140 GENERAL BIOLOGY. 



the spinal cord. Note especially at the level 

 of the shoulder : 



1. The brachial plexus, made up of the 5th to 



the 8th cervical and the 1st thoracic nerves 

 inclusive. It gives off four chief nerves ; 

 follow them out and see what regions they 

 innervate. 

 In the region of the leg : 



2. The lumbro-sacral plexus, made up of the 



5th to the 7th lumbar and of the 1st to the 

 3d sacral nerves, inclusive. It gives off 

 three chief nerves ; follow them out. 

 C. The Brain. 

 1. Externals. 



With bone forceps cut away as much of the skull 

 as may be necessary to free the brain. Take 

 it out and put it into a dish of formic aldehyde 

 solution or of alcohol. 

 Find the parts visible on the surface. 

 On the dorsal side : 



(a) The olfactory lobes. 



(b) The cerebral hemispheres. 



(c) The pineal gland. 



(d) The cerebellum. 



(e) The medulla, etc. 

 On the ventral side : 



(a) The olfactory lobes. 



(b) The cerebral hemispheres. 



(c) The optic nerves, chiasma, and tracts. 



