THE PROTEIDS. 43 



and sulphur, a variable amount of phosphorus, and in some instances 

 also iron. 



Their quantitative composition, moreover, is different, a,s is ap- 

 parent from the following table : 



Yolk-nuclein. Yoast-nuclein. 



Carbon 42.11 40.81 



Hydrogen 6.08 5.38 



Nitrogen 14.73 15.98 



Oxygen 31.05 31.26 



Sulphur 0.55 0.38 



Phosphorus 5.19 6.19 



Iron 0.29 . . 



The nucleins occur widely distributed both in the animal and the 

 vegetable world, and are of special importance as food-stuffs, in so 

 far as the iron which some contain is only accessible to animals 

 in this form. They are essentially albumins which are closely com- 

 bined with a phosphoric acid radicle. In certain forms, however, 

 this group is not only united to an albuminous radicle, but also with 

 certain basic substances, such as adenin, hypoxanthin, guanin, and 

 xanthin. These bodies belong to the class of the so-called xanthin, 

 alloxuric, or purin bases, and in combination with a phosphoric acid 

 radicle constitute the so-called nucleinic acids. Individually these 

 various bodies will be considered in another section of this work, 

 but it may here be mentioned that the nucleinic acids and the 

 nucleinic bases not only occur in the animal body in combination 

 with albumins, but also as such. 



According to the combination of the albuminous group with 

 phosphoric acid only, or through this with the nucleinic bases, the 

 nucleins are now divided into two groups, viz., the so-called para- 

 nucleins, or pseudonucleins, and the nuclear nucleins proper. 



All nucleins possess the character of strong acids. They are 

 soluble in solutions of the hydrates of the alkalies, less readily so 

 in dilute solutions of the alkaline carbonates and in concentrated 

 hydrochloric acid. In water and alcohol they are for the most part 

 insoluble. They are coagulated by heat, as also by alcohol, and are 

 then insoluble in solutions of the alkaline hydrates. In dilute acids 

 and in artificial gastric juice they are practically insoluble, and it is 

 thus possible to separate them from any albumins that may be 

 present at the same time. 



Like the albumins proper, they give the various color-reactions 

 which are characteristic of the albumins as a class. 



The Nucleo-albumins. The nucleo-albumins are compounds of 

 the nucleins and paranucleins with a special albuminous radicle. 

 Like the nucleins, they hence contain phosphorus, but their quan- 

 titative composition varies but little from that of the albumins 

 proper. This is no doubt owing to the fact that the nucleinic or 

 paranucleinic radicle, which enters into their construction, repre- 

 sents only a small portion of the entire molecule. Like the nucleins, 

 they occur widely distributed in the animal and vegetable world, 



