FERMENTATION 201 



liquid. Tear the filter containing the fibrinogen 

 into small pieces. Dissolve the fibrinogen which 

 sticks to the filter as a tough, elastic mass, in a 

 quantity of 8 per cent sodium chloride solu- 

 tion equal to about one-third the quantity of the 

 magnesium sulphate solution originally taken. 

 Filter off the fragments of paper. Purify by 

 reprecipitation with an equal volume of saturated 

 solution of sodium chloride. Filter. Dry as 

 before, and add a small quantity of water to the 

 finely divided filter to which the precipitate 

 clings. This water will take a small quantity of 

 salt from the precipitate, and in this dilute saline 

 solution the fibrinogen will dissolve. 1 



Precipitation of Fibrinogen by Fibrin Ferment. 

 Add to the dilute saline solution of fibrinogen a 

 solution containing fibrin ferment. 



Fibrin will gradually form. 



AMMONIACAL FERMENTATION OF UREA BY 



UREASE 



1. Place 100 c.c. fresh human urine in each 

 of three clean flasks marked A, B, G. To B and 

 C add 1 c.c. of urine that has become ammoniacal 

 upon standing in the atmospheric air. Add also 



1 Hammarsten : Archiv fiir die gesammte Physiologic, 1879, 

 xix, p. 563. Also idem, 1880, xxii, p. 431. Hammarsten's first 

 publication was in Nova acta regia societas scientiarum Upsali- 

 ensis, 1878, (3), ix. 



