THROMBOSIS. 225 



immediately after coagulation has taken place, when it still exhibits 

 the dark-red colour and jelly-like consistency of a recent clot. It 

 continues to contract from day to day till it shrinks up entirely, 

 and after the lapse of a few months disappears, leaving not a 

 trace of its former presence behind. This continuous decrease in size 

 is associated with a decolorisation and condensation of its substance; 

 it loses its original dark-red hue, until at length it comes to be 

 only a shade redder than the wall of the vessel which contains it ; 

 it grows drier and more tough ; whereas originally it lay loosely 

 upon the walls of the vessel, at a later period it blends with 

 them, assuming the character of a little plug of connective 

 tissue, which seems rather to belong to the surrounding con- 

 nective tissue and the wall of the vessel than to the blood. The 

 progress of these alterations as seen by the unaided eye is eluci- 

 dated by the microscope as follows : 



§ 191. I have already said that in the recent non-laminated 

 thrombus the colourless corpuscles are distributed among the 

 red ones at tolerably uniform intervals. It used formerly to be 

 supposed that all further changes started from these colourless 

 elements. At the present day, the organisation of clots, in com- 

 mon with many other morbid processes, is explained by the 

 activity of migratory corpuscles. Artificial thrombi have been 

 produced by tying arteries in the lower animals ; cinnabar has 

 then been injected into the blood, and its leucocytes impregnated 

 with this finely-granular material, which is easily recognisable 

 under the microscope. It was found that those cells from which, 

 on the second or third day after the occurrence of coagulation, 

 the organising process appeared to set out, contained cinnabar ; 

 the inevitable inference being that they had migrated into the 

 clot from without. These cells then put forth processes in 

 various directions which meet one another and unite to form a 

 delicate protoplasmic network with nuclei in its nodal points 

 (fig. 71, h.) Even at this stage the structure of the clot might 

 be compared to that of a connective substance ; its corpuscular 

 elements being represented by the leucocytes, and its inter- 

 cellular substance by the mass of red blood-corpuscles and the 

 fibrin. And this, if the phrase may be allowed, is the fundamental 

 idea which underlies the whole organising process and which 

 tends forthwith to realise itself. 



Shortly after this primary differentiation has taken place, the 



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