16 THE IMPORTANCE OF DOMESTIC FLIES 



of typhoid fever by house-flies. In 1902, after the 

 lesson of the South African War, Firth and Horrocks, 

 of the Royal Army Medical Corps, kept some blue- 

 bottles and some house-flies in a large box measuring 

 4 ft. by 3 ft. by 3 ft. ; it was fitted with a glass side. The 

 flies had been fed on material contaminated with the 

 typhoid bacillus. Some culture-jellies were left ex- 

 posed in the box, and after a few days the bacilli 

 were found growing on the culture media. This 

 experiment was repeated, and the typhoid germs were 

 grown from the legs, wings, and bodies of the flies. 

 Hamilton, at Chicago, in 1903, caught eighteen flies 

 in and about rooms occupied by typhoid cases, and 

 states that she found the Bacillus typhosus in five of 

 them. Ficker, in 1903, caught flies in a house at 

 Leipsig, where eight cases of typhoid had occurred; 

 he isolated the germ from them. Dr. Graham Smith 

 describes some experiments carried out by Ficker. He 

 kept the flies in 10-litre flasks into which he had 

 introduced some sugar, strips of blotting-paper, and 

 some typhoid bacilli grown on broth. The broth was 

 spread on the glass of the flasks, and partly absorbed by 

 the blotting-paper. After eighteen to twenty-four hours 

 the flies were transferred to clean flasks. He found the 

 flies to survive over four weeks in captivity if protected 

 from the cold and fed on sugar, bread-and- water, or milk. 

 The flies were moved into clean flasks every two or three 

 days. They were at last killed with ether and crushed, 

 and their remains transferred to gelatine, on which the 

 typhoid bacillus was found growing twenty-three days 

 after the flies had been exposed to infection. Dr. 

 Graham Smith concludes that " the evidence regarding 

 the part that flies may play in the spread of typhoid 

 fever may therefore be accepted as quite conclusive." 



