80 



HELEN DEAN KING 



The data given in table 6 served as the basis of construction 

 for the graphs shown in figure 3 and in figure 4. 



A comparison of the graphs in figures 3 and 4 with the corre- 

 sponding graphs in figures 1 and 2 shows that there was very httle 

 difference between the two inbred series (A and B) as regards the 

 body-weight increase with age in the animals of the various 

 generation groups. In the B series, as in the A series, males and 



Fig. 3 Graphs showing the increase in the weight of the body with age for 

 males belonging to various generation groups of the B series of inbred rats (data 

 in table 6; lettering as in fig. 1). 



females in the sixteenth to the eighteenth generation groups 

 (graph A) were heavier animals at any given age than were those 

 of subsequent generations; while the rats of the twenty-second 

 to the ' twenty-fourth generation groups showed a much less 

 vigorous growth than did the animals in the earlier groups. 

 The rats in the twenty-fifth generation of the B series increased 

 in body weight very slowly during the adolescent period, as the 

 position of graph D in figures 3 and 4 indicates; but in the adult 



