202 THE PHYSIOLOGY OF LAUGHTER. 



tain of the articulatoiy and vocal muscles, but also those 

 which expel air from the lungs. 



Should the feeling to be expended be still greater in 

 amount — too great to find vent in these classes of muscles 

 — another class comes into play. The upper limbs are set 

 in motion. Children frequently clap their hands in glee ; 

 by some adults the hands are rubbed together ; and others, 

 under still greater intensity of delight, slap their knees and 

 sway their bodies backwards and forwards. Last of all, 

 when th-e other channels for the escape of the surplus nerve- 

 force have been filled to overflow^ing, a yet further and less- 

 used group of muscles is spasmodically affected : the head 

 is thrown back and the spine bent inwards — there is a slight 

 degree of what medical men call opisthotonos. Thus, then, 

 without contending that the phenomena of laughter in all 

 their details are to be so accounted for, we see that in their 

 ensemble they conform to these general principles : — that 

 feelins: excites to muscular action ; that when the muscular 

 action is unguided by a purpose, the muscles first affected 

 are those which feeling most habitually stimulates ; and 

 that as the feeling to be expended increases in quantity, it 

 excites an increasing number of muscles, in a succession 

 determined by the relative frequency with which they re- 

 spond to the regulated dictates of feeling. 



There stUl, however, remains the question with which 

 we set out. The explanation here given api^lies only to the 

 laughter produced by acute pleasure or pain : it does not 

 apply to the laughter that follows certain perceptions of 

 incongruity. It is an insufficient explanation that in these 

 cases, laughter is a result of the pleasure we take in es- 

 caping from the restraint of grave feelings. That this is a 

 part-cause is true. Doubtless very often, as Mr. Bain says, 

 ♦* it is the coerced form of seriousness and solemnity with- 

 out the reality that gives us that stiff position from which 

 a contact with triviality or vulgarity relieves us, to our up* 



