But sunshine not only controls in this wonderful manner the action of the living bacillus, but it also operates upon the products elaborated by disease organisms. Thus the microbe producing lock-jaw or tetanus may be grown in broth, and the latter may be subsequently passed through a porcelain or a Berkefeld filter, so that the resulting liquid is entirely deprived of all germ life. This tetanus-filtrate, as it is called, is endowed with very powerful toxic properties, and it will retain its lethal action even when kept for upwards of three hundred days, providing it is screened from all light; but place such filtrates in diffused light, and they lose their poisonous 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 unknown to permit of our adequately 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 sunshine plays any part in the predisposition of animal life to infection.