SELECTED PAPERS 



born in Haarlem two centuries ago as the son of a physician, who in 

 1790 published his 'Travel Notes', and described his experiences 

 gathered during a sojourn of five years in Turkey, to which country 

 he apparently lost his love. Anxious about a Russian threat against 

 Constantinople, he developed in his book a method of defense based 

 upon the possibility of artificially spreading bubonic plague among 

 the inhabitants of an aggressor country. It is hard to decide which is 

 the more striking in Van Woensel's narrative: the diffidence with 

 which he develops his idea, or the almost lyrical commentary devoted 

 to the efficacy of the defense measure advocated. 



While I have thus far only spoken of the influence exerted by disease- 

 producing representatives of the invisible world on humanity and its 

 activities, other and in themselves quite innocent microbes have not 

 remained entirely without effect. A striking example may be found in 

 the so-called 'miracle bacterium', nowadays known under the scient- 

 ific name of Serratia marcescens. This ubiquitous species possesses the 

 property of producing a red pigment in consequence of which a local- 

 ized development of the bacterium leads to the formation of red- 

 coloured patches, showing an unmistakable resemblance to a blood 

 spot. Particularly favourable substrates for multiplication of this organ- 

 ism are starchy foodstuffs such as bread and polenta (corn-meal mash) . 

 It is not surprising that at a time when the natural origin of such 

 'blood' formation was unknown, superstition attached far-reaching sig- 

 nificance to this phenomenon. In old chronicles many entries can 

 be found concerning the consequences; a summary of these reports 

 can be found in publications by Ehrenberg, Scheurlen, and Har- 

 rison. The reactions of the human mind to the occurrence of 'blood', 

 especially if this appeared on the eucharist, were quite divergent. 

 Sometimes it was accepted as a miracle, and thus led to an enhanced 

 devotion of the faithful. Raphael's famous painting, 'The Miracle of 

 Bolsena', attests to this type of effect. Not less frequently, however, 

 was the phenomenon interpreted differently, and was blamed on the 

 unbelievers, particularly among the Jewish population. Repeatedly 

 these have had to pay for it by hundreds being burned at the stake, 

 and this has tempted Scheurlen to the remark that the wholly innocent 

 miracle bacterium is responsible for more deaths than many a patho- 

 gen. In 18 19 an epidemic occurrence of red discolouration of diverse 



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