SENSATIONS OF TASTE 



705 



2. Aristotle's Touch Experiment. Roll the tips of the middle and 

 index fingers over a marble and note that the sensation from the two fingers 

 is interpreted as that of a single object. Now cross the fingers and repeat 

 the experiment. This time there is the sensation of touching two spheres. 



3. Temperature Sensations. It is a common experience that the 

 hand brought in the neighborhood of a warm or a cold object develops the 

 sensation of warmth or cold. Examine a given small area of the back of 

 the hand with the thermoesthesiometer. Certain points will give stronger 

 sensation of heat than others. Map these out carefully. Examine the same 

 area for the cold. A large number of cold spots will be found and they will 

 not coincide with the warm spots, figure 421. 



The stimulation for the hot and cold spots does not depend upon the 

 absolute temperature, but on the relative temperature. Insert the hand in 

 water that feels lukewarm. Place the same hand in a cup of quite warm 

 water for a moment, then reinsert it in the lukewarm water. This will now 

 feel cold. 



FIG. 481. Localization of Taste. Bitter ; acid ; salt, ; sweet ; T, 



tonsils; FC, foramen cecum; CF, circumvallate papilla; FP, fungiform papilla. (Hall.) 



4. Sensations of Taste. The distribution of taste organs in the 

 tongue is shown in figure 481. Examine your own tongue for organs of 

 sweet, acid, saline, and bitter, using solutions of i to 2 per cent, salt, 10 per 

 cent, sugar, 2 to 5 per cent, acid, 5 per cent, acetic acid, and o.i per cent, 

 quinine. 



Wipe the tongue dry and apply the solution named from the tip of a glass 

 rod. The best form of rod is about 15 cm. long by o. 5 cm. in diameter, and 

 has one end drawn out to a slender pencil-shaped tip and of a size which 

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