Standardization Of Tuberculin: Assay on The Basis of The Spermatocyte Reaction

Abstract

The reason for this is that we do not know what the active principle of tuberculin is. No preparation containing the active principle and nothing else has ever been made. We do not know whether there is a single active principle or several responsible for the tuberculin reaction. We are far from sure of the general chemical nature of the substance which is active. In gross chemical fractionation of tuberculin, activity remains with the protein portion. This does not necessarily mean that the active substance is protein. It may be merely absorbed by protein. Furthermore, on finer fractionation protein fractions which are not active can be separated from tuberculin.' Hence chemical evaluation, such as is practiced in the assay of opium or belladonna root, is at present an impossibility. Chemical assay being out of the question, we are forced to fall back on some biologic method. Biologic methods are available for the measurement of active principles in biologically active preparations when the chemical nature of the active principle is imperfectly understood, or chemical analysis is extremely difficult. Biologic assay is officially recognized by the United States Pharmacopeia in the case of several drugs, notably digitalis and aconite, and in the case of the antitoxic serums for diphtheria and tetanus. Another well-known biologic evaluation is that used in the assay of insulin. The dosage of diphtheria and tetanus antitoxins and diphtheria toxin-antitoxin mixtures, and of insulin, is based on biologically deter-