107 



Tab.le VIl.T prpMentp a comp'irMtlve aunnury oonHiBtinti 

 cf the dalJy Hveraj/es of nil the inbred and all the control 

 rats. Ti'rom thii=< table are constructed the comi^arjitive ourvef? 

 cf lenrnint,. Erom the eleventh day the f.lgureR for learnjnt; 

 time of the normal ratp are lern than thoBe of the inbred s. 

 The absolute retention of the normals iB stroni^er than that 

 of the inba-.eds. In the five trials to tent the effects of pre- 

 vious traininti the time of the norinaly is less each day than 

 that of the inbred rats. 



In these criteria of ability the rats of the normal 

 control series are shown, on the average, to be superior to 

 those of the inbred aeries. Body length of the inbred rats 

 used in the preliminary inclined plane is, on the avera^^e, 

 slightly greater than is the case with the norrasils; body weit;ht, 

 however, is a trifle less. The average actual brain weig}it of 

 the inbreds is leas than that of the^ normals. The relative 

 brain weight (in reference to body lent^th) of the inbreds 1p 

 11.61,"? less than that of the normals. The relative brain weight 

 (in reference to body weight) of the inbreds is ll,fir\'.' less 

 than that of the normals. Although killed at a later at^e, the 

 percentage of water in brain and cord of the InKreds is great- 

 er thfn is the case with the normals. 



The tables of comparative summaries of preliminary 

 inclined plane results support the hypothesis that the deter- 

 ioration of brain weight in a strain of rate is accompanied 

 by deterioration in the ability to form habits. 



In Plate VII is shown the curve of learnJnii (left) 

 and of relearnin^i (right) of the inbred rntH compared with 

 thosp of the normnl control. The inbred curve if shown by the 

 solid line, that of the control by the broken line. The ordi- 

 nates give the time in secondn, and the abBciflsae the number 



