444 O F M A N H O O D. 



Next to the eyes, the mouth and lips have 

 both the greateft motion and expreffion. Thefe 

 motions are excited by the paffions, and the vari- 

 ous forms of the mouth mark their different cha- 

 raders and modifications. The organs of fpeech 

 give the mouth an animation fuperior to every 

 other part of the face. The vermilion of the lips, 

 and the whitenefs of the teeth, fo much excel 

 the other colours of the face, that they attradt 

 our chief regard. We fix our eyes on the mouth 

 of the fpeaker ; every word, every articulation, 

 produces different motions on the lips ; and, 

 however rapid, it is eafy to diftinguifh them from 

 each other. The deaf learn to diftinguifh thefe 

 motions fo accurately, that they often know the 

 fentiments of the fpeaker merely by attending 

 to the motions of his lips. 



In man, and in all other animals, the under- 

 jaw is alone endowed with the power of motion. 

 The crocodile, the opinion of Ariftotle and ma- 

 ny other naturalifts notwithflanding, is not an 

 exception : I have examined many flieletons of 

 that animal, and have found, by the nature of 

 the articulation, that the under-jaw alone was 

 moveable. In the human foetus, and in 

 monkeys, the under-jaw is greatly advanced be- 

 fore the upper. The deformity, in adults, is 

 equal, whether the under-jaw be too prominent, 

 or too much deprefled : It ought to be nearly 

 on a level with the upper. Strong paffions, as 

 well as languor, often produce an involuntary 



motioa 



