The liver is the largest gland in the body, its weight being on an average from 48 to 58 ounces in the adult male and 40 to 50 ounces in the female.
In its Function the liver is related to the intestinal canal and the blood. The formation of bile is probably the least of its functions, but as the bile pigment is derived from the haemoglobin, there must be a destruction or removal of effete red blood-corpuscles in the liver. A more important function is the preparation of glycogen, whatever may be the uses to which this substance is put. The liver also seems to have important relations to the free fat of the body, and under certain circumstances stores it up in its substance (see Fatty Infiltration).
The functions of the liver being thus manifold and somewhat obscure, the effects of disease on it are difficult to disentangle. Many of the diseases cause atrophy of its proper tissue, but they nearly all at the same time affect either the body as a whole or the vascular arrangements of the abdomen which are so peculiarly related to the liver.
The Circulation of the liver is very peculiar and claims special attention, because most diseases of the organ produce important effects upon it. Most of the blood comes to the liver by the Portal vein, and the proper hepatic tissue is arranged in relation to the ultimate ramifications, and they are in immediate connection with the hepatic lobules. The Hepatic lobule is a group of.hepatic cells with blood-vessels, measuring about the twentieth of an inch in diameter, and having in man a polygonal or somewhat globular shape. The interlobular vein lying outside the lobule sends capillaries into it, and these seeking the centre of the lobule open into the central or intralobular vein which is the radicle of the hepatic vein. Between the capillaries lie the hepatic cells, which are arranged in rows or cylinders radiating from the centre of the lobule like the capillaries. The stellate cells of Kupffer lie between the hepatic cells and the capillaries and seem to be intimately connected with both.
Blood is also brought to the liver by the Hepatic artery which supplies chiefly the connective tissue and walls of the blood-vessels. Its capillaries terminate in veins which open into the interlobular veins (according to Cohnheim and Litten), so that this blood also finds its way into the hepatic capillaries and on into the hepatic vein.
The Connective tissue of the liver is often described as if it formed a special covering to the portal vein, being called Glisson's capsule. It really forms a supporting stroma which holds the portal vein, the hepatic artery, and the hepatic duct, which all lie side by side. The lymphatic channels are also contained in it. In swine the connective tissue surrounds each lobule and defines it distinctly from its neighbour, but in man it stops short at the interlobular vein, and except where this vein is, the lobules at their margins merge into each other, and their capillaries are in communication. Examination of Fig. 405, p. 891, in which the lobules are demarcated by fatty infiltration, will show how they run into one another at their peripheries. Although no proper fibrillated connective tissue is present inside the lobules, yet a fine reticulum accompanies and supports the capillaries.
The circulation in the portal vein, and especially in the capillaries of the liver, must be unusually slow. The blood before it reaches the liver has passed through one set of capillaries, and here it passes through a second set; it has therefore lost very largely the force derived from the contractions of the heart. It is probably for this reason that the liver is so frequently the seat of secondary deposition as in tuberculosis, cancers, etc., and of the deposition of solid pigments. We may suppose that as the blood moves so slowly there will be time for any granular material to settle down and produce its special effects. We know that when vermilion is injected into the blood it is found largely in the liver. Similarly the pigment containing iron present in the blood in pernicious anaemia is found largely there.
The Hepatic ducts running in the connective tissue along with the portal vein and hepatic artery are lined with cylindrical epithelium. These are connected with the biliary capillaries, which originate inside the lobules and seem to be in part formed by the hepatic cells themselves, each cell having on its surface a groove which, with a corresponding groove in the cell opposed to it, forms a tube.
The liver is liable to local alterations in colour, in the form of pale anaemic areas, from the pressure of neighbouring structures, as the ribs, or distended loops of intestine. It frequently also assumes a blue colour from decomposition, especially where it is in contact with the transverse colon.
There are some curious cases in which Cavities filled with gas develop throughout the liver after death. These are due to decomposition, the agents of which have been conveyed to the liver before death. The condition may be associated with a similar appearance in the spleen, and it occurs chiefly in cases of septic wounds.
General works - Budd, Dis. of liver, 2nd ed., 1852; Murchison, Clin, lect. on dis. of liver, etc., 2nd ed., 1877; Anstie, in Beynolds' Syst. of med., iii., 1871; Habershon, Path, and treatment of some diseases of liver, 1872; Frerichs, Dis. of liver, transl. Syd. Soc, 1858-61; Charcot, Lecons sur les malad. du foie, 1877; Hanot et Gilbert, Malad. du foie, 1888.