256 ABDOMEN 



inguinal ring, into a persisting, though shrunken, processus 

 vaginalis, the action of the abdominal pressure will, thence- 

 forth, tend to distend the inguinal canal and force the 

 abdominal contents further and further along it, until they 

 eventually protrude through the subcutaneous inguinal ring. 

 The coverings of such a hernia will naturally be the con- 

 stituent parts of the abdominal wall in the inguinal region : 

 that is, from within outwards, (i) peritoneum, (2) extra-peri- 

 toneal fat, (3) internal spermatic portion of transversalis fascia, 

 (4) cremasteric fascia, (5) external spermatic fascia, (6) super- 

 ficial fascia, and (7) skin. A hernia which travels obliquely 

 through the abdominal wall, along the line of the inguinal 

 canal, is called an oblique inguinal hernia^ and, as the neck of 

 the hernial sac lies to the lateral side of the inferior epigastric, 

 it is called a lateral inguinal hernia. If the cavity of the per- 

 sisting processus vaginalis, into which the hernia has passed, 

 is still continuous with the cavity of the tunica vaginalis, 

 the herniated viscus or peritoneal fold will enter the tunica 

 vaginalis of the testis ; but, if the cavity of the upper part of 

 the processus vaginalis has been separated from that of the 

 lower part by the formation of an oblique or transverse 

 septum, the upper part of the processus, with its contained 

 hernia, may be forced downwards either anterior or posterior 

 to the lower part, or the lower end of the upper part may 

 invaginate the upper end of the lower part. Herniae differen- 

 tiated from each other by the relationship which the upper 

 part of the processus, containing the herniated viscus, bears 

 to the lower part, the tunica vaginalis, are described by 

 surgeons under special names which the student will find 

 fully explained in manuals of surgery. There are, however, 

 other forms of inguinal hernia which do not pass through the 

 abdominal inguinal ring, but through the posterior wall of the 

 canal, on the medial side of the inferior epigastric artery, 

 between it and the obliterated part of the umbilical artery, or, 

 still more medially, between the obliterated part of the 

 umbilical artery and the lateral border of the rectus. Such 

 herniae, because they do not pass obliquely along the inguinal 

 canal but more directly through its posterior wall, are called 

 by the surgeon direct inguinal hernia. As there are no con- 

 genital diverticula of the peritoneum in these regions such 

 herniae must be due either to the slow distension of weak 

 points in the posterior wall of the inguinal canal, under the 



