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256 THE BLOOD.
of fibrin (Dastre). The blood constituents that are active in fibrinolysis
are still unknown, but they are without doubt of enzymotic nature.
It must be mentioned that a strong fibrinolysis takes place in blood
after acute phosphorus poisoning (Jacoby and others), after extirpation
of the liver (Nolf), and also when the coagulability of the blood has been
reduced by the injection of proteoses (Nolf, Rulot 1
).
A pure fibrinogen solution may be kept at the ordinary temperature
until putrefaction begins without showing a trace of fibrin coagula-
tion. But if to this solution is added a water-washed fibrin-clot or a
little blood-serum, it immediately coagulates, and may yield a perfect
typical fibrin. The transformation of the fibrinogen into fibrin requires
the presence of another body contained in the blood-clot and in the serum.
This body, whose importance in the coagulation of fibrin was first observed
by Buchanan 2
, was later rediscovered by Alexander Schmidt,3
and
designated as fibrin ferment or thrombin. The nature of this enzymotic
body has not been ascertained with certainty. Even after careful
purification it gives very faint protein reactions and it is a much disputed
question whether it is a globulin or a nucleoprotein. It is a fact that
powerfully active solutions of thrombin can be obtained that do
not give either the reactions for globulins or nucleoproteins. Fibrin fer-
ment is produced, according to Pekelharing,4
by the influence of soluble
calcium salts on a preformed zymogen existing in the non-coagulated
plasma. Schmidt admits the presence of such a mother-substance
of the fibrin ferment in the blood, and calls it prothrombin. The con-
version of this mother-substance into thrombin is a very complicated
process, which will be discussed under the coagulation of the blood.
Thrombin behaves like other enzymes in that the very smallest amount of
it produces an action, and its solution becomes inactive on heating. The
velocity of coagulation is dependent upon the quantity of thrombin,
and indeed a time law has been proposed for the action of thrombin.
According to Fuld the action of thrombin, at least within certain limits,
follows Schutz’s law, and according to Stromberg the thrombin follows
in its action a time law, which at least in the beginning, corresponds to
1
Jacoby, Zeitschr. f. physiol. Chem., 30; Nolf, Arch, intern, de Physiol., 3, 1905;
Rulot, 1. c.
2
London Med. Gazette, 1845, 617. Cit. by Gamgee, Journal of Physiol, 1879.
3
Pfliiger’s Arch., 6; see also Zur Blutlehre, 1892, and Weitere Beitriige zur Blut-
lehre, 1895.
* Pekelharing, Verhandl. d. Kon. Akad. d. Wetensch. te Amsterdam, 1892, Deel 1;
ibid., 1895, and Centralbl. f. Physiol., 9; Wright, Proc. Roy. Irish Acad. (3), 2; The
Lancet, 1892, and On Wooldridge’s Method, etc., British Med. Journal, 1891; Lilien-
feld, Hamatol. Untersuch. Arch. f. (Anat. u.) Physiol., 1892; Ueber Leukocyten und
Blutgerinnung, ibid.; Halliburton and Brodie, Journal of Physiol., 17 and 18; Huis-
kamp, Zeitschr. f. physiol. Chem., 32; Pekelharing and Huiskamp, ibid., 39.
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