FUNGI : EXTERNAL INFLUENCES. 177 



formation of conidia is retarded by the more refractive blue 

 and violet rays. 



A number of experiments have been undertaken to test 

 the effect of electricity on fermentation organisms. Results 

 have shown that the electric current has no influence, if care 

 is taken to prevent the heat developed by the current from 

 influencing the bacteria. Whatever significance the electric 

 current may be said to possess, such, for instance, as the 

 preservation of fermented liquids, must be ascribed to the 

 chemical effect of the current. So far as its action in regard 

 to wine is concerned, the evidence is contradictory. By the 

 treatment of water the number of germinable spores has been 

 considerably reduced. The action of ozone on water has 

 already been referred to. In the treatment of yeast in a 

 fermenting fluid, it has also been shown that the electro- 

 chemical changes brought about by the current have a fatal 

 effect on the yeast. 



It is a well-known fact that fungi are highly resistant to 

 the influence of pressure. Bacteria, for instance, are found 

 in the ocean at such a depth that they must be exposed to a 

 pressure exceeding 100 atmospheres. According to Melsens, 

 yeast cells can withstand a pressure of 8,000 atmospheres. 



Chlopin and Tamman also found that bacteria, as well as 

 yeast and moulds, could endure a pressure of as much as 

 3,000 kilos, per square centimetre. A rapid rise of pressure 

 to this point, followed by instantaneous release produced only 

 a slightly injurious effect. The fermentative activity was 

 only retarded under long-continued pressure. An attempt 

 has been made to utilise the combined action of pressure, and 

 oxygen or carbon dioxide to sterilise bacterial liquids, without, 

 however, much success. 



With regard to the influence of rest and of motion, it may 

 be observed that the organisms of fermentation thrive well 

 both in and upon quiescent substrata. Yeast also, as is well 

 known, not only withstands active motion in its culture 

 medium, but responds to it by a more active development. 

 The different species of bacteria respond in varying degrees 

 to violent shaking. Thus cholera bacilli cannot withstand 

 shaking, but no effect is produced on typhus bacilli. Buchner 



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