XIII.] THE FKOG. 197 



through the cloaca, into the rectum : uncoil the 

 intestine and spread out the mesentery, so far as 

 is possible without cutting the latter. 



a. The spleen: a small red body lying in the 

 mesentery, near its attachment to the back 

 of the abdomen. 



/3. The stomach: an elongated sac on the left 

 side of the abdominal cavity: the narrower tube 

 (oesophagus) opening into its anterior end. 



7. The intestine: its length and varying diame- 

 ter; especially the great width of its rectal 

 portion : its posterior termination in the cloaca. 



& The pancreas: a pale-coloured compact mass 

 lying in the mesentery near the commencement 

 of the intestine. 



e. The mesentery : its width ; mode of attach- 

 ment to the intestine ; the blood-vessels running 

 in it. 



b. Divide the oesophagus close to the stomach and 

 the rectum near the cloaca : remove all the portion 

 of alimentary canal between these two points,, 

 cutting through the mesentery. 



a. Pass a probe up the oesophagus into the mouth. 



/3. Open the upper end of the intestine and snip 

 off a bit of its internal layer (mucous membrane) 

 and mount in normal saline solution: examine 

 with -J- obj.; on the fragment will be found 

 minute prominences (representing the villi of 

 the higher animals) covered by a closely-set 

 layer of cells (epithelium}* 



