HOMO MILITANS 



vest. That in later years this plague has not made itself felt to the same 

 degree is exclusively due to the powerful defense measures that were 

 devised by the phytopathologists. Even the meteorologist has been 

 recruited for this fight, as many of you will realize from the radio 

 messages sent out during the summer. 



Besides insects and fungi mention should be made of a totally dif- 

 ferent class of living organisms that constitute a threat to our food 

 provision. No doubt you will know that numerous plant diseases have 

 now been shown to be caused by viruses, i.e., contagious entities so 

 small that they pass through filters with pores that retain every par- 

 ticle that can be seen with the aid of even the best microscopes. The 

 remarkable feature of these viruses is that at least some of them have 

 been isolated in a pure form from infected plants, and have been 

 characterized as definite chemical substances, viz., nucleoproteins. Nat- 

 urally this has raised the question whether these agents may lay claim 

 to the predicate 'living', a notion that is supported by their ability to 

 multiply in the diseased plant. I shall not discuss this problem now, and 

 would rather call your attention to the fact that the phytopathologists 

 are unanimous in their opinion that lately the number of virus dis- 

 eases encountered among our cultivated plants has greatly increased, 

 and apparently is still increasing. Professor Smit, Rector Magnificus 

 of the Agricultural College, has recently discussed this aspect in a 

 trenchant manner, and elaborated the idea that this increase in virus- 

 es should be viewed as nature's reaction against man's abuses of the 

 earth's surface. Behind this army of viruses we may discern the spectre 

 of Homo ignorans. 



If in this connexion we realize that it is currently necessary to adopt 

 extensive measures in order to keep our plant material free from 

 viruses, a factor on which our present significant export of seed pota- 

 toes is based, it will be clear that in future an even heavier and more 

 extensive task will be delegated to Homo militans in this particular 

 field. 



But non-human forms of life threaten humanity not merely by cur- 

 tailing the food supply. Numerous living organisms, among which the 

 bacteria and viruses predominate, are potentially able to choose man 

 himself as a nutrient substrate. Too little does the layman realize that 

 the absence of pandemics during the past few decades, and hence the 

 fact that infectious diseases have not made serious inroads on hu nan 



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