CHEMORECEPTION 135 



pated from the relationship found for the higher members of the series, 

 although it is doubtful that the entire difference can be explained in 

 this way. It may be noted also (Fig. 80) that the inflections in the 

 curves relating thresholds to molecular size occur at increasing chain 



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 \ 



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-- ALCOHOLS IN WATER 

 O ALCOHOLS IN GLYCOL 



• ALCOHOLS IN MINERAL OIL 



0.0 



0.4 



0.8 



LOG NUMBER OF C ATOMS 



12 



Fig. 79. Rejection thresholds of aqueous, glycol, and oil solutions of 

 primary alcohols by Phormia. (From Dethier, 1951.) 



lengths in passing from the less to the more water-soluble species. At 

 the same time the predominant importance of lipoid affinity is sugges- 

 ted by the logarithmically increasing stimulating power of both 

 lower and higher members of all series, as well as by the inverse 

 relationship between water solubility and stimulating effectiveness in 

 comparisons of the several series with each other. 



K 



