704 



NERVOUS SYSTEM OF THE HORSE 



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 l)ranches 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. iHohypogastricus). It passes outward between the quadratus lum- 

 borum and the psoas major, and divides at the outer border of the latter into an 

 anterior or superficial and a posterior or deep branch. The anterior or superficial 

 branch passes over the upper edge of the internal oblique, descends l:)etween that 

 muscle and the external oblique, perforates the latter, and runs downward and back- 

 ward and ramifies under the skin of the posterior part of the flank and the outer 

 surface of the thigh. It gives branches to the transversus and obliquus externus 

 abdominis. The posterior or deep branch is smaller; it runs downward and back- 



Cruut of (luiphnigm-. 



Duiph 



Ldbt UltdLU 



Ilio-hynogdst) I 



ncroc — 

 Ilio-mquinal nerve 

 External sjnrmatic _ 

 nerve 

 Exkr)ud culdnrous.^ 



nerve ^y/ 



Sjjmpathth 



li luiL^ 7 



Insertion oj quad- 

 ratus lumborian 



Anterior pni u^ 

 lumbosacral ph rus \l" 



Obtuiator nerve - 

 Femoral nerve 



Splanchnic nerve 

 Last intercodal arteries 

 First lumbar arteries 



Attachments of psoas major 

 Body of vertebra 

 External spermatic nerve 

 " " Trunk of lumbar arteries 



Sixth lumbar artery 



Ventral sacro-iliac 

 ligament 



Fig. 524. — Lu.mb.\r Nerves of Horse, Ventral View (After Schmaltz, Atlas il. Anat. d. Pferdes.) 



ward beneath the peritoneum to the outer border of the rectus abdominis, gives 

 branches to the internal oblique, and terminates in the rectus abdominis. 



The ventral branch of the second lumbar nerve is connected by an anastomotic 

 branch with that of the third nerve. It gives off a large branch to the psoas muscle 

 and an inguinal branch, and is continued as the ilio-inguinal nerve. The inguinal 

 branch (N. spermaticus externus) runs backward in the su]:)stance of the psoas 

 minor, emerges a short distance in front of the circumflex iliac vessels, and runs 

 backward and downward under the ]i(>ritoneum to the internal inguinal ring. It 

 gives branches to the internal ol)li(|ue muscle and descends in the inguinal canal 

 along the outer border of the cremaster (to which it detaches filaments) and ends 

 subcutaneously in the scrotum and prepuce in the male, the mammary gland in the 

 female. The ilio-inguinal nerve (N. ilioinguinalis) may l^e regarded as the con- 

 tinuation of the ventral l)ranch. It runs parallel with the ilio-hypogastric nerve 

 and has a similar arrangement. Its anterior or superficial branch i^erf orates the 

 external oblique muscle a little in front of the point of the hip, runs downward on 

 the front of the thigh and the outer surface of the stifle, and gives off cutaneous 

 branches. The posterior or deep branch runs behind and i)arallel with that of the 



