242 THE CARRIAGE OF TVI'HOII) FEVER BY FLIES 



county of Durham can in a large measure be causally associated. 

 These are the extremely filthy domestic arrangements, by which 

 excremental matters are retained in the immediate vicinity of 

 dwellings." The account goes on to state " The general position 

 as regards the relation between conservancy methods and enteric 

 fever may be stated thus : throughout England and Wales counties 

 persisting in the use of conservancy methods of dealing with 

 excremental matters and not having adopted the water-carriage 

 system have excessive enteric fever, in all instances in which 

 industrial conditions imply considerable aggregations of popula- 

 tion." 



One of the most important investigations on the relation of 

 flies to intestinal disease was that of Jackson (1907). He in- 

 vestigated the sanitary condition of New York Harbour and found 

 thai; in many places sewer outfalls had not been carried below 

 low-water mark, consequently solid matter from the sewers was 

 exposed on the shores, and that during the summer months on 

 and near the majority of the docks in the city a large amount of 

 human excreta was deposited. This was found to be covered with 

 flies. The report, considered as a mere catalogue, is a most severe 

 indictment against the insanitary condition of this great water 

 fi'ont. By means of spot-maps he shows that the cases of typhoid 

 are thickest near the points found to be most insanitary. He 

 shows, as English investigators have also shown, how the curves 

 of fatal cases correspond with the temperature curves and with 

 the curves of the activity and prevalence of flies which were 

 obtained bv actual counts. He also adduced bacterioloQ^ical 

 evidence, and it is stated that one fly was found to be carrying 

 over one hundred thousand faecal bacteria. 



An instructive example of the part which flies may play not 

 only in the carriage of typhoid bacilli to persons near the infected 

 matter, but also, through the medium of milk, to a larger number 

 of people, is communicated by Taylor (Colorado State Board of 

 Health, U.S.A.) to the New York Merchants' Association. He 

 says : " In the city of Denver Ave had a very sad as well as a plain 

 demonstration of the transmission of typhoid fever by flies and 

 milk. Early in August of this year the wife of a dairyman was 

 taken with typhoid fever, remaining at home about three weeks 



