THE COAGULATION OF THE BLOOD 59 



that coagulation shall occur in salted plasma. When these 

 are removed by dialysis, coagulation never occurs. He further 

 proved that calcium does not act like a ferment, since it is 

 incapable of coagulating either the fibrinogen in a hydrocele 

 fluid or solutions of this globulin. Salts of strontium in a 

 less degree act like salts of calcium. 



Arthus and Pages l decalcified blood by the addition of 

 1 gramme of potassium oxalate to a litre of dog's blood or by 1*5 

 to 3 grammes of sodium fluoride (Arthus 2 ), or by a strong solu- 

 tion of alkaline soaps. The oxalated plasma clotted simply on 

 the readdition of calcium chloride. Arthus and Pages believed 

 that oxalated plasma contained thrombin, since it could coagulate 

 fibrinogen solutions ; and since, together with other experi- 

 ments, it was shown that the yield of fibrin was characteristically 

 raised or lowered by the calcium content of the plasma, they 

 concluded that calcium played a definite part in the second 

 phase of coagulation, and that fibrin was really a calcium 

 compound of fibrinogen. Pekelharing 3 repeated and extended 

 this work, and showed that although oxalate-plasma does not 

 contain thrombin, it does undoubtedly contain a zymogen or 

 prothrombin, which on being activated by calcium becomes 

 an enzyme — in fact, is thrombin. The zymogen of a salt-plasma 

 can be thrown down together with the globulins, and such a 

 precipitate contains thrombin, while a similar precipitate thrown 

 down from oxalate plasma has no ferment power, but acquires 

 this on the addition of calcium chloride. Therefore the zymogen 

 termed prothrombin becomes thrombin on the addition of 

 calcium, and when once at this stage its activity can be shown 

 to be no longer destroyed by the subsequent addition of an 

 oxalate. Arthus and Pages considered that calcium essentially 

 played its part in the second phase of coagulation ; while 

 Pekelharing demonstrated that during the first phase, when a 

 formation of thrombin takes place, this was effected by salts 

 of lime. In this way the ferment was fully formed from its 

 zymogen stage. In the second phase of coagulation Pekelharing 

 considered that the ferment handed on the lime, so that it was 

 associated with fibrinogen, and thus yielded a calcium compound 



1 Arch, de Physiologie, xxii. p. 739, 1890. 



2 Journ. de Phys. 1901. 



3 Intern. Beitrage f. Virchow's Festschrift, 1891 ; Deutsche vied. Wochenschrift , 

 p. 1133, 1892. 



