822 NERVOUS SYSTEM OF THE HORSE 
THE LUMBAR NERVES 
There are six pairs of lumbar nerves (Nn. lumbales) in the horse, the last of 
which emerge between the last lumbar vertebra and the sacrum. The anterior two 
or three are about the same size as the thoracic nerves, but the others are much 
larger. 
Their dorsal branches are small in comparison with the ventral ones. They 
are distributed to the muscles and skin of the loins and croup in a fashion similar 
to those of the thoracic nerves. 
The ventral branches are connected with the sympathetic by small rami 
communicantes, and give branches to the sublumbar muscles. Those of the first 
two nerves are arranged in a manner analogous to the corresponding branch of the 
last thoracic nerve. 
The ventral branch of the first lumbar nerve is termed the ilio-hypogastric 
nerve (N. iliohypogastricus). It passes outward between the quadratus lum- 
Splanchnic nerve 
Last intercostal arteries 
Diaphragm ~<— First lumbar arteries 
Last thoracic 
merve 
'— Altachments of psoas major 
‘~~ Body of vertebra 
— External spermatic nerve 
~ > Trunk of lumbar arteries 
Llio-hypogastric 
nerve ———_.... 
Tlio-inguinal nerve 
External spermatic — 
Nerve 
External cutaneous 
Sympathetic 
trunks 7 
hs “pe 
~ Ventral sacro-iliac 
~ ligament 
Insertion of quad- 
ratus lumborum ~ 
Anterior part of J 
lumbo-sacral plecus \=—— 
Obturator nerve ~~~ 
Femoral nerve 
Bisa 
Fic. 656.—Lumpar Nerves or Horse; Ventray View. (After Schmaltz, Atlas d. Anat. d. Pferdes.) 
borum and the psoas major, and divides at the lateral border of the latter into a 
superficial and deep branch. The superficial or cutaneous branch passes over the 
dorsal edge of the internal oblique, descends between that muscle and the external 
oblique, perforates the latter, and runs downward and backward and ramifies 
under the skin of the posterior part of the flank and the lateral surface of the thigh. 
It gives branches to the transversus and obliquus externus abdominis. The deep 
(or muscular) branch is smaller; it runs downward and backward beneath the 
peritoneum to the lateral border of the rectus abdominis, gives branches to the 
internal oblique, and terminates in the rectus abdomuinis. 
The ventral branch of the second lumbar nerve is usually connected by an 
anastomotic branch with that of the third nerve. It gives off a large branch to the 
psoas major and is continued as the ilio-inguinal nerve (N. ilioinguinalis). This 
divides like the ilio-hypogastrie into superficial and deep branches. Its superfi- 
cial branch perforates the external oblique muscle a little in front of the point of 
the hip, runs downward on the front of the thigh and the lateral surface of the 
stifle, and gives off cutaneous branches. The deep branch runs behind and parallel 
with that of the ilio-hypogastricus and detaches branches to the abdominal muscles. 
