THE EFFECT OF THYROID FEEDING ON THE 

 MOULTING PROCESS AND FEATHER STRUC- 

 TURE OF THE DOMESTIC FOWL. 



HARRY BEAL TORREY AND BENJAMIN HORNING. 



I. 



In the course of investigations on some of the endocrines and 

 their functional correlations in the domestic fowl, it was observed 

 that the addition of desiccated thyroid to the ration of Brown 

 Leghorn and White Leghorn chicks led to striking modifications 

 in the form of the first set of rectrices, and in the course of the 

 first moult (Horning and Torrey, 1923). The form of the 

 rectrices was modified conspicuously by the shortening of the 

 vane and the lengthening of the naked region of the shaft. 

 A characteristically "quilled" feather was the result, though 

 somewhat reduced in total length. The course of the moult was 

 modified by the maintenance of base-to-tip continuity between 

 first and second rectrices, in sharp contrast to the normal in- 

 dependent and discontinuous development of these feathers. 



The results of this experimentally produced hyperthyroidism, 

 and others to be considered in another place, were then examined 

 for the light they might throw upon the role of the thyroid 

 hormone in feather differentiation, possibly in processes of 

 differentiation in general. Feathers afford certain advantages 

 as material, for they give permanent records of the progressive 

 changes that occur in the feather germ during their development. 

 But it is only of such a period that they do give reliable records, 

 obviously enough, for once grown, they are removed from the 

 influence of experimental procedures to which they might earlier 



have been susceptible. 



2. 



The following experiment is typical and with the accompanying 

 tabulation will suffice to establish the fact that desiccated thyroid 

 given in appropriate doses produces "quilling" of the rectrices 

 of chicks of both sexes, with or without gonads. 



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