THE ACTION OF DIPHTHERIA TOXIN UPON THE CIRCULATION

¹ Pharmacological Laboratory, University of Edinburgh

The effects of diphtheria toxin on the circulation and respiration only appear many hours after its injection even when a dose that is many times that ultimately fatal is injected intravenously. All attempts to analyse its action in acute experiments are therefore futile, and further light can be thrown on its effects only by examining the condition of animals subjected to it many hours previously and comparing their symptoms with those of controls. In a series of such experiments, the blood pressure was found to be lower than in the controls and this appeared to be due to failure of the central vasomotor mechanism. No evidence of direct action on the peripheral vasoconstrictor nerves, or on the vessels of the heart, was obtained.