Page:The American Cyclopædia (1879) Volume X.djvu/543

 LIVER 537 transverse fissure, the gall bladder lying be- tween it and the right lobe ; and on the right lobe, depressions corresponding to the right portion of the transverse colon, and to the right kidney and supra-renal capsule. In the carnivora and rodents, portions of the liver rudimentary in man are highly developed ; in these there are five distinct parts, a central or principal lobe, and a right and left lateral lobe, each with a lobular appendage. The liver is in great part covered with a shining peritoneal or serous envelope ; an investment of areolar tis- sue also is spread over the organ, extending into the interior, and forming thin but dense sheaths to the vessels and canals, called the capsule of Glisson. The blood vessels of the liver are the hepatic artery and veins and the vena portas ; in the foetus the maternal blood is brought to the liver by the umbilical vein ; the lymphatics are numerous, and the nervous filaments are supplied from the pneumogastric nerve and the hepatic plexus of the sympathet- ic. The proper tissue of the liver is composed of a great number of polygonal masses, about fa or T ^ of an inch in diameter, generally called lobules or acini, of a foliated appear- ance from the branching distribution of the hepatic veins in the centre of each; in the spaces left between the polygonal lobules lie the branches of the vena portse, hepatic ar- tery, and duct, each lobule giving the charac- teristic structure of the organ. The vena por- H.v. A Section of part of the Liver to show the hepatic vein (If. F.), with the lobules or acini (Z.) of the liver, seated upon its walls, and sending their intralobular veins into it. tse, which receives the venous blood from the digestive organs, divides and subdivides in the liver like an artery, till it reaches the inter- lobular spaces, forming a freely anastomosing network throughout the organ, and constitu- ting the intralobular veins; after ramifying on the capsules they enter the lobules and be- come lobular veins, their terminal branches ending in the intralobnlar or hepatic vein. The hepatic artery, a branch of the great coe- liac axis from the aorta, sends its branches to all parts of the organ, supplying the walls of Glandular Cells from the Human Liver. the vessels and ducts, and the lobules through the interlobular spaces. The lobules or acini are made up of a great number of minute glandular cells, the "liver cells;" transpa- rent rounded or polygonal bodies, y^Vo of an inch in diameter, slightly granular in tex- ture, and each one containing a round or oval nucleus and nucleolus. These cells often con- tain granules of yellow coloring matter, and one, two, or three oil globules of various sizes. An abundance of minute capillary blood ves- sels penetrate into the substance of the lobule, ramify around and among the liver cells, and thus bring the blood into intimate relation with the glandular tissue of the organ. The blood coming from the alimentary canal by the portal vein reaches the hepatic vein only after having passed through the capillary circula- tion of the liver itself ; and it is during this passage that various important changes take place having for their object partly the modi- fication of the blood itself, and partly the pro- duction of new substances in the tissue of the liver. In the first place, the blood, in passing through the liver, loses a great portion of its fibrine (a fact fully established by the obser- vations of Simon, Lehmann, Bernard, and Brown-Se"quard), so that the blood drawn from the hepatic vein always has less fibrine than that taken from the portal vein, and sometimes has so completely disappeared that the hepatic blood will not coagulate at all. What be- comes of this fibrine is not positively known ; but it is doubtless transformed into some other substance, required either for the nutrition of the liver itself, or for use in some other part of the circulation. Secondly, a kind of ani- mal sugar is formed in the substance of the liver, and this independently of any vegetable or saccharine materials taken with the food. This sugar appears first in the solid substance of the hepatic tissue, where it exists on an average, at the moment of death, in the pro- portion of at least 2| parts in 1,000. The su- gar, however, is not formed directly from tho