Abstract
The writer recently reported 1 the effect of castration upon the bill color of the male English Sparrow. In brief, the effect is a gradual disappearance of the pigment until the characteristic ivory-colored bill of the capon is established by the end of the sixth week.
A set of experiments was planned to test the possible restoration of the black color by injection of male hormone into sparrow capons. The male hormone was extracted with chloroform from the urine of men of approximately 20 years average age. The preparation was standardized in rat units using the seminal vesicle test as the criterion of standardization. Fourteen capons that had been castrated for 6 months were divided into 4 groups. Two individuals served as controls and the remaining 12 were divided into 3 groups of 4 each.
The individuals of group I received 3/4 of a rat unit daily for 25 days; those of Group II were given 1/6 of a rat unit daily for the same period; individuals of Group III each received 1/15 of a rat unit daily for 25 days. A noticeable change in bill color was evident after 8 days of injection. At the end of the experimental period the bills of the individuals receiving the high dosage were black like that of normal males during the breeding season. The capons receiving the low dosage had the anterior half of the bill blackened, but the basal portion remained light. Group II showed an intermediate condition. While the entire bill was dark in color, the black was not as intense as in Group I. The deposition of pigment always begins at the apex of the bill and proceeds in a posterior direction, thus indicating a gradient of threshold values, falling off from the base toward the tip of the bill.
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