158 MAMMALIA. 



sacral nerves combine with the hypogastric plexus for supplying the bladder and 

 rectum, and others from the pudendal 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 in its 

 course ; posterior trunks of the same nerves form a posterior caudal nerve, which also 

 sends off branches to the posterior 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, to which it gives branches also to 

 the straight muscle, the external and internal vast muscles, and the crural, and sends 

 off the saphenus, which, accompanied by a large branch of the femoral artery, as well as 

 by the saphena vein, descends across the thigh to the inner part of the leg, com- 

 municates with a filament from the obturator, and is continued to the foot, giving 

 filaments in its course to the fascia and skin. The obturator nerve on emerging from 

 the pelvis gives branches to the pectineal muscle, the triceps and gracile, 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 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 geminous, and then passes behind the tendon of the internal obturator to the 

 lower portion of the geminous and square muscles ; the sciatic passes close to the 

 insertion of the internal obturator muscle, and upon or behind the geminous and square 

 muscles, then behind the trochanter covered by the origin of the biceps to which it 

 gives a branch ; it sends off a large branch which divides into others for the semi- 

 membranous and semi-tendinous muscles. About the middle of the thigh it separates 

 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 tendon of Achilles to the 

 posterior tibial nerve, and is distributed on the skin at the outer side of the leg and 

 heel. It then gives branches to the gastrocnemius muscle, and passes between the 



