20 PHYSICAL EXPRESSION. 



applied to the cylinder carrying the foil, so as to 

 cause this to move under the needle of the sounding 

 plate, making it vibrate. 



Impressionability and retentiveness may be ob- 

 served in animals acting in modes almost analogous 

 to those seen in the telephone and the phonograph. 

 Take as an example a child whose attention is 

 attracted by a musical box in action, so that it turns 

 towards it and listens. The sound of the musical 

 box causes vibrations in the child's apparatus of 

 hearing. Suppose that the child is playing with a 

 toy when the music commences ; attracted by the 

 sound, the child's head turns away from its toy 

 towards the musical box, and he claps his hands. 

 This is one effect, one expression of the impres- 

 sion received. Further, the child will, after a 

 certain number of repetitions of the same tune, 

 be so far impressed as to be able to hum the tune, 

 in part at least, under the stimulus of pleasure or a 

 request from the mother; this indicates the per- 

 manency of the impression. The action of vital 

 force in the child is, of course, necessary to repro- 

 duce the tune ; this corresponds to the mechanical 

 energy supplied from without to the cylinder of the 

 phonograph. 



Another class of expression that must now be 

 considered is what may be termed "empirical ex- 

 pression." Here the expression, or objective sign 

 observed, is not the direct outcome of the intrinsic 

 property or function which it indicates, but we 

 infer from the presence of the objective sign that 

 the special property is present. This inference is 



