1864.] Canrrrnter on Correlation of Physical and Vital Forces. 79 
these agencies he considers to be the immediate source of the forces 
which are generated by it. In treating of these forces, however, he 
dwells chiefly on the production of Motion, Heat, Light, and Electri- 
city by living bodies; touching more slightly upon the phenomena of 
Growth and Development, which constitute, in the eye of the Physio- 
logist, the distinct province of vitality. In a Memoir of my own 
“On the Mutual Relations of the Vital and Physical Forces,” pub- 
lished in ‘ The Philosophical Transactions for 1850,’* I aimed to show 
that the general doctrine of the ‘ Correlation of the Physical Forces,” 
propounded by Mr. Grove, was equally applicable to those Vital forces, 
which must be assumed as the moving powers in the production of 
purely Physiological phenomena; these forces being generated in 
living bodies by the transformation of the Light, Heat, and Chemical 
Action supplied by the world around, and being given back to it 
again, either during their life or after its cessation, chiefly in Motion 
and Heat, but also to a less degree in Light and Electricity. This 
Memoir attracted but little attention at the time, being regarded, I 
believe, as too speculative; but I have since had abundant evidence 
that the minds of thoughtful Physiologists as well as Physicists are 
moving in the same direction; and as the progress of science since 
the publication of my former Memoir would lead me to present some 
parts of my scheme of doctrine in a different form,t I venture again 
to bring it before the public in the form of a sketch (I claim for it no 
other title) of the aspect in which the application of the principle of 
the “ Conservation of Force” to Physiology now presents itself to 
my mind. 
If, in the first place, we inquire what it is that essentially distin- 
guishes Vital from every kind of Physical activity, we find this 
distinction most characteristically expressed in the fact that a germ 
endowed with Life developes itself into an Organism of a type 
resembling that of its parent; that this organism is the subject of 
“incessant changes, which all tend in the first place to the evolution of 
its typical form, and subsequently to its maintenance in that form, 
notwithstanding the antagonism of Chemical and Physical agencies 
which are continually tending to produce its disintegration ; but that 
as its term of existence is prolonged, its conservative power declines 
so as to become less and less able to resist these disintegrating forces, 
to which it finally succumbs, leaving the organism to be resolved by 
their agency into the components from which its materials were ori- 
ginally drawn. The history of a living organism, then, is one of 
incessant change ; aud the conditions of this change are to be found 
* At this date the labours of Dr. Mayer were not known either to myself or 
(so far as 1am aware) to anyone else in this country, save the late Dr. Baly, who, 
a few months after the publication of my Memoir, placed in my hands the pamphlet 
‘Die Organische Bewegung ;’ to which I took the earliest opportunity in my 
power of drawing public: attention i in ‘ The British and Foreign Medico-Chirurgical 
Review’ for July, 1851, p. 237. 
+ I have especially profited by a memoir on ‘The Correlation of Physical, 
Chemieal, and Vital Force, and the Conservation of Foree in Vital Phenomena,’ 
by Prof. Le Conte (of South Carolina College), in Silliman’s ‘American Journal’ 
for Noy, 1859, reprinted in ‘The Philosophical Magazine’ for 1860. 
