
OF THE DOCTRINE OF VITAL AFFINITY. 391 
seem analogous to them,—so as to ascertain laws peculiar to this set of phe- 
nomena. 
Dr Davuseny refers also to a passage in the writings of Dr Bostock, in which 
he speaks of reference to the operation of the vital principle, or to any vital affi- 
nities, ‘“‘as one of those delusive attempts to substitute words for ideas, which 
have so much tended to retard physiological science ;” or, as it may be more 
simply expressed, as only a reference to an occult cause, or a confession of ignorance 
on the subject. On this I would observe, that if, by merely using the term Vital 
Affinity, we were to suppose that we offered a sufficient explanation of any pheno- 
mena, I would agree with Dr Bostock. But I use the term only as defining 
the department of human knowledge to which these phenomena are to be refer- 
red, and in which the explanation of them (7. ¢., the law according to which they 
take place), is to be found; and thus using it, | maintain that there is nothing 
delusive or unscientific in thus limiting and fixing the object of our inquiries. 
The investigation of the law or laws by which vital affinities are distinguished 
from the affinities of inorganic matter, is a subsequent inquiry, in which we may 
add, that some progress has been made. It is something, for example, to say 
that vital affinities shew themselves in living beings in two distinct ways; jirst, 
by the formation of new compounds, found nowhere else in nature; secondly, by 
the selection and attraction of these compounds, at different points, out of a very 
complex fluid, so as to form organised structures ; and to point out the circum- 
stances in which these powers act. It is something to say, with Dr Prov (if 
that principle is to be held as established), that in the formation of new com- 
pounds in living bodies, the elements employed by nature are not subjected 
to any new affinities, but only hindered from obeying certain of those which 
actuate them in other circumstances; while others are allowed to act. It is some- 
thing to say, that the compounds thus formed perish many times during the life 
of the structure in which they are contained,—the more rapidly as their vital pro- 
perties have been more energetically exercised; and by perishing furnish the poi- 
sonous matter which continually circulates in every living animal, and for the 
expulsion of which the organs of excretion are provided. It is something to say 
that Carbon, fixed from the atmosphere by plants, is the substratum of all the 
organic compounds of which living beings are composed; and that Oxygen, taken 
in by the lungs or gills of animals, is the great agent in forming the excretions 
by which they are constantly worn down. And I think we define and limit all 
these inquiries satisfactorily, when we say, that we seek to ascertain the laws, 
according to which ordinary chemical affinities are modified in living bodies: or 
according to which that power acts, which, by Dr Dausreny’s own admission, 
resides in living bodies, and produces chemical effects, “ but is distinct from or- 
dinary chemical forces.” 
Dr Dauseny goes on to say, that Nature has at her command an apparatus 
