BIOLOGY OF BACTERIA. 6l

hours. Cultures made within five minutes showed con-
fluent colonies of the bacilli, which became fewer and
fewer in number, until after two hours not a trace of a
bacillus prodigiosus could be found.

Wurtz and Ivermoyez assert that the nasal mucus exerts
a o-ermicidal action, but this is not substantiated. These

c> J

writers conclude that the bacteria were carried away by
the action of the cilia and trickling mucus.

It seems to have been proven by Buchner that micro-
organismal infection may take place through the lungs
without definite breach of continuity of the alveolar
walls. He mixed anthrax spores and lycopodium powder
together, and caused mice and guinea-pigs to inhale them.
Out of the 66 animals used in his experiments, 50 died of
anthrax and 9 of pneumonia. Our knowledge of the dis-
position of foreign particles in the lung probably explains
such infection by assuming that the presence of the lyco-
podium attracted numerous leucocytes to the affected air-
cells; that these took up the powder, and with it the
spores; and that the leucocytes, being cells of very sus-
ceptible animals, were unable to resist the growth into
bacilli of the spores which they had carried into the
lymph-channels.

On the other hand, it has been shown that when
the entering spores are unaccompanied by a mechanical
irritant like the lycopodium powder, but are inspired
in a pulverized liquid, infection takes place much less
readily.

Tuberculosis and pneumonia are in all probability
generally the result of the inspiration of the specific
organisms.

(c) The Skin and the Superficial Mucous Membranes.—
The entrance of bacteria into the tissues by way of the
skin is probably extremely rare if the skin is sound.
Numerous experimenters have caused infection by rub-
bing bacteria or their spores upon the skin. It would
seem probable that in these cases there must have
been some microscopic lesions into which the bacteria