THE LI\ 1:1; 



407 



phragm (septum transversum) and of the intervening ventral moentery 

 throughout which the entodermal tubules ramify, and in part (the retic- 

 ulum) from endothelium of the original venous sinusoids (Mall). 



The liver is dependent for its structural characteristics upon the 

 peculiar disposition of the connective tissue of Glisson's capsule, as also 

 of the blood-vessels whose branches it contains; for by these tissues the 

 substance of the liver is ex- 

 tensively subdivided into mi- 

 nute collections of hepatic 

 cells, each group forming an 

 anatomic unit, the lir/xi/ii- 

 lobule, which in addition to 

 the hepatic cells contains a 

 connective tissue reticulum 

 and the smaller blood-vessels 

 and secretory capillaries (bile 

 canaliculi ) . 



The hepatic lobules are 

 of cylindrical shape, about 2 

 millimeters in length and 1 

 millimeter in diameter (Bai- 

 ley). In transverse section 

 they present a polygonal 

 (hexagonal or pentagonal) 

 outline. In the dog they are 

 short polyhedra about 0.7 



millimeter high, and 0.7 millimeter in diameter; the entire liver con- 

 taining 480,000 (Mall, Amer. Jour. Anat,, 5, 3, I'HHI). They are anal- 

 ogous to the lobules of compound tuhulo-acinar glands, inasmuch as they 

 contain the secreting parenchyma of the organ, but are very dilTerent 

 from the latter in the arrangement of the secreting cells which, in the 

 human liver, do not present either a tubular or acinar structure, but 

 form solid cell columns. Thus in the human liver the tubular character 

 of the gland is scarcely apparent, yet in the liver of many o!' tin- lower 

 animals, notably in that of the turtle and frog, the cells form typical 

 tubules within the indistinct hepatic lobules. 



The bile formed by the liver cells is conveyed to the duodenum by 

 an excretory system, beginning with innumerable interlobular bile ducts 

 which receive the intralobular secretory capillaries, and, leaving the 

 lobule from all its sides, find their way through the interlobular con- 



FIG. 380. FROM A SECTION OF THE TURTLE'S 

 LIVER, SHOWING THE TUBULAR ARRANGE- 

 MENT OF THE PARENCHYMA. 



a, blood capillary, partially filled with clotted 

 blood; b, vascular endothelium; c, darkened 

 central portions of the hepatic cells; d, periph- 

 eral portion of the hepatic cells. Osmium 

 tetroxid; carmin. X 400. (After Shore and 

 Jones.) 



