Defence of the Doctrine of Vital Affinity against the objections
stated to it by Humboldt and Dr. Daubeny. By Dr.
Alison. Communication for the “ Examiner ” by S. A.
Lewis, M. D., Philadelphia.
The object of this paper was to fix attention on the great
physiological discovery which has been gradually effected during
the present century, of the mode in which certain of the elements
contained in the earth’s atmosphere, under the influence of light,
and of a certain temperature, are continually employed in main-
taining that great vital circulation, of which vegetable structure,
animal structures, the air and the soil, are the successive links;
and to point out that the most essential and fundamental of the
changes here effected—particularly the formation of the different
organic compounds in the cells of vegetables—are strictly chemical
changes, at least as clearly distinct from any chemical actions
yet known to take place in inorganic matters, as the vital con-
tractions of muscles are distinct from any merely mechanical
causes of motion ; and justifying the statement of Dr. Daubeny
that there appears to be a “power, residing in living matter,”
and producing chemical effects, in fact manifesting itself most
unequivocally by the chemical changes which result from it,
“ distinct, at least in its effects, from ordinary chemical and
physical forces.”
But after having made this statement, Dr. Daubeny, according
to the author of this paper, has thrown a degree of mystery over
the subject which is quite unnecessary and even unphilosophical,
by refusing to admit, and quoting Humboldt, who has changed
his opinion upon the subject, and now likewise declines to admit
that these changes are to be regarded as vital; both authors (as
well as several other recent English authors) maintaining that as
we do not know all the conditions under which ordinary chemical
affinities act in living bodies, we are not entitled to assert that
these affinities may not yet be found adequate to the production
of the chemical changes which living bodies present; and that
until this negative proposition is proved, it is unphilosophical
and delusive to suppose the existence of any such power as that
to which the term vital affinity has been applied by the author of
this paper and several other physiologists.
In answer to this, it is here stated, that as we cannot, strictly
speaking, define life or vitality, we follow the strict rules of
philosophy, in describing what we call living bodies, whether
vegetable or animal, and then applying the term vital or living,
as the general expression for everything which is observed to take
place only in them, and which is inexplicable by the physical
laws, deduced from the observation of the other phenomena of
nature ; that according to this, the only definition of which the
term vital admits, or by which the objects of Physiology can be
defined, Dr. Daubeny has already admitted, in the expressions
above quoted from him, that chemical as well as mechanical
changes in living bodies fall under the denomination vital; and
that as the rule of sound logic is “ affirmantibus incumbit pro-
batio,” and as it is just as probable priori, that with a view to
the great objects of the introduction of living beings upon the
earth, the laws of chemistry, as those of mechanics, should be
modified or suspended by Almighty Power, this author maintains
that we are as fully justified in referring all great essential
chemical phenomena which are peculiar to living bodies, to peculiar
affinities which we term vital, as Haller was to ascribe the peculiar
mechanical movements of living bodies to the vital property of
irritation ; and to throw on the mechanical physiologists of his
day the burden of proving, if they could, that the laws of motion
perceived in dead matter were adequate to explain them.
In illustration of the importance, both in Physiology and
Pathology, of this principle being held to be established, Dr.
Alison adduced two examples, first, the utter failure of the very
ingenious theory of Dr. Murray to explain, on ordinary chemical
principles, the simplest and most essential phenomena of healthy
secretion; and, secondly, the now generally admitted inadequacy
of any theory of inflammation, which does not regard a modifica-
tion of the affinities peculiar to life, and here termed vital, as
the primary and essential change, in the matter concerned in
that process.*
* Jamieson, Edinburgh N. P. Journal, October, 1852.
Dr. Alison’s paper may be seen in extenso, in the Edinburgh
Ph. Trans. 1851-52.