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PRINCIPLES OF ANIMAL BIOLOGY 



These regions as a rule merge imperceptibly into each other, yet each 

 shows certain characteristic structural features and each occupies a 

 certain portion of the intestine. The duodenum receives the secretions 

 of two large digestive glands, the liver and the pancreas. In the frog 

 the secretions of these two glands are discharged through the common 



int 



Fig. 82. — Digestive and nervous systems of a triclad turbellarian. y, ganglionic mass; int, 

 intestine; n, nerve; M. pharynx. {After Lang.) 



bile duct into the middle region of the duodenum. A reservoir, the gall 

 bladder, attached to the liver and connected with the bile-duct, serves as 

 a storage place for the bile, one of the secretions of the liver. The small 

 intestine is connected at its posterior end with the large intestine which in 

 the frog is subdivided into two portions, namely, the rectum and the 

 cloaca. The term cloaca is used to designate that portion of the large 



