WORKS BY T. MITCHELL PRUDDEN, M.D.

The Story of the Bacteria, and Their
Relations to Health and Disease

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The

Story of the Bacteria

And their

Relations to Health and Disease

By

T. Mitchell Prudden, M.D.

SECOND EDITION, REVISED AND ENLARGED

ILLUSTRATED

THE

UNIVERSITY

OF

G. P. Putnam's Sons

New York and London
IRnfcfcerbocfcet
1910

COPYRIQHT, 1889

BY

T. MITCHELL PRUDDEN
COPYRIGHT, 1910

BY

T. MITCHELL PRUDDEN

Ube ImCcfeerbocfcer preaa, flew

'

;.vo

BIOLOGY

LIBRARY

G

PREFACE

TO THE FIRST EDITION

THE bacteria are so often nowadays the
subject of discussion and discourse; so much
which is at once disquieting and untrue is said
about them, and they are withal of such prac-
tical importance to the health and well-being
of everybody, that it has seemed to the writer
worth while to bring together in some simple
fashion a little of our knowledge about them.

The aim then of this book is to present
some facts from a small corner of the domain
of Science in such form as will be plain to the
unscientific, and with these some extracts from
the lore of the physician which will, it is
hoped, be both interesting and useful to the
lay reader.

T. M. P.

307119

PREFACE

TO THE SECOND EDITION

SOME twenty years ago, when the first
edition of this little book was issued, bac-
teriology was in its early infancy. It is an
infant still, but grown more lusty and articu-
late. These minute plants, the bacteria,
logically belong in the purlieus <jf the botanist.
But he has always turned the cold shoulder to
them.

So at first they were popularly regarded as
the foster children of Medicine. But little by
little, the arts and the industries and the
farmer have found them out so that to-day
this modest bailiwick of the biological sciences,
which we call bacteriology, is held in trust
by a syndicate of scientific folk, of whom
the medical men are perhaps the most con-
spicuous.

Our tread along the pathways which bac-
teriology opened has become firmer as the

vi Preface

years have passed, and out of its revelations
we have won treasures of knowledge, of in-
sight, and practical beneficence to man, which
lie far beyond even the dreams of an earlier
day.

While the revision of the book, for this
second edition, has been everywhere exten-
sive, the greater changes and additions have
been made in the sections relating to disease
and its prevention.

The addition of pictures and the enlarged
scope of the book, it is hoped, will make it
useful to the new generation of readers,
whose outlooks for increased efficiency and
happiness in life, is curiously interlinked with
the performances of these invisible earth
neighbors of ours, whose story is here briefly
rehearsed. T. M. P,

CONTENTS

CHAPTER PAGE

I. — THE CELLS OF THE HUMAN BODY — WHAT

THEY ARE AND WHAT THEY Do . . I

II. — BACTERIA AND SOME OF THE THINGS WHICH

THEY Do . . . . . .14

III. — How THE BACTERIA ARE STUDIED . . 28

IV. — SOME BACTERIAL CURIOSITIES ... 43

V. — AGRICULTURAL CONJURERS , . 55

VI. — BACTERIA AS MAN'S INVISIBLE FOES . . 60

VII. — THE BACTERIA OF WOUNDS AND OF SURGICAL

DISEASES ...... 70

VIII. — THE BACTERIA OF CONSUMPTION OR TUBER-
CULOSIS ....... 83

IX. — TYPHOID FEVER AND ITS RELATIVES . . 100

X. — ASIATIC CHOLERA . . . . .109

XI. — PNEUMONIA, INFLUENZA, AND COLDS . 115

XII. — DIPHTHERIA AND TETANUS . . . 125

XIII. — A ROUND-UP OF UNDESIRABLES . . . 131

XIV. — SAFEGUARDS OF THE BODY AGAINST DISEASE. 141

XV. — How SCIENCE HELPS THE BODY IN INFECTION 155

Contents

CHAPTER PAGE

XVI. — THE COMMON SOURCES OF BACTERIAL IN-
FECTION . . . . . .175

XVII. — WATER AND ICE AS SOURCES OF INFECTION 184

XVIII. — HAZARDS OF THE AIR .... 199

XIX. — A DANGEROUS NEIGHBOR . . . .211

XX. — THE END OF THE STORY . . . .216

INDEX ......... 223

ILLUSTRATIONS

PAGE

Fig. i. FORMS OF BACTERIA . . . .15

" 2. — FLAGELLA OF BACTERIA ... 17

" 3. — SPORES IN BACTERIA .... 20

Plate I. — TUBE CULTURES OF BACTERIA . . 34

" II. — PLATE CULTURES IN PETRI DISHES . 36

" III. — COLONIES OF BACTERIA ... 38

" IV. — A BACTERIAL CULTURE SHOWING THE

FORMATION OF GAS .... 40

Fig. 4. — STREPTOCOCCI FROM A CULTURE . . 41

" 5. — STAPHYLOCOCCUS FROM A CULTURE . 42

" 6. — BACILLI FROM A CULTURE ... 42

Plate V. — NODULES ON CLOVER ROOTS . . 56

Fig. 7. — NODULE BACTERIA .... 58

14 8. — STREPTOCOCCUS PYOGENES ... 72

" 9.— STAPHYLOCOCCUS PYOGENES ... 73

ix

Illustrations

PAGE

Fig. 10. — TUBERCLE BACILLI .... 84

Plate VI. — TUBERCLES IN THE LUNG ... 86

" VII. — A TUBERCLE IN THE LUNGS : HEALED . 88

" VIII. — TUBERCULOUS CAVITIES IN LUNG . . 90

IX. — CULTURES OF THE TUBERCLE BACILLUS . 92

X. — A SNEEZE PLATE CULTURE ... 94

Fig. ii. — THE BACILLI OF TYPHOID FEVER . 101

12. — THE PNEUMOCOCCUS . . . .116

13. — BACILLUS DIPHTHERIA . . . .126

14. — TETANUS BACILLI .... 128

Plate XI. — LEUCOCYTES AND PHAGOCYTES . . 146

Fig- 15- — PHAGOCYTES AND VACCINES . . . 167

Plate XII. — A DIRTY HUMAN LUNG . . . 202

" XIII. — TRACKS OF A WANDERING "TYPHOID

FLY" 214

The Story of the Bacteria

THE STORY OF THE BACTERIA

CHAPTER I

THE CELLS OF THE HUMAN BODY — WHAT THEY
ARE, AND WHAT THEY DO

BEFORE beginning to study those low-
liest and smallest forms of life, the
bacteria, I wish to ask my reader to look with
me in this chapter at some of the higher and
more complex forms of living things. In do-
ing this we shall be following the course which
scientific research has taken, and from the
vantage-ground thus gained we shall be able
the more easily to spell out the simple but
significant story of the bacteria, which it is
the purpose of this little book to tell.

In general anatomy we learn that the body
consists of a bony framework, around which

2 The Story of the Bacteria

various tissues and organs are securely and
compactly grouped. When we have learned
the size, shape, number, relations, and names
of all these parts, our study of macroscopic or
general anatomy is done. If, however, enter-
ing that department of science known as
histology, or minute anatomy, we trace the
manner in which these parts are made beyond
the point where the naked eye can avail us,
we find that they are all composed of certain
tiny organisms called cells, and that these
cells are held together and associated by cer-
tain materials which lie between them.

Just as the chemist has his atoms and
molecules, to which in the last analysis he re-
fers the properties which all known substances
possess, and explains by differences in their
nature and movements the various chemi-
cal phenomena which matter exhibits, so we
may refer both the structural features and all
the activities of the animal body back to the
structure and activities of our elements — the
cells. While the chemist, however, must infer
the existence of his atoms from their deeds,
armed with the microscope we can see our

The Cells of the Body 3

cells, observe the things they do, and definitely
trace out their life-history.

Cells are little masses of matter of peculiar
chemical constitution, and of varied shape and
consistence, which at some time exhibit that
complex of phenomena which we call life: and
the life of one of the higher animals is simply
the sum of the more or less independent but
co-ordinated lives of the cells which compose
it, all acting in harmony.

Living things differ from the non-living in
that they have certain activities through which
their life is expressed. In the first place, they
are capable, in spite of various opposing forces,
of maintaining their individuality, and by
holding a balance between waste on the one
hand and assimilation on the other, a series of
capacities arises which we call nutrition,
growth, and development. Living things, in
the second place, possess certain activities by
means of which they are capable of producing
new individuals like themselves — in other
words, they are endowed with the power of
reproduction. Lastly, living bodies, in re-
sponse to varied influences, are capable of

4 The Story of the Bacteria

doing certain things in the way of movements
or of elaboration of peculiar chemical products,
etc., and these are called their functions.

It will be observed that in enumerating
these activities I have spoken of them not as
characteristic of man, or of any special animal
or plant, but of living things in general. All
life finds expression in these ways. The means
by which the living being does these things
may be in one case exceedingly primitive, and
in another very complicated, but this does not
alter the essential character of the ends which
it achieves.

If you tie a bit of muslin over a water faucet
and allow the water to trickle slowly through
it for a few hours, you will find on removing
it that a more or less abundant greenish scum
has collected on the cloth. Wash this care-
fully into an open dish, and let it remain for a
few days in a light warm place, and then
examine the sediment under a microscope,
and you will find a very celebrated creature.
It is called an amoeba. It looks like a little
lump of transparent or slightly granular jelly.
You will see it thrusting out portions of itself

The Cells of the Body 5

in the form of longer or shorter arms, and
then withdrawing them and sending out
others in another place, apparently in the
most aimless way; or you may see it rolling
itself over and over, or, if I may so say, flow-
ing along so that it travels with considerable
speed. Perhaps some microscopic vegetable
may lie in its way, and it will flow over and
enclose this, and, after digesting -portions of it,
expel the residue from whichever side or sur-
face of its body may be most convenient. If,
in a quiescent condition, it be touched by an
external object, you may see it move in direct
response to the irritation. If you are fortu-
nate in your observation, you may see a con-
striction appear around some part of the lump,
which grows gradually deeper until a portion
of the mass separates from the rest and crawls
off on its own hook as a new and independent
amoeba. It has no lungs and yet it breathes;
no mouth, still eats; no definite shape, yet
grows; no nerves, yet is sensitive; no sex,
yet may give birth to endless progeny.

Now this amoeba is one of the lowest and
simplest of creatures, and is the type of a

6 The Story of the Bacteria

cell — a creature which is composed of a single
cell — and all the activities which I have men-
tioned as characteristic of living things are
exhibited in it. It is a perfectly independent
being, doing everything for itself, and doing
nothing particularly well, except, perhaps,
performing the function of reproduction, which
it does with such ease and nonchalance
as leaves little to be desired. The young
which it produces are just like the parent,
single cells, and their very first post-natal act
may be to give birth to other amcebas.

Now let us advance a step in the scale of
being, to an animal composed of several cells.
There is a little creature, one of the group of
sponges, called olynthus. Let us start with
the ovum of the animal, which is a single cell,
not very unlike the amoeba in appearance.
Under suitable conditions, this cell divides as
the amoeba does, and two cells are produced,
just exactly alike. They do not separate,
however, as do the amoebas, to become inde-
pendent individuals, but remain fastened
together; then each cell divides again, and
these still further, until we have a little mass

The Cells of the Body 7

of cells all looking alike, and the whole some-
what resembling a mulberry in shape. But
now a change comes; the cells on the outside
become longer than the rest, and little hair-
like processes, called cilia, grow out from them
and begin to vibrate to and fro, and, acting
like tiny oars, propel the little creature through
the sea. Presently the rest of the cells arrange
themselves so as to form a central cavity, with
an opening at one side, the whole looking like
a tiny cup. The animal now attaches itself to
a sea-weed or a rock, and no longer needing
the locomotive cilia, they disappear; but as it
can no longer travel, it can no longer seek its
food, which must be brought to it. Accordingly
we presently find that through the sides of its
body little holes appear, and the cells lining
the central cavity lengthen and develop cilia,
whose vibrations maintain a current of water
through the body, which brings with it oxygen
and food. This is the adult olynthus.

Now observe, if you please, what has hap-
pened in the development of this little crea-
ture. A single cell divided into several cells,
at first all just alike, and all doing the same

8 The Story of the Bacteria

thing. But soon, as if in response to the
growing needs of the animal, certain of the
cells developed a special apparatus, and a
special capacity for performing rapid move-
ments, and this capacity was associated with
changes in the form of the cells, — a specializa-
tion which signalized its advance to a higher
type of existence.

Just here we come upon the great principle,
in a very simple form, upon which the enor-
mous differences between higher and lower
animals rest, — the principle of the physiologi-
cal division of labor in cells. The more
perfect the individual is, the more elaborate
do we find the expression of this principle.

The difference between the amoeba and the
olynthus from our present point of view — that
which makes of the latter a higher animal than
the former — is that it has a certain group of
cells set apart to do a special thing, to move
rapidly; amoeba moves, but not so rapidly
nor with such directness. If another group of
cells were set apart in olynthus to do the
digesting, no new cell powers would be devel-
oped which the amoeba does not possess; the

The Cells of the Body 9

primitive assimilating power would simply be
specialized and intensified, and the animal
would have risen to a higher grade of being.

It would not be difficult, did space permit, to
trace the manner in which, as we pass upward
in the animal series, certain groups of cells be-
come more and more elaborate in structure as
they assume higher and more specialized ca-
pacities. We cannot tarry for this, but will
glance for a moment at the exhibition of this
principle in the development of man. In man,
too, life commences in a single cell called the
ovum; a cell which, though harboring poten-
tialities of the highest order, in many respects
greatly resembles our little denizens of the
water. This cell, under suitable conditions,
divides and subdivides, forming a little cluster
of cells all looking alike. Then these cells
arrange themselves in layers; some of them
assume special forms as they increase in num-
ber, and develop special capacities, and group
themselves to form the various tissues and
organs of the mature body, which finally is
formed of a grand community of co-ordinated
groups of cells, some of which have acquired

io The Story of the Bacteria

the power to do special things in the most
perfect way, while others have remained in a
condition of comparatively low organization.
Let us look at two examples of these two
types of cells from the adult body — first at
certain muscle cells. These in the very young
animal look just like many other cells; they
are individuals, they are alive and their life
finds expression, just as the amoeba's does, in
certain activities — nutrition, growth, function,
and reproduction. Presently they become
longer than their neighbors, little striations
appear along their sides, they grow long and
narrow until at last they are little thread-like
bodies with a very complicated internal struct-
ure, and are grouped in bundles to form the
muscles as we see them with the naked eye.
The peculiarities of structure of these muscle
fibres are necessary for the performance of the
work which they have specially to do — namely,
the accomplishment of rapid and powerful
movements. Now the capacity of the muscle
cells for doing this work has been acquired, if
I may say so, at the expense of some of the
other capacities which they originally possessed

The Cells of the Body n

in common with other cells. Thus the power
of reproduction is in them almost if not quite
completely absent. They can also no longer
seek out and take up crude food, but it has to
be prepared for and brought to them, and in
order that this may be done certain other cells
in the body develop the power of elaborat-
ing a peculiar fluid — gastric juice, which helps
to change the crude food so that it finally
becomes fitted for the nourishment, among
others, of the special workers, the muscle
cells; other cells — the red blood cells — de-
velop the capacity of bringing them oxygen,
and in doing so have lost many capacities
which are possessed by lower forms. Other
cells develop in a peculiar way to form the
nerves by which all the various parts of the
body are brought into harmonious action, and
so on. Thus we see in the higher animals
each highly developed cell working for the
others as well as for itself and for the organ-
ism as a whole, only its chief endeavor is con-
centrated in some one special thing, and as a
result of this concentration some of the more
general cell powers are lost or diminished.

12 The Story of the Bacteria

Did time permit, I should like to picture for
you the character and destiny of some of the
lower forms of cells, which we find in the hu-
man body, — those which have not undergone
that differentiation in structure and function
which belongs to higher types; to speak of
the marvellous potentialities which are dor-
mant in them; to show you how their very
simplicity of existence, the absence of special
powers, and their boundless capacity for re-
production particularly fit them to become the
conservators of the individual; to indicate
what an important role some of them play
in the healing of wounds and in the formation
of new tissues. So we are not to think of the
lower forms of cells in the body as insignifi-
cant, because under ordinary circumstances
their being and performances are humble
and inconspicuous, for they seem to be ever
ready, either resting quietly in their tiny nooks
within the solid tissues, or driven restlessly in
the rushing torrent of the blood, to assume
again the lowly but active powers of embry-
onic cells, and begin when necessary the work
of reproduction and repair.

The Cells of the Body 13

These cells have, too, a most important r61e,
as we shall see by and by, in combating the
incursion of certain forms of bacteria which
now and then obtrude themselves into this
happy family of cells which makes up the
human body.

We have thus seen that all the varied struct-
ures and functions of the human body are but
the combined expression of the structure and
lives of the cells which compose it, all co-ordi-
nated and working in harmony by means of a
self -built, cellular mechanism. Starting with
the type of the most simple of living things,
a single cell, the finished organism is an
aggregate of the progeny of the original cell,
some groups of which have developed special
forms and powers, in accordance with a uni-
versal principle in nature. So the doctrine of
evolution, even should the record of the rocks
be incomplete and perfect continuity in the
grouping of living species fail, still finds
epitomized in every animal and plant which
has escaped from the primitive simplicity of
the lowest forms, a most pertinent illustration
and convincing proof.

CHAPTER II

BACTERIA AND SOME OF THE THINGS WHICH
THEY DO

THERE are many very good reasons for
believing that when life first appeared
upon the earth it showed itself in a very sim-
ple and primitive form, in some such form
perhaps as we have seen in the amoeba or
other simple cells. But as the ages passed, in
accordance with the principles of the physio-
logical division of labor, which we have glanced
at in the last chapter, many of the living
beings gradually assumed more and more
complex forms and capacities.

Not all living things, however, shared in
these evolutionary changes. There is, in fact,
a great group of lowly plants, so small as to
be quite invisible to the naked eye, and which
until within a few years have been entirely

14

What Bacteria Do 15

unknown to man, which still linger in the
primitive simplicity which we imagine to have
belonged to the earth's earliest denizens.
These are the bacteria.

So small are the bacteria, and so simple in
their structure and activities, that it has not
been an easy task
for scientific men
to decide whether
they belonged
among animals or
plants. It is now
definitely settled,

J FIG. I. — FORMS OF BACTERIA

however, that they

are plants, and are closely related to the sea-
weeds.

Bacteria vary a good deal in shape, but
in general they are either spheroidal or ovoidal,
like a billiard-ball or an egg; or rod-shaped,
like a lead-pencil; or spiral-shaped, like a
cork-screw. Some are separate, some clus-
tered. Fig. i:

They are in general so very small that we
can hardly form a conception of them except
by comparison with some well-known objects.

16 The Story of the Bacteria

One of the most common of the bacteria is a
little rod, so small that if you were to put fif-
teen hundred of them end to end, the line
would scarcely reach across the head of an
ordinary pin. If you look at them with a
magnifying power so great that, if it could be
applied to him, it would make a man look
about four times as tall as Mount Washington,
they do not look larger than this. We can
see, however, that they are made up of a
slightly granular material surrounded by a
somewhat denser envelope.

The bacteria appear under the microscope
as pale translucent bodies, and the student
usually finds it necessary, in order to see their
outlines clearly, to stain them with some
one of the aniline dyes — red, or blue, or violet,
— when they become very distinct.

When they are alive and suspended in fluids
many of the rod-like and spiral bacteria can
perform the most elaborate and astonishing
series of movements. They swim slowly, they
turn about, they roll over, they wriggle, dart
forward, retreat, bang against one another,
rest awhile, sway to and fro, plunge off again,

What Bacteria Do 17

and so on through varying phases of move-
ment until the head swims and the eye tires in
following them. This move-
ment, in some of the bac-
teria at» least, is induced by
a little hair-like projection
from the end of the organ- FIG. 2. — FLAGELLA

« • 1 M -11 OF BACTERIA

ism, which vibrates rapidly
to and fro — Fig. 2. It is very difficult to
see these little projections or flagella, even
with the most powerful microscopes, but,
notwithstanding this, they have actually
been photographed, and in some cases
the image of the flagella, which failed to
make an impression on the retina, has been
caught and fixed by the sensitive plate in the
camera.

Warmth, moisture, oxygen, and some or-
ganic matter are the simple conditions re-
quired for the activities of the bacteria.

When the conditions are favorable they may
increase in number to a degree which is limited
only by their surroundings. A little constric-
tion appears around one of the bacteria; it
grows a little longer, a partition forms across

i8 The Story of the Bacteria

the middle, and in the place of one there are
two full-fledged bacteria. These may at once
fall apart and each new individual go on di-
viding as before, or they may cling together,
forming threads or chains of varying length,
or clumps or masses.

So rapid is this mode of reproduction that
a single germ by this process of growth and
subdivision- may give rise to more than sixteen
and a half millions of similar organisms within
twenty-four hours. It has been calculated by
an eminent biologist that, if the proper condi-
tions could be maintained, a little rod-like
bacterium, which would measure only about a
thousandth of an inch in length, multiplying
in this way, would in less than five days make
a mass which would completely fill as much
space as is occupied by all the oceans on the
earth's surface, supposing them to have an
average depth of one mile.

Let not the timid soul tremble, however, for
the principle of the survival of the fittest and
the influences of environment have kept our
prolific organisms so well in check that the
world had grown very old and its favored

What Bacteria Do 19

nursling, man, pretty well along in experience
and skill before ever he recognized the exist-
ence of these his microscopic contemporaries
and possible ancestors.

The struggle for existence goes on, where
varying forms of bacteria are growing, as
fiercely as ever it did among more highly or-
ganized beings. One race succeeds another,
one species adapts itself to the conditions
which brought about the extinction of its
predecessors. Hardy individuals struggle with
their weaker neighbors as the food grows scanty
in their microscopic seas, and the weaker goes
to the wall.

Many forms possess the power of living and
multiplying in the manner described above so
long as the proper conditions prevail, but when
life, owing to some change in the environment
becomes no longer possible, the vital powers
collect themselves in a little shining mass in
one end of the bacterium, which surrounds
itself by a dense membrane, and in this form,
which is called a spore, — Fig. 3, — it can survive
adverse conditions which in the ordinary form
would have destroyed its life. Restore it

20 The Story of the Bacteria

to the needed conditions and the spore swells
into a bacterium again, and the roots of
a new ancestral tree begin to sprout.

These bacteria are really very simple forms
of cells, and like the cells
which we have looked at in
the last chapter, their life
expresses itself in certain
activities; they move, they
nourish themselves and
grow, they reproduce their
kind. They have the power in carrying on
the processes of their own nutrition, when
moisture and air are present, of tearing to
pieces, in the chemical sense, dead organic
material, using up such parts of it as they need
for their own purposes, and setting free the
rest in such form as to be available for the use
of other living things.

Everybody knows who thinks about it, that
the supply of such material as makes up the
bulk of the tissues of man, animals, and plants,
on this earth, is limited. So that if things were
not so arranged that living beings should have
the use of the material which goes to make up

What Bacteria Do 21

their bodies for only a comparatively short
time, the supply would run short and new
beings could not continue to appear.

When that mysterious group of activities
which we call life ceases to be manifested, in
animals and plants alike, if moisture and oxy-
gen and sufficient warmth are present, that
process known as putrefaction or decay begins,
by which the old combinations of matter are
broken up and the material set free for the use
of other beings. Now just here enter the
bacteria. It is they who tear these old organic
compounds asunder, using a little of them
as may suit their own needs, and turning
over the rest to their earth neighbors, who
have got higher up the scale of being, but
not yet so far as not to need absolutely and
hourly oxygen, hydrogen, nitrogen, and carbon,
to keep their life's furnaces a-going.

It is a very motley group of chemical
substances which these bacteria set free in
feeding themselves on nature's waste organic
materials. Sometimes these are very bad-
smelling gases, sometimes aromatic substances,
sometimes they are sweet, sometimes they are

22 The Story of the Bacteria

sour. But sooner or later they are used by
some animal or plant, and so again enter the
domain of life.

Thus ever in ceaseless alternations between
life and death these elemental combinations
come and go. And ever since life emerged
from its primal simple forms on the earth,
the bacteria have silently gone on tearing
the worn-out and useless to pieces and turning
it over in new combination to other forms of
life.

It was formerly believed that such lowly
organisms as the bacteria could spring at once
into being wherever in nature the conditions
were favorable, but this notion of spontaneous
generation, has long since been given up, be-
cause it was shown to have depended upon
insufficient and crude observation. We now
believe that every living thing comes from some
pre-existing living thing, be it man, beast,
plant, or cell, and this principle holds true as
well among the bacteria as among more highly
organized beings.

There is an enormous number of different
species of bacteria, each one of which appears to

What Bacteria Do 23

preserve its individual character under all the
varying conditions and vicissitudes to which
it is subject. They are to be found every-
where in nature. Where putrefaction and de-
cay are going on they are most abundant, but
where any form of life can exist they are pres-
ent, either dry and inactive, or where moisture
and food are present, growing and multiplying
in such degree as their surroundings will per-
mit. In all natural surface waters, in the soil,
on all fruits, vegetables, and plants; in the
nose, mouth, digestive canal, and excreta
of men and animals; on the skin, wherever
dust can go or collect, there are bacteria of
various forms in greater or smaller numbers.
They are the scavengers in the economy of
nature.

The great bacterial laboratory of the earth
is the soil. Here the most wonderful things
happen under the friendly influence of these
tiny germs. With the aid of other lowly liv-
ing things, they help in the gradual erosion
of the rocks, from which the mineral ingre-
dients of the soil arise. They pull the tissues
of dead trees and plants and animals asunder,

24 The Story of the Bacteria

setting free moisture and gases, and working
the whole stuff over into the vegetable mould,
from which the farmer wins a living for us all.
Sometimes the farmer deliberately sets the
bacteria at work, through the silos in which his
crops are made more useful for the food of cat-
tle. He keeps them busy in his manure heaps,
which they "ripen" for the special needs of
the soil. He uses them in making vinegar.

One of the most important of the chemical
elements in the growth of plants, as we shall
see more fully later, is nitrogen. In the water
and earth certain bacteria manipulate nitro-
gen in the most astonishing fashion, getting
it finally into proper shape for the uses of plant
life.

It is bacteria which make milk turn sour.
Other forms give to butter and to cheese their
distinctive flavors. Some of them help the
farmer in the ways which we have spoken
of and in many others. But there are bacteria
which play him false. His fruit decays when
they get inside through bruises. They injure
his vegetables when they find a chance. His
meat and milk and eggs go bad, when the

What Bacteria Do 25

wrong sort of bacteria get at them. His fence
posts, his timber, and even his planted seeds
rot; his hay heats and mildews; his water
tanks get foul, — all through the action of
bacterial pests. But in the long run the
beneficent bacteria win out, if the farmer
bacteriologist knows what to do and when to
do it, and stands by his job.

The folks who tan leather, those who rot
the flax plants to get them ready for the
making of linen thread, and the people who
cure the tobacco leaf for the smoker's delecta-
tion, are all jugglers on a large scale with
capacities and whims of special forms of living
bacteria. On the other hand, sugar manu-
facturers and bakers are often greatly pestered
by the presence of certain bacteria, which
hamper their operations or damage their pro-
ducts. The canning industries are engaged in
a ceaseless warfare with bacteria which some-
times destroy their stuff and disgust their
customers.

So common and abundant are the bacteria
that we are constantly taking enormous num-
bers of them into our systems with all of our

26 The Story of the Bacteria

uncooked food. We should not, however,
think of these little organisms which we thus
unwittingly consume as things necessarily un-
clean or unwholesome. For they are only little
cells after all, and nearly all the food which we
consume, whether animal or vegetable, is made
up of masses of cells which are either fit to eat
in their natural condition, as in the pulp of
fruits, or become so by simple cooking or other
preparation.

There is really very little difference, so far as
wholesomeness is concerned, between the few
thousand vegetable cells which we call bacte-
ria which may be clinging to the surface of a
grape, and a few hundred vegetable cells of
larger size of which the grape itself is com-
posed. Both are alike worked over by the
digestive organs, under ordinary conditions,
into nutritive material for the uses of the
body.

There are poisonous vegetables, and there
are, more 's the pity, as we shall see by and
by, poisonous bacteria, but we do not shudder
as we swallow a mushroom to think what
might have happened to us if we had swallowed

What Bacteria Do 27

a poisonous toadstool instead. We simply
trust to the gardener, or, if he be dishonest
or ignorant, see to it ourselves that the poison-
ous are not liable to get in with the other
plants, and then go on enjoying our delicacies
like sensible people.

It will thus be seen that the r61e of the
bacteria in nature, though humble and silent,
is an exceedingly important one. They are
indispensable to the continuance of the higher
forms of life upon the earth. They may well
be called, in general, man's invisible friends;
for without them the earth would soon be
depopulated and lapse into what at first it
was — a lifeless waste.

CHAPTER III

HOW THE BACTERIA ARE STUDIED

IF you take a small wisp of hay, put it in
an open jar, and, covering it with water,
set it in a warm place for a day or two, you
will presently see that the water which was at
first perfectly clear, begins to get turbid, and,
after a while, a grayish scum collects on the
top. Now the water begins to give off a dis-
agreeable odor of decay. This is what has
happened: The bacteria of various forms,
which, in the dried condition, were clinging to
the hay, or which were in the water, have mul-
tiplied to such an extent that they made the
water turbid, and many of the mobile forms
have sought the surface, where the oxygen
was most abundant. The solution of or-
ganic material from the hay has furnished

an abundance of food, and as the bacteria

28

How Bacteria Are Studied 29

have torn this into simpler forms to get the
particular elements which they needed for
their own use, the freed material, in part in
the form of bad-smelling gases, has either
been set free into the air or remains absorbed
in the water.

If you examine a tiny droplet of the water
from time to time with the microscope, you
will find that it is swarming with various forms
of bacteria, rods, balls, and perhaps spirals,
many of them in active motion. But you will
notice that from day to day the prevailing
forms change. One day the little rods will be
most abundant; the next, these may have
largely disappeared, and perhaps the little
balls are the most common forms. Then
perhaps a new set of rods or balls will appear
of a different size from the first. After a
while you will find that the bottom of the jar
has become covered with a light-colored sedi-
ment, and the water has become clearer.

The bacteria of one form or another have
gone on dividing and subdividing, breaking up
the dissolved organic matter in the water until
either they had used up the special form of

30 The Story of the Bacteria

material which was best suited to their needs,
or until the material which they had set free
had so far accumulated as to prevent their fur-
ther growth, and then they died, self -poisoned,
just as a man might who should be shut up in
a tight room until the accumulation of the
products of his respiration and excretion had
made further life impossible. Or they may
die because other species of bacteria growing
in the same fluid furnish material which
poisons their neighbors. So the proces-
sion of life goes on, until the bottom of
the jar becomes a veritable graveyard of
races.

Some forms of the bacteria, however, which
seem dead, and fall with the rest to the bot-
tom of the jar, are really only in a resting
stage; they have formed spores within them-
selves in the manner described above, and may
lie dormant until the proper conditions come
again, when they may spring into renewed
activities. But new species may from time to
time fall into the jar from the air and find in
the water, which was rank poison for the dead
species at the bottom, just the food they need,

How Bacteria Are Studied 31

and so will the drama of life and death be
enacted anew for long periods.

In such a confusing mixture as this the stu-
dent finds it no easy task to make out much
except differences in form and movement,
in the jumble of tiny plants. What he needs
to do is to get each species by itself, so that
he can cultivate it alone, and find out what it
is and does under more simple conditions.

For this purpose it is best to use some solid
substance on which bacteria will grow.

Boiled potatoes, which have been carefully
cleansed and sterilized — that is, free from any
bacteria from the soil or air — by steaming, will
do very well for some bacteria. These are
cut in halves, with knives sterilized by heat,
being held in the fingers which have been
freed from living germs by washing with
corrosive sublimate, and placed under steril-
ized bell- jars or in tubes, so that they may
not be contaminated by the accidental falling
upon them of bacteria from the air. Now, by
means of a platinum wire set in a glass handle,
which has been sterilized by heating to red-
ness, a tiny bit of the bacteria-containing

32 The Story of the Bacteria

material is spread upon the cut surface of the
potato, and the latter is covered again and set
away for a day or two in a warm place. Usu-
ally at the end of this time, if all goes well,
there will be a growth of the bacteria on the
potato so large as to be quite visible to the
naked eye. This growth, or " colony, " as
it is called, which is made up of myriads of
individual bacteria, the offspring of those
planted, in many cases presents very character-
istic ways of growing or special colors, etc.,
characters often by which particular species
of bacteria may be distinguished from all
others, even without the aid of the microscope.
This gross appearance of the growing colonies
is useful in the recognition of species which
under the microscope look very much alike.
Just as in agriculture, if one were in doubt
as to two specimens of seed which closely
resembled one another — say turnip and rape,
for example — by sowing them in the ground
and observing the resulting plants, all doubt
would be removed.

In thus planting the invisible and minute
bacteria, and allowing them to grow until such

How Bacteria Are Studied 33

large masses of colonies are formed that we
can readily see and study them with the naked
eye, we are realizing in another field a project
which was urged with a good deal of persist-
ency some years ago for finding out if there
were inhabitants in the moon, and for com-
municating with them.

It was proposed to build in outline on some
great plain on the earth's surface, like that of
Siberia, a gigantic structure so large that, even
assuming that the lunar inhabitants had no
telescopes, it would be visible to them. This
structure was to have some simple suggestive
mathematical form like a circle or triangle.
Seeing such a thing appear on the earth's sur-
face, it was thought that the lunar inhabitants
would probably "catch on"-— this phrase was
not known in those primitive times — and erect
a similar structure, and thus communication
would be established. The moon project fell
through, but, as we have seen by a somewhat
similar device, we actually make the inhabit-
ants of an unseen world communicate to us
to-day some of the secrets of their hidden life.

But the knowledge derived from the mode

34 The Story of the Bacteria

of growth of bacteria on potatoes is limited,
because as the potato is opaque we can see
only the surface of the colony; and, further-
more, not all the bacteria grow well on pota-
toes, and some do not grow upon them at all.
So the next step is to make some transparent
solid substance which shall be a suitable soil
for bacterial growth. One of the most common
and useful substances for this end is a 10 per
cent, solution of gelatin which is mixed with
beef tea, pepton, and a little common salt,
and then made neutral or slightly alkaline by
carbonate of soda. This mixture, carefully
heated so as to destroy all bacteria which
might be present in its ingredients, is filled
into ordinary glass test-tubes which have been
sterilized by a high temperature. These are
filled about one third full of the gelatin mixture,
and the opening is stopped by a plug of cotton
batting. Through a long plug of cotton, bac-
teria cannot pass ; the air can enter and leave
the tube, but all bacteria are caught by the
fibres of the cotton. After the gelatin has
become cool and solid, by means of a steril-
ized platinum wire, some of the bacteria are

PLATE I. — TUBE CULTURES OF BACTERIA

The two tubes at the left contain gelatin culture medium and show
different ways of growing of two species. The tubes at the right show a
rough surface growth on a white egg mixture. Notice the cotton plugs
which allow the air to enter but keep out all contaminating germs from
the pure cultures.

of THE

UNIVERSITY

OF

ILIFQW

How Bacteria Are Studied 35

introduced into the gelatin, the cotton plug
being removed for an instant for this purpose.
Being transparent, the gelatin permits us to
see from the sides as well as from the surface
the exact mode of growth of the particular
form of bacteria introduced into the tube,
and thus we learn a new set of characteristics
for the different species (see Plate I).

But if we need to keep our bacteria at a
higher temperature than that of an ordinary
room, say at the temperature of the body, at
which alone some forms will grow, the gelatin
would melt and the bacteria would be scat-
tered through it, and the characteristic mode
of growth of the masses or colonies would be
lost. So, for this purpose we use, instead of
gelatin, agar-agar, a material derived from
a sea-weed, which in i per cent, solution
forms a gelatinous solid transparent mass,
which may be heated to above the temper-
ature of the body without fluidifying. To
this are added, as to the gelatin, beef-tea,
pepton, etc.

By the use of these various soils, or "culture
media," as they are called, and many others

36 The Story of the Bacteria

such as beef -tea, milk, blood-serum, etc., we
can arrive at a series of characteristics in
the mode of growth of various bacteria by
which, together with their form when seen
under the microscope, we can distinguish
them one from the other, just as the naturalist
distinguishes from each other nearly related
animals and plants.

! It is obviously of the greatest importance,
as we have seen above, that we should be able
to separate different species of bacteria from
one another in the living condition, so that we
may have growths or colonies which shall con-
tain one species alone without admixture with
any other. These are called "pure cultures.'*
This is by no means an easy task, as will be
appreciated when we consider how exceedingly
minute the organisms are, and how much dan-
ger there is that the bacteria floating every-
where invisibly in the air may become mixed
with those forms which we are studying. By
a very simple device elaborated by Dr. Koch,
of Berlin, we are, nevertheless, able at any
time to separate one species from another with
the utmost certainty, or from a mixture of

PLATE II. — PLATE CULTURES IN PETRI DISHES

The upper dish contains a few colonies, the lower shows
many, of various sizes.

How Bacteria are Studied 37

many species to get into separate tubes pure
cultures of each species by itself. This is
accomplished by what is called the "plate
culture," the details of which are as follows:
Suppose we have a mixture, say a sample of
impure drinking water, which contains four
different species of bacteria, which we wish
to get into pure cultures in separate tubes.

We mix a small amount of the bacteria-
containing water with a much larger amount of
the above-described nutrient gelatin, melted
by heat. Then we pour this mixture into a
shallow glass dish with a glass cover, called a
Petri dish, which has been carefully sterilized
by heat, so as to form a thin layer. This
soon cools and becomes solid. The Petri
dish is covered to keep out any bacteria which
may be floating in the air, and to prevent its
drying, and is set away at the temperature
of the living-room. The individual bacteria
which were scattered through the gelatin layer
will presently commence to grow.

After a few hours or days, as the case may
be, if we look at the gelatin-film (see Plate III)
we see, sometimes with the naked eye, some-

38 The Story of the Bacteria

times only under the microscope, little points
or masses scattered through the gelatin, which
are colonies of bacteria, each one consisting
of hundreds or thousands of the organisms
which have grown from the single organism
which was fixed at that point as by a solid
wall when the gelatin cooled.

Of course, it sometimes happens that two or
more of the original germs either of the same
or different species were solidified in the gela-
tin when it cooled at the same place, and then
the resulting colony will consist of all the
organisms which have grown at this point,
mixed together or growing closely side by
side. In most cases, however, the little colo-
nies are composed of the descendants of a
single germ, and if we put the gelatin plate
under the microscope we can see the different
forms of the colonies which have grown from
the different species. The differences in the
mode of growth of the bacteria when planted
and studied in this way are manifold: some
are colored, red, green, yellow, orange, violet,
brown, etc.; some are colorless, some have
sharply defined smooth edges, some are jagged

PLATE III. — COLONIES OF BACTERIA

The larger of these colonies growing on gelatin in a Petri
dish show fringed borders which are characteristic of the species.

How Bacteria are Studied 39

or fringed — see Plate III ; some are beaded, or
send out little spines; some cause the gelatin
in their immediate vicinity to liquefy, so that
they come to lie in a little pool of fluid in a pit
or depression in the solid gelatin.

Now, by examining the plate microscopically
we can not only see how many different forms
of colonies there are — and each different form
of colony indicates a difference in the spe-
cies of bacteria composing it, — but nothing is
simpler than, directly under the microscope, to
take out on the tip of a sterilized .platinum
wire little bits from each one of the different
forms of colonies, and transfer them to sepa-
rate tubes of gelatin. Thus we secure "pure
cultures" of all the different forms of bacteria
which were contained in the original mixture.
Thus, minute as the individual bacteria are, ly-
ing far below the power of unaided vision, we
are able to manipulate them with as much cer-
tainty as the agriculturist does his larger plants.

When we have thus got different species of
bacteria separated from one another in the
form of pure cultures, we can experiment on
them in many ways, and learn their varying

40 The Story of the Bacteria

characteristics. We can plant them under
such conditions that their oxygen supply is
limited, and learn whether they do or do not
thrive; we can see whether they grow best at
high or low temperatures, whether they form
gas or not, and what degrees of heat or cold
will kill them. We can grow them in large
quantities, and study the chemical compounds
which result from their life processes. We can
apply to them various chemical substances
which are called germicides, or disinfectants,
and find out to which of these and in what
strength they most readily succumb.

In this way a large number of different
species of bacteria have been studied, and
these have been arranged in groups which
have some characters in common. So that
already, although the study of the bacteria by
the new methods is of recent date, we have the
outline of analysis tables, something like those
made for the identification of the higher
plants in Gray's Botany, for instance, by
the use of which the student can identify
certain of the better known forms which he
may come across in his studies.

PLATE IV. — A BACTERIAL CULTURE SHOWING THE
FORMATION OF GAS

The cut shows the lower end of a tube of gelatin into
which a needle was thrust on the tip of which were a few gas-
forming bacteria. As these have grown along the puncture
gas bubbles have collected.

How Bacteria are Studied 41

The nomenclature in bacteriology is still in
a rather chaotic condition, but a beginning has
been made. The term bacteria (singular, bac-
terium) applies to the whole class of organisms
of whatever shape. They are also sometimes
called " germs," or ' 'mi-
crobes," or "micro-organ-
isms," which means small
living beings. The round
or spheroidal form is
called ' l coccus, ' ' which
means a berry; the plural
is cocci. The botanical FIG.4._STREPTOCOCCI
name of the most com- FROM A CULTURE
mon form of the round
or spheroidal bacteria is Micrococcus — that
means "a little berry." Thus there is a
species of micrococcus which produces a yel-
low color when it is growing in masses. This
species is called Micrococcus luteus — the yel-
low micrococcus.

Another genus among the spheroidal bac-
teria is called Streptococcus — "a chain of ber-
ries"— Fig. 4 — because the little balls tend to
cling together and form longer and shorter

42 The Story of the Bacteria

tA

chains as they grow. Another, growing in
masses, is called Staphylococcus — "a bunch
of berries" — Fig. 5. Then
among the rod -shaped bac-
teria the most common genus
is called Bacillus (plural,
bacilli), and some of the
FIG. 5.— STAPHYLO- Species of this genus are

COCCUS FROM A

CULTURE among the most common and

abundant forms — Fig. 6.
Thus with a temporary and provisional sys-
tem of classification, the work of studying
and describing the bacteria
is steadily going on. And
if to see and describe living
beings on which no human
eye has ever rested before
be satisfying, it will be long
before the sighs of bacteri-

1 • -I A 1 -, FIG. 6. — BACILLI

ological A I e x a n d e r s are FROM A CULTURE
heard in this unseen world,
whose very shores have been barely touched
by the new explorers.

CHAPTER IV

SOME BACTERIAL CURIOSITIES

MOST travellers, and some people who
stay at home, too, have now and then
been mystified and delighted, when not
frightened, to see in the night-time that
wavering, cold, uncanny, but beautiful light,
sometimes tinged with the most exquisite
green or blue, which is commonly called phos-
phorescence. Sometimes it is seen in decay-
ing plants or wood; sometimes bays or inlets
of the sea are fairly luminous with it. The
surface of dead fish and of meat and various
kinds of vegetables often becomes so bright
as to illuminate the storage rooms in which
they lie.

Some time since there was brought to the
laboratory for examination a cluster of sau-
sages which had been destined to grace a

43

44 The Story of the Bacteria

boarding-house breakfast- table. To the con-
sternation of the maid who went into the dark
cellar for them in the early morning, there
hung in the place of the sausages a fiery
effigy which seemed to her more like the
quondam spirits of their mysterious ingredi-
ents than the unctuous homely friend of the
homeless boarder.

The explanation of this is now simple
enough without recourse to the supernatural;
for it has been recently shown that this
curious light which various organic sub-
stances emit is due, in many cases at least,
to the enormous numbers of certain kinds of
bacteria which are present on their surfaces,
hard at work feeding on the organic com-
pounds which are present and undergoing
decay. Pure cultures of these singular bac-
teria have been made and cultivated in con-
siderable quantities. These bacterial masses,
together with the tubes in which they were
growing, have been placed in a dark room
with an open watch beside them, and bacterial
masses, tubes, and all actually photographed
by their own light, the pointers of the watch

Some Bacterial Curiosities 45

showing distinctly the time of day. So it
would seem that this cousin of the will-o'-
the-wisp — no doubt often mistaken for him —
is no malevolent genius after all, but a quiet
little citizen working away as diligently as
he can to make the world more comfortable
for his betters.

It has long been known by the makers of
beverages that alcohol is formed in certain
sugary mixtures by a process called fermen-
tation, and that this tearing to pieces of the
sugar into other compounds, one of which is
alcohol, is accomplished by a little living
organism called yeast, closely related to the
bacteria. In the earlier days of beer- and
wine-making it was often found that the beer
did not work or ferment properly, and that
wine would get sour or bitter. We now know
that these irregularities are due to the fact
that certain kinds of bacteria are apt to get
into the wine or beer during the manufacture,
and when they do a bitter struggle for food
goes on between the yeasts and the bacteria;
or the latter may bide their time, and later
in the process begin to grow and produce

46 The Story of the Bacteria

very undesirable compounds in the fluids.
So the manufacturer has to be on the alert,
and at the right moment come to the rescue
of his army of servitors, the yeast plants,
and introduce into his beer some chemical
substance which is innocuous to them but
deadly to the intruding bacteria. Or he may
raise his wine at a certain period to such a
temperature as will suffice to kill the bacteria
but not injure the flavor of the already fer-
mented juice. Here again as in the case of
the farmer we see the bacteria coming into
conflict with the purposes of their earth-
neighbor — man .

Some of the bacteria are great lovers of
oxygen, and if they are shut up in a little cell
containing a few drops of water in which a
bubble of air has been enclosed, after a while
it will be found that those forms which are
capable of locomotion have made their way
from all parts of the fluid, which is a veritable
ocean to them, and are closely clustered
around the air bubble, jostling and bumping
against one another in the most reckless way.
It seems almost as if this rush towards the

Some Bacterial Curiosities 47

oxygen were an evidence of volition in its
simplest form way down on the lowest
border-line of life.

Some forms of bacteria are exceedingly in-
vulnerable to the action of cold, and can not
only move actively about in very cold water,
but can remain alive for long periods fast
frozen in a mass of ice. Now a very curious
thing has been noticed in the ice which is
gathered in these regions and which we use
for domestic purposes, and that is, that the
so-called bubbly streaks which we usually
see in our ice blocks contain, as a rule, many
more bacteria than does the transparent ice
close by.

It has been found, on cultivating the bac-
teria from the bubbly streaks, that the species
which was most abundant here is an oxygen
lover, and is also very mobile. Now the
bubbles which collect in streaks or layers in
the ice collect during the daytime, or when
the ice is not freezing very fast below, and
there is time for the air-seeking bacteria to
gather around them in great numbers. But
now, when a clear night or a cold snap comes

48 The Story of the Bacteria

on, the ice closes around both bubbles and
bacteria, and we have formed, to use the
language of the geologist, an air and fossil-
bearing stratum. Only our bacterial fossils
are not dead, and all we have to do in order
to find out what forms of life were present
in our successive geological periods, limited per-
haps only by a night, is to melt a bit of the ice,
mix it with our culture gelatin, and in a day
or two we shall have a whole garden of grow-
ing plants, which we can study at our leisure.

But many bacteria can survive a tempera-
ture much below freezing. Experiments with
liquid air, which affords extreme degrees of
cold, have shown that exposure to more than
190° C. below zero leaves some bacteria quite
unharmed. While many bacteria thus sur-
vive extreme cold, they do not multiply at
low temperatures, so that the use of ice in
preserving foods is of great importance.

On the other hand, there are bacterial
species which prefer high temperatures. Thus
some forms flourish in the water of hot springs
at a temperature of 170° Fahrenheit. These
are called thermophylic or "heat lovers."

Some Bacterial Curiosities 49

As a rule, bacteria are soon killed by bright
sunlight, and even in diffuse daylight many
pine and die.

Among the most curious things which the
bacteriologist has to exhibit in his bacterial
conservatory is the color-forming species. It
is only when they are growing in masses, of
course, that enough color is formed to be
visible; but then one may see in the little
slimy masses which cover the surface of the
food or culture media in the tubes, every
color of the rainbow and many variations
in hue. Sometimes not only is the bacterial
mass itself brilliantly colored, but some of
the chemical substances which they form as
they grow permeate the gelatin and give it
a beautiful fluorescence, green or red.

The writer was not long ago standing be-
side a supper-table, whose sole floral decora-
tion was a bunch of large, exquisitely tinted
chrysanthemums, when a friend remarked
upon the patience and skill which had been
required to develop this magnificent flower
by artificial selection from its simple and
homely ancestor, and queried in a quizzing

50 The Story of the Bacteria

way how long it would be before somebody
would be trying to modify the colors of some
of the bacteria by the well-known horti-
cultural methods. His idea was a clever one,
but he was behind the times, for already a
German bacteriologist had, starting with a
deep purple-forming species of bacteria, and
selecting and replanting the lighter-colored
colonies, at last obtained cultures which were
nearly white, but were in other respects
essentially the same.

In many other ways the bacteriologist can
modify the life processes of bacteria by suc-
cessive generations of selective cultures. Acid
producers can be restrained, or their powers
exalted. Lovers of oxygen can be made to
go without it. The fermentative and putre-
factive capacities of many forms can be
profoundly altered. They can be adapted
to strange foods and to outlandish con-
ditions. Harmful species can be rendered
harmless and the virulence of other forms
exalted.

Thus the great and far-reaching prin-
ciples of natural selection, in accordance with

Some Bacterial Curiosities 51

which life, slowly emerging from its primeval
simplicity, at last came to be manifested in
that grand scale of living beings at the top
of which man stands supreme, are still to be
traced way down among the invisible or-
ganisms which typify the earliest and sim-
plest expression of life.

But certain of these color-forming bacteria
are sometimes very disagreeable intruders
upon domestic life. Occasionally, without
warning, the milk of a particular dairy
suddenly develops a very uncanny deep-blue
color, which, like an epidemic, spreads to all
the milk which is stored in special rooms.
This occurrence, for a long time a disagreeable
and costly mystery, is now known to be due
to a tiny bacterium of the genus Bacillus?
which, floating about in the air with the
dust, from time to time infects rooms, and,
falling into the milk, grows there, producing
the blue coloring matter.

Sometimes milk gets red instead of blue,
and then the change is due to another form
of bacteria floating with the dust. Bread,
too, may become infected in the same way,

52 The Story of the Bacteria

and the dough set aside in bake-shops over-
night to rise has not infrequently been found
in the morning resplendent with colors which
fairly rivalled those of the rising sun.

There is a species of bacteria in every good
collection, and a veritable Nestor among the
forms known to man, which has a curious
ecclesiastical history. Among all the in-
numerable natural phenomena which, by their
striking character, infrequent occurrence, and
lack of apparent cause, were in early times
relegated to the domain of the supernatural,
none perhaps was more strange and uncanny
than the sudden appearance on the moist
surfaces of articles of food of little bright-red
shiny droplets, which, gradually spreading,
at length formed large shiny, deep, rich-red
masses, looking very like drops, or masses,
or clots of blood. The story is long and
tragic of the dire calamities, unmentionable
crimes, and swift retributions which these
strange appearances of blood were supposed
to foreshadow.

This miracle of the bleeding Host has
appeared again and again in the hands of the

CHAPTER V

AGRICULTURAL CONJURERS

LIVING bodies are made up largely of
oxygen, hydrogen, carbon, and nitrogen.
While these are all very abundant in the
world, nitrogen seems to be about the most
difficult for both animals and the higher plants
to get hold of, because in the ordinary form
in which it exists in the atmosphere it is not
directly available. Man and his relatives,
the meat-eating animals, get nitrogen mostly
from other animals or from plants, and ul-
timately the nitrogen, which animals require,
comes from plants. The higher plants get
their nitrogen largely from certain chemical
compounds in the soil called nitrates, which
the bacteria have been active in forming
out of the dead stuff of former living things.
Give the farmer soil, water, air, sunshine,

55

56 The Story of the Bacteria

and seed, and his task is to get a crop. This
seems simple enough. In fact he has oxygen,
hydrogen, and carbon a plenty. The trouble
is with the nitrogen, which is so abundant
that it makes up about four fifths of the vol-
ume of the air. But plants can't eat pure
nitrogen. So the farmer has to secure it
in a roundabout way. As all animal and
vegetable substances contain nitrogen, and,
when dead and decaying under the in-
fluence of bacteria, give up those nitrogen
compounds which living and growing plants
require, he gets this dead stuff wherever he
can. His great domestic supply is from his
barnyard manure. This is in truth the most
valuable product of his farm, if he knows how
to care for and use it. But he often spends
a great deal of money in buying imported
nitrogen in the form of Chile saltpetre or
other compounds. There are commercial
laboratories which prepare artificial nitrogen
compounds for the farmer. But for all these
things he has to pay out his hard-earned cash.
Some crops, notably grain, take a great
deal of nitrogen out of the soil, so that if a

PLATE V. — NODULES ON CLOVER ROOTS

Agricultural Conjurers 57

new supply be not furnished, after a while
the land becomes impoverished. This is
one reason why there are in some parts of
the country so many abandoned farms — toe
little nitrogen — and the atmosphere full of it.

It has long been clear that if the farmer
could only directly tap the atmospheric
nitrogen, his fortune would be made. It
has been known ever since the times of the
old Romans that what is called " green
manuring," that is the ploughing under of
crops of leguminous plants, such as clover,
enriches the soil in quite a remarkable though
mysterious way. But the reason for this
common practice was left for the modern
bacteriologist to discover. And here enters
one of the most noteworthy of the bacterial
conjurers.

Farmers and other students of plants for
a long time have been familiar with certain
little nodules or tubercles (Plate V.) growing
on the roots of leguminous plants such as
clover, peas, beans, etc., and had supposed
that they indicated some kind of disease of
the plant. But a few years ago it was dis-

58 The Story of the Bacteria

covered that these root nodules are made up
largely of rod-like and irregular-shaped bac-
teria (Fig. 7). Several forms of these can
now be cultivated artificially, and it has been
found that they have the power of seizing
upon atmospheric nitrogen and working it

over into available form
for the uses of their
host. These bacteria
get into the rootlets
of the leguminous plant
and grow there as par-
asites, not at first al-
together welcomed it
would seem. But pres-
ently they begin to
satisfy the intense ni-
trogen hunger of the
clover, alfalfa, peas, and beans, and thus the
happy family lives on in mutual helpfulness.
So at last, down in this borderland of life has
been discovered the key to untold riches for the
farmer. For he now knows the importance of
root nodules and their bacteria, and can trans-
fer them from field to field, or he can get from

FIG. 7.— NODULE BACTERIA

These irregular shaped
bacteria were artificially
cultivated from the nodules
on the roots of leguminous
plants.

Agricultural Conjurers 59

the Federal Government, or from State agri-
cultural or other laboratories, artificial living
cultures of these wonder working germs with
which he may inoculate his field. Then he
may leave them in the rootlets of his crops
to conjure from the air, by day and by night,
this precious atmospheric nitrogen. This the
higher plant will thrive upon and thriftily store
away for the future uses of man and beast.

There are certain other bacteria in the
ground which can fix the atmospheric nitro-
gen as they grow and so enrich the soil. In
this way fields, which have plenty of vege-
table mould, may improve when allowed to go
fallow for a time. But the various forms of
nodule bacteria which join forces with the
peas and beans and clovers in turning air
into gold are the more dramatic conjurers
which modern science has presented to the
farmer. You will find plenty of pictures in
the books which deal with scientific agricul-
ture, showing lean beans with their nodule-
less roots beside others, the nodular and
leafy opulence of which betokens their silent
partnership with the atmosphere.

CHAPTER VI

BACTERIA AS MAN'S INVISIBLE FOES

WE have seen that the bacteria in general
are not only curious and interesting
as objects of study, but in the work which they
are ceaselessly and silently doing they are
absolutely indispensable to the continuance
of the higher forms of life upon the earth.
But unfortunately there is another darker
side to the picture. Among the myriads
of useful as well as harmless bacteria, we have
lately learned that there are a few forms which
find the most favorable conditions for their
life and growth in the bodies of men and some
of the higher animals.

Most of these do not grow well in nature
as other bacteria do, nor do they thrive on
ordinary decomposing organic matter. They

look very much like the more common

60

Bacteria as Man's Invisible Foes 61

harmless bacteria, some being little balls,
some rods, and some spirals. Like other
bacteria, they grow at the expense of the
materials with which, under favorable con-
ditions, they come in contact, and like them
they produce new chemical compounds as the
result of their life processes. When they get
into the human body, the different species
grow in different ways, and produce different
kinds of chemical compounds, and this growth
or the poisonous substances which are formed
induce disease.

Bacteria which can grow in the body and
do serious harm there are called pathogenic
or disease-inducing bacteria. The poisonous
chemical compounds which they set free as
they grow, are called toxines.

Now, before we try to comprehend how
disease can be induced by bacteria, we ought
to understand what disease is.

We have seen in the first chapter that the
human body is made up of several commu-
nities of cells, each community having ac-
quired the power of doing some special thing
for the good of the body as a whole, and that

62 The Story of the Bacteria

these cell communities are all co-ordinated so
as to act in harmony. We have seen that
these cell communities which make up this
wonderful mechanism are all originally de-
rived from a single living cell, the ovum.

What this mysterious thing is which we call
life, which from the original cell, the ovum,
is imparted to all the myriad specialized cells
which springs from it as the body grows; what
it is which determines that from one of two
cells which under the most powerful of micro-
scopes look exactly alike there shall develop
a man, and from the other an animal, we
simply do not know. We theorize, we specu-
late, we draw analogies, we give names, but
at the end we conclude that we must wait still
for more light. We do know, however, that
this self -built cellular mechanism, the body,
which is alive, has in it the power of self-
renewal: the power, when once started, to
go on doing the various things for which it is
fitted for a time, provided the proper external
and internal conditions are maintained. But
sooner or later the machinery begins to creak
and tremble, sometimes in one part, sometimes

Bacteria as Man's Invisible Foes 63

in another, sometimes everywhere, and grad-
ually or suddenly that combination of activ-
ities which we call life disappears, and the
worn-out mechanism for the first time since
it came into being is still. This is death.
There is no disease, but, as we are apt to
say — not because it means much, but because
we think we must say something, — an ex-
haustion of the vital forces. The mechanism
is worn out, and so can no longer develop out
of food and air the self-renewed impelling
force. It is death from old age. But this is
comparatively infrequent.

If the proper food, air, and surroundings
are maintained, the various co-ordinated cell
communities which we call liver, brain, kid-
neys, lungs, integument, and so forth, pro-
vided^they are properly set going in the first
place, have not only the power to go on doing
their work, but they have a well marked
capacity for overcoming and resisting dele-
terious agencies of one kind and another, —
a sort of health inertia. The muscle cells
do make shift to contract even though their
food supply be temporarily scanty; the blood

64 The Story of the Bacteria

cells will carry a certain amount of oxygen
in their ceaseless rounds of visits to the tissues,
though the air from which they get it through
the lungs be as foul and meagre as it is in
some of our fashionable theatres and churches
and school-rooms. And if certain cells or
groups of cells should be forced to work awry,
they always tend to get back to their proper
business and conditions, even against great
obstacles, just as soon as they can.

Even when large numbers of cells or cell
groups are entirely removed from the com-
munity, as by an injury, new cells can form
out of those which are left, or the duties of
the lost cells are assumed and may be per-
manently maintained by their fellows. Pa-
triotism and esprit du corps are very markedly
typified in the cell communities which to-
gether constitute the republic or common-
wealth called the body.

When important cell communities are seri-
ously injured or changed in structure so that
they cannot do well the things which they
ought to do, or when they fail to act in har-
mony, through some fault of their own or some

Bacteria as Man's Invisible Foes 65

disorder in the co-ordinating mechanism, the
failure in what we may term the rhythm
of the body's activities constitutes what we
call disease.

The part which may be the seat of the dis-
ease is as varied as are the organs and tissues
of which the body is composed.

The disturbances in the activities of the
body which result from these changes in the
structure and action of the various parts have
been so long studied that the educated
physician is usually able to tell from certain
irregularities of the body's activities what part
or parts it is which are affected. In many
cases the physician does, in some he does not,
know what is the exact cause of the disturb-
ance. In some cases, when the cause of the
disturbance is known, he can remove it either
by directing a change in the habits or by
the administration of drugs, and then the ten-
dency of the cell communities of the body to
get back into their proper condition of them-
selves alone will restore health. Sometimes
this inherent tendency is aided by the use of
medicines. Most of the body's disturbances

66 The Story of the Bacteria

tend to pass away of themselves after a longer
or shorter period, if they are not so severe as
to destroy life. Under these conditions the
duty of the physician may be only to aid
the body by food and air and proper regimen
in the work which it is doing itself. And so
through the long list of ills which come upon
the human frame from known or unknown
causes the wise physician guides and aids the
natural recuperative tendencies of the body
cells.

Among all the varied changes in structure
and disturbance in activities of the body
which thus constitute disease there are, as we
have seen, several, and these most important
ones, which have recently been proven to be
caused by bacteria. To some of these we
must now turn our attention so as to learn how
the disturbances are brought about, and what
we may do for ourselves to avoid them.

But before we enter the domain of the doc-
tors, let us devote a moment to their shib-
boleths, by which it may be known whether
we are of the elect or only dabblers.

A disease which is incited by the entrance

Bacteria as Man's Invisible Foes 67

into the body and proliferation there of
pathogenic micro-organisms is called an in-
fectious disease; the organisms, the infective
agents. These organisms are most frequently
bacteria, but other minute plants, such as
yeasts and animals called protozoa, are
sometimes to blame.

Each infectious disease has its special
features by which the doctor knows it.
These features depend upon the species of the
invading germ, its way of growing, the poison
it sets free, the length of its life span. But
the body cells have their particular vulnera-
bilities to microbic invasion and poisons.
So that in one case it is the nervous system,
in another the lungs or the blood or the
digestive system which especially suffers.
Moreover, as one rose is redder than another,
or one aromatic plant more pungent than its
fellow, so in one case the germs which gain
access to the body may involve a more
potent poison than do those of the same
species but of another strain, and then the
disease may be more virulent in type. So
also an individual may at the time of in-

68 The Story of the Bacteria

fection be more susceptible than is usual to
the ravages of the invader and thus be the
victim of a graver form of the disease.

Infectious diseases of the type of small-pox,
measles, and scarlatina, whose infective agents
are easily transmitted, are called contagious.
When it is said of an infective disease that
it is more or less readily communicable, it is
really meant that the infective agent is
communicable, not the disease. For disease
is always a process of the body and not a
thing, and so cannot be transmitted.

The elder folk were wont to think of diseases
as some sort of demons or evil spirits which
attacked the body or took possession of it,
and tried to banish these by rattles, drums,
or songs and incantations, as some of our
North American Indians do to-day. Though
we know that disease is not a thing but a
disturbance of the body processes, we still
speak of disease as attacking the body. We
say "the man was attacked by a severe
dyspepsia after eating hot plum pudding. "
But it was really not the dyspepsia, it was the
plum pudding which attacked the man.

Bacteria as Man's Invisible Foes 69

Dyspepsia, the disease, was only the process
of reaction or defence against the pudding.

So if we choose to be dramatic in our speech
we may still say that disease attacks a man.
But let us hold it in the back of our heads,
that we do not really blame the disease but
the bacteria or other factors which have set
it going.

It is well to do this, not only for the sake
of clearness of conception, but because when
we try to cure or prevent disease, it is the incit-
ing factors which we must strive to control,
and not only, or chiefly, the symptoms, which
characterize but do not constitute the disease.
For in a large proportion of cases the symp-
toms of disease are only the marks of the
efforts of the body to protect itself against
some offending condition or invading thing.
Fever and pain, cough and headache, the
halting appetite and laboring heart — these
may all be only signs of wholesome resistance
to damage, or warnings against improper
or unsafe modes of life.

I

CHAPTER VII

THE BACTERIA OF WOUNDS AND OF SURGICAL
DISEASES

ONE of the greatest dangers associated
with injuries and wounds of the body,
whether inflicted by accident or made by the
knife of the surgeon in necessary operations,
is the liability to what is known as blood
poisoning.

So great is this danger, that in earlier
wars a great many more lives were usually
lost from blood poisoning than by bullets
or cannon-balls. The cause of this form of
disease, which is so apt to complicate wounds,
was for a long time unknown. Then, as
these wounds were apt, in blood poisoning,
to be foul and bad-smelling, it was concluded

that the trouble might be that dirt or filth

70

Wounds and Surgical Diseases 71

of some sort got into them and so set up the
disease.

What the particular thing was, whether
bacteria or something else, which so gained
entrance to the body, ho one knew. But the
surgeons did not wait until they should know
all about the cause of the trouble, but began
to apply to the wounds such materials as
would actually kill germs, or, at any rate,
keep the wounds free from putrefactive
changes. Carbolic acid, dissolved in water,
was found to be efficient in this way in washing
the wounds.

Then, as it seemed more and more as if the
trouble were due to living germs falling upon
the wounds from the air with the dust, it
became the practice, when surgical operations
were being done or wounds dressed, to spray
carbolic in the air about the operator's hands
and over his instruments and upon the wounds,
and when the bandages were put on to seal
them in tightly, so that no germs could gain
access to the wound while the healing went
on. All this time the particular species of
bacteria which produced the trouble remained

72 The Story of the Bacteria

entirely unknown; indeed, it . was only an
hypothesis that the disease was due to germs
at all.

A great deal of careful laboratory work has,
however, been done on this subject, and a
great many animal experiments made, so that
now we know not only that
blood poisoning but boils,
abscesses, erysipelas, and
many other less serious in-
flammations are induced by
bacteria. We have found

FIG. 8. — STREPTO- c .* ,-, ...

coccus PYOGENES out» furthermore, that there
are two particular species
which cause the trouble in the great majority
of cases.

Both of these bacteria are little balls or
micrococci. One of them, as it grows, tends
to form chains, and so is called Streptococcus
(Fig. 8) ; the other tends to group itself in
clusters a little like a bunch of grapes, and
so is called Staphylococcus (Fig. 9).

Now, it has been further found that these
two forms of bacteria are quite abundant
where people are gathered, mostly in dirty

Wounds and Surgical Diseases 73

places; sometimes where the healthy, but
especially where sick people are crowded
together, as in hospitals. They are found in
small numbers floating with the dust in the
air, where dust lodges, and often in the
mouths and on the cloth-
ing of the people them-
selves.

It is thus evident how £j/*

the wound diseases, such Jb -f* + 9*

as blood poisoning, can

- f. ., FIG. 9- — STAPHYLO-

come about, for wherever coccus PYOGENES
infective dust falls on the
open surfaces of the wounds or on any thing
which comes in contact with them, or if the
hands of surgeons or others who dress wounds
are not free from the dangerous bacteria these
may, if not destroyed, commence to grow,
and not only by the poisonous materials
which they form as they grow, interfere with
the healing of the wounds, but they may get
into the blood and be carried to various
parts of the body, there sometimes producing
fatal results.

The modern surgeon, in the many beneficent

74 The Story of the Bacteria

operations which he performs, is not so much
concerned about the bacteria which may fall
upon the wounds from the air, as he is about
those germs which may be upon the hands
or face, or may come from the mouth or nose
or from some insignificant pustule or a boil
of himself or the attendants, because these
are more apt to be fully virulent than are bac-
teria which have been dried and sunburned in
the dust. So he does not use disinfectants as
much as was formerly the case, but sees to it
that the seat of operation in the patient, and
the hands of the attendants and all instru-
ments, towels, bandages, etc., which may touch
the wounds, are freed beforehand, as nearly
as possible, from all contaminating germs.

This is the aseptic, which has supplanted
the antiseptic surgery. The aim is to keep
bacteria out of wounds, rather than to try
to kill them with antiseptics, after they have
been allowed to get in. Clean white aprons,
caps and gowns, rubber gloves, or fresh
scrubbed hands, sterile instruments and dress-
ings— these are the insignia of aseptic surgery,
whose watchword is cleanliness.

Wounds and Surgical Diseases 75

It is one of the greatest practical triumphs
of science in modern times that the surgeon
can now so carefully plan out his operations
and treatment of wounds, that not only is
blood poisoning, as it used to prevail but a few
years ago, the greatest rarity among edu-
cated and skilful surgeons, but the most ex-
tensive operations, such as opening the great
cavities of the body, may now be done, when
they are necessary to save life or make it
endurable, with very little risk of the dangers
which formerly attended such procedures.

Childbed fever, which in former times
claimed so many victims under especially
pitiful circumstances, and which used some-
times to spread with frightful rapidity among
women whose confinement took place in hos-
pitals, is now of comparatively rare occur-
rence, because the educated physician knows
what the particular element of danger is and
how to avoid and combat it. For it has been
found that childbed fever is really a form of
blood poisoning, due to the same germs as
induce the disease in ordinary wounds.

Dr. Oliver Wendell Holmes, early in his

76 The Story of the Bacteria

career, became convinced that the poison
causing childbed fever could be carried on
the clothes of the physician from one patient
to another. What the poison was he could
not even fairly conjecture, but of the fact he
was certain. In spite of much opposition
and ridicule he urged his views, and many
lives were ultimately saved and epidemics
stayed because of his persistency in making
known his facts. To-day we not only know
that all that he urged was true, but the
poison which he assumed but could not see
has been proved to be bacteria, and we can
now cultivate them in tubes and know exactly
what will most surely destroy them. While
literature owes much to the wit and cleverness
of the genius of the breakfast-table, science
and humanity are not less debtors to the zeal
and pertinacity of the young doctor, who still
declared for his beliefs, though his more aged
and then more renowned confreres applied to
him many terms of opprobrium and disrespect.
Now let us look a little more closely at
the way in which these tiny organisms induce
inflammation, suppuration, or the formation

Wounds and Surgical Diseases 77

of pus and blood poisoning. We have seen
in the first chapter that although most of the
cells of the body have assumed special forms
and powers as the body develops out of its
embryonic period, there are some cells which
scarcely seem to have got beyond the stage
in which the simplest of the unicellular
organisms, such as the amoeba, belong. The
most prominent of these lowly organized cells
in the body are the white blood-cells or,
leucocytes as they are called. (See Plate XL)
Under ordinary conditions these go circling
round in the blood-vessels along with the red
blood-cells, or, crawling out of the blood-
vessels, slowly make their way about in the
smaller spaces in the tissues. All the things
they do under these circumstances we do
not know. But they are at any rate the
great scavengers of the body. When they
come across a particle of worn-out or foreign
material in the tissues, they take it into
themselves, just as amoeba does its food in
water, and either digest it or carry it back
to those parts of the body in which waste
material is systematically disposed of.

78 The Story of the Bacteria

But let an injury such as an open wound
occur, and the whole attitude of these leuco-
cytes changes. They get out of the blood-
vessels with all speed, in greater or less
numbers as the occasion may demand, and
gather about the edges of the wound, and after
a time they, together with some other cells of
the injured tissue, form, with the aid of the
blood-vessels near by, a mass of new tissues,
which replaces that which was lost by the
injury, and so permanently binds the edges
of the wound together. Sometimes these
white blood-cells gather in much greater
quantities about the wound than is necessary,
and then they are thrown off with some fluid
in the form of a material which we call pus.

Now to come back to the bacteria which
we are studying. When these bacteria get
into the tissues, they may begin to grow, and
as they do so they produce a small amount
of a poison which we call a toxine. This
poison acting injuriously on the tissues where
it is formed, the white blood-cells gather about
it just as they would about a wound. If the
bacteria continue to grow and multiply, the

Wounds and Surgical Diseases 79

white blood-cells may accumulate more and
more and die, the tissues may break down, and
so an abscess may be formed. Sometimes
the germs get into the blood and are carried
to various parts of the body, and wherever
they lodge abscesses may be formed, and this
constitutes one of the most dreaded forms of
blood poisoning.

Now what do the white blood-cells, the
leucocytes, accomplish under these circum-
stances?

There is good reason to believe that the
resisting capacity of the body to the incur-
sions of these living bacteria is largely resident
in the lowly organized cells, which in carrying
on their simple cellular activities assume the
role of defenders of the body against the bac-
terial invaders. If the conditions are fa-
vorable for them the white blood- and other
cells may get the upper hand of the bacteria
and stop their growth or kill them all off and
thus avert the danger. If, on the other hand,
the cells are not vigorous enough to resist
the poison set free by the bacteria and
themselves succumb to its influence, the

8o The Story of the Bacteria

way is opened to the spread of the infecting
germs.

In a later chapter on the safeguards of the
body we shall look a little more closely at
this significant battle of the cells in various
infectious diseases.

It sometimes happens that so extensive a
growth of the bacteria occurs in some local
region of the body and so much of the soluble
poison is produced that although the bacteria
may not themselves get generally distributed
the poison which they furnish may enter the
circulation, and so produce in distant parts of
the body most serious disturbance or even
cause death. The condition in which bac-
terial poisons are circulating in the blood
is called toxcemia. When the bacteria them-
selves escape from their primary seat of
growth and with their toxins gain access to
the blood the condition is called septiccemia
or bactericemia-

These bacteria of suppuration apparently
do no harm when they lodge upon the unin-
jured surface of the body, but only when
they get into the tissues through an injury

Wounds and Surgical Diseases 81

or lodge upon surfaces of the respiratory or
digestive tract or in the heart and blood-
vessels which are already the seat of disease.
When they get into the hair follicles of the
skin, however, under certain conditions they
may incite boils.

This is in brief the story of the bacteria
which most frequently induce the common
inflammations of the tissues, the compli-
cations in the healing of wounds, and the
varying phases of blood poisoning.

As pus in greater or less quantity is apt
to be produced under these circumstances,
these bacteria are called the pus-forming or
pyogenic bacteria so they are named Staphy-
lococcus pyogenes and Streptococcus pyogenes.
(See Figs. 8 and 9.)

Some other bacteria may occasionally in-
duce similar disorders in the body, but those
which have been described are the most
common and important.

In addition to their power of inciting in-
flammation alone or together, the staphy-
lococcus and the streptococcus are so common
among city folks and those who live crowded

82 The Story of the Bacteria

together, that they are frequently present in
other bacterial diseases which they may
seriously complicate.

The effects which the pyogenic as well as
other disease-inducing bacteria may produce
in the body vary considerably under different
conditions. Sometimes the general state of
the body is such that it seems to furnish very
favorable soil for their proliferation or is
especially vulnerable to their action. Some-
times the particular germs which gain access
seem to be especially virulent, perhaps from
their inherent vigor or from conditions which
we know nothing about. We are in these
diseases dealing with poisons for the human
body, but with self -propagating poisons which
from an almost infinitesimal amount may grow
to such quantities as in the end can fairly
overwhelm it.

The habits of scrupulous cleanliness afford
our best protection against the intrusions of
these germs. In vigorous general health lies
our strongest resistance to their incursions.

CHAPTER VIII

THE BACTERIA OF CONSUMPTION, OR
TUBERCULOSIS

MORE than one seventh of all the people
who die are carried off prematurely
by consumption, or tuberculosis. But it is
only recently that we have had any definite
knowledge as to its cause. For a great while
physicians have known a great deal about the
disease. They have become very expert in
detecting its advent and in tracing its course,
and came long ago to know but too well
whither it tended. It was usually regarded
as hopeless, and its treatment was entered
into rather for humanity's sake than in the
expectation of inducing a cure. To-day the
aspect of affairs has greatly altered. We
know through the illuminating discoveries
of Koch that tuberculosis is caused, and

83

84 The Story of the Bacteria

caused alone, by exceedingly minute, rod-
shaped bacteria — bacilli — which, in one way
or another, gain access to the body (Fig. 10).
When there, if the conditions are favorable,
they tend to grow, and as they do so there
form about them little masses
of new tissue, which are called
tubercles. The most com-
mon seat of the disease is the
lungs, but it may occur in
FIG. IO.-TUBERCLE any part of the body.

The tubercles which form
From the sputum in the lungs are usually lim-

of a person having ited ^ & small ft^ t

tuberculosis of the

lungs. the top of the chest. But

sometimes they are widely
scattered through the lung. Plate VI. shows
numerous tubercles — the little white spots — •
in a human lung.

Where the tubercles form the tiny air cham-
bers are destroyed and the lung becomes
solid. This is shown in Plate VII. The dark
mass just beneath the surface of the lung is
the tubercle. Around it are the air chambers
quite open and useful.

The Bacteria of Consumption 85

But after a while, the poisons of the tubercle
bacilli destroy these new-formed tubercles as
well as the lung itself and then they often be-
come friable and break down. Thus cavities
of considerable size may form in the lungs.
Plate VIII. shows a series of such cavities.

On the walls of these cavities the tubercle
bacilli often grow in enormous numbers and
as the cavities usually connect with the
bronchial tubes, the bacilli may be cast out
in the sputum.

We know that tuberculosis is never caused
by any other thing than the tubercle bacillus,
and that even in persons predisposed by in-
heritance or otherwise to the disease it cannot
occur unless this particular germ gets into the
body from outside. The germ itself has rarely,
if ever, been shown to be directly inherited.
If, therefore, we could keep this particular
germ away from human beings, there would
be no more tuberculosis, no matter what
the inherent tendencies of the individual
might be.

In fact, human beings in general are very
resistant to the incursions of the tubercle

86 The Story of the Bacteria

bacillus. This is shown by the fact that
physicians, making autopsies upon the bodies
of large numbers of persons who have died
from accidents or diseases other than tuber-
culosis, have found that nearly every adult
has at some time in his life had some small
focus of tuberculosis. This his body cells
have so successfully and promptly controlled
that he has been wholly unaware of the in-
fection. But while this shows the resisting
capacity of human beings to the tubercle
bacillus, it also indicates the wide distribution
of the bacillus in the places which man
frequents.

When an individual recovers from tubercu-
losis, the bacteria are destroyed and the new
growth which is called the tubercle is slowly
converted into dense tissue like a scar. Some-
times the body cells build a wall of scar
tissue around the bacilli and the affected
region (Plate VII.), so that the tuberculous
process may lie dormant for a long time.

Now where do tubercle bacilli come from?
Remember that they do not grow outside
the bodies of warm blooded animals, except

PLATE VI. — TUBERCLES IN THE LUNG

In this case myriads of turbercles about the size of a grain
of millet are scattered through the lung. This form of the
disease is therefore called "miliary tuberculosis."

The Bacteria of Consumption 87

in the artificial cultures of the bacteriologist
(see Plate IX.). So we need not look to
sewage, polluted water, or dirty vegetables,
or rotting stuff of any kind as fruitful sources
of distribution. It is in tuberculous human
beings and tuberculous cattle that we find
the great sources of infection.

Let us look first at the human source. The
masses of new tissue which form in the lungs
where tubercle bacilli grow are not well
supplied with blood, and so under the in-
fluence of the poisons which the bacilli set
free as they grow and flourish and die they
are apt to become friable and break down and
then little particles of them containing myriads
of living virulent germs are coughed up and
discharged in the sputum. So the sputum
of persons with tuberculosis of the lungs
and the secretions in their mouths and some-
times the nose and their lips often swarming
with bacilli are the immediate sources of
distribution of these sinister germs.

Now, if the material which consumptive
persons cough up and spit out were always
destroyed at once by being burned or received

88 The Story of the Bacteria

into a dish of some efficient disinfectant, one
of the greatest dangers of the spread of the
disease would be removed. But unfortu-
nately this is in fact very rarely done. Thou-
sands of consumptives are walking about the
streets of our large towns or visiting places
of assembly, who discharge the infectious
material coughed up from the lungs upon
the pavements or floors. This dries, and
shortly is ground up, and takes its place
among the rest of the floating dust of the air.
Essentially the same thing takes place in
rooms in which consumptives are confined,
if intelligent precautions are not taken to
destroy or convey away the discharged ma-
terial. It has been found by actual experi-
ment that a considerable number of living
tubercle bacilli may be lodged, together with
other dust particles, high up on the walls of
hospital wards in which consumptives are
unintelligently cared for, in situations to
which they could haye been conveyed only
through the air as ordinary dust is. The same
material allowed to dry on handkerchiefs may
in a similar way become a source of danger,

PLATE VII. — A TUBERCLE IN THE LUNG — HEALED

In this photograph of a highly magnified tubercle,
which has healed by the formation of scar-like tissue
about it, one sees the minute air chambers of the lung
surrounding the solid tubercle. At the site of the tuber-
cle the air chambers, and hence the usefulness of this
portion of the lung, have been destroyed.

The Bacteria of Consumption 89

not only to others, but may cause a fresh
infection of the patient himself.

Bacteria never rise from thoroughly moist
surfaces. One might spread a thick layer
of living bacteria of any kind, no matter how
infectious, over an exposed surface, and,
provided it was kept thoroughly moist, might
breathe with impunity the air sweeping in
strong currents over it, because the germs
always cling most tenaciously to such sur-
faces. Of course a current of air strong
enough to sweep the particles of fluid bodily
off from their position would be efficient in
spreading the infectious material. The im-
portant point which this statement emphasizes
is that the breath of tubercular persons
is not infectious; the air itself passing over
the moist surfaces of the respiratory passages
and the mouth carries no germs. The act
of kissing, however, might lend itself most
efficiently to the transmission of the living
bacilli.

So also they may be conveyed through the
use of uncleansed eating utensils, dishes, hand-
kerchiefs, towels, etc., used by a consumptive.

90 The Story of the Bacteria

There is another way in which tubercle
bacilli are transmitted which though less
generally recognized is in some respects more
significant than the conveyance by dust or
contaminated articles, or by direct contact
of the sick with the well, and this is by
coughing and sneezing. While the tubercle
bacillus can remain alive for some time when
dried in dust, it becomes less and less virulent,
and strong daylight or direct sunlight kills it
in a few days or hours. So that the tubercle
bacillus in ordinary dust tends to become less
and less a menace.

In explosive coughing and in sneezing, fine
particles — in sneezing a veritable spray —
may be sent forth for several feet into the air.
Now in these particles fully virulent tubercle
bacilli may be contained, often in great num-
bers. The fine spray of sneezing frequently
floats for a considerable time in the air and
may be breathed in by others.

Plate X. shows a Petri plate placed three
feet from the face during a vigorous sneeze.
The colonies growing after four days on the
surface of the gelatin show how many living

PLATE VIII. — TUBERCULOUS CAVITIES IN THE LUNGS

In the upper parts of this lung, the tuberculous
tissues have been destroyed, broken down and cast ofr,
leaving rough irregular cavities communicating with
the bronchial tubes. In the walls of these cavities tu-
bercle bacilli thrive and may be discharged in large
numbers with the sputum.

The Bacteria of Consumption 91

germs were widely dispersed in the air. Of
course those which fell upon this small dish,
three inches across, form but a small proportion
of the number expelled.

It is thus clear that both safety and decency
require that in coughing and sneezing, the
handkerchief, or at need the hand, should be
held before the mouth and nose. This ob-
vious rule of propriety is also a counsel of
security under all circumstances, since the
mouth and nose of many persons, not tuber-
culous and not even themselves ill, contain
infective organisms which, gaining a foothold
upon more vulnerable individuals may lead
to serious disease.

Now all these facts are extremely disagree-
able both to hear about and to tell, and they
can only be infinitely distressing to the vic-
tims of tuberculosis and to their friends and
associates; but all the same they are facts,
stubborn, abiding, and significant. The
sooner we recognize the truth that every
consumptive person may, if proper precau-
tions are not taken, be an actual and active
source of infection, not only to those who

92 The Story of the Bacteria

immediately come in contact with him, but to
those who, either where he is, or where he
has been, are forced to breathe dust-laden air,
the better will it be for all concerned.

Of course no intelligent person would infer
from this statement of facts regarding the
sources of infection with tubercle bacilli
through the air, that everybody who goes upon
the street or enters a hospital or a theatre
is going, or is even liable, to acquire tubercu-
losis. For, in the first place, the infecting
material, even under the worst conditions
is enormously diluted by the circulating air
and the tubercle bacilli are killed by sunlight,
so that the individual chances of coming
in contact with the dangerous material are
slight.

In the second place, the average healthy
individual is not predisposed to the disease
at all, and could be affected only under es-
pecially favorable conditions. Third, the
amount of infecting material is apt, in trans-
mission by the air, to be small, and this is a
condition which diminishes the chances of
danger from such exposure.

9

PLATE IX. — CULTURES OF THE TUBERCLE BACILLUS

These cultures are of several weeks' growth on coagulated
blood-serum. They were derived from different sources and the
variations in growth to be observed mark different strains of the
species.

The Bacteria of Consumption 93

Finally, every individual has in his respira-
tory tubes an arrangement of tiny cells whose
free surfaces are covered with little hair-like
processes called cilia. These are ceaselessly
waving to and fro, and tend to sweep up and
away from the lungs foreign particles which
may be breathed in with the air. But not-
withstanding all these conditions which serve
to guard the exposed individual against the
disease-producing bacteria, it still remains true
that no man can acquire tuberculosis without
getting into his body this particular bacillus
from some infected individual or animal.

Now as to tuberculous cattle as sources of
infection. Formerly the meat of such cat-
tle, which might be eaten uncooked, was a
noteworthy menace. But the State and
Federal control of diseases of cattle, — whose
health by the way excites a much more vivid
interest in governmental circles than does
the health of man, — is now so effective that
we need not consider it further here. But
the milk of tuberculous cows frequently con-
tains virulent tubercle bacilli and frequently
comes to the markets.

94 The Story of the Bacteria

Infection from this source is more common
in young children than in adults, and the
bacilli may enter the system through the
tonsils or through the bowels. In children
the infection may apparently remain latent
for years, only revealing itself in small nodules
in the neck or chest or abdomen. But there
is evidence that in later life these local seats
of infantile tuberculosis may become sources
of general infection. By boiling or properly
pasteurizing the milk for infants, this risk
may be avoided.

The conclusions which almost thrust them-
selves upon us from what we have thus learned
about tuberculosis are very plain. Tubercu-
lous meat and milk ought never to get into
the markets. Milk contaminated with tu-
bercle bacilli may be rendered harmless by
heat.

It would be very difficult to stop by any
sort of legal enactment the spread of the
tubercle bacilli by means of the air or by
personal contact from man to man. But
a thorough acquaintance of all persons with
the fact that a consumptive patient may be

PLATE X. — A SNEEZE PLATE CULTURE

See the explanation in the text.

The Bacteria of Consumption 95

a source of actual danger to all about him,
unless the proper precautions are adopted,
would do much to lessen the evil.

Steamship and railroad companies should
be obliged to furnish separate accommo-
dations for persons thus affected, so that no
well person should ever be forced in the
exigencies of travel to expose himself to the
liability of infection.

Such regulations and discriminations as are
here suggested would of course often be
extremely annoying to the victims of the
disease and their friends as well as to all
immediately concerned. But some such un-
derstanding must be come to, unless people
are to go on needlessly dying from this most
important disease.

The best way of disposing of the sputum
of consumptive persons, which, if allowed to
dry, may, as we have seen, become the source
of active danger to themselves as well as to
others, is by burning.

It may be received into small cheap wooden
or pasteboard boxes, which are now made and
sold very cheap by the druggists, and which

96 The Story of the Bacteria

at frequent intervals, together with their
contents, should be burned in the stove,
furnace, or fireplace. When handkerchiefs
or cloths are used to receive the material
coughed up, these should be either burned as
early as possible, or soaked for several hours
in a five per cent, solution of carbolic acid
and then boiled and washed. But the use
of handkerchiefs and cloths is to be avoided
for this purpose as much as possible, because
they afford most favorable conditions for the
drying and distribution of the infectious
material.

The acts of coughing and sneezing should
be made innocuous by the use of the hand-
kerchief. Utensils used by consumptives
should be separately and properly cleansed
and boiled. Kissing by consumptives should
be avoided.

But while we are thus led by the knowledge
which has been gained of the tubercle bacillus
to a more precise notion as to what should be
done to prevent the spread of the disease,
what has the accumulated lore to offer of hope
or comfort to those already stricken? In the

The Bacteria of Consumption 97

first place, the physician can now say
positively by finding the bacilli in the material
discharged from the lungs, in many cases
even in very early stages, that the lung is
out of order.

We now know that consumption is by no
means a hopeless disease, especially if it be
detected in its early stages. We know that
the cells of the body, if they are in a properly
active and vigorous condition, have a ten-
dency to destroy the germs. In a large pro-
portion of cases if the disease be early
discovered, the wise physician, by recommend-
ing life in the open air, improved conditions of
hygiene, proper exercise and food, along the
lines which Trudeau has spent so many in-
spiring and fruitful years in developing, may
hold out to his patient a good hope of ultimate
recovery or of prolonged and comfortable
life. Patent medicines and advertised cures
for consumptives are one and all futile,
fraudulent, and pernicious.

We battle to-day with a known and com-
prehensible foe, and no longer grope in the
dark after a mysterious and unknown enemy.

98 The Story of the Bacteria

The hope of the enlightened physician looks
out towards a time when we may have learned
some direct and efficient means of destroying
the invading germs in the body, or neutral-
izing its poisons. But, in the meantime, by
aiding the body's inherent means of cure, he
feels himself no longer helpless.

Finally as to individual measures of pre-
vention. Remember that the healthy human
body is not good soil for the tubercle bacillus.
Keep the body strong and well by good, plain,
properly cooked food and plenty of it, and by
proper exercise, sleep, and recreation. Look
out for the milk. Avoid dissipations whether
in work or play or idleness or worry or drink
or tobacco. Get all the fresh air you can.
Let your breath be deep and strong. Sleep
with the windows open. Keep clean. Cul-
tivate cheerfulness. Don't neglect colds, for
while they do not directly lead to consump-
tion the vigor of the body may be so lowered
by their long continuance as to be more
susceptible.

Do what you may as a good citizen to get
the people educated to stop promiscuous

The Bacteria of Consumption 99

spitting, to care for the discharges of tuber-
culous persons, to let the sunlight and air
into living rooms and assembly places, and
suppress the dust nuisance indoors and out.
Then go about your business and don't fret
over tuberculosis.

Of course not all persons can secure all
of these desirable things. But most persons
can secure some of them. When in doubt
consult the doctor.

CHAPTER IX

TYPHOID FEVER AND ITS RELATIVES

^YPHOID fever is one of the serious and
common diseases, occurring among all
classes of people, which is definitely known
to be induced by bacteria. The germs of
this disease are little rods or bacilli considera-
bly larger than those which cause tubercu-
losis (Fig. n).

There are several forms of low fever, and
some other diseases due to various causes,
which considerably resemble typhoid fever,
and are not infrequently mistaken for it.
But genuine typhoid fever is caused by this
particular germ, and no other, and is never
induced in any other way. The lower animals
do not have typhoid fever.

The typhoid bacillus is not known to grow
outside the body to any considerable extent

100

Typhoid Fever and its Relatives 101

except in milk and when artificially cultivated
by the biologist for purposes of study. But
it may remain alive for several weeks outside
the body in milk, in water, in the soil, or
under other conditions.

The typhoid germ in the large majority of
cases, enters the body with
food or drink by the intes-
tinal canal. When it gets
into the intestines, if the
conditions are favorable, it
multiplies, and enormous FIG- "-—THE BA-

i r ,1 CILLI OF TYPHOID

numbers of the germs are FEVER

thus sometimes produced.
Some of these often gain access to the blood
and to certain of the internal organs, as the
gall bladder and urinary bladder, but many of
them either complete their existence in the
intestinal canal, or are cast out in the living
condition with the diarrhoeal discharges which
so constantly accompany this disease and in
the urine.

As the typhoid bacilli in this disease grow
and multiply in the bowels, or elsewhere,
they form a soluble poison — toxin — which is

102 The Story of the Bacteria

absorbed, just as some kinds of food might
be, and carried to various parts of the body,
producing effects which we recognize as
symptoms of the disease.

The great and important source of in-
fection— the means by which the disease is
usually spread — is these discharges from the
bowels and the urine containing the living,
virulent typhoid bacilli.

Here we have an essentially similar con-
dition of affairs to that in tuberculosis, namely,
bacteria of a particular species inducing a
disease which, without them, could not or
does not, so far as we know, occur and after
inducing the disease in an individual, being
discharged alive and virulent from the body.
Here, as in tuberculosis, although the mode of
infection is somewhat different, if all the dis-
charges from persons suffering from the dis-
ease could be immediately destroyed, all
danger of infection, so far as we know, would
be removed. Typhoid fever is thus a com-
municable and a preventable disease.

Typhoid fever affects man alone, and he
alone forms the source of infection. But,

Typhoid Fever and its Relatives 103

unfortunately, the bacteria are not generally
destroyed, and the house-mates of the patient,
or those whose water or milk or food supply
become contaminated directly or indirectly
from his discharges are liable to succumb to
the same malady.

But there is another significant source of
virulent typhoid bacilli which has only re-
cently become known. It has been discovered
that long after complete recovery from ty-
phoid fever the urine and the intestinal
waste, — the latter even for many years, —
may contain the bacilli, which apparently
get domesticated in the gall bladder or else-
where, and while no longer harmful to their
host, are yet fully virulent for others should
the chances of communal life bring them into
contact with food.

Thus to a single cook has been traced the
infection of twenty-six persons in seven
different families to whose gastronomic exi-
gencies she uncleanlily ministered. A threat-
ening epidemic of typhoid has been started
by a person concerned with the milk supply
of a large city district, though he had not

104 The Story of the Bacteria

for many years been the victim of typhoid.
In these two cases cited, the bacteriologist
was able to cultivate in the laboratory from
the discharge of these two entirely healthy
persons virulent typhoid bacilli and show
that these were present in enormous numbers.

Such persons, now known to be common
among convalescents from this fever, are
called " typhoid carriers. " The possibility of
danger when such persons are concerned with
food supplies or food preparation are obvious.

The lesson of this unpleasant revelation is
that our standards of personal cleanliness
must be more exacting, if we are to be reason-
ably secure against chance infection from
" typhoid carriers. "

Altogether the probabilities are that in the
majority of cases the typhoid-fever germs are
most frequently carried and consumed in
milk and in water which have in some way
been polluted by human waste containing
the typhoid germ.

It seems quite incredible, when put down
in black and white on paper, that responsible
and sane persons of ordinary intelligence,

Typhoid Fever and its Relatives 105

knowing that typhoid fever is caused by a
living germ, knowing that this is thrown off
from the body in the living condition and
without being destroyed, is allowed to run
through the sewer pipes into the nearest
stream or lake, should for an instant consent
to have the water of this stream or lake taken
from within a short distance of the sewer
opening, and often in line of direct current,
and distributed in their houses unpurified,
and used upon their tables. And yet it
would be but the telling of old stories for the
writer to cite case after case in which this
offence against common decency, to say
nothing of good taste, is practised under
conditions much more flagrant than these.
And then Providence or Fate is shouldered
with the responsibility when the careless or
ignorant persons themselves, or the innocent
victims of their criminal neglect, are stricken
with typhoid fever.

Typhoid discharges thrown upon the banks
of drinking water reservoirs, or streams, in
winter, from the camps of repair gangs, have
in many instances been washed into the water

io6 The Story of the Bacteria

by the spring floods at the cost of many
hundreds of lives.

Milk supplies should be especially guarded,
because milk, when not kept very cold, is a
good culture medium for the typhoid bacillus,
so that a slight primary contamination may
become fairly pestilential before the milk
reaches the consumer.

Oysters, which unscrupulous dealers place
in sewage-polluted water to grow plump so
that the guise of freshness may impose upon
their victims, have many times been the
cause of typhoid fever.

Direct conveyance of the bacilli from the
patient to nurses, attendants, or friends should
not be possible with reasonable care.

Typhoid bacilli may remain alive in ice for
many weeks though they gradually die out.
It is therefore not without risk, as it certainly
is without decency, that one permits the use
for drinking of ice which has been cut from
sewage-polluted waters.

Flies, which have access to typhoid dis-
charges, may carry and deposit upon human
food to which they next address their in-

Typhoid Fever and its Relatives 107

dustries, virulent typhoid bacilli in large
numbers. In the Spanish American war there
were many victims of gross neglect in sanita-
tion in whose destruction red tape and the
common house-fly played a conspicuous r61e.
We shall consider this nefarious insect more
at length in a later chapter.

Typhoid discharges should always be ren-
dered harmless at once by heat or be disin-
fected with carbolic acid or some other
effective agent, no matter where they are to
be finally disposed of, and this should be
done whether the doctor does his duty in the
matter, or, as is sometimes the case, neglects it.

So long as the excreta of typhoid patients
are not systematically disinfected but are
allowed to pass into sewers and cesspools,
or are thrown on to the soil whence they
pollute watercourses; so long as a high
standard of personal cleanliness is not re-
quired in those who deal with milk and other
food supplies, — we must expect that this
typhoid fever, which is a disgrace to our
boasted civilization, because wholly unneces-
sary, will flourish here and there.

io8 The Story of the Bacteria
Dysentery

There is another bacillus at least first
cousin to the typhoid germ to which is at-
tributable certain forms of bowel trouble all
the world over, and called the Bacillus
dysenterice. There are several types of these
small pests. They are transmitted, as are
their typhoid relatives, from the discharges
of patients mostly through water, milk, and
direct contact, or by flies. Like typhoid
fever, the infectious forms of dysentery are
filth diseases and need not occur with proper
attention to sanitation.

CHAPTER X

ASIATIC CHOLERA

HISTORY records many tragic stories of
sudden outbreaks of fatal disease which,
spreading like wildfire among the people, have
brought untold miseries and countless deaths.

In early times these frightful whirlwinds of
disease were looked upon as penal visitations
of the Supreme Powers, and, in the utter
panic which they so often induced, little was
done in the way of studying their nature or
staying their progress.

Among the more important of these tragic
epidemics which have been experienced and
carefully observed since science has with-
drawn the veil of superstition from them,
stands Asiatic cholera.

In some parts of the world this disease is

constantly present and claims each year a

109

no The Story of the Bacteria

varying number of victims. But Europe
and America are in general free from it, save
that now and then, coming from its home in
the Far East, it sweeps along the seaboard or
over the country, bringing in a greater or
less degree the old-time panic and misery
and death in its train. Occasionally it finds
lodgment upon our own shores and has
penetrated into the interior.

Now up to within a few years we have not
known what the cause of this disease really
was. It seemed to be something which could
be brought in ships and wrapped up in cloth-
ing, and was evidently communicable from
man to man. Such measures of stopping the
spread of the disease by isolating the sick,
and such general regulation of the diet and
habits as seemed from experience best adapted
to protect the well, were formulated and
practised. But the lack of knowledge as to
the exact nature of the infective agent fre-
quently rendered futile the one and uncertain
the others.

To-day we know that Asiatic cholera is
caused by a little curved bacillus, which on

Asiatic Cholera in

getting into the intestinal canal of human
beings multiplies with such rapidity that
within a few days or hours the body may be
overwhelmed with the poisonous material
which it eliminates as it grows. We know
that in certain stages of the disease the living
germs are discharged from the body in vast
numbers, and that if moisture be present
they may remain alive outside of the body
for long periods and may even multiply.
They can thus remain alive for some time in
water and on the moist surfaces of vegetables
and fruits and clothing.

There is no good reason for believing that
any other germ or organism than this par-
ticular curved bacillus ever induces Asiatic
cholera, or that the disease is ever caused by
anything else. The only known way in which
the infective agent is conveyed from man to
man is by the taking into the intestinal canal,
either by water or food or in some other way,
some of the cholera bacilli which have come
directly or indirectly from some human victim
of the disease.

The germs may remain alive for a long time

ii2 The Story of the Bacteria

if kept moist, and so the disease may be con-
veyed for long distances in bundles of in-
fected clothing. A few hours of thorough
drying, or steaming, or the application of
suitable disinfectants, such as strong carbolic
acid or corrosive sublimate, readily secures
total destruction of the life of the germs.
1 In Asiatic cholera, as in all of the other
bacterial diseases which we have thus far
studied, predisposition of the individual is an
important factor in the acquirement of the
disease. This simply means that there are
certain conditions of the body cells which
render them less able to resist the incursions
of foreign organisms like the bacteria, or
which furnish conditions favorable to their
growth and proliferation.

We have seen that in tuberculosis this pre-
disposition to the disease, whatever its exact
nature is, may be in a certain degree heredi-
tary. In Asiatic cholera, a disordered con-
dition of the digestion appears to favor the
occurrence of an attack of the disease. In
typhoid fever, analogous predisposing fac-
tors seem to determine that when exposed to

Asiatic Cholera 113

the same risk of infection one individual may
be attacked with the disease and another not.
But alike in all these forms of bacterial
disease the particular species of bacteria
belonging to each must be present, predispo-
sition or no predisposition, or the disease
cannot occur.

Typhoid fever and cholera are often called
filth diseases, and to bad food, foul air, sewer
gas, and overcrowding, their occurrence has
often been attributed. This is in a sense
true, since these adverse conditions are apt
to induce a state of the body which renders
it less resistent than it should naturally be
to various deleterious agencies. But no im-
aginable degree of unsanitary conditions could
ever induce tuberculosis, or typhoid fever, or
Asiatic cholera without the presence of the
particular germ which causes each. None
of these diseases can spring up among any
class or condition of people without the in-
troduction of the germ from outside.

The recently acquired knowledge of the
cause of Asiatic cholera has thus far aided
but little in the treatment of persons already

ii4 The Story of the Bacteria

its victims. On the other hand, knowing
definitely, as we now do, what causes the
disease, how and under what conditions it
spreads, and what will destroy the germs, we
are to-day in a condition, wherever sanitary
and proper quarantine regulations are effi-
ciently carried out, to largely prevent the access
of the disease to our country, to stay the
progress of an epidemic at its very outset,
and to promptly allay the panic which the
advent of a mysterious and deadly scourge
is so prone to incite.

CHAPTER XI

PNEUMONIA, INFLUENZA, AND COLDS

Pneumonia

PNEUMONIA is an inflammation of the
lungs, and is usually incited by bacteria.
The species which is the most common in-
citant of the disease in grown people is called
Pneumococcus. But in children and some-
times in adults the pyogenic bacteria, which
we have looked at in a former chapter, and
other forms are also frequently at work.

You see that here in pneumonia we have
a disease which, unlike tuberculosis and
typhoid, may be induced by any one of
various forms of germs and not infrequently
several forms act together.

In the most common type of pneumonia
in adults the bacteria almost always get

"5

n6 The Story of the Bacteria

into the blood, so that there is what we have
learned to call a bacteriaemia as well as an
inflammation of the lungs. In the lungs a
great many leucocytes as well as other ma-
terial accumulates in the air spaces and this
sometimes makes the patient short of breath.
The pneumococcus is a
very minute lance-shaped or-
ganism, which is often sur-
rounded by a transparent

FIG. 12.— THE PNEU- J

MOCOCCUS capsule (Fig. 12). It can be

This shows the artificially cultivated, but

delicate transparent it is a very sensitive and

capsule which sur- short-lived thing, easily killed

rounds the bacteria. J

by drying, by sunlight, and
ordinary disinfectants such as carbolic acid.
It is present in the mouth and nose of a
considerable proportion of healthy persons
to whom it ordinarily does no harm. Just
what the conditions are which set this germ
at work in the lungs, we do not know very
definitely. Old people and infants are par-
ticularly susceptible. Feeble, overworked, ill-
nourished, debilitated folks, and those who
stay in very dusty places are also liable to

Pneumonia, Influenza, and Colds 117

pneumonia. It is most frequent in the late
winter and the spring because then the general
resistance of the body has been commonly
lowered by the long overstrain and confine-
ment of the season's work.

Pneumonia is essentially an indoor disease,
or if it occur among out-door folks this is
almost always because they have been to
town or have consorted with house dwellers
who habitually harbor the pneumococcus.
Exposure to cold and wet, contrary to the
common belief, plays but an insignificant
part in predisposing to this disease.

In the United States, pneumonia is one of
the most frequent and serious of the infectious
maladies. Over ten per cent, of all who die
are victims of this largely preventable disease.

Through unguarded sneezing and coughing,
by the uncared for sputum of those who are
suffering from pneumonia, the pneumococcus
may be distributed in virulent form to those
who do not harbor it.

If we safeguard ourselves against these out-
side sources of contamination and attend
properly to the toilet of the mouth and keep

n8 The Story of the Bacteria

as well as may be in good physical condition,
not neglecting colds or inflammations of
the ear or eye, which are themselves often
due to the pneumococcus, and keep out of
dusty places, we shall have done our part in
turning the cold shoulder to this uncanny
neighbor to which we are so often unwittingly
the host.

In serious pneumonia there is evidence of
a profound internal poisoning of the body,
doubtless largely due to the great number of
pneumococci which are present in the affected
lung. These poisons or toxins as we call them,
the body cells strive to dispose of as best they
may, in ways which we shall consider in a later
chapter. For this purpose the body cells
must have plenty of oxygen. That means
all the fresh air the patient can use. The
modern physician, following the way along
which Dr. Northrup has so skilfully and
persistently led, recognizes this supreme need
of fresh air in the treatment of pneumonia,
and so with the body of the patient properly
protected, keeps the windows wide open.
This arming of the body with fresh air is

Pneumonia, Influenza, and Colds 119

one of the most effective of the modern ways
of fighting bacteria and their poisons.

Influenza

It is popular nowadays for both doctors
and laymen to call severe colds influenza
or "the grip/' But genuine contagious in-
fluenza, which occasionally sweeps around
the world, a veritable plague out of the Far
East, and in one after another of the countries
which it crosses puts a large share of the
people to bed with all sorts of miseries, is
apparently incited by a special bacillus which
is very small even for bacilli. It can be cul-
tivated in tubes and is very well known
nowadays in the laboratory as well as at the
discouraged bedside.

The Bacillus influenzae is, however, still
somewhat of an enigma, because it, or several
organisms quite like it, are found in a good
many abnormal conditions, especially in-
volving the respiratory organs. However,
we know definitely enough that the influenza
bacillus is transmitted from the sick to the

120 The Story of the Bacteria

well by the discharges from mouth and nose,
especially by unguarded spitting, coughing,
and sneezing. It is readily killed by drying
and by disinfectants, and does not ap-
parently thrive outside the bodies of human
beings. But it may linger alive and virulent
for a long time in the mouth and nose of
convalescents or those associated with pa-
tients, and so it is carried all over the world
when once the virulent strain gets started
as it did in 1889-91.

The safeguards against influenza lie, as in
so many of the infections, in care for the
general health, proper care of the secretions,
and judicious toilet of the mouth. The doc-
tor knows best what to do when you have
got it, and it is well to call him in, for there
is much misery while it is going on and serious
results sometimes if you are indiscreet, and he
can almost always help the body to overcome
or outwit the unwelcome intruders.

Colds

Of all the infectious diseases, the so-called
"colds" are the most frequent. We have all

Pneumonia, Influenza, and Colds 121

had them and all know how unpleasant they
are, and how apt we are sooner or later to
recover from them. What we do not so
commonly realize is that if they are neg-
lected they greatly predispose the body to
much more serious infective maladies.

Common colds are incited by a variety
of micro-organisms among the more common
of which are the pneumococcus and strep-
tococcus, and bacilli which closely resemble,
if they are not identical with, a mild type of
the influenza germ. Probably several other
species are also guilty, but conviction waits
upon further evidence. Some forms of colds
are distinctly communicable, and run through
families or groups of closely associated persons.

The popular impression, crystallized in the
name, that they are primarily due to ex-
posure to cold weather, to drafts, to fog and
wet, is largely false. All these things, as
well as indigestion, overexertion, or anything
else which lowers the body's vigor and re-
sistance, may be and doubtless are con-
tributory factors, — the spark which lights
the powder. But without the germs there

122 The Story of the Bacteria

would be no "colds," as certainly as without
the powder there would be no explosion.

People who really live out-of-doors do not
often have colds. When they come to town,
or get into closed rooms with the sneezing,
coughing urbanites, who live and move and
have their being in an atmosphere invisibly
lurid with bacteria fresh from infected sources,
then the outdoor folks catch, not the cold,
but the germ which does it.

Colds, like pneumonia and tuberculosis, are
indoor diseases and savor of closed rooms,
foul and dusty air, crowded assembly places.
The vigorous jubilant home-comer from his
summer outing, who has been blown and
rained upon, who has spent shivering nights
under the stars, who has "cooled off" in the
wind and tramped in the water, who has pro-
longed his swim till he was blue, with never a
trace of ill, gets a cold a week after he comes
back to town. He blames the open window
by which he sat to relieve himself of the
stuffiness of his city home. But he forgets
the ill cleaned dusty car with its scores of
germ-dispensing occupants in which he trav-

Pneumonia, Influenza, and Colds -123

elled home, or the filthy theatre, never in-
telligently cleaned at all most likely, in which
he whiled away an evening just to get in
touch with the spirit of the town. These,
and not the fresh air at his window, gave him
the real inspirers of his cold.

Keep the body vigorous by good food and
water, by plenty of work and play, but don't
overdo either. Adopt the old Chinese pro-
verb "Do nothing too much. " Get the fresh-
air habit. Open the windows in the bedroom
and in all rooms. Keep down the dust.
Get every possible hour out-of-doors. Keep
the skin clean and the body as lightly clothed
as is comfortable. Woollen underwear does
not prevent colds. A proper toilet of the
mouth is not to be neglected. Finally, like
a good citizen, join the forces now engaged
in securing cleaner air in all assembly places,
in cars, shops, hotels, stores, theatres, courts,
churches, as well as at home. Frown upon
the folks who sneeze and cough and spit in
fashion worse than brutish. Then if you do
get colds now and then, as you will, — for
sanitary decency is not to be won in a

124 The Story of the Bacteria

day, — you will have a fair chance for a light
infection.

If people with acute colds could and would
sequester themselves for a few days and rest
while the body overcomes the invaders, it
would be much better for them and an active
source of infection for others would be
removed.

CHAPTER XII

DIPHTHERIA AND TETANUS

Diphtheria

P\IPHTHERIA is a disease most frequent
1— J in children, in which a membrane is
apt to form in the air passages, which may
make breathing difficult or impossible. There
are also symptoms of serious general disorder,
as if the body were profoundly poisoned.

The disease is incited always by a pecul-
iar, often club shaped bacterium called the
Bacillus diphtherias (Fig. 13). It is killed by
boiling for a minute or by disinfectants, but
may live for months in the air. This bacillus
is present in enormous numbers in the mem-
brane, and sometimes gains entrance to the
body. But the chief damage to the victim
of diphtheria is a powerful poison which the

125

126 The Story of the Bacteria

germ manufactures as it grows, and which is
absorbed into the blood. This disease is
therefore a toxczmia.

The bacillus of diphtheria is readily cul-
tivated in beef tea or on the usual solid bac-
terial foods, where it produces the same poison
that is formed in the disease
process. We shall return to
this diphtheria poison or
toxin a little later, when we
look at the various ways in

FIG. 13. — BACIL- .

LUS DIPHTHERIA which the body protects it-
self against pathogenic bac-
teria, and the ways which modern science has
discovered to help it.

While diphtheria is a very serious disease,
the use of antitoxin, the nature of which we
shall consider farther on, has robbed it of its
greatest terrors and very much reduced its
frequency. It is rare in animals.

The diphtheria bacilli are often conveyed
from the sick to the well by the material
discharged from the mouth and nose, either
directly, or by eating utensils, towels, etc.
Furthermore the bacilli often remain for

Diphtheria and Tetanus 127

many weeks or months alive in the mouths and
throats of those who have recovered from the
disease. They are also frequently found in the
mouths of well persons exposed to the disease,
as well as of those who are not known to have
associated with diphtheria patients.

This is one of many reasons why we should
try to avoid exchanging mouth secretions
with others by avoiding the use of common
drinking vessels or towels, and by more
seemly sneezing and coughing; why children
should not suck pencils and pass them on,
or indulge the friendly impulse to share the
handkerchief or chewing gum. This is why
adults, as well as children, should not in-
salivate the leaves of books and papers as they
turn them over by wetting the fingers in the
mouth. Finally the story of the diphtheria
bacillus as of the pneumococcus and the tu-
bercle germ suggests the propriety of less
catholicity than is usual as to whom, and
more circumspection as to how, we kiss.

Tetanus or Lockjaw
Tetanus is induced by a remarkable bacillus

128 The Story of the Bacteria

common in the cultivated soil, in street dust,
and in the droppings of the horse and other
herbivorous animals. The bacilli when grow-
ing in the body produce an intense poison,
which acts especially through and upon the
nervous system. Thus powerful spasms of the

muscles are produced,
and when the muscles
of the jaw are affected,
they become rigid,
hence the common

FIG. 14. — TETANUS BACILLI

Showing spores name lockjaw.

The bacillus of te-
tanus does not grow well in contact with
oxygen, and when it finds itself under un-
favorable conditions for growth, it forms
a spore which is very resistent to external
influences, and drying, heat, disinfectants,
etc., which ordinarily kill bacteria. Then
it stands pat and waits for something bet-
ter to turn up. The bacteriologist, how-
ever, can cultivate it by shutting oxygen out
of his tubes and plates and consulting its
peculiar tastes in other ways. The bacillus
when forming spores is shaped something

Diphtheria and Tetanus 129

like a tennis racquet, with the shiny spore in
the larger end (Fig. 14).

The horse and some other animals only
occasionally develop tetanus, though one
great source of the bacillus is horse manure.

Humans get tetanus by dirty wounds,
usually bruised or punctured. Pure cultures
or spores of the germ are not apt to induce
tetanus in wounds, but when other bacteria
or dirt are introduced into a wound with the
tetanus bacilli these are apt to grow. Thus
it is that although spores of the bacillus of
tetanus are very widely distributed in nature,
the disease is not common, because it is only
in punctured or lacerated wounds, in which
spores and dirt are lodged together, that the
proper conditions exist for the growth of this
finicky citizen. This is why those who care
for horses, those who handle manure, and the
boy who celebrates the "Fourth" with a
toy pistol are the most frequent victims of
lockjaw. There are some regions in which the
soil contains a great many spores, so that
tetanus frequently follows even slight punc-
tured wounds.

130 The Story of the Bacteria

Careful cleaning and disinfection of dirty
wounds, especially those which are lacerated
or punctured, is the proper safeguard against
this common bacillus.

It is finally noteworthy that while inmost
of the bacterial diseases the infectious agent
is transmitted more or less directly from the
sick to the well, and is usually more virulent
the more direct and recent the conveyance
is, we have in tetanus almost the only ex-
ample of pathogenic bacteria widely and
persistently contaminating the soil. But it
is so particular in its habits that it is only now
and then that it falls afoul of human beings.

It has been possible through experiments
on animals to prepare an effective antitoxin
for the tetanus poison. Its usefulness is,
however, considerably limited by the fact that
the symptoms of tetanus do not develop until
the germ toxin has gained a powerful hold
upon the nervous system, when it may be too
late to neutralize it with the artificial anti-
body.

CHAPTER XIII

A ROUND-UP OF UNDESIRABLES

Meningitis

THERE is another ball-shaped microbe or
coccus closely related to the pneumo-
coccus which is responsible for a very serious
communicable disease prone to affect children
by an inflammation of the covering membrane
of the brain and spinal cord. As this mem-
brane is called the meninges, the disease is
named cerebro-spinal meningitis, and the
microbe is called the meningococcus. It is
found sometimes in the nose and throat of
its victims and their associates. It has been
cultivated and carefully studied. Dr. Flexner
at the Rockefeller Institute for Medical Re-
search in New York has secured from horses
treated with cultures of the meningococcus

131

132 The Story of the Bacteria

a curative serum which has been used all
over the world and has saved many lives.

Gonorrhcea

There is still another of this uncanny family
of cocci called the gonococcus, which is the
inspirer of great misery and leads to many
deaths.

It is the nemesis of the licentious and
debauchers of the racial instinct, and in their
retribution their many innocent victims share.
It is the cause of a large part of the blindness
of infancy.

Syphilis

Syphilis is a disease which is primarily almost
always dependent upon an infringement of
the laws governing the racial instinct, and is
usually the penalty of depraved associations.
Retribution to the offender often lasts through
life, and the innocent are often hopelessly
involved.

The inciting agent of syphilis is a minute
spiral bacterium whose life history is not yet

A Round-up of Undesirables 133

known since it has not been artificially culti-
vated and so cannot be studied free from
complicating conditions.

The infective organism is naturally limited
to the human race, though monkeys can be
experimentally infected.

Except for the few instances in which by
accident the infective agent has been conveyed,
it is seldom known to be a source of danger to
those of honorable life, except through inti-
mate association with its victims.

The Plague

The plague, or "black death" as they called
it when it ravaged Europe in the middle ages,
has a very ancient and sinister history. You
may read about it in the pages of Bocaccio
or Defoe. It had largely disappeared from
Europe for a century and a half. But in the
latter part of 1900 it started afresh in China
and India, and gradually worked its way into
the Americas. It has never fairly gained a
foothold in the United States, thanks to
effective quarantine, except in San Francisco,

134 The Story of the Bacteria

where for a long time there have been scatter-
ing cases.

The plague bacillus is short and plump and
grows very easily in cultures and in such
characteristic ways that it is readily recognized.
It is easily killed by drying, sunlight, and
disinfectants.

<. In one form of the disease pneumonia is a
prominent feature, and then the germ may be
transmitted from the sick to the well by the
discharges from mouth and nose.

But in severe epidemics of plague the num-
ber of persons affected is so large that some
other mode of transmission of the bacillus
than by personal contact has to be assumed.
And here we come upon a keen reminder that
some of the lower animals which we cordially
despise, as is the case with the house-fly, are
significant factors in the discomfort which
man derives from inheriting the earth.

It has been found that in plague epidemics
rats share with man in the predilections of
the plague bacillus, having an enormous
mortality of their own. The evidence indeed
is strong that man derives his plague bacilli

A Round-up of Undesirables 135

from the rat. But the question is how?
Rats do not often bite men or closely consort
with them, nor do they notably contaminate
human food. But rats have fleas and when
these bite infected rats they borrow the
bacilli with the blood and if then they bite
a man the bacilli may be directly introduced
into his system.

Much study has shown that, in fact, in
countries and regions where plague prevails
the rat and the flea are potent factors in
transmission.

In California where plague has been lurking
for some years, some of the ground squirrels
have become infected with plague bacilli and
while this is not yet of threatening- import-
ance, it is disquieting that the infective agent
has not long since been completely destroyed.

Smallpox and its Relatives

It is very interesting that with all our study
of micro-organisms and long familiarity with
these diseases, smallpox, measles, and scar-
let fever should still remain riddles among the
common infections. These diseases are all

136 The Story of the Bacteria

characterized by an eruption on the skin.
The old Greeks knew them and called it a
"flowering out," and so we call the lot "the
exanthemata." We do not know what incites
them. The search for bacteria has thus far
failed.

It has been conjectured that minute ani-
mals— protozoa — may be to blame. Some
morning we shall probably learn in the papers
that a tired-eyed worker in the laboratory
has found the clue, and we shall wonder that
we did n't always know it.

But though we do not yet know what in-
cites them, we have for .one — smallpox — so
efficient a preventive in vaccination, that it
has largely lost its terrors in civilized and
intelligent communities, and has ceased to
figure largely in health statistics. This
happy state has been secured through the
wisdom and vigilance of health authorities,
which must be ceaselessly maintained.

Hydrophobia or Rabies

Here is another infectious disease usually
acquired through animals, in this country,

A Round-up of Undesirables 137

usually the dog. The nature of the infective
agent is unknown. It is apparently not
bacterial. Learned folks guess it to be a
protozoan.

But nevertheless here, as in smallpox, a
most effective method of prevention has been
devised by Pasteur, so that one bitten by a
mad dog has the best of chances to escape the
disease if he will but promptly apply for
treatment to the appropriate laboratories
maintained by health departments and others.
The nature of the preventive treatment in
hydrophobia is considered briefly elsewhere in
this book.

Malaria

This wearisome malady is not induced by
bacteria and so is only smuggled in here to
round out the census of common infections.
It is due to a tiny animal, a protozoan, which
is conveyed from the sick to the well through
the bite of a particular species of mosquito
called Anopheles. The germ itself is named
Plasmodium malar ice. It takes the two of

138 The Story of the Bacteria

them to get the better of their big brother,
man.

But man has more brains and has found out
that the weakest link in the chain of his
inoculation is the mosquito, and when he
drains the marshes in which most of the little
buzzing brethren breed, and screens his
windows against the plebeian minority to
whom stale water in old bottles, tin cans,
water butts, and puddles is birthplace, his
" shakes" disappear and he becomes a worth-
while citizen again.

Yellow Fever

This is a tropical disease but may flourish
in temperate climates in summer. It ceases
when the frost comes. It is certainly infec-
tious, it does not affect the lower animals,
and we do not know what living thing incites
it. It was formerly supposed to be contagious
and the infective agent carried in the clothing.
But through a series of brilliant recent re-
searches, it is now known that the yellow-
fever germ is carried from the sick to the well

A Round-up of Undesirables 139

by a particular species of mosquito called
Stegomyia, which sucks blood and the parasite
from the patient and transfers it to persons
whom he may later visit.

There is a very fascinating story in the dis-
covery of the yellow-fever mosquito and his
significance to man, but we cannot tell it here.
We may only say that when they screened
the mosquito away from the fever patients
so that he could not get infected blood, they
stamped out yellow fever in Havana, and
can control it anywhere by keeping tab on
Stegomyia.

It is sadly aggravating to the scientific
folk to realize that though they can get an
infected mosquito which they know contains
the deadly infective parasite somewhere in
his interior, no cultivating, no microscoping
or any other scrutiny has succeeeded in
recognizing the living thing which must be
right under their eyes. It probably is a
protozoan, and it is demonstrably so small
that the most powerful microscopes fail to
reveal it. It seems to be one of a very baf-
fling group of living beings causing disease,

140 The Story of the Bacteria

which are called ultra-microscopic, and which
no man has really distinctly seen except in
masses.

Whooping-cough and Mumps belong among
the milder infective maladies, but their incit-
ing agents have not yet been clearly identified.

There are many other diseases of men and
animals incited by bacteria which are of much
less importance than those which we have
glanced at in our hurried survey. But the
limits of this little book do not permit us to
dwell upon them.

CHAPTER XIV

SAFEGUARDS OF THE BODY AGAINST DISEASE

WHEN we try to learn more about the
human body than we can by ob-
serving its form and structure and the various
obvious things which it can do, we are led
back to the time when that mysterious potency
called life stole in upon the earth in the pri-
meval silences. And we are obliged to trace
the changes which, through stress of circum-
stance, have slowly shaped, out of a single
cell, the various cell communities and their
marvellous correlated activities which make
the human being of to-day.

All these changes have been brought about
by the adaptation of form and activity to new
environments. And we can discern here and

there through all the various cells and organs,

141

142 The Story of the Bacteria

and all the things they do, the marks of
earlier stages of development.

The uncouth ancestral being, which by and
by was to be moulded into man, once had
need of more bowel space than he now re-
quires. But when this became unnecessary
a segment of it wasted away, leaving a weazen
remnant which we call the appendix, and
which gives some folks a good deal of bother
now and then. There was a weak spot in the
lower abdomen once when man's progenitor
went on all fours. This interested him not at
all then. But when his descendant got along
in his development so as to stand up on his
hind legs, the pressure of the bowels on this
weak spot was much increased, and so some
people find a knuckle of intestine pressing
out in what we call a rupture or hernia. Thus
we might go on a good while with these marks
of forgotten histories cropping out occasion-
ally in the last of the long ancestral line.

But what especially concerns us now, is
the more subtle marks of evolution in the
intimate performances of the body cells.
Whatever capacities they now possess and

Safeguards against Disease 143

use so cleverly for the welfare of the whole
community, they have acquired, as we have
said, through long ages of adaptation to new
conditions. By adaptation we mean making
the best of it. Now this power -of. adaptation
the body cells possess to-day, subject to the
work and strain of ordinary life. The body
cells can adapt themselves to new kinds of
food and to more or less of it, to changes of
temperature, to new forms of work, and so on.
Life is, in fact, a constant adjustment to
varying conditions. If these new conditions
become too extreme, the efforts of adaptation
are exaggerated, the capacity is overstrained,
the rhythm of correlated activities is broken,
and this is disease. But the pull of the
ancestral experiences, which we call heredity,
is ever back to the balanced activities called
health. This pull of the ancestral experiences
is what the doctors have in mind when they
abandon the Saxon tongue and speak of the
vis medicatrix natures, — the healing power of
nature.

Now, all this is important in studying the
safeguards of the body against disease, be-

144 The Story of the Bacteria

cause the biggest safeguard which the body
has against disease is this capacity of the
cells to adapt themselves, within reasonable
limits, to new and often adverse conditions.
This is combined with their habit, acquired
through several millions of years of inherited
experience, of getting back into the old ways
again as soon as possible. These are the
powers which the doctor must work with and
not against, with his regimen and diet, with
his fresh air and sunshine, with his counsel
and cheer, as well as with his less impor-
tant offerings of drugs. These body cells
tend to get back at their tasks again after
the adventures which circumstances force
upon them, because their ancestors, all the
way up the line, did so and survived, weav-
ing their experiences into the vitals of their
descendants; while collateral branches which
did n't do it, perished. Some folks call this
the principle of the survival of the fittest.

Another of the body's most potent safe-
guards is its power to dispose of poisonous
substances, which are developed within it,
or get in from outside. With our food we

Safeguards against Disease 145

take in a very nondescript mess of chemical
substances, and incidentally a good many mill-
ions a day of bacteria. The intestinal processes
spell death to myriads of bacteria with which
our uncooked foods are mingled. The chemi-
cal substances are pulled to pieces by the diges-
tive juices, and a part of this refined food-stuff
gets into the blood. The residue is regularly
and safely disposed of. The part which gets
into the blood is robbed of some of its harm-
ful ingredients in the liver or elsewhere. The
rest of the internal waste gets out through
the kidneys or lungs or by the sweat-glands
of the skin. The selected elements of the
food finally come to the body cells, which
proceed to tear it further to pieces, use what
they want, and again set free another set of
residues, some of them very poisonous if
retained in the body, but in health got safely
rid of again by the kidneys, lungs, and skin.
Thus it is that while in the ordinary course
of life we are constantly beset with varied
and subtle poisons, the mechanism of the
body is so nicely adjusted that we are saved
from harm by our cells, some of which feed

146 The Story of the Bacteria

and thrive upon poisons which without these
curious proclivities would inevitably damage
or destroy them, and us. This power of the
body cells and organs to destroy and dispose
of internal waste and poisonous material is,
then, the second of our great protective
agencies against disease.

The bacterial poisons are disposed of through
the very agencies which are constantly guard-
ing our bodies from harm by the home-made
poisons which we ourselves elaborate. These
agencies consist largely of new chemical
unions into which the poisons are forced to
enter, thus losing their identity and their
harmfulness.

Another important safeguard of the body
is certain tiny cells, the most significant of
which we have glanced at in an earlier chapter,
the leucocytes or white-cells of the blood (see
Plate XI., i). Although the body can main-
tain its form and structure and go on doing
its work, often beyond the orthodox threescore
years and ten, it is in fact constantly changing.
New cells are forming and old ones are dying,
some are damaged and must be speedily

?

'*•'

PLATE XI. — LEUCOCYTES AND PHAGOCYTES

I. — Shows a leucocyte or white blood cell with its irreg-
ular shaped nucleus and the translucent delicate cell-body.

2.— Shows a leucocyte which has taken into its body
particles of soot, breathed in by its owner from dusty air.
This leucocyte is thus, for the time being, a phagocyte.

3. — This phagocyte has taken into its body several bac-
teria— micrococci — a few of which have been partially de-
stroyed.

4- — This is one of the larger phagocytes of the body
which has in its interior, portions of other smaller dead cells.
These are here undergoing disintegration.

Safeguards against Disease 147

replaced, and there is everywhere more or less
wear and tear. Now in all these changes
there is first and last a good deal of dead stuff
to be disposed of.

|:.; While other cells here and there lend a hand
in this scavenger work, it is the leucocytes
which bear the brunt of it, and it is in truth
a busy life they lead. Fragments of dead
cells or tissue (Plate XI., 4), particles of foreign
material which accidentally may have got into
the tissues, they engulf (Plate XI., 2). Some
of these they sooner or later digest and thus
dispose of, or if this be not feasible, they carry
them off to safe places of deposit within the
body. The regular leucocyte dumping grounds
of our busy interiors are the so-called lymph-
glands or lymph-nodes, of which we have
many snugly stored in appropriate places—
in the neck, the armpit, the groin, at the root
of the lungs, and within the abdomen.

Here various types of scavenger cells fore-
gather and work over their never ending
supply of booty from the farthest recesses of
the body. If through the subtle chemistry
of their own juices they can convert the stuff

148 The Story of the Bacteria

into soluble or nutrient or harmless form they
do so. If it is too intractible for that, it is
stowed away on the spot in dormant cells or
in the crannies of the node, where it is less
harmful than in the thoroughfares or special
workshops of the great community.

These leucocytes are par excellence the
wandering cells of the body — for not only
do they share with the red blood cells in the
passive transportation, which the blood and
lymph currents afford, but unlike the red
cells they have noteworthy locomotive
capacities of their own; so that they can
crawl about in the minute crannies of the
tissues where the tiniest fragment of a useless
particle is to be found. A few other cells share
in the locomotive powers of the leucocytes.

The leucocytes and other cells which take
foreign particles into their interiors have
received a special name — Phagocytes — which
means "devouring cells." This is only a sort
of trade name, suggesting one of many occu-
pations of the white blood cells, and when
other cells share this special task they, too,
become for the moment phagocytes. Thus

Safeguards against Disease 149

the leucocytes do not cease to be leucocytes
when they become phagocytes, any more
than a son of Erin ceases to be an Irishman
when he becomes a plumber.

The leucocytes, as well as some other body
cells, have the further useful capacity of
secreting and under certain conditions setting
free, such chemical substances in solution
as dissolve refractory tissues, dead bone, for
example, and so clear the ground for new
growth.

Thus far we have been considering harmful
stuff in the body, such as poisons and dead
particles, and the ways in which the body
protects itself against them. Now let us
look at some more striking aliens, themselves
alive, which often intrude upon the balanced
life of the healthy man.

The presence of bacteria in the body is of
varying significance, depending upon where
they are and what their pedigree. The healthy
skin keeps out most of them. The ever
swinging cilia in the windpipe sweeps them
out in hosts. In the mouth and nose many
are destroyed, but many lead here a placid,

150 The Story of the Bacteria

harmless life. Along the digestive canal they
swarm. But these are mostly harmless, some
even lending a hand, perhaps, in reducing our
complex foods to simple forms. The tonsils
are rather weak points in the body armor,
for through them several objectionable germs,
among them the tubercle bacillus, sometimes
enter.

When bacteria get into the real interior —
for the lungs and bowels we may wisely
remember, are only infoldings from the ex-
terior— when they get into the very tissue
itself, and into the blood, even then nothing
very startling happens, as a rule. The power
of the leucocytes and other cells to take up
dead stuff comes in handy here, for when the
average bacterium is encountered in the homes
of the leucocytes, it is either engulfed forth-
with or poisoned first and swallowed after-
wards (Plate XI., 3).

It is only now and then with the very few
of the thousands of species of bacteria which
are co-inhabitors of the earth with us, that
difficulties arise.

There are doubtless a good many interesting

Safeguards against Disease 151

stories in the relationship of bacteria to man
if we could only wander back along the ways
of evolution. For we have all grown up
together through the ages, we and the bacteria,
each adapting himself to the requirements
of the other. When this mutual adjustment
is secured, we do each other no harm. Our
cells and the bacterial cells then work hand in
hand. Infectious diseases are the efforts of
adaptation to conditions which have not yet
become usual. That the invading micro-
organisms in infection also have their hour
of storm and stress, as they encounter the
damaging forces which our cells command,
is proven every time we get well.

Bacteria, as we have seen, make trouble
in the body very little by their mere physical
presence, but by poisons which some of them
form and set free as they live and grow, or
which they store up to be liberated when they
die and break to pieces. So when in our
cherished interiors the poison-breeding bac-
terial cell encounters our well bred body cell,
it is a battle in which the weapons are poisons.
For some of the fluids and digestive juices

OF THE
IIMIVFRSITY

152 The Story of the Bacteria

which our own cells elaborate are just as much
poisons for the bacteria as is their venomous
stuff for us.

In the end it is the old story of the survival
of the fittest. When these two types of cell
meet, each trying to get a living in its own
way wherever it has been stranded by the
wave of circumstance, a new environment is
established for the body cell and for the
bacterium. And what we dramatize as a
battle, is really only the attempt of each to
adapt itself to the new conditions furnished
by the other; so that each can go on and get
a living. The one which adapts itself most
readily and completely and quickly wins, by
survival.

We please our fancy sometimes, by making
heroes of the leucocytes, dashing at the in-
truders in their hereditary bailiwicks, regardless
of the risks which they so hardily incur. Let
us not indulge in too much of this, lest haply
we too be found among the nature fakirs.
For, in fact, they are impotent pieces of the
game played by physical and chemical forces,
and they have to set about the battle willy-

Safeguards against Disease 153

nilly, just as much as the magnetized needle
has to swing to the north, quite without
concern whether the ship does or does not go
upon the rocks.

The thing which we want to glean from the
rehearsal of this cell contest is, that in both
animal cell and bacterial cell the capacities
of ordinary life, in this emergency, are set
vigorously at work to meet the requirements
of a new situation, and upon the way they meet
it depends their fate. But while the two
kinds of cell may sway and modify a little
their every -day functions in their own pro-
tection, they no more forge new weapons,
than would a stone-mason who should rap an
imminent foot-pad over the head with his
hammer.

When these doughty cells succumb to the
bacterial poisons which they encounter, they
are picked up as dead stuff by other forms
of cells (Plate XL, 4), and with the dead in-
vading hosts are decently disposed of.

So at last we see that the body protects
itself against bacteria and their poisons by
the use of the same agencies which it has made

154 The Story of the Bacteria

effective through ages of experience in keeping
its interior fresh and wholesome and clear
of its own refuse and the intruding flotsam
and jetsam of a dusty world.

But through all these marvellous adaptive
processes by which the body maintains its
balance among the pitfalls of a sorely jostled
life, is felt the steady pull of heredity back
to the line of health. This we fondly drama-
tize as the beneficent touch of good old
Mother Nature. But it really is the ultimate
impress upon the cell republic and its citizens,
every one, of the unrecorded adaptations to
the conditions of each hour, whether for
good or ill, since the first living cell appeared,
surprised and lonesome, upon a hitherto
inanimate earth.

CHAPTER XV

HOW SCIENCE HELPS THE BODY IN INFECTION

WE have seen how, through many ex-
cellent arrangements in our cells, we
manage to keep alive in spite of a great many
threatening conditions. In fact, good Mother
Nature — let us again risk the phrase — makes
a pretty good job of it, in a large proportion
of cases, whether we know how she does it
or not. But there are a great many people
on the earth and a great many, for them,
malignant bacteria. The body machines of
many folks are woefully abused or sadly
handicapped in the race of life. So in the
long run Nature scores many failures. If
you want to get an idea how many there
are of these, look at the death-rate from
bacterial diseases in any district of the United
States in a single year, and you will see that

155

156 The Story of the Bacteria

she seems to be overworked or lacks resources.
In New York City, for example, in 1907 there
were between 8,000 and 9,000 deaths from
tuberculosis of the lungs; nearly 700 from
typhoid fever, about as many from scarlatina;
over i, 600 from diphtheria, and more than
600 from cerebro-spinal meningitis. This
looks as if Nature needed help, as in truth
she does.

Now let us see how science is trying to lend
a hand.

It is clear, in a general way, how the body
protects itself against harmful bacteria by
its power of neutralizing their poisons, by
destroying them with its cells, and by its
inherent tendency to get well, whatever hap-
pens. But science must know more than this.
If it is going to help to neutralize poisons it
must know more of the processes which the
body uses for this purpose. If it is to rein-
force the efforts of the cells in killing and
destroying bacteria, it should get behind the
scenes and learn, if possible, how this is done
in the single-handed conflicts which mark
each hour of life.

How Science Helps the Body 15?

Animal species differ in their capacity to
protect themselves against germs and their
poisons. Many bacteria deadly to some of
the lower animals are harmless to man, and
vice versa. This freedom from danger of
special microbic invasion is called immunity.
Since it is born with the individual, it is called
natural or hereditary immunity. Some of the
factors concerned in this we have already
considered.

But there is another phase of immunity
which we must look at a little more closely.
People who recover from some of the infectious
diseases, such as small-pox, measles, scarlet
fever, and in a less degree from typhoid fever,
diphtheria, and others, are protected for a
longer or shorter time from a subsequent
attack. Such people enjoy, while it lasts,
what is very properly called acquired immunity,
an immunity acquired through an experience
of the disease itself. Now what is it in the
bodies of these people who have successfully
weathered an infectious disease which pro-
tects them from another attack? If we could
answer this question we should evidently be

158 The Story of the Bacteria

well on the way toward understanding the
nature of acquired immunity. They must
be in some way different from their fellows
and must have either acquired some new
qualities which they did not possess before
their disease adventure, or old protective
agencies must have been reinforced.

How light has been thrown, little by little,
on this important subject by the busy self-
sacrificing workers, both in the laboratory
and at the bedside, makes an interesting
story which we cannot now stop to tell. But
the fact is, that when certain poisons, espe-
cially those formed by bacteria, get into the
body, some of the body cells proceed forth-
with to make and set free chemical substances
which unite with the poisons, changing their
character and making them harmless.
Through this action of his cells, the recovering
victim of an infection destroys the poisons as
they are made. The bacteria which make
the poisons are thus robbed of their chief
significance and do not particularly concern
the patient any further. So he gets well.
But something more may happen. His cells,

How Science Helps the Body 159

which were stimulated in the poison-emerg-
ency to produce neutralizing stuff, speedily
fall into the habit of making it, and go on
doing so, often for a long time, after the
master of the cells has recovered and after
his actual necessity for it has ceased.

Now at last we see why he cannot soon
suffer from the same disease again. His
body contains a good deal of the protective,
poison-neutralizing agent, and his cells go on
making more for a time, so that he goes about
poison-proof. By and by, however, the old
hereditary pull back to the usual routine is
felt, the emergency cell activity wanes, the
excess of protective material disappears, and
the acquired immunity passes away. So
the hero of this dramatic story of disease
takes his place again among ordinary mortals.

Now in scientific speech certain poisons are
known as toxins. And so this cell-made
emergency stuff, which robs the toxins of
their power, is known as antitoxin. Anti-
toxins are effective only against the special
poisons which inspire the cells to their pro-
duction— that is, they are specific. An anti-

160 The Story of the Bacteria

toxin for the diphtheria bacillus poison, for
example, would not at all protect against the
tetanus poison, or vice versa.

As soon as research had gone thus far into
the problem of immunity, the thought of the
lonesome worker in the laboratory turned, as
it is wont to do, with every new outlook,
toward the needs of suffering mortals. If
in the body of an infected animal, as is the
case in man, this protective antitoxin may
be formed in excess — so ran the thought of
the investigator — might it not be possible
to treat animals with special forms of bacteria
or their poisons, and when their cells have been
educated to the overproduction of the specific
antitoxin, draw off some of the blood con-
taining it, and by introducing this into the
body of a human victim of the disease, save
him from impending death by poison? This
significant and humane suggestion has been
worked out into a practical system. And
now the world over are laboratories from which
are derived life-saving antitoxins of various
kinds.

Among these the first to be secured and the

How Science Helps the Body 161

most important is the antitoxin of diphtheria.
This is prepared from the horse. It is not
necessary to cause the horse to endure
diphtheria, as we know it, at all. For if
the poison which the diphtheria bacillus
sets free, when it is grown in beef -tea cultures
in the laboratory, with all the germs filtered
off, be put into the horse, his cells get to work,
just as ours do when we have the disease,
diphtheria, and just as his would if the bacilli
were allowed to grow in his body. Presently
antitoxin begins to mingle with his blood.

The horse lends himself readily at first to
small, then to increasing doses of the potent
diphtheria poison. He becomes readily im-
mune and he is so big that he furnishes a large
amount of blood without apparent inconven-
ience. When the animal is poison proof, no
longer showing any ill effects to doses of the
toxin so large that if given at first they would
have been inevitably fatal, he is bled from
a large vein in the neck. The blood is set
in a cool place and clots, clear fluid, the serum,
separating from the rest. This yellowish
clear serum contains the antitoxin.

1 62 The Story of the Bacteria

All these operations are most carefully done
so that the antitoxic serum is pure and clean,
and it is introduced beneath the skin of the
patient with a small syringe made for the
purpose.

This is a hasty outline of the story of
diphtheria-antitoxin-making. You see, the
cells of the horse make antitoxin to protect
themselves and him from the toxin which is
artificially introduced by his skilled attendant.
This antitoxin will neutralize diphtheria toxin
wherever it encounters it, whether in a test-
tube or in the body of a poisoned child facing
imminent death. The child is struggling to
make what antitoxin he can for himself. If
his cells can make it in plenty and make it
soon enough, he may recover unaided. But
the antitoxic serum of the horse is just as
good; it works quickly, it raises high the
chances of a successful issue.

Since the introduction of diphtheria anti-
toxin the mortality from diphtheria has
been reduced quite 75 per cent. Just what
this means in the saving of life and in the
relief of suffering, only those can realize who

How Science Helps the Body 163

saw diphtheria in the old days and have read
the sinister story of the early statistics.

But the antitoxin of diphtheria is also of
the greatest value in the prevention of the
disease among those who have been exposed
to infection in families, schools, and elsewhere.

The immunity which the child secures
through the diphtheria which it survives, is
won at great cost and risk. It is called active
immunity. Through it the body cells have
adapted themselves to a new unfavorable
environment. On the other hand, the im-
munity conferred upon the child by the anti-
toxin which the horse manufactures, is called
passive immunity. The effect is immediate
and quite under control. But the protection
is short-lived and the body soon eliminates
the foreign agent from its blood and tissues.
The antitoxin does not destroy the diphtheria
bacilli. The body cells take care of them as
soon as the blight of the poison is effaced.

In similar fashion valuable curative anti-
toxins are made for cerebro-spinal meningitis
and for tetanus, and, though less successful,
for a few other infections.

164 The Story of the Bacteria

Of course the eager workers in the labora-
tories have tried to get antitoxins for many
other of the bacterial diseases. But somehow
the method did not seem to work so well in all.
There are many obvious reasons why this
should be, but they are too complex to con-
sider here. There is little doubt that as
research goes on still further discoveries will
be made of effective antitoxins.

In the meantime, however, the student of
bacterial diseases has turned to other phases
of the protective mechanism. Active im-
munity can be secured in other ways than by
the weathering of an infection. Thus it has
been found that if a mass of disease-inducing
bacteria, from an artificial culture, be killed
by heat and portions of these be introduced
into the body, its cells gradually adapt them-
selves to the poisons which the dead bacteria
contain, so that the body is in a measure
protected from an attack of the disease of
which they are the regular incitants.

Thus with typhoid fever, Asiatic cholera,
and plague, important practical results have
been secured. The persons thus forearmed

How Science Helps the Body 165

are found to be much less liable to acquire
the disease in prevailing epidemics. These
results are due to the fact that some patho-
genic bacteria, instead of setting toxic sub-
stances free as they grow, store them up in
their bodies. Later when these are killed by
heat and degenerate, the toxins are set free,
inciting the body cells to their protective
activities.

We have thus far been considering the
ways in which the body may be helped to
free itself from the presence and action of
poisons produced by disease-inciting germs.
Now what can be done to help the body to
kill and destroy the bacteria themselves and
so stop the poison fountains at their sources?

It has long been known that the body
fluids kill bacteria in enormous numbers, even
those of serious infectious maladies, and we
have much knowledge of the chemical agencies
by which this is accomplished.

It has been shown that there are two groups
of substances in the body fluids, one at least
of which may be increased in artificial im-
munization, which, when acting together,

1 66 The Story of the Bacteria

have the power to induce disintegration and
destruction of bacteria. This action is called
lytic, which means dissolving. Thus we now
speak of the destructive action of the body
fluids on the bacteria as bacteriolytic. There
is reason to believe that one of the most
important agencies of the body in protecting
itsjslf against invasive micro-organisms is this
bacteriolytic power of its fluids. This power
is the same as the body has always made use
of in disposing of its own dead or useless
cells, but it is here diverted to new ends to
meet an emergency.

While there appears to be in this new
knowledge of bacteriolysis the brightest prom-
ise of future practical usefulness in the
control of infection, we need to know more
about the cells which make these protective
substances and the conditions of their forma-
tion before we can effectively lend a hand. •

But it has been found that by introducing
into the body, in certain infections, some of the
killed bacteria which incite them, the body
cells are stimulated to produce substances
which so alter such of these bacteria as are

How Science Helps the Body 167

already at their destructive work, that they
become an easier prey for the ever vigilant
phagocytes (Fig. 15). The bodies of the killed

FIG. 15. — PHAGOCYTES AND VACCINES

This cut shows two phagocytes from animals infected
with staphylococcus pyogenes — the common pus-forming
bacterium. The animal from which the cell at the left was
taken was untreated. The animal from which the right hand
cell was taken had been treated with " vaccine" consisting of
a culture of these organisms killed by heat. Many more
bacteria have been taken up by the phagocyte of the vac-
cine treated animal.

bacteria thus used are called vaccines and the
substances produced by the body cells under
their influence are known as opsonins. This
name is derived from a Latin word which means
"I prepare food for." The manufacture of

1 68 The Story of the Bacteria

opsonins by the body cells under the inspira-
tion of vaccines has been most effective in
infections by the pyogenic cocci. Though
called by the same name, these new " vaccines "
have nothing to do with the vaccine lymph
which is used to prevent small-pox.

It is generally believed to-day that most of
the substances in the body fluids which kill
and destroy bacteria are furnished in part at
least by the leucocytes. So these doughty
defenders of the cell republic reach marauding
bacteria, not only when alive by personally
swallowing them, but by setting free germ-
killing stuff when they have succumbed.

Based upon this knowledge of the effective
action of the leucocytes in setting free pro-
tective stuff, Dr. Hiss has proposed to secure
leucocytes in quantity from the lower animals
— the rabbit for example, — and to introduce
an extract of these into the bodies of persons
suffering from acute infections, thus rein-
forcing their capacity for resistance.

This method of treatment is still under
investigation. But the reports of those who
have applied it in a variety of human in-

How Science Helps the Body 169

fections seem to indicate that the extracts of
alien leucocytes used in this way may be of
great value.

The incitants of small-pox and hydrophobia
are as yet unknown, though they are prob-
ably not bacteria. But we have methods of
preventive inoculation in both of these serious
diseases which are remarkably effective.

These methods both depend upon the
gradual adaptation of the body cells to an
infectious agent. At first material of slight
virulence is used; then that which is more
potent. Thus presently the body cells, with-
out the acquirement of the disease by the
individual, have become so fully adapted to
the new conditions, that the body is protected
from the disease altogether.

In small-pox the virus of diminished viru-
lence is secured by passing it through the
body of an insusceptible animal, the calf.
Then, while it does not induce small-pox
in man, it protects man from it.

In hydrophobia the unknown living in-
fective agent, which is present in the nervous
system of rabic animals, through the method of

170 The Story of the Bacteria

Pasteur, is treated by drying the nerve tissue
in the air, in which process its virulence
steadily diminishes. Thus it is possible to
get 'material of all grades of strength. So
that if a person bitten by a mad dog be injected
at first with a long-dried material, then day
after day with that which has been dried for
a shorter time, at length with no symptoms
whatsoever to indicate that his cells have
been responding to a powerful infective agent,
he has acquired complete immunity or pro-
tection from the disease, which has not been
permitted to develop.

The mortality from hydrophobia before the
day of preventive inoculation was about six-
teen per cent. Through this treatment it has
been reduced to about two tenths of one per
cent.

In the early days of our knowledge of
bacteria, the highest hope was cherished that
it would soon be possible to destroy bacteria
in the body by disinfectants. But this hope
soon faded, for it was found that any such sub-
stance strong enough to be effective would kill
the body cells as soon as it would the bacteria.

How Science Helps the Body 171

But there is one infective disease — malaria,
not induced by bacteria, but by micro-
organisms belonging among the protozoa, in
which the early dream is realized. For in
most cases quinine suffices to destroy the
organism without damaging the man. Thus
by quinine and mosquito screens and drain-
ing the swamps, this pest of many coun-
tries and neighborhoods may be effectively
suppressed.

We have thus learned that there is an
immunity to infection which faces, species,
and individuals naturally enjoy or may acquire
by a successfully encountered attack of an
infectious disease. We have seen that the
body cells possess a marvellous power of
adapting themselves to new adverse condi-
tions, by the use, to new ends, of capacities
by which the usual life is carried on. So
when one recovered from diphtheria or typhoid
fever is for a time immune, we know that this
marks an adaptation of his cells to a new
environment, evanescent it is true, but analo-
gous with those adjustments by which in the
long processes of evolution new traits were

172 The Story of the Bacteria

fostered as plants and animals slowly rose to
higher types.

But beyond this we have found out that we
can secure an artificial cell adaptation by
proxy in the horse, and through his cells,
educated for the occasion, secure the precious
juices which not only can confer immunity
upon the well, but can save those already
stricken. In these and many other ways
which we have but glanced at in passing,
we can reinforce to-day the subtle safeguards
of the body against the minute incitors of
infection.

If we compare our knowledge of infectious
diseases to-day with that which was current
twenty-five years ago, it is evident that an
advance has taken place which is fairly
revolutionary. Then we did not even know
what caused most of the infections. The
efforts to cure them were uncertain and in-
effective, and preventive measures were largely
futile. To-day we know what the causes of
most of these diseases are, how the recupera-
tive forces of the body meet them, in many
instances what we can do to help these forces,

How Science Helps the Body 173

and finally how these scourges of mankind
can be controlled by a little honest and in-
telligent cleanliness.

Now step by step as this knowlege has
grown, it has been necessary to use the lower
animals in studying the action of these new-
found micro-organisms, and the ways to prevent
their ravages. These animal experiments are
always most carefully performed, anaesthetics
being used whenever necessary, by the hu-
mane and self-sacrificing devotees to the
advancement of knowledge. Without the free
and untrammelled use of the lower animals
for experimental purposes, children would
still be suffering and dying by thousands
from diphtheria each day, the world over, and
the doctors would be helpless to save them or
largely stop their sufferings. The pitiful victims
of cerebro-spinal meningitis would still face
a hopeless future. We should be back in the
old age of helplessness towards most of the
infectious maladies.

It is well for us all to realize this, because a
number of persons, a part of whom are igno-
rant but well-meaning, a part ignorant and

174 The Story of the Bacteria

malicious, are stirring about and endeavoring
to interfere by legislation with the advance-
ment of science through that research which
involves the use of certain of the lower
animals.

It is one of the duties which good citizenship
lays upon the informed and the honest, to
see to it that the crusade of short-sighted
ignorance and falsehood, which its devotees
name anti-vivisection, shall not be permitted
to stay the progress and cloud the outlooks
of beneficent research.

CHAPTER XVI

THE COMMON SOURCES OF BACTERIAL
INFECTION

AS we glance back over the ground which
we have traversed together, we see
that the most common bacterial diseases
which in this country we are apt to come in
contact with, so far as they are definitely
known to us, are tuberculosis, typhoid fever,
diphtheria, influenza, pneumonia, and the
wound diseases or blood poisoning.

We have seen that in most of these diseases
the infective agent is liable to spread from one
individual to another, because it is not de-
stroyed by disinfectants, or in some other
way, as soon as possible after it is discharged
from the diseased person.

We have seen that the most common ways
in which the virulent bacteria are spread are
by personal contact or by the food we eat,

175

176 The Story of the Bacteria

the air we breathe, and the water we drink.
If any of these necessities of life contain
the living germs of these diseases, there
is a liability of the infection of healthy or
predisposed individuals.

The liabilty to acquire these diseases is
always increased in direct proportion to the
crowding together of the sick and the well
under unsanitary conditions in large communi-
ties. This is not because filth and dirt are in
themselves infectious, but because pathogenic
bacteria are liable to become mingled with the
rest. In other words, there is a simply filthy
filth, and there is a pathogenic filth, and the
two are very apt to go together.

No gas, however foul, no accumulation of
dirt, no degree of malnutrition or misery or
overcrowding can induce an infectious disease.
It is always and everywhere some particular
form of disease-producing germ which causes
the trouble. The other influences bear largely
upon the chances of incurring the disease, and
often determine the severity of its course or
its fatal ending, but they alone cannot cause it.

It is not the great and sweeping epidemics,

Sources of Bacterial Infection 177

dramatic and frightful as they are, which
carry off prematurely the largest number of
people; but it is the bacterial diseases which
we have constantly with us, and to which
we have become so accustomed that we do
not usually realize their vast importance, and
against which systematic and persistent cru-
sades on the part of the health authorities are
only occasionally and fitfully undertaken.

Civilized communities have ceased to fear
Asiatic cholera very much, because we have
learned that it is easily suppressed by proper
sanitation. The traditional ravages of the
plague are possible only among the filthy in
person and surroundings. Small-pox we do
not now seriously dread, because immunity
can be secured by a scratch upon the skin.
Diphtheria and cerebro-spinal meningitis have
largely lost their terrors since the discovery of
the life-saving antitoxins. Hydrophobia is
fully within our control.

But how is it with some of the less dramatic
germ diseases which we have always with us,
although we have known for many years how
they can be largely prevented?

1 78 The Story of the Bacteria

Malaria ravages large districts, because we
do not drain the puddles and will not harden
our hearts against the mosquito.

Typhoid fever claims its victims singly
and in wholesale — more than thirty thousand
die every year in the United States — chiefly
because we are not yet ready to see that our
sewage is disposed of elsewhere than in our
drinking waters.

Tuberculosis, the king of the revels in this
dance of death, ends a lingering illness in
fully one hundred and fifty thousand persons
annually in this country alone. And these
multitudes perish prematurely because we
do not insist upon the most obvious require-
ments of personal hygiene and the simplest
details of public and private sanitation.

In fact, our science is far ahead of our prac-
tice, and it now rests largely with the people and
the health officials whom they select to guard
their interests to say whether or not in the
next decade we shall enter into our birthright.

It is not difficult to suggest broadly the
things which must be done if we are to profit
as we may by the promise of preventive medi-

Sources of Bacterial Infection 179

cine. Honest hygiene must be taught in
schools and colleges. Public-health officers
must know more about sanitation than about
politics, and there must be educational in-
stitutions where their special duties can be
learned. An enlightened public sentiment
must sustain them in their efforts to promote
the general welfare, even though the individual
may now and then be inconvenienced.

But when efficiency shall have been secured
in the public-health administration, a large
responsibility will still rest upon the citizen.

He can get clean food, pure water, and un-
polluted air by asking for them and insisting
that he have them. But he must insist, and
he must be vigilant.

The danger of infection with disease-pro-
ducing bacteria which we may encounter in
the ordinary paths of life lurk, as we have
seen, for the most part, either in food, or air,
or water. Let us now look at these sources
of danger a little more closely.

Food Infection
\Milk. This is such an excellent food for

i8o The Story of the Bacteria

bacteria that though practically germ-free
when it comes from the cow, before it reaches
the consumer it may, if not kept cool, contain
millions of germs in a single spoonful.

It has been found that milk which contains
a great many bacteria, though these may not
be of a kind which ordinarily induce disease,
in infants and young children may cause serious
even fatal digestive disturbances. But well-
known disease-inducing bacteria often get
into milk. Tubercle bacilli may come from
the tuberculous cow. Typhoid bacilli may
get into the milk in careless handling di-
rectly or indirectly from typhoid-fever cases
or from "typhoid carriers," or by the use of
sewage-polluted water in washing the cans;
or flies in their wanderings may contaminate
it. Similarly, the bacteria of diphtheria or
the unknown organism of scarlatina are
known not infrequently to be conveyed in
milk.

All of these sources of danger should be,
and in many communities are in a measure,
controlled by the public-health authorities.
Much has been done to secure safety by im-

Sources of Bacterial Infection 181

proved sanitation of the dairies, and to-day
in many places, by paying a little more, the
consumer may get milk which comes from
carefully supervised dairies and intelligently
controlled dealers. This is called certified milk.

It is possible by the boiling of milk, or by
properly exposing it to a lower temperature for
a considerable time, called pasteurizing, to
destroy the dangerous germs. If the house-
holder is not averse to taking a little extra
trouble, a domestic pasteurizer may be used
on the kitchen range for each day's supply of
milk and cream. Then, he may go about his
business and worry no more about milk.
The Freeman pasteurizer is well adapted to
household use and requires no special skill
in management.

Meat and Vegetables. The meat of tubercu-
lous cattle is not likely in civilized communi-
ties to be a serious source of evil, because
official inspection is widely practised and few
people eat uncooked meat.

As the germs of various diseases may be
floating in the air in densely populated dis-
tricts, and are often present in farm and

1 82 The Story of the Bacteria

market garden manures, all fruit, vegetables,
and salads should be thoroughly washed
before they are eaten. If such articles are
to be cooked, though not so vital a matter,
washing is at least a contribution to decency.
The exposure of such foods upon the side-
walk in cities, as is so often done, is a filthy
practice, and this alone should decide the
householder to dispense with the supplies of
any dealer who persists in it.

There is no doubt that the germs of typhoid
fever, and when it is prevalent those of
Asiatic cholera, are conveyed by food con-
taminated by the discharges of sick persons
or the activities of flies. This, of course, is
most frequent among the poorer people in
towns whose market stalls are in the gutter,
and whose living-rooms, alike for sick and well,
must serve at once as kitchen, dining-room,
garbage reservoir, and bed-chamber. But
among those more fortunately circumstanced,
the conveyance of the diphtheria and the
typhoid germs on uncleansed spoons, dishes,
etc., as well as through contaminated food, is
of no infrequent occurrence.

Sources of Bacterial Infection 183

The general recognition of the importance
of sanitation has brought to the front a host
of harpies who worry the people with foolish
tales of bacterial dangers in order to exploit
alleged disinfectants.

Chemical disinfectants are seldom needed
in the household regime, except for the excreta
of victims of infectious disease. Then the
counsel of the doctor, not the fatuities of the
advertisers, should guide the selection. For
general purposes, soap, hot water, and proper
scrubbing are the best cleansers.

It should be borne in mind that bad odors
in the habitations and assembly places of
mankind are to be prevented, not concealed.
The dribbling, at considerable expense, of aro-
matic oils and solutions about toilet-rooms
— masking but not removing the sources and
risks of bad odors — is a mark of one of the
more common triumphs of predatory misin-
formation, over the ignorance of well-meaning
householders and managers.

CHAPTER XVII

WATER AND ICE AS SOURCES OF INFECTION

Contaminated Water

WE have seen in another part of this
book that natural surface waters al-
ways contain considerable numbers of living
bacteria of various kinds, which are growing
and proliferating there, and no doubt actually
purifying the water in a certain way by feeding
upon and removing from it organic material
which has collected or been dissolved. Now
these bacteria in moderate numbers, under
ordinary conditions, are not at all harmful to
the consumer of the water for drinking or
culinary purposes.

But, on the other hand, if the water be-
comes stagnant and the ordinarily harmless

bacteria collect in very large numbers, it has

184

Water and Ice 185

been shown by bitter experience that the use
of the water may give rise to serious acute
disorders of the digestive system. Cholera
morbus and the so-called winter cholera are
apparently sometimes caused in this way.
Young children are especially susceptible to
the bad influences of such water, and the
boiling of it, or the change of supply, has
repeatedly been found sufficient to stop attacks
of cholera inf antum or the summer diarrhoea of
young children.

On the whole, however, the bacteria which
water naturally contains as it is found in
lakes, running streams, and good springs are
usually quite harmless.

The frequent real and serious dangers from
impure drinking-water do not lie in the bacte-
ria which naturally occur there at all, but in
those which get into it from outside, through
pollution by the waste from animals and
human beings, and especially from human
beings who are the victims of some bacterial
disease.

Polluted water may convey the bacteria
which cause Asiatic cholera, and the same is

1 86 The Story of the Bacteria

true for diphtheria or the wound diseases,
and doubtless many others, but the spread of
these latter diseases in this way is no doubt
quite infrequent.

It is typhoid fever, whose germs, of all
those which cause disease, are, so far as we
now know, most apt to be spread by pol-
luted water. The discharges from persons ill
of typhoid fever, thrown without disinfection
into the vaults of country or village out-houses
—which, in an appalling number of cases, are
in direct communication, through under-
ground channels, with the wells, or with
springs from which the farmer supplies the
family or guests, — may pass, with but a very
moderate dilution into the digestive tracts of
the unsuspecting victim. It is ignorance, and
carelessness, not Fate which, under these
conditions, sets up an epidemic of typhoid
fever.

The water supplies of large towns come, for
the most part, either from large rivers, or
lakes, or artificial reservoirs along the course
of smaller streams, or from artificial wells,
which, piercing the upper strata, gain access

Water and Ice 187

to the deep underlying collections. Now in
the surface water supplies, as from rivers or
from lakes, man is his own worst enemy,
because the most serious dangers from impure
waters arise from its contamination with
human waste.

Many great water supplies, which, under
ordinary conditions, are good, are constantly
liable to become sources of danger, because
the sewage from dwellings is discharged, if
not into them, still, so near to them that it
may now and then enter, being washed in by
rains or in some other way. This, under
ordinary conditions, may, if the sewage be
largely diluted in the reservoirs or streams, be
simply disgusting and filthy, though not posi-
tively dangerous. But if, as is at any time
liable to happen, typhoid-fever discharges in
considerable quantity get into the waste-pipes
and so into the water, the danger of the spread
o£ this disease becomes of great importance.

Another great source of water supply for
large cities and towns is the rivers on whose
banks they are built. The water is usually
taken at a point some distance above the

1 88 The Story of the Bacteria

town, so as to avoid the sewage of the town
itself, which, as a rule, is allowed to escape
directly into it. But in almost all cases, in
thickly settled countries, there are other
towns on these streams above the points at
which the water is taken, polluting it with
their sewage. Now so prevalent is typhoid
fever all over the civilized world that the
sewage of every large town is liable to contain
greater or less numbers of living typhoid
bacilli

In older countries where the sanitary dan-
gers which always grow with the increase and
massing together of the people have been
longer observed and more definitely recog-
nized than in our own, legal enactments have
long been in force to prevent the pollution of
streams which might be sources of water sup-
ply of towns. But still large cities have found
it necessary to further protect themselves
against disease -producing organisms and
against filth, by the maintenance of filtering
systems on a large scale, by which the
dangerous elements of a contaminated water
may be largely or entirely removed.

Water and Ice 189

We should not forget that contaminated
water always tends to purify itself in certain
ways when exposed to the air in large volumes,
as in lakes or running streams. Nor should
we lose sight of the fact that a moderate
amount of sewage, when poured into a large
volume of water, becomes so considerably
diluted, that its dangerous elements are much
less numerous in any given glass or volume
of water than in sewage itself. But such con-
siderations can afford but little real consola-
tion to those who find themselves forced to
drink sewage, even though it be very largely
diluted. The sewage may contain one hun-
dred thousand typhoid germs to one teacupful,
while the diluted mixture has in it not more
than one to the same volume. But it should
never be forgotten that the one germ is capa-
ble of multiplying in the human body to an
enormous extent, and for this reason, in the
living bacterial poison dilution is of much less
significance than in ordinary poisons which are
not alive and self-propagating.

The fact is, that in view of all that we have
seen of the nature of bacteria and their dis-

190 The Story of the Bacteria

ease-producing powers, sewage-polluted water
from wells, or springs, or rivers, or lakes, ought
not to be used for drinking and culinary pur-
poses without some system of purification
which is demonstrably efficient.

The new methods of bacterial analysis of
water, which have been described in the earlier
pages of this book, can give a clue sometimes
as to whether or not a given water has actually
been polluted with sewage, or human or animal
waste, and especially whether the modes of
purification to which it has been subjected,
either naturally or artificially, have actually
been efficacious in removing the living germs.
But intelligent inspection of the sources is
usually better than any laboratory analysis
in determining whether a water is improperly
polluted.

It is thus evident that upon the intelligence,
knowledge, and fidelity, of the authorities
largely rests the responsibility of pure water
supplies for cities and towns, and the house-
holder is to a large degree at the mercy of
these officials, so far as his protection against
the acquirement of bacterial disease, especially

Water and Ice 191

typhoid fever, is concerned. For it has been
shown over and over again, by the most care-
ful and elaborate experiments and examina-
tions, that the small so-called faucet filters,
and pretty much all the reservoir domestic
filters, do not separate the bacteria from
contaminated water in a reliable way. The
water is often strained by them and so
freed from its coarser floating particles, and
then may appear quite clear and limpid,
and some of the bacteria may be at first re-
moved; but after a little while not only do
these small filters let the invisible bacteria
through their pores in large numbers, but
they may actually afford breeding- and lurk-
ing-places for the living germs, — the disease-
producing forms among the rest.

Filtration on a large scale in properly
arranged systems appears to be the only
reliable way of freeing contaminated water
mechanically from its bacterial ingredients.

Boiling of water for half an hour will,
however, kill the bacteria, and to this, in the
last resort, the householder must have recourse
to when the water supply is justly suspected

192 The Story of the Bacteria

be causing and fostering disease. This purifi-
cation of water by boiling may be done by the
householder himself, or, if he can afford it,
he may supply himself with the distilled and
aerated water which is now furnished in many
towns.

But, after all, when the facts about the dan-
gers of a polluted water supply become gener-
ally known, it ought not to be necessary for
the householder to adopt any domestic pre-
cautions against water infection in towns or
cities. If politics, or private or corporate
greed, or general ignorance or apathy stand
in the way of sanitary reform, the outlook for
the water consumer is indeed not encouraging.
But even these obstacles in the way of com-
fortable existence have been and may again
be set aside.

There are other ways, safer and more
economical in the long run, of disposing of
sewage than by running it into the reservoirs
and water courses which are the inheritance
of all the people. The common law, decency,
and prudence all forbid it. Sooner or later,
and the sooner the better, the protection of our

Water and Ice 193

drinking-water sources and closely land-
locked waters altogether will be secured.
Then there will be a big drop in the tale of
preventable disease.

Those who dwell in the country, and those
who repair thither in the summer, should be
very watchful of the water which comes from
the ordinary wells. It is quite true that the
water which soaks into the majority of wells
in the country and in villages has been filtered,
and more or less purified, as it passed through
the soil and earth about the well. But in a
great many cases the surface water runs
directly into the well at the top. Washing is
not infrequently done in its immediate vicinity,
and the waste and dirty water runs directly, or
with but little filtration, back into the com-
mon receptacle. The vaults of out-houses,
barn-yards, and pigstyes are often in close
proximity to the well, on establishments which
in circulars and newspapers figure as country
health resorts. And this is by no means true
alone of those which are inexpensive and primi-
tive, but almost equally so of many of the
more fashionable and popular establishments.

13

194 The Story of the Bacteria

Every person who goes or sends his family
into the country in the summer, should per-
sonally inspect the drinking-water supply and
assure himself that it is good. This is actu-
ally of far greater importance than the size
of the rooms, the price of board, or the di-
versity of amusements, or any other of the
score of things about which one so scrupu-
lously inquires before laying out the sum-
mer campaign.

Wells ought to be cemented water-tight for
from eight to twelve feet below the surface.
They should rise several inches above the
level of the ground, which should be cemented
and made to slope away in all directions
from the opening, so that drippings and sur-
face water may be carried off to a distance of
several feet before they soak into the ground.

It should always be borne in mind that the
water of ordinary wells is simply surface
water, which has filtered down through the
soil, and collected in the reservoir which the
well excavation makes, and that in closely
populated regions the soil, which originally
may have been efficient as a filter, may finally

Water and Ice 195

become so filthy as not only no longer to
cleanse the water, but to actually contaminate
it as it percolates through.

It is difficult to lay down rules by which the
safety of country and village wells may be
judged. But a very moderate acquaintance
with sanitary principles will usually guide one
to a just opinion. The argument which the
enquirer is most apt to encounter favoring the
salubrity of a country or village well, is that
the owners' fathers and grandfathers drank
water from the well all their lives, and they
and their families lived to a good old age. But
the fact is frequently lost sight of that the
slops and sewage of this long-lived race have
usually been accumulating in the soil about
the house, as the years have sped, and as
their towns and villages have grown the stables
and hog-pens have neared the ancestral roof-
tree. In short, that the sanitary conditions
have entirely changed. The fact is, that
wells, as they exist in most villages, and on
many farms in this country, are an abomina-
tion and a perpetual menace to the health and
lives of those who use them.

196 The Story of the Bacteria
Impure Ice

The use of ice in preserving food and for
drinking purposes has become a very impor-
tant factor in modern life, and a means of
incalculable benefit to all classes of people.

It was formerly believed that freezing de-
stroyed in large measure the impurities of
water, and within certain limits this is true.
But it has been found, as the result of a long
series of careful experiments by numerous in-
vestigators, that those important contamina-
ting elements in polluted water, the bacteria,
may resist for long periods the influences of
cold. Good ice is so clear and beautiful that
it is difficult to believe that it may harbor
among its crystals large numbers of even such
tiny bodies as the bacteria, but this is never-
theless quite true.

It has been found that the ordinary do-
mestic ice contains large numbers of bacteria.

It has been further found that that most
dreaded form of bacteria, the typhoid bacillus,
may remain for long periods living and
virulent in solid ice blocks.

Water and Ice 19?

It follows directly from these simple but
undeniable facts that the sources of our ice
supply should be carefully scrutinized in the
interests of the public health. But, unfor-
tunately, under the influence of the old idea
that water was thoroughly purified by freez-
ing, it has become the general practice of
many of the dealers to get their ice from
almost any source, however unclean, which
is near or accessible enough to the market to
afford a profit.

However, the typhoid bacilli gradually die
off in ice so that after several months it may
have purified itself. While this is reassuring,
it is not enough.

Ice should not be cut, at least when it is
to be used for drinking purposes, from any
source which would not be good if it were
used for drinking unfrozen.

The dumping of city garbage in vacant lots
or in the water in the vicinity of towns is one
of those barbaric fly-breeding practices which
strangely enough still widely prevails in spite
of the fact that both efficient and cheap
apparatus for burning it are well known and

198 The Story of the Bacteria

employed by many of the more intelligent
and cleanly communities. Thus the soil and
the shores of streams and other bodies of
water near towns are often polluted.

If sewage were everywhere systematically
destroyed, instead of being permitted to run
into and pollute the streams and lakes, which,
from their size and situation, afford the natural
water and ice supplies to towns in their vicin-
ity, the problem, on which so much depends,
of obtaining pure and safe water and ice
would be much easier of solution.

CHAPTER XVIII

HAZARDS OF THE AIR

THE only way the air which we breathe
can be infective, that is, can be the
means of transmitting disease-inducing bacte-
ria, is, under ordinary conditions, by carrying
as dust the dried but living germs from some
infected individual or animal along with other
and less harmful dust. Thus it is that our
recently won knowledge of bacteria and other
minute organisms has brought a new sig-
nificance into the problems of ventilation.
Foul air we still know to be bad and capable
of fostering serious susceptibility to disease,
but the specific and most significant elements
of positive danger are in the floating dust.

The possibility of taking infective bacteria
into the nose, mouth, and lungs with the air
out-of-doors, especially in large cities, is

always with us. But ordinarily the dilution

i99

200 The Story of the Bacteria

of the dangerous elements by winds and air
currents is so vast as to reduce greatly the
chances of evil effects from swallowing or
inhaling them. Still, in large towns, whose
streets are not faithfully cared for, the prob-
ability of being obliged to pass through clouds
of dust whenever one goes upon the streets,
especially in the windy seasons, is very un-
pleasantly suggestive of danger, and more
than suggestive of filth.

But after all, it is in living-rooms and in
places of assembly that we must look for the
most frequent sources of danger. Here the
dusty air is undiluted, is swept round and
round by interior currents, and breathed over
and over again.

Among workers in very dusty trades such
as indoor stone cutters, miners, and steel
grinders, dust is a direct incitant of serious
disease of the lungs. Under the ordinary
conditions of life dust is rather a predisposing
factor, making the lungs and body at large
more susceptible than it should be, to the
incursions of disease-inducing germs.

When much dust gets into the lungs the

Hazards of the Air 201

phagocytes take it up as fast as they can and
carry it along the lymph channels. Some
of it is left in little cell masses called lymph
nodules which are placed along the course of
these channels. Some is carried along to the
clusters of lymph-nodes at the base of the
lungs. These lymph nodules and lymph-
nodes are thus places of deposit for foreign
things gathered by phagocytes. In these, too,
as we have seen, the phagocytes complete their
destruction of bacteria and various tissue
fragments which they have gathered.

Now if these important way stations and
places of final disposal become blocked up by
excessive amounts of dust brought to them,
the body is deprived of one of its important
safeguards against infection.

How much of this sooty dust people
sometimes accumulate in their lungs is seen
in Plate XII. This figure is a copy of a
photograph of a lung of a resident of a large
city, who had spent several hours each day,
for years, in public assembly places. The
amount of black dust is deposited over the
surface of the lung in the lymph nodules

2O2 The Story of the Bacteria

spoken of above. The lymph-nodes at the
root of the lung not shown in the picture were
much enlarged and jet black.

While, as we have seen above, there is a
certain hereditary predisposition to tuber-
culosis which is resident in the body cells
themselves and of the exact nature of which
we are quite ignorant, there is little doubt
that one of the most important reasons why
tuberculosis is apt to run in families is that
children and relatives of consumptives are
more liable than others to come in direct
contact with the disease-producing germs,
which have been thrown off from the bodies
of their house-mates under conditions which
permit of their transmission. This may take
place through sneezing and coughing or by
the drying of excretions and their conversion
into dust. What has long been considered
as hereditary transmission of tuberculosis is
largely household infection.

Theatres and churches, especially the former,
are apt, as is well known, to be altogether
inadequately ventilated. The headache and
malaise which are so prone to follow a visit

PLATE XII. — A DIRTY HUMAN LUNG

A slight depression at the upper part of this lung marks a
small area of healed tuberculosis. The distribution of the pig-
ment in streaks was caused by the pressure of the lung against
the ribs.

Hazards of the Air 203

to many of our theatres, are evidences of
the high temperature, increasing moisture,
and bad air which we are usually forced to
breathe there; but the more subtle dangers
here, as. elsewhere, lurk in the dust which
equally with the bad air is forced upon us.

No adequate means exist in most theatres
for ridding the air of the dust. The best of
them indeed are swept and " dusted" system-
atically and the larger particles of dirt
collected and removed. But the floating
dust is simply stirred up, and after settling
is stirred again by the so-called duster, and
so partially removed from the seats, but
it settles again on the floors, to be again set
in motion by the entering and retiring
audience. It would be safe to say that
the most effective method of removal of
the floating dust from many of our popular
theatres and churches is by its lodgment in
the throats and lungs or on the clothing of
the people who visit them.

Some of the newer and better theatres are
furnished with improved and sufficient venti-
lating apparatus, some even have vacuum

2O4 The Story of the Bacteria

cleaners but some of them have neither, and
while in the majority we admire the chaste
gilding and sumptuous upholstery of the
interior, and complacently reflect that at
length the law has forced builders of places
of amusement to afford a measurable degree
of security against being burned alive, those
elements of danger in large assemblies, more
important and more subtle than all the rest
put together, namely, inadequate ventilation
and cleaning, are seldom commented upon or
thought about.

Recent studies have shown us that the
earlier and still prevalent conceptions of the
requirements of good ventilation were inexact.
It is commonly thought that in un ventilated
assembly rooms where many persons are
foregathered, the dullness, headache, and
"dopey" feeling, which everybody has ex-
perienced, are due to lack of oxygen and to
the accumulation in the air of carbonic acid
gas and various human poisons which the
people set free.

But in fact these all appear to be of second-
ary importance. It has been shown by most

Hazards of the Air 205

elaborate and convincing experiments that the
slow poisoning, which under these conditions
we suffer, is self -poisoning, due to the high
temperature and accumulated moisture of
the air. These interfere with the necessary
burning up of refuse products within the body
and prevent the usual and continually neces-
sary excretion through the lungs and the skin
of poisonous stuff of our own making. If we
cannot get rid of this in these ways we
inevitably suffer.

It has been shown by an experiment with a
man in a box, who is allowed to get self-
poisoned in this way, that if the air be cooled
and the moisture removed so that the lungs
and skin may both give off their poison-laden
vapors, the man at once freshens up, his
headache passes and he is quite recovered
without any more oxygen or any less carbonic
acid in his miniature chamber.

Now this does n't mean that oxygen, and
plenty of it, is n't necessary for the welfare
of man, or that an excess of carbonic acid is
not bad for him. But it does mean that some
of the most striking bad effects of ill ventilated

2o6 The Story of the Bacteria

places are due to agencies which- the current
principles of ventilation almost wholly ignore.

What science requires to-day is not only
plenty of oxygen and not too much carbonic
acid, but proper temperature and moisture of
the air. If we add to these requirements
freedom from floating dust, we shall have set
down the least which should satisfy a lover of
fresh air in his enforced thralldom to the
petty, damaging, and increasing tyrannies of
in-doors.

In dwelling-houses, the problem of ven-
tilation is in many respects simpler than in
large assembly rooms, because to a certain
extent the householder is aware of the possi-
bilities of dust infection, from the condition
of health of the inmates, and can act accord-
ingly. But even here, under ordinary con-
ditions, there seems to be, from what we have
learned about the bacteria, more reasons than
we have before appreciated for securing ade-
quate ventilation and cleaning.

The ordinary practice of occasionally stirring
up the settled dust with a feather-duster should
give place to the use of moist cloths or dry

Hazards of the Air 207

cloths frequently shaken out-of-doors, so that
the dust may be removed and not simply
redistributed. This becomes the more impor-
tant if any inmate of the house is suffering
from one of the bacterial diseases.

In the interests of health the fitting of
houses with simpler furniture or less heavy
hangings and fixed carpets is greatly to be
desired.

It is from human waste that the larger part
of the infective stuff comes which we should
avoid, and it is, most of all, in floating dust
and the spray of uncouth sneezers that this
passes from one to another.

If we could gradually wean ourselves, in
public places at least, from the carpet, that
storehouse of floating filth, sending up unseen,
with every footfall, its clouds of often in-
fectious dust, to irritate the delicate recesses
of our lungs; if we might venture to suggest to
the well-meaning but usually wholly unin-
structed or wofully misinstructed delegates
of Hygeia in our cars, offices, theatres, schools,
churches, and homes, that dust is to be got
rid of, not simply set astir by the feather-

208 The Story of the Bacteria

duster, we could largely reduce those affections
of the respiratory organs which are a most
serious and a growing menace to our modern
life in towns to-day.

In fact, the household and general procedure
need be neither complex nor burdensome,
which amply fulfils the conditions of clean-
liness. But the cleanliness which modern
sanitation requires cannot be secured without
the exercise of informed intelligence.

The regulation of the sick-room, and its
communication with the rest of the house, is a
matter on which the advice of the physician
should be sought. First and foremost should
stand the systematic and careful destruction
of the infectious material in all discharges of
whatever sort from diseased persons, by burn-
ing or by the proper disinfecting solutions
such as five per cent, carbolic acid. In this
solution the discharges should be allowed
to soak for several hours before they are
thrown into the sewer or otherwise disposed of.
As to the cleansing of rooms after their
occupancy by persons who have suffered
from bacterial diseases, directions should be

Hazards of the Air 209

obtained from the physician or from the
health authorities.

The danger of infection with the germ of
tuberculosis through the air by unguarded
sneezing and coughing, and by dust, is very
widespread, because consumptive persons are
often for long periods not confined to their
houses, or rooms, or beds, but may be more or
less active centres of infection by mingling
with the well in all the ordinary walks of life.
We have seen already by what comparatively
simple means a large part of the danger of
the spread of tuberculosis and diphtheria might
be prevented.

The risk of dust infection from diphtheria,
and probably from other somewhat similar
diseases, such as measles and scarlet fever, is
more apt to be limited to rooms or houses
where the disease has occurred, because the
victims of these diseases are usually sick
enough to be confined to the house or bed.
But there are, as all physicians know, fre-
quently enough cases of these diseases in
which the patients go about among their
fellows throughout the whole course of the
14

210 The Story of the Bacteria

illness, or at least for some time after it is
fully established.

The possibility of infection from any of
the diseases which we have been considering,
through dust and the spray of sneezing and
coughing, emphasizes the importance of
breathing through the nose and keeping the
mouth shut except when it is necessary to have
it open.

Finally the outraged observer of contemp-
orary manners is sometimes tempted to regret
that the altruism of to-day may not sanction
the maintenance of mediaeval oubliettes,
into which the spitter in unseemly places,
the trailer of her skirts upon the streets, the
ministers in public upon our sidewalks to the
private exigencies of their dogs, might all
be quietly dropped together.

CHAPTER XIX

A DANGEROUS NEIGHBOR

IT is not among lions and tigers, reptiles or
snakes, — save possibly the Indian cobra,
that we have to look for man's most
destructive animal enemy. These mostly
stay at home and mind their business. And
if an unwary man now and then suffers from
them, it is an even chance that it is his own
fault.

But the house-fly — for with him this chapter
chiefly deals — wanders about, and gets its
objectionable person onto or into almost
everything. It breeds chiefly in manure and
garbage heaps. It revels in almost all those
things which to the normal modern man
seem dirty, filthy, and disgusting. Then it
wanders over the food and persons of men,

211

212 The Story of the Bacteria

women, and children whenever opportunity
offers.

This is certainly bad enough, and the
excreta which we euphemistically name fly-
specks, mark the scope of its summer ex-
cursions. But the worst of it is, that the
bacteria which are swarming in most of the
stuff the house-fly eats and dabbles his feet
and tongue in, are in large degree alive, after
they have passed the department of his
interior, and they stay long alive upon his feet.

Now when the house-fly feeds upon infective
human excreta — as he does whenever he gets
a chance, — the typhoid bacilli or the tubercle
bacilli or the contemptible brood which in-
cites dysentery and the protean summer
ailments of both old and young, may be
carried directly and in full virulence to the
food and persons of the well.

It has been shown by hundreds of accu-
rate scientific observations that the house-fly
is the conveyor of infective stuff, especially
of typhoid fever, but also of the other mala-
dies which we have named.

If the fly which favors us with his addresses

A Dangerous Neighbor 213

has come, as is most likely the case, from a
revel in simple filth, he is just a nuisance, if
from infective filth, he is also a menace.

Flies are fond of milk, and they usually fall
in. After this beauty bath in which a few odd
thousands of living bacteria are transferred
to the milk, the fly may scramble out. But
most bacteria, among them the typhoid
bacilli, grow excellently in milk. Thus again
and again have typhoid epidemics started
through the intervention of the domestic fly.

A very simple experiment will illustrate
what happens when a house-fly with dirty
feet walks over food stuff on which bacteria
can grow. One of the Petri plates, which was
described in an early chapter, was partly
filled with warm nutrient gelatin in which
bacteria flourish. When it cooled, a smooth,
solid surface was formed. An unwary house-
fly was caught and his legs and body were
dipped into a dish of very dirty sewage water.
He was pinched a little, to quell his flying
ambitions, and set down upon the surface
of the gelatin. Here he was permitted to
wander about for a moment and then met his

214 The Story of the Bacteria

destiny. The plate was covered and set in a
warm place for three days. Wherever his
feet touched the gelatin, and where the body
dragged, the bacteria grew. The result is
seen in Plate XIII. The track of the wander-
ing fly is marked in colonies of living bacteria,
many thousands in each.

Similar results follow the contamination of
milk by dirty flies. So also foods which flies
visit and fresh berries in city markets are
planted with germs of varying potency.

It is from improperly cared for discharges of
typhoid patients that the chief danger comes.
In the country the unsanitary out-houses
which disgrace the age and in the cities which
discharge their sewage into adjoining waters,
there is abundant opportunity for fatal con-
tamination of food through the fly. So
flagrant are the offences and so significant are
the results, especially in connection with
typhoid fever, that it has been suggested by a
distinguished entomologist that this fly known
to science as Musca domestica should hence-
forth be called the Typhoid fly.

But I suppose that there is something to be

PLATE XIII. TRACKS OF A WANDERING "TYPHOID FLY "

See explanation in the text.

A Dangerous Neighbor 215

said in extenuation of the faults of any
criminal, even in the world of insects. If
flies could talk, and would, they might well
respond to the indictment by calling the
attention of Homo sapiens to the fact that it is
his unsanitary manure heaps and garbage piles,
which afford the defendant its breeding places.
That the chief offence is in dispersing danger-
ous stuff which man, in defiance of sanitation
and decency, spreads abroad. That screening
the houses will largely keep the accused out
anyway. The defence might well be summar-
ized— "No careless man, no typhoid fly." At
any rate if we bear this suggestion in mind, act
upon it, and then kill all the household flies
we can, the typhoid fever statistics will surely
score a noteworthy measure of improvement.
There are many other insects which play
man false in conveying to him various kinds
of infectious plants and animals of the micro-
scopic world. Among these the mosquito
and ticks are the most important. But we
have already said enough about these, and so
need not further prolong this short indulgence
in entomological muckraking.

CHAPTER XX

THE END OF THE STORY

SO important is the subject of the causation
of disease by these minute organisms,
and so full is this field of the promise of
practical and far-reaching benefit to man, that
large numbers of scientific workers all over the
civilized world are eagerly and patiently de-
voting their time and skill to the study of
bacteria.

Great care and technical facility are re-
quired to carry on successfully this kind of
investigation, and it is not at all surprising,
since we have known how to study bacteria for
but a short time, that we should as yet know
very little about many of the bacterial dis-
eases, or that we should often be mistaken
in our interpretations of what we do know.

There is the greatest temptation for workers
216

The End of the Story 217

in this field to magnify the importance of
their observations, or to claim as world-
reforming discoveries the results of imperfect
observation or misinterpreted facts.

But in spite of mistakes and misinterpreta-
tions, in spite of the runaway enthusiasms
which now and again lead the disciples of the
new light to ignore the solid groundwork of
experience which was founded in the old, we
are daily gaining new facts and more com-
manding points of view, and the science of
medicine has entered upon a new and brilliant
epoch in its history.

The mysterious veil which has for so long
hung over some of the most widespread and
terrible diseases, is gradually being drawn
aside, and we now stand face to face with
known and understood and no longer, for
the most part, with mysterious and incompre-
hensible foes.

Thirty years ago it would have seemed an
idle tale had one said that he could cultivate
at will in the laboratory the very living essence
and causes of such diseases as consumption,
typhoid fever, Asiatic cholera, diphtheria, and

218 The Story of the Bacteria

more of the uncanny brood, and could study
and manipulate them as the gardener does his
larger plants, and from the knowledge thus
gained plan new and efficient means for treat-
ing and preventing the diseases which they
cause. But all this is strictly true to-day, as
we have seen in our review of man's invisible
foes and the ravages which they can cause.

And so at last we are at the end of our
story, so far as in such simple and hurried
fashion it can be told to-day. It is a story
which in parts is full of disquieting and un-
pleasant revelations, of facts which at first
sight seem to make life under modern condi-
tions less simple and attractive, and Nature,
less man's friend. But after all there are
few things more disquieting and unpleasant
and unfriendly, to most people, than are
disease and death, and these, sooner or later,
will thrust themselvs into the attention of
everybody, be he cognizant or not of the
varied disregard of nature's laws which for
the most part they follow.

It should not be forgotten by those who are
disposed to close their eyes to the disagreeable

The End of the Story 219

and malign influences which, in the guise of
disease-producing bacteria so frequently sur-
round them, that the rights of others, as well
as their own mental ease, are at stake in this
matter. One has the right, so far as he is
himself concerned, to indulge in almost any
dietetic uncleanliness, or disregard of sanitary
rule with which he may elect to be satisfied.
But he has no right to expose himself unneces-
sarily to the acquirement of such diseases as
will render him a source of either positive or
possible danger to his fellow men.

Among all the myriads of invisible agencies
which are ceaselessly working for man's weal,
we have discovered a few which are his deadly
foes. We have seen that if one looks at the
matter intelligently, the means of largely
avoiding the evil effects of these dangerous
earth-neighbors of ours are comparatively
simple and effective, if we do not hide our
heads, or shirk, or waste our time in protesta-
tions and regrets.

The fact is that with the increasing com-
plexities of modern life, especially in towns
and cities, we are subjected to a great many

220 The Story of the Bacteria

conditions which constantly threaten the
welfare of our physical machinery. So that
we are forced to pay attention to a host of
threatening agencies which in earlier and
simpler times could be safely ignored. This
is a part of the price which we must pay for
what we are pleased to call modern civilization.
It should not be forgotten that underlying
all the protective measures which have been
devised by science against infectious maladies
is the living body machine which each of us
controls for himself. If through the various
phases of unwholesome living so largely in
evidence to-day, the machine is lacking in
vigor, then by so much are the chances of
recovery lessened when the shadow of disease
falls across our path.

Not too much work nor too much play;
not too much food and drink — but enough;
good air and intelligent cleanliness in houses,
assembly places, and public conveyances —
if these conditions be fulfilled in such way
and measure as the hygiene and sanitation of
the day demand, we shall go far to establish
our birthright to threescore years and ten.

The End of the Story 221

And our immunity to infectious disease,
whether we brought it into the world with us,
or achieve it under the ministrations of the
physicians, will most closely confirm the
promise of science.

There are many of the uncanny and disa-
greeable things of life from which it were
better that most of us turned away our eyes.
But the avoidance of some of those forms of
illness, whose causes have been considered in
this little book, is so closely dependent upon a
general knowledge of their nature that the
offence of unpleasant revelations may, it is
hoped, be forgiven by the reader in view of the
ultimate and universal good which these lines
have been penned to foster.

INDEX

PAGE

Abscess 79

Adaptation, marks of . 141

" of body and bacteria ....... 151

Agar, as culture medium ........ 35

Agricultural conjurers ......... SS

Air, bacteria in .......... 199

" bad 204

" dust in . . . . . . . . . .199

1 dusty, in tuberculosis ........ 88

' hazards of . . . . . . . . .199

' indoors .......... 200

" outdoors .......... 200

Alcohol, yeasts in ......... 45

Amreba 4

Animal experimentation i?3

Anopheles 137

Antitoxin 159

" action of ......... 162

of diphtheria . . . . . . . 126, 161

" of meningitis ........ 163

of tetanus . 130, 163

Anti-vivisectionists . . . . . . . . .174

Appendix ........... 142

Asiatic cholera .......... 109

Bacilli 42

Bacillus no

of Asiatic cholera no

" " diphtheria 125

" " dysentery ......... 108

" " influenza 119

" plague ......... 134

" " tetanus 128

223

224 Index

PAGE

Bacillus of tuberculosis 84

" typhoid fever . . . . . . . .100

prodigiosus . S3

Bacteraemia .......... 80

Bacteria, action of sunlight on ....... 49

activities of . . . . . . . . .20

agar cultures of ........ 35

" agricultural 55

antagonistic 54

as foes .......... 60

" foods ......... 26

" friends . . . . . . . . .27

" pests . . . . . . . . 25, 51

battles of, in body . . . . . . . .152

classification of . . . . . . .42

cold, action of, on . . . . . . . .47

colonies of . . . . . . . 32, 38

colors formed by ....... 38, 49

cultivation of . . . . . . . .31

culture selective of . . . . . . .50

tubes ........ 34

dead, as curative agents . . . . . . .164

disposal of, in body ....... 149

destruction of, in body ..... 150, 165, 170

disease-inducing . . . . . . . .161

" sources of . . . . .176

division of . . . . . . . .17

ecclesiastical . . . . . . . . .52

" flagella of 17

forms of ......... 15

freezing of ......... 47

friendly 54

" gas-forming ......... 40

in agriculture ........ 24

"air 199

" beer 45

" " domestic life 51

" farm life 24

" hay infusion ........ 28

" "ice 47, 196

" industries ......... 25

" " manure ...... 56

Index 225

PAGE

Bacteria, of plant nodules 58

" soil . 23

" water 184

" " wine ......... 45

" light-forming ........ 43

" methods of study ........ 28

movements of ........ 16

multiplication of . . . . . . 1 7. r 8

nitrogen collecting . . . . . . . 24, 55

nomenclature of . . . . . . .41

occurrence of ........ 23

oxygen-loving ........ 46

natural protection against 149

pathogenic ......... 61

" phosphorescent 43

" products of . . . . . . . .21

pyogenic . . . . . . . . .81

size of .16

species of 36, 4<>

" spores of ........ 19, 3<>

study of 28

" thermophylic ........ 48

Bacterial curiosities ......... 43

Bacteriology, growth of 216, 217

Bacteriolytic substances ........ 166

Bacterium . . . . . . . . . . .41

Beef tea, culture medium ........ 36

Beer, bacteria in . . . . . . . . . .45

Bleeding Host, bacteria of 52

Blood poisoning .......... 70

Blood-serum, culture medium . . . . . . .36

Body, disease in . . . . . . . . . .62

health of 63

safeguards of 141, 149

" structure of I

Boils 72, 81

Butter, bacteria in ......... 24

Carpets, unsanitary ......... 207

Cattle, tuberculosis in . . . . . . . . .93

Cells i, 3

" blood — red n

15

226 Index

PAGE

Cells, blood — white 77

" ciliated . . . 93

' evolution in ........ 12, 13

4 muscle . . . . . . . . . .10

' scavenger .......... 147

' wandering . . . . . . . . . 148

Cerebro-spinal meningitis . . . . . . . 131, 156

Cheese, bacteria in 24

Childbed fever . . 75

Cholera, Asiatic . . . . . . . . . .109

food infection in . . . . . . . 182

protective agents 164

bacillus . . . . . . . . . .no

winter .......... 185

Ciliated cells .......... 93

Coccus . . . . . . . . . . .41

Colds 120, 122, 123

Communicable diseases ........ 68

Consumption .......... 83

Contagious diseases . 68

Coughing, risks of 209

Dead tissues, disposal of . . . . . . .147

Death-rate ........... 155

Diphtheria . . . . . . . . . . .125

antitoxin ........ 126, 162

bacillus of . . . . . . . . 125, 126

deaths from . . . . . . . .156

dust and .......... 209

" milk and 180

safeguards against . . . . . . .127

toxaemia of . . . . . . . .126

Disease, attacks of ......... 68

bacterial ......... 66

communicable ........ 68

contagious ......... 68

infectious ......... 67

nature of 61

Disinfectants 183

Division of labor, physiological ....... 8

Dust in air .......... 199

" " houses .......... 206

Index 227

PAGE

Dust in lungs 200, 201

" " theatres. 203

" tubercle bacilli in 88

Dusting, improper 203, 206, 207

Dusty trades .......... 200

Dysentery 108

Erysipelas . . . . . . . . . . .72

Evolution . . . . . . . . . . 13, 142

Exanthemata .......... 136

Fake sanitation .......... 183

Fermentation .......... 45

Fever, childbed ........ t . 75

' typhoid .......... 100

' yellow .......... 138

Filtration, water ......... 188, 191

Flagella f. .17

Fleas and plague ......... 135

Flexner . . . . . . . . . . .131

Flies .......... 182, 211, 212

Fly track culture 213

Food, infection by 178, 182

Freeman . . 181

Garbage, pollution by, of water and ice ...... 197

Gelatin as culture medium ........ 34

Gonococcus .......... 32

Gonorrhoea .......... 132

Green manuring . . . . ... . . . .57

Health, maintenance of ........ 220

" natural tendency to 143

Hernia 142

Hiss 168

Holmes 75

Horse for antitoxin . . . . . . . . .161

Hydrophobia 136, 169, 170

Ice 196

" bacteria in ......... 47, 196

" typhoid pollution of ........ 106

228 Index

PAGE

Ice, self-purification of . . . . . . . . . 197

Immunity 157

" acquired . . . . . . . . .157

" active ......... 163

forms of . . . . . . . .171

natural . 157

nature of . 159

passive . 163

to poisons . . . . . . . . .158

Infection, reduction of risks of . . . . . .177

sources of . . . . . . .175

prevention of . . . . . . . .178

and nostrum mongers , . . . . . .183

Infectious disease . .67

food 179

material, disposal of ....... 208

Inflammation .......... 76

Influenza . . . . . . . . . . .119

Kissing, risks of . . . . . . . . . .89

Koch 36, 83

Leucocytes .......... 77, 79, 146

as heroes ......... 152

extracts of 168

Life, nature of . . . . . . . . 3, 62

Lockjaw 127

Lungs, cavities in 85

" dust ......... 200, 201

tubercles in 84

Lymph-glands .......... 147

Lymph-nodes .......... 147

" dust in ......... 201

Lytic substances . . . . . . . . .166

Malaria 137, i?i. i?8

Man, development of ......... 9

Manure, bacteria in' . . . . . . . . 24, 56

Measles I3S

Meat 93, 181

Meningitis 131

antitoxin 163

Meningococcus . . . . . . . . . .131

Index 229

PAGE

Micrococcus 41

Milk, blue Si

" certified .......... 181

" culture medium ......... 36

" flies in ... 213

" infection by 179

" pasteurization of 94

"red Si

" tubercle bacilli in ........ 94

" typhoid bacilli in ........ 106

Mortality in United States 156

Mosquito and malaria . . . . . . . . 137

" yellow fever 139

Mumps ........... 140

Musca domestica ......... 214

Muscle cells IO

Nitrogen, bacteria and ........ 55

Nodule bacteria . . . . . - . . . .58

Northrup 118

Olynthus 6

Opsonins ........... 167

Oxygen, bacterial lovers of . . . . . . . .46

Oysters, typhoid bacilli in ........ 106

Pasteur 170

Pasteurization 181

Phagocytes .......... 148

Plague 133, 134, 164

Plasmodium malariae ......... 137

Pneumonia 115, 116

" fresh air in . . . . . . . ri8

Poisons, bacterial, in body ....... 146, 151

disposal of, by body ....... 144

Potatoes as culture media . . . . . . .31

Prevention of disease . . . . . . . . .178

Pus 78

Putrefaction, bacteria in 21

Rabies, see Hydrophobia.

Rats and plague 135

230 Index

PAGE

Safeguards of the body 141

Scarlatina . 135, 180, 209

Scarlet fever . . 135, 180, 209

Scavenger cells .......... 147

Septicaemia .......... 80

Sewage in water 187, 192

Silos, bacteria in . . . . . . . . . .24

Small-pox 135, 169

Sneeze plate culture ......... 90

Sneezing, dangers of ...... 90, 117, 120, 209

Soil, bacteria in . . . . . . . . . .23

Spitters, uncouth . . . . . . . . .210

Spontaneous generation . , . . . . . .22

Spores of bacteria ......... 19

Spray from sneezing ......... 90

Sputum, dangers of 87

" disposal of ......... 95

Squirrels and plague ......... 135

Staphylococcus . . . . . . . . 42, 72, 81

Stegomyia ........... 139

Streptococcus 41, 72, 81, 121

Suppuration ......... 76, 80

Surgery, aseptic 74

Syphilis 132

Tetanus . . . . . . . . . . .127

antitoxin 130, 163

" bacillus of 128

Theatres, dust in 203

Toxaemia . . . . . . . . . .80

Toxines 78, 159

Tubercle bacilli 84

' cultures of . . . . . .8-7

1 effect of sunlight on ...... 90

" in cattle 93

" " " dust 88

" milk ........ 94

' limits of risks from ...... 92

" sources of 86

" spread of 89, 90

" in coughing 90

" " sneezing ...... 90

Tubercles 84

Index 231

PAGE

Tubercles healing of .86

Tuberculosis . 83

" avoidance of . . . . • • .98

" cattle 93

cure of 97

death from 156

from dust 209

" meat 181

" milk 180

house infection by ....... 202

public conveyance, infection by .... 95

lung 84

persistence of . . . . . • • • J78

44 predisposition to 85, 202

recovery from ........ 86

14 resistance to . . . . . . .86

" sneezing and coughing in 209

44 treatment of . . . . . . .97

Tuberculous sputum ........ 87, 95

Typhoid bacilli 100

1 conveyance, direct, of . . . . . 106

" in ice 106, 196, 197

" " milk 106

44 4< " oysters ... .... 106

44 " " water 105

44 " sources of ........ ioi

44 " spread of, by flies 106, 212

44 "carriers" ........ 104, 180

44 excreta, destruction of ....... 107

fly . .214

44 fever .......... IOO

41 deaths from ........ 156

' eating utensils in . . . . . .182

" " flies in 212

1 milk in . . . . . . . . .180

" persistence of . . . . . . .178

' protective inoculation forj ..... 164

41 sewage .......... 104

Vaccines 167

Vegetables, infective . . . . . . . . .181

Ventilation 202, 204, 206

232 Index

PAGE

Water " . 184

' bacteria in •••..... 184

bacterial analysis of . . . . . . . I9o

' boiling of IQI

1 filtration of l88> IQI

polluted IOS, 185, 192

' self -purification of .189

' sewage in l87

' supplies I86> IQ3

' typhoid bacilli in 105, 1 86

Wells, dangers of ••»•..... 193

construction of . . . . . . . . .194

Whooping cough . . . . . . . . , t i^Q

Wine, bacteria in 4S

Wound diseases .......... 70

Wounds, healing of . . . . . . . .78

Yeast in alcohol making ........ 45

Yellow fever .......... 138

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