THE TYPHOID FLY, OR HOUSE FLY. 27 



has just been stated indicates that even under city conditions the 

 influence of this fly in the spread of this disease has been greatly 

 underestimated. It is not claimed that under city conditions the 

 house fly becomes by this argument a prime factor in the transfer 

 of the disease, but it must obviously take a much higher relative 

 rank among typhoid conveyers than it has hitherto assumed. Per- 

 haps even under city conditions it must assume third rank — next to 

 water and milk. 



It is not alone as a carrier of typhoid that this fly is to be feared. 

 In the same way it may carry nearly all the intestinal diseases. It 

 is a prime agent in the spreading of summer dysentery, and in this 

 way is unquestionably responsible for the death of many children 

 in summer. One of the earliest accurate scientific studies of the 

 agency of insects in the transfer of human disease was in regard to 

 flies as spreaders of cholera. The belief in this agency long pre- 

 ceded its actual proof. Dr. G. E. Nicholas, in the London Lancet, 

 Volume II, 18T3, page 724, is quoted by Nuttall as writing as follows 

 regarding the cholera prevailing at Malta in 1849 : '' My first im- 

 pression of the i^ossibility of the transfer of the disease by flies was 

 derived from the observation of the manner in which these voracious 

 creatures, jDresent in great numbers, and having equal access to the 

 dejections and food of patients, gorged themselves indiscriminately 

 and then disgorged themselves on the food and drinking utensils. 

 In 1850 the Su'perh, 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 into Malta Harbor, 

 but without communicating with the shore, the flies returned in 

 greater force, and the cholera also with increased violence. After 

 more cruising at sea, the flies disappeared gradually with the subsi- 

 dence of the disease." 



Accurate scientific bacteriological observations by Tizzoni and 

 Cattani in 1886 showed definitely active cholera organisms in the 

 dejecta of flies caught in the cholera wards in Bologna, Italy. These 

 observations w^ere subsequently verified and extended by Simonds, 

 Offelmann, Macrae, and others. 



With tropical dysentery and other enteric diseases practically the 

 same conditions exist. In a report by Daniel D. Jackson to the 

 committee on pollution, of the Merchants' Association in New York, 

 published in December, 1907, the results of numerous observations 

 upon the relation of flies to intestinal diseases are published, and the 

 relation of deaths from intestinal diseases in New York City to the 



