1896.) INTESTINAL TRACT OF BIRDS. 137 
upon Chauna’, LIamthus able to display more clearly the relations 
of the individual cases to each other and to what I take to be the 
primitive type, and to show the mesentery and the intestinal veins. 
The intestinal tract was removed from the body-cavity after section 
of the esophagus and of the rectum above the cloaca. The 
stomach was placed to the right with its ventral side uppermost, 
and the loops of the intestine were folded outward. ‘The con- 
dition of the material made it impossible to inject the vessels in 
enough cases to serve for comparison; but copious washing and 
the passage of a jet of water through the canal oxygenated the 
clotted blood in the veins and made it possible to trace their 
course. Where I was able to trace them, I found that the 
arteries followed the veins closely ; but it is only the veins that I 
describe here. 
In the simplest possible condition the intestine would run a 
straight course from the stomach to the cloaca, suspended to the 
dorsal wall of the body-cavity by a fold of mesentery. The 
intestine grows longer than the length of the body-cavity, and, 
in consequence, is thrown into a series of folds. The first of 
these, usually a single distinct loop, contains the pancreas ; then 
follows a more irregularly folded portion, the mesentery of which 
is an arc of a circle, with its diameter attached to the dorsal body- 
wall, and the median point of its circumference stretching toward 
the ventral body-wall in the region where the yolk-sac was attached. 
The rectum is a portion of the gut which usnally retains the 
primitive straight condition. In fig. 1, which I drew from a dis- 
Fig. 1. 
Alligator mississipiensis; intestinal tract, showing a simple condition. 
1 “On the Anatomy of Chawna chavaria,” P. Z. 8. 1895, pp. 350-358, 
