SELECTED PAPERS 



connexion be considered as an euphemism; in many respects it would 

 be better to indicate the situation by saying that the germs are lying 

 in wait. For often it are merely slight changes in environmental condi- 

 tions that suffice to rouse this dormant life to abundant activity which 

 leads to a rapid multiplication of the living units. Usually this process 

 is associated with changes in the life-inducing substrate so profound 

 that these cannot escape being observed even by the layman. I need 

 but remind you of the cases of food spoilage known to all of you from 

 domestic experience. And that the substance of the chairman's gavel 

 is no less exposed to potential menace is something of which every one 

 can immediately be convinced by paying a visit to the lofts of the 

 'Trippenhuis' where it will be noted how drastically the solid wooden 

 rafters of Justus Vingboons creation have fallen prey to the activities 

 of microbial life.* 



Nevertheless, as documentation for the ubiquitousness of life the 

 incidentally chosen example of a physically rather unimpressive ob- 

 ject such as the chairman's gavel may perhaps inspire you but little. 

 Let me therefore state that the microbiologist has encountered living 

 organisms in atmospheric strata some miles high, as well as in oceanic 

 sediments more than six miles below sea level; furthermore, that he 

 has found them in the water of the Dead Sea which, on account of the 

 high concentration of various salts, has acquired a bad reputation, 

 although the predicate 'dead' is evidently not applicable ; and likewise 

 in hot springs so warm that they would scald the human hand. 



A second aspect of life with which the microbiologist is conversant 

 is the surprisingly great quantitative significance of the microbial 

 world. It is known that our green plant kingdom on which man and 

 animals depend for their existence draws its nourishment from the air, 

 absorbing atmospheric carbon dioxide, and liberating oxygen. Reli- 

 able estimates show that the intensity of this carbon dioxide assimila- 

 tion by the existing flora is so great that the carbon dioxide content of 

 the atmosphere would be depleted in some 30-40 years unless carbon 

 dioxide would be returned to the air in some manner or other.. Now 

 it is quite certain that this supplementation is largely due to the fact 

 that in nature the dead plant material is reconverted into carbon 



* The 'Trippenhuis' is the name of the building occupied by the 'Koninklijke 

 Nederlandse Akademie van Wetenschappen'; it was built in 1660- 1664 by Justus 

 Vingboons as a domicile for the Trip family. 



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