peritoneal inoculations in animals have been productive
of more or less typical typhoid lesions. Among the
most successful efforts in this direction are the experi-
ments of Cygnaeus and Seitz, who, by the inoculation
of the typhoid bacillus into dogs, rabbits, and mice,
produced in the small intestines conditions that were
histologically and to the naked eye analogous to those
found in the human subject, but their results were not
constant. Of a number of experiments made by Ab-
bott, with the same object in view, only one positive
result followed the introduction of typhoid bacilli into
the circulation of rabbits. In this case the ulcer in
the ileum was macroscopically and microscopically iden-
tical with those found at autopsy in the small intestines
of the human subject dead of this disease. The bacilli
were found in the spleen.
Experiments indicate that the presence of other bac-
teria in the body, and of exposure to the effect of nox-
ious gases in lowering the natural resistance of the
individual, render him more susceptible to infection
from typhoid fever and, indeed, from other infectious
diseases.
But whatever conclusions may be drawn from these
results, with regard to the typhoid process in animals,
typhoid fever in the human subject is now recognized
BACILLUS TYPHOSUS. 409
as a true infection, caused by the introduction and
growth of typhoid bacilli. It belongs to that class of
infectious diseases which are known as metastatic that
is to say, diseases in which the specific bacilli do not
abound in the entire circulation, as in septicaemia, nor
remain localized in one place, but are distributed in
groups throughout the body. The characteristic lesions
of typhoid fever are seated in the lymphatic structures of
the intestine namely, the solitary follicles and patches
of Peyer, the mesenteric glands, and the spleen. The
liver and kidneys are less commonly attacked. Wher-
ever found the typhoid bacilli are observed to be arranged
in groups or foci; only occasionally, as in the walls of
the intestine, are they singly or loosely aggregated to-
gether. These foci are formed, most probably, during
life, as is proved by the degenerative changes often
seen about them; but it is possible that the bacilli may
also multiply somewhat after death.
The production of the lymph-nodules so often found
in typhoid fever in the internal organs is due to the
effects of the toxic substances eliminated by the typhoid
bacilli. This hyperplasia is particularly evident in the
lymphatic structures of the intestine, these being more
directly under the influence of the concentrated products
of the bacilli. To these, however, other inflammatory
processes are added, until finally necrosis or sloughing
of the tissues takes place. Possibly all these series of
changes may be at times caused solely by the products
of the typhoid bacilli which are gathered at certain
points. There is no question, however, that usually
other organisms take part in the production of these
processes in the intestines, but it remains to be deter-
mined when they begin to do so. In typhoid fever
410 BACTERIOLOGY.
necrosis of the tissues of the internal organs is of
comparatively rare occurrence. Caseation of the mes-
enteric glands, which is commonly observed, is due
probably to mixed infection. There are, however, a
number of cases now on record in which the typhoid
bacillus has played the part of pus producer. Cases
of sacculated and general peritonitis, subphrenic ab-
scess, osteomyelitis, periostitis, and inflammatory pro-
cesses of other kinds have been reported as being
due to the typhoid bacillus. Kruse also reports an
abscess of the spleen which contained only bacillus
typhosus, and typhoid abscess of the liver has been
recorded by many. In certain cases of typhoid pneu-
monia, serous pleurisy, empyema, and meningitis,
typhoid bacilli exclusively have occurred. The in-
flammation produced may or may not be accompanied
by the formation of pus. As argument against the
observations above cited there has been brought forward
the supposition that probably the real cause of the
disease had been destroyed before the entrance of the
typhoid bacillus. Though this may be true of some
cases, as in pneumonia, which is caused usually by the
short-lived pneumococcus, there is no reason to doubt
the causal relation of the typhoid bacillus to the other
diseases, inasmuch as it has been proved by numerous
investigations.
Such cases, however, are of comparatively rare occur-
rence, because only exceptionally do the bacilli suffi-
ciently mass together in such numbers as to become
pus producers. As a rule, when complications occur
in typhoid fever they are due to secondary or mixed in-
fection with the staphylococcus, pneumococcus, strepto-
coccus, pyocyaneus, and colon bacillus. Frequently
BACILLUS TYPHOSUS. 411
these bacteria are found side by side with the typhoid
bacilli; in such cases it is difficult to say which was the
primary and which was the secondary infection.
The peculiar arrangement of the typhoid bacilli in the
body can only be explained by their passage through
the circulation; and this is proved by the bacilli being
found in the spleen almost constantly and in smaller
numbers in the blood itself. Thus, Neuhauss has had
nine positive results out of fifteen in cultures from vein
blood.
The typhoid bacillus can be transmitted also from
the blood of the mother to the foetus (E berth, Fraenkel,
etc.). In one case reported by Ernst a living child,
four days after birth, showed evidences of general
typhoid infection, icterus and rose-spots. Frascani
reports that in animal experiments he has frequently
found typhoid bacilli in the foetus.
Not infrequently typhoid bacilli are found in the
secretions. They are present in the urine in about 20
per cent, of the cases in the third and fourth week of
typhoid fever. Slight pathological lesions in the kid-
neys almost always occur in typhoid fever, but severe
lesions also sometimes occur. In a case under our ob-
servation the urine was distinctly purulent and crowded
with typhoid bacilli. The bacillus typhosus is not
commonly found in the sweat, but Geisler observed it
once. It has also been detected, though rarely, in the
sputum and secretions of the throat.
In cases of pneumonia due to the typhoid bacillus it
is abundantly present in the sputa, and care should be
taken to disinfect the expectoration of typhoid patients.
According to Chiari, in typhoid fever the bacilli are
almost always present in the gall-bladder. The bacilli
412 BACTERIOLOGY.
are frequently eliminated by the feces being derived
from the inflamed^ mucous surface of the intestines;
their growth within the intestinal canal itself, even if
it occurs to a limited extent, is probably not extensive.
Methods of Infection. With regard to the mode of
invasion of the typhoid bacilli, there is no doubt that
it is principally by way of the mouth, through the
stomach to the intestines. Mayer reports a particularly
convincing illustration of this fact in a case where death
ensued on the second day of the disease. On autopsy
were found hypersemia of the lungs, spleen, and kid-
ney; in the lower portion of the ileum great enlarge-
ment of the solitary follicles and patches of Peyer, but
nowhere a trace of necrosis or loss of substance; nor
were the mesenteric glands enlarged. Microscopically
an extraordinary deposit of characteristic bacilli were
found in the submucosa and interstitial spaces of the
muscles; many hundred bacilli lay in one field. On
the other hand, several cases are recorded in which the
intestinal changes were entirely wanting, and only a
localization of bacilli and lesions in the mesenteric
glands and spleen revealed the nature of the infection.
Inasmuch as they were present in the lymph-glands
which belong to the intestines, it may be assumed,
thinks Kruse, who reports one of these cases, that the
bacilli were here more rapidly absorbed than usual with-
out multiplying to any extent in the intestines. The
case mentioned by Guarnieri is also worthy of notice:
in this there was apparently a primary infection of the
gall-ducts, with no accompanying lesions in the intes-
tine. Bacilli were found in the blood twelve days be-
fore death, and on autopsy pure cultures were obtained
from the liver and spleen.
BACILLUS TYPHOSUS. 413
Not only do the very great majority of cases exam-
ined bacteriologically and pathologically, but the epi-
demiological history of the disease, prove that the
chief mode of invasion of the typhoid bacillus is by
way of the mouth and stomach. The infective mate-
rial is discharged principally by means of the excretions
and secretions of. the sick namely, by the feces, the
urine, and occasionally by the sputum.
Of considerable practical importance is it to know for
what length of time the typhoid bacillus is capable of
living outside of the body; but, unfortunately, owing
to the great difficulties in proving the presence of this
organism in natural conditions, our knowledge on this
point is very deficient. In feces the length of life of
the typhoid bacilli is very variable; sometimes they
live but a few hours, usually a few days, exceptionally
for very long periods. Thus, according to Uffelmann,
typhoid bacilli may remain alive in feces for five and
a half months, and, according to Karlinski, for at least
several months. Foote says that they can be found in
living oysters for a month at a time. Their life in
feces and in water, however, is usually very much
shorter. As a rule, they can be detected in water no
longer than fourteen days after introduction. The
life of the typhoid bacillus varies according to the
abundance and varieties of the bacteria associated with
it and according to the presence or absence of such in-
jurious influences as high temperature, light, desicca-
tion, etc., to which it is peculiarly sensitive. That the
bacilli do live much longer under favorable circum-
stances, as to protection and nourishment, than is gen-
erally supposed, is shown by the fact, as reported by
Buschke, that they were found in an old bone-centre
414 BACTERIOLOGY.
seven years after the original infection. There is no
reason to deny that such opportunities for a latent ex-
istence of the typhoid bacillus may not occur outside
of the body. Indeed, many epidemics of typhoid
fever can only be accounted for by some such assump-
tion of latency in or outside of the body.
The bacilli may reach the mouth by means of infected
fingers or articles of various kinds, or by the ingestion
of infected food, milk, water, etc., or by more obscure
ways, such as the contamination of food by flies and
other insects, or by the inhalation through the mouth
of dust containing typhoid bacilli. Of the greatest
importance, however, is the production of infection
by contaminated drinking-water or through drinking-
water or milk, which is the most plausible explana-
tion for the majority of epidemics of typhoid fever.
In many cases indirect proof of this mode of infec-
tion has been found in the known contamination of
the water with typhoid feces or urine, and in some few
cases it has been confirmed by direct proof in finding
the bacilli. Examples of infection from water and
milk have come frequently under our direct observa-
tion for instance, a large force of workmen obtained
their drinking-water from a well very near to their
work. Typhoid fever broke out, and continued to
spread until the well was filled up. Investigation
showed that some of the sick, before their discovery,
repeatedly infected the soil surrounding the well with
their urine and feces. Another instance of milk in-
fection secondary to water infection was the case of a
milk dealer whose son came home suffering from
typhoid fever. The intestinal movements were thrown
into a small stream which ran into a pond from which
BACILLUS TYPHOSUS. 415
the milk cans were washed. A very alarming epidemic
of typhoid developed, which was confined to the houses
and asylums supplied with this milk. In our late war,
not only water infection but food infection was notice-
able, as in the case of a regiment where certain com-
panies were badly infected, while others nearly escaped.
Each company had its separate kitchen and food-supply,
and much of the infection could be traced to the food.
In this, as in all infectious diseases, individual sus-
ceptibility plays an important role in the production of
infection. Without a suitable soil upon which to grow
the seed cannot thrive. There must in many be some
disturbance of the digestion, excesses in drinking, etc.,
or a general weakening of the power of resistance of
the individual, caused by bad food, exposure to heat,
overexertion, etc., as with soldiers and prisoners, for
example, to bring about the conditions suitable for the
production of typhoid fever.
The supposition that the breathing of noxious gases
is conducive to the disease, though possibly true to a
certain extent, as some animal experiments already
referred to would seem to indicate, has not yet been
conclusively proven; nor do Pettenkofer's investiga-
tions, into the relation of the frequency of typhoid
fever to the ground-water level, satisfactorily explain
the occurrence of the disease in most cases, whether
sporadically or in epidemics.
Immunization. Specific immunization against experi-
mental typhoid infection has been produced in mice,
guinea-pigs, rabbits, dogs and other animals by the
usual method of injecting at first small quantities of
the living or dead typhoid culture and gradually in-
creasing the dose. The blood-serum of animals thus
416 BACTERIOLOGY.
immunized has been found to acquire protective and
curative bactericidal and perhaps feeble antitoxic prop-
erties against the typhoid bacillus. These character-
istics have also been observed in the blood-serum of
persons who are convalescent from typhoid fever
(Pfeiffer and Kolle, Widal and Chantemesse). Re-
cently the attempt has been made to employ the
typhoid-serum for the cure of typhoid fever in man,
but no marked results have been obtained. The injec-
tion in man of very small amounts (0.3 c.c. of bouillon
culture) of dead typhoid bacilli produces for a day or
two a slight fever reaction, to be followed in a few days
by the development of bactericidal substances in the
blood, which apparently are sufficient in amount to
give immunity for some weeks. The use of immu-
nized serum, or when this cannot be obtained of dead
cultures, would seem to be advisable where great
danger of typhoid infection exists.
The Diagnosis of Typhoid Fever, or rather of Typhoid
Infection, by Means of the Widal or Serum Reaction.
The chief practical application of our knowledge of the
specific substances developed in the blood of persons
sick with typhoid fever has been in the way of
diagnosis. In view of the interest which has been
manifested in this test, and of the fact that it is now
so largely used, a brief history of the investigations
which led up to its discovery may be given.
In 1894-95, Pfeiffer showed that when cultures con-
taining dead or living cholera spirilla or typhoid bacilli
are injected subcutaneously into animals or man, specific
protective substances are formed in the blood of the in-
dividuals thus treated. These substances grant a more
or less complete immunity against the invasion of the
BACILLUS TYPHOSUS. 417
living germs of the respective diseases. He also de-
scribed the occurrence of a peculiar phenomenon when
a portion of a fresh culture of the typhoid bacillus on
agar is added to a small quantity of the serum of an
animal immunized against typhoid and the mixture
injected into the peritoneal cavity of a non-immunized
guinea-pig. After this procedure, if from time to time
minute drops of the liquid be withdrawn in a capillary
tube and examined microscopically, it is found that the
bacteria, which were formerly and in control animals,
which remain, actively motile and vigorous, become
in a very short time, under the influence of the serum,
entirely motionless and later dead. They are first im-
mobilized, then they become somewhat swollen and
agglomerated into balls or clumps, which gradually
become paler and paler, until finally they are dissolved
in the peritoneal fluid. This process takes place regu-
larly in about twenty minutes, provided a sufficient
degree of immunity be present in the animals from
which the serum was obtained. The animals injected
with the mixture of the serum of immunized animals
and typhoid cultures remain unaffected, while control
animals treated with a fluid containing only the serum
of non-immunized animals mixed with typhoid cultures
die. Pfeiffer claimed that the reaction of the serum
thus employed is so distinctly specific that it may serve
for the differential diagnosis of the cholera vibrion or
typhoid bacillus from other vibrions or allied bacilli,
such as Finkler's and Prior's or colon groups.
In March, 1896, Pfeiffer and Kolle published an
article entitled " The Differential Diagnosis of Typhoid
Fever by Means of the Serum of Animals Immunized
Against Typhoid Infection/ ' in which they claimed
27
418 BACTERIOLOGY.
that by the aid of the presence or absence of this reac-
tion in the serum of convalescents from suspected
typhoid fever the nature of the disease could be deter-
mined. It was further found if the serum of an animal
thoroughly immunized to the typhoid bacillus was
diluted with 40 parts of bouillon, and a similar dilu-
tion made of the serum of non-immunized animals,
and both solutions were then inoculated with a culture
of the typhoid bacillus and placed in the incubator at
37 C., that after the expiration of one hour macro-
scopical differences in the culture could be observed,
which increased in distinctness for four hours and then
gradually disappeared. The reaction occurring is de-
scribed as follows : In the tubes in which the typhoid
culture is mixed with typhoid serum the bacilli are
agglomerated in fine, whitish flakes, which settle to the
bottom of the tube, while the supernatant fluid is clear
or only slightly cloudy. On the other hand, the tubes
containing mixtures of bouillon with cholera or coli
serum, or the serum of non-immunized animals inocu-
lated with the typhoid bacilli, became and remained
uniformly and intensely cloudy. These serum mix-
tures, examined microscopically in a hanging drop,
show distinct differences. The typhoid serum mixture
inoculated with the typhoid bacilli exhibits the organ-
isms entirely motionless, lying clumped together in
heaps; in the other mixtures the bacilli are actively
motile.
These observations were made independently by
Gruber and Durham, who maintained, however, that
the reaction described by Pfeiffer was by no means
specific, and that when the reaction is positive the
diagnosis still remains in doubt, for the reaction is
BA CILL US TYPHOS US. 419
quantitative only, and not qualitative, so far as the
cholera spirillum and typhoid bacillus, at least, are
concerned. They conclude, nevertheless, that these
investigations will render valuable assistance in the
clinical diagnosis of cholera and typhoid fever. It
developed through further research that before the
development of the bactericidal substances agglutina-
tive substances usually appeared in the blood.
WIDAI^XES^ The first practical application of the
use Trf^serum, however, for the early diagnosis of
typhoid fever on a more extensive scale was made by
Widal, and reported with great fulness and detail in a
communication published in June, 1896. Widal con-
firmed the reaction as above described, proved that the
agglutinative reaction was one of infection and usually
occurred early, elaborated the test, and proposed a
method by which it may be practically applied for
diagnostic purposes. Since then the serum test for
the diagnosis of typhoid fever has come into general
use in bacteriological laboratories in all parts of the
world, and though the extravagant expectations raised
at the time when Widal first announced his method of
applying this test have not been entirely fulfilled, it
has, nevertheless, proved to be of great assistance in
the diagnosis of obscure cases of the disease, and it is
now one of the recognized tests for the differentiation
of the typhoid bacillus.
It should also be mentioned that to Wyatt Johnson,
of Montreal, belongs the credit of having brought this
test more conspicuously before the public by intro-
ducing its use into municipal laboratories, suggesting
that dried blood should be employed in place of blood-
serum (Widal having previously noticed that drying
420 BACTERIOLOGY.
did not destroy the agglutinating properties of typhoid
blood); and that in October, 1896, the serum test was
regularly employed in the New York Board of Health
Laboratory for the routine examination of the blood-
serum of suspected cases of typhod fever. Since then
numerous health departments have followed the example
set by those of Montreal and New York.
USE OF DRIED BLOOD. Directions for Preparing
Specimens of Blood. The skin covering the tip of the
finger or the ear is thoroughly cleansed, and is then
pricked with a needle deeply enough to cause several
drops of blood to exude. Two fair-sized drops are then
placed on a glass slide, one near either end, and allowed
to dry. Paper may also be employed, but it is not as
good, for the blood soaks more or less into it, and
later, when it is dissolved, some of the paper-fibre is
apt to be rubbed off with it. The slide is placed in a
box for protection.
Preparation of Specimen of Blood for Examination.
In preparing the specimens for examination the dried
blood is brought into solution by adding to it and mix-
ing it with about five times the quantity of water ; then
a minute drop of this decidedly reddish mixture is
placed on a cover-glass, and to it is added a similar
drop of an eighteen to twenty-four-hour-old bouillon
culture of the typhoid bacillus, which, if it has a slight
pellicle, should be well shaken. The drops, after being
mixed, should have a faint reddish or pink tinge. The
cover-glass with the mixture on the surface is inverted
over a hollow slide (the edges about the concavity
having been smeared with vaseline, so as to make a
closed chamber), and the hanging drop then examined
under the microscope (preferably by gaslight), a high-
BACILLUS TYPHOSUS.
421
power dry lens (about 1/8 inch) being used, or, some-
what less serviceably, a 1/12 oil-immersion lens.
THE REACTION. If the reaction takes place rapidly
the first glance through the microscope reveals the com-
pleted reaction, all the bacilli being in loose clumps
and nearly or altogether motionless (Fig. 53). Be-
FlG. 53.
Widal reaction. Bacilli gathered into one large and two small clumps, the
few isolated bacteria being motionless or almost so.
tween the clumps are clear spaces containing few or no
isolated bacilli. If the reaction is a little less complete
a few bacilli may be found moving slowly between the
clumps in an aimless way, while others attached to the
clumps by one end are apparently trying to pull away,
much as a fly caught on fly-paper struggles for freedom.
If the agglutinating substances are still less abundant
the reaction may be watched through the whole course
of its development. Immediately after mixing the blood
and culture together it will be noticed that the bacilli
422 BACTERIOLOGY.
move more slowly than before the addition of serum.
Some of these soon cease all progressive movement,
and it will be seen that they are gathering together in
small groups of two or more, the individual bacilli
being still somewhat separated from each other. Grad-
ually they close up the spaces between them, and clumps
are formed. According to the completeness of the
reaction, either all of the bacilli may finally become
clumped and immobilized or only a small portion of
them, the rest remaining freely motile, and those
clumped may appear to be struggling for freedom.
With blood containing a large amount of agglutinating
substances all the gradations in the intensity of the re-
action may be observed, from those shown in a marked
and immediate reaction to those appearing in a late and
indefinite one, by simply varying the proportions of
blood added to the culture fluid.
Pseudo-reactions. If too concentrated a solution of
dried blood from a healthy person is employed there
will be an immobilization of the bacilli, but no true