A most interesting account of snake-charmers is given by Drummond Hay, in his book on Western Barbary, in which he relates his experiences with some of these wonderful individuals belonging to the sect called Eisowy. Members of this sect, he mentions, frequently handled scorpions and poisonous reptiles without fear or hesitation, and they were never attacked by them. He was present at one of their exhibitions of feats with snakes in which they both allowed themselves to be bitten and provoked the snake to bite them. The charmer thus bitten then in his turn ate or chewed the reptile, which, he remarks, writhing with pain, bit him in the neck and hands till it was actually destroyed by the Eisowy's teeth.
In South Africa snake poison is actually taken as a protection against snake-bites, and if we turn to the Lancet of the year 1886, we shall find a letter from Mr. Alfred Bolton stating that his curiosity had been aroused by the fact that while in South Africa cattle and horses frequently died from the effect of snake-bites, the natives themselves seldom or never appeared to suffer any inconvenience from such injuries other than would follow any accident which would set up local inflammation. On inquiry he found that they were in the habit of extracting the poison gland from the snake immediately it is killed, squeezing it into their mouths and drinking the secretion, thereby apparently acquiring absolute immunity from snake-bites. So impressed was Mr. Bolton by what he observed that he adds: "I can no longer refuse to believe in the efficacy of the snake virus itself as a remedy against snake poison."
Savage tribes have learnt from bitter experience how to protect themselves from snake-bites, and it is well known that they have a method of inoculation which they employ with success. The Creoles of Surinam use an ointment as a protection against snake-bites, which is regarded as highly efficacious. It is reputed to consist principally of the pounded head of a rattlesnake, which concoction would therefore include the contents of the venom glands. This is then mixed with the juices of a certain plant, which addition probably mitigates the intensity of the venom by acting as a diluent. This substance is generally applied by making an incision in the wrist or forearm and rubbing it in, after which individuals thus treated appear to enjoy security from the venom of snake-bites.
What applies to serpent venom would also appear to hold good in regard to other poisons, such as that contained in the sting of a bee. This poison is extraordinarily tenacious of its irritant properties, and, unlike eel poison, retains its virulence even when exposed to high temperatures.
An interesting memoir on the immunity of the bee-keeper from the effects of bee poison was published a short time ago by Dr. Langer in a German scientific journal. He issued a number of circulars with questions to be answered, and sent these to more than a hundred bee-keepers in different parts of the country, with the result that a hundred and forty-four stated that they were now immune to bee poison, nine having been fortunately endowed with a natural immunity to this irritant, whilst only twenty-six out of the whole number applied to stated that they were still susceptible.
This condition of immunity to bee poison is obtained after a varying number of stings have been inflicted; in some cases thirty, at the rate of from three to four a day, are sufficient to ensure freedom from further discomfort, but the inoculations may have to be prolonged up to one hundred stings to secure complete immunity.
In experiments carried out on animals this immunity to bee poison has been also induced by repeated application of the irritant. It was formerly generally supposed that the irritant nature of a bee's sting was due to the presence of formic acid; but inasmuch as bee poison can retain its poisonous character in spite of being submitted to heat, which would effectually volatilise the formic acid present, this assumption must be abandoned, and opinion is more inclined now to regard this irritant substance as partaking of the nature of an alkaloid.
Before closing this brief review of some of the most recent discoveries which have been made in the domain of immunity, we must mention some extremely suggestive and important researches on the poison of tetanus, or lock-jaw, which have emanated from Dr. Roux's laboratory at the Institut Pasteur in Paris.
It will perhaps be remembered that Pasteur, when working at hydrophobia, experienced the greatest difficulty in exciting rabies in animals with certainty, and that it was only when the fact of its being a disease which essentially affects the nervous system of the animal was taken into account that it occurred to him to cultivate the virus in the medium for which it had seemingly the greatest affinity, viz. the nervous tissue of an animal; it was only on taking this step that he succeeded in invariably provoking rabies in the animals under experiment.
In the case of tetanus we have another disease affecting the nerve-centres of the body, and although many authentic cases have been cited in which the treatment with anti-tetanic serum has been entirely successful, a great many instances have occurred in which it has been of no avail at all, more especially when the disease has obtained a firm hold on its victim. Now Dr. Roux has not only been carrying out experiments to ascertain what is the result of directly attacking, as Pasteur did in the case of rabies, the nerve-centres of an animal with the tetanus toxin, but he has also taken another and very important step further, and has investigated, not only the action of the toxin, but also that of the anti-toxin on the nerve-centres of an animal suffering from tetanus.
In describing the cerebral inoculations which he has conducted on animals, Dr. Roux points out that the operation, in itself, is attended with no pain or even inconvenience to the animal in question, that subsequently it eats with its usual appetite, and shows no signs of discomfort.
First, as regards the infection of an animal with the tetanus virus introduced directly into the brain, it has been found that very much smaller quantities produce a fatal result than when subcutaneously inoculated. Thus, a rabbit which received two cubic centimetres of the poison under the skin took four days to succumb to tetanus, whilst one-twentieth of the quantity inoculated into the brain sufficed to kill another rabbit of the same size in less than twenty hours.
Another very instructive example of this susceptibility of the nerve-centres for certain poisons is afforded in the case of rats and the toxin of diphtheria. Rats possess a natural immunity from this substance, and can successfully withstand a dose of diphtheria poison introduced under the skin which would infallibly kill several rabbits. This state of immunity, however, entirely disappears when the toxin is brought directly in contact with nervous tissue, for a very small quantity of diphtheria poison – insufficient to cause under ordinary circumstances even a passing swelling at the seat of inoculation – will, when introduced into the brain of a rat, kill the animal.
Again, rabbits are generally credited with possessing high powers of resisting the action of morphia, a large dose of this substance introduced subcutaneously producing no result whatever. A cerebral inoculation, however, of a minute quantity of morphia causes an immediate reaction, and the animal, after remaining in a more or less dazed condition for several hours, finally succumbs to this drug. Dr. Roux is inclined to regard this difference in the susceptibility exhibited by animals to one and the same poison as being due to a good deal of the toxin, when subcutaneously introduced, failing to reach the nerve-centres, it having been destroyed or arrested in the system before it could attack them.
What is the nature of the subtle forces which may so beneficially intervene between the toxin and its victim has long been a problem which has excited the interest and ingenuity of some of the most brilliant scientific authorities of the day, and it is one which, even in the hands of men like Metchnikoff, is still awaiting a satisfactory solution!
The important point was next approached by Dr. Roux as to whether an animal, successfully trained to withstand large doses of the poison, as ordinarily introduced, could also resist it when directly inoculated into the brain. Is, in fact, the undoubted immunity to tetanus poison which may be possessed by an animal due to the nerve-centres having become insensible to this substance? The answer to this question would appear to be in the negative, for animals artificially protected from tetanus poison introduced under the skin succumbed to a small dose inoculated direct into the brain, which would otherwise have not produced even a slight passing tetanic affection of the limb where the inoculation was made. Immense numbers of experiments were made under varying conditions, but the result was fully confirmed, showing that the nerve-centres had not acquired any immunity to the poison, although the blood serum of the victims to such cerebral inoculations was proven over and over again to be endowed with strong protective properties against tetanus poison.
The endeavour was then made to, in Dr. Roux's words, "place the anti-toxin where the toxin is working," and preserve the vital force of the nervous tissue. To arrest tetanus by substituting cerebral for subcutaneous inoculations of the anti-tetanic serum was the next feat attempted. Several guinea-pigs and rabbits were inoculated subcutaneously with virulent doses of tetanus poison sufficient to kill them in about seventy hours; some were subsequently treated with anti-toxic serum introduced in the ordinary way under the skin, whilst others were inoculated with from six to seven drops of this protective serum direct into the brain. The results were extraordinarily successful. Although but a few drops of the anti-toxin were used for the cerebral inoculations, the animals survived the otherwise fatal doses they had received of the toxin; whilst out of seventeen guinea-pigs which received subcutaneous inoculations of the anti-toxin only two recovered, and the quantity of the anti-toxin employed reached as much as from ten to twenty cubic centimetres in some of the experiments, contrasting in a remarkable manner with the few drops which sufficed in the case of the cerebral inoculations.
Dr. Roux sums up this splendid result in the following modest words: "Il ne suffit pas de donner de l'anti-toxine, il faut la mettre au bon endroit."
The significance and far-reaching application of this most important discovery cannot easily be overestimated. Hitherto the preparation of an anti-toxin has been the chief point considered, but Dr. Roux and his able coadjutor, M. A. Borrel, have shown how great may be the results which attend its method of administration, and have opened up an entirely new direction for investigation.
Although the subject of immunity is not, as we have seen, by any means wholly a latter-day creation, yet its approach and consideration from a modern point of view, assisted by the resources and equipment provided by modern scientific methods, justifiably entitles the nineteenth century to claim it as its own discovery.
However brilliant and successful the labours may be of those who will follow in the future, subsequent generations will know how to venerate those great leaders of scientific thought, amongst whom we must rank Pasteur, to whose genius the world owes so great a debt of gratitude, and the vast extent of whose labours cannot be adequately measured at the present day by reason of the restricted scientific horizon which encircles public opinion in this country.
THE END
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