The most satisfactory method of arriving at a_classification of smells seems to be the method of exhaustion ; but the results so far obtained do not furnish any basis for such a system. Nagel points out as the greatest difficulty in the way that when the organ is fatigued by one smell, its sensitivity does not remain quite unimpaired for one 1arge group of odors, and utterly fail for another group ; but on the contrary, is usually more or less impaired for all odors.[1] Analysis by exhaustion is complicated experimentally by the fact that smells do not fall away steadily, but oscillate at the stimulus-limen, as do mimmal sensations in other departments. In the case of smell this oscillation depends on slight variations in the rate and manner of breathing, as well as on the ordinary ebb and flow of the attention. The apparent “rivalry” of odors is due to this fluctuation at the limen.[2] Moreover, it is only the last component of the mixture to disappear, which is ever really isolated by the exhaustion-process.
Zwaardemaker adopts, with some modification, the old classification of Linnæus, which really has only a subjective basis, though Zwaardemaker attempts, without signal success, to give it a chemical one. On the principle that even a most unsatisfactory system is better than none, some pains have been taken in the experiments to be described to procure smells from as many of Zwaardemaker's classes as possible, and to compare results for representatives of the same class and of different classes. Zwaardemaker's classes of pure olfactory qualities are as follows :[3]
- Ethereal smells—including all the fruit odors (a class taken from Lorry).
- Aromatic smells—including all such odors as that of camphor, spicy smells, and the odors of anise and lavender, lemon and rose, and almond.
- Fragrant smells—including the odors of most flowers, of vanilla, and of such gums as tolu and benzoin.
- Ambrosiac smells—including the odor of amber, and all the musk odors.
- Alliaceous smells—including the odors of garlic, asafœtida, gum ammoniac, vulcanized India rubber, fish, bromine, chlorine and iodine, etc.
- Empyreumatic smells—including the odors of toast, tobacco smoke, pyridin, naphtha, etc., (a class taken from von Haller).
- Hircine smells-—including the odors of cheese, sweat, rancid fat, etc., etc.
- ↑ Op. cit., p. 86.
- ↑ P. 98.
- ↑ Op. cit., pp. 233–235
