MAMMALIA. 681 



Numerous exceptions, of course, occur to the above summary ; 

 but it would be useless to notice them in a survey so general as 

 the present. 



Even where no caecum exists, the separation between the large 

 and small intestines is generally indicated by a valve (ileo-cotic) 

 formed by the lining membrane of the bowel : this, for example, 

 is the case in the Sloths and Armadillos. 



(771.) In all the Mammalia that possess a caecum, this organ 

 appears to be a prolongation of the colon beyond the point at 

 which the small intestine enters its cavity. The caecum thus 

 formed varies materially, both as relates to its size, shape, and 

 structure : in animals that live upon vegetables, and even in some 

 that are omnivorous, it is generally very large, gathered into sac- 

 culi, and often distinctly glandular ; but in such as live upon flesh 

 it is always small, and its cavity smooth, resembling a small intes- 

 tine. 



(772.) The assistant chylopoietic viscera, namely, the liver, 

 the pancreas, and the spleen, are constructed upon the same prin- 

 ciples as in the human subject, and, except in a few minor circum- 

 stances, offer little to arrest our particular notice. 



(773.) The liver occupies the same position as in Man, being 

 principally situated in the right hypochondrium, where it is se- 

 curely suspended by broad folds of peritonaeum connecting it to 

 the abdominal surface of the diaphragm and to the circumjacent 

 parts. It is most frequently, especially in the more active carni- 

 vorous families, divided by deep fissures into several lobes ; a dis- 

 position whereby the free movement of this part of the body is 

 evidently facilitated. The gall-bladder, when present, which is 

 not invariably the case, receives the bile indirectly through a cystic 

 duct derived from the hepatic, so that the biliary fluid, poured 

 into the duodenum through a ductus communis choledochus, is de- 

 rived either immediately from the liver, or is regurgitated from the 

 gall-bladder as occasion requires. 



The pancreas resembles the human in every particular, and its 

 secretion enters the duodenum at the same point as that of the 

 liver. 



The spleen is always attached to the stomach by a duplicature 

 of the peritonaeal lining of the abdomen, and is organized in the 

 same manner as that of Man, except in the CETACEA, where this 

 viscus is divided into several small portions quite distinct from each 

 other. 



