answer the arguments I have just
heard. I will not allow any facts or laws from the action of dead matter
to apply to living structures; the blood is a living fluid, and of this
we are sure that it does not burn in respiration. The terms warmth and
cold, as applied to the blood of animals, are improper in the sense in
which they have been just used; all animals are, in fact, warm-blooded,
and the degrees of their temperature are fitted to the circumstances
under which they live, and those animals, the life of which is most
active, possess most heat, which may be the result of general actions,
and not a particular effect of respiration. Besides, a distinguished
physiologist has rendered it probable that the animal heat depends more
upon the functions of the nerves than upon any result of respiration. The
argument derived from change of colour is perfectly delusive; it would
not follow if carbon were liberated from the blood that it must
necessarily become brighter; sulphur combining with charcoal becomes a
clear fluid, and a black oxide of copper becomes red in uniting with a
substance which abounds in carbon. No change in sensible qualities can
ever indicate with precision the nature of chemical change. I shall
resume my view, which I cannot be said to have fully developed. When I
stated that carbonic acid was formed in the venous blood in the processes
of life, I meant merely to say that this blood, in consequence of certain
changes, became capable of giving off carbon and oxygen in union with
each other, for the moment inorganic matter enters into the composition
of living organs it obeys new laws. The action of the gastric juice is
chemical, and it will only dissolve dead matters, and it dissolves them
when they are in tubes of metal as well as in the stomach, but it has no
action upon living matter. Respiration is no more a chemical process
than the absorption of chyle; and the changes that take place in the
lungs, though they appear so simple, may be very complicated; it is as
little philosophical to consider them as a mere combustion of carbon as
to consider the formation of muscle from the arterial blood as
crystallisation. There can be no doubt that all the powers and agencies
of matter are employed in the purposes of organisation, but the phenomena
of organisation can no more be referred to chemistry than those of
chemistry to mechanics. As oxygen stands in that electrical relation to
the other element