hygiene, but also to its therapeutic use, particularly in the
treatment of phthisis, goitre, and some affections of the nervous
system. But in our brief and general survey of Etiology this topic
must be left without discussion, since no disorder appears to be
traceable to elevation alone, beyond the temporary prostration on
exertion, with hemorrhages from the nose, lungs, etc., often produced
in those who climb to great mountain-heights or ascend rapidly in
balloons. It has been shown by ample experience that considerable
populations may live in ordinary health through long periods at
altitudes more than 10,000 feet above the level of the ocean.
Depression below the surface of the earth has never become a part of
human experience beyond the limit of a few hundred feet. Miners living
underground in a few places in Europe have been found to exhibit
comparatively feeble health, but the privation of sunlight, the
confined atmosphere, and the dampness of such unnatural abodes will
suffice to account for these effects.
Under functional causation of disease we may include all excessive,
deficient, or abnormal exercise of any of the organs of the body. To
simple excess may be ascribed the scrivener's or bank-officer's
paralysis of the muscles of the hand used in continuous writing; brain
{135} exhaustion from mental labor or anxiety, unrelieved by
sufficient sleep; and sexual impotence, temporary or lasting (or
sometimes even general paralysis), from inordinate sexual or sensual
indulgence.
Deficiency of functional exercise is observed to produce disability,
as when the muscles of a limb, for instance, are for a long time
restrained from use. Surgeons meet with this inconvenience (unless
assiduously guarded against) when a fractured limb is kept long at
rest in a fixed position. Atrophy of the mammæ in single women of
retired lives is common; atrophy of the testicles in unmarried men
much less so. These changes, however, are physiological, not
pathological; upon alteration of conditions--_e.g._ marriage--the
atrophy will disappear altogether.
Abnormal functional action as a cause of morbid results is seen when
the eyes are injured by reading, writing, or doing any delicate work
in a bad light; for instance, late twilight. Also, in a secondary or
accessory manner, when a near-sighted person, having the action of the
muscles of convergence in excess of his accommodation, or a
long-sighted (hyperopic) person, whose accommodation is in excess of
convergence, suffers from asthenopia, perhaps with headache, distress,
nausea, etc. Another example of abnormal functional exercise and its
effects is that of self-abuse, where the unnatural mechanical
imitation of the physiological act of sexual coition induces
disturbances of the nervous and circulatory systems, besides debility
from excess.
Ingestive causation is a sufficiently fit designation for all errors
of diet, as well as misuse of medicines, and poisoning. Starvation or
inanition belongs to the same category by negation. Gluttony and
intemperance are major members in the ingestive series, while haste in
taking food, without mastication, and the use of heavy bread, unripe
fruit, and other indigestible articles, account for many cases of
dyspepsia and some of colic, cholera morbus, diarrhoea, etc. With
young children, especially, no more frequently acting cause of
disorder exists than dietetic mismanagement, most of all during the
period of dentition, and earlier, when, from absence or insufficiency
of mother's milk, they have to be artificially fed. Then the supply of
good fresh cow's, goat's, or ass's milk may carry them well through
infancy, while a regimen of arrowroot or gum-arabic and water, or
stale, half sour milk, may either starve or sicken them to death. On
the subject of poisons and of misuse of medicines we have no occasion
here to make special remark. Only it may be mentioned that the
possibility of either is always to be remembered by the physician in
making up his mind in regard to the origin of symptoms observed.
Enthetic causation is a large subject, including all origination of
disease by the introduction of morbid materials from without the
body.[6] Medical opinion has generally accepted, and facts fully
sustain, the recognition of three groups of enthetic disorders, viz.:
those which are personally contagious; such as are locally epidemic;
and epidemic diseases. Of the first group it will suffice to mention,
as an example, syphilis; of the second, intermittent fever; of the
third, influenza.
[Footnote 6: Simon has proposed the term exopathic to indicate the
origin of such maladies; autopathic disorders being those which
originate within the body itself.]
Were all maladies whose causation is evidently of external origin
capable of the same clear discrimination as these, we should have no
difficulty with the present topic. But, in fact, no subject connected
with {136} the history of disease has become surrounded by more
intricate controversy. Many times the same facts are, or appear to be,
explicable in two or three different ways. What some hold to be proofs
of contagion from person to person, others are ready to account for by
the subjection of a number of persons or of a whole community to
either a common local or a widespread migrating (epidemic) influence.
It is sometimes impossible, in the nature of things, to obtain an
absolute demonstration of the truth of one or another of these
theories without such experiments upon human beings as are
impracticable.
While endeavoring to ascertain the limits of our present knowledge
upon these questions, let us first notice what are the most positive
facts concerning them, some of which are common to the whole group or
class of what have been, since Liebig, often called zymotic,[7] but
latterly more often enthetic, diseases.
[Footnote 7: The term zymotic has, with many authors, fallen into
disrepute, chiefly because Liebig's hypothesis concerning the
chemico-physical action of ferments, as well as of contagia, has lost
ground in comparison with the vital or disease-germ theory. Yet the
analogy between fermentation, putrefaction, and the action of a virus
on an animal organism persists; whatever may be the theory of their
explanation, something appears to be common or similar in all these
processes.]
These diseases may be enumerated as follows:
1. _Only produced by contact or inoculation_.
Primary Syphilis,
Gonorrhoea,
Vaccinia,
Hydrophobia.
2. _Contagious also by atmospheric transmission through short
distances_.
Variola,
Varioloid,
Varicella,
Measles,
Diphtheria,
Scarlatina,
Rötheln,
Mumps,
Whooping Cough,
Typhus,
Relapsing Fever.
3. _Endemic, occasionally epidemic_.
Malarial Fevers (Intermittent, Remittent, and Pernicious Fever),
Dengue,
Yellow Fever.
4. _Other zymotic or enthetic diseases_.
Influenza,
Cerebro-spinal Fever,
Erysipelas,
Puerperal Fever,
Tropical Dysentery,
Typhoid Fever,
Cholera,
Plague.
As all observers are agreed in regard to the personal transmission of
the first named of these series (variola, etc.), we need to give
attention here only to the other groups; except merely to say that the
easily demonstrable existence of a morbid material (virus) in the
instances of primary syphilis, gonorrhoea, variola, and vaccinia
presents a very cogent analogical argument for the presumption that
all clearly contagious (even {137} though non-eruptive) maladies, such
as mumps and whooping cough, must also have a morbid material as their
essential cause; and also in favor of the supposition that a morbid
material may probably be the "causa sine quâ non" of each of the other
maladies which are known to be endemic or epidemic. A few theorists
only have argued in favor of any other view than this. Sir James
Murray and Dr. Craig of Scotland, and Dr. S. Littell of Philadelphia,
have sustained an electrical hypothesis, and Oldham and others have
advocated one connected with changes of bodily temperature, or ozone,
etc., for the origination of certain endemic and epidemic diseases.
But all the facts point toward the existence of material causes,
specific for each of these disorders, and many observations and much
ingenuity of reasoning have been brought to bear upon the question as
to their intimate nature.
Are these materiæ morborum merely inorganic elements or compounds
entering human bodies and acting there as chemical poisons? Against
such a supposition we have, as almost decisive objections, not only
the absence, under the most searching analysis, of any chemical
peculiarity in the air of malarious or otherwise infected regions, but
also the clinging of many endemic and epidemic causes (as known by
their effects) to particular localities, notwithstanding the
recognized law of the diffusion of gases which must antagonize such
concentration. Therefore, we may rule out, as highly improbable at
least, the hypothesis of the inorganic gaseous nature of malaria, as
well as of the essential causes of yellow fever, cholera, plague, and
the other analogous diseases.
By the once general use of the term zymotic, there is suggested a line
of thought which has been quite prevalent since the prominence of
Liebig's teachings in chemical physiology, until recently. That great
chemist did not imagine that a true zymosis or fermentation occurs
under the action of a virus upon the human economy. His thought was
more clearly expressed, in the phraseology of the late Dr. Snow of
London, as the theory of continuous molecular change. Its most
striking physical instance or analogue is the extension of flame from
a burning body to combustible matter within its reach. Sugar formation
from starch by diastase, and the change of albumen into peptone by
pepsin, are familiar examples, in organic materials, of the
propagation of molecular movement in special directions and with
characteristic results.[8] It does not seem to be more than a short
step from these to the processes which we study in fermentation,
putrefaction, septicæmia, and the multiplication of small-pox
contagion, from the smallest inoculation, in the human body.[9]
[Footnote 8: In anticipation of the argument concerning the necessity
of the action of minute living organisms to produce fermentation,
putrefaction, and specific diseases, emphasis may be here laid upon
the fact that the above named changes, and many others like them, are
produced, in the absence of such organisms, by chemical agents formed
in the body, or even (as when sulphuric acid changes starch to sugar)
by inorganic substances. Pasteur considers that the yeast-cell
secretes a sort of diastase which changes starch or cane-sugar into
glucose, on which the cell then lives, decomposing the glucose into
alcohol, carbonic acid, etc. Koch and others now assert that a
bacillus produces the souring of milk, and another the butyric acid
fermentation.]
[Footnote 9: The assertion of some advocates of the "germ theory of
disease," that only living organisms reproduce their kind, loses
weight as an argument in view of the natural history of small-pox and
analogous diseases; unless it be proved that every particle of
contagious matter is (at one time at least) a living organism.]
But here comes in a new hypothetical factor, introduced by the aid of
{138} the microscope, although anticipated conjecturally before actual
discoveries in this field were made certain. So prominent is this
subject in the discussions of the present time, under the expression
"the germ theory of disease," that we are justified in giving
attention to it here somewhat at length.
Stahl proposed a purely chemical theory of fermentation early in the
seventeenth century. Not much later Hauptmann suggested the probable
causation of epidemic diseases by minute living organisms. Linnæus[10]
revived this hypothesis in the eighteenth century. These two topics of
inquiry, with the intermediate one of putrefaction, then received much
attention, at first apart, but afterward with recognition of their
analogies. When Fabroni, Cagniard de la Tour, Schwann, and Kützing
had, with the aid of the microscope, made familiar the life-history of
the yeast-fungus[11] (Saccharomyces cerevisiæ), more close
consideration still was given to these remarkable changes in organic
materials and forms, dead and living.
[Footnote 10: Linnæus accepted the asserted observation by Rolander of
acari in the stools in dysentery. The great naturalist deviated
somewhat here from his usual carefulness and accuracy, as that
observation was not afterward verified.]
[Footnote 11: Lëuwenhoek, however, had observed and described it in
1680.]
Starting from the physical basis of inorganic chemistry, Liebig
followed the series up from the so-called catalytic[12] action by
which the presence of a substance, itself apparently unchanged,
induces reaction between two or more other bodies, to those which
occur within plants and animals, as examples of vital chemistry. Such
is the influence of diastase or invertin, which in the seeds of plants
brings on the conversion of starch into sugar and of cane-sugar into
glucose and levulose. Such is the agency of ptyalin in the saliva, of
pepsin in the gastric juice, and of pancreatin or trypsin in the
secretion of the pancreas, in the processes of digestion. From these
it appears to be an easy transition to those changes which occur in
organic matter no longer living, as in the fermentation of vegetable
juices and the putrefaction of animal tissues.[13] Liebig endeavored
to explain these also in the same manner as the chemico-vital
processes; and he then went farther to apply the same generalization
to the propagation of disease, by what is called virus, in the
instances of contagious, endemic, and epidemic maladies.
[Footnote 12: The idea expressed by this term was especially favored
by Berzelius and Mitscherlich.]
[Footnote 13: It is noticeable, however, although generally forgotten,
that the one set of changes and assimilations (namely, those of
digestion) are formative actions of life, and the others destructive,
in the direction of, or subsequent to, death.]
But, meanwhile, observation and speculation gave almost equal
prominence to the importance of minute living organisms in the
apparent instigation of all these evidently analogous changes of
fermentation, putrefaction, suppuration, septicæmia (Piorry, 1835),
infection, and contagion.
Upon this side the leading investigator for many years has been
Pasteur. As long ago, however, as 1813 Astier, and in 1840 Henle of
Berlin, and near the same time Sir Henry Holland of London and Dr. J.
K. Mitchell of Philadelphia, gave expression to opinions of a similar
kind, based upon many important facts before very much overlooked. By
exact experimentation, moreover, Schwann, Helmholtz, Schroeder, and
Dusch ascertained that the agent or agents causative of fermentation
and putrefaction can be detained by heated tubes, by animal membranes,
{139} and by cotton wool, anticipating the later observations of
Pasteur,[14] Tyndall, Chauveau, and others to the same or similar
effect. These results of experiments are commonly understood to prove
the particulate character of the agents so studied. What may be called
an era in the practical application of etiological inquiry dates from
the introduction by Lister (about 1860) of the principles of
antiseptic surgery, based upon the theory that disease-germs, derived
from the atmosphere or other external sources, are the essential
causes of suppuration, septicæmia, pyæmia, gangrene, etc. following
injuries or operations.
[Footnote 14: Pasteur's experiments with long-drawn bent tubes had
especial significance.]
So far from this inquiry being yet terminated, while experiments and
observations have become more and more numerous and elaborate,
opinions continue to differ; and we must yet await the time when, by
successively excluding, one after another, all the sources of error, a
truly scientific conclusion may be obtained.
Roughly speaking, it may be said that parties in the debate are
chiefly ranged upon two sides--those who favor the probability that
only chemical, not vital, action is to be traced in fermentation,
putrefaction, suppuration, infection, and contagion; and those who
regard minute organisms, discovered or undiscovered, as causative of,
and indispensable to, all these processes.
Without intention of injustice to other able investigators, the
principal names so far associated with the former of these views may
be thus mentioned: Panum (1856), Robin, Bergmann, Liebig, Colin,
Lebert, Vulpian, Onimus, B. W. Richardson,[15] Beale,[16] Senator,
Rosenberger, Hiller, Nægeli, Schottelius, Harley, Jacobi, Curtis, and
Satterthwaite. Of those maintaining, in some form and with more or
less positiveness, the disease-germ theory, the most conspicuous,
especially as observers, have been Tuchs (1848), Royer (1850),
Davaine, Branell, Pollender, Pasteur, Tyndall, Lister, Mayrhofer,
Ortel, Letzerich, Nassiloff, Hueter, Toussaint, Hansen, Salisbury,
Klob, Hallier, Basch, Virchow, Neisser, Eberth, Tommasi Crudeli,
Klebs, Talamon, Schüller, Tappeiner, Cohnheim, Koch, Baumgarten,
Buchner, Aufrecht, Birch-Hirschfeld, Greenfield, and Ogston. Besides
these the elaborate studies of microphytes by Cohn, and those of Coze
and Feltz, Waldeyer, Recklinghausen, and others upon septic poisoning,
have been of acknowledged importance; and the experimental labors of
Burdon Sanderson in England, and Sternberg,[17] H. C. Wood, and Formad
in the United States (under the auspices of the National Board of
Health), possess great value. But the scientific caution of these last
inquirers, like that of Magnin, has prevented them from formulating,
as yet, positive and final opinions upon the subject. It is not saying
too much to assert nearly the same of {140} several of those mentioned
above, as inclining to one or the other side of the controversy.[18]
[Footnote 15: Dr. Richardson has long contended for the doctrine first
proposed by Panum, that a peculiar chemical agent, (called by Bergmann
_sepsin_) is the cause of blood-poisoning from virulent absorption or
inoculation. Latterly, attention has been called by Selmi and other
observers to the existence of complex compounds called _ptomaïnes_ in
decomposing animal substances--_e.g._ the human body after
death--these having considerable resemblance in their toxic action to
the poisonous vegetable alkaloids.]
[Footnote 16: Opposed at least to the ordinary form of the germ theory
of disease.]
[Footnote 17: Sternberg's observations and experiments (following
those of Pasteur) with the inoculation of animals with saliva, proving
that even when taken from perfectly healthy men this may be fatally
poisonous to animals, possess remarkable interest. They do not seem,
however, to be decisive either way in regard to the germ theory of
infection.]
[Footnote 18: Billroth and Cohnheim are among those who have changed
their opinions on this subject after prolonged investigation.]
It would appear, then, that the data for a final conclusion have not
yet been made certain. Several hypotheses are conceivable, and
capable, each, of plausible support:
1. The purely chemical theory of Liebig, Gerhardt, Bergmann, Snow of
London, and B. W. Richardson.
2. The bioplastic hypothesis of Beale, according to which germinal
matter may be detached from a living body and planted, while yet
retaining vitality, upon another, and there may undergo changes more
or less morbid, and destructive of the body by which it has been
received. This theory of migrating or transplanted bioplasts has
received very little support besides that of its distinguished author.
3. That the minute organisms discovered so constantly upon diseased
parts of plants and animals (_e.g._ ergot of rye, _Peronospora
infestans_ of potato-rot, _Botrytis Bassiana_ of silk-worm muscardine,
_Panhistophyton_ of silk-worm pebrine, _Empusa muscæ_ of the fly,
_Achorion_, _Tricophyton_, _Oidium_, and _Leptothrix_ of human
affections of the skin and mucous membranes) are incidental or
accidental only[19]--acting, as R. Owen observes, {141} most commonly
as natural scavengers in the consumption of effete organic material;
but that they may become noxious under two sorts of
circumstances--viz. when their numbers are enormously increased, as is
known to be the case with trichinæ in the human body, and also when
they are brought in considerable number into contact with bodies
already diseased, or at least suffering under depression of vital
energy.
[Footnote 19: This possibility has not been as yet altogether ruled
out in regard to Koch's _Bacillus tuberculosis_; concerning which
active discussion has been going on during the past year or two
(1882-83). A very large number of observers confirm the statement that
the bacilli are found in most specimens of tubercle. Several, also,
have repeated with success Koch's inoculation experiments, in which
tubercle appeared to be propagated by carefully isolated bacilli. But
many facts still stand in the way of the conclusion that the bacillus
is the causa sine quâ non of tuberculosis. First, examples of the
production of phthisis by apparent contagion or infection are few.
Although Dr. C. T. Williams found bacilli in the air of the wards of
the Hospital for Consumptives at Brompton, yet of the experience of
that hospital Dr. Vincent Edwards, for seventeen years its resident
medical officer, reports as follows: "Of fifty-nine resident medical
assistants who lived in the hospital an average of six months each,
only two are dead, and these not from phthisis. Three of the living
are said to have phthisis. The chaplain and the matron had each lived
there for over sixteen years. Very many nurses had been in residence
for periods varying from months to several years. The head-nurses,"
says the writer, "sleep each in a room containing fifty patients. Two
head-nurses only are known to have died--one from apoplexy; the other
head-nurse was here seven months, was unhappily married, and some time
afterward died of phthisis. Of the nurses now in residence, one has
been here twenty-four years, two twelve years, one eight years, one
seven years, one six and a half years, and one five years. No
under-nurse, as far as I am aware, has died of phthisis. All the
physicians who have attended the in-and-out patients during the past
seventeen years are living, except two, who did not die from
phthisis."
Against the inoculation and inhalation experiments of Villemin,
Tappeiner, Koch, Wilson Fox, and others, by which the specific
character of tubercle has been said to be proved, must be placed those
of Sanderson, Foulis, Papillon, Lebert, Waldenburg, Schottelius, Wood
and Formad, Robinson, and others, by which tubercles have been induced
by the injection, inoculation, or inhalation of various non-tubercular
materials. In answer to the argument from these, it is asserted by
Koch and his supporters that "there is no anatomical or morphological
characteristic of tubercle," its only sufficient test being its
inoculability. This is almost begging the question; at all events, it
leaves it, for the present, unsettled. Moreover, tubercular deposits
do not always contain bacilli, as has been shown by Spina, Sternberg,
Formad, Prudden (_N.Y. Medical Record_, April 14 and June 16, 1883).
The last named made, in one well marked case, six hundred and
ninety-five sections from ninety-nine tubercles in different portions
of a tuberculous pleura, all of Koch's precautions being observed in
the examination. Belfield (_Lectures on Micro-Organisms and Disease_)
admits the possibility that tuberculosis may be produced by either of
several causes. It has, at least, not yet been demonstrated that the
tubercular tissue is more than a nidus or favorable "culture-ground"
for the bacilli, or that, in the presence of a constitutional
predisposition, they may not merely promote a more rapid destruction
of the invaded organs or tissues.]