FIBRIN FORMATION. 249 



the body, tine granular threads of fibrin seem to start from the 

 white cells, and radiate from them in a stellate manner. 



Alex. Schmidt believes that a great number of white blood 

 cells undergo chemical disintegration the instant the blood is 

 shed, and he considers that the fibrin ferment, and probably other 

 fibrin generators, are the result of the destruction of these weak 

 cells ; and he excludes the red corpuscles from taking any share 

 in the process. 



However, there is good evidence that the plasma and the disks 

 can give rise to all the fibrin factors, and we know that in the 

 circulation white cells must be destroyed and yet cause no coag- 

 ulation. 



Moreover, if some blood be allowed to flow into a fine capillary 

 tube, the white cells can be seen to move away from the red disks, 

 and the formation of the clot a delicate fibrin network inclosing 

 the disks may be watched. Here the white cells exhibit mani- 

 festations of life for a considerable time after the clot has been 

 formed, and their death could not have been the source of the 

 fibrin factors. 



In conclusion, then, we can only suppose that as in other tissues 

 some chemical changes must go on in the elements of the blood. 

 These changes give rise to new products which may produce 

 fibrin, and hence cause coagulation. But so long as the elements 

 of the blood are frequently brought into close relationship with a 

 healthy vessel wall, the fibrin factors are either produced in 

 such small quantity as to be ineffectual, or they are altered, 

 destroyed, or taken up by the intima and possibly utilized for its 

 nutrition. When the blood is removed from the vessels, the pro- 

 duction of the fibrin factors proceeds effectually, either on account 

 of the blood elements undergoing destructive changes, and accu- 

 mulating the products fibrin generators ; or owing to the im- 

 possibility of re-integration, the fibrin factors suddenly appear as 

 a product of lethal chemical change or decomposition. 



In accepting the first view, we only adopt the theory of John 

 Hunter, who thought coagulation was an act of life. If we adopt 

 the other view, we must needs say it is an act of death. But, 



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