THE LUMBOSACRAL PLEXUS 



Fig. 476. 



the internal of the first toe, internal and external of the second, internal and external of the 

 third, and external of the fourth digit. 



Comparison of the Lumbo-sacral Plexus in Man with that of Animals. 



It is usual, in human anatomy, to describe a lumbar and a sacral plexus. 



The lumbar plexus is constituted by the anastomoses of the anterior branches of the five 

 lumbar nerves ; > these are united by fine filaments, which are not intricately associated. The 

 divisions of this plexus are distinguished as collateral and terminal branches. The first, 

 destined to the upper part of the limb and the skin covering the external genital organs, are 

 represented in Solipeds by the ramifications of the lumbar nerves, which have been separately 

 described. The terminal branches are 

 the obturator crural, and anterior 

 femoral (or anterior crural). There is 

 nothing to be said respecting the ob- 

 turator nerve ; it leaves the pelvis by 

 the obturator foramen, as in all the 

 animals mentioned. The crural has 

 been described as having four terminal 

 branches: the internal and external 

 musculo-cutaneous, the nerve of the 

 triceps crureus {muscular branch), and 

 the internal saphenous. The two 

 musculo-cutaneous branches have their 

 analogue in the Horse, in the filament 

 we have named the accessory branch 

 of the internal saphenic. The nerve 

 of the triceps is expended in the an- 

 terior rectus, and the vastus intern us 

 and externus. The saphenic de- 

 scends between the muscles of the 

 inner aspect of the tliigh, beneath the 

 aponeurosis, and becomes superficial 

 at a short distance from the condyle 

 of the femur, giving a patellar branch 

 that divides in the skin of the knee, 

 and a tibial branch that is expended 

 on the inner face of the tarsal articula- 

 tions and the foot. 



The sacral plexus comprises the 

 first three sacral nerves, to which is 

 added a lumbo-sacral branch furnished 

 by the lumbar nerves, and a fine fila- 

 ment that ascends from the fourth 

 eacral. 



Ten collaterals and a terminal 

 branch arise from this plexus. 



The collateral branches are divided 

 into intra-pelvic and extra-pelvic: 

 they are five in each group. The first 

 are destined to the muscles of the 

 inner aspect of the pelvis, and to those 

 of the perineum and the skin of this 



lumbar plexus of man. 

 1, Right gangliated cord of .sympathetic ; 2, abdominal 

 aorta ; 3, 3, last dorsal nerves ; 4, psoas parvus ; 5, 

 quadratus lumborum ; 6, psoas magnus; 7, 7, ilio- 

 hypogastric nerves; 8. iliacus iuternus; 9, 9, ilio- 

 inguinal nerve; 10, lumbo-sacral nerve; 11, genito- 

 crural nerve; 12, gluteal nerve; 13, iliac branch of 

 ilio-hypogastric nerve; 14, sacral plexus; 15, 1.5, 15, 

 external cutaneous nerves; 17, transversalis abdomi- 

 nis; 19, obliquus internus ; 21, obliquus externus; 

 23, 23, anterior crural nerves ; 25, 25, obturator 

 nerves ; 27, 27, crural branch of genito-crural nerve ; 

 2>, genital branch of genito-crural nerve; 31, external 

 iliac artery ; 33, external abdominal ring. 



region. The second are distributed to 



the muscles on the outer aspect of the pelvis, and the skin on the posterior face of the thigh. 



They are — 



1. Visceral branches that descend on the sides of the rectum and are lost in the hypogastric 

 plexus. 2. Nerve of the elevator of the anus. 3. Exmorrhoidal or anal nerve. 4. Nerve of the 

 internal obturator that apptars to arise, in the Horse, from the sciatic trunk. 5 Internal 

 fudic, which has been described with the sacral nerves. In Man this nerve leaves the pelvis 



(' Wilson says the four upper lumbar nerves and the last dorsal ; Heath gives the same 

 constitution.) 



