540 
BYRON ROBINSON. 
I 
J 
The squirrel’s (rodent’s) peritoneum is very thin and al¬ 
most transparent. It is very luxuriant and abundant. Ex¬ 
cessive long folds exist. The great omentum is large enough 
to reach into the pelvis, but is not so large as that of the car- j 
nivora (cat and dog). The relation of the great omentum 
with the transverse colon and the relation of the ascending r 
colon (with its loops) with the anterior face of the meso-duo- 
denum is distinctly that of displacement, readjustment or ap¬ 
propriation of peritoneum. But the relation of the meso- 
duodenum (of the last ascending part) with the descending 
colon is difficult to interpret. Whether the two double folds 
have blended, coalesced, or readjusted themselves will require 
further study to decide. 
How susceptible the rodentia are to peritonitis I have no 
means at present of knowing. The vigorous and extensive g; 
twixt and rotation of the stomach in rodents is remarkable. 
I found no evidence of residual peritonitis in the squirrel, as 
in man. 
The gopher (rodent) is an animal belonging to the same ; 
genera as the squirrel. Its visceral serous membrane differs 
from the squirrel in that the gopher has only one (double) 
colonic loop in the ascending colon. The double colonic 
loops I have found in solipeds (horse). They are fed by one 
artery and held in relation by one narrow mesentery. No 
doubt the similar double colonic loops in man are reversions 
(atavism) to solipeds (horse) or rodents (squirrel). i 
The difference between the peritoneum of man and squir- i 
rel (rodents) is not very great. The axial rotation in the 
squirrel’s navel loop is not quite so complete as in that of man. 
In another sense it is more complete, for all herbivora possess j 
a well-developed peritoneum and viscera, for the nature of : 
their food evolved an advanced digestive apparatus. The 
squirrel has a long, free duodenum attached to a free, long 
meso-duodenum. Both surfaces of the meso-duodenum are 
faced by shining pavement endo-thelium, which character¬ 
izes the peritoneal surface. In man the shining pavement 
endo-thelium is displaced from both sides of the meso-duode¬ 
num, leaving only the real neuro-vascular visceral pedicle. 
