BACTERIA 195 



(a) A simple experiment will, however, soon teach us that 

 they do more than merely feed on decaying matter. We take 

 two glass flasks with a little water, into which we put some animal 

 substance. Then we close both flasks with a loose wad of cotton 

 wool. The contents of one flask we leave undisturbed, but the 

 other one we boil for some time, so that the Bacteria in it may 

 be killed. The Bacteria cannot resist the temperature of boiling 

 water any more than other organisms. After a day or two we 

 shall find the contents of the unboiled flask begin to decay, that 

 in the other one remaining unaltered. But if we remove the 

 stopper from it, so that any Bacteria from the air can enter 

 into it, decay sets in here likewise. This shows that the Bacteria 

 do not only live on decaying substances, but that they are also 

 the cause of decay. In other words, there ivould be no decay on 

 the earth ivitJtout the Bacteria. 



(6) Suppose the latter were the case. Millions of corpses 

 of animals and plants would cover the earth without decaying. 

 This would result in the destruction of vegetable life, as plants 

 could not find the required food in the soil which is produced by 

 such decay. And in consequence of the destruction of vegetable 

 life also the animals could no longer exist. It is the Bacteria 

 which cause decomposition and thus are the chief cause of the 

 eternal cycle of matter in nature. 



(c) In this connection we may consider a very important 

 thing referring to agriculture. Each time the crop is removed 

 from a field, a large quantity of nitrogen, deposited chiefly in 

 the seeds, is taken away from the field together with other 

 nourishing elements of the soil. The plants are not able to 

 absorb from the air the nitrogen which they cannot do without. 

 It must, therefore, be restored somehow, and this is done by 

 manuring the field. If, however, fresh manure is used, plants 

 will not grow wel), and often die. The albuminoids contained 

 in fresh manure must be rendered soluble in order to be of 

 use to plants. This is done by the Bacteria in the soil by 

 decomposing them. Manure is thus, by the agency of Bacteria, 

 transformed into such a state that it can be used by the plants as 

 nourishment. 



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