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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 gallbladder , which is simply a reservoir for 
the bile. 
The so-called liver of Invertebrates is more like the 
Pig. 92,—-Liver of the Dog, F, F; D, duodenum and intestines; P, pancreas; r, 
spleen ; c, 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; df, diaphragm; VC, vena cava; C, heart. 
