702 



SPINAL NERVES. 



jnibic, or scrotal branch runs parallel to Pou- 

 part's ligament, in company with, but above, 

 the small external cutaneous, reaches the ex- 

 ternal ring, and divides into internal tern.inal 

 branches supplying the skin over the pubis ; 

 and external ones supplying the scrotum in 

 the male, and the labia pudencli in the female. 

 The lower musculo-cutaneous (small muscu- 

 lo-cutaneous small inguino-cutaneous small 

 abdominal) is a thin delicate nerve, arising 

 generally from the first lumbar, sometimes from 

 the large musculo-cutaneous, is directed down- 

 wards and slightly outwards, along the back 

 part of the psoas, a little in front of the inner 

 border of the quadratus lumborum, crosses the 

 iliacus interims about its upper fourth, and 

 reaches the anterior third of the crest of the 

 ileum. There it is lost by communicating with 

 the large musculo-cutaneous, or, as is generally 

 the case, passes after this communication as a 

 very delicate nerve between the internal ob- 

 lique and transversalis, supplying the lower 

 part of these muscles, but principally the 

 latter, and parallel to Poupart's ligament, per- 

 forates the former muscle at the outer ring, 

 and terminates in a manner similar to the 

 pubic or scrotal branch of the upper mus- 

 culo-cutaneous, in the scrotum and pubic in- 



tegument. 



The genito-crural nerve (external sper- 

 matic internal inguinal) derived from the 

 second lumbar nerve, and sometimes from the 

 communicating branch between the first and 

 second, passes directly forwards to the anterior 

 part of the psoas muscle, along which it de- 

 scends vertically to the femoral arch. It lies 

 behind the spermatic vessels, and is crossed 

 by the ureter. Having reached Poupart's 

 ligament, it divides into two branches, an in- 

 ternal or genital, and an .external or crural. 

 The genital is directed across the external iliac 

 artery (to which it supplies a few filaments) 

 to the chord, lying below it as far as the in- 

 ternal ring. Prior to entering the inguinal 

 canal the transversalis and internal oblique re- 

 ceive a few reflected branches from it. The 

 nerve then accompanies the chord, crosses the 

 epigastric vessels, supplies the cremaster 

 muscle, runs immediately in front of Gimber- 

 nat's ligament, and terminates in the scrotal 

 integument in the male, and labia pudendi in 

 the female, supplying also the integument at 

 the upper and inner part of the thigh, and 

 communicating with the inferior pudenclal 

 nerve. The crural branch (femoral-cuta- 

 neous), having given off several delicate fila- 

 ments to be distributed to the transversalis 

 and internal oblique, crosses the circumflex 

 ilii vessels, passes underneath Poupart's liga- 

 ment, a little to the outside of the femoral 

 artery, pierces the fascia immediately below 

 the ligament, and becomes cutaneous, sup- 

 plying the skin of the thigh at the middle 

 part of its upper third. The division of the 

 genito-crural into its terminal branches is 

 subject to considerable variation, sometimes 

 taking place either immediately after it has 

 emerged from within the psoas, or within the 

 psoas directly after its origin from the plexus. 



The crural division is at times also extremely 

 small, the external cutaneous then having a 

 more extensive distribution than ordinary. 



The external cutaiuous (external inguinal) 

 is a branch from the second or from the 

 second and third lumbar, or is occasionally 

 derived from the outer part of the crural 

 nerve. It passes from beneath the outer 

 border of the psoas below its middle, runs 

 across the iliacus towards the space between 

 the two spinous processes of the ilium, lying 

 behind the transversalis fascia. It then passes 

 beneath Poupart's ligament, and divides into 

 an interior and posterior branch. The poste- 

 rior passes outwards and backwards over the 

 fascia, covering the tensor vaginae femoris, 

 and supplies the integument at the upper, 

 outer, and back part of the thigh. The ex- 

 tent of distribution of this branch is subject 

 to variation, owing to the circumstance of a 

 corresponding branch being occasionally sup- 

 plied either by the great musculo-cutaneous, 

 or by the genito crural, when the trunk of 

 the external cutaneous itself comes from the 

 anterior crural. In such instances this branch 

 is small and insignificant, if it exist at all. 

 The anterior branch becoming cutaneous about 

 the upper fifth of the thigh, soon divides into 

 an external and internal, directed downwards, 

 over the fascia covering the anterior and outer 

 part of the rectus muscle. The external di- 

 vision terminates in the integument at the 

 middle third of the outer part of the thigh ; 

 the internal at the lower third of the thigh, 

 above and to the outside of the patella. 



The crural nerve (femoral) is by far the 

 largest branch of the lumbar plexus, and is 

 placed in the substance of the psoas muscle 

 between the external cutaneous, and the ob- 

 turator, below the level of the former and 

 above that of the latter, from which it diverges 

 at an acute angle. It is formed by the union 

 of the second with the outer branch of the 

 third lumbar nerve, by part of the fourth, and 

 generally by their communicating branch. It 

 is destined to supply the integuments of the 

 front of the thigh, and all the muscles at its 

 anterior and outer portion. 



Having emerged from the psoas muscle it 

 is directed forwards and outwards between 

 that muscle and the iliacus to Poupart's liga- 

 ment, under which it passes, and entering the 

 thigh becomes flattened and expanded, and 

 divides into a scries of divergent terminal 

 branches, the trunk occasionally bifurcating 

 before so doing. 



The nerve in its course within the pelvis is 

 situated behind the iliac division of the trans- 

 versalis fascia, external to the iliac artery, and 

 gives off a few branches to the psoas and ili- 

 acus. Outside the sheath of the femoral vein 

 and artery it is separated from the latter by 

 the intervention of the psoas muscle. 



The terminal branches may be divided into 

 superficial and deep ; the first consisting of 

 the internal, and middle cutaneous, and branches 

 1o the femoral vessels and pcctinccus : the second 

 of branches to the quadriceps extensor cruris, 

 and the cutaneous branch of the inner and 



