256 LAMARCK, HIS LIFE AND WORK 
To make sure whether the exercise of life tends to 
extend and develop the organization, it suffices to con- 
sider the state of the organs of any animal which has 
just been born, and to compare them in this condition 
with what they are when the animal has attained the 
period when its organs cease to receive any new 
development. Then we will see on what this organic 
law is based, which I have published in my Recherches 
sur les Corps vivans (p. 8), @.e., that— 
«The special property of movement of fluids in 
the supple parts of the living body which contain 
them isto open’ (/7ayer) there routes, «places ot 
deposit and tissues; to create there canals, and con- 
sequently different organs; to cause these canals and 
these organs to vary there by reason of the diversity 
both of the movements as well as the nature of the 
fluids which occur there; finally to enlarge, to elon- 
gate, to divide and to gradually strengthen (affermir) 
these canals and their organs by the matters which 
are formed in the fluids in motion, which incessantly 
separate themselves, and a part of which is assimilated 
and united with organs while the rest is rejected.’ 
“Secondly, the continual employment of an organ, 
especially if it is strongly exercised, strengthens this 
organ, develops it, increases its dimensions, enlarges 
and extends its faculties. 
“This second law of effects of exercise of life has 
been understood for along time by those observers 
who have paid attention to the phenomena of organ- 
ization. 
“Indeed, we know that all the time that an organ, 
ora system of organs, is rigorously exercised through- 
out a long time, not only its power, and the parts 
which form it, grow and strengthen themselves, but 
there are proofs that this organ, or system of organs, 
at that time attracts to itself the principal active 
forces of the life of the individual, because it be- 
comes the cause which, under these conditions, 
