38 



aerophily", and his remarkable demonstrations regarding the prop- 

 erties of luminous bacteria, over which his audience sometimes went 

 into ecstasies. The artistic thread in BEIJERINCK'S mind is also mani- 

 fest in his often exceptionally fine drawings. The plates he added to 

 his Doctorate thesis on the galls, the drawings in his papers on "Root- 

 buds and adventitious roots", on the gummosis of the Amygdalaceae, 

 on the green algae, on Bacillus cyaneofuscus etc., all give proof of this. 

 It should not be forgotten, however, that his sister Henriette some- 

 times very ably assisted him in this part of his work. 



The aesthetic element in BEIJERINCK'S character may perhaps also 

 explain why he was apparently especially attracted by those micro- 

 bes which display beautiful colours in their cultures. We refer here to 

 his studies on Bacillus prodigiosus, Bacillus violaceus, Bacillus cyaneo- 

 fuscus, the "litmus-Micrococcus" , chromogenous yeasts, green and 

 blue algae, etc. 



The beautiful blue-green sheen of the cultures of luminous bacteria 

 may be at least partly responsible for the persistency with which 

 BEIJERINCK studied these organisms. Colour-reactions, such as the 

 cholera-red-reaction, the tyrosinase-reaction, indigo-formation etc., 

 also occur frequently amongst BEIJERINCK'S subjects of investiga- 

 tion. A predilection for regular structures such as can be for instance 

 observed in microscopical preparations of Schizosaccharomyces octo- 

 sporus and of Sarcina ventricidi may have contributed to the great 

 attention he repeatedly gave to these organisms. 



In the same line of thought BEIJERINCK'S sense of smell may have 

 led to studies on organisms producing attractive or in other ways 

 characteristic odours, as is for instance the case with the acetic ester 

 yeasts. 



BEIJERINCK'S working environment was generally characterized by 

 a picturesque disorder. Although he easily became angry over similar- 

 ly untidy work amongst his pupils, he was as a rule blind to his own 

 shortcomings in that respect. His microscope was usually surrounded 

 by dozens of inoculated culture flasks, numerous piles of culture dishes, 

 bottles with reagents, and "BEijERiNCK-shelves" loaded with tubes 

 containing pure cultures, so that he barely had room to move his 

 arm. 



In the second phase of his scientific career the plate culture was 

 his proper field of operations. This field was explored in a manner 

 that has probably never since been equalled. BEIJERINCK used to 

 emphasize that a careful and circumstantial inspection of a plate 

 culture was an unfailing source of knowledge, and it was only with 

 heartfelt grief that he finally parted with the often already quite 

 dried-up plates. It is difficult to estimate the pains taken by his 

 patient "amanuensis" KOKEE in the preparation of the endless series 

 of culture media. Every morning this worthy collaborator was sum- 

 moned by a press of the bell-button, and then in a lengthy conversa- 



