Part 24

We know very little of the nature of excitement; as however, life depends immediately on certain changes effected in the blood in respiration, and ultimately on the supply of certain nutritive matter by the lymphatics; it is reasonable to conclude, that during the action of simulating substances, from the increased force of circulation, not only more oxygene and perhaps nitrogene must be combined with the blood in respiration,[228] but likewise more fluid nutritive matter supplied to it in circulation.

[228] See Dr. Beddoes’s _Considerations_, _part_ 1. _page_ 26. His observations in the note in the last section, will likewise apply here.—Is not healthy living action dependant upon a certain equilibrium between the principles supplied to the blood by the pulmonary veins from respiration and by the lymphatics from absorption? Does not sensibility more immediately depend upon respiration? Deprive an animal under stimulation, of air, and it instantly dies; probably if absorption could be prevented, it would likewise speedily die. It would be curious to try whether intoxication from fermented liquors cannot be prevented by breathing during their operation, an atmosphere deprived of part of its oxygene.

By this oxygene and nutritive matter excitability may be kept up: and exhaustion consequent to excitement only produced, in consequence of a deficiency of some of the nutritive principles, which are supplied by absorption.

When nitrous oxide is breathed, nitrogene (a principle under common circumstances chiefly carried into the blood by the absorbents in fluid compounds) is supplied in respiration; a greater quantity of oxygene is combined with the blood than in common respiration, whilst less carbonic acid and probably less water are evolved.

Hence a smaller quantity of nutritive matter is probably required from the absorbents during the excitement from nitrous oxide, than during the operation of stimulants; and in consequence, exhaustion from the expenditure of nutritive matter more seldom occasioned.

Since Research III. has been printed, I have endeavoured to ascertain the quantities of nitrogene produced when nitrous oxide is respired for a considerable time. In one experiment, when I breathed about four quarts of gas in a glass bell over impregnated water for near a minute, it was diminished to about two quarts; and the residuum extinguished flame.

Now the experiments in Research II. prove that when nitrous oxide is decomposed by combustible bodies, the quantity of nitrogene evolved is rather greater in volume than the pre-existing nitrous oxide. Hence much of the nitrogene taken into the system during the respiration of nitrous oxide, must be either carried into new combinations, or given out by the capillary vessels through the skin.

It would be curious to ascertain whether the quantity of ammoniac in the saline matters held in solution by the secreted fluids is increased after the respiration of nitrous oxide. Experiments made upon the consumption of nitrous oxide mingled with atmospheric air by the smaller animals, would go far to determine whether any nitrogene is given out through the skin.

The various effects of nitrous oxide upon different individuals and upon the same individuals at different times, prove that its powers are capable of being modified both by the peculiar condition of organs, and by the state of general feeling.

Reasoning from common phænomena of sensation, particularly those relating to heat, it is probable that pleasurable feeling is uniformly connected with a moderate increase of nervous action; and that this increase when carried to certain limits, produces mixed emotion or sublime pleasure; and beyond those limits occasions absolute pain.

Comparing the facts in the last division, it is likely that individuals possessed of high health and little sensibility, will generally be less pleasurably affected by nitrous oxide than such as have more sensibility, in whom the emotions will sometimes so far enter the limits of pain as to become sublime;[229] whilst the nervous action in such as have exquisite sensibility, will be so much increased as often to produce disagreeable feeling.

Modification of the powers of nitrous oxide by mixture of the gas with oxygene or common air, will probably enable the most delicately sensible to respire it without danger, and even with pleasurable effects: heretofore it has been administered to such only in its pure form or mingled with small quantities of atmospheric air, and in its pure form even the most robust are unable to respire it with safety for more than five minutes.

[229] Sublime emotion with regard to natural objects, is generally produced by the connection of the pleasure of beauty with the passion of fear.

The muscular actions[230] sometimes connected with the feelings produced by nitrous oxide, seem to depend in a great measure upon the particular habits of the individual; they will usually be of that kind which is produced either by common pleasurable feelings or strong emotions.

[230] The immortal HARTLEY has demonstrated that all our motions are originally automatic, and generally produced by the action of tangible things on the muscular fibre.

The common actions of adults may be distinguished into two kinds; voluntary actions, and mixed automatic actions. The first are produced by ideas, or by ideas connected with passions. The second by impression, or by pleasure and pain.

In voluntary action, regular associations of ideas and muscular motions exist: as when a chemist performs a pre-conceived experiment.

In mixed automatic actions, the simple motions produced by impression are connected with series of motions formerly voluntary, but now produced without the intervention of ideas: as when a person accustomed to play on the harpsichord, from accidentally striking a key, is induced to perform the series of motions which produce a well-remembered tune.

Evidently the muscular actions produced by nitrous oxide are mixed automatic motions.

Hysterical affection is occasioned by nitrous oxide, probably only in consequence of the strong emotion produced, which destroys the power of the will, and calls up series of automatic motions formerly connected with a variety of less powerful but similar feelings.

The quickness of the operation of nitrous oxide, will probably render it useful in cases of extreme debility produced by deficiency of common exciting powers. Perhaps it may be advantageously applied mingled with oxygene or common air, to the recovery of persons apparently dead from suffocation by drowning or hanging.

The only diseases in which nitrous oxide has been hitherto employed, are those of deficient sensibility.—An account of its agency in paralytic affections, will be speedily published by Dr. Beddoes.

As by its immediate operation the tone of the irritable fibre is increased, and as exhaustion rarely follows the violent muscular motions sometimes produced by it, it is not unreasonable to expect advantages from it in cases of simple muscular debility.

The apparent general transiency of its operation in the pure form in single doses has been considered as offering arguments against its power of producing lasting changes in the constitution. It will, however, be easy to keep up excitement of different degrees of intensity for a great length of time, either by administering the unmingled gas in rapid successive doses, or by preserving a permanent atmosphere, containing different proportions of nitrous oxide and common air, by means of a breathing chamber.[231] That single doses nevertheless, are capable of producing permanent effects in some constitutions, is evident, as well from the hysterical cases as from some of the details—particularly that of Mr. M. M. Coates.

[231] See R. IV. Div. I. page 478.

As nitrous oxide in its extensive operation appears capable of destroying physical pain, it may probably be used with advantage during surgical operations in which no great effusion of blood takes place.

From the strong inclination of those who have been pleasantly affected by the gas to respire it again, it is evident, that the pleasure produced, is not lost, but that it mingles with the mass of feelings, and becomes intellectual pleasure, or hope. The desire of some individuals acquainted with the pleasures of nitrous oxide for the gas has been often so strong as to induce them to breathe with eagerness, the air remaining in the bags after the respiration of others.

As hydrocarbonate acts as a sedative,[232] and diminishes living action as rapidly as nitrous oxide increases it, on the common theory of excitability[233] it would follow, that by differently modifying the atmosphere by means of this gas and nitrous oxide, we should be in possession of a regular series of exciting and depressing[234] powers applicable to every deviation of the constitution from health: but the common theory of excitability is most probably founded on a false generalisation. The modifications of diseased action may be infinite and specific in different organs; and hence out of the power of agents operating on the whole of the system.

[232] R. IV. Div. I. page 467.

[233] That of Brown modified by his disciples.

[234] Supposing the increase or diminution of living action when produced by different agents, uniform, similar and differing only in degree; it would follow, that certain mixtures of hydrocarbonate and nitrous oxide, or hydrogene and nitrous oxide, ought to be capable of supporting the life of animals for a much longer time than pure nitrous oxide. From the experiments in Res. III. Div. I. it appears however, that this is not the case.

It would seem, that in life, a variety of different corpuscular changes are capable of producing phænomena apparently similar; so that in the science of living action, we are incapable of reasoning concerning causes from effects.

Whenever we attempt to combine our scattered physiological facts, we are stopped by the want of numerous intermediate analogies; and so loosely connected or so independant of each other, are the different series of phænomena, that we are rarely able to make probable conjectures, much less certain predictions concerning the results of new experiments.

An immense mass of pneumatological, chemical, and medical information must be collected, before we shall be able to operate with certainty, on the human constitution.

Pneumatic chemistry in its application to medicine, is an art in infancy, weak, almost useless, but apparently possessed of capabilities of improvement. To be rendered strong and mature, she must be nourished by facts, strengthened by exercise, and cautiously directed in the application of her powers by rational scepticism.

APPENDIX.

No. I.

_Effects of Nitrous Oxide on Vegetation._

In July 1799, I introduced two small plants of spurge into nitrous oxide, in contact with a little water over mercury; after remaining in it two days, they preserved their healthy appearance, and I could not perceive that any gas had been absorbed. I was prevented by an accident, from keeping them longer in the gas.

A small plant of mint introduced into nitrous oxide and exposed to light, in three days became dark olive and spotted with brown; and in about six days was quite dead.—Another similar plant, kept in the dark in nitrous oxide, did not alter in color for five days, and at the end of seven days, was only a little yellower than before. I could not ascertain whether any gas had been absorbed.

I introduced into nitrous oxide through water, a healthy budding rose, thinking that its colors might be rendered brighter by the gas. I was disappointed, it very speedily faded and died; possibly injured by the solution of nitrous oxide in water.

Of two rows of peas just appearing above ground; I watered one with solution of nitrous oxide in water, and the other with common water daily, for a fortnight. At the end of this time, I could perceive no difference in their growth, and afterwards they continued to grow equally fast.

I introduced through water into six phials, one of which contained hydrogene, one oxygene, one common air, one hydrocarbonate, one carbonic acid, and one nitrous oxide, six similar plants of mint, their roots being in contact with water and their leaves exposed to light.

The plant in carbonic acid began to fade in less than two days, and in four was dead. That in hydrogene died in less than five days; that in nitrous oxide did not fade much for the first two days, but on the third, drooped very much, and was dead at the same time as that in hydrogene. The plant in oxygene for the first four days, looked flourishing and was certainly of a finer green than before, gradually however, its leaves became spotted with black and dropped off one by one, till at the end of ten days they had all disappeared. At this time the plant in common air looked sickly and yellow, whilst that in hydrocarbonate was greener and more flourishing than ever.

I have detailed these experiments not on account of any important conclusions that may be drawn from them; but with a view of inducing others to repeat them, and to examine the changes effected in the gases. If it should be found by future experiments, that hydrocarbonate generally increased vegetation, it would throw some light upon the use of manures, containing putrefying animal and vegetable substances, from which this gas is perpetually evolved.

The chemistry of vegetation though immediately connected with agriculture, the art on which we depend for subsistence, has been but little investigated. The discoveries of Priestley and Ingenhousz, seem to prove that it is within the reach of our instruments of experiment.

No. II.

APPROXIMATIONS TO THE _Composition and Weight of the aëriform_

_COMBINATIONS of NITROGENE_

At temperature 55°, and atmospheric pressure 30.

+------+-------+--------------+---+------+------+---------+---------+ | | |100 Cubic In. | |grains| |Nitrogene| Oxygene | | | +--------------+---+------+------+---------+---------+ |Nitro-| With | Nitrogene | | 30.04| | | | | gene | Oxy- | Oxygene | | 35.06| | | | | | gene +--------------+---+------+ 100 +---------+---------+ | | |Atmospher. air| w | 31.10|grains| 73.00 | 27.00 | | | |Nitrous oxide | e | 50.20| are | 63.30 | 36.70 | | | |Nitrous gas | i | 34.26|com- | 44.05 | 55.95 | | | |Nitric acid | g | 76.00| posed| 29.50 | 70.50 | | | | | h | | of +---------+---------+ | | | | | | |Nitrogene|Hydrogene| | +-------+--------------+---+------+ +---------+---------+ | | With | | | | | | | | | hydro-|Ammoniac | | 18.05| | 80.00 | 20.00 | | | gene | | | | | | | +------+-------+--------------+---+------+------+---------+---------+

No. III.

_Additional Observations._

_a._ In Res. 1st. Div. IV. Sect. III. in the analysis of nitrous gas by pyrophorus, as no absorption took place when the residual nitrogene was exposed to water, I inferred that if any carbonic acid was formed it was in quantity so minute, as to be unworthy of notice. A few days ago, I compleatly decomposed a quantity of nitrous gas by pyrophorus, when the residual nitrogene was exposed to solution of strontian, the fluid became slightly clouded; but no perceptible absorption took place.

_b._ If there was the least probability in any of Dr. Girtanner’s speculations on the composition of Azote,[235] the experiments on the exhausted capacity[236] of the lungs in Res. III. might be supposed inconclusive. But there appears to be no more reason for supposing that hydrogene is converted into nitrogene by respiration, than for supposing that it is converted into water, carbonic acid or oxygene; for all these products are evolved when that gas is respired. From the comparison of Exp. 1 with Exp. 3, Res. iii. Div. ii. Sec. 4, it is almost demonstrated that no ascertainable change is effected in hydrogene by respiration. The experiment of the accurate Scheele in which hydrogene after being respired thirty times in a bladder wholly lost its inflammability, may be easily accounted for from its mixture with the residual gases of the lungs.

[235] Annales de Chimie, 100; and Mr. Tilloch’s Phil. Magazine. 24.

[236] I regret much that I could not procure Dr. Menzies’s observations on Respiration, while I was making the experiments on the capacity of the lungs: they would probably have saved me some labor.

About a fortnight ago, I respired, after forced voluntary exhaustion of my lungs, my nose being accurately closed, three quarts of hydrogene in a silk bag, at four intervals, for near five minutes. After this it was highly inflammable, and burnt with a greenish white flame in contact with the atmosphere; but was not so explosive as before.[237]

[237] If loosely combined carbon exists in venous blood, hydrogene may probably dissolve a portion of it when respired and become slightly carbonated. At least there is as much probability in the supposition that carbon in loose affinity may combine with hydrogene at 98° as that it may combine with oxygene.

_c._ From what we have lately heard of the curious experiments of Mr. Volta and Mr. Carlisle, it is very probable that the conversion of nitrous gas into nitrous oxide when exposed to wetted zinc, copper and tin, in contact with mercury, as described in Res. I. Div. V. may in some measure depend on the action of the galvanic fluid. Whilst I was engaged in the experiments on this conversion, Dr. Beddoes[238] mentioned to me some curious facts noticed by Humboldt and Ritter, relating to the oxydation of metals by the decomposition of water, which induced me to examine the phænomena with more attention than I should have otherwise done.—I recollect observing that some of the wetted zinc filings in nitrous gas on the side of the jar not in contact with the surface of mercury, were very slowly oxydated. Whilst on the surface of the mercury where small globules of that substance were mingled with the filings of zinc, the decomposition went on much more rapidly; possibly through the medium of the moisture, a series of galvanic circles were formed.

[238] Dr. BEDDOES has since favoured me with the following account of these facts.

“Mr. Humboldt (ueber die gereizte Faser I. 473, 1797) quotes part of a letter from Dr. Ash, in which it is said that _if two finely polished plates of homogeneous zinc be moistened and laid together, little effect follows—but if zinc and silver be tried in the same way, the whole surface of the silver will be covered with oxydated zinc. Lead and quicksilver act as powerfully on each other, and so do iron and copper._—Mr. Humboldt (p. 474) says that, in repeating this experiment, he saw air-bubbles ascend, which he supposes to have been hydrogene gas from the decomposition of water—When he placed zinc simply on moist glass, the same phænomena took place, but more slowly and later. The quantity of oxyd of zinc upon the glass alone was in 20 hours to that on the silver as one to three.

In a very ingenious but obscurely written tract by Mr. Ritter, entitled, _Evidence that the galvanic action exists in organic nature_, _8vo. Jena, 1800_—The author observes, that the care of Dr. Ash and Mr. Humboldt that the metals should touch each other in as many points as possible was superfluous, even if we could grant that two metallic plates might be made by polishing, to touch in a number of points. To shew that it was sufficient if by touching in one point only they should form a compleat galvanic circle, he dropped a single drop of distilled water upon the bust of a large silver coin. A piece of pure zinc was placed with its one end on the edge of the coin, while the other was supported by a bit of glass. The drop of water was neither in contact with the glass nor with the point at which the metals touched. The materials were left in this situation for four hours at the temperature of 68°. On taking them apart, the water had become quite milky and had half disappeared; and Mr. Ritter actually separated a quantity of white oxide that had been produced in the experiment.

The pieces of metal were cleaned and laid together in the same manner, only that now a piece of paper was put between the metals at their former point of contact. In four hours first, and afterwards in ten, a faint ring of oxide only had been produced of which the quantity could not be estimated, nor could it be separated. In this case, the zinc had scarce lost any thing of its splendour; in the former it had been corroded. In many repetitions of the experiment, he found that far more oxide was formed when the metals touched, than when they were separated to the slightest distance by an insolating body, even air.

On exposing these apparatuses with somewhat more water to a considerable heat for four minutes, the water in the interrupted circle continued quite clear, while that in the other had become milk-white.

The same phænomena were presented by other pairs of metals in a degree proportional to their galvanic activity; viz. by zinc and molybdæna, zinc and bismuth, zinc and copper, as also with tin and silver, tin and molybdæna, and lead and silver. The experiment with tin was particularly decisive, for when in contact with no other metal it was scarcely at all oxydated by water, though oxydation took place when tin was brought into contact with silver, and both were connected at the other end by a drop of water—What therefore took place in Dr. Ash’s experiment, arose from an aggregation of galvanic circles of different forms.

By the foregoing experiments, concludes Mr. Ritter, which though capable of the most various modifications, uniformly coincide in their main result, it is abundantly proved that _galvanic circles can be formed of merely inorganic bodies, by whose completion there is produced an action which ceases when the circle is opened_. The manner in which this has been shewn, proves also that _this action can effectuate sensible modifications in organic bodies_; and the process by which these modifications have been effected, made it evident that they _were not consequences of a momentary action of the circle, but of an action that is kept up while the circle remains entire_; for the process which brought this action under the cognizance of the senses went on, while the circle was unbroken, and its figure not brought back to that of a line.

It is scarce necessary to observe that the experiments here quoted, are far from being the only ones on which the above conclusions rest.”

_T. B._

_d._ In Res. II. Div. I. it is stated, that nitrous oxide during its solution by common water, expels about ¹/₁₆ of atmospheric air the volume of the water being unity.

From the delicate experiments of Dr. Pearson, on the passage of the electric spark through water, it appears however probable, that much more than ¹/₁₆ of atmospheric air is sometimes held in solution by that fluid,[239] possibly the whole of the air is not expelled by nitrous oxide, owing to some unknown law of saturation by which an equilibrium of affinity is produced, forming a triple compound.

[239] Possibly a ratio exists between the solubility of gases in water, and the solubility of water in gases. It is probable from Mr. Wm. Henry’s curious experiments on the muriatic acid, that the absolute quantity of water in _many_ gases, may be ascertained by means of its decomposition by the electric spark.

No. IV.

DESCRIPTION OF A MERCURIAL AIRHOLDER.

Suggested by an inspection of Mr. WATT’S Machine for containing Factitious Airs.

_By WILLIAM CLAYFIELD_.