LAMARCK’S THEORY OF DESCENT 34 
SJ 
In explaining the second law he says: 
“The foundation of this law derives its proof from 
the third, in which the facts known allow of no 
doubt; for, if the forces of action of an organ, by 
their increase, further develop this organ—namely, 
increase its size and power, as is constantly proved 
by facts—we may be assured that the forces by which 
it acts, just originated by a new want felt, would 
necessarily give birth to the organ adapted to satisfy 
this new want, if this organ had not before existed. 
‘In truth, in animals so low as not to be able to 
feel, it cannot be that we should attribute to a felt 
want the formation of a new organ, this formation 
being in such a case the product of a mechanical 
cause, as that of a new movement produced in a part 
of the fluids of the animal. 
“Tt is not the same in animals with a more compli- 
cated structure, and which are able to feel. They 
feel wants, and each want felt, exciting their inner 
feeling, forthwith sets the fluids in motion and forces 
them towards the point of the body where an action 
may satisfy the want experienced. Now, if there 
exists at this point an organ suitable for this action, 
it is immediately cited to act; and if the organ does 
not exist, and only the felt want be for instance press- 
ing and continuous, gradually the organ originates, 
and is developed on account of the continuity and 
energy of its employment. 
“Tf I had not been convinced: 1, that the thought 
alone of an action which strongly interests it suffices 
to arouse the zuner feeling of an individual; 2, that a 
felt want can itself arouse the feeling in question ; 
3, that every emotion of zzner feeling, resulting 
from a want which is aroused, directs at the same 
instant a mass of nervous fluid to the points to be set 
in activity, that it also creates a flow thither of the 
fluids of the body, and especially nutrient ones; that, 
finally, it then places in activity the organs already 
