880 APPENDIX. 



Soluble in distilled water 



Aqueous solution not coagulated on boiling Peptones. 



Aqueous solution coagulated on boiling ...... Albumins. 



Insoluble in distilled water : 



Soluble in NaCl solution 1 per cent Globulins. 



Soluble in HC1 0. 1 per cent, in the cold | Acid- and Alkali- 



Insoluble in NaCl solution 1 per cent. . j albumin. 



Insoluble in HC1 0. 1 per cent, in the cold, but soluble ) 77- 7 



at60q \ Fllrm - 



Insoluble in HC1 0. 1 per cent, at 60 C. ; soluble in strong acids. 



Soluble in gastric juice Coagulated albumin. 



Insoluble Lardacein. 



Such a classification is, however, obviously a wholly artificial one, useful for tem- 

 porary 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 pro- 

 teids, and 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. 



[ENZYMES. 



Enzymes are unorganized soluble ferments, such as ptyalin, p'epsin, trypsin, 

 amylopsin, rerinin, fibrin-ferment, etc., and have been considered in various parts 

 of this work.] 



NITROGENOUS NON-CRYSTALLINE BODIES ALLIED TO PROTEIDS. 



These resemble the proteids in many general points, but exhibit among them- 

 selves 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 hydrotytic treatment, large 

 quantities of leucin and in some cases tyrosin. They are all amorphous. 



Mucin. (0,35.75. H, 6.81. N, 8.50. C, 48.94. )' 



The characteristic component of mucus. Its exact composition is not yet known, 

 the figures given above being merely an approximation. 



As occurring in the normal condition it gives to the fluids which contain it the 

 well-known ropy consistency, and can be precipitated from these by acetic acid, 

 alcohol, alum, and mineral acids ; the latter, if in excess, redissolve the pre- 

 cipitate, but this is not the case with acetic acid. In its precipitated form it is 

 insoluble in water, but swells up strongly in it, and this effect is increased by the 

 presence of many alkali salts. Alkalies and alkaline earths dissolve it readily. 

 Its solutions do not dialyse ; they give the proteid reactions with Millon's 

 reagent and nitric acid, but not that with sulphate of copper, and are precipitated 

 by basic lead acetate only when neutral or faintly alkaline. According to Eichwald, 2 



i Eichwald, Ann. d. Chem. u. Pharm., Bd. cxxxiv. S. 198. *Op. cit. 



