120 • ^ 



But anybody reading Iwanowski's 1899 paper will have to 

 acknowledge that this author, even seven years after he made his 

 discovery, was not at all aware of its tremendously far-reaching 

 importance, the main part of the paper being devoted to an attempt 

 to prove contrary to all available evidence the bacterial nature of the 

 contagious agent. 



In contrast to Iwanowski's attitude, Beijerinck expresses 

 throughout his paper a firm belief in the existence of an autonomous 

 sub-microscopical form of life, and he also stresses his conviction that 

 the case of the mosaic disease will not stand alone. In a final para- 

 graph he mentions several instances of plant diseases which might 

 equally be due to a ''contagium fluidum", and it is clear that he al- 

 ready foresaw the great significance which virus diseases would acqui- 

 re in phytopathology. 



In this first paper, Beijerinck did not give much attention to the 

 consequence of his findings from the standpoint of general biology. 

 However, he enlarged on this point in 1913 in the very attractive 

 address he delivered in the joint meeting of the sections of the Ko- 

 ninklijke Akademie van Wetenschappen at Amsterdam i). In this 

 address which bore the title "Infusions and the discovery of bacteria" 

 he dealt with the question of submicroscopical life in an eloquent way, 

 as may be judged from the following translation of his concluding 

 remarks : 



"The existence of these contagia proves that the concept of life — 

 if one considers metabolism and proliferation as its essential charac- 

 ters — is not inseparably linked up with that of structure ; the criteria 

 of life, as we find it in its most primitive form, are also compatible 

 with the f luid state." 



And somewhat further on : 



'Tn its most primitive form, life is, therefore, no longer bound to. the 

 cell, the cell which possesses structure and which can be compared to a 

 complex wheel-work, such as a watch which ceases to exist if it is 

 stamped. down in a mortar. 



"No ; in its primitive form life is like fire, like a flame borne by the 

 living substance ; — like a flame which appears in endless diversity and 

 yet has specificity within it; — which can adopt the forms of the 

 organic world, of the lank grass-leaf and of the stem of the tree; — 

 which can be large and which can be small : a molecule can be af lame ; 

 — which can be so nearly luke warm as not to scorch the human 

 hand ; — which is bound up with a material foundation and yet leads 

 to immaterial consequences ; — which yields energy and converts 

 energy into other forms ; — which acts as a catalyst that brings about 

 in its environment changes all out of proportion to its own size; — 

 which consumes oxygen and excretes carbon dioxide; — which ab- 



1) Jaarboek der Koninklijke Akademie van Wetenschappen voor 1913. 



