DIAGNOSIS OF STRANGULATED HERNIA. 
267 
sac must become more or less filled with intestinal contents, which enter 
through the anterior portion of the intestinal tube, but cannot escape. 
Distension may finally become so great that the hernial ring acts as a 
ligature, and incarceration results after this fashion. The forward move¬ 
ments 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 an 
indiarubber tube, may produce faecal 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 
Figs. 121, 122. —Showing mechanism of incarceration of intestine 
(a) Efferent, (z) Afferent, portion of intestinal loop. 
posterior portion of the loop diminish the passage undei ceitain ciicum- 
stances, and produce similar results. In man extensive 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. But both in men and animals the first causes may be so varied 
that they cannot usually be explained, and therefore the question is heie 
of no great importance. 
The views on omental strangulation are just as vaiied, though all 
coincide in declaring that omental hernia) are much seldomei stiangulated 
than intestinal. Some, like Rose, altogether doubt its occurrence, and 
have supported their opinions by experimentally ligaturing the omentum. 
Others allow its occurrence, and insist that its symptoms aie similai 
to those of strangulation of the intestine, but less pronounced, because 
the circulation alone is interfered with, and faecal stasis does not occur. 
Diagnosis is seldom difficult. As a rule, symptoms of. colic appear, 
and in carnivora vomiting. The pain is regular and lasting. In cases 
of colic in ruptured horses care should therefore invariably be taken to 
