THE CARDIO-ACCELERATOR FIBERS IN THE VAGUS NERVE OF THE DOG

Abstract

Electrical stimulation of the cervical vago-sympathetic trunk and of the vagus rootlets intracranially demonstrates the existence of efferent cardio-accelerator fibers. The vagal cardio-accelerator fibers are present predominantly if not entirely in the right vagus nerve. The vagal cardio-accelerator mechanism cannot be excited re-flexly by stimulation of the carotid sinus or of the sensory fibers of the vagus nerve or the superior laryngeal nerve. Acute anemia of the brain excites the vagal cardio-accelerator mechanism. Acute cephalic anemia increases the rate of the completely denervated heart by a humoral mechanism. The characteristics of the accelerator response to stimulation of the vagal accelerators indicates that sym-pathin is probably the chemical mediator at the nerve endings in the heart. The role of the accelerator fibers of the vagus nerve in the normal regulation of the heart rate is discussed.