DIPHTHERIA 195 



Fliigge (Zeitschr. f. Hyg., 1894) that the diphtheria bacillus 

 perishes at that degree of dryness which is necessary to 

 permit the formation of dust. The accuracy of this state- 

 ment is a matter of considerable importance, as it practically 

 determines the extent to which the air can be regarded as 

 a means of distributing the infection. The experiments of 

 Reyes {Annali d'lgiene Sperimentale, 1895, v., 501), 

 however, contradict this statement. Working with virulent 

 agar cultures, he suspended small portions in sterilised 

 distilled water, and infected with the emulsion, cloth, silk, 

 blotting-paper, earth and sand. He exposed these in 

 various experiments, both in sunlight and in the dark, and 

 both dry and wet. In some experiments the drying was 

 conducted with sulphuric acid, and in others mere evapora- 

 tion, as would occur in practice, was employed. In one 

 case, with the object of directly examining Fliigge's conclu- 

 sion, a quantity of infected powdered mud was placed in a 

 sterile drying-stove, through which a current of air passed 

 continually, watch-glasses containing sterilised water being 

 placed at various heights in- the stove. All these glasses 

 proved to be infected with the organism, which was of full 

 virulence. The net outcome of this research is to establish 

 that the presence of moisture favours the growth of the 

 organism, although it does not immediately perish on 

 desiccation. Thus, when desiccated in the presence of 

 sulphuric acid, it may survive as long as forty-eight hours. 

 When, however, it is desiccated in the ordinary way, it will 

 remain alive in cloth, silk or paper, for several days ; in 

 sand for over two weeks ; and in powdered mud up to a 

 hundred days. The survival is still longer when these 

 media are moist, and extended in the case of sand to more 

 than 120 days. Exposure to diffused sunlight only reduces 

 the life of the organism by a few days, and temperature 

 within ordinary atmospheric Hmits exercises no appreciable 



13—2 



