LAMARCK'S THEORY OF EVOLUTION 257 



makes the functions of other organs to be diminished 

 in power. 



" Thus not only every organ or every part of the 

 body, whether of man or of animals, being for a long 

 period and more vigorously exercised than the others, 

 has acquired a power and facility of action that the 

 same organ could not have had before, and that it has 

 never had in individuals which have exercised less, 

 but also we consequently remark that the excessive 

 employment of this organ diminishes the functions of 

 the others and proportionately enfeebles them. 



" The man who habitually and vigorously exercises 

 the organ of his intelligence develops and acquires a 

 great facility of attention, of aptitude for thought, 

 etc., but he has a feeble stomach and strongly limited 

 muscular powers. He, on the contrary, who thinks 

 little does not easily, and then only momentarily fixes 

 hrsaHenRon7"wKil'e habitually giving much exercise 

 to his muscular organs, has much vigor, possesses an 

 excellent digestion, and is not given to the abstemi- 

 ousness of the~"savant and man of letters. 



" Moreover, when one exercises long and vigorously 

 an organ or system of organs, the active forces of 

 life (in my opinion, the nervous fluid) have taken such 

 a habit of acting {^porter) towards this organ that they 

 have formed in the individual an inclination to con- 

 tinue to exercise which it is difficult for it to over- 

 come. 



" Hence it happens that the more we exercise an 

 organ, the more we use it with facility, the more does 

 it result that we perceive the need {besoin) of continu- 

 ing to use it at the times when it is placed in 'action. 

 So we remark that the habit of study, of application, 

 of work, or of any other exercise of our organs or of 

 any one of our organs, becomes with time an indis- 

 pensable need to the individual, and often a passion 

 which it does not know how to overcome. 



" Thirdly, finally, the effort made by necessity to 



17 



