72 
Pasteur and Jus Work, 
through the injury produced by organised ferments, is not 
normally perfected," said Pasteur. 
The vitality of the germs oi Jlachcrie was much greater than 
those oi pebrine, which, if dried, perished within a year ; whereas 
the former retained their life for several years. The dust of a 
silkworm nursery infected by Jiacherie appeared under the 
microscope largely made up of cysts or spores of vibrios, which 
would remain latent until wet or damp roused them into 
activity. Falling on the leaves which serve as food, they are 
carried into the intestines of the silkworms, grow and multiply 
there, and cause illness, unless the worms are vigorous, when 
they may be digested with the food. It is a struggle for life 
between the silkworms and the vibrios, in which the former are 
unfrequently victorious. 
Accidental Jlaclierie could be prevented by hygienic precau- 
tions ; but when hereditary, i.e. developed through diminished 
vitality of eggs or embryo, Pasteur resorted to the microscope, 
by which information as to the health of the worms, chrysalides, 
and moths for egg production, could be obtained. 
After the most patient study of this compound disease of 
silkworms, Pasteur had arrived at such knowledge of its causes, 
course, and different manifestations, that he could at will pro- 
duce either form — pcbynne or JI.acherie, and could so regulate its 
intensity as to have it appear, experimentally, on a given day, 
almost at a given hour. But a remedy for the evil was not so 
readily devised. One form, flackerie, was capable of com- 
paratively easy control, by care in feeding, and keeping the 
surroundings in a proper state. 
With the other form — pebrine — by far the most serious, pre- 
ventive measures were not so soon arrived at ; but through 
a series of observations, as simple as they were ingenious, 
Pasteur concluded that the cause was to be combated in the 
eggs, and, acting on this view, he ultimately triumphed over 
the scourge. 
The process now most successfully pursued in the silk- 
growing districts, for avoiding the plague, is described as 
follows : — 
The cocoons are finished, and the appearance of the moths 
alone is waited for. They arrive, and tliey pair. Then begins 
the work of the cultivator, who is careful about the production 
of the eggs. He separates the couples at the end of the day,, 
laying each female moth by itself on a little linen cloth sus- 
pended horizontally. The females lay their eggs. After the 
laying, the attendant takes each female in turn, and secures her 
by a pin passed through the wings to a folded corner of the little 
