PRESIDENTIAL ADDRESS XVU 



agriculturalist the friendly bacteria are as essential as the soil or 

 the seasons. It has been asserted, I do not i\now how truly, 

 that given the choicest soil for some special crop, not a blade 

 would grow if all the factors— the earth, seed, water and air — 

 had been absolutely deprived of bacterial life. 



Certainly it has been proved that the complex process of nitri- 

 fication, the process by which nitrogen from "rv^/»/(; substances: — 

 decomposing animal and vegetable bodies, manures, itc. — is trans- 

 formed, or )ni)ii')-iilis('il, into ammonia, nitrous and nitric acids, 

 depends upon micro-organic action, and that the conversion is a 

 double one. One set of bacteria changes the ammonia into nitrous 

 acid, and a totally dittVivnt set transforms the latter into nitric, 

 which unites with soil ingredients to form nitrates. The process 

 is an oxidising one, but it is one of the fundamentals of agricul- 

 tural chemistry. 



And the daii'yman has to put up occasionally with the 

 enmity of unfriendly bacteria : the souring of his milk ; its some- 

 time bitter, tainted, or soapy taste ; its blue, red, or yellow 

 colour ; its slimy consistence, are due to the growth in the milk 

 of unusual bacteria. On the other hand, the ripening of his 

 cream, and much more importantly, the ripening of his cheese, 

 giving it the special flavour which finds acceptance in the market, 

 are but the effects of his allies, the friendly bacteria. The flavour 

 of cheese is a bacterial growth of a fermentative character giving 

 rise to decomposition, which, in the case of Limburger and some 

 others, is not very difficult to discover. 



It is true, then, that our lunch of bread, butter, cheese, and 

 beer is composed of articles whose very existence is undoubtedly 

 dependent upon or absolutely due to micro-organic life, and it is 

 at least probable that their final digestion in our economy may 

 be assisted by similar agencies. 



And to finish well our luncheon, we light the soothing 

 weed, and as drowsily we watch the lazy curling smoke, do we for 

 a moment dream that the fragraiice and the aroma are due to 

 bacterial causes ? Yet so it is; ere the tobacco leaves are fit for 

 use, they have to go through many processes, some of which, at 

 least, are fermentative. " The special quality of tobacco is in 

 part' dependent upon the peculiar type of fermentation that gives 

 rise to the flavour and the aroma of the tobacco, and as the 

 number of species of bacteria which are found upon the tobacco 

 leaves in the various stages of its preparation is quite large, it is 



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