THE BABBIT. 129 



14. In the region of the shoulder carefully trace several 

 nerves on each side as they unite to form the brachial 

 plexus, branches from which supply the fore limb. 



15. In the region of the hips, in like manner trace sev- 

 eral large nerves to their union in the lumbo-sacral 

 plexus, the main nerve from which may be followed 

 down the back of the thigh, the sciatic nerve. 



16. Compare the color of the brain with that of the spinal 

 cord. 



17. Make a drawing of the brain and spinal cord. Re- 

 move the brain and cord with the plexuses, and put 

 the whole into alcohol. 



TEDS BRAIN OF THE BABBIT. 



(Alcoholic Specimen.^ 



The brain of a cat or dog is better, being larger. Take 

 a brain well hardened in alcohol, or a strong solution of bi- 

 chromate of potash, and review the parts as named above. 



1. Press down the cerebellum to see the deep groove 

 between it and the cerebrum. The thin membrane 

 covering the brain and dipping into the grooves is 

 the pia mater. 



2. Press down the medulla oblongata, and tear away the 

 pia mater where it passes from the cerebellum to the 

 medulla oblongata. Note, between the medulla and 

 the cerebellum, a space covered by a thin membrane. 

 Cut through this membrane ; the cavity is the fourth 

 ventricle of the brain. Observe the two ridges 

 bounding the sides of the fourth ventricle. At their 

 point of divergence, observe the opening of fche central 

 canal of the spinal cord. 



