15 
WiLM (a) found them destroyed in four hours’ exposure to the sun. 
The German Plague Commission ( b) made tests in Bombay in this 
manner: The various objects (glass, silk threads, wool) were saturated 
with a virulent agar culture of the bacillus pestis. One-half of the 
objects were exposed to direct sunlight. The other half were laid away 
^in a dark place for control. 
^ ^ In very thin layers on glass the bacillus was killed in one hour. 
] In thicker layers on glass they were pathogenic for mice after three 
hours but not after four hours. 
jk;. In silk threads they were killed after three hours’ sunning. 
^ In wool they were virulent for mice after eight hours. 
Other tests were made with well grown agar cultures placed in the 
i; sunlight. In one or two hours in the sun they still contained active 
organisms. After a whole day’s sunning they were dead. The cultures 
are warmed very much in the sun ; therefore, other tests were made by 
placing the agar tube in water and keeping in the sun one and one-half 
^liours. At the end of the test the temperature of the water was 39° C. 
I The bacillus was alive and virulent. 
j The following report of the experiments on the viability of the plague 
^ bacillus was published by S. L. Eappoport, (c) St. Petersburg. The 
f material used was allowed to soak in bouillon cultures of bacillus pestis 
in a dark closet for twenty-four hours, then exposed for successive days 
I to all the sunlight obtainable, or to dry heat. 
I 
Temperature and time required to kill. 
Material. , 
20 C. 
(68 F.) 
36 C. 
(96. 8 F.) 
60 C. 
(140 F.) 
80 C. 
(176 F.) 
Silt t.lirf'fld 
Days. 
19 to 24 
Days. 
13 
Minutes, 
75 
Minutes. 
15 
15 

10 to 17 
5 
30 
paper 
10 to 24 
45 
15 
T.inen thread 
9 to 13 
4 
30 
15 
15 
thrpftfl 
13 to 23 
5 
60 
VIABILITY ON VARIOUS OBJECTS. 
( In sputum kept fluid, the German Plague Commission(^?) found the 
; bacillus of pest infectious after teii days. 
Hankin (c) made researches on various articles of produce to deter- 
I mine their susceptibility to endanger or support the bubonic microbe, 
j He shows that the various descriptions of flours and grain usually 
I stored in Bombay contain no trace of the bubonic microbe and also 
I demonstrates that grain purposely infected does not permit of the exist- 
I ' ence of the microbe for more than about four days. 
‘ — 
' a Uber die Pestepidemic in Hongkong ini Jahre 1896. HvgienLsche Kundsclian, 1897, 
« Bd. VII. 
I b Loc. cit. , page 277. 
: c Quoted by Walter Wyman, Surgeon-General IMariue-Hospital Service, in “The 
I j Bubonic Plague,’’ Treasury Department Document No. 2165. 
(Z Kaiserliche Gesundheitsamte, Bd. 16, Berlin, 1899. 
e The Plague in India, 1896, 1897, Vol. II, Appendices I-IV, page 10 eZ seq. 
lil 
