366 SCIEXCE PROGRESS. 



to the same class of substances/ The other principal new 

 fact that has been discovered is the great importance of 

 calcium salts in the process, though as to the exact way 

 in which these salts exercise their intiuence there is con- 

 siderable diversity of opinion. 



My reason for once more returning to this subject is 

 that within the last few months Hammarsten has broken 

 the silence of twenty years, and once more attacked the 

 problem. In the paper" he has published, one notes again 

 the hand of the master ; there is the same thoroughness and 

 lucidity which were so evident in his older work, though it 

 is interesting to note that experiments in vitro are still 

 exclusively relied on to support his conclusions. The 

 special subject with which he deals is the role played by 

 calcium salts in the production of fibrin from fibrinogen, 

 and his endeavour to settle the differences between rival 

 theories is attended with considerable success. I propose 

 to devote the remainder of this paper to a brief considera- 

 tion of his experiments and their results. 



Thouo^h Hammarsten himself, Green, Rinoer and 

 Sainsburv, Freund and others had noticed the acceleratinor 

 action of salts of lime in promoting coagulation, it w^as not 

 until Arthus discovered that coagulation can be prevented 

 by decalcifying the blood by the addition of an alkaline 

 oxalate, and Pekelharing had followed up this work with 

 new experiments, that the calcium salts were recognised 

 universally as a sine cpia non in the process of blood-clotting. 



There are two possible stages in the process where the 

 favouring action of calcium salts might come in ; one of these 

 is in the genesis of the fibrin-ferment, and the other is in the 

 action of the fibrin-ferment in converting fibrinogen into 

 fibrin. Arthus believes that there is a very close resem- 

 blance between the clotting of milk by rennet, and that of 

 blood by fibrin-ferment. In the curdling of milk by rennet, 

 the first action is the action of the ferment itself producing a 



^ For the identification of fibrin-ferment as a nucleo-proteid see 

 Pekelharing Centralb. f. Physiol., vol. ix., p. 102, 1895 > Halliburton, 

 Journal of Physiol., vol. xviii., p. 314, 1895. 



- Zeitsch. f. Physiol. Chem., vol. xxii., p. 333, 1896. 



