Abstract
Summary
(1) In a series of 600 photoelectric determinations of the prothrombin time of 100 normal individuals, the mean value for citrated plasma was 12.6 seconds as compared to 13.8 seconds for oxalated plasma. (2) The standard deviation was 0.15 second for citrated as compared to 0.19 second for oxalated plasma. (3) The onset of clotting is more easily determined photoelectrically with citrated than with oxalated plasma. This is evidenced by a more distinct swing of the galvanometer lightbeam because no precipitate but a soluble complex of calcium citrate is formed upon addition of calcium chloride.
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