PROGNOSIS OF STRANGULATED HERNIA. 523 



Strangulation or incarceration is the condition in which the 

 hernial ring compresses the contents and interferes with normal 

 circulation of blood and passage of ingesta through the intestinal 

 loop. In consequence of this compression the return of blood through 

 the veins is first checked. In them blood-pressure is lower, and the 

 walls weaker, and therefore circulation is more easily interfered 

 with than in the arteries, whose strong walls and high blood-pressure 

 oppose considerable resistance to compression. Blood continues, 

 therefore, to enter by the arteries even after the inception of strangu- 

 lation, and soon produces a severe venous congestion, usually associated 

 with more or less extensive rupture of small vessels and haemorrhage. 

 Infective inflammation of the intestinal wall follows, blood-stained 

 serum is exuded, the hernial fluid increases, and in consequence of 

 mixture with blood becomes red in colour. The hernial contents, 

 especially the serosa of the intestine, are dark red or black, and this 

 coloration is distinctly and usually sharply bounded by the ring-like 

 circle of compression, which is usually grey and anaemic. Both this 

 anaemia and the venous congestion impair nutrition in the stran- 

 gulated parts, which if not relieved undergo necrosis. Stasis adds 

 to the disturbance thus produced, because the imprisoned intestinal 

 contents putrefy, irritate the mucous membrane, and co-operate 

 with defective circulation in inducing necrosis of the mucous 

 membrane. 



Necrosis first shows itself at two points, viz., in the deepest portion 

 of the hernial contents, where circulation surfers most, and at the 

 line of strangulation. It is well to remember, from the clinical stand- 

 point, that dark colour is not always a proof of necrosis. The latter 

 is usually typified by the presence of grey patches on the surface 

 of the peritoneum, or of ulcerative changes in the hernial contents. 

 Necrosis is suggested by the presence of offensive fluid or gas in the 

 hernial sac. The anterior portion of the bowel — that is, the part 

 nearest the stomach— appears greatly distended with food, whilst 

 the posterior portion may be empty and narrower than normal. 



Causes. Strangulation was formerly believed to be produced 

 by spasmodic contraction of the hernial ring ; but, apart from the 

 fact that in most ruptures such contraction seems scarcely possible, 

 it is not to be imagined that active contraction could continue so 

 long. Such views are no longer entertained, and the cause of 

 strangulation is to be sought rather in the character of the hernial 

 contents. Inflammatory swelling near the neck of the hernia may 

 in exceptional cases cause incarceration, but is exceedingly rare. 

 The primary factor in incarceration is usually increase in the hernial 



