The final choice of a suitable dilution of a given toxin will be made, partly from the difficult comparison with other known toxins, but mainly from the results of clinical observations in patients in the early stage of scarlet fever and in convalescents.

It is difficult to titrate scarlet fever toxin with accuracy. It will probably be found that by careful choice of subject and by several readings of the reactions at different intervals after the injection, one can differentiate between toxins of values x and 2x.