Part 18

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.

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 was separated 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

Carbonic acid 4,0 Oxygene 3,7 Nitrogene 17,3 Hydrogene 78,0 ————— 103,0

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°, it must 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

Nitrogene 21,9 Carbonic acid 4,9 Oxygene 5,0 ———— 31,8

[194] Annales de Chimie, vol. 1, page 279.

[195] This is only an imperfect approximation; the ratio of the increase of expansibility of gases to the increase of temperature, has not yet been ascertained. It is probable that the expansibility of gases is altered by their mixture.

[196] For there is no reason to suppose the production of nitrogene.

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

Carbonic acid 4,8 Oxygene 4,6 Nitrogene 21,0 Hydrogene 153,6 ————— 184,0

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 my lungs 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

Carbonic acid 4,1 Oxygene 5,5 Nitrogene 24,4

_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 a _uniform_ mixture 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, when brought 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

Carbonic acid 3,1 Oxygene 4,5 Nitrogene 18,8 Hydrogene 115,6 ————— 142,0

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

Nitrogene 20,9 Oxygene 5,8 Carbonic acid 4,0 ———— 30,7

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 the exhalents, 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

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.