STUDY OF THE CROP-SAC WEIGHT METHOD FOR PROLACTIN ASSAY1,

INCREASE in crop-gland weight following prolactin treatment is widely used in estimating quantities of this hormone. The known factors that influence this response have recently been discussed in an excellent review (Riddle and Bates, 1939). Subsequently, these authors found a more than 3-fold variation in sensitivity from time to time in the same race of pigeons (1941). The present report confirms much of Riddle and Bates study of this assay method. Certain changes, however, are suggested in the dose-response curve that they proposed (1939) and evidence is presented that the breed of pigeons we have both used has changed in responsiveness to prolactin over a period of a few years. White Carneau pigeons were used exclusively being shipped at 6 weeks of age from Sumter, South Carolina; the prolactin injections were started 3 or 4 days later. The pigeons were of the same breed, age, and from the same source as those used by Bates and Riddle