AUTHOR 8 ABSTRACT OP THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, JUNE 30 



STUDIES ON INBREEDING 



IV. A FURTHER STUDY OF THE EFFECTS OF INBREEDING ON THE 



GROWTH AND VARIABILITY IN THE BODY WEIGHT 



OF THE ALBINO RAT 



HELEN DEAN KING 



The Wistar Institute of Anatomy and Biologij 



EIGHT CHARTS 



In order to complete the series of records for the first twenty- 

 five generations of inbred albino rats, data showing the growth 

 and variability in the body weights of individuals belonging in 

 the sixteenth to the twenty-fifth generations are given in the 

 present paper. 



Five htters from each generation of the two inbred series (A 

 and B), comprising a total of 296 males and 310 females, were 

 used for this study. The rats in these litters were selected in 

 the same manner, and they were weighed at the same age periods, 

 as were the individuals of the seventh to the fifteenth generations 

 for which body-weight records were taken (King, '18). The 

 data for the animals in the different generations of the inbred 

 strain are therefore strictly comparable. 



During the past three years, when most of the weighings were 

 taken, it was not possible to rear the animals under environ- 

 mental and nutritive conditions that were as favorable to growth 

 and to fertility as those existing previously. Owing to economic 

 conditions incident to the war, it became necessary to make a 

 radical change in the character of the food that the rats received. 

 The 'scrap' food (carefully sorted table refuse), on which the 

 animals of the earher generations seemed to thrive exceedingly 

 well, had to be replaced by a ration that consisted, for the most 

 part, of oats and corn, with the occasional addition of various 

 kinds of vegetables and a little meat. Some of the available 



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THE JODRNAl. OP EXPERIMENTAL ZOOLOGY, VOL. 29, NO. 1 



