Page:Eleanor Gamble - The Applicability of Weber's Law to Smell.pdf/9

Rh errors involves a discussion of the essentials of a satisfactory olfactometric method, and a detailed description of the method and apparatus actually employed. The literature of difference-determinations in smell amounts practically to pages 180–181 and pages 188–194 in Die Physiologie des Geruchs of Dr. H. Zwaardemaker, now professor of physiology in the University of Utrecht. The work was translated into German from Dr. Zwaardemaker’s manuscript by Dr. A, Junker von Langegg, and was published in Leipzig in 1895, The experiments to be described are in the main a realization of suggestions of Dr. Zwaardemaker’s, of which some are contained in his book, and some few were made in personal letters, The olfactometric method used was, of course, his. This method was first applied in 1888, and is now familiar in most psychological laboratories. To quote from Science, XV, 44: “Dr. Zwaardemaker of Utrecht has constructed an instrument which he calls an olfactometer. It consists simply of a glass tube, one end of which curves upward to be inserted into the nostril, A shorter movable cylinder made of the odoriferous substance fits over the straight end of this glass tube. In inhaling, no odor is perceived so long as the outer does not project beyond the inner tube. The farther we push forward the outer cylinder, the larger will be the scented surface presented to the inrushing column of air, and the stronger will be the odor perceived.”

We are indebted to Dr. Zwaardemaker for the words “olfactometry” and “olfactometer” (replacing the older “osmometer”), “odorimetry” and “odorimeter.” Olfactometry is that branch of psychophysics which is concerned with the measurement of the keenness of smell. The distinction between the keenness and the delicacy of smell must be kept in mind, On the delicacy of smell depends the discrimination of olfactory qualities. On its keenness depend the bare sensing of odors and the discrimination of them as more or less intense, Odorimetry is a ' side-issue” of olfactometry. It is concerned not with the sense-organ, but with the measurement of the intensity of smell-stimuli considered as objectively as possible. For the unit of keenness of smell, Zwaardemaker uses the word “olfactus,” and for the normal stimulus-limen for each odorous substance he employs the companion word “olfacty.” If, for example, a subject’s stimulus-limen on the olfactometer is 10 mm, when the normal stjmulus-limen used is