As soon as I had discovered that nitrous oxide was respirable, and
possessed of extraordinary powers of action on living beings, I was
anxious to be acquainted with the changes effected in it by the venous
blood. To investigate these changes, appeared at first a simple
problem; I soon however found that it involved much preliminary
knowledge of the chemical properties and affinities of nitrous oxide.
After I had ascertained by experiments detailed in the preceding
Researches, the composition of this gas its combinations, and the
physical changes effected by it in living beings, I began my enquiry
relating to the mode of its operation.
Finding that the residual gas of nitrous oxide after it had been
breathed for some time in silk bags, was chiefly nitrogene, I at first
conjectured that nitrous oxide was decomposed in respiration in the
same manner as atmospheric air, and its oxygene only combined with the
venous blood; the following experiments soon however convinced me of my
error.
II. _Absorption of Nitrous Oxide by venous blood. Changes effected in
the blood by different Gases._
_a._ Though the laws of the coagulability of the blood are unknown,
yet we are certain that at the moment of coagulation, a perfectly new
arrangement of its principles takes place; consequently, their powers
of combination must be newly modified. The affinities of living blood
can only be ascertained during its circulation in the vessels of
animals. At the moment of effusion from those vessels, it begins to
pass through a series of changes, which first produce coagulation, and
finally its compleat decomposition.
Consequently, the action of fluid blood upon gates out of the vessels,
will be more analogous to that of circulating blood in proportion as it
is more speedily placed in contact with them.
_b._ To ascertain the changes effected in nitrous oxide by fluid venous
blood.
A jar, six inches long and half an inch wide, graduated to,05 cubic
inches, having a tight stopper adapted to it, was filled with
nitrogene, which is a gas incapable of combining with, and possessing
no power of a action upon venous blood. A large orifice was made in the
vein of a tolerably healthy man, and the stopper removed from the jar,
which was brought in contact with the arm so as to receive the blood,
and pressed close against the skin, in such a way as to leave an
orifice just sufficient for the escape of the nitrogene, as the blood
flowed in. When the jar was full, it was closed, and carried to the
pneumatic apparatus, the mercury of which had been previously a little
warmed. A small quantity of the blood was transferred into another
jar to make room for the gas. The remaining quantity equalled exactly
two cubic inches; to this was introduced as speedily as possible,
eleven measures equal to,55 cubic inches of nitrous oxide, which
left a residuum of ¹/₃₂ only, when absorbed by boiled water, and was
consequently, perfectly pure. On agitation, a rapid diminution of the
gas took place.
In the mass of blood which was opaque, but little change of color could
be perceived; but that portion of it diffused over the sides of the
jar, was evidently of a brighter purple than the venous blood.
It was agitated for two or three minutes, and then suffered to rest; in
eight minutes it had wholly coagulated; a small quantity of serum had
separated, and was diffused over the coagulum. This coagulum was dark;
but evidently of a more purple tinge than that of venous blood; no gas
had apparently been liberated during its formation.
The nitrous oxide remaining, was not quite equal to seven measures;
hence, at least four measures of it had been absorbed.
To ascertain the nature of the residuum, it was necessary to transfer
it into another vessel, but this I found very difficult to accomplish,
on account of the coagulated blood. By piercing through the coagulum
and removing part of it by means of curved iron forceps, I at last
contrived to introduce about 4½ measures of the gas into a small
cylinder, graduated to,25 cubic inches, in which it occupied of course,
nearly 9 measures; when a little solution of strontian was admitted to
these, it became very slightly clouded; but the absorption that took
place did not more than equal half its bulk. Consequently, the quantity
of carbonic acid evolved from the blood, or formed, must have been
extremely minute.
On the introduction of pure water, a rapid absorption of the gas took
place, and after agitation, not quite 3 measures remained. These did
not _perceptibly_ diminish with nitrous gas; their quantity was too
small to be examined by any other test; but there is reason to suppose
that they were chiefly composed of nitrogene.
From this experiment, it appeared that nitrous oxide is absorbed when
placed in contact with venous blood; at the same time, that a very
minute quantity of carbonic acid and probably nitrogene is produced.
_c._ In another similar experiment when nearly half a cubic inch of
nitrous oxide was absorbed by about a cubic inch and three quarters of
fluid blood, the residual gas did not equal more than ⅛, the quantity
absorbed being taken as unity. This fact induced me to suppose that
the absorption of nitrous oxide by venous blood, was owing to a simple
solution of the gas in that fluid, analogous to its solution in water
or alcohol.
To ascertain if nitrous oxide could be expelled from blood impregnated
with it, by heat; I introduced to 2 cubic inches of fluid blood taken
from the medial vein, about,6 cubic inches of nitrous oxide. After
agitation, in seven minutes nearly,4 were absorbed. In ten minutes,
after the blood had completely coagulated, the cylinder containing it,
was transferred in contact with mercury, into a vessel of solution of
salt in water; this solution was heated and made to boil. During its
ebullition, the whole of the blood became either white or pale brown,
and formed a solid coherent mass; whilst small globules of gas were
given out from it. In a few minutes, about,25 of gas had collected.
After the vessel had cooled, I attempted to transfer this gas into
a small graduated jar in the mercurial apparatus, but in vain; the
mass in the jar was so solid and tough, that I could not remove it.
By transferring it to the water apparatus, I succeeded in displacing
enough of the coagulum to suffer the water to come in contact with
the gas; an absorption of nearly half of it took place; hence, _I
conjecture_, that nitrous oxide had been given out by the impregnated
blood.
_d_. Some fresh dark coagulum of venous blood, was exposed to nitrous
oxide. A very slight alteration of color took place at the surface of
the blood, perceptible only in a strong light, and a minute quantity of
gas was absorbed. A taper burnt in the remaining gas as brilliantly as
before, hence, it had apparently suffered no alteration.
_e_. To compare the physical changes effected in the venous blood
by nitrous oxide, with those produced by other gases, I made the
following experiments.—I filled a large phial, containing near 14 cubic
inches, with blood from the vein of the arm of a man, and immediately
transferred it to the mercurial apparatus. Different portions of it
were thrown into small graduated cylinders, filled with the following
gases: nitrogene, nitrous gas, common air, oxygene, nitrous oxide,
carbonic acid, and hydrocarbonate.
The blood in each of them was successively agitated till it began
to coagulate; and making allowances for the different periods of
agitation, there was no marked difference in the times of coagulation.
The color of the coagulum in every part of the cylinder, containing
nitrogene, was the same very dark red. When it was agitated so as to
tinge the sides of the jar, it appeared exactly of the color of venous
blood received between two surfaces of glass; no perceptible absorption
of the gas had taken place.
The blood in nitrous gas was dark, and much more purple on the top than
that in nitrogene. When agitated so as to adhere to the jar as a thin
surface, this purple was evidently deep and bright. An absorption of
rather more than ⅛ of the volume of gas had taken place.
The blood in oxygene and atmospheric air, were of a much brighter
tinge than that in any of the other gases. On the top, the color was
vermilion, but no perceptible absorption had taken place.
The coagulum in nitrous oxide, when examined in the mass was dark,
and hardly distinguishable in its color from venous blood; but when
minutely noticed at the surface where it was covered with serum, and in
its diffusion over the sides of the jar, it appeared of a fine purple
red, a tinge brighter than the blood in nitrous gas. An absorption had
taken place in this cylinder, more considerable than in any of the
others.
In carbonic acid, the coagulum was of a brown red, much darker than the
venous blood, and a slight diminution of gas had taken place.
In the hydrocarbonate,[190] the blood was red, a shade darker than the
oxygenated blood, and a very slight diminution of the gas[191] was
perceptible.
[190] The hydrocarbonate employed, was procured from alcohol, by means
of sulphuric acid. This gas contains more carbon, than hydrocarbonate
from water and charcoal.
[191] The curious fact of the reddening of venous blood by
hydrocarbonate, was discovered by Dr. Beddoes.
_f._ To human blood that had been saturated with nitrous oxide whilst
warm and constantly agitated for four or five minutes, to prevent its
uniform coagulation, oxygene was introduced; the red purple on the
surface of it, immediately changed to vermilion; and on agitation,
this color was diffused through it. On comparing the tinge with that
of oxygenated blood, no perceptible difference could be observed.
No change of volume of the oxygene introduced, had taken place; and
consequently, no nitrous oxide had been evolved from the blood.
_g._ Blood, impregnated with nitrous gas, was exposed to oxygene; but
after agitation in it for many minutes, no change of its dark purple
tinge could be observed, though a slight diminution of the oxygene
appeared to take place.
_h._ Blood that had been rendered vermilion in every part by long
agitation in atmospheric air, the coagulum of which was broken and
diffused with the coagulable lymph through the serum, was exposed to
nitrous oxide; for some minutes no perceptible change of color took
place; but by agitation for two or three hours, it evidently affirmed a
purple tinge, whilst a a slight absorption of gas took place. It never
however, became nearly so dark as venous blood that had been exposed to
nitrous oxide.
_i._ Blood, oxygenated in the same manner as in the last experiment,
the coagulum of which had been broken, was exposed to nitrous gas. The
surface of it immediately became purple, and by agitation for a few
minutes, this color was diffused through it. A slight diminution of the
gas was observed. On comparing the tinge with that of venous blood that
had been previously exposed to nitrous gas, there was no perceptible
difference.
_k._ Blood exposed to oxygenated muriatic acid is wholly altered in its
constitution and physical properties, as has been often noticed; the
coagulum becomes black in some parts, and brown and white in others.
Venous blood, after agitation in hydrogene or nitrogene, oxygenates
when exposed to the atmosphere in the same manner as simple venous
blood. I had the curiosity to try whether venous blood exposed to
hydrogene, would retain its power of being oxygenated longer than
blood saturated with nitrous oxide: for this purpose some similar black
coagulum was agitated for some time in two phials, one filled with
hydrogene, the other with nitrous oxide. They were then suffered to
rest for three days at a temperature from about 56° to 63°. After being
opened, no offensive smell was perceived in either of them, the blood
in hydrogene was rather darker than at the time of their exposure,
whilst that in nitrous oxide was of a brighter purple. On being
agitated for some time in the atmosphere, the blood in nitrous oxide
became red, but not of so bright a tinge as oxygenated venous blood.
The color of the blood in hydrogene did not at all alter.
_l._ To ascertain whether impregnation with nitrous oxide accelerated
or retarded the putrefaction of the blood; I exposed venous blood in
four phials, the first filled with hydrocarbonate, the second with
hydrogene; the third with atmospheric air, and the fourth with nitrous
oxide. Examined after a fortnight, the blood in hydrogene and common
air were both black, and stunk very much; that in hydrocarbonate was
red, and perfectly sweet; that in nitrous oxide appeared purple and had
no disagreeable smell.
In a second experiment, when blood was exposed for three weeks to
hydrocarbonate and nitrous oxide, that in nitrous oxide was darker than
before and stunk a little; that in hydrocarbonate was still perfectly
sweet. The power of hydrocarbonate to prevent the putrefaction of
animal matters, was long ago noticed by Mr. Watt.
_m._ Having accidentally cut one of my fingers so as to lay bare a
little muscular fibre, I introduced it whilst bleeding into a bottle of
nitrous oxide; the blood that trickled from the wound evidently became
much more purple; but the pain was neither alleviated or increased.
When however, the finger was taken out of the nitrous oxide and exposed
to the atmosphere, the wound smarted more than it had done before.
After it had ceased to bleed, I inserted it through water into a vessel
of nitrous gas; but it did not become more painful than before.
From all these observations, we may conclude,
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 from _d._ In the fluid blood, as we shall see
hereafter, nitrous oxide is absorbed by the attractions of the whole
compound.