OTHER DISEASES OB" DOMESTIC ANIMALS. 151 



young, and those which survive the fourth moult 

 shrink and shrivel away ; they can hardly creep on to 

 the heather to spin their cocoon, and produce scarcely 

 any silk. 



On an examination of the worms which have died 

 of this disease, De Quatrefages ascertained the presence 

 of minute stains on the skin and in the interior of 

 the body, which he compared to a sprinkling of 

 black pepper; hence the name pebrine. Under the 

 microscope these stains assume the form of small 

 mobile granules like bacteria, which Cornalia termed 

 vibratile corpuscles, on account of their movements. 

 Finally, Osimo and Vittadini ascertained the existence 

 of these corpuscles in the eggs, and consequently 

 showed that the epidemic might be averted by the 

 sole use of healthy eggs, of which the soundness 

 should be established by microscopic examination. 



It was at about this date, 1865, that Pasteur under- 

 took the exhaustive study of pebrine; but Bdchamp 

 was the first to pronounce the disease parasitic, 

 resembling muscardine in this respect, and caused by 

 the attacks of a microbe — or microzyma, to adopt 

 B^champ's name — of which the germ or spore is derived, 

 from the air, at first attacking the silkworm from 

 without, but multiplying in its interior, and developing 

 with its gi'owth, so that the infected moth is unable 

 to lay its eggs without depositing the spores of the 

 microbe at the same time, and thus exposing the 

 young grub to attack as soon as it is born. Pasteur's 



