SUNSHINE AND LIFE 85 



properties, requiring, however, upwards of ten 

 weeks to become entirely harmless ; if, on the 

 other hand, they be exposed to sunshine, they 

 are completely deprived of their toxic character 

 in from fifteen to eighteen hours. Again, as little 

 as five hours' sunshine is sufficient to greatly 

 modify the toxic action of diphtheria cultures. 

 It is of interest also to note that even the venom 

 of the rattlesnake, that most potent of all poisons, 

 cannot emerge unscathed from an exposure to 

 sunshine maintained during a fortnight. 



Interesting as all these isolated observations 

 are, they indicate what an immense amount yet 

 remains to be done before we can hope to have 

 any connected conception of the mechanism, so 

 to speak, of insolation. At present there is too 

 large an allowance, which we are compelled to 

 make, for the unknowp to permit of our ade- 

 quately manipulating this marvellous agency in 

 relation to bacteriological problems. But who 

 shall say what part has been, and is being still, 

 played by sunshine in determining the individual 

 character of microbes, operating as it has done 

 from time immemorial upon countless generations 

 of these minute germs of life ? 



The problem of insolation has been attacked 

 from an entirely novel point of view by Dr. 

 Masella, who has endeavoured to find out whether 



