FIBRIN, is a substance contained in the bodies of animals both in a fluid and in a solid state ; in the fluid state it exists in the blood, and in the solid state in muscular fibre, but the fibrin of venous blood differs from that of arterial blood. When separated from the other constituents of the blood, fibrin appears in the form of long white elastic filaments ; it is inodorous, tasteless, and insoluble in water whether cold or hot, but by long-continued boiling a portion is dissolved. When dried at a gentle heat, it loses about four-fifths of its weight, which loss is water, and it becomes then horny and translucent, and very much resembles albumen which has been coagulated. Acetic acid and fresh fibrin, when kept for some hours in contact, form a transparent gelatinous mass which is soluble in water. Solution of potash dissolves fibrin. Its com position is precisely similar to that of coagu lated albumen, and they have several proper ties in common.
That variety of fibrin which constitutes muscular fibre is so interwoven with nerves, vessels, and cellular and adipose tissue, that its properties are probably always more or less modified by foreign matters. To obtain the
fibrin of a muscle, it must be finely minced, and washed in repeated portions of water at 60° or 70° till all colouring and soluble sub stances are withdrawn, and till the residue is colourless, insipid and inodorous. It is then strongly pressed between folds of linen, by which it is rendered semitransparent and pul verulent.
There is also a substance called Vegetable Fibrin, which is obtained from wheat flour by the following process :—Make the flour into a paste, and wash it on a fine sieve with a small stream of water. The gluten of the flour will remain, and a milky liquid will pass through the sieve, which when suffered to rest will in a few hours become clear by depositing the starch bywhich it was rendered turbid. If this clear liquor be boiled, a flocculent precipitate is formed in it, which, when washed, dried, and purified by boiling mther, has the same composition as animal fibrin. When heated, it coagulates, and possesses the properties of coagulated albumen.