FARCIN DU BCEUF.	271
Upon potato very dry scales of a pale-yellow color
rapidly develop.
The growth upon blood-serum is less luxuriant, but
similar to that upon agar-agar.
In milk the organism produces no coagulation by its
growth, and does not alter the reaction.
Microscopic study always reveals the organism as the
same tangled mass of filaments seen in the tissues. The
old cultures are rich in spores, which are very small and

fig, 71.—Streptothrix of farcin clu boeuf growing on glycerin agar-a^ar.
develop upon the most superficial portions of the growth.
These spores resist the penetration of stains to a rather
unusual extent.
Cultures retain their virulence for a long time : Nocard
found one virulent after it had been kept for four months
in an incubating oven at 40° C.
The streptothrix of farcin du bccuf is pathogenic for
guinea-pigs, cattle, and sheep; dogs, rabbits, horses, and
asses are immune.
When the culture or some pus containing the micro-