THE

FORMATION OF POISONS

BY

MICRO-ORGANISMS.

A BIOLOGICAL STUDY OF THE GERM THEORY OF DISEASE.

BY

G. V. BLACK, M.D., D.D.S.
ii

4

PHILADELPHIA:

P. BLAKISTON, SON & CO.,

No. 1012 WALNUT STREET.

1884.

"B-fe

Entered according to Act of Congress, in the year 1884, by

G. V. BLACK, M.D.,
In the Office of the Librarian of Congress, at Washington, D. C.

PRESS OF WM. F. FELL & Co.,

1220-24 Sansom Street,

Philadelphia.

PREFACE.

The historical portion of this volume has been condensed
from notes made from time to time in the study of the
subject. With the view of making it as short as possible,
I have given only those experiments and observations that
seemed important to a proper understanding of the subject,
avoiding all but the most necessary details; aiming at the
same time to preserve all that will be of real advantage to the
general student. Many familiar names will be missed, for
the reason that many have written, and some of them very
well indeed, who have developed no distinctive fact or
thought that is of service in the farther progress of the sub-
ject. When we come to analyze any such subject, most men
are surprised to find how few have been instrumental in the
development of the real basic facts on which our knowledge
of it rests. Therefore, if we can properly estimate the import
of the matter presented, the history of the development of
any such subject may be briefly written. Whether or not I
have determined wisely, the intelligent reader must judge.

The second part was written because I had something to
say that I thought ought to be said at the present time. The
men who have been most instrumental in the development of
this subject have given us little else than the experimental
facts. These will satisfy the minds of but very few. Most
of us appreciate any subject more if we understand why these
things are so. It is this why that I have sought to supply.
This I leave for intelligent discussion to sift, and separate the
good grains from the chaff.

G. V. BLACK, M. D., D. D. S.

JACKSONVILLE, June 2d, 1884.

iii

TABLE OF CONTENTS.

PAGE

Preface iii

FIKST PART.

FIRST LECTURE.

Introduction — First Traces — Incentives to the Study — First Definite
Announcement of the Germ Theory — Phlogiston — Zymosis —
Jenner— Fermentation Hypothesis — Vaccine — Beginning of the
Nineteenth Century— Early Discoveries — Astier— Schwan — Lie-
big's Views — Difficulties — Schroeder's Discoveries — Schroeder's
Conclusions — Pasteur and his Work — Needham and Spallanzani
—Pasteur's Plan of Work 11 to 34

SECOND LECTURE.

Bastian and his Work — Archebiosis — Logical Sequence — Difficulties —
Modes of Propagation of Micro-organisms — Utilizing Discoveries
— Lister's Antiseptic Surgery — Nature of the Evidence— Direct
Examinations for Micro-organisms — Evidence Unsatisfactory —
Miasm and Contagion — Miasmatic Contagion — Infection Experi-
ments— Discussions by Important Men 35 to 56

THIRD LECTURE.

Beale's Work — The Amoeboid Theory of Contagion — Pasteur — The
Bacillus Anthracis— Koch and his Work— Aniline Staining — Dry
Slide Cultivations — Infection Experiments — Pathogenic Micro-
organisms now certainly Demonstrated — What is Necessary for
the Demonstration of a Pathogenic Micro-organism — The Evi-
dence that Pathogenic Micro-organisms are Different from
ordinary Bacteria — Spores and Habits of Micro-organisms —

Summary 57 to 76

V

VI . TABLE OF CONTENTS.

SECOND PAKT.

FOURTH LECTURE.

Production of Poisons by Micro-organisms — Propositions — Necessity
for a Physiological Study of the Subject— Digestion and Absorp-
tion— Propositions — Primary Digestion — Absorption — Nutritive
Digestion— Soluble Ferments — Digestion by the Yeast Plant-
Mr. Lister's Experiments — Digestion by Bacteria — Digestion by
the Higher Plants— Sach's Experiments— Sprouting of Seeds —
Diastase— Nutrition 79 to 95

FIFTH LECTURE.

The Yeast Plant— Cellular Digestion in the Higher Animals — Re-
sorptive Digestion — Resorption of the Roots of the Milk Teeth —
Digestion of Blood Clot — Digestion of Animal Ligatures — Diges-
tion of Sponge — Necrosed Bone — Pathological Formation of
Soluble Ferments — Relation of Soluble Ferments to Living Tis-
sues— Parasites 96 to 110

SIXTH LECTURE.

Waste Products — Life as a Force — Law of the Formation of Waste
Products — The Nature of Waste Products — Waste Products of
the Higher Animals ; of the Higher Plants ; of Bacteria— Alka-
loids Ill to 128

SEVENTH LECTURE.

Poisons Developed by Micro-organisms — Farther Investigation
Needed — Physiological Changes in Micro-organisms — Manner
of Action — Inflammations and Pus Formation — Blood Dis-
eases 129 to 146

APPENDIX.

Dental Caries; its Relation to the Germ Theory of Disease 149 to 169

PART FIRST.

ACKNOWLEDGMENT.

This volume contains a series of lectures, delivered before
the students of the Chicago College of Dental Surgery and a
number of practitioners who were ticketed especially for this
course. The Lectures now appear in their present form
through the co-operation and kindly assistance of the Officers
and Faculty of that Institution, to all of whom I gratefully
acknowledge myself indebted for many favors.

THE AUTHOR.

A STUDY

OF THE

GERM THEORY OF DISEASE.

HISTORICAL.

INTRODUCTION.

In presenting an historical sketch of the Germ Theory of
Disease, it will be my effort to review briefly the ideas, con-
troversies and experiments, that have gradually led up to
our present knowledge concerning it. At present I know of
no single treatise on this subject from which those who have
not followed its now extensive literature can gain a clear
view of it, obtain a just conception of its magnitude, of the
labor that has been bestowed upon it, or of its immense im-
portance. The history of this subject in its completeness,
would be a history of the efforts of men to stay the ravages
of epidemic and contagious diseases ; a history of the efforts
of men to understand the causes of plagues and pestilences ;
a history of the efforts of men to see farther, and still farther,
into the secret causes which produce sickness and diminish
the longevity of the race. I cannot, however, give more
than a brief synopsis of the principal thought, experiment
and discussion, bearing most directly upon, and finally lead-
ing to the adoption of present theories. The literature of
2 11

12 THE GERM THEORY OF DISEASE.

the subject is DOW quite extensive, and is, for the most part,
scattered through works upon disease in general, more es-
pecially works on surgery. Very few books were written
especially on this branch of medicine until quite recently ;
and these generally dealt with some particular phase of the
subject, or with the very recent experimentation, giving little
or no account of preceding inquiries. Therefore it is very
difficult for one who takes up the subject now to gain a
comprehensive view of it as a whole. It will be my object
to supply such a view in a short and concise recital of the
thought, experiment and discussion, that has been most eifect-
ive in leading to our present knowledge, and most essential
to an understanding of the work now being done in this
field.

FIRST TRACES.

For many centuries these ideas consisted in vague con-
jectures, arrived at from the study of contagion — an undefined
something that could pass from the sick to the well, and cause
disease. We find that Ulysses (Homer's Odyssy, Book XXII),
used sulphurous acid to destroy the odor and toxic products
of decomposition.

Early in the history of Greece we find that men had
learned that certain localities were unhealthy. Their notion
seemed to be that something obnoxious to health was being
generated at these places; and we find them acting with
judgment in regard to the location of their hospitals and
important buildings. The physicians of antiquity observed
that, in epidemic diseases the then existing theories were in-
sufficient. They recognized that there was something extra-
ordinary to deal with. They spoke of a " constitutio pestilens "
and of a "genus epidemicus," but as to the nature of this
constitution of disease they had few clear ideas.

Diodorus found an explanation of the cause of the Athenian

INCENTIVES TO THE STUDY. 13

Plague in the circumstance that " a great multitude of people
from all quarters streamed into the city, and being cramped
for room, breathed corrupted air." Decomposing filth, social
squalor, bad weather, etc., were regarded as causes of disease,
by both physicians and laymen.

INCENTIVES TO THE STUDY.

When we turn our attention to the contagious diseases, to
the great plagues of past times, and watch the progress of
thought in regard to them, the absence of knowledge of the
means of staying their progress, the utter helplessness of the
people in times of pestilence, seems simply terrible. Without
a knowledge of the diseases of a country, we find it difficult
to understand aright its history or its civilization. These
great diseases have often destroyed the army of the conqueror,
or given the death blow to an advancing civilization, and
have left a strange and enduring impress upon the intellectual
life of great communities. It is generally known how, in the
Fourteenth Century, the most deadly of all the pestilences that
are recorded in past history — the Black Death — changed the
direction of intellectual and social activity throughout the
chief part of the civilized world, and showed its impress on
the developments of succeeding centuries. We can gain but
a faint idea to-day, through what we have seen around us,
of the devastation that may be caused by epidemic diseases
running without check ; or of the significance they have had
in the progress of civilization.

The terrible results of epidemic and contagious diseases
have furnished the strongest possible incentives to the study
of the underlying causes. In all ages of the world the effort
to understand them has been unceasing.

14 THE GERM THEORY OF DISEASE.

FIRST DEFINITE ANNOUNCEMENT.

The first definite announcement of a belief that disease is
caused by organic germs, that I have found, was in the time
of the Roman Empire.

De-re-Rustica, Varro and Columella, refer the origin of
malarious fevers to the entrance of low organisms into the
body. But they seem not to have given the special observa-
tions upon which their conclusions were founded. All along
down the centuries, the idea was frequently expressed that the
plague of the day was caused by minute organisms.

This doctrine, however, obtained wide recognition when
some sort of basis for such theories was furnished by the
microscopic demonstration of very minute living organisms,
invisible to the naked eye. Especially after the discovery of
the spermatozoa by Leuwenhoeck in 1677. These were then,
and for years afterwards, supposed to be real animals. It
having now been demonstrated, apparently, that real animals
were living in the bodies of men, the doctrine that diseases
were caused by minute organisms spread far and wide. Among
the best known advocates of this theory were Kirchen, Lancici,
Valisneri, Raumum, and Linne. But even those who best
understood the theory never reached anything more than
rough conceptions ; while many lost themselves in wild ex-
aggerations. The animals causing disease were described as
flying about in the air, something like swarms of insects, with
crooked bills and sharp claws ; and one writer proposed to
destroy them during epidemics by the blowing of horns and
the firing of cannon. We can readily conceive that such
fantasies would bring down ridicule upon the whole theory ;
and in time these wild notions were dissipated and the germ
theory slept.

ZYMOSIS. 15

PHLOGISTON.

But amid these fantasies there was a deep vein of earnest
observation and thought. Physicians saw a pestilence strike
a community as a spark strikes among shavings, and kindling,
attack person after person in society, as fire would leap from
house to house in a city. Sydenham says : " Ita ignis ignein
generat et maligno infectus morbo socium inficit."

Stahl supposes a principle of inflammability or the matter
of -fire in composition with other bodies, an hypothetical
element supposed to be pure fire, fixed in combustible bodies,
in order to distinguish it from fire in action or in a state of
liberty. This was called " Phlogiston." A similar supposi-
tion obtained in regard to epidemic and contagious diseases,
viz., that there was some substance or force in man himself,
which, when once put in motion, acted similarly to fire and
spread with deadly effect. To this day, remedies directed
against inflammation or inflammatory conditions are called
an tiph logistics. This theory of the origin and propagation of
epidemic diseases seems to have been much discussed.

ZYMOSIS.

Another hypothesis was based on the known action of fer-
ments, which is maintained to this day, the present germ
theory being considered within the limits of this hypothesis.
It was seen that yeast, when added to certain compounds con-
taining sugar, caused certain phenomena. That a very small
quantity of the yeast was necessary for a beginning, and that
this would be reproduced continuously. It could be carried
from vat to vat of grape juice for any number of times, and
the more fermentation accomplished the more the ferment
increased. It was found, also, that this kind of fermentation
would begin, but less promptly, without the addition of yeast,
and that in this case also the yeast was formed. Now they

16 THE GERM THEORY OF DISEASE.

reasoned that the action of epidemic and contagious diseases
was the same. From the sick person it seemed that a sub-
stance or force was conveyed to the well. Thus, one sick
person may infect a dozen, and each of these a dozen more,
etc., so that the disease is rapidly diffused through a com-
munity. It will be seen at once that the similarity between the
phenomena of these diseases and the phenomena of fermenta-
tion is very close. These two hypotheses gave rise to much
discussion. They seem to have stood side by side until the
one merged into the other, for the more they were discussed
the more similar they seemed to become. Finally, the first is
lost sight of and the Zymotic theory of epidemics and con-
tagions, as developed by Willis in 1659, has continued to be
the generally accepted theory.

JENNER.

When Jenner discovered the relation of the vaccine disease
to smallpox, and began the use of the vaccine virus as a pro-
tective against that malady in 1798, there came a much
greater confidence in the fermentation, or as it is called, the
zymotic theory of contagion. Here the physician had a body
that he could carry about and use at will, as he could yeast.
He could introduce this disease-producing yeast, or virus, into
the skin of a healthy person, and after a certain time, a disease
would manifest itself; just as he could introduce yeast into a
solution of sugar, and after a certain time, find the phenomena
of fermentation. A small amount of either was sufficient ; in
each case a certain period of rest was observed before the
characteristic manifestations declared themselves ; a stage of
incubation. In each case the peculiar product first used was
largely increased. In case of the vaccine, a dozen could be
vaccinated from the product of the first vaccination, just as
from the product of the fermentation of a single butt of must

NINETEENTH CENTURY. 17

enough yeast could be produced to quickly start fermentation
in a dozen more; and so on, ad infinitum, in both cases. The
phenomena of the one following precisely the role of the phe-
nomena of the otfcpw* in every respect, only one was the fer-
mentation of sugar, and the other was the production of the
disease, Vaccina.

Neither did the likeness stop here; but, as we shall see, it
went much further. It was then well known that a certain
amount of heat destroyed the power of yeast forever. Trial
showed that precisely the same thing happened with the
vaccine virus. Furthermore, it was well known that when
a solution of sugar has been under the process of fermentation
until that process has spontaneously ceased, a further fermenta-
tion could not be had by adding more yeast; although un-
fermented sugar may remain in the solution. The results
when completed are completed once for all; and for a new
trial a new mixture must be had. Or in other words, the
result of fermentation prevents fermentation of the same
character again taking place. These phenomena are again
repeated by the vaccine virus. A person once vaccinated is
rendered insusceptible to further vaccination; at least for
some years. All these facts taken together furnished the
strongest possible proof of the identity of the two processes,
at least in mode of operation; however wide the difference
in the results. And the well known fact, that in the great
majority of the then known contagious diseases, one attack
rendered the subject of it incapable of again taking the same
malady, served to extend the theory to all diseases of this class.

NINETEENTH CENTURY.

This is the condition in which we find the theory of zymotic
diseases at the beginning of the present century. To say that
this theory was universally accepted and satisfactory, would

18 THE GERM THEORY OF DISEASE.

be untrue. Very many denied the relevance of the facts
brought forward, and sought other explanations; but without
gaining much favor. Earnest men were examining the act
of fermentation ; and especially seeking the causes of putrefac-
tion. Why should a dead body pass so quickly into a state
of putrefaction? Enough was known to convince many
thoughtful men that putrefaction was not caused by anything
inherent in the flesh itself; for, under some circumstances,
decomposition did not take place. They had learned to pre-
vent it, at least for a long time, in meats that were preserved
for food. Many other circumstances came up which furnished
food for thought, and which shook the faith in the idea that
fermentation of vegetable substances and putrefaction of
animal tissues were truly spontaneous and inherent in the
nature of such bodies.

EARLY DISCOVERIES.

In the first decade of the sixteenth century, Von Helmont
had shown that the gas arising from fermentation was different
from common air ; was carbon dioxide. And the other pro-
duct, alcohol, had been known from the earliest historic times,
but it was not isolated until the fifteenth century, though its
distillation was regularly practiced in the eighth. It had been
shown by Gay-Lussac, that grape juice does not ferment in
vacuo. This was discovered in a now classical series of
experiments, in which this experimenter caused clean grapes
to ascend through the mercury of a large barometer into the
Toricellian vacuum, and then crushed them by means of a mer-
curial column. This juice remained unchanged, but the addi-
tion of small quantities of air set up fermentation. Stahl, in
1731, arrived at the conclusion that fermentation and putre-
faction were similar or identical processes. This was also the
opinion of Justus Liebig, one hundred years later.

EARLY DISCOVERIES. 19

In 1680 the Dutch professor Leuwenhoeck began the
examination of yeast under the microscope, and found it to
consist of minute ovoid or globular particles. But the imper-
fection of the instruments of his time prevented the discovery,
which seemed so near, of the nature of these particles. Ex-
periments of various kinds were instituted by many persons, a
few of which may be mentioned : A bladder was filled with a
solution of sugar and suspended in another solution of sugar,
to which yeast had been added. While fermentation went
regularly on in the fluid in the containing vessel, the fluid in
the bladder did not partake in the fermentation. A vessel was
divided into two compartments by a partition of filtering
paper, a solution of sugar placed in each and yeast added to
one. Fermentation went on promptly in the compartment to
which the yeast was added, but the other remained free from
fermentation. Many other experiments are also recorded, all
tending to show that fermentation is something different from
ordinary chemical action. But the men of the time seemed
unable to understand the significance of their experiments,
which, to us, prove conclusively that the substance causing
fermentation is participate and not soluble, otherwise it would
pass through the filters and produce its results.

In 1787 Fabroni affirmed that " the matter which decom-
poses sugar is a vegeto-animal substance; it resides in par-
ticular utricles in grapes, as well as in corn. When grapes
are crushed this glutinous matter is mixed with the sugar.
Directly the two substances come in contact, effervescence and
fermentation commence."

Astier, in 1813, asserted that "the matter of ferment,
recognized by Fabroni as an animal substance, was alive and
derived its nourishment from the sugar, whence resulted the
rupture of the equilibrium between the elements of this body.
By this theory," said he, "it is easily explained that all the

20 THE GERM THEORY OF DISEASE.

causes which kill animals or hinder their development must
be opposed to fermentation " (Schutzenberger, page 38).
This seems to be the first appearance of the modern germ
theory in a definite form, and the first announcement of the
true theory of the antiseptics. Astier, however, regarded the
living substance as composed of animalcules. A number of
observers within the next few years seem to have arrived at
the same conclusion.

SCHWAK

The next real advance was made about the year 1838,
when Schwan and La tour, each independently, took up the
microscopic inquiry, with improved instruments, and dis-
covered that the granules of yeast were membranous bags,
which exhibited all the morphological characters of vegetable
cells, and under proper conditions increased and multiplied, in
the biological sense. The conclusion was quickly reached by
them, that it was the life and growth of the plant which
caused the chemical changes of fermentation ; and that the
products, carbon dioxide and alcohol, were excrementitious
products of the plants.

At this time Schwan was working on spontaneous genera-
tion, which he very distinctly negatived. He also, together
with Schultz and Helmholtz, was the first to establish the fact
that putrefaction would not occur without the presence of cer-
tain minute organisms, which might be destroyed by boiling;
and then, that air deprived of these organisms by being heated,
or by filtering through sulphuric acid, might be admitted
and yet no decomposition would occur. This destroyed the
hypothesis previously held, that oxygen was the active agent
in decomposition ; yet it was not generally accepted. It is to
this discovery that we owe our ability to preserve fruits,
meats, etc., in cans hermetically sealed, which has conferred
such blessings upon mankind.

LIEBIG'S OPPOSITION. 21

EFFECTS OF SCHWABS DISCOVERIES.
These brilliant discoveries very soon attracted general at-
tention to the subject from the scientific world, and as iden-
tical theories, as we have shown, had long been held as to the
modes of propagation and action of contagious diseases, and
of fermentation and putrefaction, the theory of a contagiurn
vivum again came to -the front, and was urged by some of the
strongest minds of the time. The new theory, however, was
destined to fight its way inch by inch. Every new fact that
was put forth had to pass the most rigid criticism that the
opponents of the theory could bring to bear upon it ; and for
a time it seemed as if it would be crushed out of existence
notwithstanding its apparent demonstration.

LIEBIG'S OPPOSITION.

The strongest opponent of the vital theory, as it seems to
me, was the then comparatively young Professor of Chemistry
at Giessen, Germany, Justus Liebig. Liebig' s view of fer-
mentation is practically the same as that enunciated by Willis
in 1659, and maintained by others in the succeeding years ;
but it is in Professor Liebig's writings that the view reached
its highest stage of development and can be best studied. It
merits the closest scrutiny, for it has been the principal oppo-
nent with which the germ theory has had to contend. If we
follow the contests between the chemists on the one side and
the vitalists on the other, up to the present time, and analyze
the arguments adduced by the chemists, we will find that the
very few new facts which they have brought forward have all
been based on the plan of Liebig's arguments. There has
been nothing essentially new, nor has his argument been
strengthened. In the years 1840-42, in response Jx) an invi-
tation of the British Association for the Advancement of Sci-
ence, Professor Liebig wrote a series of papers upon animal,

22 THE GERM THEORY OF DISEASE.

vegetable and agricultural chemistry and the chemical trans-
formations, including the action of the different ferments,
yeast, putrefaction, contagion, miasrn, etc., in which he antago-
nized the vital theory of each of these with all the vigor of his
wonderful intellect, and for the time crushed the rising confi-
dence in the new theory.

The arguments brought forward by Liebig may be summed
up as follows : u Fermentation is a result of the catalytic action
of a decomposing body in contact with compounds of feeble
molecular affinity, which is brought about in accordance with
the following law of dynamics: A molecule set in motion by
any power can impart its own motion to another molecule
with which it may be in contact." Yeast, he argued, is a pro-
duct of the decomposition of gluten, and is necessarily a de-
composing body, and when added to must or wort, sets up in
these bodies a motion of their molecules similar to its own, by
which their saccharine elements are converted into the simpler
and more stable compounds, carbonic acid and alcohol.

But the action upon the gluten is to convert it into a body
identical with the original yeast. And thus the yeast seemed
to grow ; but it is not a growth in the biological sense. This,
he contended, is demonstrated by adding yeast to a pure solu-
tion of sugar, in which case, although the fermentation pro-
ceeds promptly, the quantity of the yeast not only did not
increase, but actually diminished, being expended in the act
of decomposition.

Putrefaction, he says, is just the same process, but with a
different molecular motion. These molecular motions might
reproduce themselves or not, as the substance on which they
acted contained the substance from which they were pro-
duced or not. Miasms and contagions were considered as
being of the same character.

His idea of a chemical force more powerful than the vital

23

force appears, also, in his explanation of the manner in which
poisons and medicines act. The manner in which inorganic
poisons (medicines) gain admission to the tissues is -owing, in
most cases, to the formation of a chemical compound by the
union of the poison with the constituents of the organ upon
which it acts ; it is owing to a chemical affinity more powerful
than the vitality of the organ. Each of these substances, in
its transit, produces a peculiar disturbance in the organism ; in
other words, they exercise a medicinal action upon it, but
they, themselves, suffer no decomposition. It is only when
the solutions are diluted to a certain degree with water that
they are absorbed by auimal tissues. In respect to this
physical property of the animal tissues, alcohol resembles the
inorganic salts.

Miasms and contagions were thus explained: "A miasm is
a form of molecular force developed during the decomposition
of vegetable bodies under certain peculiar circumstances,
which has the power of setting up similar decompositions in
the human blood ; but not finding in the blood or tissues the
proper substance for its own reproduction, like yeast in sugar,
it is not reproduced. Therefore, such diseases are not con-
tagious."

" Contagious poisons find in the human blood and tissues
substances from which they reproduce themselves, as yeast in
must or wort is reproduced from the gluten ; consequently,
these diseases are conveyable from the sick to the well ; in
some instances by contact only, as in syphilis, in which case
the physical form of the substance is that of a solid. In
other instances through the air, in which case the physical
form is that of a gas." He says, "several kinds of contagions
are propagated through the air ; so that, according to the view
already mentioned (of a contagium vivum), we must ascribe
life to a gas, that is, to an aeriform body."

24 THE GERM THEORY OF DISEASE.

He thus recognized a gaseous form of ferments.

We have already spoken of the fact that when fermentation
spontaneously ceased, it could not again be set up ; and its
application to those contagious diseases which can, ordinarily,
be had but once by the same individual. This theory was
elaborated anew by Liebig, with telling effect against the vital
theory. It was considered that in must or wort there is a
certain substance that is decomposed by the peculiar molecular
motion of vinous fermentation, namely, sugar; while the other
portions of the compound are not necessarily affected. The
blood is a very complex substance, containing many compounds
held together by feeble molecular affinities, any one of which
may be decomposed. In case of the contagious diseases, the
decomposing body which causes the particular disease acts
upon some single compound of the blood, decomposing it.
If this particular component of the blood be very important
to the vital processes, the disease will be very grave. If, on
the other hand, this particular compound be not very im-
portant, the disease will be correspondingly light. Now in
the progress of the disease this particular compound is all
decomposed, as the sugar in grape juice, and if the patient
has been able to withstand the shock, he returns to health
with this one compound of the blood lacking, and it often
happens that it is replaced very slowly, if at all ; therefore,
the patient is protected for a time or permanently.

•Liebig explained the susceptibility of children to certain
diseases while adults were insusceptible, by assuming that the
constituent of the blood upon which the molecular motion
poison acted in the child was absent in the adult. He also
explained the differences in susceptibility of different indi-
viduals in the same way.

Finally, Liebig says, "all the supposed proofs of the vitality
of contagions are merely ideas and figurative representations,

25

fitted to render the phenomena more easy of apprehension by
our senses, without explaining them. These figurative ex-
pressions, with which we are so willingly and easily satisfied
in all sciences, are the foes of all inquiries into the mysteries
of nature; they are like the Fata Morgana, which show us
deceitful views of seas, fertile fields and luscious fruits, but
leave us languishing when we have most need of what they
promise. It is certain that the action of contagions is the
result of a peculiar influence dependent upon chemical forces,
and in no way connected with the vital principle.77

Liebig claimed that this poisonous substance could not be
isolated, because it consisted of a peculiar form of molecular
motion. But in many cases the substances containing this
molecular motion poison could be had, which substance in
itself was not poisonous, as was shown by exposing it to heat,
thus rendering it innocuous by destroying this peculiar mo-
lecular power.

He also points out the fact that very many of these poisons
are destroyed in the human stomach in the act of digestion,
and that others are not. He explains these phenomena in
this way. All of these ferment poisons owe their power to
the peculiar molecular movement started and maintained by
the act of decomposition. Now, when they come in contact
with stable compounds they are unable to communicate their
own movements to these associated molecules, and are con-
sequently inert, or unable to propagate decomposition. But,
if the intermixed substance is composed of molecules held
together feebly, the molecular movement is communicated to
them, and they pass into a state of decomposition.

Now the juices of the stomach are acid, and among the
noxious substances many are alkaline, but some are acid.
It therefore happens that when an alkaline organic poison or
ferment is introduced into the stomach, its molecular force is

26 THE GERM THEORY OF DISEASE.

antagonized by the acid juices it meets there and its molecular
movement destroyed.

If, however, the noxious element be acid in its reaction,
the juices of the stomach do not interfere with its molecular
movement, but rather favor it. And instead of being de-
stroyed, it is rendered even more virulent. This action of
the stomach, he argues, is a very positive proof of the chemical
nature of these poisons.

It is a noteworthy fact that in this essay Prof. Liebig
practically ignores the microscopic demonstrations of the yeast
plant. He evidently regarded it as, to a large extent, a fiction
of the brain of over-zealous investigators, using what was
in that day considered very high powers of the microscope.
Not believing in the existence of the yeast plant, or the
organisms of disease, he says, "The vital principle is only
known to us through the peculiar forms of its instruments;
that is, through the organs in which it resides. Hence, what-
ever kind of energy a substance may possess, it is amorphous
and destitute of organs from which the impulse, motion or
change proceeds ; it does not live."

The basis which he gives for the proof of the existence of
life stands to-day in its full power. And if he is at last
beaten in the argument, it is because facts have been brought
forward and proven by incontrovertible observation that will
satisfy this basis. This basis is contained, practically, in one
sentence, which I quote: "Our notion of life involves some-
thing more than mere reproduction, namely, the idea of an
active power exercised by virtue of a definite form, and pro-
duction and generation in a definite form."

DIFFICULTIES. 27

DIFFICULTIES.

From that time to the present the controversy has been
unceasing. Those who believed that the vital theory was
true still maintained it, for they had seen definite forms re-
produced in definite forms, by virtue of definite forms. They
returned to their microscopes and followed again the growth
of the yeast plant. They saw again the buds given off from
the cells, and reproduce other cells, like in every respect to
the mother cell; and these in turn reproduce other cells of
the same likeness; satisfying the basis as given by Prof.
Liebig.

But the microscopes of that day were poor, trained ob-
servers were scarce, the subject was new, the modes of de-
monstration were comparatively clumsy, and in many respects
faulty. Under these difficulties progress was exceedingly
slow, at best; and for a time no substantial advance was
made. But gradually, as the number of the observers of it
increased, the yeast plant, as the active principle of yeast, and
upon which its action was dependent, was accepted by a large
proportion of the learned men of the world. It is, however,
a noteworthy fact that many of those who accepted this re-
fused to accept the vital principle for the other fermentations;
which would seem naturally to follow. This refusal seems to
have found a basis in certain arguments brought forward by
Prof. Liebig, especially such as the following : If oxamide be
brought in contact with oxalic acid dissolved in water, the
following changes take place : the oxamide is decomposed by
the oxalic acid, provided the necessary conditions for their
exercising an action on each other be present. Although the
oxamide is not at all soluble, the elements of water unite
with it, and ammonia- is one product formed and oxalic acid
the other, both in the proportions to form a neutral salt.
Here the contact of the oxamide and the oxalic acid induces

28 THE GERM THEORY OF DISEASE.

a transformation of the oxamide, which is decomposed into
oxalic acid and ammonia. As much oxalic acid exists after
the decomposition as was added, and still possesses its original
power; and more oxamide will be decomposed in the same
way, if added. This may be kept up continuously, and any
amount of the oxamide decomposed, by a very minute por-
tion of the oxalic acid.

Quite a number of similar chemical decompositions are
known, and while they cannot be considered as bodies in a
state of decomposition, as Liebig claimed the excitors of
fermentation were, the processes had long been considered as
very closely related. Now as these processes were admitted
by all to be purely chemical, no process should be considered
vital until it was definitely proven.

This required that each one of these be investigated on its
own merits and proven independent of all others.

In this work the theory has, perhaps, suffered as much from
its over-zealous followers, who hastily published untenable
views, arrived at by hasty and ill-digested experiments, as
from its opponents.

SCHROEDER.

Schroeder was, perhaps, the first to make a new and sub-
stantial point that has stood the test of adverse criticism. As
we have stated, Schwan had demonstrated that decomposition
would not occur in sterilized fluids upon the introduction of
air that had been heated or passed through sulphuric acid.
This, as a demonstration of the existence of life, was appa-
rently demolished by Liebig, who claimed that the heat, or the
acid either, was sufficient to destroy the molecular motion upon
which, as he claimed, the power of ferments depended. Now
Schroeder, in 1854, admitted air filtered through cotton
batting, with the idea that this would catch any solid par-
ticles in the shape of spores or germs. His experiment was a

SCHROEDER. 29

perfect success. Sterilized fluids kept just as perfectly when
sealed with a wad of cotton, as when sealed hermetically.
This, as it became established, effectually disposed of the
theory of gaseous ferments. But the claim was now made
that the dried remains of decomposing bodies might fly about
in the air and renew their molecular motions on being again
moistened, and that these would be kept out of sterilized
fluids by the cotton batting, the same as was claimed for
living germs.

The following are the conclusions of Schroeder : —

1st. " All vegetable or animal forms derive their origin
from other living vegetable or animal beings. Omne vivum
ex vivo.

2d. " When a series of specific products of fermentation
and putrefaction are developed at a certain spot, germs which
originate the process have been conveyed to that spot through
the medium of the air. Such is certainly always the case with
regard to germs of mould, and to the ferments of wine, milk
and urine.

3d. " Vegetable and animal matter in which all germs
have been destroyed by boiling, and which, while yet in a
hot state, has been shut off from the direct influence of the
external air by means of cotton- wool, remains perfectly free
from mould, fermentation or putrefaction. The germs, which
otherwise would be supplied by the air, are arrested in the
passage of the latter through the cotton-wool.

4th. " The germs of most vegetable and animal substances
are destroyed by exposure for a short time to a temperature of
100° C. (212° F.)

5th. " But milk, yelk and meat contain germs which are
not thus killed. Boiling at a high temperature, under higher
pressure, or long-continued boiling at 100° C., will, however,
always suffice to destroy these germs.

30 THE GERM THEORY OF DISEASE.

6th. " The germs in milk, yelk of eggs and meat, after
having been boiled a short time, are still capable of being de-
veloped into the specific ferment of putrefaction, and some-
times, also, those of yelk ; at least, into long and indolent
vibriones.

7th. " The specific ferment of putrefaction is of an animal
nature. It develops itself and multiplies at the expense of
albuminous compounds, but does not multiply under those
conditions alone which supply all the requisites for vegetable
growth." (Sydenham Society's Year Book for 1862. An-
nalen der chemie u pharmacie, vol. 117.)

PASTEUR.

The next important advance may be best illustrated by the
labors of M. Pasteur, in his sealed-flask cultivations, although
he was not the first to employ this particular mode of study.
Shutzenberger mentions that this kind of cultivation was first
performed by Needham, in London, who published a work on
this subject in 1745, in which it seems that he maintained the
hypothesis of the de novo origin of infusoria. Spallanzani, a
celebrated Italian physiologist, took the matter up, which re-
sulted in a lengthy controversy, in which Spallanzani refuted,
by experiment, the conclusions of Needham. The contro-
versy turned on this point. Spallanzani was not satisfied with
heating the hermetically sealed flasks containing the infusion
for several minutes, merely the time required to cook a hen's
egg and destroy the germ, as Needham expressed it, but he
kept them boiling for an hour ; after which no infusoria were
found. (Shutzenberger on Fermentation, page 311.)

The plan of Pasteur was practically this : He reasoned
that if he could grow the yeast plant in sealed flasks until all
gluten with which it was first connected could be certainly got
rid of, he could then study the plant in all its purity, and

PASTEUE. 31

effectually disprove the molecular motion theory. He, there-
fore added a small quantity of yeast; as pure as possible, to
some cultivation fluid which had been effectually sterilized by
heat and contained no gluten, and carefully sealed it. After
this had passed through the stage of fermentation, another
flask was prepared in the same way; and under the utmost
precautions that nothing else should be introduced from with-
out, a drop was taken from the first with a pipette, and added
to the second, and so on, to the fiftieth generation, and in many
of his experiments more than this number. These flasks
were, of course, kept at the proper temperature for the develop-
ment of fermentation. The result of this series of experiments
seemed to satisfy Liebig's basis for the recognition of living
beings; the yeast plant reproducing itself after its own form,
for generation after generation, continually, and after the
fiftieth or the one hundredth generation, again producing its
characteristic effects upon must or wort, namely, vinous fer-
mentation. They did more than this. It is well known that,
under certain conditions of temperature, vinous fermentation
passes into acetic fermentation, with the production of vinegar.
Now, in his investigations, Pasteur found that he was able to
separate these forms of fermentation by special management
of the cultures. By taking at the beginning a fermentation
contaminated by the acetic process and keeping the temperature
high, the acetic acid plant, the microderma, flourished, while
the vinous plant, the torula, gradually died out. He thus
rendered the conditions unfavorable to the one and favorable
to the other ; and by this operation and the reverse one he
succeeded, after passing the culture through many generations,
in obtaining the vinous yeast plant entirely pure, and the
acetic yeast plant entirely pure, each of which would al-
ways produce its characteristic fermentation and nothing else.
And what is more, he found the plants to be characterized by

32 " THE GERM THEORY OF DISEASE.

different forms, which remained constant. I use this simply
as an illustration of the plan of what was known as fractional
cultivations. The same was done with the lactic acid fer-
mentation, and its characteristic plant isolated and established.
In time and by this process several others have been success-
fully isolated and established, until all of the processes here-
tofore known as fermentations have been certainly connected
with living organisms, without which none of them can succeed.

Pasteur, after working out vinous and acetic fermentations,
and that peculiar fermentation which destroys, in its turn,
the vinegar, has followed up the process of the complete
return of the fruit \o the primitive inorganic state.

After the fermentation of the vinegar, Pasteur next ex-
amined the putrid fermentations, or decompositions, as they
are usually called. The principal agents in these he found
to be certain very active bodies which he called vibrios, and
which multiply with remarkable rapidity in the depths of the
mass, as much as possible apart from oxygen. This charac-
teristic position serves to distinguish them from the ordinary
bacteria, which require oxygen for their growth and are found
near the surface. 9

These vibrios of Pasteur are the proper authorities which
administer upon the ruined estates of dead bodies, animal and
vegetable.

Countless swarms of bacteria may assist them, by their
presence near the surface, by fixing any oxygen which would
otherwise be absorbed by the fluid and hinder the work of
the vibrios, which work without free oxygen. Pasteur has
grown these vibrios in flasks, from which every particle of
free oxygen has been removed, and found them to be the
true agents of decomposition.

His fluid for this purpose was prepared by placing in a
three-liter flask of water the following salts : —

PASTEUR. 33

Pure lactate of lime Grams 75.0

Phosphate of ammonia u 0.5

Phosphate of potash " 0.4

Chloride of magnesium a 0.3

Sulphate of ammonia " 0.2

Sulphate of soda a trace.

Pasteur has also cultivated, individually, many other organ-
isms, and noted their peculiarities. The extreme high tem-
perature borne by the spores of the ordinary moulds is very
wonderful. For instance, the Penicilliurn Glaucum grew
after being exposed for a considerable time to a dry heat
of 248° F. and 257° F. It was the same with the spores of
other mucidiues. At 266° F. the power of growth was lost
in them all.

Spores of the bacterium lactis were destroyed at 250° F.

Pasteur also made many experiments to determine the
prevalence of germs in the air. He placed fermentable
fluids in flasks, boiled, and sealed them while hot; after
they were cold he broke the end of the tube, letting the air
enter unmodified, then sealed them again at once. It often
happened that no organisms developed in these flasks, but
they generally did in Paris. In the open country only eight
out of twenty developed germs. On the Jura only five out
of twenty. On Mountanvert, in a wind blowing from a
glacier, only one out of twenty contained germs.

There was one point of failure in Pasteur's work which it
seemed impossible to settle by his plan. In all his experi-
ments the organisms are transferred to his flasks together with
a minute portion of the fermenting fluid containing them.
Now the claim is made that it is this minute portion of decom-
posing fluid that sets up and maintains the act of fermenta-
tion, instead of the organisms, as claimed by Pasteur. This
claim has much influence with all those who are inclined to
the views of Baron Liebig, and its force must be admitted.

31 THE GERM THEORY OF DISEASE.

Pasteur's work made a very marked impression upon the
opinions held by the scientific world. Although the general
facts as developed had, in a measure, been accepted before,
there had not been so clear a demonstration of them. The
result was a vast increase of confidence in the germ theory of
disease, as held by Schwan and others nearly a quarter of a
century before. And when Liebig wrote his last paper on
this subject in 1870, reaffirming his old doctrine, with some
modifications, it produced but little impression upon the grow-
ing faith in the new doctrine, which now numbered among its
adherents a large number of the most thoughtful and best
informed scientists. (See Half-yearly Compendium, July,
1870, page 38, for Brief of Liebig's article.)

The following statement contains Pasteur's conclusions :
t( The chemical act of fermentation is essentially a correlative
phenomenon of the vital act, beginning and ending with it.
. . . There is never any fermentation without there being
at the same time multiplication of globules, or the continued
consecutive life of globules already formed."

SECOND LECTURE.

BASTIAN.

The presentation of this subject would be incomplete with-
out some reference to the view of the de novo origin of life,
" Archebiosis." This view has been held by learned men in
all historical ages of the world, though it has never, at any
time, been generally adopted. Such a view was, perhaps,
more prevalent in the fourteenth and fifteenth centuries than
at any other time in the world's history. Bastian, the great-
est exponent of that view, however, lives in the present, and
I have thought best to defer mention of it to this time,
especially as it affects our subject, " The Germ Theory of
Disease/7 only incidentally.

This great experimentalist, in his theories, does not depart
markedly from the theory held by the chemists and vitalists,
but in a large degree adopts the views of both and forms a
connecting link between the two. It is, also, Here again note-
worthy that the facts developed by either and both these are
made to serve Dr. Bistian's purpose almost as well as those
developed by himself. Taking the molecular movement
theory, as developed by the great exponent of that view of
fermentation, Liebig, he claims that this same molecular
movement, under certain circumstances, actually passes over
into vital manifestations, furnishing the living forms found
in the culture fluids contained in the experimental flasks of
Pasteur.

He claims to have produced these living forms experiment-
ally, especially from infusions of hay and turnips, which he
first boiled in his flasks, and while boiling, hermetically sealed,

36 THE GERM THEORY OF DISEASE.

and afterward exposed to favoring conditions of temperature
and light. With these and other infusions treated in this
manner, he found within a few days multitudes of living
forms.

In order that these shall develop, he says that the flasks
should not be more than half or one-third full, and that
above the fluid there should be a partial vacuum. When it
was urged against his conclusions, that the temperature was
not sufficiently high, nor sufficiently prolonged, he increased
both, running the temperature to 300° F., but still obtained
the same result.

Dr. Bastian enters into a very exhaustive argument, using
the facts developed by both the chemists and vitalists, for
the maintenance of his theory.

He claims, stoutly, that the molecular motion theory of
Liebig is the true one, as far as it goes, but does not go far
enough, and quotes largely from him, while he also claims
that the fermentation theory of the vitalists is true, from the
point where they begin, but they do not begin early enough,
and quotes largely from them. In a word, Dr. Bastian claims
that these two theories are the opposite ends of a complete
cycle of manifestations, with the middle and most important
manifestations left out by both parties; i. e., that the one
passes over into the other.

He takes the case of the production of vinegar. In the
ordinary and natural production of vinegar, the fermentation is
always accompanied by the presence of, or as Dr. Bastian claims,
the production of, the plant known as the Mycoderma Aceti.

The chemists claim that this plant is an accident of the
fermentation, and not necessary to the operation, and succeed
by other means in producing vinegar, without the presence of
the plant.

The vitalists admit the production of vinegar by purely

BASTIAN. 37

chemical means, claiming that this production is not properly
by fermentation, and cite the fact that the oil of almonds and
a host of other substances naturally vegetable products may
be produced by the chemists through purely chemical pro-
cesses. Dr. Bastian now claims that both processes of the
production of vinegar are fermentative, and that the second
form (vital) is a more fully developed form of the first
(chemical), and that the one, under favoring conditions, will
pass over into the other without any introduction of germs.

Other scientists and experimentalists have very generally
denied the correctness of Dr. Bastian's results, and set up
the claim that he has not used sufficient care in the exclusion
of germs, or that the heat to which his infusions were ex-
posed was not sufficiently high, or not repeated sufficiently
often, to destroy germs or spores not yet hatched. Moreover,
other experimenters have failed to confirm his results. What-
ever be the final judgment as to the correctness of Dr. Bastian's
views, it is certain that this course of experiments and the
discussion which they invoked greatly extended our know-
ledge of the preserving of fruit in cans, so that we are now
able to preserve articles which previously had resisted our
efforts. One of these is green corn, which seems to require that
it be sealed up at the boiling temperature, and then boiled for
a number of hours each day or two, until five or six boilings
have been had.

This is accounted for in this way. The spores of certain
organisms find green corn a very suitable soil for their de-
velopment, and while the boiling temperature will destroy
the developed organisms it will not aifect the spores. There-
fore these must be hatched and then destroyed. Hence the
intervals of boiling must be continued from time to time,
until all spores are hatched and destroyed. After which the
corn will keep for any length of time.

38 THE GERM THEORY OF DISEASE.

LOGICAL SEQUENCE.

We may now turn our attention especially to the germ
theory of disease; and in doing so, it will be necessary to go
back to the discoveries of Schwan and Latour. It was shown
that after the discovery that vinous fermentation was depend-
ent upon the yeast plant, it was at once assumed that all other
fermentations, decompositions, miasms and contagions were
also dependent upon the life force.

This assumption was a logical sequence to the then existing
ideas, for it had long been held by the wisdom of the world
that all these processes, including contagions and miasms, were
of the same order, of the same genus, and were brought about
by forces of the same nature. But when this assumption was
put forth under the new phase of the matter resulting from
the discoveries of Schwan and Latour, it was vehemently
denied by a host of scientific men, even among many who
accepted the yeast plant as the true explanation of vinous fer-
mentation.

DIFFICULTIES.

This, as we have seen, rendered it necessary that the facts
of each process heretofore regarded as fermentation should be
proven upon its own merits.

The work was at once begun, and the more ordinary fer-
mentative processes were developed with considerable rapidity,
and have finally been completely worked out and definitely
settled, as has been shown.

The proof, however, that the ordinary decompositions, con-
tagious and miasms belonged to the same class and were
brought about in the same manner, was maintained with but
slight success.

The organisms found in these were of a different order and
the most of them more minute, and for a long time it was im-
possible to classify them. Manufacturers of microscopes were

DIFFICULTIES. 39

urged to make improvements in object glasses, in order that
these minute, ever busy objects might be- better seen. And
the observer was compelled to await the tedious operations of
the maker of microscopes before he could proceed satisfactorily
with his work, and then usually found that the gain was but
slight.

The subject became more and more complex the more it
was studied. It was found that in each decomposition there
were varieties of organisms. When one person found an
organism which he regarded as distinctive of a certain process
or disease, and published his results to the world, it was
usually quickly shown that this same organism was to be
found in widely different situations, entirely disconnecting it,
as a cause, with the processor disease claimed.

This kind of disappointment recurred time after time, until
many of the best men turned away from the subject with dis-
gust, believing the theory incapable of demonstration.

It was proven beyond question that many, at least, of the
bacteria were incapable of producing disease, and the view
that these forms were the accidents of the process, merely
accompaniments, were mere scavengers and had no causative
relation to it, gained wide credence.

There was much reason for this view. It was in harmony
with what is seen to be going on around us every day.
Animals are found everywhere that do the work of the
scavenger. As the buzzards flock to the dead carcass, so the
bacteria swarm on the decompositions.

However, a hawk is sometimes found among the buzzards,
for the want of the opportunity of attacking living prey, and
if the two were diminished in size to the mere specks -which
represent the bacteria, the work of distinguishing between
them would be difficult indeed. In surgery especially, cases
were continually occurring which seemed to indicate that the

40 THE GERM THEORY OF DISEASE.

apparent scavengers became the destroyers of living structures,
and there was still a large number of workers who believed
that the distinctive features of these organisms could and
would be developed in the course of time, and they continued
the work steadily and firmly.

MODES OF PEOPAGATION.

Knowledge of these organisms was gradually extended.
They were gradually divided into groups, according to their
forms and modes of propagation. They have been found to
multiply in three different ways.

1st. By simple budding, as in the yeast plant.

2d. By fission, in which one individual simply divides
into two.

3d. By true spores or eggs, developed in their interior, as
eggs are developed in the interior of the segments of the
tapeworm.

The forms are quite numerous. The round and oval forms
are called micrococci, and the short, stem-like forms bacilli ;
the spiral forms spirilli ; while a large number remain with
the common name bacteria connected with a descriptive
adjective, as bacteria termo.

More recently the name of the disease found to be, or sup-
posed to be, produced by the particular form has been
attached, as bacillus anthrax, bacillus tuberculosis, etc.

Many other names have been used, but those given seem
now to be taking their places.*

* Any one who wishes to study these forms particularly should have
Cohn's Classification, which is the most complete yet made out, and will
doubtless serve as the basis of all future efforts in this direction. Magnin,
in his little book, " Bacteria," gives this classification in very convenient
form.

UTILIZING DISCOVERIES. 41

UTILIZING DISCOVERIES.

Schroeder's discovery, in 1854, that the ferments floating in
the air could be filtered out by cotton batting, together with
the confirmation of Schwan's conclusions by Pasteur, who
had continued his fractional cultivations, applying them to
the decompositions, led to an effort to make use of these dis-
coveries in the treatment of wounds, although at that time no
individual bacterium had been proven to be the cause of
disease.

However, microscopic investigation had shown that they
were abundant in wound secretions, and especially abundant
in those that took on a bad condition.

These facts, together with the favorable course usual with
comminuted fractures in which the skin was not broken, as
compared with similar fractures with the skin broken, caused
many to regard the difference as in some way connected with
the bacteria.

Heretofore, this difference in the healing of such wounds
had been charged to the admission of the oxygen of the air ;
which had formerly been supposed to be the active agent in
fermentation and decomposition. It had now been shown,
experimentally, by Schwan and Latour, and recently con-
firmed in the most decisive manner by Pasteur, that the
fermentations and decompositions were caused by organic
germs.

Schroeder had demonstrated that these germs could be
filtered out, and the air thus treated would not cause de-
composition. The old hypothesis was completely disproved ;
and it was most natural to the thought of the time to ascribe
the difference to the introduction, through the medium of the
air, of the germs of bacteria.

Following up this train of thought, Mr. Lister, then of
Glasgow, Scotland, was the first to make a determined effort

42 THE GERM THEORY OF DISEASE.

to reduce it to practice in surgery. Antiseptics had already
been long known, and Mr. Lister began his operations by
thoroughly disinfecting his own hands, all instruments, sponges,
and everything that would come in contact with the wound,
including the patient's skin in the neighborhood of the part
to be operated upon. He then caused the air in which the
operation was done to be disinfected by a continuous spray
of dilute carbolic acid, until the wound was closed. Finally
the wound was so sealed up as to prevent the ingress of germs
from without. He found in actual practice that operation
wounds thus treated generally healed without inflammation,
and without one drop of pus ; simulating in every respect
the healing of subcutaneous wounds. The publishing of these
results by Mr. Lister, in 1865, startled the surgeons of the
world, and many grave heads shook doubtingly, as the words
were pondered.

The new plan, however, was tried, far and wide. It was a
matter that every skillful surgeon could do for himself, test
for himself, and judge of for himself. Although failures
were made, the aggregate of results were so vastly superior
to anything heretofore attained, that it completely revolu-
tionized hospital practice throughout Europe.

EXPLANATORY.

This statement requires a word of explanation. The effect
was not so much felt in private practice, or in small private
institutions. The reason for this difference may be explained
in this way. It had long been demonstrated that large public
hospitals became unfavorable to operation or accident wounds.
In large institutions, all open wounds were prone to take a
bad course as compared with similar wounds in private prac-
tice. The supposition that such hospitals became infected
with this class of disease-producing germs had already been

NATURE OF THE EVIDENCE. 43

widely entertained ; and now the antiseptic method of Lister
was found to remove the difficulty, and render the treatment
of wounds in such hospitals as effective and safe as the same
class of wounds in private practice, and in most cases even
more so. This grand achievement of the germ theory lent
an immense impulse to the study of the subject. Every great
surgeon became a student of fermentative change, and of the
influence of living organisms, no matter what his bias on the
subject. As might reasonably be expected a corresponding
advance has been attained.

Up to that time no one particular organism had been
singled out and proven to stand in a causative relation to
any one disease.

But now the study of the individual character of the
organisms found in wound secretions, and in the tissues
immediately after death from particular diseases, sprang to
the front, and has been carried forward by the most acute
minds of our times.

NATURE OF THE EVIDENCE.

We may now turn our attention to the examination of the
evidence upon which these views were based. The theory, so
far as it relates to the production of disease, has been founded
on fragmentary evidence, not upon demonstration. And it
must be said, also, that much of this fragmentary evidence
has been of the nature of what lawyers would call circum-
stantial evidence. The nature of the evidence, as a matter of
fact, may be thus stated : It had long been believed that fer-
mentation, decomposition, ruiasm and contagion were caused
by processes similar or identical in their nature. It has been
proven that fermentation and decomposition are dependent
upon the life and growth of certain microscopic organisms.
Therefore, miasmatic and contagious diseases are caused by
3*

44 THE GEHM THEORY OF DISEASE.

microscopic organisms. This kind of evidence has served as
the basis of practice, and been the means of producing im-
provements in the management of wounds particularly,
greater than the most sanguine theorist could have expected
thirty years ago.

DIRECT EXAMINATION.

It may surprise some when I say that the first definite
demonstration of micro-organisms in the tissues of those dying
of traumatic disease was made by Rindfleisch, in 1866. Reck-
]inghausen and Waldeyer demonstrated the same thing about
the same time. Directly afterward, Birsch Hirschfield found,
by extended examinations, that the unhealthfulnessof a wound
stood in direct relation to the numbers of spherical bacteria
found in the pus of that wound. He also found that the
blood of pysemic patients contained bacteria during life.

HIRSCHFIELD.

Dr. Birsch Hirschfield, on examining daily the pus coming
from a wound, found that, with the ushering in of the first
symptoms of pyaBmia, the pus showed a corresponding change,
consisting in the presence of micrococci, either in pairs, strings
or zooglea (masses of micro-organisms, of whatever kind, often
imbedded in a gelatinous mass, the latter especially when
pyaemia was far advanced or rapid in its course), and in an
altered appearance of the pus corpuscles, which were finely
granular, of less definite outline and lustre, and showed
their nuclei very distinctly, without the addition of reagents.

The blood of such patients contained similar micrococci,
and its white corpuscles had undergone a change very similar
to that of the pus corpuscles. He sometimes found that pus
from a pya3mic patient would contain besides these a quantity
of the bacterium termo or bacterium lineola, which are the

NATUBE OF MIASM AND CONTAGION. 45

common bacteria of putrescent matters, while micrococci,
according to Cohn, Klebs and Hirschfield, are not to be con-
sidered as the ferment of putrefaction. (American Journal,
page 542, Oct. 1873.)

This is the first recognition of a particular form of micro-
organism in connection with a given condition that has stood
against adverse criticism.

EVIDENCE UNSATISFACTORY.

Within a few years a great mass of such evidence as this
was accumulated. It will be seen at once that this kind of
evidence is fractional and not conclusive. It shows the
presence of rnicro-organisms, but it is in no way conclusive as
to the practical effects of these organisms in causing any given
disease. It was not shown that the disease could not progress
without the organisms.

NATURE OF MIASM AND CONTAGION.

During this time a theory was developed for the explana-
tion of the spread of certain epidemic diseases, which deserves
mention, not only for its intrinsic merit, but for the reason
that it has, by directing thought into new channels, greatly
enlarged our knowledge of the cause of epidemics and
increased our means of defence against them. We have here-
tofore spoken only of miasras and contagions.

A miasm, according to the germ theory of disease, is an
organism developed, under certain circumstances, in the soil,
decaying vegetation, marshes, etc., of certain localities, which
can enter the human body and cause disease, but cannot grow
a second time in the body of another person — at least does not
pass from the sick to the well — and is, therefore, not a con-
tagion.

A contagion is an organism whose habitat, by nature or

46 THE GERM THEORY OF DISEASE.

adaptation, is the human body, and the spores of which can
pass from one person to another, either by contact or through
the air, and cause disease in others.

MIASMATIC CONTAGION.

A third class partakes of the nature of both, but differs
from both. It is supposed to be an organism which has one
period of development in the human body and another period
without the human body, and that these two stages are
required for its full development. Therefore, such diseases
are not contagious; they cannot pass from one to another
until they have found a suitable soil for the second stage of
development and completed their spores. When this has
been accomplished, they are again ready for the production of
the disease in man, and not before.

In this way whole regions of country become infected, and
persons are struck down with the disease without having seen
one sick of it, or having been very near them. Cholera, Yellow
Fever, Typhoid Fever, and various other diseases belong to
this class. They are called miasmatic contagious diseases.

This theory is not based upon any demonstration yet made,
either in the human subject or upon animals, but rests upon
the known life history of certain parasites of the vegetable
kingdom and circumstantial evidence.

Among the most familiar and best proven of the vegetable
parasites which run through this kind of cycle, is the
common uredo or rust on wheat. This parasite requires two
separate growths to complete its spores. Indeed, it seems to
have a double set of spores. The spore formed on wheat
will not again grow upon wheat, but will grow on the leaves
of certain bushes, especially the barberry bush. And the
spores formed on these bushes will, in turn, grow on wheat,
thus completing its cycle of existence.

INFECTION EXPERIMENTS. 47

It may be that the organisms of the miasmatic contagions
require free oxygen at a certain stage of existence, especially
for the hatching of the spores formed in the body, after which
the organism itself may enter the body, and multiplying,
cause disease. Some examples of this nature have been
observed in organisms inhabiting putrid substances. The
hatching and early stages of existence take place on the
surface, but the after life, the real activity of the organism,
is in the depths of the mass, away from free oxygen. Ac-
cording to this idea the spores passing out from the sick
person must first find a suitable soil for hatching and the
beginning of development, before they are ready for growth
iii the human body.

The efforts already made on this theory, for the prevention
of the spread of epidemics, have been sufficiently successful
to furnish an additional point of circumstantial evidence in
favor of its correctness.

INFECTION EXPERIMENTS.

Turning again to the experimental evidence, we find that
fragmentary experimentation has taken a new departure.
Men have arisen from their microscopes and begun injecting
the bacterian fluids collected from wounds, and from those
dead of disease, into animals, and watching their effects.
In the first of these, the animals seemed to have been killed
outright by the amount of poisonous material injected, and
nothing was gained.

Cose and Feltz were the first to obtain valuable results.
They injected a small quantity of blood from a patient just
dead of puerperal fever, into rabbits. The rabbits sickened
and died of the disease induced. The blood from these was
injected into other rabbits, which also died after a disease of
the same nature. This was repeated many times, always

48 THE GERM THEORY OF DISEASE.

with the same results. These observations were repeated and
corroborated by a very large number of observers, within a
short time, and Davaine claims that after twenty-five successive
transmissions, he found one-trillionth part of a drop of blood
sufficient to cause the disease and produce death. The disease
induced, however, was pya3inia. And in these experiments
this remained constant, no matter -what disease the patient
had from whom the blood was taken.

The developments of this series of experiments were very
curious. It was found that if the blood was filtered, and the
serum thus obtained injected, sickness and death resulted,
but no pyaBinic abscesses occurred. The disease induced was
different. Now, a long time ago, pya3mia was supposed to be
caused by the absorption of pus. This was denied, and after
much discussion of the subject, there was an effort to abandon
this term, which was supposed to misrepresent the facts.
Septicaemia was introduced instead. The new name, how-
ever, only partially succeeded in displacing the old ; for, when
septicaemia occurred, with the formation of abscesses, it was
still termed pyaemia, to distinguish this accompaniment. This
series of experiments seemed to demonstrate that, in the one
case, septicaBmia is caused by absorption of the fluids con-
taminated by the effete material of the cocco-bacteria ; while
the other, pyremia, is caused by both the absorption of the
fluids and the entrance of the cocco-bacteria.

Recently, however, it has been shown that each .variety is
caused by a special form of micro-organism. The organism
causing septica3inia being so minute as to get through the
filter, had escaped the earlier investigators. Dr. Koch of
Berlin, and others, have clearly demonstrated that the fluids
deprived of bacteria will produce transient poisoning ; or if
in sufficient quantity, will kill; demonstrating its poisonous
nature.

THIERSOH. 49

With this study came a much greater confidence in the
germ theory on the part of many zealous observers. Yet
many held to the views of Liebig, and showed that, with the
exception of gaseous ferments, which were certainly disproved,
all the facts could be accounted for on the molecular motion,
or chemical theory. It was claimed that the dried remains
of decomposing bodies might fly about in the air, in the form
of fine particles, and renew their effects on being moistened,
as claimed for organic germs, and be kept out of wounds, or
be destroyed by the same means; that while micro-organisms
were accompaniments, they were not a cause of disease. We
will give the views held by some of the great men of the
time, as showing the drift of the thought and the entangling
of views that have occurred.

THIERSCH.

Professor Thiersch, writing in 1875, after alluding to the
success of the Lister method of treating wounds, and sketching
the history which led to its adoption, seems at that time
not to have been fully convinced of the truth of the germ
theory of the origin of septic influences. Granting the full
force of Schroeder's discovery, he thinks it still possible that
the power of generating putrefaction may exist in the fluid
product of putrefaction independently of organisms; that this
power may be retained in the dry remains of such fluids,
which float in the atmosphere, and be filtered out by cotton,
the same as claimed for organic germs. Consequently, he
then considered the question an open one, as to whether or
not putrefaction can progress without organic germs. He
also objects to the deductions from these experiments, because
albuminous substances are always changed by heat in the ex-
perimental flasks. The argument, or claim, that bacteria are
secondary to chemical changes, had been very widely held, and

50 THE GERM THEORY OF DISEASE.

it was not without strong grounds in its favor. In Pasteur's
flasks the organisms were always transferred to fresh flasks,
together with a small quantity of the fermented fluid, which,
it was claimed, prepared the way for the development of the
bacteria.

LISTER.

Mr. Lister, at the London Congress, Vol. 2, page 371-2,
relates that he drew blood, with antiseptic precautions, from a
vein of an ox, into small, purified bottles, and allowed it to
clot. He then introduced various quantities of ordinary tap-
water (London hydrant water) into the different bottles. He
was surprised to find that even eight or ten drops failed to set
up putrefaction in the blood serum, while the one-hundredth
part of a drop of the same water was always sufficient to set
up putrefaction in milk. He experimented with the blood of
various animals with the same results.

He found, however, that if the blood serum was diluted
with water purified by boiling, the smallest portion of tap-
water would then set up decomposition. He also found that
putrefying blood, very largely diluted with water, purified by
boiling, did not readily set up putrefaction, while the smallest
possible amount of the undiluted putrefying blood set up the
process at once. Speaking of the result, he says : " How it is
that diffusion of the bacteria renders them incapable of
developing in the serum, I do not profess to understand. It
may, perhaps, be, that when the bacteria are introduced
directly from putrid blood, the products of the putrid fer-
mentation adhering to them may induce, chemically, an altera-
tion in the normal quality of the serum, which, when thus
impaired, may prove amenable to the nutritive energies of the
micro-organisms] while, conversely, copious ablution with
water may remove from them the associated substances which
may thus act as their pioneers. The view might be otherwise

DR. SALMON. 51

expressed by saying that the bacteria, per se, are unable to
grow in normal serum, and can only develop in the liquid
when vitiated, whether by the addition of water or by the
action of small quantities of the acrid products of decompo-
sition.

" Or, again, it seems to me conceivable that the normal
serum may oppose an insuperable obstacle to the nutritive
attractions of an individual bacterium, but that this may be
overcome by the associated attractions of several of the
organisms in close proximity, after the analogy of the more
energetic operation of a concentrated solution of a chem-
ical reagent. But whatever be the explanation the fact re-
mains."

I give the first statement of Mr. Lister as the strongest
statement of the view against the primary causative effects of
bacteria that I have seen, while I regard the second as
approaching very nearly a true explanation of the facts in the
case. I will refer to this again.

One fact Mr. Lister thinks demonstrated beyond question.
Pure blood resists decomposition under circumstances in which
very many other substances decompose, and that a blood clot is
a much better antiseptic dressing than was supposed. Most
forms of bacteria must be grouped together in some numbers
before they can live and grow in blood ; while a single bac-
terium lactis detached from others and washed with purified
water will be'sufficient to start decomposition in milk.

DE. SALMON.

The idea that pathogenic bacteria must be grouped together
in considerable numbers in order to grow in the blood or
tissue of animals, has recently been strongly confirmed by the
experiments of Dr. Salmon (see Medical Record, April 7th,
1883), in his experiments with u dilutions" of the organisms

52 THE GERM THEORY OF DISEASE.

of chicken cholera. This experimenter finds that dilutions
of the fluid containing these organisms first produce a mild
type of the disease which they induce, and finally, as the
dilution is increased, fail entirely to produce an effect, although
there may still remain in the drops injected a number of the
organisms. He believes the vital energies of the animal
resist the growth of the organisms, and that numbers are
required to overcome this. We will allude to this again.

BILLROTH.

Billroth, in the course of his inquiries in the early part of
the sixth decade, published in 1874, came to the conclusion
that organisms were present in the human body and in the
bodies of animals in a state of health. And he supposed
that in case of injury they need not be introduced from with-
out in order to develop in a wound and produce sepsis, but
that they may come from the tissues beneath, and if the con-
ditions of the wound be not rendered unfavorable for them,
they may develop sepsis. Professor Thiersch seems to have
attached great importance to this view.

In the same publication, Professor Billroth held, also, the
view that bacteria were the accompaniments of disease, but
denied that they were a cause. His view of contagion seems
to have been divided somewhat between those of Liebig and
those of Beale (vide infra), that is, he seems to have regarded
both these as operative causes or modes of formation of con-
tagious matters.

In his introduction to a report on surgery, in 1876, he takes
occasion to speak of this subject again, and seems to have very
materially modified his views, as will be seen by the following
sentence, which I quote: "I still hesitate to accept uncon-
ditionally the assurance of our best observers, that zymotic
germs have much to do with the causation of erysipelas,

VIECHOW. 53

diphtheritis, septicaemia and pyaemia, but in hospital gan-
grene there appears to be no doubt that the disease is so
caused."

Since that time Billroth has fully recognized the demon-
strations of Dr. Koch. (See Belfield's Lectures.)

PROF. THIERSCH.

Prof. Thiersch relates the following accidental infection
experiment: "At the end of March, 1871, the recently
finished St. Jacob's Hospital was brought into use. Some
of the furniture from the old hospital (which was not in
use because it was infected with hospital gangrene), was piled
up in one of the courts. After some weeks it had disappeared,
and the author was informed that it had been removed to
a more fitting place. Two days later, a virulent type of
hospital gangrene appeared in two wards (of the new hospital),
remote from each other. A search for the cause of this
gangrene, which had not been introduced from without, ex-
posed the fact that the old infected furniture had been stowed
in two basement rooms, from which these two wards drew
their fresh air."

VIRCHOW.

Prof. Virchow speaking on this subject at the International
Congress at London, especially of the claim so often made
that micro-organisms could only exist in diseased organs, that
they were scavengers, which only attacked the dead or dying,
said he thought the view was one-sided. It was necessary
to distinguish between different forms of these organisms.
Some very virulent organisms can multiply anywhere, in all
tissues and at all times.

"The bacillus anthracis had no need of diseased tissues.
It is vigorous enough to destroy any tissue, and will develop
itself in a short time, from the point of introduction, into a

54 THE GEKM THEORY OF DISEASE.

large focus of disease. So with diphtheria. It is not neces-
sary for any diseased part to exist before the disease com-
mences; that is, the organism finds its way into healthy
parts."

" The action, then, of the virulent organisms is very differ-
ent, and it is more philosophical to explain the facts in this
way, than to refer the differences to .the mode of action of
the parts."

" Part of them (kinds) will penetrate into the interior of
cells, and there multiply, while the cells will perish, destroyed
by the evolution of the parasitic organism."

In other cases (kinds) the organisms pass between the cell
elements into the interstices of the tissues, or into the inter-
cellular substance. In this case the action of the organisms
upon the cells is not direct. The cells are only affected by
some matter secreted by the organisms, or by some chemical
substance produced by the action of the latter upon the fluids
of the body.

PKOF. KLEBS, OF PRAGUE.

Prof. Klebs, of Prague, a worker in this field, of great
ability, in his address upon this subject at the London
Medical Congress, discussed the views of Bastiau, of the
spontaneous generation of organisms; and in summing up,
says that " since it is abundantly shown, by observation which
is trustworthy and reliable, that the material cause of disease
is introduced from without, therefore, the subject of spon-
taneous generation has no weight in this discussion."

" Those organisms produced in the body, or those normally
inhabiting healthy tissues, if such were proven to exist, could
not be regarded as a cause of disease. Only one possibility
can here be entertained. Can the organisms ordinarily exist-
ing in the healthy body (if such there be, which Klebs denies)

VOLKMAN. 55

be so changed, on account of change in the fluids which they
inhabit, that they may become a cause of disease. No dis-
ease has been shown to arise under conditions which would
make this seem probable." Continuing, he says, "We may
proceed from this proposition as the basis of future inquiry."
" Specific diseases are caused only by specific organisms."
" The question now arises, whether specific differences of a
morphological nature, which remain constant, can be shown
to exist in such organisms, so that, beforehand, their nature
can be shown by their forms." " It is possible that the
specific effects may be due to fine chemical differences in the
working of these organisms." " But, happily, even here the
general law of nature holds good, that difference of perform-
ance is represented by difference of form, and that within the
same form lines there are different grades, only, of perform-
ance or capability."

Prof. Klebs thinks that the knowledge already attained is
sufficient to demonstrate that the forms of the organisms
causing disease do remain constant, and produce the same
phenomena and nothing else, under given conditions. - He
attempts a classification, but admits that our knowledge is
not yet sufficient for a satisfactory basis.

VOLKMAN.

Prof. Volkman, of Halle (London Congress, vol. ii, page
362), took strong grounds in favor of the germ theory. He
says, "We know of no suppuration which does not depend
on the influence of organic ferments. ... In the worst con-
stitutions, and with the most disordered state of health, no
suppuration takes place if septic infection is prevented. . . .
If we could completely exclude all organic ferments, the
largest open wounds and the most extensive loss of tissue
would heal without suppuration."

56 THE GERM THEORY OF DISEASE.

LISTER'S REPLY.

This was evidently regarded by Mr. Lister as a very ex-
treme view. And he replied, speaking very strongly against
the conclusions reached by Prof. Volkman, Klebs, and some
others. He says, "But, gentlemen, while I am more than
ever convinced of the relations of micro-organisms to disease
processes in wounds, I propose to utter, this morning, what
seems to me to be a needed note of warning against a tend-
ency to exaggeration in this direction. This exaggeration,
if such there be, is largely due to the success of the anti-
septic treatment."

After speaking of the certain success of the antiseptic
treatment of wounds, and the banishment of septicaBinia,
pyaBtnia, hospital gangrene, etc., he says, " Such success pro-
ceeding from a mode of treatment designed especially to
exclude bacteria, may suggest that all inflammations are due
to micro-organisms, and that suppuration, acute or chronic,
is always due to similar agencies. Gentlemen, I believe this
to be a very exaggerated view of the matter, and a view
which may tend to have a serious influence on our practice."

" For example, if we believe inflammations are due only
to the invasions of microscopic organisms, to what purpose
do we employ counter-irritation."

Mr. Lister then goes on to show that inflammation does
arise, in very many instances, without the aid of micro-organ-
isms, and from a variety of causes, both in wounds and sepa-
rate from wounds. That abscesses form, and pus forms, in
many instances, under circumstances that exclude bacteria.
Also, that strict search has shown the pus, under such cir-
cumstances, to be free from bacteria.

THIRD LECTURE.

BEALE.

It will not be out of place to notice here the peculiar views
of Dr. Lionel S. Beale.

In a work published in 1870, entitled, "Disease Germs;
their Nature and Origin," Dr. Beale holds a view of this
subject different from the more generally accepted theory, and
differing entirely from both Schwan and Liebig as to the
nature of contagions. We should say, however, that this view
was not entirely original with Dr. Beale, but he has given the
most perfect exposition of it.

In respect to bacteria, he regards them as accidental accom-
paniments of disease ; their home is among dead matter,
having nothing to do with the living. Further, they are of
no distinct species or form ; a spore may produce this or that
form, according to its environment, and nothing can be pre-
dicated of the action of any particular form. They are
scavengers only.

The action of a contagion is not a fermentative process in
any respect, either in accordance with Liebig and the chemists,
or in accordance with the views of Schwan and Pasteur. All
the facts he thinks susceptible of a different explanation.

Dr. Beale regards disease germs as being derived directly
from the human tissues by a process of physiological degrada-
tion— by a metamorphosis of functional activity — without
there being necessarily any change of form from the normal
cell or bioplasm. This is the bioplasm theory of contagion.
It has also been termed the amoaboid theory.

Dr. Beale believes contagious disease germs to consist of

57

58 THE GERM THEORY OF DISEASE.

outgrowths from the white corpuscles of the normal blood,
excited by germs of a similar nature. This outgrowth occurs
in successive changes in the physiological activity of the bio-
plasm of each successive globule of living matter, as new
globules are given off from the parent globule, uutil the type
of the exciter of the change has been reached more or less per-
fectly. After these changes have been induced, and have run
their course, many of these bioplasts die and are eliminated
from the system. But very many are eliminated in the living
state, and the person or animal, if it has been able to with-
stand the attack, returns to a state of health.

The germs eliminated in the living state have acquired a
wonderful tenacity of life, and are capable of living for a very
considerable time in the atmosphere. They have the power
of entering into the circulation of another animal by way of
mucous membranes and otherwise. And when so entered, they
induce precisely the same changes in the blood as before
described.

This is an extension to the contagious diseases, with some
change of form, of the theory now generally held as to the
nature of the formation of neoplasms, or new growths in the
form of tumors, such as cancer, sarcoma, etc.

These are regarded as changes in the physiological character
of the cells of the part, by which they take on new properties
resulting in abnormal proliferation of cells with like charac-
teristics. These cells, when transplanted to other animals,
will, if the conditions be favorable for them, grow and mani-
fest all their acquired physiological characters. In this way,
epithelial cancer may be transferred from man to the animals,
or from person to person, perhaps, as readily as syphilis from,
person to person, except that the cancer cells must be actually
grafted into the second person.

Moreover, it is generally recognized that the infiltration

BEALE. 59

which occurs so generally in carcinoma is due to the wander-
ing of young cells or bioplasts from the seat of the tumor,
which have, through a process of physiological degradation,
acquired new properties by which they are enabled to initiate
a new focus of disease wherever they may lodge in the tissue.
These are found to wander along the course of the lymph
streams especially, and to a lesser extent along the blood
streams. There is also a certain wandering among the
neighboring tissues, infiltration.

Such diseases, however, are never contagious, in the ordinary
sense of that term, and such cells do not acquire any power of
continued life when isolated from the animal economy.

In arguing the point, Dr. Beale does not insist that in each
individual case the white corpuscles of the blood must pro-
duce the germs of contagion. f< For," he says, " the facts may
be accounted for solely by the proliferation and growth of the
acquired germs or those that have been implanted from with-
out. But," he says, " the fact that living matter of the blood
of one individual will live in the blood vessels of another,
that the skin, periosteum and other tissues may be trans-
planted and grafted, prepare us for the remarkable circum-
stance, demonstrated by experiment, that living pus bioplasts,
which have, indeed, been derived from normal bioplasm, may
traverse long distances, free and independent, and then, gain-
ing access to other organisms, may live and grow and multiply
in them, and establish changes of the same kind as those which
were taking place at the seat of their origin."

In speaking of the first origin of contagions, he says, "It is
possible that the exceedingly minute living particles which
constitute the ( contagium ' of contagious diseases may be the
degraded offspring of some kind of normal living matter or
bioplasm, which originally possessed comparatively exalted

tissue-forming, or other formative powers The

4

60 THE GERM THEORY OF DISEASE.

phenomena which occasion the formation of ordinary pus,
may, if they continue to occur for a long period of time,
determine the development of a specific pus, which has still
more marvelous powers of vitality. So, I think, it may
reasonably be argued that if the ordinary feverish state be
prolonged for a considerable time, and be severe in degree, it
is likely that the bioplasm in the blood, collected in the
capillaries, may give origin to bioplasm with marvelously
increased power of retaining its vitality and of growing and
multiplying. The particles of this making their way through
the vessels and escaping may live for a considerable time, and
having entered the blood of another person may excite in it
the changes which accompanied its own development."

" Finally," Dr. Beale says, " it is not probable that disease
germs have sprung from insects, or animalcules, or any kind
of vegetable organisms ; neither have they originated in the
external world and seized upon man ; but they have been de-
rived by direct descent from the normal living bioplasm of
the organism. They have originated in man, and if man is
not, indeed, responsible for their origin,'he has certainly him-
self imposed the conditions favorable to their production and
dissemination."

It is worthy of note that the experimental proof upon
which Dr. Beale relies for his theory is similar to that upon
which others have relied for proof that bacteria cause disease,
namely, injection by pus and fluids from the tissues, and
observations of the transmission of contagions, the means by
which they may be prevented, etc. He does not pretend that
the character of such contagious bioplasm can be determined
by microscopic study, but on the contrary, distinctly asserts
that it cannot, and further, that the study of the subject gives
no hope whatever of demonstration by this mode of inquiry;
fur the reason that the bioplasmic forms give no indication

BACILLUS ANTHRAX. 61

whatever as to the character of their physiological activity.
As a theory it is very interesting, and is certainly very in-
genious, and at the same time quite plausible. It has, how-
ever, made but little impression upon the thought of the world,
and is now strictly limited to those diseases characterized by
new growths of tissue, by a great majority of the prominent
thinkers of the profession.

In the discussion of this subject at the International
Congress, this theory, as applied to contagious diseases, was
mentioned but once. Dr. Richardson, of London, held views
almost identical with those of Dr. Beale. (See American
Journal of the Medical Sciences for October, 1875, page 516,
for Dr. Richardson's views.)

Dr. John Bell holds the same views. (See Half-yearly
Compendium, January, 1872, page 112.) Also Prof. Crooks
and many other important persons ; indeed, this seems to have
been the most prevalent view in England during the eighth
decade of this century. Lister's success, however, swerved
the thought of Englishmen to the theories of Schwan and
Pasteur.

BACILLUS ANTHRAX.

While the experiments detailed in our last lecture were
being carried on mostly in Germany, Pasteur was still busy
in France with his flask cultivations. Having demonstrated
the nature of the ordinary ferments by pure cultivations
(fractional cultivations as they came to be called, the develop-
ment of one species out of many), he turned his attention to
contagious diseases, and finally hit upon some brilliant re-
sults. The most widely known and best proven of these is
the isolation of the bacillus anthrax, the contagium of that
dread disease which has made such havoc among sheep and
cattle in many parts of Europe, and also has been many
times epidemic among men with deadly effect. He obtained

62 THE GERM THEORY OF DISEASE.

this bacillus entirely pure, and succeeded in causing the dis-
ease in animals by inoculating them with it, after the fiftieth,
on to the one hundred and fiftieth generation, grown pure in
his flasks. The whole life history of the organism has been
made out, and is now substantially confirmed by a large
number of separate observers. Indeed, this bacillus is re-
cognized on sight by observers in this field of work every-
where. It can be bottled up and sent to any part of the world,
like vaccine virus, and produces the disease in regions where
it was unknown, just as readily as at home. This would
seem to be a complete demonstration of the germ theory.
Yet strangely enough its acceptance as such has been received
with extreme caution. That M. Pasteur had the virus of
anthrax, no one could doubt, but was it the bacillus, or was
it contained in some other form in the culture medium, and
thus carried from flask to flask. It was still claimed that
the molecular motion described by Liebig had not been
eliminated.

KOCH.

We have now to notice a class of experiments still more
conclusive than any preceding ones, and which are as yet
unexcelled. But it is first necessary to notice the manner in
which they were approached. These are by Dr. Koch, of
Berlin, working under the auspices of the Prussian govern-
ment.

This brilliant experimentalist has been very fortunate in
his endeavors to devise more perfect means of recognizing
very minute organisms with certainty ; and of isolating them
by pure cultures. One of his first and most important feats
was the devising of a plan of staining these organisms, by
which he was enabled to practically isolate them from the
animal tissues. By his plan of aniline staining he succeeded
in obtaining the organisms colored a dark blue, while the

KOCH. 63

tissues were rendered transparent. So completely was this
accomplished, that the animal tissues were practically gotten
out of the way of the observation of the organisms. His
plans have now been tried by a large number of investigators,
and have stood the test of adverse criticism. By this new
plan of work it was soon demonstrated that the normal tissues
of men and animals are entirely free from these organisms ;
and that the bodies before thought to be such by Billroth,
Thiersch, and many others, were, in fact, the granular con-
stituents of the blood. Billroth and others, after experiment-
ing with the new process, have fully admitted the demonstra-
tion. And the point may be considered as fully settled.

Dr. Koch now began his work by the then common plan
of injecting septic blood into the tissues of animals. At first,
his results were similar to those common with this mode of
experimentation. Too much of the material killed, by direct
poisoning, while a small amount induced disease. Even the
slightest scratch of a blade that had been dipped into the
blood of the dead house mouse on which he was experimenting
produced the disease and death, in the usual time, upon a
second mouse, i. e., from forty to sixty hours. The organism
found in the blood of the dead animals was a very minute
bacillus, which remained constant and pure. An effort, during
these experiments, to inoculate field mice with the bacillus
cultivated in this way in the house mice, failed entirely.
They proved to be in no wise susceptible to the disease.

Now, Dr. Koch, in his examinations of the tissues of the
dead house mouse of the original experiment, had found at
the point of injection an organism entirely different from
that found in the blood, and which he got rid of in the injec-
tions made afterward ; having obtained these in as perfect
isolation as he could, by the means at that time devised, and
tried them on the field mice, he was surprised to find that

64 THE GERM THEORY OF DISEASE.

they produced a different disease entirely, which was not seen
in the experiments on the house mouse, for the reason that it
was killed by the first and more quickly acting organism, be-
fore the second had time to produce its effects. This new
disease ran a course identical with the dreaded hospital gan-
grene. The organism did not pass into the circulation at all.
It spread by its growth merely, and destroyed all tissues with
which it came in contact, until vital organs were reached and
the animal destroyed. The parasite was found only in the
diseased tissue, never in the blood.

Dr. Koch says of this : " These appearances lead us to the
conclusion that the action of these micrococci in causing the
gangrene is somewhat as follows : Introduced by inoculation
into living animal tissues, they multiply, and as a part of
their vegetative process, they excrete soluble substances which
get into the surrounding tissues by diffusion. When greatly
concentrated, as in the neighborhood of the micrococci, this
product. of the organisms has such a deleterious effect on the
cells that these perish and finally completely disappear. At
a greater distance from the micrococci the poison becomes
more diluted and acts less intensely, only producing inflam-
mation and accumulation of lymph corpuscles. Thus it
happens that the micrococci are always found in the gan-
grenous tissue, and that, in extending, they are preceded by a
wall of nuclei, which constantly melts down on the side
directed towards them, while, on the opposite side it is as con-
stantly renewed by lymph corpuscles deposited afresh."

Inoculation with the juices of the dead tissue never failed
to induce the disease. Inoculation with the blood did not
induce the disease in any case. When the house mouse was
inoculated with this material, the disease induced was pre-
cisely the same as in the field mouse. Thus, these two forms
of organism, one a very minute bacillus, the bacillus septicus,

KOCH. 65

the other a chain-like cocco-bacterium, were isolated, and after-
ward obtained entirely pure by culture on dry slides — a plan
presently to be described.

Why the field mice were insusceptible to the disease so
readily induced in the house mouse, remains a profound mys-
tery. Yet it is in accord with facts that are continually
coming to light. It is a well-known fact that certain persons
resist the contagium of smallpox, while others around them
are struck down; and the same is true of every other con-
ta'nous disease. It is also a well-known fact that some

o

classes of animals are insusceptible to certain diseases common
to other animals nearly related to them. It would seem that
the organism inducing the particular disease does not find in
this or that animal a suitable habitat, but why, is unknown.

As I have said, this class of experiments had been made by
many before Dr. Koch ; but he had developed a distinctive
feature. He had demonstrated that the same tissues or fluids
might contain germs, which, when separated, would produce
separate and distinct processes of disease. Heretofore, as has
been said, this class of experiments had only succeeded in pro-
ducing septicaBmia and pyaemia, which were regarded as parts
of the same process. And this result was induced, no matter
what the disease with which the patient from whom the
material was obtained, may have died ; results very confusing
to those who believed that different diseases are induced by
distinct and separate germs.

We have already spoken of the fact that these results were
very nearly identical with ordinary blood poisoning from
wounds. Now in the discussion of Dr. Koch's experiments
a new thought was developed. The substances injected were
all contaminated with septic germs ; and these virulent germs
had killed the animals experimented upon, before other and
slower acting germs had time to produce their results. The

66 THE GERM THEORY OF DISEASE.

more the matter was discussed, the more certain it seemed
that this had been demonstrated. One point of vast import
had been attained ; and now the experimentation must pro-
ceed from the new basis. Inoculation must be with pure
virus of some particular disease ; not a supposed virus mixed
with various germs. Otherwise nothing distinctive could be
expected.

As we have said, Pasteur had gained a most happy result
from his flask cultures, in the isolation of the bacillus anthrax.
But it had cost an immense amount of labor, and shown that
the results were very uncertain at best. Besides, there was a
serious objection urged against flask cultures, in that small
portions of the fermenting fluid were always transferred to
the flasks with the organisms. The anti-vitalists claimed
that the molecular motion, poison or chemical ferments were
carried over by the small portion of fermenting fluid trans-
ferred, and that where there were fermentable fluids, this
power would be propagated. It is evident that this argu-
ment carried with it much force, for such men as Prof. Bill-
roth, Prof. Thiersch, and others of the great medical men
of the world, still considered this argument a valid one,
which still placed the causative effect of micro-organisms in
doubt.

Therefore other means of cultivation were earnestly sought.
Dr. Koch, of Berlin, was again the successful man. He de-
vised and brought into successful operation the Dry Slide
Cultivation, by which the particular organism could be watched
during its entire development, by the eye of the experimenter,
so that it could be seen, at any stage of the process, whether
or not the cultivation was contaminated by other organisms
than the one desired.

The plan was this. Suitable material to serve as food, or
soil, for the sustenance of the organism was mixed with

KOCH. 67

albumen and sterilized by heat. This was carefully reduced
to a jelly that would solidify on cooling, and spread in a thin
layer on glass slides suitable for microscopic examination.
When the slides were thus prepared, a needle was dipped in
the fluid containing the organisms and drawn quickly across
the surface of the prepared culture medium, in such a way as
to distribute the few that adhered to the needle, along the
line of its track. This preparation was then sealed up, or
otherwise protected from contamination, and kept at a suitable
temperature for the growth of the organisms, and occasion-
ally examined with the microscope. It was found that the
organisms grew well on such soil or food ; also, that it re-
quired the utmost care to prevent contaminations. These,
however, could be detected by microscopic examination, and,
whenever found, rejected. It was also found that the differ-
ent organisms present in a fluid could be separated by this
method of culture; for in drawing the needle point along
the surface of the solidified jelly, the organisms would often
be distributed singly, and would develop in little groups that
could be seen by the naked eye. The characters of each could
be determined by the microscope. These were generally found
in the form of little flakes on the surface of the jelly, and
each could be detached with a needle and conveyed to another
slide, or when desired, to a culture fluid, and kept pure.
From these pure growths the organisms are transplanted to
other slides, or culture fluids, at will, and for any number of
generations, and kept absolutely pure. Inoculations were
made with these pure cultivations; and such inoculations
were found constant in their effects, whether taken from the
fifth or the one hundredth generation.

By this process, it is believed that the difficulty heretofore
existing, as to the exclusion of a possible chemical ferment,
has been incontestably overcome. The phenomena are watched

A*

68 THE GERM THEORY OF DISEASE.

by the microscope, and the growth of the organisms is all
that is seen. This, when carried on from slide to slide, for
several generations, must disconnect the organisms from any
possible following of a chemical ferment. So palpable is this
demonstration that Billroth, Thiersch, and many others, who
had maintained a position of skepticism, have fully acknow-
ledged it.

By use of these pure dry cultivations, Dr. Koch proved his
former experiments. He also obtained and cultivated the
bacillus anthrax by this mode; the bacillus of erysipelas, the
bacillus of leprosy, and some others of less note; and last
of all, that is as yet definitely announced, the bacillus of
tuberculosis.

RESULTS.

It will be seen that this work is only just begun. While
we have circumstantial evidence of the existence of very many
disease germs, only a few have been positively demonstrated
by isolation and pure cultivations, followed by inoculations
and the production of specific forms of disease. These are the

Bacillus anthrax.

Organism of chicken cholera.

Bacillus of septicaemia.

Micrococcus of pyaBmia.

Cocco-bacterium of gangrene.

Bacillus of erysipelas.

Bacillus of tuberculosis.

Bacillus of leprosy.

Spirillum Obermeiri, the virus of relapsing fever.
Besides these, there are some others not so certainly demon-
strated. A considerable number of organisms are now pretty
well known by their continued association with a particular
form of disease, but have not yet been demonstrated by pure
cultivations and inoculations. The task of isolating one of

THE EVIDENCE. 69

these forms, to begin with, is generally extremely difficult, for
it is often associated with other forms, most of which have no
disease-producing power, and the experimenter generally has
no guide as to which is the one wanted until he has carried
it through the cultivations and has made some inoculations.
In many of the diseases he is met with another difficulty,
which he often has no guide whatever in surmounting, in the
fact that he does not know what animals are susceptible to the
disease. A considerable number of diseases in men have not
been known among animals, and under existing notions he
cannot experiment upon men. And then the work is
necessarily very slow. The thought of the present time de-
mands absolute demonstration. No possible error is admis-
sible. Dr. Koch spent two years in cultivating the bacillus
tuberculosis and making inoculations with it, before he was
satisfied to announce it. He induced the disease by inocula-
tion with this bacillus in over one hundred different animals,
watched most of them until death from the disease induced,
and examined them macroscopically and microscopically, to
be absolutely sure there was no mistake. This is what the
scientific world will demand in case of each and every disease.
The work will be very slow, and years will be required for its
accomplishment.

THE EVIDENCE.

The evidence that disease-producing bacteria are distinct
from the bacteria of the decompositions is now becoming very
clear. All the decompositions swarm with bacteria of various
kinds, that are entirely free from any causative relation to
disease, and evidently, may be tolerated in food or in contact
with the mucous membranes, and even in wounds, without
any injury whatever. Every one who eats butter which has
become even a little strong, consumes a great number of
organisms, and yet without the least injury. The same is true

70 THE GERM THEORY OF DISEASE.

of many other articles of food. It also seems probable, from
many observations, that the results of decomposition, as it pro-
ceeds to the destruction of nitrogenous compounds, flesh and
the like, destroys most disease germs such bodies may contain
at the time of death.

It has been remarked by a considerable number of observers
that blood poisoning from dead bodies will occur only before
such bodies have proceeded far in the process of decomposi-*
tion. It seems that inoculations made with the fluid product
of nearly complete decompositions do not produce character-
istic blood poisoning. This is very distinctly asserted by Dr.
Lionel S. Beale, who regards it as a strong argument in favor
of his hypothesis. He supposes that the bioplasts whicli
cause disease die during the process of decomposition, which,
he thinks, could not be claimed in the case of bacteria. How-
ever, the fact that one bacterium is often destroyed in the
presence of another, probably by the waste product of the
second being poisonous to the first, is now pretty well estab-
lished, and fully accounts for the facts observed. Alcohol is
the proper food of the mycoderma aceti, but the vinous yeast
plant will not thrive in acetic acid.

There is much reason, now, to suppose that disease germs are
less plentiful in the air than was thought a few years ago. It
is shown that a multitude of germs that induce decomposition
are not even capable of living in the blood or tissues of men
or animals when placed in them. The bacterium lactis, which
flourishes in milk and in the animal secretions generally, will
not grow in the blood or tissues of an animal. Also the bac-
terium termo, which is so widely spread, and common in
almost every atmosphere, and is now generally considered to
be the cause of the ill-smelling putrefactions, will die in the
living tissues or blood of an animal. Great numbers of
organisms grow in the mouth of almost every individual, and

THE EVIDENCE. 71

we have seen them on the margins of, and in wounds of the
mucous membranes, without in any wise interfering with the
healing process.

It would be a great mistake, however, to suppose, from
these facts, that disease-causing germs are never present in
such situations. They may, at any time, mingle with the
harmless varieties, and leaving these, enter the neighboring
parts or circulation, and produce their legitimate results,
namely, sickness of some specific kind.

Disease-producing organisms vary very much in their
power of gaining entrance into healthy blood or tissue. The
bacillus septicus and the cocco-bacterium of gangrene, the
most virulent organisms known, are totally unable to enter
normal structures. They must enter through some breach
in the surface, or await the weakening effect of other disease,
to let them in by way of the mucous membranes. But once
within the tissues, the strongest must yield to them. Others
of a less virulent nature can, of themselves, make the attack
successfully without any breach of tissue or weakening effect
of other disease. Such are the spirillum of relapsing fever,
the organism of diphtheria, and undoubtedly, also, most of
those of the contagious diseases. Still others may gain ad-
mission without a breach of continuity, but much more
readily enter through some such breach, as, for instance, the
bacillus of erysipelas.

It will thus be seen that a man, perfect in all his parts, may
go among some of the more virulent of these organisms with-
out fear. He may enter the dissecting room and work for
weeks, and even years, among the septic germs, dipping his
hands freely into the tissues and fluids, so long as his skin is
perfect. But a slight scratch upon a finger may let in the
septic germs that will speedily cause his death.

72 THE GERM THEORY OF DISEASE.

SPORES— HABITS.

It seems well demonstrated that a number of the lower
forms of life, bacteria, mycoderma, saccharomyces, etc., form
their spores under conditions other than those best suited to
the active growth of the plant. From a close scrutiny of the
manner and time of spore formation of these life forms, it
seems that they are formed only under conditions which
slowly destroy the activity of the plant. The yeast plant
forms spores only after fermentation has ceased and its multi-
plication by budding hindered. It has been asserted that the
bacillus anthracis will form spores in the cultivation flasks
only when the temperature has been allowed to fall below
that of the blood, and, therefore, cannot form them until
eliminated from the animal in which they grow, or after the
death of the animal.

A considerable number of organisms, whose natural habitat
seems to be fruits, such as grapes, cherries, etc., form spores
only when drying occurs ; that is, the plant lives on the fruit,
multiplying by budding or by fission ; but when the fruit
gives out and drying up begins, the formation of spores begins
also. This seems to be the controlling factor in spore forma-
tion in a large number of the bacterial forms. And the
philosophy of this act, when we consider it, is rather beau-
tiful, and would seem to be a special fitness of function to
needs. Rapid multiplication by the simple plan occurs in the
presence of suitable conditions for activity. When these con-
ditions begin to fail comes the organization of the spores
destined to preserve vitality under conditions unfit for active
growth.

The facts now at our disposal will not warrant the conclu-
sion that this is a law of spore formation for all these organ-
isms. Indeed, we have facts which directly controvert this
proposition.

SPORES — HABITS. 73

If Dr. Koch has traced the life history of the bacillus
tuberculosis aright, it multiplies only by the formation of
spores, never by fission or budding, and the spores are formed
under the conditions of the activity of the organism. Only
this one instance of this exclusive multiplication by spores is
recorded, however, in the whole field of research among these
forms of life. Many, however, have been found to form
their spores during the continuance of the conditions of their
activity, as the bacillus septicus, micrococci of gangrene, and
some others.

These facts have a very important bearing upon the modes
of communication of contagious and infectious diseases, and
may finally serve to explain some of their peculiarities. For
instance, if it is found that a disease-producing organism pro-
duces spores only when there is a lack of moisture, or at a
temperature below that of the human blood, it will be clear
that the spores will be produced only after elimination of the
organisms. If, in connection with this fact, it is found that
the developed organism is destroyed by drying, which is
inferred, then it becomes clear that infection will not be likely
to take place, through the medium of the air, directly from
the sick to the well. Drying of the eliminated organisms
must first occur, during which the spores are formed, 'and then
the drying must be continued until the particles are ready to
be wafted about by the air currents and in this manner be
carried to the well persons. Dr. E. D. Salmon (Medical
Record for April, 1883) has developed the idea that the intro-
duction of the spores of the bacillus anthracis produces a
different result from the inoculation with the developed organ-
ism, under certain conditions.

If this bacillus be cultivated continuously under conditions
which will not allow of spore formation, it will be weakened
in virulence, so that its introduction will cause a mild type of

74 THE GERM THEORY OF DISEASE.

the disease. If, however, this weakened bacillus be allowed
to form spores, these spores will produce the virulent type of
the disease. If this observation be confirmed by further re-
search, it will become an important element in sanitary and
prophylactic measures, especially so if it be found true of any
considerable number of disease germs.

It will be seen at once that the thought contained here has
an important bearing upon the propagation of yellow fever,
cholera and typhoid fever. If we suppose that the power of
forming spores only comes with more or less gradual drying
of the voided organisms, and that these organisms are not
eliminated by the lungs and sweat glands but only with the
excreta, therefore, not liable to be transplanted by immediate
passage through the air, we are at once able to understand
the clinical facts observed as to communicability of these
diseases.

SUMMING UP.

Having passed in review, briefly, the rise and progress of
the Germ Theory of Disease, we may sum up the principal
points thus : —

1st. In the seventeenth and eighteenth centuries, intelligent
observers of contagious diseases, after much study of the sub-
ject, came to the conclusion they were caused and propagated
by a process identical with or similar to fermentation and
decomposition.

2d. There was much study of the processes of fermentation
and decomposition, in order to arrive at a more clear under-
standing of the causes of epidemic and contagious diseases
with the view of prevention and cure. These experiments
demonstrated that the fermentations and decompositions were
something different from ordinary chemical phenomena.

3d. The yeast plant was discovered by Schwan and Latour,
in 1838. These gentlemen announced distinctly that the

SUMMING UP. 75

chemical changes of vinous fermentation are caused by the
life and growth of this plant. They disproved, by experiment,
the previous hypothesis, that oxygen is the active agent in any
of the similar processes ; and, reasoning from this discovery,
came to the conclusion that all the fermentations, decompo-
sitions, miasms and contagions were caused by the life force.

4th. These conclusions were attacked by chemists, notably,
by Professor Liebig, who denied both the facts claimed and
the conclusions arrived at, since which time there has been a
continuous discussion of the subject.

5th. In 1854, Schroeder conclusively disproved the exist-
ence of gaseous ferments claimed by chemists, by admitting
air filtered through cotton batting to sterilized fluids without
causing fermentation.

6th. From 1857 to 1861 Pasteur successfully worked out
all the more ordinary fermentations by his fractional flask
cultivations, and proved each of them to have a specific plant
growth as its cause. He also showed that none of the decom-
positions could proceed without living organisms, though the
specific organism belonging to each was not clearly made out.

7th. Basing his efforts on the results of the last two, Mr.
Lister introduced his antiseptic treatment of wounds, in 1865,
which has proved a panacea for most of the dreaded in-
fectious wound troubles in all hospital surgical practice.

8th. M. Pasteur, Dr. Koch and others have succeeded in
isolating a number of distinct disease-producing germs, and
causing the specific diseases in animals, regularly, by planting
these germs under the skin, and Dr. Koch, especially, has
succeeded in doing this after freeing the organisms of all
possible following of decomposing matter by growing them
upon dry slides.

9th. This much having been proven, the continued obser-
vation of numerous other organisms of distinct form and

76 THE GERM THEORY OF DISEASE.

character, always associated with specific forms of disease,
warrants the inference that these diseases are also caused by
specific organisms.

10th. All the foregoing taken together gives strong pre-
sumptive evidence that all contagious and infectious diseases
are produced by disease germs.

PART SECOND.

FOURTH LECTURE.

THE RELATION OF MICRO-ORGANISMS TO THE
PRODUCTION OF DISEASE.

One who has followed closely the experimentation on the
relation of micro-organisms to the production of disease, will,
I think, accept the following propositions as a basis for a
farther study of the subject: —

1st. Experiment has shown that there are many micro-
organisms which do not produce disease or injury; that the
mere presence of these life forms is not, in itself, a sufficient
cause of disease; but that there are certain micro-organisms
that uniformly induce disease when they are planted in, or
obtain entrance to, the bodies of animals or men.

2d. All through the experimentation that has been had on
this subject, it has been noticed that poisons have originated
in connection with the disease-producing organisms.

3d. These poisons seem to be a product of the organisms,
and, while produced only in connection with the life and
growth of the microscopic plants, may be separated from
them ; and, when so separated, produce direct poisoning
similar to that induced by the poisons from the higher plants.

4th. This poisoning is different from the disease that is
induced by the organisms, in that it is direct, and compara-
tively immediate; while infectious disease arises only after a
more or less definite stage of incubation.

5th. Therefore, it is probable that each infectious disease is
caused by a micro-organism that is capable of developing in
the tissues, or blood, and forming poisons through changes
wrought in the molecular forms of matter, by virtue of its

79

80 THE GERM THEORY OF DISEASE.

vital energies; or, the physiological processes of digestion,
nutrition and the formation of waste products.

These considerations suggest an extended examination of
the physiological phenomena of life, in its varied forms, as
related to matter, as the best means of gaining a clear concep-
tion of the teachings of the facts developed by experiment.
It will be seen by any one who reviews this whole subject
closely that, while the experimentation that has been had fur-
nishes the strongest evidence that disease results from the
presence of micro-organisms (is brought about in some way
through the life and growth of these lowly forms), the modus
operandi by which they induce disease has not been explained,
or such explanation has been but partial.

Indeed, thus far, the principal effort has been to show that
micro-organisms are regularly connected with certain pro-
cesses of disease, and that these in no case occur without this
accompaniment, rather than to show how they induce disease.
This was necessary, in the beginning of this work, for the
collection and collation of sufficient data upon which to con-
struct theories, and found a basis of truth, from which inquiry
might proceed to the more perfect unfolding of the mysteries of
this important subject. The Germ Theory of Disease, as it
stands to-day, is essentially a mass of unexplained facts, devel-
oped by direct experiment of the most subtle nature; so subtle,
indeed, that there are but few men who have the natural endow-
ments and rigid training necessary to verify them in a manner,
and with the certainty, that the thought of the times demands.

Under these circumstances, and with the plain fact before
us that the mere presence of the organisms is not a sufficient
cause of the diseases that experiment teaches us are induced by
them, we naturally turn to the well demonstrated fact that
micro-organisms do give rise to poisons, for an explanation of
these phenomena. It is our purpose now to make an effort

PROPOSITIONS. 81

to trace certain of the phenomena presented by the life force
in its relations to matter, with the end in view of elucidating
this difficult point. In this direction, as it seems to me, we
are most likely to find a satisfactory explanation for some of
the teachings of experiment that have seemed difficult to
understand. In these brief lectures, however, we can only
glance at the principal points necessarily involved in a com-
plete discussion of the subject.

The phenomena that we will now review will be Digestion,
Absorption, Nutrition, and the Formation of Waste Products
in the several forms of life ; after which we will study briefly
the relation which the changed forms of matter, produced by
the physiological activity of micro-organisms, may hold to
the production of disease. This is necessarily a biological
study.

DIGESTION.

Digestion is a process of solution and chemical reorganiza-
tion of food material, by which it is fitted for reception by the
life force, or is brought within the sphere of chemico-vital
influences. The material, when thus prepared, is conveyed
within the organism by absorption or osmosis. Digestion
and absorption are the admitted forerunners of all nutritive
processes — the initial steps by which nutrition is rendered
possible. This is true of all the varied forms in which the
life force is manifest, from the most minute micrococcus to
man. There are substances made use of by the life force
without digestion previous to absorption, but every living
thing is provided with this mode of food preparation.

PROPOSITIONS.

1st. All digestion is accomplished by soluble ferments,
elaborated by the organism, whether this digestion be accom-
plished in a stomach, alimentary canal, or elsewhere.

82 THE GERM THEORY OF DISEASE.

2d. Digestion is threefold in its forms : (a) Primary, (b)
Absorptive or Resorptive. (c) Nutritive or Assimilative.

Primary digestion is the ordinary method by which food is
fitted for reception by the organism. It is accomplished by
a soluble ferment, or ferments, secreted by the organism and
thrown out (a) into a cavity, stomach or intestinal canal, into
which the digestible material is brought; (6) into the sur-
rounding media in which digestible material is suspended, or
upon digestible solids or semi-solids.

Absorptive and resorptive digestion is accomplished among
the ordinary tissues, by a soluble ferment elaborated by the
tissues, under special circumstances: (a) For the removal of
tissues no longer needed, as roots of temporary teeth, of bone
during changes of form, and of other tissues after their purpose
has been served — resorptive digestion. (6) For the removal
of substances accidentally lodged in the tissues, as animal
membrane and catgut ligatures, etc. — absorptive digestion.

Nutritive digestion is performed within the tissues them-
selves, and by them. It is the act of assimilation, the act by
which nutritive material is converted into tissue and formed
material.

Primary digestion, in the higher animals, is performed in
the alimentary canal. This is accomplished by the aid of
certain substances known as soluble ferments. The term
soluble ferment is used to denote a very different thing from
an organic ferment. An organic ferment is always com-
posed of living cells, and is therefore insoluble. A soluble
ferment performs the act of digestion only, and is not capable
of reproduction ; while an organic ferment performs all the
acts of complete fermentation, and is capable of continuous
reproduction. All soluble ferments are products of the
activity of cell life, or of the life force in the cell form. In
the stomach it is found that certain cells, forming the peptic

PROPOSITIONS. 83

glands, secrete a fluid rich in pepsin, which constitutes the
true soluble ferment of the stomach, the office of which is the
conversion of food of certain known qualities into peptones or
chyme. The pancreas elaborates another soluble ferment,
pancreatin, or trypsin, which acts upon another portion of
the food. Other portions of the alimentary tract furnish
other soluble ferments, which in their turn act upon the food.
The combined effect of all these is to fit the food for reception
by the blood, through the process known as osmosis.

It will be seen at once that these processes of digestion are,
in fact, extraneous to the body ; that is, they are in receptacles
in which food material is met by appropriate soluble ferments,
by which it is dissolved and its chemical constituents re-ar-
ranged, remoleculized. (I use the word "remoleculize" to
designate that disturbance or change of the molecular form
of matter which occurs under the influence of the life force.
As an example, I may take the change that occurs in starch
in the presence of saliva, which is expressed in the following
formula : —

Starch. Water. Glucose.

C6H1005 + H20 = C6H1206

It will be seen here that the digestive body, ptyaline, does
not enter into combination, but, by its presence, causes a com-
bination of the water and starch, producing a remoleculization
with the formation of glucose. Again, the digestive body
given out by the yeast plant, when in contact with cane sugar,
dissolved in water, induces the following changes : —

Cane Sugar. Water. Glucose. Lavelose.

C^H^On + H20 == C6H1206 + C6H1206
This result is different in that two new bodies are formed
by the juncture of the two with which we began. In the use
of the word we apply it to any possible molecular change,
without expressing the character of that change. We may
say that the yeast plant destroys sugar by remoleculizing it,
5

84 THE GERM THEORY OF DISEASE.

or that alcohol is a product of the remoleculization of sugar
by the vinous yeast plant, etc.)

It is also sufficiently established that these soluble ferments
will act upon food material just as well when removed from
the cavities of the body as in them, provided a proper tem-
perature be maintained. This fact shows that soluble fer-
ments, while formed only by the life force, when once formed,
act without the life force. A soluble ferment is not itself
alive.

FERMENTS.

An example of digestion without a stomach, or the act
of digestion of food material suspended in a surrounding
medium, is found in vinous fermentation; which is accom-
plished by the torula, saccharomyces cerevisia, or yeast plant.

The history of the plant is too well known to need descrip-
tion or affirmation, other than the points needed for illustration.
When pure vinous yeast is washed with distilled water, a
peculiar substance is found dissolved in the water. This is
yielded continuously during the life of the plant. Examina-
tion has proven this substance to be a soluble ferment, having
a peculiar effect upon sugar. This has been examined by M.
Berthelot, M. Becamp and others. It has been precipitated
and obtained in the form of a powder, somewhat similar to
Pepsin, and when redissolved, has been found to retain its
original action upon cane sugar. This action is to split up
the sugar into two substances, called Glucose and Lavelose,
the formulae of which we have given above.

This reaction always takes place as the primary step in
alcoholic fermentation, and is the primary digestion which
permits of the appropriation of the food material by the yeast
plant. This is entirely analogous to the digestion of food in
the stomach of an animal, by which such food is received by
the blood to be conveyed to the tissues for their nutrition ;

FERMENTS. 85

but it is accomplished in the surrounding media instead of in
a receptacle provided for the purpose, an alimentary canal.
This is one instance of a type of digestion which I believe to
be universal in case of all unicellular animals and plants.
The formation of a stomach is a provision for the conserva-
tion of force, but it in no way changes the modus operandi
of the digestive function.

Now, if I have been understood thus far, you will probably
be enabled to understand the import of certain experiments
which have seemed involved in mystery. I will again refer
to a series of experiments by Mr. Lister, mentioned in my
last lecture, in which he says that he tried a large number of
experiments in which he found unmistakably that "it re-
quired several drops of tap-water (London hydrant water), in
which there were bacteria termo, usually one, to two, or
three, in a drop, to start putrefaction in blood serum ; while
the least possible portion of putrefying blood (containing,
probably, no greater number of bacteria), would start it at
once." He wondered at this, and says that "it may be that
some substance adheres to the bacteria, or is present in the
portion of decomposing blood, that starts the decomposition ;
whereas, the bacteria washed with pure water are free from
this."

In another paragraph, Mr. Lister, always close to the front
when searching for truth, strikes much nearer the mark. He
says : " Or again, it seems to me conceivable that the normal
serum may oppose an insuperable obstacle to the nutritive at-
tractions of an individual bacterium, but that this may be
overcome by the associated action of several of the organisms
in close proximity, after the analogy of the more energetic
operation of a concentrated solution of a chemical reagent.
But whatever be the explanation, the fact remains." In this
paragraph we find a close statement of what seems to me to

86 THE GERM THEORY OF DISEASE.

be the physiological fact in the case, only Mr. Lister seems
not to have reached the point of recognizing the general phy-
siological law appertaining to this subject.

I should explain the phenomena in this wise ; the soluble
ferment, diastase, or digestive agent given out by this bacteri-
um, must attain to a certain degree of intensity, or concentra-
tion, before it is capable of acting on blood serum. A single
bacterium is incapable of forming a sufficient quantity of
soluble ferment, when dissipated among the serum, to accom-
plish this digestion, and being incapable of appropriating the
undigested material, dies of dyspepsia; while, if a large num-
ber are massed together, there is a corresponding concentration
of the ferment substance, the digestion of the serum is accom-
plished, and the colony will flourish. The serum is speedily
decomposed.

The soluble ferment of B. termo has been practically
demonstrated by Wortnian, who has shown that starch may
be remoleculized by this organism if no other source of car-
bon is available. And that in this case a diastase (soluble
ferment) is secreted which first transforms the starch into
sugar (glucose), which is consumed by the bacteria as fast as
formed. If a potato be boiled and a slice cut from it smoothly,
to expose the surface, and this surface be exposed to the air
for a few minutes, in order that a few germs that may be
floating in the air may light upon it, and this be protected
afterwards from other germs by a bell-glass covering, with
sufficient water to prevent drying, there will be a develop-
ment of clusters of bacteria lying upon the surface. In or-
dinary summer temperature this may be seen, usually, after
two or three days, as small points of varying colors. Now,
if these points be removed, one by one, and examined with
the aid of a microscope, it will be found that each little cluster
is, as a rule, made up of micro-organisms of one distinct

FERMENTS. 87

variety, but the different clusters will usually be of different
varieties. Each of these has evidently developed from a
single germ or spore which has happened to fall at that spot.
By what means do these bacteria appropriate the starch of the
potato to their nutrition ? This material is not, as we know,
in a state fitted for the nutrition of these organisms; nor,
even in a condition in which it can be taken up by osmotic
action. The starch must be digested before it can be appro-
priated. That this digestion really takes place may easily
be shown. If we prepare the potato as above described,
watch it until the micro-organisms have grown to a greater
extent — until they have spread over the surface and the
little clusters have coalesced with each other — then cut a
very thin slice from the surface, and submit this to the chem-
ical test, we will find that a part of the starch has been
changed into glucose, or some form of sugar. This change
is the usual first act in digestion by plants, when starch is
the substance acted upon, and is the primary digestion per-
formed by the diastase, or soluble ferment secreted by these
organisms for the preparation of their food. This change
goes on very rapidly, and the greater part of the sugar formed
is at once appropriated to the nutrition of the organisms, and
its molecular form again changed. In the earlier stages of
the process or growth, it is probable that the sugar formed is
very nearly all used as fast as formed, but when the growth
becomes very luxuriant, there is a superabundant digestion
which permits us to find the traces of the sugar, which reveals
the manner in which the nutrition of the little plants is
brought about.

This process will continue until every particle of the starch
has been remoleculized. But this is only one of the series of
remoleculizations which take place. The starch is converted
into sugar, the sugar into tissue of the growing plants, and

88 THE GERM THEORY OF DISEASE.

during all this process the plants are giving off waste products.
These waste products mingle with the remains of the potato,
giving to it its offensive qualities, and it is said to be rotting.
We learn from this study that it is not necessary that food
material be dissolved in liquid in order that it may be ap-
propriated by bacteria. They are able to furnish a solvent
which will bring it into a condition fitting it for osmosis.
Otherwise bacteria would be utterly incapable of attacking
solids or semi-solids. Yet the cultivation of the pathogenic
micro-organisms on solidified media has been rendered popu-
lar by Dr. Koch, of Berlin, and it is now fully established
that they grow well upon such food. This was described in
my last lecture, and is very similar to the growing of the
organisms on the potato just described, and illustrates the
same physiological laws. Indeed, it seems to have been the
observation of the growth on the potato that led Dr. Koch
to the dry slide method. By this method, solid food mate-
rials may be prepared that are suited to the wants of the par-
ticular organism ; and, so far as I am informed, any of the
micro-organisms may be successfully cultivated by this plan,
if sufficient skill is used in the selection and preparation of
the material. Under these conditions it could not, reasonably,
be expected that the food material could be imbibed by the
organisms unless they could furnish some solvent by which
it is brought into a condition fitting it for osmotic action.

All these facts point unmistakably to the formation of
soluble ferments by the organisms, which serve the purpose,
not only of liquefying, but of changing the molecular form of
food material ; a process in which the analogy to digestion, or
conversion of food material into peptones in the stomachs of
the higher animals, is perfect.

Many of the micro-organisms seem specially adapted to
certain foods, and their digestive solvents are such as to serve

PLANTS. 89

the special purpose, as is seen in the amraouiacal fermentation
of urine. " M. Musculus has shown that we may obtain from
altered urine a soluble ferment. Upon adding to it highly-con-
centrated alcohol a precipitate is formed which may be filtered
and dried. This precipitate, not at all organized, transforms
urea into carbonate of ammonia. A temperature of 80° (176°
Fah.), destroys it. This diastase appears, then, to be a secretion
of the micrococcus urea, and perhaps the role of the bacteria is
limited, in the phenomena of fermentation, to the formation of
this secretion alone. The ammoniacal transformation of urine
would, consequently, enter into the group of fermentations by
the varieties of diastase." (Magnin on Bacteria, page 142.)

The proof here given of the production of a true digestive
body, or diastase, by the micrococcus urea is sufficiently positive;
but M. Musculus must be wrong in his supposition that the
" role of the micrococcus is limited to this one function ; " for, if
the organism does not appropriate from the results of its diges-
tion, wherewithal does it live. It may be that we have here an
example of superabundant digestion, which, as a matter of fact,
is to be expected when the natural condition is the diffusion of
the digestive solvent through masses of fluid material. But the
organism must live by remoleculizations within itself, and elim-
inate waste products. Therefore, the explanation is incomplete.

It has also been shown that the first changes which albumen
undergoes in decomposition are similar to digestion. It is first
converted into soluble forms, partly peptones, and afterward
converted into other forms.

PLANTS.

When we turn our attention to the higher forms of plant
life, we are beset with many difficulties. The botanists, it
seems, have, as a rule, endeavored to explain the growth of
plants from the chemical standpoint, and have almost univer-

90 THE GERM THEORY OF DISEASE.

sally started with the thought that the roots of the plant
absorbed water, with whatever might happen to be dissolved
in it, and from this the plant appropriated that which it could
use in the building of its tissues. This mode of reasoning
has, however, failed to give satisfaction. Many facts have
appeared from time to time which could not be explained
upon this supposition. Prominent among these is the fact
that material is continually found in plants which cannot be
found in a soluble state in the ground in which the plants
grow. Sachs (Text-Book of Botany, p. 625), in discussing this
point, says: "But a large portion of food material, especially
compounds of ammonia, potassium and phosphoric acid, occur
in the ground in a fixed conditioner as it is generally termed,
absorbed ; they are not extracted from the soil by very large
quantities of water; the roots, nevertheless, take them up with
ease. It may be supposed, in these cases, that the absorbed
food materials occur as an extremely fine coating over the
particles of soil, and can therefore only be taken up together
with them by the root hairs at the points of contact; and they
are there rendered soluble by the carbon dioxide exhaled by
the roots. This action of the roots is limited to the points of
contact; only those absorbed particles of substance which come
directly into contact with the root hairs are dissolved and
sucked up. But, since the numbers and length of the roots is
very considerable in all growing land plants, and since, also,
they are continually lengthening and forming new root hairs,
the root system comes gradually in contact with innumerable
particles of earth, and can thus take up the necessary quantity
of the substance in question. This power of the roots of tak-
ing up, by means of the acid sap, which permeates the walls
of even their superficial cells, substances which are insoluble
in pure water, presents itself in an extremely evident manner,
as I was the first to show.

SPROUTING OF SEEDS. 91

"When polished plates of marble, dolomite, or osteolite
(calcium phosphate), are covered with sand, to a depth of a
few inches, and seeds are then sown in the sand, the roots,
which strike downward, soon meet the polished surface of
the mineral, and grow upon and in close contact with it.
After a few days an impression of the root system is found
corroded in rough lines into the smooth surface ; every root
has dissolved, at the points of contact, a small portion of the
mineral, by means of the acid water which permeates its outer
cell walls.'7

Here we have, clearly set forth, and proven by experiment,
a virtual gastric juice, a substance elaborated and sent out to
meet food material, dissolve it, and render it fit to be brought
in, by osmosis, the same as in the higher animals and in the
lower forms of unicellular life.

It is not yet shown, in this case, that this is a specialized
soluble ferment substance, but it evidently acts the part of
such a substance, and, while this is so clearly shown, its com-
position makes but little difference, so far as our present pur-
pose is concerned, which is to show that all forms of life are
dependent upon digestion in some form, for the preparation
of the material upon which they subsist for absorption.

It is not claimed that all material used by the life force
must undergo this kind of change. Water is used without
such change by all forms of life, and probably many other
substances are so used.

SPROUTING OF SEEDS.

With every egg that is formed there is a provision for the
nourishment of the embryo until the animal has developed
the organs by which it is to prepare its food for assimilation.
The egg is composed of two parts, an embryo, and formed
material for the nutrition of that embryo. In the seed there
5*

92 THE GERM THEORY OF DISEASE.

is the same provision precisely. Surrounding the embryo,
there is laid up a store of formed material for the nourish-
ment of the young plant until such a time as it shall have de-
veloped its roots and leaves, the organs by which it gathers its
food, sufficiently for this purpose.

In neither of these is the food material in a condition to be
formed into the tissues of the young animator plant, without
remoleculization. It must be redigested before it can be
assimilated by the embryo. This process has been best
studied in the seed. Here it is found that the embryo elimi-
nates a true digestive substance, called diastase, the office of
which is the digestion of the store of food material. Of this
substance Regnault says : " A peculiar nitrogenous substance,
called i diastase/ which possesses the property of converting a
large proportion of fecula (starch) into dextrin, and even into
sugar, when its action is sufficiently prolonged, exists in the
germ of the cerealia and in tubercular vegetables. It appears
to be formed at the moment of germination, probably at the
expense of the albuminous matter contained in the grain, as
it resides in the very origin of the germ, and in the eye of the
tuber; and its use in the vegetable economy appears to be
that of disaggregating the amylaceous matter, and transform-
ing it into an isomeric soluble substance, which the vital
forces then change into other isomeric, but insoluble sub-
stances, such as cellulose, which is to form the framework of
the growing plant."

This substance is very well known, and its action on the
starch has been closely studied. It may be precipitated by
alcohol, and obtained in the form of a powder, and preserved
fora long time, and when redissolved in water will still pro-
duce its effect on starch. This effect, like that of other sol-
uble ferments, is not to be explained by the ordinary chemical
laws. One part of diastase will convert 2000 parts of starch

SPROUTING OF SEEDS. 93

into sugar. The office of this substance, therefore becomes
clear; it is the true digestive body of the embryo plant, by
which its store of food material is remoleculized and fitted
for its assimilation.

In the egg, this process has not been so well made out; but
enough is known to determine the fact that the store of albu-
men is profoundly changed previous to assimilation.

The perennial plant, which lies dormant in winter, is to
some extent similar, during the interval of inactivity, to the
seed. It contains within its structure formed material for
use in spring time, for the reformation of the leaves, for the
gathering and transformation of a portion of its food material.
These stores of formed material seem to be made use of much
in the same manner, and by the same means, by which they
are transformed in the seed ; that is, by means of a diastase,
or soluble ferment, formed at the proper moment for its solu-
tion. In this respect, we find a close analogy between the
plant and the animal, as we shall see further on.

I have brought forward these well-known phenomena for
the purpose of enforcing the principle lying at the very
threshold of the nutritive function ; for the purpose of impress-
ing the fact that the life force, wherever found, carries forward
its business in regular and definite forms, by regular and defi-
nite means ; and that its means to the accomplishment of the
preparation of its food material is similar throughout all its
varied forms. One form of life lives on this, another on that
food material, but the process by which food material is
brought into a state fitting it for its final assimilation by the
life force, and the building of tissue, of whatever kind or
quality, is the same in its general plan.

94 THE GERM THEORY OF DISEASE.

NUTEITION.

The digestion of nutrition is performed by the tissue itself.
When no ferment substance is divisible from the tissue the
existence of such substance has been inferred from the phe-
nomena observed. We think no one will doubt that the food
of the animal goes through further fermentation or digestion
after it is taken into the blood, at least, a certain remoleculi-
zation, by whatever name it may be called. Is this change
brought about in the blood ? Posssibly it is, to some extent,
especially during its passage through the liver, the great gland
of the blood vascular system, the soluble ferment, or diastase,
of which is well known. But the great change is brought
about by the tissues themselves.

In primary digestion there is simply an absorption of other
molecules or atoms, by the molecule of the substance under-
going digestion, or a splitting up into simpler compounds. In
the nutritive digestion (nutrition assimilation) there is a
reorganization of the elements into new tissue and formed
material. This reorganization is performed in the cells them-
selves. The substances are taken into the interior of the cells
by osmosis, and then remoleculized by act of the vital force.
This is the point, evidently, of the most intimate association
of matter with life; it is here that matter is said to be en-
dowed with life.

The products formed here are very definite. The reorgani-
zation results in tissue, each tissue selecting and building for
itself, and to itself, from the material carried in the blood
streams, obtained from the primary digestion and from the
lungs. In this reorganization and building by the tissues,
definite waste products are given back to the blood streams,
namely, carbonic acid and urea. These are cast out by the
lungs and kidneys. They are found to be incompatible with

NUTRITION. 95

life, if retained in any considerable quantity. Here, also, are
formed the secretions destined to serve the animal in the per-
formance of the digestive and other functions ; in the animal
forms mostly by specialized cells acting vicariously for the
other tissues of the body. These are special developments of
function, seen as we ascend the scale of life. But these func-
tions are also present in the unicellular forms of life, where
there is no such division of labor or function developed. It
is not a new function, but a special development of cells to
act in this matter for the whole.

FIFTH LECTURE.

YEAST PLANT.

For comparison, let us turn again to the yeast plant. Here
we have no blood streams to interfere with our study of phe-
nomena. The same cells that emit the soluble ferment which
performs the primary digestion, appropriate the results of that
digestion, not individually, but en masse. That is, each cell
individually excretes, so to speak, the material, the soluble
ferment, that performs primary digestion. This digestion is
performed by the whole amount of material excreted, inde-
pendently of the individual cell, but in the appropriation of
the results of this primary digestion, each individual cell acts
for itself only, and independently of all other cells. The
result is the building up of the tissue of the cells by remolecu-
lizing the original elements into new forms, with the elimi-
nation of waste products.

In this case the waste products are alcohol and carbonic
acid. One is the same as in the animal, carbonic acid, the
other is different. These waste products agree, in their eifects
upon the activity of the plant, with the waste products of the
animal upon its life force. Alcohol, in a certain quantity,
stops the growth, the activity, of the yeast plant which pro-
duced it, and if sufficiently concentrated, destroys it. Urea
does the same for animal life.

These excretory products differ widely among the lower
forms of life, and yet, as we shall show in another lecture, re-
tain a constant resemblance.

In case of the mycodermi aceti, the acetic acid plant, the
excretory products are carbonic acid and acetic acid. With

96

YEAST PLANT. 97

the bacteria termo, the excretory products are very complex,
consisting of ammonia, sulphuretted hydrogen, and other ill-
smelling products of putrefactive fermentation. Some of the
mucidines excrete butyric acid; other forms excrete other
waste products. Only a few of these have, as yet, been very
accurately studied.

Often, perhaps, it is by these excretory products from bacte-
ria that gain access to the blood, and are capable of living
there, that disease is produced. One case in point. Dr. Car-
ter, of India, in his very careful and laborious examination
of the blood spirillum of relapsing fever, has found that these
organisms become still, and diminish in number during the
exacerbation of the fever, and during the intervals of com-
parative freedom from the rigor of the disease they become
active and augment in numbers, until the approach of another
attack of fever. What does this mean? Certainly the
disease is not caused in this case by the primary digestion, by
the soluble ferment, as it seems to be in hospital gangrene.

The case seems reversed. Here it seems that the accumu-
lation of the excretory products of the organisms cause the
sickness ; also, that the amount present in the blood is suffi-
cient to check the development of the organism. Suppose the
yeast plant could grow in the blood, and develop its alcohol,
might it not intoxicate the man ?

The course seems to be this. The soluble ferment excreted
by the spirillum affects the patient but little, the development
proceeds, and excretory products begin to accumulate more
rapidly than they are carried away by the emunctories ; finally,
when a certain concentration has been reached, the patient is
thrown into violent fever. The bacteria are also so affected
by their own excreta that they droop and fail to flourish.
They become quiet. The patient eliminates the poison, and
all is well again with both patient and spirillum, and the

98 THE GERM THEORY OF DISEASE.

repetitions continue. But in this I am anticipating ; waste
products will be discussed in another lecture.

CELLULAR DIGESTION IN THE HIGHER
ANIMALS.

In the higher forms of life we find a division of labor in
the primary portions of the nutritive function, the prepara-
tion of the material for nutrition. Certain portions of the
animal body are set apart, so to speak, to perform this func-
tion for the whole. In the lower forms this function is
performed by the whole mass of cells as a unit, each doing a
part as an element of the mass. In proof of this we have
cited the instance of the bacterium, in blood, where digestion
can only be accomplished by the united efforts of a mass of
cells. We find, then, that in the lower forms of life cells
may act for each other in the matter of primary digestion,
and that in the higher forms of life a special development
occurs which enables certain cells to act for the general mass.
But in the matter of nutritive digestion each individual cell
must act for itself in the one case, as in the other. Here
there can, in the very nature of things, be no vicarious
function.

Is it impossible that the cells of the higher animals may
excrete digestive fluids ; soluble ferments, also, under certain
particular circumstances? We shall see.

RESORPTIVE DIGESTION.

We now approach an important point in this discussion,
the third form, or resorptive digestion.

We wish to state distinctly that all resorptiori and absorp-
tion of material not primarily fluid, that is, not simply en-
dosmotic, is of the same nature as primary digestion, and is
performed in a similar manner and by similar agencies,

RESOKPTIVE DIGESTION. 99

through a vicarious secretion of a digestive fluid, a soluble
ferment, by the proper tissues of the body.

We will take for illustration the familiar process of the
resorption of the .roots of the temporary teeth. This is a
physiological process, as all other resorptive processes are.
It is brought about by the action of certain cells which have
become known as osteo- or odontoclasts. It has been claimed
that the osteoclasts are really osteoblasts, that have changed
their function from that of builders of bone to absorbents of
bone. The distinction is not important in this lecture. These
may be only the ordinary connective tissue cells of the part in
immediate proximity with the part to be removed, which have
temporarily taken on new functions, the secretion or elabora-
tion of a soluble ferment for the removal of the roots of those
teeth which are no longer wanted. These cells perform this
act in an indirect manner. It is plain that these roots are not
removed by any mere mechanical force. These cells have no
physical power of gnawing into them. They secrete a soluble
ferment, or analogous body, which digests them, breaks them
down, and fits their material for entrance into the blood
streams by osmosis, just as solid ingesta in the stomach is
broken down and fitted to enter the circulation by osmosis.
There seems to be no foundation for the notion that the re-
sorbed product of these roots may not form proper pabulum
for the building up of other tissues; that the absorbed product
is necessarily excreted. Resorption is not a process for the
forming of waste products.

As this process has been pretty closely studied, we will
examine it a little further. From decay and other accident
the temporary teeth are very liable to lose their pulps, which
very often, we may say generally, results in the formation of
alveolar abscess at the apex of their roots. If such an abscess
exists at the time the resorption should take place, such re-

100 THE GERM THEORY OF DISEASE.

sorption fails, partially or entirely. The tissue which should
perform this function is thrown into a pathological state, and
the secretion of the soluble ferment does not take place in the
normal manner. If, however, the abscess «does not occur, or
if such abscess be cured, and the tissue in immediate proximity
to such devitalized root be perfectly healthy, it is found that
the resorption of the root goes on in a normal manner. The
mere death of the root does not interfere with resorption,
provided a physiological condition is maintained in the imme-
diately surrounding cells, which are the active agents in the
work. The soluble ferment does not depend for its action
upon the life of the tissue to be acted upon. The roots of the
teeth are simply digested, and enter the blood streams by
osmosis, as any other digested material. Nothing more, nor
less.

DIGESTION OF BLOOD CLOT.

What happens when an injury occurs, and a blood clot is
formed within the tissues? Is such a blood clot a living sub-
stance? Certainly that cannot be maintained. But it becomes
organized. How? Certainly the blood clot, as such, does
not itself become living tissue.

The process occurring here, by which the clot is removed,
is similar in kind to that of digestion — is digestion. All
around it, the connective tissue cells begin to throw out a
soluble ferment, by which the substance of the clot is dis-
solved and begins to pass into the blood streams by osmosis.
Young cells wander out into the liquefying clot in all direc-
tions, grow, and furnish their quota of fresh increment of
ferment substance to liquefy the clot. The question as to
whether any of the blood cells (white blood corpuscles) be-
come connective tissue cells under these conditions, need not
be argued pro nor con here, for it does not affect our present
purpose. Certain it is that cells are found growing out into

DIGESTION OF LIGATURES. 101

the clot, and acting very like some of the forms of bacteria.
Thus, the clot is digested and removed, and when it is gone
any surplus new tissue that may have been formed during the
activity of the process suffers the same fate. It is, in turn,
digested and removed.

DIGESTION OF LIGATURES.

Of late it has become quite the fashion, among surgeons, to
use ligatures, for deep sutures, made of digestible material,
such as catgut, animal membrane, etc. These are left in, and
it is said they are absorbed. They must be dissolved first.
They do not dissolve in ordinary liquids, nor do they dissolve
in pus, or upon pus-forming surfaces, or in the usual plasma
of the tissues. The surgeon is very careful that they be so
prepared that they shall not. He is careful that they are not
easy of digestion. The " International Encyclopedia of Sur-
gery " says: " The spontaneous solution of catgut ligatures,
when set in wounds, is caused, not by any chemical solution
of their structure, nor by any process of organization which
they undergo, but by the invasion of leucocytes, under the
operation of which they vanish, while new tissue takes their
place; but, if they be over-prepared (i. e.y rendered too diffi-
cult of digestion), this change does not occur, and they act like
foreign bodies in general."

Here we see that the ligature does not dissolve in the ordi-
nary plasma of the tissue, if properly prepared. The tissue
must approach closely a physiological condition, it must throw
out certain cells which invade it, as it would be invaded by
bacteria if they had the opportunity. These cells must throw
out their special ferment for the occasion, to digest the catgut
and make room for themselves, as would be done by bacteria ;
and thus they continue to dissolve out the foreign digestible
substance and take its place, stimulated to this action by its

102 THE GERM THEORY OF DISEASE.

presence. If, however, the substance is too difficult of diges-
tion, over-stimulation results, and instead of the soluble fer-
ment being formed, the cells degenerate, pus forms, and the
process fails.

DIGESTION OF SPONGE.

Let us examine the operation of the sponge graft. In the
sponge, as prepared for this operation, we have a material
somewhat difficult of digestion, a material that would be very
slowly acted upon by the gastric juice. From this circum-
stance, and the fact of its very minute porosity, it has, hap-
pily, been selected for the purpose of inducing granulations
for the filling out of lost tissues. What may have led to this
selection I am not informed. It was probably directed by
some accidental observation. The fact, however, is now well
established, that the tissues are stimulated, by its presence, to
fill its pores with granulations, after which the sponge itself
gradually disappears, leaving the opening filled with new
tissue.

The physiological phenomena may be thus explained : as
lias been said, the tissue is stimulated by the presence of the
sponge, and granulation proceeds actively. At the same time
a soluble ferment is thrown out, by whicli those portions of
sponge inclosed in the matrix of granulations are slowly di-
gested and pass off by osmosis. At the same time, the granu-
lations crowd into the space gainec}. This process continues
regularly, until every particle of the sponge is removed, and
its place supplied by living tissue. I think it will be clear to
every one, especially to every surgeon, that this sponge does
not dissolve in the ordinary plasma of the blood, or tissues.
The tissues are stimulated to an extraordinary proliferation of
cells by its presence. They are also stimulated to the secre-
tion of a soluble ferment, suitable for its digestion and re-
moval.

DIGESTION OF SPONGE. 103

The same process precisely is called out in the absorption
of the catgut ligature, which is progressively invaded by leu-
cocytes, which digest the foreign substance and remove it by
osmosis, making room for themselves, much as would be done
by bacteria, and when the ligature is gone we have a cord of
new living tissue in its stead. Even ivory driven into the
flesh is eaten into, digested, and portions removed, by the in-
vasion of leucocytes.

It will be noticed here, as everywhere, when this kind of
digestion occurs, the tissue is applied directly to the substance
to be digested, and invades its substance as digestion makes
room for its growth, so that the tissue is continuously in in-
timate relation with it, progressively invades it. We do not
suppose that this soluble ferment is pepsin, but a body pecu-
liar to the connective tissues, formed only in connection with a
foreign substance.

We will suggest that the sponge graft offers the most fea-
sible means of isolating this peculiar ferment. If several
sponge grafts were placed in suitable animals, as dogs, and
the animals killed at a proper time, and the grafts immediately
treated in some way similar to that employed for obtaining
pepsin from the gastric mucous membrane of the pig, this fer-
ment wTould doubtless be found. The process would perhaps
require to be varied somewhat to suit the different character
of the soluble ferment. If this soluble ferment could be had
in sufficient amount and purity, it would be of some value in
testing the different substances suggested for ligatures, etc.,
and possibly in ways not now thought of. But the principal
use of the proceeding would be the demonstration of a physio-
logical process, and the extension of exact knowledge. Such
a demonstration would furnish a new basis of fact from which
thought might radiate to the unfolding of still other facts, no
less important.

104 THE GERM THEORY OF DISEASE.

NECROSED BONE.

Take the case of necrosed bone. How is a sequestrum
formed, but by the digestion and removal of that portion
which connects it with the living bone. Can this be accom-
plished by any of the more ordinary fluids found in the
tissues ? certainly not. Then a special menstruum is formed
for the purpose of this solution. Formed where, and by what ?
Not in some distant part and sent here, but by the tissues in
immediate contact, acting by virtue of their natural endow-
ments and the stimulus of juxtaposition with an undesirable
substance. If the tissue could act without undue irritation,
the act of digestion of the part should occur, and its place
be supplied, without the formation of pus. However, this
probably never occurs, except in cases of the death of very
small portions of bone. In some cases, however, we believe it
does occur to a considerable extent. We have witnessed cases
of healing of wounds involving bone, which we can explain in
no other way. In most cases, however, the inflammation runs
so high, and continues so long, that pus forms, and prevents the
physiological action of the cells. These cells cannot perform
this function from a distance. The ferment substance, if
formed, is dissipated in the fluids; they must be in juxtaposition
with the substance to be digested, or at least, no dissipating men-
struum must intervene, in order that the integrity of the soluble
ferment may be preserved and applied directly to its work.

If this condition can be attained, dead bone will be digested
and removed. As a matter of fact, we generally find sequestra
eaten into, here and there, sometimes more, sometimes less.
These burrowings represent points where the granulations, in
a state closely approximating healthy action, have come in
contact with and invaded the dead bone. If this condition
could be maintained at all points, the sequestrum would be
completely removed.

ACTION OF TISSUES. 105

Krause (Algemeine U. Microscopische Anatomic, S. 74),
examines the osteoclasts very closely, and the manner in which
living bone is removed by them. He is of the opinion that
they furnish a secretion for this purpose, and thinks it con-
tains lactic acid. He says, ivory driven into the flesh is
absorbed by them, and that the osteoclasts are found in the
pits formed in it, as in living bone that is undergoing this
process; and quotes Kolliker, Billroth, De Morgan and
Tomes, as authority. These osteoclasts must be formed from
the ordinary connective tissue cells, or leucocytes. Not from
osteoblasts.

ACTION OF TISSUES.

Absorption under pressure is in no wise different from any
other process of absorption. A certain portion of the cells,
crowded, but not too much, take upon themselves a new
action and develop a ferment which destroys their neighbors
less favorably placed. It is well known that under pressure,
certain tissues are destroyed in preference to others. This
would be a very interesting field of research, but we have not
time to enter it in this lecture.

This we conceive to be the normal action of the tissues of
the higher animals. How do the lower forms of life differ
from these? In the vegetative sense, the difference is but
slight. They differ widely in formative power. In the very
low forms the cells fall apart instead of aggregating and
unifying into more complex compound forms. In this sense
there is a wide physiological difference, but in the matter of
digestion, nutrition, and the formation of waste products, the
similarity is very close.

106 THE GERM THEORY OF DISEASE.

SOLUBLE FERMENTS.

We have said enough to indicate the mode of action of
bacteria in destroying substances in general, and in causing
disease. Some forms may possibly cause disease by their
presence, by aggregating into groups and causing irritation,
like the animal parasites, as the itch mite; but we are per-
suaded that their general mode of action is through their
soluble ferment and the toxic properties of their waste pro-
ducts, to be examined presently. In this manner the hardest
substances are made to yield ; are melted down almost as
readily as softer materials. Soluble ferments do not depend
for their dissolving power upon either acidity or alkalinity.
Some are acid, but generally these reactions are not very
marked, and normally seem capable of considerable variation.
They seem to be Nature's solvents, manufactured by the life
force, and used for the maintenance of the creature. We can
neither form them, nor tell why they should have such power.
We can only examine them, learn their powers, and wonder
at Nature's handiwork.

PATHOLOGICAL FORMATION OF FERMENTS.

We have reason to believe, at least to suspect, that soluble
ferments are often formed in places where they are not wanted.
Tissue is stimulated to false secretion by various irritants and
in many ways. It is probable that many of the excoriating
secretions which we see about the ears, necks, and other parts,
in children, are soluble ferments given out through some mal-
condition of the tissues. In this manner much harm is accom-
plished. We will allude to this again.

We have reason to suspect that in some cases decay of the
teeth may come about in this way. We have already seen
that tooth substance is digested and removed by a soluble
ferment normally formed. Why is riot the tissue forming a

PATHOLOGICAL FORMATION OF FERMENTS. 107

soluble ferment dissolved by it ? The answer is this : Any
tissue forming a soluble ferment is protected from the action
of such ferment substance by the life force. This answer is
very clear, and is undoubtedly a general fact. But what is life
force ? Here we are more or less bewildered, for the want of
more exact knowledge. It is well known that the mucous
membrane of the stomach of a dead dog is readily digested
by the gastric juice of a living dog. Not only this; but the
gastric juice in the stomach will, after death, digest the mucous
membrane which formed it. In this direction there is a very
perfect chain of fact, fully establishing the protective power
of the life force.

These ferments are, however, constantly brought in contact
with tissues which do not form them, such as the ducts of the
glands and other surfaces over which they may be spread.
This fact might lead to an extension of our answer. Might
lead us to say that all living tissues are protected from the
solvent action of the soluble ferments.

This statement, however, goes too far. Certainly it cannot
be maintained that the roots of the temporary teeth must die
before resorption takes place.

Again ; the tissues forming the gums and mucous membrane
in advance of the erupting tooth are removed by this same
process. It cannot be claimed that they are dead tissues.
Very many other instances of the same nature might be cited.
Then it is not true that all living tissues are protected from
this digestion by the vital principle. Hence, we are driven
back upon our first statement, i. e., that any tissue forming a
soluble ferment is protected from the action of such ferment
substance by the life force. Other tissues are not so protected.
We may infer that the tissue forming the lining membranes
of the ducts of glands, and any normal receptacle of such
a fluid, would be protected from its action, just as the tissue
6

108 THE GERM THEORY OF DISEASE.

forming the secretion. But it is plain that other tissues are
not so protected, or, if so protected, that protection is in some
way withdrawn, under special circumstances. How? The
nerve force suggests itself; but this hypothesis presents serious
difficulties. It seems much more probable that the explana-
tion is to be found in the development of the power of form-
ing the soluble ferment, than in the withdrawal of the power
of resisting it. In all cases in which I have personally made
examination of the tissue advanced against resorbed surfaces,
surfaces being removed, I have found a marked change in the
general appearance of the tissue. It has taken on the appear-
ance, more or less, of granulating tissue, and these changed
cells have received the name of osteoclasts, odontoclasts, etc.,
according to their location and purpose. The fact that this
peculiar development is the accompaniment of resorption of
bone, roots of teeth, etc., is universally recognized, I believe,
by histologists. The inference, then, that this solvent-form-
ing power is a special development, would seem to be main-
tained. We conclude that this special soluble ferment is only
formed under special circumstances. Physiologically, only
in case some tissue not wanted longer is to be removed ; as
bone during growth, and consequent change of form, roots of
temporary teeth at shedding time, or when some foreign
substance has been lodged in the tissue. Pathologically,
through some irritation or other abnormal condition, the tissue
is induced to a false action. We can understand that the pres-
ence of a substance, such as a catgut ligature or a sponge,
should induce some special action of the tissue, through which
it would be freed from its presence. But how the same
phenomena should be called into play for the removal of
parts of bone during growth, for the purpose of rendering
them symmetrical and perfecting their form, is more difficult
of comprehension. Take, for instance, the phenomena of the

PATHOLOGICAL FORMATION OF FERMENTS. 109

growth of the lower jaw. In the child of five years its body
is short, just long enough to accommodate the ten deciduous
teeth. A lengthening of the body of the bone occurs, to make
room for three large permanent molars on each side. In this
lengthening the ramus of the jaw is carried back about one
and a half inches, which, in effect, protrudes the lower jaw
forward. Now this is not an interstitial growth of the
bone ; but the ramus is resorbed away from its anterior aspect
and built up posteriorly. The osteoclast cells, soluble fer-
ment-forming cells, are found there, and their effects upon
the bone may be seen. Their work, in this instance, however,
is done quite evenly and smoothly. This is the type of all
changes of form in the osseous system. It will be seen at
once that the amount of this work done during the growth,
formative stage, of the osseous system is simply immense.
The head of each bone must be trimmed down to the size of
the shaft as the bone lengthens, etc.

By what power is this action controlled ? Here we come
directly upon the unknown. If we say it is through the con-
trol of the nervous system, we will be brought face to face
with the symmetrical formation of bones in the foetus, in
which the formation of a nervous system has failed, in which
the spinal canal, or groove, has never closed, is open from end
to end, and no trace of nerves is to be found. Yet, such a
foetus has, with the exception of the spinal column and skull-
bones, developed to term, a perfectly symmetrical skeleton.
After seeing this, the idea that these processes are under the
control of the nervous system seems untenable. And I am
free to say that I have no hypothesis to advance, except to
say that they are under the control of the life force, which,
I confess, is no explanation.

110 THE GERM THEORY OF DISEASE.

PARASITES.

After what I have said, the examples I have given, it seems
plain that the work of these lowly forms of life is to cause a
remoleculization of the substances with which they come in
contact.

This power of remoleculization of certain forms of matter
is one of the especial physical attributes of the life force. It
is the one great power upon which life depends for its con-
tinued existence. No form of life can continue to exist with-
out itself exhibiting this power, or borrowing directly from a
form of life that does exhibit it in a marked degree. (It is
claimed that certain forms of parasitic plants draw from and
appropriate to themselves food material which has been assimi-
lated by their host. Even here it is most probable that there
is a form of remoleculization.)

Now, in case of parasitic plants, if this remoleculization is
of such a nature that the results are poisonous to the host,
disease follows. If, on the other hand, the results of this
remoleculization should not be poisonous to the host, the only
harm resulting would be merely from the great crowd of the
parasitic forms.

The history of the experiment and observation upon this
subject, leaves no reasonable room to doubt that remoleculiza-
tions occur which are entirely harmless, and that remoleculi-
zations occur with the production of the most deadly poisons.
While every imaginable grade between these two may occur.

SIXTH LECTURE.

WASTE PRODUCTS, CONSIDERED WITH REFER-
ENCE TO THE GERM THEORY OF DISEASE.

In the beginning of the germ theory controversy, Schwan
seems to have recognized that carbonic acid and alcohol were
the excrementitous products of the yeast plant (Annalen der
Pharmacie, Band. 29, S. 93 und 100). Liebig, in opposing
this theory, alludes to this and recognizes that this conclusion
would necessarily follow, if fermentation were proven to be
the result of life force. (Agricultural Chemistry, page 124.)
Since this time, however, this idea seems to have been lost
sight of by writers on this subject. Sometimes we see inde-
finite allusions to it; but there is no definite expression of
the general law, that all forms of life must have their specific
waste products, as they are seen in the animal forms. The
remoleculization of matter is continuous with the duration of
life. The life force is dependent upon the remoleculization
of matter for its support. No manifestation of the life force,
in any form whatever, can be conceived of without this accom-
paniment. As the steam engine is dependent upon fire for its
power, so is the life force dependent upon molecular changes in
matter for its continuous existence. As steam is dependent upon
heat for its generation, and the expansive force by which the
engine is driven, so is matter dependent upon the life force
for the changes of molecular form through which that life is
cognizable to our senses. We can have no conception of life
in the material form without the accompaniment of these
changes. Any other form of life than this must be that spiritual
condition which is not recognizable by our physical senses.

Ill

112 THE GERM THEORY OF DISEASE.

All forms of life are continually taking into themselves
fresh increment of matter in some form. This fresh incre-
ment of matter is converted into other forms, for the support
of the energies of that life which performed this conversion;
and when this is accomplished, it must give way to fresh in-
crements of matter, which undergo similar remoleculizations.
The old must give place to the new. There is no such thing
as standing still, except with certain definite provisions for
temporary inactivity. Otherwise than this, inactivity is
death. As new material is added, the old must be disposed
of, must be cast out, or built up into formed material, where
it takes no further part in the physiological activities of the
organism. Continuous molecular change of matter is the
law of physiological existence. In other words, the remolecu-
lization of matter is necessary to the support of life ; and
when this remoleculization ceases to be performed by the life
force, except under the provisions of rest, that life ceases to
exist.

As the living form must be supported by fresh increment,
so it must give back excrement. Life is not to be supported
by the continuous remoleculization of the same matter. After
it has once accomplished its function in the economy, it be-
comes unfitted for further physiological use, and is disposed
of in one of two ways. It is either built into fixed material,
or it is cast out as excrement. In either case it is disassociated
with the physiological activity of the organism. The sum of
the excrement, fixed and formed material, must, in all cases,
equal the sum of the increment. There is nothing lost, nothing
gained. All increment not present in the organism, must
have been given back to the outside world as excrement, no
matter what the form of life.

There is a general law to be observed in the formation of
excrementitious matters. Liebig, while opposing the life-

WASTE PKODUCTS. 113

theory of the fermentations, gives expression to this, as a law
of all fermentation. (I translate from Chemische Briefe, 6te
Auflage S., 258. " Die Gahrung ist stets in ihrem Resultate
eine Spaltung eineszusammen-gesetzten Atoms in eine sauers-
tofFreiche und eine sauerstoffarme Verbindung; indem sich in
der Alkohol-garung eine gewisse Quantitat von sauerstoff
von den elementen des zuckers in der form von Kohlensaure
trent, erhalten wir den brennbaren, leicht entziindlich sauers-
toffarmen Alkohol.") " Fermentation is always, in its results,
a splitting of combined atoms into a compound rich in
oxygen, and a compound poor in oxygen ; so in alcoholic fer-
mentation, a certain amount of oxygen is divided from the
sugar in the form of carbonic acid, and we obtain the inflam-
mable alcohol, poor in oxygen."

When we compare this statement with what is now known
of fermentation we find it correct. But we may do more than
this, for if we extend it so as to cover all life, in whatever
form, we find that it is still correct ; and that it is a law of
the formation of waste products. For in the animal forms
we find as excrementitious products the same carbonic acid
rich in oxygen, and urea poor in oxygen. In the higher
plants we still find the same carbonic acid rich in oxygen,
and the alkaloids and organic acids poor in oxygen. Here
we see as the final result of the remoleculizations by the life
force, waste products analogous to those of the yeast plant.
In other words we find in all forms of life a respiratory
waste product rich in oxygen, and an urinary waste product
poor in oxygen.

I have already shown that in the physiological sense, there
is a close resemblance, a certain oneness of plan existing
among all forms of life in the matter of taking food. Now
it is my purpose to show that this identity of plan is extended
to all the living forms in the matter of waste products as well.

114 THE GERM THEORY OF DISEASE.

While there are almost unending differences of outward con-
formation there is a continuous physiological sameness in them
all. While certain cells are endowed with the power of com-
bination for building wonderful forms, as in man or in the
tiger, in the lofty palm or the forest oak, others, not pos-
sessing the power of organization into complex forms, fall
apart and carry on their physiological processes singly, as iii
the yeast plant, or the mycoderma aceti. In the unicellular
organisms, all the vital functions, so far as they are differenti-
ated, are carried on in the single cell ; and in the higher
animals which proceed from the growth and development of
some single, and equally minute germ, specialization of func-
tion goes hand in hand with specialization of physical form.
Yet in all this specialization there is no radical change in the
functions of the individual cells; nor is the sum total of the
physiological phenomena modified in their nature. In the
one matter of seeds, we are amazed and confused, by the
never ending varieties of form ; but in the examination of
the physiology of seed forms and the awakening of the germ
into active life, we find each to consist of a germ with the
accompaniment of a store of formed food material for the
nutrition of that germ, until it has formed the organs for the
gathering of its own food ; and the physiological means of
using that store is practically the same in them all. If we
examine the egg, the result is the same. Among the varieties
of form there is but one plan.

In most cases, apparent new functions, seen as we ascend
the scale of life, consist, when closely examined, of vicarious
cell action. Not a new function, but a particular function
performed for the community of cells, so to speak, by certain
cells specialized for that purpose; as we have already seen
in the matter of digestion. We find the specialization of
muscular fibre for the performance of complex motion through

WASTE PRODUCTS. 115

which a portion of the cells of the body act for the whole,
but it is not a new function, but, a function that has become
specialized ; for in the unicellular forms we have motion
without muscular fibre.

So we might go on showing that the so-called specialized
functions are more highly developed attributes that are to be
found in unicellular life. But this is unnecessary.

Waste products may be divided into two classes : the
respiratory and the urinary. The respiratory product is
always rich in oxygen, while the urinary product is always
comparatively poor in oxygen. This distinguishing feature
remains constant for all forms of life, whether animal, vege-
table, or the lower forms, that are so doubtful that some have
thought it well to create for them a separate department.

The waste products of the animal forms are sufficiently
well-known. The consideration of them has been entered
into by every author who has written on the subject of
physiology; and is therefore unnecessary here. I will,
however, call attention to some important facts that will
be of use in the consideration of the variations observed
in the waste products of some of the lower forms of life.
There is, perhaps, no part of the animal frame that is abso-
lutely constant in its chemical components. All are subject
to variations within certain limits that are by no means well
defined. So it is with the waste products. While they are
constant in their general characters, they are subject to varia-
tions with changes in the character of the food employed by
the animal. For instance, if my urine is acid to-day, I may
render it alkaline to-morrow, or next day, by eating a few
oranges or lemons. The small amount of the alkaline base,
combined with the acids of the fruit, is sufficient to bring
about this change, while the acid itself is destroyed by remo-
leculization. This instance is doubly instructive, for if we
6*

116 THE GERM THEORY OF DISEASE.

take into the economy a simple substance, that substance, if not
thrown out of physiological activity, by being built into fixed
or formed material, must appear, in some form, in the waste
products ; and in this instance it is found in the form of urate
of potassa and urate of soda ; while the acid with which it was
associated, being dependent on its molecular structure for its
chemical characters, is destroyed by remoleculization. Its
component elements appear, but in other molecular forms.
Hence, the effect on the waste product is not different from
that which would have been brought about if the alkaline
base alone had been taken. This may be stated as a general
law for the organic acids combined with the alkaline bases.

All of the excremeutitious products possess toxic, or poison-
ous properties in some degree. If, by the occurrence of acci-
dent or disease, urea be retained in the blood of an animal, it
soon presents symptoms of toxaemia, and if the accumulated
urea is not speedily eliminated, the animal dies. This is a
general law of the waste products. No living being can sus-
tain life with a large percentage of its waste product retained
in its circulation. Neither can a micro-organism continue to
grow after a certain amount of its waste products have accu-
mulated in the menstruum in which it is placed. Urea may
be regarded as the alkaloid of the animal kingdom, and is the
analogue of the alkaloids of the vegetable kingdom.

WASTE PRODUCTS OF PLANTS.

The consideration of the waste products of the vegetable
kingdom is especially difficult, for several reasons : Plants are
characterized by the large amount of their formed material,
as compared with the food material consumed by them in
their processes of vital activity; and therefore, the amount of
their waste products actually excreted is proportionately small.
In them, however, other means are found for freeing their

WASTE PRODUCTS OF PLANTS. 117

circulating fluids of waste materials, than that of actual ex-
cretion as seen in the animal forms, which will be considered
farther on. There is, however, a sufficiently copious excretion
of the respiratory waste product, carbonic acid, in plants, and
in addition to this, oxygen. These are too well known to
require further comment here.

There is, also, a true excretory function performed by the
roots of plants, and by the seeds in the process of germination.
"When barley, or other grain, is caused to germinate in pure
chalk, acetate of lime is uniformly found to be mixed with

it, after the germination is somewhat advanced

In this case the acetic acid must have been given off (excreted)
by the young roots during the process of the germination of
the seed." (Vide Johnston's Agricultural Chemistry,
page 81.)

This well authenticated fact may be regarded as the foun-
dation of the theory that plants are endowed with the power
of excretion. It is supported by the authority of Decandolle,
and the convincing experiments of Macaire, although the ex-
periments of others have shown that this excretion is limited
to very small amounts of matter. Macaire seems to have
found opium in the soil in which the poppy plants grew. He
also found, in washing the soil with pure water, that it yielded
a considerable quantity of acetic acid and a trace of a brown
organic matter.

Liebig devotes considerable space to this, in his agricultural
chemistry, with especial reference to the possible effects of
these excrementitious substances on the rotation of crops.
Other chemists have also occupied themselves with it, and
while it has been definitely shown that in some special cases
plants may eliminate a sufficient quantity of excrementitious
matter to prove injurious to successive generations growing in
the same soil, the rule is that poisoning from this cause is not

118 THE GERM THEORY OF DISEASE.

to be expected. In many instances, however, it is found that
individual plants are poisonous to others growing in their
neighborhood. It is rare to see a very large black walnut
tree that has not a clearing around it, wherever it may stand
in the forest. This is not on account of its shade, but some-
thing eliminated by the tree that is hurtful to other trees. I
remember well an effort to raise corn on the south side of a
row of walnut trees. The experiment was continued for
many years. The corn was injured seriously for many feet
distant, where it was never shaded by the trees. Very many
such instances are known. Enough has been demonstrated
to show conclusively, that most of the substances formed in
the fermentations are also excreted in very small amounts, by
various plants. Even alcohol and ammonia are formed in
this way, in small quantities. Although these substances, as
a rule, contain no nitrogen, their chemical construction is such
as to show their relationship to urea, and leave no doubt that
they are properly analogues of that product in the animal
kingdom.

ALKALOIDS.

By far the most important compounds to be considered in
this connection are the alkaloids. These bear the same rela-
tion to plants that urea bears to the animal forms. There is
seen in their chemical conformation and characteristic prop-
erties a marked relationship; and yet among them is found
a wide divergence of poisonous effects. All possess, in some
degree, the power of intoxication, while a few are the most
virulent poisons known. Nearly all are composed, as urea,
of carbon, hydrogen, nitrogen, and oxygen. In a few of
them oxygen is lacking; and in all the nitrogen is in smaller
proportion than in urea. As we descend the scale, the nitro-
gen disappears, the oxygen is increased, and we have the
organic acids and alcohols. All of these are, properly, waste

ALKALOIDS. 119

products of the vegetable kingdom, though they are not all
excreted.

As we have already seen, the higher plants are marked by
the apparently small amount of their waste products and the
large amount of their formed material. The formed material
presents two very marked characteristics, which will, perhaps
be better understood if we designate them as formed material
and " fixed " material. Then we may class the formed material
as that which is elaborated and stored away for future use,
such as the starch, oil, etc., surrounding the germ in the
seeds, and in certain organs of the plant, and various other
products designed for future employment by the vital ener-
gies of the organism. The "fixed" material, on the other
hand, is such as is placed permanently beyond the vital ener-
gies of the organism. Some portions of the fixed material
may still be of use to the plant by the physical support it
gives to its organs; as lignin, which forms the stems and
branches of trees, and the bark, which serves them as a pro-
tection. They are not, however, of any further physiological
use to the plant after having once, or a few times, served as
conduits for the circulating fluids.

Although waste products may be found in the fluids of the
plant, as in the blood of the animal, it is in this fixed material
that we find the bulk of these substances; and it is here that
the toxic principles are found in greatest abundance. Instead
of being excreted, thrown out to the outer world, they are
stored in the disused cells of the wood and bark, united with
other waste products in the form of insoluble compounds.
This fact seems to have prevented an early recognition of
their real nature.

Sachs, in his text-book of botany, describes them as " de-
gradation products, which are no longer useful to the plant/'
and as " secondary products of metastasis." When we look

120 THE GERM THEORY OF DISEASE.

over the products thus set apart by Sachs, we find that nearly
all of them may be set down at once as analogues of the urine
in the animals, of the alcohol, the acetic acid, the butyric acid,
etc., of the fermentations.

It is to these products that we look for the most of the
vegetable substances now employed as medicines. The active
principles of these are the alkaloids. Therefore their effect
upon the animal economy is well known to medical students,
and need not be recited here. There are many other sub-
stances found in the same relationship to the vital energies of
the plant, which are worthy of special consideration, if we had
the time at our disposal. Tannic acid is one of the most constant
of these products, and there are a large number of others not
yet mentioned. We will only mention one other class of
substances, the coloring matters which remain in the wood
cells in a fixed condition, as a result of secondary metastasis.
Precisely similar phenomena are seen in the Micrococcus
Chromogenes, of which there are several varieties known.
All such circumstances serve to point us forward in our efforts
to explain the mysteries of nature.

BACTERIA.

When we come to consider the bacteria, and the allied
forms of life, we are at once amazed and astounded at the
wonderful power they possess in the remolecullzation of matter.
This is one of their especial characteristics. This seems to be
the form of life in which the largest amount of food material
is consumed, and the largest amount of waste products given
back, with the least building of tissue. The largest amount
of remoleculization with the least amount of formed or fixed
material. A whole jar of milk is turned sour, every particle
of its sugar of milk converted into lactic acid, and yet the
amount of the formed material is so insignificant that it re-

BACTERIA. 121

quires an acute and trained observer, provided with the best
means of search, to find a trace of it. When a small amount
of yeast is added to a solution of sugar, the whole of the
sugar will be remoleculized, producing carbonic acid and
alcohol within a few hours, with, apparently, no increase of
the yeast. In this instance, however, the yeast has grown, and
performed its function of remoleculization, under the most
difficult circumstances, for the reason that it is deprived of
the nitrogen necessary for the building up of its cellulose
and albumen. Under these circumstances the amount of yeast
may actually decrease, as was shown by Liebig many years
ago. Pasteur seems to have proven that in this case the
young yeast cells grow at the expense of the nitrogen in the
old cells, and thus destroy them to such an extent that the
whole quantity of the yeast is diminished, and the vital
energies of the plant weakened. This example serves to
show the wonderful power of these low organisms.

Then we may take the example of the destruction of the
dead carcass. The history of the experimentation of the past
shows conclusively that it does not decompose, if protected
from these low organisms. Yet within a few days it is
swarming with this form of life, in the presence of which it
melts away like ice before a summer sun. It is first attacked
by one form, which consumes and throws out its waste pro-
ducts as long as it can grow in the continually increasing
quantity of its own excreta. Then it must give way to others
that have already appeared on the scene of action, to which
the waste products of the first are no hindrance. These, in
turn, very soon give way to still other forms, which again
remoleculize the waste products of all the former that may
retain a semi-solid or a liquid form, with any residue of the
original carcass that may still remain; and in an almost
incredibly short time the whole carcass has disappeared. The

1 22 THE GERM THEORY OF DISEASE.

labors of Pasteur have thrown much light upon this subject.
The fact that the acetic acid plant will again remoleculize the
waste product of the vinous yeast plant, alcohol, and after
that the mucidines will still remoleculize the acetic acid, con-
verting it, in turn, into other compounds, is full of instruction
for all these processes. Why is it that the yeast plant cannot
grow continuously in the same menstruum, if proper food
material be furnished it? It is a well known fact that only
a certain percentage of alcohol can be formed in this way,
and that to obtain a greater percentage we must resort to
distillation. The plant is choked by its own excreta, alcohol.
If this could be eliminated the growth of the plant could be
continued.

An example of this is found in the bacterium lactis. If
lime is added to the solution, lactate of lime is formed and
the excretory product of the plant, lactic acid, is artificially
eliminated, and the plant is found to grow continuously in
the same menstruum, as long as supplied with food material,
and lime to fix or eliminate its excreta. The form of excre-
tion employed by the higher plants is artificially produced.
This law of the relation of excretory products to the life that
formed them is universal. It applies with the same force to
the micro-organisms that it does to the higher animals, or to
man himself.

It would seem that the vegetable world is divided into two
great classes of life forms, and that ifc is the office of the one
to build up, and the office of the other to tear down. Of all
the life forms, the higher plants have the greatest power of
structure building, both as regards quantity, in comparison
with the amount of the material consumed, and as to the
actual quantity of structure formed ; while, in the lower
plants, the bacteria and their allied forms, exactly the opposite
of this is found, in every particular. No other form of life

BACTERIA. 123

consumes so much in comparison to the amount of structure
built. They are emphatically the destroyers of organic forms;
physiologically constructed to and for this end. Yet, they
must digest their food ; if it be solid, or semi-solid, it must
be liquefied, in order to be absorbed. Then it must enter
into the cells by the process of osmosis, and under the influ-
ence of the life force be converted into protoplasm — albu-
minoids— into the tissue of the growing plant.

After this come the waste products. How? The cell
dies? No. This will not explain the phenomenon. If it
were the death of the cells, we would find the chemical forms
of the cells in the waste products. This is not the case.
Death does not alter the chemical forms. Therefore, there is
another remoleculization for the formation of the waste pro-
ducts ; a vital process of shedding out the used material in
two general forms. The life force letting go of the matter it
has had in its grasp, and casting it out as no longer of use to
it. The formation of waste products is not, in any true sense,
a process of dying.

Life resides in matter which it has formed into such molec-
ular groupings as will suit its purposes, but matter does not
live. Electricity may be resident for a time in the Leyden
jar, but such a jar is not electricity. It may be said to be
electrified, and matter may be said to be vivified. If life
discharges matter which it has had in its grasp, the act is a
vital one, and as all changes in matter under the influence of
the life force consist in remoleculization, so does this; hence,
waste products are always in different molecular forms from
the tissues from which they are cast off, though they consist
of the same elements. It is by a vital process, then, that the
waste products are separated from the living organism, and in
the bacteria the general laws of physiology remain unchanged.
Here, as elsewhere, we find the definite respiratory product,

124 THE GERM THEORY OF DISEASE.

and the toxic or urinary product. A sufficient number of
these have now been studied for us to gain some notion of
them; yet our knowledge is still limited to a few forms
among the bacteria and their allies. The best known is the
yeast plant. In this we have alcohol, succinic acid and glyce-
rine, as the urinary excrement. The bacterium lactis produces
lactic acid ; the mycoderma aceti produces acetic acid. These
names properly represent so many families, each of which
contains a number of varieties. Saccharine substances form
suitable food for them all. Two of them will, however, grow
equally well in substances not saccharine. Another form
produces butyric acid; another, a kind of mucus; another,
ammonia; while others still, produce as their waste products,
all of the ill-smelling products of putrefaction. I append a
table of those best known, in connection with a table of the
waste products of other forms of life, for comparison.

TABULATED STATEMENT OF THE WASTE
PRODUCTS OF VARIOUS ORGANISMS.

RESPIRATORY PRODUCTS. TOXIC PRODUCTS.

ANIMALS.

Carbonic Acid....... C02 Urea CH4N20

Creatine C4H9N302

Creatinine C4H7N30

Uric Acid C5H4N403

Hippuric Acid C9H9N, 03

PLANTS.

Carbonic Acid C02 Theine C8H10N402

Oxygen 0 Veratrine C32H52N208

Morphine C17H19N03

Quinine C20H24N202

Strychnine C21H22N202

Atropine C^HgsNOg

Piperine C1VH19N03

WASTE PRODUCTS OF VARIOUS ORGANISMS. 125

RESPIRATORY PRODUCTS. TOXIC PRODUCTS.

Carbonic Acid C02 Nicotine C10H14N2

Oxygen 0 Coniine C8H15N

Curarine C10H15N

Tannic Acid C14H1009

Acetic Acid C2H402

Citric Acid C6H8Or

Malic Acid C4H605

Oxalic Acid C2H204

BACTERIA.
Alcoholic Fermentation.

Carbonic Acid C02 Alcohol C2H6O

Succinic Acid C4H604

Glycerine C H803

Acetic Fermentation.
Carbonic Acid C02 Acetic Acid C2H402

Lactic Fermentation.
Carbonic Acid C02 Lactic Acid C3H603

Viscous Fermentation.

Carbonic Acid C02 Mannite C6H1406

Gum C12H20010

Tartaric Fermentation.

Carbonic Acid C02 Propionic Acid C3H602

Hydrogen H

Butyric Fermentation,

Carbonic Acid C02 Butyric Acid C4H803

Hydrogen H

Ammoniacal Fermentation.
Carbonic Acid C02 Ammonia NH3

(These two products unite to form ammonia carbonate.)

Putrefactive Fermentation.

Carbonic Acid C02 Valerianic Acid C5H1002

(Complex.) Ammonia NH3

Sulphydric Acid HS

Fat Acids (various eqv.) C H 0

126 THE GERM THEORY OF DISEASE.

ALKALOIDS.

There is, perhaps, no other one set of organic compounds
that have puzzled chemists more than those given in this
table, or that have been and still continue to be of more in-
terest to the scientific world. The table, as it stands, is only
intended to give an outline view of these organic matters as a
class, by setting before you fairly chosen specimens from the
different forms of life. It is not intended to be in any wise
exhaustive, but simply a comparison of these products. The
similarity of their chemical construction will be apparent at a
glance, and yet they differ greatly in their toxic properties.
Some, as strychnine, are violent poisons to the animal king-
dom. While others, as some of the acids, are mild irritants.
Most of those from the vegetable world are useful as medi-
cines, while many are highly prized as condiments. The
members of the acid series vary from the alkaloids in that
they contain no nitrogen, and they also vary as markedly in
their toxic properties. Their close similarity to the alcohols
will be noticed. It will also be noticed that some of the
waste products of higher plants are the same as those of lower
organisms. This, perhaps, would not be expected at first
glance; yet when we come to consider that all are plants, we
should expect a similarity. There is, perhaps, an important
difference to be observed here. The alkaloids of the higher
plants, from the nature of their mode of excretion, are thrown
out of physiological activity, by being combined with the veg-
etable acids, mostly in the form of insoluble salts, and thus
laid away in the " fixed material " of the plant. On the other
hand, the animal alkaloids, urea, uric acid, etc., are eliminated
in a soluble condition. In case of the micro-organisms, the
waste products are very generally eliminated in a soluble
condition also. There seem to be some exceptions to this

ALKALOIDS. 127

rule, as in the chromogenes. To what extent this may occur,
does not yet appear.

But the comparatively more abundant waste product of the
lower forms is of much importance in this connection. Those
given are from the few that have been best studied. In these
no proper alkaloids have, as yet, been made out by isolation
and exact analysis, but we cannot argue, from this circum-
stance, that none of the lower organisms produce true alka-
loids. As yet, but very few of them have been accurately
studied, and these, for the most part, have been those that
have been found useful rather than poisonous. Some exami-
nations already made show a very near approach to the deter-
mination of the nature of some of these poisonous substances;
and although no sufficient chemical analysis has yet been
made, the action of the substances upon the animal economy,
so far as trial has been had, go to show the similarity of these
poisons to the alkaloids from the higher plants. This has
been remarked by many experimenters, as I shall show pre-
sently. Therefore, we have much reason to believe that true
alkaloids, of a poisonous nature, will be isolated at no distant
day. We have already abundant evidence that poisonous
properties are developed by a number of these forms. Other-
wise, how can we account for the results of the Bacillus An-
thracis? How else can we account for sepsis, on the germ
theory, except to suppose that a poisonous alkaloid is one of
the products of the organism ? How else can we explain Dr.
Koch's results in the production of gangrene in mice, but to
suppose that some product of the remoleculizations by the
organisms spread among the tissues of the animals and de-
stroyed them wherever they went. He found that after they
had once made a beginning, the tissues were always destroyed
in advance of the growing organisms, without contact. This
strongly illustrates the idea of the formation of a poison

128 THE GERM THEORY OF DISEASE.

which is thrown out from the organism. Again, in the matter
of sepsis, already referred to, it has been abundantly shown
that the fluids contaminated by the micrococci are poisonous,
when separated from the organisms; thus proving, again, that
there is an organic poison developed, which is fully capable of
producing its effects in the absence of the life that produced
it, the same as is seen in the alkaloids from the higher plants.
This has taken the name of sepsin, after the order of the
naming of the vegetable poisons ; although it has not, as yet,
been properly isolated and examined.

SEVENTH LECTURE.

POISONS.

In this lecture I propose to examine more particularly the
evidence given by experimenters of the finding of the poison-
ous products of micro-organisms.

Koch, after injecting putrid blood into mice and noting
that a large amount killed by direct poisoning, while a very
small amount produced disease, says of the first : " No inflam-
mation can be observed in the neighborhood of the place of
injection. The internal organs are also unaltered. If the
blood taken from the right auricle be introduced into another
mouse, no effect is produced. Bacteria cannot be found in
any of the internal organs, nor in the blood of the heart. An
infectious disease has not been induced as the result of the
injection. On the other hand, there can be no doubt that
the death ef the animal was due to the soluble poison, sepsin,
which has been shown by the researches of Bergman, Panum,
and various other investigators, to exist in putrid blood. The
animal has accordingly died, not from an infectious disease,
but from a chemical poison. This supposition is confirmed
by the fact that when less fluid is introduced into the animal
the symptoms of poisoning are less marked, and are quite
absent when one, or at most, two drops are injected. After
the use of such a small quantity of blood, mice often remain
permanently without any morbid symptoms. But a third of
them will become ill after the lapse of about twenty-four
hours, during which time they have remained perfectly
healthy. The symptoms which are then present are charac-

129

130 THE GERM THEORY OF DISEASE.

teristic and constant, and are in no case preceded by any of
the symptoms of poisoning previously described."

These experiments show very distinctly that the experi-
menter was dealing with a diffusible poison of virulent
character, produced by the organisms, but acting without
them, as the alkaloids from the higher plants would act.

Dr. Sternberg says (page 257): " It is not alone by invad-
ing the blood or tissues that bacteria exhibit pathogenic
powers. Chemical products evolved during their vital activ-
ity, external to the body, or in abscesses and in suppurating
wounds, or in the alimentary canal, may doubtless be absorbed,
and exercise an injurious effect upon the animal economy.
Indeed, we have experimental evidence that most potent
poisons are produced during the putrefactive decomposition of
organic matter. The poisons resembling the vegetable alka-
loids in their reactions^ called ptomains by Selmi, who first
obtained them from the cadaver, are fatal to animals in
extremely minute doses."

Klebs said, at the International Medical Congress at
London, that the effects of micro-organisms were probably
due to fine chemical workings. Very many of the experi-
menters in this field have spoken in a, like manner of their
findings, all of which go to show that the worker in this line
of research soon comes to feel that he is dealing with a poison
evolved by the organisms he has under observation.

Gradle says (page 66): "The successive chemical stages of
the putrefactive change have as yet been incompletely traced.
The changes which albumen undergoes resemble at first the
process of digestion. It is converted into soluble forms,
partly peptone, and then split up into leucin and tyrosin. Sub-
sequently numerous volatile fatty acids, and various poly-
atomic alcohols (phenol, skatol, indol), appear, as well as a
host of other substances in traces. Amongst them are a variety

POISONS. 131

of poisonous agents, especially some alkaloids (ptomains)."
The most constant bacterial form met with in putrefaction is
the bacterium termo. Some attempts have been made to iso-
late and examine septic poisons. This, so far, has only served
to show more positively the production of poisons and the
nature of their action. Panum found the poison formed in
the decomposition of nitrogenous substances was reduced in
virulence about one-fifth by eleven hours continuous boiling
of the infusion. This continuous boiling was certainly suffi-
cient to show that the poisonous effects were not due to living
micro-organisms remaining in the fluid. In this case, more-
over, some flakes of coagulated albumen were found in the
liquid, which upon trial proved to contain a very virulent
poison. This fully Accounts for the loss of virulence by the
liquid. This experimentation shows that the substance had
none of the characters of a molecular motion poison described
by Baron Liebig; nor is it a decomposing substance or a
ferment, as each and all of these are destroyed by heat. The
chemical structure of the substance is of a more stable nature.
There is a sharp distinction manifest between the action of
these poisons when developed in the animal body by the re-
moleculization of the organisms in situ, and when developed
out of the' body, collected and administered separate from the
organisms. In the latter case, the effects produced are similar
in their general character to that of the alkaloids from the
higher plants, that is, comparatively speaking, they are im-
mediate. The disturbance is usually manifest within a few
hours at most; and if the animal withstands this immediate
effect of the poison it returns to health, i. e., all the symptoms
pass away and no disease is produced ; whereas, if the micro-
organisms which elaborate the poison are planted in the
tissues of the animal and grow, there is no such immediate
poisoning. On the contrary, it remains well for a day or
7

132 THE GEKM THEORY OF DISEASE.

more, and then the symptoms come on more slowly and grad-
ually increase in violence usually until death is induced. A
progressive disease is the result in the one case, an immediate,
but transient poisoning in the other. This difference in the
results of inoculations made with fluids rendered poisonous by
the development of micro-organisms within them, and similar
inoculations with fluids containing micro-organisms but with-
out sufficient developed poison to produce immediate effects,
has been marked by a large number of investigators and is
now perfectly well known.

Putrefaction does not always result in the formation of
virulent poisons. Many times meats, or meat infusions, may
rot away, and poisons of a very marked character cannot be
found at any stage of the process. This difference must be
explained by the fact that the same micro-organisms have not
grown in the one as in the other. If the ordinary bacteria of
decomposition are accompanied by a form that produces a
virulent alkaloid as a result of its remoleculizations, the poison
will be found, otherwise, it will not. Just as in a mass of
plants, one, or a few only of the many, will produce a viru-
lent poison, though all grow in the same soil. Again, as we
have said, the mycoderma aceti will feed upon the alcohol
formed as the waste product of the vinous yeast plant. In
the same way other micro-organisms may feed upon and
destroy, through their remoleculizations, the poisonous pro-
ducts of those that may have gone before them. Hence, it is
found that septic cadavers are apt to lose their septic characters
as decomposition advances. These facts, while they serve to
illustrate the manner of the formation of poisons, also illus-
trate the extreme complexity of the subject.

FARTHER INVESTIGATION NEEDED. 133

FARTHER INVESTIGATION NEEDED.

Many other instances of a like nature might be brought
forward, if time would permit, but it is no part of my inten-
tion to treat this subject exhaustively. Some of the cases
seem to show that the poison is of the nature of a local irri-
tant only, as appears in Dr. Koch's demonstration of the
bacillus tuberculosis ; while many others seem to be general
poisons, with special tendencies to particular organs, as is seen
in the splenic fever produced by the bacillus anthracis. This
is sufficient to show that there is much yet to be learned in
this direction ; indeed, that this work is as yet in its infancy.
In truth, the work done thus far has been in the nature of
proving that organisms are regularly connected with the fer-
mentations and decompositions, and also with certain processes
of disease, rather than any effort to show how they bring
about these results. This was necessary in the first instance,
as the forerunner of a farther and more complete understand-
ing of the subject that must come from a closer study of the
modes through which these low organisms produce their
effects. It is plain that we cannot know any one of the disease
germs until all of the products of its remoleculizations have
been isolated and studied separate and apart from the organism
itself, as has been done with the products of so many of the
higher animals and plants. I see no other plan by which we
can ever know the capabilities and all of the possibilities of
micro-organisms, in connection with the production of disease.
In most cases of the discovery of poisonous properties in the
higher plants, the specific product of the plant in which that
poison resides has proven itself capable of isolation by the
means known to chemists ; and the disease-producing poisons
of the lower organisms will do the same when the effort to
find them has been prosecuted with sufficient skill and energy.
As alcohol has been isolated, as the vegetable alkaloids have

134 THE GERM THEORY OF DISEASE.

been isolated, as the toxic elements of the waste products of
animal life have been isolated, and as, through this isolation,
the exact properties of these agents have become known to
us, so must sepsin be isolated, so must the poisonous product
of the bacillus anthracis (Anthracine) be isolated, so! must
the poisonous principle of every disease-producing germ be
isolated, and each of these studied separate and apart from
the organisms which produce them ; and in each case their
properties must be demonstrated and determined by direct
experiment, before they can be said to have been accurately
studied, and that we know their properties and capabilities.
This is the recognized means of learning the powers and
capabilities of the products of the higher plants and animals.
No one is foolish enough to deny the value, the necessity, of
the knowledge to be gained by this mode of study in the
vegetable kingdom. If there has been any truth arrived at
in all the research that has been given to the subject of the
production of disease by the lower organisms, that truth
requires to be extended, and rendered more exact, by the
modes of study we have just indicated.

PHYSIOLOGICAL CHANGES.

The question, as to whether the nature of the bacteria and
their allied forms are always essentially the same, is one that is
very important to determine. Very many persons seem to think
that the characteristics of this or that organism may be perma-
nently changed, by temporary changes in the media in which it is
grown. This is a question of the gravest importance ; and one
on which there has, as yet, been very little or no exact experi-
ment. Therefore we have nothing but conjecture ; unless,
indeed, we may regard the experiments of Pasteur, in his
efforts to moderate the virulence of the bacillus anthracis, the
organism of chicken cholera, etc., experiments in this direction.

PHYSIOLOGICAL CHANGES. 135

These, however, certainly cannot be classed as exact experi-
ments. Yet so far as they have scientific value, it is undoubtedly
in the direction of the maintenance of the proposition that the
nature of organisms may be profoundly changed by tempo-
rarily changing the media in which they are grown ; for it is on
this basis that we must account for changes in results. Such
a proposition will, however, require the most rigid proof be-
fore we can accept it as a modification of the essential nature
of the products, that will be carried, with the organism, back
into the media froui which it was transplanted.

The other proposition, that the products of the organism
change with the media in which it is grown, is of a very
different nature, and much more plausible. We all know
that our own urine may be changed from acid to alkaline,
by certain changes in diet; that the amount, and to some
extent, the quality of opium, is affected by the nature of the
soil in which the plants are grown. Still it does not appear
in these cases that the essential features of the waste products
are more than modified in some unimportant particulars.
The urine will still furnish urea, and the opium will still
furnish morphine, although each will, possibly, furnish their
characteristic product in diminished quantity. But in either
case, the original character of the product will be resumed
with the resumption of the original diet.

One would scarcely expect the yeast plant to produce a
nitrogenous alkaloid when grown in a pure solution of sugar
or starch, containing none of the element nitrogen. So an
organism whose normal habitat is nitrogenous compounds,
and whose waste products are nitrogenous, if transferred and
found to grow in pure starch, would certainly not produce a
nitrogenous alkaloid as a part of its waste product, while
growing in the starch; yet I would expect it to again produce
the nitrogenous product if replaced into nitrogenous matter ;

136 THE GERM THEORY OF DISEASE.

if, indeed, the plant retained sufficient vitality to perform its
functions. The material for the formation of the waste
product must be present in the food, otherwise it cannot be
formed. Again, it may be that the remoleculization will
be different in foods of a different nature, even though the
elements be all present. Dr. Miller informs us that, in his
experiments, he has found that the bacterium lactis produced
no acid when grown in soup ; but when a little sugar or
starch was added, the lactic acid was promptly formed. He
gives us no intimation of the nature of the waste product of
this organism when grown in the soup not sweetened. This
however, serves to show how the waste product may be
changed, temporarily, by changes in the nature of the food.
That changes of this nature may occur in a large number of
the low forms of life seems not only plausible, but probable.
But that this will affect the nature of the organism perma-
nently, is another question; and one that will require much
experiment to prove satisfactorily.

MANNER OF ACTION.

How can these low organisms produce disease? This ques-
tion is being asked by many of the thinking men of the world
to-day. Men seem to be at a loss for a reasonable answer;
such an answer as will satisfy the mind that is earnestly seek-
ing an explanation of the phenomena described by such ex-
perimentalists as Koch and Pasteur. These men have not
answered it. They tell us what they have found ; that certain
phenomena invariably follow the introduction of certain germs
into the bodies of animals; that certain germs produce certain
diseases. How do they accomplish this? what is their modus
operandi? This question must have a reasonable answer be-
fore the germ theory of disease can find a firm basis in the
minds of the masses of men. The days of hocus-pocus have

MANNER OF ACTION. 137

passed away from the medical profession forever. A few men
may take these things on faith, and wait for time to develop
the rational answer, but the many will wait, and watch for
farther developments to point out a reasonable and philosophic
answer, before they will accept this theory without reserve.
Can such an answer be given with our present knowledge of
the subject? If it be required that every step be proven by
actual demonstrated fact; if reasonable circumstantial evi-
dence be not admitted, only a few cases can be clearly made
out. But on the other hand, if the physiology, as previously
explained, be accepted, the manner of the production of dis-
ease becomes clear. I should not insist that the poisonous
substance must, in every case, be an alkaloid. But it must
be an organic compound closely akin to an alkaloid. To say
that these organisms produce disease, simply by their presence,
is not a sufficient explanation. We all know that their pres-
ence is not, in itself, a sufficient cause; for if this were so, one
organism would be as potent as another. And we all know,
who have had any experience in the examination of these
forms, that many of them are without any evil effect what-
ever; that wounds in the mouth and elsewhere heal readily
and perfectly when covered with them. We also know that
the great majority of the higher plants are innocent of any
evil effect upon the human system; and it is perfectly reason-
able that we should find the same differences to exist among
the lower plants. Many kinds of plants grow together with-
out injury to each other; but plants are found that destroy
their neighbors by the poisonous effects of their waste pro-
ducts. Then it seems plain that the differences must be found
in the peculiar products to which the particular organism gives
rise. These we have already sufficiently explained. We have,
also, sufficiently explained the modus operandi, in the de-
struction of organic substances in general. They are simply

138 THE GERM THEOEY OF DISEASE.

remoleculized, as any other food material is remoleculized;
nothing more and nothing less; and it is in the chemical re-
organization of the elements for the formation of the waste
products that poisons are evolved.

It seems perfectly natural that in this remoleculization there
should ofteu be a residue that escapes digestion; as is seen in
the so-called rotting of wood and many other substances. It
is not probable that one organism is capable of the complete
destruction of such substances; but rather, that many are
concerned in the work.

I may be permitted to make a suggestion in regard to the
cause of the difference, that is so often noticed, of the com-
parative liability of different persons to attacks by these
organisms. Several persons receive wounds. So far as can
be seen, their chances for a speedy recovery are equally good ;
but some of these develop sepsis, while others do not. Now,
much of this is explained by the fact that we are unable to
perceive the entrance of these organisms, and they may gain
admission to the one and not to the other, and we be none the
wiser until we find that sepsis is established. This is always
a possible explanation, for the history of the experimentation
on this subject shows full well that we have not, even yet,
learned to prevent the ingress of these germs with absolute
certainty. Yet over and above all of this, there is a certain
residue of cases that show that different persons are liable in
different degrees to sepsis. This has been noticed ever since
there was such a profession as medicine, and the class of
patients to which it refers have been pretty closely defined.
They are those whose powers of life have been weakened, by
whatever cause. This is said to be the resistance of the
tissues to the invasion of the organisms. How do they
resist? Now, if we accept the explanation of the formation
of the digestive bodies, as previously explained, this supposi-

MANNER OF ACTION. 139

tion becomes tenable. When an organism or spore of an
organism falls upon a cell or naked granulation of a wound,
and finds there the conditions suitable for its development, its
digestive body is at once thrown out for the preparation of
its food material which exists in the tissues with which it is
surrounded. This digestive substance proves irritant to the
cell upon which the germ has fallen. This irritation excites
the cell to throw out its peculiar digestive body for the
removal of the irritant with which it is beset. Here we get a
glimpse of the antagonists. It is cell against cell ; digestive
body against digestive body. A contest has begun. Which
will win? The stronger, of course. If the man be vigorous
and healthy and his tissues highly endowed with the energies
of life, the chances are this much in his favor ; but if, on the
other hand, his powers of life be at a low ebb, if his tissues
respond to irritants but feebly, then the chances are, this far,
in the favor of the intruding organism. In the first case, the
cell upon which the intruding germ has fallen responds
promptly to the irritation ; a substance calculated to free it
from the effects of the intruder is formed and poured out
upon it and meets the digestive body of the intruder, hinder-
ing, dissipating and nullifying its action. In this way the
intruding germ is, in many cases, possibly, overcome and
driven out. In the opposite case, where the vital powers
are at a low ebb, the response to the irritation is, perhaps,
very sluggish, the digestive body is poor in quality and
scanty in quantity, and the intruding germ has an easy
victory.

If we suppose that the intruder is a spore, a seed, with a
store of food material laid up within its shell, the case is not
different essentially. The history of the experiment on this
subject shows that during this process excretory products are
thrown off, and these may prove direct irritants that will

140 THE GERM THEORY OF DISEASE.

arouse the resistant energies of the tissues. Surely, if the
tissues are capable of forming, by reason of irritation, a
secretion that will digest a piece of ivory that has been thrust
into the flesh, which has been proven by direct experiment,
we should expect this kind of resistance to be offered to the
development of disease-producing germs.

Facts of a very decisive nature bearing on this point have
been brought to light by Dr. Sternberg, in the following
experimentation, which I quote : —

" If we add a small quantity of a culture-fluid containing
the bacteria of putrefaction to the blood of an animal, with-
drawn from the circulation into a proper receptacle, and
maintained in a culture-oven at blood heat, we will find that
these bacteria multiply abundantly, and evidence of putre-
factive decomposition will soon be perceived. But if we
inject a like quantity of the culture-fluid with its containing
bacteria into the circulation of a living animal, not only docs
no increase and no putrefactive change occur, but the bacteria
introduced quickly disappear, and at the end of an hour or
two the most careful microscopical observation will not reveal
the presence of a single bacterium. This difference we ascribe
to the vital properties of the fluid as contained in the vessels
of a living animal; and it seems probable that the little
masses of protoplasm, known as white-blood corpuscles, are
the essential histological elements of the fluid, so far as any
manifestation of vitality is concerned.

The writer has elsewhere suggested that the disappearance
of the bacteria from the circulation, in the experiment above
referred to, may be effected by the white corpuscles, which, it
is well-known, pick up, after the manner of amoeba?, any par-
ticles, organic or inorganic, which come in their way. And
it requires no great stretch of credulity to believe that they
may, like an amoeba, digest and assimilate the protoplasm of

MANNER OF ACTION. 141

the captured bacterium, thus putting an end to the possibility
of its doing any harm.

In the case of a pathogenic organism we may imagine that,
when captured in this way, it may share a like fate, if the
captor is not paralyzed by some potent poison evolved from it
(the italics are mine), or overwhelmed by its superior vigor
and rapid multiplication. In the latter event, the active career
of our conservative white corpuscle would be quickly term-
inated, and its protoplasm would serve as food for the enemy.
It is evident that in a contest of this kind the balance of
power would depend upon circumstances relating to the in-
herited vital characteristics of the invading parasite and of the
invaded leucocyte."

In these paragraphs we have the strongest evidence of the
truth of the supposition stated, of the nature of the combat
between the tissues or the white corpuscles of the blood and
the wandering cells for the tissues, on the one hand, and the
invading organisms on the other. The writer, though not
intending to put forward his own experimentation in this
work, may say that he has also seen strong evidence of the
truth of this in tissue taken directly from man to the warmed
stage of the microscope, in which the wandering cells were
found loaded with micrococci, which in many instances seemed
to be destroying the cells. Some were motionless and filled
to overflowing with the organisms, with little chains of the
micrococci extending from them, while others containing
but few of the organisms exhibited their usual motions. This
phenomenon may occasionally be demonstrated in the peculiar
granulations which are sometimes found under plates for
artificial teeth, where the gums have taken on a bad condi-
tion.

Dr. Koch has also seen micrococci in the white blood cor-
puscles, under circumstances that indicated that the blood cells

142 THE GERM THEORY OF DISEASE.

were being destroyed by them. He says: "Their relation
to the white blood corpuscles is very peculiar. They penetrate
into these and multiply in their interior. One often finds
that there is hardly a single white corpuscle in the interior of
which bacilli cannot be seen. Many contain isolated bacilli
only; others have thick masses in their interior, the nucleus
being still recognizable; while in others the nucleus can no
longer be distinguished; and finally, the corpuscle may become
a cluster of bacilli, breaking up at the margin — the origin of
which one could not have explained had there been no oppor-
tunity of seeing all the intermediate steps between the intact
white corpuscles and these masses."

With these facts before us, and with the plain teachings of
the relations of the life force to matter, as exemplified in the
phenomena of digestion, nutrition and the formation of waste
products, it seems to me we must not fail to gain an under-
standing of these processes. The cells attacked, either digest
the invading germs, or the invading germs digest them. And
here, as everywhere else in nature, the stronger will be' the
victor. In other cases, as in septicaemia, the excretions of the
bacilli do not seem to produce such marked local lesions, but
the waste products of the organisms are absorbed and act the
part of a diffusible poison, producing the general symptoms
manifested in these cases.

Again, the history of cases shows that sepsis is most liable
to occur in the early time of the healing of wounds; at a time
when the tissues may be supposed to be still suffering from
the effects of the shock. In this case it must be supposed
that the tissues are not so well able to contend with the
intruding germs as they are afterward, when the process of
granulation is going forward vigorously.

We have also experimental evidence establishing this point.
Sonnenschein found that certain bacteria with which he was

INFLAMMATIONS. 143

experimenting failed to grow in the tissues of an animal.
Believing, from the results of previous experimentation, that
sepsin injected with the hacteria favored their development,
and having found the effects of sepsin similar to that of sul-
phate of atropia, he injected a small amount of that drug with
the organisms and found that, under these conditions, they
grew and produced sepsis. It is difficult to see how the sul-
phate of atropia could aid the bacteria otherwise than by
paralyzing the tissues temporarily, preventing their resistance
until the organisms had established themselves. A number
of other experiments have developed facts of a similar nature.
Gradle says, page 123, " We do not know whether putre-
factive bacteria exert any direct influence upon the exposed
tissues. Even if that be not the case, the products of decom-
position which they engender irritate the wound in an unmis-
takable manner. This is seen in the redness and sensitiveness
of the margins of the wounds. . ... These bacteria
are always overcome by the tissues."

INFLAMMATIONS.

The question as to whether we ever have the formation of
pus without the presence of micro-organisms, has been much
discussed, pro and con, of late years, by men standing high
in the medical profession. It has even been contended that
we never have inflammation without them, notwithstanding
the well-known effects of the blister and the mustard plaster.
Did it ever occur to any, that in the blister and the mustard
plaster, we are making use of an irritant that has been pre-
pared for us by the life force, and is, to say the least, closely
akin to the irritant that we would expect from the disease-
producing organisms? But have we not mineral irritants,
and may we not produce inflammation by their use? Is not
pus a result of inflammation ? I am not unmindful of the
fact that there are several theories explaining the production

144 THE GERM THEORY OF DISEASE.

of pus; and that pus does occur under some conditions in
which the presence of inflammation, at any time previous to
its formation, is extremely difficult of demonstration. Yet
I am of the opinion that there are very few surgeons to-day
who do not regard the formation of pus as one of the results
of inflammation, and who will not naturally expect the
formation of pus to result in case of prolonged and intense
inflammatory action.

Still, the formation of pus does not necessarily occur as a
result of every severe inflammatory state; and some recent
experiments by M. I. Straus and others, in both France and
Germany, seem to show that pus will not form in inflammation
artificially excited, if micro-organisms be excluded. Other
experimenters have had other results, and the question is not
yet settled by the experimental method ; and we might with
some reason say that it cannot be so settled, until the methods
of experimentation approach more nearly perfection than they
seem to be at the present time.

However, just so long as we regard the formation of pus
to be a result of inflammation, must we expect that pus will
be formed without the presence of micro-organisms. If this
is not the true explanation of this phenomenon, if future
developments should demonstrate that these two processes are
not related to each other as cause and effect, then it may,
possibly, be shown that pus cannot form without the presence
of micro-organisms.

At the same time it must be admitted that the formation of
pus is generally accompanied by the development of micro-
organisms, and that their presence facilitates pus formation.
This is clearly the result, not of temporary, or a single appli-
cation of an irritant, but of the continuous irritation by the
secretion or excretion continuously given out by the organ-
isms ; and we have no reason, that I know of, to suppose that
the result would be much different if the same products of

BLOOD DISEASES. 145

these life forms could be gathered and continuously distributed
in the tissues artificially.

In many of Straus' experiments, and others of this class
referred to above, agents were introduced that evidently
paralyzed the tissues, and as pus formation is a vital act, it
was necessarily prevented. Every such element must be
rigorously excluded from our experimentation before the
results can be depended upon as conclusive.

BLOOD DISEASES.

The production of disease, however, is not limited to in-
flammation and pus formation. Many of the diseases now
supposed to be parasitic in their causation are not essentially
inflammatory, but are known as systemic or blood diseases.
This class of diseases are not caused by any simple irritant, but
by some toxic element developed by the organisms. As to
what this toxic element may be we have only conjecture, but
after what we have just said in reviewing the waste products
of the various life forms, this conjecture is a close approach
to knowledge. The elements of the compounds are pretty
certain to be written C H N O, in varying equivalents. It is
possible that the N may be left out of some, or that the O
may be left out of others. But this is not very probable.
We know enough of the alkaloids, to know that they may
become a potent cause of disease, if developed continuously
in the blood or tissues.

It may be said that we know of no alkaloids that will
produce the effects shown in the diseases that we see
around us. This is very true. A few years ago we knew
of no alkaloid that would produce the effect of woorara, or
quinine, or atropine, or strychnia; and when we have dis-
covered others, and have learned their effects, they will be as
easily understood as those now known to us. That systemic
disease may result in this way, is not only possible, but it

146 THE GERM THEORY OF DISEASE.

seems very probable that this will be the final solution of
the problem. Indeed, we may say that from all that is now
known, this seems certain. But it is not from the formation
of the alkaloids alone that we will find these effects produced.
The organic acids will be found to have their share in the
work; also various irritants, and the digestive bodies de-
veloped by the organisms. It will be found that, all of these
products are formed together and do their work together,
producing the complex results that we see in the complicated
forms of disease so frequently met with.

While the mere physical presence of organisms will in no
case account for the effects ascribed to them in the production
of disease, they cannot be entirely ignored. When bacteria
or micrococci are gathered together in groups and large
masses (zooglia) in the tissues, they will certainly have some
evil influence by their mere presence in such situations,
especially when this happens to be in important organs.
Also, the fixed material laid up in these cells may, after the
death of the organisms, have its influence. But I am per-
suaded that neither of these causes is the potent factor in the
production of disease.

I would not have you suppose, however, that we can have
no disease without micro-organisms. Man may be abused by
the life forms around him, and man may abuse himself. He
may eat too much good food and suffer in consequence. He
may injudiciously expose himself to the inclemencies of the
weather, and start serious inflammation of important organs.
He may exhaust his energies by overwork, and suffer all the
consequences that anaemia brings in its terrible train. He
may suffer from faults in the physiological activity of his
own tissues, from neoplasms, as cancer sarcoma, lipoma, and
very many other affections that the micro-organisms do not
have to answer for.

APPENDIX.

DENTAL CARIES.

ITS EELATIONS TO THE GERM THEORY OF
DISEASE.

Many theories have been advanced, in times past, to account
for caries of the teeth. Most of these have been vague and
indefinite, and have passed away with the advance of time.
About the beginning of the present century the vital theory,
as it was called, was prominent. By those who held this
theory, caries was supposed to result from an inflammation of
the structure of the dentine, which terminated in the final
breaking down of the part ; and as this structure is incapable
of physiological repair, a cavity was the inevitable result.
This theory seems to have been very thoroughly disproved by
the following considerations. It was observed that artificial
teeth, constructed of ivory, bone, sheep's teeth and human
teeth, were as liable to caries as the<natural teeth ; and that
this decay was, to all appearance, the result of similar, if not
precisely the same causes. This, of course, could not be the
result of vital forces existing in the structure undergoing the
process of decay. The conditions of the decaying portions
were very closely studied, to see whether or not anything
could be discovered that would show that these processes were
essentially different from each other. Some differences were
found, but the more they were studied the more evident did
it seem that these differences were not of such a nature as to
show that the processes were in any wise distinct from each
other. These studies caused the abandonment of the vital
theory; for, if dead substances decayed the same as living
ones, the forces which bring about the result must be other

149

150 THE GERM THEORY OF DISEASE.

than the vitality of the suffering organ, and therefore cannot
be the result of inflammation; it must be some force external
to the tooth, something which attacks the tooth from without.
This point seems to have been very thoroughly established,
and we supposed it was well settled in the minds of all
modern thinking men. But, curiously enough, the old notion
has recently been revived by certain gentlemen in New York.
The effort to maintain such an hypothesis, however, must
inevitably result in failure ; for in it there is a plain want of
consideration of the known facts of the subject. It need not,
therefore, detain us longer.

Caries of the teeth has been defined as a molecular disinte-
gration of the tooth's substance, or a breaking down of the
chemical constituents of the tooth, molecule by molecule.
This destruction always has its beginning on the surface of
the tooth, or in some pit, crevice, or other imperfection in the
enamel. And it spreads from this point, as the focus, in
every direction, the dentine being destroyed more rapidly
than the enamel ; hence, it usually happens that the cavity is
larger within than on the surface of the tooth. Caries does
not seem to be a simple solution of the tooth's substance;
sometimes we find nearly all of the material removed from
the cavity, in other cases we find the dentine reduced to a
pulpy or semi-gelatinous mass, in which the structure of the
dentine is more or less perfectly preserved. Some decays are
white, some are black, some have a yellow tinge — all the
shades from white to black may be found. But it was not
my intention to give a lengthy description of the results of
caries, but rather to confine myself as closely as possible to
the discussion of the probable cause of the affection ; I say
probable cause, for I do not assume that the cause or causes
are certainly known. Indeed, we may say that at the present
time there is the greatest disagreement among even the best

DENTAL CAEIES. 151

informed men on this important subject; and that it is still
very uncertain that any of the theories in regard to the matter
are correct. It is proper that I should say, however, that
more than one of these explain the phenomena with sufficient
accuracy to be of great value, both in the prevention and
treatment of this affection. It must not be supposed that a
theory must be absolutely correct to be of use. Theories are
usually contrived in the effort to explain phenomena, and it
often happens that a false theory leads to as good an applica-
tion of means to ends as the true one would do. Of this,
however, we can never have any assurance; therefore, as long
as there is a reasonable doubt the search for the truth should
continue.

The theory for the explanation of caries which has received
the greatest attention and the widest recognition in modern
times, is what is known as the acid theory. This theory seems
to account for the phenomena more perfectly than any other
that has as yet attained prominence in the minds of thinking
men. As a working theory, a basis upon which to found
principles of treatment, it has undoubtedly been the means of
good. Yet, in the scientific aspect of the subject, there is
much objection to be urged against it. A very large amount
of work has been done with the view of demonstrating the
absolute truth of this theory, all of which must be regarded
as a failure, so far as the attainment of that particular object
is concerned. The labor has not been lost, however; but, on
the other hand, has been of immense value. It is this labor,
the basis of fact which it has brought to light, that will be of
most service to us in the building up of other theories for the
explanation of the phenomena, which may serve us usefully,
until such time as theories shall be displaced by demonstra-
tion, the goal to which we are all looking forward.

According to the chemical theory, the substance of the

152 THE GERM THEORY OF DISEASE.

tooth is decomposed by an acid ; this acid acts more readily
on dentine than upon the enamel, therefore the tendency to
the enlargement of the cavity toward the internal portions of
the tooth. Some writers, as Dr. Watt, have attempted to
define the acids thus acting, and to divide decays into
classes, according as this or that acid is active in its produc-
tion. The acids that have been thus pointed out are: Nitric
acid (white decay), Sulphuric acid (black decay) and Chloro-
hydric acid (intermediate colors).

Most of those who have written on this subject, however,
have been content without specifying the particular acids so
definitely; while some have been of the opinion that these
particular acids have little or nothing to do with the matter,
and seek to show that other acids are more likely to do the
ugly work.

The origin of the acids which produce caries has been a
subject of much inquiry. A great amount of labor has been
bestowed upon this point. It has been supposed that the
saliva contained it, and very careful examinations have been
made in this direction, which have contributed to our know-
ledge of this secretion, but have thrown very little light on
the point in issue, other than to demonstrate that the cause
of decay is not to be found in this direction. It has shown
that decay occurs in mouths in which the saliva is habitually
normal; and that decay does not occur in some mouths in
which the saliva is habitually acid.

The hypothesis that the acid is furnished upon the spot,
through the decomposition of the food lodging between the
teeth, or in crevices and imperfections in the enamel, seems
much more feasible, and gives a much more satisfactory
explanation of the phenomena. According to this hypothesis,
the acid is formed in juxtaposition with the portion of the
tooth suffering from its effects, even within the cavity itself,

THE GERM THEORY OF CARIES. 153

while the general fluids of the mouth may be neutral, or
even alkaline.

The manner of the production of this acid has been a
subject of much inquiry. All, I believe, admit that it must
come in some way through fermentation or decomposition ;
at any rate, through a rernoleculization of the substances
lodged about the teeth. This leads directly to the discussion
of the much vexed question of the fermentations and de-
compositions, and the relations of the life force thereto. The
research of the last few years leaves but little doubt on this
point. These processes are the result of the activity of living
organisms. The teachings of Liebig on this subject may now
be regarded as disproved. With this point settled, the old
acid theory glides easily into the new germ theory, and we
may recommence our studies from the new standpoint we
have gained, carrying with us all the facts that have been
developed to guide us on our way.

In the study of this subject many new questions spring to
the front, and demand a hearing. Most of these have been
discussed in a former lecture ; but it now remains for us to
study their application to this particular subject. Before
doing this, however, it will be well for us to make a hasty
review of the discussions that have been had in comparatively
recent times on this point.

THE GERM THEORY OF CARIES.

Who may have first suggested that caries of the teeth is
caused by living germs, I have no definite knowledge. The
first work of importance upon this subject was by Lieber and
Rottenstein, in Germany, which appeared in 1868. These
gentlemen, in the prosecution of their studies of this question
came to the conclusion that caries must result from the
activity of micro-organisms through the production of acids.

154 THE GERM THEORY OF DISEASE.

This acid was, of course, produced in the process of fermenta-
tion; but in the light of the developments of the last few
years, their observations seem vague and very indefinite.
They attributed this result to leptothrix buccalis. The ob-
servations upon which their views were based were given at
length ; so that we are able to follow them through all their
operations, and from the care with which these were con-
ducted, judge of the merits of their deductions from them.
When we pass their work in review carefully, we must admit
that it is wanting in that extreme care that is necessary in
investigations of this delicate nature; especially is this the
case when we examine the work in the light that succeeding
years have thrown upon investigations of this class. In fact,
the modes employed in such work have been completely
revolutionized since this work appeared ; and as the general
nature of such work has been discussed in a previous lecture,
and its progress described, it need not detain ns now.

Notwithstanding the evident errors of the work of Lieber
and Rottenstein, it undoubtedly made a deep impression on
the thought of the dental profession ; and this question has
not been lost sight of for an instant. While the opinions
given were not accepted, and were, apparently, quickly dis-
proved, it lent an impetus to the study ; and though no great
work has appeared, it has been progressing in an intermittent
way, until now the profession seem to be ready to receive any
work on this subject that will bear reasonably rigid criticism.
Such a work is, fortunately, now appearing, from the pen of
Dr. Miller, who, though an American, is working in the
laboratory of Dr. Koch of Berlin. Dr. Miller is, fortunately,
in the very best position possible for the performance of this
difficult form of investigation ; and the papers that have
already appeared from his pen give much encouragement that
he will succeed in working out this subject, and in giving us

THE GERM THEORY OF CARIES. 155

the underlying facts that have so long enshrouded the cause
of caries of the teeth in mystery.

But in this we are anticipating. There is another work
which demands examination before we pass to this. The
views of Dr. Watt have received much commendation in this
country, but not so in the old. There, other men have been
prominent, and we find that while they have agreed in the
main, there are important differences between them. As we
have said, Dr. Watt has maintained that decay is caused by
the acids, nitric, hydrochloric and sulphuric, with possibly
others. In Europe the influence of these particular acids
has been very generally denied ; and the results attributed to
other acids, as the lactic, acetic, and the group known as the
organic acids. Among those that have examined this subject,
none, perhaps, have attained a wider hearing than Magitot,
of Paris. This gentleman published a work on this subject
in 1868, in which he makes an extended examination of the
subject, arriving at the conclusion that decay is caused by
acids. These acids, however, are derived from the saliva
through the process of fermentation. Dr. Magitot instituted
a long series of experiments to determine the effects of the
suspected acids on the teeth. This series of experiments show
that most of the organic acids act very feebly on the teeth
in the proportion of one to one thousand of water; and that
in the proportion of one to one hundred they act quite
energetically ; so that the teeth submitted to their action will
be completely decalcified within a few weeks or months.
Most of this series of experiments were continued, however,
for two years. The conclusion seems to be that caries may be
produced by any of the group of acids that may be developed
by the fermentation of the saliva ; these are the lactic, acetic,
butyric, etc.

Dr. Magitot states distinctly, that the agency of micro-

156 THE GERM THEORY OF DISEASE.

organisms in the production of these acids is admitted by
him, but discusses this phase of the subject no farther. He
makes no effort to determine to what extent these acids may
be formed in the mouth. All of his experiments were tried
out of the mouth, and no provision whatever was made to
ascertain the effect that fermentation may have had on his
solutions in the progress of his experimentation. This being
the case, the only result of the experiments is the determina-
tion of the strength of the solutions of these different acids
necessary to decalcify a tooth.

This, together with the facts obtained from other sources,
showing that most of these acids are the products of certain
fermentations that may go on in the mouth, gives much force
to Dr. Magi tot's conclusions.

Very soon after Dr. Magitot's work, in the same year,
indeed, came the work of Lieber and Rottenstein, to which
we have referred. The work seems to have been written for
the express purpose of showing that decay of the teeth is
caused by the life and development of the fungus known as
leptothrix buccalis. In this the authors seem to have signally
failed. They certainly make but little advance toward the
demonstration of the parasitic theory of this affection. Indeed,
they do not seem to have endeavored to show that this fungus
does more than promote decay that has already become
established.

They say, after having made an extensive examination of
the life and growth of the leptothrix, " from what has been
said, it results that two principal phenomena manifest them-
selves in the formation of dental caries, viz., the action of
acids, and the rapid development of a parasitic plant, the
leptothrix buccalis." They do not suppose the leptothrix
buccalis capable in itself of attacking the teeth, if their con-
dition be normal, but when their surfaces are once softened

THE GERM THEORY OF CARIES. 157

by acids, then the fungus may penetrate the portions thus
softened and continue the destruction. Again, they say, " It
see~ras that the fungi are not able to penetrate an enamel of
normal consistency. The dentine itself, in its normal condi-
tion of density, offers great difficulties to their entrance, and
we are not yet sure that the leptothrix could triumph over
this resistance." Again, " We cannot decide at present if
the leptothrix is able to penetrate sound dentine, when from

nny circumstance it happens to be denuded

But, if the enamel or dentine are become less resistant at
any point, through the action of acids, or if, at the surface of
the dentine, a loss of substance has occurred, then the elements
of the fungus can pass into the interior of the dental tissues,
and produce by their extension, especially in the dentine,
effects of softening and destruction much more rapid than

the action of acids alone is able to accomplish

The participation of the fungus is constant in the progress
of caries which has reached this stage. As soon as a loss
of substance can be shown, there is found the presence of
the fungus, so that the question whether or no the acids
alone could produce ravages more considerable is without
importance."

The modus operandi by which leptothrix may produce
softening of the dentine is left without explanation. We can
conceive, however, that they may do something to assist the
softening process by the outpouring of a digestive fluid. If,
however, this fungus gave a fluid that would digest a tooth,
we would think that sound teeth would be very scarce, for it
grows abundantly in every mouth.

Since the time of Lieber and Rottenstein's work we remem-
ber of no other of much importance having appeared on this
subject. The discussion has continued, however, in the jour-
nals. We cannot now undertake to review this literature,

158 THE GERM THEORY OF DISEASE.

interesting as it would be, but must content ourselves with
one writer, Dr. Miller, now of Berlin.

Dr. Miller's experiments bear the stamp of being more
carefully performed than any that have previously come to
our knowledge. This was to have been expected, from the
fact that they are the latest, giving the experimenter the
advantage of all that has gone before; and for the reason
that he is very favorably placed for such work, being in the
midst of the best experimenters of the world. Therefore his
work is looked to with unusual interest.

We need not, however, notice any but his last series of
articles, that which is now appearing. We cannot, of course,
criticise Dr. M/s work now, for we have not heard him
through ; but enough has appeared to show very clearly
what the result will be.

Dr. M. begins this series of articles with this sentence:
" During the last two years I have stated at different times
and places, as the result of many experiments, that 'the first
stages of dental caries consist in a decalcification of the tissues
of the teeth by acids, which are, for the greater part, generated
in the mouth by fermentation.7 The object of the investiga-
tions described in this and the following papers, is to deter-
mine this ferment, and the conditions essential to its action."

We see from this, that Dr. Miller begins just where Dr.
Magitot left off sixteen years ago. The discussion of the
subject during these years has given us no additional facts, as
to the essential nature of these phenomena ; but the advance
of thought in reference to the general subject of such investi-
gations has been such that no man would now repeat Dr.
Magitot's course of experimentation with the same end in
view.

I will give a very brief synopsis of Dr. M.'s course. And
while I do so, I wish you to keep in mind the object he has in

THE OERM THEORY OF CARIES. 159

view. It is admitted that decay is brought about by acids,
developed, or Dr. M. supposes them to be developed by fer-
mentation of some kind. The object of this course of experi-
ments is to find and examine this supposed ferment.

It is not necessary that I should describe in detail all the
apparatus with which the experimenter provided himself; it
is sufficient to say that all the appliances for the prevention
of error were used. The first question to determine was
whether or not the ptyaline of the saliva could so change
starch as to produce an acid. This question was soon decided
in the negative. The starch was promptly changed into sugar,
but here the reaction ceased ; the fluid remained permanently
sweet when the proper precautions were observed to prevent the
ingress of germs. This proves that the acidifying power does
not belong to the saliva. It must then be something foreign.

Now, a freshly extracted carious tooth was taken, all food
removed, the outer portions of the decayed mass saturated
with a ninety per cent, solution of carbolic acid, to destroy
any accidental germs that might be in this portion. Then,
with an instrument, purified by heat after each cut, layer
after layer of the softened dentine was removed until the
inner portions were reached. Then a slice was quickly con-
veyed to a sterilized culture medium, composed of sterilized
saliva, water, sugar and starch, and placed in an incubator,
together with another test-tube of the same culture fluid un-
infected, to serve as a check. In twenty-four hours the
infected culture became acid, while the other did not. This
remained constant in a sufficient number of experiments to
establish the fact that the acidity was due to the infection.
From the cultures that had become acid, other cultures were
infected, which also became acid, thus proving that the ex-
perimenter was dealing with a ferment that was capable of
propagating itself; an organized ferment.

160 THE GERM THEORY OF DISEASE.

Microscopic examination showed that these cultures con-
tained an organism similar to those found in the deeper layers
of carious dentine, and which remained constant in their char-
acters. Chemical examination, which seems to have been
very carefully conducted, showed the acid produced to be
lactic acid. This acid has been shown to be capable of de-
composing the teeth by M. Magitot and many others. Yet
Dr. Miller goes still further, and by placing sections of
dentine in his culture fluids that he has infected, finds that
they are decomposed by the acid formed ; while such sections
placed in such fluids not infected are not changed. Thus he
not only proves that an acid is formed, but that the acid is
formed in sufficient amount to destroy the dentine.

This, when compared with the best experimentation previ-
ously had, marks a great advance. One point seems to have
been gained. One organism has been traced thus far, and
may now be said to have been proven to be able to produce
certain of the phenomena of decay. But this is not all.
There is much yet to be done. True, one other point is
spoken of by Dr. Miller. All who have made a careful
study of caries know that there is a peculiar enlargement of
the tubules, which is not seen in dentine softened by acids
alone. Dr. Miller has been looking for this also, and not
without success; for in some sections of dentine exposed to
the action of the cultures, he found the organisms crowding
into the tubules, and tells us that he also found them en-
larged, as in natural caries of the teeth in the mouth ; indeed,
that he had before him veritable caries, artificially produced.

This delineation of results of experimentation must have
great weight in the settling of the problems at issue ; especi-
ally if they are confirmed by other competent observers.
There is nothing in these experiments that is not in harmony
with known facts, unless it be the widening of the tubules by

THE GERM THEORY OP CARIES. 161

the crowding in of the organisms. It is known, by previous
experiment, that this widening is not caused by the lactic acid
as it exists dissolved in the surrounding medium. And I think
very few will be willing to concede that the organisms can
accomplish this by physical force. This point requires further
investigation, and its study will doubtless lead to further dis-
coveries. However, we think it may be explained in advance;
at least, the effort may serve to direct experimentation.

In a previous lecture we have dwelt at some length upon
the digestive fluids of living organisms. Unexpectedly we
find use for these ideas now, for they were written before we
saw Dr. Miller's last article. I have explained how it is that
dead bone, roots of the temporary teeth, ivory driven into
the flesh, catgut ligatures, sponge, etc., are dissolved and
removed by a soluble ferment. I have also shown that the
soluble ferment of the yeast plant has been found and proven :
also that of ammoniacal fermentation; and how plants* take
up otherwise insoluble substances. Now this widening of the
tubules is a conceded fact. It is also shown that it is not
done by the lactic acid in case of other experiments ; nor can
it be done by the physical force of the organisms; but it can,
in all probability, be done by the digestive fluid of the organ-
ism. The conditions for this work of the digestive fluid is
the same as that of the granulations in widening the meshes
of the sponge and finally removing the last of it. As yet
no such soluble ferment has been demonstrated in connection
with this organism; but theoretically it must exist, and if
Dr. Miller should undertake to search for it, he will be able
to demonstrate it speedily, and determine its co-operation in
producing some of the phenomena of decay. At least, de-
termine its capabilities.* This organism cannot be said to

* Since the above was written Dr. Miller has also reported the finding
of another micro-organism that he thinks capable of producing caries.

162 THE GERM THEORY OF DISEASE.

have been definitely and completely studied until this soluble
ferment, or diastase, be found, isolated, and its capabilities
separately determined.*

It is by no means probable that this is the only organism
that may stand in a causative relation to caries. The organ-
ism of butyric fermentation, possibly that of acetic fermenta-
tion, and a large number of others of the acid fermentations
may cause decay; nor is it by any means a settled fact that
decay of the teeth may not be brought about in part by other
vital processes than the acid fermentations. Of this, how-
ever, we will speak later.

Another question may arise in this matter, and need ex-
planation. I have repeatedly said that the waste products
of an organism prevented the activity of that organism, when
collected in a certain amount. How, then, can this organism
continue to thrive in its own waste product, and thus con-
tinuously promote caries by furnishing more, and still more,
of this waste product? Simple enough. Every chemist who
has studied lactic fermentation has been in the habit of intro-
ducing some form of lime into the fermenting fluid to "fix"
the lactic acid in the form of a lactate of lime, in which case
it does not hinder the progress of the fermentation. In this
way a much larger amount of the lactic acid may be obtained,
as it is readily regained from its salts. This was learned long
before the organism was found. Now in the production of
caries, the tooth presents the lime for the formation of the
lactate, and thus furnishes the very conditions necessary to
the continuous growth of the organism.

In this connection, I wish to call attention again to a diffi-
culty that has ever existed in the study of the action of
organized germs in producing impressions of whatever kind,

* Since the above was written Dr. Miller has reported the finding of
this soluble ferment.

THE GERM THEORY OF CARIES. 163

whether it be illness or the disorganization of structures.
The power of the life force is always manifested in the remo-
leculization of matter. The chemical forces of matter are
the playthings of the life force. The molecule is compelled
to admit other elements, is split in twain, is torn to pieces for
the formation of other molecules of a different character ; and
finally, it is cast aside, so changed in its molecular and physical
characters that it is unrecognizable as the same, outside of the
chemist's laboratory. Life is an immaterial force, but its
dealings are with the material. In the study of the questions
now before us, it is with these remoleculizations of matter
that we have to deal. The mere physical power of these
low organisms, while in some peculiar positions it may
amount to something, may, as a rule, be left out of the
count entirely.

If micro-organisms decompose an organic body, they do so
by furnishing, through their remoleculizatious, a chemical
substance capable of acting on that body. And, furthermore,
this substance may, and generally is, produced by the remo-
leculization of the elements of the organic body being decom-
posed. Bacterium lactis lives at the expense of starch or
sugar.

If micro-organisms cause an illness, a fever, or an inflam-
mation, it is because that organism, in its remoleculizations of
matter, elaborates a toxic substance capable of producing
these results. What is the source of the greater number of
the toxic substances known and used in the medical world
to-day ? Take strychnia, opium, quinia, rhubarb, aconite, vera-
trurn, atropia, nicotine, and a host of others ; are they not
the results of remoleculizations by the life force as manifested
in plants ? Then take alcohol, ammonia, succinic acid, pro-
piouic acid, lactic acid, and many other toxic and irritant sub-
stances, are they not the result of remoleculizations, brought

164 THE GERM THEORY OF DISEASE.

about by the life force, as manifested in the form of micro-
organisms? Does anyone pretend that all of the toxic bodies
elaborated by micro-organisms have been found, and their
effects on the animal economy made out? Certainly not.
Then we may expect to find others, if we make the search.
It seems certain that every organism that is hurtful to man,
is so by the elaboration of some substance that has toxic or
irritant properties.

As we have said, we have no doubt that there are other
micro-organisms than the bacterium lactis that may be instru-
mental in the production of dental caries. Nor do we think
that it is necessarily only acid-producing organisms that may
produce caries or some of its phenomena. This, however,
need not be discussed now.

I wish now to turn your attention for a moment to another
class of phenomena, and make some inquiry into their possible
participation in the production of caries. I have already
spoken of the strong probability that the otherwise normal
tissues, when under the influence of certain qualities of inflam-
mation, emit a fluid of acrid and very irritating properties.
About the necks and other parts of children we sometimes
see this fluid excoriating the skin wherever it touches it,
seemingly acting the part of a caustic. I have already
referred to the fact that dead bone, ivory driven into the flesh,
sponge, catgut ligatures, etc., are dissolved and removed. This
causes us to inquire whether or not a substance may be
elaborated in the same manner in the mouth, that may have
its quota of effect in the production of the phenomena of
caries.

I was thoroughly convinced that this was the case years
ago, though I endeavored to explain the results by the
assumption that an acid was formed. This is entirely un-
necessary. Soluble ferments do not seem to depend for their

THE GERM THEORY OF CARIES. 165

action on either acidity or alkalinity. They seem to be con-
trolled by some other than the known chemical laws, and
their action is not yet understood. We have no means of ex-
plaining them. If a piece of ivory thrust into the flesh is
attacked and burrowed out in holes by a secretion thrown out
by virtue of the irritation induced, as asserted by Krause,
Kolliker and other of the most capable observers of the
world, why may not a tooth be attacked in the same way, by
virtue of an irritation of the tissues about its neck or during
the irritation consequent upon its eruption when this is
unusually prolonged? As a matter of fact, it has been ob-
served that decays are very prone to occur in just such situa-
tions as tend to confirm this hypothesis. Thirteen years ago
we drew attention to this in a paper before the Illinois State
Dental Society. Both before and since that time I have
given much attention to this point, and I am more than ever
convinced that it has much to do with the beginnings of de-
cay. I do not wish to be misunderstood in my view of this
matter. It is not my notion that decays are initiated by this
cause alone. It is only one of the first steps by which other
forces which come later are rendered operative. The means,
if you please, by which the surface of the tooth is first broken,
and by which organisms are permitted to find a lodgment.
Not a means by which a decay is carried on to the complete
destruction of the tooth. This effect cannot be produced ex-
cept while the tissues are in contact, or in very close proximity
to the part in process of solution, for the reason that the
secretion from the tissues would be dissipated in the fluids of
the mouth before they could have time to produce their
effects upon the tooth structure.

The positions at which these results are seen are — wisdom
teeth, that come through very slowly ; on the buccal surfaces
of the molars generally ; and sometimes on the labial surfaces

166 THE GEEM THEORY OF DISEASE.

of the upper incisors. In case of the wisdom teeth, the fact
that they are very often decayed before they are fully through
the gum is especially remarked ; and as a rule, if these decays
are carefully noted at a very early period of their progress,
it will be seen that they are different from other decays in
several respects. It always has its beginning under the free
margin of the gum. There is usually no change whatever
in the appearance of the tooth; the eye discovers nothing.
The surface seems normal, or, at most, the portion of the
tooth appears rather whitish ; but on trial with the excavator
the instrument will, apparently, break in through the enamel
prisms, disclosing a cavity of very slight depth. It often
happens that the enamel may be easily scraped away over a
considerable space, as though it was so much chalk. The
depth will present much variation ; often it is only a part of
the thickness of the enamel, at other times we may find it
extending into the dentine, in which it forms a veritable
cavity. If there is much depth, however, the characteristics
will have assumed the more usual type.

Occasionally we see this character of decay (if it may be so
called) in the grinding surfaces of the wisdom teeth ; occa-
sionally in the first molar also, where the tooth has come
through very slowly, and the gum has been for a long time
in a state of chronic irritation. It is characteristic of this
effect that it is as often seen on the smooth surfaces of the
teeth as in the pits and grooves. No imperfection is necessary
to prepare the way for this manifestation.

As we have said, this takes place under the gum ; is covered
by the gum. Now, as the tooth rises higher and the surface
thus affected becomes exposed, these spots are prone to become
the seat of true caries, with all of its usual manifestations.
However, very often caries does not take place. In this case
a whitish spot is seen, which gradually assumes a yellowish

THE GERM THEORY OF CARIES. 167

tinge, then brownish, and finally becomes black. This result
is brought about by the settling into, or the formation in, the
affected tissue of the black sulphurets ; as I was the first to
show. (See Report on Dental Chemistry, by Dr. H. A. Smith,
Transactions of the American Dental Association, 1874,
page 78.)

We see these spots every day upon the sides of the molars,
in every stage of coloration, from ashy white to a deep black.
They are as apt to be on the otherwise smooth surfaces as in
the pits and grooves. They may occur on any of the teeth,
but are oftenest seen in the positions named. - The decays
that so often occur on the labial surfaces of the upper in-
cisors, are often, though not uniformly, of the same character.

Those decays that occur just at the junction of the enamel
and cementum, in persons of middle age or past, also, occa-
sionally, in younger persons, in very many cases, seem to be
of the same character. Some irritation of the gum at the
immediate spot seems to be one condition of their beginning.
These also have some special characteristics not common to
other decays. If they are closely examined very early, in
their inception, it will be found that the cementum has been
removed and that the margin of the enamel has become
chalky. Soon after this, if the case continue to progress, the
gum, which till now was closely applied to the part, becomes
everted so as to expose the breach in the tooth. This often
becomes the seat of the most exquisite sensitiveness just at
the present stage of the process, which calls the attention of
the patient to the spot. Generally, however, nothing can be
seen by either patient or operator, except a slight eversion of
the gum, and the slight grooved appearance of the neck of
the tooth, which the operator is often puzzled to differentiate
from the normal form of the tooth. However, if he will
carefully press the gum away (and he will find this abnor-

168 THE GERM THEORY OF DISEASE.

mally sensitive) until he can see the root of the tooth below
plainly, it will be easy to demonstrate that there has been a
decided loss of substance. Trial with an instrument will
develop the fact that the surface within this groove is ex-
ceedingly sensitive; the dentine is exposed.

Now, if the case is left to itself, this sensitiveness will
continue for some weeks, or even months, and then abate ;
and it will be found that the case has taken on the usual
characters of decay. It may cease to progress and assume
a dark color, or it may progress rapidly, and remain of a
more or less ashy cast.

It has been our opinion that this class of decays, if that
term can be applied at this stage, is brought about in pre-
cisely the same way that the root of a permanent tooth is
partially absorbed on account of a chronic irritation of its
peridental membrane. In other words, a soluble ferment has
been called out by the irritation that has dissolved out a part
of the tissue at that point. Or, if you prefer to have it put
in that way, a true absorption has taken place which forms
the nidus for the future decay.

Another class of decays are very common, which I have
studied very closely, and which seem to be of the same
character in their inception. These begin under the free
margin of the gum, under plates that abut closely against the
teeth. These are usually very rapid in their course, evidently
for the reason that as soon as the free margin of the gum is
everted, a pocket is formed by aid of the plate, in which fer-
mentation can proceed to the very best advantage. It does
not seem that the beginning of this decay is often after the
eversion of the gum has uncovered the spot. Of course we
often see decays occur where clasps encircle the teeth that are
high up on the crown. Such must not be confounded with
those that begin at the margin of the cementum.

THE GERM THEORY OF CARIES. 109

A question of great interest here, and the findings of Dr.
Miller make it doubly so, is the composition of the fluid that
is instrumental in the absorption of bone. I believe that I
have already referred to the opinion of Krause, and others
who regard it as containing lactic acid as its active principle.
Krause bases this opinion on the behavior of the tissue form-
ing this substance toward staining agents. From his experi-
ments, it seems quite certain that the substance has an acid
reaction, but the particular acid seems to me to be undeter-
mined. The action that we see in the absorption of the roots
of the teeth is not the action of lactic acid alone. This acid
dissolves the lime salts only, leaving the tissues of the tooth
behind in the normal form, as has been well shown by Magitot
and many other capable experimenters.

This, of course, excludes the lactic acid as the exclusive
agent in the work. Nevertheless, the secretion may contain
this acid in combination with some other active principle.

INDEX.

A PAGE

Absorptive digestion 82

Absolute demonstration demanded 68

Alcohol — isolation of. 18

early distillation of. 18

Amo3boid theory of contagion 57

Antiseptics — first explanation of. 19

Antiseptic treatment introduced by Mr. Lister 41

in hospitals 42

success of. 56

Aniline staining .* 62

Alkaloids— consideration of. 118

are waste products 118

components of the 118

natural salts of the 126

isolation of the, necessary 127

relation of the alcohols to the 126

" of the organic acids to the 126

solubility of the... 126

Antiphlogistics 16

Appendix 147

Archebiosis 35

Astier's discoveries 19

Athenian plague 12

B

Bacillus Anthracis 61, 90, 127

Bacteria — Beale's views of. 57

difficulties of distinguishing varieties 38

consideration of the waste products of. 120

how they destroy a carcass 121

many of the, incapable of producing disease 39

regarded as scavengers 39

supposition as to, in open wounds 41

the accompaniments of disease, not the cause 52

the active agents in decompositions 41

their power of remoleculization of matter.... 120

poisons formed by 124

Bacterium lactis — artificial elimination of the waste products of. 122

" in soup 136

termo in blood 84

Bastian on the origin of life 35

Beale on disease germs 57

Berthelot , 84

Black death, the 13

Blood diseases 145

171

172 INDEX.

PAGE

Caries of the teeth 149

k< agency of the soluble ferments in 164

acid, or chemical theory of. 151

" B. lactisin 160

" color of 150, 166

" denned 150

" germ theory of 106

u origin of acids supposed to cause 152

widening of tubules in 160

" vital theory of. 149

Carter, Dr., of India 97

Cells — the relative power of. 114

Cellular digestion in the higher animals 98

Century— the 19th 17

Changes in the products of micro-organisms 134

Chemical changes ia putrefaction — Gradle 130

Cohn's classification of micro-organisms 40

Contagion — amoeboid theory of. 57

Beale's views of 57

first notions of. 12

modes of communication , 73

origin of. 59

not a fermentation 57

Cotton as an air filter 28

Cultures — dry slide 66

fluid employed by Pasteur 33

inoculations made from pure 67

" objections to flask 66

D

Diastase 92

" effects of, on starch 92

Decomposition — agents of. 32

Decompositions, contagions and miasms of the same class as the

fermentations 38

Denovo — origin of life 35

Difficulties of the germ theory 27, 38

Discovery of the yeast plant 20

Digestion — absorptive and resorptive 82

by the yeast plait 84

by the germs of seeds 91

by the germs of tubers 92

by the higher plants 89

by the micrococcus urea 89

cellular, in the higher animals 98

extraneous to the body 82

example of without a stomach 84

experiments by Sachs 90

of blood clot 100

" " ivory 105

INDEX. 173

PAGE

Digestion of ligatures 101

" necrosed bone 104

" solid food by bacteria 86

" sponge in the sponge graft 102

" the roots of the milk teeth 99

primary 82

propositions relating to 81

type of, in unicellular plants and animals 85

Direct examination for microscopic organisms 44

Disease Germs — Beale's views of. 57

relation of the white corpuscles to 58

E

Early discoveries 18

Effect of plagues on civilization 13

Schwan's discoveries 21

" Schroeder's discoveries 41

Evidence — nature of. 43

fractional 45

unsatisfactory 45

Excretion in plants 117

by roots of plants 117

by seeds in sprouting 117

" manner of, in plants 119

Explanatory 42

Extreme views , 56

F

Fabroni 19

Fermentation — bladder experiment 19

compared with contagion 17

compared with vaccine ." 17

different from chemical action 19

early notions of. 15

early explanations of 16

filtering paper experiments 19

hypothesis 15

Ferments— gaseous 23

gaseous, disproved 29

soluble.. 82, 106

in the changes of the form of bone 108

" relation of to living tissues 108

" pathological formation of. 106,108

relation to decay of the teeth 106

" tissue changes for forming 108

First traces 12

" definite announcement of the germ theory 14

Fixed material 119

Formed material . 119

174 INDEX.

PAGE

Gangrene in mice ........ ........................................................ 63, 127

Gay-Lussac's experiments ......................................................... 18

Germs— effect of heat upon .................................................... 29, 33

'* numbers of in the air .................................................... 33

Germ theory— first announcement of the modern ........................... 20

Gradle — chemical changes in putrefaction .............................. 130, 143

H

Hirschfield ......................................... ......... . ........................... 44

Historical ................................................................................ 11

Hospitals — antiseptic treatment in ............................................... 42

" infection experiment in ............................................. 53

" supposed infection of ........................ , ....................... 42

I

Incentives to the study of contagions ........................................... 13

Infection experiments .......................................................... . ____ 47

" of rabbits .................................................................. 47

a successful, by Davaine ................................................. 48

u with filtered fluids ....................................................... 48

Inflammations— relations of micro-organisms to ............................ 143

Introduction* .......................................................................... 11

Jenner's discovery of vaccine ..................................................... 16

K
Klebs ............................................................................... 54, 130

k on spontaneous generation ................................................ 54

' basis of future inquiry ...................................................... 55

Koch— a distinctive feature developed by ...................................... 65

experiments of. .................................... « ......................... 62

gangrene induced by .................................................. 63, 127

his experiments with mice ................................................ 63

his plan of staining ......................................................... 62

poisoning with septic matter ............................................. 128

Krause on the osteoclasts ........................................................... 105

L
Latour and Schwan .................................................................. 20

Law of the formation of the waste products ................................. 113

Lecture 1st .............................................................................. 11

" 2d .............................................................................. 35

" 3d .............................................................................. 57

" 4th .............................................................................. 79

" 5th .............................................................................. 96

" 6th .............................................................................. Ill

" 7th .............................................................................. T'O

" 8th ....................................................................... ..... 149

Leuwenhceck discovers the spermatozoa ....................................... 14

Leuwenhceck's microscopic discoveries ....................................... 1'J

INDEX. 175

PAGE

Lieber and Rottenstein on caries 153

Liebig's law of the fermentations 113

molecular motion theory still claimed 62

" explanation of susceptibility. 24

14 basis for the recognition of life 26

" explanation of fermentation 21

of the formation of yeast 22

" u " action of medicines 22

of contagions -. 23

of miasms 23

" opposition to the germ theory 21

" recognition of gaseous ferments 23

Liebig on the destruction of poisons in the stomach 25

" " vitality of contagions 24

" on excretion by plants 117

Life— de novo origin of. 35

" how supported 112

" nature of. 125, 163

Lifter's antiseptic treatment 41

" experiments with B. Termo 50, 85

" reply 56

Logical sequence 38

M

Magitot on caries of the teeth 155

Malarious fevers caused by germs 14

Manner in which micro-organisms act in producing disease 136

Miasmatic contagion 46

Miasms and contagions 45

" Liebig's explanation of. 23

Micro-organisms — classification of 40

changes in the products of. 135

dilution of. 51

destroyed by decomposition 70

destroyed by drying , 73

destroyed by the tissues 142

effects of physical presence of 146

first demonstration of, in diseased tissues 44

first demonstration of, in blood 44

first recognition of particular forms of, in connec-
tion with particular forms of disease 45

forms of 40

harmless varieties of. 69

isolation of pathogenic 68

modes of propagation 40

matter secreted by 64

non-pathogenic and pathogenic 79

no suppuration without 55

not found in normal tissues 63

not the cause of all disease 146

per se, not a sufficient cause of disease 80

176 INDEX.

PAGE

Micro-organisms — presence of, in healthy tissues 52

possible morphological differences in 55

pathogenic, now demonstrated 68

relation of, to disease processes 53

" to inflammation 143

" to pus formation 143

relation of leucocytes to : 141, 142

resistance of the tissues to 138

** virulent, action of. 53

varieties in power of disease-producing 71

Miller's experiments 158

" u with B. Lactis in soup 136

Miller on caries of the teeth 158

Molecular motion theory 22

M. Musculus 89

N

Nature of the evidence 43

Necrosed bone 104

Needham and Spalanzani 30

New functions apparent only 114

Nineteenth century 17

Nutrition 94

O

Office of micro-organisms 123

Opinion of Lister 56

" Thiersch 49, 53

Osteoclasts 108

Oxamide-oxalic acid experiment 27

Oxygen — proof that it is not the active agent in decomposition 20, 41

P

Parasites 110

Pasteur 30

11 conclusions of 34

" cultivation fluids employed by 33

u effects of his work 34

11 flask cultivations by 30

u isolates various ferments 32

u one point of failure in the experiments of 33

Pathogenic organisms demonstrated 68

Pathological formation of ferments 106

Phlogiston 15

Physiological changes in cells 59

Plants — digestion by 89

Poison destroyed by bacteria 131

u formation of by bacteria 127

a from bacteria — Panum 131

" produced by micrococci 64

Poisoning different from infection 129, 133, 151

Poisons — action of explained by Liebig 23

INDEX. 177

PAGE

Poisons — destroyed in the stomach 25

how affected by temperature 25

not always found in putrefaction, and why 132

not destroyed in the stomach 25

result from micro-organisms 124

Propositions relating to digestion 81

Ptomains 131

Pure virus necessary for inoculations 65

Putrefaction — early examination of. 18

organisms necessary to 20

explained by Liebig 22

Pyaemia — production of. 48

R

Rabbits — infection of. 47

Recklinghausen 44

Regnault on diastase 92

Relapsing fever 97

Remoleculize — definition of 83

Resorptive digestion 98

Resorption of the roots of the milk teeth 99

Rust on wheat 46

S

Sachs— experiments by 90, 239

Salmon, Dr. E. D 51, 73

Schroeder 28

Schwan 20

Seeds — sameness in physiology of. 114

11 sprouting of. 91

" varieties in the form of. Ii4

Sepsin and sulphate of atropia 143

Sepsis — poison of. 127, 129

Septicaemia and pyaemia 65

bacillus of. 64

field mice insusceptible to 65

in mice 63, 129

Soluble ferment 82

dissolving power of the 106

" of B. Lactis 162

" B. Termo 89

" micrococcus urea 86

11 the yeast plant 84

Spallanzani and Needham 30

Spermatozoa discovered 14

Sponge grafts 102

Spontaneous generation 20, 54

Spores and habits of micro-organisms 72

Spore formation 72

Stahl 15

StahPs conclusion in regard to fermentation and decomposition 18

Staining micro-organisms 62

Sternberg on poisons evolved by micro-organisms 130

178 INDEX.

PAGE

Sternberg on the relation of leucocytes to micro-organisms 140

Summary of history 74

Susceptibility — Liebig's explanation of. 24

Sydenham 15

T

The evidence 69

Theory of molecular motion 22

Thiersch 49

Thiersch's infection experiment 53

Toricellean vacuum and fermentation 18

U

Urea an alkaloid 116

Uredo 46

Urine — changes in the 115

Utilizing discoveries , 41

V

Vaccine — discovery of. 16

" experiments with 16

Varro 14

Vegetable world divided into two classes 122

Vibrios 32

Views of representative men 48-56

Virchow 53

Volkman 55

W
Waldeyer 44

Walnut trees injurious to other vegetation 118

Waste products — 6th lecture Ill

abundance of, from micro-organisms 120) 127

artificial elimination of, in B. Lactis 122

as medicines 120

" divided into two classes 113,115

effects of, on life 94

how formed 123

necessary to life 112

" not yet sufficiently studied 124

of plants 117

poisonous 116

respiratory 117

" Schwan and Liebig on Ill

11 tabulated list of 123

" the laws of. 112

" urinary 117, 124

Watt on caries of the teeth 155

Y

Yeast plant 96

digestion by the 84

Z

Zymosis 15

CATALOGUE No. 7.

OCTOBER, 1890.

A CATALOGUE

OF

BOOKS FOR STUDENTS.

INCLUDING THE

PQUIZ-COMPENDS?

CONTENTS.

PAGE

PAGE

New Series of Manuals, 2.3,4,5

Obstetrics. . . 10-

Anatomy,

6

Pathology, Histology,

ii

Biology,

ii

Pharmacy,

12

Chemistry, .
Children's Diseases,

6
7

Physiology, .
Practice of Medicine,

II
12

Dentistry,

8

Prescription Books,

12

Dictionaries,
Eye Diseases,

8
8

PQuiz-Compends ? . i<j
Skin Diseases,

15

12

Electricity, .

g

Surgery, .

13.

Gynaecology,

10

9

9

Therapeutics,
Urine and Urinary Organs,
Venereal Diseases,

9
*3
ii

Materia Medica, .

Medical Jurisprudence

10

PUBLISHED BY

P. BLAKISTON, SON & CO.,

Medical Booksellers, Importers and Publishers.

LARGE STOCK OF ALL STUDENTS' BOOKS, AT
THE LOWEST PRICES.

1012 Walnut Street, Philadelphia.

*** For sale by all Booksellers, or any book will be sent by mail,,
postpaid, upon receipt of price. Catalogues of books on all branches
of Medicine, Dentistry, Pharmacy, etc., supplied upon application.

Jg®" Gould's New Medical Dictionary Just Ready. See page ib.

THE NEW SERIES OF MANUALS.

No. 5. ORGANIC CHEMISTRY.

Or the Chemistry of the Carbon Compounds. By Prof.
VICTOR VON RICHTER, University of Breslau. Au-
thorized translation, from the Fourth German Edition.
By EDGAR F. SMITH, M.A., PH.D. ; Prof, of Chemistry
in University of Pennsylvania; Member of the Chem.
Socs. of Berlin and Paris.

" I must say that this standard treatise is here presented in a
remarkably compendious shape."— y. W. Holland ,iA.i>.t Professor
of Chemistry, Jefferson Medical College, Philadelphia.

" This work brings the whole matter, in simple, plain language,
to the student in a clear, comprehensive manner. The whole
method of the work is one that is more readily grasped than that of
older and more famed text-books, and we look forward to the time
when, to a great extent, this work will supersede others, on the
score of its better adaptation to the wants of both teacher and
student." — Pharmaceutical Record.

"Prof, von Richter's work has the merit of being singularly
clear, well arranged, and for its bulk, comprehensive. Hence, it
will, as we find it intimated in the preface, prove useful not merely
as a text-book, but as a manual of reference." — The Chemical
News, London.

No. 6. DISEASES OP CHILDREN.

SECOND EDITION.

A Manual. By J. F. GOODHART, M.D., Phys. to the
Evelina Hospital for Children ; Asst. Phys. to
Guy's Hospital, London. Second American Edition.
Edited and Rearranged by Louis STARR, M.D., Clinical
Prof, of Dis. of Children in the Hospital of the Univ.
of Pennsylvania, and Physician to the Children's Hos-
pital, Phila. Containing many new Prescriptions, a list
of over 50 Formulae, conforming to the U. S. Pharma-
copoeia, and Directions for making Artificial Human
Milk, for the Artificial Digestion of Mirk, etc. Illus.

" The author has avoided the not uncommon error of writing a
book on general medicine and labeling it ' Diseases of Children/
but has steadily kept in view the diseases which seemed to be
incidental to childhood, or such points in disease as appear to be so
peculiar to or pronounced in children as to justify insistence upon
them. * * * A safe and reliable guide, and in many ways
admirably adapted to the wants of the student and practitioner." —
American Journal of Medical Science.

Price of each Book, Cloth, $3.00 ; Leather, $3.50.

THE NEW SERIES OF MANUALS.

No. 6. Goodhart and Starr : — Continued.

" Thoroughly individual, original and earnest, the work evi-
dently of a close observer and an independent thinker, this book,
though small, as a handbook or compendium is by no means made
up of bare outlines or standard facts." — The Therapeutic Ga-
zette,

" As it is said of some men, so it might be said of some books,
that they are 'born to greatness.' This new volume has, we
believe, a mission, particularly in the hands of the younger
members of the profession. In these days of prolixity in medical
literature, it is refreshing to meet with an author who knows both
what to say and when he has said it. The work of Dr. Goodhart
(admirably conformed, by Dr. Starr, to meet American require-
ments) is the nearest approach to clinical teaching without the
actual presence of clinical material that we have yet seen." — New
York Medical Record.

No. 7. PRACTICAL THERAPEUTICS.

FOURTH EDITION, WITH AN INDEX OF DISEASES.

Practical Therapeutics, considered with reference to
Articles of the Materia Medica. Containing, also, an
Index of Diseases, with a list of the Medicines
applicable as Remedies. By EDWARD JOHN WARING,
M.D., F.R.C.P. Fourth Edition. Rewritten and Re-
vised by DUDLEY W. BUXTON, M.D., Asst. to the Prof,
of Medicine at University College Hospital.

" We wish a copy could be put in the hands of every Student or
Practitioner in the country. In our estimation, it is the best book
of the kind ever written. — N. Y. Medical Journal.

No. 8. MEDICAL JURISPRUDENCE AND
TOXICOLOGY.

NEW, REVISED AND ENLARGED EDITION.

By John J. Reese, M.D., Professor of Medical Jurispru-
dence and Toxicology in the University of Pennsyl-
vania ; President of the Medical Jurisprudence Society
of Phila. ; 2d Edition, Revised and Enlarged.

" This admirable text-book." — Amer.Jour. of Med. Sciences.

" We lay this volume aside, after a careful perusal of its pages,
with the profound impression that it should be in the hands of every

doctor and lawyer. It fully meets the wants of all students

He has succeeded in admirably condensing into a handy volume all
the essential points."— Cincinnati Lancet and Clinic.

Price of each Book, Cloth, $3,00 ; Leather, $3.50.

6 STUDENTS' TEXT-BOOKS AND MANUALS.

ANATOMY.

Macalister's Human Anatomy. 816 Illustrations. A new
Text-book for Students and Practitioners, Systematic and Topo-
graphical, including the Embryology, Histology and Morphology
of Man. With special reference to the requirements of
Practical Surgery and Medicine. With 816 Illustrations,
400 of which are original. Octavo. Cloth, 7.50; Leather, 8.50
Ballou's Veterinary Anatomy and Physiology. Illustrated.
By Wm. R. Ballou, M.D., Professor of Equine Anatomy at New
York College of Veterinary Surgeons. 29 graphic Illustrations.
I2mo. Cloth, i. oo ; Interleaved for notes, 1.25

Holden's Anatomy. A manual of Dissection of the Human
Body. Fifth Edition. Enlarged, with Marginal References and
over 200 Illustrations. Octavo. Cloth, 5.00; Leather, 6.00

Bound in Oilcloth, for the Dissecting Room, $4.50.
" No student of Anatomy can take up this book without being
pleased and instructed. Its Diagrams are original, striking and
suggestive, giving more at a glance than pages of text description.
* * * The text matches the illustrations in directness of prac-
tical application and clearness of detail." — New York Medical
Record.

Holden's Human Osteology. Comprising a Description of the
Bones, with Colored Delineations of the Attachments of the
Muscles. The General and Microscopical Structure of Bone and
its Development. With Lithographic Plates and Numerous Illus-
trations. Seventh Edition. 8vo. Cloth, 6.00
Holden's Landmarks, Medical and Surgical. 4th ed. Clo., 1.25
Heath's Practical Anatomy. Sixth London Edition. 24 Col-
ored Plates, and nearly 300 other Illustrations. Cloth, 5.00
Potter's Compend of Anatomy. Fifth Edition. Enlarged.
16 Lithographic Plates. 117 Illustrations.

Cloth, i.oo; Interleaved for Notes, 1.25

CHEMISTRY.

Hartley's Medical Chemistry. Second Edition. A text-book
prepared specially for Medical, Pharmaceutical and Dental Stu-
dents. With 50 Illustrations, Plate of Absorption Spectra and
Glossary of Chemical Terms. Revised and Enlarged. Cloth, 2. 50

Trimble. Practical and Analytical Chemistry. A Course in
Chemical Analysis, by Henry Trimble, Prof, of Analytical Chem-
istry in the Phila. College of .Pharmacy. Illustrated. Third
Edition. 8vo. Cloth, 1.50

iff" See pages 2 to 5 for list of Students' Manuals.

STUDENTS' TEXT-BOOKS AND MANUALS. T

Chemistry : — Continued.

Bloxatn's Chemistry, Inorganic and Organic, with Experiments.
Seventh Edition. Enlarged and Rewritten. 330 Illustrations.

Cloth, 4.50; Leather, 5.50

Richter's Inorganic Chemistry. A text-book for Students.
Third American, from Fifth German Edition. Translated by
Prof. Edgar F. Smith, PH.D. 89 Wood Engravings and Colored
Plate of Spectra. Cloth, 2.00

Richter's Organic Chemistry, or Chemistry of the Carbon
Compounds. Illustrated. Cloth, 3.00 ; Leather, 3.50

Symonds. Manual of Chemistry, for the special use of Medi-
cal Students. By BKANDRETH SYMONDS, A.M., M.D., Asst.
Physician Roosevelt Hospital, Out- Patient Department; Attend-
ing Physician Northwestern Dispensary, New York. lamo.

Cloth, 2.00 ; Interleaved for Notes, 2.40

Tidy. Modern Chemistry. 2d Ed. Cloth, 5.50

Leffmann's Compend of Chemistry. Inorganic and Organic.
Including Urinary Analysis. Third Edition. Revised.

Cloth, i.oo; Interleaved for Notes, 1.25

Leffmann and Beam. Progressive Exercises in Practical
Chemistry. i2mo. Illustrated. Cloth, i.oo

Muter. Practical and Analytical Chemistry. Second Edi-
tion. Revised and Illustrated. Cloth, 2.00

Holland. The Urine, Common Poisons, and Milk Analysis,
Chemical and Microscopical. For Laboratory Use. 3d
Edition, Enlarged. Illustrated. Cloth, i.oo

Van Niiys. Urine Analysis. Illus. Cloth, 2.00

Wolff's Applied Medical Chemistry. By Lawrence Wolff,
M.D.,Dem. of Chemistry in Jefferson Medical College. Clo.,i.oo

CHILDREN.

Goodhart and Starr. The Diseases of Children. Second
Edition. By J. F. Goodhart, M.D., Physician to the Evelina
Hospital for Children; Assistant Physician to Guy's Hospital,
London. Revised and Edited by Louis Starr, M.D., Clinical
Professor of Diseases of Children in the Hospital of the Univer-
sity of Pennsylvania; Physician to the Children's Hospital,
Philadelphia. Containing many Prescriptions and Formulae,
conforming to the U. S. Pharmacopoeia, Directions for making
Artificial Human Milk, for the Artificial Digestion of Milk, etc.
Illustrated. Cloth, 3.00; Leather, 3.50

Hatfield. Diseases of Children. By M. P. Hatfield, M.D. ,
Professor of Diseases of Children, Chicago Medical College.
i2mo. Cloth, i.oo; Interleaved, 1.25

Day. On Children. A Practical and Systematic Treatise.
Second Edition. 8vo. 752 pages. Cloth, 3.00; Leather, 4.00
ee pages 14 and /jr for list of f Quiz- Compends ?

8 STUDENTS' TEXT-BOOKS AND MANUALS.

Children:— Continued.

Meigs and Pepper. The Diseases of Children. Seventh
Edition. 8vo. Cloth, 5.00; Leather, 6.00

Starr. Diseases of the Digestive Organs in Infancy and
Childhood. With chapters on the Investigation of Disease,
and on the General Management of Children. By Louis Starr,
M.D., Clinical Professor of Diseases of Children in the Univer-
sity of Pennsylvania. Illus. % Cloth, 2.50

DENTISTRY.

Fillebrown. Operative Dentistry. 330 Illus. Cloth, 2.50
Flagg's Plastics and Plastic Filling, sd Ed. Preparing.
Gorgas. Dental Medicine. A Manual of Materia Medica and
Therapeutics. Third Edition. Cloth, 3.50

Harris. Principles and Practice of Dentistry. Including
Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery
and Mechanism. Twelfth Edition. Revised and enlarged by
Professor Gorgas. 1028 Illustrations. Cloth, 7.00 ; Leather, 8.00
Richardson's Mechanical Dentistry. Fifth Edition. 569
Illustrations. 8vo. Cloth, 4.50; Leather, 5.50

Sewill. Dental Surgery. 200 Illustrations, sd Ed. Clo., 3.00
Stocken's Dental Materia Medica. Third Edition. Cloth, 2.50
Taft's Operative Dentistry. Dental Students and Practitioners.
Fourth Edition. 100 Illustrations. Cloth, 4.25 ; Leather, 5.00
Talbot. Irregularities of the Teeth, and their Treatment.
Illustrated. 8vo. Second Edition. Cloth, 3.00

Tomes' Dental Anatomy. Third Ed. 191 Illus. Cloth, 4.00
Tomes' Dental Surgery, sd Edition. Revised. 292 Illus.
772 Pages. Cloth, 5.00

Warren. Compend of Dental Pathology and Dental Medi-
cine. Illustrated. Cloth, i.oo; Interleaved, 1.25

DICTIONARIES.

Gould's New Medical Dictionary. Containing the Definition
and Pronunciation of all words in Medicine, with many useful
Tables etc. % Dark Leather, 3.25 ; % Mor., Thumb Index 4.23

Cleaveland's Pronouncing Pocket Medical Lexicon, sist
Edition. Giving correct Pronunciation and Definition. Very
small pocket size. Cloth, red edges .75 ; pocket-book style, i.oo

Ixmgley • s Pocket Dictionary. The Student's Medical Lexicon,
giving Definition and Pronunciation of all Terms used in Medi-
cine, with an Appendix giving Poisons and Their Antidotes,
Abbreviations used in Prescriptions, Metric Scale of Doses, etc.
24mo. Cloth, i.oo; pocket-book style, 1.25

J8ST" Seepages 2 to 5 for list of Students' Manuals.

STUDENTS' TEXT-BOOKS AND MANUALS. 9

EYE.

Arlt. Diseases of the Eye. Including those of the Conjunc-
tiva, Cornea, Sclerotic, Iris and Ciliary Body. By Prof. Von
Arlt. Translated by Dr. Lyman Ware. Illus. 8vo. Cloth, 2.50

Hartridge on Refraction. 4th Ed. Cloth, 2.00

Meyer. Diseases of the Eye. A complete Manual for Stu-
dents and Physicians. 270 Illustrations and two Colored Plates.
8vo. Cloth, 4.50; Leather, 5.50

Fox and Gould. Compend of Diseases of the Eye and
Refraction. 2d Ed. Enlarged. 71 Illus. 39 Formulae.

Cloth, i. oo ; Interleaved for Notes, 1.25

ELECTRICITY.

Mason's Compend of Medical and Surgical Electricity.

With numerous Illustrations. i2mo. Cloth, i.oo

HYGIENE.

Parkes' (Ed. A.) Practical Hygiene. Seventh Edition, en-
larged. Illustrated. 8vo. Cloth, 4.50

Parkes' (L. C.) Manual of Hygiene and Public Health.
i2jno. Cloth, 2.50

Wilson's Handbook of Hygiene and Sanitary Science.
Sixth Edition. Revised and Illustrated. Cloth, 2.75

MATERIA MEDICA AND THERAPEUTICS.

Potter's Compend of Materia Medica, Therapeutics and

Prescription Writing. Fifth Edition, revised and improved.

Cloth, i.oo; Interleaved for Notes, 1.25

Biddle's Materia Medica. Eleventh Edition. By the late
John B. Biddle, M.D., Professor of Materia Medica in Jefferson
Medical College, Philadelphia. Revised, and rewritten, by
Clement Biddle, M.D., Assist. Surgeon, U. S. N., assisted by
Henry Morris, M.D. 8vo., illustrated. Cloth, 4.25; Leather, 5.00

Headland's Action of Medicines, gih Ed. 8vo. Cloth, 3.00

Potter. Materia Medica, Pharmacy and Therapeutics.
Including Action of Medicines, Special Therapeutics, Pharma-
cology, etc. Second Edition. Cloth, 4.00 ; Leather, 5,00

Starr, Walker and Powell. Synopsis of Physiological
Action of Medicines, based upon Prof. H. C. Wood's " Materia
Medica and Therapeutics." 3d Ed. Enlarged. Cloth, .75

Waring. Therapeutics. With an Index of Diseases and
Remedies. 4th Edition. Revised. Cloth, 3.00; Leather, 3.50
.*3~ See pages 14 and /j for list of f Quiz- Commends f

10 STUDENTS' TEXT-BOOKS AND MANUALS.

MEDICAL JURISPRUDENCE.

Reese. A Text-book of Medical Jurisprudence and Toxi-
cology. By John J. Reese, M.D., Professor of Medical Juris-
prudence and Toxicology in the Medical Department of the
University of Pennsylvania ; President of the Medical Juris-
prudence Society of Philadelphia; Physician to St. Joseph's
Hospital ; Corresponding Member of The New York Medico-
legal Society, sd Edition. Cloth, 3.00; Leather, 3.50

Woodman and Tidy's Medical Jurisprudence and Toxi-
cology. Chromo-Lithographic Plates and 116 Wood engravings.

Cloth, 7.50; Leather, 8.50

OBSTETRICS AND GYNAECOLOGY.

Byford. Diseases of Women. The Practice of Medicine and
Surgery, as applied to the Diseases and Accidents Incident to
Women. By W. H. Byford, A.M., M.D., Professor of Gynaecology
in Rush Medical College and of Obstetrics in the Woman's Med-
ical College, etc., and Henry T. Byford, M.D., Surgeon to the
Woman's Hospital of Chicago ; Gynaecologist to St. Luke's
Hospital, etc. Fourth Edition. Revised, Rewritten and En-
larged. With 306 Illustrations, over 100 of which are original.
Octavo. 832 pages. Cloth, 5.00 ; Leather, 6.00

Cazeaux and Tarnier's Midwifery. "With Appendix, by
Munde. The Theory and Practice of Obstetrics ; including the
Diseases of Pregnancy and Parturition, Obstetrical Operations,
etc. By P. Cazeaux. Remodeled and rearranged, with revi-
sions and additions, by S. Tarnier, M.D., Professor of Obstetrics
and Diseases of Women and Children in the Faculty of Medicine
of Paris. Eighth American, from the Eighth French and First
Italian Edition. Edited by Robert J. Hess, M.D., Physician to
the Northern Dispensary, Philadelphia, with an appendix by
Paul F. Munde, M.D., Professor of Gynaecology at the N. Y.
Polyclinic. Illustrated by Chromo- Lithographs, Lithographs,
and other Full-page Plates, seven of which are beautifully colored,
and numerous Wood Engravings. Students' Edition. One
Vol.,8vo. Cloth, 5.00; Leather, 6.00

Lewers' Diseases of Women. A Practical Text-Book. 139
Illustrations. Second Edition. Cloth, 2.50

Parvin's Winckel's Diseases of Women. Second Edition.
Including a Section on Diseases of the Bladder and Urethra.
150 Illus. Revised. Seepages. Cloth, 3.00; Leather, 3.50

Morris. Compend of Gynaecology. Illustrated. Cloth, i.oo

Winckel's Obstetrics. A Text-book on Midwifery, includ-
ing the Diseases of Childbed. By Dr. F. Winckel, Professor
of Gynaecology, and Director of the Royal University Clinic for
Women, in Munich. Authorized Translation, by J. Clifton
Edgar, M.D., Lecturer on Obstetrics, University Medical Col-
lege, New York, with nearly 200 handsome illustrations, the
majority of which are original with this work. Octavo.

Cloth, 6.00 ; Leather, 7.00

Landis' Compend of Obstetrics. Illustrated. 4th edition,
enlarged. Cloth, i.oo; Interleaved for Notes, 1.25

e pages 2 to 3 for list of New Manuals.

STUDENTS' TEXT-BOOKS AND MANUALS. 11

Obstetrics and Gynaecology : — Continued.

Galabin's Midwifery. By A. Lewis Galabin, M.D., F.R.C.P.
227 Illustrations. See page 3. Cloth, 3.00; Leather, 3.50

Glisan's Modern Midwifery. 2d Edition. Cloth, 3.00

Rigby's Obstetric Memoranda. 4th Edition. Cloth, .50

Meadows' Manual of Midwifery. Including the Signs and

Symptoms of Pregnancy, Obstetric Operations, Diseases of the

Puerperal State, etc. 145 Illustrations. 494 pages. Cloth, 2.00

Swayne's Obstetric Aphorisms. For the use of Students

commencing Midwifery Practice. 8th Ed. i2mo. Cloth, 1.25

PATHOLOGY. HISTOLOGY. BIOLOGY.

Bowlby. Surgical Pathology and Morbid Anatomy, for
Students. 135 Illustrations. i2mo. Cloth, 2.00

Davis' Elementary Biology. Illustrated. Cloth, 4.00

Gilliam's Essentials of Pathology. A Handbook for Students.
47 Illustrations. i2mo. Cloth, 2.00

*+*The object of this book is to unfold to the beginner the funda-
mentals of pathology in a plain, practical way, and by bringing
them within easy comprehension to increase his interest in the study
of the subject.

Gibbes' Practical Histology and Pathology. Third Edition.

Enlarged. i2mo. Cloth, 1.75

Virchow's Post-Mortem Examinations. 2d Ed. Cloth, i.oo

PHYSIOLOGY.

Yeo's Physiology. Fourth Edition. The most Popular Stu-
dents' Book. By Gerald F. Yeo, M.D., F.R.C.S., Professor of

' Physiology in King's College, London. Small Octavo. 758
pages. 321 carefully printed Illustrations. With a Full
Glossary and Index. See Page 3. Cloth, 3.00; Leather, 3.50

Brubaker's Compend of Physiology. Illustrated. Fifth
Edition. Cloth, i.oo; Interleaved for Notes, 1.25

Stirling. Practical Physiology, including Chemical and Ex-
perimental Physiology. 142 Illustrations. Cloth, 2.25

Kirke's Physiology. New i2th Ed. Thoroughly Revised and
Enlarged. 502 Illustrations. Cloth, 4.00; Leather, 5.00

Landois' Human Physiology. Including Histology and Micro-
scopical Anatomy, and with special reference to Practical Medi-
cine. Third Edition. Translated and Edited by Prof. Stirling.
692 Illustrations. Cloth, 6.50; Leather, 7.50

" With this Text-book at his command, no student could fail in

his examination." — Lancet.

Sanderson's Physiological Laboratory. Being Practical Ex-
ercises for the Student. 350 Illustrations. 8vo. Cloth, 5.00

Tyson's Cell Doctrine. Its History and Present State. Illus-
trated. Seeond Edition. Cloth, 2.00

ee pages 14 and 15 for list of ? Quiz-Compends f

12 STUDENTS' TEXT-BOOKS AND MANUALS.

PRACTICE.

Taylor. Practice of Medicine. A Manual. By Frederick
Taylor, M.D., Physician to, and Lecturer on Medicine at, Guy's
Hospital, London ; Physician to Evelina Hospital for Sick Chil-
dren, and Examiner in Materia Medica and Pharmaceutical
Chemistry, University of London. Cloth, 4.00

Roberts' Practice. New Revised Edition. A Handbook
of the Theory and Practice of Medicine. By Frederick T.
Roberts, M.D. ; M.R.C.P., Professor of Clinical Medicine and
Therapeutics in University College Hospital, London. Seventh
Edition. Octavo. Cloth, 5.50 ; Sheep, 6.50

Hughes. Compend of the Practice of Medicine. 4th Edi-
tion. Two parts, each, Cloth, i.oo; Interleaved for Notes, 1.25
PART i. — Continued, Eruptive and Periodical Fevers, Diseases

of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver,

Kidneys, etc., and General Diseases, etc.

PART n.— Diseases of the Respiratory System, Circulatory

System and Nervous System ; Diseases of the Blood, etc.

. Physician's Edition. Fourth Edition. Including a Section
on Skin Diseases. With Index, i vol. Full Morocco, Gilt, 2.50

From John A. Robinson, M.D., Assistant to Chair of Clinical
Medicine t now Lecturer on Materia Medica, Rusk Medical Col-
lege, Chicago.
" Meets with my hearty approbation as a substitute for the

ordinary note books almost universally used by medical students.

It is concise, accurate, well arranged and lucid, . . . just the

thing for students to use while studying physical diagnosis and the

more practical departments of medicine.

PRESCRIPTION BOOKS.

Wythe's Dose and Symptom Book. Containing the Doses
and Uses of all the principal Articles of the Materia Medica, etc.
Seventeenth Edition. Completely Revised and Rewritten. Just,
Ready. 32mo. Cloth, i.oo; Pocket-book style, 1.25

Pereira's Physician's Prescription Book. Containing Lists
of Terms, Phrases, Contractions and Abbreviations used in
Prescriptions Explanatory Notes, Grammatical Construction of
Prescriptions, etc., etc. By Professor Jonathan Pereira, M.D.
Sixteenth Edition. 32mo. Cloth, i.oo; Pocket-book style, 1.25

PHARMACY.

Stewart's Compend of Pharmacy. Based upon Remington's
Text-Book of Pharmacy. Third Edition, Revised. With new
Tables, Index, Etc. Cloth, i.oo; Interleaved for Notes, 1.25

Robinson. Latin Grammar of Pharmacy and Medicine.
By H. D. Robinson, PH.D., Professor of Latin Language and
Literature, University of Kansas, Lawrence. With an Intro-
duction by L. E. Sayre, PH.G., Professor of Pharmacy in, and
Dean of, the Dept. of Pharmacy, University of Kansas. i2mo.

Cloth, 2.00

SKIN DISEASES.

Anderson, (McCall) Skin Diseases. A complete Text-Book,
with Colored Plates and numerous Wood Engravings. 8vo.

Cloth, 4.50; Leather, 5.50
>&S~ See pages 2 to 3 for list of New Manuals.

STUDENTS' TEXT-BOOKS AND MANUALS. 13-

Skin Diseases : — Continued.

Van Harlingen on Skin Diseases. A Handbook of the Dis-
eases of the Skin, their Diagnosis and Treatment (arranged alpha-
betically). By Arthur Van Harlingen, M.D., Clinical Lecturer
on Dermatology, Jefferson Medical College ; Prof, of Diseases of
the Skin in the Philadelphia Polyclinic. ad Edition. Enlarged.
With colored and other plates and illustrations. lamo. Cloth, 2.50

Bulkley. The Skin in Health and Disease. By L. Duncan
Bulkley, Physician to the N. Y. Hospital. Illus. Cloth, .50

SURGERY AND BANDAGING.

Jacobson. Operations in Surgery. A Systematic Handbook
for Physicians, Students and Hospital Surgeons. By W. H. A.
Jacobson, B.A., Oxon. F.R.C.S. Eng. ; Ass't Surgeon Guy's Hos-
pital ; Surgeon at Royal Hospital for Children and Women, etc.
199 Illustrations. 1006 pages. 8vo. Cloth. 5.00; Leather, 6.00
Heath's Minor Surgery, and Bandaging. Ninth Edition. 142
Illustrations. 60 Formulae and Diet Lists. Cloth, 2.00

Horwitz's Compend of Surgery, Minor Surgery and1
Bandaging, Amputations, Fractures, Dislocations, Surgical
Diseases, and the Latest Antiseptic Rules, etc., with Differential
Diagnosis and Treatment. By ORVILLE HOKWITZ, B.S., M.D.,
Demonstrator of Surgery, Jefferson Medical College. 4th edition.
Enlarged and Rearranged. 136 Illustrations and 84 Formulae.
121110. Cloth, i.oo; Interleaved for the addition of Notes, 1.25
*#*The new Section on Bandaging and Surgical Dressings, con-
sists of 32 Pages and 41 Illustrations. Every Bandage of any
importance is figured. This, with the Section on Ligation of
Arteries, forms an ample Text-book for the Surgical Laboratory.
Walsham. Manual of Practical Surgery. For Students and
Physicians. By WM. J. WALSHAM, M.D., F.R.C.S., Asst. Surg.
to, and Dem. of Practical Surg. in, St. Bartholomew's Hospital,
Surgeon to Metropolitan Free Hospital, London. With 236
Engravings. See Page 2. Cloth, 3.00; Leather, 3.50

URINE, URINARY ORGANS, ETC.

Holland. The Urine, and Common Poisons and The
Milk. Chemical and Microscopical, for Laboratory Use. Illus-
trated. Third Edition. i2mo. Interleaved. Cloth, i.oo

Ralfe. Kidney Diseases and Urinary Derangements. 42 Illus-
trations. i2mo. 572 pages. Cloth, 2.75

Marshall and Smith. On the Urine. The Chemical Analysis of
the Urine. By John Marshall, M.D., Chemical Laboratory, Univ.
of Penna; and Prof. E. F. Smith, PH.D. Col. Plates. Cloth, i.oo

Thompson. Diseases of the Urinary Organs. Eighth
London Edition. Illustrated. Cloth, 3.50

Tyson. On the Urine. A Practical Guide to the Examination
of Urine. With Colored Plates and Wood Engravings. 6th Ed.
Enlarged. i2mo. Cloth, 1.50

Van Niiys, Urine Analysis. Illus. Cloth, 2.00

VENEREAL DISEASES.

Hill and Cooper. Student's Manual of Venereal Diseases,
with Formulae. Fourth Edition. i2mo. Cloth, 'i.oo

ee pages 14. and 15 for list of .' Quiz-Contpends f

NEW AND REVISED EDITIONS.

PQUIZ-COMPENDS?

The Best Compends for Students' Use
in the Quiz Class, and when Pre-
paring for Examinations.

Compiled in accordance with the latest teachings of promi-
nent lecturers and the most popular Text-books.
They form a most complete, practical and exhaustive
set of manuals, containing information nowhere else col-
lected in such a condensed, practical shape. Thoroughly
up to the times in every respect, containing many new
prescriptions and formulae, and over two hundred and
fifty illustrations, many of which have been drawn and
engraved specially for this series. The authors have had
large experience as quiz-masters and attaches of colleges,
with exceptional opportunities for noting the most recent
advances and methods.

Cloth, each $1.00. Interleaved for Notes, $1.25.
No. i. HUMAN ANATOMY, " Based upon Gray." Fifth
Enlarged Edition, including Visceral Anatomy, formerly
published separately. 16 Lithograph Plates, New
Tables and 117 other Illustrations. By SAMUEL O. L.
POTTER, M.A., M.D., late A. A. Surgeon U. S. Army. Professor
of Practice, Cooper Medical College, San Francisco.
Nos. 2 and 3. PRACTICE OF MEDICINE. Fourth Edi-
tion. By DANIEL E. HUGHES, M.D., Demonstrator of Clinical
Medicine in Jefferson Medical College, Philadelphia. In two parts.
PART I. — Continued, Eruptive and Periodical Fevers, Diseases
of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver,
Kidneys, etc. (including Tests for Urine), General Diseases, etc.

PART II. — Diseases of the Respiratory System (including Phy-
sical Diagnosis), Circulatory System and Nervous System; Dis-
eases of the Blood, etc.

*** These little books can be regarded as a full set of notes upon
the Practice of Medicine, containing the Synonyms, Definitions,
Causes, Symptoms, Prognosis, Diagnosis, Treatment, etc., of each
disease, and including a number of prescriptions hitherto unpub-
lished.

No. 4. PHYSIOLOGY, including Embryology. Fifth
Edition. By ALBERT P. BRUBAKER, M.D., Prof, of Physiology,
Penn'a College of Dental Surgery ; Demonstrator of Physiology
in Jefferson Medical College, Philadelphia. Revised, Enlarged
and Illustrated.

No. 5. OBSTETRICS. Illustrated. Fourth Edition. By
HENRY G. LANDIS, M.D., Prof, of Obstetrics and Diseases of
Women, in Starling Medical College, Columbus, O. Revised
E'dition. New Illustrations.

BLAKISTON'S ? QUIZ-COMPENDS ?

No. 6. MATERIA MEDICA, THERAPEUTICS AND
PRESCRIPTION WRITING. Fifth Revised Edition.

With especial Reference to the Physiological Action of Drugs,
and a complete article on Prescription Writing. Based on the
Last Revision of the U. S. Pharmacopoeia, and including many
unofficinal remedies. By SAMUEL O. L. POTTER, M.A., M.D.,
late A. A. Surg. U. S. Army ; Prof, of Practice, Cooper Medical
College, San Francisco. Improved and Enlarged, with Index.

No. 7. GYNAECOLOGY. A Compend of Diseases of Women.
By HENRY MORRIS, M.D., Demonstrator of Obstetrics, Jefferson
Medical College, Philadelphia. Illustrated.

No. 8. DISEASES OF THE EYE AND REFRACTION,
including Treatment and Surgery. By L. WEBSTER Fox, M.D.,
Chief Clinical Assistant Ophthalmological Dept., Jefferson Med-
ical College, etc., and GEO. M. GOULD, M.D. 71 Illustrations, 39
Formulse. Second Enlarged and Improved Edition. Index.

No. 9. SURGERY, Minor Surgery and Bandaging. Illus-
trated. Fourth Edition. Including Fractures, Wounds,
Dislocations, Sprains, Amputations and other operations ; Inflam-
mation, Suppuration, Ulcers, Syphilis, Tumors, Shock, etc.
Diseases of the Spine, Ear, Bladder, Testicles, Anus, and
other Surgical Diseases. By ORVILLE HORWITZ, A.M., M.D.,
Demonstrator of Surgery, Jefferson Medical College. Revised
and Enlarged. 84 Formulae and 136 Illustrations.

No. 10. CHEMISTRY. Inorganic and Organic. For Medical
and Dental Students. Including Urinary Analysis and Medical
Chemistry. By HENRY LEFFMANN, M.D., Prof, of Chemistry in
Penn'a College of Dental Surgery, Phila. Third Edition, Revised
and Rewritten, with Index.

No. ii. PHARMACY. Based upon " Remington's Text-book
of Pharmacy." By F. E. STEWART, M.D., PH. G., Quiz-Master
at Philadelphia College of Pharmacy. Third Edition, Revised.

No. 12. VETERINARY ANATOMY AND PHYSIOL-
OGY. 29 Illustrations. By WM. R. BALLOU, M.D., Prof, of
Equine Anatomy at N. Y. College of Veterinary Surgeons.

No. 13. DENTAL PATHOLOGY AND DENTAL MEDI-
CINE. Containing all the most noteworthy points of interest
to the Dental student. By GEO. W. WARREN, D.D.S., Clinical
Chief, Penn'a College of Dental Surgery, Philadelphia. Illus.

No. 14. DISEASES OF CHILDREN. By DR. MARCUS P.
HATFIELD, Prof, of Diseases of Children, Chicago Medical
College. Illustrated.

Bound in Cloth, $1. Interleaved, for the Addition of Notes, $1.25.

These books are constantly revised to keep up with
the latest teachings and discoveries, so that they contain
all the new methods and principles. No series of books
are so complete in detail, concise in language, or so well
printed and bound. Each one forms a complete set of
notes ^lpon the subject under consideration.

Illustrated Descriptive Circular Free.

JUST PUBLISHED.

GOULD'S NEW

MEDICAL DICTIONARY

COMPACT.

CONCISE.
PRACTICAL
ACCURATE.

COMPREHENSIVE
UP TO DATE.

It contains Tables of the Arteries, Bacilli, Gan-
glia, Leucomaines, Micrococci, Muscles,
Nerves, Plexuses, Ptomaines, etc.,
etc., that will be found of great
use to the student.

Small octavo, 520 pages, Half-Dark Leather, . $3.25
With Thumb Index, Half Morocco, marbled edges, 4.25

From J. M. DACOSTA, M. D., Professor of Practice and
Clinical Medicine, Jefferson Medical College, Philadelphia.

"I find it an excellent -work, doing credit to tne learning and
discrimination of the author."

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