48 PHYSIOLOGICAL CHEMISTRY. 



also of oxygen, which, by their constitution, show a relationship 

 not only among themselves, but also with uric acid. These bodies 

 are xanthin, hypoxanthin, guanin, adenin, heteroxanthin, para- 

 xanthin, and carnin. The bodies THEOBROMIN and THEOPHYLLIN 

 (both dimethyl xanthin) and CAFFEIK (trimethyl xanthin) occur- 

 ring in the vegetable kingdom also belong to this group. The 

 relation of these bodies to one another is shown in the following 

 list: 



Uric acid C 6 H 4 N 4 O 3 



Xanthin C 5 H 4 N 4 O 3 



Hypozanthin C 6 H 4 N 4 O 



Guanin C 5 H 5 N 6 O 



Adenin C 5 H 5 N 5 



Heteroxanthin C 6 H6N 4 O 2 



Paraxanthin C 7 H 8 N 4 O a 



Carnin C 7 H8N 4 O 3 



Guanin may be converted into xanthin, and adenin into hypo- 

 xanthin, by nitrous acid, also by putrefaction. Carnin is converted 

 into hydrobromic-acid hypoxanthin by bromine-water. Adenin, as 

 is shown by its formula, is a polymeric substance of hydrocyanic 

 acid, and on its decomposition with alkali yields alkali cyanides. 

 The relationship of these bodies to cyanogen is also shown by 

 GAUTIEE, who prepared xanthin synthetically from hydrocyanic 

 acid. 



The significance of the xanthin bodies as decomposition prod- 

 ucts of the cell nucleus and of nuclein was first pointed out by 

 KOSSEL, who discovered the two bodies adenin and theophyllin, 

 and his researches have greatly contributed towards the knowledge 

 of xanthin products. In those tissues in which, as in the glands, 

 the cells have kept their original state, the xanthin bodies are not 

 found free, but in combination with other atomic groups (nu- 

 cleins). In such tissue, on the contrary, as in muscles, which are 

 poor in cell nuclei, the xanthin bodies are found in the free state. 

 If the xanthin bodies, as suggested by KOSSEL, stand in close rela- 

 tionship to the cell nucleus, it is easy to understand why the mass 

 of these bodies is so greatly increased when large quantities of nu- 

 cleated cells appear in such places as were before relatively poorly 

 endowed. As an example of this we have in leucaemia blood 

 extremely rich in leucocytes. In such blood KOSSEL found 1.04 



