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The effect of counterion, solvent, and temperature on the proton nmr spectrum of the cyclononatetraenyl anion, cyclooctatetraene dianion, and tropylium cation have been investigated. In DME and THF, the lithium and sodium salts of the cyclononatetraenyl anion exist as an equilibrium mixture of contact and solvent-separated ion pairs whereas the potassium, rubidium, and cesium salts exist only as contact ion pairs. Salts of cyclooctatetrene dianion exist as contact ion pairs in all solvents examined. Lithium-7 nmr shifts support this view. The nmr spectrum of several tropylium salts shows the chemical shift of the tropylium cation to be independent of counterion but solvent dependent. These results suggest that the tropylium salts exist in solution as free solvated ions and solvent-separated ion pairs.

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In an opening address on the above subject to the Osler Club, London, on April 22, 1958, Prof. J. F. D. Shrewsbury advanced the (to me) novel suggestion that syphilis in its present form, which undoubtedly caused great alarm to health authorities in Europe in the late 90s of the 15th century, was due to the mutation about 1493 of a treponeme which had hitherto caused a milder form of treponematosis, such as Sibbens in Scotland and, under many other names, in Scandinavia and elsewhere. Thus, as I understood him, he gave T. pallidum a pedigree less than 500 years old with as parent a milder pathogen which had inhabited the world since prehistoric times. The only other attempt at fixing a length of pedigree to T. pallidum which I have been able to trace was that of H. V. Williams (1932), who, at the end of a long article describing syphilitic changes in bones found in American graves of date not later than A.D. 1300, said: "Somewhere and at some time a non-pathogenic spiral organism acquired pathogenic properties and became Spirochaeta pallida. It seems likely that this event took place less than 10,000 years ago. An antiquity so slight as even 2,000 years would present no difficulty to modem bacteriologists...." Personally, I find great difficulty in accepting Prof. Shrewsbury's thesis for the following reasons: First, it seems to postulate the existence in the Old World before 1493 of a milder form of syphilis such as, he says, Sibbens and, I suppose, the Syphiloide of Jutland and the endemic syphilis of Bosnia Herzogovina and the Middle East of today. I have not been able to trace any reference to Sibbens earlier than the 17th century.