Vol. LIU 



October, 1927 



No. 4 



BIOLOGICAL BULLETIN 



THYROID AND GONAD AS FACTORS IN THE PRO- 

 DUCTION OF PLUMAGE MELANINS IN 

 THE DOMESTIC FOWL. 1 



BENJAMIN HORNING AND HARRY BEAL TORREY. 



I. 



In a recent paper, Zavadovsky (1925, i) has described the 

 production of white feathers on pigmented fowls following 

 thyroid feeding. The dosage was excessive. Some of the birds 

 succumbed; all were highly intoxicated. The survivors soon 

 moulted. Back and wing feathers fell abundantly in the course 

 of ten days, and were succeeded by feathers that were partly 

 or wholly white. Flesh feeding did not produce these effects, 

 nor adrenal gland. The author concluded that "the thyroid 

 plays a specific role in the regulation of the growth and moulting 

 of feathers and in their pigmentation." 



In the next issue of the same publication, Zavadovsky (1925, 2) 

 described an experiment in which a mongrel black hen under 

 whose skin five dog thyroids had been grafted, developed tufts of 

 white feathers at the seat of the graft. He also observed that 

 "the new plumage which makes its appearance after the experi- 

 mental moulting is apparently much softer than the old ordinary 

 plumage." 



Since 1921, we have had some hundreds of thyroid-fed fowls 

 under observation, and have repeatedly noticed in their plumage 

 occasional feathers with defects in pigmentation similar to those 

 described by Zavadovsky. These have not been regarded as 

 satisfactory evidence of a specific role of the thyroid in feather 

 pigmentation. While they could be induced by thyroid feeding, 



1 The work on which this paper is based was done in the Zoological Laboratory 

 University of Oregon. 



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