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 carried from place to place, from creature to creature, and from person to person, through the intervention or agency of the house-fly. The medical profession are convinced that infantile mortality from epidemic diarrhœa must be attributable to summer flies. In the matter of food which becomes fly-infected after having been cooked, or of food like milk, butter, and fruit, which are consumed raw, it should be known that a single pathogenic germ of ultra-microscopic dimensions, having obtained lodgment in the body, may there multiply and originate a fatal disease. On the other hand, raw meat which has been infected may, after the bacteria have been all killed by cooking, contain excreted poison in deleterious quantity. The decomposition of infected meat begins ten or twelve hours before the bad odour is perceptible. Fortunately the omnipresent germs which most commonly deteriorate our food are not very actively deleterious, or are only slightly debilitating; yet wherever such less obnoxious germs get lodgment, there the ready prepared and most favourable breeding place for the worser kind is to be found. The various species of these evil things are not always exterminating competitors; they sometimes flourish in company, and dwell together, like the seven devils within the exorcised and sane man after his relapse, as mentioned in the Scripture. That food gets fly-blown and maggot-infected is a very disgusting fact, but the plainly visible result is of little hygienic significance apart from the more concealed facts of the fly-borne conveyance of zymotic diseases.