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 



