10 PROTEIDS. 



1. Crystallin, the globulin of the crystalline lens. 2. Vitellin. 

 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 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, are in general 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 precipitated 

 but not coagulated by even the prolonged action of alcohol. Pep- 

 tones are readily diffusible, albumoses less so. Some of the albu- 

 moses 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 precipi- 

 tates they yield with nitric acid and with ferrocyanide of po- 

 tassium in presence of acetic acid disappear when warmed and 

 reappear on cooling. 



CLASS VII. Lardacein or amyloid substance. 



Insoluble in water, dilute acids and alkalis, and saline solu- 

 tions. Converted into members of Class II by strong acids 

 and alkalis. 



1 The albumoses are classed with the peptones partly from their close relationship 

 to these substances and partly for convenience. 



