36 NUCLEIC ACIDS AS CELL CONSTITUENTS 



two principles are operative: generalization and simplification. 

 Both are necessary and both dangerous. It is obvious that we can 

 learn more geometry from the illustrations in a textbook on 

 projective geometry than from the beautiful pictures in Sir 

 D'Arcy Thompson's On Growth and Form. But it is difficult to 

 say where the danger line lies beyond which oversimplification 

 will produce a dogmatic ignorance. Should we stress the multi- 

 formity of nature, which makes us forget the simplicity of its 

 basic designs; or should the essential shape win over the ac- 

 cidental form? In Wycherley's The Country Wife a quack is ad- 

 dressed as follows: "Doctor, thou wilt never make a good chemist, 

 thou art so incredulous and impatient". If patience and credulity 

 were all the chemist needed, the problem of the nucleic acids — 

 still so baffUng and elusive — would have been solved a long time 

 ago. 



