154 
stances slightly heated, produce the union of 
oxygen and hydrogen in an explosive mixture. 
The action of sulphuric acid on alcohol in pro- 
ducing ether, without itself undergoing change, 
appears referable to the same class along with 
those just described. We may consider it 
proved, then, that many substances possess 
the power of exercising upon compound bodies 
an influence essentially distinct from what is 
known as chemical affinity—an influence which 
consists in the production of a displacement 
and new arrangement of their elements, without 
themselves directly participating in it. Assu- 
redly such a power, which is capable of effect- 
ing chemical reactions in inorganic substances 
as well as in organised bodies, though still too 
little known to be accurately explained, must 
play a far more important part throughout na- 
ture than we have hitherto been led to suppose. 
“ In defining it a new power,” says Berzelius 
with philosophic caution, “ I am far from 
wishing to deny that some connexion exists 
between its influences and the electro-chemical 
ones with which we are familiar. On the con- 
trary, I am very much disposed to recognize 
it as a peculiar manifestation of these same 
influences.”* 
Another interesting series of facts, which 
seem to confirm the theory of the operation 
of chemical affinity in the living body, is that 
which relates to the evolution of electricity 
during the ordinary processes of growth both 
in plants and animals. The late researches of 
Dr. Faraday have fully proved the identity of 
electrical attraction with chemical affinity, and 
have shown that all chemical changes are at- 
tended with a disturbance of electric equili- 
brium. If, therefore, the changes occasioned 
by the growth of organised systems are imme- 
diately governed by laws similar to those which 
preside over inorganic matter, we should ex- 
pect to find that electricity is constantly being 
developed by them in the same manner as we 
obtain it by chemical decomposition or recom- 
position. There is no deficiency of evidence that 
such is the case, as the results of late inquiries 
most abundantly testify.+ 
That chemists have not been more successful 
in imitating the operations of vital chemistry, 
by the artificial production of organic com- 
pounds, is due not only to their ignorance of 
the composition of such bodies, but to their 
want of acquaintance with the form or con- 
dition in which they must be brought together, 
in order to enter into the desired union. Every 
one conversant with chemical operations is well 
aware of the important influence thus exerted. 
A slight change of temperature, for example, 
often reverses the affinities of a body; and many 
elements are susceptible of particular actions 
when in a nascent state (i.e. when in the act 
* This eminent chemist has been quoted as an 
advocate of the doctrine of vital affinities. If such 
was formerly held by him, it is evident, from the 
tenor of the communication here referred to, that 
he has abandoned it. 
+ See the Author’s essay on the laws regulating 
vital and physical phenomena, in Edinb. Philos. 
Journal for April 1838; and Principles of General 
and Comparative Physiology, p. 379 et seq. 
LIFE. 
of being freed from some other combinatic 
which in their ordinary condition could not 
so affected. When it is considered, 
how little we know of the operation 
conditions in the laboratory of life, no 
will be felt that its results should often ap 
contrary to what might have been anti 
No reasonable ground has yet been 
for supposing that, if we had the pow 
bringing together the elements of any o1 
compound in their requisite states and p 
tions, the result would be any other 
which it is found to be in the living 
the agency of vitality, as Dr. Prout 
marks, “ does not change the prope 
elements, but simply combines them in 
which we cannot imitate.” : 
It is hoped that the foregoing statemen 
have established the probability (which 
that the present state of our kne le 
these subjects will allow us to assert) th 
affinities which hold together the eleme 
living bodies, and which govern the elabo 
of organic products, are the same as 
stantly operating in the world aro 
would seem, at any rate, premature te 
that the operations of vital chemistry a 
rected by distinct laws and due tor 
The designations organic and vital @ 
seem to have been employed by some ¥ 
to express only the peculiarities of the ¢ 
stances and conditions under which these 
usually operate, rather than any real 
in the nature of the powers themselves 
others appear to use them as provisional 
only, referring those effects to the operat 
vitality which chemistry is not yet im ac 
tion to explain. In the former sens¢ 
nifest that such employment of the ¢ 
jurious as leading to misconception. . 
latter it is petiahenn if it do not check i 
and create a prejudice against the recepti 
new facts. The period when all difficulty 
have vanished from the application of che 
laws to the phenomena of the vital ect 
may be very far distant; and in the 
“ we must be content with gathering a} 
dications which occasionally break out fro 
clouds of mystery in which the subject 
scured.” But it must not be left out 
that every fresh discovery adds to the | 
of these indications, and that they 
the same direction ; so that the probab 
the universal operation of chemical a 
the living body mes every day more 
and the difficulty in proving the existen 
distinct set of vital affinities is constan 
coming less easily surmounted. 
VI. Vita tity IN A DORMANT OR INA 
CONDITION.—There are many organised 
at particular periods of whose existen 
vital action seems to be suspended ; al 
may result either from the absence of 
muli necessary to maintain it, or fro 
change in the organism itself, by whieh 
comes for a time less capable of respon 
these stimuli. When vital action is suspé 
from the deficiency of external stimuli, | 
two things must happen ; either the vita 
the organism will be destroyed by the | 
= 
