NERVES OF LOWER EXTREMITY. 651 



gluteal region, behind the lateral cutaneous branch of the last dorsal nerve 

 (Fig. 357). The size of this nerve bears an inverse proportion to that of the 

 cutaneous branch of the last dorsal nerve. 



The hypogastric branch (Fig. 355) continues onwards between the Internal 

 Oblique and Transversalis muscles. It first pierces the Internal Oblique, and 

 near the middle line perforates the External Oblique above the external abdomi- 

 nal ring, and is distributed to the integument covering the hypogastric region. 



The llio-inguinal Nerve (inferior musculo-cutaneous), smaller than the preced- 

 ing, arises with it from the first lumbar nerve. It pierces the outer border of 

 the Psoas just below the ilio-hypogastric, and, passing obliquely across the 

 Quadratus Lumborum and Iliacus muscles, perforates the Transversalis, near 

 the fore part of the crest of the ilium, and communicates with the Ilio-hypogas- 

 tric nerve between that muscle and the Internal Oblique. The nerve then 

 pierces the Internal Oblique, distributing filaments to it, and, accompanying the 

 spermatic cord, escapes at the external abdominal ring, and is distributed to the 

 integument of the scrotum and upper and inner part of the thigh in the male, 

 and to the labium in the female. The size of this nerve is in inverse propor- 

 tion to that of the ilio-hypogastric. Occasionally it is very small, and ends by 

 joining the ilio-hypogastric ; in such cases, a branch from the ilio-hypogastric 

 takes the place of the ilio-inguinal, or the latter nerve may be altogether absent. 



The Genito-crural Nerve arises from the second lumbar, and by a few fibres 

 from the cord of communication between it and the first. It passes obliquely 

 through the substance of the Psoas, descends on its surface to near Poupart's 

 ligament, and divides into a genital and a crural branch. 



The genital branch descends on the external iliac artery, sending a few fila- 

 ments round that vessel ; it then pierces the fascia transversalis, and, passing 

 through the internal abdominal ring, descends along the back part of the sper- 

 matic cord to the scrotum, and supplies, in the male, the Cremaster muscle. .In 

 the female, it accompanies the round ligament, .and is lost upon it. 



The crural branch passes along the inner margin of the Psoas muscle, beneath 

 Poupart's ligament, into the thigh, where it pierces the fascia lata, and is dis- 

 tributed to the integument of the upper and anterior aspect of the thigh, com- 

 municating with the middle cutaneous nerve. 



A few filaments from this nerve may be traced on to the femoral artery ; 

 they are derived from the nerve as it passes beneath Poupart's ligament. 



The External Cutaneous Nerve arises from the second lumbar, or from the 

 loop between it and the third. It perforates the outer border of the Psoas 

 muscle about its middle, and crosses the Iliacus muscle obliquely, to the notch 

 immediately beneath the anterior superior spine of the ilium, where it passes 

 beneath Poupart's ligament into the thigh, and divides into two branches of 

 nearly equal size. 



The anterior branch descends in an aponeurotic canal formed in the fascia 

 lata, becomes superficial about four inches below Poupart's ligament, and divides 

 into branches, which are distributed to the integument along the anterior and 

 outer part of the thigh, as far down as the knee. This nerve occasionally com- 

 municates with the long saphenous nerve. 



The posterior branch pierces the fascia lata, and subdivides into branches which 

 pass across the outer and posterior surface of the thigh, supplying the integu- 

 ment as far as the middle of the thigh. 



The Obturator Nerve supplies the Obturator Externus and Adductor muscles- 

 of the thigh, the articulations of the hip and knee, and occasionally the integu- 

 ment of the thigh and leg. It arises by two branches : one from the third, the 

 other from the fourth lumbar nerve. It descends through the inner fibres of 

 the Psoas muscle, and emerges from its inner border near the brim of the 

 pelvis ; it then runs along the lateral wall of the pelvis, above the obturator 

 vessels, to the upper part of the obturator foramen, where it enters the thigh, 



