SELIG HECHT - 347 



Among sensory processes in animals, the photic sensitivity of My a 

 is the only one that has so far yielded to physicochemical analysis, 

 A broader application of the findings with Mya hinges to a large ex- 

 tent on the knowledge gained in the present investigation. 



A concrete physicochemical mechanism has been proposed to ac- 

 count for photoreception in Mya. Fortunately the effect of the in- 

 tensity on this mechanism has turned out to be a simple application 

 of a general principle of physics and chemistry. We are therefore in 

 a position to attack similar problems of perhaps wider interest to 

 general physiology. 



SUMMARY. 



1. In the photosensory process of Mya the latent period varies 

 inversely as the intensity of the stimulating light. 



2. Quantitative analysis of the data shows that the photochemical 

 effect of the light is a logarithmic function of its intensity, the two 

 variables being related to each other according to the well known 

 "compound interest" law. 



3. Comparison with previous experiments demonstrates that the 

 Reciprocity Law of Bunsen and Roscoe applies to the photosensory 

 process not only for the minimum energy required for a response, 

 but for a much greater range of energy application as well. 



BIBLIOGRAPHY. 



Euler, H., General chemistry of the enzymes, translation by Pope, T. H., 

 New York, 1912. 



Hecht, S., (o) Sensory equilibrium and dark adaptation in Mya arenaria, J. 

 Gen. Physiol., 1918-19, i, 545; {h) The nature of the latent period in the photic 

 response of Mya arenaria, 657; (c) The photochemical nature of the photosensory 

 process, 1919-20, ii, 229. 



Weigert, F., Die chemischen Wirkungen des Lichts, Stuttgart, 1911. 



