43^ SURGICAL APPLIED ANATOMY. [Chan. xix. 



without much effect. Aneurism of the commence- 

 ment of the gluteal artery could hardly fail to provoke 

 nerve symptoms, since the vessel runs between the 

 lumbo-sacral cord and first sacral nerve. 



Both the gluteal and sciatic arteries have been 

 ligatured through the buttock, through incisions made 

 directly over the course of the vessels. 



Henle has collected six cases where the femoral 

 artery ran down along the back of the thigh to the 

 popliteal space in company with the great sciatic 

 nerve. The abnormal vessel was in each case con- 

 tinued from a greatly enlarged sciatic artery. 



The great sciatic nerve is a continuation 

 downwards of the main part of the sacral plexus. It 

 is in this nerve that the form of neuralgia known 

 as sciatica is located. A reference to the immediate 

 relations of this nerve will show that it may readily 

 be exposed to many external influences. Thus, in the 

 pelvis it may be pressed upon by various forms of 

 pelvic tumour, and sciatica be produced in consequence. 

 Its anterior surface is in close relation with some of 

 the principal pelvic veins, and according to Erb one 

 form of sciatica may be traced to an engorged condition 

 of these vessels. Aneurism of certain branches of the 

 internal iliac artery within the pelvis, sciatic hernia, 

 and accumulation of faeces within the rectum, may all 

 cause neuralgia of this important trunk. It is said to 

 have been injured also by the pressure of the festal 

 head during tedious labours, and to be affected by 

 violent movements of the hip, a circumstance readily 

 understood if the close relation of the nerve to the 

 hip-joint be borne in mind. The nerve is also near 

 enough to the surface to be influenced by external 

 cold, and to this influence many forms of sciatica are 

 ascribed. At the lower edge of the great gluteal 

 muscle the trunk is still nearer to the surface, and 

 this fact receives illustration in a case reported in 



