2 CHEMICAL SPECIFICITY OF NUCLEIC ACIDS 



stituents are laid down and in which they develop from each 

 other. If this is done, nucleic acids will be found pretty much at 

 the beginning. An attempt to say more leads directly into empty 

 speculations in which almost no field abounds more than the 

 chemistry of the cell. Since an ounce of proof still weighs more 

 than a pound of prediction, the important genetical functions, 

 ascribed — probably quite rightly — to the nucleic acids by many 

 workers, will not be discussed here. Terms such as "template" 

 or "matrix" or "reduplication" will not be found in this lecture. 



2. IDENTITY AND DIVERSITY IN HIGH-MOLECULAR CELL 

 CONSTITUENTS 



The determination of the constitution of a complicated com- 

 pound, composed of many molecules of a number of organic sub- 

 stances, evidently requires the exact knowledge of the nature and 

 proportion of all constituents. This is true for nucleic acids as 

 much as for proteins or polysaccharides. It is, furthermore, clear 

 that the value of such constitutional determinations will depend 

 upon the development of suitable methods of hydrolysis. Other- 

 wise, substances representing an association of many chemical 

 individuals can be described in a qualitative fashion only; precise 

 decisions as to structure remain impossible. When our laboratory, 

 more than four years ago, embarked upon the study of nucleic 

 acids, we became aware of this difficulty immediately. 



The state of the nucleic acid problem at that time found its 

 classical expression in Levene's monograph^. (A number of 

 shorter reviews, indicative of the development of our conceptions 

 concerning the chemistry of nucleic acids, should also be men- 

 tioned®-^ ^) The old tetranucleotide hypothesis — it should never 

 have been called a theory — was still dominant; and this was char- 

 acteristic of the enormous sway that the organic chemistry of 

 small molecules held over biochemistry. I should like to illustrate 

 what I mean by one example. If in the investigation of a disac- 

 charide consisting of two different hexoses we isolate 0.8 mole of 

 one sugar and 0.7 mole of the other, this will be sufficient for 



