NARCOTICS 



323 



molecules. The first picture is the simpler of the two, and was used 

 particularly by Franck and coworkers. Its correctness could possibly 

 be tested by an investigation of the effect of urethan on the absorption 

 spectrum of chlorophyll in the cells (an association could reveal itself in 

 changes in this spectrum). The inhibiting effect of urethap and other 

 narcotics in strong light, where the reaction rate is hmited by an enzymatic 

 reaction, was interpreted by Ornstein, Wassink, Reman, and Vermeulen 

 (1938) as an indication that these substances interfere not only with the 



90 

 80 

 70 

 60 



^ 



50 



c 







5 40 

 c 

 30 



20 



10 



12 



20 



-4 



16 



C » 10 



Phenylurethan, molcs/U 



24 28 32 36 



Fig. 30. — Inhibition of photosynthesis 

 in Chlorella by phenylurethan (after War- 

 burg). 



50 100 150 "lO* 



Intensity, ergs /cm.Tsec 



Fig. 31. — Light curves of photo- 

 synthesis in Chlorella with and with- 

 out ethylurethan (after Wassink, 

 Vermeulen, Reman, and Katz 1938). 

 O: not inhibited; •: inhibited by 

 0.05 ml. 50% urethan in ml. 



sensitization process, but also with the enzymatic mechanism of photo- 

 synthesis, by blocking enzymes responsible for light saturation. In 

 consideration of the nonspecific capillary nature of narcotic inhibition, 

 this hypothesis is not implausible. However, another interpretation of 

 the same phenomenon also is feasible. The true saturation rate of photo- 

 synthesis in the presence of narcotics may be the same as in their absence, 

 but it may require a much more intense illumination (because a large 

 fraction of chlorophyll is enveloped by the narcotic and light absorbed 

 by it is lost for photosynthesis) . If this hypothesis is correct, a full yield 



