Section V, 1921 [29] Trans. R.S.C. 



The Effect of Thyroid Feeding on Rats on a Vitamin-deficient Diet 



By A. T. Cameron, F.R.S.C, and Andrew Moore, B.A., B.Sc. 



(Read May Meeting, 1921) 



Cameron and Carmichael have proved that when young white 

 rats are fed desiccated thyroid tissue in daily amounts bearing a 

 constant ratio to their (changing) weights, there is definite retardation 

 in the rate of growth, and at the same time they have confirmed the 

 observations of Hoskins, Herring, and others, that such feeding 

 produces marked hypertrophy of certain of the body organs, especially 

 heart, kidneys, liver, and adrenals. They have also shown that this 

 action is due to thyroxin, the specific chemical compound secreted 

 by the thyroid, and isolated by Kendall. 



In one of the early experiments of this series, by accident the 

 rats were fed a vitamin deficient diet (oatmeal and water) and it 

 appeared that thyroid accelerated the marked loss of weight which 

 this diet produced. We have therefore endeavoured to ascertain 

 whether the administration of thyroid along with a diet deficient 

 in vitamins gives simply additive effects, or w^hether the results 

 produced by either alone are increased or modified. 



Experimental Results 



We carried out a preliminary experiment on eight pigeons. Two 

 were used as controls, three fed on polished rice, and three on this 

 with daily doses of desiccated thyroid (0.38 per cent, iodine) in the 

 ratio of 1:5,000 of body-weight. The results were uncertain, but 

 the combined treatment produced a greater and more rapid fall 

 in body-weight and earlier death. It is doubtful if the onset of a 

 definite polyneuritis was accelerated. The pigeons were dissected 

 and the organs weighed, but the figures yielded no definite con- 

 clusions. 



Four experiments have been carried out with young white rats. 

 In each, rats from the same litter and of the same sex were employed, 

 and were subjected to preliminary observation over several days on 

 an unlimited bread and milk diet until the growth-rate was normal. 

 In the first experiment a direct comparison was made between rats 

 on an unlimited bread and milk diet, and others on unlimited ground 

 oatmeal and water (growth promoting vitamin deficiency). After 



