288 SURGICAL APPLIED ANATOMY, [Chap. xvi. 



ligament. In one case out of three and a half the 

 obturator artery arises from the epigastric. Out 

 of one hundred and one cases where the vessel so 

 arose it reached its destination in fifty-four instances 

 by passing along the outer side of the crural ring, 

 a position quite free from danger in herniotomy. 

 In thirty-seven cases it passed backwards across the 

 ring, and in ten instances around its inner border 

 (R Quain). When in the last-named position the 

 vessel could hardly escape being wounded in the 

 operation upon a femoral hernia. Indeed, several 

 cases have been recorded of fatal haemorrhage from 

 this abnormal vessel in such operations. In one 

 instance the pulsations of the abnormal artery were 

 felt before the parts were divided. In addition to the 

 vessels about the ring there is also a pubic vein, 

 which, ascending from the obturator vein in the 

 thyroid foramen, enters the external iliac vein. Its 

 relation to the crural ring varies in the same way 

 as the abnormal artery last named. 



The size of the femoral canal and the degree of 

 tension of its orifices varies greatly with the position 

 of the limb. If the thigh be extended, abducted, and 

 rotated outwards, these parts are made very tense, 

 while they are the most lax when the limb is flexed, 

 adducted, and rotated inwards. It is consequently 

 in the latter position that the thigh should be placed 

 when the taxis is being attempted. In herniotomy 

 the incision is made along the inner side of the 

 tumour, arid is so arranged that its centre corresponds 

 to about the upper part of the saphenous opening. 

 The constriction is usually at the neck of the sac, and 

 caused by Gimbernat's ligament. It is divided by an 

 incision directed upwards and inwards. 



Obturator hernia. In this form the gut. push- 

 ing before it a sac of peritoneum, escapes through the 

 obturator canal between the horizontal ramus of the 



