50 MUSCARDINE OF SILK-WORMS. 



54. A very curious example of the growth of Fungi within 

 the living animal body has lately been detected ; and the know- 

 ledge of it has proved of great importance. The Silk-worm 

 breeders of Italy and the South of France, especially in particular 

 districts, have been subject to a considerable loss, by a disease 

 termed Muscardine, which sometimes attacks the worms in large 

 numbers, just when about to enter the chrysalis state. This 

 disease has been ascertained to be due to the growth of a minute 

 vegetable of the Fungus tribe, nearly resembling the common 

 mould, within their bodies. It is capable of being communicated 

 to any individual from one already affected, by the introduction 

 beneath the skin of the former, of some particles from the diseased 

 portion of the latter; and it then spreads in the fatty mass 

 beneath the skin, occasioning the destruction of this tissue, which 

 is very important as a reservoir of nourishment to the animal, 

 when about to pass into a state of complete inactivity. The 

 plant spreads by the extension of its own structure; and also by 

 the production of minute germs, which are taken up by the 

 circulating blood, and carried to distant parts of the body. The 

 disease invariably occasions the death of the Silk- worm ; but it 

 does not show itself externally until afterwards, when it rapidly 

 shoots forth from beneath the skin. The Caterpillar, Chrysalis, 

 and Moth are all susceptible of having the disease communicated 

 to them, by the kind of inoculation just described; but it is 

 only the first which usually receives it spontaneously. The 

 importance of this disease to the breeders of silk- worms, led, as 

 soon as its true nature was understood, to careful inquiry into 

 the circumstances which favour the production of the fungus ; 

 and it has been shown that, if the bodies of the caterpillars, 

 which (from various causes) have died during breeding, be 

 thrown together in heaps, and exposed to the influence of a 

 warm and moist atmosphere for a few days (as has been very 

 commonly the case), this fungus almost invariably appears upon 

 them, just as other kinds of mould appear on other decaying 

 substances ; and that it is then propagated to the living worms, 

 by the diffusion of its germs through the atmosphere. The 

 knowledge of this fact, and the precautions taken in consequence, 

 have greatly diminished the mortality. 



