254 CRANIAL NERVES. 



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 specimen 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 grooves, is the Pia Mater. 



2. Press down the spinal bulb (medulla oblongata), and 

 tear away the pia mater where it passes from the cerebellum 

 to the spinal bulb. Note, between the bulb and the cere- 

 bellum, 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 

 transverse band of white fibers connecting them. 



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

 roots of the cranial nerves. 



The Cranial Nerves. 1. The Olfactory Lobes (probably 

 cut or broken off) extend forward from the fore part of the 

 cerebral hemispheres. 



2. Note that the Optic Nerves join each other before reach- 

 ing 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, are the 

 third pair of nerves. 



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

 between the cerebrum and the cerebellum. 



5. Back of these are the larger fifth pair. This pair sup- 

 ply part of the face, and send branches to the teeth. It is 

 the nerve affected in neuralgia of the face. 



6. Back of and inside of the fifth .pair are the sixth pair. 



