The Kinds of Work That Are Done by Plants 103 



belief is far from the truth, for what happens is this. The Bac- 

 teria, in order to obtain energy and material for their own pro- 

 cesses, act on the tissues or the blood in just the same way that 

 Yeast acts on the sugar, likewise forming incidentally in the act 

 various accessory substances. Now some of these substances, 

 bearing much the same relation to the Bacteria that alcohol 

 does to the Yeast, are those alkaloids or ptomaines which happen 

 to be violently poisonous to man, and it is these poisons, and not 

 the Bacteria directly, which are the cause of his death. At least 

 they are the cause of his death if they are formed more rapidly 

 than his system can antagonize them, for the body has a wonder- 

 ful power of forming antagonistic chemical substances, or anti- 

 bodies, which neutralize these poisons, — which antibodies, by the 

 WSLY, can be made to form in the body, or even can be injected 

 as antitoxins, ensuring immunity against some diseases. These 

 deadly diseases are therefore an incidental result of the respiration 

 and growth of Bacteria which are leading their own Uves in their 

 own way, as oblivious to any harm they may do as is the Yeast 

 to the benefit it confers. 



It is riot only true that fermentation, decay, and some disease, 

 are caused by the activity of Yeasts, Molds, and Bacteria, but 

 the converse is equally well-known, — that those processes occur 

 through no other agency and can be prevented entirely by killing 

 these organisms. This can be done by heat, poisons, certain 

 strong solutions, or even, in some cases, bright light; and such is 

 the basis of the various sterilizing and antiseptic processes so 

 familiar in the household, the arts, and in medicine. 



We can now express these later facts in another of our verities 

 as follows; — all fermentation and decay, and some phases of dis- 

 ease, are forms of the respiration of simple organisms which thereby 

 destroy organic matter by reduction back to the carbon dioxide, water, 

 and other elements, from which it was originally built up. 



It is thus evident that all of the carbon dioxide and water 

 built into plant substance by photosynthesis, are ultimately re- 



