Bacteria and Disease. 
By CHARLES MINOR BLACKFORD, Jr., M. D., 
OF LYNCHBURG, VA. 
Reprinted from Transactions Virginia Medical Society 189 2. Bacteria and Disease. 
By CHARLES MINOR BLACKFORD, Jr., M. D., 
OF LYNCHBURG, VA. 
From the very twilight of history men have endeavored to 
discover the causes of diseases ; and the record of the hypotheses 
that have at various times been held as solving the problem, con- 
stitute an interesting, albeit a saddening chapter in the history 
of human intelligence-saddening, because it is a record of so 
much ignorance, superstition and intolerance. 
Commencing with a theistic idea, by which all disease was 
attributed to the wrath of some outraged deity, the general 
theory of a supernatural origin for maladies can be traced 
through successive ages even to our own time; for it appeared 
in the blind fatalism that but a few weeks since caused a riot 
in Tashkend, one of the chief cities of Turkestan, over sanitary 
efforts to stay the progress of the devastating cholera. The 
many ways in which the deities of the polytheistic mythologies 
might be offended, gave a ready excuse to people who were 
unwilling or unable to admit that their own filthy habits had 
anything to do with the course of an epidemic. Homer sings 
that the plague that laid desolate the Grecian camp before Troy 
was due, not to the lack of proper sanitary precautions, but to the 
anger of Apollo, because of an insult to his priest. 
"The favoring power attends, 
And from Olympus' lofty top descends; 
Bent was his bow, the Grecian hearts to wound, 
Fierce as he moved, his'silver shafts resound. 
Breathing revenge, a sudden night he spread, 
And gloomy darkness roll'd about his head. 
The fleet in view, he twang'd his deadly bow, 
And hissing fly the feathered fates below. 
On mules and dogs the infection first began; 
And last the vengeful arrows fix'd in man. 
For nine long nights, through all the dusky air, 
The pyres, thick-flaming, shot a dismal glare." 
-Pope's Iliad, Bk. I, Lines 61-72. 2 
BACTERIA AND DISEASE. 
With the monotheism of the Hebrews, and their doctrine of 
a divine code, diseases, especially epidemics, were traced, not 
to the whim or caprice of some half human being, but to the 
punishments of a just and unerring God for infringements of 
his laws. The Jewish history bore out this theory, for the 
murrain in Egypt was the result of the direct interference of 
their God, and the disastrous results following the violation of 
their law, much of which was sanitary, was thought to be a 
manifestation of the same Almighty will. 
In accordance with that tendency of the human mind to ma- 
terialize or personify an abstract idea, diseases were looked on, 
at a later period, as a species of ogre, waiting to pounce upon 
the unsuspecting victim. Traces of this feeling are still per- 
ceptible in the common expressions, " attacks " of fevers, apo- 
plectic " seizures," and such phrases; but with the interest in 
anatomy and physiology that arose in the fourteenth and fif- 
teenth centuries, a new view came into existence, the supporters 
of which held that diseases were due to disordered conditions 
of the "humors" of the body, a hypothesis doomed to destruc- 
tion with increased physiological knowledge. This knowledge, 
however, produced a school that attributed all diseases to vari- 
ous peccant organs, especially to those of whose functions but 
little was known. The spleen thus came in for far more than 
its share of human woes, and the bile was charged with crimes 
sufficient to make one ashamed of owning an organ capable of 
secreting such a monster. Even to-day the ills attributed to 
intestinal worms are more numerous and grievous than those 
which a political party ascribes to the rule of its opponent. 
This hypothesis was productive of good results, for by its in- 
fluence, aided by the introduction of the microscope and the 
close study of pathological anatomy that it stimulated, a vast 
store of facts and observations was laid up for future genera- 
tions. 
But the most painstaking observation of a burning house, or 
of the ruins of one destroyed by fire, will prove of little utility 
in stopping or preventing a conflagration if the nature and 
origin of fire itself remain a mystery; and so it is evident that BACTERIA AND DISEASE. 
3 
the closest investigation of an organ already diseased can do but 
little toward the elucidation of the great problem of disease. 
Aid was to come from an unexpected source. 
This source was the studies based on the investigation of fer- 
mentation. The phenomenon of fermentation had been ob- 
served from the earliest times. Moses makes a difference be- 
tween leavened and unleavened bread, and states that in their 
flight from Egypt the Israelites had not time to put leaven in 
their bread. Even in more remote antiquity, Noah is cited as 
having put alcoholic fermentation to an actual test, but though 
of this respectable age, only two facts are recorded as having 
been observed in regard to it. Of these, the first is, that a 
peculiar substance (called a ferment) must be added to the fer- 
mentable material; and the second is, that this ferment is capa- 
ble of increasing itself. "A little leaven leaveneth the whole 
lump." The nature of this ferment was unknown, and con- 
tinued so till 1680, when Leuwenhoeck examined beer-yeast 
microscopically, and ascertained that it was composed of small 
globular- bodies, the precise character of which he could not 
determine. Since that time, the researches of many students, 
especially those of Pasteur of Paris, in our own time, have 
shown that yeast is a plant belonging to an order that, on ac- 
count of its action on sugars, has been called the saccharomyces. 
As a result of these investigations, and of the increased inter- 
est in biology that arose in the latter half of this century, other 
micro-organisms have received great attention, particularly those 
to which the generic name of Bacteria has been given, and 
from this study most valuable results have come. The term 
bacteria was originally applied to a single class of micro-organ- 
isms, and strictly it still is so used; but in ordinary usage, it is 
generic, and will be used as such in this paper. The effect of 
these bacterial studies is well summed up by Senn, in the in- 
troduction to his work on Surgical Bacteriology, thus: "Dur- 
ing the last fifteen years there has been more real advance made 
in surgical pathology than during twenty centuries preceding 
them. Bacteriology opened a new era for surgical pathology. 
The knowledge which has accumulated from the bacteriological 4 
BACTERIA AND DISEASE. 
investigation of disease lias opened new fields of usefulness for 
the surgeon. Many diseases hitherto treated uselessly with 
drugs by the physician are now successfully treated by surgical 
measures. At this .time surgical pathology has almost become 
synonymous with surgical bacteriology." 
Such being the case, it is highly important that something be 
known by every one of the well-established facts of this subject. 
With this in view, it will not be out of place to consider the 
various wavs in which the bacteria affect a higher organization. 
These ways may be roughly divided into two classes-one, in 
which the bacterium directly attacks and destroys the tissue in 
which it has obtained lodgement; and another, in which a bye- 
product of the life of the micro-organism is the agent that im- 
mediately does the damage. Thus, in inflammation followed by 
pus formation, the pyogenic bacteria are probably directly 
responsible; but in tetanus the active poison is an alkaloidal 
product, or a mixture of such products, resulting from the life 
of the bacillus tetanus. These alkaloidal products may be iso- 
lated, and are as certain to produce tetanus, if introduced in 
sufficient quantity into the system, as morphia is to produce its 
physiological effects. 
But in addition to the bacteria that are always pathogenic, 
there are others that are only so at times. In other words, some 
bacteria which normally are not capable of causing disease, may, 
under peculiar environment, acquire malignancy and be patho- 
genic. Conversely, some bacteria that are violently malignant, 
may, by cultivation in an unsuitable medium, become attenuated, 
so that, on inoculation, a very mild type of the disease will fol- 
low, sometimes only a local manifestation. There is reason to 
think that "comma" bacillus of Asiatic cholera exhibits these 
variations of malignancy. The environment producing these 
variations may be the soil in which the micro-organisms are 
grown-the temperature, the presence or absence of oxygen, 
and some conditions as yet unknown. The diet on which the 
subject of the experiment has subsisted has a marked influence. 
In the Bradford epidemic of anthrax, this was shown by a curi- 
ous fact. It was noticed that the majority of cases among the BACTERIA AND DISEASE. 
5 
wool-sorters occurred on Sunday, or between Saturday and Mon- 
day. This was holiday season, as the mills were closed during 
that time, and much curiosity was aroused to discover what 
excited the dormant bacilli at that time. It had been found 
that the herbivorous animals were peculiarly liable to attacks 
of this disease, and that it was difficult, if not impossible, to 
produce it in carnivorous animals. Investigation showed that 
the wool-sorters ate largely of vegetables during their brief 
holiday, and thus rendered themselves easier prey to the disease. 
The bacillus of mouse septicaemia is rapidly fatal to the house 
mouse, but is harmless to the field mouse. Here we have two 
animals of the same species responding to the same agent dif- 
ferently because of their different diet. Similarly rats vary in 
susceptibility as they are fed on vegetable or animal diet. Some 
bacteria seem to depend on the secretions of other varieties for 
malignancy, as, united, they are malignant; divided, they are 
harmless. These varieties greatly complicate the study of bac- 
teriology and in'ipede our progress toward a complete compre- 
hension of the subject. 
Before considering the separate bacteria, it may be well to 
state briefly the modes by which the different species are differ- 
entiated. These are-(1) direct microscopical examination, (2) 
the appearance of the "culture" in the tubes or other recep- 
tacle, (3) the behavior of the bacteria or their products with 
chemical re-agents, and (4) the results of inoculations practiced 
on animals. 
1. The first of these, direct examination, is when unaided by 
any of the others, of relatively little importance, as but few 
varieties possess such morphological peculiarities as to render 
them recognizable. Of course it makes out the distinction be- 
tween the cocci and the bacilli-the one appearing as minute 
dots or spheres, the other as little rods. The cocci, in turn, can 
be divided into the streptococci, which appear as rows of little 
dots; the diplococci, which are in pairs; and the staphylococci, 
which are clustered in groups. The bacilli give less scope for 
morphological classification. Some are curved, as is the comma 
bacillus; some are short, with clubbed ends, as is the bacillus 6 
BACTERIA AND DISEASE. 
typliosis; some bear a spore on one end, as the bacillus tetanus; 
some are motile, as the bacillus of relapsing fever; but, on the 
whole, mere inspection would enable one to differentiate but 
few species. 
2. The appearance of the cultures is somewhat more satis- 
factory ; indeed, some varieties have received names from the 
appearance of their cultures. They may or may not liquefy 
the medium in which the growth takes place; the growth may 
be visible on some soils and invisible on others, as the bacillus 
typliosis, which is visible in gelatine, but not so on potato. In 
some cases in which the active agent causing a disease has not 
been made out, it has at least been settled that it does not be- 
long to a certain one of these classes. Thus Sternburg,* al- 
though he has not definitely determined the bacterium of yel- 
low fever, has made out that it does not liquefy gelatine when 
access of air is permitted. Certain varieties, as the bacillus fluor- 
escens, have a peculiar color re-action; others produce nodules, 
thick or delicate cloud-like masses, spicular or branched growths, 
and some few have a characteristic odor. 
3. The behavior of the bacteria in relation to certain chemi- 
cal re-agents is frequently very characteristic. Bujwidf asserts 
that if to a ten-hour old culture of Koch's comma bacillus five 
or ten per cent, hydrochloric, nitric or sulphuric acids, be added, 
a rose-violet color is produced, which gradually grows more in- 
tense in the course of half an hour. This "cholera-red" is, so 
far as I am aware, unique. 
The re-actions with aniline dyes are of more practical im- 
portance. As a rule, the mineral acids decolorize objects 
stained with these dyes, but it is possible to fix the stains in 
certain bacteria by mordants of different kinds, so that every- 
thing else in the specimen will be decolorized but the special 
bacterium. Erlich's familiar stain for tubercle is an instance 
of this. He uses a solution of aniline oil in water as a mordant 
for gentian violet, and on decolorizing with twenty-five per 
cent, nitric acid the tubercle bacilli, if present, will retain their 
* Sternburg. Report on Etiology, etc., of Yellow Fever. P. 117. 
} Report on Cholera in Europe and India. E. O. Shakespeare. P. 641. See also 
Brieger in Deutsche Med. Woch. 1887. P. 303. BACTERIA AND DISEASE. 
7 
stain, appearing deeply colored on a colorless ground. Of 
course it is then possible to bring them into greater prominence 
by staining the ground with a deeply contrasting color. 
Aside from the re-action of the bacteria with staining re- 
agents, their behavior in regard to oxygen is of importance. 
The bacillus of tetanus grows in an atmosphere devoid of oxy- 
gen, and pure cultures may be and are best grown in hydrogen 
or nitrogen. This bears out our clinical experience by which 
we see that a deep, punctured wound is more apt to be followed 
by tetanus than an open one, other things being equal. The 
vibrios of butyric fermentation, and the putrefactive bacteria, 
show a marked difference in behavior, according to the amount 
of air present-if limited, fermentation ; if abundant, putrefac- 
tion occurring. So invariable is this law, that Pasteur de- 
scribes fermentation as "life without air." 
4. The final and conclusive test by which species of bacteria 
may be distinguished is actual experiment on a living animal. 
As this is a test of the pathogenic nature of these minute be- 
ings, it will be referred to again in another connection. 
By judicious use or the various methods indicated above, the 
micro-organisms may be classified, and then the problem of their 
relation to disease confronts us. To be regarded as the cause 
of a disease, the suspected bacterium must fulfill the following 
conditions: 
1. It must be present in all cases of the disease. 
2. It must not be found in the body except during the course 
of the disease. 
3. It must produce the disease when properly introduced into 
an animal susceptible to that particular disease. 
The second of these three conditions must be interpreted with 
liberality, for, as was shown above, there are conditions under 
which the same bacterium seems to be malignant at one time 
and not another. It is therefore possible that a micro-organ- 
ism might be in the system, and yet not produce its specific 
effect. 
It is not my purpose to go deeply into the varieties of patho- 8 
BACTERIA AND DISEASE. 
genic bacteria. A very few, and those few the ones of greatest 
practical importance, will suffice for the purpose of this paper, 
for I merely wish to show the manner in which these minute 
creatures produce specific diseases. 
The most brilliant success that bacteriology has achieved, 
from a practical point of view, has been in the treatment of 
wounds. Tyndall made a number of experiments to show that 
the motes in the air were the origins of the micro-organisms 
found in putrescent material, the result of which experiments 
can best be summed up in his own words : 
"Build a little chamber, and provide it with a door, windows, 
and window shutters; let an aperture be made in one of the 
shutters through which a sunbeam can pass; close the door and 
shutters so that no light shall enter save through this aperture. 
The track of the sunbeam is at first perfectly plain and vivid 
in the air of the room. If all disturbance of the air be avoided, 
the luminous track will become fainter and fainter, until at last 
it disappears absolutely, and no trace of the beam is to be seen. 
What rendered the beam visible at first ? The floating dust of 
the air, which, when thus illuminated and observed, is as palpa- 
ble to sense as dust or powder placed in the palm of the hand. 
In the still air, the dust gradually sinks to the floor, or sticks 
to the walls and ceiling, until finally, by this self-cleansing pro- 
cess, the air is entirely freed from mechanically suspended 
matter. 
" Thus far, I think, we have made one footing sure. Let us 
proceed. Chop up a beefsteak, and allow it to remain for two 
or three hours just covered with warm water; you thus extract 
the juice of the meat in its concentrated form. By properly 
boiling the liquid and filtering it, you soon obtain from it a 
perfectly transparent beef-tea. Expose a number of vessels 
containing this tea to the moteless air of the chamber, and a 
similar number to dust-laden air. In three days every one of 
the latter stinks, and, with the microscope, every one of them 
is found swarming with the bacteria of putrefaction. After 
three months or three years, the beef-tea within the chamber, 
if properly sterilized in the first instance, will be found as sweet 
and clear as it was the first moment it was put in. There is 
absolutely no difference between the air within and the air with- 
out, save that the one is dustless and the other dust-laden. 
Clinch the experiment thus: Open the door of the chamber 
and allow7 the air to enter it. In three days-afterward you have 
every vessel within the chamber sv^arming with bacteria, and BACTERIA AND DISEASE. 
9 
in a state of active putrefaction. Multiply your proof by building 
fifty chambers instead of one; employ every imaginable in- 
fusion of flesh, fish, fowl, and viscera, and of vegetables of 
various kinds; if in all of these cases you find the dust invari- 
ably producing its crop of bacteria, while neither the dustless 
air nor the nutritive infusion, nor both together, are ever able 
to produce this crop, your conclusion is simply irresistible that 
the dust of the air contains the germ of the crop which has 
appeared in your infusion. I repeat that there is no inference 
of experimental science more certain than this one."-Popular 
Science Monthly, December, 1876. 
Acting on these facts, and the results of Pasteur's experiments 
in the same direction, Lister conceived the idea that by exclud- 
ing these germs from a wound, or killing them should they 
gain admittance, putrefactive processes would not occur in the 
wound, and that healing by "first intention" would occur, and 
so he devoted much care and study to dressings to accomplish 
this purpose. At first shellac and carbolized putty were used, 
and a spray employed to sterilize the atmosphere in the neigh- 
borhood of the wound ; but experience has shown that much 
of the original dressing was unnecessary, and at present the 
dressings are much simpler, though equally effective. 
The principal opponent of antisepsis is Mr. Lawson Tait. 
He points with just pride to results which he asserts were ob- 
tained without antisepsis, but so thorough is his asepsis, that 
antisepsis is unnecessary. If no micro-organism be admitted, 
it is obviously useless to take measures to destroy it. He uses 
boiling water to sterilize his instruments, sponges and dressings, 
and boiled water for irrigating the field of operation. Heat is 
one of the best of germicides, and for one using heat as a steri- 
lizer to deride antisepsis and claim not to practice it, is remark- 
able. He prefers heat to chemical agents as a germicide-that 
is all. Would a surgeon using chloroform instead of ether be 
justified in saying that he did not use anaesthesia? Yet this is 
Tait's position. 
But antiseptic surgery needs no defence at my hands ; and if 
it did, the increased range of surgery, and the better results 
obtained by it, would be sufficient. 10 
BACTERIA AND DISEASE. 
Anthrax, or malignant pustule, is a disease usually originat- 
ing among cattle, and from them communicated to man. It 
particularly attacks wool-sorters, and usually ends in death from 
the many abscesses incident to the disease. The cause of this 
serious disorder has been definitely determined to be a bacillus 
found in immense numbers in the blood and tissues of those 
affected. This bacillus is micro-millimetres long and 
mm. broad. It is of great interest from a purely scientific 
point of view, as it illustrates many phenomena in relation to 
these forms of life. If tlie bacilli be cultivated in a liquid 
medium, reproduction takes place by the formation of spores, 
which are seen as bright oval spots marking the direction of 
the rods. Upon solid culture media, the rods segment trans- 
versely before giving rise to spores, the cell membrane of each 
section becoming the membrane of the spore, but having a 
small lump of protoplasm at each end, which can be stained. 
The precise significance of this variation is unknown. 
But a still more interesting fact is that the culture media 
have the power of increasing or diminishing the virulence of 
the bacilli to a great extent. If one-third per cent, of lactic 
acid be added to the cultures, the virulence of the bacteria is 
increased two-fold, whereas cultures kept at a temperature of 
107°-109° F. for three or four weeks are greatly attenuated, 
and a temperature of 131° F. deprives the bacilla of their viru- 
lence, though immunity may be obtained by inoculation with 
them. It is also found that attenuation may be obtained by 
passing the bacilli through various animals. Thus, if a rabbit 
be inoculated from a fresh culture, a guinea-pig from the rab- 
bit, a goat from the guinea-pig, and so on, the bacilli becomes 
so altered as to become incapable of transmitting the disease; 
or, at least, will only transmit a mild variety of it. There is 
evidently some analogy between this attenuation and the in- 
fluence of the diet of the subject alluded to above. 
In regard to the mode in which the bacilli of anthrax cause 
death, the most plausible view, and that best supported by ex- 
perimental evidence, is that advanced by Hoffa in Die Natur 
des ALiltzbrandgiftes, published at Weisbaden in 1886. This BACTERIA AND DISEASE. 
11 
is, in brief, that the bacilli separate the complex combinations 
in the organism into toxic substances. He made artificial cul- 
tures with the greatest care, on sterilized meat, kept for several 
weeks at a temperature of 98.6° F., and attenuated the product 
by several methods. This attenuated product he used experi- 
mentally on frogs, mice, guinea-pigs, and rabbits, and produced 
symptoms of intoxication. At first, after the inoculation, in- 
creased action of the heart and acceleration of breathing was 
observed, then the animals became somnolent, respiration deep, 
slow, and irregular, pupils dilated, temperature sub-normal, 
diarrhoea, with bloody faeces, and speedy death. At the 
necropsy, the heart was contracted, blood dark-colored, and 
ecchymoses found on the pericardium and peritoneum. No 
such results followed the injection of sterilized meat-juice, and 
the deduction was inevitable that some ptomaine elaborated by 
the bacilli was the active agent. 
The time at my disposal forbids me to go further into the dis- 
cussion of special bacteria and their specific effects; but before 
closing, I wish to speak of the ~bacillus of typhoid fever. I 
have done some experimental work with them during the past 
summer, but as yet cannot say that I have accomplished any- 
thing very definite. My cultures were made from the faeces of 
a typhoid patient, the colonies of bacilli typhoses being isolated 
as well as I could isolate them by roll-cultures. I was able to 
produce profuse diarrhoea, and at the necropsy found the lym- 
phatic glands swollen, but that is all. Whether the animal 
used (mice) are capable of taking the disease, I do not know, I 
can but state the facts as I found them.