PHYSIOLOGY. 1() ( J 



2855. This internal motion has, however, been produced 

 by an external ; for the external motion acts by contact, 

 and this is a process of polarization. Now, the interior 

 of a mass is only moved by repeated contact, or through 

 the restlessness of polarization and by a proper amount 

 of force, or one which is proportional to the mechanical 

 resistance of the mass to be excited. The last of these 

 is the stroke or blow, the first the vibration of the body. 

 By vibration or oscillation only can a body be internally 

 polarized ; for, if it does not oscillate upon the shock 

 being applied, it is still indeed set in motion, but " en 

 masse," so that the internal parts remain in a state of 

 rest. 



2856. Oscillation is distinguished from continuous or 

 progressive motion by its affecting the atoms of the body, 

 while the latter acts upon the body itself. Through 

 the vibration heat is engendered, because the poles are 

 free and the matter passes over into aether. 



2857. Vibration must endure the longest in solid 

 bodies, and thus in that which belongs to the earth. 

 Among these* the hard bodies must take precedence, 

 because the soft are of an aqueous nature. Among the 

 hard bodies again the heaviest must vibrate most effec- 

 tually, because they offer a longer resistance, and do not 

 yield so soon as light bodies to the effort made at 

 separation. The purest representative of the earth-ele- 

 ment or the metal is thus the best instrument or means 

 of vibration, and consequently the object of the motor 

 sense. 



2858. Thus as the salt of the earth-element is the 

 object of taste, and as the resin of the earth-element is 

 the object of smell, so would the metal be the object of 

 this motor sense. 



2859. But no sense-object is without its medium for 

 transmission, except in the case of the sense of feeling or 

 touch. The salt is only tasted by means of the water, the 

 Inflammable only smelt by means of the air j the metal's 

 primary motion could not therefore be perceived directly 

 by the auditory sense. It must be propagated through 



