18 ORGANISED FLUIDS. 



well defined; in the second, soft, and diffluent.* To this sub- 

 ject we shall have occasion again to refer, more at length. 



Fibrin, if left at rest for a time, undergoes a softening 

 process, and breaks up into an extremely minute granular 

 substance. This softening of the fibrin has been improperly 

 confounded with suppuration ; the softened mass, however, 

 may be distinguished from true pus by the almost complete 

 absence of pus globules. This peculiar change in the con- 

 dition of the fibrin has been noticed to occur both in blood 

 contained within and without the body, and large softened 

 clots of it are not unfrequently encountered in the heart 

 after death. The process always commences in the centre 

 of these clots. 



Formation of the Buffy Coat of the Blood. 



Surmounting the coloured portion of the clot is observed, 

 in blood taken from the system in inflammatory states, a 

 yellowish green stratum : this constitutes the buffy or 

 inflammatory crust, the presence of which was deemed of 

 so much importance by the ancient physician, and which is 

 indeed not without its pathological value. This crust con~ 

 sists of fibrin deprived of the red globules of the blood ; and 

 its mode of formation is thus easily and satisfactorily ex- 

 plained. Of the constituents of the blood, the red globules 

 are the heaviest: now, supposing that no solidification of 

 any one element were to take place, these, of course, would 

 always be found occupying the lowest position in the contain- 

 ing vessel ; the fibrin would take the second rank, and the 

 serum the third : but such, under ordinary circumstances, not 

 being the case, and the fibrin coagulating so speedily, the 

 globules become entangled in its meshes before they have 

 had sufficient time given them to enable them to obey fully 

 the impulse derived from their greater specific gravity ; and 

 thus no crust is formed. In blood drawn in inflammations, 



* It is to be remarked, that the clot is not of equal density throughout, 

 but that its lower portion is invariably softer than the upper, and this is 

 accounted for by the fact of its containing less fibrin. 



