STRUCTUEE, DEVELOPMENT, AND BIONOMICS OF HODSE-ELY. 393 
legs and bodies of flies which had been allowed to have access 
to infected material. Hamilton (1903) I’ecovered Bacillus 
ty phosu s five times in eighteen experiments from flies caught 
in two undrained privies, on the fences of two yards, on the 
walls of two houses and in the room of an enteric fever 
patient. A series of careful experiments were made by 
Sellars^ in connection with Niven’s investigations on the 
relation of flies to infantile diarrhoea. Out of thirty-one 
batches of house-flies carefully collected in sterilised traps in 
several thickly populated districts in Manchester he found, 
as a result of cultural and inoculatory experiments, that 
bacteria having microscopical and cultural characters resem- 
bling those of the Bacillus coli group were present in four 
instances, but they did not belong to the same kind or 
variety. Buchanan (1907) was unable to recover the bacilli 
from flies taken from the enteric ward of the Glasgow Fever 
Hospital. Flies were allowed to walk over a film of typhoid 
stool and then transferred to the medium (Griinbaum and 
Hume’s modification of MacConkey’s medium), and subse- 
quently allowed to walk over a second and a third film of 
medium. Few typhoid bacilli were recovered and none from 
the second and third films. Sangree (1899) performed 
somewhat similar experiments to those of Buchanan and re- 
covered various bacilli in the tracks of the flies. This method 
of transferring the flies immediately from the infected material 
to the culture plate is not vej-y satisfactory, as I have already 
pointed out (1908), as it would be necessary for the flies to 
be very peculiarly constructed not to carry the bacilli. The 
fly should be allowed some freedom before it has access to the 
medium to simulate natural conditions. Experiments of this 
kind were carried out in the summer of 1907 by Hr. M. B. 
Arnold (superintendent of the Manchester Fever Hospital) 
and mysell. Flies were allowed to walk over a film of 
typhoid stool and then were transferred to a wire cage, where 
they remained for twenty-four hours Avith the opportunity 
’ Recorded in the ‘ Report on the Health of the City of Manchester, 
1906,’ by James Niven, jjp. 86-96. 
