$ xiv.] Diseases in lower animals. 175 



according to Pasteur, by a Bacillus and by a chain-forming 

 Micrococcus, M. Bombycis, Cohn, which resembles M. Ureae 

 (see page 84) ; these organisms are introduced with the food, and 

 by decomposing it in the intestinal canal give rise first of all to 

 derangement of the digestion, and then to the death of the insect, 

 which first becomes inert, without appetite, and flabby, and soon 

 succumbs to the disease. Its dead body is soft and soon turns 

 a dark and dirty brown, putrefactive Bacteria make their ap- 

 pearance in it and it dissolves for the most part into discoloured 

 stinking matter. 



A number of other contagious and epidemic diseases in cater- 

 pillars of Lepidoptera have been recently referred by S. A. Forbes 

 to the attacks of certain forms of Micrococcus and Bacillus. 



There are two diseases among silkworms very distinct from 

 the flacherie, which is the prevalent one at the present time, 

 namely, muscardine or calcino, and the spotted disease or 

 pe'brine. Muscardine, known since the last century, was very 

 destructive to the silkworm-culture in Europe during the first 

 years of the present century, but is said to have almost entirely 

 disappeared since 1855, while it continues to be of frequent 

 occurrence among the caterpillars living in the wild state. It is 

 caused, as has been fully shown, by a Fungus, and does not 

 therefore belong to our present subject. 



Pebrine (gattine, petechia, maladie des corpuscules) has been 

 a known form of disease for some hundreds of years, and com- 

 mitted great ravages in Europe between 1850 and 1875. It 

 received the name of spotted disease from the dark spots on 

 the skin which make their appearance in the insect as it becomes 

 dull and inert, and which are caused by the presence of a micro- 

 scopic parasite, Panhistophyton ovatum, Lebert, Nosema Bom- 

 bycis, Nageli. The parasite is known under the form of small 

 colourless, highly refringent bodies of irregularly ellipsoid 

 shape, and not more than 0-4 /z in length, once termed the Cor- 

 nalian bodies, which appear in our preparations either singly, 

 or in pairs, or several connected together, and occur in all organs 



