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 sldn 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- c, j 



temal 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 pudic 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 . , , x , -n 



the medial face of the tensor fasciaj latse (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 

 mo-inguinSve 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. 



Fig. G57. — Superficial Nerves of Pel^ 

 VIC Limb and Posterior Part of 

 Trunk of Horse. 



a, Cutaneous branches of sixteenth 

 and seventeenth thoracic nerves; 6, cuta- 

 neous branches of lumbar nerves; c, cu- 

 taneous branches of sacral nerves; d, 

 cutaneous brandies of coccygeal nerves; 

 e, f, y, cutaneous branches of last thoracic 

 and first and second lumbar nerves; g', 

 end of lateral cutaneous nerve of thigh; 

 h, posterior cutaneous nerve of thigh; i, i, 

 cutaneous branches of great sciatic nerve-, 

 k, posterior cutaneous nerve of the leg; 

 I, superficial peroneal nerve; m, terminal 

 part of deep peroneal nerve; n, lateral plantar nerve; 1, obliquus ab- 

 dominis externus; S, tensor fasciae latae; 3, gluteus superficialis; 4, 

 biceps femoris; 5, semitendinosus; 6, commoa extensor; 7, lateral ex- 

 tensor; 5, flexor tendons; . 

 berger, in Leisering's Atlas.) 



great metatarsal artery. (After Ellen- 



