“…After surface contact, blood does clot quite effectively, without added thromboplastin, but it fails to do so in a number of naturally occuring clotting defects, including haemophilia. We thought that " thromboplastin" must be generated by the blood itself (Biggs, Douglas and Macfarlane 1953), and the so-called thromboplastin generation test was devised to study the process (Biggs and Douglas 1953). But it was found that the process differed from prothrombin activation by tissue factor, since Factor VII was not required.…”