The Comb of the Baby Chick as a Test for the Male Sex Hormones

This report describes a method of utilizing the 6-day chick in the bio-assay of the male sex hormone, of androsterone particularly. Much of this study was occupied in eliminating pitfalls which obscured assay. Ruzicka 1 first suggested the chick as a test object, utilizing external application to the crest region as described by Fussganger. 2 The latter claimed that external application of an extract containing only 1/50 of a capon unit gave a reaction as great as 50 times this amount, given intramuscularly to the capon.

The white leghorn responds best. Chicks younger than 6 days show a high mortality. Ten days' treatment has been found the best.

One-half-inch mesh screen must be used as flooring to automatically eliminate droppings. Controls must be segregated to avoid both contact and the possibility of swallowing droppings. Failure to avoid this mistake is evident in our earlier controls which showed comb reactions. (See Graph S 1, S 2, S 4.) Only “chick starting mash” and plenty of water are required. Crowding must be avoided. Sick and underweight chicks rarely respond well or uniformly. Ten chicks were found to be an adequate number for each group. Sex of chick plays a minimum role, although males tend to give a slightly higher response in comb weight.

Suggested technic. From the 6th day on, groups of 10 chicks were treated once daily with given amounts of crystalline andro-sterone dissolved in 0.1 cc. of sesame oil (the same sample of sesame oil has been used throughout all experiments). The oil was applied by means of a blunt hypodermic needle attached to a tuberculin syringe, 1/20 cc. along the base of each side of the comb. The amount of oil used is so small that it does not spread or soil the chick.