Cardiac activity changes in typhoid fever in dogs

Abstract

Characteristic changes in cardiac activity due to the action of typhoid toxin in full-grown dogs and young puppies are described. The response of adult dogs to the intravenous or subcutaneous injection of sublethal doses of typhoid toxin takes the form of a cyclic reaction involving the following phases: first bradycardia, second tachycardia, and third a restoration of the original bradycardia which terminates in a return to the initial condition. All these phase reflect the changes in the intensity of the tonic excitation of the vagus center of cardiac innervation. In previously atropinized dogs the above phases of the reaction are absent. In young puppies the cyclic reaction to intravenous or subcutaneous injections of the toxin is limited to the tachycardia phase only, which reflects the rise in the intensity of the tonic excitation occurring in the center of the sympathetic cardiac innervation. The action of the typhoid toxin in lethal doses not only alters the correlated duration of the reaction phases cited, but also gives rise to additional ones, both in full-grown dogs and in young puppies.