110 



him to make a thorough study of all phenomena connected with 

 fermentation. Amongst these phenomena the way in which free 

 oxygen influences the growth and the fermentative power of the yeast 

 cell has ranked as one of the most important, ever since PASTEUR 

 published his fundamental observations in 1876. If we add that the 

 Delft factory started investigations on the so-called air process of 

 yeast production as early as 1889, and in 1894 introduced this process 

 on a technical scale ') it is evident that BEIJERINCK must have had the 

 problem before him during the whole course of his industrial career. 

 At the same time we may presume that BEIJERINCK has made many 

 observations on this point which, on account of their industrial im- 

 portance, were never published. His publications are largely re- 

 stricted to the more theoretical aspects of the subject, a circumstance 

 which, at least in a way, enhances the value of these studies. 



In a lecture delivered in 1887 during the first meeting of the "Ne- 

 derlandsch Natuur- en Geneeskundig Congres" BEIJERINCK gave an 

 already authoritive survey of the problem 2 ). Herein he made the 

 point that PASTEUR'S discovery of the physiological equivalence of 

 fermentation and respiration seemed to have dethroned oxygen as 

 far as its universal indispensability for living organisms is concerned. 

 BEIJERINCK, however, maintained that even for organisms generally 

 considered to be strictly anaerobic, small quantities of oxygen are 

 necessary for the maintenance of life over long periods. This had 

 already been demonstrated in 1880 for ordinary yeast by PASTEUR'S 

 pupil COCHIN. BEIJERINCK reported that he had found the same for 

 the strictly anaerobic butyl alcohol bacteria, as also for facultatively 

 anaerobic bacteria, like the lactic acid bacteria and Bacterium aero- 

 genes. Therefore, besides its ordinary role in respiration, oxygen has 

 an "excitation function", of unknown character, which makes this 

 gas indispensable for all living beings. 



In his study on the metabolism of the pellicle forming yeasts, which 

 appeared five years later, BEIJERINCK went so far as to suggest that 

 the significance of gas evolution which so often accompanies anaero- 

 biosis is to be found in the transport of the fermentation organisms to 

 the surface of the medium, thus enabling these organisms to restore 

 their "oxygen reserve" 3 ). 



In a paper ) of 1898 BEIJERINCK returned to the subject. He first 

 of all enounced his opinion that all motile micro-organisms can, on the 

 ground of their behaviour in his "cover glass preparations", be divided 

 into two groups *). The cells of the organisms of the first group - - to 



') F. G. WALLER, Chemisch Weekblad 10, 635, 1913. 



z) Handelingen van het Eerste Nederlandsch Natuur- en Geneeskundig Congres 

 Amsterdam, 1887, p. 34. 



i) Centralbl. f. Bakt. u. Parasitenk. 11, 68, 1892. 



4 ) Proc. Kon. Akad. v. Wet. Amsterdam 1, 14, 1898. 



5 ) For a detailed description of this "cover glass preparation" method leading to 

 the so-called respiratory figures, the reader is referred to the paper in Centralbl f 

 Bakt. u. Parasitenk. 14, 827, 1893. 



