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 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- 

 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 between 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- 



er «ra of (lidpliragm:::-^,^ 



DUipiiragm 

 Last iiiU'rcostal 

 Nerve 



Ilio-hypogdfilric 

 nerve 

 Ilio-inguinai nerve— : 



External spermatic /.. 



nerve / 



External ciitanrous^^,'^^ 



nerve //-^ 



Sympnthelic 

 trunks 7 



Insertion of qu(ul- 

 ratus lumbar lun " 



Anterior p-iri of I 

 lumbosacral plexus \. 



Obturator nerve- — r: 



Femoral nerve 



Splanchnic nerve 

 Last intercostal arteries 

 ^5^ First lumbar arteries 



'~ Attachments of psoas major 

 - Body of vertebra 

 -External spermatic nerve 

 ^ Trunk of lumbar arteries 



Sixth lumbar artery 



entral sacro-iliac 

 ligament 



Fig. 524. — Lumeiak Nkhves ok Horsk, Ventral View. (After Schmaltz, Atlas d. 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 l)raiich of th{> 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 substance of the psoas 

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

 backward and downward under the ixnitoneum to the internal inguinal ring. It 

 gives brandies to the internal oblique muscle and descends in the inguinal canal 

 along the outer border of the crcmaster (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 be regarded as the con- 

 tinuation of the ventral branch. It runs parallel with the ilio-hypogastric nerve 

 and has a similar arrangennent. Its anterior or superficial 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 outer surface of the stifle, and gives off cutaneous 

 branches. The posterior or deep branch runs behind and parallel with that of the 



