142 Silkworms in India. [Vol. I. 



" With regard to diseases, however, Pasteur, after studying the subject very 

 carefully, concluded that all may be considered as varieties of four principal diseases, 

 viz. muscardine, pebrine, jlacherie, and grasserie. 



" These diseases are found to some extent intercurrent, though at times one (at 

 least one of the first three) has been more prevalent than the others, generally 

 amounting to a plague. So in 1849 we find lions. Gue'rin Meneville studying, on 

 the part of the French Academy, the then prevalent disease, the muscardine. This 

 was soon followed, in the fifties, by a veritable scourge in which the pebrine was the 

 leading feature, with flaccidity (Jlacherie) quite frequently found. The same learned 

 body appointed Pasteur to study the causes of these diseases, and after two years 

 of patient research, he devised a means, which will hereafter be described, of success- 

 fully preventing the return of the pebrine. This made way for flaccidity, which, 

 although it does not reach the importance of a plague, its effects are distinctly 

 visible upon the national crops of cocoons iu France and Italy, and I have never 

 known it to be absent from worms reared by me almost every year for nearly two 

 decades in this country (America). The grasserie has never attained any such 

 importance, but occurs in rare instances only. 



" Muscardine. — The first of these, muscardine, has been more or less destructive 

 in Europe for many years. It is of precisely the same nature as the fungus- 

 (JSmpusa muscce), which so frequently kills the common house fty, and which 

 sheds a halo of spores, readily seen upon the window pane, around its victim. 

 A worm about to die of this disease becomes languid, and the pulsations of the 

 dorsal vessel or heart become insensible. It suddenly dies and in a few hours 

 becomes stiff, rigid, and discoloured ; and finally, in about a day, a white powder or 

 efflorescence manifests itself, and soon covers the body, developing most rapidly in 

 a warm, humid atmosphere. No outward signs indicate the first stage of the disease, 

 and though it attacks worms of all ages, it is by far the most fatal in the fifth, or 

 last, age or stage, just before the transformation. 



"This disease was proved by Bassi to be due to the development of a fungus 

 [Botrytis bassiana) in the body of the worm. It is certainly infectious, the spores, 

 when they come in contact with the body of the worm, germinating and sending 

 forth filaments which penetrate the skin, and upon reaching the internal parts, give 

 off minute floating corpuscles, which eventually spore in the efflorescent manner 

 described. 



"It appears very clear that no remedies are known ; but that care in procuring 

 good eggs, care in rearing the worms, good leaves, pure, even-temperatured atmo. 

 sphere, and cleanliness, are checks to the disease. 



"As the sole means of disseminating the disease are the spores, which only appear 

 several hours after the death of the worm, the most rational means of preventing 

 the spread of muscardine is by carefully taking from the tables all dead worms as 

 soon as they are discovered ; and if the disease seems to have gained a foothold iu 

 the magnanerie, it will be well to remove the litter oftener, and give the worms 

 more space. The spores retain their power of communicating disease for at least 

 three years ; hence the importance of cleansing and fumigating. 



"Pebrine. — The disease pebrine shows itself outwardly by the dwindling away 

 of the worms and their inequality of size. Eating little, they do not grow as large 

 as when in their normal state. At tho end of a few days black spots frequently 

 make their appearance on the skin, resembling punctures or burns ; the anal horn, 

 the prolegs, the soft parts between the rings, are especially subject to these spots. 

 These spots disappear with the shedding of the skin at each molt only to reappear 

 again within a few days. In addition to these symptoms it is noticed that the 



