443 ANATOMY OF VERTEBRATES. 



widely into the left end of the stomach, leaving no blind sac 

 there : the pyloric end is bent acutely on the rest of the cavity : 

 the pylorus is very small and is defended above by a valvular 

 prominence, giving the opening a crescentic form ; the diameter of 

 the pylorus is % an inch, while that of the cardia is 1^ inch. The 

 duodenum descends abruptly from the pylorus, and is connected 

 by a continuation of peritoneum with the pyloric end of the 

 stomach. It is contracted at its origin, but soon dilates, and a 

 sacculus is formed between its muscular and mucous coats for 

 the reception of the biliary and pancreatic secretions, which after- 

 wards are conducted through a narrow passage into the intestine. 

 Having descended as far as the right kidney, the duodenum turns 

 to the left in the usual manner, but has a complete investment of 

 peritoneum through its whole course: at the left side of the 

 abdomen it carries forward this process of peritoneum, which 

 forms the mesentery in the usual manner. The small intes- 

 tines do not exceed 1^ inch in circumference, but their defi- 

 ciency in this part of their dimension is compensated by their 

 great length. The large intestines commence by a short round 

 caecum, which, in two instances, was situated close to the pyloric 

 end of the stomach : the greatest circumference of the colon 

 was 4 inches, The Walrus has a similar caecum. The interior 

 of the stomach is smooth and without rugae ; the intestines have 

 the same character. In a Seal measuring 3 feet from the snout 

 to the end of the hind flippers, the small intestines were 40 

 feet long, the large intestines 2 feet, with a caecum of nearly 

 one inch in length. The agminate glands run in long narrow 

 strips. 



§ 332. Alimentary canal of Br uta. — After exceptional instances 

 in the Marsupial (Macropus) and Quadrumanous (Semnopithecus) 

 orders, we now begin to find complex conditions of the gastric organ 

 to predominate ; the main characteristic of which in the present 

 order is, that, when a laminate epithelium covers the lining 

 membrane so thickly as to be comparable with cuticle, its most 

 constant position is at the pyloric division of the stomach. There 

 are, however, gradations, and the Armadillos retain most of the 

 preceding more simple conditions of the alimentary tube. In 

 Dasypus peba 1 the oesophagus, after the course of an inch in the 

 abdomen, terminates in a stomach of a subglobular form about 

 1^ inch from the left end : its epithelial lining ends at the cardia. 

 The lining membrane of the stomach is villous, becoming smoother 

 toward the pylorus ; to that part a few longitudinal rugae at the 



1 cxxvn". p. 142, 



