124 



COMPARATIVE ZOOLOGY. 



in the wall of tiie 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, tiiree, 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-iladder, which is simply a reservoir for 

 the bile. 



The so-called liver of Invertebrates is more like the 



Fio. 92.— Liver of the Dog, F, Fj D, duodenum and intestines: P, pnncieas; r, 

 spleen; e, stomach, /, lectnm; R, right kidney; B, gall-blndder; ch, cystic 

 duct; F, lobe of liver dissected to show distribntion of portal vein, VP, and 

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



