From the facts detailed in the preceding pages, it appears that
the immediate effects of nitrous oxide upon the living system, are
analogous to those of diffusible stimuli. Both increase the force of
circulation, produce pleasurable feeling, alter the condition of the
organs of sensation, and in their most extensive action destroy life.
In the mode of operation of nitrous oxide and diffusible stimuli,
considerable differences however, exist.
Diffusible stimuli act immediately on the muscular and nervous fibre.
Nitrous oxide operates upon them only by producing peculiar changes in
the composition of the blood.
Diffusible stimuli affect that part of the system most powerfully to
which they are applied, and act on the whole only by means of its
sympathy with that part. Nitrous oxide in combination with the blood,
is universal in its application and action.
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.