoulder joint. Fractures of the arm. Fractures of the elbow joint. Fractures of the fore-arm. Fractures of the lower extremities. Fractures of the thigh. Fractures of the leg. Fractures of the fingers and toes. Fractures of the lower jaw. Of dislocations in general. Dislscations of the arm into the arm-pit. Dislocations of the wrist. Dislocation of the ankle, with fracture of the fibula. Sect. 5. On inflammation and its consequences. External inflammations. Terminations of inflammation. Treatment of inflammation. Of suppuration. Of ulceration. Of gangrene. Malignant pustule. Gangrene of old men. Dry gangrene. Gangrene from excess of inflammation, from internal and constitutional causes. Gangrene from pressure. Gangrene from cold. _ Gangrene from mechanical injuries. Terminations of inflammation coupled with collapse. Of the sty. Ulceration of the eye-lashes. Foreign substances in the eye. Inflammation of the eye. Ulceration of the cornea. Films on the eye. Foreign bodies in the ear. Ear-ache, and suppurations of the ear. Ulcerations of the mouth. Gum-biles. Suppurations of the urinary passages. Excoriations about the mucous orifices. Chafing. Of abscesses. Run-round. Whitlow. Nails growing into the flesh. Biles. Furuncle and carbuncle. Canker, or gangrenous sore mouth of chil- dren. Burns and scalds. White swelling. Hip-joint disease. Sect. 6. Corns, warts, and moles. Soft corns. Warts. Moles. Sect. 7. Constitutional diseases. Scrofula. Of cancer. Venereal diseases. Scurvv. CHAPTER II. MEDICAL PRACTICE OR TREAT- MENT OF INTERNAL DISEASES. Sect. 1. Fever. Intermittent fever. Continued fever. Billious remittent fever. Yellow fever. Petechial or spotted fever. Sect. 2. Eruptive diseases. Small-pox. Varioloid. Chicken-pox. Cow-pox. Measles. Scarlet fever. Military fever. Nettle-rash. Prickly heat, or lichen. Shingles. Ring-worm. Itch. Rose-rash. Gum-rash. Pruriginous rash. 6 Sect. 3. Erysipelatous affections. Poisoned wounds. Erysipelas phlegmonodes, or diffused in flammation of the cellular tissue. Inflammation of the veins and absorbents. Sect. 4. Diseases of the respiratory apparatus. Catarrh. Influenza. Pleurisy. Lung fever. Consumption. Spitting of blood. Pulmonary hemorrhage. Asthma. Angina pectoris. Sect. 5. Diseases of the throat. Mumps. Quinsy. Croup. Sect. 6. Diseases of the abdomen. Cholera morbus. Spasmodic or malignant cholera. Diarrhoea, or looseness. Dysentery. Colic. Painter's colic, Liver complaint. Inflammation of the kidney. Jaundice. Passage of gall stones. Worms. Sect. 7. Diseases of fibrous tissue. Rheumatism. Gout. Sect. 8. Nervous diseases. Chorea, or St. Vitus's dance. Shaking palsy. Convulsions. Epilepsy. Hysteria. Catalepsy, or trance. Apoplexy. Palsy. Sect. 9. Prominent symptoms and accidents. Dropsy. Heart-burn. Water-brash. Flatulence. Costiveness. Indigestion; or dyspepsia. Vomiting. Hiccough. Cramp. Bleeding from the nose. Strangury. Diabetes. . Gravel. Drowning. Death from suspension. CHAPTER III. DISEASES OF MARRIED WOMEN. Of pregnancy, and the position and connex- ions of the child in the womb. Approach of labour. Of labour. Uterine hemorrhage. Of puerperal convulsions. Inversion of the uterus. Inflammation of the womb. Puerperal fever. Swelled leg, milk leg, or phlegmasia do- lens. Puerperal nervousness, mania, and melan- choly. Of palsy of the bladder. Of swelled throat. Inflammation and abscess of the mamma. Of inflammation of the nipple. CHAPTER IV. ON DISEASES OF CHILDREN. Tongue-tie. Swelled breasts. Sore navel. Of the yellow skin and jaundice of infants. On retention and suppression of urine. On painful urination. Incontinence of urine. Excessive urination, urinary consumption, or diabetes. Sore mouth, thrush, aphthae. Colic. Costiveness. Vomiting. Erysipelas. Dentition. Worms. Convulsions. Dropsy in the brain. Whooping-cough. Inflammation of the tonsils, quinsy. Cholera infantum. CHAPTER V. ON DISEASES OF ADULT FEMALES Appearance of the menses. Chlorosis, or green sickness. Suppression of the menses. Obstructed menstruation. Painful menstruation. Excessive menstruation, or flooding. Final cessation of the menses. Leucorrhosa, fluor albus, or whites. Pluritis vulvae. Falling, or prolapsus of the uterus. Retroversion, or falling of the womb back- wards. Antiversion of the womb. Polypus of the uterus. Cancer of the uterus. Appendix. Formulary. List of drugs. List of apparatus. Index to Part First. Index to Part Second. From amongst many commendatory notices of the work, the following are selected: " This work, by Dr. Reynell Coates, is by far the best of its class. We must even add, that it has contributed not a little to the removal of our fears of the doubtful if not sinister tendency of an attempt to produce a system of Popular or Domestic Medicine. Positive good will result to them who shall study and take pains to acquire a knowledge of the facts and precepts in the First Part, or that which consists mainly of an ' Outline of Anatomy' and 'Remarks on Hygiene,' in the work before us. These are an appro- priate and a necessary introduction to the Second Part, in which the brief indications in the treatment of diseases and accidents by the aids of surgery and medicine, are set forth. After a survey of his labours in these matters, we feel inclined to join in opinion with Dr. Coates, who, in his preface, expresses his belief "that the principal evils which have resulted and are likely to result hereafter from attempts at popular medical instruc- tion, are attributable rather to the manner in which the subject has been treated than to the nature of the subject itself.' So broad is the contrast between both the matter and the manner of his task, and the systems of popular medicine hitherto published, that the authorof the present treatise need not be under any apprehensions from his name being placed 'in juxtaposition with that of some previous authors, whom to rival, or with whom to affiliate, falls not within the compass of his ambition.' " " Amongst the works calculated to contribute to this desirable end, of enlightening people generally on the above important matters, we would place the ' Family Adviser' of Dr. Coates, especially that portion of it entitled ' Outline of Anatomy' and 'Remarks on Hygiene.' The first is a clear and condensed description, with illustrative .engravings, of the several parts of which the living body is composed. The second abounds with sound and practical precepts for the maintenance of these parts in their healthy state separately and in their harmonious relations with each other." " Under the successive heads of Clothing and Cleanliness, Air and Moisture, Exer- cises, the Food and Exercises of Children, Errors of Female School Discipline, and, finally, of Matrimony, the reader will find a large amount of highly instructive and avail- able matter. It is pleasant and encouraging to see a man of talents and attainments, and a shrewd, albeit peculiar observer, engaged in enlightening his fellow men on these im- portant subjects. That they will thank him, and prove their appreciation of his services to them by an observance of his precepts, we can readily believe, as we sincerely hope." Select Medical Library. " This is a very neatly executed work, from the prolific press of Carey, Lea & Blanch- ard. The title of the volume, perhaps, would not recommend it to the profession, who have had just occasion to be disgusted with treatises on domestic medicine, medical ad- visers &c; but emanating from so high a source, we shall be much disappointed if this volume does not ensure for itself a careful perusal from the scientific practitioner, for which, we will predict, he will be amply repaid. So far as we can allow ourselves to approve of epitomes on medical subjects, we must distinguish this volume as the deposi- tory of a large fund of anatomical, physiological and practical truth. But to families, travellers, members of missionary stations, and all who may be unable to procure the services of a regular practitioner, it is a valuable compendium, and for such the work was expressly designed. • "But the author, apart from this, had another object to accomplish, which the en- lightened practitioner will deem desirable, viz., the extension of correct medical know- ledg-e beyond the limits of the medical profession. We have long considered this a desideratum. Such a purpose gained, will do more towards pulling down the strong holds of quackeiy and empiricism, in their thousand Protean forms, than the fast-multi- 8 plying prosecution and accumulated verdicts of homicide can ever accomplish. A volume like this, carefully read, will enable the public to distinguish easily between the pre- tender and the man who has faithfully studied his art. When public opinion is enlight- ened, we may invoke its resistless arm to our aid in the cause of science and humanity. Give to any patient the slightest knowledge of the structure of his system, or the faintest idea of the principles of the medical art, and he will hesitate before he entrusts the re- pairing of such delicate machinery to the hands of the marvellous-loving and wonder- working quack. " We have time only for a cursory notice of the plan of the work. It is divided into two general parts, descriptive or theoretical, and practical. The first embraces a parti- cular notice of human general anatomy, enlivened with many physiological observations —a view of the principal animal functions, and their aberration from healthy action—and a very valuable chapter on hygiene. Part second treats of the symptoms of diseases and the most approved methods of treatment. " We cannot close this notice, without special commendation of many portions from which we shall be glad to make extracts. That portion of the chapter on hygiene, treat- ing of clothing, exercise, and errors in female education, should be faithfully studied by every conductor of seminaries for the education of females throughout the Common- wealth. The article on spinal curvatures we commend to them as replete with valuable hints on physical education. The clearness and simplicity of the style of the work will be admired by the profession, as well as the general reader for whom it is adapted." Boston Medical Journal. "It is with great satisfaction that we announce this truly valuable compilation, as the most complete and interesting treatise on popular medicine ever presented to the pub- lic. Simple and unambitious in its language, free from unintelligible technicalities and embracing the most important facts in Anatomy, Physiology, Hygiene, or the art of pre- serving health, and the treatment of those affections which require immediate attention, or are of an acute character—this should be in the hands of every one, more particu- larly those who, by their situation are prevented from resorting to the advice of a physi- cian, nor would the careful perusal of its pages fail to profit the inhabitants of our cities. By giving them a more accurate knowledge of the structure of the human frame and of the laws that govern its various functions, whose perfect integrity is absolutely essential to health, and even to existence; the various systems of medical charlatanry daily imagin- ed to take advantage of the credulity and ignorance of mankind, would be rendered far less prejudicial to the community than they now are. We would particularly direct attention to the chapter on Hygiene, a science in itself of the utmost importance, and ably treated in the small space allowed to it in this volume."—New York American. " Let it have a fair examination, say we—and our word for it, this most useful, and we had almost added, national publication, will progress triumphantly through many editions. Dr. Coates has rightly appreciated the mind of the Americans, and has pro- duced the only really valuable and complete work as a «Family Medicine' that we have yet seen; while he has shown the comprehensiveness of his own mind, in devoting the first part of the volume to giving plain and philosophical outlines of Anatomy, Physiolo- gy and Hygiene. A second part developes many of the mysteries of surgery, affording practical directions for the treatment of Medical and Surgical Diseases. In the earlier portion of'Popular Medicine,'therefore, the intelligent reader becomes familiar with the entire structure of the human body. He is then led into the doctrines of assimila- tion, nutrition, nervous and other irritation, inflammation, vital action and re-action, &c. - while the chapter on Hygiene, gives him valuable information with regard to food, cloth- ing, air, exercise, matrimony, &c. Thus, like a sound and skilful professor of languages —the learned Doctor begins with endeavouring to ground his readers in the grammar'of the healing art, if we may be allowed such an application of the word; well knowing the danger of total ignorance in those who administer medicine in any form or under anv circumstances. > J " To our thinking, and we have carefully examined its pages—there should be a copy of it in every American family and in every American ship; and in statin? our belief that before many years shall have passed away, such will be almost the result—we are ot opinion that we only speak the words of a true prophecy."—Saturday Chronicle NLM032044658