side of the body, immediately below the diaphragm, with which its upper surface is in contact, while its lower sur face touches the intestines and the right kidney.

FIG. 34-THE LIVER TURNED UP AND VIEWED FROM BELOW.

a, vena cava; b, vena porta; c, bile duct; d, hepatic artery; 7, gallbladder. The termination of the hepatic vein in the vena cava is not seen, being covered by the piece of the vena cava.

The liver is invested by a coat of peritoneum, which, keeps it in place. It is flattened from above downwards, and convex and smooth above, where it fits into the concavity of the lower surface of the diaphragm. Flat and irregular below (Fig. 34), it is thick behind, but ends in a thin edge in front.

Viewed from below, as in Fig. 34, the inferior vena cava, a, is seen to traverse a notch in the hinder edge of the liver as it passes from the abdomen to the thorax. At b the trunk of the vena porte is observed dividing into the chief branches which enter into, and ramify through, the substance of the organ. At d, the hepatic artery, coming almost directly from the aorta, similarly divides, enters the liver, and ramifies through it; while at c is the single trunk of the duct, called the hepatic duct, which conveys away the bile brought to it by its right and left branches from the liver. Opening into the hepatic duct is seen the duct of a large oval sac, 7, the gall-bladder. The duct is smaller than the artery, and the artery than the portal vein.

If the branches of the artery, the portal vein, and the bile duct be traced into the substance of the liver, they will be found to accompany one another, and to branch out and subdivide, becoming smaller and smaller. At

A section of part of the liver to show H. V., a branch of the hepatic vein, with L., the lobules or acini of the liver, seated upon its walls, and sending their intralobular veins into it.

length the portal vein and hepatic artery (Fig. 37, V.P.) will be found to end in the capillaries, which traverse, like a network, the substance of the smallest obvious subdivisions of the liver substance-polygonal masses of onetenth of an inch in diameter, or less, which are termed the lobules. Every lobule is seated by its base upon one of the ramifications of a great vein-the hepatic veinand the blood of the capillaries of the lobule is poured

into that vein by a minute veinlet, called intralobular (Fig. 37, H.V.), which traverses the centre of the lobule, and pierces its base. Thus the venous blood of the portal vein and the arterial blood of the hepatic artery reach the surfaces of the lobules by the ultimate ramifications of that vein and artery, become mixed in the capillaries of each lobule, and are carried off by its intralobular veinlet, which pours its contents into one of the ramifications of the hepatic vein. These ramifications, joining together, form larger and larger trunks, which at length reach the hinder margin of the liver, and finally open into the vena cava inferior, where it passes upwards in contact with that part of the organ.

Thus the blood with which the liver is supplied is a mixture of arterial and venous blood; the former brought

a, ultimate branches of the hepatic duct; b, liver cells.

by the hepatic artery directly from the aorta, the latter by the portal vein from the capillaries of the stomach, intestines, pancreas, and spleen.

What ultimately becomes of the ramifications of the hepatic duct is not certainly known. Lined by an epithelium, which is continuous with that of the main duct, and thence with that of the intestines, into which the main duct opens, they may be traced to the very surface of the lobules. Their ultimate ramifications are not yet thoroughly determined: but recent investigations

A. Section of partially injected liver magnified. The artificial white line is introduced to mark the limits of a lobule. V.P. Branches of portal vein breaking up into capillaries, which run towards the centre of the lobule, and join H. V., the intralobular branch of the hepatic vein. The

tend to show that they communicate with ininute passages left between the hepatic cells, and traversing the lobule in the intervals left by the capillaries (Fig. 37, B.). However this may be, any fluid separated from the blood by the lobules must really find its way into them.

In the lobules themselves all the meshes of the bloodvessels are occupied by the liver cells. These are manysided, minute bodies, each about 100th of an inch in diameter, possessing a nucleus in its interior, and frequently having larger and smaller granules of fatty matter distributed through its substance (Fig. 37, a). It is in the liver cells that the active powers of the liver are supposed to reside.

21. The nature of these active powers, so far as the liver is a source of loss to the blood which traverses it, is determined by ascertaining

a. The character of that fluid, the bile, which incessantly flows down the biliary duct, and which, if digestion is not going on, and the passage into the intestine is closed, flows back into and fills the gall-bladder. b. The difference between the blood which enters the liver and that which leaves it.

22. a. The total quantity of bile secreted in the twentyfour hours varies, but probably amounts to not less than from two to three pounds. It is a golden yellow, slightly alkaline, fluid, of extremely bitter taste, consisting of water with from 17 per cent. to half that quantity, of solid matter in solution. The solids consist in the first place of a somewhat complex substance which may be separated by crystallization, and has been called bilin. It is in reality a mixture of two acids, in combination with soda, one called glycocholic, and consisting of carbon, hydrogen, nitrogen, and oxygen, the other taurocholic, and containing in addition to the other elements a considerable quantity of sulphur. Besides the taurocholate and glycocholate of soda, or bile salts as they are sometimes called, the bile contains a remarkable crystalline substance, very fatty

outline of the liver cells are seen as a fine network of lines throughout the whole lobule.

B. Portion of lobule very highly magnified. a, liver cell with n, nucleus (two are often present); b, capillaries cut across; c, minute biliary passages between the cells, injected with colouring matter.