The estimate of the relative, early or late infection of two organs or
tissues may often be made with reasonable accuracy from the fact that
the lesions in one organ are old, caseated, calcified or sclerosed,
while those in the other organ are all recent, with vascular environment
and almost devoid of caseation or other degenerative process. We cannot
safely predicate our decision on the greater number of old lesions in
one organ rather than another, as the disease may have advanced much
more rapidly in the one tissue. Still less can we state with certainty
that the disease has not entered by a given channel because no lesions
are left to show the transit of the bacillus along its supposed course.
We frequently find tuberculosis of the bronchial or mesenteric glands,
when we can detect no lesion in the lung, nor intestine. The bacillus
has been passed on without establishing any lasting lesion in transit.
It is often too confidently asserted that the infected dust inhaled,
falls directly on the air cells and determines the extensive pulmonary
tuberculosis that ensues. So, on the other hand, it is often too
arrogantly assumed that tubercle bacilli ingested with food, must
necessarily show their results mainly in the intestines, mesenteric
glands and liver. That solid particles can find their way directly into
the lungs, has long been demonstrated by the pulmonary anthracosis of
the miner, and the deadly phthisis of the stone hewer and cutler. The
experiments of Cornet, Tappeiner and others in producing pulmonary
tuberculosis, by compelling the inhalation of infected spray,
corroborate this experience very satisfactorily. Yet it does not follow
that all of the offensive matter penetrated the air cells at once on the
air inhaled. The heavy particles of steel, quartz and even of coal dust
must be mainly arrested on the surface of the moist air passages, yet,
under the irritation caused by their presence and the consequent arrest
of the ciliary motion, they would slowly gravitate downward to the
pulmonary cells. In the case of the inspired tubercular spray or dust,
we must recognize the possibility of the approach of the bacillus to the
lungs through the lymph and blood channels as well. The bacilli lodged
in the pharynx, and, above all, in the tonsillar follicles, can readily
enter the lymph vessels, and are finally poured into the lower end of
the jugular vein, but a few inches from the right heart, by which they
are instantly propelled into the lungs. If then the lung is the most
receptive and least resistant organ, it may easily be that this is the
first point where the bacillus can establish a strong and effective
colony. Apart from this the colonization of the tonsillar follicles may
determine a constant supply of fresh bacilli, which may gravitate down
with the abundant mucus toward the lungs.
This tuberculous colonization of the tonsillar follicles is doubtless
the main source of the infection of the pharyngeal lymph glands, which
is so common in ox, pig and dog. It tends further to intestinal
tuberculosis through the frequent swallowing of the products of the
infected follicles. Then the infection of the pharynx and tonsils,
whether established by inhalation or deglutition, may be the first step
toward a secondary infection of the intestines.
Again the bowels can be infected by the frequent swallowing of the
expectorations brought up from the diseased lungs or bronchia.
Conversely the lungs may be easily infected secondarily from preëxisting
disease of the abdominal organs, and again primarily through the lymph
channels. With tuberculosis of the cardia or liver the bacilli can
follow the lymph vessels of the œsophagus or vena cava so as to reach
the mediastinal glands, and from these glands in a state of disease they
can easily pass into the adjacent pleural cavity and reach the lung. Or
by following the mesenteric lymphatics they reach the thoracic duct and
enjoy what is virtually for them a culture fluid, until discharged into
the jugular, which, as already stated, is but a few inches from the
right heart and lung.
Extension through the general blood stream usually takes place only when
tubercles have already become numerous and extensive in a given region
of the body, and its occurrence is the signal for a generalized
tuberculosis.
The extension from the gastro-intestinal organs, pancreas and spleen may
be considered as a partial exception. Here the infecting blood is not
the general blood stream, but has to run the gauntlet of the liver
capillaries by which the bacilli may be sifted out and delayed. This
arrest subjects the liver to secondary tuberculosis in almost all cases
of abdominal tuberculosis, and goes far to explain the extraordinary
frequency of the disease in this organ. Ingestion tuberculosis almost
necessarily leads to hepatic tuberculosis, and this notwithstanding that
the primary lesion may have been very circumscribed.
The tuberculization of such a large vascular organ as the liver,
however, paves the way for further extension, and if once extensively
diseased, the early generalization of the infection is to be dreaded.