physician, named Koch, [Footnote: This, I believe, was the first
reference to the researches of Koch made in this country. 1879.]
occupied with the duties of his profession in an obscure country
district, was already at work, applying, during his spare time,
various original and ingenious devices to the investigation of splenic
fever. He studied the habits of the rod-like organisms, and found the
aqueous humour an ox's eye to be particularly suitable for their
nutria. With a drop of the aqueous humour he mixed tiniest speck of a
liquid containing the rods, placed the drop under his microscope,
warmed it suitably, and observed the subsequent action. During the
first two hours hardly any change was noticeable; but at the end of
this time the rods began to lengthen, and the action was so rapid that
at the end of three or four hours they attained from ten to twenty
times their original length. At the end of a few additional hours
they had formed filaments in many cases a hundred times the length of
the original rods. The same filament, in fact, was frequently
observed to stretch through several fields of the microscope.
Sometimes they lay in straight lines parallel to each other, in other
cases they were bent, twisted, and coiled into the most graceful
figures; while sometimes they formed knots of such bewildering
complexity that it was impossible for the eye to trace the individual
filaments through the confusion.
Had the observation ended here an interesting scientific fact would
have been added to our previous store, but the addition would have
been of little practical value. Koch, however, continued to watch the
filaments, and after a time noticed little dots appearing within them.
These dots became more and more distinct, until finally the whole
length of the organism was studded with minute ovoid bodies, which lay
within the outer integument like peas within their shell. By-and-by
the integument fell to pieces, the place of the organisms being taken
by a long row of seeds or spores. These observations, which were
confirmed in all respects by the celebrated naturalist, Cohn of
Breslau, are of the highest importance. They clear up the existing
perplexity regarding the latent and visible _contagia_ of splenic fever;
for in the most conclusive manner, Koch proved the spores, as
distinguished from the rods, to constitute the _contagium_ of the fever
in its most deadly and persistent form.
How did he reach this important result? Mark the answer. There was
but one way open to him to test the activity of the _contagium_, and
that was the inoculation with it of living animals. He operated upon
guinea-pigs and rabbits, but the vast majority of his experiments were
made upon mice. Inoculating them with the fresh blood of an animal
suffering from splenic fever, they invariably died of the same disease
within twenty or thirty hours after inoculation. He then sought to
determine how the _contagium_ maintained its vitality. Drying the
infectious blood containing the rod-like organisms, in which, however,
the spores were not developed, he found the _contagium_ to be that which
Dr. Sanderson calls 'fugitive.' It maintained its power of infection
for five weeks at the furthest. He then dried blood containing the
fully-developed spores, and posed the substance to a variety of
conditions. He permitted the dried blood to assume the form of dust;
wetted this dust, allowed it to dry again, permitted it to remain for
an indefinite time in the midst of putrefying matter, and subjected it
to various other tests. After keeping the spore-charged blood which
had been treated in this fashion for four years, he inoculated a
number of mice with it, and found its action as fatal as that of blood
fresh from the veins of an animal suffering from splenic fever. There
was no single escape from death after inoculation by this deadly
_contagium_. Uncounted millions of these spores are developed in the
body of every animal which has died of splenic fever, and every spore
of these millions is competent to produce the disease. The name of
this formidable parasite is Bacillus anthracis. [Footnote: Koch found
that to produce its characteristic effects the _contagium_ of splenic
fever must enter the blood; the virulently festive spleen of a
diseased animal may be eaten with impunity by mice. On the other
hand, the disease refuses to be communicated by inoculation to dogs,
partridges, or sparrows. In their blood Bacillus anthracis ceases to
act as a ferment. Pasteur announced more than six years ago the
propagation of the vibrios of the silkworm disease called _flacherie_,
both by fission and by spores. He also made some remarkable
experiments on the permanence of the _contagium_ in the form of spores.
See 'Etudes sur la Maladie des Vers à Soie,' pp. 168 and 256.]
Now the very first step towards the extirpation of these _contagia_ is
the knowledge of their nature; and the knowledge brought to us by Dr.
Koch will render as certain the stamping out of splenic fever as the
stoppage of the plague of _pébrine_ by the researches of Pasteur.
[Footnote: Surmising that the immunity enjoyed by birds might arise
from the heat of their blood, which destroyed the bacillus, Pasteur
lowered their temperature artificially, inoculated them, and killed
them. He also raised the temperature of guinea-pigs after
inoculation, and saved them. It is needless to dwell for a moment on
the importance of this experiment.] One small item of statistics
will show what this implies. In the single district of Novgorod in
Russia, between the years 1867 and 1870, over fifty-six thousand cases
of death by splenic fever, among horses, cows, and sheep were
recorded. Nor did its ravages confine themselves to the animal world,
for during the time and in the district referred to, five hundred and
twenty-eight human beings perished in the agonies of the same disease.
A description of the fever will help you to come to a right decision
on the point which I wish to submit to your consideration. 'An
animal,' says Dr. Burdon Sanderson, 'which perhaps for the previous
day has declined food and shown signs of general disturbance, begins
to shudder and to have twitches of the muscles of the back, and soon
after becomes weak and listless. In the meantime the respiration
becomes frequent and often difficult, and the temperature rises three
or four degrees above the normal; but soon convulsions, affecting
chiefly the muscles of the back and loins, usher in the final collapse
of which the progress is marked by the loss of all power of moving the
trunk or extremities, diminution of temperature, mucous and
sanguinolent alvine evacuations, and similar discharges from the mouth
and nose.' In a single district of Russia, as above remarked,
fifty-six thousand horses, cows, and sheep, and five hundred and
twenty-eight men and women, perished in this way during a period of
two or three years. What the annual fatality is throughout Europe I
have no means of knowing. Doubtless it must be very great. The
question, then, which I wish to submit to your judgment is this: Is
the knowledge which reveals to us the nature, and which assures the
extirpation, of a disorder so virulent and so vile, worth the price
paid for it? It is exceedingly important that assemblies like the
present should see clearly the issues at stake in such questions as
this, and that the properly informed sense of the community should
temper, if not restrain, the rashness of those who, meaning to be
tender, become agents of cruelty by the imposition of short-sighted
restrictions upon physiological investigations. It is a modern
instance of zeal for God, but not according to knowledge, the excesses
of which must be corrected by an instructed public opinion.
*****
And now let us cast a backward glance on the field we have traversed,
and try to extract from our labours such further profit as they can
yield. For more than two thousand years the attraction of light
bodies by amber was the sum of human knowledge regarding electricity,
and for more than two thousand years fermentation was effected without
any knowledge of its cause. In science one discovery grows out of
another, and cannot appear without its proper antecedent. Thus,
before fermentation could be understood, the microscope had to be
invented, and brought to a considerable degree of perfection. Note
the growth of knowledge. Leeuwenhoek, in 1680, found yeast to be a
mass of floating globules, but he had no notion that the globules were
alive. This was proved in 1835 by Cagniard de la Tour and Schwann.
Then came the question as to the origin of such microscopic organisms,
and in this connection '`the memoir of Pasteur, published in the
'Annales de Chimie' for 1862, is the inauguration of a new epoch.
On that investigation all Pasteur's subsequent labours were based.
Ravages had over and over again occurred among French wines. There
was no guarantee that they ould not become acid or bitter, particularly
when exported. The commerce in wines was thus restricted, and disastrous
losses were ften inflicted on the wine-grower. Every one of these
diseases was traced to the life of an organism. Pasteur ascertained the
temperature which killed these ferments of disease, proving it to be
so low as to be perfectly harmless to the wine. By the simple
expedient of heating the wine to a temperature of fifty degrees
Centigrade, he rendered it inalterable, and thus saved his country the
loss of millions. He then went on to vinegar--vin aigre, acid
wine--which he proved to be produced by a fermentation set up by a
little fungus called Mycoderma aceti. Torula, in fact, converts the
grape juice into alcohol, and Mycoderma aceti converts the alcohol
into vinegar. Here also frequent failures occurred, and severe losses
were sustained. Through the operation of unknown causes, the vinegar
often became unfit for use, sometimes indeed falling into utter
putridity. It had been long known that mere exposure to the air was
sufficient to destroy it. Pasteur studied all these changes, traced
them to their living causes, and showed that the permanent health of
the vinegar was ensured by the destruction of this life. He passed
from the diseases of vinegar to the study of a malady which a dozen
years ago had all but ruined the silk husbandry of France. This
plague, which received the name of _pébrine_, was the product of a
parasite which first took possession of the intestinal canal of the
silkworm, spread throughout its body, and filled the sack which ought
to contain the viscid matter of the silk. Thus smitten, the worm
would go automatically through the process of spinning when it had
nothing to spin.
Pasteur followed this parasitic destroyer from year to year, and led
by his singular power of combining facts with the logic of facts,
discovered eventually the precise phase in the development of the
insect when the disease which assailed it could with certainty be
stamped out. Pasteur's devotion to this enquiry cost him dear. He
restored to France her silk husbandry, rescued thousands of her
population from ruin, set the looms of Italy also to work, but emerged
from his labours with one of his sides permanently paralysed. His
last investigation is embodied in a work entitled 'Studies on Beer,'
in which he describes a method of rendering beer permanently
unchangeable. That method is not so simple as those found effectual
with wine and vinegar, but the principles which it involves are sure
to receive extensive application at some future day.
There are other reflections connected with this subject which, even
were they now passed over without remark, would sooner or later occur
to every thoughtful mind in this assembly. I have spoken of the
floating dust of the air, of the means of rendering it visible, and of
the perfect immunity from putrefaction which accompanies the contact
of germless infusions and moteless air. Consider the woes which these
wafted particles, during historic and pre-historic ages, have
inflicted on mankind; consider the loss of life in hospitals from
putrefying wounds; consider the loss in places where there are plenty
of wounds, but no hospitals, and in the ages before hospitals were
anywhere founded; consider the slaughter which has hitherto followed
that of the battlefield, when those bacterial destroyers are let
loose, often producing a mortality far greater than that of the battle
itself; add to this the other conception that in times of epidemic
disease the self-same floating matter has frequently, if not always,
mingled with it the special germs which produce the epidemic, being
thus enabled to sow pestilence and death over nations and
continents--consider all this, and you will come with me to the
conclusion that all the havoc of war, ten times multiplied, would be
evanescent if compared with the ravages due to atmospheric dust.
This preventible destruction is going on to-day, and it has been
permitted to go on for ages, without a whisper of information
regarding its cause being vouchsafed to the suffering sentient world.
We have been scourged by invisible thongs, attacked from impenetrable
ambuscades, and it is only to-day that the light of science is being
let in upon the murderous dominion of our foes. Facts like these
excite in me the thought that the rule and governance of this universe
are different from what we in our youth supposed them to be--that the
inscrutable Power, at once terrible and beneficent, in whom we live
and move and have our being and our end, is to be propitiated by means
different to those usually resorted to. The first requisite towards
such propitiation is knowledge; the second is action, shaped and
illuminated by that knowledge. Of knowledge we already see the dawn,
which will open out by-and-by to perfect day; while the action which
is to follow has its unfailing source and stimulus in the moral and
emotional nature of man--in his desire for personal well-being, in his
sense of duty, in his compassionate sympathy with the sufferings of
his fellow-men. 'How often,' says Dr. William Budd in his celebrated
work on Typhoid Fever,--' How often have I seen in past days, in the
single narrow chamber of the day-labourer's cottage the father in the
coffin, the mother in the sick-bed in muttering delirium, and nothing
to relieve the desolation of the children but the devotion of some
poor neighbour, who in too many cases paid the penalty of kindness in
becoming herself the victim of the same disorder!' From the vantage
ground already won I look forward with confident hope to the triumph
of medical art over scenes of misery like that here described. The
cause of the calamity being once clearly revealed, not only to the
physician, but to the public, whose intelligent co-operation is
absolutely essential to success, the final victory of humanity is only
a question of time. We have already a foretaste of that victory in
the triumphs f surgery as practised at your doors.
********************
XIII. SPONTANEOUS GENERATION.
[Footnote: The Nineteenth Century, January 1878.]
WITHIN ten minutes' walk of a little cottage which I have recently
built in the Alps, there is a small lake, fed by the melted snows of
the upper mountains. During the early weeks of summer no trace of
life is to be discerned in this water; but invariably towards the end
of July, or the beginning of August, swarms of tailed organisms are
seen enjoying the sun's warmth along the shallow margins of the lake,
and rushing with audible patter into deeper water at the approach of
danger. The origin of this periodic crowd of living things is by no
means obvious. For years I had never noticed in the lake either an
adult frog, or the smallest fragment of frog spawn; so that were I not
otherwise informed, I should have found the conclusion of Mathiole a
natural one, namely, that tadpoles are generated in lake mud by the
vivifying action of the sun.
The checks which experience alone can furnish being absent, the
spontaneous generation of creatures quite as high as the frog in the
scale of being was assumed for ages to be a fact. Here, as elsewhere,
the dominant mind of Aristotle stamped its notions on the world at
large. For nearly twenty centuries after him men found no difficulty
in believing in cases of spontaneous generation which would now be
rejected as monstrous by the most fanatical supporter of the doctrine.
Shell-fish of all kinds were considered to be without parental origin.
Eels were supposed to spring spontaneously from the fat ooze of the
Nile. Caterpillars were the spontaneous products of the leaves on
which they fed; while winged insects, serpents, rats, and mice were
all thought capable of being generated without sexual intervention.
The most copious source of this life without an ancestry was
putrefying flesh; and, lacking the checks imposed by fuller
investigation, the conclusion that flesh possesses and exerts this
generative power is a natural one. I well remember when a child of
ten or twelve seeing a joint of imperfectly salted beef cut into, and
coils of maggots laid bare within the mass. Without a moment's
hesitation I jumped to the conclusion that these maggots had been
spontaneously generated in the meat. I had no knowledge which could
qualify or oppose this conclusion, and for the time it was
irresistible. The childhood of the individual typifies that of the
race, and the belief here enunciated was that of the world for nearly
two thousand years.
To the examination of this very point the celebrated Francesco Redi,
physician to the Grand Dukes Ferdinand II. and Cosmo III. of
Tuscany, and a member of the Academy del Cimento, addressed himself in
1668. He had seen the maggots of putrefying flesh, and reflected on
their possible origin. But he was not content with mere reflection,
nor with the theoretic guesswork which his predecessors had founded
upon their imperfect observations. Watching meat during its passage
from freshness to decay, prior to the appearance of maggots he
invariably observed flies buzzing round the meat and frequently
alighting on it. The maggots, he thought, might be the half-developed
progeny of these flies.
The inductive guess precedes experiment, by which, however, it must be
finally tested. Redi knew this, and acted accordingly. Placing fresh
meat in a jar and covering the mouth with paper, he found that, though
the meat putrefied in the ordinary way, it never bred maggots, while
the same meat placed in open jars soon swarmed with these organisms.
For the paper cover he then substituted fine gauze, through which the
odour of the meat could rise. Over it the flies buzzed, and on it
they laid their eggs, but, the meshes being too small to permit the
eggs to fall through, no maggots were generated in the meat. They
were, on the contrary, hatched upon the gauze. By a series of such
experiments Redi destroyed the belief in the spontaneous generation of
maggots in meat, and with it doubtless many related beliefs. The
combat was continued by Vallisneri, Schwammerdam, and Réaumur, who
succeeded in banishing the notion of spontaneous generation from the
scientific minds of their day. Indeed, as regards such complex
organisms as those which formed the subject of their researches, the
notion was banished for ever.
But the discovery and improvement of the microscope, though giving a
death-blow to much that had been previously written and believed
regarding spontaneous generation, brought also into view a world of
life formed of individuals so minute--so close as it seemed to the
ultimate particles of matter--as to suggest an easy passage from atoms
to organisms. Animal and vegetable infusions exposed to the air were
found clouded and crowded with creatures far beyond the reach of
unaided vision, but perfectly visible to an eye strengthened by the
microscope. With reference to their origin these organisms were
called 'Infusoria. Stagnant pools were found full of them, and the
obvious difficulty of assigning a germinal origin to existences so
minute furnished the precise condition necessary to give new play to
the notion of heterogenesis or spontaneous generation.
The scientific world was soon divided into two hostile camps, the
leaders of which only can here be briefly alluded to. On the one
side, we have Buffon and Needham, the former postulating his 'organic
molecules,' and the latter assuming the existence of a special
'vegetative force' which drew the molecules together so as to form
living things. On the other side, we have the celebrated Abbé Lazzaro
Spallanzani, who in 1777 published results counter to those announced
by Needham in 1748, and obtained by methods so precise as to
completely overthrow the convictions based upon the labours of his
predecessor. Charging his flasks with organic infusions, he sealed
their necks with the blowpipe, subjected them in this condition to the
heat of boiling water, and subsequently exposed them to temperatures
favourable to the development of life. The infusions continued
unchanged for months, and when the flasks were subsequently opened no
trace of life was found.
Here I may forestall matters so far as to say that the success of
Spallanzani's experiments depended wholly on the locality in which he
worked. The air around him must have been free from the more obdurate
infusorial germs, for otherwise the process he followed would, as was
long afterwards proved by Wyman, have infallibly yielded life. But
his refutation of the doctrine of spontaneous generation is not the
less valid on this account. Nor is it in any way upset by the fact,
that others in repeating his experiments obtained life where he
obtained none. Rather is the refutation strengthened by such
differences. Given two experimenters equally skilful and equally
careful, operating in different places on the same infusion, in the
same way, and assuming the one to obtain life while the other fails to
obtain it; then its well-established absence in the one case proves
that some ingredient foreign to the infusion must be its cause in the
other.
Spallanzani's sealed flasks contained but small quantities of air, and
as oxygen was afterwards shown to be generally essential to life, it
was thought that the absence of life observed by Spallanzani might
have been due to the lack of this vitalising gas. To dissipate this
doubt, Schulze in 1836 half filled a flask with distilled water to
which animal and vegetable matters were added. First boiling his
infusion to destroy whatever life it might contain, Schulze sucked
daily into his flask air which had passed through a series of bulbs
containing concentrated sulphuric acid, where all germs of life
suspended in the air were supposed to be destroyed. From May to
August this process was continued without any development of
infusorial life.
Here again the success of Schulze was due to his working in
comparatively pure air, but even in such air his experiment is a very
risky one. Germs will pass unwetted and unscathed through sulphuric
acid unless the most special care is taken to detain them. I have
repeatedly failed, by repeating Schulze's experiments, to obtain his
results. Others have failed likewise. The air passes in bubbles
through the bulbs, and to render the method secure, the passage of the
air must be so slow as to cause the whole of its floating matter, even
to the very core of each bubble, to touch the surrounding liquid. But
if this precaution be observed, water will be found quite as effectual
as sulphuric acid. By the aid of an air-pump, in a highly infective
atmosphere I have thus drawn air for weeks without intermission, first
through bulbs containing water, and afterwards through vessels containing
organic infusions, without any appearance of life. The germs were not
killed by the water, but they were effectually intercepted, while the
objection that the air had been injured by being brought into contact
with strongly corrosive substances was avoided.
The brief paper of Schulze, published in Poggendorf's Annalen for
1836, was followed in 1837 by another short and pregnant communication
by Schwann.