“…If we now send all the sera to say ten reputable laboratories where technical errors are unlikely, we can be quite confident that, although there may be agreement about the majority of results, there will be disagreement over the results from many cases. Experiments of this kind have often been performed, either as large-scale surveys or in the more informal exchange of sera between friendly laboratories (League of Nations, 1928;Cumming, Hazen, Sanford, Senear, Simpson, and Vonderlehr, 1935;Parran, Hazen, Mahoney, Sanford, Senear, Simpson, and Vonderlehr, 1937). Some tests are very sensitive and the results will be positive in cases (early syphilis, for example) when other tests are still negative; these sensitive tests will be much more likely to give positive results with diseases other than syphilis or even with an occasional normal person.…”