232 THE PHENOMENA OF MOTION 



tained by experiment as the connection of chemical 

 action with the phenomena of motion which we can 

 produce with the galvanic battery. All the expla- 

 nations which have been attempted are only repre- 

 sentations of the phenomenon ; they are, more or 

 less, exact descriptions and comparisons of known 

 phenomena with these, whose cause is unknown. 

 In this respect we are like an ignorant man, to 

 whom the rise and fall of an iron rod in a cylinder, 

 in which the eye can perceive nothing, and its con- 

 nection with the turning and motion of a thousand 

 wheels at a distance from the piston-rod, appear 

 incomprehensible. 



We know not how a certain something, invisible 

 and imponderable in itself (heat), gives to certain 

 bodies the power of exerting an enormous pressure 

 on surrounding objects ; we know not even how this 

 something itself is produced when we burn wood or 

 coals. 



So is it with the vital force, and with the phe- 

 nomena exhibited by living bodies. The cause of 

 these phenomena is not chemical force ; it is not 

 electricity, nor magnetism ; it is a force which has 

 certain properties in common with all causes of 

 motion and of change in form and structure in mate- 

 rial substances. It is a peculiar force, because it ex- 

 hibits manifestations which are found in no other 

 known force. 



