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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 cecum. 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 cesophagus until it reaches. 
above the posterior lobes of the liver, at which point it takes a sharp 
turn to the right under the cesophagus. 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 surfice 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 cesophagus 
and the hepatic veins, and over these latter the peritoneal membrane 
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 esophagus 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. 
