148 



Practical Zoology. 



to their union in the large sciatic nerve, which runs down the 

 thigh. 



Turn now to the head, and cut into the bone between the 

 eyes. Cautiously working backward, the whole of the brain 

 may be unroofed. Great care must be exercised, for here we 

 have one of the softest of the tissues of the body lying very 

 closely beneath one of the hardest. It is possible to do this 

 work with a strong knife, but the bone forceps save a vast 

 amount of extra work. The bone must be broken away bit by 

 bit. 



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



The tough membrane covering the brain is the dura mater. 



The fore part of the brain is the cerebrum. Note the groove 

 separating it into the right and left hemispheres. Observe the 

 ridges, or convolutions, of its surface. The prolongations of the 

 brain between the eyes are the olfactory lobes. 



Back of the cerebrum is the cerebellum. Look at the human 

 skull to see whether there is a bony partition corresponding to 

 that which separates the cerebrum from the cerebellum in the 

 rabbit. 



The widening part of the spinal cord within the skull is the 

 spinal bulb. 



Make a drawing of the brain and spinal cord, showing as 

 many as possible of the points above noted. If desired, the 

 brain and cord, with a short part of each nerve, may be re- 

 moved from the body and laid on a cushion of cotton in weak 

 alcohol. 



Directions for preparing the Brain of a Cat or Rabbit. Direc- 

 tions have been given above for uncovering the brain. To 

 remove the brain, it will be necessary to cut through the tough 

 dura mater that covers it. 



Removing this, there will be found an inner covering, the 

 pia mater, a membrane richly supplied with blood tubes, from 

 which the brain gets its nourishment. After the dura mater has 

 been removed, the anterior end of the brain may be gently lifted 



