376 BIOLOGY AND ITS MAKERS 
under the name of laws, which have been translated by 
Packard as follows: 
‘« First Law : In every animal which has not exceeded the 
term of its development, the more frequent and sustained 
use of any organ gradually strengthens this organ, develops. 
and enlarges it, and gives it a strength proportioned to the 
length of time of such use; while the constant lack of use of 
such an organ imperce} ptibly. weakens it, causing it to become 
reduced, progressively ely diminishes its faculties, and ends in_ 
its disappearance. 
‘““Sccond Law: Everything which nature has caused 
individuals to acquire or lose by the influence of the circum- 
stances to which their race may be for a long time exposed, 
and consequently by the influence of the predominant use of 
such an organ, or by that of the constant lack of use of such 
part, it preserves by heredity and passes on to the new indi- 
viduals which descend from it, provided that the changes 
thus acquired are common to both sexes, or to those which 
have given origin to these new individuals. 
“ These are the two fundamental truths which can be mis- 
understood only by those who have never observed or 
followed nature in its operations,” etc. The first law 
embodies the principle of use_and disuse, the second law that 
In 1815 his theory received some extensions of minor 
importance. The only points to which attention need be 
called are that he gives four laws instead of two,and that a 
new feature occurs in the second law in the statement that 
the production of a new organ is the result of a new need 
(besoin) which continues to make itself felt. 
Simplified Statement of Lamarck’s Views.—For practical 
exposition the theory may be simplified into two sets of facts: 
First, » those to be be classed assed under variation; and, second, those 
Oe ee ee, 
under heredity. x ariations of organs, according to Lamarck, 
