186 MICROBES, FERMENTS, AND MOULDS. 
These spores:are much more tenacious of life than 
the microbes themselves. The latter perish in a tempe- 
rature of 60°, by desiccation, in a vacuum, in carbonic 
acid, alcohol, and compressed oxygen. The spores 
on the other hand, resist desiccation, so that they can 
float in the air in the form of dust. They also resist 
a temperature of from 90° to 95°, and the effects of a 
vacuum, of carbonic acid, of alcohol, and compressed 
oxygen. 
In 1873, Pasteur, aided by Chamberland and Roux, 
carried on some experiments on a farm near Chartres, 
in order to discover why this disease is so common in 
some districts, in which its spread cannot be ascribed 
to the bite of flies. Grass,on which the germs of 
bacteridia had been placed, was given to the sheep. 
A certain number of them died of splenic fever. The 
glands and tissues of the back of the throat were 
very much swelled, as if the inoculation had occurred 
in the upper part of the alimentary canal, and by 
means of slight wounds on the surface of the mucous 
membrane of the mouth. In order to verify the fact, 
the grass given to the sheep was mixed with thistles 
and bearded ears of wheat and barley, or other prickly 
matter, and in consequence the mortality was sensibly 
increased. 
In cases of spontaneous disease it was surmised 
that the germs which were artificially introduced into 
food in the course of these experiments, are found 
upon the grass, especially in the neighbourhood of 
