Abstract
The increase in the crop weight of the common pigeon, while a valuable qualitative test, was found unsatisfactory in the quantitative assay of galactin due to the variability of groups of birds to the same amount of hormone. As the further purification of galactin requires a reliable bioassay, a more accurate method was sought.
Instead of weight, the minimum proliferation of the crop gland was found more satisfactory. This degree of crop growth is characterized by the presence of transverse strands or lobules of cellular development and considerable opaqueness when the crop is extended.
In the assay of the estrogenic hormone, Coward and Burn 1 made use of the variation in the response of rats as indicated by the percentage showing a positive reaction at various levels of administration. The adaptability of this method of bioassay to galactin has been studied. A characteristic sigmoid curve with maximum sensitivity in the region of 50% response was obtained (Fig. 1). An assay method has therefore been devised using minimum proliferation combined with the principle of percentage response.
The details of the assay method follow: Common pigeons weighing from 260 to 340 gm. are used. The fight young birds and the very heavy birds are less uniform in their response. As no sex difference has been noted, both males and females may be used. Experience indicates that about 20 birds should be used. The extract is injected once daily for 4 days just beneath the subcutaneous tissue into the breast muscle.† The crop glands are examined on the 5th day for proliferation.
Get full access to this article
View all access options for this article.