Introduction to Infectious and Parasitic Diseases: Including Their Cause and Manner of Transmission

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'^iiiii T/o.n

Satbacl) iS:olUge l.tbtars

JARVIS FUND

bequest of (500 from Mrs. Almiia Jarvis. to fulfil 1

wishes or her hueband, Edwud Jaxvla, H.D.

of Dorchester, Mass., of the

^'t-^

r

INFECTIOUS
AND PARASITIC DISEASES

LANGFELD

"This kingdom (bacterial) is a veritable fairyland. Its
inhabitants are more nimierous than the sands of the sea,
and as varying in their functions as are the inhabitants of
the animal and vegetable kingdom." ** Only a few of
them work serious harm to man, and even the harm which
these do is not out of harmony with nature as a whole.
The world as we see it can be maintained only by a har-
monious succession of life and death." (Flick, Consump-
tion, a Curable and Preventible Disease.)

"When we realize that the majority of all deaths is still
from preventible causes, most of which are already quite
familiar to us, it is manifest that this must be in a large
measure due to an indifference on our part to put into
practice even the knowledge which we already possess for
their prevention." (Abbott, Hygiene of Transmissible
Diseases.)

"The belief is growing stronger that the commimicable
diseases are more often spread through the intermediation
of mild, latent and imrecognized cases than through the
agency of fomites, that is, inanimate objects." (Rosenau,
Disinfection and Disinfectants.)

o

INTRODUCTION TO

INFECTIOUS AND
PARASITIC DISEASES

INCLUDING

THEIR CAUSE AND
MANNER OF TRANSMISSION

BY

MILLARD LANGFELD, A.B., M.B., (Johns Hopkins)

Professor of Bacteriology and Clinical Medicine, John A. Creighton Med-
ical College, Omaha; Visiting Physician, St. Joseph's and Douglas
County Hospitals, and Bacteriologist, the Omaha City

Board of Health.

With an Introduction by Lewellys F. Barker, Professor of
Medicine at the Johns Hopkins University

WITH THIRTY-THREE ILLUSTRATIONS

PHILADELPHIA

P. BLAKISTON'S SON & CO.

1012 WALNUT STREET
1907

I7l0v\x

i

^J'T

B R A v< '

CopmoBT, 1907, By P. Blaxiston's Son & Co.

i

PHnUdby

The Ma^le Press,

York. Flu

MICROFILMED
AT HARVARD

I !

To the
memory of my beloved father

'Daniel TanaM^

this book in grateful remembrance
is dedicated

PREFACE.

Primarily this book was written for the use of nurses,
in the belief that by broadening their comprehension of
infectious and parasitic diseases it would materially
assist them in performing their duties more inteUi-
gently, and with greater satisfaction to themselves.
Through the solicitations of several medical friends who
kindly looked over my manuscript, and who were of
the opinion that both physicians and students of med-
icine would find as much to interest them in its pages
as would nurses, the original design of the book was
altered somewhat. It seemed to me that if in place
of the conventional (seriatum) text-book consideration
of the above diseases the fundamental principles which
govern all were substituted, knowledge of wider utility
would be acquired, and with less effort, because much
imimportant detail could be avoided. It was my aim,
also, by reflecting current medical thought to explain
to nurses the reasons for performing many duties which
they are merely taught to do. Then, since the trained

nurse's position as medical assistant to the doctor and

..

Vll

PREFACE.

as a sanitarian has developed into one of such extra-
ordinary importance, specific information in regard
to these offices was to be given a prominent place.
For the same reasons, chapters on "Bacteriology,"
"Parasites," and "The Collection and Examination of
Secretions and Excretions" were included in the plan.
Withal, every effort was to be made to be lucid in style
and simple in treatment. Of nursing, per se, I was
not to treat.

The present volume represents my efforts to embody
the above ideas in a book.

My obligation to various authors has been heavy,
and I wish I could make suitable acknowledgment to
every one upon whom I have drawn for material;
but the character of the book obviously makes this
impracticable. Nevertheless, to Professor Roger's
"Introduction to the Study of Medicine" and "Infec-
tious Diseases," to Dr. Abott's "Hygiene of Trans-
missible Diseases," and also to Dr. Rosenau's "Dis-
infection and Disinfectants," I feel reference should
be made. Furthermore, I would be lacking in grati-
tude did I not make acknowledgment to my alma
mater, the Johns Hopkins Medical School; the book
really owes its inception to the scientific spirit and
inspiring personjility of its faculty.

To have been a student there is a hfe-long pleasurable
memory, and a distinction which I feel can be repaid
only in small measure by describing my efforts as

PREFACE. ix

feeble amplifications of its teachings. Professor Barker
was my first teacher in medicine, and to him I am
indebted for much more than his graciousness in review-
ing these pages and writing the introductory note.

The only originality claimed is in the presentation
of the subject matter. Save in a few instances, specu-
lation has not been indulged in, and only accepted
doctrines have been adhered to.

Great pleasure was taken in the writing of these pages,
although most of the work was done during moments
snatched here and there between urgent duties; whether
I was justified in my undertaking can only be told if
others derive either pleasure or profit in their perusal.

Millard Langfeld.

203 McCague Bldg., Omaha, Neb.
March 2$, 1907.

INFECTIOUS
AND PARASITIC DISEASES

LANGFELD

CONTENTS

CHAPTER I: Causes of Disease i

Health, i — Disease, i — Agents of disease, mechanical,
physical, chemical, animate, 3 — ^Infectious agents, 5 —
Parasite, 8 — Specific and non-specific infectious agents,
9 — Specific and non-specific infectious diseases, 10 —
Characteristics of infectious diseases, 12 — Local and gen-
eral infections, 19 — Combined infections, 22 — Secondary
infections, 23 — Self-limiting nature of infectious diseases,
24 — Antibodies, 25 — Agglutinins, 27 — Opsonins, 27 —
Complications, 32 — Terminal infections, 34 — Evolution
of disease, 34 — Communicable diseases, 37.

CHAPTER H: Bactemology 38

Arts and industries, 39 — Saproph)rtes, 40 — Pathogenic and
non-pathogenic bacteria, 41 — Size, 42 — Multiplication, 42
— Shape, 43 — Grouping, 44 — Distribution, 45 — Specific
and non-specific bacteria, 51 — Spores, 52 — Factors neces-
sary for the growth of bacteria, 53 — Agents harmful to
bacteria, 57 — Deodorant, 57 — ^Insecticides, 58.

CHAPTER ni: Phenomena of Infection 66

Infectious agents in disease, 68: Nimiber of bacteria in,
68 — Portalsof entry, 69 — ^^rulence, 70 — Microbic associa-
tion (symbiosis), 71 — Conve3^nce by insects, 72. The
body in relation to infections, 73: Predisposition, 74 —

xm

i

xiv CONTENTS.

Heredity, 76 — Race, 76 — Family, 79 — ^Individual, 80 —
Environment, 81 — Region, 81 — Climate, 81 — Ph3rsical
conditions, 85 — Season, 90 — Fasting, poor food, etc., 90
— Occupation, 92 — ^Age, 94.

CHAPTER IV: Iotlammation 99

Inflammation, 99 — Cardinal symptoms of inflammation,
loi — Leucocytes, 102 — Chemotaxis, 103 — Phagocytosis,
104 — Leucocytosis, 105 — Suppuration, 106 — Pyogenic
bacteria, 107.

CHAPTER V: Anhial Parasites 109

Protozoa, 11 1 — AnuBba Dysenteric^, 112 — Trypanosoma
Gantbiense, 113 — Dimi-Dum fever, 113 — Plasmodium
Malaria, 113 — Nematodes, 116 — Guinea-worm, 116 —
Filaria BancrofH, 118 — Filaria Loa, 120 — Trichiuris
trichiura, 121 — StrongyloidesiniesHnalis, 122 — Trichinella
Spiralis, 122 — Ascaris lumbricoides, 124 — Oxyuris ver-
miculariSf 125 — Uncinaria duodenalis, 126. Flat worms,
129: Trematodes, 129: — Paragonimus Wesiermanii, 130
— Opisthorchis Sinensis, 131 — Fasciola hepatica, 132 —
SchisU)somumh(emaU)bium, 132. Cestodes, 133: — Tcmia
saginata, 136 — Tcmia Solium, 136 — Bothriocephalus lotus,
137 — Dipylidium Caninum, 138 — Hymenolepsis nana,
138. ^sceral cestodes, 139: — Cysticercus cMulosa, 139
— Tcerm echinococcus, 140. Insects, 141: — Parasitic dip-
tera, 141 — (Estrus kominis, 142 — Dermatobia cyanvoentris,
143 — CompsomyiamaceUaria, 143 — SarcophagaCamaria,
143 — Pulex irritans (flea), 144 — Sarcopsylla penetrans
(sand-flea), 144 — Bed-bug, 144 — Lice, 145 — Ascaris
scabiei (itch-mite), 148 — Leptus Autumnalis (harvest-
mite), 149 — Ixodes Ricinus (wood-tick), 149.

CONTENTS. XV

CHAPTER VI: Avenues of Exir of Infectious Agents

AND Parasites from the Body 151

Expectoration and nasal secretions, 155 — Feces, 156 —
Urine, 160 — Skin, 161 — Blood through bites of insects,
162 — Suppurations, 164.

CHAPTER VH: Portals of Entry of Infectious

Agents and Parasites into the Body 166

Through wounds of skin and mucous membranes, 173 —
By mouth and nose through air, 173 — By mouth through
food and water, 175 — By genito-urinary tract, 181 — By
placenta, 182 — Cryptogenic (unknown entrance), 183.

CHAPTER Vni: Portals of Entry and Avenues of
Exit of Micro-organisms in the Various Diseases. 184
Actinomycosis, 184 — Anthrax, 185 — Bubonic plague, 186
— Epidemic cerebro-spinal meningitis, 188 — Chicken-pox
(varicella), 188 — Cholera, 189 — Dengue, 190 — Diphtheria,
190 — Dysentery (amoebic), 192 — Dysentery (bacillary),
192 — Erysipelas, 193 — Glanders, 194 — Gonorrhoea, 195 —
Hydrophobia, 196— Influenza, 197 — Leprosy, 197 — Ma-
dura foot, 198 — Malarial fever, 198 — Measles, 199 —
Mimips, 200 — Pneimionia, 200 — Relapsing fever, 201 —
Rubella, 202 — Scarlet fever, 202 — Small-pox, 207 — Epi-
demic stomatitis, 205 — Syphilis, 206 — Tetanus, 207 —
Tuberculosis, 208 — Typhoid fever, 209 — Whooping-
cough, 212 — Yellow fever, 212.

CHAPTER IX: Disinfectants and Disinfection 214

Purpose of, 214 — Heat, 216 — Gaseous disinfectants, 218
— Chemical disinfectants, liquids, 219 — Bichloride of
mercury, 221 — Formalin, 222 — Carbolic acid, 222 —
Tricresol, 223 — Milk of lime, 224 — Chloride of lime, 224.

XVI CONTENTS.

CHAPTER X: Collection and Examination of Secre-
tions AND Excretions aa6

Sputum, 226 — Diphtheritic cultures, 230 — ^Vomit, 232 —
Test-meals, 234 — Blood specimens, 236 — Typhoid fever
(Widal) outfit, 236 — Malaxia, 238 — Pus and other dis-
charges, 240 — Urine, 241 — Feces, 249.

APPENDIX 353

INDEX ass

INFECTIOUS
AND PARASITIC DISEASES

CHAPTER I.

CAUSES OF DISEASE.

Since disease is a deviation from that state of the
body which is called health, it is appropriate, before
taking up the "causes of disease," to define, briefly,
what health and disease are.

Health may be defined as that condition
Health, of the body in which all of its functions are

normally performed, to the end, that a
feeling of mental and bodily comfort is experienced. It
is a nice balance, or equilibrium, maintained between
our bodies and the surrounding world. Eating, drink-
ing, and sleeping, work, play, and rest, are factors that
should promote a general feeling of weU-being, that
in turn manifests itself in the desire and ability to eat,
drink, sleep, work, play, and rest, all normal functions
which the healthy human being craves.

Disease, on the other hand, is characterized
Disease, by a rupture in the relationship of our

bodies to our surroundings, which leads
to disturbed functions, and to unusual subjective sen-
sations and objective phenomena. Whatever breaks

2 INFECTIOUS AND PARASITIC DISEASES.

the harmony of health, in other words, whatever causes
disease, always acts so as to destroy some tissue, or to
interfere with the functions of some organ. The mod-
em conception of the causation of disease no longer
gives credence to the belief that its causes are novel
and mysterioxis, but, on the contrary, from indisputable
evidence, places them among the actual phenomena of
the physical world. Nor does it admit the spontaneous
development of disease in either the bom or the unborn,
albeit obvious instances to the contrary, since in such
cases some external agency has previously acted directly
or indirectly (e.g., through a parent) as a first cause,
and intermpted the orderly continuity of the normal
functions. Therefore, no matter what the exciting
cause of a disease may be, // invariably, and primarily,
comes from withotU the body.

When an extraneous cause acts injuriously upon a
person, his organism does not remain passive, but
reacts with all its might to counteract the cause and
repair any defect the latter's presence has given rise to.
This power of the body to protect itself lays in a defen-
sive mechanism evolved during countless ages of suc-
cessful eflForts to survive destruction against harmful
influences in the universal struggle for life. So nicely
is the body's mechanism of defense adjusted, that con-
stant re-adjustments are made to passing dangers,
under ordinary circumstances, without consciousness
being disturbed. In this way equilibrium with the

CAUSES OF DISEASE. j

outside world is maintained. Should, however, a
harmful influence be unusually strong, then the reac-
tions of re-adjustment to which it gives rise are corre-
spondingly vigorous and wide-spread, so that conscious-
ness is disturbed, functions are corrupted, and most
astonishing changes in the external appearance are
observed. These phenomena of reaction are evidence
of the battle that is being waged by the body against a
harmful force, and collectively they constitute the
symptoms of disease. All harmful influences are pro-
vocative pf disease ; yet disease does not exist unless the
reactions or s)niiptoms are suflSciently pronounced as to
upset the orderly unconscious functioning of the body.
Diseased states are also called morbid or pathological;
wherefore morbific or pathological causes are those
that bring about disease. The causes of disease are
often spoken of as agents. We divide the agents of
disease into four classes, mechanical, physical, chemical,
and animate.

A blow which breaks a bone, an obstruction
Mechanical, to respiration due to a foreign body lodging

in the larynx, a rupture of the abdominal
wall that permits a loop of the intestines to protrude,
are all instances of diseases due to mechanical agents.

Similarly, alterations in the surrounding
Physical. medium, as for example, ascending to

great heights, or working at great depths
imder pressure, produce respectively mountain-climbers'

4 INFECTIOUS AND PARASITIC DISEASES.

disease and divers' paralysis — two well-recognized
aflFections, the result of physical agents.

That diseases are often brought about
Chemical through chemical agents scarcely needs
Agents, illustration on account of the frequency

of such cases being reported by the Press,
and the familiarity of the average person with the
dangerous character of many chemicals, notably the
poisons. Ptomain poisoning, which comes from eating
various foods that have undergone a peculiar decom-
position; arsenical poisoning, numerous cases of which
were reported in London, England, a few years ago,
in which the arsenic was traced to the glucose in beer;
and painters' colic, or lead colic, a disease common in
those whose occupations bring them into close contact
with lead, are examples of diseases of chemic origin.
Indeed, among the causes of disease, the chemical
agents are by far the most numerous and the most
important, in as much as the majority of diseased
states are fundamentally, or coincidentally, of a chem-
ical nature. Most of the physical and mechanical
agencies, through the injuries they inflict on tissues,
are thereby transformed into chemical irritants, since
the resulting reactions follow largely as a result of the
absorption of dead and useless material. For example :
A person is severely burned, yet survives three days.
He does not die as a direct result of the physical agent,
fire, but from poisoning in one of the two ways ; namely,

CAUSES OF DISEASE. 5

either so large a surface of the cuticle was destroyed
that the respiratory and excretory functions of the skin
were interrupted, so that poisoning followed the reten-
tion of products which should have been excreted from
the body; or, poisoning resulted from absorption of the
detrimental products into which the skin was converted
by the fire.

Similarly, in diseases the result of mechanical forces,
while the earliest phenomena are the direct result of
the injury (shock, for example), the later reactions
follow as a sequel to the absorption of dead tissues
and inflammatory products. Indeed, reconstruction of
tissues, e.g., bone, etc., is initiated by these very prod-
ucts being absorbed, and, thereby reflexly irritating
into action those tissues and functions that bring about
repair.

The fourth group into which we divide

Animate the agents of disease is the animate.

Agents. Animate agents comprise two classes,

parasites and infectious agents, both of

which may be foimd among either the animal or

vegetable kingdom.

Before the dawn of bacteriology, phys-
Inpectious icians had already applied the term, infec-
Agents. tious, to diseases that, symptomatically,

conformed to a certain type and were con-
veyed through the air. Early in their career, bacteriol-

6 INFECTIOUS AND PARASITIC DISEASES.

ogists discovered that a number of the infectious
diseases were due to bacteria and, rather hastily, it
must be confessed, concluded that all of this class had
a similar origin. So they described an infectious
disease as "a morbid or diseased state of the body due
to the invasion and growth of bacteria." Somewhat
later it was seen that they had gone too far in formulat-
ing this definition for infectious diseases, because a
certain number were discovered which owe their origin
to animate agents that are not bacteria, namely, to
moulds and protozoa.*

Hence it has followed that the designation "infectious
disease" is restricted in its application to diseases which
conform to a certain type, and "infectious agent" to
a living organism,! microscopic in size, that is capable
of producing an infectious disease. So far as we know,
only three types of organisms produce infectious diseases,
namely, bacteria, moulds and protozoa, certain species
of each comprising the infectious agents. At present
bacteria constitute the vast majority, but it is fast

* Protozoa (literally, first animal) are the simplest organisms which
dearly belong to the animal kingdom. The characteristic which dis-
tinguishes them from all other groups of animals is the fact that each
protozoan consists of a single cell.

t Organism — composed of organs functionally necessary for the ex-
istence of the individual or race. Although unicellular plants and
animals have no organs, yet, since they perform functions analogous to
those of the higher forms of living matter, we are correct in considering
them organisms.

CAUSES OF DISEASE. 7

becoming evident that both protozoa and moulds are
of abnost, if not of equal importance, as causative
factors in infectious diseases; and that besides these,
there are other microscopic and ultra-microscopic
forms of life, not included in the three groups, that are
playing a similar r61e. For these reasons we conclude
that the only defensible definition of an infectious agent
is that it is either an animal or vegetable organism,
microscopic in size, which produces an infectious
disease. It will be observed, from the point of view
of this definition, that we classify the organisms that
produce infectious diseases not by their place in the
animal or vegetable kingdom, but by the eflFects they
produce in the living body.

The animate agents, it will be remembered, we
divided into two classes, parasites, and infectious agents.
The designations have reference both to the manner
in which the agents live upon the body, and the phenom-
ena their presence give rise to; their place in either
animal or vegetable kingdom is again disregarded.
The mode of action of the infectious agent is character-
istic, and markedly diflFerent from that of the parasite.
When it enters a living body, it aims directly at the
destruction of the latter. It multiplies rapidly, tends
to scatter its broods throughout the tissues, and all
the while gives oflF the most powerful poisons known.
This agent is wickedly implacable, neither giving nor
asking quarter. The battle that it wages with the body

8 INFECTIOUS AND PARASITIC DISEASES.

can terminate only by the destruction of one of the
combatants.

In contrast to this monster evil is the lesser,
Parasite, the parasite. A parasite is an organism

that lives within or upon another organism
called the host. The parasite's purpose is an easy
living at the expense of the host. It subtly recognizes
that it is to its interest not to inflict too great an injury.
If perchance it causes the death of the host, it is an
accident. It seldom invades the body generally.
From the foregoing is seen the reason for drawing a
distinction between parasites and infectious agents
based upon their mode of action and the effects they
produce. It should be remembered, however, that
parasites and infectious agents are not necessarily
represented by distinct organisms. Indeed, the same
microbe may live upon our bodies, or within its cavities,
at one time as a parasite, and at another time be the
cause of an infectious disease. The germ of pneu-
monia is a constant inhabitant of almost everyone's
mouth, leading there a harmless parasitic existence,
yet let the vital powers be reduced through fatigue,
exposure, or cold, and it becomes an infectious agent
through the disease (pneumonia) which it provokes.
The difference between a germ that is at one time a
parasite, and at another time an infectious agent,
depends in the latter case upon the power it has of
producing its specific poison, and also upon its chance

CAUSES OF DISEASE. 9

of finding lodgment in an appropriate situation within
the body *

Infectious agents are divided into those
Specific and that are specific, and those that are non-
Non-specific specific. By specific is understood an
Infectious organism that always provokes the same
Agents. disease; at the same time it implies that

it is the only exciting cause of that disease.
The microbes which cause typhoid fever, diphtheria,
plague, etc., are specific agents, because they are the
only germs, respectively, that can give rise to these
diseases.

A non-specific agent is an organism whose entrance
into the body is not necessarily followed by the same
disease, in fact, its eflFects are particularly characterized
by their dissimilarity; besides, its action is duplicated
by other non-specific agents. The streptococcus
pyogenes is a most excellent example of a non-specific
agent. The following are some of the diseases it
provokes: Erysipelas, puerperal fever (child-bed fever),
tonsillitis, peritonitis, abscess, etc., all affections that
exhibit a widely divergent s)niiptomatology, and each one
of which may result from entrance into the body of
an entirely different species of bacterium.

*From one view-point, all infectious agents are parasites, just as we
will see later they may also be saprophytes. But the true parasite is
never an infectious agent.

lo INFECTIOUS AND PARASITIC DISEASES.

Infectious diseases are divided into the
Specific and specific and the non-specific according
Non-specific as they result from a specific or non-
Infectious specific agent. There are some infectious
Diseases. diseases, however, in which the etiological

factor is not known, yet they are classed
with the specific maladies. This is done because the
s)niiptomatology of each is characteristic, and because
any one of them in one individual never gives rise in
another, who may contract it, to a diflFerent disease.
In this class of specific diseases, of which the causes
are not known, is small-pox, scarlet fever, measles,
chicken-pox, etc. These same diseases are also classed
as infectious, but entirely, it should be noted, on account
of their close resemblance to those infectious diseases
whose determining factor is positively known to be a
micro-organism.

In the list of infectious diseases of known and unknown
etiology which follows, it will perhaps come as a sur-
prise to the student that the cause of so many diseases
is as yet unknown ; and that those of unknown etiology
include many of our most common diseases. He
might well ask the question, why have the causes of
these every-day diseases not been discovered? There
are probably two chief reasons : First, because the causes
have been sought for as if they must be bacteria,
whereas they very likely belong to entirely diflFerent
genuses of organisms; and second, because the causes

CAUSES OF DISEASE.

II

of some diseases, at least, are probably ultra-micro-
scopic, i.e., too minute to be made out with the magnify-
ing powers of the present microscope.

It will also be noticed that syphilis is placed under
both groups. This is done because, from the evidence
accumulated thus far, it seems quite probable that the
treponema pallidum (spirochcBta pallida) of Schaudinn
and Hoflfman is the etiological factor.

SPECIFIC INFECTIOUS

DISEASES OF KNOWN

ORIGIN.

gonorrhcea.

Epidemic Cerebro - spinal

MENINGiriS.

Pneumonia (Lobar).

Tuberculosis.

Leprosy.

Glanders (Farcy).

Tetanus (Lock-jaw).

Diphtheria.

Asiatic Cholera.

Anthrax.

Typhoid Fever.

Bubonic Plague.

Influenza (La Grippe).

Malta Fever.

Relapsing Fever.

Acute Specific Dysentery

(Bacillary Dysentery).
Actinomycosis.
Mycetoma (Madura Foot).
Malarial Fever.
Amcebic Dysentery.
Syphilis.

SPECIFIC INFECTIOUS

DISEASES OF UNKNOWN

ORIGIN.

Epidemic Parotitis (Mumps).

Syphilis.

Rabies (Hydrophobia).

Yellow Fever.

Measles.

Whooping-cough.

Scarlatina (Scarlet Fever).

Variola (Small-pox).

Typhus Fever.

Vaccinia (Cow-pox, Vaccina-
tion).

Varicella (Chicken-pox).

Rubella (Rothehi).

Dengue (Break-bone Fever).

Rheumatic Fever (Rheumat-
ism).

Beri-beri.

Glandular Fever (?).

Aphthous Fever (Foot and
Mouth Disease).

Chancroid.

Trachoma (Egyptian Ophthal-
mia).

12 INFECTIOUS AND PARASITIC DISEASES.

Character- An infectious disease follows a cycle, or
isncs OF course, which is typical of the class "infec-
Infectious tious diseases." To be sure, there are
Diseases. variations from the type, sometimes very
pronounced, yet certainly never greater than one would
anticipate in view of the differences exhibited by people
in general. Moreover, the infectious agents causing
them are subject to great variations in disease-producing
power, a fact which influences the character of the
infection either for better or for worse. Concerning
these differences in pathogenicity as exhibited by infec-
tious agents, we shall have much to say in a succeeding
chapter. In this course or cycle of an infectious
disease, four stages are commonly admitted:

1. An incubation period.

2. A period of invasion.

3. A stationary period.

] 4. A period of decline.

These periods, or stages, of an infectious disease
were first created upon purely clinical grounds; but
they have been retained, because they are in entire
harmony with modem discovery and experiment, a
fact which adds another laurel to the fame of those dear
old practitioners who knew absolutely nothing of the
science of bacteriology. Besides, these periods as
named by them, remarkable to say, graphically describe
the progress of microbic action from the beginning of
a disease to its termination. An infectious disease

CAUSES OF DISEASE. 13

must be regarded as a battle to the death between the
body, on the one hand, and an infectious agent on the
other; and as the S3niiptoms of each period correspond
to various phases in the battle, we are able to recognize
which side, for the nonce, has the upper hand.

The incubation period is the time that
Incubation elapses between the entrance of the disease-
Period. causing microbe into the body and the

onset of the S3niiptoms.
When a person takes a drug which has the property
of inducing sleep, e.g., opium, or a stimulant, such as
whisky, there is observed an appreciable period between
the ingestion of either, and the beginning of the phenom-
ena which are characteristic for each drug. If we
follow these phenomena, it is observed that according
to the quantity taken, after they first began to appear,
there is a gradual increase in the number and intensity
of the S3niiptoms to a certain point, when they are
maintained for a variable period. Finally, there is a
gradual lessening of the influence until the drug is
eliminated from the body. After the elimination there
remain such phenomena as are the result of the removal
of the influence, and the re-adjustment of the economy
to its normal state. The phenomena just described
only follow in case a dose of sufficient size has been
ingested, the amount varying, naturally, with the
individual. However, when that quantity which will
produce S)niiptoms has been reached, the results are

14 INFECTIOUS AND PARASITIC DISEASES.

directly dependent upon the amount taken. There

15 no increase of the drug within the body.

When, however, we come to study the action of an
infectious agent upon the body, we find the same
interval of time between the entrance of the infectious
agent and the onset of the S3niiptoms, but there is a
very great difference in the events that take place to
produce the reactions. The amount of opium or
whisky ingested is fixed, so that whatever the eflfect, it
results from just that amount. When infectious agents
enter the body, however, they at once begin to multiply
in enormous numbers, giving oflf all the while as a
product of their activity most powerful poisons (toxins) .
When a suflftcient amount of poison has been generated,
S3niiptoms of the disease appear. In other words, the
infectious agents that gain an entrance into the body
have not of themselves sufl&cient power to produce the
disease, but act through their facility of increasing their
numbers. It is self-evident, therefore, why this period
is called the "incubation period," since it "corresponds
to the development (multiplication) of the pathogenic
agents." Clinically the incubation period is also
known as the latent period.

The incubation period varies as to time in diflferent
diseases, and in diflferent cases of the same disease.
It may only be a few hours, as in erysipelas, or it may
extend over months and years, as in hydrophobia and
leprosy. This period is of very great importance from

CAUSES OF DISEASE.

IS

a hygienic standpoint, in that it aflfects the length of
quarantine imposed upon individuals exposed to con-
tagious diseases. The following table taken principally
from Roger's "Infectious Diseases" is worthy of careful
study.

INCUBATION PERIOD OF VARIOUS INFECTIOUS

DISEASES.

Average.

Minimum.

Maximum.

Anthrax

2 (

days

I day

3 days

Bubonic Plague

4-6

ti

2 "

7 "

Chancroid

1-2

tt

I "

3 "

Cholera

2-4

tt

I "

6 "

Diphtheria

2

tt

2 "

IS "

Erysipelas

4-6

tt

3 hours

32 "

Influenza

3-4

tt

I day

s "

Glanders

3-S

tt

24 hours

3 months

Gonorrhoea

3-S

tt

i (?)-2 days

i-several weeks

Mumps

IS

tt

7 days

30 days

Malarial Fever

6-IO

tt

99 hours

several months

Recurrent Fever

s-6

tt

86 "

8 days

Measles

9

tt

4 days

14 "

Hydrophobia

20-60

tt

13 "

18 mos. to 3 yrs

Rubeola

18

tt

s "

21 days

Scarlatina

2-S

tt

7 hours

7 weeks

Small-pox

12

tt

7 days

15 days

Syphilis

20-30

tt

10 "

so "

Tetanus (Lock-jaw)

2-3

tt

3 hours

3S "

Typhoid Fever

14

tt

3 days (?)

31 "

Typhus Fever

12

tt

o(?)

33 "

Vaccinia

3

tt

3 days

7 "

i6 INFECTIOUS AND PARASITIC DISEASES.

Average,

MmiMITM.

Maximum.

Varicella

14-15 days

13 days

19 days

Whooping-cough

8

2 '*

8 "

Yellow Fever

3-4 "

2 "

6 "

Leprosy

(?)

(?)

32 years

Tuberculosis

(?) incubation period frequently long.

Dengue

4 days

3 days

5 days

Pneumonia

24 hours

(?)

2 or more days

Dysenter}'(Bacillary) 8 days

6 days

48 hours

Malta Fever

6-10 "

(?)

10 days

Beri-beri

Several months (?)

During the incubation period S3niiptoms
Period of are wanting, and, as far as the person is
Invasion. aware, he experiences nothing to indicate

that he is not in normal health. When,
however, the body awakens to the* impending danger,- it
brings its defensive forces into play in an effort to throw
off the infectious agents and their toxins. Clinically,
these reactions are represented by the first S3niiptoms
of disease, and are knov^m as the "s3niiptoms of onset."
They indicate that invasion of the body by an infectious
agent has taken place. It is for this reason that this
period is spoken of as the period of invasion.

The period of invasion also differs in various diseases,
and in various cases of the same disease. The s)niip-
toms of invasion may appear with startling suddenness,
as the chill which occurs at the onset of pneumonia, or
the convulsion in children which initiates most of the
eruptive fevers; or they may develop so gradually as

CAUSES OF DISEASE. 17

to make it impossible for the patient to say when he
really began to feel ill. This slow insidious manner
of onset is the rule in typhoid fever and pulmonary
tuberculosis.

After the period of invasion comes the
Stationary stationary period, the symptoms of which
Period. are so characteristic for each particular

infectious disease as to form the basis for
our classification of infectious diseases in general, and
of identification of any one in particular. If the
invasion be sudden, the stationary period is usually
quickly reached (in pneumonia, a few hours) ; if gradual,
the stationary period may be prolonged a week or more
(e.g., typhoid fever). The stationary period presents
more or less uniformity in S3niiptoms, with ameliora-
tions or aggravations of the symptoms correspond-
ing to oscillations of advantage of either body or
germ.

Variations from the type of the stationary period in
any infectious disease also occur with a fair degree of
frequency. The stationary period may be cut short
by the body-forces being marshaled at the onset, and
the disease end there ; or it may be prolonged far beyond
the average limits for the disease. On the other hand,
the microbes may get the upper hand from the start,
stifle (in their incipiency) the body's efforts to react
and close the picture even before the stationary period
had really begun. However, these courses are not

i8 INFECTIOUS AND PARASITIC DISEASES.

typical; in the typical case, unless the battle is decided
in favor of the microbes, the stationary period passes
into the period of decline. Where the stationary period
of any disease is abbreviated by recovery, we speak of
the disease as having been aborted ; where abbreviation
or prolongation of any disease occurs, or where marked
variations from the type take place, the disease is
spoken of as having pursued an aberrant form.

The period of decline is expressive of the
Period of victory that the body has won over the
Decline. infecting agents. This period is taken up

with the physiological re-adjustments and
anatomical repairs necessary to bring the body back
to health.

Precisely as the onset of a disease may be
Crisis and either sudden or gradual, so may the
Lysis, decline be characterized either by a most

astonishingly rapid amelioration of the
symptoms, or by slow, progressive improvement. In
the former case we speak of termination of the disease
by crisis, in the latter, by lysis.

Termination by crisis is well illustrated by pneumonia,
termination by lysis, by tjrphoid fever. Crisis is
perhaps the most peculiar and mystifying phenomenon
that ever occurs in disease. Always awaited with so
much anxiety, when if has happened it may weU be
joyously received, since it conveys to the physician the
knowledge that recovery, "e?/ which it is the residtj^

CAUSES OF DISEASE. 19

not the cause, has been eflfected. And the same is
true of lysis, it is the harbinger of the fact that the
infectious agents are being vanquished. In the matter
of termination, the rule is not always followed ; accord-
ingly, we sometimes find pneumonia terminating by
lysis, and less often, typhoid fever by crisis. One
curious exception to the usual form that crisis takes,
i.e., reduction in temperature, occurs in Asiatic cholera.
Instead of the temperature falling, it rises from below
normal (sub-normal) to normal or above normal. The
characteristic feature of the crisis is thus reversed, a
thing which is associated with the other reversal that
takes place in the stationary period of cholera, i.e., a
sub-normal temperature.

An infectious disease is due to the entrance
Local and and growth of infectious agents, and to the
General toxins (poisons) which the latter generate.
Infections. When infectious agents gain an entrance

into the body, they act in one of two ways,
namely :

(i) Either they remain localized near their portal of
entry, or in some near or distant organ, during the
whole course of the disease; or,

(2) they first establish a local lesion near their portal
of entry, or in some near or distant organ, and then,
from this as a focus, invade the whole body.

The first instance is descriptive of what is called a
local infection, the second, of a general infection. In

20 INFECTIOUS AND PARASITIC DISEASES.

both cases the toxins play the same important r61e;
yet while in the one they are formed in only one portion
of the body, in the other, since the infectious agents
are scattered, they are formed in all parts. Infectious
diseases which result from toxins eliminated by micro-
organisms growing in a circumscribed area are known
as toxcBmias, while those in which the micro-organisms
live and multiply in the blood-stream are called sep-
ticcBmias (in cases in which bacteria are the invaders,
bactericBmias). A general infection, therefore, corre-
sponds to a septicaemia, or bacteriaemia. It must not
be inferred, however, that a toxaemia always accom-
panies a local infection, for there are many local infec-
tions in which the action of the agents and their toxins
are purely local ; the word toxaemia is reserved for local
infections associated with constitutional S)niiptoms of
poisoning. To illustrate : No one would call an abscess
an infectious disease, although it represents the localized
activity of certain bacteria, and is therefore correctly
spoken of as a local infection. On the other hand,
tetanus, a constitutional disease, has as its local infection
a wound, frequently so trivial, that it has healed before
the convulsions begin which mark the onset of this
terrible disease. It is the toxins formed by the bacilli
at one point, and absorbed, which give rise to the
toxaemia.

A local, or a general infection, may be caused by either
a specific or a non-specific infectious agent, but not by

CAUSES OF DISEASE. 21

any specific or non-specific agent. Some specific
agents only give rise to local infectious diseases (toxae-
mias), while others only to septicaemias (or bacteriae-
mias). Typical examples of toxaemias due to specific
agents are furnished by diphtheria, tetanus (lock-jaw),
rabies (hydrophobia), and cholera; of septicaemias
(or bacteriaemias), by anthrax, typhoid fever, relapsing
fever, bubonic plague, influenza (La grippe), malta
fever, etc. Besides the diseases here given, there are
many others on the border-line between toxaemias and
septicaemias, that is to say, the infection may be local-
ized, yet there is a distinct tendency for the infectious
agents to invade the blood. Such a disease is pneu-
monia which, while it is often an infection localized
in the lungs, occurs in a form (croupous) in which the
pneumococci which cause it are found in the blood in
about ninety per cent of the cases. Pulmonary tuber-
culosis (consumption) is another case in point; the
disease may remain localized in the lungs for months
and even years, yet the specific bacilli often invade the
economy. When they do, the germs are distributed
everywhere, and a rapid termination of life results.
This form of tuberculosis, called by the profession
acute miliary tuberculosis, is well known to the laity
under the name of rapid^ galloping^ or quick, consump-
tion.

There is another word in current use in medicine
that requires explanation in this place, viz., pyaemia.

22 INFECTIOUS AND PARASITIC DISEASES.

By pyaemia is understood an infection in which the
micro-organisms have established suppurating foci
in different parts of the body. Where the several
localizations have had their origin in another, single
focus, the former are often, although erroneously, spoken
of as metastatic abscesses.

Heretofore the course of a disease due to
Combined only one infectious agent has been described,
Infections, and while we usually, in acute disease,

are dealing with a single or uncombined
infection, the opposite, mixed or combined infections,
are not uncommon. Thus occur together measles
and scarlet fever, measles and whooping-cough, scarlet
fever and diphtheria, typhoid fever and pneumonia,
etc. When two infections occur in the same individual,
the S3niiptoms of one disease are likely to be masked or
held in abeyance by those of the other, the extent to
which this takes place depending upon whether they
develop simultaneously or in succession. It also
depends upon the nature of the diseases. Thus pneu-
monia for a number of days may run so typical a course
in a person suffering from consumption as to deceive
the ablest clinician into believing that only one disease,
pneumonia, exists. On the other hand, pneumonia in
the alcoholic, in the sufferer from some chronic dis-
order, e.g., Bright's disease, diabetes, chronic heart
disease, or coming on during the course of an acute
infection, may be entirely overlooked in spite of the

CAUSES OF DISEASE. 23

fact that it is known to be the most frequent direct
cause of death.

However, two infections may concurrently run
typical courses in the same individual. This happens
when scarlet fever and measles develop simultaneously.

When an infectious agent attacks an
Secondary individual who is already suflFering from
Infection, the attacks of another, we speak of the

former as a secondary injection. Most
secondary infections follow as a result of the diminution
in vital resistance consequent upon the first infection.
Apart from the ordinary diseases of childhood, there
are two notable infections that are very commonly
secondary, because they take advantage of any depres-
sion in vital resistance that the body has suffered.
Their frequency and permiscuity are so well established,
that every precaution should always be taken to guard
a patient from their attack. Reference is made to
tuberculosis and pneumonia. The micro-organisms
which cause these two diseases lead all others as second-
ary invaders of the body, and undoubtedly cause a
larger number of deaths than all the diseases combined
to which they are secondary. Next to the tubercle
bacillus and the pneumococcus in point of frequency
as secondary invaders come the common pyogenic
or pus-producing bacteria, among which, it should
always be remembered, is included the microbe of
erysipelas.

34 INFECTIOUS AND PARASITIC DISEASES.

Intectious

An interesting and important phenomenon
concerning the infectious diseases is their
g self-limiting nature. Clinical evidence

Lnarmr abundantly corroborates the verity of this

statement, since treated or untreated,
every infectious disease foUows, as it were, a prescribed
course. The fact that we divide this course into periods
is a significant admission. Except in the case of a
few diseases, for which we have specifics, the progress
and termination of an infectious disease is determined
well-nigh entirely by the reactionary or fighting powers
of the body. All living things struggle for existence,
which is only another way of saying they resist de-
struction. The efforts that an organism puts forth to
survive is an inherent quality that it can no more
control than it can its birth. Therefore, when the body
is attacked by an infectious agent, it sustains the attack
with such weapons as nature, through heredity, has
supplied it for this very purpose; and to this fact, that
nature is by far the greatest healer, all physicians and
nurses cannot fail to testify.

In the sense in which self-limiting is used when refer-
ring to infectious diseases, there is, therefore, implied
the meaning that the body delimits the period of disease
irrespective of medication. It may seem to aspiring
novices in medicine a sad admission, and one that may
cause them deep disappointment, yet it cannot be
denied that infectious diseases tend to spontaneous

CAUSES OF DISEASE. 25

recovery. This curious fact is the result of natural
phenomena.

Animal experiments have taught us that

when certain substances injurious to the

Antibodies, well-being of an animal are introduced

into the blood, other substances are formed
which have the power of neutralizing
further injections of the first. Substances manufac-
tured by a living organism in this way are technically
called "antibodies;" and the antitoxins of commerce,
which are prepared from living animals by inoculating
them with the toxins (poisons) of various diseases
belong to this class. Antibodies are formed in an animal
only when the substances which give rise to them
have destroyed a certain amount of tissue, the injured
tissues supplying the stimulants which incite to activity
the protective functions of the body. When produced,
antibodies have no beneficial effects whatsoever upon
the tissues already destroyed, but act simply either to
neutralize any additional toxin which may yet j be
circulating, or which may get into the body from the
exterior at another time. For these reasons antitoxins
are intrinsically prophylactic^ rather than curative, in as
much as if inoculated into a healthy person, they guard
against disease by preventing tissue destruction ; whereas
after infection, they safe-guard the body from greater
injury than has already occurred by neutralizing any
circulating poison. It is this latter action which has

a6 INFECTIOUS AND PARASITIC DISEASES.

given them their reputation as curative principles.
The production of antibodies represents the reactionary
or fighting powers of the body above referred to, and
is its natural weapon of defense against disease.

As the result of bacterial infections, distinctly differ-
ent antibodies are formed which owe their origin to
peculiarities in attack of the infecting agents. All
bacteria produce disease through their toxins, but
because the manner in which the latter are eliminated
is not the same for all, there arise differences both in the
nature of the protective substances, and the manner in
which these substances protect. From the standpoint
of disease-production bacteria may be divided in a
broad way into two classes, viz., (i) those that attack
the body rather through a diffusible poison, which they
excrete, than by enormous reproduction; and (2) those
in which multiplication is the primary or essential
phenomenon, toxin-excretion subsidiary. Bacteria of
the first order, through their toxins, give rise to sub-
stances which neutralize the latter, that is, antitoxins.
Bacteria of the second order, contrariwise, stimulate the
body to the formation of substances antagonistic to
the bacteria themselves, i.e., antibacterial or bacteri-
cidal substances. The protection that antibodies which
are bactericidal furnish the body comes through their
power of dissolving the bacteria which cause the
disease. If immunity against infection is, therefore,
contrasted from the standpoint of the etiological agents,

CAUSES OF DISEASE. 27

it is either antitoxic or bactericidal. Technically bacteri-
cidal antibodies are known as lysins, or bacteriolysins.

Antedating and also accompan3ring the
Agglutinins, formation of the solvent antibodies (bac-
teriolysins), there appears in the blood-
serum of infected animals and persons other antibodies
which have the property of drawing together in groups
or clumps the invading bacteria. This phenomenon
is called agglutination, the substances which excite
it, agglutinins.

Agglutination, it is commonly accepted, has these
two advantages : It is a preliminary stage in the process
of immimity (it appears before the bacteriolytic sub-
stance); it facilitates the ingestion of the bacteria by
the phagocytes (phagocytosis).

Bacteriolysins and agglutinins are specific substances,
just as antitoxins are, and therefore act only when
brought into relation with such bacteria as call them
forth. This knowledge of the specificity of the agglu-
tinins is made use of for the diagnosis of various
diseases, especially typhoid fever, the examination for
agglutination in the latter disease constituting the well-
known Widal reaction.

In recovery or immunity from diseases

Opsonins, due to the second class of bacteria, i.e.,

those which attack the body largely through

multiplication, another antibody has lately come to

the fore which bids fair to overshadow all others in

28 INFECTIOUS AND PARASITIC DISEASES.

importance. This is a bactericidal antibody, opsonin
(I prepare a meal for), that acts in conjunction with the
leucoc3i;es to rid the body of invading bacteria.

Opsonin is normally found in the blood, and is
increased in immunity. It acts in such a way upon
infectious agents that they not only strongly attract the
phagocytic leucocytes (positive chemotaxis), but makes
them easier of digestion by the latter. It is well that
the associated action of opsonin and phagocytosis
has been discovered, for bacteriologists had well-nigh
despaired of producing bactericidal serums comparable
in potency to diphtheria and tetanus antitoxins; the
latter, once their toxins were separated from the bac-
teria, were comparatively easy to prepare; but in the
case of those bacteria in which little or no diffusible
poison is secreted, the problem of making immime
serums presented insurmountable difficulties. This
is the reason that in a long list of diseases, such as
typhoid fever, bubonic plague, Asiatic cholera, bacillary
dysentery, etc., immune serums have not been forth-
coming. In opsonin, however, we have a force to
work with which, it would appear, can be increased
at will, so that if the expectations of workers with
opsonins are realized, it will not be long before the
immunization and cure of the above mentioned mala-
dies will be in our hands.

It is now almost twenty years since Metchnikoff
first called attention to the part that certain white

CAUSES OF DISEASE. 29

cells in the blood take in both the prevention and cure
of infections. These cells (leucoc3i;es), which he
called phagocytes, he believed acted through their
power of taking up and digesting bacteria. During
all these years since the publication of his theory of
phagocytosis Metchnikoff has added many valuable
facts corroborating his views. In the light of the
recently discovered antibody, opsonin, his views on
the protective function of the leucocytes are strongly
supported, in that data for the first time is supplied
which explains the conditions under which phagocy-
tosis is active. Opsonin in the blood-serum of immune
animals and persons sensitizes or opsonizes the infec-
tious agents for easier destrtiction by the phagocytes.

Injuries to tissues per se produce S3nnptoms, through
the disturbance of functions which such loss to the
economy entails; but besides these S3nnptoms, there
are others, in every infectious disease, which can be
definitely ascribed to the production of the defensive
substances. The phenomena of disease, therefore,
are of a composite character, comprising both the
symptoms of injury and those of defense. What part
of the S3nnptoms each of these factors causes in a case,
it is impossible to determine, but of this we may always
feel sure (because the experimental proofs in its favor
are conclusive) no insignificant part of the fever and
general malaise in every infectious disease is a necessary
adjunct to antibody production. This fact lends the

I

30 INFECTIOUS AND PARASITIC DISEASES.

Strongest support to the view, formerly much debated,
that fever is a benign and necessary feature in the class
of diseases we are discussing. The modem concep-
tion of disease takes the position that recovery from
an infection is always brought about either through the
production of an immunizing substance by the body,
or through the introduction of the same from without.
In the body, the period of invasion marks the beginning
of antibody formation, which from this time goe-; on
until either recovery or death supervenes. If the former,
sufficient antibody is formed to equalize the bacteria
or their poisons and prevent further inroads of either
upon the tissues; if the latter, the body's defensive
mechanism fails to act through weakness, or is over-
come by the intensity and massiveness of the virus.
The use of antitoxin in disease marks the highest refine-
ment of specific medication, in that an immunizing sub-
stance is injected into a patient which can be depended
upon to counteract or neutralize a definite poisonous
(toxic) substance. It aims to take from the patient
the burden of producing antibodies, which at best is
slow and too often a doubtful quality, by injecting
them fully formed and active. These have been pre-
pared from some animal which has been subjected to
the poison and has recovered. In other words, the
immunity forced upon an animal is transferred to the
patient. From what has been said concerning the
action of antibodies in that they only neutralize

CAUSES OF DISEASE. 31

opposites, it is obvious that the earlier they are used,
the more beneficial and potent will they prove in treat-
ing disease. It is their late use after great tissue de-
struction has occurred, that is responsible for failure.
In an immune person or animal, antibodies are found
throughout the body, in largest quantity in the blood.
And it is such blood-serunty separated from the other
elements of the blood, which is the antitoxin of world-
wide fame. Antitoxin (antibody) not only causes no
reactions when injected into a patient— the animal
from which it was obtained suffered these — ^but it
causes the symptoms due to the body's efforts to produce
it on its own account to at once abate. Moreover, if
an amount sulfficient to neutralize all floating poison is
injected, the S3nnptoms due to the action of this are
also eliminated. Therefore, there only remain such
disturbances as are inevitable when tissues are destroyed
and must needs be re-formed. And here again are seen
the wonderful workings of nature. In those diseases
for which we have specifics, the body-forces play just
as important a r61e as the specifics; specifics neutralize
the bacteria and their toxins, but they cannot restore
to normal the tissues which these agents have injured,
nor the functions of organs which they have im-
paired. Repair is a function of the organism which
may be assisted but never supplanted. The part
played by the body in this respect in infectious diseases
is analogous to that which it plays in surgery. The

32 INFECTIOUS AND PARASITIC DISEASES.

surgeon, in operating for the removal of malignant
tumors or for some other urgent cause, does his utmost
when the dangerous condition for which he operates
is removed. But how much would his surgery avail,
if the body did not potentially possess amazing powi
for repair and reconstruction?*

Nearly all complications occurring in
course of diseases, whether they be infec-
tious or non-mfectious, are due to mfec-
tious agents; and the infectious agents principally at
fault are bacteria. The source of the infecting bacteria
depends upon circumstance. It may happen that the
agent has its habitat upon the individual's integument,
or within a cavity of the body leading to the exterior.
Thus, pneumonia, occurring as a complication, is
caused by the pneumococcus, a micro-organism that
almost everyone harbors in his mouth even in health.
An instance of contamination from the integument is
afforded by furunculosis (boils), a common sequel to
various infections during or after convalescence is
established.

A second source for bacteria which complicafej
disease, is found In objects, insects, and persons thai
xome in contact with the patient. Thus wounds
;soiled with earth are those In which tetanus (lock-jaw),
and gaseous gangrene, are liable to develop, becaus*
the bacteria which bring about these Infections havi
*See Chapter on loflammatioD.

'ei:^^_

ha^™
nds

w),

ausfl^H
lav^^l

CAUSES OF DISEASE. 33

their home in the ground. The bacteria that produce
pus (pyogenic bacteria) are also found in the ground.

Insects, such as flies, bed-bugs, mosquitoes, etc.,
may be the means of conveying infections. Finally,
persons may convey infections. Among persons con-
veying infections, physicians and nurses are especially
dangerous on account of the frequent and close contact
that they have with the sick.

The manner in which complications have heretofore
been spoken of places them in the same category with
secondary infections. This conception of them, how-
ever, requires qualification. Besides resulting from
invasion of the body by bacteria other than the one
producing the original infection, complications may be
due to another localization in a distant part of the body
of the same organism that produced the original infec-
tion. Under such circumstances we do not speak of
the complication as a secondary infection, but a second-
ary localization or metastasis. Ignorance of the nature of
infectious agents and their migratory tendency led, in the
past, to such names as t)^hoid-pneumonia, a designation
which is no longer countenanced because we know that
this disease, even when the pneumonia accompanies or
initiates tj^hoid, is typhoid fever with pulmonary locali-
zation of the t)^hoid bacillus in the lungs. Misconcep-
tions concerning their origin were likewise responsible
for such names as t)^ho-malarial fever, diphtheritic
tonsillitis, etc., hybrids for which there is no excuse.
3

34 INFECTIOUS AND PARASITIC DISEASES.

In the course of all chronic diseases of
Terminal whatever nature, the suflferer is particularly
Infections, prone to have his original disease com-
plicated by some infection. Indeed, it is
the latter that is the common cause of death. Pneu-
monia heads the list as a secondary invader, and also
in bringing about a termination of life. Next in point
of frequency is tuberculosis, and third, are pyogenic
infections. When secondary infections, or complica-
tions, kill, they are spoken of as terminal injections.

Whether the body ever returns to a normal
Evolution state after having recovered from an infec
OF Disease, tious disease is still an open question. In

the large majority of cases, it apparently
does, but we must always remember that time, only,
can answer this question in any individual case.
Certainly a "spell" of any one of the infectious diseases
is not regarded by the profession as interfering with
the usual expectancy.* Nevertheless, as the years go
by, we are laying more and more stress upon past
illness as a factor in present disorders.

For the most part, "diseases that owe their origin
to past illness are affections of organs," e.g., Bright's
disease, chronic heart disease, locomotor ataxia, the
organs being involved in the infectious process at the
time of the acute infection, and apparently subsiding

♦Expectancy — the mean or average duration of life of individuak
after any specified age.

CAUSES OF DISEASE. 35

with it. We say apparently advisedly, because, although
the acute inflammation subsides, it too often gives
place to a chronic inflammation that extends over
years. This chronic inflammatory state is no longer
dependent in most cases upon the infectious principle
which caused the initial lesion, but is a slow sclerosis,
or cicatrization, which consists in a gradual contraction
and substitution of the normal tissues of a part by scar
tissue. The change is especially prone to occur in
organs that have sustained an injury of one kind or
another, and is really a vicarious evolution that the
tissues are subject to. There is a danger in the new
condition that arises both from the contractions, and
the loss in organic cellular constituents, since in the
one case functions are interfered with, in the other,
metabolism* is disturbed. The seriousness of the
lesion depends upon the organ in which the original
injury was located, and its importance to the vital
processes of the body. One or two illustrations will
suffice to elucidate our point. A person has typhoid
fever and apparently makes a complete recovery. Ten,
fifteen or twenty years afterwards he seeks medical
advice for shortness of breath and cough. His case
is diagnosed as chronic heart disease. Whence came
the lesion of his heart valves ? When closely questioned,
he may remember that the physician who attended

* Metabolism — chemical change within the body in nutrition and
secretion.

36 INFECTIOUS AND PARASITIC DISEASES.

him at the time of his fever did remark that there was
some slight evidence of cardiac injury. But even this
evidence of the connection between his present trouble
and the earlier typhoid fever is now no longer necessary ;
we have learned through experience the connection.
Are typhoid bacilli causing the present trouble ? Assur-
edly not ! The original cause was an inflammation of the
heart valves from the typhoid bacilli, most likely, or
some other microbe that gained an entrance into the
blood during his attack of typhoid. The lesion of
the heart, to all appearances, healed. But a cicatrix
remained, that, according to the manner of aU cica-
trices, continued to contract, imtil through the disability
it produced in the functioning of the heart, gave rise to
symptoms. Substantially the same history is obtained
in many cases of Bright's disease (chronic nephritis),
the antecedent disease being either scarlet fever,
measles, diphtheria, or typhoid fever.

We have used the word infectious a number of times,
but purposely have avoided using another word,
namely, contagious y on account of the many loose inter-
pretations that are given it. To us it seems best to
speak of a contagion, or a contagious disease, only
when the microbe is readily communicable from person
to person by mediate or immediate contact. The
term should be used as descriptive of a quality of the
germ or of a microbic disease. It should not be used
synonymously with infectious or infection; in fact, if

CAUSES OF DISEASE. 37

the words were synonymous, we would scarcely describe
a disease, such as diphtheria, as being both infectious
and contagious. A disease may be contagious, or it
may be infectious; or it may be both contagious and
infectious. Malaria is an infectious disease, but not
contagious; scabies (itch) is contagious but not infec-
tious; diphtheria is both contagious and infectious.
Diseases exhibit at times, however, marked differences
in regard to these characteristics. Sometimes an infec-
tious disease not ordinarily contagious may, in some
manner as yet not understood, become contagious.
This happens in pneumonia, which under such cir-
cumstances partakes of the characteristics of an epi-
demic disease.

Of late years it has seemed best to some
CoMMUNi- ^^ ^^ ^^^^^ ^f ^^ indifferent

CABLE. '

manner in which the words infectious and
contagious have been used in describing a disease, to
omit them entirely, and in their stead to speak of these
diseases as communicable. This seems an excellent
innovation because only diseases caused by living things
are, strictly speaking, communicable. An objection
might be made to the term because it would include
parasitic affections, but this cannot for long have any
real force ; it is dilfficult at best to draw a nice distinction
between many diseases due to parasites and the infec-
tious agents, and we might just as well for good have
a word adaptable and usable for both.

CHAPTER II.
BACTERIOLOGY.

Bacteria (sing., bacterium) are low forms of life
that are generally conceded to belong to the vegetable
kingdom. They resemble the moulds in many ways;
in fact, one name for them is fission-moulds, a term
derived from the circumstance that multiplication of
the individual bacterium takes place by simple division
of the whole organism into two parts. They further
resemble the moulds in not possessing chlorophyl, the
green coloring matter by virtue of which in the pres-
ence of sunlight, plants are enabled to decompose
carbon dioxide and ammonia, and use their constituents
for food.

The absence of chlorophyl in bacteria necessitates
some form of proteid as food, whence results the phenom-
enon of the lowest forms of life consuming the same
kinds of food as the higher animals.

Bacteria live chiefly upon the remains of animals and
plants, to a lesser extent upon living forms of both
kingdoms. But whilst they share a common food
with animals, the disintegrations which they work in it

38

BACTERIOLOGY. 39

result in simpler and more important end-products.
These consist of the gases absolutely essential to plant
life, namely, carbon dioxide (CO2) and ammonia
(NH3). A third end-product is water (HjO).

The amount of carbon dioxide produced by animals
out of starches and sugars is insignificant in comparison
with the needs of the vegetable kingdom, and were there
no other source for this important food element, the
plant world would either sufiFer a great deficit or be
restricted in its growth. The same is true of nitrogen,
another important constituent of plants, and required
by them in an easily assimilable form, such as ammonia
(NH3). It is the peculiar ojffice of bacteria to supply
plants with the largest amounts of both of these constit-
uents. On this account they are the natural inter-
mediaries between plants and animals in point of food
production, playing by far the most important part in
the economy of nature. Without bacteria, plant-life
would be scanty or entirely wanting; and since the
animal kingdom depends upon plants for existence,
there would result a world lacking in every form of
higher animal life.

The part that bacteria play as scavengers
Arts and of the earth and providers of food for
Industries, plant-life, only displays a limited side of

their usefulness. In the arts and industries
they are as essential to modem economic life as are the
ingenious mechanical inventions of man. Many secret

40 INFECTIOUS AND PARASITIC DISEASES.

processes now in use in the arts and manufactures
are but devices to harness these natural forces. Thus
in the manufacture of linen, hemp and sponges, in the
butter, cheese, and vinegar industries, in tobacco-
curing, etc., bacteria play the important r61e.

Curiously, in the popular mind, bacteria
Saprophytes, are only associated with disease, and are

regarded with abhorrence on that account;
yet of the untold hundreds of species, only about forty
are known to produce disease in human beings.

Bacteria which are useful to mankind in so many
ways belong to the class of organisms known as obligate
saprophytes, i.e., "an organism that lives upon dead
organic matter." Bacteria that produce disease, on
the other hand, belong to the parasites and infectious
agents, a description of which has akeady been given
in the preceding chapter. However, the ability of a
bacterium to live upon dead organic matter does not
determine its status from the standpoint of the produc-
tion of disease. The obligate saprophytes, as their
name implies, are restricted to a diet of dead things;
but the parasitic bacteria, while preferably parasitic
in their habits, may nevertheless lead a saprophytic
existence. Such species are known as jacidtative
saprophytes. Most of the disease-causing bacteria
belong to this class, a factor that has proven of incal-
culable value in studying them. Indeed, bacteriology
dates its rapid progress from the time that pathogenic

BACTERIOLOGY. 41

bacteria were first grown upon an artificial pabulum in
the laboratory. The adaptability of bacteria to various
kinds of foods explains the spread of many diseases by
foods and water, and also the tenacity that certain
diseases display in clinging to a house or to clothing.
Almost everywhere there are small amounts of organic
matter and moisture, and these microscopic forms
of life which we are considering require such infini-
tesimal amounts of either, that it is possible for them
to live where nothing else can.

Harmful bacteria, that is, those that are
^A^N^"" ""^^^^^^ ""^ producing disease, are caUed
PATHOGENIC P^^^g^^^f' hamJcss varieties, or sapro-
Bacteria. phytes, are called non-pathogenic. A

pathogenic bacterium, however, cannot
always produce disease when it finds lodgment within
the body. This special characteristic is extraordinarily
variable, appearing and disappearing under a variety
of circumstances. Pathogenicity in a bacterium depends
upon its power to produce toxins (poisons), a function
which is extremely susceptible of loss by exposure
to many natural agencies. A pathogenic bacterium
that can produce its specific toxins, and therefore bring
about disease, is spoken of as virulent, one that cannot,
as non-virident. For the foregoing reasons we recognize
in all pathogenic bacteria both varieties. However,
virulence and non-virulence are evanescent qualities,
requiring only alterations in environment to be made

42 INFECTIOUS AND PARASITIC DISEASES.

to appear and disappear. What the circumstances
are that lead to this change will be explained in the
third and fourth chapters.

In size bacteria are the smallest living
Size. things that we can see with the modem
microscope. In masses they are readily
seen with the unaided eye as moist, slimy, or dry films
floating upon the surface of foul fluids or water, or
covering decomposing animal or vegetable matter.
Some of them produce beautiful colors ; others have the
peculiar property of producing phosphorescence; still
others cause the stench of decomposition.

Bacteria vary in size between five-tenths of a micro-
millimeter and twenty to forty micro-millimeters, and
as a micro-millimeter is the one-thousandth part of a
millimeter (about one-twenty-five-thousandth of an
inch), only a vague conception of their minuteness can
be formed unless one has had experience in working
with microscopic forms of life.

What bacteria lack in size they make up
in the astonishing capacity that they
possess of rapid multiplication. Each
bacterium consists of a single cell only (unicellular),
. which under favorable circumstances produces count-
less other cells. This is accomplished by simple
division (fission) of the whole cell body. The two
individuals formed out of the first one, begin dividing
into four before complete separation has taken place;

BACTERIOLOGY. 43

the four divide into eight, the eight into sixteen, the
sixteen into thirty-two. Since it takes only thirty
minutes for one cell to divide, it can be computed
approximately how many new individuals will be
formed in twenty-four hours out of a single bacterium.
Conn gives the number as "over 16,500,000 in one
day, and about 281,500,000 in two days. In three
days, at this rate of multiplication they would produce
a mass of bacteria weighing 16,000,000 pounds."
However, these figures have no practical significance,
and are given merely to convey to the reader some con-
ception of their astonishing rate of multiplication. In
nature multiplication is rapid, as may be inferred from
the great changes they work, but their activities are
limited to their usefulness. Their growth is held in
check by the products of their own metabolism (excre-
tory products), by the absence of suitable food, and by
natural forces acting upon them as they do upon all
creation.

When examined with a microscope, indi-
Shape. vidual bacteria are seen to look like so

many dots, dashes, and commas. There
are thousands of species of bacteria, yet each species
conforms more or less closely to one of these three
shapes. According to their form, therefore, they are
called, cocci, bacilli^ and spirilla, and under these
designations all known species are classified.

44 INFECTIOUS AND PARASITIC DISEASES.

To the cocci, or micrococci (sing., coccus) — ^belong
the dots or spherical forms.

Fig. I. — ^Staphylococci. Streptococci. Diplococci. Tetrads. Sarcins.

(Williams.)

To the bacilli (sing., bacillus) — the dash-like or
rod-shaped bacteria; and to the

y»

Fig. 2. — ^Bacilli of Various Forms. (Williams.)

Spirilla (sing., spirillum) — ^the spiral, corkscrew, or
comma-shaped forms.

V4/

^ 41 ^ . ^

Fig. 3. — Spirilli of Various Forms. (Williams.)

Certain of the bacteria exhibit a singular
Grouping. arrangement to each other, when examined

on a slide under the microscope, that is
peculiar and constant. This is found in the group
micrococcus. It is due to the manner of multiplication ;
the bacilli and spirilli multiply by division through

BACTERIOLOGY. 45

their shortest diameter only, whereas the micrococci,
having one diameter the same as another, may divide
in any direction. The result of this difference in the
manner of dividing is that the relationship of individual
bacteria to each other is markedly characteristic, and
permits of its use as a distinguishing feature. To
distinguish the various micrococci from each other, they
are therefore divided into the:

Staphylococci (sing., staphylococcus) — when they
are arranged in groups which bear a certain resemblance
to a bunch of grapes. Diplococci (sing., diplococcus) —
when they are arranged in pairs. Streptococci (sing.,
streptococcus) — ^when they are arranged in chains,
i.e., attached end to end in lines of longer or shorter
lengths.

When cocci show no particular arrangement to each
other they are simply spoken of as cocci or micrococci.

The foregoing divisions of the cocci are not complete,
since there are other peculiarities of grouping, but
those enumerated comprise the principal pathogenic
micrococci.

_ Bacteria may be said to be universally

distributed, being found wherever animals
and plants are. They are in the air we
breath, and in the water we drink. The surface of
the earth is covered with them; in fact the ground is
their natural home, which should not surprise us since
there organic matter is found in greatest abundance.

46 INFECTIOUS AND PARASITIC DISEASES.

Indeed, the source of the bacteria that are in the air
and water is the ground. They are carried by the
winds with dust, to which they adhere, and by water
flowing over the ground. A fact of great importance
to be remembered, however, is that bacteria cannot
rise from liquids that contain them even should a strong
current of wind blow over the liquid.

Upon our bodies bacteria are constantly present in
large numbers, and in every cavity leading to the exterior,
but in the tissues and glands of the healthy person they
are never found. The number of bacteria upon the
body bears a relationship to the cleanliness of the
individual, yet even in the most cleanly they are never
absent.

In the same way the number of bacteria in any locality
is likewise related to the number of persons, to the
density of population, and to the efficiency of the
measures practised in the disposal of waste. Any
kind of organic matter, whether it be manure heaps,
the waste from kitchens, or the dejecta and secretions
of man and animals, furnishes appropriate food for
these scavengers. The chief interest for us in this
wide distribution of bacteria is the relationship of their
presence to man and animals, especially in that it
draws attention to the danger of contamination of the
ground, the water, and food-stuffs from persons and
animals suffering from bacterial diseases, and the
spread in consequence of disease in this way.

BACTERIOLOGY. 47

The statement made a few lines above
Ground, that "the natural home for bacteria is

the ground" applies to bacteria in general,
and as the saprophytes comprise the majority of bac-
teria, it is to them chiefly that reference is made.
Nevertheless, almost any pathogenic bacterium may
find in the soil a favorable environment for a longer or
shorter period ; and even in the event that multiplication
cannot take place, the conditions may be such as to
preserve its vitality unimpaired. Therefore, as a result
of the careless disposal of infectious material and
discharges, the soil is often contaminated by micro-
organisms of a dangerous character. All pathogenic
microbes in the soil are potentially dangerous, yet the
possibilities for them doing harm is not the same for
each, since it depends upon the species of micro-organ-
ism, the physical environments of the soil, and the
purposes for which the soil is used. It should always
be remembered that when a soil is contaminated with
infectious matter, the bacteria present in it will, in dry
weather, be carried into the air with dust, and in that
way may find their way into our lungs or contaminate
our foods. The most widely distributed bacterium
in the air, and the most "generally dangerous, is the
tubercle bacillus. The typhoid bacillus is the most
frequent pollutor of wells and streams, although it
may become a most dangerous infection in the air if
the contamination of the soil is excessive and the

48 INFECTIOUS AND PARASITIC DISEASES.

hygienic conditions under which exposed individuals
live are especially bad. Just such a condition as de-
scribed pertained in the great military camps during the
Spanish-American war, and the commission, appointed
by the Surgeon- General of the army to report on the
prevalence of typhoid fever among these troops,
ascribed the stupendous morbidity to a few factors
chiefly, not the least important of which was the pres-
ence of typhoid baciUi in the dust surrounding the
camps.

Another way in which germs in the soil may infect
persons, and this is true particularly of the typhoid
bacillus and the cholera spirillum, is for the microbes
to become attached to vegetables grown in the soil,
especially if these vegetables are such as are usually
consimied raw. However, whilst the majority of
pathogenic bacteria in the soil may be regarded as
accidental contaminations, there are a few whose
natural habitat is the ground. These are the tetanus
bacillus, the bacillus of gaseous edema, and the bacillus
of malignant edema. In countries where bubonic
plague is epidemic, the specific bacillus (bacillus
pestis) seems to find a favorable environment in the
ground.

As has been said, water is most frequently
Water, polluted by the washings from contami-
nated soil. The pathogenic bacteria most
feared in water or ice are the cholera spirillum and the

BACTERIOLOGY. 49

typhoid bacillus, on account of the danger of taking
them into our intestinal tracts. Because cholera and
typhoid fever are most frequently contracted from the
drinking of polluted water, they are both spoken of as
^^water-borne diseases.^^ The same micro-organisms
are also common contaminators of other foods, the
source of the contamination, as a rule, being also
water, whether it be used to cleanse utensils, or a con-
taminated stream in which water-cress or oysters are
growing.

The danger of air as a medium for the
Air. distribution of pathogenic bacteria has
been much exaggerated, in fact, even the
number of all kinds of bacteria in the atmosphere is
not as great as is popularly supposed. True! they are
practically present everywhere, except at sea many
miles from shore, and at great altitudes; yet they are
never present in such abundance that "it rains bacteria."
At one time the profession believed that the infectious
agents of many diseases were carried in the air even
considerable distances, a belief no longer held since the
importance of the r61e that insects play in the trans-
mission of disease has been recognized.

The most widely distributed pathogenic micro-
organism in the air is the tubercle bacillus, the cause of
consumption, and a large variety of other ailments,
such as hip-joint disease, caries of the spine, etc.

Over 100,000 persons die annually from consumption

4

so INFECTIOUS AND PARASITIC DISEASES.

alone in United States, and it is estimated that there
are over 2,ocx5,ooo of people afflicted with this disease
in one form or another. AU of these suflFerers are
expectorating billions of tubercle bacilli daily. Many
of them are engaged in earning a livelihood, which takes
them into offices and homes, the atmosphere of which
they contaminate by coughing, sneezing, and expec-
torating. The atmosphere of our cities is vitiated in
the same way, but with less danger to others ; for in the
open, through the action of sun-light, through heat,
dilution, and other physical agencies, the virulence
of the bacilli is gradually diminished, and eventually
destroyed; finally the bacteria themselves are disinte-
grated. But in confined spaces, little or no destruction
of the bacilli takes place, so that there ensues in a short
time an atmosphere ladened with tubercle bacilli,
which is highly dangerous to everyone who breathes
it. The dangerous condition of such an atmosphere
is attested by the frequency of tuberculosis among
successive tenants of a house that was the abode, for a
period, of a consumptive. In quiet breathing, no
tubercle bacilli are projected into the air, but in sneezing
and coughing they are; and in the expectoration, esti-
mates of their numbers cannot be placed too high.
Thus it is that the tubercle bacilli find their way to
the ground, become dry, are ground up with the dust,
and with the latter are carried into the air and inhaled.
The moral is obvious.

BACTERIOLOGY.

SI

Pathogenic bacteria are either specific
or non-specific according as they produce
a specific or non-specific disease. In each
of these classes are found cocci, bacilli, and
spirilla. The following table contains the
most important specific and non-specific bacteria:

Specific
AND Non-
specific
Bacteria.

Non-specific Bacteria. Specific Bacteria.

Micrococci

Staphylococcus pyogenes

aureus
Staphylococcus pyogenes

citreus
Staphylococcus pyogenes

albus
Streptococcus pyogenes

(Strep, erysipelatis)
Pneumococcus
Tetragenus albus
Tetragenus citreus

Bacilli

Colon group
Pneumo-bacillus group
B. Pyocyaneus
B. Malignant edema
B. Aerogenes capsulatus
B. Proteus vulgaris

Specific Spirilla
S. Recurrent fever
S. Asiatic cholera
Spirochaeta pallida (s3^hilis)

Micrococci

Gonococcus

Diplococcus intracellularis

meningitidis
Micrococcus melitensis

(Malta fever)

Bacilli

B. Anthrax

B. Diphtheria

B. Glanders

B. Typhoid

B. Influenza

B. Tuberculosis

B. Leprosy

B. Pestis (bubonic plague)

B. Tetanus (lock-jaw)

B. Dysentery

52 INFECTIOUS AND PARASITIC DISEASES.

To separate one species of bacteria from
Spores, another, bacteriologists find it necessary

to note with the greatest accuracy the
minutest diflFerences in size, shape, arrangement,
motility or non-motility, etc., of the individuals of each
species ; also the appearances of the species when
viewed as masses with the naked eye. To do this the
bacteria are grown upon various artificially prepared
foods, called "culture media," which are valuable in
bringing out the peculiarities of the different species.
By means of cultures, the various species are also
separated one from the other, and the individual
characteristics studied. But these distinguishing char-
acteristics can have little interest for anyone unless
he works with bacteria in the laboratory. However,
one biological characteristic is of very great importance
to the practical sanitarian. Reference is made to a
resting form of certain of the bacteria that is known as
a spore. A spore is a glistening oval body into which a
bacterium is converted when the environment is un-
favorable to its growth. It corresponds to the seeds
of a plant. The spore-form of bacteria represents
more than a resting stage, however, since by virtue of
an investing membrane, they are far more resistant to
every destructive agency than the vegetative form.
Thus while a temperature of 60° Centigrade (140° F.)
kills the vegetative form of almost every bacterium in a
few minutes, spores are able to withstand the boiling

BACTERIOLOGY. S3

point for an hour or longer. Likewise, while a three
to five per cent solution of carbolic acid kills most bac-
teria in half an hour, there are spores that can live for
da3rs in the same strength of this acid.

Obviously, therefore, the sporulating bacteria are of
very great importance. Happily the number of sporu-
lating bacteria is small, a fact which lessens the diffi-
culty in disinfection, once these species are known.
The principal sporogenous (spore-producing) bac-
teria are the tetanus bacillus, the anthrax bacillus, the
bacillus of malignant edema, the bacillus aerogenes
capsulatus, and probably, the actinomyces bovis and
Madurae. Fortunately, not one of these bacteria is the
agent of a pestilential, epidemic disease.

FACTORS NECESSARY TO THE GROWTH OF BACTERIA.

The factors necessary to the growth of pathogenic
bacteria are deserving of as much attention as the
means devised for destroying them ; indeed, all methods
which aim at destroying them (disinfection) must
needs be faulty unless attention is paid to the conditions
under which they flourish. The means are not always
at hand to employ those chemical and physical agents
that experience has taught may entirely be relied upon.
Nor if they are, do the exigencies of the case, on account
of the destructive action on fabrics of the most efficient
disinfectants, or the bulk of the material to be disin-
fected, permit of their use. Furthermore, dissemina-

54 INFECTIOUS AND PARASITIC DISEASES.

tion of the infectious agents may be so wide-spread as to
make actual contact between the usual disinfectants
and the infectious agents (an essential condition for
satisfactory disinfection) absolutely impossible. Un-
der the several circumstances enumerated, it is self-
evident how valuable is the knowledge of the conditions
most favorable to the growth of bacteria, since by
removing favoring conditions and substituting harmful
ones, we can make use of most excellent means for
exterminating them. In the discussion which foUows,
only the conditions favorable to the growth of patho-
genic bacteria are treated.

There are five factors principally concerned in the
growth of bacteria, any alterations of which may be
regarded as distinctly imfavorable; these relate to food,
moisture, temperature, light, and relation to oxygen.

Pathogenic bacteria require organic (albu-
FooD. minous) material upon which to feed.

It makes little difference what the source,
whether vegetable or animal, solid or fluid, fresh or
putrid, they are adapted to all kinds. The blood and
tissues-juices of the animal body form an especially
good medium. Besides being albuminous, the material
must have an alkaline reaction. Nearly all bacteria
grow best in a slightly alkaline medium, and high
alkalinity, or moderate acidity, either sta)rs their growth
or destro3rs them. Hence the strong acids and alkalies
are true disinfectants.

BACTERIOLOGY. 55

Moisture is essential to the growth of
MoisTxmE. bacteria, in fact, complete drying, except

in the case of spores, is followed by death.
Thus the spirilla of Asiatic cholera are killed in a few
minutes by drying. However, too much reliance can-
not be placed on this factor, since an infinitesimal
amount of moisture sufiices to keep them alive indefi-
nitely.

The most favorable temperature for the
Tempera- growth of pathogenic bacteria is that of
''''^' our bodies, 98.6° F. (37° C). They will
also readily multiply at lower temperatures if other
circumstances permit. Thus the temperature of the
ordinary summer day (70° F., 24° C.) is sufficient for
rather rapid multiplication. Below this temperature,
however, growth becomes slower as the temperature is
reduced, and practically ceases at 16° C. (6o.8°F.).
Above the temperature at which bacteria grow best
(optimum temperature), only a few degrees suffice to
prevent growth (43° C, 109.4° F.).

Oxygen is another essential to the growth
Oxygen, of bacteria, but there is considerable

difference in the manner in which the
various species obtain it. The majority grow best when
oxygen, as found in the air, is supplied. A majority,
however, will not grow in the presence of free oxygen,
being compelled to obtain their oxygen from material
in which it is in combination with other elements.

INFECTIOUS AND PARASITIC DISEASES.

56

According as bacteria grow in the presence or absence
of oxygen they are called aerobesor anaerobes respectively.
Most of the aerobic bacteria grow as well without free
oxygen as with it, for which reason they are spoken of as
facultative anaerobes; but the contrary is not true; there
are few facultative aerobes.

All bacteria grow best when protected
Light. from light. This statement holds good

whether the light be natural or artificial.
These five factors are the chief ones favorable to the
growth of bacteria, and to the retention of their native
characteristics and qualities. Variations in favoring
factors, if not sufficient to destroy them, always tend to
modify their functions (prevent growth, etc.), alter their
qualities (diminish virulence), and, to a certain extent,
produce variations in form. Broadly speaking, varia-
tions acting in this way are antiseptics as opposed to
disinfectants, which latter are the means used to destroy
bacteria. Modifications in favoring factors are all
the time in nature acting to reduce the rapidity of
multiplication of bacteria, or to prevent it entirely;
or by destroying their virulence to curtail their power
to do harm. Most excellent use has been made of our
knowledge of the grovrth of bacteria both in clinical
and preventive medicine. In the treatment of wounds
suspected of containing the tetanus bacillus, it is the
practice to leave the wound exposed to the air, because
we know that the tetanus bacillus will not grow m the

1

BACTERIOLOGY. 57

presence of atmospheric air ; some physicians go a step
farther and advise the spraying of such wounds with
oxygen. In the preparation of some of the vaccines,
bacteria whose virulence has been reduced or destroyed
through subjecting them to unfavorable surroundings
are used for the inoculations, a form of vaccination
that is now being practised in typhoid fever and bubonic
plague. Because cold retards bacterial growth, is one
good reason for its use in inflammations. When the
urine is alkaline, as is usually the case in inflammations
of the bladder (cystitis), every effort is made to change
the reaction to acid and thereby make the urine an un-
favorable medium for the bacteria which cause the
cystitis.

AGENTS HARMFUL TO BACTERIA.

Agents which prevent the growth and activity of
bacteria without destroying them are called antiseptics;
those that destroy them, disinfectants or germicides.
Disinfection has as its object only the destruction of
pathogenic microbes. When an object has been ren-
dered free from all kinds of micro-organisms and their
spores it is said to be sterile, and the process by which
sterility is brought about is known as sterilization.

A deodorant is a substance that has the
Deodorant, power to destroy a noxious odor, usually

by substituting its own in place of the
other. A deodorant may or may not be a disinfectant.

S8 INFECTIOUS AND PARASITIC DISEASES.

Most of the disinfectants are also deodorants, but the
reverse, it is to be remembered, is not true. Thus for-
malin and carbolic acid are both deodorant and disin-
fecting substances, whereas musk, a deodorant, has no
disinfecting power. Bichloride of mercury, a most
powerful disinfectant, is only a deodorant if it is allowed
to act for a long period, for which reason it cannot be
used for this purpose in the sick-room. All of the dis-
infectants, when diluted, are also antiseptics. This
is important, in as much as in the strengths that many
of them are disinfectants, they are injurious to the
tissues of the body. Bichloride of mercury 1-50,000
is an efficient antiseptic, yet a strength of i-iooo is
required to kill all bacteria and their spores. The
same is true of formalin, which is antiseptic in a solution
of 1-50,000, germicidal only in a strength of 3 to 5
per cent. Substances like boracic acid, iodoform, etc.,
on the other hand, are purely antiseptic, even when
employed in concentrated form. Strong solutions of
sugar and salt, as used for domestic purposes to pre-
serve various edibles from spoiling, are antiseptic but
not germicidal.

The prominent place occupied by insects

as carriers of disease has given rise to a

new interest in substances that will kill

them. Interest centers chiefly in the discovery of an

efficient substance that will be non-poisonous, yet

generally applicable. A substance combining both of

BACTERIOLOGY. 59

these qualities has not yet been discovered. Substances
used to kill insects are called insecticides. Nearly all
the disinfectants are insecticides; formalin is a notable
exception. The most important insecticides are given
in a later chapter.

Towards agents which have a harmful action upon
them, i.e., either interfere with their growth (antisep-
tics), or destroy them (disinfectants or germicides),
bacteria exhibit distinct diflFerences in resistance — a
characteristic which varies with the species. Species
which produce spores, are not more resistant to injurious
agencies when in the vegetative state, than are the
ordinary non-sporulating bacteria. But in the form
of spores their power to resist destruction is often
marvelous. However, it is not only the sporogenous
form which is difficult to deal with; there are a few
species which, although they do not produce spores,
are nevertheless almost as difficult to kill. The tubercle
bacillus is one of these, and it is due to this fact, in con-
junction with the universal prevalence of tuberculosis,
that the tubercle bacillus has a wider distribution in
nature than any other specific pathogenic micro-or-
ganism.

The most wide-spread destruction of bacteria is
brought about through natural forces. Where actual
destruction is not accomplished, the same influences so
modify their characteristics as to render them inert.
It is in this way that pathogenic bacteria are robbed of

6o INFECTIOUS AND PARASITIC DISEASES.

their virulence and made harmless. Undoubtedly
the limitation of infectious diseases, which otherwise
would be impossible of control, is brought about in this
manner. Nature's means are simple, yet all-pervading,
wherefore she accomplishes more than the combined
efforts of men. And her forces are effective, and always
at our disposal, so that it behooves us to learn her ways
and profitably make use of her bounty. The forces
which nature employs are chiefly light, drying, dilution,
cold, and S3mibiosis (association).

Among the natural agencies destructive to
Light. bacteria, sun-light occupies the first place.

It is by far the greatest destroyer of germ-
life. Few microbes can live in direct sun-light many
hours, the pathogenies being especially susceptible to its
influence. Its destructive influence is exerted whether
the bacteria are in a dry state, or in a liquid. Moreover,
it acts upon them whether the solution is clear, or is as
foul as sewage. For example, only twelve hours'
exposure to direct sun-light is required to render sewage
free from bacteria, i.e., sterile. It also kills spores, if
the exposure is longer.

Sun-light has the power of acting directly
Dryness, upon bacteria in liquids, as has just been

stated. But it has another action equally
important which enhances its disinfecting powers to a
point scarcely equaled by any gaseous disinfectant,
namely, drying. With the exception of spores, com-

BACTERIOLOGY. 6i

plete drying prax:tically kills all pathogenic bacteria.
This statement, however, is only true where complete
drying is accomplished, a matter that we can never be
sure of unless we control the situation as is done in the
laboratory.

Besides sun-light and drying, ozone
Ozone. (nascent oxygen) also takes part in the

destruction of bacterial life. But as this
substance as formed in nature occurs only in small
quantities, its importance in this respect is difficult to
measure. More ozone is found in the country than in
cities, a factor that undoubtedly contributes to the
greater healthfuhiess of rural surroundings.

Cold, we have already learned, is unfavor-
CoLD. able to the growth of bacteria. At the

freezing temperature (32° F., 0° C.) most
bacteria succimib. However, some species exhibit con-
siderable resistance to freezing. This is true of the
micro-organisms of t)rphoid fever (t)rphoid bacillus)
and Asiatic cholera (spirillum of Asiatic cholera),
epidemics of both of which diseases have been traced
to ice as the source of the infection.

Dilution, or the diminution by dilution, of
Dilution, the number of bacteria per volume of

material in which they are contained, is
also accomplished by nature. How great a benefit
this is to man will be better explained in a succeeding

62 INFECTIOUS AND PARASITIC DISEASES.

chapter. Here reference is only made to the fact that,
as the number of bacteria which get into the body plays
a highly important part in the production of disease,
adequate dilution of infectious agents may make them
innocuous. Hence one value of dilution is evident.
Another eflFect of dilution is to separate the individual
microbes, and thereby permit of closer and more
thorough contact with them of the natural destructive
agencies. In practical disinfection dilution of the
infectious material is for this reason always practised.
If the material is semi-solid it is diluted with a disin-
fectant in which it is soluble ; or it is broken up, if not
soluble, to permit of closer contact of the disinfectant
with as much of the material as is possible. If liquids
are to be disinfected, either a liquid disinfectant is used,
or one that is soluble in the solution to be disinfected.
In any case, sufficient time (one hour for the disinfec-
tants in common use) is given for penetration.

By symbiosis is understood the living

Symbiosis . ,i r j«rc j. • r

/ • ^- X together of different species of organisms
(association). . ° ^ ^ ^

m the same medium.
It further implies that they are mutually helpful and
beneficial. Among bacteria in nature a struggle for
existence is constantly taking place, which in conjunc-
tion with other natural forces serves to keep their num-
bers within limits. Of the two classes of bacteria,
parasites and saprophytes, the saprophytes are the more
nimierous and by far the hardier, so that when they are

BACTERIOLOGY. 63

growing side by side with pathogenies, the latter get
less food and suflFer from the excretory products of the
former- Hence in the process of putrefaction, as of
sewage or of diseased carcasses, self-purification is
largely brought about by the saprophytes crowding out
the weaker pathogenies.

Another natural force tending to the
BACTERicmAL dcstruction of bacterial life is the bacteri-
Power of cidal^ action of the body-juices of all
BoDY-juicEs. living things. The number of bacteria

which rest upon our bodies, and even get
into the interior, is incalculable, yet very few do us
harm on account of this property of living matter.
This protective power of the body when displayed
against a disease is called immunity.

The destructive action of heat upon bac-
Heat. teria is so well known that it often comes as

a surprise that, in disinfection, more con-
fidence should be placed in chemicals. As a matter of
fact, there is no more efficient disinfectant than heat
if properly applied. It is also the cheapest. With few
exceptions, bacteria are killed in a few minutes at a
temperature considerably below the boiling point of
water; and at the boiling point at once. Yet it is a
common practice for both ph)rsicians and nurses to put
a family to considerable expense for chemical disinfec-
tants in a case of typhoid fever, for example, when heat

'*' Bacteria destroying.

64 INFECTIOUS AND PARASITIC DISEASES.

applied directly, or several times the quantity of boiling
water added to the material to be disinfected (stools,
for instance), and the mixture allowed to stand an hour,
is as trustworthy a practice as the use of any disinfec-
tant; and far more so than many chemicals whose
virtues are highly extolled in newspapers and medical
journals.

We have seen that although the optimum temperature
for the growth of pathogenic bacteria is that of the body
(98.6° F.), they will multiply at a much lower tempera-
ture. Above the temperature of the body, however,
the limit is small, since growth ceases at 109.4° F. (43°C.).
At 140° F. (60° C.) the vegetative forms of practically
all bacteria are destroyed if applied for ten minutes,
and the time required to destroy them diminishes as
the temperature rises. At 212° F. (100° C.) as we have
stated, they are killed immediately. The tubercle
bacillus, although only occurring in a vegetative form
(i.e., does not form spores), is an exception in that
boiling for five minutes is required to destroy it.

There are a large number of substances
Chemicals, which have a detrimental effect upon

bacteria, some merely inhibiting their
growth (antiseptics), others destroying them (disinfec-
tants). Their nimiber is too great to enumerate. Those
that interest us because they are useful in rendering
infectious matter harmless will be given in a later
chapter.

BACTERIOLOGY. 65

Cleanliness is an eflScient weapon to
Cleanliness, employ against bacteria. Too much can-
not be said in its favor. Through it we
can dispose of the most essential factor in the growth
of bacteria, namely, organic matter. Where organic
matter does not exist, bacteria cannot live and multiply.
Material of any kind, containing bacteria, is said
to be septic; when free from bacteria, aseptic. In
practical work, e.g., surgery, objects and persons are
rendered bacteria-free either through the use of antisep-
tics and disinfectants, or by mechanical cleansing with
soap and water. The two methods are distinguished
as the antiseptic, and aseptic methods respectively.

CHAPTER III.

PHENOMENA OF INFECTION.

There are two view-points from which the production

of an infectious disease must always be studied, viz.,

(i) the infecting micro-organism, and (2) the state of

the body at the time the infection occurs. Apart from

injuries and direct poisonings, there are no independent

causes of disease. When we say an infectious disease

is due to this or that micro-organism, we are making

a statement which expresses only a fraction of the true

sequence of events, since unassisted, infectious agents

probably never, imder the ordinary conditions of life,

bring about disease. To be sure, their presence in an

infectious process is indispensable, yet the mere fact

of their presence counts for naught unless the body

has been prepared, so to speak, for their invasion.

Furthermore, even in the event that the body be in a

most favorable condition for infection, there are several

conditions which micro-organisms must fulfill before

they can exercise their specific functions. For the

foregoing reasons, therefore, an infectious disease is the

result of the co-existence of a chain of fortuitous phenom-

66

PHENOMENA OF INFECTION. 67

ena which concern the body on the one hand, and the
infectious agents on the other. To illustrate : We say
that the pneumococcus is the cause of pneumonia
because this particular micro-organism is found in the
characteristic expectoration during life, and in the
lungs after death. Unquestionably, it is a necessary
factor in the disease ; but is it the sole factor ? We have
only to examine the facts in the case to discover that
it is not. In the first place, practically everyone, even
in health, harbors the pneumococcus in his mouth.
In the second place, pneumonia in robust individuals
invariably follows either fatigue and exposure to in-
clement weather, or exposure and over-indulgence in
intoxicants; often a combination of all three factors
precedes the onset. In the less robust, e.g., those
suffering from chronic ailments — (a condition in which
susceptibility to pneumonia is especially marked) it is
the pre-existing sub-normal state of the health which
permits the micro-organisms to invade the deeper air-
passages and produce the disease. Again: It is a mat-
ter of common observation that of a number of indi-
viduals exposed to the same infectious disease not all
are attacked, and that in those susceptible the disease
presents extraordinary variations as regards its mild-
ness or severity. If the microbe were the sole factor
concerned, all exposed individuals would be attacked,
and all attacked would suffer to the same degree; a
thing which everyone knows never happens. More-

68 Il^^FECTIOUS AND PARASITIC DISEASES.

over, a person may resist the action of a pathogenic
agent at one time and fall victim to it at another.

INFECTIOUS AGENTS IN DISEASE.

From the view-point of infectious agents there are
five conditions to be fulfilled before they can provoke
disease :

(i) They must be present in sufl&cient numbers.

(2) They must reach (what is for them) their portal
of entry.

(3) They must be virulent.

(4) In the case of certain pathogenic agents, disease
can result only when the agent is accompanied by one
or more other micro-organisms, or when accompanied
by a foreign body.

(5) If a disease is conmiunicated exclusively by
an insect, obviously the presence of that insect is an
essential condition.

Contrary to a wide-spread belief, there is
Number, no disease which a single infectious agent,

acting alone, can produce; that is to say,
one micro-organism of a certain species, however viru-
lent it may be, is incapable of provoking disease.
Experimentally it has been found that even in animals
very susceptible to them, it takes large numbers of a
particular micro-organism to bring about characteristic
results. In diseases occurring among persons we have
no way of determining the number of germs that pri-

PHENOMENA OF INFECTION. 69

marily enter the body, yet a wealth of facts gleaned
through experiments upon animals leads us to conclude
their numbers must be large. Clinical observations
also furnish some data in support of this view. In
cases where long and tedious operations are performed,
a wound is often exposed to the air for hours without ill
effects following. Certainly no one believes that
during the time of exposure and manipulation bacteria
do not soil the wound. On the contrary, we know they
do; but the reason harm only occasionally results from
those that enter is attributed to the fact that either they
are present in insufficient numbers and are of .low
virulence, or the vital forces of the patient are sufl&cient
to destroy them. Similar observations are made by
physicians in the repair of injuries in which either
aseptic or antiseptic precautions are utterly impossible.
Thus in the practice of mid-wifery, for example, al-
though such unfortunate surroundings are quite com-
mon, cases of puerperal fever (child-bed fever) are
so infrequent as to excite comment. Indeed, puerperal
fever occurs occasionally under conditions in which
the surroundings are ideal, probably through the ful-
fillment of the tHird condition above given, viz., extra-
ordinary virulence of the germs.

A singular peculiarity of pathogenic micro-
PoRTAL OF organisms is that in order to provoke dis-
Entry. ease, they must find lodgment in or upon

that portion of the body which offers the

70 INFECTIOUS AND PARASITIC DISEASES.

least resistance to their attack. The tissues of the body
vary in susceptibility to microbic invasion, the differ-
ence having a relation to the species of organism. Thus
there are certain bacteria which can exert a specific
action only when they gain entrance into the intestinal
tract ; to this class belong the typhoid bacillus and the
spirillum of Asiatic cholera. There are bacteria, on the
other hand, such as the tetanus bacillus, the gas bacillus,
and the common bacteria of suppurations, which may
be swallowed with impunity, in fact often are, their
characteristic effects being produced only by entrance
into a wound of the skin or a mucous membrane.
Similarly, the diphtheria bacillus has no effect upon the
imbroken skin, nor upon the mucous membranes of the
stomach or intestines, although, in the disease, countless
numbers are swallowed ; it selects per force the mucous
membranes of the nose, the pharjmx, and the posterior
nares chiefly, less often those of the conjunctiva and
the vulva.

The channel of entry, therefore, occupies an impor-
tant position when the subject of a micro-organism's
pathogenicity is under consideration, since upon it will
depend the result of the presence of a'pathogenic agent
whether the latter does or does not satisfy every other
condition necessary for its specific action.

The real power of every species of micro-
ViRULENCE. organism which produces disease lies in

its ability to secrete one or more toxins.

PHENOMENA OF INFECTION. 71

When it has this power it is said to be virulent. In
another chapter the remarkable inconstancy of the
toxicity of micro-organisms has been considered (vide
p. 41). That virulence in bacteria is an essential
phenomenon in disease-production has been abundantly
confirmed by the finding, in their propitious channels
of entry, of various pathogenic micro-organisms m
perfectly healthy individuals, the organisms so found
being commonly non-virulent varieties.

All pathogenic bacteria vary in respect to virulence,
and, as has been explained in a previous chapter, are
on this account divided into those which are virulent
and those which are non-virulent. However, it should
be remembered that non-virulent bacteria are not
without danger to individuals who carry them, and to
other persons to whom they may be conveyed, since
they may acquire virulence either before or after trans-
ference, and provoke disease.

Microbic association in disease is of
MicROBic common occurrence, the resulting mixed
Association infection usually being severer than an
(symbiosis), unmixed one. Thus in diphtheria, the

diphtheria bacillus is often associated
with the streptococcus pyogenes or the staphylococcus
pyogenes aureus; the typhoid bacillus with the bdcUlus
coli communis, a common inhabitant of the intestinal
tract. There are some bacteria, however, which cannot
exercise their power without the co-operation of another

72 INFECTIOUS AND PARASITIC DISEASES.

bacterium. To this class belongs the tetanus bacillus,
which, being an obligate anaerobic bacillus (cannot
grow in the presence of free oxygen), is compelled to
work with another germ that, by absorbing the oxygen,
makes the surroundings favorable for its growth.
This bacillus also works mischief chiefly when accom-
panied by a foreign body, as for example a sliver, powder-
grain, etc., or where there has been much laceration
of tissues. The same thing is true of the bacillus
aerogenes capstdatus.

There are a few infectious diseases, such
Conveyance as malarial fever, yellow fever, and filaria-
BY Insects, sis, in which the infectious agents are

exclusively conveyed by insects. All such
diseases are due to animal parasites, which for com-
plete development require two hosts, man and an insect.
Each host nourishes the parasite during one phase of
its growth only, so that in order to reach maturity the
latter must pass consecutively from one host to another.
Furthermore, since parasites are restricted to especial
hosts, the presence of an appropriate host for each one
is imperative if they are to be perpetuated. Therefore
it follows that the communicability of a disease by an
insect is only possible in the event of the presence of
that particular variety of insect. So circumscribed is
the world of parasitism! For instance, yellow fever
is conveyed by only one genus of mosquito (stegomyia

PHENOMENA OF INFECTION. 73

fasciata), malarial fever by a few varieties of another
(anopheles), etc.

THE BODY m RELATION TO INFECTIONS.

We have just considered the exacting conditions
which an infectious agent must fulfill to provoke disease.
The fulfillment of these conditions, however, only
meets the requirements in so far as the micro-organism
is concerned, and therefore presents but one side of the
problem; the other side, the position that the body
occupies in relation to infections, is equally important,
and it is to this phase of the question that we now turn.
A few lines above, this statement was made, "it is a
matter of common observation that, of a number of
individuals exposed to the same infectious disease, not
all are attacked; and in those susceptible, the disease
presents extraordinary variations as regards its mildness
or severity. If the microbe were the sole factor con-
cerned, all exposed persons would be attacked, and all
taking the disease would suffer to the same degree; a
thing which everyone knows never happens. Moreover,
a person may resist the action of a pathogenic agent at
one time, and fall victim to it at another." The ques-
tion that naturally presents itself is, what brings about
such radical differences in the vulnerability of individ-
uals to infectious agents ? That it is not always conse-
quent upon modifications in the agents, we know from
observations upon patients, and experiments upon

74 INFECTIOUS AND PARASITIC DISEASES.

animals. To account for it, there is obviously some
subtle difference in the vital processes of different
individuals, and in the same person at different times.

Every healthy person is by nature endowed with the
means of combating disease, but his natural defenses,
while they may be strengthened, may also be weakened
by those forces and influences which surround him.
Nor before the tribimal, disease, are all men bom equal,
since progenitors may transmit to their offspring con-
stitutions defective in defensive force. Furthermore,
during the constructive (infancy and childhood) and
degenerative (old age) periods of life the protective
forces are, on the other hand, weakened through imma-
turity, on the other, by the fact that they are declining
with age. Therefore, to environment, heredity, and
age, must we look for an explanation of any imperfec-
tion in our natural resistance to disease.

Predisposition. The absence of resistance to
disease, i.e., susceptibility, has been given the compre-
hensive title predisposition, and we characterize as
predisposing every influence or cause which tends to
weaken the vital forces and therefore predisposes to
disease. In every infection such causes always play
an important r61e, usually more important than the
infectious agents, a fact to which too little heed is given
in the hurly-burly of life. The attitude of the world
in this respect is not unlike its greater faith in the cura-
tive powers of drugs, than in a disciplinary regulation

PHENOMENA OF INFECTION.

75

of its habits. If we should s)mibolize infectious agents
as a spider, and humanity as a fly, then the web would

Infectious
Diseases

Infectious

Agents I

f Bacteria
(Fungi
Protozoa

Heredity

Race

Family

Individual

Predisposing Environ-

Region

I Climate

Causes '

ment

I Insects
Season
Occupation
Poor Food or Fasting
Unhygienic Surroundings
Previous Disease
Poisons (Alcohol, etc.)
Loss of

Blood

Shock
Laceration

Injuries
and

Operations

of Tissues

.Age

Infancy
Childhood
Adolescence
LOld Age

\

76 INFECTIOUS AND PARASITIC DISEASES.

represent predisposing causes, for only when the fly
is entangled in the web doe3 the spider attack its victim.
It will be observed that this conception of disease
does not undervalue the part that infectious agents play
as direct or exciting causes of disease, but it further
recognizes fully the preponderating influence of those
accessory, auxiliary, or predisposing causes without
which the animate agents cannot act. The analytical
chart here shown aims to elucidate graphically this
view. To be sure, all of the diverse elements represented
are not operative at the same time in any infectious
disease; but one or several always are, and these act in
combination with the infectious agents.

Heredity ^^^^"^^^g ^o the chart, it will be seen that
there are three sub-divisions to heredity,
viz., race, family, and individual.

Our knowledge of race as influencing
Race. infection is of comparatively recent date.
This knowledge, besides having an impor-
tant bearing upon etiology, is of historical interest in
explaining the errors of judgment which in the past led
to great crimes. In many notable epidemics the Jews
were singled out for persecution, because they escaped
the prevailing scourge, their immimity being ascribed
to a special knowledge of the epidemic disease. During
cholera epidemics, the relationship to drinking-water
which was recognized, they were accused of poisoning
wells, and the brutal ferocity of insensate mob-violence

PHENOMENA OF INFECTION. 77

was visited upon them. But the dispassionate reason-
ing of scientific investigation has acquitted them of
those charges by explaining their insusceptibility to
infection as a peculiarity of the Hebrew race. Thus,
by far, fewer Jews are victims of pulmonary tubercu-
losis than Gentiles, and Asiatic cholera is so rare among
them as to lead some authors to doubt that it ever
occurs. Furthermore, they suffer less severely from
other infections, and less from animal parasites, than
other races. However, it must be confessed that in the
case of the Jews (and in that of any other race, for that
matter), racial characteristics do not explain entirely
the absence of predisposition. We should err greatly
did we fail to take into account a race's habits and
customs. For instance, other things equal, the Jews
are better housed, eat more wholesome food, are more
cleanly in their habits, take better care of their children,
and are less given to intoxicants, than their Gentile
neighbors ; while all of them are still influenced more or
less by the Mosaic laws. Their standard of life, if
adopted by any people, would tend to strengthen its
vital resistance and, in some at least, would lead to
the establishment of the antithesis of predisposition,
namely, immunity.

Another factor which exercises its influence upon a
race's susceptibility, or immunity, is the length of time
it has been in contact with a disease. The first con-
flict of a race with an infectious disease often proves

INFECTIOUS AND PARASITIC DISEASES.

highly disastrous, as witness the terrible ravages of
measles among the natives of the Faroe Islands in 1846,
when out of 7,782 people, 6,000 were attacked; and also
the invasion of the Fiji Islands in 1875 by the same
malady, during which 40,000 of its 150,000 inhabitants
died. Nor is it necessary to cite examples of distant
peoples; in our own country we have an object lesson
in the Negro and the Indian. The Negro is three times
as susceptible to tuberculosis as the white inhabitants;
and the North American Indian has been well-nigh
exterminated by this "great white plague." Generally
speaking, the longer the contact of a race with an
infectious disease, the less is its predisposition to it.
Tuberculosis well illustrates this point in the respect
that the most ancient race, the Jews, suffers least from
it; other races, in inverse ratio to their antiquity.
Diminution in susceptibility through contact is prob-
ably brought about by large numbers of individuals in
successive generations surviving an infection, and
transmitting to succeeding generations their own individ-
ual resistance, together with that acquired by passing
through an attack of the disease. Yet after every
factor, such as surroundings, food, contact with a
disease, etc., has lieen considered, there is still wanting
an explanation of the fact that when two races hve
side by side, under precisely similar circumstances,
the one suffers from an infectious disease to a greater
extent than does the other. Upon no other grounds than

1

J

PHENOMENA OF INFECTION. 79

racial peculiarity, can this be explained. Animals also
exhibit the same peculiarity in susceptibility to disease.
Among cattle, Jerseys are more susceptible to tuber-
culosis than other breeds. Dogs are practically immune
to it, a fact which probably explains the high position
dog-fat holds among the ignorant as a remedy for tuber-
culosis. At a laboratory at which the writer once
worked, and where many dogs were used for experi-
mental purposes, the janitor sold large quantities of
the fat to a local charlatan who in turn disposed of it as
a specific for consumption. It must not be supposed,
however, that racial immunity, such as is frequently
the case with individuals, is ever perfect. There are
always families and individuals whose immunity is
diminished by marriage and environment, and the
whole race is subject to those diseases which are inci-
dental to age.

As the family partakes of the characteris-
Family. tics of the race, family predisposition is

subject to the same general rules as de-
scribed for races, with the exception, that marriage
between members of different races by blending the
vital forces may either increase or decrease the power
to combat disease. A similar result follows the union
of persons of the same family; and the great danger
of a summation of highly susceptible strains has led,
in many states, to the wise enactment of a law against
consanguineous marriages. An extension of this law

8o INFECTIOUS AND PARASITIC DISEASES.

to include inebriates and consumptives has many
arguments in its favor.

From the view-point of the body, individual
iNDivmuAL. predisposition is the principal factor in

the spread of infectious diseases. With
few exceptions it is operative in every case, so that the
study of the various conditions which lead to it involves
considerations of the highest importance to physicians,
nurses, and sanitarians generaUy. Individual predis-
position may either be inherited or acquired. If inher-
ited, it is seldom to any particular infection but to all.
We no longer believe in an inherited predisposition
to a special disease, as was formerly the case with tuber-
culosis, but rather in the inheritance of an especially
suscepitible state of the body-tissues which predisposes
to all manner of infections. Not alone are the children
of the consumptive markedly prone to consumption
but also the children of all parents who at the time of
conception were either in an impoverished state of
health from disease, or whose vital resistance was
depressed by alcohol, drugs, or by deprivations of one
kind or another. The reason that the consumptive's
oflFspring has fewer chances of escaping tuberculosis
than the child of the non-tuberculous, is because the
atmosphere of its home is, in the majority of cases,
through ignorance, vitiated by the germs of its parent's
malady. Besides a general predisposition such as we
have been discussing, a predisposition to local disorders

PHENOMENA OF INFECTION. 8i

is also recognized. This relates to a susceptibility of
certain organs or tissues as a result of other concurrent
infections. Thus, rheumatism predisposes to infections
of the heart; diabetes, to suppurative inflammations
(carbimcles) and gangrene of the skin and subcutaneous
tissues; enlarged tonsils and adenoids to colds, tonsil-
litis, and probably diphtheria.

Under environment is included all those

Environ- ^ i • n -i i • i

external mfluences by which man is sur-

rounded which, by exercising a deleterious
influence upon health, predispose him to disease.
Among such influences are region, season, occupation,
food, unhygienic surroundings, previous disease, poisons,
injuries, etc.

Locality may act as a predisposing cause
Region, in many ways, all of which may be grouped

under two heads, viz., (i) climate, and (2)
physical conditions.

Climatic conditions, as is well known.
Climate, differ widely in various parts of the world,

from which arise for the most part great
differences in plant and animal life. Moreover, practi-
cally everywhere, there are seasonal variations more or
less pronounced, which have their corresponding in-
fluence upon all living things. In tropical and sub-
tropical countries where a high mean temperature and
a maximum amount of moisture predominate, the
luxuriance of the foliage and the multiformity of animal

82 INFECTIOUS AND PARASITIC DISEASES.

life never cease to excite the admiration and wonder of
the traveler. While from the temperate zone, in a
direction away from the equator, vegetable and animal
life grows less and less abundant and flourishes for a
briefer period of each year, as we approach the frigid
zones. These diversities in climate have given origin
to forms of life peculiar to themselves, and attention is
directed to this most obvious phenomenon because
similar infltiences play their part in the prodtiction of
disease the world over. The living agents of disease
are either animal or vegetable, and are therefore sub-
ject to the same physical laws as govern forms higher
than they. Just as there are plants and animals indig-
enous to the several regions, so do we find pathogenic
agents in one region that are not encountered in another.
Likewise, as many plants native to temperate zones
outgrow in size and color all semblance to the original
when cultivated under tropical atmospheric conditions,
so do certain diseases common' in temperate latitudes,
where they are relatively mild, assume in the tropics a
virulence that makes of them a terrible scourge. But
here the simile of flora and fauna, and disease, ends.
Tropical plants, unless carefully nurtured, do not
prosper when transplanted in temperate climates;
whereas tropical diseases do, if circumstances are the
least propitious, when they are introduced. The
microscopic agents of disease are less sensitive in some
respects to ph)rsical agents than plants, and moreover

PHENOMENA OF INFECTION. 83

are capable of ready adaptation to new environment.
Conquest, improved methods of travel, and shorter
routes, have brought the tropics to the very doors of
Western nations, with the result, that in the great
commercial benefits accruing from easy intercourse,
there has come a menace in the guise of disease. Here
and there tropical diseases have already been introduced,
and while the number of such instances is insignificant,
and they have been successfully combated, it has excited
alarm. And well might it! Europe has a number
of times been over-run with Oriental plagues. Up to
the present these problems have been dealt with chiefly
in those countries where such diseases prevail, but who
can say when from a single imported case a herculean
task in sanitation and preventive medicine will not
confront some nation ? In temperate latitudes, tropical
heat is seasonable for one or more months each year,
a time during which the way is open for the spread of
an exotic disease. This danger the nations are cogni-
zant of, and special commissions are investigating such
diseases in those regions where they are endemic.
Whenever anything is discovered which bids fair to
prove valuable as a preventive, it is at once given a prac-
tical test, since it is obvious that the only real safe-guard
the peoples of temperate climates have against foreign
diseases, is to stamp them out in their home-country.
All of the nations have likewise founded schools of
"Tropical Medicine," where the etiology and sanitary

84 INFECTIOUS AND PARASITIC DISEASES.

control of tropical diseases are studied, and where the
same is taught to physicians and nurses whose duty
it may be, at some time, to cope with them.

An ever present danger to both natives and foreigners
in tropical coimtries is intestinal diseases. The climatic
conditions predispose to congestion of the abdominal
viscera, which predisposes the latter to infections.
Even in the absence of infectious agents, chronic
engorgement may give rise to lasting injury in one or
another organ. The liver is the organ commonly
aflFected in this way, a chronic enlargement with result-
ing torpidity in functioning, frequently making the
unfortunate sufferer an invalid for life. Lay writers,
particularly English authors, have long recognized this
affliction, and very properly held it responsible for
many disagreeable traits of character. The enlarged
liver of the retired East Indian official so often referred
to by Thackeray, is therefore not a mere creation of
the novelist's, but foimded upon fact. But the chief
interest for us in the congestion of the viscera due to
intense heat, is in the fact that it predisposes to a host
of infectious and animal intestinal parasites with which
the tropics abound. Nearly all of these agents get into
the body through the drinking-water, or from eating
raw fruits and vegetables, and the infectious disorders
which they excite are either of the intestines, or the
intestines and liver. The commonest infectious disease
of the tropics is dysentery, of which there are two

PHENOMENA OF INFECTION. 85

varieties, namely, (i) bacillary dysentery, due to a
bacillus (bacillus dysentericB, Shiga), the other, (2)
amoebic dysentery, due to the amoeba dysenteruB, an
animal organism. Next in importance to these infec-
tions are various disorders resulting from animal para-
sites. By exercising great caution in the matter of food
and drink, one may avoid the infectious and parasitic
intestinal disorders, if he cannot those solely dependent
upon climate. From the latter, too, it is not impossible
to escape, if one abstains entirely from alcoholics and
other excesses which tend to increase the amount of
blood in organs already overfilled, and if occasional
visits to cooler climates be made. The most rigid
adherence to the laws of health, combined with such
as are especially adapted to a hot country, must be
followed. These measures if carried out, and provided
the individual is free from disease in the beginning,
will ensure the same average health in a tropical as in
a temperate country.

The degree of warmth, the amount of
Physical moisture, and the physical conditions of a
CoNDrrioNs. country, all have a bearing upon predis-
position, because they supply an essential
environment for the perpetuation of forms of life which
either cause disease, or transmit it. Besides the vege-
table micro-organisms, bacteria and moulds, there are
other microscopic and larger forms of life belonging to
the animal kingdom which produce disease. Among

86 INFECTIOUS AND PARASITIC DISEASES.

these, protozoa, the lowest form of animal life, are of
prime importance. Then there are flukes, worms,
and insects. Of the pathogenic protozoa known,
nearly all depend upon suctorial insects for transmission
from one person to another. The r61e of insects in
the production of disease is large, forming a highly
important branch of medicine; and it is destined to
become much larger. Two kinds of transmission of
pathogenic micro-organisms by living agents are recog-
nized, (i) in which the insect is merely an accidental
carrier of the micro-organism; (2) in which the insect
acts as host for the micro-organism during one phase
of its life-cycle. Where the insect is an accidental
carrier of the microbe, the surface of its body, or its
excrement, has been contaminated by feeding upon
infectious material. Under such circumstances a
disease is transmitted either through the soiling of a
wound, or through the contamination of an article of
diet. While living upon the insect no increase in
numbers of the pathogenic agent takes place. Bac-
terial (and possibly a few protozoan) diseases are fre-
quently transmitted in this way. In a previous chapter
the wide-spread prevalence of typhoid fever in the
United States military camps during the Spanish-
American war was mentioned to illustrate the trans-
mission of bacteria by flies. Besides flies, ants, bed-
bugs, fleas, and ticks, may also accidentally carry
bacteria, and besides typhoid fever, insects are believed

PHENOMENA OF INFECTION. 87

to transmit at times other bacterial diseases such as
Asiatic cholera, bubonic plague, leprosy, tuberculosis,
small-pox, etc.

But where an insect acts as host for a pathogenic
agent, an entirely diflferent condition is presented. Here,
while the contamination of the host is accidental in so
far as the latter is concerned, it is a necessary sequence
on the part of the pathogenic agent. Agents of this
class are alternately parasitic upon human beings and
insects. Upon each host a supplementary develop-
ment begun in one is continued in the other. In no
other way can growth from egg to adult (life-cycle) be
accomplished. In addition to this remarkable pro-
vision, each agent, through the workings of a fixed bio-
logical law, is peculiarly restricted to especial hosts
without which it cannot develop. It follows, therefore,
that the propagation of diseases by insect-hosts is
absolutely contingent upon the presence of that partic-
ular species of insect which is the agent's natural host.
Hosts may belong to the class of suctorial (biting)
insects, or to such as are likely to get into our food or
drink. One instance of a disease due to a protozoan
which is transmitted by an insect (mosquito), is fur-
nished by malarial fever ; another, by sleeping-sickness
(trypanosomiasis), of which the African stinging fly
glossina is the host.

Among larger organisms which themselves produce
pathological conditions are insects, flukes, worms, etc.

r
I

88 INFECTIOUS AND PARASITIC DISEASES.

Most of these have as yet a circumscribed distribution,
so that the diseases which they cause are hmited to
certain regions. Examples of such diseases are parasitic
hemoptysis (puhnonary distomiasis), which is found
ahnost exclusively in China, Japan, and Formosa;
bilharziosis (endemic or Egyptian hsematuria), pre-
vailing particularly in Egypt, North Africa, Arabia and
Persia; hook-worm disease (ankylostomiasis, uncin-
ariasis), common in Porto Rica, Southern United States,
the Philippine Islands and Egypt; guinea-worm disease
(dracontiasis), occurring principally in Africa, East
Indies, and Panama. These examples suffice to show
the relationship between insects and disease on the one
hand, and regions and insects, upon the other. It is
because the physical characteristics in so large a measure
determine the insect and animal life of a country that
we include them among the predisposing causes of
disease.

In tropical and sub-tropical countries many more
diseases are due to animal infectious agents, and animal
parasites, than in temperate latitudes, and larger
numbers of both agents are transmitted by insects.
This fact again emphasizes the danger to the peoples
of temperate climates in that either pathogenic parasites
themselves, or their insect-hosts, may be imported dur-
ing the period of greatest heat and moisture, find the
conditions propitious for multiplication, and sow their
virus promiscuously. Moreover, a few may become

1

J

PHENOMENA OF INFECTION. 89

acclimated and survive the cold of the winter months,
breed fresh generations the following summer, and in
this way establish a new endemic focus for the diseases
which they carry.

A good example of an insect which acts as host for
an infectious animal micro-organism, and one which
depends for existence upon the physical conditions of a
country, is found in the species of mosquito (anopheles)
which transmits malarial fever. As the anopheles
only breeds in shallow puddles of water or slowly
moving streams, it is manifest that weU-drained regions
are likely to be free from malaria, while those presenting
an opposite condition are favorable to its introduction.
This same species of mosquito neither breeds nor bites
when the temperature is below 68 Fahrenheit, a fact
which explains the constant presence of ague in tropical
climates. High altitudes, and moimtainous regions,
because they do not present the physical conditions
necessary for the multiplication of the anopheles, are
free from malarial fever; but the same is not true for
yellow fever, which is transmitted by another species
of mosquito, the stegomyia fasciata. This species
breeds in rain-spouts, cisterns, and small collections
of water about a household. Given a favoring climate,
therefore, where the practice of storing water about
dwellings prevails, there is no reason why this pestif-
erous insect cannot become domesticated in regions
that are now outside the yellow fever zones. An

90 INFECTIOUS AND PARASITIC DISEASES.

illustration of the altitude the stegomyia may reach is
furnished by the history of yellow fever in Mexico, as
reported by the U. S. Public Health and Marine-
Hospital Service. A coramission from this Service,
called Working Party No. i, found this mosquito at an
altitude of 4200 feet above the sea level, an ascent which
they ascribe to a shortening of the time-distance
between coast and interior by the building of a railroad.
That season and disease are related phe-

Season. nomena has already been included in our
discussion of climate. It only remains to
illustrate the relationship. Yellow fever is a disease
of tropical countries, and of sub-tropical regions during
the warm months; typhoid fever occurs everywhere
chiefly in the autumn and early winter months.

The effect of season upon disease is strikingly shown
if we compare the two extremes of the year, summer and
winter. The heated term is characterized by diseases
affecting the intestinal tract, the cold and blustry
months, by affections of the respiratory organs and
joints.

Fasting, poor food, unhygienic surround-
Fasting, ings, etc., are potential factors in the pro-
PoorFood, duction of infectious diseases. They all
Etc. conduce to a low state of the vital forces;

and an impoverished body falls an easy
prey to the pathogenic agents. Nor are the effects
of other agencies grouped in our chart under environ-

PHENOMENA OF INFECTION. 91

merit dissimilar in their action. Previous disease,
alcoholism, injuries, and operations, all portend the
same end, viz., a lessening of the natural resistance.
The blood and its cells contain the largest amounts
of those active principles which combat disease, and
when it wastes, as it does in every disorder, this func-
tion is depressed or suspended. Besides being
"thinned" by disease, the blood suffers impoverishment
through poisons (e.g., alcohol, lead); through the
absence of either sufficient or nourishing food ; through
unhygienic surroundings, and by actual loss in volume
and cellular constituents in haemorrhages consequent
upon operations and injuries, and also blood sucking
parasites. In unhygienic surroundings perhaps the
most potent evil is the absence of pure air (oxygen) in
sufficient amounts to meet the normal needs of the body.
Typhoid fever furnishes a remarkable example of the
predisposing influence of a disease. After an attack
of typhoid, a person is particularly prone to diseases
of the biliary passages, such as inflammation of the
gall-bladder (cholecystitis) and gall-stone formation
(cholelithiasis). Predisposition is brought about in
the following way: During the fever, typhoid bacilli
find their way into the gall-bladder, where they are
liable to remain for months and even years, and besides
constituting a nidus there for the formation of gall-
stones, may also at any time give rise to either a catar-
rhal or suppurative inflammation of this organ.

92 INFECTIOUS AND PARASITIC DISEASES.

That occupation has a pronounced influ-
OccuPATioN. ence upon longevity is well illustrated by

the comparative mortality table appended.
Comparative mortality of men twenty-five to sixty-
five years of age, in diflferent occupations, 1881 to 1883
(Ogle):

Comparative
Occupation. Mortality.

Clergymen, priests and ministers 100

Lawyers 152

Medical men 202

Gardeners 108

Farmers 114

Commercial clerks 179

Innkeepers f liquor dealers 274

/»», hotel service 396

Brewers 245

Butchers 211

Bakers 172

Tailors 189

Book-binders 210

Builders, masons, brick-layers 174

Carpenters 147

Plumbers, painters, glaziers 216

Blacksmiths 175

Cotton manufacture 196

Cutler, scissor maker 229

FUe makers 300

Glass workers 214

Earthen-ware workers 314

Coal miners 160

Stone, slate quarries 202

Street hawkers 338

PHENOMENA OF INFECTION. 93

The laws of nearly all the States take cognizance of
the dangerous character of certain occupations by
specifying the safe-guards under which work of this
nature is to be done, and penalizing disobedience.
They further recognize that many occupations are not
in themselves so injurious to health as the unhygienic
condition of the surroundings, the crowded states of
the work-shops, and the long hours imposed. Sweat-
shops exhibit in the highest degree the evils just referred
to.

The predisposing influence of an occupation may be
exerted locally upon some organ, as the lung, or upon
the body generally. Thus pulmonary tuberculosis is of
frequent occurrence in persons whose occupations are
carried on in an atmosphere of dust peculiar to their
trades, e.g., stone-cutters, file-grinders, cutlers, cut-
glass grinders, etc., a danger which can be diminished
by placing suction hoods above the field of work.
Not all dust, however, is equally harmful, a difference
demonstrated in the case of coal miners who, while
breathing in a dust-laden atmosphere day after day
for years, are not markedly predisposed to tuberculosis.
Another example of the predisposing influence of occu-
pation upon an organ is found in seamstresses, who,
on account of the attitude assumed while working,
are predisposed to ulcer of the stomach.

Occupations which create a general predisposition
are those in which the worker is either subjected to the

94 INFECTIOUS AND PARASITIC DISEASES.

action of poisons, or in which the tension of the work
is a severe strain upon the nervous system. Some
poisons per se produce pathological states, e.g., lead,
arsenic, mercury, etc. These also tend to the produc-
tion of an impoverished state of the blood (anaemia),
constipation, etc., abnormalities which we already
have called attention to as paving the way for infections.
Occupations involving severe strains disturb the nervous
system, which in turn affects the nutrition and func-
tions of every part of the body.

In Ogle's table illustrating the comparative mortality
in the various occupations, innkeepers and liquor
dealors are seen to head the list in point of frequency.
This is not because there is an)d:hing especially injurious
in the occupation, but because the occupation usually
leads to excessive indulgence in intoxicants. So well
recognized is this association of alcoholism with the
handling or sale of liquors, that life insurance com-
panies universally regard individuals of this class as
bad "risks" and refuse to insure their lives.

The incidence of age and disease is well
Age. established. There are disorders of in-
fancy, of childhood, of adolescence, and
of old age. Middle life also has its afflictions in the
way of special diseases, but as we are limited to in-
fectious diseases, and they are not associated to any
marked extent with this period, the affections peculiar
to it will not be discussed.

PHENOMENA OF INFECTION. 95

The young infant is remarkable in its
Infancy, comparative freedom from the infectious
diseases of childhood. During late foetal
life the imbom child may suffer from a large number
of infectious diseases which perchance attack the
mother, and many instances are on record of infants
being bom with typhoid fever and small-pox; indeed
the foetus has been known to survive an attack of small-
pox and be bom with a scarred face, a circumstance
which attended the birth of the great obstetrician,
Mauriceau. To measles and scarlet fever, and even
such a virulent infection as yellow fever, the infant up
to the sixth month and often longer, is practically
immune; the same is true of typhoid fever and other
exanthemata; yet to small-pox it is highly susceptible.
From one infection in particular should the new-
bom be protected, namely, er3rsipelas of the umbilical
cord, a disease, as we have seen, which has great danger
in it for the mother also. Another infection for which
the umbilical cord is a portal of entry is tetanus, an
accident fortunately not often encountered. It occurs,
however, sporadically in a few localities where the
bacilli are numerous in the ground, and then among
the poorest and least cleanly of the people.

At the time of birth, if the mother is suffering from
gonorrhoea, the infant is liable to three localizations of
this disease, viz., in the mouth and conjunctivae of the
eyes, and in females, in the vulva also. Gonorrhoeal

96 INFECTIOUS AND PARASITIC DISEASES.

conjunctivitis (ophthalmia neonatorum) is a very
serious infection, and requires prompt treatment if
the sight is to be saved. From sixty to seventy per
cent of all blindness in the world has been caused
by it. Happily, loss of sight may be guarded against
by dropping one drop of a i per cent solution of ni-
trate of silver between the parted lids of each eye,
at birth, in all infants bom of mothers who are not
above suspicion; indeed, nearly all maternity hospit-
als and out-patient departments make this a routine
procedure.

Gonorrhoea of the vulva is also a serious affection.
Very few vaginal discharges in children have any other
origin. The disease is not only important because it
may affect the child in after years, but also because it
may cause death from peritonitis by extension of the
infection to the peritoneal cavity.

To the end of the second year diarrhoea in
Childhood, summer, and respiratory infections in

winter, are the principal diseases. From
the second year to puberty is the period of greatest
susceptibility to scarlet fever, measles, chicken-pox,
mumps, whooping-cough, and diphtheria. These years
embrace the period of childhood, and on account of
the preponderance of the above mentioned diseases
during this time the latter are called the "diseases of
childhood." Diseases peculiar to children exhibit such
variations from the same or other diseases seen in later

PHENOMENA OF INFECTION. 97

life as to have given rise to specialists. The specialty
is called pcediatrics.

Besides the general infectious diseases, children are
more predisposed to infections of the lymphatic glands
and bones than adults. The glands most frequently
affected are those of the neck (cervical) ; and the infec-
tious agents are either the tubercle bacillus, or the
common pus cocci. Inflammation of bone, osteomy-
elitis, is also a frequent affliction of childhood. The
thigh and lower leg are the most likely sites for infec-
tious foci. In this affection the tubercle bacillus, and
the pyogenic cocci, are again the common cause. The
unsightly deformity of hunchback (Pott's disease),
and the lesser evil, hip-joint disease, are also examples
of the localization of the tubercle bacillus in bone.

Young adults still exhibit some suscepti-
bility to the diseases of childhood, but in a

CENCE. Ill

much lessened degree. However, at this
period susceptibility is principally shown towards two
wide-spread diseases, pulmonary tuberculosis and
typhoid fever. Predisposition to the former is almost
entirely the result of heredity and environment; to
the latter it appears that age is the most important
contributing factor.

Pneumonia is the commonest infectious
Old Age. disease of the declining years of life, and

the principal cause of death. In men,
prostatic enlargement frequently interferes with the
7

98 INFECTIOUS AND PARASITIC DISEASES.

voiding of urine, a condition which itself predisposes to
inflammation of the bladder (cystitis). Often there
is such obstruction that "catheter-life"* is necessarily-
resorted to, with the result that infection sooner or
later occurs. This per se is not immediately dangerous
to life, although the intermittent pyrexia (fever), and
the continuous discharge of pus, sap the patient's
strength. Subsequently symptoms of toxaemia develop
either through extension of the inflammation to the
kidneys or from absorption, or from both causes.
Death finally takes place from an intensification of
the toxaemia, or from bacteriaemia. Pulmonary tuber-
culosis is also encountered in old persons, and may
also be a cause of death. Besides these affections,
there are practically no others to which a person beyond
sixty years is predisposed. Occasionally measles
attacks a patriarch, and sometimes typhoid fever, but
such instances are exceptional.

♦The condition in which a catheter is always employed when thq
bladder is to be emptied.

CHAPTER IV.
INFLAMMATION.

The changes which take place in a tissue when
injured, and all those changes which follow as a con-
sequence of the injury, constitute inflammation. In
previous chapters emphasis was laid on the fact that
the body resents injury and is quick to battle against
any agent which tends to do it harm; also, that it pos-
sesses remarkable reconstructive ability when des-
truction of tissues has occurred. Both the defensive
and reconstructive powers of the body are due to what
was termed its "defensive mechanism," a function
that has grown to its present proportions through the
operation of natural laws which govern survival and
development.

We have seen that recovery from infectious diseases
is due to the neutralization of the toxic products of
bacteria, or solution of the bacteria themselves by sub-
stances (antibodies) which are formed within the body.
The action of antibodies, however, is limited either to
the neutralization of toxins or bacteria, since they
neither repair injured tissues nor replace those destroyed.
In simple injuries from mechanical and ph3rsical causes,

99

loo INFECTIOUS AND PARASITIC DISEASES.

and also in some inflicted by many chemical and
animate ones, antibodies are not created, because the
toxins which stimulate their production are wanting.
In such instances the reactions excited at the site of the
injury suflice to coimteract the action of the damaging
agent and repair the tissues affected. But when infec-
tious agents, and also certain poisons e. g., snake venom,
produce injuries, then both antibodies and local defen-
sive phenomena are brought into action. Hence the
defensive mechanism, it will be observed, has a dual
action; one, to produce antibodies; the other, to repair
tissues injured and destroyed. The process of repair
is characterized by entirely different phenomena than
those of antibody formation, albeit both often arise
from the same source, viz., injury to cells. This differ-
ence is illustrated by the fact that while, on the one
hand, the formation of antibodies is conducted by
cells situated at a distance from the lesion, repair, on
the other, is a process which involves the lesion itself
and neighboring cells. For the process of repair the
name inflammation is used, and imder it are included
all immediate and subsequent changes in a tissue or
organ that has sustained an injury.

If it were our purpose to treat inflammations ex-
haustively, we should have to take into consideration
the various agents which produce bodily injuries, and
every tissue and organ susceptible of injury; also such
local and general conditions of the body as influence

INFLAMMATION. loi

the process in one way or another. Furthermore,
because pathogenic agents diflFer so greatly in the
reactions which they excite, and diflFerent tissues re-
spond so variously to the same or different pathogenic
agents, we would be led into a description of every
form of inflammation, both acute and chronic — a
study that would not end until almost the whole domain
of pathological anatomy would have been explored.
But such is not our purpose. There are certain fim-
damental phenomena which characterize every inflam-
mation which, while they represent the primary reactions
to injury, are, at the same time, preliminary to repair.
These we propose to explain. Besides, the evolution
of inflammations in general presents special features
which permit us to point out the protean* character of
the process without committing us to a lengthy dis-
cussion.

Four so-called cardinal symptoms of

Cardinal • n j.* i • j

inflammation are commonly recognized,
Symptoms of . , ^ j ,.. i .

-. VIZ., heat, redness, swelling and pain.

w*^,^xT To these a fifth is added by some authors,

MATION. , -^ '

interference with function. The phenom-
ena which underlie these symptoms are as follows:
Redness is due. to a dilatation of the adjacent blood-
vessels; swelling, to the increased calibre of the blood-
vessels, and to blood-serum and blood-cells which have
passed out from the walls of the former into the sur-

'i' Assuming different forms.

I02 INFECTIOUS AND PARASITIC DISEASES.

rounding tissues. Pain is due to tension and pressure
exerted on neighboring nerve-endings; heat to the
fact that there is both an increased amount of blood
in the part, and because metabolism is locally quickened.
Since the nutrition of a part is obviously disturbed by
inflammatory phenomena, there is no need to dwell
on the associated disturbance of function. Dilatation
of blood-vessels, exudation of serum, and migration
of blood-cells, are therefore the body's initial response
to injury (local reactionary phenomena), and are pres-
ent in the beginning of inflammation.

The earliest stage of inflanmiation, congestion, is
not considered beyond the borderland of health, indeed
it is the normal physiological state of a tissue or organ
when active. When, however, serum has escaped into
the tissues (effusion), this boundary has been passed,
although the part may return to normal without loss
of substance through absorption of the exudate by the
veins and lymphatics. An exudation is protective
to the body from infection both through its germicidal
powers and by dilution of toxins.

Among the early phenomena of inflam-
Leucocytes. mation is the escape of cellular elements

from the blood-vessels. These cells con-
sist of both red blood-corpuscles and larger colorless
cells, called leucocytes. There are many varieties
of leucocytes in the blood, but probably only two or
three of these have a share in the inflammatory process.

INFLAMMATION. 103

Those concerned are capable of independent move-
ment, and make their exit from the capillaries by
insinuating themselves between the cells which line
the capillary walls. The fenestra which they open
close again, but not quickly enough to prevent the escape
of a few of the red cells. Once beyond the vessel-
walls the movements of leucocytes are determined by a
mysterious force exerted by the infectious agents.
This force (chemotaxis) either attracts (positive chemo-
taxis), or repells them (negative chemotaxis).

Negative chemotaxis, however, is only
Chemotaxis. active so long as the agent is present, for

on the cessation of the agent's action, or
its elimination, leucocytes return and take up their
specific functions. In inflammatory conditions the
leucocytes have several offices to perform; they carry
off the debris of injured cells, and any foreign matter
introduced when the injury was sustained; they also
destroy by digestion invading bacteria; a third office
is to take part in the formation of new tissue. In the
last instance they are actually converted into grow-
ing tissue cells. Metchnikoff, a distinguished bacteriol-
ogist, who is our greatest authority on the place of
leucocytes in inflammation, contends that they are also
largely concerned in the production of immunizing
substances (antibodies). Be this as it may, it is plain
that the leucocytes are exceedingly valuable factors
in inflammations.

I04 INFECTIOUS AND PARASITIC DISEASES.

The most important function of leucocjrtes

Phagocy-

in local and general inflammations is to
destroy bacteria, an action which is desig-
nated phagocytic, the fimction itself, phagocytosis.

In almost every inflammatory condition
Leucocy-

of the body the number of leucocytes in

TOSIS. -^ ^

the blood is increased. Normally, there
are about 6000 of all kinds to the cubic centimeter,
but 50,000 to 60,000 are not unusual in inflanmiations.
When present in numbers above 7000, a letccocytosis
is said to be present. The explanation of this increase
of leucocytes in the blood is found in the large mmibers
required at inflammatory foci. In the discharge
from ajx abscess, for example, there are present 4 to 5
millions per cubic centimeter. The additions made
to the normal number of leucocytes in the blood are
due to the stimulated activity of the blood-forming
(hematopoietic) organs which, as occasions arise,
verily surcharge the blood with them. Whence comes
the stimulus ? Obviously from absorption of a prod-
uct formed at the site of the injury. Leucocytosis
is therefore another phenomenon which should impress
upon us the deep-seated reactions occasioned by
every injury, whether the latter gives rise to general
symptoms or not, and how far parts of the defensive
mechanism are placed from the injury. In injuries
due to mechanical and physical agents, when not com-
plicated by invading bacteria, the succeeding inflam-

INFLAMMATION. 105

mations follow an orderly progress to repair; exuda-
tions are absorbed, dead cells and their debris are
removed by the phagoc)^*es and connective tissue cells,
and either connective tissue cells or cells peculiar to the
organ or tissues involved take the place of those removed.
But most inflammations are not of this nature, being
caused or complicated by bacteria and their toxic
products. The first effect of the latter is the same in
all cases, viz., to excite the cardinal phenomena of in-
flammation ; from this point, however, the further prog-
ress and termination of the process is determined by
the interaction of three forces:

1. The nature and intensity of the invading agent.

2. The tissue or tissues in which the bacteria are
localized.

3. The local and general resistance of the individual.

Thus the same micro-organism (streptococcus pyog-
enes) which on a mucous membrane can produce a
false membrane, may in the subcutaneous tissues
give rise to an abscess, or to gangrene; or if the local
resistance is not sufl&cient, will invade the blood and
cause a bacteriaemia. Another bacterium, the tuber-
cle bacillus, produces usually tumor-like growths in
tissues, but it often causes rapid necrosis, and not in-
frequently pus.

Here it may be well to direct attention to the fact
that in infectious diseases the inflammatory process
is not confined to a single locality or organ ; but since

io6 INFECTIOUS AND PARASITIC DISEASES.

either the bacteria or their toxins, or both, are dissem-
inated throughout the body, such parts are affected as
are susceptible to their action, and in these inflamma-
tions are excited.

If early subsidence of the primary phenomena of an
inflammation does not take place, necrobiosis of greater
or lesser degree follows : in those instances where some
cell destruction was the starting point for the phenom-
ena, there is extension of the necrobiotic area. Viewed
from the stand-point of tendency, inflammations
are either destructive or constructive, that is to say,
some exhibit an immediate tendency to disorganization
of tissues, other to organization. However, to say
that the tendency of an inflammation is destructive
does not contradict what has been said of the general
purpose of inflammations, viz., defense and repair.

A microbe enters a wound in the skin,
or by way of the blood, the tissues of some
' internal organ. Through multiplication
and the excretion of toxins a focus of
necrosis is established. Coincidentally with the for-
mation of this focus the cardinal signs of inflammation
have made their appearance, and so performed their
part that the necrobiotic area is circumscribed by a
wall of leucocytes which act as a barrier against deeper
invasions. Beyond the leucoc)i:ic wall, connective
tissue cells are in active process of proliferation pre-
paratory to encroaching upon the necrotic area as it is

INFLAMMATION. 107

eliminated. Suppose the invading microbe belongs
to a species which causes suppuration. The next
stage in this form of inflammation would then be lique-
faction of the dead cells by ferments, and rupture of
the fluid contents through the skin. Gradual enlarge-
ment of the opening often permits a "c^^re" of dead
tissue not yet liquefied to be extruded. The material
escaping from such a lesion is pus, and consists chiefly
of large numbers of leucoc)^es suspended in serum and
liquefied tissues. In this discharge are also eliminated
bacteria and toxins. Leucocytes give pus its creamy
consistency and yellow color. The dead tissue having
thus been gotten rid of, healing goes on through growth
of connective tissue cells and contraction (cicatrization).
The above is a description of the formation and course
of an abscess.

Suppuration under natural conditions is practically
alwa)rs due to bacteria — a single exception among
animal infectious agents being the amoeba of dysen-
tery, which is known to cause abscess of the liver.
There are a number of bacteria which cause suppura-
tion ; some habitually, some specifically, and others acci-
dentally. The common members of these three groups
are as follows:

I. Pyogenic Bacteria.

Staphylococcus pyogenes aureus.
Staphylococcus pyogenes citreus.
Staphylococcus pyogenes albus.

io8 INFECTIOUS AND PARASITIC DISEASES.

Streptococcus pyogenes.
Micrococcus tetragenus.
Bacillus pyocyaneus.

2. Specific Pyogenic Bacteria.

Diplococcus intracellularis meningitidis.
Gonococcus.
Bacillus of glanders.
Bacillus of bubonic plague.

3. Accidental Pyogenic Bacteria.

Bacillus of anthrax.
Bacillus of tuberculosis.
Bacillus of influenza.
Bacillus of typhoid fever.

Suppuration is one example of a destructive inflam-
mation; gangrene is another.

When the inflammatory phenomena are not too
intense, the connective tissue cells tend at once to
organize about the area of injury and repair it. They
form what are called infectious nodules. This type
of inflammation is represented by syphilis and tuber-
culosis, and illustrates the antithesis of suppurative
inflammations in its immediate tendency to repair.

CHAPTER V.
ANIMAL PARASITES.

Man is host for numerous animal parasites both
large and small. A parasite, we have seen, is "an
organism which lives upon another organism called the
host." Parasites may live permanently upon their
hosts, or be only temporary inhabitants. They may
have their habitat upon the exterior of our body, when
they are called ecto-parasites; or within it (endo-para-
sites). All human ecto-parasites are either mites
(arachnida), or true insects; all endo-parasites belong
to the protozoa, trematoda, cestoda, or nematoda.

By temporary parasite is implied an organism which
seeks the human body for a single meal only, and passes
for the next to a new host. To this class belongs
mosquitoes, bed-bugs, ticks, etc. By permanent para-
site is understood an organism which, when it finds
lodgment upon or within the body, remains there
until dislodged either by accident, through the instru-
mentality of drugs, or because the host is no longer a
suitable pabulum either for further development or
for a continued existence. Death of the host, of course,

terminates the status, parasitism. Most himian endo-

109

no INFECTIOUS AND PARASITIC DISEASES.

parasites are remarkable for the complicated and un-
usual manner by which they attain maturity; indeed,
it is owing to this unusual evolution that they produce
pathological states. Nearly all require for their com-
plete growth at least two hosts, man and some other
creature, in each of which complementary stages of
development take place. They may also have a stage
of growth in water or in the ground. Taken together,
the progressive development of a parasite from egg to
adult is called its cycle. Parasites which require two
hosts to complete their cycle may pass these in hosts
which are biologically allied, as for example, the beef
and pork tape-worms, whose hosts other than man are
respectively implied in their names. Often, however,
the dissimilitude in hosts is truly remarkable, and
causes us to marvel at the ingenuity which unraveled
their cycles. Thus, the parasites of malaria, yellow
fever, and filariasis, have each a stage of development
in particular mosquitoes ; the guinea-worm, in a water-
flea; the schistoma haematobium, in a special species
of snail. The examples given above illustrate a curious
phenomenon in regard to parasites and hosts to which
there are few exceptions, viz., that each parasite is
restricted to hosts which enable it to complete its cycle,

Note: — For a fuller description than is given here of animal para-
sites, well illustrated, the general reader is referred to Tyson's " Prac-
tice of Medicine," 4th ed.; or numerous articles in Woods' "Ref.
Handbook of the Medical Sciences," last ed.

ANIMAL PARASITES. iii

and that development cannot take place in insects and
animals which do not have this relationship to the
parasites. One illustration will suffice; no other
mosquito besides the genus stegomyia fasciata can
harbor or convey yellow fever, and none besides the
genus anopheles, malaria. In the stomach of other
varieties of mosquitoes than anopheles the Plasmodia
malaria are digested.

PROTOZOA.

The smallest forms of animal life parasitic upon man
belong to the protozoa. The latter constitute that
class of organisms the individuals of which are com-
posed of only a single cell. Like bacteria, all parasitic
protozoa are microscopic in size. Their structure,
however, is far more complex, and their life-cycle is
bizarre in the extreme. Thus, some are known to
develop partly in water and partly in a host; others
entirely within the bodies of two or more hosts.

Those which have part of a cycle in water, and the
other in man, usually gain entrance into the body in the
drinking-water.

Examples of this class are found in the amoeba of
dysentery and the coccidium hominis. The last men-
tioned is probably the cause, also, of that peculiar tumor
known as epithelioma contagiosum. On the other
hand, in the case of such varieties as never reach the
external world, but spend their whole existence in
various special hosts, these are usually conveyed to

112 INFECTIOUS AND PARASITIC DISEASES.

man by one of their hosts which itself is also a human
parasite. An instance of the latter is found in the
malarial plasmodium, which is inoculated by the
anopheles mosquito.

The principal human protozoan parasites are the
ammha dysenteric, the trypanosoma gambiense, the pro-
tozoan of Dum-Dum fever, and the Plasmodium ma-
larice (three varieties).

This parasite is the cause of an acute and
Am(eba chronic dysentery principally

DvsENTEHi*:. prevalent in Egypt, India,
and tropical countries gen-
erally, although it also occasions a large
proportion of the cases of dysentery in
the United States.

The site of its activity is the large intes- coMgS^^
tine, the mucous membrane of which it Sraun.)
erodes and undermines to an extent seen in no other
malady. The organism gains entrance into the body
in the drinking-water and through polluted vegetables
which are eaten raw. There is a special tendency to
abscess of the liver in dysentery of amoebic origin, and
perforation of the abscess through the diaphragm into
the right lung is a not uncommon event. In appear-
ance this amceba is not unlike the white corpuscles of
the blood. Harmless amoebae, however, also occur
normally in the stools and must be differentiated from
the pathogenic amxba histolytica.

ANIMAL PARASITES. 113

Tr3^anosomiasis, or the infestment of the

blood with flagellated protozoa, trypano-
Trypanosoma . . ^.

^ somes, IS common among many varieties

of animals, viz., fish, birds, horses, cattle,

etc. In some it is productive of disease,
in others not. Different varieties of tr3^anosomes,
probably, are the cause respectively of the disease of
horses and cattle in India and the Philippine Islands
known as surraj and of the tsetse-fly disease or nagana
of South Africa. In man the parasite is associated
with the dreadful African "Sleeping-sickness," and is
transmitted by the stinging fly glossina.

Dum-Dum fever, or Tropical Spleno-
DuM-DuM megaly, is a protozoan infection prevalent
Fever. among the natives of India, Assam, Ceylon,

China and Egypt. The parasite, Donovan-
Leishman bodies, has been found widely distributed
in the body. The manner of transmission is unknown.

Protozoa which increase their numbers
Plasmodium by the production of spores or seeds are
Malarle. called sporozoa. When sporozoa live at

the expense of the red blood-cells of an
animal they are especially distinguished by the signifi-
cant name hcemosporidia. To the latter class belongs
the Plasmodium of malaria. The plasmodium malariae
(Laveran), of which there are three varieties, lives and
develops within, and at the cost of, the colored cor-
puscles of the blood. When first seen it appears as a

8

Description of Fig. 5.

Life history of malaria parasite, Plasmodium, 1, Sporozoite, intro-
duced by mosquito into human blood, the sporozoite becomes a schizont;
2, young schizont; 3, young schizont in a red blood -corpuscle; 4, full-
grown schizont; 5, nuclear division; 6, spores, or merozoites, from a
single mother-cell; 7, young macrogamete (female), from a merozoite,
and situated in a red blood-corpuscle; 7a, young microgametoblast
(male); 8, full-grown macrogamete; Sa, full-grown microgametoblast;
9, mature macrogamete; 9a, mature microgametoblast; 9^, resting cell,
bearing six flagellate microgametes (male); 10, fertilization of a macro-
gamete by a motile microgamete; the macrogamete next becomes an
o5kinete; 11, o5kinete, or wandering cell, which penetrates into the wall
of the stomach of the mosquito; 12, ookinete in the outer region of the
wall of the stomach, i. e., next to the body cavity; 13, young odcyst,
derived from the odkinete; 14, o5cyst, containing sporoblasts, which
develop into sporozoites; 15, older oocyst; 16, mature oocysts, con-
taining sporozoites; 17, transverse section of salivary gland of an Anoph-
eles mosquito, showing sporozoites of the malaria parasite in the gland
cells surrounding the central canal.

f i-6iillustrate schizogony (asexual production of spores); 7-16, spo-
rogony (sexual production of spores).

(FoLSOM— After Grassi and Leuckart, by permission of Dr. Carl
Chun.)

114

ANIMAL PARASITES. 115

small irregular colorless body within the red blood-cell.
This body increases gradually in size until it quite
j&lls the cell. As it grows, pigment-granules appear,
which at first are peripherally placed, but later collect
in a clump in the center of the parasite. At this stage
the parasite has matured, and its whole body splits
up into spores, or new young parasites which, upon
rupture of the red blood-corpuscle, are set free in the
blood and attach themselves to fresh' cells. In an
infected person large numbers of plasmodia appear to
reach maturity and sporulate about the same time, and
it has been found that the chills and fever correspond
with this division of the parasites.

In tertian malarial fever, the plasmodium attains
maturity in forty-eight hours, in qtcartan fever, seventy-
two hours, facts which seem to explain the regularity
of the chills in these two forms of ague. In cestivo-
autumnal fever another special variety of parasite is
concerned which attains maturity in from twenty-four
to forty-eight hours, in consequence of which the course
of this form of ague is irregular.

During the course of all the malarias there are also
formed in the blood oval, spherical, or crescentic
bodies, some of which are flagellated, others non-flagel-
lated. These are sexual elements of the parasites, the
flagellated forms constituting the males, the non-flagel-
lated, the females. Union of these in the blood, how-
ever, for some unknown reason, does not take place,

ii6 INFECTIOUS AND PARASITIC DISEASES.

but in the stomach of different species of mosquitoes
of the genus anopheles, which suck up the malarial
parasites when biting. In the mosquito's stomach,
coalescence (copulation) of the sexual elements occurs
and a new organism is formed. The new parasite in
turn forms other organisms in large numbers, which
pass from the mosquito's stomach to its body-cavity
and thence collect in its salivary glands ; from this situa-
tion they find their way into the blood of man again when
the insect bites. The forms thus inoculated give rise
to malaria.

It has been definitely proven that malarial fever can
be conveyed in only one way, viz., through the bite of a
mosquito which harbors the plasmodium, and that only
species of the genus anopheles are capable of acting
as host to this parasite. Clinically the pathological
states resulting from invasion of the body by the pro-
tozoan parasites above described are not unlike those
of an infectious disease; indeed, we regard them as
belonging to the latter class, and would therefore include
the agents which cause them among the infectious
agents. They are placed among the parasites here
simply for convenience of description.

NEMATODES.
FiLARiA Or guinea-worm, is a round worm which

Medinensis develops in the subcutaneous tissues.
(Dracunculus Qnly the female is known. The worm is
medinensis). tg^j^g^ into the stomach probably through

ANIMAL PARASITES. 117

drinkingwater containing small aquatic crustaceans
{Cyclops quadricomis) which themselves harbor the
embryos. The embryos
penetrate the intestinal
wall, reach the subcu-
taneous tissues, and
there attain full develop-
ment. The seat of elec-
tion is the lower ex-
tremities, particularly
about the heels, yet the
parasite has been found
in other parts of the
body. It is said that
the worm can be felt
beneath the skin "like
a bundle of strings."
When the worm is ma-
ture it breaks through
the integument, forming
at first a little vesicle,
later a small discharg-
ing ulcer, and from the

I , , c ii_ 1 li ■■!_ FlO' 6. — Fitaria medintnsis; a, anterior

bottom 01 tlie latter the eitrermty; O, mouth; P, papilte; b, fe-
UnnJ n *: male, reduced to less ttian half normal

head sometimes pro- ^^^i ^^. ^ 1^^^ ^^^_ (g^^,
trudes. Embryos are "fterckus.)
discharged through the opening in the skin, more par-
ticularly when water is applied. After getting rid of

ii8 INFECTIOUS AND PARASITIC DISEASES.

her larvae the worm leaves her host spontaneously. The
embryos find their way into water, often, probably, when
the host is bathing, and as has been said, develop in the
water-flea cyclops. The adult worm is of considerable
size, measuring from 50 to 80 cubic centimeters (20-32
inches) in length and a few millimeters in breadth. It
is of a white or yellowish-brown color. When the
worm begins to come out it should be left alone at first,
as it may leave spontaneously. However, it can be ex-
tracted by catching the protruding head between the
split end of a smooth stick and winding it up on the lat-
ter, a few turns a day. This is known as the Soudanese
method of extraction. Care should be taken not to
break the worm during removal, as disastrous conse-
quences may follow rupture.

The guinea-worm is widely distributed in tropical
and sub-tropical countries, but occurs most frequently
in Africa, Southern Asia, India, and Brazil. In places
where this parasite is known all water used for drinking
purposes should be boiled, and no uncooked vegetables
should be eaten. Also, since the possibility of the
worm entering the skin has not been definitely excluded,
baths should be taken in clear water only.

Known quite generally as the jUaria
B sanguinis hominis lives, as its name

implies, in the blood. Only the embryos,
however, are really present in the blood, the adult
worms having their habitat in one of the larger lymph

ANIMAL PARASITES. 119

vessels of the trunk. The mature parasites measure
from 83 millimeters (male) to 155 millimeters (female)
long, by 5 millimeters broad; the embryos are about
the diameter of a red blood-corpuscle in thickness and
about 30 times as long. This filarium is widely dis-
tributed, being found in the Southern United States,
South America, India, China, Japan, West Indian
Islands, etc.
The most important lesions resulting from the para-

O

Fig. 7. — ^Larval filaria hancrofti in blood. (Coplin.)

site and its embryos are those due to obstruction of
important lymph channels, which leads to a hyper-
plastic condition of the tissues of the parts aflFected.
On account of the huge enlargement of the parts, and
their peculiar varicose appearance, the disease is called
elephantiasis. The disease is never general, aflFecting
only either one or both legs, the scrotum (lymph scro-
timi), one or both labia, or a breast, etc.

I20 INFECTIOUS AND PARASITIC DISEASES.

Filarial embryos are looked for in fresh blood-
specimens the same as for malaria. There is a peculiar
periodicity about their appearance in the peripheral cir-
culation in the respect that they are found only at night.

Mosquitoes (culex) act . as intermediate hosts for
these filaria, abstracting the embryos from one person
and inoculating them into others. Persons suflFering
from filariasis are therefore not only a danger to them-
selves (on account of repeated inoculations) but to
others who may chance to be bitten by infested mos-
quitoes. In man again, the embryos mature, reach a
lymph vessel and there begin producing fresh embryos.

HcBmatochyluria is also caused by the flaria san-
guinis hominis. However, both this and elephantiasis
may be due to other causes.

Besides the above filaria, two others are recognized
by Manson, the Filaria diurna, the embryos of which
are foimd in the peripheral circulation during the day-
time only, and of which Manson suspects the Filaria loa
to represent the adult worm, and the Filaria perstans,
which the same author regards as the cause of a skin
eruption, craw-craw, found on the west coast of Africa.

A round worm of whitish or yellowish
Filaria Loa. color, from 20 to 40 millimeters (i and 2

inches) in length by 3 to 5 millimeters in
breadth, and found in the subcutaneous tissues, usually
of the face, but more especially in the conjunctivae.
Its movements in the skin, which are visible to the eye,

ANIMAL PARASITES. 121

cause considerable itching and pain, and in the eye-
lids inflammation and swelling. The parasite is indig-
enous to the western coast of Africa, and is of common
occurrence among the natives.

Both Americans and Europeans (chiefly missionaries)
have harbored jUaria loa after a residence in Africa,
and had them removed on returning to their respective
countries. Ward records the history of seven such
cases observed by ph3rsicians in various parts of the
United States, and has studied the specimens in a few
of them. He concurs with Manson in the opinion that
this filaria is a more mature form of the Filaria diurna.^
Removal of the parasite is accomplished by grasping
the worm firmly through the cuticle with forceps, and
cutting down upon it with scissors or knife. Care
should be taken that the skinhold on the worm is not
loosened until the worm itself is grasped, or it may
escape into the deeper tissues. The embryos of the
worm are believed to be inoculated into man by an
intermediate host, either a fly or mosquito. Prophy-
laxis in filaria loa is the same as for malaria.

The trichocephalus dispar {whip-worm) is
TRicmuRis a common parasite of the intestinal tract,
TRicmuRA. particularly the caecum. Universally dis-
tributed, it apparently does little or no
harm, although anaemia and diarrhoea have occasionally
been ascribed to its presence. Both the worm and its

* See Bui. Univ. of Neb., January, 1906.

122 INFECTIOUS AND PARASITIC DISEASES.

eggs are quite characteristic and easily recognized.
The living worm is seldom found in the stools.
Strongy- Occurs in the stools in endemic diarrhoea
LoiDEs of hot countries (Cochin-China). Has also

Intestin- been described in this country by Thayer.
ALis. Infestment only produces symptoms when

the parasites are present in large numbers. Eggs of
the parasites are probably ingested with drinking-water.

Trichiniasis, as infestment of the body
Trichinella with the trichinella spiralis is
Spiralis called, is brought about by eat-
(Trichina ing insufficiently cooked or raw
spiralis). meat (usually pork) which con-
tains the larval forms. The
yoimg embryos which are set free in the
stomach by digestion of their capsules, reach ^^^ g — r^i-
maturity in the small intestines in about chiuns tHchi-
three days. The females then give birth size' ii, male;
to innumerable larvae — 8,000 to 10,000, it is fpysonO ^ ^ ^
said — which are discharged directly into the
lymph stream, whence they finally reach the blood and
are distributed to their points of election, the voluntary
muscles. Here the young worms become encysted,
i.e., each one arranges itself in a spiral, and becomes
surrounded by an inflammatory capsule. It is to the
encapsulation of the embryos, together with a poison
which is possibly set free by them, that the symptoms
of trichiniasis are due.

ANIMAL PARASITES. 123

The female trichinella is a fine thread-like worm
measuring from 3 to 4 millimeters long; the male is
smaller, measuring 1.5 millimeters, and has two little
appendages from the hinder end (bifid).

Practically all domestic
animals may act as host
for the trichinella, but in-
festment in man is seldom
due to any other meat be-
sides pork. The disease
occurs wherever pork is
eaten. In suspected cases
the worms should be
sought in the stools, or
embryos may be obtained
by removing a small frag-
ment of the pectoral or
biceps muscle under local
anxsthesla.

If pork or other meats
re suspected of contain-
ing tnchinella, the latter '^^B"'"')
may be easily demonstrated by treating a thin section of
the tissue with a solution of caustic potash (i-io) and
viewing it with the low-power lens of a microscope.

Should the specimen be very fat, treat it with ether
or dilute acetic acid first and then with the caustic
potash solution.

INFECTIOUS AND PARASITIC DISEASES.

ASCAEIS
LUMBRI-
COTDES.

This, the common round worm of children

makes its home in the

small intestines of man.
It is the commonest
human parasite, being universally dis-
tributed.

The worm, which is from 4-8 inches
(male) to 7-1 2 inches (female) in
length and pointed at both ends, is
transversely striated and exhibits four
longitudinal bands. It has a yellow-
ish-brown or reddish color. Usually
the host harbors only a few adults —
but there may be many. The eggs of
the worm, and occasionally an adult
parasite, are passed in the stools.

The migrations of these worms are
remarkable, as they may crawl into
the stomach and be vomited, or pass
the whole length of the oesophagus
into the nose, the middle ear, or the
mouth. They have frequently been
discovered in the gall-bladder, and
have also been known to cause intes-
tinal obstruction. Ordinarily symp-
toms of their presence are absent, or
are hmited to minor nervous disturb-
ances, such as irritability, picking at

f

Fig. 10. — Ascarii
lumbricoides: to left,
male in lateral aspecl ;
to right, female, ven-
tral aspect, natural
size. (Tyson after
Raillict.)

ANIMAL PARASITES. 125

the nose, and nocturnal grinding of the teeth. How-
ever, convulsions, epileptiform attacks, vertigo, and
chorea, have also been described. The worms are
quickly expelled by santonin (gr. J-i for child, gr. 1-2
for adult) given either alone and followed by the same
quantity of calomel or a saline purge; or equal quanti-
ties of santonin and calomel may be given night and
morning until bowels are well moved.

The parasite is contracted from water or food con-
taining the ova, so that a host may not only convey the
parasites to others, but may re-infect himself.

Also known as the pin-worm^ thread-worm^

OxYURis ^^^ seat-worm, has its habitat in the caecum,

colon and rectum. It is a very common

human parasite the world over. Foimd

particularly in children, there is no period in life when

they may not be contracted.

As its name implies, it is a small thread-like worm
from 4 millimeters (male)-io millimeters (female) in
length, and is readily seen on examination of the
stools. The eggs, which are also passed in the stools,
are probably taken into the stomach with water or
salads, or directly from the contaminated hands of the
host.

The symptoms occasioned by the parasite are irrita-
bility, nocturnal restlessness, and itching, particularly
about the anus. The worms may leave the rectum at
night and deposit eggs on the perineum— or in females

136 INFECTIOUS AND PARASITIC DISEASES.

may invade the vagina. They have been found in the
appendix.

Treatment is with santonin as in infestment with
Ascaris Lumbncoides, and the daily irrigation of the
colon with strong salt water. These measures, how-
ever, do not always effect expulsion, and the worms may
be parasitic for years despite every efEort to dislodge
them. Self-pollution may be responsible in some cases,
at least, for the obstinacy with Vhich they resist removal.
The Uncinaria duodenalis (strongylus
Uncinaria duodenalis, anchylosioma dtiodenaUs, hook-
DuODENAiis. worm), is a parasitic worm which has its
habitat in the duodenum, the jejunum,
and occasionally the colon. The condition to which

Fig 13 — Tail with eipanded
I. — Tail, with expanded bursa, bursa otmaleufictnanaAmericona.
ia duodenalis. (Tyson.) (Tyson)

it gives rise is known under as many names as the
parasite, viz., anchylostomiasis, uncinariasis, hook-
worm disease, Egyptian chlorosis, etc.

ANIMAL PARASITES. 127

Iiifestment is common in both the Old and the New
World, although two distinct species of worms are con-
cerned; the Old- World Uncinaria duodenalis, and the
New- World Uncinaria Americana. The disease, which
is characterized by a grave anaemia, and in untreated
cases has a large mortality, is widely distributed in
tropical and sub-tropical countries. There are also
endemic foci in temperate climates. The island of
Porto Rico seems to sufifer more from this parasite
than any other country, one-fourth of the total deaths
in a single year (1903) having been ascribed to it. The
anaemia prevalent in our own Southern states has been
demonstrated by Stiles to have the same origin. In
temperate climates, infestment is common in tunnel-
workers and miners.

The adult worms, which measure from 8-10 milli-
meters (males) to 12-18 millimeters (females), live in
the small intestines. From a bending backwards of
the anterior extremity the name hook-worm has been
derived. They are blood-sucking parasites, and by
means of teeth and a powerful sucking apparatus attach
themselves to the mucous membrane lining the gut.
A few parasites do not cause symptoms, but where their
numbers are large — in many cases 1000 or more — the
drain upon the body is considerable, often ending
fatally. In children their presence interferes with
development. Only the eggs of the parasite appear in
the stools, where they are usually present in enormous

I

iiS INFECTIOUS AND PARASITIC DISEASES.

numbers. As they are voided in process of segmenta-
tion, they are easily recognized by examining a drop of
feces with the ordinary powers of the microscope.
Hatching takes place in water or moist earth, situations
in which the embryos may live for months. The larval
uncinaria are taken into the body in the drinking-water,
or from the hands which have been soiled with earth
containing them.

Another mode of entrance is through the skin. The
manner in which they get Into the bowels is interesting.
From the skin the embryos are carried to the right side
of the heart and to the lungs. Here they escape from
the pulmonary vessels into the air-spaces, travel up the
bronchi and larynx into the oesophagus, and by swallow-
ing find their way into the stomach and intestines. It
is believed that the tropical skin affection known as
"ground-itch," and which is usually confined to the
ankles, is caused by the entrance of embryo uncinaria.
In the duodenum and jejunum full development is
attained, with subsequent reproduction of eggs. The
cycle, it will be observed, is direct,

The diagnosis rests upon the presence of eggs in the
stools. Stiles calls attention to the value of the blotting-
paper tests for blood when a microscopic examination
cannot be made. Reference is made to this test in the
chapter dealing with the examination of the secretions
and excretions.

Expulsion of the parasites is ordinarily successfully

ANIMAL PARASITES. 129

accomplished by giving, after a day of fasting, two
doses of thymol (gr. 30 each) in brandy or whisky two
hours apart, and two hours later a dose of castor oil.
If ova are still present in the stools a few day^ later, the
same treatment should be repeated.

Prophylaxis consists in not going bare-footed in
regions where the disease prevails, in boiling the drink-
ing-water, and in scrupulous cleansing of the hands
before meals. The stools of persons harboring the
parasites should be disinfected, and treatment instituted
in all cases where eggs are found whether symptoms
of the disease are present or not.

FLAT WORMS.

Parasitic flat worms are divided into two orders,
the trematodes or flukes, and the cestodes or tape-
worms. The former are distinguished by possessing a
partial digestive canal but no anus; the latter by a
complete absence of alimentary tract.

TREMATODES.

Distomiasis is the name applied to diseases resulting
from trematodes or flukes. Flukes are mostly small,
flat, leaf-shaped worms, which, as above noted, are
without anal orifices. Usually they possess one or
more suckers and occasionally booklets. They are
mostly hermaphroditic. Only the more important
varieties will be referred to.

INFECTIOUS AND PARASITIC DISEASES.

This, the Asiatic lung fluke, is of frequent
n^*t^°™^^ occurrence in human beings in China,
Japan, Korea and Formosa, causing the
disease known as pulmonary distoraiasis
or parasitic hjemoptysis. In the United

ANIMAL PARASITES. 131

length by 4-6 millimeters in breadth, and almost as
thick as broad. It is of a pinkish or reddish-brown
color. Usually the worm inhabits the bronchial tubes
of the animal upon which it is parasitic, but it has been
found in other situations also.

The symptoms to which it gives rise are rarely serious,
consisting of a chronic cough, and a rusty (sanguineous)
expectoration. Occasionally there is severe haemopty-
sis. Ova of the parasites are found in the expectora-
tion, and from these the diagnosis is made. Nothing
is known of the manner of infestment. Stiles sounds a
note of warning by pointing to their presence in domes-
tic animals.

LIVER FLUKES.

A number of liver flukes occasionally parasitic in
man have been described, of which one, and possibly
two, are of considerable importance.

Foremost is the Chinese or Japanese liver

pisTHOR- Q^^Q Opisthorchis sinensis, which is com-

Sinensis ^^^ ^^ China, Japan, and India. This

species is somewhat larger than the lung
fluke, being from 10-20 millimeters in length by 2-5
millimeters in breadth. As its name implies, it has its
seat of election in the liver, particularly the gall-pas-
sages, and gives rise to digestive disturbances, jaundice,
anaemia and dropsy. Years elapse between the time
of infestment and death. The diagnosis rests on the
presence of eggs in the stools.

132 INFECTIOUS AND PARASITIC DISEASES.

Beyond the fact that the eggs will develop to a certain
stage in water, nothing is known of the life-history of
this parasite.

Another liver fluke, common in sheep ; it is
Fasciciola also found in cattle, hogs, horses, and
Hepatica. ruminants in general. They produce in

sheep the so-called ' ' liver-rot. ' ' The worm
is a frequent parasite of animals in the United States.
Few cases, however, have been described in human
beings an)rwhere. The symptoms of infestment are
the same as in the other liver-fluke diseases already
described. The eggs of the parasite are found in the
stools. They are taken into the body probably in
water or upon raw salads.

This fluke is distinguished from other
ScmsToso- flukes already described by the fact that it
MTO H^MA- jg ^^^^^ j^ ^^^ y^^j^ particularly the por-

(Bilharzio *^^ ^^^^ ^^^ ^^^ branches. The disease
haematobia). which it causes, haemic distomiasis, Bilhar-

ziosis, or Egyptian haematuria, is prevalent
in Egypt, Africa, Persia, and the west coast of India.
It is said to occur in Cuba and Porto Rico also. Im-
ported cases are occasionally encountered everywhere.

In this fluke the sexes are separate. The eggs of
the parasite are the chief cause of mischief.

Symptoms of the disease are practically always
referable either to the bladder or rectum. In involve-
ment of the former viscus there is pain and burning over

ANIMAL PARASITES. 133

the supra-pubic region, irritability of the bladder, and
haematuria; in the latter, straining, tenesmus, and the
passage of blood and mucus. Ova are found in either
discharge, and the diagnosis rests upon their discovery.
Haemic distomiasis is a very important disease, as its
prevalence in many countries attests. Since communi-
cation with the East has become closer, a larger number
of imported cases have been reported. Dr. Stiles is
of the opinion that the United States will sufifer from
importation of parasites by troops returning from foreign
service and by travelers. The same author leans to
the belief that a snail acts as intermediate host for the
haematobium. If this be true, before the disease can
become endemic in the United States depends upon
'^ whether there exist in the United States species of
snails which can serve as intermediate hosts, and
whether these snails actually become infected by persons
harboring the parasite." Furthermore, if snails act
as intermediate hosts, then "cases of infection are
more likely to occur in rural districts than in cities,
and country physicians will be more likely to encounter

them^^ (Stiles).

CESTODES.

Cestodes or tape-worms are flat, segmented, ribbon-
like worms which have their habitat in the smaU mtes-
tines. They are characterized by a complete absence
of a mouth or digestive tract, and nourishment is
maintained entirely by absorption of nutrient material

134 INFECTIOUS AND PARASITIC DISEASES.

through the external covering. Depending upon the
species, the length of the wonn varies from a few inches
(dwarf tape-worm) to thirty or more feet (Bothriocepha-
tus latus). The adult worm consists of a head or
scolex, a thin thread-hke neck, and a body made up
of conjoined segments or proglottides. The head is
provided with suckers, in some species with booklets
also, by means of which the worm fastens itself to the
gut and maintains its position. It is on account of these
organs of attachment that the head is often difficult
to dislodge. Yet it must be expelled if a cure is to be
effected, since growth of the worm proceeds entirely
from the head end. The neck is unsegmented. Behind
the neck, the first segments are short and narrow, but
they gradually increase in size until the adult dimensions
are attained. The size of a segment is related to its
maturity.

In each proglottidls are found both sexual elements
in various stages of development. The more mature
segments are situated towards the distal end of the
worm and contain numerous ova, in each of which is an
embryo worm. Segments containing embryos are said
to be "ripe," and it is these which are constantly sep-
arating from the less mature and being shed in the
I stools. When they appear in the stools, two or more
segments are usually found attached together. These
may have the power of independent locomotion, a

ANIMAL PARASITES. 135

that they constitute a whole worm. When eggs con-
taining embryos are taken into the stomach of a suitable
host — ^usually in water or food — the embryos are liber-
ated, pass into the small intestines, the walls of which
they penetrate, and reach various tissues and organs,
the liver, muscle, brain, etc. Here they become encysted
and develop into cysticerci or "bladder-worms," that
is to say, they are converted after a few months into a
C3rst full of fluid. From a point on the inner wall of
each cyst a little bud projects, which in time is converted
into a tape-worm head or scolex, and a sac containing
it. A cyst containing a tape-worm head is known as a
^^ measles ^^ or cysticercus cellulosce. Flesh of this kind
is said to be measled. As C)rsticerci the parasites live
indefinitely until the flesh containing them is eaten by
another host, in the intestinal tract of which they then
grow into mature tape-worms. The cycle of the cestodes
is therefore in two hosts, with possibly a short interval
between spent in water. Tape- worms parasitic in man
belong to two orders — ^the Tcmiadce and the Bothrio-
cephalidcB. The first occurs in man either as " measles "
or as tape-worms, the latter only as tape-worms. Ten
species of tape-worms have been described, of which
three, only, are known definitely to be connected with
food. These are Tcmia saginata (T. mediocanellata)
due to measly beef, Tcmia solium, to measly pork, and
Bothriocephalus latus, to infested fish, such as sturgeon,
pike, perch, and salmon.

1^6 INFECTIOUS AND PARASITIC DISEASES.

The unarmed or beef tape-worm is the com-

T«NU SAGI- ^ r ,. f 1 ■ A

,„ monest of tape-worms found in Amenca.

NATA (T. me- ^

diocanellata) -^* inhabits the small intestines. In length
it varies between 9 and 24 feet. The head,
which measures about 2 millimeters
in breadth, is pyriform and with-
out booklets, but contains four
cup-shaped suckers on its ventral
aspect. The ripe segments are
from 17-18 millimeters in length
by 8-10 millimeters in breadth-
Cattle act as intermediate hosts,
and eating uncooked beef contain-
ing the cysticerci gives rise to in-
festment in man.

Both eggs and proglottides are
passed in the stools. The proglot-
tides are easily recognized and are
diagnostic of an adult worm.
S)Tnptoms due to tape-worms may
be absent entirely, or may consist
Fig. 14.— renin medi- of occasional colic and an abnormal

xanellaia. (Gould, after ..

Leuckan.) appetite.

Or pork tape-worm is a rare parasite in

Ta;NiA the United States. In Europe it is not

Solium, uncommon. It is a smaller cestode than

tania sagmata; the head measures less than

the head of a pin (0.6-1 millimeter) ; the ripe proglottides

ANIMAL PARASITES. 137

are 10-12 millimeters long by 5-6 millimeters broad;
and the length of the whole worm varies between 6
and 9 feet. The head is provided with four suckers,
and a double row of booklets, a fact from which has
arisen the name "armed tape-worm."
The ingestion of insufficiently cooked
"measled" pork is responsible for
infestment.

Usually only a single worm is fomid
in one individual, but more may occur.
Tcenia solium is a much more danger-
ous parasite than tania saginata be-
cause man may be the host for both
the adult and bladder-worms ; on this
account a person that harbors this
parasite should be especially careful
not to carry a soiled hand to the mouth
or allow it to contaminate food.

The adult worm per se gives rise to
few or no symptoms, but if its eggs
are ingested, the embryos, besides be-
ing distributed to muscles, may also ^

. , , , . . ■" Fig. i^.—Dibethrio-

nnd lodgment in important organs, ctphaius latus. (Tyson,
e.g., the brain, eye, liver, etc. after Leuckart.)

DiBormiio- '^^^' ^^^ longest tape-worm met in man,
cEPHALus '^ commonest along the Baltic Sea, in
Latus (Both- Japan, and in Switzerland. It is also said
riocephalus to be of frequent occurrence in Munich,
latus). The parasite measures from 6 to 30 feet

138 INFECTIOUS AND PARASITIC DISEASES.

or more in length. The head is narrow transversely
(0.71 millimeters) and differs from the /(Ewta in having
two lateral grooves or bothridia as suckers. There
are no hooklets.

Fish act as intermediate hosts for the measles, stur-
geon, pike, perch, etc. In the stools of a person harbor-
ing the bothriocephalus, eggs characteristic of the worm
are found in lai^e numbers. These find their way
into water, when the embryos escape
from the eggs and lead a free existence for
an unknown period. They are finally
swallowed by their fish-hosts, from whom
man in turn acquires the adult worm.

This is a dog tape-worm
DiPYLmnjM which is widely distributed.
Caninum Its intermediate hosts are the
(tffinia cu- d(^-louse and flea, and the
cumerina). ordinary flea of man {pulex ,i^°„'^a~£(fX

irritans). Its chief interest {}f?-^}^' =^'*^''

Wetnlaod.)

in human pathology is that children occa-
sionally harbor the adult worm, contracting it from
the dog's louse or flea.

Known also as the "dwarf- tape- worm,"
Hyueno- is a short cestode parasitic in rats,
LEPsis Nana, mice, and man. The intermediate host

is not known. The worm is known
throughout Europe, and lately many cases have been
reported from the Southern United States (Stiles).

ANIMAL PARASITES. 139

Is found principally among the very poor. When many
worms are present they may give rise to severe S)niip-
toms, and may even be a cause of death. The adult
worm only measures from 10 to 15 millimeters in length.
The head is provided with four suckers, and also with
a single row of booklets.

VISCERAL CESTODES.

Whereas adult cestodes which inhabit the alimentary
tract occasion as a rule unimportant symptoms, local-
ization in various organs of the "measles" or bladder-
worms may be a very serious event. Fortunately
man may act as host for thejarval forms of only two
tape- worms, viz., '2%wia soliut^ and TcBnia echinococ-
cus; and more fortunate still, such infestment is not
common.

Or "measles," it will be remembered, is
the embryo stage of Tcmia solium or pork

^ tape-worm. Man usually harbors the adult

Cellulosa. ^ . , ^ , "^. . - .

parasite, but from the mgestion of ripe

eggs he may also become the host of the
larvae. The s)niiptoms of infestment depend on the
localization of the cysticerci. Unless a vital organ is
involved they may be trivial; but in the brain, cord, or
eye, serious mischief results. In a few cases the pres-
ence of subcutaneous nodules excited suspicion, which
was confirmed by removing one and examining with the
microscope.

I40 INFECTIOUS AND PARASITIC DISEASES.

The adult form of this cestode is found in
TAENIA Ecm- the dog, wolf, jackals, etc. Man harbors
Nococcus. the larvae. Infestment is practically only

encountered where dogs are kept in close
relationship with their masters, as in Iceland and
Australia. In other countries sporadic cases are

occasionally reported, usu-
ally in foreigners, who prob-
ably contracted the disease
elsewhere. The adult worm
/f ps jfffiHBPL is a tiny cestode from 2.5-5
V? Kl ^S^V miUimeters in length, with
V 1^1 ^Bffll^^ a head provided with four

cup-shaped suckers and a
double row of booklets.
When man ingests the ripe
ova of this worm, visceral
infestment (Echinococcus
disease) ensues. Localiza-
tion may be in any organ,
^f\ 'iT^f?^ echinococcus: j^e liver, lungs, kidney,

a, adult; o, head from ecninococcus ' *^ ' ^ •' '

cyst. On left a detached hooklet, etC. Huge CyStS enclosing

as seen in fluid from cyst. (Coplin ,

and Sevan, after Leuckart.) nUmerOUS Other CystS axe

stages in the development of
the embryos, countless numbers of which may develop
from a single egg, thus differing from the cysticercus of
other cestodes in that a single egg gives rise to only
one embryo.

ANIMAL PARASITES. 141

INSECTS-

Parasitic diptera, or two-winged flies,
Parasitic occupy an important position in relation
Diptera. to disease, since various species of this

order are harmful to man in a number of
ways. Besides the inconvenience that large numbers
of diptera cause by their bites (e.g., jigger-flea, bed-
bug, etc.), incidents which are not always unattended
with danger to health and life, others of this order may
burden the economy with their young. The latter is
accomplished in one of two ways: i. By depositing
their eggs or larv« either upon wounds or in cavities
(of the body) leading to the exterior, such as the nose,
ears, vagina, etc., or by placing them beneath the skin.
In all such instances the larvae feed in the places depos-
ited and cause such annoyance as their growth and
migrations excite.

2. In other instances the eggs or larvae are taken
into the intestinal tract with food or drink, and are
voided in the feces.

Myiasis is the technical term used to denote the con-
dition in man in which the larvae of diptera are
parasitic; and depending upon whether the larvae
(maggots) are upon the exterior or interior of the body
it is designated external or cutaneous, and internal
myiasis, respectively. Where maggots are found in the
stools care must be taken to exclude the possibility of
flies having had access to the stools, since living young

142 INFECTIOUS AND PARASITIC DISEASES.

may be deposited upon them by the latter. Mosquitoes
belong to the two-winged flies or diptera, a fact which,
if previously unknown to the reader, will now suggest a
third way in which these insects are harmful, viz.,
by acting as secondary hosts for other human parasites.
Because the relationship of mosquitoes to malaria,
yellow fever and filariasis, has already been sufficiently
elucidated, additional reference to them here would be
superfluous.

Finally, diptera may accidentally convey disease-
agents either upon their bodies or in their feces, factors
in disease that have also already been considered else-
where.

To the (Estridae or bot-flies belong those species
the larvse of which are parasitic upon man.

Dermatobia noxialis Goudot. This fly

(EsTRus is a common pest in tropical America.

HoMiNis. Known under numerous names, viz., Ver

macaque (Cayenne and Mexico), Ura
(Brazil), Torcel (Costa Rica), its larvae are deposited
upon exposed portions of the body, whence they work
their way into the subcutaneous tissues. Here, if
undisturbed, they complete their growth and issue when
mature from the abscesses to which their presence gives
rise. The larvae are quite characteristic in that one
end (head) is quite large in comparison with the other,
and there are minute spines on segments two and
three.

ANIMAL PARASITES. 143

The larvae of this fly are also common
Dermatobia ites. They are distinguished from

CyANTVEN- jo

TRis ^'^ larvae of noxialis by having no fine

spines on segments two and three, but a
row of strong hooks projecting from the hind margin of
segments four to seven (Blanchard).

Compsomyia macellaria is known through-
CoMPsoMYiA out America, but cases of myiasis due to its
Macellaria. larvae are only common in the warmer por-
tions. The larva is known as the "screw
worm." The bot-fly itself has a reddish-brown head,
a bluish-green thorax and abdomen, and the thorax
is further distinguished by three longitudinal black
stripes. The eggs are deposited upon the skin, where
they quickly hatch, and the larvae then work their way
into the subcutaneous tissues and produce abscesses.
But here and there eggs are laid in the nostrils of individ-
uals asleep. In this situation the growing worms pro-
duce a terrible state of affairs, since in their burrowings
they may destroy all the tissues of the soft palate and
posterior pharynx, and may even lay bare the hyoid
bone. As many as three hundred maggots have been
discharged from the mouth and nose of a single indi-
vidual.

This, the common blue-bottle or flesh-fly,
Sarcophaga occasionally lays its grubs in old ulcers,
Carnaria. which then have the appearance of "liv-
ing," that is to say, the maggots are as

144 INFECTIOUS AND PARASITIC DISEASES.

actively motile as when ordinarily seen in decomposing
material. Solutions of bichloride of mercury (i-iocx))
quickly rid the host of these parasites.

Or common flea is a minute red or dark-
PuLEx brown insect which is only parasitic upon

Irritans. man in countries where it is present in

great numbers. It is particularly trouble-
some in hot countries. Its eggs are not laid
in the skin, but in cracks of floors, sawdust
and dust. Its bites are irritating and may
cause wheals (hives).

The sand-flea, "jigger," "jig-
Sarcopsylla ger-flea," "chigoe" or "chique"
(pulex) is a more serious parasite than

Penetrans, the common flea. The impreg-
nated female burrows into the skin to breed ^ ^^- l^- —

Larva of pu^

her young, which are very numerous. Favor- lex irritans,
ite situations are the lower extremities and
feet, particularly beneath the nails of the toes. Painful
swellings, abscesses, and ulcers often result. The in-
sect is principally found in Central and South America,
and South Africa. The fleas may be picked out with
a needle, but one should be careful to extract them
whole since distressing sores may otherwise result.

Bed-bugs are true cosmopolitans, being
CiMEx found the world over. The body is thin

Lectularius. and flat and oval in outline. Its color

varies from a grey to a dark reddish-brown.

ANIMAL PARASITES. 145

It has a characteristic odor. It is entirely nocturnal in its
habits, sucking blood at night and hiding in the cracks
of the bed, of cupboards, etc., in the daytime. This
pest can usually be eradicated from beds, etc., by
washing with bichloride of mercury (1-500), pure
carbolic acid, or kerosene.

Where the room or building is so badly infested that
these measures do not suffice, fumigation with sulphur

2, back view.

(i pound to each 1000 cubic feet of space) is a reliable
measure. No moisture is required as in the case of
fumigation against bacteria, so that fabrics are not
necessarily injured, and the exposure need not be longer
than two or three hours.

Pediculi or lice are found chiefly in two
Pedicdli. situations on the body, in the hair of the
head (pediculi capitis), and in the pubic
hairs (pediculi pubis or inguinalis).

146 INFECTIOUS AND PARASITIC DISEASES.

Another louse is found in the seams of the clothing
(pediculus vestimenti).

This is usually found in uncleanly persons,
Pediculus but may accidentally invade the fastidious.
Capitis. A peculiarity of this louse is that its color

varies with its hosts, that is to say, it is

Fig. 21. — Ovum
of head-louse glued
tohair;X 70. (Ty-
son, after firaun.)

Fig. 22. — Pediculus capitis, X 15*
(Tyson, after Braun.)

light grey on a Caucasian, yellowish or dark-grey on the
Mongolian, and black on the Negro. The individual
lice are difl&cult to find, but their presence is assumed
by finding eggs or "nits." These are little oval glisten-
ing bodies attached to the hairs. Treatment consists
in cutting the hair and washing with kerosene.

ANIMAL PARASITES.

147

This louse is commonly known as the
Pediculus "crab-louse," from its resemblance to a
Pubis. crab. Its nits are attached to the hairs

quite close to the skin. Oftenest the nits
are only found in the pubic or adjacent hairy parts,
but they may be present on the hairs of the chest, the
axillae and even on the eye-brows.
Where the insect bites, a minute
slate-colored lesion results which
itches intensely.

The parasite is ordinarily con-
veyed from person to person
during sexual congress, but sleep-
ing with a person harboring the
parasite may be the means of
contracting it.

The "toilet" has also been

held responsible. fi^. 2^,^Pedicidus vesti-

Both the parasite and its nits ^*-;X io» circa. (Tyson,

* after Braun.)

are quickly killed by smearing

the afiFected parts with mercurial (blue) ointment.

The clothes-louse makes its home in the
Pediculus seams of the clothing and underwear. Its
Vestimenti. bites cause itching. Scratch-marks over

the back and around the waist-line usually
evidence its presence. Boiling or steaming the cloth-
ing, or hot ironing, are easy means of ridding a person
of the parasite.

148 INFECTIOUS AND PARASITIC DISEASES.

Or Sarcoptes hominis, the itch-mite, is
AcARus another parasitic insect which forms bur-
ScABiEi rows in the skin. Only the female pro-
(itch-mite). duces lesions, the purpose being the depo-
sition of her eggs. The portions of the
body selected are those where the skin is thinnest, viz.,
in the webs between the fingers, at the bend of the elbows,
in the axilla, upon the penis, at the bend of the knees,
and about the ankles. In children, burrows may be
found over the whole body.

Where the mite penetrates the skin a little vesicle is
formed, and the direction of the burrow is indicated
by a rough, dark line. However, because intense
itching always accompanies the insect's activity, the
only lesions discoverable may be scratch-marks. Itch-
ing is most complained of at night, the period when the
female is active. The itch-mite is so small that it is
seldom seen and the diagnosis of its presence is made
entirely from the character and situation of the lesions.
It is of historical interest that the first Napoleon was a
sufferer from "itch" for ten or twelve years until cured
by the physician Couvisart.

The parasite is contracted by intimate contact with
a person who harbors it.

Eradication of the mite is easily accomplished by
scrubbing the lesions with soap and a soft brush,
followed by rubbing Balsam Peru well into the bur-

ANIMAL PARASITES. 149

rows. Sulphur ointment, although highly recommended,
is not nearly so efficacious.

The harvest-mite, which is active during
Leptus July and August, is a red-colored larvte

AoroMNALis. of a variety of Trombtbidm. The latter '

lives on grasses, bushes, and grain, and its
larvae alight on man as occasion offers. The red
papules and wheals which it produces are usually

Fig. 35. — Female ot
Ixodes rieimu, gorged
full, ventral and dorsal
surfaces, f. (After Pa-
genstecher.)

situated on the ankles, but may also be found on other
parts of the body.

The wood-jack or wood-tick is a fairly

Ixodes large yellowish-brown tick, with a black

Ricmus. head and a leathery body. It is common

upon grasses and bushes, and from these

places gets upon man and beasts. It is a blood-suck-

ISO INFECTIOUS AND PARASITIC DISEASES.

ing parasite, burying its head and sometimes almost its
whole body in the integument.

In various localities, e.g., Africa, and Montana, U. S.,
fevers are described which are believed to be due to
the bites of ticks (tick-fever, Ixodiasis); the evidence
in favor of such relationship, however, is contradictory.

CHAPTER VI.

AVENUES OF EXIT OF INFECTIOUS AGENTS
AND PARASITES FROM THE BODY.

The source of every infectious disease is always
another infectious disease, that is to say, the infectious
agent has come directly or indirectly from some other
person. The spontaneous generation of disease is no
longer believed in, no more than is the spontaneous
generation of life from lifeless matter. It is true that
we cannot always trace the connection between suc-
cessive cases of the same disease, but such instances
are few in comparison with the number in which the
relationship can be proven. However, what has defi-
nitely been determined is the manner of exit from the
body of micro-organisms in practically all of the infec-
tious diseases of both known and unknown origin.
This, from a sanitary standpoint, is of surpassing
importance, because it permits of our destroying the
infectious agents at their source and when concentrated,
and thus give them no opportunity to be scattered, so
to speak, to the four winds.

It is self-evident that the communicability of a
disease bears a definite relationship to the nimiber of

151

IS2 INFECTIOUS AND PARASITIC DISEASES.

exits open to the causative agents, and that one disease
may, therefore, require greater precautions than another
to prevent its spread. In no field of public utility does
knowledge confer greater power than in sanitary
science, and in this matter of the exit of micro-organ-
isms from the body in disease we have the key to the
happiness of families, the prosperity of nations, and to
victory in wars. Moreover, it robs disease of its terrors
by suggesting protective measures which can be relied
upon to be entirely eflicient. If all of the infectious
agents were efficiently dealt with upon their exit from
the body, the various diseases to which they give rise
would in time become traditions; but until Arcadia is
attained this will not be done.

Sanitarians in order to work in an enlightened manner
must inform themselves of both the direct and indirect
sources of disease. A direct source is a diseased person,
so that this study begins with the elimination of infec-
tious agents from the body.

In general if may be stated that microbes leave the
body in six ways:

1. In the expectoration and nasal secretion.

2. In the stools.

3. In suppurations discharging externally.

4. From the skin.

5. In the urine.

6. From the blood through the bites of suctorial
(biting) insects.

AVENUES OF EXIT OF INFECTIOUS AGENTS. 153

Perhaps for completeness we should add that they
also make their exit in the lachrymal and vaginal secre-
tions ; but since there is no specific infection of the uterus,
and only a few of the conjunctiva, these exits are not of
sufiicient importance to justify an individual place in
our division of the avenues of exit. Furthermore, the
inflammatory conditions found in both these situations
might, with perfect propriety, be included under divis-
ion three.

The exit of a micro-organism from the body depends
upon the character and location of the disease, namely,
whether it be local or general. If a disease is localized
in such a portion of the body as communicates with the
exterior, the germs make their exit by that channel.
Thus, in inflammatory conditions of the lungs, the
offending microbes are discharged by way of the
passages that lead from them to the exterior. Similarly,
in infections of the uterus the infecting agents make
their exit by way of the vagina. But if, on the other
hand, the disease be general, that is, if the germs are
circulating in the blood, there may be various avenues
of exit, the urine, the skin, the sputum, the stools, and
sometimes, through the bites of insects.

Until quite recently, many diseases that we now know
to be general were looked upon as localized infections,
and therefore their agents were supposed to leave the
body by a single channel; but later researches have so
modified our views that we now believe there are very

f

IS4 INFECTIOUS AND PARASITIC DISEASES.

few infections in which the agents do not pass to the
exterior in a variety of ways. In those diseases which
are both local and general we find the roost numerous
avenues of exit, and in them it is possible for the infec-
tious agent to leave the body in every one of the six
ways enumerated above. An example of a common
disease in which the germs make their exit in at least
five ways, with a possibility of six, is furnished by
typhoid fever; in its incipiency the bacilli are localized
in the lower portion of the small, and the beginning of
the large intestines — but they soon invade the blood,
and by the latter are so distributed that they may be
eliminated in any of the secretions, in localized sup-
purations, and even by the bites of insects.

It often happens in the course of a disease that a
micro-organism will make its exit in some other way than
the channels ordinarily followed. This occurs princi-
pally when complications arise. Therefore, whenever,
in the course of an infectious disease, complications arise
in which there is a pundent or other discharge to the
exterior, these discharges should be regarded as fresh
avenues of exit for the specific micro-organisms.

To be sure, complications are often due to microbes of
a species different from the one causing the primary
infection; but in the absence of definite information to
the contrary, it is a safe rule to regard complications
as due to a migration to another part of the body of
the first invader. Thus, when an otitis media (midd)

AVENUES OF EXIT OF INFECTIOUS AGENTS, iss

eax disease) complicates diphtheria, or follows as a
sequela, the discharge from the ear is quite likely to
contain diphtheria bacilli; and in the same way the
purulent pleurisy (empyema) which often complicates
pneumonia, is usually an extension to the pleura of the
same micro-organism which caused the pneumonia.
Failure to give due regard to such considerations may
lead in certain of the infectious diseases to serious con-
sequences. Cases in point are otitis media following
diphtheria and scarlet fever, the discharges from the
throat and ear in either case remaining infectious for
weeks after recovery. The virus of scarlet fever is
especially tenacious in that way, and the records of the
disease are full of instances in which it has been con-
veyed by children with discharging ears after release
from quarantine.

The sputum is a prolific source of infection,

EXPECTOR- . I • .1 A. I.' J.

smce always m the expectoration, to a

ATION. -^ . ^ . '

lesser extent m the nasal secretions, are
discharged the microbes that give rise to inflammatory
conditions of the air-passages : the lungs, the bronchi and
trachia, the pharynx, the buccal and nasal cavities.
The inflammations in question may be primary in the
part affected, or secondary to an inflammatory process
elsewhere; or they may be part of a general disease.
An example of these various conditions is found in
pneumonia. Pneumonia may occur as an independent
infection; it may be secondary to an inflammatory

iS6 INFECTIOUS AND PARASITIC DISEASES.

process elsewhere, e.g., abscess of liver; or it may be
part of a general infection, such as t)^hoid fever.

In either the sputum or nasal secretions, or both, there- j

fore, are always found the infectious agents of diphtheria, j

influenza, scarlet fever, whooping-cough, mumps, rabies
(hydrophobia), pneumonia, tonsillitis, bronchitis, pulmo-
nary tuberculosis (consumption), tubercular laryngitis,
cerebro-spinal fever (secretion from nose ?) , measles, acute I

glanders (farcy) , actinomycosis, small-pox, leprosy (when
lesions are in nose), aphthous fever (foot and mouth dis-
ease,) echinococcus disease of the lungs, s)^hilis (primarily
in mouth), and t)^hus fever. Parasites — eggs of Para-
gonimus (Distoma) Westermaniiy in parasitic haemoptysis.

In the same secretions, but only when the respiratory
passages are also involved in the disease, are foimd the
microbes of t)^hoid fever, anthrax, bubonic plague,
actinomycosis, amoebic dysentery (in perforation of
abscess of liver into lung), syphilis (secondary), tuber-
culosis, leprosy, glandular fever ( ?), gonorrhceal stomat-
itis (child infected during parturition). In the vom-
itus, it is always to be remembered, such organisms as
cause intestinal diseases, or intestinal parasites and their
eggs, may be ejected. Thus cholera spirilla have been
found in vomited matter, as well as the eggs and even
segments of tape-worm.

As an avenue of exit for micro-organisms

Feces. the stools rank with the sputum in impor-
tance, if they do not surpass it. Besides

AVENUES OF EXIT OF INFECTIOUS AGENTS. 157

the fact that there are as many infectious processes
localized in the intestinal tract as in the air-passages, in
all of which the microbes are eliminated in the stools,
the germs of every general disease find their way into
the same passage by way of the bile. Furthermore,
a host of animal parasites are found sporadically in the
intestinal tract from which they or their eggs escape
by the natural passages. With one exception, i.e., in
consumption, the sputum is chiefly dangerous to those
immediately surrounding the patient; and even in this
disease the infection is mostly limited to dwellings,
factories, and oflices. The feces, on the contrary, are
the source of certain wide-spread infections at great
distances from the patient. This happens because the
micro-organisms causing these diseases are capable of
growth outside the body, particularly in water, and
because they are such as must be taken into the alimen-
tary canal to produce their effects.

In the matter of disposal of sewage we are still bar-
barians, if not criminals ; and the diffidence with which
the public views the pollution of its water-supply by
alvine discharges is a shame to our much vaunted
civilization. In fact, it is little short of miraculous that
a stop has not been put to it long ago, when one con-
siders the wide publicity given to the actual and possible
dangers of such a filthy and obnoxious practice. But
it is permitted to go on, with the result that there is
scarcely a city or town that does not drink water which

r

f

INFECTIOUS AND PARASITIC DISEASES.

is polluted by the sewage of another city ; and the former
places in turn pour their disease-carrying waste into
other rivers and lakes which supply the drinking-water to
still other communities. Thus is a "vicious circle" of
infection maintained. Is it surprising then that in this
way many diseases are spread, such as typhoid fever,
cholera and dysentery, and that the parasites of numer-
ous intestinal disorders are distributed to new hosts ?

But because the general public regards with indiffer-
ence the infliction of so much unnecessary suffering
and death is not a reason for physicians and nurses
taking the same attitude. Contrari-wise, since their
chosen fields give them a more intimate knowledge of
the many sources of disease springing from ignorance
and folly, and since they are thereby more Impressed
with the necessity of acting in advance of actual personal
and public calamity, it is part of their duty to humanity
to take the initiative in matters germane to their work.
Hence if the manner of sewer-dlsposal is a shame and
blot upon our civilization, the same strictures are appli-
cable to physicians and (especially) nurses if fecal
matter from a patient is infectious when disposed of.
Rendering the stools innocuous is a small yet Imperative
part of a nurse's daily routine, upon which the physician
should insist, and which the nurse should conscien-
tiously perform. At the bedside, better than anywhere
else, we command the situation in so far as the spread of
disease by sewage is concerned; and were disinfectioa

AVENUES OF EXIT OF INFECTIOUS AGENTS. 159

here always practised, we would be going a long way
towards balancing the harm that comes from the homi-
cidal practice of polluting our water-supplies with every
conceivable filth. Viewed from this standpoint, there-
fore, the stools assume in disease an importance impos-
sible to measure.

To disinfect the feces in every disease would be a
waste of time and money, besides being unscientific;
hence the reason for knowing those diseases in which
it is called for. The germs which cause the following
diseases are always passed in the stools : T)^hoid fever,
Asiatic cholera, dysentery (both amoebic and bacillary),
tuberculosis (when the bowel is affected, or the germs
are swallowed by the consumptive), bubonic plague,
cholera infantum, and anthrax; in small-pox, measles,
scarlet fever, and chicken-pox, although the etiological
factors are not known, there is no doubt that they are
expelled in the feces.

The parasites, and the eggs of parasites, found in the
stools are: Eggs and segments of various tape- worms,
eggs of round- worms (Ascaris Itdmbricoides), eggs and
worm of pin- worm (seat worm, Oxyuris vermicularis) ,
eggs and worms of uncinaria (in hook-worm disease.
Uncinariasis), worms of Strongyloides Intestinalis
(Endemic diarrhoea of hot countries), eggs of trico-
cephalus dispar, ova in Hepatica Distomiasis, ova in
Hcemic Distomiasis {Bilharziosis, Egjrptian haematuria),
larvae of common house-fly.

i6o INFECTIOUS AND PARASITIC DISEASES.

The urine is a frequent avenue of exit for
Urine. bacteria. They are found in it in practically

all diseases in which bacteria are circulating
in the blood (bacteriaemia, septicaemia), and also in
infections of the genito-urinary organs generally. In
all the eruptive fevers of known or unknown origin, the
urine should be regarded as infectious. With reference
to this secretion the profession learned a valuable
lesson in the case of typhoid fever; for a long time the
urine in this disease was entirely disregarded as a source
of infection, yet the last few years have taught us that
as an avenue of exit for the typhoid bacilli, it is infinitely
more dangerous than the stools. In the stools, the
putrefactive bacteria which are always present, are far
more vigorous than the typhoid bacilli, so that if typhoid
stools are allowed to stand a day or two, the typhoid
bacilli disappear. After recovery the bacilli are not
found in the stools unless the biliary passages are
infected. The urine, on the other hand, during the
whole course of the fever, constantlycontains the specific
bacilli, often in such numbers as to make it cloudy
(bacilluria) ; and what is far more important, the bacilli
may be present for months and years after recovery
unless means are taken to eradicate them. In view of
the latter fact it is a routine practice in many hospitals to
give during convalescence from fifteen to twenty grains
of urotropin daily, or to wash out the bladder once a
day, for several days after the temperature has reached

AVENUES OF EXIT OF INFECTIOUS AGENTS. i6i

the normal, with a solution of bichloride of mercury
(1-20,000).

The urine contains the infectious agents in the follow-
ing general diseases : Tuberculosis (also consumption ?) ,
pneumonia, typhoid fever, anthrax, bubonic plague,
influenza, malta fever, and in all other bacteriaemias or
septicaemias which are usually classed as blood-poison-
ing and are due to the streptococcus of erysipelas
(streptococcus pyogenes), or to the common bacterium
of suppuration (staphylococcus pyogenes aureus).

In local disease of the genito-urinary

In Urine organs the specific micro-organisms of the

IN Local following infections are found : Gonorrhoea,

Diseases, tuberculosis, S)^hilis (when chancer or

secondary lesion is in the urethra), in all

infectious diseases of the kidneys, bladder, etc.

Parasiies Eggs of parasites in HcEmic Distomiasis

AND Eggs of {Biharziosis, Egjrptian haematuria), em-

Parasites bryos in haematochyluria (associated with

IN Urine. filariasis).

The skin gives off freely in scaling the
Skin. infectious elements of many general dis-
eases, among which are chiefly the agents
of the eruptive fevers, such as scarlet fever, small-pox,
measles, chicken-pox, erysipelas, typhus fever, rubella,
cerebro-spinal fever (?), and s)^hilis (secondary). In
typhoid fever, typhoid bacilli have been found repeatedly

in the rose spots.
II

i62 INFECTIOUS AND PARASITIC DISEASES.

In local affections of the skin, the agents
Local in the following diseases are cast off:

Diseases Cutaneous actinomycosis, blastomycetes,
OF THE Skin, ring-worm of various parts of the body,

tinea sycosis (barber's itch), favus, tinea
versicolor, impetigo contagiosa, furunculi (boils), malig-
nant pustule (local anthrax), erysipelas, pinto (spotted
sickness), mycetoma (Madura foot), lupus vulgaris
(cutaneous tuberculosis), syphilis, leprosy, yaws, glan-
ders (farcy), etc.

Animal parasites are found in these affec-
Parasttes tions of the skin: Scabies, pediculosis
OF Skin. (pubis, capitis, vestimentorum), Craw-craw,

and Guinea-worm disease (DracunctUus
medinensis) . The larvae of the common house-fly are
sometimes found in wounds, and the grubs or larv« of
special flies (bot-fly, gad-fly, etc.), in tropical and sub-
tropical countries, quite frequently take up their abode
beneath the skin.

The blood as an avenue of exit for infec-
Blood. tious agents was a sterile field for research

until the relationship of a biting insect to a
disease was established by the discovery, in 1893, by
Theobald Smith, that a tick is the intermediate host for
the micro-organism of Texas cattle fever. Long before
this discovery physicians had suspected that mosquitoes
played a r61e in both malaria and yellow fever — but
the proofs were lacking in both diseases. These have

AVENUES OF EXIT OF INFECTIOUS AGENTS. 1^3

now been supplied, with additional evidence that another
disease, filariasis, is conveyed in the same way. It is
quite probable that many commimicable diseases whose
infectious agents are still a mystery may be transmitted
by suctorial insects — at least this is suspected — but
these are facts for future investigations to disclose.

It is often as important to know the manner of trans-
mission of a disease as its cause, because this may supply
the only data for combating it. Just this much is the
sum of our knowledge of yellow fever, yet that it may
be controlled has been conclusively proven by Major
Gorgas of the U. S. Army, in Havana, Cuba, and by
oflScers of the U. S. Public Health and Marine-Hospital
Service, in Louisiana last year (1905). The yellow
fever commission appointed by the Surgeon-General
of the U. S. Army, the commission to which we owe
our knowledge of the transmission of yellow fever by
mosquitoes, after it had made the latter discovery, was
able also to eliminate every other avenue of exit for the
causative agent except the blood, and thus made clear
the futility of attempting to circumscribe the disease by
disinfection of secretions, fomites, etc. It further
showed that extermination of mosquitoes offers the only
solution of this sanitary problem, because in no other
way can this unknown virus get out of one patient's
body and into another. Therefore, when we say a
micro-organism makes its exit in the blood, it is under-
stood that this is accomplished through the bite of an

i64 INFECTIOUS AND PARASITIC DISEASES.

insect. From the blood, through the bites of suctorial
insects, the microbes of malaria, yellow fever, filariasis
and trypanosomiasis (sleeping-sickness), always make
their exit. Dengue is also believed to be conveyed in
this way. In t)rphus fever, bubonic plague, t)rphoid
fever, and the bacteriaemias generally, there is always
the possibility of microbes being extracted when a
patient is bitten. Bed-bugs may suck out the spirilla
in relapsing fever, to prove which the disease has been
produced in a monkey by inoculating it with blood
obtained from a bug that had bitten another monkey
suffering from this infection.

In suppurative processes the micro-organ-
SuppuRA- jgj^g causing the trouble are always ex-

pelled in the escaping material. In the fol-
lowing specific infections the offending microbe is dis-
charged in the pus: Er3rsipelas, anthrax (malignant
pustule), glanders (farcy), malignant oedema, gonor-
rhoea (ophthalmia neonatorum, urethral and uterine
gonorrhoea), diphtheria, s)rphilis, tuberculosis, tetanus
(lock-jaw), leprosy, actinomycosis, amoebic abscess,
trachoma (Egyptian ophthalmia), catarrhal conjunc-
tivitis, blastomycetis, etc.

Non-specific suppurations are caused by a variety
of microbes, among which the streptococcus pyogenes,
and the several varieties of the staphylococcus, are
principally concerned; less frequently are found the
bacillus coli communis and the micrococcus tetragenus.

AVENUES OF EXIT OF INFECTIOUS AGENTS. 165

Boils, carbuncles, many pure and mixed cutaneous
suppurations, and suppurations found elsewhere in
the body, also come under this head. The guinea-
worm discharges its embryos and also makes its own
exit in a cutaneous suppuration which it excites.

In puerperal fever (child-bed fever), the infecting
micro-organism is discharged in the vaginal secretion,
or from such other suppurating foci as may be estab-
lished during the illness. In scarlet fever, small-pox,
typhoid fever, etc., when suppurations ensue, the dis-
charges contain the infectious agents.

The principal communicable specific infectious dis-
eases of the eye in which the specific micro-organisms
are discharged in pus, are gonorrhceal ophthalmia,
catarrhal conjunctivitis, diphtheritic conjunctivitis,
and trachoma (Egyptian ophthalmia).

CHAPTER VII.

PORTALS OF ENTRY OF INFECTIOUS AGENTS
AND OF PARASITES INTO THE BODY.

Microbes must observe a more regular mamier of
entering the body than leaving it, if they would produce
disease. This is due to the fact that tissues differ in
vulnerability to their attack, being favorable to the
growth of some germs, and unfavorable to others. The
same variation in susceptibility is noticed in the various
organs of the body, and in different localities even
where the tissues are not perceptibly dissimilar. From
this is would appear that bacteria are preferential in
their action, a conception that is quite generally believed.
However, while admitting that infectious agents have a
selective action, we must not overlook the part taken by
the body in limiting microbic action through its secre-
tions and anatomical peciiliarities. Thus it is well
established that the liver, through its secretions, has
astonishing germicidal powers, and that to this influence
we undoubtedly owe immunity from many infections.
Again, the comparative freedom of the eye from infec-
tion is largely a result of winking, by which act mechan-
ical removal of bacteria is accomplished. As a conse-

i66

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 167

quence of the peculiarities just explained, a microbe
cannot do harm if it enters the body unless it finds
lodgment in a situation favorable to its growth. In
other words, the microbe and opportunity must meet
for the production of disease. Example: The tetanus
(lock-jaw) bacillus is fatal if it enters a wound however
trivial, yet it may be swallowed (indeed, often is)
with impunity.

The portals of entry of infectious agents and parasites
into the body may be included under the following
heads :

1. Through woimds of skin and mucous membranes.

2. By the mouth or nose, through air.

3. By mouth, through food and water.

4. By genito-urinary tract.

5. By placenta (congenital infection).

6. Cr3rptogenic (unknown).

The immediately accessible portions of the body to
infectious agents are either covered with skin or mucous
membranes, so that in the production of disease, one
of those surfaces must be penetrated.*

If an infection can be contracted either through
wounds of the skin or mucous membranes, it is said to
be inoculaUe. It is still a question in dispute whether

'('To make this generalization clear it is only necessary to remind the
reader that the air-passages have a mucous lining from their external
openings down to their final terminations in air cells in the lungs; and
that the alimentary tract is lined with an uninterrupted sheet of mucous
membrane from inlet to outiet.

i68 INFECTIOUS AND PARASITIC DISEASES.

in this sense all infectious diseases are not inoculable,
that is to say, whether the entrance of the agent does not
depend upon some defect created in the integument or
mucous membrane by another cause. Neither the
nature of the infectious agent nor the region of the body
which is the primary site of the disease enter into the
discussion; nor is it disputed that penetration must
occur; the question is, how does it happen, whether
through the action of the bacteria themselves, or through
the agency of another cause? If an accessory catise
paves the way in all infections by interrupting the con-
tinuity of a surface, then all infectious diseases are inoc-
ulable. This latter belief, it will be recalled, is in
entire accord with views previously expressed in the
chapter on "The Phenomena of Infection," particularly
in that portion which treats of the part the body plays
in its production.

The lesions of entrance in some diseases are more
palpable than they are in others, and in others again,
they can never be found ; yet that this latter fact is not
a safe argument to use against the inoculability of a
disease will be seen from a few illustrations. Take,
for example, such a disease as yellow fever. Before
the epochal work of the medical officers of the U. S.
Army in Cuba, during 1898-99, yellow fever was
regarded as a highly contagious disease, to guard
against which it was deemed necessary not only to
subject exposed individuals to the most rigid quarantine,

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 169

but also to fumigate clothing, bedding, and even letters,
that had been in most casual contact with the sick.
The measures enforced indicate that the causative
agent was believed capable of gaining an entrance into
the body without injury to the skin or mucous mem-
branes. We now know, however, that a lesion of the
skin inflicted by a mosquito is its only means of entrance
(although we are yet in the dark as to the nature of the
agent), and that, therefore, all former methods of pre-
vention were futile in so far as control of the disease was
concerned. Into such gross errors is it possible to
fall when we apply methods of proven value in known
to unknown diseases! Another case in point: Take
typhoid fever; the t)rphoid bacillus enters the body by
the mouth in food or drink. The most obvious lesions
of the disease are seen in ulcers of the l)nnph nodes
(glands) of the lower part of the small and the beginning
of the large intestines. To affect these results the
bacilli pass through the mucous membrane of the
bowels, where they can be seen with the microscope in
stained sections after death. The specific bacilli,
however, do not stop in the sub-mucosa (sub-mucous
tissue) but pass from here into the blood, where active
growth and toxin formation is carried on. In other
words, typhoid fever belongs to the bacteriaemias, a
class of diseases characterized, as we have seen, by the
presence of bacteria in the blood. Usually the more
obvious s)nnptoms of t)rphoid fever are those referable

I70 INFECTIOUS AND PARASITIC DISEASES.

to the bowels; but the intestinal features may be com-
pletely wanting, as has been repeatedly proven by post
mortem examinations. Such cases are usually reported
as "Typhoid fever without intestinal lesions." A
study of t)rphoid fever, therefore, teaches that, while
the agents of a disease may depend for entrance into
the blood upon a gross or macroscopic lesion of a
mucous membrane, they also may enter through a nan-
demonstrable portal. It might be asked at this point,
"why do not the bacteria which get into the intestinal
tract with food, and those which have their habitat there,
often penetrate the mucosa and cause disease?" The
answer to which would be, they do, far oftener than is
generally supposed; in fact the intestinal tract is re-
garded as the chief portal of entry for many diseases
for which no atria can be found (cryptogenic infections).
That some bacteria can enter certain tissues and
attack certain localities more readily than others is
admitted, because it has been experimentally proven.
But between experiments, no matter how cimningly
devised, and disease, as ordinarily contracted, there is a
wide gap. When an animal or person is subjected to
the germs of a disease, many million times the number
of bacteria are applied than are ever present under
natural conditions. Under such circumstances mere
contact of these germs with the right mucous surface is
sufl&cient to provoke disease. This is the case, for
example, with the diphtheria bacillus, accidental infec-

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 171

tions with which having occurred in laboratories by a
culture being unwittingly drawn up into the mouth.
But under natural conditions of infection, where only
casual contact between a patient and another person
takes place, how can we believe that very many germs
reach the throat through inhalation? Certainly they
are by far not so nimierous in air as when grown in
cultures! Furthermore, in every disease, we concede
the co-operation of contributing or predisposing causes :
enlarged tonsils and adenoids in diphtheria; exposure
and alcoholism in pneumonia; indigestion, fatigue,
and over-ripe fruits, in cholera, etc. Why ? if the germs
acting alone are sufl&cient?

Finally, only a limited number of persons exposed
to an infectious disease contract it, a fact which cannot
be explained in the case of local diseases on grounds of
greater general predisposition. In diphtheria, gonor-
rhoea, cholera, etc., might it not be because in those
persons that we say are susceptible, the predisposing
causes ultimately resolve themselves into invisible
breaks or ruptures in the continuity of mucous sur-
faces ?

The subject of the inoculability of diseases has been
thus fully discussed because of our classification of the
portals of entry. We have endeavored to show that
our first group, "through wounds of skin or mucous
membranes," might be made to include practically all
diseases of known etiology. But such a division is

172 INFECTIOUS AND PARASITIC DISEASES.

ill-suited to our purpose, which is to direct attention
to the more obvious atria, and also to those portions of
the body as are most likely to be the primary or initial
seat of the various infections. S)rphilis well illustrates
our aim. Syphilis is a t)rpical inoculable disease, a
break in the integument or a mucous surface being
required for entrance of the virus. But if we only
treated of its portals of entry imder lesions of the skin
and mucous membranes, data of the highest importance
would not be included. Nothing, for example, would
be said of the fact that the initial infection is usually
found upon the genitalia, not that the infection is
hereditary. Hence, the reason for employing a classi-
fication apparently illogical.

The more obvious portals are those easiest remem-
bered, and the most practical; and therefore, imder the
inoculable diseases are placed those which are either
contracted through visible lesions, or can be inoculated,
although under natural conditions this may not seem to
occur;* and under the other divisions are grouped
those which experience has taught attack one portion
of the body rather than another. Obviously under such
a classification, a disease will often be found under two
or more heads.

♦Example: — Small-pox is ordinarily contracted by contact of an un-
vaccinated person with a patient or fomites. That it is directly inocu-
lable, the earlier practice of variolation, introduced into England by
Lady Mary Worthey Montague in 1727, shows.

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 173

The strictly inoculable infectious diseases
Skin and are tetanus (lock-jaw), S)rphilis (acquired),
Mucous lupus vulgaris (cutaneous tuberculosis).
Membranes, erysipelas, actinomycosis (cutaneous),

glanders (farcy), leprosy (?), t)rphus fever,
plague, anthrax (malignant pustule), hydrophobia,
mountain fever (?), foot and mouth disease, malarial
fever, yellow fever, filariasis (elephantiasis) blastomy-
cetes, mycetoma (Madura foot), small-pox, and soft
chancer.

Vegetable parasites are the cause of ring-worms of
various parts (tinea tonsurans, tinea circinata), barber's
itch (tinea sycosis), tinea versicolor, pinto (spotted sick-
ness), yaws, and craw-craw. Thrush is a vegetable
parasitic affection of the mucous membrane of the
tongue and cheeks of infants.

Animal parasites which gain entrance through the
skin are represented by the embryos of the uncinaria
(parasite of hook-worm disease).

Parasitic insects of the skin are Sarcoptes scabiei
(itch-mite) ; the head, body, and pubic louse; the larva of
the horse bot-fly (gastrophilus equi), which causes
"Creeping Eruption;" mosquitoes, which inoculate the
agents of malaria, yellow fever and filariasis, and prob-
ably that of dengue; and the fly glossina which prob-
ably inoculates the parasites of trypanosomiasis
(sleeping-sickness) .

The mouth is a portal of entry for infectious agents

174 INFECTIOUS AND PARASITIC DISEASES.

and parasites in both air and foods, and in the case of
many diseases both methods of conveyance are possible.
Yet because some diseases are nearly alwa5rs, or even
exclusively, contracted in one of these ways, it has
seemed best to make a division of diseases into those
inspired, and those taken in with foods and water.
For example, neither Asiatic cholera nor dysentery are
ever air-borne; nor is pneumonia contracted in either
food or drink ; yet in diphtheria, scarlet fever, small-pox,
etc., both air and foods are fruitful sources of infection.
The air, however, as a source of contagion, has been
much exaggerated in the past, particularly where trans-
mission of a disease over great distances has been laid
at its door. With the exception of diseases conveyed
by insects, such as mosquitoes, which may be blown
by winds, there is really no readily communicable
disease which is dangerous to others in the open air
at a few yards distance. The fear that many persons
have of passing a house where a contagious disease
exists is without foundation. Carelessness within the
house may be responsible for every room being danger-
ous — ^but that does not aflfect the air outside. When
carefully investigated the so-called air-borne infections
are discovered to have been carried by a third
person, or by some article used and soiled in the sick-
room. Usually it is the former. The truth is graphic-
ally presented by Dr. Rosenau who quotes Dr.
J. H. White, ^^that infectious diseases are more often

Mouth

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 175

conveyed from place to place in two shoes than in any

other way." Therefore, air-bome, as applied to a

disease, rather emphasizes the fact that the contagion

enters by way of the respiratory passages, than that it

is widely diffused in air.

By the mouth and nose through air may

^^^ enter the infectious agents in small-pox,

AND Nose ... i i .r

THROUGH chicken-pox, measles, scarlet fever, mumps,

Air. whooping-cough, pneumonia, tuberculosis,

diphtheria, plague, anthrax, epidemic cere-
bro-spinal meningitis (?), rubella and influenza.

A large number of the infectious and para-
sitic diseases are contracted exclusively
p by the pathogenic agents entering the body

Water. ^^ foods and water. This method of infec-

tion is also by no means unusual in certain
diseases for which the respiratory passages are the ordi-
nary portals of entry. Foods and water, as a rule, offer
excellent pabula for infectious agents and parasites,
and are therefore quite frequently the means by which
diseases are spread. The pollution of drinking-water by
sewage, and the harm arising therefrom, has already
been considered. Foods in relation to disease, however,
requires some further elucidation; and while it is not
our aim to take up all foods which serve as vehicles for
infectious and parasitic agents, the manner of con-
tamination of some of those consumed daily will serve
to illustrate, in a general way, how these are a source of

176 INFECTIOUS AND PARASITIC DISEASES.

disease. Furthermore, the movement of food-stuffs
from one part of a country to another, or from one
country to another, will be sufficiently dealt with to
show the possibilities of diseases being literally picked
up, carried hundreds of miles, and transplanted in
regions where they previously did not exist.

Mention has been made of the manner in which
t)rphoid fever, cholera, dysentery, etc., are contracted
from drinking polluted water. Polluted water, how-
ever, although it may not be used for drinking purposes,
may nevertheless be a source of danger from certain
foods which grow in it and are consumed raw. This
danger has been realized a number of times in the case
of oysters and clams; and while water-cress has not
yet been definitely incriminated, there is no reason
why it may not be a menace to health in the same
way.

Fruits and vegetables are sometimes polluted by the
fertilizer, especially where human excrement is used to
enrich the soil. In the United States this practice is
not so common as in certain European countries, nor
in the latter countries as in China, where it is the rule.
But the number of Chinese truck-farmers in the
United States and Cuba is not small, and steps should
be taken to illegalize the use of human excrement for
fertilizer unless it has been made innocuous by various
approved methods. Only a few years ago, during the
American occupation of Cuba, several Army Surgeons

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 177

made the filthy fanning customs of the Chinese the sub-
ject of special reports. It is scarcely necessary to
mention the way human excrement used as fertilizer is
dangerous, as it differs in no respect from fecal pollution
of water; nor that the chief danger comes from vege-
tables, berries, and salads which are eaten raw.

Pollution of berries, etc., may also come from the
persons employed in gathering them. The people
engaged in this kind of labor, while they are on the one
hand drawn from the most densely ignorant and un
cleanest of foreigners, are on the other denied for weeks
the most primitive accessories of civilization. Whole
families, men, women, and children, in the early spring
begin a migration which starts where the season opens
soonest, and ends in the fall where it closes last. Dur-
ing this, the warmest part of the year, they live in the
fields in tents or covered wagons, working from sunrise
to sunset with only such conveniences as their tempo-
rary abiding-places afford. They ask very little in the
way of comforts and get less. A bath to most of them
is ordinarily obnoxious. From their bunks day after
day they go to their work in the dawning morning,
unwashed and uncombed, to return at night to sleep,
too exhausted to make an effort to be clean. Relief
from physiological emergencies is sought where they
work, and quickly too — for the remuneration is "so
much the measure." Sickness often prevails in these
camps, typhoid fever, small-pox, scarlet fever, etc.,

IS

178 INFECTIOUS AND PARASITIC DISEASES.

and many workers harbor intestinal parasites. Need
more be said of the probability of disease being served
at our tables with fresh fruits and vegetables ? Could
the egg of a tape- worm find a more toothsome vehicle ?
And yet there are those who insist on eating berries
unwashed because they lose a little flavor in the wash-
ing!

Some articles of food are more favorable to the growth
of bacteria than others. MUk is the best. This is
unfortunate, because, besides being a natural food for
children and the greatest boon in sickness, it is next
to bread the most-used article of diet. Because it
furnishes such an excellent pabulum for bacteria, it is a
frequent vehicle by which they are carried. Sickness
in a milker, or in a dair3nnan's family, or the washing
of milk-cans in polluted water, has time and again
caused epidemics of scarlet fever, diphtheria, and
typhoid fever, a fact which calls for the enactment of
rigid laws regulating the production, handling, and
sale of milk, and severe penalties for infractions of this
law.

For a long time it has been the custom, when a few
cases of typhoid fever occur in a community, to imme-
diately impugn the character of the water-supply.
This attitude of mind is a legacy of the time when pol-
luted water was believed to be the only source of this
infection. Where large numbers of cases occur, and
especially if they are not limited to one neighborhood,

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 179

it is a wise precaution to suspect the drinking-water.
But where cases are reported sporadically, especially
in communities which have a mimicipal water system,
it is more logical to seek the source elsewhere. The
modem method of food distribution is a marvelous
development, that is comparable to other inventions of
the 19th Century. Through it perishable articles are
not only distributed from one point where the supply
exceeds the demand to others where they are needed;
but they are also held, in the case of certain foods, a
year or more — if the supply is too abundant. Nor is
the distribution of such things limited to the farther-
most boundaries of one country, but they are also
shipped from one country to another across the widest
seas. All this has come about through the expansion
of the cold storage business, and the use of refrigerator
cars, and cold storage plants on steam-ships. There
is a large and ever increasing demand for various perish-
able articles of food out of season, so that there is a
constant movement of supplies from one region to
another. Furthermore, this demand has stimulated
the speculative zeal of those engaged in the cold storage
business, with the result that "in season" enormous
storing of perishable foods is conducted. So great at
these times is the demand for these commodities for
storage, and for shipment to other parts of the country,
that in many localities where they are grown it is im-
possible to purchase in the local market either fresh

i8o INFECTIOUS AND PARASITIC DISEASES.

fowl, eggs, milk, butter, fruits and game. Hence it is
probably true, although we haven't]the support of figures
for the assertion, that more of the above mentioned
foods are eaten out of season than in.

Our reason for dwelling upon this phase of modem
economic life is to draw attention to the probability
of communicable diseases being carried with foods
from points widely separated, and the difficulty of
tracing those so carried to their source. Refrigeration
does not necessarily kill infectious agents and animal
parasites, indeed, we have already called attention to
the dangers of ice in relation to typhoid fever and cholera;
so that through this system some contaminated article
such as cream, may first be shipped five hundred miles
to a creamery, churned into butter there, held in
storage a few months, and finally be shipped another
thousand miles, or across the ocean to Europe. The
possible contamination of fruits, berries, and vegetables
by those that pluck them has been considered a few
lines above ; in the refrigerator car, therefore, we see a
way by which infectious or parasitic agents contamina-
ting such products may be transported.

By the mouth through foods and water, are taken in
the agents of typhoid fever, Asiatic cholera, small-pox,
measles, scarlet fever, tuberculosis, diphtheria, plague,
anthrax, s)rphilis, amoebic and bacillary dysentery,
actinomycosis, milk sickness, and aphthous fever (foot
and mouth disease).

PORTALS OF ENTRY OF INFECTIOUS AGENTS. i8i

The foUowing eggs, embryos, or parasites
Parasites are taken into the body with foods or water :
OR Eggs of Eggs of beef tape- worm (Tcmia saginata) ;
Parasites, eggs and larvae of pork tape-worm {tcmia

solium) ; eggs of Taenia echinococcus (dog
tape- worm), water; eggs of round worm (ascaris lumbri-
coides), water; eggs of pin-worm (Seat- worm, Oxyuris
vermicidaris), water; larvae of Guinea- worm (Dracun-
cuius medinensis)y water; larvae of trichinae (Trichinia-
sis), pork; larvae of Uncinaria (hook-worm disease),
water and soil; worm of Strongyloides Intestinalis
(endemic diarrhoea of hot countries), water (?); eggs
of tricocephalus dispar; eggs of parasite causing Bilhar-
ziosis (Egyptian haematuria), (?); larvae of common
house-fly.

The commonest infectious diseases of the

Gentto- genito-urinary organs are the so-called

URINARY "venereal diseases," gonorrhoea and syph-

Tract. iiis. Both of these infections, however,

may be found elsewhere upon the body in

persons innocent of wrong-doing. In such cases the

name of the disease is qualified by the word insontium

written after it. In the female the vulva, vagina,

urethra, and cervix of the uterus, are often the seat of

gonorrhoea and syphilis, less often, of tuberculosis.

Following abortion, or delivery at term, the uterus is

frequently infected with the streptococcus of erysipelas,

the colon bacillus (from feces), and the common mi-

i82 INFECTIOUS AND PARASITIC DISEASES.

crobes which cause suppuration. Occasionally the ex-
ternal genitals are the seal of diphtheria.

In the male, syphilitic and gonorrhoeal lesions of the
outside of the penis are common. The interior of the
urethra is seldom affected by any other disease besides
gonorrhoea. However, chancer (syphilis) of the inside
of the urethra is sometimes encountered.

The bladder in both sexes is frequently the seat of
inflammations (cystitis), the infection very often being
carried into the bladder by catheterization. Besides
getting into the bladder by way of the urethra, however,
the infection may come from the blood by way of the
kidneys. Tuberculosis of the bladder, a not uncommon
infection, usually arises in this way.
Animal The round worm has been found in the

Parasites, vagina.

Only one congenital disease occurs with
Congenital ^^^ degree of frequency, namely, syphilis,
p^ Nevertheless, a child may be bom with

Infection, almost any of the infectious diseases if

the mother is suffering at the time from the
same. Thus, in the new-bom has occurred typhoid
fever, small-pox, scarlet fever, tuberculosis, etc. In
the case of tuberculosis, however, it is surprising how
very rarely the disease is found in the children of a
consumptive mother; in fact congenital tuberculosis
is so uncommon, that tuberculosis is not regarded by the
profession as an hereditary disease.

PORTALS OF ENTRY OF INFECTIOUS AGENTS. 183

The discharges from syphilitic lesions in the infant
are highly dangerous to everyone who handles it except
its mother. In such children sores of the mouth are
common, and wet-nurses have frequently been known
to contract the disease from suckling them.

Cryptogenic infections refer to those deep-
Cryptogenic, seated affections for which a portal of

entry cannot be found. Endocarditis (in-
flammation of the heart valves), osteomyelitis (inflam-
mation of bone), etc., are illustrations of this type of
infection.

CHAPTER VIII.

PORTALS OF ENTRY AND AVENUES OF EXIT
OF MICRO-ORGANISMS IN THE VARIOUS

DISEASES.

Actinomycosis ("lumpy-jaw," "wooden tongue");
disease of man and domestic animals, particularly
bovines.

(a) Cause: Actinomyces bovis (ray-fungus); forms

spores.

(b) Localized: Lungs, bowels, subcutaneous tissues;

often about jaw or tongue.

(c) Entry: Through mouth and nose with food;

through wounds.

(d) Exit: Sputum, feces, and pus from lesions.

(e) Contracted : Doubtful whether can be communi-

cated directly, either from animal to
man, or from man to animal. Barley, oats,
or rye, seem to be vehicles for the fungus.

(f ) Disinfection : Since the actinomyces form spores,

disinfecting agents are same as for anthrax

and tetanus.

The ray-fungus can be seen with the naked eye in

the pus and secretions of lesions as whitish or yellow-

184

MICRO-ORGANISMS IN VARIOUS DISEASES, 185

ish bodies that have the appearance of j&ne grains of
sulphur; seen best if a small quantity of the pus is
pressed between two slides or watch crystals.

Anthrax (Wool-sorter's Disease, malignant pus-
tule, splenic fever) ; disease of man and domestic ani-
mals, especially sheep and cattle.

(a) Cause: Bacillus anthracis; forms spores^

(b) Localization: Subcutaneous tissues (malignant

pustule) ; lungs (wool-sorter's disease) ; in-
testinal tract; all of these lead to bacter-
iaemia (bacteria in blood) in vast majority
of cases.

(c) Entry: Through wounds or abrasions; through

mouth, eating meat or drinking milk of
infected animals; through respiratory tract
(inhaled in dust — ^wool-sorter's disease).

(d) Exit: Expectoration in pulmonic form; pus

from abscess in local form; discharges
from bowels in intestinal form.

(e) Contracted: By inhalation in sorting wool of

infected animals; by abrasion or wound
in handling flesh or hides of infected ani^
mals; by eating flesh or drinking milk
of diseased animals; by the soiling of
wounds or food-stuffs by infected flies.

(f) Disinfection and Prophylaxis: Forms spores,

therefore unusual precautions are to be
used. Bum cadavers, and contaminated

i86 INFECTIOUS AND PARASITIC DISEASES,

bedding, cloths, etc., where this is possible;
where destruction is not feasible, use
(i) Super-heated steam (15 pounds pressure), 15
minutes.

(2) Tricresol, or lysol, 2 per cent solution, for two

hours.

(3) Bichloride of mercury (1-500), for one hour.

(4) Formalin, 15 per cent solution, one and one-

half hours.

(5) Boiling water, or steam, for two hours.

Bubonic Plague (la peste, black death, etc.).

(a) Cause: Bacillus pestis; non-sporogenous.

(b) Localized: Skin and subcutaneous tissues;

lymph-glands; lungs; and intestinal tract.

(c) Entry : Wounds of skin ; nose and mouth through

air; mouth in food and water.

(d) Exit: In any of the discharges from situation

where disease is localized; therefore, sup-
purations, suppurating buboes, abscesses,
blisters, sputum, vomit, feces, urine.

(e) Contracted: By inhalation through contact

with sick; through woimds contaminated
or caused by infected fleas, flies, ants,
etc., also food and water contaminated by
the sick, or infected vermin, e.g., rats,
mice, etc.

Note : — Use all chemical disinfectants at or near the boUing point.

MICRO-ORGANISMS IN VARIOUS DISEASES. 187

(f) Disinfection: Must be thorough; bacillus not

difficult to destroy; disinfect sputum,
dejecta, urine, etc., with 5 per cent carbolic,
3-5 per cent formalin, 2 per cent tricresol,*
or boiling water the same as for other
non-sporogenous bacteria. Wash body of
patient, hands, and objects with i-iooo
bichloride of mercury. Fumigate with sul-
phur dioxide on account of its destructive
action on vermin.

(g) Prophylaxis : Vermin, particularly rats and mice,

are susceptible to plague ; indeed, the former
are believed to be the principle carriers of it.
They infect the ground, dwellings, foods, and
water. Therefore, safety lies in the destruc-
tion of all vermin in the houses. As dogs
and cattle are also susceptible to the disease,
they should be carefully protected from
exposure. Screen dwelling and rooms;
since the ground becomes infected by rats,
and infected excreta, and because wounds
of the feet and legs are frequent portals of
entry for the specific bacillus, the constant
wearing of shoes and leggins is a wise
prophylactic.
The pneumonic form of plague is especially danger-
ous to attendants because the bacilli are thrown out
in the spray in coughing and sneezing. Eat liothing

i88 INFECTIOUS AND PARASITIC DISEASES.

raw, such as rnDk, butter, cheese, etc. ; serve everything
hot. Eschew all fresh fruits and vegetaUes. Neither
wash in, nor drink of, unboQed water. The bodies of
those succumbing to the disease should be cremated.
Clothing, sheets, etc., may be disinfected with solu-
tions above given for sputum. Mop all surfaces in
the sick-room frequently with a solution of bichloride
of mercury (i-iooo). Rigid isolation and quarantine
should be instituted.

Epidemic Cerebro-spinal Meningitis.

(a) Cause: Diplococcus intraceUularis meningitidis;

non-sporulating.

(b) Localization: Membranes of brain and spinal

cord.

(c) Entry: Probably nose by inhalation.

(d) Exit: Probably nasal secretions.

(e) Contracted : Does not seem directly contagious

from sick to well, nor by fomites.

(f) Disinfection and Prophylaxis : Disinfect all secre-

tions and discharges, and all objects that
have been in contact with patient. Pro-
tect patient, and all articles that have been
in contact with patient, from insects ; there-
fore screen against flies, mosquitoes, etc.

Chicken-pox (varicella).

(a) Cause: Not known.

(b) Localization: Same as small-pox.

MICRO-ORGANISMS IN VARIOUS DISEASES. 189

(c) Entry : Probably through respiratory tract (inha-

lation).

(d) Exit : Exhalations from lungs and skin, particu-

larly in the dried scales of the latter ; in all
secretions and excretions, therefore, spu-
tum, feces, urine, tears, nose, etc.

(e) Contracted: Highly contagious.

(f) Disinfection: Same as applied to small-pox.

(g) Prophylaxis: Same as in small-pox.

Cholera.

(a) Cause: Spirillum cholerce Asiaticce (Koch),

^ ' comma bacillus ; ' ' non-sporogenous .

(b) Localization: Small and large intestines.

(c) Entry: Mouth in water and food.

(d) Exit: Discharges from bowels, sometimes in

vomit.

(e) Contracted : Is usually water-borne infection, but

may come from foods contaminated either
by soiled hands, human fertilizer, or by in-
sects which have been in contact with dis-
charges containing the spirilla.

(f) Disinfection: Spirillum has slight resisting powers,

65^ C. (149^ F.) kills in five minutes, 100^ C.
(212^ F.), destroying it at once; disinfect
stools and vomited matter with 5 per cent
solution formalin, 5 per cent solution car-
bolic acid, 2 per cent tricresol, or twice their

I90 INFECTIOUS AND PARASITIC DISEASES.

amount with milk of lime ; treat bed-linen,
etc., same as in typhoid; fumigation not
necessary if appropriate sick-room precau-
tions are taken.

(g) Prophylaxis: When cholera prevails, do not eat
any fruits or vegetables raw; boil all
water, whether used for drinking purposes
or for washing of utensils; cook all foods
well, and leave nothing exposed to the air,
best to serve everything hot; protect sick-
room, and all houses from flies, and keep
free from insects. If these precautions
are followed, one can live in a cholera
infected town and nurse cholera patients
without danger of contracting the disease.

Dengue (break-bone fever, dandy fever).

(a) Cause: Unknown.

(b) Entry and Exit: Not known.

(c) Disinfection: Not practised, since as far as

known it never proves fatal.

Diphtheria.

(a) Cause: Bacillus diphtheric^ (Klebs-Loeffler bac-

illus).

(b) Localization: All mucous membranes, usually

tonsils, phar5nix, and anterior and pos-
terior nares; occurs in larynx, when it is
called membranous croup; sometimes seen
on the vulva; may infect wounds.

MICRO-ORGANISMS IN VARIOUS DISEASES. 191

(c) Entry: By mouth and nose through air, or by

mouth through contaminated foods or
objects; only the air around the patient
is dangerous, which is made infectious
through coughing, sneezing, and careless
disposal of secretions from infected por-
tion; through wounds uncommon.

(d) Exit: Discharges from nose, mouth, pharynx

and laiynx; also from eye and vulva if
disease situated there.

(e) Contracted: Is highly contagious, spread by

contact with the sick chiefly, to a less
extent through fomites; kissing, handker-
chiefs, towels, toys, etc., may all convey
the infection.

(f) Disinfection: Boiling water kills the diphtheria

bacillus at once; direct sun-light is also
effective in about an hour ; disinfect sputum,
nasal discharge, linens, utensils, etc., with
boiling water, or with tricresol (2 per cent),
formalin (5 per cent), carbolic acid (5 per
cent) ; wipe all surfaces in room (including
floor) with bichloride of mercury (i-iooo)
daily, fumigate with sulphur or formalde-
hyde.

(g) Prophylaxis: Isolation of sick, no matter how

slight the infection, since there is no ques-
tion that diphtheria is spread by the mild

192 INFECTIOUS AND PARASITIC DISEASES.

or unsuspected cases; those in contact
with the patient should use antiseptic
gargle, disinfect hands, and avoid getting
in the way of spray of expectoration ; fumi-
gate with sulphur or formaldehyde.

Amoebic Dysentery (chronic tropical dysentery).

(a) Cause: Amoeba dysentericB, an animal parasite.

(b) Localization: Intestinal tract.

(c) Entry: Mouth through water, fresh fruits, and

vegetables.

(d) Exit: Evacuations from bowels.

(e) Contracted: From infected water, etc.

(f) Disinfection : Only the stools need be disinfected,

using the same solutions as in typhoid.

(g) Prophylaxis: Boil all water where the disease

prevails.

Bacillary Dysentery (acute epidemic dysentery).

(a) Cause: Bacillus dysentericB (Shiga); non-sporog-

enous.

(b) Localization: Intestines.

(c) Entry : Mouth, through water and foods.

(d) Exit: In evacuations from the bowels; may be

present in vomit.

(e) Contracted: Same as typhoid.

(f) Disinfection: As far as known only the stools

have to be disinfected; the bacillus has
about the same resisting qualities as the

MICRO-ORGANISMS IN VARIOUS DISEASES. 193

typhoid bacillus, the strengths given for the
various disinfectants in typhoid being
sufficient,
(g) Prophylaxis: When the disease prevails boil all
water and cook well all foods; eat neither
fruits nor vegetables raw; use same pre-
cautions as in typhoid.

Erysipelas.

(a) Cause: Streptococcus pyogenes; does not form

spores.

(b) Localization: Skin, or any wound that becomes

infected with the micro-organism.

(c) Entry : Wounds or abrasions of skin and mucous

membranes.

(d) Exit : In pus and secretions from the seat of the

inflammation ; also probably in the desqua-
mating skin from an inflamed area.

(e) Contracted : Is highly contagious to any one with

a wound; to a woman about to be confined,
or in the pusrperium; may be conveyed by
fomites, instruments, etc.

(f) Disinfection: 100° C. (212° F.) moist, kills the

streptococcus at once; all discharges
should be disinfected with the solutions in
the strengths recommended ; urine should
certainly be disinfected ; room, patient, and

bedding, clothing, etc., should b? treated

13

194 INFECTIOUS AND PARASITIC DISEASES.

as for small-pox; fumigate with formaki^
hyde or sulphur,
(g) Prophylaxis: Isolate the patient and his attendant;
latter should have nothing to do with opera-
tions, confinements, etc., during the period
of attendance on a case of er3rsipelas, and
for two weeks thereafter; during the lat-
ter period, daily disinfection of the hands,
hair, and person generally should be fd-
lowed; room where patient has been
should be thoroughly cleansed and dis-
infected.

Glanders.

(a) Cause: Bacillus maUei; is non-sporogenous.

(b) Localization: Exposed surfaces of the body

(farcy), or mucous membranes of the nose.

(c) Entry: Wounds of skin, or mucous membrane

of nose.

(d) Exit : Purulent discharges from nose ; ulcers and

abscesses; expectoration; urine.

(e) Contracted : Usually by contact with diseased an-

imals (horses and asses), or hides of same
through abrasions of skin.

(f) Disinfection: Easily destroyed by boiling, or the

usual strengths of carbolic acid, formalin,
or tricresol.

(g) Prophylaxis: Consists in the destruction of all

MICRO-ORGANISMS IN VARIOUS DISEASES. 195

diseased animals, and thorough disinfection
of the discharges and soiled dressings of
infected individuals.

Gonorrhoea.

(a) Cause: Micrococcus gonorrhwce (Neisser); non-

sporogenous.

(b) Localized: Urethra (gonorrhoea, specific urethri-

tis, clap); eye (gonorrhoeal ophthalmia,
ophthalmia neonatorum); vagina; blood;
joints; etc.

(c) Entry: Urethra, eye, vagina, occasionally

wounds.

(d) Exit: In suppurations from diseased tissues or

organs.

(e) Contracted : In urethra and vagina from irregu-

lar intercourse; in eyes of adults from pol-
luted fingers or towels, etc.; in new-bom
during birth; in female children the vagina
is infected through soiled sponges, wash-
cloths, etc.

(f) Disinfection: Micro-organism has slight resist-

ance; boiling kills it at once. Ordinary
disinfectants effective in the percentages
in which used for vegetative forms of other
bacteria.

(g) Prophylaxis: Males with acute or chronic gon-

orrhoea (gleet) should not marry until

196 INFECTIOUS AND PARASITIC DISEASES.

cured. Individuals with the disease should
be warned of the awful danger consequent
upon eye infection. The children bom of
immoral mothers, and all bom among the
lowest classes, should have instilled into
each eye immediately after birth one to two
drops of a I per cent solution of nitrate of
silver.

Hydrophobia (Rabies, Lyssa).

(a) Cause: Unknown.

(b) Localized: Wounds, primarily; secondarily, brain

and spinal cord.

(c) Entry: Through wounds.

(d) Exit: Saliva.

(e) Contracted: Through bite of mad animal, such

as dog, wolf, cat, etc. Novi says, "that
midges and flies are capable of conveying
the infection."

(f) Disinfection: Saliva, and linens, beddings, etc.,

soiled by saliva, should be boiled, or dis-
infected with one of the solutions advised
for other diseases.

(g) Prophylaxis : Kill all mad animals, and all others

bitten by same. Dogs should be muzzled.
Bites of all animals should be carefully
washed and thoroughly cauterized with
concentrated carbolic acid, or a glowing

MICRO-ORGANISMS IN VARIOUS DISEASES. 197

poker. Previously, oral suction may be
practised. Keep wound open for from five
to six weeks.

Influenza (La Grippe, Russian fever).

(a) Cause : Bacterium infltienztB; is non-sporogenous.

(b) Localized: Throat; nose; lungs; blood.

(c) Entry: By air through mouth and nose.

(d) Exit: Discharges from nose, throat, and lungs.

(e) Contracted : Probably entirely by contact with the

sick.

(f) Disinfection: Bacilli are quickly destroyed by

even weak solutions of the ordinary disin-
fectants; at once by boiling; fumigate with
formaldehyde or sulphur.

(g) Prophylaxis : Since influenza is a serious disease

in the case of the very young and the aged,
and furnishes a large proportion of the
mortality at these periods of life, the nasal
and bronchial secretions should be care-
fully disinfected in every case.

Leprosy.

(a) Cause: Bacillus leprcB; non-sporogenous.

(b) Localized: Mucous membranes and skin gener-

ally; nervous system.

(d) Exit: In suppurations from broken-down nodules

of nose, mouth and skin.

(e) Contracted: Contracted with difficulty. Long,

198 INFECTIOUS AND PARASITIC DISEASES.

intimate contact seems essential. Atten-
dants need have no fear of contracting the
disease, if reasonable precautions are
taken.

(f ) Disinfection : Not known, since germ has never

been cultivated outside the body; prob-
ably same as for tuberculosis.

(g) Prophylaxis: Cleanliness; disinfection of dis-

charges from suppurations and soiled
linens, etc. ; segregation of lepers.

Madtira Foot (mycetoma, Madura disease, pied de
Madura).

(a) Cause: Streptothrix madurae, forms spores (?).

(b) Localization: Usually feet, but may aflfect other

portions of body.

(c) Entry: Through wounds in skin.

(d) Exit: In discharges from broken-down nodules.

(e) Contracted: In countries where the disease is

common, is attributed to prick of a thorn ;
is probably not communicated from man
to man.

(f) Disinfection: Should be same as for anthrax

and tetanus.

Malarial Fever (ague, intermittent fever).

(a) Cause: Hcematozoa malaricB (sporozoa).

(b) Localized : In blood and tissues.

(c) Entry: Only through bites of mosquitoes.

MICRO-ORGANISMS IN VARIOUS DISEASES. 199

(d) Exit : In the blood solely through bites of mos-

quitoes.

(e) Contracted: By being bitten by that species of

mosquito (Anopheles) which acts as host
for the parasite.

(f ) Disinfection : Consists in the destruction of mos-

quitoes by an insecticide in the bed-room
of the sick. Pyrethrum, two pounds to each
one thousand cubic feet. Sulphur, one
pound to each two thousand cubic feet.
Where sulphur used, two hours' exposure
sufficient, and moisture (which decolorizes
and destroys fabrics) not necessary. As
pyrethrum only stuns the knats they must
be gathered up and burned after fumigat-
ing.

(g) Prophylaxis : Where malaria is prevalent, screen

rooms and houses with fine mesh screens
to keep mosquitoes out; chief danger is at
night, since anopheles is nocturnal in
its habits. Anopheles breeds in shallow
puddles and ditches, in which places the
young can be destroyed by sprinkling sur-
face of water with coal-oil about every two
weeks. Two grains of quinine three times
daily is also a wise precaution.

Measles.

(a) Cause: Unknown.

^oo llSTFECtlOUS AlfD 1>ARAS1t1C DlSfiAglKS.

(b) Localization: Eyes, nose, mouth, throat, and

skin.
{t) Eirtry: Probably air borne to mouth or nose,
{cl) Exit : Oculo-nasal secretions, saliva, breath and

desquamated skin.

(e) Contracted: By contact with sick through air;

fomites; third person.

(f) Disinfection; Same as for small-pox.

(g) Prophylaxis : Same as for small-pox.

Mumps (epidemic parotitis).

(a) Cause: Unknown.

(b) Localized : One or both parotid glands.

(c) Entry: Probably mouth.

(d) Exit: Supposedly, in saliva.

(e) Disinfection and Prophylaxis: Only sputum

need be disinfected; however, because in
the army the efficiency is severely taxed by
the orchitis which so commonly occurs
with mumps in adults, isolation and dis-
infection as for other contagious diseases
should be practised.

Pneumonia (Lobar pneumonia).

(a) Cause: Diplococcus pneumonic^ (pneumococcus,

micrococcus lanceolatus) ; is non-sporogen-
ous.

(b) Localization: Lungs; by extension, in blood,

pleural cavity and pericardium.

mCRO-ORGANISMS IN VARIOUS DISEASES. -201

(c) Entry : Respiratory channels ; normally ipresent in

almost everyone's moutb.

(d) Exit: Sputum; in discharges when empyema

(secondary to pneumonia) ruptures, or
is opened by operation; in complications,
otitis media, etc.

(e) Contracted : Exposure to cold and wet ; exposure

to pneumonia while fatigued and depressed.

(f) Disinfection: Easily destroyed by boiling; car-

bolic acid 3-5 per cent, formalin 3-5
per cent, tricresol i per cent. Sulphur or
formaldehyde fumigation.

(g) Prophylaxis: January, February, and March,

are the coldest and most disagreable months
in the year and are on this account the
months in which the greatest number of
cases of pneumonia occur. Avoid wetting
and exposure, and especially after "catch-
ing cold. ' ' Intoxicated persons are partic -
ularly susceptible to pneumonia, as are
also infants, old people, and those debili-
tated by a chronic disease. Mental de-
pression is also a predisposing cause.

Relapsing Fever ("Famine fever," seven-day fever,
etc.).

(a) Cause : Spirochata Obermeieri.

(b) Localization: Blood.

202 INFECTIOUS AND PARASITIC DISEASES.

(c) Entry: Not known, probably through bite of

insect, e.g., bed-bug.

(d) Exit: Probably through bite of suctorial insect.

(e) Contracted : Seems to be contagious ; but as only

seen where over-crowding, and where
hygienic conditions are bad, probably
conveyed by insect.

(f ) Disinfection : Nothing known of the micro-organ-

ism outside of the body.

(g) Prophylaxis: Plenty of fresh air, good food,

and personal cleanliness, are probably the
best means of avoiding the infection.
Screen houses against mosquitoes, flies,
etc., and wage war against all vermin such
as bed-bugs, roaches, etc.

Rubella (Rotheln, German measles).

(a) Cause: Not known.

(b) Localization: Blood, skin, respiratory tract.

(c) Entry: Probably through respiratory tract.

(d) Exit : Respiratory tract and probably emanations

from skin.

(e) Contracted: Resembles measles (which see) .

Scarlet Fever.

(a) Cause: Not known.

(b) Localized : Throat ; blood ; skin ; in complicating

suppurations, e.g., ear.

(c) Entry: Respiratory tract; also wounds.

I

MICRO-ORGANISMS IN VARIOUS DISEASES. 203

(d) Exit: Sputum; nasal secretions; skin, before

and during exfoliation; suppurations dur-
ing and foUowing the disease.

(e) Contracted: Contact with the disease, or with

persons and objects which have been in
contact with same; from milk handled by
persons sick or convalescent from scarlatina;
from individuals with suppurations con-
sequent upon an attack, e.g., otitis media
(middle-ear disease).

(f) Disinfection: Virus has unusual vitality; disin-

fect same as for small-pox or diphtheria.

(g) Prophylaxis : Quarantine should not be less than

forty days after the completion of desqua-
mation, and it might even be continued
longer; air-passages should be treated
antiseptically during whole period of
quarantine. Discharging ear is infectious,
and children with such a discharge have
been known to transmit the disease in this
way. Sun and air room some weeks
after case. Most rigid quarantine and
disinfection must be practised to prevent
contagion.

Small-poz (variola).

(a) Cause: Not known.

(b) Localization : Skin, conjxmctivae, mouth, cesopha-

204 INFECTIOUS AND PARASITIC DISEASES.

gus, rectum, and probably blood ; is general
infection.

(c) Entry: Probably through respiratory tract;

may also enter through abrasions, as the
former practice of variolation proves.

(d) Exit: Exhalations from lungs and skin, partic-

ularly in the dried scales of the latter;
in all secretions and excretions, therefore
in sputum, urine, feces, tears, pustules, etc.

(e) Contracted: Highly contagious; virus is in air

surrounding patient, being thrown oflF with
breath and wafted from eruption; is con-
veyed by persons and f omites ; may also be
conveyed by flies .

(f) Disinfection: Disinfect everything which has

been in contact with patient; also en-
tire room and contents. Screen windows
from flies, and kill all vermin; wipe all
surfaces of room daily with bichloride
of mercury (i-iooo); linens, etc., boil,
steam, or immerse in tricresol (2 per cent),
formalin (5 per cent), carbolic acid (5 per
cent) ; anoint patient with carbolated vase-
lin; all abscesses and ulcers should be
regarded as infectious until healed; fumi-
gate after recovery with sulphur or for-
maldehyde.

(g) Prophylaxis: Vaccination of every one during

MICRO-ORGANISMS IN VARIOUS DISEASES. 205

an epidemic, whether previously vaccinated
or not; isolation of sick, and disinfection
of patient and room after recovery.

Epidemic Stomatitis (aphthous fever, foot and mouth
disease); is disease of cattle, sheep, and pigs, which
is often transmitted to man.

(a) Cause: Unknown.

(b) Localization: Mucous membrane of mouth and

lips; also in wounds; in cattle also on tits
and udder.

(c) Entry: Mouth through milk, and wounds of

hands, arm, and fore-arm from infected
animal.

(d) Exit : From secretions of mouth, and ulcers of the

disease.

(e) Contracted: Contracted from pustules of sick

animal, or from milk, butter and cheese.

(f) Disinfection: Disinfect secretions from mouth,

also discharges from the lesions of the
disease, bandages, linens, etc., in the usual
strengths of the solutions given for other
diseases.

(g) Prophylaxis : Where epidemic in cattle, boil all

milk, and isolate all sick cattle; also indi-
viduals who take care of them ; butter and
cheese made from milk of infected animals
can also convey the disease.

2o6 INFECTIOUS AND PARASITIC DISEASES.

Syphilis (Lues).

(a) Cause: Spirochceta paUidcB {?).

(b) Localization: Practically everywhere in second

and third stages; in first stage (primary)
the initial lesion (chancer) is usually
upon the genitals; extra-genital chancers,
however, may be found upon any cutan-
eous surface; also upon lips, tongue, ton-
sils, eye-lids, or rectum.

(c) Entry: Through abrasions of skin or mucous

membrane ; through spermatozoan ; through
oyum; placenta.

(d) Exit: From discharging lesions, and with blood

when drawn.

(e) Contracted: Usually through illicit intercourse,

when primary lesion is found upon gen-
ital organs ; may be innocently contracted
through kissing, from infected handker-
chiefs, pipes, dishes, etc.; by pricking
finger during operation upon a syphilitic,
or through examination during confine-
ment. When innocently contracted is
called syphilis insontium to distinguish
it from venereal syphilis, which carries
with it an implied stigma.

(f ) Disinfection : Boiling water or steam ; usual chem-

ical disinfectants.

(g) Prophylaxis: Abstinence from irregular relations;

MICRO-ORGANISMS IN VARIOUS DISEASES. 207

ph3rsicians should impress upon all syphil-
itics the danger to others of contracting
the disease from discharges from both the
primary (chancer) and secondary (mucous
patcheSj ulcers, particularly of throat)
lesions.

Tetanus (Lock-jaw).

(a) Cause: BacUlus tetani; forms spores.

(b) Localized : Subcutaneous or sub-mucous tissues ;

usually former; umbilical cord of new-
bom.

(c) Entry : Wounds, often of trifling nature ; also in

woimds where much tearing of tissue
has occurred, especially if soiled with
earth ; compoimd fractures.

(d) Exit: In discharges from wound only.

(e) Contracted: Gim-shot or cannon-cracker wounds;

contusions in which powder, earth or other
foreign bodies driven into tissues; punc-
tured wounds of hands or feet, e.g., by
nail.

(f) Disinfection: As forms spores, prolonged boiling

or contact with powerful disinfectants
necessary, tricresol or l3rsol 2 per cent solu-
tion, two hours; bichloride of mercury
1-500, two hours. Use solutions hot.
Only discharges from woimd, and soiled

2o8 INFECTIOUS AND PARASITIC DISEASES.

dressings, need be disinfected. See an-
thrax (p. 185).
(g) Prophylaxis: Consists in thorough oj>ening and
cleansing of all wounds which have been
soiled with earth, or resulted from Fourth
of July celebrations; or in which foreign
body is imbedded in flesh. Where tet-
anus is feared, the wound should not be
sealed with dressings, but left exposed to
the air ; tetanus antitoxin shotdd be used.

Tuberculosis.

(a) Cause: Bacillus tuberculosis (Koch bacillus);

non-sporogenous, but exhibits greater resist-
ance to destructive agencies than vegetathe
forms of other bacteria.

(b) Localized : Practically everywhere ; lungs (phthi-

sis, consumption) ; l)miph glands (scrofula) ;
bones, abdominal viscera; brain, etc.

(c) Entry: Chiefly by air-passages, and by mouth

with food and drink; also through woimd
of skin and mucous membranes.

(d) Exit: In all discharges from diseased tissues or

organs. As lungs most frequently are
the seat of the disease, the sputum is the
most common vehicle of discharge.

(e) Contracted: Usually by inhalation where pro-

longed contact with consumptive ; probable

MICRO-ORGANISMS IN VARIOUS DISEASES. 209

that infants occasionally contract the dis-
ease by drinking milk from tuberculous
cows.

(f) Disinfection: Boil infected material in closed

vessel ten minutes or longer; well to bum
objects of no value. For sputum, formalin
15-20 per cent, tricresol 2 per cent, l3rsol
2 per cent are recommended; mix these
thorougly with sputimi and let stand one
hour. Fumigate with sulphur or formal-
dehyde.

(g) Prophylaxis: Chief danger is from carelessness

of the consumptive in disposal of sputum;
if careful disinfection of expectoration
and all things soiled during the act of sneez-
ing, coughing, etc., is practised, he is no
menace to others. Those immediately
surrounding the consumptive most often
fall victims, a fact better established than
heredity in this disease. Neither milk
nor meat from tuberculous cattle should
be used. Consumptives should refrain
from kissing others ; nor should they marry.
Typhoid Fever.

(a) Cause: Bacillus typhosus; is non-sporogenous.

(b) Localization: Primarily in intestinal tract or

lungs; in blood; bladder; in complicating

suppurations.
14

2IO INFECTIOUS AND PARASITIC DISEASES.

(c) Entry: By mouth, through water principally;

less often in ice, milk, and other foods; in
some localities oysters are especially dan-
gerous when eaten raw.

(d) Exit: Discharges from bowels; urine; sputum;

suppurative complications; skin; in rose-
spots; sometimes in vomit.

(e) Contracted : The specific bacillus must get into

the mouth and be swallowed; great care
must be exercised by those in attendance
upon typhoid fever patients not to contam-
inate their foods, or the foods of others.

(f) Disinfection: The bacillus is killed inmiediately

by boiling water or steam; disinfect the
sputum, the stools, discharges from the
bowels, urine, linens, eating-utensils, etc.,
by boiling, or by 5 per cent carbolic acid,
5 per cent formalin, 2 per cent tricresol,
and let stand one hour; bichloride of mer-
cury (i-iooo) may be used to disinfect the
urine. When convalescence established,
wash out bladder once daily for several
days with bichloride of mercury (1-20,-
000), or give urotropin 30 to 60 gr.
daily for the same length of time; all dis-
charges should be received in vessels con-
taining a small quantity of one of the dis-
infecting solutions, after which the balance

MICRO-ORGANISMS IN VARIOUS DISEASES. 211

is added in sufficient quantity to make up
the strength recommended,
(g) Prophylaxis : Wherever human excrement is used
as fertilizer, eat nothing raw; boil all
water whether used for drinking purposes
or for dish-washing, unless the water-
supply is above suspicion; boil the milk
and water whenever typhoid prevails, and
use no ice in water for drinking purposes;
screen house against flies.
The essential thing in prophylaxis in typhoid fever,
in fact, in all communicable diseases, is to see to
thorough disinfection of all infectious discharges in the
sick-room. If the latter were done, epidemics of com-
municable diseases could easily be controlled. The fol-
lowing directions, as given by Prof. Osier, are the pre-
cautions followed in the Johns Hopkins Hospital to
guard against the spread of typhoid fever: "Dishes
must be isolated, washed, and dried separately, and
boiled daily. Thermometers must be isolated, kept
in bichloride of mercury (i-iooo), which must be re-
newed daily. Linen, when soiled, must be soaked in
carbolic acid (1-20), for two hours before sending to
the laundry. Stools must be thoroughly mixed with
an equal amount of milk of lime, and allowed to stand
one hour. Urine must be mixed with an equal amount
of carbolic (1-20), and allowed to stand one hour. Bed-
pans and urinals must be isolated and scalded after

212 INFECTIOUS AND PARASITIC DISEASES.

each time of using. Syringes and rectal tubes must be
isolated and the latter boiled after using. Tubs should
be scrubbed daily and soaked in carbolic as the linen
is. Hands must be scrubbed and disinfected after giv-
ing tubs or working over typhoid fever patients.
Blankets, mattresses, and pillows must be sterilized
after use, in the steam sterilizer."

Whooping-cough (Pertussis).

(a) Cause: Unknown.

(b) Localization: Respiratory tract.

(c) Entry: Nose and mouth through air.

(d) Exit: Secretions from nose and mouth.

(e) Contracted : From the sick, or from room, hand-

kerchief, etc., infected by same.

(f) Disinfection: As cause not known, no data.

However, boiling water or steam, and the
usual strengths of the chemical disinfec-
tants are recommended. Fumigate with
sulphur or formaldehyde.

Yellow Fever.

(a) Cause : Not known ; mosquito (stegomyia fascicUa)

known to carry the virus.

(b) Localization: Blood.

(c) Entry: Bites of stegomyia mosquitoes.

(d) Exit : Through bites of mosquitoes.

(e) Contracted : Only by being bitten by infected mos-

quitoes.

MICRO-ORGANISMS IN VARIOUS DISEASES. 213

(f ) Disinfection : Only necessary to destroy all mos-

quitoes in sick-room and house. Sulphur
or p5rretlirum two poimds to every one thou-
sand cubic feet of space, exposure two
hoiirs.

(g) Prophylaxis: Protect sick from bites of mos-

quitoes; screen houses, use mosquito nets,
and destroy mosquitoes in house by burn-
ing sulphur or p5rrethrum; in yellow fever
zones, the breeding places of mosquitoes
should be removed or drained; persons
while out, should protect themselves from
bites.

CHAPTER IX.
DISINFECTION AND DISINFECTANTS.*

The purpose of disinfection is to prevent the spread
of the communicable diseases. In its application it
aims at the destruction of those minute forms of animal
and vegetable life which prey upon both man and
animals and cause disease. The discovery of the rela-
tionship between living pathogenic agents and disease;
of the manner in which these same agents enter and
leave the body; and the subsequent determination of
reliable methods of destroying them, marked a new
epoch in the history of medicine in so far that disinfec-
tion was for the first time placed upon a secure founda-
tion. As a result, before the unseen terrors of the air
and water we no longer wring our hands in abject and
helpless misery while thousands of our fellow-beings
are smitten by disease! Nor do we inhumanly flee
from those afflicted, leaving them not only to the mercy
of a cruel sickness, but also to those beasts among

*For most of the data in this chapter and much in the preceding, the
author has drawn freely upon Dr. Rosenau's ** Disinfection and Disin-
fectants," an incomparable book on the subject; to a lesser extent upon
Dr. Sternberg's "Lomb Prize Essay." To both authors he gratefully
acknowledges his indebtedness.

214

DISINFECTION AND DISINFECTANTS. 215

humanity who see in calamities only opportunity for
license and profit!* But with a courage bom of
knowledge, and with the consciousness of power which
the former inspires, we fight a scourge as we would a
ruthless foe.

The weapons used against infectious diseases are
disinfectants and insecticides, weapons which in our
own generation have made in civilized communities
"plagues" impossible. Indeed, were it not for the
indifference displayed by the public towards sanitary
science in not providing its health officers with ample
resources and authority, many prevailing infectious
diseases, such as tuberculosis, typhoid fever, etc., would
be far less common, and would year by year claim fewer
victims, until they too would in time come to be spoken
of as belonging to the horrors of another age.

Often, in omitting the enforcement of sanitary
measures, physicians and nurses seem callous to the
public weal, a negligence due no doubt to lack of
encouragement from the patient's family. Yet who
are in better positions to dam at their source the springs
of disease ? In every infection the patient is an incuba-
tor, as it were, for pathogenic microbes, which leave
his body by definite channels in the excretions and
secretions. If these discharges are not immediately
made innocuous, there is the probability that the infec-
tion will be spread. The task of disinfecting any

*See Walter Reed and Yellow Fever, by H. A. Kelly.

2i6 INFECTIOUS AND PARASITIC DISEASES.

dangerous discharge at the bed-side is compaxativdy
easy, and one which is properly a duty that the phys-
ician should direct, and which the nurse or family should
perform ; and were this duty, which is one to humanity,
always conscientiously discharged, foods and drinks
would not be polluted in the manner described in pre-
vious pages.

The importance of careful disinfection in the sick-
room of all infectious secretions and excretions, of bed-
linen, towels, eating-utensils, flat surfaces, etc., is
quite well understood by the public generally, and is
treated at length in text-books familiar to both phys-
icians and nurses. Nor do the descriptions of the
various disinfectants and their use differ so greatly as to
require special mention. The following brief outline
is intended solely to call attention to the most eflScient
disinfectants, and to the strengths of the chemical
disinfecting solutions commonly employed.

Heat, as has been stated elsewhere, is the
Heat. most reliable disinfectant known. Burn-
ing, or heating objects to incandescence,
renders them sterile. However, this kind of disinfec-
tion, it is obvious, is seldom practicable, and we must
fall back upon lower temperatures. Either dry or
moist heat is then available. Other things equal, moist
heat is a far more efficient destroyer of germ life than
dry heat, because it has greater powers of penetration.
Boiling tubercle bacilli in water (212° F., 100° C.) for ten

DISINFECTION AND DISINFECTANTS. 217

minutes kills them, whereas they can resist a dry heat
of 2 1 2^ F. for several hours. More efficient than boiling
is live steam, especially if it is used under a pressure of
from one to three atmospheres. Special apparatuses
called autO'ClaveSj are used for this purpose, and all
important sanitary stations possess such an equip-
ment.

The advantages of using an apparatus in which steam
under pressure can be employed are three-fold : (i) The
penetrating power of the steam is increased; (2) since
the temperature of steam rises with the pressure, its
germicidal power is accordingly enhanced ; (3) on account
of the higher temperature and greater penetration, the
time required for disinfection is greatly diminished.
As a matter of fact, the bulkiness of some articles, such
as mattresses, bales of rags, etc., practically precludes
disinfection without the use of auto-claves or especially
devised disinfecting chambers.

Besides steam, formaldehyde alone, or in combination
with steam, is used under pressure for disinfection.
Applied together in this way the two are more quickly
germicidal than either gas used alone.

Bacteria differ in regard to the temperature required
to kill them. Almost all the vegetative forms are killed
at a temperature of (60^ C, 140^ F.) if applied for ten
minutes, and boiling (100^ C, 212^ F.)destro3rs the same
at once. An exception to this rule, as we have else-
where pointed out, is the tubercle bacillus, which.

r

3i8 INFECTIOUS AND PARASITIC DISEASES.

although only occurring in a vegetative form, can with-
stand the temperature of boiling water (212° F., 100° C.)
for ten minutes. In practical work, boiling, where
possible, is resorted to for all vegetative formsof bacteria,
the length of time depending upon the mass of material
to be disinfected.

Spores of bacteria are quite difficult to kill. Where
the apparatus is at hand, steam under a pressure of
from twenty to twenty-five pounds (temperature 230° F.,
105° C. — 240° F., 115.5° C.) is used. If steam under
pressure is not available, boiling for an hour in a closed

Fig. »6.— The Pot Method ot Burning Sulptmr. (Rosenau.)

vessel is a safe rule. Fortunately, none of the epidemic
diseases is caused by a spore-forming microbe, a fact
which lightens greatly the burden and responsibility
imposed upon the disinfector.

Two gaseous disinfectants are in common
use throughout the world, formaldehyde
and sulphur dioxide. Of these, formal-
dehyde approaches more nearly our concep-
tion of an ideal disinfectant than does sulphur dioxide

Gaseous

DiSINFEC-

DISINFECTION AND DISINFECTANTS. 219

or any other. Compared with sulphur dioxide, formal-
dehyde has these distinct advantages, namely, it is non-
poisonous, is a true deodorant, and does not attack
metals, colors, or fabrics. On the other hand, it does
not destroy vermin, as does sulphur, a disadvantage
that is disappointing in the light of what recent investi-
gations have taught us of the highly important part
which various insects play in the conveyance of disease.
To obtain the best results with both formaldehyde and
sulphur requires a full knowledge of the conditions
under which they are generated, of the apparatuses used
in disinfection, and of such concomitant arrangements
of rooms, buildings, conditions of temperature and
moisture, etc., as are necessary. It is not the intent of
this chapter, however, to enter into the subject of
disinfection so extensively as such a description would
entail.

Liquid disinfectants are unequivocally

Chemical superior to gaseous ones if direct contact

by washing, immersion, or mixing, of the

Giquid). disinfectant and infectious matter can be

accomplished. Gases cannot be depended
on for more than surface disinfection, a fact which
restricts their use to the inaccessible parts of rooms,
buildings, ships, etc., and to works of art, e.g., paintings,
and fiaie fabrics.

The resistance of infectious agents to chemical dis-
infectants is subject to the same variations as their

220 INFECTIOUS AND PARASITIC DISEASES.

resistance to heat. Such vegetative forms of bacteria as
are more resistant to heat, are more resistant to chem-
icals; and the sporulating forms are even more difficult
to kill with chemicals than with steam under pressure.
Chemical disinfectants vary greatly in the strength of
each required to be efficient, and their disinfecting
powers also vary with the material to be disinfected.
Very powerful disinfectants may fail to act on account
of chemical union taking place between them and the
material in which the infectious agents are contained.
Thus both bichloride of mercury and carbolic acid
lose much of their disinfecting qualities when added to
albuminous material, on accoimt of the formation of an
insoluble albuminate which is inert. Furthermore, if
one of these substances be used in excess in the belief
that the above defect may be overcome, the end is
just as likely not to be realized, because this insoluble
combination surrounds the infectious agents and pre-
vents contact between them and the disinfectants.
In instances of this kind either the chloride of lime, the
cresols, or formalin are to be preferred. Where the
medium contains much organic matter or filth, even
where the proper disinfectant is used, much stronger
solutions than commonly employed are advisable. An
extremely valuable point to remember in applying any
of the chemical disinfectants is that the disinfecting
power of all of them is greatly enhanced if they are
heated with the material to be disinfected; and the

DISINFECTION AND DISINFECTANTS. 221

higher the temperature, the more is their disinfecting
power increased. In this way substances of feeble dis-
infecting powers may often be used to advantage. The
value of heating a disinfectant is well illustrated by com-
paring the action of carbolic acid upon the anthrax bacil-
lus and its spores. Anthrax bacilli are killed in ten sec-
onds by a one per cent solution of carbolic acid, yet its
spores can live a month in a five per cent solution. But
if the temperature of a five per cent solution of the same
acid is raised to 75^ C. (134.6° F.), they are killed in
three minutes. In all disinfection, therefore, hot solu-
tions should be used.

DISmFECTING SOLUTIONS.

Perhaps the commonest disinfectant used
BicHLORmE is bichloride of mercury (corrosive subli-
OF Mercury, mate). It is a powerful germicide, even in

weak solutions. It has several serious
drawbacks, however, which limit its usefulness ; among
these is the fact that it is a corrosive poison; that its
solutions attack practically every metal; and that it
unites with albuminous matter. For the last reason it is
not to be used as a disinfectant for the disinfection of
sputum, feces, and discharges containing albumin,
such as pus. For washing floors, walls, and other sur-
faces, a hot solution (i-iooo) is as efficient as any other
disinfectant. For ordinary purposes the i-iooo solu-
tion is the strength employed. This can be prepared

222 INFECTIOUS AND PARASITIC DISEASES.

from the tablets when a small quantity is desired, or in
larger quantity by taking

Bichloride grs. 6i J.

Citric acid or common salt grs. 6i^.

Water gallon i.

The i-iooo solution is ample for the destruction of all
non-spore-bearing bacteria at ordinary temperatures
in one-half hour. For spores, stronger solutions (1-500),
and a longer exposure (one hour), are advisable. As a
disinfectant for the hands in surgical work, and as a
moist dressing in various inflammatory conditions, this
solution of mercury is in constant use.

Formalin is used as a disinfectant in a 4 to
FoRMALm. 5 per cent solution of the 40 per cent solu-
tion of the gas in water. Its advantages as
a disinfectant are many; it does not injure most fabrics;
it attacks only two metals, iron and steel, and these
only when hot. It is non-poisonous, and albuminous
matter does not interfere with its action. It kills spores.
It is a true and efficient deodorant. Urine, feces,
sputum, and all albuminous discharges, are quickly
disinfected and deodorized by it.

Carbolic acid is a useful disinfectant and
Carbolic is with reason widely used. A 3 to 5 per
Acm (phenol), cent solution (the latter 1-20) is the

strength employed. Since it does not
kill spores, it should not be used after anthrax, tetanus,

DISINFECTION AND DISINFECTANTS. ^23

malignant oedema, and other diseases due to bacteria
which produce spores. Although it coagulates albu-
minous matter, it is not so active in this respect as bi-
chloride of mercury, and can therefore be used for the
disinfection of soiled linens, clothing, and also for
excreta. It is well to remember that carbolic acid is a
powerful corrosive poison. For liquid discharges in
cholera, typhoid, d3rsentery, etc., a 5 per cent solution
may be used, when twice the amount of carbolic to
material is advised. The mixture should be allowed
to stand four hours.

A convenient method of preparing a five per cent
solution (1-20) is as follows:

Carbolic acid (95 per cent) ozs. 6^

Water gallon i

Agitate until the acid is thoroughly dissolved in the water.

The cresols are among the most powerful
and valuable disinfectants known. None
of them are as poisonous as carbolic acid (phenol),
nor are they open to the objection that albumin-
ous material interferes with their action. They all
kill spores. Tricresol may be used in i per cent solu-
tion for the disinfection of infected discharges of all
kinds. The other preparations of the cresols, solutoly
solveol, lysol, as compared to tricresol, have a reputation
for disinfecting power in the order in which they are
named.

224 INFECTIOUS AND PARASITIC DISEASES.

Lime (quicklime), as such, is useful for the
disinfection of cadavers dead of infectious
diseases. For this purpose twice the weight of the
body in xmslaked lime is packed about the cadaver,
which should be contained in a tight cofl&n. Neither
water or moisture need be added.

Which is prepared from the slaked lime
Milk of (hydrate of lime, calcium hydrate) by add-
LiME. ing one part by weight of hydrate of lime to
eight parts of water, is a valuable disin-
fectant for excreta.

The slaked lime used in the preparation should
always be freshly made by mixing one pint of water to
two poxmds of lime. For the disinfection of stools,
an amount of milk of lime equal to the material to be
disinfected should be used, and the mixture be allowed
to stand two hours. Whitewash is slaked lime mixed
with water to the consistency of a thick cream. It is a
valuable means of disinfecting the walls and ceiling of
stables, cellars, and other rough structures.

Chlorinated lime is best adapted for the
"Cm^oRiDE disinfection of excreta and sputum. It is
OF Lime." both deodorant and disinfectant. For dis-
infecting purposes dissolve eight ounces of
the chloride of lime in a gallon of water (Sternberg).
This solution should be placed in the vessel before it
receives the discharge. From one to two quarts are
used in the case of cholera or t)rphoid stools. After

DISINFECTION AND DISINFECTANTS. 225

thorough agitation, the mixture is allowed to stand
from one-half to one hour. For sputum, an amount
equal to the volume of the sputum should be added, or
the sputum cup should be filled about one-half with the
solution before use. Chlorinated lime cannot be used
for the disinfection of fabrics or colored goods, since it
bleaches and attacks the fabric directly. The chlorin-
ated lime used in the preparation of disinfecting solu-
tions must have been contained in an air-tight receptacle,
otherwise from exposure to the air much of its disin-
fecting powers are lost. It has about the same germi-
cidal value as milk of lime.

15

CHAPTER X.

THE COLLECTION AND EXAMINATION OF
SECRETIONS AND EXCRETIONS.

This chapter in introduced as an aid in the exami-
nation and collection of specimens of the various excre-
tions, in preserving them from deterioration, and in
describing them in simple terms according to profes-
sional custom. Attention is directed only to such points
as may be of value either to the observer, or to another
by whom the specimens are to be examined and their
significance interpreted.

From many standpoints, the sputum, in
Sputum, disease, possesses very great importance.

Its bulk is made up of pathological secre-
tions, abnormal cellular elements, occasionally tissues
and rarely stones, all of which are of great diagnostic
significance ; at the same time, it is the vehicle in which
the pathogenic agents of many diseases, both local and
general, make their exit from the body. From a mere
visual examination, the trained observer can detect
the presence of features characteristic of certain dis-
eases, and abnormal ingredients that are suggestive of
disorders of certain organs; whik with the microscope

226

SECRETIONS AND EXCRETIONS. 227

he can observe the presence of bacteria, animal para-
sites or their eggs, and the various other constituents
invisible to the unaided eye.

Attention should always be given to the
Amount, amount of sputum expectorated in the

twenty-four hours, since only in this way
can an increase or decrease be definitely determined.
A daily record should be kept of the quantity, other-
wise in the rush of other work valuable information
may be lost. Especially important is a knowledge of the
amount of expectoration in case of haemorrhage, or of a
sudden large increase, as may occur when an hepatic
abscess ruptures into the lungs. The twenty-four
hours' quantity should be measured for the reason that
many patients (e.g., pulmonary tuberculosis, bron-
chiestasis) expectorate chiefly only during one or two
hours in the twenty-four, so that if the amount expelled
at this time is not taken into account, a report of a scanty
expectoration might be made.

Consistence of a sputum is another charac-
CoNsisTENCE. tcrfstic of importance; it may be thin and

watery (serous), or so heavy and tenacious
that the vessel may be inverted without spilling its con-
tents (mucoid). Mucoid sputum is seen most charac-
teristically during the stationary period of pneumonia.
Between these two extremes there may be various de-
grees of consistency, or the sputum may consist of both
elements distinctly discernible (muco-serous). Thus,

228 INFECTIOUS AND PARASITIC DISEASES.

in pulmonary tuberculosis, when the sputum-cup has
stood awhile, the contents are seen to consist of an upper
watery layer, and a lower tenacious mass which, when
shaken, is seen to be made up of round, coin-like partic-
les. This is the so-called mummidar sputum which is
characteristic of the second and third stages of consimip-
tion.

Worth remembering also is the fact that on standing
twenty-four hours or longer in a warm room, a tenacious
sputum may become liquefied through solution of its
mucus by ferments.

Much valuable information may be derived
Color, from the color of a sputum. Sputum may

vary from the clear glairy appearance of
normal saliva, to grey, yellow, green, red, brown, and
even black. A greenish or yellow color indicates either
pus (purulent), or bile (bilious) ; a red color, blood (san-
guineous); a brown or chocolate color, liver abscess;
and black, carbon, a condition resulting from the inhala-
tion of carbon particles as is practised by smokers for
pleasure or by miners from necessity.

If there is anything unusual to the odor of a
Odor. sputum, it should be noted. Most sputa

are practically odorless. However, under
certain circumstances, e.g., putrid bronchitis, the other
extreme is presented, and the offensiveness of the
expectoration beggars description. In pulmonary tu-
berculosis the sputum has a sweetish odor.

SECRETIONS AND EXCRETIONS. 229

In describing a sputum a single predomi-
nating characteristic is selected. Thus as

Description ^ i. xi. -j xi. i i.

o types we have the mucoid, the purulent,

OF A Sputum. ^^ .

the serous, and the sanguineous. Where
two or more elements are plainly mingled,
such terms as muco-purulent, muco-serous, sero-san-
guineous, and sanguino-mucopurulent, are used to de-
scribe it.

Sputum is most frequently examined for the tubercle
baciUus, and where it is to be submitted to an expert
with this object in view, the following directions should
be observed : " Collect the sputum in a clean one or two-
ounce bottle with a wide mouth and a water-tight stop-
per. The bottle should be labeled with the name of the
patient. The sputum coughed up in the early morn-
ing is to be preferred. If the expectoration be scanty,
the entire amount coughed up in the twenty-four hours
should be collected. Care should be taken that the con-
tents of the stomach, food, etc., are not ejected during
the act of coughing, and collected instead of pulmonary
sputum. Purulent, cheesy, and muco-purulent sputa
most frequently contain tubercle bacilli; pure mucus,
blood, or saliva do not as a rule contain them. When
haemorrhage has occurred, if possible some purulent,
cheesy, or muco-purulent sputum should be collected
for examination. The sputum should be forwarded in
as fresh a condition as possible."

230 INFECTIOUS AND PARASITIC DISEASES.

In suspected diphtheria, for the purpose
Diphtheritic of diagnosis, and after recovery from diph-
CuLTUREs. theria, before raising the quaxantine, to

determine the presence or absence of the
specific bacillus, it is compulsory in many cities that a
specimen be taken from the patient's throat and sent to
the municipal laboratory for examination. For this pur-
pose a special outfit is furnished consisting of two glass
tubes, one, containing a sterile swab, the other, a cream
or chocolate colored jelly which fills about one-third of
the tube. The material in the second tube is blood-
serum which has been solidified in a slanting position
by heat. To make a culture, the swab is first smeared
over the affected area in the throat, and then immediately
applied to the slanting surface of the blood-senim. The
tubes are then returned to the laboratory where the one
containing the blood-serum is placed in a warm oven
(37.5° C. — 98.6° F.) for from twelve to eighteen hours.
A stained preparation of the bacteria, which by this
time have developed upon the blood-serum, is now ex-
amined with a microscope, and the presence or absence
of diphtheria !^bacilli determined. The following di-
rections, taken from the literature of the Philadelphia
Health Department, is an illustration of the instruc-
tions which accompany the tubes:

DIRECTIONS FOR MAKING CULTURES.
"The patient should be placed in a good light, and,
if a child, properly held. In cases where it is possible

SECRETIONS AND EXCRETIONS. 231

to get a good view of the throat, depress the tongue and
rub the cotton swab gently, but freely, against any
visible exudate, revolving the wire between the fingers,
so as to bring all portions of the swab in contact with the
mucous membrane or exudate. In other cases, includ-
ing those in which the exudate is confined to the larjnix,
pass the swab as far back as possible, avoiding the
tongue, and rub it freely as described above against the
mucous membrane of the pharynx and tonsils. With-

FiG. 27. — ^Method of inoculating culture media. (Williams.)

draw the cotton plug from the culture tube, holding
it so that the portion withdrawn from the tube does not
come in contact with the fingers or with any other
substance. Insert the swab and rub it gently but
thoroughly back and forth over the entire surface of
the blood-serum. Do not allow the swab to touch
anything except the throat of the patient and the sur-
face of the serum. Do not push the swab into the
serum, nor break the surface in any way. Do not use

232 INFECTIOUS AND PARASITIC DISEASES.

tubes m which the serum is contaminated, is liquefied
or is dried up. Then replace the swab in its own tube,
plug both tubes, mark the cultiure tube with the name
of the patient for identification, and return both tubes
to the laboratory. Unsatisfactory cultures usually
result from failure to follow carefully q
the above directions." Caution: In
making cultures, to insure a successful
result, no antiseptic must have been
used in the patient's throat for an hour
preceding the taking of the culture.

In croup, a membrane is often
coughed up, which it is sometimes de-
sirable to have examined to determine
the nature of the infection, i.e., whether
diphtheria is present or not; in such
cases it is especially important that the
specimen be not placed in any preserv-
ing fluid or disinfectant, since such
solutions destroy the very agents which
it is aimed to find.

Vomiting is a feature in fig. 28.— Needles

,, 1 1 T e .^ . ^^sed for inoculating

VOMIT. local diseases of the stom- media,
ach ; in affections of neigh-
boring organs (heart, liver) ; it also occurs at the onset
and during the progress of the infectious diseases.
The points to be observed in vomiting are the time, color,
odor, quantity, and ingredients.

SECRETIONS AND EXCRETIONS. 233

The time of vomiting is important, espe-
TniE. dally in relation to meals. It should be
noticed whether vomiting immediately fol-
lows the ingestion of food, or is delayed some minutes
or hours; also whether it apparently results from the
ingestion of some particular article of diet. Vomiting
may be frequent, as in the early months of pregnancy,
or it may be sporadic, as in dilatation of the stomach.
Sudden, unexpected, vomiting practically always marks
the onset of the eruptive fevers in children.

Color is given to the vomit either by the
Color. foods ingested, or by foreign or patho-
logical constituents such as bile, blood,
mucus, etc.

As a rule the vomit is green or golden in
Bile. color from admixture with bile, a secre-
tion which is always present in intense or
continuous vomiting.

Red vomit usually results from admixture
Blood, with blood. If the blood has not been
acted upon by the digestive juices, it is
easily recognized ; but the gastric ferments may so alter
its appearance that the vomit may vary from a deep-
red to a coflFee or black color. Black vomit, it will be
remembered, is a characteristic s)nnptom in yellow
fever. Vomit may also be dark from the presence of
stercoraceous material (feces). Care should alwa3rs
be taken not to mistake food for evidence of pathological

234 INFECTIOUS AND PARASITIC DISEASES.

vomit. The writer was once sent the red vomit of a
pregnant woman for examination, haemorrhage being
suspected. The red color was due to nothing more
serious than ripe tomatoes which anyone might have
seen had they looked well.

The normal odor of the gastric contents
Odor. is acid. In disease, it may be "beefy"

from the presence of blood ; putrid in can-
cer or dilation; ammoniacal in uraemia. In stercora-
ceous vomiting it has the characteristic odor of the
stools.

Measure or gauge as accurately as pos-
QuANTiiY. sible the quantity vomited. The normal

stomach has a capacity of three pints, an
amoimt which may be increased in dilatation to three
or more quarts. The quantity vomited also furnishes
important information as to the absorptive and diges-
tive powers of the stomach, especially when considered
in connection with the amount and kind of food in-
gested. To obtain the latter data, physicians are in the
habit of giving a measured quantity of food (test-meal),
and within an hour withdrawing it with a stomach-
tube for examination.

Test-meals are given either in the morning i
Test-meals, or at noon, and, depending upon the time '

given, are called respectively test-breakfast
or test-dinner. The most common test-meal is the
breakfast. Two breakfast formulae are in common use,

SECRETIONS AND EXCRETIONS. 235

which are named after their originators, Ewald and

Boas.

Test-break- Consists of from 35 to 70 grams (2 ounces)

FAST OF of wheat bread, and of 300 to 400 cu. cm.

Ewald AND (ij to 2 glasses) of water, or weak tea

Boas. without sugar.

Consists of oatmeal soup, prepared by
Test-break- boiling down to 500 cu. cm. (17 fluid
FAST OF Boas, ounces) one liter (quart) of water to which

one tablespoonful of rolled oats has been
added. A little salt may be added, but nothing more.

Soup 400 cu. cm. (2 glasses), beefsteak
Test-dinner 200 grams (7 oimces), wheat bread 50
or Riegel. grams (if oxmces), water 200 cu. cm. (i

glass). Finely chopped meat may be sub-
stituted for the beefsteak.

Besides the contents already mentioned
Ingredients, above, the vomit always contains more

or less mucus and saliva. Food in all
stages of digestion will be noticed, and, if present, the
segments (proglottides) of tape-worms, the adult round
worm (ascaris lumbricoides), and the thread-like
trichinae. Foreign indigestible objects, which have
been swallowed, may be discovered, such as pins,
needles, whistles, etc. These are found most often in
the vomit of children, the insane, and in hysterical
subjects. In the last class of patients the most rigid
surveillance must be practised to prevent deception.

236 INFECTIOUS AND PARASITIC DISEASES.

From an examination of the blood alone,
Blood the diagnosis of a limited number of dis-

Specimens. eases can often be made. In a few, as

for example malaria, the agents of the dis-
ease can be detected with the microscope in properly
prepared specimens; in others, e.g., typhoid fever,
when a drop of blood is brought in contact with known
typhoid bacilli, a characteristic phenomenon, WidoFs
reaction, takes place, which consists in a clumping or
drawing together of the bacilli ; in still another class of
diseases, the diagnosis is made by determming the
mmiber of red and white corpuscles present in one
cubic centimeter of blood, and noting in what respects
their number and appearance dijffer from that which is
normal. In cities maintaining mxmicipal labora-
tories, outfits for the collection of specimens of blood
for the diagnosis of both malaria and typhoid fever are
supplied.

This outfit for typhoid fever consists of
Typhoid either a slip of unglazed paper, a glass
Fever slide, or a metal plate, upon which the
(Widal) blood is to be collected, and a needle for
OuTFrr. puncturing the ear or finger. These with
the directions for taking the blood are
enclosed in an envelope.

The directions for taking the blood-drop on paper
are as follows:
"Thoroughly cleanse the skin of the patient^s finger-

SECRETIONS AND EXCRETIONS.

237

tip or the lobe of the ear. After carefully drying, prick
it with a needle previously sterilized by heating over a
lamp or gas flame and allowed to cool. Allow five or
more large drops of blood to dry on the inner surface of
a piece of paper. Replace the folded paper in the en-
velope, and return to the laboratory. " Where a glass
slide or a thin sheet of metal is used in place of the

A B

Fig. 29. — ^Application of the Serum-reaction to Typhoid Bacilli. (Williams.)
A, shows the distribution of the badlli before the reaction. B, shows clump-
ing of the motionless bacilli after mixture with the serum of a case of typhoid
fever. (Diagrammatic.)

paper, the directions for the collection of the blood
specimens do not differ materially from the above.

As a rule the Widal reaction is not given by the blood
in typhoid fever before the sixth or seventh day, and
sometimes not until almost the end of the sickness ; for
this reason it is advisable to prepare a second specimen
of the blood after a few days in case the first specimen

238 INFECTIOUS AND PARASITIC DISEASES.

proves negative. In about five per cent of the cases the
reaction is never obtained during the whole course of
the disease, a fact, it would appear from recent studies,
due to the presence, as causative factor in the disease,
of another bacterium, the para-colon bacillus. Blood
from such a case when tested with a para-colon bacillus,
gives the characteristic reaction.

For the detection of the malarial parasites
Malaria, either glass slides or cover-glasses are used,

the former being given the preference by the
majority of municipal laboratories. The directions for
preparing specimens of blood in suspected malarial
fever as given by the New York Health Department,
are as follows:

"Wash two glass slides with alcohol, and wipe with
a soft, clean linen cloth (not a soiled handkerchief)
until clean and shiny. On cold, damp days the slide
should be warmed over a flame. After cleaning, the
slides must be held by the sides (F F in diagram), and
surfaces and ends not touched. Clean the patient's
ear-lobe with alcohol and prick the skin with a sterile,
surgical needle or a small pointed scalpel, so as to act-
ually incise the capillaries. The blood should not be
squeezed out, but should flow freely. Wiping oflf the
first few drops, the third or fourth drop should be
quickly (before it gets much larger than a pin head)
taken up on the edge of one end of one slide. Place
this edge on the surface of the other slide, as indicated

SECRETIONS AND EXCRETIONS.

239

in the diagram, and as soon as the blood-drop has
spread along the line of contact, draw the upper slide
gently along the surface of the lower, thus spreading
the blood in a thin film. Dry this by waving in the air.
Do not heat. Repeat the process, using the edge of
the prepared slide to spread the blood upon the other
slide. The blood should be taken before quinine has
been administered, as quinine quickly expels most of the
malarial parasites of this latitude from the capillary
blood. Under such circumstances negative reports

Fig. 30.

count for little or nothing. The blood should be drawn
just before^ during, or just after the supposed malarial
paroxysm, as the parasite is present in the capillaries
in much greater numbers at those times. "

When cover-glasses are preferred, two or more cover-
glasses are cleansed in precisely the same way as
described for slides. A small drop of blood is caught in
the center of one cover-glass by bringing the latter in
contact with the former. Then the second cover-glass
is allowed to fall gently upon the other. If the glasses
have been well cleansed, the blood will immediately

240 INFECTIOUS AND PARASITIC DISEASES.

spread in a thin layer between them, when they are at
once separated by gently drawing one over the other
in the same plane, i.e., parallel to the other.

If an examination of the red and white
Specimen FOR elements of the blood is to be made, blood
Corpuscular gj^g are prepared upon slides or cover-

EXAMINA- . ^1. J 'U ^ t

^jQjj glasses m the same way as described for

malaria.

Fig. 31. — Cover-glass is touched to summit of a drop of blood and
then allowed to fall on a second cover-glass, margins overlapping.
Method of separating cover-glasses. (Clinical Diagnosis, Boston.)

The microscopical examination of purulent
Pus AND or other discharges often permits of the
OTHER immediate discovery of the agents causing

Discharges, a disease, a fact which may be of incalcul-
able benefit to the patient, and a sure guide
for the doctor. This is the case, for example, in puru-
lent ophthalmia, a suppurative conjunctivitis most fre-
quently observed in the new-bom, although also found

I

SECRETIONS AND EXCRETIONS. 341

in adults, and which if not recognized speedily leads

to permanent blindness. Specimens of such discharges

are collected upon slides

or cover-glasses in the

same way as described for

malaria, care being eser- «

cised that the smears are

not too thick. In making

smears in this class of

cases, it is safest, on ac- 1

coxmt of the dai^er of

self-infection, to use an

object easily destroyed, as

for example a tooth-pick,

which is then burned.

No secretion during sickness is subject to
Urme. closer scrutiny than the urine. It is the

chief avenue for the elimination of nitro-
gen from the body, as well as for other substances which,
if retained, are distinctly hannful. In many diseases it
is the channel of exit for the specific bacteria from the
body. Such highly significant data bearing upon a pa-
tient's illness are obtained from a study of the urine,
that the precise condition of this secretion is always as-
certained.

Normal urine, when freshly voided, should
CoLoa. be perfectly clear or faintly cloudy. Its

color is variable, verging from a light yellow
16

242 INFECTIOUS AND PARASITIC DISEASES.

or straw, to a brownish-red. The color of all urines
deepens upon standing, while at the same time a doud
forms which gradually sinks to the bottom of the vessd
which contains it. Urines which are allowed to get
chilled are often quite cloudy or opaque, and when pre-
senting this appearance are sometimes taken to indi-
cate an abnormality in the secretion. Opacity from
this cause is quickly dissipated on the application of
heat.

Pathological urines exhibit the same variations in
shades as the normal. The color of all urines is sub-
ject to seasonal variation, being pale in winter and dark
in summer. A pale urine simply indicates an excess of
water. The color of urine is also influenced by the
food ingested.

Urines are described as:

(i) Pale or straw color.

(2) Amber.

(3) Reddish-yeUow or red (high color).

(4) Reddish-brown (dark urine).

Besides these shades the urine may be green from
bile, red from blood, black from melanin, blue from
indican or after the ingestion of methylene blue, yellow
from santonin or rheum, and milk-like from the presence
of pus or chyle (chyluria). In filariasis, the urine may
contain both chyle and blood, a condition to which the
name hcBmatochyluria has been given.

SECRETIONS AND EXCRETIONS. 243

Bile imparts to urine a yellow or greenish-
BiLE. brown color, and can usually be detected

at once upon inspection. If a urine con-
taining bile be shaken, the foam which collects upon the
top will be found of a yellowish or greenish hue even
when these colors are not pronounced in the body of the
urine. The same urine when filtered also leaves a
greenish stain upon the filter-paper.

Five to ten cubic centimeters of urine are

placed in a test-tube and treated with two

Smith's Test

^ to three cubic centimeters of tincture of

'°'' ^"" iodine (which has been diluted with alcohol

in the proportion of one to ten) in such
manner that the iodine solution forms a layer above the
urine. In the presence of bile, a distinct emerald-
green ring is seen at the zone of contact.

Blood gives urine a color which may vary
Blood, from bright red to dark brown. Such
urine turns darker upon standing. In
cases in which blood is voided, it is important that the
urine of a single micturition be passed in two or three
portions. A person voiding urine mixed with blood
is said to suffer from hcematuria. When the blood is
dissolved in the urine, i.e., the haemoglobin has left the
corpuscles, the condition is called, fuBtnoglobinuria.
Sometimes it is difl&cult to distinguish blood from bile in
urine, as both may present the same appearance. They
can usually be distinguished by dilution with water

344 INFECTIOUS AND PARASITIC DISEASES.

which ax:ts so as to bring the red color of the blood more
prominently into view.

Urine containing pus, when allowed to

Pus. stand a short time, exhibits a heavy white or

creamy precipitate. If shaken or poured

out, it is seen to be tenacious or stringy. Pus is often

associated with blood in the urine.

Salol is so frequently prescribed, that

Green attention is directed to the fact that urine

Urine, voided by a patient taking it becomes green

and eventually black upon standing.

The quantity voided in the twenty-four

Quantity, hours is subject to great variations, usually

bearing a relation to the quantity of fluids
ingested. Exercise, sleep, temperature, atmospheric
moisture, all influence the urinary secretion.

An adult ordinarily voids between twelve hundred
and fifteen hundered cubic centimeters (thirty-five to
fifty ounces) of urine in the twenty-four hours. Most
individuals do not void urine after retiring; and if this
has been the rule, a departure from this habit should be
viewed with suspicion.

Polyuria is the condition in which imusually
Polyuria, large amounts of urine are passed in the

twenty-four hours. An extreme grade of
polyuria is common in diabetes; and in that form in
which sugar is also present (diabetes mellitus), twenty-
five or more liters (quarts) is not very unusual.

SECRETIONS AND EXCRETIONS.

24S

Oliguria is that condition in which amounts
Oliguria, of urine below the average are passed.

Usually it is a very serious symptom; how-
ever, it is occasionally seen in neurasthenics.

The odor of urine is of slight significance.
Odor. The normal odor is described as like that

of ''bouillon," "oysters," or "new hay."
Uriniferous, as applied to urine, describes its odor after
decomposition has taken place. Freshly voided urines
which are uriniferous are pathological.

The specific gravity of the urine is deter-
Specific mined with an instrument called a urin-
Gravtty. ometer. With the urinometer is supplied

a cylindrical vessel which is to hold the
urine while the specific gravity is be-
ing taken. To determine the specific
gravity the cylinder is nearly filled
with urine, when the urinometer is
slowly introduced. The specific
gravity is read directly from the
scale at the upper end of the in-
strument where the surface of the
urine meets a division on the scale. ^ o- i tt •

Fig. 33. — Simple Urin-
A sample of the twenty-four hours' ometer and Accessories.

output should be employed. "^^^

Normally the specific gravity varies between loio
and 1025; pathologically, between 1002 and 1060.
Urines containing albumin have their specific gravities

246 INFECTIOUS AND PARASITIC DISEASES.

between 1005 and loio; those containing sugar, between
1030 and 1040. To be sure, these limits are often
exceeded or diminished.

The reaction of normal urine is acid,
Reaction, although specimens passed at different

times may be neutral. The reaction of a
urine is obtained by wetting pieces of filter-paper whidi
have been colored red or blue by saturation with red or
blue litmus. If a urine be acid it will impart to the blue
paper a red color; if alkaline, the red paper will be
changed to blue. Normal urines sometimes alter the
color of both papers slightly; such urines are said to be
amphoteric. The latter is of no significance.

Albumin in urine is always an indication of
Albumin, disease. Tests for its presence should be

made as a routine procedure.

To determine the presence of albumin,

Nitric (i) fill a test-tube two-thirds full of urine

Acid Test, and apply gentle heat to the upper surface

until it begins to boil. Now add a few
drops of concentrated nitric or acetic acid. Should the
urine remain clear it is free from albumin; if cloudy 1
upon boiling, and the cloud does not clear up up>on the |
addition of the acid, it contains albumin. ;

(2) Add a few cubic centimeters of con-

CoNTACT centrated nitric acid to a test-tube and,

Test. while inclining the tube at an angle of

about forty-five degrees, with a pipette let

SECRETIONS AND EXCRETIONS. 247

a few cubic centimeters of urine flow down the sides of
the tube so that it floats upon the acid. Hold the tube
straight and to the light, when if albumin be present a
white ring will be seen at the junction of the two
fluids.

Caution : Filter the urine before applying any test for
albumin.

The presence of sugar in urine is deter-

mined by heating a few cubic centimeters

of Hain's solution in a test-tube, and then

immediately, upon removal from the flame,

adding a few drops of the suspected urine. If sugar

is present the blue color of the solution will be changed to

a canary or reddish yellow. Always boil and filter

urines containing albumin before applying the test for

sugar.

Bacteria, and the eggs of animal parasites,
Foreign are also at various times eliminated in the
Substances, urine. But as this phase of the subject

is treated in detail in another chapter,
reference is made to it here for the sake of completeness
only.

At times, however, other things are voided in the urine
which should be spoken of in this place. Reference
is made to gravel and stones from the kidneys or blad-
der, hair from dermoid cysts, fecal matter (in vesico-
rectal fistula), etc. In hysterical subjects and the
insane, hairs, beans, fish-bones, etc., may be actually

348 INFECTIOUS AND PARASITIC DISEASES.

voided, or be passed oflF on the physician as having
been voided. Where the objects axe really passed
in the urine, they are introduced into the urethra or
bladder before micturition. Hair, however, may be
passed in the urine in cases of dermoid C3^ts of the
bladder.

When preparing a specimen for examina-
CoLLECTioN tion, a portion of the full twenty-four hours'
OF Specimen, secretion should be chosen. Although

this does not always furnish the inost
satisfactory sample, it is the safest rule to follow in the
absence of specific instructions. In one form of Bright's
disease, for example, albumin is present only an hour
or two after meals, and then in very small amounts,
so that the examination of a twenty-four hours' mixture
might not reveal its presence. In like maimer, in
diseases of the genito-urinary organs, the twenty-four
hours' secretion does not give as much information as
one or several specimens collected during a single act
of micturition; and in affections of these parts the
patient is directed to divide his urine while voiding it
into two or three portions. If possible always send
at least four ounces of urine for examination. Unless
the urine can be examined in a few hours, keep it in a
cool place; or add to it gr. v of boracic acid, or one
dram of chloroform, to every four ounces of urine.
Formalin, m. i to four ounces, is also an excellent
preservative.

i SECRETIONS AND EXCRETIONS. 249

[ The observations to be made of the stools

Feces. include the number, amount, consistence,

form, color, and odor of the movements, and
further, the presence or absence of mucus, blood, pus, gas
bubbles (which denote fermentation), animal parasites
(e.g., worms or segments of same), foreign bodies (e.g.,
pins, coins, etc.), gall-stones, and undigested food
particles. When blood, pus or mucus is discovered,
its relation to the rest of the movement should be noted,
that is to say, whether the same is mixed with the
stool, clings to it, or is passed separately before or after.

Normally the number of stools in different in-
NuMBER. di viduals is subject to great variations, so that

it is impossible to fix a standard which will ap-
ply to every one. Thus, while it is usual for the majority
of persons to have at least one movement in the twenty-
four hours, it is not uncommon to find some who exceed
this number by one or two stools, and still others for
whom one stool in two or three days is apparently
normal. Wide variations in the number of stools is
compatible with good health. For the average person,
however, at least one movement daily is requisite; less
than this number constitutes constipation, and more,
several loose movements, diarrhoea. Both constipation
and diarrhoea are important symptoms not only in
diseases of the alimentary tract, but of s)rstemic aflfec-
tions as well, and the history of no case is complete
without a record of the state of the bowels.

2SO INFECTIOUS AND PARASITIC DISEASES.

The amount of fecal matter does not vary
Amount, so much as the number of stools, since

the greater the nimiber, the smaller the
individual movements, and vice versa. The size of the
stool bears a relation to the kinds of food eaten, a diet
rich in vegetables and starchy foods leaving a much
larger residue than one rich in animal proteids.

The consistence of a stool depends upon
Consistence, the amount of water present. In health

the food determines the amount of the
latter, being greater with a vegetable than a proteid
diet.

Stools are described in regard to their consistency as
thin, mushy, or watery; and hard and dry (scybalous).

The color of a stool varies with the charac-
CoLOR. ter of the food ingested. It may be quite

light, as in a person restricted to a milk
diet ; green from green vegetables ; and black from a diet
containing an abundance of rare or raw meat. All
stools turn darker upon exposure to light. In disease
the stools may be golden, yellowish-green, or green,
from bile; pasty and greyish or white, in diseases
of the liver or bile passages ; red, brownish-red, coflFee-
colored, or black (tarry) from blood; dark blue from the
administration of methylene blue. Calomel turns the
stool green. The number of stools also has a bearing
upon their color, the larger the number, the lighter the
color of the individual movements.

SECRETIONS AND EXCRETIONS. 251

Examinations of the stools are frequently
advisable for the purpose of discovering,
if possible, gall-stones, animal parasites,
and eggs of parasites.

If gall-stones, worms, or any other abnor-
^ mal constituent is to be sought in the stools,

STONES, JliTC

the following procedure is advisable:
(i) Have stools for twenty-four or forty-eight hours
passed into a large vessel.

(2) Mix each stool with about a gallon of water and
stir thoroughly; let stand for one-half hour and then
carefully pour oflF most of the fluid.

(3) Add more water and mix as before.

(4) Cover another vessel with surgeon's lint, fastening
same with cord or adhesive plaster, and pour the mix-
ture upon the gauze.

In the detritus left upon the gauze, search for gall-
stones, parasites, or any other foreign object. In place
of the lint, a fine sieve may be used with which to strain
the mixture. Gall-stones vary in size from a grain of
sand to an olive and larger, and are usually of a brown-
ish-green color. They may crumple to the (ouch, or
be quite hard. Often they show the typical smooth
facets on one or more sides. The appearance of para-
sites and the kinds usually encountered, are described
in the chapter devoted to parasites.

For microscopical examination the feces should be
passed into a warmed vessel and sent to a laboratory

asa INFECTIOUS AND PARASITIC DISEASES.

at once; or in case this is not feasible, a small portion
should be poured into a wide-mouthed bottle, and while
en route to the examiner kept warm.

Parasites may be preserved for longer periods in
either weakened alcohol or whisky. Gall-stones should
be placed in a tightly stoppered bottle to prevent deteri-
oration.

APPENDIX

WEIGHTS AND MEASURES.

1. English.

I grain (gr.)

I ounce (oz.) =437-5 grains.

I pound (lb.) =i6 ounces=7ooo grains.

I minim =.91146 grain.

I fluidram =60 minims.

I fluidoimce =8 flnidrams.

I pint =20 fluidomices.

I gallon =8 pints.

2. Relations of English and Metric Systems.

I grain =64.8 milligrams.

I oimce =28.3 grams.

I poimd =453.6 grams.

I gram =15.432 grains.

I kilo =2 pounds 3 oimces.

I minim =0.059 cubic centimeter.

I fluidram =3.5 cubic centimeters.

I fluidounce =28.39 cubic centimeters

I pint =567.9 cubic centimeters.

I cu. cm =16.9 minims.

I liter =35.2 fluidoimces.

I inch =2.54 centimeters.

I foot. =30.48 centimeters.

I yard =91.44 centimeters.

I centimeter =0.39 inch.

I meter =39«37 inches.

253

2S4

APPENDIX.

TUERMOMETRIC

EQUIVALENTS.

raiGRAI

)E Fahrenheit

Centigrade FAHUENHm

IIO

230

38

1004

lOO

212

37-S

99.9

95

203

37

98.6

90

194

36.S

97-7

8S

i8S

36

96.8

80

176

35.5

9S-9

75

167

35

95

70

158

34

93-2

6S.

149

33

914

60

140

32

89.6

ss

131

31

87.8

so

122

30

86

45

"3

25

77

44

III. 2

20

68

43

109.4

IS

59

42

107.6

10

SO

41

105.8

+ s

41

40.S

104.9

32

40

104.0

- s

23

39-5

103.1

— 10

14

39

102.2

-15

+ 5

38.5

101.3

—20

- 4

Formulae for converting degrees of Fahrenheit into Centigrade
and vice versa.

F. = Fahrenheit ; C. = Centigrade ; D. = degrees.
Fahrenheit into Centigrade

(F.~32<^)X|=C.
Example: 140° F.= 140-32 X|=6o° C.
Centigrade into Fahrenheit

(C.X|)+32=F.
Example: 10° C.=ioX|+32=5o° F.

INDEX.

Abscess, amoebic, 107, 112; for-
mation of, 106, 107; from bot-
fly, 142; from flea, 144

Actinomycosis, epitome of, 184

Adolescence, typhoid fever and
tuberculosis in, 97

Age, influence on disease, 94-98

.^glutination, 27; agglutinins in,
27

Ague, 198, 199

Albumin, tests for, in urine, 246

Amoebic dysentery, 112

Antibodies, 25, 99

Antiseptics, definition of, 57;
sugar and salt, 58

Antitoxin, 25, 30

Anthrax, epitome, 185

Armed tape-worm, 137

Arsenical poisoning, 4

Ascaris lumbricoides, 124

Asiatic cholera, temperature in,

Asiatic lung fluke, 130

Bacilli, 44

Bacilluria, 160

Bacteria, 38; aerobic and anaero-
bic, 56; agents harmful to, 57;
air, 49; arts and industries,
39; in complications, 32; dis-
tribution, 45-50; in dust, 47,

48; effect on, drying, light,
ozone, heat, etc., 60-63; ^^^*s
from body, 152; expectoration
and nasal secretions, 155; fac-
tors necessary for growth, 53-
57; in feces, 156; forms of, 43;
grouping, 44; ground, 47; in
inflammations, 105; multipli-
cation, 42; pathogenic and
non-pathogenic, 41; shape, 43;
size, 42; ^in, exit from, 161;
specific and non-specific, 51;
spores, 52; suppurations, exit
in, 164; theraaal death-point,
217; in urine, 160; virulent
and non- virulent, 41; vomit,
156; in water, 48

Bacteriaemias, 20

Bactericidal, 27

Bacteriol3rsins, 27

Balsam Peru, specific in itch, 148

Bed-bugs, 144

Bichloride of mercury, 221

Bilharziosis, 132

Black death (see bubonic plague)

Bladder-worms, 135

Blood, examination of, 236; for
malaria, 238; for typhoid fever,
236; exit for infectious agents,
162

Boas, test-breakfast, 235

^SS

2S6

INDEX.

\

Bot-flies, 142, 143
Break-bone fever (see dengue)
Bubonic plague, epitome, 186,

187

Carbolic add, disinfectant, 222
Cestodes, 133
Chemotaxis, 103
Chicken-pox, epitome, 188
Childhood, diseases of, 96
Cholera, epitome, 189
Climate, a predisposing cause, 81
Coccidium hominis, 11 1
Cold-storage, danger of, 179
Combined uoiections, 22
Communicable, 37
Complications, 32
Compsomyia macellaria, 143
Congenital infections, 182
Contagious, 36
"Core," of abscess, 107
Cover-glass preparations, 240
Craw-craw, filaria in, 120
Creeping eruption, 173
Crisis, 18

Cryptogenic infections, 183
Cysticerci, 135; cysticercus cellu-
losa, 139

Defensive mechanism, dual ac-
tion of, 100
Dengue, epitome, 190
Deodorant, definition, 57
Dermatobia cyaniventris, 143 ;

noxialis, 142
Dibothriocephalus latus, 137
Diphtheria cultures, 230 ; epit-
ome, 190, 191
Disease, agents of, 3; infections,

68; evolution of, 34; predis-
posing causes, 74; defensive
mechanism in, 2

Disinfection and disinfectants,
214; definition, 57; bichloride
of mercury, 221; chlorinated
lime, 224; carbolic add, 222;
fonnalin, 222; heat, 216, 217;
lime, 224; solutol, sdveol,
l3rsol, 223; tricresol, 223

Distomiasis, 132

Dipylidium canintun, 138

Divers' paral3rsis, 4

Dum-Diun fever, 113

Dwarf tape-worm, 138

Dysentery, amoebic, 192; baciD-
ary, 192

Echinococcus disease, 140
Egyptian hematuria, 132; oph-
thalmia, II
Elephantiasis, filaria in, 119
Epidemic cerebro-spinal menin-
gitis, epitome, 188
Erysipdas, epitome, 193
Evolution, in disease, 34
Ewald and Boas, test-breakfast,

235

Fasciciola hepatica, 132

Feces, exit for bacteria and para-
sites, 159; examination of, 249;
gall-stones in, 251

Filaria Loa, 120; method of ex-
traction, 121

Filaria sanguinis hominis, 118

Flat-worms, 129

Flea (pulex irritans), 144; sand-
flea (sarcopsylla penetrans),

1

INDEX.

257

' 144; host of dog tape-worm,

Flukes, 129

Food, danger of infection from,

17s
Formalin, 222

Gall-stones, in stools, 251

Genito-urinaiy tract, infections
of, 181

Germicide, see disinfectant

Glanders, epitome, 194

Gonorrhoea, epitome, 195; infec-
tions in infants, 95, 96

Guinea-worm, 116; Soudanese
method of extraction, 118

Hsmatochyluria, due to filaria,

120
Haematuria, 243
Hemoglobinuria, 243
Harvest-mite (Leptus autum-

nalis, 149
Health, definition of, i
Hip-joint disease, 97
Hook-worm, 126
Host, flea, of dog tape-worm, 138
Human fertilizer, danger of, 176
Hydrophobia, epitome, 196
Hymenolepsis Nana, 138

Infancy, diseases of, 95
Immunity, opsonin in, 28
Infectious agents, action, 7; def-
inition, 6, 7; specific and non-
specific, 9
Infection and infectious disease,
12; combined, 22; contracted
through air or food, 175; con-

17

veyance by insects, 72; crisis
in, 18; family in, 79; general,
19; heredity in, 76; inocula-
bility, 167; latent period, 14;
lysis, 18; mixed, 71; number
of bacteria in, 68; portal of
entry in, 69; relation of body
to, 73; race, 76; secondary,
2^^ seU-limiting nature of, 24;
specific and non-specific, 10;
symbiosis in, 71; toxins in, 14;
terminal, 34; virulence of bac-
teria in, 70

Inflammation, definition, 99, 100;
cardinal symptoms, loi

Influenza, epitome, 197

Insontiimi, 181

Itch-mite, 148

Intermittent fever, see malaria

Insecticides, definition, 59

Insects, parasitic of skm, 173;
role in disease, 86-90

Ixodiasis (tick-fever), 150

Jews, immunity of, 77
Jigger-flea, 144

La Grippe, see influenza

Latent period, 14

Leprosy, epitome, 197

Leucocytes, 102

Leucoq^osis, 104

Lice, head, 146; pubic, 147;

clothes, 147
Light, effect on bacteria, 56
Lime, milk of, 224; chlorinated,

224
Liver, influence of tropics on, 84
Liver fluke, Chinese, 131

aS8

INDEX.

Liver-rot, cause of, 132
Lock-jaw (see tetanus)
Lues (see syphilis)
Lysis, 18

Madura foot, epitome, 198

Malarial fever, epitome, 198, 199;
Plasmodium of, 113-115; ter-
tian and quartan. 115

Measles, epitome, 119; in Faroe
and Fiji Islands, 78

Measles, German (see rubella).

Measles, due to embryo tape-
worms, 139

Membranous croup (see diph-
theria)

Metabolism, 35

Metastasis, in infections, 33

Metchnikoff, theory of phagocy-
tosis, 28, 103

Micrococci, 44

Milk, danger of, 178

Mosquitoes, in filariasis, 120;
malaria, 73, 116; yellow fever,
72

Mumps, epitome, 200

Mountain-climber's disease, 3

Mouth, portal of entry, 174

Myiasis, 141

Napoleon, sufferer from itch, 148
Necrobiosis, 106

Occupation, predisposing to in-
fections, 92-94; mortality table,

92
Old age, pneumonia in, 97

Ophthalmia neonatorum (see

gonorrhoea)

Opisthorchis sinensis, 131

Opsonin, 27

Organism, 6

Osier, prophylaxis in typhoid

fever, 211
Oxygen, relation of, to bacteria,

SS
Oxyuns vennicularis, 125

Painters' colic, 4

Parasite, definition, 8; kinds, 109;
cycle of development, no

Parasites, exits from body, 152;
expectoration, 156; skin, 162,
173; suppurations, 165; feces,
159; urine, 161; vomit, 156

Parasitic flies, 141

Parasitic h£mopt3rsis, 130

Paragonimus Westermanii, 130

Phagocytosis, 104; opsonin in, 38

Pin worm, 125

Pneumonia, epitome, 200; as sec-
ondary infection, 2^

Pott's disease, 97

Predisposition, 74; age, 94; in-
fluence of region, climate, 81;
individual, 80; inherited and
acquired, 80; family, 79; phys-
ical conditions of country, 85;
occupation, 92

Proglottides, of tape-worm, 134

Protozoa, 6, in

Ptomain poisoning, 4

Pus, 107

Pyaemia, 21

Pyogenic bacteria, 107; in infec-
tions of childhood, 97

Quick consumption, 21

INDEX.

259

Relapsing fever, epitome, 201
Riegel, test-dinner, 235
Round-worm, 124
Rubella, epitome, 202

Saprophytes, 40

Sarcophaga Camaria, 143

Scarlet fever, epitome, 202; ten-
acity of virus, 155

Schistosomum haematobiimi, 132

Screw worm, 143

Season, influence on predisposi-
tion, 90

Secondary infections, 23

Septicaemia, 20

Skin, exit for bacteria, 161 ; portal
of entry, 173

Sleeping sickness, 113

SnaU, host of Bilharzia haema-
tobiimi, 133

Small-pox, epitome, 203, 204

Spirilla, 44

Spores, 52; disinfection of, 218

Sputum,|examinationof, 226-229;
exit for bacteria and parasites,
156; collection of, 229; mum-
mular, 228

Staphylococci, 45

Stegomyia fasciata, in yellow
fever, 89

Stomatitis (epidemic), epitome,
205

Sterilization, definition, 57

Streptococci, 45

Strongyloides intestinalis, 122

Sugar, test for, in urine, 247

Suppuration, 106; exit for infec-
tious and parasitic agents, 164

Syphilis, epitome of, 206

Taenia saginata, 136; taenia sol-
ium, 136

Tape-worms, 133; beef, 136;
dwarf, 138; dog, 138; fish,
137; pork, 136; segments in
vomit, 156

Temperature, effect on bacteria,

55
Terminal infections, 34

Test-meak, 234

Tetanus, epitome, 207

Thread-worm, 125

Tick-fever, 150

Toxaemias, 20

Toxins, 14, 20

Trematodes, 129

Treponema (spirochaeta) palli-
dimi, II

Trichinella spiralis, 122

Trichiniasis, 122

Tricresol, 223

Tropics, predisposing influence,
81-86

Trypanosomiasis, 113

Tuberculosis, epitome, 208; in
children, 80; among Jews, 78;
negro, 78; North American
Indian, 78; as secondary in-
fection, 23

Typhoid fever, epitome, 209-
212; without intestinal lesions,
170

Ultra-microscopic, 11

Undnariaduodenalis, 126; Amer-
icana, 127

Urine, albumen, tests for, 246;
bile. Smith's test, 243; collec-
tion, 248; examination, 241;

36o

INDEX.

sped6c grayityi 245; sugar
test, 247; tjrphoid baalli in, 160

Variola (see small-poz)
Vomiti occurrence, 232; exami-
nation, 233-235

Water-borne diseases, 49
Whip-worm, 121

Whooping-cough, epitome, 213
Widal reaction, 236
Wood-tick, 149

Wool-sorter's disease (see an-
thrax)

Yellow fever, early methods of
disinfection, 168; epitome, 312;
U. S. Army conunission, 163

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