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PREVENTION OF COAGULATION. 251
the blood (in the living dog), it does not coagulate on leaving the veins
(Fano, Schmidt-Mulheim 1
). The plasma obtained from such blood
by means of centrifugal force is called peptone-plasma. According to
Arthus and Htjber 2
the caseoses and gelatoses act like fibrin proteose
in dogs. Eel serum and certain lymph-forming extracts of organs
(see Chapter VI) have an analogous action. The coagulation of the
blood of warm-blooded animals is prevented by the injection of an
effusion of the mouth of the officinal leech or a solution of the active
substance of such an infusion, hirudin (Franz), into the blood current
(Haycraft 3
). If the blood is allowed to flow directly, while stirring
it, into a neutral salt solution—best a saturated magnesium-sulphate
solution (1 vol. salt solution and 3 vols, blood) —we obtain a mixture
of blood and salt which remains uncoagulated for several days. The
blood-corpuscles, which, because of their adhesiveness and elasticity,
would otherwise easily pass through the pores of the filter-paper, are
made solid and stiff by the salt, so that they may be easily filtered
off. The plasma thus obtained, which does not coagulate spontaneously,
is called salt-plasma.
An especially good method of preventing coagulation of blood con-
sists in drawing the blood into a dilute solution of potassium oxalate,
so that the mixture contains 0.1 per cent oxalate (Arthus and Paces 4
).
The soluble calcium salts of the blood are precipitated by the oxalate,
and hence the blood loses its coagulability. On the other hand, Horne 5
found that chlorides of calcium, barium, and strontium, when present
in large amounts (2-3 per cent), may prevent coagulation for several
days. According to Arthus 6
a non-coagulable blood-plasma may be
obtained by drawing the blood into a sodium-fluoride solution until it
contains 0.3 per cent NaFl.
On coagulation there separates in the previously fluid blood an insoluble
or a very difficultly soluble protein substance, fibrin. When this separa-
tion takes place without stirring, the blood coagulates in a solid mass,
which, when carefully severed from the sides of the vessel, contracts,
and a clear, generally yellow-colored liquid, the blood-serum, exudes.
The solid coagulum which encloses the blood-corpuscles is called the
blood-clot (placenta sanguinis). If the blood is beaten during coagula-
tion, the fibrin separates in elastic threads or fibrous masses, and the
^ano, Arch f.. (anat. u.) Physiol., 1881; Schmidt-Mulheim, ibid., 1880.
2
Arch, de Physiol. (5), 8.
3
Haycraft, Proc. Physiol. Soc, 1SS4, 13, and Arch. f. exp. Path. u. Pharm., 18;
Franz, Arch. f. exp. Path. u. Pharm., 49.
4
Archives de Physiol. (5), 2, and Compt. Rend., 112.
5
Journ. of Physiol., 19.
6
Journ. de Physiol, et Path., 3 and 4.
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