Chemical Constituents of the Animal Body. 253 



HO 

 = PO C 5 H 8 3 C 6 H 4 N S (guanine group) 







PO-C 5 H 8 0.-C 5 H 4 N 5 (adenine group) 



= PO C 5 H 8 3 C 4 H 3 N 2 2 (uracil group) 

 

 = PO C 5 H 8 O 3 C 4 H 4 N 3 2 (cytosine group) 



HO 



From the above it will appear that the main differences 

 between the animal (thymus) and plant (yeast) nucleic 

 acids are that the former yields thymine instead of uracil 

 on hydrolysis, and contains a hexose instead of a pentose 

 group. 



It is of interest to note that certain nucleotides have 

 been found which are not derived directly by the hydro- 

 lysis of nucleic acid. Thus, inosinic acid, discovered by 

 Liebig in 1847 in meat extract, yields on partial hydrolysis 

 the nucleoside inosine and phosphoric, and on complete 

 hydrolysis, hypoxanthine, cZ-ribose, and phosphoric acid. 

 Guanylic acid, which has been isolated from the pancreas, 

 yields, on partial hydrolysis, the nucleoside guanosine (which 

 is identical with the guanosine obtained by Levene and 

 Jacobs from yeast nucleic acid), and on complete hydrolysis, 

 phosphoric acid, guanine, and cZ-ribose. 



In the above summary of the results of the chemical 

 investigations of nucleic acid, no attempt has been made to 

 describe the methods by means of which the various 

 hydrolysis products have been isolated. For these re- 



