The Digestive System 189 
tissue layers and not to any increase in thickness 
of the mucous membrane. In the large intestine 
the mucosa varies in thickness in the animals of 
different size as do the other layers of the wall. 
The glandular character of the lining of the large 
intestine seems to indicate that his region of the 
intestine must have some digestive or absorptive 
function and that it does not act merely as a re- 
ceptacle for fecal matter; this makes it all the more 
strange that there should not be some change pro- 
duced in its structure by five or six months of 
feeding or of fasting. 
Summary. The material used in this investiga- 
tion was taken from young animals at the end of 
a feeding period of about five months, and towards 
the end of the hibernating period after fasting for 
four or five months. 
The regions of the enteron that were studied were 
as follows: the tip and base of the tongue; the an- 
terior and posterior regions of the roof of the 
mouth; the anterior and posterior regions of the 
oesophagus; the cardiac, fundic, and pyloric regions 
of the stomach; the anterior, middle, and posterior 
regions of the small intestine; the anterior and pos- 
terior regions of the large intestine. Since the work 
was started at the end of the hibernating period, 
the tissues of that period were studied and drawn 
first. 
The only difference between the structure of the 
tip of the tongue during hibernation and during 
