SELIG HECHT 



663 



1915, p. 49) which corresponds to a temperature coefficient of between 

 2.5 and 3.0 (Hecht, 1919, b). This temperature coefficient is much 

 too high for a diffusion process, and corresponds well with those 

 observed for ordinary chemical reactions. 



a OS O./O 0./3 0.20 



a2S 



Fig. 4. The reciprocals of the latent period are derived from the data of 

 Fig. 2. The interpretation is the same as that of Fig. 3. The broken line of the 

 second series is drawn roughly parallel to the other three. It shows that the 

 points of the second series may fit fairly well around the parallel line, thus in- 

 dicating a fundamental similarity in the relationship at the different intensities. 

 This rough parallelism is found in the data of the other animals of these experi- 

 ments not recorded in the figures. 



The data, at first sight, seem compatible with the idea of a sub- 

 sidiary chemical reaction utihzing the precursor substances. This 

 conception, however, involves an inconsistency, in that it requires 

 the disappearance of the precursor materials during the latent period. 



