The ovarian follicular hormone

Abstract

It is now possible to measure quite accurately the amount of follicular hormone present in the ovaries of the larger mammals. The unit of measurement is the least amount of lipoid extract required to produce a definite physiological reaction in the spayed adult rat. This reaction to the injected hormone proves a good physiologic unit of measurement because it has a fairly sharp end point which may be determined accurately without sacrificing the test animal. It has been fully described and illustrated in earlier papers. 1 Briefly stated, the test consists of the induction of enough growth in the genital tract to cause the formation of a cornified layer in the vaginal epithelium. This growth requires about 48 hours and amounts to a complete replacement of the epithelial wall of the vagina. A positive test is indicated when cornified cells replace the leucocytes typical of the vaginal smear of the spayed control animal.

Material from pigs accurately timed with regard to its position in the 21 day oestrous cycle was collected by Dr. F. F. McKenzie, Department of Animal Husbandry, University of Missouri, in the course of his studies on reproduction. 2 The first ovary extracted was from a sow killed on the 19th day of the oestrous cycle, just as external signs of sexual activity were again appearing. This ovary weighed 7 grams and contained 9 large follicles of 10.5 mm. average diameter. The follicles were slit open and the whole ovary extracted with three changes of several times its volume of 95 per cent alcohol. The residue from evaporation of this extract was dissolved in corn oil. This solution, made up in a graded series of dilutions, was then tested by injection into spayed rats as outlined above. Results of these tests returned a total of 15 rat units of hormone.