Abstract
A comparative study of various basal diets for vitamin K assays was made on 2050 chicks. A ration was found which permitted the development of severe vitamin K-deficiency in all the animals within 15 days. A 6-hour curative blood clotting method for the determination of vitamin K was developed. The unit of vitamin K was defined and the biological response resulting from the administration of unit amounts of vitamin K reported. The unit, as defined, was found to equal 20 Dam units of vitamin K.