Chap. VIII. LAUGHTER. 205 



prostrated by prolonged and severe exertion during a 

 very hot day, and a bystander compared his eyes to those 

 of a boiled codfish. 



To return to the sounds produced during laughter. 

 We can see in a vague manner how the utterance of 

 sounds of some kind would naturally become associated 

 with a pleasurable state of mind; for throughout a large 

 part of the animal kingdom vocal or instrumental sounds 

 are employed either as a call or as a charm by one sex 

 for the other. They are also employed as the means for 

 a joyful meeting between the parents and their offspring, 

 and between the attached members of the same social 

 community. But why the sounds which man utters 

 when he is pleased have the peculiar reiterated charac- 

 ter of laughter we do not know. ^Nevertheless we can 

 see that they would naturally be as different as possible 

 from the screams or cries of distress; and as in the pro- 

 duction of the latter, the expirations are prolonged and 

 continuous, with the inspirations short and interrupted, 

 so it might perhaps have been expected with the sounds 

 uttered from joy, that the expirations would have been 

 short and broken with the inspirations prolonged; and 

 this is the case. 



It is an equally obscure point why the corners of the 

 mouth are retracted and the upper lip raised during 

 ordinary laughter. The mouth must not be opened to 

 its utmost extent, for when this occurs during a parox- 

 ysm of excessive laughter hardly any sound is emitted; 

 or it changes its tone and seems to come from deep down 

 in the throat. The respiratory muscles, and even those 

 of the limbs, are at the same time thrown into rapid 

 vibratory movements. The lower jaw often partakes of 

 this movement, and this would tend to prevent the 

 mouth from being widely opened. But as a full volume 

 of sound has to be poured forth, the orifice of the mouth 



