maladies by invading the human and other living bodies as parasites,
consuming and disorganizing their tissues, blood corpuscles,[20] etc.
Pasteur considers the abstraction of oxygen an important part of their
action.
[Footnote 20: Against this view stands especially the objection that,
as Cohn, Burdon Sanderson, and others have fully shown, bacteria and
other Schizomycetæ obtain their nitrogen, not from organized tissues,
but from ammonia, and their carbon and hydrogen from the results of
decomposition in organic tissues. (See B. Sanderson, in _Brit. Med.
Journal_, Jan. 16, 1875.) Pasteur has regarded the relation of these
organisms to oxygen as important; some of them requiring it for their
existence (ærobic), and others not (anærobic). He has defined
fermentation as "life without free oxygen."]
5. That these microbes, microphytes, or mycrozymes act not as
parasites, but as poison-producers, secreting a sort of ferment which
is the specific morbid material (Virchow); or, when multiplying in
excess of their food-material, they may die, and their dead bodies,
like other decaying organic matter, may become poisonous. This
possibility, although not distinctly suggested (so far as I know)
hitherto, appears to me to be not unworthy of consideration. That the
numbers of micro-organisms present have some important relation to
morbid conditions has long since been inferred from familiar facts.
6. That they are not generators, but carriers, of disease-producing
poisons; their vitality giving to the latter a continuance of
existence and capacity of accumulation and transportation not
otherwise possible.
Briefly, the following is a summary of the most generally accepted
classification of those microscopic organisms[21] whose rôle in the
causation of diseases is now under discussion; chiefly following Cohn
and Klebs:
_Orders_: Hyphomycetæ, Algæ, Schizomycetæ.
Hyphomycetæ, _genera_: Achorion, Tricophyton, Oidium.
Algæ, _genera_: Sarcina, Leptothrix.
Schizomycetæ, or Bacteria, _genera_: Micrococcus, Rod-bacterium,
Bacillus, Spirillum.[22]
[Footnote 21: For further details concerning these the reader is
referred to the works of Magnin, Belfield, and Gradle on _The
Bacteria_, and on the _Germ Theory of Disease_.]
[Footnote 22: Cohn also separates vibrio and spirochæte as genera
distinct from spirillum. They may, however, be regarded rather as
species of that genus. Some recent authors included bacterium and
bacillus under one genus, bacillus; against which simplification there
seems to be no valid objection.]
Micrococci (Sphærobacteria of Cohn) are asserted (under certain
conditions) by Letzerich, Wood, and Formad[23] to be causative of
diphtheria; Ogston has found them in ordinary pus; Rindfleisch,
Recklinghausen, Waldeyer, Birch-Hirschfeld, and others report them to
be always present in the abscesses of pyæmia; Buhl, Waldeyer, and
Wagner state their occurrence in intestinal mycosis; Eberth, Köster,
Maier, Burkhardt, and Osler, in ulcerative endocarditis; Orth,
Lukomsky, Fehleisen, and Loeffler, in erysipelas; Coats and Stephen in
pyelo-nephritis; Friedländer, in pneumonia; Eklund (_Plax scindens_)
in scarlet fever; Keating[24] and {142} Le Bel, in measles; Leyden and
Gaudier, in cerebro-spinal meningitis; Carmona del Valle, in yellow
fever; Prior, in dysentery; Gaffky, Leistikow, Bokai, and Bockhardt,
in gonorrhoea;[25] besides other similar observations by numerous
writers.
[Footnote 23: _Bulletin of National Board of Health_, Supplement No.
17, Jan. 21, 1882.]
[Footnote 24: _The Medical News_, Philadelphia, July 29, 1882.]
[Footnote 25: Sternberg's careful experimentation seems to show the
identity of Neisser's gonococcus with the Micrococcus ureæ, commonly
found in decomposing urine.]
Bacterium termo is regarded by leading authorities as the special
ferment or causative agent of putrefaction[26] (Billroth, Cohn).
[Footnote 26: Others have referred putrefaction to vibriones, less
precisely described.]
Bacillus includes, hypothetically at least, several species; as
Bacillus subtilis, the innocent hay-fungus; Bacillus anthracis, the
microbe of malignant pustule (anthrax, milzbrand, charbon) and the
splenic fever of sheep; Bacillus typhosus (Klebs, Eberth, Meyer) of
typhoid fever; Bacillus lepræ (Hansen, Neisser, Cornil, Koebner) of
leprosy;[27] Bacillus malariæ, reported as having been
demonstrated[28] by Klebs and Tommasi Crudeli, Marchand, Ceri, and
Ziehl; Bacillus tuberculosis (Koch, Baumgarten, 1882); the bacillus of
malignant oedema (Gaffky, Brieger, Ehrlich); that of syphilis
(Aufrecht, Birch-Hirschfeld,[29] Morrison); of glanders (Loeffler,
Schuetz, Israel, Bouchard); of pertussis (Burger); besides the
Actinomycosis of Israel, Ponfick,[30] Bollinger, and others. Koch has
very recently (1883) been reported to have discovered in Egypt the
bacillus of cholera.
[Footnote 27: Dr. H. D. Schmidt of New Orleans, an experienced
pathologist, reported (_Chicago Medical Journal and Examiner_, April,
1882) that critical examination of numerous specimens of tissues from
three cases of leprosy under his care failed to verify the existence
of bacilli as characteristic of that disease.]
[Footnote 28: Not certainly, however, as shown by Sternberg (_Bulletin
of Nat. Board of Health_, Supplement No. 14, July 23, 1881). Dr.
Salisbury of Ohio in 1866 made a series of observations, on the basis
of which he asserted the discovery of a genus of malarial microphytes,
which he referred to the family of _Palmellæ_.
The oval and spherical organisms described by Richard and Laveran as
found in the blood of malarial patients resembled micrococci rather
than bacilli.]
[Footnote 29: More recently described by him as micrococci.]
[Footnote 30: _Die Actinomykose_, 1881.]
[Illustration: FIG. 1. Micrococci: _a_, zoogloea form; _b_,
micrococcus from urine, in rosary chain; _c_, rosary chain from
spoiled solution of sugar of milk (Cohn).]
[Illustration: FIG. 2. Bacteria: _a_, zoogloea of _Bacterium termo_;
_b_, pellicle of bacteria from surface of beer; _c_, _Bacterium
lineola_, free; _d_, zoogloea form of _B. lineola_.]
[Illustration: FIG. 3. _Bacillus malariæ_ of Klebs and Tommasi
Crudeli.]
[Illustration: FIG. 4. Bacteria from gelatin solution, inoculated from
swamp-mud, X 1500 (Sternberg).]
[Illustration: FIG. 5. Vibrios in gelatin culture-fluid, X 1000
(Sternberg).]
[Illustration: FIG. 6. Protococcus from slides exposed over swamp-mud,
X 400 (Sternberg).]
[Illustration: FIG. 7. Bacilli from swamp-mud, X 1000 (Sternberg).]
[Illustration: FIG. 8. Bacilli from septicæmic rabbit, X 1000
(Sternberg).]
[Illustration: FIG. 9. Bacilli from human saliva, X 1000 (Sternberg).]
[Illustration: FIG. 10. _Bacillus anthracis_ (Sternberg).]
[Illustration: FIG. 11. _Bacillus tuberculosis_, within and outside of
pus-corpuscles (Sternberg).]
Spirillum (Spirochæta of Ehrenberg) has its best ascertained example
in the minute forms first observed by Obermeier, and afterward by many
other observers, in the blood of patients suffering with relapsing
fever. They have been found present in the blood only during the
febrile paroxysm, disappearing in the intermission and through
convalescence.
Hastening to close our consideration of this subject, we may note,
without much argument, a few of the points of difficulty needing yet
to be more fully illuminated by {143} careful observation before any
form of the germ theory can take its place as an established doctrine
in etiology:
1. The absence of the characters belonging to definite organisms[31]
in the easily-studied virus of small-pox and vaccinia stands, a
priori, against the probability of such organisms being essential to
the causation of other enthetic diseases.
[Footnote 31: The particulate character of variolous and vaccine virus
has been already alluded to, as asserted to have been shown by
Chauveau and others. Yet it is not absolutely demonstrated that
filtration may not produce an important chemical alteration in some
kinds of highly unstable organic material subjected to it. Cohn
figures a Micrococcus vacciniæ in his article on Bacteria
(_Microscopical Journal_, vol. xiii., N. S., pl. v., Fig. 2). Beale
denies (_Microscope in Medicine_, 4th ed.) the existence of any
organisms in vaccine virus. Lugginbuhl, Weigert, Klebs, Pohl-Pincus,
and others have asserted their existence, but, especially in the
absence of any successful culture experiments, it does not seem to be
proved.]
2. Analogy in nature, showing the commonly beneficial action of
nutritive processes in re-appropriating the products of organic decay
on a large or on a small scale, makes the scavenger theory of the
general function of minute cryptogamic organisms more probable, per
se, than that which holds many of them to be destructive parasites or
poison-producers in the bodies which they may inhabit. Few well known
parasites are capable of causing death in higher animals or in man.
3. These microbes are among the minutest objects which can be studied
under the microscope. Bacteria average about 1/9000 of an inch in
their longest diameter; micrococci and spores (Dauersporen, Billroth)
are yet smaller. Much care, therefore, as well as skill, must be
exercised in making observations upon them.[32] Huxley asserted a few
{144} years ago that a distinguished English pathologist had mistaken
for movements of minute living organisms the "Brownian movements" seen
in the particles of many not living substances under a high magnifying
power. One observer, at least,[33] considers that the forms designated
as bacteria and micrococci, etc. are either forms of coagulated fibrin
or granules from morbidly-altered blood-corpuscles (zoogloea of
Billroth, Wood, Formad, and others). Koch denies the validity of the
observation of organisms in tubercle by Klebs and Schüller, while
insisting upon his own demonstration of a bacillus tuberculosis.
Authorities must, by mutual confirmation or correction, remove these
obscurities.
[Footnote 32: A very interesting discovery was made by Tyndall, to the
effect that while one boiling of a liquid would sterilize it for the
time by destroying all the bacteria present, their spores might still
retain vitality and be afterward developed. By repeated exposure to a
boiling temperature, taking these spores in their developing stage,
they were destroyed, and complete sterilization was effected.]
[Footnote 33: R. Gregg, _N.Y. Med. Record_, Feb. 11, 1882. Sternberg,
however, has replied to him (_N.Y. Med. Record_, April 8, 1882, p.
368). The latter admits a doubt as to whether the granules seen within
the leucocytes by Wood and Formad in diphtheritic material, and
believed by them to be micrococci, are such, or are merely granules
formed or set free by disorganization of protoplasm within the
leucocytes. This uncertainty well illustrates the difficulty of these
investigations.
A chemical test much relied upon is, that bacteria resist the action
of acids and alkalies, which destroy granular material of animal
origin; also, that all these organisms are deeply stained by aniline
dyes and by hæmatoxylin. The most decisive test, however, is
cultivation in a liquid sterilized by heat. Koch prefers a process of
dry culture for the bacillus of tubercle.
Gradle (_Lectures on the Germ Theory of Disease_, Chicago, 1883, p.
28) says that the absolute criterion of the life of bacteria is their
power of multiplication.]
4. Bacteria and micrococci have been abundantly discovered (Kolaczck;
J. G. Richardson) in healthy bodies upon the various mucous membranes
and in the blood. The correctness of such observations has been
denied, but, so far at least as the mucous membranes are concerned, it
has been well established by Nothnagel, Sternberg, and others.
Bacteria have sometimes been found in countless numbers in fecal
discharges.
5. Bacteria become most numerous in materials of a septic or
infectious character after their period of toxic intensity has passed
by.
6. Suppuration can be produced (Uskoff, Orthmann) without the presence
of minute organisms of any kind. Bacteria have been found {145} under
Lister's antiseptic dressings without suppuration following. Paul Bert
destroyed all the microbes in a septic liquid, and yet found it to
retain its poisonous quality. Rosenberger (1881) has made similar
observations.
Panum, Coze, and Seltz, Bergmann and Schmiedeberg, Hiller, Vulpian,
Rosenberger, Clementi, Thin, and Dreyer have, by various elaborate
investigations, proved that fatal septic poisoning can be produced in
animals by the products of organic decomposition, without the presence
of living organisms. Zweifel's experiments seem to have shown that
normal blood, when deprived of oxygen, in the absence of
micro-organisms, may acquire septic properties.
As stated by Belfield,[34] many experiments by Schmidt, Edelberg,
Köhler, Nencki, and others, have shown that septicæmia may be induced
by the injection into the blood of free fibrin ferment and other
substances, in the absence of minute organisms. To such an affection
some authors now give the name sapræmia, to distinguish it from
bacterial infective disorders.
[Footnote 34: _Lectures on the Relation of Micro-organisms to
Disease_, 1883.]
Griffini ascertained that mixed saliva, filtered through porous
plates, and thus containing no microbes, will still produce septicæmia
in animals, when subcutaneously injected. Colin (1876) has denied the
conclusiveness of the experiments of Chauveau, which have been held to
prove the particulate nature of variolous and vaccine virus. Moreover,
it is well known that eggs with shells unbroken are tainted when
placed near others which are unsound.
7. While Klebs and Koch maintain the definite specificity of each
minute microphytic organism, Nægeli and Billroth assert their mutual
convertibility. Burdon Sanderson avers[35] that "the influence of
environment on organisms such as bacteria is so great that it seems as
if it were paramount." Buchner, Grawitz, Greenfield, Pasteur, Wernich,
Thorne, Willems, Law, Wood, and Formad report experiments making it
appear that modification by culture is possible with bacilli and
micrococci, converting an innocent into a malignant parasitic
organism, or a death-producing microbe into one capable only of
causing {146} a transitory and not dangerous local affection; which
nevertheless secures to the animal thus treated immunity when
subsequently exposed to the deadly infection. Most interesting have
been the successes with such culture-inoculations obtained by Buchner,
Greenfield, and Pasteur with anthrax in sheep; by Pasteur also in
chicken cholera; and by Willems and Law[36] with the lung-plague of
cattle.
[Footnote 35: _Brit. Med. Journal_, Jan. 16, 1875.]
[Footnote 36: _N.Y. Med. Record_, June 18, 1881, p. 679. Exposure to
the air for a considerable period seems to be the agency chiefly
relied upon for what may be called the dynamic modification of these
microphytes. When cultivated in the depth of a liquid, so that air is
excluded, they are supposed to acquire a habit of obtaining oxygen by
decomposing organic substances, and thus act destructively upon the
cell-elements of living bodies. Analogous differences have long since
been observed in the study of fermentation between surface and
sedimentary yeast.]
In none of these cases is there reported any morphological change
whatever in the bacillus (Grawitz) or micrococcus (Wood and Formad);
the change in the effects noted, and, in the case of the micrococci of
malignant diphtheria, the acquired capacity of reproduction through
several generations, are all.
8. The immunity against subsequent attacks on exposure (similar to the
protection given by vaccination) continues to be without full
explanation upon any theory. But it is especially difficult to
reconcile it with the hypothesis of the infection being caused by, and
dependent upon, the presence of peculiar microphytes. Why should not
these, whether as parasites or as poisons, always produce the same
effects?
9. The view entertained by Thorne, Wood, and Formad, that a common
benignant affection, such as ordinary sore throat, may be converted
into a violent infectious disease--_e.g._ malignant diphtheria--by
modification of innocent micrococci into those with lethal characters,
through local or bodily conditions, is sufficiently contravened by the
great frequency of such conditions compared with the decided relative
rarity of such malignant epidemics or endemics.
10. Throughout all the investigations which have been, and are likely
to be, conducted, there remains the extreme difficulty, if not
impossibility, of total separation between the microbes themselves and
the matter of the vehicle in which they exist--the membrane, urine,
blood, virus, artificial culture-material, or whatever it may be. All
the effects ascribable to the disease germs may be, with no more
difficulty, attributed to the toxic action {147} of a portion, however
minute, of the soil in which they have lived, whose modifications must
be concomitant with those which they undergo. It appears necessary,
therefore, at the present time, to regard this whole question as still
undecided, with a predominance of probability, however, in favor of
the view that these minute organisms, or some of them, have a direct
and important relation of some kind to the causation of specific
endemic, epidemic, and contagious diseases. Altogether, the strongest
arguments are on the side of the view that the micrococci, bacilli,
etc. cause diseases, not as parasites, living upon their victims, but
as poison-producers infecting them.[37] The germ theory continues to
be in the position of a probable hypothesis, not in that of an
established doctrine of etiological science.
[Footnote 37: This comports much the best with the general natural
history of parasites on the one hand, and of venoms, ptomaïnes, etc.
on the other. Gautier, Ogston, and others have expressed the opinion
that microphytes may produce ptomaïnes.]
Practically, the result is nearly the same as if it were altogether
settled, since it is admitted on all sides that the presence of
microphytes (bacteria, micrococci, spirilla) coincides with those
conditions under which originate several of the most malignant
diseases. Measures which prevent the appearance or promote the
destruction of these minute organisms are at least often, and to a
great degree, preventive, if not curative, of such disorders; and the
glory of Jenner's discovery, by which the ravages of small-pox have
been made (potentially at least) controllable, seems not unlikely to
be paralleled by the achievements of Pasteur and others in a similar
preventive mastery over other maladies of men and animals. There is,
therefore, no branch of inquiry in connection with medical science
more worthy of being assiduously encouraged and extended. The present
may almost be said to be, in the history of medicine, an era of
myco-pathology.
For an exhaustive study of Etiology attention would now have to be
given to the modifying influences affecting the occurrence and
character of diseases in connection with age, sex, and temperament.
But, as neither of these is ever, per se, causative of any malady, and
they merely determine some modification of the action of morbid causes
when these occur, want of space must be our justification for leaving
them to be considered, in this work, in connection with the special
causation of the different {148} diseases which will be hereafter
described. A larger treatment of our present subject belongs rather to
hygiene than to practical medicine.
MEDICAL DIAGNOSIS.
For the purposes of the medical practitioner all professional studies
unite to the end of furnishing preparation for the diagnosis and
treatment of diseases. At the bedside the cardinal questions are, How
does the present condition of our patient differ from health? and,
What ought we to do to bring about his recovery?
Diagnosis involves three main directions of inquiry: 1, as to the
general bodily state of the patient; 2, morbid changes in particular
organs, tissues, or functions; 3, as to what name properly designates
the disorder, according to accepted nomenclature.
Pathology can never be out of view in connection with either the
theoretical or the practical study of diagnosis. But it is most
closely regarded when the last of these questions is before us, since
the names of diseases generally have a more or less distinct reference
to their pathological nature. Yet clinical observation always suggests
the early use of provisional terms for recognized groupings of morbid
phenomena; and sometimes these clinical designations remain for a long
time in use because of the imperfection of pathology.
We ascertain, in practice, the nature of a given case, first, by
considering its symptoms. These are those obvious evidences of
deviation from health which the patient himself is aware of, or which
the physician readily discerns or elicits by simple inquiry or
examination.
Secondly, taking the clue furnished by symptoms, a closer inspection
is made, with the intent of finding what is the actual state of
important organs, as the heart, lungs, liver, spleen, kidneys, and
alimentary canal.
Lastly, when these means fail to remove all obscurity, or when special
scientific investigation is practicable, instruments of precision are
employed, as the thermometer, sphygmograph, ophthalmoscope,
æsthesiometer, or aspirator; or by the microscope and chemical
analyses still more minute examination is made into the particulars of
the morbid processes present and their results.
We may subdivide diagnosis, then, into: 1, symptomatology; 2,
organoscopy or physical diagnosis; 3, instrumental diagnosis.
Symptomatology.
Semeiology (from [Greek: sêmeion], a sign) is a term much in use, with
essentially the same meaning as symptomatology, but less conveniently
distinctive, since it does not so well indicate the contrast between
obvious signs, or symptoms, and those more recondite, obtained by the
methods of physical diagnosis.
Signs of disease cannot be recognized as such except by one who is
{149} familiar with the appearances, actions, and manifestations which
belong to health. Nor can they be understood, so as to infer what they
mean, without knowledge of normal physiology on the one hand, and, on
the other, of the natural history of diseases. Physiology constitutes
the etymological grammar, symptomatology the vocabulary, and diagnosis
the syntax of practical medicine. Just as grammatical knowledge will
not enable any one to read or speak a language without acquaintance
with its words, so clinical observation is necessary to the physician
over and above all the knowledge he may have of physiology and
pathology. He must learn to know diseases by sight, or at least by
personal contact and observation.