320 THE BLOOD. 



ently obtained by whipping freshly shed blood with a suitable instru- 

 ment, 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 con- 

 taminated 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 knead- 

 ing in a 5 per cent, solution of common salt ; but the other products, 

 as well as the remains 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 spontaneously coagulable. The resulting material is washed 

 with water, then with a 5 per cent, solution of sodium chloride, and 

 finally extracted with alcohol and ether. 



The fibrin then appears as a w r hite 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 ac- 

 cordingly is soluble only with difficulty. It is questionable, more- 

 over, 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. In its place two globulins or related 

 substances are then said to be found. This transformation, accord- 

 ing to some observers, is referable to adherent bacterial enzymes. 

 In dilute alkalies and acids it likewise dissolves. Stronger acids, 

 as also the proteolytic ferments, dissolve the fibrin, but at the 

 same time cause its transformation into acid albumin 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 

 elements calcium is constantly present, and, as has been seen, its 

 formation is largely dependent upon the presence of a soluble 

 calcium salt. 



According to Lilienfeld, the fibrin is not formed directly during 

 the decomposition of fibrinogen, but in its stead we obtain another 

 substance, thrombosis, which as an alkali compound is soluble in 

 water, but immediately combines with calcium, and then separates 

 out as calcium thrombosin or insoluble fibrin. Tin's idea, however, 

 is not generally accepted, and it is thought to be more likely, as 

 Pekelharing suggests, that the calcium merely transforms the pro- 

 enzyme into the fibrin ferment proper, and is then mechanically 

 carried down during the separation of the fibrin. 



The amount of fibrin which may be obtained from the blood, not- 

 withstanding its bulk, does not exceed 0.1-0.4 per cent. 



