J.i 

 erage time in seconds of the inbred and normy] control nerlea 

 during the process of relearning. The two inbred and one con- 

 trol rat failing; to lenrn the maze ^'/ere not, of course, test- 

 ed for relearninti. Of those inVjreda so tested, two had fail- 

 ed to relearn within fifty days, in consequence of which it 

 was thou^iht uselesa to carry theia further. aII the control 

 series had relearned at the end of twenty- two days. 



Tables Id and lid show, respectively, the anatoi.iic- 

 al data of the inbred and norraal control rats used in the naze 

 experiments, based upon figures sent by the v/istar Institute. 

 These tables will be treated fully in the conparative su/oina- 

 ries. 



For j^reater convenience in making a comparative stu- 

 dy I have placed together in Table III a summary consisting 

 of the daily avera^^^es of all the inbred a.nd all the control 

 rats. From this table, too, are constructed the conparative 

 curves of learning/. The table shows that two of the inbred 

 and one of the norraal rats failed to i'earn the maze habit. 

 The inbreds required, on the average, 36.62+day8 to learn; 

 the normals but 24.67+, The absolute retention of the inbreds 

 was, on the ayeni^e, 81.558 seconds; of tne normals, 59.640 

 seconds. Two of the inbreds failed to relearn; all the normals 

 had relearned at the end of twenty-two days. The inbreds re- 

 quired, on the average, 12.68-rday3 to relearn; the normals 

 but 5.75. 



In all these criteria of ability the rats of the 

 norma.] control series are shown, on the aver.^tl^j to be super- 

 ior to those of the inbred series. 



There are two possible criteria for estimating the 

 relative brain weight -- in reference to body length and in 

 reference to body weight. In a healthy normal rat the differ- 



