CHEMORECEPTOR MECHANISMS 



13 



o 

 o 



-2 



LOG too (25°C) 

 Fig. 10. Comparison in terms of thermodynamic activity of the stimulating effec- 

 tiveness of the first eight normal alcohols acting in aqueous solution (open circles) on 

 tarsal chemoreceptors and as gases (solid circles) on olfactory receptors. In each case 

 the value represents a threshold of rejection. The vertical lines represent 2.575 stand- 

 ard errors for aqueous thresholds and 2 for vapors. (Dethier and Yost, 1952.) 



i i i i 1 1 1 1 



I MM 



' I I I I M 



ACTIVITY COEFFICIENT 



Fig. 1 1 . Relation between human taste thresholds for alcohol, ethanol to octanol, 

 and the activity coefficient. Threshold values are expressed as the ratio of the molar 

 threshold in oil to the molar threshold in water. 



specificity. We know little about the mammalian receptor as a unit, because 

 only recently have potentials been recorded from it. From the stimulation of 

 entire receptor fields we know that as a general rule sugars with an alpha glu- 

 coside linkage are sweeter than others; that alpha glucose is sweeter than beta 

 glucose; that some D sugars are sweeter than the corresponding L sugars. For 



