We have seen the microbes, as our servants[1], often performing,
unbeknown to us, the work of purifying and regenerating the soil and
atmosphere. Let us now examine our enemies, for they are numerous.
Everywhere frequent--in the air, in the earth, in the water--they only
await an occasion to introduce themselves into our body in order to
engage in a contest for existence with the cells that make up our
tissues; and, often victorious, they cause death with fearful rapidity.
When we have named charbon, septicæmia, diphtheria, typhoid fever, pork
measles, etc., we shall have indicated the serious affections that
microbes are capable of engendering in the animal organism.
[Footnote 1: SUPPLEMENT, No. 446, page 7125.]
We call those diseases "parasitic" that are occasioned by the
introduction of a living organism into the bodies of animals. Although a
knowledge of such diseases is easy where it concerns parasites such as
acari and worms, it becomes very difficult when it is a question of
diseases that are caused by the Bacteriaceæ. In fact, the germs of these
plants exist in the air in large quantities, as is shown by the analysis
of pure air by a sunbeam, and we are obliged to take minute precautions
to prevent then from invading organic substances. If, then, during an
autopsy of an individual or animal, a microscopic examination reveals
the presence of microbes, we cannot affirm that the latter were the
cause of the affection that it is desired to study, since they might
have introduced themselves during the manipulation, and by reason of
their rapid vegetation have invaded the tissues of the dead animal in
a very short time. The presumption exists, nevertheless, that when
the same form of bacteria is present in the same tissue with the same
affection, it is connected with the disease. This was what Davaine was
the first to show with regard to _Bacillus anthracis_, which causes
charbon. He, in 1850, having examined the blood of an animal that had
died of this disease, found therein amid the globules (Fig. 1), small,
immovable, very narrow rods of a length double that of the blood
corpuscles. It was not till 1863 that he suspected the active role of
these organisms in the charbon malady, and endeavored to demonstrate it
by experiments in inoculation. Is the presence of these little rods in
the blood of an animal that has died of charbon sufficient of itself to
demonstrate the parasitic nature of the affection? No; in order that
the demonstration shall be complete, the bacteria must be isolated,
cultivated in a state of purity in proper liquids, and then be used
to inoculate animals with. If the latter die with all the symptoms
of charbon, the demonstration will be complete. Davaine did, indeed,
perform some experiments in inoculation that were successful, but his
results were contradicted by the experiments of Messrs. Jaillard and
Leplat, and those of Mr. Bert concerning the toxic influence of oxygen
at high tension upon microbes. As Davaine was unable to explain the
contradiction between his results and those of Messrs. Jaillard, Leplat,
and Bert, minds were not as yet convinced, notwithstanding the support
that his ideas received from Mr. Koch's researches.
In 1877 Mr. Pasteur took up Davaine's experiments, and confirmed his
affirmations step by step by employing the method of culture that he had
used with such success in his studies upon fermentation. He isolated
Davaine's bacterium by cultivating it in a decoction of beer yeast that
had been previously sterilized (Fig. 2); and after from ten to twenty
cultures, he found that a portion of the liquid containing a few
bacteria, when used for inoculating a rabbit, quickly caused the latter
to die of charbon, while the same liquid, when filtered through plaster
or porcelain, became harmless.
Davaine's bacterium develops exclusively in the blood, and is never
found at any depth in the tissues. This is due to the fact that the
alga, having need of oxygen in order to live, borrows its flow from the
blood, and thus extracts from the globules that which they should have
carried to the tissue. The animal therefore dies asphyxiated. It is on
account of the absence of oxygen in the blood that the latter assumes
the blackish-brown color that characterizes the malady, and that has
given its name of _charbon_ (coal).
The parasitic nature of charbon was therefore absolutely demonstrated,
first, by the constant presence of _Bacillus anthracis_ in the blood of
anthracoid animals, and second, by the pure culture of the parasite and
the inoculation of animals with charbon by means of it.
Davaine began the demonstration in 1863, and Pasteur finished it in
1877. These facts are now incontestable; yet, to show how slowly truth
is propagated, even in these days of telegraphs and telephones, there
might have been read a few months ago, in an interesting article on
microbes, by Dr. Fol, a distinguished savant, the statement that charbon
and tuberculosis were discovered by Dr. Koch!
New parasitic affections, whose existence was suspected, were soon
discovered and scientifically demonstrated, such, for example, as
septicæmia, or the putrefaction which occurs in living animals, which in
ambulances causes so fearful havoc among the wounded, and which proceeds
from _Bacillus septicus_. This parasite exhibits itself under the form
of little articulated rods that live isolated from oxygen in the mass of
the tissues, and disorganize the latter in disengaging a large quantity
of putrid gas. Other parasites of this class are the _micrococcus_ of
chicken cholera (Fig. 3), the _micrococcus_ of hog measles, and the
_Spirochoete Obermeieri_ of recurrent fever, discovered by Obermeier
(Fig. 5).
Besides these, there are a certain number of maladies that seem as if
they must be due to the Bacteriaceæ, although a demonstration of the
fact by the method of cultures and inoculation has not as yet been
attempted. Among such, we may cite typhoid fever, diphtheria, murrain,
tuberculosis (Fig. 4), malarial fever (Fig. 6), etc.
As may be seen, the list is already a long one, and it tends every day
to still further increase. All the progress that has been made in so
few years in our knowledge of contagious or epidemic diseases is due
exclusively to M. Pasteur and the scientific method that he introduced
through his remarkable labors on fermentation. Now that we know our most
formidable enemies, how shall we defend ourselves against them?
As we have seen, bacteria exist everywhere, mixed with the dust that
interferes with the transparency of the air and covers all objects; and
they are likewise found in water.
Under normal conditions, our body is closed to these organisms through
the epidermis and epithelium, and, as has been shown by Mr. Pasteur, no
bacteria are found in the blood and tissues of living animals. But let a
rupture or wound occur, and bacteria will enter the body, and, when once
the enemy is in place, it will be too late. One sole chance of safety
remains to us, and that is that in the warfare that it is raging against
our tissues the enemy may succumb. M. Pasteur has shown that the blood
corpsucles sometimes engage in the contest against bacterides and
come off victorious. In fact, chickens are proof against poisoning by
charbon, because, owing to the high temperature of their blood, the
bacterides are unable to extract oxygen from the corpuscles thereof.
But, if the chickens be chilled, the conditions are changed, and they
will die of charbon just as do cattle and sheep; but, as the result of
the contest cannot always be foreseen, it is necessary at any cost to
prevent bacterides from entering the body.
[Illustration: I. Bacteria of charbon (_Bacillus antracis_.) II. The
same cultivated in yeast. III. The _Micrococcus_ of chicken cholera. IV.
The _Bacillus_ of tuberculosis. V. The _Spirillun_ of recurrent fever.
VI. The _Bacillus_ of malaria.]
Under ordinary circumstances a severe hygiene will suffice to preserve
us; if a wound is received it should be washed with water mixed with
antiseptics, such as phenic acid, borax, or salicylic acid. If water is
impure, it must be boiled and then aerated before it is drunk. If the
air is the vehicle of the germs of the disease, it will have to be
filtered by means of a muslin curtain kept wet with a hygroscopic
solution, glycerine for example. Finally, when, after an epidemic,
contaminated apartments are to be occupied, the walls and floor and the
clothing must be washed with antiseptic solutions whose nature will vary
according to circumstances--steam charged with phenic acid, water mixed
with a millionth part of sulphuric acid, boric acid, ozone, chlorine,
etc.
These preventives only prove efficient on condition that they be used
persistently. Let our vigilance be lacking for an instant, and the enemy
will enter to work destruction, for it only requires a spore less than
a hundredth of a millimeter in diameter to produce the most serious
affections.
Fortunately, and it is again to Mr. Pasteur that we owe these wonderful
discoveries, the parasitic microbes themselves, which sow sickness and
death, may, through proper culture, become true vaccine viri that are
capable of preserving the organism against any future attack of the
disease that they were capable of producing; such vaccine matters have
been discovered for charbon, chicken cholera, the measles of swine, etc.
When the _micrococcus_ of chicken cholera (Fig. 3.) is cultivated, it
is seen that the activity of the microbe in cultures exposed to the air
gradually diminishes. While a drop of the liquid would, in twenty-four
hours, have killed all the chickens that were inoculated with it, its
effect after two, three, or four days considerably diminishes, and an
inoculation with it produces nothing more than a slight indisposition in
the animal, and one that is never followed by a serious accident. It is
then said that the virulence of the microbe is attenuated.
The air is the agent of this transformation that gradually renders the
bacteria benign, for in cultures made under the same circumstances as
the preceding, but with the absence of air, the activity of these algæ
is preserved for days or weeks, and they will then cause death just as
surely as they would have done at the end of one day.
What is remarkable is that animals inoculated with the attenuated
_micrococcus_ become for a varying length of time refractory to the
action of the most formidable parasites of this kind. Mr. Pasteur has
discovered two such vaccine viri--one for chicken cholera and the other
for charbon. His results have not been accepted without a struggle, and
it required nothing less than public experiment in vaccination, both in
France and abroad, to convince the incredulous. There are still people
at the present time who assert that Mr. Pasteur's process of vaccination
has not a great practical range! And yet, here we have the results; more
than 400,000 animals have been vaccinated since 1881, and it has been
found that the mortality is ten times less in these than in those that
have not been vaccinated!
An impetus has now been given, and we can look to the future with
confidence, for, if our enemies are numerous, the use of a severe
hygiene and preventive vaccination will permit us to gradually free
humanity from the terrible scourges that sap the sources of fortune and
life.--_Science et Nature_.
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