THE FUNDAMENTAL SUBSTRATES OF TASTE 



Emil von Skramlik 



Berlin 



I 



The concept of a substrate in the domain of sensory physiology should 

 include all those elements necessary for the perception of one single 

 fundamental sensation, thus consisting of the receptor at one end and the 

 perceiver at the other connected by a chain of neurones. Since there are 

 four principal qualities of taste, it may be inferred that there are four gusta- 

 tory substrates, each represented by a distinct group of uniformly working 

 taste buds. It is well known that the four substrates have different sensi- 

 tivities to gustatory substances. Most sensitive is the substrate of bitter, 

 10^^ molecules of strychnine on the tongue being enough to evoke a de- 

 finite sensation of bitter, while about 10-^ molecules of sugar are needed to 

 evoke a sweet sensation. Measured this way, the bitter substrate is one 

 hundred thousand times more sensitive than the sweet one. 



In this connection, the question has been raised whether there exists any 

 correlation between the physiological sensitivity of a substrate and its 

 pathological susceptibility to injury, because it is known that the bitter 

 substrate which is the most sensitive, is also very susceptible to damage by 

 ionizing radiation, while the other three less sensitive substrates are by far 

 less susceptible to such damage. The pathological sensitivity of the four 

 substrates may also be tested by their susceptibility to anaesthetics. Since 

 only occasional observations have been made in this regard my collabora- 

 tors and I have decided to perform a systematic investigation which will be 

 described in this paper. 



The proposed problem could be elucidated in a quantitative way by 

 measuring the thresholds of the four gustatory substrates, before, and at 

 regular intervals after the application of anaesthetic solutions to the tongue. 

 The ratio of threshold after to threshold before anaesthesia constitutes 

 a numerical measure of the effect of the anaesthetic. A high value in- 

 dicates a strong anaesthesia, while a value less than one implies that the 

 anaesthetic has caused hypersensitivity. 



II 



As gustatory test substances were used quinine hydrochloride, sodium 



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