60 THE BOOK OF THE FLY 



cleaning. Wherever it alights and walks, it prospects 

 with a touch of its trunk, which is the main instrument 

 of evil. It has a very filthy habit, from time to time, of 

 depositing pale vomit spots as well as dark-coloured 

 frccal droppings. These defilements are visible, 

 wherever it may alight on walls, windows, ceilings, 

 and especially on pendent ornaments, whereon the 

 males delight to rest. 



Its manner of feeding upon solid food is to pour 

 forth a copious supply of saliva, to regurgitate some 

 previously imbibed fluid draught, and then to re- 

 imbibe ; thus, besides devouring soft food, it dissolves, 

 befouls, and feeds on crystalline sugar and other hard 

 dry food materials. 



Its regurgitated fluid commonly swarms with bacteria, 

 microbes, and the like. Imbibed bacteria are not 

 inevitably killed in the digestive process of the fly, for 

 its excrement has been found to abound with well 

 recognisable infective germs. In the market, the shop, 

 the larder, and on our tables, the house-fly seeks every 

 opportunity of befouling and contaminating human 

 food. 



The varieties of micro-organisms are multitudinous, 

 doubtless many more in number than the microscopist 

 and the bacteriologist expert have yet isolated and 

 registered as capable of identification. Granted that 

 the majority of these are non-pathogenic to humanity, 

 still a formidable number, including some which are 

 very generally disseminated, are virulently pathogenic, 

 and many are suspect. There is no need to give a list \ 

 of all the infectious diseases which man and beast are ( 

 liable to contract, but the germs of nearly all may be J 



