35 
from the cocoon, and are often covered with bloody pimples, which be- 
come black on drying. Part of the body and the wings have a leaden 
color; but this must not be confounded with a certain natural brown- 
ness which some healthy moths exhibit, and which extends over the 
whole body; but it is only with highly diseased subjects that these 
exterior signs become visible, and to find the symptoms of the disease 
we are often obliged to resort to a microscopical examination of the 
interior of the insect. 
Internal symptoms.—“ In the interior of the body microscopic observa- 
tion reveals the presence of innumerable corpuscles of an ovoid shape 
(Plate II), filling the cells of the walls of the stomach, those of the silk 
glands, the muscles, the fatty tissues, the skin, the nerves—in a word, 
all the portions of the body. There are often so many of them that the 
cells of the silk glands become swollen and white, and appear to the 
naked eye to be sprinkled over with chalky spots; the silky liquid al- 
ways remains exempt from this parasite, but it is much less abundant 
than when the worm is in a healthy state.”* 
In 1849, M. Guérin-Méneville first noticed these floating corpuscles in 
the bodies of the diseased worms. ‘They were supposed by him to be 
endowed with independent life; but their motion was afterwards shown 
by Filippi to depend on what is known as the Brownian motion, and 
they are now included in the class Sporozoa of the Protozoa, and re- 
ferred by Balbiani to the order Microsporidie. 
These corpuscles are found in the Silk-worm in all its stages—in the 
egg, larva, chrysalis, and moth. It was for a long time a mooted ques- 
tion as to whether they were the true cause or the mere result of the 
disease; but the praiseworthy researches of Pasteur have demonstrated 
that pébrine is entirely dependent upon the presence and multiplication | 
of these corpuscles. The disease is both contagious and infectious, be- 
cause the corpuscles which have been passed with the excrement or 
with other secretions of diseased worms may be taken into the alimen- 
tary canal of healthy ones when they devour leaves soiled by them, and 
because it may be inoculated by wounds inflicted by the claws of other 
worms. The malady may be carried to a distance with the corpuseu- 
lous dust coming from infected magnaneries, and such dust holds the 
power of communicating disease from one season to another. 
When the “seed” is thus diseased it hatches irregularly and incom- 
pletely, and the larve often perish before or during the first molt. When 
the corpuscles are taken into the intestines, as above described, the 
malady usually becomes apparent, through some of the external symp- 
toms mentioned, at the end of four or five days. M. Pasteur determined 
that if the worm partook of the soiled food after the fourth molt it 
would make its cocoon, but that corpuscles would be found in profusion 
in the chrysalis and moth. If, on the other hand, the worm is thus ex- 
* Maillot, Legons, etc., pp. 96, 97, 
