mon ancestor, is strengthened in the progeny of a conscinguin- 

 eou8 union. Of the rats used in tlie experiments hereinafter 

 described it is not postu.ltited tliat the lesser ability to foi'in 

 habits is necessarily due to inbreeding; but the rats used 

 for purposes of inbreeding produced a strain having a lesser 

 relative brain weigiit, which rats, for convenience, I shall 

 hereafter refer to as the Inbred strain. The object, then, 

 of the folloving experiments is to compare the habit-forming 

 ability of tl:ie inbred strain with lesser brain v/eirhts v/ith 

 the ability of a normal control series. 



Owing to the fact that experimental v/ork on tlie brain 

 weight problem has net before been attempted there is no his- 

 tory and little literature to be presented. Donaldson-^ repro- 

 duces tables from Ilanouvrier''- showing the brain weights of 

 eminent men to be, on the aTerage, greater than those of av- 

 erage Parisians. It is not necessarily true that the specific 

 individual ^vith greater brain weight is more intelligent or 

 v.'ill contribute more to the v/orld's arts and sciences than 

 the specific individual of lesser brain weight, but, if the 

 tables of jVanouvrier axe to be believed, individuals . of great- 

 er brain v/eight are more likely to be more intelligent and 

 to do the world greater service. 



•^Lonaldson, The Growth of the Brain, London find I'ew York, 1909, 



pp. ]2e ff, 



2 

 Manouvrier, Sur 1 ' interpretation de la quantity dans 1 'Enc*- 



phale, Lc, PariH, 1865. 



The results of the experiments hereinafter describ- 

 ed agree closely with llanouvrier 'b tables. Tablep of distri- 

 bution of brain weights of the inbred strain and bormal con- 



