animal in a glass jar, so large that it formed a capacious apartment for
it, and held much more air than it could require in the course of the
experiment. The jar was covered with a closely fitting lid, and a
carefully weighed portion of chloroform was allowed to diffuse itself
through the air of the jar. The experiments were continued till the
chloroform produced no further effect. I shall pass over a number of
tentative experiments, and adduce only a few of those which were made
after I had ascertained the quantities requisite to produce the desired
effect. The results obtained in these experiments were entirely due to
the degree of dilution of the vapour; for the quantity of chloroform
employed was, in every instance, more than would have killed the animal
in a much shorter time than the experiment lasted, if it had been
conducted in a smaller jar. It is assumed that the proportions of vapour
and air remain unaltered during the experiment; for the quantity
absorbed must be limited to what the animal can breathe in the time,
which is so small a part of the whole that it may be disregarded.
_Experiment 1._ A guineapig and a white mouse were placed in a jar
holding 3,000 cubic inches, and fifteen grains of chloroform were
introduced by a tube in the lid of the jar, which was closed immediately
by a screw. The chloroform fell on some blotting paper suspended in the
jar, and in a minute or two was converted into vapour and diffused
through the air in the jar. The animals were allowed to remain half an
hour, and were unaffected by the chloroform, except that they appeared
to be a little less brisk than usual, during the first two or three
minutes after their removal.
_Experiment 2._ A guineapig was placed in the same jar, and twenty-two
and a half grains of chloroform were introduced in the same manner as
before, being three-quarters of a grain to each hundred cubic inches of
air. In two or three minutes the chloroform was converted into vapour
and diffused through the air in the jar. Six minutes afterwards the
guineapig began to stagger, and soon afterwards was unable to keep on
its legs. It was kept for half an hour in the jar, but did not become
further affected. It was occasionally quiet, but always tried to walk
when disturbed by moving the jar. When taken out, it flinched on being
pricked, and it tried to walk, although unable to support itself on its
legs. It recovered from the effects of the chloroform in three or four
minutes.
_Experiment 3._ Another guineapig was placed in the same jar, and thirty
grains of chloroform were introduced. In three or four minutes the
chloroform had evaporated and diffused itself through the air in the
jar. In two minutes afterwards the guineapig lay down, but stirred when
the jar was moved. It was allowed to remain in the jar for half an hour,
being asleep except when disturbed. When taken out it awoke and
endeavoured to walk, but was unable to support itself at first. It
flinched on being pricked. Recovered in three or four minutes.
_Experiment 4._ A cat was placed in the same jar, and the same quantity
of chloroform was introduced. In three minutes it had evaporated, and,
when ten minutes had elapsed, the cat began to stagger. Soon afterwards
it was unable to support itself on its legs; and, when a quarter of an
hour had elapsed, it seemed asleep, but raised its head when the jar was
inclined. It remained apparently sleeping till the end of an hour, when
it was taken out. It was unable to stand, but was sensible to the
slightest pinch. It recovered gradually in the course of twenty minutes.
_Experiment 5._ Sixteen grains of chloroform were put into a jar holding
1,600 cubic inches, being one grain to each 100 cubic inches of air, as
in the two last experiments. When it was converted into vapour, a white
mouse was introduced, by moving the lid a little to one side for a
moment. After running about for a minute and a half, it began to stagger
and to lose power, but it continued to run with little intermission till
three minutes had expired. After this it lay still, except when the jar
was inclined, when it always endeavoured to maintain its balance and to
walk. It also moved its limbs now and then, when not disturbed. It was
removed at the end of ten minutes, when it tried to walk, but was
unable. It did not flinch when its tail was pinched, but flinched, half
a minute after its removal, on one of its toes being pinched. It
recovered in two or three minutes.
_Experiment 6._ A guineapig was placed in the jar holding 3,000 cubic
inches, and 37·5 grains of chloroform were introduced in the same manner
as in the former experiments, being a grain and a quarter to each 100
cubic inches of air. The chloroform took three or four minutes to
evaporate and diffuse itself in the jar; and by the end of this time the
guineapig, which had been excited and running about, began to stagger,
and in two minutes longer it was unable to walk, but endeavoured to keep
its balance when the jar was inclined. At the end of a quarter of an
hour it was lying still, but moved its limbs when it was rolled over by
inclining the jar; but it made no voluntary effort. It was taken out
when thirty-three minutes had elapsed. It moved its limbs as it was
removed, though apparently not in a voluntary manner. Its limbs were not
relaxed. It was quite insensible to pricking. It recovered in about ten
minutes. The temperature in the axilla before it was put into the jar
was 100° Fah., and immediately after its removal 96°.
_Experiment 7._ A guineapig was placed in the same jar, and forty-five
grains of chloroform were introduced, being a grain and a half to each
100 cubic inches of air. In four minutes after the chloroform had
evaporated, the guineapig was unable to walk. In half a minute more it
seemed asleep, but there was a tremulous motion of the hind legs, which
continued till ten minutes had elapsed. Afterwards it lay still, but
winked now and then spontaneously. When rolled over by moving the jar,
it made no voluntary effort. It was taken out twenty minutes after the
chloroform had evaporated. It winked spontaneously, and also when the
eyes were touched. It did not flinch when the ear was pricked, but
flinched when the paw was pricked. The temperature in the axilla before
the experiment was 100°, and immediately afterwards it was 96°. The
guineapig recovered from the effects of the chloroform in ten minutes.
_Experiment 8._ A guineapig was put into the same jar, and 52·5 grains
of chloroform were introduced, being a grain and three-quarters to each
100 cubic inches of air. The chloroform evaporated in the course of four
minutes, at the end of which time the guineapig was altered in its
manner, as if partially inebriated. In two minutes more it was becoming
drowsy. A little while afterwards it was lying down. Six minutes after
the evaporation of the chloroform was complete, the guineapig made no
effort when turned over by inclining the jar, but only moved its feet,
as it were automatically. At the end of nine minutes, it was lying
quietly and breathing naturally. When fifteen minutes had elapsed it was
in the same condition, and was removed from the jar. It cried and
flinched on the foot being pricked. The temperature in the axilla was
97°. In five minutes after its removal it was fast recovering, and in
ten minutes was quite recovered.
_Experiment 9._ A guineapig was placed in the jar used in the last three
experiments, and sixty grains of chloroform were introduced in the same
manner, being two grains to each 100 cubic inches of air. In four
minutes it was all converted into vapour, and the guineapig was
beginning to be affected by it. In two minutes more it was unable to
stand or walk. In five minutes from the time when the evaporation was
complete, the guineapig showed no sign of sensibility when turned over
by inclining the jar; the breathing was natural. At the end of ten
minutes it was lying still, breathing gently forty times in the minute.
At the end of fifteen minutes it was in the same condition. From
seventeen to twenty minutes, it stretched out one of its hind legs
several times, and was doing so when taken out, at the end of twenty
minutes. It showed no sign of sensibility when pricked. The temperature
in the axilla was 96°. It began to recover gradually in a minute or two,
and recovered completely in from ten to fifteen minutes.
_Experiment 10._ A cat was placed in the same jar, and the same quantity
of chloroform was introduced in the same manner. It became quite
insensible in a few minutes after the chloroform was introduced; and it
was allowed to remain for twenty-five minutes, when it was taken out. It
was perfectly insensible to pricking, and its muscles were quite
relaxed; it was breathing gently, and the pulsations of the heart were
between sixty and seventy in the minute. It was immediately made the
subject of another experiment of drowning whilst insensible, which need
not be related in this place.
_Experiment 11._ Four grains of chloroform were put into a glass jar
holding 200 cubic inches, and when it had evaporated and was diffused
through the air in the jar, a white mouse was introduced, by momentarily
removing the cover a little to one side. A minute after its introduction
the mouse was lying, but it moved its legs for a quarter of a minute
longer. When four minutes had elapsed, the breathing became slow, and it
was taken out. It was totally insensible for the first three minutes
after its removal, and recovered during the two following minutes.
_Experiment 12._ Thirty-two grains of chloroform were diffused through
the air of a jar holding 1,600 cubic inches, being two grains to each
100 cubic inches, as in the last three experiments. A white mouse was
introduced by moving the cover a little to one side for a moment. In one
minute it was insensible, and did not make any effort on being rolled
about by inclining the jar, but it moved its paws for half a minute
longer. It remained insensible, breathing 160 times in the minute, till
it was taken out at the end of five minutes. It was quite insensible to
pinching. It began to walk in a minute or two. Its temperature before
the experiment was 98°, and immediately afterwards was 92°. The
temperature of the room was 68°.
_Experiment 13._ A guineapig was put into a jar holding 3,000 cubic
inches, and 67·5 grains of chloroform were introduced on blotting paper
suspended within the jar, being 2¼ grains to each 100 cubic inches. In
four minutes, the chloroform had all evaporated, and the guineapig was
becoming affected. In two minutes more, it was quite insensible. Eight
minutes after the chloroform had evaporated, it was lying still,
breathing forty times in the minute. During the next three or four
minutes, it moved one or other of its legs occasionally. At the end of
seventeen minutes, it was lying still, and the breathing was twenty-six
in the minute. It was taken out at the end of twenty minutes quite
insensible; in three or four minutes it began to try to walk, and in ten
minutes, was quite recovered.
_Experiment 14._ Two white mice, one being full grown, and the other
about three-quarters grown, were placed in the jar holding 1,600 cubic
inches, and forty grains of chloroform were introduced on blotting
paper, being two grains and a half to each hundred cubic inches. In two
minutes, the chloroform had evaporated, and the mice were much excited.
In another minute, they were unsteady in walking; and in a minute more,
the old mouse was lying insensible, and breathing deeply and
laboriously. In four minutes more, _i. e._, six minutes after the
chloroform had evaporated, the young mouse was insensible also, but was
moving one of its hind legs. In other four minutes, the young mouse was
breathing by slow gasps, whilst the old one continued to breathe deeply
as before. Three minutes later, i. e., thirteen minutes after the
chloroform had evaporated, the old mouse had begun to gasp, and the
young one was gasping only at intervals. They were removed, and
recovered completely in ten minutes. The young one recovered most
quickly. Their temperature, on being removed, was about 90°.
_Experiment 15._ A cat was put into the jar holding 3,000 cubic inches,
and 82·5 grains of chloroform were introduced, being two grains and
three-quarters to each hundred cubic inches. In five minutes, it had
evaporated, and the cat began to stagger in its walk. In two minutes
more, it was unable to stand. Five minutes after the chloroform had
evaporated, the cat was breathing deeply, seventy-five times in the
minute. At eight minutes, it was breathing less deeply, one hundred and
seventeen times in the minute. Ten minutes after the chloroform had
evaporated, the cat was quite insensible, and breathing one hundred and
twenty-six times in the minute. It was now taken out. The temperature in
the axilla was 98°. In half an hour after its removal from the jar, it
had recovered its consciousness, but was still drowsy.
It was now put into the jar again, and the same quantity of chloroform
was introduced in the same manner as before. In five minutes, it had
evaporated, and the cat was again insensible. In other five minutes, it
was breathing rather deeply, forty-eight times in the minute. Twelve
minutes after the chloroform had evaporated, the cat was breathing in
the same manner, but sixty-eight times in the minute. The breathing
afterwards became shallow and feeble, and half an hour after the
chloroform had evaporated, it was eighty-eight in the minute. In five
minutes more, the breathing ceased. The cat was taken out of the jar,
and the stethoscope was applied to the chest. The heart could not be
heard to beat at first, but in a short time, the cat gave a gasp, and
the heart’s action returned, and the breathing became reestablished.
_Experiment 16._ Forty-eight grains of chloroform were put into a jar
holding 1,600 cubic inches, being three grains to each hundred cubic
inches, and when it was converted into vapour and diffused through the
air in the jar, a white mouse was introduced. It ran about for a minute
and a half, and then it was unable to move any longer. In nine minutes
and a half, the breathing was getting very slow, and the mouse was
immediately removed. Before it could be got out, it appeared to have
entirely ceased to breathe, but it immediately began to gasp at
intervals. In a minute, the breathing improved, and soon became natural.
Three minutes after its removal, the mouse began to walk in a ring, and
in seven minutes, it had quite recovered.
_Experiment 17._ A guineapig was placed in a jar holding 1,600 cubic
inches, and fifty-four grains of chloroform were introduced on blotting
paper, in the manner previously explained; being three grains and
three-eighths to each hundred cubic inches of air. In four minutes, the
chloroform had evaporated, and become diffused through the air in the
jar, and the guineapig was drowsy. In three minutes more, it was lying
apparently insensible, and breathing feebly, thirty times in the minute.
After this, it kicked occasionally for a few minutes. When six minutes
had elapsed from the time when the chloroform had evaporated, the
breathing was very feeble, and apparently performed only by the
diaphragm. From fifteen to eighteen minutes, I could hardly see whether
the animal was breathing or not, and it was taken out of the glass at
eighteen minutes, when the breathing appeared to have ceased. The
stethoscope was applied to the chest, and the sounds of the heart could
scarcely be heard at first, but the breathing returned in a few seconds,
and the action of the heart improved. The guineapig gradually recovered,
but it was not able to walk for twenty-five minutes.
_Experiment 18._ Sixty grains of chloroform were introduced into the jar
employed in the last experiment, being three grains and three-quarters
to each hundred cubic inches of air contained in the jar. When it had
evaporated, and was diffused through the air, a white mouse was
introduced, whilst the lid of the jar was moved a little to one side for
a moment. It ran about at first, but suddenly ceased to run, and became
insensible, at the end of three-quarters of a minute. It lay breathing
deeply and rapidly till two minutes had elapsed, when the respiration
became slow, and it ceased at two minutes and three-quarters after the
mouse was introduced. It was removed at this time, and it gasped a few
seconds afterwards; this gasp was soon followed by another; the gaspings
became more frequent, and in a short time, the natural breathing was
resumed. In five minutes, the mouse was able to walk.
The third, fourth, and fifth of the above experiments show that one
grain of chloroform to each hundred cubic inches of air suffices to
induce the second degree of narcotism, or that state in which
consciousness and voluntary motion are disturbed, but not entirely
abolished. Now one grain of chloroform produces 0·767 of a cubic inch of
vapour at 60°, when its specific gravity is 4·2; and, when the vapour is
inhaled, it expands somewhat, as it is warmed to the temperature of the
lungs; but it expands only to the same extent as the air with which it
is mixed, and therefore the proportions remain unaltered. But air, when
saturated with vapour of chloroform at 100°, contains 43·3 cubic inches
in 100; and
As 0·767 : 43·3 :: 0·0177 : 1.
So that if the point of complete saturation be considered as unity,
0·0177 or 1–56th, will express the degree of saturation of the air from
which the vapour is immediately absorbed into the blood; and,
consequently, also the degree of saturation of the blood itself.
I find that serum of blood at 100°, and at the ordinary pressure of the
atmosphere, will dissolve about its own volume of vapour of chloroform;
and since chloroform of specific gravity 1·483 is 288 times as heavy as
its own vapour, 0·0177 ÷ 288 gives 0·0000614, or one part in 16,285, as
the average proportion of chloroform by measure in the blood, in the
second degree of narcotism.
It is evident, from the experiments numbered 9 to 12 inclusive, that two
grains of chloroform to each hundred cubic inches of the inspired air
cause a state of very complete insensibility, corresponding with what I
have designated the fourth degree of narcotism; and by the method of
calculation employed above we get 0·0354, or 1–28th, as representing the
degree of saturation of the blood, and 0·0001228 the proportion by
measure in the blood.
In experiments 6, 7, and 8, in which quantities of chloroform were
employed intermediate between one and two grains to each hundred cubic
inches of air, a moderate amount of insensibility was induced,
corresponding very much with the state of patients during operations
under chloroform.
The experiments from 13 to 18 show that quantities of chloroform,
exceeding two grains to 100 cubic inches of air, have a tendency to
embarrass and arrest the function of respiration, if the inhalation is
continued. I have not yet been able to determine satisfactorily the
exact proportion of chloroform which requires to be absorbed to arrest
the respiration of animals of warm blood. I believe there is a definite
proportion which has this effect, but there are two reasons why it is
not so easy to ascertain it, as to ascertain the proportion which causes
the minor degrees of narcotism. In the first place, the breathing often
becomes very feeble before it ceases, so that the animal inhales and
absorbs but very little chloroform, and remains on the brink of dying
for some time. In the next place, the temperature of the body falls in a
deep state of narcotism, especially in small animals; and, as the
temperature falls, the amount of chloroform which the blood can dissolve
from any given mixture of air and vapour increases.
Judging from the experiments numbered 14 to 18, three grains of
chloroform to each hundred cubic inches of air must be very nearly the
quantity which has the power of arresting the breathing when the
temperature of the body is 100°; and as three grains of chloroform
produce 2·3 cubic inches of vapour, and air at 100° is capable of taking
up 43·3 per cent. of its volume, it follows that the blood must contain
between 1–18th and 1–19th as much chloroform as it is capable of
dissolving, at the time when the respiration is arrested. In the 14th
experiment, the breathing of the two mice was on the point of being
stopped by two and a half grains of chloroform in each hundred cubic
inches of air, but during the thirteen minutes which the mice breathed
the vapour, their temperature fell to about 90°. Air, when saturated
with the vapour of chloroform at this temperature, contains 35 per
cent., and two grains and a half of chloroform yield 1·917 cubic inches
of vapour; so by a calculation similar to that made at page 68, the mice
at the time when the breathing was about to cease must have absorbed
1–18th part as much chloroform as their circulating fluids were capable
of dissolving.
The reader will have observed that, in the experiments related above,
the mice became much more quickly affected than the guineapigs and cats.
The reason of this is their quicker respiration and circulation, and
much more diminutive size. Little birds, such as linnets and sparrows,
are also very quickly affected by chloroform. Frogs are more slowly
affected, owing to their languid respiration, unless the vapour to which
they are exposed is very strong.
They can, however, owing to their low temperature, be rendered
insensible by proportions of vapour too small to affect animals of warm
blood; and as they have no proper temperature of their own, the amount
of vapour (in proportion to the air in which they are placed) that will
affect them, depends entirely on the temperature of that air.
The following experiment was several times performed on frogs with the
same result, the temperature of the room being about 55°, as it was in
winter.
_Experiment 19._ 4·6 grains of chloroform were diffused through the air
of a jar of the capacity of 920 cubic inches, and a frog was introduced.
In a few minutes, it became affected, and at the end of ten minutes, was
quite motionless and flaccid; but the respiration was still going on.
Being now taken out, it was found to be insensible to pricking: it
recovered in a quarter of an hour.
In a repetition of this experiment, in which the frog continued a few
minutes longer in the vapour, the respiration ceased, and the recovery
was more tardy. On one occasion, the frog was left in the jar for an
hour, but when taken out, and turned on its back, the pulsations of the
heart could be seen. In an hour after its removal, it was found to be
completely recovered.
The first of the experiments related above (page 60), showed that an
atmosphere containing half a grain of chloroform to each hundred cubic
inches, produced scarcely any appreciable effect on animals of warm
blood; but the following calculation explains why this quantity acts so
energetically on the frog, and proves that this creature is affected by
chloroform according to the same law as animals of warm blood. The
vapour is absorbed into the blood and lymph of the frog at the
temperature of the external air, whose point of relative saturation
therefore remains unaltered, both in the lungs and in contact with the
skin of the animal; and as half a grain of chloroform produces 0·383
cubic inches of vapour, and air at 55° contains, when saturated, 10 per
cent. of vapour; 0·0383, or 1–26th, expresses the degree of saturation
of the air, and also of the blood of the frog. And this is a very little
more than the quantity (0·0354 or 1–28th) which was calculated above to
be the greatest amount which could be absorbed with safety into the
blood of the mammalia. It must be observed, however, that the pulmonary
respiration of the frog was arrested by this proportion of 1–26th as
much chloroform as the blood would dissolve, whilst we calculated that
it required about as much as 1–18th to arrest the breathing of animals
of warm blood. It must be remembered, however, that the pulmonary
respiration of frogs is a process of swallowing air, which only goes on
when the creature is comparatively active. In the torpid state, the
respiration takes place only by the skin, and the frog never breathes
with the aid of the same muscles and nerves as mammalia and birds.