Further observations on the seat of the emetic action of the digitalis bodies

Abstract

The application of digitalis bodies directly to the vomiting center, described by Thumas, does not cause emesis.

When a digitalis body is injected into a cat in which the spinal cord has been cut at about the level of the second thoracic vertebra, vomiting does not usually occur, but when the cord is severed at the level of the 5th thoracic vertebra vomiting is not prevented.

Removal of the stellate ganglia frequently prevents this emesis, and removal of the stellate ganglia with cutting of both vagi prevents the emesis in nearly every case.

Removal of the celiac plexuses does not interfere with the emesis following the injection of digitalis bodies.

When the nerve supply to the heart is intact the injection of a digitalis body causes emesis, if the animal is in good condition. When all nerve supply to the heart is severed, digitalis does not cause emesis, but mercuric chloride still causes vomiting in the usual way.

Impulses appear to pass up from the heart to the vomiting center chiefly by the way of the sympathetic, and to a less, though probably variable, extent by way of the vagus. When the sympathetic is cut the administration of ouabain usually fails to induce emesis. This may be due to the fact that the impulses passing up the vagus are usually insufficient to set up the coordinated reflex, or it may be that in those cases where vomiting is not elicited by this drug after the sympathetic is cut the vagus does not contain any fibers concerned in this reflex.

Evidence is presented to show that digitalis bodies induce emesis by reflex action due to irritation of the heart or its appendages.

This is almost certainly a protective mechanism for the heart such as is recognized in the case of other organs.