224 MAMMALIA. 



13. First lumbar nerve; the anterior trunks of the lumbar and sacral nerves 

 supply principally the parts connected with the lower extremity, the bladder 

 and rectum ; the two superior of the posterior trunks of the lumbar supply 

 the skin as well as the sacro-lumbar and other muscles connected with the 

 posterior part of the lumbar vertebrae ; the lower five the muscles only ; the 

 posterior sacral supply the muscles connected with the posterior part of the 

 tail. The nerves are not very different from those in man except in their 

 number, and consequently in their conjunction a little higher or lower for 

 forming the nerves of the lower extremity. The anterior trunks of the three 

 first lumbar nerves give filaments to the psoas muscle, and then pass forward 

 to terminate in the abdominal muscles and skin. The fourth gives filaments 

 to the psoas and internal iliac muscles, and sends a branch to join one from 

 the third to form the external spermatic on the external iliac artery, which 

 passes through the external ring to the spermatic cord ; in a female dog this 

 was distributed on the last division of the mamma; it sends off another 

 branch which gives a filament to the external iliac artery and then joins the 

 fifth ; the rest of the fourth passes down on the exterior of the thigh to the 

 skin, and forms the external cutaneous nerve. The fifth receives a branch 

 from the fourth, gives filaments to the internal iliac muscle ; part of it is then 

 joined by a large branch from the sixth to form the anterior crural nerve ; 

 the other part, after receiving a large and small branch from the sixth, 

 becomes the obturator nerve. The sixth, having given off the preceding 

 branches, joins the seventh and the first sacral, and a branch of the second, 

 for forming the sciatic nerve. The junction of the seventh lumbar and first 

 sacral gives a branch to the pyriform muscle, and a larger one to pass out at 

 the ischiatic notch to supply the gluteal muscles and the tensor of the fascia 

 of the thigh. Some branches derived from the first and second 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 



