LIVER (AS. lifer, 011G. libara, lebara, Ger. Leber; probably connected ultimately with Lat. jecur, Gk. -Tirap, lu•par, Arm. ?card, Skt. yak•t, liver). The largest gland in the body; it weighs from 3 to 4 pounds, and measures about 12 inches , from side to side, and 6 or 7 inches from its an terior to its Posterior border. It is situated in the right hypochondriac region, and reaches over to the left. it is thick and indented behind, where it crosses the convex bodies of the ver feline, convex on its upper surface, where it lies in the concavity of the diaphragm; and concave 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 times as large as the left.
The vessels of the liver are the hepatic artery, a branch of the coeliac axis (see AORTA), which supplies the organ with nutrient blood; the por tal vein, which conveys to the liver the venous blood of the intestines, spleen, and stomach; the hepatic veins, which convey the blood from the liver into the inferior versa eava; the hepatic duet, 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. The substance of the organ is composed of lobules held together by extremely fine areolar tissue, and ramifications of the minute branches of the various hepatic vessels. Each lobule is composed of a mass of hepatic cells, of a plexus of biliary duets, of a portal plexus (from the contents of which the cells obtain the biliary matters that are fonnd 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 duets is not known. 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 duet. Into the hepatic duct, the cystic duet from the neck of the gall bladder (presently to he described) enters, and the two combine to form the common duet (due tus communis choledoclivs), which opens into the duodenum. ( See DIGESTION, ORGANS AND PROCESS OF.) This common excretory duet of the liver and gall-bladder is about 3 inches in length, and of the diameter of a goose-quill.
The chemical composition of the liver in health is as follows: 68.6 per cent, of water, and
31.4 per cent. of solid constituents—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 degenera tion of the liver, the fat is enormously increased.) Sugar, varying in amount from I 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 divertic alum, or offshoot from the hepatic duet. It has somewhat the shape of a pear. and lies in a de pression on the under surface of the liver. Its use seems to be to serve as a reservoir for the deuce that the blood itself is changed by its means, in such a way as to show that this possesses an assimilating as well as a & paroling action. That the liver possesses an assimilating power on albuminous substa•es is shown by the experiments of Claude Bernard, who found that, if a solution of egg-albumen be injected into any part of the systemic circulation, albumen speedily appears (like other soluble substances which are foreign to the body) in the urine, and is eliminated as an extraneous matter; but if it be injected into the portal vein, it does not ap pear in the urine, but becomes a normal constit uent of the blood (blood-albumen), through the agency of the liver. Further, it appears from Bernard's researches that fatty matters are elab orated in the liver—the blood of the hepatic veins, which leaves the liver, containing con siderably more fat than that of the portal vein, which enters it. Sonic of this fat is doubtless burned off in the lungs; but if a de ficient supply should be introduced by the lac teals, some of it would doubtless be applied to the formative processes. • Lastly. during the last three days of incubation of the chick, the liver is made bright yellow by the absorption of the yolk, which enters the branches of the portal vein, and is then converted partly into blood eorpusctcs, which enter the circulation, and part ly into bile, which is discharged into the intes tine. Hence, there is distinct evidence, from several points of view, that the liver is an assimilating organ. The depurating action of this organ is exhibited in the secretion of bile (q.v.), by which the hydro-earbonaecous portion of the effete matters of the blood is removed, just as the nitrogenous portion is eliminated by the kidneys. The use of the bile in the digestive process is sufficiently explained in the article