GENERAL FUNCTIONS OF MICROBES 23 



The bacteroi'dia scattered through the soil are attracted 

 towards the young roots by the vegetable carbohydrates : there 

 is a positive chemiotaxis. 



The bacteroi'dia and the plant are mutually beneficial. 

 The plant supplies carbohydrate food to the bacteroi'dia, which 

 n their turn supply the plant with nitrogen. In culture a 

 viscous glairy jelly appears, which is present also in the 

 nodules, but only in their early stage. The sap rapidly carries 

 it into the body of the plant, and it is this jelly probably which 

 contains the nitrogenous food product. Some diastase 

 probably of the root liberates the nitrogen compound from the 

 cells of the bacteroi'dia. 



Nitrogenous manures are expensive, and hence the idea 

 has arisen to improve leguminous crops by planting them in 

 prepared soil, or by adding soil which has already grown 

 leguminous plants. Afterwards the attempt was made to 

 inoculate the soil with artificial cultures of the nodule 

 bacteria. The process is analogous to the injection into an 

 animal of a food substance or a drug: it is agricultural 

 bacteriotherapy . 



In observing nature, not from the point of view of any 

 single living species, man or animal, but throughout the whole 

 of her operations, one sees that the pathogenic bacteria are 

 less prominent than the useful ones one may say even that 

 all bacteria are useful and are only injurious by accident. 

 They all have their role in the cycle of matter and only destroy 

 one existence to prepare for another. 



To perceive the function of the useful bacteria, it has been 

 necessary to study all the fermentations in relation to both 

 industry and food supply : wine, beer, cider, vinegar, cheese, 

 bread, sauer-kraut, tobacco, and the leather of our shoes are 

 all more or less the result of bacterial operations. Life as a 

 whole could not continue without bacteria ; they do not create 

 life, but they supply it with the necessary material. 



We may ask ourselves now if, with nature thus provided 

 with nutritive material, the life of a particular organism might 

 be possible although it did not contain microbes in itself. 



