32 
VIABILITY IN DRIED SPUTUM. 
There seems to be a general agreement that the tubercle bacillus 
may remain alive and virulent in dried sputum for several months. 
Stone’s unusual figure of three years does not stand the light of criti- 
cism. The main point established, however, is that the tubercle 
bacillus may survive in sputum after it dries and is reduced to dust, 
so that its inhalation maybe a danger — how much of a danger depends 
upon other questions not yet solved. 
It is well known that when nonspore-bearmg bacteria are dried all 
but a few soon perish; but these few sometimes survive for unusually 
long periods of time. This rule probably holds in the case of the 
tubercle bacillus, but unfortunately we have no quantitative method 
of determining the number of tubercle bacilli remaining alive. The 
survival of a few bacilli which are virulent for experimental animals 
when injected in enormous quantities (as is usually done in laboratory 
work) would not necessarily mean that human beings are in very 
great danger from such material under natural conditions. 
The following is a tabular abstract of the literature upon the via- 
bility of the tubercle bacillus dried in sputum: 
Dried tuberculous sputum under different conditions. 
Author. 
Conditions. 
Not killed. 
Killed. 
Villamin, 1869 
Koch, 1882 
Malassez and Vignal, 1883 
Schill and Fischer, 1884 
De Thoma, 1886. 
Sormani, 1886. . 
Dried tuberculous sputum 
do 
Alternate drying and moistening eight 
times of tuberculous sputum. 
Sputum containing tubercle bacilli with 
“spores” dried on glass plates. 
Same, without “spores” 
Dried tuberculous sputum 
do 
Several hours. 
8 weeks 
12 days 
126 days 
186 days 
2 months 
Same, on linen 
6 months. 
Cadeac and Malet, 1888. 
De Souza, 1889 
Galtier, 1889 
Feltz, 1890 
Sawizky, 1891 
Stone, 1891 
Ransome and Delepine, 1894. . 
Pieces dried tuberculous lung on paper 
exposed in laboratory. 
Dried tuberculous lung allowed to de- 
compose in outer air. 
do 
do 
Dried walls of cavities insufflated; caused 
tuberculosis in 12 of 14 guinea pigs; 
time of drying not stated. 
Dried tuberculous “material” exposed 
to air and light at 30° C. 
Same, at room temperature 
Dried tuberculous sputum in road dust, 
exposed to weather. 
Same, exposed to sun 
Dried sputum in rooms 
Tuberculous sputum dried under ordi- 
nary conditions of living rooms. 
Dried tuberculous sputum 
Tuberculous sputum exposed in watch 
glasses to: 
(а) Air and light 4 days, then 15 days 
in the dark. 
(б) Air and darkness 8 days, then 11 
days in darkness. 
(c) Close cupboard 19 days 
43 days . 
76 days. 
80 days. 
150 days 
38 days 
30 days 
Over 7 months 
About 140 days 
7 to 9 months. . 
2 \ months 
3 years 
19 days 
19 days 
179 days. 
226 days. 
10 months. 
Virulence de- 
creases after 
2 months. 
Virulence lost 
at end of 4 
months. 
102 days. 
After 150 days. 
After 30 days. 
Do. 
19 days. 
