1 ; t *' * i Digitized by the Internet Archive in 2016 https://archive.org/details/compendioussyste01fyfe_0 SYSTEM ;0 F ANATOMY. A COMPENDIOUS SYSTEM O F ANATOMY. IN SIX PARTS. I. OSTEOLOGY. IX. OF THE MUSCLES. &g. HL OF THE ABDOMEN. IV. OF THE THORAX. V. OF THE BRAIN AND NERVES. VI. OF THE SENSES. FROM THE ENCYCLOPEDIA. Illustrated, "with Twelve large Copperplates. PHILADELPHIA : PRINTED BY ARCHIBALD BARTRAM, FOR THOMAS DOBSON, AT THE STONE HOUSE, No. 4fc SOUTH SECOND.STREET. 1805 , / L. • T v <>' TO ' • ! ' . ' i.; • i o I M 0 T / / WZt ,: J 2 .*-: s.i : }< '.it r: ."f ' , : 1 I . T • . 1 ■ : i , A : . 1 A • # .. iV 1 afj rui-. : n.i - - . <; ■ •a; s. • " ■/ vi r ; ;! ,'Kiasi • ' • * CONTENTS. Page. Introduction 9 1. History of anatomy ibid. 2. View of the subject in general , and plan of the following treatise 40 Part I. Osteology 57 Sect. I. Of the bones in general , with their appendages , &c. 5 8 II. Of the bones of the head 71 1. Bones of the cranium and face 72 2. Proper bones of the face 85 3. Of the teeth 91 4. os hyoides 98 III. bones of the trunk 99 1. spine ibid. 2. bones of the thorax 108 3. bones of the pelvis ill IV. Extremities 114 1. upper extremities 115 1. shoulder ibid. 2. bones of the arm 117 3. bones of the hand 121 2. lower extremities 124 1. thigh ibid. 2. rotula , or knee-pan 126 3. leg 127 ( Vi ) Page 4. Of the foot 129 4. ossa sesamoidea 133 Explanation of the plates of osteology 134, 152 Part II. Of the Soft Parts in general 157 Of the common integuments , with their appendages ; and of the muscles ibid. Sec. I. Of the skin 159 1 . scarf-skin ibid. 2. rete mucosum 160 3. cutis , or true skin 161 4. glands of the skin 162 5. insensible perspiration and sweat 163 6. nails 166 7 . hair 167 8. cellular membrane and fat 168 II. muscles 170 particular muscles 180 A table of the muscles arranged according to their situation 181 Explanation of plates XXIII. XXIV. 230,235 Part III. Of the Abdomen, or Low- er Belly. 236 Sec. I. Of the peritoneum 238 II. omentum 239 ( vii ) Page Sec. III. Of the stomach 241 IV . oesophagus 243 h . intestines 244 VI. mesentery 248 VII. pancreas 251 VIII. liver 253 IX. gall-bladder 255 X. spleen 258 XI. glandulre renales , kidneys and ureters 259 XII. urinary bladder 262 XIII. Of digestion 266 XIV. Of the course of the chyle and of the lymphatic system 278 XV. Of the generative organs ; of conception , &c. 284 1. The male organs ibid. 2. Female organs of generation 296 3. Of conception 4. Of the foetus in utero 304 4. Of the foetus in utero Explanation of plates XXV. XXVI. and XXVII. 309, 316 Part IV. Of the Thorax 318 Sec. I. Of the breasts 319 II pleura 320 III. thymus 322 IV. diaphragm ibid. V. trachea 324 * ( viii ) Page ■Sec. VI. Of the lungs 327 VII. Of respiration ' 329 VIII. Of the voice 334 IX. Of dejection 336 X. Of the pericardium , and of the heart , and its auricles 337 XI. Angiology , or a description of the blood-vessels 342 XII. Of the action of the heart , auricles , and arteries 352 XIII. Of the circulation 354 X/Fi nature of the blood 355 XF. Of nutrition 3 57 XFX Of the glands and secretions 3 59 Explanation of plate XXVIII. 364 Part V. Of the Brain and Nerves 366 Sec. I. Of the brain and its integuments ibid. II. nerves 379 Explanation of plate XXIX. 386 Part VI. Of the Senses and their Organs 390 Sec. I. Of touch ibid. II. taste 391 III. smelling 39S IV. hearing 396 V. vision 404 Explanation of plate XXX. 415 SYSTEM OF ANATOMY. ANATOMY, T HE art of dissecting, or artificially separat- ing and taking to pieces, the different parts of the human body, in order to an exact discoveiy of their situation, structure, and (eco- nomy. — The word is Greek, avaro/ni) ; derived from to dissect, or separate by cutting. INTRODUCTION. 1. History of Anatomy. This art seems to have been very ancient ; though, for a long time, known only in an im- perfect manner. — The first men who lived must have soon acquired some notions of the structure of their own bodies, particularly of the external parts, and of some even of the internal, such as bones, joints, and sinews, which are exposed to the examination of the senses in living bodies. B 10 History of Anatomy . This rude knowledge must have been gra- dually improved, by the accidents to which the body is exposed, by the necessities of life, and by the various customs, ceremonies, and superstitions, of different nations. Thus, the observance of bodies killed by violence, at- tention to wounded men, and to many diseases, the various ways of putting criminals to death, the funeral ceremonies, and a variety of such things, must have shown men every day more and more of themselves ; especially as curio- sity and self-love would here urge them pow- erfully to observation and reflection. The brute-creation having such an affinity to man in outward form, motions, senses, and ways of life ; the generation of the species, and the effect of death upon the body, be- ing observed to be so nearly the same in both ; the conclusion was not only obvious, but un- avoidable, that their bodies were formed near- ly upon the same model. And the opportu- nities of examining the bodies of brutes were so easily procured, indeed so necessarily oc- curred m the common business of life, that the huntsman in making use of his prey, the priest in sacrificing, the augur in divination, and, above all, the butcher, or those who might out of curiosity attend upon his operations, must have been daily adding to the little stock of anatomical knowledge. Accordingly we find, in fact, that the South-sea islanders, who have been left to their own observation and 'reasoning, without the assistance of letters, have yet a considerable share of rude or wild History of Anatomy. ii anatomical and physiological knowledge. Dr. Hunter informs us, that when Omai was in his museum with Mr. Banks, though he could not explain himself intelligibly, they plainly saw that he knew the principal parts of the bo- dy, and something likewise of their uses ; and manifested a great curiosity or desire of hav- ing the functions of the internal parts of the body explained to him, particularly the relative functions of the two sexes, which with him seemed to be the most interesting object of the human mind. We may further imagine, that the philoso- phers of the most early ages, that is, the men of curiosity, observation, experience and re- flection, could not overlook an instance of na- tural organization, which was so interesting, and at the same time so wonderful, more es- pecially such of them as applied to the study and cure of diseases. We know that physic was a branch of philosophy till the age of Hippocrates. Thus the art must have been circumstanced in its beginning. We shall next see from the testimony of historians and other writers, how it actually appeared as an art, from the time that writing was introduced among men 5 how it was improved and conveyed down to us through a long series of ages. Civilization and improvements of every kind, would naturally begin in fertile countries and healthful climates, where there would be lei- sure for reflection, and an appetite for amuse- ment. Accordingly, writing, and many other 12 History of Anatomy. useful and ornamental inventions and arts, ap- pear to have been cultivated in the eastern parts of Asia long before the earliest times that are treated of by the Greek or other European wri- ters ; and that the arts and learning of those eastern people were in subsequent times gra- dually communicated to adjacent countries, es- pecially by the medium of traffic. The cus- toms, superstitions, and climate of eastern coun- tries, however, appear to have been as unfa- vourable to practical anatomy, as they were inviting to the study of astronomy, geometry, poetry, and all the softer arts of peace. Animal bodies there, run so quickly into nauseous putrefaction, that the early inha- bitants must have avoided such offensive em- ployments, as anatomical inquiries, like their posterity at this day. And, in fact, it does not appear, by the writings of the Greci- ans, or Jews, or Phoenicians, or of other eas- tern countries, that anatomy was particularly cultivated by any of those eastern nations. In tracing it backwards to its infancy, we cannot go farther into antiquity than the times of the Grecian philosophers. As an art in the state of some cultivation, it may be said to have been brought forth and bred up among them as a branch of natural knowledge. The sera of philosophy, as it was called, began with Thales the Mdesian being declar- ed by a very general consent of the people, the most wise of all the Grecians, 480 years be- fore Christ. The philosophers of his school, which was called the Ionian, cultivated prin- History of Anatomy. 13 cipally natural knowledge. Socrates, the se- venth in succession of their great teachers, in- troduced the study of morals, and was thence said to bring down philosophy from heaven, to make men truly wise and happy. In the writings of his scholar and successor Plato, we see that the philosophers had care- fully considered the human body, both in its organization and functions ; and though they had not arrived at the knowledge of the more minute and intricate parts, which required the successive labour and attention of many ages, they had made up very noble and com- prehensive ideas of the subject in general. The anatomical descriptions of Xenophon and Plato have had the honour of being quoted by Longinus (§xxxii.) as specimens of sub- lime writing ; and the extract from Plato is still more remarkable for its containing the rudiments of the circulation of the blood. “The heart (says Plato) is the centre or knot of the blood-vessels ; the spring or fountain of the blood which is carried impetuously round ; the blood is the pabulum or food of the flesh ; and, for the purpose of nourishment, the body is laid out into canals, like those which are drawn through gardens, that the blood may be conveyed, as from a fountain, to every part of the pervious body.” Hippocrates was nearly contemporary with the great philosophers of whom we have been speaking, about 400 years before the Christi- an sera. He is said to have separated the pro- fession of philosophy and physic, and to have 14 History of Anatomy. been the first who applied to physic alone as the business of his life. He is likewise gene- rally supposed to be the first who wrote upon anatomy. We know of nothing that was writ- ten expressly upon the subject before ; and the first anatomical dissection which has been recorded, was made by his friend Democritus of Abdera. If, however, we read the works of Hippo- crates with impartiality, and apply his ac- counts of the parts to what we now know of the human body, we must allow his descrip- tions to be imperfect, incorrect, sometimes ex- travagant, and often unintelligible, that of the bones only excepted. He seems to have stu- died these with more success than the other parts, and tells us that he had an opportunity of seeing an human skeleton. From Hippocrates to Galen, who flourish- ed towards the end of the second century, in the decline of the Roman empire, that is, in the space of 600 years, anatomy was greatly improved ; the philosophers still considering it as a most curious and interesting branch of natural knowledge, and the physicians, as a principal foundation of their art. Both of them, in that interval of time, contributed dai- ly to the common stock, by more accurate and extended observations, and by the lights of improving philosophy. As these two great men had applied very particularly to the study of animal bodies, they not only made great improvements, es- pecially in physiology, but raised the credit History of Anatomy. 15 of natural knowledge, and spread it as wide as Alexander’s empire. Few of Aristotle’s writings were made pub- lic in his lifetime. He affected to say that they would be unintelligible to those who had not heard them explained at his lectures : and, except the use which Theophrastus made of them, they were lost to the public for above 130 years after the death of Theophrastus; and at last came out defective from bad pre- servation, and corrupted by men, who, with- out proper qualifications, presumed to correct and supply what was lost. From the time of Theophrastus, the study of natural knowledge at Athens was for ever on the decline ; and the reputation of the Ly- ceum and Academy was almost confined to the studies which are subservient to orato- ry and public speaking. The other great institution for Grecian edu- cation, was at Alexandria in Egypt. The first Ptolemies, both from their love of literature, and to give true and permanent dignity to their empire, and to Alexander’s favourite city, set up a grand school in the palace itself, with a museum and library, which, we may say, has been the most famed in the world. An- atomy, among other sciences, was publicly taught ; and the two distinguished anatomists were Erasistratus the pupil and friend of The- ophrastus, and Herophilus. Their volumi- nous works are all lost ; but they are quoted by Galen almost in every page. These pro- fessors were probably the first who were au- 16 History of Anatomy. thorised to dissect human bodies ; a peculiari- ty which marks strongly the philosophical magnanimity of the first Ptolemy, and fixes a great sera in the history of anatomy. And it was, no doubt, from this particular advantage which the Alexandrians had above all others, that their school not only gained, but for ma- ny centuries preserved, the first reputation for medical education. Ammianus Marcelli- nus, who lived about 6 50 years after the schools were set up, says, they were so fa- mous in his time, that it was enough to se- cure credit to any physician, if he could say he had studied at Alexandria. Herophilus has been said to have anato- mized 700 bodies. We must allow for exagge- ration. Nay, it was said, that both he and Erasistratus made it a common practice to open living bodies, that they might discover the more secret springs of life. But this, no doubt was only a vulgar opinion, rising from the prejudices of mankind ; and accordingly, without any good reason, such tales have been told of modern anatomists, and have been believed by the vulgar. Among the Romans, though it is pro- bable they had physicians and surgeons from the foundation of the city, yet we have no account of any of these applying themselves to anatomy for a very long time. Archagathus was the first Greek physician established in Rome, and he was banished the city on ac- count of the severity of his operations. — Asclepiades, who flourished in Rome 101 History of Anatomy. 17 years after Archagathus, in the time of Pom- pey, attained such a high reputation as to be ranked in the same class with Hippocrates. He seemed to have some notion of the air in respiration acting by its weight ; and in ac- counting for digestion, he supposed the food to be no farther changed than by a comminu- tion into extremely small parts, which being distributed to the several parts of the body, is assimilated to the nature of each. One Cassius, commonly thought to be a disciple of Asclepiades, accounted for the right side of the body becoming paralytic on hurting the left side of the brain, in the same manner as has been done by the moderns, viz. by the crossing of the nerves from the right to the left side of the brain. From the time of Asclepiades to the second century, physicians seem to have been great- ly encouraged at Rome ; and, in the writings of Celsus, Rufus, Pliny, Ccelius, Aurelianus, and Arseteus, we hnd several anatomical ob- servations, but mostly very superficial and inaccurate. Towards the end of the second century lived Claudius Gallenus Pergarnus, whose name is so well known in the medical world. He applied himself particularly to the study of anatomy, and did more in that way than all that went before him. Pie seems, however, to have been at a great loss for hu- man subjects to operate upon ; and therefore his descriptions of the parts are mostly taken from brute animals. His works contain the fullest history of anatomists, and the most C 18 History of Anatomy. complete system of the science, to be met with any where before him, or for several centuries after; so that a number of passages in them were reckoned absolutely unintelligible for many ages, until explained by the disco- veries of succeeding anatomists. About the end of the fourth century, Ni- mesius bishop of Emissa wrote a treatise on the nature of man, in which it is said were contained two celebrated modern discoveries ; the one, the uses of the bile, boasted of by Sylvius de la Boe ; and the other, the circula- tion of the blood. This last, however, is proved by Dr. Friend, in his history of phy- sic, p. 229. to be falsely ascribed to this au- thor. The Roman empire beginning now to be oppressed by the barbarians, and sunk in gross superstition, learning of all kinds de- creased ; and when the empire was totally overwhelmed by those barbarous nations, eve- ry appearance of science was almost extin- guished in Europe. The only remains of it were among the Arabians in Spain and in Asia. — The Saracens who came into Spain, destroyed at first all the Greek books which the Vandals had spared: but though their government was in a constant struggle and fluctuation during 800 years before they were driven out, they received a taste for learning from their countrymen of the east ; several of their princes encouraged liberal stu- dies ; public schools were set up at Cordova, Toledo, and other towns, and translations of History of Anatomy . 19 the Greeks into the Arabic were universally in the hands of their teachers. Thus was the learning of the Grecians trans- ferred to the Arabians. But though they had so good a foundation to build upon, this art was never improved while they were masters of the world : for they were satisfied with commenting upon Galen ; and seem to have made no dissection of human bodies. Abdollaliph, who was himself a teacher of anatomy, a man eminent in his time (at and before 1203) for his learning and curiosity ; a great traveller, who had been bred at Bagdad, and had seen many of the great cities and principal places for study in the Saracen em- pire ; who had a favourable opinion of origin- al observation, in opposition to book-learning ; who boldly corrected some of Galen’s errors, and was persuaded that many more might be detected ; this man, we say, never made or saw, or seemed to think of a human dissec- tion. He discovered Galen’s errors in the oste- ology, by going to burying-grounds, with his students and others, where he examined and demonstrated the bones ; he earnestly recom- mended that method of study, in preference even to the reading of Galen, and thought that many farther improvements might be made ; yet he seemed not to have an idea that a fresh subject might be dissected with that view. Perhaps the Jewish tenets, which the Ma- hometans adopted, about uncleanliness and pollution, might prevent their handling dead bodies ; or their opinion of what was suppos- 20 History of Anatomy. ed to pass between an angel and the dead person, might make them think disturbing the dead highly sacrilegious. Such, however, as Arabian learning was, for many ages together there was hardly any other in all the western countries of Europe. It was introduced by the establishment of the Saracens in Spain in 711, and kept its ground till the restora- tion of learning in the end of the 15th centu- ry. The state of anatomy in Europe, in the times of Arabian influence, may be seen by reading a very short system of anatomy drawn up by Mundinus, in the year 1315. It was extracted principally from what the Arabians had preserved of Galen’s doctrine ; and, rude its it is, in that age, it was judged to be so masterly a performance, that it was ordered by a public decree, that it should be read in all the schools of Italy ; and it actually continu- ed to be almost the only book which was read upon the subject for above 200 years. Cortesius gives him the credit of being the great restorer of anatomy, and the first who dissected human bodies among the moderns. A general prejudice against dissection, how- ever, prevailed till the 16th century. The emperor Charles V. ordered a consultation to be held by the divines of Salamanca, in order to determine whether or not it was lawful in point of conscience to dissect a dead body. In Muscovy, till very lately, both anatomy and the use of skeletons were forbidden, the first as inhuman, and the latter as subservi- ent to witchcraft. History of Anatomy. 21 In the beginning of the 1 5th century, learn- ing revived considerably in Europe, and par- ticularly physic, by means of copies of the Greek authors brought from the sack of Con- stantinople ; after which the number of anato- mists and anatomical books increased to a pro- digious degree. — The Europeans becoming thus possessed of the ancient Greek fathers of medicine, were for a long time so much occupied in correcting the copies they could obtain, studying the meaning, and comment- ing upon them, that they attempted nothing of their own, especially in anatomy. And here the late Dr. Hunter introduces into the annals of this art, a genius of the first rate, Leonardo da Vinci, who had been formerly overlooked, because he was of ano- ther profession, and because he published no- thing upon the subject. He is considered by the Doctor as by far the best anatomist and physiologist of his time ; and was certainly the first man we know of who introduced the prac- tice of making anatomical drawings. Vassere, in his lives of the painters, speaks of Leonardo thus, after telling us that he had composed a book of the anatomy of a horse, for his own study : “ He afterwards applied himself with more diligence to the human an- atomy ; in which study he reciprocally receiv- ed and communicated assistance to Marc. An- tonio della Torre, an excellent philosopher, who then read lectures in Pavia, and wrote upon this subject ; and who was the first, as I have heard, who began to illustrate medicine 22 History of Anatomy. from the doctrine of Galen, and to give true light to anatomy, which till that time had been involved in clouds of darkness and ignorance. In this he availed himself exceedingly of the genius and labour of Leonardo, who made a book of studies, drawn with red chalk, and touched with a pen, with great diligence, of such subjects as he had himself dissected ; where he made all the bones, and to those he joined, in their order, all the nerves, and co- vered them with the muscles. And concern- ing those, from part to part, he wrote remarks in letters of an ugly form, which are written by the left hand, backwards, and not to be un- derstood but by those who know the method of reading them ; for they are not to be read without a looking-glass. Of these papers of the human anatomy, there is a great part in the possession of M. Francesco da Melzo, a Milanese gentleman, who, in the time of Le- onardo, was a most beautiful boy, and much beloved by him, as he is now a beautiful and genteel old man, who reads those writings, and carefully preserves them, as precious re- licks, together with the portrait of Leonardo, of happy memory. It appears impossible that that divine spirit should reason so well upon the arteries, and muscles, and nerves, and veins ; and with such diligence of every thing, &c. &c.” Those very drawings and the writings are happily found to be preserved in his Britan- nic Majesty’s great collection of original draw- ings, where the Doctor was permitted to exa- History of Anatomy. 23 mine them ; and his sentiments upon the oc- casion he thus expresses : “ I expected to see little more than such designs in anatomy, as might be useful to a painter in his own pro- fession ; but I saw, and indeed with astonish- ment, that Leonardo had been a general and a deep student. When I consider what pains he has taken upon every part of the body, the su- periority of his universal genius, his particular excellence in mechanics and hydraulics, and the attention with which such a man would ex- amine and see objects which he was to draw, I am fully persuaded that Leonardo was the best anatomist at that time in the world. We must give the 15th century the credit of Leo- nardo’s anatomical studies, as he was 55 years of age at the close of that century.’’ In the beginning of the 16th century, Achil- linus and Benedictus, but particularly Beren- garius and Massa, followed out the improve- ment of anatomy in Italy, where they taught it, and published upon the subject. These first improvers made some discoveries from their own dissections : but it is not surprising that they should have been diffident of them- selves, and have followed Galen almost blind- ly, when his authority had been so long estab- lished, and when the enthusiasm for Greek authors was rising to such a pitch. Soon after this, we may say about the year 1540, the great Vesalius appeared. He was studious, laborious, and ambitious. From Brussels, the place of his birth, he went to Louvain, and thence to Pans, where anatomy 24 History of Anatomy. was not yet making a considerable figure, and then to Louvain to teach ; from which place, very fortunately for his reputation, he was call- ed to Italy, where he met with every oppor- tunity that such a genius for anatomy could desire, that is, books, subjects, and excellent draughtsmen. He was equally laborious in reading the ancients, and in dissecting bodies. And in making the comparison, he could not but see, that there was great room for improve- ment, and that many of Galen’s descriptions were erroneous. When he was but a young man, he published a noble system of anatomy, illustrated with a great number of elegant fi- gures. — In this work he found so many occa- sions of correcting Galen, that his contempo- raries, partial to antiquity, and jealous of his reputation, complained that he carried his turn for improvement and criticisms to licentious- ness. The spirit of opposition and emulation was presently roused ; and Sylvius in France, Columbus, Fallopius, and Eustachius in Italy, who were all in high anatomical reputation about the middle of this 16 th century, endea- voured to defend Galen at the expense of Ve- salius. In their disputes they made their ap- peals to the human body : and thus in a few years the art was greatly improved. And Ve- salius being detected in the very fault which he condemned in Galen, to wit, describing from the dissections of brutes, and not of the human body, it exposed so fully that blunder of the older anatomists, that in succeeding times there has been little reason for such History of Anatomy . 25 complaint. — Besides the above, he published several other anatomical treatises. He has been particularly serviceable by imposing names on the muscles, most of which are re- tained to this day. Formerly they were dis- tinguished by numbers, which were different- ly applied by almost every author. In 1561 , Gabriel Fallopius, professor of anatomy at Padua, published a treatise of ana- tomy under the title of Observations Anatomi- es. This was designed as a supplement to Vesalius; many of whose descriptions he cor- rects, though he always makes mention of him in an honourable manner. Fallopius made many great discoveries, and his book is well worth the perusal of every anatomist. In 1563 , Bartholomseus Eustachius pub- lished his Opuscula Anatomica at Venice, which have ever since been justly admired for the ex- actness of the descriptions, and the discove- ries contained in them. He published after- wards some other pieces, in which there is lit- tle of anatomy ; but never published the great work he had promised, which was to be adorn- ed with copperplates representing all the parts of the human body. These plates, after lying buried in an old cabinet for upwards of 150 years, were at last discovered and published in the year 1714 , by Lancisi the pope’s phy- sician ; who added a short explicatory text, be- cause Eustachius’s own writing could not be found. From this time the study of anatomy gradu- ally diffused itself over Europe ; insomuch that D 26 History of Anatomy. for the last hundred years it has been daily im- proving by the labour of a number of profes- sed anatomists almost in every country of Eu- rope. We may form a judgment about the state of anatomy even in Italy, in the beginning of the 17th century, from the information of Corte- sius. He had been professor of anatomy at Bologna, and was then professor of medicine at Massana ; where, though he had a great desire to improve himself in the art, and to fi- nish a treatise which he had begun on practi- cal anatomy, in 24 years he could twice only procure an opportunity of dissecting a human body, and then it was with difficulties and in hurry ; whereas he had expected to have done so, he says, once every year , according to the custom in the famous academies oj Italy. In the very end of the 16th century, the great Harvey, as was the custom of the times, went to Italy to study medicine ; for Italy was still the favourite seat of the arts : And in the very beginning of the 17th century, soon after Harvey’s return to England, his master in ana- tomy, Fabricius ab Aquapendente, published an account of the valves in the veins, which he had discovered many years before, and no doubt taught in his lectures when Harvey at- tended him. This discovery evidently affected the estab- lished doctrine of all ages, that the veins car- ried the blood from the liver to all parts of the body for nourishment. It set Harvey to work upon the use of the heart and vascular systems History of Anatomy. 27 in animals ; and in the course of some years he was so happy as to discover, and to prove beyond all possibility of doubt, the circulation of the blood. He taught his new doctrine in his lectures about the year 1616, and printed it in 1628. It was by far the most important step that had been made in the knowledge of animal bo- dies in any age. It not only reflected useful lights upon what had been already found out in anatomy, but also pointed out the means of further investigation. And accordingly we see, that from Harvey to the present time, anato- my has been so much improved, that we may reasonably question if the ancients have been further outdone by the moderns in any other branch of knowledge. From one day to ano- ther there has been a constant succession of discoveries, relating either to the structure or functions of our body ; and new anatomical processes, both of investigation and demon- stration, have been daily invented. Many parts of the body, which w T ere not known in Harvey’s time, have since then been brought to light : and of those which were known, the internal composition and functions remained unexplained ; and indeed must have remained unexplicable without the knowledge of the cir- culation. Harvey’s doctrine at first met with conside- rable opposition ; but in the space of about 20 years it was so generally and so warmly em- braced, that it was imagined every thing in physic would be explained. But time and ex- 28 History of Anatomy. perience have taught us, that we still are, and probably must long continue to be, very igno- rant ; and that in the study of the human body, and of its diseases, there will always be an extensive field for the exercise of sagacity. After the discovery and knowledge of the circulation of the blood, the next question would naturally have been about the passage and route of the nutritious part of the food or chyle from the bowels to the blood-vessels : And, by good fortune, in a few years after Harvey had made his discovery, Asellius, an Italian physician, found out the lacteals, or vessels which carry the chyle from the intes- tines ; and printed his account of them, with coloured prints, in the year 1627 , the very year before Harvey’s book came out. For a number of years after these two pub- lications, the anatomists in all parts of Europe were daily opening living dogs, either to see the lacteals or to observe the phenomena of the circulation. In making an experiment of this kind, Pecquet in France was fortunate enough to discover the thoracic duct, or com- mon trunk of all the lacteals, which conveys the chyle into the subclavian vein. He print- ed his discovery in the year 1651 . And now the lacteals having been traced from the intes- tines to the thoracic duct, and that duct having been traced to its termination in a blood-ves- sel, the passage of the chyle was completely made out. The same practice of opening living animals furnished occasions of discovering the lympha- History of Anatomy. 29 tic vessels. This good fortune fell to the lot of Rudbec first, a young Swedish anato- mist ; and then to Thomas Bartholine, a Da- nish anatomist, who was the first who appear- ed in print upon the lymphatics. His book came out in the year 16 53, that is, two years after that of Pecquet. And then it was very evi- dent that they had been seen before by Dr. Hig- more and others, who had mistaken them for lacteals. But none of the anatomists of those times could make out the origin of the lym- phatics, and none of the physiologists could give a satisfactory account of their use. The circulation of the blood, and the pas- sage of the chyle having been satisfactorily traced out in full-grown animals, the anato- mists were naturally led next to consider how these animal processes were carried on in the child while in the womb of the mother. Accordingly the male and female organs, the appearances and contents of the pregnant ute- rus, the incubated egg, and every phenome- non which could illustrate generation, became the favourite subject, for about 30 years, with the principal anatomists of Europe. Thus it would appear to have been in theo- ry : but Dr. Hunter believes, that in fact, as Harvey’s master Fabricius laid the foundation for the discovery of the circulation of the blood by teaching him the valves of the veins, and thereby inviting him to consider that sub- ject ; so Fabricius by his lectures, and by his elegant work He formato fcetu , et de formatione ovi et pulli , probably made that likewise a fa- 30 History of Anatomy. vourite subject with Dr. Harvey. But whe- ther he took up the subject of generation in consequence of his discovery of the circula- tion, or was led to it by his honoured master Fabricius, he spent a great deal of his time in the inquiry ; and published his observations in a book De generations animalium , in the year 16 51, that is, six years before his death. In a few years after this, Swammerdam, Van Horn, Steno, and De Graaf, excited great at- tention to the subject of generation, by their supposed discovery that the females of vivipa- rous animals have ovaria, that is, clusters of eggs in their loins, like oviparous animals ; which, when impregnated by the male, are conveyed into the uterus; so that a child is produced from an egg as well as a chick ; with this difference, that one is hatched within, and the other without, the body of the mother. Malpighi, a great Italian genius, some time after, made considerable advances upon the subject of generation. He had the good for- tune to be the first who used magnifying glass- es with address in tracing the first appearances in the formation of animals. Fie likewise made many other observations and improvements in the minutia of anatomy by his microscopical la- bours, and by cultivating comparative anato- my. This distinguished anatomist gave the first public specimen of his abilities, by printing a dissertation on the lungs anno 1661 ; a period so remarkable for the study of nature, that it would be injustice to pass it without particular notice. History of Anatomy . 31 At the same time flourished Laurentius Bellirras at Florence, and was the first who introduced mathematical reasoning in physic. In 1662 , Simon Pauli published a treatise De albanclis cssibus. Fie had long been admired for the white skeletons he prepared ; and at last discovered his method, which was by ex- posing the bones all winter to the weather. Johannes Swammerdam of Amsterdam also published some anatomical treatises ; but was most remarkable for his knowledge of pre- serving the parts of bodies entire for many years, by injecting their vessels. He also published a treatise on respiration; wherein he mentioned his having figures of all the parts of the body as big as the life, cut in copper, which he designed to publish, with a complete systems of anatomy. These, howe- ver, were never made public by Swammerdam; but, in 1683 , Gothofridus Bidloo, professor of anatomy at Leyden, published a work en- titled Anatomia corporis hurnani , where all the parts were delineated in very large plates al- most as big as the life. Mr. Cowper, an Eng- lish surgeon, bought 300 copies of these fi- gures ; and in 1698 , published them with an English text, quite different from Bidloo’s La- tin one ; to which were added letters in Bid- loo’s figures, and some few figures of Mr. Cowper’s own. To this work Cowper’s name was prefixed, without the least mention of Bid- loo, except on purpose to confute him. Bid- loo immediately published a very ill-natured pamphlet, called GaHelmus Cowperus citatus 23 History of Anatomy. coram tribunal i; appealing to the Royal Soci- ety, how far Cowper ought to be punished as a plagiary of the worst kind, and endea- vouring to prove him an ignorant deceitful fellow. Cowper answered him in his own style, in a pamphlet called his V indicia ; en- deavouring to prove, either that Bidloo did not understand his own tables, or that they were none of his. It was even alleged that those were the tables promised by Swam- merdam, and which Bidloo had got from his widow. This, however, appears to have been only an invidious surmise, there being un- questionable evidence that they were really the performance of Bidloo. Soon after, Xsbrandus Biembroeck, profes- sor of anatomy at Utrecht, began to appear as an author. His work contained very little original ; but he was at great pains to collect from others whatever was valuable in their writings, and his system was the common standard among anatomical students for ma- ny years. About the same time, Antonins Liewen- hoeck of Delft, improved considerably" on Malpighi’s use of microscopes. These two authors took up anatomy where others had dropt it ; and, by this new art, they brought a number of amazing things to light. They discovered the red globules of the blood : they were enabled to see the actual circula- tion of the blood in the transparent parts of living animals, and could measure the velo- city of its motion; they discovered that the History of Anatomy. 33 arteries and veins had no intermediate cells or spungy substance, as Harvey and all the preceding anatomists had supposed, but com- municated one with the other by a continua- tion of the same tube. Liewenhoeck was in great fame likewise for his discovery of the animalcula in the se- men. Indeed there was scarcely a part of the body, solid or fluid, which escaped his examina- tion ; and he almost every where found, that what appeared to the naked eye to be rude un- digested matter, was in reality a beautiful and regular compound. After this period, Nuck added to our know- ledge of the absorbent system already men- tioned, by his injections of the lymphatic glands ; Ruysch, by his description of the valves of the lymphatic vessels; and Dr. Meckel, by his accurate account of the whole system, and by tracing those vessels in many parts where they had not before been de- scribed. Besides these authors, Drs. Hunter and Monro have called the attention of the pub- lic to this part of anatomy, in their contro- versy concerning the discovery of the office of the lymphatics. When the lymphatic vessels were first seen and traced into the thoracic duct, it was natu- ral for anatomists to suspect, that as the lac- teals absorbed from the cavity of the intes- tines, the lymphatics, which are similar in figure and structure, might possibly do the same office with respect to other parts of the E 34 History of Anatomy . body : and accordingly, Dr. Glisson, who wrote in 16 54 , supposes these vessels arose from cavities, and that their use was to ab- sorb ; and Frederic Hoffman has very expli- citly laid down the doctrine of the lymphatic vessels being a system of absorbents. But anatomists in general have been of a contra- ry opinion ; for, from experiments, particular- ly such as were made by injections, they have been persuaded that the lymphatic vessels did not arise from cavities, and did not absorb, but were merely continuations from small ar- teries. The doctrine, therefore, that the lym- phatics, like the lacteals, were absorbents, as had been suggested by Glisson and by Hoff- man, has been revived by Dr. Hunter and Dr. Monro, who have controverted the experi- ments of their predecessors in anatomy, and have endeavoured to prove that the lympha- tic vessels are not continued from arteries, but are absorbents. To this doctrine, however, several objec- tions have been started, particularly by Hal- ler (Elem. Phys. 1. 24 . § 2 , 3 .) ; and it has been found, that before the doctrine of the lymphatics being a system of absorbents can be established, it must first be determined whether this system is to be found in other animals besides man and quadrupeds. Mr. Hewson claims the merit of having proved the affirmative of this question, by discover- ing the lymphatic system in birds, fish, and amphibious animals. See Phil. Trans, vol. 1-viii. and lxix. — And latterly, Mr. Cruikshank History of Anatomy. 35 has traced the ramifications of that system in almost every part of the body ; and from his dissections, figures have been made and lately published to the world. To Mr. Sheldon also we are much indebted for his illustration of this system, which promises to give great sa- tisfaction, but of which only a part has yet been published. The gravid uterus is a subject likewise'* which has received considerable improve- ments, particularly relating to one very im- portant discovery ; viz. that the internal mem- brane of the uterus, which Dr. Hunter has named decidua , constitutes the exterior part of the secundines or after-birth, and separates from the rest of the uterus every time that a woman either bears a child or suffers a mis- carriage. This discovery includes another, to wit, that the placenta is partly made up of an excrescence or efflorescence from the uterus itself. These discoveries are of the utmost conse- quence, both in the physiological question about the connection between the mother and child, and likewise in explaining the phenome- na of births and abortions, as well as in re- gulating obstetrical practice. The anatomists of this century have im- proved anatomy, and have made the study of it much more easy, by giving us more correct as well as more numerous figures. It is amaz- ing to think of what has been done in that time. We have had four large folio books of figures of the bones, viz. Cheselden’s, Albi- 36 History of Anatomy. nus’s, Sue’s and Trew’s. Of the muscles, we have had two large folios ; one from Cowper, which is elegant ; and one from Albinus, which, from the accuracy and labour of the work, we may suppose will never be outdone. Of tiie blood-vessels we have a large folio from Dr. Haller. We have had one upon the nerves from Dr. Meckel, and another by Dr. Monro junior. We have had Albinus’s, Roederer’s, Jenty’s, and Hunter’s works up- on the pregnant uterus; Weitbrecht and Le- ber on the joints and fresh bones ; Soemer- ring on the brain ; Zin on the eye ; Cotunius, Meckel junior, £*c. on the ear; Waiterus on the nerves of the thorax and abdomen ; Dr. Monro on the bursae mucosae, &c. It would be endless to mention the anato- mical figures that have been published in this century, of particular and smaller parts of the body, by Morgagni, Ruysch, Valsalva, Sanc- torini, Heister, Vater, Cant, Zimmerman, Waiterus, and others. Those elegant plates of the brain, howe- ver, just published by M. Vicq. d’Azyr, must not pass without notice, especially as they form part of an universal system of anatomy and physiology, both human and comparative, proposed to be executed in the same splendid style. Upon the brain alone 19 folio plates are employed; of which several are coloured. The figures are delineated with accuracy and clearness ; but the colouring is rather beauti- ful than correct. Such parts of this work as may be published, cannot fad to be equally History of Anatomy. 37 acceptable to the anatomist and the philoso- pher; but the entire design is apparently too extensive to be accomplished within the peri- od of a single life. In Great Britain, also, a very great anatomical work is carrying on by Andrew Bell, F. S. A. S. engraver to his Royal Highness the Prince of Wales, wdth the approbation of Dr. Monro, and under the inspection of his very ingenious assistant Mr. Fyfe. It is to compose a complete illustra- tion, both general and particular, of the hu- man body, by a selection from the best plates of all the greatest anatomists, as well foreign as British, exhibiting the latest discoveries in the science, and accompanied with copious ex- planations. The whole number of plates mentioned in the Prospectus is 240 , of which 152 are already done ; all in royal folio, To the foreign treatises already mentioned may be added those recently published by Sabbatier and Plenck on anatomy in general. In Great-Britain, the writings of Keil, Doug- las, Cheselden, the first Monro, Winslow, £kc. are too well known to need description. The last of these used to be recommended as a standard for the students of anatomy: but it has of late given place to a more accu- rate and comprehensive system, in three vo- lumes, published by Mr. Elliot of Edinburgh, upon a plan approved of by Dr. Monro, and executed by Mr. Fyfe. Dr. Simmons of London has also obliged the world with an excellent system of anatomy ; and another work, under the title of “ Elements of Ana- 38 History of Anatomy. tomy and the Animal Oeconomy:” in which the subjects are treated with uncommon ele- gance and perspicuity. In the latter part of the last century, ana- tomy made two great steps, by the invention of injections, and the method of making what we commonly call preparations. These two modern arts have really been of infinite use to anatomy; and besides have introduced an elegance into our administrations, which in former times could not have been supposed to be possible. They arose in Holland un- der Swammerdam and Ruysch, and after- wards in England under Cowper, St. Andre, and others, where they have been greatly im- proved. The anatomists of former ages had no other knowledge of the blood-vessels, than what they were able to collect from laborious dis- sections, and from examining the smaller branches of them, upon some lucky occa- sion, when they were found more than com- monly loaded with red blood. But filling the vascular system with a bright coloured wax, enables us to trace the large vessels with great ease, renders the smaller much more conspicuous, and makes thousands of the very minute ones visible, which from their delicacy, and the transparency of their natu- ral contents, are otherwise imperceptible. The modern art of corroding the fleshy parts with a menstruum, and of leaving the moulded wax entire, is so exceedingly useful, and at the same time so ornamental, that it History of Anatomy. 39 does great honour to the ingenious inventor Dr. Nicholls. The wax-work art of the moderns might de- serve notice in any history of anatomy, if the masters in that way had not been so careless in their imitation. Many of the wax-figures are so tawdry with a show of unnatural co- lours, and so very incorrect in the circum- stances of figure, situation, and the like, that though they strike a vulgar eye with admira- tion, they must appear ridiculous to an ana- tomist. But those figures which are cast in wax, plaster, or lead, from the real subject, and which of late years have been frequently made, are, of course, very correct in all the principal parts, and may be considered as no insignificant acquisition to modern anatomy. The proper, or principal use of this art is, to preserve a very perfect likeness of such sub- jects as we but seldom can meet with, or can- not well preserve in a natural state ; a subject in pregnancy, for example. The modern improved methods of preserv- ing animal bodies, or parts of them, has been of the greatest service to anatomy ; especially in saving the time and labour of the anato- mist in the nicer dissections of the small parts of the body. For now, whatever he has prepared with care, he can preserve; and the object is ready to be seen at any time. And in the same manner he can preserve ana- tomical curiosities, or rarities of every kind ■ such as, parts that are uncommonly formed ; parts that are diseased ; the parts of the preg- 40 Introduction to Anatomy. nant uterus and its contents. Large collec- tions of such curiosities, which modern ana- tomists are striving almost every where to procure, are of infinite service to the art, es- pecially in the hands of teachers. They give students clear ideas about many things which it is very essential to know, and yet which it is impossible that a teacher should be able to show otherwise, were he ever so well suppli- ed with fresh subjects. 2. View of the Subject in general , and Plan of the following Treatise. \ THE etymology of the word anatomy , as above given, implies simply dissection ; but by this term something more is usually under- stood. It is every day made use of to express a knowledge of the human body ; and a person who is said to understand anatomy, is sup- posed to be conversant with the structure and arrangement of the different solid parts of the body. It is commonly divided into Anatomy , pro- perly so called ; and Comparative Anatomy : the first of these is confined solely to the hu- man body ; the latter includes all animals, so far as a knowledge of their structure may tend to perfect our ideas of the human body. Introduction to Anatomy. 41 The term anatomy may also have another and more extensive signification : it may be employed to express not only a knowledge of the structure and disposition of the parts but likewise of their ceconomy and use. Consider- ed in this light, it will seldom fail to excite the curiosity of people of taste, as a branch of philosophy ; since if it is pleasing to be ac- quainted with the structure of the body, it is certainly more so to discover all the springs which give life and motion to the machine, and to observe the admirable mechanism by which so many different functions are exe- cuted. Astronomy and anatomy, as Dr. Hunter, after Fontenelle, observes, are the studies which present us with the most striking view of the two greatest attributes of the Supreme Being. The first of these fills the mind with the idea of his immensity, in the largeness, distances, and number of the heavenly bodies ; the last, astonishes with his intelligence and art in the variety and delicacy of animal me- chanism. The human body has been commonly enough known by the name of ?nicrocos?nus , or the little world ; as if it did not differ so much from the universal system of nature in the symmetry and number of its parts as in their size. Galen’s excellent treatise De usu partium , was composed as a prose hymn to the Crea- tor ; and abounds with as irresistible proofs of a supreme Cause and governing Provi- 42 Introduction to Anatomy. dence, as we find in modern physico-theology. And Cicero dwells more on the structure and ceconomy of animals than on all the produc- tions of nature besides, when he wants to prove the existence of the gods from the or- der and beauty of the universe. He there takes a survey of the body of man in a most elegant synopsis of anatomy, and concludes thus: u Quibus rebus expositis, satis docuisse videor, hominis natura, quanto omnes anteiret animantes. Ex quo debet intelligi, nec figu- ram situmque membrorum, nec ingenii men- tisque vim talem effici potuisse fortuna.” The satisfaction of mind which arises from the study of anatomy, and the influence which it must naturally have upon our minds as phi- losophers, cannot be better conveyed than by the following passage from the same author : “ Quae contuens animus, accepit ab his cogni- tionem deorum, ex qua oritur pietas : cui con- juncta justitia est, reliquasque virtutes : ex quibus vita beata exsistit, par et similes deo- rum, nulla alia re nisi immortalitate, quae ni- hil ad bene vivendum pertinet, cedens cceles- tibus.” It would be endless to quote the animated passages of this sort which are to be found in the physicians, philosophers, and theologists, who have considered the structure and func- tions of animals with a view towards the Cre- ator. It is a view which must strike one with a most awful conviction. Who can know and consider the thousand evident proofs of the as- tonishing art of the Creator, in forming and Introduction to Anatomy . 43 sustaining an animal body such as ours, with- out feeling the most pleasant enthusiasm ? Can we seriously reflect upon this awful subject, without being almost lost in adoration ? with- out longing for another life after this, in which we may be gratified with the highest enjoy- ment, which our faculties and nature seem ca- pable of, the seeing and comprehending the whole plan of the Creator, in forming the uni- verse and in directing all its operations ? But the more immediate purposes of anato- my concern those who are to be the guardians of health, as this study is necessary to lay a foundation for all the branches of medicine. The more we know of our fabric, the more reason we have to believe, that if our senses were more acute, and our judgment more en- larged, we should be able to trace many springs of life which are now hidden from us: by the same sagacity we should discover the true causes and nature of diseases ; and there- by be enabled to restore the health of many, who are now, from our more confined know- ledge, said to labour under incurable disor- ders. By such an intimate acquaintance with the ceconomy of our bodies, we should disco- ver even the seeds of diseases, and destroy them before they had taken root in the consti- tution. That anatomy is the very basis of surgery every body allows. It is dissection alone that can teach us, where we may cut the living body with freedom and dispatch ; and where we may venture with great circumspection and 44 Introduction to Anatomy. delicacy ; and where we must not, upon any account, attempt it. This informs the head, gives dexterity to the hand, and familiarizes the heart with a sort of necessary inhumanity, the use of cutting-instruments upon our fel- low-creatures. Besides the knowledge of our body, through all the variety of its structure and operations in a sound state, it is by anatomy only that we can arrive at the knowledge of the true nature of most of the diseases which afflict humanity. The symptoms of many disorders are often equivocal ; and diseases themselves are thence frequently mistaken, even by sensible, expe- rienced, and attentive physicians. But by ana- tomical examination after death, we can with certainty find out the mistake, and learn to avoid it in any similar case. This use of anatomy has been so generally adopted by the moderns, that the cases alrea- dy published are almost innumerable : Man- getus, Morgagni, indeed many of the best mo- dern writings in physic, are full of them. And if we look among the physicians of the best character, and observe those who have the art itself, rather than the craft of the profes- sion at heart ; we shall find them constantly taking pains to procure leave to examine the bodies of their patients after death. After having considered the rise and pro- gress of anatomy ; the various discoveries that have been made in it, from time to time ; the great number of diligent observers who have applied themselves to this art ; and the Introduction to Anatomy. 45 importance of the study, not only for the pre- vention and cure of diseases, but in furnish- ing the liveliest proofs of divine wisdom; the following questions seem naturally to arise: For what purpose is there such a variety of parts in the human body ? Why such a com- plication of nice and tender machinery ? Why was there not rather a more simple, less deli- cate, and less expensive frame ?* In order to acquire a satisfactory general idea of this subject, and find a solution of all such questions, let us, in our imaginations, make a man : in other words let us suppose that the mind , or immaterial part, is to be placed in a corporeal fabric, in order to hold a correspondence with other material beings by the intervention of the body ; and then consider, a priori , what will be wanted for her accommodation. In this inquiry, we shall plainly see the necessity or advantage, and therefore the final cause, of most of the parts which we actually find in the human body. And if we consider that, in order to answer some of the requisites, human wit and inven- tion would be very insufficient ; we need not be surprised if we meet with some parts of the body whose use we cannot yet perceive, and with some operations and functions which we cannot explain. We can see that the whole bears the most striking characters of excelling wisdom and ingenuity : but the imperfect sen- * The following beautiful representation is taken from the late Dr. Hunter’s Introductory Lecture in Anatomy. 46 Introduction to Anatomy. ses and capacity of man cannot pretend to reach every part of a machine, which nothing less than the intelligence and power of the Supreme Being could contrive and execute. First, then, the mind, the thinking, imma- terial agent, must be provided with a place of immediate residence, which shall have all the requisites for the union of spirit and body \ accordingly she is provided with the brain , where she dwells as governor and superintend- ant of the whole fabric. In the next place, as she is to hold a corre- spondence with all the material beings around her, she must be supplied with organs fitted to receive the different kinds of impressions which they will make. In fact, therefore, we see that she is provided with the organs of sense, as we call them : the eye is adapted to light ; the ear to sound ; the nose to smell ; the mouth to taste ; and the skin to touch. Further : She must be furnished with or- gans of communication between herself in the brain and those organs of sense, to give her information of all the impressions that are made upon them : and she must have organs between herself in the brain and every other part of the body, fitted to convey her com- mands and influence over the whole. For these purposes the nerves are actually given. They are chords, which rise from the brain, the immediate residence of the mind, and dis- perse themselves in branches through all parts of the body. They convey ail the different kinds of sensations to the mind, in the brain ; Introduction to Anatomy. 47 and likewise carry out from thence all her com- mands or influence to the other parts of the body. They are intended to be occasional mo- nitors against all such impressions as might en- danger the well-being of the whole, or of any particular part ; which vindicates the Creator of all things, in having actually subjected us to those many disagreeable and painful sensa- tions which we are exposed to from a thousand accidents in life. Moreover, the mind, in this corporeal sys- tem, must be endued with the power of mov- ing from place to place, that she may have in- tercourse with a variety of objects ; that she may fly from such as are disagreeable, danger- ous or hurtful, and pursue such as are plea- sant or useful to her. And accordingly she is furnished with limbs, and with muscles and tendons, the instruments of motion, which are found in every part of the fabric where motion is necessary. But to support, to give firmness and shape to the fabric ; to keep the softer parts in their proper places ; to give fixed points for, and the proper direction to its motions, as well as to protect some of the more important and tender organs from external injuries ; there must be some firm prop-work interwoven through the whole. And, in fact, for such purposes the bones are given. The prop-work must not be made into one rigid fabric, for that would prevent motion. Therefore there are a number of bones. 48 Introduction to Anatomy. These pieces must all be firmly bound toge- ther, to prevent their dislocation. And this end is perfectly well answered by the liga- ments. The extremities of these bony pieces, where they move and rub upon one another, must have smooth and slippery surfaces for easy motion. This is most happily provided for, by the cartilages and mucus of the joints. The interstices of all those parts must be filled up with some soft and ductile matter, which shall keep them in their places, unite them, and at the same time allow them to move a little upon one another. And these purposes are answered by the cellular membrane or adi- pose substance. There must be an outward covering over the whole apparatus, both to give it compact- ness and to defend it from a thousand injuries : which, in fact, are the very purposes of the skin and other integuments. Lastly, the mind being formed for society and intercourse with beings of her own kind, she must be endued with powers of expressing and communicating her thoughts by some sen- sible marks or signs ; which shall be both easy to herself, and admit of great variety ; and ac- cordingly she is provided with the organs and faculty of speech, by which she can throw out signs with amazing facility, and vary them with- out end. Thus we have built up an animal body which would seem to be pretty complete : but as it is the nature of matter to be altered and work- Introduction to Anatomy. 49 ed upon by matter ; so in a very little time such a living creature must be destroyed, if there is no provision for repairing the injuries which she must commit upon herself, and those which she must be exposed to from without. There- fore a treasure of blood is actually provided in the heart and vascular system, full of nutritious and healing particles, fluid enough to penetrate into the minutest parts of the animal ; impelled by the heart, and conveyed by the arteries, it washes every part, builds up what was broken down, and sweeps away the old and useless materials. Hence we see the necessity or ad- vantage of the heart and arterial system. What more there was of this blood than enough to repair the present damages of the machine, must not be lost, but should be re- turned again to the heart ; and for this purpose the venous system is actually provided. These requisites in the animal explain, a priori, the circulation of the blood. The old materials which were become use- less, and are swept off by the current of blood, must be separated and thrown out of the sys- tem. Therefore glands, the organs of Secre- tion, are given for straining whatever is redun- dant, vapid, or noxious, from the mass of blood ; and when strained, they are thrown out by emunctories, called organs of Excre- tion. But now, as the machine must be constant- ly wearing, the reparation must be carried on without intermission, and the strainers must always be emoloyed. Therefore there is ac- G 50 Introduction to Anatomy. tually a perpetual circulation of the blood, and the secretions are always going on. Even all this provision, however, would not be sufficient ; for that store of blood would soon be consumed, and the fabric would break down, if there were not a provision made for fresh supplies. These we observe, in fact, are profusely scattered round her in the animal and vegetable kingdoms : and she is furnished with hands, the fittest instruments that could have been contrived, for gathering them, and for preparing them in a variety of ways for the mouth. But these supplies, which we call food, must be considerably changed ; they must be converted into blood. Therefore she is pro- vided with teeth for cutting and bruising the food, and with a stomach for melting it down : In short, with all the organs subservient to di- gestion. — The finer parts of the aliments only can be useful in the constitution : these must be taken up and conveyed into the blood, and the dregs must be thrown off. With this view the intestinal canal is actually given. It sepa- rates the nutritious part, which we call chyle , to be conveyed into the blood by the system of absorbent vessels ; and the faces pass down- wards, to be conducted out of the body. Now we have got our animal not only fur- nished with what is wanted for its immediate existence, but also with the powers of protract- ing that existence to an indefinite length of time. But its duration, we may presume, must necessarily be limited : for as it is nourished, Introduction to Anatomy. 51 grows, and is raised up to its full strength and utmost perfection ; so it must, in time, in com- mon with all material beings, begin to decay, and then hurry on to final ruin. Hence we see the necessity of a scheme for renovation. Accordingly wise Providence, to perpetuate, as welPas preserve his work, besides giving a strong appetite for life and self-preservation, has made animals male and female, and given them such organs and passions as will secure the propagation of the species to the end of time. Thus we see, that by the very imperfect survey which human reason is able to take of this subject, the animal man must necessarily be complex in his corporeal system, and in its operations. He must have-one great and general system, the vascular, branching through the whole for circulation : Another the nervous, with its ap- pendages the organs of sense, for every kind of feeling : And a third, for the union and connection of all those parts. Besides these primary and general systems, he requires others which may be more local, or confined: One for strength, support, and protection ; the bony compages : Another for the requisite motions of the parts among them- selves, as well as for moving from place to place ; the muscular part of the body : Ano- ther to prepare nourishment for the daily re- cruit of the body ; the digestive organs : And one for propagating the species ; the organs of generation. 52 Introduction to Anatomy. And in taking this general survey of what would appear, a priori , to be necessary for adapting an animal to the situations of life, we observe with great satisfaction, that man is accordingly made of such systems, and for such purposes. Fie has them all ; and he has nothing more, except the organs of respira- tion. Breaming it seemed difficult to account for a priori: we only knew it to be in fact essentially necessary to life. Notwithstanding this, when w r e saw all the other parts of the bo- dy, and their functions, so well accounted for, and so wisely adapted to their several purpo- ses, there could be no doubt that respiration was so likewise : And accordingly, the disco- veries of Dr. Priestley have lately thrown light upon this function also, as will be shown in its proper place. Of all the different systems in the human body, the use and necessity are not more ap- parent, than the wisdom and contrivance which has been exerted in putting them all into the most compact and convenient form : indispos- ing them so, that they shall mutually receive, and give helps to one another ; and that all, or many of the parts, shall not only answer their principal end or purpose, but operate success- fully and usefully in a variety of secondary ways. If we consider the whole animal machine in this light, and compare it with any machine in which human art has exerted its utmost; suppose the best constructed ship that ever was built, we shall be convinced beyond the Introduction to Anatolmy . S3 possibility of doubt, that there are intelligence and power far surpassing what humanity can boast of. One superiority in the natural machine is peculiarly striking.- — In machines of human contrivance or art, there is no internal power, no principle in the machine itself, by which it can alter and accommodate itself to any injury which it may suffer, or make up any injury which admits of repair. But in the natural machine, the animal body, this is most won- derfully provided for, by internal powers in the machine itself ; many of which are not more certain and obvious in their effects, than they are above all human comprehension as to the manner and means of their operation. Thus, a wound heals up of itself ; a broken bone is made firm again by a callus ; a dead part is separated and thrown off ; noxious juic- es are driven out by some of the emunctories; a redundancy is removed by some spontane- ous bleeding ; a bleeding naturally stops of it- self ; and a great loss of blood, from any cause, is in some measure compensated, by a con- tracting power in the vascular system, which accommodates the capacity of the vessels to the quantity contained. The stomach gives information when the supplies have been ex- pended ; represents, with great exactness, the quantity and the quality of what is wanted in the present state of the machine ; and in pro- portion as she meets with neglect, rises in her demand, urges her petition in a louder tone, and with more forcible arguments. For its 54 Introduction to Anatomy . protection, an animal body resists heat and cold in a very wonderful manner, and pre- serves an equal temperature in a burning and in a freezing atmosphere. A farther excellence or superiority in the natural machine, if possible, still more aston- ishing, more beyond all human comprehen- sion, than what we have been speaking of, is the following. Besides those internal powers of self-preservation in each individual, when two of them co-operate, or act in concert, they are endued with powers of making other ani- mals or machines like themselves, which again are possessed of the same powers of produc- ing others, and so of multiplying the species without end. These are powers which mock all human in- vention or imitation. They are characterise tics of the divine Architect. Having premised this general account of the subject, we shall next consider the method to be observed in treating it. The study of the human body, as already noticed, is commonly divided into two parts. The first, which is called Anatomy , relates to the matter and structure of its parts ; the se- cond, called Physiology and Animal ceconomy , relates to the principles and laws of its inter- nal operations and functions. As the body is a compound of solids and fluids, Anatomy is divided into, 1. The Anatomy of the solids, and 2. The Anatomy of the fluids. Introduction to Anatomy. 55 I. The Solids, by which we mean all parts of our body, which are not fluid, are general- ly divided into two classes, viz. 1. The hard solids or bones. This part of anatomy is called Osteology ; which signifies the doctrine of the bones. 2. The softer solids ; which part is called Sarcology, viz. the doctrine of flesh. This division of the solids, we may observe, has probably taken its origin from the vulgar observation, that the body is made of bone and flesh. And as there are many different kinds of what are called soft or fleshy parts, Sarcology is subdivided into, (l.) Angeiology , or the doctrine of vessels; by which is commonly understood bloocl-vessels : (2.) Adenology , of glands: (3.) Neurology , of nerves: (4.) Myology , of muscles : and, (5.) Splanchnology , of the viscera or bow- els. There is, besides, that part which treats of the organs of sense and of the integuments. This division of the solids has been here mentioned, rather for the sake of explaining so many words, which are constantly used by anatomists, than for its importance or ac- curacy. For besides many other objections that might be urged, there are in the body three species of solids, viz. gristle or carti- lage, hair, and nails ; which are of an inter- mediate nature between bone and flesh ; and therefore cannot so properly be brought into the osteology or the sarcology. The cartila- ges were classed with the bones ; because the 56 Introduction to Anatomy . greatest number of them are appendages to bones : and for the like reason the hair and the nails were classed with the integuments. II. The Fluids of the human body may be divided into three kinds, which Dr. Hunter calls the crude , the general or perfect , and the local or secreted fluid. 1. By the crude fluid is meant the chyle, and whatever is absorbed at the surfaces of the body ; in other words, what is recently taken into the body, and is not yet mixed with or converted into blood. 2. The general or perfect fluid is the blood itself ; to wit, what is contained in the heart, arteries, and veins, and is going on in the round of the circulation. 3. The local or secreted , are those fluids pe- culiar to particular parts of the body, which are strained off from the blood, and yet are very different in their properties from the blood. They are commonly called secretions ; and some are useful, others excrementitious. In treating of the Physiology , it is very dif- ficult to say what plan should be followed ; for every method which has been yet proposed, is attended with manifest inconvenience. The powers and operations of the machine have such a dependence upon one another, such connections and reciprocal influence, that they cannot well be understood or explained sepa- rately. In this sense our body may be com- pared to a circular chain of powers, in which nothing is first or last, nothing solitary or in- dependent ; so that wherever we begin, we Osteology . 57 find that there is something preceding which we ought to have known. If we begin with the brain and the nerves, for example, we shall find that these cannot exist, even in idea, without the heart: if we set out with the heart and vascular system, we shall presently be sensible, that the brain and nerves must be supposed: or, should we take up the mouth, and follow the course of the aliment, we should see that the very first organ which presents itself, supposed the existence of both the heart and brain : Wherefore we shall incorporate the Physiology with the Anatomy, by attempting to explain the functions after we have demon- strated the organs. Part I. OSTEOLOGY. W E begin with the bones, which may be considered as the great support of the body, tending to give it shape and firmness. — But before we enter into the detail of each par- ticular bone, it will be necessary to describe their composition and connections, and to ex- plain the nature of the different parts which have an immediate relation to them ; as the car- tilages, ligaments, periosteum, marrow, and synovial glands. H 58 Osteology* Sect. I. Of the Bones in general , with their Appendages , &c* The bones are of a firm, and hard* sub- stance, of a white colour, and perfectly insen- sible. They are the most compact and solid parts of the body, and serve for the attachment and support of all the other parts. Three different substances are usually dis- tinguished in them; their exterior or bony part, properly so called; their spongy cells; and their reticular substance. The first of these is formed of many laminae or plates, compos- ing a firm hard substance — The spongy or cellular part is so called on account of its re- semblance to a sponge, from the little cells which compose it. This substance forms al- most the whole of the extremities of cylindrical bones. The reticular part is composed of fi- bres, which cross each other in different direc- tions. This net-work forms the internal sur- face of those bones which have cavities. The flat bones, as those of the head, are composed only of the laminae and the cellular substance. This last is usually found in the middle of the bone dividing it into two plates, and is there called diploe . * Mr. Scheele lias litely difcovered that bones contain the phofphoric acid urited with calcareous earth; and that to this combination they owe their firmnefs. Osteology. 59 Gagliardi, who pretended to have discover- ed an infinite number of claviculi* or bony processes, which he describes as traversing the laminae to unite them together, has endea- voured to support this pretended discovery by the analogy of bones to the bark of trees, in which certain woody nails have been remark- ed ; but this opinion seems to be altogether fanciful. Some writers have supposed, that the bones are formed by layers of the perioste- um, which gradually ossify, in the same man- ner as the timber is formed in trees by the hardening of the white substance that is found between the inner bark and the wood. M. Duhamel, who has adopted this opinion, fed different animals with madder and their ordi- nary food alternately during a certain time ; and he asserts, that in dissecting their bones, he constantly observed distinct layers of red and white, which corresponded with the length of time they had lived on madder or their usual aliment. But it has since been proved by Detleff, that M. Duhamel’s experiments were inaccurate, and that neither the perios- teum nor the cartilages are tinged by the use of madder, which is known to affect the bones only. We usually consider in a bone, its body and its extremities. The ancients gave the * In his Anat. OJJium nov. invent, illujlrat. he defcribes four kinds of thefe claviculi or nails, viz. the perpendicular, oblique* headed, and crooked. 60 Osteology. name of diaphysis to the body or middle part, and divided the extremities into apophysis and epiphysis. An apophysis, or process, as it is more commonly called, is an eminence con- tinued from the body of the bone, whereas an epiphysis is at first a sort of appendage to the bone, by means of an intermediate cartilage. Many epiphyses, which appear as distinct bones in the foetus, afterwards become apophy- ses ; for they are at length so completely unit- ed to the body of the bone as not to be distin- guishable from it in the adult state. It is not unusual, however, at the age of 18 and even 20 years, to find the extremities of bones still in the state of epiphysis. The names given to the processes of bones are expressive of their shape, size, or use ; thus if a process is large and of a spherical form, it is called caput , or head ; if the head is flatted, it is termed condyle. Some proces- ses, from their resemblance to a stiletto, a breast, or the beak of a crow, are called styloid , mastoid , or coracoid : others are styled ridges or spines. The two processes of the os femo- ris derive their name of trochanters from their use. A bone has its cavities as well as processes. These cavities either extend quite through its substance, or appear only as depressions. The former are called foramina or holes , and these foramina are sometimes termed canals or con- duits , according to their form and extent. Of the depressions, some are useful in articuda- tion. These are called cotyloid when they are Osteology. 61 deep, as is the case with the os innominatum, where it receives the head of the os femoris ; or glenoid when they are superficial, as in the scapula, where it receives the os humeri. Of the depressions that are not designed for arti- culation, those which have small apertures are called sinuses ; others that are large, and not equally surrounded by high brims, are styled fossa ; such as are long and narrow, furrows ; or if broad and superficial without brims, si- nuosities. Some are called digital impressions , from their resemblance to the traces of a fin- ger on soft bodies. We shall abridge this article, which is ex- ceedingly diffuse in the generality of anatomi- cal books, and will endeavour to describe it with all the clearness it will allow. The bones composing the skeleton are so constructed, that the end of every bone is per- fectly adapted to the extremity of that with which it is connected, and this connection forms what is called their articulation. Articulation is divided into diartlirosis , sy- nartlirosis , and amphiarthrosis , or moveable, immovable, and mixed articulation. Each of the two first has its subdivisions. Thus the Diarthrosis , or moveable articulation, includes, 1. The enarthrosis, as it is called, when a large head is admitted into a deep cavity, as in the articulation of the os femoris with the os innominatum. 2. Arthrodia, when a round head is articulated with a superficial cavity, as is the case of the os humeri and scapula. 3. Ginglimus, or hinge-like articulation, as in the 62 Osteology. connection of the thigh-bone with the tibia. The enarthrosis and arthrodia allow of motion to all sides ; the ginglimus only of flection and extension. The syjiarthrosis , or immoveable articula- tion, includes, 1. The suture, when the two bones are indented into each other, as is the case with the parietal bones. 2. Gomphosis, when one bone is fixed into another, in the manner the teeth are placed in their sockets. The term amphiarthrosis is applied to those articulations which partake both of the synar- throsis and diarthrosis, as is the case with the bones of the vertebrae, which are capable of motion in a certain degree, although they are firmly connected together by intermediate car- tilages. What is called symphysis is the union of two bones into one ; as in the lower jaw, for instance, which in the foetus consists of two distinct bones, but becomes one in a more ad- vanced age, by the ossification of the uniting cartilage. When bones are thus joined by the means of cartilages, the union is styled synchondro- sis ; when by ligaments, syneurosis. Cartilages are white, solid, smooth, and elastic substances, between the hardness of bones and ligaments, and seemingly of a fi- brous texture. We are not able to trace any vessels into their substance by injection, nor are they ever found tinged in animals that have been fed with madder. Osteology . 63 They may be distinguished into, 1st, Those which are connected with the bones ; and, 2dly, Those which belong to other parts of the body. The first serve either to cover the ends and cavities of bones intended for mo- tion, as in the articulations, where by their smoothness they facilitate motions, which the bones alone could not execute with so much freedom ; or they serve to unite bones toge- ther, as in the symphysis pubis, or to length- en them, as in the ribs. Many of them ossifying as we advance in life, their number is less in the adult than in the foetus, and of course there are fewer bones in the old than in the young subject. Of the second class of cartilages, or those belonging to the soft parts, we have instances in the larynx, where we find them useful in the formation of the voice, and for the attach- ment of muscles. The periosteum is a fine membrane of a compact cellular texture, reflected from one joint to another, and serving as a common covering to the bones. It has sanguiferous and lymphatic vessels, and is supplied with nerves from the neighbouring parts. It ad- heres very firmly to their surface, and by its smoothness facilitates the motion of muscles. It likewise supports the vessels that go to be distributed through the substance of the bones, and may serve to strengthen the articulations. At the extremities of bones, where it is found covering a cartilage, it has by some been im- properly considered as a distinct membrane, 64 Osteology. and named perichondrium. This, in its use and structure, resembles the periosteum. Where it covers the bones of the skull, it has gotten the name of pericranium > The periosteum is not a production of the dura mater, as the ancients, and after them Havers, imagined ; nor are the bones formed by the ossification of this membrane, at least when it is in a sound state, as some late wri- ters have supposed. The periosteum is deficient in the teeth above the sockets, and in those parts of bones to which ligaments or tendons are attached. The marrow is a fat oily substance, filling the cavities of bones. In the great cavities of long bones it is of a much firmer consistence than in the cells of their spongy part. In the former it inclines somewhat to a yellowish tinge, and is of the consistence of fat ; in the latter it is more fluid, and of a red colour. This difference in colour and consistence is owing to accidental causes ; both kinds are of the same nature, and may both be described under the common name of marrow, though some writers give the name only to the fat-like substance, and call the other the medullary juice. The marrow is contained in a very fine and transparent membrane, which is supplied with a great number of blood-vessels, chiefly from the periosteum. This membrana medullaris adheres to the inner surface of the bones, and furnishes an infinite number of minute bags or vesicles for inclosing the marrow, Osteology. 65 which is likewise supported in the cavities of the bones by the long filaments of their reti- cular substance. Besides the vessels from the periosteum, the membrana medullaris is furnished with others, which in the long bones may be seen passing in near the extremities of the bone, and sending off numerous branches that rami- fy through all the vesicles of this membrane. The bones, and the cells containing the marrow, are likewise furnished with lympha- tics. By their means, the marrow, like the fat, may be taken up in a greater quantity than it is secreted ; and hence it is that so little is found in the bones of those who die of linger- ing diseases. It is still a matter of controversy, Whether the marrow is sensible or not? We are cer- tainly not able to trace any nerves to it; and from this circumstance, and its analogy to fat, Haller has ventured to consider it as insensi- ble. On the other hand, Duverney asserts, that an injury done to this substance in a liv- ing animal was attended with great pain. In this dispute physiologists do not seem to have sufficiently discriminated between the marrow itself and the membranous cells in which it is contained. The former, like the fat, being nothing more than a secreted, and of course an inorganized, matter, may with propriety be ranked among the insensible parts, as much as inspissated mucus or any other secreted mat- ter in the body ; whereas the membrana me- dullaris being vascular, though it possesses but I 66 Osteology . an obscure degree of feeling in a sound state, is not perfectly insensible. The marrow was formerly supposed to be intended for the nourishment and renewal of the bones ; but this doctrine is now pretty ge- nerally and deservedly exploded. It seems probable that the marrow is to the bones what fat is to the soft parts. They both serve for some important purposes in the animal (econo- my ; but their particular use has never yet been clearly ascertained. The marrow, from the transudation of the oil through the bones of a skeleton, is supposed to diminish their brittleness; and Havers, who has written pro- fessedly on the bones, describes the canals by which the marrow is conveyed through every part of their substance, and divides them into longitudinal and transverse ones. He speaks of the first as extending through the whole length of the bone ; and of the latter, as the passages by which the longitudinal ones com- municate with each other. The similarity of these to the large cancelli in burnt bones, and the transudation of the oil through the bones of the skeleton, seems to prove that some such passages do actually exist. The synovial glands are small bodies,* sup- posed to be of a glandular structure, and ex- ceedingly vascular, secreting a fluid of a clear mucilaginous nature, which serves to lubricate the joints. They are placed in small cavities * It is now much doubted, however, whether the appear- ances in the joints, which are usually called glands , art any thing more than assemblages of fat. Osteology. 67 in the articulations, so as to be capable of be- ing gently compressed by the motion of the joint, which expresses their juice in propor- tion to the degree of friction. When the sy- novia is wanting, or is of too thick a consist- ence, the joint becomes stiff and incapable of flexion or extension. This is what is termed anchilosis. Ligaments are white, glistening, inelastic bands, of a compact substance, more or less broad or thick, and serving to connect the bones together. They are distinguished by different names adapted to their different forms and uses. Those of the joints are called ei- ther round or bursal. The round ligaments are white, tendinous, and inelastic. They are strong and flexible, and are found only in the joint of the knee, and in the articulation of the os femoris with the os innominatum. The bursal, or capsular ligaments, surround the whole joint like a purse, and are to be found in the articulations which allow motion every way, as in the articulation of the arm with the scapula. Of those sacs called Burse? mucosa , a few were known to former anatomists, but by much the greater number have been since discover- ed by Dr. Monro,* who observes, that they are to be met with in the extremities of the body only; that many of them are placed en- tirely on the inner sides of the tendons, be- tween these and the bones. Many others co- ver not only the inner, but the outer sides of * See Descripion of the Bursa Mucosa, fee. 68 Osteology. the tendons, or are interposed between the ten- dons and external parts, as well as between those and the bones. Some are situated between the tendons and external parts only or chiefly, some between contiguous tendons, or between the tendons or the ligaments and the joints. A few such sacs are observed where the processes of bones play upon the ligaments, or where one bone plays upon another. Where two or more ten- dons are contiguous, and afterwards separate from each other, we generally find a common bursa divided into branches, with which it communicates ; and a few bursae of contigu- ous tendons communicate with each other. — Some in healthy children, communicate with the cavities of the joints ; and in many old people he has seen such communications form- ed by use or worn by friction, independent of disease. Their proper membrane is thin and trans- parent, but very dense, and capable of con- fining air or any other fluid. It is joined to the neighbouringparts by the common cellular sub- stance. Between the bursa and the hard sub- stance of bone, a thin layer of cartilage or of tough membrane is very generally interpos- ed. To the cellular substance on the outside of the bursa, the adipose substance is con- nected; except where the bursa covers a ten- don, cartilage, or bone, much exposed to pres- sure or friction. In several places a mass of fat, covered with the continuation of the membrane of the Osteology. 69 bursa, projects into its cavity. The edges of this are divided into fringes. The inner side of the membrane is smooth, and is extremely slippery from the liquor se- creted in it. The structure of the bursas bears a strong resemblance to the capsular ligaments of the joints. 1. The inner layer of the ligament, like that of the bursae, is thin and dense. 2, It is connected to the external ligaments by the common cellular substance. 3. Between it and the bones, layers of cartilage, or the articular cartilages, are interposed. 4. At the sides of the joints, where it is not subjected to violent pressure and friction, the adipose substance is connected with the c.ellular mem- brane. 5. Within the cavities of the joints we observe masses of fat projecting, covered with similar blood-vessels, and with similar fimbriae hanging from their edges. 6. In the knee the upper part of such a mass of fat forms what has been called the mucilaginous gland of the joint , and the under part projects into the bursa behind the ligament which ties the patella to the tibia. 7. The liquor which lubricates the bursae has the same colour, con- sistence, and properties as that of the joints, and both are affected in the same manner bv J heat, mineral acids, and ardent spirits. 8. In some places the bursas constantly communi- cate with the cavities of the joints, in others they generally do so ; from which we may in- fer a sameness of structure. When we examine the fimbria! common to the fatty bodies of the joints and bursas, and 70 Osteology. which have been supposed to be the ducts of glands lodged within the masses of fat, we are not able to discover any glandular appear- ance within them. And although we observe many vessels dispersed upon the membranes of the fatty bodies and fimbrise ; and that we cannot doubt that these fimbriae consist of ducts which contain a lubricating liquor, and can even press such a liquor from them ; yet their cavities and orifices are so minute, that they are not discoverable even by the assistance of magnifying-glasses. These fimbria; appear, therefore, to be ducts like those of the ure- thra, which prepare a mucilaginous liquor, without the assistance of any knotty or glan- dular organ. Upon the whole, the synovia seems to be furnished by invisible exhalent arteries by the ducts of the fimbrise, and by oil exuding from the adipose follicles by passages not yet disco- vered. The word skeleton , which by its etymology implies simply a dry preparation, is usually applied to an assemblage of all the bones of an animal united together in their natural or- der. It is said to be a natural skeleton, when the bones are connected together by their own proper ligaments ; and an artificial one, when they are joined by any other substance, as wire, &c. The skeleton is generally divided into the head, trunk, and extremities. The first divi- sion includes the bones of the cranium and face. The bones of the trunk are the spine, ribs, sternum, and bones of the pelvis. Osteology. 71 The upper extremity on each side consists of the two bones of the shoulder, viz. the sca- pula and clavicle ; the bone of the arm, or os humeri ; the bones of the fore-arm, and those of the hand. The lower extremity on each side of the trunk consists of the thigh-bone and the bones of the leg and foot. Sect. II. Of the Bones of the Head. The head is of a roundish figure, and some- what oval.* Its greatest diameter is from the forehead to the occiput ; its upper part is call- ed vertex, or crown of the head ; its anterior or fore-part the face ; and the upper part of this sinciput , or forehead ; its sides the tem- ples ; its posterior, or hind-part, the occiput; and its inferior part the basis . The bones of the head may be divided into those of the cranium and face. * The bones of the foetus being perfectly distinct, and the muscles in young persons not acting much, the shape of the head has been supposed to depend much on the management of children when very young. Vesalius, who has remarked the dif- ference in people of different nations, observes, for instance, that ■the head of a Turk is conical, from the early use of the turban ; whilst that of an Englishman is flattened by the chin-stay. Some of the latest physiologists suppose, with good reason, that this difference is chiefly owing to certain natural causes with which we are as yet unacquainted. 72 Osteology. 1. Bones of the Cranium and Face. There are eight bones of the cranium, viz. the coronal bone, or os frontis ; the two pari- etal bones, or ossa bregmatis ; the os occipi- tis ; the two temporal bones ; the sphenoid bone ; and the os ethmoides, or cribriforme. Of these, only the os occipitis and ossa bregmatis are considered as proper to the cra- nium ; the rest being common both to the cra- nium and face. These bones are all harder at their surface than in their middle ; and on this account they are divided into two tables, and a middle spon- gy substance called cliploe. In this, as in all the other bones, we shall consider its figure, structure, processes, de- pressions, and cavities ; and the manner in which it is articulated with the other bones. The os frontis has some resemblance in shape to the shell of the cockle. Externally it is convex, its concave side being turned to- wards the brain. This bone, in the places where it is united to the temporal bones, is very thin, and has there no diploe. It is like- wise exceedingly thin in that part of the orbit of the eye which is nearest to the nose. Hence it is, that a wound in the eye, by a sword or any other pointed instrument, is sometimes productive of immediate death. In these cases, the sword passing through the weak part of the bone, penetrates the brain, and divides the nerves at their origin ; or perhaps opens Osteology . 73 some blood-vessel, the consequences of which are soon fatal. We observe on the exterior surface of this bone five apophyses or processes, which are easily to be distinguished. One of these is placed at the bottom and narrowest part of the bone, and is called the nasal process, from its supporting the upper end of the bones of the nose. The four others are called angular or orbitar processes. They assist to form the orbits, which are the cavities on which the eyes are placed. In each of these orbits there are two processes, one at the interior or great angle, and the other at the exterior or little angle of the orbit. They are called the angu- lar processes. Between these a ridge is ex- tended in form of an arch, and on this the eye- brows are placed. It is called the orbitar or superciliary ridge, and in some measure covers and defends the globe of the eye. There is a hole in this for the passage of the frontal ves- sels and nerves. This arch is interrupted near the nose by a small pit, in which the ten- don of the musculus obliquus major of the eye is fixed. From the under part of each su- perciliary ridge a thin plate runs a considera- ble way backwards, and has the name of orbi- tar ; the external and fore-part of this plate forms a sinuosity for lodging the lacrymal gland. Between the orbitar plates there is a large discontinuation of the bone, which is fill- ed up by the cribriform part of the os ethmoi- des. K 74 Osteology. On examining the inner surface of this bone at its under and middle part, we observe an elevation in form of a ridge, which has been called the spinous process ; it ascends for some way, dividing the bone into two considerable fossas, in which the anterior lobes of the brain are placed. To a narrow furrow in this ridge is attached the extremity of the falx, as the membrane is called, which divides the brain into two hemispheres. The furrow becoming gradually wider, is continued to the upper and back part of the bone. It has the falx fixed to it, and part of the longitudinal sinus lodged in it. Besides the two fossse, there are many depressions, which appear like digital impres- sions, and owe their formation to the promi- nent circumvolutions of the brain. In the foetus, the forehead is composed of two distinct bones ; so that in them the sagit- tal suture reaches from the os occipitis to the nose. This bone is almost every where com- posed of two tables and a diploe. These two tables separating from each other under the eyes, form two cavities, one on each side of the face, called the frontal sinuses. These sinuses are lined with a soft membrane, called membrana pituitaria. In these sinuses a mu- cus is secreted, which is constantly passing through two small holes into the nostrils, which it serves to moisten. The os frontis is joined by suture to many of the bones of the head, viz. to the parietal, maxillary, and temporal bones ; to the os eth- moides ; os sphenoides ; os unguis ; and ossa Osteology. 75 nasi. The suture which connects it with the parietal bones is called the coronal suture. The parietal bones are two in number ; -they are very thin, and even transparent in some places, the particular figure of each of these bones is that of an irregular square, bordered with indentations through its whole circumfer- ence, except at its lower part. It will be ea- sily conceived, that these bones which com- pose the superior and lateral parts of the cra- nium, and cover the greatest part of the brain, form a kind of vault. On their inner surface we observe the marks of the vessels of the du- ra mater ; and at their upper edge the groove for the superior longitudinal sinus. The ossa parietalia are joined to each other by the sagittal suture ; to the os sphenoides and ossa temporum by the squamous suture ; to the os occipitis by the lambdoidal suture,* so called from its resemblance to the Greek letter lambda ; and to the os frontis by the co- ronal suture. In the foetus, the parietal bones are sepa- rated from the middle of the divided os frontis by a portion of the cranium then unossified. The occipital bone forms the posterior and inferior parts of the skull ; it approaches near- ly to the shape of a lozenge, and is indented throughout three parts of its circumference. * The lambdoidal suture is sometimes very irregular, being composed of many small sutures, which surround so many lit- tle bones called ossa triquetra , though perhaps improperly, as they are not always triangular. 76 Osteology. There is a considerable hole in the inferior portion of this bone, called the foramen mag- num, through which the medulla oblongata passes into the spine. — The nervi accessorii, and vertebral arteries, likewise pass through it. Behind the condyles are two holes for the passage of cervical veins into the lateral si- nuses ; and above them are two others for\the passage of the eighth pair and accessory nerves out of the head. At the sides, and a little on the anterior part of the foramen magnum, are two processes, called the condyles, one on each side ; they are of an oval figure, and are covered with cartilage. The external surface of this bone has a large transverse arched ridge, under which the bone is very irregular, where it affords attach- ment to several muscles. On examining its inner surface, we may observe two ridges in form of a cross ; one ascending from near the foramen magnum to the top of the bone ; the upper end of this in which the falx is fixed, is hollow, for lodging the superior longitudinal sinus, and the under end has the third process of the dura mater fixed to it. The other ridge, which runs horizontally, is likewise hollow for containing the lateral sinuses. Four fossse are formed by the cross, two above and two below. In the former are placed the posterior lobes of the brain, and in the latter the lobes of the cerebellum. At the basis of the cranium, we observe the cuneiform process (which is the name given to the great apophysis at the fore part of Osteology. 77 this bone) ; it serves for the reception of the medulla oblongata. The os occipitis is of greater strength and thickness, than either of the other bones of the head, though irregularly so ; at its inferi- or part, where it is thinnest, it is covered by a great number of muscles. This bone, from its situation, being more liable to be injured by falls, than any other bone of the head, nature has wisely given it the greatest strength at its upper part, where it is most exposed to danger. It is joined to the parietal bones by the lambdoidal suture, and to the ossa temporum, by the additamentum of the temporal suture. It is likewise connected to the os sphenoides by the cuneiform process. It is by means of the os occipitis that the head is united to the trunk, the two condyles of this bone being connected to the superior oblique processes of the first vertebra of the neck. There are two temporal bones, one on each side. — We may distinguish in them two parts; one of which is called the squamous or scaly part , and the other pars petrosa from its hard- ness. This last is shaped like a pyramid. Each of these divisions affords processes and cavities : externally there are three pro- cesses ; one anterior, called the zygomatic process ; one posterior, called the mastoid or mamillary process , from its resemblance to a nipple ; and one inferior, called the styloid pro- cess, because it is shaped like a stiletto, or dag- ger. 78 Osteology. The cavities are, 1. The meatus auditorius externus. 2. A large fossa which serves for the articulation of the lower jaw ; it is before the meatus auditorius, and immediately under the zygomatic process. 3. The stylo-mastoid hole, so called from its situation between the styloid and mastoid processes ; it is likewise styled the aquaeduct of Fallopius, and affords a passage to the portio dura of the auditory, or seventh pair of nerves. 4. Below, and on the fore-part of the last foramen, we observe part of the jugular fossa, in which the begin- ning of the internal jugular vein is lodged. An- terior and superior to this fossa is the orifice of a foramen through which passes the carotid artery. This foramen runs first upwards and then forwards, forming a kind of elbow, and ter- minates at the end of the os petrosum. — At this part of each temporal bone, we may observe the opening of the Eustachian tube, a canal which passes from the ear to the back part of the nose. In examining the internal surface of these bones, we may remark the triangular figure of their petrous part which separates two fos- sae ; one superior and anterior ; the other in- ferior and posterior: the latter of these com- poses part of the fossa, in which the cerebel- lum is placed ; and the former, a portion of the least fossa for the basis of the brain. On the posterior side of the pars petrosa, we ob- serve the meatus auditorius internus, into which enters the double nerve of the seventh pair. On the under side of this process, part of a hole appears, which is common to the Osteology. 79 temporal and occipital bones ; through it the lateral sinus, the eighth pair, and accessory- nerves, pass out of the head. The pars petrosa contains several little bones called the bones of the ear ; which, as they do not enter into the formation of the cranium, shall be described when we are treat- ing of the organs of hearing. The ossa temporum are joined to the ossa malarum, by the zygomatic sutures ; to the pa- rietal bones, by the squamous sutures ; to the os occipitis, by the lambdoidal suture ; and to the sphenoid bone, by the suture of that name. This bone, from its situation amidst the other bones of the head, has sometimes been called cuneiforme . It is of a very irregular figure, and has been compared to a bat with its wings extended. It is commonly divided into its middle part or body, and its sides or wings. The fore part of the body has a spine or ridge, which makes part of the septum nari- um. The upper part of each wing forms a share of the temple. The fore part of this belongs to the orbit ; while the under and back part, termed spinous process , is lodged in the base of the skull at the point of the pars petrosa. But two of the most remarka- ble processes are the ptergoid or aliform, one on each side of the body of the bone, and at no great distance from it. Each of these pro- cesses is divided into two wings, and of these the exterior one is the widest. The other ter- minates in a hook-like process. 80 Osteology. The internal surface of this bone affords three fossse. Two of these are formed by the wings of the bone, and make a part of the lesser fossae of the basis of the cranium. The third, which is smaller, is on the top of the- body of the bone ; and is called sella turcica , from its resemblance to a Turkish saddle. This fossa, in which the pituitary gland is placed, has posteriorly and anteriorly process- es called the clinoid processes. There are twelve holes in this bone, viz. six on each side. The first is the passage of the optic nerve and ocular ar,tery ; the second, or large slit, transmits the third, fourth, sixth, and first part of the fifth pair of nerves with the ocular vein ; the third hole gives passage to the second branch of the fifth pair ; and the fourth hole to the third branch of the fifth pair of nerves. The fifth hole is the passage of the artery of the dura mater. The sixth hole is situated above the ptergoid process of the sphenoid bone; through it a reflected branch of the second part of the fifth pair passes. Within the substance of the os sphenoides there are two sinuses separated by a bony plate. They are lined with the pituitary mem- brane ; and, like the frontal sinuses, separate a mucus which passes into the nostrils. The os sphenoides is joined to all the bones of the cranium ; and likewise to the ossa max- illaria, ossa malarum, ossa palati, and vo- mer. Osteology. 81 This bone makes part of the basis of the skull, assists in forming the orbits, and affords attachment to several muscles. The os ethmoides is situated at the fore part of the basis of the cranium, and is of a very irregular figure. From the great number of holes with which it is pierced, it is some- times called os cribriforme or sieve-like bone. It consists of a middle part and two sides. The middle part is formed of a thin bony plate, in which are an infinite number of holes that afford a passage to filaments of the ol- factory nerve, From the middle of this plate, both on the outside and from within, there rises up a process, which may be easily distinguished. The inner one is called cris- ta galli , from its supposed resemblance to a cock’s comb. To this process the falx of the dura mater is attached. The exterior pro- cess, which has the same common basis as the crista galli, is a fine lamella which is united to the vomer; and divides the cavity of the nostrils, though unequally, it being generally a little inclined to one side. The lateral parts of this bone are compos- ed of a cellular substance ; and these cells are so very intricate, that their figure or number cannot be described. Many writers have on this account called this part of the bone the labyrinth. These cells are externally covered with a very thin bony lamella. This part of the bone is called the os planum , and forms part of the orbit. 82 Osteology. The different cells of this bone, which are numerous, and which are every where lined with the pituitary membrane, evidently serve to enlarge the cavity of the nose, in which the organ of smelling resides. This bone is joined to the os sphenoides, os frontis, ossa maxillaria, ossa palati, ossa nasi, ossa unguis, and vomer. The ancients, who considered the brain as the seat of all the humours, imagined that this viscus discharged its redundant moisture through the holes of the ethmoid bone. And the vulgar still think, that abscesses of the brain discharge themselves through the mouth and ears, and that snuff is liable to get into the head ; but neither snuff nor the matter of an abscess are more capable of passing through the cribriform bone, than the serosi- ty which they supposed was discharged through it in a common cold. — All the holes of the ethmoid bone are filled up with the branches of the olfactory nerve. Its inner part is likewise covered with the dura mater, and its cells are every where lined with the pituitary membrane ; so that neither matter nor any other fluid can possibly pass through this bone either externally or internally. Mat- ter is indeed sometimes discharged through the nostrils ; but the seat of the disease is in the sinuses of the nose, and not in the brain ; and imposthumations are observed to take place in the ear, which suppurate and discharge themselves externally. Osteology. 83 Before we leave the bones of the head, we wish to make some general observations on its structure and figure. — As the cranium might have been composed of a single bone, the ar- ticulation of its several bones being absolute- ly without motion, it may be asked perhaps, Why such a multiplicity of bones, and so great number of sutures ? Many advantages may possibly arise from this plurality of bones and sutures, which may not yet have been observed. We are able, however, to point out many useful ends, which could only be ac- complished by this peculiarity of structure. — In this, as in all the other works of nature, the great wisdom of the Creator is evinced, and can- not fail to excite our admiration and gratitude. The cranium, by being divided into sever- al bones, grows much faster and with greater facility, than if it was composed of one piece only. In the foetus, the bones, as we have before observed, are perfectly distinct from each other. The ossification begins in the middle of each bone, and proceeds gradually to the circumference. Hence the ossification, and of course the increase of the head, is car- ried on from an infinite number of points at the same time, and the bones consequently ap- proach each other in the same proportion. To illustrate this doctrine more clearly, if it can want further illustration, suppose it necessa- ry for the parietal bones which compose the upper part of the head, to extend their ossifi- cation, and form the fore part of the head likewise. — Is it not evident, that this process 84 Osteology. would be much more tedious than it is now, when the os frontis and the parietal bones are both growing at the same time? Hence it hap- pens, that the Heads of young people, in which the bones begin to touch each other, increase slowly ; and th*t the proportionate increase of the volume of the head is greater in three months in the foetus, than it is perhaps in twenty four months at the age of fourteen or fifteen years. The sutures, exclusive of their advantage in suspending the processes of the dura ma- ter, are evidently of great utility in prevent- ing the too great extent of fractures of the skull. — Suppose, for instance, that by a fall or blow, one of the bones of the cranium be- comes fractured. The fissure, which in a head composed of only one bone, would be liable to extend itself through the whole of it, is checked, and sometimes perhaps stopped by the first suture it meets, and the effects of the injury are confined to the bone on which the blow was received. Ruysch indeed, and some others, will not allow the sutures to be of any such use ; but cases have been met with where they seemed to have had this ef- fect, and in young subjects their utility irl this respest must be still more obvious* The spherical shape of the head seems like- wise to render it more capable of resisting ex- ternal violence than any other shape would do. In a vault, the parts mutually support and strengthen each other, and this happens in the cranium. Osteology . 85 2. Proper Bones of the Face. The face, which consists of a great number of bones, is commonly divided into the upper and lower jaws. The upper jaw consists of thirteen bones, exclusive of the teeth. Of these, six are placed on each side of the max- illa superior, and one in the middle. The bones, which are in pairs, are the os- sa malarum, ossa maxillaria, ossa nasi, ossa unguis, ossa palati, and ossa spongiosa inferi- ora. The single bone is the vomer. These are the prominent square bones which are placed under the eyes, forming part of the orbits and the upper part of the cheeks. Each of them affords three surfaces ; one ex- terior and a little convex ; a second superior and concave, forming the inferior part and sides of the orbit ; and a third posterior, irre- gular, and hollowed for the lodgment of the lower part of the temporal muscle : The angles of each bone form four process- es, two of which may be called orbitar process- es ; of these the upper one is joined by suture to the os frontis, and that below to the maxil- lary bone. The third is connected with the os sphenoides by means of the transverse su- ture ; and the fourth is joined to the zygoma- tic process of the temporal bone, with which it forms the zygoma. These bones, which are of a very irregular figure, are so called because they form the most considerable portion of the upper jaw. 86 Osteology. They are two ill number, and generally re- main distinct through life. Of the many processes which are to be seen on these bones, and which are connect- ed with the bones of the face and skull, we shall describe only the most remarkable. One of these processes is at the upper and fore part of the bone, making part of the side of the nose, and called the nasal process. An- other forms a kind of circular sweep at the in- ferior part of the bone, in which are the alve- oli or sockets for the teeth : this is called the alveolar process. A third process is united to the os malse on each side. Between this and the nasal process there is a thin plate, which forms a share of the orbit, and lies over a passage for the superior maxillary vessels and nerves. — The alveolar process has posterior- ly a considerable tuberosity on its internal surface, called the maxillary tuberosity. Behind the alveolar process we observe two horizontal lamellae, which uniting together, form a part of the roof of the mouth, and di- vide it from the nose. The hollowness of the roof of the mouth is owing to this partition’s being seated somewhat higher than the alveo- lar process.— -At the fore part of the horizon- tal lamellae there is a hole called foramen inci - sivum , through which small blood-vessels and nerves go between the mouth and nose. In viewing these bones internally, we ob- serve a fossa in the inferior portion of the nasal process, which with the os unguis and Osteology. 87 os spongiosum inferius, forms a passage for the lachrymal duct. Where these two bones are united to each other, they project somewhat upwards and forwards, leaving between them a furrow, in- to which the lower portion of the septum na- si is admitted. Each of these bones being hollow, a consi- derable sinus is formed under its orbitar part. This cavity, which is usually named after Highmore, though it was described by Fallopi- us and others before his time, is lined with the pituitary membrane. It is intended for the same purposes as the other sinuses of the nose, and opens into the nostrils. The ossa maxillaria are connected with the greater part of the bones of the face and crani- um, and assist in forming not only the cheeks, but likewise the palate, nose, and orbits. The ossa nasi form two irregular squares. They are thicker and narrower above than below. Externally they are somewhat convex, and internally slightly concave. These bones constitute the upper part of the nose. At their fore part they are united to each other, above to the os frontis, by their sides to the ossa maxillaria superiora, posteriorly and in- teriorly to the septum narium, and below to the cartilages that compose the rest of the nostrils. These little transparent bones owe their name to their supposed resemblance to a fin- ger-nail. Sometimes they are called ossa la - chrymalia 5 from their concurring with the na- 88 Osteology. sal process of each maxillary bone in forming a lodgement for the lachrymal sac and duct. The ossa unguis are of an irregular figure. Their external surface consists of two smooth parts, divided by a middle ridge. One of these parts, which is concave and nearest to the nose, serves to support the lachrymal sac and part of the lachrymal duct. The other, which is flat, forms a small part of the orbit. Each of these bones is connected with the os frontis, os ethmoides, and os maxillare su- pe rius. These bones which are situated at the back part of the roof of the mouth, between the os sphenoides and the ossa maxillaria superiora, are of a very irregular shape, and serve to form the nasal and maxillary fossa, and a small portion of the orbit. Where they are united to each other, they rise up into a spine on their internal surface. This spine appears to be a continuation of that of the superior max- illary holies, and helps to form the septum narium. These bones are joined to the ossa maxilla- ria superiora, os ethmoides, os sphenoides, and vomer. This bone derives its name from its resem- blance to a ploughshare. It is a long and flat bone, somewhat thicker at its back than at its fore part. At its upper part we observe a furrow extending through its whole length. The posterior and largest part of this furrow receives a process of the sphenoid bone. From this the furrow advances forwards, and be- Osteology. 89 coming narrower and shallower, receives some part of the nasal lamella ethmoidea ; the rest serves to support the middle cartilage of the- nose. The inferior portion of this bone is placed on the nasal spine of the maxillary and palate bones, which we mentioned in our description of the ossa palati. The vomer is united to the os sphenoides, os ethmoides, ossa maxillaria superiora, and ossa palati. It forms part of the septum nari- um, by dividing the back part of the nose into two nostrils. The parts which are usually described by this name, do not seem to deserve to be dis- tinguished as distinct hones, except in young subjects. They consist of a spongy lamella in each nostril, which is united to the spongy lamina of the ethmoid bone, of which they are by some considered as a part. Each of these lamellae is longest from be- hind forwards ; with its convex surface turn- ed towards the septum narium, and its con- cave part towards the maxillary bone, covering the opening of the lachrymal duct into the nose. These bones are covered with the pituitary membrane ; and, besides their connection with the ethmoid bone, are joined to the ossa max- illaria superiora, ossa palati, and ossa unguis. The maxilla inferior, or lower jaw, which in its shape resembles a horse-shoe, consists of two distinct bones in the foetus ; but these unite together soon after birth, so as to form M 90 Osteology. only one bone. The upper edge of this bone, like the os maxillare superius, has an alveolar process, furnished with sockets for the teeth. On each side the posterior part of the bone rises almost perpendicularly into two process- es. The highest of these, called the coronoid process, is pointed and thin, and serves for the insertion of the temporal muscle. The other, or condyloid process, as it is called, is shorter and thicker, and ends in an oblong rounded head, which is received into a fossa of the temporal bone, and is formed for a moveable articulation with the cranium. This joint is furnished with a moveable cartilage. At the bottom of each coronoid process, on its inner part, we observe a foramen extend- ing under the roots of all the teeth, and ter- minating at the outer surface of the bone near the chin. Each of these canals transmits an artery, vein, and nerve, from which branches are sent off to the teeth. The lower jaw is capable of a great variety of motion. By sliding the condyles from the cavity towards the eminences on each side, we bring it horizontally forwards, as in biting ; or we may bring the condyles only forward, and tilt the rest of the jaw backward, as in opening the mouth. We are likewise able to slide the condyles alternately backwards and forwards from the cavity to the eminence, and vice versa, as in grinding the teeth. The car- tilages, by adapting themselves to the differ- ent inequalities in these several motions of the Osteology. 91 jaw, serve to secure the articulation, and to prevent any injuries from friction. The alveolar processes are composed of an outer and inner bony plate, united together by thin partitions, which at the fore part of the jaw divide the processes into as many sockets as there are teeth. But at the back part of the jaw, where the teeth have more than one root, we find a distinct cell for each root. In both jaws these processes begin to be formed with the teeth ; they likewise accompany them in their growth, and gradually disappear when the teeth are removed. 3. Of the Teeth. The teeth are bones of a particular struc- ture, formed for the purposes of mastication and the articulation of the voice. It will be necessary to consider their composition and fi- gure, their number and arrangement, and the time and order in which they appear. In each tooth we may distinguish a body, a neck, and a root or fangs. The body of the tooth is that part which appears above the gums. The root is fixed into the socket, and the neck is the middle part between the two. The teeth are composed of two substances, viz. enamel and bone. The enamel, or the vitreous or cortical part of the tooth, is a white and very hard and compact substance peculiar to the teeth, and appears fibrous o-r 92 Osteology. striated when broken. This substance is thick- est on the grinding surface, and becoming gra- dually thinner, terminates insensibly at the neck of the tooth. Ruysch* * * § affirmed, that he could trace the arteries into the hardest part of the teeth; Lieweilhoeckf suspected the fibres of the enamel to be so many vessels ; and Monro f says, he has frequently injected the vessels of the teeth in children, so as to make the inside of the cortex appear perfectly red. But it is certain, that it is not tinged by a madder diet, and that no injection will ever reach it, so that it has no appearance of be- ing vascular $. The bony part, which composes the inner substance of the body, neck, and root of the tooth, resembles other bones in its structure, but it is much harder than the most compact part of bones in general. As a tooth when once formed receives no tinge from a madder diet, and as the minutest injections do not pe- netrate into its substance, this part of the tooth has, like the enamel, been supposed not to be vascular. But when we consider that the fangs of a tooth are invested by a perios- teum, and that the swellings of these fangs are analogous to the swellings of other bones, we may reasonably conclude, that there is a similarity of structure ; and that this bony part has a circulation through its substance, * Thefaur 10 no. 27. ■f A.rcan. Natur. continuat. Epiftol. f Anat of the Human Bones. § Hunter on the Teeth. Osteology. 93 although from its hardness we are unable to demonstrate its vessels. In each tooth we find an inner cavity, into which enter an artery, vein, and nerve. This cavity begins by a small opening, and becom- ing larger, terminates in the body of the tooth. In advanced life this hole sometimes closes, and the tooth is of course rendered insensible. The periosteum surrounds the teeth from their fangs to a little beyond their bony sock- ets, where we find it adhering to the gums. This membrane, while it incloses the teeth, serves at the same time to line the sockets, so that it may be considered as common to both. The teeth are likewise secured in their sock- ets by means of the gums ; a red, vascular, firm, and elastic substance, that possesses but little sensibility. In the gums of infants we find a hard ridge extending through their whole length, but no such ridge is to be seen in old people who have lost their teeth. The number of the teeth in both jaws at full maturity, usually varies from twenty-eight to thirty-two. They are commonly divided into three classes, viz. incisores, canini, and grind- ers or molares.* The incisores are the four teeth in the fore part of each jaw. They have each of them two surfaces ; one anterior * Mr. Hunter has thought proper to vary this division. He retains the old name of incisores to the four fore teeth, but he distinguishes the canine teeth by the name of the cuspidafi. The two teeth which are next to these, and which have been usu- ally ranked with the molares, he calls the bicuspides ; and he gives the name of grinders only to the three last teeth on each side. 94 Osteology. and convex, the other posterior and slightly concave, both of which terminate in a sharp edge. They are called incisores from their use in dividing the food. They are usually broader and thicker in the upper than in the under jaw; and, by being placed somewhat obliquely, generally fall over the latter. The canini derive their name from their re- semblance to a dog’s tusks, being the longest of all the teeth. We find one on each side of the incisores, so that there are two canini in each jaw. Their fang resembles that of the incisores, but is much larger; and in their shape they appear like an incisor with its edge worn off, so as to terminate in a narrow point. These teeth not being calculated for cutting and dividing the food like the incisores, or for grinding it like the molares, seem to be intend- ed for laying hold of substances.* The molares or grinders, of which there are ten in each jaw, are so called, because from their shape and size they are fitted for grinding the food. Each of the incisores and canini is furnished only with one fang; but in the molares of the under jaw we constantly find two fangs, and in those of the upper jaw' three fangs. These fangs are sometimes se- parated into two points, and each of these points has sometimes been described as a distinct fang. * Mr. Hunter remarks of these teeth, that we may trace in them a similiarity in shape, situation, and use, from the most imperfectly carnivorous animal, which we believe to he the hu- man species, to the lion, which is the most perfectly carnivo- rous. Osteology. 95 The two first of the molares, or those near- est to the canine teeth on each side, differ from the other three, and are with great pro- priety named bicuspides by Mr. Hunter. They have sometimes only one root, and seem to be of a middle nature between the incisores and the larger molares. The two next are much larger. The fifth or last grinder on each side is smaller and shorter than the rest ; and from its not cutting the gum till after the age of twenty, and sometimes not till much later in life, is called dens sapientice. There is in the structure and arrangement of all these teeth an art which cannot be suf- ficiently admired. To understand it properly, it will be necessary to consider the under jaw as a kind of lever, with its fixed points at its articulations with the temporal bones : — it wiiL be right to observe, too, that its powers arise from its different muscles, but in elevation chiefly from the temporalis and masseter; and that the aliment constitutes the object of re- sistance. It will appear, then, that the mola- res, by being placed nearest the centre of mo- tion, are calculated to press with a much greater force than the other teeth, independent of their grinding powers which they possess by means of the pterygoid muscles ; and that it is for this reason we put between them any hard body we wish to break. The canini and incisores are placed farther from this point, and of course cannot exert so much force ; but they are made for cutting and tearing the food, and this form seems to make amends for their deficiency in strength. 96 Osteology . There are examples of children who have come into the world with two, three, and even four teeth ; but these examples are very rare ; and it is seldom before the seventh, eighth, or ninth month after birth, that the incisores, which are the first formed, begin to pass through the gum. The symptoms of denti- tion, however, in consequence of irritation from the teeth, frequently take place in the fourth or fifth month. — About the twentieth or twenty-fourth month, the canini and two molares make their appearance. The dangerous symptoms that sometimes accompany dentition, are owing to the pres- sure of the teeth on the gum, which they ir- ritate so as to excite pain and inflammation. This irritation seems to occasion a gradual wasting of the gum at the part, till at length the tooth makes its appearance. The symptoms are more or less alarming, in proportion to the resistance which the gum affords to the teeth, and according to the num- ber of teeth which may chance to seek a pas- sage at the same time. Were they all to ap- pear at once, children would fall victims to the pain and excessive irritation ; but Nature has so very wisely disposed them, that they usually appear one after the other, with some distance of time between each. The first in- cisor that appears is generally in the lower jaw, and is followed by one in the upper jaw. Sometimes the canini, but more commonly one of the molares, begins to pass through the gum first. Osteology. 97 These 20 teeth, viz. eight incisores, four canini, and eight molares, are called tempora- ry or milk teeth , because they are all shed be- tween the age of seven and fourteen, and are succeeded by what are called the permanent or aclult teeth. The latter are of a firmer texture, and have larger fangs. These adult teeth being placed in a distinct set of alveoli, the upper sockets gradually dis- appear, as the under ones increase in size, till at length the temporary, or upper teeth, hav- ing no longer any support, consequently fall out. To these 20 teeth, which succeed the tem- porary ones, 12 others are afterwards added, viz. three molares on each side in both jaws: and in order to make room for this addition, we find that the jaws gradually lengthen in proportion to the growth of the teeth ; so that with 20 teeth, they seem to be as completely filled as they are afterwards with 32. This is the reason why the face is rounder and flatter in children than in adults. With regard to the formation of the teeth, we may observe, that in a fcetus of four months, the alveolar process appears only as a shallow longitudinal groove, divided by minute ridges into a number of intermediate depressions ; in each of which we find a small pulpy substance surrounded by a vascular membrane. This pulp gradually ossifies, and its lower part is lengthened out to form the fang. When the bony part of the tooth is formed, its surface begins to be incrusted with the enamel. How N 98 Osteology. the latter is formed and deposited, we are not yet able to determine. The rudiments of some of the adult teeth begin to be formed at a very early period, for the pulp of one of the incisores may general- ly be perceived in a foetus of eight months, and the ossification begins in it soon after birth. The first bicuspis begins to ossify about the fifth or sixth, and the second about the seventh year. The first adult grinder cuts the gum about the 12th, the second about the 18th, and the third, or dens sapientice , usually between the 20th and 30th year. The teeth, like other bones, are liable to be affected by disease. Their removal is like- wise the natural consequences of old age ; for as we advance in life, the alveoli fill up, and the teeth, especially the incisores, fall out. When this happens, the chin projects forward, and the face is much shortened. 4. Of the Os Hyoides .* The os hyoides, which is placed at the root of the tongue, was so called by the ancients on account of its supposed resemblance to the Greek letter v. * This hone is very seldom preserved with the skeleton, and cannot be included among the bones of the head, or any other division of the skeleton Thomas Bartholin has perhaps very properly described it among parts contained in the mouth ; but the generality of anatomical writers have placed it, as it is here, after the bones of the face. Osteology. 99 It will be necessary to distinguish in it, its body, horns, and appendices. The body, which is the middle and broad- est part of the bone, is so placed that it may be easily felt at the fore part of the throat. Anteriorly it is irregularly convex, and its in- ner surface is unequally concave. Its cornua, or horns, which are flat and a little bent, be- ing much longer than the body part, may be described as forming the sides of the «. The appendices, or little horns, as they are called by M. Windslow, and some other writers, are two processes which rise up from the articu- lations of the cornua with the body, and are usually connected with the styloid process on each side by means of a ligament. The uses of this bone are to support the tongue, and afford attachment to a great num- ber of muscles ; some of which perform the motions of the tongue, while others act on the larynx and fauces. Sect. III. Of the Bones of the Trunk. T he trunk of the skeleton consists of the spine, the thorax, and the pelvis. 1. Of the Spine. The spine is composed of a great number of bones called vertebra, forming a long bo- ny column, in figure not much unlike the let- ter f This column, which extends from the 100 Osteology. head to the lower part of the body, may be said to consist of two irregular and unequal pyramids, united to each other in that part of the loins where the last lumbar vertebra joins the os sacrum. The vertebras of the upper and longest py- ramid are called true vertebra , in contradis- tinction to those of the lowermost pyramid, which, from their being immoveable in the adult, are styled f Jse vertebra. It is upon the bones of the spine that the body turns ; and it is to this circumstance they owe their name, which is derived from ihe Latin verb vertere , to turn. The true vertebras are divided into three classes of cervical, dorsal and lumbar verte- bras. — The false vertebrae consist of the os sa- crum and os coccygis. In each vertebra, as in other bones, it will be necessary to remark the body of the bone, its processes, and cavities. The' body, which is convex before, and concave behind, where it assists in forming the cavity of the spine, may be compared to part of a cylinder cut off transversely. Each vertebra affords seven processes. The first is at the back part of the vertebra, and from its shape and direction is named the spinous process. On each side of this are two others, which, from their situation with re- spect to the spine, are called transverse pro- cesses. The four others are styled oblique or articular processes. They are much smaller than the spinous or transverse ones. Two of Osteology. 101 them are placed on the upper, and two on the lower part of each vertebra, rising from near the basis of each transverse process. They have gotten the name of oblique processes, from their situation with respect to the processes with which they are articulated ; and they are sometimes styled articular processes , from the manner in which they are articulated with each other; the two superior processes of one vertebra being articulated with the two infe- rior processes of the vertebra above it. Each of these processes is covered with cartilage at its articulation, and their articulations with each other are by a species of ginglimus. In each vertebra, between its body and its processes, we find a hole large enough to ad- mit a finger. These holes or foramina, corre- spond with each other through all the vertebrae, and form the long bony channel in which the spinal marrow is placed. We may likewise observe four notches m each vertebra. Two of tnese notches are at the upper, and two at the lower part of the bone, between the oblique processes and the body of the ver- tebra. Each of these notches meeting with a similar opening in the vertebra above or be- low it, forms a foramen for the passage of blood-vessels, and of the nerves out of the spine. The bones of the spine are united toge- ther by means of a substance, which in young subjects appears to be of a ligamentous, but in adults more of a cartilaginous nature. This intervertebral substance, which forms a kind 102 Osteology. of partition between the several vertebras, is thicker and more flexible between the lumbar vertebrae than in the other parts of the spine, the most considerable motions of the trunk being performed on those vertebrae. This substance being very elastic, the extension and flexion of the body, and its motion backwards and forwards, or to either side, are performed with great facility. This elasticity seems to be the reason why people who have been long stand- ing, or have carried a considerable weight, are found to be shorter than when they have been long in bed. In the two first instances the intervertebral cartilages (as they are usu- ally called) are evidently more exposed to compression than when we are in bed in an horizontal posture. In advanced life these cartilages become shrivelled, and of course lose much of their elasticity. This may serve to account for the decrease in stature and the stooping forward which are usually to be observed in old peo- ple. Besides the connection of the several verte- brae by means of this intervertebral substance, there are likewise many strong ligaments, both external and internal, which unite the bones of the spine to each other. Their union is al- so strengthened by a variety of strong muscles that cover and surround the spine. The bones of the spine are found to dimi- nish in density, and to be less firm in their texture in proportion as they increase in bulk; so that the lowermost vertebrae, though the Osteology. 103 largest, are not so heavy in proportion as the upper ones. By this means the size of these bones is increased without adding to their weight : a circumstance of no little importance in a part like the spine, which, besides flexi- bility and suppleness, seems to require light- ness as one of its essential properties. In very young children, each vertebra con- sists of three bony pieces united by cartilages which afterwards ossify. There are seven vertebrae of the neck — they are of a firmer texture than the other bones of the spine. Their transverse process- es are forked for the lodgment of muscles, and at the bottom of each we observe a fora- men, through which pass the cervical artery and vein. The first and second of these ver- tebrae must be described more particularly. The first approaches almost to an oval shape — On its superior surface it has two cavities which admit the condyles of the occipital bone with which it is articulated. This verte- bra, which is called atlas from its supporting the head, cannot well be described as having either body or spinous process, being a kind of bony ring. Anteriorly, where it is articu- lated to the odontoid process of the second vertebra, it is very thin. On its upper surface it has two cavities which admit the condyles of the occipital bone. By this connection the head is allowed to move forwards and back- wards, but has very little motion in any other direction. 104 Osteology. The second vertebra has gotten the name of dentatci , from its having, at its upper and an- terior part, a process called the odontoid or tooth-like process , which is articulated with the atlas, to which this second vertebra may be said to serve as an axis. This odontoid pro- cess is of a cylindrical shape, somewhat flat- tened, however, anteriorly and posteriorly. At its fore-part where it is received by the atlas, we may observe a smooth, convex, articulat- ing surface. It is by means of this articula- tion that the head performs its rotatory motion, the atlas in that case moving upon this odon- toid process as upon a pivot. But when this motion is in any considerable degree, or, in other words, when the head moves much ei- ther to the right or left, all the cervical verte- brae seem to assist, otherwise the spinal mar- row would be in danger of being divided trans- versely by the first vertebra. The spinous process of each of the cervi- cal vertebrae is shorter, and their articular pro- cesses more oblique, than in the other bones of the spine. These 12 vertebrae are of a middle size be- tween those of the neck and loins. At their sides we may observe two depressions, one at the upper and the other at the lower part of the body of each vertebrae; which uniting with similar depressions in the vertebrae above and below, form articulating surfaces, covered with cartilages, for receiving the heads of the ribs; and at the fore-part of their transverse process Osteology , 105 (excepting the two last) we find an articulating surface for receiving the tuberosity of the ribs. These five vertebras differ only from those of the back in their being larger, and in hav- ing their spinous processes at a greater dis- tance from each other. The most consider- able motions of the trunk are made on these vertebrae; and these motions could not be per- formed with so much ease, were the process- es placed nearer to each other. The os sacrum, which is composed of five or six pieces in young subjects, becomes one bone in more advanced age. It is nearly of a triangular figure, its infe- rior portion being bent a little forwards. Its superior part has two oblique processes which are articulated with the last of the lumbar ver- tebrae ; and it has likewise commonly three small spinous processes, which gradually be- come shorter, so that the lowermost is not so long as the second, nor the second as the up- permost. Its transverse processes are formed into one oblong process, which becomes gra- dually smaller as it descends. Its concave or anterior side is usually smooth, but its poste- rior convex side has many prominences (the most remarkable of which are the spinous pro- cesses just now mentioned,) which are filled up and covered with the muscular and tendi- nous parts behind. This bone has five pair of holes, which af- ford a passage to blood-vessels, and likewise to the nerves that are derived from the spinal marrow, which is continued even here, being O 106 Osteology. lodged in a triangular cavity, that becomes smaller as it descends, and at length termi- nates obliquely at the lower part of this bone. Below the third division of the os sacrum, this canal is not completely bony as in the rest of the spine, being secured at its back part only by a very strong membrane, so that a wound at this part must be extremely dangerous. The os sacrum is united laterally to the os- sa innominata or hip-bones, and below to the coccyx. The coccyx, which, like the os sacrum, is / in young people made up of three or four dis- tinct parts, usually becomes one bone in the adult state. It serves to support the intestinum rectum ; and, by its being capable of some degree of motion at its articulation with the sacrum, and being like that bone bent forwards, we are en- abled to sit with ease. This bone is nearly of a triangular shape, being broadest at its upper part, and from thence growing narrower to its apex, whejre it is not bigger than the little finger. It has got its name from its supposed re- semblance to a cuckow’s beak. It differs greatly from the vertebrae, being commonly without any processes, and having no cavity for the spinal marrow, or foramina for the transmission of nerves. The spine, of which we have now finished the anatomical description, is destined for ma- ny great and important uses. The medulla spinalis is lodged in its bony canal secure from Osteology. 107 external injury. It serves as a defence to the abdominal and thoracic viscera, and at the same time supports the head, and gives a ge- neral firmness to the whole trunk. We have before compared it to the letter f and its different turns will be found to render it not very unlike the figure of that letter. — In the neck we see it projecting somewhat for- ward to support the head, which without this assistance would require a great number of muscles. — Lower down, in the thorax, we find it taking a curved direction backwards, and of course increasing the cavity of the chest. Af- ter this, in the loins, it again projects forwards in a direction with the centre of gravity, by which means we are easily enabled to keep the body in an erect posture, for otherwise we should be liable to fall forward. Towards its inferior extremity, however, it again recedes backward, and thus assists in forming the pel- vis, the name given to the cavity in which the urinary bladder, intestinum rectum, and other viscera are placed. If this bony column had been formed only of one piece, it would have been much more easily fractured than it is now : and by confin- ing the trunk to a stiff situation, a variety of motions would have been altogether prevent- ed, which are now performed with ease by the great number of bones of which it is compos- ed. It is firm, and yet to this firmness there is added a perfect flexibility. If it be required to carry a load upon the head, the neck be- 108 Osteology. comes stiff with the assistance of its muscles, and accommodates itself to the load, as if it was composed only of one bone — In stooping likewise, or in turning to either side, the spine turns itself in every direction, as if all its bones were separated from each other. In a part of the body, like the spine, that is made up of so great a number of bones, and intended for such a variety of motion, there must be a greater danger of dislocation than fracture ; but we shall find, that this is very wisely guarded against in every direction by the processes belonging to each vertebra, and by the ligaments, cartilages, &c. by which these bones are connected with each other. 2. Of the Bones of the Thorax. The thorax, or chest, is composed of ma- ny bones, viz. the sternum which is placed at its anterior part, twelve ribs on each side which make up its lateral parts, and the dor- sal vertebras which constitute its posterior part. These last have been already described. The sternum is the long bone which ex- tends itself from the upper to the lower part of the breast anteriorly, and to which the ribs and the clavicles are articulated. In children it is composed of several bones united by cartilages ; but as we advance in life, most of these cartilages ossify, and the ster- num in the adult state is found to consist on- Osteology. 109 ly of three pieces, and sometimes becomes one bone. It is however generally described as being composed of three parts — one superior, which is broad, thick, and short ; and one in the middle, which is thinner, narrower, and longer than the other. It terminates at its lower part by a third piece, which is called the xyphoicl , or sword- like cartilage, from its supposed resemblance to the blade of a sword, and because in young subjects it is commonly in a cartilaginous state. We have already observed, that this bone is articulated with the clavicle on each side. It is likewise joined to the fourteen true ribs, viz. seven on its right and seven on its left side. The ribs are bones shaped like a bow, form- ing the sides of the chest. There are twelve on each side. They are distinguished into true and false ribs : The seven upper ribs which are articulated to the sternum are call- ed true ribs , and the five lower ones that are not immediately attached to that bone are call- ed false ribs. On the inferior and interior surface of each rib, we observe a sinuosity for the lodgment of an artery, vein, and nerve. The ribs are not bony through their whole length, their anterior part being cartilaginous. They are articulated with the vertebrae and sternum. Every rib (or at least the greater number of them) has at its posterior part two processes ; one at its extremity called the head of the rib, by means of which it is articulated 110 Osteology. with the body of two vertebrae ; and another, called its tuberosity, by which it is articulated with the transverse process of the lowest of these two vertebra?. The first rib is not arti- culated by its extremity to two vertebrae, be- ing simply attached to the upper part of the first vertebra of the back. The seven superi- or or true ribs are articulated anteriorly with the sternum by their cartilages ; but the false Iribs are supported in a different manner — the eighth, which is the first of these ribs, being attached by its cartilage to the seventh ; the ninth to the eighth, &x. The two lowermost ribs differ likewise from all the rest in the following particulars : they are articulated only with the body of the ver- tebra, and not with a transverse process ; and anteriorly, their cartilage is loose, not being attached to the cartilages of the other ribs ; and this seems to be, because the most consi- derable motions of the trunk are not perform- ed on the lumbar vertebrae alone, but likewise on the two last vertebrae of the back ; so that if these two ribs had been confined at the fore part like the other ribs, and had been likewise articulated with the bodies of two vertebrae, and with the transverse processes, the moti- on of the two last vertebra, and consequently of the whole trunk, would have been impeded. The ribs help to form the cavity of the tho- rax ; they afford attachment to different mus- cles ; they are useful in respiration ; and they serve as a security to the heart and lungs. Osteology . XU 3 . 0/* the Bones of the Pelvis. The pelvis is composed of the os sacrum, os coccygis, and two ossa innominata. The two first of these bones were included in the account of the spine, to which they more pro- perly belong. In children, each os innominatum is com- posed of three distinct bones ; but as we ad- vance in life the intermediate cartilages gradu- ally ossify, and the marks of the original se- paration disappear, so that they become one irregular bone ; still however continuing to re- tain the names of ilium, ischium, and pubis, by which their divisions were originally dis- tinguished, and to be described as three dif- ferent bones by the generality of anatomists. The os ilium forms the upper and most consi- derable part of the bone, the os ischium its lower and posterior portion, and the os pubis its fore part. The os ilium or haunch bone, is articulated posteriorly to the os sacrum by a firm cartila- ginous substance, and is united to the os pu- bis before and to the os ischium below. Its superior poruon is thin, and terminates in a ridge called the crista or spine of the ilium, and more commonly known by the name of the haunch. This crista rises up like an arch ; being turned somewhat outwards, so as to re- semble the wings of a phaeton. Externally this bone is unequally prominent and hollowed for the lodgment of muscles; in- ternally we find it smooth and concave. At 112 Osteology . its lower part there is a considerable ridge on its inner surface. This ridge extends from the os sacrum, and corresponds with a similar prominence both on that bone and the ischi- um ; forms with the inner part of the ossa pu- bis what in midwifery is termed the brim of the pelvis. The crista or spine, which at first is an epi- physis, has two considerable tuberosities ; one anteriorly, and the other posteriorly, which is the largest of the two : these, from their pro- jecting more than the parts of the bone below them, have gotten the name of spinal process- es. From the anterior spinous process, the sartorius and tensor vaginae femoris muscles have their origin ; and below the posterior process we observe a considerable niche in the bone, which, in the recent subject, is formed into a large foramen, by means of a strong ligament that is stretched over its low- er part from the os sacrum to the sharp-point- ed process of the ischium. This hole affords a passage to the great sciatic nerve, and to the posterior crural vessels under the pyriform muscle, part of which likewise passes out here. The os ischium, or hip-bone, which is of a very irregular figure, constitutes the lower lateral parts of the pelvis, and is commonly divided into its body, tuberosity, and ramus. The body forms the lower and most consider- able portion of the acetabulum, and sends a sharp-pointed process backwards, called the spine of the ischium. To this process the li- Osteology. 113 gament adheres, which was just now spoken of, as forming a foramen for the passage of the sciatic nerve. — The tuberosity, which is the lowest part of the trunk, and supports us when we sit, is large and irregular, affording origin to several muscles. From this tubero- sity we find the bone becoming thinner and narrower. This part, which has the name of ramus or branch, passes forwards and up- wards, and concurs with the ramus of the os pubis, to form a large hole called the foramen magnum ischii , or thyroideum , as it is some- times named, from its resemblance to a door or shield. This hole, which in the recent subject is closed by a strong membrane called the obturator ligament, affords through its whole circumference attachment to muscles. At its upper part where we observe a niche in the bone, it gives passage to the obturator vessels and nerves, which go to the inner part of the thigh. Nature seems every where to avoid an unnecessary weight of bone, and this foramen, no doubt, serves to lighten the bones of the pelvis. The os pubis or share-bone, which with its fellow forms the fore-part of the pelvis, is the smallest division of the os innominatum. It is united to its fellow by means of a strong cartilage, which forms what is called the sym- physis pubis. In each os pubis we may distinguish the body of the bone, its angle, and ramus. The body or outer part is united to the os ilium. The angle comes forward to form the sym- P 114 Osteology. physis, and the ramus is a thin process which unites with the ramus of the ischium, to form the foramen thyroideum. The three bones we have described as com- posing each os innominatum, all assist in form- ing the acetabulum, in which the head of the os femoris is received. This cavity is every where lined with a smooth cartilage, excepting at its inner part, where we may observe a little fossa, in which are lodged the mucilaginous glands of the joint. We may likewise notice the pit or depression made by the round ligament, as it is improper- ly called, which, by adhering to this cavity and Jto the head of the thigh-bone, helps to secure the latter in the socket. These bones, which are united to each other and to the spine by many very strong ligaments, serve to support the trunk, and to connect it with the lower extremities ; and at the same time to form the pelvis or bason, in which are lodged the intestines and urinary bladder, and in women the uterus ; so that the study of this part of osteology is of the utmost importance in midwifery. It is worthy of observation, that in women the os sacrum is usually shorter, broader, and more hollowed, the ossa ilia more expanded, and the inferior opening of the pelvis larger than in men. Sect. IV. Of the Extremities. These parts of the skeleton consist of the upper extremity and the lower. Osteology, 115 1. Of the Upper Extremity. This consists of the shoulder, the arm, and. the hand. 1. Of the shoulder. The shoulder consists of two bones, the clavicula and the scapula. The former, which is so named from its re* semblance to the key in use amongst the an- cients, is a little curved at both its extremities like an italic f It is likewise called jugulum , or collar-bone, from its situation. It is about the size of the little finger, but longer, and be- ing of a very spongy substance is very liable to be fractured. In this, as in other long bones, we may distinguish a body and two extremi- ties. The body is rather flattened than round- ed. The anterior extremity is formed into a slightly convex head, which is nearly of a tri- angular shape. The inferior surface of the head is articulated with the sternum. The posterior extremity, which is flatter and broad- er than the other, is connected to a process of the scapula, called acromion. Both these articulations are secured by ligaments, and in that with the sternum we meet with a move- able cartilage, to prevent any injury from fric- tion. The clavicle serves to regulate the motions of the scapula, by preventing it from being 116 Osteology. brought too much forwards, or carried too far backwards. It affords origin to several mus- cles, and helps to cover and protect the sub- clavian vessels, which derive their name from their situation under this bone. The scapula, or shoulder-blade, which is nearly of a triangular shape, is fixed to the posterior part of the true ribs, somewhat in the manner of a buckler. It is of a very un- equal thickness, and, like all other broad, flat bones, is somewhat cellular. Exteriorly it is convex, and interiorly concave, to accommo- date itself to the convexity of the ribs. We observe in this bone three unequal sides, which are thicker and stronger than the body of the bone, and are therefore termed its costce. The largest of the three, called also the basis, is turned towards the vertebrae. Another, which is less than the former, is below this ; and the third, which is the least of the three, is at the upper part of the bone. Externally the bone is elevated into a considerable spine, which rising small at the basis of the scapula, becomes gradually higher and broader, and divides the outer surface of the bone into two fossae. The superior of these, which is the smallest, serves to lodge the supra spinatus muscle ; and the inferior fossa, which is much larger than the other, gives origin to the infra spinatus. This spine terminates in a broad and flat process at the top of the shoulder, called the processus acromion , to which the clavicle is articulated. This process is hollowed at its lower part to allow a passage to the supra and Osteology. 117 infra spinati muscles. The scapula has like- wise another considerable process at its upper part, which, from its resemblance to the beak of a bird, is called the coracoid process. From the outer side of this coracoid process, a strong ligament passes to the processus acromion, which prevents a luxation of the os humeri up- wards. A third process begins by a narrow neck, and ends in a cavity called glenoid , for the connection of the os humeri. The scapula is articulated with the clavicle and os humeri, to which last it serves as a ful- crum ; and by varying its position it affords a greater scope to the bones of the arm in their different motions. It likewise gives origin to several muscles, and posteriorly serves as a de- fence to the trunk. 2. Bones of the Arm. The arm is commonly divided into two parts, which are articulated to each other at the el- bow. The upper part retains the name of arm, properly so called, and the lower part is usu- ally called the fore-arm. The arm is composed of a single bone call- ed os humeri. This bone, which is almost of a cylindrical shape, may be divided into its bo- dy and its extremities. The upper extremity begins by a large, round smooth head, which is admitted into the glenoid cavity of the scapula. On the upper and fore part of the bone there is a groove for lodging the long head of the biceps mus- 118 Osteology . cle of the arm ; and on each side of the groove, at the upper end of the bone, there is a tuber- cle to which the spinata muscles are fixed. The lower extremity has several processes and cavities. The principal processes are its two condyles, one exterior and the other inte- rior, and of these the last is the largest. Be- tween these two we observe two lateral protu- berances, which, together with a middle cavi- ty, form as it were a kind of pully upon which the motions of the fore-arm are chiefly per- formed At each side of the condyles, as well exteriorly as interiorly, there is another emi- nence which gives origin to several muscles of the hand and fingers. Posteriorly and superi- orly, speaking with respect to the condyles, we observe a deep fossa which receives a consi- derable process of the ulna ; and anteriorly and opposite to this fossa, we observe another, which is much less and receives another pro- cess of the same bone. The body of the bone has at its upper and anterior part a furrow which begins from be- hind the head of the bone, and serves to lodge the tendon of a muscle. The body of the os humeri is hollow through its whole length, and, like all other long bones, has its marrow. This bone is articulated at its upper part to the scapula. This articulation, which allows motion every way, is surrounded by a capsu- lar ligament ; that is sometimes torn in luxa- tion, and becomes an obstacle to the easy re- duction of the bone. Its lower extremity is articulated with the bones of the fore-arm. Osteology. 119 The fore-arm is composed of two bones, the ulna and radius. The ulna or elbow-bone is much less than the os humeri, and becomes gradually small- er as it descends to the wrist. At its upper part it has two processes and two cavities. Of the two processes, the largest, which is situ-* ated posteriorly, and called the olecranon , is admitted into the posterior fossa of the os hu- meri. The other process is placed anteriorly, and is called the coronoid process. In bending the arm it enters into the anterior fossa of the os humeri. This process being much smaller than the other, permits the fore-arm to bend inwards ; whereas the olecranon, which is shaped like a hook, reaches the bottom of its fossa in the os humeri as soon as the arm be- comes straight, and will not permit the fore- arm to be bent backwards. The ligaments likewise oppose this motion. Between the two processes we have describ- ed, there is a considerable cavity called the sygmoid cavity, divided into two fossae by a small eminence, which passes from one pro- cess to the other ; it is by means of this cavity and the two processes, that the ulna is articu- lated with the os humeri by ginglimus. At the bottom of the coronoid process interi- orly, there is a small sygmoid cavity, which serves for the articulation of the ulna with the radius. The body of the ulna is of a triangular shape : Its lower extremity terminates by a small head and a little styloid process. The Osteology. 12 ® ulna is articulated above to the os humeri — both above and below to the radius, and to the wrist at its lower extremity. All these ar- ticulations are secured by means of ligaments. The chief use of this bone seems to be to sup- port and regulate the motions of the radius. The radius, which is so named from its sup- posed resemblance to the spoke of a wheel, is placed at the inside of the fore-arm. It is somewhat larger than the ulna, but not quite so long as that bone. Its upper part is cylin- drical, hollowed superiorly to receive the out- er condyle of the os humeri. Laterally it is admitted into the little sygmoid cavity of the ulna, and the cylindrical part of the bone turns in this cavity in the motions of pronation and supination.* This bone follows the ulna in flexion and extension, and may likewise be moved round its axis in any direction. The lower extremity of the radius is much larger and stronger than its upper part ; the ulna, on the contrary, is smaller and weaker below than above ; so that they serve to supply each other’s deficiencies in both those parts. On the external side of this bone, we ob- serve a small cavity which is destined to re- ceive the lower end of the ulna ; and its low- er extremity is formed into a large cavity, by means of which it is articulated with the bones * The motions of pronation and supination may be easily described. If the palm of the hand, for instance, is placed on the surface of a table, the hand may be said to be in a state of pronation ; but if the back part of the hand is turned towards the table, the hand will be then in a state of supination. Osteology. 121 of the wrist, and on this account it is some- times called manubrium manus. It supports the two first bones of the wrist on the side of the thumb, whereas the ulna is articulated with that bone of the wrist which corresponds with the little finger. Through the whole length both of this bone and the ulna, a ridge is observed, which affords attachment to an interosseous ligament. This ligament fills up the space between the two bones. 3. Bones of the Hand. The carpus or wrist consists of eight small bones of an irregular shape, and disposed in two unequal rows. Those of the upper row are articulated with the bones of the fore-arm, and those of the lower one with the metacarpus. The ancient anatomists described these bones numerically ; Lyserus seems to have been the first who gave to each of them a par- ticular name. The names he adopted are founded on the figure of the bones, and are now pretty generally received, except the first, which instead of (the name given to it by Lyserus, on account of its sinus that ad- mits a part of the os magnum), has by later writers been named Scaphoides or Naviculare. This, which is the outermost of the upper row (considering the thumb as the outer side of the hand), is articulated with the radius ; on its inner side it is connected with the os lu- nare, and below to the trapezium and trape- Q 122 Osteology. zoides. Next to this is a smaller bone, called the os lunar e : because its outer side, which is connected with the scaphoides, is shaped like a crescent. This is likewise articulated with the radius. On its inner side it joins the os cuneiforme, and anteriorly, the os magnum and os unciforme. The os cuneiforme, which is the third bone in the upper row, is compared to a wedge, from its being broader above, at the back of the hand, than it is below. Posteriorly it is articulated with the ulna, and anteriorly with the os unciforme. These three bones form an oblong articulat- ing surface, covered by cartilage, by which the hand is connected with the fore-arm. The os pisiforme, or pea-like bone, which is smaller than the three just now described, though generally classed with the bones of the upper row, does not properly belong to either series, being placed on the under surface of the os cuneiforme, so as to project into the palm of the hand. The four bones of the se- cond row correspond with the bones of the thumb and fingers ; the first, second, and fourth, are from their shapes named trapezi- um. , trapezoides , and unciforme ; the third, from its being the largest bone of the carpus, is styl- ed os magnum. All these bones are convex towards the back, and slightly concave towards the palm of the hand ; their articulating surfaces are covered with cartilages, and secured by many strong ligaments, particularly by two ligamentous ex- Osteology. 123 pansions, called the external and internal an- nular ligaments of the wrist. The former ex- tends in an oblique direction from the os pisi- forme to the styloid process of the radius, and is an inch and an half in breadth ; the latter or internal annular ligament is stretched from the os pisiforme and os unciforme, to the os sca- phoides and trapezium. These annular liga- ments likewise serve to bind down the tendons of the wrist and fingers. The metacarpus consists of four bones, which support the fingers ; externally they are a little convex, and internally somewhat con- cave, where they form the palm of the hand. They are hollow and of a cylindrical shape. At each extremity they are a little hollow- ed for their articulation ; superiorly with the bones of the carpus, and inferiorly with the first phalanx of the fingers, in the same man- ner as the several phalanges of the fingers are articulated with each other. The five fingers of each hand are composed of fifteen bones, disposed in three ranks call- ed phalanges : the bones of the first phalanx, which are articulated with the metacarpus, are the largest, and those ef the last phalanx the smallest. All these bones are larger at their extremities than in their middle part. We observe at the extremities of the bones of the carpus, metacarpus, and fingers, seve- ral inequalities that serve for their articulation with each other ; and these articulations are strengthened by means of the ligaments which surround them. 124 Osteology . It will be easily understood that this multi- plicity of bones in the hand (for there are 27 in each hand) is essential to the different mo- tions we wish to perform. If each finger was composed only of one bone instead of* three, it would be impossible for us to grasp any thing. 2. Of the Lower Extremities. Each lower extremity is divided into four parts, viz. the os femoris, or thigh bone : the rotula, or knee pan ; the leg and the foot. 1. Of the Thigh. The thigh is composed only of this bone, which is the largest and strongest we have. It will be necessary to distinguish its body and extremities : its body, which is of a cylindri- cal shape, is convex before and concave be- hind, where it serves to lodge several muscles. Throughout two-thirds of its length we ob- serve a ridge called lined aspera , which origi- nates from the trochanters, and after running for some way downwards, divides into two branches, that terminate in the tuberosities at the lower extremity of the bone. At its upper extremity we must describe the neck and smooth head of the bone, and like- wise two considerable processes: the head, which forms the greater portion of a sphere unequally divided, is turned inwards, and re- ceived into the great cotyloid cavity of the os Osteology. 125 innominatum. At this part of the bone there is a little fossa to be observed, to which the round ligament is attached, and which we have al- ready described as tending to secure the head of this bone in the great acetabulum* The neck is almost horizontal, considered with re- spect to its situation with the body of the bone. Of the two processes, the external one, which is the largest, is called trochanter major ; and the other, which is placed on the inside of the bone, trochanter minor. They both afford at- tachment to muscles. The articulation of the os femoris with the trunk is strengthened by means of a capsular ligament, which adheres every where round the edge of the great co- tyloid cavity of the os innominatum, and sur- rounds the head of the bone. The os femoris moves upon the trunk in every direction. At the lower extremity of the bone are two processes called the condyles, and an interme- diate smooth cavity, by means of which it is articulated with the leg by ginglimus. All round the under end of the bone there is an irregular surface where the capsular li- gament of the joint has its origin, and where blood-vessels go into the substance of the bone. Between the condyles there is a cavity pos- teriorly, in which the blood-vessels and nerves are placed, secure from the compression to which they would otherwise be exposed in the action of bending the leg, and which would not fail to be hurtful. 126 Osteology. At the side of each condyle externally, there is a tuberosity, from whence the lateral liga- ments originate, which are extended down to the tibia. A ligament likewise arises from each con- dyle posteriorly. One of these ligaments passes from the right to the left, and the other from the left to the right, so that they inter- sect each other, and for that reason are called the cross ligaments. The lateral ligaments prevent the motion of the leg upon the thigh to the right or left ; and the cross ligaments, which are also attached to the tibia, prevent the latter from being brought forwards. In new-born children all the processes of this bone are cartilaginous. 2. The Rotula, or Knee-pan. The rotula, patella, or knee-pan, as it is differently called, is a flat bone about four or five inches in circumference, and is placed at the fore-part of the joint of the knee. In its shape it is somewhat like the common figure of the heart, with its point downwards. It is thinner at its edge than in its middle part ; at its fore-part it is smooth and some- what convex ; its posterior surface, which is more unequal, affords an elevation in the mid- dle which is admitted between the two con- dyles of the os femoris. This bone is retained in its proper situation by a strong ligament which every where sur- Osteology . 127 rounds it, and adheres both to the tibia and os femoris ; it is likewise firmly connected with the tibia by means of a strong tendinous liga- ment of an inch in breadth, and upwards of two inches in length, which adheres to the lower part of the patella, and to the tubero- sity at the upper end of the tibia. On account of this connection, it is very properly consi- dered as an appendage to the tibia, which it follows in all its motions, so as be to it what the olecranon is to the ulna. There is this difference, however, that the olecranon is a fixed process ; whereas the patella is movea- ble, being capable of sliding from above down- wards and from below upwards. This mobi- lity is essential to the rotatory motion of the le &‘ In very young children this bone is entirely cartilaginous. The principal use of the patella seems to be to defend the articulation of the knee from external injury; it likewise tends to increase the power of the extensor muscles of the leg, by removing their direction farther from the centre of motion in the manner of a pulley. 3. Of the Leg. The leg is composed of two bones: of these the inner one, which is the largest, is called tibia ; the other is much smaller, and named fibula. The tibia, which is so called from its re- semblance to the musical pipe of the ancients, 128 Osteology. has three surfaces, and is not very unlike a triangular prism. Its posterior surface is the broadest ; anteriorly it has a considerable ridge called the shin, between which and the skin there are no muscles. At the upper ex- tremity of this bone are two surfaces, a little concave, and separated from each other by an intermediate elevation. The two little cavities receive the condyles of the os femoris, and the eminence between them is admitted into the cavity which we spoke of as being be- tween the two condyles ; so that this articula- tion affords a specimen of the complete gin- glimus. Under the external edge of the up- per end of this bone is a circular flat surface, which receives the head of the fibula. At the lower and inner portion of the tibia, we observe a considerable process called mal- leolus interims. The basis of the bone termi- nates in a large transverse cavity, by which it is articulated with the uppermost bone of the foot. It has likewise another cavity at its low- er end and outer side, which is somewhat ob- long, and receives the lower end of the fibula. The tibia is hollow through its whole length. The fibula is a small long bone situated on the outside of the tibia. Its superior extremi- ty does not reach quite so high as the upper part of the tibia, but its lower end descends somewhat lower. Both above and below, it is articulated with the tibia by means of the lateral cavities we noticed in our description of that bone. Osteology. 129 Its lower extremity is stretched out into a coronoid process, which is flattened at its in- side, and is convex externally, forming what is called the malleolus externus or outer ankle . This is rather lower than the malleolus inter- nus of the tibia. The body of this bone, which is irregularly triangular, is a little hollow at its internal sur- face, which is turned towards the tibia ; and it affords like that bone, through its whole length, attachment to a ligament, which from its situa- tion is called the interosseous ligament. 4. Of the Foot. ' b') \ n The foot consists of the tarsus, metatarsus, and toes. The tarsus is composed of seven bones, viz. the astragalus, os calcis, os naviculare, os cu- boides, and three others called cuneiform, bones. The astragalus is a large bone with which both the tibia and fibula are articulated. It is the uppermost bone of the foot ; it has se- veral surfaces to be considered ; its upper, and somewhat posterior part, which is smooth and convex, is admitted into the cavity of the tibia. Its lateral parts are connected with the malleoli of the two bones of the leg ; below, it is articulated with the os calcis, and its an- terior surface is received by the os naviculare. All these articulations are secured by means of ligaments. R 130 Osteology. The os calcis, or calcaneum, which is of a very irregular figure, is the largest bone of the foot. Behind, it is formed into a considerable tuberosity called the heel ; without this tube- rosity, which supports us in an erect posture, and when we walk, we should be liable to fall backwards. On the internal surface of this bone, we observe a considerable sinuosity, which affords a passage to the tendon of a muscle : and to the posterior part of the os calcis, a strong tendinous cord called tendo achillis* is attach- ed, which is formed by the tendons of seve- ral muscles united together. The articulation of this with the other bones is secured by means of ligaments. The os naviculare, or scaphoides, (for these two terms have the same signification), is so called on account of its resemblance to a little bark. At its posterior part, which is concave, it receives the astragalus ; anteriorly it is ar- ticulated with the cuneiform bones, and late- rally is connected with the os cuboides. The os cuboides forms an irregular cube. Posteriorly it is articulated with the os calcis ; anteriorly it supports the two last bones of the metatarsus, and laterally it joins the third cu- neiform bone and the os naviculare. Each of the ossa cuneiformia, which are three in number, resembles a wedge, and from this similitude their name is derived. They * This tendon is sometimes ruptured by jumping, dancing, or other violent efforts. Osteology. 131 are placed next to the metatarsus by the sides of each other, and are usually distinguished into os cuneiforme externum , medium or mini- mum ^ and internum or maximum. The supe- rior surface of these bones, from their wedge- like shape, is broader than that which is be- low, where they help to form the sole of the foot ; posteriorly they are united to the os na- viculare, and anteriorly they support the three first metatarsal bones. When these seven bones composing the tar- sus are viewed together in the skeleton, they appear convex above, where they help to form the upper part of the foot ; and concave under- neath, where they form the hollow of the foot, in which the vessels, tendons, and nerves of the foot are placed secure from pressure. They are united to each other by very strong ligaments, and their articulation with the foot is secured by a capsular and two lateral liga- ments ; each of the latter is covered by an an- nular ligament of considerable breadth and thickness, which serves to bind down the ten- dons of the foot, and at the same time to strengthen the articulation. The os cuneiforme externum is joined late- rally to the os cuboides. These bones complete our account of the tar- sus. Though what we have said of this part of the osteology has been very simple and con- cise, yet many readers may not clearly under- stand it : but if they will be pleased to view these bones in their proper situation in the 132 Osteology . skeleton, all that we have said of them will be easily understood. The metatarsus is made up of five bones^ whereas the metacarpus consists only of four. The cause of this difference is, that in the hand the last bone of the thumb is not includ- ed among the metacarpal bones ; whereas in the foot the great toe has only two bones. The first of these bones supports the great toe and is much larger than the rest, which nearly re- semble each other/in size. These bones are articulated by one extremi- ty with the cuneiform bones and the os cuboi- des, and by their other end with the toes. Each of the toes, like the fingers, consists of three bones, except the great toe, which is formed of two bones. Those of the other four are distinguished into three phalanges. Although the toes are more confined in their motion than the fingers, yet they appear to be perfectly fitted for the purposes they are de- signed for. In walking, the toes bring the centre of gravity perpendicular to the advanc- ed foot ; and as the soles of the feet are natu- rally concave, we can at pleasure increase this concavity, and form a kind of vault, which adjusts itself to the different inequalities that occur to us in walking; and which, without this mode of arrangement, would incommode us exceedingly, especially when bare-footed. Osteology. 133 4 . Of the Ossa Sesamoidea. Besides the bones we have already de- scribed, there are several small ones that are met with only in the adult skeleton, and in persons who are advanced in life ; which, from their supposed general resemblance to the seeds of the sesamum, are called ossa sesa- moidea. They are commonly to be seen at the first joint of the great toe, and sometimes at the joints of the thumb ; they are likewise now and then to be found at the lower extremity of the fibula, upon the condyles of the thigh- bone, under the os cuboides of the tarsus, and in other parts of the body. Their size and num- ber seem constantly to be increased by age and hard labour ; and as they are generally found in situations where tendons and ligaments are most exposed to the action of muscles, they are now generally considered as ossified por- tions of ligaments or tendons. The upper surface of these bones is usual- ly convex, and adherent to the tendon that co- vers it ; the side which is next to the joint is smooth and flat. Though their formation is accidental, yet they seem to be of some use, by raising the tendons farther from the centre of motion, and consequently increasing the power of the muscles. In the great toe and thumb they are likewise useful, by forming a groove for the flexor tendons. 134 Osteology. EXPLANATION OF THE PLATES OF OSTEOLOGY. Plate. XIX. Fig. 1, A Front-view of the Male Skele- ton. A, The os frontis. B, The os parietale. C, The coronal suture. D, The squamous part of the temporal bones. E, The squamous su- ture. F, The zygoma. G, The mastoid pro- cess. H, The temporal process of the sphe- noid bone. I, The orbit. K, The os malae. L, The os maxillare superius. M, Its nasal process. N, The ossa nasi. O, The os un- guis. P, The maxilla inferior. Q, The teeth which are sixteen in number in each jaw. R, The seven cervical vertebrae, with their inter- mediate cartilages. S, Their transverse pro- cesses. T, The twelve dorsal vertebrae, with their intermediate cartilages. U, The five lumbar vertebrae. V, Their transverse pro- cesses. W, The upper part of the os sacrum. X, Its lateral parts. The holes seen on its fore part are the passages of the undermost spinal nerves and small vessels. Opposite to the holes, the marks of the original divisions of the bone are seen. Y, The os ilium. Z, Its crest or spine, a, The anterior spinous processes, b, The brim of the pelvis. c ? Axa to my Osteology. 135 The ischiatic niche, d, The os ischium, e, Its tuberosity, f, Its spinous process, g, Its crus, h, The foramen thyroideum. i, The os pubis, k, The symphysis pubis. 1, The crus pubis, m, The acetabulum, n, The se- venth or last true rib* o, The twelfth or last false rib. p, The upper end of the sternum, q, The middle piece, r, The under end, or cartilage ensiformis. s, The clavicle, t, The internal surface of the scapula, u, Its acro- mion. v, Its coracoid process, w, Its cervix., x, The glenoid cavity, y, The os humeri, z. Its head which is connected to the glenoid ca- vity. 1, Its external tubercle. 2, Its inter- nal tubercle. 3. The groove for lodging the long head of the biceps muscle of the arm. 4, The internal condyle. 5, The external condyle. Between 4 and 5, the trochlea. 6, The radius. 7, Its head. 8, Its tubercle. 9, The ulna- 10, Its coronoid process. 11, 12, 13, 14, 15, 16, 17, 18, The carpus ; compos- ed of os naviculare, os lunare, os cuneifor- me, os pisiforme, os trapezium, os trapezoi- des, os magnum, os unciforme. 19, The five bones of the metacarpus. 20, The two bones of the thumb. 21, The three bones of each of the fingers. 22, The os femoris. 23, Its head. 24, Its cervix. 25, The trochanter major. 26, The trochanter minor. 27, The internal condyle. 28, The external condyle 29, The rotula. 30, The tibia. 31, Its head* 32, Its tubercle. 33, Its spine. 34, The mal- leolus interims. 35, The fibula. 36, Its head. 37, The malleolus externus. The tarsus is 136 Osteology. composed of, 38 , The astragalus; 39 , The os calcis ; 40 , The os naviculare ; 41 , Three ossa cuneiformia, and the os cuboides, which is not seen in this figure. 42 , The five bones of the metatarsus. 43 , The two bones of the great toe. 44 , The three bones of each of the small toes. Fig. 2. A Front-view of the Skull. A, The os frontis. B. The lateral part of the os frontis, which gives origin to part of the temporal muscle. C, The superciliary ridge. D, The superciliary hole through which the frontal vessels and nerves pass. E E, The orbitar processes. F, The middle of the transverse suture. G, The upper part of the orbit. H, The foramen opticum. I, The foramen lacerum. K, The inferior orbitar fis- sure. L, The os unguis. M, The ossa na- si. N, The os maxillare superius. O, Its na- sal process. P, The external orbitar hole through which the superior maxillary vessels and nerves pass. Q, The os malae. R, A passage for small vessels into, or out of, the orbit. S, The under part of the left nostril. T, The septum narium. U, The os spongi- osum superius. V, The os spongiosum infe- rius. W, The edge of the alveoli, or spongy sockets, for the teeth- X, The maxilla infe- rior. Y, The passage for the inferior maxil- lary vessels and nerves- Osteology . 137 Fig. 3. A Side-view of the Skull. A, The os frontis. B, The coronal suture. C, The os parietale. D, An arched ridge which gives origin to the temporal muscle. E, The squamous suture. F, The squamous part of the temporal bone ; and, farther for- wards, the temporal process of the sphenoid bone. G, The zygomatic process of the tem- poral bone. H, The zygomatic suture. I, The mastoid process of the temporal bone. K, The meatus auditorius externus- L, The orbitar plate of the frontal bone, under which is seen the transverse suture. M, The pars plana of the ethmoid bone. N, The os unguis. O, The right os nasi. P, The superior maxilla- ry bone. Q, Its nasal process. R, The two dentes incisores. S, The dens caninus. T, the two small molares. U, The three large molares. V, The os malse. W, The lower jaw. X, Its angle. Y, The coronoid process. Z, The condyloid process, by which the jaw is articulated with the temporal bone. Fig. 4. The posterior and right Side of the Skull. A, The os frontis. B B, The ossa parieta- lia. C, The sagittal suture. D, The parie- tal hole, through which a small vein runs to the superior longitudinal sinus. E, The lamb- doid suture. F F, Ossa triquetra. G, The os occipitis. H, The squamous part of the temporal bone. I, The mastoid process. K, S 138 Osteology. The zygoma. L, The os ma be. M, The tem- poral part of the sphenoid bone. N, The su- perior maxillary bone and teeth. Fig. 5. The external Surface of the OsFron- TIS. A, The convex part. B, Part of the tem- poral fossa. C, The external angular process. D, The internal angular process. E, The na- sal process. F, The superciliary arch. G, The superciliary hole. H, The orbitar plate. Fig. 6. The Interior Surface of the OsFron- tis. A A, The serrated edge which assists to form the coronal suture. B, The external an- gular process. C, The internal angular pro- cess. D, The nasal process. E, The orbi- tar plate. F, The cells which correspond with those of the ethmoid bone. G, The passage from the frontal sinus. H, The opening which receives the cribriform plate of the ethmoid bone. I, The cavity which lodges the fore part of the brain. K, The spine to which the falx is fixed. L, The groove which lodges the superior longitudinal sinus. PLATE XX. Fig. 1 . A Back-view of the Skeleton. A A, The ossa parietalia. B, The sagit- tal suture. C, The lambdoid suture. D, The A N A.' I’ OMY Osteology. 139 occipital bone. E, The squamous suture, F, The mastoid process of the temporal bone. G, The os malse. H, The palate-plates of the superior maxillary bones. I, Tne maxilla in- ferior. K, The teeth of both jaws. L, The seven cervical vertebras. M, Their spinous processes. N, Their transverse and oblique processes. O, The last of the twelve dorsal vertebrae. P, The fifth or last lumbar vertebra. Q, The transverse processes. R, The obli- que processes. S, The spinous processes. T, The upper part of the os sacrum. U, The posterior holes which transmit small blood- vessels and nerves. V, The under part of the os sacrum which is covered by a mem- brane. W, The os coccygis. X, The os ili- um. Y, Its spine or crest. Z, The ischia- tic niche, a, The os ischium, b, Its tubero- sity. c, Its spine, d, The os pubis, e, The foramen hydroideum. f, The seventh or last true rib. g, The twelfth or last false rib. h, The clavicle, i, The scapula, k, Its spine. 1, Its acromion, m, Its cervix, n, Its supe- rior costa, o, Its posterior costa- p, Its infe- rior costa. q, The os humeri, r, The radi- us. s, The ulna, t, Its oleclarnon. u, All the bones of the carpus, excepting the os pi- siforme, which is seen in plate XIX. fig. 1. v, The five bones of the metacarpus, w, The two bones of the thumb, x, The three bones of each of the fingers, y, The two sesamoid bones at the root of the left thumb, z, The os femoris. 1, The trochanter major. 2, The 140 Osteology. trochanter minor. 3, The linea aspera. 4, The internal condyle. 5 , The external condyle. 6 6 , The semilunar cartilages. 7, The tibia. 8 , The malleolus internus. 9, The fibula. 10 , The malleolus externus. 11 , The tarsus. 12 , The metatarsus. 13, The toes- Fig- 2 - The External Surface of the left Os Parietale. A, The convex smooth surface- B, The pari- etal hole. C, An arch made by the beginning of the temporal muscle- Hg. 3. The Internal Surface of the same bone. A, Its superior edge, which, joined with the other, forms the sagittal suture- B, The anterior edge, which assists in the formation of the coronal suture. C. The inferior edge for the squamous suture- D, The posterior edge for the lambdoid suture. E, A depres- sion made by the lateral sinus- F F, The prints of the arteries of the dura mater. Fig. 4. The External Surface of the Left Os Temporum- A, The squamous part- B, The mastoid pro- cess. C, The zygomatic process. D, The styloid process. E, The petrosal process. F. The meatus auditorius externus. G, The gle- noid cavity for the articulation of the lower jaw. H, The foramen stylo-mastoideum for the portio dura of the seventh pair of nerves I, Passages for blood-vessels into the bone.. Osteology, 141 K, The foramen mastoideum through which a vein goes to the lateral sinus- Fig. 5. The Internal Surface of the Left Os Temporum. A, The squamous part; the upper edge of which assists in forming the squamous suture* B, The mastoid process. C, The styloid pro- cess- D, The pars petrosa. E, The entry of the seventh pair, or auditory nefve. F, The fossa which lodges a part of the lateral sinus- G, The foramen mastoideum. Fig. 6. The External Surface of the Osse- ous Circle, which terminates the meatus auditorius externus. A, The anterior part. B, A small part of the groove in which the membrana tympani is fixed. N- B. This with the subsequent bones of the ear, are here delineated as large as the life- Fig. 7- The Internal Surface of the Osseous Circle. A, The anterior part- B, The groove in which the membrana tympani is fixed- Fig- 8. The Situation and Connection of the Small Bones of the Ear. A, The malleus. B, The incus- C, The os orbiculare. D> The stapes- 142 Osteology . Fig. 9. The Malleus, with its Head, Handle, and Small processes. Fig. 10- The Incus, with its Body, Superior and Inferior Branches. Fig. 11* The Os Orbiculare. Fig. 12- The Stapes, with its Head, Base, and two Crura. Fig- 13- An Internal View of the Labyrinth of the Ear. A, The hollow part of the cochlea, which forms a share of the meatus auditorius inter- nus- B, The vestibulum. C C C, The semi- circular canals. Fig- 14- An External View of the Labyrinth. A, The semicircular canals- B, The fenes- tra ovalis which leads into the vestibulum. C, The fenestra rotunda which opens into the cochlea- D, The different turns of the cochlea. Fig. 15* The Internal Surface of the Os Sphe- noides. A A, The temporal processes. B B, The pterygoid processes- C C, The spinous pro- cesses. D D, The anterior clinoid processes. E, The posterior clinoid process- F, The an- terior process which joins the ethmoid bone. G, The sella turcica for lodging the glandula pituitaria. H, The foramen opticum. K, The foramen lacerum. L, The foramen rotun- Osteology. 143 dum. M, The foramen ovale. N, The fora- men spinale. Fig. 16. The External Surface of the Os Sphenoides. A A, The temporal processes. B B, The pterygoid processes. C C, The spinous pro- cesses. D, The processus azygos. E, The small triangular processes which grow from the body of the bone. F F, The orifices of the sphenoidal sinuses. G, The foramen la- cerum. H, The foramen rotundum. I, The foramen ovale. K, The foramen pterygoide- um. Fig. 17. The External View of the Os Eth- MOIDES- A, The nasal lamella. B B, The grooves between the nasal lamella and ossa spongiosa superiora. C C, The ossa spongiosa superio- ra. D D, The sphenoidal cornua. See Fig. 16. E. Fig. 18. The Internal View of the Os Eth- MOIDES* A, The crista galli- B, The cribriform plate, with the different passages of the ol- factory nerves. C C, Some of the ethmoidal cells. D, The right os planum. E E, The sphenoidal cornua. Fig. 19- The right Sphenoidal Cornu. Fi g. 20. The left Sphenoidal Cornu. 144 ' Osteology. Fig. 21. The External Surface of the Os Oc* cipitis. A, The upper part of the bone. B, The superior arched ridge. C, The inferior arch- ed ridge. Under the arches are prints made by the muscles of the neck. D D, The two condyloid processes which articulate the head with the spine. E, The cuneiform process. F, The foramen magnum through which the spinal marrow passes. G G, The posterior condyloid foramina which transmit veins into the lateral sinuses. H H, The foramina lin- gualia for the passage of the nine pair of nerves* Fig. 22. The Internal Surface of the Os Oc- CIPITIS. A A, The two sides which assist to form the lambdoid suture. B, The point of the cuneiform process, where it joins the sphe- noid bone. C C, The prints made by the posterior lobes of the brain- D D, Prints made by the lobes of the cerebellum. E, The cruciform ridge for the attachment of the pro- cesses of the dura mater. F, The course of the superior longitudinal sinuses. G G, The course of the two lateral sinuses. H, The foramen magnum. II, The posterior condy- loid foramina. * Osteology. 145 Plate XXL Fig. 1* A Side-view of the Skeleton. A A, The ossa parietalia. B, The sagittal suture. C, The os occipitis. D D, The lamb- doid suture. E, The squamous part of the tem- poral bone- F, The mastoid process. G, The meatus auditorius externus. H, Th,e os fron- tis. I, The os malse. K, The os maxillare superius. L, The maxilla inferior. M, The teeth of both jaws. N, The seventh, or last cervical vertebra- O, The spinous processes. P, Their transverse and oblique processes. Q, The twelfth or last dorsal vertebra- R, The fifth, or last lumbar vertebra. S. The spinous processes. T, Openings between the verte- brae for the passage of the spinal nerves. U, The under end of the os sacrum. V, The os coccygis. W, The os ilium. X, The an- terior spinous processes. Y, The posterior spinous processes. Z, The ischiatic niche- a, The right os ilium. b, The ossa pubis, c, The tuberosity of the left os ischium, d, The scapula- e, Its spine, f, The os humeri, g, The radius, h, The ulna, i, The carpus, k, The metacarpal bone of the thumb. 1, The metacarpal bones of the fingers, m. The two bones of the thumb, n, The three bones of each of the fingers, o, The os femoris. p, Its head- q, The trochanter major, r. The external condyle- s, The rotula. t, The tibia. T 146 Osteology. u, 1 he fibula, v, The malleolus externus. w, The astragalus, x, The os calcis. y, The os naviculare. z, The three ossa cuneiformia. 1, The os cuboides. 2, The five metatarsal bones. 3 , The two bones of the great toe. 4, The three bones of each of the small toes. Fig. 2- A View of the Internal Surface of the Base of the Skull. AAA, The two tables of the skull with the diploe. B B, The orbitar plates of the frontal bone. C, l he crista galli, with cribri- form plate of the ethmoidal bone on each side of it, through which the first pair of nerves pass. D, The cuneiform process of the occipi- tal bone. E, The cruciform ridge. F, The foramen magnum for the passage of the spi- nal marrow. G, The zygoma, made by the joining of the zygomatic processes of the os temporum and os malse. H, 'I he pars squa- mosa of the os temporum. I, The pars mam- millaris. K, The pars petrosa. L, The tem- poral process of the sphenoid bone. M M, The anterior clinoid processes. N, The pos- terior clinoid process. O, The sella turcica. P, The foramen opticum, for the passage of the optic nerve and ocular artery of the left side. Q, The foramen lacerum, for the third, fourth, sixth, and first of the fifth pair of nerves and ocular vein. R, The foramen rotundum, for the second of the fifth pair. S, The fora- men ovale, for the third of the fifth pair. T, The foramen spinale, for the principal artery of the dura mater, U, The entry of the au- Osteology. 147 ditory nerve- V, The passage for the lateral sinus. W, The passage of the eighth pair of nerves. X, The passage of the ninth pair- Fig. 3* A View of the External Surface of the Base of the Skull. A, The two dentes incisores of the right side. B, The dens caninus- C, The two small molares. D, The three large molares. E, The foramen incisivum, which gives passage to small blood-vessels and nerves. F, The palate- plates of the ossa maxillaria and palati, joined by the longitudinal and transverse palate su- tures. G, The foramen palatinum posterius, for the palatine vessels and nerves- H, The os maxillare superius of the right side. 1, The os malas. K, The zygomatic process of the temporal bone. L, 1 he posterior extremity of the ossa spongiosa. M, The posterior extre- mity of the vomer, which forms the back-part of the septum nasi. N, The pterygoid process of the right side of the sphenoid bone. O O, The foramina ovalia. PP, The foramina spinalia. Q, Q,, The passages of the internal carotid ar- teries. R, A hole between the point of each pars petrosa and cuneiform process of the occipital bone, which is filled up with a ligamentous sub- stance in the recent subject. S, The passage of the left lateral sinus. T, The posterior condyloid foramen of the left side- U, The foramen mastoideum. V, The foramen mag- num. W, The inferior orbitar fissure. X, The glenoid cavity, for the articulation of the low- er jaw. Y, The squamous part of the temporal 148 Osteology. bone. Z, The mastoid process, at the inner side of which is a fossa for the posterior belly of the digastric muscle, a, I he styloid pro- cess. b, 1 he meatus auditorius externus. c, The left condyle of the occipital bone, d, The perpendicular occipital spine, e e, The infe-i rior horizontal ridge of the occipital bone, f f, The superior horizontal ridge, which is oppo- site to the crucial ridge where the longitudinal sinus divides to form the lateral sinuses, g g g, The lambdoid suture, h, The left squamous su- ture. i, The parietal bone- Fig. 4. The anterior surface of the Ossa Nasi. A, The upper part, which joins the os fron- tis. B, The under end, which joins the car- tilage of the nose. C, The inner edge, where they join each other. Fig. 5. The posterior surface of the Ossa Nasi. A A, Their cavity, which forms part of the arch of the nose. B B, Their ridge or spine, which projects a little to be fixed to the fore- part of the septum narium. Fig. 6. The external surface of the Os Max- illare Superius of the left side. A, The nasal process. B, The orbitar plate. C, The unequal surface which joins the os make. D, The external orbitar hole. E, The opening into the nostril. F, The pa- Osteology. 149 late-plate. G, The maxillary tuberosity. H, Part of the os palati. I, The two dentes inci- sores. K, The dens caninus. L, The two small dentes molares. M, The three large dentes molares. Fig. 7. The internal surface of the Os Max- ill are Superius and Os Palati. A, The nasal process. B B, Eminences for the connection of the os spongiosum inferius. D, The under end of the lachrymal groove. E, Tne antrum maxillare. E, The nasal spine, between which and B is the cavity of the nos- tril. G, The palate-plate. H, The orbitar part of the os palati. I, The nasal plate. K, The suture which unites the maxillary and pa- late bones. L, The pterygoid process of the palate bones. Fig. 8. The external surface of the right Os Unguis. A, The orbitar part. B, The lachrymal part, C, The ridge between them. Fig. 9. The internal surface of the right Os Unguis. This side of the bone has a furrow opposite to the external ridge ; all behind that is irre- gular, where it covers part of the ethmoidal cells. 150 Osteology. Fig. 10. The external surface of the left Os Mal£. A, The superior orbitar process. B, The inferior orbitar process. C, The malar pro- cess. D, The zygomatic process. E, The orbitar plate. F, A passage for small vessels into or out of the orbit. Fig. 11. The internal surface of the left Os Malje. A, The superior orbitar process. B, The inferior orbitar process. C, The malar pro- cess. D, The zygomatic process. E, The internal orbitar plate or process. ^ig. 12. The external surface of the right Os Spongiosum Infeiuus. A, The anterior part. B, The hook-like process for covering part of the antrum maxil- lare. C, \ small process which covers part of the under end of the lachrymal groove. D, The inferior edge turned a little outwards. Fig. 13. The internal surface of the Os Spon- giosum Inferius. A, The anterior extremity. B, The upper edge which joins the superior maxillary and palate bones- Fig. 14. The posterior and external surface of the right Os Palati. A, The orbitar process. B, The nasal la- mella. C, The pterygoid process. D, The palate process. Osteology . 151 Fig. 15. The anterior and external surface of the right Os Palati. A, The orbitar process. B, An opening through which the lateral nasal vessels and nerves pass. C, The nasal lamella. D, The pterygoid process. E, The posterior edge of the palate process for the connection of the velum palati. F, The inner edge by which the two ossa palati are connected. Fig. 16 - The right side of the Vomer. A, The upper edge which joins the nasal lamella of the ethmoid bone and the middle cartilage of the nose. B, The inferior edge, which is connected to the superior maxillary and palate bones. C, The superior and pos- terior part which receives the processus azy- gos of the sphenoid bone. Fig. 17- The Maxilla Inferior. A, The chin* B, The base and left side. C, The angle. D, The coronoid process. E, The condyloid process. F, The beginning of the inferior maxillary canal of the right side, for the entry of the nerve and blood-vessels. G, The termination of the left canal- H, The two dentes incisores. I, The dens caninus. K, The two small molares. L, The three large molares. Fig. 18 . The different classes of the Teeth. 1, 2, A fore and back view of the two ante- rior dentes incisores of the lower jaw. 3, 4, 152 Osteology. Similar teeth of the upper jaw. 5, 6, A fore and back view of the dentes canini. 7, 8, The anterior dentes molares. 9, 10, 11, The posterior dentes molares. 12, 13, 14, 15, 16, Unusual appearances in the shape and size of the teeth. Fig. 19. The external surface of the Os Hy OIDES. A, The body. B B, The cornua. C C, The appendices. Plate XXII. Fig. 1 . A Posterior View of the Sternum and Clavicles, with the ligament connect- ing the clavicles to each other. a, The posterior surface of the sternum, b b, The broken ends of the clavicles- c c c c, The tubercles near the extremity of each cla- vicle. d, The ligament connecting the cla- vicles. Fig. 2. A Fore-view of the Left Scapula, and of a half of the Clavicle, with their Ligaments. a, The spine of the scapula, b, the acro- mion. c, The inferior angle- d, Inferior cos- ta. e, Cervix, f, Glenoid cavity, covered with cartilage for the arm-bone, g g, The capsular ligament of the joint- h, Coracoid ' Osteology. 153 process, i, The broken end of the clavicle, k, Its extremity joined to the acromion. 1, A ligament coming out single from the acromion to the coracoid process, m, A ligament com- ing out single from the acromion, and dividing into two, which are fixed to the coracoid pro- cess- Fig. 3. The Joint of the Elbow of the Left Arm, with the Ligaments. a, The os humeri, b, Its internal condyle, c c, The two prominent parts of its trochlea appearing through the capsular ligament, d, The ulna, e, The radius, f, The part of the ligament including the head of the radius. Fig. 4. The Bones of the Right-Hand, with the Palm in view. a, The radius, b, The ulna, c, The sca- phoid bone of the carpus, d, The os lunare. e, The os cuneiforme. f, The os pisiforme. g, Trapezium, h, Trapezoides. i, Capita- turn. k, Unciforme. 1, The four metacar- pal bones of the fingers, m, The first pha- lanx. n, The second phalanx, o, The third phalanx, p, The metacarpal bone of the thumb, q, The first joint, r, The second joint. Fig. 5. The Posterior View of the Bones of the Left Hand- The explication of Fig. 4. serves for this figure ; the same letters pointing out the same bones, though in a different view. U 154 Osteology. Fig. 6. The Upper Extremity of tlie Tibia, with the Semilunar Cartilages of the Joint of the Knee, and some Ligaments. a, The strong ligament which connects the rotula to the tubercle of the tibia, b b, The parts of the extremity of the tibia, co- vered with cartilage, which appear within the semilunar cartilages* c c, The semilunar car- tilages- d, The two parts of what is called the cross ligament. Fig- 7- The Posterior View of the Joint of the Right Knee. a, The os femoris cut- b, Its internal con- dyle. c, Its external condyle, d, The back part of the tibia, e, The superior extremity of the fibula, f, The edge of the internal se- milunar cartilage, g, An oblique ligament. h, A larger perpendicular ligament, i, A li- gament connecting the femur and fibula. Fig. 8- The Anterior View of the Joint of the Right Knee. b, The internal condyle* c, Its external condyle, d, The part of the os femoris, on which the patella moves, e, A perpendicu- lar ligament, f f, The two parts of the cru- cial ligaments, g g, The edges of the two moveable semilunar cartilages, h, The tibia. i, The strong ligament of the patella, k, The back part of it where the fat has been dis- sected away. 1, The external depression, m, The internal one. n, The cut tibia. Osteology. 155 Fig. 9. A View of the inferior part of the Bones of the Right Foot. a, The great knob of the os calcis. b, A prominence on its outside, c, The hollow for the tendons, nerves, and blood-vessels, d, The anterior extremity of the os calcis. e, Part of the astragalus, f, Its head covered with cartilage, g, The internal prominence of the os naviculare. h, The os cuboides. i, The os cuneiforme internum; k, — Medium; 1, — Externum, m, The metatarsal bones of the four lesser toes, n, The first — o, The second — p, The third phalanx of the four les- ser toes, q, The metatarsal bones of the great toe. r, Its first — s, Its second joint. Fig. 10. The Inferior Surface of the two large Sesamoid Bones, at the first Joint of the Great Toe. Fig. 11 * The Superior View of the Bones of the Right Foot. a, b, as in Fig. 9. c, The superior head of the astragalus, d, &c. as in Fig. 9. Fig. 12. The View of the Sole of the Foot, with its Ligaments. a, The great knob of the os calcis. b, The hollow for the tendons, nerves, and blood- vessels. c, The sheaths of the fiexores pol- licis and digitorum longi opened, d, The strong cartilaginous ligament supporting the head of the astragalus, e, h, Two ligaments which unite into one, and are fixed to the 156 Osteology. metatarsal bone of the great toe. f, A liga- ment from the knob of the os calcis to the metatarsal bone of the little toe. g, A strong triangular ligament, which supports the bones of the tarsus, i, The ligaments of the joints of the five metatarsal bones. Fig. 13. a, The head of the thigh bone of a child, b, The ligamentum rotundum con- necting it to the acetabulum, c, The capsu- lar ligament of the joint with its arteries in- jected. d, The numerous vessels of the mu- cilaginous gland injected. Fig. 14. The Back-view of the Cartilages of the Larynx, with the Os Hyoides. a, The posterior part of the base of the os hyoides. b b, Its cornua, c, The appendix of the right side, d, A ligament sent out from the appendix of the left side, to the sty- loid process of the temporal bone, e, The union of the base with the left cornu, f f, The posterior sides of (g) the thyroid carti- lage. h h, Its superior cornua, i i, Its in- ferior cornua, k, The cricoid cartilage. 1 1, The arytenoid cartilages, m, The entry into the lungs, named glottis, n, The epiglottis, o o, The superior cartilages of the trachea, p, Its ligamentous back part. Fig. 15. The Superior Concave surface of the Sesamoid Bones at the first joint of the Great Toe, with their Ligaments, a, Three sesamoid bones, b, The liga- mentous substance in which they are formed. Of the Integuments , &c. 157 Part II. OF THE SOFT PARTS IN GE- NERAL ; Of the Common Integuments , with their appen- dages ; and of the Muscles. A NATOMICAL writers usually proceed to a description A>f the muscles after having finished the osteology ; but we shall deviate a little from the common method, with a view to describe every thing clearly and dis- tinctly, and to avoid a tautology which would otherwise be unavoidable. All the parts of the body are so intimately connected with each other, that it seems impossible to convey a just idea of any one of them, without being in some measure obliged to say something of others ; and on this account we wish to mention in this place the names and situation of the principal viscera of the body, that when mention is hereafter made of any one of them in the course of the work, the reader may at least know where they are placed. After this little digression, the common in- teguments, and after them the muscles will be described ; we then propose to enter into an examination of the several viscera and their different functions. In describing the brain. 158 Of the Integuments , &c. occasion will be taken to speak of the nerves and animal spirits. The circulation of the blood will follow the anatomy of the heart, and the secretions and other matters will be intro- duced in their proper places. The body is divided into three great cavities. Of these the uppermost is formed by the bones of the cranium, and incloses the brain and cere- bellum. The second is composed of the vertebrse of the back, the sternum, and true ribs, with the additional assistance of muscles, membranes, and common integuments, and is called the thorax — It contains the heart and lungs. The third, and inferior cavity, is the abdo- men. It is separated from the thorax by means of the diaphragm, and is formed by the lumbar vertebrae, the os sacrum, the os- sa innominata, and the false ribs, to which we may add the peritonaeum, and a variety of muscles. This cavity incloses the stomach, intestines, omentum or cawl, liver, pancreas, spleen, kidneys, urinary bladder, and parts of generation. Under the division of common integuments are usually included the epidermis, or scarf- skin, the reticulum mucosum of Malpighi, the cutis or true skin, and the membrana adi- posa — The hair and nails, as well as the se- baceous glands, may be considered as appen- dages to the skin. Of the Integuments , &c. 159 Sect. I. Of the Skin. 1. Of the Scarf -skin. The epidermis, cuticula, or scarf-skin, is a fine, transparent, and insensible pellicle, des- titute of nerves and blood-vessels, which in- vests the body, and every where covers the true skin. This scarf-skin, which seems to be very simple, appears, when examined with a microscope, to be composed of several la- minse or scales which are increased by pres- sure, as we may observe in the hands and feet, where it is frequently much thickened, and becomes perfectly callous. It seems to adhere to the cutis by a number of very mi- nute filaments, but may easily be separated from it by heat, or by maceration in water- Some anatomical writers have supposed that it is formed by a moisture exhaled from the whole surface of the body, which gradually hardens when it comes into contact with the air. They were perhaps induced to adopt this opinion, by observing the speedy regeneration of this part of the body when it has been by any means destroyed, it appearing to be renewed on all parts of the surface at the same time ; where- as other parts which have been injured, are found to direct their growth from their circum- ference only towards their centre. But a demon- strative proof that the epidermis is not a fluid 160 Of the Integuments , &d. hardened by means of the external air, is that the foetus in utero is found to have this cover- ing. Lieuwenhocck supposed its formation to be owing to the expansion of the extremities of the excretory vessels which are found eve- ry where upon the surface of the true skin. Ruysch attributed its origin to the nervous papillae of the skin; and Heister thinks it pro- bable, that it may be owing both to the pa- pillae and the excretory vessels. The cele- brated Morgagni, on the other hand, contends,* that it is nothing more than the surface of the cutis, hardened and rendered insensible by the liquor amnii in utero, and by the pressure of the air. This is a subject, however, on which we can advance nothing with certainty. The cuticle is pierced with an infinite num- ber of pores or little holes, which afford a passage to the hairs, sweat, and insensible per- spiration, and likewise to warm water, mer- cury, and whatever else is capable of being taken in by the absorbents of the skin. The lines which we observe on the epidermis be- long to the true skin. The cuticle adjusts it- self to them, but does not form them- 2. Of the Rete Mucosum. Between the epidermis and cutis we meet with an appearance to which Malpighi, who first described it, gave the name of rete muco- sum, supposing it to be of a membranous structure, and pierced with an infinite number of pores; but the fact is, that it seems to be * Adversar. Anat. n. Animadver. 2. 161 Of the Integuments , &?c. nothing more than a mucous substance which may be dissolved by macerating it in water, while the cuticle and cutis preserve their tex- ture. The colour of the body is found to depend on the colour of this rete mucosum ; for in ne- groes it is observed to be perfectly black, whilst the true skin is of the ordinary colour. The blisters which raise the skin when burnt or scalded, have been supposed by some to be owing to a rarefaction of this mucus ; but they are more probably occasioned by an increased action of the vessels of the part, together with an afflux and effusion of the thinner parts of the blood* .3. Of the Cutis, or True Ski?i. The cutis is composed of fibres closely compacted together, as we may observe in lea- ther, which is the prepared skin of animals. These fibres form a thick net-work, which every where admits the filaments of nerves, and an infinite number of blood-vessels and lymphatics. The cutis, when the epidermis is taken off, is found to have, throughout its whole sur- face, innumerable papillae, which appear like very minute granulations, and seem to be cal- culated to receive the impressions of the touch, being the most easily observed where the sense of feeling is the most delicate, as in the palms of the hands and on the fingers. X 162 Of the Integuments , &c. These papillae are supposed by many ana- tomical writers to be continuations of the pul- py substance of nerves, whose coats have ter- minated in the cellular texture of the skin. The great sensibility of these papillae evi- dently proves them to be exceedingly nervous ; but surely the nervous fibre llae of the skin are pf themselves scarcely equal to the formation of these papillae, and it seems to be more pro- bable that they are formed like the rest of the cutis. These papillae being described, the uses of the epidermis and the reticulum mucosum will be more easily understood ; the latter serving to keep them constantly moist, while the for- mer protects them from the external air, and modifies their too great sensibility. 4. Of the Glands of the Skin. In different parts of the body we meet, within the substance of the skin, with certain glands or follicles, which discharge a fat and oily humour that serves to lubricate and soft- en the skin. When the fluid they secrete has acquired a certain degree of thickness, it approaches to the colour and consistence of suet ; and from this appearance they have de- rived their name of sebaceous glands. They are found in the greatest number in the nose, ear, nipple, axilla, groin, scrotum, vagina,, and prepuce. Besides these sebaceous glands, we read, in anatomical books, of others that are de- Of the Integuments , &c. 163 scribed as small spherical bodies placed in all parts of the skin, in much greater abundance than those just now mentioned, and named mi- liary, from their supposed resemblance to mil- let-seed. Steno, who first described these glands, and Malpighi, Ruysch, Verheyen, Windslow, and others, who have adopted his opinions on this subject, speak of them as hav- ing excretory ducts, that open on the surface of the cuticle, and distil the sweat and mat- ter of insensible perspiration ; and yet, not- withstanding the positive manner in which these pretended glands have been spoken of, we are now sufficiently convinced that their existence is altogether imaginary. 5. Of the Insensible Perspiration and Sweat. The matter of insensible perspiration, or in other words, the subtile vapour that is continu - ally exhaling from the surface of the body, is not secreted by any particular glands, but seems to be derived wholly from the extremities of the minute arteries that are everywhere dis- persed through the skin. These exhaling ves- sels are easily demonstrated in the dead sub- ject, by throwing water into the arteries ; for then small drops exude from all parts of the skin, and raise up the cuticle, the pores of which are closed by death ; and in the living subject, a looking-glass placed against the skin, is soon obscured by the vapour. Bidioo fancied he had discovered ducts leading from the cutis to 164 Of the Integuments , &c. the cuticle, and transmitting this fluid ; but in this he was mistaken. When the perspiration is by any means in- creased, and several drops that were insensi- ble when separate, are united together and con- densed by the external air, they form upon the skin small, but visible, drops called sweat* ** This particularly happens after much exercise, or whatever occasions an increased determin- ation of fluids to the surface of the body ; a greater quantity of perspirable matter being in such cases carried through the passages that are destined to convey it off. It has been disputed, indeed, whether the insensible perspiration and sweat are to be considered as one and the same excretion, dif- fering only in degree ; or whether they are two distinct excretions derived from different sources. In support of the latter opinion, it has been alleged, that the insensible perspi- ration is agreeable to nature, and essential to health, whereas sweat may be considered as a species of disease. But this argument proves nothing ; and it seems probable, that both the insensible vapour and the sweat are exhaled in a similar manner, though they differ in quantity, and probably in their qualities ; the former being more limpid, and seemingly less impregnated with salts than the latter : at any rate we may consider the skin as an emuncto- ry through which the redundant water, and * Lieuwenhoeck asserts that one drop of sweat is formed by the conflux of fifteen drops of perspirable vapour. .i Of the Integuments , &c. 165 sometimes the other more saline parts of the blood, are carried off. But the insensible per- spiration is not confined to the skin only — a great part of what we are constantly throwing off in this way is from the lungs. The quantity of fluid exhaled from the human body by this insensible perspiration is very considerable. Sanctorius* an Italian physician, who indefati- gably passed a great many years in a series of sta- tical experiments, demonstrated long ago what has been confirmed by later observations, that the quantity of vapour exhaled from the skin and from the surface of the lungs, amounts nearly to 5-8ths of the aliment we take in. So that if in the warm climate of Italy a person eats and drinks the quantity of eight pounds in the course of a day, five pounds of it will pass off by insensible perspiration, while three pounds only will be evacuated by stool, urine, saliva, &c. But in countries where the degree of cold is greater than in Italy, the quantity of perspired matter is less ; in some of the more northern climates, it being found not to equal the discharge by urine. It is likewise observ- * The inseTi'sible perspiration is sometimes distinguished by the narr.e of this physician, who was born in the territories of Venice, and was afterwards a professor in the university of Pa- dua. After estimating the aliment he took in, and the sensible secretions and discharges, he was enabled to ascertain with great accuracy the weight or quantity of insendble perspiration by means of a statical chair which he contrived for this purpose; and from his experiments, which were conducted with great industry and patience, he was led to determine what kinds of solid or li- quid aliment increased or diminished it. From these experi- ments he formed a system, which he published at Venice in 1614, in the form of aphorisms, under the title of 61 Ars de Medicina Statica.” 166 Of the Integuments , &c. ed to vary according to the season of the year, and according to the constitution, age, 4Slx, diseases, diet, exercise, passions, fkc. of different people. From what has been said on this subject, it will be easily conceived, that this evacuation cannot be either much increased or diminish- ed in quantity without affecting the health. The perspirable matter and the sweat are in some measure analogous to the urine, as ap- pears from their taste and saline nature.* And it is worthy of observation, that when either of these secretions is increased in quantity, the other is diminished ; so that they who per- spire the least, usually pass the greatest quan- tity of urine, and vice versa. 6. Of the Nails, The nails are of a compact texture, hard and transparent like horn. Their origin is still a subject of dispute. Malpighi supposed them to be formed by a continuation of the papillae of the skin : Ludwig, on the other hand, maintained, that they were composed of the extremities of blood-vessels and nerves ; both these opinions are now deservedly rejected. They seem to possess many properties in common with the cuticle ; like it they are nei- ther vascular nor sensible, and when the cuti- * Minute chrystals have been observed to shoot upon the clothes of men who work in glass-houses. Haller E/em. Phys. Of the Integuments , &c. 167 cle is separated from the true skin by macera- tion or other means, the nails come away with it. They appear to be composed of different layers, of unequal size, applied one over the other. Each layer seems to be formed of lon- gitudinal fibres. In each nail we may distinguish three parts, viz. the root, the body or middle, and the ex- tremity. The root is of a soft, thin, and white substance, terminating in the form of a cres- cent ; the epidermis adheres very strongly to this part ; the body of the nail is broader, red- der, and thicker, and the extremity is of still greater firmness. The nails increase from their roots, and not from their upper extremity. Their principal use is to cover and defend the ends of the fingers and toes from external injury. 7. Of the Hair. The hairs, which from their being general- ly known do not seem to require any definition, arise from distinct capsules or bulbs seated in the cellular membrane under the skin.* Some * Malpighi, and after him the celebrated Ruysch, supposed the hairs to be continuations of nerves, being of opinion that they originated from the papillae of the skin, which they consi- dered as nervous ; and as a corroborating proof of what they advanced, they argued the pain we feel in plucking them out ; but later anatomists seem to have rejected this doctrine and con- sider the hairs as particular bodies, notarising from the papillae (for in the parts where the papillae abound most there are no hairs,) but from bulbs or capsules, which are peculiar to them. 168 Of the Integuments , &c. of these bulbs inclose several hairs. They may be observed at the roots of the hairs which form the beard or whiskers of a cat. The hairs, like the nails, grow only from below by a regular propulsion from their root, where they receive their nourishment. Their bulbs, when viewed with a microscope, are found to be of various shapes, In the head and scrotum they are roundish ; in the eye- brows they are oval ; in the other parts of the body they are nearly of a cylindrical shape. Each bulb seems to consist of two membranes, between which there is a certain quantity of moisture. Within the bulb the hair separates into three or four fibrillae ; the bodies of the hairs, which are the parts without the skin, vary in softness and colour according to the difference of climate, age, or temperament of * Their general use in the body does not seem to be absolutely determined ; but hairs in par- ticular parts, as on the eye-brows and eye-lids, are destined for particular uses, which will be mentioned when those parts are described. 8. Of the Cellular Membrane and Fat. The cellular membrane is found to invest the most minute fibres we are able to trace ; so that by modern physiologists, it is very pro- * The hairs differ likewise from each other, and may not be improperly divided into two classes ; one of which may include the hair of the head, chin, pubes, and axillae ; and the other, the softer hairs, which are to be observed almost every where on the surface of the body. Of the Integuments , &c, 169 perly considered as the universal connecting medium of every part of the body. It is composed of an infinite number of mi- nute cells united together, and communicating With each other. The two diseases peculiar to this membrane are proofs of such a commu- nication ; for in the emphysema all its cells are filled with air, and in the anasarca they are universally distended with water. Besides these proofs of communication from disease, a fa- miliar instance of it may be observed among butchers, who usually puncture this membrane, and by inflating it with air add to the good ap- pearance of their meat. The cells of this membrane serve as re- servoirs to the oily part of the blood or Fat, which seems to be deposited in them, either by transudation through the coats of the ar- teries, that ramify through these cells, or by particular vessels, continued from the ends of arteries. These cells are not of a glandular structure, as Malpighi and others after him have supposed. The fat is absorbed and car- ried back into the system by the lymphatics. The great waste of it in many diseases, par- ticularly in the consumption, is a sufficient proof that such an absorption takes place. The fulness and size of the body are in a great measure proportioned to the quantity of fat contained in the cells of this membrane. In the living body it seems to be a fluid oil, which concretes after death. In graminivo- rous animals, it is found to be of a firmer con- sistence than in man. Y 170 Of the Muscles. The fat is not confined to the skin alone, being met with every where in the interstices of muscles, in the omentum, about the kid- neys, at the basis of the heart, in the orbits, &c. The chief uses of the fat seem to be to afford moisture to all the parts with which it is connected ; to facilitate the action of the muscles ; and to add to the beauty of the body, by making it every where smooth and equal. Sect. II. Of the Muscles. The muscles are the organs of motion. The parts that are usually included under this name consist of distinct portions of flesh, suscepti- ble of contraction and relaxation ; the motions of which in a natural and healthy state, are subject to the will, and for this reason they are called voluntary muscles. But besides these, there are other parts of the body that owe their power of contraction to their mus- cular fibres ; thus the heart is of a muscular texture, forming what is called a hollow mus- cle ; and the urinary bladder, stomach, intes- tines, 8tc. are enabled to act upon their con- tents, merely because they are provided with muscular fibres. These are called involuntary muscles, because their motions are not depen- dent on the will. The muscles of respiration, being in some measure influenced by the will, are said to have a mixed motion. Of the Muscles. 171 The names by which the voluntary muscles are distinguished, are founded on their size, figure, situation, use, or the arrangement of their fibres, or their origin and insertion. But besides these particular distinctions, there are certain general ones that require to be noticed. Thus, if the fibres of a muscle are placed parallel to each other in a straight direction, they form whftt are styled a rectilinear muscle ; if the fibres cross and intersect each other, they constitute a compound muscle ; a radiated one, if the fibres are disposed in the manner of rays; or a pcnniform muscle, if, like the plume of a pen, they are placed obliquely with re- spect to the tendon. Muscles that act in opposition to each other, are called antagonists ; thus every extensor muscle has a flexor for its antagonist, and vice versa . Muscles that concur in the same ac- tion are styled congeneres. The muscles being attached to the bones, the latter may be considered as levers that are moved in different directions by the contrac- tion of those organs. The end of a muscle which adheres to the most fixed part is usually called the origin , and that which adheres to the more moveable part, the insertion , of the muscle. In every muscle we may distinguish two kinds of fibres ; the one soft, of a red colour, sensible and irritable, called fleshy fibres ; the other of a firmer texture, of a white glisten- ing colour, insensible, without irritability or the power of contracting, and named tendinous 172 Of the Muscles. fibres. They are occasionally intermixed ; but the fleshy fibres generally prevail in the belly or middle part of a muscle, and the tendi- nous ones in the extremities. If these tendi- nous fibres are formed into a round slender chord, they form what is called the tendon of the muscle ; on the other hand, if they are spread into a broad flat surface, the extremity of the muscle is styled aponeurosis. The tendons of many muscles, especially when they are long and exposed to pressure or friction in the grooves formed for them in the bones, are surrounded by a tendinous sheath or fascia, in which we sometimes find a small mucous sac or bursa mucosa , which obviates any inconvenience from friction. Sometimes we find whole muscles, and even several mus- cles, covered by a fascia of the same kind, that affords origin to many of their fibres, dip- ping down between them, adhering to the ridges of bones, and thus preventing them from swelling too much when in action. The most remarkable instance of such a covering is the fascia lata of the thigh. Each muscle is inclosed by a thin covering of cellular membrane, which has been some- times improperly considered as peculiar to the muscles, and described under the name of pro- pria membrana musculosa. This cellular co- vering dips down into the substance of the muscle, connecting and surrounding the most minute fibres we are able to demonstrate, and affording a support to their vessels and nerves. Lieuwenhoeck fancied he had discovered, by Of the Muscles . 17 $ means of his microscope, the ultimate division of a muscle, and that he could point out the sim- ple fibre, which appeared to him to be an hun- dred times less than a hair ; but he was after- wards convinced how much he was mistaken on this subject, and candidly acknowledged, that what he had taken for a simple fibre was in fact a bundle of fibres. It is easy to observe several of these fasci- culi or bundles in a piece of beef, in which, from the coarseness of its texture, they are very evident. The red colour which so particularly distin- guishes the muscular or fleshy parts of ani- mals, is owing to an infinite number of blood- vessels that are dispersed through their sub- stance. When we macerate the fibres of a muscle in water, it becomes of a white colour like all other parts of the body divested of their blood. The blood-vessels are accompa- nied by nerves, and they are both distributed in such abundance to these parts, that in endea- vouring to trace the course of the blood-ves- sels in a muscle, it would appear to be formed altogether by their ramifications ; and in an attempt to follow the branches of its nerves, they would be found to be equal in propor- tion. If a muscle is pricked or irritated, it im- mediately contracts. This is called its irrita- ble principle ; and this irritability is to be con- sidered as the characteristic of muscular fibres, and may serve to prove their existence in parts that are too minute to be examined by the eye. 174 Of the Muscles. This power, which disposes the muscles to contract when stimulated, independent of the will, is supposed to be inherent in them ; and is therefore named vis insita. This property is not to be confounded with elasticity, which the membranes and other parts of the body possess in a greater or less degree in common with the muscles ; nor with sensibility, for the heart, though the most irritable, seems to be the least sensible of any of the muscular parts of the body. After a muscular fibre has contracted, it soon returns to a state of relaxation, till it is excited afresh, and then it contracts and re- laxes again. We may likewise produce such a contraction, by irritating the nerve leading to a muscle, although the nerve itself is not affected. This principle is found to be greater in small than in large, and in young than in old, animals. In the voluntary muscles these effects of con- traction and relaxation of the fleshy fibres are produced in obedience to the will, by what may be called the vis nervosa , a property that is tiot to be confounded with the vis insita. As the existence of a vis insita different from a vis nervea , was the doctrine taught by Doctor Haller in his JElem. Phys. but is at present called in question by several, particularly Doc- tor Monro, we think it necessary to give a few objections, as stated in his Observations on the Nervous System : Of the Muscles. 175 The chief experiment (says the Doctor) which seems to have led Dr. Haller to this opinion, is the well known one, that the heart and other muscles, after being detached from the brain, continue to act spontaneously, or by stimuli may be roused into action for a con- siderable length of time ; and when it cannot be alleged, says Dr. Haller, that the nervous fluid is by the mind, or otherwise, impelled into the muscle. “ That in this instance, we cannot compre- hend by what power the nervous fluid or ener- gy can be put in motion, must perhaps be granted: But has Dr. Haller given a better explanation of the manner in which his sup- posed vis insita becomes active ? “ If it be as difficult to point out the cause of the action of the vis insita as that of the action of the vis nervea, the admission of that new power, instead of relieving, would add to our perplexity. “We should then have admitted, that two causes of a different nature were capable of producing exactly the same effect; which is not in general agreeable to the laws of nature. “We should find other consequences arise from such an hypothesis, which tend to weak- en the credibility of it. For instance, if in a sound animal the vis nervea alone produces the contraction of the muscles, we will ask what purpose the vis insita serves ? If both operate, are we to suppose that the vis nervea, impelled by the mind or living principle, gives the order, which the vis insita executes, and 176 Of the Muscles. that the nerves are the internuntii ; and so ad- mit two wise agents employed in every the most simple action ? But instead of speculating far- ther, let us learn the effect of experiments, and endeavour from these to draw plain conclu- sions. “ 1. When I poured a solution of opium in water under the skin of the leg of a frog, the muscles, to the surface of which it was appli- ed, were very soon deprived of the power of contraction. In like manner, when I poured this solution into the cavity of the heart, by opening the vena cava, the heart was almost instantly deprived of its power of motion, whe- ther the experiment was performed on it fixed in its place, or cut out of the body. u 2. I opened the thorax of a living frog; and then tied or cut its aorta, so as to put a stop to the circulation of its blood. “ I then opened the vena cava, and poured the solution of opium into the heart ; and found, not only that this organ was instantly deprived of its powers of action, but that in a few minutes the most distant muscles of the limbs were extremely weakened. Yet this weakness was not owing to the want of circu- lation, for the frog could jump about for more than an hour after the heart was cut out. “ In the first of these two experiments, we observed the supposed vis insita destroyed by the opium; in the latter, the vis nervea; for it is evident that the limbs were affected by the sympathy of the brain, and of the nervous Of the Muscles . 177 system in general, with the nerves of the heart. 3. When the nerve of any muscle is first divided by a transverse section, and then burnt with a hot iron, or punctured with a nee- dle, the muscle in which it terminates con- tracts violently, exactly in the same manner as when the irritation is applied to the fibres of the muscle. But when the hot iron, or nee- dle, is confined to the nerve, Dr. Haller him- self must have admitted, that the vis nervea, and not the vis insita, was excited. But here I would ask two questions. “ First, Whether we do not as well under- stand how the vis nervea is excited when irri- tation is applied to the muscle as when it is ap- plied to the trunk of the nerve, the impelling power of the mind seeming to be equally wanting in both cases ? ^ Secondly, If it appears that irritation ap- plied to the trunk of a nerve excites the vis nervea, why should we doubt that it can equal- ly well excite it when applied to the small and very sensible branches and terminations of the nerve in the muscle ? “ As, therefore, it appears that the suppos- ed vis insita is destroyed or excited by the same means as the vis nervea ; nay, that when, by the application of opium to the heart of a frog, after the aorta is cut and the circulation interrupted, we have destroyed the vis insita, the vis nervea is so much extinguished, that the animal cannot act with the distant muscles Z 178 Of the Muscles . of the limb; and that these afterward grow very torpid, or lose mucu of their supposed vis insita ; it seems clearly to follow, that there is no just ground for supposing that any other principle produces the contraction of a mus- cle.” The vis nervosa , or operation of the mind, if we may so call it, by which a muscle is brought into contraction, is not inherent in the muscle like the vis insita ; neither is it perpe- tual, like this latter property. After long con- tinued or violent exercise, for example, the vo- luntary muscles become painful, and at length incapable of further action ; whereas the heart and other involuntary muscles, the motions of which depend solely on the vis insita , continue through life in a constant state of action, with- out any inconvenience or waste of this inherent principle. The action of the vis nervosa on the volun- tary muscles, constitutes what is called mus- cular motion ; a subject that has given rise to a variety of hypotheses, many of them inge- nious, but none of them satisfactory. Borelli and some others have undertaken to explain the cause of contraction, by suppos- ing that every muscular fibre forms as it were a chain of very minute bladders, while the nerves which are distributed through the mus- cle, bring with them a supply of animal spi- rits, which at our will fill these bladders, and by increasing their diameter in width, shorten them, and of course the whole fibre. Of the Muscles. 179 Borelli supposes these bladders to be of a rhomboidal shape ; Bernouilli on the other hand contends that they are oval. Our coun- tryman, Cowper, fancied he had filled them witn mercury ; the cause of this mistake was probably owing to the mercury’s insinuating itself into some of the lymphatic vessels. The late ingenious Mr. Elliot undertook to account for the phenomena of muscular motion on prin- ciples very different from those just now men- tioned. He supposed that a dephlogisticated state of the blood is requisite for muscular ac- tion, and that a communication of phlogiston to the blood is a necessary effect of such action. We know that the muscular fibre is shorten- ed, and that the muscle itself swells when in action ; but how these phenomena are produc- ed, we are unable to determine. We likewise know that the nerves are essential to muscu- lar motion ; for upon dividing or making a li- gature round the nerve leading to a muscle, the latter becomes incapable of motion. A li- gature made on the artery of a muscle pro- duces a similar effect; a proof this, that a re- gular supply of blood is also equally necessa- ry to muscular motion. The cause of palsy is usually not to be sought for in the muscle affected, but in the nerve leading to that mus- cle, or in that part of the brain or spinal mar- row from which the nerve derives its origin. 180 Of the Muscles. Of the particular Muscles. As the enumeration and description of the particular muscles must be dry and unenter- taining to the generality of readers, yet can- not be altogether omitted in a work of this nature, it appeared eligible to throw this part of the subject into the form of a table ; in which the name, origin, insertion, and princi- pal use of each muscle, will be found describ- ed in few words, and occasionally its etymolo- gy when it is of Greek derivation or difficult to be understood. A TABLE of the MUSCLES, arranged according to their Situation. Of the Muscles. 181 a c ° u C- . “ O . > c 05 ^ B u S « .--g o £ - *- •rj •G O A> o "* "rt "0 O ^3 -« o Ou. V lay o u ’•“* QJ ^ bO-5 g .E ° ° ’§°e =£ J- -2 t> -o -C oyS , h0 g ^ s o *53 w -Q -C b o i-* 3 v£ S SH o a T3 2£ ^ « « a •j=« U | H Ei> E cq S — i 5J 5>*'^ *■$ .C <4-1 O a 15 6 £ 3 cS tJ bo *-• rt u 3 tf J3 <44 o CO S S3 2 w’S .. S p H £ •3 (0.2 . bJD.tJ g -a a, o *5 *G rt 2 o .u <4-« O a 3 cS 4- Q.-r a O a ^ a ° <*• ^2 4-> O lH s A ' •> .B c o ;s g u A3 a C3 6 u 'S ► •S 2 cs o I i g: u I* Qa c5 to a ■ a s O ^3 u^3 182 Of the Muscles. G rC to O b Pm O O b 3 P- CO *-* ■“O CD £■2 03 CD ’£3 y ^ P QJ o c * a5 u G "G rG a, 5 g u rt ^ _P P- <— ■ "O fj s s s 3 fc: 3 „ W 4_» _» •ti h » O W G G G • 8- £•§ «j 3 “ > P D- ? *"* -- ^ O 00 "d , to rr 1 a « o, - O 3 ^ 33 U Pi!< c o P 4 ., O Cm * O "O bO o -a 33 rt k*** 0 nt P 3 o 3 CO rt w o SS 2 -S c re Oh CL, . Oh u 3 n 8 * c — < m o C 33 S jy oj *-H. cj P- . * 2 g 1 Is CL) O G rG 03 Pm CD rj *0 Pm rt G H >£ ^ • S° o 33 3, 33 O Cm D §6 fa H- W Q CD r! W) S T 3 O U pH <-M 1) O 33 E ~ O t« *J (U (3 O 33 _ «-* O u 0 3 0 g£ O 33 33 a o *-• o .t; . w p-e E o bO t-c %'S. o CL, pgg rtf n j r" OwSlO Ph PH 33 O 33 g'So Jm O. s o P o n t s 7- ^ n . rt *_» CD n . rj u ^m +3 O G 4 - G 0 O- G w o OP S J-. PH *-rt o ^ rt 73 rJ "O ° X o3 Cl o c c L. u ci CL G G O CD CL CD ^ i- . LG 4_» 1-2 l= a h ° * ►* 184 Of the Muscles. u o ^ S b p - 2 § « ^ do o- * TJ P P d CD • — ! lO H o CD P d D d,_G > VI e.*H P to dJ P *5 O H 4j "d rU c p hj b cx 8 . E v£* 2 5 ^ d rt £ 4 G d o £ e -S, « s § o a g u ° g 73 y 33 o'S^'S § h H to d CD CD G o ro y pj .« d •S? o § -£ O CD « 33 • CJ ?* O - »-< CD d P C i _ rP P 4 _> b p . P rj p *±3 SH» _ o P k -g 3 c S o o CD 6 -•S' PM p 33 O *-» 33 P d O J^.E m '.§°' G t. ^ O s| s d CO d ° £ C C > C G o S » c a p £ c d , CD co P B o to . >. In N o o to . tp 1 G N o G « T3 G 6. Depressor labii su- From the os maxill. Into the root of the To draw the ala nasi periosis, alasque super, immediately ala nasi and upper andupperlipdown- nasi, above the gums of lip. ■wards, the dentes incisores. Of the Muscles. o ° u 33 4J rC 3 o & 6 • g Jg -a h '3 c. 33 C o * I- -Tl w OJ ^73 § 2 g G -i rS 5 4-» £ g £ £ rt O d d 3 I S-. 4J d "2 G v+H G o CL) G -2 ’r5 1/5 d LO q rtf C3 LO G CL fcO c3 . *2 ^ o 2 £ c 33 3 ^ C d 4* .JL G ° u Jh QJ ^ E'S- iO P u O O is * tfp ~ bJD ^ c d ■ -I | u v r3 o w> -T3 £ C 3 3 W> “ cl, 3 u ^ - *-J G •s ;s 4-» ri G J-. eo O H 3 O o A a (*) This muscle is in a great measure if not wholly, formed by the buccinator, rygomatici, depre38ore9, and other muscles that move the lips. Its fibres surround the mouth like a ring. 186 Of the Muscles. !* O to g'H ^ % D a. > 3 O 6 ^ o CO kT CO ^ Oj rG « ^ ^ £ T 3 0.3 S JS 3 * o 1 O £ co ^ 1 ) CO O -£ Cl, ° a, 3 CO a.^c « TJ w 'c jS -g 3 -s ? «L) CO r£ 4J (_> o T 3 f? r 3 nj - | 2 u rt — a O -73 rg £ oi .^0 O *e-E ft b 0 c S £ o o ji a j u rC 03 £ ^ o ••' +-c nd c C t: * C 3 CU W o £ .CJ c- a, CO r d to 2 o^ a.^ * g ~ T SJ'o £ co [g gj^ manduco, “ to eat.” Name. Origin. Insertion. JJ se- Pterygoideus in- From the inner sur- Into the lower jaw To raise the lower ternus. face of the outer on its inner side jaw and draw it a wing of the ptery- and near its angle. little to one side, goid process of the Of the Muscles . 187 fe o ■s -*- 1 c3 ’-d « C 13 « P « o "H 6 g -a ,-C ^ c > O O _C ■Q 13 CL, « « C » P o 43 ' u vl r- i-< 1 43 CL, ^ ^ CL, ■■ O 1 X "o u §3 Jc P^-S 13 GJ C C <-M o £ * 6 s O ^ dJ T3 D-t'Zj C ^ ^ ^ O co CL) . ^ GJ 3J t| ^ ^ L ^ t/1 T o* C3 S 2 I 6 Lh rs *5 bO . r*-* CO »- P £ e pn h rt H3 ^2 GJ <-> -c c 4-J C ( ^ ' 'u- S ^ ia PP ens the muscle acts singly. When both act, the jaw is brought horizontally forwards. (f; This broad and thin muscular expansion, which is situated immediately under the common integuments, is by Winslow named muscu us cutaneus. Ga4en gave it the name of wx.r v C ’3 10 g- 0-2 2 « b T3 *£ OJ H Ph ?« h £ tJ “ Oh' £ ■ o c « _rt M3 O Ph 0,<£ Ph V ... D O *5 6 X G o> G n3 ’■O s- £ rG o ^3 - to o ^3 9 ^3! T3 . -Q s| th or os 2 § "X3 ^ ^ « 2 * J bJj’~J fe ° o ^ to rz3 to • — ■ *_» CO *2-8 PT* JS.-2 - o 72 i 2 * t) 0 O 2" > ^3 r—. ^ ^ bS # r- - ^ tO 1*1 I O U * J-. I " 'o ^ •* 3 *s ►, i "5 rt "a w min H ■3 -? b 8 S » Cfi "3 U fi, ^ l> " 3 js ^ bJO 2 33 y3 JZ ^ 3 C u rt O £> S3 C3 o °--§ u . 75 £ O o ? > ~1 r^3 •5 o ^ 3 ^ d Ji-S - s -<£ CO _ CJ CO s a *3 lw i o a bo ; s n t; ^ oS « U £ §-5 J P« lu, 3 s s ° ,- 0,3 ^ 0,3 3 UM ~ 4-> . -C V2 g Z> rt '6 a — 33 g> Ult, “3 C O rt o DIU4J (-] -^ Cti • c ^ O oi ^3 Ti {< *o ‘8 o, g >> c« ^3 £ .2 ^ O to O }-. PM to ; o 5 ° ! "f u ^ • ?! N U £ j 4> £* 3 rt to ^ qj 5 o h ^ q »-i 3 *o O CS CO •s 6 rs *5 •g 6 S3 CO 12 *3 j-i p-. V 1B9 tilage. the thyroi.l for- wards and down- wards. 190 Of the Muscles. v> 6-2 ui rG ^ r i £ o a c E-* a. g C QJ wC CTJ -5 o 43 C *C^ ^ o^o •■G n> II Co ^ Q-i O a .i rC »■ ^ t° -*3 S - £ fl v .t- f -° • rt -> —rH G . G n *> ao 2 o XI ■ Sfl o O V* w ' * 4-> CO c* -* .G 6 ^ - o »-G 6 G >-. eS ■"O & s> -»-> C rt co £ <1> 5 T? (*) From Sis yw? (biventer,) because it has two fleshy bellies with a middle tendon. Thistendon passes through the stylo-hyoideus. (t) In some subjects we meet with another muscle, which from its having nearly the same origin, insertion, and use as this, has bee« named stylo-hyoideus alter. ($) So named from its arising near the dentes molares (nur.ai,) and its being inserted into the os hyoides. (§) From yivoow, mentum, the “ chin-” Of the Muscles. 191 a “ bcZ g^ +-) QJ C/3 j: ^ 4J C qj ‘C § 0 e a o *~ r* S.g £°- ? a QJ -r^ ~ rt > £ G C ^ c -a w c h o rt '■a > a to a |.s QJ .ti (-» a 5 OJ 2 t; -a J2 S T3 J -3 £ c/3 r> O « > bO-rj C a 2 g QJ C/3 »2 cj > £ O a g ~ G> ' QJ • > * . g G to »~ ' > a) o £7S «* s J- n. : j-i rr< . >-» QJ G ’"O — C/3 ^ ^ ^ ^ *" a 7. o a - 8s! 1 1 1 1 K~ ^ 3 Is 5 ■5 h u’O o 73 a 3 t>, O U Vi V >> 3 -p a S 60 u g^ o 0> QJ G 60 »-8~ ° •S .§o r2 *C/3 G * 60 G O QJ 1/ rS ^ QJ 6 a O *3 a o g ,i P QJ QJ G -5 to 4J G o o G . — o ~rj c/j ^ G a -H to a- o “ rn a g p- o a o as * -= as a a a £ >J5 rs G QJ ^ O C >-« a, "0 QJ o QJ QJ o jg G ^ QJ <4H riy ° C/3 ,-, ~ O T3 Pm Q-i— « Qin otj or « §*' JO rt * V3 ^ Qh- G QJ i- *, ^ O *-> d • — O 3 D ^ 4-1 P-t ±J I e g S c o 1/5 ^ as H'"? s Z 1 IN ^ a a a a- a a. QJ QJ •■“ G on G po ^ 5— ^ * O *Q '~r-\ It f. s c ? ; " ■ G QJ .5 to QJ rG > QJ 2 ». i O 13 •S '5 e’H’ - 5 rt d a s C3 Cm 'J3 C/3 O Tj > 6 03 QJ QJ ,G _Z2 j— * QJ rG -i-> QJ G G 60 ' O X5 G HH QJ rt "O G G O C/3 G a; H . r-l QJ ^ U _Q *2 3 i-> *~^ +-» G Q+h G ^ S g a ^ o a, u w G C/3 G w S To O T .2 ’5 To 6 G 60 QJ G O ffi VO c/3 o "So •6 00 o 60 P a JD LO 6\ G X o CG s p u 6 ’ 192 Of the Muscles. x .Z c G 5. S aj # G< — to to 3 O o G to -O *-* J-. G 31 & 3 3* o. y CS Ph 11 ’’cij G H .72 •-“-■o u? w O C C « -p r; ^ “ j! 7 h v3 J_, ^ cl rr 3 ™ > ' ° E| S D te ,31 o P u s o f -3 TP nS TS ^ C O 3 -a « US ~ u rt u-. bJO , o re £ E \3 Gh G $-. O, CL, G P U fJ t> (U G •2 ^ 2 "o a j3 S' 1 ^ *o c CV * G ^ £ S' a , to h o .^o u, O .C. O ^G G *- J 4-» C L- CtJ Ctf ’P Ch^C ^ o o <£ G 1/5 J r« 3 3 O . i c W o J= ±3 g * u p -2 H re c o ■ * Ti _L ^ 3 C ^ 3 , - <« ^ « 5 5 3 D * 3 - 3, » G IL & < cs a. > u ,-1 3 '■*- £-5 3 2 3 o 23 > c 5 1) re ^ -. a, 6 3 m &® •3 s 13 .5 35 a ■3 •3 rt C re p 5 -■O 3 ■3 = = d, ^ ^ M ri rt c+H MrQ O O I-TJ a> ° p J=> < (L) * g 3 S o ,P. ^ . p aj rt : c LG ° G. ti G W r- ^-> G to (-W W 4-* J G 0 O 01 JD D G ja ° ° w S O ^ .2 G-, a> *g ^ H'SH ^ ko,— > Of the Muscles. 19 ; •5 U s to G G v C > # W * -•c'S -5^ ^ gtJ-8 t g g »* £ * ^ S £* o t-M ci o ' u C ci d) o O . ft q >> s 3 6 ^ PJ y W g la-S Si 3 X J5 w OJ ^ 3”° uJ s *3 «j £ ^ ~ ja rt "0 *3 J !§ a 2 * 6 o 3 H O . "T3 X *rj G G ^ *T3 rG -*- T3 *•» «5 * be ^ § £* o ^ £ S .£ £ bo §« «j f*'* 14 0 ) ^ CO ^G O Qh « w » r< •5 % 2 £ u C a o « " ••" 1- -C C co .tT +J -m «U nJ rG . a* s- .2 C > A, n " ‘4H ^ O £ u ’S o U 'O .H ^ C -C " 3 - ’ — * *. C-W co “ O .2 £ > g . i- — V G * a, o o c .52 {_) bO eb • !C o "So Oh o o H Hbo 4J ■s a , *- ti 10 ba ■5 : B £ "O >2 ^3 u T5 •?: rt O H 1> (U 33 bO PS . < - w ~ ' 2 —• v> ?3 ^3 ’Z « t>. C ^ rt ” o n Mi! ^ h •- b oj £ £ 01 bo ■ M rr> I & 2 a £ 'E W 2 M II +J OJ d u w Jm Ph rd « • s F * 2 2 ■£ O C cl, ti a*, n - * o % o O U dd t OS r-H G tsa.rt'SiScSS u r-> r- dd <-> .rs-s « «> ^ 25 ■23 _>■ ^ "33 to ci ^."2 •M O |-c 2 u Ph T3 *5 G W . %>£ ?3 ^ o .2 * g — - u g ci !>> TJ O *5 cj o ‘5 cl u* S' £ fa <-> 1) "23 £ •£ O S *C W W +J .2 ^ *CO CTj G Xi dd dd ■a-s S Uh o o b bo ci oj a, rp rs ’c c W £r’5 u aS co^S « dd O dd i C'O 1 ^ ° *5 u c G G C ^ U O 2 , P-. PH .’S a § 2 . § £ i s < tz c o l > ci S Ou C ^ P. u "6 ^ _ £ >> ^3 3 Pb >- I) 3 ^3 3 H b* £^ « 8 O rrt 03 M H >> . JC v> ” 5) i> • A O ’ 3 s cartilage laterally. Thyreo-epiglotti- From the thyroid car- Into the side of the To pull the epiglot- Of the Muscles. C £ o "0 O J- "3 ns "O i-i G 2 4-> 0> V) '—I pS S •si "3 *n ■d QJ ^ *to O bjQ CL, Cm O S.E f C L- Cm .C TU lj r> V5 CO QJ *Z3 O ’H* S-'S o nS d w > L U (U 5 w rt Oh >• -J CC *> L L, GJ L* « Mg’? k 2o5 Li CJ CL to CL,* c, ^ c o *cc ni QJ L, *n cd J-. a, w > 3 2 w H ft. QJ 3 > en >- o 1/3 4-1 g « " \ (*) When both muscles act, the neck is drawn directly forwards. . Obliquus externus. From the lower edges Into the linea alba To compress and fup- of the eight infe- (*),ossapubis(f), port the viscera, rior ribs, near their and spine of the assistin evacuating Of the Muscles. 19-7 (U W H r* n •g-c 2 3 u u "T3 -C o ^ ’Xj c -9 o o bJD ai P p d - *“• -Q « S e,H r-J WJ to O ,_Q ^ T~1 — c3 *“* } ~ 1 & . ! J- *+H ' Ja o C SJ u ^ H c a r-H P* P-t 3 CJ .£f IS o S 8 u ■ J= ■5-d >> u « s .2 6 rQ £ W) 03 a ° -a t g 03 <3 £ 2 rt q Pi w ° ^ o v u *5 ^ ^cS •o 'S S j“ „ JJ "3 3 o U +J bO u ^ .5 S-c: ^ J3 -Td Cue C G a g o » G £ G <2 ’G > rs .y o 4-> 3 a 2 o3 G C *£ I -§ rt ^cj -o id QJ W T? " bo a v a t; D-. t, o o u q £ J3 CL, *- S n i g°a > § s ! 7g ! ^r 1 II h 6 *tS TJ O -S U oJ (O 'O C t« 3 -fi to 13 ll P-.T3 g 2 §2 P o c <- ■s-1 S,-Q , CL-d •*• q . 3 « >> § r'H l, - G .''rrl 3 5 ca „•» V. ■- cu « >■ o P o ,n PT> v G U w > « v 3 O u £ ”2 2 ^ -5 S? w ^ u .s c U ■|n *H R ^ ■& ,<3 5 (U a « 43 15 s ^ °-ES « M u -3 g 3 T3 U f • 2 OJ PS ■£ i -3 ~ ^ cr S £ ri Ji' * O cj fcuQ . _!< £ (U Cl, Cl, 3 - L. , 3 O "" “ v <4? f» cl: U i ^ c J3 « c3 *-' b OJ CTJ bJD ■ -a ° 23 -£ e u "Z 'C X S-, re - t/5 . u -5 .-£. o CJ LO C, 3= u V) IU , U T) J, r 33 C h 0 C S 3 ■*-’ g "O c< '5,-0 L3 “ “ O C •- ^ o; o; (L> o_-P * rC rs U* ■*-* *“* 3 . ^ c cS s 3 s^, C u u 3; « Uh J 3 •- O h 33 u .a O S 6 j£ ' o- S" re 3 _ 3 bo‘ 5 . E o 33 33 rt it c !t O nr •v •3 2 « 5 B 3 M u 33 .3 ^ c "34 ps s 09 •»> ^ L L ~ -H 32 -rt 3 c 2^ © j Sfl .s-s " JJ-S r ^ l4H n3 3 3 > aj u* ^ s g. >? i *> u •72 3 .2 2 D lH (L, r y 0 ^ 4- 5 5 O ^ a c ^ G a> h-H -c a s Name. Origin. Insertion. Use. 5 . Pyramidalis (*). From the anterior Into the linea alba To affift the lower and upper part of and inner edge of portion of the rec- the pubis. the rectus, com- tus. monly about two 1 99 Of the Muscles. £ 3 - S V- a CD o p .j.'T) O ^ •Tj c CO u « S C O to s~ "2 0 3 “11 -S i - T3 O > ,o > s S 6 M | 0 ^ t- > o to | 'I .£ a* .£ o T3 gj S-3 £ C -t- O tO VO TD a; c n „ 01 _ T 2 C CL J. a, v 53 w "C O 0 -H J, <0 _c3 u J= > £ CO £ t/i 31 11 QJ S s S g:s » « U o .2 i> H H pass towards the axilla in a folding manner, and with those of the latissimus dorsi form the arm-pit- Name. Origin. Insertion. Xjst. . Pectoralis minor From the upper edges Intothe coracoid pro- To move the scapu- (*). of the 3 d, 4 th, and cess of the sea- la forwards and 5 th ribs. pula. downwards, or to elevate the ribs. 200 Of the Muscles nj CL t; 3 os S Oh 0 oi CJ CO r 2 CO *n 0 ) (D C »-C 00 os T3 *-* bo b •g ^ 0 ^ 0 move wards wards. Eh Eh GJ *4H tO O iJ OJ Uh ^ U O *G G ^ QJ CO £h r— CL> O . CO rt rt Oh ^ X o-_o .b p .-H V! ID ^ ^ 0 G " O ^3 O 2 c re d J, to 4-> w _ u 6 .2 o u c bO aJ O *-» (L> tO t/J rH . > C O H l- OJ 1 o PhU o fcuO ■ T) -9 a, ° S Oi bO • -a :9 a . w Qh_q & Oh O Oh * — 1 J 3 2 rC P^. c3 s W3 G 5 h Oh J .2 ^ Qhl c o u 5 S *H o a ►H £ , ' QJ l-S 0 ba 4-> 3 Is u o w o D ut « « A rO U H G 4> Hi *d *c •£ £, > *+* o U ^ to CO 5 > QJ -M O c3 Js -g ‘T >> M ^ O fl, . *rt « « 4 -J Ph ^ CJ o 1/3 ”* V v V r* w liG’S fclsl S Ph g • •L *1 G b -a ^ t! .£*•£: rt £ o S « ^ S" c 1 s s ^ .2 -C .S G ^ 4-. -*-» ^3 L> . O > HJ W OP 3 to ^3 ^ O Q Eg ! ” 3 JS :l£s S s ^ •g z § ; ^ *£ ^ W G ^ C (U Name. Origin. Insertion. Use. 5. Sterno-costales(* ). From the cartilagoen- Into the cartilages of To depress the canU siformis, and low- the 2d, 3d, 4th, lages of the ribs, er and middle part 5th, and 6th ribs, of the sternum. Of the Muscles. 201 P Oh c: > © s o o o v>- 03 CL) 1 — 1 O 7j flj ,1; S ^ ^ -ri rt r-P G U •S ‘S 0 * « ia S .2” S ^ p, S o o 3 C ' 5 h O . JJ ' ■ « £ £ a, 4J 1/5 P J2 ^ P S ,2 E3 S So o 6 fey 3 •p b -a bp *0 i! cj >- c *h CO .3 3 Gl n g GJ o G > s®. * O f* ; « 1 SS o lu'x s GJ •S’S . 3 c w In O ^ *G C | , •“< rt ^ 5 US P ^ bO t-. qj -Q u G >-2-g :.S J ■S E G u ttj W w G u • G5 ^ . ^rz; „ zz <-> s .« C ^ ^ .5 a u: « S'* S § * I « c'C ^ cT 3 r> O u qj G co j. §,-5 2^ ==£ .« 7 . *2 w G > QJ GZ •o “ a - 3 ^ E CL, C C o'; SS a « 0 u "g -o . E »-. U (U ^ P -G > .a « G ~ -- x o a * C J S « ^ S S w £ G <£; CJ 2 ^ -T 3 .S -o a « s » "Staios co G 3 G 5/5 G G3 , P G -3 Ti -G o C4H ^ «-• * ) .S-al3^'° Mg®! u cc 3!;S.5 c:S *G > u '3 C v ^ ,. . b ^ r T) £ H ^ "G — ! -G O lG «G3 ** CD A 0 H c G £3 2^ T3 o c -2 w u c UJ « o u£ o o ?■ H g i-w +-* <0 T3 *-• ■*5 o .G »=• 8 „ c bo r» 2 J5 £ .£ W bB ‘C O o . cu .a O rG OO u rt .*2 -G I from its refemblance to a monk’s hood 202 Of the Muscles. J* 3 - O , rt ° -n W ri U 3 •S “ T3 . £ >3 « % g's a frs o 2 * •s e3 -a oS • . r— 1 £ 3 rS cl, ^ ctS o ° • c/5 Tl c/3 3 "a c .- ^ S 'l fl ° c? g* JJ £ £ s X O iS 4J J-> -o O aJ ’~~i JD O s-g S S3 . S « C b0 3 b£> O V CD £ g ■2-5 Lx ^ * I C/5 JS iG G .^x O C/5 G .*tt ° ’5. M ° JJ U rG G £ « ^ p, ° ^ Sd «■> -a a -t e <2 O m3 C/5 J- o OJ al -M O T3 c/) q .Sig; W O r-< *+3 Ch T3 0, .5 ® 2 *2u fl-2 « g rtSj3'° a? V .£?■ >• c *-> i> c •v u r rt S f» O « <-w • o IB *£3 £ *3 *3 .Q S o g: P^4 o rt U cfl CO o Ox -3 o * u -i; 05 C> 6 "S fi 1 .2 fr- s S 2 *5 Name. Origin. Insertion. Use. 5 . Levator scapulae. From the transverse Into the upper angle To move the scapula processes of the of the scapula. forwards and up- four uppermost wards, vertebrae colli. Of the Muscles. 203 O rg a a Q* T3 G rt CO "O , 04 Q- Z> . c b a ^ § ^ Sd o ^ 8*5 £ ■§ C u 03 V 0 * > £ s a r. 1 a> . rZ t&B ■H o o rt u -sc .id in ca QJ *-» n +2 U cJ t! -T 5 - c o g cu £ v ci r. »- *■* P.O n N Pi J- CO = vS o ^ p L*-« 4 h I o o to *j tn W3 £ >' O 03 ^ -2 Vi 03 O £ G -P S O o O -u 3 — O C _G -• — P p r: £ g rt £ 13 -w» rt C J- v p 5- nJ 5-* • ~~Z -O CO ^ W 'a ■» -rt V) £ rt rt O rt ? 0 ^ T3 ; * ^ 1 i-. — ^“T3 u • : o ^ £- V: o o a. 72 *o 4-> CO rt a o c QJ 'S o 4-J p •5 -S° w o AJ 1) CO rH O 5 ° qj £ " & > u ► rt O,—. u cc jo — rt S i~ O .* .£ aoa w > Ph -Cm w w O ^ b *- s: t> oj s-s s a - o ^ ^ O) © 3 - o Ul „v w to t , 4 h £ > H) 1 _ ^3 .§ i ► 2 > CU QJ cc p P-* S £ © o -c ■+“ " h s 13 o Ph rt o CO _, 2 S O to 3 C* .b o Ph Ph t o .5 Ph P Vi P P . CT 1 co ^•Ho S* fo • U So named on account of its complicated stricture. So named from its origin from the neck and its insertion into the mastoid process. Name. Origin. Insertion. Use. 13 . Obliquus inferior From thespinous pro- Into the transverse To draw the face to- capiiis. cess of the second process of the first wards the houl- cervical vertebra. cervical vertebra. der, and to move the first vertebra Of the Muscles. -- •- tJ c T 3 * C S 5 o c cj W „ n T 3 0 " G u ^ * -a 5 - e-g.* 2 3 o 1- i-H a p> * x « Ji ■s J _S rt .c ~ O "3 5“ o ^ " O ^ ^ tj u 5 5 S 2 >-£*-» « o 8 ' cu j to •XJ & r$ O u Z nC CT 2 rj O t/i C Jr O 0,^3 ^ P C 'b ,C rt wi 'tj d, 3 3 w - !2C o ,C 2 * 3 g si « 6 01 "Z 3 ’ — 1 QJ I I § « " “ u i! m ~0 ^ S * 5 J 2 bfl o ® u •« ^ 2 C rt ^ 5 > o JD .2 .5 a) ^ a C .2 S o S£S ’S — S “ 6 B g 3 t! ’ 5 - ( o 2 " S qj to i_i rj U «J CLTl 13 > e is £1 ')£ aj Cu C r* 3 rt'S ’I'S § 0 CO 13 % n 13 *■+-« . e-s g ° M > H £ S'XX B £J rt o\-S Gt 4-J 1U ■ M c/1 « M • •> U X O X ft oo rt H -.Xi c/7 P x " a> co XT3 S e a « o 2 "EL to Cr C/5 nJ ° o CL) , C] *v - £ s ^ 2 3 0-3 so ,jh s nj co C ^ CJ o rJ O P* M 't* G . o : Lh J-. pH [n > & °ci H3 to CO G 'cS .£ 13 ‘a, U3 . 2 ' ’§ *3 1 ^ ' > <-M rO wj o CL) .2 G rS Eh Gd O d -G c a IjO • G # , 1*^ , CD G <4H O 0) o O a O ^-4 s *U5 G. CL) flJ •5 +j -G a. ^2 13 > " t— 4 c s 1 J ° ^ Mi u So - L°s -G O u, ^ H rt g LG S ° 1 1 bet: ,g * e 05 13 . .5 GC o B o 2 'l, T3 t{ C Jh g — -S £■ >J /^n g- CD ^ C the dorsal, and four of the cervical vertebrae. £ J £ £ Of the Muscles. 207 0 tT'H i £,« 3 £ W OJ *> q 4_j C3 1 ^ /> Ct- ri ^ r. o G 1> O ° o E-< tn V. «1 « © .G t/i n-> co O CD y -a © o G 3 Oh © T3 © c-S fl rt O O 3 .G 4J O " h a C 3 •— , a. O-H- co G C-, O CO *— I QJ SS^ U 8 ■S 8 .J3 .S O ^ ^ a> S 3 co'O 4-» G ^ "T3 g c Cl< aJ 1) © £ > © « > yj ( -p - G U. CD Q-^-M O 3 0 2 « +-> c O G ~ u pH — CD * > Ctf CD ~ > of i « . c* Ph S °- C «-i s S ** 2 1 « . *1 +j > o 5 t4_ t, g J* ^ g ti 2: m C -G^ 3 ^ ~ « .2 -3 8 S t S ShS 3 T3 £ G G -G ^ | * s-3 ^ ■£ -G ^ N a « G c^cp ,H t S « g * -s ^ 5 >-!h» . v_ o D- - >H ■O JZ ~. ^ *3 O CJ X'S c« v > g.s O o-c H 5° c rt "S S-5^ " 8 .a ° ■= ) p '» S' b cn rt 'G *i « ^3 2 .ti C ^3 •-; 3 J 5> «SSb co ■J CZ, o v ' ^ W b£TJ bfl 1 p3 . c« v G H £ cu O i C [ _. • CO 0 (U P ~ > g v> O b ^ -9 V) & gw. z ° -2 -E5 O a G W o _o •3 C -o £ 2 SI w ■ 0) *v *4-H ’ .52 o ^ .> S -P ^ c ,o o ^ H * o o s £ £ g c <-M o P cS w ^ O § -a P ^ CU C ^ O 4-J CO Cl «-0 CU _c CL) £ ^ 23 o ^ c • — 1 CU JD > 'S +-* CO w. o S OT3 O d> iS o r 3 g ^ M 4-i 1 ! n. w ci ^ •*-* -— « m M 5-i -O c+_, P ° cS to J- - <0 3 CO P P ccj V- > 3 c* bo « s cu * CO CO p ' Cl 0 cs 0 h- 1 c/l '/) Vi (U PL, • . •N ►4 C-J S u as rt _Q -r S 5?P Si 6 C2 T3 .C -rt .£ e> U -2 13 a c C w. c o cu o - ui 'i 1 .2 1 O P !-. £• ('5 These muscles are to be found only in the neck and loins ; which have been described, as the inter-transvtrsales dorsi being rather small tendons than muscles. ■ + ) This and the fallowing pair of muscles derive their name of psoas from +•«. Iambus, on account of their situation at the anterior part of the loins. Name. Origin. Insertion. Use. 3. Iliacus interims. From the inner lip, In common with the To assist the psoas hollow part, and psoas magnus. magnus. edge of the os Of the Muscles. 209 c « >3 o Q-. o A z * o Cl. O T5 » *^ fO , 05 .2 £ • bo £ >•• G o .G s £ bo c & i H *.2 ► *- - i "" rt- jz 3 u t. Oh « S ^ " u Oh > •£ ^ '+H o o ^ % c -o 3 .S „. -a $J . ■ a § a o 32 T3 - O h *-> " 92 92 3 l^-S ^ 2 ^ > s S’S " £ O ho M G S 6 * r? J O u rC b-Q u a> .2 .2 .2 °- — Q. ^ CL) a \n 2 5 to co TJ O a; G O ■*-> , L- S o o r-G a 2 p< o ,6 G £ G O C* ’ *-i pH rt -G • — 1 *-» 3 r- b0*fl -. Ph ctf * O o2 PS o • PS ‘+s u “ - O <« 2 *> g « rt .2 S - 8 .5 S bS o, « o b H H U II J; 1 *- ,P3 ,XS .o o 'o 5 . W , nd T 3 2 .b rt ^ a g H s M « - ^ J S’ s. £ I g s 3 U « 22 JO o-a;a rs ^3 u *-> G O g 3 Orfl ^3 ^ O 53 >-. ctf e" lw O _ S g Ph u t. r& ; S.3 72 .'2 w fcJ 5 O- px, • - PS u ■. M -C rG O — 4J *-» G G §~-o “ Own) I -G H SS c qq 6 2 .5 M’S ■£ 2 pi (i o •3 C. Cfc .JL *+* 3 O •r* O .G s o & G "G to c to G CD Ctf a 2 n, A. C ' G ctf PhG> Ctf D ° rG cn *-r* 2 • 10 0 ctf ctf J-« — ■ ~ OJ r? P-. Ph ^ . rcl >-i CD to ,23 rG t— M •— *H «-> co *+5 «> 5 .2 <1> •S-g-3 •3 j's 6.2 2 O ^ to u PH 5 ■G *3 S3 b ^ o . ctf . JT s ■" b £ P-* G •S P w» G O O T) O a-S 23 ^ Ctf G *Ph Ph G CO ctf G ‘a. to ctf f 5-1 'a 2 QJ h D PL, Ctf G CO va 2 "2 e ^ O Q* cu r C-, bO g.S M ^ Name. Origin. Insertion. Use. CoracO-brachia- From the coracoid Into the middle and To roll the arm for- lis (*). process of the sea- inner side of the wards andupwards. pula. os humeri. Of the Muscles. T3 C! O Eh .s O Eh s § a 3^ o o D T3 go w u ri CO •S 8 J( S -M o r *-* 5>%' 4 - pq o » >tj C, C3 c3 ^ _ U-s is ° o a; T3 T5. rP tO 33 £ G CJ u crj 3 •- c r. X 3 co cl «.S | o E- * c/> b.G CO rj P o O r “ l H bp

> Oh TJ PH U P 2 "T3 P *p u o P l) O, J! 43 3 S “ *H-H — p b£) n *-+-• O P rn 2 o p p 2 o (lv 2 -*-< ^ *3 OXlP b0 p a p p rP to ; : • : d > !*P o CO O 03 2 p ■s c "3 S p O P 1 . 6 O T-'l? '■d p 8 j>* t- Mx ,— t — O >**£ H3 £ a g Ml (A. p p, 'iv B ^ Q..P cl.2 C 5 o 3 S-S P t> P <1> •S-d C/D G ' -Q o r< & S o •a B S . d rt g ++ S\2 w .-GO ° -id-) u u a ■S £ -d « o 3 C * S B rt ft G e s c g: u fc => c ,S-G , 4-J !1 . o ~0 a e S o e s^y-^s a >. "aco'dGo'aStuGft'd i £ -*-* <» ' « 'u *d tt ^ g «3 S s.=i s ~ °* ® 3 O te a o c g o g -I s I 8.S rC OJ 2 w +J p- *J ^ ^ | ig *5 CO cu- ,- G £ S T3 § > C O -c ~ g o 3 -a £ -5 « ’H P3 p fl g o 3 * <2 e .s •§ «■> "rt v. o ■s ^ s © -a — § bO in ^ C "J ® 1 ’§e § £ 3 ~ U pH Pm 'i-V Pm j-. PH --• CJ O o X { x, c i: w ^ . 1 c-3'^S a i 1 e G G V) 1C E U,u O r* r ^ "5 a *5^ ^-1 G * G *P^ 50 c ^ c - a. Ji 3 CJ U o ^ u o Vi CJ. S-I o W9 G 8i fcT G u Vi "u S| = o B -g = ^ G G }-. G ce ^ CJ <-* G . CJ V) O cj O HA a *S «* « w -o t5'S W g G < Fie: ris. ”3 CL ^ t« .« 'o - 5 ° ^ C ' -5 g 'C o a VO GO Ov S .£«■§£ ^gcS I ° g,~ - s’ I .2 -g Jj I « 1 ° 1 *-53§§ ■S £ ? '5 x =2 CJ 3 *-’ T3 c u 2 « o £ c u-C i? c M r-H ^•'-* rt LStri!! 2 * longus h t 9 be found, whereas this expansion is never deficient. 214 Of the Muscles. TJ c CTj & - T3 g o G a> 12 G CL) O bO § _ __ CD ^ p* G rn OS G -B3 ~ u o ra c o '■£ U h fi u O c c *■» .= ai „ a, •8 8-3 CL> Oh- t2 G TJ G r3 G ^3 u G G O « f 3 3 O X3 S qj .5 rB +-# » O T3 G O .G O O o c £ o h ° ^ K ‘tJ to ?! O n> *G O o 1 O r* *-“ * ftOTJ o o rt .G U O a> £ G *TJ G SL T> cS Ph .S in 'tS . -5 o ^ 3 O S H 2 tp U . cu N rt B ‘5. to 3 -r CO C tH • XI eo I* ■S. *d t> s crj G 3 S £ * .2 ^ -G *5 H « Name. Origin. Insertion. Use. 14 . Abductor polli- From the middle and By two tendons into To stretch the first cis longus. back part of the the os trapezium, bone of the thumb ulna, interoffeous and first bone of outwards, ligament, and ra- the thumb. Of the Muscles. -D -a j, o S S a J2 rfS S' d ^ ' 3 co cr ~d d to CTT3 O ! «« o © E* X * o H bO bo d <43 T3 d .d « o .S *0 • ■ — > 4-> * CO d d S u 3 33 33 4 -J *-» T3 cTd 3 H > p d 0 o o V a 1 2 "o TJ d . d nd .h Id rt u P-. ctf 4 -J d s.s d-,-^ 3* 3 •Sta 'o § . -3 c 3 rt .2 s TJ O C M Pm 3 1 ^3-_ SO’BoJ y£ 2-S * ~ c -a g m h s S 2 3 0 3 ■73 5-. J> G ^5 ’ G s o U) » O T 3 #-s g M c o G 4 -J G 5 ?. -a X) i; - g o PS W> C -G £H G rP a ,&o O a Os r rs s 1*5 OrS 3 £ U-4 o to G o 'P G b o 5 os Os ^ £ o> .£ *5 o PG o o u pH W 5 • o c c G o J 2 *?•«§" o o 6 *h £ ^ o ^ W C (J 0> Q-> rS 75 -a '5 bjj ; «N U rt r -P«o 2 S I „ S.s 8/5 P* ai Os rC £ 3s Os t: £ T3 G G G O £ ' P cr -O S G A P . ”C -O ; <- o Os G O Os Os O r« £ « fi « C -t3 <" Q> TD r^J CJ M O- g 2 S tfj o .5 ,g G ~G CO O 2 jz B ir «u G -S £ G L-. 3 T3 6 1 b £ p jd c ^ O — | "O to -*-• £> s ^ O to 0 o ° O <3 *" o h h E» Eh to CD g C P <2 ^ -a g "p^ o ^ -a 2 ° c CO CD G r; s j? ~ G -‘- J c • P co G *- d G QJ a S c c* £ <7 a o ,o U3 o o u (3 i bO j £~ .2 £ 1 N O a a ,o 3 aj v> C "E 2 * a* £ 2 S S a a n • 2 bO.O cu ^ rd ^ t 3 o c £ G bO *“* G II • ■— 4-* C_. CO S O O £ O CL, P X) < ’"O G P -P < VO G e *g p-t tp *35 .y "3 o S Ph :g On E e I 218 Of the Muscles. o G O 4-> d •G r C d E l O F j- o r-« C F ,*3 "0 >G -q a ^ rS g o ^ c42 G s ? > +■* o s ^ . T3 G j£ * d > > — • G rG p-O *- ._ c/3 cr, £ G !s d d -a T T3 «J fi M8 « Si S M rS .5 o3 *5 13 rG "g 5 d 60 P 15 d £ "5 IB -d j, 60 3 IS o d3 2 d 'O < H3 » d •> d 13 -*-» b S £ o G . — i e j-i •G r- *-* G 50 S-Scg S VB G G a> rG U-i O 'G bp o , S 4_i '43 rt v w S-sl d,S g Jj.2 J? *s ^9 <9 G ten o o .5 OJ ~o •g G s C d -o {3 d ^ ”2 2 « S rt « S 5 I S w «j « •5 S' d J§ 1 B « J-» ^ b rG CD - G 4-. Q. J3 V3 t4_< Cu # bp W O G ^G ^ b TJ «l, «« G G r+ D Pi G *3 .5 rfi CO a G 3 5> rg . O u | 5-i _rf< «5 •S g cT •g ° £ <-M ni G t, Z MS 2 ments, os sacrum, and os coccygis. . Glutseus medius. From the spine and Into the outer and To draw the thigh Of the Muscles. 2 IS t; "2 H3 - “ 'B o ” S C ^ -Q ^ c! w cO p- • — g J e £ -C • 10 B.3 o £: ^ S bods 3 : c £ 5 3 3 £ ■Si u 5 , c C -s r- 1 -* ~ - -3 = ° •-3 1 - u 3 S g o ° o ? « "O f-4 rO o T3 o C P r£2 *T3 C *"P • rt »- ^■4—t t. 2 a “ t S3 §* 3 ,3 s o- o £ rt rt o r- >sT2 ’> <-p« rt o — t r> SI .2, u ,Q 3e 53 s i 5 . p >« &, £j 1) - bio c 4-1 0 pGS O U C3 p 5 s J- * '“' *-M (D 3 33 1*, c r~\ rH ^ c +J 1— ] a> 4-* Pi c C 0 4-1 q u 3 »H ,1- ,3 &, o ^<- 1 -. t *-> « 6 T' t>> P 3 £ O to « 4 I! +Z in O *0 Q* o o £ £ 5-5 ^ G « 8 « £ T3 *-i C .8 QJ _ o 2 _Q G ^ G bo ^ •I 3 > fl «3 j§ «3 pH 4-» w a a rC T* - 3 ^ in ^ « 3 O •* £ « u. ; rg A 2 s .1 ‘o g U a *-*H C O ■3 ^ a c u s ? *• rt w w G qj «-G C -G H W f-i g tuberosity of the the latter is in ac* ischium and poste- tion. rior sacro-ischiatic 220 Of the Muscles. P O rd txQ 13 ^2 oo o P-, CS QJ u e CJ E -2 w a r-G *“* 'S <5 si G bO C £ o Ph S s c a> P bG-P Q OJ .O £ a: 3 ,H < CC FQ 45 a b -o ja rt ra tS S vt'S <0 l- •B c X s “ .£ 8 > Tj 2 S G O a> G . . b* .2 bjO-5 ’ c ** ^ *J p o rt >, r' 4-t G g S w *d CO o-^5 V ^ y >H ? s c .2 ••* G ^ . « rti T; OJ u c 1*3 <*> G n 1 1 S5 -S -g O T3 G — b* £ 2-g 8 ^ s s tj £ « “ B-° S’S I " ’fc'S G . *-> G t* o ■ _ „ JZ rt ■*■» O 09 r- bO £ M’S .s ’G _, n 3 a-s c * ct* o <> «* -d u ^ *± rt Xt bC « i> Jtl CJ 2 3 •£ -S £ g « _ w u u frl- <4 C3 ■8 ^ U ^ -G S H - - c ' i-* u o d G O C CJ rG i-i G G > O CJ d d 1= o 0, g* G CJ 'S O G G C* fc.S G O G * G ^ cj v- d cj *•» CX'-i-i a, o G 4-» u cj d fG 9- • ^ al) rt d 0,0 o 4-» <-+-« i_J G Oh ^ o to . — to t-. » O VG FH tO ■*-’ QJ M_, A 1- 0 CJ , G O C *0 CJ to o c G o d d G d o 6 d G ^ G C G § o d E d G g g o .2 ss C u o o g G d c u G g d £ pH « 6 2 u H d G s *So CJ G « a > U to # G . a u * o • CO CO G *G O j_. 3 4-» CJ CO sus ■u O ^ 6 G CO CJ CO 4- U-N <0 ✓ 221 (*) So named on account of its origin, which is by a broad flat tendon three inches long. (t5 Spigclitis was the firft wlio gave this the name of lartorius , or the taylor’s muscle, from its use in crossing the legs. 222 Of the Muscles. bn tn bn T3 a T3 a H3 a o E-* o TJ G *5 ct }-. <-+-< CD O CL CD o ^ g *5 Ct ■_« '-w S o CL, £ £ P ft . (U ri ft _r« £G nd o G ^ ct ^ CL. J_ G ct £ ^ L- O ■•S ^ a. £ 2 o .2 ^3 (X CD „ CD "O *-■ ° rt -S ‘ -. E c w . ,-c g| l^>1 eCf Cdi c o a JK £ *- C G rt L C ^ CD | *■« *-» 'S o ct ^ < cd T 3 £ G G r 2 tO ct o a> -G lG *-» *-» O G * ct > (*) The vastus externus, vastus internus, and crurseus, are so intimately connected with each other, that some anatomists have been in- duced to consider them as a triceps, or single muscle with three heads. Of the Muscles. 223 £ bJO C r-0 in -Ji bO~. 1= fa rt ctf £ 4J • O II s •o g'S C*~ * TJ C — ' * fa 'S c a, a-g 3 ^ k: ISl . « T! fa -a •£ a. « ■S ■§ -5 a, ° ^c^^e r S a, e^ rt£&3St*,to£g uocftooocci c -2 R 32 fa P-( fa CO VJ i j3 fcO bO rt c g o hO 5-, o ■+- fa o 3 to £ '£ *j '-■ — ^ fa! 0 .2 *T3 fa pQ O o . O CO •g *fa -2 o u o s g -T3 ~ 32 t" < s • ^2 < S . <-2 • A nus M cp "T" -C -H t- g 5 J3 ^ u C 1c -i * ft r> “ 5 fcjC o-S 0 s 1 % * c £ bJJ c rj ‘S -C 3 fa .o 0-> > r; fa ~" ?s 8 B « J= S O fa > tfl .. m le tj 1 S. i "2 -a ! •§ = s | c _r ^ c ^ ^ rt jS -=3 -o C £ o & _ ^ ^ u T3 " d cr^J c g * ^ > c jd _ ^ d o ~ c ~'N r d o .£ c n3 <; rt S <5 •- d 4> Q b0*§ h 55 c*j ^ d ■s s o u c o 5 ~ a ^ G! CL, o - S s -g <£ ~ E r8 >• 73 l£ 73 pa w U o’ rt-G 3 t; jgg, 5 £ £ •S 'B pa -5 3 44 rt d T O "H £^h -g 2 g :2 4: o <-d <£ .o 4-» rt J-« d *-• . O 5 . c «o O b .s •TJ o s. E bo 3 - a s * o a 45 S 'oO -£ ° o rs ^ u5 v • — ■ ■3 u,ii o 2 c is -3 u c fcO bO £ c c .c "-a S .£, CO *_, U ^ V) •°T3 -.3 C U) • -T-* CJ CJ •= n £ 30 o «-> bJO rt «> 57 >. T3 «•> * ^ ,-—t C 3 *5 d _C -Q <-w 0^-0° H Eh TJ ^ C rC rt ^ o w g> 3 rj O. . 52 . g gd O CL, T5 _, Sew j_» <-•. d U •. ,§~ ■P bt «* c *ri c rt -S «i £ — Ha • ■ ® J; C ^ o ^d P *& d u <+- ' o uC £ £ ~ O rj '-j— « S 8 S3 o Pi 4-» O o -a o .5 '3 £ £ £ ,9 ■'S ++ * “I V) '»»* c/) 'p t/5 P ra •G ^3 * o 3 o G •O Pi G -*H . <2 e o O 4J G - *X3 rS Lt 50 'S d o d o J3 JS d O X 4_J 4-» d d o J-* o £ S'H E g £ Ml rt .. •5 u a *-> ”0 co O d ^3 d d f~j vi/ O Cl *J ? W w jj ■3 1/1 -O t- f f-j c 4 o.^ . Li ^ U O C ti 'n r z2 rt d d CL ro #\ L* Li 1) 4— > a, d CL o 2 — CL) ^ .G S *J TO 3 d cd o 1 rt *} o ^ L 'TJ ^ t; ^ aJ g G fe O A-l rt •CL, O *-d nJ m 2 cu J> w x ~ w g-6 o,£l L o CL, C/J d 50 d 00 ^2 '-3 L. ° o ^ S .2 D P3 E *d o a. 5 3 H M C o OQ e 2 u L Name. Origin „ Insertion. Use. 10 . Extensor longus From the uppef-, out- By four tendofis into To extend the toes, digitorum pedis. er, and fore part the first Joint of the of the tibia, inter- smaller toes. Of the Muscles. 227 to 73 G O E-» ^ : £ : ^ G ~ G § - ~~ ■s c e o> *3 o j3 -u *j o S3 vm .tJ P O DO *■< O a> bJD ■a e -5^ E S <+< <+- g o O O hn C ^ -5 (U w S a,^ ■a, o P j-. G bO P3 a. Cd -. J *5 P s 228 Of the Muscles. nS G O cd y. ,-C Uh ns- o C 4_» ^ a j2 .g o o — » H a So O «_e " ■S’S (L> 3 > ° O tfc! 3 o 51 pi _y co cm 5 _c rt *q bO & 3 O •-3-S 3 1> h i-i 3 3 a., f; o J2 «-> 33 ,£- £ 3 u •- ^ r XS §£ O o nS cd G-S S G *-. G s °*« - s ^ o.2 . 3 wi O ~ rt •£ » s o o S-4 P* • Sgii .y S £ Sjg o S 2 E 2 N CL, •X) w? ■5 ’’S < s. to s ‘5 B o 4-» O G „ 3:5 < M ns from the aponeuro- sis plantaris. 5.Lumbricales pedis. From the tendons of Into the tendinous ex- To draw the toes in- the flexor longus pansion at the up- wards, digitorum pedis. per part of the toes. Of the Muscles. 229 *-» O to 4-> jj S G rG flj *-» ^ <-M o ° w 4_r uj O to • — w aj -n rt G qj u ■J3 • £o v. © o •5 >, ' ft -du© G -2 J» 5 *Cw « S o-a 1 •C £ S *§ &-* • S u.2. .2 ^ *£ ri (D in rtf w ^ y 1/5 in ^ ho ^ O ^ to O S ^ S *■* QJ <-M d O £ .H ctf o d qj r ir G r-G 0 C 5 ^ Q. u i- -2 ■S S S c G rt CJ V*-i -G O # * J 4> /-n r* O to _Q qj 2 S 4-1 Is u £ 3 o s j= u w > 4J O S 2 O ^3 *-* _ CO O U •* J > w U --• o u “ co «-> 3 g .h 113 8 o a. O CL, g - E*S 'O o CG G . H 3 .52 £ .S2 *d *> a, r 5 M ._ FT S ^*5 GN d Cj» a, to C ^ CL) CJ c S 2 3 G fi .G c 7 = -G c- h wards. All the intcrossei assist in extending the toes. 230 Of the Muscles. EXPLANATION of PLATES XXIII. and XXIV. Plate XXIII. Fig. 1- The Muscles immediately under the common teguments on the anterior part of the body are represented on the right side ; and on the left side the Muscles are seen which come in view when the exterior ones are taken away. A, The frontal muscle. B, The tendinous aponeurosis which joins it to the occipital; hence both named occipitofrontalis. C, Attol- lens aurem. D, The ear. E, Anterior au- ris. F F, Orbicularis palpebrarum. G, Le- vator labii superioris alaeque nasi. H, Leva- tor anguli oris. I, Zygomaticus minor. K, Zygomaticus major. L, Masseter. M, Or- bicularis oris. N, Depressor labii inferioris. O, Depressor anguli oris. P, Buccinator. QQ,, Platysma myoides. R R, Sterno-cleido- “mastoidaeus. S, Part of the trapezius. T, Part of the scaleni. Superior Extremity — U, Deltoides. V, Pectoralis major- W, Part of the latissimus dorsi. X X, Biceps flexor cubiti. Y Y, Part of the brachialis externus- Z Z, The begin- ning of the tendinous aponeurosis (from the biceps), which is spread over the muscles of 1 5 % Anatomy. Piat-exxin Of the Muscles. 231 the fore-arm. a a, Its strong tendon inserted into the tubercle of the radius, b b, Part of the brachialis internus- c, Pronator radii te- res. d, Flexor carpi radialis- e, Part of the flexor carpi ulnaris- f, Palmaris longus. g, Aponeurosis palmaris* 3, Palmaris brevis. 1, Ligamentum carpi annulare. 2 2, Abductor minimi digiti. h, Supinator radii longus. i, The tendons of the thumb- k, Abductor pol- licis. 1, Flexor pollicis longus. m m, The tendons of the flexor sublimis perforatus, profundus perforans, and lumbricales — The sheaths are entire in the right hand, — in the left cut open to show the tendons of the flex- or profundus petforating the sublimis. Muscles not referred to — in the left supe- rior extremity — n, Pectoralis minor, seu ser- ratus anticus minor, o, The two heads of (x x) the biceps, p, Coraco-brachialis. q q, The long head of the triceps extensor cubiti. rr, Teres major- ff, Subscapularis. 1 1, Ex- tensores radiales. u, Supinator brevis- v, The cut extremity of the pronator teres, w, Flexor sublimis perforatus. x, Part of the flexor profundus, y, Flexor pollicis longus. z, Part of the flexor pollicis brevis- 4, Ab- ductor minimi digiti. 5, The four lumbri- cales. Trunk. — 6, Serrated extremities of the ser- ratus anticus major- 7 7, Obliquus externus abdominis. 8 8, The lmea alba- 9, The um- bilicus. 10, Pyramidalis. 11 11, The sper- matic cord. On the left side it is covered by 232 Of the Muscles , the cremaster. 12 12 , Rectus abdominis. 13 , Obliquus internus- 14 14 , he. Intercostal muscles. Inferior Extremities — aa , The graci- lis. b b , Parts of the triceps, c c, Pectialis. d d , Psoas magnus- e e, Iliacus internus. yj Part of the glutseus medius- g. Part of the glutseus minimus, /z, Cut extremity of the rectus cruris, i z, Vastus externus, k , Ten- don of the rectus cruris. / /, Vastus internus. * Sartorius muscle. * * Fleshy origin of the tensor vaginas faemoris or membranosus. Its tendinous aponeurosis covers (z) the vastus externus in the right side, in m, Patella, n n, Ligament or tendon from it to the tibia, o, Rectus cruris. />, Crurasus. q q, The tibia. r r, Part of the Gemellus or gastrocnemius ex- ternus.* ///, Part of the soleus or gastroc- nemius internus. £, Tibialis anticus. zz, Ti- bialis posticus, v v, Peronasi muscles, w w, Extensor longus digitorum pedis, x x, Ex- tensor longus pollicis pedis- y, Abductor pol- licis pedis. Fig- 2- The Muscles, Glands, btc. of the Left Side of the face and neck, after the common Teguments and Platysma myoides have been taken off. a, The frontal muscle, b, Temporalis and temporal artery, c, Orbicularis palpebrarum, d, Levator labii superioris alasque nasi, e, Levator anguli oris, f, Zygomaticus. g, De- pressor labii inferioris. h, Depressor anguli 233 Of the Muscles. ©ris. i, Buccinator, k, Masseter. 1 1, Paro- tid gland- m, Its duct- n, Sterno-cleido-mas- toidseus. o, Part of the trapezius, p, Sterno- hyoidaeus. q, Sterno-thyroidaeus. r, Omo- hyoidaaus. f, Levator scapulas- 1 1, Scaleni. u, Part of the splenius. Fig. 3. The Muscles of the Face and Neck in view after the exterior ones are taken away- a a, Corru gator supercilii- b, Temporalis- c, Tendon of the levator palpebras superioris- d, Tendon of the orbicularis palpebrarum, e, Masseter. f, Buccinator, g, Levator anguli oris- h, Depressor labii superioris alasque na- si. i, Orbicularis oris- k, Depressor anguli oris. 1, Muscles of the os hyoides- m, Ster- no-cleido-mastoidaeus. Fig. 4- Some of the Muscles of the Os Hy- oides and Submaxillary Gland. a, Part of the masseter muscle- b, Poste- rior head of the digrastic. c, Its anterior head, d d, Sterno-hyoidaeus. e, Omo-hyoi- dams- f, Stylo-hyoidaeus. g, Submaxillary gland in situ. Fig. 5. The Submaxillary Gland and Duct, a, Musculus mylo-hyoidaeus. b, Hyo-glos- sus. c, Submaxillary gland extra situ, d, Its duct. Plate XXIV. Fig. 1 . The Muscles immediately under the common teguments on the posterior part G g 234 Of the Muscles. of the body, are represented in the right side;: and on the left side the Muscles are seen which come in view when the exterior ones are taken away. Head. — A A, Occipito-frontalis. B, Attol- lens aurem. C, Part of the orbicularis palpe- brarum. D, Masseter.. E, Pterygoidaeus in- ternusv Trunk. — Right side. FFF, Trapezius seu, cucullaris. G G G G, Latissimus dorsi. H, Part of the obliquus externus abdominis. Trunk. — Left side. I, Splenius- K, Part of the complexus. L r Levator scapulae. M, Rhomboides. N N, Serratus posticus inferi- or. O, Part of the longissimus dorsi. P, Part of the sacro-lumbalis. Q, Part of the semi-spinalis dorsi. R, Part of the serratus anticus major. S, Part of the obliquus in- ternus abdominis. Superior Extremity. — Right side- T t Deltoides. U, Triceps extensor cubiti- V, Supinator longus. W W, Extensores carpi radialis longior and brevior- X X, Extensor carpi ulnaris. Y Y, Extensor digitorum com- munis. Z, Abductor indicis. 12 3 , Extern- sores pollicis. Superior Extremity. — Left side, a, Su- pra spinatus. b, Infra-spinatus. c, Teres minor, d, Teres major, e, Triceps extensor cubiti. f f, Extensores carpi radiales. g, Su- pinator brevis, h, Indicator. 12 3 , Exten- sores pollicis. i, Abductor minimi digiti. k, Interossei. Inferior Extremity. — Right side. 1, Glu- trnus maximus. m, Part of the Glutseus me- Of the Muscles. 255 dius. n, Tensor vaginae femoris. o, Graci- lis- p p, Abductor femoris magnus. q, Part of the vastus internus- r, Semimembrano- sus. s, Semitendinosus- t, Long head of the biceps flexor cruris, u u, Gastrocnemius ex- ternus seu gemellus, v, Tendo Achillis. w, Soleus seu gastrocnemius internus. x x, Pe- ronaeus longus and br-evis. y, Tendons of the flexor longus digitorum pedis ; — and under them * flexor brevis digitorum pedis- z., Ab • ductor minimi digiti pedis. Inferior Extremity. — -Left side. ?n, n , o, p , y, r, s, v, w w , x x, y, zr, Point the same parts as in the right side, a , Pyrifor- mis. b b, Gemini, c r, Obturator internus. r7, Quadratus femoris. e, Coccygaeus. f The short head of the biceps flexor cruris- g g, Plantaris. h , Poplitaeus. L Plexor longus pollicis pedis. Pig. 2. The Palm of the 'Left Hand after the common Teguments are removed, to .show the Muscles of the Fingers. a, Tendon of the flexor carpi radiaiis. b, Tendon of the flexor carpi ulnaris. c, Ten- dons of the flexor sublimis perforatus, pro- fundus perforans and lumbri.cales. d, Ab- ductor pollicis. e e, Plexor pollicis 'longus- f, Flexor pollicis brevis, g, Palmaris brevis- h, Abductor minimi digiti. i, Ligamentum carpiannulare. k, A probe put under the ten- dons of the flexor digitorum sublimis ; which are perforated by 1, the flexor digitorum pro- fundus. m m m m, Lumbricales. n, Abduc- tor jpollicis. 236 Of the Abdomen . Fig 3. A Fore-view of the foot and Tendons of tne Flexores Digitorum. a, Cut extremity of the tendo Achillis. b y Upper part of the astragalus, c, Os calcis. d, Tendon of the tibialis anticus. e, Tendon of the extensor poll icis longus. f, Tendon of the peronaeus brevis, g, Tendons of the flex- or digitorum longus, with the nonus Vesalii. h h, The whole of the flexor digitorum bre- vis. Fig. 4. Muscles of the Anus. a a, An out line of the buttocks, and upper part of the thighs, b, The testes contained in the scrotum, c c, Sphincter ani. d, Anus, e, Levator ani. f f, Erector penis, g g, Ac- celerator urinse. h, Corpus cavernosum ure- thrae. Fig. 5. Muscles of the Penis. a a, b, d, e e, f f, h, point the same as in fig. 4. c, Sphincter ani. gg, Transversalis penis. Part III. OF THE ABDOMEN, OR LOWER BELLY. T HE abdomen or lower belly, extends from the lower extremity of the sternum, or the hollow, usually called the pit of the sto- mach, and more properly scrobiculus cordis , to- the lower part of the trunk- Of the Abdomen. 237 It is distinguished into three divisions call- ed regions ; of tnese the upper one, which is called the epigastric region , begins immediate- ly under the sternum, and extends to within two fingers breadth of the navel, where the middle or umbilical region begins, and reaches to the same distance below the navel. The third, which is called the hypogastric , includes the rest of the abdomen, as far as the os pu- bis. Each of these regions is subdivided into three others ; two of which compose the sides, and the other the middle part of each region. 1 he middle part of the upper region is call- ed epigastrium , and its two sides hypochondria. The middle part of the next region is the um- bilical region, properly so called, and its two sides are the flanks, or iliac regions. Lastly, the middle part of the lower region retains the name of hypogastrium, and its sides are call- ed inguina or groins. The back part of the abdomen bears the name of lumbar region. These are the divisions of the lower belly, which are necessary to be held in remem- brance, as they frequently occur in surgical and anatomical writing- We will now proceed to examine the contents of the abdomen ; and after having pointed out the names and ar- rangement of the several viscera contained in it, describe each of them separately- After having removed the skin, adipose membrane, and abdominal muscles, we disco- ver the peritonaeum or membrane that enve- lopes all the viscera of the lower belly* This being opened, the first part that presents itself 238 Of the Abdomen. is the omentum or cawl, floating on the sur- face of the intestines, which are likewise seen every where loose and moist, and making a great number of circumvolutions through the whole cavity of the abdomen. The stomach is placed in the epigastrium, and under the stomach is the pancreas. The liver fills the right hypochondrium, and the spleen is situ- ated in the left- The kidneys are seen about the middle of the lumbar region, and the uri- nary bladder and parts of generation are seat- ed in the lower division of the belly. Sect. I. Of the Peritoneum. The peritonaeum is a strong simple mem- brane, by which all the viscera of the abdo- men are surrounded, and in some measure supported. Many anatomical writers, particu- larly Winslow, have described it as being com- posed of two distinct membranous laminae; but their description seems to be erroneous. What perhaps appeared to be a second lamina, being found to be simply a cellular coat, which sends off" productions to the blood-vessels passing out of the abdominal cavity. The aorta and vena cava likewise derive a covering from the same membrane, which seems to be a part of the cellular membrane we have already de- scribed. The peritonaeum, by its productions and re- duplications, envelopes the greatest part of the abdominal viscera. It is soft, and capable of considerable extension ; and is kept smooth and moist by a vapour which is constantly ex- 23 S> Of the Abdomen. haling from its inner surface, and is returned again into the circulation by the absorbents. This moisture not only contributes to the softness of the peritonaeum, but prevents the attrition, and other ill effects which would otherwise probably be occasioned, by the mo- tion of the viscera upon each other. When this fluid is supplied in too great a quantity, or the absorbents become incapable of carrying it off, it accumulates, and consti- tutes an ascites or dropsy of the belly ; and when by any means the exhalation is discon- tinued, the peritonaeum thickens, becomes dis- eased, and the viscera are sometimes found adhering to each other. The peritonaeum is not a very vascular membrane. In a sound state it seems to be endued with little or no feeling, and the nerves that pass through it appear to belong to the abdominal muscles. Sect. II. Of the Omentum. The omentum, epiploon, or cawl, is a dou- ble membrane, produced from the peritonaeum. It is interlarded with fat, and adheres to the stomach, spleen, duodenum, and colon ; from thence hanging down loose and floating on the surface of the intestines- Its size is different in different subjects. In some it descends as low as the pelvis, and it is commonly longer at the left side than the right. This part, the situation of which we have just now described, was the only one known to the ancients under the name of epiploon ; 240 Of the Abdomen. but at present we distinguish three omenta, viz. omentum magnum colico gastricum , omen - turn parvum hepatico gastricum, ind omentum colicum. Tney all agree in being formed of two very delieate laminae, separated by a thin layer of cellular membrane. The omentum magnum colico gastricum, of which we have already spoken, derives its ar- teries from the splenic and hepatic. Its veins terminate in the vena portae. Its nerves, which are very few, come from the splenic and he- patic plexus. The omentum parvum hepatico gastricum, abounds less with fat than the great epiploon. It begins at the upper part of the duodenum, extends along the lesser curvature of the sto- mach as far as the oesophagus, and terminates about the neck of the gall-bladder, and behind the left ligament of the liver, so that it covers the lesser lobe; near the beginning of which we may observe a small opening, first describ- ed by Winslow, through which the whole pouch may easily be distended with air.* The vessels of the omentum parvum are derived chiefly from the coronary stomachic arteries and veins. The omentum colicum begins at the fore part of the ccecum and right side of the colon. It appears as a hollow conical appendage to these intestines, and usually terminates at the back of the omentum magnum- It seems to * This membranous bag - , though exceedingly thin and trans- parent, is found capable of supporting mercury, thrown into it by the same channel. Of the Abdomen. 241 be nothing more than a membranous coat of the cascum and colon, assuming a conical shape when distended with air. The uses of the omentum are not yet satis- factorily determined. Perhaps by its softness and looseness it may serve to prevent those adhesions of the abdominal viscera, which have been found to take place when the fat of the omentum has been much wasted. Some authors have supposed, that it assists in the preparation of bile ; but this idea is founded merely on conjecture. Sect. III. Of the Stomach. The stomach is a membranous and muscu- lar bag, in shape not unlike a bag-pipe, lying across the upper part of the abdomen, and in- clining rather more to the left than the right side. It has two orifices, one of which receives the end of the oesophagus, and is called the cardia , and sometimes the left and upper ori- fice of the stomach ; though its situation is not much higher than the other, which is styled the right and inferior orifice, and more com- monly the pylorus: both these openings are more elevated than the body of the stomach. The aliment passes down the oesophagus in- to the stomach through the cardia, and after having undergone the necessary digestion, passes out at the pylorus where the intesti- nal canal commences. The stomach is composed of four tunics or coats, which are so intimately connected toge- H h ■242 Of the Abdomen . ther that it requires no little dexterity in the anatomist to demonstrate them. The exterior one is membranous, being derived from the peritonaeum. — The second is a muscular tu- nic, composed of fleshy fibres which are in the greatest number about the two orifices. — The third is called the nervous coat, and within this is the villous or velvet-like coat which composes the inside of the stomach. The two last coats being more extensive than the two first, form the folds, which are observed every where in the cavity of this viscus, and more particularly about the pylo- rus ; where they seem to impede the too has- ty exclusion of the aliment, making a conside- rable plait, called valvula pylori. The inner coat is constantly moistened by a mucus, which approaches to the nature of the saliva, and is called the gastric juice ; this li- quor has been supposed to be secreted by cer- tain minute glands* seated in the nervous tu- nic, whose excretory ducts open on the sur- face of the villous coat. The arteries of the stomach called the gas- tric arteries are principally derived from the cseliac ; some of its veins pass to the splenic, and others to the yena portae ; and its nerves are chiefly from the eighth pair or par vagum. * Heister, speaking of these glands, very properly says, “ in porcis facile, in homine raro observantur for although many anatomical writers have described their appearance and figure, yet they do not seem to have been hitherto satisfactorily demon- strated in the human stomach ; and the gastric juice is. now more generally believed to be derived from the exhalent arteries oi the stomach. 24S Of the Abdomen. The account given of the tunics of the sto- mach may be applied to the whole alimentary canal; for both the oesophagus and intestines are, like this viscus, composed of four coats. Before we describe the course of the ali- ment and the uses of the stomach, it will be necessary to speak of other parts which assist in the process of digestion. Sect. IV. Of the Oesophagus. The oesophagus or gullet is a membra- nous and muscular canal, extending from the bottom of the mouth to the upper orifice of the stomach. — Its upper part where the ali- ment is received is shaped somewhat like a funnel, and is called the pharynx.. From hence it runs down close to the bo- dies of the vertebrae as far as the diaphragm, in which there is an opening through which it passes, and then terminates in the stomach about the eleventh or twelfth vertebra of the back. The oesophagus is plentifully supplied with arteries from the external carotid, bronchial, and superior intercostal arteries.; its veins empty themselves into the vena azygos, inter- nal jugular, and mammary veins, &c. Its nerves are derived chiefly from tire eighth pair. We likewise meet with a mucus in the oeso- phagus, which every where lubricates its in- ner surface, and tends to assist in deglutition. —This mucus seems to be secreted by very minute glands, like the mucus in other parts of the alimentary canal. 244 Of the Abdomen. Sect. V. Of the Intestines. The intestines form a canal, which is usu- ally six times longer than the body to which it belongs. 1 his canal extends from the py- lorus, or inferior orifice of the stomach, to the anus. It will be easily understood, that a part of such great length must necessarily make many circumvolutions, to be confined with so many other viscera within the cavity of the lower belly. Although the intestines are in fact, as we have observed, only one long and extensive canal, yet different parts have been distin- guished by different names. The intestines are first distinguished into two parts, one of which begins at the sto- mach, and is called the thin or small intestines , from the small size of the canal, when com- pared with the other part, which is called the large intestines , and includes the lower portion of the canal down to the anus. Each of these parts has its subdivisions. — The small intestines being distinguished into duodenum, jejunum, and ilium, and the larger portion into cascum, colon, and rectum. The small intestines fill the middle and fore parts of the belly, while the large intestines fill the sides and both the upper and lower parts of the cavity. The duodenum, which is the first of the small intestines, is so called, because it is about 12 inches long. It begins at the pylo- Of the Abdomen . 245 rus and terminates in the jejunum, which is a part of the canal observed to be usually more empty than the other intestines. — This appear- ance gives it its name, and likewise serves to point out where it begins. The next division is the ilium, which of it- self exceeds the united length of the duode- num and jejunum, and has received its name from its numerous circumvolutions. The large circumvolution of the ilium covers the first of the large intestines called the cacumf which seems properly to belong to the colon, being a kind of pouch of about four fingers in width, and nearly of the same length, having exteriorly a little appendix, called appendix caci. The csecum is placed in the cavity of the os ilium on the right side, and terminates in the colon, which is the largest of all the in- testines. This intestine ascends by the right kidney to which it is attached, passes under the hol- low part of the liver, and the bottom of the stomach, to the spleen, to which it is likewise secured, as it is also to the left kidney ; and from thence passes down towards the os sa- crum, where, from its straight course, the ca- nal begins to take the name of rectum. There are three ligamentous bands extend- ing through the whole length of the colon, * Anatomists have differed with respect to this division of the intestines. — The method here followed is now generally adopted ; but there are authors who allow the name of cacum only to the little appendix, which has likewise been called the vermiform ap- pendix, from its resemblance to a worm in size and length. 246 Of the Abdomen. which, by being shorter than its two inner coats, serve to increase the plaits on the in- ner surface of this gut. The anus which terminates the intestinum rectum, is furnished with three muscles ; one of these is composed of circular fibres, and from its use in shutting the passage of the anus is called sphincter ani. The other two are the levatores ani , so call- ed, because they elevate the anus after dejec- tion. When these by palsy, or any other dis- ease lose the power of contracting, the anus prolapses ; and when the sphincter is affected by similar causes, the faeces are voided invo- luntarily. It has been already observed, that the in- testinal canal is composed of four tunics ; but it remains to be remarked, that here, as in the stomach, the two inner tunics being more extensive than the other two, form the plaits which are to be seen in the inner surface of the intestines, and are called valvulce conniven- tes. Some authors have considered these plaits as tending to retard the motion of the faeces, in order to afford more time for the separa- tion of the chyle ; but there are others who attribute to them a different use : they con- tend, that these valves, by being naturally in- clined downwards, cannot impede the descent of the faeces, but that they are intended to pre- vent their return upwards. They are probably destined for both these uses ; for although these folds incline to their lower side, yet the inequalities they occasion 247 Of the Abdomen. in the canal are sufficient to retard, in some measure, the progressive motion of the faeces, and to afford a greater surface for the absorp- tion of chyle, and their natural position seems to oppose itself to the return of the aliment. Besides these valvule conniventes , there is one more considerable than the rest, called the valve of the colon ; which is found at that part of the canal where the intestinum ilium is join- ed to the colon. This valve permits the ali- mentary pulp to pass downwards, but serves to prevent its return upwards ; and it is by this valve, that glysters are prevented from passing into the small intestines.* Of the little vermiform appendix of the cae- cum, it will be sufficient to say, that its uses have never yet been ascertained= In birds we meet with two of these appendices. The intestines are lubricated by a constant supply of mucus, which is probably secreted by very minute follicles. f This mucus pro- motes the descent of the alimentary pulp, and in some measure defends the inner surface of * This is not invariably the case, for the contents of a gly- ster have been found not only to reach the small intestines, but to be voided at the mouth. Such instances, however, are not common. f Some writers have distinguished these glands into miliary, lenticular, &c. — Brunner and Peyer were the first anatomists who described the glands of the intestines, and their descrip- tions were chiefly taken from animals, these glandular appear- ances not seeming to have been hitherto satisfactorily pointed out in the human subject. — It is now pretty generally believed, that the mucus which every where lubricates the alimentary canal, is exhaled from the minute ends of arteries ; and that these ex- tremities first open into a hollow vesicle, from whence the depo- sited juice of several branches flows out through one common frifice. 248 Of the Abdomen. the intestines from the irritation to which it would, perhaps, otherwise be continually ex- posed from the aliment ; and which, when in a certain degree, excites a painful disorder called colic , a name given to the disease, be- cause its most usual seat is in the intestinum colon. The intestines are likewise frequently dis- tended with air, and this distention sometimes occasions pain, and constitutes the flatulent colic. The arteries of the intestines are continu- ations of the mesenteric arteries, which are derived in two considerable branches from the aorta. — The redundant blood is carried back into the vena portarum. In the rectum the veins are called hemor- rhoidal^ and are there distinguished into inter- nal and external : the first are branches of the inferior mesenteric vein, but the latter pass into other veins. Sometimes these veins are distended with blood from obstructions, from weakness of their coats, or from other causes, and what we call the hemorrhoids takes place. In this disease they are sometimes ruptured ; and the discharge of blood which consequent- ly follows, has probably occasioned them to be called hemorrhoidal veins. The nerves of the intestines are derived from the eighth pair. Sect. VI. Of the Mesentery. The name of the mesentery implies its sim- ulation amidst the intestines. It is in fact a Of the Abdomen. 249 part of the peritonaeum, being a reduplica- tion * of that membrane from each side of the lumbar vertebrae, to which it is firmly attach- ed, so that it is formed of two laminae, con- nected to each other by cellular membrane. The intestines, in their different circumvo- lutions, form a great number of arches, and the mesentery accompanies them through all these turns ; but by being attached only to the hollow part of each arch, it is found to have only a third of the extent of the intestines. That part of this membrane which accom- panies the small intestines is the mesentery , properly so called ; but those parts of it which are attached to the colon and rectum are dis- tinguished by the names of meso-colon and me- so-rectum. There are many conglobate glands dispers- ed through this double membrane, through which the lacteals and lymphatics pass in their way to the thoracic duct. The blood-vessels of the mesentery were described in speaking of the intestines. I i * He who only reads of the reduplication of membranes, will perhaps not easily understand how the perimnaum and pleura are reflected over the viscera in their several cavities ; for one of these serves the same purposes in the thorax that the other does in the abdomen. This disposition, for the dis- covery of which we are indebted to modern anatomists, con- stitutes a curious part of anatomical knowledge : but the stu- dent, unaided by experience, and assisted only by what the li- mits of this work would permit us to say on the occasion, would probably imbibe only confused ideas of the matter ; and it will perfectly answer the present purpose, if he considers the me- sentery as a membrane attached bv one of its sides to the lum- bar vertebrae, and by the other to the intestines. 250 Of the Abdomen . This membrane, by its attachment to the vertebrae, serves to keep the intestines in their natural situation. The idea usually formed of the colic called miserere , is perfectly errone- ous ; it being impossible that the intestines can be twisted, as many suppose they are, in that disease, their attachment to the mesente- ry effectually preventing such an accident — but a disarrangement sometimes takes place in the intestinal canal itself, which is produc- tive of disagreeable and sometimes fatal con- sequences. — This is by an introsusception of the intestine, an idea of which may be easily formed, by taking the finger of a glove, and involving one part of it within the other* If inflammation takes place, the stricture in this case is increased, and the peristaltic mo- tion of the intestines (by which is meant the progressive motion of the faeces downwards) is inverted, and what is called the iliac passion takes place. The same effects may be occa- sioned by a descent of the intestine, or of the omentum either with it or by itself, and thus constituting what is called an hernial rupture ; a term by which in general is meant the falling down or protrusion of any part of the intes- tine or omentum, which ought naturally to be contained within the cavity of the belly. To convey an idea of the manner in which such a, descent takes place, it will be necessa- ry to observe, that the lower edge of the ten- don of the musculus obliquus externus, is stretched from the fore-part of the os ilium or haunch-bone of the os pubis, and consti- tutes what is called PouparVs or Fallopius's li - Of the Abdomen. 251 garment, forming an opening, through which pass the great crural artery and vein. Near the os pubis the same tendinous fibres are se- parated from each other, and form an opening on each side, called the abdominal ring , through which the spermatic vessels pass in men, and the ligamenta uteri in women. In consequence of violent efforts, or perhaps of natural causes, the intestines are found sometimes to pass through these openings ; but the peritonaeum which incloses them when in their natural ca- vity, still continues to surround them even in their descent. This membrane does not be- come torn or lacerated by the violence, as might be easily imagined ; but its dilatibility enables it to pass out with the viscus, which it incloses as it were in a bag, and thus forms what is called the hernial sac. If the hernia be under Poupart’s ligament, it is called femoral ; if in the groin, inguinal ;* and scrotal , if in the scrotum- Different names are likewise given to the hernia as the con- tents of the sac differ, whether of omentum only or intestine, or both: — but these defini- tions more properly belong to the province of surgery. Sect. VIL Of the Pancreas . The pancreas is a conglomerate gland placed behind the bottom of the stomach, towards the first vertebra of the loins ; shaped * The hernia congenita will be considered with the male or- gans of generation, with which it is intimately connected. 252 Of the Abdomen. like a dog’s tongue, with its point stretched out towards the spleen, and its other end ex- tending towards the duodenum. It is about eight fingers breadth in length, two or three in width, and one in thickness. This viscus, which is of a yellowish colour, somewhat inclined to red, is covered with a membrane which it derives from the peritonae- um. Its arteries, which are rather numerous than large, are derived chiefly from the sple- nic and hepatic, and its veins pass into the veins of the same name. — Its nerves are de- rived from the intercostal. The many little glands of which it has been observed the pancreas is composed, all serve to secrete a liquor called the pancreatic juice , which in its colour, consistence, and other pro- perties, does not seem to differ from the sali- va. Each of these glands sends out a little excretory duct, which, uniting with others, help to form larger ducts ; and all these at last terminate in one common excretory duct (first discovered by Virtsungus in 1642 ), which runs through the middle of the gland, and is now usually called ductus pancreaticus Virt- sungi. This canal opens into the intestinum duodenum, sometimes by the same orifice with the biliary duct, and sometimes by a distinct opening. The liquor it discharges being of a mild and insipid nature, serves to dilute the alimentary pulp, and to incorporate it more easily with the bile. Of the Abdomen. 253 Sect. VIII. Of the Liver. The liver is a viscus of considerable size, and of a reddish colour ; convex superiorly and anteriorly where it is placed under the ribs and diaphragm, and of an unequal sur- face posteriorly. It is chiefly situated in the right hypochondrium, and under the false ribs ; but it likewise extends into the epigastric re- gion, where it borders upon the stomach. It is covered by a production of the peritonaeum, which serves to attach it by three oi its redu- plications to the false ribs. These reduplica- tions are called ligaments , though very differ- ent in their texture from what are called by the same name in other parts of the body. The umbilical cord, too, which in the foetus is per- vious, gradually becomes a simple ligament after birth ; and, by passing to the liver, serves likewise to secure it in its situation. At the posterior part of this organ where the umbilical vessels enter, it is found divid- ed into two lobes. Of these, the largest is placed in the right hypochondrium ; the other, which covers part of the stomach, is called the little lobe. All the vessels which go to the liver pass in at the fissure we have mention- ed ; and the production of the peritonaeum, which invests the liver, was described by Glis- son, an English anatomist, as accompanying them in their passage, and surrounding them like a glove ; hence this production has been commonly known by the name of capsula of Glisson : but it appears to be chiefly a continu- 254 Of the Abdomen. ation of the cellular membrane which covers the vena portse ventralis. The liver was considered by the ancients as an organ destined to prepare and perfect the blood ; but later discoveries have proved, that this opinion was wrong, and that the liver is a glandular substance formed for the secretion of the bile. The blood is conveyed to the liver by the hepatic artery and the vena portse. This is contrary to the mode of circulation in other parts, where veins only serve to carry off the redundant blood : but in this viscus the hepa- tic artery, which is derived from the cseliac, is principally destined for its nourishment ; and the vena portse, which is formed by the union of the veins from most of the abdominal vis- cera, furnishes the blood from which the bile is chiefly to be separated ; so that these two series of vessels serve very distinct purposes. The vena portae, as it is ramified through the liver, performs the office both of a vein and an artery ; for like the former it returns the blood from the extremities of arteries, while as the latter it prepares it for secretion. The nerves of the liver are branches of the intercostal and par vagum. The bile, after be- ing separated from the mass of blood, in a manner of which mention will be made in another place, is conveyed out of this organ by very minute excretory ducts, called poribi- liarii ; these uniting together like the excreto- ry ducts in the pancreas, gradually form larger ones, which at length terminate in a considera- ble canal called ductus hepaticus. Of the Abdomen. 255 Sect. IX. Of the Gall-bladder. The gall-bladder is a little membranous bag, shaped like a pear, and attached to the posterior and almost inferior part of the great lobe of the liver. It has two tunics ; of which the exterior one is a production of the peritonaeum. The interior, or villous coat, is supplied with a mu- cus that defends it from the acrimony of the bile. These two coverings are intimately con- nected by means of cellular membrane, which from its firm glistening appearance has gene- rally been spoken of as a muscular tunic. The gall-bladder is supplied with blood- vessels from the hepatic arteries. These branches are called the cystic arteries , and. the cystic veins carry back the blood. Its nerves are derived from the same origin as those of the liver. The neck of the gall-bladder is continued in the form of a canal called ductus cysticus, which soon unites with the ductus hepaticus we described as the excretory duct of the li- ver ; and forming one common canal, takes the name of ductus coledochus communis , through which both the cystic and hepatic bile are dis- charged into the duodenum. This canal opens into the intestine in an oblique direction, first passing through the exterior tunic, and then piercing the other coats after running between each of them a very little way. This cecono- my serves two useful purposes ; — to promote the discharge of bile and to prevent its return. 256 Of the Abdomen. The bile may be defined to be a natural li- quid soap, somewhat unctuous and bitter, and of a yellowish colour, which easily mixes with water, oil, and vinous spirits, and is capable of dissolving resinous substances. From some late experiments made by M. Cadet,* it ap- pears to be formed of an animal oil, combined with the alkaline base of sea-salt, a salt of the nature of milk, and a calcareous earth which is slightly ferruginous. Its definition seems sufficiently to point out the uses for which it is intended.f It blends the alimentary mass, by dividing and attenu- ating it ; corrects the too great disposition to acescency, which the aliment acquires in the stomach ; and finally, by its acrimony, tends to excite the peristaltic motion of the intes- tines. After what has been said, it will be conceiv- ed that there are two sorts of bile ; one of which is derived immediately from the liver through the hepatic duct, and the other from the gall-bladder. These two biles, however, do not essentially differ from each other. The hepatic bile indeed is milder, and more liquid than the cystic, which is constantly thicker and yellower; and by being bitterer, seems to possess greater activity than the other. Every body knows the source of the hepatic , bile, that it is secreted from the mass of blood by the liver ; but the origin of the cystic bile * Mem. de 1 ’ Acad, des Sciences, 1767. f The ancients, who were not acquainted with the real use of the liver, considered the bile as an excrementitious and use- less fluid. Of the Abdomen. 257 has occasioned no little controversy amongst anatomical writers. There are some who con- tend, that it is separated in the substance of the liver, from whence it passes into the gall- bladder through particular vessels. In deer, and in some other quadrupeds, as well as in several birds and fishes, there is an evident communication, by means of particular ves- sels, between the liver and the gall-bladder. Bianchi, Winslow, and others, have asserted the existence of such vessels in the human subject, and named them hepaticystic ducts; but it is certain that no such ducts exist. — In obstructions of the cystic duct, the gall-blad- der has been found shrivelled and empty: so that we may consider the gall-bladder as a reser- voir of hepatic bile ; and that it is an establish- ed fact that the whole of the bile contained in the gall-bladder is derived from the liver ; that it passes from the hepatic to the cystic duct, and from that to the gall-bladder. The differ- ence in the colour, consistence, and taste of the bile, is merely the consequence of stagna- tion and absorption. When the stomach is distended with aliment, this reservoir under- goes a certain degree of compression, and the bile passes out into the intestinal canal ; and in the efforts to vomit, the gall-bladder seems to be constantly affected, and at such times dis- charges itself of its contents. Sometimes the bile concretes in the gall- bladder, so as to form what are called gall - K k 258 Of the Abdomen. stones .* When these concretions pass into the cystic duct, they sometimes occasion ex- quisite pain, by distending the canal in their way to the duodenum ; and by lodging in the ductus choledochus communis, and obstruct- ing the course of the bile, this fluid will be absorbed, and by being carried back into the circulation occasion a temporary jaundice. Sect. X. Of the Spleen. The spleen is a soft and spongy viscus, of a bluish colour, and about five or six fingers breadth in length, and three in width, situated in the left hypochondrium, between the sto- mach and the false ribs. That side of it which is placed on the side of the ribs is convex ; and the other, which is turned toward the stomach, is concave. The splenic artery, which is a branch from the cteliac, supplies this viscus with blood, and a vein of the same name carries it back into the vena portae. Its nerves are derived from a particular plexus called the splenic , which is formed by branches of the intercostal nerve, and by the eighth pair, or par vagum. The ancients, who supposed two sorts of bile, considered the spleen as the receptacle of what they called atra bills. Havers, who * These concretions sometimes remain in the gall-bladder without causing any uneasiness. Dr. Heberden relates, that a gall-stone weighing two drams was found in the gall-bladder of the late Lord Bath, though he had never complained of the jaundice, nor of any disorder which he could attribute to that cause. Med. 'Trans. Vol. ii. Of the Abdomen . 259 wrote professedly on the bones, determined its use to be that of secreting the synovia ; and the late Mr. Hewson imagined, that it concur- red with the thymus and lymphatic glands of the body in forming the red globules of -the blood. All these opinions seem to be equally fanciful. The want of an excretory duct has occasioned the real use of this viscus to be still doubtful. Perhaps the blood undergoes some change in it, which may assist in the pre- paration of the bile. This is the opinion of the generality of modern physiologists ; and the great quantity of blood with which it is supplied, together with the course of its veins into the vena portte, seem to render this no- tion probable. Sect. XI. Of the Glandule Renales, Kidneys, and Ureters. The glandulte renales, which were by the ancients supposed to secrete the atra bilis, and by them named capsules atrabilares , are two flat bodies of an irregular figure, one on each side between the kidney and the aorta. In the foetus they are as large as the kidneys : but they do not increase afterwards in propor- tion to those parts ; and in adults and old peo- ple they are generally found shrivelled, and much wasted. They have their arteries and veins. Their arteries usually arise from the splenic or the emulgent, and sometimes from the aorta ; and their veins go to the neighbour- ing veins, or to the vena cava. Their nerves are branches of the intercostal. 260 Of the Abdomen. The use of these parts is not yet perfectly known. In the foetus the secretion of urine must be in a very small quantity, and a part of the blood may perhaps then pass through these channels, which in the adult is carried to the kidneys to supply the matter of urine. The kidneys are two in number, situated one on the right and the other on the left side in the lumbar region, between the last false rib and the os ilium, by the sides of the verte- brae. Each kidney in its figure resembles a sort of bean, which from its shape is called hidney-bean. The concave part of each kidney is turned towards the aorta and vena cava as- cendens. They are surrounded by a good deal of fat, and receive a coat from the peri- tonaeum ; and when this is removed, a very fine membrane is found investing their sub- stance and the vessels which ramify through them. Each kidney has a considerable artery and vein, which are called the emulgent. The ar- tery is a branch from the aorta, and the vein passes into the vena cava. Their nerves, which every where accompany the blood- vessels, arise from a considerable plexus, which is derived from the intercostal. In each kidney, which in the adult is of a pretty firm texture, there are three substances to be distinguished.* The outer part is glan- dular or cortical, beyond this is the vascular * The kidneys in the fcetus are distinctly lobulated ; but in the adult they become perfectly firm, smooth, and regular. Of the Abdome?i. 261 or tubular substance, and the inner part is pa- pillary or membranous. It is in the cortical part of the kidney that the secretion is carried on ; the urine being here received from the minute extremities of the capillary arteries, is conveyed out of this cortical substance by an infinite number of ve- ry small cylindrical canals or excretory ves- sels, which constitute the tubular part. These tubes, as they approach the inner substance of the kidney gradually unite together ; and thus forming larger canals, at length termi- nate in ten or twelve little protuberances call- ed papilla, the orifices of which may be seen without the assistance of glasses. These pa- pillae open into a small cavity or reservoir called the pelvis of the kidney , and formed by a distinct membranous bag which embraces the papillae. From this pelvis the urine is conveyed through a membranous canal which passes out from the hollow side of the kidney, a little below the blood-vessels, and is called ureter. The ureters are each about as large as a common writing-pen. They are somewhat curved in their course from the kidneys, like the letter f and at length terminate in the pos- terior and almost inferior part of the bladder, at some distance from each other. They pass into the bladder in the same manner as the ductus choledochus communis passes into the intestinum duodenum, not by a direct passage, but by an oblique course between the two coats ; so that the discharge of urine into the bladder is promoted, whilst its return is pre- 262 Of the Abdomen . vented. Nor does this mode of structure pre- vent the passage of fluids only from the blad- der into the ureters, but likewise air : — for air thrown into the bladder inflates it, and it con- tinues to be distended if a ligature is passed round its neck ; which seems to prove suffici- ently that it cannot pass into the ureters. Sect. XII. Of the Urinary Bladder. The urinary bladder is a membranous and muscular bag of an oblong roundish shape, situated in the pelvis, between the os pubis and intestinum rectum in men, and between the os pubis and uterus in women. Its up- per and widest part is usually called the bot- tom , its narrow part the neck of the bladder ; the former only is covered by the peritonaeum. The bladder is formed of three coats, con- nected together by means of cellular mem- brane. The external or peritonaeal, is only a partial one, covering the upper and back part of the bladder. The middle, or muscular coat, is composed of irritable, and of course muscular fibres, which are most collected around the neck of the bladder, but not so as to form a distinct muscle, or sphincter, as the generality of anatomists have hitherto sup- posed. The inner coat, though much smoother, has been said to resemble the villous tunic of the intestines, and like that is provided with a mucus, which defends it against the acrimony of the urine. 263 Of the Abdomen. It will be easily conceived from what has been said, that the kidneys are two glandular bodies, through which a saline and excremen- titious fluid called urine is constantly filtering from the mass of blood. While only a small quantity of urine is col- lected in the bladder, it excites no kind of un- easiness ; but when a greater quantity is ac- cumulated, so that the bladder is distended in a certain degree, it excites in us a certain sen- sation, which brings on as it were a voluntary contraction of the bladder to promote its dis- charge. — But this contraction is not effected by the muscular fibres of the bladder alone : for all the abdominal muscles contract in obe- dience to our will, and press downwards all the viscera of the lower belly ; and these pow- ers being united, at length overcome the re- sistance of the fibres surrounding the neck of the bladder, which dilates and affords a pas- sage to the urine through the urethra. The frecpiency of this evacuation depends on the quantity of urine secreted ; on the de- gree of acrimony it possesses ; on the size of the bladder, and on its degree of sensibility. The urine varies much in its colour and contents. These varieties depend, on age, sex, climate, diet, and other circumstances. In in- fants it is generally a clear watery fluid, with- out smell or taste. As we advance in life, it acquires more colour and smell, and becomes more impregnated with salts. In old people it becomes still more acrid and fetid. In a healthy state it is nearly of a straw co- lour. — After being kept for some time, it de- 264 Of the Abdomen. posites a tartarous matter, which is found to be composed chiefly of earth and salt, and soon incrusts the sides of the vessel in which it is contained. While this separation is tak- ing place, appearances like minute fibres or threads of a whitish colour may be seen in the middle of the urine, and an oily scum observ- ed floating on its surface. So that the most common appearances of the urine are suffici- ent to ascertain that it is a watery substance, impregnated with earthy, saline, and oily par- ticles. The urine is not always voided of the same colour and consistence: for these are found to depend on the proportion of its watery part to that of its other constituent principles. — Its co- lour and degree of fluidity seem to depend on the quantity of saline and inflammable parti- cles contained in it : so that an increased pro- portion of those parts will constantly give the urine a higher colour, and add to the quanti- ty of sediment. The variety in the appearance of the urine, depends on the nature and quantity of solid and fluid aliment we take in ; and it is like- wise occasioned by the different state of the urinary vessels, by which we mean the chan- nels through which it is separated from the blood, and conveyed through the pelvis into the ureters. The causes of calculous concre- tions in the urinary passages, are to be looked for in the natural constitution of the body, mode of life, &c. It having been observed, that after drink- ing any light wine or Spa water, it very soon Of the Abdomen. 26 5 passed off by urine, it has been supposed by some, that the urine is not altogether convey- ed to the bladder by the ordinary course of circulation, but that there must certainly exist some other shorter means of communication, perhaps by certain vessels between the sto- mach and the bladder, or by a retrograde motion in the lymphatics. But it is certain, that if we open the belly of a dog, press out the urine from the bladder, pass a ligature round the emulgent arteries, and then sew up the abdo- men, and give him even the most diuretic li- quor to drink, the stomach and other chan- nels will be distended with it, but not a drop of urine will be found to have passed into the bladder ; or the same thing happens when a ligature is thrown round the two ureters. This experiment then seems to be a sufficient proof, that all the urine we evacuate, is conveyed to the kidneys through the emulgent arteries, in the manner we have described. — It is true, that wine and other liquors promote a speedy eva- cuation of urine : but the discharge seems to be merely the effect of the stimulus they occa- sion \ by which the bladder and urinary parts are solicited to a more copious discharge of the urine, which was before in the body, and not immediately of that which was last drank ; and this increased discharge, if the supply is kept up, will continue : nor will this appear won- derful, if we consider the great capacity of the vessels that go to the kidneys ; the constant sup- ply of fresh blood that is essential to health ; and the rapidity with which it is incessantly LI 266 Of the Abdomen. circulated through the heart to all parts of the body. Sect. XIII. Of Digestion. We are now proceeding to speak of diges- tion , which seems to be introduced in this place with propriety, after a description of the abdominal viscera, the greater part of which contribute to this function. By digestion is to be understood, the changes the aliment under- goes for the formation of chyle : — these chan- ges are effected in the mouth, stomach, and small intestines. The mouth, of which every body has a ge- neral knowledge, is the cavity between the two jaws, formed anteriorly and laterally by the lips, teeth, and cheeks, and terminating posteriorly in the throat. The lips and cheeks are made up of fat and muscles, covered by the cuticle, which is con- tinued over the whole inner surface of the mouth, like a fine and delicate membrane. — Besides this membrane, the inside of the mouth is furnished with a spongy and very vascular substance called therms, by means of which the teeth are secured in their sockets. A simi- lar substance covers the roof of the mouth, and forms what is called the velum pendulum palati , which is fixed to the extremity of the arch formed by the ossa maxillaria and ossa pa- lati, and terminates in a soft, small, and coni- cal body, named uvula ; which appears, as it were, suspended from the middle of the arch over the basis of the tongue. 267 Of the Abdomen * The velum pendulum palati performs the office of a valve between the cavity of the mouth and the pharynx, being moved by se- veral muscles.* The tongue is composed of several mus- clesf which enable it to perform a variety of motions for the articulation of the voice ; for the purposes of mastication ; and for convey- ing the aliment into the pharynx. Its upper part is covered with papillse, which constitute the organ of taste, and are easily to be dis- tinguished; it is covered by the same lpem- brane that lines the inside of the mouth, and which makes at its inferior part towards its ba- sis a reduplication called franum. Posteriorly, under the velum palati, and at the basis of the tongue, is the pharynx : which is the beginning of the oesophagus, stretched out every way, so as to resemble the top of a funnel, through which the aliment passes into the stomach. The mouth has a communication with the nostrils at its posterior and upper part : with the ears, by the Eustachian tubes ; with the lungs, by means of the larynx ; . and with the stomach, by means of the oesophagus. The pharynx is constantly moistened by a fluid, secreted by two considerable glands call- ed the tonsils , one on each side of the velum palati. These glands, from their supposed re- * These are the circumflexus palati, levator palati mollis, pa- lato-pharyngasus, constrictor isthmi faucium and azygos uvulse. See pages 191, 192, 193. f These are, the genio-glossus, hyo-glossus, lingualis, and stylo-glossus. Seepage 191. 268 Of the Abdomen. semblance to almonds, have likewise been call- ed cimygdalus. The mouth is moistened by a considerable quantity of saliva. This fluid is derived from the parotid glands ; a name which by its ety- mology points out their situation to be neat the ears. They are two in number, one on each side under the os malse : and they are of the conglomerate kind ; being formed of many smaller glands, each of which sends out a very small excretory duct, which unites with the rest, to form one common channel, that runs over the cheek, and piercing the buccinator muscle, opens into the mouth on each side, by an orifice into which a bristle may be easily in- troduced. — Besides these, the maxillary glands, which are placed near the inner surface of the angle of the lower jaw on each side ; the sub- lingual glands, which are situated at the root of the tongue ; the glands of the palate, which are seated in the velum palati ; and those of the cheeks, lips, &c. together with many other less considerable ones, — pour the saliva into the mouth through their several excretory ducts. The saliva, like all the other humors of the body, is found to be different in different peo- ple : but in general, it is a limpid and insipid fluid, without smell in healthy subjects ; and these properties would seem to prove that it contains very few saline or inflammable parti- cles. The uses of the saliva seem to be to moisten and lubricate the mouth, and to assist in re- 269 Of the Abdomen. ducing the aliment into a soft pulp before it is conveyed into the stomach. The variety of functions which are constant- ly performed by the living body, must neces- sarily occasion a continual waste and dissipa- tion of its several parts. A great quantity is every day thrown off by the insensible perspi- ration and other discharges ; and were not these losses constantly recruited by a fresh supply of chyle, the body would soon effect its own dis- solution. But nature has very wisely favour- ed us with organs fitted to produce such a sup- ply ; and has at the same time endued us with the sensations of hunger and thirst, that our attention may not be diverted from the neces- sary business of nutrition- The sensation of hunger is universally known ; but it would perhaps be difficult to describe it perfectly in words. It may, however, be defined to be a certain uneasy sensation in the stomach, which induces us to wish for solid food ; and which likewise serves to point out the proper quan- tity, and time for taking it. In describing the stomach, mention was made of the gastric juice, as every where lubricating its inner coat. This humor mixes itself with the aliment in the sto- mach, and helps to prepare it for its passage into the intestines ; but when the stomach is* perfectly empty, this same fluid irritates the. coats of the stomach itself, and produces the sensation of hunger. A certain proportion of liquid aliment is re- quired to assist in the process of digestion, and to afford that moisture to the body, of which there is such a constant dissipation. — Thirst induces us to take this necessary supply of 270 Of the Abdomen. drink ; and the seat of this sensation is in the tongue, fauces, and oesophagus, which from their great sensibility are required to be kept moist : for though the fauces are naturally moistened by the mucus and salival juices ; yet the blood, when deprived of its watery part or rendered acrimonious by any natural causes, never fails particularly to affect these parts, and the whole alimentary canal, and to occasion thirst. — This is the common effect of fevers and of hard labour, by both which too much of the watery part of the blood is dis- sipated, It has been observed, that the aliment un- dergoes some preparation in the mouth before it passes into the stomach ; and this prepara- tion is the effect of mastication. In treating of the upper and lower jaws, mention was made of the number and arrangement of the teeth. The upper jaw was described as being immoveable ; but the lower jaw was spoken of as being capable of elevation and depression, and of a grinding motion. The aliment, when first carried into the mouth, is pressed between the teeth of the two jaws by a very strong and frequent motion of the lower jaw; and the tongue and the cheeks assisting in this process, continue to replace the food between the teeth till it is perfectly divid- ed, and reduced to the consistence of pulp. The incisores and canini divide it first into smaller pieces, but it is between the surfaces of the dentes molares by the grinding motion of the jaw that the mastication is completed. During this process the salival glands being gently compressed by the contraction of the 271 Of the Abdomen. muscles that move the lower jaw, pour out their saliva : this helps to divide and break down the food, which at length becomes a kind of pulp, and is then carried over the basis of the tongue into the fauces. But to effect this passage into the oesophagus, it is necessary that the other openings which were mentioned as having a communication with the mouth as well as the pharynx, should be closed; that none of the aliment, whether solid or liquid, may pass into them, whilst the pharynx alone is dilated to re- ceive it : — And such a disposition actually takes place in a manner we will endeavour to de- scribe. The trachea arteria, or windpipe, through which the air is conveyed to the lungs, is plac- ed before the oesophagus — in the act of swal- lowing ; therefore, if the larynx (for so the up- per part of the trachea is called) is not closed, the aliment will pass into it in its way to the oesophagus. But this is prevented by a small and very elastic cartilage, called epiglottis , which is attached only to the fore-part of the larynx ; so that the food in its passage to the oesopha- gus presses down this cartilage, which then co- vers the glottis or opening of the larynx ; and at the same time the velum palati being capable of some degree of motion, is drawn backwards by its muscles, and closes the openings into the nose and the Eustachian tubes. — This, howe- ver, is not all. The larynx, which being com- posed of cartilaginous rings, cannot fail in its ordinary state to compress the membranous ca- nal of the oesophagus, is in the act of degluti- tion carried forwards and upwards by muscles .272 Of the Abdomen. destined for that purpose ; and consequently drawing the fore-part of the pharynx with it, that opening is fully dilated. When the ali- ment has reached the pharynx, its descent is promoted by its own proper weight, and by the muscular fibres of the cesophagus, which con- tinue to contract from above downwards, until the aliment has reached the stomach. That these fibres have no inconsiderable sharedn de- glutition, any person may experience, by swallowing with his head downwards, when the descent of the aliment cannot possibly be ef- fected by its weight. It is necessary that the nostrils and the lungs should communicate with the mouth, for the purposes of speech and respiration: but if the most minute part of our food happens to be introduced into the trachea, it never fails to produce a violent cough, and sometimes the most alarming symptoms. This is liable to happen when we laugh or speak in the act of deglutition : the food is then said to have passed the wrong way. And indeed this is not im- properly expressed : for death would soon fol- low, if the quantity of aliment introduced into the trachea should be sufficient to obstruct the respiration only during a very short time ; or if the irritating particles of food should not soon be thrown up again by means of the cough, which in these cases very seasonably increases in proportion to the degree of irrita- tion. If the velum palati did not close the passage to the nostrils, deglutition would be performed with difficulty, and perhaps not at all ; for the 273 Of the Abdomen. aliment would return through the nose, as is sometimes the case in drinking. Children, from a deficiency in this velum palati, have been seen to die a few hours after birth ; and they who from disease or any other causes have not this part perfect, swallow with diffi- culty. The aliment, after having been sufficiently divided by the action of the teeth, and attenu- ated by the saliva, is received into the stomach, where it is destined to undergo a more consi- derable change. The properties of the aliment not being much altered at its first entrance into the stomach, and before it is thoroughly blended with the gastric juice, is capable of irritating the inner coat of the stomach to a certain degree, and occasions a contraction of its two orifices. — In this membranous bag, surrounded by the abdo- minal viscera, and with a certain degree of na- tural heat, the aliment undergoes a constant agitation by means of the abdominal muscles and of the diaphragm, and likewise by a cer- tain contraction or expansion of the muscular fibres of the stomach itself. By this motion, every part of the food is exposed to the action of the gastric juice, which gradually divides and attenuates it, and prepares it for its pas- sage into the intestines. Some observations lately published by Mr. Hunter in the Philosophical Transactions, tend to throw considerable light on the principles of digestion. There are few dead bodies in which the stomach, at its great end, is not found to M m 274 Of the Abdomen. be in some degree digested Animals, or parts of animals, possessed of the living prin- ciple, when taken into the stomach, are not in the least affected by the action of that viscus ; but the moment they lose the living principle, they become subject to its digestive powers. This seems to be the case with the stomach, which is enabled to resist the action of its juices in the living body : but when deprived of the living principle, it is then no longer able to resist the powers of that menstruum, which it had it- self formed for the digestion of its contents ; the process of digestion appearing to be conti- nued after death. This is confirmed by what happens in the stomachs of fishes : they fre- quently swallow, without mastication, fish which are larger than the digesting parts of their stomach can contain } and in such cases, that part which is taken into the stomach is more * The Abbe Spallanzani, who has lately written upon di- gestion, finds, from a variety of experiments, made upon quadru- peds, birds, and fishes, that digestion goes on for some time after death, though far less considerable than in living animals ; but heat is necessary in many animals, or at least promotes it in a much greater degree. He found also, that when the stomach was cut out of the body, it had somewhat of the power of diges- tion, though this was trifling when compared with that which took place when the stomach was left in the body. In not one of the animals wa' the great curvature of the stomach dissolved, or much eroded after death. There was often a little erosion, especially in different fishes ; in which, when he had cleared the stomach of its contents, the internal coat’was wanting. In other animals there was only a slight excoriation ; and the injury in all of them was at the inferior part, or great curvature. The coats of the stomach suffer less after death than flesh, or part of the stomach of similar animals put into it : the author assigns as a reason for this, that these bodies are invested on all sides by the gastric fluid, whereas it only acts on the internal surface of the stomach. Of the Abdomeiu or less dissolved, while that part which re- mains in the oesophagus is perfectly sound ; and here, as well as in the human body, the digesting part of the stomach is often reduced to the same state as the digested part of the food. These appearances tend to prove, that digestion is not effected by a mechanical power, by contractions of the stomach, or by heat ; but by a fluid secreted in the coats of the sto- mach, which is poured into its cavity, and there animalizes the food, or assimilates it to the nature of blood. From some late experiments by M. Sage, * it appears, that inflammable air has the proper- ty of destroying and dissolving the animal tex- ture : and as we swallow with the substances which serve us for food a great quantity of at- mospherical air, M. Sage thinks it possible, that dephlogisticated, which is its principle, may be converted in the stomach into inflam- mable air, or may modify into inflammable air a portion of the oily substance which is the principle of aliments. In this case, would not the inflammable air (he asks), by dissolv- ing our food, facilitate its conversion into chyle ? Be this as it may, the food after having re- mained one, two, or three hours in the stomach, is converted into a greyish pulp, which is usu- ally called chymus , a word of Greek etymolo- gy, signifying juice , and some few milky or chylous particles begin to appear. — But the * Hist, de 1 ’ A cademie royals des Sciences, Src. pour 1784. mem. 15. 276 Of the Abdomen. term of its residence in this bag is proportion- ed to the nature of the aliment, and to the state of the stomach and its juices. The thinner and more perfectly digested parts of the food pass by a little at a time into the duodenum, through the pylorus, the fibres of which relax to afford it a passage ; and the grosser and less digested particles remain in the stomach, till they ac- quire a sufficient fluidity to pass into the intes- tines, where the nature of the chymus is per- fectly changed. The bile and pancreatic juice which flow into the duodenum, and the mucus, which is every where distilled from the surface of the intestines, mix themselves with the ali- mentary pulp, which they still farther attenu- ate and dissolve, and into which they seem to infuse new properties. Two matters very different from each other in their nature and destination, are the result of this combination. — One of these, which is composed of the liquid parts of the aliment, and of some of its more solid particles, ex- tremely divided and mixed with the juices we have described, constitutes a very mild, sweet, and whitish fluid, resembling milk, and distin- guished by the name of chyle. This fluid is ab- sorbed by the lacteal veins, which convey it in- to the circulation, where, by being assimilated into the nature of blood, it affords that supply of nutrition, which the continual waste of the body is found to require. — The other is the re- mains of the alimentary mass deprived of all its nutritious particles, and containing only such parts as were rejected by the absorbing mouths of the lacteals. This grosser part, Of the Abdomen. 277 called the faces, passes on through the course of the intestines, to be voided at the anus, as will be explained hereafter ; for this process in the (economy cannot be well understood till the motion of respiration has been explained. But the structure of the intestines is a subject which may be properly described in this place, and deserves to be attended to. It has been already observed, that the intes- tinal canal is five or six times as long as the bo- dy, and that it forms many circumvolutions in the cavity of the abdomen, which it traverses from the right to the left, and again from the left to the right ; in one place descending, and in another extending itself upwards. It was noticed likewise, that the inner coat of the in- testines, by being more capacious than their ex- terior tunics, formed a multitude of plates plac- ed at a certain distance from each other, and called valvula conniventes. Npw this disposi- tion will be found to afford a farther proof of that divine wisdom, which the anatomist and physiologist cannot fail to discover in all their pursuits. — For if the intestinal canal was much shorter than it naturally is ; if instead of the present circumvolutions it passed in a direct course from the stomach ; and if its inner sur- face was smooth and destitute of valves ; the aliment would consequently pass with great ra- pidity to the anus, and sufficient time would be wanting to assimilate the chyle, and for the ne- cessary absorption of it into the lacteals : so that the body would be deprived of the supply of nutrition, which is so essential to life and health ; but the length and circumvolutions of 278 Of the Abdomen. the intestines, the inequality of their internal surface, and the course of the aliment through them, all concur to perfect the separation of the chyle from the fasces, and to afford the ne- cessary nourishment to the body. Sect. XIV. Of the Course of the Chyle , and of the Lymphatic System. An infinite number of very minute vessels, called the lacteal veins , arise like net-work from the inner surface of the intestines, (but princi- pally from the jejunum and ilium), which are distended to imbibe the nutritious fluid or chyle. These vessels, which were discovered by Asellius in 1622 , * pass obliquely through the coats of the intestine, and running along the mesentery, unite as they advance, and form larger branches, all of which pass through the mesenteric or conglobate glands, which are ve- ry numerous in the human subject. As they * We are informed by Galen, that the lacteals had been seen in kids by Erasistratus, who considered them as arteries carrying a milky fluid : but from the remote time in which he lived, they do not seem to have been noticed till they were discovered in a living dog by Asellius, who denominated them lacteals, and con- sidered them as serving to convey the chyle from the intestines to the liver ; for before the discovery of the thoracic duft, the use of the liver was universally supposed to be that of converting the chyle into blood. But the discovery of the thoracic duct by Pec- quet, not long after, corrected this error. Pecquet very candidly confesses, that this discovery accidentally arose from his observ- ing a white fluid, mixed with the blood, flowing out of the vena cava, after he had cut off the heart of a living dog ; which he sus- pected to be chyle, and afterwards traced to its source from the thoracic duct : this duct had been seen near an hundred years be- fore in a horse by Eustachius, who speaks of it as a vein of a particular structure, but without knowing any thing of its termi- nation or use. 279 Of the Abdomen. run between the intestines and these glands, they are styled vena; lactea primi generis : but after leaving these glands, they are found to be less numerous, and being increased in size, are then called vena lactea secundi generis , which go to deposite their contents in the thoracic duct , through which the chyle is conveyed into the blood. This thoracic duct begins about the lower part of the first vertebra lumborum, from whence it passes up by the side of the aorta, between that and the vena azygos, close to the vertebrae, being covered by the pleura. Some- times it is found divided into two branches ; but they usually unite again into one canal, which opens into the left subclavian vein, after having run a little way in an oblique course between its coats. The subclavian vein communicates with the vena cava, which passes to the right auricle of the heart. The lower part of this duct being usually larg- er than any other part of it, has been named receptaculum chyli , or Pecquet's receptacle in honour of the anatomist who first discovered it in 16 51. In some quadrupeds, in turtle and in fish, this enlargement * is more considera- ble in proportion to the size of the duct, than it usually is in the human subject, where it is not commonly found large enough to merit the name of receptaculum. Opportunities of observing the lacteals in the human subject do not often occur; but they may be easily demonstrated in a dog or * Hewson’s Exp. Inq. Part Ii. 280 Of the Abdomen. any other quadruped that is killed two or three hours after feeding upon milk, for then they appear filled with white chyle. But these Icicteals which we have described, as passing from the intestines through the mesen- tery to the thoracic duct, compose only a part of a system of vessels which perform the of- fice of absorption , and which constitute, with their common trunk the thoracic duct, and the conglobate glands that are dispersed through the body, what may be styled the lymphatic system. So that what is said of the structure of one of these series of vessels may very properly be applied to that of the other. The lymphatic veins* are minute pellucid tubes, which, like the lacteals, direct their course towards the centre of the body, where they pour a colourless fluid into the thoracic duct. The lymphatics from all the lower parts of the body gradually unite as they approach this duct, into which they enter by three or four very large trunks, that seem to form the lower extremity of this canal, or receptaculum * The arteries in their course through the body becoming gra- dually too minute to admit the red globules of the blood, have then been styled capillary or lymphatic arteries. The vessels which are here described as constituting the lymphatic system, were at first supposed to be continued from those arteries, and to convey back thelvmph, either into the red veins or the thoracic duct ; the office of absorption having been attributed to the red veins. But we know that the lymphatic veins are not continuations of the lym- phatic arteries, but that they constitute the absorbent system. There are still, however, some very respectable names among the anatomists of the present age, who contend, that the red veins act likewise as absorbents : — but it seems to have been clearly proved, that the red veins do absorb nowhere but in the cavernous cells of the penis, the erection of which is occasioned by a distention of those cells with arterial blood, 281 Of the Abdomen . chyli, which may be considered as the great trunk of the lymphatic system. The lacteals open into it near the same place ; and the lym- phatics, from a large share of the upper parts of the body, pour their lymph into different parts of this duct as it runs upwards, to termi- nate in the left subclavian vein. The lympha- tics from the right side of the neck, thorax, and right arm, £kc. terminate in the right subclavi- an vein. As the lymphatics commonly lie close to the large blood-vessels, a ligature passed round the crural artery in a living animal, by includ- ing the lymphatics, will occasion a distention of these vessels below the ligature, so as to de- monstrate them with ease ; and a ligature pass- ed round the thoracic duct, instantly after kill- ing an animal, will, by stopping the course of its contents into the subclavian vein, distend not only the lacteals, but also the lymphatics in the abdomen and lower extremities, with their na- tural fluids. * The coats of these vessels are too thin to be separated from each other ; but the mercury they are capable of sustaining, proves them to be very strong ; and their great power of con- traction, after undergoing considerable disten- tion, together with the irritability with which Baron Haller found them to be enduedf, seems N n * In the dead body they may be easily demonstrated by open- ing the artery ramifying through any viscus, as in the spleen, for instance, and then throwing in air ; by which the lymphatics will be distended. One of them may then be punctured, and mercury introduced into it through a blow-pipe. t Sur le movement du sang Ex. 295, 298. 282 Of the Abdomen. to render it probable, that, like the blood-ves- sels, they have a muscular coat. The lymphatics are nourished after the same manner as all the other parts of the body. For even the most minute of these vessels are pro- bably supplied with still more minute arteries and veins. This seems to be proved by the inflammation of which they are susceptible ; and the painful swellings which sometimes take place in lymphatic vessels, prove that they have nerves as well as blood-vessels. Both the lacteals, lymphatics, and thoracic duct,, are furnished with valves, which are much more common in these vessels than in the red veins. These valves are usually in pairs, and serve to promote the course of the chyle and lymph towards the thoracic duct, and to prevent its return. Mention has been made of the glands, through' which the lacteals pass in their course through the mesentery ; and it is to be observed, that the lymphatics pass through similar glands in their way to the tho- racic duct. These glands are all of a conglo- bate kind, but the changes which the chyle and lymph undergo in their passage through them,, have not yet been ascertained. The lymphatic vessels- begin from surfaces and cavities in all parts of the body as absorb - ents. This is a fact now universally allowed ; but how the fluids they absorb are poured into those cavities, is a subject of controversy. The contents of the abdomen, for instance, were described as being constantly moistened by a very thin watery fluid. The same thing takes place in the pericardium, pleura,, and all the 283 Of the Abdomen. e>ther cavities of the body, and this watery flu- id is the lymph. But whether it is exhaled into those cavities through the minute ends of arte- ries, or transuded through their coats, are the points in dispute. We cannot here be permit- ted to relate the many ingenious arguments that have been advanced in favour of each of these opinions ; nor is it perhaps of conse- quence to our present purpose to enter into the dispute. It will be sufficient if the reader can form an idea of what the lymph is, and . of the manner in which it is absorbed. The lymph , from its transparency and want of colour, would seem to be nothing but wa- ter ; and hence the first discoverers of these vessels styled them ductus aquosi : but experi- ments prove, that the lymph of an healthy ani- mal coagulates by being exposed to the air, or a certain degree of heat, and likewise by be- ing suffered to rest ; seeming to agree in this property with that part of the blood called the coagulcible lymph. — This property of the lymph leads to determine its use, in moistening and lubricating the several cavities of the body in which it is found; and for which, by its gela- tinous principle, it seems to be much better calculated than a pure and watery fluid would be, for such it has been supposed to be by some anatomists. The mouths of the lymphatics and lactecds , by acting as capillary tubes, seem to absorb the lymph and chyle somewhat in the same manner as a capillary tube of glass, when put into a ba- son of water, is enabled to attract the water into it to a certain height ; but it is probable that they 284 Of the Abdomen. likewise possess a living power, which assists in performing this office. In the human body the lymph , or the chyle , is probably conveyed upon this principle as far as the first pair of valves, which seem to be placed not far from the orifice of the absorbing vessel, whether lymphatic or lacteal ; and the fluid will then be propelled forwards, by a continuation of the absorption at the orifice. But this does not seem to be the only inducement to its progress towards the thoracic duct ; these vessels have probably a muscular coat, which may serve to press the fluid forwards from one pair of valves to another ; and as the large lymphatic vessels and the thoracic duct are placed close to the large arteries, which have a considerable pul- sation, it is reasonable to suppose, that they derive some advantages from this situation. Sect. XV. Of the Generative Organs ; of Conception , &c. $. 1 . The Male Organs. The male organs of generation have been usually divided into the parts which serve to prepare the semen from the blood, and those which are distended to convey it into the womb. But it seems to be more proper to distinguish them into the preparing , the containing , and the expelling parts, which are the different offices of the testes , the vesiculce seminales , and the penis ; and this is the order in which we propose to describe them. 285 Of the Abdomen. The testes are two glandular bodies, serving to secrete the semen from the blood. They are originally formed and lodged within the ca- vity of the abdomen ; and it is not till after the child is born, or very near that time, that they begin to pass into the groin, and from thence into the scrotum.* By this disposition they are very wisely protected from the inju- ries to which they would be liable to be ex- posed, from the different positions of the child at the time of parturition. The testicles in this state are loosely at- tached to the psose muscles, by means of the peritonaeum by which they are covered ; and they are at this time of life connected in a very particular manner to the parietes of the abdomen, and likewise to the scrotum, b y means of a substance which Mr. Hunter calls the ligament or gubernaculum testis , because it connects the testis with the scrotum, and di- rects its course in its descent. This guber- * It sometimes happens in dissecting ruptures, that the intes- tine is found in the same sac, and in contact with the testis. This appearance was at first attributed to a supposed laceration of the peritonaeum ; but later observations, by pointing out the situation of the testicles in the foetus, have led to prove, that the testis, as it descends into the scrotum, carries with it a por- tion or elongation of the peritonaeum, which becomes its tunica vaginalis, or a kind of sac, in which the testicle is lodged, as will be explained in the course of this section. The communica- tion between this sac and the cavity of the abdomen, is usually soon cut off ; but in some subjects it continues open during life $ and when an hernia or descent of the intestine takes place in such a subject, it does not push down a portion of the peritonaeum before it, as it must otherwise necessarily do, but passes at once through this opening, and comes in contact with tire naked tes- ticle, constituting that particular species of rupture called hernia congenita. 286 Of the Abdomen. naculum is of a pyramidal form, with its bul- bous head fixed to the lower end of the testis and epididymis, and loses its lower and slen- der extremity in the cellular membrane of the scrotum. It is difficult to ascertain what the structure and composition of this gubernacu- lum is, but it is certainly vascular and fibrous ; and, from certain circumstances, it would seem to be in part composed of the cremaster mus- cle, running upwards to join the lower end of the testis. We are not to suppose that the testicle, when descended into the scrotum, is to be seen loose as a piece of gut or omentum would be in a common hernial sac. We have already observed, that during its residence in the cavity of the abdomen it is attached to the peritoneum, which descends with it ; so that when the sac is completed in the scrotum, the testicle is at first attached only to the posterior part of it, while the fore part of it lies loose, and for some time affords a communication with the abdomen. The spermatic chord., which is made up of the spermatic artery and vein, and of the vas deferens or excretory duct of the testis, is closely attached behind to the posterior part of this elongation of the perito- naeum- But the fore part of the peritoneal sac, which is at first loose and not attached to the testicle, closes after a certain time, and becomes united to the posterior part, and thus perfectly surrounds the testicle as it were in a purse. The testicles of the foetus differ only in their size and situation from those of the adult. In Of the Abdomen. 28 Z their passage from the abdomen they descend through the abdominal rings into the scrotum, where they are supported and defended by va- rious integuments. What the immediate cause of this descent is, has not yet been satisfactorily determined. It has been ascribed to the effects of respira- tion, but the testicles have sometimes been found in the scrotum before the child has breathed; and it does not seem to be occasi- oned by the action of the cremaster muscle, because the same effect would be liable to happen to the hedge-hog, and some other quadrupeds, whose testicles remain in the ab- domen during life. The scrotum, which is the external or com- mon covering of both testicles, is a kind of sac formed by the common integuments, and ex- ternally divided into two equal parts by a pro- minent line called raphe. In the inner part of the scrotum we meet with a cellular coat called dart-os ,* which by its duplieature divides the scrotum into two- equal parts, and forms what is called septum scroti , which corresponds with the raphe. The collapsion which is so often observed to take place in the scrotum of the healthy sub- ject, when excited by cold or by the stimulus of venery, seems to be very properly attribut- * The dartos has usually been considered as a muscle, and is described as such both by Douglas and Winslow. But there iaeing no part of the scrotum of the human subject which can be- to consist of muscular fibres, Albinus and Haller have very ^^perly omitted to describe the dartos as a muscle, and consider it merelv as a cellular coat. 28 S Of the Abdomen. ed to the contractile motion of the skin, and not to any muscular fibres, as is the case in dogs and some other quadrupeds. The scrotum, then, by means of its septum, is found to make two distinct bags, in which the testicles, invested by their proper tunics, are securely lodged and separated from each other. These coats are the cremaster, the tunica vaginalis, and the tunica albuginea. The first of these is composed of muscular fibres, and is to be considered only as a par- tial covering of the testis ; for it surrounds only the spermatic chord, and terminates upon the upper and external parts of the tunica va- ginalis testis, serving to draw up and suspend the testicle.* The tunica vaginalis testis has already been described as being a thin pro- duction of the peritonaeum, loosely adhering every where to the testicle, which it includes as it were in a bag. The tunica albuginea is a firm, white, and very compact membrane of a glistening appearance, which immediate- ly invests the body of the testis and the epidi- dymus ; serving in some measure to connect them to each other, but without extending itself at all to the spermatic chord. This tu- nica albuginea serves to confine the growth of the testis and epididymus within certain limits, and by giving them a due degree of firmness, enables them to perform their pro- per functions. * The cremaster muscle is composed of a few fibres from the obliquus internus abdominis, which uniting with a few from the transversalis, descend upon the spermatic chord, and are insen- sibly lost upon the tunica vaginalis of the testicle. It serves to suspend and draw up the testicle. 289 Of the Abdomen • Having removed this last tunic, we disco- ver the substance of the testicle itself, which appears to be made up of an infinite number of very elastic filaments, which may be best distinguished after macerating the testicle in water. Each testicle is made up of the sper- matic artery and vein, and the excretory ves- sels or tubuli seminiferi. There are likewise a great number of absorbent vessels, and some branches of nerves to be met with in the tes- ticles. The spermatic arteries arise one on each side from the aorta, generally about an inch below the emulgents. The right spermatic vein commonly passes into the vena cava ; but the left spermatic vein usually empties itself into the emulgent on that side ; and it is sup- posed to take this course into the emulgent, that it may avoid passing over the aorta, which it would be obliged to do in its way to the vena cava. The blood is circulated very slowly through the spermatic artery, which makes an infinite number of circumvolutions in the substance of the testicle, where it deposites the semen, which passes through the tubuli seminiferi. These tubuli seminiferi are seen running in short waves from the tunica albuginea to the axis of the testicle ; and are divided into dis- tinct portions by certain thin membranous pro- ductions, which originate from the tunica al- buginea. They at length unite, and by an infinite number of convolutions form a sort of O o 290 Of the Abdomen. appendix to the testis called epididymis ,* which is a Vascular body of an oblong shape, situate upon the superior part of each testicle. These tubuli of the epididymis at length form an ex- cretory duct called vas deferens , which as- cends towards the abdominal rings, with the other parts that make up the spermatic chord, and then a separation takes place ; the nerves and blood-vessels passing on to their several terminations, and the vas deferens going to deposite its semen in the vesiculse seminales, which are two soft bodies of a white and con- voluted appearance externally, situated ob- liquely between the rectum and the lower part of the bladder, and uniting together at the lower extremity. From these reservoirs, t * The testicles were named didymi by the ancients, and the name of this part was given to it on account of its situation upon the testicle. -j- That the bags called veskula seminalts are reservoirs of se- men, is a circumstance which has been by anatomists universal- ly believed. Mr. J. Hunter, however, from several circumstan- ces, has been induced to think this opinion erroneous. He has examined these vesiculae in people who have died sud- denly, and he found their contents to be different in their proper- ties from the semen. In those who had lost one of the testicles, or the use of one of them, by disease,' both the vesiculae were full, and their contents similar. And in a lusus nature, where there was no communication between the vasa deferentia and ve- siculse, nor between the vesiculse and penis, the same thing took place. From these observations, he thinks we have a presumptive proof, That the semen can be absorbed in the body of the testi- cle and in the epididymis, and that the vesiculae secrete a mucus which they are capable of absorbing when it cannot be made use of : That the semen is not retained in reservoirs after it is secret- ed, and kept there till it is used; but that it is secreted at the time, in consequence of certain affections of tire mind stimulat- ing the testicles to this action. He corroborates his observations by the appearance on dissec- tion in other animals ; and here he finds, That the shape and 291 Of the Abdomen. which are plentifully supplied with blood-ves- sels and nerves, the semen is occasionally dis- charged through two short passages, which open into the urethra close to a little eminence called verumontamim. contents of the vesiculae vary much in different animals, while the semen in most of them he has examined is nearly the same ; That the vasa deferentia in many animals do not communicate with the vesiculae : That the contents of the vesiculae of castrated and perfect animals are similar, and nearly equal in quantity, in no way resembling the semen as emitted from the animal in coitu, or what is found in the vas deferens after death. He ob- serves likewise, that the bulb of the urethra of perfect males is considerably larger than in castrated animals. From the whole, he thinks the following inferences may be fairly drawn : That the bags called vesicuU seminales are not se- minal reservoirs, but glands secreting a peculiar mucus ; and that the bulb of the urethra is properly speaking the receptacle of the semen, in which it is accumulated previous to ejection. But although he has endeavoured to prove that the vesiculae do not contain the semen, he has not been able to ascertain their particular use. He thinks, however, we may be allowed upon the whole to conclude, that they are, together with other parts, subservient to tire purposes of generation. Although the author has treated this subject very ably, and made many ingenious observations, some things may be object- ed to what he has advanced ; of which the following are a few : That those animals who have bags called vesical* seminales per- form copulation quickly ; whereas others that want them, as in the dog kind, are tedious in copulation: That in tire human body, at least, there is a free communication between the vasa deferentia and vesiculae ; and in animals where the author has observed no communication between the vasa deferentia and ve- siculae, there may be a communication by vessels not yet disco- vered, and which may be compared to the hepato-cystic ducts in fowls and fishes : That the fluid in the end of the vasa defe- rentia and the vesiculae seminales are similar, according to the author’s own observation : That the vesiculae in some animals increase and decrease with the testicle at particular seasons : That in birds and certain fishes, there is a dilatation of the ends of the vasa deferentia, which the author himself allows to be a reservoir for the semen. With respect to the circumstance of the bulb of the urethra answering the purpose of a reservoir, the author has mentioned no facts which tend to establish this opinion. See Observations on certain Parts of the minimal 0 economy. 292 Of the Abdomen. Near this eminence we meet with the pros- tate, which is situated at the neck of the blad- der, and is described as being of a glandular structure. It is shaped somewhat like a heart with its small end foremost, and invests the origin of the urethra. Internally it appears to be of a firm substance, and composed of seve- ral follicles, secreting a whitish viscid fluid, that is discharged by ten or twelve excretory ducts into the urethra, on each side of the openings of the vesicuke seminales at the same time, and from the same causes that the semen is expelled. As this latter fluid is found to be exceedingly limpid in the vesiculae seminales of the dead subject, it probably owes its white- ness and viscidity to this liquor of the pros- tate. The penis, which is to be considered as the vehicle or active organ of procreation, is composed of two columns, the corpora caver- nosa, and corpus spongiosum. The corpora cavernosa, which constitute the greatest part of the penis, may be described as two cylin- drical ligamentous tubes, each of which is composed of an infinite number of minute cells of a spongy texture, which communicate with each other. These two bodies are of a very pliant texture, and capable of considerable distention; and being united laterally to each other, occasion by this union a space above and another below. The uppermost of these spaces is filled by the blood-vessels, and the lower one, which is larger than the other, by the urethra and its corpus spongiosum. These two cavernous bodies are at first only separat- 295 Of the Abdomen. ed by a partition of tendinous fibres, which allow them to communicate with each other ; but they afterwards divaricate from each other like the branches of the letter Y, and diminish- ing gradually in size, are attached, one on each side, by means of the ligamentum sus- pensorium penis to the ramus ischii, and to the inferior portion of the os pubis. The corpus spongiosum penis, or corpus spongiosum urethrse, as it is styled by some authors, begins as soon as the urethra has passed the prostate, with a thick origin almost like a heart, first under the urethra, and af- terwards above it, becoming gradually thin- ner, and surrounding the whole canal of the urethra, till it terminates in a considerable ex- pansion, and constitutes what is called the glans penis , which is exceedingly vascular, and covered with papillse like the tongue. The cuticle which lines the inner surface of the ure- thra, is continued over the glans in the same manner as it is spread over the lips. The penis is invested by the common inte- guments, but the cutis is reflected back every where from the glans as it is in the eye-lids ; so that it covers this part, when the penis is in a relaxed state, as it were with a hood, and from this use is called prepuce. The prepuce is tied down to the under part of the glans by a small ligament called franum, which is in fact only a continuation of the cu- ticle and cutis. There are many simple seba- ceous follicles called glandule odorifera, placed round the basis of the glans ; and the fluid they secrete serves to preserve the exqui- 294 Of the Abdomen. site sensibility of this part of the penis, and to prevent the ill effects of attrition from the pre- puce. The urethra may be defined to be a mem- branous canal, passing from the bladder through the whole extent of the penis, Seve- ral very small openings, called lacuna , com- municate with this canal, through which a mu- cus is discharged into it ; and besides these, there are two glands, first described by Cow- per, as secreting a fluid for lubricating the urethra, and called Cowper's glands •* and Littref speaks of a gland situated near the prostate, as being destined for the same use. The urethra being continued from the neck of the bladder, is to be considered as making part of the urinary passage ; and it likewise affords a conveyance to the semen, which we have observed is occasionally discharged into it from the vesiculse seminales. The direc- tion of this canal being first under and then before the pubis, occasions a winding in its course from the bladder to the penis not unlike the turns of the letter S. The penis has three pair of muscles, the erectores, acceleratores, and transversales. They push the blood from the crura to the fore part of the corpora cavernosa. The first origi- nate from the tuberosity of the ischium, and terminate in the corpora cavernosa. The ac- celeratores arise from the sphincter, and by * Both Heister and Morgagni observe, that they have some- times not been able to find these glands ; so that they do not seem to exist in all subjects. + Memoires de 1 ’ Acad. Royale des Sciences, 1700. 295 Of the Abdomen. their insertion serve to compress the bulbous part of the urethra ; and the transversales are destined to afford a passage to the semen, by- dilating the canal of the urethra. The arteries of the penis are chiefly deriv- ed from the internal iliacs. Some of them are supposed to terminate by pabulous orifices within the corpora cavernosa and corpus spon- giosum ; and others terminate in veins, which at last make up the vena magna dorsi penis, and other smaller veins, which are in general distributed in like order with the arteries. Its nerves are large and numerous. They arise from the great sciatic nerve, and accom- pany the arteries in their course through the penis. We have now described the anatomy of this organ ; and there only remains to be explain- ed, how it is enabled to attain that degree of firmness and distention which is essential to the great work of generation. The greatest part of the penis has been spoken of as being of a spongy and cellular texture, plentifully supplied with blood-vessels and nerves, and as having muscles to move it in different directions. Now, the blood is constantly passing into its cells through the small branches of the arteries which open into them, and is from thence as constantly return- ed by the veins, so long as the corpora caver- nosa and corpus spongiosum continue to be in a relaxed and pliant state. But when, from any nervous influence, or other means, which it is not necessary here to define or explain, the erectores penis, ejaculatores seminis, le- 296 Of the Abdomen . vatores ani, btc. are induced to contract, the veins undergo a certain degree of compres- sion, and the passage of the blood through them is so much impeded, that it collects in them in a greater proportion than they are enabled to carry off, so that the penis gradu- ally enlarges ; and being more and more for- cibly drawn up against the os pubis, the vena magna itself is at length compressed, and the penis becomes fully distended. But as the causes which first occasioned this distention subside, the penis gradually returns to its state of relaxation. §. 2. Female Organs of Generation. Anatomical writers usually divide the fe- male organs of generation into external and in- ternal. In the first division they include the mons veneris , labia pudendi , perinaum , clito- ris, nymphce , and caruncula myrtiformes ; and in the latter, the vagina , with the uterus and its appendages. The mons veneris , which is placed on the upper part of the symphysis pubis, is inter- nally composed of adipose membranes, which makes it soft and prominent : it divides into two parts called labia pudendi, which descend- ing towards the rectum, from which they are divided by the perinseum, form what is called the fourchette. The perinseum is that fleshy space which extends about an inch and an half from the fourchette to the anus, and from thence about two inches to the coccyx. 297 Of the Abdomen. The labia pudendi being separated, we ob- serve a sulcus called fossa magna ; in the up- per part of which is placed the clitoris, a small round spongy body, in some measure resem- bling the male penis, but impervious, com- posed of two corpora cavernosa, arising from the tuberosities of the ossa ischii ; furnished with two pair of muscles, the erectores clito- ridis, and the sphincter or constrictor ostii va- ginas ; and terminating in a glans, which is covered with its prepuce. From the lower part, on each side of the fossa, pass the nym- phse, two membranous and spongy folds which seem destined for useful purposes in parturi- tion, by tending to enlarge the volume of the vagina as the child’s head passes through it. Between these, about the middle of the fossa magna, we perceive the orifice of the vagina or os externum, closed by folds and wrinkles ; and about half an inch above this, and about an inch below the clitoris, appears the meatus urinarius or orifice of the urethra, much short- er, though somewhat larger, than in men, with a little prominence at its lower edge, which facilitates the introduction of the ca- theter. The os externum is surrounded internally by several membranous folds called caruncul ce myrtiformes , which are partly the remains of a thin membrane called hymen , that covers the vagina in children. In general the hymen is sufficiently open to admit the passage of the menses, if it exists at the time of their appear- ance ; sometimes, however, it has been found perfectly closed. p P 298 Of the Abdomen . The vagina, situated between the urethra and the rectum, is a membranous cavity, sur- rounded especially at its external extremity with a spongy and vascular substance, which is covered by the sphincter ostii vaginas. It terminates in the uterus, about half an inch above the os tineas, and is wider and shorter in women who have had children than in vir- gins. All these parts are plentifully supplied with blood-vessels and nerves. Around the nym- phae there are sebaceous follicles, which pour out a fluid to lubricate the inner surface of the vagina ; and the meatus urinarius, like the urethra in the male subject, is constantly moistened by a mucus, which defends it against the acrimony of the urine. The uterus is a hollow viscus, situated in the hypogastric region, between the rectum and bladder. It is destined to receive the first rudiments of the feetus, and to assist in the developement of all its parts, till it arrives at a state of perfection, and is fitted to enter into the world, at the time appointed by the wise Author of nature. The uterus, in its unimpregnated state, re- sembles a pear in shape, somewhat flattened, with its fundus or bottom part turned towards the abdomen, and its cervix or neck surround- ed by the vagina. The entrance into its ca- vity forms a little protuberance, which has been compared to the mouth of a tench, and is therefore called os tinea. The substance of the uterus, which is of a considerable thickness, appears to be com- Of the Abdomen. 299 posed of muscular and small ligamentous fi- bres, small branches of nerves, some lym- phatics, and with arteries and veins innumera- ble. Its nerves are chiefly derived from the intercostal, and its arteries and veins from the hypogastric and spermatic. The membrane which lines its cervix, is a continuation of the inner membrane of the vagina ; but the outer surface of the body of the uterus is covered with the peritonaeum, which is reflected over it, and descends from thence to the intestinum rectum. This duplicature of the peritonaeum, by passing off from the sides of the uterus to the sides of the pelvis, is there firmly con- nected, and forms what are called ligamento uteri lata ; which not only serve to support the uterus, but to convey nerves and blood- vessels to it. The ligamenta uteri rotunda arise from the sides of the fundus uteri, and passing along within the fore-part of the ligamenta lata, de- scend through the abdominal rings, and ter- minate in the substance of the mons veneris. The substance of these ligaments is vascular, and although both they and the ligamenta lata admit the uterus in the virgin state, to move only about an inch up and down, yet in the course of pregnancy they admit of consider- able distention, and after parturition return nearly to their original state with surprising quickness. On each side of the inner surface of the uterus, in the angle near the fundus, a small orifice is to be discovered, which is the begin- ning of one of the tubce Fallopianas. Each of 300 Of the Abdomen. these tubes, which are two in number, passing through the substance of the uterus, is extend- ed along the broad ligaments, till it reaches the edge of the pelvis, from whence it reflects back; and turning over behind the ligaments, about an inch of its extremity is seen hanging loose in the pelvis, near the ovarium. These extremities, having a jagged appearance, are called fimbria , or morsus diaboli. Each tuba Fallopiana is usually about three or four inches long. Their cavities are at first very small, but become gradually larger, like a trumpet, as they approach the fimbrise. Near the fimbriae of each tuba Fallopiana, about an inch from the uterus, is situated an oval body called ovarium , of about half the size of the male testicle. Each of these ovaria is covered by a production of the peritonaeum, and hangs loose in the pelvis. They are of a flat and angular form, and appear to be com- posed of a white and cellular substance, in which we are able to discover several minute vesicles filled with a coagulable lymph, of an uncertain number, commonly exceeding 12 in each ovary. In the female of riper years, these vesicles become exceedingly turgid, and a kind of yellow coagulum is gradually formed within one of them, which increases for a cer- tain time. In conception, one of these mature ova is supposed to be impregnated with the male semen, and to be squeezed out of its nidus into the Fallopian tube ; after which the ruptured part forms a substance which in some animals is of a yellow colour, and is therefore called corpus luteum ; and it is observable, that 301 Of the Abdomen. the number of these scars or fissures in the ovarium, constantly corresponds with the num- ber of foetuses excluded by the mother. §.3. Of Conception. Man, being ever curious and inquisitive, has naturally been led to inquire after the origin of his existence ; and the subject of generation has employed the philosophical world in all ages : but in following nature up to her mi- nute recesses, the philosopher soon finds him- self bewildered, and his imagination often sup- plies that which he so eagerly wishes to disco- ver, but which is destined perhaps never to be revealed to him. Of the many theories which have been formed on this subject, that of the ancient philosophers seems to have been the most simple : they considered the male semen as alone capable of forming the fcetus, and be- lieved that the female only afforded it a lodging in the womb, and supplied it with nourishment after it was perfectly formed. This opinion, however, soon gave place to another, in which the female was allowed a more considerable share in conception. This second system considered the foetus as being formed by the mixture of the semi- nal liquor of both sexes, by a certain arrange- ment of its several particles in the uterus. But in the 16th century, vesicles or eggs were discovered in the ovaria or female testicles ; the foetus had been found sometimes in the ab- domen, and sometimes in the Fallopian tubes ; 302 Of the Abdomen. and the two former opinions were exploded in favour of a new doctrine. The ovaria were compared to a bunch of grapes, being suppos- ed to consist of vesicles, each of which had a stalk ; so that it might be disengaged without hurting the rest, or spilling the liquor it con- tained. Each vesicle was said to include a lit- tle animal, almost complete in all its parts ; and the vapour of the male semen being conveyed to the ovarium, was supposed to produce a fer- mentation in the vesicle, which approached the nearest to maturity ; and thus inducing it to disengage itself from the ovarium, it passed into the tuba Fallopiana, through which it was Conveyed to the uterus. Here it was supposed to take root like a vegetable seed, and to form, with the vessels originating from the uterus, what is called the placenta ; by means of which the circulation is carried on between the mo- ther and the foetus. This opinion, with all its absurdities, con- tinued to be almost universally adopted till the close of the same century, when Lieuwen- hoeck, by means of his glasses, discovered certain opake particles, which he described as so many animalcula, floating in the seminal fluid of the male. This discovery introduced a new schism among the philosophers of that time, and gave rise to a system which is not yet entirely explod- ed. According to this theory the male semen passing into the tubas Fallopianse, one of the animalcula penetrates into the substance of the ovarium, and enters into one of its vesicles or ova. This impregnated ovum is then squeez- 303 Of the Abdomen. ed from its husk, through the coats of the ova- rium, and being seized by the fimbrise, is con- ducted through the tube to the uterus, where it is nourished till it arrives at a state of per- fection. In this system there is much ingenu- ity ; but there are certain circumstances sup- posed to take place, which have been hitherto inexplicable. A celebrated modern writer, M. BufFon, endeavours to restore, in some mea- sure, the most ancient opinion, by allowing the female semen a share in this office ; asserting, that animalcula or organic particles are to be discovered in the seminal liquor of both sexes : he derives the female semen from the ovaria, and he contends that no ovum exists in those parts. But in this idea he is evidently mista- ken ; and the opinion now most generally adopted is, that an impregnation of the ovum, by the influence of the male semen, is essential to conception.* That the ovum is to be im- pregnated, there can be no doubt ; but as the manner in which such an impregnation is sup- posed to take place, and the means by which the ovum afterwards gets into the Fallopian tube, and from thence into the uterus, are still found- ed chiefly on hypothesis, we will not attempt to extend farther the investigation of a sub- ject concerning which so little can be advanc- ed with certainty. * The learned Abbe Spallanzani has thrown much light on this curious subject, and has proved by a variety of experiments, that the animalcule exists entire in the female ovum and that the male seed is only necessary to vivify and put it in motion. — His experiments and observations are worthy the attentive perusal of every physiologist. Of the Abdomen. 304 $. 4 . Of the Fcetus in Utero. Opportunities of dissecting the human gravid uterus occurring but seldom, the state of the embryo* immediately after conception cannot be perfectly known. When the ovum descends into the uterus, it is supposed to be very minute ; and it is not till a considerable time after conception that the rudiments of the embryo begin to be ascertain- ed. About the third or fourth week the eye may discover the first lineaments of the fcetus ; but these lineaments are as yet very imperfect, it being only about the size of a house-fly. Two little vessels appear in an almost transpa- rent jelly ; the largest of which is destined to become the head of the fcetus, and the other smaller one is reserved for the trunk. But at this period no extremities are to be seen ; the umbilical cord appears only as a very minute thread, and the placenta does not as yet absorb the red particles of the blood. At six weeks, not only the head but the features of the face begin to be developed. The nose appears like a small prominent line, and we are able to dis- cover another line under it, which is destined for the separation of the lips. Two black points appear in the place of eyes, and two minute holes mark the ears. At the sides of ♦-The rudiments of the child are usually distinguished by this name till the human figure can be distinctly ascertained, and then it has the appellation of fcetus. 305 Of the Abdomen. the trunk, both above and below, we see four minute protuberances, which are the rudiments of the arms and legs. At the end of eight weeks the body of the fcetus is upwards of an inch in length, and both the hands and feet are to be distinguished. The upper extremities are found to increase faster than the lower ones, and the separation of the fingers is accomplish- ed sooner than that of the toes. At this period the human form may be de- cisively ascertained ; — all the parts of the face may be distinguished, the shape of the body is clearly marked out, the haunches and the abdomen are elevated, the fingers and toes are separated from each other, and the intestines appear like minute threads. At the end of the third month, the fcetus measures about three inches ; at the end of the fourth month, five inches ; in the fifth month, six or seven inches ; in the sixth month, eight or nine inches ; in the seventh month, eleven or twelve inches ; in the eighth month, fourteen or fifteen inches ; and at the end of the ninth month, or full time, from eighteen to twenty- two inches. But as we have not an opportu- nity of examining the same fcetus at different periods of pregnancy, and as their size and length may be influenced by the constitution and mode of life of the mother, calculations of this kind must be very uncertain. The fcetus during all this time assumes an oval figure, which corresponds with the shape of the uterus. Its chin is found reclining on its breast with its knees drawn up towards its chin, and its arms folded over them. But it Q q 306 Of the Abdomen. seems likely, that the posture of some of these parts is varied in the latter months of pregnan- cy, so as to cause those painful twitches which its mother usually feels from time to time. In natural cases, its head is probably placed to- wards the os tineas from the time of conception to that of its birth ; though formerly it was con- sidered as being placed towards the fundus ute- ri till about the eighth or ninth month, when the head, by becoming specifically heavier than the other parts of the body, was supposed to be turned downwards. The capacity of the uterus increases in pro- portion to the growth of the foetus, but with- out becoming thinner in its substance, as might naturally be expected. The nourishment of the foetus, during all this time, seems to be de- rived from the placenta, which appears to be originally formed by that part of the ovum which is next the fundus uteri. The remain- ing part of the ovum is covered by a mem- brane called spongy chorion ;* within which is another called true chorion , which includes a third termed amnios :f this contains a watery * Dr. Hunter has described this as a lamella from the inne* surface of the uterus. In the latter months of pregnancy it be- comes gradually thinner and more connected with the chorion r he has named it membrana caduca, or decidua , as it is cast off with the placenta. Signior Scarpa, with more probability, considers it as being composed of an inspissated coagulable lymph. ■f In some quadrupeds, the urine appears to be conveyed from the bladder through a canal called urachus to the allantois, which is a reservoir, resembling a long and blind gut, situated between the chorion and amnios. The human foetus seems to have no such reservoir, though fome writers have supposed that it does exist. From the top of the bladder a few longitudinal fibres are extended to the umbilical chord ; and these fibres have been con- sidered as the urachus, though without having been ever found pervious. 30.7 Of the Abdomen. fluid which is the liquor amniif in which the foetus floats till the time of its birth. On the side next the foetus, the placenta is covered by the amnios and true chorion.; on the side next the mother it has a production continued from the spongy chorion. The amnios and chorion are remarkably thin and transparent, having no blood-vessels entering into their composi- tion. The spongy chorion is opake and vas- cular. In the first months of pregnancy, the involu- cra bear a large proportion to their contents ; but this proportion is afterwards reversed, as the foetus increases in bulk. The placenta, which is the medium through which the blood is conveyed from the mother to the foetus, and the manner in which this conveyance takes place, deserve next to be considered. The placenta is a broad, flat, and spongy substance, like a cake, closely adhering to the inner surface of the womb, usually near the fundus, and appearing to be chiefly made up of the ramifications of the umbilical arteries and vein, and partly of the extremities of the uterine vessels. The arteries of the uterus discharge their contents into the substance of * The liquor arnnli coagulates like the lymph. It has been supposed to pass into the oesophagus, and to afford nourishment to the foetus ; but this does not feem probable. Children have come into the world without an oesophagus, or any communica- tion between the stomach and the mouth ; but there has been no well attested instance of a child’s having been born without a pla- centa ; and it does not seem likely, that any of the fluid can be absorbed through the pares of the skin, the skin in the foetus be- ing every where covered with a great quantity of mucus. 308 Of the Abdomen. this cake ; and the veins of the placenta, re- ceiving the blood either by a direct communi- cation of vessels, or by absorption, at length form the umbilical vein, which passes on to the sinus of the vena portse, and from thence to the vena cava, by means of the canalis veno- sus, a communication that is closed in the adult. But the circulation of the blood through the heart is not conducted in the foetus as in the adult : in the latter, the blood is carried from the right auricle of the heart through the pulmonary artery, and is returned to the left auricle by the pulmonary vein ; but a dilatation of the lungs is essential to the passage of the blood through the pulmonary vessels, and this dilatation cannot take place till after the child is born and has respired. This deficiency, how- ever, is supplied in the foetus by the immedi- ate communication between the right and left auricle, through an oval opening, in the septum which divides the two auricles, called foramen ovale. The blood is likewise transmitted from the pulmonary artery to the aorta, by means of a duct called canalis arteriosus , which, like the canalis venosus, and foramen ovale, gra- dually closes after birth. The blood is returned again from the foetus through two arteries called the umbilical arte- ries , which arise from the iliacs. These two vessels taking a winding course with the vein, form with that, and the membranes by which they are surrounded, what is called the um- bilical chord. These arteries, after ramifying through the substance of the placenta, dis- charge their blood into the veins of the uterus ; PlateXXY y 3 ref Lilad c Of the Abdomen. $09 in the same manner as the uterine arteries dis- charged their blood into the branches of the umbilical vein. So that the blood is constant- ly passing in at one side of the placenta and out at the other ; but in what particular man- ner it gets through the placenta is a point not yet determined. EXPLANATION of PLATES XXV. XXVI. and XXVII. Plate XXV. Eig. 1. Shows the Contents of the Thorax and Abdomen in situ. 1. Top of the trachea, or wind-pipe. 2 2, The internal jugular veins. 3 3, The subcla- vian veins. 4, The vena cava descendens. 5, The right auricle of the heart. 6, The right ventricle. 7, Part of the left ventricle. 8, The aorta descendens. 9, The pulmonary artery. 10, The right lung, part of which is cut off to show the great blood-vessels. 11, The left lung entire. 12 12, The anterior edge of the diaphragm. 13 13, The two great lobes of the liver. 14, The ligamentum rotundum. 15, The gall-bladder. 16, The stomach. 17 17, The jejunum and ilium. 18, The spleen. 310 Of the Abdomen. Fig. 2. Shows the Organs subservient of the Chylopoietic Viscera, — with those of Urine and Generation. 1 1, The under side of the two great lobes of the liver, a, Lobulus Spigelih 2, The li- gamentum rotundum. 3, The gall-bladder. 4, The pancreas. 5, The spleen. 6 6, The kidneys. 7, The aorta descendens. 8, Ve- na cava ascendens. 9 9, The renal veins co- vering the arteries. 10, A probe under the spermatic vessels and a bit of the inferior me- senteric artery, and over the ureters. 11 11, The ureters. 12 12, The iliac arteries and veins. 13, The rectum intestinum. 14, The bladder of urine. Fig. 3. Shows the Chylopoietic Viscera, and Organs subservient to them, taken out of the Body entire. A A, The under side of the two great lobes of the liver. B, Ligamentum rotundum. C, The gall-bladder. D, Ductus cysticus. E, Ductus hepaticus. F, Ductus communis cho- ledochus. G, Venaportarum. H, Arteria hep- atica. I I, The stomach. K K, Venae and arte- riae gastro-epiploicae, dextrae & sinistrae. L L, Venae & arterite coronariae ventriculi. M, The spleen. N N, Mesocolon, with its vessels. O O O, Intestinum colon. P, One of the li- gaments of the colon, which is a bundle of longitudinal muscular fibres. Q,Q,QQ,, Jeju- 511 Of the Abdomen. num and ilium. R R, Sigmoid flexure of the colon with the ligament continued, and over S, The rectum intestinum. T T, Levatores ani. U, Sphincter ani. V, The place to which the prostate gland is connected. W, The anus. Fig. 4. Shows the Heart of a Foetus at the full time, with the Right Auricle cut open to show the Foramen Ovale, or passage be- tween both Auricles. a, The right ventricle. b, The left ventri- cle. c c, The outer side of the right auricle stretched out. d d, The posterior side, which forms the anterior side of the septum, e, The foramen ovale, with the membrane or valve which covers the left side, f, Vena cava in- ferior passing through g, A portion of the dia- phragm. Fig. 5. Shows the Heart and Large Vessels of a Foetus at the full time. a, The left ventricle, b, The right ventri- cle. c, A part of the right auricle. d, Left auricle, e e, The right branch of the pulmo- nary artery, f, Arteria puimonalis. g g, The left branch of the pulmonary artery, with a number of its largest branches dissected from the lungs, h, The canalis arteriosus, i, The arch of the aorta, kk, The aorta descendens. 1, The left subclavian artery, m, The left ca- rotid artery, n, The right carotid artery, o, The right subclavian artery, p, The origin 312 Of the Abdomen . of the right carotid and right subclavian arteries in one common trunk. q, The vena cava su- perior or descendens. r, The right common subclavian vein. s, The left common sub- clavian vein. N. B. All the parts described in this figure are to be found in the adult, except the cana- lis arteriosus. Plate XXVI. Fig. 1 . Exhibits the more superficial Lympha- tic Vessels of the Lower Extremity. A, The spine of the os ilium. B, The os pubis. C, The iliac artery. D, The knee. E, E, F, Branches of the crural artery. G, The musculus gastrocnemius. H, The tibia. I, The tendon of the musculus tibialis anticus. On the out-lines, a, A lymphatic vessel be- longing to the top of the foot, b, Its first di- vision into branches. c, c, c, Other divisions of the same lymphatic vessel. d, A small lymphatic gland. e, The lymphatic vessels which lie between the skin and the muscles of the thigh, f, f, Two lymphatic glands at the upper part of the thigh below the groin. g, g, Other glands. h, A lymphatic vessel which passes by the side of those glands with- out communicating with them ; and, bending towards the inside of the groin at (i), opens into the lymphatic gland (k). 1, 1, Lympha- tic glands in the groin, which are common, to the lymphatic vessels of the genitals and those Of the Abdomen. 313 of the lower extremity. m, n, A plexus of' lymphatic vessels passing on the inside of the iliac artery. Fig. 2. Exhibits a Back View of the lower Ex- tremity, dissected so as to show the deeper- seated Lymphatic Vessels which accompany the Arteries. A, The os pubis. B, The tuberosity of the ischium. C, That part of the os ilium which was articulated with the os sacrum. D, The extremity of the iliac artery appearing above the groin. E, The knee. F F, The two cut surfaces of the triceps muscle, which was divided to show the lymphatic vessels that pass through its perforation along with the cru- ral artery. G, The edge of the musculus gra- cilis. H, The gastrocnemius and soleus, much shrunk by being dried, and by the soleus be- ing separated from the tibia to expose the ves- sels. I, The heel. K, The sole of the foot. L, The superficial lymphatic vessels passing over the knee, to get to the thigh. On the out-lines ; M, The posterior tibial artery, a, A lymphatic vessel accompanying the posterior tibial artery, b, The same vessel crossing the artery, c, A small lymphatic gland, through which this deep-seated lymphatic vessel passes, d, The lymphatic vessel passing under a small part of the soleus, which is left attached to the bone, the rest being removed. e, The lym- phatic vessel crossing the popliteal artery, f, g, h, Lymphatic glands in the ham, through R r 3L4 Of the Abdomen. which the lymphatic vessel passes, i, The lymphatic vessel passing with the crural ar- tery, through the perforation of the triceps muscle, k, The lymphatic vessel, after it has passed the perforation of the triceps, dividing into branches which embrace the artery (1). m, A lymphatic gland belonging to the deep- seated lymphatic vessel. At this place those vessels pass to the fore part of the groin, where they communicate with the superficial lym- phatic vessels, n, A part of the superficial lymphatic vessel appearing on the brim of the pelvis. Fig. 3. Exhibits the Trunk of the Human Subject, prepared to show the Lymphatic Vessels and the Ductus Thoraeicus. A, The neck. B B, The two jugular veins. C, The vena cava superior. D D D D, The subclavian veins. E, The beginning of the aorta, pulled to the left side by means of a li- gature, in order to show the thoracic duct be- hind it. F, The branches arising from the curvature of the aorta. G G, The two caro- tid arteries. H H, The first ribs. I I,. The trachea. K K, The spine. L L, The vena azygos. M M, The descending aorta. N, Tlie cceliac artery, dividing into three branch- es. O, The superior mesenteric artery. P, The right crus diaphragmatis. Q. Q, The two kidneys. R, The right emulgent artery. S S, The external iliac arteries, g d, The musculi pso&\ T, The internal iliac artery. 315 Of the Abdomen. AJ, The cavity of the pelvis. X X, The spine of the os ilium. Y Y, The groins, a, A lym- phatic gland in the groin, into which lympha- tic vessels from the lower extremity are seen to enter, b b , The lymphatic vessels of the lower extremities passing under i Poupart’s li- gament. c c, A plexus of the lymphatic ves- sels lying on each side of the pelvis, d , The psoas muscle with lymphatic vessels lying upon its inside, e, A plexus of lymphatics, which having passed over the brim of the pel- vis at (c), having entered the cavity of the pelvis, and received the lymphatic vessels be- longing to the viscera contained in that cavity, next ascends, and passes behind the iliac ar- tery to (g). f Some lymphatic vessels of the left side passing over the upper part of the os sacrum, to meet those of the right side, g, The right psoas, with a large plexus of lymphatics lying on its inside, h / 1 , The plexus lying on each side of the spine, i i t, Spaces occupied by the lymphatic glands, k, The trunk. of the lacteals, lying on the under side of the supe- rior mesenteric artery. The same dividing into two branches, one of which passes on each side of the aorta ; that of the right side being seen to enter the thoracic duct at ( m ). m, The thoracic duct beginning from the large lymphatics. «, The duct passing under the lower part of the crus diaphragmatis, and un- der the right emulgent artery, o, The thora- cic duct penetrating the thorax. j&, Some lym- phatic vessels joining that duct in the thorax. The thoracic duct passing under the curva- ture of the aorta to get to the deft subclavian 316 Of the Abdomen. vein. The aorta being drawn aside to show the duct, r, A plexus of lymphatic vessels passing upon the trachea from the thyroid gland to the thoracic duct. Plate XXVII. Fig. 1 . Represents the Under and Posteriori Side of the Bladder of Urine, &c. a, The bladder, b b, The insertion of the ureters, c c, The vasa deferentia, which con- vey the semen from the testicles to d d, The vesiculae seminales, — and pass through e, The prostate gland, to discharge themselves into f, The beginning of the urethra. Fig. 2. A transverse Section of the Penis. g g, Corpora cavernosa penis, h, Corpus cavernosum urethras, i, Urethra, k, Septum penis. 1 1, The septum between the corpus cavernosum urethrae and that of the penis. Fig. 3. A longitudinal Section of the Penis. m m, The corpora cavernosa penis, divided by o, The septum penis, n, The corpus ca- vernosum glandis, which is the continuation of that of the urethra. \XAXX W[<\ XTX ° lli vx \ Of the Abdomen. 3i7 Fig. 4. Represents the Female Organs of Ge- neration. a, That side of the uterus which is next the os sacrum. 1, Its fundus. 2, Its cervix, b b, The Fallopian or uterine tubes, which open into the cavity of the uterus ; — but the other end is open within the pelvis, and surrounded by c c, The fimbriae. d d, The ovaria. e, The os internum uteri, or mouth of the womb, f f, The ligamenta rotunda, which passes without the belly, and is fixed to the labia pu- dendi. g g, The cut edges of the ligamenta lata, which connects the uterus to the pelvis, h, The inside of the vagina, i, The orifice of the urethra, k, The clitoris surrounded by (1,) The prseputium. m m, The labia puden- di. n n, The nymphae. Fig. 5. Shews the Spermatic Ducts of the Testicle filled with Mercury. A, The vas deferens. B, Its beginning, which forms the posterior part of the epididy- mis. B, The middle of the epididymis, com- posed of serpentine ducts. D, The head or anterior part of the epididymis unravelled, e e e e, The whole ducts which compose the head of the epididymis unravelled, f f, The vasa deferentia. g g, Rete testis, h h, Some rectilineal ducts which send off the vasa defe- rentia. i i, The substance of the testicle. 318 Of the Thorax. Fig. 6. The right Testicle entire, and the Epididymis filled with Mercury. A, The beginning of the vas deferens. B, The vas deferens ascending towards the abdomen. C, The posterior part of the epididy- mis, named globus minor. D, The sperma- tic vessels inclosed in cellular substance. E, The body of the epididymis. F, Its head, named globus major. G, Its beginning from the testicle. H, The body of the testicle, inclosed in the tunica albuginea. PART IV. OF THE THORAX. HE thorax, or chest, is that cavity of the trunk which extends from the clavi- cles, or the lower part of the neck, to the dia- phragm, and includes the vital organs, which are the heart and lungs ; and likewise the trachea and oesophagus. — This cavity is formed by the ribs and vertebrae of the back, covered by a great number of muscles, and by the common integuments, and anteriorly by two glandular bodies called the breasts. The spaces between the ribs are filled up by muscular fibres, which from their situation are called intercostal mus- cles. Of the Thorax. 31 & Sect. I. Of the Breasts. The breasts may be defined to be two large conglomerate glands, mixed with a good deal of adipose membrane. The glandular part is com- posed of an infinite number of minute arteries, veins, and nerves, The arteries are derived from two different trunks; one of which is called the internal , and the other the external , mammary artery. The first of these arises from the subclavian, and the latter from the axillary. The veins every where accompany the arteries and are distinguished by the same name. The nerves are chiefly from the vertebral pairs. Like all other conglomerate glands, the breasts are made up of a great many small distinct glands, in which the milk is secreted from the ultimate branches of arteries. The excretory ducts of these several glands gradually uniting as they approach the nipple, form the tubuli lactiferi, which are usually more than a dozen in num- ber, and open at its apex, but have little or no communication, as has been supposed, at the root of the nipple. These ducts, in their course from the glands, are surrounded by a ligamen- tary elastic substance, which terminates with them in the nipple. Both this substance, and the ducts which it contains, are capable of consi- derable extension and contraction ; but in their natural state are moderately corrugated, so as to prevent an involuntary flow of milk, unless the distending force be very great from the accu- mulation of too great a quantity. 320 Of the Thorax. The whole substance of the nipple is very spongy and elastic : its external surface is un- even, and full of small tubercles. The nipple is surrounded with a disk or circle of a different colour, called the areola ; and on the inside of the skin, under the areola, are many sebaceous glands, which pour out a mucus to defend the areola and nipple : for the skin upon these parts is very thin ; and the nervous papillae lying very bare, are much exposed to irritation. The breasts are formed for the secretion of milk, which is destined for the nourishment of the child for some time after its birth. This secretion begins to take place soon after de- livery, and continues to flow for many months in very large quantities, if the woman suckles her child. The operation of suction depends on the principles of the air-pump, and the flow of milk through the lactiferous tubes is facilitated by their being stretched out. The milk, examined chemically, appears to be composed of oil, mucilage, and water, and of a considerable quantity of sugar. The gene- rality of physiologists have supposed that, like the chyle, it frequently retains the properties of the aliment and medicines taken into the stomach ; but from some late experiments,* this supposition appears to be ill-founded. Sect. II. Of the Pleura. The cavity of the thorax is everywhere lined by a membrane of a firm texture called pleura. It is composed of two distinct portions or bags, * Journ. de Med. 1781. Of the Thorax. 321 which, by being applied to each other laterally, form a septum called mediastinum ; which di- vides the cavity into two parts, and is attached posteriorly to the vertebras of the back, and anteriorly to the sternum. But the two laminae of which this septum is formed, do not every where adhere to each other ; for at the lower part of the thorax they are separated, to afford a lodgment to the heart ; and at the upper part of the cavity, they receive between them the thymus. The pleura is plentifully supplied with arteries and veins from the internal mammary and the intercostals. Its nerves, which are very inconsiderable, are derived chiefly from the dorsal and intercostal nerves. The surface of the pleura, like that of the pe- ritonaeum and other membranes lining cavities, is constantly bedewed with a serous moisture* which prevents adhesion of the viscera. The mediastinum, by dividing the breast into two cavities, obviates many inconveniences, to which we should otherwise be liable. It pre- vents the two lobes of the lungs from com- pressing each other when we lie on one side ; and consequently contributes to the freedom of respiration, which is disturbed by the least pressure on the lungs. If the point of a sword penetrates between the ribs into the cavity of the thorax, the lungs on that side cease to per- form their office ; because the air being ad- S s * When this fluid is exhaled in too great a quantity, or is not properly carried off, it accumulates and constitutes the hy- drops pectoris. 322 Of the Thorax . mitted through the wound, prevents the dila- tation of that lobe ; while the other lobe, which is separated from it by the mediastinum, remains unhurt, and continues to perform its function as usual. Sect. II. Of the Thymus. The thymus is a glandular substance, the use of which is not perfectly ascertained, its excretory duct not having yet been discovered. It is of an oblong figure, and is larger in the foetus and in young children than in adults, being sometimes nearly effaced in very old subjects. It is placed in the upper part of the thorax, between the two laminae of the mediastinum ; but at first is not altogether contained within the cavity of the chest, being found to border upon the upper extremity of the sternum. Sect. IV. Of the Diaphragm . The cavity of the thorax is separated from that of the abdomen, by a fleshy and mem- branous substance called the diaphragm or midriff. The greatest part of it is composed of muscular fibres; and on this account sys- tematic writers usually place it very properly among the muscles. Its middle part is tendi- nous, and it is covered by the pleura above, and by the peritonaeum below. It seems to have been improperly named septum transver- sum , as it does not make a plane transverse di- 323 Of the Thorax. vision of the two cavities, but forms a kind of vault, the fore-part of which is attached to the sternum. Laterally it is fixed to the last of the true ribs, and to all the false ribs 5 and its lower and posterior part is attached to the vertebrae lumborum, where it may be said to be divided into two portions or crura.* The principal arteries of the diaphragm are derived from the aorta, and its veins pass into the vena cava. Its nerves are chiefly derived from the cervical pairs. It affords a passage to the vena cava through its tendinous part, and to the oesophagus through its fleshy portion. The aorta passes down behind it between its crura. The diaphragm not only serves to divide the thorax from the abdomen, but by its mus- cular structure is rendered one of the chief agents in respiration. When its fibres con- tract, its convex side, which is turned towards the thorax, becomes gradually flat, and by in- creasing the cavity of the breast, affords room for a complete dilatation of the lungs, by means of the air which is then drawn into them by the act of inspiration. The fibres of the di- aphragm then relax ; and as it resumes its for- mer state, the cavity of the thorax becomes gra- dually diminished, and the air is driven out again from the lungs by a motion contrary to the former one, called exspiration. * Anatomical writers have usually described the diaphragm as being made up of two muscles united by a middle tendon ; and these two portions or crura form what they speak of as the inferior muscle , arising from the sides and fore-part of the vertebrae. 324 Of the Thorax. It is in some measure, by means of the dia- phragm, that we void the faeces at the anus, and empty the urinary bladder.. Besides these offi- ces, the acts of coughing, sneezing, speaking, laughing, gaping, and sighing, coula not take place without its assistance ; and the gentle pressure which all the abdominal viscera re- ceive from its constant and regular motion, can- not fail to assist in the performance of the se- veral functions which were ascribed to those viscera. Sect. V. Of the Trachea. The trachea or windpipe, is a cartilaginous and membranous canal, through which the air passes into the lungs. Its upper part, which is called the larynx , is composed of five cartilages. The uppermost of these cartilages is placed over the glottis or mouth of the larynx, and is called epiglottis , which has been before spoken of, as closing the passage to the lungs in the act of swallowing. At the sides of the glottis are placed the two arytenoide cartilages, which are of a very complex figure, not easy to be described. The anterior and larger part of the larynx is made up of two cartilages ; one of which is called thyroides or scutiformis , from its being shaped like a buck- ler ; and the other cricoides or annularis , from its resembling a ring. Both these cartilages may be felt immediately under the skin, at the fore-part of the throat, and the thyroides, by its convexity, forms an eminence called po- 325 Of the Thorax. mum adami , which is usually more considerable in the male than in the female subject. All these cartilages are united to each other by means of very elastic, ligamentous fibres ; and are enabled by the as sistance of their several muscles, to dilate or contract the passage of the larynx, and to perform that variety of motion which seems to point out the larynx as the principal organ of the voice ; for when the air passes out through a wound in the trachea, it produces no sound. These cartilages are moistened by a mucus which seems to be secreted by minute glands situated near them. The upper part of the trachea is covered anteriorly and laterally by a considerable body, which is supposed to be of a glandular structure, and from its situation near the thyroid cartilage is called the thyroid gland ; though its excretory duct has not yet been discovered, or its use ascertained. The glottis is interiorly covered by a very fine membrane, which is moistened by a constant supply of a watery fluid. From the larynx the canal begins to take the name of trachea or aspera arteria , and extends from thence as far down as the third or fourth verte- bra of the back, where it divides into two branches which are the right and left brom chial tube. Each of these bronchi* ramifies * The right bronchial tube is usually found to be somewhat shorter and thicker than the left ; and M. Portal, who has published a memoir on the action of the lungs on the aorta in respiration, obferves that the left bronchial tube is closely connected by the aorta ; and from some experiments he is induced to conclude, that in the first respirations the air only enters into the right lobe of the lungs. Mcmoires de V Academic Roy ale des Sciences, 1769. 326 Of the Thorax. through the substance of that lobe of the lungs to which it is distributed, by an infinite number of branches, which are formed of car- tilages separated from each other like those of the trachea, by an intervening membranous and ligamentary substance. Each of these cartilages is of an angular figure ; and as they become gradually less and less in their diameter, the lower ones are in some measure received into those above them, when the lungs, after being inflated, gradually collapse by the air being pushed out from them in exspiration. As the branches of the bronchi become more minute, their cartilages become more and more angular and membranous, till at length they are found to be perfectly membranous, and at last become invisible. The trachea is furnished with fleshy or muscular fibres ; some of which pass through its whole extent longitudinally, while the others are carried round it in a circular direction ; so that by the contraction or relaxation of these fibres, it is enabled to shorten or lengthen itself, and likewise to dilate or contract the diameter of its passage. The trachea and its branches, in all their ramifications, are furnished with a great num- ber of small glands which are lodged in their cellular substance, and discharge a mucous fluid on the inner surface of these tubes. The cartilages of the trachea, by keeping it constantly open, afford a free passage to the air which we are obliged to be incessantly respir- ing ; and its membranous part, by being capable 327 Of the Thorax. of contraction and dilatation, enables us to re- ceive and expel the air in a greater or less quan- tity, and with more or less velocity, as may be required in singing or in declamation. '1 his membranous structure of the trachea poste- riorly, seems likewise to assist in the descent of the food, by preventing that impediment to its passage down the oesophagus, which might be expected if the cartilages were complete rings. The trachea receives its arteries from the carotid and subclavian arteries, and its veins pass into the jugulars. Its nerves arise from the recurrent branch of the eighth pair, and from the cervical plexus. Sect. VI. Of the Lungs. The lungs fill the greater part of the cavity of the breast. They are of a soft and spongy texture, and are divided into two lobes, which are separated from each other by the me- diastinum, and are externally covered by a production of the pleura. Each of these is divided into two or three lesser lobes ; and we commonly find three in the right side of the cavity, and two in the left. To discover the structure of the lungs, it is required to follow the ramifications of the bron- chi, which were described in the last section. These becoming gradually more and more minute, at length terminate in the cellular spaces or vesicles, which make up the greatest part of the substance of the lungs, and readily communicate with each other. 328 Of the Thorax . The lungs seem to possess but little sensibili- ty. Their nerves, which are small and few in number, are derived from the intercostal and eighth pair. This last pair having reached the thorax, sends off a branch on each side of the trachea, called the recurrent , which reas- cends at the back part of the trachea, to which it furnishes branches in its ascent, as well as to tne oesophagus, but it is chiefly distributed to the larynx and its muscles. By dividing the recurrent and superior laryngeal nerves at their origin, an animal is deprived of its voice. There are two series of arteries which carry blood to the lungs : these are the arterias bron- chiales, and the pulmonary artery. The arterise bronchiales begin usually by two branches ; one of which commonly arises from the right intercostal, and the other from the trunk of the aorta : but sometimes there are three of these arteries, and in some sub- jects only one. The use of these arteries is to serve for the nourishment of the lungs, and their ramifications are seen creeping every where on the branches of the bronchi. The blood is brought back from them by the bron- chial vein into the vena azygos. The pulmonary artery and vein are not in- tended for the nourishment of the lungs ; but the blood in its passage through them is de- stined to undergo some changes, or to acquire certain essential properties (from the action of the air), which it has lost in its circulation through the other parts of the body. The pulmonary artery receives the blood from the right ventricle of the heart, and dividing into 3 29 Of the Thorax . two branches, accompanies the bronchi every where, by its ramifications through the lungs ; and the blood is afterwards conveyed back by the pulmonary vein, which gradually forming a considerable trunk, goes to empty itself into the left ventricle of the heart ; so that the quantity of blood which enters into the lungs, is perhaps greater than that which is sent in the same proportion of time through all the other parts of the body. Sect. VII. Of Respiration. J Respiration constitutes one of those func- tions which are properly termed vital , as being essential to life ; for to live and to breathe are in fact synonymous terms. It consists in an alternate contraction and dilatation of the tho- rax, by first inspiring air into the lungs, and then expelling it from them in exspiration. It will perhaps be easy to distinguish and point out the several phenomena of respira- tion ; but to explain their physical cause will be attended with difficulty, for it will natural- ly be inquired, how the lungs, when emptied of the air, and contracted by exspiration, be- come again inflated, they themselves being perfectly passive ? How the ribs are elevated in opposition to their own natural situation ? and why the diaphragm is contracted down- wards towards the abdomen? Were we to as- sert that the air, by forcing its way into the cavity of the lungs, dilated them, and conse- quently elevated the ribs, and pressed down T t 330 Of the Thorax. the diaphragm, we should speak erroneously. What induces the first inspiration, it is not easy to ascertain ; but after an animal has once respired, it would seem likely that the blood, after exspiration, finding its passage through the lungs obstructed, becomes a stimulus, which induces the intercostal muscles and the diaphragm to contract, and enlarge the cavity of the thorax, in consequence perhaps of a certain nervous influence, which we will not here attempt to explain. The air then rushes into the lungs ; every branch of the bronchial tubes, and all the cellular spaces into which they open, become fully dilated ; and the pul- monary vessels being equally distended, the blood flows through them with ease. But as the stimulus which first occasioned this dilata- tion ceases to operate, the muscles gradually contract, the diaphragm rises upwards again, and diminishes the cavity of the chest ; the ribs return to their former state ; and as the air passes out in exspiration, the lungs gradu- ally collapse, and a resistance to the passage of the blood again takes place. But the heart continuing to receive and expel the blood, the pulmonary artery begins again to be distend- ed, the stimulus is renewed, and the same process is repeated, and continues to be re- peated, in a regular succession, during life : for though the muscles of respiration, having a mixed motion, are (unlike the heart) in some measure dependent on the will, yet no human being, after having once respired, can live many moments without it. In an attempt to hold one’s breath, the blood soon begins to Of the Thorax . 331 distend the veins, which are unable to empty their contents into the heart ; and we are able only, during a very little time, to resist the. stimulus to inspiration. In drowning, the cir- culation seems to be stopped upon this, prin- ciple ; and in hanging, the pressure made on the jugular veins, may co-operate with, the stoppage of respiration in bringing on death. Till within these few years physiologists were entirely ignorant of the use of respira- tion. It was at length discovered in part by the illustrious Dr. Priestley. Pie found tha.t the air exspired by animals was phlogistica- ted ; and that the air was fitter for respiration, or for supporting animal life, in proportion as it was freer from the phlogistic principle. It had long been observed, that the blood in pas- sing through the lungs acquired a more florid colour. He therefore suspected, that it was owing to its having imparted phlogiston to the air: and he satisfied himself of the truth of this idea, by experiments, which showed, that the crassamentum of extravasated blood, phlo- gisticated air in proportion as it lost its dark colour. He farther found, that blood thus reddened had a strong attraction for phlogis- ton ; insomuch that it was capable of taking it from phlogisticated air, thereby becoming of a darker colour. From hence it appeared that the blood, in its circulation through the arte- rial system, imbibes a considerable quantity of phlogiston, which is discharged from it to the air in the lungs. This discovery has since been prosecuted by two very ingenious physiologists, Dr. Craw- 332 Of the Thorax. ford and Mr. Elliot. It had been shown by professors Black and Irvine, that different bo- dies have different capacities for containing fire. For example, that oil and water, when equally hot to the sense and the thermometer, contain different proportions of that principle ; and that unequal quantities of it are required, in order to raise those substances to like tem- peratures. The inquiries of Dr. Crawford and Mr. Elliot tend to prove, that the capaci- ties of bodies for containing fire are diminish- ed by the addition of phlogiston, and increas- ed by its separation : the capacity of calx of antimony, for example, being greater than that of the antimony itself. Common air con- tains a great quantity of fire ; combustible bo- dies very little. In combustion, a double elec- tive attraction takes place ; the phlogiston of the body being transferred to the air, the fire contained in the air to the combustible body. But as the capacity of the latter is not increas- ed so much as that of the former is diminish- ed, only part of the extricated fire will be ab- sorbed by the body. The remainder there- fore will raise the temperature of the com- pound ; and hence we may account for the heat attending combustion. As the use of respira- tion is to dephlogisticate the blood, it seems probable, that a like double elective attraction takes place in this process ; the phlogiston of the blood being transferred to the air, and the fire contained in the air to the blood ; but with this difference, that the capacities being equal, the whole of the extricated fire is absorbed by the latter. The blood in this state circulating Of the Thorax. 335 through the body, imbibes phlogiston, and of course gives out its fire ; part only of which is absorbed by the parts furnishing the phlogis- ton, the remainder, as in combustion, becom- ing sensible ; and is therefore the cause ol the heat of the body, or what is called animal heat. In confirmation of this doctrine it may be observed, that the venous blood contains less fire than the arterial ; combustible bodies less than incombustible ones ; and that air contains less of this principle, according as it is render- ed, by combination with phlogiston, less fit for respiration.* In ascending very high mountains, respira- tion is found no become short and frequent, and sometimes to be attended with a spitting of blood. These symptoms seem to be occa- sioned by the air being too rare and thin to dilate the lungs sufficiently ; and the blood gradually accumulating in the pulmonary ves- sels, sometimes bursts through their coats, and is brought up by coughing. This has likewise been accounted for in a different way, by sup- posing that the air contained in the blood, not receiving an equal pressure from that of the atmosphere, expands, and at length ruptures the very minute branches of the pulmonary vessels ; upon the same principle that fruits and animals put under the receiver of an air- pump, are seen to swell as the outer air be- comes exhausted. But Dr. Darwin of Litch- * See Crawford’s Experiments and Observations on Animal Heat, and Elliot’s Philosophical Observations. 334 Of the Thorax. field has lately published some experiments, which seem to prove, that no air or elastic vapour does exist in the blood-vessels, as has been generally supposed ; and he is induced to impute the spitting of blood, which has sometimes taken place in ascending high moun- tains, to accident, or to violent exertions ; as it never happens to animals that are put into the exhausted receiver of an air-pump, where the diminution of pressure is many times greater than on the summit of the highest mountains. Sect. VIII. Of the Voice. Respiration has already been described as affording us many advantages ; and next to that of life, its most important use seems to be that of forming the voice and speech. The ancients, and almost all the moderns, have considered the organ of speech as a kind of musical instrument, which may be compared to a flute, to an hautboy, to an organ, &x. and they argue after the following manner. The trachea, which begins at the root of the tongue, and goes to terminate in the lungs, may be compared to the pipe of an organ, the lungs dilating like bellows during the time of inspiration ; and as the air is driven out from them in exspiration, it finds its passage strait- ened by the cartilages of the larynx, against which it strikes. As these cartilages are more or less elastic, they occasion in their turn more or less vibration in the air, and thus produce Of the Thorax. 335 the sound of the voice ; the variation in the sound and tone of which depends on the state of the glottis, which, when straitened, pro- duces an acute tone, and a grave one when dilated. The late M. Ferein communicated to the French Academy of Sciences a very ingenious theory on the formation of the voice. He con- sidered the organ of the voice as a string , as well as a wind , instrument ; so that what art has hitherto been unable to construct, and what both the fathers Mersenne and Kircher so much wished to see, M. Ferein imagined he had at length discovered in the human body. He observes, that there are at the edges of the glottis certain tendinous chords, placed hori- zontally across it, which are capable of consi- derable vibration, so as to produce sound, in the same manner as it is produced by the strings of a violin or a harpsichord : and he supposes that the air, as it passes out from the lungs, acts as a bow on these strings, while the efforts of the breast and lungs regu- late its motion, and produce the variety of tones. So that according to this system the variation in the voice is not occasioned by the dilatation or contraction of the glottis, but by the distention or relaxation of these strings, the sound being more or less acute in propor- tion as they are more or less stretched out. Another writer on this subject supposes, that the organ of voice is a double instrument, which produces in unison two sounds of a dif- ferent nature ; one by means of the air, and the other by means of the chords of the glot- S3 6 Of the Thorax. tis. Neither of these systems, however, are universally adopted. They are both liable to insuperable difficulties ; so that the manner in which the voice is formed has never yet been satisfactorily ascertained : we may observe, however, that the sound produced by the glottis is not articulated. To effect this, it is requir- ed to pass through the mouth, where it is dif- ferently modified by the action of the tongue, which is either pushed against the teeth, or upwards towards the palate ; detaining it in its passage, or permitting it to flow freely, by con- tracting or dilating the mouth. Sect. IX. Of Dejection. By dejection we mean the act of voiding the faeces at the anus 5 and an account of the man- ner in which this is conducted was reserved for this part of the work, because it seemed to require a knowledge of respiration to be perfectly understood. The intestines were described as having a peristaltic motion, by which the feces were gradually advancing towards the anus. Now, whenever the feces are accumulated in the intestinum rectum in a sufficient quantity to become troublesome, either by their weight or acrimony, they excite a certain uneasiness which induces us to go to stool. — To effect this, we begin by making a considerable in- spiration ; in consequence of which the dia- phragm is carried dow'nwards towards the low- er belly ; the abdominal muscles are at the Of the Thorax. 337 same time contracted in obedience to the will ; and the intestines being compressed on all sides, the resistance o.f the sphincter is over- come, and the feces pass out at the anus ; which is afterwards drawn up by its longitu- dinal fibres, which are called levatores ani , and then by means of its sphincter is again con- tracted : but it sometimes happens, as in dy- senteries for instance, that the feces are very liquid, and have considerable acrimony ; and then the irritation they occasion is more fre- quent, so as to promote their discharge with- out any pressure from the diaphragm or ab- dominal muscles ; and sometimes involuntari- ly, as is the case when the sphincter becomes paralytic. Sect. X. Of the Pericardium , and of the Heart and its Auricles. The two membranous bags of the pleura, which were described as forming the medias- tinum, recede one from the other, so as to af- ford a lodgment to a firm membranous sac, in which the heart is securely lodged ; this sac, which is the pericardium , appears to be com- posed of two tunics, united to each other by cellular membrane. — The outer coat, which is thick, and in some places of tendinous com- plexion, is a production of the mediastinum ; the inner coat, which is extremely thin, is re- flected over the auricles and ventricles of the heart, in the same manner as the tunica con- 11 u 338 Of the Thorax. junctiva, after lining the eye-lids, is reflected over the eye. This bag adheres to the tendinous part of the diaphragm, and contains a coagulable lymph, the liquor pericardii , which serves to lubricate the heart and facilitate its motions ; and seems to be secreted and absorbed in the same manner as it is in the other cavities of the body. The arteries of the pericardium are derived from the phrenic, and its veins pass into veins of the same name ; its nerves are likewise branches of the phrenic. The size of the pericardium is adapted to that of the heart, being usually large enough to contain it loosely. As its cavity does not extend to the sternum, the lungs cover it in inspiration ; and as it every where invests the heart, it effectually secures it from being in- jured by lymph, pus, or any other fluid, ex- travasated into the cavities of the thorax. The heart is a hollow muscle of a conical shape, situated transversely between the two laminae of the mediastinum, at the lower part of the thorax ; having its basis turned towards the right side, and its point or apex towards the left — Its lower surface is somewhat flat- tened towards the diaphragm. Its basis, from which the great vessels originate, is covered with fat, and it has two hollow and fleshy ap- pendages, called auricles . — Round these seve- ral openings, the heart seems to be of a firm ligamentous texture, from which all its fibres seem to originate ; and as they advance from 339 Of the Thorax. thence towards the apex, the substance of the heart seems to become thinner. The heart includes two cavities or ventricles , which are separated from each other by a fleshy septum ; one of these is called the rights and the other the left , ventricle ; though per- haps, with respect to their situation, it would be more proper to distinguish them into the anterior and posterior ventricles. The heart is exteriorly covered by a very fine membrane ; and its structure is perfectly muscular or fleshy, being composed of fibres which are described as passing in different di- rections ; some as being extended longitudi- nally from the basis to the apex ; others, as taking an oblique or spiral course ; and a third sort as being placed in a transverse direction.* — Within the two ventricles we observe seve- ral furrows ; and there are likewise tendinous strings, which arise from fleshy columns in the two cavities, and are attached to the valves of the auricles : That the use of these and the other valves of the heart may be understood, it must be observed, that four large vessels pass out from the basis of the heart, viz. two arteries and two veins : and that each of these vessels is furnished with a thin membranous production, which is attached all round to the borders of their several orifices, from whence hanging loosely down they appear to be divid- ed into two or three distinct portions. But as * Authors differ about the course and distinctions of these fibres ; and it seems right to observe, that the structure of the heart being more compact than that of other muscles, its fibres are not easily separated. 340 Of the Thorax. their uses in the arteries and veins are differ- ent, so are they differently disposed. Those of the arteries are intended to give way to the passage of the blood into them from the ven- tricles, but to oppose its return : and, on the contrary, the valves of the veins are construct- ed so as to allow the blood only to pass into the heart. In consequence of these different uses, we find the valves of the pulmonary ar- tery and of the aorta attached to the orifices of those vessels, so as to have their concave surfaces turned towards the artery ; and their convex surfaces, which mutually meet toge- ther, being placed towards the ventricle, only permit the blood to pass one way, which is into the arteries. There are usually three of these valves belonging to the pulmonary artery, and as many to the aorta ; and from their figure they are called valvule semilunares. The com- munication between the two great veins and the ventricles is by means of the two appen- dages or auricles into which the blood is dis- charged ; so that the other valves which may be said to belong to the veins, are placed in each ventricle, where the auricle opens into it. The valves in the right ventricle are usually three in number, and are named valvule? tri- cuspides ; but in the left ventricle we common- ly observe only two, and these are the valvulce mitrales. The membranes which form these valves in each cavity are attached so as to pro- ject somewhat forward ; and both the tricus- pides and the mitrales are connected with the tendinous strings, which were described as arising from the fleshy column a. By the con- 541 Of the Thorax. traction of either ventricle, the blood is driv- en into the artery which communicates with that ventricle ; and these tendinous strings being* gradually relaxed as the sides of the ca- vity are brought nearer to each other, the valves naturally close the opening into the au- ricle, and the blood necessarily directs its course into the then only open passage, which is into the artery ; but after this contraction, the heart becomes relaxed, the tendinous strings are again stretched out, and, drawing the valves of the auricle downwards, the blood is poured by the veins into the ventricle, from whence, by another contraction, it is again thrown into the artery, as will be described hereafter. The right ventricle is not quite so long, though somewhat larger, than the left ; but the latter has more substance than the other: and this seems to be, because it is in- tended to transmit the blood to the most dis- tant parts of the body, whereas the right ven- tricle distributes it only to the lungs. The heart receives its nerves from the par vagum and the intercostals. The arteries which serve for its nourishment are two in number, and arise from the aorta. They sur- round in some measure the basis of the heart, and from this course are called the coronary arteries. From these arteries the blood is re- turned by veins of the same name into the au- ricles, and even into the ventricles. The muscular bags called the auricles are situated at the basis of the heart, at the sides of each other; and, corresponding with the two ventricles, are like those two cavities dis- 342 Of the Thorax. tinguished into right and left. These sacs, which are interiorly unequal, have externally a jagged appendix ; which, from its having been compared to the extremity of an ear, has given them their name of auricles. Sect. XI. Angiology , or a Description of the Bloocl-vessels. The heart has been described as contracting itself, and throwing the blood from its two ven- tricles into the pulmonary artery and the aor- ta, and then as relaxing itself and receiving a fresh supply from two large veins, which are the pulmonary vein and the vena cava. We will now point out the principal distributions of these vessels. The pulmonary artery arises from the right ventricle by a large trunk, which soon divides into two considerable branches, which pass to the right and left lobes of the lungs ; each of these branches is afterwards divided and sub- divided into an infinite number of branches and ramifications, which extend through the whole substance of the lungs ; and from these branch- es the blood is returned by the veins, which, contrary to the course of the arteries, begin by very minute canals, and gradually become larger, forming at length four large trunks called pulmonary veins , which terminate in the left auricle by one common opening, from whence the blood passes into the left ventricle. From this same ventricle arises the aorta or great artery , which at its beginning is nearly 343 Of the Thorax. an inch in diameter ; it soon sends off two branches, the coronaries , which go to be dis- tributed to the heart and its auricles. After this, at or about the third or fourth vertebra of the back, it makes a considerable curva- ture ; from this curvature * arise three arte- ries; one of which soon divides into two branch- es. The first two are the left subclavian and the left carotid, and the third is a com- mon trunk to the right subclavian and right carotid ; though sometimes both the carotids arise distinctly from the aorta. The two carotids ascend within the subcla- vians, along the sides of the trachea ; and when they have reached the larynx, divide into two principal branches, the internal and external carotid. The first of these runs a lit- tle way backwards in a bending direction ; and having reached the under part of the ear, pass- es through the canal into the os petrosum, and entering into the cavity of the cranium, is distributed to the brain and the membranes which envelope it, and likewise to the eye. The external carotid divides into several branches, which are distributed to the larynx, pharynx, and other parts of the neck ; and to the jaws, lips, tongue, eyes, temples, and all the external parts of the head. * Anatomists usually call the upper part of this curvature aorta ascendens ; and the other part of the artery to its division at the iliacs, aorta descendens : but they differ about the place where this distinction is to be introduced ; and it seems sufficiently to answer every purpose, to speak only of the aorta and its curva- ture . 344 Of the Thorax. Each subclavian is likewise divided into a great number of branches. It sends off the vertebral artery , which passes through the openings we see at the bottom of the transverse processes of the vertebras of the neck, and in its course sends off many ramifications to the neighbouring parts. Some of its branches are distributed to the spinal marrow, and after a considerable inflection it enters into the crani- um, and is distributed to the brain. The sub- clavian likewise sends off branches to the mus- cles of the neck and scapula ; and the medias- tinum, thymus, pericardium, diaphragm, the breasts, and the muscles of the thorax, and even of the abdomen, derive branches from the subclavian, which are distinguished by different names, alluding to the parts to which they are distributed ; as the mammary , the phrenic , the intercostal , &c. But notwithstand- ing the great number of branches which have been described as arising from the subclavian, it is still a considerable artery when it reach- es the axilla , where it drops its former name, which alludes to its passage under the clavi- cle, and is called the axillary artery ; from which a variety of branches are distributed to the muscles of the breast, scapula, and arm. — But its main trunk taking the name of brachi- alis , runs along on the inside of the arm near the os humeri, till it reaches the joint of the fore-arm, and then it divides into two branch- es. This division however is different in dif- ferent subjects; for in some it takes place high- er up and in others lower down. When it happens to divide above the joint, it may be 345 Of the Thorax. considered as a happy disposition in case of an accident by bleeding ; for supposing the artery to be unfortunately punctured by the lancet, and that the haemorrhage could only be stop- ped by making a ligature on the vessel, one branch would remain unhurt, through which the blood would pass uninterrupted to the fore- arm and hand. One of the two branches of the brachialis plunges down under the flexor muscles, and runs along the edge of the ulna ; while the other is carried along the outer sur- face of the radius, and is easily felt at the wrist, where it is only covered by the common integuments. Both these branches commonly unite in the palm of the hand, and form an ar- terial arch from whence branches are detached to the fingers. The aorta , after having given olf at its cur- vature the carotids and subclavians which con- vey blood to all the upper parts of the body, descends upon the bodies of the vertebras a lit- tle to the left, as far as the os sacrum, where it drops the name of aorta , and divides into two considerable branches. In this course, from its curvature to its bifurcation, it sends olf several arteries in the following order: 1. One or two little arteries, first demonstrated by Ruysch as going to the bronchi, and called arteria bronchinaies Ruyschii. 2. The arteriae cesophageae. These are commonly three or four in number. They arise from the fore- part of the aorta, and are distributed chiefly to the (Esophagus. 3. The inferior intercostal arteries, which are distributed between the fibs in the same manner as the arteries of the X x 346 Of the Thorax. three or four superior ribs are, which are de- rived from the subclavian. These arteries send off branches to the medulla spinalis. 4. The diaphragmatic or inferior phrenic arteries, which go to tne diaphragm, stomach, omentum, duodenum, pancreas, spleen, liver, and gall- bladder. 5. The cceliarc, which sends off the coronary-stomachic, the splenic, and the hepa- tic artery. 6. The superior mesenteric artery, which is distributed to the mesentery and small intestines, 7. The emulgents, which go to the kidneys. 8. The arteries, which are distri- buted to the glandulae renales, 9. The sper- matic. 10. The inferior mesenteric artery, which ramifies through the lower portion of the mesentery and the large intestines. — A branch of this artery which goes to the rectum is call- ed the internal hemorrhoidal. 11. The lum- bar arteries, and a very small branch called the sacra , which are distributed to the mus- cles of the loins and abdomen, and to the os sacrum and medulla spinalis. The trunk of the aorta, when it has reached the last vertebra lumborum, or the os sacrum, drops the name of aorta , and separates into two forked branches called the iliacs. Each of these soon divides into two branches ; one of which is called the internal iliac , or hypogas- tric artery , and is distributed upon the contents of the pelvis and upon the muscles on its out- er side. One branch, called pudenda commu- nis, sends small ramifications to the end of the rectum under the name of hannorrhoulales extern ce, and is afterwards distributed upon the penis. The other branch, the external ill- 347 Of the Thorax. ac, after having given off the circumflex artery of the os ilium and the epigastric, which is distributed to the recti-muscles, passes out oi the abdomen under Poupart’s ligament, and takes the name of crural artery. It descends on the inner part of the thigh close to the os femoris, sending off branches to the muscles, and then sinking deeper in the hind part of the thigh, reaches the ham, where it takes the name of popliteal : after this it separates into two considerable branches ; one of which is called the anterior tibial artery ; the other di- vides into two branches, and these arteries all go to be distributed to the leg and foot. The blood, which is thus distributed by the aorta to all parts of the body, is brought back by the veins, which are supposed to be conti- nued from the ultimate branches of arteries ; and uniting together as they approach the heart, at length form the large trunks, the ve- na cava ascendens, and vena cava descendens. All the veins which bring back the blood from the upper extremities, and from the head and breast, pass into the vena cava descendens ; and those which return it from the lower parts of the body terminate in the vena cava ascen- dens ; and these two cavas uniting together as they approach the heart, open by, one common orifice into the left auricle. It does not here seem to be necessary to fol- low the different divisions of the veins as we did those of the arteries ; and it will be suffi- cient to remark, that in general every artery is accompanied by its vein, and that both are dis- tinguished by the same name. But, like many 348 Of the Thorax . other general rules, this too has its excep- tions.* The veins for instance, which accom- pany the external and internal carotid, are not called the carotid veins , but the external and in- ternal jugular. — In the thorax, there is a vein distinguished by a proper name, and this is the azygos , or vena sine pari. This vein, which is a pretty considerable one, runs along by the right side of the vertebras of the back, and is chiefly destined to receive the blood from the intercostals on that side, and from the lower half of those on the left side, and to convey it into' the vena cava descendens. In the abdo- men we meet with a vein, which is still a more remarkable one, and this is the vena porta , which performs the office both of an artery and a vein. It is formed by a re-union of all the veins which come from the stomach, intestines, omentum, pancreas, and spleen, so as to com- pose one great trunk, which goes to ramify through the liver ; and after having deposited the bile, its ramifications unite and bring back into the vena cava, not only the blood which the vena portae had carried into the liver, but likewise the blood from the hepatic artery. Every artery has a vein which corresponds with it ; but the trunks and branches of the veins are more numerous than those of the arteries. — The reasons for this disposition are perhaps more difficult to be explained ; the blood in its course through the veins is much farther re- moved from the source and cause of its mo- * In the extremities, some of the deep-seated veins, and all the superficial ones, take a course different from that of the arteries. Of the Thorax. 349 tion, which are in the heart, than it was when in the arteries ; so that its course is consequent- ly less rapid, and enough of it could not pos- sibly be brought back to the heart in the mo- ment of its dilatation, to equal the quantity which is driven into the arteries from the two ventricles, at the time they contract ; and the equilibrium which is so essential to the conti- nuance of life and health would consequently be destroyed, if the capacity of the veins did not exceed that of the arteries, in the same pro- portion that the rapidity of the blood’s motion through the arteries exceeds that of its return through the veins. A large artery ramifying through the body, and continued to the minute branches of veins, which gradually unite together to form a large trunk, may be compared to two trees united to each other at their tops ; or rather as having their ramifications so disposed that the two trunks terminate in one common point; and if we farther suppose, that both these trunks and their branches are hollow, and that a fiuid is inces- santly circulated through them, by entering in- to one of the trunks and returning through the other, we shall be enabled to conceive how the blood is circulated through the vessels of the human body. Every trunk of an artery, before it divides, is nearly cylindrical, or of equal diameter through its whole length, and so are all its branches when examined separately. But eve- ry trunk seems to contain less blood than the many branches do into which that trunk sepa- rates ; and each of these branches probably 350 Of the Thorax. contains less blood than the ramifications do into which it is subdivided : and it is the same with the veins ; the volume of their several ramifications, when considered together, being found to exceed that of the great trunk which they form by their union. The return of the blood through the veins to the heart, is promoted by the action of the muscles, and the pulsation of the arteries. And this return is likewise greatly assisted by the valves which are to be met with in the veins, and which constitute one of the great distinctions between them and the arteries. These valves, which are supposed to be form- ed by the inner coat of the veins, permit the blood to flow from the extremities towards the heart, but oppose its return. They are most frequent in the smaller veins. As the column of blood increases, they seem to become less necessary ; and therefore in the vena cava as- cendens, we meet with only one valve, which is near its origin. The arteries are composed of several tunics. Some writers enumerate five of these tunics ; but perhaps we may more properly reckon only three, viz. the nervous , muscular , and cuticular coats. The veins are by some anatomists de- scribed as having the same number of coats as the arteries ; but as they do not seem to be ir- ritable, we cannot with propriety suppose them to have a muscular tunic. We are aware of Dr. Verschuir’s* experiments to prove that the jugular and some other veins possess a * De Arteriarum et Venarum vi irritabili, 4to. Of the Thorax. 351 certain degree of irritability; but it is cer- tain, that his experiments, repeated by others, have produced a different result ; and even he himself allows, that sometimes he was unable to distinguish any such property in the veins. Both these series of vessels are nourished by still more minute arteries and veins, which are seen creeping over their coats, and ramifying through their whole substance, and are called vasa vasorum : they have likewise many mi- nute branches of nerves. The arteries are much stronger than the veins, and they seem to require this force to be enabled to resist the impetus with which the blood circulates through them, and to impel it on towards the veins. When the heart contracts, it impels the blood into the arteries, and sensibly distends them ; and these vessels again contract, as the heart becomes relaxed to receive more blood from the auricles : so that the cause of the contrac- tion and dilatation of the arteries seems to be easy to be understood, being owing in part to their own contractile power, and in part to the action of the heart ; but in the veins , the effects of this impulse not being so sensibly felt, and the vessels themselves having little or no con- tractile power, the blood seems to flow in a constant and equal stream : and this, together with its passing gradually from a small channel into a larger one, seems to be the reason why the veins have no pulsatory motion, except the large ones near the heart ; arid in these it seems to be occasioned by the motion of the dia- phragm, and by the regurgitation of the blood in the cavas. 352 Of the Thorax. Sect. XII. Of the Action of the Heart , Auricles , and Arteries. The heart, at the time it contracts, drives the blood from its ventricles into the arteries ; and the arteries being thus filled and distended, are naturally inclined to contract the moment the heart begins to dilate, and ceases to supply them with blood. These alternate motions of contraction and dilatation of the heart and ar- teries, are distinguished by the names of systole and diastole. When the heart is in a state of contraction or systole, the arteries are at that instant distended with blood, and in their diastole ; and it is in this state we feel their pulsatory motion which we call the pulse. When the heart dilates, and the arteries contract, the blood is impelled onwards into the veins through which it is returned back to the heart. While the heart, however, is in its systole, the blood cannot pass from the veins into the ventricles, but is detained in the auricles, which are two reservoirs formed for this use, till the diastole, or dilatation of the heart, takes place ; and then the distended auricles contract, and drive the blood into the ventricles ; so that the auricles have an alternate systole and diastole as well as the heart. Although both the ventricles of the heart contract at the same time, yet the blood pass- es from one to the other. In the same mo- ment, for instance, that the left ventricle drives the blood into the aorta, the right ven- tricle impels it into the pulmonary artery, Of the Thorax. 353 which is distributed through all the substance of the lungs. The blood is afterwards brought back into the left ventricle by the pulmonary vein, at the same time that the blood is returned by the cavas, into the right ventricle, from ail the other parts of the body. This seems to be the mode of action of the heart and its vessels ; but the cause of this action has, like all other intricate and interesting sub- jects, been differently explained. It seems to depend on the stimulus made on the different parts of the heart by the blood itself, which by its quantity and heat, or other properties,* is perhaps capable of first exciting that motion, which is afterwards continued through life, in- dependent of the will, by a regular return of blood to the auricles, in a quantity proportion- ed to that which is thrown into the arteries. The heart possesses the vis insita , or prin- ciple of irritability, in a much greater degree than any other muscle of the body. The pulse is quicker in young than in old subjects, be- cause the former are cat. par. more irritable than the latter. Upon the same principle we may explain, why the pulse is constantly quick- er in weak than in robust persons. Y y * Dr. Harvey long ago suggested, that the blood is possessed of a living principle ; and Mr. J. Hunter has lately endeavoured to revive this doctrine : in support of which he has adduced many ingenious arguments. The subject is a curious one, and deferves to be prosecuted as an inquiry which cannot but be interesting to physiologists. Of the Thorax. 354 Sect. XIII. Of the Circulation. After what has been observed of the structure and action of the heart and its auricles, and likewise of the arteries and veins, there seem to be but very few arguments required to demonstrate the circulation of the blood , which has long since been established as a medical truth. This circulation may be defined to be a perpetual motion of the blood, in consequence of the action of the heart and arteries, which impel it through all the parts of the body, from whence it is brought back by the veins of the heart. A very satisfactory proof of this circulation, and a proof easy to be understood, may be de- duced from the different effects of pressure on an artery and a vein. If a ligature, for instance, is passed round an artery, the vessel swells considerably between the ligature and the heart ; whereas if we tie up a vein, it only be- comes filled between the extremity and the ligature, and this is what we every day observe in bleeding. The ligature we pass round the arm on these occasions, compresses the super- ficial veins ; and the return of the blood through them being impeded, they become dis- tended. When the ligature is too loose, the veins are not sufficiently compressed, and the blood continues its progress towards the heart ; and, on the contrary, when it is made too tight, the arteries themselves become compressed ; .355 Of the Thorax. and the flow of the blood through them being impeded, the veins cannot be distended. Another phenomenon, which effectually proves the circulation, is the loss of blood that every living animal sustains by opening only a single artery of a moderate size ; for it con- tinues to flow from the wounded vessel till the equilibrium is destroyed which is essential to life. This truth was not unknown to the an- cients ; and it seems strange that it did not lead them to a knowledge of the circulation, as it sufficiently proves, that all the other vessels must communicate with that which is opened. Galen, who lived more than 1500 years ago, drew this conclusion from it ; and if w r e far- ther observe, that he describes (after Erasis- tratus, who flourished about 450 years before him) the several valves of the heart, and de- termines their disposition and uses, it will ap- pear wonderful, that a period of near 2000 years should afterwards elapse before the true course of the blood was ascertained. This discovery, for which we are indebted to the immortal Harvey, has thrown new lights on physiology and the doctrine of diseases, and constitutes one of the most important periods of anatomical history. Sect. XIV. Of the Nature of the Blood. Blood, recently drawn from a vein into a bason, would seem to be an homogeneous fluid 356 Of the Thorax. of a red colour ;* but when suffered to rest, it soon coagulates, and divides into two parts, which are distinguished by the names of cras- samentum and serum. The crassamentum is the red coagulum, and the serum is the water in which it floats. Each of these may be again separated into two others ; for the crassamen- tum, by being repeatedly washed in warm wa- ter, gives out all its red globules, and what remains appears to be composed of the coagu- lable lymph, f which is a gelatinous substance, capable of being hardened by fire till it becomes perfectly horny : and if we expose the serum to a certain degree of heat, part of it will be found to coagulate like the white of an egg, and there will remain a clear and limpid water, resembling urine both in its appearance and smell. The serum and crassamentum differ in their proportion in different constitutions ; in a strong person, the crassamentum is in a great- er proportion to the serum than in a weak one ;f and the same difference is found to take place in diseases. $ * The blood, as it flows through the arteries, is observed to be more florid than it is in the veins ; and this redness is acquir- ed in its passage through the lungs. Vid. feet. vii. -f* It may not be improper to observe, that till of late the coa- gu/able lymph has been confounded with the serum of the blood, which contains a substance that is likewise coagulable, though only when exposed to heat, or combined with certain chemical substances ; whereas the other coagulates spontaneously when exposed to the air or to rest. J Hewson’s Experim. Enq. Part I. $ When the blood separates into serum and crassamentum, if the latter be covered with a crust of a whitish or buff colour, it has been usually considered as a certain proof of the blood’s being in a state of too great viscidity. This appearance commonly taking place in inflammatory diseases, has long served to confirm the Of the Thorax. 357 Sect. XV. Of Nutrition. The variety of functions which we have de- scribed as being incessantly performed by the living body, and the continual circulation of the blood through it, must necessarily occasion a constant dissipation of the several parts which enter into its composition. In speaking of the insensible perspiration, we observed how much was incessantly passing off from the lungs and the surface of the skin. The discharge by urine is likewise every day considerable ; and great part of the bile, saliva, Stc. are excluded by stool. But the solid, as well as the fluid parts of the body, require a constant renew al of nutritious particles. They are exposed to the attrition of the fluids which are circulated through them ; and the contraction and relax- ation they repeat so many thousand times in every day, would necessarily occasion a disso- lution of the machine, if the renewal was not proportioned to the waste. It is easy to conceive how the chyle formed from the aliment is assimilated into the nature theory which ascribes the cause of inflammation to lentor and ob- structions. But from the late Mr Hewson’s experiments it ap- pears, that when the action of the arteries is increased, the blood, instead of being more viscid, is, on the contrary, more fluid than in the ordinary state, previous to inflammation ; and that in con- sequence of this, the coagulable lymph suffers the red globules, which are the heaviest part of the blood, to fall down to the bot- tom before it coagulates ; so that the crassamentum is divided into two parts : one of which is found to consist of the coagula- ble lymph alone (in this case- termed the bvjf) ; and the other, partly of this and partly of the red globules. 358 Of the Thorax. of blood, and repairs the loss of the fluid parts of our body ; but how the solids are renewed, has never yet been satisfactorily explained. The nutritious parts of the blood are probably deposited by the arteries by exsudation through their pores into the tela cellulosa ; and as the solid parts of the body are in the embryo only a kind of jelly, which gradually acquires the degree of consistence they are found to have when the body arrives at a more advanced age ; and these same parts which consist of bones, cartilages, ligaments, muscles, Ike. are sometimes reduced again by disease to a gela- tinous state ; we may, with some degree of probability, consider the coagulable lymph as the source of nutrition. If the supply of nourishment exceeds the degree of waste, the body increases ; and this happens in infancy and in youth : for at those periods, but more particularly the former one, the fluids bear a large proportion to the solids ; and the fibres being soft and yielding, are pro- portionably more capable of extension and in- crease. But when the supply of nutrition only equals the waste, we neither increase nor de- crease ; and we find this to be the case when the body has attained its full growth or acme : for the solids having then acquired a certain degree of firmness and rigidity, do not permit a farther increase of the body. But as we ap- proach to old age, rigidity begins to be in ex- cess, and the fluids * bear a much less propor- * As the fluids become less in proportion to the solids, their acrimony is found to increase ; and this may perhaps compen- sate for the want of fluidity in the blood by diminishing its co- hesion. Of the Thorax . 359 - lion to the solids than before. The dissipation of the body is greater than the supply of nour- ishment; many of the smaller vessels become gradually impervious ;* and the fibres losing their moisture and their elasticity, appear flac- cid and wrinkled. 1 he lilies and the roses dis- appear, because the fluids by which they were produced can no longer reach the extremities of the capillary vessels of the skin. As these changes take place, the nervous power being proportionably weakened, the irritability and sensibility of the body, which were formerly so remarkable, are greatly diminished ; and in advanced life, the hearing, the eye-sight, and all the other senses, become gradually im- paired. Sect. XVI. Of the Glands and Secretions . The glands are commonly understood to be small, roundish, t,r oval bodies formed by the convolution of a great number of vessels, and destined to separate particular humours from the mass of blood. They are usually divided into two classes ; but it seems more proper to distinguish three kinds of glands, viz. the mucous, conglobate, and conglomerate. The mucous glands , or follicles, as they are most commonly called, are small cylindrical * In infancy, the arteries are numerous and large in respect to the veins, and the lymphatic glands are larger than at any other time of life ; whereas, in old age, the capacity of the ve- nous system exceeds that of the arteries, and the lymphatic sys- tem almost disappears. 360 Of the Thorax. tubes continued from the ends of arteries. In some parts of the body, as in the tonsils, for example, several of these follicles may be seen folded together in one common covering, and opening into one common sinus. These folli- cles are the vessels that secrete and pour out mucus in the mouth, oesophagus, stomach, in- testines, and other parts of the body. The conglobate glands are peculiar to the lymphatic system. Every lymphatic vein pass- es through a gland of this kind in its way to the thoracic duct. They are met with in dif- ferent parts of the body, particularly in the axilla, groin, and mesentery, and are either solitary or in distinct clusters. The conglomerate glands are of much great- er bulk than the conglobate, and seem to be an assemblage of many smaller glands. Of this kind are the liver, kidneys, fkc. Some of them, as the pancreas, parotids, fkc. have a granu- lated appearance. All these conglomerate glands are plentifully supplied with blood-ves- sels ; but their nerves are in general very mi- nute, and few in number. Each little granu- lated portion furnishes a small tube, which unites with other similar ducts, to form the common excretory duct of the gland. The principal glands, and the humours they secrete, have been already described in different parts of this work; and there only remains for us to examine the general structure of the glands, and to explain the mechanism of secretion. On the first of these subjects two different systems have been formed ; each of which has had, and still continues to have, 361 Of the Thorax . its adherents. One of these systems' was ad- vanced by Malpighi, who supposed that an ar- tery entering into a gland ramifies very mi- nutely through its whole substance ; and that its branches ultimately terminate in a vesicu- lar cavity or follicle, from whence the secreted fluid passes out through the excretory duct. This doctrine at first met with few opponents ; but the celebrated Ruysch, who first attempt- ed minute injections with wax, afterwards dis- puted the existence of these follicles and as- serted, that every gland appears to be a con- tinued series of vessels, which after being re- peatedly convoluted in their course through its substance, at length terminate in the ex- cretory duct. Anatomists are still divided be- tween these two systems : that of Malpighi, however, seems to be the best founded. The mode of secretion has been explained in a variety of ways, and they are all perfectly hypothetical. In such an inquiry it is natural to ask, how one gland constantly separates a particular humour, while another gland se- cretes one of a very different nature from the blood ? The bile, for instance, is separated by the liver, and the urine by the kidneys.. Are these secretions to be imputed to any particu- lar dispositions in the fluids, or is their cause to be looked for in the solids ? It has been supposed, that every gland con- tains within itself a fermenting principle, by which it is enabled to change the nature of the blood it receives, and to endue it with a par- ticular property. So that, according to this system, the blood, as it circulates through the Z z 362 Of the Thorax. kidneys, becomes mixed with the fermenting principle of those glands, and a part of it is converted into urine ; and again, in the liver, in the salival and other glands, the bile, the saliva, and other juices, are generated from a similar cause. But it seems to be impossible for any liquor to be confined in a place expos- ed to the circulation, without being carried away by the torrent of blood, every part of which would be equally affected ; and this sys- tem of fermentation has long been rejected as vague and chimerical. But as the cause of se- cretion continued to be looked for in the fluids, the former system was succeeded by another, in which recourse was had to the analogy of the humours. It was observed, that if paper is moistened with water, and oil and water are afterwards poured upon it, that the water only will be permitted to pass through it; but that, on the other hand, if the paper has been pre- viously soaked in oil instead of water, the oil only, and not the water will be filtered through it. These observations led to a supposition, that every secretory organ is originally furnish- ed with a humour analogous to that which it is afterwards destined to separate from the blood ; and that in consequence of this disposition, the secretory vessels of the liver, for instance, will only admit the bilious particles of the blood, while all the other humours will be excluded. This system is an ingenious one, but the dif- ficulties with which it abounds are unanswer- able ; for oil and water are immiscible ; where- as the blood, as it is circulated through the body, appears to be an homogeneous fluid* 363 Of the Thorax. Every oil will pass through a paper moistened only with one kind of oil ) and wine, or spirits mixed with water, will easily be filtered through a paper previously soaked in water. Upon the same principle, all our humours, though differing in their other properties, yet agree- ing in that of being perfectly miscible with each other, will all easily pass through the same filtre. — But these are not all the objec- tions to this system. The humours which are supposed to be placed in the secretory vessels for the determination of similar particles of the blood, must be originally separated without any analogous fluid ; and that which happens once, may as easily happen always. Again, it sometimes happens from a vicious disposi- tion, that humours are filtered through glands which are naturally not intended to afford them a passage, and when this once has hap- pened, it ought, according to this system, to be expected always to do so : whereas this is not the case ; and we are, after all, naturally led to seek for the cause of secretions in the solids. It does not seem right to ascribe it to any particular figure of the secretory vessels ; because the soft texture of those parts does not permit them to preserve any constant shape, and our fluids seem to be capable of accommodating themselves to every kind of figure. Some have imputed it to the differ- ence of diameter in the orifices of the differ- ent secretory vessels. To this doctrine ob- jections have likewise been raised ; and it has been argued, that the vessels of the liver, for instance, would, upon this principle, afford a 364 Of the Thorax. passage not only to the bile, but to all the other humours of less consistence with it. In reply to this objection, it has been supposed, that secondary vessels exist, which originate from the first, and permit all the humours thinner than the bile to pass through them. Each of these hypotheses is probably very remote from the truth. i EXPLANATION of PLATE XXVIII. This plate represents the Heart in situ, all the large Arteries and Veins, with some of the Muscles, £kc. Muscles, &c. — Superior Extremity.- — a, Masseter. b, Complexus. c, Digastricus. d, Os hyoides. e, Thyroid gland, f, Levator scapulae, g, Cucullaris. h h, The clavicles cut. i, The deltoid muscle, k, Biceps flexor cubiti cut. 1, Caraco-brachialis. m, Triceps extensor cubiti. n, The heads of the pronator teres, flezor carpi radialis, and flexor digito- rum sublimis, cut. o, The flexor carpi ulna- ris, cut at its extremity, p, Plexor digitorum profundus, q, Supinator radii longus, cut at its extremity, r, Ligamentum carpi transver- sale. s, Extensores carpi radiales. t, Latis- simus dorsi. u, Anterior edge of the serratus anticus major, v v, The inferior part of the diaphragm, w w, Its anterior edge cut. x x, The kidneys, y, Transversus abdominis, z, Os ilium. * * Plate XW II! Of the Thorax. 365 Inferior Extremity. — a , Psoas magnus, Iliacus internus. c, The fleshy origin of the tensor vaginae femoris. d d , The ossa pubis cut from each other, e, Musculus pectineus cut from its origin. /, Short head of the tri- ceps abductor femoris cut. g , The great head of the triceps. /z, The long head cut. i, Vas- tus internus. Vastus externus. /, Crure- us. ra, Gemellus. w, Soleus. o, Tibia, p , Peronaeus longus. g, Peronaeus brevis, r, Fibula. He art and Blood-vessels.-— A, The heart, with the coronary arteries and veins. B, The right auricle of the heart. C, The aorta ascen- dens. D, The left subclavian artery. E, The left carotid artery. F, The common trunk which sends off the right subclavian and right carotid arteries. G, The carotis externa. K, Arteria facialis, which sends off the coronary arteries of the lips. I, Arteria temporalis pro- funda. K, Aorta descendens. L L, The iliac arteries, — which send off M M, The fe- moral or crural arteries. N. B. The other arteries in this figure have the same distri- bution as the veins of the same name : — And generally, in the anatomical plates, the description to be found on the one side, points out the same parts in the other. 1, The fron- tal vein. 2, The facial vein. 3, Vena tem- poralis profunda. 4, Vena occipitalis. 5, Vena jugularis externa. 6, Vena jugularis interna, covering the arteria carotis commu- nis. 7. The vascular arch on the palm of the hand, which is formed by, 8, The radial ar- tery and vein, and, 9, The ulnar artery and 366 Of the Brain and Nerves. vein. 10 10, Cephalic vein. 11, Basilic vein, that on the right side cut. 12, Median vein. 13, The humeral vein, which, with the me- dian, covers the humeral artery. 14 14, The external thoracic or mammary arteries and veins. 15, The axillary vein, covering the artery. 16 16, The subclavian veins, which, with (6 6) the jugulars, form, 17, The vena cava superior. 18, The cutaneous arch of veins on the fore part of the foot. 19, The vena tibialis antica, covering the artery. 20, The vena profunda femoris, covering the ar- tery. 21, The upper part of the vena saphena major. 22, The femoral vein. 23 23, The iliac veins. 24 24, Vena cava inferior. 25 25, The renal veins covering the arteries. 26 26* The diaphragmatic veins. PART V. OF THE BRAIN AND NERVES. Sect. I. Of the Brain and its Integuments. HE bones of the cranium were described in the osteological part of this work, as inclosing the brain, and defending it from ex- ternal injury : but they are not its only pro- tection ; for when we make an horizontal sec- tion through these bones, we find this mass 367 Of the Brain and Nerves. every where surrounded by two membranes,* the dura and pia mater. — The first of these lines the interior surface of the cranium, to which it every where adheres strongly,! but more particularly at the sutures, and at the many foramina through which vessels pass between it and the pericranium. The dura mater % is perfectly smooth and inelastic, and its inner surface is constantly bedewed with a fine pellucid fluid, which every where sepa- rates it from the pia mater. The dura mater sends off several considerable processes, which divide the brain into separate portions, and prevent them from compressing each other. Of these processes there is one superior and longitudinal, called the falx or falciform pro - cess , from its resemblance to a scythe. It arises from the spine of the os frontis, near the crista galli, and extending along in the direction of the sagittal suture, to beyond the lambdoidal suture, divides the brain into two hemispheres. A little below the lambdoidal * The Greeks called these membranes meninges : but the Ara- bians, supposing them to be the source of all the other mem- branes of the body, afterwards gave them the names of dura and pia mater ; by which they are now usually distinguished. ! In young subjects this adhesion is greater than in adults ; but even then, in the healthy subject, it is no where easily sepa- rable, without breaking through some of the minute vessels by means of which it is attached to the bone. ! This membrane is commonly described as consisting of two laminae ; of which the external one is supposed to perform the of- fice of periosteum internum to the cranium, -while the internal one forms the folds and processes of the dura mater. In the na- tural state, however, no such separation is apparent.; like other membranes, we may indeed divide it, not into two only, buc many laminae ; but this division is artificial, and depends on the dexterity of the anatomist. 368 Of the Brain and Nerves. suture, it divides into two broad wings or ex- pansions called the transverse or lateral process- es, which prevents the lobes of the cerebrum from pressing on the cerebellum. Besides these there is a fourth, which is situated under the transverse processes, and being continued to the spine of the occiput, divides the cere- bellum into two lobes. The blood, after being distributed through the cavity of the cranium by means of the ar- teries, is returned, as in the other parts of the body, by veins which all pass on to certain channels, situated behind these several pro- cesses. These canals or sinuses communicate with each other, and empty themselves into the in- ternal jugular veins, which convey the blood into the vena cava. They are in fact triangu- lar veins, running through the substance of the dura mater, and, like the processes, are dis- tinguished into longitudinal and lateral; and where these three meet, and where the fourth process passes off, we observe a fourth sinus, which is called torcular ; Herophilus, who first described it, having supposed that the blood at the union of these two veins, is, as it were, in a press. Besides these four canals, which were known to the ancients, modern anatomists enu- merate many others, by giving the appellation of sinuses to other veins of the dura mater, which for the most part empty themselves into some of those we have just now described. There are the inferior longitudinal sinus, the superior and inferior petrous sinuses, the ca- 369 Of the Brain and Nerves. 'vernous sinuses, the circular sinus, and the anterior and posterior occipital sinuses. These sinuses or veins, by being conveyed through a thick dense membrane, firmly sus- pended, as the dura mater is, within the cra- nium, are less liable to rupture ; at the same time they are well supported, and by running every where along the inner surface of the bones, they are prevented from pressing on the substance of the brain. To prevent too great a dilatation of them, we find filaments (called chorda JBillisii , from their having been first noticed b\ Willis) stretched across their cavi- ties ; and the oblique manner in which the veins from the brain run through the substance of the brain into these channels, serves the purpose of a valve, which prevents the blood from turning back into the smaller and weaker vessels of the brain. The pia mater is a much softer and finer membrane than the dura mater ; being exceed- ingly delicate, transparent, and vascular. It in- vests every part of the brain, and sends off an infinite number of elongations, which insinu- ate themselves between the convolutions, and even into the substance of the brain. Tins membrane is composed of two laminae ; of which the exterior one is named tunica arachnoiclea , from its thinness, which is equal to that of a spider’s web. These two laminae are intimate- ly adherent to each other at the upper part of the brain, but are easily separable at the basis of the brain, and through the whole length of the medulla spinalis. The external layer, or tunica araehnoidea, appears to be spread uni- 3 A 370 Of the Brain and Nerves. formly over the surface of the brain, but with- out entering into its furrows as the inner layer does ; the latter being found to insinuate itself between the convolutions, and even into the interior cavities of the brain. The blood-ves- sels of the brain are distributed through it in their way to that organ, and are therefore di- vided into very minute ramifications, before they penetrate the substance of the brain. There are several parts included under the general denomination of brain. One of these, which is of the softest consistence, and fills the greatest part of the cavity of the cranium, is the cerebrum , or brain properly so called. Another portion, which is seated in the infe- rior and posterior part of the head, is the cere- bellum ; and a third, which derives its origin from both these, is the medulla oblongata. The cerebrum is a medullary mass of a mo- derate consistence, filling up exactly all the upper part of the cavity of the cranium, and divided into two hemispheres by the falx of the dura mater. Each of these hemispheres is usually distinguished into an interior , a mid- dle, and a posterior lobe. The first of these is lodged on the orbital processes of the os fron- tis : the middle lobes he on the middle fosste of the basis of the cranium, and the posterior lobes are placed on the transverse septum of the os occipitis, immediately over the cerebel- lum, from which they are separated by the la- teral processes of the dura mater. These two portions afford no distinguishing mark of se- paration ; and on this account Iialler, and many other modern anatomists, omit the distinction Of the Brain ancl Nerves. 371 ef middle lobe, and speak only of the anterior and posterior lobes of the brain. The cerebrum appears to be composed of two distinct substances. Of these, the exte- rior one, which is of a greyish or ash-colour, is called the cortex , and is somewhat softer than the other, which is very white, and is call- ed medulla or substantia alba. After having removed the falx, and separat- ed the two hemispheres from each other, we perceive a white convex body, the corpus cal- losum, which is a portion of the medullary substance, uniting the two hemispheres to each other, and not invested by the cortex. By making an horizontal incision in the brain, on a level with this corpus callosum, we dis- cover two oblong cavities, named the anterior or lateral ventricles , one in each hemisphere. These two ventricles, which communicate with each other by a hole immediately under the plexus choroides, are separated laterally by a very fine medullary partition, called septum lucidum , from its thinness and transparency. The lower edge of this septum is fixed to the fornix, which is a kind of medullary arch (as its name implies) situated under the corpus callosum, and nearly of a triangular shape. Anteriorly the fornix sends off two medullary chords, called its anterior crura; which seem to be united to each other by a portion of me- dullary substance, named commissura anterior cerebri. These crura diverging from one ano- ther, are lost at the outer side of the lower and fore-part of the third ventricle. Posteri- orly the fornix is formed into two other crura. "372 Of the Brain and Nerves. which unite with two medullary protuberances called pedes hippocampi , and sometimes cornua ammonis , t .at extend along the back part of the lateral ventricles. The concave edge of the pedes hippocampi is covered by a medul- lary lamina, called corpus fmbriatum. Neither the edges of the fornix, nor its pos- terior crura, can be well distinguished, till we have removed the plexus choroides. This is a production of the pia mater, which is spread over the lateral ventricles. Its loose edges are collected, so as to appear like a vascular band on each side. When we have removed this plexus, we dis- cover several other protuberances included in the lateral ventricles. These are the corpora striata, the thalami nervorum opticorum, the tubercula quadrumgemina, and the pineal gland. The corpora striata are two curved oblong eminences, that extend along the anterior part of the lateral ventricles. They derive their name from their striated appearance, which is owing to an intermixture of the cortical and medullary substances of the brain. The thala- mi nervorum opticorum , are so called, because the optic nerves arise chiefly from them, and they are likewise composed both of the cortex and medulla. They are separated from the corpora striata only by a kind of medullary chord, the geminum centrum semi-circulare. The thalami are nearly of an oval shape, and are situated at the bottom of the upper cavity of the lateral ventricles. They are closely 373 Of the Brain and Nerves. united, and at their convex part seem to be- come one body. Anteriorly, in the space between the thala- mi, we observe an orifice by which the lateral ventricles communicate, and another leads down from this, under the different appella- tions of foramen commune anterius , vulva iter ad infundibulum , but more properly iter ad ter- tium ventriculum and the separation of the, thalami from each other posteriorly, forms another opening or interstice called anus. This has been supposed to communicate with the third ventricle ; but it does not, the bottom of it being shut up by the pia mater. The back part of the anus is formed by a kind of medul- lary band, which connects the thalami to each other, and is called commissura posterior ce- rebri. Behind the thalami and commissura poste- rior, we observe a small, soft, greyish, and oval body, about the size of a pea. This is the glandula pinealis ; it is described by Galen, under the name of conarion , and has been ren- dered famous by Descartes, who supposed it to be the seat of the soul. Galen seems for- merly to have entertained the same opinion. Some modern writers have, with as little rea- son, imagined that the soul is placed in the corpus callosum. The pineal gland rests upon four remarka- ble eminences, disposed in pairs, and seated immediately below it. These tubercles, which by the ancients were called testes and nates , have, since the time of Winslow, been more commonly named tuber cula quadrugemina. 374 Of the Brain and Nerves. Under the thalami we observe another ca- vity, the third ventricle, which terminates an- tenorly in a small medullary canal, the infun- dibulum, that leads to the glandula pituitaria. It has been doubted, whether the infundi- bulum is really hollow ; but some late experi- ments on this part of the brain* by Professor Murray of Upsal, clearly prove it to be a me- dullary canal, surrounded by both laminae of the pia mater. After freezing the brain, this channel was found filled with ice; and de' Haen tells f us, he found it dilated, and filled with a calcareous matter.^ The soft spongy body in which the infundi- bulum terminates, was by the ancients sup- posed to be of a glandular structure, and des- tined to filter the serosity of the brain. Spi- gelius pretended to have discovered its excre- tory duct, but it seems . certain that no such duct exists. It is of an oblong shape, com- posed, as it were, of two lobes. In ruminant Animals it is much larger than in man. From the posterior part of the third ventri- cle, we see a small groove or channel, de- scending obliquely backwards. This channel, which is called the aqueduct of Sylvius , though It was known to the ancients, opens into ano- ther cavity of the brain, placed between the cerebellum and medulla oblongata, and called the fourth ventricle. * Disp. de Infundibulo Cerebri. f Ratio Med. tom. vi. p. 271. I The under part of it, however, appears to be impervious ; at least no injection that can be depended on has been made to pass from it into the glandula pituitaria without laceration of parts. 375 Of the Brain and Nerves. The cerebellum , which is divided into two lobes, is commonly supposed to be of a firmer texture than the cerebrum ; but the truth is, that in the greater number of subjects, there Appears to be no sensible difference in the con- sistence of these two parts. It has more of the cortical than of the medullary substance in its composition. The furrow that divides the two lobes of the cerebellum leads anteriorly to a process, composed of medullary and cortical substan- ces, covered by the pia mater ; and which, from its being divided into numerous furrows, resembling the rings of the earth-worm, is named processus vermiformis. This process forms a kind of ring in its course between the lobes. The surface of the cerebellum does not af- ford those circumvolutions which appear in the cerebrum; but instead of these, we observe a great number of minute furrows, running pa- rallel to each other, and nearly in a transverse direction. The pia mater insinuates itself into these furrows. When we cut into the substance of the cere- bellum, from above downwards, we find the medullary part running in a kind of ramifying course, and exhibiting an appearance that has gotten the name of arbor vita. These ramifi- cations unite to form a medullary trunk ; the middle, anterior, and most considerable part of which forms two processes, the crura cere- helli, which unite with the crura cerebri, to form the medulla oblongata. The last furnish- es two other processes, which lose themselves 376 Of the Brain and Nerves. under the nates, and thus unite the lobes of the cerebellum to the posterior part of the ce- . rebrum. Under the nates we observe a trans- verse medullary line, or linea alba, running from one of these processes to the other ; and between them we find a very thin medullary damma, covered with the pia mater, which the generality of anatomists have (though seemingly without reason) considered as a valve formed for closing the communication between the fourth ventricle and the aquaeduc- -tus Sylvii. Vieussens named it valvula ma- jor cerebri. The medulla oblongata is situated in the mid- dle, lower, and posterior part of the cranium, and may be considered as a production or con- tinuation of the whole medullary substance of the cerebrum and cerebellum, being formed by the union of two considerable medullary processes of the cerebrum, called crura cerebri , with two other smaller ones from the cerebel- lum, which were just now spoken of under the name of crura cerebelli. The crura cerebri arise from the middle and lower part of each hemisphere. They are se- parated from each other at their origin, but are united below, where they terminate in a mid- dle protuberance, the pons Varolii , so called, because Varolius compared it to a bridge. This name, however, can convey no idea of its real appearance. It is, in fact, nothing more than a medullary protuberance, nearly of a se- nt -spherical shape, which unites the crura ce- rebri to those of tne cerebellum. 377 Of the Brain and Nerves. Between the crura cerebri, and near the an- terior edge of the pons Varolii, are two tuber- cles, composed externally of medullary, and internally of cineritious, substance, to which Eustachius first gave the name of eminently mamillares. Along the middle of the posterior surface of the medulla oblongata, where it forms the anterior part of the fourth ventricle, we observe a kind of furrow which runs downwards and terminates in a point. About an inch above the lower extremity of this fissure, several me- dullary filaments are to be seen running up- wards it on each side in an oblique direction, so as to give it the appearance of a writing- pen ; hence it is called calamus scriptorius. From the posterior part of the pons Varolii, the medulla oblongata descends obliquely back- wards ; at its fore-part, immediately behind the pons Varolii, we observe two pair of emi- nences, which were described by Eustachi- us, but received no particular appellation till the time of Vieussens, who gave them the names of corpora olivaria and corpora pyrami- dalia. The former are the outermost, being placed one on each side. They are nearly of an oval shape, and are composed of medulla, with streaks of cortical substance. Between these are the corpora pyramidalia, each of which terminates in a point. In the human subject these four eminences are sometimes not easily distinguished. The medulla spinalis or spinal marrow , which is the name given to the medullary chord that is extended down the vertebral ca- 3 B 37B Of the Brain and Nerves . nal, from the great foramen of the occipitai bone to the bottom of the last lumbar vertebra, is a continuation of the medulla oblongata. Like the other parts of the brain, it is invested by the dura and pia mater. The first of these, in its passage out of the cranium, adheres to the foramen of the os occipitis. Its connection with the ligamentary substance that lines the cavity of the spine, is only by means of cellular mem- brane ; but between the several vertebrae., where the nerves pass out of the spine, it sends off prolongations, which adhere strongly to the vertebral ligaments. Here, as in the cranium, the dura mater has its sinuses or large veins. These are two in number, and are seen run- ning on each side of the medullary column, from the foramen magnum of the os occipitis to the lower part of the os sacrum. They communicate together by ramifying branches at each vertebra, and terminate in the verte- bral, intercostal, and sacral veins. The pia mater is connected with the dura mater by means of a thin transparent sub- stance which from its indentations between the spinal nerves has obtained the name of ligamentum denticulatum. It is somewhat firm- er than the tunica arachnoidea, but in other re- spects resembles that membrane. Its use is to support the spinal marrow, that it may not affect the medulla oblongata by its weight. The spinal marrow itself is externally of a white colour ; but upon cutting into it we find its middle-part composed of a darker coloured mass, resembling the cortex of the brain. When the marrow has reached the first lumbar yer- Of the Brain and Nerves. 379 tehra, it becomes extremely narrow, and at length terminates in an oblong protuberance ; from the extremity of which the pia mater sends off a prolongation or ligament, resem- bling a nerve, that perforates the dura mater, and is fixed to the os coccygis. The medulla spinalis gives rise to 30 or 3 1 pair of nerves, but they are not ail of the same size, nor do they all run in the same direc- tion. The upper ones are thinner than the rest, and are placed almost transversely : as we descend we find them running more and more obliquely downwards, till at length their course is almost perpendicular, so that the low- ermost nerves exhibit an appearance that is called cauda equina, from its resemblance to a horse’s tail. The arteries that ramify through the differ- ent parts of the brain, are derived from the internal carotid and from the vertebral arteries. The medulla spinalis is supplied by the ante- rior and posterior spinal arteries, and likewise receives branches, from the cervical, the infe- rior and superior intercostal, the lumbar, and the sacral arteries. Sect. II. Of the Nerves. The nerves are medullary chords, differing from each other in size, colour, and consist- ence, and deriving their origin from the me- dulla oblongata and medulla spinalis. There are 39, andsometimes 40, pair of these nerves; 38 0 Of the Brain and Nerves . nine* of which originate from the medulla oblongata, and 30 or 31 from the medulla spi- nalis. They appear to be perfectly inelastic, and likewise to possess no irritability. If we irritate muscular fibres, they immediately con- tract ; but nothing of this sort happens if we irritate a nerve. They carry with them a co- vering from the pia mater ; but derive no tu- nic from the dura mater, as hath been gene- rally, though erroneously, supposed, ever since the time of Galen, f the outer covering of the nerves being in fact nothing more than the cel- lular membrane. This covering is very thick, where the nerve is exposed to the action of muscles ; but where it runs through a bony ca- nal, or is secure from pressure, the cellular tunic is extremely thin, or altogether wanting. We have instances of this in the portio mollis of the auditory nerve, and in the nerves of the heart. By elevating, carefully and gently, the brain from the basis of the cranium, we find the first nine pair arising in the following order: 1, The nervi olfactorii, distributed through the pituitary membrane, which constitutes the or- gan of smell. 2. The optici, which go to the * It has been usual to describe the ten pair of nerves as aris- ing from the medulla oblongata ; but as the tenth pair arise in the fame manner as the other spinal nerves, Santorini, Heister, Haller, and others, seem very properly to have classed them among the nerves of the spine. -}• Baron Haller and Professor Zinn seem to have been the first who demonstrated, that the dura mater is reflected upon and adheres to the periosteum at the edges of the foramina that afford a passage to the nerves out of the cranium, and vertebral •canal, or is soon lost in the cellular substance, Of the Brain and Nerves. 381 eyes, where they receive the impressions of visible objects. 3. The oculorum motores, so called because they are distributed to the mus- cles of the eye. 4. The pathetici, distributed to the superior oblique muscles of the eye, the motion of which is expressive of certain passions of the soul. 5. The nerves of this pair soon divide into three principal branches, and each of these has a different name. Its upper di- vision is the ophthalmicus, which is distribut- ed to various parts of the eyes, eye-lids, fore- head, nose, and integuments of the face. The second is called the maxillaris superior , and the third maxillaris inferior ; both which names allude to their distribution. 6. The abducto- res ; each of these nerves is distributed to the abductor muscle of the eye, so called, because it helps to draw the globe of the eye from the nose. 7. The auditorii,* which are distribut- ed through the organs of hearing. 8. The par vagum, which derives its name from the great number of parts to which it gives branch- es both in the thorax and abdomen. 9. The linguales, or hypo-glossi, which are distribut- ed to the tongue, and appear to contribute both to the organ of taste and to the motions of the tongue. f * This pair, soon after its entrance into the meatus auditorius internus, separates into two branches. One of these is of a very- soft and pulpy consistence, it is called the portio mollis of the se- venth pair, and is spread over the inner part of the ear. The other passes out through the aqueduct of Fallopius in a firm chord, which is distinguished as the portio dura, and is distribut- ed to the external ear and other parts of the neck and face. f Heister has summed up the ufes of these nine pair of nerves in the two following Latin verses : 382 Of the Brain and Nerves . It has already been observed, that the spi- nal marrow sends off 30 or 31 pair of nerves ; these are chiefly distributed to the exterior parts of the trunk and to the extremities. They are commonly distinguished into the cervical , dorsals lumbar , and sacral nerves. The cervical, which pass out from between the several vertebrae of the neck are eight'*' in number ; the dorsal, twelve ; the lumbar, five ; and the sacral, five or six ; the number of the latter depending on the number of holes in the os sacrum. Each spinal nerve at its origin is composed of two fasciculi of medullary fibres. One of these fasciculi arises from the anterior, and the other from the posterior, surface of the medulla. These fasciculi are separated by the ligamen- tum denticulatum ; after which we find them contiguous to one another. They then perfo- rate the dura mater, and unite to form a con- siderable knot or ganglion. Each of these “ O'faciens, cernens, oculosque movnis, paliensque, “ Gas tans, abducens, audiensque, magans que, loquinsquc .” * Besides these, there is another pair called accessorii , which ari-es from the medulla spinalis at its beginning; and ascending through die great foramen of the os occipitis into the cranium, passes out again close to the eighth pair, with which, however, it does not unite ; and it is afterwards distributed chiefly to the muscles of the neck, back, and scapula. In this course it sends off filaments to different parts, and likewise communicates with several other nerves. Physiologists are at a loss how to account for the singular origin and couise of these nervi accessorii. The ancients considered them as branches of the eighth pair, distri- buted to muscles of the scapula : Willis likewise considered them as appendages to that pair, and on that account named them ac - cessorii. They are sometimes called the spinal pair ; but as this latter name is applicable to all the nerves of the spine indiscrimi- nately, it seems better to adopt that given by Willis. 383 Of the Brain and Nerves. ganglions sends off two branches ; one ante- rior, and the other posterior. The anterior branches communicate with each other at their coming out of the spine, and likewise send off one, and sometimes more branches, to assist in the formation of the intercostal nerve. The knots or ganglions of the nerves just now spoken of, are not only to be met with at their exit from the spine, but likewise in vari- ous parts of the body. They occur in the nerves of the medulla oblongata, as well as in those of the spine. They are not the effects of disease, but are to be met with in the same parts of the same nerves, both in the foetus and adult. They are commonly of an oblong shape, and of a greyish colour, somewhat in- clined to red, which is perhaps owing to their being extremely vascular. Internally we are able to distinguish something like an intermix- ture of the nervous filaments. Some writers have considered them as so many little brains ; Lancisi fancied he had dis- covered muscular fibres in them, but they are certainly not of an irritable nature. A late writer, Dr. Johnstone,* imagines they are in- tended to deprive us of the power of the will over certain parts, as the heart, for instance ; but if this hypothesis were well founded, we should meet with them only in the nerves lead- ing to involuntary muscles ; whereas it is cer- tain, that the voluntary muscles receive their nerves through ganglions. Doctor Monro, from observing the accurate intermixture of the Essay on the Use of the Ganglions of the Nerves. 384 Of the Brain and Nerves. minute nerves which compose them, considers them as new sources of nervous energy. f The nerves, like the blood-vessels, in their course through the body, communicate with each other ; and each of these communications constitutes what is called a plexus , from whence branches are again detached to different parts of the body. Some of these are constant and considerable enough to be distinguished by particular names, as the semilunar plexus ; the pulmonary plexus; the hepatic , the cardiac, &c. It would be foreign to the purpose of this work, to follow the nerves through all their distributions ; but it may be remembered, that in describing the different viscera, mention was made of the nerves distributed to them. There is one pair, however, called the intercostal , or great sympathetic nerve , which seems to require particular notice, because it has an almost universal connection and correspondence with all the other nerves of the body. Authors are not perfectly agreed about the origin of the intercostal ; but it may perhaps not improperly be described, as beginning from filaments of the fifth and sixth pair ; it then passes out of the cranium, through the bony canal of the carotid, from whence it descends laterally close to the bodies of the vertebrae, and receives branches from almost all the vertebral nerves ; forming almost as many ganglions in its course through the thorax and abdomen. It sends off an infinite number of branches to the viscera in f Observations on the Nervous System. Of the Brain and Nerves. 385 those cavities, and forms several plexuses with tiie branches of the eighth pair or par vagum. That the nerves are destined to convey the principles of motion and sensibility to the brain from all parts of the system, there can be no doubt ; but how these effects are produced, no one has ever yet been able to determine. The inquiry has been a constant source of hypothesis in all ages, and has produced some ingenious ideas, and many erroneous positions, but with- out having hitherto afforded much satisfactory information. Some physiologists have considered a trunk of nerves as a solid chord, capable of being divided into an infinite number of filaments, by means of which the impressions of feeling are conveyed to the sensorium commune. Others have supposed it to be a canal, which afterwards separates into more minute channels; or, perhaps, as being an assemblage of many very small and distinct tubes, connected to each other, and thus forming a cylindrical chord. They who contend for their being solid bodies, are of opinion, that feeling is occasioned by vibration : so that, for instance according to this system, by pricking the finger, a vibration would be occasioned in the nerve, distributed through its substance ; and the effects of this vibration, when extended to the sensorium, would be an excital of pain. But the inelasticity, the softness, the con- nection, and the situation of the nerves, are so many proofs that vibration has no share in the cause of feeling. 3 C 386 Of the Brain and Nerves. Others have supposed, that in the brain and spinal marrow, a very subtile fluid is secreted, and from thence conveyed through tl^e imper- ceptible tubes, which they consider as existing in the nerves. They have farther supposed, that this very subtile fluid, to which they have given the name of animal spirits , is secreted in the cortical substance of the brain and spi- nal marrow, from whence it passes through the medullary substance. This, like the other system, is founded altogether on hypothesis ; but it seems to be an hypothesis derived from much more probable principles, and there are many ingenious arguments to be brought in its support. EXPLANATION of PLATE XXIX. Fig. 1 . Represents the Inferior part of the Brain; — the Anterior part of the whole Spine, including the Medulla Spinalis ; — with the origin and large portions of all the Nerves. AA, The anterior lobes of the cerebrum. BB, The lateral lobes of the cerebrum. CC, The two lobes of the cerebellum. D, Tuber annulare. E, The passage from the third ventricle to the infundibulum. F, 1 he me- dulla oblongata, which sends off the medulla spinalis through the spine. G G, That part of the os occipitis which is placed above (H FI) the transverse processes of the first cervical vertebra. I I, 6tc’. The seven cervical verte- OMY Plate XXIX 387 Of the Brain and Nerves. bras, with their intermediate cartilages. K K, &c. The twelve dorsal vertebrae, with their intermediate cartilages. L L, &tc. 1 he five lumbar vertebrae, with their intermediate car- tilages. M, The os sacrum. N, The os coc- cyges- Nerves. — 1 1, The first pair of nerves, nam- ed olfactory , which go to the nose. 2 2, The second pair, named optic , which goes to form, the tunica retina of the eye. 3 3, The third pair, named motor oculi ; it supplies most of the muscles of the eye-ball. 4 4, The fourth pair, named pathetic, — which is wholly spent upon the musculus trochlearis of the eye. 5 5, The fifth pair divides into three branches. — The first, named ophthalmic , goes to the orbit, supplies the lachrymal gland, and sends branches out to the forehead and nose. — - The second, named superior maxillary , sup- plies the teeth of the upper jaw, and some of the muscles of the lips. — The third named in- ferior maxillary , is spent upon the muscles and teeth of the lower jaw, tongue, and mus- cles of the lips. 6 6, The sixth pair, which, after sending off the beginning of the intercos- tal or great sympathetic, is spent upon the ab- ductor oculi. 7 7, The seventh pair, named auditory , divides into two branches. — I he largest, named portio mollis, is spent upon the internal ear. The smallest, portio dura, joins to the fifth pair within the internal ear by a re- flected branch from the second of the fifth ; and within the tympanum, by a branch from the third of the fifth named chorda tympani ~ 388 Of the Brain and Nerves. VicL fig. 3. near B. 8 8, &c. The eighth pair, named par vagum , — which accompanies the intercostal, and is spent upon the tongue, la- rynx, pharynx, lungs, and abdominal viscera. 9 9, The ninth pair, which are spent upon the tongue. 10 10, &c. The intercostal, or great sympathetic, which is seen from the sixth pair to the bottom of the pelvis on each side of the spine, and joining with all the nerves of the spine ; — in its progress supplying the heart, and, with the par vagum, the contents of the abdomen and pelvis. 11 11, I he accessorius, which is spent upon the sternocleido-mastoi- dseus and trapezius muscles. 12 12, The first cervical nerves; — 13 13, The second cervical nerves ; — both spent upon the muscles that lie on the neck, and teguments of the neck and head. 14 14, The third cervical nerves, which, after sending olf (15 15, &c.) the phrenic nerves to the diaphragm, supply the muscles and teguments that lie on the side of the neck and top of the shoulder. 16 16, The brachial plexus, formed by the fourth, fifth, sixth, se- venth cervicals, and first dorsal nerves ; which supply the muscles and teguments of the su- perior extremity. 17 17, The twelve dorsal, or proper intercostal nerves, which are spent upon the intercostal muscles and some of the large muscles which lie upon the thorax. 18 18, The five lumbar pairs of nerves, which supply the lumbar and abdominal muscles, and some of the teguments and muscles of the inferior extremity. 19 19, The sacro-sciatic, or posterior crural nerve, formed by the two inferior lumbar, and three superior of the os Of the Brain and Nerves. 389 sacrum. This large nerve supplies the great- est part of the muscles and teguments of the inferior extremity. 20, The stomachic plexus, formed by the eighth pair. 21 21, Branches of the solar or caeliac plexus, formed by the eighth pair and intercostals, which supply the stomach and chylopoietic viscera. 22 22, Branches of the superior and inferior mesen- teric plexuses, formed by the eighth pair and intercostals, which supply the chylopoietic vis- cera, with part of the organs of urine and generation. 23 23, Nerves which accompany the spermatic cord. 24 24, The hypogastric plexus, which supplies the organs of urine and generation within the pelvis. Fig. 2, 3, 4, 5. Shows different Views of the Inferior part of the Brain, cut perpendicu- larly through the Middle, — with the Origin and large Portions of all the Nerves which pass out through the Bones of the Cranium, —and the three first Cervicals. A, The anterior lobe. B, The lateral lobe of the cerebrum. C, One of the lobes of the cerebellum. D, Tuber annulare. E, Corpus pyramidale, in the middle of the medulla ob- longata. F, The corpus olivare, in the side of the medulla oblongata. G, The medulla ob- longata. H, The medulla spinalis. Nerves. — 1 2 3 4 5 6 7 8 and 9, Pairs of nerves. 10 -10, Nervus accessorius, which comes from — 11, 12, and 13, The three first cervical nerves. 390 Of the Senses and their Organs. PART VI. OF THE SENSES AND THEIR ORGANS. I N treating of the senses, we mean to con- fine ourselves to the external ones of touch , taste , smelling , hearing , and vision. The word sense, when applied to these five, seems to imply not only the sensation excited in the mind by certain impressions made on the body, but likewise the organ destined to receive and transmit these impressions to the sensorium. Each of these organs being of a peculiar struc- ture, is susceptible only of particular impres- sions, which will be pointed out as we pro- ceed to describe each of them separately. Sect. I. Of Touch. The sense of touch maybe defined to be the faculty of distinguishing certain properties of bodies by the feel. In a general acceptation, this definition might perhaps not improperly be extended to every part of the body possess- ed of sensibility,* but it is commonly con- * In the course of this article, mention has often been made of the sensibility or insensibility of different parts of the body : it will therefore, perhaps, not be amiss to observe in this place, that many parts which were formerly supposed to possess the most exquisite sense, are now known to have but little or no feeling, at least in a sound state ; for in an inflamed state, even the bones, the most insensible parts of any, become susceptible Of the Senses and their Organs. 391 fined to the nervous papillae of the cutis, or true skin, which, with its appendages, and their several uses, have been already de- scribed. The exterior properties of bodies, such as their solidity, moisture, inequality, smooth- ness, dryness, or fluidity, and likewise their degree of heat, seem all to be capable of mak- ing different impressions on the papillae, and consequently of exciting different ideas in the sensorium commune. But the organ of touch, like all the other senses, is not equally deli- cate in every part of the body, or in every subject ; being in some much more exquisite than it is in others. Sect. II. Of the Taste. The sense of taste is seated chiefly in the tongue ; the situation and figure of which are sufficiently known. On the upper surface of this organ we may observe a great number of papillae, which, on account of their difference in size and shape, of the most painful sensations. This curious discovery is due to the late Baron Haller. His experiments prove, that the bones, cartilages, ligaments, tendons, epidermis, and membranes (as the pleura, pericardium, dura and pia mater, periosteum, &c. may in a healthy state be considered as insensible. As sensibility depends on the brain and nerves, of course different parts will possess a greater or less degree of feeling, in proportion as they are supplied with a greater or smaller number of nerves. Upon this principle it is, that the skin, muscles, stomach, intestines, urinary bladder, ureters uterus, vapina peni , tongue, and re- tina, are extremely sensible, while the lungs and glands have only an obscure degree of feeling. 392 Of the Senses and their Organs. are commonly divided into three classes. The largest are situated towards the basis of the tongue. Their number commonly varies from seven to nine, and they seem to be mucous follicles. Those of the second class are some- what smaller, and of a cylindrical shape. They are most numerous about the middle of the tongue. Those of the third class are very minute, and of a conical shape. They are very numerous on the apex and edges of the tongue, and have been supposed to be formed by the extremities of its nerves. We observe a line, the linea lingua’ mediana, running along the middle of the tongue, and dividing it as it were into two portions. To- wards the basis of the tongue, we meet with a little cavity, named by Morgagni foramen ccecum , which seems to be nothing more than a common termination of some of the excretory ducts of mucous glands situated within the substance of the tongue. We have already observed, that this organ is every where covered by the cuticle, which, by forming a reduplication, called the franum , at its under part, serves to prevent the too great motion of the tongue, and to fix it in its situation. But, besides this attachment, the tongue is connected by means of its muscles and membranous ligaments, to the lower jaw, the os hyoides, and the styloid processes. The principal arteries of the tongue are the linguales, which arise from the external carotid. Its veins empty themselves into the external jugulars. Its nerves arise from the fifth, eighth, and ninth pair. Of the Semes and their Organs. 395 The variety of tastes seems to be occasioned by the different impressions made on the papil- lae by the food. The different state of the pa- pillae with respect to their moisture, their figure, or their covering, seems to produce a consider- able difference in the taste, not only in differ- ent people, but in the same subject, in sickness and in health. The great use of the taste seems to be to enable us to distinguish wholesome and salutary food from that which is unhealthy ; and we observe that many quadrupeds, by having their papillae* very large and long, have the faculty of distinguishing flavours with infinite accuracy. Sect. III. Of Smelling. The sense of smelling, like the sense of taste-, seems intended to direct us to a proper choice of aliment, and is chiefly seated in the nose, which is distinguished into its external and in- ternal parts. The situation and figure of the former of these do not seem to require a defini- tion. It is composed of bones and cartilages, covered by muscular fibres and by the common integuments. The bones make up the upper portion, and the cartilages the lower one. The septum narium, like the nose, is likewise in part bony, and in part cartilaginous. These bones and their connections were described in the osteology. 3 D * Malpighi’s description of the papilla;, which has been copied by many anatomical writers, seems to have been taken chiefly from the tongues of sheep. 394 Of the Senses and their Organs . The internal part of the nose, besides the ossa spongiosa, has six cavities or sinuses, the maxillary, the frontal, and the sphenoid, which were all described with the bones of the head. They all open into the nostrils ; and the nose likewise communicates with the mouth, larynx, and pharynx, posteriorly be- hind the velum palati. All these several parts, which are included in the internal division of the nose, viz. the in- ner surface of the nostrils, the lamellae of the ossa spongiosa, and the sinuses, are lined by a thick and very vascular membrane, which, though not unknown to the ancients, was first well described by Schneider,* and is therefore now commonly named membrana pituitaria Schneideri. This membrane is truly the organ of smelling; but its real structure does not yet seem to be perfectly understood. It appears to be a continuation of the cuticle, which lines the inner surface of the mouth. In some parts of the nose it is smooth and firm, and in others it is loose and spongy. It is constantly moist- ened by a mucous secretion ; the finer parts of which are carried off by the air we breathe, and the remainder, by being retained in the sinuses, acquires considerable consistence. The manner in which this mucus is secreted has not yet been satisfactorily ascertained ; but it seems to be by means of mucous follicles. Its arteries are branches of the internal max- illary and internal carotid. Its veins empty themselves into the internal jugulars. The first pair of nerves, the olfactory, are spread * De Catarrho, lib. iii. Of the Senses and their Organs. 395 over every part of it, and it likewise receives branches from the fifth pair. After what has been said of the pituitary membrane, it will not be difficult to conceive how the air we draw in at the nostrils, being impregnated with the effluvia of bodies, ex- cites in us that kind of sensation we call smell- ing. As these effluvia, from their being ex- ceedingly light and volatile, cannot be capable in a small quantity of making any great im- pression on the extremities of the olfactory nerves, it was necessary to give considerable extent to the pituitary membrane, that by this means a greater number of odoriferous parti- cles might be admitted at the same time. When we wish to take in much of the effluvia of any thing, we naturally close the mouth, that all the air we inspire may pass through the nos- trils ; and at the same time, by means of the muscles of the nose, the nostrils are dilated, and a greater quantity of air is drawn into them. In many quadrupeds, the sense of smelling is much more extensive and delicate than it is in the human subject ; and in the human sub- ject it seems to be more perfect the less it is vitiated by a variety of smells. It is not al- ways in the same state of perfection, being na- turally affected by every change of the pitui- tary membrane, and of the lymph with which that membrane is moistened. 3 96 Of the Senses and their Organs. Sect. IV. Of Hearing. Before we undertake to explain the man- ner in which we are enabled to receive the im- pressions of sound, it will be necessary to de- scribe the ear, which is the organ of hearing. It is commonly distinguished into external and internal. The former of these divisions in- cludes all that we are able to discover without dissection, and the meatus auditorius, as far as the tympanum and the latter, all the other parts of the ear. The external ear is a cartilaginous funnel, covered by the common integuments, and at- tached, by means of its ligaments and muscles* to the temporal bone. Although capable only of a very obscure motion, it is found to have several muscles. Different parts of it are dis- tinguished by several names ; all its cartila- ginous part is called ala or wing , to distin- guish it from the soft and pendent part below, called the lobe . Its outer circle or border is called helix , and the semicircle within this, antihelix. The moveable cartilage placed im- mediately before the meatus auditorius, which it may be made to close exactly, is named tragus ; and an eminence opposite to this at the extremity of the antihelix, is called anti- tragus. The concha is a considerable cavity formed by the extremities of the helix and an- tihelix. The meatus auditorius, which at its opening is cartilaginous, is lined with a very thin membrane, which is a continuation of the fcuticle from the surface of the ear. Of the Senses and their Organs. 397 In this canal we find a yellow wax, which is secreted by a number of minute glands or follicles, each of which has an excretory duct. This secretion, which is at first of an oily con- sistence, defends the membrane of the tym- panum from the injuries of the air ; and by its bitterness, prevents minute insects from enter- ing into the ear. But when from neglect or disease it accumulates in too great a quantity, it sometimes occasions deafness. The inner extremity of the meatus is closed by a very thin transparent membrane, the membrana tympani, which is set in a bony circle like the head of a drum. In the last century Rivinus, professor at Liepsic, fancied he had discovered a hole in this membrane, surrounded by a sphincter, and affording a passage to the air, between the external and internal ear. Cow- per, Heister, and some other anatomists, have admitted this supposed foramen, which cer- tainly does not exist. Whenever there is any opening in the membrana tympani, it may be considered as accidental. Under the mem- brana tympani runs a branch of the fifth pair of nerves, called chorda tympani ; and beyond this membrane is the cavity of the tympanum, which is about seven or eight lines wide, and half so many in depth ; it is semispherical, and every where lined by a very fine membrane. There are four openings to be observed in this cavity. It communicates with the mouth by means of the Eustachian tube. This canal, - which is in part bony and in part cartilaginous, begins by a very narrow opening at the anteri- or and almost superior part of the tympanum. 398 Of the 'Senses and their Organs. increasing in size as it advances towards the palate of the mouth, where it terminates by an oval opening. This tube is every where lined by the same membrane that covers the inside of the mouth. The real use of this ca- nal does not seem to have been hitherto satis- factorily ascertained ; but sound would seem to be conveyed through it to the membrana tympani,, deaf persons being often observed to listen attentively with their mouths open. Opposite to this is a minute passage, which leads to the sinuosities of the mastoid process ; and the two other openings, which are in the internal process of the os petrosum, are the fenestra ovalis, and fenestra rotunda, both of which are covered by a very fine membrane. There are three distinct bones in the cavity of the tympanum ; and these are the malleus, incus, and stapes. Besides these there is a fourth, which is the os orhiculare , considered by some anatomists as a process of the stapes, which is necessarily broken off by the violence we are obliged to use in getting at these bones ; but when accurately considered, it seems to be a distinct bone. The malleus is supposed to resemble a ham- mer, being larger at one extremity, which is its head, than it is at the other, which is its handle. The latter is attached to the mem- brana tympani, and the head of the bone is articulated with the incus. The incus , as it is called from its shape, though it seems to have less resemblance to an anvil than to one of the dentes molares with its roots widely separated from each other, is Of the Senses and their Organs. 399 distinguished into its body and its legs. One of its legs is placed at the entry of the canal which leads to the mastoid process ; and the other, which is somewhat longer, is articulat- ed with the stapes, or rather with the os orbi- culare, which is placed between them. The third bone is very properly named stapes , being perfectly shaped like a stirrup. Its basis is fixed into the fenestra ovalis, and its upper part is articulated with the os orbicu- lare. What is called the fenestra rotunda, though perhaps improperly, as it is more oval than round, is observed a little above the other, in an eminence formed by the os petro- sum, and is closed by a continuation of the membrane that lines the inner surface of the tympanum. The stapes and malleus are each of them furnished with a little muscle, the sta- pedeus and tensor tympani. The first of these, which is the smallest in the body, arises from a little cavern in the posterior and upper part of the cavity of the tympanum ; and its tendon, after passing through a hole in the same ca- vern, is inserted at the back part of the head of the stapes. This muscle, by drawing the stapes obliquely upwards, assists in stretch- ing the membrana tympani. The tensor tympani,* or interims mallei, as it is called by some writers, arises from the cartilaginous extremity of the Eustachian tube, and is inserted into the back part of the handle * Some anatomists describe three muscles of the malleus ; but only this one seems to deserve the name of muscle ; what are called the externus and obliquas mallei, seeming to be ligaments rather titan muscles. 400 Of the Senses and their Organs . of the malleus* which it serves to pull inwards, and of course helps to stretch the membrana tympani. The labyrinth is the only part of the ear which remains to be described. It is situated in the os petrosum, and is separated from the tympanum by a partition which is every where bony, except at the two fenestrae. It is com- posed of three parts ; and these are the vesti- bulum, the semicircular canals, and the coch- lea. The vestibulum is an irregular cavity, much smaller than the tympanum, situated nearly in the centre of the os petrosum, between the tympanum, the cochlea, and the semicircular canals. It is open on the side of the tympa- num by means of the fenestra ovalis, and com- municates with the upper portion of the coch- lea by an oblong foramen, which is under the fenestra ovalis, from which it is separated only by a very thin partition. Each of the three semicircular canals forms about half a circle of nearly a line in diameter, and running each in a different direction, they are distinguished into vertical , oblique , and ho- rizontal. These three canals open by both their extremities into the vestibulum ; but the vertical and the oblique being united together at one of their extremities, there are only five orifices to be seen in the vestibulum. The cochlea is a canal which takes a spiral course, not unlike the shell of a snail. From its basis to its apex it makes two turns and a half ; and is divided into two canals by a very thin lamina or septum, which is in part bony Of the Senses and their Organs. 401 and in part membranous, in such a manner that these two canals only communicate with each other at the point. One of them opens into the vestibulum, and the other is covered by the membrane that closes the fenestra ro- tunda. The bony lamella which separates the two canals is exceedingly thin, and fills about two-thirds of the diameter of the canal. The rest of the septum is composed of a most deli- cate membrane, which lines the whole inner surface of the cochlea, and seems to form this division in the same manner as the two mem- branous bags of the pleura, by being applied to each other, form the mediastinum. Every part of the labyrinth is furnished with a very delicate periosteum, and filled with a watery fluid, secreted as in other cavities. This fluid transmits to the nerves the vibrations it receives from the membrane closing the fenes- tra rotunda, and from the basis of the stapes, where it rests on the fenestrum ovale. When this fluid is collected in too great a quantity, or is compressed by the stapes, it is supposed to escape through two minute canals or aque- ducts, lately described by Dr. Cotunni,* an in- genious physician at Naples. One of these aqueducts opens into the bottom of the ves- tibulum, and the other into the cochlea, near the fenestra rotunda. They both pass through the os petrosum, and communicate with the ca- vity of the cranium where the fluid that passes through them is absorbed ; and they are lined 3 E r * De aqu®ductibus Auris Human® Intern®, 8vo, 1760. 402 Of the Senses and their Organs , by a membrane which is supposed to be a pro- duction of the dura mater. The arteries of the external ear come from the temporal and other branches of the exter- nal carotid, and its veins pass into the jugular. The internal ear receives branches of arteries from the basilary and carotids, and its veins empty themselves into the sinuses of the dura mater, and into the internal jugular. The portio mollis of the seventh pair is dis- tributed through the cochlea, the vestibulum r and the semi-circular canals ; and the portio dura sends off a branch to the tympanum, and other branches to the external ear and parts near it. The sense of hearing , in producing which all the parts we have described assist, is occa- sioned by a certain modulation of the air col- lected by the funnel-like shape of the external ear, and conveyed through the meatus audito- rius to the membrana tympanh That sound is propagated by means of the air, is very ea- sily proved by ringing a bell under the receiv- er of an air-pump the sound it affords being found to diminish gradually as the air becomes exhausted, till at length it ceases to be heard at all. Sound moves through the air with in- finite velocity ; but the degree of its motion seems to depend on the state of the air, as it constantly moves faster in a dense and dry, than it does in a moist and rarefied air. That the air vibrating on the membrana tympani communicates its vibration to the dif- ferent parts of the labyrinth, and by means of Of the Senses and their Organs. 403 the fluid contained in this cavity affects the au- ditory nerve so as to produce sound, seems to be very probable ; but the situation, the mi- nuteness, and the variety of the parts which compose the ear, do not permit much to be ad- vanced with certainty concerning their mode of action. Some of these parts seem to constitute the immediate organ of hearing, and these are all the parts of the vestibulum.: but there are others which seem intended for the perfection of this sense, without being absolutely essential to it. It has happened, for instance, that the mem- brana tympani, and the little bones of the ear, have been destroyed by disease, without de- priving the patient of the sense of hearing.* Sound is more or less loud in proportion to the strength of the vibration and the variety of sounds seems to depend on the difference of this vibration ; for the more quick and fre- quent it is, the more acute will be the sound, and vice versa. Before we conclude this article, it will be right to explain certain phenomena, which will be found to have a relation to the organ of hearing. Every body has, in consequence of particu- lar sounds, occasionally felt that disagreeable sensation which is usually called setting the teeth on edge : and the cause of this sensation * This observation has led to a supposition, that a perforation of this membrane may in some cases of deafness be useful ; and Mr. Cheselden relates, that, some years ago, a malefactor was pardoned on condition that he should submit to this operation ; but the public clamour raised against it was so great, that it was •thought right not to perform it. 404 Of the Senses and their Organs. may be traced to the communication which the portio dura of the auditory nerve has with the branches of the fifth pair that are distributed to the teeth, being probably occasioned by the violent tremor produced in the membrana tym- pani by these very acute sounds. Upon the same principle we may explain the strong idea of sound which a person has who holds a vi- brating string between his teeth. The humming which is sometimes perceiv- ed in the ear, without any exterior cause, may- be occasioned either by an increased action of the arteries in the ears, or by convulsive con- tractions of the muscles of the malleus and stapes, affecting the auditory nerve in such a manner as to produce the idea of sound. An ingenious philosophical writer* has lately dis- covered that there are sounds liable to be ex- cited in the ear by irritation, and without any assistance from the vibrations of the air. Sect. V. Of Vision. The eyes, which constitute the organ of vi- sion, are situated in two bony cavities named orbits , where they are surrounded by several parts, which are either intended to protect them from external injury, or to assist in their motion. The globe of the eye is immediately covered by two eye-lids or palpebrae, which are com- * Elliot’s Philosophkal Observations on the Senses of Vision and Hearing, 8vo. Of the Senses and their Organs. 405 posed of muscular fibres covered by the com- mon integuments, and lined by a very fine and smooth membrane, which is from thence ex- tended over part of the globe of the eye, and is called tunica conjunctiva. Each eye-lid is cartilaginous at its edge ; and this border which is called tarsus , is furnished with a row of hairs named cilia or eye-lashes. The cilia serve to protect the eye from in- sects and minute bodies floating in the air, and likewise to moderate the action of the rays of light in their passage to the retina. At the roots of these hairs there are sebaceous folli- cles, first noticed by Meibomius, which dis- charge a glutinous liniment. Sometimes the fluid they secrete has too much viscidity, and the eye-lids become glued to each other. The upper border of the orbit is covered by the eye-brows or supercilia, which by means of their two muscles are capable of being brought towards each other, or of being carried upwards. They have been considered as serv- ing to protect the eyes, but they are probably intended more for ornament than utility.* The orbits in which the eyes are placed, are furnished with a good deal of fat, which af- fords a soft bed on which the eye performs its several motions. The inner angle of each or- bit, or that part of it which is near the nose, is called cantlius major , or the great angle ; and the outer angle, which is on the opposite side of the eye, is the canthus minor , or little angle. * It is observable, that the eye-brows are peculiar to the hu- man species. 406 Of the Senses and their Organs. The little reddish body which we observe in the great angle of the eye-lids, and which is called caruncula lachrymalis , is supposed to be ol a glandular structure, and, like the follicles of the eye-lids, to secrete an oily humour. But its structure and use do not seem to have been hitherto accurately determined. The surface of the eye is constantly moistened by a very fine limpid fluid called the tears, which is chief- ly, and perhaps wholly, derived from a large gland of the conglomerate kind, situated in a small depression of the os frontis near the out- er angle of the eye. Its excretory ducts pierce the tunica conjunctiva just above the cartila- ginous borders of the upper eye-lids. When the tears were supposed to be secreted by the caruncule, this gland was called glandula inno- minata ; but now that its structure and uses are ascertained, it very properly has the name of glandula lachrymalis. The tears poured out by the ducts of this gland are, in a natur- al and healthy state, incessantly spread over the surface of the eye, to keep it clear and trans- parent, by means of the eye-lids, and as con- stantly pass out at the opposite corner of the eye or inner angle, through two minute orifi- ees, the puncta lachrymalia being determined into these little openings by a reduplication of the tunica conjunctiva, shaped like a crescent the two points of which answer to the puncta. * It sometimes happens, that this very pellucid fluid, which moistens the eye, being poured out through the excretory ducts of the lachrymal gland faster than it can be carried off through the puncta, trickles down the cheek, and is then strictly and pro- perly called tears. Of the Senses and their Organs. 407 This reduplication is named membrana , or val- vula semilunaris. Each of these puncta is the beginning of a small excretory tube, through which the tears pass into a little pouch or re- servoir, the sacculus lachrymalis, which lies in an excavation formed partly by the nasal process of the os maxillare superius, and part- ly by the os unguis. The lower part of this sac forms a duct called the ductus ad nares, which is continued through a bony channel, and opens into the nose, through which the tears are occasionally discharged.* The motions of the eye are performed by six muscles ; four of which are straight and two oblique. The straight muscles are dis- tinguished by the names of elevator , depres- sor, adductor , and abductor, from their se- veral uses in elevating and depressing the eye, drawing it towards the nose, or carrying it from the nose towards the temple. All these four muscles arise from the bottom of the or- bit, and are inserted by flat tendons into the globe of the eye. The oblique muscles are intended for the more compound motions of the eye. The first of these muscles, the obli- quus superior, does not, like the other four mus- cles we have described, arise from the bottom of the orbit, but from the edge of the fora- men that transmits the optic nerve, which se- parates the origin of this muscle from that of * When the ductus ad nares becomes obstructed in conse- quence of disease, the tears are no longer able to pass into the nos* trilji ; the sacculus lachrymalis becomes distended ; and inflam- mation, and sometimes ulceration taking place, constitute the disease called fistula lachrymalis. 408 Of the Senses and their Organs . the others. From this beginning it passes ill a straight line towards a very small cartilagin- ous ring, the situation of which is marked in the skeleton by a little hollow in the internal orbitar process of the os frontis. The tendon of the muscle after passing through this ring, is inserted into the upper part of the globe of the eye, which it serves to draw forwards, at the same time turning the pupil downwards. The obliquus inferior arises from the edge of the orbit, under the opening of the ductus lachrymalis ; and is inserted somewhat poste- riorly into the outer side of the globe, serving to draw the eye forwards and turn the pupil upwards. When either of these two muscles acts separately, the eye is moved on its axis ; but when they act together, it is compressed both above and below. The eye itself, which is now to be described, with its tunics, hu- mours, and component parts, is nearly of a spherical figure. Of its tunics, the conjuncti- va has been already described as a partial co- vering, reflected from the inner surface of the eye-lids over the anterior portion of the eye. What has been named albuginea cannot pro- perly be considered as a coat of the eye, being in fact nothing more than the tendons of the straight muscles spread over some parts of the sclerotica. The immediate tunics of the eye, which are to be demonstrated when its partial coverings, and all the other parts with which it is sur- rounded, are removed, are the sclerotica, cor- nea, choroides, and retina. Of the Senses and their Organs. 409 The sclerotica , which is the exterior coat, is every where white and opaque, and is join- ed at its anterior edge to another, which has more convexity than any other part of the globe, and being exceedingly transparent is called cornea .* These two parts are perfectly different in their structure ; so that some ana- tomists suppose them to be as distinct from each other as the glass of a watch is from the case into which it is fixed. The sclerotica is of a compact fibrous structure ' r the cornea, on the other hand, is composed of a great num- ber of laminae united by cellular membrane. By macerating them in boiling water, they do not separate from each other, as some writers have asserted ; but the cornea soon softens, and becomes of a glutinous consistence. The ancients supposed the sclerotica to be a continuation of the dura mater. Morgagni, and some other modern writers, are of the same opinion ; but this point is disputed by Winslow, Haller, Zin, and others. The truth seems to be, that the sclerotica, though not a production of the dura mater, adheres intimately to that membrane. The choroides is so called because it is fur- nished with a great number of vessels. It has likewise been named uvea, on account of its re- semblance to a grape. Many modern anatomi- cal writers have considered it as a production of the pia mater. This was likewise the opinion 3 F * Some writers, who have given the name of cornea to all this outer coat, have named what is here and most commonly called sclerotica, cornea opaca ; and its anterior and transparent portion, cornea luctda. 410 Of the Senses and their Organs. of the ancients ; but the strength and thickness of the choroides, when compared with the deli- cate structure of the pia mater, are sufficient proofs of their being two distinct membranes. The choroides has of late generally been de- scribed as consisting of two laminae ; the inner- most of which has been named after Ruysch, who first described it. It is certain, however, that Ruysch’s distinction is ill founded, at least with respect to the human eye, in which we are unable to demonstrate any such structure, al- though the tunica choroides of sheep and some other quadrupeds may easily be separated into two layers. The choroides adheres intimately to the scle- rotica round the edge of the cornea ; and at the place of this union, we may observe a little whitish areola, named ligamentum ciliare , though it is not of a ligamentous nature. They who suppose the choroides to be com- posed of two laminae, describe the external one as terminating in the ligamentum ciliare, and the internal one as extending farther to form the iris, which is the circle we are able to distin- guish through the cornea ; but this part is of a very different structure from the choroides ; so that some late writers have perhaps not im- properly considered the iris as a distinct mem- brane. It derives its name from the variety of its colours, and is perforated in the middle. — This perforation, which is called the pupil or sight of the eye, is closed in the foetus by a very thin vascular membrane. This membrana pu- pillaris commonly disappears about the seventh month. Of the Senses and their Organs. 411 On the under side of the iris we observe ma- ny minute fibres, called ciliary processes , which pass in radii or parallel lines from the circum- ference to the centre. The contraction and dilatation of the pupil are supposed to depend on the action of these processes. Some have considered them as muscular, but they are not of an irritable nature: others have sup- posed them to be filaments of nerves ; but their real structure has never yet been clearly ascertained. Besides these ciliary processes, anatomists usually speak of the circular fibres of the iris, but no such seem to exist. The posterior surface of the iris, the ciliary processes, and part of the tunica choroides, are covered by a black mucus for the purposes of accurate and distinct vision ; but the man- ner in which it is secreted has not been deter- mined. Immediately under the tunica choroides we find the third and inner coat, called the retina , which seems to be merely an expansion of the pulpy substance of the optic nerve, extending to the border of the crystalline humour. The greatest part of the globe of the eye, within these several tunics, is filled by a very transparent and gelatinous humour of conside- rable consistence, which, from its supposed resemblance to fused glass, is called the vitre- ous humour. It is invested by a very fine and delicate membrane, called tunica vitrea , and sometimes arachnoicles . — It is supposed to be composed of two laminae ; one of which dips into its substance, and by dividing the hu- 412 Of the Senses and their Organs , mour into cells adds to its firmness. The fore-part of the vitreous humour is a little hollowed, to receive a very white and trans- parent substance of a firm texture, and of a lenticular and somewhat convex shape, named the crystalline humour. It is included in a capsula, which seems to be formed by a sepa- ration of the two laminae of the tunica vitrea. The fore-part of the eye is filled by a very thin and transparent fluid, named the aqueous humour , which occupies all the space between the crystalline and the prominent cornea — The part of the choroides which is called the iris, and which comes forward to form the pupil, appears to be suspended as it were in this humour, and has occasioned this portion of the eye to be distinguished into two parts. One of these, which is the little space between the anterior surface of the crystalline and the iris, is called the posterior chamber; and the other, which is the space between the iris and the cornea, is called the anterior chamber of the eye.* Both these spaces are completely filled with the aqueous humour.f * We are aware that some anatomists, particularly Lieutaud, are of opinion, that the iris is every where in close contact with the crystalline, and that it is of course right to speak only of one chamber of the eye ; but as this does not appear to be the case, the situation cf the iris and the two chambers of the eye are here described in the usual way. f When the crystalline becomes opaque, so as to prevent the passage of the rays of light to the retina, it constitutes what is called a cataract ; and the operation of couching consists in re- moving the diseased crystalline from its bed in the vitreous hu- mour. In this operation the cornea is perforated, and the aque- ous humour escapes out of the eye, but it is constantly renewed again in a very short time. The manner, however, in which it is secreted, has not yet been determined. Of the Senses and their Organs. 415 The eye receives its arteries from the in- ternal carotid through the foramina optica ; and its veins pass through the foramina lacera, and empty themselves into the lateral sinuses. Some of the ramifications of these vessels ap- pear on the inner surface of the iris, where they are seen to make very minute convolu- tions, which are sufficiently remarkable to be distinguished by the name of circulus arteriosus , though perhaps improperly, as they are chief- ly branches of veins. The optic nerve passes in at the posterior part of the eye, in a considerable trunk, to be expanded for the purposes of vision, of which it is now universally supposed to be the im- mediate seat. But Messrs. Mariotte and Mery contended, that the choroides is the seat of this sense ; and the ancients supposed the crystalline to be so. Besides the optic, the eye receives branches from the third, fourth, fifth, and sixth pair of nerves. The humours of the eye, together with the cornea, are calculated to refract and converge the rays of light in such a manner as to form at the bottom of the eye a distinct image of the object we look at; and the point where these rays meet is called th & focus of the eye. On the retina, as in the camera obscura , the ob- ject is painted in an inverted position; and it is only by habit that we are enabled to judge of its true situation, and likewise of its dis- tance and magnitude. To a young gentleman who was born blind, and who was couched by Mr. Cheselden, every object (as he expressed himself) seemed to touch his eyes as what he A14t Of the Senses and their Organs. felt did his skin ; and he thought no objects so agreeable as those which were smooth and regular, although for some time he could form no judgment of their shape, or guess what it was in any of them that was pleasing to him. In order to paint objects distinctly on the retina, the cornea is required to have such a degree of convexity, that the rays of light may be collected at a certain point, so as to termi- nate exactly on the retina. — If the cornea is too prominent, the rays, by diverging too soon, will be united before they reach the retina, as is the case with near-sighted people or myopes ; and on the contrary, if it is not suf- ficiently convex, the rays will not be perfectly united when they reach the back part of the eye ; and this happens to long-sighted people or presbi , being found constantly to take place as we approach to old age, when the eye gra- dually flattens.* These defects are to be sup- plied by means of glasses. He who has too prominent an eye, will find his vision improv- ed by means of a concave glass ; and upon the same principles, a convex glass will be found useful to a person whose eye is natu- rally too flat. * Upon this principle, they who in their youth are near sight- ed may expect to see better as they advance in life, as their eyes gradually become more flat. \n ATOMY Plate AW Of the Senses and their Organs. 415 EXPLANATION OF PLATE XXX. Figure 1 . Shows the Lachrymal Canals, after the Common Teguments and Bones have been cut away. a, The lachrymal gland, b, The two punc- ta lachrymalia, from which the two lachry- mal canals proceed to c, The lachrymal sac. d, The large lachrymal duct, e, Its opening into the nose, f, The caruncula lachrymalis. g, The eye-ball. Fig. 2. An interior View of the Coats and Humours of the Eye. a a a a, The tunica sclerotica cut in four angles, and turned back, b b b b, The tunica choroides adhering to the inside of the sclero- tica, and the ciliary vessels are seen passing over — c c, The retina which covers the vitre- ous humour. d d, The ciliary processes, which were continued from the choroid coat, e e, The iris, f, The pupil. Fig. 3. Shows the Optic Nerves, and Mus- cles of the Eye. a a, The two optic nerves before they meet, b, The two optic nerves conjoined, c, The 4 16 Of the Senses and their Organs . right optic nerve, cl, Musculus attollens pal- pebrse superioris. e, Attollens oculi. f, Ab- ductor. g g, Obliquus superior, or trochle. aris. h, Adductor, i, The eye-ball. Fig. 4. Shows the Eye-ball with its Muscles. a, The optic nerve, b, Musculus trochle- aris. c, Part of the os frontis, to which the trochlea or pully is fixed, through which, — d, The tendons of the trochlearis passes, e, At- tollens oculi. f, Adductor oculi. g, Abduc- tor oculi. h, Obliquus inferior, i, Part of the superior maxillary bone to which it is fixed, k. The eye-ball. Fig. 5. Represents the Nerves and Muscles of the Right Eye, after part of the Bones of the orbit have been cut away. A, The eye -ball. B, The lachrymal gland. C, Musculus abductor oculi. D, Attollens. E, Levator palpebrte superioris. F, Depres- sor oculi. G, Adductor. H, Obliquus superi- or, with its pully. I, Its insertion into the sclerotic coat. K, Part of the obliquus inferior. L, The anterior part of the os frontis cut. M, The crista galli of the ethmoid bone. N, The posterior part of the sphenoid bone. O, Trans- verse spinous process of the sphenoid bone. P, The carotid artery, denuded where it pass- es through the bones. Q, The carotid artery within the cranium. R, The ocular artery. Of the Senses and their Organs. 417 Nerves. — a a, The optic nerve, b, The third pair. — c, Its joining with a branch of the first branch of the fifth pair, to form 1, — The lenticular ganglion, which sends off the ciliary nerves, d. e e, T he fourth pair, f, The trunk of the fifth pair, g, The first branch of the fifth pair, named ophthalmic. — h, The frontal branch of it. i, Its ciliary branches, along with which the nasal twig is sent to the nose, k, Its branch to the lachrymal gland. 1, The lenticular ganglion. m, The second branch of the fifth pair, named superior max- illary. n, The third branch of the fifth pair, named inferior maxillary, o, The sixth pair of nerves, — which sends off p, The beginning of the great sympathetic, q, The remainder of the sixth pair, spent on c, The abductor oculi. Fig. 6. Represents the head of a youth, where the upper part of the cranium is sawed off, — to show the upper part of the brain, covered by the pia mater, the vessels of which are minutely filled with wax. A A, The cut edges of the upper part of the cranium. B, The two tables and interme- diate diploe. B B, 1 he two hemispheres of the cerebrum. C C, The incisure made by the falx. D, Part of the tentorium cerebello super expansum. E, Part of the falx, which is fixed to the crista galli. 3 G 418 Of the Senses and their Organs. Fig. 7. Represents the parts of the External Ear, with the Parotid Gland and its Duct. a a, The helix, b, The antihelix, c, The antitragus. d, The tragus. e, The lobe of the ear. f, The cavitas innominata. g, The scapha. h, The concha. i i, The parotid gland. k, A lymphatic gland, which is often found before the tragus. 1, The duct of the parotid gland, m, Its opening into the mouth. Fig. 8. A view of the posterior part of the external ear, meatus auditorius, tympanum, with the small bones, and Eustachian tube of the right side. a, The back part of the meatus, with the small ceruminous glands, b, The incus. c, Malleus, d, The chorda tympani. e, Mem- brana tympani. f, The Eustachian tube, g, Its mouth from the fauces. Fig. 9. Represents the anterior part of the right external ear, the cavity of the tympa- num — its small bones, cochlea, and semicir- cular canals. a, The malleus, b, Incus with its long leg, resting upon the stapes, c, Membrana tym- pani. d, e, The Eustachian tube, covered by part of — f f, The musculus circumfiexus palati. 1, 2, 3, The three semicircular canals. 4, The vestible. 5, The cochlea. 6, The por- tio mollis of the seventh pair of nerves. Of the Senses and their Organs. 419 Fig. 10. Shows the muscles which compose the fleshy substance of the Tongue. a a, The tip of the tongue, with some of the papillae minimae. b, The root of the tongue, c, Part of the membrane of the tongue, which covered the epiglottis. d d, Part of the mus- culus hyo-glossus. e, The lingualis. f, Ge- nio-glossus. g g, Part of the stylo-glossus. THE END. * ' - . * 4 . .. ** • / •o dp. $•