bile duct 



heart 



gall bladder 



falciform ligament 

 (ventral mesentery) 



oviduct 



gall bladde 

 pancreas. 



colonic loop 



bile duct 



anterior expansion 

 of stomocfi 



hepatic portal vein 

 ventral abdominal vein 



duodenum 



spleen (largely in right 

 wall of stomach) 



pyloric end of stomach 

 pancreas 



terminal end of 

 small intestine 



Figure 9-8. Ventral views of the viscera of /guano. A, ventral viev/ of contents of body cavity; 

 B, loop of the stomach and relationships of the pancreas; C, bile and pancreatic ducts entering gut; 

 D, large intestine with its colonic loop and mesentery— stomach rotated to observer's right. 



the Stomach. The Meckel's tract and first part of the large 

 intestine are not rotated, with the result that the latter comes 

 to lie below and in front of the former— rather it lies above 

 it suspended from a relatively unmodified dorsal mesentery. 

 The duodenal loop of the bird and reptile is usually at least 

 partly closed, while that of the mammal is an open arc. 



In Iguana or Tiipinambis a unique situation is observed: 

 the stomach encircles the mass of the small intestine. In 

 most tetrapods the small intestine coils behind the stomach. 



The turtle agrees with the mammal in most features includ- 

 ing rotation of the middle part of the gut; however, it lacks 

 the greater omentum (omental bursa) and the spleen lies 

 above the caecal end of the large intestine. It is possible that 

 the primitive mammal, or the mammal-like reptile, had the 

 midgut rotated, and that this condition is shared as a com- 

 mon heritage with the turtle. It is just as possible that the 

 turtle acquired this rotation independently, starting from the 

 simpler gut condition observed in the other reptiles. The 



260 . THE VISCERA 



