Silkworm Disease. 71 



ever, was intelligible to the sericulturist. In consequence of sea- 

 fogs, when the air is laden with moisture, the rearing of silk- 

 worms is not attempted near the sea. I have seen the rearing 

 of silkworms recommended as an Irish industry, as the soil and 

 climate would suit the mulberry-tree ; the fact that the humidity 

 of the climate would be prejudicial to the silkworm had been 

 overlooked. But the disease which persistently and universally 

 attacked the reariugs year after year, which baffled all treat- 

 ment, and which promised nothing but ruin, was apparently 

 beyond discovery as to its nature until Pasteur undertook the 

 enquiry. When first requested to do so he hesitated, not only 

 having other important investigations under weigh, but, as he 

 himself expressed it, " I know nothing about silkworms ; I do 

 not think I have ever even seen one." The rejoinder to this 

 was, " So much the better; you will enter into the investigation 

 with an open mind." An " open mind," by the way, seems to 

 be very much in vogue at the present day with certain people, 

 and on all sorts of subjects too. However, M. Pasteur com- 

 menced the investigation of the disease, and I will endeavour to 

 place before you as shortly as I can the results he obtained. 



When one speaks of the disease, one refers to Pebrine, about 

 to be described, and when one speaks of silkworms, one refers to 

 the larvae of hoinbyx mori ; Pebrine being the most important 

 disease as Bombyx wori is the silk-producer j)«/' excellence. 



Our English peasant or labourer keeps a pig or a few fowls to 

 eke out his income, but in South France peasants and others 

 rear silkworms instead, investing their money in rearing-houses 

 and appliances, and in growing mulberry-trees. 



In years before Pebrine — or the pepper disease, one of its 

 symptoms being the appearance of small black spots resembling 

 pepper scattered over the worms, — before, I say, this disease 

 became such a scourge, each rearer of silkworms retained, at the 

 end of the season, some of the finest cocoons he had reared for 

 the purpose of continuing the breed. He thus sacrificed a 

 certain amount of silk to ensure eggs from healthy parents ; for 

 the silk of cocoons devoted to this purpose was not wound off, 

 and the moth freed itself in the natural way by making a hole in 

 the cocoon from which it emerged. Each rearer therefore pro- 

 vided himself with seed from year to year from moths he had 

 himself reared, and of whose health he had been assured. Had 

 this course but continued, little probably would have been heard 

 of Pebrine, except as quite a casual disease. 



But some ingenious individual conceived the idea of rearing 

 silkworms, not for the silk they produced, but solely for the eggs 

 which the moths would produce. Thus was started a trade 

 which supplied eggs in almost any quantity, and so cheaply that 

 the individual peasant no longer sacrificed any of his cocoons to 



