130 WALTER JONES 



acid). (Kossel and Neuman (a) (b) (c), 1893, 1894.) It will, therefore, 

 be necessary and sufficient to examine two nucleic acids in o^der to get a 

 knowledge of them all. 



The Fundamental Groups of Yeast Nucleic Acid. When yeast nu- 

 cleic acid is heated for a short time with very dilute sulphuric acid, part 

 of its molecule easily undergoes hydrolysis with the formation of pentose, 

 phosphoric acid and two purine derivatives (guanine and adenine). But 

 when the nucleic acid is submitted to severe hydrolysis by heating wit 

 stronger sulphuric acid in an autoclave at 160, a second part of its molt 

 cule is decomposed with the formation of pentose and phosphoric acic 

 as before, but in addition, two pyrimidine derivatives (cystosine anc 

 uracil). So that by hydrolysis with mineral aeid in one way or another, 

 yeast nucleic acid produces six substances. 



1. Phosphoric Acid 



2. Pentose 



3. Adenine 



4. Guanine 



5. Cytosine 



6. Uracil 



These six substances constitute the fundamental groups of which ^^ 

 nucleic acid is composed, and as will 'be seen later, the same six substance^ 

 are formed when yeast nucleic acid is decomposed by physiological agents. 

 One of them is so simple as to require no treatment ; the other five shoulc 

 be discussed. 



Pentose. There are theoretically possible, eight aldo-pentoses of the 

 formula C 5 H 10 O 5 . The substance which is obtained from yeast nucleic 

 acid is that one of the eight possibilities that has the geometrical config- 

 loinT Cdled dex{r - ribose ' (Levene and Jacobs (c) (g) (h), 1909, 1909, 



CHO 

 HCOH 

 HCOH 

 HCOH 



CH 2 OH 



rat01 ! H^T? ^ foimd ^ rarel ? in nature > * ** 

 has ^eat physiological significance, but at present we can only 



fer d-ribose to the general metabolism of the carbohydrates: in which 

 case , does not properly fall into a discussion of nucleic acids. 



, Both cytosine 



(Kossel and Stendel (a) (6), 1902, 1903) and uracil 



