332 MAN --AN ADAPTIVE MECHANISM 



conditions of adequate stimulation to motor activity. 

 Every one of the causes of laughter, when analyzed, 

 resolves itself into a stimulation to motor activity of 

 some kind. 



Quite by accident this point was tested in our 

 laboratory during the course of some experiments on 

 fear. A keen, snappy fox terrier was completely 

 muzzled by winding a strip of adhesive plaster around 

 his jaws, so as to include all but the nostrils. He 

 was then turned loose upon a rabbit. When the 

 aggressive terrier and the rabbit found themselves 

 in close quarters, the instinct of each animal asserted 

 itself. The rabbit crouched in fear, while the terrier, 

 with all the assurance of its kind when confronted 

 by its natural prey, rushed upon the rabbit as if to 

 seize it, his muzzle glancing off at each attempt and 

 the attack ending in awkward failure. These actions 

 were witnessed, at various times, by various scientific 

 visitors, and in every instance the sight provoked 

 laughter. This laughter was undoubtedly due to the 

 fact that in the mind of each onlooker the spectacle of 

 the savage terrier rushing upon the helpless rabbit as 

 if to mangle it aroused a strong desire to exert a 

 muscular act to prevent cruelty. This integration 

 caused a conversion of potential into kinetic energy in 

 the brain-cells, and a discharge of activating secre- 

 tions into the blood stream, for the purpose of pro- 

 ducing the muscular action. \Vhen the danger was 

 unexpectedly averted, the preparation for muscular 

 activity was appropriated by the neutral muscular 

 reaction of laughter. 



In children, almost any unexpected phenomenon, 



