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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
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
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
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
sub-  stance 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
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
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
Our special interest centres round the actual discoveries. Having prepared colonies or "cultures" of
 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
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
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?