Allkn. Association in the Guinea Pig. 359 



cortices owing to the fact that medullation in the guinea pig ap- 

 pears to be more advanced. 



Very httle change occurs in the central nervous system 

 chuing the first three days of the guinea pig's life. Medullation 

 then increases quite steadily but slowly as compared with the 

 white rat. When the white rat is thirty-five days old it has a 

 neural development at the same stage as the thirty day guinea 



pig- 



Our conclusion then is that the guinea pig is psychically 

 mature soon after birth, and at that time has a well medullated 

 nervous system ; furthermore, the degree of development of the 

 nervous system corresponds to that of the white rat at 23-27 

 days, or its period of psychical maturity. 



[67] 



