CHAPTER III. 



OF THE EXCITING CAUSE OF ORGANIC MOVEMENTS. 



We have seen that Hfe is a natural phenomenon which itself produces 

 several others, and that it results from the relations existing between 

 the supple containing parts of an organised body and the contained 

 fluids of that body. We cannot conceive the production of this 

 phenomenon, that is to say, the presence and continuance of the move- 

 ments constituting active life, unless we imagine a special exciting 

 cause of these movements, a force which animates the organs, controls 

 the activities and all the organic functions, — a spring, in short, of which 

 the permanent though variable tension is the driving energy of all 

 vital movements. 



There can be no doubt that the visible fluids of a living body and the 

 solid parts which contain them are irrelevant to the cause that we are 

 here seeking. All these parts together constitute the machinery of 

 movement, if I may revert to the parallel already drawn ; and it is 

 not the function of any of them to supply the force in question, that is, 

 the motive power or exciting cause of the movements of life. 



We may be certain that if there were no special cause to stimulate 

 and maintain orgasm and irritability in the supple and containing 

 parts of animals, and to produce in plants an obscure orgasm by 

 promoting direct movement of their contained fluids, the blood of 

 animals which have a circulation and the transparent whitish serum 

 of those that have not, would remain at rest and would rapidly 

 decompose together with the solid parts. 



In the same way, if there were no exciting cause of vital movements, 

 if there were no force or spring to endow a body with active life, the 

 sap and special fluids of plants would remain motionless, would de- 

 generate and be exhaled, and finally compass the death and desiccation 

 of these living bodies. 



The ancient philosophers felt the necessity for a special exciting 

 cause of organic movements ; but not having sufficiently studied 



