EXPERIMENTS WITH BACILLUS TUBERCULOSLS 271 



Cobb (1905) is of the opinion that by the infection of human 

 food after feeding upon tubercular sputum flies may be an im- 

 portant factor in the dissemination of tuberculosis, and the force 

 of his remarks is not mitigated by the acrid criticisms of Mays 

 (1905). 



Lord (1904) made a careful series of experiments as a result 

 of which he reached the following conclusions : Flies may ingest 

 tubercular sputum and excrete tubercle bacilli, the vinilence of 

 which may last for at least fifteen days. The danger of human 

 infection from tubercular fly specks is by the ingestion of the 

 specks on food. Spontaneous liberation of tubercle bacilli from 

 fly specks is unlikely. If mechanically disturbed, infection of the 

 surrounding air may occur. He suggests that tubercular material 

 (sputum, pus from discharging sinuses, faecal matter from patients 

 •sN'ith intestinal tuberculosis, etc.) should be carefully protected 

 from flies lest they act as disseminators of the tubercle bacilli. 

 During the fly season greater attention should be paid to the 

 screening of rooms and hospital wards containing patients with 

 tuberculosis and laboratories where tubercular material is examined. 

 As these precautions would not eliminate fly infection by patients 

 at large, food stuffs should be protected from flies which may 

 already have ingested tubercular material. The importance of 

 these conclusions will be realised by those who are acquainted with 

 recent work on tubercular infection by way of the alimentary 

 tract. 



Graham-Smith (1910) carried out a series of experiments ^vith 

 flies artificially infected with B. tuberculosis. A large number of 

 flies freshly caught were allowed to feed upon an emulsion of 

 a culture of human tubercle bacilli in syrup. After feeding, the 

 flies were transferred to a clean cage and fed dail}- on syrup. 

 Smear preparations were made from the crop and intestinal 

 contents of these flies which were caught at intervals. Smears 

 were also made from vomit and faecal material. As a result it 

 was found that under experimental conditions the tubercle bacilli 

 were present in the crop for three days. In the intestine they 

 were found in considerable numbers up to six days and were still 

 present after twelve days and possibly longer. In the faeces they 

 were numerous up to the fifth day and occasionally found up to 



