1 -24 



THE COCKROACH I 



structure as the oesophagus and crop ; its chitinous lining is 

 hairy, and thrown into longitudinal folds which become much 

 more prominent in the lower part of the tube. The junction of 

 the small intestine with the colon is abrupt, and a strong 

 annular fold assumes the character of a circular valve (fig. 68). 

 From the circular valve the colon extends for nearly an inch. 

 Its diameter is somewhat greater than that of the chylific 

 stomach, and uniform throughout, except for a lateral diverticu- 

 lum or ccecum, which is occasionally but not constantly present 



Fig. 68. Junction of Small Intestine with Colon. X 15. 



towards its rectal end. The fore part of the colon is thrown 

 into a loose spiral coil. A constriction divides the colon from 

 the next division of the alimentary canal, the rectum. 



The rectum is about J inch long, and is dilated in the middle 

 when distended. Six conspicuous longitudinal folds project 

 into the lumen of the tube. These folds are characterised by 

 an unusual development of the epithelium, which is altogether 

 wanting in the intermediate spaces, where the chitinous lining 

 blends with the basement-membrane, both being thrown into 



