TASTE 357 



The threshold-stimulus for the different parts of the body-surface 

 varies widely. In general the sensitivity of a tactile region is roughly 

 proportional to the amount of its use in touching or being pressed upon. 

 Von Frey, using Hensen's method of stimulating with glass-wool fibers 

 ranging in surface from 0.002 to 0.06 sq. mm., found the following 

 thresholds for various regions. 



Grams per square 

 millimeter. 



Tongue and nose 2.0 



Lips 2.5 



Finger-tip and forehead 3.0 



Back of finger 5.0 



Palm, arm, thigh . . 7.0 



Forearm 8.0 



Back of hand ...... 12.0 



Calf, shoulder 16.0 



Back of upper arm ) 



Abdomen [ 26.0 



Outside of thigh J 



Shin and sole 28 . 



Back of forearm 33 . 



Loins 48.0 



When it is remembered that sometimes these stimulating fibers were 

 not more than y^Vo sc l- mm - m area > the great sensitivity of the tongue 

 and nose, for example, is readily seen. In some cases even 0.001 gram 

 actual pressure is readily felt. On the forehead, tongue, etc. (Euten- 

 berg), an increase of pressure of 3 or 4 per cent, was found to be percep- 

 tible. 



Two points at the skin- temperature are felt as two (rather than as one) 

 when only 1.1 mm. apart on the tongue-tip of a man, but on the middle 

 of the back and on the thigh when 67 mm. apart they are felt as one. 



How the sense of location is served by these organs is a complete 

 mystery. Every spot we can touch on the skin has a "local sign" (Lotze) 

 by which the individual knows just where on his body that particular 

 spot is located. However produced, and whether native (congenital) or 

 .acquired by infinite touches in combination with vision, muscle-sense, 

 etc., it is a strong argument for the theory of "the specific energy of 

 nerves" in its newer form that the central nervous system represents 

 somehow in its cells and fibers the whole body. 



TASTE. 



The sense of taste furnishes us most of the pleasure derived from 

 eating, which in turn assures us the full complement of the food required 

 by the organism. Its end-organs help reflexly to cause the secretion of the 

 digestive juices. Lastly, it serves sometimes as a means of discriminating 

 between the beneficial and the harmful among eatable substances, for 

 most proper foods are pleasant to the average palate. 



