121 



sorbs nutrients, can multiply itself and divide; — which does not 

 originate by spontaneous generation, but is propagated bv another 

 flame." ^ 



However vague these thoughts may be, yet they seem to justify the 

 eulogy which another great microbiologist, Félix d'Hérelle, 

 pronounced twelve years later in the Amsterdam Academy: 



"On a beaucoup discuté la conception de Beijerinck, mais je 

 ne pense pas qu'on en ait saisi toute la profondeur. Toute la biologie 

 reposait, repose encore, sur l'hypothèse fondamentale que l'unité de 

 matière vivante, c'est la cellule. Beijerinck Ie premier, s'est affranchi 

 de ce dogme, et a proclamé de fait, que la vie n'est pas Ie résultat d'une 

 organisation cellulaire, mais dérive d'un autre phénomène, qui ne 

 peut dès lors résider que dans la constitution physico-chimique d'une 

 micelleprotéique." i). 



Those who have been watching the recent developments in the 

 study of the viruses, especially the developments arising from Stan- 

 ley's great discovery of crystalline mosaic virus, will commend the 

 appositeness of the consideration formulated by d'Hérelle. It even 

 may be expected that thoughts like these are bound to play an im- 

 portant róle in the further elucidation of the phenomenon of Hfe. 



That Beijerinck in his later years retained his concern with the 

 problems of submicroscopical life may be inferred from the fact that 

 he published an essay on "Pasteur and ultramicrobiology" in 1922, on 

 the occasion of the centenary of Pasteur's birthday 2). 



g. Investigations on lactic acid bader ia. 



One of the chief contributions of Beijerinck to general bacterio- 

 logy has been his early recognition of the existence of the natural 

 group of true lactic acid bacteria. At the time that Beijerinck 

 entered the bacteriological field, and for many years after, there was 

 still a strong tendency to consider any bacterium as a lactic acid 

 bacterium, if under certain conditions it produced lactic acid from 

 sugars. Beijerinck's work has done much to promote the view that 

 the term "lactic acid bacterium" should be restricted to representati- 

 ves of a natural group of bacteria, which, in addition to their property 

 of producing lactic acid, have many other characteristics in common. 

 It should be added, however, that it was only the appearance in 1919 

 of Orla-Jensen's monograph "The Lactic Acid Bacteria" that 

 brought finality to the discussion. 



Beijerinck's occupations with the lactic acid bacteria had a two- 

 fold origin. In the first place, his activity in the fermentation industry 

 forced him to give fuU attention to the various types of lactic acid 

 bacteria which play either a desirable or an undesirable róle in the 



1) Versl. Afd. Natuurk. Kon. Akad. v. Wet. Amsterdam 34, 835, 1925. 



2) Chemisch Weekblad 19, 525. 1922. 



