ALBUMINS OR PROTEINS. 139 



only in the cells, but also in all the fundamental and basic elements, dis- 

 tinctively separates the animal from the vegetable world. As the plants 

 are capable of utilizing the very diverse carbohydrates in building up 

 the various polysaccharides, so the animal organism is able to assimilate 

 the simple proteins (those of milk, for example) for its nourishment, pro- 

 ducing the large number of albuminous substances found in the cells and 

 tissues. The albuminoid and albumoid groups are good illustrations of 

 how the animal organism utilizes the proteins for its varied functions, and 

 how it adjusts the composition to the function. 



We shall now discuss the proteids, or compound proteins. We can 

 do this rather rapidly, because the non-albuminous component of the 

 proteids is the more interesting, and will be considered elsewhere. The 

 large number of nucleoproteids. belong to this group. They are com- 

 posed of albumin and nucleic acid. The former may consist of certain 

 of the protein groups previously mentioned. We are acquainted with 

 compounds of nucleic acids with histons, as well as with protamines. It 

 is an open question as to whether other proteins do not likewise partici- 

 pate in the formation of nucleoproteids. It must be admitted, how- 

 ever, that the very existence of the nucleoproteids has been questioned. 1 

 Nucleic acid has the property of precipitating protein from solution. In 

 preparing the nucleoproteids we only extract the various organs with, 

 for instance, water. On adding acid, generally acetic acid, the nucleo- 

 proteids are precipitated from the extract. We can imagine that the 

 nucleic acid is present in the extract perhaps in the form of its sodium 

 salt, together with the albumin. As a matter of fact, by acidifying, the 

 nucleic acid is freed, which precipitates the soluble albumin. We can, by 

 adding nucleic acid to albuminous substances, obtain precipitates which 

 are very much like nucleoproteids. Nucleoproteids have, however, also 

 been obtained by " salting-out." 2 It is, therefore, very probable that 

 the nucleoproteids are present, as such, in the various organs. 



We do not, at present, know the manner of linking between the nucleic 

 acid and the protein. There are apparently various kinds of combina- 

 tion. For instance, 0.8 per cent of hydrochloric acid is sufficient to 

 separate histon from the nucleo-histon obtained from the thymus gland; 

 on the other hand the pancreas-proteid is decomposed into nuclein and 

 albumin, even in neutral solution on boiling. The composition is not as 

 simple as the name nucleoproteid might indicate. There seems to be more 

 than a mere combination of nucleic acid and protein. If a nucleoproteid 

 is decomposed, we, of course, obtain a protein, for instance histon. The 



1 I. Bang: Z. physiol. Chem. 30, 508 (1900). T. B. Osborne and I. F. Harris: ibid. 

 38, 85 (1902). 



2 F. Malengreau: La Cellule, 17, 339 (1900). W. Huiskamp: Z physiol. Chem. 32, 

 145 (1901) ; 39, 55 (1903). 



