76 Original Articles. [ Jan. 
ON THE APPLICATION OF THE PRINCIPLE OF “CON- 
SERVATION OF FORCE” TO PHYSIOLOGY.* 
Part I. The Relations of Light and Heat to the Vital Forces of Plants. 
By Witt1am B. Carpenter, M.D., F.R.S., F.LS., F.GS. 
In every period of the history of Physiology, attempts have been 
made to identify all the forces acting in the Living body with those 
operating in the Inorganic universe. Because muscular force, when 
brought to bear on the bones, moves them according to the mechanical 
laws of lever-action, and because the propulsive power of the heart 
drives the blood through the vessels according to the rules of hydrau- 
lics, it has been imagined that the movements of living bodies may be 
explained on Physical principles ;—the most important consideration 
of all, namely, the source of that contractile power which the living 
muscle possesses, but which the dead muscle (though having the same 
chemical composition) is utterly incapable of exerting, being alto- 
gether left out of view. So, again, because the digestive process, 
whereby food is reduced to a fit state for absorption, as well as the 
formation of various products of the decomposition that is continually 
taking place in the living body, may be imitated in the laboratory of 
the Chemist; it has been supposed that the appropriation of the 
nutriment to the production of the living organized tissues of which 
the several parts of the body are composed, is to be regarded as a 
chemical action,—as if any combination of albumen and gelatine, fat 
and starch, salt and bone-earth, could make a living Man without the 
constructive agency inherent in the germ from which his bodily fabric 
is evolved. 
Another class of reasoners have cut the knot which they could not 
untie, by attributing all the actions of living bodies for which physics 
and chemistry cannot account, to a hypothetical “ Vital Principle ” ; 
a shadowy agency that does everything in its own way, but refuses to 
be made the subject of scientific examination ; like the ‘‘ od-force” or 
the “spiritual power ” to which the lovers of the marvellous are so fond 
of attributing the mysterious movements of turning and tilting 
tables. 
A more scientific spirit, however, prevails among the best 
Physiologists of the present day ; who, whilst fully recognizing the 
fact that many of the phenomena of living bodies can be accounted for 
by the agencies whose operation they trace in the world around, sepa- 
rate into a distinct category—that of vital actions—such as appear to 
differ altogether in kind from the phenomena of Physics and Che- 
mistry ; and seek to determine, from the study of the conditions under 
which these present themselves, the laws of their occurrence. 
In the prosecution of this inquiry, the Physiologist will find it 
greatly to his advantage to adopt the method of philosophizing which 
distinguishes the Physical Science of the present from that of the past 
* To be concluded in our next Number. 
