IN THE ANIMAL ORGANISM. 215 



organs, and is effected by a distinct system of or- 

 gans, possessing the property of communicating and 

 extending the motion which they receive. We find 

 the power of the animal to change its place and to 

 produce mechanical effects by means of its limbs, 

 dependant on a second similar system of organs or 

 apparatus. Both of these systems of apparatus, as 

 well as the phenomena of motion proceeding from 

 them, are wanting in plants. 



In order to form a clear conception of the origin 

 and source of the mechanical motions in the animal 

 body, it may be advantageous to reflect on the mo- 

 dus operandi of other forces, which in their mani- 

 festations are most closely allied to the vital force. 



When a number of plates of zinc and copper, 

 arranged in a certain order, are brought into con- 

 tact with an acid, and when the extremities of the 

 apparatus are joined by means of a metallic wire, a 

 chemical action begins at the surface of the plates 

 of zinc, and the wire, in consequence of this action, 

 acquires the most singular and wonderful properties. 



The wire appears as the carrier or conductor of a 

 force, which may be conducted and communicated 

 through it in every direction with amazing velocity. 

 It is the conductor or propagator of an uninterrupted 

 series of manifestations of activity. 



Such a propagation of motion is inconceivable, if 

 in the wire there were a resistance to be overcome ; 

 for every resistance would convert a part of the 

 moving force into a force at rest. 



