ALPHABET OF THE CELL 113 



feasible^. The lipids had to wait longest. Whereas the existence 

 of many different tissue lipoproteins had been recognized for 

 quite some time^, it is only recently that the occurrence of specific 

 lipid polymers is being discussed^- *. 



Which types of compounds then, we could ask, are responsible 

 for the specific character of a cell? The answer is obvious. If we 

 assume that all chemical and physical features of the cell are 

 preserved without change within the species, but serve to distin- 

 guish the particular cell from that of other species, we must say 

 that it is the aggregate of all cellular constituents that defines 

 chemical specificity. But this does not mean that all substances 

 are equally decisive in maintaining hereditary continuity; some 

 may be causes, others merely symptoms. There is much reason 

 for the assumption that the directive influence on the mainte- 

 nance of cell specificity must be sought within the class of highly 

 polymerized plastic constituents, at any rate, the proteins and the 

 nucleic acids. 



3. ON THE ALPHABET OF THE CELL AND SOME LANGUAGE 

 DIFFICULTIES 



When a science approaches the frontiers of its knowledge, it 

 seeks refuge in allegory or in analogy. The latter attempt — and I 

 consider it preferable to the first — has enlisted the support of 

 modern disciplines, such as cybernetics or information theory^. 

 A subordinate analogy to the maintenance of cellular specificity, 

 but one, perhaps, more easily grasped, is that of the manner in 

 which communication is brought about through language. This 

 should not be taken to mean that I consider the cell as a system 

 of phonemes; for we have no right to introduce such concepts as 

 intelligence or mind into the working of the cell. But the com- 

 parison with communication through words will, at least, serve 

 to explain the meaning of a term much used in these days, 

 namely, biological information. I have dealt with this problem 

 before^^' ^^ and can be brief here. A very tentative definition of 

 biological information could describe it as the aggregate of all 



References p. 125 



