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 elements of animal matter which has been called electropositive, it may be supposed that some electrical function is exercised by oxygen in the blood; but this is a mere hypothesis.  An attempt has been made founded on experiments on the decomposition of bodies by electricity to explain secretion by weak electrical powers, and to suppose the glands electrical organs, and even to imagine the action of the nerves dependent upon electricity; these, like all other notions of the same kind, appear to me very little refined.  If electrical effects be the exhibition of certain powers belonging to matter, which is a fair supposition, then no change can take place without their being more or less concerned; but to imagine the presence of electricity to solve phenomena the cause of which is unknown is merely to substitute one undefined word for another.  In some animals electrical organs are found, but then they furnish the artillery of