CHEMICAL BASIS OF THE ANIMAL BODY. 1167 



CLASS III. Globulins. 



Insoluble in distilled water, soluble in dilute saline solu- 

 tions. 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 mag- 

 nesium 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 mem- 

 bers 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 neutralization 

 and heated in suspension in water. They are also obtained by 

 the prolonged action of alcohol in excess upon members of 

 Classes I., III., and IV. Their solubilities, except in solutions 

 of neutral salts, in which they are insoluble, are in genera] 

 similar to, but less than, those of Class IV. 



CLASS VI. Albumoses and peptones. 



The true peptones are extremely soluble in water. They 

 are not precipitated by acids, alkalis, neutral salts or many of 

 the reagents which precipitate other proteids. They are pre- 

 cipitated but not coagulated by even the prolonged action of 

 alcohol. Peptones are readily diffusible, albumoses less so. 

 Some of the albumoses are readily soluble in water, some are 

 less soluble. They are distinguished from peptones by being 

 precipitated when their solutions are saturated with neutral 

 ammonium sulphate. They yield precipitates with many of the 

 reagents which precipitate other proteids, and it is specially 

 characteristic that the precipitates they yield with nitric acid 

 and with ferrocyanide of potassium in presence of acetic acid 

 disappear when warmed and reappear on cooling. 



