60 SCIENCE PROGRESS 



of this globulin which was known as fibrin. In the theory of 

 Lilienfeld, 1 though the existence of thrombin is accepted, the 

 idea that it plays any important part in the process of coagula- 

 tion is denied, and the behaviour of calcium in the process is. 

 regarded as identical with the views suggested by Arthus, 

 for whom fibrin was a calcium compound of fibrinogen or a 

 thrombosin curd. Alexander Schmidt, however, denied the 

 specific action of calcium for either phase of the coagulation 

 process ; its presence in a coagulable fluid only favours the 

 conversion of a zymogen into an enzyme and the formation of 

 fibrin from fibrinogen. He therefore included calcium salts 

 with these substances, which, like strontium, and possibly 

 barium, exert a directly favouring influence on the rate and 

 extent of the coagulation process. 



These conflicting views have been completely explained by 

 Hammarsten, 2 whose researches were directed towards affording 

 a sufficient answer to two questions : 



i. Are salts of lime absolutely necessary in order that fibrin- 

 ferment shall act upon fibrinogen ? 



2. Can the whole coagulation process in its two phases occur 

 in the absence of calcium salts ? 



Hammarsten showed that the total calcium content of blood 

 is in two states. That portion which is in solution can alone 

 be precipitated by oxalate, while another portion, which is 

 probably united in organic combination with the proteins of 

 the plasma, cannot be detached. The non-coagulability of 

 oxalated plasma is therefore a matter related to that fraction 

 of the calcium which can be precipitated. When oxalate-plasma 

 is cooled to o°, Pekelharing had already shown that a granular 

 precipitate gradually separates out ; and in proportion as this 

 occurs, so does oxalate-plasma lose its peculiar property of 

 coagulating on the addition of calcium chloride. It was a 

 logical deduction that this separated material was essential for 

 coagulation, and from the supernatant oxalated plasma Hammar- 

 sten precipitated a calcium-free fibrinogen by lime-free sodium 

 chloride, and found that a calcium-free fibrinogen could be caused 

 to clot on the addition of a calcium-free solution of thrombin. 

 By this experiment it was conclusively proved that the presence 

 of calcium is quite unnecessary^ for the conversion of fibrinogen 



1 See Text-book of Physiology, ed. by Schafer, vol. i. p. 172. 



2 Zeitschrift f. physiol. Chemie, xxii. p. 333, 1896, and ibid, xxviii. 1899 



