762 SPONTANEOUS CONGESTION AND INFECTIOUS DISEASES. 
117,000,000 of francs, or nearly five millions sterling. What may be the 
sum which would represent the money value of all the industries connected 
with the working up of the raw silk thus produced is more than I can pre- 
tend to estimate. Suffice it to say, that the city of Lyons is built upon French 
silk, as much as Manchester was upon American cotton, before the civil war. 
Silkworms are liable to many diseases ; and even before 1853 a peculiar epi- 
zootic, frequently accompanied by the appearance of dark spots upon the 
skin (whence the name of “ Pebrine ” which it has received), had been 
noted for its mortality. But in the years following 1853 this malady broke 
out with such extreme violence, that in 1856 the silk crop was reduced to 
a third of the amount which it had reached in 1853 ; and up till within the 
last year or two it lias never attained half the yield of 1853. This means 
not only that the great number of people engaged in silk-growing are some 
thirty millions sterling poorer than they migli have been ; it means not only 
that high prices have had to be paid for imported silkworm eggs, and that, 
after investing his money in them, in paying for mulberry-leaves and for 
attendance, the cultivator has constantly seen his silkworms perish and him- 
self plunged in ruin ; but it means that the looms of Lyons have lacked 
employment, and that for years enforced idleness and misery have been the 
portion of a vast population which in former days was industrious and well- 
to-do. 
In 1858 the gravity of the situation caused the French Academy of 
Sciences to appoint commissioners — of whom a distinguished naturalist, M. 
de Quatrefages, was one — to inquire into the nature of this disease, and, if 
possible, to devise some means of staying the plague. In reading the report 
made by M. de Quatrefages in 1850, it is exceedingly interesting to observe 
that his elaborate study of the Pebrine forced the conviction upon his mind 
that in its mode of occurrence and propagation, the disease of the silkworm 
is, in every respect, comparable to the cholera among mankind. But it 
differs from the cholera, and, so far, is a more formidable disease, in being 
hereditary, and in being, under some circumstances, contagious, as well as 
infectious. The Italian naturalist, Filippi, discovered in the blood of the 
silkworm affected by this strange disease a multitude of cylindrical corpus- 
cles, each about l-6000th of an inch long. These have been carefully studied 
by Lebert, and named by him Panhistophyton ; for the reason that, in sub- 
jects in which the disease is strongly developed, the corpuscles swarm in 
every tissue and organ of the body, and even pass into the undeveloped 
eggs of the female moth. But are these corpuscles causes, or mere concomi- 
tants of the disease ? Some naturalists took one view and some another; 
and it was not until the French Government, alarmed by the continued 
ravages of the malady, and the inefficiency of the remedies which had been 
suggested, despatched M. Pasteur to study it, that the question received 
its final settlement ; at a great sacrifice, not only of the time and peace of 
mind of that eminent philosopher, but, I regret to have to add, of his health. 
But the sacrifice has not been in vain. It is now certain that this devas- 
tating, cholera-like Pebrine is the effect of the growth and multiplication of 
the panhistophyton in the silkworm. It is contagious and infectious because 
the corpuscles of the panhistophyton pass away from the bodies of the 
deceased caterpillars, directly or indirectly, to the alimentary canal of healthy 
silkworms in their neighbourhood ; it is hereditary, because the corpuscles 
enter into the eggs while they are being formed, and consequently are 
carried within them when they are laid, and for this reason, also, it presents 
the very singular peculiarity of being inherited only on the mother’s side. 
There is not a single one of all the apparently capricious and unaccountable 
phenomena presented by the Pebrine, but has received its explanation from 
the fact that the disease is the result of the presence of the microscopic 
