256 HISTORY OF THE HUMAN BODY 



and is wholly supplied from this source. Exhibiting a superb 

 example of the constancy of a muscular innervation, the 

 branches of this nerve expand and differentiate into the mus- 

 cle which it supplies, and with the migration of the latter 

 to the face there comes also the nerve; and it thus happens 

 that this element, originally the motor nerve of the hyoid 

 region, comes to be called the " facialis," corresponding to the 

 region in which it is met with in Man, whose anatomy first at- 

 tracted especial attention. 



That this system of facial muscles was primarily developed 

 for the purpose of regulating the orifices of the mouth and 

 the organs of special sense there can be no question, but 

 the high degree of specialization attained in the higher pri- 

 mates suggests a totally distinct function, that of communi- 

 cation of the moods of the animal to its associates, that is, a 

 language. That some outward expression for the developing 

 power of thought should show itself pan passu with the de- 

 velopment of brain was to be expected, and it appears that 

 at about the point at which this muscular differentiation became 

 apparent, that is, among the lemurs, the various cries 

 produced by the larynx became insufficient and were supple- 

 mented by the development of mimetic muscles, through the 

 medium of which far more subtle shades of meaning could be 

 expressed. For a time, therefore, in the anthropoid precur- 

 sors of man, both forms of intercommunication must have ex- 

 isted side by side, and have been of about equal value or with 

 some advantage in favor of the mimetic muscles, as in the 

 apes of the present day; but when, by the shortening of the 

 snout and the consequent flattening of the dental arcade a 

 greater differentiation of articulate sounds became possible, 

 these latter became more and more employed as the better 

 medium of intercommunication, and the help of the facial 

 muscles became less and less necessary. Corresponding to 

 this change, many of the mimetic muscles, such as those of the 

 ears, the nose, and the scalp, show in man less power than 

 in the apes, while those of the cheeks and lips, employed as 

 auxiliary to the production of articulate sounds, have reached 

 a still higher degree of development. 



