6Q Mammalia, Digestive Si/stefn. 



feeders : but, taking all Orders together, it is usually more 

 extended in Mammalia than in other Yertebrata. 



The presence of a Caecum and ileocaecal valve generally 

 marks off the Intestinal Canal into the two main divisions, 

 called from the difference of their calibre in Man, ' Small' and 

 * Large ' intestine, names which lose their significance in 

 many lower Orders : of these two, the Small Intestine is 

 usually the longer, and beset on the inside with Villi of 

 various size, or with elongated longitudinal folds in the place 

 of Yilli. The 'ductus communis choledochus' conveys the 

 Bile into the Duodenal segment, and, prior to opening into the 

 Intestine, is generally joined by the Pancreatic duet ; and 

 runs for a space between the muscular and mucous coats of 

 the Intestine, where a dilatation of the duet is sometimes 

 found. The Ccecum may be small and conical, large, or 

 sacculated, and occasionally, though very rarely, double. 

 The presence and size of the Caecum varies directly with 

 the nature of the food, being either absent or small in 

 flesh feeders, and highly developed in vegetable feeders. 

 Further, it would appear, from the Rodentia, that the Caecum 

 is large, when food is but slightly nutritious and little 

 varied ; while it is small when nutritious food is readily 

 obtainable. A Veroniform appendix to the Caocum is most 

 exceptional. 



The clusters of Peyer's glands are as a rule considerably 

 developed. 



The Mesentery is usually of greater extent than in Man : 

 a large and small Omentum are regularly present ; but the 

 great Omentum, which is said to be peculiar to Mammalia, 

 CO- existing with the diaphragm, does not always overlie the 

 same parts. Large Omental processes with accumulated fat 

 are never continued from the urinary bladder, and rarely 

 from the pelvic or other regions of the abdominal walls, as 

 they are in most Reptilia. Small processes from the serous coat 



