148

ANATOMY.

low the arteria caliaca from the aorta, arises the mesenteriea su\w'-rior, whose branches are distributed upon the whole of the uitesri-num jejunum and ilium, part of the colon, and sometimes onebranch upon the liver. A little lower than the superior mesentericartery arise the usiulgents, whirh are the arteries of the kidnies;and a little lower than the enrolments, anterior to the aorta, arisethe arteria - spennatica - , which are distributed to the genital partsin men. Laterally, and lower down, the aorta sends branches tothe loins, called lumbales; and one forward, to the lower part ofthe colon and the rectum, called mesenteriea inferior, be-tween the- arteria cccliaca, mesenteriea superior and inferior,and the branches of each near the intn-tines, there are large com-municant branches to convey tire blood from one to another, whenthey are either compressed bv excrements, or from any othercause. The aorta, as soon as it divides upon the loins, sends oilan artery into the pelvis upon the o> sacrum, called arteria sacra;and the branches into which the aorta divides, are called iliaca - .These again, at about the distance of two inches, divide into exter-nal and internal. The iliaca. - interna: first send oil’ the umbilicalarteries, which are obliterated in adult bodies, except at their be-ginnings, which are kept open for the collateral branches on eachside, one to the bladder, and one to the penis in men, and in wo-men to the uterus. The rest of these branches are bestowed uponthe glula’i muscles, and upper part of the thighs. The iliaca: ex-terna 1 run over the ossa pubis into the thighs ; and as they pass outof the abdomen, they send oil' branches, called epigastrica-, to thefore-part of the integuments of the abdomen, under the recti mus-cles. The epigastric r.rlerirs send each a branch into the pelvis,and through the foramina of the ossa innominata to the musclesthereabouts. As soon as tin* iliac artcrv has passed out of the ab-domen into the groin, it is called inguiiialis, and in the thigh c.rura-lis. Here it sends a large branch to the back part of the thigh;but the great trunk is continued internally between the llexors andextensors of the thigh, and passing through the insertion of the tri-ceps muscle into the ham, it is there called poplitea. It then, be-low the joint, divides into two branches, one of which is calledtibialis antica, which pa.-ses between the tibia and fibula down thefore-part of the leg, and is bestowed upon the great toe, and onebranch to the toe next to the great one, and another between thesetoes, to communicate with the tibialis postica ; which artery, soonafter it is divided from the antica, sends off the tibialis media,which is bestowed upon the muscles of the leg. The tibialis pos-lica goes to the bottom of the foot and all the lesser toes. Thetibialis antica is disposed like the cubitalis superior ; the posticalike the cuhitalis interior ; and the media 1 in each have also likeUses. These arteries are uniform in most bodies, but the lesserbranches are distributed like the branches of trees, in so differenta manner in one body from another, that it is highly probable notwo bodies are exactly alike, nor even the two sides in any onesubject.

Veins.

The Vein 's arise from the extremities of the arteries, and com-pose trunks which accompany the arteries in almost every part ofthe body, and hear the same names. The veins of the brain un-load themselves into the sinuses, and the sinuses into the internaljugulars and eervieals; and the internal jugulars ami cevvicnls intothe subclavians, which joining, make the cava descendens. Theinternal jugulars are seated near the carotid arteries, and receivethe blood from all the parts which are supplied bv the carotids,except the hairv scalp and part of fhe neck, whine veins enter intothe external jugulars, which run immediateU under the museulusqnadratus genie, often two on each side.

The Cervicai. Vein ’s descend, two through the foramina in thetransverse processes of the cervical vertebra - , and tw o through thegreat foramen of the spine, and on each side the spinal marrow.These join at the lowest vertebra vf the neck, and then empty intothe subclavians, and at the interstices of all the vertebra - commu-nicate with each other.

The Vein 's of the F.xtremitiks are more than double thenumber of the arteries, there being one placed on each side of eachartery, even to the smallest branches that we can trace, besidesthe veins which lie immediately under thy skin. Tho-e which ac-company the arteries have the same names with the arteries :(hose w hich run immediately under the skin on the hack of thehand, have no proper names ; thev run from thence to the bendof the elbow, when; the uppermost is called cephalica, the next

mediana, and the last basilica. These all communicate near thejoint of the elbow, and then send one branch which is more di-rectly from the cephalica, and bears that name until it enters thesubclavian vein. It passes immediately under the skin, in mostbodies, between the flexors and extensors of the cubjt, on the up-per side of the arm. .’Tim other branches joining, and receivingthose which accompany the arteries of the cubit, they pass withthem 1)v the artery of ihe arm into the subclavian vein. The ce-phalic vein, as it runs up the arm, is very visible in most men, butin children is rarely to he seen.

In the thorax, besides the two cava - , there is a vein calleda/.vgos. or vena sine pari. It is made up of the intercostal, phre-nic, and bronchial reins, and enters the descending cava near theauricle, as if its use was to divert the descending blood from fall-ing loo directly upon the blood in the ascending cava, and to di-rect the blood of the descending cava into the auricle.

In the abdomen, besides the cava ascendens, and other veinswhich are named like the arteries, there is one large vein, calledvena porta - . Its branches arise from all those of the caliac andtwo mesenteric arteries, except those branches of the cceliac andsuperior mesenteric, which are bestowed on the liver, anil unitingin one trunk, enter the liver. In this situation it is again distri-buted like an artery, and has its blood collected and brought intothe cava by the branches of the cava in the liver ; this vein beingmade use of instead of an artery to carry the blood to the liver,for the separation of bile. I he blood moves here considerablyslower than in the arteries, this slow circulation being probablynecessary for tlie secretion of the bile.

In the leg the veins accompany the arteries, in the same manneras in the arm, the external veins of the foot being on the upperside ; ami from them is derived one called saphena, w hirh is con-tinued on the inside of the limb through its w hole length, ami liasdilferent names given it according to the different places throughwhich it passes.

The Arteries have three coats each ; the middle one muscu-lar, and the external and internal, membranous. The \ kins aresaiii to have the same, though this is to be doubted. In the inside ofthe veins there are many valves, especially in the low er extremi-ties. These hinder anv reflux of the \fnal blood, which otherwisewould happen from the frequent actions of the muscles on the out-sides of the veins. Both the arteries and veins, as they run on theinside of the limb, or as thev appear in parts that are liable to greatdistension, as the stomach, intestines, uterus, <xc. are curved insuch a manner, as to comply with those distensions by beingmerely straightened, and without being lessened in their diameters.

Absorbent System.

The absorbent system consists of the lacteals, the lymphaticvessels, the thoracic duct, which is their common trunk, ami theconglobate glands.

1 he Lacteals begin from the intestinal tube, and can generallybe seen in anv large quadruped that is killed two or three bom'safter earing. Thev then appear tilled with a white chyle; butthev do not always contain a tluid of this colour; for, if the animalhe opened long alter a meal, they are found distended with a li-quor that is transparent and colourless like the lymph. In birdsthe ehvle is never found white, but always transparent; so thatthese vessels might, with some propriety, he called the lymphaticsof the intestines.

The Lymphatic Vessels are small pellucid lubes that cxi-t inmost parts of the human body. Their thuds are giTierally as co-lourless as water; a cirnmisiance which procured them at lirst thename of ductus aquosi, and afterwards that of va-a Ivmphatica-The course of the lymph, like that of the ch\le, is Irom the ex-treme parts of the bodv towards the centre, and many of <helvmphatie vessels lie close to the large blood-vessels. It theiefmea ligature he made on the blood-vessels <>t the extremities of aliving animal, or of one ju>t dead, that ligature, by embracingthe lymphatics, will stop the course of the lymph, which, by dis-tending the vessels, will make them visible below the ligature.All the lacteals, and most of tlw*. Umphatic icssels, open into thethoracic (hu t, which lies upon the spine, ami runs up towards theneck, where it commonly opens into the angle between the in-ternal, jugular, and subclavian veins of the left side: and thus boththe chyle and lymph are mixed with the blood. (Sec Plate Will,fig. ‘J.; If therefore a ligature be made on the thoracic duct

immediately