THE DERIVED ALBUMINS. 59 



THE DERIVED ALBUMINS. 



Fibrin. Fibrin occupies a unique position among the albumins. 

 So far as its general chemical composition goes, it is unquestionably 

 closely related to the albumins proper. It contains carbon, hydro- 

 gen, nitrogen, oxygen, and sulphur in very much the same propor- 

 tion as the true albumins, and, like these, yields the usual decomposi- 

 tion-products on hydrolysis. On the other hand, fibrin is insoluble 

 in the common solvents of the true albumins, viz., in water and 

 neutral saline solutions, while acids and alkalies cause its solution, 

 but at the same time also its denaturization with the formation of 

 acid albumin or alkaline albuminate. In this respect fibrin is closely 

 related to the coagulated albumins. It merits its place among the 

 derived albumins by reason of its being itself a derivative of a true 

 albumin, namely, fibrinogen. (Its relation to this and its rdle in the 

 coagulation of the blood will be considered in a future chapter.) 



The Coagulated Albumins. The coagulated albumins result 

 from the albumins proper through the influence of heat, prolonged ex- 

 posure to strong alcohol, especially in the presence of a neutral salt, 

 and in the case of fibrin at least, which, as we have just seen, is 

 closely related to this group, through the activity of a specific fer- 

 ment. They differ from the true albumins in their extreme resist- 

 ance to all neutral solvents, and also to dilute acids and alkalies. 

 Stronger acids and alkalies cause their dissolution, with the simul- 

 taneous formation of acid albumins or alkaline albuminates. 



The Albuminates. The albuminates, as has been pointed out, 

 result from the native albumins after their denaturization by acids 

 and alkalies. Aside from their quantitative composition, they differ 

 from each other only in so far as they have resulted through the 

 action of an acid or an alkali. The alkaline albuminates thus con- 

 tain less sulphur and less nitrogen than the acid albumins, as a 

 portion of the sulphur and the so-called ammo-nitrogen have been 

 split off. Both the acid albumins and the alkaline albuminates are 

 insoluble in neutral solvents, and are therefore precipitated from 

 their solutions on neutralization. They are soluble, on the other 

 hand, in solutions of the alkaline hydrates, in dilute solutions of 

 sodium carbonate, in hydrochloric acid, and with a little more diffi- 

 culty in strong acetic acid. From their acid solutions they are pre- 

 cipitated by salting with ammonium sulphate or sodium chloride. 

 Through the action of an alkali acid albumin can be transformed into 

 alkaline albuminate, but it is, of course, manifest that the reverse 

 cannot occur. In the living body the denaturization of all albumins is 

 effected during the process of digestion, and invariably precedes the 

 formation of albumoses and peptones. 



The Albumoses. The albumoses result from the albumins 

 proper, and also from the albuminoids and the albuminous radicles 

 of the proteids, through the action of the so-called proteolytic fer- 

 ments, or during their hydrolytic decomposition by means of acids 



