262	PATHOGENIC BACTERIA.
lungs. Israel has pointed out certain cases of human
actinomycosis beginning in the peribronchial tissues,
probably from inhalation of the fungi.
The occurrence of three distinct elements as compo-
nents of the rays served to class this organism among
the pleomorphous bacteria in the genus Cladothrix,
where it has remained undisturbed for at least a decade.
Recent researches have, however, changed the view held
by some bacteriologists in regard to the actinomyces, and
caused them to regard the organism as a bacillus. If it
be a bacillus, the central zone of granular cocci-like
elements is to be regarded as consisting of individuals
in process of rapid division and spore(?)-formation, the
mycelial zone as consisting of perfect individuals, and
the peripheral zone, with the rosette-like, club-shaped
elements, as consisting of individuals partly degener-
ated through the activity of the cells and tissue-juices
(involution-forms).
Jones is of the opinion that the disease, if not inden-
tical with, is closely allied to, tuberculosis, and that the
occasional branched forms of tubercle bacilli prove the
tendency of the individual bacillus to form a reticulum.
When the mycelial threads are carefully examined, the
branchings, which appear distinct upon hasty inspection,
are found to be more the effect of a peculiar relation
which the threads bear to one another than actual bifur-
cations, so that it must be regarded as very questionable
whether these threads ever so divide.
The organism may be grown upon artificial culture-
media, as has been proven by Israel and Wolff.
Upon agar-agar or glycerin agar-agar it forms trans-
lucent colonies, about the size of a pin's head, of firm,
almost cartilaginous, consistence. These colonies consist
of bacillary individuals, sometimes seemingly branched.
In bouillon similar dense globular organisms can be
grown. The blood-serum colonies, which grow simi-
larly to the agar-agar colonies, are rather more luxuri-
ant, and slowly liquefy the medium.