.92>. The inbred d irtriL\i t ion ifi from .70;'; to .95*1; thftt of 

 the novi'iMls from .84;.- to l.Ob^'. The average I'elative brain 

 weit;ht (with reference to body lent^tli) of the f;ixty-two nor- 

 nal rats if^ .9?3bl;.'; that of the inbredp is .fi73?b:.', or 6,44;' 

 lens than that of the normal h. 



In order to comparp the ability of the rate of the 

 leprer brain vei^it strtdri (inbred ratfi) vith a norna] control 

 peries tiiree experimentB v/ere used: 



1. The raz.e, in \vhich all the ratr, used vere riven five trials 

 daily until they hed learned perfectly, or, fnilint, to learn, 

 had worked one hundred days' (500 trials). At the expiration 



of sixty days after perfect learning the rats, except those 

 failing to learn, v/ere tested for retention and relearnint^ 

 until relearnin^ was perfect, or, failing: relearnin^;, for fif- 

 ty days (250 trials). 



2. The Preliminft.ry Inclined Plane, in vhich cill the ratp used 

 were t.iven five trials daily for twenty days (lOO trials); 



at the expiration of sixty days after tliis period they were 

 all tested for retention and relearnint ^or a period of five 

 days (25 trials), 



3. The Inclined Plane, in which all the rats used were .vi"^?" 

 three trials daily until they had learned perfectly, or, fail- 

 ing, to learn, h;^d v/orked one hundred days (300 trials). At the 

 expiration of Hixty days after perfect learninji the rats, ex- 

 cept those failin^; to learn, v/ere tested for retention and 

 relearnint until relearnin,/ was perfect. 



In rill these experiments the str; in of ratr of lenr.er 

 relative brain weight (the inbred?) learned less veil, on the 

 averate, than the nornnl control scricE. In the r.tize and in- 

 clined plane experimente the average number of days required 

 to learn and relearn and the time of absolute retention wr« 



