Curt E Richter ^05 



12. Taste thresholds may vary with internal Jieeds. Taste-threshold tests 

 showed that normal rats were able to distinguish sodium chloride solution 

 from water in concentrations of 1:2,000, while adrenalectomized rats, which 

 have much lower blood-sodium values, due to the increased excretion of so- 

 dium from the body, made the distinction in solutions of 1:33,000 (Richter 

 and McLean^"). 



13. Rats and Jniman beings have almost identically the same taste thresholds. 

 Thus, the taste thresholds were practically the same for sodium chloride (0.055 

 per cent for rats, 0.087 P^^' cent for human beings); for sucrose (0.5 and 0.41 

 per cent respectively); for phenylthiocarbamide 0.0003 '^^^'^ 0.0003 P^^ cent 

 respectively) (Richter and Clisby""). 



14. The ability to make beyieficial selections apparently deperids npoyi taste, 

 not on experience or the effects produced by the substances. After section of 

 taste nerves, adrenalectomized rats no longer selected salt. The lower taste 

 threshold of adrenalectomized rats also brings evidence to support this view. 

 Rats showed an increased appetite for salt solution in concentrations which 

 could not possibly have had any physiological effect. 



\^. Inability to ?nake beneficial selections may depend oji inherited taste 

 dejects, that is, 07t the inability to taste certain substances. Salmon and Blakes- 

 lee^ and Blakeslee"* showed that a small percentage of people are unable to 

 taste the bitter phenylthiocarbamide. We have found many individuals who 

 are unable to taste sucrose in concentrations as high as 16 percent, or riboflavin 

 in crystalline form. Blakeslee and Fox"" and Snyder^ reported that inability 

 to taste phenylthiocarbamide is inherited as a Mendelian recessive. Some of 

 our observations indicate that the inability to taste riboflavin and alcohol may 

 also be inherited. 



16. All of the various types of self-selection behavior form part of Claude 

 Bernard's concept of the constancy of the internal environment. Bernard^^ and 

 Cannon^" pointed out and enumerated physiological mechanisms which help 

 to maintain homeostasis, or a steady state. These self-selection experiments 

 have shown that behavior mechanisms, that is, responses of the total organism, 

 are used to maintain a constant internal en\ ironment (Richter^''). 



REFERENCES 



1. Evvard. J. M.: Proc. Iowa Acad. Scis. 22:375, 1915- 



2. Evvard, J. M.: Iowa Agricult. Exper. Statn. Bull. no. 1 18, 1929. 



3. Pearl, R., and Fairchild, T. E.: Amer. Jl.Hyg. 1:253. i92i- 



4. Dove, W. P.: Amer. Natiirlst. 69:469, 1935. 



5. Le^vis, S. L.: .\mer. Pigeon Jl. 16:21 1, 1927. 



6. Stearns, G. L., and Hollander, W. F.: Amer. Pigeon Jl. 28:355, 1939. 



7. Godden, W.: Jl. Agric. .Sci. 16:78, 1926. 



8. Orr, J. B.: Minerals in Pastures (London: 1929). 



9. Theiler, A.; Green, H. H., and \'iljoeii, P. R.: Repts. Director \'eterin. Resrch., I'nion 



South Africa 3/4:9, 1915- 



10. Oshorn, T. B., and Mendel, L. B.: Jl. Biol. Chem. 20:351, 1915. 



11. Mitchell, H. S., and Mendel, L. B.: Amer. Jl. Physiol. 58:211, 1921. 



