PHYSICAL EXPRESSION. 



this subject is one of wide interest; but it must be 

 treated of here according to the general purposes of 

 the volume, and according to the principles and 

 modes of expression already enunciated. We are 

 here dealing only with material things and with 

 the action of physical forces. 



The human face may be spoken of as that part 

 of the head which lies in front of a vertical plane 

 passing just anterior to the ears. This includes the 

 anterior portion of the skull with the soft parts 

 attached thereto. These soft parts consist of the 

 facial muscles which move the features of the face, 

 and certain muscles of mastication ; the interstices 

 between the muscles are filled in with fat. Skin 

 covers the whole face ; it is in part adherent to the 

 subjacent muscles, and is moved by them. The skin 

 is continuous with the mucous membrane at the 

 openings for the mouth, nose, and eyes. 



The facial muscles proper, the muscles of expres- 

 sion, are supplied with motor stimulus by branches 

 of the facial nerve, the muscles of mastication being 

 supplied by the motor division of the fifth pair of 

 brain nerves. Vessels supply blood to all these 

 parts and to the skin. Branches of the sympathetic 

 nerve supply the muscular walls of the small 

 arteries, and by their action control the amount of 

 blood supply ; palsy of the sympathetic nerve on 

 one side leads to flushing of that half of the face ; 

 thus the mobile colour of the face is largely con- 

 trolled by the sympathetic nerve. 



When we look at a human face we may observe 

 its form, colour, and conditions of mobility. The 



