THE SENSE OF TASTE 



5'7 



TABLE 4. Salt Thresholds in Man (in Molar Concentrations) 



Substance 

 Lithium chloride 

 Ammonium chloride 

 Sodium chloride 



Potassium chloride 

 Magnesiiun chloride 

 Calcium chloride 

 Sodium fluoride 

 Sodium bromide 

 Sodium iodide 



Formula 

 LiCl 

 NH4CI 

 NaCl 



Mol. VVt. 

 42.4 



53-5 

 58.5 



Median 

 025 

 004" 

 01'' 



oy 



017 

 015" 



KCl 74.6 



MgCb 95.23 



CaClj 110-99 



NaF 42 . 00 



NaBr 102.91 



Nal 14992 



* a, Cox & Nathans (57); b, Fabian & Blum (74); c, Frings (79) 

 et al. (123): g, Richter & MacLean (181); h, von Skramlik (198): i, Hober & Kiesow (106). 

 » Mean value. '' Sensitivity threshold. ' Recognition threshold. 



'^ Hahn (92) has reported one subject with a threshold for NaCl of less than 13 X io~'m. This is difficult to 

 value is far beyond the values commonly reported. 



Range 

 . 009- . 04 

 .001-. 009 

 . 00 I - . 08 

 ■OO3-.085 

 .001 -.07 

 .003-. 04 

 . 002- . 03 

 .001-. 04 

 .008-. 04 

 . C04- . I 



3 

 8 

 10 

 6 

 3 



1 



2 

 3 



d, e, g<i 

 g. h 



h, i 



005 

 024 

 028 

 ; d, Hopkins (no); e, Janowitz & Grossman (in), 1, Knowlcs 



terpret for the 



TABLE 5. Mean Salt Qjioticnt (M NaCl/M 'Salt') 

 for Different Salts* 



NH, 



K 



Ca 



Na 

 Li 



Mg 



CI 

 2.83 

 1.36 

 1.23 

 1 .00 

 0.44 

 0.20 



2.44 

 0.54 



0.77 

 0.57 



Br 

 ..83 

 I .16 



0.91 

 0.79 



SO, 

 1.26 

 0.26 



1-25 

 o.oi 



NOi 

 1.03 

 o. 14 



0.17 

 0.23 



HCOi 



0.23 



Quotients show the molar concentration of NaCl required 

 to match the saltiness of the comparison salt. 

 * From von Skramlik (198). 



saltiness ignoring all other components. Table 5 

 showing the mean values for each of several series of 

 salts gives the following cation series in the case of the 

 chlorides: NH4 > K > Ca > Na > Li > Mg. 

 This closely resembles the series found (79) in a 

 comparative study of rejection thresholds in animals 

 and detection thresholds in man. Frings' (79) attempt 

 to relate a single property, cation mobility, to the 

 stimulating efficiency of electrolytes across all species 

 is premature in view of the demonstrated species 

 differences in sensitivity based on electrophysiological 

 study (21, 163). The typical series for carnivores; 

 NH4 > Ca > Sr > K > Mg > Na > Li may be 

 contrasted with that for the rat; Li > Na > NH4 > 

 Ca > K > Sr > Mg which is typical of the rodent 

 cla.ss. The differences in the relation of sodium to 

 potassium in the two orders is striking. Sodium is 

 very effective in rodents but relatively ineffective in 

 carnivores, whereas potassium is relatively ineffective 

 in both. Beidler ?< al. (21) have pointed out that the 

 sodium/potassium ratios in the red blood cells are 



high (16. 1 ) for carnivores and low- (0.12) for rodents, 

 perhaps indicati\'e of a species difference in the 

 physicochemical make up of the membranes of the 

 receptors. The seriation NH3 > K > Na > Li found 

 in the withdrawal reaction of the frog and other 

 lower arjuatic forms when these solutions are applied 

 to the integument is probably due to the less dif- 

 ferentiated common chemical sensitivity (52, 109, 



153)- 



The anion series based on tabic 5 for sodium salts 



is SO4 > CI > Br > I > HCO3 > NO:,. Among 

 invertebrates the following seriation has been de- 

 scribed; I > Br > NO3 > CI. In the chorda tympani 

 of the rat, the anion has a much smaller effect than 

 the cation but the following series can be noted: 

 CI = Br > NO;, > citrate > SO, > CO., (18). 



Such ionic .seriations (variously called Hofmeister 

 series, lyotropic series, etc.) can be demonstrated in a 

 number of other phenomena as the penetration into 

 cells or adsorption on surfaces (105). Beidler (19) has 

 recently developed a theory which provides some basis 

 for choosing among these possibilities. His basic 

 taste equation is: 



C 

 R 



Rt„ IlRn 



where C equals the concentration of the stimulus, R 

 is the response magnitude of chorda tympani dis- 

 charge, Rm is the maximal response magnitude and 

 A' is an equilibrium constant. A plot of C/R against 

 C yields a straight line with a slope equal to i/Rm 

 and a y intercept equal to i/K'Rm- The equation is 

 similar to Langmuir's adsorption isotherm and to the 



