NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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immunity which is established in other animals as the result of continued
treatment with cobra-venom, and that it is unconnected with the presence of
any material of the nature of the antivenene on which artificial immunity
depends. This phenomenon is not an exceptional one, as parallels to it have
been already recorded in connection with other examples of natural and
artificial immunities to the action of toxins, such as that of diphtheria.* It
would have been satisfactory indeed to have entertained the belief that in the
bodies of venomous snakes we have to deal with factories in which not only
toxins but their antidotes are elaborated, but in the meantime there are no
good grounds for doing so.
In addition to the preceding experiments in which cobra-serum was
employed in connection with cobra-venom, an additional one was carried out
in which the latter was replaced by daboia-venom.
Experiment XVI.— A fowl received 0.01 gramme of dry daboia-venom,
or an amount equivalent to a double minimal lethal dose for acute intoxication
when dissolved in 0.5 C.C. of water, in 1 C.C. of solution of dry cobra-serum
of the ordinary strength, i.e., containing 0.1 gramme of the dry material
per C.C.
No local muscular action attended the injection, nor did any general
symptoms of acute intoxication ensue, but the normal symptoms of chronic
intoxication made their appearance, and death occurred on the following day.
The phenomena in this instance are precisely parallel to those which were
present in the experiment in which a solution of dry antivenene was used as a
vehicle for the introduction of daboia-venom. Just as in that case, there was
a complete suppression of all symptoms of acute intoxication owing to the
diluted form in which the venom was introduced and to the delay in absorption
incident on the nature of the vehicle, and the subsequent occurrence of fatal
chronic intoxication owing to the amount of the dose employed.
D.—Results of experiments on the establishment of artificial
immunity by means of treatment with venom.
(a ) EXPERIMENTS ON THE ESTABLISHMENT OF IMMUNITY TO COBRA-
VENOM.
(1) Experiments on the elect of repeated subcutaneous injections of Venom.
Experiment I. —A common monkey ( Macacus rhesus) received an injection
of 0.00025 gramme of dried cobra-venom, of which 0.0025 constituted a
* Nature, December 12, 1895, page 139.
Medical Officers of the Army of India.
8 1
minimal lethal dose for animals of the same species and weight. The treat-
ment was followed by no appreciable effect, but 2 days later a dose of 0.0005
gramme was followed by marked drowsiness. After this a series of gradually
increasing doses of venom was steadily introduced at intervals of a few days'
duration for a period of 11 months, at the close of which the animal was
taking 0.05 gramme, or 20 times a minimal lethal dose, without showing any
appreciable symtoms of intoxication. An interval of 5 weeks was now
allowed to elapse, and a dose of 0.05 gramme again administered without giving
rise to any symptoms. After another interval of 2 months' duration 0.05
gramme was once more administered, and was followed merely by a certain
temporary amount of dulness. Unfortunately, the continuation of the experi-
ment was prevented owing to the death of the animal some time after the
last occasion on which venom had been administered and before the interval
of 4 months, which was to have elapsed ere renewed treatment was under-
taken had been completed.
This experiment is of course an imperfect one, as it does not absolutely
determine the length of time to which artificial immunity, arrived at by
habitual treatment with venom, lasts; the data do not determine whether it is
temporary or permanent, but they are at all events sufficient to show that it
differs from that which is capable of arising under the influence of treatment
with antivenene in being of a very persistent character. The phenomena do
not, as in the case of the immunity arising in connection with the use of
antivenene, indicate the mere introduction of a ready-made antidote which is
capable of retaining its activity for a certain time after entering the circulation,
but the establishment of a local manufacture of an antidote within the system.
They are only explicable as dependent on the fact that the access of the venom
to the system not only gives rise to intoxication, but to the reactive, systemic
manufacture of an antidote which constitutes the active principle which is
present in the preparations of serum which are described as antivenenes.
(2) Experiments on the effects produced by ingestion of Cobra-venom.
Experiment II. —A monkey (Macacus rhesus) was treated with doses of
cobra-venom for a period of 16 months. During this time it invariably
received at least one dose per week, and each of these habitual, methodical
doses latterly contained 0.1 gramme of dried venom. During the greater part
of the time, moreover, it received a large number of additional casual doses
weekly, as, after it had been ascertained that the ingestion of the venom gave
rise to no appreciable symptoms of intoxication, any residual solutions of
venom, such as were constantly in hand in connection with the conduct of
other experiments, were at once administered to it in place of being thrown
away or stored up. A minimal lethal dose of dried cobra-venom was finally
administered to it.
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Symptoms of intoxication appeared after an interval of 4½ hours, and death
occurred 5½ hours later.
Experiment III. —A monkey (Macacus rhesus ) received by the mouth
a dose of 0.2 gramme, i.e. , 80 times the amount of a minimal lethal dose when
administered subcutaneously, and on the following day a subcutaneous injection
of 0.0025, or a minimal lethal dose of dried cobra-venom.
Symptoms of intoxication appeared within 2 hours after the injection of
the venom, and death occurred 5½ hours later.
These experimental results are again in conflict with those which Professor
Fraser seems to have obtained, and which have led him to adopt the view,
which has been habitually entertained by the serpent-charmers of this country,
that the ingestion of venom is a means of securing immunity against its action
when directly introduced into the system. The result in Experiment III certainly
shows that the ingestion of an amount of venom 80 times as great as that
constituting a lethal dose when entering the system directly is incapable of
producing any appreciable effect on the action of a minimal lethal dose
administered subcutaneously 24 hours later, and that of Experiment 11, that the
prolonged and habitual ingestion of smaller quantities of venom is equally
inefficacious. The fact that the ingestion of even very large quantities of
venom is certainly not necessarily followed by the occurrence of any appre-
ciable symptoms of intoxication, and that neither the habitual ingestion of
venom nor a single ingestion of a very large quantity of venom is necessarily
in any way protective, cannot but suggest the possibility that in those cases in
which protective effects do seem to follow such treatment they have arisen in
connection with the presence of breaches of continuity or other abnormalities
in the surface of the mucous membrane of the alimentary tract allowing of the
absorption of a certain amount of crude venom, rather than with any analysis
of the venom by the normal digestive apparatus, such as Professor Fraser
supposes to occur, in the course of which those constituents giving rise to
intoxication are separated from those which cause the reactive formation of anti-
venene and which alone are subsequently absorbed.
Had there been any evidence conclusively indicating that the immunity
against the action of their own venom, which is enjoyed by cobras, is necessarily
dependent on the constant presence of a material of the nature of antivenene
in their blood, there might have been some ground for anticipating that a
chronic habitual ingestion of venom, such as must take place in their case,
would lead to the establishment of immunity. But, as on the one hand there
is nothing to show that cobrine blood habitually contains antivenene, and on
the other there is conclusive evidence that an excessively high relative immu-
nity against the toxic action of cobra-venom may be present in perfectly harm-
less snakes such as Zamenis mucosus, in which no habitual ingestion of venom
Medical Officers of the Army of India.
83
can possibly occur, it would have been somewhat surprising had the result of
the treatment been uniformly satisfactory. There is no evidence whatever
to show that the natural immunity of venomous snakes to the toxic action of
their own venom is normally dependent on any process of auto-inoculation,
seeing that immunity of exceedingly high degree is present in certain species
of perfectly harmless snakes, in which no process of auto-inoculation can
possibly be carried on, and that there is nothing to show that the blood of
venomous snakes necessarily and normally contains any appreciable quantity
of antivenene, or, in other words, of the antidotal material which is normally
elaborated in connection with the access of venom to the system. Moreover,
the mere fact that cobras are endowed with an excessive immunity not only
against their own venom, but also against viperine venom, is of itself almost
conclusive proof that the exemption cannot be essentially dependent on any
process of auto-inoculation, seeing that cobrine antivenene is powerless against
viperine venom. It has, however, yet to be experimentally demonstrated
whether the immunity of venomous and non-venomous snakes to the action
of venom is not, partially at all events, connected with an excessive systemic
reactive manufacture of antivenene when venom does enter the system. The
immunity is certainly not dependent on the normal presence of a large quan-
tity of antivenene in the blood, but this, of course, does not exclude the
possibility that it may be due to an excessively active manufacture of anti-
venene under the influence of the access of venom to the system, or, in other
words, under the influence of the normal stimulus to such manufacture.
Should it turn out to be the case that natural immunity is in any degree appre-
ciably dependent on such excessive reactive manufacture of antivenene, we
shall at once have a satisfactory explanation of the conflicting statements which
are on record in regard to the antidotal properties of cobra-serum, for it is
clear that under such circumstances, whilst normal cobra-serum would possess
no antidotal properties, serum derived from cobras in which auto-inoculation
had taken place in connection with abnormalities in the mucous membrane of
the digestive tract would necessarily be highly antidotal in relation to the
amount of venom which had been absorbed.
Another point which must be taken into account in endeavouring to
explain the discrepancies existing between the results which have been obtained
in different series of experiments in regard to the properties of cobra-serum is
that facilities for the occurrence of processes of auto-inoculation in snakes are
likely to be present in very varying degrees under different circumstances. In
the case of perfectly healthy snakes, which are obtaining their food naturally,
the chances of the occurrence of any auto-inoculation must necessarily be very
much smaller than they are in the case of unhealthy snakes, or in snakes which
have to he forcibly fed. The hamadryad (Naia Bungarus) although apparently
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a very intelligent and ultimately tameable animal, initially resents captivity to
such an extent that it will frequently practically starve itself to death. Under
these circumstances, and taking the value of the species into account, we have
found it necessary in the Zoological Garden at Alipur to feed newly-captured
individuals artificially for some time after they have been acquired. This is
done by means of forcibly cramming them with the legs of fowls, which are
thrust into their mouths and then passed down their throats by the aid
of external pressure, and anyone who has ever seen the process carried
out can have no doubt that the chances of auto-inoculation, which must be
present under such circumstances, must be infinitely greater than they are in
the case of snakes spontaneously partaking of their natural ophidian diet.
When, therefore, one hears of instances in which the serum of the blood of
venomous snakes has appeared to be endowed with an immunising property, one
is justified in enquiring how far there is any satisfactory evidence that the
snakes were perfectly healthy and feeding naturally before one regards the
endowment as a natural one.
In the meantime, however, there is nothing to show that the conflicting
nature of the evidence in regard to the antidotal property of cobra-serum can be
satisfactorily explained on such grounds as the above. The results of one or
two experiments only are not, of course, finally decisive in regard to the ques-
tion of the presence of any reactive elaboration of antivenene in the system of
venomous snakes in response to the access of their own venom to the system,
but those of the following experiments appear at all events clearly to show that,
even if antivenene be produced under such circumstances, the amount which is
elaborated is neither necessarily excessive or in any way proportionate to the
degree of immunity which is present, and therefore afford additional evidence
that the natural immunity of venomous snakes is not essentially and primarily
dependent on any processes of auto-inoculation or of exceptionally energetic
development of antivenene when venom is otherwise introduced into the system.
A cobra, weighing 780 grammes, received an injection of 0.75 gramme of dry
cobra-venom dissolved in 3 C.C. of water, or an amount sufficient to have
proved fatal to 1,000 fowls of one kilo in weight. No unequivocal symptoms of
intoxication followed. The snake was quiet and somewhat dull during the
course of the following day, but as the weather was cyclonic in character, with
a relatively low temperature, violent continuous rainfall, and dense clouds, this
may not have been in any way owing to the treatment. Forty-eight hours
after the injection had been performed, the snake was decapitated and its blood
collected and allowed to coagulate. After contraction of the clot and separation
of the serum had occurred, 5 C.C. of the latter were used as the medium in which
0.01 gramme of dried cobra-venom, of which 0.00075 gramme constituted a
minimal lethal dose for fowls of 1 kilo in weight, was dissolved. Two fowls
—
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does not necessarily contain any material conferring any immunity against the
action of venom on susceptible animals, and in this case we have conclusive
evidence that it may contain lethal quantities of venom without giving rise to
any appreciable symptoms of intoxication in the snake from whose blood it
has been derived. In this instance the amount of venom present in the blood
of the snake was so great as to give rise to fatal intoxication in a susceptible
animal on the access of the serum to its system; but had the blood of the snake
been less highly charged with venom, appreciable symptoms of intoxication
might have failed to appear in the recipient animal, and yet a certain amount
of reactive elaboration of antivenene might have been initiated in its system,
and have determined a proportionate degree of insusceptibility to the action of
subsequent doses of venom. Auto-inoculation may certainly provide for the
presence of a certain amount of venom in the blood of venomous snakes, and
may, therefore, endow it with a certain protective property dependent not on
its containing any ready-made antivenene, but on its acting as a stimulant to
the elaboration of antivenene in the system of susceptible animals when it
gains access to their circulation.*
(b) EXPERIMENTS ON THE ESTABLISHMENT OF IMMUNITY TO
DABOIA-VENOM.
Experiment IV.—A fowl received an injection of 0.002 gramme of dried
daboia-venom in 0.5 C.C. of water, the lethal value of the material being such
that 0.004 gramme in 0.5 C.C. of water constituted a certain minimal lethal dose,
followed by violent general convulsions, and death within a period of 10 minutes.
Local muscular action was well marked at the site of introduction of the
venom, and within the course of the following ten minutes spasmodic jerking
movements of the head set in, and continued to be present for some time.
Subsequently, during the rest of that day and the whole of the following one,
the bird exhibited symptoms of chronic intoxication, probably dependent on
nervous exhaustion succeeding the excessive nervous stimulation. During this
time the bird remained very dull and sitting almost motionless, but, 24 hours
later complete recovery seemed to have occurred.
On the third day after the beginning of the experiment a renewed injection
of 0.003 gramme of venom was administered in the same site as the first one.
No local action followed, and no general symptoms appeared, save a certain
amount of temporary drowsiness, and half an hour later it began to feed greedily.
On the following day an injection of 0.004 gramme of venom was adminis-
tered in the leg opposite to that which had formed the site of the two previous
* Since the above passage was written further experiments have confirmed these observations in
demonstrating that the serum of the blood of cobras, which have been treated with excessive doses of
cobra-venom, has no protective or immunising property whatever, but may for some time contain
enough unaltered venom to cause it to give rise to fatal intoxication in susceptible animals.
Medical Officers of the Army of India. 8 7
ones. Local muscular action was well marked, and 7 minutes later violent
general convulsions set in, and terminated in death immmediately after.
The suppression of all local and general symptoms of nervous irritation,
which attended the second administration of the venom in this case, in spite
of the coincident increase in the dose which was employed, was probably
merely the result of retarded absorption connected with the local irritant
effects induced in the tissues by the primary one, for the acutely fatal effect
of a correspondingly augmented dose, when introduced on the subsequent day
in a fresh site, clearly shows that no considerable rise in degree of immunity
had up to that time been established as the result of any reactive systemic
manufacture of antivenene.
Experiment V.—A fowl received an injection of 0.001 gramme of dry
daboia-venom of the same lethal value as that employed in the previous
experiment, in 0.5 C. C. of water.
Local muscular action occurred, but no appreciable general symptoms of
either acute or chronic intoxication followed.
January 13th. —Forty-eight hours after the previous treatment, it received
0.002 gramme in 0.5 C. C. of water in the same site. A mere trace of local mus-
cular action was present. The bird presently sat down, leaning on one side owing
to spasmodic extension of the leg into which the venom had been introduced,
the persistent extension being accompanied by occasional spasmodic twitchings.
The eyes were half closed and occasionally completely shut, and gular move-
ments of swallowing were frequent and conspicuous.
The clonic twitchings and general rigidity of the leg gradually diminished,
and after about an hour and-a-half the bird had begun to dress its feathers and
was looking quite bright.
January 14th. —It was feeding freely and only somewhat dull, and on the
following day it was to all appearance perfectly well.
January 16th.—An injection of 0.002 was administered in the opposite leg,
and was followed by distinct local muscular twitching. No further symptoms
of nervous irritation, however, manifested themselves. The bird appeared to
be somewhat dull for a short time, but 12 minutes after the injection of the
venom it was feeding greedily.
January 17th. —An injection of 0.003 gramme of venom was administered
in the same site as the injection of the previous day. No local muscular action
occurred. The bird for some time sat motionless, with its eyes frequently closed,
but half an hour after the administration of the venom, when some grain was
introduced into the cage, it stood up and began to feed. It had, however, little
appetite, and soon sat down again and remained motionless.
January 20th.—The bird was now apparently quite well, and 0.004 gramme
of venom in 0.5 C. C. of water, or a normal minimal lethal dose for acute
intoxication, was administered to it.
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It sat down drowsily, and within the course of ten minutes slight spasmodic
jerking of the wings and legs set in, and continued to be present during the next
20 minutes. They then disappeared, and shortly after, when grain was
introduced into the cage, the bird stood up and began to feed greedily. It
remained very quiet for some hours, and then appeared to have completely
recovered from all effects of the treatment.
January 24th. —An injection of 0.005 gramme of dried venom in 0.5 C. C.
of water was administered. No local action followed, but within ten minutes
after the injection had taken place, slight spasmodic twitchings of the extre-
mities appeared. Very shortly afterwards, however, it got up, and began to
feed greedily when supplied with grain.
January 27th.—An injection of 0.006 gramme of venom in 0.5 C. C. of
water was administered. No local action whatever, and only very slight
spasms of the affected limb appeared within the course of the following ten
minutes. A quarter of an hour after receiving the injection, the bird got up
and began to feed greedily.
January 30th. —An injection of 0.007 gramme of venom in 0.5 C. C. of
water was administered. No symptoms of any kind either local or general
followed.
After this period no effects seemed to be produced by the series of cumu-
lative injections which were administered at intervals of two or three days'
duration, save that the bird gradually became accustomed to associate the
treatment with a subsequent dole of grain, and was consequently in a state of
excited expectancy of the latter.
The administration of repeated doses of daboia-venom was continued until
the 21st of February, on which date for the second time a dose of 0.0 16
gramme, or four times a minimal lethal dose of venom, produced no appreciable
effects, either acute or chronic, although a similar dose administered to an
unprotected fowl gave rise to violent convulsions and death a minute after the
injection had been effected.
January 22nd.— A dose of 0.001 gramme of dried cobra-venom, of which
0.00075 constituted a minimal lethal dose, was now administered.
Symptoms of cobrine intoxication appeared 3½ hours later, and death
occurred 13 hours after the injection had been effected.
The phenomena which presented themselves in connection with the pro-
gress of this experiment are noteworthy in two respects. In the first place
those which were present during the earlier portion of it clearly indicate that,
then at all events, the administration of progressively increasing doses of
venom did not lead to any disproportionately excessive systemic reactive
manufacture of antivenene, but that the quantity of the antidote actually
available at any one time was very little in excess of that necessary to equili-
brate the effects of an amount of venom equivalent to that present in the