The Abdomen 289 



weakness of the abdominal parictes, traumatism, or the presence of 

 a predisposing factor in the form of a dilated inguinal canal and 

 congenital herniated broad ligament. It occasionally occurs subse- 

 quent to abdominal section, especially when the incision is made in 

 the aponeurotic tissue of the linea alba, through yielding of the cica- 

 tricial tissue of the wound. Hobday places the general percentage 

 of hernias resulting from celiotomy at four or five. In an extensive 

 experience, both clinical and experimental, I never have had the 

 misfortune to meet with it, which I attribute to the fact that I have 

 always avoided incising directly in the linea alba. La Torre experi- 

 mented on twenty-five dogs and determitjed that hernia after celio- 

 tomy was chiefly due to defective union of the muscular layer or 

 relaxation of the cicatrix, following incision through the linea alba. 

 This was not likely to occur when the incision was made through the 

 muscle. If made directly in the linea alba, before closing it, the 

 aponeurotic tissue should be removed as far as the muscular sub- 

 • stance of the recti muscles. 



There is always risk to be encountered from the presence of 

 a hernia, through incarceration or strangulation taking place or 

 through parturition being rendered impossible. In one fatal case 

 of inguinal hernia which I attended, the lesion had existed four 

 years, the portion of protruding bowel finally becoming strangulated. 

 A hernia is said to be incarcerated when the peristalsis of the re- 

 tained gut is arrested, generally through adhesions having formed, 

 and the lumen is obstructed by impacted feces. A hernia is said to 

 be strangulated when the return of the venous blood is impeded. 

 This is followed by stasis of the arterial flow, edema, and serous 

 exudation, which increases the distension of the sac. Finally, these 

 changes lead to migration of intestinal bacteria and gangrene. Both 

 these conditions are treated of fully under Intestinal Obstruction. 



Symptoms and Diagnosis. Hernia is recognized as an elastic 

 fulness or swelling, by more or less disappearance of the same when 

 the animal is placed in the dorsal position, and by its reappearance 

 when placed in the erect, excepting in the case of the gravid uterus 

 and irreducible and strangulated forms. It may also be replaced by 

 taxis. It is often tympanitic, disappears with a gurgling sound, and 

 becomes tense if the subject is made to cough. It is never painful 

 unless inflamed. In a recent hernia the contents are, as a rule, easily 

 reducible and the sac retains its natural thin, translucent condition, 



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