306 



E. R. HOSKINS 



TABLE 1 



Average gross body-weight of normal albino rats at various ages (in comparison 

 ivith data from Donaldson, Jackson and King), showing variability probably due 

 to various causes. 



1 King's data partly from her table 3, partly estimated from her chart 3. 



2 The 21 day group includes only the larger 'winter-born' rats. 



^ The 150 day group includes only the smaller 'summer-born' group. 



lower. At 150 days (table 1) the averages are slightly less 

 than Donaldson's and King's, but somewhat greater than 

 Jackson's. 



As shown in table 1, the females at six weeks (40 days) aver- 

 age heavier than the males in the control group. This agrees 

 with the results of Donaldson ('06) and Jackson ('13), but not 

 with King ('15). 



The difference in the rate of growth of the body length and 

 tail length of my rats, as compared with the data of Jackson 

 ('15) and of Donaldson's Wistar tables is shown in table 2. It 

 may be seen that my rats averaging 13 weeks old are longer 

 than Jackson's rats at 5 to 13 months. Had the table included 

 my entire autopsied series of 59 males and 59 females the differ- 

 ence would have been slightly greater, as seen in tables 6 and 7. 

 The ratio between the tail length and the body length is dif- 



