PUPILLODILATOR REACTIONS TO SCIATIC AND DIENCEPHALIC STIMULATION: A COMPARATIVE STUDY IN CAT AND MONKEY

Abstract

Comparative studies of pupillodilatation obtained on sciatic nerve and diencephalic stimulation were made in the cat and monkey. In the cat, the reflex pupillodilatation observed with sciatic stimulation was not abolished by section of the cervical sympathetic trunk, the trigeminal nerve or by lesions of the hypothalamus, but the reaction was eliminated by section of the oculomotor nerve. In contrast, this reflex pupillodilatation in the monkey (Macaca mulatto) was abolished or greatly reduced by cutting the cervical sympathetic, while it failed to disappear after section of the 3d cranial nerve. Similarly the pupillary dilatation obtained on stimulation in the thalamus and dorsal hypothalamus in the cat was little reduced by section of the cervical sympathetic but could not be elicited after section of the oculomotor nerve. Stimulation of the hypothalamus in the monkey resulted in bilateral pupillary dilatation which again was abolished or greatly diminished by interruption of the cervical sympathetic, but could still be observed after destruction of the 3d nerve. In each sp. pupillary dilatation was accomplished by both sympathetic excitatory and parasympathetic inhibitory neural mechanisms. In the cat, inhibition of the parasympathetic factor was predominant while in the monkey excitation of the sympathetic mechanism was of greater importance.