CHAPTER VIII. 



THE BRAIN. 



THE muscles are the executive organs. But the seat of 

 the Will is the brain. 



Let us study its structure and relations in order to come 

 nearer to an understanding of its functions. 



Directions for preparing the Brain of a Cat or Rab- 

 bit. Directions have been given on page 32 for uncover- 

 ing 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 with the handle of the scalpel and the under surface 

 studied, following the directions in rinding the cranial nerves. 



The brain may be studied while it is fresh, but it is- more 

 easily handled after it has been hardened. Lay the brain 

 in weak alcohol, about twenty-five per cent. It should rest 

 on a layer of cotton, otherwise it may be very much flattened 

 by its own weight, and get a good deal out of shape. Later 

 transfer it to fifty per cent alcohol, and then to seventy-five 

 per cent, or use a solution of alcohol and formalin as fol- 

 lows : 95 per cent alcohol, 60 parts ; 2 per cent formol, 40 

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

 volume. (See Appendix for another formula.) When it is 

 well hardened, it may be sliced with a sharp scalpel as di- 

 rected. 



The Brain of the Rabbit (Alcoholic Specimen). The 



253 



