2U2 THE PHYSIOLOGY OF LAUGIITEK. 



tain of the articulatory 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 lind vent in these classes of muscles 

 another class comes into play. The upper limbs arc set 

 iu motion. Children frequently clap their hands in glee ; 

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

 under still greater intensity of delight, slap their knees and 

 sway their bodies backwards and forwards. Last of all, 

 &quot;when the other channels for the escape of the surplus nerve- 

 force have been lillcd to overflowing, 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. Tims, 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 con form to these, general principles; that 

 feeling excites to muscular action ; that when the muscular 

 action is unguided by a purpose, the muscles first affected 

 are those &quot;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 still, however, remains the question with which 

 we set out. The explanation here given applies 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 insuilicient explanation that in these 

 cases, laughter is a result of the pleasure AVC 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, 

 &quot; it is the coerced form of seriousness and solemnity with 

 out the reality that gives us that stilf position from which 

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



