A textbook of human physiology / translated from [the] 6th German edition by W. Stirling.

  • Landois, Leonard
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: A textbook of human physiology / translated from [the] 6th German edition by W. Stirling. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    82/980 page 30
    coagulates (owing to the formation of the fibrin), and passes into a trembling jelly. If, however, it be beaten with a glass-rod, the fibrin is obtained as a white stringy mass, adhering to the rod. The quantity of fibrin in a given volume of plasma is very .small (p. 'M), although it varies much in different cases. (B) With Admixture.—Blood flowing from an artery is caught in a tall vessel containing 4th of its volume of a concentrated solution of sodic sulphate {Heivsov) —or in a 25 per cent, solution of magnesic sulphate (1 vol. to -i vols, blood— Simmer)—or 1 vol. blood with 2 vols, of a 4 per cent, solution of monophosphate of potash (Masia). When the blood is mixed with these fluids and put in a cool place, the corpuscles subside, and the clear stratum of plasma mixed with the salt.s may be removed with a pipette. [The plasma so obtained is called salted plasma.] If the salts be removed by dialysis, coagulation occurs ; or it may be caused by the addition of water (Jo/i. Milller). Blood which is mixed with a 4 per cent, solution of common salt does not coagulate, so that it also may be used for the preparation of i)lasma. [For frogs' blood Johannes Miiller used a J- per cent, solution of cane-sugar, which permits the corpuscles to be separated from the plasma by filtration. The plasma mixed with the sugar coagulates in a short time.] 27. FIBRIN—COAGULATION OF THE BLOOD.—General Characters.— Fibrin, is that substance which, becoming solid in shed blood, in plasma and ia lymph causes coagulation of these fluids. In these fluids, w^hen left to themselves, fibrin is formed, consisting of innumerable, excessively delicate, closely-packed, microscopic, doubly refractive fibrils (fig. 7, E). These fibrils entangle the blood- corpuscles as in a spider's web, and form with them a jelly-like solid mass called the blood-clot or placenta sanguinis. At first the clot is very soft, and after the first 2 to 15 minutes a few fibres may be found on its sui'face ; these may be removed with a needle, while the interior of the clot is still fluid. The fibres, ultimately extend throughout the entire mass, which, in this stage, has been called cruor. After from 12 to 15 hours the fibrin contracts, or, at least, shrinks more and more closely round the corpuscles, and a fairly solid, trembling, jelly-like clot, which can be cut with a knife, is formed. During this time the clot takes the shape of the vessel in which the blood coagulates, and expresses from its substance a fluid-—the blood-serum. Fibrin may be obtained by washing away the corpuscles from the clot with a stream of water. Crusta Phlogistica.—If the corpuscles subside very rapidly, and if the blood coagulates slowly, the upper stratum of the clot is not red, but only yellowish, on account of the absence of coloured corpuscles. This is regularly the case in horse's blood, and in human blood it is observed especially in inflammations ; hence this layer has been called crusta phlogistica. Such blood contains more fibrin, and sa coagulates more slowly. The crusta is formed under other circumstances, e.g., with increased sp. gr. of the corpuscles, or diminished sp. gr. of the plasma (us in hydremia and chlorosis), whereby the corpuscles sink more rapidly, and also during pregnancy. The taller and narrower the glass, the thicker is the crusta (compare § 41). The upper end of the clot, where there are few corpuscles, shrinks more, and is therefore smaller than the rest of the clot. This upper, lighter-coloured layer is called the buffy coat ; but it gradually passes both in size and colour into the normal dark- coloured clot. [Sometimes the upper surface of the clot is concave or cupped. The older physicians attached great importance to this condition, and also to the occurrence of the bully coat.] Defibrinated Blood.—If freshly-shed blood be beaten or whipped with a glass- rod, or with a bundle of twigs, fibrin is deposited on the rod or twigs in the form of a solid, fibrous, yellowish-white, elastic mass, and the blood which remains is called dejibrinated blood (p. 29). [The twigs and fibrin must be washed in a stream of water to remove adhering corpuscles.]
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