134 



THE FROG 



CHAP. 



the hepatic ducts, thence making its Nvay eitlier directl)' into 

 the intestine or into the gall-bladder (p. 70). The whole 

 liver, which is the largest gland in the Ijody, is traversed by 

 a complex network of capillaries (/>.c), supplied partly by 

 the hepatic artery, partly by the portal vein ; and, from the 

 blood thus supplied, the liver-cells obtain the materials 

 necessary to enable them to discharge their function of 

 secreting the bile. 



The liver-cells have, however, other functions, one of 

 which is to manufacture, in addition to bile, a substance 



. 42. — A, small portion of a ';ection of the frog's p,increa.s ; H, dl.agram showing 

 the connection hetween the lobttles and ducts 

 c. connective tissue covering of the gland ; d. duct ; /. lobules ; 7tH. nuclei. 



called glycogen or animal starch. This is stored up in the 

 cells in the form of minute insoluble granules, which, being 

 afterwards transformed into soluble sugar, pass into the 

 blood and so to the tissues. 



The Pancreas. — Sections of this gland (Fig. 42) show 

 it to be made up of microscopic masses or lohiiks (/), each 

 of which consists of a cluster of gland-cells enclosing a very 

 narrow central space. The cavities of adjacent lobules com- 



