CHEMICAL BASIS OF THE ANIMAL BODY. 



CLASSIFICATION OF THE PnoTEiDs 1 . 

 The following classification is both convenient and concise. 



CLASS I. Native albumins. 



Soluble in distilled water. Solutions coagulated on heating, es- 

 pecially in presence of a dilute (acetic) acid. Not precipitated by 

 carbonates of the alkalis or by sodium chloride, or generally by 

 solutions of neutral salts. 



1. Egg-albumin. Serum-albumins. 



CLASS II. Derived albumins (Albuminates). 



Insoluble in distilled water and in dilute neutral saline solutions ; 

 soluble in acids and alkalis. Solutions not coagulated by boiling. 



1. Acid-albumin. 2. Syntonin. 3. Alkali-albumin. 4. 

 Casein or Native alkali-albumin 3 . 



CLASS III. Globulins. 



Insoluble in distilled water, soluble in dilute saline solutions. 

 Soluble in very dilute acids and alkalis : if the acids and alkalis 

 are strong they are rapidly changed into members of Class II. 

 Readily precipitated by saturating their dilute saline solutions with 

 neutral salts such as sodium chloride or magnesium sulphate. 



1. Crystallin, the globulin of the crystalline lens. 2. Vi- 

 tellin. 3. Paraglobulin or Serum-globulin. 4. Fibrinogen. 5. 

 Myosin. 6. Globin. 



CLASS IV. Fibrins. 



Insoluble in water. Soluble with difficulty in strong acids and 

 alkalis, and undergoing a simultaneous change into members of Class 

 II. Soluble by the prolonged action of moderately strong (10 p.c.) 

 solutions of neutral salts, with simultaneous change into members of 

 Class III. 



CLASS V. Coagulated proteids. 



Products of the action of heat on members of Classes I., III. and IV. 

 or of Class II. when precipitated by neutralisation and heated in sus- 



1 See Hoppe-Seyler, Hdbch. Ed. v. S. 265. Drechsel in Ladenburg's Handwor- 

 terbuch. d. Chem. Bd. in. S. 550. Dauilewski, Arch. d. Sci. phys. et nat. (3) T. 7 

 (1882), Nr. 4. 



2 Casein differs in many respects from the other members of this class, but in its 

 general reactions is more closely allied to them than to the members of any other 

 class. In its ready precipitability by neutral salts it shews some affinity to the 

 globulins. 



