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 Pagés! 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’), 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*® 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 ofa 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 Pagés 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, oe 
2 Journ. de Phys. 1g0l. 
3 Intern. Bettrage f. Virchow’s Festschrifi, Re Deutsche med. Wochenschrift, 
p. 1133, 1892. 
