124 



COMPARATIVE ZOOLOGY. 



in the wall of the stomach ; in Mollusks, by a cluster of 

 sacs, or follicles, forming a loose compound gland. In 

 Vertebrates, a true liver, the largest gland in the body, 

 is well defined, and composed of a multitude of lob- 

 ules (which give it a granular appearance) arranged on 

 the capillary veins, like grapes on a stem, and contain- 

 ing nucleated secreting cells. It is of variable shape, 

 but usually two, three, or five lobed, and is centrally 

 situated in Mammals, just below the diaphragm. In 

 most Vertebrates, there is an appendage to the liver, 

 called the gall-bladder, which is simply a reservoir for 

 the bile. 



The so-called liver of Invertebrates is more like the 



FIG. 92. Liver of the Dog, F, F; D, duodenum and intestines; P, pancreas; r, 

 spleen ; e, stomach , /, rectum ; R, right kidney ; B, gall-bladder ; ch, cystic 

 duct; P, lobe of liver dissected to show distribution of portal vein, VP, and 

 hepatic vein, vh; d, diaphragm; VC, vena cava; C, heart. 



