A Dosage Response Equation for Androgen Assay by the Chick Comb Method. ∗

Abstract

In previous reports on the relation between dosage of crystalline androsterone (A)† and mean comb weight (W) of white leghorn chicks, we described experiments involving 582 chicks in 5 monthly series. Each series consisted of 6 “gamma-groups” of chicks; 1 , 2 i.e., each bird received a total dose of 0, 10, 20, 30, 40 or 50γ androsterone in 0.35 cc of sesame oil, 0.05 cc being applied to the comb daily from the 3rd to the 9th day after hatching. The comb was excised and weighed on the 10th day.

In the work now reported the number of series was increased to 10 (1439 chicks) over a period of 12 months, but in addition to W, A, N_m, and N_f, we recorded B_o and B. We also continued to run a control (zero γ) group of chicks with each series, as a measure of variations in spontaneous comb growth activity associated with season and batch of chicks. Using these combined data, we investigated graphically and statistically the desirability of applying to W for any series and sex a simple correction for mean comb weight of the corresponding controls (W_c ). Apart from sex difference, the improvement in the dose-response relation effected by this correction (W — W_c) was very small and probably negligible in the presence of corrections for B and B_o. Analysis of the data was therefore continued without such corrections. Graphs of W for each gamma-group (sexes separate) against A (Fig. 1) show that the data conform roughly to parallel straight lines, but a curvilinear fit may be closer. However, the graph for W against log A (Fig. 2) fits no better than the linear relation; this is confirmed by the identity of the corresponding correlation coefficients.