THE ORIGIN OF PLATELETS

Abstract

Platelet changes were investigated in heart-lung preps. in dogs. Tocantins'' technique was used in counting platelets except that syringes were calibrated with needles attached and a soln. of urea was used as a diluting fluid, permitting counts to be made in 1/10 dilution of the original sample. Although heparin prevented coagulation of the perfusing blood, the platelets showed clumping and a sharp reduction in numbers within a few mins. after establishing the external circuit. In 10 preps. surviving from 1-4 hrs. only 1 showed a return of the platelet count to the level existing before operation, and when platelets were reduced in the blood before its use in perfusion, the count tended to level off after only a limited recovery. The clumping bore an inverse relationship to the platelet recovery. No satisfactory evidence of platelet production in the lungs was obtained in these studies and the possibility of special factors which might influence platelet formation was discussed.