PLACE OF MICROORGANISMS IN NATURE 19 



succeeded to this proof others to the effect that bacteria 

 are ubiquitous, and that they are carried in dust or probably 

 alone by air currents. His experiments also showed that 

 spontaneous generation (the arising of living forms anew 

 from the elements of nature, and not from preexisting living 

 forms) does not occur. The results of Pasteur's work received 

 practical application also at the hands of Koch and Lister. 

 The former devised methods for the cultivation and study 

 of the individual species and followed this up by discovering 

 the organisms causing tuberculosis, anthrax, and cholera. 

 Lister, shocked by the appalling mortality in the hospitals 

 from gangrene and septic poisoning, established methods 

 by which bacteria from the air and from infected cases were 

 excluded from healthy surgical cases. The basic principles 

 of modern antiseptic and aseptic surgery are due to him. 



Throughout all the history of microbiological develop- 

 ment it has been possible to progress more rapidly and 

 definitely with bacteria than with protozoa. Bacterial life 

 and activity can be controlled very largely now, but as yet 

 little or nothing is known of the important vital activities 

 of the minute animals. 



As in the case of bacteria, so the earliest records of pro- 

 tozoa are those of Van Leeuwenhoek's animalculse. Their 

 natural history has been gradually developed by Jablot, 

 Dujardin, Prowaczek, and Biitschli, and the present leaders 

 in the field, Calkins and Doflein. However, it is only within 

 the last score of years that we have been familiar enough 

 with these lowest animal forms to be sure of their species 

 identity, and we are yet imperfectly informed as to their 

 vital phenomena. 



PLACE OF MICROORGANISMS IN NATURE. ' 



The studies of the life history of bacteria and protozoa 

 have been the work of botanists, chemists, and physicians. 

 Through this combined effort it has become known that 



