We shall next proceed to study the effect, on the response of the sensitive cell, of all those conditions which influence the normal response of the retina. We shall then briefly inquire whether even the abnormalities sometimes met with in retinal responses have not their parallel in the responses given by the inorganic.
Fig. 101.—Influence of Temperature on Response
Illumination 20″, obscurity 40″.
In (a) is shown a series of responses at 20° C.—the record exhibits slight fatigue. (b) is the slight irregular response at 50° C. (c) is the record on re-cooling; it exhibits ‘staircase’ increase.
Effect of temperature.—It has been found that when the temperature is raised above a certain point, retinal response shows rapid diminution. On cooling, however, response reappears, with its original intensity. In the response given by the sensitive cell, the same peculiarity is noticed. I give below ([fig. 101], a) a set of response-curves for 20° C. These responses, after showing slight fatigue, became fairly constant. On raising the temperature to 50° C. response practically disappeared (101, b). But on cooling to the first temperature again, it reappeared, with its original if not slightly greater intensity ([fig. 101], c). A curious point is that while in record (a), before warming, slight fatigue is observed, in (c), after cooling, the reverse, or staircase effect, appears.
Fig. 102.—Response-curves for Increasing Duration of Illumination from 1″ to 10″