The ideal serologic test for syphilis would be one which satisfies certain practical and logical criteria. It should give positive reactions with the serums of all patients with a syphilitic infection; it should give negative reactions with the serums of nonsyphilitic persons; furthermore, it should be relatively inexpensive and simply performed by the average hospital laboratory. Unfortunately, such an ideal test is not available. Theoretically, a test employing cultured pathogenic Nichols strain Treponema pallidum as an antigen could be expected to fulfill these criteria. To date, however, the cultivation of this micro-organism has never been realized, despite the efforts of Noguchi1-3 and others. In an attempt to culture this treponeme Nelson4 devised a medium which is capable of maintaining the life of the virulent Nichols strain T. pallidum for as long as 14 days with a half-life of 6 to 8 days. Unfortunately,