In breathing the nitrous oxide, I could not distinguish between the
first feelings it occasioned and an apprehension of which I was unable
to divest myself. My first definite sensation was a dizziness, a
fulness in the head, such as to induce a fear of falling. This was
momentary. When I took the bag from my mouth, I immediately laughed.
The laugh was involuntary but highly pleasurable, accompanied by
a thrill all through me; and a tingling in my toes and fingers, a
sensation perfectly new and delightful. I felt a fulness in my chest
afterwards; and during the remainder of the day, imagined that my taste
and hearing were more than commonly quick. Certain I am that I felt
myself more than usually strong and chearful.
In a second trial, by continuing the inhalation longer, I felt a thrill
in my teeth; and breathing still longer the third time, became so full
of strength as to be compelled to exercise my arms and feet.
Now after an interval of some months, during which my health has been
materially impaired, the nitrous oxide produces an effect upon me
totally different. Half the quantity affects me, and its operation is
more violent; a slight laughter is first induced,[224] and a desire
to continue the inhalation, which is counteracted by fear from the
rapidity of respiration; indeed my breath becomes so short and quick,
that I have no doubt but the quantity which I formerly breathed, would
now destroy me. The sensation is not painful, neither is it in the
slightest degree pleasurable.