COAGULATION OF THE BLOOD. 717 



during life, is repaired by corpuscles newly formed in the system. The 

 physiological endowments of these corpuscles, especially of the red 

 ones, are quite peculiar, and are as characteristic as those of any of 

 the structural elements of the solid tissues. With regard to the liquor 

 sanguinis, in which the corpuscles float, it also has vitality, and must 

 be regarded as the liquid, intercellular or internuclear, matrix of a 

 fluid tissue; for it is originally elaborated with the corpuscles, in the 

 interior of conjoined nucleated cells. The vitality of the liquor san- 

 guinis is probably, however, like that of the intra- or inter-cellular 

 parts of the solid tissues, dependent upon its corpuscles, gymnoplasts, 

 or nuclei, which are its real centres of growth; just as the semifluid 

 nervous substance, the somewhat firmer sarcous elements, the areolar 

 fibres, and the yet denser matrix of cartilage, or the solid deposit of 

 osseous tissue, appear to be dependent upon the nuclei proper to those 

 tissues respectively. 



The vitality of the blood is merely a vegetative life, its inherent vital 

 properties being strictly nutritive, and including neither contractility 

 nor sensibility. The fluidity of the liquor sanguinis is an indispensable 

 condition to the life of the whole body, and such vitality as it or the 

 corpuscles possess, must be constantly exercised in the maintenance 

 of that condition. So, reciprocally, the persistence of the vital prop- 

 erties of the blood implies, within certain limits, the maintenance of 

 its peculiar fluid state and chemical constitution. Yet, as we shall 

 immediately see, the remarkable change which takes place in one con- 

 stituent of the liquor sanguinis viz., in the fibrinogen, or fibrin, 

 which, when blood is drawn from the body, solidifies into delicate 

 fibrils, and, entangling the corpuscles, gives rise to the phenomenon 

 known as the coagulation of the blood is, by many eminent physiolo- 

 gists, regarded as a vital act. 



The Coagulation of the Blood. 



This phenomenon, already elsewhere noticed (p. 60), does not con- 

 sist of a solidification of all the elements of the blood, but of that of 

 the fibrin alone, of which, on an average, not above 3 parts exist in 

 1000 of blood. The effects of this change in so small a quantity of 

 fibrin, are very remarkable. A few minutes after blood is drawn from 

 a vein or artery, it appears to set, or stiifen, into a red jelly-like mass 

 or clot; from the surface of this, yellowish transparent drops of fluid 

 very soon exude,* 1 which then run together in little pools ; the red 

 mass slowly shrinks, forces more and more of the transparent fluid 

 from it, becomes more and more solid, and, at the end of from twenty- 

 four to forty- eight hours, constitutes a clot equal in bulk to about one- 

 third of the total volume of the blood, the rest now consisting of the 

 yellow fluid, which is named the serum. This serum contains most of 

 the water, besides the albumen, salts, and extractives of the blood ; 

 whilst the clot, coagulum, or crassamentum, is composed of the fibrin, 

 together with the red and white corpuscles. The clot still contains, 

 however, some serum, and, in order to remove this, it is necessary to 



