INTRODUCTION. 



Bacteriology and Microbiology. The science of Bacteriology 

 occupies a somewhat peculiar position among the natural 

 sciences, partly because of its recent development and partly 

 because of the overshadowing importance of its practical appli- 

 cations. As bacteria are microscopic plants, some have con- 

 sidered bacteriology as a minor division of botany; but the 

 methods of work and the practical applications of bacteriology 

 have little in common with those of the more ancient science. 

 Indeed were it not for the importance of these little organisms 

 to the chemist, the pathologist, the physician and the agricul- 

 turist, we should hear little about them. 



The foundations of the science were laid by Pasteur (1858) 

 by the introduction of media and methods for artificial culture 

 of bacteria and the separation of mixtures into pure culture by 

 the laborious and uncertain but nevertheless successful method 

 of dilution in fluid media, thus making possible the accurate ex- 

 perimental study of microbes. Robert Koch (1872-1882) con- 

 tributed much to the establishment of the new science by intro- 

 ducing the use of solid media and the method of plating for the 

 isolation of pure cultures and especially by his wonderful 

 achievements in investigation of the pathogenic bacteria by 

 his new methods. Koch used potatoes, and aqueous humor 

 and blood serum rendered solid by the addition of gelatin. He 

 first employed the anilin dyes in staining bacteria (1877), 

 microphotography of bacteria (1877), homogeneous immersion 

 objectives and the Abbe illuminating apparatus (1878). Much 

 of our modern technic has been devised by his pupils and 



