INTRODUCTION. 25 



system are the most highly developed, and prove successive 

 degrees of simplification as we descend in the scale. The 

 muscles in the human body are more than five hundred in 

 number, and almost every movement is produced, not by 

 the action of one, but of several of them. The muscular 

 system in man not only moves the body but expresses 

 thought and emotion, and is capable of a very high degree 

 of education. The accomplished tragedian and musician 

 manifest in their performances, the degree to which the 

 muscles of expression and voluntary motion may be educated. 

 The body of man is capable, through the agency of his highly 

 developed nervo-muscular system, of an infinite variety of 

 movement and expression. In man, the muscles of expres- 

 sion are chiefly in the face. In conversation, all persons to 

 a greater or less extent communicate thought by the expres- 

 sion of their countenance. In some, however, the muscles 

 of expression respond more readily to the emotions of the 

 mind than in others, every shade of thought and feeling 

 being beautifully depicted in their faces.* In the inferior 

 animals, the expression of which they are capable is much 

 more limited, and is confined to other parts of the body. 

 The dog wags his tail, the cat elevates her back, the horse 

 erects his ears, and the game-cock spreads out his ruff of 

 feathers on his head. The countenance of the inferior ani- 

 mals is in general devoid of expression. Kage and fear are 

 almost the only passions which are expressed in their faces. 

 Their muscular movements are susceptible of education, as 

 is evident from the performances of dancing dogs and bears, 



# Human Physiology designed for Colleges and the Higher Classes 

 in Schools, and for General Reading, by Worthington Hooker, M. D., 

 Professor of the Theory and Practice of Medicine in Yale College. 

 Chapter xiii. page 222. 



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