1901] MICROSCOPICAL JOURNAL. 185 
sunlight do not penetrate very deeply. It is therefore 
safe to say that objects may be efficiently disinfected on 
the surface by exposing them all day to a bright sun,pro- 
vided the temperature in the sun is above 30° C. The 
plague bacillus was kept alive a long time in moist gar- 
den earth, especially when kept cool. It dies very quick- 
ly in dry earth. We were not able to keep it alive longer 
than twenty-four hours at any temperature in dry earth. 
As moist earth will preserve the life of the bacillus it is 
easy to understand how the infection may live in dirty | 
dwellings. It requires no stretch of the imagination to 
understand how the infection may be conveyed by the dirt 
and dust of moist, sunless habitations. 
We have not succeeded in keeping plague alive very 
long when dried upon the surface of objects ; even on 
plush, carpet, paper, wood, sawdust, bone, etc., it usually 
dies within a few days. In porous substances such as 
sponge we found it alive after one hundred and twenty- 
five days, when allowed to dry,at 19° C. Here again tem- 
perature plays an important role, for at 37° C., all the 
other conditions being the same, it lived only two days. 
A bacillus of plague lives long in albuminous matter. 
Clothing and bedding are especially apt to be contamin- 
ated with the discharges from buboes and blisters, spu- 
tum, etc. Articles so infected and kept in a cool, moist 
place could retain the active infective principle a very 
long time. Clothing and bedding may harbor the bacil- 
lus of plague for months. In one instance we kept it alive 
on a piece of crash ninety-seven days; in albumin gela- 
tine balls one hundred and twenty-five days; in sponge, 
also, one hundred and twenty-five days; in wool fifty- 
two days. 
According to our results the plague bacillus cannot live 
long in letter mail. In seven tests made with cultures 0: 
the organism on paper we found that it usually died with- 
in twenty-four hours. At most it kept alive eight days 
