SECRETION. 



403 



THE LIVER. 



The liver is a large gland situated in the upper and right side 

 of the abdominal cavity, where it is held in position largely by liga- 

 ments formed by reduplications of the peritoneal investment. In 

 the adult it weighs, freed of blood, from 1300 to 1700 grams. The 

 liver is connected with the duodenal portion ot the intestine by the 

 hepatic duct, /jf It receives blood both from the hepatic artery and from 

 the portal vein, and in this respect differs from all other glands in 

 the body. The epithelial structures of the liver are inclosed by a 

 firm fibrous membrane, known as Glisson's capsule. At the trans- 

 verse fissure it invests and follows tne blood-vessels, which there 

 enter, in all their ramifications through the gland. 



Structure of the Liver. The liver is composed of an enor- 

 mous number of 

 small masses, rounded, 

 ovoid, or polygonal 

 in shape, called lo- 

 bules, measuring 

 about one millimeter 

 in diameter and sepa- 

 rated from one an- 

 other by a narrow 

 space in which are 

 to be found blood- 

 vessels, lymphatics, 

 hepatic ducts, sup- 

 ported by connective 

 tissue. In the pig this 

 space and its con- 

 tained elements is 

 quite distinct, sharply 

 marking out the 

 border of th lobule (Fig. 184). This is not so apparent in man. 

 Each lobule is made up of irregular or polygonal shaped cells measur- 

 ing about 30 to 40 micromillimeters in diameter. These cells are 

 arranged in a radial manner from the center to the circumference of 

 the lobule (Fig. 185). Each cell possesses one and at times two nuclei. 

 There is no evidence for the existence of a distinct cell-wall. The 

 cell protoplasm frequently contains globules of fat, granules of a 

 proteid nature, granules of glycogen, pigment material, etc. The 

 appearance presented by the cell will vary considerably, according to 

 the time it is observed. Thus there may be a complete absence of 

 these constituents, when the cell may present a series of vacuoles 

 separated by bands of protoplasm. The cells are the secreting 



FIG. 184. SECTION or LIVER OF PIG, SHOWING VERY 

 DIAGRAMMATIC ALLY THE LOBULES, a. Interlobu- 

 lar connective tissue, b, c. Branches of portal vein 

 and of hepatic artery, d. Bile-ducts. e. Intra- 

 lobular vein. (Piersol.} 



