PRACTICAL CONSIDERATIONS : ABDOMINAL HERNIA. 1767 



and of the transversalis and internal oblique muscles (cremaster muscle), makes its 

 region of exit from the abdomen i. e. , of its entrance into the inguinal canal the 

 area in the abdominal wall best adapted by reason of its weakness and its shape to 

 favor the exit of viscera. ($) This spot is situated near the lowest level of the 

 inferior zone of that cavity, i.e. , at a level at which, when the size of the cavity is 

 either temporarily decreased (as during coughing or straining), or relatively 

 decreased (as when the upper zone is compressed by tight lacing), or actually 

 decreased (as by intra-abdominal fat, or by a tumor or ascites), the outward thrust 

 of the abdominal viscera is added to by their superincumbent weight. (c~) The peri- 

 toneum over the lower part of the anterior abdominal wall is thin and loosely attached, 

 so that it is unable to offer much effective resistance to distention by pressure from 

 within. Such distention is favored by the funnel-shaped depression at this point, 

 and, having once begun, its influence in localizing a hernia is obvious, (d) The 

 union of the iliac fascia with the transversalis fascia, which is strongest in the imme- 

 diate vicinity of Poupart's ligament, presents an insuperable obstacle to the descent 

 of hernia external to the internal ring, (e) The conjoined tendon of the trans- 

 versalis and internal oblique muscles inserted into the crest of the pubes and the ilio- 

 pectineal line is strong internally, but has an ill-defined outer edge ; while that por- 

 tion of the tendon which is derived from the internal oblique has generally a less 

 extensive attachment than that from the transversalis muscle, so that the space 

 between the border of the rectus and the internal ring is closed by the two tendons 

 conjoined at the innermost part, farther outward by the transversalis tendon alone, 

 while near the entry of the cord there may be a space unprotected by tendon or 

 muscle (Macready). The thinnest and least protected portion of the inner posterior 

 wall of the canal is therefore that adjacent to the inner edge of the internal abdominal 

 ring (Ibid.). It should be noted that Treves is inclined to consider the resistant 

 power of the normal abdominal wall as less over Hesselbach's triangle than over the 

 external inguinal fossa ; but even if this is true, the existence of the internal ring and 

 of the canal more than compensates for it in favoring hernia. 



These facts sufficiently explain the frequency of oblique inguinal hernia of the 

 acquired form (vide infra), i.e., the form in which the congenital deficiencies or 

 definite pathological changes next to be mentioned are not demonstrable, although 

 it is not unlikely that some original or acquired defect of the abdominal wall in the 

 neighborhood of the hernial orifices is present in the great majority of cases of hernia 

 of this as of all varieties. (_/) The not infrequent total or partial patency of the 

 vaginal process gives rise to a number of subvarieties of inguinal hernia {congenital, 

 infantile, funicular) , all of which are oblique, i.e., enter the inguinal canal at the 

 internal ring and to the outer side of the epigastric artery. These herniae, depend- 

 ing on anomalies in the closure of the processus vaginalis, have been variously sub- 

 divided and defined, often with unnecessary complexity. It will suffice here to say 

 that congenital hernia (Fig. 1488) is due to complete patency of the vaginal process, 

 the cavity of which is directly continuous with the cavity of the abdomen, the sac 

 of the hernia enclosing both its visceral contents and the testicle, which lie in con- 

 tact. Although the condition leading to the formation of this hernia is truly con- 

 genital, the hernia itself is very rarely in existence at the time of birth, but is apt to 

 occur in early life when intra-abdominal pressure is either habitually or suddenly 

 increased. It should be remembered that, although a true congenital hernia neces- 

 sarily depends upon a patent processus vaginalis, patency of the process may exist 

 without hernia. A fold of peritoneum at the edge of the infundibuliform fascia 

 partly screening the abdominal opening of such a process has been described and 

 has been thought to aid in preventing hernia (Macready). In women patency of 

 the canal of Nuck acts similarly as a predisposing cause of congenital hernia, which 

 is, however, of great rarity, on account of the narrowness of the canal itself, the fact 

 that its internal orifice is still smaller, and supposedly by reason of the relatively 

 larger size and greater distinctness in the female than in the male of the peritoneal 

 and fascial fold covering the entrance to the canal. 



Infantile hernia (Fig. 1489) results from occlusion of the processus vaginalis at 

 the internal ring only, the visceral pressure, aided by the attachments of the guber- 

 naculum testis above described, carrying this septum and the neighboring perito- 



