34 



C. L. SADROX 



Fkj. 17. DNA aiamenl 



on the process of extraction of DNA from the living organisms, and the 

 conditions that have to be realized in order to obtain reproducible results 

 do not yet seem to be clearly established. However, a proteolytic enzyme 

 treatment (chymotrypsin or even trypsin ) of samples of different charac- 

 ters removes the discrepancies observed before the treatment. The assump- 

 tion " that the enzyme breaks residual protein bridges between different 

 particles seems to be in agreement with the observed facts. Nothing is 

 known about the eventual existence of such residual bridges inside the par- 

 ticle. 



(6) The particles in dilute solution are not identical. It is not yet clear 

 if they have different molecular weights and, consequently, different shapes 

 and dimensions, or if there is no correlation between their molecular weight 

 and their shape. Particularly, the question is open whether, in a given sam- 

 ple, the particles possess a uniform molecular weight. Electron micrographs 

 could, perhaps, give an answer. The examination of filament -shaped par- 

 ticles ( Fig. 17) does not lead to precise conclusions. 26 



When, on the other hand, the particles occur in globular form (Fig. 18 ), J ' 



26 C. E. Hall, J. Biophys. Biochem. Cytol. 2, 625 (1955). 



27 R. Vendrely, C. Vendrely, and C. Sadron, Exptl. Cell Research 15, 222 (1958). 



