496 SESSION V. DISCUSSION 



M. I. Gol'din (U.S.S.R.): 



In connection with the work of Fracnkcl-Conrat and Schramm on the reconstruction 

 of the tobacco mosaic virus and the elucidation of the part played by ribonucleic acid in 

 the infectivity of the virus, I should like to call attention to the recent work of Wang & 

 Commoner [i] in which they obtained the complementary results. According to their 

 account, a mixture of deoxyribonucleic acids from a healthy tobacco plant and non- 

 infective protein from tobacco infected with the tobacco mosaic virus in corresponding 

 combinations turned into the active virus of tobacco mosaic. 



As Prof. Stanley rightly said, it is necessary to come to an agreement as to what we 

 include in the concept of life. The virus particle is often called the virus molecule, it is 

 held to be alive and some virologists even call it an organism. 



One may speak of the virus molecule as living but having many of the properties of 

 non-living material (e.g. the phenomenon of crystallization and its unimolecular structure), 

 but it is also permissible to regard a virus as something non-living which has many of 

 the properties of a living thing. 



The ability to mutate and general variability of tobacco mosaic and other viruses are 

 evidence in favour of their living nature. However, one must note, in the first place, that 

 the evidence for the variability of tobacco mosaic virus is based on an imperfect method 

 of separating the pure virus from a single necrosis. In our work, pubhshed in 1956 [2], 

 we have set forth a more satisfactory process based on the separation of viruses by taking 

 samples from the lower side of the necrosis. Furthermore, there is evidence that one 

 necrosis may be caused by two viruses. If this is so, the method of separation from a 

 single necrosis cannot be used without specially critical assessments, so that this method 

 does not give a complete guarantee of the isolation of a single virus. 



I suggest that we must differentiate between variation and variability. We find ourselves 

 confronted with a paradox. The living nature of the virus is vouched for by its variability, 

 but this very variability is shown to exist by means of an argument which assumes, a 

 priori, that viruses are living. I will make the example clearer. The variation of the tobacco 

 mosaic virus in the test-tube experiments of Fraenkel-Conrat and others only differs 

 from a chemical reaction by reason of the later introduction of the virus particles into a 

 living cell, but what occurs there, and what or who is responsible for these changes — 

 that is still a question. 



In conclusion, I should like to touch on the work which I have done in collaboration with 

 Brodskii and Fedotina [3]. It is known that viral inclusions are very similar to the protein 

 inclusions of healthy plants, and I should say that they are suspiciously similar. Using 

 ultraspectromicroscopy, we have shown that the protein inclusions in the healthy tuber 

 of the potato are nucleoproteins. The same is true of the intranuclear inclusions in cow- 

 wheat (Melampyrum nemorosum). 



Thus, nucleic acids (nucleoproteins) may not only be centres of activity in the living 

 cell, but may also function as inert products of the same sort as excretory products. 



I believe that the correct approach is not simply to regard viruses as living rudiments 

 which may provide evidence for elucidating the nature of other complicated systems, but, 

 on the contrary, to study these various systems and phenomena in the living cell and in 

 their interactions with the virus, in order to understand the nature of viruses without pre- 

 judging the question as to whether they are living or non-living. 



REFERENCES 



1. T. Wang & B. Commoner, Proc. Nat. Acad. Sei., Wash., 42, 831, 1956. 



2. M. Gol'din, Dokl. Akad. Nauk S.S.S.R., 108, 151, 1956. 



3. M. Gol'din, V. Brodskiï & V. Fedotina, Zh. obshch. Biol, 17, 393, 1956. 



R. L. Berg (U.S.S.R.): 



On Accelerating the Tempo of Evolution 



I should like to comment on the part of Prof. Pauling's paper in which he discusses 

 the rate of the elementary evolutionary process. This is an important question. It gives 



