246 THE BLOOD. 



Fibrinogen may be easily separated from the salt-plasma or oxalate- 

 plasmaby precipitation with an equal volume of a saturated NaCl solution. 

 It must be observed that the oxalate-plasma can only be employed 

 after the precipitate, containing proenzymes, and produced by exposure 

 to cold, has settled and been filtered off. If this is not done then the 

 fibrinogen is always impure. A neutralization of the plasma is not 

 necessary, and is not to be recommended. For further purification 

 the precipitate is pressed, redissolved in an 8-per cent salt solution, the 

 nitrate precipitated by a saturated salt solution as above, and after 

 being treated in this way three times, the precipitate at last obtained 

 is pressed between filter-paper and finely divided in water. The fibrinogen 

 dissolves with the aid of the small amount of NaCl contained in itself, 

 and the solution may be made salt-free by dialysis with very faintly 

 alkaline water. The fibrinogen can be nearly freed from fibrin-globulin f 

 which will be spoken of later, by precipitating with double the volume 

 of saturated sodium-fluoride solution, redissolving in water with 0.05- 

 per cent ammonia, and then neutralizing this solution, treated with 

 NaCl, and repeating this several times. Fibrinogen may also, accord- 

 ing to REYE, 1 be prepared by fractionally precipitating the plasma with a 

 saturated solution of ammonium sulphate. We have no knowledge as to 

 the purity of the fibrinogen so prepared. From transudates we ordi- 

 narily obtain a fibrinogen which is strongly contaminated with lecithin 

 and which can hardly be purified without decomposing it. The methods 

 for the detection and quantitative estimation of fibrinogen in a liquid were 

 formerly based on its property of yielding fibrin on the addition of a little 

 blood, of serum, or of fibrin ferment. REYE has suggested the fractional 

 precipitation with ammonium sulphate as a quantitative method. The 

 value of this method has not been sufficiently tested. 



Fibrinogen stands in close relation to its transformation product, 

 fibrin. 



Fibrin is the name of that protein body which separates on the so- 

 called spontaneous coagulation of blood, lymph, and transudates as well 

 as in the coagulation of a fibrinogen solution after the addition of serum 

 or fibrin ferment (see below). 



If the blood is beaten during coagulation, the fibrin separates in 

 elastic, fibrous masses. The fibrin of the blood-clot may be beaten to 

 small, less elastic, and not particularly fibrous, lumps. The typical 

 fibrous and elastic white fibrin, after washing, stands, in regard to its 

 solubility, close to the coagulated proteins. It is insoluble in water, 

 alcohol, or ether. It expands in hydrochloric acid of 1 p. m., as also in 

 caustic potash or soda of 1 p. m., to a gelatinous mass, which dissolves at 

 the ordinary temperature only after several days ; but at the temperature 

 of the body it dissolves more readily, although still slowly. Fibrin may 

 be dissolved by dilute salt solutions after a long time at the ordinary tem- 



1 W. Reye, Ueber Nachweis und Bestimmung des Fibrinogens, Inaug.-Diss. Strass- 

 burg, 1898. 



