'34 



THE FROG 



The liver-cells are glandular and secrete the bile, which, 

 as it is formed, drips into the bile-passages and passes into 

 the hepatic ducts, thence making its way either directly into 

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

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

 a complex network of capillaries (^/), arising partly from 

 the hepatic artery, partly from 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. 



FIG. 42. A, small portion or a section 01 the frog's pancreas ; B, diagram showing 



the connection between the lobules and ducts. 

 c. connective-tissue covering the lobules ; d. duct ; /. lobules ; nil. nuclei. ]&fK 



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

 which is to manufacture a substance 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 lobules (/), each 

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



