SUNSHINE AND LIFE 73 



have on the bactericidal potency of the sun's 

 rays, for the remarkable fact was established that 

 when immersed in water anthrax spores are far 

 less prejudicially affected by sunlight than when 

 exposed in ordinary culture materials such as 

 broth or gelatine. Thus it was only after one 

 hundred and fifty-one hours' insolation in Thames 

 water that these spores were entirely destroyed, 

 whilst a few hours' exposure in the usual culture 

 media is generally sufficient for their annihilation. 

 In water not subjected to insolation anthrax spores 

 were found to retain their vitality for several 

 months. 



In case the reader should be tempted to com- 

 pare these results with those obtained by Buchner, 

 it must be borne in mind that whereas those ex- 

 periments were made with bacilli, these were 

 directed to determine the behaviour of spores in 

 water, which are some of the hardiest forms of 

 living matter with which we are acquainted. 

 This alone would sufficiently explain the results 

 obtained, whilst each variety of microbe may be, 

 and doubtless is, differently affected during in- 

 solation. 



We know now that a remarkable improvement 

 takes place in the bacterial condition of water 

 during its prolonged storage in reservoirs, and 

 although, no doubt, the processes of sedimenta- 



