42 THE STOMACH^ 



times termed the villous, from its velvety appearance. Its color is very 

 variable ; it is folded into rugas, which admit of variations in the disten- 

 tion of the stomach, without interference with the structure or functions 

 of the membranes of which they are a part. The cardiac orifice is pli- 

 cated, and the opening into the duodenum is through a circular fold with 

 a central aperture the pyloric valve, which being surrounded with a 

 band of muscular fibres, acting as a sphincter, the passage from the stom- 

 ach to the intestine may be entirely obstructed. 



The stomach is seen in 

 section Fig. 2, a being the 

 oesophagus ; b, the greater 

 extremity ; c, the smaller 

 curvature; d, the great 

 curvature; e, the pyloric 

 or less end ; /, A, the du- 

 odenum ; <7, place of entry 

 of the ductus communis 

 choledochus and pancre- 

 atic duct. The place of 



Section of the human stomach showing its mucous interior. J 



is the cardiac region: the 



membrane is there plicated. The place of junction of the duodenum is 

 the pyloric region. , 



The typical form of the digestive apparatus is a sac with one aperture, 

 Types of the winch serves the double purpose of affording an entrance to 

 stomach. nutritive material, and an outlet to undigested remains. In a 

 higher condition it may be conceived of as a tube open at both ends, and 

 having a sac-like swelling on its middle part. The portion of the tube 

 anterior to the sac is the type of the oesophagus, its aperture answering 

 to the mouth, the sac-like swelling being the type of the stomach, and the 

 tube leading from it representing the intestinal canal. In the more ele- 

 mentary of such forms, vessels arise from the walls of the digestive cav- 

 ity, and pass to all other parts of the system. These serve to convey the 

 elaborated material. Certain appendages are soon to be discovered in 

 connection with this simple digestive mechanism. They are for the 

 preparation of salivary, gastric, pancreatic,' or biliary juices. In size or 

 development they vary with the habits of life of the animal, or with the 

 nature of its food. Indeed, the same remark may be made as respects 

 the entire digestive tract of the highest tribes. Thus, in the bat the 

 length of the intestine is to that of the body as three to one, but in the 

 sheep as twenty-eight to one. The ruminants generally have an intes- 

 tinal tube of great length. In man and in monkeys the proportion is 

 about five or six to one. Again, as regards construction, there are many 





