Blood Platelets and Blood Clotting. 6i 



others. Of greater interest than citrate are the anticoagulants 

 which do not affect calcium. A plasma was obtained by drawing 

 blood into an equal volume of a I per cent, solution of MnCl 2 in 

 0.9 per cent. NaCl. If this is treated with enough Na 2 HP0 4 to 

 precipitate the manganese, it coagulates quite readily. On centri- 

 fuging this plasma at a moderate speed to remove red cells and 

 leucocytes (this also throws down some platelets), the coagulation 

 is slightly deferred. By filtering through a clay filter a plasma is 

 obtained which is not coagulated at all by Na 2 HP0 4 . Further 

 evidence is furnished by making use of the fact that platelets on 

 disintegrating yield a vasoconstrictor material. 1 The manganese 

 chloride plasma when tested on artery rings gives no constriction, 

 but on addition of Na 2 HP0 4 it clots and gives marked constriction. 

 This is the same result obtained with citrate and CaCl 2 , and 

 indicates clearly that the change taking place on adding Na 2 HP0 4 

 is disintegration of platelets. 



The observation of Buerker that MgS0 4 preserves platelets 

 I have verified by centrifuging a magnesium sulphate plasma 

 fractionally and staining the sediment with Wright's stain. The 

 same was observed with NaCl and Na 2 S0 4 . It is, however, much 

 more difficult to separate platelets from plasmas containing high 

 concentration of salts (NaCl, MgS0 4 , Na 2 S0 4 ) than with oxalate 

 citrate or fluoride, one reason being that on centrifuging the leuco- 

 cytes and platelets do not form a well-marked zone, but largely 

 sink into the red cell layer. 



If a fresh salted plasma (I have used MgS0 4 and NaCl) is 

 thoroughly centrifuged to remove the platelets as far as possible, 

 this plasma when compared with the cell containing residue after 

 dilution of both with normal saline, shows a much greater clotting 

 time, or does not clot at all. The high concentration of salts does 

 not permit the use of the test for vasoconstrictor material. 



Hirudin also as tested by Buerker's or Deetjen's method pre- 

 serves platelets. O'Connor 2 and others have found that hirudin 

 prevents the liberation of vasoconstrictor material in shed blood. 

 This indicates that hirudin prevents coagulation not only by an 

 antithrombin action, but also by preserving platelets. Which of 



1 Zucker and Stewart, Zenlr. f. Physiol., 27, 85 (1913). 

 ' Arch. f. Exp. Path, and Pharmakol., 67, 195 (1912). 



