CONTENTS OF THE ABDOMEN. 15 



transmission of the spermatic cords, blood-vessels, &c., are 

 not to be considered as simple perforations made abruptly ; 

 but the edges of these foramina are formed by tendinous mem- 

 branes turned inwards, and continued so as to compose a cylin- 

 drical tube, which becomes gradually so thin that it cannot be 

 readily distinguished from the cellular membrane with which 

 it is connected.* The blood-vessels, &c., pass along this tube 

 before they go through the apertures. 



It is evident from the construction of this cavity, that it is 

 essentially different from the thorax. It has no power of spon- 

 taneous dilation whatever: it yields passively to the distension 

 of the stomach and intestines, during deglutition, and when air 

 is extricated from the aliment, &c. ; but it is particularly cal- 

 culated for compressing its contents by the contraction of the 

 muscles which compose it. The diminution of its capacity, 

 which is thus effected, not only takes place to a great degree, 

 but occasionally with great force. The diaphragm and the 

 abdominal muscles may be considered in some measure as 

 antagonists of each other. When the diaphragm descends, if 

 the abdominal muscles are passive, they are distended by the 

 contents of the abdomen, which are forcibly pressed from 

 above : but if the abdominal muscles act at the same time, an 

 effort to diminish the cavity in every direction takes place, 

 and the contained parts are compressed with more or less 

 force according to the exertion made. This will be very evi- 

 dent upon examining the situation of the diaphragm and of 

 the abdominal muscles. When their force is considered, it will 

 also be very obvious that the various outlets of the cavity are 

 constructed most advantageously ; otherwise hernia or protru- 

 sion of its contents would be a daily occurrence. 



The abdomen contains, 1st, The Stomach and the whole 

 Intestinal Tube, consisting of the small and the great intestines. 



2d. The Assisting Chylopoietic Viscera, the Liver, the 

 Pancreas, and the Spleen. 



* The student of anatomy, when engaged with this subject, will be gratified 

 by the examination of Sir Astley Cooper's plates relating to hernias. 



