156 TRANSFORMATION OF PNEUMOCOCCAL TYPES 



same specific type as that of the heat-killed microorganisms from which the 

 inducing material was recovered. 



2. Methods for the isolation and purification of the active transforming ma- 

 terial are described. 



3. The data obtained by chemical, enzymatic, and serological analyses 

 together with the results of preliminary studies by electrophoresis, ultracen- 

 trifugation, and ultraviolet spectroscopy indicate that, within the limits of the 

 methods, the active fraction contains no demonstrable protein, unbound lipid, 

 or serologically reactive polysaccharide and consists principally, if not solely, of 

 a highly polymerized, viscous form of desoxyribonucleic acid. 



4. Evidence is presented that the chemically induced alterations in cellular 

 structure and function are predictable, type-specific, and transmissible in 

 series. The various hypotheses that have been advanced concerning the 

 nature of these changes are reviewed. 



CONCLUSION 



The evidence presented supports the belief that a nucleic acid of the desoxy- 

 ribose type is the fundamental unit of the transforming principle of Pneumo- 

 coccus Type III. 



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