EXPRESSION OF EMOTIONS IN MAN AND ANIMALS. 265 



side, and depressed its ears ? Even still less can I believe 

 that my dog voluntarily put on his dejected attitude and 

 "hot-house face," which formed so complete a contrast 

 to his previous cheerful attitude and whole bearing. It 

 can not be supposed that he knew that I should under- 

 stand his expression, and that he could thus soften my 

 heart and make me give up visiting the hot-house. 



Hence, for the development of the movements which 

 come under the present head, some other principle, dis- 

 tinct from the will and consciousness, must have inter- 

 vened. This principle appears to be that every move- 

 ment which we have voluntarily performed throughout 

 our lives has required the action of certain muscles ; and, 

 when we have performed a directly opposite movement, 

 an opposite set of muscles has been habitually brought 

 into play — as in turning to the right or to the left, in 

 pushing away or pulling an object toward us, and in lift- 

 ins: or lowering a weight. 



THE PRINCIPLE OF THE ACTION OF THE EXCITED XERY- 

 OUS SYSTEM ON THE BODY. 



Expression The most striking case, though a rare and 



tions, abnormal one, which can be adduced of the 



page 66. direct influence of the nervous system, when 

 strongly affected, on the body, is the loss of color in the 

 hair, which has occasionally been observed after extreme 

 terror or grief. One authentic instance has been record- 

 ed, in the case of a man brought out for execution in 

 India, in which the change of color was so rapid that it 

 was perceptible to the eye. 



Another good case is that of the trembling of the 

 muscles, which is common to man and to many, or most, 

 of the lower animals. Trembling is of no service, often 



