124 GENERAL BIOLOGY. 



Diagram ! 



B. The Peripheral Nervous System. 



1. On the dorsal wall of the body-cavity note : 



the thoracic spinal nerves coming from be- 

 tween the vertebrae and passing out between 

 the ribs. 



2. The brachial plexus, a network of nerves at 



the base of the neck. Trace the distribu- 

 tion of the chief nerves given off from it. 



3. The lumbar plexus in the lumbar region. 



Two nerves are given off from it ; what do 

 they innervate ? 



4. The sciatic plexus. The sciatic nerve is given 



off ; what is its course ? 

 Diagram ! 



C. The Brain. 



1. Externals. 



As the brain lies in the cranial cavity, note : 

 (a) The cerebral hemispheres. 

 (6) The olfactory nerves. 



(c) The optic lobes. 



(d) The cerebellum. 



(e) The medulla oblongata. 

 Diagram ! 



JZemove the dorsal arches of the first two verte- 

 brce, cut through the spinal cord, and turn 

 the brain forward, carefully cutting all the 

 nerves. 

 On the ventral side note : 



