ALIMENTARY CANAL, ETC., OF AMIURUS CATUS. 389 



termination and the commencement of the midgut. This constric- 

 tion gives rise on its inner surface to a low pyloric valve. 



The lining membrane of the pylorus is pale in contrast to the 

 color of the cardia and coecum. Its folds are at first low and broad, 

 but approaching the valve they become higher and thinner, and are 

 arranged longitudinally. 



The midgut passes forward beside the oesophagus until it reaches 

 above the posterior lobes of the liver, at .which point it takes a sharp 

 turn to the right under the oesophagus. In this transverse portion 

 it receives the pancreatic and bile ducts, after which it turns back- 

 ward to run on the right of, and on a level with, the stomach. 

 Behind, it is thrown into loops of greater or less magnitude, which 

 rarely touch one another, and may number from eight to twelve. 

 The part of the midgut in the neighbourhood of the stomach is pro- 

 vided with slightly thicker muscular walls than the posterior half. 



The outer serous coating is unpigmented. The longitudinal folds 

 on the inner surf ice are thick and high, but their continuity is not 

 distinctly marked, owing to slight transverse furrows, which give to 

 a fold the appearance of a series of low villi. 



The lumen of the midgut is separated from that of the endgut or 

 rectum by a circular valve which is of little height in the relaxed 

 specimen, but when distended by chromic acid and alcohol, and thus 

 hardened, it is broad, thin and semi-membranous, leaving a lumen of 

 small diameter in the centre. The folds of the midgut in the neigh- 

 bourhood are distinctly longitudinal and pass over into those of the 

 midgut. Its course is quite straight but for the slight downward 

 curve to terminate in the vent. 



The body cavity and the pericardial chamber are separated by a par- 

 tition formed of the partially apposited pericardial and peritoneal mem- 

 branes which contain between them a quantity of aponeurotic fibres. 

 This aponeurotic wall, as it is called, is perforated by the oesophagus 

 and the hepatic veins, and over these latter the peritoneal membi-ane 

 is continued to join that covering the liver forming a support for 

 that organ. From the aponeurotic wall the mesentery spreads out 

 on each side, above and backward, enclosing the duct of the air- 

 bladder between its folds. Below the oesophagus the membrane runs 

 out over the liver to form its serous coat. This fold also passes 

 down over the stomach on the commencement of the midgut when, 

 it embraces the gall-bladder, the bile and pancreatic ducts. 



