Nitrogene 23,0
Carbonic acid 4,1
Oxygene 4,9
_d._ In many experiments made in the mercurial airholder on the
capacity of my lungs under different circumstances, I found that I
threw out of my lungs by a full forced expiration at temperatures from
58° to 62°
cub. cub.
in. in.
After a full voluntary inspiration, from 189 to 191
After a natural inspiration, from 78 to 79
After a natural expiration, from 67 to 68
So that making the corrections for temperature, it would appear, that
my lungs in a state of voluntary inspiration, contained about 254
cubic inches; in a state of natural inspiration about 135; in a state
of natural expiration, about 118; and in a state of forced expiration
41.[197]
[197] This capacity is most probably below the medium, my chest is
narrow, measuring in circumference, but 29 inches, and my neck rather
long and slender.
As the exhausted capacity as well as impleted capacity of the internal
organs of respiration must be different in different individuals,
according as the forms and size of their thorax, fauces, and bronchia
are different, it would be almost useless to endeavour to ascertain a
standard capacity. It is however probable, that a ratio exists between
the quantities of air inspired in the natural and forced inspiration,
those expired in the natural and forced expiration, and the whole
capacity of the lungs. If this ratio were ascertained, a single
experiment on the natural inspiration and expiration of common air,
would enable us to ascertain the quantity of residual gas in the lungs
of any individual after a compleat forced expiration.[198]
[198] Dr. Goodwyn in his excellent work on the connexion of life with
respiration, has detailed some experiments on the capacity of the lungs
after natural expiration. He makes the medium capacity about 109 cubic
inches, which agrees very well with my estimation.—page 27.
V. _Additional observations and experiments on the Respiration of
Nitrous Oxide._
_a._ Having thus ascertained the capacity of my lungs, and the
composition of the residual gas of expiration, I proceeded to reason
concerning the experiments in section III, on the respiration of
nitrous oxide.
In Exp. I. nearly 100 cubic inches of nitrous oxide, making the
corrections on account of the common air, were respired for half a
minute. In this time, they were reduced to 62 cubic inches, which
consisted of 3,2 carbonic acid, 29 nitrous oxide, 4,1 oxygene, and 25,7
nitrogene.
But, as appears from the last section, there existed in the lungs
before the inspiration of the nitrous oxide, about 32 cubic inches of
gas, consisting of 23 nitrogene, 4,1 carbonic acid, and 4,9 oxygene,
temperature being reduced to 59°. This gas must have been perfectly
mingled with the nitrous oxide during the experiment; and consequently,
the residual gas in the lungs after the experiment, was of the same
composition as that in the airholder.
Supposing it as before, to be about 32 cubic inches: from the rule of
proportion, they will be composed of
Nitrous oxide 14,7
Nitrogene 13,3
Carbonic acid 1,9
Oxygene 2,1
And the whole quantity of gas in the lungs and the airholder, supposing
the temperature 59°, will equal 94 cubic inches, which are composed of
Nitrous oxide 43,7
Nitrogene 39,0
Carbonic acid 5,2
Oxygene 6,1
————
94
But before the experiment, the gas in the lungs and airholder equalled
134 cubic inches, and these, reckoning for the common air, were
composed of
Nitrous oxide 100
Nitrogene, 24,3
Carbonic acid 4,1
Oxygene 5,6
Hence, it appears, that 56,3 cubic inches of nitrous oxide were
absorbed in this experiment, and 13,7 of nitrogene produced, either
by evolution from the blood, or decomposition of the nitrous oxide.
The quantities of carbonic acid and oxygene approach so near to those
existing after the respiration of hydrogene, that there is every reason
to believe that no portion of them was produced in consequence of the
absorption, or decomposition of the nitrous oxide.
_b._ In Exp. 2, calculating in the same manner, before the first
inspiration, a quantity of gas equal to 216,5 cubic inches at 47°,
existed in the lungs and airholder, and these 216,5 cubic inches were
composed of
Nitrous oxide, 182,0
Nitrogene 24,9
Carbonic acid 4,1
Oxygene 5,5
——————
216,5
After the compleat expiration, 160 cubic inches remained in the lungs
and airholder, which was composed of
Nitrous oxide 110,6
Nitrogene 36,3
Carbonic acid 6,8
Oxygene 6,3
Hence, it appears, that 71,4 cubic inches of nitrous oxide were
absorbed in this experiment, and about 12 of nitrogene produced. The
quantity of carbonic acid and oxygene is rather greater than that which
existed in the experiments on hydrogene.
_c._ From these estimations, I learned that a small quantity of
nitrogene was produced during the absorption of nitrous oxide in
respiration. It remained to determine, whether this nitrogene owed its
production to evolution from the blood, or to the decomposition of a
portion of the nitrous oxide.
Analogical evidences were not in favour of the hypothesis of
decomposition. It was difficult to suppose that a body requiring the
temperature of ignition for its decomposition by the most inflammable
bodies, should be partially absorbed and partially decompounded at 98°,
by a fluid apparently possessed of uniform attractions.
It was more easy to believe, that from the immense quantity of
nitrogene taken into the blood in nitrous oxide; the system soon
became overcharged with this principle, which not being wholly
expended in new combinations during living action, was liberated in
the aëriform state by the exhalents, or through the moist coats of the
veins.
Now if the last rationale were true, it would follow, that the
quantity of nitrogene produced in respiration, ought to be increased
in proportion as a greater quantity of nitrous oxide entered into
combination with the blood.
_d._ To ascertain whether this was the case, I made after full
voluntary exhaustion of my lungs, one full voluntary inspiration and
expiration of 108 cubic inches of nitrous oxide. After this, it filled
a space nearly equal to 99 cubic inches. The quantities of carbonic
acid and oxygene in these were not determined; but by the test of
absorption by water, they appeared to contain only 18 nitrogene; which
is very little more than should have been given from the residual gas
of the lungs.
In a second experiment, I made two respirations of 108 cubic inches
of nitrous oxide nearly pure. The diminution was to 95. On analysing
these 95, I found to my great surprise, that they contained only 17
nitrogene. Hence, I could not but suspect some source of error in the
process.
I now introduced into a strong new silk bag, the sides of which were
in perfect contact, about 8 quarts of nitrous oxide. From the mode of
introduction, this nitrous oxide must have been mingled with a little
common air, not however sufficient to disturb the results.
I then adapted a cork cemented to a long curved tube to my right
nostril; the tube was made to communicate with the water apparatus;
and the left nostril being accurately closed, and the mouth-piece of
the silk bag tightly adapted to the lips, I made a full expiration
of the common air of my lungs, inspired nitrous oxide from the bag,
and by carefully closing the mouth-piece with my tongue, expired it
through the curved tube into the water apparatus. In this way, I made
nine respirations of nitrous oxide. The expired gas of the first
respiration was not preserved; but part of the gas of the second,
third, fifth, seventh and ninth, were caught in seperate graduated
cylinders. The second, analised by absorption, consisted of about 29
absorbable gas, which must have been chiefly nitrous oxide; and 17
unabsorbable gas, which must have been chiefly nitrogene; and the third
of 22 absorbable gas, and 8 unabsorbable. The fifth was composed of 27
to 6; the seventh of 23 to 7, and the ninth of 26 to 11.
_e._ Though the results of these experiments were not so conclusive as
could be wished; yet, comparing them with those of the experiments in
section III. it seemed reasonable to conclude, that the production of
nitrogene was increased, in proportion as the blood became more fully
impregnated with nitrous oxide.
From this conclusion, compared with the phænomenon noticed in section
2, and in Div. I. section 4, I am induced to believe that the
production of nitrogene during the respiration of nitrous oxide, is
not owing to the decomposition of part of the nitrous oxide, in the
aëriform state _immediately_ by the attraction of the red particles
of venous blood for its oxygene; but that it is rather owing to a new
arrangement produced in the principles of the impregnated blood, during
circulation; from which, becoming supersaturated with nitrogene, it
gives it out through the moist coats of the vessels.
For if any portion of nitrous oxide were decomposed immediately by the
red particles of the blood, one should conjecture, that the quantity of
nitrogene produced, ought to be greater during the first inspirations,
before these particles became fully combined with condensed oxygene.
If on the contrary, the whole of the nitrogene and oxygene of the
nitrous oxide were both combined with the blood, and carried through
the pulmonary veins and left chamber of the heart to the arteries;
then, supposing the oxygene chiefly expended in living action, whilst
the nitrogene was only partially consumed in new combinations, it
would follow, that the venous blood of animals made to breathe nitrous
oxide, hyper-saturated with nitrogene, must be different from common
venous blood; and this we have reason to believe from the phænomena in
Div. I. section 4, is actually the case.
_f._ Besides the nitrogene generated during the respiration of nitrous
oxide, we have noticed the evolution of other products, carbonic
acid,[199] and water.
[199] The oxygene as we have before noticed, most probably wholly
existed in the residual gas.
Now as nearly equal quantities of carbonic acid are produced, whether
hydrogene or nitrous oxide is respired, provided the process is carried
on for the same time; there is every reason to believe, as we have said
before, that no part of the carbonic acid produced, is generated from
the immediate decomposition of nitrous oxide by carbon existing in the
blood.
Consequently, in these experiments, it must be either evolved from the
venous blood; or formed, by the slow combination of the oxygene of the
residual air of respiration with the charcoal of the blood.
But if it was produced by the decomposition of residual atmospheric
air, it would follow, that its volume must be much less than that
of the oxygene of the residual air, which had disappeared; for some
of this oxygene must have been _absorbed_ by the blood, and during
the conversion of oxygene into carbonic acid by charcoal, a slight
diminution of volume is produced.
In the experiments when nitrous oxide and hydrogene were respired for
about half a minute, the medium quantity of carbonic acid produced, was
5,6 cubic inches nearly.
Now we will assume, that the quantity of carbonic acid produced, is
in the ratio of the oxygene diminished; and there is every reason to
believe, that in the expiration of atmospheric air, the expired air and
the residual air are nearly of the same composition.
Hence, no more carbonic acid can remain in the lungs or be produced
from the residual gas after the compleat expiration of common air,
than that which can be generated from a volume of atmospheric air
equal to the residual gas of the lungs.
The residual gas of the lungs, after compleat expiration, equals at
55°, 32 cubic inches, and 32 cubic inches of common air contain 8.6
cubic inches of oxygene.
But in the experiments on the respiration of hydrogene, not only
5.6 cubic inches of carbonic acid were produced, but more than 4 of
residual oxygene remained unabsorbed.
Hence it appears impossible that all the carbonic acid evolved from the
lungs during the respiration of nitrous oxide or hydrogene could have
been produced by the combination of charcoal in the venous blood with
residual atmospheric oxygene: there is consequently every reason to
believe that it is wholly or partially liberated from the venous blood
through the moist coats of the vessels.
_g._ The water carried out of the lungs in solution by the expired gas
of nitrous oxide, could neither have been wholly or partially formed
by the decomposition of nitrous oxide. The coats of the vessels in the
lungs, and indeed in the whole internal surface of the body, are always
covered with moisture, and the solution of part of this moisture by
the inspired heated gas, and its deposition by the expired gas, are
sufficient causes for the appearance of the phænomenon.
There are no reasons for supposing that any of the residual atmospheric
oxygene is immediately combined with fixed or nascent hydrogene, or
hydrocarbonate, in the venous blood at 98°, by slow combustion, and
consequently none for supposing that water is immediately formed in
respiration.
The evolution of water from the vessels in the lungs, is almost certain
from numerous analogies.
_h._ As from the experiments in section II. it appeared that nitrous
oxide was capable of being combined with oxygenated blood, and vice
versa, blood impregnated with nitrous oxide capable of oxygenation; I
was curious to ascertain what changes would be effected in nitrous
oxide when it was respired, mingled with atmospheric air or oxygene.
For this purpose, without making a very delicate experiment, I breathed
in the large mercurial airholder about 112 cubic inches of nitrous
oxide, mingled with 44 of common air, for near half a minute, in the
usual mode. The gas, after expiration, filled a space nearly equal to
119. I did not exactly ascertain the composition of the residual gas;
it supported flame rather better than common air, and after the nitrous
oxide was absorbed, gave much less diminution with nitrous gas than
atmospheric air.
_i._ I breathed a mixture of four quarts of nitrous oxide with three
quarts of hydrogene, in a dry silk bag, for near a minute; an evident
diminution was produced; but on account of the mode of experimenting it
was impossible to determine the quantity of nitrous oxide absorbed, or
the exact nature of the products. When a taper was introduced into a
little of the residual gas, it inflamed with a very feeble explosion.
Now a mixture of 4 parts nitrous oxide and 3 hydrogene, detonates when
inflamed with very great violence.
_k._ Nitrous oxide can be respired without danger by the human animal
for a much longer time than that required for the death of the smaller
quadrupeds in it.
I have breathed it two or three times in a considerable state of
purity, in a dry silk bag, for four minutes and quarter and four
minutes and half: some diseased individuals have respired it for
upwards of five minutes.
In the infancy of my experiments, from general appearances, I thought
that the proportion of nitrous oxide absorbed in respiration was
greater in the first inspirations than the last; but this I have
since found to be a mistake. In the last respirations the apparent
absorption is indeed less; but this is on account of the increased
evolution of nitrogene from the blood. When nitrous oxide is respired
for a long time, the last inspirations are always fuller and quicker
than the first; but the consumption by the same individual is nearly in
the ratio of the time of respiration. Three quarts, i. e. about 174
cubic inches, are consumed so as to be unfit for respiration, by an
healthy individual with lungs of moderate capacity, in about a minute
and quarter; six quarts, or 348 cubic inches, last generally for two
minutes and half or two minutes and three quarters; eight quarts, or
464 cubic inches, for more than three minutes and half; and twelve, or
696 cubic inches, for nearly five.
The quantities of nitrous oxide absorbed by the same individual, will,
as there is every reason to suppose, be different under different
circumstances, and will probably be governed in some measure by the
state of the health. It is reasonable to suppose, that the velocity of
the circulation must have a considerable influence on the absorption
of nitrous oxide; probably in proportion as it is greater a larger
quantity of gas will be consumed in equal times.
I am inclined from two or three experiments, to believe that
nitrous oxide is absorbed more rapidly after hearty meals or during
stimulation from wine or spirits, than at other times. As its
absorption appears to depend on a simple solution in the venous blood;
probably diminution of temperature will increase its capability of
being absorbed.
_l._ The quantities of nitrous oxide absorbed by different individuals,
will probably be governed in some measure by the size of their lungs
and the surface of the blood vessels, all other circumstances being the
same.
From the observations that I have been able to make on the absorption
of nitrous oxide, as compared with the capacity of the lungs, the range
of the consumption of different individuals does not extend to more
than a pint, or 30 cubic inches at the maximum dose.
We may therefore conclude, that the medium consumption of nitrous oxide
by the respiration of different individuals, is not far from two cubic
inches, or about a grain every second, or 120 cubic inches, or 60
grains every minute.
_m._ When nitrous oxide is breathed in tight silk bags, towards the end
of the experiment as the internal surface becomes moist, as I have
before mentioned, a certain quantity of common air penetrates through
it and becomes mixed with the residual gas of the experiment; but this
quantity is always too small to destroy any of the effects of the
nitrous oxide. The residual gas of the common air, the nitrogene and
carbonic acid produced in the process, and the residuum of the admitted
atmospheric air, hardly ever amount after the experiment, to one half
of the volume of the nitrous oxide absorbed. There is consequently, a
perfect propriety in successively inspiring and expiring the whole of
a given quantity of nitrous oxide, till it is nearly consumed. In the
respiration of nitrous oxide as the gas is absorbed and not decomposed,
little will be gained in effect, by perpetually inspiring and expiring
new portions, whilst an immense quantity of gas will be idly wasted,
and this circumstance, considering the expence of the substance, is of
importance.