196 Journal of Comparative Neurology. 



or branches, which enter the sympathetic system. The ventral 

 division has two main branches, a lateral, piercing the muscles 

 at the side and giving off dorsal and ventral branches, and 

 a ventral, extending well towards the median line in front, run- 

 ning for the most part between the muscles, but finally piercing 

 them and supplying the skin in front. This ventral branch of 

 the eleventh nerve usually becomes sub-cutaneous in a region 

 somewhat below the umbilicus. It usually anastomoses freely 

 with similar branches from the tenth and twelfth nerves. 



In addition, the primary ventral division of the eleventh 

 nerve may give off near the spinal column a branch of commu- 

 nication to the corresponding branch of the twelfth thoracic 

 nerve. 



The twelfth thoracic nerve likewise has the characteristics of 

 a segmental nerve, supplying the region immediately caudal to 

 that supplied by the eleventh nerve. The lateral branch usu- 

 ally extends well down over the middle third of the iliac crest. 

 In addition to the ventrolateral nerve, or in place thereof, the 

 ventral division may give rise, usually near the spinal column, 

 to the ileo-hypogastric nerve. This nerve runs to the ventral 

 third of the iliac crest, there divides and sends an iliac branch 

 over the lateral hip region and a ]iypogastric branch to the ab- 

 domen just above the pubis. This nerve bears varied and often 

 very intimate relations to the ventro-lateral nerves. More 

 rarely origin is given to the ileo-ingiiinal nerve. This nerve has 

 a course very similar to that of the ileo-hypogastric but supplies 

 a more ventral region of the hip, and the skin of the pubic re- 

 gion and root of the penis and of the scrotum and the adjacent 

 part of the thigh. There are often anastomoses between the 

 ileo-inguinal and the ileo-hypogastric nerves. The iliac branch 

 of the former is often wanting. 



The first lumbar nerve has no true ventro-lateral branch. 

 Its place is usually supplied by the ileo-hypogastric and ileo- 

 inguinal nerves which have many of the characteristics of ven- 

 tro-lateral nerves. In addition, the first lumbar usually gives 

 rise to the gcniio-cntral nerve or to one of its branches. This 

 nerve, sometimes with separate genital and crural branches, runs 



