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The Contemporary 

Science Series 




i .*' 

Bought of 


No. 1012 Walnut Street, 










Cornell University 

The original of tliis book is in 
tine Cornell University Library. 

There are no known copyright restrictions in 
the United States on the use of the text. 






Director of the Laboratories of the Conjoint Board of t/ie Royal Colleges of Pltysicians 

i^Lond,) and Surgeons {Eno-.) ; 'Formerly Research Scholar o/the 

HonouraOle Grocers' Company. 










I'. ■■->-' 


IN the following pages an attempt is made to give some 
account of the main facts in Bacteriology, and of the 
life-history of Bacteria and closely allied organisms, and also 
to discuss the more important theories as to the part played 
by them in Nature's Economy ; especially in their relation 
to the commoner fermentative, putrefactive, and disease pro- 

It may be held by some of my readers that too much pro- 
minence is given to certain questions, whilst others have 
been relegated to a comparatively obscure position, and that 
some points have been accentuated, perhaps at the expense 
of others ; but to such criticism it may be answered that 
whilst some facts carry conviction along with them, others 
can only be properly appreciated when seen by stage lights. 
On the other hand, many points have of set purpose been 
lightly touched upon because experience is constantly 
bringing home the fact that what is new to-day may be 
out of date to-morrow. I have, therefore, thought it better, 
in most instances, to confine myself to an exposition of well- 
accredited facts and to a discussion of some of the more 
stable theories. 

Being privileged to hold a Sanitary Research Scholarship 
of the Honourable Grocers' Company for some years, I 
was enabled to devote considerable time to the study of the 
relations of Bacteria to Disease, especially in the case of 
tuberculosis, and many of the interpretations of facts here 
mentioned are based on observations then made ; the re- 


mainder are drawn chiefly from th'e works enumerated at 
the end of each section. These lists, however, represent but 
a small part of the enormous mass of literature dealing with 
Bacteria and their Products, which has accumulated durimg 
the last decade. 

To Professor Loffler's admirable work, "Vorlesungen 
iiber die geschichtliche Entwickelung der Lehre von den 
Bacterien," and to Mr. Watson Cheyne's "Antiseptic 
Surgery," I am specially indebted for much information and 
guidance in my search for facts and papers dealing with the 
earlier history of the subject. 

It may be said of the Appendix that it is given, not with 
the object of supplying intending workers with every known 
method of research, and with full descriptions of every 
organism with which they may have to deal, but simply to 
enable them to commence work, and to recognize the 
commoner forms of Bacteria, of which about one hundred 
and forty are here described. 

I take the opportunity of expressing my thanks to Dr. 
Cartwright Wood, who, whilst revising the proof sheets, 
has made several valuable suggestions ; to my former as- 
sistant, Mr. Coghill, now of the Royal Veterinary College, 
and to Mr. Andrew Pringle, both of whom have made for 
me beautiful photo-micrographs, which, however, can be but 
imperfectly reproduced by any photo-mechanical process 
now available. 

G. S. W. 



Introduction - ... 

Growth of Subject — Place of Bacteria in Nature — Pure Cultures 
— Morphology — Physiology — Protoplasm governed by same 
laws whether in higher or lower Plants or Animals — Relation 
of Bacteria to everyday Processes — Fermentations, Butyric, 
Lactic, Colour, &c. — Brewing — Baking — Kephir making — 
Flax preparation — Digestion — Putrefaction — Nitrification, 
Mineralization — Relation of Bacteria to Water Supply — Fil- 
tration — Sewage — Modes of Transference of Pathogenic Bac- 
teria from Patient to Patient, or from Water or Earth to 


What are Bacteria? 

Structure — Myco-prolein — Limiting Membrane — Gelatinous 
Capsule — Special Cell Contents — Oxide of Iron — Sulphur — • 
Colouring Material — Flagella — Modes of Multiplication and 
Development — Division — Rate of Vegetative Multiplication 
— Endospores — Arthrospores — Classifications of Cohn, Van 
Tieghem, Zopf, Winter and Rabenhorst, De Bary and 
Hueppe, Fliigge, Baumgarten, &c. 


The History of Bacteriology 

Earliest Workers — Kircher's Contagium Animatum — Bacteria in 
Fermentation, Putrefaction, and Disease — Early Classifica- 
tions — Miiller — Abiogenesis — Needham — Biogenesis — 
Bonnet — Spallanzani — Schultz's Experiments — Schwann — 
Later Experiments — Pasteur — Bastian — Colour and Fer- 
mentation — Cohn and Naegeli's Classification — Henle's 
Researches and Postulates — Pasteur's Researches on Fer- 


mentation and Putrefaction—" Flower of Wine "— " Flower 
of Vinegar " — Bacteria as Scavengers — Pasteur on Silkworm 
Disease, and Wine Disease— Germs killed by Carbolic Acid- 
Origin of Antiseptic Treatment. 

Bacteria as the Causes of Disease - - 7S-86 

Anthrax — PoUender-Davaine-Rayer-Laplat and Jaillard's 
Observations controverted by Davaine — Pyaemia and Sep- 
ticaemia — Salisbury on Bacteria as the Cause of certain 
Fevers — Johanna Liiders' and Hallier's Observations on 
Pleomorphism or Polymorphism— Burdon Sanderson, Hoff- 
man, arid others, state that there is no Connection between 
Bacteria and the Higher Fungi — Demonstration of Infective 
Element in Anthrax Blood— Bacteria found in Organs in 
certain Diseases — Sarcina in Stomach — Specific Organisms — 
Specific Activities. 


Fermentation . 87-1 14 

Fermentation, a Key to the Whole Position — Chemical Fer- 
mentations — Illustrations — Organic Fermentations — Al- 
coholic Fermentation — Result of Activity of Living Proto- 
plasm — Lactic and Butyric Fermentations — Cagniard Latour 
— Schwann— Reess — Hansen — Liebig's Theory of Fermenta- 
tion — High Beer — Low Beer — Methed of obtaining Pure 
Yeasts— Hansen's Classification of the Saccharomyces — Spore 
Formation — Film Formation — Character of Species of Sac- 
charomyces — Metschnikoft's Monospora — Torulae. 


Fermentation (continued) 115-144 

Soluble Constituents of Yeast — Action of these upon Sugar — 
Conversion of Glycogen in the Liver and other Tissues — 
Growth 6f Yeast-Cells in Organic and Inorganic Fluids — 
Fermentation of Fruit Juice — ^robic and Anaerobic Fer- 
mentations — Effect of Free Oxygen on Yeast-Cells — Fer- 
mentation not necessarily equal to Growth of Yeast — 
Enzyme or Unorganized Ferment a Secondary Function — • 
Function depends partly on Organism, partly on Medium in 
which it is Growing — Peptonizing Function usually requires 
presence of Oxygen — Various kinds of Fermentation : Lactic, 
Urea, Butyric, Ammoniacal, Acetic — Formation of Fatty 
Acids — Mycoderma Aceti — General Processes of Fermenta- 
tion — Hoppe-Seyler's Classification. 



Parasites and Saprophytes i4S-i49 

Putrefactive Bacteria — Pigment-forming Bacteria — Enzyme- 
forming Bacteria — Non-pathogenic, Saprophytic, Parasitic, 
Pathogenic Bacteria — SarcinaVentriculi — Leptothrix Buccalis 
— Facultative Saprophytes — Facultative Pathogenic Para- 
sites — Anthrax Bacillus — "Pathogenic," "Parasitic," "Sa- 
prophytic," merely Relative Terms. 


Cholera - 150-170 

Cholera a Parasitic Disease — Early Observations on the Comma 
Bacillus — Characters — Methods of Staining — Methods of 
Isolation — Use of Plate Method in Practical Public Health 
Work— Tube Cultures— Motility of Cholera Bacilli— Potato, 
Blood-serum, and Milk Growths — Behaviour in Water and 
Sewage — Infection of Man through Agency of Bacillus — 
Early Inoculation Experiments — Koch — Nicati and Rietsch 
— Macleod — Difficulties — Cholera in Guinea-pigs — Position 
of Bacilli in Tissues — Presence of Spores doubtful. 


Cholera (continued) ■ - - 171-193 

Pettenkofer's researches — Saprophytic and Parasitic Stages of 
Cholera Bacillus — Temperature Conditions — Relation to 
Epidemics — Moisture — Ground Water — Flushing — Cholera 
in Shanghai Endemic but Intermittent — Cholera Endemic at 
the Mouth of the Ganges — Vitality of Cholera in Old 
Cultures — Relation of this to Quiescent Periods during Parts 
of the Year — Gastro-intestinal Irritations prepare for Cholera 
■ — Chinese Vegetables — Cholera Poison formed in the In- 
testine, absorbed into Body — Inoculation against Cholera 
— Garaaleia's Experiments — Germicides useful in attacking 
the Cholera Bacilli — Water Supply, Pilgrimages, Feasts pre- 
disposing to Cholera — Quarantine except in Harbours Use- 
less — Time and Place Dispositions. 


Typhoid Fever - 194-204 

Typhoid Fever a Bacterial Disease — Recklinghausen's Observa- 
. tions — Klein — Eberth — Klebs — Coats — The Bacillus — 
Method of Staining — Position in Tissues — Gaffky's Observa- 
tions — Pure Cultures — Excretory Products — Experiments on 
Animals— Mixed Infections — Action of Light and Heat on 
Typhoid Bacilli — Pseudo-typhoid Bacilli. 




Tuberculosis 205-243 

Tuberculosis a widespread Disease — Tlie Tubercle Bacillus — 
Koch — Baumgarten — Spores seen by Watson Cheyne— Re- 
lation of Organisms to Tissues — Bacillus in Tuberculosis of 
Animals — Tubercle Bacilli as Saprophytes — Bacilli cultivated 
outside the Body by Koch — Methods — Temperature Rela- 
tions — Cultivation on Different Media — Channels of In- 
fection — Ransome — Williams — Cornet — Conditions of In- 
fection — Methods of Disinfection — Tuberculosis at Different 
Ages — Tubercle in Milk — Diagnosis of Tuberculosis in Cattle 
— Tuberculous Meat — Koch's Method of Treatment — 
Nature of Virus and Mode of Action — Is Immunity con- 
ferred ? — Koch's Method a New Departure — Sterile Products 
cause Marasmus ; Maffiicci — Indications for Treatment. 


Leprosy 244-252 

Distribution of Leprosy — Similarity to Tuberculosis — Description 
of Disease— " Tubercular," " AniESthetic," "Mixed"— The 
Leprosy Bacillus — Method of Staining — Position— Leprosy 
Cells — Bacilli Resistant and Grow Slowly — Cultivation Ex- 
periments mostly Negative — Theories of Cause of Leprosy. 


Actinomycosis 253-261 

Nature of the Disease — Differences in Cattle, Man, Pig, and 
Horse — Methods of Preparation and Examination of the 
Fungus— Microscopic Appearances of Fungus in different 
Animals — Nature of Clubs — Cultivation Experiments — 
History of Actinomyces — The Actinomyces a Streptothrix. 


Glanders - 262-270 

Glanders — Farcy — Clinical Appearances of the Disease — 
Chauveau's observations on Glanders Poison — Loffler and 
Schiitz— Method of Demonstrating the Glanders Bacillus — 
The Bacillus — Methods of Cultivation — Glanders in Various 
Animals — Farcy in Man — Temperature relations of Bacillus — 
Desiccation — Germicides. 



Anthrax . . 271-286 

The Bacillus Anthracis — Early Observations — PoUender — 
Davaine — Koch — Pasteur — Methods of Examination — Ap- 
pearances of Bacillus under Different Conditions — ■ Spore 
Formation — Non-spore Bearing Bacilli — The Vitality of the 
Bacillus and of the Spores — Cultivation Experiments — Cover- 
glass Preparations — Inoculations into Animals — Methods of 
Infection — Anatomical Characters of Malignant Pustule — 
Animals Affected — Spores not formed in the Living ' Body — 
The Disposal of Anthrax Carcases — Various Disinfectants — 
Pathogenic and Saprophytic Anthrax — Buchner's Experi- 
ments on Anthrax Bacillus and Bacillus Subtilis — Hueppe 
and Wood's Experiments. 


Tetanus . - 286-296 

Tetanus a Specific Infective Disease — A Wound Fever — Organism 
found by Nicolaier in the Soil taken from Streets and Fields 
— Experiments on Animals — Symptoms of Disease — Pure 
Cultivations Obtained — Description of Organisms — Charac- 
teristic Shape — Spore Formation — Organism Anaerobic — 
Cultivations — Kitasato's Method of Cultivating the Organism 
— The Bacillus found only at the Seat of Inoculation — Wide 
Distribution of Spores — Bossano's Examination of Earth — 
Vaillard and Vincent's Observations— Tetanus Bacillus a 
Facultative Saprophyte — Conditions under which Tetanus 
is Contracted — Poisoned Arrows. 


Diphtheria - - 297-313 

Diphtheria an Infective Disease — The Organism found in the False 
Membrane in its Deeper Parts — Method of Staining the 
Bacillus — Characters of the Bacillus — Involution Forms — 
Cultivation Methods — Appearance of Colonies — Nutrient 
Media — Results of Inoculation Experiments — Klein's Bacilli 
differ _somewhat from Loffler's — Streptococci found in 
Diphtheria Poison — ^ Extreme Virulence — ^^Resemblance to 
snake-bite poison — Toxicity — Predisposing Conditions — 
Conditions fatal to the Bacillus — Roux and Yersin's Observa- 
tions — Fraenkel's Observations — Attenuated Diphtheria Virus 
— Increase of Virulence. 



Hydrophobia - 3 '4 33° 

Pasteur's Experiments— Attempts to Demonstrate Micro-organisms 
—Hydrophobia does not arise Spontaneously — Disease not 
Confined to Man or Canine Animals— Pasteur's Early Ex- 
periments with Saliva Unsuccessful — Successful Experiments 
— Symptoms of the Disease — Position in which Virulent 
Material is Found — Different Animals Differently Affected — 
Alteration of Virulence — Method of Preparing Inoculation 
Material — Description of Experiments — Joseph Meister the 
First Patient Treated — Method of Treatment now Adopted — 
Treatment of Wolf Bites— The Time Factor in the Disease- 
Rationale of Inoculation Method — Filtered Virus Non- 
Virulent — Method of Inoculation — Description of Depart- 
ments, Apparatus and Methods of Working in the Pasteur 


Bacteria of the Mouth - 336-346 

The Mouth a Good Forcing Ground for Bacteria — Food Material 
—Kinds of Bacteria found in the Mouth by Miller and Vignal 
— Bacteria in the Teeth in Caries, in Milk Teeth, and in 
Abscesses — Combination of Lactic Acid with Lime Salts — 
Organisms Attack Decalcified Base Substance — Artificial 
Decay — Mode of Invasion of Teeth by Bacteria — Poisonous 
Saliva — Micrococcus of Sputum Septicaemia — Pneumococcus 
— Other Organisms found in the Mouth — Septicaemia fol- 
lowing Slight Operations in the Mouth. 


The Bacteria of Colour and Phosphorescenxe - 347-355 

Colour-Forming Bacteria — Micrococcus Prodigiosus — Magenta 
Micrococcus^Beggiotoa Roseopersicina — Bacillus of Blue 
Milk — Sulphur Pigments — Iron Pigments — Bacillus 
Fluorescens Putidus — Phosphorescent Bacteria — Six Species 
— Method of Cultivation — Conditions under which they 
produce Light. 


Poisonous Alkaloids and Albuminoids - 356-367 

Early Observations — Burrows, Kerner, Panum, &c. — Ptomaines 

Leucomaines — Brieger's Work — The Alkaloids, Poisonous 

and Non-Poisonous — General and Local Reactions — 

Structure and Composition— Sketch of Chemistry — Cholera 


Poisons and other Members of this Group— Mussel Poisons : 
two Classes, viz., those Without Oxygen and those Con- 
taining Oxygen — Ptomaines the Result of the Activity of 
Micro-organisms — Lbffler's Experiments on Diphtheria 
Poison, an Enzyme — Roux and Yersin's Diastase — Hankin, 
Albumose — Brieger and Fraenkel, Toxalbumen — Method 
of Preparation of Albumoses and of Toxalbumens — Near 
Relationship of Proteid Poisons and the Ptomaines — Martin's 


Vaccination 368-381 

Natural Immunity — Ingrafting of Small-pox — Jenner's Discovery 
— Klebs — Pasteur — Chauveau — Grawitz's Theory — Buchner's 
Theory — Metschnikoff's Work — Greenfield's Observations 
on Anthrax— Toussaint's Vaccinal Fluid — Pasteur's Classical 
Experiments — Other Methods of Diminishing Virulence — 
Chauveau's Soluble Poison Experiments — Protection by 
Alkaloids, Albumoses and Toxalbumens — Saprophytic 
" Anthrax " — Hueppe and Wood — Antagonism by Blue-pus 
Products — Immunity not the same as Antagonism — Sum- 
mative Action of Bacteria. 


Bacteria in Air, Earth, and Water - . 381-391 

Spores in the Air in Hospitals — Effects of Currents and Altitude — 
Direction of Wind — Nature of Country over which it passes 
— Frankland's, Carnelley's, Haldane's and Petri's Experi- 
ments — Few Bacteria in the Air of Sewers — Tyndall's 
Glycerine Chamber — Examination of Air — Koch's Method — 
Miquel's Method — Hesse's Apparatus — Modified Hesse's 
Apparatus — Miquel's Sugar Method — Bacteria in Water — 
Effect of Standing — Sluggish Movement — Oxidation of Or- 
ganic Matter in Water — Organisms carried by Sewage — 
Number of Organisms in Water — Method of Procedure in 
Analysing Water — Pfuhl's Flasks — Petri's Dishes — Pe- 
truschky's Flask — Plate Cultivations — Cooling Apparatus — 
Von Esmarch's Tube Cultures — Effect of Rains, Frosts and 
Thaws — Relation of Bacteria to Ammonia — Basis on which 
to determine whether Water is fit for Drinking or not — 
Filtration — Method of Examination of Soil. 

Appendix 397-44: 

Indices -•-■-.. 443-451 




Growth of Subject — Place of Bacteria in Nature — Pure Cultures — Morph- 
ology — Physiology — Protoplasm governed by same laws whether in 

^ higher or lower Plants or Animals — Relation of Bacteria to everyday 
Processes — Fermentations, Butyric, Lactic, Colour, &c. — Brewing — 
Baking — Kephir making — Flax preparation — Digestion — Putrefaction 
— Nitrification, Mineralization — Relation of Bacteria to Water Supply 
— Filtration — Sewage — Modes of Transference of Pathogenic Bacteria 
from Patient to Patient, or from Water or Earth to Patient. 

WITHIN the last decade bacteria have laid a very strong 
hold on the thought and imagination of the scientific 
world, and have come to be looked upon as playing a most 
important part, not only in the production of disease and in 
fermentation, but also in many everyday processes hitherto 
supposed to be dependent on very different causes. In 
consequence of this, bacteriology has been raised to the 
dignity of a science, and its ramifications have become 
so numerous and so wide-spreading that many of the 
other sciences, and even some of the arts, have been freely 
pressed into the service of one or other of its branches. 
The evolution of the science for long went on but slowly ; 
the study of bacteria remained almost entirely in the 
hands of the botanists, although now and again scientific 
medical, men, whose powers of observation and deduction 
were far superior to the methods of experimentation that 
had been at their command, made shrewd guesses at the 
causal relationship between the growth of certain bacteria 


within and without the body and the etiology of certain 
infective diseases, and certain processes of putrefaction and_ 
fermentation. At first bacteria were claimed for both the 
animal and vegetable kingdoms by the workers in each, 
and the fortunes of war seemed for long to favour the 
zoologists ; but after a sharp struggle the fission fungi, as 
they are called, were relegated to the domain of botany, and 
now for many years the morphology of these organisms has 
been an object of most careful study by scientific botanists. 
Bacteria were, however, so minute that it was impossible to 
study them very accurately with the older microscopes, and 
for long the group contained very few species, whilst in 
addition to the fallacies connected with actual observation of 
size, form, and methods of reproduction, there were others 
that resulted from the fact that it was impossible, "until com- 
paratively recent years, to obtain what are now known as 
pure cultivations ; forms that were utterly dissimilar in 
morphological characters were supposed to be stages of the 
developmental cycle of the same organism, although they 
might be, and probably were, really nothing but different 
organisms that were capable of growing in a common 
medium. When at length more or less pure cultivations 
of certain organisms were obtained, botanists were able 
to study, in some cases very completely, the ■ life-history 
and morphology of various forms of bacteria, and great ad- 
vances in bacteriological science were made. Still no very 
accurate observations on the functions or physiological 
chemical processes associated with the life-history of bacteria 
and allied forms were made, a;nd many of the biological 
questions, some of which had already been answered as 
regards animal and the higher vegetable protoplasm, still 
remained as in a sealed book so far as this lowly vegetable 
protoplasm was concerned. 

In the last ten or twelve years, however, owing to the vast 
irriprovements that have been made in, the methods of culti- 
vation of these organisms, and especially of obtaining what 
are known as pure cultures, i.e., cultures that contain a single 
species of organism only, most valuable data as to the func- 
tions and biological chemistry of these minute specks of 
vegetable protoplasm have been rapidly accumulated. 

Pasteur's wonderful observations on yeasts first opened 
up the wav for future workers. His practicallv pure cul- 


tures were obtained by a kind of physiological separation, 
to obtain which he fed his yeasts on food specially suited to 
their nutrition — more suited to their wants, in fact, than to 
those of any micro-organisms with which they are usually 
found associated — and they were thus enabled to develop so 
luxuriantly that they prevented the growth of almost all 
other organisms, which might have found their way into the 
nutrient medium along with them. These cultures were 
comparatively pure, the presence of the small number of 
other organisms not being sufficient to vitiate the main 
general results. 

Klebs (1873) tried to obtain pure cultures by his fractional 
method, which \yas simply the removal of those organisms 
that vegetated most luxuriantly in any special fluid to another 
flask, making special cultures of these, and so on until com- 
paratively pure cultures were obtained. The difficulty, how- 
ever, was that only the commoner forms could thus be 
separated and even then they could not be relied upon as 
being absolutely pure. 

This method (the "maas '' method),is even now sometimes employed to 
obtain pure cultivations of cholera bacillus. A drop of the discharge from 
a cholera patient containing a large number of organisms besides the 
specific cholera bacillus, when placed in broth which is so prepared as to 
be specially suited to the nourishment of the cholera organism, soon 
becomes almost a pure culture, as the cholera bacilli are able to multiply 
in an extraordinary degree at their " optimum " temperature and to far 
outnumber all the other organisms present, and it becomes a much easier 
matter to obtain from the broth culture a pure culture of the "comma" 
bacillus than directly from the cholera discharge itself. It may be said to 
correspond to the passing of a mixed culture through an animal. Certain 
organisms — those that are "pathogenic " — can grow luxuriantly whilst the 
others make a much weaker struggle for existence. 

As soon as it became evident that no further steps of any 
very great importance could be taken unless pure cultiva- 
tions were used, various workers set themselves to devise 
methods by which single organisms might be isolated, and 
from which a "pure-bred stock" might be raised. Then 
Roberts (1874) and Cohn (1876) obtained pure cultures of 
different forms of spore-bearing bacilli, especially the bacillus 
subtilis, by subjecting the fluid to the heat of 100° C, by 
which all non-spore-bearing forms were killed off. This 
method, however, has a very limited application, though 
combined with other methods, it enabled Kitasato to obtain 


pure cultures of the tetanus bacillus. Salomonsen (1876) 
observing that the dark colour which makes its appearance in 
defibrinated ox blood always commences as minute points, 
concluded that each of these patches was due to the changes 
set up by micro-organisms growing at these points. He 
therefore drew such defibrinated blood into a capillary tube, 
and by carefully noting the appearances presented in the tube 
was able to follow the development of a variety of organisms 
which, when few in number, were separated by considerable 
intervals of bright red blood in which no organisms could be 
seen, though in time these gradually ran together. Lister 
(1878) and Naegeli (1879) obtained their pure cultivations by 
a kind of fractionating method, in which they distributed a 
number of organisms into large quantities of fluid by making 
greater and greater dilutions of their organisms in broth, 
until the dilution was such that a single drop did not con- 
tain more than a single organism, and a series of such 
drops introduced into a number of flasks containing sterilized 
broth gave a large proportion of pure cultivations. With 
the pure cultivations so obtained the first really accurate ex- 
periments in connection with the physiological chemistry of 
bacteria were carried on. This method, however, though a 
very great advance on any that had hitherto been devised, 
was somewhat complicated, and it was open to certain other 
objections (though it is still most useful in many investiga- 
tions). It was not until Koch, perfecting Klebs' and Brefeld's 
gelatine method, was able to " fix " the organisms in situ as 
it were, in the nutrient medium, that the bacteria could be 
kept isolated, the resulting colonies studied and then removed 
to other media for further examination. The method was 
so simple and so reliable that it was eagerly seized upon 
by those who were interested in the solution, not of 
botanical problems merely, but of many questions con^ 
nected with putrefaction, fermentation, and disease that 
had cropped up so frequently, but which had to be left 
without a satisfactory answer, and which, in consequence 
of Davaine's and Pasteur's researches, were again assuming 
such prominence. 

In the first place, experimenters were able to put to the 
test the many observations that had been made on both the 
structure and the function of micro-organisms. Once a pure 
culture became available, it was an easv matter to dete.rmin** 


the conditions under which a special bacterium would grow. 
It could be transferred from medium to medium ; it could 
be placed under aerobic and anasrobic conditions ; or it 
could be plied with antiseptic or other special reagents, and 
its behaviour under varying conditions or in the presence of 
these material could be accurately observed. There was no 
longer any danger of one form being mistaken for the de- 
velopmental stage of a totally different organism, and much 
ponfusion as regards classiiication was gradually done away 
with, though the effects of the observations made on impure 
cultivations still make themselves felt in the obscurity 
that enshrouds certain groups which are still met with 
even in some of the better known classifications. As 
these pure cultivations were obtained it. gradually became 
more apparent that, for practical purposes, it would be 
necessary to base our classification on certain specific cha- 
racters of the organism ; and as in all processes in which 
bacteria play a part they are usually met with in a single 
and special form, it was originally found advisable to take 
these special forms as the diagnostic features in making such 
classification. The features of form and size, however, were 
merely superficial characters, and as a more careful study 
of bacteria was made, especially by the French school, 
it was found that the biological characters afforded a much 
more satisfactory basis of classification, especially, however, 
when taken in conjunction with the morphological features ; 
so that the media on which they grow, the products to 
which they give rise, the methods in which they cause the 
breaking down of dead or living protoplasm, the actions and 
reactions that take place between them and living animal 
and vegetable cells, and the effects upon them of organic 
and inorganic antiseptic substances, are now all taken into 
account in drawing up any classification. Thus we have 
yeasts that cause fermentation and yeasts that do not, whilst 
nearly related to them are ascomycetes that are essentially 
parasitic in their character ; we have micrococci that set up 
urea fermentation, micrococci that form pigment, others 
that give rise to suppuration or that apparently assist in the 
production of diphtheria ; and so on, throughout the whole 
of these low vegetable forms. The appearance under the 
microscope can, of course, give us no information on many 
of these points, and it is only by a most careful study of the 


life-history of these organisms that any accurate information 
has been obtained. 

Within quite recent years it has been observed that very 
marked modifications of certain of the features may be ob- 
tained by subjecting the micro-organisms to conditions 
different from those under which they are ordinarily met 
with ; and as the outcome of these observations the way 
has been opened up for the study of the evolution, perhaps 
not of the micro-organisms themselves, but of their specifiq 
functional characteristics. It has been found, for instance, 
that under certain conditions, yeasts that ordinarily set up 
active alcoholic fermentation are no longer able to do so ; that 
by continued cultivation outside the body and in certain special 
media the anthrax bacillus loses much of its virulence ; ,whilst 
the tubercle bacillus, the cholera bacillus, the organisms met 
with in diphtheria and in other diseases, may, under certain 
conditions of cultivation, lose their disease-producing power 
in a most remarkable degree. On again being placed under 
conditions of a more favourable nature these organisms 
resume their pathogenetic or disease-producing properties. 
The same variations are met with in the colour-forming 
species of bacteria, according as the conditions under which 
they exist are favourable or unfavourable to the accentuation 
of certain functions of the protoplasm. 

It will be evident from a consideration of all these facts that 
bacteria must be looked upon as being governed by much the 
same laws which govern other plants and animals ; that they 
are composed of protoplasm, the functions of which may be 
modified in various ways, and the forms of which may become 
more fully differentiated, and that where greater differentia- 
tion takes place the modification of function is always in the 
direction of greater specialization ; that the conditions suit- 
able for the existence of the more lowly organized and 
functionally less specialized organisms need to be less 
specialized than do those that are necessary for the growth 
of the more highly developed fungi ; and that, consequently, 
the bacteria of disease and putrefaction are, with few excep- 
tions, of a comparatively low form, although the functions 
of the protoplasm of these less specialized bacteria become 
more specialized as they dwell for a longer and longer 
period under any special set of conditions, one phase or 
power of the protoplasm being drawn out and developed in 


excess and frequently at the expense of, some of the others, 
sometimes even at the expense of the hving or resisting power 
itself of the organism. In all cases, however, it should be 
remembered that the differences in protoplasm are diiferences 
in degree rather than in kind, and that the laws which govern 
animal and other vegetable protoplasm govern the proto- 
plasm of bacteria, and that the results of all investigations 
that have been carried on in connection with them must 
conform as strictly to physiological laws as any work that has 
hitherto been done in the domain of animal or vegetable 
biology ; and that where discrepancies of any kind, or appa- 
rent departures from ordinary physiological laws, are met 
with, the facts must be carefully revised, and if the dis- 
crepancies still continue, then so much the worse for either 
the facts or the laws. The " facts " are still incorrect or the 
laws must be revised. 

There has grown, then, and still continues to grow, a 
science dealing with microbiology in all its morphological 
and physiological phases. Facts have gradually been accu- 
mulated, observations have succeeded observations, patient 
work and powerful concentration have played their part in 
elaborating our knowledge of the habits of micro-organisms 
without and within the higher plants and animals ; the 
conditions under which the modes of life of micro-organisms 
may be altered have been investigated ; the effects that 
they or their secretions exert on living and dead proto- 
plasm have been most conscientiously examined ; the 
conditions that are essential in order that these organisms 
may stimulate the activity of living protoplasm, and the 
phases through which this protoplasm passes, from the 
stimulated condition to degeneration and death, have all been 
carefully studied. The organisms that have been found in 
certain diseases have been identified and classified, their 
modes of propagation and the channels by which they are 
conveyed from one host to another, sometimes through 
intermediate saprophytic or non-parasitic stages, have been 
determined, and the whole subject has been so prepared, 
that the great epoch-making minds of such men as Pasteur, 
Chauveau, Lister, and Koch, being brought to bear on 
these questions have found sufficient material at their 
disposal on which to generalize, and have placed before the 
world theories that appear to be more like fairy tales 


than deductions made as the results of sober scientific 
investigation and thought. These men have also, how- 
ever, been able to obtain many new facts, and to point 
out the gaps that still remain to be filled in before the 
theories so admirably expounded can be proved to demon- 
stration. The French can boast of their Davaine and Pasteur, 
who, assisted by Chauveau and others, have given to us the 
germ theory of disease and the theories of fermentation and 
protective inoculation. In Germany, Klebs, Cohn, Koch, 
and their followers, have made marvellous contributions to 
the study of bacteria, and additions to our knowledge of their 
relation to disease. The Danes have furnished O. F. Miiller, 
Warming, Panum, Salomonsen, Bang, and Chr. Hansen, 
who, seizing most of what was good in both the French and 
German schools, have succeeded in making most valuable 
contributions to various branches of the subject ; whilst, in 
this country, Burdon Sanderson, Greenfield, Klein, Watson 
Cheyne, and others, have all contributed their share, though 
Lister's name must always stand pre-eminent for the mag- 
nificent work which he has done in the domain of antiseptic 
surgery, by the evolution and perfecting of which he has 
done more, both directly and indirectly, to ameliorate the 
suffering, and to diminish the mortality in surgical cases, 
than has been achieved by the most brilliant operators the 
world has produced during the last century. 

Many of the processes of everyday life are intimately 
associated with the specific activities of micro-organisms ; we 
are constantly meeting with these organisms, and it is now 
proved, beyond all dispute, that their presence is not merely 
accidental but is absolutely essential to the carrying on of, 
one might almost say, the most commonplace operations. 
Take, for example, those that are associated with the different 
processes of fermentation. Leaving for the moment the 
yeasts or saccharine ferments, I may refer first to the 
butyric acid ferment — Clostridium butyricum — which plays 
a most important part in interfering with the ordinary course 
of the saccharine fermentation. It decomposes starch and 
cellulose without requiring the presence of oxygen ; it, like 
other micro-organisms, appears to require for its nutrition, 
nitrogenous material, and, especially in the presence of the 
lactic acid ferment, it brings about the conversion of sugar 
into butyric acid ; it is, as might be anticipated, one of the 


bacteria most frequently met with in some of the forms of 

It must be remembered however that this is not the only 
organism that gives rise to the butyric acid fermentation ; 
several other bacteria, differing most markedly in many of 
their features, from the Clostridium butyricum, generally, 
however, like that organism, carrying on their work in the 
absence of free oxygen, have the power of setting up alone, 
or in conjunction with the Clostridium butyricum, the 
butyric fermentation. In ripened cheese, part of the flavour 
at any rate is due to the products formed in the ripening 
curd in the presence of this organism. 

The lactic acid fermentation so frequently met with 
in milk, is also the result of the vital activity of several 
organisms, Pasteur and Lister both describing lactic acid 
bacteria and micrococci. Hueppe also describes a special 
bacterium which he says has the power of breaking up milk 
sugar and saccharose into lactic acid and carbonic acid ; 
whilst from material taken from the mouth and teeth he 
succeeded in separating two micrococci, both of which had 
the power of converting sugar into lactic acid, and by a 
series of experiments he also proved that certain of the 
pigment-forming bacteria, such as Bacillus prodigiosus — 
the organism that gives rise to what is knoAvn as bleed- 
ing bread — supply so much lactic acid as a result of 
their metabolic processes, that in their presence milk is 
curdled, the casein being precipitated. Further, even a 
pathogenic form of micro-organism — micrococcus osteomye- 
litis — is said by Krause to set up the same reaction. 
Jorgensen mentions that " Delbruck found that in a mash 
prepared from dry mould and water, lactic acid was first 
formed at a temperature of 50° C, and from this he draws the 
conclusion that in this case the active lactic acid ferment 
. has its maximum temperature at this degree of heat." 
This is an exceedingly interesting fact, for as Schottelius 
and Wood have pointed out, as the temperature rises the 
Bacillus prodigiosus loses its power of forming a pigment,, 
and if it is grown on potato or bread paste for example, 
in an incubator at blood heat instead of at the temperature 
of the room, the colour is gradually lost and the culture no 
longersmells of herring brine, but the power of forming lactic 
acid from milk sugar, with the accompanying precipitation 


of the casein, is frequently considerably increased ; so that 
it would appear that the energy required for the building 
up of the pigment substance was in this case diverted into 
another channel, and lactic acid, and perhaps other sub- 
stances, are produced in place of the usual pigment. 

This example may afford some idea of the complexity of 
the problems that have to be grappled with by bacterio- 
logists, and it may also help to explain how such difFererit 
results have been obtained by different observers, and how it 
still may be possible to reconcile statements which at first 
sight appear to be in direct opposition. 

It is a well-known fact that if the lactic acid fermentation 
once obtains a footing, in a solution of sugar for example, 
many of the other putrefactive bacteria find it impossible 
to develop. On the other hand, whilst the lactic acid 
organism cannot grow beyond a certain point, yeasts 
are perfectly able to develop where there is a certain 
quantity of acid present. This has been adduced as an 
explanation of the fact that comparatively pure yeast 
fermentation may go on even in the presence of the lactic 
acid organism, when it is unable to make further head- 
way and when other putrefactive organisms are unable to 
grow at all. 

Another fermentation, the results of the careful studies 
of which have been utilized in the commercial production of 
vinegar, is that due to the acetic acid ferments Mycoderma 
aceti and Mycoderma Pastorianum, by the action of either 
of which alcohol is converted into acetic acid. 

In all the works on brewing, lists of micro-organisms that 
give rise to such conditions as bitterness, muddiness, various 
colorations — red, yellow, green, etc. — are given, and it is 
pointed out at the same time that all appear to give rise 
to some form of acid. It is supposed, for example, that 
certain species of sarcinse are responsible for the sour and 
bitter tastes which are sometimes developed in beer ; a similar 
organism is also described as giving rise to the red colour 
which is sometimes developed in white beer, though it may 
be remarked that in this case a rod-shaped bacterium is also 
frequently present, and may be answerable for the presence 
of the substances that so seriously alter the taste of this 
beverage. A series of other organisms, which Lindner 
speaks of as Pediococci, all produce acid, and give rise to 


unsoundness of beer, but as they are readily killed at a 
temperature of 60° C, they may easily be got rid of. 

In the process of baking, as carried on in this country, 
there is a regular conversion of some of the starch of the 
flour into sugar by the yeast used — this sugar being in 
turn converted into alcohol and carbonic acid gas, to 
the setting free 'of which the " rising " of bread is due. 
The baking that follows serves three purposes ; it kills 
the ferment, it fixes the remaining starchy matter in posi- 
tion, and it drives oif the alcohol and the carbonic acid. In 
the baking of other kinds of bread certain other organisms 
are said to play a part ; for" instance, the Saccharomyces 
minor (Engel) was supposed to be the active fermenting 
agent in the manufacture of rye bread, but more recently 
this organism has been superseded, and the work of fermen- 
tation has been assigned to a bacillus — Bacillus Panificans 
(Laurent) — which in pure cultivations was found to be capable 
of setting up all the characteristic fermentation changes in the 
dough of black bread. This organism is made up of short 
motile rods, from which threads may be formed, these threads 
(in which spores are sometimes found) interlacing to form a 
film, especially when it is grown on the surface of nutrient 
liquids. Its spores are almost as resistant as those of the 
hay bacillus, and can only be killed by being subjected to 
boiling heat for a period of at least ten minutes. 

Jorgensen, summing up Laurent's investigation, says : 
" The bacillus usually dissolves the gluten substance of the 
dough, grows in starch paste, and in mixtures of saccharose 
and mineral substances. It is found in an active state in 
large quantities in bread, and according to the author's 
researches, it can withstand for twenty hours the action of 
an artificial gastric juice. In the excreta it is found still 
" more abundantly, and it appears to be generally distributed 
in plants and in various substances." More recent researches, 
however, have thrown some discredit even on the Bacillus 
Panificans ; Diinnenberger maintaining that these bacteria 
are merely an impurity, and that in all cases the' fermenta- 
tion of bread is due to an alcoholic-forming organism — a 
saccharomyces in all cases proving the best agent for bring- 
ing about this fermentation. 

Certain forms of unsoundness of bread are also due to 
micro-organisms. In addition to bleeding-bread (caused by 


the growth of the Bacillus prodigiosus), which has served the 
purpose of the miracle-monger before to-day, sticky reddish- 
brown patches have been described as occurring in unsound 
bread, in which various bacilli, such as the ordinary potato 
bacillus. Bacillus liodermos, Bacillus mesentericus vulgatus, 
have been found, and on analysis of these patches dex- 
trine, dextrose, starch, sugar, and even a small quantity of 
peptone, have been separated ; moulds of other fungi are 
also found in unsound bread. 

In 1882, Kern described the peculiar ferment known as 
kephir grains, by means of which the Caucasians set up a 
double alcoholic and acid fermentation in milk. 

These kephir grains, says De Bary, in the fresh living state 
are " white bodies, usually of irregular roundish form,'Equal 
to or exceeding a walnut in size. They have their surface 
roughened with blunted projections, and furrowed like a 
cauliflower ; they are of a firm, tough, gelatinous consistence, 
becoming gradually cartilaginous, and are of a yellow colour 
when dried ; they are chiefly composed of a rod-shaped bacte- 
rium," many of these being united to form long threads, 
arranged in a kind of felt or network, the meshes of which 
are filled with a tough gelatinous membran«, which binds 
the organisms together into a kind of zooglcea mass. This 
rod-shaped organism is known as Dispora caucasica as at 
the end of each rod is a rounded spore. 

Along with these may usually be found a small proportion 
of a yeast-like fungus which, however, is merely entangled 
in the gelatinous mass, although it certainly undergoes 
develogment by sprouting. There is also present the 
ordinal Bacterium lactis which, with a number of other 
impurities, adheres to the kephir grains ; this also occurs in 
the milk itself. To prepare the specially fermented milk, 
one volume of these kephir grains is moistened and added 
to about six or seven volumes of fresh milk, the whole is 
protected from the dust, but is exposed to the air for about 
twenty-four hours at the ordinary temperature of the room, 
and is frequently shaken ; the milk is then poured off and a 
fresh quantity added ; the milk that is poured off is mixed 
with double its quantity of fresh milk, put into bottles, well 
corked, and frequently shaken. This bottled sour milk 
soon becomes sparkling and effervescent, and is ready for 
use after it has been bottled for a day or two. It then con- 


taifis lactic acid, a considerable quantity of carbonic acid, 
which varies " according to the temperature and the duration 
of the fermentation, but is sometimes sufficient to burst the 
bottle or drive out the corks." The liquid contains about 
one per cent, of alcohol. 

We have already seen that the kephir grains and the 
sour niilk, together, contain (i) a yeast fungus which is 
capable of bringing about the fermentation of grape sugar ; 
(.2) the bacillus of lactic acid ; and (3) the rod-shaped bacteria 
that predominate in the gelatinous mass of the tough grains. 
Now, though this yeast fungus can set up the fermentation of 
inverted milk sugar, it cannot affect the milk sugar itself, so 
that we must look elsewhere for the inverting power. 

This appears to be contained in an enzyme, or ferment, 
that is produced by a large number of bacteria, amongst 
others by the rod-shaped organisms already referred to, 
and by the lactic acid bacillus, and these were supposed 
to prepare the milk sugar for the action of the yeast fungus. 
This appeared to be a perfectly satisfactory explanation, until 
De Bary found that, by violent agitation of the souring milk 
to which no kephir grains have been added, alcoholic 
fermentation may still be induced ; so that it would appear 
that by freely oxygenating the milk during the process of 
lactic acid fermentation, when in fact the molecules are being 
re-arranged, oxygen is taken up into chemical combina- 
tion, and alcohol and carbonic acid are generated ; water, in 
all probability, being formed as this goes on. This is 
adduced as one of the processes of fermentation by free 
oxidation, and is an example of a chemical fermentation 
giving results similar to those yielded by biological fer- 
mentation. Until, however, it can be demonstrated that 
De Bary was working with material in which all impurities 
were excluded, these results can scarcely be accepted as abso- 
lutely reliable. 

In the kephir, which is a perfectly fluid mass, we have a 
quantity of lactic acid. Now, it is a well-known fact that, 
under ordinary circumstances, when milk turns sour, there 
is a precipitation of the curd which forms a more or less 
solid coagulated mass. What has become of this coagulum 
in the kephir ? If a piece of meat be exposed to the action 
of putrefactive germs, it will be found that after a time it 
is reduced to a soft, pulpy, almost liquid mass. In the same 


way, a number of the nitrogenous foods taken into the 
stomach are softened and otherwise very considerably 

These materials have in both cases undergone what is 
known as a process of peptonization : from coagulable or 
colloid albumen they have been converted into a much more 
soluble and diffusible albuminoid, and are thus prepared for fur- 
ther changes as they are acted on directly by living animal or 
vegetable protoplasm. This peptonization appears, however, 
to be also brought about by an enzyme which is elaborated 
by certain bacteria, especially by such as are associated 
with putrefaction and with the digestive processes. In the 
case of the kephir it was thought that the peptonization 
took place as a result of the action of an enzyme, formed 
by the rod-shaped organisms of the zoogloea mass of the 
kephir grains, and it was argued that this must be a soluble 
ferment which could diffuse from the gelatinous mass in 
which the grains were embedded into the milk ; it could 
there act on the casein as it was gradually precipitated, or 
possibly even before precipitation took place ; for it was 
observed that these rod-shaped organisms were never found 
outside the gelatinous masses, and therefore could not be 
acting directly on the casein. 

This is well enough in theory, but as equally good kephir 
can be produced by the oxidation effected by free movement 
of the sour milk, the peptonization cannot be solely due to 
these organisms. It may be urged that other organisms 
may; in the presence of a large quantity of oxygen, supply 
the peptonizing function in an acid fluid in which, under 
ordinary conditions, they would not be able to exist, the 
large amount of free oxygen driven into the milk enabling 
them to obtain a supply of energy, to live and carry on their 
function even in the presence of the special lactic acid bacteria, 
which seize with avidity the whole or a part of the oxygen 
contained in the milk, according to the quantity present, in 
this instance a part only, as there is such a large supply 
under the above conditions.' 

It has already been mentioned that the Clostridium 

' For the further description of the kephir grains the reader is referred to 
E. Kern, "Bot. Ztg.," 1882, p. 264; Alexander Levy, "Deutsche Medi- 
cinal Zeitung," 1886, p. 783 ; De Bary, " Lectures on Bacteria," translation, 
Oxford, 1887. 


butyricum or Bacillus amylobacter plays an important part 
in determining the butyric acid fermentation of the vegetable 
acids, and that it plays an active part in the ripening of 
cheese. Because of its action on cellulose, and then of its 
further action on dextrine and glucose, it also has much to 
do with the decomposition and destruction of the cellulose 
of fleshy and juicy plant tissues, and its aid is requisitioned 
in the separation of these parts from the tougher fibre of 
hemp, flax, and similar materials, as in the process of macera- 
tion the enzyme converts the cellulose into butyric acid. 

Van Tieghem holds that much the same processes go on 
in the stomachs of ruminant animals, and that the Bacillus 
amylobacter, which is usually found there, thus does a very 
large part of the work which, otherwise, would have to be 
performed by the epithelial cells of the stomach itself. This 
bacillus, however, acts not only upon cellulose and starch 
paste, but it also exerts a most important action on nitro- 
genous substances. Fitz and Hueppe have both pointed out 
that the casein of milk is first coagulated in the presence of this 
organism, is then peptonized and liquefied by the action of its 
enzyme, and that the products thus formed are afterwards 
converted into certain lower compounds, such as leucine, 
tyrosine, and even ammonia, all of which are constantly met 
with during the processes of both digestion and decomposition. 
Duclaux also showed by experiment that an organism, which 
resembles the bacterium amylobacter very closely in many 
respects, sets up a series of similar changes in the casein of 
milk, and in casein that has been converted into cheese ; 
and he showed that the process of " ripening " brought 
about in the presence of the Tyrothrix bacillus, is due to 
the peptonization and liquefaction of some of the substances 
of which unripe cheese is composed ; certain secondary or 
ultimate products similar to those above mentioned being 
found during the ripening process. 

That bacteria are general scavengers is now generally 
acknowledged, and almost innumerable observations have 
been made with the object of proving that the presence of 
certain definite organisms is essential for the perfect breaking 
down of dead or effete animal and vegetable matter. It has 
already been mentioned that some species have the power 
of breaking up cellulose and of converting it into much 
simpler substances, both externally and in the alimentary canal. 


Bienstock went so far as to describe a particular bacillus 
which, he considered, was able by itself to produce the whole 
series of changes that occur in the contents of the intestine 
and in putrefying albumen or fibrine. This organism he 
describes as being somewhat smaller than the Bacillus subtilis; 
it is rod-shaped, but at one end there is usually a small 
enlargement, in the centre of which a clear round spore 
may be seen. It is from this feature that the organism 
derives its name of "Drum-stick" bacillus. Cultivated on 
fibrine it disintegrates it and gives rise to the formation of 
leucine, tyrosine, carbonic acid, water, and ammonia, and 
of traces of other putrefactive products. The process does 
not however stop at this point ; the bacillus still continues 
to act on the leucine and tyrosine, and decomposes them 
into still simpler compounds ; whilst, if it be introduced 
at once into a prepared solution of one of these earlier 
decomposition products, tyrosine for example, it continues 
the breaking-down process just as if it were still acting, 
on the tyrosine which had been formed during the process 
of ordinary putrefaction. As De Bary points out, however, 
this bacillus cannot claim a monopoly of the work connected 
with putrefaction. If any putrefying fluid be examined, 
countless organisms, will be found, and amongst these very 
different species may be observed. There are rods of different 
sizes both as regards thickness and length, spirals of different 
forms, micrococci of different sizes and arranged in different 
groupings, one or other organism predominating according to 
the nature of the putrefaction process, of the material that 
is being broken down and the stage at which the breaking- 
down process has arrived. It would appear in fact as 
though there were developed special organisms for the setting 
up of special fermentations, and also that after the breaking 
down has been carried a certain length by one organism, the 
aid of another is invoked to complete the process more 
thoroughly and more expeditiously. We have in this, as in 
the case of the process of digestion, an exemplification of 
the fact that nature economizes her resources as much as 
possible ; she does not call on the animal cells of the alimen- 
tary tract to do work that can be equally well done by 
micro-organisms, nor does she demand the exercise of more 
than orie or two functions from each of the simple proto- 
plasmic specks that we call bacteria. To each one is assigned 


its special work and, though it is possible that many of them 
started with certain powers in common, it seems that through 
the exercise of some of these common powers under special 
conditions they have become gradually so diflferentiated 
functionally, that, as amongst organisms more highly 
developed, each is able to carry on its own work best at 
those special stages of the putrefactive process at which it 
is found. It might at first sight appear that all this can 
have but little bearing on any practical work in which we 
are engaged, or in which we take an interest, but on more 
careful consideration it will be found that these putrefac- 
tive organisms really keep up the circulation of matter, 
utilizing the excretions of living beings and the carcases of 
dead animals and plants, after breaking them down into 
their simplest constituents, to supply those elements that 
are necessary for the nutrition of plants, allowing them to 
present themselves in their most assimilable forms, and in the 
proportions most suitable for the nutrition of the growing, 
highly organized vegetable protoplasm. Bacteria in fact serve 
to transform inert organic matter into inorganic substances. 
This transformation, or ^'■Mineralization^'' in most cases, com- 
mences only after protoplasm has lost its vitality, and most 
micro-organisms are capable of attacking this dead protoplasm 
only ; though, as we shall find later, a certain number of 
bacteria have acquired the faculty of being able to attack 
even living protoplasm. The processes of decomposition 
may be divided into two kinds : first, those going on as the 
result of the activity of organisms that are capable of taking 
up their oxygen from the air, and, second, those the result 
of the activity of organisms that so break up and rearrange 
the organic molecules containing oxygen, that not only do 
they, the bacteria, take up oxygen themselves but they allow 
of its being handed on to the products to which in their 
processes of metabolism they give rise. It is probable that 
here we have to do, not only with nascent oxygen, but that 
we have certain products set free during the process of 
decomposition which seize upon oxygen with very great 
avidity. This decomposition or rearrangement is spoken 
of as a process of nitrification, or a conversion of the nitro- 
genous elements into ammonia, nitrous and nitric acids, 
carbonic acid and water, or, speaking more generally, it 
may be said to be a process of mineralization of the organic 


forms of nitrogen, phosphorus, carbon, and hydrogen, 
during which they become finally oxidized or mineralized to 
nitric acid (HNO3), phosphoric acid (H3PO4), carbonic acid, 
CO,, and water, H^O. In nature this process goes on in 
the superficial layers of the earth or in the presence of the 
atmosphere. That it takes place much more readily near the 
surface of the ground and in porous earth can easily be 
understood if what takes place in the oxidation that goes 
on in spongy platinum is borne in mind. In the earth we 
have a spongy material, the upper surface of which is well 
supplied with air, and usually also with moisture ; there is 
also a certain amount of organic matter present on which 
micro-organisms feed, and any additional organic matter 
brought to this spongy mass is rapidly seized upon by the 
micro-organisms, is oxidized, and thus prepared for the 
nutrition of the plants that are growing in this soil. So 
necessary is this whole process of oxidation by micro- 
organisms that Duclaux insists that soil rendered sterile (as 
regards micro-organisms), and supplied only with sterilized 
water and air, is incapable of supplying sufficient nutrient 
material to plants to enable them to flourish even moder- 
ately well. All the organisms found in these superficial 
layers under ordinary conditions are aerobes ; in the deeper 
layers of the soil are micro-organisms that give rise to the 
second kind of decompositions. These bacteria, which are 
anaerobic (that is, they can flourish without being supplied 
with free oxygen) in character, have a special power of taking 
up the oxygen that is contained or combined in the products 
which have filtered down from the surface where the decom- 
positions by direct oxidation are going on. Living away from 
the atmosphere and being unable to obtain or to utilize 
free oxygen, these organisms have developed the faculty of 
being able to wrest oxygen, by force, as it were, from the 
oxygen-containing bodies that come down to them from 
nearer the surface, sometimes however using part only of 
the combined oxygen and setting free another part by 
which further oxidation may go on ; in doing this they 
carry the process of decomposition a stage further, and 
after the altered organic materials have been attacked by 
these anaerobic organisms they appear to contain little that 
will provide nutrition for micro-organisms of any kind ; so 
that, after we come to a certain depth, bacteria are not 


to be found in the soil. This depth, usually reckoned at 
about twelve feet, varies of course according to the nature 
of the soil, its moisture, porosity and temperature, and 
also according to the amount of organic matter that lies on 
the surface ; cultivated ground always containing more 
organisms and to a greater depth than fallow ground having 
the same geological characters. 

The relation of all this to our water supply is obviously 
one of paramount importance. If water be taken from near 
the surface of soil in which there is a large quantity of 
organic matter present, there must necessarily be a large 
number of putrefactive organisms in it, especially those of 
an aerobic nature ; if however we take water directly from 
the deeper layer, these putrefactive organisms are usually 
absent, but a number of " water " organisms are now present, 
which under special conditions, especially if the water be 
kept perfectly quiet and unoxygenated, and a high tempera- 
ture be maintained, can develop in the water, from which 
they may in turn be cultivated by certain well-known 
methods. If water be taken from a much deeper layer, 
micro-organisms are found to be almost or altogether absent, 
and not only micro-organisms, but organic matter, although 
in some cases in which micro-organisms are almost entirely 
absent, organic matter may still be present in appreciable 
quantities. The superficial layers of earth in this case act, 
not only as a mechanical, but also as a biological, filter ; 
the water, with its contained organic matter, passes through 
the successive layers in which bacteria can grow, and gradu- 
ally percolates to those layers of earth where there are no 
organisms. It has been demonstrated that even deep natural 
water contains facultative aerobic organisms, unless it is 
obtained at once after it has undergone natural filtration — 
that is water that has not stood in an underground basin — 
when it may be almost germfree. The organisms cannot go 
down with the water ; first, because they are held back 
mechanically, the soil acting as a porous filter, by which solid 
particles, extremely minute as they are, are kept back ; but, in 
addition, and quite apart from this purely mechanical effect, 
the bacteria (many of which are unable to develop without 
oxygen) cannot leave the surface with impunity, and such as 
are carried down by the action of the water die as their 
supply of oxygen is gradually cut off ; for, in consequence 


of the rapid oxidation that is going on at the surface, very 
little free oxygen is left for the use of bacteria at even a 
short distance from the surface. It will, of course, be 
objected that this does not apply to the anaerobic bacteria, 
but in their case it must be remembered that only a certain 
definite proportion of oxidized material can reach them from 
above, most of the organic matter having already been 
converted into inorganic material and used up by growing 
plants ; the supply is very rapidly cut off, the reduction 
of what remains after the plants are satisfied being com- 
pleted, and the bacteria cannot continue to live, because they 
can no longer obtain any material for their nutrition. 

All the knowledge that has been gained concerning the pro- 
cess of putrefaction has not been collected in a day, and it was 
onlyby a careful marshalling of facts as they were accumulated, 
and by filling in, sometimes merely with suggestions, gaps that 
still remained, that the theory of the filtration and biological 
and chemical purification of water has been built up. But to 
the practical hygienist it is not sufficient to know that water 
coming from springs deep down in the earth is free from 
organisms, and that it may be drawn and consumed with 
impunity as it rises from the ground. He has something 
more to consider ; he has to consider under what conditions 
it can be kept fit for drinking purposes, and by what means 
it can be most readily and safely distributed to those who 
use it. He has to remember that water at rest containing 
organic matter, and exposed to the hot rays of the sun, soon 
teems with organisms that may or may not be perfectly 
harmless ; he has to bear in mind the nature of the ground 
, from which water is collected, whether it comes from 
cultivated areas or from regions in which there is sewage of 
any kind ; for upon these factors depend the absence or 
presence of bacteria from the water supply. Further, he 
may be faced with the problem of how to transform a 
supply of biologically impure water into a supply fit for 
drinking purposes. 

The mere chemical analysis of water will not give suffi- 
cient information to guide a sanitary engineer on these 
points, though it will indicate to him the lines on which 
he will have to work. For example, it is quite possible to 
have a water containing a considerable quantity of organic 
material which, through its treatment by sand filters, or by 


some similar process, may contain no micro-organisms, and 
may be perfectly fit to drink so long as it is fresh, although, 
if it were allowed to stand in a warm place and exposed to 
dust and germs of various kinds, there would soon develop 
in it such an enormous number of organisms that it would 
be looked upon as totally unfit for drinking purposes. On 
the other hand, water containing little or no organic matter 
might be so contaminated by certain disease germs that it 
would be absolutely dangerous to health, and even life, if 
used for domestic purposes. 

The relation of bacteria to sewage need not be insisted 
upon, as it is evident that with such a large quantity of 
organic matter, in which putrefactive changes must be rapidly 
going on, bacteria of many kinds must necessarily appear, 
and it is easy to conceive that an enormous number of 
different species might be present, especially where the 
sewage is diluted as it flows into comparatively pure water. 

Let us observe how a disease-producing organism may 
find its way into water that is used for drinking or other 
purposes, and thence may attack a comparatively healthy 
individual. In typhoid fever, a germ, which will after- 
wards be described, has been found. It has special charac- 
teristics, and may be separated as a pure culture. A patient 
has typhoid fever ; the bacilli which we find specially in the 
walls of the alimentary tract pass out along with the excreta, 
and, under ordinary circumstances., would be killed by the 
addition of disinfectant fluid to the stool ; but, as frequently 
happens, some of the excreta without the addition of a 
disinfecting fluid by chance finds its way into the drains, or, 
worse still, on to the surface of the soil near a well or some 
other source of water supply. The typhoid bacillus con- 
tinues to multiply in the water or in the organic matter 
of the sewage, from which it ultimately finds its way into 
the water, and although such water may appear pure 
enough (it is often beautifully clear and sparkling), as soon 
as it is taken into a slightly disordered stomach and 
intestinal canal, the bacillus gains a foothold, and another 
patient is attacked with typhoid fever. This may happen 
simply through the rinsing out of a milk pail. A patient 
partaking of milk (a most admirable nutrient medium for 
the growth of the typhoid bacillus) from such a pail is 
struck down with " Typhoid." Another example : there 


is a small drum-stick shaped bacillus, similar to the putre- 
factive bacillus described by Bienstock, which, on making 
its way into a surgical wound, sets up a series of changes in 
the tissues, accompanied by the production of a most 
virulent poison, which, acting apparently on the nervous 
system, gives rise to reflex spasms and convulsions, and 
a condition known as lock-jaw or tetanus is set up. 
This organism is found on the manure heap, in cultivated 
soil, and even in water that comes from such soil ; it is also 
found in the dust of hay, straw, and even in the harness and 
cloths used for equipping the horse. If water containing 
these organisms be used for the purpose of washing a con- 
tused wound, or if any of the above dirt or dust should obtain 
access to such a wound — often merely a most insignificant 
bruise — tetanus or lock-jaw is set up with terrible certainty, 
and the patient very frequently succumbs to the disease. 

Innumerable other instances might be given in proof of 
the statement that the knowledge, first, of the forms, and, 
secondly, of the biological and physiological characteristics 
of the various micro-organisms, is now absolutely necessary 
for a thorough understanding of even many everyday pro- 
cesses. The colour formed in " blue milk " is due to the action 
of a micro-organism ; ^s also are the phenomena of bleeding 
bread, the Cape meal orange ferment, and the characteristic 
appearance of green cheese. As a result of the knowledge 
gained through the study of the life history of septic 
organisms, thousands of valuable lives have been saved in 
our surgical wards alone ; large industries have, through 
Pasteur's indefatigable exertions, been preserved from almost 
absolute ruin ; as a result of the observations of numerous 
investigators, our knowledge of certain classes of diseases is 
gradually becoming more precise and accurate, and the 
time has now arrived when we may look forward to a 
system of medicine in which, by preveetive and curative 
inoculation, we shall be able to grapple successfully with 
some of the deadliest forms of disease with which we have 
at present helplessly and almost hopelessly to contend. 


The following works may be consulted : 
Bienstock. — Zeitschr. i. KUn. Med. Bd. viii. p. i, 1884. 
CoHN. — Beitr. z. Biologic der Pflanzen, Bd. 11., 1876. 


DuCLAUx. — Chimie. Biologique Encyclop. Chimique, Paris, 

DuNNENBERGER. — Bakt. chem. Unters. Ueber d. Beim. 

Aufgehen des Brodteiges wirkenden Ursachen. — Bot. 

Centralbl., 1888. 
FiTZ. — Ber. d. Deutsche chem. Gesellschaft, 1876-1884. 
Hansen. — Meddel fra. Carlsberg Laborat., Copenhagen. 
HuEPPE. — Der Bakt. Forsch., 1889. 
Jorgensen. — The Micro-organisms of Fermentation 

(transL), 1889. 
Klebs. — Beitr. z. Kenntn. d. Mikrokokken. — Arch. f. 

Exp. Path., Bd. i., 1873. 
Koch. — ^Mitt. a. d. k. Gesundheitsamt, Bd. i., 1881. 
Lister. — ^Trans. of the Path. Soc. Lond., vol. xxix., p. 425, 

Naegeli. — Nageli u. Schwendener. — Das Mikroskop, 1877 ; 

Theorie der Gahrung, 1879. 
Pasteur. — Etudes sur le vin, 1866 ; Etudes sur le Vinaigre, 

1868 ; Etudes sur le Biere, 1876. 
Roberts. — Phil. Trans., vol. clxiv., p. 457, 1874. 
SalomonseN. — Bakterialogisk Teknik., Copenhagen, 1890. 
Van Tieghem. — Bull de la Soc. Bot. de France, p. 128, 

1877 ; p. 25, 1879. 

What are Bacteria? 

Structure — Myco-protein — Limiting Membrane — Gelatinous Capsule — 
Special Cell Contents — Oxide of Iron — Sulphur — Colouring Material 
— Flagella — Modes of Multiplication and Development — Division — 
Rate of Vegetative Multiplication — Endospores — Arthrospores — 
Classifications of Cohn, Van Tieghem, Zopf, Winter and Rabenhorst, 
De Bary and Hueppe, Fliigge Baumgarten, &c. 

Under the general term Bacteria may be included those 
minute, rounded, ellipsoid, rod-shaped, thread-like, or spiral 
forms of vegetable organisms sometimes spoken of as be- 
longing to the class of lower fungi. They are also known as 
Fission fungi (the Schizomycetes of the Germans) ; a term 
applied to them because of their multiplication by a process 
of division, transverse to the longitudinal axis in the case 
of the rod-like forms, but varying somewhat in the case 
of the rounded organisms. Each single organism consists 
of a small speck of protoplasm or vegetable albumen, to 
which may be given the name of cell, as although these 
specks are so minute that they can be seen and studied only 
with the aid of the very best optical appliances at our 
command, it is found that they are by no means simple in 
structure, nor are they in all cases even similar. This proto- 
plasmic speck is differentiated into certain well-defined parts. 
The round cells or micrococci, the simplest of all forms, 
are seldom more than i-2S,oooth part of an inch in diameter ; 
the elongated cells have, on an average, the same diameter, 
or they may be a little more, and are from i-i 2,000th part 
to i-6,oooth part of an inch in length, though there are 
marked deviations from these dimensions in certain forms. 
Accepting the above figures as being accurate, it would 
require 25,000 of these spherical cells, placed in a row, or 
the same number of the longer ones, placed side by side, to 
make up a chain or band one inch in length. The vegetable 


albuminoid or protoplasmic substance of bacteria was first 
analysed and described by Nencki, who, because of the 
nitrogen contained in it, and because of the similarity of 
its structure to animal and vegetable protoplasm, looked 
upon it as a proteid material ; he gave to it the name of 
myco-protein or fungus protein.' During certain periods 
of the existence of these micro-organisms, especially in cer- 
tain species, this white of egg or jelly-like substance, which 
invariably occupies the central part of the cell, is perfectly 
transparent and is slightly more refractile than water ; at 
other periods, or in other species, it may be finely or 
coarsely granular ; under certain conditions still more marked 
and characteristic changes may occur, vacuoles or clear spaces 
making their appearance. It is usually extremely resistant 
to the action of acids and even of alkalies. 

That this myco-protein cannot always be of the same 
composition is evident from the fact that minute granules of 
chlorophyll or of fat may be made out lying in the substance of 
the protoplasm in special species, whilst in others small starch 
or sulphur granules, or particles of different kinds of pigment 
may be observed. This speck of vegetable albumen is really 
the active part of the cell, and it is in this that we obtain 
those histo-chemical colour or staining reactions that are so 
characteristic of the protoplasm of the higher vegetable and 
animal cells which, as is well known, seem to have a 
peculiar affinity for certain dyes or stains. Carmine, for 
example, is taken up most voraciously by the nucleus or 
central portion of the cell which then assumes a brilliant 
carmine hue, not by any means equal throughout ; in 
consequence of this inequality the minute structure of 
the nucleus may be readily and even accurately studied. 
The surrounding protoplasm, which appears to be less 
active, is much less vividly stained, whilst the cell wall, 
which is the least active part of the cell and serves as little 
more than a boundary wall of formed material, if present 
at all, remains, in the majority of cases, quite unstained. 
Logwood, the aniline dyes, or iodine may be substituted for 
carmine, with the general result that the same staining 
reactions as regards the different parts of these cells are 
almost invariably obtained. 

' Analysis of myco-protein : Water, 84.81; albumen, 13.207; fat, 1. 198; 
asb, 0.638; extractives, 0.327. 


Exactly the same reactions are given when one of the 
above colouring reagents or stains is added to a mass of 
micro-organisms. The individual cells or organisms are 
brought prominently into view, the central jelly-like speck 
of protoplasm is most vividly stained in each, and reasoning 
from analogy, certain authors have looked upon this active 
part as the nucleus of the micro-organismal cell. Sur- 
rounding the central protoplasm is a dense, sometimes 
lamellated, thin skin or sheath which acts as a limiting or 
protecting membrane. It very frequently contains a sub- 
stance known as cellulose, almost, if not quite, identical 
in composition with that forming the hard covering of 
the vegetable cells that are found in the higher plants. In 
other bacteria, in fact in the majority of them, the limiting 
membrane seems to consist of a firm layer composed of 
gelatinous material, sometimes stiff and rigid, or it may 
be more or less elastic or pliable. Between the central 
stained portion and the limiting sheath there sometimes 
exists a narrow unstained area which by some is said to 
be a space produced artificially by the chemical action 
on the protoplasm of staining and other reagents ; others, 
however, hold that it is a kind of modified protoplasm 
which, surrounding the more active nuclear protoplasm, 
divides it from the limiting membrane. Outside this limit- 
ing membrane, or more strictly speaking, continuous with 
it, there may usually be seen a mass of gelatinous or muci- 
laginous matter which does not take on any special stain, 
and which serves to separate the individual cells, or, to speak 
more accurately, to bind them together into littje grojjps. It is 
due to the presence of this gelatinous materiarthat we have 
those frog-spawn masses or jelly-like lumps that are met 
with in certain germ fermentative processes. These masses, 
in which the organisms are embedded, as it were, in the 
softened jelly-like part of their sheaths, are known as 
zoogloea masses or masses of living glue. If the cells 
remain isolated when the membrane becomes gelatinous, 
capsules or highly refractile areas are seen around each 
cell, when examined under the microscope. These may 
sometimes be very delicately stained by certain methods 
(Gram's method, see Appendix). As examples, may be taken 
the capsule that surrounds the bacillus of pneumonia (Fried- 
lander), the false Diplococcus of pneumonia and certain 


Other organisms such as the Leuconostoc mesenteroides, 
which is not pathogenic, and the Actinomyces or Ray 
fungus. It is rather a curious fact, as Friedlander pointed 
out, that this gelatinous capsule is formed only under certain 
conditions, and he noted that in the case of the bacillus 
of pneumonia the capsule could not always be demonstrated ; 
that it occurred in the bacilli found in the lung tissue or in 
the prune juice sputum so characteristic of the disease, but 
that it could not be made out in the organisms grown oh 
such cultivation media as peptonized beef jelly. In the case 
of the Ray fungus or Actinomyces, the organism that causes 
wooden-tongue or Actinomycosis in cattle, this swelling of 
the capsule at one end of the organism and not at the other 
gives rise to a very peculiar club-shaped appearance of the 
threads, and as these are frequently arranged so that the 
thin ends of the rods are grouped together, whilst the 
swollen ends are placed at the periphery of the radius, a 
most peculiar and characteristic radiate arrangement of 
wedge or club-shaped rods is the result. In some cases - 
bacteria first divide and multiply whilst they are embedded 
in this common gelatinous mass, and it is only after they 
have undergone a certain development that each organism 
becomes invested with its own capsule and is allowed to lead 
an independent life. 

It appears that in most cases in which the organisms con- 
tain natural colouring matter, it is deposited in the capsule 
and not in the protoplasm itself, and that the red, magenta, 
blue, and yellow colouring particles that are met with in 
this position give rise to the naked eye colour that is seen 
where large masses of these organisms are growing. The 
beautiful brown that is seen in Crenothrix and Cladothrix, 
not only in the capsule, but in the surrounding cultivation 
medium, is due to the presence of oxide of iron which the 
organism is able to separate from water, or from other 
media in which that substance is held in suspension or com- 

The composition of the limiting or external membrane, 
as already pointed out, varies somewhat in different organ- 
isms ; in many cases it appears to consist merely of an 
altered myco-protein, but in others, as, for example, in 
Bacillus anthracis, it is composed of a material analogous 
to the casein of plants, combined with a substance which 


has many points of resemblance to the mucine found in the 
tissues, especially the embryonic tissues of animals. This 
capsule of the B. anthracis, unlike myco-protein, contains 
no sulphur, is soluble in dilute alkalies, but insoluble in 
water and acetic acid. 

Dallinger some time ago pointed out that at each pole of 
an organism which he had studied most thoroughly (the Bac- 
terium termo, a small oval organism not now recognized 
as a species) there was developed an extremely delicate 
flagellum which, he assumed, had something to do with 
propelling the organism through the fluid in which it 
was growing, as this organism exhibited most active move- 
ments in such fluid. As a considerable number of other 
organisms also possess this same motion in fluid media, it 
was argued that as in the case of the above organism and 
of other cells that have an extreme degree of motility, 
there would also be found flagella or cilia such as are 
met with in the swarm cells of certain algae, where cilia 
or flagella are continued directly froir; the protoplasm, 
through the cell membrane, if present, and so to the out- 
side of the organism. Although the existence of these 
flagella was suspected in many bacteria, they could actually 
be demonstrated in the case of some of the larger organisms 
only. Now, however, the number of bacteria in which flagella 
have been seen has been gradually but surely increased, and 
lately Loffler has described and photographed most exquisite 
lash or thread-like filaments, single or in little groups, in 
Koch's cholera bacillus, in the bacillus associated with the 
causation of typhoid fever, and in a considerable number 
of other motile bacteria. 

Whether these cilia and flagella are developed from the 
protoplasm of the organism, or whether they are merely 
secondary modifications of the external membrane, remains 
as yet a doubtful point. It is quite possible that in many, 
even of the motile forms, flagella are entirely absent ; the 
organism in such case relying for its motile power on con- 
traction of the protoplasm within an elastic or not too 
rigid membrane. In a straight rod-like organism an un- 
dulating movement may often be observed, whilst both 
rotary and undulating movements are met with in spiral 
organisms, though these latter are very frequently supplied 
with well-formed flagella. It is possible that in certain species. 

What are bacteria ? 29 

in which inotion is very slight, if not entirely absent, the 
flagella serve to set up currents round the organism by which 
food is brought to, and excretions removed from, the bacillus. 
These flagella may be met with as a single pair, or we may 
have three or four pairs attached to the same organism. They 
stain like the membranes, and appear to develop only in those 

Photo-micrograph of Spirillum Undala, with pair of well-marked flagella at each 
eDd. X 1000. 

organisms that have special affinity for oxygen, for as soon 
as the ciliated forms reach the surface of a fluid, they lose 
their cilia or they become much less active. This latter, 
however, seems to be the more probable explanation, for 
Lofiler has shown that many organisms are provided with 
cilia, which at one time were supposed to possess nothing of 


the kind. Up to the present, however, micrococci, the 
Bacillus anthracis, and many other organisms, cannot be said 
to be supplied with flagella or cilia, and in many organisms 
in which there seems to be independent movement, really 
-nothing but the so-called Brownian movement can be dis- 
tinguished when they are examined in fluid, a movement 
that may be observed equally well when particles of 

Photo-micrograph of Cladothrix Dichotoma with pseudo-branching filaments, 
with well-marked tranverse divisions, x looo. 

inorganic colouring matter are suspended in a fluid 
medium and examined under the microscope. 

The simplest form of division or multiplication met with 
in bacteria is that known as vegetative multiplication, in 
which, taking as an example a short rod-shaped bacillus, 
there is first an increase in the length of the rod, then a zone 
of constriction in the middle of this lengthened rod, and then 


division, complete or partial, of this lengthened rod into 
two shorter daughter-cells. Under suitable conditions these 
two again increase in length, each again is divided into two, 
and so regular chains or swarms of bacteria are developed. 
The first sigh of division is a delicate transverse mark or 
line across the middle of the bacterium in a plane at right 
angles to the longitudinal axis of the cell. 

By staining, as De Bary recommends, with an alcoholic 
solution of iodine and causing the young protoplasm to 
retract, it may be made out that this line is due to the 
ingrowth of the cell membrane from the periphery towards 
the centre so as to form a septum, more or less com- 
plete, between the little rods of protoplasm, which are 
thus gradually cut oiF from one another by the constricting, 
and growing in, cell membrane. 

In the rod-shaped bacteria this division takes place in one 
plane only — at right angles to the longitudinal axis of the 
rod— and when it is imperfect or incomplete it gives rise to 
chain-bacteria or Strepto-bacteria.* 

The individual bacteria of which the chain consists are 
held together in series by the constricted but incompletely 
divided membranous portion. 

Similar divisions take place in the rounded bacteria or 
micrococci, and we have then chain-cocci or strepto-cocci 
formed, but instead of going on to form or remaining in 
long chains, they may be arranged in pairs, and are then 
spoken of as diplococci. There is sometimes division taking 
place in two dimensions of space, the one at right angles to 
the other, a good example of which is seen in the Bacterium 
Merismopcedioides described by Zopf, in which the lines of 
divisions are placed at right angles to one another, but in 
one surface plane, z.e., at the surface of a fluid. In other 
cases there appear to be. division, multiplication, and 
growth in three directions. To obtain an idea of what 
occurs, suppose that a two-inch cube is divided into single 
cubes, each one inch in diameter : and that these single-inch 
cubes then grow until each reaches the size of the original 
two-inch cube, when it, in turn, is again divided into one- 

■ A long spiral may divide into short curved rods, as in the case of the 
Cholera bacillus. In Cladothrix, where there is a false branching, the 
terminal cell before branching, instead of dividing transversely divides 
vertically, and then the division again goes on transversely. 


inch cubes. This mode of division was first demonstrated by 
Goodsir in the Sarcina ventriculi. 

We have already seen that these minute organisms are 
endowed with great power of movement and locomotion, 
a fact on which stress has been laid in connection with 
their rapid diffusion through fluids ; but an equally im- 
portant factor in the bringing about of this rapid diffusion 
is their extreme prolificness. If they can obtain sufficient 
food, and if the food is of exactly the right nature, the rate 
at which bacteria grow is marvellous. From actual experi- 
ment it has been found that if in a cubic centimetre of 
any specimen of water, we find, say, a couple of hundred 
organisms ; on standing for twenty-four hours the number 
will have risen to about S,ooo per c. c. ; at the end of another 
twenty-four hours, to 20,000 ; and on the fourth day they 
are uncountable. Cohn calculated that a single germ could 
produce, by simple fission, as above described, two of its kind 
in one hour ; in the second hour these would be multiplied to 
four, and in three day they would, if their surroundings were 
ideally favourable, form a mass which can scarcely be reckoned 
in numbers — or if reckoned, could scarcely be imagined — 
4,772 billions. If we reduce this number to weight, we find 
that the mass arising from this single germ would, in three 
days, weigh no less than 7,500 tons. Fortunately for us, they 
can seldom get food enough to carry on this appalling rate 
of development, and a great number die both for want of 
food, and because of the presence of other conditions un- 
favourable to their existence. Vegetative multiplication 
only takes place when the conditions are extremely favour- 
able to the growth of the organism. If nutrition is in- 
terfered with in any way, or if the removal of excretory 
products is obstructed, or if there be a large amount of 
oxygen present marked changes may at once be observed in 
the appearance of the protoplasm of the micro-organism. It 
becomes granular, then a small bright point appears in each 
cell ; this point gradually increases in size until its diameter 
may be greater than that of the original organism. This 
large, clear, rounded, ovoid, or rod-shaped node is known as a 
spore, or resting-spore. It is really the seed or egg formed 
by the bacterium, by which the species may be continued 
although the parent should perish. The shape varies slightly 
in different species, but in every case it has a dark limiting out- 

What are bacteria ? 


line ; it is devoid of colour, and is highly refractile. The dark 
outline of the spore is usually surrounded by a pale, soft, 
gelatinous envelope, the substance of which may, in some 
cases, be accumulated . in rather larger quantity near the two 
poles of the refractile body. As soon as these glistening 

photo-micrograph of Bacillus subtilis, with well-developed free endospores. . 
Those in focus are seen to have clear centre and dark outline, x looo. 

bodies make their appearance, degeneration of the protoplasm 
of the bacteria in which they are found invariably follows, 
but the period at which the death of the protoplasm actually 
takes place varies in different cases. Where the spores are 
small they may lie for some time embedded in the protoplasm 


34 BACtERlA. 

of the cell, which, only as it degenerates or dies, leaves the 
resting -spore free to be carried about from place to place by 
currents of air or water, to be developed when the conditions 
of moisture, temperature, and food supply again become suffi- 
ciently favourable. Where the diameterof the spore exceeds 
that of the bacterium, it may be situated in the centre, giving 
rise to a spindle-shaped organism, or it may be at one end, 
when the organism becomes clubbed or pendulum-shaped. 
The spore in this case appears to escape more readily, and 
before the complete disintegration of the bacterium has taken 
place ; the side or end of the swollen organism gives way and 
allows of the spore being set free. This is only one kind of 
spore formation, and is spoken of by De Bary as endospore 
formation. It is met with in some varieties of vibriones, in 
many of the bacilli and in certain of the spirilla (Cornil 
and Babes) ; whilst Zopf describes similar spore formation as 
occurring in certain micrococci, and Escherich points out 
that he obtained undoubted spores in sarcina pulmonum, 
?>., bodies that admitted of double staining. 

A second kind of spore, to which is given the name of 
Arthrospore, is also described by De Bary, Hueppe and 
others. In this there is a combination of spore formation 
and of fission ; the mother-cell undergoes division into a series 
of daughter-cells, a few of which differ from the rest in very 
important and essential points. There appear to be two 
kinds of arthrospores ; one form, met with in Leuconostoc, 
for example, where simple vegetative division of small round 
bacteria goes on regularly, so long as the conditions are 
favourable, and a regular chain is formed. In this chain 
there appear at intervals, micrococci, which differ from the 
remainder of the elements of the chain in the following 
points : As soon as the conditions of nutrition are altered 
they do not, like the other parts of the chain, die off, 
but they become "somewhat larger than the rest, acquire 
a more distinct outline, become thicker-walled, and their 
protoplasm grows darker. Eventually tbey become free by 
the deliquescence of the gelatinous envelopes, and may 
claim the name of spores, because, when placed in the fresh 
nutrient solution, they develop into new rows of beads like 
those of the mother plant." Here is a body which has most 
of the characteristics of the resting-spore or seed, but it is not 
formed within the protoplasm of the vegetative organism, 


but by a process of fission, and as a result of the vegetative 
division of the organism. It is quite possible, however, that 
there is just as much differentiation of the protoplasm in 
this case, as there is where the spore is formed within the 
cell ; the only distinction being that the separation between 
the spore and the vegetative element of the chain takes place 
at an earlier stage, and more completely than in endosporous 
reproduction. The reverse takes place, however, in the 
Bacterium Zopfii, which during the vegetative or fission stage 
consists of short rods, then of motionless filaments, and, if 
the temperature be lowered from 30° C. to 25° C. of short 
motile rods. As soon, however, as the conditions become 
unfavourable, especially when the nutrient material in which 
they are growing is exhausted, the rods, apparently, by a 
simple process of fission are divided up into short roundish 
cells, which retain their vitality for a considerable time, and 
which, when again placed under favourable conditions, act 
as spores, ?'.«., they develop into the original characteristic 
rod-shaped bacteria. 

In organisms in which spores are not found, the con- 
ditions for their existence and propagation must always 
remain favourable or they die out very rapidly, having no 
specially resistant phase to enable them to tide over their 
period of adversity ; and had we to deal with asporous 
organisms only^ they could, probably, by an organized 
attack, be rapidly and completely exterminated. The vege- 
tative organisms, as distinguished from their spores, cannot 
survive the prolonged action of heat ; — a comparatively 
low temperature, 60° C. or less, being usually sufficient to 
kill them, whilst the weaker chemical germicidal reagents 
are quite sufficient to render them altogether innocuous 
and inactive. The spores, on the other hand, can withstand 
the action of a temperature anything short of 100° C. for a 
considerable length of time. Cold and dessication have no 
effect upon them, for after being submitted to any of these, 
spores will, if placed under suitable conditions, develop into 
the more characteristic vegetative forms. 

It must be borne in mind, however, that certain organisms 
may, by careful acclimatization, be accustomed to exist and 
even develop at extreme temperatures. Globig has shown that 
certain bacteria found in the soil can only grow at a tempera- 
ture of 50° C. or more, and" that they can flourish up to 


70° C, whilst certain forms of " Light " bacilli can, accord- 
ing to Fischer, grow luxuriantly at a temperature of 0° C. 

It should be remembered, however, that arthrospores 
are much less resistant to all germicidal reagents than 
are endospores ; indeed, they are able to withstand a 
temperature only about as high as that at which the 
vegetative forms succumb ; whilst some of the endospores 
are capable of withstanding dry heat of 105°, 110°, and even 
130° C. They are certainly more resistant to the action of 
some of the weaker germicidal reagents, but they withstand 
for a short time only, or not at all, the action of the more 
powerful ones. 

From the nature of the dense membrane that surrounds 
these spores, their staining has always been a matter of 
extreme difficulty. They stood out most distinctly as clear 
spaces in the deeply stained protoplasm of the cell, but could 
not be stained. By subjecting the spore-containing organisms 
to the action of dry heat at 110° C. for half an hour or an 
hour, as suggested by Buchner, or by exposing them to the 
action of concentrated sulphuric acid for fifteen seconds, or 
to a longer treatment with concentrated caustic potash, the 
membrane is so altered that the staining reagents are enabled 
to penetrate into the substance of the spore and act on its 
protoplasm, and impart to it a characteristic colour. If this 
heating be excessive the protoplasm of the bacillus may be 
destroyed when it in turn refuses to take on the stain, 
although the spore itself may, under these circumstances, be 
stained most beautifully, this fact also indicating that the 
spore is more resistant to the action of heat than is the 
vegetative cell. Hueppe, Babes, and Neisser have all 
described arthrospores as making their appearance at the 
end of Koch's cholera bacillus, which may become free, says 
Hueppe, and from which, he thinks, he has seen the bacillus 
being developed.' 

■ In order to stain endospores, the best fluid to use is probably Ehrlich's 
aniline water fuchsin solution. Sections are left in this for several days, 
they are then decolorised with 25% solution of nitric acid, washed thoroughly 
in water and alcohol, to which a trace of ammonia has been added ; a con- 
trast stain is obtained by treating for a few minutes with a dilute solution 
of methylene blue. In some cases the acid removes the fuchsin from 
the spores also ; it is then well to wash simply with alchohol and stain 
with methylene blue as a contrast stain. Instead of leaving cover glass 
preparations for so long a period in the fuchsin they may be heated along 


These so-called arthrospores of the cholera bacillus do 
not, however, give the ordinary reactions of spores, nor 
are they any more resistant to the action of heat and 
germicidal agents than the vegetative forms themselves : 
they must therefore still be looked upon as pseudo-spores. 
True spores, then, appear to be special protoplasmic cells, 
which are first developed in the mother cells and are then 
surrounded by a very thin, but hard and dense membrane. 
It is this dense covering that protects the delicate proto- 
plasm within, against the action of the numerous destructive 
influences to which the spore is exposed. 

If this structure be borne in mind, it becomes evident that 
dry heat must necessarily be less efficacious than moist, in 
determining the destruction of the spore. Dry heat causes no 
swelling of the protoplasm within, whilst moist heat causing 
swelling brings about rupture of the softened membrane by 
pressure from within, and the unprotected protoplasm, exposed 
under most unfavourable conditions, is at once rendered inert. 
It appears probable that this process of expansion from 
within also comes into play whenever spores are placed 
in conditions favourable to their development, i.e.^ when 
they are placed in a warm medium in which are present both 
nutriment and moisture. 

The first change then noticed is that the clear, strongly 
refractile protoplasm becomes cloudy or granular, the dark 
outline is not quite so prominent and the clear boundary 
line "or limiting membrane appears to swell somewhat, 
and the spores gradually assume the form of an ordinary 
vegetative cell. In some cases, however, as soon as the 
spore begins to swell, the delicate outer sheath may be seen 
to split either longitudinally as in the Bacillus amylobacter, 
or across the middle as in Bacillus subtilis. In either case 
there is a swelling of the softened gelatinous layer which 
causes the removal of the firm membrane. This thin, firm, 
delicate membrane may come away in the form of two 
separate cups, or there may be simply a transverse slit 
through which the germinating spore escapes. Having 
once made its way from the membrane, vegetative division 
at once sets in, the segmentation always taking place at 

with the fluid almost to boiling point for ten or fifteen minutes. The 
after procedure is as above. The spores most difficult to stain are those 
of the bacilli of tuberculosis, and of typhoid fever. 


right angles to the long axis of the young organism, as has 
already been described. It was at one time thought that in 
the case of Bacillus subtilis division at first went on longitu- 
dinally, but it has now been demonstrated that the general 
rule is not departed from, the well-known appearance being 
due to the fact that after rupture of the membrane the two 
halves remaining attached by a kind of hinge are thrown 
outwards, the ends of the vegetative spore protoplasm remain- 
ing within these little cups, and the body growing rapidly 
before division takes place ; a kind of loop is thus formed 
which gradually becomes longer and longer, and the two 
limbs which were supposed to be the result of a longitudinal 
division are nothing more than the two ends of the same 
rod. After a time transverse divisions may be seen in the 
diiFerent parts of the loop, the ends escape from the cups 
formed by the halves of the opened-up spore capsule, 
the rods straighten out and assume the regular straight 
form. There are other modifications of the same process 
of development from the spore, but the above are the 
essential or most important forms. 


Our present classification of Bacteria is based upon that given 
by Cohn. He arranged these organisms into four groups, 
taking as his characterising feature the form that was most 
commonly assumed by each organism. His first group con- 
sisted of rounded bacteria or cocci — the Sphsero-bacteria ; the 
second group was made up of short rods, or cylinder- shaped 
bacteria — -Micro-bacteria ; longer rods or thread-like organ- 
isms — the Desmo-bacteria — were placed in the third group ; 
and to the fourth group were assigned screw-shaped or spiral 
bacteria — the Spiro-bacteria. According to this author the 
cocci consist of rounded or ellipsoid bodies, .5 to 2ju' in 
diameter, the smaller ones being spoken of as Micrococci, 
the larger as Mega- or Macro-cocci. They are found singly, 
or may be grouped in pairs or in longer chains. The 
micro-bacteria or short rods are more variable in their size, • 
measuring ifi in diameter and a little more than that in 
length ; but when the length of an organism reaches more 

_ » l/t = 0.001 mm. = looooo gth part of a metre = js^g^th part of an 


than about twice its diameter, it is usually spoken of as a 
Bacillus :— the length of a bacillus may be eight or ten times 
the diameter, which ranges from i/« to 2;.. In some cases 
these bacteria take the shape of short stout spindles or lemons, 
especially during the stage of spore formation, when they are 

Photo-micrograph of Proteus Vulgaris Bacillus, in the form of short rods, x looo. 

spoken of as Clostridium forms, of which an exceedingly 
good example is the spore-bearing Bacillus butyricus. 

Bacilli increase in length, and, becoming more or less 
jointed as vegetative division takes place, form the long 
delicate jointed threads which are spoken of as Lepto- 
thrix forms when there is no apparent branching, but if 
pseudo-ramifications, such as are found in Cladothrix dicho- 
toma and are due to vertical division taking place in one of 
the terminal cells, are present, we have the Cladothrix form. 


The Spiro-bacteria vary very much, not only in size but also 
in length and in general appearance. 

In some instances other isolated features have determined a 
nomenclature. For example, the appearance of sulphur 
in one series of forms has determined a species of Ophido- 
monades ; whilst the form and length of curves have also been 
used as a distinguishing feature. The organism is spoken of as 
a Vibrio when the curves are slightly marked ; if the curves 

Photo-micrograph of Bacillus Figuraus in which Leptothrix form is 
well seen, x 150. 

are short and slightly pronounced and the organism is thin 
it is known as a Spirochasta ; a ribbon-shaped spiral is a 
Spiromonad, and a spindle-shaped spiral, a Spirulina. 


ScMzopkytes, Thallophytes that develop by division or by 

endogenous germinating cells. 


Tribe i. 

A. Free cells arranged in pairs or fours. 
Cells round — chroococcus (Naegeli). 
Cells cylindrical — synechococcus (Naegeli). 

B. Cells united into zoogloea masses by homogeneous gelatinous sub- 


a. Cellular membrane shading off into the intercellular substance. 
Cells round — micrecoccus (Hallier). 

Cells cylindrical — bacterium (Dujardin). 

b. Intercellular substance arranged in concentric layers. 
Cells round — glseocapsa. 

Cells cylindrical — glseothece. 

C. Cells forming circumscribed zooglcea masses with a definite shape. 

a. Families arranged in flat layers in a single plane — merismopedia. 

b. Cells rounded, arranged in a zoogloea mass forming a network — 


c. Cells cylindrical or wedge-shaped, the families divided by con- 

strictions — coelosphaerium . 

d. Cells forming families, dividing in several planes, colourless 

cubical cells with a, quadrate arrangement — sarcina. 

e. A large and indefinite number of colourless cells — ascococcus. 

Tribe 2. 
Filamentus forms in which the cells are thread-shaped. 

A. Without branching. 

1. Colourless cylinders with little sign of division, very delicate, when 

short — bacillus, when long — leptothrix. 

2. Similar filamenls, but thicker and longer — beggialoa. 

3. Filaments deeply divided at intervals with colourless spore-bearing 

tissue and a well developed sheath — crenothrix. 

4. Spiral filaments. 

Short and undulating — vibrio. 

Short with rigid spirals — spirillum. 

Long with flexible spirals and containing phycochrome — spiro- 

Filaments long and spirals flexible — spirulina. 

5. Filaments in chains without phycochrome — streptococcus (strepto- 


6. Zoogloea masses or cylindrical cells. 
When colourless — myconostoc. 

In chains — nostoc. 

Filaments thinner at one end — rivolaria. 

B. Filaments with pseudo ramifications — cladothrix. 

Cylindrical colourless filaments — streptothrix. 

If may be of interest to some to glance over a few of the 
classifications suggested by different authors, and to compare 
the bases on which these classifications are made. Cohn, as 
we have seen, classifies entirely according to the elementary 
form of the organism, the nature of the membrane and the 
mode of division. Van Tieghem founded his classification 


on much the same features, but he also takes into considera- 
tion some of the physiological and biological characters, the 
nature of the processes set up by them, the resulting products 
and the nature of the division. 

Van Tieghem places all the schizomycetes in a family which 

Photo-micrograph of Bacillus Figuraus Leptothrix and rod forms, x looo. 

he calls bacteria, a family closely related to the nostocaceae 
apd the oscillaria of the Algae ; he divides them into micro- 
cocci ; bacteria or short rods ; bacilli or short threads ; 
longer threads, without any definite sheath, being called 
leptothrix ; with a sheath, crenothrix ; with a sheath and 
undergoing division, cladothrix. 


The genus vibrio consists of spiral filaments which break 
up into short fragments. 

The spirillum consists of longer filaments that have a 
helicoid arrangement. 

The spirochsete, of greater length, are spirilla with more 
numerous turns of the spiral. 

Micrococci, arranged in zooglcea masses and held together 
by a thick layer of gelatinous material, he called ascococcus ; 
when held together, but without or with less of this gelatinous 
material, he gave them the name of punctula. 

Bacteria united by this gelatinous material are called 
ascobacteria ; without the gelatinous envelope, polybacteria ; 
bacteria in the form of spiral threads, and massed together, 
form the myconostoc. 

These bacteria are again divided according to their pro- 
perties of forming colouring matter, chromogenes ; of setting 
up fermentation, the zymogenes ; and of giving rise to 
disease in animals or plants, the pathogenes. 
'He gave a further classification based on the mode of 
division of the primary cells : 

1. The bacteria in which the division takes place in one 
axis only. This includes micrococcus, bacterium, bacillus, 
leptothrix, crenothrix, cladothrix, vibrio, spirillum, spiro- 
chsete, ascococcus, punctula, ascobacteria, polybacteria, and 

2. The meristae, in which a membranous thallus divides 
in two directions but on one plane only, giving rise to the 
formation of characteristic tetrads. 

3. The sarcinae, in which there is division in three direc- 
tions, so that the resulting masses always remain cubical in 

ZopPs classification rests (Fliigge, "Etiology of Infective 
Diseases," p. i8o) on the doctrine of pleomorphism, which 
cannot be accepted as in any way proved except in the case 
of a few well-known non-pathogenic forms ; but his classifica- 
tion may be accepted as a basis from which to work in bring- 
ing proof or disproof of the theory of pleomorphism, al- 
though it is not at present, at any rate, founded on a large 
number of facts. 

Zopf, who has studied most carefully the subject of pleo- 
morphism, holds that several forms may occur in the cycle 


of development of any species, and he has determined that 
both form and developmental series must be used in drawing 
up a classification. 

Group I. — CoccACE^ — These are as yet only known in the coccus form. 
To these the following genera belong : 

1. Streptococcus (cocci arranged in threads like strings of beads). 

2. Merismopedia, tablet cocci (division in two directions, leading to the 

formation of tablet-like flat layers of cells). 

3. Sarcina, packet cocci (division in three directions, leading to the 

formation of bale-like colonies). 

4. Micrococcus (the cocci become aggregated in irregular heaps). 

5. And ascococcus (the heaps of cocci accompanied by marked formation 

of gelatinous material). 
Group 2. — Bacteriace.^. — These possess chiefly coccus, rod, and thread 
forms ; the former may be absent ; in the latter there is no distinction 
between base and apex. Threads straight or screw-like. Genera : 

1 . Bacterium, forms cocci and rods, or only rods which are arranged in 

rows to form ordinary threads ; spore formation absent or unknown. 

2. Spirillum, threads screw-like, formed only of rods, or of rods and 

cocci ; spore formation absent or unknown. 

3. Vibro, threads screw-like, spore formation in the longer or shorter joints 

4. Leuconostoc, forms cocci and rods, spore formation in cocci. 

5. Bacillus, cocci and rods, or only the latter in the form of simple or 

twisted threads ; spore formation present. 

6. Clostridiu77i, the bacillus form in which the spore formation occurs in 

peculiar enlarged rods. 
Group 3.— Leptothriche/e. — Coccal, rod, and thread forms; the latter 
show a distinction between base and apex ; threads straight or screw-like, 
spore formation not demonstrated. Genera : 

1 . Crenothrix, threads jointed and enclosed in a sheath, cells contain no 

sulphur granules ; inhabit water. 

2. Beggiatoa, threads thicker than Crenothrix, indistinctly articulated, 

cells contain sulphur granules ; inhabitants of water. 

3. Phraginidiolhrix, threads without sheaths, successive divisions very 

numerous ; cells contain no sulphur ; inhabit water. 

4. Leptothrix, threads with or without sheaths, divisions not very 

numerous or well marked ; cells devoid of sulphur. 
Group 4. — Cladothriche^. — Show coccus, rod, thread, and spirillar 
forms. The thread form is provided with a sheath, well-marked segments 
and pseudo-branches. Spore formation not yet demonstrated. Genus : 

Winter and Rabenhorst's classification, though very con- 
venient, is far from scientific, but it serves especially well 
for the classification of micro-organisms that are found in 
disease, as these, as met with in their host, usually correspond 
to one stage only of Zopf 's developmental cycle of any special 

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WHAT Are bacteria. 47 

Van Tieghem and De Bary, followed by Hueppe, laying 
great stress on the method of reproduction, have made two 
great divisions of bacteria — those which form endospores and 
those which form arthrospores ; but as Fliigge points out, 
this division is of little service for practical purposes, as 
spore formation is at present so imperfectly understood, that 
it is most difficult to follow the exact method of sporogenous 
reproduction in a Schizophyte. Winter and Fliigge attempt 
to get rid of their objection to Cohn's classification by speci- 
ally modifying it to contain only the pathogenic organisms. 
They take no account, as already stated, of any morphological 
developmental cycle or of any biological features, but they 
give a useful and practical classification. 

Quite recently it has been suggested that bacteria should 
be classified according to the number and arrangement of 
the flagella developed, but as such classification is necessarily 
based on a single characteristic, and that one of the least 
important, and. as it will be some time before a complete 
examination can be made in order to determine the number 
and arrangement of these flagella, such a classification may 
for the present be left out of consideration. The same 
holds good as regards Baumgarten's classification ; he 
divides bacteria into two groups — those which appear to 
assume a single form only (the Monomorphic) and those in 
which pleomorphism is a well-developed characteristic. In 
each he has three genera. In the first : the coccus, the 
bacillus and the spirillum ; and in the second : the spirulina, 
the leptothrix and the cladothrix. A similar remark applies 
to these, however, that applies to Zopf's classification. It 
may be of some service as a provisional classification, 
especially to those who are engaged in the study of the 
morphology and life history of bacteria. To the pathologist, 
however, these classifications are of comparatively little value 
except in so far as by their aid the morphologist is able to 
supply him with information as to the life history of bacteria 
outside the body. 


Author already quoted. Hueppe. 
BucHNER. — Centralbl. f. Bakt. u. Parasiteuk. Bd. iv., 1888. 
CoHN.— Beitr. z. Biol. d. Pflanzen. Bd. i.. Heft. 2, 1872 ; 
Bd. I., Heft. 3, 1875. 


*CoRNiL AND Babes. — Les Bacteries. Paris, 1890. 
Dallinger. — Monthly Journ. of Micro. Set. Sept., 1875. 
DE Bary. — Morphologie u. Physiologie der Pilze Handbuch 

der physiol. Botanik. Bd. 11., Leipzig, i866. 
Dujardin. — Histoire Naturelle des Zoophytes. Paris, 1841. 
Ehrenberg. — Die Infusionsthierchen als voUk. organismen. 

Leipzig, 1838. 
FLtJGGE. — Die Mikro-organismen. Leipzig, 1886. (Trans. 

Watson Cheyne, New Syd. Soc. London, 1890). 
GooDSiR. — Edin. Med. and Stir g. Journ. ., p. 430, 1842. 
*L6ffler. — Vorlesungen, iiber, die Geschichtliche En- 

twicke lung der Lehre von den Bacterien. Leipzig, 

Neisser. — Virchow's Archiv. Bd. 84, 1881. 
Van Tieghem.— Traite de Botanique. 1883. 
ZoPF. — Die Spaltpilze. Breslau. 

Those marked * contain full lists of papers and references. 

The History of Bacteriology. 

Earliest Workers — Kircher's Contagium Animaium — Bacteria in Fermenta- 
tion, Putrefaction and Disease— Early Classifications— Miiller — Abio- 
genesis — Needham — Biogenesis — Bonnet — Spallanzani — Schultz's 
Experiments — Schwann — Later Experiments — Pasteur — Bastian — 
Colour and Fermentation — Cohn and Naegeli's Classification — Henle's 
Researches and Postulates — Pasteur's Researches on Fermentation and 
Putrefaction — " Flower of Wine " — " Flower of Vinegar " — Bacteria 
as Scavengers — Pasteur on Silkworm Disease, and Wine Disease — 
Germs killed by Carbolic acid — Origin of Antiseptic Treatment. 

Since Athanasius Kircher mistook blood and pus corpuscles 
for small worms, and built up on his mistake a new theory 
of disease and putrefaction, and since Christian Lange, the 
professor of Pathological Anatomy in Leipzig, in the preface 
to Kircher's book (1671) expressed his opinion that the 
purpura of lying-in-women, measles, and other fevers were the 
result of putrefaction caused by worms or animalculae, a 
" Fathologia Animata " has, from time to time, been put 
forward to explain the causation of disease. Crude as was 
his theory, and imperfect as were the observations on which 
it was based, it is marvellous that Kircher, with the simple 
lenses that he had at his disposal, magnifying only some 
thirty-two diameters or one thousand times, was able to 
make out as much as he did. The observations that he 
made were, naturally enough, not generally credited ; and 
the theories he formulated were received with chilling in- 
credulity by most of his contemporaries. 

Remarkable as were Kircher's observations, still more 
wonderful were those of Anthony Van Leeuwenhoek, a 
native of Delft in Holland, who in his youth had learned 
the art of polishing lenses, and who was able, ultimately, to 
produce the first really good microscope that had yet been 
constructed. Not only did Leeuwenhoek make his micro- 
scope, but he used it to such good purpose that he was able 



to place before the Royal Society of London a series of 
most interesting and valuable letters giving the result of his 
researches on minute specks of living protoplasm. The 
results of these observations are fully detailed in his collected 

Towards the end of 1675 he discovered in water, in an 
infusion of pepper, in the intestinal canals of horses, flies, 
frogs, pigeons, fowls, and even in his own diarrhoea stools, 
small moving and living forms of such extreme minuteness 
that other observers with the best apparatus they had at 
command, even with the accurate and lucid description he 
gave, could not for long confirm his results. It was not, 
however, until 1683 that he actually described and depicted 
minute organisms in material taken from the teeth, that 
we can at present recognize from his descriptions and 
drawings as bacteria. Describing them, he says : " I saw 
with very great astonishment, especially in the material 
mentioned, that there were many extremely small animals 
which moved about in a most amusing fashion ; the largest 
of these" (represented by him in an admirable figure) 
" showed the liveliest and most active motion, moving 
through rain-water or saliva like a fish of prey darts through 
the water ; this form, though few in actual numbers, was 
met with everywhere. A second form moved round, often 
in a circle, or in a kind of curve ; these were present in 
greater numbers. The form of a third kind I could not 
distinguish clearly ; sometimes it appeared oblong, some- 
times quite round. They were very tiny, in addition to 
which they moved forward so rapidly that they tore through 
one another : they presented an appearance like a swarm of 
midges and flies buzzing in and out between one another. 
I had the impression that I saw several thousands in a 
single drop of water or saliva which was mixed with a 
small part of the above-named material not larger than a 
grain of sand, even when nine parts of water or saliva were 
added to one part of the material taken from the incisor or 
molar teeth. Further examination of the material showed 
that out of a large number which were very different in 
length, all were of the same thickness. Some were curved, 
some straight, lying irregularly and interlaced." Since, he 
says, "I had seen minute living animalculae of the same shape 
in water, I endeavoured most carefully to observe whether 


these also were living or not, but I was unable to recognize 
even the slightest movement as a sign of life." 

In the material taken from the teeth of an old man who never cleaned 
his teeth, Leeuwenhoek found an inconceivable number of living animalcnlfe 
which darted about more quickly than any he had ever seen before ; " the 
largest were present in very great numbers, and waved about by the 
locomotion of their bodies. Besides these, other animalculae were present 
in such large numbers that the whole water seemed to be alive." 

This admirable account really contains the first accurate 
description of the rod-shaped bacteria, motile and motionless, 
of longer threads or bacilli, of the spiral threads or spirilla, 
and of rounded micro-organisms or micrococci. It was con- 
siderably improved upon in a letter to the Royal Society, 
dated October i, 1692, in which he speaks of small rounded 
animalculae, the diameter of which is a thousand times less than 
that of a fine grain of sand ; of organisms having a somewhat 
greater diameter than the round ones, and being five or six 
times as long as they were broad, equally thick throughout 
their whole length, and which moved slowly backwards and 
forwards through a bending of their bodies. Along with 
these he describes what are evidently spirilla, with their 
characteristic movements, " a few organisms about the same 
length or slightly longer, which moved their bodies in 
comparatively marked curves, swam forwards or backwards, 
or twisted themselves in an extremely lively fashion." He 
also observed still longer and more sluggish organisms, 
sometimes straight and sometimes bent. 

Although Leeuwenhoek did not attempt to theorize as to 
the meaning of the presence of these organisms in the 
mouth, we find that, in 1713, after finding similar organisms 
in the greenish pellicle formed on the surface of the water 
in an aquarium, he came to the conclusion that the organ- 
isms seen on the teeth found their way into the mouth 
through the medium of the drinking-water that had been 
stored in barrels, and that some of these found there a nidus 
in which they might multiply. 

The world that Leeuwenhoek thus opened up so 
thoroughly was rapidly invaded by other observers and 
theorists. The thoughtful physicians of the time beUeved 
that at last they had found the fons et origo mah\ and 
Nicolas Andry, reviewing Kircher's "Contagium Ani- 
matum," replaced his worms by these newly-described 


animalculse or germs,, and pushing the theory to its 
legitimate and logical conclusion, he also evolved a germ 
theory of putrefaction and fermentation. He maintained 
that air, water, vinegar, fermenting wine, old beer, and sour 
milk, were all full of germs ; that the blood and pustules of 
smallpox also contained them, and that other diseases, very 
rife about this period, were the result of the activity of these 
organisms. Such headway did he make, and such conviction 
did his arguments carry with them, that the mercurial 
treatment much in vogue at that time was actually based on 
the supposition that these organisms, the causa causantes of 
disease, were killed by the action of mercury and mercurial 

With a kind of prophetic instinct, and certainly as the 
result of keen observation, Varro and Lancisi ascribed the 
dangerous character of marsh or swamp air to the action of 
invisible animalculse ; in fact the theory was so freely and 
forcibly propagated that even where no micro-organisms 
could be found their presence was inferred, with the inevi- 
table result, as Loffler points out, that these "inconceivable" 
worms became the legitimate butts for the shafts of ridicule ; 
and in 1726 there appeared in Paris a satirical work, in 
which these small organisms received the name of "fainter," 
" body-pincher," " ulcerator," " weeping fistula," " sensual- 
ist ; " the whole system was thus laughingly held up to 
satire, and the germ theory of disease completely dis- 
credited. Linnaeus, however, with his wonderful powers of 
observation and deduction, considered that it was possible 
that there might be rescued from this "chaos" small living 
beings which were as yet insufficiently separated and ex- 
amined, but in whichiie firmly believed might lie not only the 
actual contagium of certain eruptive diseases, and of acute 
fevers, but also the exciting causes of both fermentation and 

The man, however, who of all workers earliest recognized 
the importance of Linnaeus' observations was a Viennese 
doctor, Marcus Antonius Plenciz, who with great shrewd- 
ness recognized the prime importance of these organisms 
in connection with the etiology not only of contagious 
diseases, but also of putrefaction. He it was who, at this 
time, insisted upon the specific character of the infective 
agent in every case of disease : for scarlet fever there was a 


scarlet fever seed or germ — a seed which could never give 
rise to smallpox. He showed that it was possible for this 
organism to become disseminated through the air, and for it 
to multiply in the body ; and he explained the incubation 
stage of a febrile disease as dependent on the growth of a 
germ within the body during the period after its introduc- 
tion, when its presence had not yet been made manifest. He 
very rationally explained the differences in the character of 
the symptoms and the severity of the same disease by refer- 
ring them to differences in the constitutions and surround- 
ings of the patients. As regards putrefaction, having 
corroborated Linnaeus' observations and found countless 
animalculae in putrefying matter, he came to the conclusion 
that this process was the result of the development, 
multiplication, and carrying on of the functions of nutri- 
tion and excretion by these germs ; the products of 
fermentation being the volatile salts set free by the organ- 
isms, which, multiplying rapidly by forming seeds or eggs, 
rendered the fluid in which they developed thick, turbid, 
and foul. This theory, admirable as it was, and accurate as 
it has since been proved to be, could not then be based on 
any very extensive or detailed observation, and we find that 
some of the most prominent and brilliant men of the 
period did not feel justified in accepting the explanation that 
Plenciz had offered as to the causes of disease and fermenta- 
tion processes; and it was not until the years following 1831 
that any real advance could be made in our knowledge of 
the presence of a " Contagium vivum," or living contagium 
element in the production of disease and fermentation. 
Previous to this, however, there was being gradually 
accumulated a large mass of facts bearing on these wonder- 
fully interesting minute living organisms, and numerous 
isolated observations were constantly being made by various 
workers, none of whom, however, were sufficiently master 
of their subject to enake them to make any systematic 
attempt at classification of their accumulated facts, and the 
scientific results were consequently comparatively small, 
standing in no proportion to the amount of work expended 
and the number of observations made. 

The first attempt to reduce this chaos to something like 
order was made by Otto Friederich Miiller, of Copenhagen. 
He thoroughly appreciated the work he was taking in hand. 


With a well-defined plan he set himself to systematize and 
arrange the various organisms that had been described by 
previous observers — commencing with Leeuwenhoek and 
ending with Spallanzani. 

When the nature of the optical apparatus Mailer had at his disposal is 
taken into consideration, it must be acknowledged that he succeeded in a 
most marvellous manner in classifying, on the Linnsean system, the minute 
organisms with which he had to deal. Under the head of Infusoria 
he divided them into two classes — those that could be seen with the 
naked eye, and those that were invisible except with the assistance 
of a microscope. The latter class he again divided into Membranacea, 
or those forming thin surface membranes, and Crassuiscula, or those 
forming thick membranes ; these latter, including Monas, Proteus, Volvox, 
Enchelys, and Vibrio, representing, he maintained, the lowest forms of 
animal life. Of Monas he described no fewer than ten species, and of 
Vibrio he was able to distinguish, by utilizing the characters of form, 
motion, nidus or cultivation medium, and other biological features, thirty- 
one species. Relying, however, principally on the form of the organism, 
he described rounded and slightly oval forms, shorter and longer rods, 
rounded and truncated cork-screw-shaped and snake-like organisms, 
undulating but not spiral in their movements, and also long threads or 

Although he did not fully recognize the importance of his 
- observation he described in certain organisms little shining 
points, arranged in series at regular intervals, especially in 
the rod-shaped forms, points which we must now conclude 
were spores. It is certainly not remarkable that he should 
never have understood the full significance of these spores, 
as even ninety years later, with all the additional light 
that had then been thrown on the subject, these bodies ^ere 
still not properly understood. Later observers laid stress on 
the rapidity of movement of the vibriones or lineolae, which 
were gradually separated from the other forms of lower 
organisms. The vibriones then described, including lineola, 
rugula, bacillus, and spirillum, correspond more or less per- 
fectly with our bacteria of the present day. 

Many advances were made after Muller's work was com- 
pleted as regards the morphology of these organisms, but 
the question .as to whence these minute forms came still 
remained unanswered. Whether they were the result of 
spontaneous generation, or were the progeny of pre- 
existing forms, was the question which for over a century 
occupied the minds of those engaged in scientific research 
and speculation. Some observers, prominent amongst whom 


were Hartsoeker, Reaumur, and Joblot, considered, though 
they had no great amount of evidence to adduce in support 
of their theory, that bacteria were the progeny of minute 
organisms which were present in myriads in the air, from 
which they were deposited on fruits, plants, and other matter, 
whence they made their way into the various infusions 
prepared from them. In this country a prophet arose in the 
person of Dr. Needham, who was really the first to suggest 
an attempted solution of the question by a theory of abioge- 
nesis, or spontaneous generation. Needham at first thought 
that these vibriones, or " plant animals," as he called them, 
arose from plants by special vegetative power, and that from 
the plant-animals, by a process of evolutionary accretions, 
other organisms again arose. He tried to prove, by boiling 
a beef infusion and keeping it and allowing it to putrefy 
in a well-stoppered bottle (a most scientific method), that 
these zoophytes could not owe their origin to germs which 
outside insects or organisms had brought into the infusion, 
as he considered that the boiling should have destroyed the 
germs originally in the fluid, and as no new germs could, he 
thought, make their way into the closely-stoppered vessel, 
the resulting organisms must be the result of the action of 
a special vegetative force. This apparently logical and 
fascinating theory was accepted by many whose names had 
great weight in the scientific world. Needham's observations 
were repeated time after time with the same results, and his 
theory met with wide acceptance. 

To very critical minds it appeared, however, that these 
experiments of Needham's left loopholes for the inser- 
tion of other explanations than those which he gave, and 
Bonnet, of Geneva, suggested that the vessels used by 
Needham were not hermetically sealed, that an almost 
invisible opening would be quite sufficient to serve as a 
means of entrance to organisms so minute as those with 
which he was dealing, and that on the other hand there was 
a possibility that the germs were so far resistant to increase 
of temperature that they might live through a short period 
(a few minutes only) of treatment with boiling water. Abbot 
Spallanzani followed up, by his wonderful experiments, the 
theoretical criticism of Bonnet. After convincing hiniself 
that organisms did actually develop in unboiled infusions 
even when the outer air was rigorously excluded, he argued 


that the germs of micro-organisms, or eggs, as he termed 
them, might exist on the walls of the vessel, on the material 
of which the infusion was made, or suspended in the air 
within the vessel. To get rid of these germs from the vessels 
he heated the latter on the fire, then filling them rapidly 
with his infusions he allowed them to cool, and sealed them 
hermetically, but he still found that after a few days a 
number of organisms made their appearance. Could the 
organisms have got in along with the air during the process 
of cooling ? 

To set this question at rest he made a number of infusions in 
hermetically-sealed flasks, and boiled them for a whole hour, 
with the result that in flasks so treated no organisms made 
their appearance : if, however, the sealing was in any way 
interfered with, organisms soon made their appearance, and 
he concluded that living germs were necessary for the 
development of putrefactive organisms. This fact once 
established, the whole question was much simplified, and the 
principle on which it rested was soon utilized in Paris and else- 
where in the methods adopted for insuring the preservation 
of various food Stuffs — methods which, with few modifications, 
have been handed down to the present day. It was of course 
objected that Spallanzani had shut out air from his vessels, 
or, that he had so altered the constitution of the air which still 
remained, that it was not possible for these minute organisms 
to develop in it. This objection was met in 1836 by F. 
Schulze, who put the question to himself, " If the access of 
atmosphere, light, and heat, to substances in flasks included 
of itself all the conditions for the primary formation of 
animal or vegetable organisms." To prove that this was not 
the case, Spallanzani's conditions of absolute freedom from 
germs capable of development in the infusion must be 
obtained, and, secondly, air must be admitted to this infusion 
in considerable quantities ; but the air so admitted must be 
perfectly free from germs. 

Schulze proceeded as follows : he filled a flask half full of distilled water, 
to which he added various animal and vegetable substances. He gives the 

following description of the further methods of procedure : " I then closed 

it with a good cork, through which I passed two glass tubes bent at right 
angles, the whole being air-tight ; it was next placed in a sand bath and 
heated until the water boiled, and thus all parts had reached the temperature 
of 2 1 2" F. While the watery vapour was escaping by the glass tubes I 
fastened, at each end, an apparatus which chemists employ for collecting 


carbonic acid gas ; that on the left was filled with concentrated sulphuric 
acid, and the other with solution of potash. By means of the boiling heat 
every living organism and all germs in the flask, or in the tubes, were 
destroyed, and all access was cut off by the suphuric acid on the one side 
and by the potash on the other. I placed this easily-moved apparatus 
before my window, where it was exposed to the action of light, and also, 
as I performed my experiments during the summer, to that of heat. At 
the same time I placed near it an open vessel, with the same substances 
that had been introduced into the flask, having also subjected them to 
the boiling temperature. In order now to renew constantly the air within 
the flask I sucked with my mouth, several times a day, the open end of the 
apparatus filled with a solution of potash, by which process the air entered 
my mouth from the flask through the caustic Uquid, and the atmosphere > 
entered the flask from without through the sulphuric acid. The air was of 
course not at all altered in its composition by passing through the sulphuric 
acid in the flask, but if sufHcient time was allowed for the pass^e the 
portions of living matter, or matter capable of becoming animated, were 
taken up by the acid and destroyed. From May 28th till the beginning of 
August I continued uninterruptedly the renewal of the air in the flask 
without being able, without the aid of a microscope, to perceive any living 
animal or vegetable substance, although, during the whole of the time, I 
made my observations almost daily on the edge of the liquid, and when at 
last I separated the different parts of the apparatus I could not find in the 
whole liquid the slightest trace of infusoria confervse or of moulds ; but all 
the three presented themselves in great abundance a few days after I had 
left the flask standing open. The vessel which I placed near the apparatus 
contained on the following day vibriones and monads, to which were soon 
added larger polygastria, infusoria, and afterwards rotatoria." 

Schulze was thus able to prove that the sterility was not 
dependent upon any alteration in the air within the flask, or 
to the small quantity of air contained in it, and that it was not 
due to any alteration brought about in the liquid by the heat- 
ing process, as on the one hand a large quantity of air 
was passing through the flask, whilst on the other the fluid 
that had been boiled, but which was left exposed, rapidly 
underwent decomposition, a decomposition that was accom- 
panied by the development of micro-organisms in very 
large numbers. The objection that some particles of sul- 
phuric acid drawn in with the air might affect the growth 
of organisms was met by Schulze by further experiments ; 
and Schwann, who, instead of using sulphuric acid, used 
heat as a means of destroying any particles that might 
be present in the air that was drawn into the flask, 
corroborated Schulze's statements. Now came further 
objections from the supporters of abiogenesis, who stated, 
most definitely and categorically, that these workers were 
not dealing with germs at all, but simply with particles of 


albuminoid matter floating in the atmosphere, as a result of 
the vegetative power of which, organisms of various kinds, 
according to the conditions by which these particles find 
themselves surrounded, were caused to be developed. In 1 854 
Schroeder and Von Dusch made a great advance ; they proved 
that simple filtration through a layer of cotton wool was 
sufficient to deprive the air of its organisms, and so to render 
it unfit to produce decomposition in infusions from which 
germs had already been eliminated by heat ; and no longer 
than thirty years ago Hoffmann, Chevreul and Pasteur 
demonstrated that it was quite sufficient to draw out, and 
bend downwards, the neck of a bottle in which the germ- 
free infusion was contained, in order to ensure the 
continuance of a non-putrefactive condition, and the 
perfect freedom of the fluid contained within the flask 
from germs : they argued that germs obey the law of 
gravitation, like all other solid particles, when not blown 
about by currents, and must settle down upon an upper 
surface, so that when the tube was bent downwards the 
organisms could not fall into the mouth. Tyndall gave 
demonstrative proof of this in his exquisite experiment of 
removing all particles from a glass chamber, first proving 
their entire absence by passing through the chamber a ray 
of light which could only be seen so long as particles 
remained suspended in the atmosphere. As soon as the ray 
of light disappeared from view he placed vegetable infusions 
which had been sterilized by heat within the chamber, with 
the result that they remained free from any trace of organic 
life for several weeks together. Schwann had already pointed 
out that blood, taken with certain precautions and introduced 
into a flask in which the air was kept germ free, might be 
preserved for a considerable length of time, without the 
development of micro-organisms, and later (1857) Van der 
Broek showed that the juice of grapes, and urine as well as 
blood, might be kept free from decomposition and the 
presence of organisms if the apparatus into which they were 
received was first thoroughly sterihzed by means of heat, 
and if the substances were not allowed to come in contact 
with the outside air. 

Numerous observers, especially Burdon Sanderson, Roberts, Lister, 
Chiene and Ewart, and Watson Cheyne in this country, and Rindfleisch, 
Klebs, Cazeneuve and Livon, Leube, Hauser and Marchand abroad, con- 


firmed these observations and made many new ones in connection with the 
behaviour of milk, egg albumen, vegetable substances kept under certain 
conditions, and pieces of organs from freshly-killed animals to which 
organisms from the external air were not allowed to gain access. 

It seemed as though the adherents of abiogenesis had not 
a leg left on which to stand ; but owing to the fact that 
certain organisms, especially when contained in such media 
as milk and cheese, withstand the action of very considerable 
heat, they still contested every^ inch of ground, though their 
foothold was being gradually but surely cut away from 
beneath them. Milk, which was one of the strongholds of 
the abiogenists, was first sterilized, with absolute certainty, 
by Schroeder, who attained his end by subjecting the fluid 
for a considerable time to a temperature of ioo° C, and then 
by Pasteur, who heated it to iio° C, for a short time only. 
Cheese still remained to them, and as late as 1872 Bastian 
placed a small piece of this substance in an infusion of white 
turnip which had been filtered and carefully sterilized. This 
was then boiled in a flask for ten minutes, and whilst still 
boiling was hermetically sealed ; at the end of three days 
countless living organisms were produced, as Bastian held, 
from non-living albuminoid material ; but Cohn, repeating 
the experiment, explained that the resting spores or resistant 
germs were enclosed in the substance of the cheese, and that 
they were thus able to resist the high temperature to which 
the outer surface of the cheese, but not its centre, was 
exposed. Duclaux's later experiments with the Tyrothrix 
of cheese, which resists the action of a very high temperature 
for a considerable time, also helps to explain Bastian's results. 
The matter has now been set at rest, and it is an accepted 
belief that bacteria or microbes, as these lowly organized 
forms are now called, may be destroyed by heat and by 
certain chemical reagents, and that when once destroyed in 
any medium, no other organisms can rise from their ashes, 
the medium remaining perfectly free from putrefactive 
changes until fresh germs are introduced from without. 
Harvey's famous dictum, omne vivum ex ovo, has thus come 
to have a far wider meaning than that which he originally 
attached to it. The triumphs of surgery, of preventive 
inoculation, of hygiene in relation to specific infective 
diseases, of preservation of food, have had their origin in 
the knowledge gained during the battle which waged round 


the question of Spontaneous Generation or generatio 
cequwoca ; and to the disciples of that school every acknow- 
ledgment must be made and due credit assigned for the 
attitude of scepticism and free ingenious and honest criticism 
which they passed concerning half-formed and inadequately- 
supported theories and imperfectly-conducted experiments, 
for to their efforts is certainly due the fact that the 
experiments of their opponents became more and more 
perfect, and if to-day we have perfect methods of sterilization 
and of making pure cultivations, it is because nothing was 
taken for granted, and because able men on both sides of the 
controversy were ranged against one another to fight the 
matter to the death. 

Whilst this battle over the origin and development of these micro- 
organisms was going on, intermittent attempts were made to improve on 
the classification that had been drawn up by Miiller, but it was only as 
the optician supplied observers with better microscopic apparatus that 
any further advances could be made. Ehrenberg, however, took up the 
question and divided the Monad family into rounded and rod-shaped forms ; 
these latter — Vibriones — ^he described as undergoing transverse division, 
as they increased in length. These he sub-divided into Bacteria, or short, 
straight, inflexible organisms; Vibriones, longer and more flexible; Spirilla, 
or inflexible spiral forms ; and the Spirochsetse, or the flexible spiral organisms. 
If to this classification we add the Cocci or rounded forms, we have prac- 
tically a rude model of that adopted by authors at the present time. In his 
vibriones he had six varieties, of which lineola, rugula, and bacillus, had 
already been described by Miiller, but subtilis, tremulans, and prolifer, 
were new. In consequence, however, of the want of marks of characteri- 
zation, Ehrenberg himself was very doubtful as to the propriety of his 
system of division or nomenclature. His spirillum comprises three forms, 
the old vibrio undula of Miiller, the ordinary spirillum, and a new kind of 
spirillum (Tenue). These three differed from one another only as regards 
length and thickness, the Vibrio undula having only from one to one and a 
half spiral windings, the others being merely longer or thicker. His genus, 
Spirochseta, contained a single form only, the Spirochseta plicatilis, an 
organism of great length, but of very small diameter. 

In consequence of the active snake-like and rotary move- 
ment of these organisms, Ehrenberg was fully convinced 
that he had to deal with animals, and this opinion was uni- 
versally accepted down to the time when Davaine gave his 
opinion that bacteria must be classified as really belonging 
to the vegetable kingdom. 

In 1840 colour characteristics were brought into play as a 
means of distinguishing certain organisms, and we find that 
Fuchs and Ehrenberg describe Vibrio cyanogenus and Bacil- 



lus xanthogenus, as giving rise during their growth in milk to 
characteristic blue and orange colorations. He described the 
exciting cause as small chain-like organisms, and considered 
that they were the cause of both the colour formation and 
the acid fermentive changes. As early as 1819 we iind the 
first description of bleeding bread, the organismal cause of 
which, Ehrenberg, in later years, was able to cultivate on 

Photo-micrograph of Bacillus Prodigiosns. x looo.— Organism forms heautiful 
red colour of bleeding bread, bloody sweat, &c. 

various food media, boiled potatoes, Swiss cheese, and white 
bread. He describes the organisms of which the coloured 
mass was made up as being exceedingly minute, and as 
having a characteristic movement quite distinct from the 
so-called Brownian or molecular movement. 

Some idea of the size of these orgatiisms may be obtained from Ehren- 
berg's calculation that a cubic inch would contain from 46,656,000,000,000 
to 884,736,000,000,000 plants ; this organism he called Monas prodigiosa. 


but it is difficult to associate the characters that he gave with any of the red 
pigment forming organisms now known. 

Felix Dujardin added very little to the actual classifications given by 
Miiller and Ehrenberg, but he brought out several most important facts. 
In certain large vibrios he was able to make out distinct bifurcation, the 
two new limbs becoming segmented transversely ; he was also able to 
recognize an outer membrane or resistant covering on these organisms, and 
within this a gelatinous or protoplasmic material. This led him to doubt 
whether, after all, he was dealing with an animal form, and several of the 
forms described he relegated to the plant kingdom as Algae — "Vibrio subtilis 
of the Oscillaria. 

As Loffler points out, although Dujardin was not able 
to make any further advances on the classifications of Miiller 
and Ehrenberg, his observations on the chemistry of bacteria 
were most important. He describes as specially suitable for 
the development of bacteria, fluids containing such substances 
as phosphate of soda, hyponitrous acid and oxalate of am- 
monia and carbonate of soda, and he points out that the 
nitrogen from the oxalate of ammonia is gradually used up 
in the presence of organic substances. 

With the exception of Dujardin, as we have seen, all observers up to 
1852 had looked upon bacteria as belonging to the animal kingdom, but 
in this year Perty announced that of these minute organisms, some 
belong to the animal and some to the vegetable kingdom, whilst a 
certain number appeared to him to stand on the borderland between the 
two. These vibriones, he says, are colourless or sometimes blue, yellow, 
or reddish, never green, organisms, with scarcely a trace of any differentia- 
tion of their substance ; they have a spontaneous or automatic movement ; 
they increase in number by transverse division, partial or complete ; when 
this is incomplete, chains or threads are formed. He divides them into 
Spirilla or spiral threads, Bacteria or winding or straight threads, and he 
thinks that the bacteria have not only an active animal life, but that they 
also pass through a stage during which they must be looked upon as vege- 
table in character : a double existence which he assigned to other forms. 

In 1854 Cohn insisted even more strongly on the plant 
nature of these micro-organisms. He, too, described zooglcea 
masses, and he summed up his researches as follows : — (i) 
All vibriones seem to belong to the vegetable kingdom, and 
they exhibit a very close relationship to the larger algae. (2) 
In respect of their want of chlorophyll, and ol their occurrence 
in putrefying infusions, the vibriones belong to the group of 
water fungi (mycophyceae). (3) Bacterium termo is the 
active, moving form of a closely-related species of palmella 
and tetraspora zooglcea. (4) Spirochaete plicatilis belongs 
to the species spirulina, which we can at once indicate as a 


particular species. (5) The long non-wavy vibrios (vibrio, 
bacillus, &c.), are related to the more delicate beggiatoa 
(oscillaria). (6) The shorter vibrios and spirilla, which 
correspond in both form and motion to the oscillarias and 
spirulinae, he was unable to localize in his system of classifi- 

In 1857 Naegeli collected all the forms then known, which 
had certain characteristic physiological features in common, 
into a group which he termed Schizomycetes or fission fungi, 
a group which is now fully recognized by botanical mor- 
phologists and physiologists. He included all those lower 
forms of plant-life in which chlorophyll was absent, and 
which contained carbon, oxygen, hydrogen, and nitrogen in 
definite proportions, which elements they were not able to 
assimilate and utilize in building up their own substance 
from inorganic materials. They, like the other fungi and 
animals, can utilize as food only such material as is presented 
to them in the form of living or dead organic matter held 
in solution, or combined with a considerable quantity of 
water. The processes going on within their protoplasm are 
so intimately connected with oxidization that they usually set 
free no uncombined oxygen, and this characteristic feature 
along with their want of chlorophyll colouring matter Naegeli 
looked upon as the special feature by which they might be dis- 
tinguished from ordinary fungi. Amongst his fission fungi 
he placed the forms bacterium, vibrio, spirillum, sarcina, the 
mother of vinegar, the yeast fungus, the organism associated 
with the silkworm disease — a small colourless oval organism, 
somewhat resembling a yeast, which he named Nosema 
bombycis — most of which were characterized by the features 
which are now recognized as belonging to the fission fungus 
group. The relation of these to disease and fermentation 
Naegeli declined to discuss. 

Although Leeuwenhoek had described certain micro- 
organisms in the tartar of the teeth and in various secre- 
tions and excretions so accurately and minutely, it was not 
until 1837 that any definite attempt was made to associate 
them with the products of a disease ; in that year, how- 
ever, Donne described an Infusorian, which he likened 
the vibrio lineola of MuUer, as occurring in pus in 
s)rphilitic diseases. This he thought at first was simply 
a vibrio associated with the putrefaction of the pus, 


but as he was afterwards unable to find this same infu- 
sorian in the pus taken from other abscesses, and in putre- 
fying material that had been exposed to air, he was led to 
inquire whether it was really characteristic of syphilitic 
contagion, and whether it played any part in the trans- 
mission of syphilitic infection. Although he afterwards 
retired from his first position he carried out a series of 
most careful and ingenious experiments, through which he 
was led to believe that very characteristic vibriones were 
associated with the causation and transmission of syphihs, 
and he thus opened up a series of most interesting questions, 
the answers to which, though differing somewhat from those 
given by Donne himself, were nevertheless destined ulti- 
mately to be very much on the same lines as those that he 
had laid down. 

It is interesting to notice that the monad forms which at the present 
day are again coming prominently forward in connection with the produc- 
tion of certain diseased conditions, were early recognized and described by 
Donn^, and that Rudolph Wagner also described a species of monad as 
occurring in cancer of the lip. 

As was to be expected, however, the connection of micro- 
organisms with fermentation was proved long before a 
similar association was made out between micro-organisms 
and disease, and in the same year that Donne published his 
results, Cagniard-Latour and Schwann, who had been work- 
ing independently, announced that the yeast cells (torula 
cerevisiae), originally described by Leeuwenhoek, and which 
were found to grow in grape juice and malt wort were to be 
associated with fermentation — that they were indeed the 
cause of this process. 

For long, although the intimate connection between the 
process of fermentation and specific infective diseases was 
widely recognized, the efforts of most scientific observers 
were directed towards the elucidation of the causes of fer- 
mentation and putrefaction. It was, in fact, suggested that 
cholera might be due to the action of some ferment-causing 
organism, which might become lodged in and multiply in 
the intestine. 

In 1837, moreover, Bassi described a kind of yeast fungus, 
which he thought must be the cause of a miasmatic con- 
tagious disease in silkworms. He found extremely minute 
spores, on and within the bodies of the silkworms affected, 


and although parasites had long been accepted as the cause 
of certain diseases in plants, this was really the first fully- 
described and well-authenticated instance of a fungus para- 
site giving rise to disease in any members of the animal 

As the direct outcome of these researches, Henle, in 1840, 
was led to believe that the cause of miasmatic, infective and 
contagious diseases must be looked for in living fungi or 
other minute living organisms, and although he was unable, 
experimentally, to satisfy himself of the accuracy of his 
position, he was fully convinced that he was working in the 
right direction. It would indeed have been difficult, at that 
period, to satisfy every condition that he required to be 
fulfilled ; the methods now in use were then unknown 
and have only been perfected by workers as it has been 
found necessary, from time to time, to comply in the most 
minute detail with Henle's conditions, and as, one point 
being carried, it has been found necessary to advance on 
others. The first of these was that a specific organism should 
always be associated with the disease under consideration. 
As such presence, however, might be accidental, these 
organisms were to be found not only in pus but actually in 
the living body. As they might be, even then, merely 
parasitic, and not associated directly with the causation of 
the disease, it would be necessary to isolate the germs, the 
contagium organisms and the contagium fluids, and to 
experiment with these separately with special reference to 
their power of producing similar disease in other animals. 
We now know that it has only been by strict compliance 
with all these conditions, again postulated by Koch, that the 
most brilliant scientific observers and experimentalists in 
England, France, and Germany have been able to determine 
the causal connection between micro-organisms and disease. 
After Henle's work appeared a regular fungus fever set in ; 
many skin diseases were proved to be the result of the 
action of fungi, and numerous internal diseases were, on 
very imperfect evidence, said to be due to parasitic agency ; 
and a large number of diseases which we now consider to be 
caused by the action of certain specific organisms in the 
system, were deemed, on very imperfect data however, to 
be due to these fungi. Cholera and typhoid fever became 
subjects of great interest, the stools from patients suffering 



from these diseases were carefully examined for organisms, 
and bacteria and monads were carefully described, but in 
no case could any definite proof be obtained that any of 
these stood in any causal relation to either of these diseases. 

It was at this stage that Pasteur took up the work initiated 
by Cagniard-Latour and Schwann, who had first noted the 
connection between the growth of the yeast organism and 
fermentation. He applied to other processes of fermentation, 
such as those of lactic acid, butyric acid, and acetic acid, the 
same process of experiment and reasoning which they had fol- 
lowed, and he was able eventually to prove that the organic 
ferment in each case had specific characteristics, not only as 
regards its physiological action in setting up a certain definite 
form of fermentation, but also as regards the special mor- 
phology and mode of growth of the organisms that were 
found during and at the end of the process. 

As these experiments of Pasteur's are now classical it 
may be well briefly to indicate the lines on which he worked. 
He first carefully observed the nature of the organic material 
in which certain fermentations took place, studying, both 
synthetically and analytically, the best medium for his 
purpose ; he then, by careful microscopical study, determined 
what organisms developed most rapidly during the special 
fermentation process. After making an artificial solution of 
the substance to be fermented, he added a small quantity of 
albuminoid material, and a trace of the ash of the special 
yeast that he wished to grow, in order that there might be 
sufficient of the necessary salts for the nutrition of the 
organism. This fluid was carefully sterilized by being boiled 
in flasks, to which only filtered air afterwards had access. 
To the germ-free solution he added a small quantity df his 
special yeast, and if he then obtained a characteristic 
fermentation with the production of the natural special 
fermentation products, accompanied by rapid growth and 
multiplication of the organism that he had introduced, he 
came to the conclusion that this organism was the cause of 
the special fermentation. 

In i8S7 Pasteur described a new yeast (the cells of which 
were much smaller than the ordinary beer yeast), which gave 
rise to the formation of lactic acid from sugar, and he pointed 
out that the nitrogenous material which was necessary for 
the production of lactic acid was really needed for the 


nutrition of the growing yeast, but that otherwise it did 
not exert any influence in transforming the sugar into lactic 
acid, as had hitherto been maintained by Liebig. 

Some idea of the delicacy of Pasteur's experiments may be gathered 
from his observations on the conversion of racemic or paratartaric acid by 
a, living ferment into right-tartaric acid (which in turn was capable of 
undergoing further fermentation) and into left-tartaric acid, which remained 
unaltered. He had already noted that the material in which fermentative 
changes took place, determined, in a very marked degree, the nature of the 
fermentation process. For instance, on adding dust, which of course con- 
tained a considerable number of different organisms, to sterilized urine, an 
ammoniacal or putrefactive fermentation took place ; whilst on adding the 
same dust to sterilized milk an acid fermentation, as evidenced by the 
curdling of the milk, ensued, whilst in each case there seemed to be a 
special development of one particular organism. He had of course to 
contend with the difKculties involved in obtaining isolated organisms or 
pure cultivations, and for this reason he was for some time heavily handi- 

All the forms of ferment-producing organisms which 
Pasteur had studied up to this point he spoke of as 
vegetable or yeast forms, and it was long before he was 
able to induce butyric acid fermentation. He at length 
found, however, a form which he distinguished as an 
infusiorian, in contradistinction to the vegetable or yeast 
form. This he describes as occurring in the form of small, 
straight, cylindrical rods, somewhat rounded at the ends, 
occurring either singly or in jointed chains of three, four, 
or more, about 2/i broad and from two to ten times as 
long as broad. The organism has a slight gliding motion, 
and its reproduction takes place apparently by vegetative 
growth and transverse division. The physiological or bio- 
logical peculiarity of this organism is that it can exist 
apparently without a trace of organic nitrogen ; whilst, like 
the vegetable ferments with which Pasteur had been working, 
it can also live without oxygen, and although in form it is 
like a vibrio, it differs from the vibrios in this respect and 
also in that it is able to bring about fermentation. 

In 1863 he found a second anaerobic "vibrio," which he 
succeeded in cultivating. He prepared a solution contain- 
ing tartarate of lime, ammonia, potassium, and yeast ash, 
rendered it sterile or germ-free by boiling, and covered it 
with a thick layer of oil. To the fluid thus prepared he 
added a minute quantity of the organic deposit resulting 
from spontaneous fermentation of tartarate of lime ; the 


was followed by a typical fermentation in the fluid, from 
which air was excluded by the film of oil spread over the 
surface. On microscopical examination of both the artificial 
and the spontaneous fermentations, he found " vibriones " 
ifi thick and 50^ long. It was objected that in the 
spontaneous fermentation a certain quantity of air must 
necessarily remain in the fluid in which the organism was 
growing, so that the presence of oxygen could not be 
inimical to the growth of this " anasrobic " organism (a 
name that Pasteur gave to those organisms that are not 
dependent upon the oxygen of the air for their growth and 
development). He met this objection with proof that, 
grown along with other organisms, such as bacterium 
termo, which were dependent upon free oxygen for their 
existence, the latter developed and grew for a short time in 
the fluid and so used up what oxygen there was present 
in solution, at which point they were unable to develop 
further, so that other resulting changes must be due to the 
growth of the special anaerobic organism. Passing from 
the butyric acid fermentation, and taking it as an analogy, 
Pasteur continued his researches on putrefactive processes 
in which nitrogenous substances and acrid arid offensive 
smelling materials are formed, and he eventually came to 
the conclusion, which had already been expressed by Mit- 
scherlich in 1843, that as yeasts gave rise to fermentation so_ 
" vibriones " must be the cause of putrefaction ; and, going 
further, he assumed, what has since been proved to be 
erroneous, that the whole of the vibriones of putrefaction 
were anaerobic, that is, they could give rise to their specific 
products only when they were removed from the influence 
of the action of the oxygen of the air. 

In connection with the subject of anserobiosis, Pasteur pointed out that 
the mycoderms known as " flower of wine," "flower of vinegar," &c., 
were able to produce different forms of fermentation according to the 
presence or absence of oxygen. Mycoderma aceti, for instance, bringing ' 
about the splitting up of sugar into alcohol, i.e., setting up an alcoholic 
fermentation when there is too little oxygen present, but in presence of 
abundance of oxygen giving rise to the formation of acetic acid, then setting 
up what is kno\vn as the acetic fermentation. 

These researches eventually led Pasteur to the conclusion 
well stated by Duclaux, that " whenever and wherever there 
is decomposition of organic matter, whether it be the case 


of a herb or an oak, of a worm or a whale, the work is 
exclusively done by infinitely small organisms. They are 
the important, almost the only, agents of universal hygiene ; 
they clear away more quickly than the dogs of Constantinople 
or the wild beasts of the desert, the remains of all that has 
had life ; they protect the living against the dead ; they do 
more : if there are still living beings, if, since the hundreds 
of centuries the world has been inhabited, life continues, it 
is to them we owe it." Without them the surface of the 
earth would be covered with dead organic matter, the 
remains of plant and animal bodies, which, retaining the 
elements necessary -for the building up of new plant-life 
and animal bodies, would soon cut off the food supply of 
new plants and animals ; life would be impossible because 
the work of death would be incomplete, or, as Pasteur puts 
it, "because the return to the atmosphere and to the 
mineral kingdom of all that which has ceased to live would 
be totally suspended." From his experiments on fermenta- 
tion and putrefaction Pasteur, by a very natural transition, 
turned his attention to the diseases of wine, and then to 
those of the silkworm — diseases that specially affected two 
important French industries. After most careful research 
he found that the acetic fermentation, viscosity, bitterness 
and turning flat of wines, were all due to the action of 
certain organized ferments, most of which he was able to 
isolate and study. 

The acid fermentation, he found, was produced by the mycoderma aceti, 
which consists of short rod-like forms, about double as long as broad, 
slightly constricted in the middle ; these individual elements, being joined 
together in long chains, which, as they grow on the surface of the wine, 
interlace with one another and form a regular film or skin. The bitterness 
of wine he ascribed to the presence and action of branched tortuous 
filaments of about l.^/i to 4fi in diameter, these chains having a 
peculiar knotted appearance. The turning flat of wine was due to the 
presence of delicate unbranched filaments about Iji in diameter, which 
under certain conditions are broken up into short segments which some- 
what resemble the bacilli met with in a lactic acid fermentation. The 
cause of the viscosity of wine was an organism made up of cocci about 
l.2fi in diameter, often arranged in chains of considerable length. He 
found, indeed, that the relations of cause and effect were invariable ; wher- 
ever certain forms were present in addition to the yeasts, or were intro- 
duced after the yeasts, the result was a special fermentation superadded to 
the wine fermentation. 

The genius who had shed such a flood of light on the 


causation and prevention of wine disease now turned his 
attention to the ravages of the " spot " disease or " pebrine " 
amongst silkworms, a disease that at one time threatened 
to destroy the flourishing silk industries of France. The 
organisms found in this disease had already been described 
by Naegeli as Nosema Bombycts, and by Latour as Panhis- 
tophyton, small, gUstening, oval corpuscles which appeared to 
be endowed with life and to lead a parasitic existence in the 
tissue of the silkworm caterpillars. Pasteur was able to 
demonstrate their presence not only in the butterflies which 
develop from these worms, but also in the eggs they laid, 
and he found that where any one of the three forms was 
affected, the corpuscles were passed on to the next stage. 
He was able to show that they increased in the body, that 
they were the cause of the disease, and that by careful ex- 
amination and destruction of the affected eggs and the 
preservation of the healthy ones, the disease could gradually 
be eliminated. He found that another disease, the lethargy 
of silkworms, was also probably caused by the presence of 
micrococci, arranged in the form of chains, in the intestinal 
canal of the worms. Pasteur had thus succeeded in showing 
the relationship between certain micro-organisms and certain 
wine diseases, but he had also been able to demonstrate a 
causal relation between certain lowly-organized, parasitic 
organisms and a special disease in animals or insects. He 
had, in fact, demonstrated that certain specific organisms, 
endowed with definite morphological and physiological 
characters, gave rise by their presence to specific and 
characteristic diseases ; he had by observation and experi- 
ment extricated the theory of a living contagium from a 
condition of chaos, and he had assigned to definite organ- 
isms, each a special role in the production of certain forms 
of fermentation, of putrefaction, and of disease ; and although 
much was still left, and still remains to be done, in the 
identification and classification of those organisms, he had 
separated a few distinct forms, and instead of assigning to 
these a general and common action in the production of the 
above processes, he had allotted to each one its own part. 
This he was able to do with such clearness and to place his 
experiments so lucidly before the scientific world, that there 
could be no doubt as to his meaning ; the consequence 
being that he soon secured a large following of enthusiastic 


workers from amongst his contemporaries. On the other 
hand, however, he brought forward those who were by their 
researches led in opposite directions, or who, with less perfect 
methods, could not make their facts fit in with his theory, 
or who could not repeat or confirm his experiments. 

The most important point that he wished to demonstrate 
was that which related to the specific character of the various 
ferments in fruit juices. He was attacked most vigorously 
on this subject by Lemaire, Bechamp, Hoffmann, and others, 
each of whom pointed out that in any fermentation experi- 
ments that he had made he had never seen a single organism 
only. (He had, in fact, never been working with pure cultiva- 
tions). This was undoubtedly a vary forcible objection, and one 
which had to be met, but one which was easily enough over- 
come as methods of separation and isolation became perfected. 
Bechamp, who had found what he termed granules in the 
cells of living plants and animals, and even in fossil remains, 
held that these microzymas, as he called them, remained 
alive ; that they set up various forms of fermentation ; that 
under different conditions of food, separation from the cell, 
and external influences generally, they ran together, became 
altered in shape, and underwent various changes, so giving 
rise to the various forms which Pasteur had described ; all 
these processes going on concurrently or subsequently to the 
various changes that occurred in fermentative and pathogenic 
processes. He would, however, have nothing to do with any 
specific organism ; he considered that all organisms were 
merely the result of a new grouping and alteration of these 
microzymas separated from the cells, and that they were 
specifically affected by the various altered conditions in which 
they found themselves when removed from the cell in which 
they naturally occur. Both Pasteur's positions were thus 
attacked. His first contention was that germs were the 
cause of fermentation in disease, and secondly, that each 
fermentation was due to the specific action of a definite 
organism. In his first contention his position was materi- 
ally strengthened by the observations of Lemaire who, after 
proving that the presence of carbolic acid was inimical to 
the life of the higher animals and plants, carried his re- 
searches a step further, and proved that the lower organ- 
isms were similarly affected by the same material, and he 
found that the addition of a small quantity of carbolic acid 


to fluids, in which putrefaction and fermentation would 
ordinarily take place, prevented the incidence of these 
processes. He found at the same time that the fermen- 
tations set up by chemical ferments, such as diastase and 
synaptase, remained entirely unaffected by the action of 
carbolic acid, and the result of his earlier experiments 
led him to believe that the process of fermentation was 
due to the action of living organized creatures which, hke 
the higher plants and animals, could be killed by the 
carbolic acid. When they were allowed to develop freely 
they brought about fermentation ; when their growth was 
stopped, or they were killed, fermentation could not go on. 
The same reasoning, he thought, might be applied to 
infection and miasma, and he concluded that disease pro- 
cesses were the result of fermentations or decompositions 
going on within the tissues, and brought about by the 
above or similar organisms. Pus formation was the result 
of the action of germs falling from the surrounding air 
into a wound. By the application of his germicidal re- 
agents to wounds, vaccine vesicles, and suppurating 
surfaces, he attempted to destroy these organisms out- 
side the body whilst they were actually attacking the weak 

This was really the first step in the direction of an anti- 
septic treatment of wounds. Whilst treating by his method 
Avounds in the human subject and in the dog he saw " that 
pus remained entirely absent, or was reduced to a minimum, 
putrid alterations were absent," and the wound healed 
rapidly. All these results were due, he maintained, to the 
destruction of the microzoa or infusoria by his carbolic acid 
lotions. The paramount importance of this theory was only 
afterwards fully appreciated and worked out by Lister, who 
saw that, owing to the difficulty of killing germs after they 
had once made their way into the tissues, it was absolutely 
necessary that such organisms should be prevented from 
gaining access to the wounds at all, and it is upon the 
attainment of this end that his well-known antiseptic treat- 
ment depends for its success. 

Accepting the truth of the statement that germs were the 
cause of fermentation. Lister also came to the conclusion, 
independently, that germs entering the wounds from outside 
might be the cause of suppuration, and since germs were 


floating in the air, were suspended in water, and were 
attached to the instruments and bandages that were used 
in the treatment of wounds, he determined that it was 
necessary, by using some germicidal reagent, to kill all such 
suspended and adherent organisms before the various 
materials mentioned were allowed to come in contact with 
the wounded tissues. With a combination of experimental 
resource, patience, and brilliancy almost unparalleled in the 
history of surgical science, he, step by step, built up a theory 
and practice of antiseptic surgery, a theory and practice 
which rapidly revolutionized the treatment of wounds and 
the routine of ward management. He thus introduced a 
system which has affected the practice not only of those who 
believe in its accuracy, but of those who cannot bring them- 
selves to accept all its details, but who have nevertheless 
accepted its principles, sometimes even unwittingly. 


Authors already mentioned. Duclaux, Davaine, Dujardin, 

Ehrenberg,* Hueppe,* LoefHer, Naegeli and Roberts. 

Andry, Nicolas. — De la generation des vers dans le corps 
de I'homme. Amsterdam, 1701. 

Bonnet. — Consideration sur les corps organises, 2 t. 
Amsterdam, 1762. 

Bastian. — Beginnings of Life, London, 1872 ; Proc. of the 
Roy. Soc, No. 14S, 1873; Nature^ 1873 ; Centralbl 
f. d. Med. Wissensch, p. 521, 1876 ; Linnean Soc. Journ., 
Vol. 14, 1877 ; On Fermentation and the Appearance 
of Bacilli, Micrococci and Torulae in boiled fluids. Lond 

Bassi. — Del mal del segno, calcinaccio o mocardino. Milan 

Chiene and Ewart. — Journ. Anat. and Phys., p. 448 

April, 1878. 
*Cheyne, Watson. — Antiseptic Surgery. London, 1882. 
Cazeneltve and Livon. — Revue Mensuelle, p. 733, 1877. 
CoHN.— Beitr. zur Biol, der Pflanzen. Bd. l, heft 3, 1875. 
Cagnlard-Latour. — Comptes rendus de I'Acad. des. Sc, 

t. 4, p. 905, 1873- ,. . ^ . ^ , 

Hartsoeker. — Essai de dioptnque. Fans, p. 226, 1094. 
Hoffmann. — Botanische Zeit., 5 and 6, i860. 
Henle. — Handbuch der rationnellen Pathologic. 1853. 


Klebs.— Arch. f. Exp. Path. u. Pharm. Bd. ii., p. 206, 

Leeuwenhoek. — Omnia opera sive arcana nature ope micro- 

scopiorum Exactissimorum detecta, 1722. 
Lister. — Trans, of Roy. Soc, Edin., 1875 ; Micro. Joiirn., 

Leube.— Zeitsch fur. Klin. Med. Bd. in., 1881. 
MuLLER. — Animalcula infusoria fluviatilia et marina, 

Hauniae (1786). 
Needham. — Observations upon the generation, composition, 

and decomposition of animals and vegetable substances, 

London, 1749 ; Notes sur les Nouvelles decouvertes de 

Spallanzani, Paris, 1768. 
Pasteur. — Etudes sur la biere, 1876 ; Comptes rendus, t. l., 

p. 306, i860 ; Comptes rendus, t. lvi., p. 734, 1863 ; 

Annal de Chimie et de Phys., 1 862-1 864; Etudes sur 

la Maladie des vers a soie, &c., Paris, 1870. 
Louis Pasteur. — His Life and Labours. By his son-in- 
law. Paris, 1883. Trans. Lady Claud Hamilton. 

London, 1885. 
RiNDFLEiscH. — Virch. Arch. Bd. liv., p. 397. 1872. 
Spallanzani. — Phys. u. Math. Abhand. Leipzig, 1769. 
ScHULZE. — Gilberts Ann. de Phys. u. Chemie. Bd. xxxix., 

p. 836, 1836. 
Schwann. — Gilberts Ann. de Phys. u. Chemie. Bd. li. 

Schroederand VON DusCH. — Ann. der Chemie und Pharm., 

Bd. Lxxxix., 1854 ; Journ. f. pract. Chemie, t. lxi., 1854. 
Sanderson, Burdon. — Quarterly Journ. Micr. Science., vol. 

XI., p. 323, 1871. 
Tyndall.— Phil. Trans., 1876-77 ; Haze and Dust, Nature, 

Jan. 27, 1870 ; Essays on the floating matter of the air 

in relation to Putrefaction and Infection, London. 

Van der Brock.— Annalen. der Chemie und Pharm., Bd. 

cxv., i860. 
Wagner. — Arch, der Heilkunde. Bd. xv., p. i, 1874. 
Those marked * give full lists of references. 

Bacteria as the Causes of Disease. 

Anthrax — PoUender — Davaine— Rayer — Laplat and Jaillard's Observations 
controverted by Davaine — Pyaemia and Septicsemia — Salisbury on 
Bacteria as the Cause of certain Fevers— Johanna LUders' and Hallier's 
observations on Pleomorphism or PoI)nnorphism — Burden Sanderson, 
Hoffman, and others, state that there is no Connection between Bacteria 
and the Higher Fungi — Demonstration of Infective Element in Anthrax 
Blood — Bacteria found in Organs in certain Diseases — Sarcina in 
Stomach — Specific Organisms — Specific Activities. 

The bacterium which, in its relation to the cause of a specific 
infective disease in man and the higher animals, has been 
most thoroughly studied is the Bacillus anthracis, an organism 
which, not only on account of its size but also because of its 
powers of adapting itself to conditions both outside and 
within the body, has been recognized comparatively easily, 
and cultivated in artificial fluids and on other nutrient media 
in which it grows luxuriantly, so that it has been possible to 
study more or less carefully its morphological and physio- 
logical characters. This bacillus was observed by Pollender 
as early as 1849 in the blood from the enlarged and pulpy 
spleens of cows that had succumbed to anthrax or splenic 
fever. He recognized that the bacilli were not fragments of 
broken-down vessels or coagulated fibrin, as had been sug- 
gested, but that they were probably small vegetable organ- 
isms similar to those described by Dujardin as "vibrio 
bacillus," and he suggested that it was quite possible that 
these organisms were in some way or other associated with 
the appearance of anthrax disease. 

In the following year, and before Pollender's description 
had been published (his full description was published in 
1855), Davaine and Rayer described motionless thread-like 
organisms and rods in the blood taken from animals affected 
with splenic fever. These observations were confirmed by 
other observers, but it was not until 1 863 that the micro-organ- 


ism was supposed to have any definite relation to the fever. 
Davaine, at that time stimulated by Pasteur's investigations 
on the relation between micro-organisms and the butyric 
fermentation, was led to suggest that these rods were, in all 
probability, the actual and specific cause of the disease, which 
suggestion, along with his observations on certain cases of 
malignant pustule that were published in the following 
year, may be looked upon as the first real attempt to 
demonstrate the connection between the Bacillus anthracis 
and the diseases known as malignant pustule and splenic 
fever. Although he did not furnish rigorous proof of the 
connection he was so far successful that, except for the 
cultivation of organisms outside the body and the pro- 
duction of the disease by means of the inoculation of pure 
cultivations, work which Koch afterwards completed, 
Davaine left no proof wanting. 

In the meantime, however, Delafond had demonstrated the 
constant presence of the rodlets in the blood of animals affected 
with splenic fever, and had also suggested their plant-like 
nature. Davaine found that he was able to transmit the 
disease to healthy animals by means of the inoculation of 
blood that contained these rods ; whilst where the rods were 
absent, although the blood might be exactly the same in 
other respects so far as he was able to observe, he could not 
produce the disease. He found that a single drop of diseased 
blood contained from eight to ten millions of these forms, and 
that by diluting the blood a million times, he was still able to 
produce the disease by inoculation. Subsequent observers, 
especially Leplat and Jaillard, objectingto his conclusions, said 
that similar rods had been found in other diseases. They 
pointed out that other elements in the blood — an extremely 
complex fluid — might be the cause of the infective disease, and 
that the rodlets themselves might be only an accidental factor. 
Leaving this safe ground, however, their further criticisms 
were based on the supposition that all the rod-shaped bodies 
were identical in structure and life history, and that conse- 
quently they should have the same effect when introduced 
into the body, and they concluded that because similar 
organisms taken from vegetable infusions did not produce 
anthrax, that therefore the rodlets in the blood could not be 
the specific infective agent. Davaine's answer was that their 
contradiction of his statements was due entirely to misconcep- 


tion. He pointed out the different physiological characters 
of organisms- taken from different media, and showed that 
different conditions were essential to the existence of different 
organisms, and, in connection with a number of inoculation 
experiments that they had carried on (with material sent 
by him, which they allowed to undergo decomposition, 
and by means of which rabbits were killed but no rods were 
afterwards found in their blood), that they had produced no 
anthrax because the incubation period was too short, because 
the splenic enlargement was absent, because the animals 
underwent much more rapid putrefaction, and because the 
disease was capable of being transmitted to birds — a class 
which up to that time had not been found to be susceptible 
to this disease. During this controversy Davaine pointed out 
that Pyemia and Septicaemia could not be produced by the 
inoculation of true anthrax virus. He described the bacteridia 
of anthrax as totally devoid of movement in the blood, 
and carefully distinguished between them and putrefactive 
bacteria ; he demonstrated how these latter could, by their 
presence and activity, diminish the activity of the anthrax 
bacteria, and could in turn produce a septic condition, which 
was in all essential respects absolutely different from splenic 
fever. He demonstrated that these vibriones were vegetable 
and not animal, and recognized the most important fact that 
the environment, mode of nutrition, and products of excre- 
tions of the anthrax micro-organism had a most marked 
influence in modifying its activity and virulence. He did not 
believe in the possibility of infecting the organism of the 
foetus in utero, basing his belief on Brauell's and his own 
experiments, and advanced the theory that the immunity 
enjoyed by the foetus was due to the filtering action of the 
placenta which, he contended, did not allow of the passage 
of solid particles either from the maternal to the foetal 
circulation or in the opposite direction. 

He concluded also that certain species of animals were 
much more susceptible to the disease than others. He was 
convinced at that time that malignant pustule, malignant 
oedema and anthrax were all due to the presence of the same 
organisms in animals or in man, 'and in fact he initiated the 
whole theory of contagion from animals to man and vice 
versd, and opened up the immense and fertile field of the 
comparative pathology of infective diseases. In 1868 he 


almost completed his proof of the causal relation of the 
organism to the disease by the ingenious method of mixing 
a drop of virulent blood with a large quantity of water, and 
using the bacteria which fell as sediment as the medium 
with which to inoculate susceptible animals. With this 
sediment he was always successful in producing anthrax, 
whilst inoculation with the water taken from near the 
surface invariably gave negative results. 

It was not a perfect proof, however, and it was left for 
Pasteur with his filtration process, and for Koch by his 
pure cultivation process on solid media, to complete the 
proof that Davaine so ardently desired and worked to obtain. 

In view of our latter-day knowledge of bacteria, it is 
interesting to note that as late as 1870, or only twenty years 
ago, these bacilli of anthrax were declared to be albuminoid 
crystals ; whilst within the last ten years they have been 
described as being built up from the d'ebris of fibrinous 

About this time a great impetus was given to the theory 
of a living contagion — an impetus which unfortunately im- 
pelled numerous workers and theorizers to see the cause of 
disease in every germ that they found. First, Pasteur had 
formulated his germ theory of fermentation and putrefac- 
tion ; Davaine, in his descriptive and controversial papers, 
had insisted upon the connection between his anthrax rods and 
splenic fever, and in the animal parasitic world the etiological 
relation between trichina spiralis (a small round worm) and an 
acute fever, met with especially in pigs, had been fully demon- 
strated. Salisbury, in this country, thought that he had found 
the organisms that were the cause of intermittent and remit- 
tent fevers, of malaria, and of certain other forms of specific 
disease, but he was quite unable to give proof in any single 
instance. In Germany, HalUer took up the subject with 
eagerness. He was led to investigate the subject of Poly- 
morphism of the bacteria or fission fungi — a theory that had 
been advanced by Tulasne in 1851, and had been later 
worked out by Tulasne and De Bary. It was held, indeed, 
that yeast was simply a form or stage in the develop- 
ment of certain mould fungi, such as the Penicillia or 

Pasteur had already pointed out the physiological likeness 
between the yeasts and the bacteria in their power of pro- 


ducing fermentation processes, and Hallier, who was well 
acquainted with these researches, concluded that if the yeast 
cells were part of a developmental cycle, the bacteria might 
also be taken to represent only short resting stages of the 
same or similar cycles. This was an especially seductive 
theory, as up to this time the origin of these minute forms 
had, as we have seen, been enshrouded in mystery, and had 
provided matter for the keenest controversy. 

A lady, Johanna Liiders, was firmly convinced that the 
lower bacteria and yeasts developed in some way or other 
from the individual parts of the mycelium of certain fungi, 
or from their spores. Her observations were repeated, and 
there was a general concurrence of opinion that the bacteria 
were derived in some way from fungi and from other higher 
plant forms. 

Hallier, with his isolation apparatus, which consisted 
really of Schwann's apparatus, to which an air-pump and a 
cotton wadding filter were added, and his cultivation ap- 
paratus, which corresponds practically to the potato-jar of 
to-day, with water to take the place of bichloride of mercury 
solution, came to the conclusion that the cause of almost 
every infective disease was to be looked for in bacteria, 
monads, and cocci, which in their turn were nothing but 
forms produced during the developmental cycle of one or 
other of the fungi aspergillus, penicillium, mucor, &c. 

Loffler says, in summing up the results of Hallier's re- 
searches, " He put forward the hypothesis that all contagia and 
miasmata are the products of fungi or algae which alone, on 
account of their small size, are able to pass through the fine 
capillary vessels, and that it was only necessary, in order to 
determine the nature of the original cause, first to find out the 
micrococcus and then to trace it back to the fungus to which 
it owed its existence." By such new ideas, propounded with 
such an air of conviction and authority, Hallier made a most 
profound impression on both the lay and scientific world. 
The whole system was so simple and clear and every part 
contributed so easily and naturally to form one harmonious 
whole ; every assertion was so definitely supported by micro- 
scopic observation and cultivation experiments that no doubt 
as to the correctness of the demonstrations seemed to be 

It was a somewhat noteworthy fact, however, that the pern- 


cillium occurred so frequently in his cultivations, and, as 
Brefeld and others pointed out, however complete Hallier's 
isolation apparatus might be in itself, he did not take sufficient 
care to prevent the entrance of the spores of these various fungi 
when he introduced the micrococci and bacteria which he 
wished specially to study, so that, although nothing fresh 
might be added after he had introduced the seed material, 
his seed material itself might be a mixture of various kinds, 
and along with it he could not be sure that the spores of the 
larger fungi had not entered. It was a case, said Brefeld, of 
covering with a waterproof a man already drenched with 
rain. So faulty, indeed, were these experiments considered 
to be by Burdon Sanderson in this country, by Hoffmann, 
Rindfleisch, Manassein, and Ferdinand Cohn abroad, that 
these observers undertook various experiments to prove 
that not only was there no connection between bacteria and 
the higher fungi, but that there were actually cases in which 
the micrococci did not develop into the longer rod-shaped 
bacteria. Moulds could only be developed in artificially pre- 
pared food solutions when the seeds or spores of moulds 
were sown ; whilst bacteria seeds or germs, when obtained 
free from the germs of moulds, would in similar solution 
give rise to the development of bacteria only. There 
-was soon a reaction against the whole of Hallier's teaching, 
and it was now pointed out that he had seldom or never 
been able to reproduce any disease by inoculating cultiva- 
tions of the organisms that he grew, and the theory of living 
contagion fell into discredit, though the fact must not be 
ignored that Salisbury's and Hallier's work led to further 
consideration of many points associated with the relation 
of bacteria to disease, and that eventually it exerted a 
marked influence on the germ theory of disease. Hallier 
undoubtedly laid great stress on the fact that a micro- 
coccus was the cause of certain diseases, and he pointed out 
that its extreme minuteness was in favour of its being able 
to enter readily and retain firmly its position in the body. 

In 1868-9 Davaine and Chauveau succeeded in demon- 
strating that in all probability the infectious element 
in anthrax blood (Davaine), and in glanders pus and 
vaccine lymph (Chauveau), and in vaccine lymph (Burdon 
Sanderson) was not merely a soluble poison, but some 
solid material, such as a leucocyte, and probably a 


hiicro-organism. The blood or pus was diluted many times 
with water, the sediment was washed again and again, each 
time being allowed to settle at the bottom, after which the 
supernatent fluid was found to have no effect in producing 
any disease, whilst the sediment which contained pus organ- 
isms and " fine granulations " almost invariably set up the 
disease process. The virus must accordingly, these observers 
thought, be a solid poison, and must be looked upon as a 
particulate body. These observations thus confirmed, to a 
certain extent, Hallier's suggestion that a micrococcus or 
a bacterium was the cause of most specific infective diseases. 

From this time onwards a large mimber of observations were made on 
various infectious diseases and micro-organisms. Micrococci were found in 
diphtheria, in scarlet fever, in rinderpest, septicaemia, and in other specific 
infective conditions, though Traube, in 1864, had made what might be con- 
sidered the first practical application of what had been discovered to be an 
important pathological condition when he demonstrated the fact that, if 
bacteria found their way into the bladder by means of a dirty catheter, a 
severe attack of inflammation of the bladder followed — an observation which 
was supplemented by Klebs, who demonstrated the connection between 
small abscesses in the kidney and the introduction of micro-organisms into 
the bladder. But with all these records there was very little of definite 
value to demonstrate the causal relationship between bacteria and disease, 
and even when fragments of diphtheritic membrane and of the wall of 
abscesses were introduced under the skin of an animal, and gave rise to 
both local and constitutional symptoms, there was no proof forthcoming 
that these were due to the micro-organism, and not to such special chemical 
products as had already been separated from putrid and diseased materials. 
Panum had demonstrated, in 1856, that it was possible to obtain from decay- 
ing flesh infusions an extremely poisonous substance, and his results were 
confirmed by numerous observers, some of whom succeeded in combining 
with acids the "basic" substance that Panum had separated; the sul- 
phate of this base when injected into frogs proved fatal, and eventually 
Ziilzer and Sonnenschein prepared what they described as a septic alkaloid 
which was stable in character, and in its reactions resembled most remark- 
ably the vegetable alkaloids, atropin and hyoscyamin. It was natural that 
as these materials could be separated by chemical means from diseased and 
putrefying materials, they should be looked upon as the primary and real 
etiological factors in the transmission of disease. In i87iihowever, Reckling- 
hausen, turning his attention to bacteria, was able to show that in the organs 
of patients affected with various infective diseases (such as blood-poisoning, 
and puerperal fever, typhoid fever, acute articular rheumatism, gangrene of 
the lung) small accumulations of micrococci were present, and that these 
were probably the cause or the agent by which deposits of the abscesses or 
gangrenous patches occurred in different parts of the body and in different 
organs. These micrococci were described as having an exceedingly sharp 
outline, as being extremely resistant to strong acids and alkalies, and, in 
fact, as being in most other respects like those that had been described as 


82 BACfERiA. 

occurring in diphtheria and in abscesses of the kidney. These results, with 
some modifications and additions, were almost immediately confirmed by 
Waldeyer and Weigert ; Recklinghausen and Weigert concluding that these 
micrococci were all in the lymphatic vessels, Waldeyer, on the other hand, 
holding that some, at any rate, were contained in the blood-vessels. 

In 1873 E. Klebs found in pus, organisms which he de- 
scribes most graphically as rod-like bodies, the so-called 
bacteria, motionless, frequently grouped in short chains, or 
in longer threads. He also found numerous micro-spores, 
very minute refractile organisms, whose diameter might be 
at most -S/j, some lying isolated and free, and having 
oscillating movements, others linked together in rosary-like 
threads. Having found them in the discharges he examined 
granulation tissue (raw or " proud " flesh), in lymph canals, in 
spaces in the septa or partitions between muscles, in inflamed 
marrow of bones, and in the ulcerating cartilage of diseased 
and injured joints, in the walls of blood-vessels and in thrombi 
or clots formed in the vessels and attached to their walls. 
These organisms were in all cases situated near the primary 
wound (the researches were carried on during the Franco- 
Prussian war), but having found the micro-organisms in this 
position he next traced them to the abscesses that formed 
in distant internal organs in cases of pyaemia. In fact, 
wherever there were points of secondary disease or suppura- 
tion, there he was able to demonstrate the presence of these 
organisms ; whilst in very severe cases of blood-poisoning he 
was actually able to demonstrate their presence in the circu- 
lating blood. In consequence of this constant presence of the 
bacteria and micrococci in these various disease areas, he 
felt justified in concluding that the organisms he had observed 
and described were the cause of the pysemic and septicasmic 
conditions, and that also to their action was due the forma- 
tion of pus, of abscesses, and even of ulcerative inflamma- 
tions of the vessel walls. There can be little doubt that 
the ingenious experiments devised and carried out by him 
and his pupils formed a groundwork on which succeeding 
investigators found it possible to build up the present mag- 
nificent structure. He conceived the idea of separating the 
micro-organism from the poison which it produced by 
means of baked clay cylinders, and found that fluid so treated, 
although it gave rise to constitutional disturbance when in- 
jected into the blood or under the skin, did not induce 


Suppuration, nor did it cause death : but if to this a quantity 
of the micro-organisms were added, and the fluid was then 
injected into dogs, these animals succumbed to a true pyaemia, 
accompanied by the formation of abscesses, especially near 
the points of inoculation. He showed that these organisms 
were not present in the normal healthy blood ; he also, 
by means of ingenious apparatus, which he contrived or 
modified, was able to observe the actual multiplication of the 
micrococci under the microscope. He introduced the method 
of fractional cultivation, but not in the complete form in 
which it was afterwards used by Lister and Pasteur, as he 
relied on the more vigorous growth of a certain organism 
that was placed in a special fluid and under special con- 
ditions, rather than on the dilution and isolation of individual 
organisms in small drops of fluid. Klebs was, however, able, 
by his biological method, to obtain comparatively pure culti- 
vations of several bacteria and micrococci, and he was the 
first to distinguish the division going on in various planes. 

Klebs' anatomical investigations were confirmed by numerous cbservers, 
Birch-Hirschfeld, Heiberg, Orth, and Hueter, the last of whom tried to 
build up a system of pathology on the basis of the researches that had 
already been carried out ; these, however, afforded very incomplete data on 
which to work. Pyaemia was, he considered, the result of the invasion of 
the tissues by micrococci, with the formation of little plugs in the vessels, 
around which abscesses were developed ; septicaemia was a general poison- 
ing by absorption from a localized formation of bacteria in the body ; and a 
third form, which he looked upon as putrid poisoning, was the result of the 
absorption of poisonous matter formed by vibriones existing outside the 
body. The only difficulty in the matter was that the same organism 
appeared to produce very different conditions, such as pyaemia, septi- 
caemia, puerperal fever, pyelo-nephrilis, typhoid fever, phthisis, small- 
pox, diphtheria, cholera, rinderpest, whilst even in the healthy body 
organisms were sometimes found, especially in certain positions, a fact 
which at that time was not reconcilable with the various theories that had 
been advanced. Another objection stated was that as the bodies of patients 
who had died of pyemia and septicaemia putrefied rapidly, they formed an 
especially good medium in which innocuous organisms might grow, and it 
was maintained that organisms were found in such bodies after death, 
because of the special suitabihty of the soil for their growth, and that they 
were therefore probably rather to be looked upon as accidental concomitants 
and consequences than as essential factors in the production of disease. 

There now also appeared great activity in the French 
school : Pasteur had shown that most of the processes of 
putrefaction were due to the presence of motile, anaerobic 
vibriones, whilst Davaine had observed only non-motile rod- 



lets in the blood of animals that died from anthrax. The 
latter was further able to prove to Jaillard and Laplat that 
these non-motile organisms of virulent anthrax were actually 
rendered inert by the growth amongst them, or alongside 
of them, of motile putrefactive organisms, and that the 
action of the anthrax organism was also considerably modified 
by the growth of septic organisms, which, in turn, when 
introduced into an animal by inoculation, were capable of 
producing a disease which might perfectly easily be distin- 
guished from anthrax. The knowledge that the septic con- 
dition was not due to ordinary putrefactive organisms was 
further augmented by Birch-Hirschfeld, who demonstrated 
that pus which when fresh was infective lost much or all of its 
specific activity when putrefactive organisms were allowed to 
grow in it ; so that these putrefactive bacteria at any rate could 
not be looked upon as playing any part in the production of 
Avound infection. Then specific forms began to be associated 
with specific disease conditions, or kinds of putrefaction and 
fermentation ; the Goodsirs described sarcina in the acid con- 
tents of dilated stomachs ; Trecul found his Bacillus 
amylobacter, with its characteristic tadpole shape, which 
gave rise to no wound infection, and numerous others were 
observed, none of which could be proved to have produced 
septic conditions. An organism which produced the color- 
ation met with in blue milk was described by Fuchs, and 
another perfectly distinct micro-organism was described by 
the same observer as giving rise to a yellow colour in 
milk. That the milk was not absolutely necessary for the 
nutrition of these organisms he proved by making artificial 
cultivations on other media, and he gave very fully the 
conditions under which they could continue to exist ; they 
were destroyed by a temperature of 50° R. to 55° R. ; freez- 
ing did not interfere with their power of propagation when 
again thawed, and after being dried and again moistened 
they were able to develop in milk and to give rise to the 
characteristic coloration. 

The way was thus being prepared for the discovery that 
specific organisms had, under certain conditions, specific 
actions and activities. If a peculiar organism was found 
to be associated with the production of a special kind of 
colouring matter, and if special fermentation and putre- 
.faction processes were induced by individual organisms, was 


it not probable, in the light of Davaine's work, that special 
diseases would ultimately be found to be associated, not all 
with the same organism, but each with a special form ? 


Authors already mentioned. Cohn, Chauveau, Dujardin, 
Hoffmann, Klebs,* Loffler, Schwann. 
Brauell. — Virchow's Arch. Bd. ii., p. 132, 1857 ; Bd. xiv 

p. 432, 1858. 
Brefeld. — Bot. Unters ii Schimmelpilz. Leipzig, 1074. 
BiRCH-HiRSCHFELD. — Archiv. der Heilkunde. Bd. xiii., p. 

389, 1872, and Bd. xiv., p. 193, 1873. 
Davaine. — Revue Scientifique. Ser. in., t. v., p. 78. Comp- 

tes rendus, pp. 320, 351, 386. 1865. 
Delafond. — Recueil de med. vet. i860. 
DE Bary. — Untersuch. ii d. Brandpilze. Berlin, 1853. 

Bot. Zeitung, 1854. 
FucHS. — Gurlt. u. Hertwig's Magazin f. d. gesammte Thier- 

heilkunde, Bd. vii. 
GooDSiR. — Ediii. Med.Jonrn., vol. lvii. 1842. 
Heiberg. — Die puerperalen u. pyamischen Processe. Leip- 
zig, 1873- 
Hueter. — Die allgemeine Chirurgie. Leipzig, 1873. 
Jaillard and Laplat. — Comptes rendus, t. lix., p. 748, 

1864 ; and t. Lxi., pp. 368, 523 ; 1865. 
Koch. — Cohn's Beitr. z. Biol. d. Pflanzen, Bd. 11., p. 277, 

LiJDERS, Johanna. — Schultze's Archiv. fur Mikr. Anat., 

Bd. III., p. 317, 1867. 
ManasseIn. — Wiessener's Mikr. Unters. Stuttgart. 1872. 
Orth. — Virch. Arch. Bd. Lvni., p. 437, 1873. 
Pasteur. — Comtes rendus, t. lii. 1861. 
Panum. — Bibhotek for Laegar, 1856. 
PoLLENDER. — Casper's Vierteljahrschrift, Bd. viii., p. 432, 

Rindfleisch.— Virch. Arch. Bd. liv., p. 397, 1872, 
Salisbury. — Amcr. Journ. of Med. Science^ Jan., 1866, and 

Jan., 1868. 
Sanderson, Burdon. — Nature^ vol. ^'III., p. 478. Bnt. 

Med. Journ., p. 119, 1878. Quart. Journ. Micro, Sc. 




Trecul.— Comtes rendus, t. lxl, p. 156, 1865 ; and t. lxv., 

p. 927, 1867. 
TuLASNE. — Comtes rendus. t. xxxii., p. 427-470. March, 

Von RECKLfNGHAUSEN. — Virch. Arch. Bd. xxx., p. 366, 1 864. 
Weigert. — Centralbl. f. d. Med. Wiss., No. 39. 1871. 
Zuelzer und Sonnenschein.— Berl. Klin. Wochenschr. 

No. 12, p. 121, 1869 and 1872. 

* Full list of references given. 


Fermentation : a Key to the Whole Position— Chemical Fermentations- 
Illustrations— Organic Fermentations— Alcoholic Fermentation— Re- 
sult of Activity of Living Protoplasm — Lactic and Butyric Fermenta- 
tions — Cagniard Latour — Schwann— Reess— Hansen — Liebig's Theory 
of Fermentation— High Beer— Low Beer — Method of obtaining Pure 
Yeasts — Hansen's Classification of the Saccharoniyces — Spore Forma- 
tion — Film Formation — Characters of Species of Saccharomyces — 
Metschnikoff 's Monospora — Torulas. 

From what has preceded it will be evident that if any light 
is to be thrown on the subject of the production of organic 
poisons in the course of disease a careful study of the subject 
of fermentation is a necessary preliminary ; for, taken in its 
widest sense, fermentation includes all those processes in 
which there is the formation of special ferments and of 
special products as the result of the life-history of certain 
vegetable organisms. It is quite as rational to speak of a 
putrefactive as of an alcoholic fermentation, and we might 
even go beyond this and speak of a colour fermentation or a 
disease fermentation, as the organisms by which one or the 
other is started, and the conditions under which they are 
carried on, have many features in common, and, in fact, do 
not differ more than do the causes and conditions that are 
already known as associated with true alcoholic fermenta- 

Fermentation consists, essentially, in the breaking up of 
chemical compounds, the molecules of which they are com- 
posed being separated from one another for a brief period, 
and then allowed to combine and form simpler and more 
stable compounds. Owing to the setting free of such energy 
as has been stored up in the highly complex fermentable 
substance which is no longer required to maintain the 
high level of combination, a certain proportion of this 
energy is released in the form of heat, the temperature of 


a fermenting fluid being found to rise without the addition 
of any external heat. An object lesson may be used to 
illustrate the processes of breaking down and re-combination 
that go on m fermentation. Let us suppose that we have 
a tall tower built up of two kinds of blocks, placed one on the 
top of another ; first a large block and then three small ones, 
then another large block and then three more small ones ; 
let us consider that there are pulling on these blocks elastic 
bands of different strengths, one very strong one between the 
two large blocks, another very strong one between each pair 
of the small blocks, and two sets of three weaker bands run- 
ning from the larger blocks to the smaller ones ; these sets 
of blocks are so arranged that if left perfectly undisturbed 
they will remain piled up one on another forming a tower of 
considerable height. The higher the tower the more easily, 
as a rule, will it be upset, though this depends on the way in 
which the larger and smaller blocks are distributed in the 
structure. If, now, some disturbing element comes in, and 
if one of the blocks is withdrawn or is even slightly shaken, 
the whole structure may collapse, even the movement 
of a small top block may bring this about by altering the 
tension on one of the elastic bands, so disturbing the 
equilibrium of tension on the whole tower, that the two 
large blocks, with their strong elastic band, are set free 
and fall to the ground ; the pairs of smaller blocks, with 
their strong uniting bands, also fall to the ground, and the 
other thin bands of which we have before spoken are now so 
far stretched or broken that their influence in holding the 
different sets of blocks together may now be left altogether 
out of account. But in falling fronf the top of the tower to 
the bottom energy of position has been lost, and in falling 
and striking the ground a block may do a certain amount of 
work ; if it were in connection with a series of pulleys it 
might be made to lift a certain weight ; if it were to strike 
the ground with suflScient force it might produce a flash of 
light, or a certain amount of heat. We are, perhaps, not 
justified in stating that this is exactly analogous to what 
takes place in fermentation, but it is sufficiently so to 
explain the nature of the process, if we consider that the 
kinds of blocks that are built into our tower are multiplied. 
In the most characteristic and best form (for our purposes) of 
fermentation that can be taken as an example, we have 


grape sugar, consisting of three kinds of blocks, six of car- 
bon, twelve of hydrogen, and six of oxygen, all built into a 
high tower of twenty-four blocks (sugar, CeH^Oe). In the 
process of fermentation the equilibrium is disturbed, and we 
have the tall tower replaced by four smaller ones, two con- 
sisting of three blocks each (2CO„ carbonic acid), and two 
consisting of nine blocks each (2CjH60, alcohol), and the 
heat that is evolved in the process may be represented by 
the sum of the figures representing the distances which these 
various blocks have had to fall from the high tower into the 
lower ones, multiplied by the figures representing the mass 
of the volumes. Other features have to be taken into 
account, but the above example will serve to explain part of 
our meaning. But this is not all. The children's line of 
" soldiers " may be used to explain another feature : a 
child arranges its wooden " bricks " in a long line, placing 
them on end ; if they are all of equal length the distances be- 
tween them are also made equal ; if they are of unequal length, 
they are so arranged that one block falling will just touch the 
one next to it. If the end block be now so disturbed that it 
loses its unstable equilibrium, and so falls as to acquire a 
stable equilibrium, it not only loses its own unstable equili- 
brium, but it upsets that of the brick next to it, which in 
turn acts on its neighbour, and so on till the whole line is 
brought to the ground. If, instead of upsetting the first brick 
at once, you simply give it a slight tap and only just move it, 
instead of falling over, it sways backwards and forwards for a 
little but then settles into its original position ; you give 
it another tap, it sways a little further, but still returns to 
its erect position ; whilst if now you give it a good strong 
push, or if two of you tap it at the same time, over goes the 
brick, bringing along with it the whole line to a condition 
of stable equilibrium. The towers or the rows of erect 
bricks are fermentable substances, the disturbing forces are 
those agents that bring about fermentation, and the smaller 
towers or the bricks laid down in rows instead of on end are 
the products of fermentation. The larger number of smaller 
towers contain exactly the same elements as did the smaller 
number of larger ones. They had energy of position, which 
is converted into kinetic energy, exactly in proportion to the 
distance that the elements have to fall ; some of the energy 
appearing in the form of heat^ other parts being used up in 


the rearrangement that takes place when the smaller towers 
are formed. It may be asked, How does the tilting over of 
the bricks bear on all this ? The first tap that you give 
them may be said to represejit the action of some ferment ; 
the tap that your friend gives at the same time may be held 
to represent one of the conditions essential for the production 
of a ferment, say the presence of a certain amount of light ; 
whilst the tap that a second friend gives may be looked upon 
as representing a certain degree of temperature ; it may be 
a forcible tap, representing 40° C, or it may be a slighter one, 
representing a temperature of 20° C. only, in which case you 
do not get sufficient energy out of the ferment to start the 
process. One or two only of your taps may upset certain 
towers or certain lines of bricks, but other towers that have a 
somewhat broader basis or a more definite arrangement 
require the whole three forces to be applied, and these have 
to be applied in certain definite proportions if the same 
results are to be obtained in every case. Thus, for example, 
by graduating the power of the disturbing force, the equili- 
brium of your tower may be simply upset and the elastic 
bands drawing in certain directions cause a rearrangement 
of the blocks according to the strength with which these 
bands pull ; if, however, instead of simply just distributing 
the equilibrium to allow of the new arrangements taking 
place, your tower is struck with a sledge hammer, or over- 
turned by a pistol shot, or by the explosion of a charge of 
dynamite near it, the conditions are so altered that you 
cannot rely upon any plan of rearrangement being adhered 
to. As a result you simply obtain a series of disconnected 
blocks or of much smaller and irregular towers. It will be 
said that this regular breaking up is exactly what takes place 
in the breaking up of chemical combinations. This is perfectly 
true, for that is exactly what fermentation is. It is the upset- 
ting of the equilibrium of unstable compounds by most deli- 
cately adjusted forces which are so accurate, so constant, and 
so delicate, that the stronger affinities of certain elements for 
one another are allowed to act to their full extent, and regular 
stable combinations are formed always in a definite manner. 
Let us take first such a substance as nitrogen trichloride or 
nitrogen teriodide. If a sharp blow be given to a small quantity 
of either of these materials, or if either be heated to a certain 
temperature, it will immediately break down into nitrogen 



md chlorine, or into nitrogen and iodine. Thus a tower 
nade of 2NCI3, or of two large and six small blocks, ;s trans- 
"ormed into two towers, one composed of two large blocks 
md one of six small ones, or rather into four towers, one 
;omposed of the two large blocks and three each composed 
)f two small ones (2NCl3=N^ + 3 CI,), and along with the 
"ailing of these molecules into their lower positions there is 
I setting free of energy which manifests itself in the form of 
leat and light. Consider now that in your tower or in your 
■ow of bricks you have continual oscillation going on ; the 
elastic bands are being continually pulled upon by certain 
'orces which we may say are light and heat ; there is continual 
notion in every part of the tower, or the bricks standing on 
;nd are continually oscillating backwards and forwards, but 
aever sufficiently far to disturb the equilibrium completely, 
ffhen suddenly a third element of disturbance sets in, a small 
)rganism comes near and wishes to take out one of the 
slocks from the tower for its own use ; it seizes the time 
.vhen the oscillation is greatest, and giving a little extra pull 
t removes the block, seizes on it firmly and immediately, and 
:he rest of the tower collapses ; or in the case of the swaying 
)ricks, although it has no power alone to upset the first brick 
n the row, by striking it just when its oscillation is at one 
;xtreme phase it assists light or heat, pushes this first sway- 
ng brick a little further and causes the collapse of the whole 
ine. Bunge gives a series of exarnples of the breaking down 
)f such chemical substances into simpler materials, and shows 
low certain ordinary chemical substances along with heat, or 
!ven heat alone, may act as fermentation exciters. Thus he 
)oints out how a blow can initiate the breaking up of nitro- 
glycerine into carbonic acid, water, nitrogen, and oxygen. 

Nitro-glycerine is highly unstable, not so much from the 
lements which it contains as from the method of arrange- 
nent of the atoms of the elements. Some oxygen has been 
nduced to unite with nitrogen, a substance for which under 
irdinary circumstances it has little affinity, it having at the 
ame time a much stronger affinity for both carbon and 
lydrogen than these have for one another ; rapid and exten- 
ive oscillations are constantly going on, the slightest increase 
if which must be followed by a new arrangement of mole- 
ules. A sharp tap so increases these oscillations that the 
quilibrium of the tower is disturbed, the weak bands between 


the oxygen and the nitrogen are severed, and the free oxygen is 
immediately pounced upon by the carbon and the hydrogen, 
which are set free from one another, each of these elements 
taking up a certain quantity of the freed oxygen ; the 
atoms of nitrogen having, of course, a strong affinity for one 
another, combine, and a small portion of oxygen is set free. 
The amount of energy released here is very great indeed, 
and it is the more readily observed, and even measured, 
from the fact that the process goes on rapidly and. violently, 
as it usually does where the resolution is that of a very 
complex body, into extremely simple substances. Other 
examples given by Bunge are the resolution of nitrogen 
trichloride into its constituent elements by " contact with 
various substances, such as phosphorus, phosphorus com- 
pounds free from oxygen, selenium, arsenic, some resins 
(other kinds being inert), non -volatile oils, &c. ; " and he 
instances chlorate of potash, which splits up into chloride 
of potash and oxygen at a certain temperature, and, in 
the presence of binoxide of manganese, ferric oxide or 
oxide of copper at a much lower temperature ; he says : 
"The presence of this substance probably so modifies the 
heat-wave, that the atoms of the chlorate of potash are more 
easily thrown into responsive vibrations, and thus decom- 
posed. In the same way peroxide of hydrogen decomposes 
on being brought into contact with platinum, gold, silver, 
binoxide of manganese, &c. In these cases it is called an 
effect of contact, or a catalytic effect. We can form the 
following hypothesis of the process which goes on here, as 
in the cases above cited : The substance which acts ' cata- 
lytically ' exercises an attraction on one of the atoms in the 
unstable molecule. It does not necessarily always unite 
with the atom, but the unstable arrangement of the atoms 
in the molecule is invariably altered to a stable one." 

Now let us see what actually takes place when grape sugar, 
of which we have already spoken, is being split up into 
alcohol and carbonic acid. We have seen that there is a 
rise of temperature quite distinct from any heat that is 
applied to bring about the fermentation. It has been proved 
that in some way or other the presence of the yeast-plant 
has a very definite effect in starting a process of fermenta- 
tion, and there are theories as to the role that this yeast- 
plant plays in starting the fermentation. In the first place, 

tfERMENTAflON. 93' 

t can only bring about the detachment of the molecules or 
)ricks of a substance when the motion of the molecules of 
hat substance is started or extended by the action of a 
lertain degree of heat ; thus fermentation will not take place 
mless the material to be fermented is kept at a temperature 
)f from io° to 40°. This increased temperature acts, pro- 
)ably, in two ways : first, by increasing the motion of the 
nolecules as above stated, and secondly, by enabling the 
)rotoplasm to act more energetically, by increasing the rate 
md extent of molecular motion within the organism itself. 
The determining motion, according to Bunge, " might pro- 
ved from the vital functions of the cell. But it is likewise 
:onceivable that certain substances occur in the cell, and 
hat these substances act in a similar manner to the catalytic 
)odies in the examples adduced above." Heat and moisture 
ire both necessary factors in all processes of fermentation, 
mt neither of these alone can give rise to it. 

Pasteur, who was really the first to understand this sub- 
ect so far as to be able to throw light upon it for others, 
ooked upon " fermentation, properly so called, as a chemical 
)henomenon, co-relative with physiological actions of a pecu- 
iar nature," the elements in which the peculiar physiological 
ctions were manifested being spoken of as ferments which 
vere not dead albuminoid matter, as held by Liebig and his 
chool, but actually living organisms " of a peculiar nature 
a this sense, that they have the property of exercising all 
he functions of their life, not excepting ' vegetative multi- 
ilication,' without necessarily employing the oxygen of the 
tmospheric air ; " and he thus generalizes his results : 
' Guided by all these facts, I have been gradually led to 
Dok upon fermentation as a necessary consequence or mani- 
sstation of life when that life takes place without the direct 
ombustion due to free oxygen." This opened up exceed- 
Digly wide and important questions : Was it possible that 
11 living plant-cells might have the power of inducing ' 
jrmentation in a more or less marked degree? and did 
easts differ from other living cells only in the fact that 
hey had more marked powers of acting on certain carbo- 
lydrates, and of exciting alcoholic fermentation ? Experi- 
lents on fruit, on barley, on leaves, all went to prove that the 
lementary cells of plants possessed within themselves this 
lower of inducing fermentation of sugar that was already 


present or of sugar that was artificially introduced. By a 
natural transition from the observation of vegetable cells to 
a study of animal cells, we are led to consider how impor- 
tant may be the part played by these latter in the digestive 
tract and in the tissues of the body, especially when they are 
called upon to act in conjunction with vegetable ferments, 
either in normal or in abnormal positions. Fermentation, 
then, may be looked upon as an ordinary chemical trans- 
formation of certain substances taking place as the result of 
the action of " living " cells, the nature of the fermentation and 
of the substances ultimately resulting being due, firstly, to the 
nature of the fermented body ; secondly, to the nature of 
the organism which induces the fermentation ; and thirdly, 
to the physical conditions under which the fermentation takes 
place. Thus the results may be extremely complicated if a 
mixture of ferments, say an alcoholic, a lactic, and a butyric, be 
sowed in a single nutrient material ; but if we sow only one, 
say the alcoholic, the sugar will split into alcohol and carbon 
dioxide ; if we sow the butyric fermentation, butyric acid 
will be formed as a result of the splitting up of the sugar ; 
and so on. As will later be seen, the special name of any 
fermentation serves to indicate merely that some special 
product predominates. In the alcoholic fermentation, alcohol 
is the chief product, but there are also formed as bye pro- 
ducts, glycerine, succinic acid and a number of other 
substances, the amount and nature of these bye products 
varying, first, with the yeast, and second, with the condi- 
tions under which it is allowed to grow. The character and 
aroma of beer and wine indeed depend essentially on the 
formation of such bye products — compound athers. It is of 
course possible, nay, eyen probable, that what bacteriologically 
may be termed impurities, may effect the same result, and 
that special aroma and flavour may depend upon the presence 
of small quantities of other organisms than the special yeast 
used. Further, the activity of the process is dependent 
in a very marked degree upon the nature of the fermenting 
substance, and a medium which may afford ample material 
for the carrying on of one kind of fermentation is absolutely 
valueless as a medium for other fermentations. The only 
real difference that exists between a pure alcoholic or butyric 
fermentation and the complicated fermentations which take 
place in the animal body or in putrefactive processes is, 


that in the one we have a single ferment only, playing its 
part, acting on comparatively simple and non-complicated 
media, whilst in the other we have a complex substratum 
for the growth of the organisms and a considerable variety 
of organized ferment cells. 

Fermentation may be considered from two points of view — 
first, as merely a chemical process which is started by the 
products of micro-organisms or yeasts, in which it resembles 
many other chemical reactions which are initiated by light, 
heat, a blow, or some other molecular activity unassociated 
directly with organic life ; whilst, under the second heading, 
it may be looked upon as due to the action of living proto- 
plasm or cells, special fermentations being induced by special 
organic forms. The soluble products of these organisms, 
however, appear to play a secondary part in the process of 
fermentation, some accelerating, others interfering with it. 
The process appears to be associated with the necessity which 
there is for the organized ferments to obtain certain elements 
for their growth and development — elements which can only 
be obtained under special conditions, and which, if obtained 
otherwise, do not lead to the breaking down of the substance 
which should be fermented in the usual fashion. 

As we have already seen, the early history of bacteriology 
was almost entirely associated with the work that was done in 
connection with fermentation, and it was not till Cagniard- 
Latour demonstrated that his yeast was made up of small cells 
which appeared to be capable of reproducing themselves by 
budding, that the inevitable conclusion was drawn that these 
globules of yeast were really composed of vegetable proto- 
plasm, and that it was in consequence of their growth and 
proliferation that sugar solutions underwent the process of 
fermentation with the evolution of carbonic acid gas and 
the production of alcohol. Schwann and Kiitzing, indepen- 
dently, arrived at the came conclusions after obtaining the 
same results, and other observers' soon corroborated the 
observations made by these pioneers, although the whole 
facts were not discovered at once, and the knowledge of the 
structure and life-history of the yeast-cell that we now 

' Kieser, 1814 (Schweigger's Journal, No. 12, p. 229) described spheri- 
cal corpuscles, all of nearly the same size, which were transparent and 
motionless, and Desma^ieres depicted yeast globules in 1826 ("Ann. des 
Sciences Naturelles," p. 4). 


possess has only gradually been accumulated. These cells 
are composed of a granular protoplasm surrounded by a 
definite envelope. When these vesicles or cells are watched 
during their development, growth, and multiplication, there 
may be seen, at or near one or other extremity of each, 
small protoplasmic bodies, which are projected beyond the 
general outline of the cell, and which gradually but surely 
increase in size. Ultimately there is a constriction, more 
or less marked, between the original cell and the bud, and 
the bud grows to the size of the parent cell ; the same 
process is repeated time after time, until there is formed 
a chain or series of ellipsoidal or rounded yeast-cells. At 
one time it was supposed that there was no development 
either of spores or of mycelial chains, but, thanks to the 
researches of Reess, by whom the presence of spores within 
the cells of certain forms of yeast was demonstrated, and to 
those of Hansen, who was able to confirm their observations 
as regards spore formation, and also to demonstrate the 
presence of typical chain mycelia as well as of the budding 
form of mycelium, these organisms have been put into a 
separate family by botanists, who have given them the name 
of Saccharomyces, sugar fungi, or yeasts. These saccharo- 
myces are indeed to be looked upon as fungi, for although 
they are closely related to the algas in many respects they 
contain no chlorophyll. 

Many of the later observers made very definite statements, 
founded apparently on very accurate data, that the process of 
alcoholic fermentation is closely bound up in the question of 
organized ferments ; nevertheless Liebig continued to defend 
his doctrine of unorganized ' ferments with great ingenuity 
and vigour. His theory was that fermentation was the result 
of " internal molecular motion which a body in the course 
of decomposition communicates to other matter in which the 
elements are connected by a very feeble aflSnity " (Schiitzen- 
berger, on Fermentation, p. 40). " YeaSts, and in general 
all animal and vegetable matter in a state of putrefaction, 
will communicate to other bodies the condition of decom- 
position in which they are themselves placed. The motion 
which is given to their own elements by the disturbance 
of equilibrium is also communicated to the elements of 

' The term unorganized is not here used in its modern signification, 
which will be mentioned in the next chapter. 


bodies which come into contact with them." Thi: 
was nothing more than an extension of Willis' and Stahl'i 
view of fermentation ; they held that a ferment is a bodj 
which has a peculiar internal motion which is capable o: 
being transmitted from the ferment to a fermentable matter 
So fascinating and plausible a theory, of course, received wid( 
recognition, and until Pasteur's admirable demonstrations o 
his theory of fermentation were made, had received ver3 
general acceptance, especially amongst German chemisti 
and biologists. The mechanical theory and the theory o 
catalytic forces as used in the old sense have now beer 
laid aside, and the vitalist theory — expressed in the following 
words by Turpin : " Fermentation as effect, and vegetatior 
as cause, are two things inseparable in an act of decom 
position of sugar " — has taken the field against all opponents 
This theory is that living organisms build up structure; 
and develop energy from the materials in which the] 
live, and break up by their vital activity, either directly 
or through a soluble ferment, the sugar in which the] 
grow. In this theory albuminoid material is considerec 
to be necessary for the process of fermentation or decom 
position only in so far as it is required for the nutritioi 
of the micro-organism, it being denied that nitrogeneou 
elements play any such part, as that ascribed to them bi 
Liebig, of producing the molecular motion, which bring 
about the splitting up of the sugar, by undergoing a spon 
taneous decomposition. Albuminoid material, in fact, i 
merely an accompaniment of the process of fermentation— 
a necessary one, no doubt, but one not in any way playinj 
the part of causal factor. 

What takes place in brewing, a process which, though unti 
recently incompletely understood, has long been carried oi 
on an enormous scale in most northern countries ? Malt i 
barley in which a certain proportion of the starch of th^ 
grain has been converted into sugar by the process knowi 
as "malting." This consists essentially in moistening th' 
grain several times, keeping it at a temperature high enougl 
to promote its sprouting, during which a substance callei 
diastase is developed as the result of the vital activity c 
the cells in the germinating grain which acting on the stard 
converts it into sugar. As soon as this takes place th 
sprouting is stopped by raising the temperature and then b; 


drying the grain to kill the young plant and so prevent 
further sprouting. To obtain a fermentable liquid, a solution 
of the sugar and of the other soluble constituents of the 
malt is made in hot water ; this is allowed to cool to a 
temperature of about i6° C. A certain quantity of " high " 
yeast is then added to the solution, and during the pro- 
cess of fermentation the temperature may run up to i8° or 
20° C. After a time httle bubbles of carbonic acid gas are 
seen to rise, the yeast increases in quantity and gradually 
rises to the surface, whence it is skimmed off, and may be 
again used to set up fermentation, if still pure. The fluid 
becomes bright, clear, and sparkling (from the presence of 
carbonic acid), and contains a certain proportion of alcohol ; 
whilst the sugar, if the fermentation has been properly 
carried on, has almost entirely disappeared. This is what 
is known as "high yeast" fermentation. It goes on most 
readily at a comparatively high temperature, and the yeast 
rises to the surface as it is formed, bringing up with it 
a certain proportion of the impurities contained in the 
liquid, the heavier particles falling to the bottom. The 
process goes on rapidly, but unless great care is taken it 
is said that there is a danger that impurities may get in, 
and that secondary fermentations may be set up, though this 
is a position now scarcely tenable in these days of India Pale 

The " low " fermentation is brought about by a ferment 
which acts more slowly, at a much lower temperature, and 
through the agency of yeast-cells that sink to the bottpHTas 
they are formed. This fermentation of beer must be allowed 
to go on at a temperature of from 4° to 5° C, and the fluid 
is not completely ripened until the end of about fourteen 
days. This low temperature is maintained in the small 
breweries by inverted cones of metal, containing ice, which 
are allowed to float in the fermenting liquid ; they are kept 
constantly supplied with ice, and the number used is regulated 
according to the temperature of the external air. In the larger 
breweries the same results are obtained by passing currents 
of purified cool air over the surface of the fermenting tanks, 
which, as a rule, are underground, so as to allow of the 
temperature being maintained at an extremely equable 
level. Formerly all beer was made by the high fermenta- 
tion process, a system that still prevails in this country, but 


in Germany, Austria, and Scandanavia, and also in France, 
the low fermentation has now almost entirely ousted the high 
form. There can be little doubt that this is due, in part at 
any rate, to the impetus that Pasteur's studies gave to the 
subject of the careful examination of yeast ; he pointed out 
that at the higher temperature there was greater danger of 
contamination by organisms which produce other fermenta- 
tions than the alcoholic, and that these micro-organisms 
unable to flourish at the lower temperature, would at the 
higher temperature grow most luxuriantly. This of course is 
undoubtedly true, but it should be remembered that where 
the brewing is in the hands of men in a small way of business 
the conditions are very different from those where all the 
apparatus and skill that capital can command are at the 
disposal of the brewer. If it were once known which was the 
best kind of yeast for high beer fermentation it would be 
possible to obtain pure cultivations, and with it so to conduct 
the beer fermentation by attending most carefully to the 
cleanliness of the vessels in which beer is made and stored as 
to obtain a very pure beer, having excluded all organisms that 
by their fermentation miglit render it unsound. The low beer 
may be brewed in smaller quantities and under less favourable 
conditions as regards the possibility of keeping the yeast pure 
than at higher temperatures. The yeast then used causes the 
fermentation to go on at such a low temperature, that a large 
number of the organisms which usually give rise to impurity in 
the beer cannot multiply. Such beer, however, can only be 
stored when the temperature is kept very low, for as soon as 
this begins to rise the dormant spores of other organisms 
begin to develop, set up various acid fermentations and spoil 
the beer. The different methods of brewing are also deter- 
mined in part at any rate by the climates of the different 
countries the cool, light beer apparently being more palatable 
in warm continental countries ; the heavier, with its own 
peculiar flavour, being usually more sought after in this 

Given pure yeasts, thorough cleanliness, and means of 
keeping out other organisms, both beers may be kept sound 
even though the temperature be comparatively high. To 
obtain such pure yeast it is necessary first to take a single 
cell, and from this to grow a series of buds and chains in a 
sterilized wort, to break this up into separate portions of seed 


material, to produce other crops from this, and so on until a 
sufficient quantity of pure yeast is obtained to bring about 
the special fermentation in the large mass of wort. This 
method has another very great advantage — it enables an 
investigator to take a single yeast-cell and to follow it in its 
life-history ; in doing this Hansen completed the work that 
Pasteur had commenced. 

As the process of obtaining pure cultures is of great interest not only to 
scientific investigators but also to practical men, we may here give it in brief.' 
In a Pasteur flask containing wort, a cultivation of the yeast to be experi- 
mented on is started and carried on as vigorously as possible. A quantity 
of water, that has previously been sterilized by boiling, is added to the 
growth ; the yeast-cells in a drop of given size are then counted under the 
microscope. Let us suppose that ten cells are found ; a drop of similar size 
is then transferred to a flask containing a known volume, say 20 c.c. of 
sterilized water, so that we have one yeast-cell for each 2 c. c. of water. 
The flask containing the 20 c.c. of water with the added 10 yeast-cells, 
is now thoroughly shaken and then divided equally, i c.c. being placed 
in each of twenty flasks containing sterilized wort;^ If the separation has 
been complete ten out of twenty flasks should contain one organism each ; 
but this of course cannot be absolutely depended upon. After carrying 
the process to this stage Hansen shakes the flasks very vigorously, by 
which he separates the cells as far as possible from one another, puts them 
in an incubator, and allows them to remain perfectly still, so that the cells 
may sink to the bottom or become attached to the walls of the flask. If 
there are more cells than one in any flask, they should have been completely 
separated by the final shaking, and each will probably take up a separate 
position on the wall or bottom of the flask, and at the end of several days 
" the flasks are carefully lifted and examined, and it is noted whether one 
or more white specks have been formed on the walls of the glass ; if only one 
such speck is found we have then a pure culture." This method is especially 
useful in the case where the yeast-plants are at all weakly, as all yeasts grow 
much more luxuriantly and strongly in a fluid medium than they do on gelatine 
plates, even when wort is added to the gelatine in order to render it more 
suitable for the nutrition of the yeast. Where the species are mixed, but 
where the individuals that we desire to separate are vigorous, the gelatine 
method may be used with advantage, especially as the individual colonies 
can then be examined from time to time, or continuously observed under 
the microscope as they pass through their various phases of development. 

The characteristic appearances that were said at one time 
to belong to the yeast-plants have been proved by Hansen 
to be really non-existent, except in a very limited sense. 
He maintains that the shape and relative size of the cells 
and the appearance of the protoplasm of a yeast-plant are 

» For the method of carrying on the process on a large scale see Jorgen- 
sen's work. 
' I c.c. or one cubic centimetre = about 16 minims. 


not really specific characteristics. He finds that within 
certain limits the same species, under diiferent external 
conditions, may exhibit very different appearances, but he 
also holds, and brings forward very strong proof in support 
of his position, that there are limits to the influence which 
can be exerted on the cells of a species, and that different 
species exhibit very different characteristics when placed 
under similar conditions ; thus, for example, Saccharomyces 

rhotomicrograph of Saccharomyces Cerevisi*. x 500. Mother cells with small 
buds coming off. Yeast from an Edinburgh Brewery. 

-cerevisiae, when developed in the ordinary manner and then 
grown vigorously for twenty-four hours at a temperature of 
27° C, exhibits the ordinary appearance of rounded or ovoid 
cells with a formation of septa in some cases, and with more 
or less well-developed cells in others ; whilst this same 
organism, when cultivated at 7.5° C, occurs in the form of 
dense colonies with beautiful mycelium-like branchings. 


As Hansen's work is the most recent and most complete that 
has yet been carried out, we may give a short account of 
the species that he describes in his classification as quoted by 
Zopf. He divides the yeasts into three groups : Saccharomyces 
cerevisise, ii-S/t most frequently 8-6/i in diameter, which 
contains a single species only ; Sacch. Pastorianus, 17-2. S/tt 
average diameter S-y/i, in which he describes three species, 
all of them oblong or sausage-shaped ; whilst the third group, 
Sacch. Ellipsoideus, 13-2.51(4 in diameter, the most usual size 
being about 8-7/t, in which most of the cells are oval or 
rounded. These forms so overlap one another that by 
mere microscopic examination it is impossible to determine 
whether we are dealing with absolutely pure cultures or not. 

Hansen's researches were carried on practically, and on a 
most extensive scale, in connection with a large brewing 
industry at Old Carlsberg in Copenhagen, and he very 
naturally turned his attention to the classification of beer 
yeasts for the purpose of obtaining pure and healthy yeasts 
for the production of beer. 

Taking up the subject where Pasteur nad left off he, 
however, again went over some of the old ground, and 
studied the various yeasts with the greatest care ; cultivated 
them in all kinds of media, noted their behaviour under 
different conditions as regards temperature, moisture, presence 
or absence of oxygen and the like ; and as the result of 
prolonged and ingenious experimental work he was able to 
dispel much of the inaccuracy that had grown up around the 
subject, and to give detailed accounts of the life histories of 
the saccharomyces. He found that the older observers had 
not understood the conditions under which spore formation 
occurs ; that it was not possible, as Reess had stated, to classify 
the saccharomyce by a mere microscopic examination, in 
which the characters relied upon were necessarily merely the 
form and size of the cells and spores. He also pointed out 
that even Reess' observations on the conditions under which 
spores were formed were not to be relied upon. That they 
were not the result of the yeast being attacked by mould 
fungi or bacteria, as Reess and Van Tieghem had maintained, 
both of whom believed that spores were evidence of disease 
in the yeast-cells, he was soon convinced. Nor could he 
believe that Wiesner and Brefeld, who made very careful 
study of yeasts, without, however, enjoying the advantages of 


methods for obtaining pure cultivations, were right. These 
observers had ascribed to certain forms of yeasts the power 
of forming spores ; whilst in others the same power was 
denied, Wiesner holding that spores could not develop from 
pressed yeast, although the^ could from beer yeast, and 
Brefeld maintaining that cultivated yeast had lost its power 
of forming spores, whilst the wild yeast still retained this 
faculty. To evolve some kind of order from this confusion 
was the task that Hansen set himself ; he wished to determine 
the conditions under which ascospores could be formed. 

For this purpose he used the method of complete aeration that is obtained 
by the use of Engel's gypsum blocks. To well-baked plaster of Paris add 
distilled water until the plaster is nearly liquid ; pour this on to a sterilized 
glass plate, on which rests a small mould of thin metal or paper, made rather 
less than the vessel in which the experiment is to be carried on. These 
blocks are first thoroughly sterilized by means of heat, after which a small 
particle of yeast is placed on the upper surface of one of them, an air 
chamber is sterilized, and in this a small vessel containing water, in 
which the block rests, is kept. The whole vessel may be placed in an 
incubator if any special temperature is required, or it may be left at the 
ordinary temperature of the room. 

He found that the following conditicwis were necessary for 
the perfect formation of spores : a plentiful supply of air 
(oxygen) and moisture ; a certain temperature — the most 
suitable for the six forms that he examined being about 25° 
C. ; a young condition of the protoplasm of the yeast-cells, 
the older cells with their thickened walls appearing seldom, 
if ever, to give rise to spores. As regards temperature, he 
found that the extremes, at which the individuals of the 
different species grow, vary somewhat, the lowest tempera- 
ture at which they are developed being from .5° to 3° C. ; 
whilst at the other extreme he found that they could still 
grow at a temperature of 37.5° C He found that spores 
became visible as irregular bodies formed from the cell 
contents in a period of about thirty hours from the com- 
mencement of the sowing of the yeast-cells when the 
temperature was kept near the higher extreme, or as low 
down as 25° C. ; but working with lower temperatures, 
differences occur in the different species, though in none of 
them does the development of spores take place so rapidly 
as at the higher temperatures ; for example, he found that at 
11.5° C. the Saccharomyces cerevisise does not form spores 
until a period of ten days has elapsed ; whilst, on the other 


hand, Saccharomyces Pastorianus II., kept under exactly the 
same conditions, gives evidence of the commencement of 
spore formation after seventy-seven hours ; i.e.^ supposing that 
the previous conditions have been the same for the species 
experimented upon. 

This single observation proved to be of enormous impor- 
tance to brewers, for Hansen's pupils, Holm and Poulsen, 
determined that it was possible by Hansen's method to show 
that pure cultivated yeasts produced spores at a much later 
date — under similar conditions — than did those saccha- 
romyces that were capable of producing certain diseases in 
beer when present in proportions of -^th of the yeasts intro- 
duced ; and as it was found possible to determine by this 
method the presence of wild yeasts when they occurred in 
the proportion of aroth of the whole of the yeast used, it was 
an easy matter to determine within a very short time whether 
a yeast was fit to be used for brewing purposes or not ; in the 
case in point, forty hours at the temperature of 25° C. was 
sufficient for the purpose. It was found, indeed, that all 
the bottom yeasts might be separated from one another by 
making cultivations at a temperature of 15° C. and at 
25° C. 

Having obtained these pure cultivations, and being so 
successful with the study of the spores, Hansen turned his 
attention to the other characters, by the use of which he was 
able to separate in a still more definite manner the various 
species of saccharomyces one from another. He subjected 
to a most careful examination the films which appeared on 
the surface of liquids that were undergoing fermentation. 
It had been supposed that the Sacch. mycoderma was the 
result of a yeast fermentation ; but Hansen found that the 
saccharomyces film was something quite different from the 
film formed by the Sacch. mycoderma, and he came to the 
conclusion that film formation must be looked upon as a 
phenomenon that may be met with under certain conditions 
wherever micro-organisms are or have been growing. Here 
again the presence of a plentiful supply of air is an absolute 
necessity ; another essential condition is a state of perfect 
rest of the surface of the fluid in which the process of yeast 
growth and fermentation is going on. It is interesting to note 
that when carbonic acid gas is passed through the fluid and is 
allowed to. accumulate on the surface these films are not formed, 


io that in fermenting tanks in which, of course, large quantities 
5f carbonic acid gas accumulate the films are not usually met 
^ith. From this one may gather how laboratory experiments 
nay go wrong, or give untranslatable results, when the exact 
;onditions met with in nature, or on a large scale, are not 
idhered to ; it also explains the difiFerent results that 
lave been obtained by various workers, the conditions in 
:heir experiments not always being the same. For instance, 
n Chamberland or ordinary flasks covered with filter paper 
he film forms will develop rapidly as soon as the primary 
ermentation is completed ; whilst in the closed Pasteur 
lasks, in which the air cannot be changed rapidly, the 
ilms grow comparatively slowly. 

To produce these films Hansen proceeded as follows : 
laving obtained his pure cultivations, drop cultures were 
nade into car.efully sterilized four-ounce flasks, half filled with 
terilized wort and protected from falling particles by being 
:overed with sterilized filter paper. As soon as the films be- 
:ame apparent to the naked eye they were examined. They 
ippear, according to Hansen, as small opaque points, which 
Gradually increase in size and then run together, forming 
rregular patches floating on the upper surface, with a con- 
vexity on the side resting on the fluid. The film at length 
)verspreads the whole surface and becomes adherent to the 
vail of the flask at the margins ; on shaking the flasks much 
)f the film can be made to sink, but a new one forms to fill 
ip the gaps that are left. 

These young films he divided into two groups, the first 
onsisting of Sacch. cerevisiae, Sacch. Pastorianus II., Sacch. 
llipsoideus II., in none of which could he find mycelium-like 
olonies (at one time it seemed that Hansen's researches had 
iemonstrated this fact) ; whilst in the second group, which 
ncluded Sacch. Pastorianus I. and III. and Sacch. ellipsoideus 
., such mycelial colonies were early developed. Later 
esearches have tended to show that this division is very 
nuch a matter of time, and that it cannot now be looked 
ipon as having any real scientific value. 

As regards the temperature at which these films are 
leveloped Sacch. cerevisiae and Sacch. ellipsoideus I. are 
ieveloped between 38° and 6° C, the three Pastorianus 
'arieties between 34° and 3° C. ; Sacch. ellipsoideus II., 38° 
o 40° C, and 3° C. The film of this latter appears to be the 


most vigorous at all temperatures, at 13° C. it develops so 
quickly and vigorously that it out-distances all the others, 
giving at 23° C. a film covering the whole of the surface in from 
six to twelve days ; whilst the others at the same tempera- 
ture only gave a much more delicate film in from three to 
five weeks. The next to this as regards rapidity of the forma- 
tion of the film is Sacch. Pastorianus III., which at the 
temperature of a warm room forms a film much more rapidly 
than any except Sacch. ellipsoideus II. 

It may be noted, in connection with the limits of tempera- 
ture at which this film formation takes place in the three 
Pastorian varieties, that they cease to develop and form 
spores at a temperature of 36° to 38° C, if this be con- 
tinued for ten or eleven days ; whilst the other three species 
all continue to grow for a much longer period. 

In addition to the forms studied by Hansen others may 
be mentioned. Below is appended a short classification of 
the more important forms of yeasts, with some of their more 
characteristic features. 

The Saccharomycetes or yeast fungi are a family of 
ascomycetes, divided into two very unequal groups — the 
Saccharomycesof Reessand the Monaspores of Metschnikoif ; 
the mode of spore formation is somewhat similar in the 
two, the only difference being that in the saccharomyces the 
spores are rounded and are sometimes multiple in the same 
sporangium, whilst in monaspora there is in each cell a 
single needle-shaped spore developed. In the first genus are 
included the following forms : 

I. Saccharomyces cerevtstce, may be looked upon as a 
typical English high yeast, some of the characteristics 
of which have already been described. It grows as rounded 
or slightly ellipsoidal cells, which give off small cells by 
budding ; in the earlier stages of film formation there are 
formed delicate mycelial-like threads, but as the film becomes 
older longer and more regular threads are formed. In the 
yeast-cells nuclei are frequently to be made out, especially on 
being stained with osmic acid or hsematoxyline. These nuclei 
are very distinctly seen in old cultivations. 

The development of ascospores takes place most rapidly (after twenty hours) 
at 30°C., most slowly (after ten days) at from 11° to 12° C, and stops alto- 
gether below this. The spores may be very distinctly seen, as they are highly 
refractile, and their walls are well defined. They are usually from 2. 5 to 6;« 


n diameter. Film formation takes place most rapidly (seven to ten days) 
t a temperature of from 20° to 22°, most slowly (two to three months) at 
°to 7°C., and ceases altogether at 38° C. , andat5°C., at the other extreme, 
ietween 20° and 30° C, the cells are frequently sausage-like and irregular ; 
rom 6° to 15° C. the cells. are usually like the parent cells in younger 
ultivations, but in older cultivations the forms are like those already 

This species, like all those investigated by Hansen, secretes 
. peculiar substance, which, acting on saccharose or crude 
ane sugar, inverts it to " invert " sugar ; the yeast then brings 
.bout the fermentation of this latter substance, and also of 
lextrose and maltose, giving rise to the formation of alcohol 
.nd carbonic acid gas, with an evolution of heat and great 
nultiplication of the yeast-cells. It does not seem to exert 
.ny action on lactose or milk sugar. In this respect these 
erments resemble mucor racemosus, which first brings about 
he inversion of cane-sugar ; it also secretes invertase, which 
lauses inversion of saccharose, the products of which it 
erments ; it also sets up a weak fermentation in beer wort 
if the maltose and dextrose present in that liquor. 

Reess' genus of Saccharomyces ellipsoideus Hansen divides 
nto two — I. and II. 

2. Saccharomyces ellipsoideus I. is really a " wild " species 
if wine ferment ; in beer wort it grows as a low yeast. It is 
isually rounded or ellipsoidal in shape, though it sometimes 
issumes the sausage form. The spores, of which two to four 
.re usually found in a single ascus, are from 2 to 4^ in 

These spores develop most rapidly (in twenty-one hours) at 25° C, most 
lowly (eleven days) at 7.5° C, and are not formed at all at 32.S°C. at the 
ne extreme, and at 4° C. at the other. Grown on the surface of beer wort 
elatine, its colonies form a peculiar net-work along the line of the inocula- 
ion streak. The surface membrane is fonned rapidly (eight to twelve 
ays) at a temperature of from 33° to 34° C, most slowly (sixty to ninety 
ays) at 6° to 7° C. ; it is always a delicate membrane, and cannot be grown 
t 5° C. on the one hand and at 38° C. on the other. 

The most characteristic growth takes place at from 13° to 
5° C, when it occurs as a complicated branching mass, 
dth elongated cells, or threads, arranged in rows, with 
everal lateral processes coming off at the points of junction, 
lecondary branches are formed at the constrictions of the 
•rimary branches. 

It appears to exert as powerful and rapid a fermenta- 


tion process as does the Saccharomyces cerevisiae on the 
various carbo-hydrates on which that ferment acts. 

3. Saccharomyces ellipsoideus II. is also a " wild " or wine 
fermentation yeast which gives rise to the muddiness of beer. 

It is essentially a low yeast, the film that forms is exceedingly 
delicate ; it makes its appearance in from three to four days &i a tempera- 
ture of 33° to 34° C, but not for five or six months at 3° to 5^C. At 
2° and at 40° C. no film forms. Young cultivations at 15 C. are 
usually somewhat rounded or egg-shaped, whilst the older cultures show 
longer mycelial rods, with forked transverse shoots given off at the joints. 
Asci containing from two to four spores may be egg-shaped, slightly 
irregular or elongated. The spores measure from 2 to Sft m diameter ; 
they are developed most rapidly at 29° C, most slowly at 8° C, and are 
not formed at above 35° or below 4° C. 

Hansen does not look upon Saccharomyces Pastorianus as 
a pure species ; he divides it into three. 

4. The first of these, Sacch. Pastorianus I. (Hansen), is a 
wild yeast, spores of which frequently occur in the atmosphere 
of breweries. It gives an unpleasant bitter taste to beer ; it, 
also, is a bottom ferment, occurring as elongated ellipsoidal 
or pear-shaped cells, from which small apical or lateral 
branches may be given off. 

The asci are usually elongated or rounded; they may contain two 
spores or multiples of two, up to eight or even more. The spores vary 
very much in size from 1.5 up to 5;*; are developed most readily 
(twenty-four hours) at a temperature of 27.5° C. ; most slowly (fourteen 
days) at a temperature of 3° to 4° C. The spore formation ceases at .5° C, 
and at 31.5° C. The films are usually very delicate, are developed most 
readily (seven to ten days) at from 26° to 28° C, most slowly (five to^six 
months) at from 3° to 5° C. , development ceases altogether at 34° and 2° C. 
At from 3° C. to 15° C. mycelial-like threads are developed pretty freely in 
this film and most irregular forms make their appearance ; many irregular 
club and skittle-shaped and other forms are formed in the older films, but 
fewer in the younger ones ; in these films the cells are usually smaller. 

5. Saccharomyces Pastorianus II. (Hansen) was also 
separated from the air of the brewery. In gelatine made 
with yeast water it grows along the line of the inoculation 
streak (at 15° C. at the end of sixteen days) in the form of 
colonies with smooth edges. It is a feeble top fermentation 
yeast when grown in beer wort. 

The sedimentary cells of this yeast are mostly elongated, but they may 
be slightly rounded, varying considerably in size. The cells found in the film 
are rounded, egg-shaped, or somewhat elongated. The spores are from 2 
to 5n in diameter ; the asci are usually elongated and the spores occur in 
multiples of two. They are formed most rapidly (twenty-seven hours) 



at a temperature of 23° C, most slowly (seventeen days) at 3° to 4° C, 
and cease to be formed at 29° C. and at .5° C. 

This yeast gives rise to neither cloudiness nor to any 
unpleasant bitter taste. It secretes an invertase and causes 
fermentation of all the carbo-hydrates that are fermented by 
the other yeasts of this group. In old cultures of the films 
the cells are small, very irregular in shape, and thread-like, 
like the preceding. 

6. Saccharomyces Pastorianus III. (Hansen) is, according 
to Hansen, one of the causes of turbidity in beer. Grown on 
yeast water gelatine at a temperature of 15° C, at the end of 
sixteen days the colonies present peculiarly fringed edges ; 
grown in wort it gives rise to a top fermentation, and causes 
considerable turbidity with a production of alcohol and 
carbonic acid gas. 

The spore formation is very much hke that in the preceding species ; it takes 
place most rapidly (twenty-eight hours) at 25° C, most slowly (nine days) 
at 8.5° C, and ceases at 29° and at 4° C. The film appears in the form of 
small flakes most rapidly (seven to ten days) at 26° to 28° C, most slowly 
(five to six months) at 3° to S°, and ceases altogether at 34° and 2°. Here 
again the elongated or sausage form predominates, but large and small 
rounded and oval cells are also present in the sedimentary forms in the 
films at from 20° to 28° C. The cells are of much the same shape as are those 
of the sedimentary yeast, but at a temperature of from 15° down to 3° C. 
there are elongated mycelial-like threads which in old cultures become still 
more characteristic. These mycelial-like threads are developed at the 
above temperature, which is much lower than in the case of the threads in 
Saccharomyces Pastorianus I., where they are most characteristic at a 
temperature of 13° to 15° C. At the same temperature, 15° to 3° C, the 
cells in Saccharomyces Pastorianus II. are oval and rounded. 

Hansen describes in less detail a number of other ferments 
which produce alcohol from sugar. 

7. Saccharomyces Ludwtgtt, though found in the sap of 
oaks, grows freely in yeast water, when it appears as a peculiar 
caseous mass or as fungus-like specks which float in the 
fluid. One great peculiarity of this form is that it may be 
so modified by cultivating it in- beer wort through several 
generations at a temperature of 25° C. that it does not form 
spores, or that it forms them but slowly. The spores, 
when formed, are usually from one to four in number, but 
there may be more ; the cells of the film are usually con- 
siderably elongated. The film formation goes on most 
rapidly at about 25° C. ; at the ordinary temperature of 


the room it goes on very slowly, taking a whole month to 
form a comparatively delicate membrane. In very old 
cultures well-marked mycelium formation may be met with 
in which the cells are ellipsoidal, elongated, or sausage- 
shaped, or somewhat club-shaped. It is capable of acting 
on grape sugar ; it inverts cane sugar and ferments it ; but 
has no action on maltose, lactose, or dextrine in yeast water, 
nor does it attack starch. 

8. Saccharomyces Marxtanus, named after its describer, 
was first found in wine. Hansen studied it most closely. 
He found that in beer it develops as small ellipsoidal 
and egg-shaped cells, with here and there sausage-shaped 
cells, which are often combined into colonies. There 
are developed on a quiescent fluid small viscid masses, some 
of which remain on the surface whilst others sink to the 
bottom. The film develops exceedingly slowly, but in it 
are found cells which resemble very closely those of the films 
of the first six species of Saccharomyces described. The 
true film contains oval and short sausage-shaped cells. 
The spores are not freely developed. When it is grown on 
solid nutrient media spores are more frequently formed, in 
which case they are usually oval or kidney-shaped. In beer 
wort this yeast is not very active, nor is it able to ferment mal- 
tose, but it acts vigorously on saccharose, inverting it and then 
fermenting it with great activity ; it also acts upon dextrose. 

9. Saccharomyces extguus, found by Hansen in German 
yeast, differs from the preceding saccharomyces in the fact 
that it forms no mycelial threads on beer wort, or on solid 
nutrient media. It forms spores, but sparsely, and the film 
is exceedingly delicate, the cells of which this is made up 
being short rod-shaped or ovoid. It acts on the sugars exactly 
as does the Saccharomyces Marxianus. 

10. A somewhat peculiar saccharomyces belonging to this 
group is the Saccharomyces memhrancefaciens^ which forms 
on beer wort a bright yellow tough scum, composed of long 
and sausage-like cells, which may be closely packed together 
or may occur singly. It forms spores rapidly, liquefies nutrient 
gelatine, and is peculiar from the fact that it does not cause 
fermentation of any of the ordinary carbo-hydrates, nor has 
it any effect in inverting cane sugar. 

11. Saccharomyces minor (Engel), who describes it as 
spherical cells 6/* in diameter, arranged in chains of 6-9 


elements. The spore-forming cells are larger 7-8. 5/j, and 
contain from 2-4 spores 3.5/n in diameter. He ascribes to 
this ferment the action of fermentation in bread, a notion 
that has since been scouted and again accepted. 

12. Saccharomyces conglomeratus (Reess), Hansen thinks 
is simply a form that may be met with in old films of all- the 
six species that he specially investigated, and in recent works 
this species has been dropped. 

13. Saccharomyces aptculatus, described by Reess, can 
scarcely be said to be a true saccharomyces, although 
it is included amongst them by Zopf as a doubtfiil 
member of the group ; it has not yet been ascertained 
to have any spore formation, and is therefore retained by 
Hansen in this group only provisionally. It occurs in fer- 
mented wine and spontaneously fermented beer, and, in the 
hot seasons, on sweet succulent fruits, such as cherries, goose- 
berries, plums, or grapes ; whilst in the winter it is found in 
the soil beneath the trees that bear these summer fruits. It 
occurs in cultivation fluids as lemon-shaped cells — ^hence the 
name — though under certain conditions it assumes elongated, 
crescent-shaped, and rod-shaped forms. It gives off buds of 
two kinds : one oval, the other lemon-shaped. It is a bottom 
yeast giving rise to a feeble alcoholic fermentation ; it does 
not invert cane sugar, but acts on dextrose in yeast water, 
but does not ferment it completely. Mixed with Saccharo- 
myces cerivisiae it retards the action of the latter. 

An organism that was long classified with the true yeasts 
is the Rosahefe or Pink yeast of the Germans. Accord- 
ing to Hansen, however, no spores are formed during any 
phase of its development and for the present he excludes it 
from the Saccharomyces or true yeasts. It belongs rather to 
the Torulae. 

Genus II. (i) Monospora (MetschnikoflF). The single mem- 
ber of this group, Monospora cusptdata, is of interest princi- 
pally because of the elaborate researches that have been made 
by Metschnikoif on its relation to a pecuhar disease of the 
Daphnia, a small fresh-water crustacean. It occurs as a bud- 
ding mycelial thread made up of elongated cells which before 
spore formation become elongated ; there then appears a long, 
thin needle-like body situated in the centre of the cell in its 
long axis. This spore is taken into the alimentary canal of 
the Daphnia, whence it is driven through the walls by the 


peristaltic action of the muscles of the intestine. It thus 
passes into the body cavity or into other tissues, where it 
is immediately attacked by the white blood corpuscles, or 
by the connective tissue corpuscles ; or it may first become 
developed into the rod-shaped vegetative form. When it 
has- once commenced to divide it is no longer attacked by the 
above cells (which Metschnikoff speaks of as the phagocytes) of 
the insect. If the Daphnia is in moderately good health the 

Photomicrograph of Rosahefe. x looo. Rose-coloured yeast (?) No spores 
have been found, and Hansen does not classify it with the yeasts. 

monospora is gradually overcome, but if the insect is feeble, 
or if the monospora is ingested in very large quantities, it 
multiplies so rapidly that the animal may eventually succumb 
to its attacks. This form is specially interesting from the 
fact that it afforded some of the strongest proofs of Metschni- 
koff's phagocyte theory that he was able to obtain. 

We have already seen that the yeast-cell is usually 
observed in a fermenting liquid as a rounded or ovoid body. 



that it gives rise to buds by sending out small processes from 
its wall, and that these latter then become detached from the 
mother cell. This cell consists of a distinct membrane and 
of protoplasm, the former of which may be thicker or thinner 
according to the age of the cell, whilst the latter may vary 
very considerably. Whilst the cell is merely growing actively, 
the plasma or cell contents are homogeneous and highly re- 
fractile, but when it is placed in beer wort or other highly 
nutritive media, it multiplies rapidly and gives rise to the 
fermentation of the sugar and maltose, and the protoplasm 
becomes differentiated and undergoes certain changes. Large 
clear spaces, which are supposed to contain the more fluid 
■part of the protoplasm (vacuoles), are formed ; cloudy 
granular change occurs in the other protoplasm ; and larger 
fat globules also make their appearance. As the cell gets 
older, and consequently less active, the finely granular proto- 
plasm accumulates as a thin layer inside the cell wall, whilst 
the centre is occupied by clear fluid, in which are floating a 
number of fatty granules and globules. 

It would appear that this last is a somewhat degenerated 
condition, and that it is due to imperfect nutrition, for if a 
few of these cells are transferred to a fresh rich nutrient 
medium, the protoplasm becomes again modified, the cloudy 
granules disappear, small shoots of the clear plasma pass into 
the large central cavity, small rounded vacuoles are formed 
in place of this large central cavity ; these in turn become 
subdivided, and eventually the whole cell is again occupied 
by clear protoplasm. By appropriate staining, especially of 
an older cell, a nucleus may be distinguished, whilst under 
certain conditions, to be afterwards mentioned, spores or 
ascospores are formed. 

Other organisms which in certain respects resemble the 
yeast fungi are the Torulae, which Pasteur described as being 
somewhat of the nature of yeasts, but different in the fact 
that they were unable to give rise to such marked alcoholic 
fermentation. Hansen, however, was able to show that this 
was not a suflSciently distinct characteristic, as some of the 
saccharomyces give rise to the formation of little or no 
alcohol, whilst, on the other hand, some of the Torulas set 
up very marked alcoholic fermentation. The great point 
of distinction is, that none of the Torulae, so far as has 
yet been observed, are capable of producing endospores ; all 



of them multiplying by budding, some of them also giving 
rise to the formation of mycelia. It is of course quite possible 
that such a classification may not hold good, as it has been 
suggested that some of the torulse could not be definitely 
brought within it, as far as non-sporulation is concerned. 
Hansen describes seven species varying in size from i-S to 
8/i ; some invert cane sugar ; some give rise to scarcely 
a trace of alcohol, whilst others produce as much as 6.2 per 
cent, of alcohol. They occur as spherical or elongated cells, 
and cannot be distinguished by the microscope alone from 
the round cells of the different species of saccharomyces. 
As a group they have not much action on maltose, and only 
some of them affect dextrose. 


Fermentation {^continued). 

Soluble Constituents of Yeast — Action of these upon Sugar— Conversion of 
Glycogen in the Liver and other tissues— Growth of Yeast-Cellsin Organic 
and Inorganic Fluids — Fermentation of Fruit Juice — JEtohKc and Anae- 
robic Fermentations — Effect of Free Oxygen on Yeast-Cells — Fermen- 
tation not necessarily equal toGrowth of Yeast — Enzyme or Unorganized 
Ferment a Secondary Function — Function depends partly on Organism, 
partly on Medium in which it is Growing — Peptonizing Function 
usually requires presence of Oxygen — ^Various kinds of Fermentation : 
Lactic, Urea, Butyric, Ammoniacal, Acetic — Formation of Fatty 
Acids — Mycoderma Aceti— General Processes of Fermentation — 
Hoppe-Seyler's Classification. 

On approaching the subject of fermentation by yeast we find 
at the very outset that Pasteur and others had noticed a 
very remarkable pecuUarity of the water in which yeast had 
been mixed, and from which it had again been separated. 

It was observed that a certain substance, perfectly soluble in 
water but precipitable by alcohol, had the peculiar property 
of inverting saccharose into equal quantities of dextrose and 
laevulose, and it was at once assumed that this invertin, 
invertase, or some similar substance, produced through the 
vital activity of the yeast-cells, was necessary to bring about 
conversion of starch into sugar (diastase), or of saccharose into 
invert sugar (invertin), before the cells could bring about a true 
fermentation, or splitting up and hydration into alcohol 
and carbonic acid gas, with certain other products to be 
mentioned immediately. It was noticed by Bertholot and 
Hoppe-Seyler, moreover, that, even if the living organisms 
were first killed by the addition of ether, the invertase or 
invertin still continued to act, and was able to invert a 
quantity of saccharose altogether out of proportion to the 
amount of inverting material present. In consequence of 
the latter part of this observation, many physiologists and 
chemists maintain that the action of the invertin is essenti- 
ally due to the setting up of a certain rate and length of 


molecular vibration, such wave rate and length being trans- 
mitted through the whole body of material to be inverted. 
In fact, that the addition of the invertin is simply the light- 
ing of the spark that fires the whole train. There is some- 
thing very fascinating in this theory, and it certainly explains 
many, otherwise, obscure chemico-physical questions con- 
nected with these two subjects — inversion and fermentation. 
We see- at any rate that part of the process takes place 
entirely outside the yeast-cells, and may go on even when the 
organisms that produce the inverting material have been killed 
or completely removed. There are other similar examples 
of conversion by purely chemical means, as, for instance, 
where, on the addition of a dilute acid, such as sulphuric 
acid at a certain temperature, starch is converted into glucose, 
the heat and the acid setting up such molecular vibration 
amongst the molecules composing starch, that in the dilute 
acid there is a rearrangement of molecules, water is taken up, 
and by hydration of the starch glucose is produced. In 
this case the conversion takes place much more rapidly and 
completely at a temperature of 130° C. thaii at 100° C. 

In a similar manner glycogen may be converted into 
a sugar that will reduce Fehling's solution. This process 
goes on in the liver and other organs and tissues of man and 
animals, in which, probably, the secretions of the cells take 
the place of the sulphuric acid and the high temperatune, 
or of the protoplasm of yeast and other vegetable cells. 
Let us now, however, see what relation the yeast-cells 
themselves (as apart from their products) are supposed to 
bear to the real process of fermentation. If it were possible 
to obtain an absolutely pure solution of sugar, ?>., a solution 
containing no nitrogenous elements of any kind, and if we' 
were to place in this a minute quantity of yeast, we should 
find that a very slight fermentation might take place — i.e., 
there would be an almost inappreciable diminution in the 
quantity of sugar present ; a small quantity of alcohol and 
carbonic acid gas would be developed, but very shortly the 
process would stop, and there would be no marked increase 
in the number of yeast-cells found in the whole solution. If 
now we were to add a small quantity of nitrogen in the form 
of an albuminoid substance and a certain quantity of ex- 
tractives and salts, such as are, found in the ashes of burnt 
yeast, there would very quickly be observed a very different. 


State of matters ; first there would be very marked turbidity 
of the fluid. If we were using a high yeast this turbidity 
would rapidly become more and more marked, and there 
would rise to the surface a yellow scum ; bubbles of car- 
bonic acid gas would be seen rising in the liquid, and a 
spirituous or alcoholic taste would soon become pronounced. 
If from the first fluid, i.e., the fluid in which there was 
jiothing but pure sugar, we were to examine the very 
minute quantity of yeast, we should find that, although 
■there was apparently an attempt at budding in a few of the 
cells, in most cases there are a series of clear globules with- 
in the yeast-cells, that there is a very large proportion of thick 
walled granular cells (which have certain other peculiarities), 
that, in fact, throughout the whole we have evidence of very 
little proliferative activity, andthat young, vigorous, healthy, 
yeast-cells, budding and giving rise to other cells by vegeta- 
tive activity, are conspicuous by their absence. A micro- 
scopic examination, in the case of the yeast growing in the 
sugar solution containing a small quantity of albuminoid 
material and extractives, reveals a very different state of 
matters ; here the yeast-cells are in a state of extraordinary 
activity, buds are being thrown off from the extremities, 
terminally or laterally, the protoplasm is evidently exceedingly 
active, vacuolation is conspicuous by its absence, except in 
certain cells, and we are at once struck by the extraordinarily 
large proportion of young vigorous cells — the more active the 
process the greater the number of the new cells, and the 
larger the quantity of yeast formed. In one case the 
yeast-cells die of starvation, although large quantities of 
sugar are present ; and as the yeast-cells have not been 
able to grow and reproduce by the exertion of their vege- 
tative activity, they have not been able to resolve the 
sugar into alcohol and carbonic acid ; badly nourished or 
dead yeast-cells, therefore, exert little or no influence in 
bringing about an alcoholic fermentation. In the other case 
the cells have supplied to them all the elements necessary 
for the nutrition of their protoplasm. The carbon, the 
hydrogen, and the water, may all be obtained from the sugar 
solution, albuminoid material of course supplies the requisite 
nitrogen, whilst the ash of yeast, which has been added, con- 
tains all the other elements necessary for the nutrition of 
the yeast-cells. 


Under these conditions, the cells, as we have seen, may 
undergo rapid development, growth, and multiplication, and 
we have an increase in the amount of yeast, and at the same 
time in the amount of alcohol and carbonic acid gas gene- 
rated. These two experiments afford most exact evidence 
that Liebig's theory was essentially incorrect, and that 
Pasteur's theory that true fermentation was the result of the 
action of the living protoplasm, gives us the key to the whole 

It was, naturally enough, objected that as the fermen- 
tation process could not go on except in the presence of an 
albuminoid material, this might really be the cause of the 
whole process, and many most elaborate experiments were 
brought forward to prove that it was this organized but 
dead material that was the real and primary factor in the 

Pasteur, however, equal to the occasion, was able to 
demonstrate in a most convincing manner, that the nitrogen 
might be supplied to the organism in the form of inorganic 
salts, instead of being presented as albuminoid material. 
He utilized for his purposes a mixture containing 1 50 c.c. of a 
10 per cent, solution of sugar candy, .5 grammes of the ash 
of yeast, .2 grammes of bitartaric of ammonia, and .2 
grammes of sulphate of ammonia. He found, on introducing 
Saccharomyces Pastorianus into this solution, that a some- 
what slow but very complete transformation of the sugar 
took place, and that the nitrogen from the ammonia was used 
up by the growing yeast-cells, which at the same time 
increased enormously in number. It was thus evident that 
these mineral salts could take the place, in fermentable liquids, 
of " media of natural composition." He found, however, that 
the process went on more slowly, that somewhat peculiar 
forms of yeast showed themselves, and that an essential factor 
for the success of the experiment was that no other organisms 
should be allowed to make their way into the fermenting 
solutions — i.e., the absolute purity of the various materials of 
which the nutrient solution was composed, and of the ferment 
itself, must be guaranteed, and any relaxation of the strict 
conditions of extreme purity was invariably followed by an 
interference with the vital manifestations and physiological 
actions of the yeast organisms. 

It would appear, indeed, that although the fermentation 


is, under such conditions, very complete if sufficient time is 
allowed for the process, the yeast-cells experience a certain 
difficulty in wresting the nitrogenous elements from the 
inorganic ammonia salts, and that all other conditions must 
be extremely favourable, in order to allow of their taking up, 
and utilizing for their own use, inorganic nitrogenous material. 
The presence of other organisms, for example, that have a 
stronger affinity for nitrogen in this form, i.e., organisms 
which are better adapted to exist under such conditions, 
and which can, by their vital activity, interfere with the 
growth of the yeast-cells, remove from the sphere of action 
of the yeast-cells material that is absolutely necessary for their 
rapid and perfect morphological and biological development, 
as a result of which fermentation and hydration of the sugar 
do not take place in the ordinary way ; other substances or 
bye products are formed, and the decomposition of the sugar 
is incomplete, or is irregularly carried out. 

What, then, are the conditions necessary for the growth of 
the fermenting organism in a fermentable fluid ? In the pro- 
cess of wine-making it is a well-known fact that the fermenta- 
tion is set up by some organism, which, though present 
either as young cells or as spores on the outside of the grape, 
cannot attack the juice so long as the skin remains 
unbroken — a fact brought out by Davaine at a very early 
stage of his researches. When, however, the grapes are 
plucked, the skins are bruised and the juice is set free, the 
fermenting organism, — the wine yeast or Saccharomyces 
eUipsoideus, or some similar variety — utilizing the grape 
juice, which contains not only sugar but also all the ele- 
mentary constituents necessary for its nutrition, — grows 
vigorously and sets up the vinous fermentation. It is 
a remarkable fact, but one well known to wine pressers and 
fermenters, that for the commencement of this vinous fer- 
mentation there must be an access to free oxygen, or oxygen 
mixed merely mechanically with nitrogen of the air to the 
fluid that has to be fermented, as without this the yeast 
spores and old yeast-cells are utterly unable to develop or to 
give rise to active and vigorous yeast-cells. Pasteur insists 
that we have evidence of the necessity for the presence of 
such free oxygen in the fact that the fermentation of grapes 
takes place much more rapidly and completely when the 
grapes are left attached to the stalks of the bunches, by 


which means there is a freer circulation of air allowed to 
take place through the fermenting mass than when they are 
plucked from the stalks and pressed and fermented. Of 
course, it might be objected that the air is useful merely in 
carrying the yeast cells into contact with the fermentable 
fluid, but numerous experiments have been carried on to 
prove that the presence of oxygen is absolutely necessary 
for the resuscitation of old and spore-bearing yeast-cells. 
This is in itself a most remarkable circumstance, and a very 
significant one when it is borne in mind how very diflferent 
the conditions are under which the later stages of fermenta- 
tion are best carried on. It must be remembered, however, 
that the conditions most favourable for the multiplication 
and production of a sufficient number of active cells are not 
by any means the conditions most favourable for the decom- 
position by the cells of the largest amounts of sugar 

In our large breweries (as is sometimes brought home to us 
only too closely by the reports of the death from suffocation by 
carbonic acid gas, of men who go down into vats to clean them 
out) there is always, as the fermentation process goes on, a very 
great accumulation of carbonic acid gas on the surface of the 
fermenting liquid ; so dense and so deep is this layer that it is 
at once seen how impossible it is for much free oxygen from 
the atmosphere to obtain access to the yeast-cells. Any 
oxygen they utilize for the building up of their protoplasm 
must be derived either from air held in solution in the fer- 
menting liquid (which can only be a very small amount, as 
the boiling of the wort must have driven out a very large 
proportion of such air from the fluid), from the small amount 
of oxygen that can pass through the layer by diffusion, or it 
must be derived from the breaking down of those substances 
rich in oxygen that are contained in the malt solution. 

In the same way in the later stages of wine-making the fer- 
mentation is allowed to go on in large casks ; carbonic acid gas 
here also rises to the surface, fills the cask up to the bung-hole 
and gradually flows over, and, as the carbonic acid gas comes 
in minute bubbles to the surface from all parts of the fluid, it 
can scarcely be imagined that any large amount of free oxygen 
can be left in suspension in the fermenting grape juice ; and 
certainly very little can find its way from without, as the car- 
bonic acid gas is pouring out from the bung hole in such 
considerable quantities. The fermentation at this stage, then. 


is going on very rapidly; there is a growth and multi- 
plication of the yeast-cells, a transformation of the sugar into 
alcohol and carbonic acid gas — all without the presence of free 
oxygen. Pasteur set himself to reconcile these two apparently 
contradictory facts, and as a result of his observations he 
made one of the most important of his discoveries, important 
in its relation to the life history of both fermentative and 
pathogenic organisms ; and specially important because of 
the parts that the aerobic and anaerobic conditions under 
which organisms exist play in determining the growth of these 
organisms and the spread of certain specific infective diseases. 
He found that old cells with thick membranes, even con- 
taining spores, were not able to multiply in media other- 
wise suitable unless oxygen was present ; and that the vigour 
of the rejuvenating process depended to a very great extent 
on the amount of free oxygen that was contained within the 
fermenting fluid. He found, in fact, that with these cells, as 
in the case of fungi and of other animal and vegetable cells, 
a sudden and complete cutting oiF of the supply of free 
oxygen immediately proved fatal to them, so that the cells 
which had been exposed to the air for some time — that is, which 
had acquired an aerobic habit — were rendered inactive by the 
cutting off of the supply of oxygen. Along with this he 
found that the yeast organisms could multiply in liquids 
containing nutrient materials for a considerable length of 
time before there was any appearance of alcohol in the fluid. 
After a time, however, the free oxygen being used up, it 
would naturally be expected that the growth of the yeast-cells 
would also come to an end, but such was not found to be the 
case. The yeast-cells continued to multiply, the oxygen in the 
fluid was used up and replaced by carbonic acid gas, and car- 
bonic-acid gas was found on the surface, cutting off any further 
oxygen supply from without. How was it that these cells 
went on multiplying ? Pasteur answered the question as 
follows : During the gradual elimination of oxygen the yeast- 
cells, having once become vigorous from the presence of a 
good supply of oxygen, and of other nutrient requisites, 
had acquired an activity that they did not before possess ; 
they had at the same time become gradually acclimatized, 
and their protoplasm had become so far altered that, as the 
free oxygen was partially cut off', it was able to wrest from the 
sugar what oxygen it required for the building up of its own 


substance, and as the free supply was more and more cutoff it 
became gradually more able to take what it required from the 
sugar solution — that is, it was gradually acclimatized. In 
reading this if instead of oxygen the word energy be used it 
would appear that we should have a more accurate 
physiological statement. It has already been stated that, in 
the presence of a free supply of oxygen, relatively less alcohol 
is formed than under conditions of anserobiosis ; it appears as 
though the oxidation is too complete ; there is enough oxygen 
to supply not only the wants of the living organism but also 
those open bonds of combination in the various molecules that 
are unsatisfied when the yeast takes for its own use certain 
constituent atoms from these molecules, and as a conse- 
quence very perfect oxidation is brought about and alcohol 
is transformed into carbonic acid gas and water. In the 
anaerobic condition that is brought about when the oxygen 
in the fluid is used up, and as the carbonic acid gas accumu- 
lates on the surface in the flask or in the vat, the vigorous 
yeast-cells are able to separate sufficient oxygen for their own 
use from the sugar, or sugar and water, disturbing the com- 
positions of the fluid, and necessitating further rearrange- 
ment of the remaining molecules ; additional oxygen can- 
not be brought from without to satisfy the vacant bonds, and 
other very definite products are formed. These products are 
comparatively stable even when afterwards exposed to free 
oxygen but not to oxygen in a nascent condition, and we have 
as a result the alcoholic fermentation. Here, in fact, are two 
essentially different metabolic processes at work in the proto- 
plasm of the yeast-cells. When oxygen is freely supplied 
the anabolic or building-up processes predominate, a fact 
evidenced by the rapid division of the yeast-cells under these 
conditions ; whilst, when oxygen is excluded, the catabolic 
or breaking-down processes are in the ascendant, as shown 
by the larger amount of the medium decomposed, accom- 
panied, however, by a slower multiplication of the yeast-cells. 
Summing up, Pasteur says : — 

" This being so, it is evident, we repeat, that to multiply in a fermentable 
medium, quite out of contact with oxygen, the cells of yeasts must be 
•extremely young, full of life and health, and still under the influence of the 
vital activity which they owe to the free oxygen which has served to form 
them and which they have perhaps stored up for a time. When older they 
reproduce themselves Vfith much difficulty when deprived of air, and 


gradually become more languid, and if they do multiply it is in strange and 
monstrous forms. A little older still, they remain absolutely inert in a 
medium deprived of free oxygen. This is not because they are dead ; for in 
general they may be revived in a marvellous manner in the same liquid if it 
has first been aerated before they are sown. ... At this point we must 
observe — for it is a matter of great importance — that in the operations of 
the brewer there is always a time when the yeasts are in this state of 
vigorous youth of which we have been speaking, acquired under the in- 
fluence of free oxygen, since all the worts and all the yeasts of commerce 
are necessarily manipulated in contact with air, and so impregnated more or 
less with oxygen. The yeast immediately seizes upon this gas and acquires 
a state of freshness and activity which permits it to live afterwards out of 
contact with air, and to act as a ferment. Thus, in ordinary brewery prac- 
tice, we find the yeast already formed in abundance even before the earliest 
signs of external fermentation have made their appearance. In this first 
phase of its existence yeast lives chiefly like an ordinary fungus." 

But as soon as the process of fermentation ends, and some- 
times even before the whole of the sugar has been converted, 
the yeast if originally not sufficiently rejuvenated gradually 
loses its power of living by deriving its oxygen from its 
nutrient medium, and the cells revert to their original con- 
dition of senescence. They become dormant, and until again 
supplied with oxygen can bring about no further fermenta- 
tion. It is for this reason that to obtain the best fermenting 
yeasts, cultivations must always be made in the presence of 
free oxygen, and although this was done before Pasteur 
explained the reasons for its necessity, it is now carried on in 
a much more systematic manner. Brewers knew perfectly 
well that they had to clear out their vats from time to time, 
not only to get rid of foreign organisms, but also that they 
might obtain oxidation or more perfect aeration in the early 
stages of the process of fermentation. 

It is very interesting to note that Pasteur, although laying 
such stress on the connection between vital processes in the 
cell and the process of fermentation, at the same time holds a 
very definite opinion that the vegetative activities of the yeast- 
cells are independent of their characters as ferments ; and 
he maintains that the presence of oxygen, although increas- 
ing the activity of the cells as regards their subsequent 
power of setting up a rapid fermentation, may, nevertheless 
during its presence, give rise to weakening of their 
fermenting action. He says : — 

" Free oxygen imparts to the yeast an increasing vital activity, but at the 
same time qud oxygen, impairs rapidly its power as yeast inasmuch as under 


this condition yeast approaches the state in which it can carry on its vital 
process after the manner of an ordinary fungus ; the mode of life, i.e., in 
which the ratio between the weight of sugar decomposed, and the weight of 
the new cells produced, will be the same as holds generally among organ- 
isms which are not ferments. In short, varying the form of expression a 
little, it may be concluded, from the sum total of observed facts, that the yeast 
which lives in the presence of oxygen, and can assimilate as much of that 
gas as is necessary for its perfect nutrition, ceases to be a ferment at all. 
Nevertheless, yeast formed under these conditions, and subsequently brought 
into the presence of sugar, away from the infiuence of air, would decom- 
pose more in a given time than in any other series of conditions unfler. 
which it could be placed. The reason is, that yeast which has formed in 
contact with air, having the maximum of free oxygen that it can assimilate, 
13 fresher and possessed of greater vitality than that which has been formed 
without air or with an insufficiency of air." 

In other words, when the ordinary respiratory power which 
it has in common with the fungi is reduced to its lowest 
point, after the protoplasm of the cell has been thoroughly 
rejuvenated, its fermentive power in the absence of oxygen 
reaches its maximum. 

It is thus evident that the processes which go on in fermen- 
tation are similar in kind to those chemical metamorphoses 
that are constantly being brought about in the animal and 
vegetable organisms ; the only difference being, first, in the 
nature of the material that is broken up ; second, in the 
nature of the cells that bring about the metamorphoses ; and 
third, in the exact nature of the ultimate products of the 
various processes ; the difference in all cases being not so 
much in kind as in degree. As to the exact nature of the 
process, there is much difference of opinion, some authorities 
holding that it is necessary for the whole of the sugar which 
is altered by the living cell of beer-yeast to penetrate or 
pass, by a process of endosmosis, through the membranous 
envelope of the cell and become an integral part of the 
cell protoplasm, and that, unless this takes place, the 
resolution of sugar into alcohol, glycerine, carbonic acid 
gas, succinic acid, &c., cannot take place. It is necessary, 
in fact, that the whole of the sugar should be, as it 
were, digested by the yeast-cells, and combined in great 
part into protoplasm before it can be converted into the 
various substances above mentioned, which are, on this 
assumption, merely the excretory products of the vegetable 
cells feeding on a definite kind of nutrient material. We 
have seen, however, that the cells of yeast secrete a definite 


substance, invertin, which has the power of materially 
altering the carbo-hydrates to which it is added, and from 
our knowledge of the functions of other cells we should be 
led to expect that these cells may exert some influence on the 
fermenting fluid without the whole of the sugar actually be- 
coming part of the cell ; or perhaps that, on the other 
hand, the protoplasm may set up such molecular motion in 
its immediate neighbourhood, especially at certain tempera- 
tures, that a certain area of the sugar present is so acted 
upon that some of its molecules are set free for the use of 
the yeast-cell, and that the others can only rearrange them- 
selves in a definite manner ; and that, as a result, we have 
hydration and the formation of alcohol, carbonic acid gas, 
and water, the most stable elements that can be formed 
under the existing conditions, and out of the molecules of 
oxygen, hydrogen, and carbon that are available. There 
may be slight modifications giving rise to the formation of 
succinic acid or other bye products, as a greater or less 
number of accidental or superfluous molecules are set free 
to become converted into the superfluous or additional 

It is a well-known fact, that when yeast is placed under 
conditions of moisture and warmth suitable for its develop- 
ment, if there be suflScient nutriment present, but sugar 
be withheld, or even if nitrogenous elements be kept from 
from it, it becomes soft, and certain marked changes go on in 
the substance of the cell. 

Bechamp found under such conditions leucine and tyrosine, 
both of them products of protoplasmic metamorphoses, a 
soluble albuminous substance coagulable by heat, an enzyme, 
a peculiar gummy substance, phosphates and acetic acid, 
along with which there was of course the production of a 
certain amount of alcohol, some carbonic acid gas, and pure 

Schiitzenberger, repeating the experiments, found other 
products, such as xanthine, hypoxahthine, carnine, and 
guaine, that pointed most distinctly to a process of meta- 
morphoses of the protoplasm, and by a series of most inge- 
nious experiments he found that yeast in distilled water 
lost in five days about 9 per cent, of its protoplasm. That is, 
in yeast there are certain soluble elements that- can be re- 
moved by washing with distilled water, leaving the insoluble 


protoplasm, which can be filtered, calcined, and weighed ; 
after the process of self-digestion, which goes on when the 
yeasts are deprived of saccharine fluids, a further quantity of 
9 per cent, is transformed from insoluble protoplasm into 
the soluble elements above mentioned. The protoplasm 
has, in fact, been living on itself, and, showing how indis- 
solubly these metabolic changes are associated with the 
process of fermentation, both alcohol and carbonic acid gas 
are formed in the process. Yeast, then, has the power of 
disassimilating its substance by a series of steps into simpler 
bodies, but under favourable conditions it may be said to 
exert its metabolic power only in breaking down in a very 
superficial way large quantities of the medium on which it is 
grown — sugar. It is specifically adapted to break down this 
sugar as far as the stage of alcohol formation, but most yeasts 
cannot carry disintegration further. Other organisms, how- 
ever, have the power of carrying on the process as far as the 
formation of acetic acid for example, at which point another 
organism may again intervene and take up the work. We 
have thus the yeast forming alcohol and then dying out as 
it were, then the Mycoderma aceti comes in and does its 
work, and later various putrefactive organisms may continue 
the breaking-down process. On the other hand it must be 
remembered that whilst yeast sets up the alcoholic fermenta- 
tion, Hueppe's lactic acid bacillus gives rise to the production 
from sugar of lactic acid, whilst the Bacillus amylobacter or 
the bacillus of the butyric fermentation causes the sugar 
to be split up directly into butyric acid. We have here 
an example of three specific actions or fermentations of the 
same substance by the intervention of three different sets of 
organisms, and it is quite possible that other organisms effect 
an even further transformation into H^O and COj at one 
step, the organism being specially adapted at each stage for 
the work that it has to carry on, or perhaps it would be 
better to say that the conditions are adapted to the organism. 
As might be expected, such self-digesting yeast is materially 
weakened ; it is no longer in a position to absorb much 
oxygen, and, if the process be long enough prolonged, both 
the power of absorbing oxygen and the power of inducing 
fermentation are lost. But if the water that has been used 
to wash yeast, t'.e., water containing the soluble products 
necessary for the perfect nutrition of the yeast cells, be 


added to the exhausted yeast, the conditions of nutrition 
are rendered so favourable that the yeast cells again acquire 
in a most marked degree their original and characteristic 
power of absorbing oxygen, of vegetative proliferation, and 
of setting free alcohol and carbonic acid gas. 

We may briefly give in his own words the position that Schiitzenberger 
holds, so that it may be compared with Pasteur's position, previously stated. 
"The cell ferment is not developed in the absence of free oxygen, even in 
its most favourable medium, the must of grapes. The ferment, in process of 
development, continues to increase in suitable media, even in the absence 
of all trace of oxygen, as M. Pasteur had already shown. The contrary 
assertions of Brefeld are erroneous. M. Pasteur's theory, according to 
which yeast, in the absence of air, takes from the sugar the oxygen neces- 
sary for its development, is not well founded; in fact, this development 
stops long before the greater part of the .sugar is decomposed. Is it from 
the albuminoid matter that the ferment takes its oxygen in the absence of 
air ? Yeast sets up alcoholic fermentation in a solution of pure sugar in 
the absence of all trace of oxygen, but without developing. This is 
contrary to the affirmation of M. Pasteur that fermentation is bound up 
with the organization of the yeast, or is a phenomenon correlative to the 
vital activity of the cells." 

We find that in nature there is, in protoplasm, not only an 
extreme adaptability to surrounding circumstances, but an 
attempt to utilize, as far as possible, the whole of the 
energy set free from cells. We find that in this matter 
the protoplasm of yeast cells differs in no essential respect 
from other kinds of protoplasm, and we have already seen 
that in the process of fermentation of saccharose there is a 
preliminary change brought about by the soluble products 
of the yeast-cells (invertin), by which we obtain dextrose and 
levulose, both of which materials may, under certain con- 
ditions, be split up into alcohol and carbonic acid gas. 

It may now, further, be noticed that if the fermentation 
be stopped at a comparatively early stage, there is found in 
the fermenting solution a larger quantity of levulose than 
of dextrose ; i.e., the dextrose is more readily converted into 
the characteristic products of fermentation than is the levu- 
lose. It has also been proved that if the yeast-cells be heated 
to a temperature of about 60° C, they are destroyed, as is 
evidenced by the fact that they are no longer able to 
multiply, and they never give further evidence of vitality. 
But there is left in the fluid a substance known as enzyme 
(li/^ii/tn, leaven— yeast), which, added to the mixture of dextrose 
and levulose, does not affect the levulose in the slightest. 


(This may also be done by using the Pasteur-Chamberland 
filter, which keeps back the yeast-cells, but allows the enzyme 
to pass.) It is only on the addition of living yeast, or that 
yeast in which there is active protoplasm capable of actually 
digesting and transforming food materials, that the levulose 
becomes transformed into dextrose. 

We have here three very significant statements, all 
of them attested by eminent authorities, which seem to 
explain many of the anomalies and disagreements in indi- 
vidual statements. The process of inversion is reduced to. a 
purely chemical one, in which the chemical reagents bring- 
ing it about are manufactured by the living protoplasm ; 
apart from which, however, it is able to exist and act so thaf 
saccharose is converted into dextrose and levulose merely 
by the action upon it of the chemical products or enzymes 
contained in yeast water ; whilst the conversion, and cer- 
tainly the fermentation of levulose, can only take place when 
this material comes into actual contact with the living pro- 
toplasm, from which it seems, necessarily, to be more closely 
associated with the actual process of digestion. 

This is a decided step in advance in assisting to explain 
the process of fermentation, of digestion in the higher 
animals, and of those changes that take place in putrefactive 
and pathogenic processes. It also appears to throw light on 
some of the points in dispute on fermentation. 

For example, we can easily understand how different the 
results would be in cases where experimenters use yeast as 
the fermenting agent, and crude saccharose as the fermentable 
substance in one case, and yeast with dextrose in another. 

The process of inversion of the saccharose by the invertin 
into dextrose and levulose is carried out easily enough, 
whether oxygen be present or not, and this dextrose is easily 
broken up by the yeast. When we come to the levulose, 
however, it is a different matter, as this substance can 
apparently only be converted into dextrose when it is in 
direct contact with the protoplasm of the cell, and so long as 
food materials and oxygen can be obtained from other sources 
there is not the same tendency for the protoplasm to take up 
this levulose that there is when other sources of food supply 
are cut off. The active and rejuvenated cells are still able to 
utilize the levulose, whereas older cells, which, as we have 
seen, after self-digestion lose even their power of transforming 


dextrose, lose their power of transforming levulose at a still 
earlier period. 

This enzyme function, although so intimately associated 
with the vital activity of protoplasm and so usually possessed 
by cells, is considered by Hueppe to be a secondarily derived 
function of the protoplasm, and to be reUlly a modification 
or development of the primary power of digestion possessed by 
all protoplasm independent of the action of enzymes, only 
to be met with when the conditions for the growth of the 
organism and the development of its functions are most per- 
fectly combined. It is, as Cartwright Wood says, a function 
developed in such a high degree, that it may actually be 
temporarily separated from the protoplasm which develops it. 
It must be looked upon as something separate, and as some- 
thing that can act, under favourable circumstances, apart 
from protoplasm, economizing the energy of the proto- 
plasm, and utilizing the most suitable products for the nutri- 
tion of the organism and for the manifestation of its special 
functions. Under less favourable conditions, where the pro- 
toplasm has to struggle for existence, as it were, this enzyme 
function is withdrawn ; and although the protoplasm can 
still exert its characteristic powers of digestion and of forma- 
tion of special products, these processes take place within 
the cell, they are of a less specialized nature, and are, in fact, 
the primary and inherent functions of the cell protoplasm, 
which are capable of doing their work within the protoplasm, 
but are not so highly differentiated that they can act exter- 
nally to it. The primary function is, then, not separable 
from the protoplasm. This formation of enzymes is of special 
interest in relation to the processes of disease ; for it is found 
that, by modifying the conditions under which an organism 
grows, or by varying its food, special ferments come into 
operation. For instance, Lauder Brunton and M'Fadyean, 
experimenting with a certain organism, found that if it were 
grown on peptonized beef jelly, it would give_ rise to an 
enzyme which was capable of liquefying the gelatine. If this 
organism were now introduced into a solution of starch, it 
would continue to grow, but it could give rise to no diastatic 
ferment — i.e., it was incapable of transforming, except within 
its own protoplasm, the starch material into sugar, or into 
material that it could utilize for its own nutrition. If, how- 
ever, successive generations of this same organism were cul- 



tivated on starch, there came a period at which it generated 
a diastatic ferment, which could be separated from the solu- 
tion, and which alone, and without any direct intervention 
of the protoplasm, could bring about a transformation of 
starch into sugar — i.e., a secondary separable diastatic func- 
tion had been developed, in addition to the primary digestive 
function of the organism. When tajten back to the gelatine 
from the starch, the organism had lost its power of liquefy- 
ing gelatine ; but this again it regained, after being again 
cultivated, through a series of generations, on gelatine. 

It is quite possible that this may be a somewhat too strong 
statement of Lauder Brunton's and M'Fadyean's position. It 
may be that they maintain only that the organism when 
grown on starch produces the diastatic ferment, whilst when 
on albumen it forms a peptonizing substance. It may be 
merely a temporary modification just as under analagous 
conditions, the cholera bacillus when grown on sugar produces 
butyric acid, whilst when grown on albumen it forms 

It is thus evident that special forms of fermentation require 
that, in addition to a special kind of protoplasm, there shall 
be a special nutrient material — a fact that explains some of 
the different results that have, from time to time, been 
recorded. The yeasts, as we have seen, are capable of fer- 
menting dextrose and of producing a substance, invertin, by 
which the saccharose, or cane sugar, is converted into dex- 
trose and levulose — both fermentable substances. Wood 
points out that only three yeasts are known that are able to 
ferment milk sugar directly, although many of the bacteria 
are able to invert and bring about its fermentation. He says 

" Of still greater interest is the varying manner in which the same organism 
conducts itself towards different albuminoids. ... As a general rule, those 
organisms which liquefy gelatine are able to coagulate milk, and then 
peptonize casein which has been separated ; but some organisms which 
peptonized gelatine are without action on the milk, and some that are 
inoperative on gelatine peptonize milk, though this is exceptional " ; and he 
further says that even the manner in which " milk is peptonized is subject to 
considerable variations, and that, although the vast majority first coagulate 
the casein and then dissolve it, certain microbes seem to peptonize the 
casein directly. . . . Very striking is the way in which the same organism 
conducts itself to the different albuminoids, gelatine, fibrin, blood-serum, 
and egg albumen. One organism is unable to liquefy gelatine, but pep* 
ionizes fibrin ; another liquefies the gelatine, but cannot peptonize the 


egg albumen. . . . They must, accordingly, be regarded as specific in their 
nature, depending on the specific nature of the protoplasm of which they 
are merely further differentiations." 

Micro-organisms, when grown under such conditions that 
oxygen cannot gain access to them — under conditions of 
anaerobiosis — usually appear incapable of developing their 
separable peptonizing enzyme function, as they are no longer 
able to liquefy the gelatine in which they are growing. The 
fact that this separable enzyme function could be kept in 
temporary abeyance was utilized by Chantemesse and Widal, 
to prevent the liquefaction that takes place in plate cultiva- 
tions where a certain specific organism requires a considerable 
time for its complete development. By adding dilute carbolic 
acid to their nutrient medium they found that the peptonizing 
power of the organisms was interfered with ; whilst if the 
carbolic acid solution was sufficiently weak, even the more 
delicate organisms still retained sufficient vitality to enable 
them to grow on the surface of the carbolized gelatine. 

Having corroborated the above observations, Hueppe and 
Wood sought to obtain the same results while avoiding the 
dangers resulting from the use of such a substance as carbolic 
acid, by offering for the nutrition of the organism a certain 
preparation of a material which would enable it to develop 
the diastatic, instead of the peptonizing ferment ; and, by 
adding glycerine to the gelatine, they found, as they expected, 
that Lauder Brunton's and M'Fadyean's experiments were 
practically repeated. The organisms feeding on the glycerine 
did not in most cases attack the gelatine, and the peptonizing 
became exchanged for a diastatic ferment ; plate cultivations 
were not so rapidly liquefied, and bacilli of very slow growth 
could thus be separated from impure cultivations, in which 
organisms that ordinarily exert a liquefying or peptonizing 
function were present in considerable numbers. 

Our knowledge of most other fermentations, although 
being gradually increased, is still in a somewhat nebulous 
condition, for the reason that no one has as yet (with 
the exception of those who have worked at the matter 
from the industrial point of view) taken up the matter 
thoroughly since it became possible to obtain pure cultiva- 
tions of any single organism, the whole energy of bacterio- 
logists having been diverted to the consideration of the very 
important questions that have come up to be answered in 


connection with the production of specific infective diseases 
in man and animals by micro-organisms. 

There has, indeed, been so much work to be done in 
separating out the causal bacterial agents in these diseases, 
that there has been little time or energy left to be devoted 
to anything more than a most cursory study of the 
chemical and biological processes of the non-pathogenic 
forms. We do know, however, something about the man- 
nitic fermentation of sugar, the lactic, the butyric, the 
ammoniacal, and the acetic fermentation ; and, speaking 
generally, these processes are essentially the same as those 
which take place in ordinary alcoholic fermentation, the 
differences being that the protoplasm cells of the ferment 
differ from those of yeast both in morphological and bio- 
logical characteristics, and that the composition of the 
end - products is also different. The food material acted 
upon by different protoplasm, and giving rise to different 
results, may be the same ; the fermentation is still brought 
about by a process of hydration or some other specific 
process, and is intimately associated with the vital activity 
of the special ferment. In the mannitic fermentation 
the sugar is converted by hydration into dextrose and 
levulose, after which comes the conversion of some of the 
sugar into gum, and of some into mannite, during which 
second part of the process there is also an evolution of carbon 
dioxide and the formation of water. Mannite is a sugar to 
which a molecule of hydrogen has been added ; gum, a 
cane sugar from which one molecule of water has been sub- 
tracted. The viscous change that takes place as the fermen- 
tation proceeds is due to the formation of this gummy 
material in the fluid. Pasteur described the special man- 
nitic ferment as consisting of chains of small cocci, each 
coccus having a diameter of 1.2 to i.$fi of an inch. 
These, like the yeasts, require nitrogenous material, in 
addition to salts, extractives, and sugar, in order that they 
rriay develop. This form of fermentation is specially in- 
teresting, from the fact that it is to it that the ropiness of 
the white wines is due — a ropiness which, as Pasteur pointed 
out, might be prevented by heating the wine for a few 
minutes at a temperature of 60° C, or, as suggested by 
Frangois, by the addition of a certain proportion of tannin, a 
substance which appears to interfere most markedly with 
the development of the viscous fermentation organism. 


In the lactic acid fermentation it does not appear to be 
necessary that any process of hydration should take place, 
as there is here merely an exact division of one molecule of 
sugar into two molecules of lactic acid, there being neither 
addition nor loss of either oxygen or hydrogen. It must, 
however, be borne in mind that the lactic acid fermentation 
is frequently accompanied by the formation of CO^, in which 
case, of course, the process is not nearly so simple. 

By fermenting lager beer at from 30° to 34° C, Chr. Hansen found that 
there was developed a form of bacterium made up of long chains, of dumb- 
bell or hour-glass shaped organisms, of bacteria as long curved or straight 
threads i whilst at irregular intervals were formed spindle-shaped or club- 
shaped bacteria, even when the nutrient conditions still continue good at a 
late stage of the growth. That these organisms, however, were not all 
alike, Hansen proved by the fact that some of them are stained yellow by 
iodine, whilst with others a blue reaction was obtained. The conditions 
necessary for the development of this organism, and the production of acetic 
acid, are a high temperature — from 30° to 34° C. — and a plentiful supply 
of oxygen. So necessary is this latter that a film forming on the surface 
is all that there is to denote the presence of an organism, the fluid 
beneath, from which free oxygen is cut off, remaining perfectly clear ; and 
Hansen even gives this as a diagnostic feature to enable an observer to 
determine whether he is dealing with pure cultivations of these mycodermi 
or rot, as, wherever other bacteria are present, roughly speaking, turbidity 
is set up. 

It is a curious fact that the pure lactic fermentation cannot 
go on when the medium is too acid, and it is only by remov- 
ing the lactic acid as it is formed that a complete trans- 
formation even of milk sugar into lactic acid can be obtained. 
This fact was observed long before the exact nature of the 
process was understood ; and in all the earlier methods 
devised for the preparation of this substance the daily 
neutralization of the fluid with chalk or carbonate of soda 
played a most important part. That the process is essen- 
tially the same as the others, in so far as it is the result 
of the activity of micro-organisms, was proved by Pasteur, 
who found that by sowing the lactic acid ferment, which 
he described as composed of small globules or short 
joints, either isolated or in mass, in a fluid which he 
had found specially suitable for alcoholic fermentation, 
active lactic fermentation was coincidentally set up, and 
lactic acid was found present along with the resulting 
alcohol ; whilst, as we already know, if no lactic acid fer- 
ment be introduced, either accidentally or intentionally, no 


lactic acid fermentation ever takes place. Although this is 
true in a certain degree, it is found, as has already been 
stated, that there are actual differences in degree as to the 
readiness with which the various sugars undergo the alco- 
holic and lactic fermentations. For instance, although the 
glucoses are readily converted into lactic acid, the saccharoses, 
which are specially fermentable by the saccharomyces, are 
not very easily transformed into lactic acid ; whilst, on the 
other hand, sugar of milk, which does not readily yield 
alcohol, may be comparatively easily converted into lactic 
acid. Muscle sugar and mannite, neither of which can be 
converted into alcohol, may both be broken up into lactic 
acid, as may all those substances that are specially affected 
by the butyric fermentation. 

It was for some time thought that the fermentation of 
urea, through which carbonate of ammonia is frequently met 
with in the urine, was the result of a single micrococcus, the 
micrococcus ureae, a small organism about in in diameter, 
which may occur in pairs, in tetrads, or in longer chains, and 
which, in the presence of suitable nutrient materials, and of 
urea, either in artificial solution or in urine, determines a 
regular hydration of these substances and their conversion 
into carbonate of ammonium. 

Since the time of Pasteur's researches, however, Leube 
has found an organism about double 'the size of the above 
and arranged in chains, which rapidly decomposes solutions 
of urea into carbonate of ammonia. It differs, too, from 
Pasteur's organism in that it peptonizes or digests gelatine, 
causing it to liquefy, and it appears that, unlike some 
other bacilli and sarcinse that can set up a feeble urea 
fermentation, it is quite as powerful an ammoniacal ferment 
as the small micrococcus ureae described by Pasteur, as in 
both of them the fermentation can go on most vigorously, even 
in the medium that has become distinctly alkaline, z.e., the 
carbonate of ammonia accumulates until about 13 per cent, 
of this substance has been formed ; these two microbes may 
be said to bear the same relation to the other urea-forming 
bacteria that the Saccharomyces cerivisiae and the other 
more powerful alcohol-forming yeasts have to the weak 
saccharomyces and other sugar fermenting organisms. 
That this power is not confined to a single organism is not 
remarkable, since it is quite possible by boiling the urea in 


water, or, better still, in slightly alkaline solution, to bring 
about direct hydration of the urea into ammonium car- 

When it is asked what value the study of fermentation has been to the 
cause of medicine, it is not necessary to go further for an example than 
this urea fermentation. In the operations of the older surgeons it 
was very frequently recorded that the introduction of instruments into the 
bladder (in which, of course, was a solution of urea) was followed by a 
regular fermentation, which too frequently led to the death of the patient ; 
and it having been determined that micro-organisms were the cause of this 
fermentation, it became an easy matter to prevent their introduction by 
careful sterilization of the instruments ; and, as a result, such ammoniacal 
fermentation within the bladder is now a matter of very infrequent occur- 
rence, and is, in those cases in which it does occur, the result not so much 
of accident as of carelessness on the part either of the patient or of the 
surgeon. So marked, indeed, has this been, that even those who sneer at 
bacteriology and antiseptics have been compelled to accept new methods 
of procedure in r^;ard to the cleanliness of their instruments, a cleansing 
which means simply the removal of these minute vegetable protoplasmic 
organisms, which, on being introduced into the suitable fermenting medium 
in the bladder (or elsewhere), give rise to the alkaline fermentive, putre- 
factive and other processes. 

In an interesting chapter on the butyric fermentation of 
putrefaction, Schiitzenberger points out that in the process 
of putrefaction or putrid fermentation, as it may be called, 
there is a formation of butyric acid, one only of a series of 
fatty acids formed under similar conditions ; accompanying 
this there occurs a transformation of glucose, starch, lactic 
acid, albuminoid substances, and the various fruit acids, into 
these fatty acids, into carbon dioxide, and into certain 
hydrogen compounds. From a very large number of these 
substances lactic acid with or without carbon dioxide is 
formed, whilst the lactic acid may be further split up into 
butyric acid, carbon dioxide, and hydrogen. 

From this chapter we may borrow some of the formulae to 
show how easy and how rational is the transformation from 
these substances into the fatty acids. Other substances 
may also be formed, these being further broken down or 
separated as the case may be. Glucose, as we have already 
seen, is, under the action of the lactic acid ferment, converted 
into lactic acid, and this under the action of the butyric 
ferment, a small rod-shaped organism from 1.8 to i8/» in 
length and i.5/iin breadth is converted into butyric acid, 
carbon dioxide, and hydrogen. These micro-organisms 


are straight, somewhat rounded at the extremities, single, or 
arranged in short chains of three or four elements ; if placed 
in a nutrient medium similar to that in which yeast grows, 
they are reproduced by a process of vegetative division, 
especially if this medium be neutral, or slightly alkaline, and 
if it be kept at a temperature of 40° C. » 

The fonnula of the process of sphtting up is given as first 

CeH^O s ^ 2C3H6O3 

I Molecule Glucose 2 Molecules of Lactic Acid 

The two Molecules of Lactic acid are then transformed into 

C4H8O. 2Ca , 

I Molecule of Butyric Acid 2 Molecules Carbon Dioxide 

2 Molecules Hydrogen 
In the same way two molecules of malic acid are broken up into two of lactic 
acid and two of carbon dioxide, and the lactic acid is again transformed as 
above, that is, 2C4H6OS = 2C3H6O3 + 2CO2 = C^UeO, + 4COj + 2H2. 
This butyric acid formation is only one of a group, and we find that where 
lactic fermentation is going on in an impure condition propionic acid, 
CjHsOa, acetic acid, C2H4O2, and valerianic acid, CjHioOs, are produced, 
and glycerine fermented for some time with beer yeast, is split up into pro- 
pionic acid mixed with formic and acetic acids, giving a kind of compound 
of putrefaction products. 
A very ingenious formula is quoted by Schiitzenberger to show how 

the fatty acids are formed from sugar : — — — (CsHiaOe) = 

[C„H,nOJ ^ ( n— 2)CH.a p-^^jj^jj. ^j,;j j^g ,Q^ggj ^j j,^g ^ ^ .J 
Fatty Acid Formic Acid ■' 

group, being immediately converted into carbon dioxide and hydrogen. The 
presence of lime or organic matter appears to modify this process some- 
what, and to give rise to the formation of secondary vegetable acids. For 
instance, two molecules of malic acid, 2C4H6O5, break up into succinic acid, 
C4H6O4, and tartaric acid, 2C4H6O6, and from these are formed, from the 
tartaric acid the fatty acetic acid, C2H4O2 -|- CO2 + H2, and from the 
succinic acid the fatty valerianic acid, carbon dioxide and hydrogen, 
CsH„02 + 3CO2 -I- H2. 

These transformations have this in common, that they 
are all brought about by the presence of minute organisms, 
that the conditions of the development of these organisms 
are similar to those met with in other fermentation pro- 
cesses, and that theirs are the principal products formed 
during the process of putrefactive fermentation, which also 
in all cases requires the presence of these minute organisms, 
the spores of which, as we have seen, seem to be everywhere 


present. Here, as in the case of the yeasts, we find both 
aerobic and anaerobic organisms. The aerobic forms give 
rise to oxidation of certain of the products of decomposi- 
tion, one of these, nascent hydrogen, especially taking up 
oxygen, as a result of which water is formed ; the an- 
aerobic organisms, which may be said to complete the 
process of putrefactive fermentation, only commence to grow 
when the serobic organisms have used up all the readily 
available oxygen such as that dissolved in a liquid, on the 
surface of which there has formed a kind of film, by the 
intervention of which aeration from the external air is greatly 
interfered with. 

We have already noted this film growing on yeasts, when it 
appears to assist the carbon dioxide developed during the pro- 
cess of fermentation in keeping off the oxygen of the atmo- 
sphere, and to allow of these anaerobic organisms carrying on 
their growth without the further intervention of a free oxidiz- 
ing agent. The products of these anaerobic organisms, of 
course, differ from the products of the aerobic fermentations 
in so far that they contain less oxygen, the sulphuretted 
hydrogen, hydrogen, and nitrogen being released in a more 
or less free condition and uncombined with oxygen, the 
oxygen of the original fluid being used up in the formation 
of such substances as leucine, C5H,„(NH,)CO OH ; tyrosine 

QhJ^ (NHJCO, OH) ; the volatile fatty acids ; some 

compound ammonias, and, of course, carbon dioxide ; the 
two latter of which, as already seen, may be formed from 
urea (CO(HN=),) by simple hydration, the more highly 
organized substances,, such as leucine and tyrosine, being, 
during the process of fermentation, further converted into 
ammonia and the fatty acids. 

From the variety of the products of these fermentations 
it is evident that we have to do, not with a simple conver- 
sion by means of any single organism into the simplest and 
ultimate elements of decomposition, but that vte have a 
series of breakings down or stages of decomposition by which 
the highest (and most unstable) organic materials are 
gradually transformed into the lowest and most stable. It 
will be found, however, that the process is not quite so 
straightforward and simple as above stated, as some of the 
energy released during the formation of a number of lower 


and more stable compounds is utilized in the presence of 
animal and vegetable protoplasm in building up higher and 
more stable materials ; though at the later stages of decom- 
position these become fewer in number, and eventually 
become oxidized into the more stable forms — a free access of 
air to the products of anaerobic decomposition always leading 
to their oxidation. Hydration almost invariably occurs 
during each of these stages. 

Schiitzenberger says, "Nothing resembles putrid fermentation, with 
reference to the derived products, more nearly than the change which takes 
place in the constituent parts of yeast, when left to itself without nourish- 
ment, deprived of sugar and oxygen. 

We see, in fact, the appearance of leucine, tyrosine, sarcine, &c. 
This is the first step ; the action stops there, and goes no further ; the 
yeast, or the special soluble ferment which it secretes, is unfit to attack 
these bodies again ; but if we wait for the development of vibrios, we 
shall find the production of ammonia, carbon dioxide, and volatile fatty 
acids at the same time that the leucine partly disappears." 

Fermentation by oxidation can only be set up by organisms 
in the presence of a free supply of oxygen, and the process in 
such cases appears to be due to special organisms which, 
attacking the substance to be ferihented, remove some of its 
constituents, set free others, especially carbon and hydrogen, 
which, in their nascent condition, are seized upon by the 
oxygen of the air, and so water, or water and carbonic gas, 
are formed. 

In the commonest of these fermentations by oxidation, 
the acetic fermentation of alcohol, the free access of air is 
as absolutely essential for the growth of the organism as 
it is for the special stage of the fermentation of the alcohol 
into acetic acid. 

If the mycoderma aceti be sowed in wine, freety exposed 
to the air at a temperature from 24° to 27° C, chemists hold 
that there is hydration of alcohol by the combination of an 
atom of free oxygen with two atoms of its hydrogen water, OH^, 
and aldehyde QH^O, being formed, the latter of which, by 
further oxidation, in turn becoming converted into, C^H^O^, 
acetic acid. At a certain stage this process of acidiiication 
stops, owing to the quantity of acid developed, but if this be 
removed and fresh alcohol be added, the acidification again 
commences, and so on, as long as the mycoderma remains 
active, can obtain sufficient oxygen, and sufficient alcohol 


on which to act. If, however, the supply of either oxygen 
or alcohol be cut off, the ordinary mode of life of the 
mycoderma is at once interfered with. It uses up part of 
its own protoplasm by internal metabolism, continues to act 
on the acetic acid, and converts it into simple substances, 
water and carbon dioxide, at the same time retaining 
molecules of carbon, hydrogen, and oxygen for its own use. 
The mycoderma is, then, no longer so much an enzyme-former 
or an organism with a thick celled wall, that acts principally 
on the suitable nutrient medium by means of its chemical 
products, and gives rise to a definite chemical process ; but 
is now rather a mass of protoplasm endowed only with 
its primary digestive powers, by means of which it can 
convert organic matter into its very simplest forms or ele- 
ments. There is very complete oxidation, and instead of 
alcohol and acetic acid being formed as intermediate products 
that can be easily separated, the substances are at once 
converted into water and carbon dioxide, the ultimate 
products of perfect oxidation. 

It is sometimes said that the mycoderma in the true 
vinegar fermentation is in a weakly condition ; it is cer- 
tainly not in its most active condition, but the state appears 
to be one rather of quiescence or advanced development, in 
which the formation of a thick membrane and the produc- 
tion of a separable enzyme are characteristic features, rather 
than one that can be spoken of as a condition " of incomplete 
or tardy development." 

To show that the process was not merely a physical one, 
as was suggested even by Pasteur, Mayer showed that by 
simply heating the acidifying fluid to a temperature at 
which the mycoderma is killed all oxidation is arrested, and 
he also showed that the temperature at which oxidation of 
concentrated alcohol goes on in spongy platinum is at a 
temperature above 35° C, at which point it is completely 
stopped in the presence of the mycoderma aceti, in addition 
to which " physiological acidification " can only take place 
in a weak solution of alcohol. 

Pasteur's observations and results led to the adoption 
of what is known as the Orleans process of making vine- 
gar, which, as given by Schiitzenberger, is as follows : — 
"The mycoderma aceti is made up of small, slightly 
elongated cells, with a transverse diameter of from 1.5 


to 3/», united in short chains, or curved rods. Con- 
striction and division take place between the segments of 
the chain as the process of vegetation goes on. A small 
quantity of this mycoderma, which occurs as a wrinkled 
membrane on the surface of liquids that are undergoing 
acetic fermentation, is first sowed on the surface of an 
aqueous liquid containing two per cent, of" alcohol, one per 
cent, of vinegar, and traces of alkaline and alkaline-earthy 
phosphates. When the surface is covered with the mem- 
brane the alcohol begins to acidify. This action being fully 
set up, some alcohol, wine, or beer mixed with alcohol, is 
each day added to the liquid, in small quantities ; this is 
continued till the oxidation becomes slower ; the acetification 
is then allowed to terminate, and the vinegar is drawn off. 
The membrane is collected, washed, and employed for a new 
operation. It is better always to give the plant sufficient 
alcohol, so that its activity may not be exerted on the 
acetic acid. Nor ought it to remain too long out of the 
liquid, or it would lose its active force ; finally, it is better 
to moderate its development, to prevent burning oxidation." 
These last few lines are of special interest, as they show how 
markedly favourable conditions of nutrition, and the supply 
of special materials on which the organisms may act, modify 
the process set up by the acidifying organism ; just as certain 
organisms will select glycerine or sugar from a peptone 
gelatine medium before they begin to act on the gelatine itself, 
so the mycoderma aceti, under certain conditions, confines its 
attention entirely to the alcohol, converting it into acetic 
acid and then leaving it ; whilst, as soon as the glycerine in 
the one case and the alcohol in the other, are completely used 
up, or as soon as the activity of the protoplasm becomes so 
great that it cannot derive sufficient material from the one, 
it immediately attacks the other, and continues the oxidizing 
process. Not only so, but the various organisms appear to 
be specialized at the different stages of the resolution of 
organic matter ; each, during the stage at which it can 
perform its share of the work, appearing not only to multiply 
much more rapidly than the other organisms with which it 
is found but actually holding them in check. In this 
respect the vegetable protoplasm of the lower organisms is 
only like the protoplasm of the cells of the higher animal 
organisms. In relation to pathogenic processes this is a 


point of very considerable interest, for we find that under 
certain conditions there comes to be a contest between the 
animal cells and the lower vegetable cells. As Wood well 
puts it, " the reaction of the cells upon each other may turn 
on the sum of the conditions of existence to which they are 
exposed happening to favour one more than the other, thus 
when two organisms are sown together in a culture fluid, 
which will overgrow the other may depend upon the relative 
quantity of the two primarily introduced, the nature and 
reaction of the media, and the temperature at which they 
are held." Fermentation, then, is due to the action of highly 
specialized cells. That this is so is indicated by the usual 
presence of enzymes and also by the fact that they exert this 
specific action in their highest degree only under a certain 
set of specific conditions which vary in the case of each 
organism. Each organism has become adapted to a 
certain medium, and is so specialized as to have the power of 
splitting it up under certain conditions in a specific way. 
This is also indicated by the fact that as the conditions 
become unfavourable, less and less of the specific product 
(relatively to the bye products) is produced. Although we 
shall have more to say in connection with the subject of the 
specific infectivity of micro-organisms in disease, it may here 
be pointed out that fermentation is due, in great part, to the 
action of cells which have the power of developing a special 
enzyme function ; that these cells are usually more highly 
specialized during the stages when they bring about their 
specific action ; that this is associated to a certain extent with 
diminished activity of the protoplasm directly on the sub- 
stances to be fermented ; that most processes where there is 
the formation of an enzyme, or a special poison, take place 
most actively when there is a complete or partial cutting off 
of the supply of oxygen ; that the cells in this condition 
usually develop a more or less perfect cell membrane which 
characterizes the formation of zoogloea masses ; that this in- 
complete oxidation also characterizes the formation of 
toxines ; that the same rules hold good in the formation of 
most of the products of the lower vegetable organisms 
and of the individual cells of animal tissues with complete 
oxidation and the formation of carbonic acid gas and 
water ; that when incomplete oxidation takes place various 
specific products make their appearance ; but that even in 


the presence of a full supply of oxygen, protoplasm under 
certain conditions cannot bring about complete oxidation, 
and as a result some of the intermediary products of fer- 
mentation and decomposition may be formed. 

It is evident, then, that all ferments may be classed under 
two great heads : firstly, the organized ferments or the active 
unstable protoplasmic cells of yeasts, bacteria, of plants and 
animals.- Secondly, the unorganized ferments or enzymes 
which we have spoken of as the separable functions of more 
highly developed cells, both of them being, however, as- 
sociated with the nutritive and other metabolic changes of 
protoplasm, be this protoplasm that of simple vegetable cells 
or of highly organized gland cells. Hoppe-Seyler classifies 
the whole of the fermentations as follows : — I. ferments which 
bring about hydration or cause hydrolysis, these being divided 
into [a) those that act like boiling mineral acids, all of which 
belong to the enzyme group ; and (5) ferments acting like 
caustic alkalies in which we have the process of decomposition 
(i) of fats into glycerine and fatty acids as in saponification, 
which results from the action both of the organisms directly 
and of the unorganized ferments, (2) decomposition of amido 
— 'Or ammonia-nitrogen compounds which is also usually 
associated with hydrolysis. II. In the second group, Hoppe- 
Seyler places fermentations in which there is transference 
of oxygen from the hydrogen to the carbon atoms. As 
examples of this we have (a) lactic acid fermentation in 
which there is decomposition of certain carbohydrates into 
lactic acid ; this, as we have seen, being always associated with 
the presence and activity of a certain group of micro- 
organisms, (5) the alcoholic fermentation brought about in a 
similar manner by yeasts, (c) putrefactive decomposition 
changes, (i) of simple inorganic compounds such as combi- 
nations of the fatty acids with lime, or (2) of organic com- 
pounds such as fibrin and other proteids. Then we have 
also the acetic fermentation already referred to, nitrification 
or mineralization, chromogenic fermentation and that series 
of changes in which we have the production of ptomaines. 

Such a classification is specially important when we come 
to consider the relation of the ordinary fermentation pro- 
cesses to those that are set up during the course of disease in 
animals and in plants. 

fermentation. i43 


Authors already mentioned. Fliigge, Davaine, Roberts, 
Tyndall, Fitz. 
Bechamp. — Comptes rendus, t. lvi., pp. 969, 1086, 1231, 

1863 ; t. LXi., pp. 374, 408, 1865 ; t. LXXV., p. 1036, 

1872 ; t. xciii., p. 78, 1881. 
BouTROux. — Comptes rendus, t. lxxxvi., p. i, 1878. 
BuNGE. — Text Book of Phys. and Path. Chem. (Transl. : 

Wooldridge). London, 1890. 
Brefeld. — Botanische Zeitung, 1875; Die Hefepilze, Leipzig, 

Chantamesse and Widal. — Gazette Hebdomadaire, p. 146, 

Cagniard-Latour. — Ann. Chim. Phys., 2nd ser., t. xv., 1820. 
Desmazieres. — Ann. desSc. Naturelles, t. x., p. 4, 1826. 
DuBRUNFANT. — Comptes rendus, t. xlii., p. 945, 1856. 
Engel. — Les ferments alcooliques. 1872. 
Hoppe-Seyler. — Zeitschr. Physiolog. Chemie, Bd. x., p. 36, 

Hueppe.— Mitth. a. d. Ges. Amt., Bd. 11., p. 309, 1884. 
HuEPPE AND Wood. — Lancet. Dec. 7, 1889. 
Hansen, Chr. — Meddel. fra Carlsberg Lab. Copenhagen, 

1879, '81, '83, '86, '88 ; AUgem. Zeitschr. f. Bierbrauerei 

u. Malzfabr. 1883-87 ; Zeitschr. f. d. ges. Brauwesen, 

1884, and republished in Munich, 1888. 
Holm and Poulsen. — Meddel. fra Carlsberg Lab., Bd. 11., 

JoRGENSEN.— Micro-Organisms of Fermentation (Trans.), 

London, 1889. 
KiESER.— Schweiggers Journ., 1814, No. xii., p. 229. 
Leube.— Virch. Arch., Bd. c, p. 540, 1885. 
LiEBiG.— Ann. de Chimie et de Phys., 2nd ser., t. lxxi., 

p. 178, 1839. . 

Lister.— Pharmac. Journ. and Trans., vol. viii., 3rd series, 

Mayer. — Die Lehre von den chemischen Fermenten. Heidel- 
berg. 1882. 

Pasteur. — Ann. de Chimie et Physique, 3me Serie., t. lviii., 
p. 323, i860 ; Etudes sur le vin, 1866 ; Etudes sur le 
vinaigre, 1868 ; fitudes sur la bi&re, 1876 ; Comptes 
rendus, 1876, t. lxxxiii., p. 173 ; Lecture faite a I'Acad. 

144 , BACTERIA. 

de Med., 1878, 26 Nov. ; Comptes rendus, 1861, t. Ul. ; 

1864, t. LVI. 
Reess. — Botanische Untersuchungen uber die Alkohol- 

gahrungs-pilz. 1870. 
ScHUTZENBERGER. — On Fermentation. London, 1886. 
Schwann. — Poggendorf Annal., 1837, Bd. 41, p. 184. 
Tr^ul. — Comptes rendus, t. lxi., pp. 432, 553, 1865 ; t. 

Lxv., pp. 513, 927, 1867. 
TuRPiN. — Comptes rendus, t. vii., p. 369, 1838. 
van Tieghem. — Ann. d. Sc. nat. Bot. Serie vi, t. 4, 1878. 
WiESNER. — Sitzungsber. der Wiener Akademie, Bd. lix., 

Willis. — De Fermentatione. 1659. 
Wood, Cartwright. — Lab. Reports Roy. Coll. Phys., Edin., 

1890, p. 253. 


Parasites and Saprophytes. 

Putrefactive Bacteria — Pigment-forming Bacteria — Enzyme-forming Bacteria 
— Non-pathogenic, Saprophytic, Parasitic, Pathogenic Bacteria — 
Sarcina Ventriculi — Leptothrix Buccalis — Facultative Saprophytes — 
Facultative Pathogenic Parasites — Anthrax Bacillus — Pathogenic, 
Parasitic, Saprophytic, merely Relative Terms. 

In order that rauch of what occurs in the following chapters 
may be understood, it is necessary that some idea should be 
given of the way in which the terms saprophytic, parasitic, 
and pathogenic are used. The first of these is not so impor- 
tant ; the term saprophytic as applied to bacteria is being 
gradually supplanted by the term non-pathogenic, especially 
in works dealing with the relation of micro-organisms to 
disease. Speaking generally, saprophytic bacteria are those 
bacteria that have the power of obtaining the nutriment 
they require for their building up, and for the carrying on of 
their vital functions, from dead vegetable or animal substances 
only. They are not able to invade the tissues of living 
animals and plants, but they play an important part, as we 
have already seen, in bringing about oxidation of various 
organic materials and of giving rise to certain definite com- 
pounds. To this class belong the putrefactive bacteria, and 
many of the pigment-forming bacteria ; the yeasts or fermen- 
tation fungi are also to be looked upon as purely saprophytic 
in character ; and such organisms as the Bacillus amylo- 
bacter, the lactic acid bacillus, and the like, are all probably 
to be classified in this group. 

The subdivision of the group has been attempted by 
many workers, and the saprophytic organisms have been 
arranged according to their power of action on the various 
carbo-hydrates and on proteid substances. Others have 
taken their products as a basis on which to classify 
them, and enzyme-forming, pigment-forming, or alcohol- 



forming organisms have all been described ; but as their 
powers of decomposing different substances and of giving 
rise to pigment or to certain enzymes necessarily overlap one 
another, or are met with in the same individual under 
different conditions, it remains an exceedingly diiBcult matter 
to give any classification founded on the above, mixed 

Some of the organisms which, at present, are supposed to 
be saprophytic in character, may eventually be found to be 
parasitic under certain conditions, and it is for this reason 
that the term non-pathogenic is gradually ousting the older 
botanical term of saprophytic. 

Parasitic bacteria are those which are able to flourish on 
or within the substance of plants or animals. In animals 
they live in the various cavities of the body, or in certain 
cases in one or other of the nutrient fluids of the body, and 
they derive their food from these fluids, or from the nutrient 
materials that are taken in by the host. The ordinary terms 
of obligate parasites, facultative saprophytes, and facultative 
parasites, can scarcely be used in connection with these 
minute organisms, as, with very few exceptions, all the 
parasitic bacteria have now been cultivated outside the body 
and under such conditions that it is evident that some of 
those which were at one time looked upon as purely parasitic 
have a saprophytic stage of existence ; so that nearly all, if 
not all, the parasitic bacteria must be looked upon as facul- 
tative parasites, or parasites that can develop almost as well 
saprophytically as they can parasitically, or facultative 
saprophytes, or saprophytes that can develop almost as 
well parasitically as they can saprophytically. 

We know of course that all parasitic bacteria are not 
pathogenic, and that we have along the alimentary tract, 
and even in the respiratory tract, a large number of para- 
sitic organisms. The Sarcina ventriculi, for example, first 
described by Goodsir, may be taken as a purely parasitic 
organism. It is found especially in dilated stomachs. A 
drop of fluid taken from the contents of such a stomach 
frequently contains a number of organisms which present a 
curious appearance under the microscope. They are very 
like the typical bale of wool or goods tied with a strong 
cord in three directions. Other sarcinas are saprophytic as 
well as parasitic, but the Sarcina ventriculi has not yet been 


satistactorily cultivated outside the body, or if it has, it has 
always become somewhat altered in appearance. Sarcinae 
have also been found in the bladder, in the air passages, 
in the intestines, and even in the blood, but most of these 
can be cultivated on nutrient gelatine. None of these 
organisms are pathogenic so far as at present can be made 
out ; they appear to be simply accidentally associated with 
certain conditions, as in the case of dilated stomachs, in 
which they are not always present, but in which they 
frequently occur, apparently because the acid fermentation 
that goes on in the accumulated contents renders them 
specially favourable media for the development of these 
sarcinse. The non-pathogenic parasitic bacteria of the mouth 
were amongst the first organisms observed by Leeuwen- 
hoek ; they are found on the gums, on the sordes covering 
the teeth, and on the mucous membrane of the mouth. 
The forms of these we shall mention later. Although most 
of these are parasitic and non- pathogenic, one form, the 
Leptothrix buccalis (an old term embracing probably several 
species, and one not now very generally used), is also patho- 
genic in the sense that it invades the teeth, and gives rise 
to what is known as caries, or rotting of the teeth, but even 
this has to obtain help from some of the other non-patho- 
genic species found (some of the micrococci), which give rise 
to the formation of lactic acid from the sugar of old food, 
an acid that, combining with the lime salts of the teeth, 
softens them, and so allows of the penetration of the lepto- 
thrix form. 

Pasteur has suggested that other facultative saprophytes 
are t,hose met with in the alimentary tract, where he thought 
they appeared to assist in carrying on the decomposition of 
the nutrient materials, assisting, under certain circumstances, 
the animal tissues of the body to carry on the process of 
digestion without interfering in any marked degree with the 
nutrition of the tissues of the host by absorbing any of the 
material that could be utilized by these tissues for their own 
nutrition. This, however, is now considered to be question- 
able. The organism of cholera finding its way into the 
alimentary canal, acts as a pathogenic parasite, but here 
only from the fact that by its growth and metabolic activity 
it gives rise to irritant toxic materials, which exert most 
injurious effects both locally and constitutionally. 


As another example of a facultative pathogenic parasite, 
the anthrax bacillus may be cited. It may develop actually 
in the tissues, as in woolsorters' disease, where it occurs in 
the bronchial mucous membrane ; in the lymphatic tissue 
spaces, and in the pleural cavities ; or in the blood, as in 
cases of accidental inoculation. It may also occur in the 
blood in woolsorters' disease, the bacillus readily making its 
way from the air vesicles and tubes into the pulmonary 
circulation. In this connection it may be mentioned that 
anthrax bacillus cannot undergo its whole developmental 
cycle within the body ; the vegetative stages only having 
been found in parasitic anthrax ; whilst growing on^ dead 
tissues at a favourable temperature spore formation is 
invariably noticed at some period or other during the life 
history of the anthrax rods, so that the bacillus must be 
looked upon as a facultative saprophyte. Another point to 
which attention may be drawn is that bacteria must be 
looked upon as essentially and primarily saprophytic organ- 
isms. By a process of long and gradual acclimatization or 
adaptation, certain species have become so altered, either 
temporarily or permanently, that they are able to exist as 
parasites. It will always be found, however, that the 
tendency to revert to the saprophytic or non-pathogenic 
condition is more marked than their tendency to become 
transformed into the parasitic and pathogenic condition. It 
has been found, for example, that anthrax bacillus passed 
through a series of cultivations in gelatine, or hog-cholera 
bacillus " similarly treated, loses a great deal of its patho- 
genic power. This loss of pathogenic power may take 
plac^ in two directions, either by the organism losing its 
power of development in living tissues, or by losing its 
virulent specific poison. The cholera organism cultivated 
outside the body usually loses much of its pathogenic power. 
By appropriate treatment, such as cultivating at the body 
temperature in specially prepared broth through a number 
of generations, this pathogenic activity may, however, be 
restored. We must therefore look upon pathogenicity, para- 
siticism, and saprophyticism as mere relative terms ; the 
conditions necessary for the development of the saprophytic 
mode of life being more widely met with than are those 
in which the parasitic life may become developed, most 
organisms become more or less permanently adapted to 


them, so that it is only under special circumstances that 
parasitic and pathogenic organisms are developed. The 
importance of this fact will be evident when we consider 
the epidemiological importance of the presence and mode 
of life of micro-organisms both outside and within the 



Cholera a Parasitic Disease — Early Observations on the Comma Bacillus 
■ — Characters — Methods of Staining — Methods of Isolation — Use of 
Plate Method in Practical Public Health Work — Tube Cultures — 
Motility of cholera bacilli — Potato, Blood-serum, and Milk Growths 
— Behaviour in Water and Sewage — Infection of Man through Agency 
of Bacillus — Early Inoculation Experiments — Koch — Nicati and 
Rietsch — Macleod — Difficulties— Cholera in Guinea-pigs — Position of 
Bacilli in Tissues — Presence of spores doubtful. 

On account of its general interest there are few examples 
that can more appropriately be taken to illustrate the rela- 
tions between a special bacillus and a special disease than 
that afforded by Koch's discovery of the comma bacillus 
in cases of Asiatic cholera, and its relations to that disease. 
The study of the disease itself, since its appearance in this 
country in the great epidemic of 1^32, has had a peculiar 
fascination for epidemiologists and skilled hygienists. Its 
development, behaviour, and whole general history appeared 
to be shrouded in mystery, and phenomena, the explana- 
tion of which seemed to be utterly beyond the powers of 
experts of all kinds to give, were at one period constantly 
being observed, recorded, and discussed. Now, however, 
through the laborious but brilliant researches initiated by 
Pettenkofer at the head of one school, and by Koch in a 
very different one, much of this air of mystery has been dis- 
pelled, and many of the doubts and difficulties that sur- 
rounded the subject have been gradually cleared away as 
workers under one or the other of these great leaders have 
gained fresh knowledge and elucidated new facts. Take, 
for example, the question of the spread of cholera from 
its home in Lower Bengal, in the delta of the Ganges, 
to surrounding districts and distant countries. At first such 
spread was thought to be most erratic and inexplicable. 
Now, however, although it appears from time to time to have 


made almost unaccountable leaps and divergencies, it has 
been found to follow a very definite line of advance in the 
course of the various epidemics, and although there may 
have occurred sporadic cases which could be traced to no 
definite source of contagion or infection, which have proved 
a stumbling-block to many conscientious workers and ob- 
servers, it is generally acknowledged that the evidence 
accumulated through the researches of Koch and his fol- 
lowers, both in Germany and in Great Britain, and of 
several enthusiastic workers in France, can leave little doubt 
in the minds of most of those who study the subject care- 
fully, that cholera is a parasitic disease, that it travels along 
the ordinary lines of commerce by railways, caravans and 
ships, from the regions in which it is endemic to those 
centres of trade and religion which, by their imperfect sanitary 
arrangements, by the want of cleanliness of their inhabitants, 
by meteorological conditions, and on account of bad water 
supply, are ready for its reception and propagation. In the 
European epidemics, of which up to 1885 there had been 
six exceedingly severe ones during the present century, the 
disease has, in every case, followed the lines of trade. 

Before the three last epidemics (1865, 1873, 1884) cholera 
usually came to. Europe by what may be called the Con- 
tinental routes — the caravan routes through Persia, Asia 
Minor, and Russia ; but in the three last it came by the 
Mediterranean or maritime route, first by land through 
Egypt, brought there by Mecca pilgrims, and thence to 
the seaports of France, Italy, and Spain, whence it gradually 
made its way northward and inland, spreading over the 
whole of Europe. 

At the mouth of the Yang-Tsze, as instanced by Macleod, 
of Shatighai, cholera breaks- out regularly at certain seasons 
of the year, but he adduces evidence of great value to show 
that although it may be imported directly from India, 
between which and Shanghai there is at least weekly com- 
munication, just as there is between India and the Nile delta 
region, it is probably, in the strictest sense, an endemic disease 
of that region. 

It can be readily understood, after the fearful ravages which 
it made in places in which it was not actually endemic, 
and after it had decimated the population in certain parts 
of India, in Egypt, in the low-lying portions of Persia, and 


Asia Minor and in Europe, that many observers should be 
anxious to find out the ultimate cause of the disease, and 
as early as 1848 Virchow, and in 1849 Pouchet, Brittan, and 
Swaine found numbers of vibriones in the discharges^ of 
choloraic patients, without, however, being able to assign 
to them or prove for them any specific r6le in the causation 
of the disease. 

Following up these researches Philippe Pacini, setting 
himself to look for a causal agent, frequently found in 
cholera stools small micro-organisms which were charac- 
terized by active and peculiar movements. These observa- 
tions, however, as well as those of Klob, who looked upon 
the cause of cholera as an accumulation of fungi in the 
intestines, and those of Boehm and Hallier (all published 
in 1867), who believed that they had found the cause in a 
peculiar fungus which was found to grow in certain forms 
of grain imported from India, not only did not receive 
adequate proof, but were, like all preceding observations, 
entirely unreliable. Then followed the experiments by 
Hayem and Raynaud, carried on during the epidemic of 1873, 
which, however, again were equally futile and without definite 
results, and it was not until Koch, going out with the 
German Cholera Commission to Egypt and India, was able 
to demonstrate a peculiar species of bacterium as the causal 
agent that any definite proof of the micro-organismal nature 
of the contagium of the disease could be obtained. 

Since that time, however, the amount of work published 
on the subject has been so great that cholera has now a 
special " literature" of its own. The report of the German 
Commission was speedily followed by that of the French 
Government, who sent out MM. Straus, Roux, Nocard, and 
Thuillier, the last of whom fell a victim to his assiduity and 
zeal in carrying on the work of investigation in Egypt. In 
this country Klein and Heneage Gibbes, Cunningham and 
Lewis, Roy, Graham Brown and Sherrington, Watson 
Cheyne, and Macleod have, with very different voices, some 
supporting Koch's verdict, others opposing it, reported on 
the subject ; with the general result that until further and 
more convincing opposing evidence is forthcoming, Koch's 
comma bacillus, of which the following is a brief descrip- 
tion, must be looked upon as the causa causans of the 

CHOLERA. 1 53 

The ' comma ' bacillus, which is now regarded as belong- 
ing to the spirilla, usually occurs as a slightly curved rod, 
measuring from i to 2/« in length, with an average length 
of_ about i.S/t ; it is .5 to .6/* in thickness, the average 
thickness being about one-third to one-fourth of the length. 
It is therefore from one-half to one-third the length of 
the tubercle bacillus, but somewhat thicker. In place of 
occurring as single rods these organisms may be grouped 

Photo-micrograph cholera bacilli, x looo. Long spirilla^ comma, S and O shaped 
organisms. Some involution forms. 

in pairs, or in larger numbers, in which case the curve may 
be continuous or reversed, so giving rise to the formation 
either of half circles or of S-shaped curves. In cultivations 
in meat broth the bacilli may be so grouped that they form 
long wavy or spiral threads, each of which may be made up 
of ID, 20, or even 30 short turns. 

Such are the characters of the organisms which Koch found, 


almost invariably, in the stools of patients during the earlier 
stages of the disease, in the contents of the lower bowel and in 
the mucous membrane of the lower part of the small intestine. 
In fatal cases Drs. Straus and Roux thought that they 
could also see certain organisms in the blood of cholera 
patients, but they were unable to repeat their observations. 
Emmerich also described a bacillus which he said he fouiid 
constantly in the blood, organs, and intestinal contents in 
cases of cholera. This organism was, however, according to 
Fliigge, probably a common inhabitant of the intestine, the 
Bacterium Coli Communis, and it is now a generally ac- 
cepted fact that nowhere, except in the alimentary canal, 
have the comma bacilli been found in ordinary cases of 
cholera ; as the blood, the liver, the spleen, and other 
organs have all been carefully examined, and in no case, 
in which no fallacy crept in, could positive results be ob- 

The best method yet described of demonstrating the cholera bacillus in the 
discharges is that recommended by Cornil and Babes, who spread out one 
of the small white mucous fragments on a microscope slide, and then allow 
it to dry partially ; a small quantity of an exceedingly weak solution of methyl 
violet in distilled water is then flowed over it, and it is flattened out by 
pressing down on it a cover glass, over which is placed a fragment of filter ■ 
paper, which absorbs any excess of fluid at the margin of the cover glass. 
Comma bacilli so prepared and examined with an oil-immersion lens 
( X 700 or X 800) may then be seen ; their characters are the more readily 
made out because of the slight stain they take up, and because they still 
retain their power of vigorous movement, which would be entirely lost if 
the specimen were drie^, stained, and mounted in the ordinary fashion. 

The bacilli retain their curved shape and " rounded " 
extremities (which, however, may be either slightly pointed 
or thickened), but they seem to be somewhat larger when 
thus prepared than when completely dried. During the 
very early stages of the disease, and when the period of 
reaction is setting in, it is sometimes an exceedingly difficult 
matter to demonstrate the presence of the cholera organism 
in the dejecta, and several methods have been tried with 
greater or less success to obtain such a demonstration. Of 
these the plan described by Schottelius is found to be one of 
the most useful, especially in the later stages of the disease, 
where although the number of cholera bacilli may be com- 
paratively small, other bacteria are found, often in con- 
siderable numbers, in the intestinal contents. 


A small quantity of the material from the intestine is mixed with double 
its quantity of faintly alkaline meat broth, which is then allowed to stand 
at a temperature of 35° C. for about twelve hours ; at the end of that time 
the comma bacilli have multiplied to such an extent, especially where they 
are in contact with the air, that if a small portion of the pellicle from the 
surface is stained and examined, as above, it is found to consist of an 
almost pure cultivation of comma bacilli which are, however, som e what 
shorter than those usually met with. If the cultivation be left undisturbed 
for a longer period the bacilli generally grow larger, and eventually spirilla 
may be formed, but in the course of a few days the other bacteria grow 
so luxuriantly that the comma bacilli no longer predominate, and in many 
cases they are almost entirely "overgrown." From the earlier " maass" 
cultivation so prepared, in which the relative proportion of cholera bacilli 
is enormously increased, " plate " cultivations may now readily be made. 
The plate method as employed by Koch is the best, and the one least open to 
fallacy for obtaining pure cultivations. It is carried out as follows : On a 
sterilized platinum needle a drop of the above fluid, of the cholera discharge 
or of the contents of the small intestine is taken. This is introduced into 
a test tube one-third full of nutrient gelatine, liquefied at as low a tem- 
perature as possible by immersing the lower portion of the tube in warm 
water. The seeded gelatine is carefully shaken in order that the organisms 
may be disposed widely and equally throughout its substance ; three 
small drops of this are then taken on a looped platinum wire and added 
to a second tube, which is similarly shaken, and from this second tube five 
drops are transferred to a third tube. After the contents of each tube have 
been thoroughly mixed and the seed material taken for the next tube, the 
remainder is poured on to a glass plate previously sterilized ; each of the 
three plates is carefully labelled and placed under a bell jar in which the 
air has been thoroughly sterilized (see Appendix). The plate from tube 
No. I is found to contain a large number of organisms, that from tube 
No. 2 contains a much smaller number, and that from tube No. 3 a much 
smaller number still, so that as the organisms are developed (one colony 
firom each organism or group of organisms) there is sure to be sufficient 
space on one or other of the plates between the different groups to allow 
of a careful study of the growths as they extend, and at the same time there 
is a sufficient number of points to ensure the appearance of several growths 
of each kind of organism that was present in the original seed material. 

If plates made according to Koch's method be kept in 
a chamber in which the temperature is maintamed at 
a little over 20° C. small greyish or white points are first 
seen ; examined with a low power lens, each of these has 
a slight yellow tinge and a somewhat wavy margin ; as 
the " colony " increases in size its colour becomes slightly 
deeper, the margins become more and more crenated, 
and the surface somewhat granular. Slow liquefaction 
is now found to be taking place, and small funnel-shaped 
depressions, any one of which seldom measures more 
than i/i in diameter, are seen in the gelatine ; at the 


bottom of these depressions yellow pin-like masses are 
usually seen. In consequence of this liquefaction the colony 
has the appearance of a piece of ground glass with a finely 
notched margin surrounded by a clear zone. On the second 
or third day small air bubbles are seen, and on the fifth or 
sixth day the liquefaction is well marked ; at this stage the 
colony has sometimes a delicate pink tinge, a most charac- 
teristic feature when present. From these points or colonies 
growing, as we have seen, from individual organisms or 
small groups of the bacillus, pure cultivations may be made 
in test tubes containing gelatine, agar-agar, potatoes, or 
broth in or on which the growth and special characters of 
the bacillus may be watched and noted. It is sometimes 
made a matter for reproach to bacteriologists that the 
methods employed in their work, useful enough though 
they may be in conducting scientific experiments, are found 
altogether wanting when they are required for actual prac- 
tical work. The following story, which went the round of 
the medical papers, may help to remove the idea that bac- 
teriologists are mere visionaries, and to prove that the 
science, some of the problems of which they are at- 
tempting to solve, is by no means so useless as many would 
have us believe. An Italian emigrant steamer, touching 
at New York, had on board a child suffering from a sus- 
picious form of diarrhoea, though it could not be said that 
all the symptoms of Asiatic cholera were present. In order 
to determine the true nature of the disease — whether it was 
cholera or not — gelatine plate cultivations of the dejecta 
were made by a doctor in port, and the vessel was detained 
for four days ; during that period bacilli identical in ap- 
pearance with, and having all the characteristics of, Koch's 
comma bacillus were developed, and it was at once con- 
cluded that this was a case of true Asiatic or Indian cholera. 
The diagnosis was subsequently confirmed, as a series of 
other cases occurred, in all of which unmistakable symp- 
toms of Asiatic cholera were developed. An equally in- 
teresting and instructive example of the same thing was 
recorded by Pfeiffer and Gaffky when they were working in 
Koch's laboratory. At a time when there was no general 
cholera epidemic, Gonsonheim and Finthen in Germany were 
suddenly ravaged by a most deadly form of diarrhoea which 
in many features resembled true Asiatic cholera. The 


recorders, in order to determine the exact nature of the 
disease, made plate cultivations from the dejecta of some 
of the patients, and found Koch's comma bacillus ; they 
were thus able to put the matter beyond all doubt. How 
the organism came to the district, and why the outbreak 
remained localized, are questions that still remain un- 
answered. During 1890 there was a similar, but less 
localized, outbreak of fatal diarrhoea in Spain. Koch's 
bacillus was here again separated, and all doubt as to 
the nature of the disease at once removed. 

In view of these facts the immense importance of bacteriological methods, 
as permitting of rapid and definite recognition of the disease, with the possi- 
bility of taking precautionary measures as early as possible, and so prevent- 
ing a wide dissemination of the disease germs, can scarcely be insisted 
upon too strongly. 

In a puncture culture in gelatine the growth takes 
place along the whole track of the needle, first as a delicate 
white cloud, then, as it gradually becomes more and more 
marked, it forms a delicate streak, around which there 
is usually a clear space, due to the liquefaction of the 
gelatine along the tract of the needle. Near the surface the 
liquefaction goes on more rapidly than deeper down, and at 
the end of forty-eight hours there is a distinct funnel-shaped 
area, in which a clear liquid portion usually sinks somewhat 
below the level of the gelatine, and it appears as though the 
top of the funnel was closed by a small clear glass globe or 
air bubble. This appearance is apparently due to the slow- 
ness of the liquefaction, time being given for the water to 
evaporate from the liquefied gelatine. This is proved by the 
fact that if 5 per cent, gelatine instead of 8 or 10 per cent, 
be used, the gelatine liquefying more rapidly does not allow 
time for evaporation to take place, and the bubble is never 
seen. About the fourth day of the growth this " funnel " is- 
still more marked, but the upper part has become quite clear, 
the central thread havmg fallen to the lower and narrower 
part of the funnel, where it may be seen as a comparatively 
short spiral, the thread as it sinks being arranged in regular 
" bights " like those of a cable. After a time the whole of the 
upper part, say two-thirds, of the gelatine is liquefied and 
perfectly clear, then comes a layer of " white " cholera bacilli, 
which rests on the gelatine that has remained solid (this 
sediment has usually a yellowish tinge) ; and on the surface 


of the liquefied gelatine a greyish scum is found, in which 
" involution forms " may be frequently observed. 

Cultivations made with a platinum needle on the surface 
of agar-agar, grow as elevated pale translucent streaks, the 
margins of which are well defined, and in the agar imme- 
diately below the streak there occurs a slight opalescence 
which is very characteristic of the bacillus. The agar, unlike 
the gelatine, is not liquefied. As the growth becomes older 
it spreads, though not very rapidly, the band increases in 
thickness and gradually assumes a brown colour especially 
in the opalescent substratum. When the organism grows in 
meat infusion it forms a delicate greyish pellicle on the 
surface, and in such a medium the movements of the bacillus 
are most characteristic. If a single drop taken from the 
surface of such a cultivation, or even a very small fraction of 
a drop be added to a drop of meat broth faintly tinged with 
a I in 2,000 solution of methyl violet and examined in the 
moist chamber (see Appendix), the bacilli are seen to have 
most rapid movements, especially if the temperature be 
slightly raised ; Koch says, " when they accumulate in num- 
bers at the border of the droplet, and are swimming about 
actively, it seems quite as if they were a swarm of midges, 
between which, diving here and there, are long spiral-shaped 
threads, which are also moderately active." The shorter 
rods become more and more curved, and then stretch them- 
selves out, constantly moving, oscillating and twisting. • 

From numerous experiments carried on by several observers 
it appears that this motility is dependent partly on tempera- 
ture, but chiefly on the desire for oxygen which these 
organisms exhibit. In the " hanging drop " (see Appendix), 
for instance, it will be seen that the cholera bacillus separates 
itself from most other micro-organisms by its movements in 
search of a supply of oxygen, which always bring it to the 
margin of the drop ; once there, however, it loses its motility 
and remains in its acquired position, where its wants 
are supplied without any effort on its part. The cholera 
bacillus also grows on potatoes, but here it should be noted 
the growth does not go on at the ordinary temperature 
of the room, but only when the temperature is raised 
to 30° or 35° C. A fragment of blue litmus paper 
placed on the surface of a slightly moistened boiled potato 
indicates, by turning red, a slight acid reaction, which is due 


(according to Koch) to the presence of an organic (pyro- 
malic) acid. Here the acid reaction of the potato is the 
factor that interferes with the growth of the bacillus, and it 
is only when the temperature conditions become more 
favourable than usual that any growth can take place. 

The growth when started appears as a thin, moist " light 
greyish brown " mass, very similar in character, as Koch 
points out, to the glanders bacillus as grown on potato, 
except that it has not the deep or chocolate brown colour so 
characteristic of that organism. 

A most interesting fact has been observed in this connection. Potato 
cultivations of bacilh from the various cholera epidemics vary somewhat in 
colour; there are also other slight modifications in the appearance of 
the different masses, by means of which a skilled observer, who has 
cultivated the various organisms from the different localities and epidemics, 
is enabled to distinguish the bacilli of each epidemic ; and it is stated 
that in some of the German laboratories the directors can take up half a 
dozen potato cultivations and say, This is from the Naples epidemic, that 
from Egypt, and so on through the whole series. There are undoubtedly 
differences, and to the most inexperienced eye the colour of the Shanghai 
cholera growth may be seen to differ slightly from that of the Egyptian and 
that of the Naples growths. 

On blood serum and in milk these organisms grow most 
luxuriantly. They may cause slight liquefaction of blood 
serum, but in milk, which forms for them an exceedingly 
good nutrient medium, they give rise to no noticeable altera- 
tions ; it may therefore be readily understood how deadly the 
cholera organism may become if it once finds a resting place 
in milk. Its presence cannot be recognized by any peculiar 
or characteristic appearance, by taste, or by smell, as it only 
gives rise to a faintly aromatic and sweetish smell, which 
can scarcely be distinguished, except by the most practised 
nose, from the slightly aromatic smell of the milk itself. 
Dr. Simpson in The Indian Medical Gazette records a 
naturally prepared experiment, which shows at a glance 
what an important part these milk cultivations may play in 
the spread of cholera. On board the ship Ardenclutka, in 
port in Calcutta, ten men partook of the milk supplied by a 
native milk-seller who came to the ship daily ; of these ten 
men, four died of cholera, and five suffered from exceedingly 
severe diarrhoea, the tenth, who escaped, had taken only a 
small quantity of the milk. After careful investigation it 
was found that the milk had been watered with 2 5 per cent. 


of water, from a district in which it was known that several 
people were suffering from cholera. A case had been im- 
ported into this district on the second day of a certain 
month-, the dejecta from this patient drained into a tank, 
near which the milkman's house stood ; on the seventh day 
of the same month the first new case occurred among the 
milkman's neighbours, and on the same day the first case of 
diarrhoea occurred on board the Ardenclutha,.2.-a.A. two days 
later a case of undoubted cholera occurred in the ship. 
These facts are in themselves interesting and instructive, 
but they are rendered doubly so by the fact that of the other 
members of the crew, fourteen in number, who had taken 
none of the watered milk, not a single one was attacked by 
diarrhoea or cholera. 

Cholera bacilli are so little fastidious in their diet, that, 
within certain limits, they are satisfied with anything, but 
there are certain things at which even they draw the line — 
soup tnat'gre, for instance, they abhor, as also sour things ; 
acids are to them a deadly poison ; on the other hand, how- 
ever, they are somewhat exclusive in their habits, and the 
presence of other and more vulgar bacteria they cannot 
brook for long. For example, if intestinal contents or 
dejecta from a case of cholera are sprinkled on moist soil or 
damp linen kept at blood heat the comma bacilli increase 
at an enormous rate for the first twenty-four or thirty-six 
hours, and under these conditions, as already seen, there" 
may be obtained almost pure cultivations of the specific 
organism, but on the third or fourth day it begins to die 
out, and other bacteria are found to be asserting themselves 
most strongly. 

Babes has found that at a temperature of 30° C. the bacillus will grow upon 
various kinds of meat, on eggs, on various vegetables, and on moistened 
bread. It also multiplies in the dejecta from healthy patients, on cheese, 
in coffee, chocolate, eau sucree, and other kinds of fluid sugars ; but it can- 
not exist for twenty -four hours on acid fluids or vegetables, on mustard or 
onions, or in wine, beer, or distilled water. Distilled water and soup 
niaigre are never sufficient for its nutriment, and if the strength of any of 
the usual cultivation media be reduced to about a fortieth of the original 
strength, there is gradual diminution in the number of organisms ; even 
in water which contains an ordinary amount of organic and inorganic 
material in solution, multiplication of the comma bacillus does not take 
place. Where, however, there is a very large accumulation of organic 
matters, as at the margin of stagnant water, where there are large 
quantities of nutrient materials " from the presence of a variety of solid 


particles in suspension and of pieces of mud," development occurs, " especi- 
ally on the floating solid fragments. " Koch's experiments, however, have 
shown that cholera bacilli mixed with spring water were still alive after the 
lapse of a period of thirty days. In Berlin sewer water they lived only six 
to seven days, mixed vrith excrement only twenty-seven hours, and in cess- 
pool water they were not alive at the end of twenty-four hours. Babes' 
experiments, as already stated, did not bear out these statistics in their 

Infection through the agency of milk has aheady been 
mentioned, and water has been referred to as a vehicle by 
which the bacillus may be carried. Macnamara gives an 
experience of infection through water, for the absolute 
accuracy of which, in the case of such a skilled observer, 
Koch contends there can be little doubt. In a region in 
which no cholera prevailed, the dejecta from a sporadic 
case of cholera became accidentally mixed with some water, 
which, after remaining exposed to the heat of the sun for a 
whole day, was partaken of by nineteen persons, of whom 
five were attacked with unmistakable cholera within thirty- 
six hours ; the evidence here given was so conclusive that 
little doubt can be entertained as to the relation of the 
dejecta to the water, and to the subsequent cases of cholera. 
It should here be mentioned, however, that Klein, who does 
not believe in the specific nature of Koch's cholera organism, 
in order to prove his position, drank a quantity of fluid 
which was said to contain cholera material without feel- 
ing any ill effects ; and that Bochfontaine swallowed 
cholera dejecta in pills without suffering any incovenience ; 
but in both cases there is ample evidence that the persons 
experimenting upon themselves were suiFering from no gas- 
tric or intestinal derangement of any kind, and that the 
gastric juice was sufficiently active to prevent the multipli- 
cation of the cholera organisms, and it is probable that the 
fourteen men of the nineteen not attacked in Macnamara's 
case were in a similar impregnable condition. As positive 
evidence to set against the above is a most striking case that 
occurred in connection with Koch's cholera courses, carried 
on in the Hygienic Institute in Berlin. A doctor who had 
been for eight days engaged on work in the cholera course 
became affected with a slight disturbance of digestion, which 
was accompanied by diarrhoea ; he continued to get worse, 
and was at length so ill that he started for home, where he 
was almost immediately attacked with symptoms of true 



cholera, rice-water stools, great weakness, unquenchable 
thirst, diminished excretion of water, except by the bowel, and 
spasmodic contraction of the feet and toes. He was very 
anxious to have this rice-water material examined for the 
comma bacillus, and a 'quantity was despatched to Koch, 
who was able to demonstrate in and cultivate from it, true 
comma bacilli ; the patient recovered. There were no other 
cases of cholera in Germany at the time, but the doctor had 
been examining and making cultivations of the cholera 
bacillus shortly before he was attacked, and there can be 
little doubt that he had, through inattention to the rules of 
the laboratory, in some way or other, ingested some of the 
bacilli with which he had been working. 

The description of these cases of infection or non-infection 
of individuals by cholera material introduced into the 
alimentary canal, naturally opens up the way for an account 
, of the results obtained experimentally. 

Thiersch was the first to make experiments on animals 
with cholera dejecta. He fed white mice with scraps of 
filter paper, impregnated with decomposing cholera dejecta, 
but he found that plain filter paper was equally efficacious 
in causing the illness of the white mice. He was quickly 
followed by Burdon Sanderson, who carried on a similar 
series of experiments, and obtained much the same results. 
Dr. Richards, of Goolando, also attempted to produce cholera 
in pigs by feeding them with large quantities of cholera 
material, but he found that the animals died in from fifteen 
minutes to two and a half hours after the administration of 
the poisonous material, and the contents of the intestine of 
the first pig that died, when given to another, produced 
absolutely no symptoms. It was argued from this that the 
poison had not multiplied, but had been destroyed or ab- 
sorbed, or rendered inactive in the stomach of the first host, 
so that none was left to act on the second pig ; death in the 
first case being produced by rapid intoxication through the 
introduction of a large quantity of some active poison, and 
not by a poison developed in the intestinal canal as in the 
case of true cholera. This poison, whatever its nature, 
had no effect on dogs. 

Following on these came a series of experiments by Koch, 
who attempted to produce symptoms of cholera by feed- 
ing and moculating in various ways, mice, monkeys, cats, 


dogs, poultry and other animals with cholera dejecta and 
with comma bacilli ; in no case could he produce cholera, 
and on search being made for the bacilli in the stomach and 
intestine, they were invariably absent, apparently having 
been destroyed in the' stomach, as in only a few instances did 
they reach the intestine at all, and then in very small 
numbers. To demonstrate the difference between these and 
certain other bacteria, a mouse was fed with a red micro- 
organism that had been isolated in a pure condition ; and 
after a time its intestinal contents were disseminated on 
potatoes, on which small red colonies, of the same organism 
shortly made their appearance, showing that their vitality 
was not appreciably affected by their passage through the 
stomach. Having found that the comma bacillus was so 
destroyed, Koch thought that if the organism could be intro- 
duced directly into the large intestine, so as to escape the action 
of the gastric juice, it might be able to retain its vitality 
and multiply ; the results obtained, however, were in all 
cases negative, even when purgatives were previously given 
to induce an altered condition of the intestine. The only 
cases in which partially successful results were obtained were 
those of a series of rabbits into which pure cultivations of 
the bacillus were injected directly into the circulation, and 
of a number of mice, in which the cultivations were injected 
into the abdominal cavity ; the rabbits recovered in one or 
two days, after suffering from marked symptoms of intoxi- 
cation ; but the mice died at the end of the first or second 
day, bacilli in these experiments being found in the blood. 
Koch argued from these observations (i) that the gastric 
juice of the healthy stomach killed the micro-organism ; 
(2) that even when it found its way into the intestine, it was 
passed along it so rapidly that it could not take any effect on 
the healthy or even slightly irritated mucous membrane, or 
that it was actually very rapidly destroyed in the intestine 
itself. In guinea pigs, in which he attempted to produce 
cholera, he found that there was great acidity of the gastric 
juice, and that the peristaltic movements of the intestine 
were very strong and rapid. 

It will have been concluded from what has been stated 
that both naturally and in artificial cultivations there is 
some poison developed during the growth of the bacillus, 
which, when introdiiced in considerable quantities, produces 


a condition of intoxication, which would account for the 
death of those animals in which partially successful results 
were first obtained. Further, it is evidently quite possible 
that this intoxication may account for the very rapid deaths 
which occur during certain epidemics, and also for the pre- 
liminary diarrhoeas by which the intestine, in some cases at 
any rate, is prepared for the reception and multiplication 
of the cholera organism itself. It must, indeed, be looked 
upon as one of the common causes of this diarrhoea. If 
these facts be borne in mind it is possible, even without 
analyzing the further experiments on animals, to understand 
the immunity against cholera experienced byBochfontaine and 
Klein, and the susceptibility of the doctor who was attending 
the cholera course, whilst he was suffering from indigestion 
and diarrhoea. It may also be understood how infection 
occurs by milk and through water after what has been 
described, and in accordance with these facts is the experience 
of all those who have had to deal with cholera epidemics. 

Utilizing the experience gained by Koch in his experiments, Nicati 
and Rietsch performed a series of operations, by means of which they 
claimed they were able in a certain proportion of cases to produce 
typical cholera symptoms. They introduced pure cultures of the comma 
bacillus into the upper part of the intestinal canal, having previously 
tied the bile duct ; but as Koch pointed out later they were successful in 
producing true cholera, probably, only in those cases in which the intestine 
was somewhat injured during the manipulation to which it was necessarily 
subjected, and its peristaltic action interfered with, and it is very naturally 
objected that death might be due not to the action of the cholera bacillus at 
all but to this rough manipulation. The observers themselves believed that 
it was the presence or absence of bile in the small intestine which determined 
the success or failure of their experiments. 

In order to avoid the operation of opening into the 
duodenum, Koch thought that the two great factors in 
bringing about the destruction of the bacilli might be 
thrown out of court, first by neutralizing the acid reaction 
of the stomach by means of 5 c.c. of a 5 per cent, solution 
of carbonate of soda ; and, secondly, by interfering with the 
peristaltic action of the bowel. He found in test experi- 
ments that the intestinal contents remained distinctly alka- 
line for six hours after the introduction of such a solution. 
But he also found that the organism still passed through the 
stomach alive, and that it failed to produce any changes in 
the small intestine, the food and the bacilli passing frorn the 

CHOLERA. ■ 165 

stomach to the caecum in a few minutes ; the peristaltic 
action of the intestine causing such rapid passage of the 
bacillus that it was completely powerless to produce any 
characteristic symptoms of cholera, a fact the importance of 
which was accentuated when it was found that the only 
guinea pig in which any choleraic symptoms were observed, 
and in which there was any increase in the number of bacilli 
in the small intestine, was probably suffering from an attack 
of peritonitis, due to the animal having aborted just previous 
to the experiment — a condition in which, as has long been 
recognized, there is invariably interference with the peristaltic 
action of the intestine. It was possible, then, that this second 
factor might be neutralized by the introduction into the 
peritoneal cavity of some reagent, which would by its 
action cause partial or complete paralysis of the small 
intestine. For this purpose he first used opium, but he 
afterwards found that alcohol was equally efficacious. After 
administering the soda solution, and injecting into the 
stomach of the guinea pig 10 c.c. of broth, to which one or 
several drops of a pure cultivation of bacilli had been added, 
he injected into the abdominal cavity tincture of opium, in 
the proportion of I c.c. to every 200 grammes of the animal's 
weight ; the results he obtained were indeed startling. 

Of course objections were raised to the method, and it was argued that some 
of the animals died from an overdose of opium, some from blood poisoning, 
and so on. Subsequent observers found, indeed, that the dose of opium 
was somewhat too large, as some animals experimented on never awoke 
from the opium sleep. Macleod, of Shanghai, found that he obtained the 
best results by giving " repeated doses of i c.c. or less of the tincture till 
the animal was stupefied sufficiently to lie on the side or back for ten 
minutes when placed in that position." " Several times," he says, "the full 
dose recommended by Koch had to be given, but usually a smaller one 
sufficfd." Control-animals treated, according tc Macleod's method, and in 
all respects in the same way, with the exception that they received sterilized 
broth instead of cholera material, always recovered. 

The contents of the bowel or dejecta from cholera patients 
passed into the stomachs of guinea pigs so prepared, pro- 
duced cholera symptoms and death. Giving the results of 
of his experiments, Macleod states that from one of the 
animals that died after a dose of cholera material, the small 
gut contents were collected into a sterilized vessel, and 
injected (by means of a fine indiarubber flexible catheter) 
in doses of 2 c.c. into the stomach of two other animals. 

1 66 • BACTERIA. 

These two animals died, and the contents of their small 
intestine were used in the same way, and so on through ten 
generations. Of twenty-one animals thus treated, two 
recovered, nineteen died. The doses varied from 0.5 to 
2.5 c.c. 

It is sometimes argued that in consequence of the difference of the 
symptoms in animals (especially guinea pigs), and in man, under these 
conditions of infection by the stomach, the disease cannot be the same, and 
■ it is pointed out that vomiting and profuse diarrhoea are entirely absent in 
cholera, experimentally produced. Against this objection may be put the 
fact that there is usually in the guinea pig a large accumulation of fluid 
transudation in the small intestine and even in the stomach ; whilst in the 
very acute forms of cholera the pathological appearances presented in the 
intestines are almost identical with those found in man. ' In exceedingly 
acute cases the peritoneum presents a dark colour and a peculiar glistening 
mucous appearance, which is very characteristic, and seems to be associated 
with the tarry condition of the blood. The mucous surface of the intestine 
is usually congested, and in the intestinal canal is a considerable quantity 
of serous fluid, in which are floating the small white rice-like bodies which are 
merely portions of desquamated epithelium and mucus. There is usually, at 
this stage, marked injection of the vessels of the solitary glands, and at 
the periphery of the Peyers patches, and the longer the patient remains alive 
the more accentuated become these appearances. It is only in the later 
stages of the disease, or during the period of reaction, that the swelling 
of the follicles is very marked, and that more or less extensive ulceration 
of the mucous membrane may be observed. The dejecta, of course, are 
similar in character to the contents of the bowel, are watery owing to the 
great amount of serous effusion, and contain the rice-like bodies in which 
are found the comma bacilli. Bacilli are also found lying free in the 
watery fluid. The dejecta have little or no odour, and when they are 
allowed to stand they separate into two layers — an upper slightly grumous 
layer, and a lower grey deposit. "Neutral, or slightly alkaline, they con- 
tain a very small proportion of organic or inorganic salts — one to two per 
cent. — which consists of chloride of calcium, carbonate of ammonia, potash, 
salts, and a small quantity of urea. They contain little or no albumen, and 
during the first day or two no bile pigments." 

If microscopic sections of the lower part of the small 
intestine be made, and stained according to Loffler's 
method,' the bacilli may be seen with the aid of a high 

» First stain in a solution of Leonhardi's Dresden methyl violet ink, and 
then in an alkaline solution of fuchsin, which is made up as follows : 
100 c.c. aniline water. 

1 c.c. of a solution of one per cent, of caustic soda. 

2 grammes of solid fuchsin. 

The whole is well shaken, after which the specimens may be left in it for 
twenty-four hours ; the sections are then washed in distilled water acidu- 
lated with a drop of acetic acid, dehydrated in absolute alcohol, cleared up 
in cedar oil, and mounted in Xylol balsam. 


magnifying power ( x 800) beneath the loosened epithelium 
of the villi, in the follicles, and in the surrounding connec- 
tive tissue. They are especially numerous near the ileo- 
csecal valve, and are distributed, not in masses, but usually 
in ones, twos, and threes, scattered thickly through these 

On post-mortem examination of the guinea pigs, in whicli cholera had 
been experimentally produced, "the blood was fluid, thicker and darker 
than natural, the tissues of the thoracic and abdominal walls were re- 
markably dry, the small intestine was throughout distended, congested, and 
paralyzed-looking, and occupied a much larger proportion of the abdominal 
cavity than usual. The cjecum was distended with fluid or semi-fluid con- 
tents. If the animal died early the fluid was not quite clear in the small 
gut, there being present traces of food ; still the watery character was very 
manifest, and mucous flakes were abundant. If the animal died on the 
second or third day no food remains were to be seen, and the fluid in the 
small gut was the counterpart of the typical cholera stool of man. In 
either case the comma bacilli were demonstrated microscopically, and by 
cultivation as in man." 

While the organisms in the broth injected could be frequently counted in 
a microscope field, in a drop of the small bowel contents from an animal 
having received such broth, the bacilli might be so numerous that counting 
them, without dilution of the fluid examined, was an impossibility. On 
floating the bowel in water, the stripping of the epithelium could be well 
demonstrated "immediately after death," a fact which appears to dispose of 
Macnamara's assertion that this separation of the membrane is alwaj^ a 
post-mortem appearance. In animals which died about the eighth day 
the appearances were very similar to those met with in cases of Asiatic 
cholera, when the patients have succumbed during the stage of reaction, 
and no bacilli can be found in the intestinal canal or in the surrounding 
tissues. In the earlier stages the bacilli can be demonstrated in sections 
lying under the partially-detached epithelium, or in the lumina of Lieber- 
kuhn's follicles. 

In fluid cultivations, as has already been mentioned, the 
comma bacilli, or little groups of them, assume various forms, 
all of which, however, may be looked upon as made up of 
more or less perfect spirals. At the point of division, just 
before division take places, there is a small clear space which, 
by some authorities, has been looked upon as a spore. In some 
of Macleod's preparations this appearance was so marked that 
it was difficult to convince oneself that it was not due to 
actual spore formation, but as drying for twenty-four hours 
completely destroyed the activity of the bacillus in which 
these clear spaces were most marked, and as they could not 

' It isnot my intention to give the complete pathologicalanatomy of cholera, 
except so far as it is associated with the presence of the cholera bacilli. 

l68 BACtERlA. 

be stained by any of the oidinary spore-staining methods hS 
was convinced that he was not' deaUng with true endospores. 
On three occasions Hueppe-was able to demonstrate in moist 
chamber cholera cultivations on agar-agar small brilliant 
spore-like bodies which he called " Arthrospores." These 
wete placed sometimes at the extremities, sometimes in the 
middle of the comma bacillus. They appear to develop 
where the conditions of nutriment, temperature, or moisture, 
are somewhat unfavourable to the development of or 
to the very existence of the bacillus. This is proved by 
the fact that the protoplasm in the bacilli, in which these 
arthrospores are present, is stained very imperfectly with 
methyl blue; the clear bodies themselves taking on a brownish- 
red tinge. Hueppe maintains that he has observed these 
bodies germinate out into comma bacilli, and he holds that 
they are much more resistant to various germicidal reagents 
and unfavourable conditions than the vegetative form of 
bacillus. Several observers have tried to repeat these ex- 
periments, but, as any apparent spores that have been 
formed invariably failed to resist the action of drying, such 
" Arthrospore " containing bacilli, must, for the present, be 
looked upon as involution forms, similar to those described 

When these are formed the ordinary dimensions and forms of the comma 
bacillus as previously given are sometimes departed from, and in old agar- 
agar cultivations, and in old gelatine cultivations in which the surface has 
become somewhat dried, spirals are frequently found of which the con- 
stituent bacilli are considerably thicker than ordinary comma bacilli, the 
large curved forms remaining attached by delicate terminal filaments. In 
most cultivations there are slight modifications in both form and size of 
the cholera bacillus, which appear to be associated with the diificulty or 
facility with which they obtain food, water, and oxygen, and also with the 
temperature at which they are grown. For example, if ten per cent, of 
alcohol be mixed with the gelatine, or if the gelatine medium contains 
but little beef extract or peptone, and if the temperature at which the 
media are kept be very high or very low, say 45° C. on the one hand 
or 20° C. at the opposite extreme, a large proportion of spiral fila- 
ments is formed ; whilst if the medium be well adapted to the nutri- 
tion of the organism, and the cultivation be kept at a temperature 
of 36° C, short comma bacilli are almost exclusively developed. It is 
a curious fact, however, that, once developed, these various forms may 
persist or pass on their characters unchanged for one or two generations, 
even though they are now inoculated into ordinary fresh peptonized gelatins 
medium, and Cornil and Babes say that if there are inoculated simul- 
taneously, on peptonized gelatine, a fresh culture of filaments, another of 
ordinary comma bacilli, and a third with the short and only slightly curved 

dH6LfiRA. 16^ 

bacteria which are formed under various conditions, the same typical naked- 
eye appearances of the cholera bacillus are always obtained in each case, 
but on microscopical examination it is found that the first still develops in 
the form of spiral filaments, the second as comma bacilli, and the third as 
short bacteria, and that these characteristics are carried on to the fourth 

With all these modifications in form they still produce typical cholera 
symptoms when injected into the alimentary canal of animals. In addition 
to these changes there frequently appear at one extremity of the bacillus 
small cystic dilatations which are due, according to Virchow, to a kind of 
oedematous degeneration. As these dilatations make their appearance in 
certain bacilli, others of them shrivel up, and tadpole and spindle-shaped 
organisms are formed which may break down into small granules and frag- 
ments. In the later st^es of degeneration these various involution forms 
are completely sterile. In the earlier stages, so long as they take on the 
aniline colouring matter pretty freely, successful inoculations may usually 
be made, but if the unfavourable conditions are continued in the new 
cultivations, the organisms soon lose both their power of taking up the 
staining reagents and of reproduction. 

It has been stated that the comma bacillus is entirely an 
aerobic organism, and there can be little doubt that its vege- 
tative activity is much more marked when the organism is 
grown in contact with the oxygen of the air. It is certainly 
more resistant to the action of germicidal agents, and exhibits 
movements in a much more marked degree. It had been 
observed, however, that comma bacilli do not cease to multi- 
ply even when their supply of free oxygen is entirely cut off, 
but under these conditions, as Wood has pointed out, the 
bacteria are much more sensitive to external influences, and 
are very readily destroyed by acids and other germicidal 
agents. He has found, however, that where free oxygen is 
cut off, as Pasteur had observed in the case of other ferments, 
the bacilli produce a relatively much larger quantity of the 
specific toxine, or poison, than when oxygen is present, 
and by a number of ingenious experiments he showed that 
when they were grown on albuminous substances with com- 
plete exclusion of oxygen, and of substances from which 
oxygen could be easily derived, the cholera poison was pro- 
duced more energetically and more rapidly than under the 
ordinary conditions of aerobic cultivation ; probably because, 
under these conditions, much larger quantities of albumen 
must be split up to meet the energy requirements of the 

Wood and Hueppe from this argue that the bacillus gives 
rise to such important changes in the intestine because there 

1 7(3 iBACTERtA. 

we have quantities of albuminoid material which can hi 
rapidly broken up by the action of the bacilli even in the 
complete, or almost complete, absence of oxygen, which is 
supposed to rule in the intestinal canal, as a result of which we 
have the formation of large quantities of toxine and rapid in- 
toxication. But as they are voided in the dejecta after growth 
under these conditions, the cholera organisms are more easily 
destroyed than at any other time or under any other condi- 

It is very significant that in cholera, yellow fever, and typhoid fever, 
three diseases in which the manifestations are chiefly in the intestinal canal, 
and in which the evacuations apparently contain the living poison, direct 
infection from the stools appears to be the exception rather than the rule, 
and Wood explains this as due, at any rate in part, to the state in which the 
specific organisms associated with these diseases are present in the stools, 
and are dependent upon the conditions present in the intestinal canal. 
Should they find their way during this stage into the stomach of the living 
person they, being more susceptible, would be much more liable to be 
destroyed by the acid gastric juice, or to undergo attenuation ; but if they 
are allowed to live outside the body, even for a short time, they become 
more resistant in character, they multiply more readily, they are less par- 
ticular about the nature of their food, and consequently they are much more 


Cholera (continued), 

Pettenkofer's researches — Saprophytic and Parasitic Stages of Cholera 
Bacillus — Temperature Conditions — Relation to Epidemics — Moisture 
— Ground Water — Flushing — Cholera in Shanghai Endemic but 
Intermittent — Cholera Endemic at the Mouth of the Ganges — Vitality 
of Cholera in Old Cultures — Relation of this to Quiescent Periods 
during Parts of the Year — Gastro-intestinal Irritations prepare for 
Cholera — Chinese Vegetables — Cholera Poison Formed in the Intestine 
absorbed into Body — Inoculation against Cholera — Gamaleia's Experi- 
ments — Germicides useful in attacking the Cholera Bacilli — Water 
Supply, Pilgrimages, Feasts predisposing to Cholera —Quarantine 
except in Harbours Useless — Time and Place Dispositions. 

Pettenkofer's indefatigable researches on the relation of 
ground water and the drying zone to cholera epidemics have 
thrown much light on many obscure points, and have opened 
up the way for further work. He holds that the increase of 
cholera is due entirely to the increase of the " drying zone " 
near the surface of the soil — z'.e., the lowering of the level of 
the " ground water," and that the rise and fall in the level of 
this ground water is the principal factor in the production of 
conditions necessary for the outbreak of epidemics of various 
kinds. On these grounds he has itaken up a very strong 
position against the spread of cholera directly from patient 
to patient. There can be little doubt that many of Petten- 
kofer's observations are entirely in accordance with this view, 
but equally can there be little doubt that all his interpreta- 
tions of the facts he has collected are not entirely accurate, 
although, as Hueppe points out. Wood's observations offer 
solutions of questions that have hitherto been unanswerable. 
The instances are almost innumerable in which there has been 
a most remarkable immunity against the passage of cholera 
from individual to individual ; where the dead bodies have 
been buried immediately the disease has afterwards occurred, 
not in those who have had to carry out the actual burying of 

172 feACfERfA. 

the dead cholera patient, but in those to whom has fallen the 
duty, a day or two later, of washing the soiled linen used by the 
patient during life. In the first case the attendant is exposed 
to the action of the bacillus as it comes from the patient, but 
at a time, it is argued, during which the organisms are more 
readily destroyed, either in the dejecta, or by drying ; but the 
attendant who has to wash the soiled linen may be attacked 
by the bacillus after it has had time and opportunity to 
develop on the damp sheets, in the presence of air, and when 
it has acquired a greater power of resistance, and has become 
much more dangerous. It has now, in fact, lost its anaerobic 
habit, and has become adapted to its new surroundings, with 
the result that it is much more resistant and is better qualified 
to live outside the body and to resist the action of ordinary 
germicidal reagents, or of the acid gastric juice, should it find 
its way into the stomach of a fresh host. 

In similar fashion may be explained the fact that when 
the drying zone becomes limited, the cholera bacillus appears 
to die out more readily. It appears that the micro-organism 
passing directly from the faeces into very damp soil contain- 
ing insufficient oxygen to satisfy its saprophytic requirements 
is,onaccountof itsfeebleresistingpowers, "suffocated" atonce, 
or within a very short period. Where, however, the depth of 
the drying zone increases, there is more air (oxygen) in the soil, 
the organisms are more able to multiply in its presence, and, 
taking the field against other putrefactive organisms, gradually 
become more and more hardy, acquire the aerobic and sapro- 
phytic habit, and thus become more dangerous to the inhabi- 
tants of the locality in which all this occurs. It must be re- 
membered, however, that the term "drying zone" is entirely a 
relative one, and that it may still contain, as it usually does, 
sufficient moisture for the wants of the cholera organism. That 
the organism takes some little time to pass from the aerobic to 
an anaerobic condition is evident from Koch's early experi- 
ments, in which he made plate cultivations of cholera bacillus, 
and then, before the gelatine was perfectly set, covered about 
one-third of the surface with exce'edingly thin glass — cover 
glass thickness — or split mica. He then found that colonies 
grew as usual, and became visible to the unassisted eye in the 
uncovered portion of the gelatine and for a very short distance 
under the covering plate (2 mm.). He observed, however, 
that where the air (oxygen) was cut off, the colonies did not 


increase in size sufficiently to allow of their being distin- 
guished without the aid of a lens ; the power of growth to 
the size of a colony visible to the naked eye being attributed 
by Koch to the presence of the small quantity of available 
oxygen that remained in the nutrient gelatine, — growth 
ceasing as soon as this oxygen is exhausted, — the colony 
remains of small size. 

A second experiment was made by inoculating nutrient 
jelly contained in a small glass with comma bacilli ; this " was 
placed under the receiver of an air pump, another glass pre- 
pared in a similar way being placed outside the air pump as 
a control experiment. It then appeared that those bacilli 
under the air pump did not grow, while those outside the 
receiver did well. But if those which had been under the 
receiver were afterwards exposed to the action of the air, they 
then began to grow. They therefore had not been destroyed ; 
they only wanted the necessary oxygen to be able to continue 
their growth. A similar result is obtained when cultivations 
are placed in an atmosphere of carbonic acid ; whilst those 
cultivations placed for control purposes outside the carbonic 
atmosphere grow in the usual manner, those subjected to the 
action of a stream of carbonic acid remain inactive and undergo 
no development. Here also, however, they do not die ; for 
after they have been exposed to the carbonic acid for a con- 
siderable time, they again begin to grow as soon as they are 
taken out of it." In place of carbonic acid, hydrogen may 
be used, and the result is much the same. 

It cannot be assumed from these experiments that the organisms require 
to obtain free oxygen from the air in order that they may continue their 
growth, for, as has been pointed out by Hueppe and Wood, if they are 
grown on a suitable medium, such as unchanged normal albumen, they are 
able not only to exist, but to produce unusually large quantities of their 
specific poison, as they are able by the dissociation of such a medium to 
obtain all that they require for their growth and development. 

All that can be argued from Koch-'s experiments is that the bacillus has 
a saprophytic stage (although this was apparently not at first recognized by 
Koch), during which it grows and multiplies, but only under ordinary con- 
ditions where free oxygen can be obtained from the atmosphere. During 
its parasitic existence it becomes so far modified, that, still growing with 
great vigour, it produces its toxine more easily or in greater quantities in 
the absence of oxygen, other conditions being favourable. During this 
stage, however, it is much more readily affected injuriously by acids and 
other germicidal reagents, and is therefore much more easily destroyed 
than when jt has bad time to acquire its full saprophytic faculties. 


Mention has been made of the conditions as regards 
temperature that are necessary for the growth of the cholera 
bacillus when other conditions are slightly adverse._ As the 
result of an extensive series of experiments, first carried on by 
Koch, and afterwards repeated by other observers, it has been 
found that the comma bacillus flourishes most luxuriantly, 
and is most productive, at a temperature ranging between 
30° and 40° C, although it can grow at a much lower tem- 
perature, and even at several degrees above the higher point 
mentioned. At 20° C. it flourishes luxuriantly upon a 
peptonized gelatine medium. 

As early as 1884 Koch described the growth of the 
cholera bacillus at a temperature of 17° C, but as might 
be expected the growth is not nearly so prolific, and it is 
certainly considerably less rapid than at a slightly higher 
temperature. A temperature below 17° C. seems to be 
inimical to the growth of the bacillus, as at 16° C. develop- 
ment may be said to have almost ceased. It is, however, 
remarkable that an intense degree of cold does not deprive 
the organism of its power of growing, for, if after being ex- 
posed to great cold for some time, it is again placed under 
favourable conditions, it appears to regain its powers of 
rapid multiplication. Koch, to test this, submitted a culti- 
vation of the bacillus for one hour to a temperature of 10° 
C. (10° C. below freezing point), with the result that the 
nutrient medium was completely frozen. This was now 
thawed, and a cultivation made at a higher temperature and 
under favourable conditions ; the bacillus began to grow 
again almost immediately, and appeared, indeed, to have lost 
none of its vitality. These experiments accord well with, 
and verify the observations that have been made on, the 
appearance and spread of cholera epidemics in the hot and 
cold seasons. Most of the cholera-epidemics seem to have 
attained their maximum virulence during or at the end 
of the hot season of the year. In those regions that are 
periodically visited it usually breaks out in the autumn, when 
the external temperature is most favourable to the growth of 
the bacillus as a saprophyte, and when in consequence the 
micro-organism is enabled to live for a longer period outside 
the body, to give rise to numerous progeny and thus to 
multiply the possible sources of infection. On the other 
hand epidernics are of frequent Qccurrence, even in the 


coldest seasons of the year ; nay, in some cases the appear- 
ance of the cold damp season is the signal for the outbreak 
of a cholera epidemic, because not until the return of the 
cold weather, after the hot dry summerand autumn months, is 
there that dampness of soil and atmosphere which is essential 
for the existence of the organism, in addition to which the soil 
remains at a comparatively high temperature for some time 
after that of the atmosphere has fallen. Again, the external 
cold, though it may paralyse the organism for a time, does 
not destroy its vitality, but, keeping the organism in a 
passive condition, actually enables it to retain this vitality 
for a considerable period, so that, when it finds its way into 
dwellings, in which the atmosphere, owing to bad ventilation, 
is not only raised to a high temperature, but also contains a 
considerable quantity of moisture and organic matter, it is at 
once introduced to conditions that are essentially favourable 
to its saprophytic existence ; it again begins to thrive 
luxuriantly, and becomes a possible source of infection. 

The fact must not be ignored, also, that seasonal temperature plays not 
only a most important part in the determination of the amount of moisture 
in the air and in the soil, but also in the production of currents of air by 
which the organisms may be carried from point to point {though these 
currents, when the air is dry, or in hot, clear weather, play but a small part 
in the dissemination of the disease), and by its effects on certain kinds of 
vegetation, which indirectly have been proved to play an important part in 
the distribution of the cholera organism. 

On the effect of heat on the amount of moisture in the 
atmosphere, and consequently on the depth of the ground 
water, it is scarcely necessary to speak at any great length, 
but there can be little doubt, from Pettenkofer's observations, 
that siich factors do play a most important part in condition- 
ing the growth and multiplication of the cholera organism. 
The rapid removal of stagnant and upper ground water (if 
complete) is inimical to the saprophytic growth of the 
cholera organism, as even organic matter in a state of dust is 
absolutely useless as a nutrient material for the cholera 
bacillus. Where, on the other hand, there is a considerable 
quantity, of moisture in the atmosphere, even though the 
temperature be high, stagnant water is often found. 

Koch says : " On the surface or in the ground, in marshes, m docks, which 
have no outlet, in places where the ground is formed like a trough, in sluggish 
rivers and the like . . . there a constant nutrient solution can be formed and 


may accumulate in the neighbourhood of animal and vegetable decaying 
matters most readily and give the micro-organisms opportunities for growth ; " 
and he further says, " that whenever the water has a swift current, or is in 
a constant state of change, both on the surface and in the ground, these con- 
ditions occur less easily, or sometimes not at all, for the continuous current 
prevents a localized concentration of nourishment in the fluid sufficient for 
the pathogenic bacteria. The connection between the sinking of the 
ground water, and the increase of many infective diseases, we might explain 
thus : that with the sinking of the ground water, the current which exists in 
it becomes very much lessened. Besides, the mass of water lying superfici- 
ally at disposal will be considerably diminished, and therefore such a 
concentration as I have described as necessary for the growth of" the 
bacteria will be produced much sooner." 

These conditions are necessarily closely associated with 
temperature, with the nature of the sub-soil, and the pre- 
vailing winds and air currents, and the consequent affection 
of the quantity of moisture in the atmosphere, and the pro- 
duction of rain must also be taken into account, as even the 
transmission of the cholera organism is affected or interfered 
with by great dryness of the atmosphere. Where there is 
great dryness of the atmosphere the small quantities of 
cholera dejecta, which are likely to be left unnoticed, and 
therefore left disinfected by the attendants of the patient are 
so rapidly dried that they are speedily rendered inert, and 
cannot convey the infection further ; whilst the materials on 
which, in ordinary circumstances, they would thrive, are so 
dried on the surface that although the organisms may find 
their way on to them in a living condition, there is not 
sufficient moisture left to allow of the development of the 
probably somewhat weakened organism. 

As Fliigge points out, such conditions " only occur where there is a very 
great deficiency in the saturation of the air with moisture — for example, in a 
desert ... It is conceivable that in a desert climate such as is present in 
Mooltan and Lahore during the greater part of the year, and where every- 
thing dries up, as it were, under one's eyes, the conditions favourable for 
the spread of the cholera may only be present at most during the some- 
what moister or so-called ' rainy ' season (July to October). " 

Extreme wet may, however, exert an influence in interfer- 
ing with the saprophytic growth of the organism, especially 
if the rains be heavy and continuous. The conditions men- 
tioned by Koch, as inimical to the collection of organic 
material on which the organism may grow, are brought into 
play, infective dejecta are removed from the surface soil, 
from the surface drains and from the sewers, rapid and con- 


tinuous currents are created, organic matter of all kinds is 
washed away, air is driven out from the subsoil owing to the 
rising of the ground water, and all the conditions become 
unfavourable for the growth of the organism. The fact that 
vegetation has been mentioned, as associated with climate in 
the production of cholera, requires some explanation, which 
will be given later. Dr. Macleod, writing on the subject of 
chmate itself, says : 

" Cholera makes its appearance in Shanghai every summer with start- 
ling regularity. Before the end of July it is hardly met with, by the end of 
August it is well marked, in September it is in lull swing, not quite so 
virulent in October, and in the beginning of November an occasional case 
may be heard of, after which time it disappears entirely till the following 
late summer. For twenty years this has gone on with unfailing regularity 
under the observation of medical men now resident, and for how long " 
previously no one can estimate." He then goes on to describe the weather 
in June as damp and hot, in September as hot, damp, and muggy, in 
October as cool and wet during the first part, and as frosty towards the end, 
" at Christmas there is usually ice, there may be snow." He then says, "so 
far as temperature of the air is concerned, we enjoy tropical heat for nearly 
a couple of months before the disease breaks out ; it is most virulent in the 
hot, damp September, and does not disappear until after the hoar-frosty 
mornings are experienced " (the end of October). 

Dealing with the same subject Koch has stated that in 
no part of the world, of which the climate, the geology, and 
the epidemiology are known, does cholera occur all the year 
round except in the province of Bengal, and he says : 

"All authors are agreed, that the delta of the Ganges is the true home 
of cholera, and I have come to the conclusion that this is the case, and that 
there are no other places of origin of cholera in India. For the only district 
in India, where cholera prevails continually year after year in a uniform 
manner, is the delta of the Ganges. In all other places it shows marked 
variations, or it may even disappear altogether for a shorter or a longer time. 
In certain places, for example in Bombay, it never entirely disappears, but 
it is highly probable, that on account of the unusually active trade with the 
rest of India it is constantly being imported there afresh." He then 
describes this tract as a perfectly flat country only slightly raised above the 
sea level, which, during rainy seasons, is almost entirely under water in the 
lower part of the delta, where the " Ganges and the Brahmapootra break up 
into a network of water courses, in which the sea water, mixing itself with 
the river water, flows hither and thither with the tide, and at flood time 
places large tracts of the Sunderbunds under water. A luxuriant vegetation 
and an abundant animal life have developed in this uninhabited region, 
which is inaccessible to man not only on account of the floods and the 
numerous tigers, but is avoided principally on account of the_ pernicious 
fever which attacks everybody who remains there even for quite a short 
time. One can easily imagine how dense the vegetable and animal matter 



is which is given up to decomposition in the marshy districts of the 
Sunderbunds, and that here an opportunity is afforded for the development 
of micro-organisms, such as exists in scarcely any other place_ on tlie globe. 
Peculiarly favourable for this are the regions between the inhabited and 
the uninhabited parts of the delta, where the excrements of an unusally 
thickly populated country are washed away by the current, and, flowing 
here and there, are mixed with the brackish water of the Sunderbunds, 
already teeming with decaying matter. Under these peculiar conditions 
quite a distinct fauna and flora of micro-organisms must be developed 
there, to which in all probability the cholera bacillus belongs. For every- 
thing points to the cholera having its origin in this district. All the greater 
epidemics have begun with an increase of cholera in the southern portion 
of Bengal. Jessore, from which the first intimation of the epidemic of 
1817 came, lies on the borders of the Sunderbunds ; and Calcutta, which is 
now the fixed home of the cholera, is connected with the neighbouring 
Sunderbunds by a marshy and sparsely inhabited tract of land. Now the 
comma bacillus finds in this district, contiguous to its presumptive home, 
the most favourable conditions imaginable to implant itself and to spread 
from one individual to another." 

In the large towns in this cholera region there appears to 
have been no diminution in the mortality from the disease 
during the British occupation ; and until a new water supply 
was obtained and it was no longer necessary for the natives 
and others to take their water from tanks, from the Ganges, 
or from the Hoogley, even a better sanitary and drainage 
system appeared to have little effect. Once this supply was 
obtained, the mortality fell to about one third, and even a 
considerable portion of that third is to be accounted for by 
the fact that it was, and is, very difficult to impress on the 
natives the necessity of avoiding the old contaminated 
sources of water supply. Although Koch brought out these 
remarkable statistics he is still, as he says, " not a supporter of 
the exclusive drinking-water theory," and he considers " that 
the ways in which cholera can spread itself are extremely 
varied, and that almost every place has its own peculiarities 
which have to be thoroughly investigated, and the regula- 
tions which are to serve for the prevention of infection in the 
place in question must be drawn up accordingly." It is a 
remarkable fact that Koch never speaks or appears to think 
of the possibility of the existence of the cholera bacillus as a 
saprophyte. If it enters food or water it is the result of an 
accident and the organism can remain there, capable of 
development only for a short time and under exceptionally 
favourable conditions. Thus he contends that cholera is 
endemic in the Ganges only because there is a complete 


chain of cases from one year's end to the other by which the 
infection is handed on. Hueppe, on the other hand, main- 
tains, as above stated, that the bacillus can have a distinct 
saprophytic existence, and points to the fact that in places 
analogous to the delta of the Ganges it has a marked 
tendency to become endemic. 

As an example of this we may summarize the results of 
Macleod's observations on cholera in Shanghai. He says that 
" the remarkable regularity of the time of outbreak, period 
of duration, and time of cessation of the disease, so far as 
I am aware, has no parallel on record." The country round 
Shanghai is strikingly like that of the deltas of the Ganges 
and the Nile ; " in each there is the alluvial deposit, rich in 
organic matter, and the high ground-water level, yet in 
the Ganges delta the disease is prevalent all the year round ; 
at the mouth of the Yang-Tsze it occurs with the regularity 
of a crop at the same season yearly ; in the delta of the 
Nile it occurs only occasionally but at the same season as at 
the mouth of the Yang-Tsze. The two latter regions have 
at least weekly communication with India. Some causes or 
combination of causes are prevalent all the year round at the 
mouth of the Ganges ; at one season every year, viz, late 
summer and autumn at the mouth of the Yang-Tsze ; and 
at the same season, but not every year at the mouth of the 

There must then in these three regions be perfectly distinct but local 
conditions which must determine the difference in the behaviour of cholera 
in these various regions. The general characters of the soil, the ground 
water, and position are much the same, but there are well-marked differ- 
ences as regards temperature, population and methods of cultivation. In 
the delta of the Ganges cholera is absolutely endemic, it is never absent ; the 
poison, whatever may be its nature, is therefore always present. " From 
the position and climate, the temperature of the soil varies little throughout 
the year, and is never so low that some vegetable growth is not active. 
At the mouth of the Yang-Tsze (where cholera is prevalent only during 
certain parts of the year), the poison is endemic or is introduced shortly 
before the time that cholera breaks out each year, in which case it 
is curious that it should always be at the same time, there being no means 
of communication with a cholera infected country opened up specially at 
that time, communication with India being weekly. Here the climate 
admits of a greater range in the soil temperature than at the mouth of the 
Ganges, there being great extremes of both heat and cold. The soil heats 
more slowly than the air, hence perhaps it is the determining cause for the 
spread of the disease in the late summer and autumn, as already described, 
and of its absence in winter and spring. " It is evident from this statement 

l8o BACfERiA. 

that cholera does not show itself during the summer when the air tempera- 
ture is at its maximum, but only when sufficient time has elapsed to allow 
of the rising of the ground temperature or that of the earth, and as a matter 
of fact the disease occurs in Europe during the autumn months often when 
the general or atmospheric temperature has actually begun to fall, but when 
the earth temperature has attained its most equable maximum, when of 
course we have the optimum temperature conditions for the growth of 
the cholera organism in the soil. " At the mouth of the Nile the con- 
ditions are much the same as near Shanghai, except that the extremes of 
heat and cold are greater at the latter. Both have at least weekly communi- 
cation with India, both communicate through the tropics ; whilst Shanghai 
is at a distance of at least three weeks in time, Egypt is but two. The 
regularity of the yearly outbreak at Shanghai points to an endemic poison, 
the irregularity at the mouth of the Nile to the occasional introduction of 
the poison. Late summer is also the period for the Egyptian epidemics of 
any extent." 

Bearing on this, we have the fact that a cholera 
epidemic may remain dormant for months or a whole 
winter ; especially as the organisms retain their capacity 
of reproduction if they are kept moist and are supplied 
with oxygen. According to Nicati and Reitsch, cholera 
bacilli were found alive eighty-one days after they had 
been placed in the harbour water of Marseilles. Koch 
found cholera bacilli capable of reproduction after they 
had grown one hundred and forty-four days on agar, but 
in one hundred and seventy-five days these cultivations 
were found to be dead. Macleod found that pure culti- 
vations renewed but once a month retained their virulence 
for a year. Taking all these facts into consideration, it 
is easy to understand how in Shanghai the organisms 
may remain dormant for a certain period, and then under 
favourable conditions begin to grow again with increased 
activity. As Koch puts it — " One can easily imagine that in 
superficial layers of earth, in marshes, and so forth, the cholera 
•bacilli may find conditions in which they can exist preserved 
from death for five months or even longer, just as well or 
even better than on our moist agar jelly." Here then are 
three places which, although they have certain features in 
common, are characterized by certain differences, all of which 
appear to depend on climatic conditions. In the one case 
the cholera is prevalent during the whole year ; it is in fact 
endemic and continuous. In the second case cholera appears 
with the utmost regularity at certain seasons of the year, and 
then as regularly disappears. In this case the disease appears 


to be endemic, but on account of some local circumstances 
connected with temperature and vegetation it is developed 
only in crops — at harvest time, as it were. In the third case, 
in the Nile delta, the disease is extremely intermittent in its 
outbreak, and occurs only in those years in which the condi- 
tions as regards temperature, moisture, &c., are specially 
favourable for its development. In connection with local 
peculiarities as favouring the growth of the bacillus and the 
spread of the cholera, Macleod makes several very interesting 
observations, some of which bear out in a most remarkable 
manner Koch's statement as to the general laws that 
govern the spread of the disease, and also as to the minor 
local factors that determine individual outbreaks. The 
population in Shanghai he divides into three classes : resident 
foreigners, amongst whom deaths from cholera average less 
than 2 per 3000 per annum ; amongst the seafaring foreign 
population the average is very much higher, as of the sailors 
who come to port there die from cholera from 1 5 to 30 per 
1000 yearly ; whilst among the Chinese, even in the settlement, 
there are rarely fewer than from 200 to 300 deaths in a single 
season. What part then do local peculiarities and customs play 
amongst these three sets of people ? It is a fact, generally 
recognized, that any disturbance of the digestive function is 
the principal predisposing cause of the disease in a cholera 
outbreak — a fact that is explained by the absence of the 
ordinary amount of acid from the gastric juice in these 
cases ; such gastric derangement is specially met with after a 
bout of drinking. Macleod says, " Among the sailors a night 
ashore is the usual precursor of the disease, and commonly 
that indicates a large consumption of liquor." This, how- 
ever, does not account for all the cases that occur, and he 
says, " Occasionally men who have not been ashore are 
attacked. A sailor belonging to an American ship was 
attacked two or three days after arrival ; he had not been 
ashore, the ship had touched at no port for weeks before, and 
the water supplied on board had been in use during the 
voyage. The captain reported that he had specially en- 
couraged the men to eat fresh vegetables largely, and that 
he had seen the man referred to sitting on deck munching 
lettuce the day before he became ill (three of this ship's 
crew died of cholera). These vegetables had been supplied 
by Chinese bumboats." 


The custom amongst the Chinese "is to carefully collect human excreta 
and add these to water ; this mixture is then used for watering vegetables, 
&c. , so that the leaves come in for a fair share. All European and Chinese 
night soil is collected daily and carried away to be used for agricultural pur- 
poses. No night soil finds its way into drains, and there are no water closets," 
and all refuse not used directly for watering vegetables is carried into the 
country and used for agricultural purposes, so that if the poison be in the 
excreta, in China at least, its deposition in the ground is secured, and it has 
certainly been discovered empirically by European residents that vegetables 
cannot be taken with impunity. " Chinese vegetables are regarded with 
suspicion during the cholera season, more especially such as are uncooked." 

When the relation of the comma bacillus to the dejecta 
from cholera patients is borne in mind, there can be little 
wonder that the consumption of Chinese lettuces should be 
followed by an attack of cholera. In connection with the 
conveyance of cholera by means of drinking water, it may be 
objected that the Chinese do not drink water as a rule, but 
indulge in weak tea ; but here again it is stated that water 
for household use is stored in an earthenware or wooden 
vessel placed in or near the kitchen, and into this vessel 
others are dipped from time to time. The water is obtained 
from creeks or wells. Vegetables may be seen hanging over 
these vessels or lying on tables, so that though the vegetables 
are cooked, tables, dishes, cloths, and all that come in con- 
tact with uncooked vegetables furnish abundant opportunity 
for contamination of food after it has been cooked, where 
such filthy habits prevail as amongst the Chinese. They 
do not use milk as do foreigners, but they supply it, and from 
what has been said of vegetables and Chinese habits, unless 
the supply is known to be well cared for, it cannot be regarded 
as beyond suspicion of forming a vehicle for the distribution 
of cholera, typhoid, and other poisons. It is evident, then, 
that although no one set of factors alone can be looked upon 
as determining or explaining all outbreaks of cholera, the 
bacillus, so far as our present knowledge goes, must be 
looked upon as the essential factor in the causation of the 
disease ; this bacillus, like every other organism that we 
know throughout the whole animal and plant kingdoms, 
being, to a great extent, dependent on its environments for 
its very existence. In, considering this question let it be 
understood most distinctly that though the bacillus is proved 
to be the cause of the disease, it is not necessary to assume, 
as some people seem to suppose, that the careful, and in 


themselves complete, observations of the great epidemio- 
logists of this and other countries are valueless ; and as in 
time a more perfect knowledge of the conditions favourable 
or unfavourable to the growth of the organism is obtained, 
it may be expected that all observations made Vith care by 
those whose only desire is to get at the truth, will fit in and 
take their place in a large and comprehensive scheme 
through which there will ultimately be a possibility not only 
of understanding the disease more thoroughly, but of re- 
moving or combating its causes. 

It has already been pointed out how Pettenkofer's obser- 
vations may be made to agree with Koch's ; it has been seen 
that the apparently contradictory statements on the subject 
of the spread of cholera along the lines of pilgrimage and trade 
have been more or less satisfactorily explained and reconciled 
on the assumption th^t the bacillus is the cause of the disease. 
Then, too, the well-known facts of the association between 
cholera and gastric and intestinal disturbances of various 
kinds ; between it and consumption of various articles of food 
and of water from sources which are probably contaminated, 
or in which the presence of the cholera organism has been de- 
monstrated, and the facts connected with climatic conditions, 
ground water and subsoil drainage, temperature and special 
local conditions, may all be satisfactorily explained on Koch's 
comma bacillus theory. These explanations, taken with the 
fact that the comma bacillus is invariably found during cer- 
tain stages of the disease, that it has never yet been found in 
any but typical cases of cholera, that with it the disease has 
been produced in animals, experimentally, and one might 
also say in man, though accidentally (at the cholera course 
in the Hygienic Institute in Berlin), make it impossible for 
us to shut our eyes to the fact that in the cholera bacillus we 
have the only suggested causal agent that will allow of a 
satisfactory explanation of the mass of observations made up 
to the present. It had already been demonstrated that the 
bacillus was found only in the intestinal canal, when it 
naturally suggested itself to Koch that the symptoms of 
cholera were to be explained by the theory that in this 
disease there was absorption from the intestine of some 
soluble poison produced by the bacillus in situ ; that there 
was, in fact, a local formation of the poison, but a general 
absorption into the system (the " Intoxication " theory). This 


theory was at once accepted as being from every point of 
view more far-reaching and more satisfactory than the older 
one which explained all the symptoms by referring them to 
loss of water through the excessive intestinal discharges ; a 
symptom or effect was, in fact, looked upon as the cause of 
other symptoms. The earlier observations on ptomaines and 
sepsines, and Pasteur's and Hansen's later observations on 
ferments, naturally led to a search being made with the 
object of finding out any specific products of the cholera 
organism. Koch himself records the fact that he succeeded 
in preparing cultures of the comma bacillus which were so 
intensely poisonous, that when injected into animals, either 
subcutaneously or into a peritoneal cavity, there were set up 
in a few minutes all the symptoms which occurred in 
animals suffering from cholera a day or two after infection — 
" paralytic weakness of the hinder extremities, coldness of 
the head and legs, and prolonged respiration, a condition 
which usually leads after some hours to death." Buchner, 
who demonstrated, as he believed, the formation of butyric 
acid during the growth of pure cultivations, was unable to 
corroborate by any experiments of his own this view of 
Koch's, but Pouchet and Villiers were both able to extract 
from the dejecta or from the organs of cholera patients cer- 
tain products which they deemed to be characteristic. 

The former, with the aid of chloroform, extracted from cholera dejecta an 
extremely toxic oily liquid which, as it becomes oxydized in the presence of 
air and light, takes on, first a rose, and then a brown colour. It readily 
combines with hydrochloric acid to form a chloride, but again breaks down, 
in vacuo, or when the temperature is raised, or on the addition of an alkali. 
It gives the reactions characteristic of the alkaloids, and gives the blue re- 
duction coloration with ferro-cyanide of iron and perchloride of iron. 
Villiers succeeded in separating from the organs of a single cholera patient 
a couple of centigrammes of a peculiar alkaloid. On treating this with 
hydrochloric acid, there separated out a number of acicular crystals : these 
crystals have since been described by various observers, and it is stated that 
in this form the basic substance, whatever it may be, exerts comparatively 
little poisonous action, but that as soon as it is again set free from the acid 
combination, by the addition of an alkali, such as soda or potash, it exerts 
not only an extremely caustic local action, but also when injected into a 
guinea pig produces muscular tremblings and very great irregularity of the 
heart's action, the animal dying at the end of about four days.. It is im- 
possible, however, to be quite certain that these reactions were obtained with 
Villiers' pure acicular crystals, and not with one or other of the sepsines or 
toxiiies, as there is some little doubt as to the exact nature of the poison 
obtained in several of the series of experiments. Brieger, going beyond 


these researches, was able to isolate, especially from old cultures, substances 
analogous to, or identical with, cadavarine, putrescine, and choline. Carrying 
his experiments further, and cultivating the comma bacillus in media con- 
taining creatine, he produced a toxine or specific poisonous product which 
produced, when injected into the animals, dyspnoea, muscular tremors, 
cramp, and death. To this he gave the somewhat formidable name of 
Methylguanidin. Carrying his observation still further, he succeeded in 
separating from a precipitate obtained by the addition of a mercurial salt, 
two other toxines, both of which appeared to be more or less characteristic 
of the cholera growth. 

It will be noted that in all the experiments made, in which 
the toxines were obtained even from pure cultures of 
Koch's comma bacillus, the time required for their production 
and the quantities separated are out of all proportion to what 
occurs in actual cases of cholera, where, from the rapidity of 
the course of the disease and the severity of the symptoms, 
a large quantity of the poison must be developed in a very 
short time. Most of the artificial experiments, however, 
have been made on different media (usually bouillon contain- 
ing peptone) and under very different conditions from those 
which obtain in an animal. In a series of investigations 
carried out by Wood in Hueppe's laboratory, an attempt 
was made to grow cultures under precisely those conditions 
that are met with in the human intestine, with the result 
that a very rapid toxine production, and an additiorjal proof 
of the bacillary origin of the cholera virus were obtained. 
He took for his nutrient medium normal albumen, and thus 
obtained the earlier products such as the albumoses that 
occur in the breaking down of albuminoids. The presence 
of these would of course account for the greater toxicity of 
his cultures under such conditions. 

One of the earliest observations made by epidemiologists was 
that one attack of cholera protects for a certain time and to a 
certain degree against a second, and from this it was now 
argued that it should be possible to obtain a system of pre- 
ventive inoculation ; and Gamaleia, basing his work on what 
was already known of preventive inoculation in other 
diseases, commenced a series of experiments by means of 
which he hoped to construct such a method of inoculation 
against cholera. In this he was ultimately successful. He 
found that if, from a culture of the vibrio Metschm'kovt, an 
organism almost identical with the comma bacillus, both 
morphologically and physiologically, in beef broth, he took 


the pellicle which formed on the surface at the end of five 
days, sterilized it in an autoclave at 120° C, and then injected 
from two to six c.c. of the fluid expressed from the sterilized 
mass into the muscles of a guinea pig, the animal was rapidly 
and completely protected against the action of Koch's comma 
bacillus, introduced in the ordinary fashion. By further 
experiments he found that by simply keeping for several days 
the sterilized mass in which the dead bacilli still remained 
a much larger quantity of the poison could be obtained — 
sufficient, in fact, to kill the animal when given in the same 
dose as before, but still protecting the animal when exhibited 
in smaller doses. (Here the organisms could no longer be 
producing the poison, but it appears as though there was 
stored up in their body a considerable quantity which could 
only diffuse out into the fluid after a certain lapse of time.) 
To Gamaleia also we owe the knowledge that this 
organism may become very much modified in various ways, 
and some of the experiments he carried out provide us with 
an explanation of some of the most important facts connected 
with the increase and decrease in virulence of type, in cases 
that occur during the " rise and fall " of an epidemic. 

He was able to increase the virulence of the special comma bacillus in a most 
remarkable manner. After obtaining a growth of the organism in broth he 
introduced a small quantity of the culture into the lung of a white rat ; this 
was followed by an acute form of croupus pneumonia accompanied by 
marked pleurisy, the animal rapidly succumbing. With the fluid that ac- 
cumulated in the chest a second animal was inoculated in a similar fashion, 
with the result that this animal died more rapidly than the first. This 
inoculation was continued through a whole series of animals, until finally 
the rats succumbed very rapidly indeed, and an organism was found not in 
the intestine, but in very large numbers in the blood.' 

In addition to drying, acid, and the other destructive 
reagents already mentioned, it has been found that a very 
considerable number of chemical reagents arrest or prevent 
the growth of the cholera bacillus. 

Koch's list contains alcohol, 10 per cent., sulphate of iron, 2 per cent, 
(this latter acts first as an acid, and secondly as a precipitant of the 

' That this may have a bearing on Wood's observations as to the viru- 
lence of the organism in the serobic and anaerobic conditions is most evident, 
and is well worth further investigation. 


albuminoid materials on which the organism lives), alum, i per cent., 
camphor, .33 per cent., carbolic acid, .25 per cent., essence of peppermint, 
.5 per mille, sulphate of copper, 4 per mille, quinine, .2 per mille, corrosive 
sublimate, i per cent. 

Babes has found that the organisms will not develop in a gelatine 
nutrient medium which contains .5 per mille of corrosive sublimate, . i per 
mille of carbolic acid, .2 per mille of sulphate of copper, .8 per mille of 
salycilic acid, .1 per mille of thymol, 2 per mille of iodine, 2.2 per mille of 
bromine, 7 per cent, of alcohol, . 8 per mille of sulphate of quinine, .5 per mille 
of acetic acid (the action of which, however, depends to a certain extent upon 
its interference with the degree of alkalinity of the original gelatine, as the 
bacillus cannot grow in a medium in which there is more than a merely 
appreciable trace of acidity). He also tried a very interesting experiment 
in which he inverted a gelatine plate on which was placed a cholera 
culture over a watch glass or shallow vessel containing a drop of essential 
oil of mustard ; no development of the organism took place, and if the 
plate was left for twenty-four hours the organisms were all killed, as there 
was no subsequent development ; so that oil of mustard is an excellent 
disinfectant. Other active volatile principles act in very much the same 

The experiments with gelatine cultures are of special value 
because they allow demonstration of the effect that disinfec- 
tants have on the bacillus as it grows on specially favour- 
able nutrient media. Reference has already been made to the 
fact that putrefactive organisms and their products exert a 
prejudicial effect on the cholera organism, but it should be 
remembered that when the conditions are favourable there is 
usually such rapid proliferation of the cholera organism for 
the first day or two, that the others are left behind in the 
race for existence. It is, however, a case of the hare and 
the tortoise, for after a time the cholera organisms die out, 
and never again obtain a permanent footing unless a fresh 
supply of nutrient material becomes accessible. It is im- 
portant to remember this in connection with the spread 
of cholera by water supply, as it explains the immunity 
enjoyed, after a time, even in the most cholera-stricken 
regions. In India, in the regions in which the cholera is 
endemic, the wells, as a rule, are merely surface tanks into 
which sewage and surface water may be drained, and 
which are frequently on the same level as, and connected 
with, the cesspools, so that even the water supply contains a 
considerable quantity of organic matter in which organisms 
of all kinds can flourish most luxuriantly ; whilst these same 
wells, being merely dug-out pits beneath the slightly raised 
houses, are open for the reception of sewage and excreta 


of all kinds, especially in times of illness, when neither 
patients nor nurses have strength or time to see that these 
are properly removed. This source of danger is so evident, 
and is so in accordance with what one would expect, that 
efforts have been made to remove, as far as possible, all 
organic material which might serve as nutrient material for 
infective organisms from the soil and ground water, and 
also to remove as rapidly and as completely as possible not 
only dejecta, but also the water employed for cleansing hnen, 
clothing, and utensils " without allowing them to come in 
contact with the surface of the soil, with wells," with 
vegetables, and the like. 

Most hygienists are agreed that it is necessary not only 
to have a pure water supply — ?>., a supply free from all pos- 
sible contamination, derived from wells so deep, or from 
reservoirs so far from human habitations, that there is 
no possibility of contamination by sewage, dejecta, or surface 
drainage, and so carefully conveyed by conduits and pipes 
that no such contamination can take place during distribu- 
tion — but that a water supply should be s'o ample that 
dirtiness is heavily discounted. With all the improvements 
that have been made in the drainage system and water 
supply of Lower Bengal, cholera has only diminished about 
60 per cent., so that there still remain certain factors that 
favour the spread of cholera, and every now and again such 
a spread or outbreak may take place with extreme rapidity, 
and may involve a very wide area. Cleanliness, however, 
both general and personal, may be said to be the most 
important factor in the prophylaxis of cholera. Fliigge, 
for example, states most emphatically and explicitly that 
" the average cleanliness of the population has the greatest 
influence in this respect. The more cleanly the method 
of handling the sick and the infected clothes, the more care- 
fully contamination of the soil, of the water, and of various 
other objects with the dejecta is avoided, the fewer will 
be the sources of infection. The more carefully the hands 
are cleansed and the articles of food prepared, the more will 
the paths of spread from existing sources of infection be 
diminished. It is evident that in this respect marked dif- 
ferences must exist between more and less civilized countries ; 
between new and well-built, and old and cramped cities ; 
between poor and wealthy neighbourhoods ; between the 


portion of a city inhabited by the poor and that in which 
the better classes dwell." The habits of people, then, es- 
pecially as regards their food, play a most important part 

• in the propagation or restriction of cholera. The organism 
is almost invariably introduced by the mouth, so that in 
addition to passing into the alimentary canal by con- 
taminated water directly, it may also be introduced by 

, utensils, or food washed or sprinkled with such water, and 
Koch gives an excellent example of this when he describes 
the market women of Marseilles as being in the habit of 
sprinkling the vegetables exposed for sale with water from 
the street gutter, into which he proved that comma bacilli 
were constantly making their way, so that any one partaking 
of these vegetables uncooked, just as in the case of the 
American sailor at Shanghai, was taking in an unknown 
quantity, but a very appreciable and deadly dose, of the 
cholera organism and its poisonous products. Not only do 
these uncooked vegetables offer a nidus and an excellent sub- 
stratum for the growth of cholera organisms, but they often 
produce that condition of slight indigestion which along 
with an overloaded stomach is one of the most favourable 
for the development of the comma bacillus in the human 
alimentary canal. 

For the same reason feasts, fasts, Saturday night carousals 
and Sunday dyspepsias, pilgrim festivals, arrivals in port, 
and similar events are all predisposing causes of cholera, 
as in all cases there is a disturbance of the digestive function 
and a lowering of the system, due either to excess in 
drinking or in eating, or to gastric disturbance and lowered 
vitality resulting from abstinence from the use of food for 
too long a period. It is found, too, that wherever people 
assemble in large numbers in excess of the ordinary popula- 
tion, the strain on the sanitary arrangements is always 
excessive, and further, is necessarily accompanied by care- 
lessness in the selection and preparation of food. Cholera 
depends for its existence, outside those places in which it is 
endemic, on these fairs and pilgrimages, and only by 
controlling them and by attending most thoroughly to the 
sanitary conditions at the points where people are massed 
together can there be any hope of preventing the outbreak 
and spread of this insidious and deadly disease. 
It is not necessary here to do more than mention the pre- 


disposing effect of autumnal gastric disturbances and slight 
diarrhoea, which have, in many epidemics, been the in- 
variable precursors of the true Asiatic or Indian cholera. 
It is known that during an epidemic one attack of _ cholera, 
especially a severe one, exerts a great protective influence 
on those who survive, and as these consist almost ex- 
clusively of the people who under ordinary circumstances 
are again most exposed to infection, there may be natural 
breaks in the line of extension of an advancing epidemic ; 
breaks which have been used, by some authorities, as evi- 
dence of the sporadic outbreak of the disease. 

So much has the study of Koch's comma bacillus tinged 
and affected all our ways of looking at cholera epidemics 
that we now consider the conditions under which the 
bacillus can multiply and be carried from point to point, 
and the conditions that favour its development and mul- 
tiplication, instead of dealing with cholera itself as the 
entity with which we have to contend. The epidemiologist 
has now assumed the rdle of biologist in the widest sense 
of the term. The bacteriological hygienist agrees with the 
" localist " that it is necessary to get rid of all conditions 
in which the cholera poison can be propagated and dis- 
tributed, and that to this ^nd the ground water should 
be kept as free as possible from sewage, that all areas should 
be properly drained, and that everything should be done 
to render the " drying zone " as little congenial to the 
bacillus as possible ; but he goes further, and insists that 
the poison should not be allowed to be introduced into 
localities in which it does not already exist, for he believes 
that however favourable the conditions may be, there will 
be no outbreak of cholera until the bacillus is introduced 
and gains a foothold. He therefore insists on careful in- 
spection of all ships coming from India or from other cholera- 
stricken regions, though he is firmly convinced that it is 
only in seaport towns that inspection or quarantine can 
be of any value ; that if cholera makes its way beyond the 
seaport no quarantine or sanitary cordon can stop its spread ; 
that once beyond port the most careful isolation of all 
patients and disinfection of every article of clothing, feeding 
utensils, &c., should be rigidly carried out and insisted Upon; 
that the dejecta should be mixed with large quantities of 
carbolic acid, concentrated hydrochloric acid, or strong cor- 


rosive sublimate solution ; that the comma bacilli in 
rooms should be thoroughly dried and aired by throwing 
open the windows for several days, and that instructions 
should be issued as to the necessity for thoroughly personal, 
culinary, and household cleanliness, as to the avoidance 
of all water except that known to be pure, as to careful 
boiling and cooking of drinking water and food, as to the 
necessity of paying attention to the slightest gastric derange- 
ment, and as to the avoidance of all excesses in both eating 
and drinking. He pays attention then, first, to all relating 
to the power of the individual to resist any attack of the 
organisms. All place dispositions favouring the production 
of conditions of gastro-intestinal disturbance are to be care- 
fully neutralized, and in the same way all time dispositions, 
such as autumn diarrhoea, determined by the unripe or 
overripe fruits so abundant in the latter half of the year are 
to be met and counteracted ; and second, to everything 
relating to the rendering of all the environments unfit for 
the development of the comma bacillus, so that the number 
of centres from which infection may spread may be kept 
down as much as possible. 


Authors already referred to. Cornil and Babes. 
Babes. — ^Virch. Arch., Bd. xcix., p. 148, 1885. 
BocHFONTAiNE. — Comptes rendus, t. xcix., p. 845, 1884; 

t. c, p. 1 148, 1885. 
BoEHM. — Die kranke Darmschleimhaut in der Asiatischen 

Cholera mikroskopisch Untersucht. Berlin, 1838. 
Brieger. — Untersuchungen iiber Ptomaine. Beriin, 1885, 

Brittan and Budd. — London Med. Gazette. Sep., 1849. 
Buchner. — Arch. f. Hygiene, p. 361, 1885. 
BujwriD.— Centralbl. f. Bakt., Bd. iv., p. 494, 1888. 
Cantani. — Deutsch. Med. Woch. 1886. 
Cheyne, Watson.— ^rz'if. Med. Journ. April 25, May 2, 

9, 16, and 23, 1885. 
Cunningham. — Scientific Memoirs Med. Off. Indian Army, 

Pt. II., 1886, "on Cholera," Calcutta, 1885. 


Davaine. — Comptes rendus de la Soc. de Biol., 2me Serie., 

1. 1, p. 129, 1859: 
Deneke. — Deutsch. Med. Woch., No. 3, 1885. 
Emmerich. — Deutsch. Med. Woch., No. 50, 1884. 
Ermengem (Van). — Recherches sur le Microbe du Cholera 

Asiatique. Paris, Bruxelles, 1885. 
FiNKLER UND Prior. — Deutsch. Med. Woch,, No. 36, 

1884 ; Centralbl. f. AUg. Gesundheitspflege, Bd. i.. 

Heft 5, u 6. 
*Fluegge. — Deutsch. Med. Woch. Jan., 1885. 
Gaffky. — Arbeiten a. d. k. Gesundh, Bd. 11., i 2 Heft, p. 39, 

Gamaleia. — Annales de 1' Institut Pasteur, 1. 11., 1888, t. in., 

Hallier. — Das Cholera Contagium. Bot. Unters., Aerzten u. 

Naturforschern. Mitgetheilt. Leipzig, 1867. 
HuEFPE. — Beilin Klin. Woch., Nos. 46-47, 1889. 
Klebs. — Ueber Cholera Asiatica. Basel, 1885. 
Klein and H. Gibbes. — Rep. English Cholera Commission. 

Klein. — The Bacteria in Asiatic Cholera. London and New 

York, 1889. 
Klob. — Path-anat. Studien ii. d. Wesen des Cholera Pro- 
cesses. Leipzig, 1867. 
Koch. — Deutsch. Med. Woch., No. 45, 1884 ; Berlin Klin. 

Woch., No. 37A, 1885. 
Lewis. — Med. Times and Gazette. Sept. 20, 1884. 
MACLEOD AND MiLLES. — Lab. Reports, R.C.P., Edin., vol. i., 

p. 161 ; Proc. Roy. Soc, vol. xvi., p. 18. 
Macnamara. — Brit. Med.Journ., vol. i., p. 502, 1884. 
Miller. — Deutsch Med. Woch., No. 9, 1885. 
NiCATi UND RiETSCH. — Comptes rendus, t. xcix., pp. 928- 

929, 1884. 
Pacini. — Arch, de Med. Militaire de Bruxelles, 1855. 
Pettenkofer. — Zum Gegenwartigen Stand der Cholera- 

frage. Munich, see Za/zce/, July 3 and loth, 1886. 
Pfeiffer.— Deutsch. Med. Woch. 1885, 1886. 
PoucHET. — ^Comptes rendus., t. xxviii., p. 555. April 23, 

Roy, Graham, Brown and Sherrington.— Proc. Roy. Soc. 

No. 247, p. 173, 1887. 
SchoTtelius.— Deutsch. Med. Woch., No. 14, 1885. 


Straus, Roux, Nocard and Thuillier. — Comptes rendus 

de la Soc. de Biologic. Paris, t. iv., 1883. 
SwAiNE. — Lancet, pp. 368, 398, 1849. 
ViLLiERS. — Comptes rendus, t. c, p. 91, 1885. 
Weisserzug, Frank. — Zeitschr f. Hygiene. 1886. 
WooDHEAD AND WooD. — Edio. Med. Journ. April, 1890. 
* Full lists of references given. 


Typhoid Fever. 

Typhoid Fever a Bacterial Disease — Recklinghausen's Observations- 
Klein— Eberth—Klebs— Coats— The Bacillus— Method of Staining— 
Position in Tissues— Gaffky's Observations— Pure Cultures— Excretory 
Products — Experiments on Animals — Mixed Infections— Action of 
Light and Heat on Typhoid Bacilli — Pseudo-typhoid Bacilli. 

From the curious nature of the symptoms of typhoid fever, 
and from the fact that after complete recovery from an 
attack there appears to be a certain immunity (for a certain 
period at any rate) against a second, although relapses are 
of comparatively frequent occurrence, it was early supposed 
to be the result of the presence of some specific micro-organ- 
ism within the body, probably in the deeper tissues of the 
wall of certain parts of the intestinal canal, and in those 
organs, such as the spleen and lymphatic glands, that are 
specially connected or associated with that canal. Although, 
as early as 1871, Recklinghausen described in abscesses that 
were formed during the course of an attack of typhoid fever, 
microbes which he considered to be specific, and although 
Klein in this country found several varieties of micro- 
organisms in typhoid lesions, the specific organism was first 
accurately described, and distinguished from others, by 
Eberth and Klebs abroad and by Coats in this country, all 
of whom give very exact descriptions of the typhoid bacillus. 
These bacilli are short, somewhat thick rods, about 2 to 3/» in 
length and .3 to .5^ in breadth ; they are usually distinctly 
rounded at the ends, where the protoplasm is always rather 
more deeply coloured by aniline dyes than the central 
portion, which was at one time supposed to be a spore, 
though more recently this lighter coloured portion has been 
looked upon as evidence of a process of degeneration. 
These bacilli are said to be stained with difficulty, but I have 
found that if the sections in which they are present are first 


allowed to remain for about ten minutes in a i-Sth per cent, 
solution of corrosive sublimate and then stained by Gram's 
method, the bacilli are most deeply stained, although Fraenkel 
and others state that the colour is invariably discharged if 
Gram's method be used. They may also be prepared by 
Kiihne's method of first allowing them to remain in a con- 
centrated watery solution of oxalic acid, washing them 
carefully and afterwards staining with methyl blue dissolved 
in a I per cent, solution of ammonium carbonate. Sections 
may also be stained for twenty-four hours in Loffler's alkaline 
methylene blue, after which they are rinsed in water, which 
removes sufficient of the colour ; the water is driven out with 
aniline oil, the sections are allowed to dry on the slide and 
mounted in Xylol Balsam. 

The bacilli are found in the adenoid follicles, or lymphatic 
tissue of the intestine, in the mesenteric glands, in the spleen, 
and in the liver, and more rarely in the kidneys. They are 
usually collected in little clumps, and single bacilli are seldom 
if ever met with. These clumps, although readily enough 
recognized when seen, are as a rule so sparsely scattered 
through the tissues that it is often a difficult matter to find 
them, even in characteristic cases, and as Fliigge says, " It is 
only after the examination of a large number of sections that 
one or several of these deposits can be found." Gaifky, 
working in the Hygienic Institute in Berlin, was first able to 
make pure cultivations of this bacillus, and in 1884 he gave 
a very complete description of the bacilli that he was able to 
examine or to cultivate in twenty out of twenty-two cases of 
typhoid fever of which the examination was committed to his 
charge. The bacilli, when obtained pure, and cultivated in 
fluid, grew out into very long threads, both threads and short 
bacilli apparently being motile, having a peculiar wavy motion ; 
quite recently this motion has been found to be due to the 
presence of groups of lateral flagella which, waving back- 
wards and forwards, impart to the organism its peculiar 
snake-like movement. The bacillus can grow perfectly well 
both in the presence of free oxygen and also when oxygen is 
cut off, but, as in the case of the cholera organism, it appears 
to have somewhat different functions and different powers 
under the two sets of conditions ; outside the body in the 
presence of oxygen it appears to develop great " resistant " 
power and a saprophytic habit, whilst in the anaerobic con- 


dition, especially in the intestine, although its power of 
breaking up the albuminoid substances presented to it and 
of developing its specific toxines is greatly increased, its 
capability of resisting antiseptic substances is considerably 
diminished. In plate cultivations made from the organs of 
typhoid patients. Gaff ky found that the bacilli developed in 
the deeper part of the gelatine as small white points, whilst 

Photo-micrograph of Typhoid bacilli in Lymph follicle of Intestine of a child in 
which the Typhoid lesions were very characteristic, x 500. 

on the surface they grow as moist-looking greyish colonies 
with irregular margins. Under a low magnification the small 
rounded points are seen to be slightly granular ; they have 
a sharply-defined margin and are of a dirty yellow colour ; 
the superficial growths, although spreading somewhat 
rapidly, are' thin, sometimes almost transparent, and have a 
yellowish tinge when seen in the sunlight ; the margin is 


ir^egula^ and is marked by large and small indentations. 
There is no liquefaction of the gelatine around the growth. 
In a test tube cultivation the growth appears all along the 
line of the puncture and also on the surface. The surface 
culture has a peculiar mother-of-pearl look, it gradually 
spreads over the whole of the gelatine, forming a kind of 
bluish-grey film, whilst down each side of the needle track 
there is a delicate zone of the same bluish-grey colour, 
surrounded in turn by a peculiar opalescent milkiness. The 
most characteristic growth, however, occurs on sterilized 
potatoes. It is characteristic in that, even when there is a 
most luxuriant growth of the typhoid bacillus, it cannot be 
recognized by the naked eye, even at the end of three or 
four days, except by a peculiar moist appearance of the 
potato, which, taken along with the appearances in milk 
and on gelatine so far as is at present known, distinguishes 
the growth of this organism from all others. It will be 
remembered, however, that the potato is slightly acid, and 
it appears that this acidity is necessary for this typical growth, 
for on potatoes rendered slightly alkaline there appears a 
yellowish or dirty grey growth with sharply defined margins 
— a growth quite different from that above described. 
Chantemesse and Widal utilized the power of the micro- 
organism to grow in acid to help them to obtain pure 
cultivations. They prepared special tubes of gelatine by 
adding to each lo c.c. of the nutrient medium, 4 or 5 
drops of I to 20 per cent, solution of carbolic or phenic 
acid ; they did this in order to prevent the development of 
those microbes that bring about liquefaction of gelatine. 
They were perfectly successful in their attempts, although, as 
we have seen elsewhere, it does not follow that their expla- 
nation was absolutely correct ; at any rate they were able to 
separate pure t5^hoid bacilli which had all the characteristic 
appearances both on the gelatine plates and under the 

The organism itself, unlike many other bacteria, seems to 
form an acid and not an alkaline excretory product. It 
grows in a variety of media, and as I have already said, it 
appears under certain conditions to become quite saprophytic 
in habit, this being evidenced by the ease with which it may 
be cultivated outside the body, and quite recently Wolffhiigel 
found that it may develop readily in both milk and water to 


which it has gained access. This bacillus, then, has been 
found in the body ; it has also been found by Pfeiffer in the 
dejecta of typhoid patients, and now it has been found in the 
water supply, so that the chain of evidence is, so far, pretty 
conclusive. It is a somewhat important fact that the typhoid 
bacilli may remain active for a considerable length of time 
in the stools, for the bacilli in faeces kept in a sterilized 
tube for fifteen days remain alive at the end of that period, 
and vigorous cultivations could be made from such material. 
Experimenters were now confronted with the difficulty that 
typhoid fever is seldom met with except in the human subject. 
Experiments were made on animals by injecting cultures of 
the typhoid bacillus into the aural vein of rabbits, with the 
result that about 50 per cent, of the animals died, and on 
post-mortem examination it was found that the spleen and 
those glands usually affected in typhoid were somewhat 
swollen. A. Fraenkel was able to kill monkeys with in- 
jections of the bacillus, and Chantemesse and Widal point 
out that they can produce a septicaemia by injecting a con- 
siderable quantity of a culture of the bacillus into the 
peritoneal cavity of a mouse. They also found, repeating 
Fraenkel and Simmonds' experiments of injecting cultiva- 
tions into the vein of the ear, that, this was followed by 
diarrhoea and rapid emaciation at the end of several days, 
although the animals frequently recovered. When they 
were killed at the height of the disease, lesions corresponding 
to those met with in typhoid fever were found in the intes- 
tine, and bacilli were also found in the organs. 

The method that was used in the inoculation of cholera 
was afterwards resorted to, the contents of the stomach were 
rendered alkaline, the peristaltic movement of the intestine 
was paralyzed by means of full doses of opium, and the typhoid 
bacilli were injected into the alimentary canal ; most of the 
animals died, and numerous bacilli were found in the intestines 
and even in the glands, but none could be demonstrated in 
the blood. It was observed, however, that it was not neces- 
sary to have an active bacillus present in order to cause very 
serious symptoms, and even death, with typhoid cultivations ; 
and it soon came to be recognized that these symptoms were 
due to regular poisoning or intoxication by toxines and tox- 
albumens, both of which were described by Brieger as being 
present in typhoid discharges and in pure cultures of the 


typhoid bacillus. It was in typhoid fever, in fact, that this 
investigator carried on some of his earliest experiments on 
the poisonous metabolic products of pathogenic organisms, 
growing in albuminoid substances. As regards the relation of 
this special bacillus to the disease, it stands on exactly the same 
footing as that between the cholera organism and cholera, and 
it follows that most of the points that have been accentuated 
when we were considering cholera may also be accentuated 
in this instance. Klein pointed out that in typhoid lesions, 
especially in the intestinal canal, several organisms were 
usually associated, and other observers have agreed that in 
typhoid there is, very frequently, what is known as a 
" mixed infection " — «'.«., in addition to typhoid bacillus other 
organisms appear to be present and to play an important 
part. Streptococci, and septic organisms, are frequently 
found in the tissue of the spleen, liver, and wall of the intes- 
tine. It is supposed that some of these organisms play their 
part in preparing the intestine for the reception of the 
typhoid bacillus, and it is maintained that a condition of 
irritation and a removal of the epithelium, brought about by 
the action of other micro-organisms on the wall of the 
intestine, may be necessary to prepare the way for the 
entrance of the typhoid bacillus. The intestine is, in fact, pre- 
pared just as a field is prepared by the farmer by ploughing 
and manuring for the reception of the seed that he intends to 
sow. The fact that the bacilli can grow on potatoes without 
becoming evident to the naked eye indicates the possibility of 
a similar growth occurring on other articles of diet, which, 
taken into an alimentary canal that has been previously 
prepared by gastro-intestinal disturbances — diarrhoea and 
similar conditions — may set up the disease. 

It may be appropriate here to consider the action of light 
on typhoid bacilli, as although the first observations on the 
germicidal action of light were made on other organisms, in 
this country by Downes and Blunt, and these experiments 
were continued by Tyndall and a number of other workers 
both in this country and abroad, the more recent experiments 
on the action of light on bacteria have been carried out on 
typhoid bacilli. That bacteria are influenced by the action 
of light either to their advantage or their harm is very 
evident. In the one case it will be found that certam of 
the colour-producing organisms cannot exert this function 


unless Ihey are very well supplied with both air and light, 
whilst on the other hand such organisms as usually grow in 
the body appear to become markedly weaker as regards their 
power of growing and of giving rise to their special dele- 
terious products if they are freely- exposed to the light. 
Recently Dr. Janowski has made a nurnber of experiments 
by exposing growths of the typhoid bacillus to the action of 
light, and has found that it exerts a distinctly depressing 
action on the typhoid organism, an action entirely inde- 
pendent of any oxidation of the food material that might 
occur under the action of the chemical rays, these chemical 
rays acting directly upon the protoplasm and rendering it 
incapable not only of further development but of continuing 
alive. In order to prove his thesis he took a gelatine tube 
in which typhoid bacilli had been sown and exposed it to the 
action of the light on a cold winter day ; a similar tube 
inoculated with the same bacillus was wrapped up in a layer 
of black paper and then in one of white paper, this also 
was exposed in the same position. The light in this case 
delayed the development and the multiplication of the 
organism in a somewhat marked manner, as in the two pro- 
tected from the light, growth took place in three days, whilst 
in that exposed to the light, it did not commence for five 
days. Of course the growth here referred to is measured by 
the size of the colony that can be seen with the naked eye 
and although both were probably growing during the whole 
time, the rate of multiplication in the one was very consider- 
ably greater than in the other. In order that there might be 
no doubt as to the identity of the organism and the quantity 
sown in each tube, a U-shaped tube (a double Pasteur tube) 
was taken and the inoculation was made ; the fluid was 
thoroughly mixed by passing from one limb of the tube to 
the other, then one limb was protected as above and the 
other was exposed to the light ; similar results were obtained, 
the bacilli in the limb that was exposed to the light being 
considerably delayed in their development. He fdund that 
direct sunlight acting on fluid cultures of the typhoid bacillus 
kills the organisms in the short space of from four to seven 
hours, but diffused light requires a considerably longer period 
to entirely arrest the development and multiplication of the 
organisms. Instead of analysing the rays of light by means 
of a prism, as Englemann and others had done, Janowski 


made use of solutions of alum, bichromate of potash, 
Bismarck brown, fuchsine, methyl blue, gentian violet, &c. 
He found that the yellow and brown solutions filtered out 
the chemical rays and prevented the action of light upon 
the organisms almost as efficaciously as the black and white 
papers, but found that the other fluids — ^fuchsine, methyl 
blue, gentian violet, &c. — had little more effect in preventing 
the injurious action of light on the bacilli than distilled 
water or alum solution. He therefore comes to the con- 
clusion that the hurtful action of both diffused light and 
direct sunlight is due in very great measure to the chemical 
rays of the solar 'spectrum — the rays at the other end of 
the spectrum exerting comparatively little influence on the 
organism. This entirely accords with Englemann's observa- 
tions ; he found that certain chromogenic bacteria when 
examined in a drop of water and illuminated by the rays 
from a micro-spectral objective, invariably made their way to 
that part of the spectrum furthest away from the violet end, 
thus indicating that they were attempting to evade the 
chemical rays which appeared to be hurtful to them. This 
question of the action of light, especially on pathogenic 
bacteria, is one of very great importance, and Duclaux's 
dictum that fresh air and sunlight are two of the most 
powerful agents that we have with which to combat the 
onslaught of the bacteria of disease cannot be too strongly 
insisted upon. Bacteria, especially those of disease, seek out 
the dark places for their habitation, and as the exclusion of 
light to a very great extent necessitates the exclusion of fresh 
air, they find in these holes and corners places of rest whence 
they may go out to do all the harm of which they are 

Janowski also made an elaborate series of experiments on 
the eflFect of high temperature on the typhoid bacillus. He 
found that a temperature of 55° C. continued for ten minutes 
was quite sufficient to render sterile cultivations of this 
bacillus, but if this same temperature were continued for 
only five minutes he could not rely upon obtaining complete 
destruction of the organism. He also came to the conclusion 
that an extreme degree of cold, especially when continued 
for some time or where frequently repeated, had a moderately 
injurious effect upon the vitality of the typhoid bacillus ; a 
temperature of 14° C. being sufficient to kill the bacilli when 


growing in a fluid medium. When they were allowed to 
dry, however, this did not appear to hold good to nearly the 
same degree. 

These experiments are interesting in their bearing on the 
outbreaks of typhoid fever at certain parts of the year, 
especially in countries where the cold Jtppears to be exceed- 
ingly intense, and where one would naturally expect the 
development of the bacilli to be interfered with, but where 
as a matter of fact such is found not to be the case. 

Quite recently Cassedebat, examining t|ie drinking water 
supplied to Marseilles, which is a very hotbdd of typhoid fever, 
was not able to find the characteristic bacillus in any one of 
250 cultivations made of seventy specimens of water, but 
curiously enough he found three other bacilli which in many 
respects resembled the true typhoid bacillus most remark- 
ably, although they differed in certain essential character- 
istics. He points out that they all grow in tn.e phenic acid 
gelatine, and he further states that several otfter organisms 
offer quite as great resistance to this acid as the typhoid 
bacillus itself. They all present clear spaces or deeply stained 
masses of protoplasm which may easily be mistaken for spores, 
but these, like those in the true typhoid bacillus in which as 
we have seen similar bodies occur, are all killed at a tempera- 
ture of a little over 45° C. The pseudo-bacilli are very im- 
perfectly stained by Gram's method. They exhibit a lateral 
and oscillatory motion as well as a forward motion. The 
plate cultivations are so much alike, that unless all four can 
be examined simultaneously, it is a very difficult matter to 
distinguish one from the other ; their growths on potatoes, 
in broth and in milk resemble one another in a most re- 
markable manner, except that they develop with different 
degrees of rapidity, and vary somewhat as regards the alkali- 
nity and acidity of their products at the end of about thirty 
days, and also as to the degree and time of appearance of 
turbidity that is produced when these organisms grow in 
broth. In consequence of these slight differences the use of 
the various aniline staining reagents, added to such culture 
media as broth or milk in which the colours undergo 
changes under the different reactions, has been resorted to 
and described by Cassedebat, who was able by their use 
to distinguish one organism from the other. The ordinary 
cultivation methods are quite sufficient to distinguish these 


four forms as a group from most others, for which the 
typhoid bacillus itself has at different times been mistaken, 
whilst in addition to the differences above mentioned none 
of the pseudo forms are quite so toxic to white mice as the 
Eberth-Gaffky bacillus, and one of them is quite innocuous. 
Although Cassedebat was not able to find the true form in 
water taken from a supply that was open to contamina- 
tion, he found that this was not because the bacilli could not 
live in water, as in distilled water to which a cultivation was 
purposely added he could easily distinguish its presence at 
the end of forty-four days, and when added along with half 
a-dozen other forms he still found it living and active at the 
end of seventeen days. As the result of his observations he 
comes to the conclusion that the true typhoid bacillus does 
not occur in water so frequently as is sometimes represented, 
and that one or other of the pseudo-typhoid bacilli has in 
certain cases been mistaken for it. 


Authors already referred to. Brieger, Fliigge, Fraenkel. 
Almquist. — Typhoid feberns bakterie. Stockholm, 1882. 
Babes. — Journ. de I'Anatomie, p. 39, Jan., 1884. 
Beumer und Peiper. — ^Zeitschr f. Hygiene, p. 489, 1886. 
BiRCH-HiRSCHFELD. — Zcitschrift f. Epidemiologie, Bd. i., 

Brieger und Ehrlich. — Berlin Klin. Woch., No. 44, p. 661, 

Cassedebat. — Annal. de I'lnstitut Pasteur. Oct. 25, 1890. 
Chantemesse et Widal. — Arch, de Physiol, p. 217, 1887 ; 

Annal. de I'lnstitut Pasteur, t. 11., p. 54, 1888. 
Coats.— Bri'i. Med./ourn., vol. i., p. 421, 1882. 
Crooke.— Brit Med.Joum., vol. 11., p. 15, 1882. 
DowNES AND Blunt. — Proc. Roy. Soc, vol. xxvi., No. 184, 

Dec. 6, 1877. 
DowNES, Blunt, and Tyndall.— Proc. Roy. Soc, vol. xxviii.. 

No. 191, Dec. 19, 1878. 
Eberth.— Virch. Arch., Bd. lxxxl, p. 58, 1880; and Bd. 
LXXXIIL, p. 486, 1881 ; Volkmann, Klin. Vortrage, 1883. 
Fraenkel und Simmonds.— Centralbl. f. Klin. Med., p. 

737, Oct. 31, 1885 ; Der aetiologische Bedeutung des 

Typhus Bacillus, 1886. 


Gaffky. — Mitth. a. d. Gesundheitsamt, Bd. ii., p. 372, 1884. 
Jamieson. — Nature, vol. xxiv., No. 620, Sept. 15, 1881. 
Janowski. — Centralbl. f. Bakt. u. Parasitenk., Bd. viii., 

Nos. 6-9, 1890. 
Klebs. — Arch. f. Exp. Path., Bd. xiii., p. 381, 1880. 
Klein. — Reports of the Med. Officer cif the Local Gov. 

Board, 1874. 
KuHNE. — Zeitschr. f. Hygiene, Bd. i., p. 553, 1886. 
LoFFLER.— Centralbl. f. Bakt. u. Parasitenk, Bd. Vi., Nos, 

8-9, and Bd. vii.. No. 20, 1890. 
Pfeiffer. — Deutsch. Med. Woch., No. 29, 1885. 
Recklinghausen. — Wurtzburger Zeit., June 10, 1871. 
SiROTiNiN. — Zeitschr f. Hygiene. i886. 
SocoLOFF. — Virch. Arch., Bd. lxvi. 



Tuberculosis a widespread Disease — The Tubercle Bacillus — Koch — Baum- 
garten — Spores seen by Watson Cheyne— Relation of Organisms to 
Tissues — Bacillus in Tuberculosis of Animals — Tubercle Bacilli as 
Saprophytes — Bacilli cultivated outside the Body by Koch — Methods 
— Temperature Relations — Cultivation on Different Media — Channels 
of Infection — Ransome — Williams — Cornet — Conditions of Infection — 
Methods of Disinfection — Tuberculosis at Different Ages — Tubercle 
in Milk — Diagnosis of Tuberculosis in Cattle — Tuberculous Meat — 
Koch's Method of Treatment — Nature of Virus and Mode of Action 
Is Immunity conferred ? — Koch's Method a New Departure — Sterile 
'Products cause Marasmus Malfucci — Indications for Treatment. 

Tuberculosis, one of the most widespread and deadly diseases 
with which we have to deal, not in this country only, but in 
the whole of Northern Europe, has now certainly been proved 
to demonstration to be due to the presence of a specific 
micro-organism. Almost innumerable researches have been 
carried on with the object of finding out and piecing to- 
gether the various facts in the life-history of this organism, 
the products to which it gives rise, the conditions under which 
it can multiply in the human body and in the animal body, 
the nature of the very grave changes produced in the tissues, 
the mode of transmission directly and indirectly from one 
body to another, and, last, but not least, the possibility of 
combating the ravages made on the body by this organism, 
by interfering with its growth or retarding its development, 
either outside the body or after its introduction into the 

Tuberculosis and Phthisis or Consumption account for 
such an enormous percentage of deaths in our colder north- 
ern latitudes, that the subject has come to be one of intense 
interest, not only to physicians and surgeons, but to all well- 
educated people, and the subject of the treatment of tuber- 
culosis is — unfortunately perhaps for patients — taken up 


almost as exhaustively in the daily papers as it is in special 
treatises and in the medical journals. It has long been known 
that tuberculosis was an inoculable disease, but it was only 
quite recently (1883) that Koch and his pupils were able to 
demonstrate that a specific organism could be separated from 
tuberculous tissiie and cultivated outside the body — the 
cultivated organism having all the characters of the organism 
found in the tissues — and that when introduced into certain 
animals, this organism was capable of producing tubercular 
disease, the organism in turn being again demonstrable in 
the new tubercular growth. 

It was for long found to be an exceedingly difficult matter to demonstrate 
any specific micro-organisms in tubercular tissues by means of aniline or 
other nuclear stains and Baumgarten's method " was introduced after he 
had failed to attain his object by any of the ordinary methods. The 
difficulty he had, however, was that, although the tubercle bacilli un- 
doubtedly resisted the potash solution, other organisms were also more 
resistant than were the animal tissues, so that there was no great differen- 
tiation except in size and form between the tubercle bacillus and other 
bacteria. While Baumgarten was working out his method, Koch had 
completed a series of investigations, the outcome of which was that he 
proved that by the addition of a small quantity of an alkali to the aniline 
stain the dye was rendered capable of penetrating the resistant outer 
membrane of the tubercle bacillus. It was afterwards found that aniline, 
thymol, turpentine, or carbolic acid, added to the stain, bring about 
the same results ; these substances, acting, apparently, as mordants on 
the tissues. The next step in the process of demonstration of the tubercle 
bacillus was taken when it was found that this organism differed from 
others in the fact that it retained the staining reagent most tenaciously, 
even the strong mineral acids, which readily discharge the colouring matter 
from nuclei and other bacteria having little effect, if acting for a short time 
only, in taking out the stain from tubercle bacilli ; in sections stained in an 
aniline colour mixed with one of these substances and then treated with 
an acid, a most beautiful differential staining was obtained, the stained 
bacilli standing out most prominently from the unstained tissues. 

Tubercle bacilli when stained are seen as delicate rods or 
threads 1.5 to 3.5/* in length andabout .2/« in thickness, though 
these dimensions are by no means constant even in the same 
preparation, and under different conditions the variations in 
size are sometimes very marked. As in the case of anthrax 
and cholera bacilli, the methods of staining and preparation 
exert a marked influence in determining the apparent size 

' The sputum, after being dried on a cover glass and then heated to 
coagulate the albumen, was simply soaked in a solution of caustic potash. 
Sections were treated in the same manner. 


of the organism. The length is sometimes given at 2.6/* 
and the breadth as from .2 to .5/1. They are usually 
described as from a quarter to a half the diameter of a red 
blood corpuscle and longer than the bacilli of mouse septi- 
caemia, or 0.0015 to 0.003s m.m. in length. These bacilli 
always appear to have the larger dimensions when treated 
by Baumgarten's liquor potassse method. The bacilli are 

Photo-micrograph of Sputum, from a phthisical patient, containing large 
nucleated epithelial cells and characteristic tuhercle bacilli. X looo. 

usually slightly curved, or two are arranged end to end 
so as to contain an angle. At first they were described as 
not containing spores, but it was demonstrated by Watson 
Cheyne that from two to six spores may frequently be seen 
in these rods ; the spores occurring as small ovoid or rounded 
clear spaces placed at intervals in the stained thread. In 
some cases they are so prominent that they appear to 


project beyond the straight outline of the bacillus ; sometimes 
this is so much the case and the spores are packed so closely 
together, that when examined under a sufficiently high power 
the spore'bearing thread has been described as a chain of 
cocci ; by some it is maintained that this appearance is 
present only if the specimen is imperfectly stained, too much 
heated, or too long treated with a strong acid ; whilst, on the 
other hand, certain observers assert that the tubercle bacilli 
also occur in the form of regular chains of cocci. The bacillus 
is non-motile. 

Fliigge holds, however, that it is " always possible, in carefully 
prepared specimens and with the aid of good lenses, to convince one's self 
that the supposed chain of cocci does not exist, but that the delicate 
contour of the bacillus can be for the most part traced through its whole 
length, and that it is only within this contour that the alternation of stained 
and unstained zones gives the deceptive appearance of stained cocci 
separated by narrow intermittent spaces." 

The association of this organism with tubercular disease is 
undoubted ; it is found in the lungs and sputum in various 
forms of consumption, it is found also in tubercular ulcers 
of the intestine, around the vessels in tubercular inflamma- 
tion of the membranes of the brain, a condition which 
occurs frequently in children, in tubercle of the liver and 
of all other organs of the body, and in tubercular eruptions 
of the skin such as lupus. In all these cases the bacilli are 
found most abundantly at those points where the disease 
appears to be spreading into the surroiinding tissues, and 
especially where there is the formation of large multi- 
nucleated epithelioid cells. If these bacilli are present 
in considerable numbers in such an area, there will 
usually be found in the immediate neighbourhood a small 
portion of tissue that has undergone marked degenerative 
changes, the cell protoplasm is somewhat hyaline or glassy 
looking, and takes on any staining reagent, except perhaps 
picric acid, very badly ; the nucleus i^ also considerably 
altered, especially in that it no longer stains, or is stained 
very imperfectly, with carmine or the aniline dyes. At such 
a stage there can frequently be demonstrated, in these cells, 
imperfectly stained tubercle bacilli, though in some cases 
the bacilli stand out sharply and very brilliantly from 
the glassy or homogeneous looking cell. After a time 
the cells lose their outlines; they become more and more 


indistinct, until eventually nothing but the ghost of a cell is 
left. This occurs where we have what is known as the 
cheesy or caseous degeneration, in which condition nothing 
but broken-down nuclei and very rarely a tubercle bacillus 
can be distinguished. It would at first sight appear as 
though the tubercle bacilli had disappeared, root and 
branch, from this caseous centre, but if a small portion of 
the cheesy material be inoculated into an animal susceptible 
to tubercle, flourishing groups of tubercle nodules all con- 
taining tubercle bacilli are produced, first near the seat of 
inoculation, and then at points situated at some distance from 
the point of primary infection. The results of such experi- 
ments naturally led the opponents of the bacillary theory 
of tubercle to assume that the poison of tubercular virus 
was not associated with the bacillus, which they contended 
was merely of accidental or sequential and not of causal 
occurrence, as it could not be found in material which 
undoubtedly produced the disease ; but after the demon- 
stration of spores in the bacilli, and bearing in mind what was 
known of spore formation in other organisms, most observers 
were very naturally led to the conclusion that, although the 
bacilli are not to be demonstrated in these infective caseous 
masses, spores in enormous numbers are probably present, 
and that from these, bacilli are developed as soon as the sur- 
rounding conditions of nutrition, moisture, and heat are 
again sufficiently favourable. The fact that it is so difiicult 
to stain spores made it no easy task to demonstrate the 
accuracy of this theory, but it may now be held, as the out- 
come of inoculation and other experiments, that there can be 
no reasonable doubt on the subject. It is a curious fact that 
whilst in the human subject tubercle bacilli appear in many 
cases to be actually contained within the giant or other large 
cells, in some herbivora, and in fowls, the bacilli sometimes 
occur single or in small masses, apparently outside the cells. 
There are several explanations given for this, but the most 
rational appears to be that where the bacilli are few in 
number, and where they are being rapidly destroyed by the 
tissue cells, by far the larger proportion are taken up by, and 
are seen in, these cells ; this being specially observable in 
cases of chronic tuberculosis, whilst in those cases where 
the tubercle bacilli are relatively numerous, as in cattle, and 
even more markedly in the fowl and in the horse, the 



destruction of the tissue cells takes place so rapidly, in con- 
sequence of the invasion of each cell by a large number 
of bacilli, that nucleus and protoplasm break down com- 
pletely and the little group of bacilli is set free, or at any 
rate is not embedded in a mass of protoplasm, but is merely 
mixed up with the granular dkbris of the cell, from which, 

Micro-photograph of Tubercle bacilli, found in the scraping from the lung 
of a cow suffering from Perlsucht. x looo. 

or along with which, it may be carried to other parts of the 

Having found the tubercle bacillus almost invariably accom- 
panying tuberculous disease, Koch, to complete his proof, 
wished to separate the organism in the form of what is 
called a pure cultivation, in order that he might study 
its life-history, and that he might determine whether 
the organism when introduced alone into the animal body. 


could give rise to tuberculosis. With all the ordinary 
nutrient media then at his command he entirely failed to 
obtain any growth of the organism outside the animals in 
which it led its parasitic life. It depended so much upon 
these conditions of parasitic life that when removed from 
them it was no longer able to grow and multiply : it might 
still remain alive ; in fact, Cornil was able to demonstrate 
that at the ordinary temperature of the room the tubercle 
bacillus, kept in ordinary Seine water, continued to exist, but 
not to multiply, for seventy days. At length, however, Koch 
overcame the difficulties with which he had to contend, in a 
most ingenious manner, and he succeeded in growing as a 
saprophyte what had hitherto been demonstrated only as 
a parasitic organism. He argued that as the tubercular 
process developed but slowly, he would have to obtain a 
medium which would remain unaltered for a considerable 
length of time when placed in a temperature at which the 
organism could grow and multiply. He was satisfied too, 
from his early experiments, that only special substances 
would serve as nutrient material for this fastidious organism, 
and he ultimately found that solidified blood serum was by 
far the best medium on which to cultivate it, as it alone of 
the many substances which he had then tried supplied all the 
requirements of the organism. This blood serum contains 
all the elements necessary for the nourishment of the 
organism ; it remains solid at the normal temperature of 
the body, at which temperature it may be kept for a long 
enough time to allow of the development of the slowly 
growing bacillus, whilst a small amount of water might be 
left in the test tube along with the serum without dis- 
solving it, thus serving to supply the moisture requisite 
for the perfect growth of the bacillus. In consequence of 
the slowness of the growth above referred to, it is an ex- 
ceedingly difficult matter to obtain pure cultivations of the 
tubercle bacillus should it once become mixed with putre- 
factive bacteria, and it was for long deemed almost an 
impossibility to separate it from these other forms : this 
difficulty has now, however, been overcome. Most of Koch's 
earlier pure cultivations were obtained by taking as seed 
material, tubercular lymphatic glands from freshly-killed 
guinea pigs, which had been inoculated, some three or four 
weeks before, with tuberculous material. 


As this method may be looked upon as almost classical it will be well to 
give the description in Koch's own words. " A number of knives, scissors 
and forceps are heated in a flame sufficiently to free them from any adherent 
bacteria. They are then laid ready in such a manner that no further con- 
tamination of the instruments can take place. Meanwhile the animal 
immediately after being killed is fastened to a dissecting board. In order 
to avoid the flying off of particles of dirt, hairs, &c., when the skin is 
incised, the fur of the animal is freely moistened with a i to loooth solution 
of corrosive sublimate. With a pair of scissors and forceps, both still hot, 
the skin is now divided and turned back on each side sufficiently to free the 
lymphatic glands of the axilla and groin ; but the glands, if they are to be 
used to start cultivations, must not be touched with the instruments em- 
ployed for cutting through the skin. With another pair of scissors, also 
heated, a piece l to 2 c.c. cube is cut out of the side wall of the thorax, 
and the surface of the lung laid bare. A number of tubercular nodules 
are thus rendered accessible, and a few are removed as quickly as possible 
with fresh instruments, which must, however, be cooled for this purpose. 
In order to set free the bacilli contained in the nodules, the latter are cut in 
pieces or crushed with the scissors, or, better still, between two scalpels that 
have just been heated and allowed to cool. The substance thus subdivided 
and crushed is removed by means of a platinum wire fused into a glass rod 
(which, immediately before use, has been heated and allowed to cool), 
introduced into the test tube, spread out on the surface and well rubbed 
about. During this operation the test tube must be held obliquely or 
almost horizontally between the thumb and forefinger, and the cotton wool 
plug held meantime between the other fingers of the same hand in such a 
way that no contamination of it by other objects can take place. The 
transference of the substance into the solidified serum, which may for 
brevity be designated inoculation, must take place as quickly as possible in 
order that no germs of extraneous organisms from the air may alight on the 
inoculation material or enter the test tube. It is desirable also to conduct 
the experiment in a room where no dust is flying about, and in the same 
way all unnecessary movements by which dust from the clothing, &c., is 
mingled with the air are to be avoided, as experience has shown that it is to 
particles of dust that the germs of micro-organisms suspended in the air 

" In spite of all these precautions we cannot be perfectly sure of preventing 
the entrance of a few solitary germs, and it is necessary in each case to 
inoculate several (five to ten) test tubes, so that if we fail to obtain a pure 
cultivation in one or two tubes, we shall yet have others that are free from 

"The process is the same as that above described for obtaining seed 
from a pulmonary tubercle, when lymphatic glands, tubercles from the 
spleen, &c., are to be used to start a culture. The process must always be 
carried out with heated instruments, which must be changed every time a 
fresh stratum is laid bare. All preparatory incisions which do not come in 
contact with the inoculation substance itself are to be made with hot 
instruments, but the inoculation material is to be cut out with a cool pair 
of scissors and forceps. It is necessary to change the instruments constantly 
in order that impurities adhering to them after the division of the skin and 
superficial layers, may not be carried into the cultures. 

" When the organs of a recently killed or dead animal could be obtained. 


and the inoculation with substances containing tubercle bacilli was done in 
the way just given, I invariably succeeded in obtaining pure cultures. The 
result was uncertain, on the contrary, when material from human corpses or 
from cattle yiitii ferlsttcht was used, as it was always impure on the surface, 
and, moreover, was not always quite fresh when it reached me. In these 
cases I first rinsed the surface of the object repeatedly with a solution of 
corrosive sublimate (i to looo) and then cut away the upper parts in layers 
with red-hot instruments, which were changed repeatedly ; finally, I took 
the material for inoculation from a depth which justified me in concluding 
that it would be free from the bacteria which had entered the tissue after 
the death of the animal. In this way I generally succeeded in obtaining 
pure cultures even from this kind of material, particularly from small 
superficial pulmonary cavities, the outer wall of which, after treatment with 
solution of corrosive sublimate, was removed with hot instruments. 

"After the inoculation of the solidified serum with material containing 
bacilli has been accomplished, the vessels are placed in the incubator and 
kept constantly at a temperature of about 37° C. Every incubator is not 
suitable for the culture of tubercle bacilli. Growth takes place but very 
slowly, and the vessels must therefore remain in the incubator for weeks. 
So that if the incubator is so constructed as to favour rapid evaporation of 
liquids from the culture vessels, the serum gets dry before visible colonies 
of tubercle bacilli have developed. For example, an apparatus cannot be 
used in which the heat is unequally distributed, so that the vapour constantly 
present condenses in the cooler parts, e.g. , on the glass cover, and has to be 
continually replaced by moisture given off from the culture glasses. D'Ai:- 
sonval's thermostat is very convenient ; the warmth is equally distributed in 
it, and the blood serum remains almost unchanged. 

" For the first few days no alteration is to be observed in the cultures in the 
incubator. If, however, there is a change, and drops or spots of white or 
other colour form on the surface of the serum, increase more or less rapidly 
in size, render the fluid at the bottom of the glass turbid or cause the serum 
to liquefy, it is a sign that the culture is not pure, and that foreign bacteria 
have entered and choked the growth of the tubercle bacilli. If these drops 
or spots are examined they are found to consist of bacilli or micrococci 
which, by Ehrlich's method of staining, assume a different colour from the 
tubercle bacilli, and are distinct from them also in size and shape. In the 
tubes free from these impurities, the first signs of the growing colonies of 
tubercle bacilli are not visible to the naked eye for ten to fifteen days. 
They then appear as whitish points and small spots lying on the surface of 
the serum ; they have no lustre, and consequently stand out clearly from 
their moist surroundings. They are best compared to tiny dry scales 
adhering loosely to the surface of the serum. The number of the scales 
and the extent of surface covered by them vary with the richness of the 
infecting material in bacilli, and with the extent of the surface over which 
it was rubbed or spread out. 

" The individual scales attain only a limited size, so that if few are present 
they remain distinct ; but when numerous and closely packed, they coalesce 
finally and form a very thin, greyish-white, lustreless covering on the serum. 
After a fragment of the tubercular lung of a guinea-pig has been rubbed on 
serum, small whitish colonies of tubercle bacilli appear close to the greyish- 
red bit of lung, and also in its neighbourhood wherever it has been pushed 
over or pressed on to the surface of the serum by means of the platinum 


wire used to distribute the bacilli as widely as possible. The colonies in 
some cases are relatively few in number, because only a few bacilli were 
present in the pulmonary tubercles, as the examination of sections shows. 
In other cases the little colonies are much more numerous ; in many, as 
especially after inoculation with the contents of cavities very rich in bacilli, 
they soon coalesce and form a coherent membranous mass." 

From the cultivations so made other tubes were inoculated 
by lifting off the small scales with a needle bent at right 
angles, breaking the scale up somewhat so as to cover the 
point of the needle with the bacilli, and then drawing it 
along the surface of the solidified blood serum. At the end 
of ten or eleven days there became visible to the naked 
eye, and very much earlier if examined with a lens, a 
regular thin superficial layer spreading along each side of 
the track of the needle. This organism does not bring about 
the slightest liquefaction of the blood serum ; the scales are 
somewhat dry ; they are exceedingly thin, and spread only 
over the surface, no growth making its appearance in the deeper 
layers of the nutrient medium. Tubercle bacilli cultivated in 
this manner through seventy generations still continue to 
act on animals in the same way as the original or first 
culture. Similarly the bacillus grows only on the surface of 
a fluid, forming a very delicate, thin film, the organism being 
essentially aerobic in its habit. The film growing on solidified 
serum is loosely attached to the surface, and any fluid intro- 
duced, however gently, floats off a considerable portion in 
larger or smaller flakes, which do not break up, but gradually 
sink to the bottom. Koch observed , from the behaviour of the 
films when growing on the surface of fluids, or broken down 
and introduced into fluid media, that the tubercle bacilli were 
non-motile. He described the appearances of these colonies 
under the microscope, and came to the conclusion that the 
growth was perfectly characteristic, as compared with any 
other organisms known up to that time. They have the 
appearance of lines or short threads thrown into curves like 
worms, or snakes, or flourishes of a pen, thinner or thicker 
according to the age of the colony, each thread being com- 
posed of a large number of individual bacilli, arranged with 
their axes in the long axis of the thread, running parallel to 
one another, but with a small space between each, these 
being apparently occupied by some zooglcea medium. This 
arrangement can be best brought out by pressing down a 


cover glass on to the surface of a colony as it grows on 
the serum, and then removing it without sliding it in any 
way and staining by any of the usually recognized methods. 

As regards the conditions under which this organism 
exists, we have already seen that a certain amount of 
moisture is absolutely necessary for its growth, and Paw- 
lowsky was able to cultivate it, even on potato, when he 
took the precaution to keep a considerable quantity of 
moisture in contact with the growing organism, and watched 
the potato for a considerable length of time, the growth not 
being visible to the naked eye for three weeks or a month. 
Koch's great difficulty in his earlier experiments was, as we 
have already seen, to obtain a substance which, in addition to 
containing all the other elements necessary for the nutrition 
of the bacillus, would remain sufficiently moist for the 
requirements of the bacillus when exposed to a pretty high 
temperature for a considerable length of time. As regards 
temperature, it was found that, although there was an actual 
cessation of growth and development below 28°.or 29° C, 
on blood serum the organism might be exposed to very low 
temperatures for a considerable length of time without 
losing its power of again becoming active when returned to 
favourable environments. It grows best at about 37° C, 
but as soon as the temperature rises beyond 38° C. the 
development of the bacillus in the cultivation tubes begins 
to diminish in activity, and at 40° C. (Koch originally gave 
this limit as 42° C.) it ceases entirely to grow and multiply. 
It is a remarkable fact that the temperature at which the 
bacillus develops best is exactly that of the human body 
(37.8° C). In the cow and the horse, where the other con- 
ditions must also be favourable, the temperature is about 
38.3° C, in the calf a little over 39° C, whilst in the hen we 
have the maximum temperature of 40° C. 

Klein, in a series of experiments reported in 1886, finds 
that it is possible to inoculate successfully with tubercle 
taken from the human subject, also that it is possible to 
inoculate from a guinea-pig to a cow, but when inoculation 
is made from a cow to a fowl the experiment breaks down, 
and there is no tubercle produced, so that, not only can one 
modify the activity, and the power of growth of these 
bacilli outside the body by altering the temperature at which 
they grow, but it is also within the range of possibility 


to modify the bacilli by introducing them into different 
animals whose normal temperatures and other general 
metabolic conditions are different. This modification has 
more than nominal value, for it has been proved experi- 
mentally that, although the organisms in human and in' 
bovine tuberculosis are morphologically identical, they are 
not absolutely the same in all their vital and pathogenic 
characteristics. For instance, tubercle bacilli taken from 
a phthisical patient and introduced into the tissues of a cow 
will soon set up an acute general tuberculosis, whilst bacilli 
taken from a case of perlsucht, or ordinary bovine tuber- 
culosis, almost invariably give rise to the perhucht form of 
tuberculous disease, and rarely, or never, to the acute 
generalized form. It would appear that in these cases the 
microbe becomes adapted to the special conditions present 
in each host, and consequently becomes less suited to the con- 
ditions in others. It might be objected that in the case of the 
fowl the bacilli are present in enormous numbers, and that, 
therefore,, their action should be more virulent ; but, in 
answer to this, it may be pointed out that increased activity 
of growth is not necessarily always associated with increased 
virulence. In illustration of this fact, it may be pointed out 
that, after many experiments, Nocard and Roux were able 
to obtain most luxuriant cultivations of the tubercle bacillus 
on agar-agar or on blood serum, to which 6-8 per cent, of 
glycerine had been added. The organisms on these media 
grow so rapidly that they are quite visible at the end of four 
days, and at the end of twenty days, and not four weeks, as 
on ordinary blood serum, the growth seems to have reached 
its maximum, when it appears as a pale grey, thick, mamil- 
lated or reticulated, mass. In the same way luxuriant 
growths may be obtained in bouillon to which a similar 
proportion of glycerine has been added, small opaque flakes 
or flocculi first making their appearance at the surface, and 
then sinking to the bottom, where they remain. This 
growth in glycerine broth may take place at a comparatively 
low temperature, i8°-20° C, though it then goes on very 
slowly. Earlier generations of such cultivations produce 
typical tubercle nodules that grow with extreme and charac- 
teristic rapidity when inoculated, but after several generations 
of such pure cultivations have been made in these glycerine 
media, the virulence may become distinctly diminished, 


although the growths are as luxuriant as, or are actually 
more luxuriant than ever. We have in fact a kind of 
reversion to the saproph5^ic condition of the culture, a 
condition accompanied by diminished parasitic virulence. 
It is possible, therefore, that the higher temperature that is 
met with in cattle along with other conditions there present 
may have a distinct effect in diminishing the virulence of 
the organism, whilst at the same time it may play an im- 
portant role in causing its parasitic and vegetative activity 
to be increased within the body of these animals, though 
this is not necessarily accompanied by increased vegetative 
activity outside the body. As Koch pointed out at the 
International Medical Congress, of 1890, the tubercle cultures 
from fowls were quite distinct and could not be passed 
on as such from animals to animals of different species 
or by growth at different temperatures, and he con- 
cludes that although nearly related to the ordinary tubercle 
bacillus they are specifically distinct. It should be noted, 
too, that tubercle bacilli grown on glycerine agar are, 
according to Nocard and Roux, somewhat shorter than 
the bacilli met with in tubercular sputum, that they 
also contain numerous ovoid spores, but that otherwise 
they are exactly like those described by other observers in 
various animals and on other media. As has been already 
mentioned, there was necessarily a doubt whether any disease 
could be tubercular if it was not possible by special methods to 
demonstrate in histological preparations the presence of the 
bacillus. This histological demonstration is, however, after 
all, a clumsy method, and in many cases it has been found 
possible to obtain demonstrations of the tuberculous nature 
of a disease by inoculation experiments when the organisms 
have been so few that they have escaped the notice of the 
most careful observers. It may therefore be confidently 
anticipated that more and more proof of the tuberculous 
nature of lupus, scrofula, cold abscesses, and bone disease will 
be gradually accumulated. 

As early as 1843 it had been demonstrated that tubercular 
material from dead subjects when inoculated into rabbits 
produced tuberculosis ; in 1865 these experiments were 
repeated and extended by Villemin, and other observers have 
from time to time confirmed the results that were then 
obtained. Koch's observations and experiments have now. 


however, placed the matter on a much surer footing ; he has, 
as we have seen, succeeded in separating a specific bacillus 
from tuberculous material, with which he has been able to 
produce tuberculosis with the utmost certainty, so that, 
instead of dealing with comparatively large fragments of 
diseased tissue, he has worked with particles so small that 
they can only be distinguished with the aid of the best 
microscope and the use of special methods of preparation. 
This, of course, has cleared up many points which hitherto 
have been very obscure, and, most important of all, it has 
enabled us to determine the channels by which human beings 
may become affected with the disease, especially in connec- 
tion with the respiratory passages and by way of the 
alimentary canal, and through wounds or damaged tissues. 

It has been demonstrated that in the sputum of patients 
suffering from phthisis, in those cases where the softened 
lung tissue is breaking down and is being expectorated, an 
enormous number of tubercle bacilli may often be met with, 
though they may be present in comparatively small num- 
bers ; so frequently is this the case, that the presence (in 
different numbers from day to day) of tubercle bacilli in 
the sputum, or their absence, is relied upon as a diagnostic 
feature by attention to which the physician is enabled not 
only to determine the rapidity with which breaking down is 
going on, but even to obtain very considerable assistance 
in arriving at a decision as to whether a disease is tubercular 
or not.' 

Until quite recently not the slightest attempt has been made either to 
prevent the_ diffusion of such sputum, or to disinfect it in any way, and it 
has been said, with some considerable degree of truth, that a very large 
quantity of virulent tuberculous material has been allowed to be freely dis- 
seminated, with the result that it must have been the lot of many individuals 
to contract tuberculosis by means of the inhalation of particles of dried 
tuberculous sputum in which active tubercle bacilli or their spores were 
necessarily entangled. That the sputum contained the elements which 

' In making an examination of sputa for tubercle bacilli, the fact that 
the bacilli are most numerous in the small yellow caseous points should 
always be borne in mind. Such points should be carefully searched for, 
crushed between two cover glasses, dried, stained, and examined. Single 
bacilli may be found elsewhere, but masses can, as a rule, be found in these 
disintegrating points only. It is only where disintegration has commenced 
that any reliance can be placed on the numbers of tubercle bacilli as 
affording any assistance in forming a diagnosis and prognosis, 



were the exciting causal agents of the disease had been experimentally 
proved, even before the actual discovery of the bacillus was made, and 
dogs, which had been in the habit of taking up the sputum of tuberculous 
persons, had been known to contract the disease, an observation that was 
fully corroborated by further experiment. Similarly it had been related 
how barn door fowls in a country district, which for a long time were 
perfectly healthy, were suddenly attacked by an outbreak of tuberculosis 
after a phthisical patient had come to live at the farm. The expectorations 
of this patient were voraciously devoured by the fowls, with the result that 
tuberculosis of a most virulent nature broke out in a most extraordinary 
fashion amongst the brood. Feeding experiments were also made to 
corroborate this accidental experiment ; and more recently similar acci- 
dental experiments have been recorded both in France and in this country. 

In the case of certain micro-organisms the products of 
putrefaction exert such a deleterious influence on them that 
they are destroyed very readily and rapidly. Again, in the 
case of the cholera bacillus, desiccation at once proves fatal, 
not only to its growth, but also to its actual virulence and 
power of infection. In the case of the tubercle bacillus, 
however, observers, both in France and in Germany, very 
early pointed out that putrefaction and drying could exert 
but little influence on the number of the bacilli, whilst dry- 
ing alone interfered only slightly with their virulence, as it 
was quite easy to inoculate rabbits with sputum that had 
been dried at a temperature of 30° C. Later, Galtier found 
that maceration and putrefaction for a period of five days, 
and even intermittent freezing and melting, did not interfere 
with the transmission of the disease by means of the bacillus. 
Other observers have demonstrated that the bacillus remains 
virulent after it has been exposed, in sputum,for forty days, and 
even after 186 days if it is carefully protected from the action 
of the air. It is, of course, concluded from these experiments 
that, difficult as it is to cultivate the specific micro-organism 
of tuberculosis outside the body as a saprophyte, the parasitic 
form (or its spores) still retains its vitality and power of 
development for a considerable length of time — and under 
what would appear to be very unfavourable circumstances — 
even when removed from its host. The way was thus 
being thoroughly prepared for Dr. Georg Cornet's researches 
on infection in hospitals and rooms where phthisical 
patients were treated. Dr. Ransome had, early in the con- 
troversy, demonstrated the presence of tubercle bacilli in the 
air respired by tuberculous patients ; and Dr. Williams, in 
1883, suspended glass plates smeared with glycerine for a 


period of iive days in one of the ventilating shafts of the 
Brompton Hospital for Consumption. Washing off the 
glycerine "with distilled water, the fluid was mixed with a little 
mucilage and evaporated down to one-half, and then examined 
for the bacilli," and in this he was able to demonstrate bacilli 
in fair numbers. In a thoroughly purified ward a number 
of non-phthisical patients were placed, with the result that 
no bacilli were found in the air carried off by the extraction 
shaft ; whilst in another ward, filled with consumptive 
patients, the washings from a plate exposed for fourteen 
days in the extraction shaft contained numerous bacilli. 
Similar experiments have been made by other observers, but it 
was left for Cornet to make a systematic examination of the 
dust in rooms were phthisical and non-phthisical patients 
were treated. By numerous careful inoculation experiments, 
he demonstrated the fact that the expectorations from 
phthisical patients are a source of a very real and appreci- 
able danger. The bacilli are not only exhaled, in small 
numbers no doubt, but he finds that they are also con- 
tained in very considerable numbers in the dried sputum 
obtained from handkerchiefs, bed linen used by phthisical 
patients, and in the sputum that has made its way on to the 
floor and walls through the dirty habits of many of the 
patients. His experiments extended over a very considerable 
period, and to the rooms of private patients in hospitals, in 
lunatic asylums, &c. ; he even found bacilli in the streets 
and open spaces in a certain proportion of cases where 
tuberculous patients were collected together. These results 
have the greater value from the fact that in no case did he 
consider his experiments complete unless the dust with 
which he was experimenting, when inoculated into animals, 
produced the disease. It follows from all this that infection, 
as the result of inhalation of the dried virus, is one of the 
most common forms with which we have to contend, this 
being especially the case in older people, amongst whom 
pulmonary tuberculosis is most commonly met with, but in 
whom, as in children, pulmonary catarrh seems invariably to 
precede the tubercular disease. In children, the catarrhal 
inflammation of the lungs that so frequently accompanies 
such conditions as measles, scarlatina, diphtheria, whooping- 
cough, and other similar conditions, may very frequently 
become tubercular in character. 

Tuberculosis. 221 

There seems, in these cases, to be, first, a weakened con- 
dition and impaired power of resistance of the epithelial 
cells lining the small bronchi, the smaller air passages and 
the air vesicles making up the spongy tissue of the 
lung. The bacilli in the air and dust then finding their way 
to a surface already weakened and specially prepared as it 
were for their reception, recommence their parasitic life, 
multiply, and make their way further into the tissues, where 
they set up the changes associated with tubercular disease. 
It is evident from aU this that much work still lies ready 
to our hand in connection with the spread of tubercle, 
and that if we could only persuade people to look upon 
tubercle as an infectious disease similar in character to 
scarlet fever, though not so rapidly developed, much 
would have been done to prevent its spread, and a great 
advance in preventive medicine would have been made. 
Through the work of Koch, Cornet, and others, the Ger- 
mans have come to look upon perfect cleanliness in the 
treatment of phthisical patients as absolutely essential. 
Pocket handkerchiefs and bed linen used by phthisical 
patients are most carefully sterilized by means of bichloride 
of mercury, hot air, steam, or other germicidal agents ; 
patients are strongly enjoined not to expectorate except into 
receptacles specially made for the purpose, receptacles that 
can be carried about, can be most readily cleaned, and in 
which expectorations can be easily disinfected. Of course, 
the results of all this are not yet manifest, but it may be 
confidently anticipated that within a comparatively short 
time a considerable diminution in the number of phthisical 
patients in Germany will have to be recorded ; not to be 
compared, perhaps, with the diminution of cases of other 
diseases, but still a very appreciable one. 

As a single example we may take the Grand Duchy of Baden, where 
there was a diminution of deaths from tuberculosis from 3.08 per 1,000 
inhabitants in 1882 to 2.80 per 1,000 in 1887, or no less than .28 per 
1 ,000. Were this to be equalled in the British Isles, and the patients were 
not carried off by other diseases, the saving to our community would be 
nearly 10,000 lives per annum. 

We may here mention the various disinfectants used. By far the best is 
heat, especially moist heat. Sunlight, or even ordinary daylight, will, ac- 
cording to Koch, kill tubercle bacilli in from a few minutes to five or six days. 
Koch has also proved that a number of ethereal oils, some of the so-called 
aniline or tar dyes, mercury in the form of vapour and silver and gold com- 

222 ■Bacteria.. 

pounds, all exert an inhibitory effect on the growth of tubercle bacillus ; the 
compounds of cyanogen and gold, especially, even in a solution diluted to one 
part of cyanide of gold to two millions of the solvent substance, checking the 
growth of tubercle bacilli. Carbolic acid also kills the bacilli if it is allowed 
to act in considerable strength and for a lengthened period ; but none of 
these can, for a moment, be compared as regards not oiily efficiency and 
cheapness, but for facility of application, with steam or boiling water. All 
disinfection should be just as completely carried out when a phthisical patient 
leaves a room or ward as if a case of scarlet fever had been treated there ; 
the walls, floor, and even the roof should be thoroughly washed and disin- 
fected by means of hot water or lime. During treatment in such apart- 
ments no patient should be allowed to expectorate on the floor ; and glass 
or porcelain spitoons, which can easily and safely be boiled in water, should 
be placed for the reception of all sputa. During the time that corridors, 
steps, and rooms are being cleaned and disinfected, they should be kept 
quite moist, in order that' as little dust as possible' may arise from the clean- 
ing operations. No room that has been occupied by a phthisical patient 
should be used until it has been thoroughly disinfected ; the bedding and 
curtains should be well boiled, the blankets steamed, the mattresses dis- 
infected, all the furniture washed with soap and water, the carpets and 
upholstering thoroughly beaten in the open air, the dust of which should 
be caught in straw (such straw and the paper taken from under the carpets 
should always be burned), the floor thoroughly washed with soap and hot 
water, and the wall paper rubbed down with freshly baked bread. In 
San Remo all these methods of procedure have been brought under the 
notice of the hotel-keepers, and they are advised to carry them out in 
connection with the whole of their rooms at the end of each season, not 
only the sleeping rooms, but also the public rooms. 

The alimentary canal is probably the next most important 
channel of infection. Evidence of infection by this channel 
was first obtained by the feeding experiments already referred 
to, but further evidence of it has been noted in the ulcera- 
tion of the intestine that is so frequently met with in 
phthisical patients, and which appears to be due to the action 
of bacilli contained in the sputum passing down the gullet 
through the stomach in cases where the gastric juice is not 
very active, and so to the intestine in which ulceration occurs 
in the course of the tubercular process as the result of the 
pathogenic activity of the bacilli. In children this mode of 
infection is comparatively common, and tubercular ulceration 
of the intestine, or tubercle of the glands connected with the 
intestinal tract, is of frequent occurrence. 

In 127 cases of tuberculosis in children that I examined this tubercular 
ulceration was found in 43 ; whilst in 100 cases, or nearly 79 per cent, of 
the whole, the glands were in some stage or other of tubercular degenera- 
tion. It would thus appear that tuberculosis connected with the intestine 
is of frequent occurrence in children, and we should therefore argue that 



the infection, in these cases at any rate, frequently takes place by the ali- 
mentary canal. The age at which these tubercular glands were found is 
very significant ; during the first year of life there were 4 cases ; from i to 
2j years, 33 ; from 3 to 5J years, 29 ; from 6 to 7J years, 12 ; from 8 to 10 
years, 13 ; and from II to 15 years 9 cases. In 14 cases these glands only 
were affected. 

Bolitz (Inaugural Dissertation, Kiel) gives similar figures, but on a more 
extensive scale. 

Out of 2,576 children whose bodies were submitted to 3. post mortem ex- 
amination in Kiel during the years 1873-1889, there were 424 cases of 
tuberculosis, or 16.4 per cent, of the whole mortality. 

The following shows the percentages of the whole of the deaths from 
tuberculosis at each of the different ages : — 

Still-born children . 0.0 per cent. 

Up to 4 weeks old 0.0 ,, 
„ S-io .. 0-9 .. 

>> 3-5 months old 8.6 ,, 
„ 6-12 „ „ 18.3 „ 
,, 1-2 years ,, 26.8 ,, 

Up to 2-3 years old 33.0 percent. 

.. 3-4 .. » 29.6 „ 

)i 4~S » » 31-8 „ 

.. S-io „ „ 34.3 „ 

., 10-15 " >• 30-1 

Here, again, as where the lung is attacked, we must look 
upon the bacillus as the exciting cause, but tissue weakness 
as the predisposing cause. These conditions may be summed 
up as follows : — 

(a) The presence of the bacillus tuberculosis in such a 
position and for such a length of time that it obtains a coign 
of vantage, so to speak, from which to attack the tissues of 
the body. 

(3) Some weak point in the epithelial surface " made by 
disease, or due to irritation or bad food," by which the organ- 
isms may attack the deeper tissues in sufficient numbers to 
ensure their being able to hold their own in the struggle for 
supremacy that ensues. 

(c) The comparatively low vitality of these deeper tissues 
brought about by imperfect nutrition or irritation ; the cells 
of which they are composed being no longer able to deal 
successfully with any large number of bacilli that can under 
ordinary circumstances find their way thus far. 

As regards the possibility of the bacillus tuberculosis being 
present in the intestinal canal, it should be remembered that 
the class of patients amongst whom abdominal tuberculosis is 
most rife, consists of infants, which during the first year of 
their life, and sometimes for a longer period, are suckled at 
the breast ; after this, however, the diet is extremely mixed, 
and as a rule it is extremely unsuitable ; but it is in by far the 


larger proportion of cases, even amsngst the poorer classes, 
partially, at any rate, composed of cows' milk. During this 
first year of their life, children with tuberculosis of the 
mesenteric glands, or of those glands connected with the 
intestine, form a very small proportion of the cases of infantile 
tuberculosis. Whilst the child is suckled by its mother there 
is little tubercle, but after this first year there is a very rapid 
rise in the mortality from tubercle. It is a somewhat singular 
fact that although tuberculosis is frequently met with in 
young married women, tubercular disease of the breast is 
extremely rare, so rare, indeed, that one observer, Dr. Huber- 
maas, who took great interest in this subject, was able to 
collect the records of only some eight cases. In cattle, on 
the other hand, where the mammary gland carries on its 
functions when the animals are placed under conditions 
which are far from healthy, or at any rate far from normal, 
this tubercular disease of the milk gland is not by any means 
of infrequent occurrence. 

Some of the earliest experiments from which actual proof 
of the infective nature of tuberculous material was obtained 
were those made by Gerlach and Chauveau, who used the milk 
of tuberculous cows to feed young animals ; though tubercu- 
losis was not produced in every case, the former was successful 
in a sufficient number to justify his conclusion that there was 
some specific virus in the milk of tuberculous cows which 
could, when ingested, produce tuberculosis of the alimentary 
tract, or of the glands associated with it. Numerous experi- 
ments on young pigs, some of them accidental, others de- 
signed, and others on calves and hens, have been recorded, 
in which tuberculosis has evidently followed their being 
fed with tuberculous milk. At the International Medical 
Congress held in Copenhagen in 1884, Professor Bang, of the 
Royal Veterinary School in that city, gave the results of a care- 
ful examination of twenty-seven cases of tubercular disease 
of the udder in cattle, in the milk of which he was able to 
demonstrate the presence of tubercle bacilli, both directly 
under the microscope and in the sediment obtained by means 
of the use of a centrifugal separator. With this milk, or with 
the separated sediment, he was able to produce tuberculosis 
both by inoculation and by ingestion. Another observer, 
Nocard, was able to demonstrate the presence of the specific 
bacillus in milk in eleven cases, and Professor M'Fadyean and 


I also found tubercle bacilli in the milk from six cows out of 
six hundred examined. So certainly are the bacilli found in 
cases of tubercular disease of the udder that certain authori- 
ties maintain that it is possible to diiferentiate between the 
simple and the tubercular inflammation of the udder in the 
cow merely by means of a microscopic examination of the 
milk. (See Appendix). 

This question of tubercle in milk has now assumed such importance that . 
much attention has been given to it abroad, and in Denmark a most 
complete system of inspection has been instituted in connection with one 
of the largest milk supply associations in the world ; and private enterprise, 
guided by Prof. Panum and Mr. Busck of Copenhagen, has indicated 
a way in which the State might tread vrith very great advantage. In 
connection virith this association, six special veterinary surgeons, in addition 
to local practitioners, are constantly employed in keeping watch over the 
cattle that supply the milk to it. One of these veterinary surgeons alone, 
specially retained, examines eight hundred cattle fortnightly, and makes 
most careful notes (notes that I had an opportunity of examining) of the con- 
dition of every animal. Bang, to whose energy and observations the opening 
up of the tuberculosis question is very greatly due, contends that a diagnosis 
of tubercular disease of the udder can generally be made without difficulty 
during life and in the very early stages of the disease. With this conclusion 
it is somewhat difficult to agree, but much more may be done in the way of 
careful and systematic examination than is done at present, and in Denmark 
they have certainly systematized the examination of cattle to a far greater 
extent than we have succeeded in doing. As it may be of interest to 
mention the points on which the veterinary surgeon should depend in 
making his diagnosis, they may, so far as I was able to follow the routine 
of a number of inspectors, all of whom however differed slightly in their 
methods, be briefly summed up in the following : — 

(a) First of all the sub-maxillary glands are examined ; these are easily felt, 
and any change is readily made out. 

(6) The glands at the root of the neck and those in front, of the haunch 
bones are always carefully examined. The glands in the flank should be 
equal in size, about the size of the middle finger, and not hard. Mere 
enlargement, even when considerable, is, however, not looked upon as of 
great importance if it is perfectly equal on the two sides. 

(c) The animal is made to cough by means of pressure on the trachea, 
and the lungs are carefully examined during and after the coughing. 

The condition of the slan over the flanks is carefully observed ; it should, 
in a healthy animal, be " loose," like that of a dog, soft and pliable ; any 
adhesion, hardness, or harshness, should be carefully noted._ 

(d) The udder is carefully examined for inequality of size and for any 
induration. It is a somewhat curious fact that tuberculous disease usually 
affects the hind quarters of the udder, which become hard and knotty, but 
not painful ; whilst in acute inflammation of the udder, the anterior quarters 
are quite as much afiected as the posterior ; the pain is usually very acute, 
and the process is accompanied by much more marked febrile symptoms. 

(e) Then the glands above the udder, high up between the quarters, are 



most carefully examined. In cases of tubercular disease of the udder these 
glands are invariably affected, are unequal in size, and the larger one, 
corresponding to the affected quarter, is usually considerably indurated. 

(/) Careful auscultation is carried out at least once a month. The fore- 
foot of the side that is being examined being always well advanced. The 
normal expiration sound lasts half as long as the normal inspiration, and 
if this rhythm is deviated from in anyway, a further and thorough examina- 
tion of the lungs should always be made. 

{g) The examination is continued still further if the slightest suspicion of 
tubercular disease is aroused by the above investigation, and an examination 
per rectum is made, with the object of determining whether there is any 
tubercle of the peritoneum or not. As the onset of the disease in the udder 
is so rapid, and as, as yet, it is held by most observers that the bacilli may 
make their appearance in the milk, even where the udder is not directly 
affected, it follows that if there is the slightest suspicion of the existence of 
tubercular disease in a cow, the milk from that animal should not be put 
into the milk supply, and as a matter of fact, on the Danish farms above re- 
ferred to, it is not sent to town, but it is either thrown out, or after being 
most thoroughly disinfected by prolonged boiling, is given to the pigs. 

{A) The farmer keeps a record of the quantity of milk given by each cow, 
and a note of what is done with it ; and any milk that is put out of the 
supply by the veterinary surgeon, or by the farmer himself, on account of 
suspected disease, is paid for by the company, or the difference between the 
full value and the value as pig food. 

Any other inflammatory condition of the udder is carefully noted, and 
even then the milk is wdthdrawn from the regular supply. 

(«■) A small quantity of milk is always drawn off by the veterinary sur- 
geon, who carefully notes its colour. If it is too thin and watery looking he 
immediately condemns it ; whilst if it loses the peculiar blue tinge that 
freshly-drawn milk from a healthy cow almost invariably has, and takes on 
even a slight yellow tinge instead, the milk from the infected quarter is not 
used for any purposes, although the milk from the other quarters may be 
used, after being thoroughly boiled, for the feeding of pigs. 

The authorities of the association insist rigidly on the fortnightly in- 
spection, because it has been observed that very great swelling may appear 
as a sign of udder tuberculosis in from ten to fourteen days, as in this posi- 
tion the onset of the tuberculous disease is usually much more rapid than in 
the lungs, in which the process in a very large majority of cases appears to be 
far more chronic in character. In all cases, tlie condition of the glands 
must be systematically and carefully observed. 

In the light of recent events, too, it is to be hoped that Koch's tuberculin 
may be utilized in the diagnosis of tuberculosis in cattle, and that satis- 
factory results may thus be obtained. 

In consequence of the rapid onset of the disease diag- 
nosis without regular inspection is almost impossible, 
and it is probable that the swelling of the udder is only 
one of the later manifestations of the disease, the glands 
above the udder apparently being a far more reliable 
index. Professor M'Fadyean and I were so much struck 


with this difficulty of diagnosis, that in a paper read at a 
meeting of the Pathological Section of the British Medical 
Association, held in Dublin, August, 1887, we stated that it 
appeared to us "that where, as is very frequently the case 
with cows kept in towns, a complete history of the diseased 
condition of the udder is not obtainable, a differential diag- 
nosis of mammitis (inflammation of the milk glands) is by 
no means easy, except by microscopic demonstration of the 

Tubercle bacilli arranged around a closed up milk-duct in a case of 
Tuberculous disease of the udder of a cow. x looo. 

bacilli in the milk ; which may also fail if ,a most careful 
search is not made" ; and Principal Walley, dealing with 
the same subject, says, " that he could not undertake to 
diagnose, with accuracy, tubercular mammitis in every case, 
nor even in a majority of cases " ; and he states that in 
specimens of the udders of tuberculous cows he has ex- 
amined, after death, he has found good examples of tubercu- 
losis in the mucous membrane of the milk sinuses without 


the occurrence of any induration of the milk gland, " indeed," 
he adds, " I may say that no veterinary surgeon could, during 
life, have diagnosed the existence of tubercular mastitis 
(tubercular inflammation of the udder) without the aid of 
a microscope." That tubercle bacilli make their way into 
the milk, when there is tubercular ulceration in the milk- 
ducts, can be readily understood, and has frequently been 
shown ; but it has also been demonstrated by Professor 
M'Fadyean that in cases of tuberculosis, bacilli may be 
found lying free in what are otherwise apparently healthy 
milk ducts. Fresh evidence is being accumulated every 
day, but these facts alone, when considered along with 
the occurrence of bacilli in milk, with the feeding experi- 
ments already recorded by so many observers, and taken in 
connection with the great prevalence of tubercle 'in certain 
classes of animals, afford strong presumptive evidence that 
milk is a source of tubercular infection, especially in children, 
and in those in whom, on account of imperfect nutrition 
and impaired digestion, the walls of the alimentary canal are 
less able to resist the invasion of the organism known as 
Koch's Bacillus Tuberculosis. 

The danger of contracting tuberculosis from taking meat 
from cattle affected with the disease is perhaps not so great 
as that associated with the drinking of tuberculous milk ; 
it is nevertheless one with which the sanitary authorities 
will have to deal, and one to guard against which it is 
necessary to take very considerable precautions. There can 
be little doubt that in those cases where the disease is 
localized to any one of the viscera at the time of the 
death of the animal, there is little danger to be anticipated 
from eating the well-cooked flesh from other parts of that 
animal ; and if we could be absolutely certain that the 
localization was complete, all would be well. Even in cases 
where the flesh is taken from animals in advanced stages of 
tuberculous disease there would be a certain proportion of 
cases in which no evil results would follow, and one observer 
who made sixty-two experiments with such flesh boiled for 
ten or fifteen minutes, found that only 35.5 per cent, of the 
inoculated animals became tuberculous. Even in cases of 
generalized tuberculosis Nocard failed in thirty-nine out of 
forty cases to transmit the disease by means of raw muscle 
juice injected into the peritoneal cavity of guinea pigs, but 


he succeeded in the fortieth. Other observers, however, 
have been more successful, and in two rabbits I was able 
to produce tuberculosis by injection into the peritoneal 
cavity of the raw juice expressed from the intercostal 
muscles of a tuberculous cow after all tuberculous pleura 
had been carefully " stripped " ; whilst the juice taken 
from the muscle of the thigh injected into two other rabbits 
was perfectly innocuous. The danger of infection by the 
consumption of meat from tuberculous cows may have been 
much exaggerated, but that there is a very appreciable 
danger must most certainly not be lost sight of by our 
Medical Officers of Health and the Veterinary Inspectors of 
the Board of Agriculture. 

Koch, as we have seen, had discovered a specific or- 
ganism which he had been able to cultivate outside the 
body ; he had inoculated and produced tubercle ; and he 
had found certain germicidal agents which were capable of 
destroying the organism outside the body. He, and the 
many interested workers who had investigated the subject, 
had found that it was more difficult to inoculate certain 
animals successfully than others. It had been observed even 
that certain individuals of the same species were much more 
refractory to the action of the virus than others, and it 
very naturally suggested itself to those workers, that there 
were two conditions which would have to be determined 
before any systematic and organized attack could be made 
on the tubercle bacillus within the body. The tubercle 
bacillus itself might be developed under such conditions that 
its virulence might be more or less modified. For example, 
Koch found that all his cultivations made on blood serum 
retained their power of growing in animal tissues in A most 
extraordinary degree, and for long this substance was the 
only nutrient medium used for the cultivation of the tubercle 
bacillus. It was found, indeed, that the other combinations 
used for the cultivation of other organisms up to that time 
were valueless as nutrient substrata for the tubercle bacillus. 
Nocard and Roux, however, found, as we have seen, that on 
the addition of a certain percentage — 6-8 per cent. — of 
glycerine to peptonized broth, solidified by the addition of 
agar, they could obtain a nutrient medium on which the 
tubercle bacillus would grow most luxuriantly. After it had 
passed through several generations of cultivations on this 


medium, the virulence of the organism, or its power of 
growing in tissues, was distinctly diminished — i.e., the 
organism was in a condition to be much more readily de- 
stroyed by the cells of the animal body, which appeared to 
keep the upper hand throughout the struggle, very few of the 
cells being destroyed, as is the case when virulent tubercle is 
used, where although a number of the tubercle bacilli are un- 
doubtedly destroyed, the degeneration of the proliferated cells 
is so extensive that caseous nodules are formed, and the typical 
appearance of caseating tubercle are presented in the inocu- 
lated area. The second factor, though equally important, and 
though recognized indirectly by all physicians, could not put 
itself so fully in evidence as the first, and it was only ^ter 
Metschnikoff had made his beautiful observations on the daph- 
nia and on the separating tail of the tadpole and the phagocyte 
action of certain cells in these processes, that any direct evi- 
dence of the bearing of the activity of the cells of the tissues 
of the body on the destruction of micro-organisms within the 
body could be definitely adduced. Then, indeed, began the 
narration of the history of the battle between the cells and 
the bacilli. If the bacilli were weak, or were present in small 
numbers only, the cells were invariably the victors ; if the 
cells were degenerated, or were badly nourished, or if their 
vitality was low, the bacilli proved themselves the more 
powerful. How these results were brought about soon 
became the subject of most violent controversy, and in the 
controversy thus raised explanations of facts that had hither- 
to puzzled scientific workers were projected and forced home. 
Let us here, however, examine only those facts that appear 
to have a special bearing on the subject of tuberculosis. 
A perfectly healthy individual, placed under favourable con- 
ditions as regards food, fresh air, and exercise, is never 
attacked successfully by tubercle bacilli, the active, vigorous 
tissue cells being perfectly competent to destroy any bacilli 
that may make their way into the lungs, the pharynx, or the 
intestine ; whilst even in cases of direct inoculation into a 
wound, if the wound heals rapidly, no tubercular process 
may result, the tubercle bacilli, as we have said, being 
destroyed by the cells. It may be, indeed, that certain 
secretions of the cells — i.e.., those substances that bear the 
same relation to the connective tissue cells that an enzyme 
bears to the yeast-cells — also exert a deleterious action on the 


bacilli in the healthy individual, and in a minor degree 
even in individuals with weaker tissues ; the activity of the 
bacilli is so interfered with or modified that they can be 
readily attacked and devoured by the tissue cells, which, as has 
long been known, have a most remarkable power of taking 
up into their substance many effete materials and particles 
of dead or inorganic matter. On the other hand, certain 
excretions, by accumulating in the blood and in the lymph 
spaces, may impair the activity of these tissue cells and so 
render them less able — (i) to secrete their protective material, 
and (2) to wage war directly against the bacilli ; whilst, in 
turn, the bacilli on their side, as we have already seen, secrete 
a material that has a most injurious action on the tissue 
cells, causing them to swell up and eventually to become 
hyaline. This material is only a poison when in large or 
comparatively large quantities ; in smaller doses it acts 
in the first instance as an irritant or stimulant, stimula- 
ting the protoplasm to exert all its powers against the 
advancing bacteria, powers that are so strongly exerted (un- 
less the conditions of nutrition and excretion are specially 
favourable) that they are rapidly exhausted. It has been 
observed that in those cases where phthisis was curable the 
cure has been effected only by careful nutrition of the 
tissues, and that as soon as they have been brought up to 
a certain standard of health the disease has been checked, in 
many cases permanently ; on the other hand it has been 
found that when the tissues have again fallen below /a;* there 
has been a fresh outbreak of the disease. These facts are in 
themselves sufficiently interesting and suggestive, but as we 
shalL see they have a further important bearing on the 
question of the curability of the tubercular phthisis. 

It has been observed that a process of localization occurs 
even when large caseous patches have been formed, and it 
has been found that around these patches, just as around an 
abscess, there is always erected a kind of barrier, made up 
of vigorous connective tissue cells, small, round and larger 
epithelioid cells ; the blood vessels in this cellular zone 
being comparatively numerous and of considerable size. We 
have, in fact, in this arrangement of the blood vessels and 
cells, a making of roads (the blood vessels) for the bringing 
up and massing of forces (the active cells) around the 
enemies' camp (the tubercular or caseous mass with the con- 


tained bacilli or spores), and by a process of close siege pre- 
venting the organisms from making their way outwards, and 
confining them entirely to their own territory, _so_ that, 
when they have utilized what food material there is in the 
degenerated cells, they are no longer able to exist as vege- 
tative bacteria, and only the spores remain — which may, 
however, remain latent for a very long period awaiting a 
favourable opportunity for another attack on weakened 
tissues. These spores or hibernating germs are confined 
within the same area, and the dthris with its contained 
spores is gradually encroached upon by the surrounding 
tissues until, eventually, if the mass is not large it may be 
entirely absorbed, though, owing to the amount of fibrous 
tissue that is formed by the attacking cells after their activity 
is somewhat diminished, this process of absorption sometimes 
goes on very slowly. 

It was an easy enough matter, when the history of the 
development of the tubercle bacillus was known, to kill the 
organism outside the body, and Koch found that a very large 
number of germicidal substances were capable of interfering 
with its growth ; but unfortunately most of these germicides 
also exerted an injurious effect on the tissues, so that what 
was gained in one direction was lost in another. 

In most other diseases in which preventive or curative 
inoculation by means of vaccines — less virulent cultures of 
the microbes — to accustom the animal to the action of the 
poison and so enable it to resist the more virulent, has been 
attempted, the aim has been to render the bacilli less, and the 
cells more active, and to develop in these cells a special activity. 

By accident, as he tells us, Koch found that by injecting 
tubercle virus into the subcutaneous tissues of guinea- 
pigs which had been previously inoculated with tuberculosis, 
the tissue in which the tubercle bacilli were acting was 
actually destroyed and an eschar or slough was formed 
at the point of inoculation ; whilst although the bacilli 
were not directly destroyed, they remained embedded 
in a mass of food material that was gradually but surely 
used up to supply the needs of these bacilli, and 
eventually they had to go into winter quarters. But 
the products of the tubercle bacilli appear to act in 
some way on the tubercles already formed ; they do 
something more than bring about complete degenera- 


tion of the weakened cells. In the immediate neighbour- 
hood of the young tuberculous tissue, z>., in those cells 
that have been slightly affected by the products of the 
tubercle bacillus it sets up a further reaction ; it stimulates 
these cells, and at the same time causes a dilatation of the 
vessels and probably also an increase in their number (this 
latter may be only apparent) ; a larger amount of food 
material is brought up for the nutrition of these cells, 
excreted matter is more readily carried away both by vessels 
and lymphatics, and in consequence of this, cells that have 
been too far stimulated by the tubercle poison to recover, 
die off, whilst those that are still capable of living, even 
under the excessive stimulation, proliferate and help to form 
the barrier between the dead mass and the surrounding 
normal tissues. In this way it would appear that in certain 
cases of tuberculous disease, Koch has produced an imitation 
of the natural process of cure. By a process of combined 
reasoning and experimentation, and basing his method of 
procedure on the one that had been already adopted in con- 
nection with the preparation of vaccines for other diseases, 
Koch succeeded in obtaining a substance with which, in a 
certain degree, at any rate, he was able to combat the 
advance or to modify the tuberculous disease in animals. 

As this advance in the treatment of tuberculosis marks a 
most important point in the history of the disease, and in 
order that there may be no misconception as to Koch's exact 
position, it may be well to give in his own words the descrip- 
tion of the discovery, composition, and probable mdde of 
action of the remedy. 

He says, in describing the observations, by the considera- 
tion of which he was led to take the lines of experimentation 
that ultimately led him to success : " If a healthy guinea-pig 
be inoculated with a pure cultivation of tubercle bacilli, the 
inoculation wound generally becomes glued over or sealed, 
and appears to heal up during the next few days. It is only 
in the course of from ten to fourteen days that a hard nodule 
is formed^ which soon opens, forming an ulcerating spot which 
persists until the death of the animal ; if an animal that is 
already tuberculous be inoculated the course of events is 
very different. The most suitable animals for this experi- 
ment are those which have already been successfully inocu- 
lated four or six weeks previously. In the case of an animal so 


treated the small secondary inoculation wound becomes 
sealed at first, but no nodule is formed ; a peculiar change 
takes place at the point of (primary) inoculation. As early 
as the first or second day the point becomes hard and dark- 
coloured — a condition that is not confined to the point of 
inoculation— and spreads around for about 0.5 to i centi- 
metre. During the next few days it becomes more and 
more clear that the epidermis thus changed is necrotic, and 
finally it is thrown off, and a flat ulcerated surface remains, 
which generally heals quickly and completely, without infec- 
tion being carried to the neighbouring lymphatic glands. 
Thus the inoculated tubercle bacilli act quite differently 
on the skin of a healthy guinea-pig, and on that of a 
tuberculous one. But this remarkable action does not 
belong exclusively to living tubercle bacilli, it also be- 
longs in the same degree to dead ones, whether they be 
killed by low temperature of long duration, which I at 
first tried, or by boiling heat, or by the action of certain 

" This peculiar fact having been ascertained, I followed it 
up in all directions, and then further found that pure culti- 
vations of tubercle bacilli thus killed, after they are ground 
down and suspended in water, may be injected under the 
skin of healthy guinea-pigs in large quantities without 
producing anything but local suppuration. Tuberculous 
guinea-pigs, on the other hand, are killed by an injection of 
very small quantities of suspended cultures within a time 
varying from six to forty-eight hours, according to the dose ; 
a dose which is just insufficient to kill the animal being 
sufficient to produce a widespread necrosis of the skin in the 
region of the point of (primary) inoculation. If the fluid 
with its suspended matter be still further diluted, so that it 
is scarcely turbid to the eye, the animals remain alive ; and 
if the injections be continued at intervals of one or two days 
a noticeable improvement in their condition soon sets in ; 
the ulcer at the point of inoculation becomes smaller, and 
finally cicatrization takes place. This is never the case 
when such treatment is not resorted to. The swollen lym- 
phatic glands become smaller, the condition as regards 
nutrition improves, and the progress of the disease is 
arrested, if it is not already so far advanced that the animal 
dies of debility. 


"These facts formed the basis of a therapeutic method 
against tuberculosis. But an obstacle to the practical em- 
ployment of fluids containing in suspension the dead 
tubercle bacilli was found in the fact that the tubercle 
bacilli are not (readily) absorbed ; they disappear, and 
remain for a long time unchanged in situ, producing 
larger or smaller suppurating centres. It was clear, there- 
fore, that in this method the curative effect on the tuber- 
- culous process was obtained by a soluble substance, diffused 
so to speak, into the fluids that surround the tubercle bacilli, 
and transferred without delay to the circulating fluids of the 
body ; whereas that which has the pus-forming quality 
seems to remain bound up in the tubercle bacilli, or at any 
rate to be only very slowly dissolved or washed out. Thus 
the only important thing that remained to be done was to 
carry out the process that takes place within the body — 
outside of it also — and if possible to extract and isolate the 
curative substance from the tubercle bacilli. This problem 
required long and continued experimentation, but at last I 
succeeded, by the help of a 40 to 50 per cent, solution of 
glycerine, in extracting the active principle from the tubercle 
bacilli. My further experiments on animals, and finally on 
human beings, were made with liquid thus obtained ; and 
in this way, also, the liquid which I supplied to phy- 
sicians and surgeons in order that they might repeat the 
experiments, was obtained. The remedy with which the new 
therapeutic treatment of tuberculosis is carried out, is, there- 
fore, a glycerine extract of pure cultivations of tubercle 

" In addition to the active principle there pass from the 
tubercle bacilli into the simple extract all other substances 
soluble in 50 per cent, glycerine, and therefore it is found to 
contain a certain quantity of mineral salts, pigment, and 
other unknown substances — extractives, &c. Some of these 
substances can be readily separated, as the active principle 
is insoluble in absolute alcohol, by which it can be preci- 
pitated, not pure certainly, but in combination with such 
other extractive matters as are also insoluble in alcohol. 
The colouring matter, too, can be separated out so that it is 
possible to obtain from the extract a colourless dry substance, 
which contains the active principle in a much more concen- 
trated form than does the original glycerine solution. 


" This purification of the glycerine extract has, however, no advantages as 
regards practical application, as the substances removed have no action on 
the human organism, so that the purifying process would only involve un- 
necessary expense. The constitution of the active principle can, as yet, be 
only a matter of conjecture. 

" It appears to me, indeed, to be a derivative of albuminous 
bodies, and to be closely related to them, but it does not 
belong to the group of so-called toxalbumens, as is proved 
by the fact that it can withstand high temperature, and in 
the dialyzer it passes quickly and easily through the mem- 
brane. The quantity of active principle present in the 
extract is in all probability very small. I estimate it at a 
fraction of I per cent. Thus, if my assumption be correct, 
we have to deal with a substance, the action of which on the 
tuberculous organism, far surpasses that of the strongest 
drugs known. 

" Various hypotheses may of course be formed as to the 
specific mode of action of the remedy on tuberculous tissue. 
Without in any way affirming that mine is the best possible 
explanation, I imagine the process to be as follows : The 
tubercle bacilli in their growth produce in the living tissues — 
just as in the artificial cultivations — certain substances which 
exert various but always deleterious influences on the living 
elements surrounding them, the cells. Amongst these 
substances is one which, in a certain concentration, destroys 
living protoplasm, and causes it to undergo a transformation 
into the condition called by Weigert, ' coagulation-necrosis.' 
The tissue having thus become necrotic, the conditions are 
so unfavourable to the nutrition of the bacillus that it is 
unable to undergo further development, and finally, in some 
cases, it dies off. In this way I explain the remarkable 
phenomenon, that in organs freshly attacked by tuberculous 
disease — ^for instance, in a guinea-pig's spleen or liver filled 
with grey nodules — numerous bacilli are found, whilst bacilli 
are rare or entirely absent when the enormously enlarged 
spleen is made up of whitish substance in a condition of 
coagulation-necrosis, such as is often met with in guinea- 
pigs that die of tuberculosis. A solitary bacillus, however, 
cannot produce necrosis at any great distance from itself, for, 
as soon as the necrosis has covered a certain area, the growth 
of the bacillus — and, in consequence, the production of the 
necrosis-producing substance — diminishes, and thus a sort 


of mutual compensation is set up, and to this is due the fact 
that the growth of isolated bacilli is so remarkably restricted, 
as for example, in the case of lupus, in scrofulous glands, &c. 
In such cases the necrosis extends only over a part of the 
cell, which then, in its further growth, assumes the pecuhar 
form of a giant cell. I thus follow in this statement of my 
views the explanation of the growth of giant cells first given 
by Weigert. Now if the necrosis-producing substance were 
artificially added to that contained in the tissue surrounding 
the bacillus, then the necrosis would extend further, and 
thus the conditions of nutrition of the bacillus would 
become much more unfavourable, than is usually the case. 
Then, not only would the more completely necrosed tissues 
disintegrate, slough, and — where this is possible — take with 
them the enclosed bacilli, carrying them outside the body, 
but the growth of the bacilli would also be interfered with 
to such an extent that they would die off much sooner than 
they do under ordinary conditions. It is in calling forth 
such changes that, to my mind, the action of the remedy 
seeems to consist. It contains a certain amount of the 
necrosis-producing substance, of which a correspondingly 
large dose has a deleterious influence — even in healthy 
persons — on certain elements of the tissues, probably on the 
white blood corpuscles or cells closely related to them, thus 
giving rise to the fever and the whole peculiar complex of 
symptoms that supervenes. In tuberculous persons a much 
smaller quantity suffices to cause, at certain spots — i.e., 
wherever tubercle bacilli vegetate, and have already impreg- 
nated their surroundings with the necrosis-producing sub- 
stance — a more or less extended necrosis of cells with the 
production of the accompanying conditions that affect the 
entire organism. In this way it is possible to explain — at 
least for the present — in a provisional manner, the specific 
influence which the remedy, in certain well-recognized doses, 
exercises on tuberculous tissue, as well as the possibility of 
increasing the doses in so remarkable a fashion, and, finally, 
to explain the curative effect which the remedy undoubtedly 
exerts where the conditions are at all favourable for its 

The substance to which the name of Tuberculin has been given 
has been analyzed, and is found to be "a syrupy, slightly foaming 
liquid (sp. gr. 1015 ?) of brown sherry colour, its aqueous solutions 


showing a greenish florescence. In odour it resembles elder yeast or leaven, 
combined with a sweet aromatic admixture, such as honey. If slowly 
heated, the smell of yeast gives way to an agreeable odour resembling 
fruits ; on further heating, the smell becomes like that of fresh bread 
crust," but without the acid fruit odour. If the heating of the material is 
continued, " the smell assumes the empyreumatic character exhibited by 
burning albuminous matter and carbonizing horny substances. Only an 
extremely small quantity of ash (under i per cent.) was obtained. The 
liquid shows a neutral reaction. " It was found to contain a small quantity 
of mucine, indicated by a turbidity on the addition of dilute acetic acid, 
which is increased on the addition of potassium ferrocyanide, indicating the 
presence of albumen. Peptones are present in considerable quantities. 
There is a slight reducing action obtained when the fluid is heated with 
Fehling's solution j there was no reaction with acid bichromate of potassium, 
so that acids and ptomaines are ubsent ; but it was assumed, as would now 
appear incorrectly, that toxalbumens, or albumoses, globulins, or enzymes 
must be the substances to which the material injected by Koch owes its 
special properties. 

Any description of the lymph other than that given by 
Koch himself must be the result merely of guess-work, but 
even guesses will sometimes afford indications as to the lines 
on which researches are at present being carried out, not 
only in connection with tuberculosis, but with several other 
most deadly and wide-spread diseases. The peculiarity of 
this method of treatment is, that it is not known to pro- 
tect against an attack of tuberculosis, though Koch states 
that he hopes his guinea-pigs will be protected from future 
attacks ; it is used solely as a therapeutic agent to check or 
stop the disease after it has once obtained a foothold in the 
body. It is thus in principle more like Pasteur's inoculation 
against hydrophobia, for the inoculation is made after the 
patient has been inoculated with the disease virus ; and it is 
also similar in certain points, though the principle is different, 
to the protective inoculation obtained by Hankin, who, by 
means of albumoses obtained from anthrax cultivations, has 
been able to produce immunity against anthrax, though not to 
cure, after that disease was once induced ; and that Dr. Cart- 
wright Wood and I carried on with the pyocyanin products 
in rabbits, to tide them over an attack of anthrax the bacilli of 
which were introduced into the subcutaneous tissue shortly 
before, or immediately after, the injection of the pyocyanin. 
We, however, considered that the pyocyanin had not acted 
directly on the anthrax bacillus, but that it acted by stimu- 
lating the cells ; whilst Koch's "lymph" acts (i) by destroy- 
ing the tuberculous tissue, and rendering it unfit for the 


nutrition of the bacillus, and (2) by setting up a localized 
reaction in the neighbourhood of the bacilli, by means of 
which the cells are so stimulated that they are able, as we 
have already seen, to prevent the extension of the bacilli into 
the surrounding parts. 

Koch's fluid may not accomplish all that is expected from it ; 
it may, in fact, be found that Koch has not completed his ex- 
periments, but he has made a wonderful advance in our know- 
ledge of the conditions necessary for the combating of micro- 
organisms ; and has extended the observation of the earlier 
workers at the globulines and albumoses who really opened up 
the way for the advance of the numerous workers who have re- 
cently come into the field. It would, however, take us beyond 
the scope of the present work to saymore aboutthis marvellous 
discovery of Koch's. Let it always be remembered that tubercle 
destroys the tissues in which it grows, and that the treatment 
by Koch's method completes the process of destruction, if. 
this is not already accomplished ; so that, under the very 
best conditions, phthisis can only be stopped, and, although 
a comparative cure may be obtained, highly differentiated 
tissues once destroyed can never be restored or replaced. 

It will thus be seen that although Koch has selected a 
special irritant material as that which it was found 
necessary to separate in order to obtain the results that 
he wished, and has obtained the sequence of specific (?) 
stimulation of the cells, he has departed from the usually 
accepted methods, in that he acts directly on the tissue cells, 
and leaves the bacilli to die of starvation. It is not now a 
case of the cells destroying or modifying the activity of the 
bacilli ; it is simply, in the first instance, a cutting off, or 
rather a rapid exhaustion, of the substances required for the 
nutrition of the bacilli ; the baciUi remain, and although 
they may eventually undergo retrogressive changes, it appears 
probable that their spores remain for some time, at any rate, 
ready to break out should favourable conditions again pre- 
sent themselves. Apart from this local action, however, the 
fact cannot be ignored that where the tissues are not already 
too far weakened, or the cells so imperfectly nourished that 
they cannot react to stimulus, the liquid injected by Koch 
may exert a general and specific action on the tissue cells 
through which they are acclimatized, as it were, to resist the 
poison ; so that it is quite possible that a partial immunity 


as regards the tubercle bacillus may be acquired. It is 
probable that the tuberculin acts as a stimulant on all cells, 
and that to the increased metabolic changes that are set up 
is due the general reaction that is described as following on 
the exhibition of this material. 

That this is not entirely a fanciful explanation may be 
argued from an example. It is a fact, well known to those 
who have charge of tuberculous patients suffering from 
diseased glands — scrofulous glands, as they are called — that 
so long as these glands remain uninjured and are subjected 
to no stimulation, and so long as the nutrition of the patients 
keeps fairly good, they remain as a rule comparatively free 
from pulmonary phthisis and other forms of tuberculosis ; 
whilst other members of the same family, existing under the 
same conditions, both as regards hygiene and nutrition, 
become affected with the commoner and more fatal forms of 
the disease. 

A further illustration may be taken from the difference 
that exists between children of the lower classes and those 
met with in other grades of society — children in a sick 
children's hospital frequently having every organ crammed 
with, or almost replaced by, tubercular nodules and cavities, so 
that it seems marvellous that the unfortunate children could 
have remained alive at all ; whilst children better nourished, 
but not previously affected by any form of tubercle, appear 
to succumb very easily, when comparatively localized tubercle 
has been developed. In these cases, however, it is usually 
found that some vital organ such as the brain is affected. 

It would appear that, in these cases, the tissues may de- 
velop greater resistance in consequence of the circulation 
in the fluids of the body of the soluble products ; but 
that when this acquired resistance is once lost, or is over- 
come, the stimulation exhausts the cells, and they now 
more easily fall a prey to the active tubercle bacilli. It 
must, however, in this connection, be pointed out that the 
products of the tubercle bacillus, or sterilized cultures of the 
organism, when introduced subcutaneously into healthy 
fowls or guinea-pigs, produce a condition which is spoken of 
as "marasmus ;" and as early as i879,Maffucci, as the result 
of a series of experiments, concluded that these sterilized cul- 
tures when left in the body, exerted such a marked influence on ■ 
the tissues, that they induced emaciation, atrophy of the liver 


cells, and of the cells of the diiferent parts of the spleen, and 
that they also set up certain changes in the circulation, the 
result of which, was seen in marked congestion of the lungs, 
kidney, spleen, &c. These experiments were no doubt sug- 
gested by the similar changes that are met with in the 
human subject in the course of tubercular disease, even in 
those organs that are not directly affected by the tuberculous 
infiltrations. Recently he has confirmed and extended his 
former observations ; and it will be interesting to see whether 
the conditions met with in patients injected according to 
Koch's method, are similar to those observed in animals 
experimented on by Maffucci's method. 

How far the object of Koch's endeavours will be attained 
still remains to be seen, and his method has been, and will 
be, put to most severe tests for it involves the question of 
life or death to thousands, nay, tens and hundreds of thou- 
sands. There appears little doubt that in lupus (a tuber- 
culous skin disease) the process has been checked, "and, in 
some cases, at any rate, it has not again broken out for a 
considerable period after the treatment had been stopped. 
There also appears to be pretty reliable evidence in favour 
of his contention that there is an amelioration of the condition 
of the patient and an improvement in the disease in certain 
other forms of tuberculosis ; but the use of the remedy has 
not been sufficiently prolonged to allow of our arriving at 
any very definite conclusion, however favourable our opinions 
may be. Virchow, the greatest pathologist of the age, has 
found, in a number of cases that have come under his obser- 
vation — a comparative small number when the enormous 
number that have been injected is taken into consideration 
— that the characteristic degeneration of the tissues of the 
young tubercle is not always brought about, that the locali- 
zation of the disease is not by any means perfect, that there 
is a tendency of tubercle material that should be " thrown 
off" to continue the infection and even increase its 
rapidity of spreading, especially in the lungs, and _ that 
in some cases the bacilli, instead of being rendered inert, 
appear to take on greater activity, and to be carried in 
the various currents in the body, even to parts situated at 
some distance from the original tuberculous focus. We 
must bear in mind, however, that almost all the cases that 
up to the present have been brought to the post-mortem 



table have been cases in which the disease was far advanced, 
and in which Koch's inoculative treatment has been sought 
as a last resource by physicians and patients alike. 

A most important point to be remembered in connection 
with tuberculosis is that under favourable conditions it is an 
extremely curable disease ; such conditions, however, must 
be very far-reaching and must include a sufEcient and 
suitable supply of food to the patient, perfect oxidation of 
the tissues, and facilities for the excretion of effete products. 
The effects of climate, of exercise, of pure mountain air,_ free 
ventilation in houses and of generally favourable hygienic 
conditions, are all due to the promotion of the healthy 
condition of the tissues and of the increased vitaUty of the 
cells ; this vitality increasing their power of resistance and 
enabling them to cope successfully with the bacilli and their 
products with which they may be brought in contact. It 
should not be left out of count, however, that we may, by 
the use of suitable drugs, be able to exert an antidotal 
influence by means of which, acting directly on or through 
the cells, these cells may be put in a still better position for 
resisting the attacks of the tubercle bacilli and their products. 
This antidotal system of treatment, if it could be carried out 
by means of drugs, should prove far more efficacious than the 
use of any means of treatment that we have at present at 
our disposal, especially if it could be combined with some 
of these latter. 

This is not the place to discuss the medical aspects of the 
question ; but the above facts are mentioned in connection 
with the biological problems associated with the action and 
inter-action of the bacilli and of the cells of the body. 


Bang. — Proc. Internat. Med. Congress, Copenhagen, vol. i.. 

Path. Sec.,, p. ii., 1884. 
Baumgarten. — Zeischrift f. Wissensch Mikroskopie, Bd. i., 

1884 ; Deutsch. Med. Woch., Bd. viii., p. 305, 1882. 
Bolitz. — Journ. Com. Path, and Therapeutics, p. 370. 

Dec, 1890. 
Bollinger. — Baier Aerztl Int. Blatt., 1883 ; Centralbl. f. d. 

Med. Wiss., Bd. xxi., p. 600, 1883. 
Cheyne, Watson. — Practitioner^ vol. xxx., p. 241, 1883. 
CoHNHEiM. — Uebertragbarkeit der Tuberculose. Berlin, 1877. 


Cornet.— Ztschr f. Hyg., Bd. v., p. 191, 1889 ; Ueber 

Tuberculose, Leipzig, 1890. 
FliJgge. — Ztschr f. Hyg., Bd. 11., 1882. 
Gaffky. — Mitth. a. d. k. Gesundheitsamt, Bd. 11., p. 126, 

Gerlach. — Comptes rendus. Feb. 10 and 24, 1868. 
HuBERMAAS. — Beitrag z. Klin. Chir. Mitth. a. d. Chir. 

Khnik z. Tiibingen, Bd. 11., p. 45, 1886. 
JoHNE. — Die Geschicht. der Tuberculose. 1883. 
Koch.— Berlin Khn. Woch., Bd. xv., p. 221, 1882 ; Mitth. 

a. d. k. Gesundheitsamt, Bd. 11., p. i, 1884 ; Deutsch. 

Med. Woch., No. 10, 1883. 
M'Fadyean and Woodhead. Brit. Med. Assoc. Dublin, 

Aug., 1887. 
Maffucci.— Centralbl. f. Allg. Path, u Path. Anat., Bd. i.. 

No. 26, Dec. 15, 1890. 
Metschnikoff. — Annales de I'Institut Pasteur, 1888-9. 
NoCARD. — Amer. Vet. Rev., N. Y., vol. iii., p. 258, 1884-5. 
NoCARD AND Roux. — Annalcs de I'Institut Pasteur, t. i., 

p. 19, 1887. 
Pawlowsky.— Ann. d. I'Institut Pasteur, t. 11., p. 303, 1888. 
ToussAiNT. — Comptes rendus, t. xciii., pp. 281, 322, 350, 

741, 1881. 
ViLLEMiN. — Etude sur la Tuberculose. Paris, 1868. 
Walley. — Edin. Med.Journ., p. 1088, 1888. 
Weigert. — Deutschen. Med. Woch., No. 24, 1883 ; and No. 

3S, 1885. 

•Williams, C. T. — Lancet, vol. i., p. 312, 1883 ; Pulmonary 
Consumption, 1887. 

Woodhead. — ^Tabes Mesenterica and Pulmonary Tubercu- 
losis. Reports from the Lab. R. C. P. Ed., vol. i., 
p. 179, 1889. 

WiJRZBURG. — Mitth. a. d. k. Gesundheitsamt, Bd. 11., p, 89, 

Wesener. — Futterungstuberculose. 1885. 

See also Comptes rendus et Memoires de la Congress de la 
Tuberculose. Paris, 1 888-1 890. 

For the more recent controversy on Tuberculosis and Tuber- 
culin, see' Lancet and British Med. Journal. 

The earher literature is given very fully in Cornel and Babes 
" Les Bacteries." 



Distribution of Leprosy— Similarity to Tuberculosis — Description of Dis- 
ease — Tubercular, Anaesthetic, Mixed — The Leprosy Bacillus — Method 
of Staining — Position — Leprosy Cells — Bacilli Resistant and Grow 
Slowly — Cultivation Experiments Mostly Negative — Theories of Cause 
of Leprosy. 

Within the last fewyearsleprosy has, metaphorically speaking, 
returned to life in this country. The occurrence of a case in 
one of our market attendants has created more commotion, and 
has put in train a more complicated machinery, than phthisis, 
with its thousands and tens of thousands of victims was for 
long able to set going. Nevertheless, we can now afford to 
think of leprosy as almost a thing of the past, as far as our 
own country is concerned, although we still come across 
traces of its sojourn amongst us in our Libertons, or Leper 
towns, or Leptons, that indicate only too surely that this 
disease was looked upon with the greatest dread by our 
ancestors of the Middle Ages, who evidently took pains 
to keep in their own regions, and within their own asylums, 
the lepers of that period. With the exception of certain 
isolated areas along the shores of Spain, and in Portugal, 
in Norway, some parts of Sweden and Iceland, in Italy, 
Reumania, and Hungary, in the Balkan Peninsula, and in 
Greece where the disease is still endemic, leprosy is now 
rarely seen in Europe ; but in certain parts of Asia and 
Africa it is still frequently met with. It is found doing its 
fell work in the Sandwich Islands, in Mexico, in Cuba, in some 
parts of Central America, in the north-east of South America, 
and in the Argentine Republic, in the north-east and north- 
west of Africa, in Guinea, and in Cape Colony, and in Mada- 
gascar, along the shores of the Black Sea, in Persia, Arabia, 
India, China, the Malay Archipelago, Japan, in Asia, and in 
New Zealand. 


From the whole nature of the symptoms, and from the 
course of the disease, it was long considered to be a disease 
somewhat similar to tuberculosis, and the discovery, by 
Armauer Hansen, in 1880, of a specific leprosy bacillus, 
which was found to be present in enormous numbers in the 
lymph channels of the skin in cases of leprosy, paved the 
way, for the reception of Koch's discovery of the tubercle 

It was for some time supposed that the tubercular and 
anaesthetic forms of leprosy were different in their origin, and 
that they might possibly be due to the action of different 
bacilli, although it was of course known that in some cases 
there was a kind of mixed leprosy. The fact that the two 
diseases were the same was, however, strongly accentuated 
when it became evident that the same kind of bacillus was 
found in all three forms of the disease — the tubercular, the 
anaesthetic, and the mixed. 

Before a description of the morphological characters of the 
bacillus is given, the characters of the various forms of the 
disease may be briefly indicated, in order that the patho- 
logical changes produced by the bacillus may be more fully 
understood, and that the bacilli may be followed and localized 
in the tissues. In tubercular leprosy there usually appear 
small irregular spots, sometimes brown, sometimes some- 
what purple. These spots occur on the face or on the 
limbs ; they gradually project so as to form more or less 
marked tubercles, which vary very considerably in size. 
There is irregular thickening of the tissues under the skin 
of the face, which gives rise to a most curious facial expres- 
sion, the patient appearing melancholy or jubilant according 
to the folds affected ; the tissues about the various orifices 
of the face, mouth, eyes, nostrils become swollen, and are 
often studded with tubercles, the lower lip becomes heavy 
and hangs down in a curious fashion ; these alterations giving 
the face what is described as the "leonine" appearance. 
Sometimes sensibility is interfered with, or it may be alto- 
gether abolished. These tubercles are not confined to the 
tissues immediately under the skin ; they may also be found 
in the submucous tissue of the mouth, larynx, and pharynx ; 
and small nodules may even be met with — especially wiiere 
the swelling is marked — around the eye in the soft tissue of 
the eyelids. These nodules frequently ulcerate, especially m 


the later stages of the disease. On the fingers the thickened 
patches and ulcerations may extend so far and so deep that 
part of the finger may be actually separated and thrown off, 
first, however, becoming dry and black or mummified. The 
patients may linger on in this condition for a considerable 
length of time ; or the tubercles may, leaving dis- 
coloured patches, in which sensibility is entirely wanting, and 
which, in consequence, very rapidlyundergo ulceration,usually 
brought on by injury, the patient, unable to feel, allowing the 
parts to be injured without making any effort to save them. 
The second form — anaesthetic leprosy — commences in much 
the same way, except that the discoloured patches are somewhat 
smaller, and may be red or brown ; in some cases the patches 
have a peculiar glistening or silvery-white appearance. The 
pigmented patches, which are often very widely distributed, 
have, especially where they attain any very great size, a dull, 
pallid centre, with a line of brown, or brown and red coloura- 
tion, surrounding it. Some of the smaller spots are anaes- 
thetic, whilst, in addition, there may be large areas in which 
sensation is markedly diminished or altogether abolished; the 
hair falls out ; there is marked atrophy of the skin and the 
cellular tissue immediately beneath, this giving rise to a 
very wrinkled appearance of the face ; and the patient, as in 
the other kind of leprosy, becomes dull and heavy-looking, 
as though he had lost all interest in external affairs. Here 
also injury to the extremities is of very frequent occur- 
rence, partly owing to the fact that the patient cannot feel, 
but partly also, because the nutrition of the skin is markedly 
interfered with. Other skin diseases, the formation of 
vesicles, and so forth, are often met with. Either form may 
gradually pass into the other, in which case we have what 
are known as mixed varieties of the disease. 

In order to demonstrate the presence of the bacillus in 
one of the nodules in a case of tubercular leprosy, it is only 
necessary to tie an india-rubber ring somewhat firmly around 
the base of one of them until it becomes pale from the blood 
supply being cut off, and then, with a needle-shaped lancet 
or the point of a sharp knife, to make a small puncture, 
from which a clear fluid exudes. In this may be found an 
enormous number of bacilli. These bacilli resemble the 
tubercle bacilli in a most remarkable manner, the only 
difference being that they are, if anything, slightly shorter. 


They may be stained by almost any of the methods that are 
used for staming the tubercle bacillus, although here any 
method that is used must be slightly modified, as the bacilli 
characteristic of leprosy are rather more easily decolorized 
by acids than are the tubercle bacilli. The Ziehl-Neelsen 
method, with a contrast stain of methyl blue, gives most 
admirable results, or Gram's method may be used. The 

Bacilli from Juice of a Leprosy Nodule, x 500. 

bacilU so stained are seen to be from 4 to 6/* in length and 
.3/t in breadth ; they are more constant in size than are the 
tubercle bacilli, and, as a rule, are not marked by the curves 
that are almost characteristic of that organism ; their ends 
appear to be slightly pointed. It was at one time considered 
to be beyond controversy that these bacilli contained spores ; 
but more recent observations on these and other organisms 
have led observers to the conclusion that what were at one 


time considered to be spores are not spores at all, but are 
appearances due to the alterations that have taken place in the 
protoplasm during the processes of preparation and staining. 
As it is not yet certain that the bacilli can be cultivated, little 
evidence either for or against the spore theory can at present 
be adduced. These bacilli, to be seen in their characteristic 
form, should be examined as they lie in the thickened nodules 
of the skin or in the mucous membrane of the mouth and 
larynx, in the thickened nerves, in the lymphatic glands, in 
the spleen, or in the liver. If a thin section be made of a 
nodule of the skin, and the specimen be stained with fuchsin, 
and decolorized with a mineral acid, and a contrast stain 
of methylene blue be obtained (see Appendix), it will be 
found that, throughout the section, branching lines or small 
rounded points of bright red may be seen on a blue back- 
ground ; these bright red areas are nothing but masses of 
leprosy' bacilli which fill the lymphatics of the skin, and, as 
one would expect, interfere very seriously with its nutrition. 
There seems to be a considerable difference of opinion as to 
whether these bacilli actually invade the cells or whether 
they lie free in the lymph channels ; there can be no doubt 
that a very large number of them ultimately are seen as free 
bacilli lying in these spaces, the difference of opinion being 
as to the nature of the so-called "lepra" cells. There are 
usually found in cases of leprosy a number of large proto- 
plasmic masses, which are said to be multi-nucleated, and 
are spoken of as giant cells, and in these are found numerous 
bacilli. In younger nodules there are smaller masses of 
protoplasm, in which nuclei and bacilli may be distinctly 
seen. At the meeting of the British Medical Association, 
held in Dublin in 1887, Dr. Unna, of Hamburg, placed 
before the members his views on many of these so-called 
lepra cells. He contended that the rounded outline was 
due in many cases to the form of the lymphatics, and he 
showed in his specimens that the rounded section was equal in 
diameter to the longitudinal section of one of these lymphatics 
filled with bacilli ; that the longitudinal section proved that 
we have here to deal simply with a lymph channel blocked 
with leprosy bacilli, and therefore that the rounded masses - 
are merely transverse sections of these stuffed lymph chan- 
nels. He also maintained that these so-called cells, with 
their contained bacilli, were merely masses of these organisms 


which were held together by gelatinous material ; and that 
even where there were apparently globular masses in the 
lymphatic channels, they were nothing but these zooglcea 
masses, whilst a great number of the organisms were lying 
entirely free, the nuclei of the so-called lepra cells again being 
the nuclei of the walls of the lymphatics or of the lymph 
cells that had become embedded in the gelatinous mass. 
Many competent observers, however, maintain that the lepra 
cells have a real existence, and there can be little doubt that 
bacilli may be found in large cells squeezed from a leprosy 

One of the most marked distinctions between tuber- 
culous and leprous tissue is, that in tubercle .the bacilli 
are comparatively few in number, especially when they 
are met with in the more chronic cases — the only cases 
that could possibly be mistaken for leprosy ; whilst in 
leprosy the bacilli are almost invariably present in enor- 
mous numbers in the lymph channels of the tissues in 
which they are growing, on which they seem to exert com- 
paratively little destructive influence, as they remain for a 
considerable length of time in an almost quiescent condition, 
setting up little change, but undergoing no retrogressive 
changes themselves. Cornil and Babes record that in a 
small fragment of a leprous nodule that had been left in 
an envelope, forgotten for nearly ten years, they were still 
able to stain the bacilli very distinctly ; and sections that 
had been stained in picro carmine and kept mounted in 
glycerine for a number of years, it was found, might 
still be stained so as to bring the bacilli into prominence. 
Then, too, leprosy affects the skin and nerves specially, 
rarely the lungs and serous membranes. Tuberculosis, on the 
contrary, affects the latter very frequently, and very rarely 
the former. From the enormous number of bacilli that are 
found in the lymph spaces, it can be readily understood that 
when ulceration of a nodule takes place, these organisms 
are to be found in large numbers in the blood and serum 
that is discharged from the ulcerated surfaces. Although 
this is the case it is a somewhat peculiar fact that this 
organism is seldom found in the superficial layers of the 
epithelium covering the nodule, although in the ducts of 
sebaceous glands, and around the hairs of the skin, as Babes 
demonstrated, the baciUi may be present in considerable 


numbers ; they are seen in the internal sheath of the hair, 
from which they may, in some few cases, pass through the 
epithehum, and so to the surface ; this is, however, a very 
rare condition. As a rule, leprosy bacilli are not met with 
in the blood ; but in the febrile condition that occurs shortly 
before death, bacilli have been described as being found in 
the circulating blood taken at some distance from any nodule. 
As the leprosy nodules may be found in all parts of the 
body so also may the bacilli. In cases of anaesthetic leprosy 
the bacilli may usually be readily demonstrated lying in the 
dilated lymphatics of the thickened and nodulated nerves. 
Here, too, as in tubercle, the lymphatic glands are distinctly 
infiltrated. . From its resemblance to tubercle, and from the 
fact that its specific bacillus is found so constantly associated 
with the disease, being most numerous in those positions 
in which the leprous processes are most advanced, but being 
present from the very commencement of the tubercle forma- 
tion, it is evident that the bacillus bears a constant — probably 
a causal — relation to the disease, and it was therefore supposed 
that leprosy might be carried from one individual to another 
through its agency ; that, in fact, the disease was a specific 
infective disease and was inoculable. 

Numerous experiments, made with the object of proving 
this thesis, have, however, failed. (Babes and Klarindero 
mention, in support of the contagious nature of the disease, 
the case of a child that developed leprosy on the lips and 
cheeks during the time that it was being suckled by a 
leprous mother, and Dr. Castor and many others insist on 
the communicability of the disease. A patient has recently 
been reported to be dying from leprosy, the result of inocu- 
lation in 1884. The patient was a condemned criminal in 
Honolulu, who elected to be inoculated with leprosy by Dr. 
Arning in place of being hanged). Even the inoculation of 
fragments of leprous tissue gave rise in all recorded experi- 
ments to no true leprosy, unless the patients were already the 
subjects of the disease. The cultivation of the bacillus has 
also proved to be a most difficult matter.. Neisser observed 
a number of small pellicles that appeared to shoot out from 
small particles of tissue introduced into consolidated blood 
serum, kept at a temperature of between 37° C. and 38° C. 
Bordoni Uffi-eduzzi obtained growths from the marrow of 
a bone in which there were a number of free leprosy bacilli ; 


these appeared on serum (to which a quantity of glycerine 
had been added) that was maintained at a temperature of 
37° C. These he described as dehcate, thin, slightly yellow 
films with irregular borders ; on glycerine agar they are said - 
to have developed as small grey rounded isolated points 
usually at the end of ten days or a fortnight ; secondary 
cultivations, however, made their appearance at the end of 
forty-eight hours, and after the first few cultivations the 
organism could be grown on serum or on ordinary gelatine 
and agar, but much more slowly than when glycerine had 
been added. From the general description, and the im- 
perfect staining obtained, some doubt must remain as to the 
true nature of these bacilli. Babes also was able to obtain 
cultivations on similar media, even from other organs ; he 
described the growths as being very like those of diphtheria ; 
upon serum they appeared as pale yellow elevated plates, 
glistening and waxy-looking and surrounded by a transparent 
indented zone ; the cultures emitted a peculiar characteristic 
odour. They developed all along the track of the needle, 
especially in glycerine gelose ; the rods were elongated, but 
there appeared to be a number of involution forms, and 
many of the bacilli were much more plump than usual, and, 
bearing out Unna's observations, they appeared to be sur- 
rounded by a clear capsule somewhat similar ta that met 
with around Friedlander's pneumonia organism. Babes was 
not successful in making secondary cultivations, nor was he 
able to produce the disease by inoculating with his cultiva- 
tions any of the animals that he had in his laboratory. 
Until these experiments are confirmed by other observers 
they can scarcely be accepted as conclusive, as it requires a 
much longer series of successful cultivations and more 
careful comparison of the organism as it appears in the 
tissues with that found in the cultures, than either Bor- 
doni Uffreduzzi or Babes have made, to set the matter 
at rest. Still they have indicated the lines on which future 
work may be done, and we may anticipate that before long 
Dr. Bevan Rake, Dr. Castor and others, may continue their 
experiments with the enormous amount of material which 
they have at their disposal and give to the world most im- 
portant results. 

None of the numerous non-bacillary theories as yet put 
forward to account for leprosy appear to be sufficiently well 


supported to be able to oust the bacillary theory from its 
present position. Leprosy is found in all climates ; it is not 
specially confined to the seashore, it occurs in regions where 
fish diet cannot be resorted to, and where other articles of diet 
such as pork and rice (to both of which have been ascribed a 
causal agency in the production of this disease) are not used 
at all. The only factor that is common to all forms of the 
disease, and that is met with in every case, is the leprosy 
bacillus, and in spite of the fact that we have not yet been 
able to trace the method of contagion or infection through 
the agency of this bacillus, we must, from what is known of 
the presence and action of bacilli in other diseases, assign to 
it the role of leprosy producer, until much stronger evidence 
than we have yet obtained can be adduced in favour of any 
other cause. 


Authors already quoted. Cornil and Babes. 
Arning. — Virch. Arch., Bd. xcvii., p. 170, 1884. 
Babes. — Arch, de Physiol., July, p. 42, 1883 ; Comptes 

rendus, t. xcvi., pp. 1246, 1323, 1883. 
Babes and Klarindero. — Congres Intern, de Dermatologie 

a Paris, 1889. 
Bevan Rake. — Reports on the Trinidad Leper Asylum, 

1888-90 ; Monats-Hefte f Prakt. Dermatologie, Bd. vii., 

No. 12, 1889. 
BoRDONi Uffreduzzi. — Zeitschr f. Hygiene, Bd. in., p. 178, 

Felkin, R. W. — On the Geographical Distribution of some 

Tropical Diseases, p. 36. Edinburgh, 1889. 
Hansen. — ^Virch. Arch., Bd. lxxix., p. 32, 1880. 
HiRSGH. — Handbook of Geographical and Historical Path- 
ology, vol. III., New Syd. Soc, 1885. 
Leloir. — Memoires de la Soc. de Biologie, p. loi, 1885. 
Neisser. — Virch. Arch., Bd. lxxxiv., p. 514, 1881. 
Unna. — Brit. Med. Assoc, Dublin, 1887 ; Deutsch Med. 

Woch., 188S-1886. 
ViRCHOW. — Berlin Klin. Woch., Bd. xii., No. 18, p. 123. 


Nature of the Disease— Differences in Cattle, Man, Pig, and Horse — 
Methods of Preparation and Examination of the Fungus — Microscopic 
Appearances of Fungus in Different Animals — Nature of Clubs — 
Cultivation Experiments — History of Actinomyces — The Actinomyces 
a Streptothrix. 

A DISEASE that was for long very imperfectly understood, 
and which has been described under very different names, is 
Actinomycosis, which, in 1876, was first recognized by 
Bollinger as being of parasitic origin. The disease mani- 
fests itself in cattle, frequently in the jaws, where it is 
known in various parts of the country as wen, osteo-sarcoma 
or bony sarcoma, malignant tumour of the palate, or in 
the tongue, where it may be recognized as " wooden 
tongue ; " the pharynx or the loose tissues under the skin of 
the head and neck, or even the trunk, may also be affected. 
In the pig, abscesses with running sores are most frequently 
found in the milk gland and in the tissues around the 
pharynx ; whilst in horses it is usually found as " scirrhous 
cord," a condition well known to veterinary surgeons, though 
as Professor M'Fadyean points out, it may also be met 
with in the tongue of the horse. This curious disease has 
also been known to attack the human subject, in whom the 
lesion resembles in its characters that met with in the pig, 
the parasite giving rise, by its presence, to abscesses in the 
lungs, to pus in the pleural cavity, and to similar conditions 
in other organs ; the bones, especially those of the spinal 
column, are frequently attacked, and " cold abscesses " or 
chronic gatherings form in those cases where sinuses from 
which matter may escape are met with. 

It is interesting to note in this connection that even in the 
pig the lung is sometimes riddled with similar cold abscesses, 
and that there is frequently breaking down of areas of 


bone in the cervical and dorsal vertebrae. Those who had 
examined the condition only in the human subject and in the 
pig describe the disease as consisting essentially of a sup- 
purative process, whilst those who have examined " wooden 
tongue " in cattle, and " scirrhous cord " of the horse, maintain 
that the process, though sometimes leading to softening, is 
essentially of the granuloma or new young tissue formation 
type. These differences, however, appear to be due rather 
to the nature of the tissues in which the growths occur than 
to any difference in the character of the organism that 
produces them, for it is found that in many cases in which the 
bones are attacked in the cow the lesion takes on a suppura- 
tive character. It was, however, the non-suppurative form 
that was first described, and it will therefore be better to 
examine it in the first instance. In " wooden tongue " of 
the ox, on superficial examination, firm hard points may be 
seen scattered over the surface, varying in size from that of a 
millet seed to that of a split pea. On incising one of these, 
it is found to be firm and fibrous at the periphery and especi- 
ally in the small nodules ; the centre may be soft but not 
purulent, or, rarely, gritty and almost calcareous ; in the larger 
nodules little fibrous bands running through them form a kind 
of net-work, and in the centre of each mesh is a similar 
soft point. If this softened caseous point be removed with 
the point of a knife and examined under the low power of 
the microscope ( a 50) it will usually be found to contain, 
embedded in a small mass of cells, a small core, which by 
transmitted light is yellow or brownish in colour, dashed 
■ with a tinge of green. This little mass is seen to be com- 
posed of a kind of 'Star made up of a number of wedge- 
shaped rays, the apices of the wedges meeting in the 
centre, the bases being rounded ; looking down on the 
centre of this cord it appears as though there are 
rounded instead of wedge-shaped bodies (this is simply 
because we are looking down on the rounded ends of the 
wedges). If now one of the " bony " tumours, or one of the 
tumours in the fibrous covering of the bone, where the 
tumours are usually of larger size, be examined, it will be 
observed that the fibrous net- work is exceedingly well marked, 
especially as on section the softened caseous centre gives way 
very readily : in the softened material similar " rayed " or 
star-like organisms may be found. In the material that is 


discharged from the " cold abscesses " which are formed in the 
pig or in the human subject, similar small yellow points 
(which appear as green or greenish yellow grains, even 
when examined with the naked eye) may be found on 
examination under the microscope. The pus discharged 
from these abscesses has an exceedingly characteristic appear- 
ance ; it is usually yellow or brownish yellow in colour, 
is extremely granular, of a peculiar slimy consistence, 
and contains the green points that may be said to be 
specially diagnostic of the actinomycotic condition. The 
small green points when taken from the cow are very 
frequently somewhat gritty, this being due apparently to the 
deposition of particles of lime in the core ; but the particles 
that come from the pus in the human subject are usually 
soft and tallow-like, so that they can be readily flattened out 
between two cover glasses. The appearance of the actino- 
myces or " ray fungus " in cattle, as first described, was 
so exceedingly characteristic that it was thought it could 
not be mistaken for anything else, and the corresponding 
condition in the human subject was for some time over- 
looked, simply because the same typical appearances were 
not always developed ; and it was only after some time that, 
transition stages being found, first in cattle and then in the 
human subject, the real nature of this fungus was thoroughly 

On examination of the fungus under a high magnifying 
power, when the sections have been properly stained, the 
organism is found to be like the capitulum of a daisy, the 
sterile flo\!'ers in the centre corresponding to the club- 
shaped rays, and if we conceive of two of these heads of 
flowers as placed base to base, or stalk to stalk, we may 
obtain an idea of the appearance of the ray fungus as a whole ; 
the organism in sections of course having the appearance 
of sections through the little ball formed by the two heads. 
The clubs, however, are not all simple, but in some cases 
branch, sometimes dichotomously, sometimes irregularly, 
compound clubs being thus formed. 

In a tumour examined by Professor M'Fadyean, the transi- 
tion stages between the forms sometimes found in the human 
subject, and those most frequently seen in cattle, are met with ; 
and as I have had the privilege of seeing Professor M'Fadyean's 
specimens I shall follow pretty closely his descriptions, as 


I consider that the interpretation he gives of the appearances 
presented is perhaps the most satisfactory that has yet been 
published. The tumour from an ox was fleshy in consistence, 
had a faint pink colour, and was studded with minute softened 
pink points, and in each of these points was found an 
actinomyces colony, at the margin of which, however, only 
a few of the characteristic clubs could be found, the centre 
being finely granular. On making sections of these tumours, 
that had been hardened in alcohol, and staining by Gram's 
method (see Appendix), and examining under a high magnify- 
ing power. Professor M'Fadyean observed that the colony 
consisted of three distinct elements, though, in many 
instances, the club-like bodies were absent. The first element 
is a coccus about .5/* in diameter ; these cocci are usually 
arranged in chains consisting of ten or fifteen elements, a few 
of them are usually found in the centre of the mass, but 
immediately outside this they are exceedingly numerous, so 
numerous indeed that they appear to be more like masses 
than chains ; as we approach the margin again the chains 
radiate outwards and are very distinctly seen. Where they 
are not very numerous, some larger cocci may be seen under- 
going regular vegetative division, so giving rise to the forma- 
tion of diplococci. 

The second element is a thread-like leptothrix or clado- 
thrix, a number of which, interlacing freely, form a kind of 
felted net-work, especially in the centre of the colony. As 
we pass outwards, however, they gradually assume a more 
regular radiate arrangement, and near the periphery " they 
sometimes shoot out in a tendril-like manner beyond the 
coccus heaps already described." These threads vary very 
considerably in length ; sometimes they are divided into 
short bacilli or even into cocci ; in other cases long threads 
without any sign of division may be seen. The diameter of 
these threads is usually greater than that of the cocci. They 
are described " as some nearly straight, others gently curved, 
and occasionally they show short nodules almost like a 
spirillum." Near the margin these threads sometimes 
become branched just as in the case of the club-like forms 
already mentioned. The club-like forms when met with 
here appear to bear a definite relation to the threads ; they 
are only found at the margin of the fungus mass ; they are 
arranged radiately with the ends of the clubs outermost ; 


they vary much in length, and are usually quite simple, " but 
some carried lateral buds, and occasionally two appear to be 
carried by a common stalk." These buds are best stained by 
the Ziehl-Neelsen method ; some of them exhibit a very 
important relation to the leptothrix forms already described, 
the thread appearing to be continued into the centre of 
the club, the outer part of which is formed by a homo- 
geneous, somewhat faintly stained material. This axial 
thread may be divided into longer or shorter segments, 
corresponding apparently to the bacilli and cocci forms. 
They are usually most divided and are undergoing most 
marked changes in the larger clubs, whilst there are also 
small rounded bodies, which appear to be essentially of the 
nature of cocci, surrounded by the same material that forms 
the thickened club. In some of the smaller colonies of the 
actinomyces Professor M'Fadyean describes cocci only, which 
are usually arranged in short chains or in little groups. 
They are embedded in masses of leucocytes, some being 
actually within the cells, and appearing to be the points 
from which the larger colonies start, the cocci being carried 
by the leucocytes from point to point. Other colonies 
contain only cocci and thread forms, the threads in this case 
appearing to be developed from cocci, whilst those colonies 
in which clubs are present appear to be in a still more 
advanced stage of development. 

By some observers the club-like forms have been described 
as the spore-bearing parts of the organism, and are spoken of 
as Conidia or Basidia, but it appears from the above case, 
and from those that have been described in the human 
subject, that the thickened extremity is due merely to a 
kind of involution process, and occurs in the older thread- 
like organisms as the result of a growth and swelling 
of the outer sheath of the Cladothrix threads, this sheath 
corresponding, in fact, to the gelatinous material which is 
formed in zoogloea masses of other organisms, or to the 
capsule first described by Friedlander which is formed around 
the bacillus of pneumonia. When these clubs are once de- 
veloped the central part may be only partially active, whilst 
the periphery remains passive, but extremely resistant to the 
attacks of the surrounding cells, which attack the club- 
shaped masses very vigorously, the large thickened clubs 
being frequently found in various stages of degeneration 



within the large masses of protoplasm found in this 

In the human subject the felted network, the cocci and 
the bacilli are usually most numerous ; they are, in fact, 
said to be typical of actinomyces in the human subject. 
Here again the involution or club-forms are frequently 
met with, especially in the pus that is discharged from 
the abscesses of the lungs or of bone. The slimy pus 
in these cases, however, appears to contain a considerable 
proportion of the " mucine," that in cattle goes to form the 
thickened sheaths above described. The process of evolution 
of the "Ray" fungus is much the same in the human 
subject as in the abnormal case already described as occurring 
in the cow. 

It is interesting to note that most of the experiments 
that have been made on the cultivation of this organ- 
ism have been attended with complete failure — a failure 
that in some measure, at any rate, appears to be due to 
to the fact that almost all experimenters have used for their 
inoculating material only those colonies in which the club- 
shaped organisms have become well developed. The first 
attempt that was at all successful was made by Bostrom, 
who, throwing aside the club-like processes, took for his 
inoculating material the central network, selecting as far as 
possible young growing colonies for his seed material. His 
method of procedure was as follows : With the utmost 
care he removed small colonies, which were at once in- 
troduced into sterilized gelatine, with which a "plate" 
cultivation was made. After a few days any points that 
were found to be pure, ?>., around which other organ- 
isms were not growing, were removed from the gelatine 
with a sterilized platinum needle, and were crushed- be- 
tween sterilized glass plates ; with the platinum needle, 
stroke cultivations were made on ox blood serum, and 
agar-agar. A finely granular growth first made its appear- 
ance along the line of inoculation ; this gradually became 
more marked, then small yellowish red nodules were seen, 
around which delicate branched processes spread out ; these 
yellowish masses soon began to run together, and at the end 
of seven or eight days were covered with a delicate fluffy 
white layer. This growth apparently went on best at the 
temperature of the body, and on microscopic examination 


of the structures, cocci, segmented threads, longer threads 
and clubs were all found ; threads and clubs alike in most 
cases being characterized by a branching similar to that met 
with in the fungus as it grows in the human body. Inocula- 
tion of this fungus into the peritoneal cavity of rabbits and 
other animals was usually attended with positive results. 
Later, by attending to the same details as regards the nature 
of the seed material, M. WolfF, J. Israel, and Babes have 
all succeeded in cultivating this organism on agar-agar, 
blood serum, and especially on the raw white of egg, 
according to Hueppe's method (see Appendix), and with the 
cultivations so obtained actinomycosis has been produced 
experimentally in animals. 

From all these facts it will be gathered that actinomy- 
cosis is the result of the activity of a living organism 
introduced into, and existing as a parasite in, the animal 
tissues ; that the same organism may be found in animals 
and in the human subject, that the club-shaped organism is 
really an involution stage, and that the characteristic growth 
is the mycelial thread-like mass which appears to develop 
from the cocci. The fact that we are unable to cultivate 
from the clubs alone, affords ample evidence that, in place 
of being spore-bearing masses, they are merely encysted, or 
thick-walled, involution forms. 

^ As to the mode of infection, it has been pointed out that 
the actinomyces has been found lodged, in the crypts of the 
tonsils of the pig and of the human subject, and that the 
parasite evidently leads an epiphytic life on barley and other 
cereals. It may be introduced from without through 
wounds, as in cases of scirrhous cord in horses, or through 
inoculation, by means of accidental scratches of the skin, or 
of the mouth and pharynx, and it is recorded that a case of 
primary mediastinal actinomycosis in the human subject 
was in one case supposed to be traced to perforation of the 
bapk of the throat by a barley spikelet swallowed by the 
patient. In pigs the mammary affection is thought to 
be due to the entrance of the actinomyces into the teat 

In Denmark the farmers attach so little importance to 
infection from animal to animal, that cows in which these acti- 
nomycotic tumours are well developed are allowed to run 
with the rest of the herd, at any rate until suppuration 


commences ; when this occurs, however, the animals are 
usually slaughtered. 

I may here summarize what is known of the history of a 
colony in the words of M'Fadyean, who has given the subject 
much careful study, and to whose authority in this matter 
I attach much weight. 

" I. It has its starting point in one or more cocci trans- 
ported by the plasma currents, or by the agency of a carrier 
cell (leucocyte). 

"2. The cocci multiply by elongation and subsequent 
fission. When undisturbed by the surrounding leucocytes 
their growth and multiplication are after the manner of a 
streptococcus, but frequently they become irregularly 
grouped together (Staphylococcus heaps). 

" 3. By elongation, some of the cocci give rise directly to 
short bacillary forms, and through these to long filaments. 

" 4. The further extension of the colony is effected by the 
growth and multiplication of both threads and cocci. The 
former multiply by segmentation into bacillary elements, 
which may again elongate to leptothrix forms. 

"5. The leptothrix filaments may give rise by close 
segmentation to coccus forms. 

" 6. The formation of clubs and similar forms is evidence 
of diminished vegetative power of the filaments (possibly also 
cocci), in connection with which they originate. 

" 7. The growth of a colony may be arrested at any stage 
by the agency of the animal cells (leucocytes), or by failure 
in the supply of the necessary pabulum. In that event the 
majority of the threads tend to develop clubs at their outer 
ends (involution forms). The central cocci and the remainder 
of the filaments then disintegrate ; but the clubs which offer 
a greater (passive) resistance to the surrounding cells may 
persist for an indefinite period." 

From what is here stated, and from what I have already 
said, it will be evident that we have here to deal not with 
an ordinary "mould" fungus, but rather with a form of 
streptothrix that undergoes dichotomous division at certain 
points. It must therefore be looked upon as possibly 
one of the Cladothrix algse, or more probably as one of 
the Schizomycetes in which the Cladothrix formation occurs, 
and which has been described as closely allied to the strepto- 
thrix Forsteri. 

actinomycosis. 26 1 

The following works may be consulted : 
AcLAND. — Brit. Med. Joiirn.., vol. i., p. 1159, 1886 ; Trans. 

Path. Soc, vol. XXXVII., p. 546, 1886. 
Bang. — Tidskrift for Veterinaer, 1883. 
Bollinger. — Centralbl. f. d. Med. Wiss., No. 27, p. 481, 

BosTROM. — Verh. d. Congr. f. Inn. Med. Wiesbaden, p. 94, 

*Crookshank. — Manuel of Bacteriology, London, 1890 ; 

Medico Chir. Trans., vol. lxxii., p. 175, 1889. 
Delepine. — Trans. Path. Soc. 1889. 
Israel, J. — Virch. Arch., Bd. lxxiv., Heft, i, p. 15, 1878 ; 

Bd. Lxxviii., Heft. 3, p. 373, 1889 ; Bd. xcvi., Heft, i, 

p. 175, 1884. 
Johne. — Deutsch. Zeitschr. f. Thiermed. 
*M'Fadyean. — Journ. Com. Path, and Therap., vol. 11., 

p. I, 1889. 
Perroncito. — Giornale di Anat. Fisiol. e. Pathol. 1875. 
PoNFiCK.— Die Aktinomykose des Menschen, Berlin, 1881 \ 

Breslauer Aerztl. Zeitschr., 1882. 
Treves. — Lancet, vol. i., p. 107, 1884. 
Wolff. — Virch. Arch., Bd. xcii., Heft. 2, p. 252, 1883. 
* Full references given. 



Glanders — Farcy — Clinical Appearances of the Disease — Chauveau's obser- 
vations on Glanders Poison — Loffler and Schiitz — Method of Demon- 
strating the Glanders Bacillus — The Bacillus — Methods of Cultivation 
— Glanders in Various Animals — Farcy in Man — Temperature relations 
of Bacillus — Desiccation — Germicides. 

Although one of the best known, and, from its anatomo- 
pathological point of view, best described of all diseases with 
which the veterinary surgeon has to deal, it was long before 
most observers in the veterinary schools could be brought 
to look upon glanders as a contagious infective disease. 
It is found especially in the horse and the ass, but as in 
the case of tetanus, it may also be encountered in other 
animals. When it occurs in or under the skin it is known 
as Farcy, and in this form is usually found in man. 
The primary disease is usually in the respiratory passages, 
the lungs and the skin, especially around the orifices of the 
nostrils and mouth ; the parts secondarily affected may be 
those in communication with the lymphatics from an in- 
fected area, or we may have distinct metastatic abscesses (or 
abscesses at some distance from the original focus of the 
disease), the material in such cases being carried apparently 
by the blood along the course of the blood vessels. In all 
cases the intensity of the disease appears to be in direct 
ratio to the number and rapidity of formation and softening 
of the small nodules, the process, as we shall find, being 
determined by the presence and activity of a specific bacillary 
organism that has made its way into the tissues. The 
small nodules, whether they occur in the skin or on 
the mucous membrane, say of the septum of the nose, 
appear as small grey, gelatinous-looking points about the 
size of a millet seed. In spite of this gelatinous appearance 
they are usually comparatively firm in consistence. Under 


the microscope each of these points is found to be made up 
of granulation tissue, consisting of small round cells very 
like leucocytes or lymph corpuscles, a few larger nucleated 
cells, with here and there fragments of disintegrating con- 
nective tissue. After a time, as the nodules become rather 
larger, the centre assumes a yellowish appearance, or ~small 
opaque points may be seen, and ultimately at these points we 
have the tissue breaking down into soft, pulpy, or caseous, 
purulent material. The small nodules met with in the 
early stages of the disease, are usually surrounded by a deeply- 
congested area, and if they occur in the nostril the mucous 
membrane covering them is greatly congested, and there is 
great discharge of water, or of very watery " matter," from 
the nostril. As the nodules become softened in the centre, 
ulceration of the tissues near the surface takes place, the 
softened centre escapes, and a " punched-out " ulcer is left. 
These ulcers may gradually run into one another, and from 
the fact that the mucous membrane is congested and thick- 
ened, the loss of tissue seems to be very great — much greater 
than it really is. Along the lines of the lymphatics, and in 
the lymphatic glands communicating with the ulcerating 
surfaces, there is great inflammation and induration, what are 
known as "farcy-pipes " being formed. Here just the same 
processes are carried on as when the disease occurs in the 
mucous membrane, in the lungs and in the glands at its root, 
the lymphatics being of course similarly affected. It will thus 
be seen that glanders resembles, in a most remarkable man- 
ner, certain other infective diseases already described, such as 
leprosy, tubercle, actinomycosis, &c., and, as a matter of fact, 
numerous observations were early made with the view of 
proving, first, that this was really the case ; and, secondly, 
that the contagious element was a contagium vivum, and 
probably a form of micro-organism. Chauveau, as early 
as 1869, inferred from a series of interesting and most 
ingenious experiments that the poison was particulate in 
character, and was, very probably, present in the leucocytes. 
In December, 1882, Loffler and Schutz made known the 
results of experiments by which they had been able to demon- 
strate the presence of a bacillus which appeared to have 
a distinct causal relation to the disease ; and about the same 
time Bouchard, Capitan, and Charrin also described an 
organism in glanders — an organism, however, the charac- 


ters of which were somewhat different from those ascribed 
by LofHer and Schiitz to their bacillus. 

As I have from time to time had opportunity of verifying 
a number of the points insisted upon by these latter, and as it 
is now generally accepted that the LofHer-Schiitz bacillus 
is th'e one really associated with the disease, this organism 
may be briefly described. 

The best method of demonstrating the bacillus is to take a small particle 
of the softened central part of a nodule and squeeze it out between two 
cover glasses ; all superfluous matter from the edge is carefully removed, 
and the covers are then treated in the ordinary way, after which they are 
stained in a mixture of concentrated alcoholic solution of methyl blue, one 
part to three parts of a i in I0,0CX) liquor potassse solution ; the cover 
glass is rinsed for about a second in a one per cent, solution of acetic acid 
which has been tinged to the colour of Rhine wine by the addition of a 
watery solution of tropseolin. It is then quickly washed with distilled 
water, then with absolute alcohol, cleared up with cedar-oil and mounted 
in benzol- or xylol-balsam. Sections of a nodule that has been 
hardened in absolute alcohol should first be placed for a few minutes in 
weak caustic potash solution, after which they may be transferred to the 
stain and treated as above. An even better method of staining is to use 
Ziehl Neelsen carbolic fuchsin or carbolic methylene blue, and then to 
decolorize the tissues with distilled water, or with a two per cent, solution of 
hydrochloric acid. Kiihne's carbolic-methylene blue method may also be 
be used for staining sections of tissues. 

After preparation there may be seen minute rods from 
2.5 to 5/t in length, which are usually one-fifth to one- 
eighth of their own length broad. They are always more 
numerous where cell proliferation is going on most rapidly. 
From the fact that these organisms do not take on any stain 
at all readily, and also that they are very easily decolorized, 
it is often an exceedingly difficult matter to distinguish 
them from nuclei and nuclear detritus, both of which take 
on staining material in much the same manner as the 
bacilli, and it is only by the exercise of the greatest care 
and by the use of the very best optical appliances that these 
organisms can with certainty be distinguished in the tissues. 
It is, therefore, all the more necessary to obtain pure culti- 
vations of the glanders bacillus in order that its characters 
may be accurately described, and to determine whether it 
really plays an important etiological part in the production 
of the disease. 

The first successful attempt to cultivate this specific 
.bacillus was made by Schiitz in 1882. Adopting the strictest 


precautions to prevent the entrance of extraneous organisms, 
he took small particles of the grey translucent material 
surrounding the caseous centres of some of the above 
described • nodules from the liver, lung, spleen, and lym- 
phatic glands of a glandered horse. These small particles 
carefully broken down, were inoculated on fluid and solid 
blood serum from the horse and from the sheep, and also 
in broths made from the flesh of the dog, horse, fowl, 
and ox, and even in various fruit and vegetable infu- 
sions. For two days no indication of the presence of any 
growth could be observed on any of these media, but on 
the third day the fruit infusion became slightly turbid, and on 
the gelatinized serum there appeared numerous small, clear, 
transparent, yellow, slightly elevated drops, like drops of a 
yellowish fluid that had been splashed on the surface of the 
serum. In eight to ten days these became slightly cloudy or 
milky.^ On examining one of these small drops under the 
microscope it was found to consist entirely of masses of short, 
rod-like bacilli, similar to those already described as present 
in the glanders nodules, giving the same colour reactions, 
being perfectly distinct in this respect from the tubercle 
bacilli, which, as regards size and general appearance, they 
very closely resemble. 

Similar bacilli were found in tlie fluid media, and were usually in 
the form of pure cultures, that is, only this single kind of organism was 
present. In some cases there were impurities, but these were so evident to 
the naked eye that they could be detected at once, such impure cultivations 
being thrown aside. 

The bacillus is usually straight or slightly curved, is 
rounded at one end, and if any difference at all can be 
observed between it and the tubercle bacillus, it is slightly 
shorter and perhaps thicker than that organism, especially 

' In order to obtain growths on sterilized potatoes some of the nasal 
discharge from a glandered horse should be mixed with from 100 to 10,000 
parts of boiled distilled water, and a few drops of this mixture run over 
the surface of the potato. Three days after inoculation there appear spots 
of an amber-like growth; these points, as they increase in size, become 
redder and more opaque, the colour deepening until it becomes like " copper 
oxide." The manner of growth, according to Loffler, is quite characteristic; 
there are only two which are at all like it, the bacillus of blue pus (the 
growth of which has a yellowish-brown tinge on potato but none of the 
amber transparency and a peculiar pearly iridescence), and the cholera 


when it is grown in a fluid medium. It exhibits no movement. 
With pure cultivations, obtained in this way, and propagated 
for several generations outside the body, Loffler and Schiitz 
succeeded by careful inoculation in producing typical glanders 
in various animals, the artificially infected animals pre- 
senting on examination exactly the same appearances as the 
animals that had been naturally infected, and from the nodules 
artificially produced the typical glandsrs-bacillus_Could again 
be cultivated and passed on to othefanimals, whereTlie^in 
turn, gave rise to the usual-syrffptoms of the disease. \ 

In making these experiments they came across a most 
interesting point. In an old horse which they inoculated, arid 
that was apparently quite healthy at the time of the opera- 
tion, they observed that the disease remained perfectly 
localized, and that the ulcers very early evinced a marked 
tendency to heal. The animal, however, was killed, and on 
making a post-mortem examination it was found that it h^d 
already, in all probability, been affected with glanders, and th^l 
this had been running its course for some considerable lengtS] 
of time, as not only were there old scars on the septum 
nasi, but there were old caseous masses scattered through 
the lungs. We have here an exactly analogous condition 
to that recently observed by Koch in the case of guinea- 
pigs already affected with tuberculosis, on which he made the 
observations that led him to the discovery of his protecting 
fluid ; this animal had been "protected" against the general 
outbreak of glanders which usually results from an artificial 
inoculation by a previous chronic attack of the disease. 

In order to illustrate the method of procedure in such cases, we may give 
a short resume of one of Loffler and Schiitz' series of experiments. Two 
horses were inoculated — one twenty years old from the eighth cultivation, 
and the other two years old from the fifth serum cultivation that had 
originally been taken from a [guinea-pig which had in turn been inoculated 
from a. fourth generation (also grown on serum), originally -taken from 
another animal. Both these horses were inoculated on each side of the 
neck and on the breast ; and the younger animal was also inoculated in the 
posterior nares. This was purposely omitted in the older animal, in order 
to see whether the ulcers would occur in the. nasal mucous membrane if it 
were left intact, as far as direct inoculation was concerned. At the end 
of a few days both horses had been attacked ; they ate badly ; diffuse boggy 
swellings made their appearance at the points of inoculation ; they were stiff 
in the joints, the hair was ruffled, and on the eighth day farcy pipes corres- 
ponding in their distribution to the course of the lymphatic vessels and glands 
of the affected area could be distinctly felt under the skin. At this time 


the swellings at the points of inociilation had ulcerated, and were dis- 
charging an opaque, greenish-yellow fluid. On the twelfth day an ulcer 
about the size of a shilling appeared on the skin of the forehead ; its margins 
were thickened, and it was so deep that it extended down to the bone ; 
there was a discharge from both nostrils, at the margins of which it dried 
into thin yellow crusts or scales ; then small ulcers with indurated and 
thickened margins appeared on the nasal mucous membrane in both 
animals ; in fact there were here all the characteristic features usually associ- 
ated with glanders. These two animals died within twenty-four hours of 
each other, and typical glanders lesions were found in the tissues after 
death. Guinea-pigs inoculated with material from these cases exhibited 
similar characteristic symptoms and lesions ; they died in from fifteen to 
fifty days, and on post-mortem examination it was found that the 
characteristic macro- and microscopic appearances were present in all of 
the lesions. 

In the study of the specific infective diseases, it has been 
found that certain animals are especially susceptible to 
one specific virus, whilst others are but little affected, and 
that in the case of a second virus, things may be exactly 
reversed — the non-susceptible animal remaining entirely 
immune, or, in place of a constitutional disease being set up, 
only small local lesions making their appearance. It is 
therefore necessary for experimental purposes to determine 
in all cases what small and easily-kept animals are susceptible 
to a given disease, and what are unaffected or are only 
slightly affected by the virus of that disease. 

In the special case of glanders it is a matter of very great importance, 
from the diagnostic point of view, that the guinea-pig is very susceptible to 
the disease, the natural virus or pure cultivations of the glanders bacillus 
setting up a typical disease which eventually brings about the death of 
the animal. Similar inoculations into a rabbit produce merely a slight 
rise of temperature, some local irritation accompanied by swelling, and per- 
haps by slight ulceration, without any further constitutional or general 
symptoms. Having found that this is the case as regards these two ani- 
mals where the inoculations are made from animals that are undoubtedly 
glandered, it is evident that in a doubtful case of glanders, strong proof for 
or against the specific nature of the disease may be obtained bymoculating 
rabbits and guinea-pigs with material from the doubtful sources ; if the 
guinea-pig dies with characteristic symptoms, and the lesions remain local 
in the rabbit, there is strong presumptive evidence (it might almost be 
said, definite evidence) that the suspected case is one of glanders 

In connection with this immunity (complete or partial) or 
susceptibility of different animals to this disease, it should be 
pointed out that the human subject may be inoculated either 
through wounds or scratches or through the apphcation of 

268 , SACTERtA. 

the nasal discharge of a glandered animal to the mucous 
membrane of the nose or mouth. There are, undoubtedly, 
cases recorded of glanders occurring in the human subject, 
but these are not so numerous as they might be if it were 
possible to put all those cases described as acute or chronic 
bood poisoning under their proper heading. An old friend of 
mine, the late Dr. Howard Bendall, in a Thesis presented 
for the degree^ of M.D. in the University of Edinburgh, 
1882, described a case of acute farcy in man, and collected the 
records of 68 similar cases, a number that might now be 
very considerably added to. Of all the cases of acute farcy, 
47 in number, only 6 were cured ; whilst of 21 more chronic 
cases no fewer than 15 recovered or were partially cured : the 
acute cases run a very rapid course, the duration of the disease, 
however, varying from 4 to 47 days, the average course of 
the disease being from 2 to 3 weeks. In chronic farcy the 
patients died in from 50 days to 14 months, whilst of those 
that recovered, the disease lasted as long as two and a half 
years. It has now been proved beyond doubt that this 
disease of farcy in man is due to the action of the same 
bacillus that is found in the glanders of the horse, this 
minute organism having been found both in the blood and 
in the contents of pustules taken from a man affected with 

Cattle are completely immune against glanders as regards spontaneous 
infection, and only localized ulceration, which rapidly heals, follows inocu- 
lation. The goat is somewhat susceptible to the disease, though it 
appears to occupy a position between cattle and the horse in this respect. 
Sheep are fairly susceptible, but the disease runs its course very slowly, 
and appears to resemble the chronic farcy in man. Lions, tigers, 
and cats may all become affected, the disease in such cases running a 
very rapid course. Dogs react to the poison very much as do rabbits. 
So markedly is this the case that it has been suggested that the glanders 
bacillus might be attenuated by passing it through the dog before it is inocn- 
lated into horses and asses. It should be pointed out, however, in connec- 
tion with all these experiments, that if a very concentrated virus, such as a 
pure cultivation of the bacillus, especially in considerable quantities, be 
inoculated even into a rabbit, a generalized disease may be set up, whilst 
ii weaker virus, such as that contained in the discharge from the nasal 
mucous membrane of a horse, will produce nothing but localized symptoms. 
(This element of quantity can never be ignored in making experiments 
with bacteria of any kind.) Field mice are extraordinarily susceptible 
to the glanders poison, whilst white mice and house mice are quite exempt. 
The pigeon appears to be the only bird that is at all susceptible to the 

GLANDERS. . 269 

We have already spoken of bodies that looked like spores 
in these bacilli, but from the fact that the glanders virus, 
both in fluids and in tissues, loses its vitality after fifteen days' 
drying, it must be assumed that the organism does not form 
endospores similar to those that are found in bacillus subtilis, 
for example. The bacillus grows best at a temperature of 
37° C, it will not grow at 20° C, nor at 45° C. at the other 
extreme. At 22° C. it commences to grow slowly, whilst 
at 25° C. it flourishes most luxuriantly, although it rapidly 
loses its virulence when cultivated for several genera- 
tions outside the body. Commenting on this fact, LofBer 
points out that glanders is essentially a disease of hot 
countries, where the comparatively high temperature appears 
to be extremely favourable to the development of the bacillus 
outside the body, especially in such materials as fodder, 
manure, and stable refuse generally. 

We have interesting evidence of this in statistics collected by Krabbe, 
who gives the following proportion of horses affected with disease per 
annum per 100,000 horses in the following countries : Norway, 6 ; Den- 
mark, 8.5 ; Great Britain, 14 ; Sweden, 57 ; Wurtemburg, 77 ; Russia, 78 ; 
Servia, 95 Belgium, 138; the French Army, 1,130; the AJgerian Army, 

As already mentioned, desiccation for twenty-one days is 
usually quite sufficient to prevent the multiplication of the 
bacillus when placed in nutrient media. Consequently it 
may be possible, by proper ventilation, to diminish the mor- 
tality from this disease even in the warmest countries.' 

Another agent which helps greatly in preventing the mul- 
tiplication of this bacillus is putrefaction, as the organisms or 
products developed during that process appear to interfere 
very markedly with the growth and multiplication of the 
glanders bacillus. The most satisfactory of all disinfectants, 
however, is heat, and it has been proved experimentally that 
a temperature of 55° C, continued for ten minutes only, 
is quite sufficient to destroy the Isacillus, and with it the 
infective power of the virus, from the fact that no spores, 
probably, are formed to perpetuate the species. A spray of 
steam would therefore, in all probability, be the most 

■ Loffler, however, was able to kill with a virus that had been dried on 
silk threads for eighty-nine days, and Fraenkel states that the organisms or 
their spores withstand drying. 


serviceable and the most available of all disinfecting agents, 
or perhaps, better still, a thorough washing out of the in- 
fected stalls with boiling water. Chlorine and carbolic acid 
are both capital disinfectants. A 2 per cent, solution of 
carbolic acid applied for twenty-four hours kills the glanders 
bacillus, and a solution of 4 per cent, applied to the nasal 
discharge for a single minute renders it perfectly innocuous. 
A I per cent, solution of permanganate of potash, 0.23 or even 
a 0.16 solution of chlorine water, or one-fifth per mille solu- 
tion of corrosive sublimate, will also render the bacillus 
perfectly innocuous within a couple of minutes. By means 
of any of these the process of disinfection may be carried 
on in stables in which glanders has occurred, with the 
greatest ease and with absolute certainty. 


The following works may be consulted : ,' ' 

Bendal, How^ard. — Graduation Thesis Univ. of Edin. (1882. 
Bouchard, Capitan and Charrin. — Bull, de I'Acadjfaa^, 

Rev. de Med. Francaise. Dec. 30, 1882. /■ 

Chauveau. — Comptes rendus, t. lxviii.. No. 14, 1869. ^ 
Fleming. — Manual of Vet. Sanitary, Science and Police, vol. 

I., p. 509, 1875. 
Grunwald. — Oesterr. Monatsschr. f. Thierheilkunde, No. 4, 

Israel. — Berl. Klin. Woch., No. 11, 1883. 
Krabbe. — Deutsch. Zeitschr. f. Thiermed, Bd. i., Heft. 4, 

p. 286, 1875. 
*L6ffler. — Arbeit a. d. k. Gesundheitsamt, Bd. i., p. 141, 

Loffler and SchuTz. — Deutsch. Med. Woch. Dec, 1882. 
*M'Fadyean and Woodhead. — Reports National Vet. 

Assoc. 1888. 
ScHiJTz. — Journ. Comp. Med. and Surg., vol. vii.. No. i, p. 

196, 1886. 
Vulpian and Bouley. — Bull, de I'Acad. de Med. 1883. 
Wassilieff. — Deutsch. Med. Woch., Bd. ix.,No. 11, p. 135, 

Weichselbaum. — Wien. Med. Woch., No. 24, p. 754, 1884. 
* Full references given. 



The Bacillus Anthracis — Early Observations — PoUender— Davaine — Koch 
— Pasteur — Methods of Examination — Appearances of Bacillus under 
Different Conditions — Spore Formation — Non-spore Bearing Bacilli — 
The Vitality of the Bacillus and of the Spores — Cultivation Experi- 
ments — Cover-glass Preparations — Inoculations into Animals — Methods 
of Infection — Anatomical Characters of Malignant Pustule — Animals 
Affected — Spores not formed in the Living Body — The Di^sposal of 
Anthrax Carcases — Various Disinfectants — Pathogenic and Sapro- 
phytic Anthrax — Buchner's Experiments on Anthrax Bacillus and 
Bacillus Subtilis — Hueppe and Wood's Experiments. 

Anthrax, or splenic fever, is perhaps the best known of all 
the specific infective bacillary diseases. The Bacillus An- 
thracis, compared with other pathogenic organisms, is of 
very considerable size ; it is from 5/t to 20/t long, and i toi. 5/t 
broad. It multiplies with very great rapidity in the blood of 
certain animals, and may be very easily cultivated outside 
the body ; in consequence of these features it was the first 
organism that was proved definitely to be associated with a 
specific disease, and it was certainly one of the first to be 
recognized as occurring in both animals and in man. 

In 1849, Pollender, and in 1850, Rayer and Davaine 
described these organisms as occurring in the blood of animals 
that had succumbed to splenic fever ; then again, in 1857, 
Brauell, examining the blood of a man affected with anthrax, 
found this same bacillus. 

Later, as already described, Pasteur's wonderful experiments 
on fermentation were published, and these led Davaine, in 
1863, to commence a series of observations on anthrax, which, 
carried on until 1873, gave everything but absolute proof that 
the anthrax bacillus was the actual exciting cause of this malig- 
nantdisease. This proof, however, was not supplied until 1876, 
when Koch, who had then been working at the subject for 


some time, furnished most rigorous proof of Davaine's hypo- 
thesis. At the same time he was able to give much additional 
information as to the development, mode of production, and 
general life-history of the organism — information that could 
only have been obtained by a long continued and careful 
study of the organism outside the body. 
The following year Pasteur also succeeded in cultivating 

Fhoto-micrograph of Anthrax bacilli in a preparation of the fresh spleen pulp of a 
cow that had died from splenic fever, x looo. 

this organism as a saprophyte and from that time up to the 
present new facts have constantly been garnered, and our 
knowledge of the biological history of this organism has 
been greatly extended. 

To observe the organism, a drop of blood is taken from 
the spleen of a cow (or of any other animal that has died of 
anthrax), and spread out between two cover glasses ; these are 

ANTHRAX. i273 

then separated, and one of them is at once lowered on to a 
drop of three-quarter per cent, salt solution, the other being 
set aside to dry, after which it may be gently heated in the 
flame of a spirit lamp and then stained in a water solution 
of methylene blue, well washed in water and alcohol, and 
mounted in a drop of water or glycerine. In the unstained 
specimen there will be found lying between the red blood cor- 
puscles a number of short rods of the size above mentioned, 
each of which has slightly rounded ends ; sometimes also 
there may be seen a delicate transverse mark running across 
the middle, this being especially well marked when the rods 
are longer than usual. The centre of each rod in the stained 
specimen appears to be quite homogeneous, and is usually 
deeply stained ; around this deeply stained portion is a kind 
of sheath which remains unstained, or is only slightly tinged 
by the colouring reagent. In some cases there is also at the 
point of junction, on each side of the transverse line, a some- 
what oval area slightly stained, so that when a number of 
these rods are placed end to end without being separated 
they have very much the appearance of a finger with the 
joints slightly enlarged, or of a bamboo cane with its charac- 
teristic thickenings placed at almost regular intervals. Both 
rods and threads are perfectly motionless. In other cases, in 
place of a mere transverse line, there is the appearance pre- 
sented of two bacilli that have only recently become separated 
from one another, still close together, however, and often so dis- 
posed that they enclose an angle. In the coloured prepara- 
tion the same thing is observed. It is now seen that where 
the rods obtain any considerable length they are distinctly 
segmented, each chain being divided into a number of short 
rods, and at regular intervals at the points of segmenta- 
tion there is usually a slight swelling, although as yet there 
is no trace or evidence of any spore formation. 

In cases of wool-sorters' disease, which is very frequently 
accompanied by pleurisy, these organisms may be found in 
the fluid that accumulates in the chest as long threads, 
which may be grouped together in a kind of network or 
felt, the individual threads of the bundles often reaching 
an enormous length without there being any appearance oi 

A similar growth of long threads has also been obtained by 
cultivating the bacilli, from the blood of the guinea-pig 



affected with anthrax, for two or three hours in aqueous 
humour, the threads then become elongated, the marks of 
division afe not nearly so distinct, and the threads remain 
homogeneous. It is possible, therefore, that the appearances 
met with in the fluid in the chest are due to the fact that the 
organisms have been allowed to remain at rest in the 
exudation, and that a process of cultivation has been going 

Photo-micrograph — Modified Anthrax bacillus — longer threads leptothrix form, x looo. 

on. In preparations made from the blood it is found that the 
corpuscles are somewhat irregular in shape, that they are 
running together in little irregular masses, and that the 
bacilli are much more numerous than the blood corpuscles. 
As regards the size of the bacilli it may be observed that the 
rods vary not only in length (in the same animals), but that 
they are of different breadths according as they develop in 


one species or in another, those found in a guinea-pig being 
thicker than those seen in the mouse or sheep, whilst those 
in the rabbit are thinner than any of those above mentioned. 

If one or two of these bacilU be placed in a moist cell, in 
what is called a hanging drop of nutrient broth, and the 
temperature be kept at about 37° C, the organism may be 
kept under observation under the microscope during thewhole 
course of its development. First, the short rods so increase 
in length that they may ultimately cover a whole field of the 
microscope, the protoplasm at the same time becoming 
granular ; then a large number of very minute points make 
their appearance, the hyaline appearance is gradually lost, 
and the threads become quite opaque. A little later, if the 
observation be continued, it will be found that instead of a 
single thread, httle bundles of the same long threads make 
their appearance, in which there are found, at pretty regular 
intervals, the highly refractile bodies with well-defined 
margins and sheaths which have already been described as 
spores. When the spores occur in long threads there is 
usually a slight enlargement at the point at which the spofe 
is situated, and this, with the bright shining point, gives to 
these spore-bearing threads an appearance that is described 
as being like a chain of pearls. In many cases the spores 
make their appearance in the shorter rods.' In place of the 
regular forms above described there are others, or involution 
forms, which are found to present themselves when the 
organism is grown under unfavourable conditions ; for ex- 
ample, irregular moniliform threads are usually met with 
where the temperature is too high or too low, the soil is 
exhausted and so on. 

It has been found by Lehmann, Hime, Buchner, Behringj 
and Roux that anthrax bacilli may be obtained that do not 
give rise to spores. This appears really to be due to all 
interference with the vitality of the protoplasm, as asporo^ 
genous organisms are best obtained by acting upon them 
with antiseptics, be these chemical or physicaL Roux, for 
example, was able to obtain asporogenous bacilh, and bacilli 
that remained asporogenous for several generations, simply 

' The development of the spore has already been described, as most of 
the descriptions of the setting free and development of the spores are taken 
from observations made on this species and described by Koch, Buchner^ 
Prazmowski and others. 


by immersing them for some time in 1,000 parts of nutrient 
fluid, to which one part of carbolic acid had been added. 
Under these circumstances the growth of the organism is 
not completely prevented, but no spores appear to be de- 
veloped. It cannot multiply at a temperature below 16° C. 
nor above 45° C, 30° to 37° C. being the optimum tempera- 
ture. It is distinctly aerobic in its growth, and cannot 
develop unless it can obtain a pretty free supply of oxygen. 

It has already been stated that the organisms which occur in 
the blood are homogeneous, and it is a well-known fact that 
spores are never developed in the bacillus that grows in the 
blood, the multiplication there being entirely vegetative in 
character, and being due to fission or division of the rods as 
they increase in length. The same thing holds good even in 
the dead body so long as it remains intact ; when once, how- 
ever, the blood is allowed to come to the surface and in con- 
tact with oxygen, spores are very rapidly formed within the 
bacilli. This spore formation will not take place below from 
24° to 26° C. (Koch says 18° C), and then only in the 
presence of oxygen, so that they can best be seen in those 
bacilli that are cultivated on the surface of such nutrient 
substrata as agar-agar, solidified blood serum, and potato, or 
in fluid media through which a pretty constant stream of 
oxygen is allowed to pass. 

In this respect the spore formation of anthrax bacilli ap- 
pears to agree with the sporulation of yeasts, which, it will be 
remembered, takes place best on a surface of plaster of Paris 
that is constantly kept moist and well supplied with air. 

Anthrax bacilli as distinguished from the spores are very 
readily killed. The ordinary putrefactive processes that 
are undergone in the decomposition of carcases in which 
these organisms have been present during life, especially if 
the air be excluded, cause the death of these bacilli in about 
a week. The temperature of boiling water maintained for a 
few seconds kills the bacilli, but, according to Klein, boiling 
for ten minutes is not to be relied upon to kill the spores 
although Koch states that at 100° C. the spores are killed in 
five minutes. The bacilli are killed by a two minutes' ex- 
posure to a one per cent, solution of carbolic acid in water, 
whilst the spores may remain alive for more than a week in 
a similar solution. They must be kept for nearly a week in 
a three per cent, solution, and twenty -four days in a five per 


cent, solution if these reagents are to have any lethal effect 
on them. Carbolic acid in oil — five per cent, solution 
— had little more, if any, effect than pure olive oil. The spores 
remain alive, for an indefinite period almost, in a five per cent, 
solution of olive oil. Sulphurous acid vapour in the propor- 
tion of one to one hundred of air kills the bacilli in half an 
hour, but the spores resist the same antiseptic for seventy-two 
hours. Corrosive sublimate in one per mille of water suffices 
to kill spores by simply wetting them. 

These tests of the vitality of the spores, however, were 
made by inoculating them into gelatine after they had been 
treated with the antiseptic. If, in place of inoculating into 
a nutrient medium of this nature, the spores are introduced 
into the circulating blood of a living animal, it has been found 
by Klein that it requires much longer exposure and much 
stronger solutions to hinder the development of the spores 
into bacilli and prevent the production of anthrax. '- 

We have already stated that the organism cannot con- 
tinue its growth at any temperature above 45° C, but it may 
still remain alive up to about 60° C. if this temperature be 
not continued for too long a period, the spore-bearing bacilli, 
though themselves killed at this temperature, leave their 
spores, which will withstand a temperature of 100° C- if 
continued only for a short time, and start into life and iiito 
active vegetative growth when again placed under suitable 
conditions. The only other physical condition that appears 
to be fatal, or at any rate injurious, to anthrax spores is 
strong sunlight ; this appears to deprive them in whole or 
in part of their powers of further development in a most 
remarkable manner, always causing distinct attenuation of 
their pathogenic virulence before completely destroying 
them. _ _ . 

The best way of maintaining cultures of anthrax bacillus is ' 
to take a drop of anthrax blood, sow it on a potato or a^gar-agar,., 
allow it to grow there for several days at about 30° C. until 
spores are well developed, triturate a small quantity of the 
growth with some distilled water, place a number of silk 
threads which have previously been sterilized by heat in this 
mixture, and then dry them carefully, cut into short lengths,' 
and keep them in a stoppered bottle or in a plugged test tube. ; 
From these threads cultivations may be made on almost any 
artificial nutrient medium. In addition to the media already 


^mentioned, starchy materials, vegetable infusions, hay and 
meat infusions, and even sterilized alkaline urine, may be used, 
the only thing that appears to interfere with their growth being 
an acid reaction. Even this, however, may be present to a 
slight degree if other conditions are favourable ; for example, 
the anthrax bacillus grows readily on potato, which gives a 
slightly acid reaction. On gelatine plates colonies grow and 
are visible to the naked eye, on the second or third day, as 
small white points which gradually spread outwards, and as 
they come to the surface cause a slight liquefaction of the 
surrounding gelatine ; they are then seen as small white 
masses with wavy margins lying in a clear space, formed by 
the liquid gelatine. When examined under the low power 
they appear as round dark-green points with an irregular 
outline ; on the second or third day this irregularity, 
becomes much more marked and, as Fliigge describes it, 
when it reaches the surface of the gelatine " the dark 
remnant of the deeply-placed colony can only be seen, in 
the middle. Around this centre, however, there is a light- 
brown or light-grey shimmering mass, which consists; of 
numerous wavy, curling bundles, recalling the appearance of 
locks of hair or snakes on the head of a Medusa. Ultimately, 
individual threads, or bundles of threads, branch oif from 
the irregular periphery, and grow over the gelatine iq various 
directions. At the same time the gelatine is liquefied over a 
small area ; the colonies, which have now a diameter of 2 
to 4 mm., begin to float and break down at their margins, 
under the action of the fluid formed." 

An exceedingly good method of obtaining a permanent record of the 
appearance of these colonies, is to lower a cover glass on to one of them 
and then to raise it carefully without sliding it over the surface, so as to 
take an imprint "of the colony upon the glass; the surface of the' colony 
adheres to the glass and a thin layer is removed. This, when stained 
with fuchsine or methyl blue and mounted in Canada balsam, gives an 
exceedingly faithful "impression" of the appearance of one of these masses. 

The puncture cultivations of the bacillus anthracis pre- 
sent most characteristic appearances. Along the track of 
the inoculating needle there appear delicate feathery rays,., 
which pass for some distance into the gelatine ; small lateral ^ 
rays are given off" from these, and the whole of the young : 
growth has a peculiar feathery appearance. These rays are 
always longer near the surface, and gradually become snorter . 


and fade oif as the lower part of the track is reached. After 
a time the gelatine begins to liquefy, and slowly the feather- 
like mass sinks to the bottom of the liquefied medium, 
eventually forming an opaque white layer, which is found to 
consist of bacilli in diiferent stages of degeneration. The 
upper kyer of the gelatine, though perfectly clear, is now 
quite fluid. This process of liquefaction comes on first along 
the track of the needle, near the surface, and gradually 
extends downwards until the whole needle track has dis- 
appeared. We have then in the tube, the upper liquefied 
gelatine, then the opaque layer of bacilli, and lastly the 
clear solid gelatine below. If agar-agar be used in place 
of gelatine, much the same appearances are presented ; 
there is a smooth glistening greyish-white surface growth J 
and the feathery rays appear to get more and more solid as 
the growth continues, but no liquefaction takes place. On 
solidified blood serum the colonies grow as g[reyish-white 
layers oh the surface, and the medium is very slowly liquefied. 
On sterilized cooked potatoes the bacillus grows as a creamy- 
white somewhat parchment-like granular mass, which rises 
above the surface for some little distance but never extends 
far in a lateral direction ; it has a peculiar dry appearance.- 
The growths on potatoes, as on other media, take place at 
the ordinary temperature of the room. This organism can 
be very readily inoculated into certain animals, with results 
that may be looked upon as very definite ; for example,' 
if with a needle the point of which has been dipped into 
the spleen of a cow that has died from anthrax a mouse be 
pricked at the root of the tail, it will di& in from seventeen 
to eighteen hours, enormous numbers of bacilli being found 
in its blood. It has been observed that in the case of some- 
what larger animals, such as the guinea-pig, death does not 
take place till a rather later period ; for instance, a guinea- 
pig setoned with a silk thread containing spores of anthrax 
bacillus will die on about the second or third day. If the 
animal be examined after death, it will be found that near 
the seat of inoculation there is usually very little to indicate 
that this was the point at which, the infective material was 
introduced. Should, however, the inoculation be made into- 
the abdominal wall, there is usually marked cedematous' 
swelling of the peritoneum ; there may be small haemor-^ 
rhages into the subcutaneous tissue, and there is usually' 


some emphysema ; the abdominal muscles are pale, moist, 
and are evidently in a condition of cloudy swelling, or in 
some cases there may be in the muscles, near the point of 
inoculation, hyaline degeneration. The spleen is enlarged, 
soft, and pulpy, and appears to contain a very large quantity 
of blood ; it is dark in colour. The liver also is changed ; it 
has a half-boiled look, and contains a considerable quantity 
of blood. The lungs are bright red and the cavities of the 
heart are distended. As already stated, the blood and lymph 
from the tissues contain the bacilli in very considerable 
numbers. If sections of various organs and tissues are 
afterwards made, it will be found that the bacilli are most 
numerous near the capillary vessels or in those small 
venules that arise from the capillaries. They are found 
in all parts of the spleen and in the small venules of the 
liver. They may also be found in the small capillaries of 
the glomeruli of the kidney. 

Another method of infection, especially met with in wool- 
sorters' disease, is by the air passages, a condition that was 
most carefully described by Greenfield in this country, and 
has since been made the subject of careful observations by 
Buchner in Germany. It appears that the spores are inhaled 
along with dust from hair, wool, &c. ; they develop in the 
air passages of the lung, make their way through the alveolar 
membrane or through the walls of the bronchi, and so into 
the lymph channels and blood vessels of the lung. In 
some cases, however, they appear to " operate " from 
the air channels themselves, and, multiplying in these 
positions, give rise to a kind of pneumonia. The air vessels 
become filled with sero-fibrinous exudation, in which the 
bacilli may develop most rapidly, the walls of the alveoli 
become cedematous ; the bacilli make their way from these 
points into the circulation, and general anthrax is set up. 
Pleurisy, with effusion into the thoracic cavity, as already 
mentioned, may also develop in these cases, and the walls 
of the bronchi appear to be invaded by the bacillus. It has 
been found that if the bacillus is taken into the alimentary 
canal the acid contained in the stomach usually destroys it. 
If, however, resistant spores make their way into the alimen- 
tary canal, they may pass untouched through the stomach 
and so into the alkaline contents of the intestine. At the 
body temperature they are then under very suitable conditions 



for development into the vegetative forms ; and as they are 
developed they make their way, especially through damaged 
epithelial cells which they gradually push to one side, into 
the deeper layers of the intestinal wall, into the lymph 
channels, or directly into the blood vessels, so giving rise, in 
many cases, to a general infection. 

Susceptibility of animals to infection through the intes- 

Photo-micrograph of Anthrax badlli in the blood vessels of the mesentery of a mouse. 
At one or two points the bacilli may be seen lymg m the substance of some of the 
white blood cefls (phagocytes), x 375. 

tinal canal varies very greatly, the guinea-pig, which is veiy 
susceptible to the disease conveyed by inoculation, withstand- 
ing a very large dose of the spores when given by the 
stomach, whilst sheep and cattle, both of which are more 
resistant as regards inoculation, are comparatively easily in- 
fected through the alimentary canaL I have stated that at 
the point of inoculation in animals there is usually no evi- 


dence at all that it has been the point of entrance of the 
bacilli, but in the human subject there very frequently 
occurs at the point where the bacilli enter a wound, a 
marked local reaction, the result apparently of an effort 
on the part of the tissues to prevent the further advance 
of the bacilli. There is first irritation at the point of in- 
oculation, this usually occurring in from one to three days 
after the inoculation ; about a day later a minute vesicle 
surrounded by a zone of inflammatory redness and swelling 
makes its appearance. The serum in this vesicle becomes 
brown, and gradually a kind of mortification is set up ; 
other vesicles, forming a ring, appear around the original 
point ; these in turn become brown or black, until 
gradually an extensive black scar is formed. If these 
little pustules, with the surrounding tissue, be freely 
excised and the wound well cauterized with strong carbolic 
acid, there may be no return of the disease ; in fact, if the 
removal be free enough, this result is most certainly ob- 
tained ; but if the inflammation be allowed to go on 
unchecked, there is gradual extension of the vesication, 
sloughing, and blackening, until a very considerable area 
is affected, the bacilli sooner or later making their way into 
the blood vessels and giving rise to general anthrax. In the 
vesicles, and also in the tissues around the point of inocula- 
tion, anthrax bacilli can usually be found in considerable 
numbers, the tissues are somewhat cedematous, and there is 
an increase of leucocytes in the inflamed area. When the 
blackening commences there are usually found along with 
the bacilli, or in some cases in the centre of the ulcer re- 
placing them, chains of micrococci ; these are seldom seen 
in the very early stages, but in the later stages they are 
almost invariably present. 

The animals most susceptible to this disease are sheep, 
mice, rabbits, guinea-pigs, and, according to Flijgge, horses, 
hedgehogs and sparrows, all of which die or are very 
ill when the organism is inoculated directly into the sub- 
cutaneous tissue. Most birds are not readily inoculated, and 
for a long time it was found impossible to kill fowls by means 
of anthrax. White rats, old dogs, and amphibians are ex- 
ceedingly resistant to the disease in almost any form ; cattle, 
too, which are readily infected through the alimentary canal, 
are but slightly susceptible to anthrax introduced by direct 


inoculation into the tissue. It has been found, however, that 
by reducing the temperature of the fowl and by raising that of 
a frog, these animals may be infected by inoculation, and they 
have even under certain conditions been killed. The usual 
method of infection in man, of course, is by the skin, and it is 
found that anthrax usually affects those who attend on or 
slaughter animals that are subject to this disease, so that those 
usually affected are butchers, grooms, and others engaged 
in similar employments. During the time that I was acting 
as physician to the Western Dispensary in Edinburgh, which 
was situated near the public abattoir, several cases of localized 
poisoning and two of general anthrax poisoning came under 
my charge within a comparatively short time. These were all 
cases of butchers, who having slight scratches on their hands 
or arms, had been infected by the blood of animals that they 
had killed which were suffering from splenic fever. Tanners, 
skin-dressers, and wool-sorters are also specially liable to this 
form of the disease, though the latter class are also very 
frequently affected through the lungs. In certain regions 
where the disease seems to be almost endemic the spores of 
the bacillus may make their way into the alimentary canal 
of the human and other subjects, through the medium of 
food or water. 

It has already been stated that the anthrax bacillus within 
the body of an animal is incapable of forming spores, but in 
those cases where the bacilli can make their way from the 
lungs into the -saliva, from the mouth, or from the lower 
part of the alimentaiy canal, whence they are discharged 
with the secretions, spores may be readily enough formed. 
• Consequently an affected animal must always remain a centre 
of infection, and even the dung from a diseased animal may 
contain a large number of spores which, when scattered over a 
field, are sufficient to infect whole herds or flocks. The only 
way in which to get rid of the infection in such a case is to 
burn the animal at once, or to bury it deep down in the 
earth. This latter method of disposing of the animal should 
only be resorted to where it is possible to bury it six or seven 
feet deep. It is a well-known fact that the organism cannot 
form spores where oxygen is absent, and at any tempera- 
ture below 12° C., and below this temperature the bacilli are 
incapable of existing for any length of time. At a distance 
of six or seven feet from the surface the temperature of the 


ground is usually below 12° C, so that animals piit below 
this depth, even if swarming with bacilli, cannot be 
looked upon as centres of infection ; the organisms, no 
longer able to form spores, soon lose their virulence and 
die out altogether. In order to get rid of any spore- 
bearing bacilli, all discharges or blood that may have 
escaped at the place where the animal lay after death 
should be carefully disinfected with 5 per cent, carbolic acid. 
It was for long thought that by cultivating the anthrax 
bacillus through a great number of generations on ordinary 
nutrient media it could gradually be converted into the 
hay bacillus or the bacillus subtilis — a very similar 
organism, but one that has no pathogenic properties — and 
Buchner, in a published series of experiments, claimed that 
he had obtained this conversion, and that in the same way 
he could again turn back the wheel from the hay bacillus to 
the pathogenic form. These results, however, fiave not been 
repeated, although many have tried similar experiments ; 
but Hueppe and Wopd, by using a species of earth bacillus, 
which, in its morphological characters and method of growth 
on nutrient media, appears to be almost identical with 
anthrax bacillus (but possesses no pathogenic properties), 
have found that it must be very nearly related phylogene- 
tically, from the fact that when inoculated into animals it 
acts as a kind of vaccine, and renders the animal immune to 
an attack of anthrax. 

It will be well, however, to take up this and other ques- 
tions relating to anthrax in connection with vaccination and 


The following works may be consulted : 
Bollinger. — Centralbl. f. d. Med. Wiss., No. 27, p. 417, 

Brauell. — Virch. Arch., Bd. xl, Heft. 2, p. 121, 1857, and 

Bd. XIV., Heft. S, 6, p. 432, 1858. 
Buchner. — Nageli's Untersuch. u Nied. Pilze ; Eine neue 

Theorie u. Erziel d. Immunitat gegen Infectjonskran- 

kheiten Munchen, 1883 ; Virch. Arch., Bd. xci.. Heft. 

3, p. 410, 1883. 
Chauveau. — Comptes rendus. 1880-1885. 
Davaine. — Comptes rendus, 1 863-1 866. 


Greenfield. — Proc. Roy. Soc, vol. xxx., p. 557, 1880. 
JouBERT. — Comptes rendus, t. xcvi., p. 641, 1883. 
Klein. — Rep. Med. Off. Local Gov. Board, p. 207, 1882. 
Koch. — Beitr. zur. Biol. der. Pflanzen, Bd. 11., p. 277, 

1876 ; Mitth. a. d. k. Gesundheitsamt, Bd. i., p. 49, 

*M'Fadyean and Woodhead. — Reports Nat. Vet. Assoc, 

Pasteur. — Comptes rendus, t. lxxxiv., p. 90, 1877, t. xcvi., 

p. 979, 1883 ; Rev. Scientifique, Jan. 20, 1883. 
PoLLENDER. — Casper's Vierteljahrsschrift, 1875. 
Prazmowski. — Biol. Centralbl., Bd. iv., No. 13, p. 393, 1884. 
Roger et Davaine. — Bull, de la Soc. de Biol, de Paris, 

ToussAiNT. — Comptes rendus, t. lxxxiv., p. 503, 1877. 

See also various papers in Centralbl. f. Bakt. u. Parasitenk ; 
Annales de I'Institut Pasteur ; Cornil and Babes Las Bac- 
teries ; Hueppe he. cit. and L6ffler, Vorlesungen uber Die 
Geschichtliche Entwickelung def Lehre von den Bacterien, 
Leipzig, 1887. 

* Full references given. 



Tetanus a Specific Infective Disease — A Wound Fever— Organism found 
by Nicoiaier in the Soil taken from Streets and Fields — Experiments 
on Animals — Symptoms of Disease — Pure Cultivations Obtained — 
Description of Organisms-— Characteristic Shape — Spore Formation — 
Organism Anserobic — Cultivations — Kitasato's Method of Cultivating 
the Organism — The Bacillus found only at the Seat of Inoculation — 
Wide Distribution of Spores — Bossano's Examination of Earth — 
Vaillard and Vincent's Observations — Tetnaus Bacillus a Facultative 
Saprophyte — Conditions under which Tetanus is Contracted — Poisoned 

Traumatic tetanus, or convulsions resulting from poison- 
ing associated with an open wound, was for long sus- 
pected to be the result of some condition similar to septic 
or hospital fever ; that it was an infective disease was 
recognized by many of the older surgeons, and attempts 
were made at a very early date to treat it as a traumatic 
infective disease. That this -poisoning was the result of 
the activity of an organism, which made its way to a wound 
and there flourished and gave rise to the characteristic pro- 
ducts and symptoms, was not the result of direct experiment 
made with the object of finding out such an organism, 
although attempts were not wanting to demonstrate its 
presence in the wounds and along the course of the nerves 
in cases of tetanus. All efforts, however, proved un- 
successful until after an organism obtained from other 
sources had been obtained and described, and an artificial 
tetanus had been produced. 

In 1884 Nicoiaier, working with soils obtained from the 
streets and from the fields, found that these when inoculated 
into certain animals produced effects different from those 
produced by soils taken from cultivated gardens and from 
woods. The former he found, when a small particle was 
placed in a little pocket under the skin of mice, rabbits, 


and guinea-pigs, gave rise to symptoms which he described 
as tetanic in character. In from two to four days after 
the inoculation the hind-quarters of the animal became 
paralysed, first the one near the seat of inoculation, then the 
other ; then rigidity came on followed by loss of motion ; the 
forelegs were in turn affected, then the neck, and at length 
the whole of the body became rigid, and sometimes curved as 
in tetanic convulsions occurring in the human subject.' On 
examination after death there was found, at the point of in- 
oculation, a small abscess, in the pus of which were several 
species of micro-organisms. One of these, when obtained 
pure or practically pure, if inoculated into another animal 
produced exactly the same symptoms. Nicolaier was not 
able to obtain any perfectly pure cultivations, but he 
described an organism which was afterwards separated by 
Kitasato and by Tizzoni and Mdlle. Cattani independently. 
This organism, although never directly demonstrated in the 
earth that produced the disease, is constantly found in the 
pus of the abscess, in the walls of this abscess, and even in 
the immediately surrounding tissues. It occurs as long 
delicate threads scarcely thicker than the bacilli of mouse 
septicaemia with slightly rounded ends ; like some other 
organisms, especially those met with in putrefactive pro- 
cesses, they give rise to spores which are usually developed 
at the end of the shorter rods into which the long threads 
break up ; this spore, forming the head of what is called 
the drum-stick-shaped bacillus, is usually large and may be 
seen as a clear mass causing enlargement of one end of the 
bacillus. The spore develops best at the temperature of the 
blood, and undw favourable conditions is completely formed 
about thirty hours after multiplication has commenced ; 
at the temperature of the room this does not occur for about 
a week, although the organism itself developes readily enough 
at this temperature. The rods are motile. Owing to the fact 
that the organism is anaerobic and that the presence of 
oxygen interferes very greatly with its development (it is 
said that oxygen kills it altogether), it proved a somewhat 
difficult matter to obtain perfectly pure cultivations, although 
when once it had been recognized that the organism was 
anaerobic, plate cultivations were readily enough obtained 

' For further description of the disease see "Micro-Organisms," Dr. C 
Fliigge, New Sydenham Society, 1890. 


by keeping the plates on which the nutrient medium 
was spread in an atmosphere of hydrogen. When puncture 
inoculations are made in tubes of gelatine to which grape 
sugar has been added, there is no growth along the part 
of the. track of the needle near the surface, but in the 
deeper part away from the air, there is a moderately 
luxuriant growth which appears in the form of a central 

Specimen from pure culture of the Tetanus Bacillus, with enlarged 
spore-bearing "drum-stick "ends. X looo. 

streak, from which numerous spikes pass laterally into 
the surrounding medium. The culture at this stage has 
very much the appearance of a spruce-fir, the lower branches 
{i.e., those in the deeper part of the gelatine where the 
access of oxygen to the organism is entirely cut off) 
being longer and more distinctly marked than those nearer 
the surface. Later this characteristic appearance is lost, 
the organism invades the whole of the nutrient medium, 


forming a kind of cloud ; the gelatine becomes softened, 
and there is emitted a peculiar fusty smell which appears to 
be almost characteristic of this organism. 

Most of the earlier experiments were somewhat unsatis- 
factory, and considerable doubt was cast on this organism as 
a producer of tetanus from the fact that in many cases pus that 
was known to contain this specific bacillus, and even old pure 
cultivations of the organism, failed to set up the characteristic 
symptoms when inoculated in the usual manner. More 
recent observers, however, have pointed out that the tetanus 
bacillus, like many others of the septicaemia group, is virulent 
only so long as it is grown under anaerobic conditions. This 
is especially the case in those organisms in which there has 
not been time for the spores to develop ; so that when 
grown in the presence of free oxygen (when that is possible), 
or when exposed to the air after the growth has been com- 
menced under favourable conditions, and has gone on for 
some time, but before there has been time for the formation 
of spores, the organism rapidly loses its virulence, or, as we 
have seen, dies off altogether. Experiments made by inocu- 
lating the pus from tetanic patients often gave entirely nega- 
tive results. Here it was evident that the failure was due, 
in many cases at any rate, to the fact that the pus with its 
contained organisms had been exposed to the air for some 
time, and the bacilli had been compelled to grow under 
conditions unfavourable to the retention of their specific viru- 
lence, before they were used for purposes of inoculation. In 
such organisms, as we should expect, it is found that spores 
are not seen, or they are very imperfectly developed, and it 
may be in the case of the older cultures, where these 
spores are developed into the young bacilli, that these, 
not having attained their full resisting power, die off very 
readily in the presence of oxygen. By paying attention to 
this point it has gradually been proved, almost beyond doubt, 
that the tetanus that may be produced in white mice or 
guinea-pigs by the inoculation of small particles of garden 
earth, is of the same nature as the tetanus that is produced 
by the inoculation of the pus from a primary wound which 
has apparently given rise to tetanus in the human subject. 
Further, now that the conditions under which the organism 
exists have been studied, and its anaerobic character 
recognized, pure cultivations have been made, and it has 


been proved that the disease may be produced without 
fail if certain definite precautions are taken before the 
inoculation be made. One great difficulty connected with 
the obtaining of pure cultivations was, of course, that 
under the conditions favourable to the growth of the 
tetanus organism, other anaerobic bacteria would also 
take the opportunity of developing. Some only of these 
other organisms, however, give rise to the formation of 
spores, and this occurs at a later date than in the case of the 
tetanus bacillus. Kitasato, very ingeniously, made this fact 
the stepping-stone to the cultivation of a pure growth of the 
spore-bearing tetanus bacillus. As we have already seen, 
spores of many bacteria can readily withstand a high tem- 
perature (in some cases of even ioo° C., if this is not continued 
for too long a time, and they will withstand for a con- 
siderable period the action of a temperature of 80° C), whilst 
the vegetative or fully developed forms are killed off very 
rapidly at a comparatively low temperature. Kitasato's 
method of procedure was as follows : From the immediate 
neighbourhood of the suppurating wound of a patient who 
had died from tetanus, he took a small fragment of tissue, 
and placing it under suitable nutrient conditions, ?>., in the 
specially prepared gelatine at a temperature of little over 
30° C, and in an atmosphere of hydrogen, he obtained 
a very luxuriant growth of anserobic organisms ; amongst 
these he observed that the drum-stick-shaped organisms 
developed their spores at a much earlier period than any 
of the others that were growing in his cultures. As soon 
as these spores made their appearance he raised the tem- 
perature to 80° C, with the result that all those bacteria, 
in which spores were not already developed, were very 
rapidly destroyed ; the tetanus bacilli were also destroyed 
(that is, the vegetative forms were destroyed), but the spores 
still retained their vitality, and on being transferred to 
suitable nutrient media, and placed under other suitable 
conditions, they " hatched " out into the vegetative form, and 
a pure cultivation of the tetanus bacillus was obtained. It 
is a rather curious fact that here, as in the case of diphtheria, 
the organism seems to be localized at the actual point of 
inoculation, for although, as we have seen, the bacilli, how- 
ever numerous in the pus and in the walls of the abscess, and 
in the infiltrated tissues immediately around the abscess. 


are confined to a well-defined and localized area, and the 
most careful researches, conducted with the help of both 
cultivation and histological methods, have hitherto failed to 
enable any observer to demonstrate the presence of these 
organisms in the internal organs. It would appear, then, 
that as in the case of septicaemia and diphtheria, the poison 
is manufactured by the organisms at the site at which they 
are actually introduced, and that from this point it is absorbed 
into the body, and is carried to the special tissues on which 
it acts. Brieger, indeed, was able to separate from the 
limb of a patient who had died from tetanus an exceedingly 
virulent basic poison or ptomaine which he speaks of as tetanin, 
whilst he also found a very poisonous proteid substance, 
tetano-toxin, which he called a toxalbumen, a substance of 
which we shall have to speak in a later chapter. 

At first sight it appears somewhat extraordinary that the 
development of the tetanus bacillus should be so extremely 
localized, and that the localization should be confined to a 
position so near the surface — i.e., to the surface of a compara- 
tively open wound, to which the oxygen of the atmosphere 
might at first sight appear to have easy enough access. 

When, however, we come to think more carefully of the 
conditions that prevail in the wound, this does not seem 
quite so extraordinary. In the first place, there is, covering 
it, a layer of pus which, as is well known, has little power of 
holding oxygen in solution, any small quantity that is there 
being gradually taken up by the leucocytes that escape to the 
free surface or into the abscess, and utilized by them for their 
own purposes. Beneath this, especially in the later stages 
of infiltration, and before the capillary vessels of the granula- 
tion tissue have begun to form, or are fully formed, the supply 
of oxygen must necessarily be comparatively small, and any 
that is present is promptly taken up by the active wandering 
and proliferating connective tissue cells. Here then we have 
the conditions under which the tetanus bacillus is enabled to 
flourish ; there is a condition of anserobiosis, or oxygen famine. 
Beyond this, however, where the infiltration is not so great, 
and where the vessels are considerably dilated, the red blood 
corpuscles are constantly bringing up their fresh supplies of 
oxygen to the tissues, and in consequence the fluids at some 
little distance from the wound contain more oxygen than 
there is near the surface of the wound, and the conditions 


are consequently much less favourable for the continued 
existence of the tetanus bacillus. 

The spores of the tetanus bacillus seem to have a remark- 
ably wide distribution. Originally they were only cultivated 
from garden soil, but successful inoculations have since been 
made with such material as the sweepings of a hay-loft, and the 
dust that had accumulated on the furniture of horses. The 
specific bacillus has been found on the grime on a man's hand, 
and on imperfectly cleansed surgical instruments. Tetanus 
is said to be specially associated with the horse, but the more 
recent observers insist that this is simply because the horse is 
susceptible to the action of the bacillus and its poison, and 
because the germs have such a widespread — in fact, an almost 
universal — distribution. How universal this distribution is 
may be gathered from the fact that M. Bossano, who was 
able to obtain the soil from forty-three different regions in 
various parts of the globe, got positive results with twenty- 
seven of them. With the soil from these forty -three places 
he inoculated a number of animals, introducing a small por- 
tion, about the size of a pea, into a little subcutaneous pocket 
of a white mouse or a guinea-pig, and with the soil obtained 
from twenty-seven of these places tetanus was produced in 
from two to four days. He says of the soil obtained from 
England, that from Bath produced tetanus in two out of 
three white mice inoculated, both of them dying in about 
two days. Soil from Portsmouth did not contain tetanus 
bacilli, whilst that from Plymouth and from Manchester 
caused the death of some of the animals that were inoculated 
with it, all the characteristic symptoms of tetanus being 
developed. Speaking colloquially, a worker at the Brown 
Institute told a friend that they grew the tetanus bacillus in 
the garden there. From his experiments Bossano concluded 
that soils which contain much organic matter, almost in- 
variably contain tetanus bacilli, and that latitude, climate, 
and special meteorological conditions, have far less influence 
on its development than defective drainage, imperfect hy- 
gienic conditions, and the degree of cultivation of the soil. 
It appears, however, that our methods of cultivation are not 
yet perfect, for it is an undoubted fact that failures to pro- 
duce tetanus with pure cultivations are of very common 
occurrence, even in the hands of those best fitted to carry on 
experiments of this kind. So markedly is this the case that 


Chantemesse and Widal at one time thought that the pre- 
sence of other organisms was necessary in order that the 
tetanus bacillus might act, and it has been suggested that 
aerobic organisms which have great avidity for free oxygen 
must also be present in order to allow of the development 
of the full virulence of the anaerobic tetanus bacillus. It is 
a fact, whatever may be the explanation, that the tetanic 
organism soon loses its virulence under cultivation, especially 
when it is grown " pure." 

Recently, however, Vaillard and Vincent, as the result 
of a series of most careful observations, have arrived at the 
conclusion that it is usually the tetanus poison — which 
they compare to snake poison — and not the organism 
itself that gives rise to the tetanic symptoms in animals 
that are infected experimentally. They also find that until 
the organism has grown in artificial culture media for 
some time it has not the power of setting up disease, a 
fact that was accounted for when they found that no poison 
was developed until some time after the organism had begun 
to grow, the production of the poison appearing to go on 
simultaneously with the formation of a peptonizing enzyme. 
Even spores, when injected alone, could not set up tetanic 
symptoms, but when these were injected along with other 
organisms such as lactic acid bacillus, or even with lactic acid 
itself, with bacillus prodigiosus, or into a bruised wound, or 
where they were injected along with a quantity of their 
own poison, tetanus was invariably set up. The tetanus 
organisms form their poison slowly, and in healthy tissues 
they are rapidly destroyed by the tissue cells long before 
they have time to form sufficient poison to produce the 
nervous symptoms of tetanus ; whilst in the cases above 
mentioned the tissue cells are so engaged in removing the 
other foreign matter, or are so paralyzed by the action of 
the lactic acid, or the small portions of tetanus poison, that 
they are not able to contend on equal terms with the tetanus 
bacilli, which being under favourable conditions grow rapidly, 
give rise to the formation of the special poison, and the 
patient succumbs. This remarkable poison in doses of 25 
millegrammes is quite sufficient to kill a rabbit, or the 2Sth 
of a millegramme to kill a mouse. 

The tetanus bacillus is a facultative saprophyte, the nature 
of the wounds through which tetanus is inoculated bearing 


out in a most remarkable fashion the experimental proofs 
that have been already adduced. A horse which, in the stable 
and in the field, always collects a certain quantity of earth 
on his skin and in his hoofs, may be easily inoculated ; he, 
in turn, may readily inoculate a man or another animal by a 
kick with the sharp iron of his dirty shoe. Gardeners, agri- 
cultural labourers, and all who work with horses or in the 
soil, bear on their hands a virus which only needs a bruise or 
a cut, but especially the former, to allow of its setting up the 
characteristic symptoms of tetanus. Soldiers, during a cam- 
paign, when their garments and equipments are soiled from 
contact with the ground during their camping and bivouack- 
ing are always more liable to the disease than when they are 
hurt accidentally during times of peace. It is also pointed out 
that in warm countries where people are in the habit of sleep- 
ing out in the open air and on the ground, tetanus is very 
frequently met with as the result of comparatively slight 
wounds, whilst amongst children during the years they 
crawl on the ground, or play in gardens or in fields, 
tetanus is always more common than in later life, when the 
parts that come in contact with the ground are usually pro- 
tected by shoes and gaiters. Many of these facts are well 
known to savage tribes, whose powers of observation and 
opportunities for experimentation are of a very high and 
extended order, and we find that Dr. Ledantec, in an interest- 
ing account of the poisonous arrows used by the inhabitants of 
Santa Cruz, of the Solomon Isles, and of the New Hebrides, 
■ speaking of the deaths from this cause of Bishop Patteson 
and Commodore Goodenough, with their companions, refers 
to the fact that they were all attacked by tetanus, or lockjaw. 
He gives a short description of these poisoned arrows. They 
are about three feet in length ; the shaft is made of a reed, then 
comes a middle portion composed of hard wood, and lastly a 
point which is usually composed of a fragment of human bone, 
which is carefully sharpened to a very fine point, and is so 
fixed that it readily snaps off on the slightest shock. With a 
sticky substance obtained from an incision made in the 
bark of a tree, the point composed of the fragment of bone 
is smeared. This fluid, on exposure to the air, becomes 
thicker, and of a more viscid consistence. Thread is then 
wound in a spiral direction round and round the sticky 
point. A quantity of soil from the edge of a mangrove 


swamp is taken in a cocoanut shell, or some similar vessel, 
and into this the arrow-head is plunged. It is then carefully 
dried in the sun, after which the thread is removed, when 
a roughened point covered with a film of dry mud and 
dust is left. In this mud there are probably both septic 
vibrios and tetanus bacilli, the former, however, are rapidly 
killed by exposure to the sun, whilst the tetanus bacillus of 
Nicolaier, which, as we have seen, developes a well-formed 
spore at one extremity, may remain active for months and 
even years, although, as the savages well know, the poison 
gradually becomes more and more attenuated, until old 
arrows are known to become entirely inoffensive, except as 
mere mechanical weapons of warfare or hunting. 

Stanley, speaking of the hunting appliances and offensive 
weapons of the pigmies whom he encountered during his 
African wanderings, makes a similar interesting observation, 
to the effect that these small specimens of humanity use arrows 
so poisoned that the slightest scratch with one of them pro- 
duced one of two things, tetanus (or convulsions), which is 
evidently due to the action of a poison similar to that above 
described, or death, accompanied by peculiar gangrenous 
sloughs at the seat of the wound, which is very probably 
associated, so far as we can see, with malignant oedema or 
"black quarter," a condition that was also described by 
Nicolaier as resulting from the inoculation of soil collected 
from gardens and forests. These pigmies are described as 
dwellers in the dense forests of that part of Central Africa 
through which Stanley travelled. 


The following works may be consulted : 
Arloing et L^on Tripier.— Arch, de Physiol. Normale et 

Path., t. III., p. 235, 1870. 
Belfanti u Pescarolo.— Centralbl. f. Bakteriol. u. Parasi- 

tenk, Bd. v.. No. 20, p. 680, and No. 21, p. 710 ; Bd. 

VI., No. 10, p. 283, 1889. 
BoNOME.— Fortschr. der Med., Bd. v.. No. 21., p. 690, 1887. 
BossANO. — Comptes rendus, t. cvii., p. 1172, 1888; Re- 

cherches Experimentales sur I'Origine Microbienne du 

Tetanos, 1890. 
Brieger.— Bericht. d. deutsch. Chem. Gesellsch., Bd. xix. 


Brieger und Fraenkel. — Berlin Klin. Woch., pp. 241, 

248, 1890. 
Carle e Rattone.— Giornale della R. Acad, de Med. di 

Torino. March, 1884. 
Clarke. — Trans. Roy. Irish Acad. 1789. 
Chantemesse et Widal. — Les Bacteries, Cornil and Babes, 

t. I., p. 567, et seq., 1890. 
Faber (Knud). — Om Tetanus som Infektionssygdom. 

Copenhagen, 1890. 
Flugge. — Die Micro-Organismen, Leipzig, 1886, Tran. 

W. Watson Cheyne, New. Syden. Soc, 1890. 
KiTASATO. — Kongress f. Chirurgie, 1889. 
KiTASATo UND Weyl. — Zeitschr. f. Hygiene, Bd. viii., pp. 

41, 404, 1890. 
Koch.— Mitt, aus d. k. Gesundheitsamte, Bd. l, 1881. 
KussMAUL. — Deutsch. Arch. f. Klin. Med., Bd. il, Heft, i, 

p. 1, 1873. 
Ledantec. — Annal de I'Institut Pasteur, t. iv., Nov. 25, 

Marshal Hall. — On the Diseases and Derangements of the 

Nervous System. London, 1841. 
Nicolaier. — Beitr. zur. Aetiol. des Wundstarrkrampfes. 

Dissert. Gottingen, 1885. 
Nocard. — Recueil. de Med. Vet., t. iv.. No. 18, p. 617, 1887 ; 

Arch. Vet., 1882. 
RiETscH. — Comptes rendus de I'Acad. d. Sc, t. cvji., p. 400, 

Rose. — Ueber d. Starrkrampf., 1870. 
Sanchez-Toledo and Veillon. — Arch, de Med. Exp^rim. 

Bd. II., p. 709, 1890. 
Saxtorph. — Clinisk Chir. 3dje. Del. Copenhagen, 1878. 
Simpson, Sir J. Y. — Works, vol. i., 1871. 
Tizzoni and Cattani. — Riforma Medica. April, 1889. 
Vaillard et Vincent. — Annal. de I'Institut Pasteur. 

Jan., 1891. 
Verhoogen et^ Baert. — Premieres Recherches sur la 

Nature et I'Etiologie du Tetanos. Bruxelles, 1890. 
Verneuil. — Soc. de Chir., t. xi., pp. 327, 438, 1885. 
Wiedermann. — Zeitschr. f. Hygiene, Bd. v., p. 522, 1889. 



Diphtheria an Infective Disease — The Organism found in the False Mem- 
brane in its Deeper Parts — Method of Staining the Bacillus — Characters 
of the Bacillus — Involution Forms — Cultivation Methods^Appearance 
of Colonies — Nutrient Media — Results of Inoculation Experiments — 
Klein's Bacilli differ somewhat from Ixifder's — Streptococci found in 
Diphtheria Poison — Extreme Virulence — Resemblance to snake-bite 
poison — Toxicity — Predisposing Conditions — Conditions fatal to the 
Bacillus — Roux and Yersin's Observations — Fraenkel's Observations 
— Attenuated Diphtheria Virus — Increase of Virulence. 

Although it has long been known that diphtheria was 
an extremely infectious disease, it is only within compara- 
tively recent years that any reliable information as to the 
nature of the specific infective poison has been forth- 
coming. Even when the organic nature of other specific 
infective poisons had been practically proved many difficulties 
still remained to be overcome ; in most other cases where 
the disease could be proved to be the result of the vital 
activity of a micro-organism, such organism could usually 
be found in a pure condition, or greatly predominating 
over all others, in the blood, in the internal organs, or in 
some special fluid in the body. This was found not to 
be the case in diphtheria. Most careful and elaborate 
researches were entered upon, but it was found impos- 
sible to demonstrate any special organism as occurring in 
the blood, in the lymph, or in any of the organs of the 
body. The only position in which any could be found was 
in the false membranes (corjiposed of fibrinous lymph and 
altered epithelial cells) that are found in the throat, and it 
was at once surmised — a surmise that was afterwards found to 
be correct — that the poison which gives rise to the constitu- 
tional symptoms must be formed at the point at which the 
micro-organisms are found, and that, being of an exceedingly 
diffusible nature, it is thence absorbed and carried to various 


parts of the body, giving rise to heart failure, or to certain 
forms of paralysis, partly through its action on the nervous 
system and partly owing to its interference with the 
nutrition of the various tissues of the body. Here again, 
however, those who were studying the subject were con- 
fronted with another difficulty ; there were so many forms 
of micro-organisms that found in this false membrane a suit- 
able subsoil on which to "grow, it was almost impossible 
with the methods then at command to separate them and so 
to obtain pure cultures, in order that the specific and bio- 
logical characters of each might be investigated. 

In 187 s Klebs found in the false membranes a small bacillus 
with rounded ends, and with, here and there, small clear spaces 
in its substance, a bacillus that was not readily stained, that 
grew luxuriantly in broth, and which, inoculated into animals, 
gave rise to a peculiar dirty fibrinous-looking slough at 
the seat of inoculation. He found, however, that in certain 
cases this bacillus was absent, the predominating organism 
then seeming to be a micrococcus arranged in masses or in 
short chains. This, when cultivated in broth, gave rise to 
the formation of chains of considerable length. As a result 
of these observations he described diphtheria as occurring in 
two forms, one form resulting from the action of one organ- 
ism, the second being caused by the other. 

These researches were "continued by other workers, and 
Formad, in America, came to the conclusion that the rod- 
shaped bacillus had little to do with the disease, but 
that the stieptococcus, or chain-forming micrococcus, was 
the real exciting cause. Matters remained at this stage 
for some time^in fact, until Loffler took up the subject. 
After examining a number of cases of diphtheria, he found 
that, although there are numerous organisms in the false 
membranes or diphtheritic patches, these were mostly near 
the surface, and many of them were simply the organisms 
that were usually found in the mouth now growing under 
more favourable conditions of nutrition. He found, however, 
that in the deeper layers, or at the inner margin of the layer 
of exudation, the Klebs bacillus might almost invariably be 
found. It was more deeply situated than any of the others, 
and was always most numerous in the oldest part of the 
membrane. This was in cases of pure diphtheria. In the 
so-called diphtheritic sore throats met with, in other diseases. 


especially in scarlet fever, the streptococcus appeared to be 
the predominant and characteristic organism. 

These rods described by Klebs and Loffler vary much 
in length, but they average from 3 to 6/j ; they are straight 
or slightly bent, one end or both sometimes being a little 
swollen. There may be deeply stained or bright glistening 
points in the protoplasm, though these are not usually met 
with. Babes indeed describes spores as occurring in the 
diphtheria bacillus, but, as is mentioned later, these are not 
real endospores but consist merely of altered protoplasm. 

In order to stain the bacillus it is only necessary to remove a small 
fragment of the false membrane by means of a piece of absorbent cotton 
wool tied firmly to a pair of forceps or to a pen holder ; from this it is trans- 
ferred to a scrap of blotting-paper, and thence to a cover glass, where it is 
broken down as finely as possible, heated over a flame in the ordinary 
fashion, and stained with Lofiier's alkaline methylene blue, or by Gram's 
gentian violet method (washing thoroughly with water before attempting to 
examine), or by a method adopted by Roux and Yersin, who use a blue, com- 
posed of equal parts of aqueous solution of violet dalilia and methyl green, 
with water added until a clear, but not too deep, blue is obtained. A drop 
of this is placed on the slide, the cover glass on which the fragments are 
dried is inverted and lowered on to it, the superfluous fluid is removed with 
a piece of blotting-paper, and the organism is examined at once. 

The vital characteristics of the organism may be used in separating it 
from false membranes, even where contamination from the organisms of the 
mouth and pharynx has occurred ; and it is recommended that in order, 
wherever there is any doubt, to be absolutely certain of the diagnosis of 
diphtheria, cultivations on blood serum should be made. 

The specific diphtheria bacilli appear to be stained more 
readily and more deeply than any of the organisms that 
usually accompany them. They occur in small groups, as 
short, straight, or curved rods, with ends sometimes pointed, 
sometimes curved ; they are never absent from cases of true 
diphtheria in the early stages, and in some_ cases the 
membrane consists of an almost pure cultivation of the 
bacillus. In older cases, however, the organisms do not 
stain so equally ; many pear-shaped and club-shaped bacilli 
are present, and, in some very old membranes, it is difficult 
or impossible to distinguish any characteristic bacilli, the ac- 
companying organisms becoming more numerous, especially 
as thesurface becomes foetid and softened. In such cases the 
specific organisms can only be found entangled in the 
deeper fibrinous net-work. 

Roux and Yersin hold that microscopic examination gives the most precise 


information, even in the case of dried false membranes sent from a distance 
wrapped in linen or blotting-paper. They also hold that where improve- 
ment is taking place, the specitic bacilli become less numerous, the other 
microbes increasing in number, and that this may be followed day by day 
with a microscope, the course and prognosis of the disease being indicated 
by the changes that are met with. They also hold that at the beginning of 
a case of diphtheria it is possible to predict a favourable issue from the 
presence of a small number only of the specific bacilli, and a large number 
of other forms, and they also believe that some of the micro-organisms met 
with under these conditions interfere with the growth and activity of the 
specific bacillus. 

The Kleb's-LofHer bacillus cannot be cultivated outside the 
body on peptone meat gelatine, as it will not grow sufficiently 
rapidly at the room temperature to outpace the putrefactive 
organisms which accompany it ; it was, therefore, found 
impossible to make plate cultivations in order that the 
different forms might be separated. 

By mixing the membrane with boiled distilled water and 
allowing drops of the mixture to trickle over the surface of 
solidified blood serum, Loffler succeeded in obtaining pure 
cultivations. Wyssokowicz, using agar instead of gelatine 
for making plate cultivations, and incubating at 35° C, was 
able, on a small percentage of his plates, to obtain pure 
cultivations of the characteristic diphtheria bacillus ; most 
of his plates, however, were overgrown with putrefactive 
and other non-pathogenic organisms. 

To obtain a somewhat purer inoculating material, put a scrap of mem- 
brane between blotting-paper, or on a cover glass in a test tube, allow it to 
dry, and then heat to a temperature of 98° C. for a whole hour — a tempera- 
ture which few ordinaiy organisms can withstand for even a less time than 
this — so that, when the dried material from a cover glass so treated is 
inoculated on solidified blood serum, a very pure cultivation is usually 

Roux and Yersin adopted a simpler method. They used a 
platinum needle beaten out at the end to form a kind of spa- 
tula ; on this they took a particle of the false membrane from a 
case of diphtheria and then made stroke cultivations on the 
surface of the solidified blood serum, using the same needle 
without re-charging for some half-dozen tubes. When these 
are incubated at from 33° to 35° C. the bacilli rapidly make 
their appearance ; they are visible at the end of twenty hours 
and have a characteristic appearance in forty-eight hours. 
This rapid growth is very characteristic of the diphtheria 


bacillus, which appears to be the only organism of all those 
found in the membrane that can form colonies visible 
to the naked eye in twenty hours. Such colonies grow as 
small rounded greyish white points, the centre of each of 
which is more opaque than the periphery ; they spread 
rapidly, form greyish rounded discs, and continue to develop 
so quickly that they are very evident before the other 
organisms have begun to form a colony at all visible to the 
naked eye. From these points, inoculations on to blood 
serum may be made. 

Probably the best nutrient material for the diphtheria organism is that 
recommended by Loffler ; it is composed of three parts of blood serum, 
one part of neutralized broth, to which has been added i per cent, of pep- 
tone, . S per cent, of common salt, and i per cent, of grape sugar. Ordinary 
blood serum comes next, and then agar-agar j^Uy. On E^ar plates the 
colonies situated in the substance are coarsely granular, dark brown, and 
somewhat rounded or oval ; although where several colonies have run to- 
gether they may give rise to somewhat irregular outlines. The superficial 
colonies are much lighter in colour, are not so dense, and have an irregular 
scalloped border. 

These cultivations are found to be made up of bacilli 
similar to those described by Klebs ; they are not quite so 
long as the tubercle bacillus, but are rather thicker, the 
extremities, which are more deeply stained than the central 
portion, are often slightly enlarged. In older cultivations 
the rods are not uniformly coloured, and there may be seen 
in the substance of the protoplasm bodies which somewhat re- 
semble spores. It was soon noticed that with this inequality 
of staining, certain other changes in the organism might be 
met with ; so-called involution forms make their appearance. 
In these the bacilli are cut up into small rounded masses of 
protoplasm, some of which have a less diameter than that of 
the bacillus, whilst ethers may be considerably larger and are 
oval in shape. These involution or degenerate forms soon 
make their appearance where the conditions for the growth 
and development of the bacillus are unsatisfactory, and it is 
supposed that many of the failures to find the typical rod- 
shaped bacilli in old diphtheritic membranes are due, in some 
measure, at any rate, to the occurrence of these involution 
forms in the later stages of the disease, where the membrane 
is invaded by putrefactive and other organisms which inter- 
fere with the growth of the specific bacillus. It is also 


found that the diphtheria bacillus has a tendency to lose 
its virulence on cultivation. 

It was at first concluded that the bright, strongly refrac- 
tile particles and deeply stained granules were more or 
less perfectly developed endospores, and that some of the 
involution forms might possibly be arthrospores. Although, 
however, the organisms remain alive and potentially active 
after being subjected to drying for a considerable time, a 
moist temperature of 58° C. is quite sufficient to kill them 
oif, which would scarcely be the case were these bodies true 

The bacillus, as we have seen, grows freely on meat fluids that have an 
alkaline reaction, but as it grows it first renders these media slightly acid, 
but later, if there is free access of air, the fluid again becomes alkaline. 
The acid reaction is always most marked in those cases in which there is 
glycerine in the cultivation medium. The organism grows " in vacuo," 
but more slowly than in air ; the exclusion of air, however, interferes with 
the formation.of acid, so that under these conditions the bacillus may retain 
its vitality for a period of six months, or even longer. Examined in a fluid 
medium it is found to be quite motionless. 

Although Loffler was able to produce some of the symp- 
toms of diphtheria by the inoculation of this bacillus on an 
excoriated mucous membrane, he was not satisfied that this 
was the real causa causans of the disease, and it was left for 
Roux and Yersin to demonstrate the intimate causal relation 
that actually exists between this organism and true diphtheria. 
They repeated LofiSer's experiments of inoculating the bacilli 
on the damaged mucous membrane of rabbits, guinea-pigs, 
and pigeons, and in all cases they found that characteristic 
diphtheritic patches were produced. Injected under the skin, 
the bacillus causes swelling at the point of inoculation, and the 
animal dies with symptoms of acute poisoning. In some cases 
there is found' congestion and eifusion into the serous cavities ; 
in others there is evidence of fatty degeneration of the liver, 
similar to, but more acute than that met with in cases 
of diphtheria in the human subject. A very important 
point determined by them was, that if death did not take 
place too rapidly, characteristic diphtheritic paralysis usually 
supervened. The bacillus in these cases was found only at 
the point of inoculation, and even in the most congested 
organs it could not be demonstrated either in the blood 
channels or in the lymph spaces, whilst it often disappeared 


even from the seat of inoculation during the latter stage of 
the disease ; — another fact that helps to explain LofBer's 
inability to find the organism in certain of his causes. 

From all this it is concluded that the local symptoms of 
diphtheria are due to the action of a specific bacillus on a 
weakened mucous membrane or on a wounded surface ; that 
once having gained a footing it gives rise to an acute in- 
flammatory process, probably by the direct action of the 
poisonous material that it forms on the cells and on the 
blood vessels in the immediate neighbourhood ; this caustic 
action is so intense that the epithelial cells undergo de- 
generation, — the fibrinous lymph and leucocytes which are 
exuded also become more or less rapidly degenerated — and 
give rise to the grey false membranous patches that are so 
characteristic of true diphtheria. When the growth of the 
organism is rapid, and where the area of surface attacked 
is extensive, the amount of poison developed may be very 
■ great indeed, and where this latter is greater than can be 
dealt with in the inflammatory area, owing to the rapidity 
with which it is produced by a large number of organisms, 
especially when they are situated deep down in the 
tissues, there is rapid absorption of the poison, but not of 
the bacilli, into the system, and the characteristic constitu- 
tional symptoms of the disease are set up. We must thus 
distinguish carefully between the local action of the bacillus 
and its products, and the toxic constitutional effects of these 

Additional proof that these products are the active agents in 
the causation of the disease was found in the fact that from 
pure cultures of the diphtheria bacillus there maybe separated, 
by means of Chamberland's porcelain filter, a special chemical 
substance, or series of substances, which, after being proved 
quite free from bacilli and injected under the skin of animals, 
gives rise to all the constitutional symptoms and lesions of 
the disease that follow the inoculation of the bacillus itself, 
the only feature wanting being the false membrane, which 
usually does not make its appearance. Animals into which 
small doses are injected are frequently attacked by diph- 
theritic paralysis. 

Of course it has been objected that the diphtheria pro- 
duced in animals is not necessarily the same thing, nor is it 
necessarily due to the same organism, as the diphtheria of 


man. Loffler himself has examined the diphtheria of a 
calf, and he acknowledges that it is not even related to the 
diphtheria of the human being. 

Klein considers that cats are especially susceptible to 
diphtheria, and that they may act as the intermediate hosts 
for the development of the diphtheria bacillus between two 
human patients, whilst he also holds that cows may be 
inoculated, especially on the udders, with diphtheria bacillus, 
the disease manifesting itself in the form of small pustules. 
He considers that milk from such cows may readily become 
the agent by means of which the disease is spread. Eminent 
veterinarians, however, are strongly opposed to this view, 
and it can yet scarcely be maintained that Klein has fully 
proved his point, although he seems to have obtained strong 
evidence in support of his position. As he is now working 
most carefully at the subject, however, it may be well to 
suspend judgment until he publishes a full report of his 
observations and experiments. 

Klein's bacilli, however, undoubtedly differ in certain 
essential points from the bacillus described by Loffler ; most 
important of all in the fact that whilst Loffler never suc- 
ceeded in obtaining growths of his bacillus at the ordinary 
temperature of the room, and was not able to grow it in 
gelatine, those that Klein describes as occurring in the 
pustules on the ulcerated udder of the cow grow luxuriantly 
in gelatine at the ordinary temperature of the room. 

Klein describes a second bacillus as growing slowly upon 
gelatine, but this he does not consider to be so important as 
the more rapidly growing one. 

Young rabbits and guinea-pigs are the animals with 
which most experiments have been made. It has been found 
that rats and mice enjoy almost perfect immunity from 
the disease, a fact which has recently been utilized by 
Behring in connection with the production of an immunity 
against diphtheria in rabbits and guinea-pigs. 

We shall have to wait for further light on these points, 
but from what we have already seen, young rabbits, guinea- 
pigs, and young dogs, may undouitedly contract diphtheria, 
or something very similar to that disease ; both local and 
toxic symptoms resulting from the introduction of the 
poisonous material. It must be borne in mind that there 
are usually several kinds of bacteria present, that the compli- 

blPHfHERIA. 305 

Cations of the disease are numerous, and that it undoubtedly 
.occurs as a complication in other diseases. But when all this 
is taken into consideration the fact must still be accepted 
that careful clinical observation and experimental investi- 
gation have been made by many thorough workers, and that 
these jvorkers have assigned to a special bacillus the power 
of giving rise to at least one form of diphtheria. It is 
possible that the streptococcus may play an important part 
in certain cases of diphtheria, but this has not yet been 
actually proved ; whikt the evidence in favour of the specific 
infective Klebs-LofHer bacillus is now almost overwhelming. 

As regards the streptococci that are found in this disease, it appears that 
these organisms so fully described by Klebs, Forniad, and Prudden and 
Northrup, and later by Loffler and Babes, when inoculated give rise to 
local inflammation, and even to inflammation of joints, &c. ; in no case, 
however, do they appear to give rise to the formation of a false or a fibrinous 
membrane. No doubt they play a part in the preparation of the tissues 
for the diphtheria by weakening them so as to enable them to ofler less 
resistance to the action of the specific organism. These streptococci 
may actually make their way into distant organs of the body, and it 
has been found possible to make pure cultivations of them from such 
organs. These, then, differ very markedly, as regards their distribution in 
the body, from the diphtheria bacillus, which grows only at the point of 
inoculation, manufactures all the poison in that position, the poison only 
being carried into the body ; the bacilli remaining in situ, multiply 
during the advance of the disease, and degenerate as soon as the tissues 
begin to obtain the upper hand, which they do in all cases where recovery 
occurs, and even in some cases where the patients afterwards die from the 
effects of the absorption of the specific poison. 

The diphtheria bacillus, having been obtained pure, was 
naturally seized upon by LofBer, then by Roux and Yersin, 
and, lastly, by Brieger and Fraenkel for their experiments on 
toxalbumens ; the way having been paved somewhat by 
Hankin's discovery of albumoses in certain anthrax culti- 
vations] ' '•'■' 

■ The diphtheritic poison is always ' inost active when alka- 
line ; during the acid' period already mentioned, the toxic 
power is very considerably diminished. Moreover, if ati 
acid be added to a virulent alkaline filtered liquid, its 
poisonous activity is immediately diminished ; but, curiously 
enough, this property is immediately regained when thfe 
fluid is again neutralized by the addition of a fixed alkali. 
So virulent is the alkahne liquid that one-fifth of a cc. of 
the filtered fluid, from a cultivation of the diphtheria bacillus 


3o6 feACtERlA. 

that has been allowed to grow for forty-two days, proves 
fatal to a guinea-pig in about thirty hours. Larger doses, 
from 4 to 20 cc. injected into dogs of various sizes kills 
them in from fourteen to twenty-six hours. In doses of 
2 cc. it proves fatal in four to six days. In all cases the 
symptoms are those of more or less acute poisoning, re- 
sembling septic poisoning in some respects and phosphorus 
or metallic poisoning in others. A dose of less than i cc. 
of the filtered liquid injected into a dog of middle size causes 
a temporary paralysis, very similar to the post-diphtheritic 
paralysis of the human subject. It is a curious feature that 
when paralysis occurs in a rabbit, death invariably ensues ; 
but in both the pigeon and the dog, especially in the latter, 
recovery may frequently follow this condition just as in the 
case of the human being. Sheep are susceptible to the 
action of diphtheritic poison, but rats and mice are unaffected 
by it. The effects on other animals have been already 

It is always a difficult matter to determine what is the 
nature of an organic poison. In the first place it is produced 
in such small quantities that it is difficult to obtain 
sufficient to determine, even by chemical analysis, its exact 
nature. Further, it is so unstable that it may become 
completely altered by the various reagents that have 
to be used in separating it out from the mixture in 
which it occurs. A rise of temperature beyond a certain 
point is fatal to its activity, and it undergoes various oxida- 
tions under the least provocation. Roux and Yersin consider 
that this special poison has certain features in which it 
resembles the diastases. Thus, when heated in sealed 
tubes over a water bath to 58° C. for a couple of hours, 
the toxic activity is diminished at least seven-eighths of its 
original power ; whilst very large doses of the filtered poison 
that has been heated to 100° C. may be introduced into the 
veins of a rabbit, or under the skin, without producing any 
immediate effect, although symptoms are produced later 
which can only be due to the action of this material as a 
modified diphtheritic poison. Like diastase, the diphtheritic 
poison is rapidly modified by sunlight in presence of air, but 
if air be excluded the diminution in toxic activity brought 
about by exposure to sunlight is comparatively slight. 
On evaporating a filtered diphtheritic bacillus culture in 


vacuo over sulphuric acid at a temperature of 25° C, a sub- 
stance is left which is soluble in water, and possesses marked 
toxic properties. It is insoluble in strong alcohol, and may 
be precipitated by it from a watery solution in greyish white 
flakes. It passes slowly through a dialyzing membrane. 
The addition of lime water and a solution of phosphoric 
acid to the filtered culture liquid causes an entangling 
precipitation of the poison, phosphate of lime appearing to 
hold it more tenaciously than any other substance. The 
filtered fluid thus treated loses its toxicity, whilst the gela- 
tinous precipitate inoculated into an animal kills with the 
utmost certainty, though perhaps on account of the slightl}^ 
insoluble nature of the substance formed, somewhat more 
slowly. To form some idea of the virulence of the poison 
produced by these diphtheritic organisms, Roux and Yersin's 
calculations that I cc. of the active liquid evaporated 
in vacuo leaves I centigramme of dried residue, may be 
accepted. Deducting from this the weight of the ash and 
the portion soluble in alcohol which has no toxic action, 
there remain four-tenths of a milligramme of organic 
material, of which only a small proportion can be diph- 
theritic poison ; even this quantity, however, is sufficient to 
kill eight guinea-pigs, two rabbits, or one medium-sized dog. 
If the latter does not succumb to the poison it remains ill 
for some time. Like snake-bite poison, however (which 
Waddell has shown to be weakened on being exposed to 
peptic digestion, a change that is ascribed to the breaking 
down of the albun;ose), it may be taken into the stomach 
in much larger quantities without giving rise to any very 
serious effect. This poison, when injected into the veins 
or into the subcutaneous tissue, appears to act specially 
on the walls of the blood vessels, giving rise to vascular 
dilatations, minute haemorrhages, and the small oedematous 
patches so characteristic of certain forms of the disease. 
It can scarcely be too strongly insisted on that the activity of 
a poison formed by a micro-organism is not at all the same 
thing as virulence, ' which must be defined, according to 
Roux and Yersin, as the power that a pathogenic organism 
possesses of continuing to live and carry on its functions in 
the tissues of the animal or human host. For example, one 
might take a young culture of the diphtheria bacillus in which 
the bacilli are vigorous, but in which the quantity of poison 



developed is as yet small ; inoculating this into an animal it 
would be found that death would take place at the end of a 
certain period, and that, on examination at the point of 
inoculation, numerous bacilli, evidently the result of vege- 
tative growth of the micro-organism within the tissues at 
this point, might be demonstrated ; whilst on the other hand, 
if an old cultivation (in which the organisms are weak, and 
in which many involution forms are present, but in which 
there is a large quantity of poison which has been developed 
by the micro-organisms during their period of activity, and 
which from standing has become diffused into the liquid) be 
inoculated, death will be produced very rapidly, but no 
organisms can be found at the seat of inoculation ; there is 
set up, in fact, a true toxic condition. If the residues left on 
the filter from the above cultures were inoculated, it would be 
found that in the case of the young culture, death of the 
animal would take place at very much the same period as 
when the unfiltered culture was inoculated ; whilst in the 
case of the old culture the period at which death takes place 
is very much delayed ; in the one case, the organisms 
are active, although deprived of the poison which they form ; 
they can live in the tissues, and can produce fresh poison ; 
whilst the older organisms and involution forms, no longer 
able to develop in the tissues, and deprived by the filtration of 
the poison they produced whilst they were active, sometimes 
do not cause the animal to succumb even at a late date. 

This virulence, then, is associated with the power of a microbe to develop 
in the body of a living animal, a power which may be considerably increased 
by passage of the organism through a series of suceptible animals, the 
bacillus acquiring a more and more parasitic habit in each successive host. 
■Researches on micro-organisms are of no value to medicine unless they 
throw light directly or indirectly on the cause of disease, and so enable 
the physician to combat its advance. At first sight it would seem that in 
the case of the diphtheria bacillus there is, on account of the extreme activity 
of the poison, little hope of rendering the tissues of an animal resistant to 
its action, as even very minute doses produce marked poisonous effects. On 
the other hand, however, we have, from the nature and position of the 
development of the poison, indications as to treatment and also as to 
prevention of the disease. 

The indications as to prevention are of course similar to 
those for other micro-organismal diseases ; if we know the 
natural history of the diphtheria bacillus, we know at what 
poiiit it is most vulnerable, the conditions favourable for its 


development can be removed, and unfavourable conditions 
substituted ; whilst, as regards treatment, it is evident that, 
because of the energetic toxic action of the material formed 
by the organisms, diphtheria should be attacked as early as 
possible. If sufficient time be allowed to the bacilliis to 
form a large dose of the poison, it is useless to remove the 
false membranes, as, though the bacilli may be then destroyed, 
sufficient poison may have passed into the system to cause 
the death of the patient, " for in diphtheria, contrary to what 
occurs in most other infective maladies, the infection is not 
produced by the invasion of the tissues by a microbe, but 
by the difiusion through the organism of a toxic substance 
prepared on the surface of a mucous membrane altogether 
outside the body, so to speak." 

The bearing of recent researches on the prevention of 
the spread of an outbreak of diphtheria can only be fully 
understood when some of the facts that they brought to 
light are enumerated. It was found, for instance, that the 
presence of the diphtheria bacillus in the mouth is not 
necessarily followed at once by the appearance of the diph- 
theritic membrane, and it appears that these bacilli can exert 
little or no injurious eflfect where the mucous lining of the 
throat, larynx, &c., remains sound and unaffected by minor 
diseases. When once, however, we have such conditions as 
inflamed tonsils or inflammation and ulceration of the mucous 
membrane, the diphtheria bacilli find a soil ready prepared 
for their reception, and t5rpical diphtheritic symptoms are the 
result. That such ulcerated sore throats, inflammation of the 
tonsils, and similar conditions usually precede outbreaks of 
diphtheria, has for long been a well recognized clinical fact ; 
these experiments give the explanation of it, whilst they also 
afford indications as to the mode of treatment. Antiseptic 
throat washes, not merely gargles, plenty of fresh air, and good 
nourishing food, are what are required. Kill the germs as 
far as possible by means of the antiseptics, and strengthen 
the tissue cells by plenty of oxygen, and by promoting the 
excretion of effete products, by food and exercise, so that the 
cells shall be able to form their protective products and shall 
also be able to play their part as phagocytes when called 
upon to do so. Another important point to be borne in 
mind is that the disappearance of the bacilli from the mouth 
is not simultaneous with the removal of the false membrane, 


and Roux and Yersin have found that the specific bacterium 
may persist in the mouth for several days (in one case four- 
teen days) after all traces of the membrane have disappeared, 
and they give the good practical advice that diphtheritic 
patients who are becoming convalescent should not be 
allowed to associate with their school-fellows, play-mates or 
families, for at least a fortnight after the membrane has 
disappeared ; and that it is quite as important to wash out 
the throat freely three or four times a day with disinfecting 
lotions as that the clothes and bed linen should be 
thoroughly disinfected. As regards the tenacity of life 
exhibited by these bacilli, it is found that at the ordinary 
temperature of the room these organisms retain their 
vitality for a period of at least six months, and pro- 
bably considerably longer. As the temperature rises this 
period is gradually diminished, for we find that at 33° C. 
the organisms succumb in about five months ; whilst at 
39° C. they are are found to be no longer capable of living 
and of multiplying when introduced into solidified blood 
serum or glycerine-agar. When deprived of air and pro- 
tected from the light, even when kept at the ordinary 
temperature, they may continue capable of germinating, 
when introduced on to a suitable soil, for a period of 
thirteen months. If they are dried and are kept at the 
temperature of the room, they are killed in four months, at a 
temperature of 33° C. they are killed in three months, and 
at a temperature of 45° C. in four days. If a fragment of 
the false membrane containing bacilli be removed, wrapped 
in sterilized paper, or linen, and be carefully protected from 
the action of light, cultivations may be made from it at any 
time during a period of five months. If, however, instead of 
keeping it dry and in the dark, fragments of these mem- 
branes are exposed to the light and moistened and desiccated 
alternately, the virus is destroyed much more rapidly. From 
all this, and from the fact that the bacillus is destroyed by 
moist heat at 58° C, it is evident that by far the best method 
of disinfecting clothes, the floor, the walls, and furniture, is 
by the use of a liberal supply of boiling water ; for although 
a temperature of 98° C. (dry), continued for an hour is 
necessary to destroy the vitality of the bacillus, moist heat 
at a very much lower degree (acting only for a minute 
or two, according to the temperature) is sufficient to dis- 


infect everything on which it is allowed to act. In the case 
of the cholera bacillus we have already pointed out that 
under certain conditions it is capable of producing a much 
more violent form of disease than in others. 

Rbux and Yersin have been able to demonstrate that the virulence of the 
bacillus of diphtheria undergoes marked modifications even during the 
progress of an attack of diphtheria in the same individual, and they believe 
that the condition of the patient is modified not only by the alterations in 
the number of the bacilli, but also by their virulence at different stages. 
They find, for example, that in the early stages of the disease (except in 
very rare cases) the number of bacilli is comparatively small, but that as 
the disease advances the number of virulent bacilli present also increases 
rapidly, this being tested both by microscopic examination and by cultiva- 
tion and inoculation experiments ; whilst, on the other hand, as the case 
approaches cure the bacilli that can be isolated are not only fewer in 
number, but those that are cultivated are not nearly so active, for when 
inoculated into animals they produce neither such marked constitutional 
symptoms nor such severe local reactions. It is indeed believed that 
the virulent and non-virulent bacilli represent a difference in degree of 
virulence only, and not a morphological or specific difference, that the 
difference is one of degree and not one of kind, and that the pseudo- 
diphtheritic bacillus described by Loffler and Hoffman is really only the 
organism undergoing a kind of saprophytic phase which is interpolated in 
the life of the parasitic bacillus. 

Roux and Yersin obtained an imperfectly attenuated virus first by 
keeping the dried membrane for a considerable time, when they found 
that cultivations from them of bacilli, in which were present all the typical 
appearances and morphological characteristics, when inoculated into 
animals had lost their virulence. They found that they were able to 
diminish the virulence of the diphtheritic organisms growing in broth 
by passing currents of air at 39.5° C. through this medium, and that if 
the process was continued too long the bacilli were completely deprived 
of life. It would appear that this was simply an interference with the 
vitality of the organism which was deprived of one function after another 
until it was killed altogether. They found it impossible, however, by 
these methods to graduate the attenuation, and although they proved 
that the virulent bacillus alone could elaborate the toxic material, and then 
only under favourable conditions, the virulence became modified as the 
conditions were altered, the activity of the toxine being also modified ; 
these conditions could not be controlled except in a very rough and in- 
adequate fashion. 

Recently Fraenkel has found that by heating cultures of 
the diphtheria bacillus to a temperature of 65° or 70° C. and 
injecting from 10 to 20 cc. of such cultures into guinea-pigs, 
after an interval of fourteen days subcutaneous injections of 
even the most virulent diphtheria poison had no effect. If 
however, the animals were again injected within the 
prescribed period of fourteen days they succumbed to the 


diphtheria poison. On the other hand, the diphtheritic virus 
applied to an abraded mucous membrane even after fourteen 
days was capable of producing typical local symptoms. These 
points, if confirmed, indicate that the immunity against 
diphtheria may not be so easily acquired as in some other 
diseases, or, if acquired, it must be through the application 
of methods different from those hitherto described. 

Another feature that is brought into special prominence 
by the recent researches on diphtheria is, that the attenuated 
diphtheria bacillus requires the fulfilment of certain con- 
ditions before it can again acquire the virulent form, one of 
these being that it shall be allowed to grow on the surface of 
the fauces, or outside the body altogether, in the presence 
of certain organisms, such as the streptococci found in 
erysipelas, or those streptococci that occur in the throat 
affections of scarlet fever, measles, and similar diseases. It 
is quite possible that other organisms have the same effect, 
and that the attenuated diphtheria bacillus growing outside 
the body may become so virulent that it is capable of pro- 
ducing a very grave form of diphtheria, but from what 
occurs in outbreaks of diphtheria — in which the first cases, as 
a rule, are mild, successive cases becoming gradually tnore 
and more severe until an extremely fatal form of diphtheria 
attacks susceptible individuals — it would appear that the 
growth on mucous surfaces of this bacillus, along with these 
streptococci, is specially favourable to the development of the 
virulent form of the organism. 

These experiments exemplify in a most remarkable manner the use that 
bacteriological investigations have been to medicine, and Roux and Yersin 
sum up the practical outcome of their researches as follows : — " The best 
method of arresting the spread of diphtheria is to recognize the disease 
as early as possible ; consequently a precise diagnosis should be made by 
microscopic examination of the false membranes, and this should be con- 
firmed by cultivations on blood serum." As the former takes only a few 
minutes, and as the latter gives results in twenty-four hours, both these 
methods are available in private practice or where patients can be sent to 
an observation ward. 

" Active diphtheritic virus can remain in the mouth for a long time after 
the malady is cured. Consequently diphtheritic patients should only be 
allowed to resume their ordinary mode of life when they are no longer 
bearers of the bacillus. 

" Diphtheritic virus retains its virulence for a long time when kept in a 
dried state. It is therefore necessary to disinfect in a steam sterilizing 
apparatus the linen and all articles that have been in contact with diphtheri- 
tic patients. 


" The attenuated virus of diphtheria is widely distributed and it readily 
regains its virulence. It is therefore necessary at the very commencement 
of simple forms of throat disease, and of those associated with measles 
and scarlatina, to practice careful and frequent swabbing of the throat with 


Works that may be consulted : 
Babes. — Virch. Arch., Bd. cxix., Heft. 3, p. 460, 1890. 
Behring and Kitasato. — Deutsche. Med. Woch, Bd. xvi., 

No. 49, p. 1 113, Dec, 1890. 
Brieger and Fraenkel. — Berlin Klin. Woch., Bd. xxvii., 

No. II, p. 241, and No. 49, p. 1133, i8qo. 
Chantemesse and Widal. — Semaine Med., May 14, and 

Bull, de I'Acad. de Med., June 5, 1890. 
Gamaleia. — Annal. de I'Institut Pasteur, p. 609, 1889. 
Grancher. — Bull, de I'Acad. de Med. 1890. 
Klebs. — Beitrage zur Kenntniss der pathogenen Schizomy- 

ceten ; Archv. f. exp. Path. u. Pharm, Bd. iv., Heft 

I, 2, p. 107, and Heft. 3, p. 207, 1875 ; Verhand. des 

Congresses f. inn. Med., 11., Abtheilung, Wiesbaden, p 

143, 1883 
Klein. — Centralbl. f. Bakt. u. Parasitenk, Bd. vii.. No. 2 5, 1 890, 
KoLiSKO and Paltauf. — Centralbl. f. Bact. u Parasitenk 

Bd. v.. No. 22, p. 735, 1889. 
Loffler. — Mittheil. a. d. k. Gesundheitsatnte, Bd. 11., p 

421, 1884 ; Centralbl. f. Bakt. u. Parasitenk, Bd. 11., p 

105, 1887 ; Deutsch. Med. Woch., Bd. xvi., No. 5, p, 

81, and No. 6, p. 108, 1890. 
Oertal. — Deutsche. Arch. f. Klin. Med., Bd. viii., Heft. 3 

4, p. 242, 1871. 
Prudden and Northrup. — Internal. Journ. of Med. Sci 

Vol. xcvii., p. 562, 1889. 
Roux AND Yersin. — Annal. de I'Institut Pasteur, t. 11., No 

12, p. 629, 1888 ; t. III., No. 6, p. 273, 1889 ; t. iv., No 

7, p. 38s, 1890. 
Ruffer. — Brit. Meif.Jourit., p. 202, July 26, 1890. 
Talamon. — Progres Medical, pp. 112, 498, 1881. 
Waddell. — Scien. Memoirs by Med. Officers of the Army 

in India, Part iv., p. 47, 1889. 
Wood and Formad. — Med. Times and Gazette, Phil., Dec 

4, 1880 ; Bull. Nat., Bd., Health, No. 17, 1882. 
Zarniko. — Centralbl. f. Bakt. u. Parasitenk, Bd. vi.. No. 6, 

p. 153, No. 7, p. 177, and Nos. 8, 9, p. 224, 1889. 


Pasteur's Experiments — Attempts to Demonstrate Micro-organisms — 
Hydrophobia does not arise Spontaneously — Disease not Confined to 
Man or Canine Animals — Pasteur's Early Experiments with Saliva 
Unsuccessful — Successful Experiments — Symptoms of the Disease — 
Position in which Virulent Material is Found — Different Animals 
Differently Affected — Alteration of Virulence — Method of Preparing 
Inoculation Material — Description of Experiments — Joseph Meister 
the First Patient Treated — Method of Treatment now Adopted — 
Treatment of Wolf Bites — The Time Factor in the Disease — Rationale 
of Inoculation Method — Filtered Virus Non- Virulent — Method of 
Inoculation — Description of Departments, Apparatus and Methods of 
Working in the Pasteur Institute. 

By some it may be objected that in a work on micro-organ- 
isms the subject of hydrophobia can scarcely be legitimately 
considered. When it is remembered, however, that the 
methods adopted and the principles involved in the study of 
the production of this disease are in many respects the same 
as those concerned in other diseases in which bacteria 
undoubtedly play the part of causal agents, and when, too, 
it is remembered that Pasteur's researches on the production 
of immunity against the attack of this disease were carried 
on under the full conviction that in hydrophobia the excit- 
ing cause is a poison, the most probable source of which is a 
vegetable organism, one has, I think, ample excuse for the 
introduction of this subject. When further we take into 
consideration the extreme interest of the subject, both from 
a scientific and from a practical point of view, any remaining 
objection should at once fall to the ground. To treat the 
subject in a purely historical or chronological order, it would 
be necessary, in the first instance, to describe Pasteur's experi- 
ments ; but in order to clear the ground it may be well to 
give a short resume of the attempts that have been made 
to find, cultivate, and inoculate a specific organism that might 
be causally associated with rabies. Pasteur, Chamberland, 


and Roux all made most careful search for organisms in the 
various tissues of animals affected by hydrophobia, and, 
although they at first imagined that they had been successful, 
they ultimately came to the conclusion that the small round 
micrococcus-like bodies that they found were not associated 
with the disease or had only an indirect relation to it. In 
1884 Gibier was able to demonstrate in the medulla of 
animals suffering from hydrophobia small rounded refractile 
bodies, which looked like micrococci aggregated into small 
masses. He demonstrated their presence by mashing down 
the medulla in sterilized distilled water, and then adding 
two or three times the quantity of water, and examining 
some of the opaque fluid thus obtained, under the microscope. 
Those organisms which remained in fragments of the cere- 
bral substance were perfectly motionless, whilst those that 
were free in the fluid exhibited a certain motility. No such 
bodies could be obtained, by a similar method of treatment, 
from healthy brains. Although these bodies resembled 
micro-organisms in many respects, they could be only faintly 
tinged with the aniline colours, and it was never found 
possible to make cultivations into any nutrient media with 
which experiments were made. In 1885 Fol brought before 
the French Academy of Sciences some observations made on 
sections of the cord taken from rabid animals prepared by 
Weigert's haematoxyline method.' 

He found in specimens so prepared, small granules re- 
sembling micrococci, not only in the lymph spaces of the 
neuroglia but even between the axis cylinder and its medul- 
lary sheath, the cavities in some cases being of very consi- 
derable size, and containing these small granules in large 
masses. Each granule is perfectly distinct and takes on a 
deep violet stain, they are about .2/* in diameter, are some- 
times arranged as diplococci, but seldom or never in chains 
of any considerable length. Fol believed that he was 
able to cultivate these organisms, but only directly from 
the cord itself, and he describes a slight cloudiness of the 
medium (broth) as making its appearance after the intro- 

' Weigert's method. Cords hardened in bichromate of potash and then 
transferred to sulphate or acetate of copper solution. Sections coloured with 
solution of I part haematoxyline crystals, 90 of water, and 10 parts of 
alcohol, then decolorized by a solution of 2.5 of ferrocyanide of potassium, 
2 parts of borax, and too parts of water. 


duction of small fragments of the spinal cord. This cloud 
is thrown down at the end of the fourth day, and the pre- 
cipitate when inoculated into a healthy animal produces a 
modified form of hydrophobia, modified, however, only in that 
there is a longer period of incubation than in the ordinary 
disease. He found on treating a thin film of this fluid, dried 
on a cover glass, as he had treated the sections of the cord, 
that small groups of micrococci might be demonstrated, and 
he concluded that he had cultivated the specific organism. 

Cornil and Babes appear to doubt the accuracy of these 
observations ; they have never been able to make out any 
other granules than those which are invariably met with in 
sections of healthy nerve tissues that have been stained by the 
Weigert method. Babes, however, claims that he has been 
able to demonstrate in the brain and in the cord of rabid 
animals groups of rounded micro-organisms, with a diameter 
three to four times as great as that of the organism described 
by Fol ; these are stained in situ by Loffler's alkaline 
methylene blue solution, which gives them a peculiar rose 

They may be cultivated on blood serum at a temperature 
of 37° C, on agar-agar, and upon nutrient gelatine made with 
an extract of the brain of a rabbit. In cultivations the 
organism grows slowly, appearing as a faint grey spot at the 
end of several days. The growths spread best in the deeper 
part of the gelatine. A pure culture of the second or even 
of the third generation when inoculated into animals occa- 
sionally produces hydrophobia, but in most cases the cul- 
tures have no pathogenic properties, and it must therefore 
be concluded that _the microbe has either lost its virulence, 
or that it is not the actual cause of the disease. From what 
has been learned of the causation of other infective diseases 
it is quite conceivable that there exists in addition to this 
micrococcus some hitherto undemonstrable element, which 
along with the organism is capable of producing the disease. 
For example, in preparations of the brain and of the cord, 
another microbe is also occasionally met with. This second 
special micrococcus can only be coloured by using Gram's 
staining method, and by leaving the sections for a consider- 
able length of time in the staining reagent. It affects speci- 
ally the surface of the brain, and is there found in cells 
which " frequently also contain fatty and proteid granules," 


These latter correspond to some of the cocci described by 

From Babes' description of the larger organism growing in the deeper 
parts of the gelatine, and also in vacuo, it is evident that the organism is 
anaerobic ; other organisms (micrococci) grow on the surface in the form of 
grey, yellowish, dry streaks, when they are in the form of large cocci arranged 
in chains, or as curved spindle-shaped bacilli. In all these forms the 
micrococci or rounded points within the bacilli are stained pinkish with 
Loffler's methylene blue ; whilst the intermediate substance and the bodies 
of the curved bacilli take on a blue tinge. Similarly, spindte-shaped curved 
organisms have been found in the cerebral substance of rabbits and guinea- 
pigs suffering from rabies ; whilst curved thick motile bacilli have been 
found in the blood of rabbits during the stage of fever that precedes the 
regular nervous symptoms of rabies ; the inoculation of such blood, how- 
ever, seldom produces rabies ; in fact, blood from almost any rabid animal 
produces few or none of the symptoms of ordinary rabies. Ptomaines 
have been described as present in the nerve centres taken from rabid 
animals, and it is claimed that with the separated poisons, symptoms 
analagous to those of true hydrophobia have been produced, but the experi- 
ments, although probably accurate, are as yet too few in number to allow 
of their being very seriously discussed. 

It is, however, doubtful whether the real causal agent has yet been 
observed. It appears to be quite as probable that one of the lower animal 
protozoa, coccidia, psorosperms or the like, may be the real cause of the 
disease as that a bacterium" stands in this relation to hydrophobia. In 
the same way it has been suggested that the acute exanthemata from 
which organisms have not as yet been in most cases successfully cultivated 
may have a similai causa causans. 

It was very early determined that hydrophobia or rabies 
never arises spontaneously ; the actual date at which the 
implantation of the disease took place could easily be traced, 
as it was found that in the human subject the outbreak of 
the disease always bore a definite relation to some such 
injury as the bite of a rabid dog, wolf, or cat, or it might be, 
to the licking of an abraded surface by an apparently 
healthy animal, especially a dog which afterwards was known 
to develop symptoms of hydrophobia. 

This disease is not confined to man and the animals men- 
tioned. It has been observed that rabbits, deer, guinea-pigs, 
and even horses may be similarly affected. Although the 
disease had been described most carefully from its clinical 
point of view, and although the saliva of a rabid animal was 
siipposed to contain a specific infective material which was 
probably the cause of rabies, Hydrophobia or Rage, it was 
not until 1880 that Pasteur set himself to study the virus of 
this terrible disease. His first experiments were made with 

3l8 teACTERlA. 

the saliva from a child in whom the disease was developing 
as the result of the bite of a mad dog. He took a httle of 
the saliva from this child and introduced it into a small 
pocket under the skin of a healthy rabbit ; he found the 
animal dead at the end of a couple of days. Taking some 
of the_ saliva of this animal, he treated another rabbit 
in a similar manner with a like result, but he also dis- 
covered that the blood of the first rabbit when introduced 
under the skin of another rabbit also produced the disease 
in a most virulent form, so virulent indeed that the old 
question of septic versus other specific infective organisms 
again cropped up, and it was suggested that the animals 
had died of septic poisoning due to the presence of ordinary 
septic organisms in the saliva, and therefore in the blood 
of the animal that had first been inoculated with the 
saliva. The fact, also, that the symptoms of hydrophobia in 
many cases resemble so markedly those of another form of 
blood poisoning — tetanus or lockjaw — and the extremely 
rapid course that it ran in the animals inoculated, made it 
a matter of extreme difficulty to determine the exact nature 
of the symptoms, and rendered it impossible for Pasteur to 
say whether he was dealing with hydrophobia or with some 
other form of specific infective poisoning. He found, how- 
ever, that it was specially in the later stages of the disease 
that hydrophobic symptoms became tetanic in character. 
After the bite there may be no symptoms at all for a month 
or six weeks, or even in some cases for twelve months, during 
which time the poison lies latent in the -system, or though 
active, gives rise to no symptoms. This period is known, 
technically, as the period of incubation. At the end of this 
incubation period the wound first of all becomes slightly 
uncomfortable ; there is itching, and the heat becomes almost 
intolerable, especially as this is usually accompanied by a 
sharp stinging pain ; the patient becomes feverish and very 
thirsty ; the face is pallid and has a peculiar anxious expres- 
sion, the muscles of the face being drawn and restless, and 
gradually this expression amounts to one of actual terror or 
horror. On the second or third day the patient becomes 
much more excited, is restless in every sense of the word, 
and a very peculiar feature is that he has a characteristic 
habit of giving a suspicious side glance as though con- 
stantly looking out for some hidden danger ; then as the 

ttVfiROPHOBIA. 319 

fever advances a rambling delirium supervenes ; the thirst 
increases, but along with this there is great difficulty in 
swallowing — especially fluids — and after making one or 
two attempts to swallow, the very sight of water suggests 
such horrors that thirsty as the patient is, he is anxious to 
avoid it. Then muscular tremors are noted, these become 
more and more marked and violent spasms are easily 
stimulated as in tetanus. A sharp sound, a touch, a bright 
light, or even a breath of air, may give rise to violent muscular 
convulsions, and eventually the patient is slowly suffocated 
as in tetanus. One can well imagine that to a man of 
Pasteur's temperament and mode of thought such a terrible 
disease as that, the symptoms of which I have just sketched, 
would just be the subject that would fascinate him. Here was 
a problem surrounded by difficulty but of such a character 
that the very difficulties invited success ; whilst if success 
were attained he would have the satisfaction of feeling that 
he had done something more to alleviate human suffering — 
more even than he had already accomplished ; hence the 
preliminary experiments we have already mentioned. In 
order to convince himself that the disease which he had 
produced in the rabbit was really hydrophobia he must 
obtain the poison in a perfectly pure condition ; as he had 
already found that Galtier's experiments as regards the blood 
of rabid animals were incorrect, he determined to repeat the 
same experiments with fluid taken from the cavities of the 
brain and spinal cord ; here again he was successful, for 
although Galtier had been unable to produce the disease 
with such fluid, Pasteur found that by taking a few drops of 
the cerebro-spinal fluid and introducing it under the outer 
membrane of the brain (chloroforming a rabbit and removing 
a small round disc of bone from the skull cap, then replacing 
the bone and stitching up the wound, which healed almost 
immediately) hydrophobic symptoms were rapidly developed. 
This fluid from the central nervous system of a hydro- 
phobic rabbit contained no septic organisms, and as the 
disease was rather more slowly developed after the inocu- 
lation of such virus (although it could be induced with 
absolute certainty) than when saliva was used, he discontinued 
the use of the latter, the inoculations being now made from 
animal to animal and always with the cerebro-spinal fluid. 
Fragments of the brain and spinal cord introduced under the 

326 BACTERtA. 

dura mater (the outer skin or covering of the brain) produce 
similar effects. Nerves were also found to contain the viru 
but the saliva, as we have seen, and the salivary glam 
introduced in the above manner produced a much moi 
virulent and rapid form of the disease than the other tissue 
and fluids mentioned : quite as virulent a form, in fact, i 
when the animal was actually bitten by a rabid animal. 

Finding that these tissues and fluids taken from a rabi 
animal varied in their virulence, and knowing that in th 
case of anthrax virus the virulence may be diminished c 
increased by inoculating into an animal of another specie: 
he made another series of experiments, as a result of whic 
he found, that although virus taken from similar position 
say, the cerebro-spinal fluid, had always the same action i 
the same species, when the fluid was taken from an anim; 
of a different species it was weaker or stronger as the ca: 
might be. Thus in a dog the virus is of constant strengt! 
and inoculations made from dog to dog kill the animal wit 
the same incubation period, the same symptoms, and pract 
cally in the same time. When inoculated from the dog i 
the monkey, however, the virus becomes less virulent ; 
is said to be attenuated or weakened, the attenuation b 
coming more and more marked in successive inoculatioi 
from monkey to monkey ; the course of the dise^ becom 
longer and longer, until eventually there m^come a tin 
at which the virus, when introduced under the skin or inl 
the cranial cavity, is not sufficiently active to cause the deal 
of this species. If this attenuated fluid be now inoculate 
into a rabbit, a dog, or a guinea-pig, it still remains con 
paratively weak for a time, through successive inoculatioi 
on these animals — i.e., at first it does not kill, then it kill 
"but only after a considerable time ; but gradually tl 
virulence returns, until at length it reaches its original lev 
of malignancy ; whilst, if the successive inoculations ai 
made in rabbits with primary fluid from either the dog ( 
the monkey, the virulence may hecome so exalted that it 
considerably greater even than that of the virus taken froi 
the street dog, which at one time was supposed to be tl 
most virulent form except that of hydrophobic wolves, whic 
has always been known to be specially fatal ; the virulen( 
is doubled as the inoculation period is reduced to about or 


Having found, then, that the virus could be intensified or 
modified, and that different animals were affected in a 
diiferent degree by the same virus, Pasteur set himself to 
work out the question whether it was possible so to alter the 
resistance of an individual that a virulent hydrophobic 
material would have little or no eifect on the tissues. The 
only way in which this could be done appeared to be by the 
introduction of an attenuated virus into the animal that was 
to be rendered immune, as in the case of anthrax, and so to 
accustom the tissues to the presence of the specific poison, 
rendering them better able to resist a stronger poison ; he 
thought, in fact, that by successive inoculations of stronger 
and stronger poisons he would be able gradually to " accli- 
matize" the tissues to the presence of even the strongest 
virus, and so enable them to deal with it successfully, probably 
by converting it into innocuous proteid materials, so rendering 
it harmless to the delicate and highly organized cells of the 
nervous system. In his earlier experiments he obtained an 
attenuated virus by inoculating a monkey, from which he 
took material from the central nervous system with which 
to inoculate a series of rabbits ; each rabbit supplied a 
slightly more powerful virus with which to inoculate another 
one of the series. He thus obtained inoculation material of 
all degrees of virulence. With material from each rabbit 
in the series he inoculated twenty dogs, each one receiving 
a stronger and stronger dose each time it was inoculated. 
Out of the twenty dogs so treated only about three-quarters 
were protected against virulent hydrophobia ; but this for a 
first series of experiments was a most extraordinary success, 
and so satisfied and delighted Pasteur that he was encouraged 
to continue his research ; eventually the results he obtained 
were even more remarkable. 

Having observed that the cords of rabbits that had been 
dead for some time contained a less virulent poison than the 
cords of freshly-killed animals — this being.especially the case 
in dry weather — he adopted a method based on this observa- 
tion, by means of which he was able from the same cord to 
obtain inoculating materials of very different degrees of 
virulence, this varying according to the length of time that 
had intervened between the death of the animal and the use 
of its cord for protective injection. He proceeded as follows : 
Having sterilized a glass flask plugged with cotton wool by 



dry heat, he filled it to the depth of three-quarters of ar 
inch, or an inch with some hygroscopic material such as 
solid potassium hydrate ; it was then ready for use. 

A rabbit was previously inoculated in the following 
manner : The skin over the part of the skull covering th« 
brain is carefully saturated with a 5 per cent, solution of car- 
bolic acid. (This serves two purposes : first, it purifies the 
skin through which the knife is to pass, and, secondly, i1 
renders the skin and the tissues beneath perfectly insensible 
to pain, so that the rabbit will remain perfectly quiet while 
the operation goes on ; it does not apparently suiFer ever 
discomfort, and I have seen a rabbit going on eating whilst 
the operation was being performed. I have also seen the 
operations performed as in the Pasteur Institute, while the 
animal was under the influence of chloroform ; but I have 
never yet seen it done without either a local or a general 
anaesthetic being administered). An incision is made through 
the insensitive tissues so as to give either a cruciform incision 
or a semi-circular flap, the soft tissues are dissected from the 
bone, and then with a small tube with teeth at the end, and 
a sliding pin in the centre (a trephine), a little circular disc 
of bone is removed, as far as possible without injuring the 
external covering membrane of the brain. 

With a subcutaneous injection syringe, carefully purified 
by means of some chemical germicidal reagent, or heat, a very 
minute quantity of the cerebro-spinal fluid, taken from an 
animal that has succumbed to the disease, is then injected 
under the dura-mater (the membrane above mentioned), 
which is immediately beneath the bone of the skull. The 
disc of bone is then replaced ; the wound is closed by means 
of a couple of stitches ; a pad of cotton wadding, carefully 
purified by heat, is used to dry the skin as much as possible ; 
after which a little of the same cotton wadding is used as a 
dressing ; this dressing is kept in position by a free ap- 
plication of flexile collodion, the two together forming an 
air proof shield, through which no organisms from the 
external air can make their way to the wound, which, as 
a rule, heals up most perfectly in less than a couple oi 
days. The operation does not appear to afiect the animal 
so treated in the slightest, and until the seventh day it 
appears to be as lively as any of its companions ; it then 
gradually begins to lose the power of the muscles, first 


in the hind legs, then gradually in the muscles through^ 
out the body ; other nervous symptoms appear, the animal 
becomes unconscious and comatose, and about the tenth day 
after inoculation it dies. The cord is taken out as soon 
after death as possible, and great care is exercised to prevent 
organisms, septic, putrefactive, or any others, from finding 
their way to the surface of the cord, which as soon as re- 
moved is suspended by a sterilized silk thread in the flask, 
the air of which, having been rendered extremely dry by the 
potash, now absorbs a very large proportion of moisture 
from the cord, and prevents it from undergoing putrefactive 
change. Originally the cord was left in this flask from twenty- 
four hours to fifteen days, the material from the cord that had 
been left for fifteen days having almost or completely lost its 
virulence, the one day cord remaining nearly as virulent as 
a cord that had undergone no desiccation. 

On the 26th of October, 1885, Pasteur described this 
method to the French Academy of Sciences. He showed 
that by inoculating animals on ten successive days with 
fragments of different cords, each beaten up with twice its 
volume of sterilized bouillon, commencing with the weakest 
virus, and continuing until he had used an emulsion from 
the cord that had been exposed only two or three days to 
the dried air, and kept pretty constantly at a temperature of 
17° or 18° C, they were protected against hydrophobia, even 
when extremely virulent virus was afterwards injected sub- 
cutaneously, or into the membranes of the brain. Of fifty dogs 
so treated (no two exactly in the same way), every one was 
refractory to the disease in proportion to the theoretical 
degree of protection that had been given ; such protection 
lasting apparently for at least two years, and probably more. 

Having obtained such success with dogs the next step 
was to protect patients who had already been bitten by 
mad dogs or wolves. The first human being so inoculated 
against hydrophobia was a little boy, Joseph Meister, aged 
nine years, who, on the 4th of July, 1885, was bitten so 
severely on the arms and legs by a mad dog, that it was 
with difficulty the poor child could walk. He was at- 
tended to by a doctor who cauterized the worst of the 
wounds with carbolic acid, but not until twelve hours after 
the child had been bitten. As the dog was undoubtedly 
mad, and as there was little chance of the survival of the 


child in the ordinary course of events, Pasteur resolved, 
after consulting with Professors Vulpian and Grancher, who 
agreed to share the responsibility, to treat the boy as he had 
treated the dogs that he had already been successful in pro- 
tecting. During the following ten days he made thirteen 
injections : — 

2 on the 1st day with emulsions made from cords that had been exposed 
to the air in the Sask for 14 and 10 days respectively : 

2 on the 2nd day ,, ,, 1 1 and 9 days respectively 

I „ 3rd day „ „ 8 days 

I „ 4th day „ „ 7 days 

and so on until .the loth day, when he inoculated with the cord of a rabbit 
that had died on the same day, i.e., the cord in which the rabic virus still 
retained its full virulence. 

For every injection that was made into the child, a corre- 
sponding one was made into a test rabbit, and it was found 
that the five rabbits inoculated with the first five injecting 
materials, had no hydrophobia, whilst the other eight 
succumbed to the disease ; the period at which the animals 
succumbed being gradually shortened as the cords exposed 
to the dry air for the shorter times were inoculated. It 
was remarkable that although the later vaccines proved 
fatal to rabbits, in the patient, prepared by the previous 
inoculations, they did not produce the slightest discomfort, 
he never had the faintest symptom of hydrophobia, and 
now, five years later, we are told that the boy is still alive 
and well. Since that time an enormous number of patients 
have been inoculated, and it certainly appears from statistics, 
given monthly in the " Annales de I'Institut Pasteur," that 
the percentage of deaths after inoculation has been much 
lower than in those patients left without the anti-rabic 

Babes, in order to make the virus as constant as possible, 
finds that it is advisable to make a mixture of cords from three 
or four different days {i.e., cords that have been exposed to the 
drying process for different periods), and to inoculate at least 
twice a day, or more frequently in serious cases, such as 
those in which there are wounds about the face, or where 
the wounds are inflicted by a mad wolf; the period of 
treatment now also is longer, in addition to which much 



larger quantities of the protective material are used, especi- 
ally in severe cases. 

Take as an example of this method of treatment, one given by Cornil 
and Babes in their work on bacteria, that of a child severely bitten about 
the face, which only came under treatment four days after it had been 

On the 1st day it received injections of 2 grammes of emulsion, made up 
of cords that had been exposed 13, 12, 11, and 10 days respectively. 

On the 2nd day 2 grammes 
3rd day ,, 

4th day ij grammes 
5th day 

6th day 2 grammes 
7th day ,, 

8th day „ 

9th day ,, 

loth day i J grammes 
1 2th day 2 grammes 
13th day „ 

14th day „ 

15th day „ 

1 6th day I J grammes 
l8th day 2 grammes 
19th day ,, 

20th day ,, 

2ist, 22nd days. 2 
23rd, 24th days. ,, 
25th, 26th days. „ ,, 
On the nth and 17th 

,, 10, 9, 8, and 7 days 
7. 6, S, 4, days 

, , 4 and 3 days 

, , 3 and 2 days 

,, 8 and 7 days 

,, 7 ^"d 6 days 

, , 6 and 5 days 

, , S and 4 days 
4 and 3 days 

,, 8 and 7 days 

,, 7 ^^^ 6 days 

, , 6 and 5 days 

,, S and 4 days 

,, 4 and 3 days 

„ 8 days 

„ 7 days 

,, 6 days 

,, 5 days 
4 days 

„ 3 days 
days there was no treatment. 

At Bucharest, where wolf bites are of frequent occurrence, the treatment 
may last for more than a month, four and five injections being made on the 
first few days, and as much as 12 or 13 grammes of the emulsion being 
injected per diem ; the whole series of attenuations being gone through in 
mixtures of three each in three days. Then the same process is gone 
through with mixtures of two attenuations, and lastly, the emulsions from 
single cords throughout the whole series are injected. For instance, on the 
1st day there are injected 4 grammes of an emulsion, made from the cords 
of 13, 12, and II days; then 4 grammes from the 12, n, and 10 days; 
3 from the II, 10, and 9 days ; then 2 from the 10, 9. and 8 days ; the last 
injection on the 3rd day consisting of I gramme of the 3, 2, i days, or the 
strongest vifus ; then on the 4th day similar injections are made of the most 
virulent virus ; on the 5th day 16 grammes of the weaker virus from the 
I2th to 9th days are injected ; and on the 30th day 4 grammes of the strong 
virus (2 days) are injected. This treatment is modified for special cases, 
but this is an example of the treatment for very severe biles. 

Bujwid adopted a somewhat different process, he injected 2 grammes 
daily of the mixture of 12 and 10 day cords on the first day ; 8 and 7 day 
cords on the second day ; 6 and S cords on the third ; 4 and 3 on the 


fourth, and then again 12 and 10 cords on the fifth, and so on through a 
third series, the whole treatment lasting 14 or IJ days. ' . 

Cornil and Babes have collected some most interesting statistics, which 
we may here quote. In the Institut Pasteur in 1886, out of 2,682 cases 
treated, there was a mortality of 13.4 per 1,000 ; in 1887, in 1,778 cases, 
a mortality of 11. 2 per 1,000; in 1888 7.7'-per. 1,000; and in 1889 5.4 
per 1,000. In St. Petersburg, in 484 patients treated, the mortality was 
26.8 per 1, 000; in Odessa, in 1,135 treated, 1 7. 1 per 1,000; in Moscow, 
out of 107 treated, 34 per 1,000 ; but out of 500 inoculated with stronger 
virus, and for a longer period, the mortality was only 13 per 1,000. At 
Warsaw, of 297 people treated by the milder method, 80 per 1,000 suc- 
cumbed ; whilst of 370 inoculated by the intensive method, none succumbed 
to hydrophobia. At Charkow, of 233 treated, there was a mortality of 
38 per 1 ,000 ; at Turin, of 502 treated in cases where the dogs were un- 
doubtedly rabid, there was a mortality of 25 per 1,000; at Bucharest, out 
of 310 patients, a mortality of only 2.9 per 1,000 ; at Naples, of several 
hundreds treated, the mortality was only 15 per 1,000; and at Havannah, 
where there were 170 patients, only 6 succumbed. 

The factor of time between the bite and the commence- 
ment of the treatment plays a most important part, and it 
has been found that there is always the greatest success 
obtained in the cases of those patients who submit them- 
selves for treatment within two or three days of being bitten. 
One of the most convincing proofs of the efficacy of this 
inoculation that has been given, is that recorded by Babes. 
Thirteen men and thirty animals, cattle, horses, pigs, and dogs, 
he states, were attacked by rabid wolves ; of the thirteen men 
so attacked, twelve came to Bucharest for treatment, and all 
of them recovered except one whose head was fearfully torn 
and lacerated by the fangs of a wolf; the thirteenth man, 
who would not present himself for treatment, died of 
hydrophobia. A very significant fact was that every one of 
the thirty animals succumbed to typical hydrophobia. The 
patient who died succumbed ten days after the completion 
of a very intense and prolonged treatment (thirty-two days). 
The other patients were then subjected to a further treat- 
ment during six days of mixtures of two cords from the 
twelve days down to the one day ; and as we have seen they 
all recovered. 

It is interesting to note in connection with ' Galtier's 
early observations, which were at first supposed to be dis- 
proved by Pasteur, that they were confirmed by Nocard 
and Roux, and by Vestea and Zagari, who have proved 
that the injection into the blood of rabic virus does not 
always produce hydrophobia, and that in certain ruminants, 


such as the sheep and the goat, the Intravenous injection of 
rabic virus, although it does not produce hydrophobia, 
protects these animals against rabic infection. It is now 
generally acknowledged that when properly performed, the 
inoculation of even very large quantities of virus may be 
safely carried out, and as it is found that greater success 
is obtained where these larger quantities are injected we may 
look forward to still greater improvement in the treatment of 
this disease, and to even further diminished mortality. 

This process of inoculation in hydrophobia brings up a 
phase of the vaccination question that has not yet been fully 
developed but one that appears to be destined to cast an 
important light on some of the questions relating to im- 
munity. Pasteur's explanation of the results he obtained 
does not appear to be entirely satisfactory. I am inclined 
to think that the explanation advanced by Wood and myself, 
that the treatment consists essentially in causing the tissues 
to acquire a tolerance before the microbe has had time to 
develop, is more in accordance with facts. The tissue cells 
are acted upon by increasingly active virus, each step of 
which acclimatizes the cells for the next stronger virus, until 
at length when the virus formed by the micro-organisms 
introduced at the time of the bite comes to exert its action, 
the tissues have been so far altered or acclimatized that they 
can continue their work undisturbed in its presence ; and 
treating the micro-organisms themselves as foreign bodies, 
destroy them. When the cells are suddenly attacked by a 
strong dose of the poison of this virus they are so paralyzed 
that the micro-organisms can continue to carry on their 
poison -manufacturing process without let or hindrance, but 
when the cells are gradually, though rapidly, accustomed to 
the presence of the poison by the exhibition of constantly 
increasing doses they can carry on their scavenging work 
even in its presence, and the micro-organisms are destroyed, 
possibly even before they can exert their full poison manu- 
facturing powers. Some such explanation as this would 
account for the interference with the course of the disease 
even after the patient has been bitten. The micro-organism 
is localized, it takes some time to form its poisonous products, 
and whilst this is going on the whole of the nervous and other 
tissues are being gradually acclimatized by the direct applica- 
tion of small quantities of the poison artificially introduced. 


It is a most remarkable fact that although no micro- 
organisms can be found in the virus, filtration through the 
Pasteur filter keeps back the effective part of the virus, 
whilst heating to ioo° C, or even a prolonged heating to 
80° C, destroys the activity of the virus; further, an alcoholic 
extract of the emulsion does not contain any substance that 
will confer immunity, nor will it, when inoculated, produce, 
any symptoms of rabies. 

That the patients themselves have great faith in the 
treatment, we have ample evidence in the fact that so 
many present themselves for treatment. It was an ex- 
tremely interesting sight to see the members of the poly- 
glot crowd in the waiting-room brought in, one by one, 
for inoculation in the Pasteur Institute. As the patient's 
name was called out, one assistant standing at a table on 
which was arranged a row of little conical glasses, each 
covered with a paper cap, and containing an emulsion of a 
cord of a certain length of exposure, filled or partly filled 
a Pravaz syringe with emulsion from one of these glasses, 
according to the stage at which the treatment had arrived 
(determined by reference to the case book). He handed the 
syringe to the operating doctor, who, taking a fold of the 
skin (which had been previously washed and purified with 
carbolic acid, or some such antiseptic reagent), just above 
the crest of the ilium, a part very easily exposed from the 
arrangement of the attire of both males and females, inserted 
the point of the needle, injected about half a syringe full, 
withdrew the needle, diffused the fluid as far as possible by 
pressure, and the patient passed on. The syringe was 
handed back to the assistant, who carefully sterilized it by 
plunging it into hot water. The whole operation seemed to 
take only a few seconds. A continual stream kept passing 
from one room to another, each patient, as he went through, 
undergoing the same process of inoculation. Everything 
was done in the most orderly fashion, and one could not 
but feel that Pasteur, who was standing in the room whilst 
this was going on,, had every right to feel proud, not only of 
the splendid Institute in which he was working, but of the 
excellent work that was being carried on, both in the field 
of investigation and in the application for the benefit of 
suffering humanity of the results of the investigations. 
In France they manage some things better than we do, 


and, although France should not get all the credit of work 
towards which most European nations have contributed, 
through representatives of all classes, the grants from the 
Imperial treasury formed a basis on which to found the now 
celebrated Pasteur Institute, and to France and Pasteur 
much of the honour is due. The Pasteur Institute is a 
building set apart for the study of micro-biology, the most 
perfect of its kind in the world, and a short account of it 
cannot fail to prove interesting. For many of the details 
I have referred to the January number of " Annales de 
I'Institut Pasteur," 1889, as unfortunately, when I visited 
the laboratories, the place was not in full working order, 
but I saw enough to convince me that the spirit which 
animates the founder of the Institute pervades also those 
of his disciples who carry on the work he has begun. It 
covers an area of eleven thousand square metres in the 
Rue Dutot, and consists of two large blocks running parallel, 
one behind the other, united by a long corridor which runs 
from the main entrance in the front, connecting the two 
buildings, and through to the back, with a number of 
separate outbuildings scattered over the gardens behind. 
In the large block facing the street on the right are M. 
Pasteur's apartments ; on the left his laboratory occupies the 
tasement. In this laboratory he continues his researches, 
but during the time that patients bitten by mad dogs are 
being treated he may frequently be found watching with 
great interest the treatment, and chatting with those who 
have come to see the place and the method of work. In this 
block also is collected everything connected with the pre- 
paration of, and despatch of, the various vaccines — rouget de 
pore (swine fever), anthrax vaccine, etc. On the first floor 
is a large hall, which serves the double purpose of library 
and council room. This room is well lighted by four large 
windows, and is provided with the current scientific litera- 
ture, both periodicals and books, all of which may be 
consulted by the workers in the laboratories, who, however, 
are not allowed to remove them from the room. The storey 
above this is occupied by the servants and attendants of the 
institution. The large corridors, four metres and a half 
broad (nearly five yards), well lighted, run between the 
corresponding storeys from this block of buildings to the 
larger one behind, which is entirely devoted to laboratories. 


This block is divided into two wings, each about twenty- 
five metres long and fifteen metres from back to front ; in 
the right wing, on the ground floor, are the rooms set apart 
for the examination of patients who have been bitten by 
mad dogs, and for their treatment by the preventive 
inoculation method. The patients who enter the grounds 
at the right are directed by an intelligent porter through 
a door at the right of the building to a waiting-room 
heated and well hghted, surrounded with benches on 
which they may rest while waiting for their turn to 
come ; they then pass into a room where their names, 
addresses, and particulars of their cases are carefully 
recorded. After being duly registered, they are passed on 
to the inoculation apartment, where they are treated in the 
manner already described. Should any patients show 
symptoms of faintness, they are assisted into a small room 
in which is a sofa, on which they may recline ; the others pass 
out into a central passage, on the opposite side of which 
is a room where severe bites and lacerations are attended to 
surgically. Here also are an operation room, archive room, 
and others. Next to the room in which we left the faint 
patients, is the laboratory in which the preparation of the 
cords that are used for the manufacture of the virus is 
carried on. It is maintained at a constant temperature 
of 23° C. by means of 'a special regulator. Around 
this is a regular array of bottles, arranged on shelves fixed 
to the wall, and grouped according to the time that they 
have been exposed to the dry air. A screen within the 
door prevents draughts, and helps to maintain a constant 
temperature, even when the door is frequently opened. 

In the left wing, on the ground floor, is a lecture-room for 
biological chemistry, which will accommodate about fifty 
auditors ; it is separated from a laboratory by a wide door- 
way, which, when open, permits of those in the lecture-room 
seeing what is going on in the laboratory. This opening may 
be closed altogether by a large black screen, or by a ground- 
glass plate, on which lantern projections may be thrown. M. 
Duclaux, professor of biological chemistry in the Sorbonne, 
now delivers his course here, and M. Roux lectures on Prac- 
tical Micro-biology. From time to time those who are working 
in the laboratory, or others, also give demonstrations and ex- 
planations of their work and of any recent discoveries in this 


theatre. Close t o the lecture-theatre is a photographic depart- 
ment, specially designed and fitted up by M. Roux, for the re- 
production of bacteria and other microscopic objects. At the 
end of the block, at the right and left of the central corridor, are 
two rooms with well-fitted aquaria, which are specially fitted up 
for carrying on researches, under the supervision of M. Metsch- 
nikoff, on aquatic animals. The two rooms on the ground 
floor, specially set apart for experiments' upon large animals, 
are provided with a good wide door opening to the outside. 
The concrete pavement, sloping towards a green, permits of 
this being readily cleansed. The remainder of this floor is oc- 
cupied by a kind of store-room and a laboratory set apart for 
general use, in which are stored and prepared the bouillon and 
other nutrient media. Here also is carried on the glass-blow- 
ing ; a skilled artizan supplying workers with flasks, pipettes, 
tubes, and other vessels they rnay require. A large staircase 
situated at the end of the central gallery puts the labora- 
tories of the basement in easy communication with those of 
the storeys above. The first storey is divided into duplicate 
halves, one on the right, the other on the left of a passage. 
That on the left is set apart for M. Duclaux's department of 
general micro-biology ; that on the right to practical biology, 
over which M. Roux presides. The central corridor leads to 
a large concreted workroom, nearly twelve metres square, 
which is well lighted with nine large windows. Around the 
room are seven work tables, each of which is covered with a 
thick sheet of volcanic lava, the surface of which is enamelled 
so that it has the appearance of an immense sheet of porce- 
lain. Each is fitted for two workers. Every worker has 
before him a window, from which light is obtained for the 
microscope on his right or left side, according to his position. 
At the table is a gas connection, from which gas may be 
conveyed to any desired point ; here also is water, which is 
received into a sink, also of enamelled lava. A small sliding 
board, which may be drawn out and used as a desk, is placed 
on the other side of the table, away from the Central pro- 
jection which carries the sink ; this allows the worker to 
make for himself a little retreat, in. which he sits surrounded 
by all that he requires. When work is over for the day 
everything except the microscope is put away in a couple of 
small cupboards which are placed at the disposal of the worker. 
This is absolutely necessary in order that the room and the 


tables may be kept clean. Two tables placed parallel to on« 
another in the centre of the room are used for chemica! 
operations which cannot be carried on at the smaller specia! 
tables. Then there are large evaporating chambers, in whicl: 
are placed the sterilizing and incubating apparatus. Ir 
addition to the incubating apparatus used in the common 
laboratory, there is a large common room, which is reallj 
made up of three rooms : — An entrance chamber, in which 
the temperature varies somewhat from time to time ; it ton- 
tains the heating apparatus, and is specially designed as an- -aii 
cushion insulator. The second chamber — nine feet ten inches 
long, eight feet broad, and six feet high^s heated by means 
of hot water, by which it is kept at a constant temperature 
Above this, and heated in connection with it, is a thirc 
chamber, in which the temperature is intermediate betweer 
those of the two preceding ones. This group of incubating 
chambers has very little cooling surface, and is separatee 
from the outer wall by a room in which is collected anc 
washed all the dirty glass used in the laboratory. In thes< 
constant-temperature chambers are shelves and tables, or 
which may be seen all kinds of flasks, test tubes, and sterilizec 
moist chambers, in which, growing on various media, anc 
under different conditions, are all kinds of micro-organisms 
that are being experimented with in the various departments 
of the Institute. The laboratory " preparateur " has a room 
next to the laboratory, with which it communicates directly, 
so allowing ready access thereto and constant superinten- 
dence. From this small laboratory is the only entrance tc 
the museum, for the care of which the preparateur is directlj 
responsible. A special laboratory for the performance oJ 
experiments in chemical biology, and a lavatory, are alsc 
added to the suite on this floor. The laboratory and the 
room of the director of the department are placed in each 
wing. These are entered from the passage which leads tc 
the common laboratory. In the storey above this there are 
no teaching laboratories ; we have simply two series oi 
rooms, divided by a passage, each room designed to become 
a research laboratory, and fitted up to meet the require- 
ments of the savant who occupies it. Investigators have 
every facility for carrying on their work, and may, ii 
they desire it, have the advice and guidance of any of the 
directors of departments, each of whom is responsible for the 


management and work of the whole wing that is placed 
under his supervision. In the left wing M. Chamberland 
supepintends the department of applied or practical bacteri- 
ology ; in the right wing M. Gamaleia presides over the 
subject of comparative micro-biology or bacteriology. In each 
of these departments, in addition to the special incubating 
chambers required by the workers, is a general incubating 
chamber, constructed like that in the first storey, but on a 
larger scale, and also a general laboratory, in which may be 
carried on all the sterilizing, preparation of gelatine, broths, 
&c., for which special apparatus is required. 

This is the extent of the laboratory proper, but in the 
garden which surrounds the main building are found scat- 
tered other structures, apparently less important, but all 
of them required for the carrying on of the work of this 
immense establishment. 

First comes a building, parallel to the main block, in which 
is accommodation for animals, which are kept in elevated 
cages constructed of iron bars on every side ; they are so 
raised from the sloping asphalt floor, that they can readily 
be flushed. At the two ends of the building three small 
rooms have been set apart for operation on small animals that 
come to be treated in the Institute. In a special house, which 
is very well arranged for the reception of dogs, each animal 
has its special cage, where it can be properly looked after, 
watched, and fed, without it being necessary for the atten- 
dant or observer to come actually in contact with it. 
Near this is another series of animal houses, also with 
asphalt floors, which are used for stock, or for animals that 
being experimented upon require special isolation. The 
rabbits that are inoculated for the preparation of the specific 
fluid, during the incubation period of their attack of hydro- 
phobia occupy a special house, which is also kept at a con- 
stant temperature in order that the periods of incubation 
may be kept as uniform as possible. A special arrangement, 
of the cages in which these animals are enclosed allows of 
their bedding being changed and of their being kept clean 
without its being necessary to open the cage. A gutter, with 
walls of glass placed below the cages, which can be well 
flushed by a stream of water, serves to carry off the urine 
which makes its way- through the floors of the cages. Then 
come a run for hens, and smaller hen-coops, an aviary, and 


Stabling for large animals, all of which are so constructed 
that they can be kept not only in a state of perfect cleanli- 
ness, but can be thoroughly washed out with boiling water. 
They present no porous surfaces, and there is no material 
used into which germs can penetrate and become inaccessible 
to the usual microbicidal agents. Lastly, in one corner 
of the grounds are two cremating furnaces, in one of which 
gas is used, and in the other ordinary fuel. In these every 
particle of infected matter and all diseased tissues not kept for 
microscopic examination, are carefully calcined in order that 
nothing of an infective nature may be carried beyond the 
walls of the establishment. The arrangements generally are 
such that absolute cleanliness may be maintained with the 
slightest possible amount of labour, so that not only the 
workers, but also the people residing in the neighbourhood, 
may be perfectly at ease as regards any danger of infection. 
Even in the old laboratory, situated in the gardens and in 
contact with the Normal School in the Rue Vauquelin in 
the immediate vicinity of hotels, experiments with the rnost 
virulently infective diseases have for ten years been carried on 
by Pasteur and his pupils without the least accident having 
happened. The new Institute will accommodate about 
fifty workers — about fourteen in the laboratories on the 
ground floor, and the remainder in the research laboratories. 
The staff of directors and assistants consists of about fifteen 
persons, all of whom are studying some branch or other of 
micro-biology. The only passport required for working 
in the laboratory is a capacity for doing good work. If 
there is a place at liberty a good worker is always sure 
of it, and Frenchmen and foreigners alike are admitted to 
the use of these tables in one or other of the principal 
departments, of which there are six, associated with the 
names of such men as Straus, Grancher, Duclaux, Gamaleia, 
Chantemesse, Widal, Charrin, and others. These depart- 
ments are named according to the special kind of work car- 
ried on. Thus, one is devoted to the study and treatment 
of hydrophobia, another to general micro-biology, a third to 
practical bacteriology, a fourth to micro-biology applied to 
hygiene, a fifth to morphological and comparative micro- 
biology, a sixth to biological chemistry. Most extensive 
and elaborate arrangements are made for the instruction ol 
pupils in both general and special methods of bacteriological 


investigation, and the pupil, after being instructed in the 
first, will, in the laboratory of general micro-biology, follow 
out special methods, each one having his own subject and 
pursuing his research by appropriate methods. M. Roux 
takes them first in small classes, and in five or six 
weeks he gives all the general principles of work, and 
indicates all the details of technique necessary to ensure the 
competence of these pupils in ordinary matters relating to 
the study of micro-biology. In the course is included regular 
practical laboratory work ; but the main work is the carry- 
ing on of original investigation, and the results of the 
researches made by the distinguished staff and their pupils 
are now known throughout the world, whilst there still 
comes a stream of brilliant papers, such as may well fill us 
with admiring envy, and, let us hope, provoke in us a 
generous rivalry at some not far distant date. 


The following works may be consulted : 
BABES.-^Annal. de I'Institut Pasteur, t. ii., No. 7, p. 394, 

1888 ; Virch. Arch., Bd. ex., Heft. 3, p. 562, 1887. 
Babes et Lepp. — Annal. de I'Institut Pasteur, t. iii.. No. 7, 

p. 384, 1889. 
CoRNiL ET Babes. — Les Bacteries, p. 550, 1890. 
DoLAN. — Hydrophobia; M. Pasteur and his Methods. 1886. 
DowDESWELL. — Lancet, vol. i., p. 11 12, 1886 ; Journ. Roy. 

Micros. Soc, vol. vi., p. 669, 1886. 
FoL. — Comptes rendus, t. ex., p. 1276, 1885. 
Galtier. — Comptes rendus, t. cvii., p. 798, 1888. 
Gamaleia. — Annal. de I'Institut Pasteur. 1887. 
Gibier. — Comptes rendus, t. xcvi., p. 1701, 1883, and t. 

xcvm., pp. 55 and 531, 1884. 
HiME. — Lancet, vol. 11., p. 184, 1886. 
NocARD et Roux. — Annal. de I'Institut Pasteur, t. 11., No. 

7, p. 341, 1888. 
Pasteur. — Annal. de I'Institut Pasteur, 1887-1891. 
Pasteur, Chamberland, Roux et Thuillier. — Comptes 

rendus, t. xcv., p. 1187, 1882 ; t. cii., p. 531, and t. 

cm., p. 777, 1886. 
Roux ET Chamberland. — Annales de I'Institut Pasteur, 

t. II., No. 8, p. 405, 1888. 


Vestea e Zagari. — Giorn. Internat. d. sc. Med., t. ix., 

WooDHEAD AND WooD. — Comptes rendus, t. cix., 1889. 

See also Report from the Select Committee of the House 
of Lords on Rabies in dogs, Blue Book, 1887 ; and numerous 
papers and reports in the Annales de I'lnstitut Pasteur. 


Bacteria of the Mouth. 

The Mouth a Good Forcing Ground for Bacteria — Food Material — Kinds 
of Bacteria found in the Mouth by Miller and Vignal — Bacteria in the 
Teeth in Caries, in Milk Teeth, and in Abscesses — Combination of 
Lactic Acid with Lime Salts — Organisms Attack Decalcified Base 
Substance — Artificial Decay — Mode of Invasion 6f Teeth by Bacteria 
— Poisonous Saliva — Micrococcus of Sputum Septicaemia — Pneumo- 
coccus — Other Organisms found in the Mouth — Septicaemia following 
Slight Operations in the Mouth. 

It will be remembered that many of Leeuwenhoek's obser- 
vations as to the morphological appearances of the minute 
structures which he examined with his wonderful lenses, 
were made on bacteria which were found adhering to the 
teeth, and certainly some of his most interesting observations 
were on bacteria derived from this source. From what we 
now know of the biology of these organisms we can readily 
understand that the mouth should form a kind of hothouse 
or forcing-ground for their cultivation. Here is a moist 
cavity kept at a comparatively high temperature, covered 
with an epithelium which is constantly being partially or 
completely shed, to which there is ready access from the out- 
side air, and through which food material is constantly 
being passed, particles of which, despite the exercise of the 
greatest care and the utmost cleanliness, always remain in 
small crevices between the teeth, or perhaps, more important 
still, between the gums and the teeth. It is also said that the 
fact that starch is constantly being converted into sugar by 
the ptyalin is in favour of the growth of bacteria. Then we 
have the dead epithelium, which is readily attacked by 
organisms of various kinds, supplying proteid or other 
nitrogenous materials ; as a matter of fact, there are often 
found in these dead epithelial cells a number of micrococci, 
which appear to be gradually disintegrating their substance 
and utilizing the materials of which they are composed. In 



a similar way the various constituents of the teeth are made 
to serve as nutrient elements for these bacteria if once the 
protecting enamel is removed. 

One author, writing of the micro-organisms that may be 
found in the mouth, points out that almost every organism 
that has been described as occurring in any position has also 
been described as growing in this cavity ; but it is now 

photo micrograph of scraping from the teeth in which different kinds of micro-organisms 
are seen, X looo. Spirilla very imperfectly stained. 

generally accepted that about eight or ten are almost con- 
stantly met with, and that six may be said to be invariably 
present. Of these we give a short description, as they may 
be examined by any one who wishes to see what these 
organisms really are, though we warn any who may 
attempt to cultivate them that they will almost inevitably 
fail, as these special mouth organisms seem to require 


special conditions, as yet not at all understood, for their 
existence, and although one or other of them may be found 
in enormous numbers in one case, and may be comparatively 
few in another, there is usually some explanation to be 
offered for such preponderance. 

(i) The Leptothrix innominata (Miller) is found, usually, on the soft 
white material that is deposited on teeth, it may probably be out a generic 
term for more than one form, as the constituent elements of which it is said 
to be made up vary very much both in length and in thickness ; they are 
usually .5 to .8/1 thick, and though there may be shorter cells or rods, 
the organisms usually consist of tortuous non-motile threads. These rods 
and threads as a rule contain no spores. 

(2) The second form, Bacillus buccalis maximus, occurs as isolated 
bacilli or threads, generally arranged in bundles, which may interweave 
with one another. These bundles are sometimes of very considerable 
length, but each thread is divided into short rods, from I to l.2/ibroad, 
and from 2 to lo/» long. This bacillus is, as a rule, not found within the 
dentine tubules. In addition to this bacillary form there is a leptothrix 
form, in which the filaments are considerably longer, but otherwise the 
organism is much like that already described, although it is scarcely to be 
looked upon as related to the leptothrix innominata. 

(3) The next organism is one called by Miller the lodococcus vagincUus, 
which is found especially in mouths that are not properly cleansed ; it appears 
to be made up of cocci arranged as diplococci or tetrads, which are usually 
arranged and held together in a kind of sheath, though now and again a 
single coccus or diplococcus may be seen, around which no sheath can be 
demonstrated. When this organism is stained with iodine a marked 
reaction is obtained, the sheath being stained yellow, whilst the cocci are 
stained dark blue. 

One of the most interesting forms met with in the mouth is : (4) the Spiril- 
lum sputigenum (Miller), which always occurs in certain numbers, but is found 
in especially large quantities in those cases in which the presence of tartar has 
set up slight inflammation of the gums around the teeth ; it usually occurs 
in the eedematous gum just at its junction with the teeth. This organism 
has more than usual interest from the fact that it was for long supposed, by 
Lewis and Klein, to be identical with the cholera bacillus. Morpho- 
logically it certainly resembles this latter organism in many respects. The 
simplest form is that of a small curved bacillus ; sometimes two or three 
of these may be joined together to form an S-shaped organism, whilst in 
other cases it may be found as long spiral threads. This organism, as we 
have said, is almost invariably met with in the mouth, but it is curious 
that it is very seldom found between the teeth, or in carious cavities ; it 
thrives apparently upon the exudation from the slightly inflamed gums, and 
so necessary is this food for its existence that it has never yet, so far as is 
known, been cultivated in any of the artificial nutrient media outside the 
body, although (5) a somewhat thicker, curved, comma-shaped bacillus, 
identical in almost every respect (except as regards size), can be cultivated 
in gelatine quite readily at the ordinary temperature of the room. This 
differs from the first-mentioned in that it has the true comma-shape, tapering 
towards one end. 


(6) A third curved or spiral organism is also described — somewhat longer 
than the others ; it occurs in longer or shorter, straight or spiral filaments, 
which may break up into rods and even into chains of cocci ; this organism 
when cultivated in gelatine does not give rise to any liquefaction, differing 
in this respect from either the Koch's cholera or comma bacillus or the 
Finckler-Prior bacillus, the latter of which has also been described by Miller 
as occurring in the mouth. Miller maintains indeed that some of these 
curved organisms may pass into the lower parts of the alimentary canal, 
but that even when he took them from this position he never succeeded in 
making pure cultures of them ; they will not grow on any of the nutrient 
media that have been as yet devised. 

(7) Then, of these more important forms, is the Spirochete dentium or 
Spirochate denticula, which is usually found associated with the (8) Spirillum 
sputigenum, and under similar conditions ; it consists of a long spiral thread 
from 8 to 25/j in length, of which the spirals are irregular and of unequal 
thickness. Very little is known of this organism, and it is quite possible 
that the thicker spirals may represent some stage of development of the 
preceding organism, especially as in this case it is also impossible to obtain 
any artificial cultures. As already stated, other organisms are very fre- 
quently, though not invariably, met with. 

Vignal describes a number of bacteria and bacilli as occur- 
ring in the mouth and amongst these certain common forms 
that are generally recognized, such as Bacterium termo (?) 
Bacillus ulna, the potato bacillus, Bacillus alvse, and a number 
of others, whilst amongst the cocci are found the Staphylo- 
coccus pyogenes albus, and S. pyogenes aureus, &c. Hueppe 
describes organisms that give rise to the lactic acid fermenta- 
tion, whilst others, especially those giving rise to pigment 
and pathogenic bacteria of various kinds, most of them well 
recognized, have a peptonizing action, and a few appearing 
to secrete a true diastatic ferment may also be met with 
in the mouth. 

Miller gives some interesting statistics as to the action of 
the bacteria found in the mouth upon carbohydrates ; he 
finds that of twenty-two kinds of mouth bacteria which he 
mentions, "sixteen brought about an acid reaction when 
cultivated in beef extract peptone solution, four produced an 
alkaline reaction under the same conditions, whilst in the 
case of two only the reaction remained neutral. "_ Many of 
these organisms also exert an enzyme function in a some- 
what marked degree ; most of them have the power of 
peptonizing coagulated albumens, during which they give 
rise to the usual ultimate- products— sulphuretted hydrogen, 
ammonia, carbonic acid gas or combinations of these, peptones 
of course also being formed. 


In thin sections of decalcified teeth, stained with fuchsin 
and vesuvin, it is seen that bacteria are scattered, though 
somewhat irregularly, throughout the dentine (the hard 
substance of which the tooth is principally composed) that 
is undergoing decay or softening. This is always most 
marked near the surface, but it must be noticed that as the 
bacteria travel along the dentine tubules (little canals that 
run vertically through the dentine), there is usually a small 
part of the softened area in which micro-organisms are not 
seen, as it seems that these cannot make their way readily 
along the fine transverse branches that connect the vertical 
tubules, and, as Miller puts it, although the organism-s " keep 
up with the softening in the direction toward the pulp, they 
fall considerably behind in the lateral directions, so that the 
invasion, particularly in the lateral direction, is usually much 
less extensive than the softening ; " and the tubules near the 
surface always contain more bacteria than those deeper 
down in the softened area. It is important to remember 
that bacteria may be found in apparently normal dentine 
canals, whilst a similar invasion seems to go on in the roots 
of " milk " teeth, and also where abscesses have occurred 
in the roots of " permanent " teeth. It is now held by most 
of those who have given attention to the subject, that the 
bacteria which are found in decaying teeth are only playing a 
secondary part, though a very important one, in the process 
of caries. In the first instance there appears to be a soften- 
ing of the various parts of the tooth by acids, commencing 
with the enamel ; in the case of people who take perchloride 
of iron or nitro-hydrochloric acid this softening may go on 
exceedingly rapidly. As we have already seen, lactic acid 
is constantly present in the mouth, though often in very 
small quantities ; if left to act on the lime it may give 
rise eventually to softening at the margins of the gums 
and to caries, acids preparing the way for the invasion of 
various bacteria, by combining with the lime and softening 
the tooth. Where once the lime salts have been removed, 
bacteria can attack the basic substance most easily ; they are 
now in a position to make their way along the dentine 
tubules, and by the intertubular spaces, and once in this 
position they attack the surrounding tissue with very great 
vigour ; they use it as a food material, absorbing and 
digesting it until they have made their way into the greater 


part of the softened area. It was at one time stated that 
the " leptothrix buccalis," as it was called, was the organism 
that was always found in these cases, but this is now known 
not to be the case : micrococci, leptothrix threads, bacillij and 
spiral forms may all be met with even in the same decayed 
tooth, and in tubules lying close together ; the softening and 
absorption going on indiscriminately, whichever of the organ- 
isms may be attacking the basic substance. It is owing to the 
peptonizing power of these organisms that they are able to 
carry on the disintegrating process, and we thus see that 
although the bacilli may not be actually present in all parts 
of a decaying area, their products, such as lactic acid and the 
peptonizing enzyme, are really carrying on the work that 
ends in the decay of the tooth, perhaps considerably in 
advance of the bacteria themselves. In experiments carried 
on with the .object of proving that decay might take place 
in teeth removed from the mouth. Miller placed a number 
of perfectly sound teeth in a mixture of saliva and bread ; 
this mixture was renewed from time to time, whenever the 
slightest trace of alkalinity appeared, and the pulpy mass in 
which the teeth were embedded was kept at a temperature 
of 37° C. during a period of three months, with the result 
that the dentine became softened, and there was what he 
describes as a condition of " white decay " ; he found that 
where the enamel was perfect, even acids'-had no power to 
attack the dentine beneath, but in those cases where the 
enamel was soft or imperfectly developed the dentine had 
become softened by any acid that was present, and the 
canaliculi were filled with bacteria ; this gave rise to 
irregular erosion of these canals which thus appeared to be 
unequally distended. Near the surface of the tooth the 
organisms are not strictly confined to the tubules, but they 
invade the basic substance from the surface, softening it as 
they advance, but filling up the microscopic cavities as they 
are formed. 

The organisms described by Galippe and Vignal that were cultivated on 
gelatine were six in number, all occurring in decaying teeth. 

I. A short thick bacillus 1.5/a in length, and nearly as broad as long; it 
grows somewhat rapidly on gelatine, giving rise to an opaque white growth 
along the track of the needle ; it liquefies the gelatine about the third or 
fourth day, rendering it somewhat opaque, from which we should gather 
that the organism is motile ; on plates it forms colonies which are usually 


2 or 3mm. in diameter before they begin to liquefy ; after th they extend 
and liquefy very rapidly. 

2. A bacillus slightly constricted in the centre about 3/* in length, and 
about one-half as thick as long ; in cultures it is similar to No. i, except 
that it has a larger surface growth before it gives rise to any liquefaction. 

3. A bacillus very similar to No. 2, but with no constriction in the 
centre ; it has scjuare ends and frequently grows in long chains, especially in 
liquid media ; it causes only slight softening of the gelatine. 

4. Is a small thin bacillus so short that it might even be mistaken for 
a micrococcus ; it gives rise to a white growth along the needle track in 
gelatine which it turns yellow, and then causes to liquefy. 

5. Was not found in all cases (in eight out of eighteen decayed teeth). 
It is a bacillus with rounded ends, which grows almost exactly 'ike No. i. 

6. Found five times only, is a large coccus ; it was found only in 
advanced stages of decay, where the canals had been opened up by other 
organisms as it was so large that it could not make its way along the 
ordinary dentine canals ; it forms a white line along the track of the needle 
in gelatine, of which it causes no liquefaction. 

The very favourable incubating chamber of the mouth is, 
however, not monopolized by the organisms that so far have 
been mentioned, and during epidemics, or when people come 
in contact with persons suffering from various diseases, the 
organisms associated with such diseases are, as might be 
anticipated, frequently taken into the mouth, where they 
accumulate, multiply, and eventually may set up any of the 
various diseases with which they are associated in the hitherto 
healthy person. 

In the very act of developing in the mouth they are sup- 
posed to give rise to ptomaines and other poisonous products 
which may render the human saliva toxic when introduced 
by a bite or a wound into the individual himself, or into 
another individual ; in fact, septic poisoning from injection 
of the saliva from mad dogs was one of the great difficulties 
with which Pasteur had to contend in his early experiments 
on hydrophobia. Quite recently Sternberg, Fraenkel, 
Klein, and others have shown that, though the pure saliva 
as it runs into the mouth is non-pathogenic, it acquires toxic 
properties as soon as it becomes mixed with the organisms 
which are usually found in the mouth, this being especially 
the case in patients suffering from certain infective diseases. 
One observer has found that his own saliva is permanently 
so toxic that it invariably causes the death of small animals into 
which it is inoculated ; it is almost as fatal as hydrophobic 
saliva. Some of these pathogenic organisms, like those we 
have already mentioned, cannot be cultivated artificially, for it 


is sometimes found that sputum inoculated into mice or 
rabbits causes their death in a comparatively short period, 
bacteria being found in their blood ; this blood inoculated into 
another animal produces a similar disease, such as acute or 
chronic abscess formation, which may be carried on from 
generation to generation by simply inoculating a healthy 
animal with the contents of the abscess. In these cases, 
however, the organisms that are cultivated from the blood or 
the pus fail to produce any symptoms at all, and it must be 
concluded (until further evidence is obtained) that the patho- 
genic organisms cannot live on the artificial culture media, 
those that survive on these media being non-pathogenic' 
There are, however, certain pathogenic organisms found in 
the mouth which can be readily enough cultivated, the first, 
and one of the most important of which is the micrococcus 
of sputum septicaemia, which may be grown on blood serum 
or agar-agar at the temperature of the body ; it grows as a 
transparent greyish-white gelatinous coating on the surface of 
the nutrient medium, and looks almost like a dewdrop. It 
is encapsuled like the pneumococcus described by Friedlander, 
and usually occurs in sputum in the form of single or paired 
cocci ; it is found almost invariably in patients suffering 
from pneumonia, but it also occurs frequently in the mouths 
of healthy persons. When injected into animals, either 
in the sputum or as a pure cultivation, death usually occurs in 
from twenty-four to thirty-six hours ; numerous capsuled 
cocci are found in the blood, the spleen is enlarged and con- 
tains a number of organisms ; the symptoms, in fact, are 
those of an acute septicxmia. It has been observed, 
however, that pigeons and dogs are unaffected by this dis- 
ease, whilst rabbits and mice are almost invariably killed 
by its inoculation. It would appear that when it makes 
its way from the mouth to the healthy lung this organism 
has little or no power of attacking the tissues, but that 
if there be slight congestion or inflammation, just as in 
the case of inflammation of the gums around the teeth, this 
organism, finding its way from the mouth (where it may have 
existed for some time without giving any evidence of its 
presence) into the air vesicles, is enabled to grow on the 
exuded fluid constituents of the blood, and to set up at once 
• Another explanation of this will ' be found in the chapter on 


those intense inflammatory changes characteristic of croupous 
pneumonia, or acute inflammation of the lungs, and in some 
cases, where the organisms appear to be more virulent, septic 
pneumonia and gangrene of the lung. It may be, however, 
that this gangrenous pneumonia is the result of the invasion 
and action of another organism. It has already been men- 
tioned that the Streptococcus aureus and S. albus sometimes 
occur in the mouth, but it would appear that these forms 
are more frequently met with in the posterior nares and 
in the cavities of the nose. To their action is supposed 
to be due the suppuration or festering that almost invariably 
follows small operations of the mucous membrane of the 
nostrils, unless the mucous surface is previously prepared by 
careful antiseptic washing out of the cavities and by frequent 
application of antiseptics after the operation has been per- 
formed. The micrococcus tetragonus is also found in the 
mouth, whence, in cases of tuberculosis, it makes its way into 
the lungs, and is there found, especially in suppurating cavi- 
ties ; this organism, which is fatal to white mice and guinea- 
pigs, usually occurs in little packets of four, each coccus 
being about i/« in diameter. On gelatine, according to 
Eisenberg, it grows as small white colonies, which when mag- 
nified appear to have a peculiar ground glass appearance ; 
it does not give rise to any liquefaction of the gelatine. 
Various other septic forms have been isolated from sputum. 
It will thus be seen that in certain cases injury of the 
mouth, of the periosteum of the jaw, or the soft tissues of 
the pharynx, may lead to infections of very different kinds, 
but it may be laid down as a general rule that septic infec- 
tion is frequently the result of invasion from these regions, 
and very numerous are the cases recorded in which death has 
resulted even from the most trifling operations in the mouth 
and naso-pharynx. I have seen several cases where death 
has ensued, with all the symptoms of most acute septicemia, 
or with symptoms of more chronic poisoning, as in pyemia, 
from the extraction of a tooth or the lancing of the gums in 
patients with imperfectly cleansed mouths, or in persons who 
have been engaged in attendance on patients suffering from 
certain infectious diseases ; the organisms in such cases find- 
ing their way from positions in which they were cornpara- 
tively harmless, into the wounds that were unavoidably 
made, whence they invaded the lymphatics or passed 


directly into the blood stream and set up septic or other 

It is scarcely necessary here to enter into the different 
forms of septic tooth disease or to consider the points at 
which the different kinds of poison may enter, but it should 
be mentioned in the interests both of antiseptic purity and 
suffering humanity that a good stout tooth brush, plenty of 
water and some antiseptic dentrifice applied morning and 
night afford a greater safeguard against many diseases than 
most people are aware. 


The following works may be consulted : 

Abbot. — Dental Cosmos. 1879. 

BioNDi. — Breslauer arztliche Zeitschr, No. 18, Sept. 1887. 

David. — Les Microbes de la Bouche. Paris, i8go. 

FRAENKEL.-r-Verhandl. d. 3. Congr. f. inner Med. 1884. 

Galippe et Vignal. — L'Odontologie. March, 1889. 

HuEPPE. — Mitth. a. d. k. Gesundheitsamt, Bd. 11., p. 309, 

Kirk. — Dental Cosmos. 1887.' 

Klein. — Centralbl. f. Med. Wissensch, No. 30, p. 529, 1884. 

Leeuwenhoek. — Opera omnia sive arcana nature ope micros- 
copiorum exactissimorum detecta. 1722. 

*MiLLER. — Micro-organisms of the Human Mouth. Phila- 
delphia, 1890. 

Sternberg. — Bull, of the Nat. Board of Health. April 30, 

Vignal. — Arch, de Physiol, norm. et. patholog., No. 8, 1886. 
* Very full lists of literature given. 

The Bacteria of Colour and Phosphorescence. 

Colour- Forming Bacteria — Micrococcus Prodigiosus — Magenta Micrococcus 
— Beggiotoa Roseopersicina — Bacillus of JSlue Milk — Sulphur Pigments 
— Iron Pigments — Bacillus Fluorescens Putidus — Phosphorescent Bac- 
teria — Six Species — Method of Cultivation — Conditions under which 
they produce Light. 

If an organic medium, such as boiled potato, bread 
soaked in broth, or nutrient gelatine, be exposed for some, 
time to the air of an ordinary room, it will be found that at 
the end of a few days, in addition to the moulds of various 
colours that develop on it, there appear minute yellow, 
pink, or brown points, which on examination are found to 
consist of yeasts, of sarcina, of micrococci, and of bacteria, 
of which there are numerous, species that give rise to these 
coloured masses present in soil, air, and water. It is a well- 
recognised fact that most putrefactive and decomposition 
changes are associated with changes in colour of the putre- 
fying media ; these colours being due to the activity of some 
of the above colour-forming organisms which, in the exercise 
of their full assimilating and colour-forming powers, decom- 
pose nitrogenous substances, the elements of which are con- 
verted into the protoplasm of the organism, into coloured 
material, and into the other excretory products to which 
these organisms give rise. In some cases the colour is 
actually contained within the substance of the organisms ; 
usually, however, it is accumulated in the sheath, as in 
the ease of the Micrococcus prodigiosus, the organism to 
which the bright red colour of "bleeding bread" and 
" bloody sweat " is due. This pigment is quite insoluble in 
water, but by means of alcohol it may be extracted and ob- 
tained in solution ; this and other pigment-forming organisms, 
such as the magenta micrococcus, mentioned by Greenfield as 


occurring in the water of the Tweed, contain a colouring 
matter which has been described as resembling in a most 
remarkable manner the aniline dyes ; in fact, in the case of 
the pigment of the magenta micrococcus, the resemblance is 
carried so far that in old cultures even the peculiar metallic 
lustre of the aniline dyes is reproduced. Other pigments 
are soluble in water, but not in alcohol, whilst the bacterio- 
purpurin formed by Beggiatoa Roseopersicina is like chloro- 
phyll, insoluble in both alcohol and water. The name 
bacterio-purpurin, however, has been given by Engelmann 
to the pigment produced or possessed by a whole group of 
organisms. He concludes that it has, in these lower organisms, 
the function of the chlorophyll of the higher plants. If 
exposed on the microscope stage to the light of a sub-stage 
spectroscope apparatus, these bacterio-purpurin bacteria 
invariably tend to collect on that part of the slide that is 
over the ultra-red bands of the spectrum, the portion of the 
spectrum where the absorption of light by the bacterio- 
purpurin occurred. He found that the analogy with plants 
and chlorophyll became still closer from the fact that 
wherever this occurred, oxygen was set free, and that 
light in fact was necessary for- the continued existence 
of these bacteria and for the development of their 
characteristic colour - producing power. In the case of 
this organism, according to Ray Lankester, the colour is 
actually contained within the protoplasm of the organism, 
where it appears in some cases to be combined with sulphur, 
to form dark granules. In some cases the colour, inplace of 
remaining within the organism, becomes diffused into the 
surrounding media. As an example of this may be cited 
the bacillus of " blue milk," which, growing along the track 
of the needle in a gelatine culture, sends out a peculiar 
iridescent green coloration into the surrounding gelatine ; 
as time goes on this green is replaced by a smoky_ brown 
colour. Similarly the Bacillus fiuorescens putidus_ imparts 
to the gelatine, or any other material on which it is grow- 
ing, a peculiar fluorescent green, and at the same time gives 
off an odour of herring brine. 

That the decomposition of the sulphates in the presence of iron and 
organic matter plays a most important part in the production of these pig- 
ments has now been fully recognized. If it be borne in mind that sulphides 
of the various metals appear as beautiful precipitates when thrown down from 


solution it is quite evident that very minute traces of iron, say, acted upon 
by the sulphuretted hydrogen set free by the decomposition of the sulphate?, 
can easily account for the production of certain pigments. Cladothrix 
dichotoma, for example, growing in water, appears able to separate iron 
from the"surrounding substances ; this becomes accummulated in the form 
of an oxide in the sheath. In the Beggiatoa the power of reducing the 
sulphates is especially well marked, sulphur, which appears in regular 
granules in the substance of the organisms, being stored up in the proto- 
plasm to be utilized as it may be required. The sulphuretted hydrogen that 
is formed, acts on the iron and gives rise to the formation of sulphide of iron. 
In this way may be explained the presence of the pigment that is formed in 
muds where these putrefactive organisms are present, as, for example, in 
the mud of a tidal river. It should be remembered, however, that iron is 
not the only metal that may be present, and that there is always a tendency 
for the sulphuretted hydrogen to be set free from the sulphide and to give 
way to the formation of oxides, especially in the presence of air and mois- 

Only by the application of some such explanation as this 
is it possible to account for certain of the beautiful brown 
colorations that make their appearance in gelatine ; for 
example, that which surrounds the track of a needle inocu- 
lation of some of those organisms, which, though colourless 
themselves, give rise to most beautiful coloration of the 
surrounding gelatine. So important is the presence of iron 
in these cases, that Miller holds that to the action of organ- 
isms on it is due most of the discoloration that occurs in 
decaying teeth. 

He points out that the colours characteristic of decaying 
dentine only make their appearance some time after the 
process has commenced, the depth of the colour being in 
direct proportion to the length of time that the decay has 
been going on, and he considers that this coloration is 
due to the formation of sulphide of iron in the decomposing 
enamel, dentine, and pulp. He performed an experiment 
which may be repeated by any individual who is unfortunate 
enough to be compelled to have a tooth:of hisown drawn 
for decay, or who is fortunate enough to obtain one from 
some other source. He says : — 

" A tooth was cracked in a porcelain mortar, so as to thoroughly expose 
the pulp, and then placed in a mixture of dilute hydrochloric acid, to which 
was added a small proportion of a ten per cent, solution of ferrocyanide of 
potassium. The hydrochloric acid, as well as the water used for dilutmg it, 
must be free from iron ; neither must any iron implement be brought in 
contact with the freshly broken surfaces of the tooth. Those parts of the 


tooth containing iron, even in minute quantities, will, after an exposure from 
one to sixty minutes, assume a blue colour — Prussian blue being formed. 
One source of error is introduced in the necessary use of an iron instrument 
in extracting the teeth, but this will only affect those points on the external 
surface of the tooth with which the forceps come in contact, and therefore 
may be easily eliminated." He found by these experiments that there were 
minute traces of iron in Nasmyth's membrane, in the dental pulp (though 
not constantly), in carious dentine and in enamel, and he considers that it 
is quite possible that the sulphide of iron that may be formed during putre- 
faction of the pulp — a process that is set up by micro-organisms — may have 
something- to do with the discoloration, though it is quite possible that 
much of the discoloration is due to the iron that is taken into the mouth 
along with the food, the putrefactive processes set up in the mouth liberating 
the sulphuretted hydrogen, which, combining with the iron brought from 
outside, gives the discoloration already referred to. 

In addition to this coloration, the result of the formation 
of inorganic salts, we have those violet, magenta, green and 
yellow colours that appear to be distinctly organic in 
character, and to be the result of the metamorphoses of 
albuminoid substances. As above stated, these may "be 
related to the aniline colours, though this has certainly not 
yet been proved to be the case. It may be well to bear in 
mind, however, in this connection what takes place in the 
process of colour formation set up by the Bacillus fluorescens 
putidus, in which we have not only a colour resembling an 
aniline colour, but we have a distinct odour of trimethyla- 
mine, a substance nearly allied to the cyanogen compounds 
from which, as we know, the most beautiful red, blue, 'and 
yellow products are readily obtained when combining with 
iron in certain definite ways. Of course this is only given 
as an example of what might take place, and not as repre- 
senting any accurate work that has been done, for it appears 
that up to the present very little definite knowledge has been 
obtained as to the nature of the pigments contained within the 
protoplasm of micro-organisms or of those diffused from it 
into the surrounding tissues. What we do know is, that a 
large number of the saprophytic decomposition-producing 
bacteria give rise, when grown under certain conditions, to 
most exquisite colour products, that by altering the con- 
ditions, as in the case of the Micrococcus prodigiosus — subject- 
ing it to a higher temperature, for example — the power of form- 
ing these colours may remain in abeyance, the energy of the 
protoplasm being diverted into the formation of some other 
substance — in this instance, lactic acid. It has, however. 


been objected that such lactic acid formation can only take 
place in the presence of sugar.' 

In place of colour a certain amount of the energy of the 
organism may be diverted to the production of light. 
Although phosphorescent micro-organisms have for some 
little time been known to exist, and special organisms have 
been described as giving rise to phosphorescence in different 
regions, they have not been very carefully studied until com- 
paratively recently, when Forster, Tilanus, B. Fischer, Kunz, 
Beyerinck, Lehmann, and Tollhausen have added very con- 
siderably to our knowledge, not only of the morphology, but 
of the biology of these special bacteria. In certain seas, and 
especially on clear dark nights at the mouths of rivers, 
any one who has rowed over them or steamed through them 
may have observed a beautiful phosphorescence or fluorescent 
glow at the bows or at the stern of the boat. As the oars 
dip into and leave the water, they seem to shine with a pale 
phosphorescent light. All kinds of explanations have been 
given of this beautiful phenomenon, but it is now known 
to be due in part or entirely to the presence of certain low 
foims of life amongst which the bacteria take an impor- 
tant place. First of all there was described the phos- 
phorescent bacillus, then another was added, after this a 
third, and now there are described no fewer than'six of these 
light-producing bacteria, arranged in three groups of two each. 
The biological characters of these groups have been very 
carefully studied by Beyerinck, who gave the result of his 
observations in a most admirable paper presented to the 
Royal Academy of Sciences, Amsterdam, 1890. 

We may mention briefly some of the characteristic forms 
and features of these light bacilli. Photo-bactermm phos- 
phorescens, which is 1.3 to i.g/t long, and 1.5 to 1.7/i broad 
is motile and is surrounded by a gelatinous membrane ; it is 
readily cultivated on fish broth containing a small quantity of 
peptone, or in sea- water ; it also grows (though slowly) on ordi- 
nary nutrient gelatine or on nutrient gelatine to which herring 
brine or 8 per cent, common salt has been added ; it brings 
about the fermentation of glucose and maltose, its power of 
producing light being apparently closely associated with these 
fermentations, as when oxygen is cut off both the light and 

' A number of the more important colour-producing organisms will be 
found described in the Appendix. 


the ferment-forming powers of the organism are at once 
interfered with, although growth and multiplication appear to 
go on much as usual. The process of light production 
is evidently somewhat of the nature of an oxidation of the 
food elements within the protoplasm under certain definite 
conditions, the most important of these conditions being the 
presence of oxygen and a temperature ranging between 
3° and 35° C. The Photo-bacterium phosphorescens grows 
entirely as a surface colony, and although a ferment action 
is set up, there is no peptonizing power exerted, the gelatine 
remaining quite solid. 

In a tube culture the organism grows down below the surface along the 
track of the needle, but the phosphorescence is developed only on the 
surface, where the organism can obtain a plentiful supply of oxygen. In the 
neighbourhood of the colonies, after a time, the gelatine takes on a yellow- 
ish-brown tinge. On all surface growths, whether on agar, gelatine or 
potato, the growth increases in thickness rather than in surface area. It 
grows best at from 15° to 25° C. 

A rather pretty story is related in connection with this 
power of the organism to develop light. A lady, Madame 
Salomonsen, the wife of Professor Salomonsen of Copen- 
hagen, was able to obtain photographs of the light bacillus 
made on gelatine plates and so cultivated them as to form 
the letters of a complimentary message to M. Pasteur 
("Hommage a M. Pasteur") ; the photographs came out very 
distinctly, and conveyed in a most delicate and striking 
manner the message which the lady wished to send. 

Photo-bacterium Fluggeri is the most phosphorescent of 
all the light bacilli ; it grows in nutrient gelatine as longer 
and thinner threads than the preceding form. It differs 
from it also in that, although it exercises its characteristic 
light function when suppUed with peptone and glucose, 
maltose cannot take the place of glucose. Both organisms 
in setting up their fermentation processes bring about the 
evolution of CO, and hydrogen. 

If a number of fresh cod or herring, the surfaces of which have not been 
allowed to dry, be placed between a couple of plates and kept at a tem- 
perature of about 15° C. or upwards, there may be made out at the end of 
about twenty-four hours a number of small phosphorescent points, and at 
the end of a couple of days the whole of the fishes are covered with a 
phosphorescent glow; but as putrefaction sets in this glow is gradually 
lost. There may be separated from these patches an organism 1.5 


to i.g/i long and 1.3 to I.7/J broad; these rods have rounded ends 
and appear to divide exceedingly rapidly, in consequence of which 
the cells are usually almost round, and are then very like large micro- 
cocci, in fact they are sometimes compared to the Bacillus prodigiosus 
which was for long spoken of as a micrococcus. Sometimes a few organisms 
may be held together in a short chain ; the bacterium is motionless, and no 
spores have as yet been observed. On plates prepared with peptone gelatine, 
to which a small quantity of glucose, and from two to three per cent, of 
common salt have been added, the organism develops luxuriantly, giving 
rise to small white mother-of-pearl-like colonies, about the size of a pin's 
head, with no surrounding zone of liquefied gelatine. Under the microscope 
these are seen as small, round, yellowish-white, granular drops, with sharp 
but irregular margins. 

Another organism, the Plioto-bacteritim Mschert, found in 
the waters of the Baltic, peptonizes gelatine, causing it to 
liquefy very rapidly. It can exist in a medium to which a 
small quantity of raw sugar has been added, this addition of 
sugar increasing in a most remarkable manner the intensity 
of the light given off, although a large quantity of the same 
material (three to five per cent.) interferes with, or altogether 
stops, the phosphorescent activity of the organism. This 
organism is motile ; it occurs in short chains and grows on 
gelatine and agar, the former of which is liquefied by its 
action. Grown on plates, the colonies after making their 
appearance emit a kind of bluish-white light, and the 
organisms themselves as they lie at the bottom of the fluid 
gelatine have also a somewhat bluish tinge. It grows best 
at a low temperature, from 15° down to 0° C, or even lower. 

Photo-bacterium Balticum also liquefies gelatine, but more 
slowly than the above. It is not, however, dependent upon 
glycerine for its growth, and is not nearly so sensitive to the 
presence of a considerable quanity of sugar, as it can live in 
a medium containing from three to five per cent, of that 
substance. These four forms are all what may be called pep- 
tone carbon bacteria, as they cannot develop their functions 
to their highest point without the presence of some sub- 
stance from which carbon may be readily obtained such as 
sugar, glycerine, glucose, &c., as well as peptone, but the 
Photo-bacterium Fischeri and Photo-bacterium Balticum 
do not set up any ferment action as do the first two 

Beyerinck states that all four are best cultivated in fish 
broth made with sea-water, to which are added one per cent. 



of glycerine, one-quarter per cent, of asparagin, and eight 
per cent, of gelatine. 

The Photo-bactermn Indicum of the West Indies and 
the Photo-bacterium luminosum of the North_ Sea, both 
liquefy gelatine very rapidly, and appear biologically to be 
inuch more like ordinary putrefactive micro-organisms, 
though the most favourable conditions as regards tempera- 
ture for the performance of their functions differ somewhat ; 
that from the West Indies giving off most light at from 30° 
to 35° C, that from the North Sea being most active in 
this respect at about 15° C. Both of them may multiply 
and give off light in peptone gelatine without requiring 
the presence of any sugar ; in fact, they are both extremely 
sensitive to the presence of this substance, one per cent, 
preventing the phosphorescence, and three to five per 
cent, interfering with the liquefaction of the gelatine and 
eventually killing the bacteria, though, if a small amount of 
asparagin also be added to the medium in which the West 
Indian phosphorescent bacillus is growing, light may continue 
to be given off for some time. The Photo-bacterium Indicum 
is a motile rod of medium size which grows very readily on all 
the ordinary nutrient media ; the light is best seen in this 
case by taking a fish that has been boiled and inoculating 
with a fragment of the artificial culture ; there then appears 
in a very short time a soft glistening point, which is 
found to be covered with bacteria. On darkening the 
room a beautiful bluish-white light can be seen at the point 
of inoculation. The light of Photo-bacterium phosphorescens 
is yellowish. 

Beyerinck gives a number of experiments to show that the 
formation of hght bears no direct relation either to the 
respiration or to the growth of the organisms, but he finds 
that certain food substances are necessary for this light to 
make its appearance, although the, growth of the colonies 
may go on perfectly well without oxygen, even if the forma- 
tion of light be completely stopped. As soon as the 
organism is grown anaerobically, certain food substances 
also become necessary. 

the bacteria of colour and phosphorescence. 35s 


The following works may be consulted : 

Beyerinck. — Trans, of the Dutch Acad, of Scien. Amster- 
dam, 1890. 

Engelmann. — Bot. Zeit, 42-46, 1888 ; Pfluger's Arch., Bd. 
XXX., p. 9S, 1883, and Bd. xlii., p. 183, 1888. 

Fischer. — Centralbl. f. Bakt. u Parasitenk., Bd. in., Nos. 
4-S, 1888 ; and Bd. iv.. No. 3, 1888. 

Forster. — Centralbl. f. Bakt. u Parasitenk, Bd. 11., No. 12, 

Greenfield. — Scottish Fishery, Bd., Reps., vols, in., iv., and 


Katz. — Centralbl. f. Bakt. u. Parasitenk., Bd. ix., Nos. 5-8, 

Lehmann. — Centralbl. f. Bakt. u. Parasitenk., Bd. v., No. 24, 

Miller. — Micro-Organisms of the Human Mouth. Phila- 
delphia, 1890. 

Ray Lankester. — Quart.Journ. Med. Set'., vol. xiii., p. 408, 

WiNOGRADSKY. — Bot. Zeit., Nos. 31-37, 1887. 


Poisonous Alkaeoids and Albuminoids. 

Early Observations — Burrows, Kerner, Panum, &c. — Ptomaines — Leuco- 
maines — Brieger's Work— The Alkaloids, Poisonousand Non-Poisonous 
— General and Local Reactions — Structure and Composition— Sketch 
of Chemistry — Cholera Poisons and other Members of this Group- 
Mussel Poisons : two Classes, viz. , those "Without Oxygen and those 
Containing Oxygen— Ptomaines the Result of the Activity of Micro- 
organisms — Lbffler's Experiments on Diphtheria Poison, an 
Enzyme — Roux and Yersin's Diastase —Hankin, Albumose— Brieger 
and Fraenkel, Toxalbumen— Method of Preparation of Albumoses 
and of Toxalbumens — Near Relationship of Proteid Poisons and the 
Ptomaines — Martin's Observations. 

It has long been known that the products of putrefaction, 
especially those formed during the putrefaction of fish, are 
extremely poisonous. In 1814 Burrows, in this country, 
described such a poisonous substance in putrefying fish ; 
in 1820 Kerner described a poisonous alkaloid which 
resulted apparently from the decomposition of albumen ; 
it resembled in its physiological action a substance that he 
had found in poisonous sausages, and which he compared with 
atropine as regards its toxic reaction. In 1856 Panum was 
able to obtain a substance from decomposing animal matter 
which appeared to him to be derived from albuminoid 
substances through the action upon them of micro-organ- 
isms. He looked upon this as a purely chemical material. 
He was able to isolate it by dissolving it in water or 
alcohol ; in quantities of about six centigrammes it proved 
fatal to dogs, and this substance, to. which the name sepsin 
was given, came to be looked upon as the cause of putrid 
infection or intoxication. Twelve years later Bergmann 
and Schmiedeberg obtained what they took to be a similar 
substance ; it contained nitrogen, could be crystallized out 
and separated, and was also evidently the result of a putre- 
factive process. 


The first mention that is made of the probable chemical 
composition of such organic poisonous substances is found 
in a paper by Zuelzer and Sonnenschein, who describe 
as an alkaloid a substance that they were able to obtain 
from decomposing animal matter, which they said closely 
resembled atropine in its physiological actions ; it caused 
dilatation of the pupil, paralysis of the inhibitory fibres of 
the vagus, so allowing the heart's action to become accelerated, 
and paralysed the non-striped muscular fibres of the intestine. 
This alkaloid was supposed to resemble the vegetable alkaloids 
of which a considerable number had then been described : more 
recent observations have shown that these alkaloids are very 
nearly related, from the fact that they all appear to have as a 
common basis or ground structure a substance named pyri- 
dine, of which more immediately. In 1872 Armand Gautier 
described as the products of albuminous decomposition a 
number of alkaloids ; and Selmi, between 1871 and 1880, 
described what he called cadaveric alkaloids or ptomaines, 
and he was able to obtain two new alkaloids from pure 
albumen that had undergone putrefactive changes. Pouchet 
in 1880 described an alkaloid in urine, and in 1882 Bouchard 
also described alkaloids in the human urine, which, he con- 
sidered, were the result of the decomposition of proteid 
matters in the alimentary canal, and which were excreted 
from the body by the intestines and by the urine, through 
the kidneys. He concluded that these alkaloids are usually 
found in health in certain definite quantities, whilst in cer- 
tain diseases — ^typhoid fever, for instance — they may be 
enormously increased in quantity, and can then be separated 
from the urine in very considerable quantities. 

The .first ptomaine separated pure was obtained by Nencki, 
then Brieger obtained several of these alkaloids from pure 
cultivations of micro-organisms, but as early as 1880, Pasteur, 
after failing with the sterilized products of Anthrax, was 
successful in producing the symptoms of Fowl Cholera with 
the sterilized products of that organism, i.e., with the 
poisonous alkaloids or proteids. Of those in the pathogenic 
group Brieger first described the substances that he was able 
to obtain from pure cultures of the typhoid bacillus and of 
the tetanus bacillus. From the former he obtained typho- 
toxine ; from tetanus cultivations tetanine, which produces 
characteristic tetanic symptoms in animals, tetanotoxin 


which also produces some of the symptoms of that condition ; 
and two other alkaloids both of which give rise to certain 
definite _ symptoms, acting physiologically somewhat like 
strychnine. The importance of the presence of these 
substances in pure cultivations of pathogenic organisms 
can scarcely be overestimated. In the vegetable kingdom 
there are recognized whole series of substances that have 
an alkahne reaction, combine with acids to form salts, 
are evidently formed by the protoplasm of the plants in 
which they are found, and which, injected into the tissues 
of an animal or taken b}^ the stomach, exert a most 
energetic poisonous action either upon the end organs in 
muscles or upon the muscles themselves. Of these we may 
take such well-known examples as strychnine, atropine, 
nicotine, cinchonine, theba'ine, morphine, brucine, and others. 
They are all of them built up by vegetable cells and all exert 
a specific action on animals. Similarly it is found that bacteria 
— minute vegetable organisms — can build up substances, as 
they grow in dead or living animal tissues in which they are 
living as saprophytes or parasites, which substances exert 
a most deadly influence on the nerve centres or the parts 
above mentioned of animals in which they are formed or 
into which they may be injected, but in addition have an 
extremely injurious local " caustic " influence, giving rise in 
many cases to the death of the tissues with which they may 
come in contact at the points where the poison is formed, or 
at the seat of inoculation. Thus tetanine is a substance that 
appears to act through the nervous system much as does the 
alkaloid strychnine, whilst in sepsine, material formed by 
those bacteria that are found in a local abscess, we have a 
powerful acrid substance which by its caustic action causes the 
death of the cells with which it is allowed to come imme- 
diately in contact. Some of the most deadly of the poisons 
formed by micro-organisms, however, are not of the nature 
of alkaloids, but are said to belong rather to the classes of 
globulins and albumoses. A number of them, however, 
give some of the reactions of the alkaloids, but they must 
not on that account be looked upon as belonging to that 
group. Brieger includes under the term ptomaine all 
nitrogenous bases that are formed by the action of bacteria, 
such of those as are poisonous being spoken of as toxines. 
It thus happens that certain ptomaines that are formed 



during putrefactive processes are non-poisonous, whilst others 
formed during the same process may be extremely toxic ; a 
considerable number of the non-poisonous forms especially 
have been manufactured synthetically or by analysis ; tri- 
methylamine and dimethylamine, for example, both of which 
as well as Pentamethyline diamine (Cadaverine) may be 
obtained as putrefactive products and may also be prepared 
synthetically by the chemist, the artificial Cadaverine in 
sufficiently large doses giving rise to all the symptoms 
and post-mortem appearances of an attack of cholera. 
Of the poisonous kinds a substance known as betaine, 
which is closely related to nicotine and glycocol, has been 
found in both vegetable alkaloids, and in the human urine, 
in the latter being apparently the result of decomposition 
changes going on in the alimentary canal under the action of 
bacteria. It is one of the substances formed during the 
processes of decomposition of albuminoid bodies ; it also has 
been prepared in the laboratory. 

The formulas of a number of these substances is exceedingly compli- 
cated, but they all appear to be allied to or even to be derived from what 
is known as the pyridine base, a non-saturated alkaloid, derived from 
the products of dry distillation of bone or wood, from the ammoniacal 
liquor of coal distillates, and 
from the action of heat or 
strong alkaUes on the vegetable 
alkaloids. Its composition will 
behest understood by reference 
to the diagram given by Pictet 
(Fig. i). It is very nearly re- 
lated to benzol ; the only dif- HC ! CH 

ference being that one of the 
CH groups is replaced by N. 
Thus benzol has a formula 
(Fig. 2). Neither of these 
substances has all the carbon 

bonds satisfied, so that each HC^ CH 

C and the N having a bond 
free (those drawn within the 
hexagon) to combine with 
other atoms, or groups of 
atoms, there may be enormous 
numbers of derivative or addi- 
tion and substitution products formed ; for instance, all the bonds free m 
pyridine may be saturated by the addition of a single atom of hydrogen to 
each, when we have what is known as the piperidine alkaloid (Fig. 3), and 
by adding one, two or three ethyl or methyl groups to the free bonds in 
place of one, two, or three of the H's we may obtain methyl piperidine. 

Fig I. 




dimethyl piperidine, and so on throughout the whole group. In fact, where 
there are so many bonds to be acted upon the number 
of organic compounds is almost endless, and it can 
be readily seen how substances varying much in 
chemical composition can still be arranged in groups 
under a common head ; the members of each series 
having very much in common not only as regards 
HiC CHs t'^^^'^ chemical character, but, as has recently been 

pointed out, as regards their physiological action. As 
a considerable number of the benzol series have been 
manufactured by the chemist, it comes quite within 
the range of possibility that a number of the ptomaines 
T.T 1^ (especially those of the pyridine series) may also be 

W^^ CHj built up synthetically. 

The most important of the methods used for the sepa- 
ration of the ptomaines is that used by Brieger, who is 
perhaps the greatest authority on this subject. He 
goes to work with the salts of the heavy metals, and 
with picric acid. When he wishes to separate an 
alkaloid from any putrefying mass, this mass is first 
boiled with water, and then filtered ; the filtrate is then 
treated with sub-acetate of lead ; from this the lead is precipitated by 
suljjhuretted hydrogen which is passed through the filtrate, and the fluid is 
again filtered to keep back the lead sulphide. This second fiUrate is 
evaporated to about one-third of its original bulk, and is mixed with amyl- 
alcohol, it is then thoroughly washed with water, and again reduced in bulk 
by • evaporation, and sulphuric acid and ether are added ; the ether is 
evaporated, after which the remaining liquid is concentrated by careful 
evaporation to one-third of, or one-fourth of, its bulk ; the evaporation 
driving off most of the volatile fatty acids present, after which the fluid 
neutralized by the addition of baryta, is again filtered, carbonic acid gas 
is passed through it, by which baryta carbonate is thrown down which 
is separated by filtration. After careful heating over a water bath, the 
fluid is cooled, and bichloride of mercury is added, when a somewhat 
dense precipitate is formed. This precipitate is carefully washed and 
decomposed by sulphuretted hydrogen, when sulphide of mercury is 
thrown down; the fluid is again filtered and the fiUrate is evaporated 
to obtain as great concentration as possible. From the liquid so ob- 
tained all inorganic substances crystallize out first ; these are removed, 
and then in the fluid that remains "organic" acicular crystals are 
thrown down. These may be dissolved in water, but they are insoluble in 
absolute alcohol, ether, benzine, or chloroform. It is found that the sub- 
stances so given, the ptomaines, may be precipitated by the salts (especially 
the chlorides) of the heavy metals. These precipitates or crystals 
differ, however, very considerably as to their solubility ; hydrochloride of 
putrescine obtained by the above method separates out in acicular crystals, 
and on the addition of chloride of gold gives very insoluble crystals of an 
octahedral form, whilst on the addition of chloride of platinum, octahedral 
crystals which are much more soluble, ate also formed. Phospho- 
molybdic and phospho-wolframic acid added to this substance give respec- 
tively a yellow and a white crystalline precipitate. Iodide of mercury 
dissolved' in iodide of potassium also gives rise to the formation of prisms ; 


with ferrocyanide of potassium there is a yellowish amorphous precipitate; 
with picric acid a yellow precipitate composed of delicate needle-shaped 
crystals ; and with a watery solution of bichloride of mercury an exceedingly 
insoluble acicular crystalline precipitate is thrown down. This substance 
and the reactions obtained with it may be taken as typical of the whole 
group, although there are certain difierences ; for instance, cadaverine 
treated with chloride of gold gives a very soluble substance, whilst with 
chloride of platinum there are thrown down well-formed very insoluble 
crystals. Mydaleine is exceedingly soluble in most of its combinations, 
and it is at present almost impossible to separate it from the mother liquid ; 
in fact, its salts have not yet been separated, and in consequence it has 
been found impossible to determine its exact chemical nature. These, 
along with saprine, were obtained by Brieger from flesh that was being 
decomposed by the action of putrefactive micro-organisms. 

Cadaverine and putrescine are both poisonous, giving rise 
to local death of the tissues along the course of the intestine ; 
they have, however, not nearly such marked general toxic 
activity as have some of the other alkaloids. They are all 
somewhat volatile, and cadaverine as we have already seen 
is very readily formed where the cholera bacillus is allowed to 
grow and act on proteid matter such as egg albumen. Of a 
more poisonous nature is neurine, a substance that is also 
formed in connection with the putrefaction of flesh ; it has 
been separated by Brieger and is readily obtained in crystalline 
form by the addition of chloride of platinum. Choline, 
which was supposed at one time to be identical with neurine, 
and is by Brieger said to be the same substance, is really, 
hydrated neurine. These two substances are exceedingly 
toxic and appear to have an action very similar to the vege- 
table poison, curare. A very similar substance, muscarin, 
has been described by Schmiedeberg and his pupils, as 
occurring in a kind of poisonous mushroom, and was found 
to have a composition very like that of choline and neurine. 
It is an extremely toxic substance and is specially interesting 
from the fact that we have it formed as a vegetable alkaloid 
in the mushroom, whilst it has also been found in putrid 
fish, thus giving us another hnk between those so-called 
animal alkaloids found in decomposing albuminoid matter 
and the vegetable alkaloids. This substance is a most 
powerful muscle poison, its action being somewhat like 
that of eserine. 

It will be remembered that not long ago there was a sad 
case of poisoning in Dublin, in which the wife and family 
of a well-known journalist died after partaking of mussels. 


The poison in this case was probably an alkaloid substance 
that was separated from decomposing mussels by Brieger, 
who gave to it the name of mytilotoxine. Dr. Vaughan in 
America separated from cheese that had undergone putre- 
factive changes a substance that he called tyrotoxine, and 
he was able to separate from some ice cream that gave rise 
to most acute poisoning a very similar substance. 

Jacquemart, giving an account of these ptomaines, divides tliem into two 
groups — those that are fluid and are volatile, that have a peculiar characteristic 
smell, and that contain no oxygen, being in the first group ; thoSe in the 
second are sohd, non-volatile and contain oxygen. Those of the first group 
are soluble in ether and also slightly in amyl-alcohol and chloroform. The 
members of the second group are usually crystalline, are soluble in water, 
but are insoluble in alcohol, benzine, and chloroform. Although they are 
extremely unstable they unite with acids, in excess of which, however, they 
are soluble, when we have first a red colour and then a brown deposit of 
acicular crystals. An excess of chloride of platinum or strong light usually 
causes their disintegration. It should he remembered that corrosive 
sublimate does not precipitate some of these alkaloids, although there is 
undoubtedly a salt formed which can be obtained in white crystals by 
evaporating from watery solutions. The only substance that gives invariable 
reactions with all these ptomaines is phosphomolybdic acid. 

The following ptomaines contsin no oxygen : Parvoline, described in 
1881 by Gautier and Etard, who obtained this substance from putrefying 
mackerel and horse- flesh ; its formula is C9H15N (also given as C5H13N). 
It is a light yellow substance readily soluble in water, alcohol, ether, and 
chloroform, it turns brown on contact with the air ; with chloride of platinum 
'it forms a somewhat insoluble crystalline flesh-coloured substance, which 
rapidly becomes rose-coloured on exposure to the air. These authors also 
described a substance HydrocoUidine (formula CsHijN, sometimes given 
as having two atoms less hydrogen). It is a colourless, oily fluid, becoming 
brownish on exposure to the air; when treated with carbonic acid gas it 
becomes sticky. It forms a double salt with chloride of platinum, a pale 
yellow crystalline insoluble substance, though it dissolves on heating 
without undergoing any disintegration. CoUidine, with the formula 
CsHiiN, was first obtained from decomposing pancreas and gelatine. It is 
a yellowish, mobile fluid with an extremely offensive odour, very soluble in 
water, but much more soluble in methyl and ethyl alcohol and in ether. 
Neuridine, CsII,4N2, Cadaverine, CsHisNa (sometimes given as isormeric 
with neuridine). Putrescine, C4H,2N„ Saprine, CsH^Nj, and Mydaleine, 
all belonging to this group, have been already mentioned. The 
ptomaines that contain oxygen hold a kind of intermediate position 
between the above group and the Leucomames or physiological alkaloids. 

Neurine, CsHiaN (OH), is a strong base exceedingly soluble in water. 
Choline, C5H1SNO2, Muscarine, CsH.sNO, (or CsHijNOj, or Choline from 
which Hj Has been removed by nitric acid), and two other ptomaines 
described by Pouchet, and having the formula C^H.jNsOs and CsHisNsO^ 
make up the solid ptomaines of the second group ; whilst Gadinine 
C^HiyNOs is not solid, although in other repects it resembles the members 


of this second group. To this group also belong Mytilotoxine, CeHijNOs, 
Typhotoxine, QH.^NOj, and Tetanine Ci3ll22Nj04, which appears to be 
really a double pyridine molecule, and is therefore probably a mixture, as are 
also a number of the others above mentioned. 

Most of these substances are found to be associated with 
the decomposition of dead material by micro-organisms, but 
it has long been known that substances similar in many 
respects (some of them of an exceedingly poisonous nature) 
are formed in the body of the living subject, resulting from 
the purely physiological nutritive changes in the protoplasm 
of the various organs and tissues in the body ; they are 
in fact excretory products which must be got rid of, and 
which if retained interfere, in some cases very materially, 
with the vitality of the protoplasm. These were named 
kucomaines by Gautier to distinguish them from the 
ptomaines ; they are fully described in physiological text- 
books with the uric acid and creatinine groups of sub- 
stances, to one or other of which they belong as far, at all 
events, as their chemical composition is concerned. Some 
of these leucomaines are, as we have said, exceedingly 
poisonous, and when retained may give rise to very serious 
toxic symptoms. Brieger and others, however, deny that 
any such bodies are formed or at any rate have yet been 
found in the tissues of the living body or that they owe their 
existence to the tissues. They consider that they are simply 
absorbed from the intestinal canal where they are formed by 

In 1887 LofBer, when examining the products of a pure 
culture of the diphtheria bacillus that he had obtained, found 
that the fluid from which all the organisms had been 
removed by filtration through a porous porcelain cylinder, 
when injected into a guinea-pig gave both the local reaction 
and the paralytic symptoms that were obtained when the 
organism itself was introduced into the subcutaneous tissue. 
In order more readily to determine the nature of this material, 
he added to a pure culture of the organism a quantity of 
glycerine ; this wheh filtered and dropped into absolute 
alcohol gave a floculent precipitate which could be freely 
washed with alcohol without passing into solution, but on the 
addition of water it was again dissolved. It could be again 
precipitated by alcohol, and after the passing of carbonic 
acid gas through the precipitate, it retained a certain toxic 


property,— Still setting up distinct local reactions. Loffler 
eventually concluded that he was dealing with an enzyme. 

I have already mentioned Roux and Yersin's experi- 
ments, from which they also concluded that they had ob- 
tained a substance similar in many respects both to a disastase 
and to an enzyme. Hankin, working from the fact that a 
poisonous albumose had been discovered in snake poison, 
set about the task of isolating an albumose from anthrax 
cultures. He made a cultivation of anthrax bacilli, then pre- 
cipitated it by large quantities of absolute alcohol and washed 
the precipitate thoroughly to dissolve out any ptomaines 
that might be present ; this precipitate was filtered and 
dried, then re-dissolved in water and the solution passed 
through a Chamberland filter. This albumose is very 
similar in its characters to the albumoses ordinarily described, 
which really consist of albumen that has been altered by 
hydration either by super-heating by steam under pressure, 
or during the process of natural digestion, in which albumens 
are converted stage by stage into peptones. These albu- 
moses are intermediate non-coagulable hydrated .albumens. 
Some forms are soluble in water, others are insoluble. That 
described by Hankin as formed by the anthrax bacillus is a 
soluble form. Brieger and Fraenkel obtained what were 
apparently similar substances from pure cultivations of cholera 
bacillus, typhoid bacillus, tetanus bacillus, from staphylo- 
coccus aureus, and diphtheria bacillus, with all of which they 
were able to produce toxic effects, some at least of which were 
similar to those met with as the result of inoculation with 
the bacteria themselves. These observers, however, did not 
separate from the albumoses that were formed any enzymes 
that might be present, consequently they were working 
with a mixture of substances. The products that they 
obtained gave most of the reactions of albumoses ; they were 
cert^nly toxic, but they probably contained both enzymes 
and albumoses. 

As these albumoses, described though not recognized under 
that name by Wooldridge, are destined apparently to play a 
most important part in the production of immunity against 
disease, it may be well here to give a short description of the 
methods adopted by Hankin to obtain his albumose from the 
anthrax cultures, and by Brieger and Fraenkel and Babes from 
cultures of other organisms (Sidney Martin has been able to 


separate from anthrax cultures, in addition to a poisonous 
alkaloid, two albumoses, which apparently represent slightly 
different stages in the transformation of albumen into pep- 
tone) : it may be well also to give the characteristic reactions 
that are obtained with these albumoses. 

Hankin's method is as follows : A 1 per 1,000 pure solution of Liebig's 
extract of meat is carefully sterilized by being heated in a small sterilizer for 
two or three hours on two or three successive days ; to the fluid so sterilized 
a. quantity of pure fibrin is added and the whole is again sterilized " by 
repeated heating to boiling point for a short time only on each occasion " ; 
if this is heated for a longer period a considerable quantity of the fibrin is 
digested and converted into peptone, a substance that would interfere very 
considerably with the after-examination, in addition to which the anthrax 
bacillus would have little material left on which to exert its " peptonizing " 
function. This is inoculated with blood from an animal that has died from 
anthrax and is "kept at the ordinary temperature. " The cultivation is 
allowed to go on for a week, at the end of which time the albumose is 
extracted. If the flask be kept at the temperature of the body, 37° C, the 
transformation of the albumose into the peptone goes on much more rapidly. 
To separate the albumose the culture fluid is first acidulated with acetic acid, 
and then thoroughly saturated with ammonium sulphate, when there is thrown 
down a bulky precipitate of albumose. In order to concentrate the solution, 
instead of using Brieger's method of evaporation iit vacuo or under pressure at 
a low temperature he resorted to the method of diffusion or dialysis. A quan- 
tity of thymol, to prevent putrefaction, is added to a watery solution of the 
albumose, and the whole is placed in a parchment sausage skin which is im- 
mersed in a foot glass full of methylated spirit. The spirit can be changed 
after some hours if it is necessaiy to prolong the process, but this is not 
usually necessary. " In this way," says Hankin, " I have been able to bring 
400 cubic centimetres of albumose solution down to 100 in the course 
of a single night, at the ordinary temperature without risk to the albumose 
or trouble to myself. The concentrated solution is then poured into 
absolute alcohol, which precipitates the albumose and removes any im- 
purities that might be derived from the methylated spirit. This prolonged 
treatment wdth alcohol will tend to remove any free ptomaines or other 
substances soluble in alcohol." In order to remove any ferments that are 
capable of acting along with the albumose, Hankin, following Roux and 
Yersin, adds a quantity of lime water to his solution, so that, on the addi- 
tion of a solution of phosphoric acid, a gelatinous precipitate of calcium 
phosphate is produced, in the formation of which ferments are usually 
entangled and carried down, and on filtration a purer solution of albumose 
is obtained. 

Brieger and Fraenkel have adopted Hankin's method in the 
preparation of their toxalbumens, but instead of dialyzing, 
they evaporate down tn vacuo at a low temperature until 
the liquid has been reduced to less than a fourth of its 
original quantity. They again wash in alcohol and filter. 


Brieger and Fraenkel found Millon's reagent gave a 
white precipitate, which on heating became brick red in 
colour ' this indicating its proteid nature ; it is precipitated 
by magnesium sulphate in saturated solution ; it is there- 
fore not an ordinary albumen ; whilst on the addition of a 
drop of dilute sulphate of copper solution and a slight 
excess of potash solution (the so-called biuret reaction) a 
rose red and not a violet colour is given, indicating that 
this material belongs to the albumose rather than to the 
globulin group. There are a number of other tests which 
it is not here necessary to describe. 

It must be remembered, however, that these proteid 
poisons and the ptomaines are very closely bound up 
with one another. Martin indeed holds, that as some of 
the albumoses are less toxic than the alkaloids with which 
they occur and as they also have a marked alkaline reaction, 
the alkaloid may really be bound up in a nascent condition 
in the albumose molecule. This may undoubtedly be the 
case with certain vegetable alkaloids and albumoses, but in the 
cases of diphtheria and tetanus, it would appear that some of 
the so-called poisonous alkaloids owe their specific properties 
to the presence of minute traces of an enzyme, or proteid 
poison that is present along with them. It has even been 
suggested that the alkaloid may be the poisonous agent 
formed by bacteria, whilst the albumose is to be looked upon 
as the protective agent. This, however, can scarcely be 
maintained except in certain cases, as in the case of tetanus 
the poisonous agent is certainly not of an alka.loidal nature. 
Still, these points should be borne in mind by any one going 
to work at the question. It seems to be undoubtedly the 
case, that in accordance with the well-known fact that 
certain products of micro-organisms, such as those of acid or 
alcoholic fermentation, act deleteriously on the bacteria that 
produce them, especially as they accumulate in large quan- 
tities. On the other hand, it may be that these, or similar 
products in a more or less dilute form, may be necessary 

' Millon's reagent is prepared by adding one part of mercury to two 
parts of strong nitric acid, gently warming until the mercury is thoroughly 
dissolved : to one part of this mixture two parts of water are added ; a 
precipitate is formed ; the supernatent fluid only is used. A few drops 
of this solution give the above characteristic reaction with all proteid 
materials held in solution except in the presence of common salt. 


in order to allow of the growth of bacteria as parasitic 
organisms in animal tissues. 


The following works may be consulted : 
Authors already referred to. Babes, Brieger and Fraenkel, 
Hankin, Roux and Yersin. 
Bergmann und Schmiedeberg. — Med. Centralbl., No. 32, 

q.497, 1868. 
Bouchard. — Comptes rendus de la Soc. de Biol., p. 604, 

Brieger. — Untersuchungen uber Ptomaines, Three parts. 

Berlin, 1885-6. 
Gautier.— Sur les Alcaloids, &c., Paris, 1886 ; Bull, de 

I'Acad. de^Med., 2"« Serie t. xv.-xvi., 1886. 
Gautier et Etard. — Comptes rendus, t. xciv., p. 1601, 

, 1881. 
Griffiths. — Micro-Organisms. London, 1891. 
Halliburton. — Text Book of Physiology and Pathology. 

Hankin. — Proc. Roy. Soc. May 22, 1890. 
Jacquemart. — Journ. de Med. de Chir. et de Pharmacol. 

Bruxelles, No. 18, 1890. 
LoFFLER. — ^Mitth. a. d. k. Gesundheitsamte, Bd. 11., p. 421, 

1884 ; Die Geschichtliche Entwickelung der Lehre von 

den Bacterien, Leipzig, 1887 ; Deutsche. Med. Woch., 

S and 6, 1890. 
Nencki. — ^Ueber d. Zersetz. d. Gel u. d. Eiweisses b. d. Faul- 

niss Mit Pankreas. Bern., 1876 ; Berecht d. deutsch 

Chem. Gesellsch., p. 2605, 1884; Journ. f. Prakt. Chemie, 

Bd. xxvL, pp. 268, 273, 1882. 
Panum. — Bibliotek for Laeger, pp. 253-285, April, 1856 ; 

Virch. Arch., Bd. lx., p. 301, 1874. 
Pasteur. — Comptes rendus, t. xc, p. 1030, 1890. 
Selmi. — Ber. d. deutsch. Chem. Gesellsch., 1 873-1 880 ; 

Alcaloidi Venefici esostanza amiloide dall'albumina in 

putrefazione. Rome, 1879. 
SoNNENSCHEiN AND ZUELZER. — Berl. KUn. Woch., p. 123, 

Sydney Martin. — Proc. Roy. Soc. May 22, 1890. 



Natural Immunity— Ingrafting of Small-pox— Jenner's Discovery— Kleb 
— Pasteur — Chauveau — Grawitz's Theory — Buchner's Theory — Met 
schnikoff s Work — Greenfield's Observations on Anthrax — Toussaint' 
Vaccinal Fluid — Pasteur's Classical Experiments — Other Methods c 
Diminishing Virulence — Chauveau's Soluble Poison Experiments- 
Protection by Alkaloids, Albumoses and Toxalbumens — Saprophyti 
" Anthrax " — Hueppe and Wood — Antagonism by Blue-pus Product 
— Immunity not the same as Antagonism — Summative Action o 

It has long been recognized that in a number of infective 
diseases, one attack confers a certain immunity againsi 
that special disease in the future. This protective influ- 
ence may last for a very considerable period, or there may 
be merely a temporary immunity. It was early noticed, 
however, that the severity of the primary attack of the disease 
appeared to bear no very definite relation to the degree of 
immunity acquired by the patients, although immunity of 
an animal usually bears a very-direct relation to the strength 
of the vaccine which it has withstood. In fact every degree 
of immunity may be produced, though this does not always 
correspond with the severity of the symptoms. Immunity 
appears to be governed by no very regular laws, for it 
is found that even in the same species, individuals may 
differ very considerably as regards susceptibility to first 
or subsequent attacks of some of the infective diseases. It 
is known, for example, that whilst certain people have 
never more than a single attack of measles, others may 
have several, and that similarly, certain individuals are 
specially liable to the recurrence of scarlatina, suffering 
no fewer than three, four, or even more attacks. When 
differences of species are taken into account these differences 
of susceptibility are even more marked ; thus sheep and 
cattle are protected against subsequent attacks of anthrax by 


a first, whilst in the human being and in the horse, anthrax 
may occur again and again, though in all probability a 
temporary immunity is conferred by an attack even in 
these extreme cases. 

Cholera and typhoid fever both belong to the group of 
diseases of which one attack usually confer a certain degree of 
immunity against a second, the period during which this may 
last, however, varying in different cases ; in some it extends 
over a few years only, whilst in others it appears to be almost 
permanent. The acute exanthemata, of which we may take 
small-pox as an example, belongs to this latter class. 

Amongst the Turks the ingrafting or inoculating of small- 
pox matter was very early resorted to as a routine practice in 
order to produce a milder but protective attack of the disease. 
We have a record of this in one of Lady Mary Wortley Mon- 
tague's letters, dated 23rd March, 171 8, and written from Bel- 
grade, in which she describes the inoculation of her little 
boy three years old. She says : " The boy was ingrafted last 
Tuesday,and isat this timesinging and playing, very impatient 
for his supper ; I pray God that my next may give as good an 
account of him. I cannot ingraft the girl ; her nurse has 
not had the small-pox." The after progress of the patient 
in this case was satisfactory, and, as is well known. Lady 
Mary was afterwards instrumental in drawing attention to the 
matter in this country. 

Then came Jenner's remarkable discovery that similar 
immunity against small-pox might be conferred by the 
inoculation of lymph from animals that were suffering from 
what was known as cow-pox ; an attack of the one disease 
in this case conferring an immunity against an attack of the 

There has for long been the utmost anxiety on the 
part of physicians and others to obtain some explanation 
of these remarkable facts. Klebs and Pasteur explained 
them on the assumption that during the course of a first 
attack of a disease some material that was essential for the 
nutrition of the pathogenic organisms that had by this time 
been found to be associated with some of these diseases, 
had been used up, and the supply being cut off, the organ- 
isms were no longer able to exist in the body and exhibit 
the characteristic evidence of their presence. This substance 
must have been present in exceedingly small amount, as no 



alterations in the composition of the blood or other fluids ol 
the body could be determined by any methods of chemical 
analysis that could then be applied. Then came the theorj 
advanced by Chauveau and others : that just as micro-organ- 
isms when growing in artificial media produced excretorj 
products, the presence of which was inconsistent with the 
continued life of the organism ; so in the body, bacteria 
during the course of the disease gave rise to some materia] 
which might act deleteriously on their own protoplasm, and 
which, remaining in the body for a considerable length ol 
time, interfered with the growth of any similar organisms that 
might in future be introduced. Here, again, these special 
chemical products could not be detected in the blood, and 
must have been present in such infinitesimally small quan- 
tities that it is difficult to see how they could exert any very 
marked influence on the activity of the bacteria ; whilst, as 
Fliigge points out, our knowledge of the action of the tissues 
on foreign bodies of various kinds would lead us to the conclu- 
sion that any such material would be very rapidly eliminated, 
Then Grawitz suggested that in any battle between the cells 
and the bacilli that may occur in the body during the course 
of a disease, if the cells can but manage to obtain the uppei 
hand and to destroy the bacteria, they should become 
hardier, as it were, through the training of the contest, theii 
vital energy and assimilating power should be increased, 
and they should thus become able to deal in a more summarj 
manner with any organisms with which they might afterwards 
be brought into contact. Then came Buchner's theory oi 
the inflammatory cause of immunity, which offered anothei 
explanation, or modification of Grawitz's explanation. He 
argued that bacteria made their way into the body at certain 
special points, these points or seats of election differing in dif- 
ferent diseases, and that in consequence of the development ol 
the bacteria, there was a reactionary alteration, inflammatorj; 
in its nature, in the tissues, which fitted them for the future to 
resist the special organism that had previously made the 
attack ; this minute alteration in the function of the special 
cells at the seat of invasion enabling them to resist the further 
action and invasion of the same organism even at a con- 
siderably later period. Again based on the same principles 
as Grawitz's theory came the now celebrated Metschnikofl 
theory. Metschnikoff holds that the protection against the 


attacks of micro-organisms on the body is entirely due to the 
action of the amoeboid cells of the body, that these cells are 
living pieces of protoplasm, that they are constantly taking 
into their own substance all foreign particles which find their 
way into the body, that wherever there is an extra demand on 
their energies, a large number are attracted to the point at 
which the work is to be done, and that these cells acting on 
the micro-organisms just as they do on foreign bodies, take 
them up into their substance', digest and convert them 
partly to their own uses, and gradually throw into the circu- 
lating fluids of the body small quantities of effete substances 
which are removed by the ordinary physiological channels. 
Some observers, however, hold that the process is not so 
simple as it would appear ; certain bacteria secrete substances 
which appear to exert a paralysing effect on the cells, and 
may so alter them that they are unable to perform their 
proper functions ; whilst, on the other hand, the cells secrete 
in the performance of their work a material which has an 
unfavourable influence on the activity of the bacteria. This 
at first sight is an extremely feasible explanation, but when 
we come to consider more carefully the conditions under 
which immunity against diseases is conferred, we find that, 
although in certain cases an attack of one disease protects 
against an attack of a more serious and deadly malady, this 
occurs only within certain definite and well-defined groups 
of diseases ; there appears, therefore, to be something more 
than a mere general protective influence generated within 
the body. We must have specific powers of resistance 
developed in or by the cells in order that they may be able 
to resist specific bacterial activities, and the effects of specific 
bacterial poisonous products. I have in previous chapters 
spoken of the effects of the bacteria and of their products in 
protecting against the various diseases to which they them- 
selves give rise ; it may now be well to give a concrete 
example of the theories that have been advanced as to the 
nature of this protective inoculation ; let us take the develop- 
ment of the methods that have been devised for protecting 
animals against anthrax. 

It was found that on devitalizing the anthrax organism 
by one of several methods it might be introduced into the 
subcutaneous tissue of a sheep without giving rise to any 
very serious symptoms. The first note that the virulence 


of the anthrax could be modified was communicated in this 
country by Greenfield, on June 1 7, 1 880, to the Royal Society 
of London. This observer found that by cultivating anthrax 
bacilli through several successive generations, in fluid taken 
from the front part of the eye of the ox, he was able tc 
obtain a virus so modified that when injected into animals 
susceptible of being affected by ordinary anthrax, the 
animals did not die, whilst in animals injected with aqueous 
humour cultures of the twelfth generation no symptoms 
whatever were developed ; earlier cultures giving rise to a 
modified form of anthrax only. 

In the following month Toussaint intimated to the French 
Academy that he had been able to obtain a protective 
anthrax vaccinal fluid, t.e.^ one that might be inoculated 
into an animal without causing death, and which conferred 
on animals so inoculated protection against a second attack 
of the disease. 

His original method of procedure was as follows : — The blood of an 
animal dead of anthrax was carefully defibrinated by whipping and straining 
through linen and then through ten or twelve thicknesses of blotting-paper. 
Some animals were undoubtedly protected by the inoculation of this pre- 
pared blood, but the method was very uncertain ; and in some cases 
the vaccine itself caused the death of the animal. Instead, therefore, oi 
filtering the defibrinated blood, he heated it for ten minutes to a temperature 
of 55° C. With material so prepared he was able, by inoculation, to rendei 
an animal immune to the action of the more virulent anthrax bacillus. 

Pasteur, who concluded that the vaccination depended not 
on the bacterial products but on an alteration in the viru- 
lence of the bacillus which might be the result of the altered 
temperature, subjected the bacilli to a temperature of from 
42° to 43° C. ; these were found to have lost all their vitaUty at 
the end of about six weeks, this loss of vitality during the six 
weeks going on progressively in proportion to the rise of 
temperature. It is stated that at the outset the pure 
culture had all the virulence of anthrax blood ; whilst 
only half of the sheep inoculated with the culture, that 
had been heated for twelve days succumbed to anthrax. 
On the twenty-fourth day of heating, the culture, when 
inoculated, although giving rise to mild febrile disturbance, 
did not cause the death of a single animal. It was found, 
too, that if now, twelve days after the first inoculation, these 
surviving animals were inoculated with a culture from the 


twelfth day, which before had killed half the animals, there 
was still only a slight febrile disturbance, and none of the inocu- 
lated animals died. Virulent anthrax blood, might, after a 
further interval of twelve days, be introduced into animals 
that had been subjected to the double inoculation, without 
giving rise to anything more than a slight febrile condition 
similar to that noticed as resulting from the inoculation of 
the modified virus. If, however, virulent anthrax blood was 
introduced into animals in which only the first protective 
inoculation had been made {t.e., with material that had been 
cultivated for twenty-four days), a "large proportion of the 
animals died. It was evident, therefore, that it was abso- 
lutely necessary to use both a first and a second vaccine if 
the protection was to be complete. This attenuation was 
not confined to the generations of bacilli that were directly 
acted upon. If the temperature were lowered to about 35° 
C, vegetative activity was immediately set up, rods in 
enormous numbers were formed, and eventually spores might 
be observed in these rods. Now comes the interesting fact : 
the attenuated properties of the original bacilli were handed 
on to the spores ; these spores might be kept in a latent 
condition for a considerable length of time, and on being 
introduced into media suitable for their growth they sprouted 
outj not into virulent anthrax bacillt, but into modified anthrax 
bacilli, so that the conservation of the vaccine (on silk 
threads) became a comparatively simple matter. 

Pasteur attributed the diminution of the virulence of the anthrax bacillus 
to the action of heat in the presence of oxygen, but Chauveau, working on 
Toussaint's plan, found that heat alone continued for a very short period was 
quite sufficient to modify the virulence of the bacillus. Blood is taken from 
a guinea-pig about thirty-six or forty-eight hours after inoculation with an 
active virus ; it is carefully defibrinated and is run into small glass pipettes of 
about I mm. in diameter. One end is carefully sealed by heat so far from 
thi blood that the heat cannot injure the organisms ; the sealed end contain- 
ing the blood is plunged into water at a temperature of 50° C, and is kept 
in^this for about a quarter of an hour ; in this way is prepared what is 
known as the primary vaccine, corresponding to that obtained by Pasteur, 
by heating for twenty-four days. The second vaccine is heated for only 
nine or ten minutes, and corresponds to that obtained by heat at the lower 
temperature for twelve days. These vaccines are injected in the same way 
as Pasteur's at intervals of from ten to fifteen days and they are found to 
protect very fully against the most active virus. Where large quantities 
of the vaccine have to be made by this Vapid method, Chauveau used 
sterilized broth which is inoculated with anthrax blood from a newly killed 
animal ; the flasks are then kept at a temperature of 43° C. for about 


twenty hours and the temperature is then raised to 47° C. for a period of 
three hours. This is the second vaccine. The first vaccine is a culture 
made from one that has been heated for three hours at 47° C. ; this is 
incubated for from five to seven days at 35° to 37° C._, and then for one 
hour at 80°. Of these vaccines two drops are used for inoculating a sheep 
and four for cattle, the animals being injected, cattle on the outer aspect of 
the ear, sheep inside the thigh. The great drawback associated with the 
use of vaccine so prepared is that it cannot be preserved for any length of 
time, as under cultivation the original virulence is regained at once. 

Pasteur's classical experiments made in May 1881 gave 
abundant evidence of the utility of this method of treat- 
ment. On the Sth of May, twenty-four sheep, one goat, 
and six cows were inoculated with a protective vaccine ; 
twelve days afterwards they were again inoculated with a 
somewhat stronger vaccine than that at first used, and on 
the 31st of May these animals that had already been vac- 
cinated, and twenty-four sheep, one goat, and four cattle 
that had not previously been inoculated with the protective 
virus, were injected with material from a virulent anthrax 

On the 2nd of June all the animals that had been 
protected were found in apparent health ; of the others, 
twenty-one sheep and the goat were dead, two other sheep 
were dying, and the other was attacked later in the day. 
The non-vaccinated cows were not dead, but they had all 
marked local symptoms. Next day one of the vaccinated 
sheep died, but its death was said not to be due to anthrax. 
The experiment was repeated in a modified form by injecting 
a quantity of blood and spleen pulp from a sheep that had 
died of anthrax into sixteen non-vaccinated animals, and 
into nineteen protected animals, with the result that on the 
third day all the unprotected animals but one had succumbed, 
whilst the others remained apparently healthy. 

Equally good results were not always obtained by other experimenters, 
but in some cases, at any rate, the experiments appear to have failed 
through want of attention to detail rather than from any defect in the 
method itself, and from the failure to recognize that the initial virus is not 
always of the same strength, that different animals have very different 
degrees of susceptibility and natural immunity, and that the quantity of 
the virus injected very materially alters the conditions of the experiments. 
No tissues can be expected to cope equally well with large and with 
small doses. 

A number of other methods of preparing a less virulent {or vaccine) 
material have been described by different observers. Thus Toussaint 


found that if anthrax were treated with a one half per cent, solution of 
carbolic acid, it became distinctly attenuated. Chamberland and Roux 
found that fresh cultures started from one that had been subjected for 
twelve days to .16 per cent, solution of carbolic acid were fatal to 
guinea-pigs and rabbits, whilst if the time during which the bacillus was 
exposed to this solution of the acid was extended to twenty-nine days and 
a cultivation then made, such cultivation was no longer capable of killing 
a rabbit. They were thus able to produce a virus of any degree of attenua- 
tion and to preserve it for some time, as the cultures made from their 
attenuated bacilli inherited the same degree of attenuation that had been 
developed by the bacilli that had actually been treated with the acid. They 
found that bichromate of potash and other antiseptics exerted a similar 
attenuating iniluence. It has also been shown that the passage of the 
anthrax bacillus through a series of animals of a certain species will 
render the anthrax bacillus more or less virulent, according to the 
species that is used. Thus Klein found that blood taken from a white 
mouse which had died of anthrax was a protective vaccine for sheep, 
whilst Sanderson and Duguid observed that the virus obtained from a 
guinea-pig dead of anthrax was modified so far as cattle were concerned. 
Roy made a series of similar observations. It must be borne in mind, 
however, that cattle very frequently recover from anthrax under ordinary 
treatment, so that these latter observations can, as yet, scarcely be accepted 
as fully proved. 

Up to this time it had not been recognized that the 
immunity was really conferred by the action of the soluble 
products of the organism. Pasteur had indeed shown that 
the general sym.ptoms of fowl cholera could be induced by 
the inoculation of the sterilized products of the fowl 
cholera germ, and Chauveau had suggested that an 
acquired immunity was due to the action of the soluble 
products of the microbe. He argued from an observation 
that, although in pregnant sheep, anthrax bacilli with 
which they had been inoculated were unable to pass into the 
fcetus, the lambs exhibited an extraordinary immunity 
against attacks of anthrax, this immunity, he considered, 
being necessarily the result of the action of the soluble 
products that had been able to pass over from the maternal 
to the foetal circulation. We have now a whole series of 
diseases from which immunity may be conferred by the inocu- 
lation or introduction into the tissues of an animal of the 
soluble products of pure cultures of micro-organisms. 
In America, hog cholera has been vaccinated against, the 
vaccinator using the sterilized cultures of the hog cholera 
organism as his protective virus. Wooldridge, who was the 
first to adopt this principle in connection with anthrax, was 
followed by Pasteur and Perdrix, and by Hankin, whose 


researches on the albumoses formed by the anthrax organism 
have opened up a new field for the chemistry of bacteriology. 
Fowl cholera, certain forms of septicaemia, and a number of 
other diseases, amongst which may be mentiorted hydro- 
phobia, in which, however, the facts do not belong to quite 
the same order, all were brought within the same zone, 
when it was found that the introduction of the sterilized 
products of a specific organism, first in minimal doses and 
then in gradually increasing doses, could confer a protection 
against the subsequent action of even the most virulent 
organism that under ordinary circumstances gives rise to the 
same products as those injected. Gradual " acclimatization" 
is the ideal method though in most cases the results were 
obtained by a single injection. It was for long supposed 
that the products through which this immunity was con- 
ferred were of an alkaloidal nature, and there can be little 
doubt that in some cases, at any rate, these alkaloids may, if 
given for a sufficiently long period of time, and in gradually 
increasing doses, have some effect in " acclimatizing " the 
tissues to the action of the poison. As pointed out by 
Sewall, who carefully studied the substances contained in 
snake poison, the albumose contained in such poison, given 
in very minute doses to pigeons, confers upon them the 
power of withstanding seven times the ordinary deadly dose 
of snake poison, even three months after the inoculation 
has been made. A single dose of the ordinary hemi- 
albumose of proteid digestion confers a similar immunity 
against the action of this same albumose for a period of twelve 
hours. Hankin, working on this analogy, concluded that 
the albumose that he was able to separate from anthrax 
bacilli was really the substance that conferred the immunity 
against attacks of the bacillus itself, and he found that, 
although he could kill rabbits with doses of the five 
millionth of the body weight, a dose of one-ten millionth 
of the body weight rendered the animal immune to the 
action of virulent anthrax. He found that he had obtained 
an instrument of such delicacy, although of so great power, 
that he was able to protect even mice against anthrax, which 
had only been done once before — by Hueppe and Wood. It 
would appear, however, that it was necessary to allow a certain 
interval to come between the inoculation with the albumose 
and the injection of the virulent anthrax organism. This is 


an exceedingly interesting fact, for from it we gather that the 
protective material acts in much the same way as does the 
poison of the anthrax bacillus itself, showing that the 
poisonous and the protective agents may be one and the 
same, in certain diseases at any rate. We have, in fact, if we 
introduce it at the same tune as the living organism, a 
cumulative action during the earlier stages, the albumose 
helping the anthrax bacillus (by additional albumose being 
formed) to do its work. Where, however, there is an 
interval allowed between the introduction of the albumose 
and the inoculation of the virulent material, there is time 
allowed for the tissues of the body to become acclimatized, 
as it were, to the action of this special material, so that when 
the stronger poison is introduced the cells are more ready to 
deal with it. A very interesting fact in this connection is, as 
pointed out by Hueppe and Wood, that a certain putre- 
factive organism, the earth bacillus, which in all morpho- 
logical characters resembles the anthrax bacillus, and differs 
only in the fact that it does not give rise to any fatal disease, 
even in mice, was able when inoculated into mice and rabbits, 
to afford protection against anthrax that otherwise proved 
fatal to these animals. These observers concluded from this 
fact that the saprophytic organism must be closely related 
to the anthrax organism, and that it formed much smaller 
quantities of the same specific poison as the disease organisms, 
so that by its previous introduction these cells were prepared 
for the attack of the specific anthrax poison, and the disease 
was checked or modified. They indicate that the relation of 
the saprophyte to the parasite is merely a quantitative one, 
having an analogy in the relation that one of our cultivated 
flowers bears to its wild progenitor. On the other hand Wood 
and I have observed in a series of experiments that we 
carried on with the products of the blue pus bacillus that 
we had a kind of antagonistic influence exerted by the 
blue pus products on the action of the anthrax bacillus. 
That the favourable influence exerted by the blue pus pro- 
ducts in the course of an attack of anthrax was not due merely 
to an antiseptic action was proved by the fact that the anthrax 
bacillus could actually grow in the blue pus products, al- 
though, under these conditions, it was undoubtedly somewhat 
weakened ; and we came to the conclusion that we had to 
deal with a kind of biological antagonism acting indirectly 


through the cells. We observed that animals treated by 
inoculation of the blue pus products and then with anthrax 
bacillus not only passed through the disease at the time, but 
they were protected against anthrax, even of a virulent 
order, when inoculated later. This we looked upon as most 
interesting, as in other experiments that had been carried on 
with the blue pus bacillus itself as a protective agent against 
anthrax, it was found that although an attack of anthrax was 
cut short in the presence of the blue pus bacillus in a 
rabbit, it could still be so inoculated at a later date that the 
animal died with symptoms of true anthrax. The inference 
we drew was, that the action of the products of the blue 
pus bacillus and the action of the anthrax albumoses on the 
cells are essentially different but that the one may interfere 
with the action of the other. Thus, an animal that has been 
rendered immune to blue pus is none the less susceptible to 
anthrax. In our experiments the products of the blue pus 
bacillus were injected only at intervals, and during part of 
the time between these intervals there was little of the 
substance in the fluids of the body ; during these intervals 
the albumoses of the anthrax had the opportunity of acting 
on the tissue cells and of so acclimatizing them to its 
presence that immunity was conferred. Where, however, 
the blue pus bacillus was in the body, forming its products 
continuously and acting antagonistically to the anthrax 
bacillus, the tissues had never any opportunity of becoming 
acclimatized to the action of the albumoses and no immunity 
was conferred. Immunity produced by the attack of a 
specific disease must then be looked upon as an acquired 
tolerance or adaptation of the cells of our body to the specific 
poison of the special bacterium of that disease, and the pro- 
cess of recoveryfrom an attack of anthrax, for example, is really 
the development of such immunity, which gradually passes 
into the more perfect form during the course of the disease 
and remains after the patient has recovered. The antago- 
nism of the products of one organism on another which occurs 
in mixed infection can never in all probability act directly 
in the body, but through the agency of the cells in the 
body such action may come to play a most important part 
in holding in check the active poisons until an immunity can 
be acquired. On the other hand we may look forward to a 
period when it will be possible to obtain, by the action of 


one organism in the body neutralizing the action of another 
or by means of antagonizing drugs, a method of treating 
and ameliorating disease, and at the same time allowing of 
an acquisition of a condition of immunity by the patient. 
It is a well-known fact that certain substances which 
are in themselves non-poisonous or are only slightly " de- 
pressant " in their action may so restrain the powers of the 
tissue cells that organisms that are otherwise incapable of 
growing in the body are enabled to give rise to septic and 
putrefactive changes even during the life of the animal. 
Thus papain and the soluble poison of the Jequirity bean 
when introduced into the circulation both so alter the 
conditions in the body that ordinary putrefactive organisms 
can make their appearance in enormous numbers in the 
blood of the animal injected. 

It appears probable that both the antagonistic action and 
this summative action are due to the bringing into play, or 
the depressing, of certain specific functions of the proto- 
plasms of the cells by the products of different micro- 
organisms. It is not necessary that these functions should 
always be manifesting themselves ; after being once evoked 
and exercised they may remain latent for a considerable 
period and only be again called into action under the regular 
specific stimulus. It is a case of writing on the looking- 
glass with ink and with French chalk ; the ink is always in 
evidence, and we might say that it corresponds to the enzyme 
or the peptonizing functions exerted by certain cells, animal 
and vegetable, whilst the French chalk, though always there, 
is only brought out when the glass is breathed upon. This 
may be said to exemplify very roughly the specific power 
that the cell has acquired of resisting the anthrax or other 
special poison. It only comes into play when the specific 
poison is present ; it is actually present though in a latent 
condition the whole time. 


The following works may be referred to : 

Authors ah-eady quoted. * Crookshank, Fliigge, Hankin, 

BuCHNER. — Eine Neue Theorie u. Erzielung von Immunitat 
Gegen Infectionskrankheiten. Munich, 1883. 


Chamberland et Roux. — Comptes rendus, t. xcvi., pp. 

1088 and 1410. 1885. 
Charrin et Guignard. — Comptes rendus, t. cviii., p. 764, 

Chauveau. — Comptes rendus, t. xciv. 1882, and t. xcvii., 

Creighton. — The Natural History of Cow- Pox and Vaccinal 

Syphilis. London, 1887. 
Crookshank. — History and Pathology of Vaccination. 

London, 1889. 
Greenfield. — Proc. Roy. Soc. London, 1880. 
Hueppe and Wood. — Lancet, Dec. 7, 1889 ; Berl. Klin. 

Woch., No. 16, 1889. 
Jenner. — Inquiry into the Causes and Effects of Variolae 

Vaccinas, a Disease known by the name of Cow-Pox. 

London, 1800. 
Klein. — Micro-Organisms and Disease ; Report of Med. 

Officer of Loc. Gov. Bd., p. 166, 1882. 
KiTT. — Wert un Unwert der Schutzimpfungen Gegen 

Thierseuchen. Berlin, 1 886. 
Koch. — Ueber die Milzbrandimpfung. 1882. 
Metschnikoff. — Fortschritt. der Med., Bd. il, p. 558, 1884, 

Bd. v., pp. 541, 583, 732, 1887 ; Annales de I'lnstitut 

Pasteur, 1887-1890 ; Virch. Arch., Bd. xcvii., p. 502, 

1884, and Bd. cix., p. 176, 1887. 
Pasteur. — Comptes rendus, t. xcii., p. 1378, 1881, t. xcv., 

p. 1250, 1882, t. XCVI., p. 979, 1882 ; Revue Scientifique, 

III""' series, t. v., p. 82. 
Pasteur et Perdrix. — Comptes rendus, t. cvi., p. 322, 

Ruffer. — Quart. Journ. Micro. Scz., Vol. xxxii., p. 99. 

Salomonsen und Christmus Dirckinck-Holmfeld. — Fort- 
schritt der Med., Bd. 11., p. 78, 1884. 
*Woodhead and Wood. — Comptes rendus, t. cix.. No. 26, 

1889; Lancet, Feb. 22, 1890; Edin. Med. Journ., 

WooLDRiDGE. — Proc. Roy. Soc, London, p. 312, 1887. 
* Full list of references given. 

Bacteria in Air, Earth, and Water. 

Spores in the Air in Hospitals — Effects of Currents and Altitude^Direction 
of Wind — Nature of Country over which it passes — Frankland's, Car- 
nelley's, Haldane's and Petri's Experiments — Few Bacteria in the Air of 
Sewers — Tyndall's Glycerine Chamber — Examination of Air — Koch's 
Method — Miquel's Method — Hesse's Apparatus — Modified Hesse's 
Apparatus — Miquel's Sugar Method — Bacteria in Water — Effect of 
Standing — Sluggish Movement — Oxidation of Organic Matter in Water 
■ — Organisms carried by Sewage — Number of Organisms in Water — 
Method of Procedure in Analysing Water — Pfuhl's Flasks — Petri's 
Dishes — Petruschky's Flask — Plate Cultivations — Cooling Apparatus — 
Von Esmarch's Tulje Cultures — Effect of Rains, Frosts and Thaws — 
Relation of Bacteria to Ammonia — Basis on which to determine 
whether water is fit for Drinking or not — Filtration — Method of 
Examination of Soil. 

As will have already been gathered from what has been- 
stated in connection with the distribution of the cholera 
bacillus, tubercle bacillus, anthrax bacillus, and similar 
organisms, there are marked differences in the facility 
with which organisms may be carried even by currents of 
air. Those organisms that do not produce spores, and that 
are easily killed by drying, are very seldom contained in 
the air, at any rate in a condition capable of growing, whilst 
it is found that those which resist dr3dng, and especially 
those which form resting spores, may be carried about from 
place to place, either alone or adhering to dust or other 

In connection with this question of micro-organisms in 
air, there are certain general rules that should always be 
borne in mind. Their presence must, we are afraid, be 
looked upon as inevitable in those hospital wards in which 
patients suffering from infective diseases are gathered to- 
gether for treatment ; tubercle bacilli, for example, are found 
in the air of wards where phthisical patients are collected, 


whilst the special bacteria associated with other diseases 
have also been demonstrated in the air of wards specially 
set apart for the treatment of these diseases. Then, 
again, it must be remembered that there are always 
more micro-organisms in the air in those regions where 
decomposing organic matter of any kind is allowed to ac- 
cumulate, this being especially the case in positions in 
which the air cannot be continuously renewed by Currents 
setting in from other and purer regions. Consequently, 
it is found that in valleys and in low-lying country generally, 
especially where there is any accumulation of decayed vege- 
table matter, or where people are massed together in towns 
or villages, many bacteria are usually present in the air. 
Some of the organic growths obtained from such air 
belong to the mould fungi, the spores of which, as is 
well known, have considerable resisting power, and may 
be readily carried from point to point by gentle currents 
of air. As the low-l)7ing lands are left, and the hill 
country is reached, micro-organisms are comparatively 
few in number, and at certain elevations, especially where 
the temperature is low, the number of these germs of 
moulds and bacteria may sink almost to zero. Again, 
if the air brought by breezes coming from the sea on 
the one hand and from the land on the other, be examined, 
it will be found that in the former case it is im- 
possible to demonstrate the presence of organic life of any 
kind ; whilst in the latter, collected it may be at the same 
point, an enormous number of micro-organisms of different 
kinds may be met with. It is, however, impossible to give 
any general rule as to the number of organisms that should 
be found under these various conditions, though we may 
take it as a result of Aitken's experiments oh the presence 
of solid particles in the air and their relation to fogs, that 
the more solid particles there are in the air, the more micro- 
organisms of various kinds are to be found. Some idea of 
the number of organisms present at different seasons of the 
year may be gathered from P. F. Frankland's investiga- 
tions, the results of which were presented to the Royal 
Society in 1886. He determined the number of colonies 
found in two gallons of air (examined by Hesse's method), 
collected on the roofs of the Science Schools at South 
Kensington. He found fewest present during the month of 


January, on an average of 4 per two gallons (ten litres) ; the 
numbers gradually rose until August, when there was an 
average of 105, and then gradually fell, though he records 
no observations made during November and December. 
He had previously confirmed the general results of Miquel, 
Hare, and others, that as we leave the ground the number 
of micro-organisms in the air rapidly diminishes. On Nor- 
wich cathedral spire, at a height of about 300 feet he found 
in ten litres of air only seven micro-organisms on one occasion, 
and on the tower, at a height of 180 feet, he found nine, 
whilst at the base of the cathedral (in the close) eighteen 
were found. In another series of experiments made at St. 
Paul's cathedral a similar volume of air taken from the golden 
gallery yielded eleven, that from the stone gallery thirty-four, 
and that in the churchyard seventy micro-organisms. He gives 
a number of other most interesting experiments, for which, 
however, the reader must refer to the original paper. Car- 
nelley, Haldane, and Petri have been able to show that the 
number of micro-organisms in any air depends to a very great 
extent on the moisture or dryness of the atmosphere, for they 
found that in the air of sewers, which is necessarily very 
damp, the number of micro-organisms present is extremely 
small, unless rapid fermentation is going on, or there is 
splashing from irregularities in the course of the drain, or from 
falling in of sewage from a height, the bacteria always 
tending to settle and to adhere to the moist walls of the drain, 
so that unless a considerable number of the organisms are 
carried into the air by the escape of bubbles and gas, or by 
other agencies, the tendency of these organisms to gravitate 
allows of their removal from the air. Here, however, it 
appears to be the moisture on the walls that prevents the 
escape into the air, rather than any moisture in the air itself. 
Tyndall demonstrated that exactly the same thing occurred 
in his chamber coated with glycerine ; bacteria, or other solid 
particles to which these bacteria were adherent, fell to the 
floor, or were carried on to the walls, where they were held 
fast by the glycerine, the air in the chamber thus becoming 
practically sterile, or deprived of its micro-organisms ; there 
might still be an enormous number of organisms attached 
to the floor and walls, but the air itself remained absolutely 
free, and flasks opened in this chamber would remain sterile 
for a very considerable, or even an indefinite, period. Grifiiths, 


gives the result of a number of similar observations, in which 
the above statements are in the main confirmed. 

Of the methods of examination of the air for micro-organisms the 
simplest and most convenient, but perhaps the least reliable, is that of 
allowing the germs to settle on plates of sterilized gelatine or potatoes, that 
are left uncovered for a. definite length of time. Currents of air may 
completely destroy the accuracy of these results, but in rooms that 
have been left undisturbed for some time, in which the doors are 
closed, and in which no currents are set up by heat coming through the 
windows or from fireplaces,. moderately accurate average "countings" 
may be obtained. In place of these glass plates covered with gelatine, 
shallow glass trays with glass lids soon came to be used to contain the 
gelatine. Those used by Koch for this purpose are shallow glass capsules 
about half an inch deep and a couple of inches in diameter, in which the 
sterilized gelatine is placed. These are placed inside tall glass cylinders 
about five or six inches high, the mouths of which are closed with large 
cotton wadding jjlugs. The glass capsule is lowered into the cylinder and 
again removed from it by means of a piece of soft metal bent at right 
angles. After the whole has been sterilized the cotton wadding plug is 
removed, the gelatine is left exposed, say, for ten minutes, the plug is 
re-inserted, and organisms that have settled on it are allowed to develop at 
the temperature of the room. These soon make their appearance as small, 
white, yellow, or pink points, according to the nature of the germs that are 
present in the air. In addition to these, however, a number of fluffy 
white, green, or black, forms make their appearance. The former consist of 
bacteria, sarcina, or yeasts ; the latter of penicillia, mucors, and aspergilli. 

Another method of examining the dust and micro-organisms contained 
in the air is one in which an apparatus somewhat like a chemical " wash 
bottle " with the bottom knocked out is used. In the neck of the bottle 
is an india-rubber cork with two holes ; through one of these holes the long 
limb of a tube bent into a U shape, with a long limb and a short limb is 
passed ; the long limb, which is drawn out into a pretty fine point, projects 
about two-thirds down into the bottle ; in the other hole of the stopper is a 
short glass tube, to which is attached a piece of india-rubber tubing ; the 
bottom of the bottle carefully ground, is luted with vaseline on to a 
glass plate on which has been placed a microscope slide, so supported as 
to rest with its upper surface immediately under the drawn out opening of 
the longer tube. This slide has previously been coated (as recommended 
by Miquel) with a mixture of one part of grape sugar and two parts of 
glycerine. A given quantity of air is then drawn into the bottle by means 
of an aspirating apparatus, and all particles of dust, spores, or moulds, 
and organic and inorganic fragitients of all descriptions are made to 
impinge on the sticky surface, where they are retained and may afterwards 
be examined under the microscope, or, if necessary, the glycerine and 
sugar mixture may be washed into a nutrient fluid such as peptonized meat 
gelatine, and a regular biological examination of the organisms may be 
made. A modification of this seroscope used by Miquel is a flask con- 
taining a small quantity of fluid, into which the air is drawn. This apparatus 
is somewhat complicated ; it is like a Pasteur flask, with three openings, 
through one of which the air enters, the neck of the flask being continued 
as a kind of tube down into the fluid in which the organisms are to be 


cultivated. Hesse's apparatus, for the estimation of the number and nature 
of bacteria, &c., in the air, consists of a glass tube of about 18 to 25 inches 
long, and ij inches in diameter, slightly funnel-shaped at each end ; in one 
end an indiarubber bung is fixed. This has a central opening through 
which passes a short glass tube about 5 or 6 inches in length, and one 
third of an inch in diameter. In this short tube is inserted a plug of cotton 
wadding. At the other end of the larger tube are two membranes of india- 
rubber tied on separately ; the inner one has a perforation of about one-third 
of an inch in diameter, the outer one fits over this and so closes the opening. 
The tube, bung, and indiarubber membranes are then sterilized with a one 
per cent, solution of bichloride of mercury and rinsed with boiled distilled 
water. The inner cap is firmly tied in position with good stout thread, 
the tube is half filled with water, and with a pair of scissors a hole is 
clipped in the centre of the indiarubber membrane. The second cap 
is then firmly tied on, water is again poured into the tube, the bung is 
replaced, and the whole apparatus is thoroughly boiled for a quarter of an 
- hour in the steam sterilizer. After allowing time for the glass to coo), the 
bung is removed, the water is carefully poured out and liquid nutrient 
gelatine is poured in to replace it ; the bung is again fixed in position and 
the apparatus is boiled for ten minutes at 100° C, after which the tube is 
put in a cool place in a horizontal position, so that the gelatine may con- 
solidate in a thin layer along the whole length of the tube. Just as the 
gelatine is beginning to "set," the tube may be gently rocked from side to 
side so as to obtain a rather larger cultivating gelatine surface. This tube, 
so prepared, is placed in a V-shaped support resting on a tripod, where it is 
held in position by a couple of elastic bands. To this tripod an aspirating 
apparatus is fixed. This consists of two bottles, each fitted with corks 
and tubes like those of a wash bottle. These bottles are placed at different 
levels and are connected by an indiarubber band, in the middle of which 
is a pinch cock. The indiarubber tube connects the longer tubes in the 
flasks. A litre of water is then measured into the upper flask, and, by 
applying suction to the orifice of the lower flask that is now left free, 
water commences to flow from the upper into the lower flask. If now the 
second tube in the upper flask be attached to the little tube projecting from 
the bung of the tube containing the gelatine, the aspirating apparatus will 
communicate with the chamber in which the gelatine is contained; the 
outer layer of indiarubber membrane which covers the orifice in the inner 
membrane is then removed, and by setting the syphon system in operation 
water is slowly and regularly run from the one flask into the other, and a 
corresponding volume of air is drawn in at the small opening in the india- 
rubber membrane. As soon as one Utre of air has been drawn through, 
all that is necessary is to close the pinch cock, reverse the positions of the 
bottles, and repeat the whole process. This may be done until a, volume of 
from I to 5 litres of air has been drawn into and through the tube containing 
the gelatine, the micro-organisms, drawn in along with this air, settling on 
the nutrient medium in the tube. If the estimation is to be made in the 
open air, it may be necessary to draw through the tube 20 or 30 litres. 
It is, however, usually necessary to expose a number of tubes, drawing 
different quantities of air through each ; then by taking an average of 
those in which the organisms are most readily counted, a fairly accurate 
result is obtained. The flow of water, and consequently the rate of flow of 
air, maybe regulated by the introduction of pieces of glass tubing of known 



calibre into the indiarubber tube that connects the two flasks. When the 
operation is complete the tube with the contained organisms is disconnected, 
the imperforate indiarubber membrane is again tied in position, and the 
whole is set aside until the organisms begin to develop ; they may then be 
counted in situ, or with a long platinum needle special points may be 
removed for microscopic examination, or for the purpose of making pure 

In place of Hesse's tubes I have, with Mr. Coghill's assistance, devised 
a flat glass bottle with a large central opening at the top and two side 
openings just at the level of the gelatine surface. These orifices are placed 
at the opposite sides of the jar. They are used just as are Hesse's tubes, 
but possess several very obvious advantages over them. 

Another method used in estimating the number of bacteria in the air 
was that of filtering the air through tubes containing sterilized glass 
wool, asbestos, or sand ; these are now seldom used, as they all interfere 
more or less with the transparency of the gelatine. Indeed, it is often a 
very difficult matter to distinguish grains of sand from young colonies of 
organisms. In place of these substances Miquel recommends that sterilized 
cane sugar should be used. Here the method of procedure is as follows : 
Loaf sugar is carefully ground in a mortar and passed through a couple of 
metal sieves, the latter of which allows grains of not more than half a milli- 
metre in diamater to pass ; this sifted sugar is packed into a glass tube about 
eight inches long and the sixth of an inch in diameter. Near one end of 
this tube is a slight constriction, on each side of which is placed a little 
sterilized cotton wadding or glass wool, one of which serves to prevent the 
sugar from escaping at the lower end, the other acting as a sterilized plug. 
At the other end of the tube is a glass or indiarubber cap (see description 
of Pasteur-Chamberland flask in Appendix) carefully sterilized and plugged 
with cotton wadding. The tube is sterilized for an hour at 150° C, and 
allowed to cool ; the cap is then removed and the sugar, which has been 
previously well dried, is poured into the tube, which should be filled to a 
depth of about 4 to 4J inches. The whole is again sterilized at a tempera- 
ture of 150° C. When the filter is to be used the sugar is packed against 
the plug by tapping the tube gently, and is held vertically whilst 
the air is being drawn through the filter ; this may be done slowly for 
twenty-four hours, or very rapid aspiration may be carried on where it is 
required to ascertain the number of micro-organisms present in the air at 
any definite period of the twenty-four hours.- When the process is com- 
pleted, the plug nearer the aspirator is carefully removed with forceps and 
placed in a sterile glass box, which should be got ready beforehand, the 
inner plug is then removed and is put into a test tube containing a small 
quantity of liquefied nutrient gelatine ; this test tube is carefully plugged and 
laid aside, the outer plug is immediately replaced, the cap is removed and 
the sugar is poured out into a flask filled with sterilized water. A short 
indiarubber tube is then slipped over the plugged end of the glass, the 
upper end, from which the sugar has been emptied, being placed in a test 
tube containing sterilized water; this water is alternately sucked up into the 
filter tube and then expelled, until the whole of the sugar with its contained 
germs has been dissolved and driven into the test tube. This water is added 
to that of the flask and well shaken until the whole of the sugar is dissolved. 
The number and character of germs so obtained from the air are determined 
by making plate cultures. One portion should be utilized for the demon- 


stration of the different ferobic organisms present, another for the anjerobic 
species, and others may be used to determine the mere numbers of these 
bacteria that are present, there being sufiScient material for a dozen or even 
twenty analyses. If a large number of organisms be present it is necessary 
to dissolve the sugar in a large quantity of water so as to obtain a sufficiently 
dilute " solution," whilst if a small number only are expected to be present 
a smaller quantity of water should be used. 

Water is one of the most convenient vehicles for the 
distribution of micro-organisms. It has been noted that a 
shower of rain diminishes the number of bacteria suspended 
in the atmosphere in a most remarkable manner ; these 
organisms being afterwards found in the puddles in the 
road, in the pools in the sidewalks. In stagnant water and in 
surface water of all kinds bacteria may be found in enormous 
numbers, though the numbers and varieties in which they 
are present may be very considerably modified by the amount 
of organic material contained in the soil through which such 
surface water comes, by the depth at which the water is 
taken from the surface, and by the facilities for oxidation or 
aeration that may be present. In the sluggish streams of 
valleys, where there is a constant drainage from the surface 
land, and where the water is so little disturbed that the air 
of the atmosphere cannot obtain free access to the organic 
matter suspended in the water, the number of micro-organisms 
will, as a rule, be very considerable, whilst the rapidly-flowing 
shallow streams that make their way over shingle or gravelly 
beds will be found to lose their micro-organisms very rapidly 
indeed ; if the organic matter has not already been left 
behind in the sluggish reaches of the stream it is very 
rapidly converted by oxidation into the ultimate products 
of decomposition, and ordinary putrefactive micro-organisms 
at any rate are no longer able to obtain any subsistence, 
although, as Bolton maintains, the " water " bacteria 
can still flourish. They can even grow in distilled 
water. In the water that comes from springs there may 
be scarcely a single bacterium as the water rises to the 
surface, but if such spring water be allowed to stand exposed 
to dust and contamination of various kinds it very quickly 
swarms with micro-organisms just as do , the waters from 
other sources. A very small quantity of sewage, which 
really consists of water in which is suspended an enormous 
quantity of organic matter, finding its way into a water 
supply may contaminate it for a whole neighbourhood, such 


contamination being only too plainly indicated by some of the 
epidemics of typhoid fever and cholera that have from time 
to time devastated our badly drained villages both at home 
and in new countries. In view of all these facts, the 
biological analysis of water has come to be a subject of im- 
portance of the first rank, and too much stress can scarcely be 
laid on the necessity for such analysis in order to determine 
the suitability of any water supply for the purposes to which it 
is to be put ; fortunately such examination is comparatively 
easily carried out. In addition to this, however, regular 
examination is absolutely necessary both to provide an 
indication that no contamination is creeping in during the 
process of distribution and to test how filter beds where such 
are used are performing their work. Water should always 
be examined for bacteria immediately after the sample 
is drawn from its source, for although the amount of nutri- 
ment for micro-organisms may be comparatively small, it is 
all in solution, and in such a form that it can be easily 
utilized by the organisms which in the fluid make their 
way with. the utmost rapidity from one point to another. In 
consequence of these extremely favourable conditions their 
rate of multiplic3.tion is most remarkable. If a sample of 
even the purest water (containing, say, 206 germs per cc.) 
be left to stand in a room, in which the temperature is 
comparatively high and therefore suited for rapid growth of 
these organisms, it may be found that in place of 200 germs 
per cc. there may be present on the second day 5,000, on the 
third day 20,000, whilst on the fourth, as pointed out by 
Carl Fraenkel, they are almost innumerable. This multi- 
plication may go on for some time, but at length there 
comes a period at which the small quantity of food contained 
in the water is used up, the bactpria begin to die, and the 
number of living cultivatable organisms gradually falls until 
eventually it may become extremely small. 

Water for analysis is collected in a sterilized Ehrlenmeyer flask, well 
plugged with sterilized cotton wadding; in place of this a wide-mouthed 
stoppered bottle may be used. In either case the stopper or the wadding 
should be covered with an Indiarubber cap previously carefully steri- 
lized in corrosive sublimate solution and boiled distilled water. If the 
water is to be collected from a tap it should be allowed to run for several 
minutes before any is taken ; water from the surface of a pond or a river 
should be collected by means of large sterilized pipettes ; whereas if it is to 
be taken from a depth or from a well a stoppered and weighted flask is 


lowered, then, when it has reached the required depth, the stopper is 
removed, the bottle is allowed to fill, after which it is then drawn to the 
surface, the water so obtained being at once transferred to a number of 
smaller bottles prepared as above. 

Quite recently an exceedingly convenient apparatus for the collection of 
water has been described by Dr. Pfuhl. It consists of a tall glass vessel with 
a flat bottom 2.5 centimetres in diameter and 10 centimetres long, with a 
glass tube 6 or 8 centimetres long, which can be easily closed, leading from 
this vessel. To prepare this it is only necessary to sterilize by heating in 
a flame, and while the air is rarefied to seal up the point of the tube by 
heat. When this has to be filled it is plunged under water or in the running 
stream from a tap or pump, the tip of the tube is broken off with a pair of 
sterilized forceps, water rushes in and about half fills the vessel. The outer 
surface of the tube is then carefully dried with blotting-paper, gently 
warmed to drive away the moisture from the glass near the opening, and 
finally sealed as before in a spirit lamp flame. After it is thoroughly cooled 
the flask is well shaken, and should there be any leak this is made good. For 
transport these flasks are packed in zinc cases with cotton wadding and ice. 
Tp remove the water the tube is nicked with a file, broken off, and a steri- 
lized pipette is introduced. In all cases, however, there is the difficulty of 
transport, and it is a great matter if plate cultivations can be made at the 
time that the water is dravra. Petri" gets over this difficulty by making 
his cultivations in double glass dishes, which are kept in position by india- 
rubber bands ; and various other pieces of apparatus have been devised, 
perhaps the best of these being Petruschky's flask, which can be used for the 
cultivation of either Eerobic or anaerobic organisms. This consists of a thin 
flask flattened on two sides with an indentation at the neck to prevent the 
flowing out of the softened gelatine. It may be used simply with a plug of 
cotton wool. The mixture of gelatine and water is poured in and then allowed 
to settle on one of the flat sides. For anaerobic cultures, however, a couple 
of glass tubes similar to those used in a wash bottle are introduced through 
openings in an indiarubber cork. Hydrogen is driven through the bottle to 
displace the air, and the ends of these tubes are carefully sealed, the flask 
is laid on its side, and the gelatine is allowed to cool. These flasks are so 
constructed that a microscopical examination may be made through the thin 
glass walls, especially if care be taken to obtain a layer of gelatine or agar 
sufficiently thin and of equal thickness throughout. Measure the size of 
the drop delivered by a pipette in the following manner. Weigh a filter 
paper on a fine balance, then put a gramme weight into the opposite scale, 
and drop by drop deliver exactly one gramme of water on to the filter paper, 
counting the drops as this is done ; then mark the pipette with the number 
of drops that it delivers per gramme, after which it may be used for measur- 
ing the water in making gelatine plate cultivations. It is now sterilized in 
the hot air chamber at 150° C, or by being thoroughly washed out with bi- 
chloride of mercury, then with distilled water that has been boiled and 
allowed to cool, and then with absolute alcohol, the last traces of alcohol 
being driven out by the heat of a spirit lamp. If a very large number of 
organisms are present a single small drop of the water, corresponding to about 
the fiftieth part of a gramme or cc. will be sufficient, whilst a larger drop, 
the twentieth part of a gramme, or even six or eight of these drops, may 
have to be used in order to obtain a sufficient number of organisms in a 
plate cultivation. Then prepare a number of glass plates in the following 


manner : — Thin plate glass is cut into squares of four and a half inches, the 
sharp edges are removed with a file, and the glass is carefully cleaned. It may 
then be sterilized in one of the following ways : Wrap each plate separately 
in a sheet of hard tissue paper, and place in the hot air chamber, leaving it 
for about an hour subject to a temperature of 150° C. It may then be taken 
out and kept in a dry place until required for use. If the plate is required 
at once, leave it slightly damp after cleaning, then, laying hold of it with a 
pair of strong forceps, heat it carefully over a Bunsen burner or spirit lamp 
until the whole moisture disappears, great care being taken that one side at 
any rate is sterilized by the action of the flame, wrap up in a piece of steri- 
lized paper and leave it until the other materials are ready. Or the plate 
may be tilted against a clean wooden block or iron upright with the more 
carefully heated surface downwards. Bell jars and glass benches have pre- 
viously been prepared by being thoroughly washed with soap and water, 
and then with a l per l ,000 solution of bichloride of mercury ; a piece 
of absorbent filter paper thoroughly saturated with the bichloride solution 
is placed in the bottom of one of the jars ; on to this all germs that are 
suspended in the air within the jar gradually fall and are destroyed. On 
a surface made as level as possible by means of a tripod levelling apparatus 
and a small round spirit level, (if these can be obtained), a plate of metal 
resting on three metal feet is placed in a mixture of ice, salt, and water; on 
this the sterilized plate of glass, with the more carefully prepared side upper- 
most, is laid, and the whole is covered with a bell jar that has been previously 
sterilized by means of heat or of bichloride of mercury. A test tube, with 
a large overhanging cotton wadding stopper, containing gelatine or a 
mixture of agar and gelatine is taken, the stopper is removed for a second 
or two, and the lip of the glass tube is carefully heated in a flame, the 
cotton wadding stopper is also thoroughly singed and then replaced. The 
gelatine is melted by placing the tube in water at a temperature of about 
3S°~39° C. for gelatine, and a much higher one for agar gelatine. As soon 
as the medium is thoroughly melted, the quantity of water that is to be used 
is dropped from the sterilized pipette into the tube, then with a rolling 
motion the water is thoroughly incorporated with the nutrient medium, 
great care being taken that as few air bubbles as possible shall find their 
way into the viscid fluid. The plate by this time being thoroughly cooled, 
the gelatine is poured out so as to form an equal and regular layer ; it is 
spread gradually from the centre of the plate to near the margins, over 
which, however, it is not allowed to run ; it is then allowed to solidify, 
after which the plate is transferred to the bell jar prepared for its recep- 
tion. By means of slips of glass, or of glass, porcelain, or zinc benches, 
carefully sterilized, three plates may be placed in the same bell jar ; they 
are then allowed to incubate at the temperature of the room, and at the 
end of two or three days colonies of bacteria make their appearance 
(each one from a single seed if the mixing has been perfect), and may 
be isolated and described. Where the number of organisms is unknown 
the method described for the isolation of cholera organisms (see under 
Cholera, p. 155) should be utilized. It is sometimes necessary to make 
a whole series of plate cultures to obtain a single pure growth, especially 
where zooglcea masses are formed. This method is also used for the 
separation of different species of micro-organisms, and it can be easily 
understood how micro-organisms may be more or less isolated by being 
shaken in a fluid medium, and how when once they are isolated they 


are prevented from running together again, for a time at any rate, by 
the solid gelatinized medium. Where if is necessary to isolate and 
obtain pure cultures of any special organisms, the method described as 
used in separating any colony of organisms should be used (see page 155). 
Salomonsen recommends a cooling apparatus made of an ordinary plate 
on which a shallow glass dish with a ground rim rests. This is filled up 
to the surface, but not to overflowing, with water and lumps of ice, a 
plate of ground glass is fitted on to this, and then a sterilized glass cover 
or bell jar is used to cover the glass plate ; the further procedure is then 
much as above. The organisms may be counted as a whole, but it is more 
convenient to use a plate of glass marked into squares, which is sup- 
ported over the gelatine plate, a low power lens being used to define the 
smaller colonies. The colonies in a number of squares in different positions 
are counted, then the number of squares that cover the gelatine plates 
is determined, and an average is obtained from which the whole number 
of organisms may be reckonedi It must be remembered, however, that a 
small proportion of the gelatine still remains in each tube, therefore it is 
necessary when making the plate cultivation to spread the remaining 
(juantity of gelatine over the walls of the tube by keeping the tube rotating 
in water until the gelatine is fixed in position ; the organisms left in the 
tube also give rise to colonies. These should be counted and added to 
those found on the plates. In place of pktes von Esmarch recommends 
the use of test tubes. The inoculation is made, exactly as above, into 
wide test tubes containing from eight to ten cc. of nutrient gelatine, a 
second tube may be inoculated from the first, and a third from the second 
by means of the sterilized pipettes. The plug is then thrust well home 
after being singed, and a tight-fitting indiarubber cap is placed over the 
mouth of the test tube, or melted paraffin is run in to protect the wadding. 
The mixture is then effected by rolling the tube rapidly between the 
hands, keeping it in a vertical position. When the fluids are sufficiently 
mixed the tube is placed into ice-cold water and, in a horizontal position, 
is kept rotating on its longitudinal axis until the gelatine is "set" in a 
thin layer all over the walls of the tube ; the tubes are then put aside 
and kept under observation. Should the presence of a large quantity 
of oxygen be necessary, the indiarubber cap may be removed and 
the plug may be pierced at one or two points with needles that have been 
carefully heated, these needles passing through both paraflSn and gelatine. 
These tube cultivations may be made at once and on the spot, are readily 
carried about, and serve as control experiments even when plate cultivations 
are made in the ordinary manner. In place of glass plates and large moist 
chambers, glass capsules are sometimes used for making plate cultivations, 
and Petri has devised a shallow glass tray with a lid which answers the purpose 
admirably. The method of procedure is much the same as in the above 
cases, but is much simplified from the fact that the gelatine is allowed to 
cool on the floor of the capsule, the space above serving as a moist chamber. 
Before sterilization these boxes are wrapped in a sheet of the hard tissue 
paper, they are then subjected to dry heat and are ready for use at any time. 
In working with gelatine there is the disadvantage that certain organisms 
peptonizing it cause it to liquefy exceedingly rapidly ; it has the advantage 
that it is exceedingly clear, is readily melted, and solidifies rapidly. Agar- 
agar on the other hand is not liquefied by the peptonizing organisms, but it 
is not nearly so clear as the gelatine, and requires a much higher tempera- 


ture (at least 90° C.) to melt it, although, as should be borne in mind, one* 
melted it will remain fluid at 40° C. , at which temperature any ordinarj 
inoculation may be made A mixture of agar and gelatine prepared bj 
adding 5 per cent, of gelatine and .75 per cent, of agar to the peptone bee; 
broth, orothernutrient fluid combines the advantage of both gelatine and agar 
agar media. It is almost as clear as gelatine, is readily manipulated, and 
melts at a considerably lower temperature, although it will remain solic 
between at 30° and 40° C, and it is not nearly so difficult to prepare as thf 
pure agar. The number of organisms in water is always calculated pel 
cubic centimetre, but having obtained the number of organisms in thefractior 
of a cc. , it is easy enough to convert the figures to the desired standard 
In every case a sample of water should be allowed to stand in conica! 
glasses, s6 that any sediment may be obtained for microscopic and biologica' 
examination. This is especially important where the presence of pathogenic 
micro-organisms such as those of typhoid is suspected. These organism: 
are usually brought in along with sdUd particles of sewage matter, and Ic 
these they usually adhere so that they may all be deposited along wit! 
such particles. 

The conditions under which micro-organisms are mosl 
numerous in water have been aheady referred to in general 
terms. It is of course found that where great rain storms, 
or thaws after the action of frost, break up the earth's 
surface, many organisms are set free and are carried awaji 
into the water supphes, the number usually varying to a 
certain extent with the- amount of solid matter that is 
suspended in the water ; as a general but by no means in- 
variable rule it may be stated that most bacteria are found 
where there is most ammonia. It is sometimes said that il 
water does not contain more than one thousand organisms 
per cc. that it may be used with safety for drinking purposes, 
but it must be borne in mind that this thousand organisms 
may contain a larger number of pathogenic organisms, 
whilst on the other hand five thousand organisms in the 
same quantity might not include a single pathogenic germ, 
It has been found indeed that no general biological examina- 
tion will give us absolutely accurate indications as to the 
nature of bacteria in water ; to obtain such information a 
rigid examination of every species present must be carried 
out. The number of liquefying organisms has indeed 
been taken as giving an indication of the quality of water, 
and this is undoubtedly a safer plan than to take into 
consideration the mere number. A safer rule still, however, 
is to take the number of different species of organisms in a 
drinking water as indicating its purity or impurity for 
drinking purposes, for it follows that if any water contains a 


considerable number of species, there must be several centres 
from which these must be derived, each additional source, of 
course, bringing in an additional element of danger. After ex- 
amining 400 springs, wells, and streams, W. Migula concluded 
that when there are more than ten species of bacteria in any 
sample of water, especially when these are species not ordin- 
arily met with, the water should not be used for drinking 
purposes. In only 59 out of 400 was such a number of species 
obtained, whilst 169 contained more than 1,000 individuals 
per cc, 66 of these having over 10,000, and 40 over 50,000. 
He found in all 28 species, and observed that the number of 
colonies does not by any means correspond with the number 
of species, though in some cases it undoubtedly does. 
Ordinary putrefactive bacteria are almost invariably absent 
from spring water, but they are usually found where the 
number of colonies is between 1,000 and 10,000 per cc, but 
they also occur where the number of germs is below 50 cc, 
but very seldom where the number is over 10,000. Of 
course the only perfect method is to examine each separate 
species by itself and to examine carefully any organisms that 
bear the slightest resemblance to any of the pathogenic 
species. It is a good rule to observe that all water taken 
from near the surface, or spring water that has been allowed 
to come to the surface and remain there for some time before 
use, should be filtered through sand or through porcelain 
filters. If in the process of filtration pure air can be mixed 
with the water so much the better ; the best of all filters for 
this purpose being the Pasteur-Chamberland, which may be 
readily applied to every household water supply. In large 
water-purification works gravel and sand are by far the best 
filters, especially if these are frequently renewed, the old 
filtering medium being burned before being again used. 

For the examination of soil the first method used was simply to sprinkle a 
little of the earth on a plate of nutrient gelatine, and then to examine the 
organisms that grew on it. This, of course, was an exceedingly imperfect 
method. The next step was to mix a small quantity of the earth with sterilized 
nutrient gelatine in a test tube, and then to make a plate cultivation either 
on a tube or on a flat surface. Now, however, that it has been found that 
there are so many organisms on the surface of the earth, the mass of earth 
to be examined has been diluted by adding a considerable quantity of 
sterilized distilled water. This is allowed to stand for a considerable time 
in order that the two may be thoroughly incorporated into a thin brown 
liquid with as little sediment as possible, and from it plate cultivations 


are made as described in the case of water or cholera organisms. Perhaps, 
however, the most certain way of obtaining all the organisms that are in 
any sample of earth is to break it down in liquid gelatine as above 
described, and then make an Esmarch tube cultivation. It is of course an 
easy enough matter to take a sample of earth from near the surface, but it 
is much more difficult to take samples from the deeper layers, which can 
only be done by means of special boring rods, unless access can be gained 
to a clean cut surface such as those met with in the making of a drain or 
other such cutting. As most organisms, however, such as the bacilli of 
anthrax, malignant oedema and tetanus, and the aerobic putrefactive bacteria 
are usually found near the surface, and as the deeper layers are so frequently 
almost entirely free from micro-organisms, just as is the ground water that 
we find in these deeper layers, this is as a rule a matter of comparatively 
little importance. 


The following works may be referred to : 
Authors already mentioned. Fraenkel, Griffiths, Hueppe, 
Koch, Salomonsen, Tyndall. 

AiTKEN. — Trans. Roy. Soc, Edin., vol. xv., Feb. 6, 1888 ; 

Proc. Roy. Soc, Edin., vol. xvi., p. 139, 1886. 
Bolton. — Zeitschr. f. Hygiene, Bd. i., p. 76, 1886. 
BuRDON Sanderson. — Reports on the Intimate Pathology 

of Contagion. 1876. 
Carnelley, Haldane and Anderson. — Phil. Trans., vol. 

CLXxviii., p. 61, 1887. 
Frankland. — Phil. Trans. Roy. Soc, vol. clxxviii., p. 113, 

1887 ; Journ. Chem. Soc, p. 373, 1888 ; Proc. Roy. 

Soc, vol. XL., p. 509, 1886. 
Frankland and Hart. — Proc. Roy. Soc, vol. xli., p. 446, 

MiGULA. — Centralbl. f. Bakt. u. Parasitenk, Bd. viii., No. 12, 

p. 353, 1890. 
Miquel. — Annuaire de I'Observatiore de Montsouris. 1877- 

NicoLAiER. — Deutsch. Med. Woch., No. 52, 1884. 
Petri. — Zeitschr. f. Hygiene, vol. in., p. i, 1887. 
Petruschky. — Centralbl. i. Bakt. u. Parasitenk., Bd. viii., 

No. 20, 1890. 
Pfuhl. — Centralbl. i. Bakt. u. Parasitenk., Bd. viii., No. 21, 

ScHMELK. — Centralbl. f. Bakt. u. Parasitenk., Bd. iv., No. 7, 

1888, and Bd. vii., No. 4, 1890. 


Smith, Angus. — Second Report Med. Officer Local Gc 

Board. 1884. 
SoYKA.— Fortschritte. der. Med., Bd. iv., No. 9, 1886. 
Straus and Wurtz. — Annales de I'Institut Pasteur, 1. 11 

p. 171, 1888. 
Von Esmarch. — Zeitschr. f. Hygiene, Bd. i., p. 293, 1886. 
Warington. — Journ. Chem. Soc, p. 642, 1884 ; p. 727, 188 
*WooDHEAD and Hare. — Pathological Mycology. Edii] 



The short outline of bacteria and their products contained in the preced- 
ing pages will not have had the effect desired if it does not induce in a 
certain number of readers an ambition to undertake some experiments in 
bacteriolog)', in at least some of its branches. As it is often extremelj 
difficult to obtain the most elementary knowledge of the technique of a 
subject without being compelled to dive into elaborate and erudite articles, 
it has been thought advisable to supplement the descriptions of methods 
already given by a short risume of some of the simpler methods of experi- 
mental investigation (the apparatus required for which is extremely simple, 
and can be obtained at comparatively trifling cost), and to give a shorl 
description of some of the commoner forms of bacteria that they may be 
readily identified. 

Hot Air Sterilizing Apparatus. 

C. Salomonsen recommends a very inexpensive form of sterilizing oven in 
which glass utensils, metal apparatus, wadding, paper, &c., may be heated 
to about 150° C. It consists of an ordinary large-sized biscuit box, 
such as may be obtained from any grocer. A round hole is cut in the 
middle of the lid, and into this a cork is fitted to carry a thermometei 
registering to 200° C. A small hole is punched in each of the four sides neai 
the top, and similar holes are made close to the bottom. On the bottom 
of the box, inside, is fitted a piece of strong sheet iron, with the ends beni 
at right angles to raise it about two-thirds of an inch, so that materials tc 
be sterilized do not touch the metal which is in immediate contact with the 
flame. The lid is covered with a piece of felt, in the middle of which is a 
hole for the thermometer. Another piece of felt, the breadth of which is 
three-quarters the height of the box, and long enough to go round it out- 
side, is fastened round the chamber, just below the upper, and above the 
lower, air holes,~and is kept in position with stout copper wire. The box 
so prepared is supported on an ordinary tripod, between which and the box 
rests a loose piece of thin sheet iron or tin (this latter prevents the burning 
of the thin tin bottom of the box). Such a chamber may be heated by gas 
or by a small oil stove. An ordinary cooking oven may also be used as a 
hot air sterilizer. A more complicated apparatus is a double-walled sheet 
iron box of about the same size as the above, or a little larger, with a hole 
in the top to receive a thermometer, a door in front, and a movable bottom, 
which can be easily renewed from time to time as it is burned through. All 
objects placed in this sterilizing chamber must be protected against dust on 
their removal. This is done in the case of flasks and test tubes with their 
cotton wadding plugs by covering them with a layer or two of strong, hard. 


thin "preserve" or "type-writing" paper; other objects, such as watch 
glasses, slides, cover glasses, cultivation plates, &c., may be enclosed in 
small iron or copper boxes, or they may be carefully wrapped in cotton 
wadding, or in a couple of thicknesses of the above paper, before they are put 
into the oven to be sterilized. One must always be careful that the_ paper 
or wadding does not come into actual contact with the bottom or sides of 
the oven, the hot metal of which may cause singeing. Even hot air at I50°C. 
will " brown" cotton wadding or paper slightly, so that such atemperature 
in the chamber may be at once recognized, even when no thermometer can be 
obtained, by the appearance of a slight brown coloration of these materials. 

Steam Sterilizer. 

For sterilizing by means of steam, an ordinary fish kettle or potato 
steamer may be used ; either of these placed on a fire will, for private work, 
usually serve the purposes of the more complicated Koch steam sterilizer. 
In this steaming apparatus the heat penetrates rapidly and does its work 
thoroughly, moist heat being much more effective as a sterilizing agent than 
dry heat. If it is thought necessary to obtain a piece of special apparatus 
for the purpose, the best is a tin or zinc cylinder about eighteen inches high 
and six inches in diameter, to which a small water gauge is added. The 
bottom of this should be made of block tin ; the top is closed by a conical 
lid in which is a hole for a thermometer. The lid and sides are usually 
covered with felt, though this is not essential, unless economy of heat is 
advisable. The felt should not in any case extend quite to the bottom, or 
it is readily singed by the heating flame. Inside the cylinder are a couple 
of shelves, one about one inch, and the other about ten inches, above the 
level of the water ; on each rests a perforated tin plate on which tin vessels 
about four or five inches in diameter and with perforated bottoms are sup- 
ported. The objects to be sterilized are placed in these vessels, the cylinder 
is filled to a depth of three or four inches with water, the pails are put into 
their places, and the lid placed in position. After the water has com- 
menced to boil briskly, the steaming is continued for about twenty minutes, 
at the end of which time most of the pieces of apparatus are thoroughly 
sterilized. This sterilizer may be lengthened by the addition of a tin 
cylinder with a ring or collar near the base, which fits into the top of the 
sterilizing cylinder, the lid being placed at the top of the additional cylin- 
der. This lengthening portion is especially useful for sterilizing Hesse's air 
analysis tubes. 

Incubating Apparatus. 

Most of the ordinary micro-organisms may be cultivated at the temperature 
of the room, but many of the pathogenic organisms, such as the tubercle bacil- 
lus, will only grow at a temperature approximating that of the human body, 
and for the cultivation of these some sort of incubating apparatus is necessary. 
The simplest apparatus, however, if supplied with a good body of water 
or a wrapping of felt and cotton wadding, will in most cases serve our pur- 
poses. Any one with a little ingenuity will be able to devise an incubator 
for his own use, if he has a greenhouse or any warm room at his disposal, 
an ordinary oil lamp being sufficient, if properly trimmed and regulated, to 
keep a double-walled chamber covered with felt at a fairly constant 
temperature, varying only three or four degrees for months together. Where 
systematic investigation is to be carried on, however, one of the ordinary 


thermostats with regulator should be obtained, or, failing this, one of the 
small egg-hatching machines, of which there are several in the market, may 
be used. 

Sterilized Vessels for the Recei'tion or Various Media. 
Ordinary test tubes, flasks, and other special glass apparatus, are first 
carefully washed with soap and water, then with boiling solution of per- 
manganate of potash, to which a few crystals of oxalic acid are added. 
They are then rinsed with distilled water, and are allowed to drain on a 
rack for some time, after which they are carefully plugged with cotton wool, 
care being taken that the wadding inside the neck is perfectly smooth and 
firm, the tuft outside being large enough to overlap well the lip of the test 
tube. These plugs in situ may be covered with paper, which keeps off 
the dust. They are heated for an hour in the hot air chamber at 150° 
C. For the reception of fluid media, Salomonsen recommends the use of 
a small flask or test tube of which the neck or upper part is so drawn 
out that it has a comparatively narrow mouth. The mouth is closed by 
'a piece of indiarubber tube a couple of inches long. The tube is washed 
with bichloride of mercury solution, then with distilled water, is wrapped 
in hard parchment paper and sterilized at 100° C. in the steam sterilizer. 
It is then filled for half its length with cotton wadding that has been 
sterilized at 150° C. in the hot air chamber. The flasks are sterilized as 
above. For these stoppers the following advantages are claimed :^(i) In 
opening and closing the flasks, the wadding and dust that is collected on 
it are not touched. (2) The apparatus is opened and closed at a point 
which can always be easily kept free from dust. (3) The opening through 
which the inoculation is made is smaller than in the case of the ordinary 
test tubes. Chamberland has devised flasks and test tubes which differ 
from these only in having glass in place of indiarubber caps. 

Preparation of Fluid Culture Media. 
Beef Broth — Bouillon. 

To prepare beef extract for the nutrition of micro-organisms, take a 
pound of lean beef, mince it fine ; add to this a litre of pure water, mix 
thoroughly, and allow to stand in a cool place for twenty-four hours ; again 
mix thoroughly and squeeze through a cloth, passing sufficient additional 
water through the meat to again make up the quantity of fluid to a litre ; 
boil the extract thus obtained for half an hour, render it neutral, or very 
slightly alkaline, by adding a saturated solution of mixed sodium hydrate, 
sodium carbonate, and sodium phosphate ; with a bit of gummed paper 
fasten a strip of jieutral litmus paper and one of turmeric paper to the end 
of a glass rod ; as soon as the faintest alkaline reaction is obtained, add no 
more of the alkaline solution ; boil for an hour ; allow to cool, and remove 
the fat ; again filter into a large stock flask or into test tubes that have been 
plugged with cotton wadding and sterilized as above. These vessels, with 
their contents, should now be boiled in a potato steamer or other steam 
sterilizing apparatus for a quarter of an hour on each of two or even three 
successive days, the wadding plugs being protected from dust by several 
layers of paper tied over them, or by means of thin indiarubber caps that 
have been washed in a solution of corrosive sublimate. The meat extract 
may be modified by the addition of various materials, such as .5 per cent. 


of common salt, recommended by Miqiiel, or of 5 per cent, glycerine, 
which is added before the nutrient fluid is finally sterilized (first used by 
Roux and Nocard). This glycerine meat extract is, as we have already 
seen, an excellent medium for the growth of the bacillus tuberculosis. 
Albumen peptone, cane or grape sugar, acetic acid, mannite, &c., have all 
been added in various proportions and for various purposes. Liebig's extract 
of beef, in the proportion of five parts to one thousand, or Cibil's extract, 
twenty grammes to a litre, may also be used. These latter require to be very' 
carefully sterilized by Tyndall's method of discontinuous heating, in which 
the fully developed organisms are killed off in a very short time on exposure 
to a comparatively low temperature. Some of the spores that remain in 
these develop into the vegetative form during the next twenty-four hours. 
This crop is again killed by a second heating. The remaining spores, if 
any, are again encouraged to develop, and then this crop is also killed off, 
usually leaving the fluid sterile, though in some cases the process may have 
to be repeated three, four, or even five' times. Various infusions and 
decoctions of wheat or hay, of different fruits or vegetables, yeast water, 
beer wort (the latter especially for the culture of the mucors and yeasts), 
a mixture of beer wort and prune juice (especially useful for the growth of 
the various aspergilli) may be used. These should all be sterilized by 
discontinuous heating at 100° C. in the steam sterilizing apparatus for 
twenty minutes on three or four successive days. Urine, aqueous humour, 
or other fluids of the body drawn with antiseptic precautions, may all be 
used as cultivation media for certain organisms. 


Milk may also be used as a culture medium, but although it is a substance 
easily obtained, it is a somewhat difficult matter to render it absolutely 
sterile. If heated under pressure to 120° C, milk may be sterilized in 
from ten to fifteen minutes ; but in the steam sterilizing chamber, at 100° 
C. , it is necessary to heat it for an hour on the first day, and from twenty 
to thirty minutes on each of the two following days. 

Solid Culture Media. 

Bread Crumb. 

One of the simplest of the solid culture media, bread crumb, is prepared 
by taking the crumb of a loaf, drying it in small pieces, spreading it out on 
a sheet of clean paper in an oven, or on the top of a stove, or even in front 
of a warm fire ; then rubbing it through a fine sieve, or passing it through 
a coffee-mill. A small quantity of this dried crumb, sufficient to cover the 
bottom of a flask to about the depth of a quarter of an inch, is put into a 
wadding-stoppered small sterilized flask ; distilled water is added until the 
bread crumb is thoroughly moistened,-no superfluous water, however, being 
left unabsorbed. If after allowing the bread crumb to stand for about a 
quarter of an hour, it is found to be properly moistened, the flasks con- 
taining it are heated in the steam chamber on each of three successive 
days for half an hour. In place of using water, the crumb may be moistened 
with beef extract, sugar solution, dilute glycerine, or any other of the fluid 
media already referred to. This medium is used chiefly for mucors and 
should be rendered slightly acid by the addition of a small quantity of 
Tartaric or other organic acid. 


Soyka's Ground Rice Medium. 

A medium which can be used instead of bread paste is that described by 
3oyka. It is composed of ground rice, 10 grammes ; milk, 15 cc; neutral 
Deef bouillon, 5 cc. These ingredients are thoroughly mixed, and put into 
;mall covered glass dishes or small glass flasks, which are sterilized, as is 
he bread paste. It forms a beautiful solid white opaque mass, on which 
;oloured organisms may be even more easily studied than when they are 
;rown on bread paste. 

Htieppe^s Method of Cultivating on Egg Albumen. 

Eggs may also be used as culture media. The yolk is broken down and 
nixed with the white by means of thorough shaking (or the white only 
nay be used, in which case the yolk is left unbroken) ; the shell is then 
lisinfected with bichloride of mercury solution, a hole is chipped at one 
;nd, and the membrane cut through with a pair of sterilized scissors. The 
noculation is made with a pipette or a platinum needle, and then the open- 
ng is covered with a piece of sterilized cotton wadding or paper, which is 
painted over and sealed with surgical collodion. 


The simplest and most effective way in which potatoes can be used as 
solid culture media is by introducing small wedge-shaped strips into sterilized 
lest tubes. All that is here necessary is to clean the potato thoroughly, then 
iteam it for five minutes, allow it to cool, and, with a cork-borer or apple- 
;orer, cut out a cylinder from the longest diameter, remove the two ends of 
:he' cylinder with a knife, and cut obliquely across from end to end, so that 
;wo wedge-shaped portions are formed ; each of these is put into a test tube, 
prepared as follows : — Into a plugged test tube, sterilized by dry heat, a 
small piece of sterilized cotton wadding, well moistened with distilled water, 
is introduced and pushed to the bottom ; the potato wedge is then intro- 
duced so that the base rests on the surface of the moist wadding. The 
whole is boiled in the steam sterilizer for at least three quarters of an hour 
[better an hour or an hour and a half), when it is ready for use. 

If test tubes are not readily obtainable, a soup-plate and a basin, well 
washed and rinsed with a i per 1 ,000 solution of bichloride of mercury may 
be used as a sterile chamber, a couple of layers of blotting-paper soaked with 
the bichloride solution being placed in the soup-plate, on to which any 
Drganisms in the air under the basin inay fall after the sterilizing process 
das been completed and the parts of the apparatus placed in position. 
A clean and smooth-skinned potato is thoroughly scrubbed, and the eyes 
ind any diseased portions are removed with a sharp-pointed knife ; it is 
then soaked for fifteen minutes in a l per 1,000 solution of bichloride 
of mercury, after which it is washed in water, wrapped in paper, and 
steamed for half an hour ; at the end of twenty-four hours it may again 
be steamed for fifteen minutes, and allowed to cool. (A single steaming 
is, however, usually sufficient.) The hands are carefully washed first in 
soap and water, then in a i per 1,000 sublimate solution. A knife is 
sterilized by heat in a naked flame, or in the hot-air chamber at 150° C. (in 
the latter case it should first be wrapped in cotton wadding or in paper), 
and then allowed to cool. The potato is taken in the left hand, and, with 
the sterilized knife, is cut through the middle, and the two halves are intro ■ 



duced under the basin with their cut surfaces, on which the inoculations 
are to be made, uppermost. Various modifications of these methods may 
be made by individual workers, but in most cases the potato used in the test 
tube is the most convenient. 

Koch's Gelatinized Meat Peptone Medium. 
To prepare Koch's peptone meat jelly or solid- gelatine medium, covei 
one pound of beef, freed from fat and finely minced, with l,ooo cc. of water, 
to which a drop or two of hydrochloric acid may be added ; allow the mix- 
ture to stand in a cool place for twenty-four hours, and squeeze through a 
cloth, as described in the preparation of meat extract. To this fluid add lo 
grammes of albumen peptone, 5 grammes of common salt, and 100 grammes 
(75, or even 50, if the weather be cool) of Coignet's gold label gelatine. 
Mix in a two- or three-litre flask, boil for half an hour, or until the gelatine is 
thoroughly dissolved, neutralize with the alkaline solution (p. 399), and again 
boil for nearly an hour. This'length of boiling in some cases appears to be too 
prolonged, the gelatine afterwards not becoming properly solidified. In such 
cases it is necessary to add a little more gelatine, boil, and again neutralize. 
The mass is then filtered through a layer of fine white filter-paper, moistened 
with hot water in a funnel, which must be kept heated, to prevent solidifica- 
tion of the gelatine on the filter. Salomonsen recommends a very ingenious 
device, a device that may be used at almost any time, especially where only 
small quantities of gelatine are to be filtered. He pours a little of the warm 
gelatine into a filter >vhich has been previously sterilized, wanned, and 
moistened as follows : a layer of water is poured into a flask to the depth of 
half an inch, in the mouth of which rests a funnel with a clean filter-paper. 
The top of the funnel is covered with several thicknesses of filter-paper, 
over which a sheet of asbestos or « plate of zinc is laid. By heating 
the water to boiling-point for a few minutes, flask, funnel, and filter are 
at once sterilized, warmed, and moistened. The hot water is then poured 
from the flask, the funnel is replaced, its cover carefully removed, and the 
gelatine is poured into it. If the flask be placed on a non-conducting sur- 
face, a very considerable quantity of gelatine may be thus filtered. Where 
larger quantities have to be filtered, it may be necessary to obtain a double 
walled metal funnel, or, better still, an enamelled funnel with the limb 
bent at an angle. This fiinnel is fitted into the top of the steam sterilizing 
apparatus, the bent tube coming through the side. This, of course, can be 
heated for any length of time, and is useful when large quantities of gela- 
tine or agar-agar are dealt with. (This apparatus, which is comparatively 
cheap, may be obtained from Frazer, Teviot Place, Edinburgh.) Before 
filtering, it is sometimes necessary to clarify the gelatine by ^ process well 
known to cooks. The gelatine is allowed to cool to about 50° C, the 
white of an egg is broken into 100 grammes of water ; this, along with the 
broken-up shell, is added to the gelatine, with which it is thoroughly mixed. 
The whole is then boiled until the albumen coagulates and a perfectly clear 
liquid' appears between the flakes ; the mass is then filtered. 

Gelatinized Milk Serum. 

One litre of fresh milk is warmed to 60° or 70° C. Add from 70 

to 100 grammes of gelatine (according to external temperature) and 

dissolve. Boil for a few minutes, until all the casein is precipitated, 

and pass through a fine muslin strainer. The fluid is allowed to 



stand for about twenty minutes at the temperature of the body, in order 
to allow the fat to come to the surface, after which it is allowed to cool, 
and the layer of cream is carefully removed. To the resulting slightly 
opalescent fluid, i per cent, of albumen peptone is added, and the whole is 
neutralized, boiled, filtered, and sterilized and used as nutrient gelatine. 
This material, like agar-agar (which was first used by Frau Hesse), was 
introduced into bacteriological work by a lady, Madame Raskina. 

Agar- Agar Peptone Meat Jelly. 

In place of 10 per cent, gelatine, we may use 1.5 per cent, of agar- 
agar. This is prepared in much the same manner as the gelatine jelly, 

Photographs. Growths on oblique Agar-Agar surface of— 

1. White Torula. 

2. Yellow Torula. 

3. Aspergillus Albus. 

4. Scheuerlein's Cancer bacillus. 
Numbered from left to right. 

except that it requires a more prolonged boiling before it can be properly 
filtered. It is prepared in the following manner : — Cut into pieces, about 
half an inch long, 15 grammes of agar-agar, place in a porcelain basin, and 
soak in a strong solution of common salt for twenty-four hours, pick out 
the coarse particles of dirt and wash thoroughly, then drain off the water ; to 
the washed agar-agar add one of the following solutions : (i) Water, 1,000 
grammes; beef, i pound ; peptone, 10 grammes; common salt, 5 grammes; 
or (2) water, 1,000 grammes; Liebig's extract of beef, 5 grammes; albumen 
peptone, 30 grammes ; common salt, 5 grammes. 

In (i) the beef is first extracted, as in the preparation of gelatine. The 


preparation after this is the same in both cases. Boil the mixture thoroughly 
over a naked flame for about an hour (great care being required at first to 
prevent the mixture boiling over in consequence of the large amount of 
air contained in the agar-agar, which is, however, gradually boiled out). As 
a small quantity of the agar is dissolved, the boiling point is gradually raised 
until the temperature of the mixture is about 105° C., instead of 100° C, and 
the complete solution of the agar-agar is more readily brought about. As 
soon as the whole of the agar is dissolved, which is usually in about an hour, 
the mass should be filtered as quickly as possible through a very hot filter. 
To Make Glycerine Agar. — After filtration of the agar jelly, add from S 
to 8 per cent, of glycerine, i.e., 50 to 80 cc. per 1,000, sterilize and put into 
test tubes. After sterilizing, allow to cool in the oblique position in order 
to obtain a larger surface. This also applies to the other agar-agar media. 

For the preparation of Agar- Agar and Gelatine (see p. 392.) 

Koch's Sterilized Blood Serum. 

A large stoppered ^lass jar, well washed with soap and warm water, is 
sterilized either by being wrapped up in paper and heated for an hour at a 
temperature of 150° C, or by being rinsed with a i to 1,000 solution of 
bichloride of mercury, and then with absolute alcohol to remove the mercury 
salt. The stopper is greased with pure vaseline. When the animal from 
which the blood is to be collected has been stabbed the first few drops of 
blood that come should be rejected, and that which follows must be col- 
lected as carefully as possible. The jar is then placed in cold water until 
the blood coagulates, removed to the laboratory and placed in an ice box ; 
and the first few drops of coloured serum that soon make their appearance on 
the surface of the clot are carefully removed with a pipette. It is then left 
for from twenty-four to thirty-six hours, at the end of which time a quantity 
of clear serum will be found to have been expressed. In the meantime a 
pipette has been prepared by exposing it to the action of boiling water for 
ten or fifteen minutes, or by thoroughly cleaning it with hot water and 
rinsing with bichloride of mercury and alcohol and then passing it through 
a flame for the purpose of driving off' the alcohol. This pipette is used to 
transfer the clear serum from the space around the clot to the sterilized 
plugged test tubes, care being taken that the serum is not allowed to smear 
the sides of these tubes. The test tubes, with the contained clear serum, are 
placed for an hour in a water bath, which is kept at a temperature of 58° 
to 60° C. every day for a week. Each day the serum becomes clearer, and 
a small precipitate of grey powdery material collects at the bottom and a 
thin film of cholesterin forms on the surface. This water bath may be 
constructed very cheai)ly. _ It is made of tin, is about twenty-seven inches 
high and four inches in diameter, with a collar projecting about half an 
inch. Over this collar a piece of iron netting serves both as a lid and as a 
support to the thermometer, which is fixed in a cork passing through a hole 
in the centre ; or a bulb thermometer may be used. This is supported by a 
second piece of wire gauze resting at some little distance — about three- 
quarters of an inch— from the bottom of the bath. When the water has 
reached a temperature of 58° C. it is easily maintained there by means of a 
small spirit flame. In place of this simple apparatus any of the small incu- 
bating chambers sold by the chemical apparatus makers may be used for this 
discontinuous sterilization at comparatively low temperature. Special serum 


sterilizei's and inspissators may also be obtained from the apparatus makers. 
Blood serum so sterilized may be used in various ways. It may be rendered 
solid with the tube in an upright position, or when a large surface is required 
in an oblique position, by placing the tube on the sloping floor of a warm 
chainber. This slope should be such that the blood serum does not come 
within an inch of the wadding plug. To bring about the solidification the 
temperature should be kept between 65° and 68° C, at which temperature 
solidification takes place slowly, but the serum remains comparatively clear. 
Sheep's blood coagulates more rapidly than that of the calf, the time required 
varying from half an hour to an hour, according to the temperature that is 
maintained. In place of test tubes, watch glasses or covered glass dishes may 
be used to hold the serum. As the serum cools there collects in the tube a 
quantity of condensed vapour ; this, however, may be prevented by adding a 
small quantity (l per cent.) of gelatine or 6 to 8 per cent, of glycerine. TTiis 
latter prevents the formation of a dry scaly surface, and at the same time 
absorbs a considerable proportion of the condensed vapour. When glycerine 
is added the temperature required to bring about solidification is over 75° or 

LSfflet's Serum Medium. 

Loffler added to three parts of blood serum one part of the flesh infusion 

already described, I per cent, of peptone, i per cent, of grape sugar, and 

5 per cent, of common salt. The meat broth, prepared as above described 

(P- 399)1 's allowed to cool down to 50° C, and is then mixed with the serum. 

Htieppis Agar Serum. 

Hueppe uses a mixture of blood serum and agar-agar for plate cultiva- 
tions, especially where he wishes to use the plate method for the separation 
of the tubercle bacilli. He takes the sterilized serum at a temperature of 
37° C, inoculafes it, and shakes it thoroughly in order to distribute the 
organisms through it ; he then pours it into the fluid agar-agar meat peptone 
solution at 42° C. ; the mixture is again well shaken to continue the distri- 
bution of the germs equally through the fluid, and then either plate, tube, 
or flask cultivations are made ; the mass is allowed to become solid, after 
which it is kept at the temperature of the body (about 37° C), at which 
temperature it remains perfectly solid. 

To Fill Test Tubes or Flasks with Fluid Media. 

Before transferring fluid gelatine or agar-agar meat broth or other fluid 
media to test tubes or flasks, these should be previously plugged and 
sterilized, as mentioned on p. 399. With a sterilized pipette (see p. 389) 
the fluid is run into these vessels, the plug is returned, and the vessels with 
the contained nutrient medium are sterilized for ten minutes or a quarter 
of an hour on each of two successive days. As soon as the vessels are 
taken from the steamer the plugs are covered with sheets of sterilized paper, 
which are kept in position by string or indiarubber bands. 

In place of the sterilized pipette a small carefully-sterilized funnel may be 
used. The stem of this is simply inserted into the flask or test tube, and the 
amount of the medium required is poured in from small stock flasks. A burette 
with a small funnel may be used in the same way, or better still, the stock 
flasks may be fitted with an indiarubber bung in which are bored two 
holes. Through one of these holes is introduced a glass tube, at one end 


of which is a thistle-head funnel filled with sterilized cotton wadding. The 
other end dips down tufirly to the level of the nutrient medium. Through the 
other hole a short glass tube passes just to the other side of the bung ; its 
outer end is slightly bent, and is fitted-with a piece of indiarubber tubing, 
on which a pinch clip fits. Into the other end of the rubber tubing a wash- 
bottle nozzle is fitted. The gelatine is first filtered into this flask, and the 
whole is sterilized as usual, a piece of cotton wadding or paper tied in position 
serving to keep dust away from the nozzle. When tubes or small flasks are to 
be filled the gelatine is melted, the flask, inverted, is fitted into a retort stand 
ring, the nozzle is allowed to fall into the mouth of the vessel to be filled 
and the pinch clip is compressed. If care be taken to cover the nozzle 
carefully each time that the flask is used, there is very little danger of con- 
tamination from without. Fluid media may also be kept in these flasks, 
but Lister's flasks are perhaps adapted better for this purpose. 

Apparatus used for Inoculating Animals or Artificial Nutrient Media. 
Inoculating needles are made of pieces of platinum wire mounted in glass 
rods ; these are of various shapes — (i) perfectly straight, (2) with a loop for 
inoculating li