FLOWERLESS PLANTS 467 



twisted into spirals or corkscrews. Minute as they are, 

 many bacteria have threadlike appendages, with which 

 they swim actively about. 



It has been difficult to decide whether we should class 

 bacteria as plants or animals. Their food and what little 

 structure they possess are considered to show, however, 

 that they are plants, related more closely to the fungi 

 than to any other group. 



Bacteria are practically everywhere in natui?^ They 

 exist in the air as dust ; they swarm in all surface waters ; 

 the top layers of fertile soil are literally alive with them, 

 almost all of them harmless or beneficial. The udders of 

 healthy cows, the healthy human mouth, the healthy 

 stomach and intestines, all support varied florae of these 

 ubiquitous plants. Normally, however, they are not pres- 

 ent in the blood or other tissues of a healthy animal. 



Bacteria were discovered by Anton van Leeuwenhoek 

 in 1683, but were known merely as curiosities until about 

 1880, when Robert Koch and Louis Pasteur demonstrated 

 their power to cause disease. For a time people were 

 greatly alarmed ; they next bethought themselves that 

 humanity had fared well before the bacteria were discov- 

 ered and would doubtless continue to fare as well, or bet- 

 ter, thereafter. As knowledge accumulated, they realized 

 that there is no reason why bacteria should not be as good 

 to eat as other vegetables ; and finally arrived at the view 

 as expressed by a leading scientist, that a healthy human 

 body is, after all, the best microbe destroyer in the world. 

 Fresh air and sunshine, exercise, good food, vigor, and a 

 high health level give us these, and with a few reasonable 

 precautions we have practically nothing to fear. 



