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such as a sudden "booing" from behind a door, will 

 provoke laughter. In like manner, in an adult, a 

 suddenly averted threat of danger, a breach of the 

 conventions, sudden relief from acute nervous tension, 

 a surprise, indeed, any excitant, for which there is 

 no predetermined method of physical response, may 

 give rise to laughter. In the same way the laugh- 

 ter evoked by jokes may be explained. An analysis 

 of a joke shows it to be composed of two parts, a 

 first part, in which is presented a stimulus to action ; 

 and a second part, in which the story suddenly turns so 

 that the stimulus to action is unexpectedly withdrawn ; 

 and so there are jokes of the classes bankers' jokes, 

 politicians' jokes, professional men's jokes, etc. The 

 stimulus which excites one to action, by reason of his 

 permanent brain patterns, fails to elicit response from 

 another collection of brain patterns, as the foe of one 

 animal fails to inspire fear or resentment in another 

 whose path it seldom crosses. 



It is interesting to note that the respiratory system, 

 principally, is utilized for the muscular clarifying pur- 

 pose of laughter. Why are not other muscular por- 

 tions of the body utilized? Why do we not laugh 

 with our feet and hands as well ? As a matter of fact, 

 the by-products of excitation are often consumed in 

 other motor acts than those accompanying laughter, 

 as is shown often in public gatherings by the stamping 

 of feet and clapping of hands of an audience excited 

 or amused by the impassioned or humorous words of 

 a speaker ; or by the activations of enthusiastic spec- 

 tators at a championship ball game as pictured in Fig. 

 81. To be a truly adaptive phenomenon, however, 



