SUMMARY.— The rate of absorption of methyl nicotinate dissolved in water, polyethylene glycol 300, propylene glycol and tetrahydrofurfuryl alcohol was studied by measuring, in vivo, the area and duration of the erythema which it produced.

With all the solutions it was found that the slower the absorption the longer was the duration of action. This relationship did not alter, either with different sites on the back, or at different ambient temperatures.

Methyl nicotinate was absorbed more quickly from the upper than the lower back. It was also absorbed more rapidly at higher ambient temperatures. Altering the concentration of methyl nicotinate between 0·25% and 1% did not change its rate of absorption although it increased the intensity of the reaction.