74 Mr. A. B. Farn on the 



business of its own, and quite apart from worm-rearing. The 

 reelers bought the cocoons from the rearers, and reeled off the 

 silk. The reeler's license specified how many cocoons he should 

 use in making a thread, and departure from this condition was 

 unlawful. The silk produced therefore from any one reeling- 

 house was always the production of the simultaneous reeling of 

 the same number of cocoons, and frequently the whole of the 

 cocoons of one district went to one reeling-house. To this alone 

 may be attributed the superiority of Italian silk. 



We have seen the cause which intensified the Pebrine disease. 

 Now to learn from Pasteur something as to the disease itself. 

 Before he made his enquiry other investigators had observed that 

 Pebrine was accompanied by small, shining, microscopic bodies 

 within the affected worms, and that the black spots of the 

 disease seemed to be due in some change in the skin where these 

 shining bodies were located. But it was left to Pasteur to 

 demonstrate that these bodies were parasitic bodies, and were 

 the sole cause of the disease, as also to prove how readily 

 the disease can be communicated not only from silkworm to 

 silkworm, but from one rearing-house to another situated far 

 apart. He found that one healthy silkworm could communicate 

 the disease to another healthy worm, and in this way : the para- 

 sites are voided by infected worms, and may be found in the 

 frass or dejecta. It often happens that in crawling one over the 

 other some worms are wounded by the legs of other worms. The 

 three pairs of front legs in tbe worms, the prolegs, are furnished 

 with sharp terminations, which permit them to hold the leaves 

 on which they are feeding firmly, and the accidental wounds or 

 punctures above referred to are caused by these sharp legs. If 

 previous to puncturing in this way the skin of another the worm 

 has smeared these prolegs by walking over dejecta, and if the 

 dejecta came from a worm suffering from Pebrine and passing 

 these parasites, it is evident at once that here was a means by 

 which the disease could be propagated by one healthy worm to 

 another healthy worm. To test this Pasteur introduced by 

 needle puncture these parasites into a previously healthy worm, 

 and thus infected it. The leaves, too, on which the worms fed 

 might become soiled by frass containing these parasites, and 

 upon this contaminated food being ingested Pebrine would ensue. 

 This he verified by feeding healthy worms with leaves bearing 

 parasites on their surface. The dust in rearing-houses he found 

 contained the parasites, and this dust, settling on the leaves, 

 readily conveyed the disease. A rearer who had never seen 

 Pebrine universal in a rearing-house went to visit a house in 

 which the disease was rampant. He spent some time in the 

 infected house, and took the disease away with him in the 

 dust which lodged on his clothes, and introduced it with 



