254 THE BLOOD. 



per cent, and on the addition of 3-5 per cent NaCl this solution can be 

 neutralized. The fibrinogen prepared by HUISKAMP in this way retained 

 its typical properties. Fibrinogen differs from the myosin of the muscles, 

 which coagulates at about the same temperature, and from other pro- 

 tein bodies, in the property of being converted into fibrin under certain 

 conditions. Fibrinogen has a strong decomposing action on hydrogen 

 peroxide. It is quickly made insoluble by precipitation with water or 

 with dilute acids. Its specific rotation is (a) D = 52.5 according to 



MlTTELBACH. 1 



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

 plasma by precipitation with an equal volume of a saturated NaCl solu- 

 tion. 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. For further purification the precipitate 

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

 cipitated 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 dialysing with very faintly alkaline water. The 

 fibrinogen can be almost freed from fibrin-globulin, 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, according to RE YE, 2 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. 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 



1 Zcitschr. f. physiol. Chem., 19. 



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

 burg, 1898. 



