34 



THE ROYAL SOCIETY OF CANADA 



of an animal fed thyroid on a vitamin-deficient diet and the sum of 

 such losses produced by the thyroid treatment alone, and the deficient 

 diet alone, to animals of the same sex and litter. In such experiments 

 it is essential that rats of the same litter and sex be used and it is 

 difficult to secure many litters sufficiently large to permit averages 

 in one experiment. In the second experiment the thyroid dosage was 

 1 :20,000, in the others, 1 :5,000. The animals were treated at different 

 ages and for different lengths of time. The agreement between the 

 two columns is, therefore, surprisingly close, and we consider that it 

 indicates that as far as gross changes of body-weight are concerned 

 the thyroid and the deficient diet merely produce additive effects. 



TABLE IV 

 Female Rats 



Age 



Days 

 68 

 71 



74 



77 

 80 



Gain in weight 



Rati 



gm. 

 65 

 70 



76 

 71 

 76 



+6 



+9% 



Rat 2 



C. 



gm. 

 82 

 87 



91 

 94 

 101 



-fl4 

 + 16' 



Rats 



+T (1:5000) 



gm. 

 69 



74 



73 

 67 

 58 



-16 



-22% 



Rat 4 



gm. 

 71 

 76 



73 

 64 

 64 



12 



■16% 



Rat 5 



-V+T 



gm. 

 78.5 

 86 



75 

 64 

 62 



-24 

 -28% 



Weight of organs 



