THE ALIMENTARY TRACT, SPLEEN, AND MESENTERIES 265 



Jacobshagen (19 14) has made a comparative study of the relief 

 pattern of the gut lining in Amphibia. He denies the presence of 

 a pyloric valve in Salamandra — a conclusion which may be justly 

 criticized. 



4. The Stomach. 



The stomach (stom.) is conical and lies almost longitudinally along 

 the left side of the body. It narrows considerably at its posterior end, 

 and there is always a well-defined constriction between this end of 

 the stomach and the duodenum. The constriction is specially notice- 

 able when the gut is full, and a slight thickening of the wall is dis- 

 cernible in longitudinal section, so that it seems impossible to avoid 

 the conclusion that this constriction is indeed the pylorus (py.)> 

 although it must be admitted that it is less perfectly formed than in 

 many animals, and it is doubtful whether the lumen is ever completely 

 closed. 



5. The Duodenum. 



The duodenum (duo.) is short and is sharply reflexed along the 

 mesial aspect of the stomach, but follows a more transverse direction 

 relative to the body than does that organ. It is indistinguishable 

 from the rest of the intestine except that it receives the pancreatic 

 and bile ducts. 



The dorsal pancreatic duct (d.p.d.), or rather the duct of the dorsal 

 pancreas, enters the proximal end of the duodenum some 2 mm. or 

 so from the pylorus. The ventral pancreatic ducts (d.p.v.), which 

 belong to the two ventral pancreata, discharge into the common bile- 

 duct which, in turn, enters the distal end of the duodenum, some 

 4—5 mm. from the dorsal pancreatic duct (see also p. 267). 



6. The Intestine. 



The intestine (int.) is a coiled tube of a regular diameter, approxi- 

 mately equal to, or slightly smaller than, that of the duodenum. Its 

 length is about one-half that of the whole gut, measured from the 

 pharynx to the cloaca. The pattern of the internal relief of the duo- 

 denum and intestine, considered as a whole, consists of a series of 

 sinuous longitudinal ridges. The ridges are thick proximally — that 

 is, at the duodenal end — but tend to become thinner and straighter 

 towards the hinder end of the gut, until they are almost knife-like. 

 If the mucous epithelium is scraped or brushed off it is seen that 

 the underlying vascular network is also raised into ridges, and that 



