3o6 LAMARCK, HIS LIFE AND WORK 



" Moreover, owing to these diverse influences, the 

 faculties increase and become stronger by use, become 

 differentiated by the new habits preserved for long 

 ages, and insensibly the organization, the consistence 

 — in a word, the nature and condition of parts, as also 

 of the organs — participate in the results of all these 

 influences, become preserved, and are propagated by 

 generation. 



" These truths, which are only the results of the two 

 natural laws above stated, are in every case com- 

 pletely confirmed by facts ; they clearly indicate the 

 course of nature in all the diversity of its products. 



" But instead of contenting ourselves with generali- 

 ties which might be considered as hypothetical, let 

 us directly examine the facts, and consider, in the 

 animals, the result of the use or disuse of their organs 

 on the organs themselves, according to the habits 

 that each race has been compelled to contract. 



" I shall now attempt to prove that the constant 

 lack of exercise of organs at first diminishes their 

 faculties, gradually impoverishes them, and ends by 

 making them disappear, or even causing them to be 

 atrophied, if this lack of use is perpetuated for a very 

 long time through successive generations of animals 

 of the same race. 



" I shall next prove that, on the contrary, the habit 

 of exercising an organ, in every animal which has not 

 attained the limit of the diminution of its faculties, 

 not only perfects and increases the faculties of this 

 organ, but, besides, enables it to acquire developments 

 and dimensions which insensibly change it ; so that 

 with time it renders it very different from the same 

 organ in another animal which exercises it much less. 



" The lack of use of an organ, become constant by the 

 habits formed^ gradually impoverishes this organ, and 

 ends by causing it to disappear and even to destroy it. 



" As such a proposition can only be admitted on 

 proof, and not by its simple announcement, let us 



