EFFECTS OF INBREEDING ON BODY WEIGHT 



33 



the sixty day period graph C is a little above graph B, but at 

 all other points graph B is the higher of the two. At the 243 

 day period the space between the graphs represents a difference 

 of only 0.76 per cent in the average body weights of the two 

 groups of females, although the inbred females were 3.7 per 

 cent heavier than the stock females when the animals reached 

 one year of age. 



These results indicate that the rate and the extent of the 

 growth in inbred females was about the same as that of the fe- 

 males in the selected stock controls during the adolescent period, 



20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 



Fig. 12 Graphs showing the increase in the weight of the body with age 'for 

 different series of female rats (lettering as in figure 11). 



but that in the adult state the inbred females tended to be 

 slightly heavier than stock females of the same age. ' i 



As shown in various tables (4-10) and in several figures (nos. 

 2, 4, 6) rats belonging to the later inbred generations were not 

 as heavy at any given age as the animals in the seventh to the 

 ninth inbred generations. One naturally asks whether inbreed- 

 ing has lessened the growth impulse and impaired the vitality 

 after many generations so that these animals are inferior in body 

 size to normal stock animals of like age. In order to answer 

 this question, data showing the increase in the body weight 



THE JQUHNAL OF EXPERIMENTAL ZOOLOGY, VOL. 26, NO. 1 



