1st. That when nitrous oxide is agitated in fluid venous blood, a certain portion of the gas is absorbed; whilst the color of the blood changes from dark red to red purple.2dly. That during the absorption of nitrous oxide by the venous blood, minute portions of nitrogene and carbonic acid are produced, either by evolution from the blood, or from a decomposition of part of the nitrous oxide.3dly. That venous blood impregnated with nitrous oxide is capable of oxygenation; and vice versa; that oxygenated blood may be combined with nitrous oxide.
1st. That when nitrous oxide is agitated in fluid venous blood, a certain portion of the gas is absorbed; whilst the color of the blood changes from dark red to red purple.
2dly. That during the absorption of nitrous oxide by the venous blood, minute portions of nitrogene and carbonic acid are produced, either by evolution from the blood, or from a decomposition of part of the nitrous oxide.
3dly. That venous blood impregnated with nitrous oxide is capable of oxygenation; and vice versa; that oxygenated blood may be combined with nitrous oxide.
When blood separated into coagulum and serum, is exposed to nitrous oxide, it is most probable that the gas is chiefly absorbed by the serum. That nitrous oxide however is capable of acting upon the coagulum, is evident fromd.In the fluid blood, as we shall see hereafter, nitrous oxide is absorbed by the attractions of the whole compound.
III.Of the changes effected in Nitrous Oxideby Respiration.
To ascertain whether the changes effected in nitrous oxide by the circulating blood acting through the moist coats of the pulmonary veins of living animals, were highly analogous to those produced in it by fluid venous blood removed from the vessels, I found extremely difficult.
I have before observed, that when animals are made to respire nitrous oxide, a certain absorption of the gas always takes place; but the smaller animals, the only ones that can be experimented upon in the mercurial apparatus, die in nitrous oxide so speedily and occasion so slight a diminution of gas, that I judged it useless to attempt to analise the residuum of their respiration, which supports flame as well as pure nitrous oxide, and is chiefly absorbable by water.
In the infancy of my researches, I often respired nitrous oxide in alarge glass bell, furnished with a breathing tube and stop-cock, and poised in water saturated with the gas.
In two or three experiments in which the nostrils being closed after the exhaustion of the lungs, the gas was inspired from the bell and respired into it, a considerable diminution was perceived, and by the test of lime water some carbonic acid appeared to have been formed; but on account of the absorption of this carbonic acid by the impregnated water, and the liberation of nitrous oxide from it, it was impossible to determine with the least accuracy, the quantities of products after respiration.
About this time likewise, I often examined the residuum of nitrous oxide, after it had been respired in silk bags. In these experiments when the gas had been breathed for a long time, a considerable diminution of it was observed, and the remainder extinguished flame and gave a very slight diminution with nitrous gas. But the great quantity of this remainder as well as other phænomena, convinced me that thoughthe oiled silk was apparently air-tight when dry, under slight pressure, yet during the action of respiration, the moist and warm gas expired, penetrated through it, whilst common air entered through the wetted surface.
To ascertain accurately, the changes effected in nitrous oxide by respiration, I was obliged to make use of the large mercurial airholder mentioned inResearch I. of the capacity of 200 cubic inches. The upper cylinder of it was accurately balanced so as to be constantly under the pressure of the atmosphere. To an aperture in it, a stop-cock having a very large orifice was adapted, curved and flattened at its upper extremity, so as to form an air-tight mouth-piece.
By accurately closing the nose, and bringing the lips tight on the mouth-piece, after a few trials I was able to breathe oxygene or common air in this machine for two minutes or two minutes and half, without any other uneasy feeling than that produced by the inclination of the neck and chest towards the cylinder. The power of uniformly exhaustingthe lungs and fauces to the same extent, I did not acquire till after many experiments. At last, by preserving exactly the same posture after exhaustion of the lungs before the inspiration of the gas to be experimented upon, and during its compleat expiration, I found that I could always retain nearly the same quantity of gas in the bronchial vessels and fauces; the difference in the volume expired at different times, never amounting to a cubic inch and half.
By connecting the conducting pipe of the mercurial airholder, during the respiration of the gas, with a small trough of mercury by means of a curved tube, it became a perfect and excellent breathing machine. For by exerting a certain pressure on the airholding cylinder, it was easy to throw a quantity of gas after every inspiration or expiration, into tubes filled with mercury standing in the trough. In these tubes it could be accurately analised, and thus the changes taking place at different periods of the process ascertained.
Whenever I breathed pure nitrous oxide in the mercurial airholder,after a compleat voluntary exhaustion of my lungs, the pleasurable delirium was very rapidly produced, and being obliged to stoop on the cylinder, the determination of blood to my head from the increased arterial action in less than a minute became so great, as often to deprive me of voluntary power over the muscles of the mouth. Hence, I could never rely on the accuracy of any experiment, in which the gas had been respired for more than three quarters of a minute.
I was able to respire the gas with great accuracy for more than half a minute; it at first, rather increasing than diminishing the power of volition; but even in this short time, very strong sensations were always produced, with sense of fulness about the head, somewhat alarming; a feeling which hardly ever occurs to me when the gas is breathed in the natural posture.
In all the numerous experiments that I made on the respiration of nitrous oxide in this way, a very considerable diminution of gas always took place; and the diminution was generally apparently greater to the eye during the first four or five inspirations.
The residual gas of an experiment was always examined in the following manner. After being transferred through mercury into a graduated cylinder, a small quantity of concentrated solution of caustic potash was introduced to it, and suffered to remain in contact with it for some hours; the diminution was then noted, and the quantity of gas absorbed by the potash, judged to be carbonic acid. To the remainder, twice its bulk of pure water was admitted. After agitation and rest for four or five hours, the absorption by this was noticed, and the gas absorbed considered as nitrous oxide. The residual unabsorbable gas was mingled over water with twice its bulk of nitrous gas; and by this means, its composition, whether it consisted wholly of nitrogene, or of nitrogene mingled with small quantities of oxygene, ascertained.
From a number of experiments made at different times on the respiration of nitrous oxide, I select the following as the most accurate.
E. 1. At temperature 54°, I breathed 102 cubic inches of nitrous oxide, which contained near ¹/₅₀ common air, for about half a minute, seven inspirations and seven expirations being made. After every expiration, an evident diminution of gas was perceived; and when the last full expiration was made, it filled a space equal to 62 cubic inches.
These 62 cubic inches analised, were found to consist of
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 apparentdiminution 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
Consequently, in this experiment, 93,25 cubic inches of nitrous oxide had disappeared.
In each of these experiments, the cylinder was covered with condensedwatry 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 completeexpiration 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.
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 effectchanges 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 bronchialvessels 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 wasproducedby the combination of carbon loosely combined in the venous blood, with the oxygene respired, or whether it was simplygiven outas 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 sevenrespirations 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.
IV.Respiration of Hydrogene.
The hydrogene that I employed, was procured from the decomposition of water by means of clean iron filings and diluted sulphuric and muriatic acids. It was breathed in the same manner as nitrous oxide, in the large mercurial airholder.
After a compleat voluntary exhaustion of my lungs in the usual posture,I found great difficulty in breathing hydrogene for so long as half a minute, so as to make a compleat expiration of it. It produced uneasy feelings in the chest, momentary loss of muscular power, and sometimes a transient giddiness.
In some of the experiments that I made; on account of the giddiness, the results were rendered inconclusive, by my removing my mouth from the mouth-piece after expiration, before the assistant could turn the stop-cock.
The purity of the hydrogene was ascertained immediately before the experiment by the test of nitrous gas, and by detonation with oxygene or atmospheric air; generally 12 measures of atmospheric air were fired with 4 of the hydrogene, and if the diminution was to ten or a little more, the gas was judged to be pure.
After the experiment, when the compleat expiration had been made and the common temperature restored; the volume of the gas was noticed, and then a small quantity of it thrown into the mercurial apparatus by means of the conducting tube, to be examined. The carbonic acid wasseparated by from it by means of solution of potash or strontian; the quantity of oxygene it contained, was ascertained by means of nitrous gas of known composition; the superabundant nitrous gas was absorbed by solution of muriate of iron; and the proportions of hydrogene and nitrogene in the remaining gas, discovered by inflammation with atmospheric air or oxygene in the detonating tube by the electric spark.
a.The two following experiments made upon quantities of hydrogene, equal to those of the nitrous oxide respired in the experiments in the last section, are given as the most accurate of five.
E. 1. I respired at 59° 102 cubic inches of hydrogene apparently pure, for rather less than half a minute, making in this time seven quick respirations.
After the complete expiration, when the common temperature was restored, the gas occupied a space equal to 103 cubic inches nearly. These analised were found to consist of
Now as in this experiment, the gas was increased in bulk only a cubic inch; supposing that after the compleat expiration the gas in the lungs, bronchia and fauces was of nearly similar composition with that in the airholder, and that no hydrogene had been absorbed by the blood, it would follow that 24 cubic inches of hydrogene remained in the internal organs of respiration, and consequently, by the rule of proportion, about 7,8 of the mixed residual gas of the common air. And then the whole quantity of residual gas of the lungs, supposing the temperature 59°, would have been 31,8 cubic inches; but as its temperature was nearly that of the internal parts of the body, 98°, itmust have filled a greater space; calculating from the experiments of Guyton and Vernois,[194]about 37,5[195]cubic inches.
From the increase of volume, it would appear that a minute quantity of gas had been generated during the respiration, and this was, as we shall see hereafter, most probably carbonic acid.[196]Likewise there is reason to suppose, that a little of the residual oxygene must have been absorbed. Making allowances for those circumstances, it would follow, that the 37,5 cubic inches of gas remaining in my lungs, after a compleat expiration of atmospheric air at animal heat 98°, equal to 31,8 cubic inches at 59°, were composed of
E. 2. I respired for near a half a minute in the mercurial airholder at 61°, 182 cubic inches of hydrogene; having made during this time, six long inspirations. After the last expiration, the gas filled a space nearly equal to 184 cubic inches, and analised, was found to consist of
Now in this experiment, reasoning in the same manner as before, 28,4 cubic inches of hydrogene must have remained in the lungs, and likewise 5,5 of the atmospheric residual gas. Consequently, the whole residual gas was nearly equal to 34 cubic inches at 61°, which at 98° would become about 40,4 cubic inches. And reasoning as before, it would appear from this experiment, that the quantity of gas remaining in mylungs after a compleat voluntary respiration, equalled at 98, about 40 cubic inches, and at 61°, 34 nearly: making the necessary corrections; that after common air had been breathed, these 34 cubic inches consisted of
b.It would have been possible to prove the truth of the postulate on which the experiments were founded, by respiring common air or oxygene after the compleat expiration of the hydrogene, for the same time as the hydrogene was respired and in equal quantities.
For if portions of hydrogene were found in the airholder equal to those of the residual gases in the two experiments, it would prove that auniformmixture of residual gas with the gas inspired, was produced by the respiration. That this mixture must have taken place, appeared, however, so evident from analogous facts, that I judged the experimental proof unnecessary.
Indeed, as most gases, though of different specific gravities, whenbrought in contact with each other, assume some sort of union, it is more than probable, that gas inspired into the lungs, from being placed in contact with the residual gas on such an extensive surface, must instantly mingle with it. Hence, possibly one deep inspiration and compleat expiration of the whole of a quantity of hydrogene, will be sufficient to determine the capacity of the lungs after compleat voluntary exhaustion, and the nature of the residual air.
That two inspirations are sufficient, appears probable from the following experiment.
E. 3. After a compleat voluntary expiration of common air, I made two deep inspirations of 141 cubic inches of hydrogene. After the compleat expiration, they filled a space equal to rather more than 142 cubic inches, and analised, were found to consist of
Now calculating on the exhausted capacity of my lungs from this experiment, supposing uniform mixture, they would contain after expiration of common air, about 30,7 cubic inches at 58°, equal to 36 at 98°, composed of about
One should suppose a priori that in this experiment much less of the residual oxygene of the lungs must have been absorbed, than in Expts. 1 and 2; yet there is no very marked difference in the portions evolved. That a tolerably accurate mixture took place, appears from the quantity of nitrogene. The smaller quantity of carbonic acid is an evidence in favour of its evolution from the venous blood.
c.It is reasonable to suppose that the pressure upon the residual gas of the exhausted lungs, must be nearly equal to that of the atmosphere. But as aqueous vapour is perpetually given out by theexhalents, and perhaps evolved from the moist coats of the pulmonary vessels, it is likely that the residual gas is not only fully saturated with moisture at 98°, but likewise impregnated with uncombined vapor; and hence its volume enlarged beyond the increment of expansion of temperature.
Considering all these circumstances, and calculating from the mean of the three experiments on the composition of the residual gas, I concluded,
1st. That the exhausted capacity of my lungs was equal to about 41 cubic inches.
2dly. That the gas contained in my bronchial vessels and fauces, after a compleat expiration of atmospheric air, was equal to about 32 cubic inches, its temperature being reduced to 55°.
3dly. That these 32 cubic inches were composed of about
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°
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]
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]
V.Additional observations and experimentson 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 reasonconcerning 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
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
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
Hence, it appears, that 56,3 cubic inches of nitrous oxide were absorbed in this experiment, and 13,7 of nitrogene produced, either byevolution 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
After the compleat expiration, 160 cubic inches remained in the lungs and airholder, which was composed of
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 becameovercharged 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 ofnitrous 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 respirationwas 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 aëriformstateimmediatelyby 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.
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 beenabsorbedby 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, thanthat 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 partiallyformed 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 effectedin 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 veryfeeble 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 theratio 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 stimulationfrom 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 Ihave 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.
VI.On the respiration of Atmospheric Air.
Having thus ascertained the absorption of nitrous oxide in respiration, and the evolution of nitrogene and carbonic acid from the lungs during its absorption: considering atmospheric air as a compound in which principles identical with those in nitrous oxide existed, though in different quantities and looser combination, I was anxious to compare the changes effected in this gas by respiration, with those produced in nitrous oxide and oxygene; particularly as they are connected with the health and life of animals.
The ingenious experiments of Lavoisier and Goodwyn, prove the consumption of oxygene in respiration, and the production of carbonic acid. From many experiments on the respiration of common air, Dr. Priestly suspected that a certain portion of nitrogene, as well as oxygene, was absorbed by the venous blood.
b.In the following experiments on the respiration of atmospheric air in the mercurial airholder; the composition of the gas before inspiration and after expiration, was ascertained in the following manner.
Forty measures of it were agitated over mercury in solution of caustic potash, and suffered to remain in contact with it for two or three hours. The diminution was noted, and the gas absorbed judged to be carbonic acid. Twenty measures of the gas, freed from carbonic acid, were mingled with thirty of nitrous gas, in a tube of,5 inches diameter; they were not agitated,[200]but suffered to rest for an hour or an hour and half, when the volume occupied by them was noticed: and 50-mthe volume occupied, divided by 3 considered as the oxygenex, and 20-xconsidered as the nitrogene.
c.To ascertain the changes effected in atmospheric air by single inspirations,
I made, after a compleat voluntary exhaustion of my lungs, at temperature 61°, one inspiration and expiration of 141 cubic inches of atmospheric air. After expiration, they filled a space equal to 139 cubic inches nearly. These 139 cubic inches analised were found to consist of
The 141 cubic inches before inspiration, were composed of 103 nitrogene, 1 carbonic acid and 37 oxygene. The time taken to perform the inspiration and full expiration, was nearly a quarter of a minute.
I repeated this experiment seven or eight times, and the quantity of oxygene absorbed was generally from 5 to 6 cubic inches, the carbonic acid formed from 5 to 5,5, and the quantity of nitrogene apparently diminished by from 1 to 3 cubic inches.
E. 2. I made, after a voluntary expiration of common air, one inspiration and full expiration of 100 cubic inches of atmospheric air. It was diminished nearly to 98¾ or 99 cubic inches, and analised, was found to consist of
This experiment I likewise repeated four or five times, with very little difference of result, and there always seemed to be a small diminution of nitrogene. I made no corrections on account of the residual air of the lungs in these processes, because there was every reason to suppose that it was always of similar composition.
c.Before I could ascertain whether similar changes were effected in atmospheric air, by natural inspirations as by forced ones, I was obliged to practise respiration in the mercurial airholder, by differing the conducting tube to communicate with the atmosphere till I had attained the power of breathing in it naturally, without labor orattention; I then found by a number of experiments, that I took into my lungs at every natural inspiration, about 13 cubic inches of air, and that I threw out of my lungs at every expiration,[201]rather less than this quantity; about 12¾ cubic inches.
The mean composition of the 13 cubic inches of air inspired, was
That of the 12,7 of air expired
These results I gained from more than 20 experiments, so that I could not possibly entertain any doubt of this accuracy.
I found, by making a person observe my respirations when I wasinattentive to the process, that I made about 26 or 27 natural inspirations in a minute. So that calculating from the above estimations, it would follow, that 31,6 cubic inches of oxygene were consumed, and 5,2 inches of nitrogene lost in respiration every minute, whilst 26,6 cubic inches of carbonic acid were produced.
To collect the products of a great number of natural expirations so as to ascertain whether their composition corresponded with the above accounts, I proceeded in the following manner.
I fastened my lips tight on the mouth-piece of the exhausted airholder, and suffering my nostrils to remain open, inspired naturally through them, throwing the expired air through my mouth into the airholder.
In many experiments, I found that in about a half a minute, I made in this way 14 or 15 expirations. The mean quantity of air collected was 171 cubic inches, and consisted of
Comparing these results with the former ones, we find the mean quantities of air respired in equal terms rather less; but the proportions of carbonic acid, nitrogene and oxygene in the respired air, nearly identical.
e.To ascertain the changes effected in a given quantity of atmospheric air by continued respirations, I breathed after a compleat expiration, at temperature 63°, 161 cubic inches of air for near a minute, making in this time, 19 deep inspirations. After the compleat expiration, which was very carefully made, the gas filled a space nearly equal to 152 cubic inches, so that 9 cubic inches of gas had disappeared.
The 152 cubic inches analised, were found to consist of
The 161 cubic inches before inspiration, were composed of
But the residual gas in the lungs before the experiment, was of different composition from that remaining in the lungs after the experiment. Making corrections on account of this circumstance, as in section IV. it appears that about 5,1 of nitrogene were absorbed in respiration, 23,9 of oxygene consumed, and 12 of carbonic acid produced.
I repeated this experiment three times; in each experiment the diminution after respiration, was nearly the same; and the residual gas making the necessary allowances, of similar composition. So that supposing the existence of no source of error in the experiments from which the quantity and composition of the residual gas of the lungs were estimated in section IV. the absorption of nitrogene by the venous blood, appears almost demonstrated.
f.To compare the changes effected in atmospheric air by respiration of the smaller quadrupeds, with those in the experiments just detailed, I introduced into a jar of the capacity of 20 cubic inches filled with mercury in the mercurial trough, 15 cubic inches of atmospheric air which had been deprived of its carbonic acid by long exposure, to solution of potash.
Temperature being 64°, a healthy small mouse was quickly passed under the mercury into the jar, and suffered to rest on a very thin bit of cheese, which was admitted immediately after.
He continued for near 40 minutes without apparently suffering, occasionally raising himself on his hind legs. At the end of 50 minutes, he was lying on his side, and in 55 minutes was apparently dying. He was now carefully taken out through the mercury by the tail, and exposed before the fire, where he soon recovered. After the cheese had been carefully removed, the gas in the jar filled a space nearlyequal to 14 cubic inches; so that a diminution of a cubic inch had taken place. These 14 cubic inches analised, were found to consist of
The 15 cubic inches before the experiment, consisted of
Hence it appeared, that 2,6 cubic inches of oxygene had been consumed, 2 cubic inches of carbonic acid produced, and about 0,4 of nitrogene lost.
The relation between the quantities of oxygene consumed in this experiment, and the carbonic acid produced, are nearly the same as that of those in the experiments just detailed; but the quantity of nitrogene lost is much smaller.
VII.Respiration of Oxygene.
The gases before and after respiration, were analised in these experiments in the manner described in the last section, except that 3 of nitrous gas were always employed to one of oxygene.
E. I. At temperature 53°, after a full forced respiration, I respired in the mercurial airholder, for half a minute, 102 cubic inches of oxygene, making seven very long and deep inspirations. After the compleat expiration, the gases filled a space equal to 93 cubic inches; these 93 cubic inches analised, were found to consist of
The 102 cubic inches before the experiment, were composed of
The residual gas in the lungs before the experiment, was 32 cubic inches, and composed of about 23 nitrogene, 4,1 carbonic acid, and 4,9 oxygene,Section IV. The residual gas after expiration, was composed of 18,2 oxygene, 2 carbonic acid, and 11,8 nitrogene.
Hence the whole of the gas in the lungs and airholder before inspiration, was 134 cubic inches, composed of
And after respiration, 125 cubic inches, consisting of
So that comparing the quantities, it appears, that 11,4 of oxygene and 1,4 of nitrogene, were consumed in this experiment, and 3,8 of carbonic acid produced.
I was much surprised at the small quantity of oxygene that had been consumed in this experiment. This quantity was less than that expended during the respiration of atmospheric air for half a minute: the portion of carbonic acid evolved was likewise smaller. I could detect no source of inaccuracy, and it was difficult to suppose that the greater depth and fulness of the inspirations could make any difference.
E. 2. I now respired at the same temperature, after a full expiration, 162 cubic inches of gas, composed of 133 oxygene and 20 nitrogene for two minutes, imitating as much as possible, the natural respiration. After the experiment, they filled a space equal to 123 cubic inches. And when the analysis and calculations had been made as in the last experiment, it appeared that 57 cubic inches of oxygene, and 2 of nitrogene had been absorbed, whilst 21 cubic inches of carbonic acid had been formed.
Now from the estimations in the last section, it appears that 63 cubic inches of oxygene are consumed, and about 52 cubic inches of carbonic acid produced every two minutes during the natural respiration of common air. So that supposing the experiment accurate, 6 cubic inches of oxygene less are absorbed, and 30 cubic inches less of carbonic acid produced every minute, when oxygene nearly pure is respired, than when atmospheric air is respired.
Both these experiments were made in the morning, at a time when I was in perfect health; so that there could be apparently no source of error from accidental circumstances.
The uncommon and unexpected nature of the results, made me however, very sceptical concerning them; and before I would draw any inferences, I resolved to ascertain the comparative consumption of atmospheric air and oxygene by the smaller quadrupeds, for which purpose, I made the following experiment.
E. 3. Of two strong and healthy small mice, apparently of the same breed, and exactly similar.
One was introduced into a jar containing 10 cubic inches and half of oxygene, and 3 cubic inches of nitrogene, and made to rest on a bit of cheese.
The other was introduced into a jar containing fifteen cubic inches and half of atmospheric air, and made to rest in the same manner on cheese.
The mouse in oxygene began apparently to suffer in about half an hour, and occasionally panted very much; in about an hour he lay down on his side as if dying. The jars were often agitated, that the gases might be well mingled.
The mouse in atmospheric air became very feeble in 40 minutes, and at the end of 50 minutes was taken out through the mercury alive, but unable to stand.
The mouse in oxygene was taken out in the same manner after an hour and quarter, alive, but motionless, and breathing very deeply.
The gas in the jars was examined. That in the oxygene jar filled aspace exactly equal to 12,7 cubic inches, and analised, was found to consist of 1,7 carbonic acid, 2,6 of nitrogene, and 8,4 of oxygene. So that absolutely, 2,1 cubic inches of oxygene and,4 of nitrogene had been consumed, and 1,7 of carbonic acid produced.
The gas in the atmospheric air jar was diminished nearly to 14,4, and consisted of 2,1 carbonic acid, 1,4 oxygene; and 10,9 nitrogene. So that 2,7 of oxygene and,5 of nitrogene, had been consumed by the mouse; and 2,1 of carbonic acid produced.
Hence it appears, that the mouse in atmospheric air consumed nearly one third more oxygene and produced nearly one fourth more carbonic acid in respiration in 55 minutes, than the other in an hour and quarter in oxygene. And if we consider the perpetual diminution of the oxygene of the atmospheric air; from which at last it became almost incapable of supporting the life of the animal; we may conclude, thatthe quantity of oxygene consumed by it, had the air been perpetually renovated, would have been much more considerable.
I design very shortly, to repeat these experiments, and to make others on the comparative consumption of oxygene and atmospheric air, by the larger quadrupeds. Whatever may be the results, I hope to be able to ascertain from them, why pure oxygene is incapable of supporting life.
VIII.Observations on the changes effected in the blood, byatmospheric air and oxygene.
From the experiments of Mr. Cigna and Dr. Priestley,[202]it appears that the coagulum of the venous blood becomes florid at its surface when exposed to the atmosphere, though covered and defended from the immediate contact of air by a very thick stratum of serum.
Hence it is evident, that serum is capable of dissolving either the whole compound atmospheric air, or the oxygene of it.
Supposing what indeed is most probable from numerous analogies, that it dissolves the whole compound; it would follow, that the coloring of the coagulum of blood under serum, depended upon the decomposition of the atmospheric air condensed in the serum, the oxygene[203]of it combining with the red particles, and the nitrogene either remaining dissolved in the fluid, or being liberated through it into the atmosphere.
Now the circulating blood consists of red particles, floating in and diffused through serum and coagulable lymph.
In natural respiration, the red particles are rendered of a brighter tinge during the passage of the blood through the pulmonary veins. And as we have seen in the last sections, during respiration atmospheric air is decomposed; all the oxygene of it consumed,apparentlya small portion of the nitrogene lost, and a considerable quantity of carbonic acid produced.
It seems therefore reasonable to suppose, that the whole compound atmospheric air passing through the moist coats of the vessels is first dissolved by the serum of the venous blood, and in its condensed state, decomposed by the affinity of the red particles for its oxygene; the greater part of the nitrogene being liberated unaltered; but a minute portion of it possibly remaining condensed in the serum and coagulable lymph, and passing with them into the left chamber of the heart.
From the experiments on the respiration of nitrous oxide and hydrogene, it appears that a certain portion of the carbonic acid produced inrespiration, is evolved from the venous blood; but as a much greater quantity is generated during the respiration of common air and oxygene, than during that of hydrogene in equal times, it is not impossible but that some portion of it may be formed by the combination of charcoal in the red particles with the oxygene dissolved in the serum; but this can only be determined by farther experiments.
Supposing that no part of the water evolved in solution by the expired gas of common air is formed immediately in respiration, it will follow that a very considerable quantity of oxygene must be constantlycombinedwith the red particles, even allowing the consumption of a certain portion of it to form carbonic acid; for the carbonic acid evolved, rarely amounts to more than three fourths of the volume of the oxygene consumed.
Perhaps the serum of the blood is capable of dissolving a larger quantity of atmospheric air than of pure oxygene. On this supposition, it would be easy to explain the smaller consumption of oxygene in the experiments in the last section.
IX.Observations on the respirationof Nitrous Oxide.
The experiments in thefirst Divisionof this Research, prove that nitrous oxide when respired by animals, produces peculiar changes in their blood and in their organs, first connected with increased living action; but terminating in death.
From the experiments in this Division, it appears, that nitrous oxide is rapidly absorbed by the circulating venous blood, and of course its condensed oxygene and nitrogene distributed in the blood over the whole of the system.