208 SCIENCE PROGRESS 



been admirably done in an interesting historical review of the 

 subject in Walter Jones's article. 1 We will be content with 

 mentioning a number of propositions which, if not absolutely 

 certain, are not at any rate far from the truth. 



i. All "ordinary nucleic acids" (that is, nucleic acid as 

 opposed to guanylic acid) yield the same two purine bases 

 (adenine and guanine) in the same proportion. Xanthine and 

 hypoxanthine, when present, are due to the secondary action 

 of enzymes or other agencies that produce removal of the 

 NH 2 or amino-group and oxidation. 



2. All yield the same two pyrimidine bases, namely, cytosine 

 and thymine. 



3. All contain a hexose carbohydrate, the identity of which 

 is uncertain, though it is probably not dextrose. This has 

 always been Kossel's view from the fact that laevulinic acid 

 is such an abundant cleavage product. Previous statements 

 about the presence of a pentose are no doubt due to admixture 

 with guanylic acid. 



There is therefore no insurmountable difficulty in accepting 

 the hypothesis that the nucleic acids of different mammalian 

 organs are identical substances. One must naturally be 

 cautious in making the generalisation too sweeping at present, 

 especially as it has been shown that those derived from plants 

 and from fish spawn yield uracil, another pyrimidine base ; 

 uracil derived from mammalian nucleic acid is a secondary 

 product from cytosine. 



At the recent Congress of Applied Chemistry held in London 

 (June 1909) we had the advantage of hearing the latest views 

 on the nucleic acid problem from Dr. Steudel. He has carefully 

 estimated the various elements, and also the cleavage products 

 of nucleic acid, and proposes still andther empirical formula for 

 it, which differs somewhat from that advocated by Schmeideberg 

 last year. The following equation will indicate what it is, as 

 well as the way it splits up on decomposition with water and 

 oxygen : 



C,3H 57 N l5 3 oP, + 8H,0 + O, = C 5 H 5 N 5 + C 3 H 5 N 5 



[Nucleic acid] [Water] [Oxygen] [Guanine] [Adenine] 



+ C 5 H 6 N.p, + C 4 H 5 N 3 + 4C 6 H„0 6 + 4HP0 :) 



[Thymine] [Cytosine] [Sugar] [Meta-phosphoric 



acid] 



He was also able to put forward tentatively his view regarding 

 1 Journal of Biological Chemistry, 1908. 



