HUMAN ANATOMY. Digitized by the Internet Archive in 2010 with funding from Boston Library Consortium Member Libraries http://www.archive.org/details/introductiontostOOpaxt INTRODUCTION STUDY OF HUMAN ANATOMY. By JAMES PAXTON, MEMBER OF THE ROYAL COLLEGE OF SURGEONS, HONORARY MEMBER OF THE ASHMOLEAN SOCIETY, AND AUTHOR OF NOTES AND ILLUSTRATIONS TO PALEY'S NATURAL THEOLOGY. IN TWO VOLUMES, WITH ILLUSTRATIONS. Formative Fibres of the Brain. See page 134. VOLUME II. THIRD AMERICAN EDITION, WITH ADDITIONS. By WINSLOW LEWIS, Jr. M. D. DEMONSTRATOR OF ANATOMY TO THE MEDICAL DEPARTMENT OF HARVARD UNIVERSITY. BOSTON: WILLIAM D. TICK NOR Comer of Washington and School Streets. 1837. r3<+<- Entered according to act of Congress, in the year 1835, By William D. Ticknor, in the Clerk"s office of the District Court of the District of Massachusetts. CAMBRIDGE: FOLSOM, WELLS, AND THURSTON, PRINTERS TO THE UNIVERSITY. CONTENTS. CONTINUATION OF ARTICLE V.— VASCULAR SYSTEM. CHAPTER II. Page. Of the Veins in General, ... 1 Structure of Veins, . . . .2 General Department of the Venous System, 4 Veins which form the superior vena cava, . . 4 Veins which give rise to the external jugular, . 4 Veins which give rise to the internal jugular, . 5 Veins forming the subclavian veins, . . 7 Superior vena cava, . . . .11 Veins forming the inferior vena cava, . . 13 Veins forming the internal iliac vein, . . 15 Common iliac veins, .... 15 Inferior vena cava, . . . .15 Branches of the inferior vena cava, . . 16 Vertebral sinuses and veins of the spinal marrow, . 17 Veins of the heart, .... 18 Coronary Veins . . . . .18 Ardominal Department of the Venous System, 19 Vena Porta; — Branches of, . . .19 VI CONTENTS. CHAPTER III. Page. Of the Capillaries, . . . .21 ARTICLE VI. ORGANS OF ABSORPTION. CHAPTER I. Lymphatic Glands, .... 22 24 24 25 25 26 26 27 27 28 Structure of the Lymphatic Vessels, Lymphatic Glands in General, Lymphatic Glands in Particular, Lymphatic glands of the inferior extremities, Lymphatic glands of the pelvis, Lymphatic glands of the abdomen, Lymphatic glands of the thorax, Lymphatic glands of the superior extremities, Lymphatic glands of the head and neck, CHAPTER II. Particular Lymphatic Vessels, . . 29 Lybiphatic Vessels terminating in the Thoracic Duct, . . . . .29 Lymphatic vessels of the inferior extremities, . 29 Lymphatic vessels of the perinaeum, loins, etc., . 31 Deep-seated obturator, ischiatic, and genital lymphat- ic vessels, • ... 31 Lymphatics of the urinary organs, . . .32 Lymphatics of the parietes of the pelvis and abdo- men, ..... 33 Lymphatics of the stomach and intestines, . . 34 Lymphatics of the spleen, pancreas, and liver, . 36 The Thoracic Duct, . . . .37 Lymphatics which open directly into the thoracic duct, 38 CONTENTS. Vll Pago. Lymphatics of the lungs, . . - .38 Lymphatics of the diaphragm, heart, thymus, and oesophagus, .... 39 Lymphatics of the superior extremities, . . 40 Lymphatics of the anterior parietes of the thorax, 41 Lymphatics of the posterior region of the neck and thorax, . . . . .41 Lymphatics of the axilla, ... 41 Lymphatics of the head and anterior part of the neck, 42 Deep lymphatics of the head and neck, . 42 The office of the lymphatics and their glands, . 43 ARTICLE VII. NERVOUS SYSTEM. CHAPTER I. General Divisions of the Nervous System, . 44 Cerebral Department of the Nervous System, . 45 The brain in general, .... 51 The exterior of the cerebrum, . . .55 The exterior of the cerebellum, . . 56 The exterior of the pons Varolii, . . .57 The medulla oblongata, . . .58 The medulla spinalis, . . . .60 The internal organization of the brain, . 61 Chemical analysis of the brain, . . .61 Parts observed in the lateral ventricles, . . 66 The internal structure of the cerebellum, . . 69 CHAPTER II. The Membranous Envelopes of the Brain, . 74 The dura mater, . . . .74 Sinuses of the dura mater, . •■ . 75 The arachnoid membrane, . . .78 Vlll CONTENTS. The pia mater, .... Granulations of the membranes of the brain, The proper membrane of the spinal marrow, Ligamentum denticulatum, The Nerves in General, Nerves of the Cerebral Department, Olfactory, ..... Optic, ..... Motores oculorum, .... Pathetic, Trifacial, ..... 1. Ophthalmic branch, . 2. Superior maxillary, 3. Inferior maxillary, Abducent, ..... Facial, ..... Auditory, ..... Glosso-pbaryngseal, Pneumo-gastric, .... Hypoglossal, .... Spinal accessory, .... Spinal nerves, .... First pair of cervical, Second pair of cervical, Third and fourth pair of cervical, Cervical plexus, .... Fourth, fifth, sixth, and seventh pair of cervical nerves, .... Brachial, or axillary plexus, Thoracic branches, .... Nerves of the arm, . Internal cutaneous nerve, External, or musculo-cutaneous, The median nerve, .... The ulnar nerve, . Radial nerve. Page. 79 80 81 81 82 83 83 84 85 86 86 87 88 88 91 91 94 94 95 97 98 100 100 101 101 101 103 103 104 104 104 105 107 108 109 CONTENTS. IX Pago. Circumflex nerve, no Dorsal nerves, .... . 110 Lumbar nerves, 111 First lumbar, .... . in Second lumbar, 112 Third lumbar, .... . 112 Fourth and fifth lumbar, 112 Lumbo-abdominal, or lumbar plexus, . 113 Musculo-cutaneous branches, . 113 Genito-crural nerve, . 114 Crural nerve, 114 Obturator nerve, .... . 115 Lumbo-sacral nerve, . 1IC Glutaeal nerve, .... . 116 Sacral nerves, 116 Sciatic nerve, .... . 117 External popliteal nerve, 117 Internal poplitaeal nerve, . . 118 CHAPTER III. Ganglionic Department of the Nervous System, 120 Particular Ganglia, .... 122 Ganglia of the Head, . . . 122 Lenticular ganglion, .... 122 Spheno-palatine ganglion, . . . 122 Ganglia of the Neck, .... 125 Superior cervical ganglion, . . . 125 Middle cervical ganglion, .... 126 Inferior cervical ganglion, . . . 126 Cardiac nerves, ..... 126 Cardiac plexus, or ganglion, . . . 127 Thoracic Ganglia, .... 128 Splanchnic Nerves .... 128 VOL. II. X CONTENTS. Page. Great splanchnic nerve, .... 128 Small splanchnic nerve, . . . 129 Ganglia of the Abdomen, . . . 129 Semilunar ganglia and solar plexus, . . 129 The lumbar ganglia, .... 130 The sacral ganglia, .... 131 Hypogastric plexus, .... 131 Great Sympathetic Nerve, . . . 133 Formative Fibres of the Brain according to Gall and Spurzheim, .... 134 ARTICLE VIII. particular organs of sensation. CHAPTER I. The Eye and its Appendages, Eyebrows, Eyelids, The globe of the eye in general, . The sclerotica, The cornea, The choroid membrane, The ciliary circle, or ligament, The iris, The retina, The aqueous humor, . The crystalline lens, The vitreous humor, . 137 137 138 140 140 140 141 142 143 144 146 147 148 CHAPTER II. The Ear and its Appendages, The external ear, Fibro-cartilage of the ear, 150 150 152 CONTENTS. xi Page. The auditory canal, .... 153 The internal ear, .... 154 Bones of the ear, .... 155 The labyrinth, ..... 156 The cochlea, . . . . 157 The semicircular canals, .... 159 Auditory nerve, .... 159 Mechanism of hearing, .... 160 CHAPTER III. The Nose, ..... 163 Mechanism of smell, .... 165 CHAPTER IV. The Tongue, ..... 166 Taste, . . . . . .168 CHAPTER V. The Skin, . . . . .169 The dermis, . . . . .170 The rete mucosum, .... 171 The epidermis, ..... 172 The sense of touch, .... 174 The Hair, . . . . .175 Organization of the hair, . . . 177 The Nails, . . . . .177 CHAPTER VI. Muscular Sensation, .... 178 CHAPTER VII. Visceral Sensation, .... 182 Xll CONTENTS. ARTICLE IX ORGANS OF DIGESTION. The Mouth, The Palate, The Pharynx, The (Esophagus, . The Stomach, Organization of the Stomach, Office of the Stomach, The Intestinal Canal, The small intestine, . The duodenum, . The jejunum and ilium, The large intestine, The Mesentery, Digestion, . Page. 185 186 187 188 190 191 193 193 194 194 195 197 202 203 ARTICLE X. organs of respiration. The Lungs, ..... 207 Organization of the lungs, . . . 210 Changes which take place in Respiration, . 212 The Trachea and Bronchi, . . . 215 Organization of the trachea and bronchi, . 217 ARTICLE XI. ORGANS OF THE VOICE. The Larynx, . Cartilages of the larynx, 219 219 CONTENTS. X1I1 Thyroid cartilage, Cricoid cartilage, Arytenoid cartilages, Epiglottis, The ligaments of the larynx, The muscles of the larynx, Crico-thyroideus, Crico-arytenoideus posticus, Crico-arytenoideus lateralis, Thyro-arytenoideus, . Arytenoideus, Mucous membrane of the larynx, The gland of the epiglottis, The arytenoid glands, The office of the larynx, . The thyroid gland, 219 220 221 222 223 224 225 225 226 226 227 227 227 228 228 229 ARTICLE XII ORGANS OP ECEETION, Organs for the Secretion and Transmission of Tears, . . . . .230 The lachrymal gland,-. . . . 230 The caruncula lachrymalis, . . . 231 The puncta lachrymalia, . . . 231 The lachrymal sac, .... 232 The nasal duct, .... 232 The Salivary Glands, .... 232 The parotid gland, . . . . 233 The submaxillary gland, .... 234 The sublingual gland, . . . 234 The Pancreas, ..... 235 Organs for the Secretion and Transmission of the Bile, .... 236 The liver, .• . . . .236 XIV CONTENTS. Page. Ligaments of the liver, . . . 238 Envelopes of the liver, .... 239 The hepatic duct, .... 239 The gall bladder, . . . .240 Cystic duct, ..... 240 The ductus communis choledochus, . . 240 Secretion of bile, .... 241 The Spleen, ..... 242 Organization of the spleen, . . . 243 Office of the spleen, .... 243 Supra-Renal Capsules, . . . 245 The Kidneys, ..... 245 Organization of the kidneys, . . . 246 The calyces, pelvis, and ureter, . . . 247 The Bladder, .... 250 The organization of the bladder, . . . 251 The office of the kidneys and bladder, . 252 The urine, . . . . .253 ARTICLE XIII. organs op generation in the male. The Testicles and their Appendages, . . 255 Envelopes of the testicles, . . . 255 The testicles, : 256 Organization of the testicle, . . . 257 Epididymis, ..... 258 Vas deferens, .... 258 Spermatic cord, ..... 259 Vesiculoe seminales, .... 260 Prostate gland, ..... 261 Cowper's glands, . 262 Ejaculatory ducts, .... 262 CONTENTS. XV Page. Penis, ..... 264 Integuments of the penis and prepuce, . . 264 Corpus cavernosum, .... 264 Organization of the corpus cavernosum, . . 265 Urethra, ..... 266 Organization of the urethra, . . . 267 Glans penis, ..... 268 ARTICLE XIV. organs of generation, etc., in the female. Organs of Generation, and for the Nutrition of the Child, in the Female, . . 269 Organization of the Vagina, . . . 27 L The Uterus and its Appendages, . . 272 Organization of the uterus, . . 273 The broad ligaments, .... 276 The round ligaments, . . . 276 The Fallopian or uterine tubes, . . . 276 The ovaries, ..... 277 The gravid uterus, .... 280 Developement of the ovum in the uterus, . 282 Membranes which inclose the Foetus, . . 283 Liquor Amnii, ..... 284 The Placenta, ..... 284 Office of the placenta, . . . 287 Funis Umbilicalis, .... 287 Umbilical Vesicle, .... 288 The Mamm^j, ..... 2S9 Organization of the mammae, . . 289 Office of the mammas, .... 291 XVI CONTENTS. ARTICLE XV. THE FCETUS. Page. Peculiarities of the Fcetus, . . . 293 ARTICLE XVI. serous system, and cellular tissue. The Pleura and the Peritonaeum, . . 304 Omenta, or Epiploa, .... 308 Cellular Tissue, &c. . . . .311 Fat, ...... 314 Glossary, ...... 317 ANATOMY THE HUMAN BODY CHAP. II. OF THE VEINS IN GENERAL. It has been already stated, that it is the office of the arteries to convey the blood from the heart to the different parts of the body, for the purpose of nourishing and building up the animal fabric : now there is a corre- sponding series of sanguineous canals which return the blood from all the organs, again to continue the stream of the circulation ; these are the veins. By the aid of a microscope, the extreme branches of the arteries may be observed communicating with the minute radicles of the venous system, and transferring their blood to that series of vessels. The curious and beautiful phenomena of the circulation are evident, when the tail of a fish, or the web of a frog's foot, is placed in the field of a powerful magni- fier ; and we are assured of the fact of the continuity of the two sets of vessels in the human subject, by the circumstance of fine injections passing readily from the arteries into the veins. There are two departments of the venous system ; the 1st, or general department of the venous system, more ex- tensive than the other, commences in the head, trunk, and VOL. II. 1 2 VASCULAR SYSTEM limbs, and transmits the blood to the heart by the vena? cavae. The 2d, or abdominal department of the venous system, is confined to the cavity of the abdomen, and is formed by the veins of all the chylopoetic viscera, with the exception of those of the liver, and terminates in the vena portae, which subdivides and distributes the blood through the liver. The veins are far more numerous, and, considered as a whole, they are much more capacious than the arteries. The distribution of veins is somewhat similar to that of the arteries, but their number and size are greater. In general a cellular space, common to all, receives both the trunks of the two species of vessels and those of the nerves. In the head, limbs, and every other part, there are two sets of veins ; the superficial and the deep-seated ; the 1st lie immediately under the skin, or run above the fasciae, and are in some parts very large and numerous and do not possess any corresponding arteries. The 2d, or deep-seated veins, directly attend the arteries. The union between the branches of the veins is very frequent; they communicate in right lines or in arches, and the smaller are so multiplied as to form complicated meshes of net- work ; but the minute ramifications of veins ultimately form an inconceivable number of small canals in the tissue of organs, of such extreme tenuity, as to render it impos- sible to understand their final distribution. STRUCTURE OF VEINS. The veins are formed of only two membranes ; the outer is composed of longitudinal fibres, very easily distinguished in the large trunks, and surrounded by a sheath of cellular tissue, the layers of which are placed very densely on each other. The inner membrane is thin, smooth, and glossy ; OF THE VEINS. and in appearance resembles the membrane which lines the arterial tubes, but it is more extensible and less brittle. Valves are formed in the general department of the venous system ; but there are none in the system of the vena porta?, the umbilical vein, the trunk of the inferior cava, in the veins of the brain, of the vertebrae, of the spinal marrow, of the heart, of the kidneys and of the uterus.. There are but very few in the vena azygos, and pulmonary veins. These valves consist of a number of semilunar folds of the inner membrane of the vein, precisely similar to those which exist at the commencement of the aorta and the pulmonary artery. The valves are sometimes single ; they are, however, more frequently arranged in pairs, at other times there are three together. Apparently, their office is to support the column of blood, and to prevent its return by the veins from the heart to the surface of the body ; for the valves are pressed close to the sides of the vessels during its flow to- wards the heart, but they are raised when the blood, from any accidental circumstance, is disposed to pass in a retro- grade direction. Fig. 1 re- presents a vein laid open, thus showing the single, duplex, and triplex valvular appara- tus. The veins are. supplied by very minute nutrient ves- sels (vasa vasorum) and nerv- ous filaments, which ramify in the cellular membrane, and which, penetrating the venous tissue, finally terminate in the inner surface of the vessels. Veins may be distinguished from the arteries by their membranes being much thin- rig. 1. 4 VASCULAR SYSTEM ner, by their greater number and size, by their having no pulsation, by the dark color of the blood they contain, and in many instances by the peculiarity of their numerous valves. GENERAL DEPARTMENT OF THE VENOUS SYSTEM. I, VEINS WHICH, BY THEIR UNION, FORM THE EXTERNAL SUPERIOR VENA CAVA. 1. VEINS WHICH GIVE RISE TO THE EXTERNAL JUGULAR VEIN. The internal maxillary vein commences in all the parts to which the artery of the same name is distributed ; it is consequently composed of the pterygoid, spheno palatine, alveolar, infra-orhitar, mental, inferior dental, and deep OF THE VEINS. 5 temporal veins. It communicates with the sinuses of the base of the skull by means of small twigs which pass through the foramina of that region. Upon the side of the neck the internal maxillary vein frequently communi- cates with the facial and pharyngeal veins. This disposi- tion produces the pharyngeal plexus. The superficial temporal vein,g, commences in all those parts where the corresponding artery is distributed. It is composed of the middle temporal vein, f, the anterior auricular veins, and the transverse veins of the face. Thus formed it descends before the ear, and unites with the preceding. The vein which results from this union passes through the parotid gland, communicates with the internal jugular vein, and receives the following ; The posterior auricular vein, which collects the blood from the mastoid region and from the ear. The trunk then takes the name of The external jugular vein ; it extends from d to c, and is placed between the sterno-cleido-mastoideus and the platysma myoides muscles. In its course along the neck it receives the following : The cervical cutaneous, the trachelo-scapular, and other veins which arise in the vicinity of the neck and shoulder. At the inferior part of the neck the external jugular opens near c into b, the superior part of the subclavian vein, a little on the outer side of a, a, the internal jugular vein. 2. VEINS WHICH GIVE RISE TO THE INTERNAL JUGULAR VEIN. The superior cerebral veins commence upon the convex surface of the two hemispheres of the brain, from the substance of which they issue by a multitude of minute branches, and are continued into the superior longitudinal and lateral sinuses. 6 VASCULAR SYSTEM The vein of the corpus striatum is extended over the surface of that body, and, exactly following the course of the tenia semicircularis, unites with the following : The veins of the choroid plexus, which return the blood into the vence galeni, and from thence into the right sinus of the dura mater. The superior cerebellar veins convey the blood from the whole upper surface, and from the substance of the cerebellum, into the torcular herophili and the vena; GALENI. The inferior cerebellar veins unite on each side of the cerebellum, and return their blood into the corresponding lateral sinuses. The lateral and inferior cerebral veins are very numer- ous ; they unite on each side and leave the brain to open into the lateral sinuses. The ophthalmic vein commences from all parts within the orbit, and unites on each side into three or four trunks, so that this vein is formed of the lachrymal, the central vein of the retina, the infra-orbit ar, the ciliary, the ethmoidal, the palpebral, and the nasal veins. The oph- thalmic then passes out of the orbit, by the inner part of the sphenoidal fissure, and conveys the blood into the cavernous sinus. All the blood of the brain is returned into the sinuses of the dura mater, which terminate at the foramen lacerum posterius. This point is the commencement of the jugu- lar vein, and as it is here considerably dilated, it is named the sinus of the internal jugular vein. This vein advances a little forwards, and descends with the carotid artery, covered by the styloid process of the temporal bone, and by the muscles which are attached to it. It communicates at first with the external jugular vein, by a branch of large size, and at the level of the upper part of the larynx, it receives the facial vein. OF THE VEINS. 7 The facial vein, e, commences on the summit of the head and forehead, and when it has arrived at the side of the nose, near the eye, it has the name of the angular vein, and receives the blood from the ophthalmic, the palpebral, and the superciliary veins. It follows the direction we observe in the figure, receiving the dorsal veins of the nose, the superior and the inferior coronary veins of the lips, and several buccal and masseteric veins. It is afterwards augmented by the ranine, the submental, and the inferior palatine veins, and then becomes united to the internal jugular vein. A little below the facial vein, the internal jugular is aug- mented by the lingual and pharyngeal veins : and at the level with the superior edge of the larynx, it receives the superior thyroid, the occipital, and the veins of the diploe of the bones of the skull. After receiving the above branches, the internal jugular vein descends vertically at the side of the neck, and opens into the subclavian vein. 3. VEINS OF THE SUPERIOR EXTREMITY WHICH, BY UNITING, FORM THE SUBCLAVIAN VEINS, Fig. 3. The collateral arteries of the fingers, the radial and ulnar arteries, and all their divisions, are each accompanied by two venous branches, which become larger as they ascend toward the elbow joint, where they unite so as after- wards to constitute two large trunks, which run along the brachial artery and open into the axillary vein. They receive in their course all the veins which attend the divisions of the artery. The cephalic vein commences by a great number of branches, disposed in the form of a net work, on the back of the hand and upon the muscles of the thumb ; these unite into a trunk, which ascends upon the anterior and 8 VASCULAR SYSTEM external part of the fore-arm, where it forms the superficial radial vein, and on arriving at the bend of the arm unites with the median cephalic vein, which communicates with the median basilic. The united veins which form the trunk of the cephalic ascend on the outer and fore part of the arm, then bending inwards, open into the axillary vein. The basilic vein is larger than the cephalic, and is formed of three branches, which are named from their situation, the posterior ulnar, the anterior ulnar, and the median basilic veins. OF THE VEINS. 9 Fig- 3- The basilic vein as- cends on the inner part of the arm and unites frequently, as at e, with the cephalic vein. It then passes into the ax- illa, being continuous with the axillary vein. Fig. 3, b, the axillary vein. d, the cephalic vein. c, the basilic vein. f, the radial vein. g, the anterior ulnar vein. The axillary vein is therefore the result of the union of the veins of the hand, fore-arm, and arm ; it proceeds obliquely under the cla- vicle, and in front of the axillary artery, and be- comes continuous with a, the subclavian vein. See also, Fig. 4, t, the axillary, and /, the sub- clavian veins. In this course it re- ceives the circumflex veins, the inferior scapular, the long thoracic, the superior thoracic, and the acromial veins. VOL. II. 2 10 VASCULAR SYSTEM The subclavian veins, Fig. 4,/, u, extend from the infe- rior extremity of the scalenus anticus muscle to the supe- Fi». 4. rior vena cava ; but they present differences according as they are examined on the right or on the left side, on account of the position of, g, the superior vena cava. OF THE VEINS. \ \ Thus the right subclavian vein, /, is very short, and its size is always less than that of the left. The left subclavian vein, u, is much longer than the right, and receives two veins which the right does not receive ; viz. the left internal mammary and the left inferior thyroid. That part of the left subclavian vein nearest the descend- ing cava, which lies before the trachea, is generally known as the vena innominata. The two subclavian veins equally receive, besides the internal and the external jugular veins, the vertebral and the superior intercostal veins. The vertebral vein descends in the canal which contains the vertebral artery, and issuing from thence at the sixth or seventh cervical vertebra it unites with another consid- erable vein, which communicates with the lateral sinus of the dura mater by the mastoid foramen. After this union it receives numerous branches from the adjacent muscles, and opens into the subclavian vein. The right and left superior intercostal veins also dis- charge their blood into the subclavian veins. SUPERIOR VENA CAVA, g. The superior vena cava forms the grand trunk which transmits the blood of the head, the neck, the superior extremities, and a portion of the circulation of the thorax, to the heart. This vein commences opposite the cartilage of the first rib, and descends to the base of the pericardi- um, from which it receives a fibrous sheath. It then enters that membranous sac, descends vertically on the right of the aorta, and opens into the right auricle of the heart. Before entering the pericardium the superior vena cava receives the following branches : — 12 VASCULAR SYSTEM. Fig. 5. 1st. The right internal mammary vein, which differs from the left only in its termination. 2d. The inferior thyroid vein, opening into the superior vena cava, between the two subclavian veins. 3d. The vena azygos, Fig. 5, a, a, a, is remarkable for having no corresponding vein, and in forming a com- munication between the two venee cavse. It opens into the superior vena cava im- mediately above the right branches, and, passing through the pillars of the diaphragm, with the aorta and thoracic duct, opens into the inferior vena cava, or into one of the lumbar veins. 4th. The vena azygos at the convexity of its curve receives the right bronchial vein, and anteriorly branches from the aorta and oesopha- gus. To the right it receives the corresponding intercos- tal veins. To the left, to- wards the seventh rib, the vena semi-azygos, a consid- erable branch which ascends parallel to the vena azygos, on the left side of the vertebrae, and which receives the in- ferior intercostal veins of the left side. OF THE VEINS. 13 II. VEINS WHICH, BY THEIR UNION, FORM THE INFERIOR VENA CAVA. 1. VEINS WHICH, BY THEIR UNION, FORM THE EXTERNAL ILIAC VEINS. The popliteal vein commences by three veins which accompany the anterior, posterior, and fibular arteries ; the external saphena vein also contributes to its formation, by collecting the blood upon the front and outer side of the foot, and passing into the ham, opens into the popliteal vein. The femoral or crural vein is a continuation of the pop- liteal vein ', it ascends obliquely at the inner and fore part of the thigh, close to the femoral artery, following the same course up to the crural arch. In its progress it re- ceives a great number of deep branches, precisely similar to those of the artery, and the following remarkable super- ficial branch : 14 VASCULAR SYSTEM. The internal vena F;s- 6- saphena, Fig. 6, col- lects the blood from the inner part of, a, the foot and toes ; it is united to the external saphena by a transverse arch ; these united branch- es ascend before the inner ankle, and form a trunk which is continued on the inner part of the leg, and passing be- hind the inner con- dyle of the femur, it proceeds on the inside of the thigh to an opening in the fascia lata, b, where it discharges itself into, c, the femoral vein. At this part it receives several superficial abdomi- nal veins, the cir- cumflex iliac vein, and the external pudic veins. The external il- iac vein receives branches corres- ponding to the artery of the same name, and in the male it receives a large vein which originates in the envelope of the testicle. OF THE VEINS. 15 2. THE VEINS WHICH, BY THEIR UNION, FORM THE INTERNAL ILIAC VEIN. The internal iliac vein, Fig. 4, s, s, is situated in the cavity of the pelvis, behind the artery of the same name ; its branches correspond exactly to those of the artery, with the exception of the following : The vesical veins are large and very numerous, but differ according to the sex of the subject we examine. In the male they commence upon the glands and unite into two trunks, the dorsal veins of the penis, which run upon the back of that organ, and afterwards wind down- wards upon the organs of generation, and continuing their course on the sides of the bladder, and over the prostate gland, open into the internal iliac vein. In the female the vesical veins commence by the veins of the clitoris and the labia, and unite with the numerous vessels of the vagina and rectum. The sacro-lateral veins communicate in the sacral canal with the vertebral sinuses, and, emerging from the anterior sacral foramina, join the internal iliac vein. COMMON ILIAC VEINS. The common iliac veins result from the union of the ex- ternal and internal veins ; they extend from the sacro-iliac symphysis to the fifth lumbar vertebra, where they give rise to the inferior vena cava. INFEKIOR VENA CAVA. Fig. 4, U, T. The inferior vena cava is larger than the superior, and extends from the articulation of the fourth and fifth lumbar 16 VASCULAR SYSTEM vertebras to the right auricle of the heart. It ascends on the right side of the bodies of the lumbar vertebras, passes above and behind the liver, and, advancing through a wide aperture of the aponeurosis of the diaphragm, in- troduces itself into the pericardium, and enters the right auricle of the heart by an aperture which is bounded by the Eustachian valve. BRANCHES OF THE INFERIOR VENA CAVA. The middle sacral vein ascends upon the coccyx and sacrum, in the angle formed by the union of the common iliac veins. The lumbar veins are four in number on each side, and commence by an abdominal branch, and a dorsal branch, corresponding to the branches of the lumbar arteries ; the dorsal communicates by the intervertebral foramina, with the vertebral sinuses. The lumbar veins of the left side pass under the aorta, and are in consequence longer than the right. The spermatic veins, see Fig. 4, r, differ in their origin in the two sexes. In the male they commence by the spermatic plexus, the roots of which are expanded in the testicle, they anastomose with the neighbouring veins, and collect into four or five branches, which envelope the vas deferens, and, passing through the inguinal ring, unite and form a single trunk, which extends upwards and inwards on the psoas muscle, as far as the upper part of the pelvis, where the spermatic vein forms another plexus, named the corpus pampiniforme : these veins again unite and convey their blood into the inferior vena cava on the right side, and into the corresponding renal vein on the left side. In the female, the spermatic veins originate in the ovari- OF THE VEINS. 17 ura, Fallopian tube, ligamentum teres, and sides of the uterus ; they afterwards collect between the laminae of the broad ligament of the uterus, and then follow the same course as in the male. The renal veins, see Fig. A, o, o, are of great size. Their roots exactly correspond to the minute ramifications of the renal arteries. They unite in the fissure of p, p, the kid- neys, into several branches, which collect into a trunk opening into the cava. The capsular and adipose veins frequently open into the renal veins, and in other respects have the same disposition as the arteries to which they correspond. The hepatic veins have their roots in the substance of the liver : some of them are of small size and enter the vena cava separately ; others, namely, the middle hepatic veins, open into the vena cava between the right and left hepatic veins. The middle hepatic veins open into the vena cava between the right and left hepatic veins. The left hepatic veins ramify in the left lobe of the liver, and proceed from thence into the vena cava, opposite the aperture of the diaphragm, through which it passes. The right hepatic veins issue from the right lobe of the liver, and open into the vena cava below the preceding. The inferior diaphragmatic veins are two in number, and are similar to the arteries of the same name. VERTEBRAL SINUSES AND VEINS OF THE SPINAL MARROW. There exist in the whole length of the vertebral cavity two great venous canals, named the vertebral sinuses, and which communicate with the internal jugular vein. These sinuses have the same structure as the sinuses of the dura mater, in being traversed in various directions by irregularly distributed membranous bridles. VOL. II. 3 18 VASCULAR SYSTEM At their inner side, they communicate with each other by transverse sinuses, occupying the middle of the body of each vertebra, then passing under the posterior vertebral ligament, they receive the veins which transmit the blood from the envelopes of the spinal marrow, and the spongy tissue of the vertebrae. The veins of the spinal marrow accompany the arteries of that name, and open into the inferior cerebellar veins. The veins of the sacral canal are of considerable size ; they are immersed in cellular tissue, and have no adhesion to the osseous parts. Their inferior extremities are lost in very delicate ramifications upon the os coccygis. Exter- nally, they form communications with the lateral sacral veins ; and, internally, their transverse branches anasto- mose with each other. VEINS Or THE HEART. CORONARY VEINS. The great right coronary vein collects the blood from the apex of the heart, passes into the groove which sepa- rates the auricles from the ventricles, and receives a great number of lateral branches which terminate in the right auricle, close by the entrance of the inferior vena cava, where the coronary is covered by a semilunar valve. The small right coronary vein unites with the preceding, and passes in the same direction to the posterior surface of the heart. The left coronary veins are smaller than the right. They commence, with the preceding, at the apex of the heart, by numerous roots, which unite, upon the convex surface of that organ, into a single trunk, which discharges its blood with the other veins at the posterior part of the right auricle. OF THE VEINS. 19 There are a number of veins which terminate directly in the cavity of the right side of the heart, by minute orifices, which have been termed, by their original describer, the foramina thebesii. ABDOMINAL DEPARTMENT OF THE VENOUS SYSTEM. VENA P0RT.32. BRANCHES OF THE VENA PORT.E. The vena portce derives its blood from all the organs of digestion in the cavity of the abdomen, excepting the liver. It is formed principally by three large trunks, the coronary vein of the stomach, the splenic and the mesenteric veins, all which unite to form the middle part or trunk of the vena portae. The coronary vein of the stomach corresponds to the artery of the same name. It is the smallest of the three branches. It empties into the trunk of the vena porta?, behind the pyloric portion of the stomach. The splenic vein collects the blood from the spleen by a number of branches, which, after a short course, unite upon the pancreas into a single trunk, which extends from left to right to unite with the superior mesenteric vein, op- posite the vertebral column. It likewise receives the veins which correspond to the vasa breviora, the right and left gastro-epiploic, the duodenal, and the pancreatic veins, and the small mesenteric vein. The last-named vein receives the blood from the left part of the colon and the rectum. Its branches correspond to those of the inferior mesenteric artery. The superior mesenteric vein is distributed in the same manner as that of the artery of the same name, to the right, and a little in front, of which it is placed. It is 20 VASCULAR SYSTEM formed by the veins of the small intestines, and by those which correspond to the right colic arteries ; and in the mesentery it constitutes a net-work, very similar to the ramifications of the artery. At the edge of the transverse mesocolon, the trunk of this vein, after receiving several branches from the duodenum and pancreas, unites with the splenic vein. The trunk of the vena porta, is formed by the junction of the splenic and superior mesenteric veins with the coro- nary vein of the stomach ; it extends from the vertebral column to the groove of the liver, and separating into two branches, nearly at a right angle, seems to form under the liver a horizontal canal, which has been termed the sinus of the vfina porta. These vessels are extended through the lobes of the liver in innumerable ramifications. In its pas- sage under the small extremity of the pancreas, it is united to the cystic and hepatic ducts, the hepatic artery, and a number of nervous filaments and lymphatic vessels ; all which are surrounded by a fibrous envelope named the capsule of glisson. Injections thrown into the vena portas penetrate into the other vessels of the liver, and vice versa. OF THE VEINS. 21 CHAP. III. OF THE CAPILLARIES. The delicate branches of the final ramifications of the arteries and of the minute origins of the veins, are called the capillaries. In these small vessels most of the im- portant functions of life take place, as secretion, nutrition, exhalation, calorification, &cc. They are of such extreme tenuity that they escape detection by the naked eye. Their existence may be demonstrated not only by micro- scopical observation as observed in the last chapter, but by the fact, that a colored fluid may be thrown from the arteries into the veins, without any extravasation between them. There are two parts in the capillary system. One is diffused over the whole body, being placed between the terminating branches of the arteries and the roots of the veins, the other part is between the minute ramifications of the pulmonary arteries and the origins of the pulmonary veins. In the first, the arterial blood is changed to venous ; in the last, the reverse. Their intimate organization is unknown. Though these capillaries exist everywhere in the body, still they are more or less numerous in the various organs. They are more abundant in the secretory organs, the skin, the mucous membranes, and the lungs, and less so in the fibrous structures ; in short, the capillary system is as much more developed in a part, says Bichat, as it has more func- tions to sustain, and do not exist in organs in proportion to their size. ART. VI. CHAP. I. ORGANS OF ABSORPTION. The organs of absorption consist of lymphatic vessels and lymphatic glands ; the latter also are named lymphatic ganglia. This system of vessels was perfectly unknown until a celebrated anatomist of the name of Asellius. in the year 1622, discovered, upon the mesentery of a dog, white lines extending from the intestine to the glands. He observed that they contained a milk-like fluid, and hence termed them lacteals. By a series of experiments he found that these vessels absorbed the chyle, and conveyed it to the blood; and subsequent inquiries proved that the same system of vessels was minutely distributed over the whole human frame ; and that, at the angle formed by the union of the subclavian with the internal jugular vein, upon either side of the neck, one or more of these vessels discharges their contents into the current of blood. The lymphatic vessels are small pellucid tubes which occur in all parts of the body; they originate on the sur- face of the membranes, and in the tissue of all the organ- ized structures ; and they transport all the absorbed fluids to the venous system. Those absorbents which take up LYMPHATIC SYSTEM. 23 the chyle in the intestines, during the process of digestion, are named lacteals ; and, although they differ in their uses from the other absorbent vessels, they have precisely the same anatomical character. The ultimate arrangement of the lymphatic vessels has not been demonstrated, but the whole exterior of the body is known to be covered by a net-work of these vessels, placed in the subjacent cellular tissue, and others occupy the muscular intervals and organs of the body ; nor is this system of vessels confined to the limbs only, for it exists in the surface and substance of each particular organ, as in the lungs, liver, spleen, pancreas, and other viscera, where both superficial and deep-seated lymphatics are uniformly distributed. Generally these vessels are straight in their course ; but their communications with each other are very numerous, and they frequently form successive meshes. They are also remarkable for their alternate unions and divisions, so that a great number of vessels, after being collected into a single trunk, separate a second time, and again form one or more trunks, which appear most conspicuous in the vicinity of their glands. THORACIC DUCT. All the absorbent vessels discharge themselves into the subclavian and internal jugular veins, by considerable trunks, called the thoracic duct, and great right lymphatic duct. These convey the absorbed fluids into the circula- tion. See Fig. 5, d, the left, and /, the right thoracic ducts. 24 LYMPHATIC SYSTEM. STRUCTURE OF THE LYMPHATIC VESSELS. The lymphatic vessels are formed of an external cellular membrane, and an internal membrane similar to that of the veins ; the latter is folded upon itself, producing valves at intervals, which are generally disposed in pairs. These valves are usually more numerous as the vessels diminish in caliber. So that the thoracic canal contains fewer than the others. LYMPHATIC GLANDS IN GENERAL. The branches of the principal lymphatic trunks traverse a greater or less number of lymphatic glands } that is to say, small bodies of various forms and size, and collected together in greater or less quantity, or sometimes isolated. These glands are not numerous in the extremities, but they occur abundantly in the thorax and abdomen. Each gland receives lymphatic vessels, which subdivide and form an inextricable interlacement, which is lost in its substance, without our being able to trace its distribution, or display the minute structure. These glands vary in diameter from the twentieth of an inch to an inch. They are in gen- eral red and vascular ; some, however, are of a gray or blackish color. These bodies have been denominated also lymphatic ganglions, because some anatomists have sup- posed, that they bear the same relation to their vessels, as the nervous ganglions do to the nerves. The absorbents which enter the glands are called vasa inferentia, and those which pass out of them, are termed vasa efferentia. LYMPHATIC SYSTEM. Fig. 7. Fig. 8. Fig. 9. 25 Fig. 7, a lymphatic vessel. Fig. 8, a lymphatic vessel laid open, showing its valves. Fig. 9, lymphatic vessels and their glands. LYMPHATIC GLANDS IN PARTICULAR. LYMPHATIC GLANDS OF THE INFERIOR EXTREMITIES. The anterior tibial gland is the only gland in the leg. It is found between the tibia and fibula, on the lower ex- tremity of the inter-osseous ligament. The popliteal glands are three or four in number, and are situated in the ham. The inguinal glands are situated on the upper part of the thigh, and in the groin ; the superficial are found between the skin and aponeurosis, surrounding the termi- nation of the internal saphena vein ; their number varies from eight to twelve, and they are sometimes observed VOL. II. 4 26 LYMPHATIC SYSTEM. to form a chain of glands, extending from the middle and inner part of the thigh to the groin. There are three or four deep-seated inguinal glands, situated under the aponeurosis, and about the femoral arterv. LYMPHATIC GLANDS OF THE PELVIS. The hypogastric glands, ten or fifteen in number, are situated in the lateral parts of the cavity of the pelvis, and about the internal iliac vessels. On the outside of the pelvis, very small lymphatic glands are met with in the course of the gluteal and ischiatic arteries ; and in the interior of the pelvis, a number of minute glands are found upon the bladder, the uterus, and the vesiculae seminales. The sacral glands are situated in the hollow of the sacrum, between the laminae of the meso-rectum. The external iliac glands vary in number from six to fifteen ; they are situated in the course of the external iliac vessels, and form a chain of glands extending from the crural arch to the lower part of the vertebral column. LYMPHATIC GLANDS OF THE ABDOMEN. The lumbar glands are large and numerous; they occupy the region of the loins, and surround the aorta and the inferior vena cava ; they are also situated upon the crura of the diaphragm, and are thickly arranged over the renal arteries. These glands furnish vessels which immediately communicate with the thoracic duct. The hepatic, pancreatic, and splenic glands are situated round the vena porta? and along the splenic artery ; they LYMPHATIC SYSTEM. 27 receive the lymphatic vessels of the liver, aorta, and pan- creas. The mesenteric glands are numerous, sometimes exceed- ing a hundred, and are in general of considerable size ; they are situated between the two laminae of the mesen- tery, and receive the lacteals or absorbents of the chyle. See Fig. 11, c, d. The mesocolic glands are fewer than the preceding, and are placed between the laminae of the mesocolon. The gastro-epiploic glands occupy the greater and smaller curvature of the stomach ; they surround the gastro- epiploic arteries, and the coronary artery of the stomach. LYMPHATIC GLANDS OF THE THORAX. The glands of the mediastinum. Upon the diaphragm and pericardium there are six or eight of these bodies ; and there are twelve or sixteen surrounding the thymus gland, and large vessels of the base of the heart. The bronchial glands are very numerous ; they are situated before the division of the trachea, around the bronchi, and even in the interior of the lungs ; but they will be more particularly noticed in the description of the trachea and bronchi. LYMPHATIC GLANDS OF THE SUPERIOR EXTREMITY. The glands of the arm are distributed in the line of the brachial artery ; they are not often met with in the fore- arm, although, not unfrequently, we find a kxv at the bend of the arm near the inner condyle. The axillary glands are situated in the cellular tissue of the armpit, around the axillary vessels and their 28 LYMPHATIC SYSTEM. branches; they are of large size, and vary from six to twelve in number. Some are met with under the collar bone and between the ribs. LYMPHATIC GLANDS OF THE HEAD AND NECK. The glands of the skull are few in number ; several small glands are found behind the ear, and two or three are also observed under the zygomatic arch. No lymphatic glands have been traced in the interior of the skull. The glands of the face are situated upon the buccinator muscle, and along the base of the jaw, where they sur- round the anterior portion of the digastric muscle. The glands of the neck are superficial and deep-seated ; the former are situated beneath the platysma myoides, in the course of the external jugular vein and its branches. The others, called glandules concatenates, occur in the vicinity of the internal jugular vein and common carotid artery. Their size is small, but their number is very great. In children they frequently present a kind of knotty cord, extending from behind the ear to the collar bone. LYMPHATIC SYSTEM. 29 CHAP. II. PARTICULAR LYMPHATIC VESSELS. LYMPHATIC VESSELS WHICH TERMINATE IN THE THORACIC DUCT. 1. LYMPHATICS OF THE INFERfOR EXTREMITY. The superficial lymphatics of the lower extremities con- sist of very numerous vessels, which are found in the cellular tissue, between the skin and muscles. Their com- mencement can be traced with little difficulty in the toes, round which they form a very delicate plexus, and form by their successive union from sixteen to twenty branches, which cover the surface of the foot and pass up the inner side of the leg ; those of the side of the foot collect and form two or three branches, which ascend around the ten do Achillis. Thus united, the principal trunks of the lymphatics of the leg pass over the calf, and the ham, and ascend upon the inner and outer side of the thigh, approaching each other and continually communicating, until, at length, they terminate in the superficial inguinal glands. 30 LYMPHATIC SYSTEM. Fig. 10, the lymphatic vessels of the inner part of the thigh. All these vessels are immersed in the subcu- taneous cellular tissue ; and their communica- tions are so frequent and numerous, that they form, upon the foot, leg, and thigh, a net-work which completely sur- rounds these parts. The deep lymphatic vessels of the lower ex- tremities may be distin- guished into four series : namely, the anterior tibial, the posterior tibi- al, and the fibular lym- phatics, according as they accompany the an- terior and posterior tib- ial and fibular arteries. They terminate in the popliteal glands. In- deed most of the deep- seated lymphatics of the leg and foot have the same termination. These glands are con- nected together by a great number of smaller vessels which form a plexus, whence issue several trunks which ascend upon the popliteal and femoral vessels, receiving all the deep lymphatics of the thigh, and subdividing up to, a, the deep inguinal glands. LYMPHATIC SYSTEM. 31 2. SUPERFICIAL LYMPHATIC VESSELS OF THE HIPS, PERINEUM, LOINS, EXTERNAL PARTS OF GENERATION, ETC. The lymphatics of the hips are numerous, and pass over the outer and inner part of the thigh, to unite with the superficial absorbents of the perinseum, and inguinal glands. The lymphatics of the loins descend from the lumbar vertebras over the crest of the ilium, and divide in the superficial inguinal glands. The lymphatics of the lower part of the parietes of the abdomen commence on the level of the umbilicus, and form a net-work over the whole anterior region of the abdomen; they collect inferiorly into a few trunks which terminate in the superficial glands. The lymphatics of the perinceum, scrotum, and penis, are very numerous ; those of the scrotum ascend on each side to the inner part of the thigh, where they unite with those of the perinseum and penis : they all terminate in the superficial glands. In the female, the lymphatics of the external parts of the organs of generation have the same termination. 3. DEEP-SEATED OBTURATOR, ISCHIATIC, AND GENITAL LYMPHATIC VESSELS. The obturator lymphatics are distributed over the adduc- tor muscles and neighbouring parts, and take the direction of the obturator artery, through the obturator foramen, to terminate in the hypogastric glands. The ischiatic lymphatics are distributed to the muscles of the pelvis, and terminate in the same glands as the former. The glutccal lymphatics have the same distribution as the 32 LYMPHATIC SYSTEM. glutaeal artery, and, passing into the pelvis, terminate in the same glands as the preceding. The deep lymphatics of the penis and clitoris follow the course of the internal pudic artery, and terminate in the same glands. The lymphatics of the testicle are numerous, and are among the largest of the body ; some of them are the size of a crow-quill : they unite upon the spermatic cord into six or eight branches, and ascend with it towards the in- guinal ring, through which they pass to follow the sper- matic artery, and terminate in the lumbar glands. The lymphatics of the prostate gland and vesiculce semi- nales unite with those of the bladder, and enter into the hypogastric gands. The lymphatics of the uterus unite with those which are distributed to the vagina, to terminate in the same glands. Those which are found upon the broad ligament and ova- rium ascend with the spermatic lymphatics to the lumbar glands. 4. LYMPHATIC VESSELS OP THE URINARY ORGANS. The lymphatics of the bladder follow the course of its blood vessels, and open into the hypogastric glands. The lymphatics of the kidneys unite towards their fissure, and then proceed upon the sides of the aorta to the lumbar glands. The ureters also are furnished with numerous absorbents, which surround those tubes, and communicate freely with each other, and with the last-named glands. The capsular lymphatics proceed to the hepatic and splenic glands, and several pass to the glands upon the pillar of the diaphragm. LYMPHATIC SYSTEM. 33 5. LYMPHATIC VESSELS OP THE PARIETES OP THE PELVIS AND ABDOMEN. The ileo-lumbar lymphatics are a set of absorbents which originate in the iliacus muscle, and upon the hip bone ; they pass under the psoas muscle, and communicating with the inferior lumbar glands, contribute to the formation of the external iliac lymphatic plexus, or the assemblage of lymphatics which accompany the external iliac vessels. The sacral lymphatics are extended over the adipose tissue of the rectum, and region of the sacrum ; they terminate in the inferior lumbar or hypogastric glands. Those lymphatics, which contribute to form the hypogastric plexus, are placed on the sides of the pelvis, and consist of an interlacement of vessels and glands, in which the obtu- rator, glutseal, ischiatic, uterine, and vesical lymphatics terminate. The epigastric lymphatics commence in the vicinity of the umbilicus, and proceed from the interior, through the abdominal muscles and their aponeuroses ; then unite into several trunks, which descend in the course of the epigastric vessels, and terminate in the external iliac plexus. The circumflex iliac lymphatics are distributed in the integuments of the sides of the abdomen, and descend towards the crest of the ilium, to one of the external iliac glands. The lumbar lymphatics are distributed to the muscles of the lumbar region ; but they unite before the vertebral column, where their numerous communications, with those of almost all the other trunks, which have just been describ- ed, constitute the lumbar lymphatic plexus. VOL. 11. 5 34 LYMPHATIC SYSTEM. 6. LYMPHATtC VESSELS OF THE STOMACH AND INTESTINES. The lymphatics of the stomach are distributed into two distinct orders ; the superficial, which are situated beneath the peritoneal, and the deep, which are distributed to the muscular and mucous membranes. Some of these com- mence at the large extremity of the stomach, and join the lymphatics of the spleen ; others proceed from the small curvature of the stomach, and communicate with the glands in that situation, and in the vicinity of the liver. After this, they descend behind the pancreas to the roots of the thoracic duct. Although in some animals these vessels have been found to contain chyle, in the human subject they have never been observed to be filled with it. The lymphatics of the intestines are usually called the lacteals, on account of their conveying a fluid like milk from the intestines to the thoracic duct. Each lacteal takes its origin from the villi of the intestines, by numer- ous short radiated branches, and each branch is furnished with an orifice for imbibing the chyle. From the villi, the lacteals pass under the muscular membrane of the intestines, and then obliquely through it, uniting in their course into larger branches, following the course of the mesenteric blood vessels. They are found situated on each side of the arteries. It is observed that there are a much greater number of lymphatics in the small intestines than in the larger ; the descending colon and rectum present but few absorbents, and these are connected with the lumbar and hypogastric glands, or those of the mesorectum. The lacteals of the small intestines, after passing through the different glands of the mesentery, form several trunks, LVMPHATIC SYSTEM. 35 which accompany the superior mesenteric artery, until they arrive at the thoracic duct. Fie. 11. Fig. 11, a, a, part of the small intestine ; b, b, lacteals; c, the mesentery ; d, the mesenteric glands. The lymphatics of the great omentum ascend to unite with the lymphatics of the stomach, and terminate in the glands of the great curvature. 36 LYMPHATIC SYSTEM. 7. LYMPHATIC VESSELS OF THE SPLEEN, PANCREAS, AND LIVER. The lymphatics of the spleen are very numerous ; the superficial and deep branches, uniting at its fissure into a few trunks, form a plexus round the splenic vessels, and pass beneath the duodenal extremity of the pancreas, to the inferior lymphatics of the liver. The lymphatics of the pancreas proceed from the sub- stance of that gland, and unite with the lymphatics of the spleen and stomach. The lymphatics of the liver are extremely numerous, nor does any organ in the body appear to contain so many j and, like those of the other viscera, it has a superficial and a deep-seated series, which, however, so freely communi- cate, that, upon injecting the external lymphatics, the deep internal are readily filled from them. On the right lobe they collect into four fasciculi ; the first is formed by the lymphatic vessels, which commence between the laminae of the suspensory ligament, and, uniting into two or three trunks, enter the thorax near the ensiform cartilage, traverse some of the glands, and open into the thoracic duct near the left internal jugular vein. The second traverses the right lateral ligament of the liver, and divides into two series ; the one superior, which mounts into the thorax, and afterwards returns into the abdomen with the aorta, to terminate in the neighbouring glands ; the other inferior, which extends along the last ribs, and unites with the intercostal lymphatics, to open into the thoracic duct. The third fasciculus is distributed to the middle of the right lobe, and unites with the preceding at the posterior part of the liver. The fourth fasciculus commences in the anterior part of the right lobe, and unites with the deep series, and with some glands near the pylorus. In the left lobe of the liver, the lymphatics unite with LYMPHATIC SYSTEM. 37 the preceding and to those of the spleen ; those from the posterior part of the left lobe descend towards the cardia, and proceed to the glands of the small curvature of the stomach. 8. THE THORACIC DUCT. See Fig. 11. The thoracic duct, f, is the canal which receives the lymphatics from the lower half of the body, the interior of the chest, the left upper extremity, and the left side of the head and neck. It extends from the second or third lumbar vertebra as far as the left subclavian vein, and is formed by the union of, g, five or six large trunks, the result of the absorbent plexus of the abdomen. Near the aortic aperture of the diaphragm, the thoracic duct presents a very remarkable enlargement, e, the receptaculum chyli, which is placed at the anterior and left part of the second lumbar vertebra, behind, h, the aorta. Above this dilata- tion, the thoracic duct ascends into the chest, entering between the pillars of the diaphragm, with the aorta on the left side, and the vena azygos to the right. It then ascends behind the arch of the aorta, and arrives at the seventh cervical vertebra, turns inwards and downwards, then passes the thyroid artery, and the left internal jugular vein, and opens close to the latter into the subclavian vein of the same side. At its aperture there are two valves which prevent the blood from passing from the vein into the duct. Although the lymphatics have hitherto been described by anatomists as collecting into trunks to transmit their contents into the subclavians only ; Magendie * and a few other celebrated physiologists and experimentalists * Magendie, in his Physiology, relates some very curious and striking experiments, which, if confirmed by others, must set the question at rest. 38 LYMPHATIC SYSTEM. are of opinion, that many other communications, between the lymphatics and veins, take place in the extremities and other parts of the body. Professor Mayo seems to have arrived at the same conclusion ; I give his own words. " For my own part, I think it likely, that such communications do exist. At all events, when believing that they did not, I have witnessed the mercury thrown into the absorbents of the limbs unaccountably make its way into the veins." * 9. LYMPHATIC VESSELS WHICH THE THORACIC DUCT DIRECTLY RECEIVES. Several branches of lymphatics from the liver, and the glands surrounding the ceeliac artery, have been already described. The intercostal lymphatics are distributed to the mus- cles of the thorax and the intercostals ; they communi- cate with some glands found between the external and internal intercostal planes of the muscles. On the sides of the vertebrae, these vessels unite with others which pro- ceed from the spinal canal and the muscles of the back, then spread out into a plexus before the vertebral col- umn. From thence they descend and open into the thoracic duct. 10. LYMPHATIC VESSELS OP THE LUNGS. The lymphatics of the lungs are distributed upon their surface in a series of areolas of various forms, more com- monly hexagonal, and unite into a number of trunks which * Outlines of Human Physiology, by Herbert Mayo, Professor ofAnat. King's College, London. LYMPHATIC SYSTEM. 39 enter the glands, with which the bronchus is surrounded at its entrance into that organ. The deep lymphatics occupy the whole tissue of the lungs, communicate with the superficial, unite into the bronchial glands, and ascend upon the trachea. From a large bronchial gland, which is found in the angle formed by the division of the trachea, there issue several lymphatic branches, which ascend upon the tra- chea, and, traversing some glands, unite and open into the right great lymphatic vessel. Others traverse glands upon the trachea, under the thyroid gland, and collect into two trunks, which incline obliquely to the left, behind the inter- nal jugular vein, to discharge themselves into the thoracic duct. 11. SUBSTERNAL, DIAPHRAGMATIC, CARDIAC, THYMIC, AND OESOPHA- GEAL LYMPHATIC VESSELS. The substernal lymphatics commence from the upper part of the parietes of the abdomen ; they enter the thorax between the ensiform cartilage and the diaphragm, ascend behind the sternum, traverse some glands, and form some meshes, which unite into trunks, one of which communi- cates with the inferior jugular glands, and terminates in the thoracic duct. The others open on the right side into the subclavian and internal jugular veins. The lymphatics of the diaphragm are distributed on its convex surface, and unite with the intercostal and hepatic lymphatics, then proceed through the inferior glands of the mediastinum, and join the preceding behind the sternum. The lymphatics of the pericardium and thymus are a numerous set of reticulated vessels, which are intimately connected with the substernal and pulmonary lympha- tics. 40 LYMPHATIC SYSTEM. The lymphatics of the heart are distributed to the whole surface ; the principal trunks following the course of the coronary vessels. Some of these trunks ascend upon the anterior part of the aorta, and terminate in the thoracic duct ; others pass obliquely between the aorta and pul- monary artery, traverse some small glands, and arrive at the thoracic duct. The lymphatics of the oesophagus are reticulated around that tube ; they unite with those of the heart and lungs, and terminate in the predorsal ganglia. 12. LYMPHATIC VESSELS OF THE SUPERIOR EXTREMITIES. The superficial lymphatics of the upper extremities col- lect into fasciculi on the sides of the fingers, and proceed over the metacarpus to the posterior surface of the fore- arm, where their numbers are greatly increased by the addition of small vessels from that part of the extremity. Near the elbow joint the lymphatics are very distinct; and, upon the anterior surface of the fore-arm, they unite with others, which arrive from the fingers and palm of the hand. They then ascend on the fore and inner part of the arm, and, becoming large and numerous, terminate in the axillary and subclavian glands. Some of the brachial lymphatics pursue the course of the cephalic vein, and unite with some reticulated vessels and glands under the clavicle. The deep lymphatics of the upper extremities constantly accompany the arteries which are distributed to these parts, and terminate in the axillary glands. LYMPHATIC SYSTEM. 41 13. LYMPHATIC VESSELS OF THE ANTERIOR PARIETES OF THE THORAX. The lymphatics of the anterior part of the thorax com- mence immediately under the integuments, and, proceed- ing upwards and outwards, terminate in the glands of the axilla. Some of these vessels originate more deeply in the substance of the pectoralis major, pectoralis minor, and ser- ratus magnus muscles, but they have the same terminal tion, 14. LYMPHATIC VESSELS OF THE POSTERIOR REGION OF THE NECK AND THORAX. The lymphatics of the neck commence in the cellular tissue, towards the occiput, and upon the spinous processes of the neck; they descend outwardly in the direction of the fibres of the trapezius, and unite with the anterior thoracic, and dorsal lymphatics in the axilla. The lymphatics of the back commence in the integu- ments, and are extended to the whole of the muscles of the back ; like the preceding, they terminate in the axilla. 15. LYMPHATIC VESSELS OF THE AXILLA. The axillary lymphatics are remarkably reticulated, in consequence of their connexion with a great number of glands, and with the vessels which terminate in them, or issue from them. The latter concentrate into three or four trunks, which proceed round the subclavian vein, and open into it, and into the thoracic duct. Those on the right VOL. II. 6 42 LYMPHATIC SYSTEM. side generally furnish a trunk, which transmits its fluid to the angle formed by the right internal jugular and sub- clavian veins ; and is named the right great lymphatic duct. See Fig. 5,f. 16. LYMPHATIC VESSELS OF THE HEAD AND ANTERIOR PART OF THE NECK. The epicranial lymphatics are arranged on all sides be- neath the skin of the cranium, and may be distinguished into three orders of fasciculi. The occipital, the temporal, and the frontal ; all which proceed to the glands of the neck. The lymphatics of the face follow the direction of the principal veins, and proceed to the submaxillary glands. The superficial lymphatics of the neck form a plexus, which accompanies the subcutaneous veins of the neck ; they open into the right great lymphatic vessel, and the thoracic duct. 17. DEEP LYMPHATIC VESSELS OF THE HEAD AND NECK. The lymphatics of the brain. Although the most minute researches have been made in those parts, there have been discovered a few lymphatics only in the dura mater. The deep lymphatics of the tongue, palate, nose, orbits, pharynx, muscles of the face, etc. These absorbents accompany the blood-vessels, and terminate in the right and left great thoracic ducts. LYMPHATIC SYSTEM. 43 THE OFFICE OF LYMPHATIC VESSELS AND THEIR GLANDS. The most important office of the lymphatic system is to collect the chyle for the supply of the waste of the body, during the exercise of its several functions. The lymphatics, therefore, take in the fluids, it is supposed, by capillary attraction, and afterwards, by a contractile power, inherent in the vessels, conduct their contents into the mass of the blood. The absorbents also have the power of removing the solid parts of the body, and by thus making way for the disposition of new matter, contribute to the growth and renovation of the animal fabric. By means of these vessels, on the one hand, many con- tagious diseases are communicated ; and, on the other hand, diseases are removed : thus, when lymph is formed, or pus collected, or blood effused in the tissue of organs, the lymphatics have the power of taking away the extra- neous or diseased matter. And even solid tumors often are known to disappear entirely by the action of this sys- tem of vessels. The obvious use of the absorbent vessels is to convey the lymph and the chyle into the venous sys- tem ; the former, the residue of nutrition, and the latter, the product of digestion. I cannot dismiss this subject without informing the un- initiated student, that there is much difficulty in exhibiting the lymphatics. They must be injected with quicksilver, and, owing to the minuteness and delicacy of the vessels, it requires the most acute sight of the anatomist to distin- guish, and to introduce an instrument into the smaller branches. Caution and patience, however, will surmount this difficulty ; and nothing will more repay the trouble, or reflect more credit on the skill of a practical anatomist, than a good preparation of the lacteals, or other lymphatics. ART. VII. CHAP. I. NERVOUS SYSTEM. The nervous system is destined to regulate the functions of the animal economy, and to receive impressions of external objects, and transmit them to the understanding. The nervous system consists of, 1st, the brain ; 2d, the medulla oblongata ; 3d, the spinal marrow ; 4th, the nerves ; 5th, the ganglia. GENERAL DIVISIONS OF THE NERVOUS SYSTEM. There are two general departments, essentially distinct from each other, to which the nervous system may be referred; the 1st department consists of the brain and its dependencies, the 2d, of the ganglia and their nervous radiations. The first department appertains particularly to animal life ; on the one hand it is the agent which transmits impressions calculated to produce sensations ; on the other hand it serves to convey the volitions to those organs which receive them. The second department is almost invariably distributed to the organs of digestion, NERVOUS SYSTEM. 45 of circulation, respiration, and the secretions, and belongs in a more particular manner to the internal organs, where it acts a more obscure part than the preceding. The two departments frequently communicate with each other, but there is a sufficiently distinctive line to establish their dif- ference ; as a simple exposition of each will sufficiently demonstrate. I. THE CEREBRAL DEPARTMENT OF THE NERVOUS SYSTEM. This department of the nervous system, like all organs of animal life, is exactly symmetrical. The nerves com- mence alike from each side of the brain and spinal cord : hence the appellation of pair of nerves, by which the double corresponding trunk is described. This is a term which we cannot apply to the irregularly distributed gan- glionic department. Each department of the nervous system receives im- pressions of objects, and transmits them to the sensorium ; and these impressions or affections of the nerves, accom- panied by consciousness, bear the name of sensation. The nerves, which constitute the immediate instruments of sensation, are of different kinds, and are distributed in different proportions in the various organs of the body : most of them are capable of being excited by agents both from without and from within, and the impressions they receive are transmitted to the brain, their common centre, and frequently to the other organs with which they are connected. That the nerves are truly the organs of sen- sation cannot be disputed ; for sensation is found to be most acute in those parts which are furnished with most nerves, and the sensation ceases when the nerves are de- stroyed. When the nerve is stimulated, the muscle which 46 NERVOUS SYSTEM. it supplies is convulsed ; when it is tied, compressed, or divided, palsy of the muscle ensues. My present arrangement of the departments of the nervous system, is chiefly founded on the anatomy and distribution of the nerves. And here science must ac- knowledge its obligation to Sir Charles Bell, for his important discoveries, relative to the functions of the nerves. So that, by the operation of new views, many formerly received opinions must be reformed, or altogether expunged. As I proceed, therefore, in the work, I shall endeavour to demonstrate, from anatomical and physiologi- cal facts, that every part of the system has its peculiar endowment of nervous matter, fitting it for the peculiar function it has to perform. For example, it is necessary to distinguish nerves into sensitive, motive, compound and organic, and in addition to the limited number of senses, usually reckoned in the human subject, there are other inward organs of sensation, which will subsequently be described, which have distinct functions, and depend on as distinct departments of the nervous system, as either see- ing, hearing, or touch. I shall now claim the attention of the reader to the general distribution of the nervous system. The brain appears to be the most remarkable part of the nervous system, since all intellectual phenomena must be referred to the cerebral mass. This organ furnishes generally the motive for all our actions upon exterior bodies, exerts a greater or less influence upon all the pro- perties of life, establishes an active relation amongst the different organs, and is the principal agent of sympathies. It is, moreover, in a sensible relation with the objects with which we are surrounded. There are two orders of the cerebral department of nerves ; the 1st constitutes the nerves of sensation ; the 2d, the nerves of motion. NERVOUS SYSTEM. 47 The nerves of sensation of the first order, which are immediately connected with the brain, are endowed with particular properties, which adapt them to the impression of special bodies ; namely, the first pair of nerves perceives odors, the second light, the eighth sound ; and the lin- gual branch of the inferior maxillary nerve distinguishes the taste and flavor of bodies. The special senses, how- ever, I shall hereafter more particularly refer to. The medullary column, or spinal marrow, appears next in importance to the brain. It is an irregularly cylindrical prolongation of the brain ; it is not like the Grecian shaft, a simple column, but like the Gothic, a compound column, having several shafts combined. In other words, the spinal marrow is composed of four parts or cords, two on each side, which are united the whole length. From the ante- rior cord, of each side of the column, issue the nerves of motion ; from the posterior cords, the nerves of sensation. There is another column, which is only continued the length of the medulla oblongata, from which the respiratory nerves take their origin. The spinal nerves are perfectly regular in their deriva- tion and distribution. There are thirty, or thirty-two, on each side ; this variation in the statement of the number depends on the method of reckoning. Each nerve com- mences by two distinct roots ; Fig. 12, the one. c, proceeding 48 NERVOUS SYSTEM. from the anterior ; the other, b, from the posterior division of, a, the medullary column ; and each of these roots is composed of a number of small filaments, which, imme- diately after their origin, approach each other; the poste- rior filaments form, d, a ganglion, and then join the an- terior to form, e, a spinal nerve : each nervous filament must be considered as continuing distinct to its ultimate destination, though, by the union of the anterior and posterior, the several spinal nerves possess the double property of conveying sensation, and producing motion. There are other nerves of the fifth, sixth, and ninth, which are distributed separately, and are solely motive nerves ; but the fifth nerve of the encephalon is like the spinal nerves, in having a double derivation, and a two- fold function of sense and motion. Sir Charles Bell performed numerous experiments to prove the correct- ness of his theory, and these experiments have been repeated on the Continent by Magendie and others, who have been perfectly satisfied with the accuracy of NERVOUS SYSTEM. 49 his conclusions.* It must, therefore, now be considered as an established fact, acknowledged by all anatomists, that the nerves, proceeding from the anterior cord of the spinal marrow, bestow the power of muscular motion; and that those which proceed from the posterior part of the medullary column, produce sensation. When, for in- stance, the roots of the anterior nerves of the leg are divided, the animal loses all the power of moving the leg, although the limb retains its sensibility; but, if the roots of the posterior nerves are cut, the power of motion continues, though sensibility is destroyed. The experi- ments have been repeated and varied, yet with similar re- sults. Thus, on the posterior part of the spinal cord being irritated with a pointed instrument, the animal immediately manifested signs of pain ; but no apparent effect was pro- duced by irritating the anterior part. Every muscle, then, has two distinct orders of nerves ; the one a motive, and the other a sensitive ; and nerves of each of these orders are distributed to every muscular fibre. It requires, therefore, for the full operation of muscular power, two different orders of filaments, and these estab- lish a circle between the sensorium and the muscle ; so that the nerves of the one order carry the influence of the will towards the muscles, which nerves have no power of transmitting an impression back again to the brain. The nerves of the other order connect the muscles with the brain, by acting as a sensitive agent in conveying the im- pression of the condition of the muscle to the common sensorium ; but the last-mentioned nerves have no opera- tion in a direction from the brain to the muscle, and, in consequence, do not excite the muscle however irritated. We find, however, that the brain and medulla spinalis, *For details, I refer to the papers of Sir Charles Bell, in the Philo. Transac. of the Royal Society. VOL. II. 7 50 NERVOUS SYSTEM. as also the nerves communicating with them, are endowed with different properties ; the common design of which is to give us correct intelligence of the relative condition of our existence. The assemblage of these different parts has, consequently, with propriety, been called the ner- vous DEPARTMENT OF EXTERNAL LIFE, 01' of animal life. When the functions of this part of the nervous system are suspended, as by a fit of apoplexy, the individual is de- prived of feeling, and is perfectly insensible to every sur- rounding object. It has already been observed, that these nerves are endowed with two properties, viz. sensibility, and vis- motrix ; hence, it follows, that there must be nerves of sensation and motion. And physiological experiments, and the observations drawn from pathological anatomy, evidently prove, that sensation resides in the nervous fila- ments, connected with the posterior column of the medulla spinalis ; and motion in those which are extended from the anterior column. As general corollaries, the nerves of sensation receive the impressions which external agents produce upon us, and transmit them to the brain. If a ligature be applied around a nerve, or if the nerve be cut transversely, we find that sensation is totally destroyed in that part to which the nerve is distributed, because the brain is not in direct communication with it. " The brain, therefore, is the only organ that enables us to appreciate the objects which surround us ; the senses being its advanced guards, and the nerves its media of communication." 1. The senses receive impressions. 2. The nerves convey impressions to the brain. 3. The brain perceives and judges, according as they appear useful, agreeable, or hurtful. In conclusion it appears, that, without the due functions of the brain, we should neither possess external sensation, NERVOUS SYSTEM. 51 nor be competent to execute any voluntary movement ; consequently, it has been said3< with much truth, that the nervous system is, in fact, all the animal'* the other sys- tems being vegetative and automatic, and existing only to nourish and defend it. Besides the properties of sensation and volition, which are common to other animals, man is distinguished from them by that faculty which he possesses from the Creator, of being able, by means of his nervous system, to compare, associate, and judge of the impressions which he does or has received, and to deduce from them the greatest consequences. Possessing a faculty which constitutes the most beauti- ful and most noble attribute of our species, nature also ordained that its functions should correspond with the de- gree of perfection and extension of the cerebral mass. A deficiency in the general conformation of the brain, the slight developement of some of its parts, and the evident or obscure alteration occurring in its structure, are so many causes capable of deranging the whole or part of the intellectual faculties of man.f Anatomists and physiolo- gists have failed in the attempt to trace the precise differ- ences between the organization of the idiot and another man ; though there is no doubt that the defect exists in the organization of the brain, since an idiot possesses a soul in common with another man. CEREBRAL DEPARTMENT OF THE NERVOUS SYSTEM. THE BRAIN IN GENERAL. The brain is that mass which fills the cavity of the skull. It is distinguished by its divisions into the cerebrum, * Baron Cuvier. t Manec. 52 NERVOUS SYSTEM. the cerebellum, the pons varolii, and the medulla oblon- gata, all of which, in the adult, weigh about three pounds ; occasionally the brain is found to exceed this weight by- several ounces, according to the size of the head. In the dimensions of the brain there is a great difference in dif- ferent individuals. The volume is generally in proportion to the mental capacity. Let us not suppose, however, that every person having a large head is necessarily a per- son of superior intelligence, for there are many causes of an augmentation of the head besides the size of the brain. The color of the brain varies in different individuals and at different ages ; the color probably depending on the quantity of blood sent to it : hence, it has a redder hue in early than in advanced life, and becomes still more deeply colored in consequence of inflammation. The weight of the brain of a full-grown man is about three pounds ; that of a woman is somewhat less. Baron Wenzel paid great attention to this department of anatomy, and has published a very interesting table, of which the subjoined is an extract. NERVOUS SYSTEM. 53 Weight Weight Weight Proportion Age. of whole of brain of cere- of brain to brain. only. bellum. cerebellum. Grains. Grains. Grains. Male embryo of 5 months 720 683 37 18H : 1 Female embryo of 8 months 4960 4610 350 13r6r : 1 Girl at birth . . . 6150 5700 450 12| :1 Girl at 3 years old 15240 13380 1860 7T6T : 1 Boy 3 years 13050 11490 1560 7&t-l Man 18 years 20940 18474 2466 im l Man 31 years 24120 21480 2700 8A :1 Man 54 years 20580 18060 2320 731 • 1 '81 • X Man 63 years 22500 19780 2720 7 37.1 'TTS- l Man 72 years . . 22620 20200 2420 Q 42 . 1 °T2T- A Man 80 years . . 19080 j 16500 2580 fi 5 1 • 1 54 NERVOUS SYSTEM. Fig. 13. The left side of the brain and spinal marrow, shown by mak- ing a section of the cra- nium and the spinal co- lumn, and removing the dura mater. a, the convolutions of the cerebrum. b, the lamina? of the cerebellum. e, the pons varolii. g, the medulla oblon- gata. c, d, f, the medulla spinalis, extending from the first cervical to the first lumbar vertebra, and terminating in the cauda equina. The cerebrum is the largest portion of the brain, and occupies the whole upper cavity of the skull. It rests ante- riorly, upon the arches of the orbits ; in the centre, upon the middle fossa? of the base of the skull ; and posteriorly, upon the tentorium cerebelli. Fi 5.15 " of magnesia, ) The substance of the brain presents two distinct modi- fications. 62 NERVOUS SYSTEM. 1st. The cortical or cineritious substance covering the brain in general, about the sixth of an inch in thickness ; it also enters deep between its convolutions, and is dis- tributed through different parts of its interior. This part of the brain, when examined with a microscope, appears to consist of minute molecules, smaller than the red parti- cles of the blood. They are connected together by a transparent tissue, containing a serous fluid, and supplied with very minute and infinitely numerous blood-vessels. 2d. The medullary or white substance is firmer and denser than the former ; its mass is also much greater than that of the corticular substance, and is filled with a great quantity of vascular ramifications, which, on making a sec- tion of the brain, present so many red points with the blood oozing from them. All the fasciculi of medullary fibres placed in the medulla oblongata, appear to expand so as to form the mass of the brain ; and more especially to originate from the pyramidal and olivary eminences. The fibres of the former on the one side proceed to the opposite side, crossing each other, and progressively acquiring more volume as they ascend to form the cerebral mass. These two substances of the brain do not constitute one homogeneous mass, but are arranged into a great variety of eminences, cavities, lamina?, partitions, etc. differing in their color, consistence, and volume. I shall now proceed to demonstrate the brain in each of these particulars, not by attempting to unfold the structure in the manner of Reil and Spurzheim, but shall describe the several parts as they are exhibited in the recent and most familiar modes of dissection.* The corpus collosum, or commissura magna, is the centre * In order to examine the fibrous and lamelated structure of the brain, it must be immersed for a requisite time in alcohol. NERVOUS SYSTEM. 63 of communication between the hemispheres : it is seen, without making an incision, by merely separating these hemispheres with the fingers. It consists of a large por- tion of medullary matter, which by transverse fibres, in- corporates and unites the two lateral divisions of the cere- brum. The centrum ovale is the appearance which is exhibited when the brain is cut horizontally, on the level of the cor- pus callosum; the corpus callosum constitutes the centre of the great medullary mass of the cerebrum, and the cor- tical substance, being on its edges, forms the central white mass into an irregular oval. In the middle of the corpus callosum there is a longitu- dinal line called the raphe; it has a medullary cord on each side, from which numerous short transverse lines proceed, termed the transverse medullary traces. 64 NERVOUS SYSTEM. Fig. 15. Fig. 15, a transverse section of the brain, upon a level with the corpus callosura. a, a, a, the corticular part of the convolutions, with the fissures between them. b, b, the medullary part, forming the centrum ovale of VlEUSSENS. c, the raphe, on each side of which are longitudinal elevated lines, and transverse striae. In the substance of the brain we find four cavities, termed the ventricles. There are two lateral ventricles, one is situated in the central part of each hemisphere. They are of an irregular form, lying under the centrum ovale, and each having three winding prolongations termed cornua. The anterior cornua are separated from each other by a partition, called NERVOUS SYSTEM. 65 the septum lucidum ; the posterior cornua are at a consid- erable distance from each other, but as they curve inwardly and dip into the middle lobes of the brain, they approach nearer at their pointed extremities. The cavities of these ventricles are principally situated between the corpus cal- losum and the corpora striata, and tbnlami nervorum opti- coruin. Fig. 16. Fig. 16, a horizontal section of the cerebrum, a little deeper than in Fig. 15. a, a, the anterior cornua of the lateral ventricles. b, b, the posterior cornua. c, c, the corpora striata. e, c, the optic thalami. f, d, the septum lucidum, showing the fissure termed the fifth ventricle, and extending between the two letters, — g, g, the choroid plexus. VOL. II. 9 66 NERVOUS SYSTEM. The lateral ventricles communicate with each other, and with the third ventricle by an opening, named the foramen Monroianum, under the arch of the fornix. The septum lucidum, or septum of the ventricles, is a soft and thin medullary production, which is continuous above with the middle part of the inferior surface of the corpus callosum ; inferiorly, it is connected with the fornix, and forms a distinct partition between the lateral ventricles. It is composed of two laminae with a narrow cavity between them, which has been considered by Cuvier as a fifth ventricle. PARTS OBSERVED IN THE LATERAL VENTRICLES. The fornix is a flat triangular medullary body, having its upper surface contiguous to the corpus callosum, and sup- porting the septum lucidum. Its lower surface is situated upon the choroid plexus and optic thalami ; one of the an- gles is forward and the other two are towards the back part; and the foramen of Monro is under the most anterior part. The posterior angles of the fornix have a bifurcated pro- longation ; one of the branches of which is short, and loses itself in the white layer of the cornua ammonis. The other, which is long, is named the corpus fimbriatum ; it is flattened, and extends into the lowest part of the lateral ventricle. The corpora fimbriata, or tania hippocampi, are the plaiting of the margin of the processes of the fornix, which pass into the inferior cornua of the ventricles. The pes hippocampi, or cornu ammonis, is found at the termination of the line called taenia hippocampi, at the posterior prolongation of the fornix. The psalterium, or lyra, consists of numerous transverse lines, which are impressed upon the under surface of the posterior part of the body of the fornix. NERVOUS SYSTEM. 67 The choroid plexus is displayed by dividing the body of the fornix and inverting it. This plexus consists of a spongy mass of tortuous vessels and reddish granulations, covering the optic thalami and corpora striata, and contin- ued into the inferior cornua of the lateral ventricles. The plexus of each side is connected to its fellow by the velum interpositum, a vascular membrane which passes under the fornix, and lies on the third ventricle and corpora quadri- gemina. The plexus returns its blood by two parallel branches, termed the venae Galeni ; these veins run back- wards, and enter the sinus rectus. The corpora striata are two smooth cineritious pyriform eminences, broad before and contracted behind ; they are situated in the fore part of the lateral ventricle. Their color at the outside is gray, somewhat tinged with brown ; but on cutting them obliquely, cineritious and medullary substances are seen disposed in their interior, in alternate streaks. The white fibres may be traced to the original fasciculi of the corpora olivaria. The optic thalami are two oval medullary eminences, placed by the side of each other, between the diverging extremities of the corpora striata ; their upper surface forms a part of the floor of the ventricles ; their lower surface presents, externally, two prominences. The corpora geni- culata, which furnish several filaments to the optic nerve, may be seen at the inferior surface of the cerebrum. The commissura mollis is a band of a gray color, connect- ing the convex surfaces of the optic thalami. The tania semicircularis is a line of white semitranspa- rent substance, running between the convex surface of the optic thalami and the corpora striata. 68 NERVOUS SYSTEM. Fig. 17. a, a, the optic thalami, on the outer margin of which is seen the taenia semicircularis. e, e, the corpora striata. d, the cavity (termed the fifth ventricle) which exists be- tween the two lamina; of the septum lucickim. c, the anterior pillars of the fornix cut off at their base. b, the fornix turned back, showing on iis inferior surface — /, the lyra. g, the taenia semicircularis, or white line separating the surface of the corpora striata and the thalami. The commissura anterior cerebri is a short cylindrical medullary cord, extending transversely between the cor- pora striata, immediately under the anterior prolongations of the fornix. The vulva is a small aperture formed by the anterior pro- longations of the fornix, bifurcating and adhering on each NERVOUS SYSTEM. 69 side, between the corpus striatum, and the thalamus nervi optici. This aperture is the part by which the three ven- tricles communicate. The third ventricle is situated between the optic thalami and the crura cerebri ; it is a deep fissure. At the upper and fore part it communicates with the lateral ventricles, and, at the lower part, with the infundibulum. The latter opening is called iter ad infundibulum. A canal extends backwards under the tubercula quadrigemina, into the fourth ventricle. This passage is called the aqueduct of Sylvius. The anus, or foramen commune posterius, is situated behind the commissure of the optic thalami, and is the ante- rior aperture of the aqueduct of Sylvius. The commissura posterior is a transverse cord at the posterior part of the third ventricle. The pineal gland is situated beneath and behind the fornix, and above the tubercula quadrigemina ; it is a small grayish body of the size of a pea ; it is perfectly isolated from the cerebral substance, excepting at the fore part, where it is connected to the optic thalami by two medul- lary cords, — the peduncles of the pineal gland. In the adult it contains little calculi, very hard and resembling grains of coarse sand. THE INTERNAL STRUCTURE OF THE CEREBELLUM. The substance of the cerebellum is composed of cineri- tious and medullary matter, as in the cerebrum. The cineritious, however, bears a much greater proportion in the former than in the latter. The arbor vita is a beautiful tree-like appearance, which we observe on making a vertical section of the cerebellum. This appearance is formed by the peculiar arrangement of medullary and cineritious matter. 70 NERVOUS SYSTEM. The corpora resliformia are processes of medullary matter, which extend from the medulla oblongata to the medullary crura of the cerebellum. The fourth ventricle is the ventricle of the cerebellum ; the sides of this cavity are formed by i<, the anterior part by the medulla oblongata, and the upper and back part by the valvula Vieussenii. The calamus scriptorius is the groove and its pointed ter- mination in the fourth ventricle, which Vesalics conceived to have a great resemblance to a writing pen. The aqueduct of Sylvius enters the upper part of this ventricle, and the valvula Vieussenii hangs over it. Fig. 13. Fte. IS, a horizontal section of the cerebrum and an oblique division of the cerebellum. a, the anterior part of the corpus callosum. NERVOUS SYSTEM. 71 b, the corpus striatum. c, the optic thalamus. d, the taenia semicircularis. e, the anterior pillars of the fornix cut off at their base. f, the commissure of the optic thalami. g, the pineal gland, situated on the four eminences, term- ed the corpora quadrigemina. h, valvula Vieussenii. A-, the arbor vita?, shown by an oblique section of, n, the cerebellum. /, the fourth ventricle, terminating in, — ■m, the calamus scriptorius. n, the cerebellum. The arteries of the cerebrum and cerebellum are branches of the internal carotid and vertebral arteries, from the latter of which arises the basilar artery : ramifications of these vessels communicate with each other, and form, what is termed, the arterial circle of Willis. The spinal marrow receives its arteries from the verte- bral, dorsal, lumbar, and sacral arteries. The veins of the brain are very delicate in their struc- ture ; they communicate with the sinuses of the dura mater, and the sinuses pour their contents into the internal jugular veins. The veins of the spinal marrow terminate in the verte- bra], dorsal, lumbar, and sacral veins. No lymphatic vessels have yet been discovered in the brain. 72 NERVOUS SYSTEM. Fig. 19, exhibits the brain placed on its base, with a vertical incision made through the corpus callosum, as far as the anterior commissure, and continued posteriorly to the tubercula quadrigemina. The hemispheres are sepa- rated from each other and turned to each side. The sep- tum lucidum and fornix are removed. The cerebellum, in a similar manner, is divided as far as the fourth ven- tricle. a, fl, the cut edges of the corpus callosum. b,b, b, b, the tubercula quadrigemina. c, the pineal gland. d, medullary striae in the fourth ventricle, which form the beginnings of the auditory nerves. e, the third ventricle. NERVOUS SYSTEM. 73 /, part of the pituitary stem. g, the medullary portion of the cerebellum. h, the fourth ventricle. i, the calamus scriptorius, at the inferior part of the fourth ventricle. k, the medulla spinalis. 7, the taenia semicircularis. m, the peduncle of the pineal gland. n, a section of the anterior commissure of the brain. The brain is the primary organ of sensation ; the mind is supposed to be most immediately and intimately connect- ed with it, and, from observations and experiments, it is found to communicate nervous influence to all the other parts of the body. That the brain is the organ of the mind, is evident by the connexion between the brain and the organs of sense, by our consciousness, and by the mental disturbance which ensues under disease of the brain. In asserting, however, that the brain is the organ or instrument of the mind, it is not intended to convey an idea that the mind is material, but that the exercise of the mental powers depend on the living brain. VOL. II. 10 74 NERVOUS SYSTEM. CHAP. II. THE MEMBRANOUS ENVELOPES OF THE BRAIN. The membranes of the brain are called matres by the ancients, from a notion that they gave origin to all the other membranes of the body : no argument is required to refute so absurd an opinion. The membranous envelopes of the brain consist of the dura mater, the tunica arachnoidea, and the pia mater. 1. THE DURA MATER. The dura mater is the outermost envelope of the brain ; it is common to that organ and to the skull, that is, it in- closes the brain and its appendages, and performs the office of an internal periosteum to the cranium. This membrane is of a very firm and compact texture ; it is composed of tendinous-like fibres, which have a glossy, semitransparent, and pearly appearance. It is divisible by maceration into two or more fibrous layers. The outer surface of the dura mater adheres rather loosely to the bones of the skull, and is easily detached from them ; but at the sutures and foramina it is more firmly connected than elsewhere. The inner surface of the dura mater is remarkably smooth, and forms several folds, which are named the falx cerebri, the tentorium cerebelli, and the falx cerebelli. The falx cerebri is a duplicature or process of the dura mater, and has some resemblance in shape to the blade of a sickle, from which circumstance it has obtained the name of falx. It separates the two hemispheres of the brain from each other. Its upper edge, which is extended from the frontal ridge to the middle groove of the occipital bone, NERVOUS SYSTEM. 75 lodges the superior longitudinal sinus. Its lower edge passes over the corpus callosum, and contains the inferior longitudinal sinus. Its anterior extremity is attached to the crista galli ; the posterior is continued into the tento- rium, and contains the straight sinus. The tentorium cerebelli is a membranous partition which separates the cerebrum from the cerebellum. Like the falx cerebri, it is in a continual state of tension. Its outer cir- cumference contains the lateral sinus, and is connected to the edges of the lateral groove of the occipital bone. The inner edge corresponds to the cerebral protuberances. The extremities of the tentorium meet at an acute angle, and cross over each other, like the letter X, to be attached to the clinoid processes of the sphenoid bone. The falx cerebelli is a process of the dura mater, which is placed between the lobes of the cerebellum, and is extended from the internal occipital protuberance, to the great occipital foramen. The dura mater is evidently fibrous, and its fibres are very apparent in the folds just mentioned, and, in particular, at the upper part of the falx cerebri. Some minute nervous filaments have been discovered in the course of the arteries of the dura mater. The blood-vessels are not very numer- ous. The principal branches of the arteries are distributed upon the external surface ; minute ramifications only being observed on its inner surface. The smaller veins of this membrane accompany the arteries, the larger veins consti- tute the sinuses which I am about to describe, SINUSES OF THE DURA MATEK. The sinuses of the dura mater are merely the large veins of the brain, which are received into triangular canals of the dura mater ; they vary in their dimensions, and are dis- 76 NERVOUS SYSTEM. posed in a regular symmetrical manner. They are formed externally by the dura mater, and internally by a smooth membrane, similar to that which is met with in the veins. As they are constantly stretched in all points of their ex- tent, they can neither change their situation nor contract upon themselves. They are remarkable for having at in- tervals fibrous bridles, which pass irregularly from side to side of the canal. All the veins of the dura mater and of the brain pour their blood into the sinuses. Fig. 20, a, a transverse section of the superior longitudinal sinus. b, a similar section of the inferior longi- tudinal sinus. c, a portion of the cranium. The superior longitudinal sinus is a long triangular canal, which, commencing at the crista galli of the ethmoid bone, and extending along the upper edge of the falx cerebri, becomes gradually larger in its progress, and terminates in the lateral sinuses. The inferior longitudinal sinus is much smaller than the preceding, and is situated at the inferior margin of the falx, extending from its anterior third to the tentorium cerebelli, terminating posteriorly by two branches in the straight sinus. The torcular Herophiei* is an irregular cavity situated at the union of the three great folds of the dura mater ; it presents six apertures, viz.: 1st, that of the superior longi- tudinal sinus ; 2d, two inferior, corresponding to the occi- pital sinuses; 3d, one anterior belonging to the straight sinus ; 4th, two lateral openings on the right and left lead- ing into the lateral sinuses. The straight sinus is situated at the base of the falx ; it is a continuation of the vena Galeni, and extends from * The term torcular was originally applied, from a supposition that the blood is squeezed in this sinus as ia a wine press. NERVOUS SYSTEM. 77 the termination of the inferior longitudinal sinus to the torcular Herophili. The occipital sinuses are situated on ihe sides of the occipital foramen, and passing into the falx cerebelli, open into the torcular Herophili. The lateral sinuses are very large, and extend from the torcular Herophili to the commencement of the jugular veins, occupying the lateral grooves of the occipital bone, as far as the foramen lacerum posterius. The corona)-!/ sinus surrounds the pituitary fossa ; it is very small in its whole course, and opens to the right and left into the cavernous sinuses. The cavernous sinuses are very broad and short ; they are situated in the lateral grooves of the sphenoid bone. They commence beneath the anterior clinoid processes, and terminate in the inferior petrous sinuses. The outer pari- etes of this sinus contain, in their substance, the common motor, the pathetic, and ophthalmic nerves. The cavity of the cavernous sinus is occupied by a number of reticu- lated filaments ; the internal carotid artery, and the external motor nerve of the eye. Beneath the pituitary body the two cavernous sinuses communicate by the sinus transversalis sella, turcica,. The superior petrous sinuses extend from the termination of the preceding sinuses, towards the summit of the petrous portion of the temporal bone, and open into the lateral sinuses. The inferior petrous sinuses extend from the cavernous sinuses, to the inferior edge of the petrous and basilary processes, and terminate in the lateral sinuses. The anterior occipital sinus forms a communication between the two petrous sinuses and the cavernous sinus, by extending transversely, at the upper part of the basilary process. 78 NERVOUS SYSTEM. Fig. 21. A lateral view of the veins of the processes of the dura mater, termed the sinuses. a, the falx. b, the tentorium cerebelli. c, the superior longitudinal sinus. d, the straight sinus. e, the lateral sinus. f, the internal jugular vein. g, the inferior longitudinal sinus. h, the occipital sinus. i, the vena Galeni. k. the torcular Herophili. 2. THE ARACHNOID MEMBRANE. The arachnoid membrane is situated between the dura mater and pia mater ; it has been named arachnoid, from NERVOUS SYSTEM. 79 its extreme thinness, resembling a spider's web ; it is extended over the convolutions of the cerebrum, the cere- bellum, and the base of the pons Varolii. The exterior arachnoid membrane does not adhere to the other membranes of the brain, for it can be very easily raised by insufflation with a blow pips ; it possesses no ap- parent vascularity, but is constantly moistened with a serous fluid, and forms a sheath or envelope for all the nerves and all the vessels which enter or issue from the skull. This membrane also passes downwards into the vertebral canal, around the spinal marrow, and furnishes a conical sheath for each of the vertebral nerves. The interior arachnoid membrane is continuous with the preceding ; penetrating into the third ventricle by a small oval opening, found between the corpus callosum and tubercula quadrigemina, and lining the third ventricle, and extending over the choroid plexus, it is continued over the parietes of the lateral and fourth ventricles, into which it passes through the aqueduct of Sylvius. 3. THE PIA MATER. The pia mater is the third membrane of the brain ; it is a cellular, loose, transparent web, in which a multitude of blood-vessels, more or less delicate, cross each other in a thousand different directions, and it is attached to the sur- face of the brain by the minute branches of these vessels, which penetrate into the latter organ. It invests the brain on all sides, dipping into the convolutions of the hemi- spheres, and covering the superior surface of the corpus callosum ; covering inferiorly the base of the brain and the pons Varolii ; it is also reflected over the cerebellum, and sinks between its concentric laminae. 80 NERVOUS SYSTEM. The pia mater penetrates into the third and lateral ventricles by the great fissure, which is situated between the corpus callosum and the pons ~\ arolii, and by the two lateral fissures. It forms. 1st, the choroid web, a triansular membranous prolongation, lining the posterior part of the corpus callosum, and the inferior surface of the fornix, to which it adheres by numerous small vessels. 2d, the choroid plexus, an elongated fold of the pia mater, having an appearance of vascular cords, attached to the choroid web, and extending into the lat- eral ventricles, along the sides of the fornix ; this plexus communicates with that part of the external pia mater which descends between the thalami of the optic nerves and the fimbriated bodies. We perceive in the choroid plexus a number of small granulations which many ana- tomists have considered as glands ; but Chaussier asserts that thev are membranous fringes, which may be unfolded by agitating them in water. We also occasionally find among the vessels of this plexus small vesicles filled with serum. GBA.NULATIOX3 OF THE MEMBRANES OF THE BRAIN. On the various parts of the dura and pia mater, there are small whitish bodies, of the intimate texture and office of which we are entirely ignorant. The superior longitudinal sinus contains a great number of these granulations : they are designated by the name of the glands of Pacchioxi. Sometimes a few of them are found in the torcular Herophili, and at the orifices of the venas Galexi. All the other sinuses are destitute of them. Graniform bodies, similar to those met with in the sinuses, are also found in the pia mater, especially about NERVOUS SYSTEM. 81 the outside of the superior longitudinal sinus, and around the cerebral veins. The internal pia mater contains some of these granu- lations ; they are also observed in the choroid plexus, the velum interpositum, and in the web of the fourth ven- tricle. THE PROPER MEMBRANE OF THE SPINAL MARROW. The character of this membrane is sufficiently marked to distinguish it from the pia mater. It is not, therefore, a continuation of the latter, but a strong and somewhat fibrous tissue, of a yellowish color, corresponding, by its external surface, to the arachnoid, without uniting with it; laterally it is continuous with the neurilemma of the verte- bral nerves, and ligamentum denticulatum. By its internal surface it is adherent to the spinal marrow. LIGAMENTUM DENTICULATUM. The ligamentum denticulatum is a whitish, transparent, thin, but strong band, extending, on each side, between the anterior and posterior roots of the vertebral nerves, from the occipital foramen, to the termination of the spinal marrow. In the interval of each cervical and dorsal pair of nerves, its external border presents twenty or twenty- two denticulated portions, the points of which are fixed to the dura mater. Its internal border adheres to the proper membrane of the spinal marrow. Its use appears to be to keep the spinal marrow steady in its canal. VOL. II- 11 82 NERVOUS SYSTEM. THE NERVES IN GENERAL. The nerves are either cylindrical or flattened white cords, which are extended from the brain, or from the spinal mar- row, to every part of the system. All the nerves are arranged symmetrically and in pairs, and are composed of a greater or less number of filaments, connected together by cellular tissue. The filaments which terminate the branches of the nerves unite with other nervous filaments, or elude our observation in the tissue of the organs which they supply. Fig. 22, a portion of a nerve invested with its neurilemma, and consisting of dis- tinct filaments, one of which is drawn out. If two or more nervous branches are connected together by numerous filaments sent to each other, so that there results a sort of net-work, the name of plexus is given to this distribution. Fig. 23, is an instance drawn from the axillary plexus. Fig. 23. NERVOUS SYSTEM. 83 Most of the nerves are composed of a greater or less number of cords, formed of filaments of the same nature. On separating these cords and fibres, we perceive that they send frequent branches to each other, so as to form a kind of plexus in the very substance of the nerve. The neurilemma is the external membrane which forms a canal for the white medullary matter of the nerve : this may be readily shown by immersing a nerve in an alkaline solution, by which the medullary matter is removed ; and the nerve appears like a fasciculus of tubes. The olfactory nerve has no neurilemma, and it is only found round the optic nerve after its commissure. The nerves are amply supplied with blood-vessels, which are distributed on their surface, and penetrate into their substance, and between their component fasciculi. In some of the principal nerves absorbent vessels may be traced, and reasoning from analogy, we may conclude that there are no nerves destitute of them. NERVES OF THE CEREBRAL DEPARTMENT. By the older anatomists, the cerebral nerves were di- vided into nine pairs ; the facial and auditory nerves being termed the seventh pair, and the eighth consisting of the glosso-pharyngasal, par vagum, and the spinal accessory. The division at present adopted, is into twelve pairs. OLFACTORY NERVES, OR FIRST FAIR. The olfactory nerves are very soft in their texture, and after death are soon decomposed ; they should, therefore, be demonstrated in a recent subject. They are connected to the brain by three filaments; the 1st, is external and 84 NERVOUS SYSTEM. medullary, and is in union with the corpus striatum ; the 2d, internal and medullary, is united to the white sub- stance which occupies the internal part of the fissure of Sylvius ; the third is cortical, and is situated at the point of junction of the two preceding, uniting to them by its summit. At the point of their union, the olfactory nerve presents a triangular enlargement. Fig. 24, a, extending Fig. 24. horizontally forwards and inwards, and dividing into a greater or less number of branches which traverse the fora- mina of the cribriform plate of the ethmoid bone, to be distributed at d, on the turbinated bones of the nasal fossa, the septum narium, and the roof of the nasal fossa. This nerve transmits to the brain the impression which odors produce upon the pituitary membrane. OPTIC NERVES, OR SECOND PAIR. The optic nerve, with the exception of the trifacial nerve, is the largest nerve that issues from the cranium. It is connected to the optic thalami and the tubercula qua- drigemina by two bands, which are extended from these eminences to the optic thalami. The two nerves unite NERVOUS SYSTEM. 85 in front of the pituitary fossa, and are so confounded with each other, as to render it impossible to affirm, in a posi- tive manner, whether they cross each other, as many anatomists have supposed, or whether their substance is mingled and identified at their union ; the latter opinion is most probable. The optic nerves afterwards separate ; each nerve being perfectly cylindrical, isolated and enveloped in a neuri- lemma ; it then passes through the optic foramen, and, sur- rounded by the recti muscles in the orbit, arrives at the posterior and inner part of the globe of the eye ; entering the sclerotic and choroid membranes, it terminates in the retina. THIRD PAIR OF NERVES. The third pair, or motores oculorum, Fig. 25, a, are smaller than, c, the optic nerve ; each nerve is attached to the back part of the crura cerebri, by filaments which are Fig. 25. soon collected into their several trunks. These pass on the upper part of the cavernous sinus, on the outside of the foramen lacerum, into the orbit, and divide into the following branches : 1st, the superior branch, e, e, which is 86 NERVOUS SYSTEM. distributed to the superior rectus and levator palpebral ; 2d, the inferior branch, f, which supplies the other recti muscles ; 3d, a filament to the lenticular ganglion, and inferior oblique muscle. FOURTH PAIR OF NERVES. The fourth pair of nerves, or nervi pathetici, b, are the most slender of the body. Each nerve is attached by three or four filaments, beneath the tubercula quadrigemina, and the lateral part of the valve of Vieussens. This nerve turns round the crus cerebri, perforates the dura mater at the edge of the tentorium, passes the cavernous sinus on the outer side of the third nerve, and proceeds through the foramen lacerum, to supply the superior oblique muscle of the eye. FIFTH PAIR, OR TRIFACIAL NERVES. The trifacial nerves are the largest of the brain ; they are attached, first, between the corpora olivaria and resti- formia by a fasciculus of white fibres, which ascend above the posterior part of the pons Varolii, at the outer edge of which they leave the brain ; each forms a large flat cord, composed of two distinct fasciculi ; the one anterior, con- sisting of five or six filaments ; the other, which is poste- rior, forms a grayish enlargement, termed the Gasserian ganglion, from the anterior part of which proceed three branches ; viz. the ophthalmic, the superior maxillary, and the inferior maxillary. NERVOUS SYSTEM. 87 1. THE OPHTHALMIC, OR FIRST BRANCH OF THE FIFTH PAIR OF NERVES. The ophthalmic nerve passes the external part of the cavernous sinus, receiving a filament from the superior cervical ganglion, and, passing through the foramen lace- rum orbitale, divides into the lachrymal, the frontal, and the nasal nerves. The lachrymal nerve proceeds along the external part of the orbit, gives off the spheno-maxillary branch, which unites with a branch of the superior maxillary nerve ; and the molar branch, which unites with a branch of the facial nerve ; it furnishes also several branches to the lachrymal gland, and to the superior eyelid. The frontal nerve is found in the upper part of the orbit, where it divides into two filaments. The internal frontal, which is distributed to the frontal sinus, the corrugator supercilii, and frontalis muscles, and the subcutaneous cellular tissue of the forehead. The external frontal f lament passes through the supra orbitary foramen, and is distributed to the frontalis mus- cles, and to the integuments extending over the summit of the head. The nasal nerve passes under the superior oblique mus- cle ; it frequently receives a filament from the superior cervical ganglion, and furnishes a very delicate filament to the lenticular ganglion, and also, two or three ciliary fila- ments : it at length divides into two branches ; the internal nasal, which reenters the cranium by the anterior in- ternal orbitary foramen, and from thence again passes down through one of the perforations of the cribriform plate of the ethmoid bone, lo be distributed to the septum narium and the nasal fossa?. The external branch passes out of the orbit, beneath the pulley of the superior oblique 88 NERVOUS SYSTEM. muscle, and is distributed to the lachrymal passages and dorsum of the nose. 2. THE SUPERIOR MAXILLARY NERVE, OR SECOND BRANCH OF THE FIFTH PAIR. The superior maxillary nerve is extended from the ganglion of the fifth pair ; it enters through the foramen rotundum of the sphenoid bone into the spheno-maxillary fossa, where it receives filaments from the spheno-palatine ganglion ; it then passes through the infra-orbitar canal, and terminates on the cheek. It furnishes, 1st, the or- hital branch, which passes into the orbit by the spheno- maxillary fissure, and there divides into the molar and temporal filaments. 2d. The posterior and superior den- tal branches, which enter the passages in the maxillary tuberosity, and, dividing into many filaments, are distrib- uted to the roots of the three last molar teeth, and to the gums. 3d. The anterior dental branch, which de- scends into the anterior dental canal, and divides into filaments, which are distributed to the incisor, the canine, and the two small molar teeth. 4th. The infra-orbitar branches, which form the termination of the superior max- illary nerve ; these pass out by the infra-orbitar foramen, and uniting with filaments from the facial, nasal, and buccal branches, are distributed to the muscles and integuments of the cheek. 3. THE INFERIOR MAXILLARY" NERVE, OR THIRD BRANCH OF THE FIFTH PAIR. The inferior maxillary nerve passes through the fora- men ovale of the sphenoid bone, and is distributed to the lower jaw, and the muscles situated between it NERVOUS SYSTEM. 89 and the os hyoides ; it furnishes the following branches, viz. — 1st. Two deep temporal nerves, which are distributed to the inner part of the temporal muscle. 2d. The masseteric nerves, which are distributed to the articulation of the jaw and the masseter muscle. 3d. The buccal nerve, which passes between the ptery- goid muscles, and divides into six or seven filaments which are distributed to the temporal, buccinator, and levator anguli oris muscles, to the angle of the mouth, and finally to the integuments. 4th. The pterygoid nerves, two very delicate filaments which are directed downwards, and terminate in the inter- nal pterygoid muscles. The lingual or gustatory nerve, of considerable size, and which receives the filament called the corda tympani, which extends from the spheno-palatine ganglion. The lingual nerve afterwards descends between the pterygoidei muscles, and furnishes in its passage a filament to the internal pterygoid muscle ; several to the tonsils and to the superior constrictor of the pharynx ; two or three to the back part of the gums, and to the submaxillary gland ; several filaments are distributed to the sublingual gland, and to the mucous membrane of the mouth : lastly, it divides into numerous filaments which penetrate the mus- cular tissue of the tongue, and ascending towards the supe- rior surface terminate in the numerous papillae ; in conse- quence of which, this branch is considered as the principal nerve of the organ of taste. 6th. The inferior dental nerve, which enters the dental canal, and is divided into branches which are distributed to the teeth and to the cancelli of the bone : some fila- ments, named the mental nerves, pass out of the anterior maxillary foramen, and are distributed to the lower lip and chin. VOL. II. 12 90 NERVOUS SYSTEM. The auricular or superficial temporal nerve, proceeds backwards and outwards between the condyle of the jaw and the auditory canal; it communicates with the facial nerve, giving off branches to the temporo-maxillary articu- lation, and to the pavilion and integuments of the ear ; it is ultimately distributed to the integuments of the temples and forehead. Fi°\ 26, exhibits the trifacial nerve and the distribution of its three principal branches. a, the trunk of the trifacial nerve. q, the Gasserian ganglion. b, the frontal. f, the lachrymal. g, the nasal nerves of the ophthalmic branch. NERVOUS SYSTEM. r, the superior maxillary branch. Z, the malar. i, the anterior dental. h, the posterior dental. 7c, the infra orbitar nerves. c, the inferior maxillary branch. s, the two deep temporal. t, the masseteric. n, o, the lingual. e, the inferior dental. p, the sublingual nerves. SIXTH PAIR OF NERVES. The sixth pair of nerves are very small; they are at- tached to the sides of the corpora pyramidalia, each pro- ceeds to the line which separates the pons Varolii from the medulla oblongata ; here the filaments unite and pro- ceed along the basilar groove through the cavernous sinus, pass through the foramen lacerum orbitale, and are dis- tributed to the external rectus muscle of the eye. While in the cavernous sinus, the sixth nerve is placed between the ophthalmic nerve and the carotid artery., upon the surface of the latter of which, two or three filaments are extended to the great sympathetic nerve. SEVENTH PAIR OF NERVES, OR FACIAL NERVES. The facial nerve is the portio dura of the old anato- mists ; it appears beneath the posterior and external part of the pons Varolii, from the line between the corpora olivaria and restiformia ; it enters the internal auditory foramen with the acoustic nerve, then leaves the latter to 92 NERVOUS SYSTEM. proceed into the aqueduct of Fallopius, passing out of the cranium by the stylo-mastoid foramen. On a level with the hiatus Fallopii, it receives a filament of the Vidian nerve, which enters the cavity of the tympanum, under the name of corda tympani. The facial nerve also furnishes filaments to the muscles of the tympanum, the pavilion, and the integuments of the ear. On its exit from the stylo-mastoid foramen, it gives off the posterior auricular, the stylo-hyoid, and the sub-mastoid branches. The facial nerve then enters the parotid gland, and is distributed to the muscles and the integuments of the face. These branches separate and reunite at different places, so as to form a plexus on the side of the face, which has been called the pes anserinus. NERVOUS SYSTEM. 93 Fig. 27. Fig. 27, exhibits the superficial nerves of the face and neck : the parotid gland is removed to show the divisions of the facial nerve which pass through it. a, the divisions of the facial nerve, termed the pes anse- rinus. b, the supra orbitary nerve. c, the infra orbitary nerve. d, the mental nerves. e, the first cervical nerve. f, descending branches communicating with the hypo- glossal and cervical nerves. 94 NERVOUS SYSTEM. EIGHTH PAIR, OK AUDITORY NERVES. The auditory nerve is the portio mollis of the old anato- mists. It is attached over the restiform body, from the substance of a small gray band, which unites it to the floor of the fourth ventricle. We may observe also a small band which seems to unite this part of the auditory nerve, and furnishes it with a commissure. This nerve accompanies the facial, so long as it is contained in the skull and internal auditory canal ; but at the bottom of this canal it divides into branches, which are distributed to the cochlea, the vestibule, and the semicircular canals. In the description of the organ of hearing, these will be particu- larly noticed. This nerve transmits to the brain the im- pressions which sound produces upon the internal ear. NINTH PAIR OF NERVES. The glossopharyngeal, or ninth pair of nerves, is at- tached in the line which separates the corpora olivaria from the corpora restiformia ; each nerve has three or four fila- ments which unite into a single cord, which is directed through the foramen lacerura, and is separated from the pneumo-gastric nerve by the internal jugular vein. After its exit from the cranium, it sends a filament to the audi- tory canal, receives a filament from the facial, and another from the pneumo-gastric nerve ; several filaments are dis- tributed to the carotid artery, and others communicate with the cervical ganglia. It gives branches also to the muscles of the pharynx, to the mucous glands, to the fauces, and at length terminates in the tongue. It gives motion to the muscles of the tongue and pha- rynx, but more especially to those necessary for the articu- lation of the voice. NERVOUS SYSTEM. 95 TENTH PAIR OF NERVES. The pneumo-gastric nerves, or par vagum, sometimes called the eighth pair, are connected to the brain, immedi- ately beneath the preceding, behind the corpora olivaria, near the corpora restiformia. Each commences by numer- ous filaments, which unite and form two or three fasciculi, placed under each other ; but, on passing out of the cra- nium through the foramen lacerum posterius, they form a round cord, which descends with the great sympathetic, on the lateral part of the neck, on the outer side of the primi- tive carotid, and posterior to the jugular vein ; it passes into the chest behind the subclavian vein, and accompanies the oesophagus to the stomach. It presents a multitude of variations in its secondary divisions, so that we seldom find it alike in two subjects; but it constantly furnishes — 1st. The pharyngeal nerve, which is distributed to the pharynx, and forms the pharyngeal plexus. 2d. The superior laryngeal nerve, which is distributed to the muscles of the larynx, the thyroid gland, and the mucous membrane of the larynx and pharynx. 3d. The cardiac nerves. On the right side the pneumo- gastric nerve supplies two or three filaments, descending with itself to the stomach, and uniting with the cardiac filaments of the cervical ganglion ; on the left side it fur- nishes only one filament, which terminates in the cardiac plexus. 4th. The recurrent or inferior laryngeal nerves. These differ on the right and left sides; the left turns round the arch of the aorta ; the right passes round the subclavian artery : both ascend on the side of the trachea, and termi- nate at the larynx. 96 NERVOUS SYSTEM. Fie 28. Fig. 28, exhibits the general course of the deep-seated nerves of the neck and thorax. a, the superior cervical ganglion of the great sympathetic nerve. 6, the middle cervical ganglion. NERVOUS SYSTEM. 97 c, the pneumo-gastric nerve. d, d, the recurrent, or inferior laryngeal nerve. /, the pharyngeal nerve. t, the superior laryngeal nerve. s, the cardiac plexus. n, the coronary nerves. k, k, k, the cervical nerves, forming the brachial plexus. o, p, the cervical plexus. i, the commencement of the phrenic nerve from the fourth cervical nerve, g, its course over the lungs to the diaphragm. The pneumo-gastric nerve gives filaments to the oeso- phagus and stomach : it also unites by numerous radiations with the hepatic, the splenic, the coeliac, and the right gas- troepiploic plexus : other filaments are interlaced with the meshes of the solar plexus, and several expand on the vena portae, the pancreas, the duodenum, and the gall bladder. On account of the very extensive distribution, and nu- merous communications of the pneumo-gastric nerve, it is called by some authors the middle sympathetic nerve. ELEVENTH PAIR, OR HYPOGLOSSAL NERVES. The hypoglossal nerve is connected by several filaments with the fissure which separates the olivary and pyramidal eminences ; these filaments form a cord, which passes out of the cranium by the anterior condyloid foramen. The hypoglossal is then united to the pneumo-gastric nerve for a short distance, but at the angle of the jaw it is directed downwards and forwards, curving under the tendon of the digastricus, towards the tongue. From the convexity of the curve it gives off, — The descending- cervical branch. In the former mode of enumerating the cranial nerves, it was termed the descend- VOL. II. 13 98 NERVOUS SYSTEM. ens noni ; it passes in front of the internal jugular vein, and communicates with the internal branch of the cervical plex- us. The hypoglossal nerve then passes between the mylo- byoideus and hyoglossus ; it furnishes branches to the adjacent muscles, and is finally distributed to the tongue. It gives the power of motion to the muscles of the tongue ; principally, however, to those concerned in the process of mastication and deglutition. TWELFTH PAIR, OR ACCESSORY NERVE OF WILLIS. The spinal accessory nerve (called by Sir Charles Bell the superior respiratory of the trunk) is singular in its origin and progress. It commences at the lateral parts of the spinal cord ; the first point of union with the medulla spinalis is about the sixth vertebra of the cervical region ; it ascends between the ligamentum denticulatum and pos- terior roots of the cervical nerves, receiving from the latter new filaments, which increase its size ; it then passes through the great occipital foramen, and makes its exit by the for- amen lacerum posterius with the pneumo-gastric, to which it sends a filament ; it then leaves the latter and adheres to the hypoglossal, from which it again separates, passes through the sterno-cleido-mastoideus muscle, and termi- nates in the trapezius. Fig. 28, m. Recent investigations have decidedly proved, that the spinal accessory nerve, both in its commencement and disposition, conforms to the spinal nerves, and is never deprived of a posterior root, as some have imagined. This nerve gives the power of motion to the sterno- cleido-mastoideus, and to the trapezius. NERVOUS SYSTEM. 99 Fi:*r z z: z. j;»Dse £j .- . . . -.- : : . t : z -. i : : :i : - r : e : e r c = and vascnitar Jobiii- a ; ran di fiLec ~ fz:z._ Iz _ f zz_.Z5: :•: zz=sf ~e i"; : : :f: :; :~f:~~ .-?_-:" Ez~ez: =zzi '::. :: \ff: ::; :: f: ; £. Tr' : : . . r Z : : . "iZOZ ZZ-Z1 ~.-Z £Z 2 - - Z ." ." .5 Z _ 1 Ok ; • : : zzr : : '.if szzze :~;_~ zr: -~ zif 5 ze ; : naKSS&rc sf-zi ;: zze : ; :«ei ::: .7 .- :fr ~.~-. ~ : :. : - - : : - : : —•-. ■ _ ::••=. En the ' :. z f : ;-_:f : • : f : : ; zz - zz 1: _f z sz • ;: t : - - - - : f = : ; ~i: :ce : iz . e zze . : : : -. zzzz_ -::.: 1: : ._ 1 z • z r : i: : z zzzs= ~ : : BETt : _ t :. ■ . :;.::;: :m - . Lrirj : : - : : ■ -.'. lie prase arc kzezz-Ez ;:: zzf zo_r iizri: ::' zz; : -_:_ ::zzl_z zzf zzz:r~ : :: :z_.zz;zz5 :: ih£ feeios. IH THE FEMALE. 279 ?.: :-: Fig. 91, exhibits the vagina, the uterus, aud its appen- dages. a. the vagina cut open, showing on its inner surface the rugae and caruncule. b. the uterus. c. c, the broad ligaments. d. d. the round ligaments. e. e. the Fallopian tubes. f.f, the external opening of those tubes with their fim- briae. S\ g", the ovaria. 280 ORGANS OF GENERATION, &c. THE GRAVID UTERUS. When the ovum has been conveyed through the Fallopian tube, from its receptacle, into the cavity of the uterus, conception has taken place. Do the rudiments of the foetus proceed from the male or from the female ? We may pass over the theories of the ancients and moderns on generation ; at best they are but " brilliant reveries which overload the mind of the student, and do more injury than is generally supposed to the progress of science." * All that physiologists have discovered, as it regards fecunda- tion, is, that the part of the male, in the act of reproduc- tion, is to deposit the semen in the vagina at a greater or less distance from the orifice of the uterus. The function which the female discharges is more obscure. The uterus, at impregnation, is supposed to attract the semen and direct it to the ovarium by means of one of the Fallopian tubes, whose fimbriated extremity closely embraces that organ. The contact of the semen occasions the rupture and delivery of one of the ova, and the fluid that passes from it, or the ovum itself passes into the uterus, where the new individual is to be developed. The time which intervenes between the instant of fecun- dation and the delivery of the child, is called ulerogestation, or pregnancy ; it is generally nine calendar months, or forty weeks. When the ovum has arrived in the cavity of the uterus, it closely unites with the interior of this organ ; here it re- ceives the materials necessary for its growth, and acquires, by degrees, a considerable volume : the uterus yields to this augmentation, and consequently, changes its form and position. MaGENDIE. IN THE FEMALE. 281 During the first three months of pregnancy, the devel- opement of the uterus is inconsiderable, and takes place in the hollow of the pelvis; but, in the fourth, as the organ becomes larger, this cavity will no longer contain it, and it rises into the hypogastrium. The uterus continues to in- crease in all directions until the eighth month, when it occupies a large space in the abdomen, compresses and displaces the surrounding organs, and crowds the intestines into the lumbar and iliac regions, and its fundus reaches the epigastric region. After this period the fundus recedes towards the umbilicus. The cervix uteri becomes softer and wider about the fourth month, and afterwards diminishes in length, and is so expanded as to entirely disappear; at the seventh month the uterus has an ovoid form, and its volume is twelve times larger than in its unimpregnated state. The appendages of the uterus are also considerably altered in relation to the adjoining part; the laminae of the peritonseal folds, that form the broad ligaments, separate and assist in forming a covering to the uterus. The vagina is increased in length. The ovaria, retained by their ves- sels, do not ascend with the fundus uteri; but, with the Fallopian tubes, are now situated on its lateral parts. The round ligaments are thicker, more vascular, and yield to its elevation. The abdominal parietes suffer very considerable disten- tion, so that the umbilical depression is entirely obliterated. As the magnitude of the uterus increases, it assumes a cellular appearance of a deep red color, and its fibres be- come more evident. On the exterior, they take a direction I have already described ; but the internal fibres of the uterine tissue have some analogy with those of the heart and the tongue, in presenting an inextricable interlacement, where no regular arrangement can be distinguished. Its interior surface contains, immediately after impregnation, vol. ii. 36 282 ORGANS OF GENERATION, &c. an albuminous layer, which increases with the organ in the earlier periods of pregnancy, and subsequently becomes a vascular membrane. Dr. Hunter, who first carefully described it, called it the decidua, from its being ultimately cast off from the uterus. It is supposed to favor the adherence of the ovum to the internal surface of the uterus. The arteries are now observed to have very frequent communications, and in their course are remarkably en- larged and convoluted. But the veins are much larger than the arteries, their diameter, as we have stated, being such as to distinguish them as sinuses; these materially contribute to form the great bulk of the uterine parietes. The lymphatic vessels also become very voluminous. It is evident that the quantity of blood that traverses the uterus, is in relation to the changes it has undergone, and the new functions it is required to fulfil. DEVELOPEMENT OF THE OVUM IN THE UTERUS. The ovum is quite unattached during the first period of its abode in the uterus ; but in the course of the second month its dimensions have increased ; it becomes covered with filaments which ramify in the manner of blood- vessels, and are implanted into the decidua. About the third month they exist on one side of the ovum only, and are connected with that part of the deciduous membrane, forming the placenta. The ovum in the remainder of its surface presents a flocculent layer, sometimes termed the decidua reflexa. The ovum, at the termination of the second month, is of the size of an egg ; and, when there has been an abor- tion, we trace very distinctly the membranes which inclose the embryo, viz. — IN THE FEMALE. 283 MEMBRANES WHICH INCLOSE THE FtETUS. 1st. The amnion, a membrane placed next to and directly enveloping the fetus; it is very thin and pellucid, but firm in texture, and not easily torn ; it covers the pla- centa, is reflected over the umbilical cord, and terminates at the umbilicus. It is united to the chorion by the inter- vention of a gelatinous substance. 2d. The chorion, a flocculent, spongy membrane, com- pletely investing the ovum, and lining the uterus; this membrane is considerably thicker in the earlier than in the more advanced stages of utero-gestation : it then becomes transparent, and is united to the amnion in the manner just mentioned. 3d. The decidua, which may be properly considered as the membrane lining the cavity ; it is much thicker than either of the other membranes, but its texture is less dense, and it is very easily torn. It is placed between the proper membranes of the impregnated ovum and the ute- rine surface. The decidua is only formed by the uterus during impregnation : its formation commences with con- ception. At first it is a mere fluid secretion, which after- wards assumes a flocculent membranous appearance; it increases in extension and thickness in proportion to the evolution of the uterus. It is adherent to the inner sur- face of that organ, and is extended over the chorion, to which it is connected by a vascular attachment; it is always thrown off after parturition. The decidua serves as a capillary system, intended to be the medium of communication between the blood-vessels of the mother and the fetus. The decidual vessels receive the arterial blood of the former, and these vessels are ex- tended over a very considerable surface of tabular struc- ture, which, in its distribution, is in apposition with the 284 ORGANS OF GENERATION, &c. infinite ramifications of the umbilico-placental vessels at innumerable points ; and by these means the required changes in the blood of the foetus are as effectually pro- duced, as the changes called for in the pulmonic blood are produced by the peculiar arrangement of the pulmonary apparatus. When the arterial blood of the mother has produced the desired effect on that of the foetus, it is re- turned by the decidual veins to the surface of the uterus, where it enters into the general venous system of the mother. LIQJJOR AMNII. The membranes contain a quantity of fluid termed liquor amnii, which is augmented in proportion to the advanced state of gestation. According to Professor Vau- quelin, it is formed of water, albumen, soda, muriate of soda, and phosphate of lime. The uses of this fluid are to afford a soft medium for the residence of the foetus, to which it allows a free motion, and protects its delicate structure from any external injury, to which, from the exer- tions of the mother, it might occasionally be liable. The waters of the amnios are also useful in parturition, by dila- ting the orifice of the uterus, and lubricating the external organs of generation. THE PLACENTA. (Fig. 95.) The placenta is a rounded, oblong and soft mass, by means of which the ovum is attached most intimately to the uterus. This body is generally about eight inches in its greatest diameter, six in the smallest, and one thick ; but it gradually becomes thinner towards the circumfer- IN THE FEMALE. 285 ence. Its thickest portion is where the umbilical cord is connected to it. This organ forms a most important part of the uterine contents : its structure is entirely vascular, with the simple interposition of cellular membrane ; so that in its general substance, when excluded from the uterus, it is found to consist of the different branches and divarications of the umbilical arteries and veins, united together by a fine cellular tissue. The whole of this organ is strictly fcetal : it contains within its structure cells or sinuses of consider- able extent, into which the uterine vessels at the point of contact open, and over which their contents are circulated and returned, as long as the organ is attached to the uterine surface. This cellular part of the placenta has acquired the name of the maternal portion. The placenta possesses within its structure the means of two distinct circulations, each of which is continued through distinct channefs : the one passes the blood from the uterine parietes into the placental cells, and returns it back to the uterus : this is properly the maternal circula- tion, and continues as long as the placenta is attached to the uterine surface. The other conveys the blood of the child from its body, and back again through the numerous ramifications of the umbilical vessels : this forms the fozlal circulation. These two circulations are so completely separate and distinct, that they do not interfere with each other : each is entirely unconnected with, and independent of the other ; as far as positive communications of vessels are concerned, the fcetal vessels do not pass their contents into the placental cells, neither do the uterine vessels, communicating with the placental cells, pass their contents into the fcetal structure. There is no mixture of fcetal and maternal blood ; and no circulating communication, direct or indirect, exists between the foetus, from apposition at 286 ORGANS OF GENERATION, a chorus, this membrane being supplied with many blood-vessels in the quadruped. Choroides, so called on account of its many [blood-vessels, re- sembling the chorion. Chyle, {%vXgg, the juice), the milk-like fluid in the lacteal vessels. Crystalline, (ygvaralkog), a term applied to the lens, from its resemblance to ice. Clavicula, (dim. of clavis, a key), the clavicle or collar-bone ; so called from its resemblance to an ancient key. GLOSSARY. 321 Clinoid, (mXIvij, abed, and sldog, shape), processes of the sella Tur- cica of the sphenoid bone, so called from their resemblance to a couch. Clitoris, (zkdm, to conceal), a part of the female pudendum con- cealed by the labia majora. Coccyx, (>:6y.;:v'i, a cuckoo), the lower end of the spine, so called from its resemblance to the beak of that bird. Cochlea, {y.6/loq, a conch), a cavity of the ear resembling the shell of a snail. Ccecum, the blind intestine. Ccehaca, (y.odla, the belly), the name of an artery in the abdomen. Colon, (y.ojlor), the first portion of the large intestine. Commissura, (committo, to join together), applied to parts which unite the hemispheres of the brain. Concha, (x6yxv> a shell), applied to the hollow of the ear from its resemblance to a shell. Condyle (y.ovdvlog, a joint, a knuckle, a knot), an eminence in several of the joints. Conglobate, (conglobatus, gathered together in a circle), a gland subsisting by itself, like those of the absorbent system. Conglomerate, (conglomcratus, heaped together), a gland com- posed of various glands. Coraco ; names compounded with this word belong to muscles Avhich are attached to the coracoid process of the scapula. Coracoid, (y.oQu'c, a crow, and tldoc, resemblance), like the beak of a crow. Cornu, (a horn), applied to a process resembling a horn. Coronary, (corona, a crown), vessels so called from surrounding the parts like a crown. Coronoid, (y.oQwvi}, a crown, and fidog, shape), a process shaped like a crown. Corpus Callosum, (corpus, a body, and callus, hard), part of the medullary substance of the brain, supposed to be firmer than the rest. VOL. II. 41 322 GLOSSARY. Corticalis Substantia, (cortex, bark), the exterior or cortical substance of the brain. Cost,e, (custodio, to guard), the ribs, because they guard the heart, etc. Cotyledons, (xoxvlrj, a cavity), glands, in some animals, dispersed over the chorion. Cotyloid, {v.oxvh), an old measure, and ddog, shape), the cavity for receiving the head of the thigh-bone, resembling the rotuli. CoxtE, the haunches. Cranium, (y.garlov, the skull, quasi, xagavlov, from y.ugu), the head. Cremaster, (xgEfxdoii, to suspend), a muscle so called, because it suspends the testicle. Cribriform, (cribrum, a sieve), perforated like a sieve. Cricoid, (xglxog, a ring, and sldog, shape), the annular cartilage of the larynx. Crista Galli, a portion of the ethmoid bone, so called from its resemblance to a cock's comb. Crista, a term applied to other parts which resemble a crest. Crura, (cms, a leg), applied to some parts, from their resemblance or analogy to a leg. Crypts, (xgimTa, to hide), mucous follicles which are concealed. Cubitus, (a cubando), that part of the arm from the elbow to the wrist j because the ancients, during meals, used to recline upon it. Cuboides, (xvfiog, a cube, and eldog, shape), a bone of the foot, resembling a cube. Cucullaris, (cucullus, a cowl or hood), a broad muscle of the scapula, so called from its shape. Cuneiform, (cuncus, a wedge), wedge-shaped. Cuticula, (the dim. of cutis, the skin), the scarf-skin. Cutis, the skin. Cysticus Ductus (xvaxig, a bladder, ductus, a duct), the duct lead- ins from the gall-bladder. GLOSSARY. 323 D. Dartos (digw, to excoriate), muscular fibres which contract the scrotum. Decidua, (decido, to fall off), a membrane thrown off from the uterus after parturition. Deltoid, (Jifoa, the fourth letter of the Greek alphabet, and udoc, shape), resembling the Greek letter J. Dermis, {digfiu), the more solid skin. Detrusor Urin.e, (detrudere), to thrust or squeeze out of. Diaphragm, (diuygdoaa, to partition), the transverse muscle which separates the thorax from the abdomen. Diastole, (diaariila, to relax), the dilatation of the heart, auricles, and arteries, opposed to systole, the contraction of the same parts. Diarthrosis, (diag&Qoa, to articulate), a movable connexion of bones. Digastric, (dig, twice, and yuaTijq), a belly, having two bellies. Diploe, (Sinloog, double), the spongy substance between the two tables of the skull. Duodenum, (duodenus, consisting of twelve, viz. fingers' breadth), the first portion of the small intestine, so called from its general length. Dura Mater, [durus, hard, and mater, a mother), the outermost membrane of the brain ; the ancients finding it harder than, and supposing it to give origin to, the other membranes of the body. E. Elaine, (iIoaov, oil), the more fluid part of one of the proximate principles of fat. Embryo, (iv, in, and (iqvm, to germinate), the ovum in utero before the fourth month, after which it is called foatus. 3 2 4 GLOSSARY. Emulgents, (cmnlgeo, to milk out), the arteries, and veins of the kidneys, so called because, according to the ancients, they strained, and, as it were, milked the serum through the kidneys. Emunctores, (emungo, to wipe away), glands which, according to the ancients, received the excrementitious matter from the noble parts ; as the parotids from the brain, the axillary glands from the heart, and inguinal glands from the liver. Enarthrosis, (ei>, in, and ug&gov, a joint), an articulation of bones, the same as arthrosis. Encephalon, (fV, in, and %scpaXfh the head), the brain. Enteric, (sycsgov, an intestine), belonging to the intestines. Epicranium, (tnl, and xgavtov), the integuments and aponeurotic expansion which are extended over the cranium. Epidermis, (inl, upon, and digi&a, the skin), the cuticle. Epididymis, (inl, upon, and dtdvpog, twins, the testicles), the small oblong body which lies above the testicle. Epigastric, (inl, upon, and yaar^g, the stomach), the superior part of the abdomen. Epiglottis, (Jm, upon, and ylaulq, lingula), one of the five carti- lages of the larynx, situated above the glottis. Ephippium, {in), upon, and Innoc, a horse), part of the os sphenoi- des, so called from its resemblance to a saddle. Epiphysis, (enl, upon, and (pvw, to grow), see Apophysis. Epiploon, (ini, upon, and nlia, to sail), the omentum, or that serous membrane of the abdomen which covers the intes- tines, and hangs from the bottom of the stomach. Ethmoid, (>]#|Uoc, a sieve), so called because it is perforated like a sieve. Falciform, (falx, a scythe), shaped like a scythe. Fascia, (fascia, a band), a membranous expansion of certain muscles like a sheath. Fasciculus, a little bundle, diminutive of fascis, a bundle. GLOSSARY. 325 Fauces, (the plural of faux), the top of the throat. Fibrin, a peculiar organic compound, which is the most abundant constituent of the soft solids of animals. Fibula, (a clasp), the lesser bone of the leg, which is thus named from being placed opposite to the part where the knee-buckle or clasp was formerly used. Fimbria, a fringe, a term applied to parts of a fringe-like appearance. Fcetus, the child in the womb past the fourth month, and fully formed. Follicle, (follis, a bag), very minute secreting cavities. FrjEnum, (a bridle), the membranous ligament under the tongue, and the one tying the prepuce to the glans. G. Galactophorous, (yula, milk, and cpsga, to carry), conveying the milk. Ganglion, (yuyyhov,) an enlargement in the course of a nerve. Gastric, {yaazrtq, the stomach), appertaining to the stomach. Gastrocnemius, (yaoTi)^, the belly, and xvypr], the leg), the muscle forming the thick of the leg. Gastro-Epiploic, (yaatrjo, the stomach, and inlnloov, the caul), be- longing to the stomach and omentum. Gelatine, (gelu), jelly. Genio, (yh'siov, the chin) ; names compounded with this word be- long to muscles attached to the chin. Gestation, (gestatio utcrina), the period of pregnancy. Ginglymus (yiyylviiog, a hinge), articulation admitting flexion and extension. Glandula, (dim. of glans), a nut or acorn. Glenoid, yXrtvi], a cavity), a part having a shallow cavity. Gliadine, {ylin, glue), one of the constituents of gluten. Glomer, a convoluted bundle of glands. Glosso, {ylmaaa, the tongue) ; names compounded with this word are applied to muscles attached to the tongue. 326 GLOSSARY. Glottis, (ylwTxlg, lingula), the superior opening of the larynx. Gluteus, (yXovtbg, the buttock), muscles forming part of the but- tocks. Gompiiosis, (yo/Mfoco, to drive in a nail), an articulation of bones, like a nail in a piece of wood. H. Hemorrhoidal, (afym, blood, and §ia} to flow), a term applied to the vessels of the rectum, because they often bleed. Harmonia, (ugfiovla, a close joining), a species of immovable artic- ulation. Helix, (dlu, to turn about), the outer bar or margin of the external ear. Hepatic, (ijumq, the liver), applied to parts belonging to the liver. Hyaloid, (valog, glass), the capsule of the vitreous humor of the eye. Hymen, (the god of marriage), the membrane situated at the en- trance of the virgin vagina. Hyo ; names compounded with this word belong to muscles which are attached to the — Hyoides, Os, (v and tldog, shape), a bone of the tongue resembling the Greek upsilon, v. Hypochondrium, (too, under, and xordgog, a cartilage), the upper region of the abdomen, under the cartilages of the ribs. Hypogastric, (ino, under, and yaaT^q, the belly), the lower region of the fore part of the abdomen. Hypoglossus, {ynb, under, and ylwaaa, the tongue), parts which lie under the tongue. Hypothenar, (vnb, under, and &evag, the palm of the hand), one of the muscles contracting the thumb. I. Ileum, {dim, to turn), a portion of the small intestine, so called from being found convoluted. GLOSSARY. 327 Incisores, (incidere, to cut), the fore-teeth. Incus, (an anvil), a small bone of the internal ear, with which the malleus is articulated. Index, (indico, to point out), the fore-finger. Infundibulum, (a funnel), a tube leading from the brain to the pituitary gland. Innominatum, parts which have no proper name. Interfemineujm ; vide Perin/eum. Interosseous, (inter and os), a term applied to parts situated between bones. Iris, (the rainbow), the membrane round the pupil of the eye, deriving its name from its various colors. Ischium, (to%co, to support), that part of the os innominatum upon which we sit. Jejunum, (empty), a portion of the small intestine, so called from being generally found empty. Jugale, Os, the zygoma. Lacunje, (little cavities), the excretory ducts of the urethra, vagina, etc. Lambdoidal, resembling the Greek lambda, A. Lamella, dim. of — Lamina, a scale or plate. It is used for the foliated structure of bones or other organs. Larynx, (ld§v/$), the superior part of the trachea. Linea Alba, a white line formed by the meeting of the tendons of the abdominal muscles. Lumbricales, (lumbricus, an earth-worm), four muscles of the hand and foot. 328 GLOSSARY. M. Masseter, (jUKffora'o/iat, to chew), a muscle which assists in chewing. Mastoid, (fjuxowg, a breast), shaped like a nipple or breast. Maxilla, the jaw. Meconium, (ni'ixav, a poppy), the excrements of the foetus are thus called, because they have some resemblance to opium in color. Mediana Vena, the middle vein of the arm, between the basilic and cephalic. Mediastinum, {medium, the middle), a middle portion separating parts from each other. Medulla Spinalis, the spinal marrow or cord. Membrana Nictitans, (nicto, to wink), a membrane with which birds can occasionally cover the eye. Meninges, {(irjviy^, a membrane,) membranes which inclose the brain. Mesentery, (juaroc, the middle, and hxtgov, the intestine), the membrane in the middle of the intestines, by which they are attached to the spine. Meseraic, (/.liaoc, the middle, and ugaia, the small intestine), the same as the last article. Mesocolon, (/xeaog, the middle, y.wlov, the colon), that part of the mesentery in the middle of the colon. Metacarpus, {fitrca, after, and y.agnog, the wrist), that part of the hand between the carpus and fingers. Metatarsus, (/xna, after, and tmqooc, the tarsus), that part of the foot between the tarsus and toes. Mitralis Valvula, (mitra, a mitre), valves at the left ventricle of the heart, like a mitre. Molar Teeth, the double, or grinding teeth. Mucus, (^via, the mucus of the nostrils), a transparent, saline, glutinous fluid. Mylo, (/xvki], a grinder tooth) ; names compounded of this word belong to muscles that are attached near the grinders. GLOSSARY. 329 Myoides Platysma, a muscular expansion on the neck. See Pla- TYSJ1A. Myology, (fxvg and Xoyog), the doctrine of the muscles. N. Naviculare, (navicula, a small boat), a bone of the carpus, and also of the tarsus. Neurilemma, (vsvqov, a nerve, and ksufxa, a coat), the sheath of a nerve. Neurology, (vsvqov, a nerve,) the doctrine of the nerves. Nymph.e, two semicircular glandular membranes in the pudendum muliebre, so called because they direct the course of the urine. O. Odontoides, (odovg, a tooth, and tldog, shape), tooth-like. CEsophagus, (ol'a, to carry, cpdyoa, to eat), the canal leading from the pharynx to the stomach, carrying what is swallowed into the stomach. Olecranon, (uXsvi), the cubit, xgavov, the head), the elbow, or head of the ulna. Omentum, (omen, a guess), the caul, so called because the ancient priests prophesied from an inspection of this viscus. Omo, (ojjUoc, the shoulder) ; names compounded of this word belong to muscles which are attached to the scapula. Omo-Plata, (o)f.iog, the shoulder, and nluivg, broad), the scapula or shoulder-blade. Ophthalmic, (ocpfralpog, an eye), relating to the eye. Organ, (ogyavov), a part which has a determined office in the ani- mal economy. Osmazome, (oapri, flavor, and 'Qafiog, broth), a peculiar principle obtained from muscular fibre, having the taste and smell of broth. Osteology, [oaxiov, bone, and koyog, a discourse), the doctrine of the bones. vol. ii. 42 330 GLOSSARY. Palpi, (palpo, to grope or feel one's way), feelers. Pampiniformis, (pampinus, a vine-tendril, vl\\& forma, shape.) The spermatic vessels form a plexus, which, from its similitude to the tendrils of a vine, is called pampiniformis. Pancreas, (jjuv, all, and y.giag, flesh), a gland of the abdomen. Panniculus Carnosus, (pannus, a covering, and caro, flesh,) a fleshy covering. Parenchyma, (naQzyxt-m, to pour through), a substance connecting the vessels, etc. of the lungs, liver, etc. Parietalia, (paries, a wall), bones of the cranium, serving as a wall to the brain. Parotid, (notgu, near, and cutoj, the gen. of org, the ear), a gland situated near the ear. Patella, (dim. of patina, a pan), the knee-pan. Pathetics, (nuSog, passion), the fourth pair of nerves, because by means of these, the eyes express certain passions. Pelvis, (mXv$, a basin), the basin of the kidneys, or the lower part of the abdomen, in which the bladder and rectum (and in women also the uterus) are contained. Pericardium, (n?gl, around, and xag5la, the heart), the membrane surrounding the heart Perichondrium, (nfgl and zorSgog), synovial membrane covering cartilage. Pericranium, (ntgl, around, and y.gavlov, the cranium), the mem- brane covering the bones of the cranium. PeriNjEum, (nsgivict), to flow round, because that part is generally moist), the space between the external parts of generation and the anus. Periosteum, (ntgl, around, and oaitov, a bone), the membrane surrounding the bones. Peristaltic, {jiigiaiiMw, to contract), the motion of the intestines. Peritonaeum, (jitgniru, to extend round), the membrane lining the abdomen, and covering its organs. GLOSSARY. 331 Perone, (ntQovi}), the fibula or small bone of the leg. Petrosum, Os, (nsTgrt, a rock), part of the temporal bone. Phalanx, (an army), the bones of the fingers and toes are called phalanges, from their regularity. Pharynx, (cpugvyS), a membranous bag at the back end of the mouth, leading to the stomach. Phrenic, [q>givsc, the diaphragm, tpgijV, the mind, because the dia- phragm was supposed to be the seat of the mind), the name of a nerve, etc. Physiology, (qivaig, nature), that science which has for its object a knowledge of the actions and functions of the living body. Pi a Mater, the innermost membrane around the brain. Picromel, (my.Qog, bitter, and fxih, honey), the characteristic prin- ciple of bile. Pisiform, (pea-iike), a term applied to the fourth bone of the first row of the carpus. Pituitary, (producing phlegm), a term applied to the membrane of the nose, etc. Placenta, (nla$, a cake), the after-birth. Plantaris, (planta, the sole), parts situated in the sole. Platysma-Myoides, (nluTvq, broad, ^vg, a muscle, and ildoq, shape), a muscle of the neck. Pleura, (nlivgu, the side), a serous membrane lining the cavity of the thorax. Plexus, (plccto, to weave together), a kind of net-work of blood- vessels or nerves. Pneumonic, {nvsv^uav, the lung), appertaining to the lungs. Popliteus, (poples, the ham), a muscle of the leg. Prepuce, the fore-skin of the penis, which the eastern nations gen- erally cut off. Processus, (procedo, to start out), an eminence of bone. Prostate, (nqb, before, and 'iarTjfn, to stand), a gland situated be- fore the vesiculcB seminales. Psoas, (ipocu, the loins), a muscle so named from its situation. Pterygoid, (mega, a wing,) a process resembling a wing. 332 GLOSSARY. Pterygo-Staphylini, (ntigvS, a wing, and aToccpvXi], a grape), mus- cles arising from the pterygoid process of the os sphenoides, and inserted into the uvula. Pudenda, (pudor, shame), the parts of generation. Pupilla, (a little puppet), the round aperture in the iris of the eye. Pylorus, (nvXtogog, the keeper of a gate), the lower orifice of the stomach, guarding the entrance of the bowels. Pyramidalis, a muscle having the form of a pyramid. Pyriform, (pyrus), a muscle having the form of a pear. R. Rachidian, {gaxig, the spine), appertaining to the spine. Radius, (the spoke of a wheel), the small bone of the fore-arm. Ranular, like a frog or toad. Raphe, {guma, to sew,) a line having the appearance of a seam. Rectum, the straight gut, the last of the intestines. Region, a term applied to the respective divisions of the body. Renal, appertaining to the kidney, from — Renes, the kidneys, through which the urine flows. Retina, (rete, a net), the net-like expansion of the optic nerve on the inner surface of the eye. Rhomboides, a muscle so called from resembling a geometrical figure, (fjofifiog), the sides of which are equal, but not right angled. Rotula, (dim. of rota, a wheel), the knee-pan. S. Sacrum, (sacred), a bone so called because it was offered in sacrifice. Sagittalis, (sagitta, an arrow), a suture in the cranium. Saliva, the fluid secreted in the mouth. Salvatella, (salvo, to preserve), a vein of the foot, the opening of which was said to preserve health and cure melancholy. Sanguis, the blood. Saphena, (aat)v, a wedge), shaped like a wedge. Sphincter, (a, to pour), the stomach. Styloid, {stylus, a pencil), a process like a pencil on the temporal and other bones. Succenturiatus, (succenturiare, to supply the place of another). Suture, (sutura, a seam), an appearance which is most obvious in that union of the bones of the skull constituting the dove- tail suture. Symphysis, (av/xcpva, to grow together), the connexion of bones which have no manifest motion. Synarthrosis, (ovv, with, and aq&Qov, a joint), articulation with- out manifest motion. Synchondrosis, (aitv, with, and xovdgog, a cartilage), articulation by means of intervening cartilage. Syndesmology, (avrdiufiog, a ligament), the doctrine of ligaments. Syndesmosis, the connexion of bones by ligaments. Syneurosis, (ovv, with, and vevqov, a nerve), the connexion of bones by tendon, formerly mistaken for nerve. Synthesis, (avvxl&ijfii, to put together), the anatomical connexion of the bones of the skeleton. Syssarcosis, (ovv, with, and ouo$, flesh), the connexion of bones by muscle. Systole, (ovotsIXoo, to contract) ; vide Diastole. T. Talus, (a die), a bone of the tarsus. Tarsus, the space between the bones of the leg and the metatarsus. Temporal ; bones, etc. have been so named on account of occupy- ing the region of the head on which the hair generally first begins to turn gray, thus indicating the age. Tendon, (tsivm, to extend), a fibrous cord at the extremity of a muscle. Tentacula, (tento, to seize), organs by which certain animals attach themselves to surrounding objects. GLOSSARY. 335 Teres, (round,) the name of a muscle. Testis, (a witness, quia est quasi testis virilitatis,) the testicle. Thalamus, (d-uhtfiog, a bed), applied to a part of the brain from which the optic nerve takes its origin. Theca, (a sheath) ; the spinal canal is often called theca vertebralis. Thenar, (the palm of the hand), a muscle extending the thumb. Thorax, (d-wgotg, the chest), or that part of the body which contains the heart and lungs. Thymus, &vjuog, a bulbous root), a temporary gland in the thorax. Thyreo ; names compounded with this word belong to muscles which are attached to the — Thyroid, (dvgtbg, a shield), a cartilage of the larynx compared to a shield. Tibia, (a pipe or flute), the great bone of the leg. Tonsils, the round glands placed between the arches of the palate. Trachea, (rga^iig, rough), the windpipe. Tragus, (a goat), a small eminence of the external ear, upon which hair often grows like the beard of a goat. Trapezoid, like a trapezium. Trochanter, {rqoxaco, to run or to roll), a process of the thigh bone, the muscles inserted into which greatly contribute to the action of running. Trochlea, (jgoxtdia, a pulley), a kind of cartilaginous pulley. Trochlearis, an articulation where one part moves round another like a pulley. Tub,e FallopianjE, two canals at the fundus uteri, of a trumpet form, described by Fallopius. Tympanum, the drum of the ear. U. Ulna, (uXivi), the cubit), one of the bones of the fore-arm. Umbilicus, (oncpakog), the navel. Urachus, (ovqov, urine, and ^'eo, to pour), a ligament of the bladder, occupying the place of the urinary passage of the foetal quadruped, which goes into the allantois. 336 GLOSSARY. Ureter, (ovqov, urine), the canal that transmits the urine from the kidney into the bladder. Urethra, (ovq^Squ), the canal through which urine passes from the bladder. Uterus, (vazigoc, matrix), the womb. Uvea, (uva, a grape), the posterior lamina of the iris. Uvula, the pendulous body which hangs down from the middle of the soft palate. Valves, (valves, folding doors), little membranes preventing the return of the fluids in the blood-vessels and absorbents. Ventricle, (venter, the stomach), applied in anatomy to the cavities of the brain and heart. Vertebrae, (verto, to turn), the bones of the spine. Vesicle, (vesica, bladder,) a small bladder-like cavity. Vomer, (a ploughshare), a bone of the nose. X. Xiphoid, (|/qpoc, a sword), like a sword, a term applied to the carti- lase of the sternum. Zygoma, (£170?, a yoke), the arch formed by the zygomatic pro- cesses of the temporal and cheek bones. , CD ., to o= i 3S c£> us CO « i S «= - CO — CO CO —a - SS *° . ■"0 = *■ i>j o .£•• OS ro CO "ij c=. ■■ i 3> c=> -:i- l f 1 > 1 1 O Z • ~» •jT ] . — 1 C~ ] Z e=> "~ 1 - C3 — 1 - C3 " 1 """. - O . "7*" ~ J "-■i - a •?fjl Q i LIBRARY OF THE UNIVERSITY OF MASSACHUSETTS MEDICAL CENTRE AT WORCESTER