COMPARATIVE ZOOLOGY. 
124 
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; F, lobe of liver dissected to show distribution of portal vein, VP, and 
hepatic vein, vh; d, diaphragm; VC, vena cava; C, heart. 
