A Modification of the Method of Dale and Laidlaw for Standardization of Posterior Pituitary Extract

The activity of a posterior pituitary extract is still generally determined by the method intro- duced by Dale and Laidlaw (1912).They used the uterus of a virgin guinea-pig, and the assay consisted in setting limits to the potency of the test solution in terms of the standard solution by the usual ABBA grouping of doses.The method suffered from three defects.1. Suitable guinea-pigs were relatively scarce. The assay often required many hours.3. The error of the method was about 20 per cent (Gaddum, 1938).