372 SCIENCE PROGRESS. 



fibrin-ferment in shed, that is, in dead or dying, blood had 

 next to be discovered. Here Schmidt and Hammarsten 

 were agreed, and their lead has been followed by the 

 greater number of subsequent investigators, that it was the 

 disintegration of the colourless corpuscles which led to the 

 shedding out of this new material. 



The whole theory so propounded may be put briefly 

 as follows : When the blood is within the blood-vessels, 

 one of the constituents of the plasma, a proteid of the 

 globulin class called fibrinogen, exists in a soluble form. 

 When the blood is shed, the fibrinogen molecule is split up, 

 the comparatively insoluble substance, fibrin, being the 

 principal product of its disintegration. This change is 

 brought about by a special unorganised ferment called the 

 fibrin-ferment, which does not exist in healthy blood 

 contained in healthy blood-vessels, but is one of the products 

 of the disintegration of the white corpuscles that occurs when 

 the blood leaves the blood-vessels or comes into contact with 

 foreign matter. 



Now this was a very good working theory ; it possesses 

 the merit of comparative simplicity, and is in accordance 

 with the experimental evidence which was at the disposal of 

 Schmidt and of Hammarsten. It is the theory which is given 

 as gospel in most of the leading text-books on Physiology. 

 But workers all round are beginning to doubt if it is true, 

 or, at least, if it is the whole truth. There can be no 

 doubt that fibrin-ferment prepared by Schmidt's method 

 does cause coagulation in certain forms of plasma, obtained 

 from the blood by preventing it from coagulating by such 

 means as admixture with neutral salt. The weak point in 

 the theory has always been recognised to be the fact that 

 injection of fibrin-ferment into the circulation of a living 

 animal does not cause intravascular clotting-. Hence it was 

 necessary to tack on to the theory the postscript that the 

 living vessels possess in some way a power either to 

 counteract the action of fibrin-ferment, or to destroy it. 



Looked at from another point of view, too, the theory, 

 after all, only shifts the matter a little farther back, for we 

 have now to ask the cause of the disintegration of the 



