THE HOUSE-FLY 13 



THE RELATION OF THE HOUSE-FLY TO DISEASE 



Notes of suspicion have been sounded against the house- 

 fly by far-seeing physicians for many years, but nothing 

 definite was proven against this insect until comparatively 

 recent times. It has now been definitely proven that 

 house-flies can and do carry, both externally and inter- 

 nally, certain disease producing germs. For example, 

 it has been shown by several observers that the bacilli 

 of typhoid fever may be carried on the feet, legs, bodies, 

 and in the alimentary canals of flies. Moreover, the bacilli 

 pass through the alimentary tract and are voided in the 

 "specks" in a virulent condition. The typhoid bacillus 

 has been recovered from flies caught in undrained privies. 



The bacillus of cholera has also been found in great 

 numbers on the bodies of flies and has been found in fly 

 "specks" within 17 hours after the insects have been 

 fed upon cholera infected material and the bacilli have 

 persisted in the "specks" for several days. Moreover, 

 flies infested with these germs have been shown to carry 

 them to milk. 



It is also held that the house-fly may carry the tuber- 

 culosis bacillus and deposit it on food. Several experi- 

 menters have found the bacillus in the intestines and ex- 

 crement of flies that have been fed on the sputum of 

 tuberculous patients. There is evidently grave danger 

 of infection through the agency of house-flies. Every one 

 has noted the avidity with which flies seem to feed on 

 expectorated saliva. 



House-flies are charged with the conveyance and dis- 

 tribution of the germs of infantile diarrheal diseases. 

 Jackson showed that the mortality of bottle-fed infants 



