CHAP. IV.] THE BLOOD. METHODS OF HESEARCH. 181 



the apparatus is determined when empty. The caoutchouc cap having 

 been momentarily withdrawn, 30 or 40 c.c. of uncoagulated blood are 

 allowed to flow into the beaker ; the cap is replaced and the blood is 

 stirred with the little spatula, until the fibrin has separated. The 

 apparatus is then weighed. This operation being completed, the 

 caoutchouc cap is removed, the beaker filled with distilled water, 

 and the contents stirred by the aid of the spatula which is left in situ. 

 When the fibrin has subsided the red supernatant liquid is decanted. 

 The beaker is then filled up again with a 1 3 per cent, solution of 

 common salt, the contents again stirred and allowed to subside. 

 These operations are repeated until the fibrin is almost colourless ; 

 the beaker is then filled up once or twice with distilled water, 

 the water decanted, and then the fibrin is transferred to a small 

 weighed filter, washed with boiling alcohol, and then dried in the hot- 

 water oven at 100 C., or preferably in the hot-air oven at 110 C.; the 

 filter and its contents are then placed between two, weighed, ground 



FIG. 36. WATCH-GLASSES, WITH CLIP, IN WHICH FILTEKS ARE ALLOWED TO COOL AND 



WEIGHED. 



watch-glasses (Fig. 36) held together by a clip, and weighed. On 

 subtracting the weight of the watch-glasses, clip, and filter-paper from 

 the total weight found, the weight of the fibrin contained in the 

 amount of blood analysed is ascertained. 



Determina- if it be required to determine the amount of fibrin 



iltedBi^T 1 " in blood which has alread y coagulated, the total weight 

 of the blood having been determined by weighing, the 

 whole is thrown upon a filter made of well- washed calico. When 

 the serum has drained through, the filter is tied so as to enclose 

 the clot in a little bag. This is then kneaded between the fingers, 

 whilst a stream of water is allowed to play upon it continuously. 

 After long-continued washing, the whole, or nearly the whole, of the 

 coloured corpuscles having been removed from the clot, the cloth is 

 opened, when it is found to contain filaments of fibrin, which are 

 more or less completely decolorized ; these are collected by means 

 of a pair of forceps, and transferred to a small beaker, washed with 

 weak salt solution, and afterwards with water, and treated as in 

 Hoppe-Seyler's method. 



