THE LUMBAR NERVES 
823 
It joins a branch of the external spermatic nerve, and the trunk so formed de- 
scends the inguinal canal, to be distributed to the external genital organs and the 
surrounding skin in the inguinal region. 
The ventral branch of the third lumbar nerve is connected by a small anasto- 
motic branch with the second nerve and furnishes a root of the lumbo-sacral plexus. 
It gives off a branch to the psoas muscles, the external spermatic nerve, and 
is continued as the lateral 
cutaneous nerve. The ex- 
ternal spermatic nerve (N. 
spermaticus externus) passes 
backward in the substance of 
the psoas minor and divides 
into two branches. One of 
these, the muscular branch, 
emerges in front of the circum- 
flex iliac vessels and goes to the 
cremaster and internal oblique 
muscles. The other, the in- 
guinal branch, emerges behind 
the vessels Just mentioned. It 
then runs lateral to and parallel 
with the external iliac artery 
and descends in the medial 
part of the inguinal canal. It 
emerges at the external ring 
with the external pudie artery 
and ramifies in the external 
genital organs and the skin of 
the inguinal region. The lat- 
eral cutaneous nerve of the 
thigh (N. cutaneus femoris 
lateralis) runs backward in 
the substance of the psoas 
muscles and emerges at the 
lateral border of the psoas 
minor. It then passes outward 
and backward on the iliac fas- 
cia and accompanies the pos- 
terior branch of the circumflex 
iliac artery. With this vessel 
it perforates the abdominal 
wall by passing between the 
external oblique and the iliacus 
a short distance below the 
point of the hip, descends on 
Fic. 657.—Superricia, Nerves or Pei 
vic Limp anp PosterioR PART OF 
TrouNK oF Horse. 
a, Cutaneous branches of sixteenth 
and seventeenth thoracic nerves; b, cuta- 
neous branches of lumbar nerves; c, cu- 
taneous branches of sacral nerves; d, 
cutaneous branches of coccygeal nerves; 
e, /, g, cutaneous branches of last thoracic 
and first and second lumbar nerves; g’, 
end of lateral cutaneous nerve of thigh; 
kh, posterior cutaneous nerve of thigh; i, i, 
cutaneous branches of great sciatic nerve; 
k, posterior cutaneous nerve of the leg; 
1, superficial peroneal nerve; m, terminal 
part of deep peroneal nerve; n, lateral plantar nerve; 1, obliquus ab- 
dominis externus; 2, tensor fascie late; 3, gluteus superficialis; 4, 
biceps femoris; 
tensor; 8, flexor tendons; 9, great metatarsal artery. 
berger, in Leisering’s Atlas.) 
5, semitendinosus; 6, common extensor; 7, lateral ex- 
(After Ellen- 
the medial face of the tensor fascie late (near its anterior border), and ramifies 
subcutaneously in the region of the stifle. 
The origin and disposition of some of the foregoing nerves are variable. 
In some cases the 
ilio-inguinal nerve ends in the psoas major, and appears then to be absent. The mode of formation 
of the inguinal nerves is inconstant. 
The ventral branches of the fourth, fifth, and sixth lumbar nerves concur in 
the formation of the lumbo-sacral plexus. 
