THE ANIMAL ORGANISM 



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part of the body cavity by a thin membrane, the mesentery, which 

 provides a pathway for blood vessels and nerves to the intestine. 

 The mesentery really consists of two thin sheets, right and left, 

 continuous at the point of insertion in the body wall with the 

 parietal peritoneum, and surrounding the intestine at the free 

 edge, where it forms the visceral peritoneum, or serous membrane. 



Fig. 11. — Rana pipiens, male; ventral half of abdominal wall and parts of 

 pectoral and pelvic girdles removed to show internal anatomy. B, bladder; C, 

 colon (large intestine); Cl, cloaca; D, duodenum; G, gall bladder; H, heart; 

 I, ileum; K, kidney; L, liver; Lu, lung; O, oviduct; S, stomach; T, testis. 



The visceral peritoneum, the mesentery, and the parietal peri- 

 toneum are therefore different parts of a continuous epithelium. 

 The lungs, liver, and pancreas have a similar relation to the 

 peritoneum. The kidneys, on the other hand, are retroperitoneal 

 — behind the peritoneum — which refers to the fact that the 

 parietal peritoneum is fastened against the ventral faces and 

 edges only of the kidneys. The dorsal surfaces of the kidneys 

 are attached directly to the body wall. The term mesentery, in 



