162 



THE HUMAN BODY. 



plexus. It supplies the lower part of the trunk, the but- 

 tocks, the front of the thigh, and medial side of the leg. 



The sacral plexus is formed by the anterior primary 

 branches of the fifth lumbar and the first four sacral 

 nerves, which unite into one great cord and so form the 



FIG. 65. The cervical and brachial plexuses of one side of the Body. 



sciatic nerve, which is the largest in the Body and, running 

 down to the back of the thigh, ends in branches for the 

 lower limb. The roots of the trunks which form the sacral 

 plexus arise from the lumbar enlargement of the cord. 



