Carbonic acid 3,2
Nitrous oxide 29,0
Oxygene 4,1
Nitrogene 25,7
————
62,0
————
Hence, accounting for the two cubic inches of common air previously
mingled with the nitrous oxide, 71 cubic inches had disappeared in this
experiment.
In the last respirations, the quantity of gas was so much diminished,
as to prevent the full expansion of the lungs; and hence the apparent
diminution was very much less after the first four inspirations.
E. 2. At temperature 47°, I breathed 182 cubic inches of nitrous oxide,
mingled with 2½ cubic inches of atmospheric air, which previously
existed in the airholder, for near 40 seconds; having in this time
made 8 respirations. The diminution after the first full inspiration,
appeared to a by-stander nearly uniform. When the last compleat
expiration was made, the gas filled a space equal to 128 cubic inches,
the common temperature being restored. These 128 cubic inches analised,
were found to consist of
Carbonic acid 5,25
Nitrous oxide 88,75
Oxygene 5,00
Nitrogene 29,00
Consequently, in this experiment, 93,25 cubic inches of nitrous oxide
had disappeared.
In each of these experiments, the cylinder was covered with condensed
watry vapor exactly in the same manner as if common air had been
breathed in it. It ought to be observed that, E. 1. was made in the
morning, four hours and half after a moderate breakfast; whereas, E.
2. was made but an hour and quarter after a plentiful dinner; at which
near three fourths of a pint of table-beer had been drank.
From these experiments we learn, that nitrous oxide is rapidly
absorbed by the venous blood, through the moist coats of the pulmonary
veins. But as after a compleat voluntary exhaustion of the lungs,
much residual air must remain in the bronchial vessels and fauces,
as appears from their incapability of compleatly collapsing, it is
evident that the gas expired after every inspiration of nitrous oxide
mast be mingled with different quantities of the residual gas of the
lungs;[192] whilst after a complete expiration, much of the unabsorbed
nitrous oxide must remain as residual gas in the lungs. Now when
a complete expiration is made after the breathing of atmospheric
air, it is evident that the residual gas of the lungs consists of
nitrogene,[193] mingled with small portions of oxygene and carbonic
acid. And these are the only products found after the respiration of
nitrous oxide.
[192] By lungs, I mean in this place, all the internal organs of
respiration.
[193] Because these products are formed during the respiration of
common air.
To ascertain whether these products were partially produced, during
the process of respiration, as I was inclined to believe from the
experiments in the last section, or whether they were wholly the
residual gases of the lungs, I found extremely difficult.
I at first thought of breathing nitrous oxide immediately after my
lungs had been filled with oxygene; and to compare the products
remaining after the full expiration, with those produced after a full
expiration of pure oxygene; but on the supposition that oxygene and
nitrous oxide, when applied together to the venous blood, must effect
changes in it different from either of them separately, the idea was
relinquished.
I attempted to inspire nitrous oxide, after having made two
inspirations and a complete expiration of hydrogene; but in this
experiment the effects of the hydrogene were so debilitating, and the
consequent stimulation by the nitrous oxide so great, as to deprive
me of sense. After the first three inspirations, I lost all power of
standing, and fell on my back, carrying in my lips the mouth-piece
separated from the cylinder, to the great alarm of Mr. Patrick Dwyer,
who was noting the periods of inspiration.
Though experiments on successive inspirations of pure nitrous oxide
might go far to determine whether or no any nitrogene, carbonic acid
and oxygene were products of respiration, yet I distinctly saw that it
was impossible in this way to ascertain their quantities, supposing
them produced, unless I could first determine the capacity of my lungs;
and the different proportions of the gases remaining in the bronchial
vessels after a compleat expiration, when atmospheric air had been
respired.
In some experiments (that I made on the respiration of hydrogene,
with a view to determine whether carbonic acid was _produced_ by
the combination of carbon loosely combined in the venous blood,
with the oxygene respired, or whether it was simply _given out_ as
excrementitious by this blood) I found, without however being able to
solve the problem I had proposed to myself, that in the respiration of
pure hydrogene, little or no alteration of volume took place; and that
the residual gas was mingled with some nitrogene, and a little oxygene
and carbonic acid.
From the comparison of these facts with those noticed in the last
section and in R. III. Div. I. there was every reason to suppose
that hydrogene was not absorbed or altered when respired: but only
mingled with the residual gases of the lungs. Hence, by making a full
expiration of atmospheric air, and afterwards taking six or seven
respirations of hydrogene in the mercurial airholder, and then making
a compleat expiration, I conjectured that the residual gas and the
hydrogene would be so mingled, as that nearly the same proportions
should remain in the bronchial vessels, as in the airholder. By
ascertaining these proportions and calculating from them, I hoped to be
able to ascertain with tolerable exactness, the capacity of my fauces
and bronchia, as well as the composition of the gas remaining in them,
after a complete expiration of common air.