GROWTH AFFECTED BY FEEDING DUCTLESS GLANDS 



309 



TABLE 2 



Comparison of data for younger and older groups of control (muscle-fed) albino rats 

 with Jackson's data and Donaldson' s tables, showing growth of body length and 

 tail length. 



* If all the thirteen weeks old rats on experiment are included, the number of 

 females and males changes to 28 and 29 respectively, and the lengths of the body 

 and of the tail are but very slightly changed. (See tables 7 and 8.) 



ferent in the different series. In all of my groups of rats the 

 tails are relatively shorter than those of Jackson's rats, and 

 than those at corresponding body lengths in Donaldson's tables. 

 If, instead of the age, the body weight is taken for the basis 

 of comparison, a similar difference in the ratio of the tail length 

 to the body length of the two series is evident. 



The growth of the albino rat in weight and length under dif- 

 ferent circumstances thus varies considerably. A norm must 

 therefore be established not only for each strain but also for 

 each litter under a given set of environmental conditions. If, 

 however, similar litters from the same strain are kept under simi- 

 lar conditions variability will be at a minimum. 



For a comparison of the various organs and parts of the rats 

 with those described by previous writers, data are shown in 

 tables 8 and 9 for relative (percentage) weights, and in tables 

 4, 5, 6 and 7 for absolute weights. Data from Donaldson's 

 Wistar tables for rats of corresponding body weights and lengths 

 are included in tables 4 and 5. The body weight in general is 

 slightly greater in the Wistar norms than in my rats of corre- 

 sponding body length, excepting the younger males. As to the 

 individual organs, it is evident that in some cases the weights in 

 my series are nearer to those of Donaldson's tables at correspond- 

 ing body lengths, while in others they are nearer those of cor- 

 responding body weight. Some differences are due probably 



