o the snake, let us see what will
be the consequence; the reptile first begins to move, and opens its
eyes and mouth; when the heat has been applied for some time, it
crawls about in search of food, and performs all the functions of
life. Here then, dead matter, when applied to a living body,
produces living functions; for if the heat had not been applied, the
snake would have continued senseless, and apparently lifeless. In
more perfect animals, the effects produced by the action of dead
matter on them, are more numerous, and are different in different
living systems, but are in general the following--sense and motion
in almost all animals, and in many the power of thinking, and other
affections of the mind. The powers, or dead matters, which are
applied, and which produce these functions, are chiefly, heat, food,
and air. The proof that these powers do produce the living
functions, is in my opinion a very convincing one, namely, that when
their actions are suspended, the living functions cease; take away,
for instance, heat, air, and food from animals, and they soon become
dead matter, and it is not necessary that an animal should be
deprived of all these to put a stop to the living functions; if any
one of them be taken away, the body sooner or later becomes dead
matter: it is found by experience, that if a man be deprived of air,
he dies in about three or four minutes; for instance, if he be
immersed under water; if he be deprived of heat, or in other words,
exposed to a very severe degree of cold, he likewise soon dies; or
if he be deprived of food, his death is equally certain, though more
slow. It is sufficiently evident then, that the living functions are
owing to the action of these external powers upon the body. What I
have here said, is not confined to animals, but the living functions
of vegetables are likewise caused by the action of dead matter upon
them. The dead matters, which by their action produce these
functions, are principally heat, moisture, light, and air. It
clearly follows therefore, from what I have said, that living bodies
must have some property different from dead matter, which renders
them capable of being acted upon by these external powers, so as to
produce the living functions; for if they had not, the only effects
which these powers could produce, would be mechanical, or chemical.
Though we know not exactly in what this property consists, or in what
manner it is acted on, yet we see, t