168 PASTEUR AND HYDROPHOBIA III 



note at p. 113. But in other cases the toxin and 

 the vaccin seem almost certainly to be distinct. From 

 what we know of the complexity of the chemical 

 changes and the variety of substances produced 

 by Bacteria and other schizophyta in fermentations 

 set up by them elsewhere than in a living animal's 

 body, it would not be surprising if eventually we 

 should be able to discover and isolate in the case of 

 each kind of pathogenic microbe several toxins and 

 several vaccins. The great object of this line of 

 research in the future will be to obtain by artificial 

 culture of the microbe, and subsequent treatment of 

 the products of its life, the vaccin of each infective 

 disease in its chemically pure condition, free from 

 admixture with any of the toxin, and free from the 

 microbe itself. We have to subdue and utilise these 

 ultra -minute organisms, and to make them render 

 service to man, as we have done with larger and even 

 more deadly enemies. Already we employ a microbe 

 to prepare our drink and to lighten our bread, and 

 another to produce our vinegar, and a third to flavour 

 our cheese. We shall hereafter be able to breed these 

 dainty cattle and select strains suitable for our uses, 

 making the domesticated protect us from the un- 

 trained kinds, even as the dog guards us from the 

 wolf. 



We now know from M. Pasteur himself what he 

 had not explained in 1886, viz. that he has been 

 guided in his work on preventive inoculations, and 

 especially in that on hydrophobia, by the theory that 

 the toxin and the vaccin are two distinct soluble 



