Reciprocal Innervation of Antagonistic Eye Muscles. ∗

Abstract

Reciprocal innervation of antagonistic eye muscles has been more or less generally accepted since the time of the experiments of Sherrington. 1 Recently, however, some controversy has arisen, due chiefly to the experiments of Tilney and Pike 2 and of Lorente de Nó. 3 These investigators have concluded that the law of reciprocal innervation is not valid in the case of antagonistic eye muscles. It therefore seemed to us desirable to further investigate this problem. The animals we used in our experiments were dogfish (Mustelus californicus and Triakis semifasciatis). In order to demonstrate the phenomenon of reciprocal innervation we have employed a slightly different method from any used heretofore. Instead of stimulating the cerebral hemisphere or rotating an animal around one of its principal body axes to evoke eye movements, we employed the method used by Maxwell. 4 Briefly, this method consists in exposing a semicircular canal and subsequently applying a mechanical stimulus to its ampulla.

Labyrinthine excitation invariably results in conjugate movement of the eyes, the direction of which depends upon the particular structure which is stimulated. When a stimulus is applied to the ampulla of the right horizontal canal, the eyes turn to the left in the horizontal plane. Stimulation of the left horizontal ampulla causes both eyes to turn to the right. The most important muscles concerned in the production of ocular rotation in the horizontal plane are the rectus internus and rectus extmnus. In order to test the reciprocal action, these muscles were detached from the bulb of the right eye and were connected by means of threads to recording levers (modification of the Bartels 5 method used by Maxwell and Huddlestone.