APP.] CHEMICAL BASIS OF THE ANIMAL BODY. 723 



Insoluble in distilled water : 



Soluble in NaCl solution 1 per cent Globulins. 



Insoluble 



( Acid- and Alkali- 

 Soluble in HC1 '1 per cent, in the cold 



Insoluble in HC1 '1 per cent, in the cold, but] 



( Fibrin. 

 soluble at 60 



Insoluble in HC1 '1 per cent, at 60 ; soluble in strong acids. 



Soluble in gastric juice Coagulated albumin. 



Insoluble ,, Lardacein. 



Such a classification is however obviously a wholly artificial one, 

 useful for temporary purposes, but in no way illustrating the natural 

 relations of the several members. Nor is a division into 'native' 

 and 'derived' proteids much more satisfactory. It is true that we may 

 thus put together serum- and egg-albumin, with vitellin, myosin. 

 and fibrin, on the one hand; and peptones, coagulated proteids, 

 accl acid- with alkali-albumin, on the other. But in what light are we 

 to consider casein, seeing that though a natural product, it has so many 

 resemblances to alkali-albumin ? Moreover the system of classification 

 must be useless which would place fibrinoplastic globulin and fibrinogen 

 in the same class as fibrin, and yet we can hardly speak of either of the 

 two former bodies as derived proteids. If the view be true that when 

 fibrin is converted into peptone the large molecule of the former is split 

 up, with assumption of water, into two smaller molecules of the latter, 

 one belonging to the 'anti' and the other to the 'hemi' group, we might 

 speculate on a possible classification of all proteids into hemi-proteids, 

 anti-proteids and holo-proteids. Thus serum- and egg-albumin, myosin, 

 and fibrin would be undoubtedly holo-proteids, peptones either anti- or 

 hemi-proteids, and we should have to distinguish probably in the 

 heterogeneous group of derived albumins both anti-, hemi- and holo- 

 proteid members. It is possible, moreover, that fibrinoplastic and 

 fibrinogenous globulin and casein may be natural hemi- or anti-proteids 

 and not holo-proteids. But we have at present no positive knowledge 

 on these points. 



NITROGENOUS NON-CRYSTALLINE BODIES ALLIED TO PROTEIDS. 



These resemble the proteids in many general points, but exhibit 

 among themselves much greater differences than do the proteids. As 

 regards their molecular structure nothing satisfactory is known. Their 

 percentage composition approaches that of the proteids, and like these 

 they yield, under hydrolytic treatment, large quantities of leucin and in 

 some cases tyrosin. They are all amorphous. 



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