TEMPORARY PARALYSIS OF THE VAGUS MECHANISM IN THE TURTLE HEART BY SODIUM CITRATE AND SODIUM OXALATE

¹ Department of Physiology, Stanford University, California

1. Sodium citrate and sodium oxalate solutions were injected into the blood of the turtle until the vagus inhibitory mechanism of the heart became temporarily paralyzed; recovery came about gradually, at variable rates in different animals—requiring twenty to sixty minutes for complete recovery.

2. Paralysis appeared to be due to the lowering of the free calcium ions in the body—especially in the heart—by the salts injected; the same paralysis could be obtained by local application of small quantities of the salt solutions upon the crescent. Immediate recovery of vagus inhibition (after paralysis by local applications) was obtained by washing the crescent with Ringer's solution. The results accord with the finding of other investigators (using perfusion experiments), that calcium is necessary in a perfusion fluid for cardiac inhibition by vagus stimulation.

3. With increasing doses of sodium citrate, paralysis first appeared at the synapses between pre- and postganglionic fibers of the cardiac vagus; and then a slightly larger dose seemed to paralyze, also, the postganglionic cardiac inhibitory mechanism for a very short interval.