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COAGULATION OF THE BLOOD. 317
According to Pekelhalixg ’
thrombin is the lime compound of
prothrombin, and the process of coagulation consists, according to him,
in the thrombin transferring the lime to the fibrinogen, which is thereby
converted into an insoluble lime compound, fibrin. Among the objec-
tions to this theory can be mentioned, the fact that fibrin has not
been obtained absolutely free from lime, but still so poor in lime
(Hammarsten 2
) that if the lime belongs to the fibrin, its molecule
must be more than ten times greater than the haemoglobin molecule,
which is not probable. These as well as many other observations
indicate that the lime is carried down by the fibrinogen only as a
contamination.
If, as it seems, the lime is not of importance in the transformation
of fibrinogen into fibrin in the presence of thrombin, still this does not
contradict the above-mentioned observations of Arthus and Pages that
the lime salts are necessary for coagulation of blood and plasma. It
is very probable that the lime salts, as admitted by Pekelharing, are
a requisite for the transformation of prothrombin into thrombin.
If we attempt to summarize the more or less contradictory investi-
gations and views as given in the preceding pages, we can consider the
following facts as conclusive: In the first place, two bodies, the fibrin-
ogen and the thrombin, are necessary for the coagulation. The fibrinogen
exists preformed in the plasma. The thrombin, on the contrary, does
not occur in living blood, at least not in appreciable amounts as such,
but is formed from another substance, the prothrombin. The presence
of calcium salts is necessary for the formation of this thrombin, while
the calcium salts are not necessary for the enzymotic transformation
of fibrinogen into fibrin. Besides the calcium salts also other substances,
the zymoplastic active substances, are active in the formation of thrombin
from its mother-substance, and these zymoplastic substances stand in
some relation to the form-elements of the blood.
The formation of thrombin and the relation of the form-elements
therewith are still unexplained and disputed questions.
It is a question whether the mother-substance of thrombin exists in
the plasma of the circulating blood or whether it is a body eliminated
from the form-elements before coagulation. We have two opposing
views on this question, namely, those of Alex. Schmidt and of Pekel-
haring. According to Schmidt prothrombin occurs preformed in the
circulating plasma, and it is transformed into thrombin by the zymo-
plastic substances which pass out from the form-elements. Pekel-
haring, on the contrary, holds the view that the plasma does not contain
1
See footnote 4, p. 256, and especially Virchow’s Festschrift, 1, 1891.
2
Zeitschr. f. physiol Chem., 28.
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