316. The general termination of these vessels is into the Thoracic Duct; for an account of their immediate origin, see the first part of the present article. They are much more numerous than the blood-vessels, and they communicate frequently and freely with each other. In their progress they are connected with the glands before described; like the veins they are superficial and deep-seated. The first consists of very numerous vessels, which lie between the skin and the cellular membrane, and the muscles under the skin; while the second set accompanies the arteries and supply all the internal parts by extensive and minute ramifications.

317. In commencing our account of the lymphatics from the lower extremities, we may state that a very great number of the superficial lymphatic accompany the greater saphna vein. They may be first traced from the toes, where they run somewhat like arteries and veins, they form a plexus over the toes, from which branches are transmitted over the top of the foot to the inner part of the leg; another set on the outer side of the foot cross over the front of the tibia, and enter what are called popliteal glands, which are situated round the popliteal artery; on the

Distribution.

The inguinal portion runs centrad of the fascia and inguinal glands, mesiad of the crural nerve and iliacus internus muscle, and laterad of the crural vein and pectineus.

The femoro - tibial portions runs poplitead behind the fascia, the sortorius muscle, and the aponeurosis, passing from the vastus internus to the adductor magnus. The last portion runs

distad and fibulad, then distad between the condyles of the femur, peripherad of the capsular ligament and popliteus muscle, and centrad of the gastrocnemius externus muscle, dividing into two tibials, the one running rotulad, the other poplitead to the foot.

Connection.

The branches from the

crural arteries inosculate freely with each other.

inner side of the thigh a large number of these vessels are found, which lead to the lymphatic glands of the groin, some passing on without entering these glands. The deeper-seated lymphatics of the lower extremities first accompany the plantar arteries, and run up the leg by the sides of the posterior tibial artery; other, but less numerous branches, accompany the tibial and fibulian arteries; these lymphatics are first connected with the popliteal glands, from which three or four large branches peep upwards along the femoral artery to become connected with the inguinal glands. These glands likewise receive the lymphatics from the sciotum, the penis, the glutei muscles; and into the upper series of them many lymphatics also enter from the superficial parts of the abdomen and pelvis.

318. The lymphatic vessels of the upper extremity scarcely need to be described, as they for the most part in their course accompany the veins, where they are superficial, and the arteries when deep-seated. Some of them pass into small glands in the vicinity of the puminal artery, but for the most part they do not enter any glands until they reach the axilla; some pass on between the pectoral and deltoid muscles to be inserted into glands at the under part of the clavicle. Into the axiliary and clavicle glands,

pass also the greater number of lymphatics from the sides of the thorax, and from the mammæ. From these glands, (the axillary,) large lymphatic vessels pass out, and by their union form a trunk, which on the left side of the body leads to the thoracic duct near to its termination. On the right side, the trunk thus formed by the lymphatic vessels, principally of the upper extremity, joins with the large lymphatic trunk, called the trunk of steno.

319. The Thoracic duct.-This is formed by the lymphatic vessels of the lower extremity, and by the trunk formed from the lacteal vessels. It first appears in the form of a sac, called the receptacle of the chyle, which is a bag of a pyriform shape, placed on the first or second vertebra of the loins; it is about two-thirds of an inch in length; towards its upper part it gradually contracts, and at length forms the tube which is properly the duct; this is not above a line in diameter; it passes up from the sac close to the spine, at first behind the aorta; it then perforates the diaphragm, and is found on the right side of the aorta, passing on between that vessel and the vena-azygos, and at length terminating at the junction of the internal jugular and subclavian veins of the left side of the body.

320. The lacteal vessels, like the lymphatics, are found in two sets, which communicate with each other. They take their rise from the villi of the intestines, pass obliquely through their coats, uniting, as they pass out, so as to form larger and larger branches. From the intestines they run along the mesentery towards the spine; passing through glands on the mesentery, and at length uniting, they form two or three trunks which accompany the superior mesenteric artery, till they reach the right side of the aorta, and here they terminate in the thoracic duct. The lacteals of the small intestines are more numerous than those of the larger. Their course likewise, and termination, are somewhat different; some from the latter accompany the inferior mesenteric artery, and communicate with the large lymphatic vessels near its root.

321. It now remains for us to trace the thoracic and abdominal lymphatics. In the lungs there are two sets also of lymphatics, the superficial and the deep-seated. The former running chiefly between the lobules, some passing over them, and all going to the bronchial glands, where they are joined by the deep-seated lymphatics, that go along the branches of the trachea and the pulmonary artery. Having passed through these glands, the principal part of those from the left lung forms a trunk which terminates in the thoracic duct, behind the division of the trachea; then there are other lymphatics of the left lobe which pass through glands behind the arch of the aorta, and which are likewise common to those of the heart, the lymphatics of which organ accompany the carotid arteries. These last vessels are much smaller than those of the lungs. The absorbents of the right lung, after leaving the bronchial glands, form three or four principal trunks, one of which commonly ascends on to the fore part of the vena cava superior, and opens into the duct of steno that terminates in the veins on the right side of the neck.

322. In describing the abdominal lymphatics we shall trace them from the termination of those from the inferior extremities; these having reached the trunk of the body, and passed under Poupart's ligament appear upon the sides of the pubic bones near the pelvis. A part of them passes up along with the iliac artery upon the brim of the pelvis; and another dips down into the pelvic cavity joining the internal iliac artery, near the sciatic notch. At this place they are joined by the lymphatics of the pelvic viscera, particularly of the bladder, and vesicula seminales of the male, and from the uterus in the female; and there are likewise several branches which pass through the sciatic notch from the neighbourhood of the glutei muscles, branches before referred to.

323. On the outside of the iliac artery upon the psoas muscle several considerable branches of lymphatics likewise pass; of these, one part passes up to the loins, and goes under the aorta in different branches, getting from the left to the right side and joining the thoracic duct; and another passes under the iliac arteries, and appears upon the sacral bone. The lymphatic vessels from either side, having in part joined upon the right lumbar region form here a large plexus, and pass through several glands; into this plexus large branches are received from the left plexus; and having at length got up as high as the second vertebra of the loins, the junction here of the lymphatics and the lacteals constitutes the thoracic duct, before described.

324. All the abdominal viscera have both superficial and deep-seated lymphatics; the stomach has two sets, the one running upon its lesser, and the other upon its greater, curvature. Of these the former accompanies the coronary artery, and passes through some glands which lie by its sides. The other set passes from the great curvature of the stomach, partly to the left and partly to the right side. Those on the left side receive the lymphatics of the first half of the great omentum, and pass through some lymphatic glands which lie close upon the right gastric artery, and near the lesser curvature of the duodenum, form a considerable plexus. Into this plexus the lymphatics from the spleen enter, as also those from the gall-bladder, and the deeperseated lymphatics of the liver; and from it several branches proceed, which open into the thoracic duct, near the termination of the large trunk of the lacteals; this duct, we have said, being thus the common receptacle of the absor bent and lacteal vessels. The lymphatics of the liver lie, the one set upon the surface of the organ, and the other by the branches of large blood-vessels in its centre; they however communicate with each other very freely. Most of the lymphatics that lie upon the convex surface of the liver, run towards its falciform ligament, and pass through the diaphragm into the glands, which are situated on the anterior part of the pericardium. Others of them run towards the lateral ligaments of the liver, where they pass through the diapraghm, and afterwards run on its upper surface to unite with those from the ligamentum latum. There is however here, as elsewhere, considerable variety in the course and dis

tribution of these vessels. From the glands on the anterior part of the pericardium just mentioned, a large trunk ascends behind the sternum in the anterior mediastinum, and usually joins the thoracic duct near its termination. Sometimes there are two trunks or more on each side of the chest; those on the left side ending in the thoracic duct, those on the right going into the lymphatic trunk on that side of the neck. The lymphatics on the concave surface of the liver, run towards the porta of the organ; having joined those from the centre of the liver, they pass into glands on the vena portæ ; and afterwards end in the thoracic duct, near the root of the superior mesenteric artery. The lymphatics of the kidney run from its outer towards its inner edge, and pass through the lumbar glands. Into the plexus of lymphatics belonging to the kidneys, the lymphatics also of the glandulæ renales enter. The lymphatic vessels of the kidneys are very small in their natural state, and scarcely visible excepting under circumstances of disease. The lymphatic vessels of the spleen pass from the concave side of that viscus, and join branches which run along the sinuosity of the pancreas.

325. The Lymphatic glands, it will be inferred from the above description of the vessels to which they are attached, are much more numerous in some than in other parts. They es pecially abound in the axilla, in the groin, at the sides of the neck, and at the great division of the aorta into the two iliac vessels.

BRAIN AND NERVES.

326. For an account of the general structure and composition of these organs, we refer our readers to the commencement of this article. The brain, properly so called, occupies all the upper part of the cavity of the skull, and in its form or figure corresponds with the form of the cranium. It is divided into two portions, called hemispheres, each of which is again subdivided into lobes which are three in number, the anterior one resting upon the orbitar process of the frontal bone, the middle occupying the cavity formed by the sphenoid and temporal bones, and the posterior resting upon that expanse of the dura mater which is called the tentorium cerebelli. The division of the brain into two hemispheres only goes down to a certain extent; it is effected by what is called the falciform process of the dura mater, and if, according to the common mode of demonstrating the brain, the two hemispheres are sliced off and removed, the flattened surface presenting itself, or the white portion of it, is named centrum ovale; but first, upon taking out the dividing membrane from between the hemispheres, a broad white plate uniting these hemispheres is perceived; this is named the corpus callosum, along which a groove passes longitudinally, transmitting transverse fibres. Under the corpus callosum the lateral ventricles are situated, which are divided into right and left by an exceedingly thin membrane named septum lucidum: this membrane is placed between the corpus callosum and the fornix, which last is formel by a sort of continuation of the posterior bead of the corpus cal

losum it has a division into four parts, called crura; the under surface of the fornix is impressed by a number of grooves, so disposed as to resemble in some measure the strings of a lyre. When it is removed the lateral ventricles of the brain are fully exposed to view, and the following parts now come into view: the corpora striata, which are two prominences of a striated appearance, from being composed partly of white and partly of brown matter; and the two thalami nervorum opticorum, which intervene between the posterior parts of the corpora striata; these bodies are united by what is called the commissura mollis from its soft texture and medullary appearance. In each lateral ventricle there is likewise found lying upon the thalami a congeries of vessels called plexus choroides, which are stretched over the pineal gland and the corpora quadrigemina: these last, which are likewise called nates and testes, come into view upor removing the plexus at the back part of what is named the third ventricle; the other body (the pineal gland) is placed over the nates. The third ventricle is a deep fissure situated under the commissura mollis, and from it the funnel-like cavity called infundibulam runs forward towards the pituitary gland, which is a small oblong-shaped substance situated upon the sphenoidal bone. Under the anterior part of the body of the fornix, and over the fore part of the third ventricle, the lateral ventricles communicate with each other by a small oval foramen. In what are called the descending cornua of the ventricles, there are two rounded bodies which are joined to the posterior extremity of the corpus callorum; these are named pedes hippocampi. The sharp point at the extremity of each of the posterior cornua of the lateral ventricle is called ergot.

327. The cerebellum, or smaller brain, occupies the inferior cavities of the occipital bone, and is found covered by the tentorium, under the posterior lobes of the proper or large brain. Like the brain itself, the cerebellum is divided into two great lobes or hemispheres, each being subdivided into lobules; a vertical section of this part discovers the fourth ventricle, which extends from the testes on to the back part of the cerebellum; at the under part of this (the fourth ventricle) an angular impression is found, which is called calamus scriptorius. The cerebellum is joined to the cerebrum by chords which are inserted into the substance of the cerebellum, and the fibres of which are described as being intermixed with those of the medulla oblongata.

328. This (the medulla oblongata) is a combination of the cerebrum and cerebullum; it is of a conical shape, with its base next to the brain, and it is extended on as far as the large foramen of the occipital bone, when it takes the name of spinal chord, or medulla spinalis. It is on the under surface of the brain that the medulla oblongata is placed, and can therefore only be seen by inverting the whole mass. There are four crura or processes from the cerebrum and the cerebellum, which first form by their junction the tuber annulare or pons variolii; and the medulla oblongata is the cone-like substance between this and the spinal chord.

329. The spinal chord then, or, as it is vul

garly called, spinal marrow, is continued from the medulla oblongata through the foramen magnum occipitalis down the cavity of the spine; it is covered by the same membranes as the brain; is likewise composed, like the brain, of brown and white matter. It has been divided into cervical, dorsal, and lumbar portions, where there are enlargements for the lateral transmission of nerves as we shall immediately see; and its lower extremity is expanded out into several filaments, which, together, are called cauda equina. It is necessary to say, that each nerve derived from the spinal marrow, as it is transmitted, consists of an anterior and posterior bundle of fibres, and that in the posterior bundle, as distinct from the anterior, a ganglion is found.

330. Having thus given a general description of the brain and spinal chord; or, as some speak, the cranial and spinal brain, we now proceed to trace the nervous ramifications; and in so doing we shall pursue the ordinary method of anatomists, reserving for the article PHYSIOLOGY the discussion of the questions that have recently been agitated respecting the mode in which they actually originate, or are connected with the brain and spine, and with each other; as likewise the combined and separate purposes they serve in the animal economy.

331. The nerves, then, have been divided into two main classes, viz. the cerebral and spinal nerves, or those from the brain directly, and those from the spinal chord; the first set are principally from the basis of the brain, or medulla oblongata; of these there are nine, or, according to some, ten pairs; the tenth being, or being not considered a nerve of the spine.

332. The first pair, or olfactory nerves, take their rise from the corpora striata, and running under the anterior lobes of the brain approach each other as they pass forwards, and are at length ramified upon the turbinated processes of the ethmoid bone, and upon the septum narium.

333. The second or optic arise, according to some, from the thalami nervorum opticorum, according to others from the nates and testes; they form a junction at the sella turcica, and afterwards dividing, pass out at their proper orifice in the sphenoid bone to be expanded upon the retina of the eye.

334. The third, or motores oculorum, are traced from the inferior part of the crura cerebri; they pass out at the foramen lacerum, and are distributed upon most of the muscles of the eye. 335. The fourth pair arise from over the passage to the fourth ventricle; they likewise pass on through the foramen lacerum, and are spent upon the larger oblique muscle of the eye.

336. The fifth pair, or trigemini, arise by the side of the tuber annulare; and, having perforated the dura mater, divide into three great branches; the ophthalmic or orbitar, the maxillaris superior, and the maxillaris inferior.

337. The ophthalmic branch, as it passes through the foramen lacerum, and is about to enter the orbit, transmits a small branch which assists in the formation of the great intercostal; it then passes on to the lachrymal gland and parts about the eye, sending off one considerable branch to the membrane of the nose and integu

ments of the forehead.

338. The superior maxillary branch passes through the large round foramen of the sphenoid bone, and gives nerves to the palate, sphenoida! sinus, and nostrils; the trunk of the nerve passes through at the top of the antrum, gives branches to the teeth of the upper jaw, and is at length spent upon the orbicularis palpebrarumi muscle, the nose, and upper lip; here it is that the branches of this nerve seem to unite with those of the seventh.

339. The inferior maxillary branch passes out at the foramen ovale and is distributed, as its name implies; but besides sending branches to the muscles about the lower jaw, and to the salivary glands, it likewise supplies the external ear, uniting with the portio dura of the eighth pair, and likewise with the ninth pair.

340. The sixth pair, or abducentes, arise from the tuber annulare; they pass within the cavernous sinuses, and then through the foramen lacerum to the abductor muscle of the eye; a branch from this nerve, joining with the ophthalmic branch of the fifth pair, is described as forming the origin of the intercostal.

341. The seventh pair, or auditory, arising by the side of the tuber annulare, goes into the meatus auditorius internus, one part loses its firm coat, and is ramified upon the internal parts of the organ of hearing; this is the portio mollis of anatomists; the other, the portio dura, goes through the canal of Fallopius, and comes out of the skull with its investments, supplying the muscles about the pharynx and neck, and communicating with the maxillary branches of the fifth pair.

342. The eighth pair arise from the medulla oblongata, and consist on each side of the par vagum and glosso-pharyngeus, both of which pass out from the skull at the foramen common to the temporal and occipital bones; a branch from the glosso-pharyngeal nerve joins with the digastric branch of the portio dura; branches likewise are given off from the glosso-pharyngeus, which, uniting with the pharyngeal branches of the other division of the nerve, form the plexus, which lies over the internal carotid artery, and from which nerves go to the heart. The glossopharyngeal then supplies the tonsil, the upper part of the pharynx, the epiglottis, and the root of the tongue.

343. The par vagum runs straight down the neck, near the carotid artery and jugular vein, in its course giving off several branches to the pharynx and larynx. When it has entered the thorax it splits into two portions, the anterior of which supplies the pericardium, sends branches to join with those of the intercostal that go to the heart, and then it takes a winding and retrogade course, on the right side turning round the subclavian, and on the left the ductus arteriosus; it then again mounts upwards on the side of the œsophagus to be lost in the larynx. This is I called the recurrent nerve. The other branch of the right pair goes to the supply of the œsophagus, the lungs, and the stomach, and joins the intercostal immediately below the diaphragm.

344. The ninth pair appear first at the lower part of the corpora pyramidalia, they pass out through the superior condyloid foramina; the nerves of the opposite side are conjoined with the suboccipital nerve by a cross branch; it then

descends down the neck and transmits a branch called the descendens noni, the trunk of the nerve then passing upon the hyoglossus muscle divides into branches which join the lingual branch of the fifth pair, to be lost in the substance of the tongue.

345. The tenth pair, considered by some as the first of the cervical nerves, take their rise from the very beginning of the spinal chord, and their branches are expanded upon the oblique and extensor muscles of the head.

346. Before describing the spinal nerves and their branches, it will be right to trace the ramifications of the intercostal, which together with the par vagum of the eighth pair constitutes the great sympathetic nerve of anatomists. We have already said that the ophthalmic branch of the fifth pair transmits a small branch which assists in the formation of the great intercostal, and that this is joined by a branch from the sixth pair subservient to the same purpose; these, when they have left the petrous bone, are joined by branches from the eighth, ninth, and tenth pairs, as well as with the first and second of the spinal nerves; these together form a very large ganglion, from which the nerve, now first named intercostal, goes out, and descends down the neck with the carotid artery, supplying in its course the flexor muscles of the head and neck, and communicating with the cervical nerves. As it is about to enter the thorax, another ganglion or plexus is found which supply the trachea and the heart, joining, as we have before intimated, with branches of the eighth pair, to furnish these cardiac nerves. Then the main nerve runs down on the side of the vertebræ, receiving everywhere additional branches from the spinal chord till it passes through the diaphragm, and a large bundle or ganglion is formed close by the glandulæ renales, into which the eighth pair enters. From a similar ganglion on each side the nerves of the intestines, liver, spleen, pancreas, and kidneys are derived; and the extremity of the nerve itself is sent down into the pelvis, supplying the parts and organs contained in that cavity.

347. We now proceed to trace the spinal nerves. These have been divided into four orders, viz. seven of the neck or the cervical nerves; twelve of the back or dorsal nerves; five of the loins or lumbar nerves; and six of the os sacrum or sacral nerves: making in all thirty pairs. We have already said, and it is important to observe, that each nerve transmitted from the spine, consists of an anterior and posterior bundle of fibres.

348. The first cervical nerve passes out from between the first and second vertebræ; and after sending off branches, which communicate with the tenth and second vertebral is spent upon some of the muscles of the neck, and on the occipital integuments.

249. The second cervical communicates with the ninth from the brain, and with the first and third of the neck; it likewise joins by branches the portio dura of the seventh pair, and partly supplies the parotid gland and external ear.

350. The third cervical is transmitted from between the third and fourth vertebræ, soon

communicating with the second, and sending down a large branch, which, being joined by another from the fourth, constitutes the phrenic nerve, which runs along the pericardium, and is spent upon the diaphragm. Its other branches are transmitted to the integuments and muscles of the shoulder

351. The fourth cervical, after sending off branches to help in the formation of the phrenic, runs straight to the axilla, where it meets with the fifth, sixth, and seventh cervicals, and with the first dorsal; all these sink into the interstices of the scaleni muscles; and all of them are so often conjoined and blended after they have given off nerves to the muscles of the neck, shoulder, arms, and chest, and to the integuments, that when the several ramifications go off in the axilla to the different parts of the superior extremity, it is impossible to determine which of them the branches belong to. The considerable branches into which they have been divided are six; and to each of these distinguishing names have been given, viz.

352. The cutaneus, which runs down the fore part of the arms, and supplies the integuments as far as the palm of the hand and fingers.

353. The perforans casserii, or musculo cutaneous, which passes through the coracobrachialis muscle; and, after supplying the biceps and the brachialis internus, is spent upon the wrist and back of the hand.

354. The ulnar.-This nerve runs along the ulna, after supplying the extensors of the arm and integuments of the elbow, and is at length lost in the back of the hand, among the interosseous muscles, and the little and ring finger.

355. The radial or median goes down the fore part of the arm along the radius, giving branches as it passes to the neighbouring muscles; then, dividing at the annular ligament of the wrist, it is spent upon the back of the hand, and upon the thumb, fore finger, middle finger, and one half of the ring finger.

356. The muscularis.-This runs down the fore part of the arm to be lost in the flexors of the wrist and fingers.

357. The articular, which runs almost round the top of the os humeri, and supplies the extensors and retractors of the arm, and elevators of the humerus.

358. To these may be added, the subscapularis which gives nerves to the muscles of the scapula; descending upon the fore part of the spine of that bone, it is lost among the muscles that lie upon its dorsum.

359. The twelve dorsal nerves of each side as soon as they escape from between the vertebræ send a branch forward to join them all; and they soon likewise give branches backwards to the muscles that raise the trunk of the body, ther principal trunk being extended outwards to come at the furrow in the lower edge of each rib, in which they run towards the anterior part of the chest, between the internal and external intercostal muscles, giving off branches in their course to the muscles and ligaments of the thorax.

360. The first dorsal, it has already been said, contributes to form the brachial nerves; and it is further particular in this circumstance that the