ACTION OF LIGHT ON MICRO-ORGANISMS 377 



virulent in these waters, after upwards of six months' 

 exposure to diffused daylight. 



On the other hand, the degeneration of the anthrax 

 in the unsterilised Thames water was observed to be 

 distinctly more rapid in these flasks exposed to day- 

 light than in those preserved in the dark. Thus, in 

 the case of the unfiltered Thames water (daylight) the 

 special method (see page 283) of examination revealed 

 no anthrax from May 17, 1892, whilst in the same 

 water, kept both in the incubator and refrigerator, 

 anthrax was discovered by the same method on July 9, 

 1892. 



The following experiments were made to test the 

 virulence of the flasks which had been thus exposed to 

 diffused daylight : 



Animal Experiment. On October 8, 1892, 1 c.c. of 

 water from the flask ' 1 I, Thames water, unfiltered, 

 infected with anthrax on March 18, 1892, and exposed 

 to daylight since April 9, 1892,' was subcutaneously 

 injected into a white mouse. The mouse did not 

 succumb, but was alive thirty-two days after the 

 operation. 



This result was to be anticipated, seeing that the 

 corresponding flasks 3 I and 3 R, which had not been 

 exposed to daylight, also failed to kill mice. 



Animal Experiment. On October 7, 1892, 1 c c. of 

 water from the flask 6 5 I, Thames water, paper- 

 filtered, infected with anthrax on March 18, 1892, and 

 exposed to daylight since April 9, 1892,' was subcu- 

 taneously injected into a white mouse. The mouse did 

 not die, but was still alive thirty-three days after the 

 operation. 



A corresponding flask, 1 E, which had not been 

 exposed to daylight did kill a mouse, so that the viru- 

 lence had in this case been reduced by the exposure. 



