CHEMICAL EXAMINATION OF THE BLOOD. 337 



solution with diluted acetic acid. The salts are then removed by 

 dialysis, when the ferment can be precipitated by a suitable addi- 

 tion of acetic acid. 



To test for the fibrin-ferment, Arthus has suggested the use of 

 fluoride-plasma of dogs. In such plasma, as also in the correspond- 

 ing product of horses (Fuld), coagulation cannot be brought about 

 without the ferment; neither the addition of a calcium salt nor at- 

 tempts at activation by treating a portion with alkali and adding it 

 to the rest will succeed. If then coagulation does occur after adding 

 a solution to be tested, we may infer that the fibrin-ferment was 

 present in the latter. 



Fibrin. Fibrin is formed during the spontaneous coagulation of 

 all albuminous solutions which contain fibrinogen, soluble calcium 

 salts, and cellular elements that can give rise to the fibrin-ferment 

 and its kinase. It is most conveniently obtained by whipping 

 freshly-shed blood with a suitable instrument, when the fibrin is 

 deposited as an elastic, stringy material, which may be freed from 

 adhering corpuscles by thorough washing and kneading in running 

 water. Such fibrin, however, is still contaminated with serum- 

 globulin and certain phosphorus-containing substances which have 

 resulted from the decomposition of leucocytes. The serum-globulin 

 may be removed by separate washing and kneading in a 5 per cent, 

 solution of common salt ; but the other products, as well as the re- 

 mains of the corpuscles of the blood, can scarcely be removed. To 

 obtain pure fibrin, therefore, it is necessary to start with filtered 

 plasma or with filtered transudates, which are beaten with a piece 

 of whalebone, after adding a little serum, if the fluid is not sponta- 

 neously coagulable. The resulting material is washed with water, 

 then with a 5 per cent, solution of sodium chloride, and finally ex- 

 tracted with alcohol and ether. 



The fibrin then appears as a white stringy substance, which is 

 somewhat elastic, but is easily rendered brittle on contact with 

 alcohol or on warming the substance in water to a temperature of 

 75 C. It is closely related to the coagulated albumins, and accord- 

 ingly is soluble only with difficulty. It is questionable, moreover, 

 whether solution of the substance can be accomplished without 

 causing its decomposition. If fibrin is thus placed in a 5 to 10 per 

 cent, solution of sodium chloride, or a 6 per cent, solution of sodium 

 nitrate, and kept at a temperature of 40 C., it first swells up and 

 gradually disappears as such. What takes place under those con- 

 ditions is not known. In dilute alkalies and acids it likewise dis- 

 solves. Stronger acids, as also the proteolytic ferments, dissolve the 

 fibrin, but at the same time cause its transformation into acid albu- 

 min and albumoses. In water, alcohol, and ether it is entirely 

 insoluble. 



The elementary analysis of fibrin gives 52.68 parts of carbon, 

 6.83 of hydrogen, 16.41 of nitrogen, 1.1 of sulphur, and 22.48 

 of oxygen. It is to be noted, further, that in addition to these 



22 



