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 for this purpose between a living and a dead microbe of the same kind so that the vaccines which roused her to her protective efforts were composed of dead microbes which could do no harm. We had proved the efficacy of this treatment in peace time by our experiences in India and elsewhere but its employment in this War put it to a still severer test, and that it was successful is shewn by the fact that typhoid has played but a subordinate part in the losses by disease instead of being the formidable item that one might have anticipated.

Equally brilliant has been the success of the other method, in which we directly assist Nature in her provision of an adequate quantity of the antidote to the poison which the special microbe generates and by which it kills. To do this we have to use Nature's own methods of production of the antidote. Its preparation defies our chemical skill. But we can get her to manufacture it for us by injecting the poison into the blood of some other animal under conditions which make her specially bountiful in 53