Chapter VIII: Preface (8)

How many—we may well ask—how many of these fixed stars—suns like our own—are there? Roughly speaking, we can see with the naked eye, reckoning both the northern hemisphere and the southern together (for the stars seen from the former are other than those seen from the latter), about 8000. Not many after all, one is inclined to say. But stop a minute and hear what the telescope reveals. With the best telescope about one hundred million can be seen, less and less brilliant and more difficult to see in proportion to their remoteness. And now we go further even than that. For within the last thirty years the great science of astronomy has been rejuvenated by the application of photography to its task. The invention of the “dry” plate, a sensitive photographic plate which does not spoil by prolonged exposure as the “wet” plate does, enables the astronomer to keep his telescope fixed by slow-moving clockwork on to a given region of the sky for four or five hours or more, and the very faint stars, invisible by the aid of the most powerful telescope—stars the light from which is so feeble that it could not affect the plate in a few seconds or minutes, have time by the continued action of their faint light to print themselves on the plate and sign, as it were, a definite record of their existence for man to see and measure, though they are themselves for ever invisible to his eye. It is not possible to say how many may be recorded in this way by photography; it depends on length of exposure. But some thousands of millions of stars can certainly be so recorded. These “unnumbered hosts” are of various degrees of brightness, and by methods which astronomers have invented, but cannot be described here, it is actually known how they differ in size from one another (many are far bigger than our sun), and with some approach to certainty, how far off they are. Stars of four, five, ten, and more “light-years” away from us are well known. Astronomers actually estimate the decreasing abundance in space of stars as one passes from a sphere or spatial envelope of fifty light-years’ distance to one of 250 light-years. Finally, reasons have been given of late for considering many of the “photographic” stars to be at a distance of 32,000 light-years. I will not produce the awful figure in miles, but the reader can refer back to the number of billion miles in a light-year! And what is beyond that? No one has seen, nor can any one guess. We cannot imagine a limit to space; neither can we imagine unending space dotted with an infinity of suns!

It is a legitimate and, indeed, a necessary inference, from what we know of these millions of suns—intensely hot, light-giving spheres—that they, too, like our own sun, are accompanied by much smaller bodies, planets which circle round them, as our sun’s planets circle round him. Those planets have cooled down, as have those of the solar system, and so do not give out light. In any case, they are too small to be seen at so vast a distance. It is, on the whole, probable that the changes on some—indeed, many—of these planets have led to the production of living material similar to, but not necessarily identical with, that on this earth. It is, on the whole, more likely than not that there are intelligent beings existing on the planets of thousands of suns invisible to our eyes: suns revealed only by the print on a photographic plate of their light, which has taken thousands of years to travel from the regions of unseen obscurity to us. To have arrived by sober observation and reasoning at this conception is, indeed, a tremendous flight of human thought and ingenuity!

It is the courage, the audacity—one may almost call it the superhuman calmness—of astronomers, in the face of this truly overwhelming immensity—that not only redeems their study from the oppressive and terrifying character with which it at first assails the human spirit, but gives to their proceedings and discoveries, so far as the ordinary man can follow them, an unequalled fascination. The daring, the patience, the accuracy, and the supreme intellectual gifts of the great astronomers rightly fill other men with pride in the fact that there are human minds capable of revealing things of such stupendous vastness and of indicating their order and relation to one another. It is a splendid fact, and one which must give hope and courage to all men, that the astronomer’s mind does not totter—it is equal to his task. Astronomers are, in fact, triumphant: they are very far indeed from suffering from the depression which Mr. Hardy’s young star-gazer experienced.

Among the many conclusions of astronomers as to the movements of the “heavenly bodies” none is more strange and mysterious in its suggestion than that recently arrived at to the effect that in all this vast array of millions of stars, the limits of which we can neither discover nor imagine, there are two huge streams moving in opposite directions, and in one or other all the stars are involved. Whence do they start? Where are they going? There is no answer. Another conclusion, which is arrived at quite simply by the examination with the spectroscope of the light coming from the star named Vega by astronomers, is that our sun and its attendant planets are moving towards that star. It is true that it is many billions of miles away from us, but we are rushing towards it somewhat rapidly according to mundane notions—namely, at the rate of nineteen miles a second! That, I think, is a fact likely to make the sentimental young astronomer as miserable as any of the records of immensity. In fact, the only comfort to be got in view of this fact is in the enormous distances which separate us from other stars, and the length of time which must elapse before any serious consequence can ensue from this alarming career. And there is further the probability that the general result of attractions and repulsions in the vast roadway of space will, when the time comes, take us safely past Vega, just as a motor-car passes safely through the traffic and obstructing “refuges” and lamp-standards of the London streets as you recline in it, abandoned to the natural forces described as “chauffeurs.”

The spectroscope has done no less than photography to reanimate the study of astronomy. The fact is that, with these two helping means of observation, it has become possible for the ordinary man to witness and appreciate some of the discoveries of astronomers, though the true and accurate handling of all that is revealed concerning the stars is essentially a matter of measurement, and therefore only to be dealt with strictly by mathematicians. The desire to obtain ever more and more accurate measurement of the movement and the size of the heavenly bodies is the mainspring of all astronomical discovery, and, indeed, the attempt to gain more and more detailed measurement of the factors at work is the motive—more or less immediate—of all accurate investigation of nature. Recently the astronomers of the Royal Observatory at Greenwich have photographed the new comet (the third of 1907) in a way in which no comet has ever been photographed before. On many consecutive nights for several weeks they were at work photographing it on the dry plate, at intervals of two or three hours, and the pictures obtained (which I have seen at the rooms of the Royal Astronomical Society) show the most wonderful changes of form of its tail, so that they look more like the record of the changes of some living creature than those of a heavenly body. Already, in October 1909, Halley’s comet, which has been anxiously awaited, has been seen, though it is not expected to be bright and visible to all until May 1910. Comets are among the exceptional delights of the astronomer—that is to say, big comets, for two or three small comets visible only by a telescope or by photography turn up every year. Some comets are expected visitors, others make their appearance quite casually, some because they apparently have no regular period, some because that period is as yet undiscovered. Edmund Halley was the first to discover the law of movement of a comet and to predict the return in 1758 of that seen in 1682. He did not live to witness the verification of his prediction. This comet, now called Halley’s comet, was, he conjectured, the same which had appeared in 1531 and in 1607. His prediction of its return proved to be a year out (owing to perturbations caused by Neptune and Uranus, two planets undiscovered in his day), but it appeared in 1759, and went round once again and reappeared in 1835, and now is eagerly expected by astronomers to appear in full brilliancy in 1910. Its period is about seventy-five or seventy-six years.

XXIV

COMETS

A comet is so called from the hair-like stream of light or “tail,” which stretches to a greater or less length from its bright head or “nucleus.” A large comet, when seen to greatest advantage, may have a tail which stretches across one-third of the “vault of heaven,” and may be reckoned by astronomers at as much as one hundred and twenty million miles long. Donati’s comet—which some of my readers will remember, as I do, when it visited us in 1858—was of this imposing size. Halley’s comet, on the other hand, when it was last “here,” namely, in 1835, showed a tail estimated by astronomers to be fifty million miles long. The tail was more than twice as long when Halley’s comet appeared in 1456. There was a big comet “on view” in 1811—the year celebrated for its wine—and in recent times a fine comet appeared in 1861, and another (Coggia’s comet) in 1874.

The ancient records of comets are naturally full of exaggeration. Up to Milton’s time—two hundred and fifty years ago—they caused the greatest terror and excitement by their sudden appearance in the sky. This is due to the fact that mankind from the very earliest periods of which we have record has not merely gazed at the “starry host” by night in solemn wonder, but even in early prehistoric times studied and watched the stars so as to know much of their movements and regular comings and goings. The earliest priests, the earliest “wise men,” were those who knew the stars and could fix the seasons by their place; the earliest temples—Stonehenge, and others older still—were star-temples or observatories, and their priests were astronomers. To such a pitch did reverence for star-knowledge attain that our ancestors confused the astral signs of changing season and cycle with the cause itself of change, and attributed all kinds of mundane events and each man’s fate to “the influence of the stars.” Hence the sudden appearance of a flaming comet was held to be a portent, and was always supposed either to foretell or even to produce some very unpleasant event, such as a big war or a pestilence, or the death of some one supposed to be of consequence. The earliest Greek poetry enshrines the superstition, which is handed on by Virgil, and finally by Milton. In Pope’s translation of the _Iliad_ we find the helmet of the terrible Achilles described as shining

“Like the red star, that from his flaming hair
Shakes down diseases, pestilence, and war.”

And Milton, in 1665, in his _Paradise Lost_, wrote—

“On th’other side,
Incenst with indignation, Satan stood
Unterrifi’d; and like a comet burn’d,
That fires the length of Ophiuchus huge
In th’ Arctic sky, and from his horrid hair
Shakes pestilence and war.”

In this year of the celebration of the tercentenary of Milton’s birth, it is not a little curious to find that John Milton, himself a scholar of St. Paul’s School, wrote those lines when Edmund Halley, the future Astronomer Royal, had just entered the same great school, then standing in St. Paul’s Churchyard, as it did when I was “one of the fishes,” and used to see men hanging in the Old Bailey—I once saw five[5]—on Monday mornings as I passed on my way to the school. To a Pauline it is not without significance that the return of Halley’s comet is awaited within a year of Milton’s tercentenary, and that the greatest astronomer and the greatest poet of their age were London boys and Paulines.

Ancient records tell of comets of gigantic size, of the shape of a sword, the head as big as the moon, and so on. There is no reason to suppose that within historic times there have been any much bigger than that of 1858. Milton, in the lines above quoted, was not referring to an imaginary comet, but to one which actually did appear when he was a boy of ten (1618), in the constellation called Ophiuchus. It was of enormous size, the tail being recorded as longer even than that of 1858. It was held responsible by educated and learned men of the day for disasters. Evelyn says in his diary, “The effects of that comet, 1618, still working in the prodigious revolutions now beginning in Europe, especially in Germany.” The comet of 1665 was, with equal assurance, regarded as the cause of the Great Plague of London. In that year was published the first number of the _Philosophical Transactions_ of the Royal Society of London, then recently founded “for the promotion of natural knowledge.” It contains an account of a paper by a learned French gentleman, M. Auzout, in which an attempt is made to predict the movements among the stars of the comet of 1664. Astronomers had long known and been able to predict the movements of the planets and the swinging of the constellations, but, as the French author observes, “all the world had been hitherto persuaded that the motions of comets were so irregular that they could not be reduced to any laws.” He also hoped, by examining the movements of the comets of 1664 and 1665, to determine “the great question whether the earth moves or not.” At that time the earth was “suspected” to move round the sun, but no proof of that motion had been given. M. Auzout did not succeed in his laudable attempt, simply because Newton’s great discovery of the law of gravitation had not then been made.

Edmund Halley was the intimate friend and passionate admirer of Newton. He paid out of his own pocket for the publication of Newton’s _Principia_ by the Royal Society in 1686, the society having expended all its available funds in printing a great work on _Fishes_ (which shows how at the first, as now, the society cared for the whole range of the study of Nature). Halley was able to show that comets move regularly round the sun, in obedience to the same law of gravitation which controls the movements of the planets and of our earth itself; so that many of them are regular members of the solar system. Halley especially calculated out the form of the orbit of the comet of 1682 as an ellipse, and the time of its journey and recurrence, or “period,” as it is called, which he showed to be about seventy-five or seventy-six years. He predicted its recurrence in 1758. Halley died in 1742, at the ripe age of eighty-six, having, amongst other good deeds, founded the Royal Society Club, which still dines every Thursday in the session. His comet reappeared in 1759, a few months later than he had, owing to incomplete details used in his calculation, expected; but the accuracy of his scheme of its movement was demonstrated. It duly appeared again in 1835, and it is now awaited in the spring of 1910. Halley himself had identified his comet with that of 1607 and of 1531, and lately, by the aid of records from an ancient seat of astronomical observation—actually from China—it has been traced back to the month of May in the year 240 B.C. It has caused consternation and terror times enough since then, of some of which we have record. Finally, it has become the leading instance of the triumph of scientific knowledge and accuracy over ignorance and superstition. Halley’s comet caused great alarm in Rome in the year 66 A.D. A thousand years later (1066) it was seen when William the Conqueror was preparing to descend on the coast of England, and is actually represented in the Bayeux tapestry. A number of men are drawn (or rather “stitched”), with fingers pointed and eyes raised to a shape in the sky which resembles a star-fish with a large triangular-ribbed petticoat attached to it, ending in eight flames or tongues (Fig. 45). The picture is labelled “Isti mirant stella.” There is now no doubt, as accurate calculations have demonstrated, that William the Conqueror’s “star” was Halley’s comet—a fact which must give its reappearance in 1910 an additional interest in the eyes of Englishmen.

The shape given to the representations of stars in old pictures and engravings is a puzzle. Why do they represent a star by the shape of a star-fish? No star ever looks like that, or produces a picture of that shape on the retina. The thing is purely conventional. The shape which we call “star-shaped”—a term we apply to flowers and other things—is not in the least like a real star as seen by an unprejudiced person. What one really sees is an ill-defined point of light. The pretended conventional star of ancient drawings perhaps arose from the simple artifice of picturing tongue-like flames around or upon any representation of a fire or a source of light—“to show what it was meant to be.” Then the notions of perfection and symmetry in regard to the celestial bodies led to the “tongues” being arranged for the purposes of draughtsmanship as perfectly symmetrical-pointed rays of a six- or eight-limbed geometrical design—and latterly it is possible that the mystical figure known as the “pentacle” was utilised by astrologers and others as the emblem of a star. However they arose, neither the weird and astonishing representations of mediæval times nor the geometrical decorative “stars” of later date seem to have any relation to an attempt to represent a star as it really appears to the human eye and the interpreting brain behind it.

The orbits of comets, says Professor Turner, of Oxford, in a delightful lecture delivered in Dublin in the summer of 1908, from which I have culled many interesting facts and presented them to my readers, “differ from those of the planets in being far more highly elliptical. Our own path round the sun is nearly a circle, so that our distance from him remains nearly the same all the year round; but the distance of a comet from the sun varies greatly from ‘perihelion,’ when it is near, and consequently bright, to ‘aphelion,’ when he is so distant and faint that we lose sight of him.” The sun is not at the centre of the ellipse described by a comet’s path, but is quite near to one end of it, so that comets approach the sun far more closely than do the planets, some taking so close a turn round the sun that the heat from it to which they are exposed is 2000 times as great as that which the earth receives. If the orbit of a comet is really elliptic, then there at last comes a time, though it may be only after thousands of years, when the comet, having rounded the sun at close quarters, and journeyed off into space, has his journey brought to a turning-point at the other end of the ellipse, and begins to draw near again, advancing towards the sun. The length of the orbit of Halley’s comet is about 3255 million miles, and the breadth at its broadest is about 800 million miles, and he takes about thirty-eight years to travel the full length (along the curve) and thirty-eight years to come back again! Other comets have other lengths and breadths of orbit, and take longer or shorter periods to go round. But the conditions of attraction affecting a comet may be such that the return journey never occurs. They may be such that the comet goes on indefinitely travelling away from our sun, until he is caught by some other star, and his orbit changes its shape, with the new sun as attracting centre. These are the “wandering comets” as distinct from the “periodic comets,” which have been shown to conform to Halley’s scheme of their movement and recurrence.

And now some one will ask, perhaps impatiently, “What, after all, is a comet?” We have seen that many are continuously, and others casually, members of the solar system. What do they consist of? Spectrum-analysis shows that they consist chiefly of the chemical element carbon.[6] Though they have weight, and are attracted by the sun, yet they seem to be for all their size and terrifying shape and glare incredibly light and airy things. Herschel declared that the tail of a big comet probably consisted of but two or three pounds of solid matter—diffused, rarefied, and luminous. And the head or nucleus certainly does not weigh many hundreds of tons. In the eighteenth century astronomers observed a comet pass right in among the moons of the planet Jupiter. You might expect the moons to be terribly knocked about by such an impact. They were not; they were not deflected in the smallest appreciable degree from their position and regular movement! One is naturally inclined to look upon the tail of a comet as something like the smoke of a railway engine trailing behind the advancing “head.” As a matter of fact, it does not always trail behind, but is always turned away from the sun, so that when the comet is travelling away from the sun the tail is in front! It is now held that the tail is caused by the radiant energy (light and heat) of the sun, blowing, as it were, the lighter particles from the incandescent head, and causing them to spread out in a long track of variable shape. The photographs of the third comet of the year 1908 show that the tail can vary to an astonishing extent and with great rapidity—that is to say, in four or five hours. It is seen in those photographs as a scimitar-like curved blade, then with a second head or nucleus behind the leading one, then actually bent like the letter Z, and then divided into seven distinct diverging “plumes,” and then it returns to its former simple shape—all in the course of a few days. Astronomers have now shown that there is a close connection between comets and the showers of “shooting stars” or meteors which frequently strike the earth’s atmosphere. It is considered probable that comets eventually break down into streams of meteors, and that their “life” (if one may use that term) is, relatively to that of other heavenly bodies (which are all undergoing change and, in many cases, decay), not a very long one. But there are no facts at present known which enable us to tell whether a given comet is young or old, and it would have been a decided shock had it been found that Halley’s comet, which has so happily spent every seventy-sixth year with us for so many centuries, had “burst up,” or by “indisposition” had been unable to pay his usual visit as expected in 1910.

FOOTNOTES

[5] The pirates of the _Flowery Land_.

[6] I am indebted to Mr. Rolston, of the Solar Physics Observatory, South Kensington, for some information on this matter.

Generally speaking, it appears that the spectra of these bodies indicate carbon—in some form—as the principal constituent.

As to the particular form of carbon, there is still a considerable doubt, so much that, in describing the spectrum of Morehouse’s comet, Professor Frost says (_Astrophysical Journal_, xxix., p. 59, 1909):—“We avoid the still unsettled question of the ‘carbon’ bands (of the so-called ‘Swan’ spectrum) which have been so often ascribed to a hydrocarbon, specifically acetylene, and we use for them the simple designation ‘carbon.’”

In addition to this “carbon” there is the cyanogen spectrum present in most cases.

Sodium and iron have been detected in the spectra of some few comets, _e.g._ Wells (1882, ii.), whilst Holmes (1892) showed only continuous spectrum.

An interesting suggestion is made by Newall, namely, that the spectrum is not indicative of the _comet’s_ composition, but of that of the medium through which the body passes. Thus the persistent identification of the cyanogen bands in cometary spectra is attributed, primarily, to the “heating up” of cyanogen existing, free, in circum-solar space.

Till 1907 most of the cometary spectrograms showed only the “carbon” and cyanogen radiations, but in Daniel’s comet of that year, and in Morehouse’s of 1909, other lines were detected for which origins have not, as yet, been found.

Thus, some form of carbon + unknown + (occasionally) sodium and iron seems to sum up our present knowledge of cometary composition.

XXV

ABOUT CHOLERA

What is this terrible disease which every few years travels from the banks of the Indian Ganges, where it is always present, and makes its way to one or more of the great cities of Europe, killing its thousands with horrifying rapidity? The word “cholera” is used by the great Greek physician of antiquity, Hippocrates, and by his followers down to the days of our own Sydenham, to describe a malady which occurs commonly in summer, is often of severe character, but rarely fatal, and is characterised by the exudation from the walls of the intestine of copious fluid, usually accompanied by vomiting and sometimes by “cramps.” This malady is now distinguished by physicians as “simple cholera,” or European cholera, the last name being misleading, since the disease occurs all over the world. It is caused by a special microbe, which multiplies in the intestines and produces a poison. Other microbes produce similar results. One which causes luminosity in foul salt water has been found to produce cholera-like results when cultivated in a state of purity and swallowed by man. Other poisons besides those produced by microbes set up a sort of “cholera” in animals and man. Drugs of both mineral and vegetable origin have this effect, as every one knows, and are used in small quantities to produce purging. Microbes which are noted for other obvious effects which they produce by the poisons they form in man’s intestines—such as the microbe of typhoid fever—also produce cholera-like purging.

But the name “cholera,” or “the cholera,” is now applied without any further qualification to what would be more correctly described as “Indian cholera,” or “epidemic cholera.” It is a disease which first became known to Europeans in India in 1817, less than a hundred years ago. It resembles “simple” cholera in its general features, but is usually much more violent in its attack, and often causes complete collapse in two or three hours from its onset, and death in as many more. The main point about it is, however, that it is a quickly spreading “epidemic” disease; it invades a whole population, and travels from place to place along definite routes. Although the outbreak of cholera in India in 1817 was the first to attract the attention of Europeans, it was nothing new in India, and was recognised in distant ages by Hindu writers. Its usual name on the delta of the Ganges is “medno-neidan.” Ninety per cent. of the population perished of cholera in some districts of India in 1817, and English troops were attacked by it with terrible results.

Cholera gradually made its way in subsequent years through Persia to Russia, and at last to Western Europe; but it was not until late in the year 1831 that Indian cholera arrived for the first time in England, and in the following year it caused something like a panic. There have been at least three subsequent outbursts of Indian cholera (before that of the year 1908) which have reached Europe, and two of these have reached England and caused profound alarm and anxiety. That in 1854 reached us just before the Crimean War, and caused such rapid and numerous deaths in London, especially in the West End (St. James’s, Westminster), that the corpses were removed in carts as in the days of the plague. It was then that the Broad Street pump became famous, and the carefully demonstrated history of a cesspool leaking into the well of the pump, of the existence of a cholera patient in the house to which the cesspool was attached and of the infection with cholera of healthy people who sent all the way from Hampstead to fetch what they thought was the beautifully pure, cool, and palatable water of Broad Street, St. James’s, caused a most vivid and salutary impression on the public mind. The “water-carriage” of the cholera infection was established as a fact, and the subsequent abolition of surface wells and pumps, as well as of cesspools, in London and other cities was the result. Indeed, the active development of sanitation and sanitary measures of all kinds in Great Britain may be traced to the panic caused by the cholera in 1854 and to the well-founded conviction that it was in the power of the community, by the construction of sewers and the provision of untainted water-supply, to protect itself against such disaster in the future.

Years passed by, and still the actual germ of cholera was unknown. In India it was not even admitted that its diffusion was especially connected with water-supply. The methods of observing with the microscope those minute swarming organisms which are called “bacteria” became immensely improved. They were isolated, cultivated in purity, and the activity of a vast number of different kinds of different shapes, sizes, and modes of growth was ascertained. They were distinguished according to their shape as bacilli, spirilla, micrococci, and so on, and separate kinds were characterised—one producing ordinary putrefaction, another the souring of milk, another the “cheesing” of the same fluid, another the destruction of teeth and of bone, another the terrible anthrax of cattle or wool-sorters’ disease, another (a spiral thread in the blood this!) the recurrent fever of East Europe—each producing its own special poison or other chemical substance.

So it went on till Koch, of Berlin, discovered the bacillus of tubercle and Hansen that of leprosy. Others had failed to find what Koch now found as the result of a special mission on behalf of the German Imperial Government to India (undertaken as nearly as I can recollect about the year 1884)—namely, the living organism (Fig. 46) which by its growth in man’s intestine causes Indian cholera. Koch found a spiral threadlike “bacterium” in cholera patients, which readily breaks up into little curved segments like a comma (each less than the one ten-thousandth of an inch in length), and swarms by the million in the intestines of such patients. He showed that it can be cultivated in dilute gelatinised broth, and obtained in spoonfuls. It was, however, only with great difficulty that he could produce cholera in animals by administering this pure concentrated growth of cholera germs to them.

Then a most courageous thing was done. A great and very acute investigator of cholera in Munich, Pettenkofer by name—who did not believe that Koch’s comma-bacillus was really the effective germ of cholera—himself swallowed a whole spoonful—many millions—of the cultivated cholera germ. His assistants did the same—and none of them suffered any ill effect! Few, if any, of the investigators of this question gave up, as a consequence, their conviction that Koch’s bacillus was the real and active cause of cholera. They supposed that it must be necessary for the human intestine to be in a favourable condition—an unhealthy condition—for the Koch’s bacillus to multiply in it. It was by this time known that bacteria of all kinds are exceedingly sensitive in regard to the acidity or alkalinity, the oxygenation or de-oxygenation of the fluids and organic substances in which they can, when exactly suited, multiply with tremendous rapidity. Thus the tubercle bacillus cannot be cultivated on pure blood-serum, but if a trace of glycerine be added to the serum the tubercle bacillus grows, divides, multiplies like yeast in a brewing-vat. A little later Pettenkofer’s audacious experiment was repeated by Dr. Metchnikoff in Paris. He swallowed a cultivated mass of the cholera germ on three successive days, and had no injurious result. Others in his laboratory did the same, with the result of only a slight intestinal disturbance. But of a dozen who thus put the matter to the proof in the Institut Pasteur, one individual acquired an attack of true Indian cholera, accompanied by all the most violent symptoms, which very nearly caused his death. This experiment put an end to all discussion, and demonstrated, once for all, that the comma-bacillus (or spirillum) of Koch is really capable of producing Indian cholera, and is the actual agent of this disease.

The circumstances which determine whether the cholera-bacillus, when it gets into the human intestine, will develop and cause an attack of cholera, or will simply be digested or will remain alive, but inactive, for a time, have yet to be exactly determined. Obviously a knowledge of them must be of immense importance. Certain experiments show that other minute parasitic organisms—especially those called _Sarcina_ (Fig. 46, _e_), which often, but by no means always, are abundant in the human intestine—favour the growth of the cholera-bacillus—in fact, prepare the ground or soil, as we may call it, for that deadly organism. This has been shown experimentally by sowing cholera-bacillus on plates of slightly acid gelatine, or jelly. It will not grow on this, but if at certain points on the surface of the jelly the _Sarcina_ organism is planted, then it is found that all around the points where the _Sarcina_ is growing the cholera-bacillus also flourishes and multiplies. And it seems probable that, just as there are microbes which are adjuvant or helpful to the cholera microbe, so there are others which are repressive or destructive of it. We know that this is the case with regard to some other microbes—namely, that a microbe which will flourish abundantly on a prepared jelly if it is alone, is entirely repressed and arrested in its growth by the presence of one other ascertained kind. It is, in fact, thus that some of the commoner putrefactive kinds of microbes occurring in river water are repressive of the typhoid-bacillus, which, if it should get there, flourishes best in the purest water or in water containing no other microbe. There is some ground for thinking that in certain districts there may be microbes present which make their way into the human intestine, and then actually repress the cholera-bacillus, should it subsequently be taken in with food or water. It would, of course, be of immense importance to discover such a microbe, if it exist, and the inquiry is at the present moment proceeding in Paris.

A very striking and at first sight astonishing fact in regard to this subject is that there are a very large number and variety of microbes habitually present in the human digestive tract. There are so many different kinds—differing altogether from one another in their chemical action—which are present in greater or less abundance in this tract from one end to the other, that no one is at present able to say even approximately how many there are, nor to give anything like a complete account of their properties. The fact is that their isolation and study, and the definite determination of their properties, is not an easy job. Many workers are engaged on it, and it will be years before the matter is threshed out. One most curious result of these studies is that a person may have the cholera-bacillus in his intestine—not growing with any activity, but still alive—and yet be perfectly well. He can, therefore, carry the cholera-bacillus from one locality to another and spread the disease, and yet be entirely devoid of suspicion, free himself from disease, and certified as healthy! The same is true of the bacillus of typhoid fever. Persons who have had typhoid fever have been shown to retain the typhoid-bacillus flourishing for as long as fourteen years afterwards in their intestine, without any ill effects to themselves, and to have been the constant source of infection and disease to those living in the same house with them by spreading the bacillus. The classical case of this is that of a woman who carried on a baker’s business at Strasburg. Infection by and protection from microbes is by no means so simple a thing as it is sometimes represented to be.

Now that we are quite sure as to Koch’s comma-bacillus, or spirillum, being the definite poison-producing agent causing Indian cholera, it is comparatively easy to understand its mode of dispersal and infection, and consequently how to avoid its attack. It is cultivated in the laboratories devoted to the study of such matters—kept in confinement, so to speak, for ten years and more—and its properties and conditions of life are well known. For instance, it is destroyed by “dryness,” hence it cannot be carried in a living infective state as “dust” in the air. It is also destroyed by exposure to a heat a good deal below that of boiling water, so that water itself can be freed from it by boiling, and food dipped in boiling (or nearly boiling) water, or heated on a metal tray beneath which a spirit or gas flame is burning, can be rendered safe just before it is swallowed, even when cholera is rife in the neighbourhood. Ordinary lime is a great destroyer of the bacillus, and can be used on a large scale to abolish it in refuse.

When the cholera is near one cannot be too scrupulously clean. The fingers must be carefully washed with antiseptic before a meal, and everything purified by heat only a few moments before being put into the mouth, since flies and careless handling may soil food or anything else exposed in a cool condition even for a few minutes. It is best when cholera is actually present in the house or town in which you live to swallow nothing which has been allowed to get cool; everything should be heated and eaten when hot. Mephistopheles, in Goethe’s _Faust_, complains of the swarming, pullulating life on the earth. He—the great destroyer—says:

“How many have I sent to grass!
Yet young, fresh blood, do what I will
Keeps ever circulating still.
In water, in the earth, in air,
In wet, dry, cold—everywhere
Germs without number are unfurl’d,
And but for fire, and fire alone,
There would be nothing in the world
That I could truly call my own.”

The version is Sir Theodore Martin’s. Mephistopheles might be a bacteriologist explaining the difficulty of dealing with disease germs. In any case, it is the Mephistophelian spirit of annihilation, and flame as its instrument, which man brings to his service in the contest with cholera germs.

The great carriers of cholera are human beings themselves travelling in caravans, pilgrimages, shiploads. For the fact has now been established that a man may harbour inside him the cholera-bacillus without its multiplying largely or rendering him seriously ill. Once it is brought by such an individual into a favourable locality, it is spread by water contaminated by him, and yet used for drink and domestic purposes; and also it is spread by his touching things in which the bacillus can grow, such as cooked food, fruits, etc., swallowed subsequently by unsuspecting purchasers or employers. You have, in order to avoid cholera (and similar infections), not only to have very clean fingers yourself, but to see to it that your servants’ fingers are clean also, or else that anything they touch is afterwards heated for a few minutes to near boiling-point before you let it enter your mouth. A little history illustrative of the need of this precaution is on record. In Egypt during a recent outbreak of cholera there was a very wealthy lady who lived alone in an isolated palace under the charge of a physician. She had a delicate appetite; her food was most carefully prepared. She drank and used only boiled sterilised water; no one was allowed to approach her except her servants, who never left the palace grounds, and were in good health. She sickened of cholera and died. It was a puzzle as to how she had acquired the infection. Her physician at last discovered that she daily partook of cold chicken-broth, prepared carefully by her cook. The cook, though practically well, was found to be infected with the cholera-bacillus, which had probably lodged in his intestine some weeks previously at the commencement of the outbreak of the disease in Egypt. Though living in him the cholera-bacilli had not found a favourable field of growth. This man in handling the cold broth, the cloth used to rub the spoon with which it was stirred, or the basin itself, had, it was found by making the actual experiment, been able to transfer the minute bacillus to the cold broth, a most favourable and nourishing medium for its growth, and so his isolated carefully guarded employer received an abundant crop of the bacilli and developed a fatal attack of cholera. Had the lady taken the broth hot, there would have been no living cholera-bacillus in it, and if she had thus guarded herself in regard to all food, by the use of heat and great cleanliness, she would have escaped infection.

The most interesting development of knowledge and speculation with regard to the microbes which infest the human intestine and other regions of the human body is (as I mentioned above) connected with the fact that one kind or species of microbe has the power of favouring the growth of another, if present alongside of it, and that another kind has the power of checking or antagonising its growth. Thus common putrefactive microbes of river water are hostile to the cholera-bacillus and to the typhoid-bacillus. Those disease-producing bacilli live longest and best in very pure water! Thus, too, it is found that the microbe of sour milk—the lactic-bacillus—is antagonistic to the common putrefactive microbe of the intestinal contents—the well-known bacillus coli. In virtue of the acid which it produces, the microbe of sour milk arrests the excessive growth and activity of the putrefactive bacillus coli. Hence the utility of sour milk in many cases of intestinal trouble. We contain within us a microbian flora of such variety and abundance of kinds and so nicely balanced in their antagonisms and co-operations in a healthy man, that one cannot wonder at the timidity of the medical man who hesitates to interfere with their conflicts and established _modus vivendi_. Yet that seems to be the direction in which action will have to be taken. It seems likely that in different localities—towns, forests, highlands, lowlands, seaboards—there are prevalent different microbes which enter the bodies of human visitors and act as disturbers of the native microbian flora previously established in the stranger.

That there are great differences in the microbian flora (including herein minute moulds and fungi as well as bacteria) of different localities, is shown by the great experiment of cheese-making which mankind carries on. Each kind of cheese—Stilton, Cheshire, Dutch, Roquefort, Gruyère, Gorgonzola, etc.—is the result of the combined and successive action on milk of a vast number of microbes; and it is the fact that the combination which produces any given kind of cheese is only found and (unconsciously of the exact nature of what he is doing) brought into activity by man at certain places. You cannot make Cheshire cheese in France nor Gruyère in Cheshire, and so on. It is suggested—and the matter is being pursued by experiment and observation at the present time in France—that possibly amongst the other things which go to make up the qualities of the air which agrees or disagrees with one in any given locality—are the local microbes. This must not be regarded as a conclusion which has been fully worked out—it is an ingenious and promising suggestion made by Metchnikoff as the result of some observations, and will be fully inquired into. The fact which I have mentioned above (p. 242)—that the presence of the microbe _Sarcina_ favours the growth of the cholera-bacillus—indeed, enabling it to grow and flourish in conditions in which it was inert until the _Sarcina_ was “sown” alongside of it—renders it worth investigating the question as to whether there are “local” germs or microbes which in this or that region are abundant and get into man’s food and drink, and so into his intestine, and become established there, helping or antagonising the growth of other microbes already there or subsequently introduced. Thus, to the various considerations in regard to the “air” of a locality, such as rarefaction, moisture, temperature, movement, ozone, and the perfumes and exhalations of pine trees, rosemary, and sweet-smelling grasses, which seem to be those which are the most likely to affect the health of inhabitants and visitors, it is not improbable that we must add the influence of an invisible local flora of microbes. The inquiry is a long and laborious one, but it will be carried through. The microbes, whether in air or water, or on the surfaces of things, can be collected by washing them into warm liquid gelatine. Then the gelatine is poured out on a plate, and hardens as a thin sheet of jelly. This is protected from all further contamination, and, after a few hours, each invisible microbe embedded immovably in the jelly makes itself apparent. It multiplies enormously whilst remaining stuck to one spot, and is no longer invisible, but presents itself to the eye as a little sphere, or disc, of characteristic shape, colour, and quality, consisting of many hundred thousands of crowded microbes produced by the growth and division of the original invisible one. Some dozens or some hundreds of little growing “dots,” and of many various kinds, will thus reveal themselves in the jelly according to the number and kinds of utterly invisible parent microbes introduced by your “washings” into the jelly. And so the investigator has the means of getting at each kind of invisible microbe quite detached from the others, and of separating it for further cultivation and experiment as to its chemical and disease-producing qualities. These microbial gardens of jelly-plates are, indeed, a wonderful revelation and a fitting “horticultural” accompaniment to the dark and gloomy forests of rampant wild microbes in our insides, where all are struggling for the soil, one crushing out another by its sheer exuberance, a third choked by the encircling luxuriance of a fourth, just as the trees, mosses, and climbers of a tropical jungle are budding, pushing, grasping, destroying one another in their irrepressible growth.

Pettenkofer, of Munich, when he found (as Metchnikoff did later) that the cholera-bacillus could be swallowed in spoonfuls without producing any harm, came to the conclusion that, though it was a necessary agent of the disease “cholera,” yet that there was still an unknown additional determining “cause” of a local character which must be present in order to render the “cholera-bacillus” effective. Metchnikoff is now seeking this “local” cause and parallel antagonistic causes, in the microbian flora of localities which locally effect an entry into the human body, and are, on the one hand, “favourable,” or on the other hand “antagonistic.” Take as a concrete example Versailles. When cholera has been rife in Paris, there has been no cholera at Versailles. There is something at or about Versailles which does not permit cholera to flourish in men who live there. The guess—the hypothesis—which is being investigated at this moment, is that there is possibly a microbe present at Versailles which enters into the microbial jungle of the intestine of mankind there, and is inimical to, repressive of, the cholera-bacillus when it also arrives there. Similarly, the suggestion is entertained, and is being experimentally tested, that there is in Paris a microbial inhabitant of the intestine which is favourable to the energetic growth of the cholera-bacillus when it puts in an appearance, but that this favouring (as yet undetermined) microbe does not exist at Versailles.

These imaginings and guesses as to favouring and antagonising microbes must not be confused with the definitely ascertained facts as to the cholera-bacillus. But they are quite sufficiently important and probable to justify their narration to a discreet and sympathetic public.

XXVI

SEA-BREEZES, MOUNTAIN AIR, AND OZONE

Fifty years ago people were very fond of talking about “ozone,” and the word is popularly used nowadays to signify a mysterious attribute of the air of the sea-coast or moorland without its real significance being generally understood. When Sir Oliver Lodge the other day warned people against hurting their nasal passages by sniffing up an unduly strong dose of ozone produced by a special ozone-making apparatus, I am inclined to think that most people who read what he said wondered what “ozone” might be.

In the eighteenth century it was noticed that the sparks from a frictional electrical machine are accompanied by a peculiar pungent smell in the air. Many years after that, namely in 1840, the great chemical experimenter, Schönbein, the friend and correspondent of Faraday and discoverer of gun-cotton, found that the smell in question is produced by a special gas, which is formed in the air when electric discharges take place. He found that this gas was a powerful oxydiser—would, in fact, oxydise iodide of potassium so as to set free iodine—and thus its presence could be detected by means of paper slips coated with a mixture of starch and iodide of potassium. When they were exposed in air which contained even minute traces of this strange gas they became purple-blue, owing to the liberation of iodine and the formation of its well-known blue combination with the starch. Schönbein found that in breezy, fresh places his test-papers turned blue, and concluded from that (confirmed by other evidence) that this smelling gas, to which he gave the name ozone—which simply means “the smelling stuff”—is present in good, ordinary atmospheric air, as well as in artificially “electrified” air. It is destroyed when such air is heated above the boiling-point of water, and seems to be, as it were, “taken out” of the air by all sorts of dead organic matter, so that it is not present in the air of large cities. I remember that when I was a boy we used to test the air for ozone with Schönbein’s papers (I am aware that their colour change is not absolute proof of the presence of ozone, as other oxydising gases might, if present, act in the same way), and we used to find more ozone when a south-west wind was blowing than in a north-easter!

Schönbein wrote sixty papers on ozone—but its real nature was made out by others who succeeded him, chiefly by Andrews, of Belfast, and Tait, of Edinburgh. It turns out that ozone is a condensed form of the elemental gas oxygen—squeezed, as it were, and literally “intensified,” so that three measures of oxygen gas become only two of ozone. It very readily changes back again—two measures of ozone expanding to form three of oxygen. It is produced by the action of an electric discharge upon oxygen gas driven over the discharge and in greatest quantity when that kind of gently-buzzing electric spark which is called “the silent discharge” is used. It can be produced in quantity by passing atmospheric air, or better, pure dry oxygen gas through a glass tube in which such a silent discharge is made to take place. As much as seventeen parts in a hundred of the gas can be thus converted into “ozone,” and some twenty years ago two French chemists succeeded in getting even a larger proportion, and by submitting it to a tremendous pressure at a temperature of 100 degrees below the freezing-point of water, they obtained pure ozone as a transparent liquid. It was of a dark indigo-blue colour, and somewhat dangerous and explosive when the pressure under which it had formed was removed. Ordinary oxygen gas has since then been also liquefied in the laboratory: it is of a paler blue colour.