CHANGES IN THE BLOOD. 79 



readily coagulates at 105° F. The precipitate of paraglobulin 

 forms a granular powder, whilst that of fibrinogen adheres to the 

 sides of the vessel as a sticky deposit. 



The theory of Schmidt now seems to be superseded by that of 

 Hammersten, and his researches have led him to conclude that 

 fibrino-plastin is quite unnecessary for coagulation, and that the 

 fibrin is formed from one body, — viz., fibrinogen, which is 

 present in plasma when it has been acted upon by the fibrin 

 ferment, which, however, has not as yet been obtained in the 

 pure state. 



Neither Hammersten nor Schmidt assert that this body is of 

 the nature of a ferment, but they use the term for convenience. 

 It is quite certain that fibrin may be formed, when no fibrino- 

 plastin is present, by the addition of calcic sulphate or casein 

 prepared in a certain way ; but as yet the views of specialists 

 on this subject are by no means settled. Halliburton argues 

 that the ferment supposed to be the determining agent in 

 coagulation is really itself a proteid — in fact cell globulin ; but 

 as several experiments of others seem to show that the salt 

 extract of fibrin can be very completely freed from all proteid 

 matter without any loss of fermentive activity, this ferment can 

 scarcely be a globulin. On the other hand, it might be assumed 

 that the coagulative povv'er is really due to the calcium sulphate 

 (Green), which salt is well known to favour clotting even in 

 very dilute solutions. But finally, as against this latter sup- 

 position, remains the fact that in solutions of the fibrin ferment 

 which have been most carefully freed from everything giving 

 proteid reactions, and also carefully freed from saline matters 

 by dialysis, the power of inducing coagulation only becomes lost 

 after heating to about 154° F., a condition that could by no 

 means influence calcium sulphate, even if traces of it were 

 present. Buchanan in 1831, Mantegazza in 1871, and Schmidt a 

 year later, had all suspected that the white cells were the 

 source of a ferment connected with coagulation. 



Among several recent methods of separating the ferment, 

 perhaps the best is the prolonged action of strong alcohol — 

 fifteen times the volume of the serum used — for two weeks or 

 more. Subsequent filtering, drying and powdering the precipi- 

 tate, and dissolving it in distilled water to twice the original 

 volume of the serum, gives an extract with which coagulating 

 experiments can be made. 



