ACTION OF LIGHT ON MICRO-ORGANISMS 



351 



the results with anthrax spores obtained by Pansini, 

 possibly the real interpretation being that they had not 

 developed on the gelatine plates when the incubation of 

 the latter was discontinued. 



One more table may be quoted, which deals with the 

 behaviour of anthrax spores when dried on cover-glasses 

 and exposed to the sun : 



Dried Anthrax Spores l 



Cover-glass kept in the dark .... 1,015 colonies 



exposed 30 minutes to light . . 396 



1 hour . . 208 



2 hours . . 48 



3 , 30 



4 , 34 



5 , 8 



6 , 3 



7 , 3 

 8. hours and more to light . 



Thus Pansini remarks that the spores of anthrax in 

 a dry state are more capable of resisting the action of 

 light than in a moist condition ; in the latter case an 

 exposure of from 30 minutes to 2 hours, as before men- 

 tioned, being found sufficient to destroy them. 



Pansini was further able to confirm the observations 

 made by Gaillard, that light acted deleteriously on the 

 production of pigment by bacteria. As regards the 

 attenuation of the virus of anthrax by the agency of 

 light, Pansini was less successful in the results he ob- 



o " 



tained than Arloing in his experiments already referred 

 to. 



As regards the effect of light on pigment-producing 

 organisms some interesting investigations made by 



1 The authors were unable to discover in what medium Pansini dried 

 the spores, whether water, broth, or gelatine, &c. This is of importance, 

 as will be seen later from the results obtained by Moment in his desic- 

 cation experiments with anthrax spores. 



