LIVER, THE, is the largest gland in the body; it weighs from 3 to 4 lbs., and meas lures about 12 in. from side to side, and 6 or 7 in. from its anterior to its posterior border. It is situated in the right hypochondriac rerrion, and reaches over to the left; being thick and indented behind, where it crosses the convex bodies of the vertebrte; •convex on its upper surface, where it lies in the concavity of the diaphragm; and con .cave below, where it rests against the stomach, colon, and right kidney. This lower surface presents a fissure dividing the organ into a right and a left lobe.
The liver is retained in its position by five ligaments. Besides the right and left lobe, there are three smaller lobes. The great bulk of the organ is, however, made up of the right lobe, which is six thnes as large as the left.
The vessels of the liver are the hepatic artery, which comes off from the cceliac axls (q.v.), and supplies the organ with nutrient blood; the portal vein, which conveys to the liver the venous blood of the intestines, spleen, and stomach, and from which (after the vessel has ramified like an artery) the bile is secreted;* the hepatic veins, which convey the blood from the liver into the inferior veua cava; the hepatic duct, which carries off the bile from the liver; and the lymphatics.
The liver, both on its surface and internally, is of a dark reddish tint, which is so well known that the term liver-colored is universally recorrnized. The substance of the ,organ is composed of lobules held together by extremel;fine areolar tissue, and rarnifi ,cations of the minute branches of the various hepatic vessels. Each lobule is composed of a mass of hepatic cells, of a plexus of biliary ducts, of a portal plexds (from the con tents of which the cells obtain the biliary matters that are found in their interior), of a branch of the hepatic vein, and of minute arteries. The exact mode in which the bile formed in the cells makes its way into the origin of the ducts, is not known with cer tainty. The numberless minute ducts gradually run into one another, until, as they
emerge from the lower surface of the liver, they are reduced to two large trunks, which soon unite to form the hepatic duct. Into the hepatic duct, the cystic duct from the neck of the gall-bladder (presently to be described) enters, and the two combine to form the common duct (ductus eommunis eltoledochus), which opens into the duodenum (see DIGESTION). This common excretory duct of the liver and zall-bladder is about 3 in. in length, and of the diameter of a goose-quill.
The cheinical composition of the liver has been studied by Dr. Beale, who finds that the organ in health contains 68.6 per cent of water, and 31.4 per cent of solid constitu ents—of which 3.8 are fat, 4.7 albumen, while the rest is made up of vessels, salts, and extractive matters. (In the diseased condition known as fatty degeneration of the liver —which, by the way, is artificially induced in the geese which contribute to the forma tion of Strasburg pie, or pate de fois gras—the fat is enormously increased; in one remark able case analyzed by Dr. Beale, it amounted to 65.2 per cent of the whole weight of the organ.) Sugar, varying in amount from 1 to 2 per cent, is also found; and inosite, uric acid. sarcine, xanthine, and leueine usually occur in traces.
The gall-bladder may be regarded as a divertieulum or offshoot from the hepatic duct. It has somewhat the shape of a pear, and lies in a depression on the under surface of the liver. Its use seems to be to serve as a reservoir for the accumulation of the bile, when its flow into the intestine is interrupted, as it is always found full after a long fast, and empty when digestion is going on. That the gall-bladder is not an essential appendix to the liver, is shown by 'the fact that it is absent in many genera of mammals. Thus, it is present in the ox, sheep, and goat, but absent in the horse and many other herb ivore.