246 PATHOGENIC BACTERIA.
with typical lepra lesions of all the viscera, especially
While the lepra bacillus has much in common with the
tubercle bacillus, there is not the slightest evidence of
any real identity. It has already been shown that lepra
bacilli do not grow upon artificial media, and that they
cannot be readily transmitted by inoculation. The fol-
lowing description will show that the relation of the
bacilli to the lesions is entirely different from that of
the tubercle bacilli to the tubercles.
Like the Bacillus tuberculosis, the Bacillus leprae proba-
bly only occurs in places frequented by persons suffering
from the disease. That individuals are infected by the
latter less readily than by the former bacilli probably
depends upon the fact that leprous infection seems to
take place most commonly by the entrance of the organ-
isms into the individual through cracks or fissures in
the skin, while the tuberculous infection occurs through
the more accessible respiratory and digestive apparatus.
Once established in the body, the bacillus by its growth
produces chronic inflammatory nodes—the analogues of
The nodes of lepra consist of various kinds of cells
and of fibres. Unlike the tubercles, the lepra nodes are
vascular, and much of the embryonal tissue completes
its formative function by the production of fibres. The
bacilli are not distributed through the nodes like tubercle
bacilli, but are found in groups enclosed within the proto-
plasm of certain large cells—the i 4 lepra cells.'' These
cells seem to be overgrown and partly degenerated lym-
phoid cells. Sometimes they are anuclear, sometimes
they contain several nuclei (giant-cells).
Lepra nodules do not degenerate like tubercles, and
the formation of ulcers, which constitutes a large part of
the disease, seems largely due to the action of external
agencies upon the feebly vital pathological tissue, which
is unable to recover itself when injured.
According to the recent studies of Johnston and Jamie-