ORGANS OF DIGESTION. 



cava or contiguous veins which pass into the same trunk. 

 The nerves are numerous, supplying the diaphragm, and 

 come from the phrenic, pneumogastric, spinal, and sym- 

 pathetic. 



Function. This muscle is an important agent in respira- 

 tion. By its contraction its convex surface descends, and 

 thus the diameters and cavity of the chest are enlarged and 

 more air allowed to enter the lungs in respiration. By its 

 contraction it also acts in concert with the abdominal mus- 

 cles in vomiting, expelling the fasces, and in parturition. 

 By its relaxation the diaphragm ascends into the cavity of 

 the chest, diminishes this cavity and thus aids in expira- 

 tion. The inferior wall will be examined in another place. 



SECTION II. 

 ORGANS OF ABDOMINAL DIGESTION. 



These comprise, 1. The organ of cliymification, consist- 

 ing of the stomach; 2. The organs of cliylification, com- 

 posed of the small intestine and the large intestine, which 

 however more properly belongs to the function oifcecation ; 

 B. Assistant organs of digestion, composed of the liver, 

 the pancreas, and the spleen. 



Before giving the description of the abdominal viscera 

 separately, it is necessary first to premise a few general ob- 

 servations upon the peritoneum, a membrane which is com- 

 mon to each and the whole, and which forms the lining 

 membrane of the abdominal walls. 



Peritoneum, (xtpitMtiv, to extend around.) The perito- 

 neum is a serous membrane, and the largest one in the 

 body. Like all serous membranes, it is a shut sac. This is 

 true of the male peritoneum, but in the female there is an 

 opening at the extremities of the Fallopian tubes, which 

 Mr. Harrison observes is more apparent than real, for he 

 thinks it probable that these fimbrias are closed at all times 

 except when in contact with or adhering to the ovaries. 

 Thus, in ascites, the water is never found escaping by 

 these openings, nor air, nor fluid, when injected in the dead 



