Wonders of Scientific Discovery - Charles Gibson

The Discovery of Microbes

A merchant's hobby—Microscopic living organisms—Spontaneous generation—Pasteur's great discovery—What microbes are like—What they are—Some animal microbes—Microbes and sunlight—Experimenting upon microbes—Frozen meat—Microbes' assistance in bread-making—Microbe scavengers—Protecting the living against the dead—Disease germs—A cold in the head—The way of fighting microbes—Epidemics of enteric fever—Sterilising milk—A world of life beyond the microscope

We have become quite familiar with the idea of a world of invisible microbes existing around and within us. The direct connection between this invisible world and the infectious diseases of the human body has made us realise the great importance of the discovery of microbes. How, then, was this discovery made?

Nearly three hundred years ago a linen draper in Holland made a hobby of microscopy. So enthusiastic was he that he was not content with the simple microscopes of those days. He set about making improvements, and in time made the first true microscope on the principles which we use to-day. Our present interest is not in the instrument, but in what it enabled him to discover. With the aid of this instrument he was able to see minute micro-organisms in water, in the intestines of animals, and in the saliva of the mouth. As these tiny organisms could "swim backwards and forwards and twist themselves in an extremely lively fashion," he thought that they were a low form of animal life, and so he called them "animalcule".

This discovery did not receive much attention, as it was believed that the presence of the microscopic objects was merely accidental, and for a long time those little living organisms were left to themselves. But in the middle of the eighteenth century it was observed that the micro-organisms were always present in any substance undergoing decomposition or putrefaction. Then an Italian priest, Spallanzani, who became a great anatomist, made the discovery that if vegetable matter were hermetically sealed in a flask, and then boiled for some time, no living organisms could be found in it, and so long as it was kept protected from the air decomposition would not set in. When he admitted air to the flask then there were signs of decomposition, and he could trace micro-organisms in the decaying matter.

These early experiments were not extended much until about the middle of the nineteenth century. Then it was discovered that air might be present and do no harm if it was purified by passing it through sulphuric acid, or through tubes raised to a high temperature. In this way it was discovered that the air of itself had no ill effect, but that the air carried the micro-organisms which brought about decomposition.

It had been supposed for a long time that living organisms might arise within vegetable and animal matter and bring about decomposition and putrefaction. The name of "spontaneous generation" was given to the supposed origination of living organisms within a substance, but this discovery of the air carrying the organisms to the substance, and the discovery that the boiled substance kept protected from the air could not decay, went to show that there was no such thing as spontaneous generation. However, it is well known that long-established ideas die hard, and the true death-knell of spontaneous generation was not sounded until the famous French chemist, Louis Pasteur, made a series of further experiments.

Pasteur collected dust from the air, and by placing it in suitable media he was able to obtain these living organisms, proving beyond doubt the invisible world of life did exist in the atmosphere. He took samples of dust from the air of various places. He discovered that in the air of the Swiss mountains there were practically no living organisms. There were more in the air of the valleys, though comparatively few in any fresh country air, whereas in the air of towns there were present a hundred, or even hundreds, for every single one in fresh air.

Although it had been known for some time that these living micro-organisms were present always in putrefying matter, it had not been suggested that they were the cause of the decomposition. This discovery belongs to Pasteur, and the enormous value of this discovery cannot be over-estimated. The layman probably thinks of Pasteur in connection with hydrophobia, but, important as that work was, as we shall see later, it is not of the same far-reaching importance as his earlier discovery.

The first important practical application of Pasteur's discovery, that all fermentation is due to the presence of living micro-organisms, was the work of the late Lord Lister, which will be dealt with in the succeeding chapter.

Before tracing the discovery of microbes in connection with diseases it will be well to form a clear idea of the nature of these tiny organisms. We have seen that at first they were believed to belong to the animal kingdom. It is very amusing to find some intelligent people of to-day picturing microbes as infinitesimally small insects.

On one occasion the present author was examining some photo-micrographs which had been taken by a friend. Among these were some photographs of the cheese-mite, the sheep-tick, and such-like microscopic creatures. There were also some photographs of different bacteria. A visitor happened to ask what the photographs represented. He was told that there were some pictures of microbes among them, and when he saw the uppermost photograph, which happened to be the cheese-mite, he mistook it for a microbe and said, "These are the little villains that hunt us out and give us so much trouble." The average man would not make this mistake, but many people who have taken no special interest in the subject have curious ideas as to the appearance and the capabilities of these microscopic creatures.

Speaking generally, all these micro-organisms belong to the vegetable world, but to describe them as microscopic plants might be a little misleading. They belong to that family of vegetable life which we describe as fungi. But again, we are all familiar with that umbrella-like fungus which we call a mushroom, and which has no leaves or roots or green chlorophyl, but we must not picture microbes as microscopic mushrooms, nor even as moulds. So far as the most powerful microscopes can detect, these microbes are all of very simple construction. Before they can be seen and studied they require to be magnified five hundred to a thousand diameters. Some are in the form of little round cells, some are like tiny rods, while others have a bent or spiral form. There is also a class having a thread-like appearance, known as the higher bacteria. When some microbes are prepared with chemical stains they show little hair-like processes extending from their ends and sides.

In the early days of bacteriology some workers described some micro-organisms as plant animals and others as animal plants. The difficulty was so great that other workers made a class between animal and vegetable, but this only tended to complicate matters. It was because of these difficulties that a French scientist suggested the word "Microbe" (Greek: mikros, small, bios, life), which could include all micro-organisms whether vegetable or animal. To the outsider it might seem ridiculous to worry whether a speck of jelly-like substance was animal or vegetable, but to the scientist it is different, for there is a distinction in their method of assimilating food.

But, as already stated, the great majority of microbes are vegetable; only a very few may be classed as very low forms of animal life. These few include the microbes responsible for the tropical diseases, malaria, sleeping-sickness, and such-like, of which more will be said in the succeeding chapter.

When it was discovered by the bacteriologist that he could grow colonies of the different microbes in suitable media, such as pure beef-broth, he was able to study the life history of each class. It was discovered that there are different methods of reproduction. In the round, the rod-shaped, and the spiral forms the microbe merely becomes constricted at one particular place and then divides into two, each of these parts growing to full-size and then dividing in the same manner as their parent had done.

A second method of reproduction takes place by the formation of a "spore"—a minute glancing globule within each microbe. This is seen in some of the rod-shaped forms. When the spore is freed by the death of the parent microbe, it grows into a young microbe, which in turn at once begins to multiply by division. The rate of multiplication is enormous; thousands may result from a single germ in a few hours, provided the conditions are quite favourable to growth. Fortunately for man all conditions are not favourable, or microbes and not man would be in possession of the planet.

We need not be alarmed by the fact that microbes are all around us, not only in the air we breathe and the water we drink, but within our own bodies. We may go about with the microbe of pneumonia in our mouth and not suffer any inconvenience, for if our tissue is in a healthy condition it does not prove a good breeding-place for microbes. These protective conditions are particularly prominent in the tissue surrounding the entrance to the throat, and also in the tonsils. These parts defy the entrance of intruding microbes. This fact alone should impress us with the great importance of keeping our bodies in a fit condition.

Even if the microbes succeed in entering our blood-vessels, they meet with natural enemies in the blood, as was mentioned in the previous chapter, and this meeting results in a battle. It is the fierceness of this battle which raises the temperature and causes the fever in the invaded person. In most cases the microbes act indirectly by producing chemical poisons that bring about the disastrous effects.

Our special interest centres round the actual discoveries. Having prepared colonies or "cultures" of specific microbes, the bacteriologist can expose these cultures to different conditions and watch the results. He cultivates these colonies by placing some of the microbes in a suitable medium in a test-tube, and then by keeping it at a certain temperature in an incubator he can breed large colonies. In this way it has been discovered that an exposure to sunlight prevents the growth of the microbes. In testing for the effect of sunlight, a tube containing a culture may be covered with black paper to shelter it, and then only a small window cut in the paper to admit the Sun's rays to one particular part; at this place there is an arrestment of growth, while at all the sheltered parts the microbes multiply as usual.

By means of other experiments it was discovered that most microbes could be killed off by heat. Indeed, at a temperature of 150 degrees Fahrenheit few bacteria can live. This temperature is fifty degrees above that of the human body. The discovery that a high temperature spells death to the microbes has led to some practical applications, such as the disinfection of the clothes of infectious patients, the sterilising of milk and other foods, and the sterilising of all surgical instruments and dressings.

Other experiments led to the discovery that some bacteria, although they or their spores can survive an intense degree of cold, have their activities arrested by a freezing temperature. Hence the practical application of freezing or "chilling" meat, in which condition it may be carried from the ends of the Earth without fear of its becoming affected by microbes.

Fortunately it is only a very small variety of microbes that give rise to diseases in man. Many microbes are man's good friends. On one occasion the author was being shown over a large bread factory at work, and when the manager was explaining how at a certain stage the dough or "sponge" was laid aside for an hour and a half, the author remarked that this was to give the microbes another chance of assisting the men in their work, whereupon the manager protested vehemently that there were no microbes in his bread. When it was pointed out that the whole actions of the yeast were due to the activities of microbes, the manager remarked that if that were so "they must be very healthy microbes."

The average man pays more attention to the disease germs than to those others which aid man in all processes in which fermentation plays a part. But far more important than these actions of the microbes is the function of that class which acts as the scavengers of the Earth. What would be the condition of the surface of the Earth if all the carcasses of all the creatures that ever lived had been allowed to accumulate where they fell? What would be our plight if even all the vegetable matter that ever existed had remained, as it was, where it fell? Our thanks are due to myriads of these invisible microbes for ridding us of these dead remains of life; microbes protect the living against the dead. It is the action of the microbes which has decomposed these substances and broken them up into simple elements capable of being assimilated by new vegetation. Here we see a complete cycle of life.

The first disease germ to be discovered was that which produces "anthrax" in cattle, and more rarely in man. More than sixty years ago micro-organisms were discovered in the blood of animals that had succumbed to anthrax (splenic fever), but it could not be proved that the presence of these bacteria was the cause of the trouble. Not for a quarter of a century was there any positive proof to be found, until the great German bacteriologist Robert Koch showed that the disease was entirely consequent upon the invasion of these microbes.

Koch's discovery dates back to 1876, and a few years later was followed by the detection of the microbes which give rise to—suppuration or inflammation, tuberculosis (consumption), tetanus (lock-jaw), diphtheria, typhoid fever, cholera, and others. A little later (1892) an extremely small microbe was discovered to be the cause of that prevalent trouble "influenza." Even an ordinary cold in the head is due to the presence of microbes; quite a large variety are responsible for this common trouble.

Colds are not caught by mere exposure to cold. We have the record of a whaling vessel long away from land, and all the crew perfectly free from colds, although greatly exposed to very low temperatures. But one day the steward brings out an old floor rug that had not been unrolled since leaving land. The steward shakes the rug, and not long afterwards all on board are suffering from cold in the head. In our imagination we see the microbes freed from their captivity and, floating in the air, they enter the breathing apparatus of the sailors.

Similar evidence has been given by Arctic explorers. Again, the survivors of the ill-fated Titanic  were exposed to extreme cold, from which a number of the passengers and crew died, but they did not suffer from cold in the head.

Not long after the different disease germs were isolated and systematically studied, a most valuable discovery was made. It had been found that the harmful agency of microbes was due to chemical poisons or "toxins" which they produced in the blood. Indeed, it had been recognised that in all resulting changes brought about by microbes, whether disease germs or otherwise, their actions were due to these chemical effects. It was found possible to filter a fluid culture of microbes by means of a very fine porcelain filter, so that the microbes were entrapped in the pores of the porcelain, while the poisonous toxins leaked through. An experiment was made with the toxin obtained in this way from diphtheria germs, and when an injection of this toxin was given to an animal it was found to bring about the disease just as though the microbes themselves had been present. Similar results were found to occur with relation to tetanus (lock-jaw). After repeated injections it was found that there was formed in the blood of the animal a substance which was named "anti-toxin." When some blood is drawn from the animal, and allowed to form a clot, there separates a fluid "serum," which if injected into the blood of a person suffering from diphtheria, neutralises the poisons produced by the diphtheric germs. The earlier in the fight this serum is injected the better chance has it of victory. Would anyone object to such experiments being made upon living animals, when thousands of children's lives are saved each year as a result of this one discovery?

Our picture is this. The microbes produce a poison, and the tissues of the body produce an antidote to neutralise it. These facts have been used as a means of diagnosing diseases. A sample of blood is taken from the patient and sent to a bacteriological laboratory. If typhoid fever is suspected, the bacteriologist dilutes a drop of the blood and brings it in contact with typhoid bacteria. If the bacteria become clumped together, he is sure that the patient's case is typhoid fever, for the patient's blood will have no effect upon other disease germs. The same serum diagnosis is carried out in connection with a number of other suspected troubles, such as cholera and meat-poisoning.

It has been discovered that some microbes, such as that of leprosy, cholera, typhoid, and others, which prove so serious in the case of man, have no effect at all when injected into the blood of animals. This is the case with most of man's infectious diseases, and we have the converse, that few of the infectious diseases from which animals suffer have any effect upon nan. On the other hand, it should be noted that such microbes as the typhoid germs may be entrapped by living oysters, placed at the exits of rivers carrying town drainage to the sea. When such oysters have been eaten raw, epidemics of typhoid fever have resulted. The moral is not necessarily to avoid oysters, but to prohibit the placing of oysters in such positions, no matter how well the oysters may thrive there. Within recent years the drainage of large towns is treated so that it is freed of any infectious germs before it enters the river.

Because dead animal flesh is decomposed by microbes we need not be afraid of eating meat, lest some harmful microbes enter our system. We must remember that the microbes that act as the scavengers are not disease germs. These latter are rarely found in meat, and on such rare occasions are probably due to preventable causes.

The germs of enteric, or typhoid, fever have been carried , by ice-cream and have produced epidemics of enteric, but this fact does not condemn the use of ice-cream. In one case when typhoid germs were found in ice-cream which was being sold in the streets of London, it was discovered that the ice-cream had actually been made in a room where a patient was suffering from typhoid fever.

It would not do if we were too easily scared, for there is plenty of proof that at times fresh milk is the means of spreading several kinds of disease germs; it would be a great mistake to avoid the use of milk. It is certainly wise to sterilise the milk, and thus kill off the germs, during any known epidemic in the immediate neighbourhood.

While we have seen immense strides made in our knowledge by the discoveries related in the present chapter, no one must imagine that we have discovered all that exists. Although deliberate search has been made for the germs of such diseases as scarlet fever, measles, and typhus, effort has so far failed. Recent investigations indicate that there exists a world of living organisms beyond the reach of the most powerful microscope. Who can guess what future discoveries are held in store for us or our descendants?