THE BRAIN 237 



lin as follows : 95 per cent alcohol, 60 parts ; .2 per cent formol, 40 

 parts. The liquid need not be changed if used in sufficient volume. 



The Brain of the Rabbit {Alcoholic Specimen}. The brain of 

 a cat or dog is better, being larger. Take a brain well hardened, and 

 review the parts as named above. It is very desirable to have a speci- 

 men in which the arteries have been injected. 



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 groove is the pia mater. 



2. Press down the spinal bulb and tear away the pia mater where 

 it passes from the cerebellum to the spinal bulb. Note, between the 

 bulb 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 

 the point of their divergence, observe the opening of the central canal 

 of the spinal cord. 



3. Gently separate the cerebral hemispheres, and note the trans- 

 verse band of white fibers connecting them. 



4. Examine the under surface of the brain, and find the roots of the 

 cranial nerve. 



The Cranial Nerves and their Functions. i. The 



olfactory lobes extend forward under the fore part of the 

 cerebral hemispheres. They are the nerves of smell. 



2. The optic netves, or nerves of sight, join each other 

 before reaching the brain. Only the first and second pairs 

 of cranial nerves directly enter the cerebrum. 



3. Back of the optic nerves, near the middle line, is the 

 third pair of nerves. The third, fourth, and sixth pairs 

 of cranial nerves control the muscles of the eyeballs. 



4. The fourth pair extend up on each side into the 

 groove between the cerebrum and the cerebellum. 



5. Back of these is the larger fifth pair, the trigeminal. 

 This pair supplies part of the face, and sends branches to 

 the teeth. It is the nerve affected in neuralgia of the 

 face. Besides being the nerve of sensation for most of the 



