CHAPTER X. 



THE ABDOMEN AND THE ORGANS OF 

 DIGESTION AND EXCRETION. 



The Abdominal Cavity. Below the diaphragm and 

 separated from the lowest cavity of the trunk, the 

 pelvis, only by an invisible plane drawn through the 

 brim of. the true pelvis, is the abdominal cavity, which 

 may be said in a general way to contain the organs 

 of digestion and the kidneys. It is protected behind 

 by the vertebrae and anteriorly by the lower ribs above 

 and below by muscular walls, which make possible the 

 complete bending of the body. These muscles are 

 for the most part large and very strong and the greater 

 number are inserted, in part at least, into a median 

 tendinous line, the linea alba, which passes from the 

 ensiform cartilage of the sternum above to the sym- 

 physis pubis below. 



Muscles. The external obligue muscles form the outer- 

 most layer of the abdominal wall. They rise from 

 the external surface of the eight lower ribs on either 

 side and are inserted in the anterior half of the iliac 

 crest as well as by aponeurosis in the linea alba, where 

 each joins its fellow from the opposite side, the fibers 

 running downward and inward like the fingers in the 

 trouser's pocket. Along the lower border of the apo- 

 neurosis is a broad fold, Poupart's ligament. The in- 

 ternal oblique rises on either side from the outer half 

 of Poupart's ligament and the anterior part of the crest 

 of the ilium and is inserted into the crest of the os pubis, 

 the cartilages of the lower ribs, and the linea alba. 

 Its fibers run at right angles to those of the external 

 oblique. These oblique muscles serve to compress the 

 viscera, to flex the body, and also assist in expiration. 



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