348 ZOOLOGICAL PHILOSOPHY 



fluid which takes place in proportion as it works towards the production 

 of animal actions. 



Of the Consumption and Drainage of the Nervous Fluid in 

 THE Production of Animal Actions. 



The nervous fluid, set in motion by the animal's inner feeling, is 

 thus the motive power of the actions of these living bodies ; hence it 

 is used up in working its effects, and it would ultimately be exhausted 

 and incapable of producing any further activity, if the individual's 

 will kept it continually at work. 



The nervous fluid, which is constantly being formed throughout 

 life, is as constantly being consumed by the use which the individual 

 makes of it. 



One part of this fluid is kept occupied independently of the animal's 

 will in the maintenance of vital movements and of the functions 

 necessary to life. 



The other part of the fluid is at the service of the individual and can 

 be used either for the production of its acts and movements, or for the 

 performance of its various acts of intelligence. 



The individual thus uses up its invisible fluid in a degree proportional 

 to the duration of the action which it produces, or to the effort which 

 that action requires ; and it would exhaust the whole of the available 

 part, if it continued too long to carry out actions which required 

 much of it. 



Hence arises the need of rest after a certain period of action : the 

 individual falls asleep while the exhausted fluid is recuperated. 



The loss of strength, and consequently of the nervous fluid which 

 gives strength, becomes manifest therefore in all actions that are too 

 prolonged or are painful, and for that reason called fatiguing. 



If you take too long a walk, you become fatigued after a period 

 relative to your strength ; if you run, you become fatigued much 

 sooner, for you dissipate the principle of your strength much more 

 rapidly and copiously ; lastly, if you take a weight of fifteen or twenty 

 pounds, and hold it out with your arm extended horizontally, you will 

 at first find the action quite easy because you have the wherewithal 

 to do it, but as your motive principle is rapidly used up, the weight 

 soon seems heavier and harder to hold, and in a short time the action 

 becomes altogether impossible. 



Your organisation, however, remains the same throughout, for, if it 

 were to be examined, no change would be found in it from the first 

 moment, when the action was started, to the moment when you could 

 no longer support the weight in question. 



Is it not obvious that the real difference is only in the dissipatioii 



