Bradycardia in the vitamin B1-deficient rat and its use in vitamin B1 determinations

IN an earlier paper [Drury et al., 1930] it was shown that rats suffering from vitamin B1 deficiency had low heart rates. When vitamin B1 was administered rapid cures resulted, the effect on the heart rate being proportional to the amount of vitamin allowed. It was suggested that this action on the heart might form the basis of a very convenient, rapid and accurate method for estimating the vitamin. Vitamin B2 and various other food constituents were without similar action. During the past three and a half years this method has been in continuous use in this laboratory where it forms our usual routine method of test in vitamin B assays. As a result of this further experience-during which several hundred tests in all have been carried out-we have had the opportunity of collecting further evidence as to the advantage of the method and have examined its degree of accuracy when carefully checked against other standard methods of vitamin B1 assay. In the present paper we present a typical set of results, illustrating the use of the method in practice. The principal examples which we give relate to tests on the materials selected for investigation in 1930 by the sub-committee appointed in this country to examine methods and standards for vitamin B1, preparatory to the adoption of the League of Nations International Standard. These materials were (1) the "activated acid clay" standard, and certain specimens of (2) yeast,