Pathogenic Bacteria

TURER CUL OSIS. 22$

consist in nodes, nodules, or collections of agminated
nodules, called tubercles, scattered irregularly through
the tissues, which are devitalized or disorganized by
their presence. When tubercle bacilli are introduced
beneath the skin of a guinea-pig, the animal shows no
sign of disease for a week or two; it then begins to lose
appetite and gradually to diminish in flesh and weight.
Examination at this time will show a nodule at the point
of injection and enlargement of the neighboring lymphatic
glands. The atrophy increases, the animal shows a febrile
reaction, and at the end of a varying period of time,
averaging about twelve weeks, dies. Post-mortem ex-
amination shows a cluster of tubercles at the point of
inoculation, enlargement of lymphatic glands both near
and remote from the primary lesion (due to the presence
of tubercles), and a widespread invasion of the lungs,
liver, kidneys, peritoneum, and other organs and tissues,
with tuberculous tissue in a more or less advanced con-
dition of necrosis. Sometimes there are no tubercles
discoverable at the point of inoculation. There is no
regularity iu the distribution of the disease. Tubercle
bacilli are demonstrable in immense numbers in all the
diseased tissues. The disease as seen in the guinea-pig is
more extended than in other animals because of its greater
susceptibility, and the death of the animal is more rapid
than in other species for the same reason. In rabbits the
lesion runs a longer course with similar lesions. In
bovines and sheep the infection is generally first seen
in, and is principally confined to, the alimentary appa-
ratus and the associated organs, though pulmonary dis-
ease also occurs. In man the disease is chiefly pulmonary,
though gastro-intestinal and general miliary forms are also
common. The development of the lesions in whatever
tissue or animal always depends upon the distribution of
the bacilli by the lymph or the blood, and is first inflam-
matory, then degenerative, in type.

The experiments of Koch, Pruclden and Hodeuphyl,
and others have shown that when dead tubercle bacilli

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