1 8 HUMAN PHYSIOLOGY. 



GLOBULINS. 



The members of this group are insoluble in water and in saturated solu- 

 tions of sodium chlorid and magnesium sulphate and ammonium sulphate. 

 They are soluble, however, in dilute saline solutions e. g., sodium chlorid 

 (one per cent.), potassium chlorid, ammonium chlorid, etc. They are coag- 

 ulated by heat. 



(a) Serum-globulin or Paraglobulin. This protein, as its name 

 implies, is found in blood-serum, though it is present in other animal 

 fluids. When precipitated by magnesium sulphate or carbon dioxid, 

 it presents itself as a flocculent substance, insoluble in water, soluble 

 in dilute acids and alkalies, and coagulating at 75 C. 

 (6) Fibrinogen. This protein is found in blood plasma in association 

 with serum-globulin and serum-albumin. It is also present in lymph- 

 tissue fluids and in pathologic transudates. It can be obtained from 

 blood-plasma which has been previously treated with magnesium 

 sulphate on the addition of a saturated solution of sodium chlorid. 

 It is soluble in dilute acids and alkalies, and coagulates at 56 C. 



(c) Myosinogen or Myogen. This protein is a constituent of the 

 protoplasm of the muscle-fibers. During the living condition it is 

 liquid, but after death it readily undergoes decomposition into an 

 insoluble portion known as myogen fibrin. It is soluble in dilute 

 hydrochloric acid and dilute alkalies. It coagulates at 56 C. 



(d) Globin. This is a product of the spontaneous decomposition of 

 the coloring matter of the blood hemoglobin and arises when the 

 latter is exposed to the air. 



(e) Crystallin or Globulin. This is obtained by passing a stream of 

 CO 2 through a watery extract of the crystalline lens. 



DERIVED ALBUMINS OR ALBUMINATES. 



The proteins of this group are derived from both native albumins and 

 globulins by the gradual action of dilute acids and alkalies, and may be 

 regarded as compounds of a protein with an acid or an alkali. 



(a) Acid-albumin. This is formed when a native albumin is digested 

 with dilute hydrochloric acid (0.2 per cent.) or dilute sulphuric acid 

 for some minutes. It is precipitated by neutralization with sodium 

 hydroxid (o.i per cent, solution). After the precipitate is washed, 

 it is found to be insoluble in distilled water and in neutral saline solu- 

 tions. In acid solutions it is not coagulated by heat. 

 (6) Alkali-albumin. This is formed when a native albumin is treated 

 with a dilute alkali e. g., o.i per cent, of sodium hydroxid for five 



