inbreedinti. As in the case of inbred rats the youn^ v/err tak- 

 en fron the niother at the ajc of thirty daye. The oysten of 

 nunbering individual normal rata as appears in the tables in 

 38 follows: the first letter, S, signifies that it is a stan- 

 dard or normal control rat, the letters within the parenthe- 

 sis {^ive the pedigree and the figures give the indivicual num- 

 ber. For example, S(C/EE)70d' is analyzed as follows: standard 

 or normal control series, C father, E maternal grandfather, 

 B maternal grandmother, individual 70, male. 



^\Tien taken from the mother the males v/ere kept in 

 ca^es separate from the females. In order to keep conditions 

 constant neither males nor females were allowed to mate. As 

 solitude may affect behavior, from three to five rats were 

 kept in each cage. The cages were sufficiently large (24"xl5" 

 xl5") to permit this. Cages were frequently disinfected with 

 a preparation, Creso Dip, the principal Ingredient of which 

 is carbolic acid. A layer of clean chips and shavings was kept 

 on the floor. The food, from date of weaning, consisted of 

 bread soaked in milk (no water), and, tv/ice a week, grain and 

 sunflower seeds. Temperature was kept as uniformly as possible 

 at 70°r. In order to facilitate this a small gas heater was 

 instPdled and it proved very efficient durin^^ the coldest days 

 of winter. As the animal laboratory is located in the basement 

 the temperature, during the sursmer-, rarely rose above cur norm. 



At the age of sixty days the rats intended for ex- 

 perimental purposes were placed on a short allowance of feed- 

 int time (thirty minutes) in order to prepare them for experi- 

 mentation. The experiments were begun uniformly at the age 

 of seventy days. Care was taken in each experiment to use the 

 same number of males and females in the control series as in 

 the inbred; this was necessary because, as in nan, the relat- 



