22 SOURCES OF THE FIBRIN FACTORS. [BOOK i. 



the blood-vessels and the blood is maintained, coagulation does not 

 take place ; but when this relation is disturbed by the more or 

 less gradual death of blood-vessels, or by their more sudden disease 

 or injury, or by the presence of a foreign body, coagulation sets in. 

 Two additional points may here be noticed. 1. Stagnation of 

 blood favours coagulation within the blood-vessels, apparently 

 because the blood-vessels, like other tissues, demand a renewal 

 of the blood on which they depend for the maintenance of their 

 vital powers. 2. The influence of surface is seen even in the 

 coagulation within the vessels. In cases of coagulation from 

 gradual death of the blood-vessels, as in the case of an excised 

 jugular vein, the fibrin, when its deposition is sufficiently slow, is 

 seen to appear first at the sides, and from thence gradually, 

 frequently in layers, to make its way to the centre. So in 

 aneurism, the deposit of fibrin is frequently laminated. In cases 

 where coagulation results from disease of the lining membrane, the 

 rougher the interior, the more speedy and complete the clotting. 

 So also a rough foreign body, presenting a large number of surfaces 

 and points of attachment, more readily produces a clot when intro- 

 duced into the living blood-vessels than a perfectly smooth one. 



We may perhaps go a step further, for there are certain weighty 

 reasons for believing that in normal circulating blood all the fibrin- 

 factors are not present in the plasma, and that a disturbance of the 

 equilibrium between the blooid and the blood-vessels gives rise to 

 coagulation by inducing changes in certain corpuscles, either the 

 ordinary white corpuscles or corpuscles of a special kind, whereby 

 one or more of the fibrin-factors are discharged into the plasma. 



1. When blood is received direct from the blood-vessels into 

 alcohol, the aqueous extract of the precipitate contains little or no 

 fibrin-ferment. If the blood be allowed to stand a little while before 

 being thrown into alcohol some ferment makes its appearance ; and 

 the longer, up to clotting, that the blood stands before being treated 

 with alcohol, the more efficacious is the aqueous extract of the 

 precipitate. Fibrin-ferment therefore seems to make its appearance 

 in blood after being shed. 



2. When blood, kept from clotting by exposure to cold 

 or through being retained by ligatures in a living blood-vessel, is 

 allowed to stand till the corpuscles have sunk, the upper layers of 

 the plasma, free from both red and white corpuscles, exhibit when 

 removed very little power of coagulation and, upon examination, are 

 found to contain a very small quantity only of fibrin-ferment. 



3. We have reasons for thinking that when blood is shed, 

 certain number of corpuscles, which we may speak of as 



w -f j^hite corpuscles, leaving it for the present uncertain whether 

 J.<sthey are to be regarded as a special kind of corpuscles or not, 

 are broken- up and disappear. 



Putting these facts together we are led to think that normal 

 plasma circulating in the normal blood-vessels contains 



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