124 INSECTS AND MAN 



incredible ; that one house fly can carry about its body as 

 many as five hundred million germs is almost beyond 

 belief, yet the estimated number is not the result of guess- 

 work but of careful experiment. Looking at the matter 

 from the most favourable point of view, and supposing each 

 fly to carry only five hundred and fifty bacteria from place 

 to place, the supposition is not pleasant. A goodly number 

 of these bacteria would assuredly be pathogenic, or disease- 

 producing, and a fly, laden with only fifty typhoid germs, 

 and making an attempt on its life in a jug of milk, is an 

 obvious source of danger, for these germs increase with 

 surprising rapidity in such a favourable medium as milk. 

 Speaking of the house fly, or, as it is called in America, 

 the typhoid fly, Howard says : " And as for the typhoid fly, 

 that a creature born in indescribable filth and absolutely 

 swarming with disease germs should practically be invited 

 to multiply unchecked, even in great centres of population, 

 is surely nothing less than criminal." 



" Moore (1853) drew attention to the necessity of guard- 

 ing food against flies, because, he supposed, they might 

 disseminate cholera, adding: 'Flies in the East have not 

 far to pass from diseased evacuations or from articles 

 stained with such excreta, to food, cooked and uncooked.' 

 Nicholas (1873) writes that in 1849, when cholera prevailed 

 at Malta: 'My first impression of the possibility of the 

 transfer of the disease by flies was derived from the 

 observation of the manner in which these voracious 

 creatures, present in great numbers, and having equal access 

 to the dejections and food of the patients, gorged them- 

 selves indiscriminately and then disgorged themselves on 

 the food and drinking utensils. In 1850 the Superb, in 

 common with the rest of the Mediterranean squadron, was 

 at sea for nearly six months ; during the greater part of 

 the time she had cholera on board. On putting to sea the 

 flies were in great force ; but after a time the flies gradually 

 disappeared, and the epidemic slowly subsided. On going 



