Abstract

1. Hydrocyanic acid administered intravenously to rabbits in doses of 0.5 to 1 mg. per kilo or sodium cyanide in doses of 1 to 2 mg. per kilo causes temporary stoppage of the respiration in passive expiration for periods varying from a few seconds to nearly four minutes. The injection must be made rapidly.

2. The respiratory center is more sensitive to hydrocyanic acid than the vaso-motor center and the latter is apparently more sensitive than the cardio-inhibitory center.

3. The action of hydrocyanic acid on the respiration and circulation resembles so closely that of certain other drugs which cause temporary stoppage of the respiration (phenylmethylisoxazolchlormethylate; Tappeiner), tetramethyl-ammonium chloride (Jodlbauer), quaternary paverin bases (Pohl) and protocatechyl-tropeine (Marshall) that it suggests the possibility that these drugs owe their activity as does hydrocyanic acid to their power to inhibit physiological oxidation in the cells upon which they act.

4. We have established that a definite antagonism exists between hydrocyanic acid and sodium iodosobenzoate in regard to the respiratory center. This antagonism would further indicate that iodosobenzoate is capable of accelerating normal physiological oxidation.