286 HARRY BEAL TORREY AND BENJAMIN HORNING. 



birds recorded in Table I., more pronounced than in the birds 

 of Table II., followed a heavier dosage of thyroid. And after 

 the exceptionally large daily ration of I gram of dessicated thyroid 

 one of our adult males already mentioned replaced 3 pairs of 

 moulted remiges with feathers the proximal portions of whose 

 vanes presented the deformities that characteristically follow 

 starvation. There were pigmentation defects also, but these 

 will be considered at another time. 



The second consequence of thyroid feeding, namely, the 

 acceleration of feather differentiation and eruption, would seem 

 to involve an acceleration of division processes in the cells of 

 the feather germ. According to Champy (1922) thyroid added 

 for twenty-four hours to water containing frog tadpoles acceler- 

 ates cell division in certain zones and tissues far beyond normal 

 velocities. Ebeling (1924), using much more satisfactory meth- 

 ods, has established the accelerating effect on cell division of 

 substances secreted by living thyroid which is added to cultures 

 of fibroblasts in vitro. Whether thyroxin would act similarly is 

 not yet known. Thyroxin (Squibb's) does not accelerate the 

 division rate of Paramecium, but, on the contrary, in dilutions of 

 I : 1,000,000 actually depresses it (Riddle and Torrey, 1923; 

 Torrey, 1923, 1924; Torrey, Riddle and Brodie, 1925). The 

 evidence from our present material will be offered at a later date. 



ZOOLOGICAL LABORATORY, 

 UNIVERSITY OF OREGON, 

 March 12, 1924. 



BIBLIOGRAPHY. 

 Champy, C. 



'22 L'action de 1'extrait thyroidien sur la multiplication cellulaire. Arch. 



Morph. Exp. et Gen. 58 pp. 

 Ebeling, A. H. 



'24 Action de 1'epithelium thyroidien en culture pure sur la croissance des 



fibroblastes. C. R. Soc. Biol., XC., 1449- 

 Horning, B., and Torrey, H. B. 



'23 Effect of Thyroid Feeding on the Moulting of Fowls. Abs. in An. Rec.. 



XXIV., 399- 

 Jones, L. 



'07 The Development of Nestling Feathers. Lab. Bull. 13, Oberlin College. 

 Riddle, M. C., and Torrey, H. B. 



'23 The Physiological Response of Paramecium to Thyroxin. Abs. in An. 

 Rec. XXIV., 396- 



