NUCLEIC ACIDS, DECODING, ETC. 169 



not apply, so it must be No. 3. But are we concerned with words 

 here, and is arbitrariness what we would ascribe to nature? The 

 understanding of words, the translation of ciphers, even the 

 reception of signals, they all require the intervention of intel- 

 ligence, either directly or indirectly. I had been interested in this 

 problem for quite a while, long before I read Teilhard de Chardin 

 from whose book {Le Phenomene Humain) the old saying of 

 TertuUian seemed to arise in a new and disturbing version: 

 Animal naturaliter christianum. He found consciousness, i.e., 

 mind, everywhere, though in different degrees, in the mineral and 

 the protein, in the virus and in man. Now, this is a dangerous, a 

 slippery path; and I am afraid to take even the first step on it. 

 For if I fear anything, it is the mystic with the shde rule. Poets 

 look better without their laboratory coats. The vapor pressure of 

 pneuma should remain unmeasured. To study the effect of mental 

 concentration on reaction velocity I leave to the next century. 



In any event, when the word "code" is used in the context of 

 cellular specificity, most people will know what it signifies in a 

 loose sense, though many may be baffled by its concrete meaning 

 and even more by the manner in which it is supposed to operate. 

 For this reason, we were all elated — though perhaps with dif- 

 ferent degrees of fervor — by the announcement, a few months 

 ago, that the amino acid code had been broken through the dis- 

 covery that several uridylic acids in a row, perhaps three or more, 

 coded for phenylalanine. These findings were soon confirmed and 

 extended in other laboratories, so that it would now seem that 

 the coding units for all amino acids are known, though there still 

 are some uncertainties, especially with regard to the sequence 

 within the triplets. There were, of course, some very baffUng 

 circumstances, e.g., the unexpected preponderance of uracil in all 

 coding units and also the observation that poly-U was enormously 

 more effective in incorporating phenylalanine than were any of 

 the other coding units for their respective amino acids. 



We had a very direct interest in all these questions, for we 

 were determining the frequency of the all-pyrimidine runs in 

 various species of DNA; and there should have been a direct 



