208 INITIATIVE IN EVOLUTION 



in two layers, a deep and a superficial. This covers like a hood at 

 the third month the head and neck of the embryo, and later assumes 

 on the face its specialised form of certain bands which operate 

 round the eyes and mouth. As they are of the striated kind these 

 muscles can be moved at will, but their main action is much more 

 under the government of the mental processes of their possessor. 

 As they are fundamentally the same in apes and man very little 

 new muscular structure arises in man, and little more than shaping 

 or refining takes place. 



The facial muscles which operate round the orbit have less 

 mental action represented in them than those of the mouth, though 

 the action of the special elevator of the upper eyelid is conspicuous 

 among the expressions of a vigorous person. Both apes and man 

 have muscles on each side which raise or lower the angles of the 

 mouth, draw the angles upwards and outwards, and raise the upper 

 and depress the lower lip ; and, though the muscle of the mouth 

 which corresponds to the orbicularis of the eye is not a continuous 

 structure, but formed of interrupted bundles of fibres, it is powerful 

 in closing the lips and active in the expressions. There are also in 

 man scattered oblique fibres in the substance of the lower lip, 

 well -developed and closely-set in a sucking child, and these in the 

 adult are scattered and less conspicuous. 



There is thus a remarkable set of structures in the face of a 

 higher primate which convey mental emotion. As they also belong 

 to animals with a high degree of convolution of brain, though 

 certain are found in lower mammals, their specialisation is only to 

 be accounted for by the long -continued involuntary expression of 

 mental states existing in the particular form of primate. Professor 

 Keith says in the work before referred to : " Muscles supplied by the 

 facial nerve are the physical basis into which many mental states 

 are reflected, and in which they are realised . Through them mental 

 conditions are manifested. It is found that the differentiation 

 of this sheet into well-marked and separate muscles proceeds 

 pari passu with the development of the brain. The more 

 highly convoluted the brain of any primate the more highly 

 specialised are its facial muscles," 1 and he points out in a 

 smaller work 2 that in the gibbon, and monkeys of the Old and 

 New Worlds the facial system becomes simpler and at the same 

 time more robust, and he pictures the facial muscles as the 

 " servants of the brain." 



1 Embryology. 



2 The Human Body. 



