The nitrous oxide employed in the following experiments, was procured
from nitrate of ammoniac, and received in large jars, filled with water
previously saturated with the gas. The animal was introduced into the
jar, by being carried under the water; after its introduction, the jar
was made to rest on a shelf, about half an inch below the surface of
the water; and the animal carefully supported, so as to prevent his
mouth from resting in the water.
This mode of experimenting, either under water or mercury, is
absolutely necessary, to ascertain with accuracy the effects of
pure gases on living beings. In some experiments that I made on the
respiration of nitrous oxide, by animals that were plunged into jars
of it opened in the atmosphere, and immediately closed after their
introduction, the unknown quantities of common air carried in, were
always sufficient to render the results perfectly inaccurate.
Animals suffer little or nothing by being passed through water.
That the phænomena in these experiments might be more accurately
observed, two or three persons were always present at the time of their
execution, and an account of them was noted down immediately after.
_a._ A stout and healthy young cat, of four or five months old, was
introduced into a large jar of nitrous oxide. For ten or twelve moments
he remained perfectly quiet, and then began to make violent motions,
throwing himself round the jar in every direction. In two minutes
he appeared quite exhausted, and sunk quietly to the bottom of the
jar. On applying my hand to the thorax, I found that the heart beat
with extreme violence; on feeling about the neck, I could distinctly
perceive a strong and quick pulsation of the carotids. In about three
minutes the animal revived, and panted very much; but still continued
to lie on his side. His inspirations then became longer and deeper, and
he sometimes uttered very feeble cries. In four minutes the pulsations
of the heart appeared quicker and feebler. His inspirations were at
long intervals, and very irregular; in five minutes the pulse was
hardly perceptible; he made no motions, and appeared wholly senseless.
After five minutes and quarter he was taken out, and exposed to the
atmosphere before a warm fire. In a few seconds he began to move, and
to take deep inspirations. In five minutes he attempted to rise on his
legs; but soon fell again, the extremities being slightly convulsed.
In eight or nine minutes he was able to walk, but his motions were
staggering and unequal, the right leg being convulsed, whilst the
other was apparently stiff and immoveable; in about half an hour he
was almost completely recovered.
_b._ A healthy kitten, of about six weeks old, was introduced into
nitrous oxide. She very soon began to make violent exertions, and
in less than a minute fell to the bottom of the receiver, as if
apoplectic. At this moment, applying my hand to her side, I felt the
heart beating with great violence. She continued gasping, with long
inspirations, for three minutes and half; at the end of five minutes
and half she was taken out completely dead.
_c._ Another kitten of the same breed was introduced into nitrous
oxide, the day after. She exhibited the same phænomena, and died in it
in about five minutes and half.
_d._ A small dog that had accidentally met with a dislocation of the
vertebræ of the loins, and was in great pain, as manifested by his
moaning and whining, was introduced into a large jar of nitrous oxide.
He immediately became quiet, and lay on his side in the jar, breathing
very deeply. In four minutes his respiration became noisy, and his
eyes sparkled very much. I was not able to apply my hand to the
thorax. In five minutes he appeared senseless, and in seven minutes was
perfectly dead.
_e._ A strong rabbit, of ten or twelve months old, was introduced into
nitrous oxide. He immediately began to struggle very much, and in a
minute fell down senseless: in two minutes the legs became convulsed,
and his inspirations were deep and noisy: in less than five minutes he
appeared perfectly dead.
_f._ A rabbit of a month old introduced into nitrous oxide, became
senseless in less than a minute; the pulsations of the heart were very
strong at this moment: they gradually became weaker, and in three
minutes and half the animal was dead.
_g._ Another rabbit of the same breed, after being rendered senseless
in nitrous oxide in a minute and half, was taken out. He soon became
convulsed; in a minute began to breathe quickly; in two minutes
attempted to rise, but staggered, and fell again on his side. His
hinder legs were paralytic for near five minutes. In twenty he had
almost recovered.
_h._ A middle sized guinea-pig was much convulsed, after being in
nitrous oxide for a minute. In two minutes and half he was senseless.
Taken out at this period, he remained for some minutes by the side of
a warm fire, without moving; his fore legs then became convulsed; his
hind legs were perfectly paralytic. In this state he continued, without
attempting to rise or move, for near an hour, when he died.
_i._ A large and old guinea-pig died in nitrous oxide, exhibiting the
same phænomena as the other animals, in about five minutes and quarter.
A young one was killed in three minutes and half.
_j._ A small guinea-pig, after breathing nitrous oxide for a minute and
half, was taken out, and placed before a warm fire. He was for a few
minutes a little convulsed; but in a quarter of an hour got quite well,
and did not relapse.
_k._ A large mouse introduced into nitrous oxide, was for a few
seconds very active. In half a minute he fell down senseless; in a
minute and quarter he appeared perfectly dead.
_l._ A mouse taken out of nitrous oxide, after being in it for half a
minute, continued convulsed for some minutes, but finally recovered.
_m._ A young hen was introduced into a vessel filled with nitrous
oxide. She immediately began to struggle very much; fell on her breast
in less than half a minute, and in two minutes was quite dead.
_n._ A goldfinch died in nitrous oxide in less than a minute.
In each of these experiments a certain absorption of the gas was always
perceived, the water rising in the jar during the respiration of the
animal. From them we learn
1st. That nitrous oxide is destructive when respired for a certain time
to the warm-blooded animals, apparently previously exciting them to a
great extent.
2dly. That when its operation is stopped before compleat exhaustion is
brought on, the healthy living action is capable of being gradually
reproduced, by enabling the animal to respire atmospheric air.
3dly. That exhaustion and death is produced in the small animals by
nitrous oxide sooner than in the larger ones, and in young animals of
the same species, in a shorter time than in old ones, as indeed Dr.
Beddoes had conjectured a priori would be the case.
Most of the animals destroyed in these experiments were examined after
death; the appearances in their organs were peculiar. To prevent
unnecessary repetitions, an account of them will be given in the fourth
section.
III. _Effects of the respiration of Nitrous Oxide upon animals, as
compared with those produced by their immersion in Hydrogene and Water._
Before the following experiments were made, a number of circumstances
had convinced me that nitrous oxide acted on animals by producing some
positive change in their blood, connected with new living action of the
irritable and sensitive organs, and terminating in their death.
To ascertain however, the difference between the effects of this gas
and those of hydrogene and non-respirable gases, I proceeded in the
following way.
_a._ Of two healthy rabbits of about two months old, of the same breed,
and nearly of the same size.
One was introduced into nitrous oxide. In a half a minute, it had
fallen down apparently senseless. On applying my hand to the thorax,
the action of the heart appeared at first, very quick and strong, it
gradually became weaker, and in two minutes and half, the animal was
taken out quite dead.
The other was introduced into a jar of pure hydrogene through water.
He immediately began to struggle very much, and in a quarter of a
minute fell on his side. On feeling the thorax, the pulsations of the
heart appeared very quick and feeble, they gradually diminished; his
breathing became momentarily shorter, and in rather more than three
quarters of a minute, he was taken out dead. Dr. Kinglake was present
at this experiment, and afterwards dissected both of the animals.
_b._ Of two similar rabbits of the same breed, nearly three months
old. One was introduced into nitrous oxide, and after being rendered
senseless by the respiration of it for nearly a minute and half, was
exposed to the atmosphere, before a warm fire. He recovered gradually,
but was occasionally convulsed, and had a paralysis of one of his
hinder legs for some minutes: in an hour he was able to walk. The
other, after being immerged in hydrogene for near half a minute, was
restored to the atmosphere apparently inanimate. In less than a minute
he began to breathe, and to utter a feeble noise; in two minutes
was able to walk, and in less than three minutes appeared perfectly
recovered.
_c._ A kitten of about two months old, was introduced into a jar of
nitrous oxide, at the same time that another of the same breed was
plunged under a jar of water. They both struggled very much. The
animal in the nitrous oxide fell senseless before that under water had
ceased to struggle, and to throw out air from its lungs. In two minutes
and three quarters, the animal under water was quite dead: it was taken
out and exposed to heat and air, but did not shew the slightest signs
of life. At the end of three minutes and half, the animal in nitrous
oxide began to gasp, breathing very slowly; at four minutes and three
quarters it was yet alive; at the end of five minutes and quarter it
appeared perfectly dead. It was taken out, and did not recover.
From these experiments it was evident, that animals lived at least
twice as long in nitrous oxide as in hydrogene or water. Consequently
from this circumstance alone, there was every reason to suppose that
their death in nitrous oxide could not depend on the simple privation
of atmospheric air; but that it was owing to some peculiar changes
effected in the blood by the gas.
IV. _Of the changes effected in the Organisation of warm-blooded
Animals, by the respiration of Nitrous Oxide._
The external appearance of animals that have been destroyed in nitrous
oxide, is very little different from that of those killed by privation
of atmospheric air. The fauces and tongue appear of a dark red, and the
eyes are dull, and a little protruded. Their internal organs, however,
exhibit a very peculiar change. The lungs are pale brown red, and
covered here and there with purple spots; the liver is of a very bright
red, and the muscular fibre in general dark. Both the auricles and
ventricles of the heart are filled with blood. The auricles contract
for minutes after the death of the animal. The blood in the left
ventricle, and the aorta, is of a tinge between purple and red, whilst
that in the right ventricle is of a dark color, rather more purple
than the venous blood. But these appearances, and their causes, will
be better understood after the following comparative observations are
read.
_a._ Of two similar rabbits, about eight months old, one A, was killed
by exposure for near six minutes to nitrous oxide, the other, B, was
destroyed by a blow on the head.
They were both opened as speedily as possible. The lungs of B were
pale, and uniform in their appearance; this organ in A was redder, and
every where marked with purple spots. The liver of A was of a dark and
bright red, that of B of a pale red brown. The diaphragm of B, when
cut, was strongly irritable; that of A rather darker, and scarce at all
contractile. All the cavities of the heart contracted for more than 50
minutes in B. The auricles contracted for near 25 minutes with force
and velocity in A: but the ventricles were almost inactive. The vena
cava, and the right auricle, in A, were filled with blood, apparently a
shade darker than in B. The blood in the left auricle, and the aorta,
appeared in A of a purple, a shade brighter than that of the venous
blood. In the left auricle of B it was red.
I opened the head of each, but not without injuring the brains, so
that I was unable to make any accurate comparison. The color of the
brain in A appeared rather darker than in B.
_b._ Two rabbits, C and D, were destroyed, C by immersion in nitrous
oxide, D in hydrogene: they were both dissected by Dr. Kinglake.
The blood in the pulmonary vein and the left auricle of C was of a
different tinge, from that in D more inclined to purple red. The
membrane of the lungs in C was covered with purple spots, that of D was
pale and uniform in its appearance. The brain in C was rather darker
than in D; but there was no perceptible effusion of blood into the
ventricles either in D or C. The liver in C was of a brighter red than
in health, that in D rather paler.
_c._ In the last experiment, the comparative irritability of the
ventricles and auricles of the heart and the muscular fibre in the two
animals, had not been examined. That these circumstances might be
noticed, two rabbits, E and F were killed; E under water in about a
minute, and F in nitrous oxide in three minutes. They were immediately
opened, and after a minute, the appearance of the heart, and organs of
respiration observed.
Both the right and left ventricles of the heart in F contracted but
very feebly; the auricles regularly and quickly contracted; the aorta
appeared perfectly full of blood. In E, a feeble contraction of the
left sinus venosus and auricle was observed; the left ventricle did not
contract: the right contracted, but more slowly than in F. In a few
minutes, the contractions of the ventricles in F had ceased, whilst
the auricles contracted as strongly and quickly as before. The blood
in the pulmonary veins of F was rather of a redder purple than in E;
the difference of the blood in the vena cava was hardly perceptible,
perhaps it was a little more purple in F. The membranous substance of
the lungs in F was spotted with purple as from extravasated blood,
whilst that in E was pale. The brain in F was darker than in E. On
opening the ventricles no extravasation of blood was perceptible. The
auricles of the heart in F contracted strongly for near twenty minutes,
and then gradually their motion became less frequent; in twenty-eight
minutes it had wholly ceased. The right auricle and ventricle in E,
occasionally contracted for half an hour. The livers of both animals
were similar when they were first opened, of a dark red; that of F
preserved its color for some time when exposed to the atmosphere;
whilst that of E almost immediately became paler under the same
circumstances.
The peristaltic motion continued for nearly an equal time in both
animals.
_d._ The sternum of a young rabbit was removed so that the heart and
lungs could be perceived, and he was introduced into a vessel filled
with nitrous oxide; the blood in the pulmonary veins gradually became
more purple, and the heart appeared to beat quicker than before, all
the muscles contracting with great force. After he had been in about
a minute, spots began to appear on the lungs, though the contractions
of the heart became quicker and weaker; in three minutes and half he
was quite dead; after death the ventricles contracted very feebly,
though the contractions of the auricles were as strong almost after the
end of five minutes as at first. This animal was passed through water
saturated with nitrous oxide; possibly this fluid had some effect on
his organs.
Besides these animals, many others, as guinea-pigs, mice and birds,
were dissected after being destroyed in nitrous oxide; in all of them
the same general appearance was observed. Their muscular fibre almost
always appeared less irritable than that of animals destroyed, by
organic læsion of part of the nervous system, in the atmosphere. The
ventricles of the heart in general, contracted feebly and for a very
short time; whilst the auricles continued to act for a great length of
time. The lungs were dark in their appearance, and always suffused here
and there with purple; the blood in the pulmonary veins when slightly
observed, appeared dark, like venous blood, but when minutely examined,
was evidently much more purple. The blood in the vena cava, was darker
than that in the pulmonary veins. The cerebrum was dark.
In a late experiment, I thought I perceived a slight extravasation of
blood in one of the ventricles of the brain in a rabbit destroyed in
nitrous oxide; but as this appearance had not occurred in the animals
I had examined before, or in those dissected by Dr. Kinglake, and Mr.
King, Surgeon, I am inclined to refer it to an accidental cause. At my
request, Mr. Smith, Surgeon, examined the brain of a young rabbit that
had been killed in his presence in nitrous oxide; he was of opinion
that no effusion of blood into the ventricles had taken place.
In comparing the external appearance of the crural nerves in two
rabbits that had been dissected by Dr. Kinglake, having been destroyed
one in hydrogene, the other in nitrous oxide, we could perceive no
perceptible difference.
It deserves to be noticed, that whenever the gall bladder and the
urinary bladder have been examined in animals destroyed in nitrous
oxide, they have been always distended with fluid; which is hardly ever
the case in animals killed by privation of atmospheric air.
In the infancy of my experiments on the action of nitrous oxide upon
animals, I thought that it rendered the venous blood less coagulable;
but this I now find to be a mistake. The blood from the pulmonary
veins of animals killed in nitrous oxide, does not sensibly differ in
this respect from the arterial blood of those destroyed in hydrogene,
and both become vermilion nearly in the same time when exposed to the
atmosphere.
In describing the various shades of color of the blood in the preceding
observations on the different dissected animals, the poverty of
the language of color, has obliged me to adopt terms, which I fear
will hardly convey to the mind of the reader, distinct notions of
the differences observable by minute examination in the venous and
arterial blood of animals that die of privation of atmospheric air,
and of those destroyed by the action of nitrous oxide. This difference
can only be observed in the vessels by means of a strong light; it
may however be easily noticed in the fluid blood by the introduction
of it from the arteries or veins at the moment of their incision,
between two polished surfaces of white glass,[186] so closely adapted
to each other, as to prevent the blood from coming in contact with the
atmosphere.
[186] The colour of common venous blood, examined in this way,
resembles that of the paint called by colour-men red ochre; that of
blood saturated with nitrous oxide, approaches to the tinge of lake.
Having four or five times had an opportunity of bleeding people in
the arm for trifling complaints, I have always received the blood in
phials, filled with various gases, in a mode to be described hereafter.
Venous blood agitated in nitrous oxide, compared with similar blood
in common air, hydrogene, and nitrogene, was always darker and more
purple than the first, and much brighter and more florid than the
two last, which were not different in their color from venous blood,
received between two surfaces of glass. It will be seen hereafter, that
the coagulum of venous blood is rendered more purple when exposed to
nitrous oxide, whilst the gas is absorbed; likewise that blood altered
by nitrous oxide, is capable of being again rendered vermilion, by
exposure to the air.
The appearances noticed in the above mentioned experiments, in the
lungs of animals destroyed in nitrous oxide, are similar to those
observed by Dr. Beddoes, in animals that had been made to breathe
oxygene for a great length of time.
There were many reasons for supposing that the large purple spots
in the lungs of animals destroyed in nitrous oxide, were owing to
extravasation of venous blood from the capillary vessels; their coats
being broken by the highly increased arterial action. To ascertain
whether these phænomena existed at a period of the action of nitrous
oxide, when the animal was recoverable by exposure to the atmosphere.
I introduced a rabbit of six months old, into a vessel of nitrous
oxide, and after a minute, when it had fallen down apparently
apoplectic, plunged him wholly under water; he immediately began to
struggle, and what surprised me very much, died in less than a minute
after submersion. On opening the thorax, the blood in the pulmonary
veins was nearly of the color of that in animals that have been simply
drowned. The lungs were here and there, marked with a few points;
but there were no large purple spots, as in animals that have been
wholly destroyed in nitrous oxide: the right side of the heart only
contracted. In this experiment, the excitement from the action of the
gas was probably carried to such an extent, as to produce indirect
debility. There are reasons for supposing, that animals after having
been excited to but a small extent by the respiration of nitrous oxide,
will live under water for a greater length of time, than animals
previously made to breathe common air.
V. _Of the respiration of mixtures of Nitrous Oxide, and other gases,
by warm-blooded Animals._
_a._ A rabbit of near two months old, was introduced into a mixture of
equal parts hydrogene and nitrous oxide through water. He immediately
began to struggle; in a minute fell on his side; in three minutes
gasped, and made long inspirations; and in four minutes and half, was
dead. On dissection, he exhibited the same appearances as animals
destroyed in nitrous oxide.
_b._ A large and strong mouse was introduced into a mixture of three
parts hydrogene to one part nitrous oxide. He immediately began to
struggle very much, in half a minute, became convulsed, and in about a
minute, was quite dead.
_c._ Into a mixture of one oxygene, and three nitrous oxide, a small
guinea-pig was introduced. He immediately began to struggle, and in two
minutes reposed on his side, breathing very deeply. He made afterwards
no violent muscular motion; but lived quietly for near fourteen
minutes: at the end of which time, his legs were much convulsed. He was
taken out, and recovered.
_d._ A mouse lived apparently without suffering, for near ten minutes,
in a mixture of 1 atmospheric air, and 3 nitrous oxide, at the end of
eleven minutes he began to struggle, and in thirteen minutes became
much convulsed.
_e._ A cat of three months old, lived for seventeen minutes, in a
very large quantity of a mixture of 1 atmospheric air, and 12 nitrous
oxide. On her first introduction she was very much agitated and
convulsed, in a minute and half she fell down as if apoplectic, and
continued breathing very deeply during the remainder of the time,
sometimes uttering very feeble cries. When taken out, she appeared
almost inanimate, but on being laid before the fire, gradually began to
breathe and move; being for some time, like most of the animals that
have recovered after breathing nitrous oxide, convulsed on one side,
and paralytic the other.
_f._ A goldfinch lived for near five minutes in a mixture of equal
parts nitrous oxide and oxygene, without apparently suffering. Taken
out, he appeared faint and languid, but finally recovered.[187]
[187] Small birds suffer much from cold when introduced into gases
through water. In this experiment, the goldfinch was immediately
inserted into a large mouthed phial, filled with the gases, and opened
in the atmosphere.
VI. _Recapitulation of facts relating to the respiration of Nitrous
Oxide, by warm-blooded Animals._
1. Warm-blooded animals die in nitrous oxide infinitely sooner than in
common air or oxygene; but not nearly in so short a time as in gases
incapable of effecting positive changes in the venous blood, or in
non-respirable gases.
2. The larger animals live longer in nitrous oxide than the smaller
ones, and young animals die in it sooner than old ones of the same
species.
3. When animals, after breathing nitrous oxide, are removed from it
before compleat exhaustion has taken place, they are capable of being
restored to health under the action of atmospheric air.
4. Peculiar changes are effected in the organs of animals by the
respiration of nitrous oxide. In animals destroyed by it, the arterial
blood is purple red, the lungs are covered with purple spots, both the
hollow and compact muscles are _apparently_ very inirritable, and the
brain is dark colored.
5. Animals are destroyed by the respiration of mixtures of nitrous
oxide and hydrogene nearly in the same time as by pure nitrous oxide;
they are capable of living for a great length of time in nitrous oxide
mingled with very minute quantities of oxygene or common air.
These facts will be reasoned upon in the next division.