Chap. VIII. LAUGHTER. 209 



of the orbicular muscles; and that now, through associa- 

 tion and long-continued habit, the same muscles are 

 brought into slight play whenever any cause excites in 

 us a feeling which, if stronger, would have led to laugh- 

 ter; and the result is a smile. 



Whether we look at laughter as the full development 

 of a smile, or, as is more probable, at a gentle smile as 

 the last trace of a habit, firmly fixed during many gen- 

 erations, of laughing whenever we are joyful, we can 

 follow in our infants the gradual passage of the one into 

 the other. It is well known to those who have the charge 

 of voting infants, that it is difficult to feel sure when cer- 

 tain movements about their mouths are really expressive; 

 that is, when thev reallv smile. Hence I carefully 

 watched my own infants. One of them at the age of 

 forty-five days, and being at the time in a happy frame 

 of mind, smiled; that is, the corners of the mouth were 

 retracted, and simultaneously the eyes became decidedly 

 bright. I observed the same thing on the following 

 day; but on the third day the child was not quite well 

 and there was no trace of a smile, and this renders it 

 probable that the previous smiles were real. Eight days 

 subsequently and during the next succeeding week, it 

 was remarkable how his eyes brightened whenever he 

 smiled, and his nose became at the same time trans- 

 versely wrinkled. This was now accompanied by a little 

 bleating noise, which perhaps represented a laugh. At 

 the age of 113 days these little noises, which were al- 

 ways made during expiration, assumed a slightly differ- 

 ent character, and were more broken or interrupted, as 

 in sobbing; and this was certainly incipient laughter. 

 The change in tone seemed to me at the time to be con- 

 nected with the greater lateral extension of the mouth 

 as the smiles became broader. 



In a second infant the first real smile was observed 



