6 INTRODUCTION 



be considered the founder of bacteriology, but it remained 

 for Robert Koch (1843-1910), by his epoch-making discov- 

 eries, to place bacteriology in the position of an independent 

 science. In 1876, Koch, an obscure German physician, pub- 

 lished his article on the relation of Bacterium anthracis to 

 splenic fever in cattle. The relation was stated so clearly and 

 the arguments were so convincing that the paper attracted 

 wide attention and furnished a model for investigation of the 

 relation of microorganisms to disease processes. Six years 

 later he described a new method for isolating bacteria. This 

 was by means of a cleverly devised liquefiable solid medium 

 and is known as the gelatin plate culture method. The im- 

 portance of the discovery of this method to the development 

 of bacteriology cannot be overestimated. About this time 

 also Koch aided and encouraged the development of the 

 bacteriological microscope provided with an oil immersion 

 lens and an Abbe condenser. He also developed and applied 

 the use of the anilin dyes, first introduced into microscopical 

 . technique by Weigert. Following this work, the discoveries 

 in bacteriology have been rapid and almost continuous. In 

 a general way, however, the important discoveries have 

 been grouped about discoveries or modifications of technique. 

 For example, following the use of the anilin dyes and the 

 perfected microscope, the bacteria of a considerable number of 

 the important diseases were discovered, as, for instance, those 

 of relapsing fever, pneumonia, typhoid fever, and the protozoan 

 of malaria. Following the introduction of the plate culture 



