DISSECTION OF THE LOWER EXTREMITY 



127 



branches of these vessels are found at this stage of the 

 dissection. What is the canal of Alcock? 



(bd) Terminal branches of the medial circumflex artery (A. cir- 

 cumflexa femoris medialis). What is the "crucial anas- 

 tomosis" ? 



FIG. 48. 



A. glutaea 

 superior 



A. perforans 

 prima 



r 



Arteries of the gluteal region. The Mm. glutaeus max. and med. are, in great part, removed. (After 

 Gegenbaur, Lehrb. der Anat. des Mensch., Leipzig, 1899, 7 Aufl., Bd. il. p. 285, Fig. 545.) 



Nerves. (Fig. 49.) 



(a) Above the M. piriformis: 



(aa) Superior gluteal nerve (N. glutaeus superior}. 



(b) Below the M. piriformis: 



(ba) Great sciatic nerve (TV. ischiadicus) . This nerve often 

 divides into two branches (N. peronaeus communis and 

 N. tibialis) over the piriformis muscle. The nerve sup- 

 plying the M. obturator internus and M. gemellus su- 

 perior will be found lying just lateral to the pudic 

 vessels. It rests upon the base of the spina ischiadica. 

 To expose the nerve to the quadratus femoris and gemel- 

 lus inferior, reflect the gemelli muscles under which it 

 runs. When traced as far as the gemellus inferior exer- 

 cise great care and avoid injury to the twig passing into 



