The quantitative estimation of diphtheria and tetanus toxoids. 1. The flocculation test and the Lf-unit

Considerable confusion exist in the quantitative estimation of diphtheria and tetanus toxoids. The present paper is the first in a series of papers comparing various quantitative methods. It describes the flocculation test, gives a mathematical model for the three-dimensional reaction surface, and suggests different designs which facilitate the unbiased calculation of the end-point.