32 PROTEIDS. 



* 



Fibrin, as ordinarily obtained, exhibits a filamentous structure, the 

 component threads possessing an elasticity much greater than that of 

 any other known solid proteid. 



If allowed to form gradually in large masses, the filamentous 

 structure is not so noticeable, and it resembles in this form pure india- 

 rubber. Such lumps of fibrin are capable of being split in any 

 direction, and no definite arrangement of parallel bundles of fibres 

 can be made out. 



Fibrin is insoluble in water and dilute saline solutions. It is also 

 ordinarily insoluble in dilute acids (HC1) if their action takes place at 

 ordinary temperatures and is not prolonged, merely becoming swollen 

 and transparent in the acid and returning to its original state if the acid 

 is removed by an excess of water or careful addition of an alkali. By 

 prolonged action at ordinary temperatures, or a shorter action at 40, 

 the fibrin is profoundly changed and certain forerunners of the 

 peptones which may be finally formed (at 40) are produced. It is 

 similarly insoluble in dilute alkalis and ammonia, but passes more 

 readily into solution in these reagents, if their action is prolonged or 

 the temperature is raised, than is the case with dilute acids. The 

 behaviour of fibrin towards solutions of neutral salts is peculiar and 

 important. As already stated, fibrin prepared by simply whipping 

 blood is insoluble in dilute saline solutions. But its solubility is 

 dependent upon the conditions under which it is separated out from 

 the blood. In accordance with this, Denis 1 described three forms of 

 fibrin to which he gave, the names of 1. Fibrine concrete modifiee. 

 2. Fibrine globuline. 3. Fibrine concrete pure. The first is what 

 we now know as ordinary fibrin obtained by whipping arterial blood 

 (human in Denis' work). The second he obtained by the spontaneous 

 clotting of human venous blood, and this readily swells up to a slimy mass 

 in 10 p.c. NaCl. The third he prepared by * whipping ' human venous 

 blood under certain precautions, and found it to be soluble in dilute 

 salt solution by one or two hours' treatment with the same at 40. 

 Quite apart from Hammarsten's partial confirmation of Denis' state- 

 ments there is but little reason for doubting the accuracy of so careful 

 a worker. The possible solubility of fibrin under certain conditions in 

 saline solutions of moderate strength obtained considerable importance 

 in the controversy between Schmidt and Hammarsten as to the nature 

 of the processes involved in the clotting of blood. When on the other 

 hand fibrin is subjected to the prolonged action of more concentrated 

 (10 p.c.) solutions of neutral salts, and the salt solution is frequently 

 renewed, the fibrin may be finally completely dissolved, being converted 



1 For reference see p. 29. 



