Summary
A method for measuring six plasma or serum factors required for intrinsic thromboplastin
formation is described by which various dilutions of normal serum are used to correct
the abnormal TGT obtained with specifically deficient blood. When the arithmetic product
of the minimum clotting time and the corresponding incubation time are plotted against
the logarithm of the concentration of the particular factor in question, a rectilinear
relationship is obtained for factors V, VIII, IX, XI and XII, and a hitherto unrecognized
new serum factor (Thorium Vulnerable Factor, TVF). This correlation does not hold
for factor X. Thus far no mathematical or biochemical equation could be formulated
to explain the empiric observations.
Other reported assay procedures are discussed.