294 THE PHYSIOLOGY OF REPRODUCTION 



phosphorus, not easily soluble in cold water, but readily dis- 

 solved by alkalies or ammonia. They are precipitated from 

 their solutions by mineral acids and by alcohol. They form 

 insoluble salts with the heavy metals and with barium, 

 calcium, and strontium. If pure, they do not give the colour 

 reactions for proteins. They rotate polarised light to the 

 right. A solution of nucleic acid, acidified with acetic acid, 

 gives a precipitate with protein solutions. By boiling the 

 watery solutions the nucleic acids are partially decomposed. 1 

 Complete hydrolysis is brought about by treatment with hot 

 acids. The main products of hydrolysis which are thus 

 obtained can be grouped under five headings : 



1. Phosphoric acid. 



2. Laevulinic acid, a substance formed by the oxidation 

 of carbohydrates, and indicating the presence of a hexose (some 

 nucleic acids contain a pentose). 



3. Derivatives of purine 



(1) N = CH (6) 



(2) HC C (5)-NH(7)\ 



I! II >CH (8) 



(3) N-C (4)-N (9)^ 



namely 



Adenine = 6 - Aminopurine ; Hypoxanthine = 6 - Oxypurine ; 

 Guanine = 2 Ainino-6 Oxypurine ; Xanthine = 2-6 Dioxypurine. 



Of these only adenine and guanine are present as such in 

 the nucleic acid molecule, while hypoxanthine and xanthine 

 are formed from them in the process of hydrolysis by a 

 secondary reaction. 



4. Derivatives of pyrimidine 



(1) N = CH(6) 



! I 



(2) HC CH (5) 



II II 



(3) N-CH(4) 



namely 



Cytosine = 6 Amino-2 Oxypyrimidine 



Uracil = 2 - 6 - Dioxypyriniidine 

 Thymine = 5 Methyl -2 -6 Dioxypyriniidine (Methyl-Uracil). 



1 For literature for nucleic acid see Steudel, " Nucleine, Nucleinsjiuren 

 und ihre Spaltungsprodukte," Biochemiachea Centralblatt,vo\. vi.,1907; also 

 Burrian, lac. cit. ; Levene, Zeitechr.f. phys. Chemie, vols. xxxii. to 1., Biochem. 

 Zeitschr., vols. iv., v., and ix. 



