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

  • Landois, Leonard
Date:
1888
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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.

    83/980 page 31
    Coagulation of Plasma.—^Plasma shows phenomena exactly analogous, save that the clot is not so well marked, owing to the absence of the resisting corpuscles ; there is, however, always a soft trembling jelly formed when plasma coagulates. [In Hewson's experiment on the blood of a horse tied in a vein, he found that the plasma coagulated—fibrin being formed, so that he showed coagulation to be due to changes in the plasma itself (§ 29).] Properties of Fibrin.—Although the fibrin appears voluminous, it only occurs to the extent of 0-2 per cent. (01 to 0-3 per cent.) in the blood. The amount varies considerably in two samples of the same blood. It is insoluble in water and ether; alcohol shrivels it by extracting water; dilute hydrochlox-ic acid (0*1 per cent.) causes it to swell up and become clear, and changes it into syntonin or acid- albumin 249, III.). When fresh, it has a greyish-yellow fibrous appearance, and is elastic ; when dried, it is horny, transparent, brittle, and friable. When fresh it dissolves in 6-8 per cent, sohxtious of sodium nitrate or sulphate, in tlihxte alkalies, ami in ammonia, thus forming alkali-albuminate. Heat does not coagulate these solutions. [It is also soluble in, or rather decomposed by, 5-10 per cent, solutions of neutral salts, e.g., NaCl, yielding two fibro-globulins {Green).] Hydric peroxide is rapidly decomposed by fibrin into water and 0 (Tlieaard). Fibrin which has been exposed to the air for a long time is no longer soluble in solution of potassic nitrate, but in neurin {lUauthncr). During putre- faction it passes into solution, albumin being formed. Fibrin contains, entangled in it, ferric, calcic, and magnesic phosphates, and calcium sulphate whose origin is unknown. Time for Coagulation.—The first appearance of a coagulum occurs in man's blood after 3 minutes 45 seconds, in woman's blood after 2 min. 20 sec. {H. iV«m'). Age has no ell'ect; with- drawal of food accelerates coagulation {H. Vierordt), 28. GENERAL PHENOMENA OF COAGULATION.—I. Blood in direct contact with living unaltered blood-vessels does not coagulate. [Hewsou (1772) found that when he tied the jugular vein of a horse in two places, and excised it, the blood did not coagulate for a long time.] Briicke filled the heart of a tortoise with blood which had stood 1-5 minutes exposed to the air at 0, and kept it in a moist chamber ; at 0 C. the blood was still uncoagulated in the contracting heart after eight days. Blood in a contracting frog's heart preserved under mercury does not coagulate. If the wall of the vessel be altered by pathological processes {e.f/., if the intima becomes rough and uneven, or under- goes inflammatory change), coagulation is apt to occur at these places. Blood rapidly coagulates in a de<id heart, or in blood-vessels (but not in cajiillaries) or other canals {e.g., the ureter). If blood stagnates in a living vessel, coagulation begins in the central axis, because here there is no contact with the wall of the living blood-vessel. 11. Conditions which Hinder or Delay Coagulation.—{a) The addition of small quantities of alkalies, ammonia, or concentrated solutions of neutral salts of the alkalies and earths (alkaline chlorides, sulphates, phosphates, nitrates, carbonates). Magnesic sulphate acts most favourably in delaying coagulation (1 vol. solution of 28 per cent, to 3J vols, blood of the horse). (6) Precipitation of the fibrino-plastin by adding weak acids, or CO.^. By the addition of aceiic acid until the reaction is acid, coagulation is coini)letely arrested. A large amount of CO^, delays it, hence venous blood coagulates more slowly than arterial, and the blood of suffocated persons remains fluid for the same reason. {<:) The addition of egg-albumin, syrup, glycerine, and much water. If un- coagulated blood be brought into contact with a layer of already-formed fibrin, coagulation occurs later. {d) By cold (0° C.) coagulation may be delayed for one hour. If blood is frozen at once, after thawing it is still fluid, and then coagulates [Hewson). When shed blood is under high pressure it coagulates slowly. (e) Blood of embryo-fowls does not coagulate before the twelfth or fourteenth day of incubation {Boll); that of the hepatic vein very slightly ; menstrual blood shows
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