The author prepared an improved Schick solution, using the borate buffer solution for the dilution of toxin instead of the usual pepton water, in order to preventpseudoreaction. Field works were carried out with school boys in villages and in cities, in order to determine the criteria ofreadings for this solution.
The results were as follows.
1. The readings should be made on the fourth day, a day earlier than with the usual solution, and the boundary of positive reaction should be set on 10 mm diameter of redness. Contrast solution is not necessary.
2. The rate of positive Schick test was estimated to be about 10% in cities and 20% in villages. This rate corresponds well to the higher incidence of diphtheria in villages than in cities.
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