BACILLUS OF TUBERCULOSIS. 265 
methylene-blue with caustic potash. More recently 
Ehrlich devised a method of staining which proved 
to be better, viz., the use of a solution of an aniline 
color—fuchsin or methyl-violet—in a saturated aqueous 
solution of aniline oil and decolorization of other bac- 
teria with a solution of a mineral acid, to be followed 
by a contrast stain, such as methylene-blue. (Plate 
I., Figs. 1 and 2.) Various modifications of Ehrlich’s 
method are noyeommonly used. The carbol-fuchsin 
yemployed; it has the advan- 
keeping well. The tubercle 
_ also by Gram’s method of 
11S: recommended for general use. 
Biological Chi aoters. The bacillus tuberculosis is a 
parasitic, aérobic, non-motile bacillus, and grows only 
at a temperature of about 37°C. It has been assumed 
that this bacillus is capable of forming spores. The 
refractile spaces, however, are not found to possess the 
regular shape and brilliancy of ordinary spores, nor have 
they any greater resisting power to heat, desiccation, 
etc., than the homogeneous bacilli. Exposure to 60° C. 
in water destroys them in fifteen minutes. The bacilli 
have, however, a somewhat greater resisting power than 
most other pathogenic bacteria, since frequently the 
bacilli resist desiccation at the ordinary temperatures 
for months; many bacilli die, however, soon after dry- 
ing. Portions of the lung from a tuberculous cow, dried 
and pulverized, produced tuberculosis in guinea-pigs at 
the end of 102 days (Cadéac and Malet). They retain 
their vitality for a considerable time in putrefying ma- 
terial. Cold has no effect upon them. When dry the 
more resistant organisms stand dry heat at 100° C. for 
hours; but when moist, as in milk, they are more quickly 
bacilli can‘ 
staining, butithis: 
