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with ammonium sulphate? In agreement with its modest function, the 

 molecular weight of this biocatalyst is probably not more than 70,000; 

 a low value that sharply contrasts with that of the giant virus mole- 

 cules to which must, after all, be ascribed the much more radical role 

 of a catalyst for synthetic oxido-reductions. 



But the recent studies of Warburg and co-workers are of particular 

 importance in connexion with the following. According to a prelimin- 

 ary report, Warburg and Christian have found that the above men- 

 tioned nucleotide can form complexes with various proteins isolated 

 from yeast, each complex acting as a dehydrogenation catalyst. Now, 

 whereas one complex dehydrogenates an oxidizable substrate like 

 Robison ester to the corresponding phosphohexonic acid, another per- 

 forms a much more extensive oxidation which even leads to the liber- 

 ation of carbon dioxide. Here we see, therefore, an oxido-reduction 

 reaction chain unmistakably determined by the nature of the col- 

 loidal protein carrier. 



If now we return into the mist of the virus field we may try whether, 

 by the light of this extremely interesting result, we can begin to distin- 

 guish some shapes also here. Is it not very tempting to imagine, in 

 connexion with Janssen's line of thought, that the virus protein after 

 its penetration into the cell takes possession of the nucleotides or nucleic 

 acids that function as prosthetic groups in the normal cellular syn- 

 theses? The result would be a shunt of the normal biosynthesis in the 

 direction of a synthesis of virus protein. That is to say that along with 

 a disruption of the harmony of the various synthetic entities of the 

 infected cell there will occur a multiplication of the virus. Is not such 

 a concept eminently suitable to render understandable also the alarm- 

 ing increase in the number of plant virus diseases that has been noted 

 by all phytopathologists? Might not this be the result of the fact that 

 the much more intensive cultivation of recent years has greatly in- 

 creased the chances for contact between various plants, thus opening 

 the possibility that synthetic entities of certain species might find their 

 way into the cells of different species? May this not also throw light 

 on the still so mysterious behaviour of 'virus carriers', apparently 

 healthy varieties of cultivated plants that nevertheless can transfer 

 virus diseases to sensitive clones? Cannot one accept more readily the 

 conclusion that a particular normal synthetic entity of the carrier race 

 causes the disorganisation of the cells of a sensitive variety than the as- 



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