CH. III.] NUCLEOPROTEIN. 63 



It is converted by guanase into di-oxy-purine, or xanthine, 



-OH 



Hypoxanthine, or xanthine, are oxidised by xanthin 

 oxydase into 2, 6, 8 tri-oxy-purine, or uric acid 



< 

 OH (see page 292). 



OH 



The pyrimidine bases are less complicated than the 

 purine bases. The pyrimidine ring is 



(1) N CH (6) 



(2) HC CH (5) 



II II 



(3) N CH (4) 



Uracil is 2-6-di-oxy-pyrimidine. 



Thymine is 2-6-di-oxy- 5 -methyl pyrimidine, or 5 -methyl 

 uracil. 



Cytosine is 6-amino-2-oxy-pyrimidine. 



Practically nothing is known as to their behaviour in 

 the body. 



72. Preparation of nucleoprotein. Lymphatic glands of the 

 ox or sheep, or the thymus of a calf are freed from fat, finely minced, 

 ground with sand and extracted for twelve hours with ten times their 

 weight of distilled water in a large bottle, a small amount of toluol or 

 chloroform being added to prevent decomposition. The bottle 

 should be shaken vigorously at frequent intervals to break up the 

 gelatinous masses that sometimes form. The fluid is strained and 

 centrifugalised to remove all debris (filtration being very slow). 

 This fluid contains both nucleoprotein and nucleo-histone. 



73. To a portion add dilute acetic acid till no more precipitate 

 is produced, and place on the water-bath at 37 C. for a few minutes. 



