OBTURATOR NERVE. ACCESSORY. 



663 



is larger than usual, and descends along the posterior border of the sartorius to the 

 inner side of the knee, where it perforates the fascia, communicates with the internal 

 saphenous nerve, and extends down the inner side of the limb, supplying the skin as 

 low as the middle of the leg. 



Fig. 438. 



Fig. 438. THE LUMBAR PLEXUS FROM 



BEFORE, WITH THE DISTRIBUTION OP 



SOME OF ITS NI-.RVES (slightly altered 

 from Schmidt). | 



cr, the last rib ; J, quadratus lura- 

 boruni muscle ; c, oblique and traus- 

 verse muscles cut near the crest of the 

 ilium and turned down ; d t pubes ; e, 

 adductor brevis muscle ; /, pectineus 

 dhided and turned outwards ; g, adduc- 

 tor lougus; 1, ilio-hypogastric nerve ; 

 2, ilio-inguinal ; 3, external cutaneous; 

 4, anterior crural ; 5, accessory obtu- 

 rator ; 6, obturator united with the ac- 

 cessory by a loop round the pubes; 7, 

 geuito-crural in two branches cut short 

 near their origin ; 8, 8, lumbar portion 

 of the gangliated sympathetic cord. 



When this cutaneous branch of the 

 obturator nerve is present, the internal 

 cutaneous branch of the anterior crural 

 nerve is small, the size of the two 

 nerves bearing an inverse proportion 

 to each other. 



B. The posterior or deep part 

 of the obturator nerve, having 

 passed through some fibres of the 

 external obturator muscle, crosses 

 behind the short adductor to the 

 fore part of the adductor mag- 

 DUS, where it divides into many 

 branches, all of which enter those 

 muscles, excepting one which is prolonged downwards to the knee-joint. 



(a) The muscular branches supply the external obturator and the great adductor 

 muscle, with the short adductor also when this muscle receives no branch from the 

 anterior division of the nerve. 



(b) The articular branch for the knee rests at first on the adductor magnus, but 

 perforates the lower fibres of that muscle, and thus reaches the upper part of the 

 popliteal space. Supported by the popliteal artery, and sending filaments around 

 that vessel, the nerve then descends to the back of the knee-joint, and enters the 

 articulation through the posterior ligament. (Thomson, " London Med. and Surg. 

 Journal," No. xcv.) 



ACCESSORY OBTURATOR NERVE. 



The accespory obturator nerve, a small and inconstant nerve, arising from 

 the obturator nerve near its upper end, or separately from the same nerves 

 of the plexus, descends along the inner border of the psoas muscle, over the 

 pubic bone, and, passing behind the pectineus muscle, ends by dividing into 

 several branches. Of these one joins the anterior branch of the obturator 

 nerve ; another penetrates the pectineus on the under surface ; whilst a 

 third enters the hip-joint with the articular 'artery. 



