ADDRESS. IxXXvii 



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 

 epizootic, frequently accompanied by the ai^pearance of dark spots upon the 

 skin (whence the name of " Pebrine " which it has received), had been noted for 

 its mortahty. But in tlie 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 has 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 might 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 atten- 

 dance, the cultivator has constantly seen his silkworms perish and himself 

 plunged in ruin, — but it means that the looms of Lyons have lacked employ- 

 ment, and that for years enforced idleness and misery have been the por- 

 tion 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 Eeport* 

 made by M. de Quatrefages, in 1859, 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, FUippi, discovered in the blood of the silkworms 

 affected by this strange disease a multitude of cylindrical corpuscles, each 

 about -g-inro °^ ^^ ^^^^^ long. These have been carefully studied by Lebert, 

 and named by him PanJiistopliyton ; for the reason that, in subjects 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 concomitants, 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 ma- 

 lady and the inefficiency of the remedies which had been suggested, dis- 

 patched 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 PanTiistopliytoii in the silkworm. It is contagious and infectious 

 because the corpuscles of the Panhistophi/ton pass away from the bodies of 

 the diseased 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 



* Etudes gur les Maladies Actuelles des Vers i Soie, p. 53. 



