INGUINAL HEENIA. 391 



region. Both of these structures are normally accompanied by 

 a patent process of peritoneum in the foetus, which should close 

 some few weeks before birth ; in many instances, however, it 

 remains as an unclosed tube, ready to receive bowel or omentum 

 when the intra-abdominal pressure is raised sufficiently high. 



The serous sac, continuous with the parietal peritoneum lining 

 the anterior abdominal wall, finds its way through the parietes 

 in an oblique manner. It commences at the region known as 

 the deep (or internal) abdominal ring. In the foetus and young 

 infant this is situated almost immediately above the crest of the 

 os pubis, but as growth proceeds, and particularly when adult 

 life is reached and the pelvis developed, it gradually recedes 

 upwards and outwards, till at last it is found a finger's breadth 

 above the middle of Poupart's ligament. This so-called "ring" 

 is in reality a slit-like depression in the fascia transversalis, 

 readily seen from the abdominal aspect if the parietal peritoneum 

 is stripped off external to the deep epigastric artery. 



The neck of the sac then passes along the inguinal canal, which 

 passage is oblique, running downwards and inwards, and of very 

 short length in the young subject, but measuring from one and 

 a half to two inches in the adult. The boundaries of this passage 

 are of great importance, and should be thoroughly understood 

 before undertaking an operation upon an inguinal hernia. 



Anteriorly, that is superficially, there are placed the skin ; two 

 layers of superficial fascia, one containing fat, superficial epigastric 

 vessels and some cutaneous nerves, and the other, the deeper, 

 being of a more fibrous texture ; then the aponeurotic fibres of the 

 external oblique muscle, running in the same direction as the 

 canal itself ; and in front of the outer half of the passage, and 

 therefore covering and protecting the deep abdominal ring, the 

 arching muscular fibres of the internal oblique and a few of the 

 transversalis arising from the external half of .Poupart's liga- 

 ment. These fibres are of much moment, seeing that they arch 

 over the cord or the round ligament, and becoming the conjoined 

 tendon, are inserted into the crest of the os pubis, deep to the 

 cord or round ligament. Thus, when they contract, they tend to 



