The number and variety of recognised smells being so great, then, one can readily understand how difficult it is to construct a classification of odours. Many attempts have, in fact, been made, but, depending as they do more or less upon subjective sensation, no two classifiers give us the same classification. Indeed, a division of all smells into “nice,” “neutral,” and “nasty” would be about as good as many much more ambitious efforts.
Zwaardemaker’s is the classification most usually followed at present, and as it is to him we owe most of our knowledge of scientific olfaction, we shall detail it here :
(1) Ethereal or fruity odours; (2) aromatic, including as sub-classes camphrous, herbaceous, anisic and thymic, citronous, and the bitter almond group; (3) balsamic, with sub-groups floral, liliaceous, and vanillar; (4) ambrosial or muscous ; (5) garlicky (including garlic), oniony, fishy, and the bromine type of odour; (6) empyreumatic (guaiacol) ; (7) caprylic (valerianic acid) ; (8) disgusting ; and (9) nauseating.
The subjective character of these classes is obvious, especially in the last two groups, but, apart from that objection, most people will be inclined to protest when they learn that chloroform and iodoform arc put into the first, the ethereal or fruity, group, while it is suggested, though to be
