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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 Reye,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 Nachweifl und Bestimmung des Fibrinogens, Inaug-Diss. Strass-
burg, 1898.
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