304 SURGICAL APPLIED ANATOMY. [Chap. XVL 



muscles, while below it is the angle formed by 

 the union of Poupart's ligament with the transver- 

 salis fascia. The herniated bowel is contained within 

 a " sac," which is always formed of peritoneum. In 

 congenital hernia the sac exists already formed in the 

 form of an abnormally patent "processus vaginalis." 

 In acquired herniae the sag consists of that part of the 

 parietal peritoneum which the gut pushes before it in 

 its descent. 



The external abdominal ring is readily felt by 

 invaginating the scrotum with the point of the finger, 

 and then passing the digit up in front of the cord. 

 If the nail be kept against the cord the pulp of the 

 finger can readily recognise its triangular slit-like 

 opening. Under ordinary circumstances in adults it 

 will just admit the tip of the little finger.* The 

 internal ring is situate about half an inch above the 

 middle of Poupart's ligament. 



There are two principal forms of inguinal hernia, 

 which can be best understood by a view of the anterior 

 abdominal parietes from within. From such an aspect 

 it will be seen that the peritoneum is marked by three 

 linear ridges that run, roughly speaking, from the 

 umbilicus to the pelvic brim. One of these ridges 

 follows the middle line from the navel to the syinphysis, 

 and represents the urachus; a second, that may be 

 indicated by a line drawn from the middle of Poupart's 

 ligament to the navel, represents the deep epigastric 

 artery ; while between these two, and much nearer to 

 the epigastric vessel than to the middle line, is the line 

 formed by the obliterated hypogastric artery. By 

 means of these ridges the peritoneum is made to pre- 

 sent three fossae, an external to the outer side of the 



* In cases of congenital or acquired absence of the cord the 

 external ring may be almost obliterated. Paulet quotes from 

 Malgaigne the case of an old man whose testicle had been removed 

 in infancy and in whom the external ring was so small as to be 

 scarcely recognisable. 



