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INTRODUCTORY  LECTURE,
BEFORE THE
ALBANY MEDICAL COLLEGE,
DELIVERED OCTOBER 3, 1848.
   BY THOMAS HUN, M. D.,

PROFESSOR OF THE INSTITUTES OF MEDICINE.
     ALBANY:
JOEL MUNSELL, PRINTER.
       1849.____
       SfSBHew
 
 
LECTURE.
Gentlemen :
    I do not know how I can occupy an hour
more  profitably for you who  are  commencing
the study of medicine, than in pointing out the
direction which medical investigations are tak-
ing at the present day, and in explaining the
method which presides over them.
   In ancient times, and even up to a very recent
period,  medicine has been, for the most part,
under the dominion of general theories or sys-
tems, which professed to  explain  all the phe-
nomena presented by man in a state of health
and disease, by means of  a few general princi-
ples, which were assumed as the basis of the
system.   You have  all, without doubt, read of
the humoral pathology, of the systems of Boer-
haave,  of Brown, of Cullen,  and  of Broussais,
and besides these, I might enumerate a host of
others, through which medicine has passed.  I do
 not propose now, to  give any exposition of these
 systems, but only to explain their nature, and 
                      4
to show how they differ from medicine founded
on positive  science.  It is important that this
difference should be well understood, because
all these  systems are liable to serious  objec-
tions, which have brought  them into merited
disrepute, and in the minds of many, this same
disrepute has been unjustly extended to scientific
medicine.  I wish therefore to show, how medi-
cine founded on systems, differs from  medicine
founded on positive science,  and that the objec-
tions which have been urged against the former,
do not apply to the latter.
   In order that you may understand well what
is meant  by medical  systems, as  opposed to
medical science, it will be necessary for  me to
make  a few observations  on  the  origin  and
progress of other sciences, and on the  different
forms through which they have passed.
   It is a remarkable fact, that the human mind,
in attempting to comprehend the great problem
of the universe, has always commenced with
the  most difficult  questions;  with questions
which, if not entirely beyond the reach of our
faculties, must, at least, be reserved for the most
advanced periods of science.  Thus we find the
earliest philosophers occupied with the nature
of matter, with the  constitution  of its atoms, 
                     5
with the number and nature of the elements,
and a host of similar inquiries, which, those who
are now engaged in the cultivation of the phy-
sical sciences, pass by as idle, or as beyond the
reach of their means of investigation.   It was
only after a series of vain attempts  to grasp at
once  the whole problem of nature,  that the
human mind learned to estimate its own powers,
and discovered the method by  which this pro-
blem could be  attacked with success.  Modern
science is  occupied only with phenomena and
their  relations; ancient philosophy neglected
these phenomena  or appearances,  and sought
for that which was beneath them and real. We
study the changes  which matter undergoes; the
ancients sought to discover what matter is, and
what is its essence.   We study the relations of
phenomena, to arrive at the laws regulating their
order of succession,  and strive  to  make these
laws  more  and more general; the ancients en-
deavored to seize at once on some initial prin-
ciple, by which all the changes and appearances
of the world might be explained.   Our science
is susceptible of practical application, and con-
tributes  to  the well being and  improvement of
 the human condition;  ancient  philosophy had 
                     6
no practical utility, and served only to gratify a
taste for speculation.
  If, for example, we turn to ancient systems of
philosophy, to see what account they give of the
constitution of the world, and of its mode of origin,
we find them first seeking for some element as
the beginning or principle of all  things, and
when they have  fixed on some such principle,
such as fire, or air, or water, they  show how,
out of this, the world was evolved.  Or they seek
for the ultimate  atoms out  of which matter is
formed, and show how the world has originated
from the aggregation of such atoms.  The phi-
losopher  considered the phenomena presented
by the things around him,  as unworthy  of hjs
regard, and his system takes but little note of
them.  These  systems,  consequently, do  not
deal in facts, but  in hollow  speculations,  so
vaguely expressed, that men might dispute about
them forever, without coming to any conclusion.
  You will be more  struck with the character
of these systems of cosmogony, if you compare
them with the parallel science of geology, as it
is now received and cultivated.   Modern geolo-
gy gives  us the results of a patient  examination
of the substances, out of which the crust of the 
                      7
earth is formed,  of its different layers, of the
remains  of animals and  vegetables  found in
them, of their order of superposition,  and from
this  anatomy  of the  earth, conclusions are
drawn, as to its primitive condition and mode of
origin.  This is a positive  science of facts and
their relations, and  differs widely from the phi-
losophical systems  of the  ancients, founded on
speculations  more or less ingenious, but unsup-
ported by facts.
   These remarks concerning the different phases,
through which physical science in general has
passed, before finding  its true end and method,
are especially applicable to the science of man.
The human organism, with its complicated struc-
ture and  its varied  phenomena,  is a  unit; it is
animated by a single force which makes all its
actions combine  harmoniously to produce one
general result. Hence the first point which sug-
gested itself to early inquirers, was to  determine
the nature of this force; for this being known all
the  resulting phenomena  would admit  of an
easy explanation.   Properly understood,  this is
a legitimate  problem,  but ancient philosophy
apprehended  it very  differently from modern
science, and  sought for its solution  by  a verv
different  method.  Modern   science  occupies 
                      8
itself only with the manifestations of life,  stu-
dies all the phenomena presented by the living
body, seeks for their relations, which it expresses
by laws,  and tends by degrees to make these
laws more and more general, until it may attain
to the ultimate law of the whole organism.  By
this method, we begin at the circumference, and
feel our way along the radii to the centre.  It is
a long and  laborious  process,  which  has ex-
hausted the powers of many generations,  and
will require the labors of many more, before the
work is accomplished.  Ancient philosophy oc-
cupied itself with discussions about the nature
and  essence of life, about the vital principle in
itself, and not in its manifestations, and sought
to divine at once, by an effort of genius, the pri-
mordial law by which all the phenomena of the
organism were to be explained.  In this method,
the philosopher  places himself at once at the
centre, and seeks for the circumference.  It leads
to no true knowledge, nor to any useful practical
result.
  Similar methods have been  applied to the
study of disease.  Modern science  studies the
phenomena of disease, as presented in disorders
of function, and in alterations of structure, seeks
for the relations of these phenomena, and com- 
                     9
pares them with what occurs in a state of health.
The ancients more ambitiously sought for a gene-
ral theory of disease, and inquired into its essence,
rather than its manifestations.   In this way,
have been formed the medical systems, which,
mixed up with more or less of positive science,
have continued to prevail, long after other de-
partments of science had adopted the true me-
thods of investigation. What I have said of the
general character of ancient philosophy, applies
to these systems: their  authors neither appre-
hended  the true end  of science,  nor did  they
possess the true method  for its cultivation.
   It would be  tedious and unprofitable for me
to attempt to give an exposition of these systems;
some attributed diseases to the pneuma; others,
adopting the  general ideas of Epicurus, main-
tained that man results from an  accidental re-
union of atoms which affect a determinate form,
and that the regular or irregular movement of
these  atoms in  the vacuum assigned to them,
gives rise to health or to disease.  As we come
 down to modern times,  the language of the
systems becomes more intelligible, and  they
express great truths more clearly, but  they are
all tainted with the same defects. The system
of Brown, which has prevailed almost in our
                2 
                     10
day, is founded on a great truth; "Life is main-
tained by stimuli." But in developing this truth,
the author arrived at  a general classification of
all diseases into sthenic and asthenic, and the
treatment was reduced to the greatest simplicity,
for one had merely  to determine to which  of
these classes, any particular disease belonged,
and to employ the remedy calculated to over-
come the  condition present.   There is here no
reference to particular organs, nor to alterations
of structure which may have occurred in them;
there is no attempt to  explain the mechanism
of disease, nor to trace it to organic derange-
ments ; indeed the whole matter is so vague and
speculative, that one might practise under this
system, without  knowing any thing about  the
 structure of the body or its functional actions.
   Though the general character of all medical
 systems was such as I have described, you must
 not suppose that they were made up exclusively
 of speculations, and contained no facts.  These
 speculations expressed a certain view of facts,
 but the view was one-sided and exclusive, and
 hence, while the system incorporated a portion of
 facts known at the time, these were imperfectly
 stated and perverted, so  as to be made to meet
 the  requirements of the system.  In many  sys- 
                     11
tems, for example, diseases were attributed to
alterations of the fluids, and so far undoubtedly
they expressed a truth, but these  alterations as
described, were for  the  most  part imaginary,
such as viscidity or tenuity, or alkalinity or acidi-
ty, and medicines were directed to be employed
from their imagined aptitude to overcome these
imaginary alterations.
   Systems, like these, having the double defect
of being exclusive, and of being hollow specu-
lations, have  by  turns reigned in the medical
world. At a time, when the facts of the science
are  few and  imperfectly  observed, a man  of
genius seizes  in some  particular  face  of the
truth, and on this he proceeds  to found his sys-
tem.  Being exclusive,  the  system necessarily
refuses to admit many  facts within its frame
 work, and these, the  author refuses to  see,  or
boldly denies.  The system, adopted with en-
 thusiasm by ardent disciples, continues to flour-
 ish, until the exceptional facts become so nu-
 merous  and so obvious, that they serve as the
 foundation of a  new system, which springs  up
 to be  destroyed  in  its turn, in consequence of
 the same defects.  Thus medicine has oscillated
 from vitalism to  humoralism, and then to solid-
 ism, then to  recommence  a similar course, so 
12
that from its history it would seem to have been
always  turning in the  same circle without im-
provement.  This is,  however, not altogether
true, for although, from the wrong direction in
which medical investigations have been pushed,
the results obtained have not been in proportion
to the labor bestowed on them, yet, in the midst
of these oscillations, medicine has been advanc-
ing as a science,  and gradually approaching to a
true method.
   While the great mass of philosophers was oc-
cupied  with unprofitable  speculations and pre-
mature  attempts to  solve the  great problems of
science, by the force  of genius, rather than by
patient  observation, there always were others
who pursued  the less pretending, but more use-
ful course of observing nature, as presented to
the senses.  Among the results of the labors of
this latter class, we may rank the  admirable
observations  of  Hippocrates  on the  course of
disease, the contributions of Aristotle to natural
science, the  discoveries  in anatomy, &c.  In
other words, a positive science, founded on  ob-
servation and experiment, was growing up by
 the side of the philosophical systems,  and these
systems, as they succeeded each other, incorpo-
 rated more and  more of  the facts accumulated 
                     13
by the labors of the  true observers of nature.
Indeed, these systems have served as important
auxiliaries  to the advancement of positive sci-
ence, because they served to bind together scat-
tered facts, and because new facts were elicited
by the attempts to support or refute the  conclu-
sions of the systems.  In this way, the systems,
which in the beginning were hollow specula-
tions void of facts, in the progress  of time ap-
proached more closely to the character of posi-
tive science, until this latter character became
predominant.
  The last system which prevailed in the medical
world, and the last which will prevail, was that
of Broussais, which, some fifteen or twenty years
ago, created such a sensation, and was  adopted
with such enthusiasm by the rising generation
of that day.  Promulgated at a time when posi-
tive science  had penetrated into every depart-
ment of nature, it partook largely of this charac-
ter,  and was only defective, as a premature
attempt at generalization, without a sufficient
number of facts to serve as a basis.  The great
fault of  the  author lay in the attempt to frame
a system,  which should  embrace the whole
science of man, in a state of health and disease,
while the science was yet in its infancy; it was 
                     14
the effort of a man of genius to accomplish an
impossible task; it was as though an astronomer
living before Kepler, should have attempted to
frame an astronomical system like that of New-
ton.  Hence, while as  a system it has fallen,
the facts and generalizations attained under its
influence, still remain.   It has been succeeded
by no  other  system,  but by positive science,
which has now taken the place of all systems.
  If you would now see medical systems,  you
must look for them, not in the  medical world,
but in the world of imposture and dupery; such
is homoeopathy with its noted dictum,  Similia
similibus curantur;  or Thomsonianism, which
cures diseases on the  principle that "heat  is
life, and cold is death."  To such base uses are
the cast off garments of medicine now turned.
  Systems  and vague speculations have  now
passed away from medicine, and have been suc-
ceeded by positive science, founded on observa-
tion and experiment.   In place of an art founded
on systems, we now have an art founded on the
science of man in a state of health and disease;
that is,  founded on  physiology  and pathology.
We no longer  inquire  into the  essence  of life,
nor  into the  nature  of  the  vital principle;
nor  do  we  look  for  an  initial  principle by 
                     15
which to explain the phenomena of health and
disease, but we study these phenomena, analyze
them, seek for their relations and express these
relations by general laws.  In any given case of
disease, we trace the phenomena present to the
organic derangements on which they depend,
and then explain as far as we can, their mode of
generation and order of succession.   In many
cases, the explanation is defective, for medicine
is as  yet too  imperfect to have attained to the
high degree of generalization to  which some of
the other sciences, as astronomy, have arrived.
In these cases, we can at least measure the ex-
tent of our knowledge, and not deceive ourselves
by vague discourse  and speculation, "darken-
ing counsel by words without meaning."
   Positive science is founded on facts; it studies
only  phenomena and their relations.   It does
not seek to go behind the phenomena, to specu-
late about the essence of matter or of mind, or
the nature of causation;  it deals only with
materials furnished by the  senses or by con-
sciousness.   It does  not  seek to explain why
phenomena succeed each in this or that order;
but only inquires what that order is; it merely
assumes that their order of succession is  inva-
riable, and seeks for the laws expressing it.  It 
                     16
demands reasoning and research, for these rela-
tions are not obvious to the senses, but must be
sought out with great labor; but it requires also
that all its results should be susceptible of veri-
fication by the senses.
  When we have  discovered the relations of
phenomena, or their order of succession, we are
enabled to predict  results; and when  we can
predict results, we can arrange circumstances to
procure a  desired  result.  This knowledge is
science; this application is art.   Herein lies the
whole secret of man's knowledge of nature, and
of his dominion over nature.
  It has taken the human race many ages of
fruitless efforts in a false direction,  to learn at
last, that man can know nothing of nature, but
phenomena and their laws, and that his domin-
ion over nature can only be attained  by obedi-
ence to these laws.   Since these  great truths, so
simple and so  fertile,  have been  known  and
acted on, physical science has made an immense
and constantly increasing progress, and the arts
have advanced in a proportionate  degree,  and
are  daily astonishing us by new and brilliant
results.  Now, what science was, when it existed
under the name of astrology and alchemy, so
was medicine as a system, to medicine as a 
                     17
positive science; and the art of medicine now
firmly  established on this foundation, has al-
ready entered in a career of improvement which
holds out the prospect of results as brilliant and
useful as those  presented by the  other  arts.
It is true, that the results as yet attained  in
practical medicine, are less striking than those
presented by the other  arts,  for medicine has
been the last to  feel the impulse  derived from
the  true method of investigating  nature.  The
language and the false method of systems even
now continue to infest our science, though they
are rapidly disappearing.  A glance at the pro-
gress of medicine since a more sound method
has presided over its cultivation, justifies the
 most sanguine hopes for the future.   If we look
back, we find that it is a little over two hundred
years, since the  circulation  of the  blood was
explained  by  Harvey, and   one  can  scarcely
conceive of a  science of physiology, while this
 movement, intimately concerned in  every vital
 act, was unknown.  Anatomy had,  before that,
pointed out the general structure of the organs,
but their uses were, for the most part, unex-
plained.  Since  that time, physiology has felt
the impulse communicated to the other sciences,
and is now making so rapid progress, that the
               3 
                     18
text books, in which the advances of the science
are posted up, must  be written over every few
years.   Corresponding progress has been made
in anatomy, especially in microscopic anatomy,
which is  opening a  new field of research, and
is changing the whole face of physiology; and
within a few years, Liebig  has pointed out new
applications of organic  chemistry to the  expla-
nation of the phenomena of life, which may be
ranked  among  the most brilliant achievements
of modern science.
   Nor has this progress been confined to the
science of man in a state of health.  Within
the last twenty years, the phenomena of disease
have been  studied  with a care  and method
which were before unthought of.   Pathological
anatomy has been cultivated with great zeal and
success, and here also the microscope, which pro-
mises to be for our science, what the  telescope
is for astronomy, has revealed a host of organic
changes,  which were before  unknown.   The
chemical relations of the fluids in  disease, are
becoming intelligible, and  the  alterations as at
present demonstrated, present  a  singular con-
trast with the qualities vaguely attributed to
them, by the old humoral pathologists.
   Improvements in  the art of medicine must 
                      19
 follow such progress in the science.  Indeed is
 it not obvious, that  in order to cure diseases, it
 is necessary first of  all to understand the struc-
 ture  and actions of the  body in which they
 occur?   Vague discussions about the essence of
 disease, or the vital principle, can be of no use to
 us in devising a remedy for any given  diseased
 condition, just as men  could never construct a
 steam engine, nor attain any useful mechanical
 result, by investigating the essence of matter, or
 the constitution of its atoms.
   In every disease, we have a certain alteration
 in the fluids, or solids, or both of the body, whether
 it is appreciable by  our  senses  and present
 means of investigation, or not; and this altera-
 tion interferes mechanically, or chemically, or
 vitally, with  the due performance of function.
 If we can point out this alteration, and  show,
 how, in accordance with the known laws of the
 organism, it  produces the  functional derange-
 ments which  are present, then we  may be said
 to understand the disease, and we may judge
 of its curability and  devise the proper remedies.
 When we cannot thus trace the diseased actions
 to their source, we must practise with a prudent
empiricism, as I shall explain presently.
  In  a case of disease, we have, first of all, to 
                     20
study the various functional derangements  or
symptoms by which it is manifested to us; then
to interpret these symptoms, and refer them  to
the organic  alteration  on which  they depend,
and lastly to devise the means of removing this
lesion, or of palliating it, if it can not be re-
moved.   Such is the problem presented to us
in every case of disease, and you can readily see,
what an amount of scientific knowledge it de-
mands.
  To render more obvious, the difference between
medicine founded on positive science, and medi-
cine founded on  systems or vague generalities,
I will  illustrate it by an  example.  For  this
purpose, I will take some well marked disease,
and see  how it will be explained.
  According to Brown, dropsy is a disease  of
asthenia, and this is all that it is  important for
us to know.   The treatment is as simple as the
pathology: the asthenic condition is overcome
by stimulants;  therefore stimulants will  cure
dropsy.
  According to others, who adopt a vague  and
general  kind of reasoning, but more nearly allied
to positive science than the last, dropsy is caused
by a want of balance between the action of the
exhalent vessels and the absorbents, and  hence 
                     21
we must use remedies which will  diminish the
exhalation and increase absorption.  Without
stopping to criticise this pathology, further than
to say, that it merely states the fact that an effu-
sion exists, in different words, let me pass at
once  to  the view which positive  science will
take of the disease.
  It has been demonstrated by observation and
experiment,  that  dropsy may be produced by
different organic lesions.  Thus, it may be caused
by a venous congestion long maintained, and a
venous congestion may be kept up locally by an
obstruction of a large vein, or by disease of the
liver, or it may be general and depend on dis-
ease of the heart, impeding the circulation of the
blood.   Again, dropsy may depend on a disease
of the kidney, manifested  by a peculiar altera-
 tion in the  urine, and in which, the urea  is not
 separated from the blood.  And it may depend
 on other causes.  When a  particular  case  is
 brought  before us for investigation, we  must
 then determine, to which of these  lesions it is
 to be referred, before we can judge of its cura-
 bility, or of the proper remedies.   Suppose, for
 example, that with the dropsy, we find physical
 signs indicating a disease of  the heart, and that
 the course of the effusion has corresponded with 
22
 what would be produced by a mechanical im-
 pediment to the circulation, depending on such
 a cause.  We can then trace all  the  symptoms
 to  this starting point, and can  explain  their
 mode of production.  We can also judge of the
 possibility of curing the  disease,  and the best
 mode of arriving at the cure, if  possible, or of
 palliating when we can not  cure.
  To the follower  of the system, all dropsy is
 alike;  it is an asthenic disease, and  it  is to be
 cured  by remedies  supposed to overcome this
 condition.   No matter whether it depends on
 disease of the  heart, or of  the liver,  or of the
 kidneys, or of the  blood;  the  follower of the
 system applies the same remedy indiscriminate-
 ly to all these different lesions, of which his sys-
 tem does not  lead  him  even  to suspect  the
 existence.   All that he cares to know about the
 disease is, that it is asthenic!
  Such is the  difference between  the  clear and
 definite explanation of a disease, which consists
 in referring it to some organic lesion, and the
 vague  and unsatisfactory accounts given by the
 systems  which attempt  to  bring every thing
 within their principles, apparently so simple, but
 in reality so unmeaning.   Many systems, as has
been already remarked,  contain  a portion of 
                     23
positive science, and so far may be of some use
in practice;  but as systems they are worthless,
and even  worse, for  they give an  air of know-
ledge to ignorance.
  I have occupied some time in explaining the
nature of  medical systems, and in pointing out
their  defects, not because there is any danger
that you will, at this day, be tempted to embrace
them, but rather to make you see  clearly the
difference between them and  scientific  medi-
cine, and thus prevent  you from adopting a
popular prejudice against the latter, which ap-
plies only to the former.   Scientific  medicine,
like medical systems, requires reasoning, but the
one reasons on facts, and the other on specula-
tions; and  as the false  reasoning of systems
leads to  absurdities and mischief in practice,
some men have fallen into a distrust of all rea-
soning, and have attempted to find a practice on
experience alone, or on empiricism.   Now, that
you understand the difference between scientific
 medicine and medical systems, I will show you
the difference, as well as the  resemblance be-
 tween scientific medicine and empiricism.  Let
 me first  show  how empiricism has its  origin,
 and wherein it finds its justification.
   When  men have once  adopted a system, and 
24
still more, when they have  invented  one, they
are exceedingly averse  to  admit any opposing
facts  or reasoning; they try to make facts bend
to the system,  rather than to make the sytem
bend  to facts.  This remark does not apply to
medicine  alone, for we  find the same perver-
sity manifested in theology, in  morals and  in
politics.   A system  or  a  theory is  always
founded on some truths,  and leads to  some true
conclusions,  but also contains errors, which,
though they may not strike  us, when existing
only in germ, in the principles of the  system,
become more and more apparent, as it is de-
veloped and carried out to its logical conclusions.
Now it so happens that when an imperfect sys-
tem or theory leads to some absurd conclusions,
the partisan is  very apt  to adopt these  conclu-
sions, however  repugnant they may be to com-
mon  sense, rather than abandon  his  system.
Numerous examples of this disposition to reject
all facts adverse to an adopted theory, might be
adduced in medicine.  We find,  for example,
that in low fevers, the patient  sometimes falls
into a state of prostration, which can  only be
relieved by stimulants freely administered, but
a disciple of Broussais  would refuse to admit
the truth of such facts, because his system main- 
                     25
tains, that this prostration depends on an inflam-
mation of the nervous cenres, and that for this
reason, it  is impossible that  stimulants should
be otherwise than injurious.   On the other hand
the disciple of Brown could not be made to see
that stimulants were  ever injurious  in  fever,
because his system maintains that  they are as-
thenic diseases, and consequently require stimu-
lants.  To such absurdities does a partiality for
preconceived views carry the human mind, that
a medical philosopher once said, " I had rather
be  in  error with  Galen, than right with  any
body else."
   There are, however, some  men to whom, sys-
tems or theories present no attractions;  men of
good common sense, without much capacity for
 reasoning, men who care little for logic, and a
 great deal  for the evidence of their eyes  and
 ears; practical men as they  are called.   These
 men, struck with  the absurdities to which  sys-
 tems, when pushed  to their consequences,  give
 rise, are led to reject all reasoning, and to  rely
 only on experience.   These  men are empirics,
 and this mode of practice is empiricism.  (I use
 these  terms not, in  the bad sense ordinarily at-
 tached to them.)
   Empiricism is  the protest of common sense
                4 
                     26
against  the  absurdities  to which a blind adhe-
rence to the conclusions of theories gives  rise;
but a pure empiricism is perhaps the most  dan-
gerous of all systems.  It professes to be founded
on experience, but it is the experientia fallax of
which Hippocrates speaks.  Scientific medicine
also professes to be founded on experience, and
so far would seem  to accord  with empiricism,
but the  experience, in the two  cases, is of a very
different nature.  Let us see now what is the
exact difference between scientific practice and
empiricism.  I will begin by an example.
  The empiric has observed,  that in a certain
number of cases, a given  diuretic  or purgative
has removed a dropsical effusion; he has noted
this fact as the result  of his  experience,  and
when another similar  case presents itself, he
administers the same remedy.   This is empi-
ricism;  it is the mode of reasoning and practice
of the vulgar,  who say to you, such a remedy
has been found good for  such a disease, and
therefore recommend it in all such diseases for
the future.
   Now let us observe a learned physician called
to this case of dropsy.  He too is going to appeal
to experience,  in support of what  he does, but
it will  be experience of a very  different  kind. 
                     27
He knows that dropsy may depend on different
lesions,  such as of the heart, veins, liver, kid-
neys, &c, and knows the  diagnostic  signs by
which these lesions maybe detected during life.
Mark, he has learned this too by experience, for
how does he know that dropsy may be  caused
by disease of the heart, except by having found
such disease in persons who have died of dropsy,
and  by experiments and observations on living
animals, that obstruction of the  circulation is
capable of causing dropsy;  and as regards the
diagnostic  signs, he has found by experience,
that certain physical signs observed during life,
correspond with certain lesions after death. You
see then,  the one appeals to experience  as well
as the other.  The empiric calls this experience
of science,  theory; but whatever it may be
called,  it is founded on the  evidence  of the
senses.
   But let  us now see  which  of the two will
have the advantage in practice.   The  empiric
has found that a certain remedy has cured cer-
tain cases  of dropsy,  though it has sometimes
failed.  Why does it ever fail ?  By his method,
he can find no answer to this question; he must
be guided by what on the whole seems indicated
by his experience.  The scientific physician has 
                     28
analyzed this complex fact, dropsy; he has taken
it apart, and has found that it  may depend on
several  very different  organic  lesions, so  that
what, to the eye of the empiric, appeared always
as one disease, in reality is a symptom of seve-
ral very different diseases.   The same remedy
can  not be adapted  to all these  lesions,  and
hence he explains the occasional failure of the
empiric's cure.   If it is proper for dropsy caused
by cardiac disease, it may be very inappropriate
for that caused  by disease  of the  kidney.  He
seeks not then for a remedy capable of remov-
ing this general condition  dropsy, but for the
remedies capable of removing  each  of the or-
ganic lesions into which he has decomposed it.
You easily see whose practice will be the most
certain.
  A host of similar illustrations may be adduced.
The empiric says this mixture cured my cough,
therefore it  will cure your cough.   This is an
appeal to experience, but it  is a fallacious ex-
perience.  Wherein lies the fallacy?  Simply
in this;  that the two cases may not be similar.
Cough may depend on  a  number of organic
lesions, and the same remedy is not adapted to
all these lesions; for example, an opiate may
be the proper remedy for a cough depending on 
                     29
nervous irritation, but not at all for one depend-
ing on inflammation.   Empirical experience
will then fail us in practice, unless the two cases
are in all respects alike.
  These instances  may  serve  to give you  an
idea of the difference between practice founded
on empirical experience, and  practice founded
on science, but as you may not yet see clearly
the difference between empirical experience and
science, I will present the matter in another
form, and with as much clearness and precision
as I can.
  When we adapt means to produce an end, we
must first know  that the  means will produce
the end, that is, all our contrivances are founded
on a knowledge of the course of nature.  This
knowledge  is science, the application of this
knowledge, is art.
   Knowledge of nature exists in two  forms,
which  differ in degree,  but not  in  kind,  but
which, for our present purpose, must  be  distin-
guished.  Every body knows something of the
course  of nature, such as  that day succeeds to
night, that the seasons follow each other in  a
certain order, that heavy bodies fall to the earth,
that  plants  and animals  grow.  This  is  the
knowledge possessed by the great mass of men, 
                    30
and it is on this knowledge that they act.  How
does this  knowledge differ from  science?  It
would require much time to examine this ques-
tion in all its bearings, but for the present pur-
pose, it may suffice to show how popular know-
ledge expresses only the relations between com-
plex phenomena, while science seeks to express
the relations between simple phenomena.  Phe-
nomena,  as presented in nature are  complex,
and are made up of elementary phenomena, and
while popular  knowledge goes no farther than
to seek for  the  relations between these  com-
plex phenomena, science analyzes them, reduces
them to their elements, and finds  the  relations
between these elementary phenomena. The laws
of nature  are  nothing  more  than the expres-
sion of the relations between simple phenomena.
Hence while it is true, that science is made  up
of facts and their relations, it is also true, that in
order to attain to science, it  is not enough to
use our eyes and hands.  The facts are visible
and tangible, but the relations are not obvious
to the  senses.   To find these  we must take  the
facts apart, and see what is contained in them.
That the candle before me is giving out light
and .heat, is obvious to any one whose  senses
are perfect;  but  by science, we know also that 
                     31
there is here going on a combination of oxygen
and hydrogen generating water, and of oxygen
and carbon generating carbonic acid, and other
elementary acts accompanying the combustion.
Any one  can see water rising in a pump some
thirty-six feet, but science makes us also to see
in this, the atmosphere  pressing on the surface
of the water, the reaction of the particles of the
water on each other, causing the column to rise
until  it equals in  weight  a column  of  atmos-
phere, and hence too, shows why water will not
rise so high in a pump on a mountain, as at the
level of the sea.
   The relations of phenomena are invariable;
they  always succeed each  other in the same
order, and hence when we have found the rela-
tions between  simple phenomena, we  have a
law with no exceptions;  but a change in any
of the conditions of a complex  phenomenon,
changes the result, and hence by the study of
 complex phenomena, we do not arrive at univer-
 sal laws.  Popular knowledge says  that heavy
 bodies fall  to the earth;  but to  this there  are
 exceptions; it  is not a universal law, for a bal-
 loon rises in the air;  the simple fact that masses
 of matter have a tendency to approach each
 other, is universally true, and  embraces  the 
                     32
complex"phenomenon of the fall of a stone and
of the rising of a balloon.  For this  reason, sci-
ence, whenever it has attained to  a  complete
analysis of phenomena, lays down  laws which
are universal and certain; common experience,
which sees phenomena in the gross, can only
attain to probability.
  While popular knowledge or common expe-
rience  and science are both founded on  facts
observed by the senses, they often differ in their
conclusions, and sometimes their  conclusions
are precisely the reverse.  Science says there
are antipodes; experience says that every thing
must fall off the lower half of the earth; science
says the earth  is spherical and moves  with im-
mense velocity;  experience says it is an extend-
ed plain and motionless;  science says, the earth
goes round the  sun;  experience says, the  sun
goes round the earth.  Remark,  that while each
arrives at an opposite conclusion, they both ap-
peal to the senses in support of their conclusions.
The one has seen, the other  has looked and
reasoned.
  Popular  knowledge is sufficient for the great
mass of men.   Thousands light their candles
every evening, without having ever suspected
that the presence of oxygen gas is necessary 
                     33
for the success of the  operation, and pump up
water without ever having  thought of atmos-
pheric pressure.   The arts, however, require the
kind of knowledge we call, science.   Popular
knowledge would never suffice for making  a
match to ignite by friction, nor for  constructing
a steam engine.
   Such are the two forms of knowledge, which
as you see, differ greatly in  degree, but not in
kind, for  popular experience  has  attempted  a
rude  analysis of phenomena, and science has,
only in rare instances, attained to a perfect ana-
lysis.  Practically, however,  the  difference  is
sufficiently  obvious.   Now  empiricism is art
founded on the observation of the relations  of
complex phenomena;  scientific art is founded
on the observation of the  relations of pheno-
mena as analyzed by science.
   We are now prepared to  understand what  is
 meant  by certain and uncertain sciences.  The
certainty or uncertainty of a science,  depends
not on the relations of the phenomena, for these
 are always invariable, but on the degree to which
we have  succeeded in analyzing them.  There
are some departments  of nature, in which the
analysis of phenomena has been pushed so far
as to furnish us with simple phenomena, which
                5 
                     34
give us what are called, ultimate laws.  Of this
character, is the law of gravitation, which ex-
presses a  simple relation,  and to which no ex-
ception exists.  When we have arrived at such
laws,  we  can predict with absolute  certainty,
whatever  depends on their operation,  as is re-
markably  exemplified in  the  science  of astro-
nomy, which gives  us the means  of determin-
ing, from  the present condition of the heavenly
bodies, their position  at any past or any future
time.   The  sciences,  in which we have arrived
at ultimate laws, are called certain sciences.
  In other sciences, the analysis of phenomena
has been less complete, and here we have laws
of more generality than those  derived  from po-
pular  experience, but not ultimate laws,  and
consequently the power of prediction does not,
in such cases, rise higher than probability.  Such
sciences  are then  uncertain.  We know, for
example,  that opium will in general procure
sleep, and that aloes will purge,  and the  condi-
tions which must be present, in order that these
medicines should produce such results, but, in
no  given  case, can we predict  with absolute
certainty,  that a grain of opium will, or will not,
produce sleep.  The reason is, that we have not
analyzed the phenomena presented by the living 
                     35
body, so as to arrive at their ultimate laws; we
have  not determined  the  elementary action of
opium on the nervous fibre, but only the com-
plex fact,  that, in most cases, it  causes sleep,
and  as a variation in  any of the unknown ele-
ments which go to make up this complex fact,
will cause a variation in the result, our power
of prediction cannot  rise  higher  than proba-
bility.
  Suppose one only knew of a steam boat, that
a fire in the furnace  would make the paddles
revolve; this would be an empirical law, derived
from the experience of a complex fact, and would
hold good in most cases, but would sometimes
fail.   It would fail whenever there was no water
in the boiler, or when the steam did not act on
the piston, or when the  machinery was broken.
The elementary movements, such  as the expan-
sion of the steam when heated, or its condensa-
tion when cooled, never  fail.   The  engineer,
knowing all the  elementary acts which concur
to produce the general result, would know in all
cases, why the fire in the furnace failed to make
the paddles revolve, and when it was going to
fail, the man whom we  have supposed ignorant
of these elementary acts would only know that 
                     3f>
the law founded on  his experience, sometimes
holds good and sometimes fails.
  Now our knowledge of the  action of opium
on  the body, is analogous to that of the person
who only knows of the steam boat,  that  the
paddles usually revolve, when there  is  a  fire
in the furnace.  Between the introduction of
opium into the body and the sleep produced,
there are  many intermediate  elementary acts,
of most of  which we are ignorant,  and as  a
modification of any one of those unknown  ele-
mentary  acts  may  change  the result, we  are
liable to disappointment, just like the person in
the case  we have supposed, in regard  to  the
steam  boat.  The elementary action of opium
is as invariable as that of heat in causing  the
expansion of steam; and  one who should  un-
derstand all these elementary acts, would predict
the effects of opium in any given case, with as
much  certainty, as the engineer can predict in
any given steam boat, whether a fire in the  fur-
nace will cause the paddles to revolve.
  What I have said of the action of opium on
the body, applies to medical science in general.
We have, to a certain extent, analyzed the phe-
nomena presented by the human body in a state 
                      37
of health and disease, but we have not succeeded
in pushing  this analysis so far,  as to arrive at
phenomena of absolute simplicity, or at ultimate
laws.  Hence,  while our power of prediction is
vastly superior to that  furnished  by a coarse
popular experience of complex phenomena, it is
far from entire  certainty.  In other words, medi-
cine is an imperfect  science.
  All art being founded on the power of predic-
tion afforded by science, it will be more or less
fallible, in proportion as this prediction is more
or less certain.  Empiricism, which is art founded
on the observation of phenomena in their great-
est degree of complication, is most of all liable
to error.  Scientific  art  will be infallible when
founded on  ultimate laws, as in some rare cases
it is, and when founded on laws of less generality,
will be in the  same  degree fallible.  Since me-
dical science is imperfect, since the laws it fur-
nishes are not expressions of simple phenomena,
medical art must be fallible.  We cannot there-
fore  require of the physician that he  should
always be successful, nor even that his antici-
pations should always be realized, for his  art
can not be in advance of his science.
  We have now  attained  a  point of view at
which we  may readily  appreciate the relative 
                     38
advantages of empirical and of scientific medi-
cine.   The empiric sees  a certain remedy cure
a certain group of symptoms, and without fur-
ther examination, he notes this  fact and acts
upon it.  In some cases,  this mode of practice
is successful and  tolerably certain, as for exam-
ple,  in  the treatment  of intermittent fever by
Peruvian bark.  But this is not common; dis-
eases are indeed classified and described in books
as though  they were  well defined existences,
but they do not  so present themselves  at the
bed-side. They here appear as disordered actions
of different organs, which are  grouped together
to form innumerable  combinations.  Of the
cases met with in practice, not  one in twenty
corresponds in all respects, with the descriptions
found  in  books,  and  hence  the  physician  is
compelled to rely on general  principles,  which
he must apply to the individual case before him,
and  not on  mere  empirical rules.  The  physi-
cian at the bed side, is  like the general of an
army in face of the enemy.   There are  princi-
ples of attack and defence, with which the gene-
ral  must be  acquainted, but  there can be no
special rules which he can follow blindly, for
the reason, that in each battle, there are pecu-
liarities of position, of numbers, of formation of 
                     39
the ground, which cannot be provided for in ad-
vance, and  which demand the application of
his science  to  the  individual case.  It would
appear supremely absurd, for a general  to seek
for some rule by which he could gain  battles,
and for the physician to look for rules for curing
diseases, without appealing to the general prin-
ciples of his science,  presents an absurdity less
obvious perhaps, but not less real.
   In  scientific  medicine, we do not  consider it,
sufficient to have observed that a given  remedy
has cured a given disease, for the circumstances
are so numerous, that we cannot judge of the
effect of the remedy,  nor how far the cure de-
pended on it.  We endeavor  therefore to trace
 the symptoms  to the organic lesions which pro-
 duce them, and to show the effects of such organic
lesions according to the known laws of the or-
 organism.    To recur  to  a former illustration;
 we trace a dropsical effusion to a  disease of the
 heart, and show how such a disease would cause
 cause the effusion.   We address our  remedy
 then to  the  lesion which  causes  the symptom,
 and  not to  the symptom  which may depend on
 very different  lesions.  In a word, we endeavor
 to decompose the  disease  into  its elements,
 rather than to cure it  in the gross. 
                      40
   I repeat, however, that  in no case have we
arrived at any thing like  an ultimate law  in
medicine.  The fundamental vital action, nutri-
tion, is not a simple act, but very complex, and
we have not succeeded in  analyzing it, so as to
show all its elements.  In like manner; the com-
monest form of disease, inflammation, is defined
by its symptoms,  but the precise nature of the
deviation from health has not been pointed out,
and indeed never can  be, until we have a com-
plete knowledge of the nutritive  act.   From this
imperfection of medical science, it follows that
all the practice  founded on it,  is more or less
uncertain.  In some instances,  our  practice is
purely empirical,  as when we give bark in inter-
mittent fever.  In other cases, we analyze the
phenomena to a certain extent, as when we find
dropsy depend on a granular degeneration of the
kidneys, but here we cannot point out precisely
what this alteration is, nor why it hinders the
separation of  the urea from the blood,  nor can
we even  tell why the kidneys in  health separate
urea from the  blood.  So that the difference be-
tween empirical and scientific medicine reduces
itself to this, that the former attempts no analysis
of the phenomena  of  disease, while the  latter
plunges as deep as possible into this  analysis, 
                     41
but without in the present state of the science,
reaching any  ultimate  law,  and consequently
without attaining to absolute certainty in prac-
tice.
  It is plain then, that there can be no question
as to the superiority of scientific practice  over
empiricism, any more than there can be of sci-
ence over popular knowledge.  That which has
given countenance  to empiricism as a method,
is the tendency already alluded to, of adhering
to a theory or  system even when the absurd re-
sults to  which it logically leads are  manifest.
This is, however, not an  objection to scientific
practice, but only to a blind adherence to the
conclusions of a false science. When our science
leads to mischievous practice,  it should be  at
once abandoned as false, for the best test of the
soundness of  our principles,  is to be found  in
tbe conclusions which may be logically deduced
from them.
  Undoubtedly empiricism has its uses, and has
introduced many important improvements into
our art.  The  properties of all the medicines we
possess, have  been discovered empirically, and
even at this day, we could not suspect from any
of the chemical or mechanical properties of jalap
or of ipecacuanha, that the one would purge and
               6 
                     42
the other vomit.   Many of the most  valuable
remedies have been discovered in the same way,
as for example, Peruvian bark  in intermittent
fever, and mercury in syphilis.
  The two modes of practice, though not sepa-
rated by a well defined line, differ widely in their
method and in their tendencies.  The  empiric
seeks for remedies for  diseases, the scientific
practitioner seeks to understand the disease, to
trace it to its starting point, and to explain it by
the known laws of the organism.  The practice
of the latter must be to a certain extent, empiri-
cal and uncertain, because he has no  ultimate
laws on which to found it, and in some cases
must be  purely empirical,  inasmuch as he  can
not give any explanation of the disease or of the
mode of action of the remedy which he has found
to cure it.   The empiric discards  all science as
the foundation of practice, while the scientific
practitioner employs the science which, imper-
fect as it is, is all that has thus far been attained
by  the human mind, without refusing to profit
by  empirical experience when science fails him.
   But while we allow to empiricism its full place
in practical medicine,  and admit that  scientific
practice in its present  condition, is only an en-
lightened empiricism, we look to science for the 
                     43
future improvements in our  art.   Medical sci-
ence is now so far advanced  as to have become
more and more adapted to  practical uses, and
in many directions,  our analysis  of the pheno-
mena of life has been pushed so  far, as to give
the promise of arriving  at ultimate laws.  But
without resting on any such problematical antici-
pations, if we look  backwards to see what has
been done within the last fifty years, we will find
that the improvements of our art have depended,
not  on the discovery of new remedies,  but on
the progress of our  science.   The modern im-
provements in  diagnosis, which  have rendered
medical practice so much more certain and safe,
have all been results of scientific observations.
If we can treat diseases of the lungs and of the
heart with more success now than formerly, the
'reason is, not that we  have  new remedies, but
that we understand better than before the lesions
of these organs,  and  have  improved means of
detecting them.  In almost  every medical jour-
nal, we find some new remedy for consumption,
which  is greedily procured by  the  seekers of
cures, and with what result ?  why not one of
 these remedies continues in favor for more than
a few years, while the researches of Laennec
into the morbid anatomy of the  disease  and his 
                     44
new means of diagnosis remain, and will forever
remain, as our guides to practice.  And I will
now predict with great confidence, that if ever
a remedy is to be found for this disease, it will
result from an investigation of the nature of tu-
bercular deposit, and the conditions which give
rise to it, and not from a blind search after cures.
The truth is, we have remedies enough if we
only knew how to use them.  When I see  a
man ignorant of medical  science greedily de-
manding new medicines and new combinations,
it seems to me as  though a sign painter should
think he could make a fine picture, if he could
only procure the colors and brushes of some
great artist.
  We hear a great deal, in our profession, about
practical knowledge  and  practical men.   All
knowledge, whether it be of an eclipse of Jupi-
ter's satellites, or of the germination of a grain
of wheat, is susceptible of practical application,
and so far is practical;  and other things being the
same, he will be the best fitted for practice who
has the most knowledge. There is, undoubtedly,
a  certain  tact, a  certain faculty of invention
which  some men  do  not possess, and without
which, one cannot become a great practitioner,
though  he  may be well versed in science, but 
                     45
be assured that the fault here lies in his want
of this tact, and not in his possession of learn-
ing.   If he  knew less, he would be still less
capable of practice.  Look into the lives of all
the great masters of our art,  and you will find
them profoundly acquainted with the science of
their day, and the principles of the art, and not
practical men in the sense of being ignorant.  I
have never known  theoretical knowledge de-
cried, except by those who did not possess it.
  If, then, you  would become truly eminent  in
your profession,   study well  the  theoretical
branches.  Learn the science of medicine before
you  attempt to learn,  and still less to practise
the art.  Undoubtedly the great physician must
be formed at the bed side, and not in the study,
but  you will profit by your bed side experience,
precisely in proportion as you came armed with
science, which will enable you to  comprehend
what you see.   The nurse sees disease  all her
life,  and learns nothing but to be self-sufficient;
so there are practitioners of medicine who boast
of the experience of a long life,  and yet have
never learned any thing, for the reason that they
did  not  possess  enough  of  science, to  furnish
them a key to  the comprehension of what was
passing under their eyes.  It is with them as it 
                     46
would be with a man who should look at books
all  his life, without having  learned to read.
Make it a point  then during your studies here,
to understand diseases rather than to learn pre-
scriptions and remedies.  This is the time for
you to learn  the  science of medicine, the prac-
tice you will be learning all the rest  of your
lives,  and you will profit  by the latter precisely
in proportion, as you are  well grounded in  the
former.