44 
Proceedings of Royal Society of Edinburgh. [dec. 5, 
After being exposed to tbe dry heat for three and four months, 
the vitality of this micro-organism and its spores was not destroyed. 
But, after being heated for five and six months the vitality of the 
microbe was completely destroyed; for no growths made their 
appearance in sterilised blood serum kept at a temperature between 
37° and 39° C. for nearly two months. 
From these experiments it will be seen that Bacillus tuberculosis 
is capable of being dried up in the dust of the atmosphere for 
several months without its vitality being impaired. 
V. Bacillus tuberculosis disseminated by Flies, Paper, &c. 
It has been shown that farm animals may be inoculated through 
the bite of flies with Bacillus anthracis (the Bacteridia of Davaine); 
and Pasteur [Bulletin de V Academic de Medecine, 1880) has 
shown that the casts of Lumbricus terrestris may contain the germs 
of splenic fever, at the same time possessing all their original viru- 
lence. Eecently, MM. Spillman and Haushalter [Gomptes Rendus 
Hebdomadaires des Seances de V Academic des Sciences , vol. cv. 
[Illo. 7], 16th August 1887) have discovered that the common house 
fly in consumptive hospitals is very often seen upon the expectora- 
tions of the patients. Some of these flies were caught and placed 
under bell-glasses, and subsequently it was found that their excre- 
ments contained numbers of Bacillus tuberculosis. 
Eecently, I have cultivated (using every possible aseptic 
precaution) from the envelopes containing the letters from Mr 
Snodgrass (already mentioned), in sterilised solid blood serum 
growths which had all the macroscopical appearances of Bacilhis 
tuberculosis. These pure cultivations gave serpent-like twistings in 
cover-glass impressions, — and under the higher powers of the 
microscope the characteristic form of Bacillus tuberculosis when 
stained by the Ehrlich and other methods.* 
From this investigation we draw the conclusions — (1) that the 
saliva of consumptive patients used in moistening an envelope may 
* Although I had been experimenting with Bacillus tiiberculosis for some 
time, there were no chances of my cultivation plates and tubes becoming con- 
taminated with Bacillus tuberculosis from sputum, &c., or with foreign 
microbes. They were inoculated from the envelopes in a room (with closed 
doors and windows) away from my laboratories ; and further, I had changed 
my clothes and disinfected my hands. 
