XIII.] THE FROG. 197 



through the cloaca, into the rectum : uncoil thf 

 intestine and spread out the mesentery, so far as 

 is possible without cutting the latter. 



a. The spleen: a small red body lying in th( 

 mesentery, near its attachment to the bad 

 of the abdomen, 



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

 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 recta 

 portion : its posterior termination in the cloaca 



5. The pancreas: a pale-coloured compact masi 

 lying in the mesentery near the commencemen 

 of the intestine. 



6. The mesentery : its width ; mode of attach 

 ment to the intestine ; the blood-vessels runnint 

 in it. 



b. Divide the oesophagus close to the stomach an< 

 the rectum near the cloaca : remove all the portioi 

 of alimentary canal between these two points 

 cutting through the mesentery. 



a. Pass a probe up the oesophagus into the mouth 



yS. Open the upper end of the intestine and sni] 

 off a bit of its internal layer (mucous membrane 

 and mount in normal saline solution: examim 

 with ^ obj.; on the fragment will be founc 

 minute prominences (representing the villi 

 the higher animals) covered by a closely-se 

 layer of cells {epithelium)^ 



