INTRODUCTION 



Even nowadays, the number of people who claim the title of 

 "microbiologist" is very small. This is easily understood if one traces 

 the origin of the scientists who have materially contributed to our 

 knowledge of the microbe world. As a rule it will then become appa- 

 rent that they have interested themselves in micro-organisms only 

 because they wanted to apply their microbiological experiences to 

 various other branches of science, such as human or animal pathology, 

 phytopathology, industrial or agricultural bacteriology etc. This 

 implies that they prefer to remain physicians, veterinarians, phyto- 

 pathologists, technologists or agronomists. 



Only botanists and zoologists who rightly do not accept any barrier 

 between "higher" and "lower" living organisms, have now and then 

 made disinterested studies of microbes. But the title of "microbiolo- 

 gist" has too narrow a sense for these scientists who hate the restrict- 

 ion imposed by the name, and they avow the unity of living nature by 

 calling themselves "biologists". 



If any one, BEIJERINCK was entitled to the qualification of "bio- 

 logist". Yet, in the second half of his scientific career, he often gave 

 unmistakable proof that he took a special pride in the title "micro- 

 biologist". In doing so, BEIJERINCK undoubtedly wished to emphasize 

 that the study of micro-organisms not only calls for special techniques 

 quite foreign to the science of the higher organisms, but also for a 

 special intellectual and mental outlook which is only gradually gained 

 by a continued occupation with microscopic life. In that sense BEIJE- 

 RINCK was more than a biologist ; he was in addition one of the first 

 truly great "microbiologists" of his age and probably of all time. 



In the following pages an attempt will be made to justify this eulo- 

 gy. In the next chapter the circumstances will be set forth which led 

 BEIJERINCK to microbiology, and to his first investigations in this 

 field. In a following chapter a general outline will be given of his devel- 

 opment as a microbiologist, whilst in a final chapter the chief con- 

 tributions made by BEIJERINCK to the science of microbiology will be 

 dealt with in more detail. 



