In a former report concerning the substances involved in the coagulation of the blood of the new-born,1 the prothrombin was estimated by a comparison of the time necessary for plasma treated with sodium oxalate to clot after various amounts of calcium chloride were added, as described by Howell.2 During the course of further experimentation in this field, we became dissatisfied with this method.
Whether the platelets alone are the source of prothrombin is still open to considerable controversy. However, as plasma from which all platelets have been removed will not clot for a great length of time and, conversely, plasma containing a high concentration of platelets coagulates rapidly, it seems fair to assume that the platelets are at least the principal source of prothrombin. For this reason the following studies were made.
Our previously described method3 for obtaining natural venous plasma was used. Platelet counts were
LESLIE EI, SANFORD HN. THE SUBSTANCES INVOLVED IN THE COAGULATION OF THE BLOOD OF THE NEW-BORN: V. PROTHROMBIN; QUANTITATIVE AND QUALITATIVE STUDIES OF PLATELETS IN THE NORMAL INFANT. Am J Dis Child. 1936;51(3):590–593. doi:10.1001/archpedi.1936.01970150094007
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