EXTERNAL OR OBLIQUE HERNIA. 423 



protruding parts receive as a covering the prolongation from the margin 

 of the opening. 



The external abdominal ring (fig. 185, c ) is the outlet of the inguinal 

 canal, and through it the spermatic cord reaches the surface of the body. 

 This aperture is placed in the aponeurosis of the external oblique muscle, 

 near the crest of the pubes ; and from the margin a prolongation is sent 

 on the parts passing through it (p. 410)." 



Course and coverings of the hernia'. "A piece oPintestine leaving the 

 abdomen with the cord, and passing through the inguinal canal to the 

 surface of the body, will 'obtain a covering from every stratum in the 

 lateral part of the wall of the abdomen, except from the transversalis 

 muscle. 



It receives its investments in this order : As the intestine is thrust out- 

 wards, it carries before it first the peritoneum and the subperitoneal fat, 

 and enters the tube of the fascia transversalis, F (infundibuliform fascia), 

 around the cord. Still increasing in size it is forced downwards to the 

 lower border of the internal oblique muscle ; where it will have the cre- 

 masteric fascia, o, applied to it. The intestine is next directed along the 

 front of the cord to the external abdominal ring, and in passing through 

 that opening receives the investment of the intercolumnar or spermatic 

 fascia. Lastly, as the hernia descends towards the scrotum, it has the 

 additional coverings of the superficial fascia and the skin. 



In a hernia which has passed the external abdominal ring, the cover- 

 ings from without inwards are the following: the skin and the superficial 

 , fa.*cia, the spermatic and cremasteric fascia?, the fascia transversalis, the 

 subperitoneal fat, and the peritoneum or hernial sac. Two of the cover- 

 ings, viz., the peritoneal and subperitoneal, originate as the gut protrudes, 

 but the rest are ready formed around the cord, and the intestine slips in- 

 side them. The different layers become much thickened in a hernia that 

 has existed for some time. 



Diagnosis. If the hernia is small and is confined to the wall of the 

 belly, it gives rise to an elongated swelling along the inguinal canal. If 

 it has proceeded farther, and entered the scrotum, it forms a flask-shaped" 

 tumor with the large end below, and the narrow neck occupying the in-.- 

 guinal passage. 



Whilst efforts are being made to force back a piece of protruded intes- 

 tine during life, the direction of the canal, and the situation of the internal 

 abdominal ring should be borne in mind. 



Seat of stricture. The protruded intestine may be constricted at the 

 internal abdominal ring; in the inguinal canal by the fleshy internal ob- 

 lique muscle ; and at the external abdominal ring. 



The stricture is placed usually at the inner abdominal ring, and may be 

 produced in two ways : either by a constricting fibrous band outside the 

 narrowed neck of the tumor, or, by a thickening and contraction of the 

 peritoneum itself at the inner surface of the neck. 



Division of stricture. To set free the intestine, an incision is made 

 down to the internal abdominal ring ; and, all fibrous bands outside the 

 peritoneum being divided, the intestine is to be returned into the abdo- 

 men by gentle pressure. 



Supposing the intestine cannot be replaced in the abdomen after the 

 previous steps have been taken, the surgeon proceeds to lay open the peri- 

 toneum, and to divide the internal stricture, from within out, on a director 



