FIBRIN FORMATION. 255 



cells, the firmer the clot. In pathological exudations, also, and 

 those acute serous collections which coagulate on removal from 

 the body, fine 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, de- 

 stroyed, 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 ac- 

 count of the blood elements undergoing destructive changes, and 

 accumulating the products fibrin generators ; or owing to the 

 impossibility of reintegration, 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 



