> THE 
MQDE OF ENTRANCE 
OF THE 
Bacillus Tuberculosis 
INTO THE 
SYSTEM. 
BY 
LAWRENCE F. FLICK, M.D. 
Reprint from the Times and Register, October 19,1889. 
PHILADELPHIA 
MEDICAL PRESS COMPANY* LIMITED, 
1889, THE MODE OF ENTRANCE OF THE BACIL- 
LUS TUBERCULOSIS INTO THE SYSTEM. 
LAWRENCE F. FLICK, M.D, 
ONE of the most important questions to be settled 
about the etiology of tuberculosis, is how the 
bacilli gain entrance into the system ; for the prophy- 
laxis against the disease depends largely upon its 
solution. It is generally held that they gain admis- 
sion through the lungs by inhalation. This view 
has apparently been accepted without much inquiry 
as to its correctness, and even many interesting ex- 
periments have been performed to bolster it up, al- 
though it is upon its face entirely at variance with the 
teachings of physiology and of clinical experience. 
It is generally admitted that the bacillus tubercu- 
losis cannot live in the air unless protected by some 
foreign substance, such as pus, or, in other words, that 
it cannot maintain its existence when isolated. Those 
who hold the theory that it is inhaled, claim that it 
gains admission through the medium of pulverized 
sputa, which is wafted about as dust. Now, the first 
question that arises is, can pulverized sputa be in- 
haled ? or, to put it more precisely, can it be carried 
to the air cells or even into the bronchioles by the 
inspired air? A careful study of the mechanical 
construction and of the physiological conduct of the 
respiratory tract would lead us to believe that foreign 
bodies of any material size cannot readily be carried 
into the lungs by the air. It is a law of physics that 2 
a foreign body carried by the air will be deposited 
upon the first obstruction that can resist the force of 
the air that carries the body. Nature has laid ob- 
structions in the way of foreign bodies all along the 
respiratory tract, thereby indicating that nothing was 
to enter that tract but air. The stiff hairs in .the 
nostrils, the formation of the nose and pharynx, 
offering many surfaces for the impingement of foreign 
bodies, and above all the high sensitiveness of the 
mucous membrane lining the respiratory tract, whereby 
an expulsive effort is brought about the instant a 
foreign body touches it, are all safeguards against 
the introduction of foreign bodies into the lungs by 
means of inhalation. It is questionable therefore 
whether enough dried up tubercular sputa could be 
carried into the lungs by the inspired air, and if it 
could be carried in whether it would be allowed to 
remain there for a sufficient length of time to set up 
tuberculosis. 
But even admitting that some pulverized dried-up 
tubercular sputa may pass all the barriers setjip by na- 
ture and gain admission into the lungs with the inspired 
air, and having been deposited upon the respiratory 
mucous membrane, may resist all expulsive efforts to 
dislodge it, how will the tubercular bacillus get into 
the lung tissue? It will have to go in .either by 
absorption or by penetration, for in most cases of 
tubercular inflammation of the lungs the disease is in 
the lung tissue itself and not upon the mucous mem- 
brane. If it enters by absorption it is taken up by 
the lymphatic system and carried into the circulation, 
thus taking a roundabout way to get into the lung tis- 
sue. If it enters by penetration it must first escape from 
the pus in which it has been imbedded, and as soon 3 
as it does so it is exposed to the germicidal influence 
of the air. In the event of either method of entrance 
it must, moreover, run the gauntlet of the phagocytic 
power of the blood. Now, considering the small 
amount of dried up tubercular sputa that can gain 
entrance into the lungs by inhalation, and the diffi- 
culties which the tubercular bacillus necessarily en- 
counters in its efforts to get into the lung tissue and 
to establish a colony there, it looks very improbable 
that inhalation is the ordinary method by which the 
tubercular bacillus gains entrance into the system. 
The inhalation theory of the tubercular bacillus is 
equally at variance with clinical experience. The 
fact that tubercular inflammation mostly begins in 
the apices of the lungs instead of in the base, the 
appearance of the disease primarily in the membranes 
of the brain, in the alimentary tract, in the pleurae, 
and in bones and such glands as the ovaries and tes- 
ticles, and the immunity of the many persons who 
are constantly exposed to inhalation of tubercular 
sputa dust, are all clinical phenomena which militate 
against the theory. If the tubercular bacillus gains 
entrance into the system by inhalation, we ought 
always to find the primary tubercular disease in the base 
of lungs or in the lymphatic glands. Of all parts of the 
lungs the apices are the least likely to become the 
receptacles of foreign matter by inhalation, first be- 
cause of their inactivity, and second because of their 
position; so that when they even do become the pri- 
mary seat of tubercular disease, the bacillus does not 
likely first get its lodgment there. The fact that 
the disease so seldom develops primarily in that part 
of the body in which it first gains lodgment would 
therefore bring us to the conclusion that if the bacillus 4 
tuberculosis gains entrance into the system by inha- 
lation, it must do so by the absorption process, and 
if the bacillus is absorbed we have a right to expect 
the primary seat of the disease to be found in the 
lymphatic glands. If the inhalation theory were cor- 
rect, everybody ought, moreover, to die of tuberculo- 
sis ; for with the amount of dried up tubercular sputa 
that necessarily flies about in the air in street cars 
and in work-shops, it is difficult to understand how 
anybody chn escape the disease. 
But what about the experiments that have been 
performed in support of the theory, and which seem 
to demonstrate it beyond question or quibble? The 
most forcible experiments that have come to my 
-knowledge are those of Koch, which consisted of 
Tubbing up tubercular matter in water, spraying it 
into an enclosure, and compelling animals to inhale 
the spray. The animals all contracted tuberculosis, 
which result proved that when tuberculous matter is 
introduced into the system, tuberculosis results ; but 
proved nothing more. The weak point in the ex- 
periments was that there was no precaution taken 
against the entrance of tubercular matter into the 
stomach. Spray readily condenses upon obstructing 
surfaces, and in these experiments considerably more 
tubercular matter must have been deposited in the 
pharynx and found its way into the stomach than 
was carried into the bronchial tubes by the inspired 
air. 
Another theory about the manner in which the 
bacillus tuberculosis gains entrance into the system, 
and one which seems to have few believers is, that it 
gains admission through the stomach. Everybody 
apparently admits that it can gain entrance in this 5 
way, but few are willing to concede that this is the 
ordinary or usual way. Whether it is or not will, of 
course, remain for future experiments to positively 
determine; but physiology and clinical phenomena 
certainly seem to indicate that it is. 
In the first place, it must be conceded that the 
alimentary tract is the ordinary avenue into the sys- 
tem for all extraneous matters. Its construction, 
machinery, and mechanism are all adapted to the ex- 
peditious conveyance of matter from without the 
body into the body. Its purpose is to supply the 
body with food, and in health and the complete per- 
formance of its functions it is capable in a measure 
of discriminating against deleterious matter, or of 
rendering it innocuous. The stomach has the power 
of destroying animal life, and stands sentinel to all 
that enters the body ; but only exercises that power 
when in possession of all its faculties. In the 
mechanical process of conveying food into the body, 
micro-organisms and parasitic animals of all kinds, 
either in the larval or developed state, likewise find 
their way in, and unless they are deprived of life by 
the stomach, will get into the system, seek out a con- 
genial soil, and develop and reproduce themselves. 
In this way all parasitic animals which prey upon 
the internal organs of man, of which we have any- 
thing like definite knowledge, gain their admission 
into the body. Is it likely that the bacillus tubercu- 
losis forms an exception ? Certainly the stomach is 
the physiological way for it to enter. 
Upon the theory that the bacillus tuberculosis 
gains entrance into the system through the stomach, 
the clinical phenomena of tuberculosis are quite in- 
telligible. 6 
From the days of Hippocrates it has been observed 
that the forerunner of phthisis is a disordered stomach. 
So close is the relation between the two diseases, that 
many have been led to look upon dyspepsia as the 
cause of consumption. The part which the stomach 
plays is, however, entirely a passive one. Because 
of its deranged condition, and its consequent inability 
to destroy the bacillus tuberculosis, the latter gains 
entrance into the system, by being allowed to pass 
unharmed into the intestines, being absorbed by the 
lacteals into the thoracic duct, and being carried with 
the ch}de into the circulation. The bacillus in taking 
this course into the body, encounters no obstruction 
or difficulties after passing the stomach, at least until 
it encounters the blood corpuscles, and is well sup- 
plied with the necessary pabulum for its subsistence 
on the way. 
The clinical facts that tuberculosis appears most 
frequently in the lungs, that its favorite site in the 
lungs is the apex, that in children, it appears most 
frequently in the intestinal canal and the membranes 
of the brain, that its primary seat may be in the 
periosteum, the ovaries or testicles, the pleura, or, in 
fact, in any remote part of the body, can all be explained 
upon the theory that the bacillus gains its entrance 
through the stomach. The contents of the thoracic 
duct, after mixing with the venous blood, are first of 
all carried into the lungs; consequently, a larger 
number of tubercle bacilli enter the lungs, than any 
other organ or part of the body. It has been shown 
that the blood exercises a phagocytic influence over 
bacteria, hence, the farther the bacilli advance in the 
circulation, the fewer survive, and the more remote 
an organ or part of the body is from the entrance of 7 
the contents of the thoracic duct, the less its chances 
are of becoming infected with tuberculosis. The 
brain, the intestines, and the various organs in 
the abdominal cavity, probably receive the largest 
supply of arterial blood in the order mentioned, 
and, practically, receive it about the same distance 
from the entrance of the contents of the thoracic 
duct. We would, therefore, expect that the lungs, 
the brain, and the intestines, would be the most 
frequent seats of primary tuberculosis, in the order 
mentioned, and so we find them in practice. But 
the number of bacilli that enter an organ or part 
of the body, is not the only factor that determines 
the primary seat of the disease; the nature of the soil 
plays an important role. It has long since been 
recognized that anything which interferes with the 
free active circulation of an organ or tissue, predis- 
poses it to tuberculosis. Hence we find the apices 
of the lungs, the congested membranes of the brains 
of teething children, the irritated alimentary canal of 
bottle-fed babies, the bruised periosteum, the thick- 
ened pleura, the congested ovaries, spleen, liver, and 
kidneys, becoming the selected soil for the develop- 
ment and reproduction of the bacillus tuberculosis. 
It is also easily understood upon this theory, why 
so many persons who are exposed to tuberculosis, 
fail to contract it. The immunity is generally ascribed 
to improper soil, and whilst this may be part of the 
reason, it is not the whole reason; for it has been 
frequently proven by experiment on animals, that the 
disease will develop in any soil, if the bacilli are 
introduced in large enough numbers into the circula- 
tion. There are two factors in operation in the non- 
occurrence of tuberculosis in those persons who are 8 
exposed, first the bacilli-destructive power of tbe 
healthy stomach, and second the phagocytic power 
of the blood. Persons who have healthy stomachs, 
and who do not overburden them with too much or 
improper food, and who take sufficient exercise in a 
pure atmosphere to secure them a free circulation of 
well-oxygenized blood, will not contract tuberculosis, 
no difference what the exposure. To contract the 
disease it is necessary first, to be in such contact with 
infected persons or objects as to enable the bacillus 
to get into the stomach; second, to possess such a 
stomach as will, because of temporary or permanent 
disability to destroy the bacillus, allow it to pass into 
the circulation ; third, to have in some parts of the 
body localized spots or a spot of torpid circulation, 
which offer a congenial soil for the development and 
propagation of the bacilli. 
In my paper on the contagiousness of phthisis I have 
shown thqt some social relations between parties are 
probably necessary for the conveyance of tuberculosis 
from person to person, and that proximity of habita- 
tions and casual contact are in themselves not suf- 
ficient. It will not be difficult to understand, how 
tubercular matter finds its way into the stomach, if 
we for a moment reflect upon social customs. Be- 
cause of the universal practice on the part of con- 
sumptives, of expectorating into handkerchiefs, or 
into open space, it is almost impossible to come in 
contact with them, or to remain for any length of 
time in a place occupied or frequented by them, with- 
out getting some bacilli into one’s stomach. The lips 
and hands of consumptives who use handkerchiefs 
extensively, are necessarily smeared with tubercular 
sputa, and any persons kissing them, or shaking hands 9 
with them, can scarcely avoid conveying the disease 
germ into their own stomachs, unless they wash 
themselves before partaking of food or drink. Drink- 
ing out of the same vessels and eating with the 
same utensils as consumptives, without prior cleans- 
ing ; swallowing the dried-up tubercular sputa that 
is deposited upon the pharynx by the inspired air; 
the handling and serving of food by consumptives, 
such as that by waiters, cooks, grocers, fruiters, and 
milk dealers, suggest some of the ways in which 
tubercular matter may find its way into the stomach. 
Whilst I do not wish to be understood that con- 
sumption cannot enter the system by way of inhala- 
tion, I claim that the stomach is the usual mode of 
entrance, and that there is ordinarily very little 
danger of contracting the disease through the lungs 
themselves. The part which inhalation plays in the 
etiology of the disease, is the mechanical part of car- 
rying the tubercular sputa into the nares and pharynx, 
from whence it finds its way into the stomach. The 
whole question can, however, I think, be satisfactor- 
ily settled by experiment, and I hope at some future 
time to be able to illustrate what I have set forth in 
theory.