Concluding Note

Abstract

It may possibly be thought strange that more has not been said in this book about the modern, very powerful techniques — various forms of chromatography and spectrometry, for example — now being increasingly applied, together with extremely useful methods of statistical analysis, by a growing number of investigators to the study of olfaction. The value of all these procedures should certainly not be underestimated. But, as Moulton has pointed out in his most valuable contributions to the subject, the sense of smell is much more sensitive than is the flame ionization detector of a gas-liquid chromatograph. We still cannot rely, he remarks, on micro-analytical procedures to detect all odorants present in concentrations detectable by the nose; we cannot be sure that electro-physiological processes may not be misleading; and we know no enzyme system that can respond to the very low concentrations of some odorants that are sufficient to excite the receptor. Above all, he says, we must never forget that “present theories of odor qualitiy have a major weakness. Because many of the properties of the molecule are interrelated, it is not sufficient to show that a high correlation exists between a given set of molecular properties and subjectively-derived estimates of odor quality. It must also be shown that a similar correlation does not exist with other properties. At the moment few, if any, of the odor theories seem detailled enough to indicate how such a critical test could be made.”