The Spinthariscope and Retinal Excitability

Abstract

I HAVE recently been making a series of observations upon retinal excitability, and have used, among other test stimuli, the well known flashing scintillations of a pocket spinthariscope. The special value of the instrument in this connection is the subminimal or minimal intensity of the retinal excitation judged by the disappearance or appearance of visual sensation. The method used by physiologists for ascertaining whether any given condition alters the excitability of a tissue is that of stimulating periodically the tissue by subminimal or minimal exciting agencies under constant conditions and then changing one of these conditions; if, as the result of such change, the subminimal or inadequate stimulus becomes adequate, the excitability of the tissue has been raised by the change; if, on the other hand, the minimal or adequate stimulus becomes inadequate, then the excitability of the tissue has been lowered by the change.