42 THE ALBUMINS. 



is to be noted, moreover, that the portion which remains in solution 

 represents from-three-fifths to four-fifths of the entire amount that 

 was originally present, but it appears that, barring their different 

 solubility in water, both portions are identical. 



Some of the globulins may also, in part at least, be precipitated 

 from their neutral solutions by copious dilution with water, by pass- 

 ing a current of carbon dioxide through the solution, or by acidifying 

 with acetic acid or some other organic acid. If an excess of the 

 acid, however, is added, they again dissolve. All globulins are 

 coagulated by heat, and it is to be noted that the greater number 

 also pass into the coagulated state when kept long under water. 



Like the true albumins, the globulins contain nitrogen in at least 

 three forms, viz., as ami do-nitrogen, as diamino-nitrogen, and as 

 mono-amino-nitrogen. They contain less sulphur than the albu- 

 mins, but not less than 1 per cent. 



The Vitellins. The vitellins are apparently closely related to 

 the globulins and the albumoses. Some of them, such as the 

 aleurons of seeds and the so-called yolk-platelets, which are found 

 in the eggs of certain fish and amphibia, occur in crystalline 

 form, and still others may also be made to crystallize artificially. 

 As has been mentioned, these crystalline bodies do not represent 

 the pure albumins, however, but are probably compounds of albu- 

 mins with various salts and lecithins. 



Both animal and vegetable vitellins are soluble in dilute saline 

 and alkaline solutions; they are precipitated from these by acidify- 

 ing with dilute acetic acid, by passing a current of carbon dioxide 

 through the solutions, and by salting with magnesium sulphate or 

 sodium sulphate to saturation. Unlike the globulins, they cannot 

 be precipitated from their solutions by saturation with sodium 

 chloride. 



The vitellins proper do not contain phosphorus, as is frequently 

 stated, but in the eggs of birds and fish they are commonly found 

 in combination with lecithins and nucleins, both of which are rich 

 in phosphorus. Like the common albumins and globulins, they 

 contain also sulphur, but in variable amounts. 



THE PROTEIDS. 



The proteids differ from the albumins in being more complex 

 bodies, and consist essentially of an albuminous radicle, which is 

 variously combined with a non-albuminous group. This may be of 

 the nature of a phosphoric acid radicle, or a carbohydrate group, or 

 a pigment. In this manner the nucleins, the glucoproteids, and the 

 hemoglobins result. The nucleo-albumins, further, which also 

 belong to this group, are formed through the union of an albu- 

 minous radicle with a nuclein. 



The Nucleins. The nucleins differ from the true albumins 

 in containing, in addition to carbon, hydrogen, nitrogen, oxygen. 



