878 THE NERVES. 



The second nei-ve, situated beneath the preceding, appears to be detached 

 from the posterior border of the great sciatic nerve. It is placed on the external 

 surface of the sciatic ligament, is directed backwards in passing below the croupal 

 portion of the rectus femoris, and vastus externus and internus, passes through 

 these muscles above the ischial tuberosity, descending underneath the sacral 

 portion of the semitendinosus, soon to leave its deep track and become superficial. 

 It escapes from between the latter muscle and the three just named, and is lost 

 beneath the skin covering the posterior part of the thigh. Its deep portion gives 



POSTERIOR PORTION OF THE LUMBO-SACRAL PLEXtTS. 



I, Conjoining fasciculi of the three first sacral nerves ; 2, 3, 4, 5, anterior gluteal nerves ; 6, 6', 8, 

 posterior gluteal nerves; 7, 9, branches which traverse the great sciatic ligament, and com- 

 municate between the posterior gluteal branches and the divisions of the internal pudic nerve ; 

 10 11 12, 13, great sciatic nerve and its crural branches; 14, small femoro-popliteal nerve; 15, 

 its cutaneous or peroneal-cutaneous branch. 



off collateral branches which reinforce the divisions of the internal pudic nerve, 

 as well as filaments to the long branch of the semitendinosus muscle. 



5. Great Sciatic or Great Femoro-popliteal Nerve (Figs. 201, 13 ; 



475, 1, 2). 



This enormous nerve (the largest in the body), issues by the great sciatic 

 opening in the form of a wide band, which is applied to the external face of the 

 sciatic hgament. Comprised at first between that ligament and the middle 

 gluteus, it is directed backwards in passing over the fixed insertion of the 

 gluteus internus, and arrives behind the gemelli and quadratus femoris muscles. 

 On leaving this point, it is inflected to descend behind the tliigh, where it is 

 lodged in the muscular sheath formed for it by the biceps, the semitendinosus 



