146 
electricity, at least we have reason to believe it 
is of a similar nature, and has the power of 
regulating electrical operations.” 
We shall now inquire into the precise import 
attached to the term by those who continue to 
employ it. It has been well remarked by 
Mr. Mayo that the word principle, “ charac- 
teristic of a less advanced state of science, has 
been generally employed (as the final letters of 
the alphabet are used by algebraists) to denote 
an unknown element, which, when thus ex- 
, is more conveniently analysed.” Thus, 
it has been customary to speak of the pringiple 
of gravity, of electricity, or of magnetism, as 
the unknown causes of certain phenomena, 
whilst these are imperfectly comprehended. In 
so far, however, as the laws of these pheno- 
mena are understood, they terminate in referring 
all the results to simple properties of matter, 
from which they may be deduced by demon- 
strative reasoning, just as geometrical theorems 
from the postulates on which they are founded. 
But in the science of physiology the term has 
been employed in a less justifiable sense. It 
must be admitted on all hands, that the condi- 
tions of vital phenomena are not yet determined 
with sufficient precision to enable us to refer 
all observed facts, through the medium of 
general laws, to ee vital properties ; and 
there would be no objection, save the proba- 
bility of its abuse, to the employment of the 
term “ Vital Principle,” like “ Nisus formati- 
vus” or “ Organic Force,” as a convenient ex- 
pression for the sum of the unknown Le ae 
which are developed by the action of these 
ak ain But to this limit physiologists 
ave unfortunately not restricted themselves. 
They have regarded it as a distinct entity en- 
dowed with properties of its own, in virtue of 
which it acts upon matter,—removing its par- 
ticles from the pale of physical and chemical 
laws,—transforming them into organised tis- 
sues,—endowing these tissues with new pro- 
perties,—prompting their actions,—preserving 
their composition in defiance of external in- 
fluences which would tend to disintegrate them, 
—and finally quitting them, or being itself 
worn out with them, so as to leave the frame- 
work without its protecting influence, deprived 
of which it speedily falls to decay. 
Of the character of this principle, its expo- 
sitors leave us very much in the dark. Of all 
modern writers, Dr. Prout is probably the one 
who has most plainly expressed himself on it. 
In his Gulstonian Lectures* he informs us that, 
“ In all cases it must be considered an ultimate 
rinciple, endowed by the Creator with a 
culty little short of intelligence, by means of 
which it is enabled to construct such a mecha- 
nism, from natural elements, and by the aid of 
natural agencies, as to render it capable of 
taking further advantage of their properties, 
and of making them subservient to its use.” 
The fallacies involved in this supposition have 
been elsewhere so ably exposed+ that we shall 
not here stop to discuss it; but in our survey 
* Medical Gazette, vol. viii. p. 261. 
+ Roberton on Life and Mind, p. 36 et seq. 
LIFE. 
of the nature and causes of vital actio 
shall take occasion to inquire whether any st 
hypothesis is called for, or whether it is. 
worse than useless by complicating what 
otherwise readily explicable on simple and 
losophical principles. 
III. Narure AND CAUSES OF VITAL At 
It has been already pointed out that a 
changes in the external world are the rest 
the properties of inorganic matter, calle 
exercise by the means appropriate to ex 
stimulate each to activity; and we may 
observe that these means are different fo 
property. Thus, to develope the da 
perty of gravitation in any mass of maj 
should only have to bring it within thesp 
attraction of any other mass. But to de 
the dormant electrical property of a loa 
a mass of iron alone would serve. 
operation in chemistry is founded 
same principle, each substance 
being capable of responding, in a | 
io to itself, to the influence o 
rought to bear upon it. Now, he 
liar this idea may seem, it has been too 
neglected in the investigation of vital 
mena; and notwithstanding that we 
find a similarity of action, when the or 
structure, on the one hand, and the 
which call its oe tte into activity, 
other, are identical—and a difference m 
of these conditions always producing @ 
rence in the result,—physiologists have & 
the habit of looking to some other age 
the cause of the variation. It is tru 
occasionally meet with instances in 
result is different, without our being a 
detect any change in either of the co 
but, knowing as we do how very 
alteration in the structure of a tissue 6 
will at once destroy or entirely cha nge 
properties, we cannot wonder that they: 
undergo important modifications withe 
sources being perceptible to our prese 
of research; and, as will h 
fully shown, every extension of our po} 
observation renders this doctrine more pr 
When we analyse the mass of phet 
which are presented to us by the vital 
of the organised world, we find that t 
susceptible of reduction into distine 
by which the study of them is much 
Thus, all living beings introduce 
own structure alimentary materials deriy 
external sources; and all likewise subm 
fluid ingredients to the influence of thee 
they inhabit, in such a manner that a ret 
change occurs between them. In this 
we arrive at the notion of the distinct fu 
of living beings, each of which @ 
regarded (in its simplest form) as a g 
phenomena of similar character and 
to the same causes. Thus, the funt 
respiration, when stripped of all the ac 
times associated with it, is essentially th 
throughout the whole organized world: 
the simplicity of the changes involved 
* See Prin, of Gen, and Comp. Phys. ¢ * 
il 
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