ON LAUGHTER. 351 



from some one pointing a finger at the ticklish places, this avalanche- 

 like process may be incited from central centers, thus producing, 

 although in a modified degree, the pleasant phenomena in question? 

 It would be in such a case another form of circular reaction. 



Among the parts not mentioned by Sully(^> as subject to ticklish- 

 ness might also be mentioned the palate and the lips or any part ren- 

 dered more or less sensitive, as in the case of sores. The palate, in 

 many cases at least, may be tickled by having the tip of the tongue 

 pass lightly backwards or forwards over its surface. In certain 

 physical moods such ticklishness with me is almost unbearable. 

 The reactions observable upon the recovery by a limb of its normal 

 condition after having been 'asleep' are identical in some respects 

 with certain phenomena of tickling. A German child remarked in 

 my hearing that champagne 'schmeckte ebenso wie eingeschlafene 

 Fiisse.' 



In visual and auditory perception there may be induced some of 

 the phenomena of tickling. A medical friend of mine informs me 

 that certain notes in deep solemn music affect his epigastric muscles 

 in a sort of shock reaction. The quivering can be induced by false 

 notes at times. As to the deepest causal factor, I should say that 

 tickling is the result of vaso-motor shock. In addition to these cases 

 the phenomena of tickling may be autogenous in nature, that is to 

 say, vaso-motor changes may be induced in the skin without apparent 

 external stimulation. These changes are known at times to produce 

 the phenomena of tickling. 



If hypotheses are in order, I might suggest that as the attitude 

 of disgust and dislike may be an incipient act of vomiting or the 

 rejection of unpalatable food, so the smile may betoken an attitude 

 of the whole organism in which the inception of food is the most 

 striking characteristic. These actions which are obviously so useful 

 in matters of food may have become in the course of social evolution 

 associated with other affairs because of their eminently social sym- 

 bolic value. The lower animals must perforce express themselves 



(1) Sully, Essay on Laui?hter, London. 1902. 



