958 PHYSIOLOGY 



SODIUM FLUORIDE PLASMA might be expected to act like oxalate 

 plasma since sodium fluoride is a precipitant of lime salts. This salt 

 has, however, the additional property of causing a certain amount of 

 fixation of the formed elements of the blood as 'well as of the blood- 

 platelets. If it be thoroughly centrifuged so * that the plasma is 

 obtained free from these constituents it will no longer clot with lime 

 salts * nor even with lime salts plus tissue extracts, but will clot 

 readily on addition of thrombin. Although it still contains a certain 

 amount of thrombogen, this is entangled and carried down in the 

 precipitate of calcium fluoride which is produced by the addition of 

 lime salts, so that the thrombokinase has nothing on which to exercise 

 its effect. Sodium fluoride plasma is therefore useful, like magnesium 

 sulphate plasma, as a test for the presence of thrombin. If water be 

 added to the sodium fluoride blood so as to destroy some of the formed 

 elements and liberate their constituents into the plasma, it is possible 

 to produce clotting by the simple addition of lime salts. 



HIRUDIN PLASMA. The action of hirudin is that of an anti- thrombin. 

 It apparently combines with and neutralises fibrin ferment. Hirudin 

 plasma can therefore be made to clot by the addition of fibrin ferment 

 in sufficiently large quantities to combine with all the hirudin present 

 and leave an excess over in the fluid. 



PEPTONE PLASMA presents many difficulties in the explanation 

 of its behaviour. Peptone itself has apparently no influence on the 

 coagulation of the blood. Blood received into peptone solution 

 clots as rapidly as when received into salt solution. On the other hand, 

 if blood be received into peptone blood obtained by the injection of 

 large doses of peptone into the veins of another animal, the mixture 

 does not clot, showing that peptone blood contains some substance 

 which inhibits the processes of coagulation. This ' anticoagulin ' 

 must be produced by the organism itself as a result of the injection 

 of peptone, and evidence has been brought forward by Delezenne and 

 others that the seat of formation of the anticoagulin is in the liver. 

 Whether the anti-substance partakes of the characters of an anti- 

 thrombin or of an antikinase has not yet been definitely ascertained. 

 Peptone plasma can be made to clot by the addition of tissue extracts 

 even in small quantities. It still contains all the fibrin factors since 

 it will clot on simple dilution or on the passage of a current of carbon 

 dioxide. It needs, however, the addition of large quantities of fibrin 

 ferment to bring about coagulation. 



THE TRANSUDATIONS 



The earlier work on the mechanism of coagulation was largely 

 carried out on the fluids obtained from the pericardial or pleural 

 * According to Rettger this statement is incorrect. 



