262 Proceedings of Poyal Society of Edinburgh. [sess. 
two tubes (inoculated from the contents of the sealed tubes) after 
thirteen days’ incubation. Four more tubes were opened after an 
exposure for two months at 32° C. (dry heat). Inoculations from 
two “open” tubes revealed the vitality of this microbe after 
sixteen days’ incubation; — and inoculations from the two sealed 
tubes proved the vitality of the micrococci after the lapse of twenty- 
one days’ incubation. The remaining tubes were examined in a 
similar manner after the lapse of three, four, six, and eight months 
respectively. 
After an exposure at 32° C. (dry heat) for three, four, and six 
months, the vitality of Micrococcus chlorinus was not destroyed. 
And finally, after being dried up for eight months, the vitality of 
this microbe was completely destroyed ; for no growths made their 
appearance in sterilised nutrient beef-broth kept at a temperature 
between 32° and 36° C. for nearly three months. 
A similar series of experiments were performed with other micro- 
organisms (the final inoculations being made in different media so 
as to suit each case). The results were as follows : — 
After an Exposure at 32° C. (dry heat) for : — 
1 
month. 
2 
months. 
3 
months. 
4 
months. 
5 
months. 
6 
months. 
7 
months. 
8 
months. 
Micrococcus rosaceus , 
L* 
L 
L 
L 
... 
D 
D 
D 
Bacterium allii, 
L 
L 
L 
L 
L 
L 
D 
D 
Micrococcus prodi- 
giosus, 
Bacillus tuberculosis , 
L 
L 
L 
D 
D 
D 
L 
L 
L 
L 
D* 
D 
From these experiments, it will be seen that various microbes are 
capable of being dried up in the dust of the atmosphere for several 
months without losing their vitality. 
M. Duclaux ( Comptes Rendus , vol. 100, pp. 119 and 186) proved 
that the germs of certain species of Tyrothrix, especially Tyrothrix 
scaber , are not destroyed by at least three years’ exposure in a dry 
state to air of a tropical temperature, but were killed by exposure to 
direct sunlight at the same temperature for some weeks. 
L = living. D = dead. 
