Experiments with an isomer of caffein

Physiological tests were made with 1:7: 9-trimethyl-2: 8-dioxy-purine. Its action was in every respect weaker than that of caffein. The toxicity was about one tenth that of caffein, the minimum fatal dose of 1:7: 9-trimethyl-2: 8-dioxy-purine for frogs being 4.0 to 4.5 grams per kilo. Renal activity as shown by experiments on rabbits, was only moderately stimulated in some cases and was very feeble in others although large doses were given intravenously. Perfusion experiments on the isolated frog heart indicated that an increase in force of cardiac action without altering the frequency may be caused by concentrations of 0.1 and 0.2 per cent. in Ringer's solution, but this effect was never very pronounced.

Prepared and kindly donated to this laboratory by Dr. C. O. Johns of this Bureau.