95 



several hours, only the contents from the deeper portions of 

 the tumours being used. 



For the purposes of the experiments both Musca domestica 

 and Stomoxys calcitrans were bred artificially and the cultures 

 kept going in the laboratory. 



The culture of Stomoxys calcitrans was kept going for 

 twelve months, when it was allowed to die out. The flies 

 maintained their vigour and size throughout this period. 

 They were fed daily on a rabbit, and were allowed to deposit 

 their eggs on fermenting lawn clippings taken from a lawn 

 where contamination by horse-dung was excluded. 



Musca domestica was fed on a mixture of horse serum, 

 sugar, and water, and was allowed to deposit its eggs on 

 sterilized horse-dung. It was found most convenient to use 

 these artificial cultures of the flies, for in this way experiments 

 could be made during that time of the year when specimens 

 are difficult to obtain in the field, and also, the number of fly 

 larvae developing in a given culture could be more easily 

 regulated. As in most of the experiments an attempt was 

 made to obtain flies heavily infested with larvae, it was 

 important to regulate the number of fly larvae developing 

 in a culture. 



The stomachs were sometimes examined a few hours after 

 removal, but for the most part not until twenty-four hours, 

 and sometimes as long as forty-eight hours, after removal. 

 The worms were always found to be alive and active, although 

 in those collected from stomachs examined from twenty-four 

 to forty-eight hours after removal, activity had considerably 

 decreased. This loss of activity was an advantage when 

 specimens had to be examined microscopically. Only on one 

 or two occasions was a stomach found in which no worms could 

 be detected. A complete examination for the presence of all 

 possible, species was not made, but a rough idea was usually 

 obtained of the number of species present. Only in one case 

 was Hahronema microstoma found to be present in very large 

 numbers without any other species. It was found to be more 

 commonly present than was at first expected, and in most of 

 the stomachs examined could be found, although often only 

 very few specimens were present. Hahronema muscae was 

 found to be present in most of the stomachs examined, and 

 usually in large numbers. This worm was found to be more 

 closely associated with the mucous membrane than Hahronema 

 microstoma, and quite commonly the head of the parasite was 

 buried in the gastric glands. This parasite is usually orange- 

 coloured, and sometimes more red, suggesting the presence of 

 blood in the body of the worm. Chemical tests for blood were 

 obtained with extracts from these worms. 



