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form this doctrine was held by the ancient philosophers of 
Greece, who believed that life was an independent principle, 
capable of being added to and again removed from ordinary 
matter. Later, it was held that in some central spot in the 
living organism there existed some kind of guiding, directing, 
and all-pervading power, or “ vital principle,” capable of 
“ influencing all the organs and tissues of the body in much 
the same way as the master builder controls and directs the 
operations of his workmen.” — (Beale.) Later still, again, it 
has been held that there is inherent in the protoplasm of the , 
living body a peculiar power, which, for want of a better 
term, may be called “ vital force,” and which disappears from 
the organism when death takes place. This power is supposed 
to be in association with every particle of living matter, and 
is believed to be independent of the correlated series of 
physical and chemical forces. It is asserted to be superior to 
the ordinary forces of the universe in kind and order , and to 
control and regulate these. There is thus no reason to regard 
it as a mere “ aspect ” of matter, or as necessarily ceasing to 
exist when separated from the material substratum with which 
alone we know it to be associated. — (Beale.) 
The vitalistic doctrine of life admits of various modifica- 
tions and diverse reservations ; but all forms of this doctrine 
agree in believing that there exists in the living organism 
something which is not merely a form of one of the ordinary 
physical or chemical forces, but is superior to these. On the 
other hand, all modifications of the physical doctrine of life 
agree in believing that the forces displayed by the living body 
are nothing more than the ordinary correlated forces of the 
universe in another form. 
We may now compare these theories a little more minutely. 
In the first place, it is to be at once admitted that a large pro- 
portion of the phenomena exhibited by every living being are 
clearly physical and chemical, and are therefore due to the 
action of the ordinary correlated forces. Here is where the 
real difficulty of the case arises. It is impossible to deny that 
many of the actions of animals are purely or mainly physical 
and chemical. The point is — are all the actions of the living 
organism of this nature, or are some of them due to something 
else, distinct from the physico-chemical forces of the correlated 
series ? Every one acquainted with the modern doctrine of 
the “ conservation of energy ” will admit at once that the 
mechanical and chemical forces of the organism are derived • 
entirely from the transformation of the ordinary physical 
forces. Digestion is carried on by a modification of ordinary 
chemical affinity. Animal heat is derived from chemical com- 
