64 



THE ROYAL SOCIETY OF CANADA 



The total gain in weight was greater in thyroid-fed animals 

 than in their controls in 11 cases out of 17. 



The results are shown graphically in figures 1 to 3 (the curves 

 were slightly smoothed by taking the weights for each third day). 

 The curves for males of experiment 4 illustrate very clearly the con- 

 siderable potential variation in growth of animals even of the same 

 sex and litter. Nevertheless the thyroid-rats during thyroid-feeding 

 had growth-rates one equal to, the other less than that of the slower 

 growing control, while subsequently their acceleration was so great 

 that finally they both exceeded in weight the faster growing control. 



C>n. 

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Fig. 2 



