158 RESPONSE IN THE LIVING AND NON-LIVING 



CHAPTEK XVIII 



INORGANIC RESPONSE INFLUENCE OF VARIOUS CONDITIONS 

 ON THE RESPONSE TO STIMULUS OF LIGHT 



Effect of temperature Effect of increasing length of exposure Relation 

 between intensity of light and magnitude of response After-oscillation 

 Abnormal effects : (1) preliminary negative twitch ; (2) reversal of 

 response ; (3) transient positive twitch on cessation of light ; (4) decline 

 and reversal Resume. 



WE shall next proceed to study the effect, on the re- 

 sponse 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. 



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 tem- 

 perature to 50 C. response practically disappeared 

 (101,6). 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 



