THE DESIGN AND PRECISION OF PIGEON CROP SAC ASSAYS FOR PROLACTIN

The 'local ' method of pigeon crop assay, involving injection of prolactin into the skin overlying the crop, was found to be much more sensitive than the systemic method. It suffers, however, from two drawbacks: first, the problem of finding a suitable method to measure the response; and secondly, the considerable variation in response between birds, especially when pigeons of unknown origin and age must be used. The results of measuring the re-sponse by cutting out and weighing the stimulated area are described, together with the use of a balanced incomplete block design which, using 30 pigeons in a (2+2) dose assay, gave an index of precision (\g=l\)of 0\m=.\2or less