2/0 LECTURES ON IMMUNITY 



Schmidt prepared this fibrin-ferment by precipitating blood- 

 serum with 15 to 20 times its volume of alcohol. The 

 precipitate was filtered and dried. This precipitate con- 

 tains a rather large quantity of fibrin-ferment which coagu- 

 lates the fibrin contained in blood-plasma. 



It is possible to prepare solutions of plasma as well as 

 of fibrin-ferment nearly free of calcium ions, by the addi- 

 tion of oxalates or fluorides to the blood. On mixing 

 these two coagulations occur, although there are oxalate 

 ions present in excess. From this experiment it has been 

 concluded that calcium ions are not necessary in the coagu- 

 lation of fibrin. The conclusion is not quite binding, for 

 there are always calcium ^ions present, although in very 

 minute quantity. A more accurate examination of this 

 question would be profitable. On the other hand, it is cer- 

 tain that the ions of calcium, strontium, and barium accel- 

 erate to a high degree the coagulation of fibrin. On the 

 whole, the different salts seem to exert upon the coagula- 

 tion of fibrin an influence similar to that upon milk. 

 The presence of acids is favourable to the plasmatic coagu- 

 lation. 



In the coagulation of plasma (as in that of casein, ac- 

 cording to Hammarsten's investigations) two different 

 phases may be observed, according to the opinion of Bor- 

 det and Gengou. 1 The one, the transformation of the so- 

 called fibrinogen, contained in the plasma, into fibrin, may 

 proceed as the result of the action of the ferment in the 

 absence of calcium salts ; the second process, the coagula- 

 tion, requires the presence of calcium ions. Hence a 

 perfect analogy exists between the coagulations of plasma 

 1 Bordet and Gengou: Ann, de Plnst. Pasttur, 18. 26 (1904). 



