The auther carried out precipitin ring test by adding 2% gelatin to its medium. The results were as follows: 1) The ring test reacted in 2% gelatin solution at 37°C. was able to be stopped and kept as it is by cooling (0°C.) 2) The reaction ring was able to be preserved by upper method for a month at 0°C, except extremely dense part. 3) The velocity of reaction in this method shows slower than that of general method at 37°C, but reaction titer is equal to that of usual method.