C. H. Danforth 



163 



except for three pinfeathers, the middle of which was selected for treatment. Approximately 

 10 mg. of salve, presumed to contain 0.02 mg. of testosterone propionate applied with the tip 

 of a small camel's-hair brush. This treatment was repeated daily from Aug. 11-22 inclusive. 

 Aug. 22: weight 495 gm.; comb 38, pale. Aug. 29: weight 525 gm.; comb 36. 



When fully developed the treated feather and one other of the same age showed a cocky 

 tip and henny vane, resembling somewhat the middle specimens in figure 2. The third feather 

 of the same age was somewhat intermediate, but at least a dozen younger ones were almost 

 completely feminized and similar to the two on the right in figure 2. Others, medial and 

 slightly anterior, were intermediate, while still others further anterior were cocky and ap- 

 parently entirely uninfluenced. 



It is doubtful if the comb was really affected at all in this case in spite of the 

 rather widespread effect on the feathers. Considering the number of feathers 

 influenced, it would appear that when applied to the skin as a salve less than 

 1 .5 gammas of testosterone propionate a day for each feather is adequate to 

 produce feminization of the plumage with little, if any, other effect. 



The crystalline testosterone was applied by pushing small particles into the 

 skin. The exact amount administered was generally difficult to determine since 

 the pieces frequently crumbled somewhat in the process of being embedded. 

 Similar pieces, or group of pieces, carefully compared with the original were 

 weighed on a delicate balance and the amount implanted estimated on that 

 basis. Another protocol will show the procedure and results with this method. 



Golden Sebright, hatched Apr. 20, castrated May 27. July 30: not weighed; comb about 31. 

 Seven cm. anterior to the uropygial gland, areas 23-24 mm. in diameter were plucked on each 

 side of the midline. In the center of the right area a bit of testosterone propionate, not more 

 than 0.5 mg. in weight, was pushed into a pocket in the skin and the whole area covered with 

 a protecting film. The left side was treated in exactly the same \\ay except that no testosterone 

 was administered. Aug. 5: weight 450 gm.; comb 37, tip bleeding. Aug. 9: weight 470 gm.; 

 comb 41, red. Aug. 15: weight 480 gm.; comb 39. Growth of pinfeathers greater on the right 

 side. Aug. 29: Weight 590 gm.; comb 40, fairly good color. New feathers on left all definitely 

 cocky in form and color. Those on the right similar except for three in the center of the area. 

 Two of these appear to be typically henny, one intermediate. When fully groAvn the two 

 former proved to be entirely henny in form and color, but rather longer than usual. Figure 3 

 shows similar results in an experiment in which a silver Sebright was used. It would appear 

 that in these cases enough testosterone -svas absorbed to raise the general level abo\e the 

 threshold for comb response but not to the threshold for feather response, except in the im- 

 mediate vicinity of the implant itself. 



These experiments seem to make it clear that the effects observed in HH 

 birds following the injection of testosterone are not due to any general effect 

 mediated indirectly through the thyroid. They do not eliminate the possibility 

 that thyroid secretion and possibly several other hormones are ordinarily more 

 or less involved in the production of henny plumage. At the present time we 

 know that in birds of the formula HH which have been deprived of their 

 testes but not their thyroids the reaction of developing pinfeathers can be 

 changed from that shown in plate 1, figure 1, ^, to that in plate i, figure 1, c, by 

 the application of thyroxin, of estrone, or of testosterone, and that the effects 

 of the two latter are direct and local. Whether or not there are other hormones 



