chap, iv.] LIVER OF VERTEBRATES. 175 



bladder is absent, though the ducts may be enlarged 

 at their extremity; sometimes (hippopotamus) it is 

 present or absent, and, in the lemurs, it may be seen 

 on the convex aspect of the liver. Sometimes the 

 segments of the liver are greatly subdivided, and there 

 are considerable differences in the depth of the fissures; 

 thus, in the porpoises, the two segments are subequal 

 and no further divided, while in the seal there are a 

 number of minute notches. 



The liver is often adapted to the form of the body 

 of its possessor, being elongated in elongated, truncated 

 in shorter forms ; in the lower Vertebrates it largely 

 retains its primitive bilobate character. The ducts by 

 which its secretion passes into the intestine vary con- 

 siderably in number and arrangement, and even closely 

 allied forms may or may not be provided with the 

 reservoir which is known as the gall bladder. 



In Vertebrates with " hot blood " the bulk of the 

 liver is, in proportion to the size of the animal, less 

 than in the so-called cold-blooded orders ; this, no 

 doubt, is to be associated with the greater demand 

 which is made by the former on the store of fat which 

 accumulates in the liver, and which is more rapidly 

 used up by them than by those animals in which 

 oxydation is less extensive. The observations that 

 have been as yet made on the " glycogenic " function 

 of the liver have been directed rather to a study of 

 the mode of production of this starchy compound 

 than to the differences which obtain in different groups 

 of Vertebrates. 



A special outgrowth of the wall of the intestine 

 gives rise in most Vertebrates to an important diges- 

 tive or ferment-producing organ, the pancreas. It 

 is ordinarily connected with the duodenal region of 

 the intestine, into which its duct often directly opens ; 

 in other cases, as in the frog, the duct opens into the 

 bile duct. The details of the comparative physiology 



