370 MICRO-ORGANISMS IN WATER 



to sunlight; on incubation the spores germinated uni- 

 formly throughout the dish. This shows, on the one 

 hand, that the dry spores are acted upon by light in 

 the absence of food materials, and on the other that the 

 particular degree of insolation to which the agar -agar 

 was subjected did not appreciably diminish its nutritive 

 value as regards the germination of anthrax spores. 

 The results are, therefore, confirmatory of those origin- 

 ally obtained by Downes and Blunt with casual mixtures 

 of bacteria. 



The Action op Light upon Micro-oeganisms in 

 Water 



So far we have been considering the action of light 

 upon various micro-organisms when present in different 

 culture media, such as broth, gelatine, agar-agar, and 

 potatoes ; but we must now survey what has been done 

 in ascertaining the behaviour of micro-organisms during 

 insolation in various waters. The literature on this 

 branch of the subject is exceedingly meagre. Straus, 

 in the paper already referred to, states that anthrax 

 spores are able to resist the effect of insolation in dis- 

 tilled water over a long period. 



Arloing,^ in carrying out investigations to meet the 

 criticisms of Straus, made the following experiments 

 with anthrax spores in water. Flasks containing sterile 

 distilled water were inoculated with spores ; two were 

 kept in the dark, whilst the remainder were exposed 

 to the action of the sun in February. After varying 

 lengths of time the flasks were withdrawn, and nutritive 

 bouillon added to the water, after which they were 

 placed in the incubator and kept at 35° C. Last of aU 

 broth was added to the flasks kept in the dark, and 



^ ' Les Spores du B. Anthracis sont reellement tudes par la Lumi^re 

 solaire,' Comptes rendus, vol. civ., 1887, p. 701. 



