36 PROPERTIES OF FIBRIN. [BOOK I. 



It is in the latter form that fibrin always separates from blood when 

 it is stirred or shaken with foreign matters. When dried, fibrin 

 presents the appearance of a greyish white solid. In order to purify 

 fibrin it is carefully dried at a temperature not exceeding 110C., 

 and is then reduced to powder; the powder is successively and 

 repeatedly treated with water holding hydrochloric acid in solution, 

 with alcohol and with ether. However carefully the process of 

 purification may be carried out, fibrin always retains a small quantity 

 of inorganic salts amounting to about 0*9 in 100 parts. 



Properties Fresh fibrin is an elastic substance, as evidenced by the 

 of Fibrin. wa y j n which se rum is squeezed out of the clot which forms 

 in plasma or blood. 



Fibrin belongs to the group of proteid or albuminous substances, 

 from the majority of which it differs in that once formed it is in- 

 soluble in pure water, though it has not been subjected to the action 

 of heat OF acids or metallic salts. 



Fibrin has the following elementary composition ; C, 52'6 : H, 7'0 : 

 N, 17'4 : S, 1-2 : 0, 21'8. 



Freshly prepared moist fibrin is soluble in a 6 per cent, solution 

 of potassium nitrate, if digested with it for some time at a tempe- 

 rature of 30 or 40. It is similarly soluble in solutions of sodium 

 chloride, and in a 10 per cent, solution of magnesium sulphate. The 

 solutions of fibrin in the neutral salts are coagulated by heating to 

 60 or 65, by the addition of acids and of alcohol, and by the addition 

 of powdered magnesium sulphate. 



Denis asserted that fibrin obtained from arterial blood is not 

 soluble in 10 per cent, solutions of the neutral salts, whilst that 

 obtained by stirring venous blood is soluble in the same solutions. 



When placed in water containing about 5 parts of hydrochloric 

 acid in 1000, moist fibrin swells into a transparent jelly, which does 

 not dissolve. In water containing 1 part of hydrochloric acid per 

 1000, fibrin dissolves in a few hours, at a temperature of 40 C. The 

 fibrin is in this process converted into so-called acid-albumin or 

 syntonin. Solutions of syntonin are not precipitated when they are 

 boiled ; when they are carefully neutralized, the proteid which had 

 been dissolved is thrown down in the form of gelatinous flakes which 

 are insoluble in water, but are readily soluble in dilute solutions of 

 acids, of alkalies and alkaline carbonates. Acetic and phosphoric acids 

 exert a similar action to hydrochloric acid. From the acetic solution 

 of fibrin, potassium ferrocyanide throws down a white precipitate. 



When digested at the temperature of the animal body in dilute 

 solutions of ammonia, or of potassium or sodium hydrate, fibrin 

 dissolves, and the solutions are not coagulated by heat, but are pre- 

 cipitated by mercuric chloride, lead acetate, and copper sulphate. 



Fibrin possesses the power of decomposing solutions of hydric 

 peroxide, H 2 a , which enter into effervescence, owing to the libera- 

 tion of oxygen ; if it be first immersed in a tincture of guaiacum 

 and afterwards in a solution of hydric peroxide or in a mixture of 



