580 SPINAL NERYES. 



The iliac branch pierces the Internal and External oblique muscles imme- 

 diately above the crest of the ilium, and is distributed to the integument of the 

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

 293). The size of this nerve bears an inverse proportion to that of the cutaneous 

 branch of the last dorsal nerve. 



The hypogcutric branch 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 abdominal ring, and is 

 distributed to the integument covering the hypogastric region. 



The ILIO-INGUINAL NEEVE (inferior musculo-cutaneous), smaller than the pre- 

 ceding, 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 Quad- 

 ratus lumber um and Iliacus muscles, perforates the Transversalis, near the fore- 

 part of the crest of the ilium, and communicates with the ilio-hypogastric 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 proportion to that of the ilio- 

 hypogastric. Occasionally it is very small, and ends by joining it ; in such cases, 

 a branch from the ilio-hypogastric takes the place of that nerve, or the nerve may 

 be altogether absent. 



The GEXITO-CEUEAL NEEVE 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 distri- 

 buted to the integument of the upper and anterior aspect of the thigh, communi- 

 cating 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 EXTEENAL CUTANEOUS NEEVE arises from the second lumbar, or from the 

 loop between it and the third. It perforates the outer border of the I 3 soas muscle 

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

 diately 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 integument 

 in this region as far as the middle of the thigh. 



The OBTUEATOE NEEVE 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 



