210 pbesident's address. 



Pasteur in 1865, as to the origin and best means of prevention 

 of the silkworm disease called pelrme. This disease, which 

 first came prominently into notice in the year 1853, was one 

 which threatened by the alarming proportions which it assumed, 

 to ruin the silk-industry of France and even of the world. In 

 that year (1853) the quantity of silk manufactured in Prance 

 was computed at 26,000,000 kilos of cocoons, — in 1865 at only 

 4,000,000 kilos, this reduction being entirely attributable to the 

 ravages of pelrine. The amount thus lost to France and Italy 

 in thirteen years is estimated at no less than £120,000,000 

 sterling. It would be a mistake, however, to suppose that the 

 disease exerting this baneful effect was by any means a new 

 one, for M. Pasteur found that the oldest specimens which he 

 could procure from museums and elsewhere contained the germs 

 of the disease, and that animals even from Japan, in which 

 country the breed remained in a practically healthy state, were 

 likewise tainted. There can, in fact, be no doubt that the highly 

 artificial conditions of silk culture in Europe had so far debili- 

 tated the constitution of the moth as to make it an easy prey to 

 the morbific germs. The disease shows itself in the form of 

 black spots on the larva of the motli, the eggs of which do not 

 hatch out well. The larvae themselves may die off, or if not the 

 resulting moths are weak and the next generation still worse, 

 the silk of the cocoons being at the same time poor both in 

 quantity and quality. A disease affecting so important an in- 

 dustry had naturally attracted the attention of naturalists, and 

 in 1849 M. Guerin Meneville observed in the bodies of the 

 affected worms minute organisms which he described as " vibra- 

 tory corpuscles." These were also noticed and described more 

 fully by Signer Cornalia, but nothing resulted from the re- 

 searches. It was not until 1865, when M. Pasteur accepted 

 from the French Government a commission to investigate the 

 nature of the disease, that the true nature of the microbes 

 became known. He shewed conclusively that these corpuscles 

 were not only a symptom but were the actual cause of fehrine, 

 that they were parasitic organisms, and that they were commu- 

 nicated to successive generations of insects by direct contact or 



