THE CHEMICAL CONSTITUTION OF THE 

 PROTEINS. 



PART I. 

 INTRODUCTION. 



THE proteins, of which we know some forty or fifty natural ones 

 occurring in both animals and plants, are divided according to their 

 origin, solubility, coagulability on heating and other physical char- 

 acteristics into the following groups : 



I. Protamines, e.g., salmine, sturine, clupeine, scombrine, cyclop- 



terine, cyprinine. 



II. Histones, e.g., thymus histone, Lota histone, Gadus histone, 

 histone from blood corpuscles. 



III. Albumins, e.g. y ovalbumin, conalbumin, serum albumin, various 



vegetable albumins. 



IV. Globulins, e.g., serum globulin, fibrinogen and its derivative 



fibrin, myosinogen and its derivative myosin occurring in 

 the muscles of animals ; legumin, conglutin, amandin occur- 

 ring in plants, and some crystalline vegetable globulins, e.g., 

 edestin, excelsin. 

 V. Glutelins, e.g., glutenin in wheat, oryzenin in rice, soluble in 



very dilute alkali. 

 VI. Gliadins, e.g., wheat-gliadin, hordein, zein, occurring in cereals 



and soluble in 70-80 per cent, alcohol. 

 VII. Phosphoproteins, e.g., caseinogen, vitellin, ichthulin. 

 VIII. Scleroproteins, e.g., keratin from hair, horn, feathers, egg- 

 membrane. Collagen, gelatin, elastin. Silk-fibroin, silk- 

 gelatin. 

 IX. Conjugated Proteins : 



(a) Nucleoproteins : nucleic acid in combination with protein, 



generally I., II., III. 



(b) Chromoproteins : chromogenic substance in combination 



with protein, e.g., haemoglobin. 



PT. I. I 



