SESSION IV. DISCUSSION 373 



of anaphylaxis which enables one to demonstrate the very slightest contamination by 

 protein such as cannot be determine chemically. If these preparations had no power 

 to sensitize guinea pigs to protein, this would be an important criterion of their purity. 

 Immunologists, in general, cannot understand why biochemists so seldom and so incon- 

 fidently use immimological methods in their experiments. I should Uke to draw your 

 attention to the fact that immunological methods enable one to distinguish, not only be- 

 tween the different compositions of various substances (not necessarily proteins), but also 

 between their structures. For a long time nobody could differentiate chemically or im- 

 munologically between normal and immune globuHns. Recently Adler has shown that they 

 may be differentiated by the method of indirect haemagglutination. In our laboratory a 

 clear differentiation has been achieved by using the method of anaphylaxis and desensi- 

 tization. As immune globuHns now provide one of the most satisfactory models for the 

 study of protein synthesis, the great attraction of immunological methods for bringing 

 about biochemical separations is that they are certainly effective. I should Uke to remark 

 that the hypothesis of the matrix, which provides a good explanation for the formation 

 of antibodies, is hard to apply to the phenomena discovered by Fraenkel-Conrat and 

 Schramm. When one nucleic acid is introduced into a healthy plant there is, of course, 

 no ready-made matrix in the plant for the synthesis of viral protein. It follows that in this 

 case, as was shown convincingly in Fraenkel-Conrat's remarkable experiments on the 

 hybridization of viruses, the nucleic acid acts as a genetic determinant, controlling the 

 formation of a similar matrix, if only such a matrix is generally formed in this case. 



A process which is, to some extent, analogous is seen in the transformation of pneumo- 

 cocci. An alteration in the specificity of the polysaccharide antigen is brought about in 

 them by deoxyribonucleic acid which, of course, has no matrix for the reproduction of a 

 polysaccharide antigen. 



The question of the mechanism of action of a genetic determinant, such as nucleic acid, 

 obviously is of the greatest importance at present. It would therefore undoubtedly be 

 interesting to carry out a detailed immunological study of a disease induced by a single 

 nucleic acid. Immunological studies could, at least, reveal the time and quantity of the 

 formation of the virus, even before the signs of the disease became manifest. They could 

 thus yield some information as to the process of formation of virus particles, both infective 

 and non-infective. 



Essential information as to the specific structure of the protein synthesized under the 

 control of the nucleic acid might also be obtained by immvmological methods. 



V. Ryzhkov (U.S.S.R.): 



I should Uke to touch upon some logical questions, the consideration of which is 

 especiaUy important when we are faced with such difficult problems as those with which 

 we are now dealing. 



First there is the question of the definition of life. I should Uke to recall the statement 

 of Engels that a definition is of Uttle scientific value. The content of an idea must be 

 revealed in its entirety, but this has already ceased to be a definition. I think that the place 

 of viruses in nature can be understood, not on the basis of a formal short definition, but 

 only by a study of aU the connections in which viruses exist in nature. The fact that viruses 

 are capable of multipUcation might indicate their living nature to a lesser extent than the 

 fact that viruses circulate in nature as actual living creatures, for the isolated organoids of 

 cells are also capable of multiplication. 



I should Uke to caU attention to the fact that we still do not know much about viruses 

 in a state of biological activity. We have in our hands preparations of virus particles which 

 have been fuUy studied, but we now know that virus particles represent the spore stage 

 of viruses. One can as Uttle judge the life of viruses from their spore stages as one can 

 judge the Ufe of bacteria from their spores or the Ufe of a wheat plant from a well-dried 

 grain of wheat. 



I should Uke to raise a protest against reference to virus particles as molecules. In scale 

 they are on a molecular level, but their structure is biologically adapted to function and 



