THE COAGULATION OF THE BLOOD 223 



thrombin to thrombin is faciUtated by it. It is held, however, that 

 fibrin ferment as such is not present in the tissues. 



Admixture of Neutral Salts. — When present in small amounts, the 

 neutral salts act rather favorably upon coagulation, but tend to retard 

 this process as soon as their quantity surpasses a certain minimum. 

 Thus, a 27 per cent, solution of magnesium sulphate prevents the clot- 

 ting for a long time, if 1 part of it is added to 3 or 4 parts of blood. 

 Sodium sulphate in half-saturated solution manifests a similar action, 

 but it must be mixed with an equal quantity of blood. In all these 

 instances the corpuscles settle very slowly, but their deposition may 

 be hastened by centrifugalization. The supernatant plasma, known 

 as "salted plasma, '^^ may be made to clot later on by diluting it suffi- 

 ciently with water or by the addition of a few drops of a solution of 

 thrombin. If the "salted" blood is left standing for a day before it is 

 centrifugalized, the plasma does not clot. 



Biirker emphasizes the fact that weak solutions of magnesium 

 sulphate tend to preserve the thrombocytes, so that it is possible to 

 obtain them from the supernatant plasma long after the red cells 

 have separated out. The deduction, therefore, seems justified that 

 weak solutions of the neutral salts inhibit the formation of the thrombin, 

 while strong solutions prevent the interaction between this agent and 

 the fibrinogen.^ 



Weak solutions of sodium chlorid do not influence the coagulation, 

 while concentrated solutions of this salt manifest an action similar 

 to that of the salts mentioned previously. Thus, it is possible to 

 prevent the clotting by drawing the blood into an equal volume of 

 a 10 per cent, solution of this salt. Sodium carbonate in concentrated 

 solution and bile salts also retard this process. 



Decalcification of the Blood. — Arthus and Pages^ have shown that 

 the blood from which the calcium has been removed, remains fluid 

 for an indefinite period of time. This end may be attained by col- 

 lecting it in a 0.1 to 0.3 per cent, solution of sodium or ammonium 

 oxalate. It should be remembered, however, that it may be made to 

 clot at any time subsequently by adding a proper amount of a calcium 

 salt to it. Furthermore, it has been shown that the mere presence of 

 dissolved calcium is not sufficient to incite clotting, but that it must be 

 made available in the form of a salt held in an ionized state, for example, 

 as calcium chlorid or sulphate. The oxalated blood may be subjected 

 to centrifugalization, after which the plasma derived from it, may be 

 treated in the same manner as other non-coagulable plasmas. Thus, 

 horse-blood containing 0.1 per cent, sodium oxalate, will yield a 

 perfectly clear, yellowish plasma which displays no tendency to clot 

 under ordinary conditions. But if this plasma is warmed and mixed 

 with a solution of calcium chlorid drop by drop in excess, it will give 



1 A. Schmidt, Zur Blutlehre, Leipzig, 1892. 



2 Bordet and Gengou, Ann. Inst. Past., xviii, 1904, 90. 



3 Jour. Phys., xxii, 1890, 739. 



