1176 



PEOTEIDS. 



adheres to the twigs is then washed in a current of water until 

 all the haemoglobin of the entangled corpuscles is removed and 

 it is now quite white. The washing is greatly facilitated if 

 the fibrin is very finely chopped before it is washed, and if it 

 is frequently kneaded and squeezed with the hand during the 

 washing. In this way it may be obtained quite white in a few 

 hours. The washing is also much facilitated if the blood is 

 mixed with an equal bulk of water before it is whipped. It is 

 obvious that fibrin prepared by the above method must be in an 

 extremely impure condition, for it contains a not inconsider- 

 able admixture of the remains of the white corpuscles and the 

 stromata of the red. It can only be prepared pure during the 

 clotting of either filtered or centrifugalized iced-plasma or salt- 

 plasma, or by the action of purified fibrin-ferment on pure fibrin- 

 ogen. In accordance with this, fibrin as ordinarily obtained 

 leaves a variable amount of granular residue Avhich contains 

 phosphorus during its digestion by pepsin. No such residue 

 is observed when fibrin from filtered plasma is digested with 

 pepsin, but in no other essential respect does the one fibrin 

 differ from the other. 



Fibrin, as ordinarily obtained, exhibits a filamentous struc- 

 ture, 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. B}* 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 si in ply 

 whipping blood is insoluble in dilute saline solutions. When 

 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 dis- 

 solved, being converted into members of the globulin class. 

 Most observers agree that the globulin thus chiefly formed 



