524 



PROGNOSIS OF STRANGULATED HERNIA. 



contents ; conversely this increase may be a result of incarceration. 

 Let us imagine a case : A horse affected with hernia suffers from 

 tympanites ; the increased intra-abdominal pressure thrusts a large 

 portion of bowel and omentum from the abdominal cavity into the 

 hernial sac ; on account of the increase of the hernial contents the 

 ring becomes too narrow ; it presses on the enlarged contents and 

 interferes with circulation in the parts which it surrounds, and in- 

 carceration results (Figs. 389 and 390). Or let us fancy that in the 

 posterior portion of the intestinal tube — that is, in the portion 

 through which the intestinal contents are returned from the hernial 

 sac into the abdominal cavity — some check occurs, causing fa?cal 

 stasis. Necessarily the hernial sac must become more or less filled 

 with intestinal contents, which enter through the anterior portion 



/^ 



Figs. 389, 390.— Showing mechanism of incarceration of intestine- 

 (a) Efferent. (:) Afferent, portion of intestinal loop. 



of the intestinal tube, but cannot escape. Distension may finally 

 become so great that the hernial ring acts as a ligature, and incar- 

 ceration results after this fashion. The forward movements of 

 intestinal contents may be variously impeded. Thus the posterior 

 portion of intestine not infrequently becomes twisted either in the 

 hernial sac or in the peritoneal cavity, particularly at its point of 

 exit from the ring, and the twist, which acts like a kink in a rubber 

 tube, may produce fsecal stasis in the hernial sac and incarceration. 

 In the same way gradual distension of the anterior portion of the 

 loop of intestine lying in the hernial sac may displace or compress 

 the posterior portion, and bring about faecal stasis and incarceration. 

 According to Rose, folds of mucous membrane in the posterior portion 

 of the loop diminish the passage under certain circumstances, and 

 produce similar results. Jn man statistics have been accumulated 

 on the mechanism of strangulation, and attempts have also been 

 made to solve the question of its origin by experiments on animals. 



