Standardization of Typhoid and Paratyphoid Vaccines —I. The Value of the Gates Apparatus and Total Nitrogen Determinations*

T HE multiplicity of methods proposed for determining the " strength " of bacterial vaccines indicates that all fall short in respect to one or the other of the two essential requirements, simplicity and precision. It usually happens that when simplicity is sought accuracy is sacrificed. When precision is demanded the method becomes complicated or cumbersome. In principle, the methods proposed may be classified as those of: