EXTERNAL CUTANEOUS NERVE. 



The Branches of the lumbar plexus are the 



Musculo-cutaneous, Crural, 



External-cutaneous, Obturator, 



Genito-crural, Lumbo-sacral. 



The MUSCULO-CUTANEOUS NERVES, two in number, superior and infe- 

 rior, proceed from the first lumbar nerve. The superior musculo- cutaneous 

 nerve (ilio-scrota], ilio-hypogastricus), passes outwards between the poste- 

 rior fibres of the psoas magnus, and crossing obliquely the quadratus 

 lumborum to the middle of the crest of the ilium, pierces the transversalis 

 muscle, and gives off a cutaneous branch. It then winds along the crest 

 of the ilium between the transversalis and internal oblique, and divides 

 into two branches, abdominal and scrotal. The abdominal branch is con- 

 tinued forwards parallel with the last intercostal nerve to near the rectus 

 muscle, to which it sends branches and perforates the aponeuroses of the 

 internal and external oblique to be distributed to the integument of the 

 mons pubis and groin. The scrotal branch^ opposite the anterior superior 

 spinous process of the ilium, communicates with the inferior musculo- 

 cutaneous nerve, and passes forward to the external abdominal ring. It 

 then pierces the cremaster muscle and accompanies the spermatic cord in 

 the male, and the round ligament in the female, to be distributed to the 

 integument of the septum or external labium. The inferior musculo- cuta- 

 neous nerve (ilio-inguinal) also arises from the first lumbar nerve. It is 

 much smaller than the preceding, crosses the quadratus lumborum below 

 it, and curves along the crest of the ilium to the anterior superior spinous 

 process, resting in its course upon the iliac fascia. It there pierces the 

 transversalis fascia and muscle, communicates with the scrotal branch of 

 the ilio-scrotal nerve, and passes along the spermatic canal with the sper- 

 matic cord to be similarly distributed. 



The EXTERNAL CUTANEOUS NERVE (inguino-cutaneous) proceeds from 

 the second lumbar nerve. It pierces the posterior fibres of the psoas 

 muscle ; and crossing the iliacus obliquely, lying upon the iliac fascia, to 

 the anterior superior spinous process of the ilium, passes into the thigh 

 beneath Poupart's ligament. It then pierces the fascia lata at about two 

 inches below the anterior superior spine of the ilium, and divides into two 

 branches, anterior and posterior. The posterior branch crosses the tensor 

 vagina? femoris muscle to the outer and posterior side of the thigh, and 

 supplies the integument in that region. The anterior nerve divides into 

 two branches which are distributed to the integument upon the outer bor- 

 der of the thigh, and to the articulation of the knee. 



The GENITO-CRURAL proceeds also from the second lumbar nerve. It 

 traverses the psoas magnus from 'behind forwards, and runs down on the. 

 anterior surface of that muscle arid beneath its fascia to near Poupart's 

 ligament, where it divides into a genital and a crural branch. The genital 

 branch (n. spermaticus seu pudendus externus) crosses the external iliac 

 artery to the internal abdominal ring and descends along the spermatic 

 canal, lying behind the cord to the scrotum, where it divides into branches 

 which supply the spermatic cord and cremaster in the male, and the round 

 ligament and external labium in the female. At the internal abdominal 

 ring this nerve sends off a branch which after supplying the lower border 



