^0. 3. ] Silkworms in India. 143 



prolegs do not seem to attach themselves easily to objects. In the chrysalis the 

 abdomen is very much swollen, and the rings stretched. In a highly diseased 

 moth the wings are wrinkled as when they emerge from the cocoon, and are 

 often covered with bloody pimples, which become black on drying. Part of the 

 body and wings have a leaden colour. But this must not be confounded with a 

 certain natural brownness 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 microscopical examination of the interior of the insect. 



"In the interior of the body microscopical observation reveals the presence of innu- 

 merable corpuscles of an ovoid shape 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 always remains exempt from this parasite, but is 

 much less abundant than when the worm is in a healthy state. 



" These corpuscles are found in the silkworm in all its stages in the egg, larva, 

 chrysalis, and moth. It was for a long time a mooted question as to whether they 

 were the true cause or the mere result of the disease ; but the praiseworthy researches 

 of Pasteur have demonstrated that pebrine is entirely dependent upon the presence 

 and multiplication of these corpuscles. The disease is both contagious and infectious, 

 because the corpuscles which have been passed with the excrement or with other 

 secretions of diseased worms may be taken into the alimentary 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 corpusculous 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 incompletely, and the 

 larvae 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 symptoms 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 exposed to contagion 

 just before spinning, the chrysalis will show the parasites only during its last davs, 

 while they will be abundant in the moth. 



" From the mother moth the corpuscles pass into the egg and give rise to the 

 diseased seed already remarked upon. Disease in the male will not, however, affect 

 its progeny. The egg is formed while the insect is still in the chrysalis state, and it 

 has been ascertained that, where the corpuscles become abundant only during the last 

 days of this stage, they enter into the seed to a very small degree only, if at all. For 

 this reason eggs are sometimes found to be entirely pure, though the issue of a 

 highly pebrinous parent. The development and multiplication of these corpuscles, 

 though ordinarily very rapid, is insignificant in the egg until the formation of the 

 larva begins. It will be easily understood that, though the parasite may exist in the 

 vitellus of the egg, its detection may be extremely difficult. 13ut when the develop- 

 ment of the embryo has commenced, the number of corpuscles grows also, so that 

 just before, or, better still, just after, the time of hatching, they may be found by 

 hundreds upon a casual observation. Upon a microscopical examination at this time, 



