1326 HUMAN ANATOMY. 



b. The anterior branch (r. anterior), the more superficial, descends in front of the obturator 

 externus and adductor brevis muscles and between the pectineus and the adductor longus. 

 Having reached the interval between the adductores brevis and longus it separates into its 

 terminal branches. 



Branches of the anterior division are: {aa) the articular, {bb) the muscular, {cc) the 

 cutaneous, [dd) the coimnuiiicatitig and {ee) the vascular. 



aa. The articular branch leaves the obturator at the inferior margin of the obturator 

 foramen and passes through the cotyloid notch to supply the hip joint. 



bb. The muscular branches supply the adductores brevis and longus and the gracilis. 



The branch to the adductor brevis enters the muscle near the upper margin of the anterior 

 surface. 



The branch to the adductor longus enters the posterior surface of the muscle and some- 

 times gives off the cutaneous branch of the obturator (see below). 



The branch to the gracilis passes inward behind the adductor longus and enters the deep 

 surface of its muscle. 



cc. The cutaneous branch (r. cutaneus) (Fig. mo) is variable in size and maintains an 

 approximately even balance with the internal cutaneous branch of the anterior crural. Some- 

 times arising from the nerve to the adductor longus, it becomes superficial in the middle of the 

 thigh by passing between the adductor longus and the gracilis. It supplies the integument of 

 the lower inner portion of the thigh and beneath the sartorius forms an inosculation with 

 branches of the internal cutaneous and internal saphenous nerves, called the subsartorial or 

 obturator plexus. 



dd. The commtmicating branches consist of twigs which unite in the pelvis with the accessory 

 obturator nerve and in the thigh anterior to the capsular ligament of the hip joint with the 

 anterior crural. 



ee. The vascuktr branch enters Hunter's canal along the mesial edge of the adductor longus 

 and spreads out over the lower portion of the superficial femoral artery. 



c. The posterior branch (r. posterior), the deeper, pierces the anterior fibres of the 

 obturator externus muscle and descends in the cleft between the adductores brevis and magnus, 

 and in the latter situation splits into its terminal twigs. 



Branches of the posterior division are : {aa) the muscular and {bb) the articular. 



aa. The muscular branches supply the obturator externus, the adductor magnus and the 

 adductor brevis. 



The branch to the obturator externus is additional to the twig from the main trunk of the 

 obturacor which supplies that muscle. It arises from the posterior surface of the posterior 

 division and enters the superficial surface of the muscle. 



The branch to the adductor magnus is associated with the branch to the knee and leaves 

 the latter as the conjoint nerve passes through the substance of the adductor magnus. 



The branch to the adductor brevis enters the posterior surface of the muscle and is 

 present only when the usual branch from the anterior division is absent. 



bb. The articular branches are destined for the supply of the hip and knee joints. 



The branch to the hip joint consists of one or two fine twigs which pass beneath the 

 pectineus to be distributed to the antero-median portion of the capsular ligament. 



The branch to the knee joint or the geniculate branch continues the course of the posterior 

 division. Associated with the nerve to the adductor magnus, it courses down the anterior sur- 

 face to the adductor magnus, which it pierces at the lower portion of .the thigh. Here its muscu- 

 lar fibres terminate in the adductor magnus while the articular portion enters the popliteal space. 

 The nerve continues downward on the popliteal artery, to which it distributes filaments, and 

 finally terminates by enteririg the knee joint through the posterior ligament. 



Variations. — In rare instances the root from the second lumbar nerve is absent. Branches 

 are sometimes given off to the obturator internus and to the pectineus. Tiny branches have 

 been found going to the obturator artery and to the periosteum of the pelvic surface of the os 

 pubis. In a cadaver dissected in the anatomical laboratory of the University of Pennsyl- 

 vania the obturator of the right side divided into the usual anterior and posterior branches, but 

 both of them passed posterior to the adductor brevis. On the left side the normal arrangement 

 was present. In another specimen in the same laboratory the branch from the main trunk to 

 the obturator externus muscle lay to the outer instead of the inner side of the obturator nerve. 



7. The Accessory Obturator Nerve. 



The accessory obturator nerve is an inconstant branch of the lumbar plexus, 

 being found in 29 per cent, of the cadavers examined (Eisler). Its fibres arise from 

 the third and fourth lumbar nerves, with an occasional root from the fifth ; it may be 

 derived from the third alone. The roots of origin are situated between those of the 

 anterior crural and the obturator, and the nerve may be intimately associated with 

 either of these two, usually the former. 



