DIGESTIVE ORGANS 21 



Turn the liver for wards, and note the stomach lying beneath its 

 left lobe. Pass the handle of a seeker through the mouth and 

 down tJie oesophagus into the stomach. 



[//* the specimen be a female, remove tie ovaries and oviducts 

 completely, taking care not to damage the alimentary canal ] 



1. The Alimentary Canal. 



a. The oesophagus is a short wide tube leading from the 



buccal cavity to the stomach. 



b. The stomach is a wide tubular sac about an inch and a 



half in length : it is narrower behind, and separated 

 from the duodenum by a distinct pyloric constriction. 



Cut open the stomach longitudinally along its left side, and 

 wash out its contents : note the handle of the seeker already in- 

 serted through the mouth; also the longitudinal folds of the 

 mucous membrane lining the stomach, which increase the extent 

 of its surface. 



c. The duodenum is the first part of the intestine, rather 



more than an inch in length : beyond the pylorus it is 

 bent back so as to lie parallel to the stomach. At its 

 further end it is continuous with the small intestine. 



d. The small intestine is a slender convoluted tube about 



four and a half inches long, opening at its distal end 

 by a small orifice into the large intestine. 



e. The large intestine is a short straight tube about an 



inch and a quarter long : it is very much wider than 

 the small intestine, and opens behind to the exterior 

 at the cloacal aperture. 



f. The cloaca in the frog is continuous with the large 



intestine, into it open the renal and genital ducts 

 as well as the bladder : it will be described more 

 fully when considering the urinary and reproductive 

 organs. (See Chap. VIII.) 



2. The Liver. 



The liver is a large reddish-brown organ, divided into right 

 and left lobes, connected together by a narrow bridge of liver- 

 tissue. Of the two lobes the left one is much the larger, and 

 is again subdivided into two. 



