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58 scrape of on the inhaling-tube. While Zwaardemaker's mixture of gum ammoniae and gutta-percha is black and brittle like licorice, ours was yellowish gray, contained strings of gutta-percha, and made the inhaling-tube cloudy and sticky, We did succeed in obtaining stimulus-limina with it when the inhaling-tube was first cleaned, but we believe that the end of the tube was probably soiled most of the time during difference-determinations. We have not excluded the results for Russian leather because its odor, like that of most of the liquids, was just liminal when the instrument was closed, and the results harmonized with the others. Since most of the liquids had this error of the equal but unmeasured increment, it is not surprising that the values of $Δr/r$ run higher for them than for solids. It will be noticed that they run highest for valerianic acid, which was particularly troublesome in escaping from the instrument. Yet as the results for coumarine, heliotropine, and musk show $1/3$ as the most common value, we must conclude that the vatue of $Δr/r$ lies comewhere between $1/3$ and $1/4$.

Some of the substances showed an interesting difference of quality with difference of intensity. Thus several subjects thought that oil of camphor smelt like nutmeg when weak, and like turpentine when strong. The slight odor of the paraffine appeared when a strong stimulus was given with coumariue. T. said that heliotropine smelled like heliotrope on the left (the better) side of her nose, and like hitter-almonds on the right. (As a matter of fact the two smells are closely allied.) Se. said that the tallow smelled like onions in his poorer nostril, Fluctuations at the limen were also noted. Coumarine and heliotropine, when weak, were said to come “in whiffs” or “waves,” and K. always spoke of weak smells as “scattered.”

Section 3. Results of Other Methods.

Table VII gives some of the results obtained by the method of just noticeable differences modified in the direction of the method of minimal changes, as described in Chapter I, Section 4, and shows the agreement of these results with those reached by the ordinary method. C. M. stands for “Combination Method.”

We used red rubber with the true method of minimal changes because Zwaardemaker had done so. The cylinder was obtained from Utrecht. The experiments of which the results are given in Table VIII extended through five laboratory-hours. It is needless to say that the instrument was manipulated entirely by the experimenter.