NERVES OF MAMMALIA. 179 



junction of the first and second sacral gives a branch to the pyri- 

 forin muscle, and a larger one to pass out at the ischiatic notch to 

 supply the gluteal muscles and the tensor fascia?. Some branches 

 derived from the second and third sacral nerves combine with the 

 hypogastric plexus for supplying the bladder and rectum, and 

 others from the pudenda! nerves for the muscles connected with 

 the anus and tail. A branch of the second sacral nerve joins the 

 third for forming the anterior caudal nerve, which receives the 

 anterior trunk of each remaining spinal nerve, and passes deep in 

 the anterior part of each side of the tail, giving off branches into 

 its course ; the posterior or dorsal trunks of the same nerves form 

 a nerve, which also sends off branches to the dorsal muscles and 

 skin of the tail. 



The anterior crural nerve passes between fibres of the iliac 

 muscle, then under Poupart's ligament at the inner side of the 

 sartorius ; it gives branches to this, to the rectus femoris, the 

 external and internal vasti, and the cruralis, and sends off the 

 saphenus nerve, which descends across the thigh to the inner part 

 of the leg, communicates with a filament from the obturator, and 



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is continued to the foot, giving filaments in its course to the 

 fascia and skin. The obturator nerve, on emerging from the 



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pelvis, gives branches to the pectineal muscle, the triceps, and 

 gracilis, and sends a branch to communicate with the saphenus 

 nerve ; several fine branches pass down on the inner side of 

 the thigh for the fascia and integuments. The sciatic nerve, 



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on emerging from the pelvis, communicates with the internal 

 pudendal ; it sends a branch to the internal obturator muscle, 

 and one which gives a filament to the upper portion of the 

 gemelli, and then passes behind the tendon of the internal 

 obturator to the lower portion of the gemelli and quadratus 

 muscles. The sciatic passes close to the insertion of the in- 

 ternal obturator muscle, and upon or behind the gemelli and 

 quadrati muscles, then behind the trochauter covered by the 

 origin of the biceps to which it gives a branch : it sends off a large 

 branch w r hich divides into others for the semimembranosus and 

 semitendinosus muscles. About the middle of the thigh it sepa- 

 rates into the posterior tibial and peroneal nerves. 



The posterior tibial nerve sends off a long slender branch 

 which descends on the posterior part of the gastrocnemius muscle 

 to the outer side of the leg, sends a branch behind the tendo 

 A chillis to the posterior tibial nerve, and is distributed on the 

 skin at the outer side of the leg and heel. It then gives 



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