Sensitivity of the Baby-Chick Comb to Male Sex Hormone. ∗

Of the various existing tests for the male sex hormone, that of the capon comb is generally recognized as being the most satisfactory. The cost of capons and their upkeep is a hindrance to wide use of this test. If baby chicks can be utilized to test for male hormone properties, the cost of such tests will be materially reduced.

The purpose of this investigation was to determine whether the comb of the baby chick is sufficiently sensitive to the action of male sex hormone to warrant the more extensive experiments necessary to establish that the baby chick may be used as a test object. †

As a preliminary experiment 3 groups of day-old, Single-comb White Leghorn chicks (7 chicks to the group) were injected subcutaneously with the male hormone product testosterone. A fourth group of 7 chicks was carried as controls. Group 1 received 25 gamma daily, and group 3 received 100 gamma. After 4 injections, 2 chicks of Group 1, 5 chicks of Group 2 and all those in Group 3 showed a definite increase in comb growth. Injections were continued on 3 chicks selected from Group 3. After 14 daily (except Sunday) injections these 3 chicks were photographed with their controls. Fig. 1 shows one of these chicks with its control.

In a second series of experiments, 117 other chicks were injected, some with testosterone and some with androsterone. Single-comb White Leghorns and Rhode Island Reds of both sexes were used. Their ages varied from 1 to 10 days of age, and injections of various amounts of material were made either in the base of the comb or in the breast muscle. Table I shows the results obtained.