166 ELEMENTARY BIOLOGY. [XIII. 



on the right side of the abdominal cavity, being held in its 

 place by a mesenteric fold of the peritoneum. From the 

 comparatively narrow neck of the packet, the small intestine 

 proceeds backwards in the middle line and opens into the 

 anterior end of the dilated large intestine or colon and rectum. 



The inner wall of the stomach is raised up into a number 

 of strong longitudinal folds which project into its cavity and 

 give it a stellate appearance in transverse section. Much 

 more delicate continuations of these folds are continued into 

 the small intestine and are there joined by transverse folds. 



The opening of the ileum into the colon is valvular, its 

 edges projecting backwards into the cavity of the colon. 

 On the dorsal aspect, this presents a slight forward dila- 

 tation, which may be regarded as a rudiment of a caecum. 



The liver is very large, and is divided into two lobes 

 united by a mere bridge, dorsally and anteriorly. The 

 left lobe is further subdivided into two. The gall bladder 

 is attached to the posterior and dorsal face of the right lobe. 

 The biliary duct opens into the duodenum, at some distance 

 behind the pylorus, and its termination is embraced by the 

 base of the slender pancreas. 



The rounded spleen lies in the mesentery, projecting 

 more to the left than to the right side, just above the point 

 at which the duodenum passes into the ileum. 



The apparatus of circulation in the Frog consists of the 

 blood and lymph vessels and their contents. 



The lymph is a colourless fluid containing colourless 

 nucleated corpuscles which exhibit amoeboid movements : 

 it is contained partly in large spaces immediately beneath 

 the integument ; in the pleuroperitoneal cavity and pro- 

 bably in the other serous cavities ; and, partly, in capillaries 

 and larger trunks which are interlaced with and accompany 

 the blood-vessels. The largest of the trunks is the great 



