Abstract

1. A simple method for fractionating "the gonad-stimulating principle" of the pituitary body into a follicle-stimulating and a luteinizing fraction is described.

2. The follicle-stimulating fraction (C) aside from exciting follicular maturation, stimulates tubal, uterine and vaginal development as well, and acts in this capacity only in the presence of the ovaries. It may stimulate the production of oestrogenic substance and cause striking uterine development without producing any increase in weight or other recognizable changes in the ovaries. The luteinizing fraction (B) causes striking increase in the blood supply to the ovaries and the luteinization of follicles. Maximum luteinization is obtained at any given dose level when fraction C precedes fraction B in the order of injection.

3. Gross descriptive, statistical and histological evidences are offered to show that fractions B and C are different. Double-injection experiments with appropriate controls are given as proof of difference. The destruction of the luteinizing principle by formal titration of a mixture of the two factors is independent chemical evidence for two active gonad-stimulating components.

4. In no instance has ovulation been observed in animals significantly stimulated by these pituitary preparations.

5. No instance of precocious breeding of animals stimulated to their first oestrus or to repeated rhythmic oestrus has been observed.

6. The preparations are more stable in aqueous solution at alkaline than at acid pHs; even in the form of a dry powder the luteinizing hormone undergoes deterioration on standing.