294 HISTORY OF THE HUMAN BODY 



of serous membranes, applied two and two, each pair holding 

 between them the blood and absorbent vessels naturally be- 

 longing to a mesentery. The cavity of the bag is the lesser 

 peritoneal cavity of human anatomy, and its mouth, opening 

 into it behind the stomach, is the foramen cpiploicnm [foramen 

 of Winslow]. In most mammals'The bag is Twfclely open, but 

 in man the foramen is much reduced in size and the layers 

 forming the pendulous fold are fused together, and form a 

 four-layered apron that hangs below the stomach and covers 

 the intestinal folds. 



The remainder of the canal below the pylorus forms the in- 

 testine, and although this has been divided for convenience 

 into several more or less definite regions, they are for the most 

 part artificial in character. The most definite of these are 

 the cloaca of Amphibia and Sauropsida, and the large in- 

 testine of mammals [intestinum crassuni], both enlargements 

 of the posterior portion of the intestinal tract, but probably not 

 equivalent to one another; in distinction from this the re- 

 mainder is termed the small intestine [intestinum tenue"]. In 

 this latter the most definite subdivision is defined by the en- 

 trance of the bilary and pancreatic ducts ; and the space be- 

 tween the pylorus and this point is designated the duodenum. 

 This portion often forms a conspicuous loop, consisting of 

 ascending and descending limbs, which enclose the pancreas 

 between them. 



The liver and the pancreas, the two digestive glands asso- 

 ciated with this region, are derived from the mucosa of the 

 intestines, from which they arise as ev aginations, the former 

 ventral, the latter dorsal. As they increase in size they pro- 

 trude beyond the intestinal walls and force their way between 

 the two layers of their respective mesenteries, as a result of 

 which relation they become invested with a serous membrane 

 continuous with that covering the intestines (peritoneum), and 

 remain attached by ligaments both to the latter and to the body 

 wall. These relations are clearly shown in the accompanying 

 diagrams (Fig. 82), which show the origin of these organs 

 from the intestine, their serous investment and their dorsal and 



