_An Address delivered August 2, 1877, on the Anniversary of the
Foundation of the Institute for the Education of Army Surgeons._
It is now thirty-five years since, on the 2nd August, I stood on the
rostrum in the Hall of this Institute, before another such audience as
this, and read a paper on the operation of Venal Tumours. I was then
a pupil of this Institution, and was just at the end of my studies. I
had never seen a tumour cut, and the subject-matter of my lecture was
merely compiled from books; but book knowledge played at that time a
far wider and a far more influential part in medicine than we are at
present disposed to assign to it. It was a period of fermentation,
of the fight between learned tradition and the new spirit of natural
science, which would have no more of tradition, but wished to depend
upon individual experience. The authorities at that time judged more
favourably of my Essay than I did myself, and I still possess the
books which were awarded to me as the prize.
The recollections which crowd in upon me on this occasion have brought
vividly before my mind a picture of the then condition of our science,
of our endeavours and of our hopes, and have led me to compare the past
state of things with that into which it has developed. Much indeed has
been accomplished.
Although all that we hoped for has not been fulfilled, and many things
have turned out differently from what we wished, yet we have gained
much for which we could not have dared to hope. Just as the history of
the world has made one of its few giant steps before our eyes, so also
has our science; hence an old student, like myself, scarcely recognises
the somewhat matronly aspect of Dame Medicine, when he accidentally
comes again in relation to her, so vigorous and so capable of growth
has she become in the fountain of youth of the Natural Sciences.
I may, perhaps, retain the impression of this antagonism, more freshly
than those of my contemporaries whom I have the honour to see assembled
before me; and who, having remained permanently connected with science
and practice, have been less struck and less surprised by great
changes, taking place as they do by slow steps. This must be my excuse
for speaking to you about the metamorphosis which has taken place in
medicine during this period, and with the results of whose development
you are better acquainted than I am. I should like the impression
of this development and of its causes not to be quite lost on the
younger of my hearers. They have no special incentive for consulting
the literature of that period; they would meet with principles which
appear as if written in a lost tongue, so that it is by no means easy
for us to transfer ourselves into the mode of thought of a period
which is so far behind us. The course of development of medicine is an
instructive lesson on the true principles of scientific inquiry, and
the positive part of this lesson has, perhaps, in no previous time been
so impressively taught as in the last generation.
The task falls to me, of teaching that branch of the natural sciences
which has to make the widest generalisations, and has to discuss the
meaning of fundamental ideas; and which has, on that account, been not
unfitly termed Natural Philosophy by the English-speaking peoples.
Hence it does not fall too far out of the range of my official duties
and of my own studies, if I attempt to discourse here of the principles
of scientific method, in reference to the sciences of experience.
As regards my acquaintance with the tone of thought of the older
medicine, independently of the general obligation, incumbent on every
educated physician, of understanding the literature of his science and
the direction as well as the conditions of its progress, there was in
my case a special incentive. In my first professorship at Königsberg,
from the year 1849 to 1856, I had to lecture each winter on general
pathology--that is, on that part of the subject which contains the
general theoretical conceptions of the nature of disease, and of the
principles of its treatment.
General pathology was regarded by our elders as the fairest blossom of
medical science. But in fact, that which formed its essence possesses
only historical interest for the disciples of modern natural science.
Many of my predecessors have broken a lance for the scientific defence
of this essence, and more especially Henle and Lotz. The latter, whose
starting-point was also medicine, had, in his general pathology and
therapeutics, arranged it very thoroughly and methodically and with
great critical acumen.
My own original inclination was towards physics; external circumstances
compelled me to commence the study of medicine, which was made
possible to me by the liberal arrangements of this Institution. It
had, however, been the custom of a former time to combine the study
of medicine with that of the Natural Sciences, and whatever in this
was compulsory I must consider fortunate; not merely that I entered
medicine at a time in which any one who was even moderately at home in
physical considerations found a fruitful virgin soil for cultivation;
but I consider the study of medicine to have been that training which
preached more impressively and more convincingly than any other
could have done, the everlasting principles of all scientific work;
principles which are so simple and yet are ever forgotten again; so
clear and yet always hidden by a deceptive veil.
Perhaps only he can appreciate the immense importance and the fearful
practical scope of the problems of medical theory, who has watched the
fading eye of approaching death, and witnessed the distracted grief
of affection, and who has asked himself the solemn questions, Has all
been done which could be done to ward off the dread event? Have all
the resources and all the means which Science has accumulated become
exhausted?
Provided that he remains undisturbed in his study, the purely
theoretical inquirer may smile with calm contempt when, for a time,
vanity and conceit seek to swell themselves in science and stir up a
commotion. Or he may consider ancient prejudices to be interesting and
pardonable, as remains of poetic romance, or of youthful enthusiasm. To
one who has to contend with the hostile forces of fact, indifference
and romance disappear; that which he knows and can do, is exposed to
severe tests; he can only use the hard and clear light of facts, and
must give up the notion of lulling himself in agreeable illusions.
I rejoice, therefore, that I can once more address an assembly
consisting almost exclusively of medical men who have gone through the
same school. Medicine was once the intellectual home in which I grew
up, and even the emigrant best understands and is best understood by
his native land.
If I am called upon to designate in one word the fundamental error
of that former time, I should be inclined to say that it pursued a
false ideal of science in a one-sided and erroneous reverence for
the deductive method. Medicine, it is true, was not the only science
which was involved in this error, but in no other science have the
consequences been so glaring, or have so hindered progress, as in
medicine. The history of this science claims, therefore, a special
interest in the history of the development of the human mind. None
other is, perhaps, more fitted to show that a true criticism of the
sources of cognition is also practically an exceedingly important
object of true philosophy.
The proud word of Hippokrates,
ἰητρὸς φιλόσοφος ἰσόθεος,
‘Godlike is the physician who is a philosopher’, served,
as it were, as a banner of the old deductive medicine.
We may admit this if only we once agree what we are to understand as
a philosopher. For the ancients, philosophy embraced all theoretical
knowledge; their philosophers pursued Mathematics, Physics, Astronomy,
Natural History, in close connection with true philosophical or
metaphysical considerations. If, therefore, we are to understand the
medical philosopher of Hippokrates to be a man who has a _perfected_
insight into the causal connection of natural processes, we shall in
fact be able to say with Hippokrates, such a one can give help like a
god.
Understood in this sense, the aphorism describes in three words the
ideal which our science has to strive after. But who can allege that it
will ever attain this ideal?
But those disciples of medicine who thought themselves divine even in
their own lifetime, and who wished to impose themselves upon others as
such, were not inclined to postpone their hopes for so long a period.
The requirements for the φιλόσοφος were considerably moderated. Every
adherent of any given cosmological system, in which, for well or ill,
facts must be made to correspond with reality, felt himself to be a
philosopher. The philosophers of that time knew little more of the laws
of Nature than the unlearned layman; but the stress of their endeavours
was laid upon thinking, upon the logical consequence and completeness
of the system. It is not difficult to understand how in periods of
youthful development, such a one-sided over-estimate of thought could
be arrived at. The superiority of man over animals, of the scholar over
the barbarian, depends upon thinking; sensation, feeling, perception,
on the contrary, he shares with his lower fellow-creatures, and in
acuteness of the senses many of these are even superior to him. That
man strives to develop his thinking faculty to the utmost is a problem
on the solution of which the feeling of his own dignity, as well as of
his own practical power, depends; and it is a natural error to have
considered unimportant the dowry of mental capacities which Nature had
given to animals, and to have believed that thought could be liberated
from its natural basis, observation and perception, to begin its
Icarian flight of metaphysical speculation.
It is, in fact, no easy problem to ascertain completely the origins of
our knowledge. An enormous amount is transmitted by speech and writing.
This power which man possesses of gathering together the stores of
knowledge of generations, is the chief reason of his superiority over
the animal, who is restricted to an inherited blind instinct and to
its individual experience. But all transmitted knowledge is handed
on already formed; whence the reporter has derived it, or how much
criticism he has bestowed upon it, can seldom be made out, especially
if the tradition has been handed down through several generations. We
must admit it all upon good faith; we cannot arrive at the source; and
when many generations have contented themselves with such knowledge,
have brought no criticism to bear upon it; have, indeed, gradually
added all kinds of small alterations, which ultimately grew up to large
ones--after all this, strange things are often reported and believed
under the authority of primeval wisdom. A curious case of this kind is
the history of the circulation of the blood, of which we shall still
have to speak.
But another kind of tradition by speech, which long remained
undetected, is even still more confusing for one who reflects upon
the origin of knowledge. Speech cannot readily develop names for
classes of objects or for classes of processes, if we have not
been accustomed very often to mention together the corresponding
individuals, things, and separate cases, and to assert what there is
in common about them. They must, therefore, possess many points in
common. Or if we, reflecting scientifically upon this, select some
of these characteristics, and collate them to form a definition, the
common possession of these selected characteristics must necessitate
that in the given cases a great number of other characteristics are
to be regularly met with; there must be a natural connection between
the first and the last named characteristics. If, for instance, we
assign the name of mammals to those animals which, when young, are
suckled by their mothers, we can assert further, in reference to
them, that they are all warm-blooded animals, born alive, that they
have a spinal column but no quadrate bone, breathe through lungs,
have separate divisions of the heart, &c. Hence the fact, that in the
speech of an intelligent observing people a certain class of things are
included in one name, indicates that these things or cases fall under
a common natural relationship; by this alone a host of experiences are
transmitted from preceding generations without this appearing to be the
case.
The adult, moreover, when he begins to reflect upon the origin of his
knowledge, is in possession of a huge mass of everyday experiences,
which in great part reach back to the obscurity of his first childhood.
Everything individual has long been forgotten, but the similar traces
which the daily repetition of similar cases has left in his memory have
deeply engraved themselves. And since only that which is in conformity
with law is always repeated with regularity, these deeply impressed
remains of all previous conceptions are just the conceptions of what is
conformable to law in the things and processes.
Thus man, when he begins to reflect, finds that he possesses a wide
range of acquirements of which he knows not whence they came, which he
has possessed as long as he can remember. We need not refer even to
the possibility of inheritance by procreation.
The conceptions which he has formed, which his mother tongue has
transmitted, assert themselves as regulative powers, even in the
objective world of fact, and as he does not know that he or his
forefathers have developed these conceptions from the things
themselves, the world of facts seems to him, like his conceptions, to
be governed by intellectual forces. We recognise this psychological
anthropomorphism, from the _Ideas_ of Plato, to the immanent dialectic
of the cosmical process of Hegel, and to the unconscious will of
Schopenhauer.
Natural science, which in former times was virtually identical with
medicine, followed the path of philosophy; the deductive method seemed
to be capable of doing everything. Socrates, it is true, had developed
the inductive conception in the most instructive manner. But the best
which he accomplished remained virtually misunderstood.
I will not lead you through the motley confusion of pathological
theories which, according to the varying inclination of their authors,
sprouted up in consequence of this or the other increase of natural
knowledge, and were mostly put forth by physicians, who obtained fame
and renown as great observers and empirics, independently of their
theories. Then came the less gifted pupils, who copied their master,
exaggerated his theory, made it more one-sided and more logical,
without regard to any discordance with Nature. The more rigid the
system, the fewer and the more thorough were the methods to which the
healing art was restricted. The more the schools were driven into a
corner by the increase in actual knowledge, the more did they depend
upon the ancient authorities, and the more intolerant were they
against innovation. The great reformer of anatomy, Vesalius, was cited
before the Theological faculty of Salamanca; Servetus was burned at
Geneva along with his book, in which he described the circulation of
the lungs; and the Paris faculty prohibited the teaching of Harvey’s
doctrine of the circulation of the blood in its lecture rooms.
At the same time the bases of the systems from which these schools
started were mostly views on natural science which it would have been
quite right to utilise within a narrow circle. What was not right was
the delusion that it was more scientific to refer all diseases to one
kind of explanation, than to several. What was called the solidar
pathology wanted to deduce everything from the altered mechanism of
the solid parts, especially from their altered tension; from the
_strictum_ and _laxum_, from tone and want of tone, and afterwards
from strained or relaxed nerves and from obstructions in the vessels.
Humoral pathology was only acquainted with alterations in mixture.
The four cardinal fluids, representatives of the classical four
elements, blood, phlegm, black and yellow gall; with others, the
acrimonies or dyscrasies, which had to be expelled by sweating and
purging; in the beginning of our modern epoch, the acids and alkalies
or the alchymistic spirits, and the occult qualities of the substances
assimilated--all these were the elements of this chemistry. Along with
these were found all kinds of physiological conceptions, some of which
contained remarkable foreshadowings, such as the ἔμφυτον θέρμον, the
inherent vital force of Hippokrates, which is kept up by nutritive
substances, this again boils in the stomach and is the source of all
motion; here the thread is begun to be spun which subsequently led a
physician to the law of the conservation of force. On the other hand,
the =πνεῦμα=, which is half spirit and half air, which can be driven
from the lungs into the arteries and fills them, has produced much
confusion. The fact that air is generally found in the arteries of dead
bodies, which indeed only penetrates in the moment in which the vessels
are cut, led the ancients to the belief that air is also present in the
arteries during life. The veins only remained then in which blood could
circulate. It was believed to be formed in the liver, to move from
there to the heart, and through the veins to the organs. Any careful
observation of the operation of blood-letting must have taught that, in
the veins, it comes from the periphery, and flows towards the heart.
But this false theory had become so mixed up with the explanation of
fever and of inflammation, that it acquired the authority of a dogma,
which it was dangerous to attack.
Yet the essential and fundamental error of this system was, and still
continued to be, the false kind of logical conclusion to which it was
supposed to lead; the conception that it must be possible to build a
complete system which would embrace all forms of disease, and their
cure, upon any one such simple explanation. Complete knowledge of the
causal connection of one class of phenomena gives finally a logical
coherent system. There is no prouder edifice of the most exact thought
than modern astronomy, deduced even to the minutest of its small
disturbances, from Newton’s law of gravitation. But Newton had been
preceded by Kepler, who had by induction collated all the facts; and
the astronomers have never believed that Newton’s force excluded the
simultaneous action of other forces. They have been continually on the
watch to see whether friction, resisting media, and swarms of meteors
have not also some influence. The older philosophers and physicians
believed they could deduce, before they had settled their general
principles by induction. They forgot that a deduction can have no more
certainty than the principle from which it is deduced; and that each
new induction must in the first place be a new test, by experience, of
its own bases. That a conclusion is deduced by the strictest logical
method from an uncertain premise does not give it a hair’s breadth of
certainty or of value.
One characteristic of the schools which built up their system on
such hypotheses, which they assumed as dogmas, is the intolerance of
expression which I have already partially mentioned. One who works upon
a well-ascertained foundation may readily admit an error; he loses, by
so doing, nothing more than that in which he erred. If, however, the
starting-point has been placed upon a hypothesis, which either appears
guaranteed by authority, or is only chosen because it agrees with that
which it is _wished_ to believe true, any crack may then hopelessly
destroy the whole fabric of conviction. The convinced disciples must
therefore claim for each individual part of such a fabric the same
degree of infallibility; for the anatomy of Hippokrates just as much
as for fever crises; every opponent must only appear then as stupid or
depraved, and the dispute will thus, according to old precedent, be
so much the more passionate and personal, the more uncertain is the
basis which is defended. We have frequent opportunities of confirming
these general rules in the schools of dogmatic deductive medicine.
They turned their intolerance partly against each other, and partly
against the eclectics who found various explanations for various forms
of disease. This method, which in its essence is completely justified,
had, in the eyes of systematists, the defect of being illogical. And
yet the greatest physicians and observers, Hippokrates at the head,
Aretæus, Galen, Sydenham, and Boerhaave, had become eclectics, or at
any rate very lax systematists.
About the time when we seniors commenced the study of medicine, it was
still under the influence of the important discoveries which Albrecht
von Haller had made on the excitability of nerves; and which he had
placed in connection with the vitalistic theory of the nature of
life. Haller had observed the excitability in the nerves and muscles
of amputated members. The most surprising thing to him was, that the
most varied external actions, mechanical, chemical, thermal, to which
electrical ones were subsequently added, had always the same result;
namely, that they produced muscular contraction. They were only
quantitatively distinguished as regards their action on the organism,
that is, only by the strength of the excitation; he designated them
by the common name of _stimulus_; he called the altered condition
of the nerve the _excitation_, and its capacity of responding to a
stimulus the _excitability_, which was lost at death. This entire
condition of things, which physically speaking asserts no more than
that the nerves, as concerns the changes which take place in them after
excitation, are in an exceedingly unstable state of equilibrium; this
was looked upon as the fundamental property of animal life, and was
unhesitatingly transferred to the other organs and tissues of the body,
for which there was no similar justification. It was believed that none
of them were active of themselves, but must receive an impulse by a
stimulus from without; air and nourishment were considered to be the
normal stimuli. The _kind_ of activity seemed, on the contrary, to be
conditioned by the specific energy of the organ, under the influence
of the vital force. Increase or diminution of the excitability was the
category under which the whole of the acute diseases were referred, and
from which indications were taken as to whether the treatment should be
lowering or stimulating. The rigid one-sidedness and the unrelenting
logic with which Robert Brown had once worked out this system was
broken, but it always furnished the leading points of view.
The vital force had formerly lodged as ethereal spirit, as a Pneuma
in the arteries; it had then with Paracelsus acquired the form of an
Archeus, a kind of useful Kobold, or indwelling alchymist, and had
acquired its clearest scientific position as ‘soul of life’, _anima
inscia_, in Georg Ernst Stahl, who, in the first half of the last
century, was professor of chemistry and pathology in Halle. Stahl had a
clear and acute mind, which is informing and stimulating, from the way
in which he states the proper question, even in those cases in which he
decides against our present views. He it is who established the first
comprehensive system of chemistry, that of phlogiston. If we translate
his phlogiston into latent heat, the theoretical bases of his system
passed essentially into the system of Lavoisier; Stahl did not then
know oxygen, which occasioned some false hypotheses; for instance, on
the negative gravity of phlogiston. Stahl’s ‘soul of life’ is, on the
whole, constructed on the pattern on which the pietistic communities
of that period represented to themselves the sinful human soul; it is
subject to errors and passions, to sloth, fear, impatience, sorrow,
indiscretion, despair. The physician must first appease it, or then
incite it, or punish it, and compel it to repent. And the way in which,
at the same time, he established the necessity of the physical and
vital actions was well thought out. The soul of life governs the body,
and only acts by means of the physico-chemical forces of the substances
assimilated. But it has the power to bind and to loose these forces, to
allow them full play or to restrain them. After death the restrained
forces become free, and evoke putrefaction and decomposition. For the
refutation of this hypothesis of binding and loosing, it was necessary
to discover the law of the conservation of force.
The second half of the previous century was too much possessed by the
principles of rationalism to recognise openly Stahl’s ‘soul of life.’
It was presented more scientifically as vital force, _Vis vitalis_,
while in the main it retained its functions, and under the name of
‘Nature’s healing power’ it played a prominent part in the treatment of
diseases.
The doctrine of vital force entered into the pathological system of
changes in irritability. The attempt was made to separate the direct
actions of the virus which produce disease, in so far as they depended
on the play of blind natural forces, the _symptomata morbi_, from
those which brought on the reaction of vital force, the _symptomata
reactionis_. The latter were principally seen in inflammation and in
fever. It was the function of the physician to observe the strength
of this reaction, and to stimulate or moderate it according to
circumstances.
The treatment of fever seemed at that time to be the chief point; to be
that part of medicine which had a real scientific foundation, and in
which the local treatment fell comparatively into the background. The
therapeutics of febrile diseases had thereby become very monotonous,
although the means indicated by theory were still abundantly used,
and especially blood-letting, which since that time has almost been
entirely abandoned. Therapeutics became still more impoverished as
the younger and more critical generation grew up, and tested the
assumptions of that which was considered to be scientific. Among the
younger generation were many who, in despair as to their science, had
almost entirely given up therapeutics, or on principle had grasped
at an empiricism such as Rademacher then taught, which regarded any
expectation of a scientific explanation as a vain hope.
What we learned at that time were only the ruins of the older
dogmatism, but their doubtful features soon manifested themselves.
The vitalistic physician considered that the essential part of the
vital processes did not depend upon natural forces, which, doing their
work with blind necessity and according to a fixed law, determined
the result. What these forces could do appeared quite subordinate,
and scarcely worthy of a minute study. He thought that he had to deal
with a soul-like being, to which a thinker, a philosopher, and an
intelligent man must be opposed. May I elucidate this by a few outlines?
At this time auscultation and percussion of the organs of the chest
were being regularly practised in the clinical wards. But I have
often heard it maintained that they were a coarse mechanical means of
investigation which a physician with a clear mental vision did not
need; and it indeed lowered and debased the patient, who was anyhow a
human being, by treating him as a machine. To feel the pulse seemed the
most direct method of learning the mode of action of the vital force,
and it was practised, therefore, as by far the most important means of
investigation. To count with a repeater was quite usual, but seemed to
the old gentlemen as a method not quite in good taste. There was, as
yet, no idea of measuring temperature in cases of disease. In reference
to the ophthalmoscope, a celebrated surgical colleague said to me that
he would never use the instrument, it was too dangerous to admit crude
light into diseased eyes; another said the mirror might be useful for
physicians with bad eyes, his, however, were good, and he did not need
it.
A professor of physiology of that time, celebrated for his literary
activity, and noted as an orator and intelligent man, had a dispute
on the images in the eye with his colleague the physicist. The latter
challenged the physiologist to visit him and witness the experiment.
The physiologist, however, refused his request with indignation;
alleging that a physiologist had nothing to do with experiments;
they were of no good but for the physicist. Another aged and learned
professor of therapeutics, who occupied himself much with the
reorganisation of the Universities, was urgent with me to divide
physiology, in order to restore the good old time; that I myself
should lecture on the really intellectual part, and should hand over
the lower experimental part to a colleague whom he regarded as good
enough for the purpose. He quite gave me up when I said that I myself
considered experiments to be the true basis of science.
I mention these points, which I myself have experienced, to elucidate
the feeling of the older schools, and indeed of the most illustrious
representatives of medical science, in reference to the progressive set
of ideas of the natural sciences; in literature these ideas naturally
found feebler expression, for the old gentlemen were cautious and
worldly wise.
You will understand how great a hindrance to progress such a feeling on
the part of influential and respected men must have been. The medical
education of that time was based mainly on the study of books; there
were still lectures, which were restricted to mere dictation; for
experiments and demonstrations in the laboratory the provision made was
sometimes good and sometimes the reverse; there were no physiological
and physical laboratories in which the student himself might go to
work. Liebig’s great deed, the foundation of the chemical laboratory,
was complete, as far as chemistry was concerned, but his example had
not been imitated elsewhere. Yet medicine possessed in anatomical
dissections a great means of education for independent observation,
which is wanting in the other faculties, and to which I am disposed
to attach great weight. Microscopic demonstrations were isolated
and infrequent in the lectures. Microscopic instruments were costly
and scarce. I came into possession of one by having spent my autumn
vacation in 1841 in the Charité, prostrated by typhoid fever; as pupil,
I was nursed without expense, and on my recovery I found myself in
possession of the savings of my small resources. The instrument was not
beautiful, yet I was able to recognise by its means the prolongations
of the ganglionic cells in the invertebrata, which I described in
my dissertation, and to investigate the vibrions in my research on
putrefaction and fermentation.
Any of my fellow-students who wished to make experiments had to do
so at the cost of his pocket-money. One thing we learned thereby,
which the younger generation does not, perhaps, learn so well in the
laboratories--that is, to consider in all directions the ways and
means of attaining the end, and to exhaust all possibilities, in the
consideration, until a practicable path was found. We had, it is true,
an almost uncultivated field before us, in which almost every stroke of
the spade might produce remunerative results.
It was one man more especially who aroused our enthusiasm for work in
the right direction--that is, Johannes Müller, the physiologist. In his
theoretical views he favoured the vitalistic hypothesis, but in the
most essential points he was a natural philosopher, firm and immovable;
for him, all theories were but hypotheses, which had to be tested by
facts, and about which facts could alone decide. Even the views upon
those points which most easily crystallise into dogmas, on the mode of
activity of the vital force and the activity of the conscious soul, he
tried continually to define more precisely, to prove or to refute by
means of facts.
And, although the art of anatomical investigation was most familiar to
him, and he therefore recurred most willingly to this, yet he worked
himself into the chemical and physical methods which were more foreign
to him. He furnished the proof that fibrine is dissolved in blood; he
experimented on the propagation of sound in such mechanisms as are
found in the drum of the ear; he treated the action of the eye as an
optician. His most important performance for the physiology of the
nervous system, as well as for the theory of cognition, was the actual
definite establishment of the doctrine of the specific energies of
the nerves. In reference to the separation of the nerves of motor and
sensible energy, he showed how to make the experimental proof of Bell’s
law of the roots of the spinal cord so as to be free from errors; and
in regard to the sensible energies he not only established the general
law, but carried out a great number of separate investigations, to
eliminate objections, and to refute false indications and evasions.
That which hitherto had been imagined from the data of everyday
experience, and which had been sought to be expressed in a vague
manner, in which the true was mixed up with the false; or which had
just been established for individual branches, such as by Dr. Young for
the theory of colours, or by Sir Charles Bell for the motor nerves,
that emerged from Müller’s hands in a state of classical perfection--a
scientific achievement whose value I am inclined to consider as equal
to that of the discovery of the law of gravitation.
His scientific tendency, and more especially his example, were
continued in his pupils. We had been preceded by Schwann, Henle,
Reichert, Peters, Remak; I met as fellow-students E. Du Bois-Reymond,
Virchow, Brücke, Ludwig, Traube, J. Meyer, Lieberkühn, Hallmann; we
were succeeded by A. von Graefe, W. Busch, Max Schultze, A. Schneider.
Microscopic and pathological anatomy, the study of organic types,
physiology, experimental pathology and therapeutics, ophthalmology,
developed themselves in Germany under the influence of this powerful
impulse far beyond the standard of rival adjacent countries. This was
helped by the labours of those of similar tendencies among Müller’s
contemporaries, among whom the three brothers Weber of Leipzig must
first of all be mentioned, who have built solid foundations in the
mechanism of the circulation, of the muscles, of the joints, and of the
ear.
The attack was made wherever a way could be perceived of understanding
one of the vital processes; it was assumed that they could be
understood, and success justified this assumption. A delicate and
copious technical apparatus has been developed in the methods of
microscopy, of physiological chemistry, and of vivisection; the latter
greatly facilitated more particularly by the use of anæsthetic ether
and of the paralysing curara, by which a number of deep problems
became open to attack, which to our generation seemed hopeless.
The thermometer, the ophthalmoscope, the auricular speculum, the
laryngoscope, nervous irritation on the living body, opened out to
the physician possibilities of delicate and yet certain diagnosis
where there seemed to be absolute darkness. The continually increasing
number of proved parasitical organisms substitute tangible objects for
mystical entities, and teach the surgeon to forestall the fearfully
subtle diseases of decomposition.
But do not think, gentlemen, that the struggle is at an end. As long
as there are people of such astounding conceit as to imagine that they
can effect, by a few clever strokes, that which man can otherwise only
hope to achieve by toilsome labour, hypotheses will be started which,
propounded as dogmas, at once promise to solve all riddles. And as long
as there are people who believe implicitly in that which they wish to
be true, so long will the hypotheses of the former find credence. Both
classes will certainly not die out, and to the latter the majority will
always belong.
There are two characteristics more particularly which metaphysical
systems have always possessed. In the first place man is always
desirous of feeling himself to be a being of a higher order, far beyond
the standard of the rest of nature; this wish is satisfied by the
spiritualists. On the other hand, he would like to believe that by his
thought he was unrestrained lord of the world, and of course by his
thinking with those conceptions, to the development of which he has
attained; this is attempted to be satisfied by the materialists.
But one who, like the physician, has actively to face natural forces
which bring about weal or woe, is also under the obligation of
seeking for a knowledge of the truth, and of the truth only; without
considering whether, what he finds, is pleasant in one way or the
other. His aim is one which is firmly settled; for him the success
of facts is alone finally decisive. He must endeavour to ascertain
beforehand, what will be the result of his attack if he pursues this or
that course. In order to acquire this foreknowledge of what is coming,
but of what has not been settled by observations, no other method is
possible than that of endeavouring to arrive at the laws of facts by
observations; and we can only learn them by induction, by the careful
selection, collation, and observation of those cases which fall under
the law. When we fancy that we have arrived at a law, the business of
deduction commences. It is then our duty to develop the consequences
of our law as completely as may be, but in the first place only to
apply to them the test of experience, so far as they can be tested, and
then to decide by this test whether the law holds, and to what extent.
This is a test which really never ceases. The true natural philosopher
reflects at each new phenomenon, whether the best established laws of
the best known forces may not experience a change; it can of course
only be a question of a change which does not contradict the whole
store of our previously collected experiences. It never thus attains
unconditional truth, but such a high degree of probability that it is
practically equal to certainty. The metaphysicians may amuse themselves
at this; we will take their mocking to heart when they are in a
position to do better, or even as well. The old words of Socrates, the
prime master of inductive definitions, in reference to them are just as
fresh as they were 2,000 years ago: ‘They imagined they knew what they
did not know, and he at any rate had the advantage of not pretending
to know what he did not know.’ And again, he was surprised at its not
being clear to them that it is not possible for men to discover such
things; since even those who most prided themselves on the speeches
made on the matter, did not agree among themselves, but behaved to each
other like madmen (τοῖς μαινομένοις ὁμοίως).[28] Socrates calls them
τοὺς μέγιστον φρονοῦντας. Schopenhauer[29] calls himself a Mont Blanc,
by the side of a mole-heap, when he compares himself with a natural
philosopher. The pupils admire these big words and try to imitate the
master.
[Footnote 28: Xenophon, _Memorabil._ I. i. 11.]
[Footnote 29: Arthur Schopenhauer, _Von ihm. über ihn von Frauenstadt
und Lindner_. Berlin, 1863, p. 653.]
In speaking against the empty manufacture of hypotheses, do not by
any means suppose that I wish to diminish the real value of original
thoughts. The first discovery of a new law, is the discovery of a
similarity which has hitherto been concealed in the course of natural
processes. It is a manifestation of that which our forefathers in a
serious sense described as ‘wit’; it is of the same quality as the
highest performances of artistic perception in the discovery of new
types of expression. It is something which cannot be forced, and which
cannot be acquired by any known method. Hence all those aspire after
it who wish to pass as the favoured children of genius. It seems, too,
so easy, so free from trouble, to get by sudden mental flashes an
unattainable advantage over our contemporaries. The true artist and
the true inquirer knows that great works can only be produced by hard
work. The proof that the ideas formed do not merely scrape together
superficial resemblances, but are produced by a quick glance into the
connection of the whole, can only be acquired when these ideas are
completely developed--that is, for a newly discovered natural law,
only by its agreement with facts. This estimate must by no means be
regarded as depending on external success, but the success is here
closely connected with the depth and completeness of the preliminary
perceptions.
To find superficial resemblances is easy; it is amusing in society,
and witty thoughts soon procure for their author the name of a clever
man. Among the great number of such ideas, there must be some which
are ultimately found to be partially or wholly correct; it would be a
stroke of skill _always_ to guess falsely. In such a happy chance a
man can loudly claim his priority for the discovery; if otherwise, a
lucky oblivion conceals the false conclusions. The adherents of such a
process are glad to certify the value of a first thought. Conscientious
workers who are shy at bringing their thoughts before the public
before they have tested them in all directions, solved all doubts, and
have firmly established the proof, these are at a decided disadvantage.
To settle the present kind of questions of priority, only by the date
of their first publication, and without considering the ripeness of the
research, has seriously favoured this mischief.
In the ‘type case’ of the printer all the wisdom of the world is
contained which has been or can be discovered; it is only requisite
to know how the letters are to be arranged. So also, in the hundreds
of books and pamphlets which are every year published about ether,
the structure of atoms, the theory of perception, as well as on the
nature of the asthenic fever and carcinoma, all the most refined shades
of possible hypotheses are exhausted, and among these there must
necessarily be many fragments of the correct theory. But who knows how
to find them?
I insist upon this in order to make clear to you that all this
literature, of untried and unconfirmed hypotheses, has no value in
the progress of science. On the contrary, the few sound ideas which
they may contain are concealed by the rubbish of the rest; and one who
wants to publish something really new--facts--sees himself open to the
danger of countless claims of priority, unless he is prepared to waste
time and power in reading beforehand a quantity of absolutely useless
books, and to destroy his readers’ patience by a multitude of useless
quotations.
Our generation has had to suffer under the tyranny of spiritualistic
metaphysics; the newer generation will probably have to guard against
that of the materialistic hypotheses. Kant’s rejection of the claims
of pure thought has gradually made some impression, but Kant allowed
one way of escape. It was as clear to him as to Socrates that all
metaphysical systems which up to that time had been propounded were
tissues of false conclusions. His _Kritik der reinen Vernunft_ is a
continual sermon against the use of the category of thought beyond
the limits of possible experience. But geometry seemed to him to do
something which metaphysics was striving after; and hence geometrical
axioms, which he looked upon as _à priori_ principles antecedent to
all experience, he held to be given by transcendental intuition, or as
the inherent form of all external intuition. Since that time, pure _à
priori_ intuition has been the anchoring-ground of metaphysicians. It
is even more convenient than pure thought, because everything can be
heaped on it without going into chains of reasoning, which might be
capable of proof or of refutation. The nativistic theory of perception
of the senses is the expression of this theory in physiology. All
mathematicians united to fight against any attempt to resolve the
intuitions into their natural elements; whether the so-called pure or
the empirical, the axioms of geometry, the principles of mechanics, or
the perceptions of vision. For this reason, therefore, the mathematical
investigations of Lobatschewsky, Gauss, and Riemann on the alterations
which are logically possible in the axioms of geometry; and the
proof that the axioms are principles which are to be confirmed or
perhaps even refuted by experience, and can accordingly be acquired
from experience--these I consider to be very important steps. That
all metaphysical sects get into a rage about this must not lead you
astray, for these investigations lay the axe at the bases of apparently
the firmest supports which their claims still possess. Against those
investigators who endeavour to eliminate from among the perceptions of
the senses, whatever there may be of the actions of memory, and of the
repetition of similar impressions, which occur in memory; whatever, in
short, is a matter of experience, against them it is attempted to raise
a party cry that they are spiritualists. As if memory, experience, and
custom were not also facts, whose laws are to be sought, and which are
not to be explained away because they cannot be glibly referred to
reflex actions, and to the complex of the prolongation of ganglionic
cells, and of the connection of nerve-fibres in the brain.
Indeed, however self-evident, and however important the principle may
appear to be, that natural science has to seek for the laws of facts,
this principle is nevertheless often forgotten. In recognising the law
found, as a force which rules the processes in nature, we conceive it
objectively as a _force_, and such a reference of individual cases to
a force which under given conditions produces a definite result, that
we designate as a causal explanation of phenomena. We cannot always
refer to the forces of atoms; we speak of a refractive force, of
electromotive and of electrodynamic force. But do not forget the _given
conditions_ and the _given result_. If these cannot be given, the
explanation attempted is merely a modest confession of ignorance, and
then it is decidedly better to confess this openly.
If any process in vegetation is referred to forces in the cells,
without a closer definition of the conditions among which, and of the
direction in which, they work, this can at most assert that the more
remote parts of the organism are without influence; but it would be
difficult to confirm this with certainty in more than a few cases. In
like manner, the originally definite sense which Johannes Müller gave
to the idea of reflex action, is gradually evaporated into this, that
when an impression has been made on any part of the nervous system,
and an action occurs in any other part, this is supposed to have been
explained by saying that it is a reflex action. Much may be imposed
upon the irresolvable complexity of the nerve-fibres of the brain. But
the resemblance to the _qualitates occultæ_ of ancient medicine is very
suspicious.
From the entire chain of my argument it follows that what I have
said against metaphysics is not intended against philosophy. But
metaphysicians have always tried to plume themselves on being
philosophers, and philosophical amateurs have mostly taken an interest
in the high-flying speculations of the metaphysicians, by which they
hope in a short time, and at no great trouble, to learn the whole
of what is worth knowing. On another occasion[30] I compared the
relationship of metaphysics to philosophy with that of astrology to
astronomy. The former had the most exciting interest for the public at
large, and especially for the fashionable world, and turned its alleged
connoisseurs into influential persons. Astronomy, on the contrary,
although it had become the ideal of scientific research, had to be
content with a small number of quietly working disciples.
[Footnote 30: Preface to the German translation of Tyndall’s
_Scientific Fragments_, p. xxii.]
In like manner, philosophy, if it gives up metaphysics, still possesses
a wide and important field, the knowledge of mental and spiritual
processes and their laws. Just as the anatomist, when he has reached
the limits of microscopic vision, must try to gain an insight into the
action of his optical instrument, in like manner every scientific
enquirer must study minutely the chief instrument of his research as
to its capabilities. The groping of the medical schools for the last
two thousand years is, among other things, an illustration of the harm
of erroneous views in this respect. And the physician, the statesman,
the jurist, the clergyman, and the teacher, ought to be able to build
upon a knowledge of physical processes if they wish to acquire a true
scientific basis for their practical activity. But the true science of
philosophy has had, perhaps, to suffer more from the evil mental habits
and the false ideals of metaphysics than even medicine itself.
One word of warning. I should not like you to think that my statements
are influenced by personal irritation. I need not explain that one
who has such opinions as I have laid before you, who impresses on his
pupils, whenever he can, the principle that ‘a metaphysical conclusion
is either a false conclusion or a concealed experimental conclusion,’
that he is not exactly beloved by the votaries of metaphysics or of
intuitive conceptions. Metaphysicians, like all those who cannot give
any decisive reasons to their opponents, are usually not very polite
in their controversy; one’s own success may approximately be estimated
from the increasing want of politeness in the replies.
My own researches have led me more than other disciples of the school
of natural science into controversial regions; and the expressions of
metaphysical discontent have perhaps concerned me even more than my
friends, as many of you are doubtless aware.
In order, therefore, to leave my own personal opinions quite on
one side, I have allowed two unsuspected warrantors to speak for
me--Socrates and Kant--both of whom were certain that all metaphysical
systems established up to their time were full of empty false
conclusions, and who guarded themselves against adding any new ones. In
order to show that the matter has not changed, either in the last 2,000
years or in the last 100 years, let me conclude with a sentence of one
who was unfortunately too soon taken away from us, Frederick Albert
Lange, the author of the ‘History of Materialism.’ In his posthumous
‘Logical Studies,’ which he wrote in anticipation of his approaching
end, he gives the following picture, which struck me because it would
hold just as well in reference to solidar or humoral pathologists, or
any other of the old dogmatic schools of medicine.
Lange says: The Hegelian ascribes to the Herbartian a less perfect
knowledge than to himself, and conversely; but neither hesitates to
consider the knowledge of the other to be higher compared with that of
the empiricist, and to recognise in it at any rate an approximation to
the only true knowledge. It is seen, also, that here no regard is paid
to the validity of the proof, and that a mere statement in the form of
a deduction from the entirety of a system is recognised as ‘apodictic
knowledge.’
Let us, then, throw no stones at our old medical predecessors, who
in dark ages, and with but slight preliminary knowledge, fell into
precisely the same errors as the great intelligences of what wishes
to be thought the illuminated nineteenth century. They did no worse
than their predecessors except that the nonsense of their method was
more prominent in the matter of natural science. Let us work on. In
this work of true intelligence physicians are called upon to play a
prominent part. Among those who are continually called upon actively to
preserve and apply their knowledge of nature, you are those who begin
with the best mental preparation, and are acquainted with the most
varied regions of natural phenomena.
In order, finally, to conclude our consultation on the condition of
Dame Medicine correctly with the epikrisis, I think we have every
reason to be content with the success of the treatment which the school
of natural science has applied, and we can only recommend the younger
generation to continue the same therapeutics.