In 1949, one of us (L.M.) reported the transmission of Borrelia dugesii by Ornithodoros turicata. As Ornithodoros dugesi is the normal tick vector of this spirochete, this was the first reported major break in the specific tick-spirochete relationship in the Western Hemisphere. In 1952, the senior author of this report requested a strain of B. dugesii for further studies. As 0. dugesi was not available the strain was forwarded in Ornithodoros coriaceus, from which spirochetes have never been recovered, as collected in nature, and which did not transmit the spirochetes by feeding. The 0. coriaceus were, therefore, triturated in a minimal amount of physiologic saline and the triturate was injected into two white mice from which a strain of spirochetes was readily recovered.