PARASITIC FDKGI AND MOULDS. 51 



into chrysalides are only thrown away when they are 

 found on removing the cocoons. The clouds of dust 

 dispersed by the silkworms perpetuate the disease 

 in the best-ordered factories. When the heather is 

 thrown out of window, and the rooms are swept to 

 get rid of the dust, the spores float in the air and 

 are dispersed by the wind. 



Damp favours the development of the fungus, and 

 the introduction of healthy silkworms into an infected 

 breeding-house will not extirpate the disease. In order 

 to attain this object, it is necessary to get rid of all 

 the dead silkworms before the development of the 

 spores, and to destroy their bodies by burning them 

 with the heather, or with quicklime. The breeding- 

 houses should then be completely emptied, and the 

 compartments should be purified and disinfected in 

 the ordinary way by fumigation with sulphur, and 

 washed with chlorine water, before fresh sUkworms are 

 placed in them, 



IX. Parasitic Fungi of the Skin and Mucous 

 Membrane of Men and Animals. 



The skin-diseases of man and animals which are 

 termed tinea are caused by the presence of parasitic 

 fungi, just as the itch is produced by the presence 

 of animals belonging to the group Acarii^. These 

 diseases are rendered eminently contagious by the 

 dissemination of the spores of these fungi, which will 



