e with cold, and
faint with hunger, more than twenty times the quantity would have
done those who were warm, and well fed; and had it not been for the
spirit having such power to act upon men, in their condition, they
never could have outlived the hardships they experienced. All these
facts, and many others which might be brought, establish beyond a
doubt the truth of the law I have mentioned, namely, that when the
powerful action of the exciting powers ceases for some time, the
excitability accumulates, or becomes more capable of receiving their
actions.

The second law is, that when the exciting powers have acted with
violence, or for a considerable time, the excitability becomes
exhausted, or less fit to be acted on, and this we shall be able to
prove by a similar induction. Let us take the effects of light upon
the eye; when it has acted violently for some time upon the optic
nerve, it diminishes the excitability of that nerve, and renders it
incapable of being affected by a quantity of light that would at
other times affect it. When you have been walking out in the snow,
if you come into your room, you will scarcely be able to see any
thing for some minutes. Look stedfastly at a candle for a minute or
two, and you will with difficulty discern the letters of a book,
which you were before reading distinctly; and if you happen to cast
your eyes upon the sun, you will not see any thing distinctly for
some time afterwards.

Let us next consider the matter of heat: suppose water to be heated
lukewarm, if you put one hand into it, it will feel warm; if you now
put the other hand into water, heated for instance to 120 degrees or
130 degrees, and keep it there some time, we will say, two minutes;
if then you take it out, and put it into the lukewarm water, that
water will feel cold, though still it will seem warm to the other
hand; for, the hand which had been in the heated water, has had its
excitability exhausted by the application of heat. Before you go
into a warm bath, the temperature of the air may seem warm and
agreeable to you, but after you have remained for some time in a
bath that is rather hot, when you come out, you feel the air
uncommonly cool and chilling.

Let us now examine the effects of substances taken into the stomach;
and as the effects of spirituous, and vinous liquors, are a little
more remarkable than food, we shall make our observations upon them.

A person who is unaccustomed to drink these