AGRICULTURAL INDUSTRIES. 201 



casting comes on later than with the healthy specimens, in the fourth 

 making- a difference of from eight to fourteen days, and the larger 

 proportion of the worms die before reaching the spinning age. The 

 body becomes soft, assumes a dirty yellow colour, with peculiar 

 spots appearing first on the hairy parts. These seem at first scarcely 

 darker than the skin, but grow gradually larger and more noticeable 

 in shade, run together in irregular shapes, and are finally pitch- 

 black and shining. The excretions are more liquid than in a 

 healthy state, and covered with yellow slime, which hardens on 

 exposure to air, flows of itself, becomes black, and often obstructs 

 the passage. When dead the worm soons dissolves into a sickening 

 black slime. The disease often appears first toward the end of the 

 development of the silkworm, but carries on its work in the chry- 

 salis, so that the ravages of the plague are plainly to be observed in 

 the forthcoming butterfly. Much more important than these out- 

 ward indications and symptoms are the workings of the disease in 

 the body of the insect. After a most careful study of these, it has 

 been found that the surest sign of the Pebrine is the presence of cer- 

 tain small egg-shaped, ellipsoidal or cylindrical bodies, 0'005-0"002 

 mm. in length, rounded at both ends, which look like oil drops when 

 brought to the light. These "Corpusculs vibrants" were first in- 

 vestigated and described by Prof Cornalia of Milan, and are known 

 in consequence as the Cornalian corpuscles. The nature of these 

 organisms, Nosenia bombycis, Naegl., was stated much later. They 

 are found in all parts of the diseased worm, in the excretions also, 

 and propagate themselves from generation to generation. The 

 healthy butterfly has none of them, but they reappear in its eggs. 

 Upon this fact, following the teaching of the celebrated physiolo- 

 gist, Pasteur, has been founded the only successful remedy, or, 

 rather, the means of controlling and removing the disease, which, 

 consistently employed, has wrought the best results. It consists 

 in a careful microscopic test of those butterflies reserved for breed- 

 ing, and of their eggs, and the separation of every suspicious insect 

 and particle, the special directions and prescriptions for which 

 would take up too much time and space. It must be mentioned 

 in this connection that the notion of Liebig and others of his time, 

 that mulberry culture works a gradual weakening and chemical 

 change of food through exhaustion of the soil, and thus largely 

 causes the disease, was entirely erroneous, as I showed some 

 eighteen years since.^ 



The summers of 1856, 1862 and 1865 were the worst seasons 

 known to silk-culture in modern times. They were all marked in 

 Southern Europe by sultry temperatures and long continuing rains 

 throughout the breeding period. This abnormal and unfavourable 

 weather, without doubt, largely increased the ravages of the disease. 

 In Italy the cocoon harvest, which yielded in 1857 forty million kg. 



1 Rein: " Dergegenwartige Stand des Seidenbaues." Frankfurt a/M . 1868 

 pp. 22-24. 



